Astragalus and Paeoniae radix rubra extract inhibits liver fibrosis by modulating the transforming growth factor-β/Smad pathway in rats

It has been previously demonstrated that Astragalus and Paeoniae radix rubra extract (APE) had a protective effect against liver fibrosis in mice. The present study aimed to investigate the hepatoprotective effect of APE on CCl(4)-induced hepatic fibrosis in rats. Liver fibrosis was induced in male Sprague-Dawley rats by intraperitoneal injection of 50% CCl(4) twice a week for eight weeks. Organ coefficients, serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), hexadecenoic acid (HA), laminin (LN), procollagen type III (PCIII), hydroxyproline (Hyp), glutathione (GSH-Px), malondialdehyde (MDA), superoxide dismutase (SOD) and transforming growth factor β1 (TGF-β1) levels were measured in rats with hepatic fibrosis. Histopathological changes in affected livers were studied using hematoxylin-eosin and Masson’s trichrome staining. The expression of transforming growth factor-β/Smad pathway proteins, α-smooth muscle actin (α-SMA), collagen I and collagen III was observed in fibrotic livers using western blot analysis. The present study observed significant reductions in serum levels of AST, ALT, HA, LN, PCIII and Hyp in APE-treated (2.6 and 5.2 g/kg) rats, indicating the significant hepatoprotective effects of APE. Furthermore, the depletion of GSH-Px and SOD, in addition to the accumulation of MDA in liver tissue was suppressed by APE (2.6 and 5.2 g/kg). Pathological assessment of CCl(4)-induced fibrotic livers revealed a significant reduction of liver injury and development of hepatic fibrosis in rats treated with APE (2.6 and 5.2 g/kg). Moreover, APE (2.6 and 5.2 g/kg) decreased the elevation of TGF-β1, α-SMA, collagen I and collagen III expression, inhibited Smad2/3 phosphorylation as well as elevated the expression of the TGF-β1 inhibitor Smad7. These results suggested that APE may protect against liver damage and inhibit the progression of CCl(4)-induced hepatic fibrosis. The mechanism of action of APE is hypothesized to proceed via scavenging free radicals, decreasing TGF-β1 levels and blocking of the TGF-β/Smad signaling pathway.