Nicotinic Acetylcholine Receptor Alpha7 Subunit Mediates Vagus Nerve Stimulation-Induced Neuroprotection in Acute Permanent Cerebral Ischemia by a7nAchR/JAK2 Pathway
Xin-xin Lu, Zhong-qiu Hong, Zhi Tan, Ming-hong Sui, Zhi-qiang Zhuang, Hui-hua Liu, Xiu-yuan Zheng, Tie-bin Yan, Deng-feng Geng, Dong-mei Jin
Department of Rehabilitation Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China (mainland)
Med Sci Monit 2017; 23:6072-6081
The role of nicotinic acetylcholine receptor alpha7 subunit (a7nAchR) in the treatment of acute cerebral ischemia by VNS has not been thoroughly clarified to date. Therefore, this study aimed to investigate the specific role of a7nAchR and explore whether this process is involved in the mechanisms of VNS-induced neuroprotection in rats undergoing permanent middle cerebral artery occlusion (PMCAO) surgery.
MATERIAL AND METHODS: Rats received a7nAChR antagonist (A) or antagonist placebo injection for control (AC), followed by PMCAO and VNS treatment, whereas the a7nAChR agonist (P) was utilized singly without VNS treatment but only with PMCAO pretreatment. The rats were randomly divided into 6 groups: sham PMCAO, PMCAO, PMCAO+VNS, PMCAO+VNS+A, PMCAO+VNS+AC, and PMCAO+P. Neurological function and cerebral infarct volume were measured to evaluate the level of brain injury at 24 h after PMCAO or PMCAO-sham. Moreover, the related proteins levels of a7nAChR, p-JAK2, and p-STAT3 in the ischemic penumbra were assessed by Western blot analysis.
RESULTS: Rats pretreated with VNS had significantly improved neurological function and reduced cerebral infarct volume after PMCAO injury (p<0.05). In addition, VNS enhanced the levels of a7nAchR, p-JAK2, and p-STAT3 in the ischemic penumbra (p<0.05). However, inhibition of a7nAchR not only attenuated the beneficial neuroprotective effects induced by VNS, but also decreased levels of p-JAK2 and p-STAT3. Strikingly, pharmacological activation of a7nAchR can partially substitute for VNS-induced beneficial neurological protection.
CONCLUSIONS: These results suggest that a7nAchR is a pivotal mediator of VNS-induced neuroprotective effects on PMCAO injury, which may be related to suppressed inflammation via activation of the a7nAchR/JAK2 anti-inflammatory pathway.
Keywords: alpha7 Nicotinic Acetylcholine Receptor, Brain Ischemia, Janus Kinase 2, Neuroprotective Agents, vagus nerve stimulation