title: Nitrogen monoxide (no) and glucose: unexpected links between energy metabolism and no-mediated iron mobilization from cells.
abstract: Nitrogen monoxide (NO) affects cellular iron metabolism due to its high affinity for this metal ion. Indeed, NO has been shown to increase the mRNA binding activity of the iron-regulatory protein 1, which is a major regulator of iron homeostasis. Recently, we have shown that NO generators increase (59)Fe efflux from cells prelabeled with (59)Fe-transferrin (Wardrop, S. L., Watts, R. N., and Richardson, D. R. (2000) Biochemistry 39, 2748-2758). The mechanism involved in this process remains unknown, and in this investigation we demonstrate that it is potentiated upon adding d-glucose (d-Glc) to the reincubation medium. In d-Glc-free or d-Glc-containing media, 5.6 and 16.5% of cellular (59)Fe was released, respectively, in the presence of S-nitrosoglutathione. This difference in (59)Fe release was observed with a variety of NO generators and cell types and was not due to a change in cell viability. Kinetic studies showed that d-Glc had no effect on the rate of NO production by NO generators. Moreover, only the metabolizable monosaccharides d-Glc and d-mannose could stimulate NO-mediated (59)Fe mobilization, whereas other sugars not easily metabolized by fibroblasts had no effect. Hence, metabolism of the monosaccharides was essential to increase NO-mediated (59)Fe release. Incubation of cells with the citric acid cycle intermediates, citrate and pyruvate, did not enhance NO-mediated (59)Fe release. Significantly, preincubation with the GSH-depleting agents, l-buthionine-[S,R]-sulfoximine or diethyl maleate, prevented NO-mediated (59)Fe mobilization. This effect was reversed by incubating cells with N-acetyl-l-cysteine that reconstitutes GSH. These results indicate that GSH levels are essential for NO-mediated (59)Fe efflux. Hence, d-Glc metabolism via the hexose monophosphate shunt resulting in the generation of GSH may be essential for NO-mediated (59)Fe release. These results have important implications for intracellular signaling by NO and also NO-mediated cytotoxicity of activated macrophages that is due, in part, to iron release from tumor target cells.
authors.affiliation: Iron Metabolism and Chelation Group, the Heart Research Institute, 145 Missenden Rd, Camperdown, Sydney, New South Wales 2050, Australia.
authors.forename: R N
authors.initials: RN
authors.lastname: Watts
authors.forename: D R
authors.initials: DR
authors.lastname: Richardson
mesh_terms: D000818:Animals; D002460:Cell Line; D019343:Citric Acid / Q000494:pharmacology; D004187:Disaccharides / Q000494:pharmacology; D004734:Energy Metabolism; D005947:Glucose / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D017136:Ion Transport; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D051379:Mice; D009005:Monosaccharides / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology*; D009603:Nitroso Compounds / Q000378:metabolism; D019289:Pyruvic Acid / Q000494:pharmacology; D013696:Temperature; D014168:Transferrin / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D004187:Disaccharides; D007502:Iron Chelating Agents; D009005:Monosaccharides; D009566:Nitrates; D009603:Nitroso Compounds; D014168:Transferrin; D014475:Uncoupling Agents; C028283:diferric transferrin; D019343:Citric Acid; D009569:Nitric Oxide; D019289:Pyruvic Acid; D007501:Iron; D005978:Glutathione; D005947:Glucose