Published online before print August 25, 2009
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Division of Molecular Cell Immunology and Allergology, Nihon University Graduate School of Medical Science, Tokyo, Japan
1. Correspondence: Division of Molecular Cell Immunology and Allergology, Nihon University Graduate School of Medical Science, 30-1 Oyaguchikami-cho Itabashi-ku, Tokyo 173-8610, Japan. E-mail: ysuzuki{at}med.nihon-u.ac.jp
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 LTC4 release via Ca2+ influx through thiol-sensitive, store-independent channels. Here, we report that NO generated independently of NOS activity mediates the store-independent Ca2+ influx. Exposure of mast cells to Ag (I) resulted in increased intracellular NO levels and NO2–/NO3– contents in the extracellular fluid. The NO increase was blocked by NO scavenger Hb and DTT but not by NOS inhibitors such as amino-BH4 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 β-hexosaminidase release and LTC4 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 Ca2+ influx, and none of the drugs blocked CRAC channel activity. Finally, Ag (I)-induced Ca2+ influx was distinct from LTCC activity in terms of its sensitivities to wortmannin and LTCC antagonists and the effects of Cav1.2 LTCC gene silencing. These data show that NOS-independent NO regulates mast cell activation positively via a unique store-independent Ca2+ influx pathway. The present findings suggest multiple sources and functions of NO in mast cell biology.
Key Words: silver • Ca2+ channel
