1999 Progress Report: PAH Metal Mixtures-Human in Vitro Mutagenicity Studies
EPA Grant Number:
PAH Metal Mixtures-Human in Vitro Mutagenicity Studies
The State University of New York at Albany
EPA Project Officer:
Klieforth, Barbara I
November 1, 1998 through
October 31, 2001
(Extended to October 31, 2003)
Project Period Covered by this Report:
November 1, 1998 through October 31, 1999
Chemical Mixtures in Environmental Health (1998)
Land and Waste Management
Intensive investigations are underway to address the long-term goal of assessing carcinogenic risks from exposure to environmental polycyclic aromatic hydrocarbon (PAH)/metal mixtures. In particular, studies were directed at elucidating the effects and mechanisms of mixtures of the most hazardous PAHs and metals on the induction of CYP1A1, 1A2, and 1B1 in human cells by each of the PAHS; and at determining the effects of mixtures of PAHs and metals on the susceptibility of PAHs individually to be bioactivated by CYP1 and epoxide hydrolase and to produce mutations in human cells.
Environmental PAHs and metals coexist, and such mixtures could affect the carcinogenicity of PAHs. One possible mechanism involves modification of PAH induction of the PAH-bioactivating CYP1A and 1B. The effect on PAH-mediated CYP1A and 1B induction of As, Pb, Hg, or Cd (ranked as the most hazardous environmental metals by EPA and ATSDR) has thus been investigated. Human, hepatic HepG2 tumor cells, hepatocytes, and T-47D cells were selected as models. Induction of CYP1A1 by benzo[a]pyrene (BAP), benzo[b]fluoranthene (BBF), dibenzo[a,h]anthracene (DBAHA), benzo[a]anthracene (BAA), or benzo[k]fluoranthene (BKF) was probed by ethoxyresorufin-O-deethylase activity (EROD) in multi-well plates of cells. Cells rapidly took up PAHs from the medium; by 24 hours, only 14 percent remained in the medium, and no detectable PAH bound to well walls. Induction efficiency (relative to dimethyl sulfoxide controls) was, for example, in the order DBAHA (29-fold) > BKF (19-fold) > BAA (7-fold) > BAP (6-fold) > BBF (1-fold). The metals did not affect cell viability up to concentrations of: As, 5 µM; Pb, 250 µM; Hg, 5 µM; and Cd, 2.5 µM. At 1 µM, all of the metals decreased levels of PAH-induced CYP1A and CYP1B1 activities (inhibition of metabolic activity was excluded) by variable extents and in a PAH-dependent manner. With BAP as inducer, decreases in induction were, for example: As, 33 percent; Cd, 29 percent; Hg, 19 percent; and Pb 13 percent. Future studies will resolve the mechanism of metal-mediated decreases in PAH induction. We conclude that these metals in environmental PAH mixtures could diminish PAH carcinogenic potential by decreasing PAH-mediated induction of their bioactivation by CYP1A1.
The second year will be devoted to extending our observations of the effects of the metals in greatly diminishing the induction of human CYP1A and 1B by PAHs to mixtures of the metals, and to mechanistic evaluations using molecular biology techniques. Studies will be conducted with mixtures of the five PAHs to determine how they influence each other's CYP1 induction in human hepatocytes and human cell lines. Engineered human lymphoblastoid cells expressing CYP1A1, 1A1, and 1B1 individually and CYP1A1 and 1B1 together, each transfected with human epoxide hydrolase, will be used to test for effects of metals and other PAHs on PAH-mediated DNA damage by evaluating unscheduled DNA synthesis.
No journal articles submitted with this report: View all 25 publications for this project
polycyclic aromatic hydrocarbon, PAH, metals, metabolism, carcinogen, mutagen, cellular, enzymes, biology.
, RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, Waste, Environmental Chemistry, Health Risk Assessment, chemical mixtures, Risk Assessments, Biochemistry, Physical Processes, Molecular Biology/Genetics, mutagenic properties, exposure, environmental mutagens, mutatgenicity studies, PAH, PAH metal mixtures, characterizing chemical mixtures, human exposure, bioactivation, bioaccumulation, cancer risk, environmental chemicals, human health risk, carcinogenic, cell culture, epoxide hydrolase enzyme, human in vitro mutagenicity studies
Progress and Final Reports:
2000 Progress Report
2001 Progress Report
2002 Progress Report