Activation by Pathogen- and Damage-Associated Molecular Patterns Regulates the Expression of RANTES in Primary Hepatic Stellate Cells

While the chemokine RANTES is known to play an important role in the pathogenesis of liver fibrosis, little is known about its regulation by the innate immune system. Therefore, we studied the role of Toll-like receptors (TLRs) and Retinoic acid-inducible gene I (RIG-I) like receptors (RLRs) in the activation of hepatic stellate cells (HSC). Primary isolated murine and human HSCs were stimulated with TLR1–9, RIG-I ligands or co-incubated with primary isolated hepatocytes. Gene expression was assessed by quantitative RT-PCR, while RANTES production was additionally assessed by ELISA. Functional assays included induction of necrosis or apoptosis, inhibition experiments with pharmacological inhibitors of signaling pathways as well as proliferative and migration assays. TLR3 activation by Poly I:C (Polyinosinic:polycytidylic acid) was the most potent stimulus of RANTES production in vitro and in vivo. RIG-I could also induce the expression of RANTES via the TBK1/IKKε signaling pathway. As endogenous ligands, supernatants from necrotic but not from apoptotic hepatocytes mediated the expression of RANTES in an NFκB-dependent manner. Migration of HSC was stimulated primarily through TLR3, which could be completely blocked by antibodies against RANTES. In addition, RANTES could stimulate the proliferation of HSCs and upregulate the expression of PRR-related genes. Conclusions: The data suggest that activation of TLRs and RLRs by pathogen- and damage-associated molecular patterns is able to induce the up-regulation of RANTES via different signaling pathways. This sheds new light on the role of the innate immune system in the activation of HSC which may be of particular relevance for the pathogenesis of liver fibrosis.