ABSTRACT
Traditional risk assessment of potential endocrine-disruptive pollutants, including PCBs, focus mainly on the effects of parent compounds. Still, biotransformation results in systemic exposure to PCBs and their bioactive metabolites. In the present paper, the effects of twenty ultra-pure non-dioxin-like (NDL) PCBs and their environmentally relevant hydroxy- (OH-) and methylsulfonyl- (MeSO(2)-) metabolites on aromatase activity and their glucocorticoid properties were investigated. Although most NDL-PCBs were inactive, PCB28 inhibited aromatase activity in human placenta microsomes with an IC(50) of 2.2µM. Most of these NDL-PCBs were weak (ant-)agonist of the glucocorticoid receptor (GR). Interestingly, four OH-metabolites of the commonly found NDL-PCB180 were able to inhibit aromatase activity (LOECs in the low µM range) and showed anti-glucocorticoid properties (LOECs in the low nM range), in a concentration-dependent manner. Further, four MeSO(2)-PCBs slightly inhibited aromatase activity and showed anti-glucocorticoid properties. Although, these effects were also associated with cytotoxicity, they were dependent on the position of the MeSO(2)-group on the biphenyl ring. Our results are the first to show that OH-PCBs are both anti-glucocorticoids and aromatase inhibitors. Taken together, these results for PCBs again support the common idea that risk assessment of the endocrine disruptive potential of PCBs should also include their metabolites.
Subject(s)
Aromatase Inhibitors/toxicity , Endocrine Disruptors/toxicity , Mesylates/toxicity , Polychlorinated Biphenyls/toxicity , Receptors, Glucocorticoid/antagonists & inhibitors , Aromatase/biosynthesis , Aromatase/chemistry , Aromatase Inhibitors/chemistry , Aromatase Inhibitors/metabolism , Cell Line , Cell Survival/drug effects , Endocrine Disruptors/chemistry , Endocrine Disruptors/metabolism , Enzyme Induction/drug effects , Female , Genes, Reporter/drug effects , Humans , Hydroxylation , Mesylates/chemistry , Microsomes/enzymology , Osmolar Concentration , Placenta/enzymology , Polychlorinated Biphenyls/chemistry , Polychlorinated Biphenyls/metabolism , Pregnancy , Pregnancy Proteins/antagonists & inhibitors , Receptors, Glucocorticoid/agonists , Receptors, Glucocorticoid/genetics , Receptors, Glucocorticoid/metabolism , Recombinant Fusion Proteins/agonists , Recombinant Fusion Proteins/antagonists & inhibitors , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Response Elements/drug effects , Risk Assessment/methodsABSTRACT
An inter-laboratory exercise was performed with a yeast estrogen bioassay, based on the expression of yeast enhanced green fluorescent protein (yEGFP), for the determination of estrogenic activity in extracts of calf urine samples. Urine samples were spiked with 1 and 5 ngmL(-1) 17beta-estradiol and 17alpha-ethynylestradiol, 10 and 50 ngmL(-1) mestranol, and 100 ngmL(-1) testosterone and progesterone. Sample extracts of blank and spiked urine samples were prepared at our laboratory and sent to seven laboratories together with a reagent blank, a DMSO blank, and eight 17beta-estradiol stock solutions in DMSO ranging in concentration from 0 to 545 ngmL(-1). Sample extracts and standards were coded and tested blindly. A decision limit (CCalpha) was determined based on the response of seven blank urine samples. Signals of the negative controls, e.g. urine samples spiked with 100 ngmL(-1) testosterone or progesterone, were all below the determined CCalpha and were thus screened as compliant. Positive controls, i.e. the urine samples spiked at two levels with 17beta-estradiol, 17alpha-ethynylestradiol and mestranol, were almost all screened as suspect, i.e. gave signals above the determined CCalpha. Determined EC(50) values calculated from the 17beta-estradiol dose-response curves obtained by the seven laboratories ranged from 0.59 to 0.95 nM.
Subject(s)
Biological Assay/methods , Estrogens/urine , Yeasts/metabolism , Animals , Biological Assay/standards , Cattle , Clinical Laboratory Techniques , Estrogens/chemistry , Estrogens/isolation & purification , Green Fluorescent Proteins/chemistry , Luminescent Agents/chemistryABSTRACT
It is well known that ultraviolet (UV) radiation induces erythema, immunosuppression and carcinogenesis. We hypothesized that chronic exposure to solar UV radiation induces adaptation that eventually prevents the suppression of acquired immunity. We studied adaptation for UV-induced immunosuppression after chronic exposure of mice to a suberythemal dose of solar simulated radiation (SSR) with Cleo Natural lamps, and subsequent exposure to an immunosuppressive dose of solar or UVB radiation (TL12). After UV dosing, the mice were sensitized and challenged with either diphenylcyclopropenone (DPCP) or picryl chloride (PCl). To assess the adaptation induced by solar simulated radiation, we measured the proliferative response and cytokine production of skin-draining lymph node cells after immunization to DPCP, the contact hypersensitivity (CHS) response to PCl, and thymine-thymine (T-T) cyclobutane dimers in the skin of mice. After induction of immunosuppression by SSR or by TL12 lamps, the proliferative response of draining lymph node cells after challenge with DPCP, or the CHS after challenge with PCl, showed significant suppression of the immune response. Chronic irradiation from SSR preceding the immunosuppressive dose of UV failed to restore the suppressed immune response. Reduced lipopolysaccharide-triggered cytokine production (of IL-12p40, IFN-gamma, IL-6 and TNF-alpha) by draining lymph node cells of mice sensitized and challenged with DPCP indicated that no adaptation is induced. In addition, the mice were not protected from T-T dimer DNA damage after chronic solar irradiation. Our studies reveal no evidence that chronic exposure to low doses of SSR induces adaptation to UV-induced suppression of acquired immunity.
