MicroRNA-199a-5p Induced Autophagy and Inhibits the Pathogenesis of Ankylosing Spondylitis by Modulating the mTOR Signaling via Directly Targeting Ras Homolog Enriched in Brain (Rheb).

BACKGROUND/AIMS: Ankylosing spondylitis (AS) is an inflammatory and immune disease leading to disability. Autophagy has been identified as a potential player in understanding the pathogenesis of AS.

METHODS: MiRNA-199a-5p and autophagy-related gene expression were determined by qRT-PCR or Western blot. Cytokine production was determined using ELISA assays. Proliferation was determined by MTT assay. MiRNA-199a-5p and Ras homolog enriched in brain (Rheb) were upregulated or downregulated by overexpression of plasmid or siRNA transfection.

RESULTS: Expression of miRNA-199a-5p, and autophagy-related genes LC3, beclin1, and ATG5 was significantly decreased in T cells of AS patients. Serum concentrations of TNF-α, IL-17, and IL-23 were promoted in AS patients, compared to healthy controls. MiRNA-199a-5p expression levels also showed significant negative correlations with the Ankylosing Spondylitis Disease Activity Score (ASDAS) and modified Stoke Ankylosing Spon dylitis Spinal Score (mSASSS) of AS patients. In Jurkat T cells and T cells isolated from AS patients, miRNA-199a-5p overexpression promoted autophagy-related genes expression and decreased TNF-α, IL-17, and IL-23 levels, whereas inhibition of miRNA-199a-5p attenuated these effects. As a direct target of miRNA-199a-5p, Rheb inhibition led to a striking decrease in the phosphorylation of the mechanistic target of rapamycin (mTOR) and induced autophagy. Moreover, pcDNA3.1-Rheb effectively reduced the inhibiting effects of mTOR signaling caused by miRNA-199a-5p overexpression. All effects were offset by pretreating with rapamycin (an mTOR antagonist).

CONCLUSIONS: AS patients with advanced spinal damage had decreased autophagy levels and that miRNA-199a-5p may induce autophagy and inhibit the pathogenesis of AS by modulating the mTOR signaling via direct targeting Rheb.