In mammalian cells, apoptosis can be induced via two major pathways. First, the death receptor pathway (extrinsic pathway), which is triggered by binding Fas ligand (FasL) to Fas (CD95) with subsequent activation

of caspase-8, which in turn activates the effectors caspases 3, 6, 7 [9–12]. This pathway is considered an important apoptotic system in cancer [13] because FasL is one of the effector molecules of cytotoxic T cells. The second apoptosis pathway (the intrinsic pathway) is induced by mitochondria in response to DNA damage, oxidative stress and viral proteins [5]. Mitochondria-dependent apoptosis is amplified by pro-apoptotic genes (Bax, Bad, Bak and others) whereas molecules like Bcl-2 or Bcl-xL act as anti-apoptotic. These proteins converge at #Ilomastat randurls[1|1|,|CHEM1|]# the mitochondrial permeability transition pore that regulates the release of apoptotic regulatory proteins, such as procaspase-9, and cytochrome C [14]. There Selleckchem Temsirolimus have been many studies indicating that apoptosis of hepatocytes plays a significant

role in the pathogenesis of HCV infection [15], although various apoptotic pathways were proposed [16]. For example, many studies demonstrated that HCV core protein suppresses apoptosis mediated by cisplatin, c-myc, TNF-α, or the Fas signaling pathway [17], whereas others showed that the core protein sensitizes Fas, TNFα, or serum starvation-induced apoptosis [18]. The precise mechanisms for the involvement of the HCV core protein on the apoptotic pathways are not fully understood. For example, core protein-dependent inhibition of TNF-α and CD95 ligand-induced apoptosis has been described in a hepatoma cell line [19, 20]. In other models, overexpressed HCV core protein did not prevent CD95 ligand induced apoptosis in hepatoma cells or transgenic mice overexpressing HCV core protein [17, 21].

Until recently, the lack of an infectious HCV tissue culture system did not allow to study the impact of HCV infection on hepatocyte apoptosis [22]. The present study was performed to determine the changes in apoptotic machinery accompanying HCV infection both in vitro and in vivo. For the in vitro study, we developed a HCV PAK6 replication system in HepG2 cell line, which may reflect to some extent the in vivo situation. Successful infection and propagation of the virus was assessed by detection of HCV-RNA using nested RT-PCR with specific primers, detection of increased titer by real time PCR, and virus passage to naïve cells. The HCV-HepG2 cell line was then used to study the long term effect of HCV infection on the apoptosis regulatory genes (Fas, FasL, Bak, Bcl-2, and Bcl-xL). This was correlated with the apoptotic activity in the cells by determining the expression levels of caspases 3, 8, and 9. We further assessed protein expression and mRNA levels of the same group of genes in liver tissues tissue samples obtained from patients with chronic hepatitis (CH) and hepatocellular carcinoma (HCC).