Effects Of Preconditioning With Diazoxide On Apoptosis Induced By Focal Cerebral Ischemia-reperfusion Injury In Rats And Its Mechanisms

AIM: To investigate the protective of preconditioning with diazoxide on apoptosis induced by focal cerebral ischemia-reperfusion injury in rats and possible mechanisms by an animal model of reversible middle cerebral occlusion (MCAO-I/R).METHODS : MCAO model was produced by intraluminal suture technique. 32 male S-D rats were allocated to four groups randomly: 1.sham-operate group(S group,control group); 2. ischemia-reperfusion injury model group(IR group); 3.diazoxide-preconditioning group(Dz group); 4. Glibenclamide and diazoxide preconditioning group(Dz+Gl group). At 2h of occlusion, 2h and 24h of reperfusion, the extent of neurological deficits was evaluated by Longa's model. Morphological changes of brain were observed. Brain cell apoptosis of each group was tested by TUNEL technique and the apoptotic index (AI) was calculated. The relative quantitation of bcl-2 and caspase-3 mRNA expression of each group were measured by RT-PCR technique. RESULTS: (1) In IR group,as for S group,the neurological syndromes andthe injury change of brain histology were showed, apoptotic cells increased and AI was elevated(p<0.01), the relative quantitation of bcl-2 and and caspase-3 mRNA expression were higher(p<0.01). (2)Precondition with diazoxide(a mitoKATP opener) could reduce neurological deficits score and brain injury change, significantly less apoptotic cells and AI lower than that in IR group(p<0.01), the relative quantitation of bcl-2 expression is higher(p<0.05) but caspase-3 lower than that in IR group(p<0.05). (3) Protective effects of diazoxide were abolished glibenclamide(a mitoKATP blocker).CONCLUSIONS: mito-KATP opener inhibited ischemia-reperfusion injury inducing cell apoptosis by up-regulating bcl-2mRNA expression and down-regulating caspase-3 mRNA expression in rat. These beneficial effects may suggest a possible new target for neuroprotection.