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AIM:To investigate the significance of protein kinase C(PKC),P44/42 mitogen-activated protein kinase (MAPKs)and heat shock protein (HSP)70 signal transduction duringhepatocyte ischemic preconditioning.METHODS:In this study we used an in vitro ischemicpreconditioning (IP) model for hepatocytes and an in vivomodel for rat liver to investigate the significance of proteinkinase C (PKC),P44/42 mitogen-activated protein kinase(P44/42 MAPKs) and heat shock protein 70 (HSP70) signaltransduction in IP.Through a normal liver cell hypoxicpreconditioning (HP) model in which cultured normal livercells were subjected to 3 cycles of 5 min of incubationunder hypoxic conditions followed by 5 min of reoxygenationand subsequently exposed to hypoxia and reoxygenationfor 6 h and 9 h respectively.PKC inhibitor,activator andMEK inhibitor were utilized to analyze the phosphorylationof PKC,the expression of P44/42 MAPKs and HSP70.Viability and cellular ultrastructure were also observed.Byusing rat liver as an in vivo model of liver preconditioning(3 cycles of 10-min occlusion and 10-min reperfusion),invivo phosphorylation of PKC and P44/42MAPKs,HSP70expression were further analyzed.AST/ALT concentration,cellular structure and ultrastruture were also observed.All the data were statistically analyzed.RESULTS:Similar results were obtained in both in vivoand in vitro IP models.Compared with the control withoutIP (or HP),the phosphorylation of PKC and P44/42 MAPKsand the expression of HSP70 were obviously increased inIP (or HP) treated model in which cytoprotection could befound.The effects of preconditioning were mimicked bystimulating PKC with 4β phorobol-12-myristate13-acetate(PMA).Conversely,inhibiting PKC with chelerythrineabolished the protection given by preconditioning.PD98059,inhibitor of MEK (the upstream kinase of P44/42MAPKs),also reverted the cytoprotection exerted by preconditioning.CONCLUSION:The results demonstrate that preconditioninginduces a rapid activation of P44/42MAPKs and PKC activationplays a pivotal role in the activation of P44/42 MAPKs pathway that participates in the preservation of liver cells.HSPexpression is regulated by signals in PKC dependent P44/42 MAPKs pathway.
To investigate the significance of protein kinase C (PKC), P44 / 42 mitogen-activated protein kinase (MAPKs) and heat shock protein (HSP) 70 signal transduction during hepatocyte ischemic preconditioning. METHODS: In this study we used an in vitro ischemic preconditioning (IP) model for hepatocytes and an in vivomodel for rat liver to investigate the significance of proteinkinase C (PKC), P44 / 42 mitogen-activated protein kinase (P44 / 42 MAPKs) and heat shock protein 70 (HSP70) signal transduction in IP. Through a normal liver cell hypoxic preconditioning (HP) model in which cultured normal liver cells were subjected to 3 cycles of 5 min of incubation under hypoxic conditions followed by 5 min of reoxygenation and succeeded to hypoxia and reoxygenation for 6 h and 9 h respectively. PKC inhibitor, activator and MEK inhibitor were utilized to analyze the phosphorylation of PKC, the expression of P44 / 42 MAPKs and HSP70. Viability and cellular ultrastructure were also observed. By using rat liver as an in vivo model of liver preconditioning (3 cycles of 10-min occlusion and 10-min reperfusion), invivo phosphorylation of PKC and P44 / 42 MAPKs, HSP70expression were further analyzed. AST / ALT concentration, cellular structure and ultrastruture were also observed. All the data were analyzedathered .RESULTS: Similar results were obtained in both in vivo and in vitro IP models. Compared with the control without IP (or HP), the phosphorylation of PKC and P44 / 42 MAPKs and the expression of HSP70 were significantly increased in IP (or HP ) treated model in which cytoprotection could befound.The effects of preconditioning were mimicked bystimulating PKC with 4β phorobol-12-myristate 13-acetate (PMA) .Conversely, inhibiting PKC with chelerythrine abolished the protection given by preconditioning. PD98059, inhibitor of MEK (the upstream kinase of P44 / 42 MAPKs), also reverted the cytoprotection exerted by preconditioning. CONCLUSION: The results demonstrate that preconditioninginduces a rapid activation of P44 / 42 MAPAPKs and PKC activation by a pivotal role in the activation of P44 / 42 MAPKs pathway that participates in the preservation of liver cells. HSP Expression is regulated by signals in PKC dependent P44 / 42 MAPKs pathway.