Telomerase Reverse Transcriptase Prevents Doxorubicin-induced Microvascular Endothelial Dysfunction
Authors: Brandt Lukas , Hader Shelby , Beyer Andreas 
Published: May 2024

Introduction & Objective: Doxorubicin (Dox) is a frequently used chemotherapeutic known to induce cardiovascular (CV) complications by impairing microvascular- and cardiac function. We previously submitted an abstract showing that Dox-induced microvascular dysfunction preceded Dox-induced cardiac dysfunction and thus microvascular dysfunction might contribute to the damage of the heart itself.>Microvascular function specifically relies upon the adequate release of the vasodilator nitric oxide (NO). Our previous work showed that Telomerase Reverse Transcriptase (TERT), the catalytic subunit of telomerase, is necessary for physiological release of NO to mediate vasodilation. NO suppresses reactive oxygen species (ROS) levels. While Dox correlates with increased ROS production and suppressed TERT activity, attenuated TERT activity may explain the elevated levels of ROS after Dox exposure. The objective of this study was to determine whether TERT transcriptional activation is suffcient to protect against Dox-induced microvascular endothelial- and cardiac dysfunction. We utilized cycloastragenol (CAG) as transcriptional activator. Hypothesis: We hypothesized that TERT transcriptional activation is suffcient to prevent or attenuate Dox-induced endothelial dysfunction. Methods: WT or TERT loss-of-function rats on a Sprague Dawley background were assigned to untreated control-, CAG-, Dox and CAG+Dox groups. Animals were ~14 weeks of age to start the six-week protocol. Dox and CAG+Dox animals received one weekly IP Dox-injection (3x 4mg/kg*BW). CAG administer via diet with 50-60mg of CAG/day*BW. Microvascular function was assessed six-weeks after the first dose of Dox via videomicroscopy. Vasodilator responses to flow (flow-mediated dilation; FMD) and mediators of dilation (NO, H2O2) via fluorescent probes were evaluated. Cardiac function was evaluated using echocardiography. Human microvessels were treated either with 100nM Dox or 1μM CAG or a combination of both. Results: Dox treatment resulted in reduction in FMD in both WT and TERT mutant animals. Smooth-muscle dependent vasodilation was not impaired indicating endothelial impairment. CAG prevented Dox-induced endothelial dysfunction in WT but not TERT mutant rats. AGS499 another activator of TERT showed similar results suggestion a TERT mediated phenotype. Dox-treated WT animals exhibited an increase in H2O2 but not NO production. This phenotype was opposite in CAG+Dox WT animals. TERT mutant animals showed an increase in H2O2 but not NO production even without Dox. To assess which vasodilator mediates dilation to flow, we used L-NAME and PEG-Catalase to block NO- and H2O2, respectively. In CAG+Dox WT animals, L-NAME blocked the vasodilatory response to flow, while PEG-Cat blocked the vasodilatory response non-significantly. Similarly, we observed this protective effect of TERT in the human microcirculation. Human adipose microvessels treated over-night with Dox showed no vasodilatory response to flow while CAG+Dox treated vessels dilated normally similar to untreated control vessels. Smooth muscle function was not affected in neither group. Conclusion: We show evidence that TERT prevents Dox-induced endothelial dysfunction in an in vivo model and using human tissue. We highlight the specificity to TERT by a) using a genetic model lacking normal TERT activity and b) showing similar results using two different compounds which have been shown to activate TERT/promote TERT transcriptional activation. Ultimately, the present data shows that CAG is a potential therapeutic to counteract the detrimental effects of Dox treatment in the CV system via TERT signaling. RO1 HL133029-01. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.