Effect of Melatonin during Recovery of Tissue Injury after Intestine Ischemia-Reperfusion

ABSTRACT

PURPOSE: It is now well recognized that reperfusion of ischemic tissues initiates a complex series of reactions that can paradoxically injure tissues. Apoptosis occurs in select cell populations during morphologic development and during cellular injury, including oxygen radical exposure, ischemia-reperfusion, and sepsis. Thus, in this study, we examined relation of the melatonin effect to the injection time and the dose, and role of melatonin in apoptosis. METHODS: Intestinal ischemia-reperfusion injury was induced in rats by clamping the superior mesenteric artery for 30 minutes. After reperfusion injury for 30 minutes, the experimental group was administered melatonin (10 mg/kg) intraperitoneally and the control group received saline and ethanol. At 30 minutes, 60 minutes, and 90 minutes, 1) pulmonary histological assessments (interstitial PMNs/10HPFs and lung (alveolar) injury score), 2) alveolar microvascular permeability assessments (wet-weignt to dry-weight ratio and lipid peroxidation activity, malondialdehyde, MDA), and 3) western blotting assessments (p53, p21, Bax, and bcl-2) were made. For comparison, long- time (60-minute) reperfusion and double- dosage melatonin (20 mg/kg) were also studied. RESULTS: The lung injury score was 1.00+/-0 in the melatonin group at 90 minutes and 3.28+/-0.30 in the saline group (p0.05). A marked difference was found between the ischemia-reperfusion control group and the experimental group at 90 minutes regarding lipid peroxidation activity (Malondialdehyde, 16.45+/-0.19 micrometer vs 10.93+/-0.11 micrometer, p<0.01). In the melatonin group, p21 expressions were found to be much more than in the control group. But, p53, bcl-2, and Bax expressions were found to be in the control group. CONCLUSION: Melatonin injection within 60 min after reperfusion may promote recovery of reperfusion injury, but double-dose melatonin injection was inefficacious. Also, melatonin inhibit apoptosis by p21 expression.