Gestational and lactational exposure to di-isobutyl phthalate via diet in maternal mice decreases testosterone levels in male offspring

Prenatal phthalate exposure and neurodevelopmental differences in twins at 2 years of age

BACKGROUND

Previous studies of singletons evaluating prenatal phthalate exposure and early neurodevelopment reported mixed results and the associations could be biased by parental, obstetrical, and genetic factors.

METHODS

A co-twin control design was employed to test whether prenatal phthalate exposure was associated with children's neurocognitive development. We collected information from 97 mother-twin pairs enrolled in the Wuhan Twin Birth Cohort between March 2016 and October 2018. Fourteen phthalate metabolites were measured in maternal urine collected at each trimester. Neurodevelopmental differences in twins at the age of two were examined as the outcome of interest. Multiple informant model was used to examine the covariate-adjusted associations of prenatal phthalate exposure with mental development index (MDI) and psychomotor development index (PDI) scores assessed at 2 years of age based on Bayley Scales of Infant Development (Second Edition). This model also helps to identify the exposure window of susceptibility.

RESULTS

Maternal urinary levels of mono-2-ethyl-5-oxohexyl phthalate (MEOHP) (β = 1.91, 95% CI: 0.43, 3.39), mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) (β = 1.56, 95% CI: 0.33, 2.79), and the sum of di-(2-ethylhexyl) phthalate metabolites (∑DEHP) (β = 1.85, 95% CI: 0.39, 3.31) during the first trimester showed the strongest and significant positive associations with intra-twin MDI difference. When stratified with twin chorionicity, the positive associations of monoethyl phthalate (MEP), monoisobutyl phthalate (MiBP), mono-n-butyl phthalate (MBP), monobenzyl phthalate (MBzP), individual DEHP metabolites, and ∑DEHP exposure during pregnancy with intra-twin neurodevelopmental differences were more significant in monochorionic diamniotic (MCDA) twins than those in dichorionic diamniotic (DCDA) twins.

CONCLUSIONS

Neurodevelopmental differences in MCDA twins were strongly associated with prenatal phthalate exposure. Our findings warrant further confirmation in longitudinal studies with larger sample sizes.

The toxicity of microplastics and their leachates to embryonic development of the sea cucumber Apostichopus japonicus

Microplastic pollution has been widely detected across the global ocean, posing a major threat to a wide variety of marine biota. To date, the deleterious impacts of microplastics have predominantly been linked to their direct exposure, while the potential risks posed by the leachates emanating from microplastics have received comparatively less attention. Here, the toxicity of virgin plasticized polyvinyl chloride (PVC) microspheres and their leachates were evaluated on the embryo-larval development of sea cucumber Apostichopus japonicus using an in-vitro assay. Results showed that a significant toxic effect of both PVC microspheres and their leachates on the embryo development and larval growth of sea cucumbers follows a dose-dependent and time-dependent pattern. Nonetheless, the toxicity of PVC leachates surpasses that of the microspheres themselves. Abnormal developmental phenotypes, such as aberrant gastrulation, misaligned mesenchymal cells, and delayed arm development, were also observed in embryos and larvae treated with PVC. Further chemical analyses of PVC microspheres and leachates revealed the existence of five distinct phthalate esters (PAEs), with DIBP (diisobutyl phthalate) and DBP (dibutyl phthalate) exhibiting higher concentrations in the PVC leachates. This finding suggests that the elevated toxicity of plastic leachate may be attributed to the leaching of phthalate additives from the plastic particles.

Associations of environmental phthalate exposure with male steroid hormone synthesis and metabolism: An integrated epidemiology and toxicology study

Humans are simultaneously and constantly exposed to various lipophilic chain phthalate acid esters. The association of urinary phthalate metabolites with altered male steroid hormone synthesis and metabolism was examined using epidemiology and toxicology studies. We measured 8 phthalate metabolites [monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), mono-benzyl phthalate (MBzP), mono-n-octylphthalate (MOP), mono-(2-ethylhexyl) phthalate (MEHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP)] and two sex hormones [testosterone (T) and estradiol (E₂)] in single serum and repeated spot urine samples among 451 reproductive-age males. Moreover, in vitro experiments with Leydig cell MLTC-1 steroidogenesis and liver cell HepG2 efflux in response to mixed and individual phthalates were designed to simulate real-world scenarios of human exposure. As a joint mixture, the phthalate metabolite was inversely associated with serum T and E₂ concentrations but positively associated with urinary T and E₂ concentrations. Combined with in vitro experiments, DEHP metabolites were identified as the predominant contributor to the decline in hormone synthesis, and ATP-binding cassette (ABC) gene activation might be involved in hormone excretion. Exposure to environmentally relevant phthalates was associated with both altered steroid synthesis and excretion, which provides additional insights into the endocrine-disrupting potential of phthalates.

Exploring personal chemical exposures in China with wearable air pollutant monitors: A repeated-measure study in healthy older adults in Jinan, China

The health impact of airborne contaminants has been challenging to assess due to current limitations in measurement technologies. The emergence of wearable passive samplers coupled with high resolution mass spectrometry (HR-MS) chemical analysis has enabled comprehensive characterization of personal exposures. We conducted a repeated-measure study among 84 older adults in Jinan, China, as part of the Biomarkers for Air Pollutants Exposure (China BAPE) study. Study objectives were: 1) to characterize the occurrence, magnitude, and distribution of personal exposure to airborne contaminants; 2) to evaluate the temporal variation of chemical exposures across the study population; and 3) to identify behavioral and environmental factors that influence the observed variance in chemical exposures. The FreshAir wristband was worn by participants for three consecutive days each month from September 2018 to January 2019 and collected with paired time-activity logs. Passive air samplers were also deployed in parallel at a local outdoor air monitoring station. Spearman's Rho trend test and trajectory cluster analysis were used to identify exposure trends and variation patterns, respectively. Out of the 70 airborne compounds of potential concern screened, 26 compounds from 10 chemical classes were found to be above detection thresholds across >70% of the study population. Personal exposures were predominantly characterized by nine polycyclic aromatic hydrocarbons (PAHs), four phthalates, three nitroaromatics, and two volatile organic compounds (VOCs). Phthalate personal exposures were positively correlated with outdoor temperatures while the inverse relationship was observed for certain PAHs (p < 0.05). Specifically, dimethyl phthalate (r_s = 0.31) decreased as temperatures declined, while nitrobenzene (r_s = -0.35) and naphthalene (r_s = -0.40) increased as temperatures decreased. Compared to levels measured at the outdoor air monitoring site, personal exposure of phthalates was elevated (p < 0.05) and hexachlorobutadiene was lower across participants (p < 0.01). Personal exposure of these chemicals was further found to be weakly associated with daily duration participants spent outdoors. Individuals formed distinct clusters based on trajectories of chemical exposures across the sampling period (September to January), potentially suggestive of distinct emission sources. In conclusion, we demonstrate the feasibility of characterizing the occurrence and magnitude of personal exposure to airborne chemical contaminants using passive wristband samplers. The temporal variability of these personal exposure profiles was highlighted and with distinct trends identified across different groups of individuals. Future studies will integrate this data with other omics datasets collected from this population of Chinese older adults to investigate associations between exposure profiles and health relevant biomarkers, to provide evidence in feasibility of disease prevention through environmental improvements.

In utero exposure to phthalates and reproductive toxicity in rodents

Phthalates, widely used as plasticizers, are contained in many everyday products. Human biomonitoring studies detect their presence in biological fluids of a large part of the population worldwide. Maternal exposure during pregnancy has been related with aberrations in the reproductive growth of male infants. Rodent studies show that gestational exposure to single phthalates elicits reproductive toxicity in both sexes. Early aberrations include inhibition of gonadal sex determining gene expression and steroidogenesis, histopathology, and disturbed gametogenesis, leading later in life to dysfunctions in sperm production and oocyte reserves. Animal studies of in utero exposure to mixtures of phthalates, better mimicking human exposures, revealed analogous reproductive dysfunctions with the single compounds, but also indicated the combined actions and cumulative effects exerted by these chemicals. Further understanding the underlying mechanisms and the species differences in phthalate-induced reproductive toxicity will help to improve the risk assessment for human exposure to these toxicants.

Transcriptomic responses predict the toxic effect of parental co-exposure to dibutyl phthalate and diisobutyl phthalate on the early development of zebrafish offspring

Dibutyl phthalate (DBP) and diisobutyl phthalate (DiBP) have been reported to exhibit reproductive toxicity in vertebrates. However, the combined effect of DBP and DiBP on offspring of exposed parents remains unclear, especially for aquatic organisms such as fish. The aims of this study were to assess the effects of parental co-exposure to DBP and DiBP on early development of zebrafish offspring, and to explore the potential molecular mechanisms involved. The early developmental indicators and transcriptomic profiles of F1 larvae were examined after parental exposure to DBP, DiBP and their mixtures (Mix) for 30 days. Results showed that parental exposure to DBP and DiBP, alone or in combination, resulted in increased hatchability at 48 hpf and heart rate at 96 hpf, and increased the prevalence of malformations and mortality in F1 larvae. Generalized linear model (GLM) suggested an antagonistic interactive effect between DBP and DiBP on mortality and malformations of F1 larvae. The transcriptomic analysis revealed that the molecular mechanisms of parental co-exposure were different from those of either chemical alone. Disruption of molecular functions involved unfolded protein binding, E-box binding and photoreceptor activity in F1 larvae. These findings provide initial insights in the potential mechanism of action of parental co-exposure to DBP and DiBP.

The reproductive toxicity and potential mechanisms of combined exposure to dibutyl phthalate and diisobutyl phthalate in male zebrafish (Danio rerio)

Dibutyl phthalate (DBP) and diisobutyl phthalate (DiBP) are phthalate compounds frequently detected in the environment. Despite increasing awareness of their toxicity in human and animals, the male reproductive toxicity of their combined exposure remains elusive. The purposes of this study were to investigate whether combined exposure to DBP and DiBP could induce male reproductive toxicity, and to explore the potential toxicological mechanisms. Adult male zebrafish were exposed to DBP (11, 113 and 1133 μg L^-1), DiBP (10, 103 and 1038 μg L^-1) and their mixtures (Mix) (11 + 10, 113 + 103, 1133 + 1038 μg L^-1) for 30 days, and their effects on plasma hormone secretion, testis histology and transcriptomics were examined. Highest concentrations of Mix exposure caused greater imbalance ratio of T/E2 and more severe structural damage to testis than single exposure. These effects were consistent with the testis transcriptome analysis for which 4570 genes were differentially expressed in Mix exposure, while 2795 and 1613 genes were differentially expressed in DBP and DiBP, respectively. KEGG pathway analysis showed that both single and combined exposure of DBP and DiBP could affect cytokine-cytokine receptor interaction. The difference was that combined exposure could also affect steroid hormone synthesis, extracellular matrix receptor interaction, retinol metabolism, and PPAR signaling pathways. These results demonstrated that combined exposure to DBP and DiBP could disrupt spermatogenesis and elicit male reproductive toxicity in zebrafish.

Prenatal and early childhood exposure to phthalates and childhood behavior at age 7 years

BACKGROUND

Emerging evidence suggests that phthalate exposure may be associated with behavior problems in children and that these associations may be sex specific.

METHODS

In a follow up study of 411 inner-city minority mothers and their children, mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBzP), monoisobutyl phthalate (MiBP), monethyl phthalate (MEP) and four di-2-ethylhexyl phthalate metabolites (DEHP) were quantified in maternal urine samples collected during the third trimester and in child urine samples at ages 3 and 5 years. The Conners' Parent Rating Scale-Revised: Long Form (CPRS) and Child Behavior Checklist (CBCL) were administered to the mothers to assess children's behavior problems at 7 years of age. The analysis included children with available measures of CBCL, CPRS and phthalates measured in maternal urine. We performed both Quasi-Poisson regression and a mixture analysis using Weighted Quantile Sum(WQS) regression to assess the risk for CPRS scores and for internalizing and externalizing behaviors (from the CBCL) following intra-uterine exposure to the phthalate metabolites for boys and girls separately.

RESULTS

Among boys, increases in in anxious-shy behaviors were associated with prenatal exposure to MBzP (Mean Ratio [MR] = 1.20, 95%CI 1.05-1.36) and MiBP (Mean Ratio (MR) = 1.22, 95%CI 1.02-1.47). Among girls, increases in perfectionism were associated with MBzP (MR = 1.15, 95%CI 1.01-1.30). In both boys and girls, increases in psychosomatic problems were associated with MiBP (MR = 1.28, 95%CI 1.02-1.60), and MnBP (MR = 1.28, 95%CI 1.02-1.59), respectively. Among girls, decreased hyperactivity was associated with two DEHP metabolites, mono(2-ethyl-5-oxohexyl) phthalate (MR = 0.83, 95%CI 0.71-0.98) and mono(2-ethyl-5-hydroxyhexyl) phthalate (MR = 0.85, 95%CI 0.72-0.99). Using weighted Quantile Sum logistic regression, no associations were found between the Weighted Quantile Sum (WQS) of phthalate metabolites and CPRS scores or externalizing and internalizing behaviors. Nonetheless, when the analysis was performed separately for DEHP and non-DEHP metabolites significant associations were found between the WQS of DEHP metabolites and social problems in boys (OR = 2.15, 95%CI 1.13-4.06, p-value = 0.02) anxious-shy problems in girls (OR = 2.19, 95%CI 1.15-4.16, p = 0.02), and emotional lability problems in all children (OR = 0.61, 95%CI 0.38-0.97, p = 0.04). MEHP and MEOHP were the most highly weighted DEHP metabolites in WQS mixture. The analysis performed with CBCL scale corroborated these associations.

CONCLUSION

Concentration of non-DEHP metabolites was associated with anxious-shy behaviors among boys. DEHP phthalate metabolites were associated with decreased hyperactivity and impulsivity among girls on CPRS scores. These findings lend further support to the adverse associations between prenatal phthalate exposure and childhood outcomes, and clearly suggest that such associations are sex and mixture specific.

Long-term 1-nitropyrene exposure induces endoplasmic reticulum stress and inhibits steroidogenesis in mice testes

1-Nitropyrene (1-NP) is a representative nitro-polycyclic aromatic hydrocarbon from diesel exhaust. Recently, we found that maternal 1-NP exposure caused fetal growth retardation and disturbed cognitive development in adolescent female offspring. To investigate long-term 1-NP exposure on spermatogenesis and steroidogenesis, male mice were exposed to 1-NP (1.0 mg/kg/day) by gavage for 70 days. There was no significant difference on relative testicular weight, number of testicular apoptotic cells and epididymal sperm count between 1-NP-exposed mice and controls. Although long-term 1-NP exposure did not influence number of Leydig cells, steroidogenic genes and enzymes, including STAR, P450scc, P45017α and 17β-HD, were downregulated in 1-NP-expoed mouse testes. Correspondingly, serum and testicular testosterone (T) levels were reduced in 1-NP-exposed mice. Additional experiment showed that testicular GRP78 mRNA and protein were upregulated by 1-NP. Testicular phospho-IRE1α and sliced xbp-1 mRNA, a downstream molecule of IRE1α, were elevated in 1-NP-exposed mice. Testicular phospho-PERK and phospho-eIF2α, a downstream molecule of PERK pathway, were increased in 1-NP-exposed mice. Testicular NOX4, a subunit of NAPDH oxidase, and HO-1, MDA, two oxidative stress markers, were increased in 1-NP-exposed mice. Testicular GSH and GSH/GSSG were decreased in 1-NP-exposed mice. These results suggest that long-term 1-NP exposure induces reactive oxygen species-evoked ER stress and disrupts steroidogenesis in mouse testes.

Phthalates and Sex Steroid Hormones Among Men From NHANES, 2013-2016

CONTEXT

Phthalates are commonly found in commercial packaging, solvents, vinyl, and personal care products, and there is concern for potential endocrine-disrupting effects in males. The commonly used di-2-ethylhexyl phthalate (DEHP) has progressively been replaced by seldom studied compounds, such as bis-2-ethylhexyl terephthalate and 1,2-cyclohexane dicarboxylic acid di-isononyl ester (DINCH).

OBJECTIVE

To investigate the associations between the urinary phthalate metabolites and serum sex steroid hormone concentrations in a nationally representative sample of adult males.

DESIGN, SETTING, PARTICIPANTS, AND INTERVENTION

This was a cross-sectional analysis of data from the 2013-2016 National Health and Nutrition Examination Survey among 1420 male participants aged ≥20 years.

MAIN OUTCOME MEASURES

Serum levels of total testosterone, estradiol, SHBG, and derived sex hormone measurements of free testosterone, bioavailable testosterone, and free androgen index were examined as log-transformed continuous variables.

RESULTS

Phthalate metabolites were not statistically significantly associated with sex hormone concentrations among all men. However, associations varied by age. High molecular weight phthalates were associated with lower total, free, and bioavailable testosterone among men age ≥60. Specifically, each doubling of ΣDEHP was associated with 7.72% lower total testosterone among older men (95% confidence interval, -12.76% to -2.39%). Low molecular phthalates were associated with lower total, free, and bioavailable testosterone among men age 20 to 39 and ∑DINCH was associated with lower total testosterone among men age ≥40.

CONCLUSIONS

Our results indicate that males may be vulnerable to different phthalate metabolites in age-specific ways. These results support further investigation into the endocrine-disrupting effects of phthalates.

Evaluation of carvacrol on pituitary and sexual hormones and their receptors in the testicle of male diabetic rats

Diabetes mellitus (DM) is a complex metabolic disease and it is also closely associated with a reduction in fertility in male patients. The purpose of the present study was to investigate the antidiabetic effect of carvacrol (CRV), as a potent antioxidant, on the numbers of germ cells and Sertoli cells in testicular tissue, and the messenger RNA (mRNA) and protein expression of some genes involved in spermatogenesis, including luteinizing hormone/choriogonadotropin receptor ( LHCGR), follicle-stimulating hormone receptor ( FSHR), and steroidogenic factor 1 ( SF-1), as well as hormones such as luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T), and insulin. Adult male Wistar rats ( n = 32) were randomly divided into four groups (eight animals per group), including healthy control that received 0.2% Tween 80, diabetic control group, the diabetic group treated orally with CRV (75 mg/kg), and CRV group that received orally CRV (75 mg/kg). The duration of the treatment period lasted 8 weeks. In the diabetic group, the numbers of Sertoli cells and germ cells were significantly decreased, while the treatment with CRV prevented the degree of the damage to the cells mentioned earlier. CRV administration elevated the concentrations of insulin, T, FSH, and LH. Moreover, treatment with CRV significantly enhanced the levels of the mRNA and protein expression of SF-1, LHCGR, and FSHR. According to the obtained results, CRV administration could prevent the deleterious effects of DM on testicular germ cells, and it increases the levels of hormones and some essential genes, such as SF-1, LHCGR, and FSHR, involved in the process of spermatogenesis.

Maternal exposure to fine particle matters cause autophagy via UPR-mediated PI3K-mTOR pathway in testicular tissue of adult male mice in offspring

Epidemiological studies have shown that particulate matters are closely related to human infertility. However, the long-term risk of particulate matters exposure in early life is rarely considered. For the first time this study is designed to explore and elucidate the mechanism of maternal exposure to fine particle matters (PM_2.5) on autophagy in spermatogenic cells of adult offspring. Pregnant C57BL/6 mice were randomly divided into four groups. The 4.8 mg/kg.b.w group and the 43.2 mg/kg.b.w group were administered with different doses of PM_2.5. The membrane control group was administered with PM_2.5 sampling membrane and the control group received no treatment. The exposure was performed every three days from the day after vaginal plug was checked until delivery for a total of 6 times. The results showed that sperms motility and sperms concentration decreased, and sperm deformity increased in adult male offspring. The expression of SOD decreased and MDA increased. Moreover, the level of GRP78/ATF6 and P62 was upregulated, and the expression of PI3K/Akt/mTOR/p-mTOR was down-regulated. This suggests that early-life exposure to PM_2.5 can induce autophagy through the PI3K/Akt/mTOR pathway mediated by unfolded protein response in adult testicular tissue. PM_2.5 may pose a significant role and long-term threat to adult after early-life exposure.

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.

Hazards of diisobutyl phthalate (DIBP) exposure: A systematic review of animal toxicology studies

BACKGROUND

Biomonitoring studies indicate a trend towards increased human exposure to diisobutyl phthalate (DIBP), a replacement for dibutyl phthalate (DBP). Recent reviews have found DIBP to be a male reproductive toxicant, but have not evaluated other hazards of DIBP exposure.

OBJECTIVE

To inform chemical risk assessment, we performed a systematic review to identify and characterize outcomes within six broad hazard categories (male reproductive, female reproductive, developmental, liver, kidney, and cancer) following exposure of nonhuman mammalian animals to DIBP or the primary metabolite, monoisobutyl phthalate (MIBP).

METHODS

A literature search was conducted in four online scientific databases [PubMed, Web of Science, Toxline, and Toxic Substances Control Act Test Submissions 2.0 (TSCATS2)], and augmented by review of regulatory sources as well as forward and backward searches. Studies were identified for inclusion based on defined PECO (Population, Exposure, Comparator, Outcome) criteria. Studies were evaluated using criteria defined a priori for reporting quality, risk of bias, and sensitivity using a domain-based approach. Evidence was synthesized by outcome and life stage of exposure, and strength of evidence was summarized into categories of robust, moderate, slight, indeterminate, or compelling evidence of no effect, using a structured framework.

RESULTS

Nineteen toxicological studies in rats or mice met the inclusion criteria. There was robust evidence that DIBP causes male reproductive toxicity. Male rats and mice exposed to DIBP during gestation had decreased testosterone and adverse effects on sperm or testicular histology, with additional phthalate syndrome effects observed in male rats. There was also evidence of androgen-dependent and -independent male reproductive effects in rats and mice following peripubertal or young adult exposure to DIBP or MIBP, but confidence was reduced because of concerns over risk of bias and sensitivity in the available studies. There was also robust evidence that DIBP causes developmental toxicity; specifically, increased post-implantation loss and decreased pre- and postnatal growth. For other hazards, evidence was limited by the small number of studies, experimental designs that were suboptimal for evaluating outcomes, and study evaluation concerns such as incomplete reporting of methods and results. There was slight evidence for female reproductive toxicity and effects on liver, and indeterminate evidence for effects on kidney and cancer.

CONCLUSION

Results support DIBP as a children's health concern and indicate that male reproductive and developmental toxicities are hazards of DIBP exposure, with some evidence for female reproductive and liver toxicity. Data gaps include the need for more studies on male reproductive effects following postnatal and adult exposure, and studies to characterize potential hormonal mechanisms in females.

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.

Maternal exposure to di-n-butyl phthalate induces alterations of c-Myc gene, some apoptotic and growth related genes in pups’ testes

The aim of this study was to investigate the effects of maternal exposure to di-( n-butyl) phthalate (DBP) on testicular development and function in pre-pubertal and post-pubertal male rat offspring. Fourteen pregnant female rats were equally divided into two groups: a control group and a DBP-treated group. During gestation day (GD) 12 to postnatal day (PND) 14, the control group was administered 1 ml/day corn oil, and the DBP-treated group was administered DBP 500 mg/kg/day by oral gavage. On PND 25 (pre-puberty) and PND 60 (post-puberty), blood for serum and the testes were collected from five male offspring of each group. To determine the relationship between the methylation state of the c-Myc promoter and the expression of the c-Myc gene, some apoptotic-related genes, such as p53 and Bax, the anti-apoptotic Bcl-2 gene, and some growth arrest-related genes, such as BRD7 and GAS1, were examined. Compared with the control ( p < 0.05), at pre-puberty, DBP induces c-Myc hyper-methylation with significant downregulation for c-Myc, p53, Bax genes, and significant upregulation for Bcl-2, BRD7, and GAS1, while at post puberty, the methylation state and expression of c-Myc and apoptosis-related genes returned to control levels in the same sequence with the fold change in the expression of BRD7 and GAS1 genes. These findings suggest that DBP induced a transient pre-pubertal increase in c-Myc promoter methylation that may be associated with disruption of both apoptotic and growth mechanisms in the testes.

Health-Relevant Phenotypes in the Offspring of Mice Given CAR Activators Prior to Pregnancy

Hepatic induction in response to drugs and environmental chemicals affects drug therapies and energy metabolism. We investigated whether the induction is transmitted to the offspring. We injected 3-day- and 6-week-old F0 female mice with TCPOBOP, an activator of the nuclear receptor constitutive androstane receptor (CAR, NR1I3), and mated them 1-6 weeks afterward. We detected in the offspring long-lasting alterations of CAR-mediated drug disposition, energy metabolism, and lipid profile. The transmission to the first filial generation (F1) was mediated by TCPOBOP transfer from the F0 adipose tissue via milk, as revealed by embryo transfer, crossfostering experiments, and liquid chromatography-mass spectrometry analyses. The important environmental pollutant PCB153 activated CAR in the F1 generation in a manner similar to TCPOBOP. Our findings indicate that chemicals accumulating and persisting in adipose tissue may exert liver-mediated, health-relevant effects on F1 offspring simply via physical transmission in milk. Such effects may occur even if treatment has been terminated far ahead of conception. This should be considered in assessing developmental toxicity and in the long-term follow-up of offspring of mothers exposed to both approved and investigational drugs, and to chemicals with known or suspected accumulation in adipose tissue.

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.

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.