Oxidative responses of human and murine macrophages during phagocytosis of Leishmania chagasi.
Leishmania chagasi, the cause of South American visceral leishmaniasis, must survive antimicrobial responses of host macrophages to establish infection. Macrophage oxidative responses have been shown to diminish in the presence of intracellular leishmania. However, using electron spin resonance we demonstrated that murine and human macrophages produce O2-during phagocytosis of opsonized promastigotes. Addition of the O2- scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl to cultures resulted in increased infection, suggesting that O2- enhances macrophage leishmanicidal activity. The importance of NO. produced by inducible NO synthase (iNOS) in controlling murine leishmaniasis is established, but its role in human macrophages has been debated. We detected NO. in supernatants from murine, but not human, macrophages infected with L. chagasi. Nonetheless, the iNOS inhibitor N(G)-monomethyl-L-arginine inhibited IFN-gamma-mediated intracellular killing by both murine and human macrophages. According to RNase protection assay and immunohistochemistry, iNOS mRNA and protein were expressed at higher levels in bone marrow of patients with visceral leishmaniasis than in controls. The iNOS protein also increased upon infection of human macrophages with L. chagasi promastigotes in vitro in the presence of IFN-gamma. These data suggest that O2- and NO. each contribute to intracellular killing of L. chagasi in human and murine macrophages.
Gantt
K R
KR
Immunology Program, Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA.
Goldman
T L
TL
McCormick
M L
ML
Miller
M A
MA
Jeronimo
S M
SM
Nascimento
E T
ET
Britigan
B E
BE
Wilson
M E
ME
D000818:Animals; D001854:Bone Marrow Cells / Q000201:enzymology / Q000473:pathology; D002478:Cells, Cultured; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D018314:Leishmania infantum / Q000187:drug effects / Q000254:growth & development / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000201:enzymology / Q000473:pathology; D008264:Macrophages / Q000276:immunology / Q000378:metabolism* / Q000469:parasitology*; D051379:Mice; D009000:Monocytes / Q000201:enzymology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000633:toxicity; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000037:antagonists & inhibitors / Q000378:metabolism; D016877:Oxidants / Q000633:toxicity; D018384:Oxidative Stress / Q000276:immunology*; D010587:Phagocytosis / Q000276:immunology*; D012333:RNA, Messenger / Q000096:biosynthesis; D013113:Spin Labels; D013481:Superoxides / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000633:toxicity; D019323:omega-N-Methylarginine / Q000494:pharmacology
D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D009573:Nitrites; D016877:Oxidants; D012333:RNA, Messenger; D013113:Spin Labels; D013481:Superoxides; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C001803:tempol