title: Protein tyrosine kinase involvement in the production of superoxide anion by neutrophils exposed to Aroclor 1242, a mixture of polychlorinated biphenyls.
abstract: Neutrophils produce superoxide anion (O2-) when exposed in vitro to Aroclor 1242, a mixture of polychlorinated biphenyls (PCBs). The mechanism for this effect shares some similarities with the mechanism by which the physiologic agonist f-Met-Leu-Phe (fMLP) activates neutrophils. Since production of O2- in response to fMLP involves GTP-binding proteins and protein tyrosine kinases (PTKs), the current study was undertaken to determine whether these signalling pathways are involved in PCB-induced neutrophil activation. Neutrophils exposed to Aroclor 1242 or fMLP produced significant O2-. Pretreatment of intact neutrophils with pertussis toxin or cholera toxin or exposure of permeabilized cells to GDPbetaS significantly inhibited O2- production in fMLP-treated neutrophils but did not alter the response to Aroclor 1242. Pretreatment with genistein, an inhibitor of PTKs, significantly inhibited O2- production in both Aroclor 1242- and fMLP-treated neutrophils; however, daidzein, a structural analogue of genistein which lacks activity against PTKs, was without effect. Exposure of neutrophils to Aroclor 1242 resulted in an increase within 1 min in tyrosine phosphorylation of proteins in the 40 and 60 kDa molecular mass ranges which persisted for up to 10 min. Similar results were obtained with 2,2',4,4'-tetrachlorobiphenyl (2,2',4,4'-TCB), a PCB congener that stimulates O2- production. In contrast, 3,3',4,4',5-pentachlorobiphenyl (3,3',4,4',5-PeCB), a congener that does not generate O2-, caused only a transient increase in tyrosine phosphorylation of proteins in the 40 kDa range with no effect on 60 kDa proteins. These data suggest that Aroclor 1242 activates neutrophils to produce O2- by a mechanism that requires tyrosine kinase activity; however, heterotrimeric G-proteins are not likely to be involved.
authors.affiliation: Department of Pharmacology and Toxicology, Institute for Environmental Toxicology, Michigan State University, East Lansing 48824, USA.
authors.forename: P K
authors.initials: PK
authors.lastname: Tithof
authors.forename: S
authors.initials: S
authors.lastname: Watts
authors.forename: P E
authors.initials: PE
authors.lastname: Ganey
mesh_terms: D000818:Animals; D001140:Aroclors / Q000633:toxicity*; D019204:GTP-Binding Proteins / Q000378:metabolism; D019833:Genistein; D007529:Isoflavones / Q000494:pharmacology; D008297:Male; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D018375:Neutrophil Activation; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013481:Superoxides / Q000378:metabolism*
chemical_list: D001140:Aroclors; D007529:Isoflavones; D013481:Superoxides; C027423:aroclor 1242; D009240:N-Formylmethionine Leucyl-Phenylalanine; D011078:Polychlorinated Biphenyls; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D019204:GTP-Binding Proteins