Protection of U937 cells from free radical damage by the macrophage synthesized antioxidant 7,8-dihydroneopterin.
Interferon-gamma stimulation of human macrophages causes the synthesis and release of neopterin and its reduced form 7,8-dihydroneopterin (7,8-NP). The purpose of this cellular response is undetermined but in vitro experiments suggests 7,8-NP is an antioxidant. We have found 7,8-NP can protect monocyte-like U937 cells from oxidative damage. 7,8-NP inhibited ferrous ion and hypochlorite mediated loss of cell viability. Fe++ mediated lipid peroxidation was effectively inhibited by 7,8-NP, however, no correlation was found between peroxide concentration and cell viability. Hypochlorite was scavenged by 7,8-NP, preventing the loss of cell viability. 7,8-NP was less effective in inhibiting H2O2-mediated loss of cell viability with significant inhibition only occurring at high 7,8-NP concentrations. Analysis of cellular protein hydrolysates showed none of the oxidants caused the formation of any protein bound DOPA or dityrosine but did show 7,8-NP prevented the loss of cellular tyrosine by HOCl. Our data suggests macrophages may synthesize 7,8-NP for antioxidant protection during inflammatory events in vivo.
Gieseg
S P
SP
Free Radical Biochemistry Laboratory, Department of Zoology, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. s.gieseg@zool.canterbury.ac.nz
Whybrow
J
J
Glubb
D
D
Rait
C
C
D000578:Amidines / Q000494:pharmacology; D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004295:Dihydroxyphenylalanine / Q000378:metabolism; D005609:Free Radicals / Q000633:toxicity*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006997:Hypochlorous Acid / Q000494:pharmacology; D007501:Iron / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008264:Macrophages / Q000737:chemistry*; D019798:Neopterin / Q000031:analogs & derivatives; D011621:Pteridines / Q000737:chemistry / Q000494:pharmacology*; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D020298:U937 Cells / Q000187:drug effects*
D000578:Amidines; D000975:Antioxidants; D005609:Free Radicals; D011621:Pteridines; D017392:Thiobarbituric Acid Reactive Substances; C000976:7,8-dihydroneopterin; D004295:Dihydroxyphenylalanine; D019798:Neopterin; D006997:Hypochlorous Acid; C046728:2,2'-azobis(2-amidinopropane); D006861:Hydrogen Peroxide; D007501:Iron