Role of mitochondrial permeability transition pore of hippocampai neurons in process of hydrogen-rich saline attenuating global cerebral ischemia-reperfusion injury in rats

Abstract

Objective To investigate the role of mitochondrial permeability transition pore (mPTP) of hippocampal neurons in process of hydrogen-rich saline attenuating global cerebral ischemia-reperfusion (I/R) injury in rats.Methods Seventy-two male Sprague Dawley rats,weighing 250-300 g,were randomly divided into six groups ( n =12 each):sham operation group (group S),cerebral ischemia-reperfusion group (group IR),normal saline group (group NS),hydrogen-rich saline group (group H),atractyloside group (group A) and hydrogen-rich saline + atractyloside group (group HA).Global cerebral I/R injury was produced by four-vessel occlusion method.Bilateral vertebral arteries were cauterized.Then bilateral common carotid arteries were occluded for 15min and followed by reperfusion.In groups H and HA,hydrogen-rich saline 5 ml/kg was injected intraperitoneally immediately after reperfusion,while equal volume of normal saline was injected in the other four groups.The rats in groups A and HA received intracerebroventricular injection of atractyloside 15 μl 10 min before reperfusion,while groups NS and H received intracerebroventricular injection of equal volume of normal saline.After the neurological behavior was evaluated at 24 h of reperfusion,8 rats in each group were sacrificed and the hippocampi were immediately isolated and homogenized followed by density gradient centrifugation.The opening degree of mPTP was assayed with spectrophotometry and the mitochondrial membrane potential (MMP) was detected with Rhodamine 123 method.Four rats in each group were killed at 72 h of reperfusion and the brains were removed for microscopic examination of the area CA1 of the hippocampus and determination of the number of normal pyramidal neurons.Results Compared with group S,the neurological behavior was compromised,MMP was decreased and mPTP opening degree was enhanced in the other five groups ( P ＜ 0.05).The neurological behavior was better,MMP was increased and mPTP opening degree was decreased in groups H and HA as compared with group IR ( P ＜ 0.05).Compared with group H,the neurological behavior was compromised,MMP was decreased and mPTP opening degree was enhanced in group HA ( P ＜ 0.05).Compared with group IR,the number of normal pyramidal neurons at 72 h of reperfusion in the CA1 region of the hippocampus was higher in group HA ( P ＜0.05).The injury of the CA1 region of the hippocampus at 72 h of reperfusion was attenuated in group H as compared with groups IR,NS,A and HA.Conclusion Hydrogen-rich saline can attenuate global cerebral I/R injury throngh inhibiting the mPTP opening and reducing the dissipation of MMP,thus maintaining the mitochondrial function. Key words: Hydrogen; Reperfusion injury; Brain; Mitochondrial permeability transition pore; Membrane potentials