title: Endogenous and exogenous cardiac glycosides: their roles in hypertension, salt metabolism, and cell growth.
abstract: Cardiotonic steroids (CTS), long used to treat heart failure, are endogenously produced in mammals. Among them are the hydrophilic cardenolide ouabain and the more hydrophobic cardenolide digoxin, as well as the bufadienolides marinobufagenin and telecinobufagin. The physiological effects of endogenous ouabain on blood pressure and cardiac activity are consistent with the "Na(+)-lag" hypothesis. This hypothesis assumes that, in cardiac and arterial myocytes, a CTS-induced local increase of Na(+) concentration due to inhibition of Na(+)/K(+)-ATPase leads to an increase of intracellular Ca(2+) concentration ([Ca(2+)](i)) via a backward-running Na(+)/Ca(2+) exchanger. The increase in [Ca(2+)](i) then activates muscle contraction. The Na(+)-lag hypothesis may best explain short-term and inotropic actions of CTS. Yet all data on the CTS-induced alteration of gene expression are consistent with another hypothesis, based on the Na(+)/K(+)-ATPase "signalosome," that describes the interaction of cardiac glycosides with the Na(+) pump as machinery activating various signaling pathways via intramembrane and cytosolic protein-protein interactions. These pathways, which may be activated simultaneously or selectively, elevate [Ca(2+)](i), activate Src and the ERK1/2 kinase pathways, and activate phosphoinositide 3-kinase and protein kinase B (Akt), NF-kappaB, and reactive oxygen species. A recent development indicates that new pharmaceuticals with antihypertensive and anticancer activities may be found among CTS and their derivatives: the antihypertensive rostafuroxin suppresses Na(+) resorption and the Src-epidermal growth factor receptor-ERK pathway in kidney tubule cells. It may be the parent compound of a new principle of antihypertensive therapy. Bufalin and oleandrin or the cardenolide analog UNBS-1450 block tumor cell proliferation and induce apoptosis at low concentrations in tumors with constitutive activation of NF-kappaB.
authors.affiliation: Institut für Biochemie und Endokrinologie, Fachbereich Veterinärmedizin, Justus-Liebig-Universität Giessen, Frankfurter Str 100, Giessen, Germany. wilhelm.schoner@vetmed.uni-giessen.de
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Schoner
authors.forename: Georgios
authors.initials: G
authors.lastname: Scheiner-Bobis
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D002018:Bufanolides / Q000378:metabolism / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002301:Cardiac Glycosides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use; D002319:Cardiovascular System / Q000187:drug effects / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D003920:Diabetes Mellitus / Q000378:metabolism / Q000503:physiopathology; D004077:Digoxin / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D015394:Molecular Structure; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010042:Ouabain / Q000378:metabolism / Q000494:pharmacology; D012965:Sodium Chloride / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000959:Antihypertensive Agents; D000970:Antineoplastic Agents; D002018:Bufanolides; D002301:Cardiac Glycosides; C093896:marinobufagenin; D012965:Sodium Chloride; D010042:Ouabain; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium