Effect of Hepatitis C virus proteins on the production of proinflammatory and profibrotic cytokines in Huh7.5 human hepatoma cells

Hepatitis C virus (HCV) is a widespread dangerous human pathogen. Up to 80% of HCV-infected individuals develop chronic infection, which is often accompanied by liver inflammation and fibrosis and, at terminal stages, liver cirrhosis and cancer. Treatment of patients with end-stage liver disease is often ineffective, and even patients with suppressed HCV replication have higher risk of death as compared with noninfected subjects. Therefore, investigating the mechanisms that underlie HCV pathogenesis and developing treatments for virus-associated liver dysfunction remain an important goal. The effect of individual HCV proteins on the production of proinflammatory and profibrotic cytokines in hepatocellular carcinoma Huh7.5 cells was analyzed in a systematic manner. Cells were transfected with plasmids encoding HCV proteins. Cytokine production and secretion was accessed by immunocytochemistry and ELISA of the culture medium, and transcription of the cytokine genes was assessed using reverse transcription and PCR. HCV proteins proved to differ in effect on cytokine production. Downregulation of interleukin 6 (IL-6) production was observed in cells expressing the HCV core, NS3, and NS5A proteins. Production of transforming growth factor β1 (TGF-β1) was lower in cells expressing the core proteins, NS3, or E1/E2 glycoproteins. A pronounced increase in production and secretion of tumor necrosis factor α (TNF-α) was observed in response to expression of the HCV E1/E2 glycoproteins. A higher biosynthesis, but a lower level in the cell culture medium, was detected for interleukin 1β (IL-1β) in cells harboring NS4 and IL-6 in cells expressing NS5В. The finding was possibly explained by protein-specific retention and consequent accumulation of the respective cytokines in the cell.