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Background: TH2 inflammation and bronchial smooth muscle cell (BSMC) hyperplasia are characteristic features of asthma, but whether these phenomena are linked remains unknown. This study aims to define the effect of the TH2 cytokines IL-4 and IL-13 on human BSMC proliferation when administered alone or in combination with the fibroblast growth factor 2 (FGF2) growth factor. In addition, the effects of the proinflammatory mediators TNFα and IL-1β and the involvement of members of the well-known family of platelet-derived growth factor (PDGF) mitogens were tested. Methods: BSMC proliferation was measured by crystal violet staining and PDGF and PDGF receptor (PDGFR) expression were determined by RT-PCR, immunocytochemistry, ELISA, flow cytometry and dot plot analysis. Results: Neither IL-4 nor IL-13 alone induced BSMC proliferation, despite both being potent inducers of PDGF-CC. However, following a pretreatment with FGF2, which increased PDGFR α chain expression, both IL-4 and IL-13 increased FGF2-induced BSMC proliferation in a time- and concentration-dependent manner. TNFα and IL-1β did not affect basal or FGF2-induced BSMC proliferation, but both proinflammatory mediators enhanced the proliferative synergism between FGF2 and the TH2 cytokines. Conclusions: IL-4 and IL-13 potently induce FGF2-primed BSMC proliferation via an autocrine loop involving PDGFRα and PDGF-CC, and this proliferative synergism is amplified by proinflammatory cytokines.

To identify new regulators of antiviral innate immunity, we completed the first genome-wide gene silencing screen assessing the transcriptional response at the interferon-β (IFNB1) promoter following Sendai virus (SeV) infection. We now report a novel link between WNT signaling pathway and the modulation of retinoic acid-inducible gene I (RIG-I)-like receptor (RLR)-dependent innate immune responses. Here we show that secretion of WNT2B and WNT9B and stabilization of β-catenin (CTNNB1) upon virus infection negatively regulate expression of representative inducible genes IFNB1, IFIT1 and TNF in a CTNNB1-dependent effector mechanism. The antiviral response is drastically reduced by glycogen synthase kinase 3 (GSK3) inhibitors but restored in CTNNB1 knockdown cells. The findings confirm a novel regulation of antiviral innate immunity by a canonical-like WNT/CTNNB1 signaling pathway. The study identifies novel avenues for broad-spectrum antiviral targets and preventing immune-mediated diseases upon viral infection., Author Summary The innate immune system is the first line of defense for organisms that possess an adaptive immune system. It allows a rapid immune response upon viral infections, in addition to propagating an antiviral state in neighboring cells. In an attempt to identify new proteins that are involved in antiviral responses, we completed the first genome-wide RNA interference (RNAi) screen by individually silencing the expression of 15,000 human genes to assess their role in the induction of type I interferon-β (IFNB1) upon Sendai virus (SeV) infection. We identified 237 potential modulator genes for which negative or positive actions of gene products were mapped to the different steps of the antiviral responses. Among these genes, we find two members of the WNT family WNT2B and WNT9B that negatively regulate the IFNB1 response. We show that SeV infection induces the secretion of WNT ligands, stabilization of β-catenin (CTNNB1) and decreases expression of IFNB1 in a feedback mechanism. We further demonstrate that inhibition of glycogen synthase kinase 3 (GSK3) reduces the antiviral innate response in a CTNNB1-dependent manner. The findings suggest that drugs targeting this newly identified canonical-like WNT/CTNNB1 signaling pathway may be therapeutically useful to modulate viral replication or virus-induced inflammation.

To identify new regulators of innate antiviral immunity, we completed the first genome-wide gene silencing screen assessing the transcriptional response at the interferon-β gene (IFNB1) promoter following Sendai virus (SeV) infection. We identified 237 potential modulator genes for which negative or positive actions of gene products were mapped to the different steps of the antiviral responses from virus sensing, signal propagation/amplification up to the feedback regulation. In the present study, we will report on specific proteins that promote IFNB1 expression and innate antiviral response. The functional genomics screen uncovers a novel link between WNT family members and innate antiviral immunity. We show that virus-induced secretion of WNT2B and WNT9B down regulates IFNB1 and ISG56 expression in a β-catenin (CTNNB1)-dependent mechanism. The antiviral response is drastically reduced by GSK3 inhibitors but completely restored in CTNNB1 knockdown cells. The findings confirm a novel regulation of the innate antiviral response by a canonical WNT/GSK3/CTNNB1 pathway in a negative feedback mechanism. The study identifies novel avenues for therapeutically regulating innate immunity for effective treatment of viral infection and prevention of excessive response in autoimmune diseases.