title: α1-adrenergic drugs exhibit affinity to a thapsigargin-sensitive binding site and interfere with the intracellular Ca2+ homeostasis in human erythroleukemia cells.
abstract: Even though the erythroleukemia cell lines K562 and HEL do not express α1-adrenoceptors, some α1-adrenergic drugs influence both survival and differentiation of these cell lines. Since Ca2+ is closely related to cellular homeostasis, we examined the capacity of α1-adrenergic drugs to modulate the intracellular Ca2+ content in K562 cells. Because of morphological alterations of mitochondria following α1-adrenergic agonist treatment, we also scrutinized mitochondrial functions. In order to visualize the non-adrenoceptor binding site(s) of α1-adrenergic drugs in erythroleukemia cells, we evaluated the application of the fluorescent α1-adrenergic antagonist BODIPY® FL-Prazosin. We discovered that the α1-adrenergic agonists naphazoline, oxymetazoline and also the α1-adrenergic antagonist benoxathian are able to raise the intracellular Ca2+-content in K562 cells. Furthermore, we demonstrate that naphazoline treatment induces ROS-formation as well as an increase in Δψm in K562 cells. Using BODIPY® FL-Prazosin we were able to visualize the non-adrenoceptor binding site(s) of α1-adrenergic drugs in erythroleukemia cells. Interestingly, the SERCA-inhibitor thapsigargin appears to interfere with the binding of BODIPY® FL-Prazosin. Our data suggest that the effects of α1-adrenergic drugs on erythroleukemia cells are mediated by a thapsigargin sensitive binding site, which controls the fate of erythroleukemia cells towards differentiation, senescence and cell death through modulation of intracellular Ca2+.
authors.affiliation: Institute of Pathophysiology and Immunology, Center of Molecular Medicine, Medical University of Graz, Heinrichstrasse 31A, 8010 Graz, Austria. robert.fuchs@medunigraz.at
authors.forename: Robert
authors.initials: R
authors.lastname: Fuchs
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Schraml
authors.forename: Gerd
authors.initials: G
authors.lastname: Leitinger
authors.forename: Ilse
authors.initials: I
authors.lastname: Letofsky-Papst
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Stelzer
authors.forename: Helga Susanne
authors.initials: HS
authors.lastname: Haas
authors.forename: Konrad
authors.initials: K
authors.lastname: Schauenstein
authors.forename: Anton
authors.initials: A
authors.lastname: Sadjak
mesh_terms: D018663:Adrenergic Agents / Q000494:pharmacology*; D058646:Adrenergic alpha-1 Receptor Agonists / Q000494:pharmacology; D058668:Adrenergic alpha-1 Receptor Antagonists / Q000494:pharmacology; D000375:Aging / Q000187:drug effects; D001665:Binding Sites / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects*; D006801:Humans; D020014:K562 Cells; D004915:Leukemia, Erythroblastic, Acute / Q000188:drug therapy* / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D009278:Naphazoline / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology*
chemical_list: D018663:Adrenergic Agents; D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D017382:Reactive Oxygen Species; D018340:Receptors, Adrenergic, alpha-1; D019284:Thapsigargin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D009278:Naphazoline; D002118:Calcium