Effects Of Astrocytes Gap Junction Communication Regulation On Neurovascular Unit Damage And Repair In Rats Brain After Cerebral Ischemia

Objective:In the process of brain ischemia, the function of reactive astrocytes determine the outcome of neuronal damage and repaies. It has been shown that the gap junction protein expressed on end feet of astrocytes was increased in ischemic brain. However, the potential role of gap junction communication in the ischemic pathological process has not been demonstrated. In this study, we aimed to clarify the interaction of gap junction communication and neurovascular unit (NVU) dynamic changes in ischemic brain. Moreover, the effects of gap junctional inhibitor on the proliferation and activation of astrocytes, the vessel function and neuronal damage were also investigated.Methods:Rats were subjected to middle cerebral artery occlusion (MCAO) to induce focal ischemia in the brain. The NVU dynamic changes after MCAO were observed by immunofluorescence staining. The3D-reconstruction of the NVU was established by confocal microscope scanning the Z axis to show the constructure relationship of each cellular componenet of NVN. The protein expression of GFAP and Cx43, the proliferation and activation of astrocytes, as well as the changes of vessel density in the brain of rats after MCAO were detected by immunofluorescence staining and Western Blots.Laser Doppler flowmetry was applied to study the blood flow velocity and reperfusion of ischemic penumbral in MCAO rats.Results;1) In the boundary zone of rat brain after ischemia, astrocytes became reactive when occlusion occured. First, the end feet enveloping the vessels were broken and cell body became hypertrophy. Then the proliferated and activated astrocytes enveloped the vessels again which finally induced these vessels collapse. The astrocytes of ipsilateral hippocampus began to proliferate and activate after MCAO and peaked at day7after MCAO.2) Under normal conditions, Cx43protein was localized in the end feet of astrocytes enveloping vessles. After MCAO, Cx43expression in the ischemic region increased with time3) The gap junction inhibitor CBX could significantly decrease the proliferation and activation of the astrocytes after MACO.4) After MCAO, the administration of CBX could decrease the blood perfusion,downregulate the AT1R expression. Meanwhile, CBX treatment increased the eNOS protein expression and NO production, thus dilating the relative vessels in the ischemic penumbral region.Conclusion:The gap junction protein are widely expressed in CNS. The inhibition of gap junction could inhibite the proliferation and activation of astrocytes and dilate the vessels of ischemic penumbral after MCAO, which may attenuate the neuronal damage of ischemic brain. Therefore, gap junction may be the potential thrapeutical target of stroke.