title: Cytokine gene expression during ontogeny in murine thymus on activation of the aryl hydrocarbon receptor by 2,3,7,8-tetrachlorodibenzo-p-dioxin.
abstract: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) binds and activates the aryl hydrocarbon receptor (Ah-R), an endogenous transcription factor that is expressed in the thymus. TCDD exposure leads, among other effects, to thymus atrophy and immunosuppression. We previously analyzed the interference of TCDD with differentiation processes in fetal thymus organ cultures and found that in the presence of TCDD, the proliferation rate of immature (CD4- CD8- and CD4- CD8+ HSA+) thymocytes is inhibited, whereas the maturation along the CD4/CD8 path is accelerated. Moreover, the differentiation of thymocytes is skewed by TCDD at < or = 40% (compared with approximately 15% without TCDD) of the CD8 single-positive subset of future cytotoxic T cells, and apparently more cells audition for and pass positive selection. The fetal murine thymus expresses functional Ah-R mRNA, as shown by reverse transcription-polymerase chain reaction and TCDD-inducible CYP1A1 and CYP1B1 expression. Because the differentiation of thymocytes is to a considerable extent controlled by cytokines and many cytokine genes are potential targets of the Ah-R due to Ah-R-binding elements (xenobiotic response elements) in their promoters, we analyzed the cytokine expression in fetal thymus organ culture exposed to TCDD. Fetal thymi were cultured from gestation day 15 for < or = 8 days, thus covering ex vivo the period after population of the thymus anlage until birth. We show with semiquantitative reverse transcription-polymerase chain reaction that more interleukin (IL)-1beta, IL-2, IL-6, tumor growth factor (TGF)-beta3, and tumor necrosis factor-alpha are produced in TCDD-exposed thymi, whereas other cytokines (e.g., TGF-beta1, PAI-2, or IL-4) are only slightly up- and down-modulated during the culture period or not modulated at all (e.g., IL-1beta, IL-7, interferon-gamma, and TGF-beta2).
authors.affiliation: Medical Institute of Environmental Hygiene, Heinrich-Heine-University of Düsseldorf, Germany.
authors.forename: Z W
authors.initials: ZW
authors.lastname: Lai
authors.forename: C
authors.initials: C
authors.lastname: Hundeiker
authors.forename: E
authors.initials: E
authors.lastname: Gleichmann
authors.forename: C
authors.initials: C
authors.lastname: Esser
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D015139:Blotting, Southern; D019363:Cytochrome P-450 CYP1A1 / Q000187:drug effects / Q000235:genetics; D065633:Cytochrome P-450 CYP1B1; D016207:Cytokines / Q000235:genetics*; D004268:DNA-Binding Proteins; D005260:Female; D005333:Fetus / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009924:Organ Culture Techniques; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D016133:Polymerase Chain Reaction; D018336:Receptors, Aryl Hydrocarbon / Q000187:drug effects* / Q000235:genetics; D013950:Thymus Gland / Q000187:drug effects* / Q000378:metabolism; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics
chemical_list: C497397:Arnt protein, mouse; D016207:Cytokines; D004268:DNA-Binding Proteins; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001189:Aryl Hydrocarbon Hydroxylases; C585498:Cyp1b1 protein, mouse; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1