Superfund Research Program
Effects Related Biomarkers of Toxic Exposures
Project Leader: Terrance J. Kavanagh
Grant Number: P42ES004696
Funding Period: 1995 - 2006
Many contaminants at Superfund sites are known to cause oxidative stress through their reactions with biologically important molecules including proteins, lipids and DNA. Oxidative stress plays an important role in a number of diseases including cardiovascular disease, pulmonary fibrosis, diabetes, Parkinson's disease and Alzheimer's disease. Because the endogenous antioxidant glutathione serves an important protective role against chemically-induced oxidative stress, and because glutathione is altered in a number of diseases, project investigators have begun to examine the role of the rate limiting enzyme in glutathione synthesis, glutamate-cysteine ligase (GCL), in their pathophysiology. In preliminary studies, they have found that a genetic variation that occurs quite commonly in GCL in humans is associated with disease severity in cystic fibrosis (CF) and in the age of onset of type 1 diabetes mellitus (T1DM) in female patients.
Using mouse embryonal cell technology, Dr. Kavanagh's team has generated mice missing the GCL modulatory subunit (GCLM) gene. They replaced a part of this gene with a bacterial gene that will allow them to monitor the expression of the GCLM gene by a simple staining technique. These mice will be used to assess the effects of oxidative stress inducing agents on GCLM expression in vivo and to determine the role of GCLM in protecting mice from oxidative stress.
In collaboration with Dr. Hooper, these researchers have assessed whether GCL genes are appropriate biomarkers of heavy metal exposure in small mammals captured at a Superfund site (Anaconda Smelter site, MT). They have examined GCLC, GCLM, and metallothionein (MT) gene expression in the livers of deer mice captured at this site. In separate studies, Dr. Hooper and colleagues had established the extent of heavy metal contamination (arsenic, cadmium, lead, zinc, and copper) in these animals. Project investigators have found a correlation between gene expression and liver cadmium and lead concentrations, depending upon the gender and age of the animals. Interestingly, a correlation has also been found between GCLC and GCLM mRNA expression suggesting possible co-regulation.
Taken together, these results confirm the utility of GCL as a biomarker of exposure to chemicals that cause oxidative stress and underscore its potential importance as a marker of susceptibility in humans exposed at Superfund sites. They also suggest that GCL expression in wildlife might serve as a sensitive biomarker to measure the effectiveness of remediation efforts at Superfund sites.