title: 2,2',4,4'-Tetrachlorobiphenyl upregulates cyclooxygenase-2 in HL-60 cells via p38 mitogen-activated protein kinase and NF-kappaB.
abstract: Polychlorinated biphenyls (PCBs) are ubiquitous, persistent environmental contaminants that affect a number of cellular systems, including neutrophils. Among the effects caused by the noncoplanar PCB 2,2',4,4'-tetrachlorobiphenyl (2244-TCB) in granulocytic HL-60 cells are increases in superoxide anion production, activation of phospholipase A(2) with subsequent release of arachidonic acid (AA) and upregulation of the inflammatory gene cyclooxygenase-2 (COX-2). The objective of this study was to determine the signal transduction pathways involved in the upregulation of COX-2 by 2244-TCB. Treatment of HL-60 cells with 2244-TCB led to increased expression of COX-2 mRNA. This increase was prevented by the transcriptional inhibitor actinomycin D in cells pretreated with 2244-TCB for 10 min. The increase in COX-2 mRNA was associated with release of (3)H-AA, phosphorylation of p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinases, increased levels of nuclear NF-kappaB and increased superoxide anion production. Bromoenol lactone, an inhibitor of the calcium-independent phospholipase A(2), reduced (3)H-AA release but had no effect on COX-2 mRNA, protein or activity. Pretreatment with SB-202190 or SB-203580, inhibitors of the p38 MAP kinase pathway, prevented the 2244-TCB-mediated induction of COX-2 and phosphorylation of p38 and ERK MAP kinases. These inhibitors did not alter (3)H-AA release. Treatment with PD 98059 or U 0126, inhibitors of the MAP/ERK (MEK) pathway, prevented the 2244-TCB-mediated activation of ERK but had no effect on COX-2 induction or p38 phosphorylation. 2244-TCB treatment did not affect c-Jun N-terminal kinase (JNK) phosphorylation. 2244-TCB exposure increased the amount of nuclear NF-kappaB. This increase was prevented by pretreatment with p38 MAP kinase inhibitors, but not by pretreatment with MEK inhibitors. Pretreatment with inhibitors of NF-kappaB prevented the 2244-TCB-mediated induction of COX-2 mRNA. 2244-TCB-mediated increases in superoxide anion were prevented by the NADPH oxidase inhibitor apocynin or the free radical scavenger 4-hydroxy TEMPO, but neither of these inhibitors affected the 2244-TCB-induced changes in COX-2 mRNA levels or (3)H-AA release. Taken together these data suggest that p38 MAP kinase-dependent activation of NF-kappaB is critical for the 2244-TCB-mediated upregulation of COX-2 mRNA.
authors.affiliation: Department of Pharmacology and Toxicology, Center for Integrative Toxicology and National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Bezdecny
authors.forename: Peer
authors.initials: P
authors.lastname: Karmaus
authors.forename: Robert A
authors.initials: RA
authors.lastname: Roth
authors.forename: Patricia E
authors.initials: PE
authors.lastname: Ganey
mesh_terms: D000704:Analysis of Variance; D016718:Arachidonic Acid / Q000378:metabolism; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D004785:Environmental Pollutants / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D042381:Granulocyte Precursor Cells / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D016328:NF-kappa B / Q000187:drug effects* / Q000378:metabolism; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000187:drug effects*; D018709:Statistics, Nonparametric; D013481:Superoxides / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000187:drug effects* / Q000378:metabolism
chemical_list: D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D012333:RNA, Messenger; D013481:Superoxides; D016718:Arachidonic Acid; C035976:2,4,2',4'-tetrachlorobiphenyl; D011078:Polychlorinated Biphenyls; D051546:Cyclooxygenase 2; D048051:p38 Mitogen-Activated Protein Kinases