title: The bisphosphonate ibandronate stimulates reverse cholesterol transport out of monocytoid cells by enhanced ABCA1 transcription.
abstract: Nitrogen-containing bisphosphonates used in osteoporosis act by interference with pyrophosphorylated intermediates of the sterol pathway and are internalized by monocytes/macrophages, key players in atherogenesis. We therefore studied the effects of ibandronate on monocytic cholesterol homeostasis. In differentiated human MM6 cells and freshly prepared human PBMCs lipoprotein receptor transcription was quantified by real-time RT-PCR and receptor-mediated cellular cholesterol handling by lipoprotein-driven uptake and efflux assays. Low nanomolar concentrations of ibandronate reduced cellular cholesterol content despite reactive up-regulation of the LDL receptor. Simultaneously, the transcription of the cellular cholesterol exporter ABCA1 was severalfold stimulated, whereas the scavenger receptor CD36 was down-regulated. Thereby, ibandronate decreased the cellular uptake of modified LDL and enhanced the efflux of cholesterol to delipidated HDL. Geranylgeraniol antagonized the stimulation of ABCA1 expression by ibandronate. Ibandronate in low pharmacologic concentrations redirects monocytic cholesterol handling from favouring foam cell formation towards enhanced reverse cholesterol transport.
authors.affiliation: Institute for Prophylaxis of Cardiovascular Diseases, University of Munich, Germany.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Strobach
authors.forename: Reinhard L
authors.initials: RL
authors.lastname: Lorenz
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology*; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D004164:Diphosphonates / Q000494:pharmacology*; D006706:Homeostasis; D006801:Humans; D000077557:Ibandronic Acid; D008075:Lipoproteins, HDL / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000737:chemistry / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011106:Polyisoprenyl Phosphates / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D018955:CD36 Antigens; D004164:Diphosphonates; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D011106:Polyisoprenyl Phosphates; D011973:Receptors, LDL; D002784:Cholesterol; C002963:geranylgeranyl pyrophosphate; D000077557:Ibandronic Acid