OBJECTIVETo investigate the anti-oxidative stress and anti-fibrotic mechanisms of adiponectin by examining effects on oxidative stress levels and expression of fibrosis-related signaling factors, including transforming growth factor-beta 1 (TGFb1), collagen I (COL-1), and the adenosine monophosphate-activated protein kinase (AMPK) pathway by using an in vitro HSC-T6 cultured cell system.

METHODSActivated HSC-T6 cells were pre-treated with 1.0 mug/mL adiponectin for 0, 30, 60 and 120 min, or left untreated to serve as controls, and both groups were then exposed to 5 mumol/L H2O2; a portion of the adiponectin-treated oxidative stress-induced cells were treated with an AMPK inhibitor (Compound C). The effects on mRNA levels of TGFb1. and COL-1 were analyzed by real-time PCR, in the levels of secreted TGF-b1 and COL-1 were detected by enzyme-linked immunosorbent assay of supernatants, and in the phosphoAMPK and AMPK protein expressions were detected by Western blotting.

RESULTSCompared to the H2O2 group without adiponectin pre-treatment, the H2O2 group with adiponectin pre-treatment showed significantly increased activity of superoxide dismutase (SOD), decreased content of malondialdehyde (MDA), and decreased gene and protein expressions of TGF-b1 and COL-1 (P less than 0.05). Moreover, inhibition of the AMPK pathway inhibited these adiponectin-mediated effects. The H2O2 group with adiponectin pre-treatment also showed increased levels of phospho-AMPK protein expression, with the maximum effect detected after 120 min of the adiponectin pre-treatment (P less than 0.01).

CONCLUSIONInhibition of oxidative stress is one of the mechanisms of the anti-fibrotic effects of adiponectin. Adiponectin can attenuate oxidative stress levels, resulting in down-regulation of TGFb1 and COL-1 expression through activation of the AMPK pathway.