Date on Master's Thesis/Doctoral Dissertation

8-2022

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Physiology and Biophysics

Degree Program

Physiology and Biophysics, PhD

Committee Chair

LeBlanc, Amanda

Committee Co-Chair (if applicable)

Williams, Stuart K.

Committee Member

Williams, Stuart K.

Committee Member

DeFilippis, Andrew

Committee Member

Tyagi, Neetu

Committee Member

Cole, Marcie

Author's Keywords

Coronary microvascular disease; aging; stromal vascular fraction; mitochondria; oxidative stress; ROS

Abstract

Background: Coronary Microvascular Disease (CMD) presents in aging post-menopausal women with chronic angina due to microvascular hyperconstriction. The objective was to identify mechanisms of adipose stromal vascular fraction’s (SVF) restorative effects on vasodilation. We hypothesize aging-induced CMD is caused by a) abrogated flow-mediated dilation (FMD) due to loss of nitric oxide signaling and b) ROS-dependent βADR desensitization & internalization, reversible by ameliorating mitochondrial dysfunction and oxidative stress with SVF. Methods: Coronary microvessels were isolated from female rats either young, old, or old with SVF tail-vein injection (OSVF). Pressure myography, RNA-sequencing, immunofluorescence, Western blotting, and morphological analysis were performed to compare between groups the density and function of αADR and βADR and their downstream effectors, redox state, antioxidant and prooxidant protein expression and function, mitochondrial dynamics, respiratory function, and mitophagy. Contributors to FMD were determined by measuring FMD +/- scavengers/inhibitors of FMD mediators. The contribution of ROS and nitrosylation to β1ADR desensitization and internalization was determined by exogenous ROS or sodium nitroprusside (SNP) exposure prior to concentration response to isoproterenol +/- inhibitors of desensitization and internalization. Results: Aging is associated with faulty FMD and β1ADR-mediated dilation alongside mitochondrial dysfunction. SVF attenuates baseline ROS and prooxidant expression in aging with enhancement of mitochondrial membrane potential, oxygen consumption, ATP production, antioxidant expression and glutathione, but not nitric oxide. Mitochondrial dynamics shifted away from hyperfission in aging with recovery of fusion with SVF therapy. These effects culminated in restored FMD and β1ADR-mediated dilation. The acute signaling mediator for FMD was nitric oxide during youth, hydrogen peroxide in aging, shifting to peroxynitrite with SVF therapy. Vasorelaxation to β1ADR-agonism was mechanistically linked to ROS and nitric oxide in an age-dependent manner via their effects on desensitization and internalization. Conclusions: SVF reverses chronic aging-associated oxidative stress and blunted FMD to young control levels while utilizing acute peroxynitrite FMD signaling. We introduce a novel axis by which ROS impacts β1ADR receptor trafficking, the ROS/RNS-β1ADR Desensitization and Internalization Axis. ROS accumulation in aging leads to β1ADR desensitization and trafficking into endosomes, whereas SVF reduces oxidative burden in this axis to restore functional β1ADR at the plasma membrane.

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