Peroxisome Proliferator-Activated Receptors: Mediators of Phthalate Ester-Induced Effects in the Male Reproductive Tract?

Systemic investigation of di-isobutyl phthalate (DIBP) exposure in the risk of cardiovascular via influencing the gut microbiota arachidonic acid metabolism in obese mice model

Phthalate esters (PE), a significant class of organic compounds used in industry, can contaminate humans and animals by entering water and food chains. Recent studies demonstrate the influence of PE on the development and progression of heart diseases, particularly in obese people. Di-isobutyl phthalate (DIBP) was administered orally to normal and diet-induced obese mice in this research to assess cardiovascular risk. The modifications in the microbial composition and metabolites were examined using RNA sequencing and mass spectrometry analysis. Based on the findings, lean group rodents were less susceptible to DIBP exposure than fat mice because of their cardiovascular systems. Histopathology examinations of mice fed a high-fat diet revealed lesions and plagues that suggested a cardiovascular risk. In the chronic DIBP microbial remodeling metagenomics Faecalibaculum rodentium was the predominant genera in obese mice. According to metabolomics data, arachidonic acid (AA) metabolism changes caused by DIBP were linked to unfavorable cardiovascular events. Our research offers new understandings of the cardiovascular damage caused by DIBP exposure in obese people and raises the possibility that arachidonic acid metabolism could be used as a regulator of the gut microbiota to avert related diseases.

The association between phthalate exposure and pubertal development

Antiandrogenic effect of phthalates have been reported; however, results regarding the effect of phthalate exposure in pubertal children have been inconsistent. We aimed to investigate the relationship between phthalate exposure and pubertal development, especially whether high molecular weight phthalates (HMWP) and low molecular weight phthalates (LMWP) are differently associated in boys and girls. Urinary phthalate metabolites (4 HMWPs and 3 LMWPs) in Korean children (236 boys and 202 girls, aged 10 to 12 years) were measured. The association between phthalate levels and pubertal development (pubertal stages self-reported by parents and sex steroid levels) was analyzed by generalized linear regression after adjusting for age, body mass index z score, and premature birth and/or low birth weight. Both the highest quartile of HMWP (Q4 vs Q1, adjusted odds ratio [OR], 0.238; 95% confidence interval [CI], 0.090-0.627; p = 0.004) and LMWP (Q4 vs Q1, adjusted OR, 0.373; 95% CI, 0.151-0.918; p = 0.032) were inversely associated with pubertal stages in boys, whereas the highest quartile of LMWP (Q4 vs Q1, adjusted OR, 2.431; 95% CI, 1.024-5.768; p = 0.044) was significantly related to advanced pubertal stages in girls. Testosterone levels in boys were significantly lower at the highest quartile of HMWP (adjusted β = - 0.251; 95% CI, - 0.476 to - 0.027; p = 0.028). However, in girls, we could not find any significant relationship between HMWP or LMWP and estradiol levels.

CONCLUSIONS

Our results suggest that phthalate exposure, especially exposure to the HMWP, may have inverse association with male pubertal development. Further investigation is required to verify the relationship of phthalate exposure and pubertal development in girls.

WHAT IS KNOWN

• Exposure to phthalates may have antiandrogenic effects. • Studies on the association between phthalates and pubertal development have yielded inconsistent results.

WHAT IS NEW

• Phthalate levels were inversely associated with self-reported pubertal stages in boys. • Exposure to phthalates might have a negative influence on male pubertal development.

Pioglitazone ameliorates cisplatin-induced testicular toxicity by attenuating oxidative stress and inflammation via TLR4/MyD88/NF-κB signaling pathway

BACKGROUND

Cisplatin (CIS) is a chemotherapeutic agent widely used to cure several cancers. It exerts detrimental cellular effects that restrain its clinical application as an antineoplastic agent, as testicular damage. Pioglitazone (PIO), a peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonist, is used to treat type-2 diabetes mellitus. PIO has been reported to exert anti-inflammatory and antioxidant effects in different tissues. The present study aimed to investigate the effect of PIO in a rat model of cisplatin-induced testicular toxicity and address the possible role of the Toll-like receptors (TLR4) / myeloid differentiation factor 88 (MyD88) / nuclear factor-kappa B (NF-kB) signal pathway.

METHODS

Rats received a single dose of cisplatin (7 mg/kg, IP) on the first day and PIO (10 mg/kg, P.O.) for 7 days. At the end of the treatment period, rats were killed. Testicular weights, histopathological alterations, and serum testosterone levels were determined. Moreover, tissue samples were collected for the estimation of oxidative stress parameters, inflammatory markers, and the determination of TLR4 /MyD88/NF-kB signaling.

RESULTS

Concurrent PIO administration with CIS markedly improved testicular weights, histopathological alteration, and serum testosterone level changes. Moreover, Concurrent PIO administration abrogated oxidative stress status and inflammatory markers caused by CIS administration. Furthermore, PIO inhibited the expression levels of TLR4, MyD88, and NF-κBp65, proteins that are activated by CIS administration.

CONCLUSION

These findings suggested that PIO can protect against cisplatin-induced testicular toxicity in rats through inhibition of the TLR4 /MyD88/NF-kB signal pathway.

Environmentally relevant DEHP exposure during gestational and lactational period inhibits filamin a testicular expression

Toxicological studies have revealed that DEHP exposure during pregnancy may induce developmental disorders, especially in male offspring, leading to morphological and functional alterations in the reproductive system by mechanisms that should be investigated. Thus, the aim of this work was to analyze the testicular toxicity induced by an environmentally relevant DEHP dose during development and its impact on FLNA, a protein that participates in the blood-testis barrier assembly. We used male Wistar rats exposed to DEHP during pregnancy and lactation. The results showed that DEHP exposure during development and lactation increased body weight, decreased gonadal weight and shortened anogenital distance. This phthalate induced morphological changes in the testis, suggestive of hypospermatogenesis. DEHP exposure decreased the number of FLNA positive cells and the expression of FLNA and claudin-1 in prepubertal testes. Furthermore, DEHP inhibited FLNA and claudin-1 protein expression in adult male rats. These results indicated that exposure to DEHP during gestation and lactation perturbed testis development and suggested that FLNA is a target protein of DEHP, possibly contributing to the phthalate-induced damage on BTB.

Effects of Di-(2-Ethylhexyl) Phthalate (DEHP) on Gamete Quality Parameters of Male Koi Carp (Cyprinus carpio)

In this study, we evaluated gamete quality parameters of mature male koi carp (Cyprinus carpio) exposed to three different concentrations (1, 10, and 100 µg/L) of di-(2-ethylhexyl) phthalate (DEHP). After 60 days of exposure, there was a significant decrease in the gonadosomatic index (GSI) of males exposed to 10 and 100 µg/L of DEHP. Histological analysis of the testes revealed impaired histoarchitecture, including inflammatory cells, intratubular vacuoles, and swollen seminiferous tubules in treatment groups. Gamete quality parameters like sperm production, motility, spermatocrit, and sperm density values were significantly decreased at the 10 and 100 µg/L concentrations. Biochemical compositions, including glucose, cholesterol, and total protein levels, were significantly changed in the treatment groups. Similarly, the ionic compositions of seminal fluid (Na, K, Ca, and Mg) also varied in the treatment groups. Furthermore, the 11-ketotestosterone levels were decreased, and the 17-β estradiol levels were increased in the DEHP-treated groups. The mRNA expression levels of reproduction-related genes, including Fshr, Lhr, Ar, Erα, and Erβ, were significantly changed in the DEHP-treated males in a dose-dependent manner. In conclusion, the findings of this study confirmed that environmentally relevant exposure to DEHP may contribute to a decline in the gamete quality of male fishes.

Putative adverse outcome pathways for silver nanoparticle toxicity on mammalian male reproductive system: a literature review

BACKGROUND

Adverse outcome pathways (AOPs) are conceptual frameworks that organize knowledge about biological interactions and toxicity mechanisms. They present a sequence of events commencing with initial interaction(s) of a stressor, which defines the perturbation in a biological system (molecular initiating event, MIE), and a dependent series of key events (KEs), ending with an adverse outcome (AO). AOPs have recently become the subject of intense studies in a view to better understand the mechanisms of nanomaterial (NM) toxicity. Silver nanoparticles (Ag NPs) are one of the most explored nanostructures and are extensively used in various application. This, in turn, has increased the potential for interactions of Ag NPs with environments, and toxicity to human health. The aim of this study was to construct a putative AOPs (pAOP) related to reproductive toxicity of Ag NPs, in order to lay the groundwork for a better comprehension of mechanisms affecting both undesired toxicity (against human cell) and expected toxicity (against microorganisms).

METHODS

PubMed and Scopus were systematically searched for peer-reviewed studies examining reproductive toxicity potential of Ag NPs. The quality of selected studies was assessed through ToxRTool. Eventually, forty-eight studies published between 2005 and 2022 were selected to identify the mechanisms of Ag NPs impact on reproductive function in human male. The biological endpoints, measurements, and results were extracted from these studies. Where possible, endpoints were assigned to a potential KE and an AO using expert judgment. Then, KEs were classified at each major level of biological organization.

RESULTS

We identified the impairment of intracellular SH-containing biomolecules, which are major cellular antioxidants, as a putative MIE, with subsequent KEs defined as ROS accumulation, mitochondrial damage, DNA damage and lipid peroxidation, apoptosis, reduced production of reproductive hormones and reduced quality of sperm. These successive KEs may result in impaired male fertility (AO).

CONCLUSION

This research recapitulates and schematically represents complex literature data gathered from different biological levels and propose a pAOP related to the reproductive toxicity induced by AgNPs. The development of AOPs specific to NMs should be encouraged in order to provide new insights to gain a better understanding of NP toxicity.

Occurrences and potential lipid-disrupting effects of phthalate metabolites in humpback dolphins from the South China Sea

Phthalate esters (PAEs) are ubiquitous environmental contaminants, arising growing public concern. Nevertheless, information on the exposure and risks of PAEs in wildlife remains limited. Here, we conducted the first investigation of the occurrences, spatiotemporal trends, and potential risks of twelve metabolites of PAEs (mPAEs) in 74 humpback dolphins from the northern South China Sea during 2005-2020. All twelve mPAEs (∑₁₂mPAEs: 9.6-810.7 ng g^-1 wet weight) were detected in the dolphin liver, and seven major mPAEs showed increasing trends during the study period, indicating high PAE contamination in the coastal environment of South China. Monoethylhexyl phthalate accounted for over half of the ∑₁₂mPAE concentrations. The accumulation of mPAEs in the dolphins was neither age-dependent nor sex-specific. Compared to parent PAEs, mPAEs generally induced higher agonistic effects on the dolphin peroxisome proliferator-activated receptor alpha/gamma (PPARA/G) as master regulators of lipid homeostasis. Although short-term in vitro assays revealed no significant activation of dolphin PPARA/G by tissue-relevant doses of mPAEs, long-term in vivo evidence (i.e., correlations between hepatic mPAEs and blubber fatty acids) suggested that chronic exposure to mPAEs might have impacted lipid metabolism in the dolphin. This study highlighted the potential health risks of PAE exposure on marine mammals.

Pharmacological perturbation of peroxisome-proliferator-activated receptor gamma alters motility and mitochondrial function of bovine sperm

BACKGROUND

Sperm transit through the female reproductive relies upon maintenance of sperm motility. Peroxisome-proliferator-activated receptor gamma (PPARγ) is a ligand-activated nuclear transcription factor with roles in glucose metabolism and reproductive processes including placental function. PPARγ roles in the mammalian postejaculatory sperm function are incompletely defined.

OBJECTIVES

Determine expression, localization, and functions of PPARγ in postejaculatory bovine sperm.

MATERIALS AND METHODS

Frozen-thawed bovine sperm from three to four different bulls were pooled and subjected to immunofluorescence and western blot for detection and localization of PPARγ. Functions in sperm energetics were explored through the addition of pharmacological inhibition (GW; GW9662) and activation (Ros; Rosiglitazone) in the culture medium at 0 and 24 h under non-capacitating conditions. Samples were analyzed for sperm kinematics (CASA) and mitochondrial membrane potential (MMP; JC-1 fluorophore).

RESULTS

PPARγ was detected in bovine sperm and co-localized to the acrosome with re-localization to the equatorial region in acrosome-compromised sperm. The addition of Ros 50 µM for 24 h maintained superior total and progressive motility of sperm compared to vehicle control (VC-DMSO 0.01%). The PPARγ antagonist GW 1 µM was detrimental to both total and progressive motility. A challenge experiment (Ros + GW) partially rescued total and progressive motility phenotypes observed with GW incubation. GW-treated samples had a lower number of sperm with high MMP at 24 h compared to Ros or VC. The negative GW MMP phenotype was reversed with the addition of Ros + GW. Likewise, GW-treated samples had more sperm with low MMP compared to VC and Ros, and this phenotype was partially restored with Ros + GW.

CONCLUSION

PPARγ is expressed in post-ejaculatory bovine sperm with regulatory roles in sperm motility and MMP. These findings implicate PPARγ as a novel regulator of postejaculatory mammalian sperm energetics through non-canonical signaling mechanisms.

Endocrine disruptors and endometriosis

Endometriosis is a hormone-dependent inflammatory gynecological disease of reproductive-age women. It is clinically and pathologically characterized by the presence of functional endometrium as heterogeneous lesions outside the uterine cavity. The two major symptoms are chronic pelvic pain and infertility, which profoundly affect women's reproductive health and quality of life. This significant individual and public health concerns underscore the importance of understanding the pathogenesis of endometriosis. The environmental endocrine-disrupting chemicals (EDCs) are exogenous agents that interfere with the synthesis, secretion, transport, signaling, or metabolism of hormones responsible for homeostasis, reproduction, and developmental processes. Endometriosis has been potentially linked to exposure to EDCs. In this review, based on the robust literature search, we have selected four endocrine disruptors (i) polychlorinated biphenyls (PCB)s (ii) dioxins (TCDD) (iii) bisphenol A (BPA) and its analogs and (iv) phthalates to elucidate their critical role in the etiopathogenesis of endometriosis. The epidemiological and experimental data discussed in this review indicate that these four EDCs activate multiple intracellular signaling pathways associated with proinflammation, estrogen, progesterone, prostaglandins, cell survival, apoptosis, migration, invasion, and growth of endometriosis. The available information strongly indicates that environmental exposure to EDCs such as PCBs, dioxins, BPA, and phthalates individually or collectively contribute to the pathophysiology of endometriosis. Further understanding of the molecular mechanisms of how these EDCs establish endometriosis and therapeutic strategies to mitigate the effects of these EDCs in the pathogenesis of endometriosis are timely needed. Moreover, understanding the interactive roles of these EDCs in the pathogenesis of endometriosis will help regulate the exposure to these EDCs in reproductive age women.

Health effects associated with phthalate activity on nuclear receptors

Phthalates are endocrine disruptors, widely used as plasticizers to impart flexibility in plastics, and as solvents in personal care products. Due to their nearly ubiquitous use in consumer products, most humans are exposed to phthalates daily. There has been extensive research on the reproductive health effects associated with phthalate exposure, but less attention has been paid to other actions. This review aims to summarize the known action of phthalates on different nuclear receptors. Some phthalates bind to and activate the estrogen receptor, making them weakly estrogenic. However, other phthalates antagonize androgen receptors. Some high molecular weight phthalates antagonize thyroid receptors, affecting metabolism. Several phthalates activate and interfere with the normal function of different peroxisome proliferator-activated receptors (PPARs), receptors that have critical roles in lipid metabolism and energy homeostasis. Some phthalates activate the aryl hydrocarbon receptor, which is critical for xenobiotic metabolism. Although phthalates have a short half-life in vivo, because people are continuously exposed, studies should examine the health effects of phthalates associated with long-term exposure. There is limited research on the effects of phthalates on health outcomes aside from reproductive function, particularly concerning are childhood adiposity, behavior, and learning. There is also limited information on actions of phthalates not mediated via nuclear receptors. Humans are exposed to multiple chemicals simultaneously, and how chemical mixtures act on nuclear receptor activity needs study. Although we know a great deal about phthalates, there is still much that remains uncertain. Future studies need to further examine their other potential health effects.

The p-Phthalates Terephthalic Acid and Dimethyl Terephthalate Used in the Manufacture of PET Induce In Vitro Adipocytes Dysfunction by Altering Adipogenesis and Thermogenesis Mechanisms

Public health concerns associated with the potential leaching of substances from Polyethylene terephthalate (PET) packaging have been raised due to the role of phthalates as endocrine-disrupting chemicals or obesogens. In particular, changes in the environment such as pH, temperature, and irradiation can improve contaminant migration from PET food packaging. In this study, the in vitro effects of p-phthalates terephthalic acid (TPA) and dimethyl terephthalate (DMT) on murine adipocytes (3T3-L1) were evaluated using concentrations that might be obtained in adult humans exposed to contaminated sources. TPA and, in particular, DMT exposure during 3T3-L1 differentiation increased the cellular lipid content and induced adipogenic markers PPAR-γ, C/EBPß, FABP4, and FASN, starting from low nanomolar concentrations. Interestingly, the adipogenic action of TPA- and DMT-induced PPAR-γ was reverted by ICI 182,780, a specific antagonist of the estrogen receptor. Furthermore, TPA and DMT affected adipocytes’ thermogenic program, reducing pAMPK and PGC-1α levels, and induced the NF-κB proinflammatory pathway. Given the observed effects of biologically relevant chronic concentrations of these p-phthalates and taking into account humans’ close and constant contact with plastics, it seems appropriate that ascertaining safe levels of TPA and DMT exposure is considered a high priority.

Testicular toxicity of bisphenol compounds: Homeostasis disruption of cholesterol/testosterone via PPARα activation

The widespread application of bisphenols (BPs) has made them ubiquitous in the environment. Although the side effects of bisphenol A (BPA) substitutes have received increasing attention, studies on their reproductive toxicity remain lacking. In this research, the effects of BPA and its substitutes, including bisphenol S (BPS), bisphenol F (BPF), and bisphenol AF (BPAF), on the male reproductive system were evaluated. Results proved that these BPs disturbed germ cell proliferation, induced germ cell apoptosis, and perturbed sperm physiologies and spermatogenesis, which resulted from the disruption of testosterone (T) biosynthesis in Leydig cells (LCs). Importantly, in vitro and in vivo studies indicated that the exhausted cholesterol in LCs accounted for the reduced T production. Furthermore, the knockdown of peroxisome proliferator-activated receptor alpha (PPARα) remarkably ameliorated the downregulation of cholesterogenesis-related genes (i.e., Hmgcs1, Hmgcr, and Srebf2), indicating that PPARα played a critical role in BPs-induced testicular dysfunction. Overall, our studies indicated that BPS, BPF, and BPAF could induce testicular toxic effects similar to that of BPA, which were associated with the PPARα pathway.

Investigation of a derived adverse outcome pathway (AOP) network for endocrine-mediated perturbations

An adverse outcome pathway (AOP) is a compact representation of the available mechanistic information on observed adverse effects upon environmental exposure. Sharing of events across individual AOPs has led to the emergence of AOP networks. Since AOP networks are expected to be functional units of toxicity prediction, there is current interest in their development tailored to specific research question or regulatory problem. To this end, we have developed a detailed workflow to construct an endocrine-relevant AOP (ED-AOP) network based on the existing information available in AOP-Wiki. We propose a cumulative weight of evidence (WoE) score for each ED-AOP based on the WoE scores assigned to key event relationships (KERs) by AOP-Wiki, revealing gaps in AOP development. Connectivity analysis of the ED-AOP network comprising 48 AOPs reveals 7 connected components and 12 isolated AOPs. Subsequently, we apply standard network measures to perform an in-depth analysis of the two largest connected components of the ED-AOP network. Notably, the graph-theoretic analyses led to the identification of important events including points of convergence or divergence in the ED-AOP network. These findings can suggest potential adverse outcomes and facilitate the development of new endpoints or assays for chemical risk assessment. Detailed analysis of the largest component in the ED-AOP network gives insights on the systems-level perturbations caused by endocrine disruption, emergent paths, and stressor-event associations. In sum, the derived ED-AOP network can provide a broader view of the biological events disrupted by endocrine disruption, as well as facilitate better risk assessment of environmental chemicals.

Phthalate Exposure, PPARα Variants, and Neurocognitive Development of Children at Two Years

Background: The PPARα gene may be crucial to the neurotoxic effect of phthalates. However, epidemiological studies considering the neurodevelopmental influence of phthalates interacting with genetic susceptibility are limited. We hypothesized phthalates could interact with the PPARα gene, synergistically affecting neurocognitive development.

Methods: A total of 961 mother-infant pairs were involved in this study. The concentrations of phthalate metabolites in maternal urine during pregnancy were detected. Children’s neurocognitive development was estimated with the Bailey Infant Development Inventory (BSID). Genetic variations in PPARα were genotyped with the Illumina Asian Screening Array. We applied generalized linear regression models to estimate genotypes and phthalate metabolites’ association with children’s neurocognitive development.

Results: After adjusting for potential confounders, the mono-n-butyl phthalate (MnBP) concentration was negatively associated with Psychomotor Development Index (PDI) (β = −0.86, 95% CI: −1.67, −0.04). The associations between MnBP and neurocognitive development might be modified by PPARα rs1800246. Compared with low-MnBP individuals carrying rs1800246 GG genotypes, high-MnBP individuals with the AG + AA genotype had a higher risk of neurocognitive developmental delay, with the odds ratio of 2.76 (95% CI:1.14, 6.24).

Conclusions: Our current study revealed that prenatal exposure to MnBP was negatively correlated with children’s neurocognitive development, and PPARα rs1800246 might modify the association.

Transcriptome and in silico approaches provide new insights into the mechanism of male reproductive toxicity induced by chronic exposure to DEHP

Di-(2-ethylhexyl) phthalate (DEHP) can affect the male reproductive system in vertebrates, but the underlying molecular mechanism is still elusive. Therefore, in this study, we aimed to dig the in-depth mechanism of DEHP-induced reproductive toxicity on male zebrafish via testicular transcriptome using embryo exposed at the environmentally relevant concentration (ERC) of 100 μg/L for 111 days. Moreover, our results were further confirmed via in silico technique and bioassay experimental in vitro (cell lines) and in vivo (zebrafish). The results showed DEHP exposure could affect male spermatogenesis, altered gonad histology, and reduced egg fertilization rate. Transcriptome analysis identified 1879 significant differentially expressed genes enriched in the exposure group. Twenty-seven genes related to three pathways of reproduction behavior were further validated by qPCR. In silico molecular docking revealed that DEHP and its metabolism bind to the zebrafish progesterone receptor (Pgr), suggesting the potential disruption of DEHP to the normal Pgr signaling. To further validate it, a wild-type Pgr plasmid and its mutants on specific binding sites were constructed. The transfection and microinjection experiment demonstrated that these binding sites mutations of Pgr affected the expression levels of male reproductive toxicity. Taken together, our study provided new insight into the molecular mechanisms of male reproductive toxicity induced by DEHP, and Pgr may serve as an important target binding by DEHP pollution, which needs further study in the future.

The probable mechanism of reduced androgen level in COVID-19 patients

COVID-19, caused by the SARS-CoV-2, has challenged the health care systems of the world. Although the pulmonary complications of the infection have received extensive attention, addressing the other complications (e.g., changes in androgen levels) could further provide a more efficient understanding of the disease, which might aid in combating it. Since the association between androgens and the expression and activity of SARS-CoV-2 receptors has been proven and anti-androgen-based therapies have been considered in this regard, addressing various aspects of androgen level changes can be constructive. The present paper examines the possible mechanisms of changes in androgen levels by the virus. It seems that the infection of the gonads by the SARS-CoV-2 could reduce the androgen levels by affecting different cellular pathways.

Genomic and Hormonal Biomarkers of Phthalate-Induced Male Rat Reproductive Developmental Toxicity Part II: A Targeted RT-qPCR Array Approach That Defines a Unique Adverse Outcome Pathway

Previously, we demonstrated that exposure to some diortho-phthalate esters during sexual differentiation disrupts male reproductive development by reducing fetal rat testis testosterone production (T Prod) and gene expression in a dose-related manner. The objectives of the current project were to expand the number of test compounds that might reduce fetal T Prod, including phthalates, phthalate alternatives, pesticides, and drugs, and to compare reductions in T Prod with altered testis mRNA expression. We found that PEs that disrupt T Prod also reduced expression of a unique "cluster" of mRNAs for about 35 genes related to sterol transport, testosterone and insulin-like hormone 3 hormone syntheses, and lipoprotein signaling and cholesterol synthesis. However, phthalates had little or no effect on mRNA expression of genes in peroxisome proliferator-activated receptor (PPAR) pathways in the fetal liver, whereas the 3 PPAR agonists induced the expression of mRNA for multiple fetal liver PPAR pathway genes without reducing testis T Prod. In summary, phthalates that disrupt T Prod act via a novel adverse outcome pathway including down regulation of mRNA for genes involved in fetal endocrine function and cholesterol synthesis and metabolism. This profile was not displayed by PEs that did not reduce T Prod, PPAR agonists or the other chemicals. Reductions in fetal testis gene expression and T Prod in utero can be used to establish relative potency factors that can be used quantitatively to predict the doses of individual PEs and mixtures of phthalates that produce adverse reproductive tract effects in male offspring.

Placental outcomes of phthalate exposure

Proper placental development and function relies on hormone receptors and signaling pathways that make the placenta susceptible to disruption by endocrine disrupting chemicals, such as phthalates. Here, we review relevant research on the associations between phthalate exposures and dysfunctions of the development and function of the placenta, including morphology, physiology, and genetic and epigenetic effects. This review covers in vitro studies, in vivo studies in mammals, and studies in humans. We also discuss important gaps in the literature. Overall, the evidence indicates that toxicity to the placental and maternal-fetal interface is associated with exposure to phthalates. Further studies are needed to better elucidate the mechanisms through which phthalates act in the placenta as well as additional human studies that assess placental disruption through pregnancy with larger sample sizes.

Epi-mutations for spermatogenic defects by maternal exposure to di(2-ethylhexyl) phthalate

Exposure to environmental factors during fetal development may lead to epigenomic modifications in fetal germ cells, altering gene expression and promoting diseases in successive generations. In mouse, maternal exposure to di(2-ethylhexyl) phthalate (DEHP) is known to induce defects in spermatogenesis in successive generations, but the mechanism(s) of impaired spermatogenesis are unclear. Here, we showed that maternal DEHP exposure results in DNA hypermethylation of promoters of spermatogenesis-related genes in fetal testicular germ cells in F1 mice, and hypermethylation of Hist1h2ba, Sycp1, and Taf7l, which are crucial for spermatogenesis, persisted from fetal testicular cells to adult spermatogonia, resulting in the downregulation of expression of these genes. Forced methylation of these gene promoters silenced expression of these loci in a reporter assay. These results suggested that maternal DEHP exposure-induced hypermethylation of Hist1h2ba, Sycp1, and Taf7l results in downregulation of these genes in spermatogonia and subsequent defects in spermatogenesis, at least in the F1 generation.

Umbelliferone ameliorates oxidative stress and testicular injury, improves steroidogenesis and upregulates peroxisome proliferator-activated receptor gamma in type 2 diabetic rats

OBJECTIVES

Diabetes mellitus (DM) is a chronic disease associated with serious complications, including male infertility. Umbelliferone (UMB) is a coumarin with promising antioxidant, anti-inflammatory and other beneficial effects. This study investigated the ameliorative effect of UMB against testicular injury, oxidative stress and altered steroidogenesis in rats with type 2 DM.

METHODS

Rats received a high fat diet for 4 weeks followed by a single injection of streptozotocin. Diabetic rats were treated with UMB or pioglitazone (PIO) for 6 weeks and samples were collected for analysis.

KEY FINDINGS

Diabetic rats exhibited hyperglycemia, insulin resistance and dyslipidemia associated with increased serum pro-inflammatory cytokines, and decreased gonadotropins and testosterone. UMB significantly ameliorated metabolic alterations, decreased pro-inflammatory cytokines, and increased gonadotropins and testosterone levels. UMB prevented testicular injury, suppressed lipid peroxidation and nitric oxide and increased antioxidants in diabetic rats. In addition, UMB upregulated testicular gonadotropins receptors, steroidogenesis markers (steroidogenic acute regulatory protein, cytochrome P450 family 17 subfamily A member 1 [CYP17A1], 3β-hydroxysteroid dehydrogenase [3ß-HSD] and 17ß-hydroxysteroid dehydrogenase [17ß-HSD]), and peroxisome proliferator-activated receptor gamma (PPARγ) expression.

CONCLUSIONS

UMB prevents testicular injury by preventing metabolic alterations, suppressing oxidative damage and inflammation, and boosting antioxidant defenses in diabetic rats. UMB enhanced pituitary-gonadal axis and steroidogenesis and upregulated testicular PPARγ in diabetic rats. Thus, UMB may represent a protective agent against testicular injury and sexual dysfunction associated with chronic hyperglycemia.

Nontraditional Risk Factors for Obesity in Modern Society

Overweight and obesity, which have rapidly increased around the world in recent years, are significant health problems. They can lead to various morbidities, including cardiovascular diseases, cerebrovascular diseases, type 2 diabetes, some types of cancer, and even death. Obesity is caused by an energy imbalance due to excessive calorie intake and insufficient energy consumption, and genetic factors and individual behavioral problems are also known to be major contributing factors. However, these are insufficient to explain the surge in obesity that has occurred in recent decades. Recent studies have suggested that environmental factors arising from the process of socioeconomic development and modernization contribute to this phenomenon. These environmental factors include light pollution due to artificial lighting, air pollution, endocrine-disrupting chemicals, and reduced exposure to green spaces due to urbanization of residential areas. In this manuscript, the findings and mechanisms of these novel risk factors causing overweight and obesity are reviewed.

Impact of gestational exposure to endocrine disrupting chemicals on pregnancy and birth outcomes

With the advent of industrialization, humans are exposed to a wide range of environmental chemicals, many with endocrine disrupting potential. As successful maintenance of pregnancy and fetal development are under tight hormonal control, the gestational exposure to environmental endocrine disrupting chemicals (EDC) have the potential to adversely affect the maternal milieu and support to the fetus, fetal developmental trajectory and birth outcomes. This chapter summarizes the impact of exposure to EDCs both individually and as mixtures during pregnancy, the immediate and long-term consequences of such exposures on the mother and fetus, the direct and indirect mechanisms through which they elicit their effects, factors that modify their action, and the research directions to focus future investigations.

Impact of endocrine-disrupting chemicals on steroidogenesis and consequences on testicular function

Testicular steroidogenesis is a tightly regulated process that produces the androgens important for the development, maintenance and function of the male reproductive system. These androgens are also essential for overall health, and well-being. Disruptions in the ability of the testis to form steroids can result in developmental abnormalities, dysfunction, and infertility. Endocrine-disrupting chemicals (EDCs) can interfere with the intricate signaling and metabolizing networks that produce androgens and promote their dysfunction. These chemicals are found ubiquitously in our environment, as they are integral components of products that are used every day. The effects of EDCs, such as bisphenols, phthalates, and alkyl chemicals, have been studied independently, revealing deleterious effects; but the combined influence of these structures on steroidogenesis has yet to be completely elucidated. This manuscript presents an updated review on EDC mixtures and their impact on testicular function and fertility, highlighting new findings that illustrate the anti-androgenic capabilities of EDC mixtures.

Reproductive toxic potential of phthalate compounds - State of art review

Phthalates are pervasive compounds, and due to the ubiquitous usage of phthalates, humans or even children are widely exposed to them. Since phthalates are not chemically bound to the plastic matrix, they can easily leach out to contaminate the peripheral environment. Various animal and human studies have raised vital health concern including developmental and reproductive toxicity of phthalate exposure. The present review is based upon the available literature on phthalates with respect to their reproductive toxic potential. Common reproductive effects such as declined fertility, reduced testis weight, variations in accessory sex organs and several female reproductive disorders appeared to be largely associated with the transitional phthalates. Among the higher molecular weight phthalates (≥ C7), di-isononyl phthalate (DINP) produces some minor effects on development of male reproductive tract and among low molecular weight phthalates (≤C3), di-methyl (DMP) and di-isobutyl (DIBP) phthalate produce some adverse effects on male reproductive system. Whereas transitional phthalates such as di-butyl phthalate, benzyl butyl phthalate, and di-(2-ethylhexyl) phthalate have shown adverse effects on female reproductive system. Owing to these, non-toxic alternatives to phthalates may be developed and use of phthalates could be rationalized as an important issue where human reproduction system is involved. Though, more epidemiological studies are needed to substantiate the reported findings on phthalates.

Postnatal exposure to DINP was associated with greater alterations of lipidomic markers for hepatic steatosis than DEHP in postweaning mice

The toxicity of the endocrine disruptor di(2-ethylhexyl) phthalate (DEHP) has been extensively studied for its hormonal dysregulation, obesogenic effect and associated metabolic diseases. DEHP's primary substitute di-isononyl phthalate (DINP), however, although increased in annual production globally, requires better understanding of its health effect. Our previous work reported disruptions in plasma lipid profiles, but the metabolic responses following phthalate exposure in the liver, particularly the entire hepatic lipidome, have been lacking. A targeted lipidomic technique was applied to accurately quantify a total of 363 lipid species in the liver of neonatal mice after exposure to a daily dose of 4.8 mg/kg body weight/day from birth throughout lactation. Distinct patterns of disruption for each sum of lipid classes or sub-classes between the genders were the most noticeable. Following DINP administration, female pups were subject to greater changes in phosphatidylethanolamines, bis(monoacylglycero)phosphate and ceramides. In contrast, the males exhibited less changes in the phosphoglycerol backbone-based molecules, whereas glycerol and cholesterol esters were more disrupted by DINP. DEHP, however, induced less changes overall compared to DINP. These findings highlighted the predominant lipidomic disruption of DINP on glycerol (diacylglycerides and triacylglycerides) and/or cholesterol (in ester or free form) molecules in neonatal mice across genders, suggesting the genesis of hepatic steatosis occurring at as early as post weaning. Collectively, these findings question the suitability of DINP as a safe DEHP substitute and warrant further investigation on longer-term exposure to elucidate its effect on chronic liver diseases.

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.

Application of a combined aggregate exposure pathway and adverse outcome pathway (AEP-AOP) approach to inform a cumulative risk assessment: A case study with phthalates

Advancements in measurement and modeling capabilities are providing unprecedented access to estimates of chemical exposure and bioactivity. With this influx of new data, there is a need for frameworks that help organize and disseminate information on chemical hazard and exposure in a manner that is accessible and transparent. A case study approach was used to demonstrate integration of the Adverse Outcome Pathway (AOP) and Aggregate Exposure Pathway (AEP) frameworks to support cumulative risk assessment of co-exposure to two phthalate esters that are ubiquitous in the environment and that are associated with disruption of male sexual development in the rat: di(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DnBP). A putative AOP was developed to guide selection of an in vitro assay for derivation of bioactivity values for DEHP and DnBP and their metabolites. AEPs for DEHP and DnBP were used to extract key exposure data as inputs for a physiologically based pharmacokinetic (PBPK) model to predict internal metabolite concentrations. These metabolite concentrations were then combined using in vitro-based relative potency factors for comparison with an internal dose metric, resulting in an estimated margin of safety of ~13,000. This case study provides an adaptable workflow for integrating exposure and toxicity data by coupling AEP and AOP frameworks and using in vitro and in silico methodologies for cumulative risk assessment.

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.

Dichotomy of bisphenol A-induced expression of peroxisome proliferator-activated receptors in hepatic and testicular tissues in mice

Environmental and dietary exposure to bisphenol A (BPA) and its toxicological consequences are extensively reported. BPA has multiple cellular targets. One of the mechanisms of action of BPA involves interaction with and activation of nuclear receptors (NRs) including peroxisome proliferator activated-receptors (PPARs). PPARs regulate genes involved in adipogenesis, and metabolism of glucose, lipid and cholesterol. Study of tissue and dose specific PPAR expression may decipher the toxicity outcome of BPA exposure. We studied expression of three forms of PPARs in mouse liver and testes exposed to BPA for 14 days. mRNA and protein expression of all forms of PPAR increased linearly (monotonic) with the dose in the liver while non-monotonic but dose specific effects were observed in the testes showing a differential pattern of expression. However, histopathological study showed a dose-dependent pattern of changes in liver as well as testes demonstrating a monotonic effect. These findings imply that other PPAR-independent mechanisms may play a role in BPA-induced pathological changes. The present study warrants exploration of the role of PPARs in BPA-induced effects on male reproductive functions and offers an insight into the peculiar response of BPA at low subchronic levels which may be helpful in designing appropriate risk assessment framework.

Phthalate-Induced Fetal Leydig Cell Dysfunction Mediates Male Reproductive Tract Anomalies

Male fetal Leydig cells in the testis secrete androgen and insulin-like 3, determining the sexual differentiation. The abnormal development of fetal Leydig cells could lead to the reduction of androgen and insulin-like 3, thus causing the male reproductive tract anomalies in male neonates, including cryptorchidism and hypospadias. Environmental pollutants, such as phthalic acid esters (phthalates), can perturb the development and differentiated function of Leydig cells, thereby contributing to the reproductive toxicity in the male. Here, we review the epidemiological studies in humans and experimental investigations in rodents of various phthalates. Most of phthalates disturb the expression of various genes encoded for steroidogenesis-related proteins and insulin-like 3 in fetal Leydig cells and the dose-additive effects are exerted after exposure in a mixture.

DEHP and DINP Induce Tissue- and Gender-Specific Disturbances in Fatty Acid and Lipidomic Profiles in Neonatal Mice: A Comparative Study

Di-isononyl phthalate (DINP) is considered one of the main industrial alternatives to di(2-ethylhexyl)phthalate (DEHP), a well-known chemical with various toxic effects including the disruption with lipid metabolism. However, the potential effects of DINP on lipid metabolism have rarely been investigated in mammals. Our study demonstrated that exposure of neonatal mice to DEHP and DINP at a daily dose of 0.048 or 4.8 mg/kg from postnatal day 0 (PND0) to PND21 caused nonmonotonic as well as tissue- and gender-specific alterations of total fatty acid (FA) compositions in plasma, heart, and adipose tissues. However, the patterns of disruption differed between DEHP- and DINP-treated groups. On the basis of targeted lipidomic analyses, we further identified gender-specific alterations of eight lipid classes in plasma following DEHP or DINP exposure. At the higher dose, DEHP induced decreases in total phosphatidylcholines and phosphatidylinositol (PI) in females and increases in phosphatidylethanolamines (PEs) and triglycerides in males. By contrast, DINP at the higher dose caused alterations of PEs, PIs, phosphatidylserines, and cholesterols exclusively in male mice, but no changes were observed in female pups. Although the most significant dysregulation of lipid metabolism was often observed for the higher dose, the lower one could also disrupt lipid profiles and sometimes its effects may even be more significant than those induced by the higher dose. Our study for the first time identified tissue- and gender-specific disruptions of FA compositions and lipidomic profiles in mice neonatally exposed to DINP. These findings question the suitability of DINP as a safe DEHP substitute and lay a solid foundation for further elucidation of its effects on lipid metabolism and underlying mechanisms.

Transcriptomic analysis reveals potential mechanisms of toxicity in a combined exposure to dibutyl phthalate and diisobutyl phthalate in zebrafish (Danio rerio) ovary

Phthalate esters (PAEs), which are notable plasticizers, can be prolific contaminants in aquatic environments, and have been shown to induce reproductive toxicity. However, the studies concerning their toxicity towards aquatic species are based on individual chemicals, and the combined toxicity of PAEs to aquatic organisms remains unclear. The aim of this study was to explore the potential toxicity mechanisms associated with combined exposure to dibutyl phthalate (DBP) and diisobutyl phthalate (DiBP) in adult female zebrafish ovaries. Zebrafish were exposed to DBP, DiBP and their mixtures for 30 days, and their effects on ovarian histology, plasma sex hormones and ovarian transcriptomics were investigated. Plasma estradiol (E2) levels were significantly decreased by 38.9% in the DBP-1133 exposure group and 41.0% in the DiBP-1038 exposure group. The percentage of late/mature oocytes was also significantly decreased by 17.3% under DBP-1133 exposure and 16.2% under DiBP-1038 exposure, while that under combined exposure was not significantly affected. Nevertheless, transcriptome sequencing revealed 2564 differentially expressed genes (DEGs) in zebrafish ovaries after exposure to the mixtures. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEGs were involved in the neuroactive ligand-receptor interaction, GnRH, progesterone-mediated oocyte maturation, oocyte meiosis and steroid hormone biosynthesis signaling pathways. These results revealed that combined exposure exerts potential reproductive toxicity at the molecular level.

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

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

Prenatal and ancestral exposure to di(2-ethylhexyl) phthalate alters gene expression and DNA methylation in mouse ovaries

Di(2-ethylhexyl) phthalate (DEHP) is a commonly used plasticizer and known endocrine disrupting chemical, which causes transgenerational reproductive toxicity in female rodents. However, the mechanisms of action underlying the transgenerational toxicity of DEHP are not understood. Therefore, this study determined the effects of prenatal and ancestral DEHP exposure on various ovarian pathways in the F1, F2, and F3 generations of mice. Pregnant CD-1 dams were orally exposed to corn oil (vehicle control) or DEHP (20 μg/kg/day-750 mg/kg/day) from gestation day 10.5 until birth. At postnatal day 21 for all generations, ovaries were removed for gene expression analysis of various ovarian pathways and for 5-methyl cytosine (5-mC) quantification. In the F1 generation, prenatal DEHP exposure disrupted the expression of cell cycle regulators, the expression of peroxisome-proliferator activating receptors, and the percentage of 5-mC compared to control. In the F2 generation, exposure to DEHP decreased the expression of steroidogenic enzymes, apoptosis factors, and ten-eleven translocation compared to controls. It also dysregulated the expression of phosphoinositide 3-kinase (PI3K) factors. In the F3 generation, ancestral DEHP exposure decreased the expression of steroidogenic enzymes, PI3K factors, cell cycle regulators, apoptosis factors, Esr2, DNA methylation mediators, and the percentage of 5-mC compared to controls. Overall, the data show that prenatal and ancestral DEHP exposure greatly suppress gene expression of pathways required for folliculogenesis and steroidogenesis in the ovary in a transgenerational manner and that gene expression may be influenced by DNA methylation. These results provide insight into some of the mechanisms of DEHP-mediated toxicity in the ovary across generations.

Effects of in utero and lactational exposure to phthalates on reproductive development and glycemic homeostasis in rats

Prenatal exposure to phthalates is associated with reproductive and metabolic systems alterations. We investigated the effects of in utero and lactational exposure to Di-(2-ethyl-hexyl) phthalate (DEHP) and Di-n-butyl phthalate (DBP) on the reproductive system and glycemic homeostasis in male and female offspring of rats. Pregnant rats were exposed to equimolar doses (0.018, 0.18 and 1.8 mmol/kg/day) of DEHP or DBP corresponding to 7, 70, and 700 mg/kg/day for DEHP and 5, 50, and 500 mg/kg/day for DBP, respectively, by oral gavage from gestation day 13 to postnatal day 21, and using canola oil as vehicle control. Male and female offspring were examined for body weight development, external markers of prenatal androgenization and puberty onset, plasma concentrations of glucose and insulin, insulin tolerance (ITT), glucose-stimulated insulin secretion (GSIS), and the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and pancreatic and duodenal homeobox 1 protein (PDX-1). Male and female rats exposed to the highest doses of DEHP and DBP exhibited increased fasting glucose levels. In rats exposed to DEHP 700 mg/kg/day we also observed a reduced glucose decay rate (Kitt) following insulin administration and decreased insulin secretion in the GSIS assay. Male offspring exposed to DEHP 700 mg/kg/day had reduced anogenital distance (AGD) on PDN 4 and delayed preputial separation at puberty, while female offspring exposed to DEHP 70 and 700 mg/kg/day and to the highest DBP dose had delayed vaginal opening. Our results suggest that maternal treatment with DEHP and DBP can induce a wide range of metabolic and reproductive alterations in offspring rats, with more pronounced effects following DEHP exposure.

The Role of Dietary Phytoestrogens and the Nuclear Receptor PPARγ in Adipogenesis: An in Vitro Study

BACKGROUND

Phytoestrogens, naturally occurring plant chemicals, have long been thought to confer beneficial effects on human cardiovascular and metabolic health. However, recent epidemiological studies, have yielded conflicting outcomes, in which phytoestrogen consumption was both positively and negatively correlated with adiposity. Interestingly, several dietary phytoestrogens are known to stimulate or inhibit the activity of the peroxisome proliferator-activated receptor gamma (PPARγ), a key physiological regulator of adipogenesis.

OBJECTIVE

The objective of this study was to test the hypothesis that the pro- or anti-adipogenic activity of phytoestrogen chemicals is related to the ability to activate PPARγ in adipocytes.

METHODS

The effects of resveratrol and the soy isoflavones genistein and daidzein on adipogenesis were examined in cell-based assays using the 3T3-L1 cell model. In parallel, ligand-mediated alterations in PPARγ target gene expression were measured by quantitative polymerase chain reaction. The agonist/antagonist activities of phytoestrogens on PPARγ were further assessed by quantifying their ability to affect recruitment of transcriptional cofactors to the receptor.

RESULTS

Resveratrol displayed significant anti-adipogenic activities as exhibited by the ability to antagonize PPARγ-dependent adipocyte differentiation, down-regulate genes involved in lipid metabolism, block cofactor recruitment to PPARγ, and antagonize the effects of the PPARγ agonist rosiglitazone. In contrast, genistein and daidzein functioned as PPARγ agonists while also displaying pro-adipogenic activities.

CONCLUSIONS

These data provide biological evidence that the pro- or anti-obesity effects of phytoestrogens are related to their relative agonist/antagonist activity on PPARγ. Thus, PPARγ-activation assays may enable the screening of dietary components and identification of agents with adipogenic activities. https://doi.org/10.1289/EHP3444.

Adverse Maternal, Fetal, and Postnatal Effects of Hexafluoropropylene Oxide Dimer Acid (GenX) from Oral Gestational Exposure in Sprague-Dawley Rats

BACKGROUND

Hexafluoropropylene oxide dimer acid [(HFPO-DA), GenX] is a member of the per- and polyfluoroalkyl substances (PFAS) chemical class, and elevated levels of HFPO-DA have been detected in surface water, air, and treated drinking water in the United States and Europe.

OBJECTIVES

We aimed to characterize the potential maternal and postnatal toxicities of oral HFPO-DA in rats during sexual differentiation. Given that some PFAS activate peroxisome proliferator-activated receptors (PPARs), we sought to assess whether HFPO-DA affects androgen-dependent development or interferes with estrogen, androgen, or glucocorticoid receptor activity.

METHODS

Steroid receptor activity was assessed with a suite of in vitro transactivation assays, and Sprague-Dawley rats were used to assess maternal, fetal, and postnatal effects of HFPO-DA exposure. Dams were dosed daily via oral gavage during male reproductive development (gestation days 14-18). We evaluated fetal testes, maternal and fetal livers, maternal serum clinical chemistry, and reproductive development of F1 animals.

RESULTS

HFPO-DA exposure resulted in negligible in vitro receptor activity and did not impact testosterone production or expression of genes key to male reproductive development in the fetal testis; however, in vivo exposure during gestation resulted in higher maternal liver weights ([Formula: see text]), lower maternal serum thyroid hormone and lipid profiles ([Formula: see text]), and up-regulated gene expression related to PPAR signaling pathways in maternal and fetal livers ([Formula: see text]). Further, the pilot postnatal study indicated lower female body weight and lower weights of male reproductive tissues in F1 animals.

CONCLUSIONS

HFPO-DA exposure produced multiple effects that were similar to prior toxicity evaluations on PFAS, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), but seen as the result of higher oral doses. The mean dam serum concentration from the lowest dose group was 4-fold greater than the maximum serum concentration detected in a worker in an HFPO-DA manufacturing facility. Research is needed to examine the mechanisms and downstream events linked to the adverse effects of PFAS as are mixture-based studies evaluating multiple PFAS. https://doi.org/10.1289/EHP4372.

Maternal supplementation with corn oil associated or not with di-n-butyl phthalate increases circulating estradiol levels of gerbil offspring and impairs sperm reserve

This study evaluated the consequences of gestational exposure to di-n-butyl phthalate (DBP) for testicular steroidogenesis and sperm parameters of the adult gerbil and the interference of corn oil (co), a vehicle widely used for administration of liposoluble agents, on DBP effects. Pregnant gerbils received no treatment or were treated from gestational day 8 to 23 via gavage with 0.1 mL/day of co only or containing DBP (100 mg/kg/day). Maternal co intake enhanced serum estradiol levels and testicular content of ERα, and reduced sperm reserve of adult offspring. Gestational DBP exposure caused dyslipidemia, increased serum and intratesticular estradiol levels and reduced sperm reserve and motility. Thus, maternal co supplementation alters circulating estradiol and impairs sperm quantity and quality of offspring. Gestational DBP exposure alters lipid metabolism and testicular steroidogenesis and worsens the negative effects of co on the sperm reserve and motility of gerbil. Therefore, co interferes with the reproductive response to DBP.

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.

Potential impact of the herbicide 2,4-dichlorophenoxyacetic acid on human and ecosystems

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is applied directly to aquatic and conventional farming systems to control weeds, and is among the most widely distributed pollutants in the environment. Non-target organisms are exposed to 2,4-D via several ways, which could produce toxic effects depending on the dose, frequency of exposure, and the host factors that influence susceptibility and sensitivity. An increasing number of experimental evidences have shown concerns about its presence/detection in the environment, because several investigations have pointed out its potential lethal effects on non-target organisms. In this review, we critically evaluated the environmental fate and behavior of 2,4-D along with its eco-toxicological effects on aquatic, plants and human life to provide concise assessment in the light of recently published reports. The findings demonstrate that 2,4-D is present in a low concentration in surface water of regions where its usage is high. The highest concentrations of 2,4-D were detected in soil, air and surface water surrounded by crop fields, which suggest that mitigation strategies must be implanted locally to prevent the entry of 2,4-D into the environment. A general public may have frequent exposure to 2,4-D due to its wide applications at home lawns and public parks, etc. Various in vivo and in vitro investigations suggest that several species (or their organs) at different trophic levels are extremely sensitive to the 2,4-D exposure, which may explain variation in outcomes of reported investigations. However, implications for the prenatal exposure to 2,4-D remain unknown because 2,4-D-induced toxicity thresholds in organism have only been derived from juveniles or adults. In near future, introduction of 2,4-D resistant crops will increase its use in agriculture, which may cause relatively high and potentially unsafe residue levels in the environment. The recent findings indicate the urgent need to further explore fate, accumulation and its continuous low level exposure impacts on the environment to generate reliable database which is key in drafting new regulation and policies to protect the population from further exposure.

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

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

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

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

Effects of endocrine disrupting chemicals on estrogen receptor alpha and heat shock protein 60 gene expression in primary cultures of loggerhead sea turtle (Caretta caretta) erythrocytes

The loggerhead turtle (Caretta caretta) can be considered a good indicator species for studying the ecological impact of endocrine disrupting chemicals (EDCs) on wildlife. However, the effect of these environmental pollutants on nuclear steroid hormone signaling has not yet been addressed in sea turtles mainly due to the legal constraints of their endangered status. Here we describe the use of primary erythrocyte cell cultures as in vitro models for evaluating the effects of different EDCs on the expression of estrogen receptor α (ERα). In addition, we evaluated erythrocyte toxicity caused by EDCs using Alamar Blue assay and heat shock proteins 60 (HSP60) expression. Primary cultures of erythrocytes were exposed to increasing concentrations of 4-nonylphenol (4NP), Diisodecyl phthalate (DiDP), Tri-m-cresyl phosphate (TMCP) and Tributyltin (TBT) for 48h. Alamar Blue demonstrated that exposure of erythrocytes to each contaminant for up to 48h led to a significant impairment of cellular metabolic activity at 100μM, with the exception of TBT. Moreover, our data indicate that loggerhead erythrocytes constitutively express ERα and HSP60 at the transcript level and respond to EDCs by up-regulating their expression. In this regard, ERα was up-regulated in a dose-dependent manner after 48h exposure to both 4NP and TMCP. Interestingly, the dosage-dependent effects of DiDP on ERα expression were opposite in comparison to that obtained following exposure to the other tested compounds. This work provides the first indication regarding the potential of primary erythrocytes as study models for evaluating the effects of EDCs on sea turtles.

Prediction of liver toxicity and mode of action using metabolomics in vitro in HepG2 cells

Liver toxicity is a leading systemic toxicity of drugs and chemicals demanding more human-relevant, high throughput, cost effective in vitro solutions. In addition to contributing to animal welfare, in vitro techniques facilitate exploring and understanding the molecular mechanisms underlying toxicity. New ‘omics technologies can provide comprehensive information on the toxicological mode of action of compounds, as well as quantitative information about the multi-parametric metabolic response of cellular systems in normal and patho-physiological conditions. Here, we combined mass-spectroscopy metabolomics with an in vitro liver toxicity model. Metabolite profiles of HepG2 cells treated with 35 test substances resulted in 1114 cell supernatants and 3556 intracellular samples analyzed by metabolomics. Control samples showed relative standard deviations of about 10–15%, while the technical replicates were at 5–10%. Importantly, this procedure revealed concentration–response effects and patterns of metabolome changes that are consistent for different liver toxicity mechanisms (liver enzyme induction/inhibition, liver toxicity and peroxisome proliferation). Our findings provide evidence that identifying organ toxicity can be achieved in a robust, reliable, human-relevant system, representing a non-animal alternative for systemic toxicology.

Potential effects of low molecular weight phthalate esters (C16H22O4 and C12H14O4) on the freshwater fish Cyprinus carpio

The aim of the present study is to assess the toxic effect of dibutyl phthalate (DBP) and diethyl phthalate (DEP) on the freshwater fish Cyprinus carpio. The median lethal concentrations of DBP and DEP for 96 h are found to be 35 and 53 mg L-1, respectively. Fish were exposed to 3.5 mg L-1 (Treatment I) and 1.75 mg L-1 (Treatment II) of DBP and 5.3 mg L-1 (Treatment I) and 2.65 mg L-1 (Treatment II) of DEP for a period of 35 days. The DBP and DEP exposed fish show a concentration based toxic effect on the selected parameters of this study. The hematological parameters, such as hemoglobin (Hb), hematocrit (Hct) and erythrocyte (RBC), were found to decrease in the DBP and DEP treated fish, whereas their leucocyte (WBC) count increased compared to that of the control groups. A biphasic response is noted in the erythrocyte indices, such as mean cellular volume (MCV), mean cellular hemoglobin (MCH) and mean cellular hemoglobin concentration (MCHC), throughout the study period. Exposure to DBP and DEP caused a significant (p < 0.05) decrease in sodium (Na+), potassium (K+), and chloride (Cl-) levels in the gill and brain of the fish throughout the study period when compared to that of their respective controls. The plasma protein level decreased in all the treatments, whereas the plasma glucose level significantly increased in the DBP and DEP exposed fish. Maximum inhibition of Na+/K+-ATPase activity was noticed in the gill and brain of the fish exposed to DBP and DEP. The cholinesterase (ChE) activity in the brain of the fish significantly decreased throughout the study period. A significant (p < 0.05) increase in glutamate oxaloacetate transaminase (GOT) and glutamic pyruvate transaminase (GPT) activity was noted in the fish exposed to both toxicants. The antioxidant enzymatic parameters such as superoxide dismutase (SOD) and catalase (CAT) activities were found to decrease in the gill and liver of the DBP and DEP treated fish, whereas a significant (p < 0.05) increase in lipid peroxidation (LPO) was observed. The above mentioned parameters could be used as potential biomarkers in clinical trials for the assessment of plasticizers. This study provides indispensable information towards future research on the effect of plasticizers on non-target organisms including humans.