title: Low doses of ouabain protect from serum deprivation-triggered apoptosis and stimulate kidney cell proliferation via activation of NF-kappaB.
abstract: It now generally is agreed that Na,K-ATPase, in addition to its role in the maintenance of Na+ and K+ gradients across the cell membrane, plays a role in communicating information from the extracellular environment to intracellular signaling pathways. It was reported recently that interaction between ouabain-bound Na,K-ATPase and the 1,4,5-trisphosphate receptor (IP3R) triggers slow calcium oscillations and activation of NF-kappaB. Here it is demonstrated that this signaling pathway can serve to prevent cell death and promote cell growth. Rat renal proximal tubular cells in primary culture first were grown in the presence of 10% serum and then exposed to 0.2% serum for 24 h to induce apoptosis. Serum starvation increased the apoptotic index from 1.21 +/- 0.26 to 14.01 +/- 1.17%. Ouabain in concentrations that did not inhibit Na,K-ATPase activity (1 to 10 nM) completely abolished the apoptotic effect of serum starvation. Ouabain protection from apoptosis was not observed when release of calcium from intracellular stores via the IP3R was prevented. It was shown that the NH2 terminal tail of the Na,K-ATPase alpha subunit plays a key role in ouabain-triggered calcium oscillations. It was found that ouabain did not protect from apoptosis in serum-deprived cells that expressed a mutant Na,K-ATPase alpha subunit with deletion of the NH2 terminal tail. Ouabain exposure (10 nM for 24 h) significantly increased translocation of NF-kappaB from cytoplasm to nucleus. Helenalin, an inhibitor of NF-kappaB, abolished the antiapoptotic effect of ouabain. Ouabain (0.1 to 10 nM) also was found to stimulate proliferation and increase the viability of kidney cells. These effects were abolished when release of calcium via the IP3R was prevented.
authors.affiliation: Karolinska Institutet, Department of Woman and Child Health, Astrid Lindgren Children's Hospital, Stockholm, Sweden.
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.forename: Sergey
authors.initials: S
authors.lastname: Zelenin
authors.forename: Anita
authors.initials: A
authors.lastname: Aperia
authors.forename: Oleg
authors.initials: O
authors.lastname: Aizman
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000187:drug effects; D008297:Male; D016328:NF-kappa B / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology*; D021122:Protein Subunits; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D016328:NF-kappa B; D021122:Protein Subunits; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium