Microglia Autophagy Mediated by TMEM166 Promotes Ischemic Stroke Secondary to Carotid Artery Stenosis

Ischemic stroke can be a serious complication of selective carotid endarterectomy (CEA) in patients with carotid artery stenosis (CAS). The underlying risk factors and mechanisms of these postoperative strokes are not completely understood. Our previous study showed that TMEM166-induced neuronal autophagy is involved in the development of secondary brain injury following cerebral ischemia-reperfusion injury in rats. This current study aimed to investigate the role of TMEM166 in ischemic stroke following CEA. In the clinical part of this study, the quantitative analysis demonstrated circulating TMEM166, interleukin 6 (IL-6), and C-reactive protein (CRP) levels were significantly elevated in patients who suffered an ischemic stroke after CEA compared to those who did not. Furthermore, non-survivors exhibited higher levels of these proteins than survivors. In the preclinical part of this study, a middle cerebral artery occlusion (MCAO) model was implemented following CAS simulation in TMEM166^-/- mice. We found TMEM166 expression was positively correlated with the degree of ischemic brain injury. Ad5-TMEM166 transfection aggravated ischemic brain injury by inducing microglial autophagy activation and release of inflammatory cytokines. Accordingly, TMEM166 deficiency reduced brain inflammation and inhibited excessive microglial autophagy through the mammalian target of rapamycin (mTOR) pathway. These findings suggest that TMEM166 may play a key role in the development of ischemic injury after CEA and may serve as a biomarker for risk assessment of postoperative ischemic stroke.