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Role of protein phosphorylation in activation of phospholipase A2 by the polychlorinated biphenyl mixture Aroclor 1242.

Abstract：

:Polychlorinated biphenyls (PCBs) activate neutrophils to induce degranulation and undergo superoxide production through a mechanism that involves stimulation of phospholipase A(2) (PLA(2)). Since the biochemical processes leading to the PCB-induced activation of this enzyme are unknown, the objective of this study was to determine whether protein phosphorylation has a role in this mechanism. Isolated rat neutrophils were labeled with [(3)H]-arachidonic acid ([(3)H]-AA), and activation of PLA(2) was determined from release of radioactivity into the medium. Exposure to the PCB mixture Aroclor 1242 induced release of [(3)H]-AA, and pretreatment with bromoenol lactone (BEL), an inhibitor of calcium-independent PLA(2), diminished release by 80%. Genistein, an inhibitor of tyrosine kinases, caused a small but significant decrease in Aroclor 1242-stimulated release of [(3)H]-AA. Daidzein, a genistein analog with no activity to inhibit tyrosine kinases, had no effect on [(3)H]-AA release. An inhibitor of p38 mitogen-activated protein kinase (MAPK), SB203580, did not affect Aroclor 1242-induced PLA(2) activity at concentrations selective for p38 MAPK; however, PD 98059, which inhibits MAPK kinase (MEK), decreased [(3)H]-AA release to about the same extent as genistein. Treatment of neutrophils with Aroclor 1242 induced phosphorylation of p44 MAPK, and this phosphorylation was unaffected by BEL but was inhibited by PD 98059. Staurosporine, a nonselective inhibitor of protein kinase C (PKC), inhibited PCB-induced release of [(3)H]-AA. Ro 32-0432, a selective inhibitor of PKC(alpha) and PKC(beta1), produced the greatest degree of inhibition (40%) among the tested protein kinase inhibitors. These results suggest that tyrosine kinases, PKC, and the MEK/MAPK pathway are involved in a fraction of Aroclor 1242-induced activation of PLA(2).

journal_name

Toxicol Appl Pharmacol

journal_title

Toxicology and applied pharmacology

authors

Olivero J,Ganey PE

doi

10.1006/taap.1999.8827

subject

Has Abstract

pub_date

2000-02-15 00:00:00

pages

9-16

issue

eissn

0041-008X

issn

1096-0333

pii

S0041-008X(99)98827-0

journal_volume

163

pub_type

杂志文章

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Role of protein phosphorylation in activation of phospholipase A2 by the polychlorinated biphenyl mixture Aroclor 1242.