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 the present study, we explored in more detail the necessary requirements for neopterin to modulate the effects of hydrogen peroxide in a luminol-dependent chemiluminescence assay. We demonstrate that neopterin enhances 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 important role in macrophage-mediated effector mechanisms.