Rho/Rho kinase is a key enzyme system involved in the angiotensin II signaling pathway of liver fibrosis and steatosis.
OBJECTIVE
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.


CONCLUSIONS
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.
Kitamura
Kumi
K
Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.
Tada
Shinichiro
S
Nakamoto
Nobuhiro
N
Toda
Kyoko
K
Horikawa
Hitomi
H
Kurita
Satoshi
S
Tsunematsu
Satoshi
S
Kumagai
Naoki
N
Ishii
Hiromasa
H
Saito
Hidetsugu
H
Hibi
Toshifumi
T
D000410:Alanine Transaminase / Q000097:blood; D000577:Amides / Q000494:pharmacology / Q000627:therapeutic use; D000804:Angiotensin II / Q000378:metabolism*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D001219:Aspartate Aminotransferases / Q000097:blood; D001562:Benzimidazoles / Q000494:pharmacology / Q000627:therapeutic use; D001713:Biphenyl Compounds / Q000494:pharmacology / Q000627:therapeutic use; D002478:Cells, Cultured; D002796:Choline Deficiency / Q000150:complications* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D004249:DNA Damage; D004195:Disease Models, Animal; D005234:Fatty Liver / Q000188:drug therapy / Q000201:enzymology / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000188:drug therapy / Q000201:enzymology / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009929:Organ Size; D018384:Oxidative Stress; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011725:Pyridines / Q000494:pharmacology / Q000627:therapeutic use; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013777:Tetrazoles / Q000494:pharmacology / Q000627:therapeutic use; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000577:Amides; D047228:Angiotensin II Type 1 Receptor Blockers; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D013777:Tetrazoles; D014409:Tumor Necrosis Factor-alpha; D000804:Angiotensin II; C108830:Y 27632; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D054460:rho-Associated Kinases; D020741:rho GTP-Binding Proteins; C077793:candesartan cilexetil