Mitogen-activated protein kinases (MAPKs) and nuclear factor (NF)-ĸB signaling have been recognized for their causal connection with liver fibrosis. Hence, it is encouraging to discover drugs that can modify the interactions between these signaling cascades. It has been suggested that glucagon-like peptide-1 receptors (GLP-1Rs) might have a role in the observed hepatoprotection of dipeptidyl peptidase-4 inhibitors other than vildagliptin (VLD). Consequently, we aimed to elucidate the mechanisms underlying its potential antifibrotic activity in a CCl4-intoxicated mouse model. VLD increased the percentage of viable CCl4-intoxicated primary rat hepatocytes in vitro. It also attenuated hepatic fibrosis, improved liver function, and prolonged survival of CCl4-intoxicated mice in a dose-dependent manner. This hepatoprotection might be mediated mainly through interference with extracellular signal-regulated protein kinase 1/2 phosphorylation, the most downstream signal of the MAPK pathway. In addition, VLD hepatoprotective activity could be partially mediated through inhibition of p38α phosphorylation and phosphorylation-induced NF-ĸB activation. As a result, VLD downregulated profibrogenic mediators, such as tumor necrosis factor α, transforming growth factor β, tissue inhibitor of metalloproteinase 1 and platelet-derived growth factor BB. Consequently, decreased expression levels of fibrosis markers, such as hydroxyproline and α smooth muscle actin, were confirmed. VLD showed a strong trend toward increasing the antioxidant defense machinery of fibrotic tissue, and we confirmed that GLP-1Rs were not implicated in the observed hepatoprotection. Since VLD poses little risk of hypoglycemia and is a safe drug for patients with liver injury, it may be a hopeful candidate for adjuvant treatment of liver fibrosis in humans.
Keywords: ERK1/2; Fibrosis; GLP-1R; NF-κB; Vildagliptin; p38α.
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