title: Critical role of the α1-Na(+), K(+)-ATPase subunit in insensitivity of rodent cells to cytotoxic action of ouabain.
abstract: In rodents, ubiquitous α1-Na(+), K(+)-ATPase is inhibited by ouabain and other cardiotonic steroids (CTS) at ~10(3)-fold higher concentrations than those effective in other mammals. To examine the specific roles of the CTS-sensitive α1S- and CTS-resistant α1R-Na(+), K(+)-ATPase isoforms, we compared the effects of ouabain on intracellular Na(+) and K(+) content, cell survival, and mitogen-activated protein kinases (MAPK) in human and rat vascular smooth muscle cells (HASMC and RASMC), human and rat endothelial cells (HUVEC and RAEC), and human and rat brain astrocytes. 6-h exposure of HASMC and HUVEC to 3 μM ouabain dramatically increased the intracellular [Na(+)]/[K(+)] ratio to the same extend as in RASMC and RAEC treated with 3000 μM ouabain. In 24, 3 μM ouabain triggered the death of all types of human cells used in this study. Unlike human cells, we did not detect any effect of 3000-5000 μM ouabain on the survival of rat cells, or smooth muscle cells from mouse aorta (MASMC). Unlike in the wild-type α1(R/R) mouse, ouabain triggered death of MASMC from α1(S/S) mouse expressing human α1-Na(+), K(+)-ATPase. Furthermore, transfection of HUVEC with rat α1R-Na(+), K(+)-ATPase protected them from the ouabain-induced death. In HUVEC, ouabain led to phosphorylation of p38 MAPK, whereas in RAEC it stimulated phosphorylation of ERK1/2. Overall, our results, demonstrate that the drastic differences in cytotoxic action of ouabain on human and rodent cells are caused by unique features of α1S/α1R-Na(+), K(+)-ATPase, rather than by any downstream CTS-sensitive/resistant components of the cell death machinery.
authors.affiliation: Laboratory of Biological Membranes, Faculty of Biology, M. V. Lomonosov Moscow State University, room 169, Vorob'evy Gory 1/12, Moscow, 119899, Russia.
authors.forename: Olga A
authors.initials: OA
authors.lastname: Akimova
authors.forename: Artem M
authors.initials: AM
authors.lastname: Tverskoi
authors.forename: Larisa V
authors.initials: LV
authors.lastname: Smolyaninova
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Mongin
authors.forename: Olga D
authors.initials: OD
authors.lastname: Lopina
authors.forename: Jennifer
authors.initials: J
authors.lastname: La
authors.forename: Nickolai O
authors.initials: NO
authors.lastname: Dulin
authors.forename: Sergei N
authors.initials: SN
authors.lastname: Orlov
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D001921:Brain / Q000166:cytology; D002316:Cardiotonic Agents / Q000633:toxicity*; D016923:Cell Death / Q000187:drug effects*; D002460:Cell Line; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology; D010042:Ouabain / Q000633:toxicity*; D011188:Potassium / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D002316:Cardiotonic Agents; D010042:Ouabain; D012964:Sodium; D020929:Mitogen-Activated Protein Kinase Kinases; C499075:Atp1a1 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium