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The signal transduction mechanism involved in kazinol B‐stimulated superoxide anion generation in rat neutrophils
Author(s) -
Wang Jih P,
Tsao Lo T,
Raung Shue L,
Lin Chun N
Publication year - 1998
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0702106
Subject(s) - protein kinase c , staurosporine , superoxide , wortmannin , stimulation , microbiology and biotechnology , phorbol , chemistry , signal transduction , respiratory burst , biology , phosphatidylinositol , biochemistry , endocrinology , enzyme
1 In this study, the underlying mechanism of stimulation of respiratory burst by kazinol B, a natural isoprenylated flavan, in rat neutrophils in vitro was investigated. 2 Kazinol B concentration‐dependently stimulated the superoxide anion (O 2 [dot over 2] − ) generation, with a lag but transient activation profile, in neutrophils but not in a cell‐free system. The maximum response (13.2±1.4 nmol O 2 [dot over 2] − 10 min −1 per 10 6 cells) was observed at 10 μ M kazinol B. 3 Pretreatment of neutrophils with phorbol 12‐myristate 13‐acetate (PMA) or formylmethionyl‐leucyl‐phenylalanine (fMLP) significantly enhanced the O 2 [dot over 2] − generation following the subsequent stimulation of cells with kazinol B. 4 Cells pretreated with EGTA or a protein kinase inhibitor staurosporine effectively attenuated the kazinol B‐induced O 2 [dot over 2] − generation. However, a p38 mitogen‐activated protein kinase (MAPK) inhibitor SB203580 and a phosphoinositide 3‐kinase (PI3K) inhibitor wortmannin had no effect on the kazinol B‐induced response. 5 Kazinol B significantly stimulated [Ca 2+ ] i elevation in neutrophils, with a lag and slow rate of rise activation profile, and this response was attenuated by a phospholipase C (PLC) inhibitor U73122. Kazinol B also stimulated the inositol bis‐ and trisphosphate (IP 2 and IP 3 ) formation with a 1 min lag time. 6 The membrane‐associated PKC‐α and PKC‐θ but not PKC‐ι were increased following the stimulation of neutrophils with kazinol B. It was more rapid and sensitive in the activation of PKC‐θ than PKC‐α by kazinol B. Kazinol B partially inhibited the [ 3 H]phorbol 12,13‐dibutyrate ([ 3 H]PDB) binding to the neutrophil cytosolic PKC. 7 Neither the cellular mass of phosphatidic acid (PA) and phosphatidylethanol (PEt), in the presence of ethanol, nor the protein tyrosine phosphorylation were stimulated by kazinol B. In addition, the kazinol B‐induced O 2 [dot over 2] − generation remained relatively unchanged in cells pretreated with ethanol or a tyrosine kinase inhibitor genistein. 8 Collectively, these results indicate that the stimulation of the respiratory burst by kazinol B is probably mediated by the synergism of PKC activation and [Ca 2+ ] i elevation in rat neutrophils.British Journal of Pharmacology (1998) 125 , 517–525; doi: 10.1038/sj.bjp.0702106