title: Evidence against the involvement of nitric oxide in the modulation of telomerase activity or replicative capacity of human endothelial cells.
abstract: Telomerase, a reverse transcriptase involved in the maintenance of telomere function and cellular replicative capacity, is thought to be regulated by nitric oxide (NO). Here, we have used pharmacological tools and RNA interference to re-assess the role of NO in the regulation of telomerase and senescence of human umbilical vein endothelial cells. Acute or chronic treatment of these cells with the NO donors diethylenetriamine/NO (DETA-NO) or S-nitroso-N-acetylpenicillamine (SNAP) at concentrations which generated NO in the 1-300 nM range did not modulate telomerase activity. Similarly these agents did not affect cellular replicative capacity during long-term sub-cultivation. The NO synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (1 mM) reduced basal levels of c-GMP by 50% but had no effect on telomerase activity or replicative capacity. Withdrawal of ascorbic acid increased the intracellular pro-oxidant capacity, reduced telomerase activity and increased the accumulation of senescent cells upon serial passage in culture. However, this shift to a more oxidative redox state did not unmask the putative capacity of NO to modulate telomerase or senescence. Infection of cells with a lentiviral vector expressing a small hairpin RNA targeted against endothelial NOS inhibited endogenous NO production completely but failed to affect the decrease of telomerase activity or the accumulation of senescent cells observed with passage in culture. Our findings suggest that physiological concentrations of NO do not modulate telomerase levels or replicative capacity of endothelial cells, regardless of their cellular oxidative status.
authors.affiliation: The Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: Ying
authors.initials: Y
authors.lastname: Hong
authors.forename: Marisol
authors.initials: M
authors.lastname: Quintero
authors.forename: Nanci M
authors.initials: NM
authors.lastname: Frakich
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Trivier
authors.forename: Jorge D
authors.initials: JD
authors.lastname: Erusalimsky
mesh_terms: D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D016922:Cellular Senescence; D042783:Endothelial Cells / Q000201:enzymology*; D020868:Gene Silencing; D006801:Humans; D009569:Nitric Oxide / Q000032:analysis / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D019098:Telomerase / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection / Q000379:methods; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D020030:Nitric Oxide Donors; D034741:RNA, Small Interfering; C110881:S-nitro-N-acetylpenicillamine; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D019098:Telomerase; D010396:Penicillamine