Scavenging of reactive oxygen species by a glycolipid fraction of Mycobacterium avium serovar 2.
Previous experiments indicated that MIF-A3, a peptidoglycolipid extracted from Mycobacterium avium serovar 2 (Mycobacterium paratuberculosis 18), inhibits the killing of Candida albicans by activated bovine peripheral blood-derived macrophages and murine thioglycollate-elicited peritoneal macrophages in vitro. Subsequent in vitro data from our laboratory indicated that this reduction in killing may be related to the ability of MIF-A3 to scavenge reactive oxygen species (ROS). In this study we examined this hypothesis directly by determining if MIF-A3 reduced exogenous H2O2-induced candidacidal activity. When Candida albicans was incubated with H2O2 (4 mM) alone, colony-forming units/ml x 10(4) (CFU/ml) were 0.4 +/- 0.1 (mean +/- SE, n = 4) as compared to 11.3 +/- 2.0 CFU/ml in control (untreated) cultures (p < .05). The addition of catalase at concentrations > or = 6.8 U/ml, completely blocked the fungicidal effect of H2O2. However, reducing the amount of catalase from 6.8 U/ml to 3.4 U/ml resulted in a loss of scavenging activity, which was associated with a 50% increase in H2O2-mediated killing. Substituting MIF-A3 (400 micrograms/ml) for catalase, also reduced H2O2-induced fungicidal activity. In the absence of MIF-A3, H2O2 reduced Candida albicans to less than 10(3) CFU/ml. However, in the presence of MIF-A3 the CFU/ml of Candida albicans increased 7.5-fold. Based on concentration-response curves of H2O2 inhibition vs. increasing amounts of catalase we determined that the relative inhibitory capacity of the MIF-A3 (400 micrograms/ml) was approximately 1.0 U/ml "catalase equivalents." These findings provide direct evidence that MIF-A3 can scavenge H2O2, and reduce H2O2-induced killing of Candida albicans.
Scherer
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TA
Division of Pulmonary Diseases, Mount Sinai Medical Center, University of Miami, FL 33140, USA.
Lauredo
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IT
Abraham
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WM
D000818:Animals; D002176:Candida albicans / Q000187:drug effects; D002374:Catalase / Q000494:pharmacology; D002417:Cattle; D016166:Free Radical Scavengers; D006017:Glycolipids / Q000494:pharmacology*; D006020:Glycopeptides / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000276:immunology; D051379:Mice; D009162:Mycobacterium avium / Q000737:chemistry*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013864:Thioglycolates / Q000494:pharmacology
D016166:Free Radical Scavengers; D006017:Glycolipids; D006020:Glycopeptides; C106012:MIF A3; D017382:Reactive Oxygen Species; D013864:Thioglycolates; D006861:Hydrogen Peroxide; D002374:Catalase