Project description:Systemic sclerosis (SSc) is a chronic autoimmune disease characterized with fibrosis of skin and multiple vital organs, but the immunological pathogenesis of SSc remains largely unknown. We show here that microRNA-19b (miR-19b) promotes IL-9-producing CD4+ T cells (Th9) that exacerbate SSc. Specifically, TGF-b plus IL-4 induced expression of TNF receptor associated factor 6 (TRAF6) through phosphorylated Smad3 linker region site Serine 213 (p-Smad3L-Ser213) and activated it through K63 ubiquitination by suppressing the leucine-rich-repeat-containing protein 3 (NLRC3). TRAF6 consequently formed complex with and activated TGF-b activated kinase 1 (TAK1). TAK1 promoted nuclear factor kappa B (NFκB) p65 activation, which then specifically upregulated miR-19b. miR-19b activated Il9 gene expression and promoted Th9 differentiation by directly targeting and suppressing atypical E2F family member E2f8 gene, a repressor for Il9 gene transcription. Importantly, Th9 cells played a critical role in the development and pathogenesis of experimental SSc by promoting the fibrosis in mice induced with Bleomycin. miR-19b and IL-9 were increased in CD4+ T cells in experimental SSc in mice and also in patients with SSc. Strikingly, inhibition of miR-19b resulted in fewer Th9 cells and attenuated fibrotic manifestations and ameliorated the disease in SSc mice. Our study identifies miR-19b as a key factor of Th9 cells that are involved in the pathogenesis of SSc. Our findings should have clinical implications for patients with SSc.
