Endocrine Disruption: Structural Interactions of Androgen Receptor against Di(2-ethylhexyl) Phthalate and Its Metabolites

Urinary phthalate metabolites associated with bone mineral density in adults: Data from the NHANES 2011-2018

Phthalates (PAEs) are common environmental endocrine disruptors and environmental bone poisons that can reduce bone mineral density (BMD). The purpose of this study is to investigate whether the concentration of PAE metabolites in urine is related to BMD in many parts of adult bones. We examined a series of cross-sectional data of male (n = 1835) and female (n = 1756) participants aged 18 to 59 years old in the National Health and Nutrition Examination Survey from 2011 to 2018 and measured urine PAE metabolites and dual-energy X-ray absorption to determine BMD (total body, lumbar spine, and pelvis). We used linear regression to test the correlation between a single phthalate biomarker and BMD. After adjusting all confounding variables, MEHP was positively correlated with BMD of total body, lumbar spine and pelvis, and BMD levels of the total body, lumbar spine and pelvis decreased with the increase of MECPP concentration. We used the restricted cubic spline function to test the nonlinear correlation between PAE biomarkers and BMD. The results show that urinary PAE metabolites have a nonlinear relationship with total body BMD, lumbar spine BMD, and pelvic BMD. With the increase in the PAE concentration, the BMD level first increased and then decreased, showing an inverted U-shaped trend (P < 0.05). Gender stratification also shows the same related trend. PAEs may be related to the BMD of adults. When the concentration of PAEs increases to a certain threshold, it will lead to a significant decrease in BMD.

Reduced ovarian cholesterol and steroid biosynthesis along with increased inflammation are associated with high DEHP metabolite levels in human ovarian follicular fluids

The plasticizer di(2-ethylhexyl) phthalate (DEHP) is known to have endocrine-disrupting properties mediated by its many metabolites that form upon exposure in biological systems. In a previous study, we reported an inverse association between DEHP metabolites in the human ovarian follicular fluid (FF) and the responsiveness of the follicles to controlled ovarian stimulation during in vitro fertilization (IVF) treatments. Here, we explored this association further through molecular analysis of the ovarian FF samples. Ninety-six IVF patients from Swedish (N = 48) and Estonian (N = 48) infertility clinics were selected from the previous cohort (N = 333) based on the molar sum of DEHP metabolites in their FF samples to arrive at "high" (mean 7.7 ± SD 2.3 nM, N = 48) and "low" (0.8 ± 0.4 nM, N = 48) exposure groups. Extracellular miRNA levels and concentrations of 15 steroid hormones were measured across FF samples. In addition, FF somatic cells, available for the Estonian patients, were used for RNA sequencing. Differential expression (DE) and interactions between miRNA and mRNA networks revealed that the expression levels of genes in the cholesterol biosynthesis and steroidogenesis pathways were significantly decreased in the high compared to the low DEHP group. In addition, the DE miRNAs were predicted to target key enzymes within these pathways (FDR < 0.05). A decreased 17-OH-progesterone to progesterone ratio was observed in the FF of the high DEHP group (p < 0.05). Additionally, the expression levels of genes associated with inflammatory processes were elevated in the FF somatic cells, and a computational cell-type deconvolution analysis suggested an increased immune cell infiltration into the high DEHP follicles (p < 0.05). In conclusion, elevated DEHP levels in FF were associated with a significantly altered follicular milieu within human ovaries, involving a pro-inflammatory environment and reduced cholesterol metabolism, including steroid synthesis. These results contribute to our understanding of the molecular mechanisms of female reprotoxic effects of DEHP.

SLC7A11 as a therapeutic target to attenuate phthalates-driven testosterone level decline in mice

INTRODUCTION

Phthalates exposure is a major public health concern due to the accumulation in the environment and associated with levels of testosterone reduction, leading to adverse pregnancy outcomes. However, the relationship between phthalate-induced testosterone level decline and ferroptosis remains poorly defined.

OBJECTIVES

Herein, we aimed to explore the mechanisms of phthalates-induced testosterone synthesis disorder and its relationship to ferroptosis.

METHODS

We conducted validated experiments in vivo male mice model and in vitro mouse Leydig TM3 cell line, followed by RNA sequencing and metabolomic analysis. We evaluated the levels of testosterone synthesis-associated enzymes and ferroptosis-related indicators by using qRT-PCR and Western blotting. Then, we analyzed the lipid peroxidation, ROS, Fe2+ levels and glutathione system to confirm the occurrence of ferroptosis.

RESULTS

In the present study, we used di (2-ethylhexyl) phthalate (DEHP) to identify ferroptosis as the critical contributor to phthalate-induced testosterone level decline. It was demonstrated that DEHP caused glutathione metabolism and steroid synthesis disorders in Leydig cells. As the primary metabolite of DEHP, mono-2-ethylhexyl phthalate (MEHP) triggered testosterone synthesis disorder accompanied by a decrease in the expression of solute carri1er family 7 member 11 (SLC7A11) protein. Furthermore, MEHP synergistically induced ferroptosis with Erastin through the increase of intracellular and mitochondrial ROS, and lipid peroxidation production. Mechanistically, overexpression of SLC7A11 counteracts the synergistic effect of co-exposure to MEHP-Erastin.

CONCLUSION

Our research results suggest that MEHP does not induce ferroptosis but synergizes Erastin-induced ferroptosis. These findings provide evidence for the role of ferroptosis in phthalates-induced testosterone synthesis disorder and point to SLC7A11 as a potential target for male reproductive diseases. This study established a correlation between ferroptosis and phthalates cytotoxicity, providing a novel view point for mitigating the issue of male reproductive disease and "The Global Plastic Toxicity Debt".

Sex-Specific Associations between Prenatal Exposure to Di(2-ethylhexyl) Phthalate, Epigenetic Age Acceleration, and Susceptibility to Early Childhood Upper Respiratory Infections

Di(2-ethylhexyl) phthalate (DEHP) is a common plasticizer that can affect immune system development and susceptibility to infection. Aging processes (measured as epigenetic age acceleration (EAA)) may mediate the immune-related effects of prenatal exposure to DEHP. This study's objective was to examine associations between prenatal DEHP exposure, EAA at three months of age, and the number of upper respiratory infections (URIs) from 12 to 18 months of age using a sample of 69 maternal-child pairs from a Canadian pregnancy cohort. Blood DNA methylation data were generated using the Infinium HumanMethylation450 BeadChip; EAA was estimated using Horvath's pan-tissue clock. Robust regressions examined overall and sex-specific associations. Higher prenatal DEHP exposure (B = 6.52, 95% CI = 1.22, 11.81) and increased EAA (B = 2.98, 95% CI = 1.64, 4.32) independently predicted more URIs. In sex-specific analyses, some similar effects were noted for boys, and EAA mediated the association between prenatal DEHP exposure and URIs. In girls, higher prenatal DEHP exposure was associated with decreased EAA, and no mediation was noted. Higher prenatal DEHP exposure may be associated with increased susceptibility to early childhood URIs, particularly in boys, and aging biomarkers such as EAA may be a biological mechanism. Larger cohort studies examining the potential developmental immunotoxicity of phthalates are needed.

Integrated Studies on Male Reproductive Toxicity of Bis(2-ethylhexyl)-tetrabromophthalate: in Silico, in Vitro, ex Vivo, and in Vivo

Bis(2-ethylhexyl)tetrabromophthalate (TBPH) has been widely detected in the environment and organisms; thus, its toxic effects on male reproduction were systematically studied. First, we found that TBPH can stably bind to the androgen receptor (AR) based on in silico molecular docking results and observed an antagonistic activity, but not agonistic activity, on the AR signaling pathway using a constructed AR-GRIP1 yeast assay. Subsequently, we validated the adverse effects on male germ cells by observing inhibited androgen production and proliferation in Leydig cells upon in vitro exposure and affected general motility and motive tracks of zebrafish sperm upon ex vivo exposure. Finally, the in vivo reproductive toxicity was demonstrated in male zebrafish by reduced mating behavior in F0 generation when paired with unexposed females and abnormal development of their offspring. In addition, reduced sperm motility and impaired germ cells in male zebrafish were also observed, which may be related to the disturbed homeostasis of sex hormones. Notably, the specifically suppressed AR in the brain provides further evidence for the antagonistic effects as above-mentioned. These results confirmed that TBPH affected male reproduction through a classical nuclear receptor-mediated pathway, which would be helpful for assessing the ecological and health risks of TBPH.

Associations of phthalates with prostate cancer among the US population

Human exposure to harmful phthalates has raised global health concerns. According to cellular and molecular investigations, phthalates and their metabolites can promote prostate cancer (PCa). Despite being a prevalent cancer afflicting the global male population, the epidemiological association between phthalates and prostate cancer remains understudied. This work aims to investigate whether phthalate metabolites are related to prostate cancer. Moreover, we sought to understand whether their elevated concentrations are associated with increased serum concentrations of prostate-specific antigen (PSA), among non-prostate cancer interviewees. According to National Health and Nutrition Examination Survey (NHANES) data from 2003 to 2010, we screened eligible men aged 20 years or older. Then, crude and multivariate regression models were constructed to assess the relationship. The phthalates significantly related to PCa were analyzed based on variables associated with PCa status and PSA. The molar sum ∑di-2-ethylhexyl phthalate (∑DEHP) was simultaneously associated with increased risk of PCa and increasing PSA concentrations. Among PCa-related phthalates, high molecular weight phthalate metabolites included mono-benzyl phthalate (MBzP) and three metabolites of DEHP. In summary, phthalates are potentially associated with prostate tumorigenesis in the US population. However, additional in-depth prospective studies in different ethnic groups are required to validate the causality between both.

Mono(2-ethylhexyl) phthalate induces transcriptomic changes in placental cells based on concentration, fetal sex, and trophoblast cell type

Phthalates are ubiquitous plasticizer chemicals found in consumer products. Exposure to phthalates during pregnancy has been associated with adverse pregnancy and birth outcomes and differences in placental gene expression in human studies. The objective of this research was to evaluate global changes in placental gene expression via RNA sequencing in two placental cell models following exposure to the phthalate metabolite mono(2-ethylhexyl) phthalate (MEHP). HTR-8/SVneo and primary syncytiotrophoblast cells were exposed to three concentrations (1, 90, 180 µM) of MEHP for 24 h with DMSO (0.1%) as a vehicle control. mRNA and lncRNAs were quantified using paired-end RNA sequencing, followed by identification of differentially expressed genes (DEGs), significant KEGG pathways, and enriched transcription factors (TFs). MEHP caused gene expression changes across all concentrations for HTR-8/SVneo and primary syncytiotrophoblast cells. Sex-stratified analysis of primary cells identified different patterns of sensitivity in response to MEHP dose by sex, with male placentas being more responsive to MEHP exposure. Pathway analysis identified 11 KEGG pathways significantly associated with at least one concentration in both cell types. Four ligand-inducible nuclear hormone TFs (PPARG, PPARD, ESR1, AR) were enriched in at least three treatment groups. Overall, we demonstrated that MEHP differentially affects placental gene expression based on concentration, fetal sex, and trophoblast cell type. This study confirms prior studies, as enrichment of nuclear hormone receptor TFs were concordant with previously published mechanisms of phthalate disruption, and generates new hypotheses, as we identified many pathways and genes not previously linked to phthalate exposure.

Sex-specific Effects of Endocrine-disrupting Chemicals on Brain Monoamines and Cognitive Behavior

The period of brain sexual differentiation is characterized by the development of hormone-sensitive neural circuits that govern the subsequent presentation of sexually dimorphic behavior in adulthood. Perturbations of hormones by endocrine-disrupting chemicals (EDCs) during this developmental period interfere with an organism's endocrine function and can disrupt the normative organization of male- or female-typical neural circuitry. This is well characterized for reproductive and social behaviors and their underlying circuitry in the hypothalamus and other limbic regions of the brain; however, cognitive behaviors are also sexually dimorphic, with their underlying neural circuitry potentially vulnerable to EDC exposure during critical periods of brain development. This review provides recent evidence for sex-specific changes to the brain's monoaminergic systems (dopamine, serotonin, norepinephrine) after developmental EDC exposure and relates these outcomes to sex differences in cognition such as affective, attentional, and learning/memory behaviors.

Evaluation of the toxicological effects of atrazine-metolachlor in male rats: in vivo and in silico studies

The types and mechanisms of atrazine-metolachlor toxicity, an herbicide composed of atrazine (ATR) and metolachlor (MET), need to be further investigated. This study evaluated the toxic actions of ATR-MET by in vivo and in silico methods. Here, varying doses of ATR-MET were orally administered to rats once daily for twenty-one days using normal saline as control. Molecular docking was used to characterize the binding of ATR and MET with androgen receptor (AR) to predict their potential endocrine-disrupting effects, using testosterone as benchmark. ATR-MET-induced-testicular toxicity (reduced sperm motility, count, and daily sperm production and increased live/dead ratio) was accompanied with testicular oxidative stress (diminished level of reduced glutathione, activities of glutathione-S-transferase, superoxide dismutase and catalase and increased level of malondialdehyde). Furthermore, ATR-MET induced cardiovascular toxicity (increased levels of plasma total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides) with concomitant induction of renal toxicity (increased plasma creatinine and urea levels), and hepatotoxicity (increased plasma bilirubin, alkaline phosphatase, acid phosphatase, alanine aminotransferase and aspartate aminotransferase). Binding energy and amino acid interactions from in silico study revealed that MET possessed endocrine-disrupting capacity. In conclusion, exposure to atrazine-metolachlor could promote cardiovascular, renal, hepatic, as well as reproductive impairment in experimental male albino rats.

Oral exposure to DEHP may stimulate prostatic hyperplasia associated with upregulation of COX-2 and L-PGDS expressions in male adult rats

Di-(2-ethylhexyl) phthalate (DEHP), a typical environmental endocrine disruptor (EED), can disrupt estrogen and androgen secretion and metabolism process, thus inducing dysfunctional reproduction such as impaired gonadal development and spermatogenesis disorder. Prostaglandin synthases (PGS) catalyze various prostaglandins biosynthesis, involved in inflammatory cascade and tumorigenesis. Yet, little is known about how PGS may impact prostatic hyperplasia development and progression. This study concentrates predominantly on the potential prostatic toxicity of DEHP exposure and the mediating role of PGS. In vivo study, adult male rats were administered via oral gavage 30 μg/kg/d, 90 μg/kg/d, 270 μg/kg/d, 810 μg/kg/d DEHP or vehicle for four weeks. The results elucidated that low-dose DEHP may cause the proliferation of the prostate with an increased PCNA/TUNEL ratio. Given the importance of estrogens and androgens in prostatic hyperplasia, our first objective was to evaluate the levels of sex hormones. DEHP improved the ratio of estradiol (E₂)/testosterone (T) in a dose-dependent manner and upregulated estrogen receptor alpha (ERα) and androgen receptor (AR) expressions. Prostaglandin synthases, including cyclooxygenase-2 (COX-2) and lipocalin-type prostaglandin D synthase (L-PGDS), were significantly upregulated in the ventral prostate. COX-2 and L-PGDS might mediate the tendency of prostatic hyperplasia induced by low-dose DEHP through estradiol/androgen regulation and imbalance between proliferation and apoptosis in vivo. These findings provide the first evidence that prostaglandin synthases contribute to the tendency toward benign prostatic hyperplasia induced by DEHP. Further investigations will have to be performed to facilitate an improved understanding of the role of prostaglandin synthases in DEHP-induced prostatic lesions.

Prediction of the endocrine-disrupting ability of 49 per- and polyfluoroalkyl substances: In silico and epidemiological evidence

The toxic effects of per- and polyfluoroalkyl substances (PFASs) on humans are mediated by nuclear hormone receptors (NHRs). However, data on the interaction of PFASs and NHRs is limited. Endocrine Disruptome, an inverse docking tool, was used in this study to simulate the docking of 49 common PFASs with 14 different types of human NHRs. According to the findings, 25 PFASs have a high or moderately high probability of binding to more than five NHRs, with androgen receptor (AR) and mineralocorticoid receptor (MR) being the most likely target NHRs. Molecular docking analyses revealed that the binding modes of PFASs with the two NHRs were similar to those of their corresponding co-crystallized ligands. PFASs, in particular, may disrupt the endocrine system by binding to MR. This finding is consistent with epidemiological research that has linked PFASs to MR-related diseases. Our findings may contribute to a better understanding of the health risks posed by PFASs.

Multiple transcriptomic profiling: potential novel metabolism-related genes predict prepubertal testis damage caused by DEHP exposure

The toxic effect of di(2-ethylhexyl) phthalate (DEHP) on prepubertal testes was examined in this study. We treated 3-week-old male mice with 4.8 mg/kg/day (milligram/kilogram/day) (no observed adverse effect level), 30 mg/kg/day (high exposure dose relative to humans), 100 mg/kg/day (level causing a reproductive system disorder), and 500 mg/kg/day (dose causing a multigenerational reproductive system disorder) of DEHP via gavage. Obvious abnormalities in the testicular organ coefficient, spermatogenic epithelium, and testosterone levels occurred in the 500 mg/kg DEHP group. Ribonucleic acid sequencing (RNA-seq) showed that differentially expressed genes (DEGs) in each group could enrich reproduction and reproductive process terms according to the gene ontology (GO) results, and coenrichment of metabolism pathway was observed by the Reactome pathway analysis. Through the analysis of common genes in the metabolism pathway, we discovered that DEHP exposure at 4.8 to 500 mg/kg or 100 mg/kg caused the same damages to the prepubertal testis. In general, we identified two key transcriptional biomarkers (fatty acid binding protein 3 (Fabp3) and carboxylesterase (Ces) 1d), which provided new insight into the gene regulatory mechanism associated with DEHP exposure and will contribute to the prediction and diagnosis of prepuberty testis injury caused by DEHP.

Endocrine Disruptors and Prostate Cancer

The role of endocrine disruptors (EDs) in the human prostate gland is an overlooked issue even though the prostate is essential for male fertility. From experimental models, it is known that EDs can influence several molecular mechanisms involved in prostate homeostasis and diseases, including prostate cancer (PCa), one of the most common cancers in the male, whose onset and progression is characterized by the deregulation of several cellular pathways including androgen receptor (AR) signaling. The prostate gland essentiality relies on its function to produce and secrete the prostatic fluid, a component of the seminal fluid, needed to keep alive and functional sperms upon ejaculation. In physiological condition, in the prostate epithelium the more-active androgen, the 5α-dihydrotestosterone (DHT), formed from testosterone (T) by the 5α-reductase enzyme (SRD5A), binds to AR and, upon homodimerization and nuclear translocation, recognizes the promoter of target genes modulating them. In pathological conditions, AR mutations and/or less specific AR binding by ligands modulate differently targeted genes leading to an altered regulation of cell proliferation and triggering PCa onset and development. EDs acting on the AR-dependent signaling within the prostate gland can contribute to the PCa onset and to exacerbating its development.

Phthalate metabolites: Characterization, toxicities, global distribution, and exposure assessment

Phthalates are plasticizers in various products and regarded as endocrine disruptors due to their anti-androgen effects. Environmental occurrence and toxicities of parent phthalates have been widely reported, while the current state of knowledge on their metabolites is rarely summarized. Based on the available literature, the present review mainly aims to 1) characterize the potential metabolites of phthalates (mPAEs) using the pharmacokinetics evidences acquired via animal or human models; 2) examine the molecular and cellular mechanism involved in toxicity for mPAEs; 3) investigate the exposure levels of mPAEs in different human specimens (e.g., urine, blood, seminal fluid, breast milk, amniotic fluid and others) across the globe; 4) discuss the models and related parameters for phthalate exposure assessment. We suggest there is subtle difference in toxic mechanisms for mPAEs compared to their parent phthalates due to their alternative chemical structures. Human monitoring studies performed in Asia, America and Europe have provided the population exposure baseline levels for typical phthalates in different regions. Urine is the preferred matrix than other specimens for phthalate exposure study. Among ten urinary mPAEs, the largest proportions of di-(2-ethylhexyl) phthalate (DEHP) metabolites (40%), monoethyl phthalate (mEP) (43%) and DEHP metabolites/mEP (both 29%) were observed in Asia, America and Europe respectively, and mono-5-carboxy-2-ethypentyl phthalate was the most abundant compounds among DEHP metabolites. Daily intakes of phthalates can be accurately calculated via urinary mPAEs if the proper exposure parameters were determined. Further work should focus on combining epidemiological and biological evidences to establish links between phthalates exposure and biological phenotypes. More accurate molar fractions (F_UE) of the urinary excreted monoester related to the ingested diesters should be collected in epidemiological or pharmacokinetic studies for different population.

Perinatal DEHP exposure modulates pituitary estrogen receptor α and β expression altering lactotroph and somatotroph cell growth in prepuberal and adult male rats

Phthalates are synthetic chemicals widely used to make polyvinylchloride (PVC) soft and flexible. Of these, Di-(2-ethylhexyl) phthalate (DEHP) is the most commonly used, with high human exposure occurring as early as the fetal developmental stage and affecting the endocrine system. We focused on the perinatal DEHP effects on pituitary estrogen receptor (ER) expression in male rats, explored their impact on lactotroph and somatotroph cell growth, and evaluated the direct effects of this phthalate on pituitary cell cultures. Our results showed that DEHP perinatal exposure was unable to modify the ERα+ pituitary cell number from prepuberal rats, but increased ERβ+ cells. In adulthood, the pituitary ERα+ cells underwent a slight decrease with ERβ showing the greatest changes, and with a significant increase observed in somatotroph cells. Also, in vitro, DEHP reduced the ERα+ cells, increased the percentage of ERβ+ pituitary cells and modified the Ki67 index, as well as decreasing the lactotrophs and increasing the somatotroph cells. In conclusion, the present study showed that DEHP induced ER expression changes in normal pituitary glands from male rats in in vivo and in vitro conditions, suggesting that DEHP could differentially modulate lactotroph and somatotroph cell growth, possibly as a consequence of ER imbalance.

Toxicological Assessment of Oral Co-Exposure to Bisphenol A (BPA) and Bis(2-ethylhexyl) Phthalate (DEHP) in Juvenile Rats at Environmentally Relevant Dose Levels: Evaluation of the Synergic, Additive or Antagonistic Effects

BACKGROUND

The general population (including children) is exposed to chemical mixtures. Plasticizers such as Bisphenol A (BPA) and Phthalates (mainly Bis(2-ethylhexyl) phthalate-DEHP) are widespread contaminants classified as endocrine disrupters which share some toxicological profiles and coexist in food and environment.

METHODS

To identify hazards of DEHP and BPA mixtures, the juvenile toxicity test-where rodents are in peripubertal phase of development, resembling childhood-was selected using exposure data from biomonitoring study in children. Biological activity and potential enhanced and/or reduced toxicological effects of mixtures due to common mechanisms were studied, considering endpoints of metabolic, endocrine and reproductive systems. The degree of synergy or antagonism was evaluated by synergy score calculation, using present data and results from the single compound individually administered.

RESULTS

In metabolic system, synergic interaction predominates in female and additive in male rats; in the reproductive and endocrine systems, the co-exposure of BPA and DEHP showed interactions mainly of antagonism type.

CONCLUSIONS

The present approach allows to evaluate, for all the endpoints considered, the type of interaction between contaminants relevant for human health. Although the mode of action and biological activities of the mixtures are not completely addressed, it can be of paramount usefulness to support a more reliable risk assessment.

Structural Aspects of Potential Endocrine-Disrupting Activity of Stereoisomers for a Common Pesticide Permethrin against Androgen Receptor

Simple Summary

Human exposure to synthetic or naturally occurring endocrine-disrupting compounds (EDCs) contaminating the environment is associated with disruption in endocrine signaling and homeostatic imbalance of hormones. Pyrethroids constitute an important class of extensively used insecticides reported to have endocrine-disrupting activity. Permethrin is one of the most commonly used pyrethroids and exists in isomeric forms. The aim of this study was to investigate and compare the potential endocrine-disrupting activity of permethrin isomers against the androgen receptor (AR). Structural binding studies showed that all permethrin isomer compounds have the potential to compete with native ligand binding in the AR ligand binding pocket. In conclusion, the results of this study suggest that human exposure to commercially produced isomeric forms of permethrin could potentially interfere with the AR function, which may lead to male reproductive dysfunction.

Abstract

Endocrine-disrupting chemicals (EDCs) are a serious global public health and environmental concern. Pyrethroids are insecticide chemicals that are extensively used for crop protection and household purposes but have been identified as EDCs. On account of their ubiquitous environmental presence, human exposure occurs via food, dermal, or inhalation routes and is associated with health problems, including reproductive dysfunction. Permethrin is the most commonly used pyrethroid, and with two chiral centers in its structure, it has four stereoisomeric forms (two enantiomer pairs), i.e., permethrin (1R,3R)-cis, permethrin (1R,3S)-trans, permethrin (1S,3S)-cis, and permethrin (1S,3R)-trans. The current study was performed for predicting the potential endocrine-disrupting activity of the aforementioned four stereoisomers of permethrin against the androgen receptor (AR). The structural binding characterization and binding energy estimations in the AR binding pocket were done using induced fit docking. The structural binding data indicated that all stereoisomers were placed stably in the AR binding pocket and that the estimated binding energy values were comparable to the AR native ligand, except for permethrin (1S,3S)-cis. Furthermore, the commonality in the amino acid interactions to that of the AR native ligand and the binding energy values suggested the potential AR-disrupting activity of all the stereoisomers; however, stereoselective differences were not observed. Taken together, the results suggest that human exposure to permethrin, either as a racemate mixture or in individual stereoisomer form, could potentially interfere with AR function, which may lead to male reproductive dysfunction.

Disruption of androgen receptor signaling by chlorpyrifos (CPF) and its environmental degradation products: a structural insight

Androgen-disruptors are chemicals that interfere with the biosynthesis, metabolism or function of endogenous androgens affecting normal male reproductive development and health. Several epidemiological studies have indicated a link between exposure to androgen disrupting chemicals with reduced sperm counts and increased infertility. The actions of androgens within target cells are transduced by the androgen receptors (ARs). Chlorpyrifos (CPF), a chlorinated organophosphorus pesticide, is known to cause impairment in both male and female reproductive systems. Recent publications have shown molecular interactions of CPF and its environmental degradation products with human progesterone receptor and human estrogen receptor. Exposure to CPF causes a marked reduction in sperm counts with lowering in serum testosterone level, which suggests possible molecular interaction of CPF with AR. The investigation to reveal the possibility and the extent of binding of CPF and some of its degradation products (chlorpyrifos-oxon [CPYO], desethyl chlorpyrifos [DEC], trichloromethoxypyridine [TMP] and trichloropyridinol [TCP]) with AR using molecular docking simulation are reported. The findings of the present docking, binding energy and molecular dynamics studies reveal that CPF and its degradation products may bind to ARs and act as a potent androgen disruptor.Communicated by Ramaswamy H. Sarma.