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Characterization of platelet‐activating factor‐induced cytosolic calcium mobilization in human eosinophils
Author(s) -
Takako Oshiro,
Yasunori Kakuta,
Sanae Shimura,
Masayuki Nara,
Kunio Shirato
Publication year - 2000
Publication title -
clinical and experimental allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 154
eISSN - 1365-2222
pISSN - 0954-7894
DOI - 10.1046/j.1365-2222.2000.00786.x
Subject(s) - thapsigargin , platelet activating factor , extracellular , egta , calcium , cytosol , fura 2 , chemistry , endocrinology , protein kinase c , medicine , biochemistry , kinase , biology , enzyme
Background Activated eosinophils play an important role in the pathogenesis of bronchial asthma and other allergic diseases, and platelet‐activating factor (PAF) is a potent activator of eosinophils. Objective To characterize the cytosolic Ca 2+ ([Ca 2+ ] i ) mobilization in human eosinophils in response to PAF. Methods [Ca 2+ ] i responses to PAF were examined in human eosinophils using a microscopic fura‐2 fluorescence‐ratio imaging system. Results PAF caused a significant and dose‐dependent increase in (Ca 2+ ) i , which consisted of an initial rapid rise followed by a sustained elevation. This PAF‐induced (Ca 2+ ) i rise was inhibited by WEB 2086, a specific PAF receptor antagonist. The addition of 5 m m EGTA or 1 m m Ni 2+ to a nominally Ca 2+ ‐free solution did not appreciably reduce the initial rise but significantly inhibited the sustained rise. The application of a protein kinase C inhibitor, Ro31‐8220, augmented the sustained increase by PAF. Thapsigargin, a microsomal Ca 2+ ATPase inhibitor, induced no appreciable change in a nominally Ca 2+ ‐free solution but induced a marked increase in (Ca 2+ ) i when changed to a Ca 2+ ‐containing solution. Conclusions The initial rapid rise and the following sustained rise in (Ca 2+ ) i by PAF depends on Ca 2+ release from the intracellular Ca 2+ stores and Ca 2+ influx, respectively, which are regulated by protein kinase C in human eosinophils. Furthermore, the so called Ca 2+ ‐capacitative entry is possibly involved in the Ca 2+ influx from the extracellular solution in human eosinophils.