title: In utero exposure to benzene disrupts fetal hematopoietic progenitor cell growth via reactive oxygen species.
abstract: It is hypothesized that the increasing incidence of childhood leukemia may be due to in utero exposure to environmental pollutants, such as benzene, but the mechanisms involved remain unknown. We hypothesize that reactive oxygen species (ROS) contribute to the deregulation of fetal hematopoiesis caused by in utero benzene exposure. To evaluate this hypothesis, pregnant C57Bl/6N mice were exposed to benzene or polyethylene glycol-conjugated catalase (PEG-catalase) (antioxidative enzyme) and benzene. Colony formation assays on fetal liver cells were performed to measure erythroid and myeloid progenitor cell growth potential. The presence of ROS in CD117(+) fetal liver cells was measured by flow cytometric analysis. Oxidative cellular damage was assessed by Western blot analysis of 4-hydroxynonenol (4-HNE) and nitrotyrosine products, as well as reduced to oxidized glutathione ratios. Alterations in the redox-sensitive signaling pathway nuclear factor-kappa-light-chain-enhancer of activated B cells (NF-kappaB) were measured by Western blot analysis of Inhibitor of NF-kB-alpha (IkappaB-alpha) protein levels in fetal liver tissue. In utero exposure to benzene caused a significant increase in ROS production and significantly altered fetal liver erythroid and myeloid colony numbers but did not increase the levels of 4-HNE or nitrotyrosine products or alter reduced to oxidized glutathione ratios. However, in utero exposure to benzene did cause a significant decrease in fetal liver IkappaB-alpha protein levels, suggesting activation of the NF-kappaB pathway. Benzene-induced ROS formation, abnormal colony growth, and decreased IkappaB-alpha levels were all abrogated by pretreatment with PEG-catalase. These results suggest that ROS play a key role in the development of in utero-initiated benzene toxicity potentially through disruption of hematopoietic cell signaling pathways.
authors.affiliation: Department of Pharmacology and Toxicology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Badham
authors.forename: Louise M
authors.initials: LM
authors.lastname: Winn
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001554:Benzene / Q000633:toxicity*; D015153:Blotting, Western; D002374:Catalase / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004785:Environmental Pollutants / Q000633:toxicity*; D005260:Female; D053686:Fetal Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005434:Flow Cytometry; D005865:Gestational Age; D019803:Glutathione Disulfide / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D020672:I-kappa B Proteins / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D018811:Maternal Exposure; D051379:Mice; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011247:Pregnancy; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013997:Time Factors; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D000447:Aldehydes; D000975:Antioxidants; D004785:Environmental Pollutants; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D017382:Reactive Oxygen Species; C070295:catalase-polyethylene glycol; D000072000:NF-KappaB Inhibitor alpha; C002744:3-nitrotyrosine; D011092:Polyethylene Glycols; D014443:Tyrosine; D002374:Catalase; D019009:Proto-Oncogene Proteins c-kit; D001554:Benzene; C027576:4-hydroxy-2-nonenal; D019803:Glutathione Disulfide