Tumor Necrosis Factor Alpha Aggravated Cerebral Ischemia And Reperfusion Injury Under Hyperglycemia In Rats

Objective Hyperglycemia contributes to the aggravated cerebral ischemiaand reperfusion injury，but the mechanism for increased brain damage is notclear.Observe apoptosis of astrocytes and expression of TNF-αand GFAP，discussthe effect of TNF-α and astrocyte in the brain ischemic rats withhyperglycemia.Explore the possible molecular mechanisms of astrocyte and TNF-α in the brain ischemia rats with hyperglycemia.Methods Using streptozotocin induced type I diabetes diabetes rat model.Through middle cerebral artery occlusion（MCAO）to establish diabetes cerebralischemia reperfusion injury of rat model.Applying histology、histochemistry、immunofluorescence and western blot to observe and contrast the histology changeof the neuron of cerebral cortex of frontal lobe and the expression of GFAP andTNF-α，cellular localization of TNF-α of diabetes hyperglycosemia cerebralischemia reperfusion group (hyperglycosemia group) and normoglycemia cerebralischemia reperfusion group (normoglycemia group) at2hours after cerebralischemia、24hours and48hours after reperfusion.Results The longa scores of the hyperglycemia group rats2h after MCAOreperfusion for24h and48h are significantly greater than the normoglycemiagroup（P＜0.05），and the neurologic injury symptoms are more serious.Thehyperglycemia group infarcts involving cortex, striatum, hippocampus and otherregions, infarct volume is significantly greater than the normoglycemia group（P＜0.05）.Gently edema occurred after reperfusion for24hours, edema was aggravated after reperfusion for48hours, and neuron was pyknosis innormoglycemia group. The pathology change was almost the same as thenormoglycemia group after reperfusion for24hours in diabetes group. Cerebraledema was aggravated and the number of pyknosis neuron were increased more afterreperfusion for48hours.The number of positive cells increased a few afterreperfusion for24hours and astrocyte was increased after reperfusion for48hours in normoglycemia group. The number of astrocyte was increased obviouslyafter reperfusion for24hours and48hours in hyperglycosemia group thannormoglycemia group(P＜0.05).The cell body became bigger obviously, cellprocess was lengthen and thicken inequable in hyperglycosemia group. Westernblot showed the expression of GFAP was obviously higher in diabetes group thanthat in normoglycemia group.Detect of TNF-α：By western blot we found thatthe expression of TNF-α of frontal cortex in normoglycemia is more thansham,obviously increase in hyperglycemic comparing with the sham andnormoglycemia. By immunofluorescence staining we found that that numbers of TNF-α-positive cells was largest in hyperglycemic,there is no immunoreactivedouble-labeled cells of TNF-α and GFAP in each group, minority immunoreactivedouble-labeled cells of TNF-α and Neun appear in sham, double-labeled cellsincreased in normoglycemic， double-labeled cells increased obviously inhyperglycemic comparing with the sham and normoglycemia..Conclusions Hyperglycemia can increase neuronal damage and enhance theexpression of GFAP in cerebral ischemia-reperfusion.Cerebral ischemia andreperfusion injury can activate the expression of TNF-α in braintissue.Hyperglycemia contributes to the aggravated cerebral ischemia andreperfusion injury may be associated with the expression of TNF-α-mediatedinflammatory response.