S-adenosyl-L-methionine attenuates oxidative stress and hepatic stellate cell activation in an ethanol-LPS-induced fibrotic rat model.

Previous studies report S-adenosyl-L-methionine (SAMe) can exert hepatoprotective effects. At present, the role of SAMe in affecting the activation and/or proliferation of hepatic stellate cells (HSCs) during alcohol-induced fibrotic disease progression is poorly understood. In the human disease state, chronic ethanol intake increases hepatic exposure to LPS and magnifies the hepatic insult leading to fibrosis and cirrhosis. In this study, we developed a "2-hit" ethanol-LPS fibrotic liver rat model with which to investigate the effects of SAMe as a hepatic antifibrotic treatment. Male rats were maintained on liquid diets containing either ethanol or isocalorically matched controls for 8 weeks. Animals received ethanol alone (E), ethanol concomitant with twice weekly LPS injections (EL), or ethanol, LPS, and daily SAMe injections. When using this model, SAMe-treated animals demonstrated significantly decreased fibrosis, oxidative stress, steatosis, and improved liver function versus the EL group. In addition, the EL group showed increased HSC activation, an effect that was abrogated by the addition of SAMe. Analysis of the transforming growth factor-beta (TGF-beta) signaling pathways demonstrated increased hepatic TGF-beta and Smad3 messenger RNA expression in the E and EL groups, which was inhibited in the presence of SAMe. Conversely, SAMe led to increased Smad7 (an inhibitor of TGF-beta signaling) messenger RNA expression. These data demonstrate chronic ethanol feeding combined with LPS induces liver fibrosis, and the addition of SAMe significantly reduces hepatic injury and fibrosis through inhibition of oxidative stress and HSC activation.