HCV-Related Proteins Activate Kupffer Cells Isolated from Human Liver Tissues

It was reported from this laboratory that Kupffer cells (KCs) were activated in patients infected with HCV. Since dendritic cells, monocytes, and macrophages were activated by stimulation with HCV-related proteins, the specific aim of this study was to investigate the role of HCV-related proteins in activation of KCs, the signal pathway of activation of KCs mediated by Toll-like receptor (TLR) 4, and the influence of HCV infection on function of KCs. Kupffer cells isolated from non-cancerous surgical specimen were co-cultured with HCV-related proteins (Core, NS3, NS4, and NS5), and production of cytokines (TNF-alpha, IL-1 beta, and IL-10) and hydrogen peroxide were assessed. Furthermore, effects of neutralization antibodies against the TLR2, TLR3, or TLR4, and cytochalasin B on the production TNF-alpha by KCs were investigated. Kupffer cells produced markedly a proinflammatory cytokine TNF-alpha by stimulation with all HCV-related proteins studied, and values were as same as production by KCs stimulated with LPS. Importantly, this production in the case of NS3 was significantly blunted by about 60% by neutralization antibodies against the TLR4, but not cytochalasin B. Production of TNF-alpha by isolated KCs stimulated with LPS was significantly greater in the HCV-infected livers than the HCV/HBV-negative livers. These results indicated that HCV-related proteins may cause prolonged activation of KCs in the HCV-infected liver, leading to accumulation of inflammatory cytokines that contribute to DNA damage and carcinogenesis. Furthermore, function of KCs was difference between patients infected with and without HCV infection.