title: Bumetanide annihilation of amphotericin B-induced apoptosis and cytotoxicity is due to its effect on cellular K+ flux.
abstract: The antifungal antibiotic amphotericin B causes considerable toxic effects during clinical therapy. We have shown previously that amphotericin B-induced cytotoxicity and apoptosis were eradicated by the Na+, K+, 2Cl- cotransport inhibitor bumetanide. To elucidate the role of K+ flux and the activity of Na+, K+ ATPase and Na+, K+, 2Cl- cotransport in apoptosis and cytotoxicity induced by amphotericin B alone and combined with bumetanide, we quantified the influx and efflux of K+ of mesothelioma cells (P31) using the K+ analogue 86Rb+ with ouabain (100 micromol/L) as the K+ influx probe. To determine the susceptibility of Candida albicans to amphotericin B when combined with bumetanide we used a plate diffusion method. Amphotericin B or bumetanide alone significantly stimulated 86Rb+ efflux during the first 15 min. However, when added simultaneously, the cellular 86Rb+ efflux was markedly decreased. Amphotericin B (3 mg/L) had no effect on immediate (15 min) total 86Rb+ influx. When bumetanide (100 micromol/L) was added, the total 86Rb+ influx was markedly reduced due to inhibition of augmented Na+, K+, 2Cl- cotransport and low Na+, K+ ATPase activity. Bumetanide did not affect the susceptibility of C. albicans to amphotericin B, which suggests that bumetanide or related drugs could be used in antifungal therapy to increase amphotericin B effectiveness without increasing its adverse effects. We suggest that bumetanide hampering of amphotericin B-induced cytotoxicity and apoptosis could be due to an immediate reduction of cellular K+ efflux as well as disordered K+ influx.
authors.affiliation: Department of Clinical Chemistry, Umeå University, S-901 87 Umeå, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Marklund
authors.forename: P
authors.initials: P
authors.lastname: Behnam-Motlagh
authors.forename: R
authors.initials: R
authors.lastname: Henriksson
authors.forename: K
authors.initials: K
authors.lastname: Grankvist
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002034:Bumetanide / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects; D004232:Diuretics / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D010042:Ouabain / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism; D012414:Rubidium Radioisotopes / Q000493:pharmacokinetics; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000903:Antibiotics, Antineoplastic; D000935:Antifungal Agents; D004232:Diuretics; D004791:Enzyme Inhibitors; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D010042:Ouabain; D000666:Amphotericin B; D000254:Sodium-Potassium-Exchanging ATPase