Mono(2-ethylhexyl)phthalate and mono-n-butyl phthalate activation of peroxisome proliferator activated-receptors alpha and gamma in breast

Exploring the intricate relationship between miRNA dysregulation and breast cancer development: insights into the impact of environmental chemicals

Breast cancer stands as the most prevalent form of cancer among women globally, influenced by a combination of genetic and environmental factors. Recent studies have investigated changes in microRNAs (miRNAs) during breast cancer progression and the potential impact of environmental chemicals on miRNA expression. This review aims to provide an updated overview of miRNA alterations in breast cancer and to explore their potential association with environmental chemicals. We will discuss the current knowledge on dysregulated miRNAs in breast cancer, including both upregulated and downregulated miRNAs. Additionally, we will review the influence of environmental chemicals, such as endocrine-disrupting compounds, heavy metals, and air pollutants, on miRNA expression and their potential contribution to breast cancer development. This review aims to advance our understanding of the complex molecular mechanisms underlying miRNA dysregulation in breast cancer by comprehensively examining miRNA alterations and their association with environmental chemicals. This knowledge is crucial for the development of targeted therapies and preventive measures. Furthermore, identifying specific miRNAs affected by environmental chemicals may allow the prediction of individual susceptibility to breast cancer and the design of personalized intervention strategies.

Isocucurbitacin B inhibits glioma growth through PI3K/AKT pathways and increases glioma sensitivity to TMZ by inhibiting hsa-mir-1286a

Aim: Glioma accounts for 81% of all cancers of the nervous system cancers and presents one of the most drug-resistant malignancies, resulting in a relatively high mortality rate. Despite extensive efforts, the complete treatment options for glioma remain elusive. The effect of isocucurbitacin B (isocuB), a natural compound extracted from melon pedicels, on glioma has not been investigated. This study aims to investigate the inhibitory effect of isocuB on glioma and elucidate its underlying mechanisms, with the objective of developing it as a potential therapeutic agent for glioma. Methods: We used network pharmacology and bioinformatics analysis to predict potential targets and associated pathways of isocuB in glioma. Subsequently, the inhibitory effect of isocuB on glioma and its related mechanisms were assessed through Counting Kit-8 (CCK-8), wound healing, transwell, Western blot (WB), reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and other in vitro experiments, alongside tumor formation experiments in nude mice. Results: Based on this investigation, it suggested that isocuB might inhibit the growth of gliomas through the PI3K-AKT and MAPK pathways. Additionally, we proposed that isocuB may enhance glioma drug sensitivity to temozolomide (TMZ) via modulation of hsa-mir-1286a. The CCK-8 assay revealed that isocuB exhibited inhibitory effects on U251 and U87 proliferation and outperformed TMZ. Wound healing and transwell experiments showed that isocuB inhibited the invasion and migration of U251 cells by suppressing the activity of MMP-2/9, N-cadherin, and Vimentin. The TdT-mediated dUTP-biotin nick end labeling (TUNEL) and flow cytometry (FCM) assays revealed that isocuB induced cell apoptosis through inhibition of BCL-2. Subsequently, we conducted RT-qPCR and WB experiments, which revealed that PI3K/AKT and MAPK pathways might be involved in the mechanism of the inhibition isocuB on glioma. Additionally, isocuB promoted the sensitivity of glioma U251 to TMZ by inhibiting hsa-mir-1286a. Furthermore, we constructed TMZ-resistant U251 strains and demonstrated effective inhibition by isocuB against these resistant strains. Finally, we confirmed that isocuB can inhibit tumor growth in vivo through experiments on tumors in nude mice. Conclusion: IsocuB may protect against glioma by acting on the PI3K/AKT and MAPK pathways and promote the sensitivity of glioma U251 to TMZ by inhibiting hsa-mir-1286a.

Gestational and lactational exposure to the emergent alternative plasticizer 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH) impairs lipid metabolism to a greater extent than the commonly used Di(2-ethylhexyl) phthalate (DEHP) in the adult rat mammary gland

Due to their endocrine disruption properties, phthalate plasticizers such as di(2-ethylhexyl) phthalate (DEHP) can affect the hormone-dependent development of the mammary gland. Over the past few years, DEHP has been partially replaced by 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH) which also have potential endocrine disrupting properties. The goal of the present study is to understand the impact of a gestational and lactational exposure to DEHP and DINCH on mammary gland development using Sprague-Dawley rats. Both plasticizers altered the adipocytes of the mammary gland fat pad of adult progeny, as demonstrated by a decrease in their size, folding of their membrane and modulations of the lipid profiles. DEHP treatments decreased the expression of Rxrα and Scd1 at the low and high dose, respectively, but did not affect any of the other genes studied. DINCH modulation of lipid metabolism could be observed at puberty by a decreased expression of genes implicated in triglyceride synthesis, lipid transport and lipolysis, but by an increased expression of genes of the β-oxidation pathway and of genes involved in lipid storage and fatty acid synthesis at adulthood, compared to control and DEHP-treated rats. A strong upregulation of different inflammatory markers was observed following DINCH exposure only. Together, our results indicate that a gestational and lactational exposure to DINCH has earlier and more significant effects on lipid homeostasis, adipogenesis and the inflammatory state of the adult mammary gland than DEHP exposure. The long-term consequence of these effects on mammary gland health remained to be determined.

Association of Urinary Phthalate and Phthalate Replacement Metabolite Concentrations with Serum Lipid Biomarker Levels among Pregnant Women Attending a Fertility Center

We examined whether urinary concentrations of phthalate and phthalate replacement metabolites were associated with lipid biomarker levels among pregnant women. This cross-sectional study included 175 women who enrolled in the Environment and Reproductive Health (EARTH) Study (2005–2017). We used linear regression models to assess the relationship between urinary phthalates and lipid biomarkers [triglycerides, total cholesterol, high density lipoprotein (HDL), non-HDL, and low-density lipoprotein (LDL) cholesterol] levels while adjusting for confounders. Pregnant women in the highest quartile of urinary mono(2-ethyl-5-carboxypentyl) phthalate (MECPP) had, overall, 14% [31 (95% CI = 6.56) mg/dL], 21% [33 (95% CI = 9.57) mg/dL] and 25% [30 (95% CI = 8.53) mg/dL] higher serum total, non-HDL and LDL cholesterol, respectively, compared to women in the lowest quartile of MECPP. Similar positive associations were found for urinary concentrations of other metabolites of di(2-ethylhexyl) phthalate, mono(2-ethylhexyl) phthalate, and mono(2-ethyl-5-oxohexyl) phthalate. Pregnant women with urinary mono-n-butyl phthalate (MBP) in the highest quartile had higher triglycerides and non-HDL cholesterol compared to women with MBP in the lowest quartile. Women with detectable concentrations of two phthalate replacement metabolites had lower HDL cholesterol compared to women with non-detectable concentrations. Gestational urinary concentrations of certain phthalate and phthalate replacement metabolites were associated with lipid levels among these women.

Association between recurrent breast cancer and phthalate exposure modified by hormone receptors and body mass index

The association between phthalate exposure and breast cancer remains controversial. We performed a prospective patient cohort design to explore the interaction between creatinine-corrected urinary phthalate metabolites and hormone receptors as well as body mass index (BMI) on recurrent breast cancer. In this follow-up study, 636 female breast cancer patients and 45 new recurrent cases diagnosed for a total of 1576.68 person-years of follow-up were recruited. Mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) was negatively associated with breast cancer recurrence, with adjusted hazard ratio (aHR) 3rd vs. 1st quartile of 0.15 (95% CI 0.04–0.51). The MEOHP presented as a non-monotonic dose–response (NMDR) curve, being U-shaped. In the stratification of hormone receptors, MEOHP still exhibited a U-shaped dose–response curve. The third quartile of MEOHP showed significant lowest recurrent risk in the status of ER-positive (aHR 0.18, 95% CI 0.05–0.66), PR-negative (aHR 0.14, 95% CI 0.03–0.63), and HER2-negative (aHR 0.24, 95% CI 0.08–0.76). Whether in BMI < 25 or in BMI ≥ 25, the third quartile of MEOHP was negatively associated with recurrent breast cancer, and there was a negative interaction on an additive scale between MEOHP and BMI (p_interaction = 0.042). The association between MEOHP and recurrent breast cancer was modified by hormone receptors and BMI.

Associations between maternal mono-(2-ethylhexyl) phthalate levels, nuclear receptor gene polymorphisms, and fatty acid levels in pregnant Japanese women in the Hokkaido study

We assessed how the interaction between mono-(2-ethylhexyl) phthalate (MEHP) in maternal sera and the maternal genotypes associated with nuclear receptors affect fatty acid levels in a prospective birth cohort study of pregnant Japanese individuals (n = 437) recruited in Sapporo between 2002 and 2005. We analyzed MEHP and fatty acids using gas chromatography-mass spectrometry. Thirteen single nucleotide polymorphisms of peroxisome proliferator-activated receptor (PPAR) alpha, PPAR gamma (PPARG), PPARG coactivator 1A (PPARGC1A), PPAR delta, constitutive androstane receptor, liver X receptor (LXR) alpha, and LXR beta (LXRB) were analyzed using real-time PCR. Multiple linear regression models were used to confirm the influence of log₁₀-transformed MEHP levels and maternal genotypes on log₁₀-transformed fatty acid levels. When the effects of the interaction between MEHP levels and the maternal PPARGC1A (rs8192678) genotype on oleic acid levels were evaluated, the estimated changes (95 % confidence intervals) in oleic acid levels against MEHP levels, maternal PPARGC1A (rs8192678)-GA/AA genotype, and the interaction between them showed a mean reduction of 0.200 (0.079, 0.322), mean reduction of 0.141 (0.000, 0.283), and mean increase of 0.145 (0.010, 0.281), respectively, after adjusting for the perfluorooctanesulfonate level. The effects of the interaction between MEHP levels and maternal LXRB (rs2303044) genotype on linoleic acid levels was also significant (p_int = 0.010). In conclusion, the interaction between MEHP and the maternal genotypes PPARGC1A (rs8192678) and LXRB (rs2303044) decreased fatty acid levels. Further, the interaction between MEHP and PPARGC1A (rs8192678) may have a greater effect on fatty acid levels than the interaction between PFOS and PPARGC1A.

Low-dose mono(2-ethylhexyl) phthalate promotes ovarian cancer development through PPARα-dependent PI3K/Akt/NF-κB pathway

The plasticizer di(2-ethylhexyl) phthalate (DEHP) and its hydrolysate mono(2-ethylhexyl) phthalate (MEHP) are major toxicants from plastics, but their association with hormone-dependent cancers has been controversial. We treated the human ovarian cancer cell lines SKOV3 and A2780 with low concentrations of DEHP/MEHP, and found that although no significant effect on cell proliferation was observed, ovarian cancer cell migration, invasion, and epithelial-mesenchymal transition (EMT) were promoted by submicromolar MEHP but not DEHP. Next, ovarian cancer patient data from The Cancer Genome Atlas (TCGA) were obtained and subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) supported enrichment and Kaplan-Meier survival analyses, which identified PI3K/Akt pathway as a pivotal signaling pathway in ovarian cancer. We found that 500 nM MEHP treatment significantly increased PIK3CA expression, which could be reversed by the knockdown of peroxisome proliferator-activated receptor alpha (PPARα). Silencing PIK3CA significantly suppressed the MEHP-induced migration, invasion and EMT. In addition, we validated that MEHP treatment promoted phosphorylation of Akt and degradation of IκB-α, thereby activating NF-κB and enhancing NF-κB nuclear translocation. In nude mice, MEHP exposure significantly promoted the metastasis of ovarian cancer xenografts, which could be suppressed by the treatment of PPARα inhibitor GW6471. Our findings showed that low-dose MEHP promoted ovarian cancer progression through activating PI3K/Akt/NF-κB pathway, in a PPARα-dependent manner.

The associations of phthalate biomarkers during pregnancy with later glycemia and lipid profiles

BACKGROUND

Pregnancy induces numerous cardiovascular and metabolic changes. Alterations in these sensitive processes may precipitate long-term post-delivery health consequences. Studies have reported associations between phthalates and metabolic complications of pregnancy, but no study has investigated metabolic outcomes beyond pregnancy.

OBJECTIVES

To examine associations of exposure to phthalates during pregnancy with post-delivery metabolic health.

DESIGN

We quantified 15 urinary phthalate biomarker concentrations during the second and third trimesters among 618 pregnant women from Mexico City. Maternal metabolic health biomarkers included fasting blood measures of glycemia [glucose, insulin, Homeostatic Model Assessment of Insulin Resistance [HOMA-IR], % hemoglobin A1c (HbA1c%)] and lipids (total, high-density lipoprotein (HDL), low-density lipoprotein (LDL) cholesterol, triglycerides), at 4-5 and 6-8 years post-delivery. To estimate the influence of the phthalates mixture, we used Bayesian weighted quantile sum regression and Bayesian kernel machine regression; for individual biomarkers, we used linear mixed models.

RESULTS

As a mixture, higher urinary phthalate biomarker concentrations during pregnancy were associated with post-delivery concentrations of plasma glucose (interquartile range [IQR] difference: 0.13 SD, 95%CrI: 0.05, 0.20), plasma insulin (IQR difference: 0.06 SD, 95%CrI: -0.02, 0.14), HOMA-IR (IQR difference: 0.08 SD, 95% CrI: 0.01, 0.16), and HbA1c% (IQR difference: 0.15 SD, 95%CrI: 0.05, 0.24). Associations were primarily driven by mono-2-ethyl-5-carboxypentyl terephthalate (MECPTP) and the sum of dibutyl phthalate biomarkers (∑DBP). The phthalates mixture was associated with lower HDL (IQR difference: -0.08 SD, 95%CrI: -0.16, -0.01), driven by ∑DBP and monoethyl phthalate (MEP), and higher triglyceride levels (IQR difference: 0.15 SD, 95%CrI: 0.08, 0.22), driven by MECPTP and MEP. The overall mixture was not associated with total cholesterol and LDL. However, ∑DBP and MEP were associated with lower and higher total cholesterol, respectively, and MECPTP and ∑DBP were associated with lower LDL.

CONCLUSIONS

Phthalate exposure during pregnancy is associated with adverse long-term changes in maternal metabolic health. A better understanding of timing of the exact biological changes and their implications on metabolic disease risk is needed.

Association between phthalate exposure and insulin resistance: a systematic review and meta-analysis update

An update on systematic review and meta-analysis was performed to explore effects of phthalate exposure on insulin resistance. A systematic literature search was performed in MEDLINE, Web of Science, and CNKI until March 2021. A conceptual framework was constructed to guide the organization and presentation of results. Besides, beta coefficients with corresponding confidence intervals were extracted from the most adjusted models. Extracted beta coefficients were transformed into correlation, and z Fisher transformation of correlation with the corresponding standard error was included in meta-analysis. Subgroup analyses were performed by age (adult vs. adolescent) and sex (female vs. male) of participants and site of study (America and Europe vs. Asia) to explore potential sources of heterogeneity. Nineteen literatures with 12,533 participants reporting on the association of exposure to specific phthalates and insulin resistance were selected. The majority of included studies revealed positive relationships of insulin resistance with different phthalate metabolites exposure. Meta-analyses were performed on 16 studies. Exposure to MnBP, MBzP, MCPP, MEHP, MEOHP, MEHHP, ∑DEHP, and high-molecular weight phthalate (∑HMWP) was associated with the increase of the homeostasis model assessment of insulin resistance (HOMA-IR) index. The results of sensitivity analyses stratified by age, sex, and site of study remained stable, suggesting the robustness of these meta-analyses. Most of heterogeneity in sensitivity analyses decreased to moderate or low degree. Exposure to MnBP, MBzP, MCPP, MEHP, MEOHP, MEHHP, ∑DEHP, and ∑HMWP was associated with the increased risk of HOMA-IR. Age, sex, and site of study might provide limited source of heterogeneity.

Mechanisms Mediating the Regulation of Peroxisomal Fatty Acid Beta-Oxidation by PPARα

In mammalian cells, two cellular organelles, mitochondria and peroxisomes, share the ability to degrade fatty acid chains. Although each organelle harbors its own fatty acid β-oxidation pathway, a distinct mitochondrial system feeds the oxidative phosphorylation pathway for ATP synthesis. At the same time, the peroxisomal β-oxidation pathway participates in cellular thermogenesis. A scientific milestone in 1965 helped discover the hepatomegaly effect in rat liver by clofibrate, subsequently identified as a peroxisome proliferator in rodents and an activator of the peroxisomal fatty acid β-oxidation pathway. These peroxisome proliferators were later identified as activating ligands of Peroxisome Proliferator-Activated Receptor α (PPARα), cloned in 1990. The ligand-activated heterodimer PPARα/RXRα recognizes a DNA sequence, called PPRE (Peroxisome Proliferator Response Element), corresponding to two half-consensus hexanucleotide motifs, AGGTCA, separated by one nucleotide. Accordingly, the assembled complex containing PPRE/PPARα/RXRα/ligands/Coregulators controls the expression of the genes involved in liver peroxisomal fatty acid β-oxidation. This review mobilizes a considerable number of findings that discuss miscellaneous axes, covering the detailed expression pattern of PPARα in species and tissues, the lessons from several PPARα KO mouse models and the modulation of PPARα function by dietary micronutrients.

Environmental chemicals, breast cancer progression and drug resistance

Breast cancer (BC) is one of the most common causes of cancer in the world and the second leading cause of cancer deaths among women. Mortality is associated mainly with the development of metastases. Identification of the mechanisms involved in metastasis formation is, therefore, a major public health issue. Among the proposed risk factors, chemical environment and pollution are increasingly suggested to have an effect on the signaling pathways involved in metastatic tumor cells emergence and progression. The purpose of this article is to summarize current knowledge about the role of environmental chemicals in breast cancer progression, metastasis formation and resistance to chemotherapy. Through a scoping review, we highlight the effects of a wide variety of environmental toxicants, including persistent organic pollutants and endocrine disruptors, on invasion mechanisms and metastatic processes in BC. We identified the epithelial-to-mesenchymal transition and cancer-stemness (the stem cell-like phenotype in tumors), two mechanisms suspected of playing key roles in the development of metastases and linked to chemoresistance, as potential targets of contaminants. We discuss then the recently described pro-migratory and pro-invasive Ah receptor signaling pathway and conclude that his role in BC progression is still controversial. In conclusion, although several pertinent pathways for the effects of xenobiotics have been identified, the mechanisms of actions for multiple other molecules remain to be established. The integral role of xenobiotics in the exposome in BC needs to be further explored through additional relevant epidemiological studies that can be extended to molecular mechanisms.

TCDD-induced antagonism of MEHP-mediated migration and invasion partly involves aryl hydrocarbon receptor in MCF7 breast cancer cells

Evidence has shown that the activation of AhR (aryl hydrocarbon receptor) can promote cancer cell metastasis. However, limited studies have been carried out on mixed exposure to endocrine-disrupting chemicals (EDCs), especially in human breast cancer. Therefore, using MCF7 human breast cancer cells, we investigated the effects of coexposure to MEHP (mono 2-ethylhexyl phthalate) and TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) on cell migration and invasion, as well as the roles of AhR and the MMP/slug pathway. Our data suggest that MEHP or TCDD can induce migration and invasion in MCF7 cells, and the promotion is partly AhR dependent. We also observed that MEHP antagonized TCDD to reduce AhR-mediated CYP1A1 expression. Subsequently, we revealed that MEHP recruited AhR to dioxin response element (DRE) sequences and decreased TCDD-induced AhR-DRE binding in CYP1A1 genes. Overall, MEHP is a potential AHR agonist, capable of decreasing TCDD-induced AhR-DRE binding in CYP1A1 genes. The antagonizing effect of coexposure led to the inhibition of the epithelial-mesenchymal transition (EMT) in MCF7 cells. Our study provides new evidence for the potential mechanisms involved in EDCs exposure and their interactions in EMT.

Associations of urinary phthalate metabolites with risk of papillary thyroid cancer

Some studies have revealed thyrotoxicity of phthalates; however, associations of phthalate exposure with papillary thyroid cancer (PTC) remain unclear. We conducted a pair-matching case-control study of 111 PTC cases and 111 age- and sex-matched non-PTC controls to examine associations between urinary concentrations of phthalate metabolites and PTC. Phthalate metabolites were determined in fasting urine specimens by ultra-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS). After adjusting for potential confounders and other phthalate metabolites, the concentrations of the sum of di (2-ethylhexly) phthalate (DEHP) metabolites in urine were positively associated with PTC [odds ratio (OR) = 5.35; 95% confidence interval (CI): 1.61-17.83], suggesting the effect of phthalates exposure on PTC development. The findings require confirmation.

Effects of di-n-butyl phthalate on photosynthetic performance and oxidative damage in different growth stages of wheat in cinnamon soils

Herein, we investigated the effects of di-n-butyl phthalate (DBP) on photosynthesis, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) content, oxidative damage, and biomass accumulation of different tissues in wheat (Triticum aestivum L) planted in cinnamon soils. The photosynthetic or fluorescence parameters (except for the intercellular carbon dioxide concentration), chlorophyll content, RuBisCO content, and biomass of roots, stems, and leaves decreased at the seedling, jointing, and booting stages under the stress of DBP. Compared with the control, the content of superoxide anions and hydrogen peroxide in the roots, stems, and leaves increased with increasing DBP concentrations at the seedling, jointing, and booting stages. The activities of superoxide dismutase (SOD) and catalase (CAT) in the roots, stems, and leaves increased under the 10 and 20 mg kg^-1 DBP treatments; however, no significant changes were observed under the 40 mg kg^-1 DBP treatment at the seedling stage (except for the SOD activity in roots). The increase in SOD and CAT activities in the roots, stems, and leaves with increasing DBP concentration at the jointing and booting stages suggested that an increase in the activities of these antioxidant enzymes may play an important role in defending against excess reactive oxygen species under DBP stress. The biomass of wheat roots, stems, and leaves decreased with an increase in DBP concentration, which was presumably caused by a decrease in photosynthesis and RuBisCO. The effect of DBP on wheat roots, stems, and leaves decreased with wheat growth.

Saponins as modulators of nuclear receptors

As plant-derived natural products, saponins have been widely applied for the dietary modification of metabolic syndrome. However, the underlying mechanisms of their preventive and therapeutic effects are still largely unclear. Nuclear receptors have been identified as potential pharmaceutical targets for treating various types of metabolic disorders. With similar structure to endogenous hormones, several saponins may serve as selective ligands for nuclear receptors. Recently, a series of saponins are proved to exert their physiological activities through binding to nuclear receptors. This review summarizes the biological and pharmacological activities of typical saponins mediated by some of the most well described nuclear receptors, including the classical steroid hormone receptors (ER, GR, MR, and AR) and the adopted orphan receptors (PPAR, LXR, FXR, and PXR).

miR-19 targeting of PTEN mediates butyl benzyl phthalate-induced proliferation in both ER(+) and ER(-) breast cancer cells

Breast cancer is the most common cancer among women worldwide. Butyl benzyl phthalate (BBP) is ubiquitous in human's environment, and is strongly linked to breast cancer development. microRNA (miRNA) is an important regulator of target genes. So far, no studies have been reported yet to reveal the action of miRNAs in BBP-mediated breast cancer cell proliferation. In this study, we showed that BBP induced proliferation of both ER(+) MCF-7 and ER(-) MDA-MB-231 breast cancer cells, proved by increased cell viability, transition of cell cycle from G1 to S phase, upregulation of proliferating cell nuclear antigen (PCNA) and Cyclin D1, and downregulation of p21. Meanwhile, the expression of oncogenic miR-19a/b and PTEN/AKT/p21 axis was also modulated by BBP. Furthermore, for the first time we revealed that miR-19 played crucial role in the promoting effect of BBP on breast cancer cells through targeting PTEN 3'UTR. Findings from this study could provide an important new perspective on the molecular mechanisms through which BBP exerts its promoting effect on breast cancer as well as its target intervention.

Organism-derived phthalate derivatives as bioactive natural products

Phthalates are widely used in polymer materials as a plasticizer. These compounds possess potent toxic variations depending on their chemical structures. However, a growing body of evidence indicates that phthalate compounds are undoubtedly discovered in secondary metabolites of organisms, including plants, animals and microorganisms. This review firstly summarizes biological sources of various phthalates and their bioactivities reported during the past few decades as well as their environmental toxicities and public health risks. It suggests that these organisms are one of important sources of natural phthalates with diverse profiles of bioactivity and toxicity.

Thermodynamics in cancers: opposing interactions between PPAR gamma and the canonical WNT/beta-catenin pathway

Cancer cells are the site of numerous metabolic and thermodynamic abnormalities. We focus this review on the interactions between the canonical WNT/beta-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR gamma) in cancers and their implications from an energetic and metabolic point of view. In numerous tissues, PPAR gamma activation induces inhibition of beta-catenin pathway, while the activation of the canonical WNT/beta-catenin pathway inactivates PPAR gamma. In most cancers but not all, PPAR gamma is downregulated while the WNT/beta-catenin pathway is upregulated. In cancer cells, upregulation of the WNT/beta-catenin signaling induces dramatic changes in key metabolic enzymes that modify their thermodynamic behavior. This leads to activation of pyruvate dehydrogenase kinase1 (PDK-1) and monocarboxylate lactate transporter. Consequently, phosphorylation of PDK-1 inhibits the pyruvate dehydrogenase complex (PDH). Thus, a large part of pyruvate cannot be converted into acetyl-coenzyme A (acetyl-CoA) in mitochondria and only a part of acetyl-CoA can enter the tricarboxylic acid cycle. This leads to aerobic glycolysis in spite of the availability of oxygen. This phenomenon is referred to as the Warburg effect. Cytoplasmic pyruvate is converted into lactate. The WNT/beta-catenin pathway induces the transcription of genes involved in cell proliferation, i.e., MYC and CYCLIN D1. This ultimately promotes the nucleotide, protein and lipid synthesis necessary for cell growth and multiplication. In cancer, activation of the PI3K-AKT pathway induces an increase of the aerobic glycolysis. Moreover, prostaglandin E2 by activating the canonical WNT pathway plays also a role in cancer. In addition in many cancer cells, PPAR gamma is downregulated. Moreover, PPAR gamma contributes to regulate some key circadian genes. In cancers, abnormalities in the regulation of circadian rhythms (CRs) are observed. CRs are dissipative structures which play a key-role in far-from-equilibrium thermodynamics. In cancers, metabolism, thermodynamics and CRs are intimately interrelated.

Estrogen modulation properties of mangiferin and quercetin and the mangiferin metabolite norathyriol

Mango fruit contain many bioactive compounds, some of which are transcription factor regulators. Estrogen receptor alpha (ERα) and beta (ERβ) are two regulators of gene transcription that are important in a variety of physiological processes and also in diseases including breast cancer. We examined the ability of the mango constituents quercetin, mangiferin, and the aglycone form of mangiferin, norathyriol, to activate both isoforms of the estrogen receptor. Quercetin and norathyriol decreased the viability of MCF-7 breast cancer cells whereas mangiferin had no effect on MCF-7 cells. We also determined that quercetin and mangiferin selectively activated ERα whereas norathyriol activated both ERα and ERβ. Despite quercetin, mangiferin and norathyriol having similar polyphenolic structural motifs, only norathyriol activated ERβ, showing that bioactive agents in mangoes have very specific biological effects. Such specificity may be important given the often-opposing roles of ERα and ERβ in breast cancer proliferation and other cellular processes.

Impact of diethylhexyl phthalate on gene expression and development of mammary glands of pregnant mouse

The widely used diethylhexyl phthalate (DEHP) is a known endocrine disruptor that causes persistent alterations in the structure and function of female reproductive system, including ovaries, uterus and oviducts. To explore the molecular mechanism of the effect of DEHP on the development of mammary glands, we investigated the cell cycle, growth, proliferation and gene expression of mammary gland cells of pregnant mice exposed to DEHP. It was demonstrated, for the first time, that the mammary gland cells of pregnant mice treated with DEHP for 0.5-3.5 days post-coitum had increased proliferation, growth rate and number of cells in the G2/S phase. The expression of cell proliferation-related genes was significantly altered after short time and low-dose DEHP treatment of mammary gland cells in vivo and in vitro. These findings showed adverse effects of DEHP on mammary gland cells in pregnant mice.

Effects of the environmental contaminants DEHP and TCDD on estradiol synthesis and aryl hydrocarbon receptor and peroxisome proliferator-activated receptor signalling in the human granulosa cell line KGN

Environmental contaminants binding to transcription factors, such as the aryl hydrocarbon receptor (AhR) and the alpha and gamma peroxisome proliferator-activated receptors (PPARs), contribute to adverse effects on the reproductive system. Expressing both the AhR and PPARs, the human granulosa cell line KGN offers the opportunity to investigate the regulatory mechanisms involved in receptor crosstalk, independent of overriding hormonal control. The aim of the present study was to investigate the impact of two environmental contaminants, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, an AhR ligand) and di-(2-ethylhexyl) phthalate (DEHP, a PPAR ligand), on gonadotrophin sensitivity and estrogen synthesis in KGN cells. Accumulation of the DEHP metabolite mono-(2-ethylhexyl) phthalate (MEHP) in DEHP-exposed cells was measured by high-performance liquid chromatography mass spectrometry, thereby demonstrating DEHP metabolism to MEHP by KGN cells. By employing TCDD ( an AhR agonist), rosiglitazone (a PPARgamma agonist) or bezafibrate (a PPARalpha agonist), the presence of a functional AhR and PPAR cascade was confirmed in KGN cells. Cytotoxicity testing revealed no effect on KGN cell proliferation for the concentrations of TCDD and DEHP used in the current study. FSH-stimulated cells were exposed to TCDD, DEHP or a mix of both and estradiol synthesis was measured by enzyme-linked immunosorbent assay and gene expression by quantitative RT-PCR. Exposure decreased estradiol synthesis (TCDD, DEHP, mix) and reduced the mRNA expression of CYP19 aromatase (DEHP, mix) and FSHR (DEHP). DEHP induced the expression of the alpha and gamma PPARs and AhR, an effect which was inhibited by selective PPAR antagonists. Studies in the human granulosa cell line KGN show that the action of endocrine-disrupting chemicals may be due to a direct activation of AhR, for example by TCDD, and by a transactivation via PPARs, for example by DEHP, inducing subsequent transcriptional changes with a broad range of effects on granulosa cell function.

Age and sex differences in childhood and adulthood obesity association with phthalates: analyses of NHANES 2007-2010

BACKGROUND

Exposure to environmental chemicals may play a role in the development of obesity. Evidence suggests phthalate exposure may be associated with obesity in children and adults.

OBJECTIVE

To examine the association of ten urinary phthalate metabolites mono-n-butyl phthalate (MnBP), mono-ethyl phthalate (MEP), mono-isobutyl phthalate (MiBP), mono-2-ethyl-5-carboxypentyl phthalate (MECPP), mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono-2-ethylhexyl phthalate (MEHP), mono-benzyl phthalate (MBzP), mono-(carboxylnonyl) phthalate (MCNP), and mono-(carboxyoctyl) phthalate (MCOP) grouped by molecular weight of their parent compounds with body weight outcomes in children, adolescent and adult participants in the National Health and Nutrition Examination Survey (NHANES) 2007-2010.

METHODS

We performed multinomial logistic regression to analyze the association between obesity and urinary phthalate metabolite concentrations in children and adolescents and adults.

RESULTS

Low molecular weight (LMW) phthalate metabolites (MnBP, MEP and MiBP) are significantly (p<0.05) associated with higher odds for obesity in male children and adolescents. High molecular weight (HMW) phthalate metabolites (MECPP, MEHHP, MEOHP, MEHP, MBzP, MCNP, and MCOP) and di-2-ethylhexyl phthalate (DEHP) metabolites (MEHHP, MEOHP, MEHP and MECPP) are significantly (p<0.05) associated with higher OR for obesity in all adults. Additionally, DEHP metabolites are significantly associated with obesity in all female adults; whereas DEHP and HMW metabolites are significantly associated with OR for obesity in males 60 years and older.

CONCLUSIONS

We found age and sex differences in the association between urinary phthalate metabolite concentrations and body weight outcomes. Reverse causation cannot be excluded since overweight and obese people will have more fat mass, they may store more phthalates, thus leading to higher excretion concentrations.

PPARγ and PPARGC1B polymorphisms modify the association between phthalate metabolites and breast cancer risk

CONTEXT

Breast cancer (BC) risk has been differentially associated with urinary levels of some phthalate metabolites.

OBJECTIVE

To investigate whether PPARγ and PPARGC1B polymorphisms modulate these associations.

MATERIALS AND METHODS

208 BC cases were age-matched with 220 population controls. Phthalate metabolites were determined by HPLC-MS. PPARγ Pro12Ala (rs1801281) and PPARGC1B Ala203Pro (rs7732671) and Val279Ile (rs17572019) were genotyped.

RESULTS

The association between mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and BC risk was positively modified in PPARγ Pro12Ala C carriers. The association with mono-iso-butyl phthalate (MiBP) in PPARGC1B Ala203Pro G carriers was negatively modified.

CONCLUSION

PPARγ and PPARGC1B polymorphisms modulate the association between phthalate exposure and BC risk.

Circulating levels of phthalate metabolites are associated with prevalent diabetes in the elderly

OBJECTIVE

Phthalates are ubiquitous industrial high-volume chemicals known as ligands to peroxisome proliferator-activated receptors (PPARs). Because PPAR-γ agonists modulate insulin sensitivity and are used to treat type 2 diabetes, we investigated whether circulating levels of phthalate metabolites are related to prevalent type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 1,016 subjects, aged 70 years, were investigated in the Prospective Investigation of the Vasculature in Uppsala Seniors Study. Four phthalate metabolites were detected in almost all participant sera by an API 4000 liquid chromatograph/tandem mass spectrometer. Type 2 diabetes was defined as the use of pharmacological hypoglycemic agents or a fasting plasma glucose >7.0 mmol/L.

RESULTS

A total of 114 subjects were shown to have diabetes. Following adjustment for sex, BMI, serum cholesterol and triglycerides, educational level, and smoking and exercise habits, high levels of the phthalate metabolites monomethyl phthalate (MMP) (P < 0.01), monoisobutyl phthalate (MiBP) (P < 0.05), and monoethyl phthalate (MEP) (P < 0.05), but not mono(2-ethylhexyl) phthalate, were associated with an increased prevalence of diabetes. Using the fasting proinsulin-to-insulin ratio as a marker of insulin secretion and the homeostasis model assessment-insulin resistance index as a marker of insulin resistance, MiBP was mainly related to poor insulin secretion, whereas MEP and MMP mainly were related to insulin resistance.

CONCLUSIONS

The findings in this cross-sectional study showed that several phthalate metabolites are related to diabetes prevalence, as well as to markers of insulin secretion and resistance. These findings support the view that these commonly used chemicals might influence major factors that are regulating glucose metabolism in humans at the level of exposure of phthalate metabolites seen in the general elderly population.

Environmental endocrine disruptors promote adipogenesis in the 3T3-L1 cell line through glucocorticoid receptor activation

The burgeoning obesity and diabetes epidemics threaten health worldwide, yet the molecular mechanisms underlying these phenomena are incompletely understood. Recently, attention has focused on the potential contributions of environmental pollutants that act as endocrine disrupting chemicals (EDCs) in the pathogenesis of metabolic diseases. Because glucocorticoid signaling is central to adipocyte differentiation, the ability of EDCs to stimulate the glucocorticoid receptor (GR) and drive adipogenesis was assessed in the 3T3-L1 cell line. Various EDCs were screened for glucocorticoid-like activity using a luciferase reporter construct, and four (bisphenol A (BPA), dicyclohexyl phthalate (DCHP), endrin, and tolylfluanid (TF)) were shown to significantly stimulate GR without significant activation of the peroxisome proliferator-activated receptor-gamma. 3T3-L1 preadipocytes were then treated with EDCs and a weak differentiation cocktail containing dehydrocorticosterone (DHC) in place of the synthetic dexamethasone. The capacity of these compounds to promote adipogenesis was assessed by quantitative oil red O staining and immunoblotting for adipocyte-specific proteins. The four EDCs increased lipid accumulation in the differentiating adipocytes and also upregulated the expression of adipocytic proteins. Interestingly, proadipogenic effects were observed at picomolar concentrations for several of the EDCs. Because there was no detectable adipogenesis when the preadipocytes were treated with compounds alone, the EDCs are likely promoting adipocyte differentiation by synergizing with agents present in the differentiation cocktail. Thus, EDCs are able to promote adipogenesis through the activation of the GR, further implicating these compounds in the rising rates of obesity and diabetes.

Exposure to phthalates and breast cancer risk in northern Mexico

BACKGROUND

Phthalates, ubiquitous environmental pollutants that may disturb the endocrine system, are used primarily as plasticizers of polyvinyl chloride and as additives in consumer and personal care products.

OBJECTIVES

In this study, we examined the association between urinary concentrations of nine phthalate metabolites and breast cancer (BC) in Mexican women.

METHODS

We age-matched 233 BC cases to 221 women residing in northern Mexico. Sociodemographic and reproductive characteristics were obtained by direct interviews. Phthalates were determined in urine samples (collected pretreatment from the cases) by isotope dilution/high-performance liquid chromatography coupled to tandem mass spectrometry.

RESULTS

Phthalate metabolites were detected in at least 82% of women. The geometric mean concentrations of monoethyl phthalate (MEP) were higher in cases than in controls (169.58 vs. 106.78 microg/g creatinine). Controls showed significantly higher concentrations of mono-n-butyl phthalate, mono(2-ethyl-5-oxohexyl) phthalate, and mono(3-carboxypropyl) phthalate (MCPP) than did the cases. After adjusting for risk factors and other phthalates, MEP urinary concentrations were positively associated with BC [odds ratio (OR), highest vs. lowest tertile = 2.20; 95% confidence interval (CI), 1.33-3.63; p for trend < 0.01]. This association became stronger when estimated for premenopausal women (OR, highest vs. lowest tertile = 4.13; 95% CI, 1.60-10.70; p for trend < 0.01). In contrast, we observed significant negative associations for monobenzyl phthalate (MBzP) and MCPP.

CONCLUSIONS

We show for the first time that exposure to diethyl phthalate, the parent compound of MEP, may be associated with increased risk of BC, whereas exposure to the parent phthalates of MBzP and MCPP might be negatively associated. These findings require confirmation.

Mono(2-ethylhexyl) phthalate induces both pro- and anti-inflammatory responses in rat alveolar macrophages through crosstalk between p38, the lipoxygenase pathway and PPARalpha

Airway inflammation is important in asthma pathogenesis. Recent epidemiological data have indicated an association between asthma symptoms in children and exposure to di(2-ethylhexyl) phthalate (DEHP). Thus, we have studied inflammatory responses in primary rat alveolar macrophages (AMs) after exposure to mono(2-ethylhexyl) phthalate (MEHP), the major primary metabolite of DEHP. First, we show that MEHP induces a dose-dependent release of the pro-inflammatory tumour necrosis factor-alpha (TNF-alpha) in AMs, giving a maximal (5-fold) increase at 0.7 mM. This concentration also induced some cell death. MEHP also induced phosphorylation of MAPK p38, while the p38 inhibitor SB 202190 reduced MEHP-induced TNF-alpha, suggesting a p38-dependent cytokine production. Next, we elucidated possible effects of MEHP on the 5-lipoxygenase (5-LO) pathway and found that MEHP caused increased leukotriene (LTB(4)) release. Further, we found that the 5-LO inhibitor nordihydrogualaretic acid (NDGA) significantly reduced both MEHP-induced TNF-alpha release and MEHP-induced formation of reactive oxygen species (ROS), supporting an involvement of the 5-LO pathway in MEHP induced inflammatory reactions. Last, we found that MK-886, a known inhibitor of peroxisome proliferator-activated receptor alpha (PPARalpha), increased the MEHP-induced TNF-alpha response. This indicates that MEPH-PPARalpha binding mediates an anti-inflammatory signal.

Effects of the mango components mangiferin and quercetin and the putative mangiferin metabolite norathyriol on the transactivation of peroxisome proliferator-activated receptor isoforms

Mangos are a source of bioactive compounds with potential health-promoting activity. This study evaluated the abilities of the mango components quercetin and mangiferin and the aglycone derivative of mangiferin, norathyriol, to modulate the transactivation of peroxisome proliferator-activated receptor isoforms (PPARs). PPARs are transcription factors important in many human diseases. Through the use of a gene reporter assay it was shown that quercetin inhibited the activation of all three isoforms of PPARs (PPARgamma IC(50) = 56.3 microM; PPARalpha IC(50) = 59.6 microM; PPARbeta IC(50) = 76.9 microM) as did norathyriol (PPARgamma IC(50) = 153.5 microM; PPARalpha IC(50) = 92.8 microM; PPARbeta IC(50) = 102.4 microM), whereas mangiferin did not inhibit the transactivation of any isoform. These findings suggest that mango components and metabolites may alter transcription and could contribute to positive health benefits via this or similar mechanisms.

Mono-(2-ethylhexyl) phthalate stimulates basal steroidogenesis by a cAMP-independent mechanism in mouse gonadal cells of both sexes

Phthalates are widely used as plasticizers in a number of daily-life products. In this study, we investigated the influence of mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of the frequently used plasticizer di-(2-ethylhexyl) phthalate (DEHP), on gonadal steroidogenesisin vitro. MEHP (25–100 μM) stimulated basal steroid synthesis in a concentration-dependent manner in immortalized mouse Leydig tumor cells (MLTC-1). The stimulatory effect was also detected in KK-1 granulosa tumor cells. MEHP exposure did not influence cAMP or StAR protein levels and induced a gene expression profile of key steroidogenic proteins different from the one induced by human chorionic gonadotropin (hCG). Simultaneous treatment with MEHP and a p450scc inhibitor (aminoglutethimide) indicated that MEHP exerts its main stimulatory effect prior to pregnenolone formation. MEHP (10–100 μM) up-regulated hormone-sensitive lipase and 3-hydroxy-3-methylglutaryl coenzyme A reductase, suggesting that MEHP increases the amount of cholesterol available for steroidogenesis. Our data suggest that MEHP, besides its known inhibitory effect on hCG action, can directly stimulate gonadal steroidogenesis in both sexes through a cAMP- and StAR-independent mechanism. The anti-steroidogenic effect of DEHP has been proposed to cause developmental disorders such as hypospadias and cryptorchidism, whereas a stimulation of steroid synthesis may prematurely initiate the onset of puberty and theoretically affect the hypothalamic–pituitary–gonadal axis.

PPARalpha and PPARbeta are differentially affected by ethanol and the ethanol metabolite acetaldehyde in the MCF-7 breast cancer cell line

The activity and/or the level of the peroxisome proliferator-activated receptors (PPARs) in liver and oligodendrocytes are regulated by ethanol. Despite the association between ethanol consumption and breast cancer risk, and the increasing evidence for an involvement of PPARs in some cancers, there have been no studies on the effect of ethanol or its metabolite acetaldehyde on PPARs in breast cancer. Using the MCF-7 breast cancer cell line, we examined the relationship between ethanol and its metabolite acetaldehyde on PPARalpha and PPARbeta transactivation. Ethanol (20 mM) reduced the potency of the PPARbeta ligand GW0742, evident by a rightward shift in the GW0742 dose-response curve, whereas for PPARalpha activation by GW7647, ethanol mediated its effects primarily through reducing efficacy as evidenced by a reduction in maximal response. Using the enzyme inhibitors 4-methylpyrazole and cyanamide and the metabolite acetaldehyde, we showed that PPARalpha and PPARbeta are differentially modulated by ethanol and acetaldehyde. While acetaldehyde is responsible for the inhibition of PPARalpha ligand inhibition with a concentration that inhibits 50% of activity (IC50) of 111 nM, acetaldehyde has no effect on PPARbeta or its ligand activation. Instead, inhibition of PPARbeta transactivation is mediated directly by ethanol. The differential effect of ethanol and acetaldehyde on PPARalpha and PPARbeta further underscores the differences between these receptors and may indicate the relevance of PPARs in the effects of ethanol in the human breast.

Di(2-ethylhexyl) phthalate induces apoptosis through peroxisome proliferators-activated receptor-gamma and ERK 1/2 activation in testis of Sprague-Dawley rats

Di(2-ethylhexyl) phthalate (DEHP) is a well-known hepatic and reproductive toxicant whose toxicity may be mediated by peroxisome proliferators-activated receptor (PPAR). This study examined the effects of DEHP on the expression of PPAR-regulated genes involved in testicular cells apoptosis. Sprague-Dawley male rats were treated orally with 250, 500, or 750 mg/kg/d DEHP for 28 d, while control rats were given corn oil. The levels of cell cycle regulators (pRb, cyclins, CDKs, and p21) and apoptosis-related proteins were analyzed by Western blot analysis. The role of PPAR-gamma (PPAR-gamma), class B scavenger receptor type 1 (SR-B1), and ERK1/2 was further studied to examine the signaling pathway for DEHP-induced apoptosis. Results showed that the levels of pRB, cyclin D, CDK2, cyclin E, and CDK4 were significantly lower in rats given 500 and 750 mg/kg/d DEHP, while levels of p21 were significantly higher in rat testes. Dose-dependent increases in PPAR-gamma and RXRalpha proteins were observed in testes after DEHP exposure, while there was a significant decrease in RXRgamma protein levels. In addition to PPAR-gamma, DEHP also significantly increased SR-B1 mRNA and phosphorylated ERK1/2 protein levels. Furthermore, DEHP treatment induced pro-caspase-3 and cleavage of its substrate protein, poly(ADP-ribose) polymerase (PARP), in a dose-dependent manner. Data suggest that DEHP exposure may induce the expression of apoptosis-related genes in testes through induction of PPAR-gamma and activation of the ERK1/2 pathway.

Effect of di(n-butyl) phthalate on testicular oxidative damage and antioxidant enzymes in hyperthyroid rats

This study compared the effects of di(n-butyl) phthalate (DBP) on the oxidative damage and antioxidant enzymes activity in testes of hyperthyroid rats. Hyperthyroidism was induced in pubertal male rats by intraperitoneal injection of triiodothyronine (T3, 10 microg/kg body weight) for 30 days. An oral dose of DBP (750 mg/kg) was administered simultaneously to normal or hyperthyroid (T3) rats over a 30-day period. No changes in body weight were observed in the hyperthyroid groups (T3, T3 + DBP) compared with controls. There were significantly higher serum T3 levels observed in the hyperthyroid rats than in the control, but the serum thyroid stimulating hormone levels were markedly lower in the hyperthyroid rats. DBP significantly decreased the weight of the testes in the normal (DBP) and hyperthyroid (T3 + DBP) groups. The serum testosterone concentrations were significantly lower in only DBP group. DBP significantly increased the 8-hydroxy-2-deoxyguanosine (8-OHdG) level in the testes, whereas the DBP-induced 8-OHdG levels were slightly higher in T3 + DBP group. Superoxide dismutase and glutathione peroxidase activities were significantly higher in the testes of the DBP or T3 + DBP groups. Catalase (CAT) activity was significantly higher in the DBP treatment group, but the T3 + DBP group showed slightly lower DBP-induced CAT activity. The testicular expression of thyroid hormone receptor alpha-1 (TRalpha-1) was significantly higher in the DBP groups, and androgen receptor (AR) expression was not detected in the DBP treatment group. In addition, DBP significantly increased the peroxisome proliferator-activated receptor-r (PPAR-r) levels in the testis. These results suggest that hyperthyroidism can cause a change in the expression level of PPAR-r in testes, and may increase the levels of oxidative damage induced by the metabolic activation of DBP.