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Lin C, He H, Kim JJ, Zheng X, Huang Z, Dai N. Osmotic pressure induces translocation of aquaporin-8 by P38 and JNK MAPK signaling pathways in patients with functional constipation. Dig Liver Dis 2023; 55:1049-1059. [PMID: 36792433 DOI: 10.1016/j.dld.2023.01.162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 12/06/2022] [Accepted: 01/26/2023] [Indexed: 02/17/2023]
Abstract
BACKGROUND Aquaporins (AQPs) maintain fluid homeostasis in the colon. The role of colonic AQPs in the pathophysiology of functional constipation (FC) remains largely unknown. AIM To explore variations in aquaporins and investigate their underlying mechanisms. METHODS Colonic biopsies were collected from patients with FC and healthy controls. The expression and localization of AQPs were evaluated using quantitative real-time polymerase chain reaction (qRT-PCR), western blot analysis, and immunofluorescence assays. Furthermore, osmotic pressure-induced cell model was used in vitro to investigate the potential relationship between AQP8 and osmotic pressure, and to reveal the underlying mechanisms. RESULTS Upregulation of AQP3 and AQP8, and downregulation of AQP1, AQP7, AQP9, AQP10, and AQP11 were observed in the patients with functional constipation. Furthermore, cellular translocation of AQP8 from the cytoplasm to the plasma membrane was observed in patients with FC. Mechanistically, the increase in osmotic pressure could activate the Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) signaling pathways, and subsequently promote the upregulation and translocation of AQP8. CONCLUSION Upregulation of AQP8 and AQP3, and translocation of AQP8 were observed in colon biopsies from patients with FC. The p38 and JNK MAPK signaling pathways are involved in the regulation of osmotic pressure-induced AQP8 variation.
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Affiliation(s)
- Chenhong Lin
- Department of Gastroenterology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Huiqin He
- Department of Gastroenterology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - John J Kim
- Division of Gastroenterology & Hepatology, Loma Linda University Health, Loma Linda, CA, United States
| | - Xia Zheng
- Department of Gastroenterology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Zhihui Huang
- Department of Gastroenterology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
| | - Ning Dai
- Department of Gastroenterology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
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2
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Shcheynikov N, Boggs K, Green A, Feranchak AP. Identification of the chloride channel, leucine-rich repeat-containing protein 8, subfamily a (LRRC8A), in mouse cholangiocytes. Hepatology 2022; 76:1248-1258. [PMID: 35445421 PMCID: PMC10126881 DOI: 10.1002/hep.32536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 04/18/2022] [Accepted: 04/19/2022] [Indexed: 12/08/2022]
Abstract
BACKGROUND AND AIMS Chloride (Cl- ) channels in the apical membrane of biliary epithelial cells (BECs), also known as cholangiocytes, provide the driving force for biliary secretion. Although two Cl- channels have been identified on a molecular basis, the Cystic Fibrosis Transmembrane Conductance Regulator and Transmembrane Member 16A, a third Cl- channel with unique biophysical properties has been described. Leucine-Rich Repeat-Containing Protein 8, subfamily A (LRRC8A) is a newly identified protein capable of transporting Cl- in other epithelium in response to cell swelling. The aim of the present study was to determine if LRRC8A represents the volume-regulated anion channel in mouse BECs. APPROACH AND RESULTS Studies were performed in mouse small (MSC) and large (MLC) cholangiocytes. Membrane Cl- currents were measured by whole-cell patch-clamp techniques and cell volume measurements were performed by calcein-AM fluorescence. Exposure of either MSC or MLC to hypotonicity (190 mOsm) rapidly increased cell volume and activated Cl- currents. Currents exhibited outward rectification, time-dependent inactivation at positive membrane potentials, and reversal potential at 0 mV (ECl ). Removal of extracellular Cl- or specific pharmacological inhibition of LRRC8A abolished currents. LRRC8A was detected in both MSC and MLC by reverse transcription polymerase chain reaction and confirmed by western blot. Transfection with LRRC8A small interfering RNA decreased protein levels by >70% and abolished volume-stimulated Cl- currents. CONCLUSION These results demonstrate that LRRC8A is functionally present in mouse BECs, contributes to volume-activated Cl- secretion, and, therefore, may be a target to modulate bile formation in the treatment of cholestatic liver disorders.
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Affiliation(s)
- Nikolay Shcheynikov
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Kristy Boggs
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Anthony Green
- Tissue and Research Pathology Core, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Andrew P Feranchak
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Pittsburgh Liver Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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3
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Li T, Tuo B. Pathophysiology of hepatic Na +/H + exchange (Review). Exp Ther Med 2020; 20:1220-1229. [PMID: 32742358 PMCID: PMC7388279 DOI: 10.3892/etm.2020.8888] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Accepted: 05/15/2020] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers (NHEs) are a family of membrane proteins that contribute to exchanging one intracellular proton for one extracellular sodium. The family of NHEs consists of nine known members, NHE1-9. Each isoform represents a different gene product that has unique tissue expression, membrane localization, physiological effects, pathological regulation and sensitivity to drug inhibitors. NHE1 was the first to be discovered and is often referred to as the 'housekeeping' isoform of the NHE family. NHEs are not only involved in a variety of physiological processes, including the control of transepithelial Na+ absorption, intracellular pH, cell volume, cell proliferation, migration and apoptosis, but also modulate complex pathological events. Currently, the vast majority of review articles have focused on the role of members of the NHE family in inflammatory bowel disease, intestinal infectious diarrhea and digestive system tumorigenesis, but only a few reviews have discussed the role of NHEs in liver disease. Therefore, the present review described the basic biology of NHEs and highlighted their physiological and pathological effects in the liver.
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Affiliation(s)
- Tingting Li
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical University, Zunyi, Guizhou 563000, P.R. China
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical University, Zunyi, Guizhou 563000, P.R. China
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4
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Liu X, Wang J, Sun L. Structure of the hyperosmolality-gated calcium-permeable channel OSCA1.2. Nat Commun 2018; 9:5060. [PMID: 30498218 PMCID: PMC6265326 DOI: 10.1038/s41467-018-07564-5] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/09/2018] [Indexed: 01/08/2023] Open
Abstract
In plants, hyperosmolality stimuli triggers opening of the osmosensitive channels, leading to a rapid downstream signaling cascade initiated by cytosolic calcium concentration elevation. Members of the OSCA family in Arabidopsis thaliana, identified as the hyperosmolality-gated calcium-permeable channels, have been suggested to play a key role during the initial phase of hyperosmotic stress response. Here, we report the atomic structure of Arabidopsis OSCA1.2 determined by single-particle cryo-electron microscopy. It contains 11 transmembrane helices and forms a homodimer. It is in an inactivated state, and the pore-lining residues are clearly identified. Its cytosolic domain contains a RNA recognition motif and two unique long helices. The linker between these two helices forms an anchor in the lipid bilayer and may be essential to osmosensing. The structure of AtOSCA1.2 serves as a platform for the study of the mechanism underlying osmotic stress responses and mechanosensing. In plants, hyperosmolality stimuli triggers opening of the osmosensitive channels, leading to a rapid downstream signaling cascade. Here, the authors solve the cryo-EM structure of an osmosensitive channel from Arabidopsis OSCA1.2 in its inactivated state.
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Affiliation(s)
- Xin Liu
- Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, 230027, Hefei, China
| | - Jiawei Wang
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Centre for Structural Biology, School of Life Sciences, Tsinghua University, 100084, Beijing, China.
| | - Linfeng Sun
- Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, 230027, Hefei, China. .,CAS Centre for Excellence in Molecular Cell Science, University of Science and Technology of China, Chinese Academy of Sciences, 230027, Hefei, China.
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5
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Kwiatkowska E, Domański L, Bober J, Safranow K, Pawlik A, Ciechanowski K, Wiśniewska M, Kędzierska K. Clinical and Biochemical Characteristics of Brain-Dead Donors as Predictors of Early- and Long-Term Renal Function After Transplant. EXP CLIN TRANSPLANT 2017. [PMID: 28621640 DOI: 10.6002/ect.2016.0145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVES Organs from brain-dead donors are the main source of allografts for transplant. Comparisons between living-donor and brain-dead donor kidneys show that the latter are more likely to demonstrate delayed graft function and lower long-term survival. This study aimed to assess the effects of various clinical and biochemical factors of donors on early- and long-term renal function after transplant. MATERIALS AND METHODS We analyzed data from kidney recipients treated between 2006 and 2008 who received organs from brain-dead donors. Data from 54 donors and 89 recipients were analyzed. RESULTS No relation was observed between donor sodium concentration and the presence of delayed graft function. Donor height was positively correlated with creatinine clearance in recipients in the 1 to 3 months after renal transplant. Donor diastolic blood pressure was negatively correlated with estimated glomerular filtration rate throughout the observation period. Donor age was negatively correlated with the allograft recipient's estimated glomerular filtration rate throughout 4 years of observation. Donor estimated glomerular filtration rate was positively correlated with that of the recipient throughout 3 years of observation. CONCLUSIONS The results of this study indicate that various factors associated with allograft donors may influence graft function.
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Affiliation(s)
- Ewa Kwiatkowska
- From the Clinical Department of Nephrology, Transplantology and Internal Medicine, Pomeranian Medical University, Szczecin, Poland
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Zhou X, Naguro I, Ichijo H, Watanabe K. Mitogen-activated protein kinases as key players in osmotic stress signaling. Biochim Biophys Acta Gen Subj 2016; 1860:2037-52. [PMID: 27261090 DOI: 10.1016/j.bbagen.2016.05.032] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 05/21/2016] [Indexed: 11/29/2022]
Abstract
BACKGROUND Osmotic stress arises from the difference between intracellular and extracellular osmolality. It induces cell swelling or shrinkage as a consequence of water influx or efflux, which threatens cellular activities. Mitogen-activated protein kinases (MAPKs) play central roles in signaling pathways in osmotic stress responses, including the regulation of intracellular levels of inorganic ions and organic osmolytes. SCOPE OF REVIEW The present review summarizes the cellular osmotic stress response and the function and regulation of the vertebrate MAPK signaling pathways involved. We also describe recent findings regarding apoptosis signal-regulating kinase 3 (ASK3), a MAP3K member, to demonstrate its regulatory effects on signaling molecules beyond MAPKs. MAJOR CONCLUSIONS MAPKs are rapidly activated by osmotic stress and have diverse roles, such as cell volume regulation, gene expression, and cell survival/death. There is significant cell type specificity in the function and regulation of MAPKs. Based on its activity change during osmotic stress and its regulation of the WNK1-SPAK/OSR1 pathway, ASK3 is expected to play important roles in osmosensing mechanisms and cellular functions related to osmoregulation. GENERAL SIGNIFICANCE MAPKs are essential for various cellular responses to osmotic stress; thus, the identification of the upstream regulators of MAPK pathways will provide valuable clues regarding the cellular osmosensing mechanism, which remains elusive in mammals. The elucidation of in vivo MAPK functions is also important because osmotic stress in physiological and pathophysiological conditions often results from changes in the intracellular osmolality. These studies potentially contribute to the establishment of therapeutic strategies against diseases that accompany osmotic perturbation.
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Affiliation(s)
- Xiangyu Zhou
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Isao Naguro
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hidenori Ichijo
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kengo Watanabe
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Yang KC, Kyle JW, Makielski JC, Dudley SC. Mechanisms of sudden cardiac death: oxidants and metabolism. Circ Res 2015; 116:1937-55. [PMID: 26044249 PMCID: PMC4458707 DOI: 10.1161/circresaha.116.304691] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 02/09/2015] [Indexed: 02/07/2023]
Abstract
Ventricular arrhythmia is the leading cause of sudden cardiac death (SCD). Deranged cardiac metabolism and abnormal redox state during cardiac diseases foment arrhythmogenic substrates through direct or indirect modulation of cardiac ion channel/transporter function. This review presents current evidence on the mechanisms linking metabolic derangement and excessive oxidative stress to ion channel/transporter dysfunction that predisposes to ventricular arrhythmias and SCD. Because conventional antiarrhythmic agents aiming at ion channels have proven challenging to use, targeting arrhythmogenic metabolic changes and redox imbalance may provide novel therapeutics to treat or prevent life-threatening arrhythmias and SCD.
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Affiliation(s)
- Kai-Chien Yang
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.)
| | - John W Kyle
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.)
| | - Jonathan C Makielski
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.).
| | - Samuel C Dudley
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.).
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8
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Della Penna SL, Rosón MI, Toblli JE, Fernández BE. Role of angiotensin II and oxidative stress in renal inflammation by hypernatremia: Benefits of atrial natriuretic peptide, losartan, and tempol. Free Radic Res 2015; 49:383-96. [DOI: 10.3109/10715762.2015.1006216] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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9
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Increased Serum Sodium Values in Brain-dead Donor's Influences Its Long-term Kidney Function. Transplant Proc 2013; 45:51-6. [DOI: 10.1016/j.transproceed.2012.07.153] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2011] [Revised: 07/07/2012] [Accepted: 07/19/2012] [Indexed: 11/17/2022]
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10
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Portincasa P, Calamita G. Water channel proteins in bile formation and flow in health and disease: when immiscible becomes miscible. Mol Aspects Med 2012; 33:651-64. [PMID: 22487565 DOI: 10.1016/j.mam.2012.03.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 03/29/2012] [Accepted: 03/31/2012] [Indexed: 12/19/2022]
Abstract
An essential function of the liver is the formation and secretion of bile, a complex aqueous solution of organic and inorganic compounds essential as route for the elimination of body cholesterol as unesterified cholesterol or as bile acids. In bile, a considerable amount of otherwise insoluble cholesterol is solubilized by carriers including two other classes of lipids, namely phospholipid and bile acids. Formation of bile and generation of bile flow are driven by the active secretion of bile acids, lipids and electrolytes into the canalicular and bile duct lumens followed by the parallel movement of water. Thus, water has to cross rapidly into and out of the cell interior driven by osmotic forces. Bile as a fluid, results from complicated interplay of hepatocyte and cholangiocyte uptake and secretion, concentration, by involving a number of transporters of lipids, anions, cations, and water. The discovery of the aquaporin water channels, has clarified the mechanisms by which water, the major component of bile (more than 95%), moves across the hepatobiliary epithelia. This review is focusing on novel acquisitions in liver membrane lipidic and water transport and functional participation of aquaporin water channels in multiple aspects of hepatobiliary fluid balance. Involvement of aquaporins in a series of clinically relevant hepatobiliary disorders are also discussed.
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Affiliation(s)
- Piero Portincasa
- University of Bari Medical School, Clinica Medica A. Murri, Department of Biomedical Sciences and Human Oncology, Policlinico Hospital, 70124 Bari, Italy.
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11
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Scapin S, Leoni S, Spagnuolo S, Gnocchi D, De Vito P, Luly P, Pedersen JZ, Incerpi S. Short-term effects of thyroid hormones during development: Focus on signal transduction. Steroids 2010; 75:576-84. [PMID: 19900468 DOI: 10.1016/j.steroids.2009.10.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 10/21/2009] [Accepted: 10/28/2009] [Indexed: 12/27/2022]
Abstract
Extranuclear or nongenomic effects of thyroid hormones are mediated by receptors located at the plasma membrane or inside cells, and are independent of protein synthesis. Recently the alphaVbeta3 integrin was identified as a cell membrane receptor for thyroid hormones, and a wide variety of nongenomic effects have now been shown to be induced through binding of thyroid hormones to this receptor. However, also other thyroid hormone receptors can produce nongenomic effects, including the cytoplasmic TRalpha and TRbeta receptors and probably also a G protein-coupled membrane receptor, and increasing importance is now given to thyroid hormone metabolites like 3,5-diiodothyronine and reverse T(3) that can mimick some nongenomic effects of T(3) and T(4). Signal transduction from the alphaVbeta3 integrin may proceed through at least three independent pathways (protein kinase C, Src or mitogen-activated kinases) but the details are still unknown. Thyroid hormones induce nongenomic effects on at least three important Na(+)-dependent transport systems, the Na(+)/K(+)-ATPase, the Na(+)/H(+) exchanger, and amino acid transport System A, leading to a mitogenic response in embryo cells; but modulation of the same transport systems may have different roles in other cells and at different developmental stages. It seems that thyroid hormones in many cases can modulate nongenomically the same targets affected by the nuclear receptors through long-term mechanisms. Recent results on nongenomic effects confirm the old theory that the primary role of thyroid hormones is to keep the steady-state level of functioning of the cell, but more and more mechanisms are discovered by which this goal can be achieved.
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Affiliation(s)
- Sergio Scapin
- Department of Cellular and Developmental Biology, Sapienza University, 00185 Rome, Italy
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12
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Singhal A, Nagarajan R, Kumar R, Huda A, Gupta RK, Thomas MA. Magnetic resonance T2-relaxometry and 2D L-correlated spectroscopy in patients with minimal hepatic encephalopathy. J Magn Reson Imaging 2010; 30:1034-41. [PMID: 19856435 DOI: 10.1002/jmri.21943] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
PURPOSE To evaluate T(2)-relaxation changes in patients with minimal hepatic encephalopathy (MHE) using T(2) relaxometry and to correlate T(2) values with brain metabolites evaluated using 2D magnetic resonance spectroscopy (MRS). MATERIALS AND METHODS Eight MHE patients and 13 healthy subjects were evaluated using T(2) relaxometry, and eight patients and nine healthy subjects underwent 2D MRS in right frontal and left occipital regions. Whole-brain T(2)-relaxation maps were compared between MHE and control subjects using analysis-of-covariance, with age and gender included as covariates. T(2) values derived from the right frontal and left occipital lobes were correlated with the metabolite ratios. RESULTS Multiple brain regions including anterior and mid cingulate cortices, right anterior and left posterior insular cortices, right prefrontal, medial frontal, and right superior temporal cortices showed significantly increased T(2) values in MHE patients compared to control subjects. MRS showed significantly increased ratios of glutamine/glutamate (Glx) and decreased ratios of myo-inositol, taurine, choline, and myo-inositol/choline (mICh) with respect to creatine (Cr_d) in patients compared to controls. Frontal Glx/Cr_d showed significantly positive correlation with T(2) values. CONCLUSION MHE patients showed significantly increased T(2) values in multiple brain regions reflecting increased free water content and T(2) values in frontal lobe correlated with the increased Glx/Cr_d ratio.
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Affiliation(s)
- Aparna Singhal
- Department of Radiological Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1721, USA
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13
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Ahmed KH, Pelster B. Ionic determinants of pH of acidic compartments under hypertonic conditions in trout hepatocytes. J Exp Biol 2008; 211:3306-14. [PMID: 18840665 DOI: 10.1242/jeb.020776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Exposure of trout hepatocytes to hypertonicity induced a decrease in acridine orange (AO) fluorescence, indicating a corresponding decrease in pH inside the lumen of acidic compartments (pH(L)). Pre-exposure of cells to the specific V-ATPase inhibitor bafilomycin A1 (0.3 micromol l(-1)) increased AO fluorescence - unmasking H(+) leaks under steady-state conditions - and partially removed the hypertonicity-induced pH(L) decrease. The sustainability of the luminal acidification, but not the acidification itself, appeared to depend on a low K(+) and a high Cl(-) conductance under hypertonic conditions. Increasing K(+) conductance using the specific ionophore valinomycin (10 micromol l(-1)) or removal of extracellular Cl(-) after an instant drop in AO fluorescence resulted in a reversal of luminal acidity. The alkalinization measured under hypertonic conditions in the absence of Cl(-) was largely attenuated when cells were bathed in HCO(3)(-)-free medium, signifying the possible presence of Cl(-)/HCO(3)(-) exchange. Under steady-state conditions, while a slight and brief pH(L) increase was measured upon exposure of cells to valinomycin, Cl(-) removal, unexpectedly, induced a decrease in pH(L), indicating a role for extracellular Cl(-) in limiting luminal acidification. This was confirmed by the substantial pH(L) decrease measured upon exposure of cells to the anion exchanger inhibitor SITS (0.5 mmol l(-1)). Furthermore, hypertonicity-induced acidification was still noticeable in the presence of SITS. On the other hand, the hypertonicity-induced acidification was significantly reduced in the absence of extracellular Na(+) or Ca(2+). However, BAPTA-AM induced an increase in steady-state pH(L) that was independent of V-ATPase inhibition. Moreover, the BAPTA-induced alkalinization was still apparent after depletion of intracellular Ca(2+) using the Ca(2+) ionophore A23187 in Ca(2+)-free medium. We conclude that pH(L) of trout hepatocytes is sensitive to hypertonicity and ionic determinants of hypertonicity. Thus, changes in pH(L) should be considered when studying pH adaptations to hypertonic stress.
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Affiliation(s)
- Khaled H Ahmed
- Institut für Zoologie and Center of Molecular Biosciences, Leopold Franzens Universität Innsbruck, Innsbruck, Austria
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14
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Portincasa P, Palasciano G, Svelto M, Calamita G. Aquaporins in the hepatobiliary tract. Which, where and what they do in health and disease. Eur J Clin Invest 2008; 38:1-10. [PMID: 18173545 DOI: 10.1111/j.1365-2362.2007.01897.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The biological importance of the aquaporin family of water channels was recently acknowledged by the 2003 Nobel Prize for Chemistry awarded to the discovering scientist Peter Agre. Among the pleiotropic roles exerted by aquaporins in nature in both health and disease, the review addresses the latest acquisitions about the expression and regulation, as well as physiology and pathophysiology of aquaporins in the hepatobiliary tract. Of note, at least seven out of the thirteen mammalian aquaporins are expressed in the liver, bile ducts and gallbladder. Aquaporins are essential for bile water secretion and reabsorption, as well as for plasma glycerol uptake by the hepatocyte and its conversion to glucose during starvation. Novel data are emerging regarding the physio-pathological involvement of aquaporins in multiple diseases such as cholestases, liver cirrhosis, obesity and insulin resistance, fatty liver, gallstone formation and even microparasite invasion of intrahepatic bile ducts. This body of knowledge represents the mainstay of present and future research in a rapidly expanding field.
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Affiliation(s)
- P Portincasa
- Department of Internal Medicine & Public Medicine, University of Bari, Italy
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15
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Schliess F, Reinehr R, Häussinger D. Osmosensing and signaling in the regulation of mammalian cell function. FEBS J 2007; 274:5799-803. [DOI: 10.1111/j.1742-4658.2007.06100.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
Changes in hepatocyte hydration are induced not only by ambient hypo- or hyperosmolarity, but also under isosmotic condition by hormones, substrates, and oxidative stress. The perfused rat liver is a well-established intact organ model with preservation of the three-dimensional hepatocyte anchoring to the extracellular matrix and/or adjacent cells, parenchymal cell polarity, liver cell heterogeneity, acinar construction, and gene expression gradients. Originally, data from the perfused rat liver indicated that changes of cell hydration independent of their origin critically contribute to the control of autophagic proteolysis and canalicular bile acid excretion. Meanwhile, the concept that cell hydration changes trigger signal transduction processes that control metabolism, gene expression, transport, and the susceptibility to stress is well accepted. This chapter summarizes evidence obtained from experiments with the perfused rat liver that integrins are osmosensors in the liver and thereby critically contribute to the Src- and MAP-kinase-dependent inhibition of autophagic proteolysis, stimulation of canalicular taurocholate excretion, and regulatory volume decrease as induced by hypoosmotic swelling. Moreover, integrin-dependent sensing of hepatocyte swelling is essential for signaling and proteolysis inhibition by insulin and glutamine. These findings define a novel role of integrins in insulin and glutamine signaling and set an example for mechanotransduction as an integral part of overall growth factor and nutrient signaling.
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Affiliation(s)
- Freimut Schliess
- Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University, Düsseldorf, Germany
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Rosón MI, Cavallero S, Della Penna S, Cao G, Gorzalczany S, Pandolfo M, Kuprewicz A, Canessa O, Toblli JE, Fernández BE. Acute sodium overload produces renal tubulointerstitial inflammation in normal rats. Kidney Int 2006; 70:1439-46. [PMID: 16955102 DOI: 10.1038/sj.ki.5001831] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The aim of the present study was to determine whether acute sodium overload could trigger an inflammatory reaction in the tubulointerstitial (TI) compartment in normal rats. Four groups of Sprague-Dawley rats received increasing NaCl concentrations by intravenous infusion. Control (C): Na+ 0.15 M; G1: Na+ 0.5 M; G2: Na+ 1.0 M; and G3: Na+ 1.5 M. Creatinine clearance, mean arterial pressure (MAP), renal blood flow (RBF), and sodium fractional excretion were determined. Transforming growth factor beta1 (TGF-beta1), alpha-smooth muscle actin (alpha-SMA), RANTES, transcription factor nuclear factor-kappa B (NF-kappaB), and angiotensin II (ANG II) were evaluated in kidneys by immunohistochemistry. Animals with NaCl overload showed normal glomerular function without MAP and RBF modifications and exhibited a concentration-dependent natriuretic response. Plasmatic sodium increased in G2 (P < 0.01) and G3 (P < 0.001). Light microscopy did not show renal morphological damage. Immunohistochemistry revealed an increased number of ANG II-positive tubular cells in G2 and G3, and positive immunostaining for NF-kappaB only in G3 (P < 0.01). Increased staining of alpha-SMA in the interstitium (P < 0.01), TGF-beta1 in tubular cells (P < 0.01), and a significant percentage (P < 0.01) of positive immunostaining for RANTES in tubular epithelium and in glomerular and peritubular endothelium were detected in G3 > G2 > C group. These results suggest that an acute sodium overload is able 'per se' to initiate TI endothelial inflammatory reaction (glomerular and peritubular) and incipient fibrosis in normal rats, independently of hemodynamic modifications. Furthermore, these findings are consistent with the possibility that activation of NF-kappaB and local ANG II may be involved in the pathway of this inflammatory process.
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Affiliation(s)
- M I Rosón
- Cátedras de Fisiopatología Farmacologia Bioquímica Clínica y Anatomía Macro y Microscópica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Piso, Buenos Aires.
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18
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Reinehr R, Becker S, Braun J, Eberle A, Grether-Beck S, Haüssinger D. Endosomal Acidification and Activation of NADPH Oxidase Isoforms Are Upstream Events in Hyperosmolarity-induced Hepatocyte Apoptosis. J Biol Chem 2006; 281:23150-66. [PMID: 16772302 DOI: 10.1074/jbc.m601451200] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hyperosmotic exposure of rat hepatocytes induced a rapid oxidative-stress(ROS) response as an upstream signal for proapoptotic CD95 activation. This study shows that hyperosmotic ROS formation involves a rapid ceramide- and protein kinase Czeta (PKCzeta)-dependent serine phosphorylation of p47phox and subsequent activation of NADPH oxidase isoforms. Hyperosmotic p47phox phosphorylation and ROS formation were sensitive to inhibition of sphingomyelinases and were strongly blunted after knockdown of acidic sphingomyelinase (ASM) or of p47phox protein. Hyperosmolarity induced a rapid bafilomycin- and 4,4 '-diisothiocyanostilbene-2,2 '-disulfonic acid disodium salt (DIDS)-sensitive acidification of a vesicular compartment, which was accessible to endocytosed fluorescein isothiocyanate-dextran and colocalized with ASM, PKCzeta, and the NADPH oxidase isoform Nox 2 (gp91phox). Bafilomycin and DIDS prevented the hyperosmolarity-induced increase in ceramide formation, p47phox phosphorylation, and ROS formation. As shown recently (Reinehr, R., Becker, S., Höngen, A., and Häussinger, D. (2004) J. Biol. Chem. 279, 23977-23987), hyperosmolarity induced a Yes-dependent activation of JNK and the epidermal growth factor receptor (EGFR), followed by EGFR-CD95 association, EGFR-catalyzed CD95-tyrosine phosphorylation, and translocation of the EGFR-CD95 complex to the plasma membrane, where formation of the deathinducing signaling complex occurs. These proapoptotic responses were not only sensitive to inhibitors of sphingomyelinase, PKCzeta, or NADPH oxidases but also to ASM knockdown, bafilomycin, and DIDS, i.e. maneuvers largely preventing hyperosmolarity-induced endosomal acidification and/or ceramide formation. In hepatocytes from p47phox knock-out mice, hyperosmolarity failed to activate the CD95 system. The data suggest that hyperosmolarity induces endosomal acidification as an important upstream event for CD95 activation through stimulation of ASM-dependent ceramide formation and activation of NADPH oxidase isoforms.
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Affiliation(s)
- Roland Reinehr
- Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University and Institut für Umweltmedizinische Forschung, D-40225 Düsseldorf, Germany
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Hilgemann DW, Yaradanakul A, Wang Y, Fuster D. Molecular Control of Cardiac Sodium Homeostasis in Health and Disease. J Cardiovasc Electrophysiol 2006; 17 Suppl 1:S47-S56. [PMID: 16686682 DOI: 10.1111/j.1540-8167.2006.00383.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
INTRODUCTION Cardiac myocytes utilize three high-capacity Na transport processes whose precise function can determine myocyte fate and the triggering of arrhythmias in pathological settings. We present recent results on the regulation of all three transporters that may be important for an understanding of cardiac function during ischemia/reperfusion episodes. METHODS AND RESULTS Refined ion selective electrode (ISE) techniques and giant patch methods were used to analyze the function of cardiac Na/K pumps, Na/Ca exchange (NCX1), and Na/H exchange (NHE1) in excised cardiac patches and intact myocytes. To consider results cohesively, simulations were developed that account for electroneutrality of the cytoplasm, ion homeostasis, water homeostasis (i.e., cell volume), and cytoplasmic pH. The Na/K pump determines the average life-time of Na ions (3-10 minutes) as well as K ions (>30 minutes) in the cytoplasm. The long time course of K homeostasis can determine the time course of myocyte volume changes after ion homeostasis is perturbed. In excised patches, cardiac Na/K pumps turn on slowly (-30 seconds) with millimolar ATP dependence, when activated for the first time. In steady state, however, pumps are fully active with <0.2 mM ATP and are nearly unaffected by high ADP (2 mM) and Pi (10 mM) concentrations as may occur in ischemia. NCX1s appear to operate with slippage that contributes to background Na influx and inward current in heart. Thus, myocyte Na levels may be regulated by the inactivation reactions of the exchanger which are both Na- and proton-dependent. NHE1 also undergo strong Na-dependent inactivation, whereby a brief rise of cytoplasmic Na can cause inactivation that persists for many minutes after cytoplasmic Na is removed. This mechanism is blocked by pertussis toxin, suggesting involvement of a Na-dependent G-protein. Given that maximal NCX1- and NHE1-mediated ion fluxes are much greater than maximal Na/K pump-mediated Na extrusion in myocytes, the Na-dependent inactivation mechanisms of NCX1 and NHE1 may be important determinants of cardiac Na homeostasis. CONCLUSIONS Na/K pumps appear to be optimized to continue operation when energy reserves are compromised. Both NCX1 and NHE1 activities are regulated by accumulation of cytoplasmic Na. These principles may importantly control cardiac cytoplasmic Na and promote myocyte survival during ischemia/reperfusion episodes by preventing Ca overload.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9040, USA.
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20
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Abstract
Alterations of cell volume induced by either aniso-osmotic environments or under the influence of hormones, concentrative amino acid uptake and oxidative stress were recognized as an independent signal contributing to the regulation of metabolism and gene expression. The regulation of cell function by hydration changes requires structures, which register fluctuations of cell hydration (osmosensing) and thereby activate intracellular signalling pathways towards effector sites (osmosignalling). Meanwhile, it is well established that osmosensing and signalling integrate into the overall context of hormone- and nutrient-induced signal transduction. Recent evidence suggests integrins to play a major role in osmosensing and signalling due to hepatocyte swelling. This review focuses on the role of integrins in sensing of hepatocyte swelling as triggered by hypo-osmolarity, glutamine and insulin and the relevance of integrin-dependent osmosignalling for inhibition of autophagic proteolysis, stimulation of canalicular bile acid excretion and regulatory volume decrease.
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Affiliation(s)
- D Häussinger
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Düsseldorf, Germany.
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21
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Schreiber R. Ca2+ signaling, intracellular pH and cell volume in cell proliferation. J Membr Biol 2006; 205:129-37. [PMID: 16362501 DOI: 10.1007/s00232-005-0778-z] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Indexed: 01/06/2023]
Abstract
Mitogens control progression through the cell cycle in non-transformed cells by complex cascades of intracellular messengers, such as Ca2+ and protons, and by cell volume changes. Intracellular Ca2+ and proton concentrations are critical for linking external stimuli to proliferation, motility, apoptosis and differentiation. This review summarizes the role in cell proliferation of calcium release from intracellular stores and the Ca2+ entry through plasma membrane Ca2+ channels. In addition, the impact of intracellular pH and cell volume on cell proliferation is discussed.
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Affiliation(s)
- R Schreiber
- Institut für Physiologie, Universität Regensburg, Universitätsstr. 31, Regensburg, D-93053, Germany.
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Stookey JD. High prevalence of plasma hypertonicity among community-dwelling older adults: results from NHANES III. JOURNAL OF THE AMERICAN DIETETIC ASSOCIATION 2005; 105:1231-9. [PMID: 16182639 DOI: 10.1016/j.jada.2005.05.003] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Indexed: 10/25/2022]
Abstract
OBJECTIVE Recent data suggest that as many as 50% of older adults may have hypertonic plasma, an indicator of cell dehydration that predicts a range of adverse outcomes. To determine if a prevalence of this magnitude could be real, this study used nationally representative data to estimate the prevalence of hypertonicity, and to test for biologically plausible associations between hypertonicity, older age, glucose dysregulation, hemoconcentration, reduced bioelectrical impedance, and water intake. DESIGN Cross-sectional. SUBJECTS Community-dwelling adults (aged 20 to 90 years) who gave blood as part of the Third National Health and Nutrition Examination Survey (N = 14,855). STATISTICAL ANALYSES Plasma tonicity was estimated from glucose, sodium, and potassium values. The weighted prevalences of mild (295 to 300 mmol/L) and overt hypertonicity (> or = 300 mmol/L) were estimated by age, sex, race/ethnicity, fasting, and glycemic status. Hyper- and normotonic (285 to 295 mmol/L) groups were compared with respect to elevated blood chemistry values, bioelectrical impedance analysis parameters, as well as total water intake (grams, % Adequate Intake, and grams per kilogram body weight), using multivariable models that adjusted for age, sex, race/ethnicity, and survey design. RESULTS Mild and overt hypertonicity were observed in 40% and 20% of the sample, respectively. Hypertonicity was positively associated with older age, Hispanic and African-American race, impaired glucose tolerance, diabetes, and hemoconcentration, and inversely associated with bioelectrical impedance analysis parameters. Hypertonicity was associated with greater total water intake in younger adults, but decreased intake in older adults. CONCLUSIONS Clinicians and researchers should be alert to hypertonicity and its causes in older adults.
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Affiliation(s)
- Jodi Dunmeyer Stookey
- Stanford Prevention Research Center, Stanford University School of Medicine, California 94305-5705, USA.
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Weissenborn K, Bokemeyer M, Ahl B, Fischer-Wasels D, Giewekemeyer K, van den Hoff J, Köstler H, Berding G. Functional imaging of the brain in patients with liver cirrhosis. Metab Brain Dis 2004; 19:269-80. [PMID: 15554422 DOI: 10.1023/b:mebr.0000043976.17500.8e] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Brain imaging techniques have provided substantial insight into the pathophysiology of hepatic encephalopathy (HE). Magnetic resonance imaging gave hint to the fact that there is an increased deposition of manganese especially in the basal ganglia. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) showed that the preference of the basal ganglia might be due to differences in regional cerebral blood flow and an additional redistribution of blood flow from the cortex to subcortical regions in cirrhotics. PET studies using ammonia as tracer showed that the cerebral metabolism of ammonia and the permeability of the blood brain barrier for ammonia is increased in cirrhotic patients compared to healthy controls. The regional ammonia supply is in accordance with the regional blood flow. In accordance with these findings fluorodesoxyglucose-PET-studies of the brain in cirrhotics showed characteristic alterations of glucose utilisation in the patients with a relative decrease of the glucose utilisation of the cingulate gyrus, the frontomedial, frontolateral, and parieto-occipital cortex, while the glucose utilisation of the basal ganglia, the hippocampus, and the cerebellum was relatively increased. These findings fit well with the clinical characteristics of early stages of HE such as deficits in attention, visuo-spatial orientation, visuo-constructive abilities, motor speed, and accuracy.
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Affiliation(s)
- Karin Weissenborn
- Department of Neurology, Medizinische Hochschule Hannover, Hannover, Germany.
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Stookey JD, Pieper CF, Cohen HJ. Hypertonic hyperglycemia progresses to diabetes faster than normotonic. Eur J Epidemiol 2004; 19:935-44. [PMID: 15575352 DOI: 10.1007/s10654-004-5729-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
To explore whether elevated plasma glucose might progress to diabetes via a mechanism that involves plasma hypertonicity, we evaluated the independent and joint effects of these variables on diabetes risk. Community-dwelling older adults (70+years), who reported no previous diagnosis of diabetes and had glucose levels below 200 mg/dl in the 1992 Duke EPESE survey, were re-interviewed in 1996 for diabetes status (n = 979). Plasma tonicity at baseline was estimated from serum glucose, sodium, and potassium measures. In logistic regression models that controlled for glucose, as well as age, sex, race, weight status, activity level, serum creatinine, history of heart disease, stroke and cancer, plasma hypertonicity (> or = 300 mOsm/l) was independently associated with increased odds of developing diabetes (OR = 2.0, 95% CI: 0.9-4.2). Hypertonicity magnified the effects of elevated glucose (> or = 125 mg/dl), such that individuals with both exposures were over four times more likely to develop diabetes than those with elevated glucose only (OR = 4.9, 95%CI: 1.7-14.3), adjusting for all covariates. When tonicity was replaced by its determinant variables, glucose, sodium and potassium, in the multivariable models, independent effects of sodium were also observed. Further work is needed to pursue plasma hypertonicity as a factor in the progression of elevated plasma glucose to diabetes.
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25
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Attuwaybi B, Kozar RA, Gates KS, Moore-Olufemi S, Sato N, Weisbrodt NW, Moore FA. Hypertonic saline prevents inflammation, injury, and impaired intestinal transit after gut ischemia/reperfusion by inducing heme oxygenase 1 enzyme. ACTA ACUST UNITED AC 2004; 56:749-58; discussion 758-9. [PMID: 15187737 DOI: 10.1097/01.ta.0000119686.33487.65] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
BACKGROUND Hypertonic saline (HTS) has been shown to modulate the inflammatory response after shock. We have previously demonstrated that heme oygenase-1 (HO-1) induction is protective against gut dysfunction in models of shock-induced gut ischemia/reperfusion (I/R). We therefore hypothesized that HTS prevents gut inflammation, injury, and impaired transit by inducing HO-1 in a model of gut I/R. METHODS Rats underwent 60 minutes of superior mesenteric artery occlusion (SMAO) and then were resuscitated with 4 mL/kg of HTS, an equal volume of lactated Ringer's (LR) solution (4 mL/kg, low volume), or equal salt LR solution (32 mL/kg, high volume) and compared with SMAO alone or shams. A separate group was pretreated with the HO-1 blocker Sn protoporphyrin IX (SNP IX) before SMAO plus HTS. At 6 hours of reperfusion, transit was determined and ileum harvested for HO-1 (anti-inflammatory) and inducible nitric oxide synthase (proinflammatory) immunoreactivity, myeloperoxidase (MPO) activity, and histologic injury. Data are expressed as mean +/- SEM (analysis of variance). RESULTS Intestinal transit was severely impaired after SMAO (2.5 +/- 0.1), improved with low- and high-volume LR solution (3.2 +/- 0.2 and 3.1 +/- 0.1, not significant), but returned to sham (4.6 +/- 0.2) with HTS (4.8 +/- 0.2). Pretreatment with SNP abrogated this protective effect. Myeloperoxidase activity was significantly increased by SMAO (SMAO, 2.3 +/- 0.3; sham, 0.4 +/- 0.05), lessened by low- and high-volume LR solution (1.5 +/- 0.3 and 1.7 +/- 0.4), but returned to sham levels with HTS (1.0 +/- 0.01). Activity with SNP IX pretreatment was significantly increased (4.04 +/- 0.8). Mucosal injury followed a similar pattern. Inducible nitric oxide synthase was increased by SMAO and low- and high-volume LR solution (0.8 +/- 0.2, 0.8 +/- 0.03, and 0.8 +/- 0.02, respectively; sham, 0.5 +/- 0.02), but significantly reduced by HTS (0.7 +/- 0.02). HO-1 was induced by SMAO and low- and high-volume LR solution (0.33 +/- 0.02, 0.32 +/- 0.03, and 0.37 +/- 0.4, respectively; sham, 0.0 +/- 0.0), but was further increased with HTS (0.49 +/- 0.04). CONCLUSION HTS resuscitation protects against inflammation, injury, and impaired intestinal transit after gut I/R in part by inducing HO-1. This is a novel mechanism of HO-1 protection.
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Affiliation(s)
- Bashir Attuwaybi
- Department of Surgery, University of Texas-Houston, Houston, Texas 77030, USA
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26
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Huang Z, Tunnacliffe A. Response of human cells to desiccation: comparison with hyperosmotic stress response. J Physiol 2004; 558:181-91. [PMID: 15146043 PMCID: PMC1664923 DOI: 10.1113/jphysiol.2004.065540] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Increasing interest in anhydrobiosis ('life without water') has prompted the use of mammalian cells as a model in which candidate adaptations suspected of conferring desiccation tolerance can be tested. Despite this, there is no information on whether mammalian cells are able to sense and respond to desiccation. We have therefore examined the effect of desiccation on stress signalling pathways and on genes which are proposed to be expressed in response to water loss through osmotic stress. Depending on the severity of the drying regime, human cells survived for at least 24 h. Both SAPK/JNK and p38 mitogen-activated protein kinases (MAPKs) were activated within 30 min by desiccation as well as by all osmotica tested, and therefore MAPK pathways probably play an important role in both responses. Gene induction profiles differed under the two stress conditions, however: quantitative polymerase chain reaction (PCR) experiments showed that AR, BGT-1 and SMIT, which encode proteins governing organic osmolyte accumulation, were induced by hypersalinity but not by desiccation. This was surprising, since these genes have been proposed to be regulated by ionic strength and cell volume, both of which should be significantly affected in drying cells. Further investigation demonstrated that AR, BGT-1 and SMIT expression was dependent on the nature of the osmolyte. This suggests that their regulation involves factors other than intracellular ionic strength and cell volume changes, consistent with the lack of induction by desiccation. Our results show for the first time that human cells react rapidly to desiccation by MAPK activation, and that the response partially overlaps with that to hyperosmotic stress.
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Affiliation(s)
- Zebo Huang
- Institute of Biotechnology University of Cambridge, Tennis Court Road, Cambridge CB2 1QT, UK
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27
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Reinehr R, Becker S, Höngen A, Haüssinger D. The Src family kinase Yes triggers hyperosmotic activation of the epidermal growth factor receptor and CD95. J Biol Chem 2004; 279:23977-87. [PMID: 15039424 DOI: 10.1074/jbc.m401519200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Hyperosmotic exposure of rat hepatocytes triggers epidermal growth factor receptor (EGFR) activation, which results in an activation of the CD95 system and sensitizes the cells toward apoptosis (Reinehr, R., Schliess, F., and Haüssinger, D. (2003) FASEB J. 17, 731-733). The mechanisms underlying the hyperosmotic EGFR activation were studied. Hyperosmotic exposure (405 mosm) resulted in a rapid activation of the Src kinase family members Yes, Fyn, and Lck. Hyperosmotic Yes, but not Fyn activation, was antioxidant-sensitive and was followed by a rapid Yes/EGFR association. PP-2 abolished the hyperosmotic activation of Fyn and Lck but not activation of Yes and EGFR and their association. However, these latter processes were prevented in the presence of SU6656. SU6656 and antioxidants, but not PP-2 and AG1478, also inhibited the hyperosmotic JNK activation. Cyclic AMP had no effect on hyperosmotic Yes and JNK activation but prevented EGFR/Yes association and EGFR activation in an H89-sensitive way. When the hyperosmolarity-induced Yes-EGFR protein complex started to disappear after 30 min, an association between EGFR and CD95 became apparent, which was followed by CD95 tyrosine phosphorylation and activation. SU6656 but not PP-2 also inhibited EGFR/CD95 association, CD95 tyrosine phosphorylation, CD95 membrane trafficking, and death-inducing signaling complex (DISC) formation. EGFR knockdown had no effect on hyperosmotic Yes activation but prevented CD95 tyrosine phosphorylation, membrane targeting, and DISC formation. Hyperosmotic EGFR and CD95 activation was also largely blunted following Yes knockdown. The data suggest that hyperosmotic signaling triggers an oxidative stress-dependent Yes activation, which is followed by JNK and EGFR activation and subsequent activation of the CD95 system. However, the functional relevance of hyperosmolarity-induced Fyn and Lck activation remains to be elucidated.
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Affiliation(s)
- Roland Reinehr
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Moorenstrasse 5, Düsseldorf D-40225, Germany
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28
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Abstract
Perturbations of cell hydration as provoked by changes in ambient osmolarity or under isoosmotic conditions by hormones, second messengers, intracellular substrate accumulation, or reactive oxygen intermediates critically contribute to the physiological regulation of cell function. In general an increase in cell hydration stimulates anabolic metabolism and proliferation and provides cytoprotection, whereas cellular dehydration leads to a catabolic situation and sensitizes cells to apoptotic stimuli. Insulin produces cell swelling by inducing a net K+ and Na+ accumulation inside the cell, which results from a concerted activation of Na+/H+ exchange, Na+/K+/2Cl- symport, and the Na+/K(+)-ATPase. In the liver, insulin-induced cell swelling is critical for stimulation of glycogen and protein synthesis as well as inhibition of autophagic proteolysis. These insulin effects can largely be mimicked by hypoosmotic cell swelling, pointing to a role of cell swelling as a trigger of signal transduction. This article discusses insulin-induced signal transduction upstream of swelling and introduces the hypothesis that cell swelling as a signal amplifyer represents an essential component in insulin signaling, which contributes to the full response to insulin at the level of signal transduction and function. Cellular dehydration impairs insulin signaling and may be a major cause of insulin resistance, which develops in systemic hyperosmolarity, nutrient deprivation, uremia, oxidative challenges, and unbalanced production of insulin-counteracting hormones. Hydration changes affect cell functions at multiple levels (such as transcriptom, proteom, phosphoproteom, and the metabolom) and a system biological approach may allow us to develop a more holistic view on the hydration dependence of insulin signaling in the future.
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Affiliation(s)
- Freimut Schliess
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Düsseldorf, Germany
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29
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Portincasa P, Moschetta A, Mazzone A, Palasciano G, Svelto M, Calamita G. Water handling and aquaporins in bile formation: recent advances and research trends. J Hepatol 2003; 39:864-74. [PMID: 14568273 DOI: 10.1016/s0168-8278(03)00294-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Piero Portincasa
- Section of Internal Medicine, Department of Internal Medicine and Public Medicine, Medical School, University of Bari, Bari, Italy
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30
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Tabary O, Muselet C, Miesch MC, Yvin JC, Clément A, Jacquot J. Reduction of chemokine IL-8 and RANTES expression in human bronchial epithelial cells by a sea-water derived saline through inhibited nuclear factor-kappaB activation. Biochem Biophys Res Commun 2003; 309:310-6. [PMID: 12951051 DOI: 10.1016/j.bbrc.2003.07.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The NaCl content of airway surface fluid is believed to be of central importance in lung pathology. To test whether the Na+ concentration could influence the inflammatory response in human bronchial epithelial cells (BECs), we investigated the interleukin (IL)-8 and RANTES expression in BECs exposed to an isotonic sea-water derived low Na+ (ISW) saline compared to isotonic 0.9% NaCl saline. Exposure of BECs to ISW saline caused a significant decrease in IL-8 and RANTES gene expression and protein production as compared to that observed with 0.9% NaCl saline. Furthermore, we observed a concomitant reduction of phosphorylated IkappaBalpha associated with a marked inhibition of NF-kappaB-DNA binding activity in BECs exposed to ISW saline as compared to 0.9% NaCl saline. These findings support a new role for Na+ in the pathogenesis of airway inflammatory disorders. Therapies targeted at lowering Na+ level in airway epithelium may be beneficial in treating inflammatory lung diseases.
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vom Dahl S, Schliess F, Reissmann R, Görg B, Weiergräber O, Kocalkova M, Dombrowski F, Häussinger D. Involvement of integrins in osmosensing and signaling toward autophagic proteolysis in rat liver. J Biol Chem 2003; 278:27088-95. [PMID: 12721289 DOI: 10.1074/jbc.m210699200] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inhibition of autophagic proteolysis by hypoosmotic or amino acid-induced hepatocyte swelling requires osmosignaling toward p38MAPK; however, the upstream osmosensing and signaling events are unknown. These were studied in the intact perfused rat liver with a preserved in situ environment of hepatocytes. It was found that hypoosmotic hepatocyte swelling led to an activation of Src (but not FAK), Erks, and p38MAPK, which was prevented by the integrin inhibitory hexapeptide GRGDSP, but not its inactive analogue GRGESP. Src inhibition by PP-2 prevented hypoosmotic MAP kinase activation, indicating that the integrin/Src system is located upstream in the osmosignaling toward p38MAPK and Erks. Inhibition of the integrin/Src system by the RGD motif-containing peptide or PP-2 also prevented the inhibition of proteolysis and the decrease in autophagic vacuole volume, which is otherwise observed in response to hypoosmotic or glutamine/glycine-induced hepatocyte swelling. These inhibitors, however, did not affect swelling-independent proteolysis inhibition by phenylalanine. In line with a role of p38MAPK in triggering the volume regulatory decrease (RVD), PP-2 and the RGD peptide blunted RVD in response to hypoosmotic cell swelling. The data identify integrins and Src as upstream events in the osmosignaling toward MAP kinases, proteolysis, and RVD. They further point to a role of integrins as osmo- and mechanosensors in the intact liver, which may provide a link between cell volume and cell function.
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Affiliation(s)
- Stephan vom Dahl
- Division of Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Moorenstrasse 5, D-40225-Düsseldorf, Germany.
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Reinehr R, Schliess F, Häussinger D. Hyperosmolarity and CD95L trigger CD95/EGF receptor association and tyrosine phosphorylation of CD95 as prerequisites for CD95 membrane trafficking and DISC formation. FASEB J 2003; 17:731-3. [PMID: 12586732 DOI: 10.1096/fj.02-0915fje] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The mechanisms underlying CD95 ligand (CD95L)- and hyperosmolarity-induced activation of the CD95 system [Reinehr, R., Graf, D., Fischer, R., Schliess, F., and Haussinger, D. (2002) Hepatology 36, 602-614] as initial steps of apoptosis were studied. Hyperosmotic exposure (405 mosmol/l) of rat hepatocytes induced within 1 min oxidative stress and antioxidant-sensitive activation of the epidermal growth factor receptor (EGFR) and c-Jun-N-terminal-kinase (JNK). After 30 min of hyperosmotic exposure EGFR associated with CD95 and CD95 became tyrosine phosphorylated. Inhibition of JNK or protein kinase C (PKC) had no effect on EGFR phosphorylation but abolished CD95/EGFR association, CD95-tyrosine phosphorylation, membrane targeting, and Fas-associated death domain/caspase 8 recruitment to CD95 [death-inducing signaling complex (DISC) formation]. Inhibition of EGFR tyrosine kinase activity prevented CD95 tyrosine phosphorylation and DISC formation but not hyperosmolarity-induced EGFR phosphorylation and EGFR association with CD95. Tyrosine-phosphorylated CD95 was enriched in the plasma membrane. All maneuvers preventing CD95 tyrosine phosphorylation inhibited CD95 membrane trafficking and DISC formation. Stimulation of EGFR by EGF induced EGFR phosphorylation but no association with CD95 or CD95 phosphorylation. Addition of CD95L also induced EGFR and JNK activation, EGFR/CD95 association, CD95 tyrosine phosphorylation, DISC formation, and CD95 membrane targeting with an inhibitor sensitivity profile similar to that of hyperosmotic CD95 activation, except that inhibition of PKC was ineffective. The data suggest that moderate hyperosmolarity or CD95L trigger oxidative stress and EGFR activation followed by a JNK-dependent EGFR/CD95association and CD95 tyrosine phosphorylation, probably through EGFR tyrosine kinase activity. This provides a signal for CD95 membrane trafficking and DISC formation.
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Affiliation(s)
- Roland Reinehr
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University Düsseldorf, Germany
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33
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Purinergic Receptors and Hepatobiliary Function. CURRENT TOPICS IN MEMBRANES 2003. [DOI: 10.1016/s1063-5823(03)01012-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Abstract
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome during the course of acute or chronic liver disease. It is functional in nature, potentially reversible and precipitated by rather heterogeneous factors. At the neurophysiological level HE is characterized by a low frequent cortico-cortical electrical coupling, which may explain the cognitive deficits and a low frequent corticomuscular coupling, which may explain the fine motor deficits. Current evidence suggests that HE is the consequence of a low grade chronic glial edema with subsequent alterations of glioneuronal communication. Different factors, such as ammonia, benzodiazepines, inflammatory cytokines can induce or aggravate astrocyte swelling, which results in the activation of osmosignaling cascades, protein modifications, alterations in gene expression and neurotransmission. Among the protein modifications nitration of critical tyrosine residues in glial proteins may play an important role. Several proteins, which are nitrated in response to ammonia, benzodiazepines, hypoosmotic astrocyte swelling or inflammatory cytokines have been identified, including glutamine synthetase and the peripheral type benzodiazepine receptor.
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Affiliation(s)
- Dieter Häussinger
- Clinic for Gastroenterology, Hepatology und Infectiology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
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35
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Ko BCB, Lam AKM, Kapus A, Fan L, Chung SK, Chung SSM. Fyn and p38 signaling are both required for maximal hypertonic activation of the osmotic response element-binding protein/tonicity-responsive enhancer-binding protein (OREBP/TonEBP). J Biol Chem 2002; 277:46085-92. [PMID: 12359721 DOI: 10.1074/jbc.m208138200] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
When cells are challenged by hyperosmotic stress, one of the crucial adaptive responses is the expression of osmoprotective genes that are responsible for raising the intracellular level of compatible osmolytes such as sorbitol, betaine, and myo-inositol. This is achieved by the activation of the transcription factor called OREBP (also known as TonEBP or NFAT5) that specifically binds to the osmotic response element (ORE) or tonicity-responsive enhancer that enhances the transcription of these genes. Here we show that p38, a subgroup of the mitogen-activated kinases activated by hypertonic stress, and Fyn, a shrinkage-activated tyrosine kinase, are both involved in the hypertonic activation of OREBP/TonEBP. Inhibition of p38 by SB203580 or by the dominant negative p38 mutant partially blocked the hypertonic induction of ORE reporter (reporter gene regulated by ORE). Similarly, hypertonic activation of ORE reporter was partially blocked by pharmacological inhibition of Fyn or by a dominant negative Fyn and was attenuated in Fyn-deficient cells. Importantly, inhibiting p38 in Fyn-deficient cells almost completely abolished the hypertonic induction of ORE reporter activity, indicating that p38 and Fyn are the major signaling pathways for the hypertonic activation of OREBP/TonEBP. Further we show that the transactivation domain of OREBP/TonEBP is the target of p38- and Fyn-mediated hypertonic activation. These results indicate a dual control in regulating the expression of the osmoprotective genes in mammalian cells.
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Affiliation(s)
- Ben C B Ko
- Department of Chemistry, The University of Hong Kong, Hong Kong
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36
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Reinehr R, Graf D, Fischer R, Schliess F, Häussinger D. Hyperosmolarity triggers CD95 membrane trafficking and sensitizes rat hepatocytes toward CD95L-induced apoptosis. Hepatology 2002; 36:602-14. [PMID: 12198652 DOI: 10.1053/jhep.2002.35447] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effect of hyperosmolarity on CD95 membrane targeting and CD95 ligand (CD95L)-induced apoptosis was studied in rat hepatocytes. CD95 showed a predominant intracellular localization in normoosmotically exposed rat hepatocytes, whereas hyperosmotic exposure induced, within 1 hour, CD95 trafficking to the plasma membrane followed by activation of caspase-3 and -8. Hyperosmotic CD95 membrane targeting was sensitive to inhibition of c-Jun-N-terminal kinase (JNK), protein kinase C (PKC), and cyclic adenosine monophosphate, but not to inhibition of extracellular regulated kinases (Erks) or p38 mitogen activated protein kinase (p38(MAPK)). Hyperosmotic CD95 targeting to the plasma membrane was dose-dependently diminished by glutamine or taurine, probably caused by an augmentation of volume regulatory increase. Despite CD95 trafficking to the plasma membrane and caspase activation, hyperosmolarity per se did not induce apoptosis. Hyperosmolarity, however, sensitized hepatocytes toward CD95L-induced apoptosis, as assessed by annexin V staining and terminal deoxynucleotidyl transferase-mediated X-dUTP nick-end labeling (TUNEL) assay. This sensitization was abolished when hyperosmotic CD95 membrane trafficking was prevented by cyclic adenosine monophosphate, PKC, or JNK inhibition, whereas these effectors had no effect on CD95L-induced apoptosis in normoosmotically exposed hepatocytes. CD95L addition under normoosmotic conditions caused CD95 membrane trafficking, which was sensitive to JNK inhibition, but not to cyclic adenosine monophosphate or inhibition of PKC, Erks, and p38(MAPK). In conclusion, multiple signaling pathways are involved in CD95 membrane trafficking. Hyperosmotic hepatocyte shrinkage induces CD95 trafficking to the plasma membrane, which involves JNK-, PKA-, and PKC-dependent mechanisms and sensitizes hepatocytes toward CD95L-mediated apoptosis.
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Affiliation(s)
- Roland Reinehr
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
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37
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Németh ZH, Deitch EA, Szabó C, Haskó G. Hyperosmotic stress induces nuclear factor-kappaB activation and interleukin-8 production in human intestinal epithelial cells. THE AMERICAN JOURNAL OF PATHOLOGY 2002; 161:987-96. [PMID: 12213727 PMCID: PMC1867255 DOI: 10.1016/s0002-9440(10)64259-9] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Inflammatory bowel disease of the colon is associated with a high osmolarity of colonic contents. We hypothesized that this hyperosmolarity may contribute to colonic inflammation by stimulating the proinflammatory activity of intestinal epithelial cells (IECs). The human IEC lines HT-29 and Caco-2 were used to study the effect of hyperosmolarity on the IEC inflammatory response. Exposure of IECs to hyperosmolarity triggered expression of the proinflammatory chemokine interleukin (IL)-8 both at the secreted protein and mRNA levels. In addition, hyperosmotic stimulation induced the release of another chemokine, GRO-alpha. These effects were because of activation of the transcription factor, nuclear factor (NF)-kappaB, because hyperosmolarity stimulated both NF-kappaB DNA binding and NF-kappaB-dependent transcriptional activity. Hyperosmolarity activated both p38 and p42/44 mitogen-activated protein kinases, which effect contributed to hyperosmolarity-stimulated IL-8 production, because p38 and p42/44 inhibition prevented the hyperosmolarity-induced increase in IL-8 production. In addition, the proinflammatory effects of hyperosmolarity were, in a large part, mediated by activation of Na(+)/H(+) exchangers, because selective blockade of Na(+)/H(+) exchangers prevented the hyperosmolarity-induced IEC inflammatory response. In summary, hyperosmolarity stimulates IEC IL-8 production, which effect may contribute to the maintenance of inflammation in inflammatory bowel disease.
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Affiliation(s)
- Zoltán H Németh
- Department of Surgery, University of Medicine and Dentistry-New Jersey Medical School, Newark 07103, USA
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38
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Abstract
Adenosine triphosphate binding cassette family transport proteins are important organic ion transporters in hepatocytes but these molecules may also exhibit other functions. In the present study we have measured the effects of substrates of the canalicular organic ion transporter multidrug resistance associated protein 2 (Mrp2) on chloride channel activation and cell volume regulation. We found that substrates such as leukotriene D(4), 17-beta-estradiol glucuronide, and the leukotriene inhibitor MK-571 accelerated the activation of chloride channels by cell swelling and activated chloride channels in cytokine-pretreated hepatocytes. Two conjugated estrogens that are not Mrp2 substrates did not produce this effect. Hepatocytes derived from a strain of transport-deficient rats (TR(-)), which lack Mrp2 expression, showed none of these substrate effects. Coincident with their ability to activate channels, the Mrp2 substrates increased the rate of volume regulatory decrease by approximately 50% (P <.01), confirming that enhanced channel activation under this condition stimulated volume regulation. In TR-hepatocytes the Mrp2 substrate had no effect on volume regulation. In conclusion, Mrp2 plays a role in regulation of chloride channel function by reducing the lag time necessary for channel activation and consequently accelerating the process of cell volume regulation. Substrates of Mrp2 affect the ability of the protein to interact with chloride channels. These findings represent an alternative function of Mrp2 in hepatocytes.
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Affiliation(s)
- Xinhua Li
- Department of Physiology and Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0641, USA
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39
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Schliess F, Häussinger D. The cellular hydration state: a critical determinant for cell death and survival. Biol Chem 2002; 383:577-83. [PMID: 12033446 DOI: 10.1515/bc.2002.059] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Alterations in cellular hydration not only contribute to metabolic regulation, but also critically determine the cellular response to different kinds of stress. Whereas cell swelling triggers anabolic pathways and protects cells from heat and oxidative challenge, cellular dehydration contributes to insulin resistance and catabolism and increases the cellular susceptibility to stress-induced damage. Intracellular accumulation of organic osmolytes, cell cycle delay and the expression of heat shock proteins provide cellular tolerance to hyperosmolarity and protect against stressors under dehydrating conditions. This article discusses some mechanisms by which alterations in cell hydration contribute to cytoprotection or cell damage. In addition, the close relationship between osmotic and oxidative stress and the contribution of isoosmotic shrinkage to apoptotic cell death are considered.
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Affiliation(s)
- Freimut Schliess
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Düsseldorf, Germany
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40
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Hoffmann EK, Hougaard C. Intracellular signalling involved in activation of the volume-sensitive K+ current in Ehrlich ascites tumour cells. Comp Biochem Physiol A Mol Integr Physiol 2001; 130:355-66. [PMID: 11913449 DOI: 10.1016/s1095-6433(01)00419-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The cell swelling-activated K+ channel in Ehrlich ascites tumour cells has a conductance of 5 pS estimated from noise analysis of the volume-sensitive whole-cell K+ current (I(K,vol)). I(K,vol) exhibits Goldman-Hodgkin-Katz type behaviour and is insensitive to clotrimazole, apamin and charybdotoxin (ChTX), but inhibited by clofilium. Its small conductance, lack of intrinsic voltage-dependence and peculiar pharmacological profile are similar to properties described for the two-pore domain background K+ TASK channels. Neither Ca2+ nor ATP work as initiators in the activation of I(K,vol). In contrast, several investigations in Ehrlich cells suggest an important role for leukotriene D4 (LTD4) in the activation of I(K,vol). Under isotonic conditions, LTD4 activates Ca2+-dependent, ChTX-sensitive K+ channels as well as Ca2+-independent. ChTX-insensitive K+ channels. The LTD4-activated, ChTX-insensitive K+ current exhibits a current-voltage relation, pharmacological profile and single channel conductance similar to that of I(K,vol), indicating that LTD4 is the signalling molecule responsible for activation of the volume-sensitive K+ channels in Ehrlich cells. Hypotonic swelling of Ehrlich cells results in translocation of the 85-kDa cytosolic (c) PLA2alpha to the nucleus where it is activated. This activation leads to an increase in arachidonic acid release followed by an increased release of leukotrienes, and is essential in cell swelling-induced activation of I(K,vol) and of the organic osmolyte channels.
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Affiliation(s)
- E K Hoffmann
- August Krogh Institute, Department of Biochemistry, University of Copenhagen, Denmark.
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41
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Häussinger D, Graf D, Weiergräber OH. Glutamine and cell signaling in liver. J Nutr 2001; 131:2509S-14S; discussion 2523S-4S. [PMID: 11533303 DOI: 10.1093/jn/131.9.2509s] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the liver, glutamine plays an important role in ammonia detoxication and the regulation of pH homeostasis ("intercellular glutamine cycle"). In addition, this amino acid regulates liver metabolism and transport by mechanisms that cannot be attributed to its metabolism. Examples include the stimulation of protein and glycogen synthesis and bile acid secretion and the inhibition of proteolysis in liver. The major trigger for such effects is an increased hepatocyte hydration due to the cumulative uptake of glutamine into the cells, which activates osmosignaling pathways involving mitogen-activated protein kinases (MAPK). Glutamine- and hypoosmolarity-induced cell swelling activates extracellular signal-regulated kinases (ERK) and p38(MAPK). Activation of these MAPK results in an increased capacity of bile acid excretion into bile due to a rapid translocation of canalicular transport ATPases from a subcanalicular storage compartment to the canalicular membrane. Similarly, glutamine augments biliary excretion of cysteinyl leukotrienes in endotoxin-treated rat livers. Also, the antiproteolytic effect of glutamine is largely due to glutamine-induced cell swelling, which activates osmosignaling pathways. Here, the glutamine-induced p38(MAPK) activation mediates the inhibition of autophagic proteolysis at the level of autophagosome formation.
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Affiliation(s)
- D Häussinger
- Department of Gastroenterology, Hepatology and Infectiology, Heinrich Heine University, Düsseldorf, Germany.
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42
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Schliess F, von Dahl S, Häussinger D. Insulin resistance induced by loop diuretics and hyperosmolarity in perfused rat liver. Biol Chem 2001; 382:1063-9. [PMID: 11530937 DOI: 10.1515/bc.2001.133] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Insulin-induced cell swelling was recently suggested to reflect an independent signal for metabolic insulin effects such as inhibition of hepatic proteolysis, which is transmitted at the level of autophagosome formation via p38MAPK activation [Häussinger et al., Gastroenterology 116 (1999), 921-935]. Here, the role of insulin-induced cell swelling in the overall context of insulin signalling towards proteolysis inhibition was studied in perfused rat liver. Loop diuretics and hyperosmolarity, which impair insulin-stimulated cell swelling, strongly blunt Erk-2 and p38MAPK activation as well as proteolysis inhibition by insulin, but are without effect on insulin-induced tyrosine phosphorylation of IR-beta and IRS-1. Inhibitors of phosphatidylinositol-3-kinase (PI3-kinase) also block insulin-induced cell swelling, MAP kinase activation and proteolysis inhibition, but the antiproteolytic response to hypoosmolarity remains unaffected. We suggest that PI3-kinase-mediated cell swelling induced by insulin is required to amplify the insulin signal to MAP kinases and thus proteolysis regulation. The perturbation of insulin-induced cell swelling may be of pathophysiological relevance for the development of insulin resistance in clinical situations associated with hyperosmotic dehydration and loop diuretic treatment.
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Affiliation(s)
- F Schliess
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Düsseldorf, Germany
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43
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Affiliation(s)
- S vom Dahl
- Division of Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, Moorenstr 5, D-40225 D sseldorf, Germany.
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44
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Lordnejad MR, Schliess F, Wettstein M, Häussinger D. Modulation of the Heme Oxygenase HO-1 Expression by Hyperosmolarity and Betaine in Primary Rat Hepatocytes. Arch Biochem Biophys 2001; 388:285-92. [PMID: 11368167 DOI: 10.1006/abbi.2001.2297] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The influence of hyperosmotic shrinkage and the osmolyte betaine on heme oxygenase HO-1 expression was studied in cultured rat hepatocytes. Hyperosmolarity transiently suppressed HO-1 induction in response to hemin or medium addition at the levels of mRNA and protein expression. Pretreatment of the cells with betaine largely restored induction of both HO-1 mRNA and protein under hyperosmotic conditions. Exposure of HO-1-expressing hepatocytes to cycloheximide unraveled a hyperosmotic acceleration of HO-1 degradation which was counteracted by betaine and the proteolysis inhibitor MG-132. The HO-1 mRNA stability remained unaffected by hyperosmolarity and betaine as shown by application of the transcription inhibitor actinomycin D. The data suggest a modulation of HO-1 expression by hyperosmolarity and betaine at the transcriptional level and at the level of proteasomal degradation. Hyperosmotic suppression of HO-1 expression was accompanied by a moderate but significant loss of hepatocyte viability, which was prevented by betaine. The hyperosmotic impairment of hepatocyte viability was insensitive to betaine in presence of the heme oxygenase inhibitor zinc protoporphyrin IX. However, treatment of the hepatocytes with bilirubin or 8-Br-cGMP improved hepatocyte viability under hyperosmotic conditions to the control niveau. Thus, stabilizing HO-1 expression may contribute to hepatocyte protection against hyperosmotic stress by organic osmolytes.
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Affiliation(s)
- M R Lordnejad
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-Universität, Düsseldorf, Germany
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45
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46
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47
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Häussinger D, Kircheis G, Fischer R, Schliess F, vom Dahl S. Hepatic encephalopathy in chronic liver disease: a clinical manifestation of astrocyte swelling and low-grade cerebral edema? J Hepatol 2000; 32:1035-8. [PMID: 10898326 DOI: 10.1016/s0168-8278(00)80110-5] [Citation(s) in RCA: 340] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- D Häussinger
- Department of Gastroenterology, Heinrich-Heine-University-Düsseldorf, Germany
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48
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Michalke M, Cariers A, Schliess F, Häussinger D. Hypoosmolarity influences the activity of transcription factor NF-kappaB in rat H4IIE hepatoma cells. FEBS Lett 2000; 465:64-8. [PMID: 10620707 DOI: 10.1016/s0014-5793(99)01719-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The influence of anisoosmolarity on NF-kappaB binding activity was studied in H4IIE rat hepatoma cells. Hypoosmolarity induced a sustained NF-kappaB binding activity whereas the hyperosmotic NF-kappaB response was only minor. Hypoosmotic NF-kappaB activation was accompanied by degradation of the inhibitory IkappaB-alpha. Protein kinase C, PI(3)-kinase, reactive oxygen intermediates and the proteasome apparently participate in mediating the hypoosmotic effect on NF-kappaB. Hypoosmolarity plus PMA induced, amplified and prolonged IkappaB-alpha degradation and NF-kappaB binding activity. Transforming growth factor beta-induced apoptosis was diminished by hypoosmolarity. However, this anti-apoptotic effect was probably not related to NF-kappaB activation.
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Affiliation(s)
- M Michalke
- Department of Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Moorenstr. 5, D-40225, D]usseldorf, Germany
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49
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Van Sluijters DA, Van Woerkom GM, Aerts JM, Meijer AJ. Sphingomyelinase treatment of rat hepatocytes inhibits cell-swelling-stimulated glycogen synthesis by causing cell shrinkage. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 266:653-9. [PMID: 10561609 DOI: 10.1046/j.1432-1327.1999.00914.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Breakdown of plasma-membrane sphingomyelin caused by TNF-alpha is known to inhibit glucose metabolism and insulin signalling in muscle and fat cells. In hepatocytes, conversion of glucose to glycogen is strongly activated by amino acid-induced cell swelling. In order to find out whether breakdown of plasma-membrane sphingomyelin also inhibits this insulin-independent process, the effect of addition of sphingomyelinase was studied in rat hepatocytes. Sphingomyelinase (but not ceramide) inhibited glycogen synthesis, caused cell shrinkage, decreased the activity of glycogen synthase a, but had no effect on phosphorylase a. Cell integrity was not affected by sphingomyelinase addition as gluconeogenesis and the intracellular concentration of ATP were unchanged. As a control, glycogen synthesis was studied in HepG2 cells. In these cells, the basal rate of glycogen production was high, could not be stimulated by amino acids, nor be inhibited by sphingomyelinase. Regarding the mechanism responsible for the inhibition of glycogen synthase a, sphingomyelinase did not affect amino acid-induced, PtdIns 3-kinase-dependent, phosphorylation of p70S6 kinase, but caused an increase in intracellular chloride, which is known to inhibit glycogen synthase phosphatase. It is concluded that the decrease in cell volume, following the breakdown of sphingomyelin in the plasma membrane of the hepatocyte, may contribute to the abnormal metabolism of glucose when TNF-alpha levels are high.
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Affiliation(s)
- D A Van Sluijters
- Department of Biochemistry, Academic Medical Center, University of Amsterdam, The Netherlands
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