FIG. 5.

H₂S suppresses IL-6-induced hepcidin expression by promoting SIRT1-mediated STAT3 deacetylation. (A) NaHS treatment promoted SIRT1 expression and reduced STAT3 acetylation in the presence of IL-6 in Huh7 cells. (B) NaBu (1 mM), an HDAC inhibitor that promotes STAT3 acetylation, successfully induced HAMP expression without IL-6. The induction was blocked by stattic (10 μM, n=5). (C) IL-6 (10 ng/ml) challenge led to the dissociation of the exogenous SIRT1-STAT3 complex, which was stabilized by NaHS in Huh7 cells. (D, E) EX-527 (10 μM), a potent SIRT1 inhibitor, reversed the inhibition of NaHS on HAMP as well as STAT3 acetylation and phosphorylation (n=5). (F) SIRT1 silencing by specific siRNA abrogated the effect of NaHS on HAMP promoter activity (n=3). Silencing efficiency is indicated in the top right corner. (G) Resveratrol, an SIRT1 activator, attenuated IL-6 (10 ng/ml)-induced HAMP expression (n=3). (H) SIRT1 overexpression significantly suppressed HAMP induction by IL-6 (10 ng/ml), which was reversed by EX-527 (10 μM) in Huh7 cells (n=5). (I) The inhibitory effects of overexpressed SIRT1 on STAT3 acetylation and phosphorylation were diminished by EX-527 (10 μM). GAPDH served as the loading control. Representative immunoblots are presented with the results of densitometry analysis. Values are presented as mean±SEM from at least three independent experiments. ^#p<0.05 and ^##p<0.01 compared with the control group; *p<0.05 and **p<0.01 compared with the IL-6 group unless indicated; ^&p<0.05. HDAC, histone deacetylase; SIRT1, sirtuin 1.