Telomerase Reverse Transcriptase Mediates Restoration of Functional Vasodilation in Isolated Coronary Microvessels of Aged Female Rats
Authors: Tracy Evan Paul , Rowe Gabrielle , Toro Laura Norwood , Beyer Andreas , LeBlanc Amanda Jo 
Published: April 2020

IntroductionReactive oxygen species (ROS) increase during aging, resulting in decreased NO signaling and the production of ROS damages cellular components including mitochondrial DNA. Telomerase Reverse Transcriptase (TERT) has ROS‐suppressing effects in the mitochondria and is decreased in coronary artery disease (CAD). Upregulation of Telomerase restores NO mediated vasodilation in CAD. We hypothesize that treatment of isolated coronary microvessels of aged female rats with peptide nucXTERT (shunts TERT to mitochondria) will increase functional vasodilation while treatment of isolated coronary microvessels from young female rats with mitoXTERT (shunts TERT away from mitochondria) will blunt functional vasodilation.MethodsIsolated coronary microvessels from young (4 months, n = 2) or old (24 months, n = 5) Fischer 344 female rats were assessed via pressure myography. Vessels were incubated for 12 hours with nucXTERT or mitoXTERT, AGS 499 (TERT activator), or a scramble peptide negative control. Vessel relaxation to dobutamine (10−5 – 10−10 M), isoproterenol (10−4 – 10−8 M), acetylcholine (10−4 – 10−9 M), and H2O2 (10−3 – 10−8 M) was assessed post‐incubation.ResultsnucXTERT and AGS 499 treated vessel percent relaxation in old rats for isoproterenol, acetylcholine, and dobutamine were increased compared to scramble treated vessels (Figure
). Compared to scramble, nucXTERT increase of percent relaxation was significant for isoproterenol at 10−4 – 10−6 M (p = .007, .003, and .013, respectively), dobutamine at 10−5 – 10−7 M (p = < .001, .016, and .016, respectively) and near significant for acetylcholine at 10−4 and 10−6 M (p = .097 and .062, respectively). Following nucxTERT and AGS 499 treatment, the percent relaxation to H2O2 (7.3% and 3.8% at max dilation, respectively) was reduced compared to scramble‐treated vessels (34.5% at max dilation)(Figure
). As expected, mitoXTERT incubation of young rat microvessels abrogated vasodilation of vessels to isoproterenol, acetylcholine, and dobutamine compared to scramble and AGS 499 responses. Hydrogen peroxide percent relaxation was increased in mitoXTERT (83.9% at max dose) compared to AGS 499 and scramble (3.79% and 34.38%, respectively).ConclusionsThe data support a vasoprotective and restorative role of TERT in coronary microvessels from aged female rats as adrenergic and acetylcholine‐mediated vasodilation were increased in nucXTERT and AGS 499 relative to the scrambled peptide. With nucXTERT, TERT was being blocked from nuclear translocation, increasing extranuclear TERT available for mitochondrial protection from ROS. Shunting TERT away from the mitochondria via mitoXTERT blunted adrenergic and acetylcholine‐mediated vasodilation as less TERT was available for mitochondrial ROS protection. Considering oxidative stress is a driver of CAD and the concomitant importance of altering vessel patency to allow for adequate blood flow to match metabolic demand, the modulation of TERT may be a holistic and plausible future clinical direction.Support or Funding InformationFunding for this project was provided by NIH RO1 AG053585 and the Gheen’s Foundation to Amanda Jo LeBlanc.Old rat isolated coronary arteriole vasoreactivity with nucXTERT peptide, AGS 499, or scramble peptide incubation. Shown as percent relaxation to isoproterenol (a) dobutamine (b) acetylcholine (c) and hydrogen peroxide (d). p ≤ 0.05 for nucXTERT (*) vs scramble. Data are presented as means ± SE, analyzed with two‐way repeated measures ANOVA followed by post‐hoc Bonferroni test.Figure 1