Role of Rho small GTP binding protein in the regulation of actin cytoskeleton in hepatic stellate cells.
OBJECTIVE
In the fibrotic response to liver injury, hepatic stellate cells are activated, leading to the myofibroblastic cell shape, with actin cytoskeletal reorganization and increased extracellular matrix production. The reorganization of actin cytoskeleton suggests that the small GTP binding protein Rho might modulate the process of this myofibroblastic change. The aim of this study was to investigate the role of Rho in the phenotypic changes of hepatic stellate cells.


METHODS
The phenotypic changes were investigated by the overexpression of Rho regulator, Rho GDI or dominant negative mutant of Rho in mouse hepatic stellate cell line, GRX cells. In activated rat hepatic stellate cells, the effects of microinjection of Botulinus toxin C3, which is the specific inhibitor for Rho, were analyzed. Furthermore, the effect of C3 on the type I collagen accumulation in hepatic stellate cells was investigated.


RESULTS
Overexpression of Rho GDI or the dominant negative mutant of Rho caused the shrinkage cell shape and suppressed stress fiber formation. Microinjection of toxin C3 caused a markedly distorted cell shape and the disappearance of stress fibers in rat stellate cells. In addition, C3 strongly suppressed collagen accumulation in activated stellate cells.


CONCLUSIONS
These results suggest that Rho regulates the actin cytoskeletal reorganization, and may be implicated in the collagen accumulation in activated stellate cells. These findings provide evidence for the role of Rho in the myofibroblastic phenotype in hepatic stellate cells.
Kato
M
M
Third Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Iwamoto
H
H
Higashi
N
N
Sugimoto
R
R
Uchimura
K
K
Tada
S
S
Sakai
H
H
Nakamuta
M
M
Nawata
H
H
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D048429:Cell Size; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020730:Guanine Nucleotide Dissociation Inhibitors; D006150:Guanine Nucleotides / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000502:physiology*; D008297:Male; D051379:Mice; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D020742:rhoA GTP-Binding Protein
D000199:Actins; D020730:Guanine Nucleotide Dissociation Inhibitors; D006150:Guanine Nucleotides; D011994:Recombinant Proteins; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D003094:Collagen; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein