title: Ascorbate uptake and antioxidant function in peritoneal macrophages.
abstract: Since activated macrophages generate potentially deleterious reactive oxygen species, we studied whether ascorbic acid might function as an antioxidant in these cells. Thioglycollate-elicited murine peritoneal macrophages contained about 3 mM ascorbate that was halved by culture in ascorbate-free medium. However, the cells took up added ascorbate to concentrations of 6-8 mM by a high-affinity sodium-dependent transport mechanism. This likely reflected the activity of the SVCT2 ascorbate transporter, since its message and protein were present in the cells. Activation of the cells by phagocytosis of latex particles depleted intracellular ascorbate, although not below the basal levels present in the cells in culture. Glutathione (GSH) was unaffected by phagocytosis, suggesting that ascorbate was more sensitive to the oxidant stress of phagocytosis than GSH. Phagocytosis induced a modest increase in reactive oxygen species as well as a progressive loss of alpha-tocopherol, both of which were prevented in cells loaded with ascorbate. These results suggest that activated macrophages can use ascorbate to lessen self-generated oxidant stress and spare alpha-tocopherol, which may protect these long-lived cells from necrosis or apoptosis.
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-6303, USA. james.may@vanderbilt.edu
authors.forename: James M
authors.initials: JM
authors.lastname: May
authors.forename: Liying
authors.initials: L
authors.lastname: Li
authors.forename: Zhi-Chao
authors.initials: ZC
authors.lastname: Qu
authors.forename: Junjun
authors.initials: J
authors.lastname: Huang
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003683:Dehydroascorbic Acid / Q000378:metabolism / Q000494:pharmacology; D005452:Fluoresceins / Q000737:chemistry; D005978:Glutathione / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D009336:Necrosis / Q000517:prevention & control; D018384:Oxidative Stress / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013864:Thioglycolates / Q000378:metabolism; D013997:Time Factors; D024502:alpha-Tocopherol / Q000378:metabolism
chemical_list: D000975:Antioxidants; D005452:Fluoresceins; D017382:Reactive Oxygen Species; D013864:Thioglycolates; C110423:dihydrofluorescein; D005978:Glutathione; D024502:alpha-Tocopherol; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid