Expression Of Interleukin-6 MRNA In Neurons And In Astrocytes After Middle Cerebral Artery Occlusion In Hypertensive Rats

Objective: IL-6mRNA increased markedly in experimental cerebral ischemia and exerts a neuroprotection effect in recent studies, although the protein production and celllar sources of IL-6 remain unclear. In this study ,we examined the cellular localization of interleukin-6 mRNA after focal cerebral ischemia in hypertensive rats, and investigated the relationship between IL-6 levels and neuronal damage. Methods: First the renovascular hypertensive rats(n=70) were made by two-kidney-two-clip. The hypertensive rats(n=62) were randomly divided into nine groups(n=6):sham-operated control group,simple ischemia 2-hour(2h) group, 3h, 6h, 12h,24h, 3-day(3d),5d,7d reperfusion after 2h of middle cerebral artery occlusion(MCAO). MCAO was achieved by inserting nylon surgical thread through the internal carotid artery(ICA) into the anterior cerebral artery(ACA). Then reperfusion was allowed for different time as mentioned above before decapitation. In sham-operated control rats,the thread inserted was only 12 millimeter lone. Level of IL-6 mRNA and celllar sources of IL-6mRNA were examined by combined in situ hybridization and immunocytochemistry. The infarction volumewas observed by 2,3,5-triphenyltetrazolium(TTC) stain. Results: (1)The cerebral infarction in hypertensive rat was the most maximum at 12 hours of reperfusion. (2)The sham group did not show any clear IL-6mRNA. The expression of IL-6mRNA was predominantantly upregulated in the periinfarct region,peaking at 24 hours of reperfusion.(3)Double staining showed that the cells containing IL-6mRNA were principal neurons. Conclusion: (1)The expression of IL-6mRNA is in neurons and is predominantantly in the periinfarct region,peaking at 24 hours of reperfusion. (2) It is indirect cue that IL-6 is closely associated with brain tissue neuroptective mechanisms against cerebral ischemia.