Zinc has been reported to prevent and reverse liver fibrosis in vivo; however, the mechanisms of its action are poorly understood. We therefore aimed to determine the antifibrotic potential of zinc.
Assessed was the influence of preincubation of rat HSCs with 30 microM ZnCl2 on ethanol- (in the presence of 4-methyl pyrazole (4-MP)) or acetaldehyde-induced toxicity, apoptosis, migration, expression of smooth muscle alpha-actin (alpha-SMA) and procollagen I, release of reactive oxygen species (ROS), tumor necrosis factor-alpha (TNF-alpha), tumor growth factor-beta1 (TGF-beta1), metalloproteinase-2 (MMP-2) and tissue inhibitors of metalloproteinases (TIMPs) production. Intracellular signals such as nuclear factor-kappaB (NFkappaB), C-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) induced by ethanol and its metabolite were also assessed.
30 microM zinc protected HSCs against ethanol and acetaldehyde toxicity and inhibited their apoptosis. Zinc inhibited the production of ROS by HSCs treated with ethanol and acetaldehyde and inhibited their migration. Zinc also inhibited ethanol- and acetaldehyde-induced TGF-beta1 and TNF-alpha production. Zinc down-regulated ethanol- and acetaldehyde-induced production of TIMP-1 and TIMP-2 and decreased the activity of MMP-2. In ethanol- and acetaldehyde-induced HSCs, zinc inhibited the activation of the p38 MAPK as well as the JNK transduction pathways and phosphorylation of IkappaB and Smad 3.
The results indicated that zinc supplementation inhibited ethanol- and acetaldehyde-induced activation of HSCs on different levels, acting as an antioxidant and inhibitor of MAPK, TGF-beta and NFkappaB/IkappaB transduction signaling. The remarkable inhibition of several markers of HCS activation makes zinc a promising agent for antifibrotic combination therapies.