Abstract 457: Telomerase Reverse Transcriptase Protects Against Oxldl Induced Endothelial Dysfunction By Positively Regulating Autophagy

Abstract

Introduction: Oxidised LDL is one of the major atherogenic agents known to cause endothelial dysfunction eventually leading to atherosclerosis. Reduction of telomerase reverse transcriptase levels have been shown to increase susceptibility to development of atherosclerosis. Apart from its conventional functions, telomerase reverse transcriptase is also known to mitigate mitochondrial stress, oxidative stress, regulate inflammation and wnt pathways. In this study, we test the hypothesis that TERT rescues endothelial dysfunction by upregulating the autophagy pathway leading to better clearance of oxLDL. Methods: Monocyte attachment assay, oxLDL uptake assay, transcytosis and TEER assays were performed to study the functional outcomes in endothelial cells with TERT overexpression and knockdown. Gene and protein expression assays were performed to study the levels of autophagy related genes and proteins. Co-immunoprecipitation was performed to study the binding partners of TERT and live cell imaging of lysosomes were performed to study autophagy kinetics. Results: Autophagy related genes and proteins were observed to significantly upregulated or downregulated upon overexpression and knockdown of TERT respectively. TERT overexpression showed 2-fold reduction in oxLDL uptake in endothelial cells(p≤0.005) whereas TERT knockdown showed 1.5-fold increase in oxLDL uptake(p<0.05). TERT overexpression in the presence of oxLDL also showed a 2-fold reduction in monocyte attachment as compared to oxLDL treated endothelial cells alone (p<0.001). TERT knockdown under oxLDL stress increased monocyte attachment by 4.2 folds as compared to controls (p<0.0001). Transcytosis assays showed a 2-fold reduction in TERT overexpressed endothelial cells and a 7-fold increase in TERT knockdown oxLDL treated endothelial cells. Further, co-immunoprecipitation and colocalization studies show that TERT binds to Rab7 protein but not LAMP1 or LC3 proteins. This binding is further increased upon oxLDL treatment. Conclusion: Our findings indicate that TERT is crucial for homeostatic endothelial functions and TERT overexpression rescues endothelial dysfunction in an atherogenic prone environment by upregulating autophagic pathway.