PROJECT SUMMARY/ABSTRACT The purpose of this F32 application is to support Dr. Kevin Murray, a promising first-year postdoctoral fellow in the laboratory of Dr. Douglas Seals, to conduct original research and receive scientific training that will prepare him to become an independent, extramurally funded investigator in the field of translational vascular physiology aimed at identifying novel interventions for improving vascular function with aging and the associated mechanisms of action. Dr. Murray will learn a variety of new technical, conceptual, and professional skills, including focused training in translational cellular and molecular vascular physiology research, in addition to training in conducting a clinical trial. His proposed research project will leverage his primary sponsor’s ongoing NIH-funded R01-funded clinical trial that seeks to establish the efficacy of the mitochondria-targeted antioxidant MitoQ for improving vascular endothelial function in older adults to determine (Aim 1) whether changes in the circulating milieu following 3 months of chronic treatment with MitoQ improves endothelial cell function by treating human aortic endothelial cells (HAECs) with plasma collected from subjects after MitoQ or placebo treatment. He will also determine (Aim 2) if reductions in oxidized low-density lipoprotein (oxLDL) following MitoQ treatment mediate improvements in endothelial cell function by ameliorating oxLDL-stimulated mitochondrial fission. Lastly, he will also explore (Aim 3) the role of changes in extracellular vesicles (EVs) with MitoQ treatment in mediating improvements in endothelial cell function and whether these potential changes are associated with alterations to miRNA content of EVs. Age-related endothelial dysfunction is largely mediated by reduced bioavailability of the vasoprotective molecule, nitric oxide (NO), as a result of excessive production of reactive oxygen species (ROS). Dysfunctional mitochondria increase with age and are a major source of excess ROS (mtROS) in the vasculature. MitoQ is a mitochondrial-targeted antioxidant and our laboratory previously showed that 6-weeks of MitoQ supplementation in older adults improved NO-mediated endothelium-dependent dilation. Preliminary data collected by Dr. Murray for this application suggest that changes to the circulating milieu following MitoQ treatment increase NO bioavailability and decrease mtROS bioactivity in HAECs ex vivo, extending the mechanisms of action by which MitoQ supplementation improves endothelial function. Guided by these strong preliminary data, Dr. Murray will aim to establish changes to the circulating milieu as a mechanism of action by which MitoQ treatment improves endothelial function by leveraging plasma samples collected from subjects during his primary sponsor’s ongoing NIH-funded R01 clinical trial. The primary sponsor is an internationally recognized, NIH-funded scientist with a strong history of successful mentoring in translational bio...