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Wang Y, Chen YY, Gao GB, Zheng YH, Yu NN, Ouyang L, Gao X, Li N, Wen SY, Huang S, Zhao Q, Liu L, Cao M, Zhang S, Zhang J, He QY. Polyphyllin D punctures hypertrophic lysosomes to reverse drug resistance of hepatocellular carcinoma by targeting acid sphingomyelinase. Mol Ther 2023; 31:2169-2187. [PMID: 37211762 PMCID: PMC10362416 DOI: 10.1016/j.ymthe.2023.05.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 04/13/2023] [Accepted: 05/18/2023] [Indexed: 05/23/2023] Open
Abstract
Hypertrophic lysosomes are critical for tumor progression and drug resistance; however, effective and specific lysosome-targeting compounds for cancer therapy are lacking. Here we conducted a lysosomotropic pharmacophore-based in silico screen in a natural product library (2,212 compounds), and identified polyphyllin D (PD) as a novel lysosome-targeted compound. PD treatment was found to cause lysosomal damage, as evidenced by the blockade of autophagic flux, loss of lysophagy, and the release of lysosomal contents, thus exhibiting anticancer effects on hepatocellular carcinoma (HCC) cell both in vitro and in vivo. Closer mechanistic examination revealed that PD suppressed the activity of acid sphingomyelinase (SMPD1), a lysosomal phosphodieserase that catalyzes the hydrolysis of sphingomyelin to produce ceramide and phosphocholine, by directly occupying its surface groove, with Trp148 in SMPD1 acting as a major binding residue; this suppression of SMPD1 activity irreversibly triggers lysosomal injury and initiates lysosome-dependent cell death. Furthermore, PD-enhanced lysosomal membrane permeabilization to release sorafenib, augmenting the anticancer effect of sorafenib both in vivo and in vitro. Overall, our study suggests that PD can potentially be further developed as a novel autophagy inhibitor, and a combination of PD with classical chemotherapeutic anticancer drugs could represent a novel therapeutic strategy for HCC intervention.
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Affiliation(s)
- Yang Wang
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China.
| | - Yan-Yan Chen
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Gui-Bin Gao
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Yang-Han Zheng
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Nan-Nan Yu
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Lan Ouyang
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Xuejuan Gao
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Nan Li
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Shi-Yuan Wen
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Shangjia Huang
- MOE Key Laboratory of Tumor Molecular Biology, The First Affiliated Hospital of Jinan University, Guangzhou 510613, China
| | - Qian Zhao
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Langxia Liu
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Mingrong Cao
- Department of General Surgery, The First Affiliated Hospital, Jinan University, Guangzhou 510613, China
| | - Shuixing Zhang
- Department of Radiology, The First Affiliated Hospital of Jinan University, Guangzhou 510613, China; MOE Key Laboratory of Tumor Molecular Biology, The First Affiliated Hospital of Jinan University, Guangzhou 510613, China.
| | - Jing Zhang
- Department of Radiology, The First Affiliated Hospital of Jinan University, Guangzhou 510613, China; MOE Key Laboratory of Tumor Molecular Biology, The First Affiliated Hospital of Jinan University, Guangzhou 510613, China.
| | - Qing-Yu He
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou 510632, China; MOE Key Laboratory of Tumor Molecular Biology, The First Affiliated Hospital of Jinan University, Guangzhou 510613, China.
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Oyebanji OA, Brewer C, Bayless S, Schmeusser B, Corbin DA, Sulentic CEW, Sherwin CMT, Chen Y, Rapp CM, Cates EE, Long Y, Travers JB, Rohan CA. Topical Photodynamic Therapy Generates Bioactive Microvesicle Particles: Evidence for a Pathway Involved in Immunosuppressive Effects. J Invest Dermatol 2023; 143:1279-1288.e9. [PMID: 36708950 PMCID: PMC10293022 DOI: 10.1016/j.jid.2022.12.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/09/2022] [Accepted: 12/13/2022] [Indexed: 01/26/2023]
Abstract
Although effective in treating actinic damage, topical photodynamic therapy (PDT) has been shown to be immunosuppressive through unknown mechanisms, which could potentially limit its effectiveness. Multiple types of environmental stressors, including PDT, can produce the immunosuppressive lipid mediator platelet-activating factor (PAF). Because PAF can produce subcellular microvesicle particles (MVPs), these studies tested whether PDT can generate PAF and MVP release and whether these are involved in PDT-induced immunosuppression. Previously, topical PDT using blue light and 5-aminolevulinic acid was found to be a potent stimulus for PAF production in mice and human skin explants and human patients, and we show that experimental PDT also generates high levels of MVP. PDT-generated MVPs were independent of the PAF receptor but were dependent on the MVP-generating enzyme acid sphingomyelinase. Patients undergoing topical PDT treatment to at least 10% of body surface area showed local and systemic immunosuppression as measured by inhibition of delayed-type hypersensitivity reactions. Finally, using a murine model of contact hypersensitivity, PDT immunosuppression was blocked by genetic and pharmacologic inhibition of acid sphingomyelinase and genetic inhibition of PAF receptor signaling. These studies describe a mechanism involving MVP through which PDT exerts immunomodulatory effects, providing a potential target to improve its effectiveness.
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Affiliation(s)
- Oladayo A Oyebanji
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Chad Brewer
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Sharlo Bayless
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Benjamin Schmeusser
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Danielle A Corbin
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Courtney E W Sulentic
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Catherine M T Sherwin
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA; Department of Pediatrics, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA; Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota, USA
| | - Yanfang Chen
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Christine M Rapp
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Elizabeth E Cates
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Yuhan Long
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota, USA
| | - Jeffrey B Travers
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA; Department of Dermatology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA; Dayton V.A. Medical Center, Dayton, Ohio, USA.
| | - Craig A Rohan
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA; Department of Dermatology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA; Dayton V.A. Medical Center, Dayton, Ohio, USA
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Houston DA, Stephen LA, Jayash SN, Myers K, Little K, Hopkinson M, Pitsillides AA, MacRae VE, Millan JL, Staines KA, Farquharson C. Increased PHOSPHO1 and alkaline phosphatase expression during the anabolic bone response to intermittent parathyroid hormone delivery. Cell Biochem Funct 2023; 41:189-201. [PMID: 36540015 PMCID: PMC10946561 DOI: 10.1002/cbf.3772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 12/02/2022] [Accepted: 12/09/2022] [Indexed: 12/24/2022]
Abstract
The administration of intermittent parathyroid hormone (iPTH) is anabolic to the skeleton. Recent studies with cultured osteoblasts have revealed that the expression of PHOSPHO1, a bone-specific phosphatase essential for the initiation of mineralisation, is regulated by PTH. Therefore, this study sought to determine whether the bone anabolic response to iPTH involves modulation of expression of Phospho1 and of other enzymes critical for bone matrix mineralisation. To mimic iPTH treatment, primary murine osteoblasts were challenged with 50 nM PTH for 6 h in every 48 h period for 8 days (4 cycles), 14 days (7 cycles) and 20 days (10 cycles) in total. The expression of both Phospho1 and Smpd3 was almost completely inhibited after 4 cycles, whereas 10 cycles were required to stimulate a similar response in Alpl expression. To explore the in vivo role of PHOSPHO1 in PTH-mediated osteogenesis, the effects of 14- and 28-day iPTH (80 µg/kg/day) administration was assessed in male wild-type (WT) and Phospho1-/- mice. The expression of Phospho1, Alpl, Smpd3, Enpp1, Runx2 and Trps1 expression was enhanced in the femora of WT mice following iPTH administration but remained unchanged in the femora of Phospho1-/- mice. After 28 days of iPTH administration, the anabolic response in the femora of WT was greater than that noted in Phospho1-/- mice. Specifically, cortical and trabecular bone volume/total volume, as well as cortical thickness, were increased in femora of iPTH-treated WT but not in iPTH-treated Phospho1-/- mice. Trabecular bone osteoblast number was also increased in iPTH-treated WT mice but not in iPTH-treated Phospho1-/- mice. The increased levels of Phospho1, Alpl, Enpp1 and Smpd3 in WT mice in response to iPTH administration is consistent with their contribution to the potent anabolic properties of iPTH in bone. Furthermore, as the anabolic response to iPTH was attenuated in mice deficient in PHOSPHO1, this suggests that the osteoanabolic effects of iPTH are at least partly mediated via bone mineralisation processes.
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Affiliation(s)
- Dean A. Houston
- Functional Genetics Division, The Roslin Institute and Royal (Dick) School of Veterinary StudiesUniversity of EdinburghMidlothianUK
| | - Louise A. Stephen
- Functional Genetics Division, The Roslin Institute and Royal (Dick) School of Veterinary StudiesUniversity of EdinburghMidlothianUK
| | - Soher N. Jayash
- Functional Genetics Division, The Roslin Institute and Royal (Dick) School of Veterinary StudiesUniversity of EdinburghMidlothianUK
| | - Katherine Myers
- Functional Genetics Division, The Roslin Institute and Royal (Dick) School of Veterinary StudiesUniversity of EdinburghMidlothianUK
| | - Kirsty Little
- Functional Genetics Division, The Roslin Institute and Royal (Dick) School of Veterinary StudiesUniversity of EdinburghMidlothianUK
| | - Mark Hopkinson
- Comparative Biomedical SciencesThe Royal Veterinary CollegeLondonUK
| | | | - Vicky E. MacRae
- Functional Genetics Division, The Roslin Institute and Royal (Dick) School of Veterinary StudiesUniversity of EdinburghMidlothianUK
| | - Jose Luis Millan
- Human Genetics ProgramSanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Katherine A. Staines
- School of Applied Sciences, Centre for Stress and Age‐Related DiseaseUniversity of BrightonBrightonUK
| | - Colin Farquharson
- Functional Genetics Division, The Roslin Institute and Royal (Dick) School of Veterinary StudiesUniversity of EdinburghMidlothianUK
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Garnacho C, Dhami R, Solomon M, Schuchman EH, Muro S. Enhanced Delivery and Effects of Acid Sphingomyelinase by ICAM-1-Targeted Nanocarriers in Type B Niemann-Pick Disease Mice. Mol Ther 2017; 25:1686-1696. [PMID: 28606376 DOI: 10.1016/j.ymthe.2017.05.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 05/19/2017] [Accepted: 05/21/2017] [Indexed: 01/01/2023] Open
Abstract
Acid sphingomyelinase deficiency in type B Niemann-Pick disease leads to lysosomal sphingomyelin storage, principally affecting lungs, liver, and spleen. Infused recombinant enzyme is beneficial, yet its delivery to the lungs is limited and requires higher dosing than liver and spleen, leading to potentially adverse reactions. Previous studies showed increased enzyme pulmonary uptake by nanocarriers targeted to ICAM-1, a protein overexpressed during inflammation. Here, using polystyrene and poly(lactic-co-glycolic acid) nanocarriers, we optimized lung delivery by varying enzyme dose and nanocarrier concentration, verified endocytosis and lysosomal trafficking in vivo, and evaluated delivered activity and effects. Raising the enzyme load of nanocarriers progressively increased absolute enzyme delivery to all lung, liver, and spleen, over the naked enzyme. Varying nanocarrier concentration inversely impacted lung versus liver and spleen uptake. Mouse intravital and postmortem examination verified endocytosis, transcytosis, and lysosomal trafficking using nanocarriers. Compared to naked enzyme, nanocarriers increased enzyme activity in organs and reduced lung sphingomyelin storage and macrophage infiltration. Although old mice with advanced disease showed reactivity (pulmonary leukocyte infiltration) to injections, including buffer without carriers, antibody, or enzyme, younger mice with mild disease did not. We conclude that anti-ICAM nanocarriers may result in effective lung enzyme therapy using low enzyme doses.
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Affiliation(s)
- Carmen Garnacho
- Department of Normal and Pathological Histology and Cytology, University of Seville School of Medicine, 41009 Seville, Spain
| | - Rajwinder Dhami
- Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Melani Solomon
- Institute for Bioscience and Biotechnology Research, University of Maryland, College Park, MD 20742, USA
| | - Edward H Schuchman
- Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
| | - Silvia Muro
- Institute for Bioscience and Biotechnology Research, University of Maryland, College Park, MD 20742, USA; Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA.
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Stauffer BB, Cui G, Cottrill KA, Infield DT, McCarty NA. Bacterial Sphingomyelinase is a State-Dependent Inhibitor of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR). Sci Rep 2017; 7:2931. [PMID: 28592822 PMCID: PMC5462758 DOI: 10.1038/s41598-017-03103-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 04/24/2017] [Indexed: 02/07/2023] Open
Abstract
Sphingomyelinase C (SMase) inhibits CFTR chloride channel activity in multiple cell systems, an effect that could exacerbate disease in CF and COPD patients. The mechanism by which sphingomyelin catalysis inhibits CFTR is not known but evidence suggests that it occurs independently of CFTR's regulatory "R" domain. In this study we utilized the Xenopus oocyte expression system to shed light on how CFTR channel activity is reduced by SMase. We found that the pathway leading to inhibition is not membrane delimited and that inhibited CFTR channels remain at the cell membrane, indicative of a novel silencing mechanism. Consistent with an effect on CFTR gating behavior, we found that altering gating kinetics influenced the sensitivity to inhibition by SMase. Specifically, increasing channel activity by introducing the mutation K1250A or pretreating with the CFTR potentiator VX-770 (Ivacaftor) imparted resistance to inhibition. In primary bronchial epithelial cells, we found that basolateral, but not apical, application of SMase leads to a redistribution of sphingomyelin and a reduction in forskolin- and VX-770-stimulated currents. Taken together, these data suggest that SMase inhibits CFTR channel function by locking channels into a closed state and that endogenous CFTR in HBEs is affected by SMase activity.
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Affiliation(s)
- B B Stauffer
- Division of Pulmonology, Allergy/Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Emory + Children's Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine and Children's Healthcare of Atlanta, 2015 Uppergate Drive, Atlanta, GA, 30322, USA
- Molecular and Systems Pharmacology program, Emory University, 201 Dowman Drive, Atlanta, GA, 20322, USA
| | - G Cui
- Division of Pulmonology, Allergy/Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Emory + Children's Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine and Children's Healthcare of Atlanta, 2015 Uppergate Drive, Atlanta, GA, 30322, USA
| | - K A Cottrill
- Molecular and Systems Pharmacology program, Emory University, 201 Dowman Drive, Atlanta, GA, 20322, USA
| | - D T Infield
- Division of Pulmonology, Allergy/Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Emory + Children's Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine and Children's Healthcare of Atlanta, 2015 Uppergate Drive, Atlanta, GA, 30322, USA
| | - N A McCarty
- Division of Pulmonology, Allergy/Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Emory + Children's Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine and Children's Healthcare of Atlanta, 2015 Uppergate Drive, Atlanta, GA, 30322, USA.
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Dai SY, Liu JJ, Sun XF, Wang N. Acid sphingomyelinase, a novel negative biomarker of ovarian cancer. Eur Rev Med Pharmacol Sci 2015; 19:2076-2083. [PMID: 26125272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
OBJECTIVE Ovarian cancer is the sixth most common cancer and the main cause of death in women. However, the molecular mechanism for the cause of the ovarian cancer has not been fully elucidated. Acid sphingomyelinase (ASM), a lipid hydrolase, has been suggested for treating cancer and may affect the development of ovarian cancer. We want to find the function of ASM in the development of ovarian cancer. PATIENTS AND METHODS Human ovarian cancer cells HO 8910 (HOCC) and human primary ovarian cells (HPOC) were transfected with ASM gene and ASM RNAi. Real-time qPCR and western blot analysis was carried out to examine the level of ASM. The growth rate of transfected and non-transfected cells was measured. Ovarian biopsies were collected from 80 ovarian cancer patients and 20 healthy subjects. RESULTS The growth rate of HOCC and HPOC was decreased by 22% and 19% in the ASM-transfected group compared with non-transfected group. Inversely, the growth rate of HOCC and HPOC was increased by 16% and 35% in the ASM-RNAi-transfected group compared with non-transfected group. In the transfected and non-transfected cells, the change level of SAM was approved by Real-time qPCR and western blot analysis. The levels of SAM were reducing with the development of ovarian cancer. CONCLUSIONS SAM is higher expressed in normal cell than that in ovarian cancer, and can be a negative biomarker for the diagnosis of ovarian cancer. SAM can be developed a new drug for the ovarian cancer therapy.
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Affiliation(s)
- S Y Dai
- Department of Obstetrics and Gynecology, the Affiliated Shengjing Hospital, China Medical University, Shenyang, China.
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Türkcan S, Masson JB, Casanova D, Mialon G, Gacoin T, Boilot JP, Popoff MR, Alexandrou A. Observing the confinement potential of bacterial pore-forming toxin receptors inside rafts with nonblinking Eu(3+)-doped oxide nanoparticles. Biophys J 2012; 102:2299-308. [PMID: 22677383 DOI: 10.1016/j.bpj.2012.03.072] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 03/20/2012] [Accepted: 03/23/2012] [Indexed: 12/26/2022] Open
Abstract
We track single toxin receptors on the apical cell membrane of MDCK cells with Eu-doped oxide nanoparticles coupled to two toxins of the pore-forming toxin family: α-toxin of Clostridium septicum and ε-toxin of Clostridium perfringens. These nonblinking and photostable labels do not perturb the motion of the toxin receptors and yield long uninterrupted trajectories with mean localization precision of 30 nm for acquisition times of 51.3 ms. We were thus able to study the toxin-cell interaction at the single-molecule level. Toxins bind to receptors that are confined within zones of mean area 0.40 ± 0.05 μm(2). Assuming that the receptors move according to the Langevin equation of motion and using Bayesian inference, we determined mean diffusion coefficients of 0.16 ± 0.01 μm(2)/s for both toxin receptors. Moreover, application of this approach revealed a force field within the domain generated by a springlike confining potential. Both toxin receptors were found to experience forces characterized by a mean spring constant of 0.30 ± 0.03 pN/μm at 37°C. Furthermore, both toxin receptors showed similar distributions of diffusion coefficient, domain area, and spring constant. Control experiments before and after incubation with cholesterol oxidase and sphingomyelinase show that these two enzymes disrupt the confinement domains and lead to quasi-free motion of the toxin receptors. Our control data showing cholesterol and sphingomyelin dependence as well as independence of actin depolymerization and microtubule disruption lead us to attribute the confinement of both receptors to lipid rafts. These toxins require oligomerization to develop their toxic activity. The confined nature of the toxin receptors leads to a local enhancement of the toxin monomer concentration and may thus explain the virulence of this toxin family.
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Affiliation(s)
- Silvan Türkcan
- Laboratoire d'Optique et Biosciences, Ecole Polytechnique, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale U696, Palaiseau, France.
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Spijkers LJA, van den Akker RFP, Janssen BJA, Debets JJ, De Mey JGR, Stroes ESG, van den Born BJH, Wijesinghe DS, Chalfant CE, MacAleese L, Eijkel GB, Heeren RMA, Alewijnse AE, Peters SLM. Hypertension is associated with marked alterations in sphingolipid biology: a potential role for ceramide. PLoS One 2011; 6:e21817. [PMID: 21818267 PMCID: PMC3139577 DOI: 10.1371/journal.pone.0021817] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 06/13/2011] [Indexed: 12/14/2022] Open
Abstract
Background Hypertension is, amongst others, characterized by endothelial dysfunction and vascular remodeling. As sphingolipids have been implicated in both the regulation of vascular contractility and growth, we investigated whether sphingolipid biology is altered in hypertension and whether this is reflected in altered vascular function. Methods and Findings In isolated carotid arteries from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats, shifting the ceramide/S1P ratio towards ceramide dominance by administration of a sphingosine kinase inhibitor (dimethylsphingosine) or exogenous application of sphingomyelinase, induced marked endothelium-dependent contractions in SHR vessels (DMS: 1.4±0.4 and SMase: 2.1±0.1 mN/mm; n = 10), that were virtually absent in WKY vessels (DMS: 0.0±0.0 and SMase: 0.6±0.1 mN/mm; n = 9, p<0.05). Imaging mass spectrometry and immunohistochemistry indicated that these contractions were most likely mediated by ceramide and dependent on iPLA2, cyclooxygenase-1 and thromboxane synthase. Expression levels of these enzymes were higher in SHR vessels. In concurrence, infusion of dimethylsphingosine caused a marked rise in blood pressure in anesthetized SHR (42±4%; n = 7), but not in WKY (−12±10%; n = 6). Lipidomics analysis by mass spectrometry, revealed elevated levels of ceramide in arterial tissue of SHR compared to WKY (691±42 vs. 419±27 pmol, n = 3–5 respectively, p<0.05). These pronounced alterations in SHR sphingolipid biology are also reflected in increased plasma ceramide levels (513±19 pmol WKY vs. 645±25 pmol SHR, n = 6–12, p<0.05). Interestingly, we observed similar increases in ceramide levels (correlating with hypertension grade) in plasma from humans with essential hypertension (185±8 pmol vs. 252±23 pmol; n = 18 normotensive vs. n = 19 hypertensive patients, p<0.05). Conclusions Hypertension is associated with marked alterations in vascular sphingolipid biology such as elevated ceramide levels and signaling, that contribute to increased vascular tone.
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Affiliation(s)
- Léon J. A. Spijkers
- Department of Pharmacology and Pharmacotherapy, Academic Medical Center, Amsterdam, The Netherlands
| | - Rob F. P. van den Akker
- Department of Pharmacology and Pharmacotherapy, Academic Medical Center, Amsterdam, The Netherlands
| | - Ben J. A. Janssen
- Department of Pharmacology and Toxicology, Maastricht University, Maastricht, The Netherlands
| | - Jacques J. Debets
- Department of Pharmacology and Toxicology, Maastricht University, Maastricht, The Netherlands
| | - Jo G. R. De Mey
- Department of Pharmacology and Toxicology, Maastricht University, Maastricht, The Netherlands
| | - Erik S. G. Stroes
- Vascular Medicine, Academic Medical Center, Amsterdam, The Netherlands
| | | | - Dayanjan S. Wijesinghe
- Department of Biochemistry, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Charles E. Chalfant
- Department of Biochemistry, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Luke MacAleese
- FOM Institute for Atomic and Molecular Physics, Amsterdam, The Netherlands
| | - Gert B. Eijkel
- FOM Institute for Atomic and Molecular Physics, Amsterdam, The Netherlands
| | - Ron M. A. Heeren
- FOM Institute for Atomic and Molecular Physics, Amsterdam, The Netherlands
| | - Astrid E. Alewijnse
- Department of Pharmacology and Pharmacotherapy, Academic Medical Center, Amsterdam, The Netherlands
| | - Stephan L. M. Peters
- Department of Pharmacology and Pharmacotherapy, Academic Medical Center, Amsterdam, The Netherlands
- * E-mail:
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Hemi R, Yochananov Y, Barhod E, Kasher-Meron M, Karasik A, Tirosh A, Kanety H. p38 mitogen-activated protein kinase-dependent transactivation of ErbB receptor family: a novel common mechanism for stress-induced IRS-1 serine phosphorylation and insulin resistance. Diabetes 2011; 60:1134-45. [PMID: 21386087 PMCID: PMC3064087 DOI: 10.2337/db09-1323] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Stress stimuli such as tumor necrosis factor (TNF) have been shown to induce insulin receptor substrate (IRS)-1 serine phosphorylation and insulin resistance by transactivation of ErbB receptors. We aimed at elucidating the potential role of p38 mitogen-activated protein kinase (p38MAPK) in mediating stress-induced ErbB receptors activation. RESEARCH DESIGN AND METHODS p38MAPK effect on ErbBs transactivation and insulin signaling was assessed in Fao or HepG2 cells, exposed to stress stimuli, and on metabolic parameters in ob/ob and C57/BL6 mice. RESULTS High-fat diet-fed mice and ob/ob mice exhibited elevated hepatic p38MAPK activation associated with glucose intolerance and hyperinsulinemia. Liver expression of dominant-negative (DN)-p38MAPKα in ob/ob mice reduced fasting insulin levels and improved glucose tolerance, whereas C57/BL6 mice overexpressing wild-type p38MAPKα exhibited enhanced IRS-1 serine phosphorylation and reduced insulin-stimulated IRS-1 tyrosine phosphorylation. Fao or HepG2 cells exposed to TNF, anisomycin, or sphingomyelinase demonstrated rapid transactivation of ErbB receptors leading to PI3-kinase/Akt activation and IRS-1 serine phosphorylation. p38MAPK inhibition either by SB203580, by small interfering RNA, or by DN-p38MAPKα decreased ErbB receptors transactivation and IRS-1 serine phosphorylation and partially restored insulin-stimulated IRS-1 tyrosine phosphorylation. When cells were incubated with specific ErbB receptors antagonists or in cells lacking ErbB receptors, anisomycin- and TNF-induced IRS-1 serine phosphorylation was attenuated, despite intact p38MAPK activation. The stress-induced p38MAPK activation leading to ErbB receptors transactivation was associated with intracellular reactive oxygen species generation and was attenuated by treatment with antioxidants. CONCLUSIONS Hepatic p38MAPK is activated following various stress stimuli. This event is upstream to ErbB receptors transactivation and plays an important role in stress-induced IRS-1 serine phosphorylation and insulin resistance.
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Affiliation(s)
- Rina Hemi
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
| | - Yafit Yochananov
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Ehud Barhod
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Michal Kasher-Meron
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Avraham Karasik
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Amir Tirosh
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
| | - Hannah Kanety
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Corresponding author: Hannah Kanety,
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Angulo S, Morales A, Danese S, Llacuna L, Masamunt MC, Pultz N, Cifone MG, De Simone C, Delgado S, Vila J, Panés J, Donskey C, Fernández-Checa JC, Fiocchi C, Sans M. Probiotic sonicates selectively induce mucosal immune cells apoptosis through ceramide generation via neutral sphingomyelinase. PLoS One 2011; 6:e16953. [PMID: 21408067 PMCID: PMC3052310 DOI: 10.1371/journal.pone.0016953] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 01/18/2011] [Indexed: 01/02/2023] Open
Abstract
Background Probiotics appear to be beneficial in inflammatory bowel disease, but their mechanism of action is incompletely understood. We investigated whether probiotic-derived sphingomyelinase mediates this beneficial effect. Methodology/Principal Findings Neutral sphingomyelinase (NSMase) activity was measured in sonicates of the probiotic L. brevis (LB) and S. thermophilus (ST) and the non-probiotic E. coli (EC) and E. faecalis (EF). Lamina propria mononuclear cells (LPMC) were obtained from patients with Crohn's disease (CD) and Ulcerative Colitis (UC), and peripheral blood mononuclear cells (PBMC) from healthy volunteers, analysing LPMC and PBMC apoptosis susceptibility, reactive oxygen species (ROS) generation and JNK activation. In some experiments, sonicates were preincubated with GSH or GW4869, a specific NSMase inhibitor. NSMase activity of LB and ST was 10-fold that of EC and EF sonicates. LB and ST sonicates induced significantly more apoptosis of CD and UC than control LPMC, whereas EC and EF sonicates failed to induce apoptosis. Pre-stimulation with anti-CD3/CD28 induced a significant and time-dependent increase in LB-induced apoptosis of LPMC and PBMC. Exposure to LB sonicates resulted in JNK activation and ROS production by LPMC. NSMase activity of LB sonicates was completely abrogated by GW4869, causing a dose-dependent reduction of LB-induced apoptosis. LB and ST selectively induced immune cell apoptosis, an effect dependent on the degree of cell activation and mediated by bacterial NSMase. Conclusions These results suggest that induction of immune cell apoptosis is a mechanism of action of some probiotics, and that NSMase-mediated ceramide generation contributes to the therapeutic effects of probiotics.
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Affiliation(s)
- Sandra Angulo
- Department of Gastroenterology, Hospital Clinic, IDIBAPS, CIBER Enfermedades Hepáticas y Digestivas (CIBERehd), Barcelona, Spain
| | - Albert Morales
- Liver Unit, Hospital Clinic, IDIBAPS, CIBERehd, Barcelona, Spain
- Department of Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona (IIBB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Silvio Danese
- Division of Gastroenterology, Istituto Clinico Humanitas, Milan, Italy
| | - Laura Llacuna
- Liver Unit, Hospital Clinic, IDIBAPS, CIBERehd, Barcelona, Spain
- Department of Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona (IIBB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Maria Carme Masamunt
- Department of Gastroenterology, Hospital Clinic, IDIBAPS, CIBER Enfermedades Hepáticas y Digestivas (CIBERehd), Barcelona, Spain
| | - Nicole Pultz
- Infectious Diseases Section, Louis Stokes Cleveland Department of VA Medical Center, Cleveland, Ohio, United States of America
| | - Maria Grazia Cifone
- Department of Experimental Medicine, University of L'Aquila, L'Aquila, Italy
| | - Claudio De Simone
- Department of Experimental Medicine, University of L'Aquila, L'Aquila, Italy
| | - Salvadora Delgado
- Department of Gastrointestinal Surgery, Hospital Clinic, IDIBAPS, CIBERehd, Barcelona, Spain
| | - Jordi Vila
- Department of Clinical Microbiology, Hospital Clinic, IDIBAPS, CIBERehd, Barcelona, Spain
| | - Julián Panés
- Department of Gastroenterology, Hospital Clinic, IDIBAPS, CIBER Enfermedades Hepáticas y Digestivas (CIBERehd), Barcelona, Spain
| | - Curtis Donskey
- Infectious Diseases Section, Louis Stokes Cleveland Department of VA Medical Center, Cleveland, Ohio, United States of America
| | - Jose C. Fernández-Checa
- Liver Unit, Hospital Clinic, IDIBAPS, CIBERehd, Barcelona, Spain
- Department of Cell Death and Proliferation, Instituto de Investigaciones Biomédicas de Barcelona (IIBB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
- Research Center for Alcoholic Liver and Pancreatic Diseases, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
- * E-mail: (JCFC); (MS)
| | - Claudio Fiocchi
- Department of Gastroenterology and Hepatology, Cleveland Clinic Foundation, Cleveland, Ohio, United States of America
| | - Miquel Sans
- Department of Gastroenterology, Hospital Clinic, IDIBAPS, CIBER Enfermedades Hepáticas y Digestivas (CIBERehd), Barcelona, Spain
- * E-mail: (JCFC); (MS)
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11
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Gupta VR, Patel HK, Kostolansky SS, Ballivian RA, Eichberg J, Blanke SR. Sphingomyelin functions as a novel receptor for Helicobacter pylori VacA. PLoS Pathog 2008; 4:e1000073. [PMID: 18497859 PMCID: PMC2374909 DOI: 10.1371/journal.ppat.1000073] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 04/15/2008] [Indexed: 12/18/2022] Open
Abstract
The vacuolating cytotoxin (VacA) of the gastric pathogen Helicobacter pylori binds and enters epithelial cells, ultimately resulting in cellular vacuolation. Several host factors have been reported to be important for VacA function, but none of these have been demonstrated to be essential for toxin binding to the plasma membrane. Thus, the identity of cell surface receptors critical for both toxin binding and function has remained elusive. Here, we identify VacA as the first bacterial virulence factor that exploits the important plasma membrane sphingolipid, sphingomyelin (SM), as a cellular receptor. Depletion of plasma membrane SM with sphingomyelinase inhibited VacA-mediated vacuolation and significantly reduced the sensitivity of HeLa cells, as well as several other cell lines, to VacA. Further analysis revealed that SM is critical for VacA interactions with the plasma membrane. Restoring plasma membrane SM in cells previously depleted of SM was sufficient to rescue both toxin vacuolation activity and plasma membrane binding. VacA association with detergent-resistant membranes was inhibited in cells pretreated with SMase C, indicating the importance of SM for VacA association with lipid raft microdomains. Finally, VacA bound to SM in an in vitro ELISA assay in a manner competitively inhibited by lysenin, a known SM-binding protein. Our results suggest a model where VacA may exploit the capacity of SM to preferentially partition into lipid rafts in order to access the raft-associated cellular machinery previously shown to be required for toxin entry into host cells. Sensitivity to toxins produced by pathogenic bacteria is largely dictated by the presence or absence of toxin receptors on the plasma membrane of host cells. VacA is an important toxin produced by the pathogenic bacterium Helicobacter pylori, which infects the human stomach and causes gastric ulcer disease and stomach cancer. VacA binds and enters human cells, and induces several changes resulting ultimately in the death of the intoxicated cells. However, the identity of the VacA receptor responsible for toxin binding and function has remained a topic of debate. In this paper, we demonstrate that sphingomyelin, a lipid on the surface of cells with important membrane structural and signaling properties, functions as a VacA receptor. We demonstrate that VacA binds to sphingomyelin, and that presence or absence of sphingomyelin on the plasma membrane dictates how much VacA binds to the cell surface, and therefore, how sensitive cells are to the toxin. The identification of sphingomyelin also provides a conceptual framework for how VacA may enter cells through specialized functional domains on the surface of cells. This is the first example of a bacterial toxin that exploits sphingomyelin as a receptor, and future work will focus on developing strategies to block VacA interactions with sphingomyelin, thereby protecting cells from the downstream consequences of toxin action.
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Affiliation(s)
- Vijay R. Gupta
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
| | - Hetal K. Patel
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Sean S. Kostolansky
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
| | - Roberto A. Ballivian
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Joseph Eichberg
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Steven R. Blanke
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
- * E-mail:
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12
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Abstract
AIM: To test the hypothesis that hydrolysis of sphingomyelin to ceramide changes the composition of tight junctions (TJs) with increasing permeability of the intestinal epithelium.
METHODS: Monolayers of Caco-2 cells were used as an in vitro model for the intestinal barrier. Permeability was determined by quantification of transepithelial flux and transepithelial resistance. Sphingolipid-rich membrane microdomains were isolated by a discontinuous sucrose gradient and characterized by Western-blot. Lipid content of microdomains was analysed by tandem mass spectrometry. Ceramide was subcellularly localized by immunofluorescent staining.
RESULTS: Exogenous sphingomyelinase increased transepithelial permeability and decreased transepithelial resistance at concentrations as low as 0.01 U/mL. Lipid analysis showed rapid accumulation of ceramide in the membrane fractions containing occludin and claudin-4, representing TJs. In these fractions we observed a concomitant decrease of sphingomyelin and cholesterol with increasing concentrations of ceramide. Immunofluorescent staining confirmed clustering of ceramide at the sites of cell-cell contacts. Neutralization of surface ceramide prevented the permeability-increase induced by platelet activating factor.
CONCLUSION: Our findings indicate that changes in lipid composition of TJs impair epithelial barrier functions. Generation of ceramide by sphingomyelinases might contribute to disturbed barrier function seen in diseases such as inflammatory, infectious, toxic or radiogenic bowel disease.
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Affiliation(s)
- Jurgen Bock
- Department of Internal Medicine I, University of Regensburg, Regensburg, Germany.
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13
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Huseby M, Shi K, Brown CK, Digre J, Mengistu F, Seo KS, Bohach GA, Schlievert PM, Ohlendorf DH, Earhart CA. Structure and biological activities of beta toxin from Staphylococcus aureus. J Bacteriol 2007; 189:8719-26. [PMID: 17873030 PMCID: PMC2168928 DOI: 10.1128/jb.00741-07] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Beta toxin is a neutral sphingomyelinase secreted by certain strains of Staphylococcus aureus. This virulence factor lyses erythrocytes in order to evade the host immune system as well as scavenge nutrients. The structure of beta toxin was determined at 2.4-A resolution using crystals that were merohedrally twinned. This structure is similar to that of the sphingomyelinases of Listeria ivanovii and Bacillus cereus. Beta toxin belongs to the DNase I folding superfamily; in addition to sphingomyelinases, the proteins most structurally related to beta toxin include human endonuclease HAP1, Escherichia coli endonuclease III, bovine pancreatic DNase I, and the endonuclease domain of TRAS1 from Bombyx mori. Our biological assays demonstrated for the first time that beta toxin kills proliferating human lymphocytes. Structure-directed active site mutations show that biological activities, including hemolysis and lymphotoxicity, are due to the sphingomyelinase activity of the enzyme.
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Affiliation(s)
- Medora Huseby
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
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14
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Bao HF, Zhang ZR, Liang YY, Ma JJ, Eaton DC, Ma HP. Ceramide mediates inhibition of the renal epithelial sodium channel by tumor necrosis factor-alpha through protein kinase C. Am J Physiol Renal Physiol 2007; 293:F1178-86. [PMID: 17634398 DOI: 10.1152/ajprenal.00153.2007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
To determine whether ceramide mediates regulation of the renal epithelial sodium channel (ENaC) by tumor necrosis factor-alpha (TNF-alpha), confocal microscopy and patch-clamp experiments were performed in A6 distal nephron cells. We found that TNF-alpha (100 ng/ml) had no effect on ENaC activity and ceramide level when the cells were grown in the presence of aldosterone, but significantly inhibited ENaC and induced ceramide production after the cells were pretreated with LY 294002, an inhibitor of phosphatidylinositol 3-kinase, for 24 h. The inhibition of ENaC induced by TNF-alpha was mimicked by exogenous sphingomyelinase (0.1 U/ml) and C(2)-ceramide (50 microM), but neither C(2)-dihydroceramide, a membrane-impermeable analog of C(2)-ceramide, nor choline, and abolished by pretreatment with GF109203X, a protein kinase C (PKC) inhibitor. C(2)-ceramide failed to affect ENaC in the cells pretreated with GF109203X, but not in the cells pretreated with PD-98059, a mitogen-activated protein kinase kinase inhibitor. C(2)-ceramide induced the externalization of phosphatidylserine (PS) in control A6 cells, but not in the cells pretreated with GF109203X. Together with our previous finding that cytosolic PS maintains ENaC activity in A6 cells, these data suggest that ceramide mediates TNF-alpha inhibition of the renal ENaC via a pathway associated with PKC-dependent externalization of PS.
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Affiliation(s)
- Hui-Fang Bao
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, USA
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15
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Finnegan CM, Rawat SS, Cho EH, Guiffre DL, Lockett S, Merrill AH, Blumenthal R. Sphingomyelinase restricts the lateral diffusion of CD4 and inhibits human immunodeficiency virus fusion. J Virol 2007; 81:5294-304. [PMID: 17344303 PMCID: PMC1900240 DOI: 10.1128/jvi.02553-06] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Previously, we reported that treatment of cells with sphingomyelinase inhibits human immunodeficiency virus type 1 (HIV-1) entry. Here, we determined by measuring fluorescence recovery after photobleaching that the lateral diffusion of CD4 decreased 4-fold following sphingomyelinase treatment, while the effective diffusion rate of CCR5 remained unchanged. Notably, sphingomyelinase treatment of cells did not influence gp120 binding, HIV-1 attachment, or fluid-phase and receptor-mediated endocytosis. Furthermore, sphingomyelinase treatment did not affect the membrane disposition of the HIV receptor proteins CD4, CXCR4, and CCR5, as determined by Triton X-100 extraction. Restriction of CD4 diffusion by antibody cross-linking also inhibited HIV infection. We therefore interpret the decrease in CD4 lateral mobility following sphingomyelinase treatment in terms of clustering of CD4 molecules. Examination of fusion intermediates indicated that sphingomyelinase treatment inhibited HIV at a step in the fusion process after CD4 engagement. Maximal inhibition of fusion was observed following short coculture times and with target cells that express low levels of CD4. As HIV entry into cells requires the sequential engagement of viral envelope protein with CD4 and coreceptor, we propose that sphingomyelinase inhibits HIV infection by inducing CD4 clustering that prevents coreceptor engagement and HIV fusion.
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Affiliation(s)
- Catherine M Finnegan
- Center for Cancer Research Nanobiology Program, National Cancer Institute, National Institutes of Health, Frederick, MD 21702-1201, USA
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16
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Gilbert SJ, Blain EJ, Jones P, Duance VC, Mason DJ. Exogenous sphingomyelinase increases collagen and sulphated glycosaminoglycan production by primary articular chondrocytes: an in vitro study. Arthritis Res Ther 2007; 8:R89. [PMID: 16696862 PMCID: PMC1779424 DOI: 10.1186/ar1961] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Revised: 04/18/2006] [Accepted: 04/20/2006] [Indexed: 01/15/2023] Open
Abstract
We previously established a role for the second messenger ceramide in protein kinase R (PKR)-mediated articular cartilage degradation. Ceramide is known to play a dual role in collagen gene regulation, with the effect of ceramide on collagen promoter activity being dependent on its concentration. Treatment of cells with low doses of sphingomyelinase produces small increases in endogenous ceramide. We investigated whether ceramide influences articular chondrocyte matrix homeostasis and, if so, the role of PKR in this process. Bovine articular chondrocytes were stimulated for 7 days with sphingomyelinase to increase endogenous levels of ceramide. To inhibit PKR, 2-aminopurine was added to duplicate cultures. De novo sulphated glycosaminoglycan and collagen synthesis were measured by adding [35S]-sulphate and [3H]-proline to the media, respectively. Chondrocyte phenotype was investigated using RT-PCR and Western blot analysis. Over 7 days, sphingomyelinase increased the release of newly synthesized sulphated glycosaminoglycan and collagen into the media, whereas inhibition of PKR in sphingomyelinase-treated cells reduced the level of newly synthesized sulphated glycosaminoglycan and collagen. Sphingomyelinase treated chondrocytes expressed col2a1 mRNA, which is indicative of a normal chondrocyte phenotype; however, a significant reduction in type II collagen protein was detected. Therefore, small increments in endogenous ceramide in chondrocytes appear to push the homeostatic balance toward extracellular matrix synthesis but at the expense of the chondrocytic phenotype, which was, in part, mediated by PKR.
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Affiliation(s)
- Sophie J Gilbert
- Connective Tissue Biology Laboratories, School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales, UK
| | - Emma J Blain
- Connective Tissue Biology Laboratories, School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales, UK
| | - Pamela Jones
- Connective Tissue Biology Laboratories, School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales, UK
| | - Victor C Duance
- Connective Tissue Biology Laboratories, School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales, UK
| | - Deborah J Mason
- Connective Tissue Biology Laboratories, School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales, UK
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17
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Morales V, Gonzalez-Robayna I, Santana MP, Hernandez I, Fanjul LF. Tumor necrosis factor-alpha activates transcription of inducible repressor form of 3',5'-cyclic adenosine 5'-monophosphate-responsive element binding modulator and represses P450 aromatase and inhibin alpha-subunit expression in rat ovarian granulosa cells by a p44/42 mitogen-activated protein kinase-dependent mechanism. Endocrinology 2006; 147:5932-9. [PMID: 16946004 DOI: 10.1210/en.2006-0635] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The proinflammatory cytokine TNFalpha has important actions at the level of the ovary, including inhibition of P450 aromatase (P450AROM) activity and the secretion of inhibin, two proteins that are markers of the granulosa cell's differentiated status. Because the transcription of both P450AROM and inhibin alpha-subunit can be suppressed in the ovary by the inducible repressor isoform of cAMP-responsive element binding modulator (ICER), we have investigated whether TNFalpha and its intracellular messenger ceramide can induce ICER expression and the mechanisms whereby the induction is accomplished. ICER mRNA levels were assessed by RT-PCR in granulosa cells treated with TNFalpha, the ceramide-mobilizing enzyme sphingomyelinase (SMase), or C6-cer, a cell-permeant ceramide analog. Rapid (3 h) yet transient increases in the four isoforms of ICER were observed in response to all treatments. Likewise, ICER protein measured by immunoprecipitation with a specific antibody increases after TNFalpha, SMase, or C6-cer treatment. The mandatory phosphorylation of cAMP-responsive element binding was also observed in response to TNFalpha, SMase, or C6-cer and shown to be prevented by the p44/42 MAPK-specific inhibitor PD098059 but no other kinase blockers. Activation of p44/42 MAPK by the cytokine and its messenger was subsequently demonstrated as well as the inhibition of ICER expression by PD098059. Finally, the blocking of p44/42 MAPK activation prevented TNFalpha inhibition of FSH-dependent increases in P450AROM and inhibin alpha-subunit mRNA levels, thus indicating that p44/42 MAPK-mediated ICER expression may be accountable for the effects of TNFalpha on the expression of both proteins.
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Affiliation(s)
- Victoria Morales
- Department of Biochemistry and Physiology, Facultad de Medicina, Universidad de Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, 35016, Spain
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18
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Strle K, Broussard SR, McCusker RH, Shen WH, LeCleir JM, Johnson RW, Freund GG, Dantzer R, Kelley KW. C-jun N-terminal kinase mediates tumor necrosis factor-alpha suppression of differentiation in myoblasts. Endocrinology 2006; 147:4363-73. [PMID: 16777978 DOI: 10.1210/en.2005-1541] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The stress kinase c-jun N-terminal kinase (JNK) was recently shown to be involved in the pathophysiology of major inflammatory conditions, including Alzheimer's disease, stroke, obesity, and type II diabetes. However, the role of JNK in regulating inflammatory events in skeletal muscle is only beginning to be explored. IGF-I is the major hormone that promotes muscle growth and development. Here we used a novel, JNK interacting protein (JIP)-derived JNK peptide inhibitor to establish that JNK suppresses the biological activity of IGF-I in skeletal muscle progenitor cells. In these myoblasts, TNFalpha and its downstream receptor substrates, neutral-sphingomyelinase (N-SMase) and N-acetyl-d-sphingosine (C2-ceramide), induce JNK kinase activity in a time-dependent manner. Consistent with these results, TNFalpha induces JNK binding to insulin receptor substrate 1 (IRS-1) but is unable to inhibit IGF-I-induced IRS-1 tyrosine phosphorylation in myoblasts that are treated with the JNK peptide inhibitor. More importantly, JNK activation induced by TNFalpha, C2-ceramide, and N-SMase is associated with reduced expression of the critical muscle transcription factor myogenin as well as the differentiation marker myosin heavy chain (MHC). The JNK peptide inhibitor, but not the control peptide, completely reverses this inhibition of both myogenin and MHC. In the absence of IGF-I, TNFalpha, C2-ceramide, N-SMase and the JNK inhibitor are inactive, as shown by their inability to affect IRS tyrosine phosphorylation and protein expression of myogenin and MHC. These results establish that the resistance of muscle progenitor cells to IGF-I, which is caused by inflammatory stimuli, is mediated by the JNK stress kinase pathway.
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Affiliation(s)
- Klemen Strle
- Laboratories of Immunophysiology, Department of Animal Sciences, University of Illinois, Urbana, Illinois 61801, USA
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Subbaiah PV, Horvath P, Achar SB. Regulation of the activity and fatty acid specificity of lecithin-cholesterol acyltransferase by sphingomyelin and its metabolites, ceramide and ceramide phosphate. Biochemistry 2006; 45:5029-38. [PMID: 16605271 PMCID: PMC1451158 DOI: 10.1021/bi0600704] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Sphingomyelin (SM), the second most abundant phospholipid in plasma lipoproteins, was previously shown to be a physiological inhibitor of the lecithin-cholesterol acyltransferase (LCAT) reaction. In this study, we investigated the effects of its metabolites, ceramide and ceramide phosphate, on the activity and fatty acid specificity of LCAT in vitro. Treatment of SM-containing substrate with SMase C, which hydrolyzes SM to ceramide, abolished the inhibitory effect of SM, whereas treatment with SMase D, which hydrolyzes it to ceramide phosphate, increased the level of inhibition. Although incorporation of ceramide into the substrate in the absence of SM activated the LCAT reaction only modestly, its co-incorporation with SM neutralized the inhibitory effect of SM. Ceramide phosphate, on the other hand, inhibited the LCAT reaction more strongly than SM. The effects of the sphingolipids on the phospholipase A and cholesterol esterification reactions of the enzyme were similar, indicating that they regulate the binding of phosphatidylcholine (PC) to the active site, rather than the esterification step. Incorporation of ceramide into the substrate stimulated the synthesis of unsaturated cholesteryl esters at the expense of saturated esters. However, these effects on fatty acid specificity disappeared when the PC substrates were incorporated into an inert diether PC matrix, suggesting that ceramide increases the availability of polyunsaturated PCs to the enzyme by altering the macromolecular structure of the substrate particle. Since the plasma ceramide levels are increased during inflammation, these results indicate that the activity and fatty acid specificity of LCAT may be altered during the inflammatory response.
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Affiliation(s)
- Papasani V Subbaiah
- Department of Medicine, University of Illinois, Chicago, Illinois 60612, USA.
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Lim CH, Schoonderwoerd K, Kleijer WJ, de Jonge HR, Tilly BC. Regulation of the cell swelling-activated chloride conductance by cholesterol-rich membrane domains. Acta Physiol (Oxf) 2006; 187:295-303. [PMID: 16734766 DOI: 10.1111/j.1748-1716.2006.01534.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
AIM The role of high cholesterol-containing microdomains in the signal transduction cascade leading to the activation of volume-regulated anion channels (VRACs) was studied. METHODS Osmotic cell swelling-induced efflux of 125I- was determined in human epithelial Intestine 407 cells and in skin fibroblasts obtained from healthy controls or Niemann-Pick type C (NPC) patients. Cellular cholesterol content was modulated by pre-incubation with 2-hydroxypropyl-beta-cyclodextrin in the presence of acceptor lipid vesicles. RESULTS Osmotic cell swelling of human Intestine 407 cells leads to the rapid activation of a compensatory anion conductance. Treatment of the cells with cyclodextrin enhanced the response to submaximal hypotonic stimulation by approx. twofold, but did not further increase the efflux elicited by a saturating stimulus. In contrast, the volume-sensitive anion efflux was markedly inhibited when cholesterol-loaded cyclodextrin was used. Potentiation of the response by cholesterol depletion was maintained in caveolin-1 deficient Caco-2 colonocytes as well as in sphingomyelinase-treated Intestine 407 cells, indicating that cholesterol-rich microdomains are not crucially involved. However, treatment of the cells with progesterone, an inhibitor of NPC1-dependent endosomal cholesterol trafficking, not only markedly reduced the hypotonicity-provoked anion efflux, but also prevented its potentiation by cyclodextrin. In addition, the volume-sensitive anion efflux from human NPC skin fibroblasts was significantly smaller when compared with control fibroblasts. CONCLUSIONS The results support a model of regulatory volume decrease involving recruitment of volume-sensitive anion channels from intracellular compartments to the plasma membrane.
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Affiliation(s)
- C H Lim
- Department of Biochemistry, Erasmus University Medical Center, Rotterdam, The Netherlands
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Diaz O, Mébarek-Azzam S, Benzaria A, Dubois M, Lagarde M, Némoz G, Prigent AF. Disruption of Lipid Rafts Stimulates Phospholipase D Activity in Human Lymphocytes: Implication in the Regulation of Immune Function. J Immunol 2005; 175:8077-86. [PMID: 16339545 DOI: 10.4049/jimmunol.175.12.8077] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Recent evidence suggests that phospholipase D (PLD) can be regulated through its association/dissociation to lipid rafts. We show here that modifying lipid rafts either by cholesterol depletion using methyl-beta-cyclodextrin and filipin or by conversion of sphingomyelin to ceramide with exogenous bacterial sphingomyelinase (bSMase) markedly activated the PLD of human PBMC. bSMase was the most potent PLD activator, giving maximal 6- to 7-fold increase in PLD activity. Triton X-100-treated lysates prepared from control PBMC and from bSMase-treated cells were fractionated by centrifugation on sucrose density gradient. We observed that bSMase treatment of the cells induced a larger ceramide increase in raft than in nonraft membranes and displaced both the Src kinase Lck and PLD1 out of the raft fractions. In addition, the three raft-modifying agents markedly inhibited the lymphoproliferative response to mitogenic lectin. To examine further the potential role of PLD activation in the control of lymphocyte responses, we transiently overexpressed either of the PLD1 and PLD2 isoforms in Jurkat cells and analyzed the phorbol ester plus ionomycin-induced expression of IL-2 mRNA, which is one of the early responses of lymphocyte to activation. We observed a 43% decrease of IL-2 mRNA level in Jurkat cells overexpressing PLD1 as compared with mock- or PLD2-transfected cells, which indicates that elevated PLD1, but not PLD2, activity impairs lymphocyte activation. Altogether, the present results support the hypothesis that PLD1 is activated by exclusion from lipid rafts and that this activation conveys antiproliferative signals in lymphoid cells.
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Affiliation(s)
- Olivier Diaz
- Institut National de la Santé et de la Recherche Médicale (INSERM) Unité Mixte de Recherche (UMR) 585/Institut National des Sciences Appliquées-LYON, Physiopathologie des Lipides et Membranes, Villeurbanne, France
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Birbes H, Luberto C, Hsu YT, El Bawab S, Hannun Y, Obeid L. A mitochondrial pool of sphingomyelin is involved in TNFalpha-induced Bax translocation to mitochondria. Biochem J 2005; 386:445-51. [PMID: 15516208 PMCID: PMC1134862 DOI: 10.1042/bj20041627] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We recently showed that targeting bSMase (bacterial sphingomyelinase) specifically to mitochondria caused accumulation of ceramide in mitochondria, and induced cytochrome c release and cell death [Birbes, El Bawab, Hannun and Obeid (2001) FASEB J., 15, 2669-2679]. In the present study, we investigated the role of this mitochondrial pool of ceramide in response to a receptor-mediated event, namely TNFalpha (tumour necrosis factor alpha), and the involvement of this mitochondrial pool of ceramide in Bax translocation to mitochondria, an event that precedes cytochrome c release. Treatment of MCF7 cells with TNFalpha caused an increase in ceramide levels in the mitochondrial fraction which accompanied Bax translocation to mitochondria. Targeting bSMase to mitochondria specifically resulted in Bax translocation to mitochondria, suggesting that the mitochondrial ceramide pool is involved in Bax translocation. Moreover, in a reconstituted cell-free system, treatment of isolated mitochondria with bSMase enhanced Bax association with mitochondrial membranes. Collectively, these results suggest that the generation of ceramide in mitochondria in response to TNFalpha is sufficient to induce Bax translocation to mitochondria and subsequent cytochrome c release and cell death.
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Affiliation(s)
- Helene Birbes
- *Department of Medicine and Ralph H. Johnson Veteran Administration, Medical University of South Carolina, SC 29425, U.S.A
| | - Chiara Luberto
- †Department of Biochemistry and Molecular Biology, Medical University of South Carolina, SC 29425, U.S.A
| | - Yi-Te Hsu
- †Department of Biochemistry and Molecular Biology, Medical University of South Carolina, SC 29425, U.S.A
| | - Samer El Bawab
- †Department of Biochemistry and Molecular Biology, Medical University of South Carolina, SC 29425, U.S.A
| | - Yusuf A. Hannun
- †Department of Biochemistry and Molecular Biology, Medical University of South Carolina, SC 29425, U.S.A
| | - Lina M. Obeid
- *Department of Medicine and Ralph H. Johnson Veteran Administration, Medical University of South Carolina, SC 29425, U.S.A
- To whom correspondence should be addressed (email )
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Oörni K, Posio P, Ala-Korpela M, Jauhiainen M, Kovanen PT. Sphingomyelinase Induces Aggregation and Fusion of Small Very Low–Density Lipoprotein and Intermediate-Density Lipoprotein Particles and Increases Their Retention to Human Arterial Proteoglycans. Arterioscler Thromb Vasc Biol 2005; 25:1678-83. [PMID: 15879301 DOI: 10.1161/01.atv.0000168912.42941.60] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Infiltration of low-density lipoprotein (LDL) into subendothelial space is an early step in atherosclerosis. In addition to LDL particles, small very low-density lipoprotein (sVLDL) and intermediate-density lipoprotein (IDL) particles are also able to enter the arterial intima and be retained within the subendothelial extracellular matrix. Here we compared how proteolysis with alpha-chymotrypsin and phospholipid hydrolysis with phospholipase A2 or sphingomyelinase (SMase) of sVLDL, IDL, and LDL particles can influence their aggregation, fusion, and binding to human arterial proteoglycans in vitro. METHODS AND RESULTS In each of the 3 lipoprotein classes, the particles became only slightly aggregated with alpha-chymotrypsin or phospholipase A2. However, the particles strongly aggregated when treated with SMase. The aggregated/fused particles were found to bind to proteoglycans in proteoglycan affinity chromatography more tightly than the native-sized counterparts. In addition, in a microtiter well assay, the binding of SMase-treated lipoproteins was enhanced: the amounts of proteoglycan-bound SMase-treated LDL, IDL, and sVLDL were 4-, 5-, and 20-fold higher, respectively, than the amounts of proteoglycan-bound native lipoproteins. CONCLUSIONS These results imply a specific role for SMase as an sVLDL- and IDL-modifying enzyme and also suggest a novel mechanism of lipid accumulation in atherogenesis, namely enhanced retention of atherogenic triglyceride-rich lipoprotein particles in intimal areas expressing extracellular SMase activity.
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Zeng C, Lee JT, Chen H, Chen S, Hsu CY, Xu J. Amyloid-β peptide enhances tumor necrosis factor-α-induced iNOS through neutral sphingomyelinase/ceramide pathway in oligodendrocytes. J Neurochem 2005; 94:703-12. [PMID: 16033420 DOI: 10.1111/j.1471-4159.2005.03217.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although accumulating evidence demonstrates that white matter degeneration contributes to pathology in Alzheimer's disease (AD), the underlying mechanisms are unknown. In order to study the roles of the amyloid-beta peptide in inducing oxidative stress damage in white matter of AD, we investigated the effects of amyloid-beta peptide 25-35 (Abeta) on proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha)-induced inducible nitric oxide synthase (iNOS) in cultured oligodendrocytes (OLGs). Although Abeta 25-35 by itself had little effect on iNOS mRNA, protein, and nitrite production, it enhanced TNF-alpha-induced iNOS expression and nitrite generation in OLGs. Abeta, TNF-alpha, or the combination of both, increased neutral sphingomyelinase (nSMase) activity, but not acidic sphingomyelinase (aSMase) activity, leading to ceramide accumulation. Cell permeable C2-ceramide enhanced TNF-alpha-induced iNOS expression and nitrite generation. Moreover, the specific nSMase inhibitor, 3-O-methyl-sphingomyelin (3-OMS), inhibited iNOS expression and nitrite production induced by TNF-alpha or by the combination of TNF-alpha and Abeta. Overexpression of a truncated mutant of nSMase with a dominant negative function inhibited iNOS mRNA production. 3-OMS also inhibited nuclear factor kappaB (NF-kappaB) binding activity induced by TNF-alpha or by the combination of TNF-alpha and Abeta. These results suggest that neutral sphingomyelinase/ceramide pathway is required but may not be sufficient for iNOS expression induced by TNF-alpha and the combination of TNF-alpha and Abeta.
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Affiliation(s)
- C Zeng
- Department of Neurology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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25
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Takeshita A, Shinoda H, Nakabayashi Y, Takano A, Matsumoto K, Suetsugu M, Miyazawa K, Tanaka S, Endo H, Tanaka S, Ueyama Y, Hanzawa A, Suda Y, Kanegae H, Yasui T. Sphingosine 1-phosphate acts as a signal molecule in ceramide signal transduction of TNF-alpha-induced activator protein-1 in osteoblastic cell line MC3T3-E1 cells. J Oral Sci 2005; 47:43-51. [PMID: 15881228 DOI: 10.2334/josnusd.47.43] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
We previously demonstrated that tumor necrosis factor (TNF)-alpha stimulated the production of activation protein (AP)-1, a transcriptional factor, in mouse osteoblastic MC3T3-E1 cells. Recent studies have shown the importance of ceramide and its metabolites as signal molecules for TNF-alpha-induced gene expression in several cell types. Therefore, our interest was to investigate whether sphingosine metabolites are involved in TNF-alpha-induced signaling in MC3T3-E1 cells. DL-threo-1-phenyl-2-hexadecanoyl-amino-3-pyrrolidino-1-propanol (PPPP), which causes accumulation of intracellular ceramide, stimulated the TNF-alpha-induced expression of the c-fos and c-jun genes. Gel shift assay clearly showed that PPPP increased the cytokine-induced specific binding of nuclear proteins to the 12-tetra-decanoyl phorbol 13-acetate-responsive element (TRE), a consensus sequence for AP-1. In addition, cell-permeable ceramide (N-acetylsphingosine, N-hexanoylsphingosine or N-octanoylsphingosine) stimulated expression of the c-fos and c-jun genes and nuclear protein binding to TRE. Interestingly, DL-threo-dihydrosphingosine (DHS), an inhibitor of sphingosine kinase, clearly blocked the ceramide analogue-induced stimulation. Sphingosine 1-phosphate (SPP) actually induced expression of these oncogenes and activated AP-1. Although TNF-alpha stimulated the AP-1-mediated expression of the monocyte chemoattractant JE/MCP-1, this stimulation was inhibited by DHS. SPP also stimulated JE/MCP-1 gene expression. The present study thus suggests that SPP acts as a signal molecule in ceramide-dependent signal transduction in TNF-alpha-induced AP-1 in osteoblastic MC3T3-E1 cells.
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Affiliation(s)
- Akira Takeshita
- Department of Oral Health and Preventive Dentistry, Meikai University School of Dentistry, Keyakidai, Sakado-city, Saitama 350-0283, Japan.
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Church LD, Hessler G, Goodall JE, Rider DA, Workman CJ, Vignali DAA, Bacon PA, Gulbins E, Young SP. TNFR1-induced sphingomyelinase activation modulates TCR signaling by impairing store-operated Ca2+ influx. J Leukoc Biol 2005; 78:266-78. [PMID: 15817701 DOI: 10.1189/jlb.1003456] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Tumor necrosis factor alpha (TNF-alpha) is a potent, pleiotrophic cytokine, which is proinflammatory but can also suppress T lymphocyte function. In chronic inflammatory disease such as rheumatoid arthritis, exposure of T cells to TNF-alpha alters their ability to mount a response by modulating the T cell receptor (TCR) signaling pathway, but the mechanisms involved remain obscure. Here, we investigated the specific role of TNF receptor 1 (TNFR1) signaling in the modulation of the TCR signaling pathway. We observed a down-regulation of the intracellular calcium ([Ca(2+)](i)) signal in Jurkat T cells after just 30 min exposure to TNF-alpha, and maximum suppression was reached after 3 h. This effect was transient, and signals returned to normal after 12 h. This depression of [Ca(2+)](i) was also observed in human CD4+ T lymphocytes. The change in Ca(2+) signal was related to a decrease in the plasma membrane Ca(2+) influx, which was apparent even when the TCR signal was bypassed using thapsigargin to induce a Ca(2+) influx. The role of TNF-alpha-induced activation of the sphingolipid cascade in this pathway was examined. The engagement of TNFR1 by TNF-alpha led to a time-dependent increase in acid sphingomyelinase (SMase; ASM) activity, corresponding with a decrease in cellular sphingomyelin. In parallel, there was an increase in cellular ceramide, which correlated directly with the decrease in the magnitude of the Ca(2+) response to phytohemagglutinin. Exogenous addition of SMase or ceramide mimicked the effects of TNFR1 signals on Ca(2+) responses in Jurkat T cells. Direct evidence for the activation of ASM in this pathway was provided by complete abrogation of the TNF-alpha-induced inhibition of the Ca(2+) influx in an ASM-deficient murine T cell line (OT-II(+/+)ASM(-/-)). This potent ability of TNF-alpha to rapidly modulate the TCR Ca(2+) signal via TNFR1-induced ASM activation can explain its suppressive effect on T cell function. This TNFR1 signaling pathway may play a role as an important regulator of T cell responses.
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Affiliation(s)
- Leigh D Church
- Department of Rheumatology, Division of Immunity and Infection, University of Birmingham, Edgbaston, UK.
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Vítkova A, Votava M. [Inhibition of hemolytic activity of Staphylococcus aureus 3-hemolysin by an exosubstance produced by some Enterococcus faecalis strains]. Epidemiol Mikrobiol Imunol 2005; 54:11-5. [PMID: 15807382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
OBJECTIVE Accidentally, some Enterococcus faecalis strains were found to inhibit the hemolysis caused by Staphylococcus aureus beta-hemolysin. The study objectives were to define the conditions under which this phenomenon appears and to characterize the inhibitory agent. MATERIALS AND METHODS Ninety-one wild strains and five type strains of E. faecalis and nine wild E. faecium strains were tested for antihemolytic activity on blood agar with 5% sheep erythrocytes prepared using the following agar bases: Columbia Agar Base (BBL, 211124), Columbia Agar (Bio Mérieux, 51026), Blood Agar Base (Bio-Rad, 64524), Blood Agar Base (Columbia) (Ferosa, 1-034), Columbia Blood Agar Base (HiMedia, M114), Blood Agar Base No. 4 (Imuna), Columbia Agar Base (Merck, 10455) and Columbia Agar Base (Oxoid, CM331). The exosubstance produced by E. faecalis strains was isolated by means of acetone precipitation and was exposed to elevated temperature and trypsin. RESULTS Thirty-three (36%) out of 91 wild strains of E. faecalis produced the substance inhibiting hemolysis caused by Staphylococcus aureus beta-hemolysin. Two out of five E. faecalis type strains and none of E. faecium strains appeared to be producers of the same substance. Inhibition of the hemolysis was observed on all of the media tested, being the most pronounced with the use of Blood Agar Base No. 4 (Imuna) and Columbia Agar Base (BBL) at pH 7.0-7.5 when cultured at 37 degrees C for 24 hours. The exosubstance lost its inhibitory effect after exposure to 70 degrees C for 15 min and to 0.1% trypsin for 30 min. The inhibitory potential against staphylococcal hemolysis correlated with the ability of strains to produce protease. CONCLUSION About one third of wild E. faecalis strains produce a protease-like substance that seems proteinaceous in nature and has an inhibitory effect on the hemolysis caused by Staphylococcus aureus beta-hemolysin.
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Affiliation(s)
- A Vítkova
- Mikrobiologické oddelení, Nemocnice Breclav, prispevková organizace
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Chung BH, Franklin F, Liang P, Doran S, Cho BHS, Curcio CA. Phosphatidylcholine-rich acceptors, but not native HDL or its apolipoproteins, mobilize cholesterol from cholesterol-rich insoluble components of human atherosclerotic plaques. Biochim Biophys Acta Mol Cell Biol Lipids 2005; 1733:76-89. [PMID: 15749058 DOI: 10.1016/j.bbalip.2004.12.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2003] [Revised: 01/21/2004] [Accepted: 12/02/2004] [Indexed: 10/26/2022]
Abstract
To examine the potential of high density lipoproteins (HDL) to ameliorate atherosclerotic plaques in vivo, we examined the ability of native HDL, lipid-free HDL apolipoproteins (apo HDL), cholesterol-free discoidal reconstituted HDL (R-HDL) comprised of apo HDL and phosphatidylcholine (PC) and PC liposomes to release cholesterol from cholesterol-rich insoluble components of plaques (ICP) isolated from atherosclerotic human aorta. Isolated ICP had a free cholesterol (FC) to phospholipid (PL) mass ratio (0.8-3.1) and a sphingomyelin (SPM) to PC mass ratio (1.2-4.2) that exceeded those of plasma membranes of cultured cells. Surprisingly, native HDL and its apolipoproteins were not able to release cholesterol from ICP. However, R-HDL and PC liposomes were effectively released cholesterol from ICP. The release of ICP cholesterol by R-HDL was dose-dependent and accompanied by the transfer of > 8 x more PC in the reverse direction (i.e., from R-HDL to ICP), resulting in a marked enrichment of ICP with PC. Compared to R-HDL, PC liposomes were significantly less effective in releasing cholesterol from ICP but were somewhat more effective in enriching ICP with PC. Native HDL was minimally effective in enriching ICP with PC, but became effective after prior in vitro enrichment of HDL with PC from multilamellar PC liposomes. The enrichment of ICP with PC resulted in the dissolution of cholesterol crystals on ICP and allowed the removal of ICP cholesterol by apo HDL and plasma. Our study revealed that the removal of cholesterol from ICP in vivo will be possible through a change in the level, composition, and physical state of ICP lipids mediated by PC-enriched HDL.
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Affiliation(s)
- Byung-Hong Chung
- Gerontology Division, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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Mogami K, Kishi H, Kobayashi S. Sphingomyelinase causes endothelium-dependent vasorelaxation through endothelial nitric oxide production without cytosolic Ca2+elevation. FEBS Lett 2004; 579:393-7. [PMID: 15642349 DOI: 10.1016/j.febslet.2004.11.100] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2004] [Revised: 09/18/2004] [Accepted: 11/02/2004] [Indexed: 11/21/2022]
Abstract
Neutral sphingomyelinase (N-SMase) elevated nitric oxide (NO) production without affecting intracellular Ca(2+) concentration ([Ca(2+)](i)) in endothelial cells in situ on aortic valves, and induced prominent endothelium-dependent relaxation of coronary arteries, which was blocked by N(omega)-monomethyl-L-arginine, a NO synthase (NOS) inhibitor. N-SMase induced translocation of endothelial NOS (eNOS) from plasma membrane caveolae to intracellular region, eNOS phosphorylation on serine 1179, and an increase of ceramide level in endothelial cells. Membrane-permeable ceramide (C(8)-ceramide) mimicked the responses to N-SMase. We propose the involvement of N-SMase and ceramide in Ca(2+)-independent eNOS activation and NO production in endothelial cells in situ, linking to endothelium-dependent vasorelaxation.
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Affiliation(s)
- Kimiko Mogami
- Department of Molecular Physiology, Yamaguchi University School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi 755-8505, Japan
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Abstract
The hepatitis C virus (HCV) core protein is believed to be one of viral proteins that are capable of preventing virus-infected cell death upon various stimuli. But, the effect of the HCV core protein on apoptosis that is induced by various stimuli is contradictory. We examined the possibility that the HCV core protein affects the ceramide-induced cell death in cells expressing the HCV core protein through the sphingomyelin pathway. Cell death that is induced by C(2)-ceramide and bacterial sphingomyelinase was analyzed in 293 cells that constitutively expressed the HCV core protein and compared with 293 cells that were stably transfected only with the expression vector. The HCV core protein inhibited the cell death that was induced by these reagents. The protective effects of the HCV core protein on ceramide-induced cell death were reflected by the reduced expression of p21(WAF1/Cip1/Sid1) and the sustained expression of the Bcl-2 protein in the HCV core-expressing cells with respect to the vector-transfected cells. These results suggest that the HCV core protein in 293 cells plays a role in the modulation of the apoptotic response that is induced by ceramide. Also, the ability of the HCV core protein to suppress apoptosis might have important implications in understanding the pathogenesis of the HCV infection.
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Affiliation(s)
- Jung Su Kim
- Department of Genetic Engineering, Division of Life Sciences, Hallym University, Chunchon 200-702, Korea
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Perkins SL, Han DP, Burke JM, Schlievert PM, Wirostko WJ, Tarasewicz DG, Skumatz CMB. Intravitreally Injected Human Immunoglobulin Attenuates the Effectsof Staphylococcus aureus Culture Supernatant in aRabbit Model of Toxin-Mediated Endophthalmitis. ACTA ACUST UNITED AC 2004; 122:1499-506. [PMID: 15477462 DOI: 10.1001/archopht.122.10.1499] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVE To determine whether human immunoglobulin attenuates the toxic effects of Staphylococcus aureus culture supernatant in a rabbit model of endophthalmitis. METHODS Immunoglobulin binding to products of S aureus strain RN4220 was tested by Western blot analysis using known toxins (beta-hemolysin and toxic shock syndrome toxin-1) and a concentrated culture supernatant containing S aureus exotoxins (pooled toxin). To induce endophthalmitis, pooled toxin was injected into the rabbit vitreous. For immunoglobulin treatment, immunoglobulin and pooled toxin were either mixed and injected simultaneously or immunoglobulin was injected immediately after or 6 hours after pooled toxin injection. Severity of endophthalmitis was graded according to a 9-day course with clinical examination (slitlamp biomicroscopy or indirect ophthalmoscopy) and evaluation of histologic sections. RESULTS The toxic effects of pooled toxin were markedly reduced when immunoglobulin was mixed with pooled toxin and injected simultaneously. Delayed injection of immunoglobulin diminished its ability to reduce toxicity. Clinical and histologic signs of toxicity were partially attenuated when immunoglobulin was injected immediately after pooled toxin, but only minimal clinically detectable reductions in toxicity were observed when immunoglobulin injection was delayed for 6 hours. CONCLUSION Pooled human immunoglobulin can attenuate the toxic intravitreal effects of a concentrated culture supernatant containing S aureus exotoxins. Clinical Relevance Immunoglobulin may represent a novel adjuvant in the treatment of bacterial endophthalmitis. To optimize the potential therapeutic benefit, maximizing the mixture of immunoglobulin with bacterial products and early intervention are likely to be important.
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Affiliation(s)
- Stephen L Perkins
- Eye Institute, Medical College of Wisconsin, Milwaukee 53226-4812, USA
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Strle K, Broussard SR, McCusker RH, Shen WH, Johnson RW, Freund GG, Dantzer R, Kelley KW. Proinflammatory cytokine impairment of insulin-like growth factor I-induced protein synthesis in skeletal muscle myoblasts requires ceramide. Endocrinology 2004; 145:4592-602. [PMID: 15256490 DOI: 10.1210/en.2003-1749] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GH and IGF-I control over 80% of postnatal growth. We recently established that TNFalpha impairs the ability of IGF-I to increase protein synthesis and promote expression of myogenin in myoblasts. Here we extend these results by showing that ceramide, a second messenger in both TNFalpha and IL-1beta receptor signaling pathways, is a key downstream sphingosine-based lipid that leads to IGF-I resistance. A cell-permeable ceramide analog, C2-ceramide, inhibits IGF-I-induced protein synthesis by 65% and blocks the ability of IGF-I to increase expression of two key myogenic factors, myogenin and MyoD. Identical results were obtained with both TNFalpha and IL-1beta (1 ng/ml). Consistent with these data, neutral sphingomyelinase (N-SMase), an enzyme that catalyzes formation of ceramide from sphingomyelin, blocks IGF-I-induced protein synthesis and expression of both myogenin and MyoD. The possibility that cytokine-induced ceramide production is required for disruption of IGF-I biologic activity was confirmed by treating C2C12 myoblasts with inhibitors of all three ceramide-generating pathways. A N-SMase inhibitor, glutathione, as well as an acidic sphingomyelinase (A-SMase) inhibitor, D609, reverse the cytokine inhibition of IGF-I-induced protein synthesis by 80% and 45%, respectively. Likewise, an inhibitor of de novo ceramide synthesis, FB1, causes a 50% inhibition. Similarly, all three inhibitors significantly impair the ability of both TNFalpha and IL-1beta to suppress IGF-I-driven expression of myogenin. These experiments establish that ceramide, derived both from sphingomyelin and de novo synthesis, is a key intermediate by which proinflammatory cytokines impair the ability of IGF-I to promote protein synthesis and expression of critical muscle-specific transcription factors.
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Affiliation(s)
- Klemen Strle
- University of Illinois, Laboratory of Immunophysiology, 207 Edward R. Madigan Laboratory, 1201 West Gregory Drive, Urbana, Illinois 61801, USA
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Abdel Shakor AB, Kwiatkowska K, Sobota A. Cell Surface Ceramide Generation Precedes and Controls FcγRII Clustering and Phosphorylation in Rafts. J Biol Chem 2004; 279:36778-87. [PMID: 15194692 DOI: 10.1074/jbc.m402170200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite the role of sphingolipid/cholesterol rafts as signaling platforms for Fcgamma receptor II (FcgammaRII), the mechanism governing translocation of an activated receptor toward the rafts is unknown. We show that at the onset of FcgammaRII cross-linking acid sphingomyelinase is rapidly activated. This enzyme is extruded from intracellular compartments to the cell surface, and concomitantly, exofacially oriented ceramide is produced. Both non-raft and, to a lesser extent, raft sphingomyelin pools were hydrolyzed at the onset of FcgammaRII cross-linking. The time course of ceramide production preceded the recruitment of FcgammaRII to rafts and the receptor phosphorylation. Exogenous C(16)-ceramide facilitated clustering of FcgammaRII and its association with rafts. In contrast, inhibition of acid sphingomyelinase diminished both the ceramide generation and clustering of cross-linked FcgammaRII. Under these conditions, tyrosine phosphorylation of FcgammaRII and receptor-accompanying proteins was also reduced. All the inhibitory effects were bypassed by treatment of cells with exogenous ceramide. These data provide evidence that the generation of cell surface ceramide is a prerequisite for fusion of cross-linked FcgammaRII and rafts, which triggers the receptor tyrosine phosphorylation and signaling.
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Affiliation(s)
- Abo Bakr Abdel Shakor
- Nencki Institute of Experimental Biology, the Department of Cell Biology, 3 Pasteur St., 02-093 Warsaw, Poland
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Abstract
A reduction in plasma membrane cholesterol is one of the early events that either triggers or is closely associated with capacitation of mammalian spermatozoa. In this investigation, we have examined the effects of cholesterol efflux on tyrosine phosphorylation, lipid diffusion, and raft organization in boar spermatozoa. Results show that a low level of cholesterol efflux, mediated by 5 mM methyl-beta-cyclodextrin (MBCD), enhances capacitation and induces phosphorylation of two proteins at 26 and 15 kDa without affecting sperm viability. Lipid diffusion rates under these conditions are largely unaffected except when cholesterol efflux is excessive. Low-density Triton X100-insoluble complexes (lipid rafts) were isolated from spermatozoa and found to have a restricted profile of proteins. Capacitation-associated cholesterol efflux has no effect on raft composition, but cholesterol depletion destabilizes them completely and phosphorylation is suppressed. During MBCD-mediated capacitation, the distribution of GM1 gangliosides on spermatozoa changes in a sequential manner from overlying the sperm tail to clustering on the sperm head. It is concluded that there is a safe window for removal of plasma membrane cholesterol from spermatozoa within which protein phosphorylation and polarized migration of lipid rafts take place. A preferential loss of cholesterol from the nonraft pool may be the stimulus that promotes raft clustering over the anterior sperm head.
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Affiliation(s)
- Sadaf Shadan
- Gamete Signalling Laboratory, Babraham Institute, Babraham, Cambridge CB2 4AT, United Kingdom
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Abstract
Leptospira interrogans causes a variety of clinical syndromes in animals and humans. Although much information has accumulated on the importance of leptospiral lipopolysaccharide in protective antibody responses, relatively little is known about proteins that participate in immune responses. Identification of those proteins induced only in the host is particularly difficult. Using a novel double-antibody screen designed to identify clones in a gene library of L. interrogans serovar Pomona expressing host-inducible proteins, we have characterized a gene (lk75.3) encoding a sphingomyelinase-like preprotein of 648 amino acids with cytotoxic activity for equine pulmonary endothelial cells and weak hemolytic activity for equine and rabbit erythrocytes. lk73.5 was found as a single gene copy in all serovars of L. interrogans but not in other Leptospira spp. except L. inadai. The open reading frame (ORF) for Lk73.5 is followed by another partially homologous sequence containing an ORF (sph-like 2) for a 28.7-kDa peptide. Lk73.5 and Sph-like 2 share 95.1 and 97.7% amino acid identity with putative sphingomyelinases Sph2 and Sph1 (N terminus) from L. interrogans serovar Lai (S.-X. Ren, G. Fu, X.-G. Jiangk, R. Zeng, Y.-G. Miao, H. Xu, Y.-X. Zhang, H. Xiong, G. Lu, L.-F. Lu, H.-Q. Jiang, J. Jia, Y.-F. Tu, J.-X. Jiang, W.-Y. Gu, Y.-Q. Zhang, Z. Cai, H.-H. Sheng, H.-F. Yin, Y. Zhang, G.-F. Zhu, M. Wank, H.-L. Huangk, Z. Qian, S.-Y. Wang, Wei Ma, Z.-J. Yao, Y. Shen, B.-Q. Qiang, Q.-C. Xia, X.-K. Guo, A. Danchinq, I. S. Girons, R. L. Somerville, Y.-M. Wen, M.-H. Shik, Z. Chen, J.-G. Xuk, and G.-P. Zhao, Nature 422:88-893, 2003). Substantial homologies to sphingomyelinases from other leptospiras and other bacteria are also present. Lk73.5 was not detected in leptospiras cultured at 30 or 37 degrees C. The recombinant protein reacted strongly with sera from recently infected mares but not with sera from horses vaccinated with commercial pentavalent bacterin. The host-inducible immunogenic Lk73.5 should have value in distinguishing vaccine from infection immune response.
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Affiliation(s)
- S Artiushin
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky 40546, USA.
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Denis M, Haidar B, Marcil M, Bouvier M, Krimbou L, Genest J. Molecular and cellular physiology of apolipoprotein A-I lipidation by the ATP-binding cassette transporter A1 (ABCA1). J Biol Chem 2003; 279:7384-94. [PMID: 14660648 DOI: 10.1074/jbc.m306963200] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The dynamics of ABCA1-mediated apoA-I lipidation were investigated in intact human fibroblasts induced with 22(R)-hydroxycholesterol and 9-cis-retinoic acid (stimulated cells). Specific binding parameters of (125)I-apoA-I to ABCA1 at 37 degrees C were determined: K(d) = 0.65 microg/ml, B(max) = 0.10 ng/microg cell protein. Lipid-free apoA-I inhibited the binding of (125)I-apoA-I to ABCA1 more efficiently than pre-beta(1)-LpA-I, reconstituted HDL particles r(LpA-I), or HDL(3) (IC(50) = 0.35 +/- 1.14, apoA-I; 1.69 +/- 1.07, pre-beta(1)-LpA-I; 17.91 +/- 1.39, r(LpA-I); and 48.15 +/- 1.72 microg/ml, HDL(3)). Treatment of intact cells with either phosphatidylcholine-specific phospholipase C or sphingomyelinase affected neither (125)I-apoA-I binding nor (125)I-apoA-I/ABCA1 cross-linking. We next investigated the dynamics of apoA-I lipidation by monitoring the kinetic of apoA-I dissociation from ABCA1. The dissociation of (125)I-apoA-I from normal cells at 37 degrees C was rapid (t((1/2)) = 1.4 +/- 0.66 h; n = 3) but almost completely inhibited at either 15 or 4 degrees C. A time course analysis of apoA-I-containing particles released during the dissociation period showed nascent apoA-I-phospholipid complexes that exhibited alpha-electrophoretic mobility with a particle size ranging from 9 to 20 nm (designated alpha-LpA-I-like particles), whereas lipid-free apoA-I incubated with ABCA1 mutant (Q597R) cells was unable to form such particles. These results demonstrate that: 1) the physical interaction of apoA-I with ABCA1 does not depend on membrane phosphatidylcholine or sphingomyelin; 2) the association of apoA-I with lipids reduces its ability to interact with ABCA1; and 3) the lipid translocase activity of ABCA1 generates alpha-LpA-I-like particles. This process plays in vivo a key role in HDL biogenesis.
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Affiliation(s)
- Maxime Denis
- Cardiovascular Genetics Laboratory, Cardiology Division, McGill University Health Center, Royal Victoria Hospital, Montréal, Québec H3A 1A1, Canada
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Park PW, Foster TJ, Nishi E, Duncan SJ, Klagsbrun M, Chen Y. Activation of syndecan-1 ectodomain shedding by Staphylococcus aureus alpha-toxin and beta-toxin. J Biol Chem 2003; 279:251-8. [PMID: 14573623 DOI: 10.1074/jbc.m308537200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Exploitation of host components by microbes to promote their survival in the hostile host environment has been a recurring theme in recent years. Available data indicate that bacterial pathogens activate ectodomain shedding of host cell surface molecules to enhance their virulence. We reported previously that several major bacterial pathogens activate ectodomain shedding of syndecan-1, the major heparan sulfate proteoglycan of epithelial cells. Here we define the molecular basis of how Staphylococcus aureus activates syndecan-1 shedding. We screened mutant S. aureus strains devoid of various toxin and protease genes and found that only strains lacking both alpha-toxin and beta-toxin genes do not stimulate shedding. Mutations in the agr global regulatory locus, which positively regulates expression of alpha- and beta-toxins and other exoproteins, also abrogated the capacity to stimulate syndecan-1 shedding. Furthermore, purified S. aureus alpha- and beta-toxins, but not enterotoxin A and toxic shock syndrome toxin-1, rapidly potentiated shedding in a concentration-dependent manner. These results establish that S. aureus activates syndecan-1 ectodomain shedding via its two virulence factors, alpha- and beta-toxins. Toxin-activated shedding was also selectively inhibited by antagonists of the host cell shedding mechanism, indicating that alpha- and beta-toxins shed syndecan-1 ectodomains through stimulation of the host cell's shedding machinery. Interestingly, beta-toxin, but not alpha-toxin, also enhanced ectodomain shedding of syndecan-4 and heparin-binding epidermal growth factor. Because shedding of these ectodomains has been implicated in promoting bacterial pathogenesis, activation of ectodomain shedding by alpha-toxin and beta-toxin may be a previously unknown virulence mechanism of S. aureus.
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Affiliation(s)
- Pyong Woo Park
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA.
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Ramer R, Weinzierl U, Schwind B, Brune K, Hinz B. Ceramide Is Involved inR(+)-Methanandamide-Induced Cyclooxygenase-2 Expression in Human Neuroglioma Cells. Mol Pharmacol 2003; 64:1189-98. [PMID: 14573769 DOI: 10.1124/mol.64.5.1189] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cannabinoids have recently been shown to induce the expression of the cyclooxygenase-2 (COX-2) isoenzyme in H4 human neuroglioma cells. Using this cell line, the present study investigates the contribution of the second messenger ceramide to this signaling pathway. Incubation of cells with the endocannabinoid analog R(+)-methanandamide (R(+)-MA) was associated with an increase of intracellular ceramide levels. Enhancement of ceramide formation by R(+)-MA was abolished by fumonisin B1, a ceramide synthase inhibitor, whereas inhibitors of neutral sphingomyelinase (spiroepoxide, glutathione) and serine palmitoyltransferase (l-cycloserine, ISP-1) were inactive in this respect. R(+)-MA caused a biphasic activation of the p38 and p42/44 mitogen-activated protein kinases (MAPKs), with phosphorylation peaks occurring after 15-min and 4- to 8-h treatments, respectively. Inhibition of ceramide synthesis with fumonisin B1 was associated with a suppression of R(+)-MA-induced delayed phosphorylations of p38 and p42/44 MAPKs and subsequent COX-2 expression. The involvement of ceramide in COX-2 expression was corroborated by findings showing that C2-ceramide and neutral sphingomyelinase from Bacillus cereus caused concentration-dependent increases of COX-2 expression that were suppressed in the presence of 4-(4-fluorophenyl)-2-(4-methylsulfonylphenyl)-5-(4-pyridyl)imidazol (SB203580, a p38 MAPK inhibitor) or 2'-amino-3'-methoxyflavone (PD98059, a p42/44 MAPK activation inhibitor). In contrast, dihydro-C2-ceramide being used as a negative control did not induce MAPK phosphorylation and COX-2 expression. Collectively, our results demonstrate that R(+)-MA induces COX-2 expression in human neuroglioma cells via synthesis of ceramide and subsequent activation of p38 and p42/44 MAPK pathways. Induction of COX-2 expression via ceramide represents a hitherto unknown mechanism by which cannabinoids mediate biological effects within the central nervous system.
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Affiliation(s)
- Robert Ramer
- Department of Experimental and Clinical Pharmacology and Toxicology, Friedrich Alexander University Erlangen, Erlangen, Germany
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Liu P, Leffler BJ, Weeks LK, Chen G, Bouchard CM, Strawbridge AB, Elmendorf JS. Sphingomyelinase activates GLUT4 translocation via a cholesterol-dependent mechanism. Am J Physiol Cell Physiol 2003; 286:C317-29. [PMID: 14522816 DOI: 10.1152/ajpcell.00073.2003] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A basis for the insulin mimetic effect of sphingomyelinase on glucose transporter isoform GLUT4 translocation remains unclear. Because sphingomyelin serves as a major determinant of plasma membrane cholesterol and a relationship between plasma membrane cholesterol and GLUT4 levels has recently become apparent, we assessed whether GLUT4 translocation induced by sphingomyelinase resulted from changes in membrane cholesterol content. Exposure of 3T3-L1 adipocytes to sphingomyelinase resulted in a time-dependent loss of sphingomyelin from the plasma membrane and a concomitant time-dependent accumulation of plasma membrane GLUT4. Degradation products of sphingomyelin did not mimic this stimulatory action. Plasma membrane cholesterol amount was diminished in cells exposed to sphingomyelinase. Restoration of membrane cholesterol blocked the stimulatory effect of sphingomyelinase. Increasing concentrations of methyl-beta-cyclodextrin, which resulted in a dose-dependent reversible decrease in membrane cholesterol, led to a dose-dependent reversible increase in GLUT4 incorporation into the plasma membrane. Although increased plasma membrane GLUT4 content by cholesterol extraction with concentrations of methyl-beta-cyclodextrin above 5 mM most likely reflected decreased GLUT4 endocytosis, translocation stimulated by sphingomyelinase or concentrations of methyl-beta-cyclodextrin below 2.5 mM occurred without any visible changes in the endocytic retrieval of GLUT4. Furthermore, moderate loss of cholesterol induced by sphingomyelinase or low concentrations of methyl-beta-cyclodextrin did not alter membrane integrity or increase the abundance of other plasma membrane proteins such as the GLUT1 glucose transporter or the transferrin receptor. Regulation of GLUT4 translocation by moderate cholesterol loss did not involve known insulin-signaling proteins. These data reveal that sphingomyelinase enhances GLUT4 exocytosis via a novel cholesterol-dependent mechanism.
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Affiliation(s)
- Ping Liu
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, IN 46202, USA
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Hertervig E, Nilsson A, Cheng Y, Duan RD. Purified intestinal alkaline sphingomyelinase inhibits proliferation without inducing apoptosis in HT-29 colon carcinoma cells. J Cancer Res Clin Oncol 2003; 129:577-82. [PMID: 12920578 DOI: 10.1007/s00432-003-0466-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2002] [Accepted: 05/22/2003] [Indexed: 02/08/2023]
Abstract
PURPOSE Sphingomyelin (SM) hydrolysis by sphingomyelinase (SMase) has become an important signalling pathway, with the product ceramide implicated in regulation of cell growth, differentiation and apoptosis. Alkaline SMase is specifically located in the intestinal tract. Marked reductions of the enzyme activity have been found in sporadic colorectal carcinomas and in both adenomas and flat mucosa of patients with familial adenomatous polyposis, indicating an anti-proliferative role in colonic cell growth. METHODS We examined the effects of a purified alkaline SMase from rat intestine and a bacterial neutral SMase on cell growth parameters in HT-29 colonic carcinoma cells. RESULTS Alkaline SMase was found to inhibit proliferation of HT-29 cells in both dose-dependent and time-dependent manners. The threshold concentration of the enzyme was approximately 2.5 microU/ml, and the maximum effect was obtained at approximately 20 microU/ml, which inhibited the cell growth by 50%. The inhibition occurred rapidly, and maximum effect was reached after 12 h of incubation. Dose-dependent inhibition of DNA synthesis was also demonstrated. The effect of alkaline SMase was preceded and accompanied by increased hydrolysis of SM and production of ceramide. Neutral SMase with equivalent hydrolytic capacity did not inhibit cell growth. Alkaline SMase did not induce apoptosis in HT-29 cells. Alkaline SMase did not inhibit growth of IEC-6 cells. CONCLUSION Alkaline SMase, at doses that induce SM hydrolysis, inhibits growth of colon cancer cells. The inhibition is attributed to an anti-proliferative effect rather than an apoptotic effect.
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Affiliation(s)
- Erik Hertervig
- Department of Medicine, Lund University Hospital, 221 85, Lund, Sweden.
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Hertervig E, Nilsson A, Nilbert M, Duan RD. Reduction in alkaline sphingomyelinase in colorectal tumorigenesis is not related to the APC gene mutation. Int J Colorectal Dis 2003; 18:309-13. [PMID: 12774245 DOI: 10.1007/s00384-002-0471-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/20/2002] [Indexed: 02/04/2023]
Abstract
BACKGROUND AND AIMS The sphingomyelin pathway is an important intracellular mechanism in regulating cell growth. The first step in this pathway is catalysed by sphingomyelinases. Alkaline sphingomyelinase is specifically located in the intestinal tract. Markedly reduced alkaline sphingomyelinase activities have been found in sporadic colorectal tumours and in familial adenomatous polyposis adenomas. Since the adenomatous polyposis coli (APC) gene is mutated in about 80% of sporadic colorectal tumors, and familial adenomatous polyposis is the consequence of a germline mutation of the same gene, we examined whether low alkaline sphingomyelinase activity is linked to APC gene mutations. PATIENTS AND METHODS Both germline and sporadic adenomatous polyposis coli gene mutations were studied. Alkaline, neutral, and acid sphingomyelinase activities were measured in the intestinal mucosa and content of multiple intestinal neoplasia mice, a murine model of familial adenomatous polyposis and compared to control mice. Alkaline sphingomyelinase activity was also measured in 11 human rectal tumors with APC gene mutation and compared with 9 control tumors without mutation. RESULTS Alkaline, neutral, and acid sphingomyelinase activities were present in the small intestine and colon in both mice types with no differences in hydrolytic capacity or distribution pattern. In sporadic rectal tumors similar alkaline sphingomyelinase activities were identified in tumors with somatic APC gene mutations as in samples without mutations. In the tumors without detectable APC mutations beta-catenin was analyzed, but no mutation was detected. CONCLUSION Alkaline sphingomyelinase is not directly linked to adenomatous polyposis coli gene mutations.
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Affiliation(s)
- Erik Hertervig
- Department of Medicine, Lund University Hospital, 22185, Lund, Sweden.
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Abstract
Previous studies suggested a central role of sphingomyelin- and cholesterol-enriched membrane rafts in the initiation of signaling via many receptors. Here, we investigated the role of membrane rafts for the function of the voltage-gated potassium channel Kv1.3. We demonstrate that Kv1.3 localizes in the cell membrane to pre-existing small, sphingolipid- and cholesterol-enriched membrane rafts. Transformation of these small rafts to large ceramide-enriched membrane platforms was achieved by stimulation of the endogenous acid sphingomyelinase, addition of exogenous sphingomyelinase or treatment of the cells with C(16)-ceramide and resulted in clustering of Kv1.3 within ceramide-enriched membrane platforms and inhibition of the channel's activity. Likewise, disruption of pre-existing small rafts inhibited Kv1.3 activity. This indicates that intact small membrane rafts are required for Kv1.3 activity and an alteration of the lipid environment of rafts inhibits Kv1.3. These data, thus, may suggest a novel concept for the regulation of ion channels by the cell membrane composition.
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Affiliation(s)
- Jürgen Bock
- Department of Molecular Biology, University of Essen, Hufelandstrasse 55, Essen 45122, Germany
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Duan RD, Cheng Y, Hansen G, Hertervig E, Liu JJ, Syk I, Sjostrom H, Nilsson A. Purification, localization, and expression of human intestinal alkaline sphingomyelinase. J Lipid Res 2003; 44:1241-50. [PMID: 12671034 DOI: 10.1194/jlr.m300037-jlr200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Sphingomyelin (SM) metabolism in the gut may have an impact on colon cancer development. In this study, we purified alkaline sphingomyelinase (alk-SMase) from human intestinal content, and studied its location in the mucosa, expression in colon cancer, and function on colon cancer cells. The enzyme was purified by a series of chromatographies. The molecular mass of the enzyme is 60 kDa, optimal pH is 8.5, and isoelectric point is 6.6. Under optimal conditions, 1 mg of the enzyme hydrolyzed 11 mM SM per hour. The properties of the enzyme are similar to those of rat intestinal alk-SMase but not to those of bacterial neutral SMase. Immunogold electronmicroscopy identified the enzyme on the microvillar membrane in endosome-like structures and in the Golgi complexes of human enterocytes. The expression and the activity of the enzyme were decreased in parallel in human colon cancer tissues compared with the adjacent normal tissue. The enzyme inhibited DNA biosynthesis and cell proliferation dose dependently and caused a reduction of SM in HT29 cells. Intestinal alk-SMase is localized in the enterocytes, down-regulated in human colon cancer, and may have antiproliferative effects on colon cancer cells.
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Affiliation(s)
- Rui-Dong Duan
- Gastroenterology Laboratory, Biomedical Center, B11, University of Lund, S-221 84 Lund, Sweden.
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Ferretti A, Knijn A, Raggi C, Sargiacomo M. High-resolution proton NMR measures mobile lipids associated with Triton-resistant membrane domains in haematopoietic K562 cells lacking or expressing caveolin-1. Eur Biophys J 2003; 32:83-95. [PMID: 12734696 DOI: 10.1007/s00249-002-0273-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2002] [Revised: 11/06/2002] [Accepted: 11/20/2002] [Indexed: 10/25/2022]
Abstract
High-resolution proton NMR spectra of intact tumour cells generally exhibit intense signals due to isotropically mobile lipids (MLs) of still uncertain nature and origin. NMR studies performed on intact wild-type and caveolin-1-infected haematopoietic K562 cells showed that, under our experimental conditions, part of the ML signals are due to lipid complexes resistant to extraction in Triton X-100 at 4 degrees C. This evidence suggests that a portion of NMR-visible lipid structures are compatible with Triton-resistant membrane rafts and therefore biophysically distinct from NMR-visible Triton-soluble lipid bodies. Similarly to lipid rafts and caveolae, the organization of the Triton-insoluble ML domains could be compromised by treatment with beta-octylglucoside or methyl-beta-cyclodextrin. Exposure to exogenous sphingomyelinase caused an increase in ML NMR visibility, indicating the possible involvement of ceramides in ML formation. The mobility of these lipids was found to be temperature sensitive, suggesting a transition in cells going from 4 degrees C to 25-37 degrees C. These new results are here discussed in the light of possible contributions of plasma membrane microdomains to NMR-visible ML signals.
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Affiliation(s)
- A Ferretti
- Laboratory of Cell Biology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
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Pankova-Kholmyansky I, Dagan A, Gold D, Zaslavsky Z, Skutelsky E, Gatt S, Flescher E. Ceramide mediates growth inhibition of the Plasmodium falciparum parasite. Cell Mol Life Sci 2003; 60:577-87. [PMID: 12737317 DOI: 10.1007/s000180300049] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In mammalian cells, ceramide mediates death by chemotherapeutic drugs. We analysed, for the first time, the role of ceramide in inhibiting growth of the malaria-causing parasite Plasmodium falciparum. Added exogenously, ceramide significantly decreased the number of parasites, and this effect was abolished by sphingosine-1-phosphate, a biological antagonist of ceramide action. Ceramide can induce death of cancer cells by decreasing glutathione levels, and in our work it induced dose- and time-dependent depletion of glutathione in P. falciparum parasites. N-acetylcysteine, a precursor of glutathione, abrogated the cytotoxic effect of ceramide. Thus, ceramide can mediate growth inhibition of P. falciparum parasites by decreasing glutathione levels. The antimalarial drugs artemisinin and mefloquine induced the death of P. falciparum parasites by sphingomyelinase-generated ceramide and by decreasing parasite glutathione levels. Altogether, ceramide was identified as a signalling molecule capable of inducing growth inhibition of P. falciparum malarial parasites.
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Affiliation(s)
- I Pankova-Kholmyansky
- Department of Human Microbiology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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Abstract
The sphingomyelin metabolites ceramide and sphingosine are mediators of cell death induced by gamma-irradiation. We studied the production of ceramide and the effects of exogenous ceramide on apoptosis in LNCaP prostate cancer cells that are highly resistant to gamma-irradiation-induced cell death. LNCaP cells can be sensitized to gamma-irradiation by tumor necrosis factor alpha (TNF-alpha) and, to a lesser degree, by the agonistic FAS antibody CH-11. TNF-alpha activated intrinsic and extrinsic apoptosis pathways and increased ceramide and sphingosine levels in irradiated LNCaP cells. CH-11 activated only the extrinsic apoptosis pathways and had a negligible effect on ceramide and sphingosine levels in irradiated LNCaP cells. Exogenous ceramide and bacterial sphingomyelinase sensitized LNCaP cells to radiation-induced apoptosis and had a synergistic effect on cell death after irradiation with TNF-alpha, but not with CH-11. Cell death effects after exposure to ceramide and irradiation were blocked by the serine protease inhibitor TLCK (Na-p-tosyl-L-lysine-chloromethylketone), but not by the caspase inhibitor z-VAD (2-val-Ala-Asp(oMe)-CH(2)F). During LNCaP cell apoptosis induced by exogenous ceramide, we observed activation of caspase-9, but not caspases-8, -3, or -7. The effect of ceramide occurred largely via the intrinsic mitochondrial apoptosis pathway and enhanced TNF-alpha, but not CH-11 effects on irradiated cells. The data show that ceramide enhanced activation of the intrinsic apoptotic pathway and enhanced cell death induced by TNF-alpha with or without gamma-irradiation. TNF-alpha and gamma-irradiation elevated levels of endogenous ceramide and activated the intrinsic cell death pathway.
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Affiliation(s)
- K Kimura
- Department of Oncology, Georgetown University, Washington, DC 20007-2197, USA
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Liza M, Chico Y, Fresnedo O, Ochoa B. Dual action of neutral sphingomyelinase on rat hepatocytes: activation of cholesteryl ester metabolism and biliary cholesterol secretion and inhibition of VLDL secretion. Lipids 2003; 38:53-63. [PMID: 12669820 DOI: 10.1007/s11745-003-1031-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
To address the role of cell membrane neutral sphingomyelinase (EC 3.1.4.12; SMase) in the regulation of cholesterol metabolism in the liver parenchymal cell, we examined the effect of exogenous neutral SMase on the metabolism of cholesteryl esters and the secretion of VLDL and biliary lipids in isolated rat hepatocytes. We show that treatment of hepatocytes with SMase (20 mU/mL) resulted in the intracellular buildup of cholesteryl esters, increased ACAT (EC 2.3.1.26) activity without affecting the ACAT2 mRNA level, and increased cytosolic and microsomal cholesteryl ester hydrolase (EC 3.1.1.13) activity. This was accompanied by increases in the secretion of biliary bile acid, phospholipid, and cholesterol and in increased cholesterol 7alpha-hydroxylase (EC 1.14.13.17) activity and levels of mRNA, as well as decreased levels of apoB mRNA and a decreased secretion of VLDL apoB (apoB-48, approximately 45%; apoB-100, approximately 32%) and lipids (approximately 55%). Moreover, the VLDL particles secreted had an abnormal size and lipid composition; they were larger than controls, were relatively enriched in cholesteryl ester, and depleted in TG and cholesterol. Cell-permeable ceramides did not replicate any of the reported effects. These findings demonstrate that the increased cholesteryl ester turnover, oversecretion of biliary cholesterol and bile acids, and undersecretion of VLDL cholesterol and particles are concerted responses of the primary hepatocytes to exogenous neutral SMase brought about by regulation at several levels. We suggest that plasma membrane neutral SMase may have a specific, ceramide-independent effect in the regulation of cholesterol output pathways in hepatocytes.
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Affiliation(s)
- Mariana Liza
- Department of Physiology, University of the Basque Country Medical School, 48080-Bilbao, Spain
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Latorre E, Collado MP, Fernández I, Aragonés MD, Catalán RE. Signaling events mediating activation of brain ethanolamine plasmalogen hydrolysis by ceramide. Eur J Biochem 2003; 270:36-46. [PMID: 12492473 DOI: 10.1046/j.1432-1033.2003.03356.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Ceramide is a lipid second messenger that acts on multiple-target enzymes, some of which are involved in other signal-transduction systems. We have previously demonstrated that endogenous ceramide modifies the metabolism of brain ethanolamine plasmalogens. The mechanism involved was studied. On the basis of measurements of breakdown products, specific inhibitor effects, and previous findings, we suggest that a plasmalogen-selective phospholipase A2 is the ceramide target. Arachidonate-rich pools of the diacylphosphatidylethanolamine subclass were also affected by ceramide, but the most affected were plasmalogens. Concomitantly with production of free arachidonate, increased 1-O-arachidonoyl ceramide formation was observed. Quinacrine (phospholipase A2 inhibitor) and 1-O-octadecyl-2-O-methyl-rac-glycerol-3-phosphocholine (CoA-independent transacylase inhibitor) prevented all of these ceramide-elicited effects. Therefore, phospholipase and transacylase activities are tightly coupled. Okadaic acid (phosphatase 2A inhibitor) and PD 98059 (mitogen-activated protein kinase inhibitor) modified basal levels of ceramide and sphingomyelinase-induced accumulation of ceramide, respectively. Therefore, they provided no evidence to determine whether there is a sensitive enzyme downstream of ceramide. The evidence shows that there are serine-dependent and thiol-dependent enzymes downstream of ceramide generation. Furthermore, experiments with Ac-DEVD-CMK (caspase-3 specific inhibitor) have led us to conclude that caspase-3 is downstream of ceramide in activating the brain plasmalogen-selective phospholipase A2.
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Affiliation(s)
- Eduardo Latorre
- Departamento de Bioquímica y Biología Molecular I, Facultad de Químicas, Universidad Complutense de Madrid, Madrid, Spain
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Kozawa O, Hatakeyama D, Tokuda H, Oiso Y, Matsuno H, Uematsu T. Sphingomyelinase amplifies BMP-4-induced osteocalcin synthesis in osteoblasts: role of ceramide. Cell Signal 2002; 14:999-1004. [PMID: 12359305 DOI: 10.1016/s0898-6568(02)00033-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We previously reported that extracellular sphingomyelinase induces sphingomyelin hydrolysis in osteoblast-like MC3T3-E1 cells and that mitogen-activated protein (MAP) kinases are involved in bone morphogenetic protein (BMP)-4-stimulated osteocalcin synthesis in these cells. In the present study, we investigated whether sphingomyelinase affects BMP-4-stimulated synthesis of osteocalcin in osteoblast-like MC3T3-E1 cells. Sphingomyelinase significantly enhanced the BMP-4-stimulated osteocalcin synthesis. Among sphingomyelin metabolites, C(2)-ceramide enhanced the BMP-4-stimulated osteocalcin synthesis while sphingosine and sphingosine 1-phosphate had little effect on the synthesis. D-erythro-MAPP, an inhibitor of ceramidase, amplified the sphingomyelinase-effect on the osteocalcin synthesis. C(2)-ceramide suppressed the BMP-4-induced phosphorylation of p44/p42 MAP kinase, while having little effect on the phosphorylation of Smad1 and p38 MAP kinase. Taken together, our results strongly suggest that extracellular sphingomyelinase enhances the BMP-stimulated osteocalcin synthesis via ceramide in osteoblasts and that the effect of ceramide is exerted at a point upstream from p44/p42 MAP kinase.
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Affiliation(s)
- Osamu Kozawa
- Department of Pharmacology, Gifu University School of Medicine, Gifu 500-8705, Japan.
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Abstract
Cytochrome P450 3A4 (CYP3A4) enzyme is responsible for the metabolic activation and inactivation of the majority of clinically used drugs in human liver and intestines. Recent studies have increasingly implicated various inflammatory stimuli to cause changes in the activities and expression levels of CYPs. However, the underlying mechanisms are largely unknown. In the present study, our studies investigated the effects of ceramide on CYP3A4 expression in human colon carcinoma HT-29 cells. Treatment with the cell-permeable ceramide analog C(6)-ceramide to the cells significantly decreased the expression of CYP3A4. By contrast, C(6)-dihydroceramide, a biologically inactive analog of C(6)-ceramide, did not affect CYP3A4 expression. We found that bacterial sphingomyelinase (SMase) and tumor necrosis factor-alpha (TNF), which are known to increase intracellular ceramide levels, also markedly suppressed the synthesis of CYP3A4. To elucidate whether nitric oxide (NO) participates in suppression of CYP3A4 expression by ceramide, the effects of NO modulators were determined. Treatment with N(G)-monomethyl-L-arginine, a competitive inhibitor of inducible nitric oxide synthase (iNOS), was able to protect ceramide-dependent CYP3A4 suppression. In contrast, the addition of S-nitroso-N-acetylpenicillamine, a NO donor, to HT-29 cells reduced CYP3A4 expression. The addition of iNOS antisense oligonucleotide prevented ceramide-mediated induction of iNOS expression and restored CYP3A4 expression. Wortmannin which is known to inhibit phosphatidylinositol 3-kinase (PI3-K) blocked CYP3A4 suppression by ceramide. Taken together, our results demonstrate that ceramide-mediated suppression of CYP3A4 is due to production of NO, which might result from activation of PI3-K.
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Affiliation(s)
- Young-Jin Chun
- College of Pharmacy, Chung-Ang University, 221 Huksuk-dong, Dongjak-gu, Seoul, Republic of Korea.
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