Antioxidants Inhibit Nuclear Export of Telomerase Reverse Transcriptase and Delay Replicative Senescence of Endothelial Cells

Abstract

Abstract-Aging is associated with a rise in intracellular reactive oxygen species (ROS) and a loss of telomerase reverse transcriptase activity. Incubation with H 2 O 2 induced the nuclear export of telomerase reverse transcriptase (TERT) into the cytosol in a Src-family kinase-dependent manner. Therefore, we investigated the hypothesis that age-related increase in reactive oxygen species (ROS) may induce the nuclear export of TERT and contribute to endothelial cell senescence. Continuous cultivation of endothelial cells resulted in an increased endogenous formation of ROS starting after 29 population doublings (PDL). This increase was accompanied by mitochondrial DNA damage and preceded the onset of replicative senescence at PDL 37. Along with the enhanced formation of ROS, we detected an export of nuclear TERT protein from the nucleus into the cytoplasm and an activation of the Src-kinase. Moreover, the induction of premature senescence by low concentrations of H 2 O 2 was completely blocked with the Src-family kinase inhibitor PP2, suggesting a crucial role for Src-family kinases in the induction of endothelial cell aging. Incubation with the antioxidant N-acetylcysteine, from PDL 26, reduced the intracellular ROS formation and prevented mitochondrial DNA damage. Likewise, nuclear export of TERT protein, loss in the overall TERT activity, and the onset of replicative senescence were delayed by incubation with N-acetylcysteine. Low doses of the statin, atorvastatin (0.1 mol/L), had also effects similar to those of N-acetylcysteine. We conclude that both antioxidants and statins can delay the onset of replicative senescence by counteracting the increased ROS production linked to aging of endothelial cells.

Actions of human telomerase beyond telomeres

“…Cells expressing these mutated hTERT exhibited reduced level of mitochondrial DNA damage induced by hydrogen peroxide treatment [29]. These observations of proapoptosis activity of hTERT in mitochondria are consistent with the experiments showing that oxidative stress induces the nuclear export of hTERT, which might contribute to the mitochondrial proapoptosis activity of hTERT [30]. However, molecular mechanisms of hTERT targeting into mitochondria and precise roles of hTERT in mitochondria remain to be investigated.…”

Endothelial progenitor cells relationships with clinical and biochemical factors in a human model of blunted angiotensin II signaling

“…37 All of these are altered in hypertension, 3,38,39 and in these alterations oxidative stress has a pivotal role. 40 Relationships between EPCs, FMD and HO-1 LA Calò et al in BS/GS patients. 29,30 In addition, despite high levels of Ang II, BS/GS patients have increased FMD and upregulation of NO system, 19,31,32 both of which are consistent with the increased number of EPC cells found in this study.…”

MiR-146a as marker of senescence-associated pro-inflammatory status in cells involved in vascular remodelling

“…Endothelial cell replicative senescence was studied by subjecting endothelial cells to subsequent passages until XIII, as previously described (Haendeler et al 2004). Cumulative population doubling (CPD) was calculated as the sum of all the changes in PD (Supplementary material and method).…”