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  • Title: Rho/Rho kinase is a key enzyme system involved in the angiotensin II signaling pathway of liver fibrosis and steatosis.
    Author: Kitamura K, Tada S, Nakamoto N, Toda K, Horikawa H, Kurita S, Tsunematsu S, Kumagai N, Ishii H, Saito H, Hibi T.
    Journal: J Gastroenterol Hepatol; 2007 Nov; 22(11):2022-33. PubMed ID: 17914985.
    Abstract:
    BACKGROUND AND AIM: The molecular mechanisms underlying the involvement of the renin-angiotensin system in hepatic fibrosis are unclear. Recently, it was reported that a Rho kinase inhibitor prevented fibrosis of various tissues and that the Rho/Rho kinase pathway was involved in the renin-angiotensin system of vascular smooth muscle cells. In this study, the involvement of the Rho/Rho kinase pathway on angiotensin II signaling in liver fibrogenesis and generation of steatosis was investigated. METHODS: Rats were fed a choline-deficient/L-amino acid-defined (CDAA) diet continuously and treated with a Rho kinase inhibitor, Y-27632, and an angiotensin II receptor blocker, TCV-116. Liver histology and hepatic stellate cell activation were analyzed. Free radical production was detected by 4-hydroxynonenal and 8-hydroxy-2'-deoxyguanosine immunostaining and the expression of tumor necrosis factor-alpha was examined. Isolated hepatic stellate cells were pretreated with a Rho kinase inhibitor, Y-27632, or an angiotensin II receptor blocker, CV-11974, and stimulated with angiotensin II, and mRNA expression of transforming growth factor-beta and alpha-smooth muscle actin was analyzed. RESULTS: Both the angiotensin II receptor blocker and the Rho kinase inhibitor improved fibrosis and steatosis of the liver in CDAA-fed rats. The increase in the number of hepatocytes positive for 4-hydroxynonenal and 8-hydroxy-2'-deoxyguanosine in CDAA-fed rats was significantly prevented by the angiotensin II receptor blocker and the Rho kinase inhibitor. The levels of tumor necrosis factor-alpha mRNA in the liver of CDAA-fed rats were significantly increased and this increase was significantly inhibited by treatment with the angiotensin II receptor blocker and the Rho kinase inhibitor. mRNA expression of transforming growth factor-beta and alpha-smooth muscle actin stimulated by angiotensin II was also significantly suppressed by these two drugs. CONCLUSION: These results suggest that the Rho/Rho kinase pathway is at least partly involved in the renin-angiotensin system and plays an important role in hepatic fibrosis and steatosis.
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