Dioxin toxicity, aryl hydrocarbon receptor signaling, and apoptosis-Persistent pollutants affect programmed cell death.
Summary of "Dioxin toxicity, aryl hydrocarbon receptor signaling, and apoptosis-Persistent pollutants affect programmed cell death."
Exogenous ligands of the aryl hydrocarbon receptor (AhR) such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related substances are highly toxic pollutants ubiquitously present in the environment. They cause a variety of toxic effects to different organs and tissues. Among other effects, TCDD exposure to laboratory animals leads to thymus atrophy and immunosuppression on the one hand, and to tumor formation on the other. Apoptosis appears to be involved in both these toxic effects: AhR activation by TCDD was discussed to induce apoptosis of immune cells, leading to the depletion of thymocytes and ultimately immunosuppression. This mechanism could help to explain the highly immunotoxic actions of TCDD but it is nevertheless under debate whether this is the mode of action for immunosuppression by this class of chemical substances. In other cell types, especially liver cells, TCDD inhibits apoptosis induced by genotoxic treatment. In initiation-promotion studies, TCDD was shown to be a potent liver tumor promoter. Among other theories it was hypothesized that TCDD acts as a tumor promoter by preventing initiated cells from undergoing apoptosis. The exact mechanisms of apoptosis inhibition by TCDD are not fully understood, but both in vivo and in vitro studies consistently showed an involvement of the tumor suppressor p53 in this effect. Various strings of evidence have been established linking apoptosis to the detrimental effects of exogenous activation of the AhR. Within this article, studies elucidating the effects of TCDD and related substances on apoptosis signaling, be it inducing or repressing, is to be reviewed.
Institute of Food Chemistry and Toxicology, University of Kaiserslautern, Kaiserslautern, Germany.
This article was published in the following journal.
Name: Critical reviews in toxicology
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21323611
- DOI: http://dx.doi.org/10.3109/10408444.2010.524635
Medical and Biotech [MESH] Definitions
Aryl Hydrocarbon Receptor Nuclear Translocator
Aryl hydrocarbon receptor nuclear translocator is a basic HELIX-LOOP-HELIX MOTIF containing protein that forms a complex with DIOXIN RECEPTOR. The complex binds xenobiotic regulatory elements and activates transcription of a variety of genes including UDP GLUCURONOSYLTRANSFERASE. AhR nuclear translocator is also a subunit of HYPOXIA-INDUCIBLE FACTOR 1.
Hypoxia-inducible Factor 1
A basic helix-loop-helix transcription factor that plays a role in APOPTOSIS. It is composed of two subunits: ARYL HYDROCARBON RECEPTOR NUCLEAR TRANSLOCATOR and HYPOXIA-INDUCIBLE FACTOR 1, ALPHA SUBUNIT.
Glucocorticoid-induced Tnfr-related Protein
A member of the TNF receptor family that was initially identified as a DEXAMETHASONE-induced protein from a T-CELL line. It may play a role in regulating APOPTOSIS and modulating immune response by T-lymphocytes. Signaling by the activated receptor occurs through its association with TNF RECEPTOR-ASSOCIATED FACTORS.
Receptors, Tumor Necrosis Factor, Member 10c
A secreted tumor necrosis factor receptor family member that has specificity for TNF-RELATED APOPTOSIS-INDUCING LIGAND. It plays a modulating role in activation of APOPTOSIS signaling.
A potent epoxide hydrase and aryl hydrocarbon hydroxylase inhibitor. It enhances the tumor-initiating ability of certain carcinogens.
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