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Dahley C, Goss KU, Ebert A. Revisiting the pK a-Flux method for determining intrinsic membrane permeability. Eur J Pharm Sci 2023; 191:106592. [PMID: 37751809 DOI: 10.1016/j.ejps.2023.106592] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/11/2023] [Accepted: 09/23/2023] [Indexed: 09/28/2023]
Abstract
Intrinsic membrane permeability is one of several factors that critically determine the intestinal absorption of a chemical. The intrinsic membrane permeability of a chemical is usually extracted from transwell experiments with Caco-2 or MDCK cells, preferably by the pKa-Flux method, which is considered the method of choice when aqueous boundary layer effects need to be excluded. The pKa-Flux method has two variants, the iso-pH method, where apical and basolateral pH are equal, and the gradient-pH method, where apical and basolateral pH are different. The most commonly used method is the gradient-pH method, as it is intended to reflect the pH-conditions in the gastrointestinal tract. However, concentration-shift effects caused by the applied pH-difference between apical and basolateral compartment in the gradient-pH method have not been considered in the evaluation of the experimental data in the past. Consequently, incorrect intrinsic membrane permeabilities have been determined. In this work, we present a revised method for extracting the intrinsic membrane permeability from gradient-pH data that considers concentration-shift effects in the basolateral aqueous boundary layer and filter as well as in the cytosol. Furthermore, we propose the use of the iso-pH method, where only concentration-shift effects in the cytosol need to be considered, as an alternative to the gradient-pH method. We use the five lipophilic bases amantadine, chloroquine, propranolol, venlafaxine and verapamil as examples to compare gradient-pH method and iso-pH method with regard to the extractability of the intrinsic membrane permeability. For lipophilic bases, the iso-pH method proves to be advantageous. All intrinsic membrane permeabilities determined in this work were substantially higher than the intrinsic membrane permeabilities reported in literature.
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Affiliation(s)
- Carolin Dahley
- Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, Leipzig 04318, Germany
| | - Kai-Uwe Goss
- Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, Leipzig 04318, Germany; Institute of Chemistry, University of Halle-Wittenberg, Kurt-Mothes-Straße 2, Halle 06120, Germany
| | - Andrea Ebert
- Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, Leipzig 04318, Germany.
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Kazyken D, Lentz SI, Wadley M, Fingar DC. Alkaline intracellular pH (pHi) increases PI3K activity to promote mTORC1 and mTORC2 signaling and function during growth factor limitation. J Biol Chem 2023; 299:105097. [PMID: 37507012 PMCID: PMC10477693 DOI: 10.1016/j.jbc.2023.105097] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 07/14/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023] Open
Abstract
The conserved protein kinase mTOR (mechanistic target of rapamycin) responds to diverse environmental cues to control cell metabolism and promote cell growth, proliferation, and survival as part of two multiprotein complexes, mTOR complex 1 (mTORC1) and mTORC2. Our prior work demonstrated that an alkaline intracellular pH (pHi) increases mTORC2 activity and cell survival in complete media in part by activating AMP-activated protein kinase, a kinase best known to sense energetic stress. It is important to note that an alkaline pHi represents an underappreciated hallmark of cancer cells that promotes their oncogenic behaviors. In addition, mechanisms that control mTORC1 and mTORC2 signaling and function remain incompletely defined, particularly in response to stress conditions. Here, we demonstrate that an alkaline pHi increases phosphatidylinositide 3-kinase (PI3K) activity to promote mTORC1 and mTORC2 signaling in the absence of serum growth factors. Alkaline pHi increases mTORC1 activity through PI3K-Akt signaling, which mediates inhibitory phosphorylation of the upstream proteins tuberous sclerosis complex 2 and proline-rich Akt substrate of 40 kDa and dissociates tuberous sclerosis complex from lysosomal membranes, thus enabling Rheb-mediated activation of mTORC1. Thus, alkaline pHi mimics growth factor-PI3K signaling. Functionally, we also demonstrate that an alkaline pHi increases cap-dependent protein synthesis through inhibitory phosphorylation of eIF4E binding protein 1 and suppresses apoptosis in a PI3K- and mTOR-dependent manner. We speculate that an alkaline pHi promotes a low basal level of cell metabolism (e.g., protein synthesis) that enables cancer cells within growing tumors to proliferate and survive despite limiting growth factors and nutrients, in part through elevated PI3K-mTORC1 and/or PI3K-mTORC2 signaling.
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Affiliation(s)
- Dubek Kazyken
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
| | - Stephen I Lentz
- Department of Internal Medicine, Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Maxwell Wadley
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Diane C Fingar
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
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Nighot M, Liao PL, Morris N, McCarthy D, Dharmaprakash V, Ullah Khan I, Dalessio S, Saha K, Ganapathy AS, Wang A, Ding W, Yochum G, Koltun W, Nighot P, Ma T. Long-Term Use of Proton Pump Inhibitors Disrupts Intestinal Tight Junction Barrier and Exaggerates Experimental Colitis. J Crohns Colitis 2023; 17:565-579. [PMID: 36322638 PMCID: PMC10115233 DOI: 10.1093/ecco-jcc/jjac168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Indexed: 12/03/2022]
Abstract
BACKGROUND Proton pump inhibitors [PPIs] are widely used to treat a number of gastro-oesophageal disorders. PPI-induced elevation in intragastric pH may alter gastrointestinal physiology. The tight junctions [TJs] residing at the apical intercellular contacts act as a paracellular barrier. TJ barrier dysfunction is an important pathogenic factor in inflammatory bowel disease [IBD]. Recent studies suggest that PPIs may promote disease flares in IBD patients. The role of PPIs in intestinal permeability is not clear. AIM The aim of the present study was to study the effect of PPIs on the intestinal TJ barrier function. METHODS Human intestinal epithelial cell culture and organoid models and mouse IBD models of dextran sodium sulphate [DSS] and spontaneous enterocolitis in IL-10-/- mice were used to study the role of PPIs in intestinal permeability. RESULTS PPIs increased TJ barrier permeability via an increase in a principal TJ regulator, myosin light chain kinase [MLCK] activity and expression, in a p38 MAPK-dependent manner. The PPI-induced increase in extracellular pH caused MLCK activation via p38 MAPK. Long-term PPI administration in mice exaggerated the increase in intestinal TJ permeability and disease severity in two independent models of DSS colitis and IL-10-/- enterocolitis. The TJ barrier disruption by PPIs was prevented in MLCK-/- mice. Human database studies revealed increased hospitalizations associated with PPI use in IBD patients. CONCLUSIONS Our results suggest that long-term use of PPIs increases intestinal TJ permeability and exaggerates experimental colitis via an increase in MLCK expression and activity.
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Affiliation(s)
- Meghali Nighot
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Pei-Luan Liao
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Nathan Morris
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Dennis McCarthy
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, University of New Mexico, Albuquerque, NM 87131, USA
| | - Viszwapriya Dharmaprakash
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Inam Ullah Khan
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Shannon Dalessio
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Kushal Saha
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | | | - Alexandra Wang
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Wei Ding
- Division of Colon and Rectal Surgery, Department of Surgery, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Gregory Yochum
- Division of Colon and Rectal Surgery, Department of Surgery, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Walter Koltun
- Division of Colon and Rectal Surgery, Department of Surgery, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Prashant Nighot
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Thomas Ma
- Division of Gastroenterology and Hepatology, Department of Medicine, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
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Kim JW, Han SH, Choi YH, Hamonangan WM, Oh Y, Kim SH. Recent advances in the microfluidic production of functional microcapsules by multiple-emulsion templating. LAB ON A CHIP 2022; 22:2259-2291. [PMID: 35608122 DOI: 10.1039/d2lc00196a] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Multiple-emulsion drops serve as versatile templates to design functional microcapsules due to their core-shell geometry and multiple compartments. Microfluidics has been used for the elaborate production of multiple-emulsion drops with a controlled composition, order, and dimensions, elevating the value of multiple-emulsion templates. Moreover, recent advances in the microfluidic control of the emulsification and parallelization of drop-making junctions significantly enhance the production throughput for practical use. Metastable multiple-emulsion drops are converted into stable microcapsules through the solidification of selected phases, among which solid shells are designed to function in a programmed manner. Functional microcapsules are used for the storage and release of active materials as drug carriers. Beyond their conventional uses, microcapsules can serve as microcompartments responsible for transmembrane communication, which is promising for their application in advanced microreactors, artificial cells, and microsensors. Given that post-processing provides additional control over the composition and construction of multiple-emulsion drops, they are excellent confining geometries to study the self-assembly of colloids and liquid crystals and produce miniaturized photonic devices. This review article presents the recent progress and current state of the art in the microfluidic production of multiple-emulsion drops, functionalization of solid shells, and applications of microcapsules.
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Affiliation(s)
- Ji-Won Kim
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
| | - Sang Hoon Han
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
| | - Ye Hun Choi
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
| | - Wahyu Martumpal Hamonangan
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
| | - Yoonjin Oh
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
| | - Shin-Hyun Kim
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
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Xing C, Xing JF, Ge ZQ. Inhibition of proteases activity in intestine needs a sustainable acidic environment rather than a transient. Drug Dev Ind Pharm 2017; 43:1648-1655. [PMID: 28541760 DOI: 10.1080/03639045.2017.1328433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
α-Chymotrypsin (α-CT) and trypsin are important components of the enzymatic barrier. They could degrade the therapeutic proteins and peptides, inhibit their activity consequently, and thereby reduce their oral bioavailability. Acidic agents, as one type of indirect protease inhibitors, have shown proof of concept in clinical trials. We report here the inactivated proteases due to acid influence can be reactivated immediately by environmental pH recovery regardless of how long the inactivation last. To keep the inactivation time of proteases for 4-5 h, we designed and prepared a sustained-release tablet containing citric acid (CA) which can effectively reduce the pH below 5.0 and maintain it for 5 h in the dissolution-reaction medium. The activity of α-CT and trypsin was quantified by analyzing the residual amount of their respective substrates BTEE and TAME. More than 80% of the substrates were survived in 5.0 h of incubation, whereas the common tablet inhibited the proteases activity for only two hours in the same experimental medium. It indicates that the sustained-release tablet loaded with CA can efficiently inhibit the α-CT and trypsin activity longer than the common tablet. The results will be beneficial for designing and formulating the peroral administration of peptide and protein drugs.
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Affiliation(s)
- Chang Xing
- a Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology , Tianjin University, Education Ministry Key Laboratory of Systems Bioengineering , Tianjin , PR China
| | - Jin-Feng Xing
- a Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology , Tianjin University, Education Ministry Key Laboratory of Systems Bioengineering , Tianjin , PR China
| | - Zhi-Qiang Ge
- a Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology , Tianjin University, Education Ministry Key Laboratory of Systems Bioengineering , Tianjin , PR China
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De Puysseleyr L, De Puysseleyr K, Vanrompay D, De Vos WH. Quantifying the growth of chlamydia suis in cell culture using high-content microscopy. Microsc Res Tech 2016; 80:350-356. [PMID: 27862609 DOI: 10.1002/jemt.22799] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 09/07/2016] [Accepted: 09/30/2016] [Indexed: 11/11/2022]
Abstract
The porcine pathogen Chlamydia suis is widespread in pig farming. Isolation of Chlamydia suis in cell culture is crucial for the generation and characterization of new isolates. However, isolation of Chlamydia suis strains from field samples is fastidious. Therefore, we exploited high-content microscopy to quantify the growth of Chlamydia suis strains in different cell lines. We found that the cell line yielding optimal propagation of Chlamydia suis differed among isolates, and we identified cell lines outperforming those routinely used for chlamydial isolation. We conclude that adaptation of the propagation procedure to the origin of the putative field isolate is highly recommended to improve the recovery rate.
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Affiliation(s)
- Leentje De Puysseleyr
- Lab of Immunology and Animal Biotechnology, Faculty of Bioscience Engineering, University of Ghent, Ghent, Belgium
| | - Kristien De Puysseleyr
- Lab of Immunology and Animal Biotechnology, Faculty of Bioscience Engineering, University of Ghent, Ghent, Belgium
| | - Daisy Vanrompay
- Lab of Immunology and Animal Biotechnology, Faculty of Bioscience Engineering, University of Ghent, Ghent, Belgium
| | - Winnok H De Vos
- Lab of Cell Biology and Histology, Faculty of Veterinary Sciences, University of Antwerp, Antwerp, Belgium.,Cell Systems and Imaging, Faculty of Bioscience Engineering, University of Ghent, Ghent, Belgium
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Walsh MF, Hermann R, Lee JH, Chaturvedi L, Basson MD. Schlafen 3 Mediates the Differentiating Effects of Cdx2 in Rat IEC-Cdx2L1 Enterocytes. J INVEST SURG 2016; 28:202-7. [PMID: 26268420 DOI: 10.3109/08941939.2015.1005780] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
AIM Mature, differentiated enterocytes are essential for normal gut function and critical to recovery from pathological conditions. Little is known about the factors that regulate intestinal epithelial cell differentiation in the adult intestine. The transcription factor, Cdx2, involved in enterocytic differentiation, remains expressed in the adult. Since we have implicated Slfn3 in differentiation in vivo and in vitro, we examined whether it also mediated differentiation in the IEC-Cdx2-L1 cell model of differentiation. MATERIALS AND METHODS IEC-Cdx2-L1 cells, permanently transfected with Cdx2 under the control of isopropyl-β-D-thiogalactoside (IPTG), were stimulated to differentiate by 16-day exposure to IPTG. Transcript levels of Cdx2, Slfn 3, and villin were determined by quantitative reverse transcriptase-polymerase chain reaction of mRNA isolated from IPTG-treated and control cells. Slfn3 expression was lowered with specific siRNA to investigate the role of Slfn3 in Cdx2-driven villin expression in IPTG-differentiated cells. RESULTS Slfn3 and villin expression were significantly greater in IPTG-treated cells. Slfn3 siRNA lowered Slfn3 expression and abolished the IPTG-induced rise in villin expression (p < .05 by ANOVA); Cdx2 expression was unaffected by Slfn3 siRNA. DISCUSSION The data indicate that the presence of Slfn3 is required for Cdx2 to induce villin expression, and thus differentiation. However, Slfn3 must also promote differentiation of Cdx2 independently since IEC-6 cells that do not normally express Cdx2 can be differentiated by a variety of Slfn3-dependent mechanisms.
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Affiliation(s)
- Mary F Walsh
- Department of Surgery, College of Human Medicine, Michigan State University, East Lansing, Michigan, USA
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Bettenworth D, Lenz P, Krausewitz P, Brückner M, Ketelhut S, Domagk D, Kemper B. Quantitative stain-free and continuous multimodal monitoring of wound healing in vitro with digital holographic microscopy. PLoS One 2014; 9:e107317. [PMID: 25251440 PMCID: PMC4174518 DOI: 10.1371/journal.pone.0107317] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 08/08/2014] [Indexed: 12/12/2022] Open
Abstract
Impaired epithelial wound healing has significant pathophysiological implications in several conditions including gastrointestinal ulcers, anastomotic leakage and venous or diabetic skin ulcers. Promising drug candidates for accelerating wound closure are commonly evaluated in in vitro wound assays. However, staining procedures and discontinuous monitoring are major drawbacks hampering accurate assessment of wound assays. We therefore investigated digital holographic microscopy (DHM) to appropriately monitor wound healing in vitro and secondly, to provide multimodal quantitative information on morphological and functional cell alterations as well as on motility changes upon cytokine stimulation. Wound closure as reflected by proliferation and migration of Caco-2 cells in wound healing assays was studied and assessed in time-lapse series for 40 h in the presence of stimulating epidermal growth factor (EGF) and inhibiting mitomycin c. Therefore, digital holograms were recorded continuously every thirty minutes. Morphological changes including cell thickness, dry mass and tissue density were analyzed by data from quantitative digital holographic phase microscopy. Stimulation of Caco-2 cells with EGF or mitomycin c resulted in significant morphological changes during wound healing compared to control cells. In conclusion, DHM allows accurate, stain-free and continuous multimodal quantitative monitoring of wound healing in vitro and could be a promising new technique for assessment of wound healing.
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Affiliation(s)
- Dominik Bettenworth
- Department of Medicine B, University Hospital Münster, Münster, Germany
- * E-mail: (DB); (BK)
| | - Philipp Lenz
- Department of Medicine B, University Hospital Münster, Münster, Germany
| | | | - Markus Brückner
- Department of Medicine B, University Hospital Münster, Münster, Germany
| | - Steffi Ketelhut
- Center for Biomedical Optics and Photonics, University of Münster, Münster, Germany
- Biomedical Technology Center, University of Münster, Münster, Germany
| | - Dirk Domagk
- Department of Medicine B, University Hospital Münster, Münster, Germany
| | - Björn Kemper
- Center for Biomedical Optics and Photonics, University of Münster, Münster, Germany
- Biomedical Technology Center, University of Münster, Münster, Germany
- * E-mail: (DB); (BK)
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Cohen L, Asraf H, Sekler I, Hershfinkel M. Extracellular pH regulates zinc signaling via an Asp residue of the zinc-sensing receptor (ZnR/GPR39). J Biol Chem 2012; 287:33339-50. [PMID: 22879599 DOI: 10.1074/jbc.m112.372441] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Zinc activates a specific Zn(2+)-sensing receptor, ZnR/GPR39, and thereby triggers cellular signaling leading to epithelial cell proliferation and survival. Epithelial cells that express ZnR, particularly colonocytes, face frequent changes in extracellular pH that are of physiological and pathological implication. Here we show that the ZnR/GPR39-dependent Ca(2+) responses in HT29 colonocytes were maximal at pH 7.4 but were reduced by about 50% at pH 7.7 and by about 62% at pH 7.1 and were completely abolished at pH 6.5. Intracellular acidification did not attenuate ZnR/GPR39 activity, indicating that the pH sensor of this protein is located on an extracellular domain. ZnR/GPR39-dependent activation of extracellular-regulated kinase (ERK)1/2 or AKT pathways was abolished at acidic extracellular pH of 6.5. A similar inhibitory effect was monitored for the ZnR/GPR39-dependent up-regulation of Na(+)/H(+) exchange activity at pH 6.5. Focusing on residues putatively facing the extracellular domain, we sought to identify the pH sensor of ZnR/GPR39. Replacing the histidine residues forming the Zn(2+) binding site, His(17) or His(19), or other extracellular-facing histidines to alanine residues did not abolish the pH dependence of ZnR/GPR39. In contrast, replacing Asp(313) with alanine resulted in similar Ca(2+) responses triggered by ZnR/GPR39 at pH 7.4 or 6.5. This mutant also showed similar activation of ERK1/2 and AKT pathways, and ZnR-dependent up-regulation of Na(+)/H(+) exchange at pH 7.4 and pH 6.5. Substitution of Asp(313) to His or Glu residues restored pH sensitivity of the receptor. This indicates that Asp(313), which was shown to modulate Zn(2+) binding, is an essential residue of the pH sensor of GPR39. In conclusion, ZnR/GPR39 is tuned to sense physiologically relevant changes in extracellular pH that thus regulate ZnR-dependent signaling and ion transport activity.
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Affiliation(s)
- Limor Cohen
- Department of Morphology, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer-Sheva 84105, Israel
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Loh JW, Saunders M, Lim LY. Cytotoxicity of monodispersed chitosan nanoparticles against the Caco-2 cells. Toxicol Appl Pharmacol 2012; 262:273-82. [PMID: 22609640 DOI: 10.1016/j.taap.2012.04.037] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Revised: 04/25/2012] [Accepted: 04/30/2012] [Indexed: 11/27/2022]
Abstract
Published toxicology data on chitosan nanoparticles (NP) often lack direct correlation to the in situ size and surface characteristics of the nanoparticles, and the repeated NP assaults as experienced in chronic use. The aim of this paper was to breach these gaps. Chitosan nanoparticles synthesized by spinning disc processing were characterised for size and zeta potential in HBSS and EMEM at pHs 6.0 and 7.4. Cytotoxicity against the Caco-2 cells was evaluated by measuring the changes in intracellular mitochondrial dehydrogenase activity, TEER and sodium fluorescein transport data and cell morphology. Cellular uptake of NP was observed under the confocal microscope. Contrary to established norms, the collective data suggest that the in vitro cytotoxicity of NP against the Caco-2 cells was less influenced by positive surface charges than by the particle size. Particle size was in turn determined by the pH of the medium in which the NP was dispersed, with the mean size ranging from 25 to 333 nm. At exposure concentration of 0.1%, NP of 25 ± 7 nm (zeta potential 5.3 ± 2.8 mV) was internalised by the Caco-2 cells, and the particles were observed to inflict extensive damage to the intracellular organelles. Concurrently, the transport of materials along the paracellular pathway was significantly facilitated. The Caco-2 cells were, however, capable of recovering from such assaults 5 days following NP removal, although a repeat NP exposure was observed to produce similar effects to the 1st exposure, with the cells exhibiting comparable resiliency to the 2nd assault.
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Affiliation(s)
- Jing Wen Loh
- Laboratory for Drug Delivery, Pharmacy, Characterisation and Analysis, University of Western Australia, Australia
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Effects of acute hypoxia/acidosis on intracellular pH in differentiating neural progenitor cells. Brain Res 2012; 1461:10-23. [PMID: 22608071 DOI: 10.1016/j.brainres.2012.04.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 03/26/2012] [Accepted: 04/20/2012] [Indexed: 01/19/2023]
Abstract
The response of differentiating mouse neural progenitor cells, migrating out from neurospheres, to conditions simulating ischemia (hypoxia and extracellular or intracellular acidosis) was studied. We show here, by using BCECF and single cell imaging to monitor intracellular pH (pH(i)), that two main populations can be distinguished by exposing migrating neural progenitor cells to low extracellular pH or by performing an acidifying ammonium prepulse. The cells dominating at the periphery of the neurosphere culture, which were positive for neuron specific markers MAP-2, calbindin and NeuN had lower initial resting pH(i) and could also easily be further acidified by lowering the extracellular pH. Moreover, in this population, a more profound acidification was seen when the cells were acidified using the ammonium prepulse technique. However, when the cell population was exposed to depolarizing potassium concentrations no alterations in pH(i) took place in this population. In contrast, depolarization caused an increase in pH(i) (by 0.5 pH units) in the cell population closer to the neurosphere body, which region was positive for the radial cell marker (GLAST). This cell population, having higher resting pH(i) (pH 6.9-7.1) also responded to acute hypoxia. During hypoxic treatment the resting pH(i) decreased by 0.1 pH units and recovered rapidly after reoxygenation. Our results show that migrating neural progenitor cells are highly sensitive to extracellular acidosis and that irreversible damage becomes evident at pH 6.2. Moreover, our results show that a response to acidosis clearly distinguishes two individual cell populations probably representing neuronal and radial cells.
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12
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Kesisoglou F, Schmiedlin-Ren P, Fleisher D, Roessler B, Zimmermann EM. Restituting intestinal epithelial cells exhibit increased transducibility by adenoviral vectors. J Gene Med 2007; 8:1379-92. [PMID: 17133338 DOI: 10.1002/jgm.981] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND AND AIMS While mature enterocytes are resistant to transduction by adenovirus type 5 (Ad5) vectors, undifferentiated cells are transduced much more efficiently. Our purpose was to study enterocyte transduction in models of intestinal wound healing. METHODS Transduction was studied ex vivo using cultures of endoscopic biopsies and in vitro utilizing Caco-2 cells in models of mucosal wound healing. Vectors carried either the LacZ or the luciferase gene. CAR (coxsackievirus and adenovirus receptor) and integrins were studied with transduction inhibition and immunofluorescent staining. RESULTS Increased transduction efficiency was observed for a subset of enterocytes with a flattened de-differentiated phenotype present at the edge of cultured biopsies. In the in vitro systems, expanding Caco-2 cell monolayers exhibited increased transducibility that was time- and dose-dependent, reaching virtually 100% in cells along the leading edge at high viral load. Bioluminescence activity of transduced expanding monolayers was up to 3-fold greater than that of non-expanding monolayers ('fence' system, 48 h, MOI 1000, p < 0.05). Mitomycin C pre-treatment did not affect levels of transduction in expanding monolayers. At the highest viral load tested, CAR or integrin blocking prior to virus application resulted in 39.4% and 45.4% reduction in transduction levels (p < 0.05). Immunofluorescence revealed altered expression of CAR on the migrating edge of the Caco-2 cultures and the expression of CAR on the apical membrane of biopsy enterocytes. CONCLUSIONS Increased CAR and integrin accessibility in migrating enterocytes mediates increased transduction by Ad5 vectors. This subset of enterocytes provides a target for the delivery of genes of interest for both research and gene therapy applications.
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Affiliation(s)
- Filippos Kesisoglou
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Michigan, Ann Arbor, MI 48109-1065, USA
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Yu CF, Sanders MA, Basson MD. Human caco-2 motility redistributes FAK and paxillin and activates p38 MAPK in a matrix-dependent manner. Am J Physiol Gastrointest Liver Physiol 2000; 278:G952-66. [PMID: 10859226 DOI: 10.1152/ajpgi.2000.278.6.g952] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The signals involved in restitution during mucosal healing are poorly understood. We compared focal adhesion kinase (FAK) and paxillin protein and phosphorylation, extracellular signal-regulated kinase (ERK) 1, ERK2, and p38 activation, as well as FAK and paxillin organization in static and migrating human intestinal Caco-2 cells on matrix proteins and anionically derivatized polystyrene dishes (tissue culture plastic). We also studied effects of FAK, ERK, and p38 blockade in a monolayer-wounding model. Compared with static cells, cells migrating across matrix proteins matrix-dependently decreased membrane/cytoskeletal FAK and paxillin and cytosolic FAK. Tyrosine phosphorylated FAK and paxillin changed proportionately to FAK and paxillin protein. Conversely, cells migrating on plastic increased FAK and paxillin protein and phosphorylation. Migration matrix-dependently activated p38 and inactivated ERK1 and ERK2. Total p38, ERK1, and ERK2 did not change. Caco-2 motility was inhibited by transfection of FRNK (the COOH-terminal region of FAK) and PD-98059, a mitogen-activated protein kinase-ERK kinase inhibitor, but not by SB-203580, a p38 inhibitor, suggesting that FAK and ERK modulate Caco-2 migration. In contrast to adhesion-induced phosphorylation, matrix may regulate motile intestinal epithelial cells by altering amounts and distribution of focal adhesion plaque proteins available for phosphorylation as well as by p38 activation and ERK inactivation. Motility across plastic differs from migration across matrix.
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Affiliation(s)
- C F Yu
- Department of Surgery, Yale University School of Medicine and Connecticut Veterans Affairs Health Care System, New Haven, Connecticut 06511, USA
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Rittler P, Demmelmair H, Koletzko B, Schildberg FW, Hartl WH. Determination of protein synthesis in human ileum in situ by continuous [1-(13)C]leucine infusion. Am J Physiol Endocrinol Metab 2000; 278:E634-8. [PMID: 10751196 DOI: 10.1152/ajpendo.2000.278.4.e634] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Efficient protein synthesis plays an important role in the physiology and pathophysiology of the human gastrointestinal tract. Because of methodological restrictions, no studies on ileal protein synthesis in situ are available in humans. We used advanced mass spectrometry techniques (capillary gas chromatography/combustion isotope ratio mass spectrometry) to determine directly the incorporation rate of [1-(13)C]leucine into ileal mucosal protein in control subjects and postoperative patients. All subjects had an ileostomy, which allowed easy access to the ileal mucosa. To examine changes in ileal protein synthesis during prolonged isotope infusion (0.16 micromol. kg(-1). min(-1), 9.6 micromol/kg prime), studies were performed over a 10-h period. Mucosal biopsies were performed after 3, 6, and 10 h of infusion. Protein synthesis was calculated separately between hour 3 and hour 6 (period 1) and hour 6 and hour 10 (period 2). Control subjects demonstrated an ileal protein fractional synthetic rate of 0.62 +/- 0.06%/h in period 1 and of 0. 52 +/- 0.08%/h in period 2 (not significant). In postsurgical subjects, ileal protein synthesis was significantly higher (1.11 +/- 0.14%/h in period 1, P < 0.01 vs. controls in period 1) but declined markedly in period 2 (0.39 +/- 0.13, P < 0.01 vs. period 1 after surgery). The rate of protein synthesis in the small bowel of control subjects is, thus far, among the lowest measured in mammals and reflects the comparably slow turnover of human ileal mucosa. Postoperative disturbances of gut integrity lead to an accelerated anabolic response. During prolonged isotope infusion, stimulated protein synthesis declines because of diurnal variations or is erroneously reduced by tracer loss due to an accelerated cell turnover.
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Affiliation(s)
- P Rittler
- Department of Surgery, Klinikum Grosshadern, Marchioninistr. 15, D-81377 Munich, Germany
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Basson MD, Yu CF, Herden-Kirchoff O, Ellermeier M, Sanders MA, Merrell RC, Sumpio BE. Effects of increased ambient pressure on colon cancer cell adhesion. J Cell Biochem 2000; 78:47-61. [PMID: 10797565 DOI: 10.1002/(sici)1097-4644(20000701)78:1<47::aid-jcb5>3.0.co;2-m] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Forces such as strain modulate intestinal epithelial biology. Shear and pressure influence other cells. The effects of pressure on human colon cancer cells are poorly understood. Increasing ambient pressure for 30 min by 15 mm Hg over atmospheric stimulated adhesion to matrix proteins of four human colon cancer cell lines and primary cells from three human colon cancers, but not bovine aortic smooth-muscle cells. This effect was energy dependent and cation dependent (blocked by azide and chelation), accompanied by tyrosine phosphorylation of intracellular proteins including focal adhesion kinase, and blocked by tyrosine kinase inhibition (genistein, tyrphostin, and erbstatin) and a functional antibody to the beta1 integrin subunit. Although pressure stimulated adhesion even in a balanced salt solution, baseline and pressure-stimulated adhesion were each substantially diminished in the absence of serum. These data suggest that relatively low levels of increased pressure may stimulate malignant colonocyte adhesion by a cation-dependent beta1-integrin-mediated mechanism, perhaps via focal adhesion kinase-related tyrosine phosphorylation. In addition to elucidating another aspect of physical force regulation of colonocyte biology, these findings may be relevant to the effects of increased pressure engendered by colonic peristalsis, surgical manipulation, or laparoscopic surgery on colon cancer cell adhesion.
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Affiliation(s)
- M D Basson
- Department of Surgery, Yale University, New Haven, CT 06520-8062, USA.
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