Superfund Research Program

Biomarkers of Exposure to Pulmonary Toxicants

Project Leader: Alan R. Buckpitt
Grant Number: P42ES004699
Funding Period: 1995-2010

Project-Specific Links

Final Progress Reports

Year:   2009  2004  1999 

Pulmonary diseases cause significant morbidity and mortality in the U.S. population. Current approaches to identify those chemicals capable of causing lung toxicity rely on testing in animals. However, species differences in the response to a particular chemical make extrapolation to humans difficult. There were three issues addressed in this project during the past year.

The first is related to completion of work begun sometime ago on merapturic acid diastereomers eliminated in the urine of animals exposed to naphthalene by both parenteral and inhalation routes. Urinary diastereomeric mercapturates have been measured in mice (susceptible) and rats (nonsusceptible) after intraperitoneal (ip) administration (1.56-200 mg/kg) or inhalation exposures (0.8-110 ppm, 4 hrs) to naphthalene. No significant differences were observed in the percentage of dose eliminated as mercapturate in urine between mice (25-34%) and rats (24-35%) or at varying doses after ip administration. Quantities of mercapturate in mouse urine after 10 ppm were similar to 12.5 mg/kg, ip. In mice, the ratio of diastereomeric mercapturates derived from the 1R,2S- to 1S,2R epoxide was 1:1 at low doses (1-3 mg/kg), increased to 3:1 at intermediate doses (50 mg/kg) and decreased to 2:1 at high doses (100/200 mg/kg). In rats, these ratios remained less than 1:1 at all doses. After inhalation, ratios were 5-6:1 at low concentrations (less than 15 ppm) and decreased to 3:1 at higher concentrations (15-100 ppm) in mice while in rats the ratios were 1:1 or less for all concentrations. These studies show that mercapturates provide good assessments of internal dose, and that there are no dramatic differences between species in the percentage eliminated as mercapturate. However, the ratios of mercapturates derived from the 1R,2S- vs 1S,2R- epoxide differ markedly and are consistent with earlier in vitro metabolism studies.

The second issue focuses on the importance of CYP2F2 in the unique susceptibility of mouse lung to a variety of chemicals. Recombinant CYP2F2 has been used to show that this protein catalyzes the rapid turnover of naphthalene, 1-nitronaphthalene and 2-methylnaphthalene to epoxides. It is important to note that recent work has shown that nitronaphthalenes and methylnitronaphthalenes are primary contributors to the mutagenicity of particulate air pollutants in the South Coast air basin of California.

The third focus of the studies conducted over the past year has been to utilize previoulsy prepared cDNA microarray chips to determine whether the pattern of gene regulation is unique for toxicants from different chemical classes. The applications of this would include: categorization of unknown chemicals with respect to possible mechanisms of action and spectrum of toxicities and assessments of the possible synergistic actions of chemical mixtures. Using these tools, researchers have examined gene expression in liver and kidney of mice at varying times after a range of doses of CdCl2, HgCl2, CCl4, dimethylnitrosamine, ethylnitrosourea, trichloroethylene, benzo(a)pyrene, 3-methylcholantherene, and diethylhexylphthalate. Data indicates that the pattern of gene regulation for these chemicals provides a fingerprint, which can be used to categorize the toxicant. For example, CdCl2 markedly upregulates metallothionine I and II and several of the heat shock proteins while both of the PAH's tested upregulated only the Cyp1a1 and 1a2 genes.