Phthalates rapidly increase production of reactive oxygen species in vivo: role of Kupffer cells

Effects of Dibutylphthalate and Steroid Hormone Mixture on Human Prostate Cells

Phthalates are a family of aromatic chemical compounds mainly used as plasticizers. Among phthalates, di-n-butyl phthalate (DBP) is a low-molecular-weight phthalate used as a component of many cosmetic products, such as nail polish, and other perfumed personal care products. DBP has toxic effects on reproductive health, inducing testicular damage and developmental malformations. Inside the male reproductive system, the prostate gland reacts to both male and female sex steroids. For this reason, it represents an important target of endocrine-disrupting chemicals (EDCs), compounds that are able to affect the estrogen and androgen signaling pathways, thus interfering with prostate homeostasis and inducing several prostate pathologies. The aim of this project was to investigate the effects of DBP, alone and in combination with testosterone (T), 17β-estradiol (E2), and both, on the normal PNT1A human prostate cell-derived cell line, to mimic environmental contamination. We showed that DBP and all of the tested mixtures increase cell viability through activation of both estrogen receptor α (ERα) and androgen receptor (AR). DBP modulated steroid receptor levels in a nonmonotonic way, and differently to endogenous hormones. In addition, DBP translocated ERα to the nucleus over different durations and for a more prolonged time than E2, altering the normal responsiveness of prostate cells. However, DBP alone seemed not to influence AR localization, but AR was continuously and persistently activated when DBP was used in combination. Our results show that DBP alone, and in mixture, alters redox homeostasis in prostate cells, leading to a greater increase in cell oxidative susceptibility. In addition, we also demonstrate that DBP increases the migratory potential of PNT1A cells. In conclusion, our findings demonstrate that DBP, alone and in mixtures with endogenous steroid hormones, acts as an EDC, resulting in an altered prostate cell physiology and making these cells more prone to cancer transformation.

Effects of single or combined exposure to bisphenol A and mono(2-ethylhexyl)phthalate on oxidant/antioxidant status, endoplasmic reticulum stress, and apoptosis in HepG2 cell line

Endocrine disrupting chemicals (EDCs) may affect many biological processes like growth and stress response. Bisphenol A (BPA) is a plasticizer that is used to harden plastics and polycarbonates. Phthalates are used to add flexibility to polyvinyl chloride containing plastics. The main metabolite of di(2-ethylhexyl) phthalate (DEHP) is mono(2-ethylhexyl) phthalate (MEHP) and it is even more toxic than the parent compound. Humans are usually exposed to these chemicals in mixtures by different routes starting from fetal period. However, there are not many studies in literature that investigate the combined effects of these chemicals. The aim of this study is to investigate toxic effects of BPA and/or MEHP on HepG2 cell line. We have evaluated cytotoxicity, cytomorphological, apoptotic changes, oxidative stress, oxidant/antioxidant status alterations, and endoplasmic reticulum (ER) stress. Combined exposure to BPA and MEHP caused alterations in oxidant/antioxidant status and ER stress marker proteins in both cytoplasmic and nuclear cellular fractions. We can suggest that combined exposure to EDCs may cause serious toxicological outcomes and more mechanistic studies are needed to determine the combined toxic effects.

Effects of a phthalate metabolite mixture on both normal and tumoral human prostate cells

Phthalates represent a group of substances used in industry that have antiandrogenic activity and are found in different concentrations in human urine and plasma. More than 8 million tons of phthalates are used each year, predominantly as plasticizers in polyvinyl chloride (PVC) products. Phthalates are widely used in everyday consumer products and improperly discarded into the environment. Furthermore, in vivo studies carried out in our laboratory showed that a mixture of phthalates, equivalent to the mixture used in this study, deregulated the expression of genes and miRNAs associated with prostatic carcinogenic pathways. Thus, this study was designed to establish an in vitro model to assess pathways related to cell survival, proliferation, apoptosis, and biosynthesis of miRNAs, using both normal and tumoral prostatic epithelial cells exposed to an environmentally relevant mixture of phthalate metabolites. Tumor (LNCaP) and normal (PNT-2) prostatic epithelial cell lines were exposed for 24 and 72 h to vehicle control or the phthalate mixture. The selected metabolite mixture (1000 μmol/L) consisted of 36.7% monoethyl phthalate (MEP), 19.4% mono(2-ethylhexyl) phthalate (MEHP), 15.3% monobutyl phthalate (MBP), 10.2% monoisobutyl phthalate (MiBP), 10.2% monoisononyl phthalate (MiNP), and 8.2% monobenzyl phthalate (MBzP). Gene expression was performed by qRT-PCR and cell migratory potential was measured using cell migration assays. Our results showed that the mixture of phthalates increased cell turnover, oxidative stress, biosynthesis, and expression of miRNAs in LNCaP cells; thus, increasing their cellular expansive and migratory potential and modulating tumor behavior, making them possibly more aggressive. However, these effects were less pronounced in benign cells, demonstrating that, in the short term, benign cells are able to develop effective mechanisms or more resistance against the insult.

Phthalate exposure enhances incidence of urinary incontinence: US NHANES, 2003-2004 and 2005-2006

The aim of this study is to investigate the associations between phthalate exposure and UI in a nationally representative sample of US adults. Cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) database was used for analysis. In total, 2,818 participants with measurements for phthalate metabolites and complete UI questionnaire data were enrolled in our study. Furthermore, seven phthalate metabolites were measured, which were obtained from urine samples and creatinine-standardized in the subsequent analyses. After dividing these phthalate metabolites into three groups, multivariable regression models were performed to evaluate the association between phthalate metabolites and UI rates. Moreover, interaction analyses and subgroup analyses stratified by gender were performed. In these seven phthalate metabolites, high level of mono-carboxynonyl phthalate (MCNP), mono-carboxyoctyl phthalate (MCOP), mono-isobutyl phthalate (MiBP), mono-n-butyl phthalate (MBP), and mono-3-carboxypropyl phthalate (MCPP) showed increased risk of UI (odds ratio (OR) = 1.52, 1.42, 1.43, 1.50, 1.51, respectively, all p value < 0.05). Trend test showed that incidence of UI increased significantly with concentration. A higher incidence of UI among participants was observed in the maximal tertile of phthalate when comparing with the lowest tertile. Subgroup analysis found that different phthalates have varying influence for different types of UI. Moreover, the analyses stratified for sex indicated that the high concentrations of MCNP and median concentrations of MCCP were associated with increase of the odds of UI in women and in men, respectively. Overall, the exposure to phthalates was positively associated with UI among US adults. Notably, different phthalates have varying influence for different types of UI, and male and female exposure to phthalate could result in the different prevalence of UI.

Aggravation of autism-like behavior in BTBR T+tf/J mice by environmental pollutant, di-(2-ethylhexyl) phthalate: Role of nuclear factor erythroid 2-related factor 2 and oxidative enzymes in innate immune cells and cerebellum

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder which manifests itself in early childhood and is distinguished by recurring behavioral patterns, and dysfunction in social/communication skills. Ubiquitous environmental pollutant, di-2-ethylhexyl phthalate (DEHP) is one of the most frequently used plasticizers in various industrial products, e.g. vinyl flooring, plastic toys, and medical appliances. DEHP gets easily released into the environment and leads to human exposure through various routes. DEHP has been described to be linked with oxidative stress in various organs in animal/human studies. Increased concentration of DEHP has also been detected in ASD children which indicates an association between phthalates exposure and ASD. However, effect of DEHP on autism-like behavior has not been investigated previously. Therefore, this study probed the effect of DEHP on autism-like behavior (marble burying, self-grooming and sociability) and innate immune cells (dendritic cells/neutrophils)/cerebellar oxidant-antioxidant balance (NFkB, iNOS, NADPH oxidase, nitrotyrosine, lipid peroxides, Nrf2, SOD, GPx) in BTBR and C57 mice. Our data show that DEHP treatment causes worsening of autism-like behavior in BTBR mice which is associated with enhancement of oxidative stress in innate immune cells and cerebellum with concomitant lack of antioxidant protection. DEHP also causes oxidative stress in C57 mice in both innate immune cells and cerebellar compartment, however there is Nrf2-mediated induction of enzymatic antioxidants which protects them from upregulated oxidative stress. This proposes the notion that ubiquitous environmental pollutants such as DEHP may be involved in the pathogenesis/progression of ASD through dysregulation of antioxidant-antioxidant balance in innate immune cells and cerebellum.

Long-Term Exposure to Low-Dose Di-(2-ethylhexyl) Phthalate Impairs Cholesterol Metabolism in Hepatic Stellate Cells and Exacerbates Liver Librosis

Phthalates are often added to plastic products to increase their flexibility. Di-(2-ethylhexyl) phthalate (DEHP) is one of the most common plasticizers. Previously, a major incident involving phthalate-contaminated foodstuffs occurred, where phthalates were deliberately added to foodstuffs as a substitute for emulsifiers, resulting in a threat to public health. DEHP exposure can cause liver damage and further lead to cancer; however, the effects of long-term exposure to low-dose DEHP on hepatic stellate cells (HSCs) and on liver fibrosis are still unclear. In this study, we showed that chronic exposure to low-dose DEHP results in an accumulation of cholesterol in HSCs by disturbing the cholesterol metabolism and enhancing endogenous cholesterol synthesis. In addition, long-term exposure to low-dose DEHP reduces the sensitivity of HSCs to platelet-derived growth factor BB (PDGF-BB)-induced proliferation by blocking the MAPK pathway. Dysfunction of mitochondrial respiration and induction of caspase 3/PARP-dependent apoptosis were observed in HSCs following chronic, low-dose exposure. The carbon tetrachloride (CCl₄)-induced liver fibrosis mouse model showed that long-term administration of DEHP significantly promoted liver damage, inflammatory infiltration, cholesterol accumulation, and deposition of hepatic collagen. In conclusion, long-term exposure to low-dose DEHP may perturb the cholesterol metabolism in HSCs and accelerate liver damage and fibrosis.

Genotoxic, metabolic, and biological responses of Chironomus sancticaroli Strixino & Strixino, 1981 (Diptera: Chironomidae) after exposure to BBP

Benzyl butyl phthalate (BBP), which is widely used in industrial production, reaches the aquatic environment, mainly owing to improper disposal of plastic products. In the water, it remains adsorbed to sedimentary particles causing toxic effects in aquatic invertebrates such as Chironomidae, which are important in maintaining ecosystem dynamics and are an important link in the food chain. However, the effects of BBP on Chironomidae are still poorly known. Thus, the toxic effects of BBP on Chironomus sancticaroli at acute (48 h), subchronic (8 d), and chronic (25 d) exposures of concentrations between 0.1 and 2000 μg·L^-1 were determined. Genotoxicity effects, changes in the oxidative stress pathway, and development and emergence of organisms were evaluated. Biochemical markers showed a reduction in cholinesterase (ChE) activity, indicating a neurotoxic effect on acute exposure (1-1000 μg·L^-1). The antioxidant pathway, glutathione S-transferase (GST) activity showed reduction on acute (0.1; 1-2000 μg·L^-1) and subchronic (1-2000 μg·L^-1) exposures and reduction in superoxide dismutase (SOD) activity at all evaluated concentrations, suggesting oxidative stress. In contrast, lipid peroxidation was not observed. DNA damage occurred on acute (10 μg·L^-1) and subchronic (10-2000 μg·L^-1) exposures, indicating genotoxic effects. At concentrations above 10 μg·L^-1, no emergence of adults occurred, while lower concentrations (0.1 and 1 μg·L^-1) showed a reduction in the number of adults, mainly males. The observed effects indicate that BBP is genotoxic and causes biochemical alterations presenting high toxicity at the population level.

A strategy to validate a selection of human effect biomarkers using adverse outcome pathways: Proof of concept for phthalates and reproductive effects

Human biomonitoring measures the concentrations of environmental chemicals or their metabolites in body fluids or tissues. Complementing exposure biomarkers with mechanistically based effect biomarkers may further elucidate causal pathways between chemical exposure and adverse health outcomes. We combined information on effect biomarkers previously implemented in human observational studies with mechanisms of action reported in experimental studies and with information from published Adverse Outcome Pathways (AOPs), focusing on adverse reproductive effects of phthalate exposure. Phthalates constitute a group of chemicals that are ubiquitous in consumer products and have been related to a wide range of adverse health effects. As a result of a comprehensive literature search, we present an overview of effect biomarkers for reproductive toxicity that are substantiated by mechanistic information. The activation of several receptors, such as PPARα, PPARγ, and GR, may initiate events leading to impaired male and female fertility as well as other adverse effects of phthalate exposure. Therefore, these receptors appear as promising targets for the development of novel effect biomarkers. The proposed strategy connects the fields of epidemiology and toxicology and may strengthen the weight of evidence in observational studies that link chemical exposures to health outcomes.

Positive association of low-level environmental phthalate exposure with sperm motility was mediated by DNA methylation: A pilot study

Accumulating evidence indicates that phthalate exposures may affect human semen quality. Epigenetic modifications such as DNA methylation might be linked chemical exposure and spermatogenesis epigenetic reprogramming. In the present study, we investigated associations between phthalate exposures, DNA methylation and sperm quality in undergoing fertility assessment male population. Urine was used for phthalate exposures monitoring, six selected metabolites (i.e., monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), monobenzyl phthalate (MBzP), mono-(2-ethylhexyl) phthalate (MEHP) and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP)) were measured by using HPLC-MS/MS. Sperm quality parameters were determined by computer-assisted semen analysis (CASA). Sperm DNA methylation patterns (long interspersed nuclear element-1(LINE-1), H19 and LIT1) were analysed employing high-melting resolution (HRM) PCR. Urinary MMP, MEHP, MEOHP, sum of DEHP metabolites (∑DEHP) and sum of selected phthalates metabolites (∑PAEs) were significantly positively associated with sperm motility. Sperm LINE-1 DNA methylation were found to be negatively associated with ∑DEHP exposure and sperm quality (ejaculate volume, total sperm number and motility). Epigenetic modification LINE-1 DNA methylation demonstrated mediating effects in association between DEHP exposure and sperm motility, and 20.7% of the association was mediated by serum LIEN-1 DNA methylation. These results extend the previous studies in association between phthalate exposures and classical semen parameters, mainly of inverse association, and sperm DNA methylation may be linked phthalate exposures and male reproductive health outcome.

Di-(2-Ethylhexyl) Phthalate Promotes Release of Tissue Factor-Bearing Microparticles From Macrophages via the TGFβ1/Smad/PAI-1 Signaling Pathway

BACKGROUND

Plasminogen activator inhibitor type 1 promotes formation of endothelial microparticles with procoagulant activity. However, it remains unclear whether di-(2-ethylhexyl) phthalate, a peroxisome proliferator-activated receptor α agonist, influences microparticle formation.

MATERIALS AND METHODS

The effect of di-(2-ethylhexyl) phthalate on release of tissue factor-bearing microparticles was investigated using human M1 macrophages.

RESULTS

Exposure of M1 macrophages to di-(2-ethylhexyl) phthalate significantly upregulated expression of plasminogen activator inhibitor type 1, whereas incubation of macrophages with small interfering RNA for peroxisome proliferator-activated receptor α attenuated it. Di-(2-ethylhexyl) phthalate significantly increased the tissue factor protein level in culture supernatants of M1 macrophages, but not M2 macrophages. After purification of proteins by centrifugal filtration, western blotting detected 2 high molecular weight bands of tissue factor-bearing microparticles in culture supernatants of M1 macrophages. The upper band showed binding to factor VIIa and tissue factor pathway inhibitor, unlike the lower band. This suggested heterogeneity of the procoagulant activity of tissue factor-bearing microparticles, presumably dependent upon encryption/decryption of tissue factor. Phosphatidylserine contributes to tissue factor decryption, and western blotting revealed that the density of phosphatidylserine was reduced in the upper tissue factor band compared with the lower band. Di-(2-ethylhexyl) phthalate also upregulated transforming growth factor-β1 protein production by M1 macrophages. Moreover, silencing of Smad2, Smad3 or Smad4 attenuated plasminogen activator inhibitor type 1 expression and tissue factor-release from macrophages after di-(2-ethylhexyl) phthalate stimulation.

CONCLUSIONS

Di-(2-ethylhexyl) phthalate promotes formation of tissue factor-bearing microparticles in human M1 macrophages via the transforming growth factor-β1/Smad/ plasminogen activator inhibitor type 1 signaling pathway.

Phthalates and Phthalate Alternatives Have Diverse Associations with Oxidative Stress and Inflammation in Pregnant Women

Exposure to environmental chemicals such as phthalates has been linked to numerous adverse pregnancy outcomes, potentially through an oxidative stress mediated mechanism. Most research examined urinary 8-iso-prostaglandin F2α (8-iso-PGF2α) as the oxidative stress biomarker. However, 8-iso-PGF2α also originates from enzymatic sources linked to inflammation. Therefore, associations between phthalates and 8-iso-PGF2α could have been misinterpreted. To clarify this, the 8-iso-PGF2α/prostaglandin F2α ratio approach was used to quantitatively distinguish between inflammation or oxidative stress derived 8-iso-PGF2α and estimate their associations with phthalate metabolites in a cohort of 758 pregnant women from The Infant Development and Environment Study (TIDES). Most urinary phthalate metabolites were associated with a significant increase in 8-iso-PGF2α. For example, a 22.4% higher 8-iso-PGF2α concentration (95% confidence interval = 14.4, 30.9) was observed with an interquartile range increase in mono- n-butyl phthalate. For most metabolites, associations were observed solely with oxidative stress derived 8-iso-PGF2α. In contrast, monocarboxy-isononyl phthalate and monoisononyl phthalate (MNP) were associated with both sources of 8-iso-PGF2α. Metabolites of the phthalate alternative 1,2-cyclohexane dicarboxylic acid, diisononyl ester (DINCH), were only associated with inflammation-derived 8-iso-PGF2α, which is interesting because DINCH metabolites and MNP have structural similarities.In conclusion, phthalates metabolites are not exclusively associated with oxidative stress derived 8-iso-PGF2α. Depending on the metabolite structure, some are also associated with inflammation derived sources, which provides interesting insights in the toxicology of phthalates.

Perinatal phthalate and high-fat diet exposure induce sex-specific changes in adipocyte size and DNA methylation

Environmental factors such as diet and endocrine-disrupting chemicals have individually been shown to mediate metabolic function. However, the underlying mechanism by which the combination disrupts adipocyte morphology and fat storage remains unknown. The current study evaluated early-life programming by diet and phthalate exposure. During gestation and lactation, pregnant Long-Evans hooded rat dams were fed either a control (C) or high-fat (HF) diet and were orally administered one of three phthalate dosages (0, 200 or 1000 μg/kg/day), yielding six groups of offspring: C-0, C-200, C-1000, HF-0, HF-200 and HF-1000. On postnatal day (PND) 90, gonadal fat pads were collected and analyzed for histology, gene expression and DNA methylation. Differences in body weight were observed only in males. Hematoxylin and eosin staining revealed larger adipocyte size in HF-0 vs. C-0 females. Exposure to 200 or 1000 μg/kg/day phthalates modulated diet-induced changes in adipose morphology. Compared to C-0 females, HF-0 females also had higher expression of the adipogenesis gene Wnt receptor, frizzled 1 (Fzd1) and the triglyceride cleaving enzyme lipoprotein lipase (Lpl). These increases in gene expression were accompanied by lower DNA methylation surrounding the transcription start sites of the two genes. Diet-driven effects were observed in unexposed females but not in phthalate-treated rats. Results suggest a sex-specific association between perinatal HF diet and body weight, adipocyte size and DNA methylation. Perinatal phthalate exposure appears to produce a phenotype that more closely resembles HF-fed animals.

Sex differences, endogenous sex-hormone hormones, sex-hormone binding globulin, and exogenous disruptors in diabetes and related metabolic outcomes

In assessing clinical and pathophysiological development of type 2 diabetes (T2D), the critical role of the sex steroids axis is underappreciated, particularly concerning the sex-specific relationships with many relevant cardiometabolic outcomes. In this issue of the Journal of Diabetes, we provide a comprehensive overview of these significant associations of germline variants in the genes governing the sex steroid pathways, plasma levels of steroid hormones, and sex hormone-binding globulin (SHBG) with T2D risk that have been observed in many clinical and high-quality large prospective cohorts of men and women across ethnic populations. Together, this body of evidence indicates that sex steroids and SHBG should be routinely incorporated into clinical characterization of T2D patients, particularly in screening prediabetic patients, such as those with metabolic syndrome, using plasma levels of SHBG. Given that several germline mutations in the SHBG gene have also been directly related to both plasma concentrations of SHBG and clinical manifestation of T2D, targeting signals in the sex steroid axis, particularly SHBG, may have significant utility in the prediction and treatment of T2D. Further, many of the environmental endocrine disrupting chemicals may exert their potential adverse effects on cardiometabolic outcomes via either estrogenic or androgenic signaling pathways, highlighting the importance of using the sex steroids and SHBG as important biochemical markers in both clinical and population studies in studying sex-specific mechanisms in the pathogenesis of T2D and its complications, as well as the need to equitably allocate resources in studying both men and women.

Di-(2-ethylhexyl) phthalate enhances melanoma tumor growth via differential effect on M1-and M2-polarized macrophages in mouse model

Phthalates are widely used as plasticizers that influence sexual and reproductive development. Here, we investigated whether di-(2-ethylhexyl) phthalate (DEHP) affects macrophage polarization that are associated with tumor initiation and progression. No changes were observed in LPS- or ConA-stimulated in vitro spleen B or T cell proliferation for 48 h, respectively. In contrast, macrophage functions were inhibited in response to DEHP for 12 h as judged by LPS-induced H₂O₂ and NO production and zymosan A-mediated phagocytosis. When six weeks old male mice were pre-exposed to 4.0 mg/kg DEHP for 21 days before the injection of B16F10 melanoma cells and post-exposed to 4.0 mg/kg DEHP for 7 days, tumor nodule formation and the changes in tumor volume were higher than those in control group. Furthermore, when male mice were intraperitoneally pretreated with DEHP for 3 or 4 weeks and peritoneal exudate cells (PECs) or bone marrow-derived macrophages (BMDMs) were incubated with lipopolysaccharide (LPS), the expression of COX-2, TNF-α, and IL-6 was reduced in DEHP-pretreated cells as compared with that in LPS-stimulated control cells. While the production of nitric oxide (NO) for 18 h was reduced by LPS-stimulated PECs and M1-type BMDMs, IL-4 expression was enhanced in LPS-stimulated BMDMs. When BMDMs were incubated with IL-4 for 30 h, arginase 1 for M2-type macrophages was increased in transcriptional and translational level. Data implicate that macrophages were differentially polarized by DEHP treatment, which reduced M1-polarzation but enhanced M2-polarization. Taken together, these data demonstrate that DEHP could affect in vivo immune responses of macrophages, leading to the suppression of their tumor-preventing ability. This suggests that individuals at high risk for tumor incidence should avoid long-term exposure to various kind of phthalate including DEHP.

The PPARα-dependent rodent liver tumor response is not relevant to humans: addressing misconceptions

A number of industrial chemicals and therapeutic agents cause liver tumors in rats and mice by activating the nuclear receptor peroxisome proliferator-activated receptor α (PPARα). The molecular and cellular events by which PPARα activators induce rodent hepatocarcinogenesis have been extensively studied elucidating a number of consistent mechanistic changes linked to the increased incidence of liver neoplasms. The weight of evidence relevant to the hypothesized mode of action (MOA) for PPARα activator-induced rodent hepatocarcinogenesis is summarized here. Chemical-specific and mechanistic data support concordance of temporal and dose-response relationships for the key events associated with many PPARα activators. The key events (KE) identified in the MOA are PPARα activation (KE1), alteration in cell growth pathways (KE2), perturbation of hepatocyte growth and survival (KE3), and selective clonal expansion of preneoplastic foci cells (KE4), which leads to the apical event-increases in hepatocellular adenomas and carcinomas (KE5). In addition, a number of concurrent molecular and cellular events have been classified as modulating factors, because they potentially alter the ability of PPARα activators to increase rodent liver cancer while not being key events themselves. These modulating factors include increases in oxidative stress and activation of NF-kB. PPARα activators are unlikely to induce liver tumors in humans due to biological differences in the response of KEs downstream of PPARα activation. This conclusion is based on minimal or no effects observed on cell growth pathways and hepatocellular proliferation in human primary hepatocytes and absence of alteration in growth pathways, hepatocyte proliferation, and tumors in the livers of species (hamsters, guinea pigs and cynomolgus monkeys) that are more appropriate human surrogates than mice and rats at overlapping dose levels. Despite this overwhelming body of evidence and almost universal acceptance of the PPARα MOA and lack of human relevance, several reviews have selectively focused on specific studies that, as discussed, contradict the consensus opinion and suggest uncertainty. In the present review, we systematically address these most germane suggested weaknesses of the PPARα MOA.

Dietary exposure to di-isobutyl phthalate increases urinary 5-methyl-2'-deoxycytidine level and affects reproductive function in adult male mice

Phthalates are a large family of ubiquitous environmental pollutants suspected of being endocrine disruptors. Epidemiological studies have associated phthalate metabolites with decreased reproductive parameters and linked phthalate exposure with the level of urinary 5-methyl-2'-deoxycytidine (5mdC, a product of methylated DNA). In this study, adult male mice were exposed to 450mg di-isobutyl phthalate (DiBP)/(kg·day) via dietary exposure for 28days. Mono-isobutyl phthalate (MiBP, the urinary metabolite) and reproductive function parameters were determined. The levels of 5mdC and 5-hydroxymethyl-2'-deoxycytidine (5hmdC) were measured in urine to evaluate if their contents were also altered by DiBP exposure in this animal model. Results showed that DiBP exposure led to a significant increase in the urinary 5mdC level and significant decreases in sperm concentration and motility in the epididymis, accompanied with reduced testosterone levels and down-regulation of the P450 cholesterol side-chain cleavage enzyme (P450scc) gene in the mice testes. Our findings indicated that exposure to DiBP increased the urinary 5mdC levels, which supported our recent epidemiological study about the associations of urinary 5mdC with phthalate exposure in the male human population. In addition, DiBP exposure impaired male reproductive function, possibly by disturbing testosterone levels; P450scc might be a major steroidogenic enzyme targeted by DiBP or other phthalates.

Acute exposure to DEHP metabolite, MEHP cause genotoxicity, mutagenesis and carcinogenicity in mammalian Chinese hamster ovary cells

Di-(2-ethylhexyl) phthalate (DEHP), the common plasticizer used in the production of polyvinyl chloride, can be converted to the more potent metabolite mono-ethylhexyl phthalate (MEHP). Epidemiological studies have shown an association with elevated induction of rat hepatic cancer and reproductive toxicity in response to MEHP exposure. However, the mechanism of genotoxicity and carcinogenicity induced by MEHP treatment remains unclear. As a means to elucidate the mechanisms of action, lethality and mutagenicity in the adenine phosphoribosyltransferase (aprt+/-) gene induced in several CHO cell types by MEHP were assessed. Dose-response relationships were determined in the parental AA8 cell line, its nucleotide repair-deficient UV5 and base repair-deficient EM9 subclones, and also in AS52 cells harboring the bacterial guanine-hypoxanthine phosphoribosyltransferase (gpt) gene and its derived AS52-XPD-knockdown and AS52-PARP-1-knockdown cells. Treatment of AS52 with MEHP led to intracellular production of reactive oxygen species (ROS) and DNA strand breaks in a dose-dependent manner. Separately, mutations in the gpt gene of AS52 cells were characterized and found to be dominated by G:C to A:T and A:T to G:C transitions. Independent AS52-mutant cell (ASMC) clones were collected for the sequential in vivo xenograft tumorigenic studies, 4 of total 20 clones had aggressive tumor growth. Moreover, microarray analysis indicated miR-let-7a and miR-125b downregulated in ASMC, which might raise oncogenic MYC and RAS level and activate ErbB pathway. Comparative evaluation of the results indicates that the principal mechanism of this mutagenic action is probably to be through generation of ROS, causing base excision damage resulting in carcinogenicity.

Application of cell-based assays for toxicity characterization of complex wastewater matrices: Possible applications in wastewater recycle and reuse

Exposure to pre-concentrated inlet or outlet STP wastewater extracts at different concentrations (0.001% to 1%) induced dose-dependent toxicity in MCF-7 cells, whereas drinking water extracts did not induce cytotoxicity in cells treated. GC-MS analysis revealed the occurrence of xenobiotic compounds (Benzene, Phthalate, etc.) in inlet/outlet wastewater extracts. Cells exposed to inlet/outlet extract showed elevated levels of reactive oxygen species (ROS: inlet: 186.58%, p<0.05, outlet, 147.8%, p<0.01) and loss of mitochondrial membrane potential (Δψm: inlet, 74.91%, p<0.01; outlet, 86.70%, p<0.05) compared to the control. These concentrations induced DNA damage (Tail length: inlet: 34.4%, p<0.05, outlet, 26.7%, p<0.05) in treated cells compared to the control (Tail length: 7.5%). Cell cycle analysis displayed drastic reduction in the G1 phase in treated cells (inlet, G1:45.0%; outlet, G1:58.3%) compared to the control (G1:67.3%). Treated cells showed 45.18% and 28.0% apoptosis compared to the control (1.2%). Drinking water extracts did not show any significant alterations with respect to ROS, Δψm, DNA damage, cell cycle and apoptosis compared to the control. Genes involved in cell cycle and apoptosis were found to be differentially expressed in cells exposed to inlet/outlet extracts. Herein, we propose cell-based toxicity assays to evaluate the efficacies of wastewater treatment and recycling processes.

Di-(2-ethylhexyl) phthalate suppresses IL-12p40 production by GM-CSF-dependent macrophages via the PPARα/TNFAIP3/TRAF6 axis after lipopolysaccharide stimulation

Activation of peroxisome proliferator-activated receptor α (PPARα) by di-(2-ethylhexyl) phthalate (DEHP) has an anti-inflammatory effect. This study investigated the potential combined influence of PPARα, tumor necrosis factor α-induced protein 3 (TNFAIP3/A20), and tumor necrosis factor receptor-associated factor 6 (TRAF6) on interleukin (IL)-12p40 production by macrophages exposed to DEHP and stimulated with lipopolysaccharide (LPS). LPS upregulated IL-12p40 expression by granulocyte-macrophage colony-stimulating factor-dependent macrophages (on day 9 of culture), whereas adding DEHP to cultures significantly attenuated the response of IL-12p40 to LPS stimulation. PPARα protein was also reduced by DEHP. Interestingly, transfection of macrophages with small interfering RNA (siRNA) duplexes for PPARα, TNFAIP3/A20, or dual oxidase 2 restored the response of IL-12p40 protein to LPS stimulation in the presence of DEHP. siRNAs for various protein kinase Cs (PKCs) (α, β, γ, or δ) also restored IL-12p40 production by macrophages exposed to LPS and DEHP. While LPS upregulated both IL-12p40 and TNFAIP3/A20 production, adding DEHP to cultures dramatically reduced IL-12p40 and TNFAIP3/A20 levels. Silencing of PKCα reduced TNFAIP3/A20 production, whereas PKCγ siRNA (but not PKCβ or δ siRNA) significantly increased TNFAIP3/A20. TRAF6 was also attenuated by macrophages with DEHP. The PPARα/TNFAIP3/TRAF6 axis may have an important role in the mechanism through which DEHP reduces IL-12p40 production by LPS-stimulated macrophages.

Mediation of the Relationship between Maternal Phthalate Exposure and Preterm Birth by Oxidative Stress with Repeated Measurements across Pregnancy

BACKGROUND

Mediation analysis is useful for understanding mechanisms and has been used minimally in the study of the environment and disease.

OBJECTIVE

We examined mediation of the association between phthalate exposure during pregnancy and preterm birth by oxidative stress.

METHODS

This nested case-control study of preterm birth (n = 130 cases, 352 controls) included women who delivered in Boston, Massachusestts, from 2006 through 2008. Phthalate metabolites and 8-isoprostane, an oxidative stress biomarker, were measured in urine from three visits in pregnancy. We applied four counterfactual mediation methods: method 1, utilizing exposure and mediator averages; method 2, using averages but allowing for an exposure-mediator interaction; method 3, incorporating longitudinal measurements of the exposure and mediator; and method 4, using longitudinal measurements and allowing for an exposure-mediator interaction.

RESULTS

We observed mediation of the associations between phthalate metabolites and all preterm birth by 8-isoprostane, with the greatest estimated proportion mediated observed for spontaneous preterm births specifically. Fully utilizing repeated measures of the exposure and mediator improved precision of indirect (i.e., mediated) effect estimates, and including an exposure-mediator interaction increased the estimated proportion mediated. For example, for mono(2-ethyl-carboxy-propyl) phthalate (MECPP), a metabolite of di(2-ethylhexyl) phthalate (DEHP), the percent of the total effect mediated by 8-isoprostane increased from 47% to 60% with inclusion of an exposure-mediator interaction term, in reference to a total adjusted odds ratio of 1.67 or 1.48, respectively.

CONCLUSIONS

This demonstrates mediation of the phthalate-preterm birth relationship by oxidative stress, and the utility of complex regression models in capturing mediated associations when repeated measures of exposure and mediator are available and an exposure-mediator interaction may exist. Citation: Ferguson KK, Chen YH, VanderWeele TJ, McElrath TF, Meeker JD, Mukherjee B. 2017. Mediation of the relationship between maternal phthalate exposure and preterm birth by oxidative stress with repeated measurements across pregnancy. Environ Health Perspect 125:488-494; http://dx.doi.org/10.1289/EHP282.

Third trimester phthalate exposure is associated with DNA methylation of growth-related genes in human placenta

Strong evidence implicates maternal phthalate exposure during pregnancy in contributing to adverse birth outcomes. Recent research suggests these effects might be mediated through the improper regulation of DNA methylation in offspring tissue. In this study, we examined associations between prenatal phthalate exposure and DNA methylation in human placenta. We recruited 181 mother-newborn pairs (80 fetal growth restriction newborns, 101 normal newborns) in Wenzhou, China and measured third trimester urinary phthalate metabolite concentrations and placental DNA methylation levels of IGF2 and AHRR. We found urinary concentrations of mono (2-ethyl-5- hydroxyhexyl) phthalate (MEHHP), and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) were significantly inversely associated with placental IGF2 DNA methylation. The associations were much more evident in fetal growth restriction (FGR) newborns than those in normal newborns. These findings suggest that changes in placental DNA methylation might be part of the underlying biological pathway between prenatal phthalate exposure and adverse fetal growth.

Associations of urinary 5-methyl-2'-deoxycytidine and 5-hydroxymethyl-2'-deoxycytidine with phthalate exposure and semen quality in 562 Chinese adult men

5-methyl-2'-deoxycytidine (5mdC) and 5-hydroxymethyl-2'-deoxycytidine (5hmdC), products of DNA methylation and hydroxymethylation processes, have been detected previously in human urine, but their associations with environmental chemicals or healthy outcomes are unclear. The present investigation explored the associations between urinary 5mdC and 5hmdC with phthalate exposure and semen quality. We assessed semen parameters including sperm concentration, motility, and morphology, before measuring urinary 5mdC, 5hmdC and 13 phthalate metabolites among 562 subfertile men from Nanjing, China. Urinary 5mdC and 5hmdC were positively associated with the levels of low molecular weight phthalate metabolites (Low-MWP), high molecular weight phthalate metabolites (High-MWP), and the sum of all phthalate metabolites (ΣPAEs), respectively. Urinary 5mdC was associated with below-reference sperm concentration (odds ratios for increasing quartiles=1.0, 2.2, 3.0, 2.0; p for trend =0.02), sperm motility (1.0, 1.1, 1.9, 1.3; p for trend =0.05), and sperm morphology (1.0, 1.4, 2.3, 1.5; p for trend =0.05). Sperm concentration was associated with the highest quartile of urinary 5hmdC [odds ratio=1.9 (95% CI: 1.1, 3.6)]. Our findings showed significant associations between urinary 5mdC and 5hmdC with phthalate metabolites and semen parameters, which suggested urinary 5mdC and 5hmdC may be promising biomarkers in future epidemiological studies.

Mono-2-ethylhexyl phthalate disrupts neurulation and modifies the embryonic redox environment and gene expression

Mono-2-ethylhexl phthalate (MEHP) is the primary metabolite of di-2-ethylhexyl phthalate (DEHP), a ubiquitous contaminant in plastics. This study sought to determine how structural defects caused by MEHP in mouse whole embryo culture were related to temporal and spatial patterns of redox state and gene expression. MEHP reduced morphology scores along with increased incidence of neural tube defects. Glutathione (GSH) and cysteine (Cys) concentrations fluctuated spatially and temporally in embryo (EMB) and visceral yolk sac (VYS) across the 24h culture. Redox potentials (Eh) for GSSG/GSH were increased by MEHP in EMB (12h) but not in VYS. CySS/CyS Eh in EMB and VYS were significantly increased at 3h and 24h, respectively. Gene expression at 6h showed that MEHP induced selective alterations in EMB and VYS for oxidative phosphorylation and energy metabolism pathways. Overall, MEHP affects neurulation, alters Eh, and spatially alters the expression of metabolic genes in the early organogenesis-stage mouse conceptus.

Mechanisms of housedust-induced toxicity in primary human corneal epithelial cells: Oxidative stress, proinflammatory response and mitochondrial dysfunction

Human cornea is highly susceptible to damage by dust. Continued daily exposure to housedust has been associated with increasing risks of corneal injury, however, the underlying mechanism has not been elucidated. In this study, a composite housedust sample was tested for its cytotoxicity on primary human corneal epithelial (PHCE) cells, which were exposed to dust at 5-320μg/100μL for 24h. PHCE cell viability showed a concentration-dependent toxic effect, attributing to elevated intracellular ROS. Moreover, when exposed at >20-80μg/100μL, dust-induced oxidative damage was evidenced by increased malondialdehyde and 8-hydroxy-2-deoxyguanosine (1.3-2.3-fold) and decreased antioxidative capacity (1.6-3.5-fold). Alteration of mRNA expression of antioxidant enzymes (SOD1, CAT, HO-1, TRXR1, GSTM1, GSTP1, and GPX1) and pro-inflammatory mediators (IL-1β, IL-6, IL-8, TNF-α, and MCP-1) were also observed. Furthermore, the mitochondrial transmembrane potential was dissipated from 9.2 to 82%. Our results suggested that dust-induced oxidative stress probably played a vital role in the cytotoxicity in PHCE cells, which may have contributed to dust-induced impairment of human cornea.

Di(2-ethylhexyl) phthalate exacerbates non-alcoholic fatty liver in rats and its potential mechanisms

Di(2-ethylhexyl) phthalate (DEHP) may be responsible for inducing alterations similar to those encountered in nonalcoholic fatty liver disease (NAFLD). The aim of the present study was to investigate the detrimental effects and possible mechanisms of DEHP on fatty liver rats directly through triggering the disorder of liver lipid metabolism or indirectly by hepatotoxic effect. Considering these effects, DEHP may play a significant role in the pathogenesis of NAFLD. In this study, high-fat diet was used to induce NAFLD in rats for eight weeks. DEHP treated groups received (0.05, 5, 500 mg/kg daily, respectively) dose by gavage during the whole experiment period. Our results indicated that the detrimental effects of DEHP on high-fat diet induced NAFLDs were mediated via increasing lipid accumulation in the liver and causing lipid peroxidation and inflammation.

Prenatal phthalate exposure, infant growth, and global DNA methylation of human placenta

Prenatal phthalate exposure has been shown to be associated with reduced fetal growth. Epigenetic changes such as DNA methylation might be a molecular mechanism through which phthalate exposure affects fetal growth. In this study, we examined associations between prenatal phthalate exposure, infant growth, and global DNA methylation in human placenta samples. We measured global DNA methylation of 119 subjects [55 fetal growth restriction (FGR) cases and 64 normal controls], as assessed by long interspersed nuclear element-1 (LINE-1) methylation, via quantitative polymerase chain reaction-pyrosequencing. Prenatal phthalate exposure was assessed by measuring maternal urinary phthalate metabolites concentrations using high-performance liquid chromatography-tandem mass spectrometry. Concentrations of mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono (2-ethyl-5-oxohexyl) phthalate (MEOHP), and SumDEHP (molar sum of MEHP, MEHHP, and MEOHP) were significantly higher in FGR cases than those in normal controls (P = 0.002, 0.003, and 0.002, respectively). Placental LINE-1 methylation were found to be positively associated with fetal birth weight standard deviation scores, and negatively associated with urinary phthalate metabolites concentrations (MEHHP and SumDEHP). Every natural-log unit increase in urinary concentrations of MEHHP and SumDEHP was associated with 0.015 (β = -0.015, P = 0.150) and 0.012 kg (β = -0.012, P = 0.167) decrease in birth weight mediated through LINE-1 methylation. These findings suggest that changes in placental LINE-1 methylation might be part of the underlying biological pathway between prenatal phthalate exposure and adverse fetal growth.

Urinary phthalate metabolites and biomarkers of oxidative stress in pregnant women: a repeated measures analysis

BACKGROUND

Phthalate exposure occurs readily in the environment and has been associated with an array of health end points, including adverse birth outcomes. Some of these may be mediated by oxidative stress, a proposed mechanism for phthalate action.

OBJECTIVES

In the present study, we explored the associations between phthalate metabolites and biomarkers of oxidative stress measured in urine samples from multiple time points during pregnancy.

METHODS

Women were participants in a nested case-control study of preterm birth (n = 130 cases, n = 352 controls). Each was recruited early in pregnancy and followed until delivery, providing urine samples at up to four visits. Nine phthalate metabolites were measured to assess exposure, and 8-hydroxydeoxyguanosine and 8-isoprostane were also measured in urine as markers of oxidative stress. Associations were assessed using linear mixed models to account for intraindividual correlation, with inverse selection probability weightings based on case status to allow for greater generalizability.

RESULTS

Interquartile range increases in phthalate metabolites were associated with significantly higher concentrations of both biomarkers. Estimated differences were greater in association with monobenzyl phthalate (MBzP), mono-n-butyl phthalate (MBP), and monoisobutyl phthalate (MiBP), compared with di(2-ethylhexyl) phthalate (DEHP) metabolites.

CONCLUSIONS

Urinary phthalate metabolites were associated with increased oxidative stress biomarkers in our study population of pregnant women. These relationships may be particularly relevant to the study of birth outcomes linked to phthalate exposure. Although replication is necessary in other populations, these results may also be of great importance for a range of other health outcomes associated with phthalates.

Regulation of bacterial lipopolysaccharide in liver toxicity caused by chlorpromazine and Z24 in Sprague-Dawley rats

LPS-induced inflammatory response could be used to establish screening models for ILT and provides a new way to reduce liver toxicity of Z24.

Phthalates induce neurotoxicity affecting locomotor and thermotactic behaviors and AFD neurons through oxidative stress in Caenorhabditis elegans

Background

Phthalate esters are ubiquitous environmental contaminants and numerous organisms are thus exposed to various levels of phthalates in their natural habitat. Considering the critical, but limited, research on human neurobehavioral outcomes in association with phthalates exposure, we used the nematode Caenorhabditis elegans as an in vivo model to evaluate phthalates-induced neurotoxicity and the possible associated mechanisms.

Principal Findings

Exposure to phthalates (DEHP, DBP, and DIBP) at the examined concentrations induced behavioral defects, including changes in body bending, head thrashing, reversal frequency, and thermotaxis in C. elegans. Moreover, phthalates (DEHP, DBP, and DIBP) exposure caused toxicity, affecting the relative sizes of cell body fluorescent puncta, and relative intensities of cell bodies in AFD neurons. The mRNA levels of the majority of the genes (TTX-1, TAX-2, TAX-4, and CEH-14) that are required for the differentiation and function of AFD neurons were decreased upon DEHP exposure. Furthermore, phthalates (DEHP, DBP, and DIBP) exposure at the examined concentrations produced elevated intracellular reactive oxygen species (ROS) in C. elegans. Finally, pretreatment with the antioxidant ascorbic acid significantly lowered the intracellular ROS level, ameliorated the locomotor and thermotactic behavior defects, and protected the damage of AFD neurons by DEHP exposure.

Conclusions

Our study suggests that oxidative stress plays a critical role in the phthalate esters-induced neurotoxic effects in C. elegans.

Mode of action framework analysis for receptor-mediated toxicity: The peroxisome proliferator-activated receptor alpha (PPARα) as a case study

Several therapeutic agents and industrial chemicals induce liver tumors in rodents through the activation of the peroxisome proliferator-activated receptor alpha (PPARα). The cellular and molecular events by which PPARα activators induce rodent hepatocarcinogenesis has been extensively studied and elucidated. This review summarizes the weight of evidence relevant to the hypothesized mode of action (MOA) for PPARα activator-induced rodent hepatocarcinogenesis and identifies gaps in our knowledge of this MOA. Chemical-specific and mechanistic data support concordance of temporal and dose-response relationships for the key events associated with many PPARα activators including a phthalate ester plasticizer di(2-ethylhexyl) phthalate (DEHP) and the drug gemfibrozil. While biologically plausible in humans, the hypothesized key events in the rodent MOA, for PPARα activators, are unlikely to induce liver tumors in humans because of toxicodynamic and biological differences in responses. This conclusion is based on minimal or no effects observed on growth pathways, hepatocellular proliferation and liver tumors in humans and/or species (including hamsters, guinea pigs and cynomolgous monkeys) that are more appropriate human surrogates than mice and rats at overlapping dose levels. Overall, the panel concluded that significant quantitative differences in PPARα activator-induced effects related to liver cancer formation exist between rodents and humans. On the basis of these quantitative differences, most of the workgroup felt that the rodent MOA is "not relevant to humans" with the remaining members concluding that the MOA is "unlikely to be relevant to humans". The two groups differed in their level of confidence based on perceived limitations of the quantitative and mechanistic knowledge of the species differences, which for some panel members strongly supports but cannot preclude the absence of effects under unlikely exposure scenarios.

The effects of di(2-ethylhexyl)phthalate on rat liver in relation to selenium status

This study was performed to determine the hepatotoxicity of di(2-ethylhexyl)phthalate (DEHP) in relation to selenium status. In 3-week-old Sprague-Dawley rats, selenium deficiency was induced by a ≤0.05 selenium mg/kg. A selenium supplementation group was given 1 mg selenium/kg diet for 5 weeks. Di(2-ethylhexyl)phthalate-treated groups received 1000 mg/kg dose by gavage during the last 10 days of the experiment. Histopathology, peroxisome proliferation, catalase (CAT) immunoreactivity and activity and apoptosis were assessed. Activities of antioxidant selenoenzymes [glutathione peroxidase 1 (GPx1), glutathione peroxidase 4 (GPx4), thioredoxin reductase (TrxR1)], superoxide dismutase (SOD), and glutathione S-transferase (GST); aminotransferase, total glutathione (tGSH), and lipid peroxidation (LP) levels were measured. Di(2-ethylhexyl)phthalate caused cellular disorganization while necrosis and inflammatory cell infiltration were observed in Se-deficient DEHP group (DEHP/SeD). Catalase activity and immunoreactivity were increased in all DEHP-treated groups. Glutathione peroxidase 1 and GPx4 activities decreased significantly in DEHP and DEHP/SeD groups, while GST activities decreased in all DEHP-exposed groups. Thioredoxin reductase activity increased in DEHP and DEHP/SeS, while total SOD activities increased in all DEHP-treated groups. Lipid peroxidation levels increased significantly in SeD (26%), DEHP (38%) and DEHP/SeD (71%) groups. Selenium supplementation partially ameliorated DEHP-induced hepatotoxicity; while in DEHP/SeD group, drastic changes in hepatic histopathology and oxidative stress parameters were observed.

Di(2-ethylhexyl)phthalate exposure impairs insulin receptor and glucose transporter 4 gene expression in L6 myotubes

Di(2-ethyl hexyl)-phthalate (DEHP) is an endocrine disrupter and is the most abundantly used phthalate derivative, which is suspected to be an inevitable environmental exposure contributing to the increasing incidence of type-2 diabetes in humans. Therefore, the present study was designed to address the dose-dependent effects of DEHP on insulin signaling molecules in L6 myotubes. L6 myotubes were exposed to different concentrations (25, 50, and 100 μM) of DEHP for 24 h. At the end of exposure, cells were utilized for assessing various parameters. Insulin receptor and glucose transporter4 (GLUT4) gene expression, insulin receptor protein concentration, glucose uptake and oxidation, and enzymatic and nonenzymatic antioxidants were significantly reduced, but glutamine fructose-6-phosphate amidotransferase, nitric oxide, lipid peroxidation, and reactive oxygen species levels were elevated in a dose-dependent manner in L6 myotubes exposed to DEHP. The present study in turn shows the direct adverse effect of DEHP on the expression of insulin receptor and GLUT4 gene, glucose uptake, and oxidation in L6 myotubes suggesting that DEHP exposure may have a negative influence on insulin signaling.

Phthalate is associated with insulin resistance in adipose tissue of male rat: role of antioxidant vitamins

Diethyl hexyl phthalate (DEHP) is a plasticizer, commonly used in a variety of products, including lubricants, perfumes, hairsprays and cosmetics, construction materials, wood finishers, adhesives, floorings and paints. DEHP is an endocrine disruptor and it has a continuum of influence on various organ systems in human beings and experimental animals. However, specific effects of DEHP on insulin signaling in adipose tissue are not known. Adult male albino rats of Wistar strain were divided into four groups. Control, DEHP treated (dissolved in olive oil at a dose of 10, and 100 mg/kg body weight, respectively, once daily through gastric intubations for 30 days) and DEHP + vitamin E (50 mg/kg body weight) and C (100 mg/kg body weight) dissolved in olive oil and distilled water, respectively, once daily through gastric intubations for 30 days. After the completion of treatment, adipose tissue was dissected out to assess various parameters. DEHP treatment escalated H(2)O(2) and hydroxyl radical levels as well as lipid peroxidation in the adipose tissue. DEHP impaired the expression of insulin signaling molecules and their phosphorelay pathways leading to diminish plasma membrane GLUT4 level and thus decreased glucose uptake and oxidation. Blood glucose level was elevated as a result of these changes. Supplementation of vitamins (C & E) prevented the DEHP-induced changes. It is concluded that DEHP-induced ROS and lipid peroxidation disrupts the insulin signal transduction in adipose tissue and favors glucose intolerance. Antioxidant vitamins have a protective role against the adverse effect of DEHP.

Chronic granulomatous disease

Chronic granulomatous disease (CGD) is a paradigm for nonlymphoid primary immune defects, and has guided elucidation of oxygen metabolism in the phagocyte, vasculature, and brain. It has been in the forefront of the development of antimicrobial prophylaxis before the advent of advanced HIV and before its routine use in neutropenia. It has been an attractive target for gene therapy and bone marrow transplantation for nonmalignant diseases. Therefore, CGD is worthy of attention for its historical interest and because it is a disease for which expert management is imperative.

Regulation of innate immunity by NADPH oxidase

NADPH oxidase is a critical regulator of both antimicrobial host defense and inflammation. Activated in nature by microbes and microbial-derived products, the phagocyte NADPH oxidase is rapidly assembled, and generates reactive oxidant intermediates (ROIs) in response to infectious threat. Chronic granulomatous disease (CGD) is an inherited disorder of the NADPH oxidase characterized by recurrent and severe bacterial and fungal infections, and pathology related to excessive inflammation. Studies in CGD patients and CGD mouse models indicate that NADPH oxidase plays a key role in modulating inflammation and injury that is distinct from its antimicrobial function. The mechanisms by which NADPH oxidase mediates killing of pathogens and regulation of inflammation have broad relevance to our understanding of normal physiological immune responses and pathological states, such as acute lung injury and bacterial or fungal infections.

Exploration of oxidative stress and inflammatory markers in relation to urinary phthalate metabolites: NHANES 1999-2006

Phthalate exposure has been associated with a wide range of adverse health outcomes in limited epidemiologic studies, and inflammation and oxidative stress have been hypothesized as potential mechanisms involved. In the present study we investigated associations between urinary concentrations of phthalate metabolites and potential blood markers of oxidative stress (bilirubin) and inflammation (alkaline phosphatase [ALP], absolute neutrophil count [ANC], ferritin [adjusted for iron status], and fibrinogen), using data from 10,026 participants in the National Health and Nutrition Examination Survey (NHANES) recruited between 1999 and 2006. After adjustment for covariates we found that bilirubin was inversely associated with several phthalate metabolites (all p-values <0.0001), including the metabolites of di-2-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DBP), in addition to monobenzyl phthalate (MBzP) and mono-(3-carboxypropyl) phthalate (MCPP). Since bilirubin is a potent antioxidant these relationships suggest that phthalates may be associated with increased oxidative stress. Many of the same metabolites were also significantly and positively related with ANC, ALP, and ferritin, suggesting phthalates may be associated with increased inflammation. These markers may be useful in other studies of low-dose exposure to environmental contaminants.

Mechanistic considerations for human relevance of cancer hazard of di(2-ethylhexyl) phthalate

Di(2-ethylhexyl) phthalate (DEHP) is a peroxisome proliferator agent that is widely used as a plasticizer to soften polyvinylchloride plastics and non-polymers. Both occupational (e.g., by inhalation during its manufacture and use as a plasticizer of polyvinylchloride) and environmental (medical devices, contamination of food, or intake from air, water and soil) routes of exposure to DEHP are of concern for human health. There is sufficient evidence for carcinogenicity of DEHP in the liver in both rats and mice; however, there is little epidemiological evidence on possible associations between exposure to DEHP and liver cancer in humans. Data are available to suggest that liver is not the only target tissue for DEHP-associated toxicity and carcinogenicity in both humans and rodents. The debate regarding human relevance of the findings in rats or mice has been informed by studies on the mechanisms of carcinogenesis of the peroxisome proliferator class of chemicals, including DEHP. Important additional mechanistic information became available in the past decade, including, but not limited to, sub-acute, sub-chronic and chronic studies with DEHP in peroxisome proliferator-activated receptor (PPAR) α-null mice, as well as experiments utilizing several transgenic mouse lines. Activation of PPARα and the subsequent downstream events mediated by this transcription factor represent an important mechanism of action for DEHP in rats and mice. However, additional data from animal models and studies in humans exposed to DEHP from the environment suggest that multiple molecular signals and pathways in several cell types in the liver, rather than a single molecular event, contribute to the cancer in rats and mice. In addition, the toxic and carcinogenic effects of DEHP are not limited to liver. The International Agency for Research on Cancer working group concluded that the human relevance of the molecular events leading to cancer elicited by DEHP in several target tissues (e.g., liver and testis) in rats and mice can not be ruled out and DEHP was classified as possibly carcinogenic to humans (Group 2B).

HCV-related proteins activate Kupffer cells isolated from human liver tissues

PURPOSE

It was reported from this laboratory that Kupffer cells (KCs) were activated in patients infected with HCV. Since dendritic cells, monocytes, and macrophages were activated by stimulation with HCV-related proteins, the specific aim of this study was to investigate the role of HCV-related proteins in activation of KCs, the signal pathway of activation of KCs mediated by Toll-like receptor (TLR) 4, and the influence of HCV infection on function of KCs.

METHODS

Kupffer cells isolated from non-cancerous surgical specimen were co-cultured with HCV-related proteins (Core, NS3, NS4, and NS5), and production of cytokines (TNF-α, IL-1β, and IL-10) and hydrogen peroxide were assessed. Furthermore, effects of neutralization antibodies against the TLR2, TLR3, or TLR4, and cytochalasin B on the production TNF-α by KCs were investigated.

RESULTS

Kupffer cells produced markedly a proinflammatory cytokine TNF-α by stimulation with all HCV-related proteins studied, and values were as same as production by KCs stimulated with LPS. Importantly, this production in the case of NS3 was significantly blunted by about 60% by neutralization antibodies against the TLR4, but not cytochalasin B. Production of TNF-α by isolated KCs stimulated with LPS was significantly greater in the HCV-infected livers than the HCV/HBV-negative livers.

CONCLUSIONS

These results indicated that HCV-related proteins may cause prolonged activation of KCs in the HCV-infected liver, leading to accumulation of inflammatory cytokines that contribute to DNA damage and carcinogenesis. Furthermore, function of KCs was difference between patients infected with and without HCV infection.

The effect of betacyclodextrin and hydroxypropyl betacyclodextrin incorporation into plasticized poly(vinyl chloride) on its compatibility with human U937 cells

Di (2-ethyl hexyl) phthalate (DEHP) is one of the main plasticizers used in poly(vinyl chloride) (PVC) medical devices and is currently the only one listed for use in the European Pharmacopoeia Monograph. It leaches out of PVC when the material is in contact with lipophilic media, for example, blood and certain nutritional feeds. Consequently, concerns have been expressed since in certain animal species, DEHP has been shown to exhibit both carcinogenic and reproductive toxic effects. Incorporation of beta cyclodextrin (BCD) and hydroxypropyl betacyclodectrin (HPBCD) into plasticized materials has been reported to decrease the leaching of DEHP. We have investigated whether this results in improved in vitro biocompatibility by measuring the responses of U937 cells to plasticized PVC in the presence and absence of added BCD or HPBCD. Growth and viability of the U937 cells, as well as tumor necrosis factor-α (TNF-α) production in contact with these materials revealed no significant difference between unmodified plasticized PVC materials and those containing BCD or HPBCD. Lipopolysaccharide (LPS) was used to elicit TNF-α production, and the response of cells to LPS in the presence of the PVC materials was evaluated. When PVC was modified by addition of HPBCD there was a significant reduction in the TNF-α production in response to LPS. Modification of plasticized PVC biomaterials by adding cyclodextrins did not significantly improve their biocompatibility. However, the HPBCD modified plasticized PVC materials caused a reduction in the production in TNF-α induced by LPS which may have implications for the inflammatory potential of these biomaterials.

Impact of product-related factors on immunogenicity of biotherapeutics

All protein therapeutics have the potential to be immunogenic. Several factors, including patient characteristics, disease state, and the therapy itself, influence the generation of an immune response. Product-related factors such as the molecule design, the expression system, post-translational modifications, impurities, contaminants, formulation and excipients, container, closure, as well as degradation products are all implicated. However, a critical examination of the available data shows that clear unequivocal evidence for the impact of these latter factors on clinical immunogenicity is lacking. No report could be found that clearly deconvolutes the clinical impact of the product attributes on patient susceptibility. Aggregation carries the greatest concern as a risk factor for immunogenicity, but the impact of aggregates is likely to depend on their structure as well as on the functionality (e.g., immunostimulatory or immunomodulatory) of the therapeutic. Preclinical studies are not yet capable of assessing the clinically relevant immunogenicity potential of these product-related factors. Simply addressing these risk factors as part of product development will not eliminate immunogenicity. Minimization of immunogenicity has to begin at the molecule design stage by reducing or eliminating antigenic epitopes and building in favorable physical and chemical properties.

Chronic granulomatous disease

Chronic granulomatous disease (CGD) was first described in the 1950s and has become a paradigm for genetic neutrophil diseases. It is characterized by recurrent infections with a narrow spectrum of bacteria and fungi as well as a common set of inflammatory complications most notably including inflammatory bowel disease. Over the last half century major advances in management have profoundly altered the major clinical issues and the life expectancy of CGD. With X-linked and autosomal recessive forms, it has been an important disease for the development of bone marrow transplantation and gene therapy. Some of the recent developments in infectious syndromes, inflammatory complications, and curative approaches are discussed in this review.

A reexamination of the PPAR-alpha activation mode of action as a basis for assessing human cancer risks of environmental contaminants

BACKGROUND

Diverse environmental contaminants, including the plasticizer di(2-ethylhexyl)phthalate (DEHP), are hepatocarcinogenic peroxisome proliferators in rodents. Peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activation and its sequelae have been proposed to constitute a mode of action (MOA) for hepatocarcinogenesis by such agents as a sole causative factor. Further, based on a hypothesized lower sensitivity of humans to this MOA, prior reviews have concluded that rodent hepatocarcinogenesis by PPAR-alpha agonists is irrelevant to human carcinogenic risk.

DATA SYNTHESIS

Herein, we review recent studies that experimentally challenge the PPAR-alpha activation MOA hypothesis, providing evidence that DEHP is hepatocarcinogenic in PPAR-alpha-null mice and that the MOA but not hepatocarcinogenesis is evoked by PPAR-alpha activation in a transgenic mouse model. We further examine whether relative potency for PPAR-alpha activation or other steps in the MOA correlates with tumorigenic potency. In addition, for most PPAR-alpha agonists of environmental concern, available data are insufficient to characterize relative human sensitivity to this rodent MOA or to induction of hepatocarcinogenesis.

CONCLUSIONS

Our review and analyses raise questions about the hypothesized PPAR-alpha activation MOA as a sole explanation for rodent hepatocarcinogenesis by PPAR-alpha agonists and therefore its utility as a primary basis for assessing human carcinogenic risk from the diverse compounds that activate PPAR-alpha. These findings have broad implications for how MOA hypotheses are developed, tested, and applied in human health risk assessment. We discuss alternatives to the current approaches to these key aspects of mechanistic data evaluation.

Vitamin C and resveratrol supplementation to rat dams treated with di(2-ethylhexyl)phthalate: impact on reproductive and oxidative stress end points in male offspring

This study was carried out to assess the influence of di(2-ethylhexyl)phthalate (DEHP) alone or associated with antioxidants on the male reproductive system in newborn rats, emphasizing the implications of oxidative stress and hormonal balance during prenatal and early postnatal periods. Wistar females were exposed by oral route to DEHP alone or associated with antioxidants from gestational day 7 to lactational day 2 according to the following treatment regimens: (C) vehicle control (canola oil + 1% Tween-80); (V) vitamin C (200 mg/kg) + canola oil; (R) resveratrol (10 mg/kg) + canola oil; (D) DEHP (500 mg/kg) + 1% Tween-80; (DV) DEHP (500 mg/kg) + vitamin C (200 mg/kg); and (DR) DEHP (500 mg/kg) + resveratrol (10 mg/kg). Two male pups per litter were randomly selected and necropsied on postnatal day 2. The brain and liver were removed and weighed and anogenital distance (AGD) was measured. Additionally, the testes were removed for assessment of intratesticular testosterone levels and histopathology; the liver was used to measure biomarkers of oxidative stress. Vitamin C and resveratrol alone did not affect the reproductive end points and did not induce oxidative stress. Exposure of dams to DEHP alone and associated with antioxidants resulted in hepatomegaly in offspring and significantly increased the incidence of multinucleated gonocytes in seminiferous cords. Testosterone and AGD presented a trend to decrease in DEHP-exposed groups. Catalase activity increased only in groups exposed to DEHP associated with antioxidants, although GST (gluthatione-S-transferase) activity decreased in all DEHP-exposed groups. The levels of hydroperoxides increased only in group exposed to DEHP associated with vitamin C. These results indicate that the association of DEHP with antioxidants was unable to ameliorate DEHP-induced reproductive changes, and the coadministration of DEHP and these antioxidants might even contribute to an overall increase in oxidative stress.