ENHANCEMENT OF HYDROGEN PEROXIDE-INDUCED LUMINOL-DEPENDENT CHEMILUMINESCENCE BY NEOPTERIN DEPENDS ON THE PRESENCE OF IRON CHELATOR COMPLEXES

We have previously shown that neopterin, 6-D-erythro-trihydroxypropyl- pteridine, synthesized by human monocytes/macrophages upon stimulation by interferon-gamma, enhances toxicity of reactive oxygen at neutral or slightly alkaline pH (7.5), but not at acidic pH (below 6.5). In th e present study, we explored in more detail the necessary requirements for neopterin to modulate the effects of hydrogen peroxide in a lumin ol-dependent chemiluminescence assay. We demonstrate that neopterin en hances hydrogen peroxide effects only in the presence of iron chelator complexes like iron-(III)- or iron-(II)-EDTA or iron-(III)-DTPA. Thus , iron chelator complexes together with neopterin may play an importan t role in macrophage-mediated effector mechanisms.