Effects of 2,2',4,4'-tetrachlorobiphenyl on granulocytic HL-60 cell function and expression of cyclooxygenase-2.
Polychlorinated biphenyls (PCBs) are persistent environmental contaminants that affect a number of cellular systems, including neutrophils. It has been demonstrated that noncoplanar PCBs (i.e., ortho- substituted PCBs) alter function of primary rat neutrophils. The objectives of these experiments were to determine if responses in a human, neutrophil-like cell line exposed to PCBs were similar to those reported for rat neutrophils and to explore further PCB-mediated alterations in neutrophil function. The human promyelocytic leukemia cell line (HL-60) was differentiated with DMSO to a neutrophil-like phenotype. Treatment of differentiated HL-60 cells with 2,2',4,4'-tetrachlorobiphenyl, a noncoplanar, ortho-substituted PCB congener, caused an increase in f-Met-Leu-Phe-induced degranulation, as measured by release of myeloperoxidase (MPO). Treatment with the coplanar, non-ortho-substituted congener 3,3',4,4'-tetrachlorobiphenyl had no effect on MPO release. 2,2',4,4'-Tetrachlorobiphenyl caused a time- and dose-dependent release of [3H]-arachidonic acid (3H-AA). A significant increase in 3H-AA release was observed after 60 min of exposure, and concentrations of 10 microM or larger increased 3H-AA release. In contrast, 3,3',4,4'-tetrachlorobiphenyl had no effect on 3H-AA release. The effect of PCBs on mRNA levels for cyclooxygenase-2 (COX-2) was examined using semiquantitative RT-PCR. COX-2 mRNA was significantly elevated in response to 2,2',4,4'-tetrachlorobiphenyl in a concentration-dependent manner. COX-2 expression was maximal by 30 min of exposure to 2,2',4,4'-tetrachlorobiphenyl. COX-2 protein and activity were also increased after exposure to 2,2',4,4'-tetrachlorobiphenyl; COX-1 protein and activity were unaffected. 3,3',4,4'-Tetrachlorobiphenyl did not increase COX-2 mRNA levels. These results demonstrate that a noncoplanar PCB alters the functional status of granulocytic HL-60 cells, causing enhanced degranulation and upregulation of COX-2, whereas a coplanar PCB lacks this activity. These data suggest that noncoplanar PCBs alter HL-60 cell function and COX-2 expression via an Ah-receptor-independent mechanism.
Bezdecny
Steven A
SA
Department of Pharmacology and Toxicology, Center for Integrative Toxicology and National Food Safety and Toxicology Center, Michigan State University, East Lansing, Michigan 48824, USA.
Roth
Robert A
RA
Ganey
Patricia E
PE
D016718:Arachidonic Acid / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects*; D051546:Cyclooxygenase 2; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018922:HL-60 Cells / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D008565:Membrane Proteins; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology; D009195:Peroxidase / Q000378:metabolism; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014316:Tritium
D004785:Environmental Pollutants; D008565:Membrane Proteins; D012333:RNA, Messenger; D014316:Tritium; D016718:Arachidonic Acid; C035976:2,4,2',4'-tetrachlorobiphenyl; D011078:Polychlorinated Biphenyls; D009195:Peroxidase; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases