Protecting effects of vasonatrin peptide against carbon tetrachloride-induced liver fibrosis

In order to investigate the effects of vasonatrin peptide (VNP), a novel man-made natriuretic peptide, on liver fibrosis, mice received carbon tetrachloride (CCl4) injection for 12 weeks and with or without VNP treatment during the last 6 weeks. Hematoxylin-eosin (HE) staining and Sirius red staining were performed to evaluate the status of liver fibrosis. After treatment of VNP, DNA and collagen synthesis of cultured HSC-T6 hepatic stellate cells were assessed by [3H]-thymidine and [3H]-proline incorporation, respectively. Additionally, involved signaling pathway was identified by radioimmunoassay to detect the levels of intracellular cGMP and by mimicking experiments using 8-br-cGMP (a membrane-permeable cGMP analog). Also, blocking experiments were performed using HS-142-1, an antagonist of guanylyl cyclase-coupled natriuretic peptide receptor (NPR), or KT-5823, the cGMP-dependent protein kinase (PKG) inhibitor. As a result, VNP markedly alleviated CCl4-induced liver fibrosis in mice. In vitro, HSC-T6 cells demonstrated a dose-dependent reduction of DNA and collagen synthesis in the presence VNP. In addition, VNP significantly increased the intracellular levels of cGMP. These effects of VNP were mimicked by 8-br-cGMP, although inhibited by HS-142-1 or KT-5823. Taken together, VNP ameliorates liver fibrosis by inhibiting collagen production from hepatic stellate cells via guanylyl cyclase-coupled NPR/cGMP/PKG pathway, indicating that VNP might be a new effective reagent in the treatment of liver fibrosis.