Endocrine disruption by di-(2-ethylhexyl)-phthalate in Chinese rare minnow (Gobiocypris rarus)

Effect of diisobutyl adipate on the expression of biomarker genes that respond to endocrine disruption and on gonadal sexual differentiation in Japanese medaka (Oryzias latipes)

Phthalate and non-phthalate plasticizers are used in polymer materials, such as plastic and rubber. It has recently been found that diisobutyl adipate (DIBA), which is considered an environmentally safe non-phthalate plasticizer, potentially acts as a thyroid disruptor in fish. Here, we investigated the sexual hormone effects of DIBA based on the expression levels of genes that respond to endocrine disruption and sexual hormone activity in the livers and gonads, and on gonadal sexual differentiation in Japanese medaka. Compared with the control group, the mRNA expression of chgH, vtg1, vtg2, and esr1 was significantly suppressed in the livers of DIBA exposed XX individuals. Furthermore, the mRNA expression of gsdf was significantly upregulated and downregulated in the gonads of XX and XY individuals, respectively. The mRNA expressions of esr1 and esr2b were significantly suppressed by DIBA exposure in the gonads of both XX and XY individuals. These observations suggest that DIBA has potential androgenic activity in Japanese medaka. However, normal testes and ovaries were observed in respective XY and XX medaka after DIBA exposure; therefore, these results suggest that DIBA may have weak androgenic activity.

Calcium supplementation and body mass index modify associations between prenatal phthalate exposure and perinatal bone ultrasound measures among pregnant women

Phthalates have endocrine activity that may interfere with bone health, particularly during pregnancy and the early postpartum period, when bone resorption increases. We evaluated associations between prenatal phthalate exposure and perinatal bone health among 289 mothers in the ELEMENT birth cohort in Mexico City who were randomized upon recruitment to receive 1,200 mg daily calcium supplementation or placebo throughout pregnancy. Spot urine samples at up to three timepoints during pregnancy were assayed for 9 phthalate metabolites. Bone integrity was assessed by quantitative ultrasound speed of sound (SOS) measurements of the phalange and distal radius at 3, 6, and 8 months of pregnancy and 1, 3, 7, and 12 months postpartum. Geometric means of specific gravity-corrected phthalate concentrations were used as overall measures of prenatal exposure. Linear mixed effect models estimated associations between phthalate exposure and repeated perinatal bone SOS measures, adjusting for age, pre-pregnancy body mass index (BMI), education, parity, calcium supplementation, and month of pregnancy/postpartum. Effect modification by calcium supplementation and BMI were assessed in sensitivity analyses. An interquartile range increase in MEP and MiBP increased pregnancy phalange z-scores (β: 0.11; 95%CI: 0.003, 0.31 and β: 0.15; 95%CI: 0.00,0.42, respectively). Higher concentrations of several phthalate metabolites resulted in lower SOS measures among women who received calcium supplements (compared to placebo group) but higher SOS measures among women with a BMI≥25 (compared to BMI<25). These results suggest that phthalate exposure may interfere with bone remodeling during pregnancy, and that consideration of effect modifiers is paramount to fully understand the effects of environmental exposures on bone health.

Effects of di-(2-ethylhexyl) terephthalate on hypothalamus-pituitary-gonad axis in adult zebrafish

Di-(2-ethylhexyl) terephthalate (DEHTP) is frequently used in food packaging and medical devices as an alternative to di-(2-ethylhexyl) phthalate (DEHP). In this study, zebrafish pairs were exposed to DEHTP for 21 d and the effects on fertility, sex hormone levels, vitellogenin levels, and transcription of genes along the hypothalamic-pituitary-gonad axis were evaluated. Results showed that mean egg numbers were significantly reduced in the 30 and 300 μg/L DEHTP groups. The adverse effects of DEHTP on hormones and gene transcripts were more prominent in males than in females. In male fish, the gonadosomatic index, hepatosomatic index, and vitellogenin concentration were significantly increased. The results of a significant decrease in testosterone (T) and an increase in the 17β-estradiol (E2)/T ratio in males exposed to 3-300 μg/L DEHTP suggest that the endocrine potential of DEHTP is similar that of DEHP. In females, genes related to gonadotropin-releasing hormone and gonadotropin were up-regulated while E2 was significantly down-regulated. These findings suggest that positive E2 feedback mechanisms in the hypothalamus and pituitary gland are activated to balance sex hormones. The effects of chronic exposure to DEHTP on the neuroendocrine system require further investigation.

Cumulative Exposure to Phthalates and Their Alternatives and Associated Female Reproductive Health: Body Burdens, Adverse Outcomes, and Underlying Mechanisms

The global birth rate has recently shown a decreasing trend, and exposure to environmental pollutants has been identified as a potential factor affecting female reproductive health. Phthalates have been widely used as plasticizers in plastic containers, children's toys, and medical devices, and their ubiquitous presence and endocrine-disrupting potential have already raised particular concerns. Phthalate exposure has been linked to various adverse health outcomes, including reproductive diseases. Given that many phthalates are gradually being banned, a growing number of phthalate alternatives are becoming popular, such as di(isononyl) cyclohexane-1,2-dicarboxylate (DINCH), di(2-ethylhexyl) adipate (DEHA), and di(2-ethylhexyl) terephthalate (DEHTP), and they are beginning to have a wide range of environmental effects. Studies have shown that many phthalate alternatives may disrupt female reproductive function by altering the estrous cycle, causing ovarian follicular atresia, and prolonging the gestational cycle, which raises growing concerns about their potential health risks. Herein, we summarize the effects of phthalates and their common alternatives in different female models, the exposure levels that influence the reproductive system, and the effects on female reproductive impairment, adverse pregnancy outcomes, and offspring development. Additionally, we scrutinize the effects of phthalates and their alternatives on hormone signaling, oxidative stress, and intracellular signaling to explore the underlying mechanisms of action on female reproductive health, because these chemicals may affect reproductive tissues directly or indirectly through endocrine disruption. Given the declining global trends of female reproductive capacity and the potential ability of phthalates and their alternatives to negatively impact female reproductive health, a more comprehensive study is needed to understand their effects on the human body and their underlying mechanisms. These findings may have an important role in improving female reproductive health and in turn decreasing the number of complications during pregnancy.

Impact of acetyl tributyl citrate on gonadal sex differentiation and expression of biomarker genes for endocrine disruption in Japanese medaka

Plasticizers are broadly classified as phthalate or nonphthalate. Recently, acetyl tributyl citrate (ATBC), an environmentally friendly nonphthalate plasticizer, was revealed to have the ability to disrupt thyroid hormone activity in fish species. Therefore, we aimed to assess whether ATBC exhibits any sex hormone (i.e., androgenic or estrogenic) activities. First, we examined the effects of ATBC on gonadal sex differentiation. Subsequently, we analyzed the different expression of biomarker genes that respond to endocrine-disrupting chemicals (EDCs) with sexual hormone activity in the liver. We observed normal testes and ovaries after both XX and XY medakas were exposed to ATBC, indicating that ATBC is not an EDCs with strong sex hormone activity and that it does not induce intersex (testis-to-ova or ovo-to-testis) or sex changes in Japanese medaka. The vitellogenin 1 (vtg1) and vitellogenin 2 (vtg2) mRNA expression levels in the liver of XX medakas were significantly reduced compared with those in the control group, whereas the expression levels of these genes in the liver of XY medakas remained unchanged. Finally, we examined the changes in the expression of biomarker genes that respond to EDCs with sex hormone activity in the gonads. The expression levels of biomarker genes did not differ significantly from that of the control group, although the expression levels of gsdf mRNA tended to increase while that of aromatase mRNA tended to decrease in the ovary of XX medakas following ATBC exposure. Conversely, the expression levels of gsdf and aromatase mRNAs in the testis of XY medakas remained unchanged. These results suggest that ATBC does not exhibit estrogenic activity, although it may have weak androgenic activity or no sexual hormone activity.

A comparative study on endocrine disrupting effects of leachates from virgin and aged plastics under simulated media in marine medaka larvae (Oryzias melastigma)

Marine plastic pollution has garnered substantial attention, but the potential endocrine disrupting effects of plastic leachates in marine organisms remain unclear. In this study, the larvae of marine medaka (Oryzias melastigma) were exposed to the leachates from virgin and aged plastics soaked in simulated seawater and fish digest for 3 days. The concentrations of vitellogenin (VTG), estradiol (E2), and 11-ketotestosterone (11-KT), as well as the transcripts of endocrine-related genes were measured in the larvae. The results revealed that endogenous E2 was more sensitive to plastic leachates than VTG and 11-KT, which was significantly affected by 26.7 % of all plastic leachates. Among all genes, estrogen receptor α was impacted mostly, being up-regulated by 53.3 % of leachates from aged plastics. The comparative results demonstrated that the leachates from plastics with different statuses caused a greater difference than those from plastics in different simulated media, and the leachates from aged plastics resulted in higher endocrine disrupting effects than those from virgin plastics. In addition, seven leached additives (plasticizers and flame retardants) could explain 25.6 % of the hormonal effects using redundancy analysis, indicating that other additives in the plastic leachates can also play important roles in regulating the endocrine system of O. melastigma larvae.

Effects of single and combined exposure to zinc and two tetracycline antibiotics on zebrafish at the early stage

Tetracycline antibiotics (TCs) and heavy metals are commonly used in livestock and poultry farming, leading to their coexistence in the aquatic environment. This coexistence causes combined toxicity to aquatic organisms. Here, zebrafish embryos were exposed to chlortetracycline (CTC), oxytetracycline (OTC), zinc chloride (ZnCl₂), and their combinations for 120 h to evaluate their adverse effects on the growth, antioxidant system, immune system, and endocrine system during the early stage of life. OTC/ZnCl₂ combined exposure significantly reduced the body weight, whereas the TCs/ZnCl₂ combination significantly increased the heart rate of zebrafish larvae, suggesting growth impairment induced by TCs and ZnCl₂. Further, combined groups showed more prominent toxicity to the antioxidant system than single groups, as revealed by related levels of enzyme activity and gene expression. In addition, the levels of most pro-inflammatory genes were downregulated, and those of NF-κB-related genes were upregulated in all treatment groups, indicating an immunosuppressive response and the potential role of NF-κB signaling, while the combined treatment was not more toxic than TCs or ZnCl₂ alone. Similarly, hormone and endocrine related gene levels were determined. Although both single and combined exposures caused certain endocrine-disrupting effects, the combined exposure did not result in higher toxicity than a single exposure. Our findings showed that a mixture of TCs and ZnCl₂ might exert greater toxic effects as compared to a single compound on some systems, providing fundamental data on the toxic effects of single and combined TC and ZnCl₂ exposure on aquatic organisms, although studies are needed to explore the underlying mechanisms.

Thyroid hormone disruption by bis-(2-ethylhexyl) phthalate (DEHP) and bis-(2-ethylhexyl) adipate (DEHA) in Japanese medaka Oryzias latipes

Pollution of water bodies with plasticizers is a serious environmental problem worldwide. In this study, we investigated the effects of plasticizers bis-(2-ethylhexyl) phthalate (DEHP) and bis-(2-ethylhexyl) adipate (DEHA) in Japanese medaka (Oryzias latipes). DEHP significantly increased the expression of all the genes tested: thyroid stimulating hormone beta subunit (tshβ-like), tshβ, deiodinase 1 (dio1), deiodinase 2 (dio2), and thyroid hormone receptor alpha (trα) and beta (trβ). However, DEHA only significantly increased tshβ at 7.4 µg/L but significantly decreased dio2 expression at 25.8, 111.1, and 412.6 4 µg/L, while other genes were not significantly affected. Both chemicals reduced eye size and total body length, but did not affect embryo development, hatching time and rate, and swimming performance. DEHA alone affected swim bladder inflation and not DEHP. This is the first report that not only DEHP but also DEHA disrupt thyroid hormone activity in fish. DEHP contamination (13.2 μg/L) was detected in tap water from Kobe, Japan; thus, tap water itself may disrupt thyroid hormone activity in Japanese medaka. Importantly, the effective concentration of DEHP for thyroid hormone-related gene expression and growth was close to or lower than DEHP concentrations reported in surface water elsewhere, indicating that DEHP contamination is a serious aquatic pollution.

Phthalate Exposures and Placental Health in Animal Models and Humans: A Systematic Review

Phthalates are ubiquitous compounds known to leach from the plastic products that contain them. Due to their endocrine-disrupting properties, a wide range of studies have elucidated their effects on reproduction, metabolism, neurodevelopment, and growth. Additionally, their impacts during pregnancy and on the developing fetus have been extensively studied. Most recently, there has been interest in the impacts of phthalates on the placenta, a transient major endocrine organ critical to maintenance of the uterine environment and fetal development. Phthalate-induced changes in placental structure and function may have significant impacts on the course of pregnancy and ultimately, child health. Prior reviews have described the literature on phthalates and placental health; however to date, there has been no comprehensive, systematic review on this topic. Here, we review 35 papers (24 human and 11 animal studies) and summarize phthalate exposures in relation to an extensive set of placental measures. Phthalate-related alterations were reported for placental morphology, hormone production, vascularization, histopathology, and gene/protein expression. The most consistent changes were observed in vascular and morphologic endpoints, including cell composition. These changes have implications for pregnancy complications such as preterm birth and intrauterine growth restriction as well as potential ramifications for children's health. This comprehensive review of the literature, including common sources of bias, will inform the future work in this rapidly expanding field.

Hazards of phthalates (PAEs) exposure: A review of aquatic animal toxicology studies

Phthalates (PAEs) are of wide concern because they are commonly used in various plastic products as plasticizers, and can found their way into the environment. However, their interaction with the environment and their toxicity in aquatic animals is still a matter of intense debate. In this review on PAEs in aquatic environments (lakes, rivers and seas), it is found that there is a large variety and abundance of PAEs in developing countries, and the total concentration of PAEs even exceeds 200 μg / L. The interaction between metabolic processes involved in the toxicity induced by various PAEs is summarized for the first time in the article. Exposure of PAEs can lead to activation of the detoxification system CYP450 and endocrine system receptors of aquatic animals, which in turn causes oxidative stress, metabolic disorders, endocrine disorders, and immunosuppression. Meanwhile, each system can activate / inhibit each other, causing genotoxicity and cell apoptosis, resulting in the growth and development of organisms being blocked. The mixed PAEs shows no cumulative toxicity changes to aquatic animals. For the combined pollution of other chemicals and PAEs, PAE can act as an agonist or antagonist, leading to combined toxicity in different directions. Phthalate monoesters (MPEs), the metabolites of PAEs, are also toxic to aquatic animals, however, the toxicity is weaker than the corresponding parent compounds. This review summarizes and analyzes the current ecotoxicological effects of PAEs on aquatic animals, and provides guidance for future research.

Acute exposure of di(2-ethylhexyl) phthalate (DEHP) induces immune signal regulation and ferroptosis in oryzias melastigma

The plasticizer di (2-ethylhexyl) phthalate (DEHP) is becoming increasingly abundant throughout the global environment as plastic pollution becomes highly severe, especially in the ocean. The adverse effects of DEHP have garnered increasing concern as they are recognized as endocrine disruptors. However, information on the effects of DEHP in marine organisms remains limited. In this study, acute toxic effects on marine medaka (Oryzias melastigma) following DEHP exposure were investigated. Transcriptome analysis was performed on the livers of medaka exposed to DEHP for 6 and 24 h. Results showed that 1595 genes were affected in all the analyzed specimens, and several genes expressed variably according to sex. Some pathways associated with immunity, metabolism, and endocrine system were significantly enriched, with the complement system appearing to be the most affected immune pathway. Pathway enrichment indicated that, under acute DEHP exposure, the immune response of females tended to be more sensitive than that of males. In addition, ferroptosis occurred in response to DEHP exposure, which resulted in an enrichment of the ferroptosis pathway along with iron overload, an increase in malondialdehyde (MDA) and lipid peroxidation (LPO) content, and a decrease in glutathione (GSH) levels. These results indicate that a form of cell death characterized by iron-dependence occurred following DEHP exposure, but the underlying mechanism requires further analysis. This study implies that DEHP can alter some molecular regulation patterns within a short period and induce cell death through ferroptosis.

Opposite effects of high- and low-dose di-(2-ethylhexyl) phthalate (DEHP) exposure on puberty onset, oestrous cycle regularity and hypothalamic kisspeptin expression in female rats

Di-(2-ethylhexyl) phthalate (DEHP) is ubiquitous in the environment and has been proposed to lead to reproductive disruption. In this study, we systematically investigated the effects of different doses of DEHP exposure on female hypothalamic-pituitary-gonadal axis development. Female Sprague-Dawley rats were gavaged with vehicle (corn oil) or DEHP (5 or 500mgkg-1 day-1) during postnatal Days (PNDs) 22-28 or PNDs 22-70. Results demonstrated that the low and high doses of DEHP exerted opposite effects on puberty onset, circulating luteinising hormone, serum oestradiol and progesterone levels, with the low dose (5mgkg-1) promoting and the high dose (500mgkg-1) inhibiting these parameters. Significant dose-related differences were also found in the D500 group with longer oestrous cycle duration, lower ovarian/bodyweight ratio, fewer corpus lutea and more abnormal ovarian stromal tissue in comparison with the oil or D5 groups. Molecular data showed that the hypothalamic Kiss1 mRNA expression in the anteroventral periventricular but not in the arcuate nucleus significantly decreased in the D500 rats and increased in the D5 rats relative to the rats in the oil group. These findings suggested that the kisspeptin system is a potential target for DEHP to disrupt reproductive development and function.

Theoretical Design of Biodegradable Phthalic Acid Ester Derivatives in Marine and Freshwater Environments

The biodegradability of phtalic acid esters in marine and freshwater environments was characterized by their binding free energy with corresponding degrading enzymes. According to comprehensive biodegradation effects weights, the binding free energy values were converted into dimensionless efficacy coefficient using ratio normalization method. Then, considering comprehensive dual biodegradation effects value and the structural parameters of PAEs in both marine and freshwater environments, a 3D‐QSAR pharmacophore model was constructed, five PAE derivatives (DBP−COOH, DBP−CHO, DBP−OH, DINP−NH₂, and DINP−NO₂) were screened out based on their environmental friendliness, functionality and stability. The prediction of biodegradation effects on five PAE derivatives by biodegradation models in marine and freshwater environment increased by 15.90 %, 15.84 %, 27.21 %, 12.33 %, and 8.32 %, and 21.57 %, 15.21 %, 20.99 %, 15.10 %, and 9.74 %, respectively. By simulating the photodegradation path of the PAE derivative molecular, it was found that DBP−OH can generate ^.OH and provides free radicals for the photodegradation of microplastics in the environment.

Reproductive dysfunction linked to alteration of endocrine activities in zebrafish exposed to mono-(2-ethylhexyl) phthalate (MEHP)

This study aimed to investigate the effect of mono-(2-ethylhexyl) phthalate (MEHP), one of the major phthalate metabolites that are widespread in aquatic environments, on reproductive dysfunction, particularly on endocrine activity in adult male and female zebrafish. For 21 days, the zebrafish were exposed to test concentrations of MEHP (0, 2, 10, and 50 μg/mL) that were determined based on the effective concentrations (ECx) for zebrafish embryos. Exposure to 50 μg/mL MEHP in female zebrafish significantly decreased the number of ovulated eggs as well as the hepatic VTG mRNA abundance when those of the control group. Meanwhile, in female zebrafish, the biosynthetic concentrations of 17β-estradiol (E2) and the metabolic ratio of androgen to estrogen were remarkably increased in all MEHP exposed group compared with those in the control group, along with the elevated levels of cortisol. However, no significant difference was observed between these parameters in male zebrafishes. Therefore, exposure to MEHP causes reproductive dysfunction in female zebrafishes and this phenomenon can be attributed to the alteration in endocrine activities. Moreover, the reproductive dysfunction in MEHP-exposed female zebrafishes may be closely associated with stress responses, such as elevated cortisol levels. To further understand the effect of MEHP on the reproductive activities of fish, follow-up studies are required to determine the interactions between endocrine activities and stress responses. Overall, this study provides a response biomarker for assessing reproductive toxicity of endocrine disruptors that can serve as a methodological approach for an alternative to chronic toxicity testing.

Chronic exposure to di-n-butyl phthalate causes reproductive toxicity in zebrafish

Di-n-butyl phthalate (DBP) is known to have adverse effects on reproduction in mammals and is pervasive in the aquatic environment. The objective of the present study was to investigate whether long-term exposure to low concentrations of DBP can affect fish reproduction. In this study, zebrafish (Danio rerio) embryos (F₀ ) were exposed to low concentrations (4.9, 13.6 and 43.8 μg/L) of DBP from 2 hours post-fertilization until sexual maturation. The results demonstrate that chronic exposure to DBP (43.8 μg/L) impaired the reproductive function of zebrafish, as verified by reduced egg production and modifications to gonadal histology of the treated fish. Plasma 17β-estradiol levels in female zebrafish decreased significantly in a concentration-dependent manner, while testosterone levels in males increased significantly when fish were exposed to 43.8 μg/L DBP. Real-time polymerase chain reaction was performed to examine selected genes in the hypothalamic-pituitary-gonadal (HPG) axis and liver. Hepatic vitellogenin gene transcription was downregulated in both males and females, suggesting that DBP possesses anti-estrogenic activity. The disturbed steroid hormones were accompanied by the significant alterations in gene expression along the HPG axis. Additionally, parental exposure to DBP caused reduced hatching and survival rate as well as decreased growth in the F₁ generation. Taken together, these results demonstrate that long-term exposure to low concentrations of DBP in zebrafish could cause reproductive toxicity, implying that DBP could have significant adverse effects on fish populations, particularly in a highly DBP-contaminated aquatic environment.

3-(4-Methylbenzylidene) camphor induced reproduction toxicity and antiandrogenicity in Japanese medaka (Oryzias latipes)

To assess the toxic effects of 3-(4-Methylbenzylidene) camphor (4-MBC) at environmentally relevant concentrations on the reproduction and development of Japanese medaka (Oryzias latipes), adult paired medaka (F0) were exposed to 5, 50, and 500 μg/L 4-MBC for 28 d in the current study. The fecundity and fertility were significantly decreased at 500 μg/L 4-MBC (p < 0.05). Histological observations showed that spermatogenesis in F0 males was significantly inhibited at 50 and 500 μg/L 4-MBC, similar to the effects obtained with all treatments of plasma 11-ketotestosterone (p < 0.05). Moreover, the plasma vitellogenin and estradiol levels in F0 females were significantly increased at 5 μg/L 4-MBC (p < 0.05). All the transcripts of hypothalamic-pituitary-gonadal (HPG) axis-related genes tested in the brains and gonads of males were significantly increased at all treatments, similar to the effects obtained for erα, erβ and vtg in the livers and in contrast to those found for arα in the livers (p < 0.05). Equal numbers of embryos were exposed to tap water and 4-MBC solutions. Significantly increased times to hatching, decreased hatching rates and decreased body lengths at 14-day post-hatching (dph) were obtained at 500 μg/L 4-MBC treatment (p < 0.05). The cumulative death rates at 14 dph were significantly increased with all the treatments (p < 0.05). Therefore, our results showed that long-term exposure to 50 and 500 μg/L 4-MBC causes reproductive and developmental toxicity and thus provide new insight into antiandrogenicity and the mechanism of 4-MBC in Japanese medaka.

Reproductive toxicity and estrogen activity in Japanese medaka (Oryzias latipes) exposed to environmentally relevant concentrations of octocrylene

The growing use of octocrylene (OC) in sunscreens has posed a great threat to aquatic organisms. In the present study, to assess its reproductive toxicity and mechanism, paired Japanese medaka (Oryzias latipes) (F0) were exposed to OC at nominal concentrations of 5, 50, and 500 μg/L for 28 d. Significant increases were observed in the gonadosomatic index (GSI) and hepatosomatic index (HSI) of F0 medaka at 500 μg/L OC (p < 0.05) without significant differences in fecundity. The fertility was significantly decreased at all treatments (p < 0.05). Significant increases in the percent of mature oocytes were observed at 5 and 500 μg/L OC, in which contrary to the percent of spermatozoa (p < 0.05). The plasma sex hormones and vitellogenin levels significantly increased in males at all treatments and in females at 50 and 500 μg/L OC (p < 0.05). In addition, the levels of fshβ and lhβ in the brains and the levels of fshr, lhr and cyp17α in the gonads were significantly upregulated in males at all treatments (p < 0.05), in line with those of ar, erα, erβ and cyp19β in the brains of male and female. The upregulation of vtg in male and female livers was observed only at 500 μg/L OC and upregulation of star and hsd3β was observed in testis at all treatments (p < 0.05). Continued exposure to OC significantly induced increases in the time to hatching, morphological abnormality rates, and cumulative death rates of F1 embryos, inconsistent with body length of F1 larvae (p < 0.05). Therefore, the responses of the exposed fish at the biochemical and molecular levels indicated reproductive toxicity and estrogenic activity of OC, providing insights into the mechanism of OC.

A preliminary ecological and human health risk assessment for organic contaminants in composted municipal solid waste generated in New South Wales, Australia

Land application of composted municipal solid waste (C-MSW) can divert waste from landfill but can also be a route of entry into the environment for contaminants. This study presents a preliminary human health and ecological risk assessment for organic contaminants in C-MSW generated in New South Wales, Australia, to identify and prioritise contaminants of concern. Following an initial screening assessment, terrestrial and aquatic risks were assessed by predicted soil and water concentrations, respectively. The assessment ranked contaminants as very high, high, medium or low priority. A qualitative review was then used to identify contaminants of concern, which included polybrominated diphenyl ethers, phthalates, bisphenol A and dibutyltin. Phenol was initially categorised as very high priority but due to its rapid degradation in soil, this is likely to be overly-conservative. The herbicides dicamba and MCPA were categorised as medium priority or higher but due to uncertainties in the data, these categories are also likely to be overly-conservative. A range of contaminants had concentrations below the screening criteria and were therefore considered low risk. Many contaminants were below the limit of reporting in all samples and were therefore not considered to be sufficiently distributed in the material to pose a risk. Some contaminants were detected in the material but could not be assessed as no criteria were available. The information from this study can be used by regulators when managing land application of C-MSW to ensure that the risks to human health and the environment are managed appropriately.

Chronic exposure to environmental concentrations of phenanthrene impairs zebrafish reproduction

Phenanthrene (PHE) is a tricyclic polycyclic aromatic hydrocarbon which distributed extensively in the aquatic environment. However, the knowledge about its impact on fish reproduction is still limited, particularly under a chronic exposure regime. In this study, we exposed zebrafish (Danio rerio) embryos to environmentally relevant concentrations (0.2, 1.0, and 5.0 μg/L) of PHE for 4 months and assessed the impact on reproduction. The results demonstrated that egg production was decreased in fish exposed to PHE, with a significant reduction at 5.0 μg/L. The exposure significantly decreased the circulating concentrations of estradiol (E2) and testosterone (T) in female fish or E2 in male fish. In addition, plasma vitellogenin levels were significantly inhibited after PHE exposure in female fish. The transcription of hypothalamic-pituitary-gonadal (HPG) axis related genes (GnRH2, FSHβ, LHβ, 17β-HSD, CYP11A1, and CYP19a) were significantly altered in a sex-specific manner. In addition, embryos derived from exposed parents exhibited increased malformation and decreased hatching success in the F1 generation. Taken together, these results demonstrate that chronic exposure to environmentally relevant concentration of PHE could cause adverse effects on reproduction and impair the development of offspring, ultimately leading to fish population decline in aquatic environment.

Androgen signaling in male fishes: Examples of anti-androgenic chemicals that cause reproductive disorders

Similar to other vertebrates, androgens regulate spermatogenesis in fishes. In teleosts, the main androgen is 11-Ketotestosterone (11-KT), which is oxidized testosterone (T) at the C₁₁ position. Compared to T, 11-KT is a nonaromatizable steroid, and does not convert to 17β-estradiol. However, circulatory levels of both T and 11-KT undergo seasonal variations along with testicular development. Physiological functions of androgens are mediated via androgen receptor (Ar). So far, nuclear Ar and membrane Ar have been identified in fishes. In the present study, we reviewed androgen biosynthesis in fishes, compared molecular structure of nuclear Ar in models of mammals and fishes, and investigated the mechanisms of action of environmental contaminants that differentially disrupt androgen signaling in fish reproduction. In the latter case, the adverse effects of vinclozolin (VZ) and bis(2-ethylhexyl) phthalate (DEHP) are compared. Both VZ and DEHP are capable of decreasing sperm quality in males. Vinclozolin causes an increase in 11-KT production associated with increases in kisspeptin (kiss-1) and salmon gonadotropin-releasing hormone (gnrh3) mRNA levels as well as circulatory levels of luteinizing hormone (Lh). In contrast, DEHP inhibits 11-KT production associated with a decrease in circulatory Lh levels. However, DEHP-inhibited 11-KT production is not associated with changes in kiss-1 and gnrh3 mRNA levels. Studies also show that VZ alters ar mRNA levels, while DEHP is without effect. These suggest that VZ and DEHP act differentially to cause androgen-dependent reproductive disorder in male fishes. Molecular analyses of the nuclear AR show that both DNA and ligand binding domains (DBD and LBD, respectively) are highly conserved within models of mammals and fishes. A phylogeny tree of the AR shows distinct clusters between mammals and fishes. In fishes, subtypes of Arα and Arβ are also separated in distinct clusters. Thus, further studies need to generate ar knockout fish model to better elucidate androgen regulation of reproduction in fishes via Ar.

Associations of Phthalates and Phthalate Replacements With CRH and Other Hormones Among Pregnant Women in Puerto Rico

CONTEXT

Phthalates are endocrine-disrupting chemicals that may be associated with adverse birth outcomes. Dysregulation of maternal endocrine homeostasis could be a possible biological pathway between phthalates and birth outcomes.

OBJECTIVE

Examine associations between 19 maternal urinary phthalate or phthalate replacement metabolites and 9 serum hormones measured over two time points during pregnancy.

DESIGN

Longitudinal study conducted in the PROTECT pregnancy cohort.

SETTING

Puerto Rico.

PATIENTS

Six hundred seventy-seven women in the first trimester of pregnancy.

MAIN OUTCOME MEASURES SERUM

CRH, estriol, SHBG, progesterone, TSH, total T3, free T4, total T4, and testosterone.

RESULTS

T3 was significantly associated with most metabolites. CRH was inversely associated with mono carboxyisononyl phthalate [MCNP; percent change (%Δ), -4.08; 95% CI, -7.24, -0.804], mono-3-carboxypropyl phthalate (MCPP; %Δ, -5.25; 95% CI, -8.26, -2.14), mono-2-ethyl-5-carboxypentyl phthalate (MECPP; %Δ, -18.4; 95% CI, -30.4, -4.37), mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP; %Δ, -13.4; 95% CI, -22.7, -2.92), and mono-2-ethyl-5-oxohexyl phthalate (MEOHP; %Δ, -12.7; 95% CI, -22.2, -2.20). Positive associations were found between numerous phthalate metabolites and free T4, T4, and the T3/T4 ratio. Testosterone was positively associated with mono hydroxybutyl phthalate (MHBP; %Δ, 4.71; 95% CI, 0.27, 9.35) and inversely associated with monoethyl phthalate (MEP; %Δ, -14.5; 95% CI, -24.3, -3.42), and relationships with MCNP and mono carboxyisooctyl phthalate (MCOP) were significantly modified by study visit. Finally, an inverse association was found between mono-2-ethyl-5-hydrohexyl terephthalate (MEHHTP), a terephthalate metabolite, and progesterone at visit 3 only (%Δ, -13.1; 95% CI, -22.3, -2.75).

CONCLUSIONS

These results indicate that exposure to phthalates may differentially impact the maternal endocrine system at different points during pregnancy, and that exposures to phthalate replacement chemicals may be particularly important to consider in future human health studies.

Environmental Pollutants Impair Transcriptional Regulation of the Vitellogenin Gene in the Burrowing Mud Crab (Macrophthalmus Japonicus)

Vitellogenesis is a pivotal reproductive process of the yolk formation in crustaceans. Vitellogenin (VTG) is the precursor of main yolk proteins and synthesized by endogenous estrogens. The intertidal mud crab (Macrophthalmus japonicus) inhabits sediment and is a good indicator for assessing polluted benthic environments. The purpose of this study was to identify potential responses of M. japonicus VTG under environmental stresses caused by chemical pollutants, such as 1, 10, and 30 µg L−1 concentrations in di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA) and irgarol. We characterized the M. japonicus VTG gene and analyzed the transcriptional expression of VTG mRNA in M. japonicus exposed to various chemicals and exposure periods. A phylogenetic analysis revealed that the M. japonicus VTG clustered closely with Eriocheir sinensis (Chinese mitten crab) VTG, in contrast with another clade that included the VTG ortholog of other crabs. The basal level of VTG expression was the highest in the hepatopancreas and ovaries, and tissues. VTG expression significantly increased in the ovaries and hepatopancreas after 24 h exposure to DEHP. Increased responses of VTG transcripts were found in M. japonicus exposed to DEHP and BPA for 96 h; however, VTG expression decreased in both tissues after irgarol exposure. After an exposure of 7 d, VTG expression significantly increased in the ovaries and hepatopancreas for all concentrations of all chemicals. These results suggest that the crustacean embryogenesis and endocrine processes are impaired by the environmental chemical pollutants DEHP, BPA, and irgarol.

Derivation of aquatic life criteria for four phthalate esters and their ecological risk assessment in Liao River

As a critical family of endocrine disruptors, phthalate esters (PAEs) attracted considerable attentions due to increasingly detected worldwide. Aquatic life criteria (ALC) for PAEs are crucial for their accurate ecological risk assessment (ERA) and have seldom been derived before. Given this concern, the purpose of the present study is to optimize the ALCs of four priority PAEs to estimate their ecological risks in Liao River. Reproductive endpoint was found to be more sensitive than other endpoints. Thus, reproduction related toxicity data were screened to derive ALCs applying species sensitivity distribution (SSD) method. ALCs of DEHP, DBP, BBP and DEP were calculated to be 0.04, 0.62, 4.71 and 41.9 μg L^-1, which indicated decreased toxicity in sequence. Then, the derived ALCs of the four PAEs were applied to estimate their ecological risks in Liao River. A total of 27 sampling sites were selected to detect and analyze the exposure concentrations of PAEs. ERA using the hazard quotient (HQ) method was conducted. The results demonstrated that DEHP exhibited higher risks at 92.6% of sampling sites, and risks posed by DBP were moderate at 63.0% sampling sites. However, risks posed by BBP were low at 70.4% of sampling sites, and there were no risks posed by DEP at 96.3% of sampling sites. The results of probabilistic ecological risk assessment (PERA) indicated that probabilities of exceeding effects thresholds on 5% of species were 60.41%, 0%, 0.12%, 14.28% for DEHP, DEP, BBP and DBP, respectively. The work provides useful information to protect aquatic species in Liao River.

New insights into the mechanism of phthalate-induced developmental effects

To investigate the biological pathways involved in phthalate-induced developmental effects, zebrafish embryos were exposed to different concentrations of di-(2-ethylhexyl) (DEHP) and di-butyl phthalate (DBP) for 96 h. Embryonic exposure to DEHP and DBP induced body length decrease, yolk sac abnormities, and immune responses (up-regulation of immune proteins and genes). The lipidomic results showed that at a concentration of 50 μg/L, DEHP and DBP significantly reduced the levels of fatty acids, triglycerides, diacylglycerol, and cholesterol. These effects are partly explained by biological pathway enrichment based on data from the transcriptional and proteomic profiles. Co-exposure to DBP and ER antagonist did not significantly relieve the toxic symptoms compared with exposure to DBP alone. This indicates that phthalate-induced developmental abnormities in zebrafish might not be mediated by the ER pathway. In conclusion, we identified the possible biological pathways that mediate phthalate-induced developmental effects and found that these effects may not be driven by estrogenic activation.

Bioaccumulation and effects of dietary exposure to the alternative flame retardant, bis(2-ethylhexyl) tetrabromophthalate (TBPH), in the Atlantic killifish, Fundulus heteroclitus

Bis(2-ethylhexyl) tetrabromophthalate (TBPH), a high production volume flame retardant chemical used as a replacement for banned flame retardants, has been detected in media and human and wildlife tissues globally. We describe bioaccumulation and biological effects from dietary exposure of TBPH to an estuarine fish, Atlantic killifish, Fundulus heteroclitus. Briefly, adult fish were fed carrier control or chemically amended diets for 28 d, followed by 14 d of control diet feeding. Diets were amended with TBPH (TBPH_LO diet, 139 μg/g dry wt, or TBPH_HI diet, 4360 μg/g dry wt) or a polychlorinated biphenyl congener (PCB153 diet, 13 μg/g dry wt), which was included as a positive control for bioaccumulation. Although bioaccumulation of either chemical correlated with fish size, only a small proportion of the TBPH offered (<0.5% total TBPH) had bioaccumulated into TBPH-treated fish by 28 d. In contrast, 24.5% of the PCB153 offered was accounted for in 28-d PCB-treated fish. Although 28-d bioaccumulated concentrations of TBPH differed by sex and treatment, sexes did not differ in their rates of TBPH bioaccumulation, and the time to achieve 50% of 28 d concentration (T1/2 ) was estimated to be 13 d. Depuration rates of TBPH did not differ by sex or treatment, and the time after exposure to achieve T1/2 was estimated to be 22 d. Independent of treatment, male fish grew faster than female fish, but for both sexes reproductive condition (gonadal somatic index) declined unexpectedly over the experimental period. Across treatments, only the TBPH_LO treatment affected growth, reducing male but increasing female growth rates by small amounts relative to respective controls. In summary, our study used very high concentrations of dietary TBPH to contaminate fish tissues above the highest levels reported to date in wild biota, yet we observed few adverse biological effects. Environ Toxicol Chem 2018;37:2350-2360. © 2018 SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Reproductive effects linked to DNA methylation in male zebrafish chronically exposed to environmentally relevant concentrations of di-(2-ethylhexyl) phthalate

Di-(2-ethylhexyl) phthalate (DEHP) possesses the potential to interfere with the male reproductive endocrine system in mammals; however, its reproductive toxicity in male zebrafish and associated epigenetic studies have not been explored. In this study, three-month-old male zebrafish were exposed to environmentally relevant concentrations of DEHP (0, 10, 33 and 100 μg/L) for 3 months, and then the impact on the reproduction of males and the underlying mechanism were investigated. Histological testing showed that an exposure concentration of 100 μg/L DEHP significantly inhibited spermatogenesis, with an associated decline in capability to fertilize untreated oocytes. Electron microscopic examinations also revealed noticeable damage to the testicular ultrastructure at the 100 μg/L DEHP exposure level. In addition, exposure to 33 and 100 μg/L of DEHP resulted in a decline of circulating testosterone (T) and an increase in the level of 17β-estradiol (E2), both of which were possibly derived from the downregulation of cyp17a1 and hsd17b3 genes and the upregulation of the cyp19a1a gene in the gonads. The DNA methylation statuses of these genes were altered within their promoter regions. A significant increase in global DNA methylation in both the male testes and their offspring larvae was observed at higher exposure concentration of DEHP. Our findings demonstrate that exposure to environmentally relevant concentrations of DEHP can damage the testes, disturbe the sex hormones production, and inhibite spermatogenesis, which ultimately impairs the reproduction of male zebrafish.

Environmentally Relevant Concentrations of Carbamazepine Caused Endocrine-Disrupting Effects on Nontarget Organisms, Chinese Rare Minnows (Gobiocypris rarus)

In the present study, Chinese rare minnows (Gobiocypris rarus) were exposed to 1, 10, and 100 μg/L of carbamazepine (CBZ) under flow-through conditions for 28 d. A hepatic-specific custom microarray identified 111 and 71 differentially expressed genes in the livers of females and males, respectively, exposed to 100 μg/L of CBZ (ratio ≥ 2, p ≤ 0.05). The levels of five differentially expressed genes associated with the hypothalamic-pituitary-gonadal (HPG) axis were quantified by qPCR, and the results indicated the feasibility of screening endocrine-disrupting chemicals using a custom microarray. The mRNA levels of genes related to the HPG axis differed significantly in different organs of Chinese rare minnows (p < 0.05). Significant differences were observed in the 11-ketotestosterone and plasma vitellogenin levels in all treatments and in the 17β-estradiol (E2) levels in the 100 μg/L CBZ treatment. In contrast, the gonadosomatic index was significantly higher in females and slightly higher in males without significant differences. A pathological analysis determined that 10 and 100 μg/L of CBZ could lead to ova-testis in males and significantly promoted ovum maturation in females. Therefore, our results demonstrate that environmentally relevant concentrations of CBZ have homologous estrogenic activity and induce reproductive toxicity in Chinese rare minnows.

Influence of DEHP on thyroid, sex steroid-related genes and gonadal differentiation in Rana chensinensis tadpoles

In the present study, responses of the Chinese brown frog (Rana chensinensis) to exposure to di-2-ethylhexyl phthalate (DEHP), a common plasticizer, during the larval period were characterized. The effects of DEHP on metamorphosis rate, thyroid hormone, thyroid histology and the expression of genes involved in the steroid hormone synthesis in gonad were investigated. Metamorphosis rate and 50 percent of the tadpoles to reach Gosner stage 42 (T_0.5 ) were significantly slower in all DEHP groups. The thyroid glands of the tadpoles exposed to DEHP clearly exhibited colloid depletion. In addition, decreased concentrations of T4 and T3 were observed in the tadpoles exposed to DEHP. Moreover, the highest DEHP exposure (10 µmol/L DEHP) showed increased ratio of females significantly. Also, up-regulation significantly of transcripts of cytochrome P450 aromatase (CYP19) gene was detected in male tadpoles exposed to DEHP. The present results indicate that this increase in estrogens could lead to female-biased sex ratio in DEHP exposure group. Taken together, the present study indicates that DEHP disrupt thyroid hormone and sex steroid signaling in R. chensinensis tadpoles. Our present observations support evidence of a crosstalk between TH and sex steroids in gonad differentiation.

Prenatal di(2-ethylhexyl) phthalate exposure and disruption of adrenal androgens and glucocorticoids levels in cord blood: The Hokkaido Study

Di(2-ethylhexyl) phthalate (DEHP) is known for its endocrine disrupting properties. We previously demonstrated that prenatal DEHP exposure is associated with decreased progesterone levels and testosterone/estradiol ratio in the cord blood. However, evidence of the effects of prenatal DEHP exposure on adrenal androgen and glucocorticoids in infants is scarce. Thus, the objectives of this study were to investigate the association between prenatal DEHP exposure and adrenal androgen and glucocorticoids, and to discuss its effects on steroid hormone profiles in infants. This is part of a birth cohort study: The Hokkaido Study on Environment and Children's Health, Sapporo Cohort. Among the 514 participants, 202 mother-infant pairs with available data on maternal mono(2-ethylhexyl) phthalate (MEHP), adrenal androgen (dehydroepiandrostenedione [DHEA] and androstenedione) and glucocorticoid (cortisol and cortisone) cord blood levels were included in this study. After adjusting for potential confounders, a linear regression analysis showed that maternal MEHP levels were associated with reduced cortisol and cortisone levels and glucocorticoid/adrenal androgen ratio, whereas increased DHEA levels and DHEA/androstenedione ratio. In a quartile model, when comparing the adjusted least square means in the 4th quartile of MEHP with those in the 1st quartile, cortisol and cortisone levels and glucocorticoid/adrenal androgen ratio decreased, whereas DHEA/androstenedione and cortisol/cortisone ratios increased. Significant p-value trends for cortisol and cortisone levels, cortisol/cortisone ratio, and glucocorticoid/adrenal androgen ratio were observed. In combination with the previous results of reduced progesterone levels and testosterone/estradiol ratio, prenatal exposure to DEHP altered the steroid hormone profiles of infants. Further studies investigating the long-term effects of DEHP exposure on growth, neurodevelopment, and gonad and reproductive function are required.

Increased Urinary Phthalate Levels in Women with Uterine Leiomyoma: A Case-Control Study

We assessed the urinary concentration of 16 phthalate metabolites in 57 women with and without uterine leiomyoma (n = 30 and 27; respectively) to determine the association between phthalate exposure and uterine leiomyoma. To evaluate exposure to di-(2-ethylhexyl) phthalate (DEHP); we calculated the molar sum of DEHP metabolites; ∑3-DEHP (combining mono-(2-ethylhexyl) phthalate (MEHP); mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP); and mono-(2-ethyl-5-oxohexyl) phthalate); ∑4-DEHP (∑3-DEHP plus mono-(2-ethyl-5-carboxypentyl) phthalate); and ∑5-DEHP (∑4-DEHP plus mono (2-(carboxylmethyl)hexyl) phthalate (2cx-MMHP)). The log transformed urinary levels of MEHP; MEHHP; 2cx-MMHP; ∑3-DEHP; ∑4-DEHP; and ∑5-DEHP in the leiomyoma group were significantly higher than those of controls. When we adjusted for age; waist circumference; and parity using multiple logistic regression analyses; we found log ∑3-DEHP (OR = 10.82; 95% CI = 1.25; 93.46) and ∑4-DEHP (OR = 8.78; 95% CI = 1.03; 75.29) were significantly associated with uterine leiomyoma. Our findings suggest an association between phthalate exposure and uterine leiomyoma. However; larger studies are needed to investigate potential interactions between phthalate exposure and uterine leiomyoma.

Developmental profiles and expression of the DNA methyltransferase genes in the fathead minnow (Pimephales promelas) following exposure to di-2-ethylhexyl phthalate

DNA methylation is an epigenetic regulator of gene expression, and this process has been shown to be disrupted by environmental contaminants. Di-2-(ethylhexyl) phthalate (DEHP) and related phthalate esters have been shown to affect development in early life stages of fish and can alter genomic methylation patterns in vertebrates. The objectives of this study were the following: (1) Describe the expression patterns of the DNA methyltransferase (dnmt) genes during early fathead minnow (FHM) development. These genes are critical for methylation and imprinting during development. (2) Determine the effects of DEHP on the development of FHM larvae [1 and 14 days post-hatch (dph)]. (3) Determine the effect of DEHP on dnmt expression and global methylation status in larval FHM. FHMs were first collected over a developmental time course [1, 3, 5, 6, and 14 days post-fertilization (dpf)] to investigate the expression patterns of five dnmt isoforms. The expression of dnmt1 and dnmt7 was relatively high in embryos at 1 dpf but was variable in expression, and these transcripts were later expressed at a lower level (>3 dpf); dnmt3 was significantly higher in embryos at 1 dpf compared to those at 3 dpf. Dnmt6 showed more of a constitutive pattern of expression during the first 2 weeks of development, and the mRNA levels of dnmt8 were higher in embryos at 5 and 6 dpf compared to those at 1 and 3 dpf, corresponding to the hatching period of the embryos. A waterborne exposure to three concentrations of DEHP (1, 10 and 100 µg/L) was conducted on 1-day FHM embryos for 24 h and on larval fish for 2 weeks, ending at 14 dpf. DEHP did not negatively affect survival, hatch rate, or the expression of dnmt isoforms in FHMs. There were no differences in global cytosine methylation following DEHP treatments in 14 dpf larvae, suggesting that environmentally relevant levels of DEHP may not affect global methylation at this stage of FHM development. However, additional targeted methylome studies are required to determine whether specific gene promoters are differently methylated following exposure to DEHP. This study offers new insight into the roles of the dnmt enzymes during FHM development.

Accumulation of di(2-ethylhexyl) phthalate causes endocrine-disruptive effects in marine medaka (Oryzias melastigma) embryos

Di (2-ethylhexyl) phthalate (DEHP) is extensively distributed in marine environments. However, limited research on the toxicological and molecular effects of DEHP on marine organisms has been conducted. Our study investigated the accumulation, elimination, and endocrine-disruptive effects of DEHP on embryonic marine medaka (Oryzias melastigma). The medaka embryos were continuously exposed to DEHP (0.01, 0.1, and 1 mg/L) or 17β-estradiol (E2, 0.01 mg/L) until hatching, and the newly hatched larvae were then transferred to clean sea water for 12 days of depuration. DEHP and E2 appeared to have no significant effects on the mortality and hatching rates of medaka embryos, but E2 exposure significantly delayed the hatching. Significantly higher DEHP embryonic burdens were detected in the group treated with higher DEHP (0.1 and 1 mg/L) at 10 dpf (days post fertilization). The recovered larvae showed an elimination tendency of DEHP during the recovery period. DEHP had no significant effects on the transcriptional responses of endocrine-disrupting biomarker genes in the 3-dpf embryos. Treatment with 0.1 and 1 mg/L DEHP elicited a significant induction of transcriptional responses of ER, PPAR, and the CYP19 genes in a concentration-dependent manner at 10 dpf, indicating endocrine disruption may be due to bioaccumulation of DEHP. With the elimination of DEHP during the depuration period, all of the effects on these genes showed no significant effects. However, 0.1 mg/L E2 significantly affected the expression of ER, PPAR, and the CYP19 genes in the exposed embryos at both 3 and 10 dpf and recovered larvae. Therefore, these results demonstrate that accumulation of DEHP caused endocrine disruption in medaka embryos and that recovery in clean sea water may weaken the endocrine-disrupting effects.

Short-term exposure to benzo[a]pyrene causes oxidative damage and affects haemolymph steroid levels in female crab Portunus trituberculatus

Concern has increased regarding the adverse effects of polycyclic aromatic hydrocarbons (PAHs) on reproduction. However, limited information is available on the effects of PAHs in crustacean. In order to determine whether benzo[a]pyrene (B[a]P) could cause reproductive toxicity on the swimming crab Portunus trituberculatus, sexually mature female crabs were exposed to environmentally relevant concentrations of B[a]P (0, 0.1, 0.5 and 2.5 μg/L) for 10 days. B[a]P treatments resulted in high accumulation in ovary, and induced oxidative stress in a dose-dependent manner on ovary of crab. Furthermore, the haemolymph estradiol (E2) and testosterone (T) levels were significantly decreased. Histological investigation also revealed the reproductive toxicity caused by B[a]P. The results demonstrated that waterborne exposure to B[a]P caused oxidative damage and disrupted sex steroids in female crab P. trituberculatus, ultimately resulting in histological alternation.

Short-term exposure to benzo[a]pyrene disrupts reproductive endocrine status in the swimming crab Portunus trituberculatus

The purpose of this study was to investigate the effect of benzo[a]pyrene (B[a]P) on reproductive endocrine disruption and explore the preliminary mechanisms in crustaceans. In this study, sexually mature female Portunus trituberculatus were exposed to 0, 0.1, 0.5 and 2.5 μg/L B[a]P for 10 days. The following were investigated: (1) Gonadosomatic Index (GSI) and oocyte diameter, (2) steroid concentrations in ovary and hemolymph, and (3) mRNA levels of genes involved in sex steroid synthesis (3β-HSD,17β-HSD) or reproduction (estrogen receptor (ER), OUT (Ovarian tumor gene) domain containing ubiquitin aldehyde-binding protein 1 (OTUB1), vitellogenin (VTG),vasa). B[a]P exposure caused significant reductions in the GSI and oocyte diameter in the crabs. Furthermore, 17β-estradiol (E2), testosterone (T) and progesterone (P) levels were inhibited significantly while 3β-HSD and 17β-HSD mRNA expressions were also decreased in a dose-dependent manner at day 10, which suggests that B[a]P can disrupt sex steroid levels through steroid synthesis pathways. In addition, high levels of B[a]P activated transcription of OTUB1 while suppressed ER and VTG expression, which indicates that exposure to waterborne B[a]P could interfere with ubiquitin-proteasome pathway and subsequently affect ER and ER-mediated gene expression. We also observed a reduction in vasa gene expression reflecting the negative effect of B[a]P on oocyte development in the molecular level. This study is the first to demonstrate in vivo B[a]P toxicity in the reproductive endocrine system of female P. trituberculatus and provided a scientific basis of the decline in crustacean populations.

The impact of long term exposure to phthalic acid esters on reproduction in Chinese rare minnow (Gobiocypris rarus)

The environmental risk of phthalic acid esters (PAEs) is of great concern. We investigated the reproductive impairment of di-(2-ethylhexyl)-phthalate (DEHP) on Chinese rare minnow, an endemic fish inhabiting the upper streams of the Yangtze River. Chinese rare minnow larvae were exposed to environmentally relevant concentrations of DEHP (0, 4.2, 13.3, and 40.8 μg/L) for 6 months. Plasma testosterone and 17β-estradiol levels decreased in females, accompanied by downregulation of cyp19a and cyp17 gene transcription in ovary. Increases in plasma testosterone concentration were observed in males, accompanied by downregulation of cyp19a gene transcription in testes. Hepatic VTG gene transcription was upregulated in males and females. Exposure to DEHP reduced egg production and inhibited oocyte maturation in females and retarded spermiation in males. Decreased egg protein content was measured in F1 embryos. These results indicate that long-term exposure to low concentrations of DEHP (13.3 μg/L) causes endocrine disruption and impairs fish reproduction.

Di-(2-ethylhexyl)-phthalate disrupts pituitary and testicular hormonal functions to reduce sperm quality in mature goldfish

Di-(2-ethylhexyl) phthalate (DEHP) interferes with male reproductive endocrine system in mammals, however its effects on fish reproduction are largely unknown. We evaluated sperm quality and investigated reproductive endocrine system in mature goldfish (Carassius auratus) exposed to nominal 1, 10, and 100μg/L DEHP. To examine DEHP estrogenic activity, one group of goldfish was exposed to 17β-estradiol (5μg/L E2) for comparison. Following 30d of exposure, sperm production was decreased and suppressed in DEHP and E2 treated goldfish, respectively. Sperm motility and velocity were decreased in goldfish exposed to 100 and 10μg/L DEHP at 15s post-sperm activation, respectively. Compared to control, 11-ketotestosterone (11-KT) levels were decreased at 10 and 1μg/L DEHP at day 15 and 30, respectively. In E2 treated goldfish, 11-KT levels were decreased compared to control during the period of exposure. E2 levels were increased in goldfish exposed to E2, but remained unchanged in DEHP treated goldfish during the period of exposure. StAR mRNA levels encoding regulator of cholesterol transfer to steroidogenesis were decreased in DEHP and E2 treated goldfish following 15 and 30d of exposure, respectively. Luteinizing hormone (LH) levels were decreased in DEHP and E2 treated goldfish following 15 and 30d of exposure, respectively. In DEHP treated goldfish, gnrh3, kiss1 and its receptor (gpr54) mRNA levels did not change during the experimental period. In E2 treated goldfish, gnrh3 mRNA levels were decreased at day 7, but kiss1 and gpr54 mRNA levels were increased at day 30 of exposure. The mRNA levels of genes encoding testicular LH and androgen receptors remained unchanged in DEHP and E2 treated goldfish. In contrast to E2 treated goldfish, vitellogenin production was not induced in DEHP treated goldfish and mRNA levels of genes with products mediating estrogenic effects remained unchanged or decreased. In conclusion, DEHP interferes with testis and pituitary hormonal functions to reduce sperm quality in goldfish and does not exhibit estrogenic activity.

A mixture of the novel brominated flame retardants TBPH and TBB affects fecundity and transcript profiles of the HPGL-axis in Japanese medaka

The novel brominated flame retardants (NBFRs), bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) and 2-ethylhexyl-2,3,4,5 tetrabromobenzoate (TBB) are components of the flame retardant mixture Firemaster 550 and both TBPH and TBB have recently been listed as high production volume chemicals by the US EPA. These NBFRs have been detected in several environmental matrices but very little is known about their toxic effects or potencies. Results of in vitro assays demonstrated potentials of these NBFRs to modulate endocrine function through interactions with estrogen (ER) and androgen receptors (AR) and via alterations to synthesis of 17-β-estradiol (E2) and testosterone (T), but in vivo effects of these chemicals on organisms are not known. Therefore a 21-day short term fish fecundity assay with Japanese medaka (Oryzias latipes) was conducted to investigate if these NBFRs affect endocrine function in vivo. Medaka were fed a diet containing either 1422 TBPH:1474 TBB or 138:144 μg/g food, wet weight (w/w). Cumulative production of eggs was used as a measure of fecundity and abundances of transcripts of 34 genes along the hypothalamus-pituitary-gonadal-liver (HPGL) axis were quantified to determine mechanisms of observed effects. Cumulative fecundity was impaired by 32% in medaka exposed to the greatest dose of the mixture of TBPH/TBB. A pattern of global down-regulation of gene transcription at all levels of the HPGL axis was observed, but effects were sex-specific. In female medaka the abundance of transcripts of ERβ was lesser in livers, while abundances of transcripts of VTG II and CHG H were greater. In male medaka, abundances of transcripts of ERα, ERβ, and ARα were lesser in gonads and abundances of transcripts of ERβ and ARα were lesser in brain. Abundances of transcripts of genes encoding proteins for synthesis of cholesterol (HMGR), transport of cholesterol (HDLR), and sex hormone steroidogenesis (CYP 17 and 3β-HSD) were significantly lesser in male medaka, which might have implications for concentrations of sex hormones. The results of this study demonstrate that exposure to components of the flame retardant mixture Firemaster(®) 550 has the potential to impair the reproductive axis of fishes.

Endocrine disrupting effects of benzotriazole in rare minnow (Gobiocypris rarus) in a sex-dependent manner

Benzotriazole (BT), an anticorrosive agent, is widely used in industrial applications and household dishwashing agents. Despite its reported toxicity to aquatic organisms, little is known about its endocrine disrupting effects. In this study, adult Chinese rare minnows (Gobiocypris rarus) were exposed to 0.05, 0.5, and 5 mg L(-1) BT for 28 d. The pathological damage in liver was associated with hypertrophy of the hepatocytes, nuclei pyknosis and vacuolization at 5 mg L(-1) groups. Additionally, the degeneration of the ovary and the stimulation of spermatogenesis were observed at 5 mg L(-1) groups. The plasma 17β-estradiol level was significantly increased in the males but decreased in the females at 5 mg L(-1) (p<0.05). In the brain, the up-regulation of CYP19B, GnRHs, and LHβ mRNA was detected across all doses (p<0.05). In the gonad, the transcriptional levels of StAR, CYP11A, 3βHSD, CYP17, 17βHSD, and CYP19A were generally decreased in the males at 5 mg L(-1) (p<0.05), whereas these genes, except for 3βHSD, were significantly increased in females at all concentrations (p<0.05). Moreover, the expression level of VTG in the livers from all exposure groups was significantly increased compared with controls (p<0.05). Taken together, our results indicate that BT could adversely affect the rare minnows in a sex-dependent manner.

Exposure to DEHP and MEHP from hatching to adulthood causes reproductive dysfunction and endocrine disruption in marine medaka (Oryzias melastigma)

Concern has increased regarding the adverse effects of di-(2-ethylhexyl)-phthalate (DEHP) on reproduction. However, limited information is available on the effects of DEHP in marine organisms. The aim of the present study was to examine whether long-term exposure to DEHP and its active metabolite mono-(2-ethylhexyl)-phthalate (MEHP) disrupts endocrine function in marine medaka (Oryzias melastigma). Marine medaka larvae were exposed to either DEHP (0.1 and 0.5mg/L) or MEHP (0.1 and 0.5mg/L) for 6 months, and the effects on reproduction, sex steroid hormones, liver vitellogenin (VTG), gonad histology and the expression of genes involved in the hypothalamic-pituitary-gonad (HPG) axis were investigated. Exposure to DEHP, but not MEHP, from hatching to adulthood accelerated the start of spawning and decreased the egg production of exposed females. Moreover, exposure to both DEHP and MEHP resulted in a reduction in the fertilization rate of oocytes spawned by untreated females paired with treated males. A significant increase in plasma 17β-estradiol (E2) along with a significant decrease in testosterone (T)/E2 ratios was observed in males, which was accompanied by the upregulation of ldlr, star, cyp17a1, 17βhsd, and cyp19a transcription in the testis. Increased concentrations of T and E2 were observed in females, which was consistent with the upregulation of ldlr. The expression of brain gnrhr2, fshβ, cyp19b and steroid hormone receptor genes also corresponded well with hormonal and reproductive changes. The liver VTG level was significantly increased after DEHP and MEHP exposure in males. DEHP induced histological changes in the testes and ovaries: the testes displayed a reduced number of spermatozoa, and the ovaries displayed an increased number of atretic follicles. In addition, the tissue concentrations of MEHP, MEHHP and MEOHP in DEHP-exposed groups were much higher than those in MEHP-exposed groups, and there were no dose- or sex-specific effects. Thus, DEHP exerts more obvious toxic effects compared with MEHP. There were some commonalities in the toxic effects and molecular mechanisms of DEHP and MEHP, suggesting that some of the toxic effects of DEHP may be induced by both DEHP itself and DEHP metabolites (including MEHP). Taken together, these results indicate that exposure to DEHP and MEHP from hatching to adulthood causes endocrine disruption with sex-specific effects in marine medaka, with males being more sensitive than females.