Inactivation of the small GTPase Rac1 protects the liver from ischemia/reperfusion injury in the rat.
BACKGROUND
In ischemia/reperfusion (I/R) injury, a massive generation of reactive oxygen species (ROS) after reperfusion is a critical factor. Rac, a member of the Rho GTPase superfamily, plays important roles in the production of ROS and activation of nuclear factor-kappaB (NF-kappaB) in vitro. However, the exact role of Rac in the ROS production and NF-kappaB activation in vivo after I/R is still obscure.


METHODS
We blocked Rac1 activity in the rat liver using adenovirus encoding a dominant negative rac1 mutant (Ad5N17Rac1) and examined whether inactivation of Rac1 could prevent ROS generation in the hepatic I/R injury. Seventy-two hours after the adenoviral infection, hepatic I/R was induced by Pringle's maneuver for 20 minutes, followed by reperfusion in the rats.


RESULTS
Ad5N17Rac1 infection significantly attenuated ROS production after reperfusion and suppressed the hepatic injury. Furthermore, N17Rac1 suppressed NF-kappaB activation and messenger RNA expression of tumor necrosis factor-alpha (TNF-alpha) and inducible nitric oxide synthetase (iNOS). Ad5LacZ, a control adenovirus, had no effect on the induced hepatic I/R injury, nor did it affect NF-kappaB activation. Immunohistochemical analysis of NF-kappaB (p65) revealed that translocation of p65 to the nucleus after reperfusion was blocked in many of non-parenchymal cells (NPCs) and in hepatocytes in the Ad5N17Rac1-infected liver.


CONCLUSIONS
We conclude that Rac1 is required in ROS generation and NF-kappaB activation after hepatic I/R in vivo, and that inactivation of NF-kappaB in NPCs and suppression of ROS generation in NPCs and hepatocytes possibly account for the protective effect of N17Rac1 in this study.
Harada
Nobuko
N
Department of Gastrointestinal Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Iimuro
Yuji
Y
Nitta
Takashi
T
Yoshida
Masanori
M
Uchinami
Hiroshi
H
Nishio
Toshihiro
T
Hatano
Etsuro
E
Yamamoto
Naritaka
N
Yamamoto
Yuzo
Y
Yamaoka
Yoshio
Y
D021581:Active Transport, Cell Nucleus; D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D004247:DNA / Q000378:metabolism; D022761:Gene Transfer, Horizontal; D008099:Liver / Q000098:blood supply*; D008297:Male; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species; D015427:Reperfusion Injury / Q000517:prevention & control*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000502:physiology*
D016328:NF-kappa B; D017382:Reactive Oxygen Species; D004247:DNA; D020830:rac1 GTP-Binding Protein