69. Oleanolic acid protects against myocardial ischemia-reperfusion injury by enhancing mitochondrial antioxidant mechanism mediated by glutathione and α-tocopherol in rats


Department of Biochemistry, Hong Kong University of Science & Technology, Clear Water Bay, HONG-KONG

The effect of oleanolic acid (OA) pretreatment on myocardial ischemia-reperfusion (I-R) injury was investigated using an ex vivo rat heart model. Pretreatment with OA at daily doses (0.6 and 1.2 mmol/kg) for 3 days significantly protected against 1-R injury in isolated rat hearts, as evidenced by the decrease in the extent of lactate dehydrogenase (LDH) leakage and improvement in contractile force recovery. The cardioprotection was associated with a slight increase in mitochondrial reduced glutathione (GSH) level and a significant increase in mitochondrial α-tocopherol (a-TOC) level, when compared with the unpretreated I-R group. To further investigate the mechanism of myocardial protection, pretreatment with a single dose of OA (1.2 mmol/kg) produced a time-dependent protection against myocardial I-R injury as assessed by LDH leakage, with the maximum extent of protection occurring at 48 hour post-dosing. The maximum cardioprotection was associated with parallel increases in mitochondrial GSH and α-TOC levels in ischemic-reperfused hearts, with the stimulation of the α-TOC level being optimal. Furthermore, buthionine sulfoximine/phorone (BSO/PHO) treatment, while abolishing the enhancing effect of OA on mitochondrial GSH, did not completely abrogate the cardioprotection against I-R injury. The remnant cardioprotection was associated with an increase in mitochondrial α-TOC level, when compared with the unpretreated I-R group with BSO/PHO. The results suggest that the cardioprotection afforded by OA pretreatment against I-R injury may at least in part be attributed to the enhancement of mitochondrial antioxidant mechanism mediated by GSH and α-TOC, particularly under I-R conditions.