The death of cardiotonic steroid-treated cells: evidence of Na+i,K+i-independent H+i-sensitive signalling.
Na/K-ATPase is the only known target of cardiotonic steroids (CTS) identified in plants, amphibians and later on in several mammalian species, including human. We focus our review on recent data implicating CTS in the tissue-specific regulation of cell survival and death. In vascular smooth muscle cells, CTS inhibited cell death triggered by apoptotic stimuli via a novel Na+i-mediated, Ca2+i-independent mechanism of expression of antiapoptotic genes, including mortalin. In contrast, exposure to CTS in vascular endothelial and renal epithelial cells led to cell death, showing combined markers of apoptosis and necrosis. This mode of cell death, termed oncosis, is caused by CTS interaction with Na/K-ATPase but is independent of the inhibition of Na/K-ATPase-mediated ion fluxes and inversion of the [Na+]i/[K+]i ratio. The intermediates of intracellular signalling involved in Na+i, K+i-independent oncosis of CTS-treated cells remain unknown. Recently, we found that this mode of cell death can be protected by modest intracellular acidification via the expression of H+i-sensitive genes. The molecular origin of intracellular Na+ and H+ sensor involvement in the development of apoptosis and oncosis is currently under investigation.
Orlov
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Centre de recherche, Centre hospitalier de l'Université de Montréal (CHUM)-Hôtel-Dieu, Montreal, Quebec, Canada. sergei.n.orlov@umontreal.ca
Hamet
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D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D002301:Cardiac Glycosides / Q000494:pharmacology*; D002414:Cations, Monovalent / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D011522:Protons; D015398:Signal Transduction / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002301:Cardiac Glycosides; D002414:Cations, Monovalent; D007473:Ion Channels; D011522:Protons; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium