tretinoin and peroxynitric-acid

When differentiated into mature macrophages by the combination of all-trans retinoic acid and 1,25-dihydroxyvitamin D3, the human promonocytic cell lines U937 and THP-1 expressed inducible nitric oxide synthase (iNOS) transcripts. During their differentiation, the cells acquired the capacity to produce not only superoxide anion (O2.-) but also nitric oxide (.NO) in response to IgG (or IgE)-opsonized zymosan. The inhibitors of the iNOS pathway, aminoguanidine and NG-monomethyl-L-arginine (L-NMMA), suppressed the production of .NO and enhanced the steady-state concentration of O2.- determined. Conversely, superoxide dismutase (SOD) scavenged the O2.- released and increased the .NO-derived nitrite concentration detected. These data suggested a possible interaction between O2.- and .NO. In differentiated U937 (or THP-1) cells, IgG or IgE-opsonized zymosan induced a strong time-dependent luminol-dependent chemiluminescence (LDCL), which was abrogated by SOD and partially inhibited by aminoguanidine or L-NMMA. Since the iNOS inhibitors did not directly scavenge O2.-, LDCL determination in the presence or absence of SOD and/or iNOS inhibitors demonstrated a concomitant production of O2.- and .NO. These radicals induced the formation of a .NO-derived product(s), probably peroxynitrite (ONOO-), which was required to elicit maximal LDCL. Finally, LDCL measurement provided a convenient tool to characterize iNOS triggering and demonstrated an interaction between NADPH oxidase and iNOS products in human macrophagic cells phagocytizing opsonized-zymosan. These findings show that in activated macrophages, iNOS activity can be involved in LDCL and support the debated hypothesis of iNOS participation to the microbicidal activity of human macrophages.

Topics: Calcitriol; Cell Differentiation; Cell-Free System; Free Radical Scavengers; Guanidines; Humans; Immunoglobulin E; Immunoglobulin G; Leukemia, Monocytic, Acute; Luminescent Measurements; Luminol; Lymphoma, Large B-Cell, Diffuse; Macrophage Activation; Macrophages; Neoplastic Stem Cells; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; omega-N-Methylarginine; Opsonin Proteins; Phagocytosis; Superoxide Dismutase; Superoxides; Tretinoin; Tumor Cells, Cultured; Xanthine; Xanthine Oxidase; Zymosan