Expression And Significance Of DNA-PKcs/Gadd45 β And GAP-43/Nogo-a In The Hippocampus Of Cerebral Ischemia Rats With Different Exercise Intensity

Objective To compare the expression of Nogo-A/GAP-43 and DNA-PKcs/GADD45 in the hippocampus of cerebral ischemia rats with different exercise intensity and explor its significance..Methods Adult male SD rats(n=80) were divided into five groups randomly:sham operation group(n=20),group of cerebral ischemia(n=20),middle exercise intensity group(n=20),high exercise intensity group(n=20). Four weeks before surgery,the exercise preconditioning rats were trained on treadmill.The speed of middle exercise intensity group was 16m/min*30(30%VO2max).The speed of high exercise intensity group was10m/min at first,then accelerated to 19.3m/min in 3minutes(70%VO2max) and hold the speed until the rats get exhausted.Global cerebral ischemia model was formed by improved four-vessel occlusion as described according to the description of Pulsinelli’s method and the rats was sacrificed at 6h 1d,3d and 7d respectively after injury.Morphological changes of hippocampus neural cells were observed by H-E staining.The activity of superoxide dismutase and malondialdehyde level in hippocampus of rat brain was measured by hydroxylamine method and TBA method respectively.DNA-PKcs,GADD45β,Nogo-A and GAP-43 protein expressions in the hippocampal CA1 region were detected respectively by Immunohistochemistry and RT-PCR technology.Result 1 Morphological observations of HE staining:Compared with sham group,neuronal cells in group of ischemia have hyperchromatic nuclei,increased cytoplasm and arranged irregularly( P<0.01).Compared with group of ischemia,neuronal cells in group middle exercise intensity have lower necrosis rate,the situation of pyknotic nuclei were released( P<0.01).But,in group high exercise intensity,the volume of neuron decreased,cytoplasm’s stain is dark,karyopyknosis are observed(P<0.01). With the time prolonging,neuron necrosis rate of each group of ischemia was increased and become the worst in 7 days(P<0.01).2 Determination of superoxide dismutase(SOD) results:Compare with sham group,the SOD activity in groups of ischemia were significantly decreased t 6h,1d,3d,7d(P<0.01).The activity of SOD in groups of ischemia was lower than middle exercise intensity group, higher than the high exercise intensity group( P<0.01).3 Malondialdehyde(MDA) determination results:Compare with sham group,the MDA levels in group of cerebral ischemia weresignificantly elevated t 6h,1d,3d,7d(P<0.01). The level of MDA was higher middle exercise intensity group, lower than the high exercise intensity group( P<0.01).4DNA-PKcs and GADD45βin immunohistochemical and RT-PCR analysis of results: In sham group,the expression of DNA-PKcs and GADD45 β expressed little in cell incytoplasm.In groups of ischemia, antigen of DNA-PKcs and GADD45 were brown and mainly distributed in nucleus.Compared with sham group, the expression of DNA-PKcs and GADD45 β in group of ischemia were significantly increased(P<0.01).Compared with group of ischemia,DNA-PKcs and GADD45 β in group middle exercise intensity showed high level of expression and increased obviously at 6h,reached a peak at 1d,decreased at 3d,reached a trough at 7d,but still higher than group of ischemia( P<0.01). DNA-PKcs and GADD45 β in group high exercise intensity were significantly decreased and showed a same variation tendency.5 Nogo-A and GAP-43 in immunohistochemical and RT-PCR analysis of results: In sham group,Nogo-A and GAP-43 expressed little in cell incytoplasm.In groups of ischemia,antigen of Nogo-A and GAP-43 were brown and mainly distributed in nucleus.Compared with sham group, the expression of Nogo-A and GAP-43 in group of ischemia were significantly increased(P<0.01).Compared with group of ischemia, Nogo-A in group middle exercise intensity showed high level of expression and increased obviously at 6h,reached a peak at 1d,decreased at 3d,reached a trough at7 d,but still higher than group of ischemia(P<0.01). With the time prolonging,GAP-43 increase progressively and reached a peak at 7d.Except for 1h,the expression of GAP-43 at other time points were all higher than group of ischemia(P<0.01). Nogo-A and GAP-43 in group high exercise intensity were significantly decreased and showed a same variation tendency(P<0.01).Conclusions Different exercise intensity on cerebral ischemia in rats cause different effects on neuronal cell loss.The mechanism were considered to be related to the expression of DNA-PKcs/GADD45 β/GAP-43/Nogo-A in hippocampus.