α-Melanocyte-stimulating hormone gene therapy reverses carbon tetrachloride induced liver fibrosis in mice

Background: Hepatic fibrosis represents a process of healing and scarring in response to chronic liver injury. Effective therapies are lacking. We have previously demonstrated that α-melanocyte-stimulating hormone (α-MSH) gene therapy protects against thioacetamide-induced acute liver failure in mice. Recent reports showed that collagen metabolism is a novel target of α-MSH. Therefore, the aim of this study is to investigate whether α-MSH gene therapy possesses anti-hepatic fibrogenic effect in mice. Methods: Liver fibrosis was induced in mice by administering carbon tetrachloride (CCl₄) continuously for 10 weeks. α-MSH expression plasmid was delivered via electroporation after liver fibrosis had been established. Histopathology, reverse-transcription polymerase chain reaction (RT-PCR), immunoblotting, and gelatin zymography were used to investigate its possible mechanisms of action. Results: α-MSH gene the rapy reversed established liver fibrosis in CCl₄-treated mice. RT-PCR revealed that α-MSH gene therapy attenuated the liver TGF-β1, collagen α1, and cell adhesion molecule mRNA upregulation. Following gene transfer, both the activation of α-smooth muscle actin (α-SMA) and cyclooxygenase-2 (COX-2) was significantly attenuated. Further, α-MSH significantly increased matrix metalloproteinase (MMP) activity with tissue inhibitors of matrix metalloproteinase (TIMP) inactivation. Conclusions: We have demonstrated that α-MSH gene therapy reversed established liver fibrosis in mice. It also prevented the upregulated fibrogenic and proinflammatory gene response after CCl₄ administration. Its collagenolytic effect may be attributed to MMP and TIMP modulation. In summary, α-MSH gene therapy may be an effective therapeutic modality against liver fibrosis with potential clinical use.