ABSTRACT
Ischemic stroke leads to a loss of blood flow to the brain and is a prominent cause of death and disability in
affected individuals. Whereas neuroprotective agents have shown limited clinical benefits for treatment of stroke,
vascular interventions are promising targets for therapy. Nevertheless, restoration of bloodflow following these
treatments is often incomplete. Surprisingly, the role of vascular survival and function within the injured tissue
following ischemia/reperfusion (I/R) is largely unexplored. Mitochondrial membrane potential (ΔΨm)
depolarization and increases in mitochondrial Ca2+ are key signaling events in cell death, but the effects of
targeting vascular mitochondrial Ca2+ signaling and ΔΨm depolarization on neuronal outcomes is unknown. Upon
reperfusion following ischemia, the production of reactive oxygen species (ROS) damages surrounding neuronal
and vascular tissues. In resistance arteries of mice, posterior cerebral artery smooth muscle cells (SMCs) are
more susceptible than endothelial cells (ECs) to cell death induced by oxidative stress imposed by H2O2.
Furthermore, vascular cells from females are more resilient to mitochondrial (intrinsic) apoptosis to H2O2
compared to males. However, the mechanisms mediating this protection in females is unknown. To address this
gap in knowledge, the Specific Aims of this project will test the central hypothesis that sex-based differences in
mitochondrial Ca2+ signaling and ΔΨm regulation underly greater vascular cell resilience to acute oxidative stress
in PCAs of female vs. male mice. To investigate these relationships, sex differences in mitochondrial Ca2+
signaling and ΔΨm depolarization during exposure to H2O2 (200 μM for 50 min) will be evaluated in isolated,
pressurized cerebral arteries and native endothelial tubes (Aim 1). Complimentary experiments will test the
effects of Ca2+ channel signaling induced by acute oxidative stress on mitochondrial Ca2+ and ΔΨm
depolarization. The proposal will additionally examine how differences in electron transport function and reverse
activation of ATP synthase between males and females contribute to greater cell death in males (Aim 2). Using
a middle cerebral artery occlusion model, experiments will evaluate the role of mitochondrial Ca2+ signaling and
ΔΨm depolarization to arterial damage in males and females following I/R in vivo (Aim 3). These findings will be
correlated to neuronal survival and behavioral deficits, to gain further understanding to how vascular survival can
improve neuronal outcomes. Gaining new understanding of how to target intrinsic mechanisms of protection
inherent to females to promote vascular resilience in the cerebral circulation following I/R injury to the brain will
yield new insight into preserving vascular function and associated neuronal outcomes. Such findings provide
foundational knowledge regarding sex differences in vascular mitochondrial function and will facilitate the
development of novel avenues for therapy targeting the vasculature for patients after stroke and other conditions
of oxidative stress in the brain such as traumatic brain injury.
