Microglial Annexin A3 Downregulation Alleviates Ischemic Injury by Inhibiting NF-κB/NLRP3-mediated Inflammation.

Abstract

Microglial inflammation is a hallmark of ischemic stroke. Annexin A3 (ANXA3) is expressed in microglia and plays a detrimental role in stroke. However, the role of ANXA3 in microglial inflammation after ischemic stroke is unclear. In this study, an ischemic stroke model was established in mice via middle cerebral artery occlusion (MCAO). The adeno-associated virus shANXA3 (AAV-shANXA3) was injected into ipsilateral cortex ischemic lesion, and the infarction volume, neurological score, and neuronal injury were examined. Moreover, primary microglia were transfected with a lentivirus (LV-shANXA3) and subjected to oxygen-glucose deprivation (OGD). Neuron viability and lactose dehydrogenase (LDH) levels of neurons cocultured with microglia were analyzed. Additionally, microglial activation and ANXA3, p-NF-κB, NLRP3 and downstream proteins of NLRP3 inflammasome (cleaved caspase-1, N-GSDMD and IL-1β) expression levels were measured. We found that microglial ANXA3 expression was increased after ischemic injury and that ANXA3 knockdown reduced the infarction volume, mitigated neurological deficits, and alleviated neuronal injuries. Additionally, ANXA3 knockdown ameliorated microglial activation and reduced the levels of p-NF-κB and inhibited NLRP3 inflammasome signaling. Furthermore, ANXA3 upregulation resulted in decreased IκBα levels, whereas ANXA3 downregulation resulted in increased IκBα levels. Notably, IκBα knockdown blocked the neuroprotective effects of AAV-shANXA3 against ischemic injury. In conclusion, microglial ANXA3 downregulation alleviates ischemic stroke by inhibiting NF-κB/NLRP3-mediated microglial inflammation, which indicates that ANXA3 may be a potential therapeutic target for ischemic stroke.