title: Nitric Oxide positively regulates Ag (I)-induced Ca(2+) influx and mast cell activation: role of a Nitric Oxide Synthase-independent pathway.
abstract: NO is generated by NOS activity and known to act as a negative regulator of mast cell activation. We reported previously that Ag (I) directly evokes mast cell degranulation and LTC(4) release via Ca(2+) influx through thiol-sensitive, store-independent channels. Here, we report that NO generated independently of NOS activity mediates the store-independent Ca(2+) influx. Exposure of mast cells to Ag (I) resulted in increased intracellular NO levels and NO(2)(-)/NO(3)(-) contents in the extracellular fluid. The NO increase was blocked by NO scavenger Hb and DTT but not by NOS inhibitors such as amino-BH(4) and L-NAME. This NO production occurred independently of the Src family kinase and PI3K activities, both of which were necessary for antigen-induced, NOS-dependent NO production. Hb and DTT reduced Ag (I)-induced beta-hexosaminidase release and LTC(4) release, whereas the NO scavengers and NOS inhibitors augmented antigen-induced mediator release. Moreover, Hb and DTT, but not the NOS inhibitors, abolished the Ag (I)-induced Ca(2+) influx, and none of the drugs blocked CRAC channel activity. Finally, Ag (I)-induced Ca(2+) influx was distinct from LTCC activity in terms of its sensitivities to wortmannin and LTCC antagonists and the effects of Ca(v)1.2 LTCC gene silencing. These data show that NOS-independent NO regulates mast cell activation positively via a unique store-independent Ca(2+) influx pathway. The present findings suggest multiple sources and functions of NO in mast cell biology.
authors.affiliation: Division of Molecular Cell Immunology and Allergology, Nihon University Graduate School of Medical Science, Oyaguchikamicho Itabashi-ku, Tokyo, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Inoue
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Yoshimaru
authors.forename: Chisei
authors.initials: C
authors.lastname: Ra
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000276:immunology* / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000276:immunology* / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects* / Q000276:immunology; D002460:Cell Line; D004229:Dithiothreitol / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006454:Hemoglobins / Q000494:pharmacology; D006801:Humans; D017997:Leukotriene C4 / Q000276:immunology / Q000378:metabolism; D008407:Mast Cells / Q000276:immunology* / Q000378:metabolism; D009569:Nitric Oxide / Q000276:immunology* / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000276:immunology / Q000378:metabolism; D012834:Silver / Q000494:pharmacology*; D000077191:Wortmannin; D001619:beta-N-Acetylhexosaminidases / Q000276:immunology / Q000378:metabolism
chemical_list: D000730:Androstadienes; D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D006454:Hemoglobins; D017997:Leukotriene C4; D009569:Nitric Oxide; D012834:Silver; D019001:Nitric Oxide Synthase; D001619:beta-N-Acetylhexosaminidases; D002118:Calcium; D004229:Dithiothreitol; D000077191:Wortmannin