Measurement of eight urinary metabolites of di(2-ethylhexyl) phthalate as biomarkers for human exposure assessment.

Human metabolism of di(2-ethylhexyl) phthalate (DEHP) is complex and yields mono(2-ethylhexyl) phthalate (MEHP) and numerous oxidative metabolites. The oxidative metabolites, mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP) and mono(2-carboxymethylhexyl) phthalate (MCMHP), have been considered to be better biomarkers for DEHP exposure assessment than MEHP because urinary levels of these metabolites are generally higher than MEHP, and their measurements are not subject to contamination. The urinary levels of the above metabolites, and of three other recently identified DEHP oxidative metabolites, mono(2-ethyl-3-carboxypropyl) phthalate (MECPrP), mono-2-(1-oxoethylhexyl) phthalate (MOEHP), and mono(2-ethyl-4-carboxybutyl) phthalate (MECBP), were measured in 129 adults. MECPP, MCMHP and MEHHP were present in all the samples analysed. MEHP and the other oxidative metabolites were detected less frequently: MEOHP (99%), MECBP (88%), MECPrP (84%), MEHP (83%) and MOEHP (77%). The levels of all DEHP metabolites were highly correlated (p<0.0001) with each other, confirming a common parent. The ? and ?-1 oxidative metabolites (MECPP, MCMHP, MEHHP and MEOHP) comprised 87.1% of all metabolites measured, and thus are most likely the best biomarkers for DEHP exposure assessment. The percentage of the unglucuronidated free form excreted in urine was higher for the ester linkage carboxylated DEHP metabolites compared with alcoholic and ketonic DEHP metabolites. The percentage of the unglucuronidated free form excreted in urine was higher for the DEHP metabolites with a carboxylated ester side-chain compared with alcoholic and ketonic metabolites. Further, differences were found between the DEHP metabolite profile between this adult population and that of six neonates exposed to high doses of DEHP through extensive medical treatment. In the neonates, MEHP represented 0.6% and MECPP 65.5% of the eight DEHP metabolites measured compared to 6.6% (MEHP) and 31.8% (MECPP) in the adults. Whether the observed differences reflect differences in route/duration of the exposure, age and/or health status of the individuals is presently unknown.     

Genotoxicity studies of di(2-ethylhexyl)phthalate and its metabolites in CHO cells

The widely used plasticizer di(2-ethylhexyl)phthalate (DEHP), its hydrolysis products mono(2-ethylhexyl)phthalate (MEHP) and 2-ethylhexanol, and also phthalic acid have been tested for clastogenic activity in cultured Chinese hamster ovary (CHO) cells. Only MEHP was found to cause chromosome damage. MEHP was without effect in the SCE and HGPRT mutation test in CHO cells. The clastogenicity of MEHP suggests a role for this compound in the observed carcinogenicity of DEHP and its positive effect in the dominant lethal assay.     

Degradation of bis(2-ethylhexyl) phthalate constituents under methanogenic conditions

The degradation of bis(2-ethylhexyl) phthalate (DEHP) and its intermediary hydrolysis products 2-ethylhexanol (2-EH) and mono(2-ethylhexyl) phthalate (MEHP) was investigated in a methanogenic phthalic acid ester-degrading enrichment culture at 37°C. 2-Ethylhexanoic acid (2-EHA), a plausible degradation product of 2-EH, was also studied. The culture readily degraded 2-EH via 2-EHA to methane which was formed in stoichiometric amounts assuming complete degradation of 2-EH to methane and carbon dioxide. MEHP was degraded to stoichiometric amounts of methane with phthalic acid as a transient intermediate. DEHP remained unaffected throughout the experimental period (330 days).Abbreviations 2-EH 2-ethylhexyl alcohol - 2-EHA 2-ethylhexanoic acid - BBP butylbenzyl phthalate - Be-CoA benzoyl Coenzyme A - CoA Coenzyme A - DEHP bis(2-ethylhexyl) phthalate - MEHP mono(2-ethylhexyl) phthalate - MSW municipal solid waste - PA phthalic acid - PAE phthalic acid ester - TMS trimethylsilyl derivative     

Determination of di(2-ethylhexyl)phthalate and mono(2-ethylhexyl)phthalate in human serum using liquid chromatography-tandem mass spectrometry

Concentrations of mono(2-ethylhexyl)phthalate (MEHP), and di(2-ethylhexyl)phthalate (DEHP), in serum of healthy volunteers were determined by high performance liquid chromatography (HPLC) with tandem mass spectrometry (LC/MS/MS). The serum was extracted with acetone, followed by hexane extraction under acidic conditions, and then applied to the LC/MS/MS. Recoveries of 20 ng/ml of MEHP and DEHP were 101+/-5.7 (n=6) and 102+/-6.5% (n=6), respectively. The limits of quantification (LOQ) of MEHP and DEHP in the method were 5.0 and 14.0 ng/ml, respectively. The concentration of MEHP in the serum was at or less than the LOQ. The concentration of DEHP in the serum was less than the LOQ. Contaminations of MEHP and DEHP from experimental reagents, apparatus and air during the procedure were less than the LOQ and were estimated to be <1.0 and 2.2+/-0.6 ng/ml, respectively. After subtraction of the contamination, the net concentrations of MEHP and DEHP in the serum were estimated at or <5 and <2 ng/ml, respectively. To decrease contamination by DEHP, the cleanup steps and the apparatus and solvent usage were minimized in the sample preparation procedures. The high selectivity of LC/MS/MS is the key for obtaining reliable experimental data from in the matrix-rich analytical samples and for maintaining a low level contamination of MEHP and DEHP in this experimental system. This method would be a useful tool for the detection of MEHP and DEHP in serum.     

乳杆菌对牛乳β-乳球蛋白致敏小鼠淋巴细胞分泌Th1/Th2型细胞因子和抗体的体外影响

为了分析乳杆菌对致敏小鼠脾淋巴细胞分泌Th1/Th2细胞因子及抗体的体外影响,用牛乳β-乳球蛋白腹腔注射BALB/c小鼠建立过敏症模型,造模成功后,分离致敏小鼠的脾淋巴细胞并与4种活/死乳杆菌(107 CFU/mL)体外共同孵育,ELISA法检测细胞上清液中细胞因子(IL-12、IFN-γ和IL-4)和抗体(总IgE、β-Lg特异性IgE和总IgG)含量。4种活/死乳杆菌均可体外调节致敏小鼠脾淋巴细胞分泌细胞因子和抗体的水平,特别是热致死的发酵乳杆菌和嗜酸乳杆菌可提高淋巴细胞IL-12和IFN-γ的分泌,抑制IL-4的分泌,使其IFN-γ/IL-4比值(代表Th1/Th2细胞平衡)高于活菌,与空白对照组比较差异显著(P<0.05)。同时,这两株热致死菌还可显著下调细胞上清液中总IgE、特异性IgE和总IgG抗体的浓度(P<0.05)。试验结果表明乳杆菌可提高牛乳β-乳球蛋白致敏小鼠脾淋巴细胞的IFN-γ/IL-4比值,进而纠正Th2占优势的Th1/Th2失衡,下调抗体分泌量,且具有菌株特异性。     

Toxicogenomic Screening of Replacements for Di(2-Ethylhexyl) Phthalate (DEHP) Using the Immortalized TM4 Sertoli Cell Line

Phthalate plasticizers such as di(2-ethylhexyl) phthalate (DEHP) are being phased out of many consumer products because of their endocrine disrupting properties and their ubiquitous presence in the environment. The concerns raised from the use of phthalates have prompted consumers, government, and industry to find alternative plasticizers that are safe, biodegradable, and have the versatility for multiple commercial applications. We examined the toxicogenomic profile of mono(2-ethylhexyl) phthalate (MEHP, the active metabolite of DEHP), the commercial plasticizer diisononyl cyclohexane-1,2-dicarboxylate (DINCH), and three recently proposed plasticizers: 1,4-butanediol dibenzoate (BDB), dioctyl succinate (DOS), and dioctyl maleate (DOM), using the immortalized TM4 Sertoli cell line. Results of gene expression studies revealed that DOS and BDB clustered with control samples while MEHP, DINCH and DOM were distributed far away from the control-DOS-BDB cluster, as determined by principle component analysis. While no significant changes in gene expression were found after treatment with BDB and DOS, treatment with MEHP, DINCH and DOM resulted in many differentially expressed genes. MEHP upregulated genes downstream of PPAR and targeted pathways of cholesterol biosynthesis without modulating the expression of PPAR’s themselves. DOM upregulated genes involved in glutathione stress response, DNA repair, and cholesterol biosynthesis. Treatment with DINCH resulted in altered expression of a large number of genes involved in major signal transduction pathways including ERK/MAPK and Rho signalling. These data suggest DOS and BDB may be safer alternatives to DEHP/MEHP than DOM or the commercial alternative DINCH.     

Morphological transformation and catalase activity of syrian hamster embryo cells treated with hepatic peroxisome proliferators,TPA and nickel sulphate

The abilities of the hepatic peroxisome proliferators (HPPs) clofibrate, di(2-ethylhexyl)phthalate (DEHP), mono(2-ethylhexyl)- phthalate (MEHP), 2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and tiadenol to induce morphological transformation and to increase the catalase activity of Syrian hamster embryo (SHE) cells were studied. DEHP, MEHP, clofibrate and tiadenol induced morphological transformation of SHE cells and increased the catalase activity. DEHP was more potent than clofibrate and tiadenol in both inducing catalase and morphological transformation, while MEHP seemed more potent than DEHP in inducing catalase, but not morphological transformation, 2,4,5-T and 2,4-D did not induce morphological transformation, but 2,4,5-T was more potent than clofibrate in increasing the catalase activity. These results show that several HPPs induce morphological transformation of SHE cells and an increase in the catalase activity. There is, however, no direct connection between these two parameters, as seen from the results of 2,4,5-T. The tumor promoter TPA, and the metal salt nickel sulphate, induced morphological transformation of SHE cells without any appreciable increase in the catalase activity. These results further corroborate the dissociation between induction of morphological transformation and the increase in catalase activity.Abbreviations Clofibrate ethyl-2-(p-chlorophenox) isobutyrate - 2,4-D 2,4-dichlorophenoxy acetic acid - DEHP di(2-ethylhexyl)phthalate - HPP hepatic peroxisome proliferator - MEHP mono(2-ethylhexyl)phthalate - SHE Syrian hamster embryo - 2,4,5-T 2,4,5-trichlorophenoxy acetic acid - tiadenol di(hydroxyethylthio)-1,10-decane     

Th 细胞因子IL-17、IFN-γ、IL-4 在狼疮性肾炎中的表达及意义

目的:探讨T辅助细胞(Th)相关细胞因子在狼疮性肾炎发病中的免疫机制作用。方法:64例系统性红斑狼疮患者和28例健康体检者作为对照,采用酶联免疫吸附测定法(ELISA法)检测所有受试者血清IL-17、IFN-γ、IL-4水平,并对其与SLEDAI、SDI、24小时尿蛋白量相关性进行研究。结果:狼疮性肾炎组血清IL-17水平显著高于狼疮无肾炎组和健康对照组(P<0.001),狼疮性肾炎组血清IFN-γ水平显著高于狼疮无肾炎组(P<0.05)和健康对照组(P<0.01),血清IL-4水平在狼疮性肾炎组、狼疮无肾炎组均显著高于健康对照组(P<0.01)。狼疮性肾炎组IFN-γ/IL-4比值显著高于狼疮无肾炎组(P<0.01)和健康对照组(P<0.05);狼疮无肾炎组IFN-γ/IL-4比值显著低于健康对照组(P<0.01)。SLE患者血清IFN-γ表达水平与SLEDAI积分呈正相关(r=0.402,P<0.05),血清IL-17、IL-4表达水平与SLEDAI、SDI、抗ds-DNA抗体、C3、24小时尿蛋白量均无相关性。结论:狼疮性肾炎患者外周血中IL-17、IFN-γ、IL-4等促炎细胞因子均有不同程度升高促起炎症发生及组织损伤,参与了狼疮性肾炎的免疫发病过程。     

Phthalates Are Metabolised by Primary Thyroid Cell Cultures but Have Limited Influence on Selected Thyroid Cell Functions In Vitro

Phthalates are plasticisers added to a wide variety of products, resulting in measurable exposure of humans. They are suspected to disrupt the thyroid axis as epidemiological studies suggest an influence on the peripheral thyroid hormone concentration. The mechanism is still unknown as only few in vitro studies within this area exist. The aim of the present study was to investigate the influence of three phthalate diesters (di-ethyl phthalate, di-n-butyl phthalate (DnBP), di-(2-ethylhexyl) phthalate (DEHP)) and two monoesters (mono-n-butyl phthalate and mono-(2-ethylhexyl) phthalate (MEHP)) on the differentiated function of primary human thyroid cell cultures. Also, the kinetics of phthalate metabolism were investigated. DEHP and its monoester, MEHP, both had an inhibitory influence on 3''-5''-cyclic adenosine monophosphate secretion from the cells, and MEHP also on thyroglobulin (Tg) secretion from the cells. Results of the lactate dehydrogenase-measurements indicated that the MEHP-mediated influence was caused by cell death. No influence on gene expression of thyroid specific genes (Tg, thyroid peroxidase, sodium iodine symporter and thyroid stimulating hormone receptor) by any of the investigated diesters could be demonstrated. All phthalate diesters were metabolised to the respective monoester, however with a fall in efficiency for high concentrations of the larger diesters DnBP and DEHP. In conclusion, human thyroid cells were able to metabolise phthalates but this phthalate-exposure did not appear to substantially influence selected functions of these cells.     

妊娠期肝内胆汁淤积症患者外周血中维生素D受体 与Th1/Th2 型细胞因子的变化

目的:研究妊娠期肝内胆汁淤积症患者外周血中维生素D受体的表达与Th1/Th2型细胞因子干扰素-γ/白细胞介素-4(IFN-γ/IL-4)的变化关系,探讨ICP发病机制。方法:选取ICP患者31例(ICP组),孕周相匹配的正常孕妇31例(正常对照组)。采用酶联免疫吸附试验(ELISA法),检测两组孕妇血清中Th1型细胞因子(IFN-γ)和Th2型细胞因子(IL-4)的水平;采用实时荧光定量逆转录-多聚酶链反应(qRT-PCR),检测两组孕妇外周血单个核细胞维生素D受体(VDR)mRNA的表达水平,采用3-磷酸甘油醛脱氢酶(GAPDH)为内参,根据相对定量公式:2-△△CT分析VDR mRNA的表达水平。结果:(1)ICP组外周血清中IFN-γ的浓度[(230.93±36.04)pg/ml]明显高于正常对照组[(138.37±25.08)pg/ml],差异有统计学意义(P<0.01)。ICP组血清中IL-4浓度[(9.99±3.19)pg/ml]和正常对照组[(8.58±2.43)pg/ml]比较,差异无统计学意义(P>0.05)。ICP组IFN-γ/IL-4比值(24.56±6.91)高于正常对照组(17.13±4.84),差异有统计学意义(P<0.05)。(2)ICP组外周血单个核细胞维生素D受体mRNA的表达明显低于正常对照组(P<0.01),正常对照组VDR的表达定义为1.0,ICP组的表达量为0.4。(3)ICP组外周血中VDR的表达水平与IFN-γ浓度呈明显负相关(r=-0.833,P<0.01),与IL-4浓度无明显相关(r=-0.109,P>0.05),与IFN-γ/IL-4比值呈负相关,但相关性不强(r=-0.356,P=0.049<0.05)。结论:ICP患者外周血Th1/Th2型细胞因子平衡由Th2向Th1偏移,可能与ICP孕妇外周血单个核细胞VDR的表达减少有关。     

Mono-(2-Ethylhexyl) Phthalate Induces Injury in Human Umbilical Vein Endothelial Cells

Mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of di-(2-ethylhexyl) phthalate (DEHP), is a widespread environmental contaminant and has been proved to have potential adverse effects on the reproductive system, carcinogenicity, liver, kidney and developmental toxicities. However, the effect of MEHP on vascular system remains unclear. The main purpose of this study was to evaluate the cytotoxic effects of MEHP on human umbilical endothelial cells (HUVEC) and its possible molecular mechanism. HUVEC cells were treated with MEHP (0, 6.25, 12.5, 25,50 and 100 µM), and the cellular apoptosis and mitochondrial membrane potential as well as intracellular reactive oxygen species were determined. In present study, MEHP induced a dose-dependent cell injury in HUVEC cell via an apoptosis pathway as characterized by increased percentage of sub-G1, activation of caspase-3, -8and -9, and increased ratio of Bax/bcl-2 mRNA and protein expression as well as cytochrome C releasing. In addition, there was obvious oxidative stress, represented by decreased glutathione level, increased malondialdehyde level and superoxide dismutase activity. N-Acetylcysteine, as an antioxidant that is a direct reactive oxygen species scavenger, could effectively block MEHP-induced reactive oxygen species generation, mitochondrial membrane potential loss and cell apoptosis. These data indicated that MEHP induced apoptosis in HUVEC cells through a reactive oxygen species-mediated mitochondria-dependent pathway.     

Phthalates Biomarker Identification and Exposure Estimates in a Population of Pregnant Women

Phthalates are known reproductive and developmental toxicants in experimental animals. However, in humans, there are few data on the exposure of pregnant women that can be used to assess the potential developmental exposure experienced by the fetus. We measured several phthalate metabolites in maternal urine, maternal serum, and cord serum samples collected at the time of delivery from 150 pregnant women from central New Jersey. The urinary concentrations of most metabolites were comparable to or less than among the U.S. general population, except for mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), three metabolites of di(2-ethylhexyl) phthalate (DEHP). The median urinary concentrations of MEHHP (109 μ g/l) and MEOHP (95.1 μ g/l) were more than 5 times their population-based concentrations, whereas the median urinary concentration of MEHP was more than 20 times higher. High concentration of MEHP may indicate a recent exposure to the parent chemical DEHP in the hospital shortly before the collection of the samples. Calculation of daily intakes using the urinary biomarker data reveals that none of the pregnant women tested had integrated exposures to DEHP greater than the Agency for Toxic Substances and Disease Registry's minimal risk levels (MRLs chronic 60, intermediate 100 μ g/kg/day). No abnormal birth outcomes (e.g., birth weight, Apgar Score, and gestational age) were noted in those newborns whose mothers had relatively greater exposure to DEHP during the perinatal period than others in this study. Significantly greater concentrations and detection frequencies in maternal urine than in maternal serum and cord serum suggest that the urinary concentrations of the phthalate metabolites may be more reliable biomarkers of exposure than their concentrations in other biological specimens.     

The endocrine disruptor mono-(2-ethylhexyl)phthalate promotes adipocyte differentiation and induces obesity in mice

The environmental obesogen hypothesis proposes that exposure to endocrine disruptors during developmental ‘window’ contributes to adipogenesis and the development of obesity. MEHP [mono-(2-ethylhexyl) phthalate], a metabolite of the widespread plasticizer DEHP [di-(2-ethylhexyl) phthalate], has been found in exposed organisms and identified as a selective PPARγ (peroxisome-proliferator-activated receptor γ) modulator. However, implication of MEHP on adipose tissue development has been poorly investigated. In the present study, we show the dose-dependent effects of MEHP on adipocyte differentiation and GPDH (glycerol-3-phosphate dehydrogenase) activity in the murine 3T3-L1 cell model. MEHP induced the expression of PPARγ as well as its target genes required for adipogenesis in vitro. Moreover, MEHP perturbed key regulators of adipogenesis and lipogenic pathway in vivo. In utero exposure to a low dose of MEHP significantly increased b.w. (body weight) and fat pad weight in male offspring at PND (postnatal day) 60. In addition, serum cholesterol, TAG (triacylglycerol) and glucose levels were also significantly elevated. These results suggest that perinatal exposure to MEHP may be expected to increase the incidence of obesity in a sex-dependent manner and can act as a potential chemical stressor for obesity and obesity-related disorders.     

Biological monitoring of the five major metabolites of di-(2-ethylhexyl)phthalate (DEHP) in human urine using column-switching liquid chromatography-tandem mass spectrometry

We present a fast and reliable on-line clean-up HPLC-method for the simultaneous determination of the five major urinary metabolites of di-(2-ethylhexyl)phthalate (DEHP) namely mono-(2-ethyl-5-carboxypentyl)phthalate (5carboxy-MEPP), mono-[2-(carboxymethyl)hexyl]phthalate (2carboxy-MMHP), mono-(2-ethyl-5-hydroxyhexyl)phthalate (5OH-MEHP), mono-(2-ethyl-5-oxohexyl)phthalate (5oxo-MEHP) and mono-(2-ethylhexyl)phthalate (MEHP). These metabolites represent about 70% of an oral DEHP dose. We for the first time succeeded to reliably quantify 5carboxy-MEPP and to identify 2carboxy-MMHP as major metabolites in native urines of the general population. The analytical procedure consists of an enzymatic hydrolysis, on-line extraction of the analytes from urinary matrix by a restricted access material column (RAM), back-flush transfer onto the analytical column (betasil phenylhexyl), detection by ESI-tandem mass spectrometry and quantification by isotope dilution (limit of detection (LOD) 0.25 microg/l). Median concentrations of a small collective taken from the general population (n=19) were 85.5 microg/l (5carboxy-MEPP), 47.5 microg/l (5OH-MEHP), 39.7 microg/l (5oxo-MEHP), 9.8 microg/l (MEHP) and about 37 microg/l (2carboxy-MMHP). The presented method can provide insights into the actual internal burden of the general population and certain risk groups. It will help to further explore the human metabolism of DEHP-an occupational and environmental toxicant of great concern.     

Association between Maternal Exposure to di(2-ethylhexyl) Phthalate and Reproductive Hormone Levels in Fetal Blood: The Hokkaido Study on Environment and Children's Health

Prenatal di(2-ethylhexyl) phthalate (DEHP) exposure can produce reproductive toxicity in animal models. Only limited data exist from human studies on maternal DEHP exposure and its effects on infants. We aimed to examine the associations between DEHP exposure in utero and reproductive hormone levels in cord blood. Between 2002 and 2005, 514 pregnant women agreed to participate in the Hokkaido Study Sapporo Cohort. Maternal blood samples were taken from 23–35 weeks of gestation and the concentration of the primary metabolite of DEHP, mono(2-ethylhexyl) phthalate (MEHP), was measured. Concentrations of infant reproductive hormones including estradiol (E2), total testosterone (T), and progesterone (P4), inhibin B, insulin-like factor 3 (INSL3), steroid hormone binding globulin, follicle-stimulating hormone, and luteinizing hormone were measured from cord blood. Two hundred and two samples with both MEHP and hormones'' data were included in statistical analysis. The participants completed a self-administered questionnaire regarding information on maternal characteristics. Gestational age, birth weight and infant sex were obtained from birth records. In an adjusted linear regression analysis fit to all study participants, maternal MEHP levels were found to be associated with reduced levels of T/E2, P4, and inhibin B. For the stratified analyses for sex, inverse associations between maternal MEHP levels T/E2, P4, inhibin B, and INSL3 were statistically significant for males only. In addition, the MEHP quartile model showed a significant p-value trend for P4, inhibin B, and INSL3 decrease in males. Since inhibin B and INSL3 are major secretory products of Sertoli and Leydig cell, respectively, the results of this study suggest that DEHP exposure in utero may have adverse effects on both Sertoli and Leydig cell development in males, which agrees with the results obtained from animal studies. Comprehensive studies investigating phthalates'' exposure in humans, as well as their long-term effects on reproductive development are needed.     

T helper cells subtypes and their cytokine gene expression affected by carvacrol in sensitized mice administered during sensitization period

Th1, Th2, Th17, and Treg cells and their cytokine gene expressions in splenocytes of control mice, ovalbumin sensitized (S), and S treated with dexamethasone and carvacrol during a sensitization period were examined. Th2 and Th17 population as well as the gene expression of IL-4, IL-17, and TGF-β were increased, but Th1, Th1/Th2 ratio, the gene expression of IFN-γ and FOXP3 as well as the IFN-γ/IL-4 ratio were decreased in S compared with control group ( P < 0.001 for all cases). Carvacrol treatment caused significant reduction of Th2 and Th17 population as well as gene expression of IL-4, IL-17, and TGF-β but increase in Treg cells, Th1/Th2 ratio, gene expressions of FOXP3, IFN-γ, and IFN-γ/IL-4 ratio ( P < 0.05 to P < 0.001). The population of Th1, Th2, Th17 cells as well as the gene expression of IL-4, IL-17, and TGF-β were significantly decreased, but only Treg was increased in the dexamethasone treatment group ( P < 0.05 to P < 0.001). Carvacrol treatment during the sensitization period showed a more specific effect on Th1/Th2 imbalance in sensitized mice than dexamethasone, which may indicate the therapeutic potentials of carvacrol in disorders associated with Th1/Th2 imbalance such as asthma.     

Mono-(2-ethylhexyl) phthalate (MEHP) regulates glucocorticoid metabolism through 11β-hydroxysteroid dehydrogenase 2 in murine gonadotrope cells

Di-(2-ethylhexyl) phthalate (DEHP) and its metabolite mono-(2-ethylhexyl) phthalate (MEHP) have been classified as toxicants to the reproductive system at the testis level and DEHP may also impair reproductive axis function at the pituitary levels. However, MEHP is 10-fold more potent than DEHP in toxicity and little is known about the toxicological effect of MEHP on pituitary. In this study, we demonstrated that 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), not 11β-HSD1, is strongly expressed in murine gonadotrope LβT2 cells. Interestingly, MEHP inhibited Hsd11b2 mRNA level and 11β-HSD2 enzyme activity in LβT2 cells at as low as 10⁻⁷ M. Corticosterone (CORT) at a concentration of 10⁻⁶ M significantly inhibited LβT2 cell proliferation after 2-day culture, and 10⁻⁶ M RU486, an antagonist of glucocorticoid receptor (GR), reversed this inhibition. However, in the presence of 10⁻⁵ or 10⁻⁴ M MEHP, the minimal concentration of CORT to inhibit the proliferation of LβT2 cells was lowered to 10⁻⁷ M, and 10⁻⁶ M RU486 was not able to completely reverse the CORT effect. In conclusion, along with the regulation of GR, 11β-HSD2 may have a key role in glucocorticoid metabolism in LβT2 cells. MEHP may participate in the glucocorticoid metabolism in LβT2 cells through inhibition of 11β-HSD2 enzyme activity. Such perturbation may be of pathological significance as MEHP may interfere with the reproductive system at pituitary level through regulation of glucocorticoid metabolism, especially in neonates with higher risk of phthalates exposure.