Role of MAPK Phosphatase-1 in Sustained Activation of JNK during Ethanol-induced Apoptosis in Hepatocyte-like VL-17A Cells

Abstract

Ethanol metabolism plays a central role in activating the mitogen-activated protein kinase (MAPK) cascade leading to inflammation and apoptosis. Sustained activation of c-Jun N-terminal kinase (JNK), one of the MAPKs, has been shown to induce apoptosis in hepatocytes. MAPK phosphatase-1 (MKP-1) has been shown to dephosphorylate MAPKs in several cells. The aim of the study is to evaluate the role of MKP-1 in sustained JNK activation as a mechanism to explain ethanol-induced hepatocyte apoptosis. VL-17A cells (HepG2 cells overexpressing alcohol dehydrogenase and cytochrome P450-2E1) were exposed to ethanol for different time periods. Western blots were performed for MKP-1, phospho-JNK, phosphotyrosine, and protein kinase Cδ (PKCδ). Electrophoretic mobility shift assays for AP-1 were performed. Apoptosis was measured by caspase-3 activity assay, TUNEL, and 4′,6-diamidino-2-phenylindole staining. Reactive oxygen species were neutralized by overexpressing both superoxide dismutase-3 and catalase genes using lentiviral vectors in VL-17A cells. Ethanol incubation markedly decreased the MKP-1 protein levels to 15% of control levels and was associated with sustained phosphorylation of p46 JNK and p54 JNK, as well as increased apoptosis. VL-17A cells overexpressing superoxide dismutase-3 and catalase, treatment with a tyrosine kinase inhibitor, or incubation of the cells with PKCδ small interference RNAs significantly inhibited the ethanol-induced MKP-1 degradation and apoptosis. Ethanol-induced oxidative stress enhanced the tyrosine phosphorylation of PKCδ, which in turn caused the proteasomal degradation of MKP-1, leading to sustained JNK activation and increased apoptosis in VL-17A cells. Ethanol metabolism plays a central role in activating the mitogen-activated protein kinase (MAPK) cascade leading to inflammation and apoptosis. Sustained activation of c-Jun N-terminal kinase (JNK), one of the MAPKs, has been shown to induce apoptosis in hepatocytes. MAPK phosphatase-1 (MKP-1) has been shown to dephosphorylate MAPKs in several cells. The aim of the study is to evaluate the role of MKP-1 in sustained JNK activation as a mechanism to explain ethanol-induced hepatocyte apoptosis. VL-17A cells (HepG2 cells overexpressing alcohol dehydrogenase and cytochrome P450-2E1) were exposed to ethanol for different time periods. Western blots were performed for MKP-1, phospho-JNK, phosphotyrosine, and protein kinase Cδ (PKCδ). Electrophoretic mobility shift assays for AP-1 were performed. Apoptosis was measured by caspase-3 activity assay, TUNEL, and 4′,6-diamidino-2-phenylindole staining. Reactive oxygen species were neutralized by overexpressing both superoxide dismutase-3 and catalase genes using lentiviral vectors in VL-17A cells. Ethanol incubation markedly decreased the MKP-1 protein levels to 15% of control levels and was associated with sustained phosphorylation of p46 JNK and p54 JNK, as well as increased apoptosis. VL-17A cells overexpressing superoxide dismutase-3 and catalase, treatment with a tyrosine kinase inhibitor, or incubation of the cells with PKCδ small interference RNAs significantly inhibited the ethanol-induced MKP-1 degradation and apoptosis. Ethanol-induced oxidative stress enhanced the tyrosine phosphorylation of PKCδ, which in turn caused the proteasomal degradation of MKP-1, leading to sustained JNK activation and increased apoptosis in VL-17A cells. Alcoholic liver damage is one of the major causes of cirrhosis. Recent evidence suggests that many cellular responses of ethanol are mediated by the modulation of mitogen activated protein kinases (MAPK) 2The abbreviations used are: MAPK, mitogen-activated protein kinase; MKP-1, MAPK phosphatase-1; PKCδ, protein kinase Cδ; eGFP, enhanced green fluorescent protein; LV, lentiviral vector; EMSA, electrophoretic mobility shift assay; ROS,reactiveoxygenspecies;SOD3,superoxidedismutase-3; JNK, c-JunN-terminal kinase; ERK, extracellular signal-regulated kinase; RT, reverse transcription; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling; DAPI, 4′,6-diamidino-2-phenylindole; siRNA, small interference RNA; E100, 100 mm ethanol; cat, catalase; DCF, 2′,7′-dichlorofluorescein; H2DCFDA, 2′,7′-dichlorodihydrofluorescein diacetate. signaling (1Aroor A.R. Kim S.D. Life Sci. 2004; 74: 2339-2364Crossref PubMed Scopus (176) Google Scholar, 2Chen J. Kim E.J. Dent P. Kunos G. Gao B. Biochem. J. 1998; 334: 669-676Crossref PubMed Scopus (99) Google Scholar). MAPK are involved in various cellular responses, including cell proliferation, differentiation, and apoptosis. Cellular responses mediated by MAPK signaling vary depending upon the intensity and kinetics of MAPKs. One of the members of the MAPK family, JNK, has been shown to be an important mediator of cellular functions. Transient activation of JNK is necessary for liver regeneration (3Schwabe R.F. Kim C.A. Uehara T. Hatano E. Bennett B.L. Schoonhoven R. Brenner D.A. Hepatology. 2003; 37: 824-832Crossref PubMed Scopus (211) Google Scholar), whereas sustained activation is involved in apoptosis (4Lin A. BioEssays. 2003; 25: 17-24Crossref PubMed Scopus (369) Google Scholar, 5Czaja M.J. Am. J. Physiol. 2003; 284: G875-G879Crossref PubMed Scopus (114) Google Scholar), and ethanol had been shown to induce the sustained activation of both isoforms of JNK (p54 JNK and p46 JNK) in hepatocytes (3Schwabe R.F. Kim C.A. Uehara T. Hatano E. Bennett B.L. Schoonhoven R. Brenner D.A. Hepatology. 2003; 37: 824-832Crossref PubMed Scopus (211) Google Scholar, 5Czaja M.J. Am. J. Physiol. 2003; 284: G875-G879Crossref PubMed Scopus (114) Google Scholar, 6Auer K.L. Kim J. Brenz-Verca S. Pirola L. Rusconi S. Cooper G. Abo A. Wymann M.P. Davis R.J. Birrer M. Dent P. Mol. Biol. Cell. 1998; 9: 561-573Crossref PubMed Scopus (114) Google Scholar, 7Graf D. Kim A.K. Fischer R. Reinehr R. Haussinger D. Gastroenterology. 2002; 122: 1411-1427Abstract Full Text Full Text PDF PubMed Scopus (96) Google Scholar). Although ethanol was found to be the activator of apoptosis via JNK activation, the mechanism by which ethanol prolongs the JNK activation is not known. MAPKs are activated by dual phosphorylation on Ser/Thr and Tyr residues, whereas 11 dual-specificity phosphatases or MAPK phosphatases (MKPs) terminate such activation (8Keyse S.M. Curr. Opin. Cell Biol. 2000; 12: 186-192Crossref PubMed Scopus (710) Google Scholar). These phosphatases exhibit differential specificity toward MAPK substrates, show distinct subcellular localizations, and have different modes of regulation. Among these phosphatases, MKP-1 was originally identified as an ERK-specific phosphatase (9Sun H. Kim C.H. Lau L.F. Tonks N.K. Cell. 1993; 75: 487-493Abstract Full Text PDF PubMed Scopus (1027) Google Scholar), and it has also been shown to dephosphorylate and inactivate JNK and p38 MAPK in a cell-specific and context-specific manner (10Franklin C.C. Kim A.S. J. Biol. Chem. 1997; 272: 16917-16923Abstract Full Text Full Text PDF PubMed Scopus (391) Google Scholar, 11Lasa M. Kim S.M. Boucheron C. Saklatvala J. Clark A.R. Mol. Cell. Biol. 2002; 22: 7802-7811Crossref PubMed Scopus (319) Google Scholar). Although, MKP-1 expression has been shown to control the phosphorylation of JNK in other cell types, there is no evidence indicating that ethanol modulates JNK phosphorylation via MKP-1 in hepatocytes. The activation of MAPKs has been shown to be regulated by the activation of tyrosine kinase (12Fanger G.R. Kim N.L. Johnson G.L. EMBO J. 1997; 16: 4961-4972Crossref PubMed Scopus (254) Google Scholar, 13Rosette C. Kim M. Science. 1996; 274: 1194-1197Crossref PubMed Scopus (943) Google Scholar), protein kinase C (PKC) (14Jarvis W.D. Kim K.L. Spector M. Kunos G. Grant S. Hylemon P. Mikkelsen R. Dent P. FEBS Lett. 1997; 412: 9-14Crossref PubMed Scopus (32) Google Scholar), or G-protein (15Luo J. Kim M.W. J. Neurosci. 1999; 19: 10014-10025Crossref PubMed Google Scholar). Several PKC isoforms have been shown to have important roles in the regulation of cell survival and apoptosis (16Whelan R.D. Kim P.J. Oncogene. 1998; 16: 1939-1944Crossref PubMed Scopus (137) Google Scholar, 17Maher P. J. Neurosci. 2001; 21: 2929-2938Crossref PubMed Google Scholar), and a series of studies suggests that PKCδ is involved in apoptosis by acting as a proapoptotic signal (18Kanthasamy A.G. Kim M. Kanthasamy A. Anantharam V. Antioxid. Redox Signal. 2003; 5: 609-620Crossref PubMed Scopus (121) Google Scholar, 19Brodie C. Kim P.M. Apoptosis. 2003; 8: 19-27Crossref PubMed Scopus (374) Google Scholar). For example, a selective inhibitor of PKCδ, rottlerin, and a dominant-negative mutant of PKCδ, attenuate apoptosis induced by phorbol ester (20Gonzalez-Guerrico A.M. Kim M.G. J. Biol. Chem. 2005; 280: 38982-38991Abstract Full Text Full Text PDF PubMed Scopus (73) Google Scholar), hydrogen peroxide (H2O2) (21Konishi H. Kim E. Taniguchi H. Yamamoto T. Matsuzaki H. Takemura Y. Ohmae K. Kikkawa U. Nishizuka Y. Proc. Natl. Acad. Sci. U. S. A. 2001; 98: 6587-6592Crossref PubMed Scopus (220) Google Scholar), UV radiation (22Fukunaga M. Kim M. Ichihashi M. Yamamoto T. Matsuzaki H. Kikkawa U. Biochem. Biophys. Res. Commun. 2001; 289: 573-579Crossref PubMed Scopus (47) Google Scholar), or etoposide (23Reyland M.E. Kim S.M. Matassa A.A. Barzen K.A. Quissell D.O. J. Biol. Chem. 1999; 274: 19115-19123Abstract Full Text Full Text PDF PubMed Scopus (231) Google Scholar). These studies demonstrate that PKCδ is one of the prime regulators of apoptosis in several cell types. However, the mechanism by which activation of PKCδ induces cell death remains largely unknown. The oxidative metabolism of ethanol by hepatocytes elicits a range of responses, including the generation of ROS, one of the important mediators of alcoholic liver injury (24Cardin R. Kim A. Fiorentino M. Cecchetto A. Naccarato R. Farinati F. Alcohol Alcohol. 2002; 37: 43-48Crossref PubMed Scopus (40) Google Scholar, 25Hoek J.B. Kim J.G. Alcohol. 2002; 27: 63-68Crossref PubMed Scopus (406) Google Scholar, 26Zhou Z. Kim L. Song Z. Lambert J.C. McClain C.J. Kang Y.J. Am. J. Pathol. 2003; 163: 1137-1146Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar, 27Liu H. Kim B.E. Bradham C. Czaja M.J. Am. J. Physiol. Gastrointest. Liver Physiol. 2002; 282: G257-G266Crossref PubMed Scopus (83) Google Scholar). The mechanism by which ethanol induces oxidative stress has been studied by several investigators (28Cederbaum A.I. J. Gastroenterol. Hepatol. 2006; 21: S22-S25Crossref PubMed Scopus (90) Google Scholar, 29Hoek J.B. Kim J.G. Semin. Liver Dis. 2004; 24: 257-272Crossref PubMed Scopus (88) Google Scholar, 30Jaeschke H. Kim G.J. Cederbaum A.I. Hinson J.A. Pessayre D. Lemasters J.J. Toxicol. Sci. 2002; 65: 166-176Crossref PubMed Scopus (1070) Google Scholar). Several reports have shown that reactive oxygen species (ROS), including H2O2, superoxide anion (O.O2), and hydroxyl (OH–) ions, are important signaling molecules regulating JNK activity (31Sakon S. Kim X. Takekawa M. Sasazuki T. Okazaki T. Kojima Y. Piao J.H. H. K. T. H. EMBO J. 2003; 22: PubMed Scopus Google Scholar, H. Kim S. S. L. H. M. Cell. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). Although it is that oxidative stress induces the phosphorylation of JNK, the role of ethanol-induced oxidative PKC activation, and the sustained activation of JNK in injury are not known. have the these and demonstrate ethanol-induced oxidative stress causes the sustained activation of JNK and apoptosis in via the of MKP-1 Cell used a cell which the alcohol and cytochrome Cell have been as Kim Hepatology. 2005; PubMed Scopus (47) Google Scholar, Kim Biochem. 2003; PubMed Scopus Google Scholar, Kim J. Biochem. Cell Biol. 2006; PubMed Scopus (99) Google Scholar). of and the generation lentiviral vectors enhanced green fluorescent protein with the were as R. Kim H. M. E. E. Biochem. Biophys. Res. Commun. 2004; PubMed Scopus Google Scholar). The was used as a control and the or catalase was by The was for with the or catalase the lentiviral vectors were and as A. Kim L. 2002; PubMed Scopus Google Scholar). The was using the to the and as G. Kim 2003; PubMed Scopus Google Scholar). of of VL-17A cells were with and or in the of for The cells were with and the was and cells were for using an activity to the The of was also by as J. Kim L. R.D. A. Hepatology. 2004; PubMed Scopus Google Scholar). was by both activity assays and Western blots as by J. Kim L. R.D. A. Hepatology. 2004; PubMed Scopus Google Scholar). Cell cells were in the of the were performed to the cells were with various such as inhibitor, MAPK inhibitor, and inhibitor, or for ethanol was and the was with the for various time to the the was to the control cells. Ethanol was also with cells overexpressing and catalase for different time to the the cells were for Western or apoptosis cells were was using and was The MKP-1 PKCδ and dehydrogenase were MKP-1 and PKCδ were for and dehydrogenase was for The were of for of for for and for by of for The were in Western and different were in cell and the protein was using The were using and to and with MKP-1 PKCδ or as H. Kim J. Yamamoto A. H. B. K. Cell 2004; PubMed Scopus Google Scholar). For of protein was with for was by incubation with and the were using and for with of The were the was in and Western blots were performed using the activation of AP-1 electrophoretic mobility shift assays were performed using a the and for were different the cells were and protein was AP-1 were with to the The were using and the the and the protein were The was by by the of the as Kim R. J. Liver 2006; 12: PubMed Scopus (88) Google Scholar, S. Kim U. 2005; PubMed Scopus Google Scholar). cells were in a and for The cells were and to and with and The of to fluorescent was measured by as Kim S. T. 2002; PubMed Scopus Google Scholar). Apoptosis cells were with different as of incubation with the cells were and for apoptosis. The was performed using the as have J. Kim L. R.D. A. Hepatology. 2004; PubMed Scopus Google Scholar). was performed using the activity was and the was performed to the the and the were VL-17A cells were cells well in a in an VL-17A with of the cells were and with of and of were with 100 of the were and for and was to of of was and the was for an the cells were and with of with a of the cells were used for the ethanol the were performed in and The was using of The were as and using and the for was as VL-17A cells were with 100 mm ethanol for to The cells were protein was and the Western blots for both and JNK were performed as of VL-17A cells with ethanol caused an in the phosphorylation of both p46 JNK and p54 JNK that increased to and was associated with an in the of AP-1 was a in caspase-3 activity VL-17A cells were for with Apoptosis was also measured by both the and staining. and cells were in and the of apoptosis was by the of cells to cells. was a in apoptosis with ethanol treatment evaluate the role of other MAPK cascade in VL-17A cells were with inhibitor, MAPK inhibitor, or inhibitor, for in by the of for a to a was to the control cells. The cells were with by caspase-3 activation assay, or and staining. The that of p38 MAPK or JNK caused a in the caspase-3 activity as well as and of not in the survival of the cells. MKP-1 is a dual specificity which is shown to be involved in JNK in various cells. studied the of ethanol on MKP-1 expression in VL-17A cells. VL-17A cells were with for and and the cells were for and protein was performed for MKP-1 and found that there was no in the MKP-1 levels dehydrogenase was used as an Western that there was a in MKP-1 protein levels in VL-17A cells with ethanol The expression was by the of MKP-1 expression to the genes and as a Ethanol has been shown to induce in via oxidative stress in hepatocytes. The show that of ethanol-induced oxidative stress cell studied of to a of the MKP-1 protein levels by both and catalase using in VL-17A cells. an the cells were with both cells and were for and catalase expression not and expression was the cells were used in The cells were for expression by and found a in levels with an in both and activity The catalase expression was studied by both Western blots and catalase and there was increased protein expression and activity in these cells. The of in of was as G. Kim 2003; PubMed Scopus Google Scholar). The cells were used as a control in the of in these cells. The that not in MKP-1 protein cells were used in the cells and cells were with for the was measured by the of to fluorescent DCF, and the intensity was and with the protein Ethanol caused an in the in VL-17A and of caused a of of cells with not in MKP-1 levels not caused a in ethanol-induced MKP-1 protein as by Western was used as a control in these Western The mechanism by which oxidative stress induced the MKP-1 degradation was had been shown in other that tyrosine phosphorylation of PKCδ induce proteasomal ethanol-induced oxidative stress caused the tyrosine phosphorylation of of tyrosine kinase by a tyrosine kinase inhibitor, or of the decreased the ethanol-induced PKCδ tyrosine phosphorylation whereas treatment of cells with the proteasomal inhibitor or PKCδ inhibitor not the tyrosine phosphorylation of the of tyrosine phosphorylation of PKCδ on MKP-1 degradation was The cells were for with rottlerin, or the proteasomal inhibitor by with for an cells were also with for of the cells with of these on the MKP-1 protein degradation studied the of MKP-1 in the activation of JNK in these cells. was with the cells for in which was by the incubation of for and cells were also with different time with ethanol caused a activation of JNK in these cells that PKCδ is involved in ethanol-induced MKP-1 VL-17A cells were with or with PKCδ as The caused of PKCδ and protein of the cells with the PKCδ not the ethanol-induced not the ethanol-induced degradation of MKP-1 protein was in VL-17A cells with PKCδ not in cells with MKP-1 was associated with a in the ethanol-induced sustained phosphorylation of p46 JNK and JNK in VL-17A cells whereas the VL-17A cells not show a in JNK activity with ethanol the of sustained JNK activation the of one of the of JNK, of VL-17A cells with caused an in AP-1 in cells. the other ethanol-induced AP-1 was inhibited in PKCδ cells VL-17A cells were with PKCδ or by incubation with for the cells were with rottlerin, or by incubation with for cells were also with for that treatment increased apoptosis in cells with siRNA, whereas was significantly inhibited in the PKCδ cells with or as measured by the caspase-3 activity and and and the study the mechanism by which ethanol induces a sustained activation of p46 JNK and p54 JNK and causes apoptosis in VL-17A cells. Several studies have that the and of JNK activation are important for cells cell or apoptosis (3Schwabe R.F. Kim C.A. Uehara T. Hatano E. Bennett B.L. Schoonhoven R. Brenner D.A. Hepatology. 2003; 37: 824-832Crossref PubMed Scopus (211) Google Scholar, 5Czaja M.J. Am. J. Physiol. 2003; 284: G875-G879Crossref PubMed Scopus (114) Google Scholar, 6Auer K.L. Kim J. Brenz-Verca S. Pirola L. Rusconi S. Cooper G. Abo A. Wymann M.P. Davis R.J. Birrer M. Dent P. Mol. Biol. Cell. 1998; 9: 561-573Crossref PubMed Scopus (114) Google Scholar, 7Graf D. Kim A.K. Fischer R. Reinehr R. Haussinger D. Gastroenterology. 2002; 122: 1411-1427Abstract Full Text Full Text PDF PubMed Scopus (96) Google Scholar). Transient activation of JNK is for liver regeneration (3Schwabe R.F. Kim C.A. Uehara T. Hatano E. Bennett B.L. Schoonhoven R. Brenner D.A. Hepatology. 2003; 37: 824-832Crossref PubMed Scopus (211) Google Scholar), whereas and JNK activation cell death (4Lin A. BioEssays. 2003; 25: 17-24Crossref PubMed Scopus (369) Google Scholar, 5Czaja M.J. Am. J. Physiol. 2003; 284: G875-G879Crossref PubMed Scopus (114) Google Scholar), and the of ethanol to hepatocytes has been shown to induce a and of JNK Y.J. Kim S.D. J. 2005; PubMed Scopus Google Scholar). However, the mechanism of JNK by ethanol has not been have used VL-17A which are cells overexpressing both alcohol dehydrogenase and to study the regulation of the sustained activation of These cells are well and Kim Hepatology. 2005; PubMed Scopus (47) Google Scholar, Kim Biochem. 2003; PubMed Scopus Google Scholar, Kim J. Biochem. Cell Biol. 2006; PubMed Scopus (99) Google Scholar). with other VL-17A cells a sustained in JNK phosphorylation and increased apoptosis with ethanol also the activation of and p38 study found that the of by ethanol was and increased to a not However, the of inhibitor not in the cell survival Ethanol also induced the activation of p38 MAPK not and caused a in apoptosis in VL-17A cells. Although reports have shown the by which oxidative stress induces p38 MAPK A. Kim K. T. C. H. S. S. K. K. H. 2005; PubMed Scopus Google Scholar, A. Kim H. K. K. H. Antioxid. Redox Signal. 2002; PubMed Scopus Google Scholar), it is that MKP-1 degradation is for the sustained activation of p38 studies are to Several studies have shown that cells exhibit JNK activation as well as enhanced of and with cells Kim X. Y. R. M.E. X. J.A. C.H. Y. J. 2006; PubMed Scopus Google Scholar, M. Kim J. H. A. R. J. 2006; PubMed Scopus Google Scholar, Kim K.A. M. K.A. T. J. 2006; PubMed Scopus Google Scholar). cells MKP-1 degradation is associated with increased Kim J.H. Kim J. Cell Sci. 2006; PubMed Scopus Google Scholar). These reports to that MKP-1 degradation a role in ethanol-induced sustained JNK activation and apoptosis. VL-17A cells with ethanol and studied the expression of Ethanol incubation caused a in the expression of Although found a in the protein of MKP-1, that there was no in MKP-1 that the regulation be a it was shown that a sustained JNK activation cell death induced by H. Kim S. S. L. H. M. Cell. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). the oxidative metabolism of ethanol elicits the generation of ROS, and is involved in apoptosis (1Aroor A.R. Kim S.D. Life Sci. 2004; 74: 2339-2364Crossref PubMed Scopus (176) Google Scholar, 5Czaja M.J. Am. J. Physiol. 2003; 284: G875-G879Crossref PubMed Scopus (114) Google Scholar, R. Kim A. Fiorentino M. Cecchetto A. Naccarato R. Farinati F. Alcohol Alcohol. 2002; 37: 43-48Crossref PubMed Scopus (40) Google Scholar, 25Hoek J.B. Kim J.G. Alcohol. 2002; 27: 63-68Crossref PubMed Scopus (406) Google Scholar, 27Liu H. Kim B.E. Bradham C. Czaja M.J. Am. J. Physiol. Gastrointest. Liver Physiol. 2002; 282: G257-G266Crossref PubMed Scopus (83) Google Scholar). oxidative stress has been shown to the MAPKs, the of the activation on the and of the both and catalase, and that ethanol-induced was significantly inhibited by cells. These that these were in the in studies the of genes the ethanol-induced degradation of the mechanism by which MKP-1 degradation is enhanced by ethanol-induced oxidative studies have shown that the tyrosine phosphorylation of PKCδ to MKP-1 degradation in cells Kim J.H. Kim J. Cell Sci. 2006; PubMed Scopus Google Scholar). other reports have shown that oxidative stress induce the tyrosine phosphorylation of PKCδ in several cells (18Kanthasamy A.G. Kim M. Kanthasamy A. Anantharam V. Antioxid. Redox Signal. 2003; 5: 609-620Crossref PubMed Scopus (121) Google Scholar, 19Brodie C. Kim P.M. Apoptosis. 2003; 8: 19-27Crossref PubMed Scopus (374) Google Scholar, H. Kim E. Taniguchi H. Yamamoto T. Matsuzaki H. Takemura Y. Ohmae K. Kikkawa U. Nishizuka Y. Proc. Natl. Acad. Sci. U. S. A. 2001; 98: 6587-6592Crossref PubMed Scopus (220) Google Scholar). that ethanol-induced oxidative stress induce the tyrosine phosphorylation of PKCδ, which in turn the proteasomal degradation of MKP-1 in cells. studied ethanol incubation increased the tyrosine phosphorylation of PKCδ and that of that of genes or a tyrosine kinase inhibitor, caused a in PKCδ tyrosine phosphorylation in VL-17A cells. incubation of with ethanol not the PKCδ tyrosine which that of also that of PKCδ or tyrosine or proteasomal activation ethanol-induced MKP-1 have shown that of ethanol in Kim Y. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, F. Kim J. C. M. Biochem. Biophys. Res. Commun. 2000; PubMed Scopus Google or in F. Kim L. Song H. H. J. Mol. Pathol. 2006; PubMed Scopus Google caused an of proteasomal show that of ethanol induces the activation of These that the of ethanol on signaling depending on of and metabolism (1Aroor A.R. Kim S.D. Life Sci. 2004; 74: 2339-2364Crossref PubMed Scopus (176) Google Scholar). that ethanol-induced oxidative stress enhanced the tyrosine phosphorylation of PKCδ, by proteasomal activation and MKP-1 to the of MKP-1 levels the JNK the cells with to ethanol or cells with there was a of MKP-1 leading to sustained activation of JNK, and a in apoptosis. it was shown that the incubation of a PKC inhibitor or a tyrosine kinase inhibitor with hepatocytes for not a in the mm ethanol-induced JNK activation Y.J. Kim S.D. J. 2005; PubMed Scopus Google Scholar). to that of PKCδ using caused a of ethanol-induced sustained JNK are several for these The levels of ethanol for a it is that MAPK activation is on the and the time of ethanol that ethanol-induced PKCδ activation is involved in MKP-1 have of the using as a PKCδ inhibitor were with the PKCδ activation is or of the the PKCδ cells were with and that the was not that the PKCδ activation is of the of PKCδ using in the of MKP-1 protein levels as well as activation of JNK in these cells. activation of JNK also decreased the AP-1 in these cells. that ethanol-induced apoptosis was significantly inhibited in the cells with PKCδ that there is a role for PKCδ in ethanol-induced apoptosis in cells. a mechanism by which ethanol induce apoptosis in cells. Ethanol-induced oxidative stress the tyrosine phosphorylation of PKCδ, which in turn the proteasomal degradation of The degradation of MKP-1 causes the sustained activation of JNK leading to increased apoptosis. The is in is that a not by which ethanol-induced PKCδ and the apoptosis cascade in cells. Cederbaum for the catalase and is a