CCL5 is induced by TLR 3 signaling in HuCCT1 human biliary epithelial cells: possible involvement in the pathogenesis of biliary atresia.

Biliary atresia (BA) is a disease of the newborn that is characterized by progressive, inflammatory and sclerosing cholangiopathy. Innate immune responses to viral components are thought to be involved in the pathogenesis of BA. It is also reported that some chemokines, such as CCL5, are possibly involved in the pathogenesis of experimental animal model of BA. We treated human biliary epithelial HuCCT1 cells with polyinosinic-polycytidylic acid (poly IC), an authentic double-stranded RNA (dsRNA) which mimics viral RNA, and analyzed the CCL5 expression by quantitative reverse transcription-PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA). To examine the regulation mechanisms of CCL5, we subjected the cells to RNA interference (siRNA) against Toll-like receptor 3 (TLR3), interferon (IFN)-ß, NF-κB p65 and IFN regulatory factor (IRF) 3. Immunohistochemical staining for CCL5 was also performed in tissues from patients with BA. Poly IC induced CCL5 expression in HuCCT1 cells. CCL5 expression induced by poly IC was inhibited by the knockdown of TLR3, p65 or IRF3, but it was not affected by knockdown of IFN-ß. Immunohistochemical staining showed that CCL5 was strongly expressed in biliary epithelial cells of patients with BA. The current study suggests that TLR3 signaling induces CCL5 expression via NF-κB and IRF3 in bile duct cells, and this pathway may be involved in the pathogenesis of BA.

Interferon (IFN)-induced protein 35 (IFI35) negatively regulates IFN-ß-phosphorylated STAT1-RIG-I-CXCL10/CCL5 axis in U373MG astrocytoma cells treated with polyinosinic-polycytidylic acid.

Interferon (IFN)-stimulated genes (ISGs) exert multiple functions in immune system. IFN-induced protein 35 (IFI35) is a member of ISGs, and has been suggested to regulate innate immune reaction. However, the physiological functions and pathological roles of IFI35 in the central nervous system are not characterized well. In the present study, we found that the expression of IFI35 was induced by a Toll-like receptor 3 (TLR3) ligand polyinosinic-polycytidylic acid (poly IC) in U373MG human astrocytoma cells. Knockdown of IFI35 using RNA interference resulted in increased expression of IFN-ß, phosphorylated STAT1 (P-STAT1), retinoic acid-inducible gene-I (RIG-I), CXCL10 and CCL5 induced by poly IC. Poly IC-induced expression of CXCL10 and CCL5 was decreased by knockdown of RIG-I. These results suggest that IFI35 may negatively regulate the TLR3-IFN-ß-P-STAT1-RIG-I-CXCL10/CCL5 axis in U373MG cells, and IFI35 may play a role at least partially in the regulation of innate immune reactions in astrocytes.