Suppression of macrophage infiltration inhibits activation of hepatic stellate cells and liver fibrogenesis in rats.
OBJECTIVE
Monocytes/macrophages infiltrate into injured livers. We tried to clarify their roles in inflammation and subsequent fibrogenesis by inhibiting their infiltration with a mutated form (7ND; 7 amino acids at the N-terminal were deleted) of monocyte chemoattractant protein 1, which may function as a dominant-negative mutant.


METHODS
Rats were injected via the tail vein with an adenovirus expressing either human 7ND (Ad7ND), a truncated type II transforming growth factor beta receptor (AdTbeta-TR), which works as a dominant-negative receptor, bacterial beta-galactosidase (AdLacZ), or saline. Seven days later, the rats were treated with dimethylnitrosamine for 1-21 days.


RESULTS
Within 24 hours after a single dimethylnitrosamine injection, macrophages were observed in livers. With a 3-day dimethylnitrosamine treatment, activated hepatic stellate cells were detectable in livers in AdLacZ-, AdTbeta-TR-, and saline-injected rats. In contrast, in the Ad7ND-treated rats, infiltration of macrophages was markedly reduced, and activated hepatic stellate cells were not detectable. After a 3-week dimethylnitrosamine treatment, fibrogenesis was almost completely inhibited, and activated hepatic stellate cells were hardly seen in livers in both Ad7ND- and AdTbeta-TR-treated rats.


CONCLUSIONS
Our results show that blockade of macrophage infiltration inhibits activation of hepatic stellate cells and leads to suppression of liver fibrogenesis. The presence of activated hepatic stellate cells in the initial phase after injury and its absence at a later phase in the AdTbeta-TR-treated livers indicate that transforming growth factor beta is not an activating factor for hepatic stellate cells, and this suggests that transforming growth factor beta is required for the survival of activated hepatic stellate cells. Our study suggests that infiltrated macrophages may themselves produce an activating factor for hepatic stellate cells.
Imamura
Michio
M
Department of Biochemistry and Molecular Pathophysiology, University of Occupational and Environmental Health, School of Medicine, Iseigaoka 1-1, Yahatanishi-ku, Kitakyushu 807-8555, Japan.
Ogawa
Tadashi
T
Sasaguri
Yasuyuki
Y
Chayama
Kazuaki
K
Ueno
Hikaru
H
D000818:Animals; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors*; D002633:Chemotaxis / Q000276:immunology*; D004128:Dimethylnitrosamine / Q000009:adverse effects; D008099:Liver / Q000166:cytology / Q000276:immunology / Q000503:physiopathology; D008103:Liver Cirrhosis / Q000139:chemically induced / Q000276:immunology* / Q000503:physiopathology; D008264:Macrophages / Q000276:immunology*; D008297:Male; D023421:Models, Animal; D009000:Monocytes / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016212:Transforming Growth Factor beta / Q000276:immunology
D018932:Chemokine CCL2; D016212:Transforming Growth Factor beta; D004128:Dimethylnitrosamine