ABSTRACT
Objective To investigate the mechanism of action of integrin α4 (ITGA4) in liver fibrosis based on the anti-liver fibrosis effect of sticky sugar amino acid (SSAA) in rats. Methods A rat model of liver fibrosis was induced by intraperitoneal injection of CCl 4 , and then colchicine and low-, middle-, and high-dose SSAA were used for intervention, with blank control group and SSAA group as control. After 12 weeks of experimental intervention, serum and liver samples were collected to measure the serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and HE staining and Sirius Red staining were used to observe the pathological conditions of liver tissue; quantitative real-time PCR was used to measure the transcriptional level of ITGA4, integrin β1 (ITGB1), transforming growth factor-β1 (TGFβ1), alpha-smooth muscle actin (α-SMA), and TIMP2 in liver tissue; Western blot was used to measure the relative protein expression levels of ITGA4, ITGB1, TGFβ1, α-SMA, MMP2, TIMP1, and TIMP2; immunohistochemistry was used to observe the protein expression of TGFβ1 and α-SMA. A one-way analysis of variance was used for comparison of continuous data between multiple groups, and the least significant difference t -test was used for comparison between two groups. Results There were significant increases in AST and ALT in the CCl 4 model group, and intervention with colchicine or low-, middle-, and high-dose SSAA reduced the levels of AST and ALT, with a significant difference between the CCl 4 model group and the other groups (all P < 0.05). HE staining and Sirius Red staining showed disordered structure of hepatic lobules and an increase in collagen fibers in the CCl 4 model group, and the structure of hepatic lobules was improved after intervention with colchicine or low-, middle-, and high-dose SSAA. The CCl 4 model group had significantly higher transcriptional levels of ITGA4, TGFβ1, α-SMA, and TIMP2 than the other groups, and there were significant reductions in the transcriptional levels of each factor after intervention with colchicine or SSAA, with a significant difference between the CCl 4 model group and the other groups (all P < 0.05). The CCl 4 model group had significantly higher protein expression levels of ITGA4, TGFβ1, α-SMA, TIMP2, and TIMP1 and a significantly lower protein expression level of MMP2 than the other groups, and intervention with colchicine or SSAA inhibited the expression of ITGA4, TGFβ1, α-SMA, TIMP2, and TIMP1 and promoted the expression of MMP2. Immunohistochemistry showed that the CCl 4 model group had significantly higher expression levels of TGFβ1 and α-SMA than the other groups, which was inhibited by intervention with colchicine or SSAA. The high-dose SSAA group had the most significant effect in reducing aminotransferases, improving lobular structure, and inhibiting the protein expression of liver fibrosis factors. Conclusion The high expression of ITGA4 in the liver is associated with the development of liver fibrosis, which is consistent with the increases in the expression of TGFβ1 and α-SMA. Inhibiting the expression of ITGA4 can provide more therapeutic targets for liver fibrosis and expand the anti-liver fibrosis mechanism of SSAA.