In vitro and in vivo evidence for anti-inflammatory properties of 2-methoxyestradiol

2-Methoxyestradiol (2MEO) is an endogenous metabolite of 17β-estradiol that interacts with estrogen receptors and microtubules. It has acute anti-inflammatory activity in animal models that is not attributable to known antiproliferative or antiangiogenic actions. Because macrophages are central to the innate inflammatory response, we examined whether suppression of macrophage activation by 2MEO could account for some of its anti-inflammatory effects. Inflammatory mediator production stimulated by lipopolysaccharide (LPS) and interferon-γ in the J774 murine macrophage cell line or human monocytes was measured after treatment with 2MEO or the anti-inflammatory agent dexamethasone. The effect of these agents on LPS-induced acute lung inflammation in mice was also examined. 2MEO suppressed J774 macrophage interleukin-6 and prostaglandin E₂ production (by 30 and 47%, respectively, at 10 μM) and human monocyte tumor necrosis factor-α production (by 60% at 3 μM). Estradiol had no effect on J774 macrophage activation, nor did the estrogen receptor antagonist 7α-[9-[(4,4,5,5,5-pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17β-diol (ICI 182,780) prevent the effects of 2MEO. The actions of 2MEO were not mimicked by the microtubule-interfering agents colchicine or paclitaxel. In mice exposed to LPS, bronchoalveolar lavage protein content, a measure of vascular leak and epithelial injury, was reduced to a comparable extent (~54%) by treatment with 2MEO (150 mg · kg⁻¹) or dexamethasone (1 mg · kg⁻¹). In addition, 2MEO reduced LPS-induced interleukin-6 gene expression. Thus, 2MEO modulates macrophage activation in vitro and has high-dose acute anti-inflammatory activity in vivo. These findings are consistent with the acute anti-inflammatory actions of 2MEO being mediated in part by the suppression of macrophage activation.

Derivation of a bisphenol A oral reference dose (RfD) and drinking-water equivalent concentration

Human exposure to bisphenol A (BPA) is due to that found in the diet, and BPA and its metabolites were detected at parts per billion (or less) concentrations in human urine, milk, saliva, serum, plasma, ovarian follicular fluid, and amniotic fluid. Adverse health effects in mice and rats may be induced after parenteral injection or after massive oral doses. Controlled ingestion trials in healthy adult volunteers with 5 mg d16-BPA were unable to detect parent BPA in plasma despite exquisitely sensitive (limit of detection = 6 nM) methods, but by 96 h 100% of the administered dose was recovered in urine as the glucuronide. The extensive BPA glucuronidation following ingestion is not seen after parenteral injection; only the parent BPA binds plasma proteins and estrogen receptors (ER). The hypothesis that BPA dose-response may be described by a J- or U-shape curve was not supported by toxicogenomic data collected in fetal rat testes and epididymes (after repeated parenteral exposure at 2-400,000 microg/kg-d), where a clear monotonic dose-response both in the numbers of genes and magnitude of individual gene expression was evident. There is no clear indication from available data that the BPA doses normally consumed by humans pose an increased risk for immunologic or neurologic disease. There is no evidence that BPA poses a genotoxic or carcinogenic risk and clinical evaluations of 205 men and women with high-performance liquid chromatography (HPLC)-verified serum or urinary BPA conjugates showed (1) no objective signs, (2) no changes in reproductive hormones or clinical chemistry parameters, and (3) no alterations in the number of children or sons:daughters ratio. Results of benchmark dose (BMD10 and BMDL10) calculations and no-observed-adverse-effect level (NOAEL) inspections of all available and reproducible rodent studies with oral BPA found BMD and NOAEL values all greater than the 5 mg/kg-d NOAELs from mouse and rat multigeneration reproduction toxicity studies. While allometric and physiologically based pharmacokinetic (PBPK) models were constructed for interspecies scaling of BPA and its interaction with ER, multigeneration feeding studies with BPA at doses spanning 5 orders of magnitude failed to identify signs of developmental toxicity or adverse changes in reproductive tract tissues; the 5-mg/kg-d NOAELs identified for systemic toxicity in rats and mice were less than the oral NOAELs for reproductive toxicity. Thus, it is the generalized systemic toxicity of ingested BPA rather than reproductive, immunologic, neurobehavioral, or genotoxic hazard that represents the point of departure. Using U.S. Environmental Protection Agency (EPA) uncertainty factor guidance and application of a threefold database uncertainty factor (to account for the fact that the carcinogenic potential of transplacental BPA exposure has yet to be fully defined and comprehensive neurobehavioral and immunotoxicologic evaluations of BPA by relevant routes and at relevant doses have yet to be completed) to the administered dose NOAEL results in an oral RfD of 0.016 mg/kg-d. Assuming the 70-kg adult consumes 2 L of water each day and adopting the default 20% U.S. EPA drinking water relative source contribution yields a 100 microg/L BPA total allowable concentration (TAC).

17β-Estradiol enhances contact hypersensitivity and IFN-γ expression in inflamed skin of BALB/c mice

The effects of 17beta-estradiol (E(2)) on mouse contact hypersensitivity (CHS) elicited at the ears by 4-ethoxymethylene-2-phenyl-2-oxazolin-5-one (OXA) were examined. Male and female BALB/c mice were sham-treated or gonadectomized, and then subcutaneously injected with E(2) twice a week for 4 weeks. The mice were sensitized by OXA application to their back and CHS was elicited at the ears. E(2) enhanced the ear swelling of all groups at 6h after the elicitation. E(2) had no effect on the mitogenesis of splenic lymphocytes or nitric oxide synthesis by peritoneal macrophages. E(2) increased the number of thymic cells in female mice, but not male mice, and had no effect on the splenic cells of either female or male mice. Evaluation of the cytokine expressions in the inflamed skin revealed that E(2) enhanced the expression of interferon-gamma, but had no effect on the expression of interleukin-4. These results suggest that E(2) affects the thymus and enhances the production of interferon-gamma in skin to augment the skin swelling in CHS elicited by OXA.