Basic Research
Copyright ©2007 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Oct 14, 2007; 13(38): 5071-5078
Published online Oct 14, 2007. doi: 10.3748/wjg.v13.i38.5071
Induction of ischemic tolerance in rat liver via reduced nicotinamide adenine dinucleotide phosphate oxidase in Kupffer cells
Kazuaki Tejima, Masahiro Arai, Hitoshi Ikeda, Tomoaki Tomiya, Mikio Yanase, Yukiko Inoue, Takako Nishikawa, Naoko Watanabe, Natsuko Ohtomo, Masao Omata, Kenji Fujiwara
Kazuaki Tejima, Hitoshi Ikeda, Tomoaki Tomiya, Mikio Yanase, Yukiko Inoue, Takako Nishikawa, Naoko Watanabe, Natsuko Ohtomo, Masao Omata, Department of Gastroenterology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
Masahiro Arai, Department of Gastroenterology, Toshiba General Hospital, 6-3-22 Higashiooi, Shinagawa-ku, Tokyo 140-8522, Japan
Kenji Fujiwara, Yokohama Rosai Hospital, 3211 Kozukue-cho, Kouhoku-ku, Yokohama-shi, Kanagawa 222-0036, Japan
Author contributions: All authors contributed equally to the work.
Correspondence to: Masahiro Arai, MD, PhD, Department of Gastroenterology, Toshiba General Hospital, 6-3-22 Higashiooi, Shinagawa-ku, Tokyo 140-8522, Japan. araima-tky@umin.ac.jp
Telephone: +81-3-37640511 Fax: +81-3-37643415
Received: May 12, 2007
Revised: July 28, 2007
Accepted: August 10, 2007
Published online: October 14, 2007
Abstract

AIM: To elucidate the mechanisms of hepatocyte preconditioning by H2O2 to better understand the pathophysiology of ischemic preconditioning.

METHODS: The in vitro effect of H2O2 pretreatment was investigated in rat isolated hepatocytes subjected to anoxia/reoxygenation. Cell viability was assessed with propidium iodide fluorometry. In other experiments, rat livers were excised and subjected to warm ischemia/reperfusion in an isolated perfused liver system to determine leakage of liver enzymes. Preconditioning was performed by H2O2 perfusion, or by stopping the perfusion for 10 min followed by 10 min of reperfusion. To inhibit Kupffer cell function or reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, gadolinium chloride was injected prior to liver excision, or diphenyleneiodonium, an inhibitor of NADPH oxidase, was added to the perfusate, respectively. Histological detection of oxygen radical formation in Kupffer cells was performed by perfusion with nitro blue tetrazolium.

RESULTS: Anoxia/reoxygenation decreased hepatocyte viability compared to the controls. Pretreatment with H2O2 did not improve such hepatocyte injury. In liver perfusion experiments, however, H2O2 preconditioning reduced warm ischemia/reperfusion injury, which was reversed by inhibition of Kupffer cell function or NADPH oxidase. Histological examination revealed that H2O2 preconditioning induced oxygen radical formation in Kupffer cells. NADPH oxidase inhibition also reversed hepatoprotection by ischemic preconditioning.

CONCLUSION: H2O2 preconditioning protects hepato-cytes against warm ischemia/reperfusion injury via NADPH oxidase in Kupffer cells, and not directly. NADPH oxidase also mediates hepatoprotection by ischemic preconditioning.

Keywords: Diphenyleneiodonium chloride, Ischemia/reperfusion injury, Ischemic preconditioning, Liver transplantation, Oxygen radicals