IL-17-triggered downregulation of miR-497 results in high HIF-1[alpha] expression and consequent IL-1[beta] and IL-6 production by astrocytes in EAE mice

• Published in: Cellular & molecular immunology 2017-11, Vol.14 (11), p.909
• Main Authors: Shan, Kai, Pang, Rongrong, Zhao, Chenhui, Liu, Xiaomei, Gao, Wenxing, Zhang, Jing, Zhao, Dan, Wang, Yingwei, Qiu, Wen
• Format: Article
• Language: English
• Subjects: Astrocytes; Experimental allergic encephalomyelitis; Hypoxia-inducible factor 1; Hypoxia-inducible factor 1a; Inflammation; Interleukin 1; Interleukin 17; Interleukin 6; miRNA; Multiple sclerosis; Rodents
• ISSN: 1672-7681; 2042-0226
• DOI: 10.1038/cmi.2017.12

Interleukin 17 (IL-17) is increasingly recognized as a key factor that contributes to the pathogenesis of multiple sclerosis (MS) and its experimental mouse autoimmune encephalomyelitis (EAE) model. However, the roles and regulatory mechanisms of IL-17-induced pro-inflammatory cytokine production in EAE mice remain largely unclear. In this study, the expression of IL-17, hypoxia inducible factor-1α (HIF-1α), IL-1β, IL-6 and microRNA-497 (miR-497), as well as their intrinsic associations, was investigated using EAE model mice and cultured astrocytes exposed to IL-17 in vitro. We observed markedly increased production of IL-17, HIF-1α, IL-1β and IL-6 in the brain tissues of EAE mice, while the expression and secretion of HIF-1α, IL-1β and IL-6 were also significantly increased when cultured primary astrocytes from mice were stimulated with IL-17. Meanwhile, the expression of miR-497 was downregulated both in vivo and in vitro. Subsequent in vitro experiments revealed that IL-17 induced the production of IL-1β and IL-6 in astrocytes through the upregulation of HIF-1α as a transcriptional factor, indicating that IL-17-mediated downregulation of miR-497 enhanced HIF-1α expression. Furthermore, astrocyte-specific knockdown of IL-17RA and HIF-1α or astrocyte-specific overexpression of miR-497 by infection with different lentiviral vectors containing an astrocyte-specific promotor markedly decreased IL-1β and IL-6 production in brain tissues and alleviated the pathological changes and score of EAE mice. Collectively, these findings indicate that decreased miR-497 expression is responsible for IL-17-triggered high HIF-1α expression and consequent IL-1β and IL-6 production by astrocytes in EAE mice.