Effects of IL-17A on fibrosis of skin and lung in a mouse model of systemic sclerosis

Abstract

Objective To analyze the expression of interleukin (IL)-17A in a mouse model of bleomycin (BLM)-induced systemic sclerosis (SSc) and to evaluate its effects on inflammation and fibrosis in skin and lung tissues. Methods Twenty-four female BALB/c mice were randomly divided into four groups: normal control group (mice were subcutaneously injected with phosphate buffer), model group (subcutaneously injected with BLM), antibody group (injected with BLM + IL-17A monoclonal antibody), homotypic control group (injected with BLM + isotype control). Pathological changes in skin and lung tissues of those mice were observed; inflammatory and fibrotic scores were assessed. Immunohistochemistry and real-time fluorescent quantitative PCR (RT-PCR) were used to detect the expression of IL-17A, TGF-β1 and typeⅠ collagen in skin and lung tissues of those mice at mRNA level. Mouse lung fibroblasts (FB) derived from the mice of model group were cultured in vitro and then were cultured with IL-17A cytokines with or without the interference of monoclonal antibodies. Expression of typeⅠ collagen and TGF-β1 at mRNA level and levels of IL-6 and TGF-β1 in the culture supernatants were detected by RT-PCR and enzyme-linked immunosorbent assay (ELISA), respectively. Results Compared with the mice of model and homotypic control groups, those of the antibody group showed mild skin thickening, skin inflammation and lung inflammation as well as lower fibrosis scores (P<0.05). The expression of IL-17A at both protein and mRNA levels and the expression of TGF-β1 and collagen typeⅠ at mRNA level in skin and lung tissues of mice of the antibody group were significantly lower than those of the model and homotypic control group (P<0.05). Results of the in vitro cell culture of SSc mice-derived lung FB with IL-17A showed that the expression of TGF-β1 and typeⅠ collagen at mRNA level and the levels of IL-6 and TGF-β1 in the culture supernatants were decreased with the interference of anti-IL-17A monoclonal antibody (P<0.05), but were still higher than those of the control group (P<0.05). Conclusion IL-17A promotes the development of inflammation and fibrosis in skin and lung tissues in the mouse model of SSc. Blocking IL-17A might inhibit fibrosis in SSc by inhibiting the production of TGF-β1, IL-6 and typeⅠ collagen. Key words: Systemic sclerosis; Anti-IL-17A monoclonal antibody; IL-17A; TGF-β1; TypeⅠ collagen