Hepatitis C Virus Induces Interleukin-1β (IL-1β)/IL-18 in Circulatory and Resident Liver Macrophages

Hepatitis C virus (HCV)-mediated chronic liver disease is a global health problem, and inflammation is believed to be an important player in disease pathogenesis. HCV infection often leads to severe fibrosis/cirrhosis and hepatocellular carcinoma, although the mechanisms for advancement of disease are not fully understood. The proinflammatory cytokines interleukin-1 beta (IL-1 beta) and IL-18 have critical roles in establishment of inflammation. In this study, we examined induction of IL-1 beta/IL-18 secretion following HCV infection. Our results demonstrated that monocyte-derived human macrophages (THP-1) incubated with cell culture-grown HCV enhance the secretion of IL-1 beta/IL-18 into culture supernatants. A similar cytokine release was also observed for peripheral blood mononuclear cell (PBMC)-derived primary human macrophages and Kupffer cells (liver-resident macrophages) upon incubation with HCV. THP-1 cells incubated with HCV led to caspase-1 activation and release of proinflammatory cytokines. Subsequent studies demonstrated that HCV induces pro-IL-1 beta and pro-IL-18 synthesis via the NF-kappa B signaling pathway in macrophages. Furthermore, introduction of HCV viroporin p7 RNA into THP-1 cells was sufficient to cause IL-1 beta secretion. Together, our results suggested that human macrophages exposed to HCV induce IL-1 beta and IL-18 secretion, which may play a role in hepatic inflammation.