Na+/K+ pump and endothelial cell survival: [Na+]i/[K+]i-independent necrosis triggered by ouabain, and protection against apoptosis mediated by elevation of [Na+]i.
Recent studies have demonstrated the tissue-specific effect of Na+/K+ pump inhibition by ouabain and other cardiac glycosides on cell viability. The vascular endothelium is an initial target of cardiac glycosides employed for the management of congestive heart failure as well as circulating endogenous ouabain-like substances (EOLS), the production of which is augmented in volume-expanded hypertension. This study examined the role of the Na+/K+ pump in the survival of cultured porcine aortic endothelial cells (PAEC). Complete Na+/K+ pump inhibition with ouabain led to PAEC death, indicated by cell detachment and decreased staining with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Based on cell swelling and resistance to benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD.fmk) a pan-caspase inhibitor, this type of cell death was classified as necrosis. In contrast to ouabain, Na+/K+ pump inhibition in K+-free medium did not affect PAEC viability and sharply attenuated apoptosis triggered by 3H decay-induced DNA damage. Necrosis evoked by ouabain was preserved after dissipation of the transmembrane gradient of K+ and Na+, whereas dissipation of the Na+ gradient abolished the antiapoptotic action of K+-free medium. Comparative analysis of these results and modulation of intracellular Na+ and K+ content by the above-listed stimuli showed that interaction of ouabain with Na+/K+-ATPase triggered necrosis independently of inhibition of Na+/K+ pump-mediated ion fluxes and inversion of the [Na+]i/[K+]i ratio, whereas protection against apoptosis under Na+/K+ pump inhibition in K+-depleted medium was mediated by [Na+]i elevation. The role of Na+/K+ pump-mediated regulation of endothelial cell survival and vascular remodelling seen in hypertension should be investigated further in context of EOLS and chronic treatment with digitalis.
Orlov
Sergei N
SN
Centre de recherche, Centre hospitalier de l'Université de Montréal, Hôtel-Dieu, 3850 rue St-Urbain, Montreal, Quebec, H2W 1T7, Canada. sergei.n.orlov@umontreal.ca
Thorin-Trescases
Nathalie
N
Pchejetski
Dimitri
D
Taurin
Sebastien
S
Farhat
Nada
N
Tremblay
Johanne
J
Thorin
Eric
E
Hamet
Pavel
P
D000818:Animals; D001011:Aorta / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009336:Necrosis / Q000503:physiopathology*; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*; D013552:Swine
D002316:Cardiotonic Agents; D004791:Enzyme Inhibitors; D010042:Ouabain; D012964:Sodium; D020169:Caspases; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium