Authors: G. Colton Gardner, J David Symons, Sohom Mookherjee, Michael Judge, Lynasi Gapelu, Sihem Boudina
Mentors: J. David Symons
Insitution: Utah Valley University
The prevalence of cardiovascular disease (CVD) is higher in residents of rural vs. urban communities, and in older vs. younger individuals. Precise mechanisms responsible for CVD are elusive, and the need for new and novel therapeutic interventions is urgent. Autophagy is a conserved process whereby damaged and dysregulated intracellular proteins are identified, tethered, and escorted to the lysosome for degradation and recycling. Emerging evidence indicates that autophagy is important in maintaining endothelial cell (EC) proteostasis and function. For example, my laboratory showed that: (i) autophagy repression specifically in ECs of adult mice produces arterial dysfunction; and (ii) indexes of autophagy are repressed in ECs of older vs. adult mice and humans that display concurrent EC dysfunction. Sequestosome 1 (p62) tethers proteins targeted for degradation and enables their entry into the autophagic pathway. The contribution from EC p62 to arterial function is unknown. To address this, p62 was depleted from ECs of adult male and female mice (KO) using genetic procedures, and results were compared to animals wherein EC p62 is intact (CON). It was hypothesized that depleted p62 would induce arterial dysfunction. The efficacy and specificity of EC p62 depletion was evaluated in both groups by measuring p62 mRNA (qPCR) and protein (immunoblotting) expression in ECs and vascular smooth muscle. At tissue collection: (i) contraction to non-receptor (potassium chloride) and α-1 receptor (phenylephrine) mediated agonists, and relaxation to endothelium-dependent (acetylcholine) and independent (sodium nitroprusside) stimuli, were measured using isometric (mesenteric arteries) and isobaric (cerebral arteries) approaches; and (ii) intravascular signaling pathways (immunoblotting) important to vasorelaxation were assessed in both groups. Our preliminary findings found no significant differences in arterial function between groups. However, our data suggests that another cohort of mice may lead to statistical significance, and this is actively being conducted. While our results indicate EC specific p62 depletion does not impact arterial responsiveness, hypoxia or ischemia might unmask differences. Additionally, even though EC specific p62 depletion was inducible, other proteins with similar roles (e.g., NBR1) might have upregulated in a compensatory manner. All of these are topics for future study and projects are being designed to investigate them. While this study did not provide enough evidence to confirm the original hypothesis, it did provide several new questions that need answers, and this will direct the future research ambitions of this ongoing project.