MITOCHONDRIAL KATP CHANNEL OPENER PREVENTS ISCHEMIA-REPERFUSION INJURY IN RAT LIVER

Abstract

P73 Aims: Ischemia-reperfusion injury is responsible for the morbidity associated with liver surgery under total vascular exclusion or after liver transplantation. To reduce the injury, ischemic preconditioning has been shown to protect some organs such as heart, kidney, and liver against a more prolonged ischemic insult. Recently, mitochondrial KATP (mito KATP) channel rather than surface KATP channels, has emerged as likely mediators of preconditioning in the heart. Therefore, it has been reported that KATP channel opener has an effect on myocardial protection via an effort to inquire into the pharmacological preconditioning action. However, the final effecter molecules of the action remain unclear. It is unclear even whether KATP channel openers can reduce ischemia-reperfusion injury in the liver. The aim of this study is to determine the effect of mito KATP channel opener, nicorandil (SG-75), on ischemia-reperfusion injury in rat liver. Methods: Male Wistar rats were used and anesthetized with urethane. The blood supply to right and middle lobe of the liver was interrupted to 73% ischemia for 45 min, followed by 120 min of reperfusion. SG-75 (3 mg/kg) was orally administered 60 min before hepatic ischemia. Rats were sacrificed at 120 min after reperfusion (IR group) and after reperfusion with SG-75 administration (SG+IR group). Samples of blood and liver tissues were collected at the indicated times. Plasma levels of ALT and LDH were measured for examination of the liver function. Apoptosis was determined by TUNEL staining. The expression of cytochrome c, Bax, Bcl-2 and caspase-3 were analyzed by western blotting. TNF-α levels of plasma and liver were quantified using ELISA. Results: Plasma levels of ALT and LDH in IR group markedly increased to 5588 ± 646 and 28270 ± 3325 (IU / L), respectively. SG-75 significantly decreased their levels by about 60% (p<0.05). TUNEL-positive hepatocytes remarkably increased in about 30% of total hepatocytes in IR group. In SG-75 group, the increase of TUNEL-positive hepatocytes was inhibited to about 10%. Levels of cytochrome c in the corresponding mitochondrial fraction of the liver did not differ between the two groups. Cytochrome c and activated caspase-3 levels in the cytosol increased in IR group and SG-75 inhibited the release of cytochrome c and activation of caspase-3. The expression of Bax and Bcl-2 significantly increased in IR group and was slightly inhibited by administration of SG-75. Hepatic TNF-α levels slightly increased after reperfusion in both groups. Conclusions: These results suggested that its protective effect of SG-75 against hepatic ischemia-reperfusion injury was correlated with the inhibition of mitochondrial cytochrome c release and caspase-3 activation. These findings demonstrate that SG-75 may also become a therapeutic drug for IR-related hepatocellular damage.