Chloroquine stimulates nitric oxide synthesis in murine, porcine, and human endothelial cells.
Nitric oxide (NO) is a free radical involved in the regulation of many cell functions and in the expression of several diseases. We have found that the antimalarial and antiinflammatory drug, chloroquine, is able to stimulate NO synthase (NOS) activity in murine, porcine, and human endothelial cells in vitro: the increase of enzyme activity is dependent on a de novo synthesis of some regulatory protein, as it is inhibited by cycloheximide but is not accompanied by an increased expression of inducible or constitutive NOS isoforms. Increased NO synthesis is, at least partly, responsible for chloroquine-induced inhibition of cell proliferation: indeed, NOS inhibitors revert the drug-evoked blockage of mitogenesis and ornithine decarboxylase activity in murine and porcine endothelial cells. The NOS-activating effect of chloroquine is dependent on its weak base properties, as it is exerted also by ammonium chloride, another lysosomotropic agent. Both compounds activate NOS by limiting the availability of iron: their stimulating effects on NO synthesis and inhibiting action on cell proliferation are reverted by iron supplementation with ferric nitrilotriacetate, and are mimicked by incubation with desferrioxamine. Our results suggest that NO synthesis can be stimulated in endothelial cells by chloroquine via an impairment of iron metabolism.
Department of Genetics, Biology, and Biochemistry, University of Torino, 10126 Torino, Italy. ghigo@molinette.unito.it
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Ghigo
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Aldieri
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Todde
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Costamagna
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Garbarino
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Pescarmona
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Bosia
D000154:Aconitate Hydratase / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002172:Canavanine / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D002738:Chloroquine / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology; D003600:Cytosol / Q000737:chemistry / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D006418:Heme / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D009955:Ornithine Decarboxylase / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013268:Stimulation, Chemical; D013552:Swine
D004791:Enzyme Inhibitors; D006146:Guanidines; D011500:Protein Synthesis Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D002172:Canavanine; D006418:Heme; D002738:Chloroquine; D003513:Cycloheximide; D007501:Iron; D019001:Nitric Oxide Synthase; D009955:Ornithine Decarboxylase; D000154:Aconitate Hydratase; C004479:pimagedine; D002118:Calcium