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DeForest N, Wang Y, Zhu Z, Dron JS, Koesterer R, Natarajan P, Flannick J, Amariuta T, Peloso GM, Majithia AR. Genome-wide discovery and integrative genomic characterization of insulin resistance loci using serum triglycerides to HDL-cholesterol ratio as a proxy. Nat Commun 2024; 15:8068. [PMID: 39277575 PMCID: PMC11401929 DOI: 10.1038/s41467-024-52105-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 08/27/2024] [Indexed: 09/17/2024] Open
Abstract
Insulin resistance causes multiple epidemic metabolic diseases, including type 2 diabetes, cardiovascular disease, and fatty liver, but is not routinely measured in epidemiological studies. To discover novel insulin resistance genes in the general population, we conducted genome-wide association studies in 382,129 individuals for triglyceride to HDL-cholesterol ratio (TG/HDL), a surrogate marker of insulin resistance calculable from commonly measured serum lipid profiles. We identified 251 independent loci, of which 62 were more strongly associated with TG/HDL compared to TG or HDL alone, suggesting them as insulin resistance loci. Candidate causal genes at these loci were prioritized by fine mapping with directions-of-effect and tissue specificity annotated through analysis of protein coding and expression quantitative trait variation. Directions-of-effect were corroborated in an independent cohort of individuals with directly measured insulin resistance. We highlight two phospholipase encoding genes, PLA2G12A and PLA2G6, which liberate arachidonic acid and improve insulin sensitivity, and VGLL3, a transcriptional co-factor that increases insulin resistance partially through enhanced adiposity. Finally, we implicate the anti-apoptotic gene TNFAIP8 as a sex-dimorphic insulin resistance factor, which acts by increasing visceral adiposity, specifically in females. In summary, our study identifies several candidate modulators of insulin resistance that have the potential to serve as biomarkers and pharmacological targets.
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Affiliation(s)
- Natalie DeForest
- Division of Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Yuqi Wang
- Division of Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Zhiyi Zhu
- Division of Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Jacqueline S Dron
- Center for Genomic Medicine and Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, USA
- Programs in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Ryan Koesterer
- Programs in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Pradeep Natarajan
- Center for Genomic Medicine and Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, USA
- Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - Jason Flannick
- Programs in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Pediatrics, Boston Children's Hospital, Boston, MA, USA
| | - Tiffany Amariuta
- Halıcıoğlu Data Science Institute, University of California San Diego, La Jolla, CA, USA
- Division of Biomedical Informatics, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Gina M Peloso
- Department of Biostatistics, Boston University School of Public Health, Boston, MA, USA
| | - Amit R Majithia
- Division of Endocrinology, Department of Medicine, University of California San Diego, La Jolla, CA, USA.
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Williams SB, Franklin B, Lemieux FA, Rand DM. Natural variation in starvation sensitivity maps to a point mutation in phospholipase IPLA2-VIA in Drosophila melanogaster. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.05.602254. [PMID: 39005416 PMCID: PMC11245103 DOI: 10.1101/2024.07.05.602254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Resistance to starvation is a classic complex trait, where genetic and environmental variables can greatly modify an animal's ability to survive without nutrients. In this study, we investigate the genetic basis of starvation resistance using complementary quantitative and classical genetic mapping in Drosophila melanogaster. Using the Drosophila Genetics Reference Panel (DGRP) as a starting point, we queried the genetic basis of starvation sensitivity in one of the most sensitive DGRP lines. We localize a major effect locus modifying starvation resistance to the phospholipase iPLA2-VIA. This finding is consistent with the work of others which demonstrate the importance of lipid regulation in starvation stress. Furthermore, we demonstrate that iPLA2-VIA plays a role in the maintenance of sugar reserves post-starvation, which highlights a key dynamic between lipid remodeling, sugar metabolism and resistance to starvation stress.
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Affiliation(s)
- Shawn B. Williams
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02906, USA
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02906, USA
| | - Brian Franklin
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02906, USA
| | - Faye A. Lemieux
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02906, USA
| | - David M Rand
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02906, USA
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3
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Nadalin S, Zatković L, Peitl V, Karlović D, Vidrih B, Puljić A, Pavlić SD, Buretić-Tomljanović A. Association between PLA2 gene polymorphisms and treatment response to antipsychotic medications: A study of antipsychotic-naïve first-episode psychosis patients and nonadherent chronic psychosis patients. Prostaglandins Leukot Essent Fatty Acids 2023; 194:102578. [PMID: 37290257 DOI: 10.1016/j.plefa.2023.102578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 05/26/2023] [Accepted: 05/31/2023] [Indexed: 06/10/2023]
Abstract
Here we investigated whether antipsychotic treatment was influenced by three polymorphisms: rs10798059 (BanI) in the phospholipase A2 (PLA2)G4A gene, rs4375 in PLA2G6, and rs1549637 in PLA2G4C. A total of 186 antipsychotic-naïve first-episode psychosis patients or nonadherent chronic psychosis individuals (99 males and 87 females) were genotyped by polymerase chain reaction analysis/restriction fragment length polymorphism. At baseline, and after 8 weeks of treatment with various antipsychotic medications, we assessed patients' Positive and Negative Syndrome Scale (PANSS) scores, PANSS factors, and metabolic syndrome-related parameters (fasting plasma lipid and glucose levels, and body mass index). We found that PLA2G4A polymorphism influenced changes in PANSS psychopathology, and PLA2G6 polymorphism influenced changes in PANSS psychopathology and metabolic parameters. PLA2G4C polymorphism did not show any impact on PANSS psychopathology or metabolic parameters. The polymorphisms' effect sizes were estimated as moderate to strong, with contributions ranging from around 6.2-15.7%. Furthermore, the polymorphisms' effects manifested in a gender-specific manner.
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Affiliation(s)
- Sergej Nadalin
- Department of Psychiatry, General Hospital "Dr. Josip Benčević", Slavonski Brod, Croatia; School of Medicine, Catholic University of Croatia, Zagreb, Croatia.
| | - Lena Zatković
- Hospital pharmacy, Clinical Hospital Center Rijeka, Rijeka, Croatia
| | - Vjekoslav Peitl
- School of Medicine, Catholic University of Croatia, Zagreb, Croatia; Department of Psychiatry, Sestre Milosrdnice University Hospital Center, Zagreb, Croatia
| | - Dalibor Karlović
- School of Medicine, Catholic University of Croatia, Zagreb, Croatia; Department of Psychiatry, Sestre Milosrdnice University Hospital Center, Zagreb, Croatia
| | - Branka Vidrih
- School of Medicine, Catholic University of Croatia, Zagreb, Croatia; Department of Psychiatry, Sestre Milosrdnice University Hospital Center, Zagreb, Croatia
| | - Antonia Puljić
- School of Medicine, Catholic University of Croatia, Zagreb, Croatia; Department of Psychiatry, Sestre Milosrdnice University Hospital Center, Zagreb, Croatia
| | - Sanja Dević Pavlić
- Department of Medical Biology and Genetics, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
| | - Alena Buretić-Tomljanović
- Department of Medical Biology and Genetics, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
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Wang YJ, Wang X, An A, Zang M, Xu L, Gong K, Song W, Li Q, Lu X, Xiao YF, Yu G, Ma ZA. Immunomodulator FTY720 improves glucose homeostasis and diabetic complications by rejuvenation of β-cell function in nonhuman primate model of diabetes. Fundam Clin Pharmacol 2022; 36:699-711. [PMID: 35064580 PMCID: PMC9546369 DOI: 10.1111/fcp.12760] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/31/2021] [Accepted: 01/19/2022] [Indexed: 12/02/2022]
Abstract
Inadequate β‐cell mass is essential for the pathogenesis of type 2 diabetes (T2D). Previous report showed that an immunomodulator FTY720, a sphingosine 1‐phosphate (S1P) receptor modulator, sustainably normalized hyperglycemia by stimulating β‐cell in vivo regeneration in db/db mice. We further examined the effects of FTY720 on glucose homeostasis and diabetic complications in a translational nonhuman primate (NHP) model of spontaneously developed diabetes. The male diabetic cynomolgus macaques of 18–19 year old were randomly divided into Vehicle (Purified water, n = 5) and FTY720 (5 mg/kg, n = 7) groups with oral gavage once daily for 10 weeks followed by 10 weeks drug free period. Compared with the Vehicle group, FTY720 effectively lowered HbA1c, blood concentrations of fasting glucose (FBG) and insulin, hence, decreased homeostatic model assessment of insulin resistance (HOMA‐IR); ameliorated glucose intolerance and restored glucose‐stimulated insulin release, indicating rejuvenation of β‐cell function in diabetic NHPs. Importantly, after withdrawal of FTY720, FBG, and HbA1c remained at low level in the drug free period. Echocardiography revealed that FTY720 significantly reduced proteinuria and improved cardiac left ventricular systolic function measured by increased ejection fraction and fractional shortening in the diabetic NHPs. Finally, flow cytometry analysis (FACS) detected that FTY720 significantly reduced CD4 + and CD8 + T lymphocytes as well as increased DC cells in the circulation. Immunomodulator FTY720 improves glucose homeostasis via rejuvenation of β‐cell function, which can be mediated by suppression of cytotoxic CD8 + T lymphocytes to β‐cells, thus, may be a novel immunotherapy to reverse T2D progression and ameliorate the diabetic complications.
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Affiliation(s)
- Yixin Jim Wang
- Crown Bioscience Inc., San Diego, California, USA.,Innoland Bioscience Inc., Taicang, China
| | | | - Annie An
- Crown Bioscience Inc., San Diego, California, USA
| | - Mingfa Zang
- Crown Bioscience Inc., San Diego, California, USA
| | - Ling Xu
- Crown Bioscience Inc., San Diego, California, USA
| | - Kefeng Gong
- Crown Bioscience Inc., San Diego, California, USA
| | | | - Qing Li
- The First People's Hospital of Taicang, Taicang Affiliated Hospital of Soochow University, Suzhou, China
| | - Xiaojun Lu
- The First People's Hospital of Taicang, Taicang Affiliated Hospital of Soochow University, Suzhou, China
| | - Yong-Fu Xiao
- Crown Bioscience Inc., San Diego, California, USA
| | - Guoliang Yu
- Apollomics Biopharmaceuticals, Inc., Hangzhou, China
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Hu X, Zhang B, Zheng X, Ji H, Feng K, Hu X, Gul I, Abbas MN, Cui H, Zhu Y. Molecular Characterization of Two Genes Encoding Novel Ca2+-Independent Phospholipase A2s from the Silkworm, Bombyx mori. Curr Issues Mol Biol 2022; 44:777-790. [PMID: 35723339 PMCID: PMC8929031 DOI: 10.3390/cimb44020054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/17/2022] [Accepted: 01/21/2022] [Indexed: 11/23/2022] Open
Abstract
Eicosanoids are crucial downstream signals in the insect immune responses. Phospholipase A2 (PLA2) catalyzes phospholipids, the initial step in eicosanoid biosynthesis. In mammals, the biological roles of Ca2+-independent Phospholipase A2 (iPLA2) have been extensively studied; however, only a few studies have attempted to explore iPLA2 functions in insects. In this study, we identified two iPLA2 genes (designated as BmiPLA2A and BmiPLA2B) in the silkworm, Bombyx mori. BmiPLA2A had a 2427 base pair (bp) open reading frame (ORF) that coded for a protein with 808 amino acids. In contrast, BmiPLA2B had a 1731 bp ORF that coded for a protein with 576 amino acids. Domain analysis revealed that BmiPLA2A had six ankyrin repeat domains, but BmiPLA2B lacks these domains. BmiPLA2A and BmiPLA2B were transcribed widely in various tissues and developmental stages with different expression patterns. The administration of 20-hydroxyecdysone increased their expression levels in the epidermis and hemocytes. Furthermore, challenged with virus, fungus, Gram-negative bacteria, and Gram-positive bacteria induced the expression of BmiPLA2A and BmiPLA2B with variable degrees along with different time points. Our findings imply that BmiPLA2A and BmiPLA2B may have important biological roles in the development and innate immunity of B. mori.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Hongjuan Cui
- Correspondence: (H.C.); (Y.Z.); Tel.: +23-6825-1713 (H.C.); +23-6825-1939 (Y.Z.)
| | - Yong Zhu
- Correspondence: (H.C.); (Y.Z.); Tel.: +23-6825-1713 (H.C.); +23-6825-1939 (Y.Z.)
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6
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Choi JW, Joo JD, In JH, Kim D, Kim Y, Choi ST, Kim JH, Jung HS. The small molecule kobusone can stimulate islet β-cell replication in vivo. J Int Med Res 2021; 49:3000605211032849. [PMID: 34320857 PMCID: PMC8330483 DOI: 10.1177/03000605211032849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVE To investigate the ability of kobusone to reduce high glucose levels and promote β-cell proliferation. METHODS Four-week-old female db/db mice were assigned to the kobusone (25 mg/kg body weight, intraperitoneally twice a day) or control group (same volume of PBS). Glucose levels and body weight were measured twice a week. After 6 weeks, intraperitoneal glucose tolerance tests and immunohistochemical studies were performed, and insulin levels were determined. The expression of mRNAs involved in cell proliferation, such as PI3K, Akt, cyclin D3 and p57Kip2, was measured by quantitative reverse transcription polymerase chain reaction (RT-qPCR). RESULTS Kobusone reduced blood glucose levels after 3 weeks and more strongly increased serum insulin levels than the vehicle. Immunohistochemistry illustrated that kobusone increased 5-bromo-2'-deoxyuridine incorporation into islet β-cells, suggesting that it can stimulate islet β-cell replication in vivo. RT-qPCR indicated that kobusone upregulated the mRNA expression of PI3K, Akt, and cyclin D3 and downregulated that of p57Kip2. CONCLUSION Our findings suggest that kobusone is a potent pancreatic islet β-cell inducer that has the potential to be developed as an anti-diabetic agent.
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Affiliation(s)
- Jin Woo Choi
- Department of Anesthesiology and Pain Medicine, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea
| | - Jin-Deok Joo
- Department of Anesthesiology and Pain Medicine, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea
| | - Jang Hyeok In
- Department of Anesthesiology and Pain Medicine, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea
| | - Daewoo Kim
- Department of Anesthesiology and Pain Medicine, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea
| | - Yongshin Kim
- Department of Anesthesiology and Pain Medicine, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea
| | - Seung Tae Choi
- Department of Anesthesiology and Pain Medicine, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea
| | - Jung Han Kim
- Department of Anesthesiology and Pain Medicine, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea
| | - Hong Soo Jung
- Department of Anesthesiology and Pain Medicine, St. Vincent's Hospital, The Catholic University of Korea, Suwon, Korea
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7
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Losada-Barragán M. Physiological effects of nutrients on insulin release by pancreatic beta cells. Mol Cell Biochem 2021; 476:3127-3139. [PMID: 33844157 DOI: 10.1007/s11010-021-04146-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 03/31/2021] [Indexed: 10/21/2022]
Abstract
Obesity and type 2 diabetes (T2D) are growing health problems associated with a loss of insulin sensitivity. Both conditions arise from a long-term energy imbalance, and frequently, lifestyle measures can be useful in its prevention, including physical activity and a healthy diet. Pancreatic β-cells are determinant nutrient sensors that participate in energetic homeostasis needs. However, when pancreatic β-cells are incapable of secreting enough insulin to counteract the reduced sensitivity, the pathology evolves to an insulin resistance condition. The primary nutrient that stimulates insulin secretion is glucose, but also, there are multiple dietary and hormonal factors influencing that response. Many studies of the physiology of β-cells have highlighted the importance of glucose, fructose, amino acids, and free fatty acids on insulin secretion. The present review summarizes recent research on how β-cells respond to the most abundant nutrients that influence insulin secretion. Taken together, understand the subjacent mechanisms of each nutrient on β-cells can help to unravel the effects of mixed variables and complexity in the context of β-cell pathology.
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Affiliation(s)
- Monica Losada-Barragán
- Grupo de investigación en Biología celular y funcional e ingeniería de biomoléculas, Universidad Antonio Nariño-Sede Circunvalar. Cra, 3 Este # 47A - 15, Bl 5, Bogotá, Colombia.
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8
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Sharma P, Sharma A, Ganga L, Satoeya N, Jha R, Srivastava M. Acidic Calcium-Independent Phospholipase A2 Regulates Eosinophil-Mediated Pathology during Filarial Manifestation of Tropical Pulmonary Eosinophilia. THE JOURNAL OF IMMUNOLOGY 2021; 206:722-736. [PMID: 33441441 DOI: 10.4049/jimmunol.2000604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 11/17/2020] [Indexed: 12/24/2022]
Abstract
Eosinophils mediate pathological manifestations during tropical pulmonary eosinophilia (TPE), a potentially fatal complication of lymphatic filariasis, by mechanisms that are incompletely understood. Using two-dimensional gel electrophoresis, mass spectrometry, flow cytometry, and pharmacological and functional studies, we identified acidic calcium-independent phospholipase A2 (aiPLA2) as the master regulator of TPE pathogenesis. FACS-sorted lung eosinophils from TPE mice exhibited aiPLA2-dependent activation characterized by heavy calcium influx, F-actin polymerization, increased degranulation, and heightened reactive oxygen species generation. Interestingly, aiPLA2 also promoted alternative activation in lung macrophages and regulated the release of inflammatory intermediates from them. Treatment of TPE mice with MJ33, a nontoxic pharmacological inhibitor of aiPLA2, lowered eosinophil counts in the bronchoalveolar lavage fluid, reduced eosinophil peroxidase and β-hexosaminidase activity, increased airway width, improved lung endothelial barrier, and lowered the production of inflammatory lipid intermediates, which significantly improved the pathological condition of the lungs. Importantly, ex vivo reconstitution of arachidonic acid to eosinophils from MJ33-treated TPE mice increased eosinophil degranulation and inflammatory lipid intermediates underlining the pivotal role of aiPLA2 in arachidonic acid metabolism. Mechanistically, phosphorylation of JNK-1 regulated phospholipase activity of aiPLA2, whereas IgG cross-linking mediated pathological activation of eosinophils. Taken together, ours is the first study, to our knowledge, to report hitherto undocumented role of aiPLA2 in regulating TPE pathogenesis.
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Affiliation(s)
- Pankaj Sharma
- Molecular Parasitology and Immunology Division, Council of Scientific and Industrial Research-Central Drug Research Institute, Lucknow 226031, India; and
| | - Aditi Sharma
- Molecular Parasitology and Immunology Division, Council of Scientific and Industrial Research-Central Drug Research Institute, Lucknow 226031, India; and.,Academy of Scientific and Innovative Research, Ghaziabad 201002, India
| | - Laxmi Ganga
- Molecular Parasitology and Immunology Division, Council of Scientific and Industrial Research-Central Drug Research Institute, Lucknow 226031, India; and
| | - Neha Satoeya
- Molecular Parasitology and Immunology Division, Council of Scientific and Industrial Research-Central Drug Research Institute, Lucknow 226031, India; and
| | - Ruchi Jha
- Molecular Parasitology and Immunology Division, Council of Scientific and Industrial Research-Central Drug Research Institute, Lucknow 226031, India; and
| | - Mrigank Srivastava
- Molecular Parasitology and Immunology Division, Council of Scientific and Industrial Research-Central Drug Research Institute, Lucknow 226031, India; and .,Academy of Scientific and Innovative Research, Ghaziabad 201002, India
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20-HETE promotes glucose-stimulated insulin secretion in an autocrine manner through FFAR1. Nat Commun 2018; 9:177. [PMID: 29330456 PMCID: PMC5766607 DOI: 10.1038/s41467-017-02539-4] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 12/07/2017] [Indexed: 01/02/2023] Open
Abstract
The long-chain fatty acid receptor FFAR1 is highly expressed in pancreatic β-cells. Synthetic FFAR1 agonists can be used as antidiabetic drugs to promote glucose-stimulated insulin secretion (GSIS). However, the physiological role of FFAR1 in β-cells remains poorly understood. Here we show that 20-HETE activates FFAR1 and promotes GSIS via FFAR1 with higher potency and efficacy than dietary fatty acids such as palmitic, linoleic, and α-linolenic acid. Murine and human β-cells produce 20-HETE, and the ω-hydroxylase-mediated formation and release of 20-HETE is strongly stimulated by glucose. Pharmacological inhibition of 20-HETE formation and blockade of FFAR1 in islets inhibits GSIS. In islets from type-2 diabetic humans and mice, glucose-stimulated 20-HETE formation and 20-HETE-dependent stimulation of GSIS are strongly reduced. We show that 20-HETE is an FFAR1 agonist, which functions as an autocrine positive feed-forward regulator of GSIS, and that a reduced glucose-induced 20-HETE formation contributes to inefficient GSIS in type-2 diabetes. FFAR1 receptor is highly expressed in beta cells and its activation has been suggested as therapy against type-2 diabetes. Here, Tunaru et al. show that 20-hydroxyeicosatetraenoic acid, produced within the islets upon glucose stimulation, acts in an autocrine manner to stimulate insulin secretion via FFAR1 activation.
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Cui L, Zhao Y, Pan Y, Zheng X, Shao D, Jia Y, He K, Li K, Chen L. Chemotherapy induces ovarian cancer cell repopulation through the caspase 3-mediated arachidonic acid metabolic pathway. Onco Targets Ther 2017; 10:5817-5826. [PMID: 29263678 PMCID: PMC5726368 DOI: 10.2147/ott.s150456] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Recurrence is one of the major causes of high mortality in ovarian cancer. However, the mechanism of ovarian cancer recurrence after chemotherapy has not been fully understood. In the present study, we investigated the effect of chemotherapy-induced tumor microenvironment on the proliferation of SKOV3 cells. We have shown that SKOV3 cells repopulated faster in the culture medium from apoptotic SKOV3 ovarian cancer cells after 24 h of etoposide phosphate (VP-16) treatment. We found that during apoptosis, cleaved caspase 3 could activate cytosolic calcium-independent phospholipase A2, which stimulated the release of arachidonic acid (AA) and triggered the production of prostaglandin E2 (PGE2). An increased level of phosphorylated focal adhesion kinase (FAK) subsequently facilitated the reproliferation of SKOV3 cells, and VP-16-induced repopulation effects were partially reversed by the FAK inhibitor PF562271. Furthermore, the plasma AA-to-PGE2 ratio and tumoral FAK expression of ovarian cancer patients after chemotherapy were significantly lower than those before chemotherapy. Taken together, our results indicate that chemotherapy-induced apoptotic cancer cells can produce PGE2-enriched microenvironment through caspase 3-mediated AA metabolic pathway, which could lead to the abnormal activation of FAK and eventually accelerate the repopulation of SKOV3 cells. Our study provides novel insight into a mechanism that may be utilized to prevent ovarian cancer recurrence in response to chemotherapy.
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Affiliation(s)
- Lianzhi Cui
- Department of Pharmacology, College of Basic Medical Sciences, Jilin University, Changchun,Clinical Laboratory, Jilin Cancer Hospital, Changchun
| | - Yawei Zhao
- Department of Pharmacology, College of Basic Medical Sciences, Jilin University, Changchun
| | - Yue Pan
- Department of Pharmacology, College of Basic Medical Sciences, Jilin University, Changchun
| | - Xiao Zheng
- Department of Pharmacology, College of Basic Medical Sciences, Jilin University, Changchun
| | - Dan Shao
- Department of Pharmacology, College of Basic Medical Sciences, Jilin University, Changchun
| | - Yong Jia
- School of Nursing, Jilin University, Changchun, China
| | - Kan He
- Department of Pharmacology, College of Basic Medical Sciences, Jilin University, Changchun
| | - Kun Li
- School of Nursing, Jilin University, Changchun, China,Kun Li, School of Nursing, Jilin University, 965 Xinjiang Street, Changchun 130021, Jilin, China, Email
| | - Li Chen
- Department of Pharmacology, College of Basic Medical Sciences, Jilin University, Changchun,School of Nursing, Jilin University, Changchun, China,Correspondence: Li Chen, Department of Pharmacology, College of Basic Medical Sciences, Jilin University, 126 Xinmin Street, Changchun 130021, Jilin, China, Email
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11
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Shridas P, Noffsinger VP, Trumbauer AC, Webb NR. The dual role of group V secretory phospholipase A 2 in pancreatic β-cells. Endocrine 2017; 58:47-58. [PMID: 28825176 PMCID: PMC5693688 DOI: 10.1007/s12020-017-1379-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 07/21/2017] [Indexed: 10/19/2022]
Abstract
PURPOSE Group X (GX) and group V (GV) secretory phospholipase A2 (sPLA2) potently release arachidonic acid (AA) from the plasma membrane of intact cells. We previously demonstrated that GX sPLA2 negatively regulates glucose-stimulated insulin secretion (GSIS) by a prostaglandin E2 (PGE2)-dependent mechanism. In this study we investigated whether GV sPLA2 similarly regulates GSIS. METHODS GSIS and pancreatic islet-size were assessed in wild-type (WT) and GV sPLA2-knock out (GV KO) mice. GSIS was also assessed ex vivo in isolated islets and in vitro using MIN6 pancreatic beta cell lines with or without GV sPLA2 overexpression or silencing. RESULTS GSIS was significantly decreased in islets isolated from GV KO mice compared to WT mice and in MIN6 cells with siRNA-mediated GV sPLA2 suppression. MIN6 cells overexpressing GV sPLA2 (MIN6-GV) showed a significant increase in GSIS compared to control cells. Though the amount of AA released into the media by MIN6-GV cells was significantly higher, PGE2 production was not enhanced or cAMP content decreased compared to control MIN6 cells. Surprisingly, GV KO mice exhibited a significant increase in plasma insulin levels following i.p. injection of glucose compared to WT mice. This increase in GSIS in GV KO mice was associated with a significant increase in pancreatic islet size and number of proliferating cells in β-islets compared to WT mice. CONCLUSIONS Deficiency of GV sPLA2 results in diminished GSIS in isolated pancreatic beta-cells. However, the reduced GSIS in islets lacking GV sPLA2 appears to be compensated by increased islet mass in GV KO mice.
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Affiliation(s)
- Preetha Shridas
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA.
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY, 40536, USA.
| | - Victoria P Noffsinger
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY, 40536, USA
| | - Andrea C Trumbauer
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
| | - Nancy R Webb
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
- Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington, KY, 40536, USA
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Liu H, Zuo F, Wu H. Blockage of cytosolic phospholipase A2 alpha by monoclonal antibody attenuates focal ischemic brain damage in mice. Biosci Trends 2017; 11:439-449. [DOI: 10.5582/bst.2017.01046] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Hui Liu
- Department of Neurology, The Brain Branch of Heibei Province Cangzhou Central Hospital
| | - Fengtong Zuo
- Department of Neurology, The Brain Branch of Heibei Province Cangzhou Central Hospital
| | - Huijun Wu
- Department of Neurology, The Brain Branch of Heibei Province Cangzhou Central Hospital
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Hormetic and regulatory effects of lipid peroxidation mediators in pancreatic beta cells. Mol Aspects Med 2016; 49:49-77. [PMID: 27012748 DOI: 10.1016/j.mam.2016.03.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Revised: 02/23/2016] [Accepted: 03/09/2016] [Indexed: 12/12/2022]
Abstract
Nutrient sensing mechanisms of carbohydrates, amino acids and lipids operate distinct pathways that are essential for the adaptation to varying metabolic conditions. The role of nutrient-induced biosynthesis of hormones is paramount for attaining metabolic homeostasis in the organism. Nutrient overload attenuate key metabolic cellular functions and interfere with hormonal-regulated inter- and intra-organ communication, which may ultimately lead to metabolic derangements. Hyperglycemia and high levels of saturated free fatty acids induce excessive production of oxygen free radicals in tissues and cells. This phenomenon, which is accentuated in both type-1 and type-2 diabetic patients, has been associated with the development of impaired glucose tolerance and the etiology of peripheral complications. However, low levels of the same free radicals also induce hormetic responses that protect cells against deleterious effects of the same radicals. Of interest is the role of hydroxyl radicals in initiating peroxidation of polyunsaturated fatty acids (PUFA) and generation of α,β-unsaturated reactive 4-hydroxyalkenals that avidly form covalent adducts with nucleophilic moieties in proteins, phospholipids and nucleic acids. Numerous studies have linked the lipid peroxidation product 4-hydroxy-2E-nonenal (4-HNE) to different pathological and cytotoxic processes. Similarly, two other members of the family, 4-hydroxyl-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), have also been identified as potential cytotoxic agents. It has been suggested that 4-HNE-induced modifications in macromolecules in cells may alter their cellular functions and modify signaling properties. Yet, it has also been acknowledged that these bioactive aldehydes also function as signaling molecules that directly modify cell functions in a hormetic fashion to enable cells adapt to various stressful stimuli. Recent studies have shown that 4-HNE and 4-HDDE, which activate peroxisome proliferator-activated receptor δ (PPARδ) in vascular endothelial cells and insulin secreting beta cells, promote such adaptive responses to ameliorate detrimental effects of high glucose and diabetes-like conditions. In addition, due to the electrophilic nature of these reactive aldehydes they form covalent adducts with electronegative moieties in proteins, phosphatidylethanolamine and nucleotides. Normally these non-enzymatic modifications are maintained below the cytotoxic range due to efficient cellular neutralization processes of 4-hydroxyalkenals. The major neutralizing enzymes include fatty aldehyde dehydrogenase (FALDH), aldose reductase (AR) and alcohol dehydrogenase (ADH), which transform the aldehyde to the corresponding carboxylic acid or alcohols, respectively, or by biding to the thiol group in glutathione (GSH) by the action of glutathione-S-transferase (GST). This review describes the hormetic and cytotoxic roles of oxygen free radicals and 4-hydroxyalkenals in beta cells exposed to nutritional challenges and the cellular mechanisms they employ to maintain their level at functional range below the cytotoxic threshold.
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Leis HJ, Windischhofer W. Calcium-independent phospholipases A2 in murine osteoblastic cells and their inhibition by bromoenol lactone: impact on arachidonate dynamics and prostaglandin synthesis. J Enzyme Inhib Med Chem 2015; 31:1203-13. [PMID: 26609885 DOI: 10.3109/14756366.2015.1114929] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
CONTEXT Bromoenol lactone (BEL) is an inhibitor of group VI phospholipases (iPLA2s), but has been shown to have severe side effects. OBJECTIVE iPLA2 characterization in osteoblasts and effect of BEL on prostaglandin (PG) E2 formation. METHODS iPLA2 expression: RT-PCR, Western Blotting. PGE2 formation: GC-MS after stimulation, treatment with inhibitors or gene silencing. Arachidonate (AA) reacylation into phospholipids, inhibitor reaction products, PGHS-1 modification proteomic analysis: HR-LC-MS/MS. AA accumulation: (14)C-AA. RESULTS iPLA2ß and iPLA2γ were expressed and functionally active. BEL inhibition up to 20 μM caused AA accumulation and enhanced PGE2 formation, followed by a decrease at higher concentrations. BEL reacted with intracellular cysteine and GSH leading to GSH depletion and oxidative stress. DISCUSSION Initial PGE2 enhancement after BEL inhibition is due to iPLA2-independent accumulation of AA. GSH depletion caused by high BEL concentrations is responsible for the decrease in PGE2 production. CONCLUSION BEL must be used with caution in a cellular environment due to conditions of extreme oxidative stress.
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Affiliation(s)
- Hans Jörg Leis
- a University Hospital of Youth and Adolescence Medicine, Medical University of Graz, Research Unit of Analytical Mass Spectrometry, Cell Biology and Biochemistry of Inborn Errors of Metabolism , Graz , Austria
| | - Werner Windischhofer
- a University Hospital of Youth and Adolescence Medicine, Medical University of Graz, Research Unit of Analytical Mass Spectrometry, Cell Biology and Biochemistry of Inborn Errors of Metabolism , Graz , Austria
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15
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Shridas P, Zahoor L, Forrest KJ, Layne JD, Webb NR. Group X secretory phospholipase A2 regulates insulin secretion through a cyclooxygenase-2-dependent mechanism. J Biol Chem 2014; 289:27410-7. [PMID: 25122761 DOI: 10.1074/jbc.m114.591735] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Group X secretory phospholipase A2 (GX sPLA2) potently hydrolyzes membrane phospholipids to release arachidonic acid (AA). While AA is an activator of glucose-stimulated insulin secretion (GSIS), its metabolite prostaglandin E2 (PGE2) is a known inhibitor. In this study, we determined that GX sPLA2 is expressed in insulin-producing cells of mouse pancreatic islets and investigated its role in beta cell function. GSIS was measured in vivo in wild-type (WT) and GX sPLA2-deficient (GX KO) mice and ex vivo using pancreatic islets isolated from WT and GX KO mice. GSIS was also assessed in vitro using mouse MIN6 pancreatic beta cells with or without GX sPLA2 overexpression or exogenous addition. GSIS was significantly higher in islets isolated from GX KO mice compared with islets from WT mice. Conversely, GSIS was lower in MIN6 cells overexpressing GX sPLA2 (MIN6-GX) compared with control (MIN6-C) cells. PGE2 production was significantly higher in MIN6-GX cells compared with MIN6-C cells and this was associated with significantly reduced cellular cAMP. The effect of GX sPLA2 on GSIS was abolished when cells were treated with NS398 (a COX-2 inhibitor) or L-798,106 (a PGE2-EP3 receptor antagonist). Consistent with enhanced beta cell function, GX KO mice showed significantly increased plasma insulin levels following glucose challenge and were protected from age-related reductions in GSIS and glucose tolerance compared with WT mice. We conclude that GX sPLA2 plays a previously unrecognized role in negatively regulating pancreatic insulin secretion by augmenting COX-2-dependent PGE2 production.
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Affiliation(s)
- Preetha Shridas
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Lubna Zahoor
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Kathy J Forrest
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Joseph D Layne
- From Saha Cardiovascular Research Center and Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington Kentucky 40536
| | - Nancy R Webb
- From Saha Cardiovascular Research Center and Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington Kentucky 40536
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Shao Y, Yuan G, Feng Y, Zhang J, Guo X. Early liraglutide treatment is better in glucose control, β-cell function improvement and mass preservation in db/db mice. Peptides 2014; 52:134-42. [PMID: 24406898 DOI: 10.1016/j.peptides.2013.11.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 11/14/2013] [Accepted: 11/14/2013] [Indexed: 02/06/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) has been proved to have effects of anti-hyperglycemia and β-cell preservation. However, it is still unclear whether there are differences between early and late GLP-1 intervention in type 2 diabetes mellitus (T2DM). We divided the mice into 5 groups: early treated group (n=7, 8-week old, fasting glucose>10mmol/l), late treated group (n=7, 10-week old, fasting glucose>20mmol/l), early control group (n=7), late control group (n=7) and wild type group (n=7). Treated group was injected with liraglutide (a GLP-1 analog) 300μg/kg bid for 4 weeks, while control group was given saline at the same time. The results showed that compared with control group, food intake and body weight gain were reduced in both early and late treated group (p<0.05), and there was no significance between the two treated groups. Early liraglutide intervention showed better improvements in glucose control, acute insulin response to glucose (AIRg) and disposition index (before vs. after treatment, AIRg 1.01±0.53 vs. 2.98±0.63, disposition index 10.81±0.89 vs. 27.4±2.15) than late intervention (AIRg 0.99±0.02 vs. 1.41±0.32, disposition index 3.47±0.38 vs. 6.43±1.62, p=0.001). The histopathology of the pancreas showed the estimated β-cell mass (BCM) was increased more in early treated group than that in late one (0.03 vs. 0.01g). Expressions of the proliferation related genes PDX-1, MafA and GLP-1 receptor (GLP-1R) in early treated group were 1.81, 2.57 and 1.59 times as much as that in late treated group. In conclusion, early liraglutide intervention was better in glucose control, β-cell function improvement and β-cell mass preservation.
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Affiliation(s)
- Yimin Shao
- Endocrinology Department, Peking University First Hospital, China
| | - Geheng Yuan
- Endocrinology Department, Peking University First Hospital, China.
| | - Yan Feng
- Huguosi Hospital of Traditional Chinese Medicine, China
| | - Junqing Zhang
- Endocrinology Department, Peking University First Hospital, China
| | - Xiaohui Guo
- Endocrinology Department, Peking University First Hospital, China
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Zhang J, Xue C, Zhu T, Vivekanandan A, Pennathur S, Ma ZA, Chen YE. A tripeptide Diapin effectively lowers blood glucose levels in male type 2 diabetes mice by increasing blood levels of insulin and GLP-1. PLoS One 2013; 8:e83509. [PMID: 24386218 PMCID: PMC3873933 DOI: 10.1371/journal.pone.0083509] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 11/04/2013] [Indexed: 01/28/2023] Open
Abstract
The prevalence of type 2 diabetes (T2D) is rapidly increasing worldwide. Effective therapies, such as insulin and Glucagon-like peptide-1 (GLP-1), require injections, which are costly and result in less patient compliance. Here, we report the identification of a tripeptide with significant potential to treat T2D. The peptide, referred to as Diapin, is comprised of three natural L-amino acids, GlyGlyLeu. Glucose tolerance tests showed that oral administration of Diapin effectively lowered blood glucose after oral glucose loading in both normal C57BL/6J mice and T2D mouse models, including KKay, db/db, ob/ob mice, and high fat diet-induced obesity/T2D mice. In addition, Diapin treatment significantly reduced casual blood glucose in KKay diabetic mice in a time-dependent manner without causing hypoglycemia. Furthermore, we found that plasma GLP-1 and insulin levels in diabetic models were significantly increased with Diapin treatment compared to that in the controls. In summary, our findings establish that a peptide with minimum of three amino acids can improve glucose homeostasis and Diapin shows promise as a novel pharmaceutical agent to treat patients with T2D through its dual effects on GLP-1 and insulin secretion.
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Affiliation(s)
- Jifeng Zhang
- Cardiovascular Center, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Changyong Xue
- Cardiovascular Center, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Tianqing Zhu
- Cardiovascular Center, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Anuradha Vivekanandan
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Subramaniam Pennathur
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
| | - Zhongmin Alex Ma
- Diapin Therapeutics Limited Liability Company, Ann Arbor, Michigan, United States of America
| | - Y. Eugene Chen
- Cardiovascular Center, Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, United States of America
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Li Z, Zhou Z, Huang G, Hu F, Xiang Y, He L. Exendin-4 protects mitochondria from reactive oxygen species induced apoptosis in pancreatic Beta cells. PLoS One 2013; 8:e76172. [PMID: 24204601 PMCID: PMC3811987 DOI: 10.1371/journal.pone.0076172] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 08/21/2013] [Indexed: 12/23/2022] Open
Abstract
Objective Mitochondrial oxidative stress is the basis for pancreatic β-cell apoptosis and a common pathway for numerous types of damage, including glucotoxicity and lipotoxicity. We cultivated mice pancreatic β-cell tumor Min6 cell lines in vitro and observed pancreatic β-cell apoptosis and changes in mitochondrial function before and after the addition of Exendin-4. Based on these observations, we discuss the protective role of Exendin-4 against mitochondrial oxidative damage and its relationship with Ca2+-independent phospholipase A2. Methods We established a pancreatic β-cell oxidative stress damage model using Min6 cell lines cultured in vitro with tert-buty1 hydroperoxide and hydrogen peroxide. We then added Exendin-4 to observe changes in the rate of cell apoptosis (Annexin-V-FITC-PI staining flow cytometry and DNA ladder). We detected the activity of the caspase 3 and 8 apoptotic factors, measured the mitochondrial membrane potential losses and reactive oxygen species production levels, and detected the expression of cytochrome c and Smac/DLAMO in the cytosol and mitochondria, mitochondrial Ca2-independent phospholipase A2 and Ca2+-independent phospholipase A2 mRNA. Results The time-concentration curve showed that different percentages of apoptosis occurred at different time-concentrations in tert-buty1 hydroperoxide- and hydrogen peroxide-induced Min6 cells. Incubation with 100 µmol/l of Exendin-4 for 48 hours reduced the Min6 cell apoptosis rate (p<0.05). The mitochondrial membrane potential loss and total reactive oxygen species levels decreased (p<0.05), and the release of cytochrome c and Smac/DLAMO from the mitochondria was reduced. The study also showed that Ca2+-independent phospholipase A2 activity was positively related to Exendin-4 activity. Conclusion Exendin-4 reduces Min6 cell oxidative damage and the cell apoptosis rate, which may be related to Ca2-independent phospholipase A2.
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Affiliation(s)
- Zhen Li
- Diabetes Center, Second Xiangya Hospital, and Institute of Metabolism and Endocrinology, Key Laboratory of Diabetes Immunology, Ministry of Education, Central South University, Changsha, China
| | - Zhiguang Zhou
- Diabetes Center, Second Xiangya Hospital, and Institute of Metabolism and Endocrinology, Key Laboratory of Diabetes Immunology, Ministry of Education, Central South University, Changsha, China
- * E-mail:
| | - Gan Huang
- Diabetes Center, Second Xiangya Hospital, and Institute of Metabolism and Endocrinology, Key Laboratory of Diabetes Immunology, Ministry of Education, Central South University, Changsha, China
| | - Fang Hu
- Diabetes Center, Second Xiangya Hospital, and Institute of Metabolism and Endocrinology, Key Laboratory of Diabetes Immunology, Ministry of Education, Central South University, Changsha, China
| | - Yufei Xiang
- Diabetes Center, Second Xiangya Hospital, and Institute of Metabolism and Endocrinology, Key Laboratory of Diabetes Immunology, Ministry of Education, Central South University, Changsha, China
| | - Lining He
- Diabetes Center, Second Xiangya Hospital, and Institute of Metabolism and Endocrinology, Key Laboratory of Diabetes Immunology, Ministry of Education, Central South University, Changsha, China
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19
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Saab-Aoudé S, Bron AM, Creuzot-Garcher CP, Bretillon L, Acar N. A mouse model of in vivo chemical inhibition of retinal calcium-independent phospholipase A2 (iPLA2). Biochimie 2013; 95:903-11. [DOI: 10.1016/j.biochi.2012.12.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 12/11/2012] [Indexed: 10/27/2022]
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20
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Hanada H, Kobuchi H, Yamamoto M, Kashiwagi K, Katsu K, Utsumi T, Kashiwagi A, Sasaki J, Inoue M, Utsumi K. Acetyl-L-carnitine suppresses thyroid hormone-induced and spontaneous anuran tadpole tail shortening. Hereditas 2013; 150:1-9. [PMID: 23489246 DOI: 10.1111/j.1601-5223.2013.02284.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Mitochondrial membrane permeability transition (MPT) plays a crucial role in apoptotic tail shortening during anuran metamorphosis. L-carnitine is known to shuttle free fatty acids (FFAs) from the cytosol into mitochondria matrix for β-oxidation and energy production, and in a previous study we found that treatment with L-carnitine suppresses 3, 3', 5-triiodothyronine (T3 ) and FFA-induced MPT by reducing the level of FFAs. In the present study we focus on acetyl-L-carnitine, which is also involved in fatty acid oxidation, to determine its effect on T3 -induced tail regression in Rana rugosa tadpoles and spontaneous tail regression in Xenopus laevis tadpoles. The ladder-like DNA profile and increases in caspase-3 and caspase-9 indicative of apoptosis in the tails of T3 -treated tadpoles were found to be suppressed by the addition of acetyl-L-carnitine. Likewise, acetyl-L-carnitine was found to inhibit thyroid hormone regulated spontaneous metamorphosis in X. laevis tadpoles, accompanied by decreases in caspase and phospholipase A2 activity, as well as non-ladder-like DNA profiles. These findings support our previous conclusion that elevated levels of FFAs initiate MPT and activate the signaling pathway controlling apoptotic cell death in tadpole tails during anuran metamorphosis.
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Affiliation(s)
- Hideki Hanada
- Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, Higashihiroshima, Japan
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Kim HW, Cheon Y, Modi HR, Rapoport SI, Rao JS. Effects of chronic clozapine administration on markers of arachidonic acid cascade and synaptic integrity in rat brain. Psychopharmacology (Berl) 2012; 222:663-74. [PMID: 22414961 PMCID: PMC3478065 DOI: 10.1007/s00213-012-2671-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 02/13/2012] [Indexed: 12/20/2022]
Abstract
BACKGROUND The mode of action of clozapine, an atypical antipsychotic approved for treating schizophrenia (SZ) and used for bipolar disorder (BD) mania, remains unclear. We tested for overlap with the actions of the mood stabilizers, lithium, carbamazepine and valproate, which downregulate arachidonic acid (AA) cascade markers in rat brain and upregulate BDNF. AA cascade markers are upregulated in BD and SZ postmortem BD brain in association with neuroinflammation and synaptic loss, while BDNF is decreased. METHODS Rats were injected intraperitoneally with a therapeutically relevant dose of clozapine (10 mg/kg/day) or with saline for 30 days, and AA cascade and synaptic markers and BDNF were measured in the brain. RESULTS Compared with saline-injected rats, chronic clozapine increased brain activity, mRNA and protein levels of docosahexaenoic acid (DHA)-selective calcium-independent phospholipase A₂ type VIA (iPLA₂), mRNA and protein levels of BDNF and of the postsynaptic marker, drebrin, while decreasing cyclooxygenase (COX) activity and concentration of prostaglandin E₂ (PGE₂), a proinflammatory AA metabolite. Activity and expression of AA-selective calcium-dependent cytosolic cPLA₂ type IVA and of secretory sPLA₂ Type II were unchanged. CONCLUSIONS These results show overlap with effects of mood stabilizers with regard to downregulation of COX activity and PGE₂ and to increased BDNF and suggest a common action against the reported neuropathology of BD and SZ. The increased iPLA₂ expression following clozapine suggests increased production of anti-inflammatory DHA metabolites, and, with increased BDNF and drebrin, clear neuroprotective action.
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Affiliation(s)
- Hyung-Wook Kim
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
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Mock JN, Taliaferro JP, Lu X, Patel SK, Cummings BS, Long TE. Haloenol pyranones and morpholinones as antineoplastic agents of prostate cancer. Bioorg Med Chem Lett 2012; 22:4854-8. [PMID: 22677312 PMCID: PMC3376906 DOI: 10.1016/j.bmcl.2012.05.038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 05/04/2012] [Accepted: 05/08/2012] [Indexed: 10/28/2022]
Abstract
Haloenol pyran-2-ones and morpholin-2-ones were synthesized and evaluated as inhibitors of cell growth in two different prostate human cancer cell lines (PC-3 and LNCaP). Analogs derived from L- and D-phenylglycine were found to be the most effective antagonists of LNCaP and PC-3 cell growth. Additional studies reveal that the inhibitors induced G2/M arrest and the (S)-enantiomer of the phenylglycine-based derivatives was a more potent inhibitor of cytosolic iPLA(2)β.
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Affiliation(s)
- Jason N. Mock
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602-2352, USA
| | - John P. Taliaferro
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602-2352, USA
| | - Xiao Lu
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602-2352, USA
| | - Sravan Kumar Patel
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602-2352, USA
| | - Brian S. Cummings
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602-2352, USA
| | - Timothy E. Long
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602-2352, USA
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Song H, Wohltmann M, Tan M, Bao S, Ladenson JH, Turk J. Group VIA PLA2 (iPLA2β) is activated upstream of p38 mitogen-activated protein kinase (MAPK) in pancreatic islet β-cell signaling. J Biol Chem 2012; 287:5528-41. [PMID: 22194610 PMCID: PMC3285329 DOI: 10.1074/jbc.m111.285114] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Revised: 12/21/2011] [Indexed: 01/09/2023] Open
Abstract
Group VIA phospholipase A(2) (iPLA(2)β) in pancreatic islet β-cells participates in glucose-stimulated insulin secretion and sarco(endo)plasmic reticulum ATPase (SERCA) inhibitor-induced apoptosis, and both are attenuated by pharmacologic or genetic reductions in iPLA(2)β activity and amplified by iPLA(2)β overexpression. While exploring signaling events that occur downstream of iPLA(2)β activation, we found that p38 MAPK is activated by phosphorylation in INS-1 insulinoma cells and mouse pancreatic islets, that this increases with iPLA(2)β expression level, and that it is stimulated by the iPLA(2)β reaction product arachidonic acid. The insulin secretagogue D-glucose also stimulates β-cell p38 MAPK phosphorylation, and this is prevented by the iPLA(2)β inhibitor bromoenol lactone. Insulin secretion induced by d-glucose and forskolin is amplified by overexpressing iPLA(2)β in INS-1 cells and in mouse islets, and the p38 MAPK inhibitor PD169316 prevents both responses. The SERCA inhibitor thapsigargin also stimulates phosphorylation of both β-cell MAPK kinase isoforms and p38 MAPK, and bromoenol lactone prevents both events. Others have reported that iPLA(2)β products activate Rho family G-proteins that promote MAPK kinase activation via a mechanism inhibited by Clostridium difficile toxin B, which we find to inhibit thapsigargin-induced β-cell p38 MAPK phosphorylation. Thapsigargin-induced β-cell apoptosis and ceramide generation are also prevented by the p38 MAPK inhibitor PD169316. These observations indicate that p38 MAPK is activated downstream of iPLA(2)β in β-cells incubated with insulin secretagogues or thapsigargin, that this requires prior iPLA(2)β activation, and that p38 MAPK is involved in the β-cell functional responses of insulin secretion and apoptosis in which iPLA(2)β participates.
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Affiliation(s)
- Haowei Song
- From the Mass Spectrometry Resource, Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, and
| | - Mary Wohltmann
- From the Mass Spectrometry Resource, Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, and
| | - Min Tan
- From the Mass Spectrometry Resource, Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, and
| | - Shunzhong Bao
- From the Mass Spectrometry Resource, Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, and
| | - Jack H. Ladenson
- the Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - John Turk
- From the Mass Spectrometry Resource, Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, and
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Ma ZA. The role of peroxidation of mitochondrial membrane phospholipids in pancreatic β -cell failure. Curr Diabetes Rev 2012; 8:69-75. [PMID: 22414059 PMCID: PMC4884441 DOI: 10.2174/157339912798829232] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 08/15/2011] [Accepted: 09/13/2011] [Indexed: 12/28/2022]
Abstract
Type 2 diabetes (T2D) is characterized by peripheral insulin resistance and pancreatic islet β-cell failure. Accumulating evidence indicates that mitochondrial dysfunction is a central contributor to β-cell failure in the pathogenesis of T2D. This review focuses on mechanisms whereby reactive oxygen species (ROS) produced by β-cell in response to metabolic stress affect mitochondrial structure and function and lead to β-cell failure. Specifically, ROS oxidize mitochondrial membrane phospholipids such as cardiolipin, which impairs membrane integrity and leads to cytochrome c release and apoptosis. In addition, ROS activate UCP2 via peroxidation of the mitochondrial membrane phospholipids, which results in proton leak leading to reduced ATP synthesis and content in β-cells - critical parameters in the regulation of glucose-stimulated insulin secretion. Group VIA Phospholipase A2 (iPLA2β) appears to be a component of a mechanism for repairing mitochondrial phospholipids that contain oxidized fatty acid substituents, and genetic or acquired iPLA2β-deficiency increases β-cell mitochondrial susceptibility to injury from ROS and predisposes to development of T2D. Interventions that attenuate the adverse effects of ROS on β-cell mitochondrial phospholipids may prevent or retard the development of T2D.
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Affiliation(s)
- Zhongmin A Ma
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Palliative Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA.
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Zhao Z, Choi J, Zhao C, Ma ZA. FTY720 normalizes hyperglycemia by stimulating β-cell in vivo regeneration in db/db mice through regulation of cyclin D3 and p57(KIP2). J Biol Chem 2011; 287:5562-73. [PMID: 22194608 DOI: 10.1074/jbc.m111.305359] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Loss of insulin-producing β-cell mass is a hallmark of type 2 diabetes in humans and diabetic db/db mice. Pancreatic β-cells can modulate their mass in response to a variety of physiological and pathophysiological cues. There are currently few effective therapeutic approaches targeting β-cell regeneration although some anti-diabetic drugs may positively affect β-cell mass. Here we show that oral administration of FTY720, a sphingosine 1-phosphate (S1P) receptor modulator, to db/db mice normalizes fasting blood glucose by increasing β-cell mass and blood insulin levels without affecting insulin sensitivity. Fasting blood glucose remained normal in the mice even after the drug was withdrawn after 23 weeks of treatment. The islet area in the pancreases of the FTY720-treated db/db mice was more than 2-fold larger than that of the untreated mice after 6 weeks of treatment. Furthermore, BrdU incorporation assays and Ki67 staining demonstrated cell proliferation in the islets and pancreatic duct areas. Finally, islets from the treated mice exhibited a significant decrease in the level of cyclin-dependent kinase inhibitor p57(KIP2) and an increase in the level of cyclin D3 as compared with those of untreated mice, which could be reversed by the inhibition of phosphatidylinositol 3-kinase (PI3K). Our findings reveal a novel network that controls β-cell regeneration in the obesity-diabetes setting by regulating cyclin D3 and p57(KIP2) expression through the S1P signaling pathway. Therapeutic strategies targeting this network may promote in vivo regeneration of β-cells in patients and prevent and/or cure type 2 diabetes.
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Affiliation(s)
- Zhengshan Zhao
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Palliative Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA
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Mitochondrial dysfunction and β-cell failure in type 2 diabetes mellitus. EXPERIMENTAL DIABETES RESEARCH 2011; 2012:703538. [PMID: 22110477 PMCID: PMC3216264 DOI: 10.1155/2012/703538] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 09/03/2011] [Indexed: 01/09/2023]
Abstract
Type 2 diabetes mellitus (T2DM) is the most common human endocrine disease and is characterized by peripheral insulin resistance and pancreatic islet β-cell failure. Accumulating evidence indicates that mitochondrial dysfunction is a central contributor to β-cell failure in the evolution of T2DM. As reviewed elsewhere, reactive oxygen species (ROS) produced by β-cell mitochondria as a result of metabolic stress activate several stress-response pathways. This paper focuses on mechanisms whereby ROS affect mitochondrial structure and function and lead to β-cell failure. ROS activate UCP2, which results in proton leak across the mitochondrial inner membrane, and this leads to reduced β-cell ATP synthesis and content, which is a critical parameter in regulating glucose-stimulated insulin secretion. In addition, ROS oxidize polyunsaturated fatty acids in mitochondrial cardiolipin and other phospholipids, and this impairs membrane integrity and leads to cytochrome c release into cytosol and apoptosis. Group VIA phospholipase A2 (iPLA2β) appears to be a component of a mechanism for repairing mitochondrial phospholipids that contain oxidized fatty acid substituents, and genetic or acquired iPLA2β-deficiency increases β-cell mitochondrial susceptibility to injury from ROS and predisposes to developing T2DM. Interventions that attenuate ROS effects on β-cell mitochondrial phospholipids might prevent or retard development of T2DM.
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Zhao Z, Wang J, Zhao C, Bi W, Yue Z, Ma ZA. Genetic ablation of PLA2G6 in mice leads to cerebellar atrophy characterized by Purkinje cell loss and glial cell activation. PLoS One 2011; 6:e26991. [PMID: 22046428 PMCID: PMC3203935 DOI: 10.1371/journal.pone.0026991] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 10/07/2011] [Indexed: 12/15/2022] Open
Abstract
Infantile neuroaxonal dystrophy (INAD) is a progressive, autosomal recessive neurodegenerative disease characterized by axonal dystrophy, abnormal iron deposition and cerebellar atrophy. This disease was recently mapped to PLA2G6, which encodes group VI Ca(2+)-independent phospholipase A(2) (iPLA(2) or iPLA(2)β). Here we show that genetic ablation of PLA2G6 in mice (iPLA(2)β(-/-)) leads to the development of cerebellar atrophy by the age of 13 months. Atrophied cerebella exhibited significant loss of Purkinje cells, as well as reactive astrogliosis, the activation of microglial cells, and the pronounced up-regulation of the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). Moreover, glial cell activation and the elevation in TNF-α and IL-1β expression occurred before apparent cerebellar atrophy. Our findings indicate that the absence of PLA2G6 causes neuroinflammation and Purkinje cell loss and ultimately leads to cerebellar atrophy. Our study suggests that iPLA(2)β(-/-) mice are a valuable model for cerebellar atrophy in INAD and that early anti-inflammatory therapy may help slow the progression of cerebellar atrophy in this deadly neurodegenerative disease.
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Affiliation(s)
- Zhengshan Zhao
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Palliative Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Jing Wang
- Department of Neurology, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Chunying Zhao
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Palliative Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Weina Bi
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Palliative Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Zhenyu Yue
- Department of Neurology, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Zhongmin Alex Ma
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Palliative Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
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Mancuso DJ, Sims HF, Yang K, Kiebish MA, Su X, Jenkins CM, Guan S, Moon SH, Pietka T, Nassir F, Schappe T, Moore K, Han X, Abumrad NA, Gross RW. Genetic ablation of calcium-independent phospholipase A2gamma prevents obesity and insulin resistance during high fat feeding by mitochondrial uncoupling and increased adipocyte fatty acid oxidation. J Biol Chem 2010; 285:36495-510. [PMID: 20817734 DOI: 10.1074/jbc.m110.115766] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Phospholipases are critical enzyme mediators participating in many aspects of cellular function through modulating the generation of lipid 2nd messengers, membrane physical properties, and cellular bioenergetics. Here, we demonstrate that mice null for calcium-independent phospholipase A(2)γ (iPLA(2)γ(-/-)) are completely resistant to high fat diet-induced weight gain, adipocyte hypertrophy, hyperinsulinemia, and insulin resistance, which occur in iPLA(2)γ(+/+) mice after high fat feeding. Notably, iPLA(2)γ(-/-) mice were lean, demonstrated abdominal lipodystrophy, and remained insulin-sensitive despite having a marked impairment in glucose-stimulated insulin secretion after high fat feeding. Respirometry of adipocyte explants from iPLA(2)γ(-/-) mice identified increased rates of oxidation of multiple different substrates in comparison with adipocyte explants from wild-type littermates. Shotgun lipidomics of adipose tissue from wild-type mice demonstrated the anticipated 2-fold increase in triglyceride content after high fat feeding. In sharp contrast, the adipocyte triglyceride content was identical in iPLA(2)γ(-/-) mice fed either a standard diet or a high fat diet. Respirometry of skeletal muscle mitochondria from iPLA(2)γ(-/-) mice demonstrated marked decreases in state 3 respiration using multiple substrates whose metabolism was uncoupled from ATP production. Shotgun lipidomics of skeletal muscle revealed a decreased content of cardiolipin with an altered molecular species composition thereby identifying the mechanism underlying mitochondrial uncoupling in the iPLA(2)γ(-/-) mouse. Collectively, these results identify iPLA(2)γ as an obligatory upstream enzyme that is necessary for efficient electron transport chain coupling and energy production through its participation in the alterations of cellular bioenergetics that promote the development of the metabolic syndrome.
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Affiliation(s)
- David J Mancuso
- Division of Bioorganic Chemistry and Molecular Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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29
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Zhao Z, Zhang X, Zhao C, Choi J, Shi J, Song K, Turk J, Ma ZA. Protection of pancreatic beta-cells by group VIA phospholipase A(2)-mediated repair of mitochondrial membrane peroxidation. Endocrinology 2010; 151:3038-48. [PMID: 20463052 PMCID: PMC2903934 DOI: 10.1210/en.2010-0016] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Mitochondrial production of reactive oxygen species and oxidation of cardiolipin are key events in initiating apoptosis. We reported that group VIA Ca(2+)-independent phospholipase A(2) (iPLA(2)beta) localizes in and protects beta-cell mitochondria from oxidative damage during staurosporine-induced apoptosis. Here, we used iPLA(2)beta-null (iPLA(2)beta(-/-)) mice to investigate the role of iPLA(2)beta in the repair of mitochondrial membranes. We show that islets isolated from iPLA(2)beta(-/-) mice are more sensitive to staurosporine-induced apoptosis than those from wild-type littermates and that 2 wk of daily ip administration of staurosporine to iPLA(2)beta(-/-) mice impairs both the animals' glucose tolerance and glucose-stimulated insulin secretion by their pancreatic islets. Moreover, the iPLA(2)beta inhibitor bromoenol lactone caused mitochondrial membrane peroxidation and cytochrome c release, and these effects were reversed by N-acetyl cysteine. The mitochondrial antioxidant N-t-butyl hydroxylamine blocked staurosporine-induced cytochrome c release and caspase-3 activation in iPLA(2)beta(-/-) islets. Furthermore, the collapse of mitochondrial membrane potential in INS-1 insulinoma cells caused by high glucose and fatty acid levels was attenuated by overexpressing iPLA(2)beta. Interestingly, iPLA(2)beta was expressed only at low levels in islet beta-cells from obesity- and diabetes-prone db/db mice. These findings support the hypothesis that iPLA(2)beta is important in repairing oxidized mitochondrial membrane components (e.g. cardiolipin) and that this prevents cytochrome c release in response to stimuli that otherwise induce apoptosis. The low iPLA(2)beta expression level in db/db mouse beta-cells may render them vulnerable to injury by reactive oxygen species.
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Affiliation(s)
- Zhengshan Zhao
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, One Gustave L. Levy Place, Mount Sinai School of Medicine, New York, NY 10029, USA
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McIntosh CHS, Widenmaier S, Kim SJ. Pleiotropic actions of the incretin hormones. VITAMINS AND HORMONES 2010; 84:21-79. [PMID: 21094896 DOI: 10.1016/b978-0-12-381517-0.00002-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The insulin secretory response to a meal results largely from glucose stimulation of the pancreatic islets and both direct and indirect (autonomic) glucose-dependent stimulation by incretin hormones released from the gastrointestinal tract. Two incretins, Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), have so far been identified. Localization of the cognate G protein-coupled receptors for GIP and GLP-1 revealed that they are present in numerous tissues in addition to the endocrine pancreas, including the gastrointestinal, cardiovascular, central nervous and autonomic nervous systems (ANSs), adipose tissue, and bone. At these sites, the incretin hormones exert a range of pleiotropic effects, many of which contribute to the integration of processes involved in the regulation of food intake, and nutrient and mineral processing and storage. From detailed studies at the cellular and molecular level, it is also evident that both incretin hormones act via multiple signal transduction pathways that regulate both acute and long-term cell function. Here, we provide an overview of current knowledge relating to the physiological roles of GIP and GLP-1, with specific emphasis on their modes of action on islet hormone secretion, β-cell proliferation and survival, central and autonomic neuronal function, gastrointestinal motility, and glucose and lipid metabolism. However, it is emphasized that despite intensive research on the various body systems, in many cases there is uncertainty as to the pathways by which the incretins mediate their pleiotropic effects and only a rudimentary understanding of the underlying cellular mechanisms involved, and these are challenges for the future.
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Affiliation(s)
- Christopher H S McIntosh
- Department of Cellular & Physiological Sciences and the Diabetes Research Group, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
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Zhao Z, Zhao C, Zhang XH, Zheng F, Cai W, Vlassara H, Ma ZA. Advanced glycation end products inhibit glucose-stimulated insulin secretion through nitric oxide-dependent inhibition of cytochrome c oxidase and adenosine triphosphate synthesis. Endocrinology 2009; 150:2569-76. [PMID: 19246537 PMCID: PMC2689792 DOI: 10.1210/en.2008-1342] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Advanced glycation end products (AGEs) are implicated in diabetic complications. However, their role in beta-cell dysfunction is less clear. In this study we examined the effects of AGEs on islet function in mice and in isolated islets. AGE-BSA or BSA was administered ip to normal mice twice a day for 2 wk. We showed that AGE-BSA-treated mice exhibited significantly higher glucose levels and lower insulin levels in response to glucose challenge than did BSA-treated mice, although there were no significant differences in insulin sensitivity and islet morphology between two groups. Glucose-stimulated insulin secretion by islets of the AGE-BSA-treated mice or AGE-BSA-treated normal islets was significantly lower than that by islets isolated from the BSA-treated mice or BSA-treated normal islets. Furthermore, AGE treatment of islet beta-cells inhibited ATP production, and glimepiride, a sulfonylurea derivative, restored glucose-stimulated insulin secretion. Further investigation indicated that AGEs inhibited cytochrome c oxidase activity by inducing the expression of inducible nitric oxide synthase (iNOS). Blocking the formation of nitric oxide with an iNOS selective inhibitor aminoguanidine reversed the inhibitory effects of AGEs on ATP production and insulin secretion. We conclude that AGEs inhibit cytochrome c oxidase and ATP production, leading to the impairment of glucose-stimulated insulin secretion through iNOS-dependent nitric oxide production.
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Affiliation(s)
- Zhengshan Zhao
- Department of Geriatrics and Adult Development, Division of Experimental Diabetes and Aging, Mount Sinai School of Medicine, New York, New York 10029, USA
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Chapter 15 Glucose‐Dependent Insulinotropic Polypeptide (Gastric Inhibitory Polypeptide; GIP). VITAMINS AND HORMONES 2009; 80:409-71. [DOI: 10.1016/s0083-6729(08)00615-8] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Zhang XH, Zhao C, Ma ZA. The increase of cell-membranous phosphatidylcholines containing polyunsaturated fatty acid residues induces phosphorylation of p53 through activation of ATR. J Cell Sci 2008; 120:4134-43. [PMID: 18032786 DOI: 10.1242/jcs.015834] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The G1 phase of the cell cycle is marked by the rapid turnover of phospholipids. This turnover is regulated by CTP:phosphocholine-cytidylyltransferase (CCT) and group VIA Ca(2+)-independent-phospholipase A(2) (iPLA(2)). We previously reported that inhibition of iPLA(2) arrests cells in G1 phase of the cell cycle by activating the p53-p21 checkpoint. Here we further characterize the mechanism of p53 activation. We show that specific inhibition of iPLA(2) induces a time dependent phosphorylation of Ser15 in p53 in the absence of DNA damage. This phosphorylation requires the kinase ataxia-telangiectasia and Rad-3-related (ATR) but not the ataxia-telangiectasia-mutated (ATM) kinase. Moreover, we identify in cell membranes a significant increase of phosphatidylcholines (PCs) containing chains of polyunsaturated fatty acids and a decrease of PCs containing saturated fatty acids in response to inhibition of iPLA(2). The time course of phosphorylation of Ser15 in p53 correlates with increasing levels of PCs containing polyunsaturated fatty acids. We further demonstrate that the PCs with linoleic acid in their sn-2 position (18:2n6) induce phosphorylation of Ser15 in p53 in an ATR-dependent manner. Our findings establish that cells can regulate the levels of polyunsaturated fatty acids in phospholipids through iPLA(2)-mediated deacylation of PCs. Disruption of this regulation increases the proportions of PCs containing polyunsaturated fatty acids and activates the ATR-p53 signalling pathway.
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Affiliation(s)
- Xu Hannah Zhang
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, NY 10029, USA
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34
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Bao S, Jacobson DA, Wohltmann M, Bohrer A, Jin W, Philipson LH, Turk J. Glucose homeostasis, insulin secretion, and islet phospholipids in mice that overexpress iPLA2beta in pancreatic beta-cells and in iPLA2beta-null mice. Am J Physiol Endocrinol Metab 2008; 294:E217-29. [PMID: 17895289 PMCID: PMC2268609 DOI: 10.1152/ajpendo.00474.2007] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Studies with genetically modified insulinoma cells suggest that group VIA phospholipase A(2) (iPLA(2)beta) participates in amplifying glucose-induced insulin secretion. INS-1 insulinoma cells that overexpress iPLA(2)beta, for example, exhibit amplified insulin-secretory responses to glucose and cAMP-elevating agents. To determine whether similar effects occur in whole animals, we prepared transgenic (TG) mice in which the rat insulin 1 promoter (RIP) drives iPLA(2)beta overexpression, and two characterized TG mouse lines exhibit similar phenotypes. Their pancreatic islet iPLA(2)beta expression is increased severalfold, as reflected by quantitative PCR of iPLA(2)beta mRNA, immunoblotting of iPLA(2)beta protein, and iPLA(2)beta enzymatic activity. Immunofluorescence microscopic studies of pancreatic sections confirm iPLA(2)beta overexpression in RIP-iPLA(2)beta-TG islet beta-cells without obviously perturbed islet morphology. Male RIP-iPLA(2)beta-TG mice exhibit lower blood glucose and higher plasma insulin concentrations than wild-type (WT) mice when fasting and develop lower blood glucose levels in glucose tolerance tests, but WT and TG blood glucose levels do not differ in insulin tolerance tests. Islets from male RIP-iPLA(2)beta-TG mice exhibit greater amplification of glucose-induced insulin secretion by a cAMP-elevating agent than WT islets. In contrast, islets from male iPLA(2)beta-null mice exhibit blunted insulin secretion, and those mice have impaired glucose tolerance. Arachidonate incorporation into and the phospholipid composition of RIP-iPLA(2)beta-TG islets are normal, but they exhibit reduced Kv2.1 delayed rectifier current and prolonged glucose-induced action potentials and elevations of cytosolic Ca(2+) concentration that suggest a molecular mechanism for the physiological role of iPLA(2)beta to amplify insulin secretion.
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MESH Headings
- Animals
- Arachidonic Acid/metabolism
- Blood Glucose/metabolism
- Blood Glucose/physiology
- Blotting, Western
- Calcium/physiology
- Cell Line, Tumor
- DNA, Complementary/biosynthesis
- DNA, Complementary/genetics
- Fasting/metabolism
- Gene Expression Regulation, Enzymologic/physiology
- Genotype
- Glucose Tolerance Test
- Group IV Phospholipases A2/biosynthesis
- Group IV Phospholipases A2/genetics
- Homeodomain Proteins/genetics
- Homeostasis/physiology
- Insulin/blood
- Insulin/metabolism
- Insulin Secretion
- Insulin-Secreting Cells/metabolism
- Insulinoma/metabolism
- Islets of Langerhans/metabolism
- Kv1.2 Potassium Channel/metabolism
- Mice
- Mice, Knockout
- Mice, Transgenic
- Microscopy, Fluorescence
- Pancreatic Neoplasms/metabolism
- Patch-Clamp Techniques
- Phospholipids/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Spectrometry, Mass, Electrospray Ionization
- Trans-Activators/genetics
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Affiliation(s)
- Shunzhong Bao
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA.
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Bacová Z, Orecná M, Hafko R, Strbák V. Cell swelling-induced signaling for insulin secretion bypasses steps involving G proteins and PLA2 and is N-ethylmaleimide insensitive. Cell Physiol Biochem 2007; 20:387-96. [PMID: 17762166 DOI: 10.1159/000107523] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2007] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND This study was undertaken to examine putative mechanisms of calcium independent signal transduction pathway of cell swelling-induced insulin secretion. METHODS The role of phospholipase A(2), G proteins, and soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) in insulin secretion induced by 30% hypotonic medium was studied using isolated rat pancreatic islets. RESULTS In contrast to glucose stimulation, osmotically induced insulin secretion from pancreatic islets was not inhibited by 10 micromol/l bromoenol lactone, an iPLA(2) (Ca(2+) independent phospholipase) inhibitor. Similarly, preincubation of islets for 20 hours with 25 microg/ml mycophenolic acid to inhibit GTP synthesis fully abolished glucose-induced insulin secretion but was without effect on hypotonicity stimulated insulin release. Glucose-induced insulin secretion was prevented by preincubation with 20 nmol/l tetanus toxin (TeTx), a metalloprotease inactivating soluble SNARE. Cell swelling-induced insulin secretion was inhibited by TeTx in the presence of calcium ions but not in calcium depleted medium. The presence of N-ethylmaleimide (NEM, 5 mmol/l, another inhibitor of SNARE proteins) in the medium resulted in high basal insulin secretion and lacking response to glucose stimulation. In contrast, high basal insulin secretion from NEM treated islets further increased after hypotonic stimulation. CONCLUSION G proteins and iPLA(2) - putative mediators of Ca(2+) independent signaling pathway participate in glucose but not in hypotonicity-induced insulin secretion. Hypotonicity-induced insulin secretion is sensitive to clostridial neurotoxin TeTx but is resistant to NEM.
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Affiliation(s)
- Zuzana Bacová
- Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovakia
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36
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Larsson-Nyrén G, Grapengiesser E, Hellman B. Phospholipase A2 is important for glucose induction of rhythmic Ca2+ signals in pancreatic beta cells. Pancreas 2007; 35:173-9. [PMID: 17632325 DOI: 10.1097/mpa.0b013e318053e022] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES Pancreatic beta cells respond to glucose stimulation with pulses of insulin release generated by oscillatory rises of the cytoplasmic Ca2+ concentration ([Ca2+]i). The observation that exposure to external ATP and other activators of cytoplasmic phospholipase A2 (cPLA2) rapidly induces rises of [Ca2+]i similar to ordinary oscillations made it important to analyze whether suppression of the cPLA2 activity affects glucose-induced [Ca2+]i rhythmicity in pancreatic beta cells. METHODS Ratiometric fura-2 technique was used for measuring [Ca2+]i in single beta cells and small aggregates prepared from ob/ob mouse islets. RESULTS Testing the effects of different inhibitors of cPLA2 in the presence of 20 mM glucose, it was found that N-(p-amylcinnamoyl)anthranilic acid (ACA) removed the oscillations at a concentration of 25 microM, arachidonyl trifluoromethyl ketone (AACOCF3) at 10 microM, and bromoenol lactone (BEL) at 10 to 15 microM. Withdrawal of ACA and BEL resulted in reappearance of the oscillations. Suppression of the arachidonic acid production by addition of 5 microM of the diacylglycerol lipase inhibitor 1,6-bis-(cyclohexyloximinocarbonylamino)-hexane (RHC 80267) effectively removed the [Ca2+]i oscillations, an effect reversed by removal of the inhibitor or addition of 100 microM tolbutamide. Suppression of the arachidonic acid production had a restrictive influence also on the transients of [Ca2+]i supposed to synchronize the beta-cell rhythmicity. Although less sensitive than the oscillations, most transients disappeared during exposure to 50 microM ACA or 35 microM RHC 80267. CONCLUSIONS The results support the idea that cyclic variations of cPLA2 activity are important for the generation and synchronization of the beta-cell [Ca2+]i oscillations responsible for pulsatile release of insulin.
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Affiliation(s)
- Gerd Larsson-Nyrén
- Department of Integrative Medical Biology, Section for Histology and Cell Biology, University of Umeå University, Umeå, Sweden.
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37
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Bao S, Li Y, Lei X, Wohltmann M, Jin W, Bohrer A, Semenkovich CF, Ramanadham S, Tabas I, Turk J. Attenuated free cholesterol loading-induced apoptosis but preserved phospholipid composition of peritoneal macrophages from mice that do not express group VIA phospholipase A2. J Biol Chem 2007; 282:27100-27114. [PMID: 17627946 PMCID: PMC2044506 DOI: 10.1074/jbc.m701316200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mouse macrophages undergo ER stress and apoptosis upon free cholesterol loading (FCL). We recently generated iPLA(2)beta-null mice, and here we demonstrate that iPLA(2)beta-null macrophages have reduced sensitivity to FCL-induced apoptosis, although they and wild-type (WT) cells exhibit similar increases in the transcriptional regulator CHOP. iPLA(2)beta-null macrophages are also less sensitive to apoptosis induced by the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin and the scavenger receptor A ligand fucoidan, and restoring iPLA(2)betaexpression with recombinant adenovirus increases apoptosis toward WT levels. WT and iPLA(2)beta-null macrophages incorporate [(3)H]arachidonic acid ([(3)H]AA]) into glycerophosphocholine lipids equally rapidly and exhibit identical zymosan-induced, cPLA(2)alpha-catalyzed [(3)H]AA release. In contrast, although WT macrophages exhibit robust [(3)H]AA release upon FCL, this is attenuated in iPLA(2)beta-null macrophages and increases toward WT levels upon restoring iPLA(2)beta expression. Recent reports indicate that iPLA(2)beta modulates mitochondrial cytochrome c release, and we find that thapsigargin and fucoidan induce mitochondrial phospholipid loss and cytochrome c release into WT macrophage cytosol and that these events are blunted in iPLA(2)beta-null cells. Immunoblotting studies indicate that iPLA(2)beta associates with mitochondria in macrophages subjected to ER stress. AA incorporation into glycerophosphocholine lipids is unimpaired in iPLA(2)beta-null macrophages upon electrospray ionization-tandem mass spectrometry analyses, and their complex lipid composition is similar to WT cells. These findings suggest that iPLA(2)beta participates in ER stress-induced macrophage apoptosis caused by FCL or thapsigargin but that deletion of iPLA(2)beta does not impair macrophage arachidonate incorporation or phospholipid composition.
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Affiliation(s)
- Shunzhong Bao
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Yankun Li
- Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032
| | - Xiaoyong Lei
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Mary Wohltmann
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Wu Jin
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Alan Bohrer
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Clay F Semenkovich
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Sasanka Ramanadham
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Ira Tabas
- Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032
| | - John Turk
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
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Jacobson DA, Weber CR, Bao S, Turk J, Philipson LH. Modulation of the pancreatic islet beta-cell-delayed rectifier potassium channel Kv2.1 by the polyunsaturated fatty acid arachidonate. J Biol Chem 2007; 282:7442-9. [PMID: 17197450 PMCID: PMC2044499 DOI: 10.1074/jbc.m607858200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucose stimulates both insulin secretion and hydrolysis of arachidonic acid (AA) esterified in membrane phospholipids of pancreatic islet beta-cells, and these processes are amplified by muscarinic agonists. Here we demonstrate that nonesterified AA regulates the biophysical activity of the pancreatic islet beta-cell-delayed rectifier channel, Kv2.1. Recordings of Kv2.1 currents from INS-1 insulinoma cells incubated with AA (5 mum) and subjected to graded degrees of depolarization exhibit a significantly shorter time-to-peak current interval than do control cells. AA causes a rapid decay and reduced peak conductance of delayed rectifier currents from INS-1 cells and from primary beta-cells isolated from mouse, rat, and human pancreatic islets. Stimulating mouse islets with AA results in a significant increase in the frequency of glucose-induced [Ca(2+)] oscillations, which is an expected effect of Kv2.1 channel blockade. Stimulation with concentrations of glucose and carbachol that accelerate hydrolysis of endogenous AA from islet phosphoplipids also results in accelerated Kv2.1 inactivation and a shorter time-to-peak current interval. Group VIA phospholipase A(2) (iPLA(2)beta) hydrolyzes beta-cell membrane phospholipids to release nonesterified fatty acids, including AA, and inhibiting iPLA(2)beta prevents the muscarinic agonist-induced accelerated Kv2.1 inactivation. Furthermore, glucose and carbachol do not significantly affect Kv2.1 inactivation in beta-cells from iPLA(2)beta(-/-) mice. Stably transfected INS-1 cells that overexpress iPLA(2)beta hydrolyze phospholipids more rapidly than control INS-1 cells and also exhibit an increase in the inactivation rate of the delayed rectifier currents. These results suggest that Kv2.1 currents could be dynamically modulated in the pancreatic islet beta-cell by phospholipase-catalyzed hydrolysis of membrane phospholipids to yield non-esterified fatty acids, such as AA, that facilitate Ca(2+) entry and insulin secretion.
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Affiliation(s)
- David A. Jacobson
- Department of Medicine, University of Chicago, Chicago, Illinois 60637
| | | | - Shunzhong Bao
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - John Turk
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
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Nolan CJ, Madiraju MSR, Delghingaro-Augusto V, Peyot ML, Prentki M. Fatty acid signaling in the beta-cell and insulin secretion. Diabetes 2006; 55 Suppl 2:S16-23. [PMID: 17130640 DOI: 10.2337/db06-s003] [Citation(s) in RCA: 300] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Fatty acids (FAs) and other lipid molecules are important for many cellular functions, including vesicle exocytosis. For the pancreatic beta-cell, while the presence of some FAs is essential for glucose-stimulated insulin secretion, FAs have enormous capacity to amplify glucose-stimulated insulin secretion, which is particularly operative in situations of beta-cell compensation for insulin resistance. In this review, we propose that FAs do this via three interdependent processes, which we have assigned to a "trident model" of beta-cell lipid signaling. The first two arms of the model implicate intracellular metabolism of FAs, whereas the third is related to membrane free fatty acid receptor (FFAR) activation. The first arm involves the AMP-activated protein kinase/malonyl-CoA/long-chain acyl-CoA (LC-CoA) signaling network in which glucose, together with other anaplerotic fuels, increases cytosolic malonyl-CoA, which inhibits FA partitioning into oxidation, thus increasing the availability of LC-CoA for signaling purposes. The second involves glucose-responsive triglyceride (TG)/free fatty acid (FFA) cycling. In this pathway, glucose promotes LC-CoA esterification to complex lipids such as TG and diacylglycerol, concomitant with glucose stimulation of lipolysis of the esterification products, with renewal of the intracellular FFA pool for reactivation to LC-CoA. The third arm involves FFA stimulation of the G-protein-coupled receptor GPR40/FFAR1, which results in enhancement of glucose-stimulated accumulation of cytosolic Ca2+ and consequently insulin secretion. It is possible that FFA released by the lipolysis arm of TG/FFA cycling is partly "secreted" and, via an autocrine/paracrine mechanism, is additive to exogenous FFAs in activating the FFAR1 pathway. Glucose-stimulated release of arachidonic acid from phospholipids by calcium-independent phospholipase A2 and/or from TG/FFA cycling may also be involved. Improved knowledge of lipid signaling in the beta-cell will allow a better understanding of the mechanisms of beta-cell compensation and failure in diabetes.
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Schaloske RH, Dennis EA. The phospholipase A2 superfamily and its group numbering system. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1246-59. [PMID: 16973413 DOI: 10.1016/j.bbalip.2006.07.011] [Citation(s) in RCA: 637] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 07/05/2006] [Accepted: 07/29/2006] [Indexed: 01/07/2023]
Abstract
The superfamily of phospholipase A(2) (PLA(2)) enzymes currently consists of 15 Groups and many subgroups and includes five distinct types of enzymes, namely the secreted PLA(2)s (sPLA(2)), the cytosolic PLA(2)s (cPLA(2)), the Ca(2+) independent PLA(2)s (iPLA(2)), the platelet-activating factor acetylhydrolases (PAF-AH), and the lysosomal PLA(2)s. In 1994, we established the systematic Group numbering system for these enzymes. Since then, the PLA(2) superfamily has grown continuously and over the intervening years has required several updates of this Group numbering system. Since our last update, a number of new PLA(2)s have been discovered and are now included. Additionally, tools for the investigation of PLA(2)s and approaches for distinguishing between the different Groups are described.
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Affiliation(s)
- Ralph H Schaloske
- Department of Pharmacology, School of Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0601, USA
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Bao S, Song H, Wohltmann M, Ramanadham S, Jin W, Bohrer A, Turk J. Insulin secretory responses and phospholipid composition of pancreatic islets from mice that do not express Group VIA phospholipase A2 and effects of metabolic stress on glucose homeostasis. J Biol Chem 2006; 281:20958-20973. [PMID: 16732058 PMCID: PMC2044498 DOI: 10.1074/jbc.m600075200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Studies involving pharmacologic or molecular biologic manipulation of Group VIA phospholipase A(2) (iPLA(2)beta) activity in pancreatic islets and insulinoma cells suggest that iPLA(2)beta participates in insulin secretion. It has also been suggested that iPLA(2)beta is a housekeeping enzyme that regulates cell 2-lysophosphatidylcholine (LPC) levels and arachidonate incorporation into phosphatidylcholine (PC). We have generated iPLA(2)beta-null mice by homologous recombination and have reported that they exhibit reduced male fertility and defective motility of spermatozoa. Here we report that pancreatic islets from iPLA(2)beta-null mice have impaired insulin secretory responses to D-glucose and forskolin. Electrospray ionization mass spectrometric analyses indicate that the abundance of arachidonate-containing PC species of islets, brain, and other tissues from iPLA(2)beta-null mice is virtually identical to that of wild-type mice, and no iPLA(2)beta mRNA was observed in any tissue from iPLA(2)beta-null mice at any age. Despite the insulin secretory abnormalities of isolated islets, fasting and fed blood glucose concentrations of iPLA(2)beta-null and wild-type mice are essentially identical under normal circumstances, but iPLA(2)beta-null mice develop more severe hyperglycemia than wild-type mice after administration of multiple low doses of the beta-cell toxin streptozotocin, suggesting an impaired islet secretory reserve. A high fat diet also induces more severe glucose intolerance in iPLA(2)beta-null mice than in wild-type mice, but PLA(2)beta-null mice have greater responsiveness to exogenous insulin than do wild-type mice fed a high fat diet. These and previous findings thus indicate that iPLA(2)beta-null mice exhibit phenotypic abnormalities in pancreatic islets in addition to testes and macrophages.
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Affiliation(s)
- Shunzhong Bao
- Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Haowei Song
- Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Mary Wohltmann
- Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Sasanka Ramanadham
- Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Wu Jin
- Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Alan Bohrer
- Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - John Turk
- Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110.
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Fensome-Green A, Stannard N, Li M, Bolsover S, Cockcroft S. Bromoenol lactone, an inhibitor of Group V1A calcium-independent phospholipase A2 inhibits antigen-stimulated mast cell exocytosis without blocking Ca2+ influx. Cell Calcium 2006; 41:145-53. [PMID: 16854462 DOI: 10.1016/j.ceca.2006.06.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Calcium-independent phospholipase A2 (iPLA2beta) has recently been suggested to regulate Ca2+ entry by activating store-operated Ca2+ channels. These studies have been conducted in mast cells using thapsigargin to deplete intracellular stores. In RBL 2H3 and bone marrow-derived mast cells (BMMCs), Ca2+ entry is critical for exocytosis and therefore we have examined whether the proposed mechanism would be relevant when a physiological stimulus is applied to these cells. Using an iPLA2beta antibody, we demonstrate that the 84kDa iPLA2beta is expressed in these mast cells. As bromoenol lactone (BEL) is a suicide-based irreversible inhibitor of iPLA2beta it was used to probe this potential mechanism. We observe inhibition of exocytosis stimulated either with antigen or with thapsigargin. However, BEL also inhibits exocytosis when stimulated using a Ca2+ ionophore A23187, which passively transports Ca2+ down a concentration gradient and also in permeabilised mast cells where Ca2+ entry is no longer relevant. Moreover, BEL has only a minor effect on antigen- or thapsigargin-stimulated Ca2+ signalling, both the release from internal stores and sustained elevation due to Ca2+ influx. These results cast doubt on the proposed mechanism involving iPLA2beta required for Ca2+ entry. Although inhibition of exocytosis by BEL could imply a requirement for iPLA2beta activation for exocytosis, an alternative explanation is that BEL inactivates other target proteins required for exocytosis.
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Affiliation(s)
- Amanda Fensome-Green
- Department of Physiology, University College London, Rockefeller Building, 21 University Street, London WC1E 6JJ, United Kingdom
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Woolcott OO, Gustafsson AJ, Dzabic M, Pierro C, Tedeschi P, Sandgren J, Bari MR, Nguyen KH, Bianchi M, Rakonjac M, Rådmark O, Ostenson CG, Islam MS. Arachidonic acid is a physiological activator of the ryanodine receptor in pancreatic β-cells. Cell Calcium 2006; 39:529-37. [PMID: 16620964 DOI: 10.1016/j.ceca.2006.02.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2005] [Revised: 02/09/2006] [Accepted: 02/26/2006] [Indexed: 11/23/2022]
Abstract
Pancreatic beta-cells have ryanodine receptors but little is known about their physiological regulation. Previous studies have shown that arachidonic acid releases Ca(2+) from intracellular stores in beta-cells but the identity of the channels involved in the Ca(2+) release has not been elucidated. We studied the mechanism by which arachidonic acid induces Ca(2+) concentration changes in pancreatic beta-cells. Cytosolic free Ca(2+) concentration was measured in fura-2-loaded INS-1E cells and in primary beta-cells from Wistar rats. The increase of cytosolic Ca(2+) concentration induced by arachidonic acid (150microM) was due to both Ca(2+) release from intracellular stores and influx of Ca(2+) from extracellular medium. 5,8,11,14-Eicosatetraynoic acid, a non-metabolizable analogue of arachidonic acid, mimicked the effect of arachidonic acid, indicating that arachidonic acid itself mediated Ca(2+) increase. The Ca(2+) release induced by arachidonic acid was from the endoplasmic reticulum since it was blocked by thapsigargin. 2-Aminoethyl diphenylborinate (50microM), which is known to inhibit 1,4,5-inositol-triphosphate-receptors, did not block Ca(2+) release by arachidonic acid. However, ryanodine (100microM), a blocker of ryanodine receptors, abolished the effect of arachidonic acid on Ca(2+) release in both types of cells. These observations indicate that arachidonic acid is a physiological activator of ryanodine receptors in beta-cells.
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Affiliation(s)
- Orison O Woolcott
- Karolinska Institutet, Södersjukhuset, Department of Internal Medicine, Research Center, SE-118 83 Stockholm, Sweden.
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Seleznev K, Zhao C, Zhang XH, Song K, Ma ZA. Calcium-independent phospholipase A2 localizes in and protects mitochondria during apoptotic induction by staurosporine. J Biol Chem 2006; 281:22275-22288. [PMID: 16728389 PMCID: PMC1829309 DOI: 10.1074/jbc.m604330200] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondria-mediated production of reactive oxygen species (ROS) plays a key role in apoptosis. Mitochondrial phospholipid cardiolipin molecules are likely the main target of ROS because they are particularly rich in polyunsaturated fatty acids. They are also located in the inner mitochondrial membrane near the ROS-producing sites. Under physiological conditions mitochondria can repair peroxidative damage in part through a remodeling mechanism via the deacylation-reacylation cycle mediated by phospholipase A2 (PLA2) and acyl-coenzyme A-dependent monolysocardiolipin acyltransferase. Here we investigate whether group VIA Ca2+-independent PLA2 (iPLA2) plays a role in the protection of mitochondrial function from damage caused by mitochondrially generated ROS during apoptotic induction by staurosporine (STS). We show that iPLA2-expressing cells were relatively resistant to STS-induced apoptosis. iPLA2 localized to mitochondria even before apoptotic induction, and most iPLA2-associated mitochondria were intact in apoptotic resistant cells. Expression of iPLA2 in INS-1 cells prevented the loss of mitochondrial membrane potential, attenuated the release of cytochrome c, Smac/DIABLO, and apoptosis inducing factor from mitochondria, and reduced mitochondrial reactive oxygen species production. Inhibition of caspase 8 has little effect on STS-induced apoptosis in INS-1 cells. Finally, we found that STS down-regulated endogenous iPLA2 transcription in both INS-1 and iPLA2-expressing INS-1 cells without affecting the expression of group IV Ca2+-dependent PLA2. Together, our data indicate that iPLA2 is important for the protection of mitochondrial function from oxidative damage during apoptotic induction. Down-regulation of endogenous iPLA2 by STS may result in the loss of mitochondrial membrane repair functions and lead to mitochondrial failure and apoptosis.
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Affiliation(s)
- Konstantin Seleznev
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, New York 10029
| | - Chunying Zhao
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, New York 10029
| | - Xu Hannah Zhang
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, New York 10029
| | - Keying Song
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, New York 10029
| | - Zhongmin Alex Ma
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, New York 10029.
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Zhang XH, Zhao C, Seleznev K, Song K, Manfredi JJ, Ma ZA. Disruption of G1-phase phospholipid turnover by inhibition of Ca2+-independent phospholipase A2 induces a p53-dependent cell-cycle arrest in G1 phase. J Cell Sci 2006; 119:1005-15. [PMID: 16492706 PMCID: PMC2917323 DOI: 10.1242/jcs.02821] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The G1 phase of the cell cycle is characterized by a high rate of membrane phospholipid turnover. Cells regulate this turnover by coordinating the opposing actions of CTP:phosphocholine cytidylyltransferase and the group VI Ca2+-independent phospholipase A2 (iPLA2). However, little is known about how such turnover affects cell-cycle progression. Here, we show that G1-phase phospholipid turnover is essential for cell proliferation. Specific inhibition of iPLA2 arrested cells in the G1 phase of the cell cycle. This G1-phase arrest was associated with marked upregulation of the tumour suppressor p53 and the expression of cyclin-dependent kinase inhibitor p21cip1. Inactivation of iPLA2 failed to arrest p53-deficient HCT cells in the G1 phase and caused massive apoptosis of p21-deficient HCT cells, suggesting that this G1-phase arrest requires activation of p53 and expression of p21cip1. Furthermore, downregulation of p53 by siRNA in p21-deficient HCT cells reduced the cell death, indicating that inhibition of iPLA2 induced p53-dependent apoptosis in the absence of p21cip1. Thus, our study reveals hitherto unrecognized cooperation between p53 and iPLA2 to monitor membrane-phospholipid turnover in G1 phase. Disrupting the G1-phase phospholipid turnover by inhibition of iPLA2 activates the p53-p21cip1 checkpoint mechanism, thereby blocking the entry of G1-phase cells into S phase.
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Affiliation(s)
- Xu Hannah Zhang
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Chunying Zhao
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Konstantin Seleznev
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Keying Song
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - James J. Manfredi
- Department of Oncological Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Zhongmin Alex Ma
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, NY 10029, USA
- Author for correspondence
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Gong MC, Arbogast S, Guo Z, Mathenia J, Su W, Reid MB. Calcium-independent phospholipase A2modulates cytosolic oxidant activity and contractile function in murine skeletal muscle cells. J Appl Physiol (1985) 2006; 100:399-405. [PMID: 16166238 DOI: 10.1152/japplphysiol.00873.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Phospholipase A2(PLA2) activity supports production of reactive oxygen species (ROS) by mammalian cells. In skeletal muscle, endogenous ROS modulate the force of muscle contraction. We tested the hypothesis that skeletal muscle cells constitutively express the calcium-independent PLA2(iPLA2) isoform and that iPLA2modulates both cytosolic oxidant activity and contractile function. Experiments utilized differentiated C2C12myotubes and a panel of striated muscles isolated from adult mice. Muscle preparations were processed for measurement of mRNA by real-time PCR, protein by immunoblot, cytosolic oxidant activity by the dichlorofluorescein oxidation assay, and contractile function by in vitro testing. We found that iPLA2was constitutively expressed by all muscles tested (myotubes, diaphragm, soleus, extensor digitorum longus, gastrocnemius, heart) and that mRNA and protein levels were generally similar among muscles. Selective iPLA2blockade by use of bromoenol lactone (10 μM) decreased cytosolic oxidant activity in myotubes and intact soleus muscle fibers. iPLA2blockade also inhibited contractile function of unfatigued soleus muscles, shifting the force-frequency relationship rightward and depressing force production during acute fatigue. Each of these changes could be reproduced by selective depletion of superoxide anions using superoxide dismutase (1 kU/ml). These findings suggest that constitutively expressed iPLA2modulates oxidant activity in skeletal muscle fibers by supporting ROS production, thereby influencing contractile properties and fatigue characteristics.
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Affiliation(s)
- Ming C Gong
- Dept. of Physiology, Univ. of Kentucky Medical Center, 800 Rose St., Lexington, KY 40536, USA
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Bao S, Bohrer A, Ramanadham S, Jin W, Zhang S, Turk J. Effects of stable suppression of Group VIA phospholipase A2 expression on phospholipid content and composition, insulin secretion, and proliferation of INS-1 insulinoma cells. J Biol Chem 2006; 281:187-98. [PMID: 16286468 PMCID: PMC2156593 DOI: 10.1074/jbc.m509105200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Studies involving pharmacologic inhibition or transient reduction of Group VIA phospholipase A2 (iPLA2beta) expression have suggested that it is a housekeeping enzyme that regulates cell 2-lysophosphatidylcholine (LPC) levels, rates of arachidonate incorporation into phospholipids, and degradation of excess phosphatidylcholine (PC). In insulin-secreting islet beta-cells and some other cells, in contrast, iPLA2beta signaling functions have been proposed. Using retroviral vectors, we prepared clonal INS-1 beta-cell lines in which iPLA2beta expression is stably suppressed by small interfering RNA. Two such iPLA2beta knockdown (iPLA2beta-KD) cell lines express less than 20% of the iPLA2beta of control INS-1 cell lines. The iPLA2beta-KD INS-1 cells exhibit impaired insulin secretory responses and reduced proliferation rates. Electrospray ionization mass spectrometric analyses of PC and LPC species that accumulate in INS-1 cells cultured with arachidonic acid suggest that 18:0/20:4-glycerophosphocholine (GPC) synthesis involves sn-2 remodeling to yield 16:0/20:4-GPC and then sn-1 remodeling via a 1-lyso/20:4-GPC intermediate. Electrospray ionization mass spectrometric analyses also indicate that the PC and LPC content and composition of iPLA2beta-KD and control INS-1 cells are nearly identical, as are the rates of arachidonate incorporation into PC and the composition and remodeling of other phospholipid classes. These findings indicate that iPLA2beta plays signaling or effector roles in beta-cell secretion and proliferation but that stable suppression of its expression does not affect beta-cell GPC lipid content or composition even under conditions in which LPC is being actively consumed by conversion to PC. This calls into question the generality of proposed housekeeping functions for iPLA2beta in PC homeostasis and remodeling.
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Affiliation(s)
- Shunzhong Bao
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Alan Bohrer
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Sasanka Ramanadham
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Wu Jin
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Sheng Zhang
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - John Turk
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
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