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

Abstract

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 (ΔΨm) is a key event in apoptosis, however, when ΔΨm is suffciently depolarized, ATP synthase can reverse directions and act as a proton pump to limit ΔΨm depolarization. We hypothesized that ATP synthase attenuates depolarization of ΔΨm 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 H2O at 36°C. Cell death was quantified with Hoechst 33342 (1 μM, labels all nuclei) and propidium iodide (2 μM, labels dead nuclei), and ΔΨm was evaluated with tetramethylrhodamine methyl ester (TMRM, 10 nM). Vessels were exposed to H2O2 (200 μM) in the presence/absence of ATP synthase inhibitor oligomycin (2 μM). H2O2 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, H2O2 evoked a more robust depolarization of ΔΨm in males vs. females and oligomycin enhanced ΔΨm depolarization to H2O2 leading to a similar response in both sexes. To directly depolarize ΔΨm, PCAs were treated with the protonophore FCCP (10 μM). Surprisingly, depolarization of ΔΨm 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 H2O2 -induced apoptosis than males by limiting depolarization of ΔΨm; and 2) oxidative stress triggers cell death through pathways in addition to ΔΨm 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.