Effect Of Mild Hypothermia On PERK Pathways Following Transient Cerebral Ischemia Reperfusion In Rats

Objective: To investigate the effect of mild hypothermia on protein kinase R-like ER kinase(PERK)and Eukaryotic translation initiation factor 2α(e If2α)and Activating transcription factor 4(ATF4)in hippocampus following transient cerebral ischemia/reperfusion(I/R)in young male rats and to evaluate its effects on the neurological behavior scores(NBS)the and apoptosis in hippocampal neurons.Methods: One hundred and forty for young male C56BL6 rats,weighing 20-30 g,were randomly divided into 3groups(n=48 each):sham operation group(group S),I/R group and mild hypothermia group(group H).Cerebral I/R was induced by bilateral common carotid artery occlusion method.and bilateral carotid arteries were occluded for15 min.Sham operation group were exposed bilateral common carotid arteries but not occluded for comparison.The surface cooling was started immediately after reperfusion and maintained for 3 h.During surface cooling,the body temperature was maintained at 32-34℃(rectal).At 6,12,24 and 72 h of reperfusion,neurological behavior scores were evaluated for all the rats.the expression of p-PERK,p-e If2α and ATF4 was determined with Western blot.Survival neurons in CA1 area was counted through HE staining.TUNEL staining was used to count the apoptotic neuronsResults: Compared with the S group,the NES in I / R group and H group were significant increased at each time point of reperfusion,the difference was statistically significant(P<0.05).In S group,the morphology of hippocampal CA1 neurons was roughly normal,the structure of the brain was clear and complete,the nucleus was centered,round or oval,and the cytoplasm was abundant,and the color was light purple.Cell shape shrinkage,nuclear pyknosis and nuclear chromatin stained increased.Large tracts of neurons are lost,sparse,and disorganized.Cell nuclear condensation or dissolution fragmentation,the color is dark purple.There was no significant difference in the apoptotic cells in the S group,and there was no significant difference between the time points(P>0.05).anchorage-dependent cell was shrinking,rounded and shed.The staining cell exhibited chromatin condensation and marginalization,nuclear fragmentation,chromatin is divided into blocks,and apoptotic bodies in the CA1 region of the hippocampus at each time point in group IR and group H compared with group S.the number of TUNEL positive neurons were significantly increased(P < 0.05),and the expression of three proteins of the mice in S groups almost no or a small amount and no significant difference were detected in the proteins expression of reperfusion at each time point among S groups(P > 0.05).The level of protein p-perk,p-e If2 alpha and ATF4 were significant increased at each point in I/R and H group(P<0.05).Compared with the I / R group,the ENS was significantly lower at each point of reperfusion in H group,and the difference was statistically significant(P<0.05).In the first 12 h,24h and 72 h,the survival of the neurons in the hippocampus was increased,and there is a loss in the cells disappeared,sparse and disordered,the nuclear condensation or dissolution were decreased in H group,the difference was statistically significant(P<0.05).The number of apoptotic neurons was significantly lower at 12,24 and 72 h of reperfusion and the expression of ATF4,p-e If2 and p-PERK were down regulated at different time points in group H than in group I/R.the difference was statistically significant(P<0.05)Conclusion: 1.Mild hypothermia could reduce neurological deficits and brain damage after cerebral ischemia/reperfusion in rats,2.Mild hypothermia could inhibit apoptosis signal pathway by down-regulate PERK,e If2α and ATF4 expression in hippocampus following transient cerebral I/R in young male C56BL6 rats,thus reducing endoplasmic reticulum stress reaction,neuronal apoptosis and cerebral I/R injury.