Hypoxia Inducible Factor-1α (HIF-1α) Mediates NLRP3 Inflammasome-Dependent-Pyroptotic and Apoptotic Cell Death Following Ischemic Stroke

Stroke is a major cause of death and long-term disability. Recent evidence suggests that hypoxia-inducible factor 1 alpha (HIF-1 alpha), a transcription factor that regulates oxygen levels, plays a key role in neurological outcomes after ischemic stroke. Accordingly, we investigated the mechanism of HIF-1 alpha on pyroptotic and apoptotic cells during ischemia/reperfusion (I/R). Adult Sprague-Dawley rats underwent 2 h of middle cerebral artery occlusion (MCAO). The rats were then exposed to 6 or 24 h of reperfusion, with or without YC-1 (HIF-1 alpha inhibitor, 5 mg/kg). Infarct volumes, along with mRNA and protein quantities of HIF-1 alpha, NLRP3, IL-18, Caspase-1, and co-localization of HIF-1 alpha, and NLRP3, were assessed. We measured apoptotic and pyroptotic cell death, gasdermin D (GSDMD) activation and lactate dehydrogenase (LDH) activity, and the infiltration of neutrophils and macrophages after ischemic stroke. HIF-1 alpha mRNA and NLRP3 inflammasome components were increased after 24 h of reperfusion. YC-1 significantly reduced the mRNA and protein expression of NLRP3, IL-18, and caspase-1; significantly decreased infarction and pyroptotic cell death after 24 h of reperfusion; attenuated the neuroinflammatory response by reducing infiltration of CD68- and MPO-positive cells after 24 h of reperfusion; and reduced apoptotic cell death following ischemic stroke. We found that HIF-1 alpha likely regulates inflammatory responses through the NLRP3 inflammasome complex, thus influencing both apoptotic and pyroptotic cell death after stroke. These findings suggest that future investigations are needed regarding HIF-1 alpha and its role as a potential molecular target in the treatment of acute ischemic stroke. (C) 2020 IBRO. Published by Elsevier Ltd. All rights reserved.