5C). Importantly, transfection of individual plasmids carrying the core, NS4B, and NS5B genes selleck screening library enhanced TNF-α-induced cell death (Fig. 5D). The effects of core, NS4B, and NS5B on NF-κB activity, IKK activity, and TNF-α-induced cell death were further enhanced by cotransfection of plasmids carrying all three of these genes. We showed that HCV

infection enhanced TNF-α-induced cell death through suppression of NF-κB activation by the action of core, NS4B, and NS5B. This mechanism may contribute to immune-mediated liver injury in hepatitis C by sensitizing HCV-infected hepatocytes to TNF-α-induced cell death (Fig. 6). HCV infection made the infected cells vulnerable to TNF-α-induced cell death by suppressing

TNF-α-induced NF-κB activation and the subsequent expression of NF-κB-dependent anti-apoptotic proteins, such as Bcl-xL, XIAP, and c-FLIPL. Down-regulation of such anti-apoptotic genes were also observed in HCV-infected liver. The effect of HCV infection was also recapitulated with the transfection of plasmids carrying the HCV core, NS4B, and NS5B genes, indicating that the core, NS4B, and NS5B proteins are responsible for the suppression of NF-κB activation. In addition, cell death was enhanced in JFH-1 HCV RNA-transfected cells and in cells harboring the H77 HCV RNA replicon. These results provide insight into the mechanism by which HCV infection alters Carfilzomib clinical trial intracellular events relevant to liver injury and the pathogenesis of hepatitis C. Multiple HCV proteins interact with host proteins involved in intracellular-signaling pathways. In the case of the NF-κB pathway, core, NS3, NS4B, and NS5A are known to regulate the activity of NF-κB. However, these previous studies investigated the effects of individual HCV proteins by transfection of each HCV genes, not by actual HCV infection.12, 26-35 Such experiment settings were not sufficient to show the comprehensive effect of HCV infection and produced inconsistent results, including inhibition of TNF-α- and Fas-mediated

apoptosis by HCV core protein. For the current study, on the other hand, we adopted the in vitro JFH-1 HCV infection 上海皓元医药股份有限公司 system that became available in 200536-38 to study the role of HCV proteins in the setting of actual infection. The value of the HCV infection model in pathophysiologic studies is demonstrated by the fact that HCV infection suppresses TNF-α-induced NF-κB activation, despite the stimulatory effect of NS5A (Fig. 5A). The NF-κB-suppressive role of core, NS4B, and NS5B overruled the NF-κB-enhancing role of NS5A in the HCV infection system, resulting in enhanced TNF-α-induced cell death. Intriguingly, decreased nuclear translocation of NF-κB was reported in HCV-infected liver in a previous study using a chimeric SCID/Alb-uPA mice model.40 Given that NF-κB inhibition facilitates cell death, our results are consistent with previous studies.