Protective Effects Of Noninvasive Delayed Limb Ischemic Preconditioning On Cerebral Ischemia-reperfusion Oxidative Injury In Rats

Objective.To study the protective effects of noninvasive delayed limb ischemic preconditioning against cerebral ischemia-reperfusion oxidative injury in rats.Method:Wistar rats were divided randomly into sham operation (Sham),ischemia-reperfusion(I/R),early cerebral ischemic preconditioning and ischemia-reperfusion(ECIP+I/R) and noninvasive delayed limb ischemic preconditioning and ischemia-reperfusion(NDLIP+I/R) groups.Rats in NDLIP+I/R group were subjected to three cycles of five minutes ischemia/five minutes reperfusion on the left hind limb,once a day for three consecutive days.On the forth day,all rats were subjected to cerebral ischemia/reperfusion injury.Rats in ECIP+I/R group were preconditioned before ischemia.Neurological score and cerebral infarct size(IS) were examined after ischemia 1 h and reperfusion 24 h.Activity of superoxide dismutase(SOD) and concentration of malondialdehyde(MDA) were measured.Total RNA was extracted from the brains and the Mn-SOD mRNA expression was studied by the method of reverse transcription polymerase chain reaction(RT-PCR).Results:①Compared with I/R group's neurological score and IS (9.00±1.75,15.8±3.64%),ECIP+I/R and NDLIP+I/R could reduce neurological score(6.29±1.68 and 6.42±2.20,P＜0.01 and P＜0.01) significantly after ischemia 1 h and reperfusion 24 h,and IS was reduced(8.95±1.69%和9.21±2.20%,P＜0.01 and P＜0.01);②Compared with I/R group(0.95±0.02 U/g),ECIP+I/R and NDLIP+I/R could decrease MPO activity(0.77±0.03 U/g and 0.78±0.06 U/g,P＜0.01 and P＜0.01);③Compared with I/R group in hippocampus(6.68±0.78 nmol/mgprot),ECIP+I/R and NDLIP+I/R could decrease concentration of MDA(5.08±0.23 nmol/mgprot and 5.12±0.57 nmol/mgprot,P＜0.01 and P＜0.01);Compared with I/R group(8.34±0.32 nmol/mgprot) in cortex,ECIP+I/R and NDLIP+I/R could decrease concentration of MDA(7.32±0.18 nmol/mgprot and 7.28±0.29 nmol/mgprot, P＜0.01 and P＜0.01);④Compared with I/R group's total SOD(82.00±5.35 U/mgprot) and Mn-SOD(34.64±4.90 U/mgprot) in hippocampus,ECIP+I/R and NDLIP+I/R could increase total SOD activity(114.84±7.99 U/mgprot and 121.06±8.25 U/mgprot,P＜0.01 and P＜0.01) and Mn-SOD activity(50.37±7.93 U/mgprot and 48.77±6.05 U/mgprot,P＜0.01 andP＜0.01);Compared with I/R group's total SOD(85.15±4.12 U/mgprot) and Mn-SOD(41.33±2.22 U/mgprot) in cortex,ECIP+I/R and NDLIP+I/R could increase total SOD activity(115.15±11.11 U/mgprot and 108.84±8.99 U/mgprot,P＜0.01 and P＜0.01) and Mn-SOD activity(50.31±3.71 U/mgprot and 51.38±6.07 U/mgprot,P＜0.01 and P＜0.01);Among all these oxidative and antioxidative substancese,there was no significance between ECIP+I/R and NDLIP+I/R.⑤The RT-PCR results indicated that compared with I/R group (0.57±0.07) in hippocampus,expression of Mn-SOD were increased in ECIP+I/R and NDLIP+I/R group(0.91±0.09 and 0.88±0.07,P＜0.01 and P＜0.01);Compared with I/R group(0.59±0.11) in cortex,expression of Mn-SOD were increased in ECIP+I/R and NDLIP+I/R group(0.98±0.10 and 0.91±0.10,P＜0.01 and P＜0.01).But there was no significant difference between ECIP+I/R and NDLIP+I/R group.Conclusion:NDLIP+I/R can decrease cerebral IS caused by ischemia-reperfusion injury(IRI);protect cerebral cell against IRI through elevating T-SOD and Mn-SOD activity,decrease the concentration of MPO and MDA,increase the expression of Mn-SOD.In short,the protective effects of NDLIP+I/R against cerebral ischemia-reperfusion oxidative injury are similar to those of ECIP+I/R,the protective effects are associated with the increase in antioxidative ability of brain.