Abstract WMP1: Neuroprotection by Normobaric Oxygen (NBO): Modulating Inflammasome (NLRP3) Activation and Stress Granule Formation in Ischemic Stroke

Abstract

Background: NBO has emerged as a promising neuroprotective strategy for ischemic stroke. Key to comprehending these effects is understanding its mechanisms. This study examines the pivotal roles of HIF-1α as an oxygen sensor, the protective emergence of stress granules (SGs) in response to various stimuli, and the inflammatory cell death process known as pyroptosis, triggered by inflammasomes. We elucidated the interplay between HIF-1α, SGs, inflammasomes in ischemia/reperfusion injury and in NBO-induced neuroprotection. Methods: A total of 132 adult male SD rats were subjected to 2 h middle cerebral artery occlusion (MCAO), followed by 2, 6, 24 or 48 h of reperfusion. At the onset of reperfusion, oxygen was inhaled for 2 h at concentration of 95% and flow rate of 2 L/min. YC-1 (HIF-1α inhibitor) was administered 2 h before MCAO. Brain damage was evaluated by infarct volumes (TTC), LDH and ROS levels (ELISA), apoptotic cell death (flow cytometry and TUNEL). Pyroptosis was evaluated by flow cytometry. mRNA and protein levels of HIF-1α and inflammasome related factors, including IL-18, IL-1β, ASC, NLRP3, TXNIP, N-GSDMD, cleaved-Caspase-1, as well as SGs proteins including DDX3X, G3BP1, TIA-1 were examined. Co-IP was used to detect the interaction between DDX3X and G3BP1, as well as DDX3X and NLRP3. Results: Infarct volumes, LDH and ROS levels, apoptotic and pyroptotic cell death, as well as HIF-1α expression were all increased after ischemia/reperfusion. All these increases were reversed by either NBO or YC-1. NBO or YC-1 further reversed the increase in expression of NLRP3 inflammasome related proteins and suppressed the interaction between DDX3X and NLRP3, thereby suppressing inflammasome activation. NBO or YC-1 stimulated the expressions of SGs proteins and facilitated the interaction between DDX3X and G3BP1, thereby promoting the formation of SGs, in association with cell protection. Conclusion: Our findings highlight the neuroprotective effects of NBO in ischemic stroke. This protection is attributed to its dual capacity to inhibit NLRP3 inflammasome activation while simultaneously promoting formation of SGs. Central to these processes, HIF-1α, as an instrumental modulator, sheds light on potential therapeutic targets for stroke intervention.