Grantee Research Project Results
Final Report: Mechanism(s) of Chloroethylene-Induced Autoimmunity
EPA Grant Number: R826409Title: Mechanism(s) of Chloroethylene-Induced Autoimmunity
Investigators: Pumford, Neil R. , Gilbert, Kathleen M.
Institution: University of Arkansas for Medical Sciences , University of Arkansas
EPA Project Officer: Aja, Hayley
Project Period: March 25, 1998 through March 24, 2001
Project Amount: $374,384
RFA: Exploratory Research - Human Health (1997) RFA Text | Recipients Lists
Research Category: Human Health
Objective:
The overall estimation for the number of people afflicted with autoimmune diseases in the United States exceeds 8.5 million, or approximately one in every 31 Americans. The development of autoimmune diseases (e.g., rheumatoid arthritis, systemic lupus erythematosus, systemic scleroderma) is believed to be multifactorial, involving both genetic and environmental components. Chemical exposures may be a major environmental influence on the development of autoimmune diseases. There is ample evidence supporting an association of chlorinated ethylenes with life-threatening autoimmune disorders such as systemic lupus erythematosus and scleroderma. However, the mechanisms by which chlorinated ethylenes cause autoimmunity are unknown.
We hypothesized that chlorinated ethylenes are metabolized to reactive intermediates that initiate an autoimmune response. The autoimmune response involves the activation of CD4+ T-cells that are stimulated by either a specific response against the chlorinated ethylene-modified proteins or a nonspecific response initiated through the release of serum factors, such as cytokines, growth factors, or unidentified factors. Either pathway will result in the activation of T-cells, which can lead to the development of inflammation.
We have shown previously that chronic exposure to trichloroethylene (TCE) in the water supply at levels commensurate with occupational exposure can promote the development of autoimmune disease (lupus and autoimmune hepatitis) in MRL+/+ mice. TCE-induced autoimmunity was accompanied by the expansion of activated CD4+ T-cells secreting increased levels of IFN-g.
Summary/Accomplishments (Outputs/Outcomes):
Human hepatocytes exposed to TCE contain TCE protein adducts similar to that found in treated rat hepatocytes. TCE in the drinking water accelerates an autoimmune response in MRL+/+ mice. CD4+ T-cells from TCE-treated mice are activated when compared to nontreated control CD4+ T-cells. The activated CD4+ T-cells secrete cytokines consistent with Th1 type of cytokines or inflammatory cytokines. Protein adduct formation is dose and time dependent following exposure in mice to TCE. Mice treated with TCE contain antibodies specific for the chemical-modified protein. There appears to be a nonspecific and specific activation of T-cells following treatment with TCE.
We investigated the possibility that TCE caused oxidative stress in MRL+/+ mice. Liver homogenate was tested for heme-protein adducts using a recently developed assay for oxidative stress. There was a dose-responsive increase in heme-protein adducts at 50 kDa and at approximately 25 kDa. Oxidative stress was even found at the lowest treatment of 21 mg/kg/day. We investigated the expression of stress proteins in the liver for additional evidence of oxidative stress in MRL+/+ mice treated with TCE. We found a dose dependent increase in the stress proteins BiP/GRP78 and endoplasmin; these are both luminal ER proteins and important chaperones. Our final evidence for oxidative stress as a mechanism in autoimmune disease caused by TCE was the demonstration of a dramatic increase reactive nitrogen species (RNS). The most sensitive marker for RNS is the reaction of peroxynitrite with tyrosine groups on proteins forming nitrotyrosine-protein adducts. Using immunohistochemistry we showed an increase in nitrotyrosine-protein adducts in the liver following TCE treatment in MRL +/+ mice. The adducts primarily are associated with kupffer cells in the liver.
Because TCE metabolism is required to promote autoimmunity, we investigated whether the immunoregulatory effects of TCE was mediated by one of its major metabolites, trichloroacetaldehyde (TCA). TCA costimulated the proliferation of murine Th1 cells in vitro. In addition to memory T-cells, TCA also activated naïve T-cells, stimulating expression of activation markers on CD4+ T-cells from MRL +/+ mice. TCA's stimulatory effects were associated with the formation of a Schiff base on T-cell surface proteins. It is hypothesized that Schiff base formation on T-cells nonspecifically stimulates T-cells, leading to autoimmune disease.
This is the first example of an environmental pollutant accelerating an autoimmune disease in an animal model. We have elicited the mechanisms involved in the acceleration of an autoimmune response by the environmental contaminant TCE to include nonspecific activation of T-cells through interaction of cell surface molecules with metabolites of TCE. We also have shown involvement of macrophage and endothelial cells in the exacerbation of autoimmune disease by TCE. The model uses treatment doses in autoimmune prone mice that are environmentally relevant, and this model can now be used to screen other environmentally important toxicants.
Grants will be submitted for further funding to both the U.S. Environmental Protection Agency and the National Institutes of Health. The laboratory will continue to work on environmental pollution and autoimmune disease. A major metabolite of TCE, dichloroacetaldehyde, a disinfection byproduct, will be a focus of continuing investigations. Investigations into the mechanisms as well as potential preventive treatment will continue to be a focus of our investigations.
Journal Articles on this Report : 6 Displayed | Download in RIS Format
| Other project views: | All 21 publications | 6 publications in selected types | All 6 journal articles |
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Gilbert KM, Griffin JM, Pumford NR. Trichloroethylene activates CD4+ T cells: potential role in an autoimmune response. Drug Metabolism Reviews 1999;31(4):901-916. |
R826409 (1999) R826409 (Final) |
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Griffin JM, Lipscomb JC, Pumford NR. Covalent binding of trichloroethylene to proteins in human and rat hepatocytes. Toxicology Letters 1998;95(3):173-181. |
R826409 (Final) |
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Griffin JM, Gilbert KM, Pumford NR. Inhibition of CYP2E1 reverses CD4+ T cell alterations in trichloroethylene-treated MRL+/+ mice. Toxicological Sciences 2000;54(2):384-389. |
R826409 (1999) R826409 (Final) |
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Griffin JM, Gilbert KM, Pumford NR. Cytochrome P450 2E1 metabolism of trichloroethylene accelerates an autoimmune response in MRL+/+ mice. Toxicological Sciences 1999;48(1-S):792 |
R826409 (Final) |
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Griffin JM, Gilbert KM, Lamps LW, Pumford NR. CD4+ T-cell activation and induction of autoimmune hepatitis following trichloroethylene treatment in MRL+/+ mice. Toxicological Sciences, 2000;57(2):345-352. |
R826409 (2001) R826409 (Final) |
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Griffin JM, Blossom SJ, Jackson SK, Gilbert KM, Pumford NR. Trichloroethylene accelerates an autoimmune response in association with Th1 T-cell activation in MRL+/+ mice. Immunopharmacology, 2000;46(2):123-137. |
R826409 (1999) R826409 (Final) |
not available |
Supplemental Keywords:
volatile organic compound, VOC, solvent, effects, drinking water, pathology, disinfection, intermediates, metabolism, human health, genetic predisposition, sensitive populations, susceptibility., RFA, Health, Scientific Discipline, Toxics, Waste, Environmental Chemistry, Genetics, Health Risk Assessment, VOCs, Environmental Microbiology, Risk Assessments, Susceptibility/Sensitive Population/Genetic Susceptibility, Disease & Cumulative Effects, Biochemistry, Hazardous Waste, genetic susceptability, 33/50, Hazardous, health effects, sensitive populations, biomarkers, chloroethylene autoimmunity, effects assessment, cytochrome P450, lupus erythematosus, scleroderma, chlorinated ethylenes, cytokines, gene-environment interaction, Tetrachloroethylene, exposure, genetic predisposition, Lymphocytes, Trichloroethylene, human exposure, rheumatoid arthritis, chemical releases, hazardous chemicals, environmentally caused disease, human susceptibility, metabolism, chloroethylenes, air emissions, Vinyl chloride, exposure assessment, groundwater, immune response, autoimmune diseases, occupational exposure, autoimmunity, air contaminant exposureProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.