ORTHO-SUBSTITUTED POLYCHLORINATED-BIPHENYLS ACTIVATE RESPIRATORY BURST MEASURED AS LUMINOL-AMPLIFIED CHEMOLUMINESCENCE IN HUMAN GRANULOCYTES

The effect of porychlorinated biphenyls (PCBs) on the activation of re spiratory burst measured as luminol-amplified chemoluminescence in hum an granulocytes is elucidated here. Chemoluminescence was stimulated i n a concentration-dependent manner (ED50 =10 mu M) by ortho-substitute d PCB congeners, while meta- and para-substituted congeners had no sig nificant effect. Two ortho-substituted PCB congeners were chosen for t he mechanistic studies, namely 2,2',4,4'-TeCB and 2,2'-DCB, since they have been used in previous studies by others. In the absence of extra cellular calcium, the respiratory burst in response to 2,2'-DCB and 2, 2',4,4'-TeCB was reduced by 63% and 82%, respectively. Bisindolylmalei mide, which inhibits protein kinase C, reduced activated chemoluminesc ence by 2,2'-DCB, 2,2',4,4'-TeCB, N-formylmethionyl-leucyl-phenplalani ne, and phorbol 12-myristate 13-acetate. Neomycin, which inhibits phos pholipase C, had a slight, but significant, effect on the 2,2',4,4'-Te CB-activated chemoluminescence but had a more pronounced effect on the 2,2'-DCB-activated chemoluminescence. 2,2'-DCB and 2,2',4,4'-TeCB sig nificantly increased phospholipase D (PLD) activity measured as the am ount of C-14-phosphatidvlbutanol formed. Ethanol (1%), a phospholipase D modulator, reduced the response to 2,2'-DCB and 2,2',4,4'-TeCB by 7 2% and 75%, respectively. Furthermore, wortmannin (25 nM), a phosphati dylinositol 3-kinase, and genistein, a more unspecific tyrosine kinase inhibitor, reduced chemoluminescence in response to PCB. In conclusio n, our results indicate that PCB-activated chemoluminescence is depend ent on the Ca2+-dependent phospholipase D or phospholipase C, phosphat idylinositol 3-kinase, and protein kinase C activation prior to activa tion of the NADPH oxidase. Defects in neutrophhil functions upon expos ure to PCB may render a greater susceptibility in the host to invading microorganisms or evoke inappropriate inflammatory responses leading to tissue injury. (C) 1998 Academic Press.