Female Sex Protects Cerebral Arteries from Mitochondrial Membrane Potential Depolarization and Cell Death Induced by Reactive Oxygen Species

Stroke and traumatic brain injury augment the production of reactive oxygen species (ROS) leading to apoptosis in cerebral arteries, and females are more resilient to vascular damage than males. Depolarization of mitochondrial membrane potential (ΔΨ m ) is a key event in apoptosis, however, when ΔΨ m is suffciently depolarized, ATP synthase can reverse directions and act as a proton pump to limit ΔΨ m depolarization. We hypothesized that ATP synthase attenuates depolarization of ΔΨ m in cerebral arteries during acute oxidative stress thus limiting cell death. Posterior cerebral arteries (PCA; ~80 μm diameter) from male and female mice (age, 4-6 mo) were isolated, cannulated, and pressurized to 90 cm H 2 O at 36°C. Cell death was quantified with Hoechst 33342 (1 μM, labels all nuclei) and propidium iodide (2 μM, labels dead nuclei), and ΔΨ m was evaluated with tetramethylrhodamine methyl ester (TMRM, 10 nM). Vessels were exposed to H 2 O 2 (200 μM) in the presence/absence of ATP synthase inhibitor oligomycin (2 μM). H 2 O 2 exposure (50 min) led to significantly (p<0.05) greater smooth muscle cell death in males compared to females (30±7.4% vs. 7±3%; n=8); there was a similar trend for endothelial cell death. Oligomycin greatly augmented apoptosis in PCAs from both males and females to ~80% and eliminated differences between sexes. Consistently, H 2 O 2 evoked a more robust depolarization of ΔΨ m in males vs. females and oligomycin enhanced ΔΨ m depolarization to H 2 O 2 leading to a similar response in both sexes. To directly depolarize ΔΨ m , PCAs were treated with the protonophore FCCP (10 μM). Surprisingly, depolarization of ΔΨ m to FCCP was greater in males vs. females, and oligomycin augmented depolarization and eliminated differences between sexes. FCCP initiated minimal (<5%) cell death at 50-min or 3-h exposure; oligomycin did not alter cell death to FCCP. We conclude that: 1) cerebral vessels from female mice possess greater resilience to H 2 O 2 -induced apoptosis than males by limiting depolarization of ΔΨ m ; and 2) oxidative stress triggers cell death through pathways in addition to ΔΨ m depolarization. Support: NIH R01NS134690. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.