Integrative Effects of Autophagy and Telomerase on Arteriolar Flow‐Mediated Dilation in Health and Coronary Artery Disease

Abstract

Flow‐mediated dilation, (FMD) is manifest by arteriolar vasodilation in response to shear stress in an endothelium‐dependent manner. Nitric oxide (NO) is the primary mechanism for FMD in health, while hydrogen peroxide (H2O2) is the dominant mechanisms of dilation in subjects with coronary artery disease (CAD). TERT, the catalytic subunit of telomerase, is responsible for maintenance of telomere length, and telomerase activity (TA) and is necessary to preserve physiological mitochondrial function under conditions of acute stress. Autophagy is a basic cellular recycling process, responding to unfolded proteins and damaged organelles. Both autophagy and TERT levels are downregulated in subjects with CAD. Inhibition of TERT in non‐CAD vessels reduces autophagy (Fig 1A), and switches the mechanism of dilation from NO to H2O2. Conversely, activation of TERT switches the mechanism of dilation from H2O2 to NO in CAD (Fig 1B.). We sought to examine whether autophagy and TA are part of the same pathway regulating microvascular FMD in healthy (non‐CAD) and CAD vessels. Human arterioles from discarded adipose tissue were isolated and prepared for videomicroscopy. Non‐CAD vessels were co‐incubated overnight with TA inhibitor (BIBR 1532; 10 μM) and an activator of autophagy (Trichostatin A, TSA; 100 nM). CAD vessels were co‐incubated with an inhibitor of autophagy (Bafilomycin A1, BAFA1; 10nM) and the transcriptional activator of TERT (AGS 499; 20 nM). Internal diameters were measured after graded increases in intraluminal pressure gradients (flow) in the presence/absence of a NOS inhibitor (L‐NAME; 100μM) or H2O2 scavenger (Peg‐Catalase, Peg‐Cat; 500 units/mL). Data are expressed as % maximal dilation. In vehicle treated vessels, the magnitude of FMD was similar between non‐CAD and CAD. Within CAD vessels, inhibition of autophagy prevented the activator of TERT (AGS) from switching the mediator of FMD from H2O2 to NO (AGS 499 + BAFA1: 84.4±9.4 vs. AGS499 + BAFA1 + L‐NAME: 92.6±6.1 vs. AGS499 + BAFA1 + Peg‐Cat: 19.1±14.0; Fig 2A, n = 3–5; P<0.05). Conversely, in non‐CAD vessels, activation of autophagy prevented the switch from NO to H2O2 typically seen during inhibition of TERT (BIBR + TSA: 86.4±9.2 vs. BIBR + TSA + L‐NAME: 36.3±12 vs. BIBR + TSA + Peg‐Cat: 73.8.9±9; Fig 2B, n = 3–5; P < 0.05,). Our data demonstrate that autophagy is distal to TERT in regulating the mechanism of FMD in human adipose arterioles and may serve as a final common pathway for determining the mechanism of FMD in human arterioles.Support or Funding InformationFunded by T32GM089586‐09 (WEH), R01‐HL133029‐02 (AMB), and R01‐HL135901‐02 (DDG)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.