Grantee Research Project Results

Final Report: Screening Disinfection Byproducts (DBPs) for Their Ability To Promote Autoimmunity

EPA Grant Number: R829417E02
Title: Screening Disinfection Byproducts (DBPs) for Their Ability To Promote Autoimmunity
Investigators: Gilbert, Kathleen M. , Pumford, Neil R.
Institution: University of Arkansas - Little Rock
EPA Project Officer: Chung, Serena
Project Period: May 24, 2002 through May 23, 2004 (Extended to May 23, 2005)
Project Amount: $250,000
RFA: EPSCoR (Experimental Program to Stimulate Competitive Research) (2001) RFA Text |  Recipients Lists
Research Category: EPSCoR (The Experimental Program to Stimulate Competitive Research)

Objective:

This work included a two-level in vivo screening procedure to directly examine the autoimmune-promoting capacity of disinfection by-products (DBPs). In the level-one screen (Objective I), inbred MRL/+ mice were treated for 4 weeks with trichloroethylene (TCE) CYP2E1 metabolites (i.e., chloral hydrate, TCA and DCA) in the drinking water. To determine whether the autoimmune-promoting capacity of DBPs is limited to TCE metabolites, three other DBPs of the halomethane class that have been reported to induce immune system alterations (i.e., chloroform, bromodichloromethane, and chlorodibromomethane) also were tested. The mice were examined for serological signs of autoimmune disease, as well as T cell expression of CD44. Because chronic treatment with a low dose of DBPs is probably most relevant to actual environmental exposure, the level two screen (Objective II) was used to confirm that two DBPs identified as effective in Objective I can induce autoimmune disease and CD4⁺ T cell alterations when administered to MRL/+ mice at lower concentrations for a longer time period (40 weeks). Lastly, in parallel with the in vivo experiments, we attempted to develop an in vitro screening assay in which flow cytometry was used to determine whether DBPs upregulate CD44 in CD4⁺ T cells in vitro (Objective III).

Summary/Accomplishments (Outputs/Outcomes):

Trichloroacetaldehyde hydrate (TCAH) and trichloroacetic acid (TCA) were administered to the drinking water of MRL+/+ mice for 4 weeks. CD4⁺ T cells from TCAH and TCA-treated MRL+/+ mice, unlike CD4⁺ T cells from control mice, demonstrated functional and phenotypic signs of activation, as evidenced by increased IFN-γ production in association with the increased percentage of CD62^lo CD4⁺ T cells. Interestingly, it was also found that the CD4⁺ T cells from the TCAH and TCA-treated mice showed a decreased susceptibility to the activation-induced cell death (AICD) form of apoptosis following re-stimulation in vitro. Demonstrating that TCAH and TCA can activate CD4⁺ T cells and inhibit their apoptosis following in vivo exposure represents a mechanism by which environmental toxicants may induce or accelerate the development of autoimmune disease.

Trichloroacetaldehyde (TCAA), at concentrations ranging from 0.04 to 1 mM, co-stimulated proliferation of murine T-helper type 1 (Th1) cells treated with anti-CD3 antibody or antigen in vitro. TCAA at similar concentrations also induced phenotypic alterations commensurate with activation (upregulation of CD28 and downregulation of CD62L) in both cloned memory Th1 cells, as well as naive CD4⁺ T cells from MRL+/+ mice. TCAA-induced Th1 cell activation was accompanied by phosphorylation of activating transcription factor 2 (ATF-2) and c-Jun, two components of the activator protein-1 (AP-1) transcription factor. TCAA at higher concentrations was also shown to form a Schiff base on T cells, and inhibition of Schiff base formation suppressed the ability of TCAA to phosphorylate ATF-2. Taken together, these results suggest that TCAA promotes T-cell activation via stimulation of the mitogen-activated protein (MAP) kinase pathway in association with Schiff base formation on T-cell surface proteins. By demonstrating that TCAA can stimulate T-cell function directly, these results may explain how the environmental toxicant TCE promotes T-cell activation and related autoimmunity in vivo.

Conclusions:

We have demonstrated that treatment of MRL+/+ mice with low doses of DBPs in vivo results in the development of immune system alterations commensurate with autoimmune disease.

We also found that in vivo or in vitro exposure to certain DBPs inhibits activation-induced cell death in T cells, a mechanism that has been shown to promote autoimmune disease. Based on this work, Dr. Blossom, a postdoctoral fellow supported by this grant, was awarded a travel grant to present the data at the 12th International Congress of Immunology in Montreal in July 2004. In addition, she examined the mechanism by which DBPs alter T cell apoptosis, and this work produced some very exciting and novel results. Dr. Gilbert published work showing that one of the DBPs described in the grant can promote signaling via Schiff base formation in T cells in vitro. The connection between T cell signaling and alterations in T cell apoptosis is now being explored. Dr. Pumford, our collaborator at the University of Arkansas in Fayetteville, provided invaluable help with toxicological evaluations of the treated mice and published a manuscript concerning the ability of toxicants including DBPs to promote autoimmune hepatitis in mice.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Publications Views

Other project views:	All 5 publications	2 publications in selected types	All 2 journal articles

Publications

Type	Citation	Project	Document Sources
Journal Article	Gilbert KM, Whitlow A, Pumford NR. Environmental contaminant and disinfection by-product trichloroacetaldehyde stimulates T cells in vitro. International Journal of Immunopharmacology 2004;4(1):25-36.	R829417E02 (2002) R829417E02 (2003) R829417E02 (Final)	not available

Supplemental Keywords:

lupus, immunotoxicology, disinfection byproducts, animal model, autoimmunity,, Health, RFA, Scientific Discipline, PHYSICAL ASPECTS, INTERNATIONAL COOPERATION, Geographic Area, Water, POLLUTANTS/TOXICS, Health Risk Assessment, Physical Processes, Risk Assessments, State, Environmental Chemistry, Drinking Water, Water Pollutants, ecological risk assessment, water quality, bioindicator, environmental risks, human exposure, animal model, Arkansas, drinking water system, drinking water treatment, exposure, other - risk assessment, autoimmunity, disinfection byproducts, chemical byproducts, diagnostic tool, disinfection byproducts (DPBs), biomarker, human health risk, alternative disinfection methods

Progress and Final Reports:

Original Abstract

2002 Progress Report

2003 Progress Report