Smad3 gene C-terminal phosphorylation site mutation exacerbates CCl4-induced hepatic fibrogenesis by promoting pSmad2L/C-mediated signaling transduction.

Current researches have confirmed that Smads, mediators of TGF-β signaling, are strictly controlled by domain-specific site phosphorylation in the process of hepatic disease. Usually, Smad3 phospho-isoform pSmad3L and pSmad3C are reversible and antagonistic; pSmad2L/C could act together with pSmad3L by stimulating PAI-1 expression and ECM synthesis to transmit fibrogenic signals. Our recent study found that pSmad3C mutation is supposed to perform a vigorous role on the early phase of liver injury and abates salvianolic acid B's anti-hepatic fibrotic-carcinogenesis. However, whether pSmad3C mutation expedites pSmad2L/C-mediated signaling transduction during hepatic fibrogenesis remains vague. Presently, Smad3 gene C-terminal phosphorylation site mutation heterozygote (pSmad3C+/-) mice were constructed to probe if and how pSmad3C retards CCl4-induced hepatic fibrogenesis by inhibiting pSmad2L/C-mediated signaling transduction. Twelve 6-week-old pSmad3C+/- C57BL/6J mice were intraperitoneally injection with CCl4 for 6 weeks to induce liver fibrogenesis. Results showed that pSmad3C mutation aggravates the relative liver weight, biochemical parameters, collagenous fibers and fibrotic septa formation, contributes to fibrogenesis in HT-CCl4 mice. Furthermore, fibrotic-related proteins TGF-β1, pSmad2C, pSmad2L, and PAI-1 were also increased in CCl4-induced pSmad3C+/- mice. These results suggest that pSmad3C mutation exacerbates hepatic fibrogenesis which relates to intensifying pSmad2L/C-mediated signaling transduction.