Electroacupuncture attenuated cerebral ischemic injury and neuroinflammation through α7nAChR-mediated inhibition of NLRP3 inflammasome in stroke rats

Background: Our previous research confirmed that electroacupuncture (EA) stimulus elicits neuroprotective effects against cerebral ischemic injury through 7 nicotinic acetylcholine receptor (alpha 7nAChR)-mediated inhibition of high-mobility group box1 release mechanism. This study investigated whether the signal transducer of alpha 7nAChR and inhibition of NLRP3 inflammasome are involved in the neuroprotective effects of EA stimulus. Methods: In adult male Sprague-Dawley rats, the focal cerebral ischemic injury was induced by middle cerebral artery occlusion (MCAO) models for 1.5 h. The expression of NLRP3 inflammasome in the penumbral tissue following reperfusion was assessed by western blotting and immunoflourescent staining. The infarct size, neurological deficit score, TUNEL staining and the expression of proinflammatory factors or anti-inflammatory cytokines were evaluated at 72h after reperfusion in the presence or absence of either alpha 7nAChR antagonist (alpha-BGT) or agonist (PHA-543,613). Results: The contents of inflammasome proteins were gradually increased after cerebral ischemia/reperfusion (I/R). EA stimulus attenuated NLRP3 inflammasome mediated inflammatory reaction and regulated the balance between proinflammatory factors and anti-inflammatory cytokines. The agonist of alpha 7nAChR induced similar neuroprotective effects as EA stimulus. In contrast, alpha 7nAChR antagonist reversed not only the neuroprotective effects, but also the inhibitory effects of NLRP3 inflammasome and the regulatory effects on the balance between proinflammatory factors and anti-inflammatory cytokines. Conclusions; These results provided compelling evidence that alpha 7nAChR played a pivotal role in regulating the activation and expression of NLRP3 inflammasome in neurons after cerebral I/R. These findings highlighted a novel anti-inflammatory mechanism of EA stimulus by alpha 7nAChR modulating the inhibition of NLRP3 inflammasome, suggesting that 7nAChR-dependent cholinergic anti-inflammatory system and NLRP3 inflammasome in neurons might act as potential therapeutic targets in EA induced neuroprotection against cerebral ischemic injury.