Title:Critical role of the alpha1-Na(+), K(+)-ATPase subunit in insensitivity of rodent cells to cytotoxic action of ouabain.
Authors:Akimova OA; Tverskoi AM; Smolyaninova LV; Mongin AA; Lopina OD; La J; Dulin NO; Orlov SN
Publication:Apoptosis. 2015 Sep;20(9):1200-10. doi: 10.1007/s10495-015-1144-y.
In rodents, ubiquitous alpha1-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 alpha1S- and CTS-resistant alpha1R-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 muM ouabain dramatically increased the intracellular [Na(+)]/[K(+)] ratio to the same extend as in RASMC and RAEC treated with 3000 muM ouabain. In 24, 3 muM 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 muM ouabain on the survival of rat cells, or smooth muscle cells from mouse aorta (MASMC). Unlike in the wild-type alpha1(R/R) mouse, ouabain triggered death of MASMC from alpha1(S/S) mouse expressing human alpha1-Na(+), K(+)-ATPase. Furthermore, transfection of HUVEC with rat alpha1R-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 alpha1S/alpha1R-Na(+), K(+)-ATPase, rather than by any downstream CTS-sensitive/resistant components of the cell death machinery.