Effects of pyrethroid insecticides on hypothalamic-pituitary-gonadal axis: A reproductive health perspective

Reproductive endocrine disruption effect and mechanism in male zebrafish after life cycle exposure to environmental relevant triclosan

Triclosan (TCS) is a wide-spectrum antibacterial agent that is found in various water environments. It has been reported to have estrogenic effects. However, the impact of TCS exposure on the reproductive system of zebrafish (Danio rerio) throughout their life cycle is not well understood. In this study, zebrafish fertilized eggs were exposed to 0, 10, and 50 μg/L TCS for 120 days. The study investigated the effects of TCS exposure on brain and testis coefficients, the expression of genes related to the hypothalamus-pituitary-gonadal (HPG) axis, hormone levels, vitellogenin (VTG) content, histopathological sections, and performed RNA sequencing of male zebrafish. The results revealed that life cycle TCS exposure had significant effects on zebrafish reproductive parameters. It increased the testis coefficient, while decreasing the brain coefficient. TCS exposure also led to a decrease in mature spermatozoa and altered the expression of genes related to the HPG axis. Furthermore, TCS disrupted the balance of sex hormone levels and increased VTG content of male zebrafish. Transcriptome sequencing analysis indicated that TCS affected reproductive endocrine related pathways, including PPAR signaling pathway, cell cycle, GnRH signaling pathway, steroid biosynthesis, cytokine-cytokine receptor interaction, and steroid hormone biosynthesis. Protein-protein interaction (PPI) network analysis confirmed the enrichment of hub genes in these pathways, including bub1bb, ccnb1, cdc20, cdk1, mcm2, mcm5, mcm6, plk1, and ttk in the brain, as well as fabp1b.1, fabp2, fabp6, ccr7, cxcl11.8, hsd11b2, and hsd3b1 in the testis. This study sheds light on the reproductive endocrine-disrupting mechanisms of life cycle exposure to TCS.

The role of the aryl hydrocarbon receptor in mediating the effects of mono(2-ethylhexyl) phthalate in mouse ovarian antral follicles†

Di(2-ethylhexyl) phthalate (DEHP) is a pervasive environmental toxicant used in the manufacturing of numerous consumer products, medical supplies, and building materials. DEHP is metabolized to mono(2-ethylhexyl) phthalate (MEHP). MEHP is an endocrine disruptor that adversely affects folliculogenesis and steroidogenesis in the ovary, but its mechanism of action is not fully understood. Thus, we tested the hypothesis that the aryl hydrocarbon receptor (AHR) plays a functional role in MEHP-mediated disruption of folliculogenesis and steroidogenesis. CD-1 mouse antral follicles were isolated and cultured with MEHP (0-400 μM) in the presence or absence of the AHR antagonist CH223191 (1 μM). MEHP treatment reduced follicle growth over a 96-h period, and this effect was partially rescued by co-culture with CH223191. MEHP exposure alone increased expression of known AHR targets, cytochrome P450 (CYP) enzymes Cyp1a1 and Cyp1b1, and this induction was blocked by CH223191. MEHP reduced media concentrations of estrone and estradiol compared to control. This effect was mitigated by co-culture with CH223191. Moreover, MEHP reduced the expression of the estrogen-sensitive genes progesterone receptor (Pgr) and luteinizing hormone/choriogonadotropin receptor (Lhcgr) and co-treatment with CH223191 blocked this effect. Collectively, these data indicate that MEHP activates the AHR to impair follicle growth and reduce estrogen production and signaling in ovarian antral follicles.

Associations of pyrethroid exposure with bone mineral density and osteopenia in adults

INTRODUCTION

This study was to investigate the correlations between pyrethroid exposure and bone mineral density (BMD) and osteopenia.

MATERIALS AND METHODS

This cross-sectional study included 1389 participants over 50 years of age drawn from the 2007-2010 and 2013-2014 National Health and Nutrition Examination Survey (NHANES). Three pyrethroid metabolites, 3-phenoxybenzoic acid (3-PBA), trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane-1-carboxylic acid (trans-DCCA), and 4-fluoro-3-phenoxybenzoic acid (4-F-3PBA) were used as indicators of pyrethroid exposure. Low BMD was defined as T-score < - 1.0, including osteopenia. Weighted multivariable linear regression analysis or logistic regression analysis was utilized to evaluate the correlation between pyrethroid exposure and BMD and low BMD. Bayesian kernel machine regression (BKMR) model was utilized to analyze the correlation between pyrethroids mixed exposure and low BMD.

RESULTS

There were 648 (48.41%) patients with low BMD. In individual pyrethroid metabolite analysis, both tertile 2 and tertile 3 of trans-DCCA were negatively related to total femur, femur neck, and total spine BMD [coefficient (β) = - 0.041 to - 0.028; all P < 0.05]. Both tertile 2 and tertile 3 of 4-F-3PBA were negatively related to total femur BMD (P < 0.05). Only tertile 2 [odds ratio (OR) = 1.63; 95% CI = 1.07, 2.48] and tertile 3 (OR = 1.65; 95% CI = 1.10, 2.50) of trans-DCCA was correlated with an increased risk of low BMD. The BKMR analysis indicated that there was a positive tendency between mixed pyrethroids exposure and low BMD.

CONCLUSION

In conclusion, pyrethroids exposure was negatively correlated with BMD levels, and the associations of pyrethroids with BMD and low BMD varied by specific pyrethroids, pyrethroid concentrations, and bone sites.

Epigenetics of inflammation in hypothalamus pituitary gonadal and neuroendocrine disorders

The hormone producing hypothalamus, pituitary and gonadal are arranged in hierarchy to form the hypothalamic-pituitary-gonadal axis (HPG axis). The axis is neuroendocrine in nature and releases hormones in response to the inputs from nervous systems. The axis maintains homeostasis and ensures smooth body functions, particularly those related to growth and reproduction. A deregulated HPG axis, such as observed under inflammation and other conditions, is therefore associated with several disorders such as polycystic ovary syndrome, functional hypothalamic amenorrhea etc. Several factors, both genetic as well as environmental, in addition to aging, obesity etc. affect HPG axis with resulting effects on puberty, sexual maturation and reproductive health. More research is now indicative of a role of epigenetics in mediating these HPG-affecting factors. Hypothalamus-secreted gonadotropin-releasing hormone is important for eventual release of sex hormones and it is subjected to several neuronal and epigenetic regulations. Gene promoter methylation as well as histone methylations and acetylations form the backbone of epigenetic regulation of HPG-axis, as the incoming reports suggest. Epigenetic events also mediate several feedback mechanisms within HPG axis and between HPG axis and the central nervous system. In addition, data is emerging for a role of non-coding RNAs, particularly the miRNAs, in regulation and normal functioning of HPG axis. Thus, the epigenetic interactions need better understanding to understand the functioning and regulation of HPG axis.

Pesticides exposure and compromised fitness in wild birds: Focusing on the reproductive endocrine disruption

Exposure of pesticides to wildlife species, especially on the aspect of endocrine disruption is of great concern. Wildlife species are more at risk to harmful exposures to the pesticides in their natural habitat through diet and several other means. Species at a higher tropic level in the food chain are more susceptible to the deleterious effects due to sequential biomagnifications of the pesticides/metabolites. Pesticides directly affect fitness of the species in the wild causing reproductive endocrine disruption impairing the hormones of the gonads and thyroid glands as reproduction is under the influence of cross regulations of these hormones. This review presents a comprehensive compilation of important literatures on the impact of the current use pesticides in disruption of both the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-thyroid axes particularly in birds addressing impacts on the reproductive impairments and overall fitness. In addition to the epidemiological studies, laboratory investigations those provide supportive evidences of the probable mechanisms of disruption in the wild also have been incorporated in this review. To accurately predict the endocrine-disruption of the pesticides as well as to delineate the risk associated with potential cumulative effects, studies are to be more focused on the environmentally realistic exposure dose, mixture pesticide exposures and transgenerational effects. In addition, strategic screening/appropriate methodologies have to be developed to reveal the endocrine disruption potential of the contemporary use pesticides. Demand for adequate quantitative structure-activity relationships and insilico molecular docking studies for timely validation have been highlighted.

Combined exposure of beta-cypermethrin and emamectin benzoate interferes with the HPO axis through oxidative stress, causing an imbalance of hormone homeostasis in female rats

The impact of pesticides on reproductive health has been increasingly recognized. β-cypermethrin (β-CYP) and emamectin benzoate (EMB) are commonly used with agricultural workers. There are few published studies on the effects of combined poisoning of these two pesticides on the reproductive system. This study investigated the toxic effects and mechanism of β-CYP and EMB on the reproductive system of female rats based on the hypothalamic-pituitary-ovarian (HPO) axis. The hypothalamic GnRH content tended to decrease, and Kiss-1 and GPR-54 mRNA and protein expression tended to increase in exposed rats. FSH content was elevated for the pituitary gland, and Kiss-1 and GPR-54 mRNA and protein expression were enhanced in all experimental groups compared with the control group. E2 content in rat ovaries and ERα mRNA and protein expression were reduced by β-CYP and EMB. Furthermore, there were interactive effects of β-CYP and EMB on FSH and E2 release, pituitary GPR-54 mRNA and protein, and ovarian ERα mRNA expression. To investigate causes of damage, oxidative damage indicators were tested and showed that exposure to β-CYP and EMB decreased GSH-Px and SOD activities in the HPO axis, increased MDA levels in the hypothalamus and ovary together with LDH activities in the HPO axis, with an interaction effect on GSH-Px and SOD activities in the hypothalamus and pituitary gland as well as on MDA in the ovary. The above results support the screening of sensitive molecular biomarkers and evaluation of the adverse effects of pesticide exposure in greenhouse operations on reproductive health.

In vivo-in vitro correlations (IVIVC) for the assessment of pyrethroid bioavailability in honey

Bioaccessibility/bioavailability is an important factor in assessing the potential human health risk via oral exposure. However, methods for accurately predicting the bioaccessibility/bioavailability of pesticide residues are still limited, preventing accurate measurements of actual exposure to pesticide residues. In this study, pyrethroid bioavailability in honey were analysed using a mouse bioassay and bioaccessibility via in vitro methods with Tenax extraction. The results demonstrated that the combined liver plus kidney data served as an appropriate biomarker to estimate the relative bioavailability. Notably, significant in vivo-in vitro correlations (IVIVC) were observed between bioavailability and bioaccessibility (R2 = 0.7898-0.9793). Estimation of the bioavailability of honey from different nectar plants using derived IVIVC confirmed that different contents and physicochemical properties might affect its bioavailability. The findings provide insight into assessing human exposure to pesticides based on bioavailability and can decrease the uncertainty about the assessment of the risk of dietary exposure to pesticides.

Emerging contaminant triclosan incites endocrine disruption, reproductive impairments and oxidative stress in the commercially important carp, Catla (Labeo catla): An insight through molecular, histopathological and bioinformatic approach

Triclosan (TCS), a broad-spectrum antimicrobial agent is ubiquitous in aquatic ecosystems; however, the mechanisms regarding TCS-induced reproductive toxicity in the teleost still remains uncertain. In this context, Labeo catla were subjected to sub-lethal doses of TCS for 30 days and variations in expression of genes and hormones comprising the hypothalamic-pituitary-gonadal (HPG) axis along with alterations in sex steroids were evaluated. Moreover, manifestation of oxidative stress, histopathological alterations, in silico docking and the potential to bioaccumulate were also investigated. Exposure to TCS may lead to an inevitable onset of the steroidogenic pathway through its interaction at several loci along the reproductive axis: TCS stimulated synthesis of kisspeptin 2 (Kiss 2) mRNAs which in turn prompts the hypothalamus to secrete gonadotropin-releasing hormone (GnRH), resulting in elevated serum 17β-estradiol (E₂) as a consequence; TCS exposure increased aromatase synthesis by brain, which by converting androgens to oestrogens may raise E₂ levels; Moreover, TCS treatment resulted in elevated production of GnRH and gonadotropins by the hypothalamus and pituitary, respectively resulting in the induction of E₂. The elevation in serum E₂ may be linked to abnormally elevated levels of vitellogenin (Vtg) with harmful consequences evident as hypertrophy of hepatocytes and increment in hepatosomatic indices. Additionally, molecular docking studies revealed potential interactions with multiple targets viz. Vtg and luteinizing hormone (LH). Furthermore, TCS exposure induced oxidative stress and caused extensive damage to tissue architecture. This study elucidated molecular mechanisms underlying TCS-induced reproductive toxicity and the need for regulated use and efficient alternatives which could suffice for TCS.

Toxicological Mechanisms of Emerging Per-/poly-fluoroalkyl Substances: Focusing on Transcriptional Activity and Gene Expression Disruption

Environmental and human monitoring studies have witnessed increasing occurrence of emerging per-/poly-fluoroalkyl substances (ePFASs) worldwide. Three classes of ePFASs, namely chlorinated polyfluoroalkylether sulfonic acids, hexafluoropropylene oxide homologues and short-chain perfluoroalkyl acids attracted the most attention. It is, therefore, the goal of this review to systematically and critically analyse the toxicity and toxicological mechanisms of these ePFASs based on the papers published between 2017 and 2022. The review summarized the main findings from both in vivo and in vitro studies, covering the hepatotoxicity of ePFASs and their interference with the endocrine system, including reproductive, developmental and thyroid toxicity. It also summarized the changes in gene expression in the hypothalamic-pituitary-thyroid axis and hypothalamic-pituitary-gonad axis of the model organisms after ePFASs exposure. The changes in gene expression in vitro and in vivo provide a clearer understanding of the toxicological mechanisms of ePFASs interference on hormonal levels (i.e., estradiol, testosterone, and thyroid hormones), developmental disturbance (e.g., swim bladder dysfunction) and lipid metabolism disruption (e.g., lipid droplet accumulation and hepatomegaly). In the end, future research directions on the toxicological mechanisms of ePFASs are suggested.

Assessment of Preschool Children's Exposure Levels to Organophosphate and Pyrethroid Pesticide: A Human Biomonitoring Study in Two Turkish Provinces

Pesticides are products developed to prevent, destroy, repel or control certain forms of plant or animal life that are considered to be pests. However, now they are one of the critical risk factors threatening the environment, and they create a significant threat to the health of children. Organophosphate (OP) and pyrethroid (PYR) pesticides are widely used in Turkey as well as all over the world. The main focus of this presented study was to analyze the OP and PYR exposure levels in urine samples obtained from 3- to 6-year-old Turkish preschool children who live in the Ankara (n:132) and Mersin (n:54) provinces. In order to measure the concentrations of three nonspecific metabolites of PYR insecticides and four nonspecific and one specific metabolite of OPs, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses were performed. The nonspecific PYR metabolite 3-phenoxybenzoic acid (3-PBA) found in 87.1% of samples (n = 162) and the specific OP metabolite 3,5,6-trichloro-2-pyridinol (TCPY) found in 60.2% of samples (n = 112) were the most frequently detected metabolites in all urine samples. The mean concentrations of 3-PBA and TCPY were 0.38 ± 0.8 and 0.11 ± 0.43 ng/g creatinine, respectively. Although due to the large individual variation no statistically significant differences were found between 3-PBA (p = 0.9969) and TCPY (p = 0.6558) urine levels in the two provinces, significant exposure differences were determined both between provinces and within the province in terms of gender. Risk assessment strategies performed in light of our findings do not disclose any proof of a possible health problems related to analyzed pesticide exposure in Turkish children.

In silico and in vivo assessment of developmental toxicity, oxidative stress response & Na+/K+-ATPase activity in zebrafish embryos exposed to cypermethrin

Cypermethrin (CYP), a synthetic type II pyrethroid pesticide, is extensively used to control pests in industrial, domestic, and agricultural environments. However, its indiscriminate use leads to a potential threat to aquatic organisms. Although several reports focussed on developmental toxicity effects, a concise study combining cardiotoxicity along with Na⁺/K⁺-ATPase activity and molecular docking of developmental proteins with CYP was lacking. This present study was designed to address this gap to comprehend the impact of CYP exposure (0, 25, 100 and 200 µg/L) on embryonic zebrafish. As a result, CYP delayed the hatching rate, reduced heart rate, increased mortality rate and induced numerous morphological abnormalities. Subsequently, CYP induced oxidative stress in treated zebrafish embryos with the concomitant increase in antioxidant enzymes (SOD and CAT) and malondialdehyde production. In addition, an alteration in AChE, NO content and Na⁺/K⁺-ATPase activity was observed, suggesting a disruption in cardiac development and ion regulation. Furthermore, AO staining showed notable apoptotic cells which are supported by alteration in apoptosis-related gene expressions. Moreover, to explore the putative targets of CYP, computational docking with developmental proteins (WNT3A, WNT8A, GATA-4, Nkx 2-5 and ZHE1) showed strong interactions and binding. Taken together, our findings provide a better understanding of assessing the ecotoxicological risk information and the mode of action underlying the development of teleost fishes following CYP exposure. Meanwhile, the pioneering nature of this study is to emphasize the future use of Na⁺/K⁺-ATPase activity as a potential toxicity biomarker and in silico molecular docking studies to complement developmental toxicity findings.

Insecticidal activity of the organotellurium 2-Phenylethynyl-Butyltellurium on the Drosophila melanogaster model

2-Phenylethynyl-Butyltellurium (PEBT) is a synthetic organotellurium compound that has shown various pharmacological properties on mammals without any signs of toxicity, but its effects on insects have not been reported before. Therefore, the aim of this study was to assess whether acute exposure to PEBT would promote an insecticidal effect against Drosophila melanogaster. The flies were exposed to three concentrations of PEBT (0.325 µmol L-1, 1.300 µmol L-1, and 5.200 µmol L-1) and a control solution (vehicle), using 450 flies per treatment (three repetitions of 150 flies), for 48 hours. Negative geotaxis and open field tests were performed (in vivo) after 24 and 48h, and acetylcholinesterase (AChE) activity was assessed (ex vivo) after 48h. Also, the mortality rate, 50% Lethal Concentration (LC50), 80% Lethal Concentration (LC80), and 95% Lethal Concentration (LC95) were calculated. Our results show that PEBT presented insecticidal activity against Drosophila melanogaster at all tested concentrations, which caused locomotor impairment and increased acetylcholinesterase activity in the flies' heads.

Androgen receptor signaling and pyrethroids: Potential male infertility consequences

Infertility is a global health concern inflicting a considerable burden on the global economy and a severe socio-psychological impact. Approximately 15% of couples suffer from infertility globally, with a male factor contribution of approximately 50%. However, male infertility remains largely unexplored, as the burden of infertility is mostly assigned to female people. Endocrine-disrupting chemicals (EDCs) have been proposed as one of the factors causing male infertility. Pyrethroids represent an important class of EDCs, and numerous studies have associated pyrethroid exposure with impaired male reproductive function and development. Therefore, the present study investigated the potentially toxic effects of two common pyrethroids, cypermethrin and deltamethrin, on androgen receptor (AR) signaling. The structural binding characterization of cypermethrin and deltamethrin against the AR ligand-binding pocket was performed using Schrodinger's induced fit docking (IFD) approach. Various parameters were estimated, such as binding interactions, binding energy, docking score, and IFD score. Furthermore, the AR native ligand, testosterone, was subjected to similar experiments against the AR ligand-binding pocket. The results revealed commonality in the amino acid-binding interactions and overlap in other structural parameters between the AR native ligand, testosterone, and the ligands, cypermethrin and deltamethrin. The estimated binding energy values of cypermethrin and deltamethrin were very high and close to those calculated for AR native ligand, testosterone. Taken together, the results of this study suggested potential disruption of AR signaling by cypermethrin and deltamethrin, which may result in androgen dysfunction and subsequent male infertility.

Perinatal exposure to low doses of cypermethrin induce the puberty-related hormones and decrease the time to puberty in the female offspring

Pyrethroid insecticides are ubiquitously detected in environmental media, food, and urine samples. Our previous epidemiological study reported a correlation between increased pyrethroid exposure and delayed pubertal development in Chinese girls. In this study, we further investigated the effects of perinatal exposure to low doses of cypermethrin (CP) on pubertal onset and hypothalamic-pituitary-ovarian axis in the female mice offspring. The treatment of CP with 60 μg/kg/day from gestation day 6 (GD6) to postnatal day 21 (PND21) significantly decreased the time to puberty in the female offspring. Exposure of CP increased the serum levels of gonadotropin-releasing hormone (GnRH) and the expression of GnRH genes in a dose-dependent manner in the female offspring. CP also induced the serum levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as the expression of gonadotropin subunit genes [LHβ, FSHβ, and chorionic gonadotropin α (Cgα)]. Furthermore, CP induced serum estradiol (E₂) levels and the expression of steroidogenesis-related genes [steroidogenic acute regulatory (StAR) and Cytochrome p 450, family 11, subfamily A, polypeptide 1 (CYP11A1)] in the ovary. In accordance with the in vivo tests, administration of CP (6.7, 20, and 60 μg/L) stimulated a dose-dependent increase in the synthesis and secretion of the puberty-related hormones in the explants of hypothalamus, pituitary, and ovary. The interference with calcium channels in the ovary may be responsible for CP-induced pubertal onset. Our study provided evidence that perinatal exposure to low doses of CP induced puberty-related hormones and decreased the time to puberty in the female offspring.

Association of long-term effects of low-level sulfamethoxazole with ovarian lipid and amino acid metabolism, sex hormone levels, and oocyte maturity in zebrafish

Sulfamethoxazole (SMZ) is an important antibiotic used to prevent and treat infections in both clinical settings and animal husbandry. High levels of SMZ may exhibit endocrine toxicity. Environmental SMZ enters the human body via food and water; however, the toxicity of environmental doses of SMZ and its effects on reproductive health are unknown. In the present study, zebrafish were exposed to low concentrations of SMZ (1000 and 5000 ng/L) from 2 h post-fertilization to 120 d post-fertilization. Consequently, the proportion of mature oocytes in adult female zebrafish ovarian tissue increased by 98.2 %, indicating that SMZ promotes ovarian maturation. Metabolomics analysis revealed significant changes in ovarian lipid and amino acid levels after SMZ treatment. An enzyme-linked immunoassay used to detect sex hormones in the ovaries showed that SMZ exposure significantly increased the levels of estradiol, a follicle-stimulating hormone, and of luteinizing hormone. Furthermore, an association analysis showed that most of the differentially expressed metabolites in the ovary were strongly correlated with the levels of sex hormones secreted by the pituitary gland. Therefore, significantly increased transcript levels of gonadotropin-releasing hormone (GnRH) and follicle-stimulating hormone detected in brain tissue suggested that SMZ may exhibit ovarian toxicity via the hypothalamus. In vitro experiments were performed to demonstrate that SMZ targets neurons in the hypothalamus. Exposure to SMZ significantly increased the GnRH content in GnRH neurons. Finally, molecular docking simulations indicated the potential interaction of SMZ with G protein-coupled receptor 54; this molecular binding can activate, synthesize, and release GnRH in neurons. In conclusion, long-term environmental exposure to SMZ may induce ovarian toxicity by affecting the hypothalamus-pituitary-gonad axis.

Domestic Exposure to Chemicals in Household Products, Building Materials, Decoration, and Pesticides: Guidelines for Interventions During the Perinatal Period from the French National College of Midwives

INTRODUCTION

We are exposed to numerous pollutants inside our homes. The perinatal period represents a particular window of vulnerability during which these exposures can have negative health effects over a more or less long term. The objective of this article is to formulate guidelines for health care professionals and intended for parents to reduce exposure to chemical pollutants at home, based on the scientific literature and already existing guidelines.

METHODS

We have followed the methodological procedures set forth by the French authority for health (HAS) to establish guidelines to limit exposure to pollutants in homes. This narrative review of the scientific literature was conducted with two principal objectives: (1) to identify priority substances emitted within homes and that have a reprotoxic potential and (2) to identify measures to limit exposure to these residential pollutants. The guidelines were developed from the data in the literature and from advice already made available by diverse institutions about environmental health during the perinatal period.

RESULTS

Domestic pollutants are numerous and come from both common (that is, shared, eg, painting, cleaning, and maintenance work) and specific (use of household pesticides) sources. Numerous pollutants are suspected or known to produce developmental toxicity, that is, to be toxic to children during developmental stages. Removing some products from the home, protecting the vulnerable (ie, pregnant women and young children) from exposure, and airing the home are among the preventive measures proposed to limit exposure to these chemical substances.

CONCLUSION

Health care professionals can provide advice to parents during the perinatal period to diminish exposure to household pollutants. The lack of interventional studies nonetheless limits the level of evidence for most of these recommendations.

First Trimester of Pregnancy as the Sensitive Period for the Association between Prenatal Mosquito Coil Smoke Exposure and Preterm Birth

Mosquito coils are efficient mosquito repellents and mosquito coil smoke (MCS) contributes to indoor air pollution. However, no prior population-based study has investigated whether prenatal MCS exposure is a risk factor for preterm birth (PTB) and whether exposure to MCS in different trimesters of pregnancy is associated with different levels of risk. The sample involved 66,503 mother-child dyads. Logistic regression models were used to examine the relationships between prenatal MCS exposure during different trimesters of pregnancy and PTB. We found that prenatal MCS exposure was associated with a greater likelihood of PTB (OR = 1.12, 95%CI: 1.05-1.20). The prenatal MCS exposure during the first trimester was associated with 1.17 (95%CI: 1.09-1.25) times the odds of being PTB, which was higher than exposure during the second trimester (OR = 1.11, 95%CI: 1.03-1.19) and during the third trimester (OR = 1.08, 95%CI: 1.01-1.16). In the stratified analysis, prenatal MCS exposure significantly increased PTB risk among girls but not among boys. Our results indicated that maternal MCS exposure during pregnancy was associated with PTB and that the first trimester might be the sensitive period. In light of these findings, public health interventions are needed to reduce prenatal exposure to MCS, particularly during the first trimester of pregnancy.

Associations between pyrethroid exposure and serum sex steroid hormones in adults: Findings from a nationally representative sample

BACKGROUND

Pyrethroids have been considered as potential endocrine-disrupting chemicals and have been shown to be associated with endocrine-related health outcomes. However, limited studies directly explored the link between pyrethroid exposure and sex hormones in the general population.

OBJECTIVES

To explore the associations between exposure to pyrethroids and serum sex steroid hormones in adults.

METHODS

We evaluated the cross-sectional associations in 1235 adults aged ≥20 years who had been assigned to the National Health and Nutrition Examination Survey (NHANES) 2013-2014. The urinary concentration of 3-phenoxybenzoic acid (3-PBA) was applied as a biomarker of human pyrethroid exposure levels. Information on sex steroid hormones, including total testosterone (TT), estradiol (E2), and sex hormone-binding globulin (SHBG) in serum were measured. Free androgen index (FAI) and the ratio of TT to E2 (TT/E2) were also calculated. The percent changes with 95% confidence intervals (CIs) for a doubling of 3-PBA concentrations in the serum sex hormone levels were estimated using generalized linear regression models.

RESULTS

The overall median concentrations of creatinine-adjusted 3-PBA were 0.58 μg/g creatinine, and 90.0% of adults had a detectable level of 3-PBA. In females, every two-fold increase in 3-PBA was associated with 4.34% (95% CI: 1.58%, 7.18%) higher levels of TT and 4.05% (95% CI: 7.03%, 1.16%) higher levels of SHBG, respectively. In males, a doubling in 3-PBA was associated with 3.02% (95% CI: 1.21%, 4.86%) increase in SHBG but 1.85% (-3.59%, -0.07%) decrease in FAI, respectively. In addition, significant non-linear associations of 3-PBA with SHBG in both males and females and TT in females were observed.

CONCLUSIONS

Environmental pyrethroid exposure was associated with altered sex hormones in adults. This study provides important epidemiological evidence for the association of pyrethroids with endocrine disruption.

Exposure to multiple pyrethroid insecticides affects ovarian follicular development via modifying microRNA expression

Pyrethroids, a class of insecticides widely used in agriculture and residential pest control, have been considered as endocrine-disrupting chemicals (EDCs). Our previous epidemiological study reported a positive association of urinary levels of pyrethroid metabolites with the risk of primary ovarian insufficiency in women, suggesting that pyrethroid exposure may be a potential risk factor for female ovarian health. In this study, female mice at gestational, lactational or peripubertal stages were exposed to eight most commonly used pyrethroids at the doses of acceptable daily intake (ADI) recommended by the World Health Organization (WHO). Gestational exposure to eight pyrethroids at ADI doses led to a significant decrease in the number of primary follicles in female offspring on postnatal day (PND) 3, and an increase in the number of atretic follicles and granulosa cell apoptosis, as well as lower estrogen and higher follicle-stimulating hormone (FSH) levels in adult female offspring. Lactational and peripubertal exposure to pyrethroid mixture had no significant effects on follicular development and ovarian functions. The data of high-throughput microRNA (miRNA) sequencing showed that 23 miRNAs were differentially expressed in the ovaries of female offspring mice on PND 1 after gestational exposure to pyrethroid mixture. The results of qPCR confirmed that miR-152-3p, miR-450b-3p and miR-196a-5p were significantly upregulated in the neonatal ovaries in the exposed group. The bioinformatic analysis indicates that the modification of the expression of ovarian miRNAs by pyrethroid exposure may disrupt the key biological processes (such as mRNA processing) and major signaling pathways (such as PI3K/Akt pathway, adipocytokine pathway and GnRH pathway) governing follicular development and ovarian functions. This study first reported that gestational exposure of female mice to multiple pyrethroids at the recommended human safe doses had irreversible adverse effects on the ovaries in female offspring in adulthood through regulating the expression of miRNAs during early developmental stages.

Exposures to deltamethrin on immature Chironomus columbiensis drive sublethal and transgenerational effects on their reproduction and wing morphology

Sublethal exposure to insecticides can trigger unintended responses in non-target insects that may disrupt reproductive and developmental performances of these organisms. Here, we assessed whether sublethal exposure to the pyrethroid insecticide deltamethrin in early life had sublethal and transgenerational effects on the reproduction (i.e., fecundity and fertility) and wing morphology of Chironomus columbiensis, an aquatic insect used as a water quality indicator. We first conducted concentration-response bioassays to evaluate the susceptibility of C. columbiensis larvae to deltamethrin. Our results revealed that deltamethrin toxicity was approximately 7-fold higher when C. columbiensis larvae where exposed to 96 h (LC₅₀ = 0.17 [0.15-0.20] μg/L) than to 24 h (LC₅₀ = 1.17 [0.97-1.43] μg/L). Furthermore, the sublethal exposures (at LC₁ = 0.02 μg/L or LC₁₀ = 0.05 μg/L) of immature C. columbiensis resulted in lower fecundity (e.g., reduced eggs production) and morphometric variation wing shapes. Further reduction in fertility rates (quantity of viable eggs) occurred at deltamethrin LC₁₀ (0.05 μg/L). Almost 80% of the fecundity was recovered with only a single recovery generation; however, two subsequent recovery generations were not sufficient to fully recover fecundity in C. columbiensis. Specimens recovered from 98.5% of wing morphometric variation after two consecutive generations without deltamethrin exposure. Collectively, our findings demonstrates that sublethal exposure to synthetic pyrethroids such as deltamethrin detrimentally affect the reproduction and wing shape of C. columbiensis, but also indicate that proper management of these compounds (e.g., concentration and frequency of application) would suffice for these insects' population recovery.

Urinary 3-phenoxybenzoic acid (3-PBA) levels and changes in hematological parameters in Korean adult population: A Korean National Environmental Health Survey (KoNEHS) 2012-2014 analysis

Pyrethroid insecticides have been broadly used as pest control in agriculture and residential spaces, exerting high effectiveness of insecticidal property and relatively low toxicity to humans. Several animal studies suggested that exposure to pyrethroids may induce hematological abnormalities, thereby altering the number of blood cells and resulting in blood disorders. However, no epidemiologic study has reported on the effect of pyrethroid insecticide exposure on hematological changes, except for occupational exposure. This study aimed to investigate the effect of urinary 3-phenoxybenzoic acid (3-PBA) concentrations on hematological parameters in a representative South Korean adult population. We analyzed data from 6296 adults enrolled in the Korean National Environmental Health Survey (2012-2014). We employed multiple linear regression analysis to evaluate the association of urinary 3-PBA levels with eight hematological profiles: white blood cells (WBCs), red blood cells (RBCs), hemoglobin, hematocrit, platelets, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). The urinary 3-PBA levels were negatively associated with WBC, RBC, and hemoglobin levels and positively associated with MCV levels. The direction and magnitude of the association between the 3-PBA and hematological parameters varied according to sex and age. The adverse effects of 3-PBA on hematological parameters were distinctive among males aged 60 years and older. In this age group, 3-PBA levels were negatively associated with the WBC, RBC, hemoglobin, hematocrit, and MCHC levels among males. This study is the first to verify that urinary 3-PBA concentrations at the levels found in a Korean population are associated with blood parameters. This finding merits further investigation to understand the impact of 3-PBA on human blood function and public health.

Synthetic Pyrethroids Exposure and Embryological Outcomes: A Cohort Study in Women from Fertility Clinic

Pyrethroids exposure has been associated with adverse reproductive outcome. However, there is no study that explores the effect of environmental exposure and embryological outcomes. This question was addressed in a prospective cohort of couples undergoing fertility treatment. The study aims to assess the association between urinary metabolites of synthetic pyrethroids and embryological outcomes (MII oocyte count, top quality embryo, fertilization and implantation rate). We included 450 women aged 25−45 undergoing assisted reproductive technology (ART) cycle at Infertility Clinic in Poland. Urine samples were collected at the time of fertility procedure(s) to assess four urinary synthetic pyrethroids concentrations (3-phenoxybenzoic acid (3PBA), cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DCCA), trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (trans-DCCA), cis-2,2-dibromovinyl-2,2-dimethylocyclopropane-1-carboxylic acid (DBCA)) using validated gas chromatography ion-tap mass spectrometry and calculated for each cycle-specific metabolite. To evaluate the effect of environmental exposure to synthetic pyrethroids and embryological outcomes (methaphase II (MII) oocyte yield, top quality embryo, fertilization rate, implantation rate), multivariable generalized linear mixed analyses with random intercepts were prepared. Urinary 3-PBA concentrations decrease MII oocyte count (p = 0.007) in the fourth quartile (>75 percentile) compared to women in the first quartile (≤25 percentile). Additionally, when 3-PBA was treated as continuous variable, the negative association between exposure to pyrethroids and MII oocyte count was also observed (p = 0.012). Exposure to other pyrethroid metabolities (CDCCA, TDCCA, DBCA) was not related to any of the examined embryological outcomes. Exposure to synthetic pyrethroids may be associated with poorer embryological outcome among couples seeking fertility treatments. As this is the first study on this topic, the results need to be confirmed in further studies.

Cis-bifenthrin inhibits cortisol and aldosterone biosynthesis in human adrenocortical H295R cells via cAMP signaling cascade

Cis-bifenthrin (cis-BF) is a common-used pyrethroid insecticide frequently detected in environmental and biological matrices. Mounting evidence highlights the endocrine disrupting effects of cis-BF due to anti-estrogenic or anti-androgenic activity. However, little is known about the exposure effects of cis-BF on adrenal cortex function. In this study, effects of cis-BF on biosynthesis of adrenal steroids, as well as the potential mechanisms were investigated in human adrenocortical carcinoma (H295R) cells. Cis-BF decreased basal production levels of cortisol and aldosterone, as well as cAMP-induced production of cortisol. Both he basal and cAMP-stimulated transcriptional levels of several steroidogenic genes were significantly down-regulated by cis-BF. As an important rate-limiting enzyme in steroidogenesis, the protein level of StAR was prohibited by cis-BF on both basal and cAMP-induced conditions. Intracellular level of cAMP was significantly reduced by cis-BF. Overall, these data suggest that cis-BF may inhibit the biosynthesis of cortisol and aldosterone via disrupting cAMP signaling cascade.

Temporal variability of organophosphate insecticide metabolites over one year in Chinese adults

Organophosphate (OP) insecticides widely used worldwide are a class of non-persistent pollutants with a short biological half-life. Most OP insecticides are rapidly metabolized in the human body to six dialkyl phosphate metabolites (DAPs), of which urinary concentrations are usually used to assess OP insecticide exposures. In this study, to understand the reliability of a single measurement of OP insecticide metabolites in representing a true longer-term average exposure, we investigated the temporal variability of urinary DAPs over one year in 114 Chinese adults aged 18-30. The detection rates for all six DAP metabolites exceeded 98%. The intraclass correlation coefficients (ICCs) of DAPs indicated poor (ICC < 0.4) to fair (ICC = 0.4-0.75) reproducibility in spot urine samples over one week, month, or year. Log-transformed DAP metabolites requested 2-12 spot urine samples per subject to offer a reliable estimate of OP insecticide exposures over several months or one year. The sensitivity and specificity for predicting subjects with the one-year average OP insecticide exposure in the highest tertile with one, two, or three urine samples varied from 0.25 to 0.991, 0.491 to 0.966, respectively. We recommend at least 3 spot urine samples for the assessment of one-year OP insecticide exposure by using log-transformed DAPs. This study offers a reference for an appropriate evaluation of a relatively long-period exposure to OP insecticides in biomonitoring and epidemiological studies.

Current insights into the microbial degradation for pyrethroids: strain safety, biochemical pathway, and genetic engineering

As a biologically inspired insecticide, pyrethroids (PYRs) exert evident toxic side effects on non-target organisms. PYRs and their general toxic intermediate 3-phenoxybenzoic acid (3-PBA) have shown high detection rates/levels in human beings recently, for which diet was identified as the major exposure route. Microbial mineralization has emerged as a versatile strategy in addressing such escalating concern. Herein, PYRs and 3-PBA biodegradation with regards to strain safety, application and surfactant were summarized. Numerous PYRs-degrading microbes have been reported yet with a minority focused on 3-PBA. Most isolates were from contaminated sites while several microbial food cultures (MFCs) have been investigated. MFCs such as Bacillus spp. and Aspergillus spp. that dominate in PYRs-degrading microbial pools are applicable candidates for agricultural by-products detoxification during the postharvest process. Subsequently, we discussed committed degradation steps, wherein hydrolase responsible for PYRs ester linkage cleavage and oxygenase for 3-PBA diphenyl ether bond rupture play vital roles. Finally, comprehensive information of the key enzyme genes is outlined along with methodologies concerning gene cloning. Cytochrome P450 monooxygenases (CYP) is competent for diphenyl ether scission. Newly-developed omics has become a feasible gene and enzyme mining technology. To achieve PYRs mineralization in feed and food commodities, the screening of MFCs rich in related enzymes and the construction of MFCs-derived genetically modified microbes (GMMs) exhibit great potential considering the safety issues.

Nylon membranes modified by gold nanoparticles as surface-enhanced Raman spectroscopy substrates for several pesticides detection

Surface enhanced Raman spectroscopy (SERS) is an attractive means for trace compound detection because of its high sensitivity, however, the poor reproducibility is a major challenge. Herein, we propose a facile SERS strategy employing the several developed test processes to improve the repeatability of the SERS analysis based on regular nylon membranes as substrates to detect trace compounds. Various methods, including in situ reduction, immersion adsorption, and filtration, were first compared to prepare composite substrates using nylon membranes and gold nanoparticles. The substrates prepared by filtration showed the best test parallelism (RSD = 7.85%). Its limit of detection (LOD) could reach 10^-8 g mL^-1 with a good linear relationship in the range 10^-8 to 10^-7 g mL^-1. Finally, three pesticide solutions were tested to verify the substrate applicability. A superior LOD of 10^-8 g mL^-1 was observed for thiram, whereas the LODs of both phorate and benthiocarb could reach 10^-6 g mL^-1. Overall, modifying nylon membrane substrates with gold nanoparticles improves the repeatability and economic viability of SERS and favors its wider commercial application for detecting trace compounds.

Severe pulmonary toxicity associated with inhalation of pyrethroid-based domestic insecticides (Bop/Sapolio): a case series and literature review

PURPOSE OF REVIEW

The current review focuses on serious pulmonary toxicity after inhalation of over the counter available pyrethroid-based insecticides. Pyrethroid is a synthetic product of pyrethrin, which in turn is the active ingredient of pyrethrum, a flower extract.

RECENT FINDINGS

On the contrary, a large gap of knowledge exists in the association of interstitial lung disease (ILD) with pyrethroids. So far, two cases of ILD, one associated with pyrethrin and one associated with pyrethrum, were described. Existing literature on both other (pulmo)toxic effects of pyrethroids in human and animals is summarized.

SUMMARY

We present three cases of severe pulmonary toxicity after inhalation of pyrethroid-based insecticides demanding hospitalization and oxygen therapy. One of these cases died. Although a causal relationship was hard to establish, these cases all demonstrated an obvious history of (repeated) pyrethroid exposure associated with ILD. Moreover, other causes of ILD as well as infections were excluded. Furthermore, studies in mammals as well as aquatic animals confirm (pulmonary) toxicity of pyrethroids. The occurrence of toxicity is dose-dependent but also associated with individual susceptibility. Therefore, we would like to acknowledge that awareness of potential hazards of commercially available insecticides containing pyrethroids to both medical physicians and the public is mandatory.

A case-control study of thallium exposure with the risk of premature ovarian insufficiency in women

Thallium exposure has been associated with female reproductive health, but little is known about its potential association with premature ovarian insufficiency (POI). In this study, a total of 169 patients with POI and 209 healthy women were recruited from Zhejiang province, China. Urinary thallium concentrations were significantly positively associated with the risk of POI [adjusted odds ratio (OR) = 1.63, 95% CI: 1.25-2.13, p < 0.001], geometric mean values of which were significantly higher in POI cases (0.213 μg/L, 0.302 μg/g for creatinine adjustment) than those of controls (0.153 μg/L, 0.233 μg/g for creatinine adjustment). Furthermore, the serum levels of follicle-stimulating hormone and luteinizing hormone were positively associated with urinary thallium concentrations, whereas anti-Mullerian hormone and estradiol were negatively correlated with thallium. To the best of our knowledge, this is the first study to provide evidence that thallium exposure at currently environmental levels is the potential risk factor for POI in women.

Epigenetic effects of parasites and pesticides on captive and wild nestling birds

Anthropogenic changes to the environment challenge animal populations to adapt to new conditions and unique threats. While the study of adaptation has focused on genetic variation, epigenetic mechanisms may also be important. DNA methylation is sensitive to environmental stressors, such as parasites and pesticides, which may affect gene expression and phenotype. We studied the effects of an invasive ectoparasite, Philornis downsi, on DNA methylation of Galápagos mockingbirds (Mimus parvulus). We used the insecticide permethrin to manipulate P. downsi presence in nests of free-living mockingbirds and tested for effects of parasitism on nestling mockingbirds using epiGBS, a reduced-representation bisulfite sequencing (RRBS) approach. To distinguish the confounding effects of insecticide exposure, we conducted a matching experiment exposing captive nestling zebra finches (Taeniopygia guttata) to permethrin. We used zebra finches because they were the closest model organism to mockingbirds that we could breed in controlled conditions. We identified a limited number of differentially methylated cytosines (DMCs) in parasitized versus nonparasitized mockingbirds, but the number was not more than expected by chance. In contrast, we saw clear effects of permethrin on methylation in captive zebra finches. DMCs in zebra finches paralleled documented effects of permethrin exposure on vertebrate cellular signaling and endocrine function. Our results from captive birds indicate a role for epigenetic processes in mediating sublethal nontarget effects of pyrethroid exposure in vertebrates. Environmental conditions in the field were more variable than the laboratory, which may have made effects of both parasitism and permethrin harder to detect in mockingbirds. RRBS approaches such as epiGBS may be a cost-effective way to characterize genome-wide methylation profiles. However, our results indicate that ecological epigenetic studies in natural populations should consider the number of cytosines interrogated and the depth of sequencing in order to have adequate power to detect small and variable effects.

Urinary metabolites of non-persistent pesticides and serum hormones in Spanish adolescent males

OBJECTIVE

To assess the relationship of urinary concentrations of ethylenethiourea (ETU), the main degradation product of ethylene bis-dithiocarbamate fungicides, 3-phenoxybenzoic acid (3-PBA), a common metabolite of many pyrethroids, and 1-naphthol (1N), a metabolite of the carbamate insecticide carbaryl, with hormone concentrations in adolescent males; and to examine interactions between pesticide metabolites and polymorphisms in xenobiotic metabolizing enzymes, including CYP2C19 and CYP2D6, in relation to hormone concentrations.

METHODS

A cross-sectional study was conducted in 134 males from the Spanish Environment and Childhood (INMA)-Granada cohort. Urine and serum samples were collected from participants during the same clinical visit at the age of 15-17 years. First morning urine void was analyzed for concentrations of ETU, 3-PBA, and 1N. Serum was analyzed for concentrations of reproductive hormones (testosterone, 17β-estradiol [E₂], dehydroepiandrosterone sulfate [DHEAS], sex hormone binding globulin [SHBG], luteinizing hormone [LH], follicle stimulating hormone [FSH], anti-Müllerian hormone [AMH], and prolactin), thyroid hormones (free thyroxine [FT4], total triiodothyronine [TT3], and thyroid stimulating hormone [TSH]), insulin growth factor 1 (IGF-1), adrenocorticotropic hormone (ACTH), and cortisol. CYP2C19 G681A and CYP2D6 G1846A polymorphisms were determined in blood from 117 participants. Multiple linear regression, interaction terms, and stratified analyses were performed.

RESULTS

Urinary ETU was detected in 74.6% of participants, 1N in 38.1%, and 3-PBA in 19.4%. Positive associations between detectable 3-PBA and TT3 and between detectable 1N and DHEAS were found, and marginally-significant associations of 1N with reduced E₂ and FSH were observed. Poor CYP2C19 and CYP2D6 metabolizers (GA and AA genotype carriers) showed a greater increase in DHEAS for detected versus undetected 1N compared with GG genotype carriers. Poor CYP2D6 metabolizers (1846 GA and AA genotypes) evidenced increased cortisol for detected versus undetected ETU.

CONCLUSIONS

The associations observed between urinary pesticide metabolites and altered thyroid and reproductive hormones are novel and should be verified in studies with larger sample size. Further research on gene-environment interactions is warranted to establish individual susceptibility to pesticides and the risk of adverse health effects.

Urinary cadmium concentrations and risk of primary ovarian insufficiency in women: a case-control study

Cadmium, a toxic heavy metal that occurs in the environment in large quantities through human activities, has been shown to have adverse effects on female reproductive health. However, the association between cadmium exposure and primary ovarian insufficiency (POI), one of the most prevalent ovarian diseases in women, has not been examined yet. This case-control study involving 169 POI cases and 209 healthy controls was conducted in Zhejiang Province, China. The urinary concentrations of cadmium were determined by inductively coupled plasma mass spectrometry (ICP-MS). In addition, serum levels of reproductive hormones, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), anti-Mullerian hormone (AMH) and estradiol, were measured. The median concentration of urinary cadmium in POI cases (0.43 μg/L, 0.58 μg/g for creatinine adjustment) was significantly higher than that of controls (0.29 μg/L, 0.43 μg/g for creatinine adjustment). The results of binary logistic regression models showed that the concentrations of urinary cadmium were positively significantly correlated with the odds ratio (ORs) of POI before the adjustment of confounders. After the adjustment, a significantly positive association was still present between the increased concentrations of cadmium and the ORs of POI (2.50, 95% CIs: 1.34-4.65 for the third tertile, p for trend = 0.001). The serum levels of FSH and LH were positively associated with urinary cadmium, while AMH and estradiol levels were inversely correlated. To the best of our knowledge, this is the first reported positive association of cadmium exposure with the risk of POI in women.

Endocrine disrupting chemicals: Impacts on human fertility and fecundity during the peri-conception period

It is becoming increasingly difficult to avoid exposure to man-made endocrine disrupting chemicals (EDCs) and environmental toxicants. This escalating yet constant exposure is postulated to partially explain the concurrent decline in human fertility that has occurred over the last 50 years. Controversy however remains as to whether associations exist, with conflicting findings commonly reported for all major EDC classes. The primary aim of this extensive work was to identify and review strong peer-reviewed evidence regarding the effects of environmentally-relevant EDC concentrations on adult male and female fertility during the critical periconception period on reproductive hormone concentrations, gamete and embryo characteristics, as well as the time to pregnancy in the general population. Secondly, to ascertain whether individuals or couples diagnosed as sub-fertile exhibit higher EDC or toxicant concentrations. Lastly, to highlight where little or no data exists that prevents strong associations being identified. From the greater than 1480 known EDCs, substantial evidence supports a negative association between exposure to phthalates, PCBs, PBDEs, pyrethroids, organochloride pesticides and male fertility and fecundity. Only moderate evidence exists for a negative association between BPA, PCBs, organochloride pesticides and female fertility and fecundity. Overall fewer studies were reported in women than men, with knowledge gaps generally evident for both sexes for all the major EDC classes, as well as a paucity of female fertility studies following exposure to parabens, triclosans, dioxins, PFAS, organophosphates and pyrethroids. Generally, sub-fertile individuals or couples exhibit higher EDC concentrations, endorsing a positive association between EDC exposure and sub-fertility. This review also discusses confounding and limiting factors that hamper our understanding of EDC exposures on fertility and fecundity. Finally, it highlights future research areas, as well as government, industry and social awareness strategies required to mitigate the negative effects of EDC and environmental toxicant exposure on human fertility and fecundity.

The function of Wls in ovarian development

WNT ligand transporter Wls is essential for the WNT dependent developmental and pathogenic processes. The spatiotemporal expression pattern of Wls was investigated in this study. Immature female mice (21-22 days old) were treated with 5 IU, pregnant mare's serum gonadotrophin (PMSG) to stimulate follicular development, followed 48 h later by injection with 5 IU, human chorionic gonadotrophin (hCG) to induce ovulation. The expression of Wls was stimulated in granulosa cells and the forming corpus luteum after hCG administration. To study the function of Wls, the Amhr2tm3(cre)Bhr strain was used to target deletion of Wls in granulosa cells. The deletion of Wls caused a significant decrease in the fertility of WlsAmhr2-Cre female mice. In female WlsAmhr2-Cre mice, decreased ovarian size and number of antral follicles were found. The number of corpus luteum in immature PMSG/hCG primed WlsAmhr2-Cre mice was much less than that in the control group. Compared with control animals, WlsAmhr2-Cre mice have lower serum progesterone levels. RNA sequencing was used to identify genes regulated by Wls after hCG treatment. Several genes known to be critical for follicle development and steroidogenesis were significantly down-regulated, such as Fshr, Lhcgr, Sfrp4, Inhba, Cyp17a1, Hsd3b1, and Hsd17b7. The expression of WNT signaling downstream target genes, Bmp2 and Cyp19a1, also decreased significantly in WlsAmhr2-Cre ovary. In summary, the findings of this study suggest that Wls is critical for female fertility and luteinization.

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.

Urinary 3-phenoxybenzoic acid (3-PBA) concentration and pulmonary function in children: A National Health and Nutrition Examination Survey (NHANES) 2007-2012 analysis

Epidemiological studies have reported association of urinary 3-phenoxybenzoic acid (3-PBA), a major metabolite of pyrethroid insecticides (PYRs), with respiratory disease. However, knowledge regarding its effect on pulmonary function in susceptible children is limited. This study aimed to assess the associations between environmental 3-PBA concentrations and pulmonary function in children aged 6-17 years. Using data on 1174 children aged 6-17 years from the U.S. National Health and Nutrition Examination Survey (NHANES) 2007-2012, the exposure to PYRs was assessed by measuring urinary 3-PBA concentrations and pulmonary function was assessed by spirometry. Multivariable linear regression and generalized linear models (GLMs) were used to examine the associations between 3-PBA concentrations and pulmonary function in children, controlling for confounders. We found that 3-PBA concentrations were inversely associated with forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), and peak expiratory flow (PEF) in the pediatric population (p-trends < 0.05). When stratified by age (6-10 and 11-17 years) and gender (boys and girls), the adverse effects of PYR exposures on pulmonary function were more pronounced among boys aged 11-17 years. Among this age group, 3-PBA concentrations were negatively associated with FEV₁, FVC, forced expiratory flow between 25% and 75% of FVC (FEF_25-75%), and PEF. However, among children aged 6-10 years, no associations were found between 3-PBA concentrations and any of the pulmonary function measures, in either boys or girls. Our findings suggest that environmental PYR exposures may adversely affect children's pulmonary function, with the strongest associations among 11-17 years old boys.

Variability of urinary pyrethroid biomarkers in Chinese young-aged men and women over one year

Pyrethroids are a class of the most commonly used insecticides. The urinary metabolites are usually used as biomarkers of pyrethroid exposures in humans. In this study, the temporal variability of urinary pyrethroid biomarkers was investigated among 114 Chinese young-aged adults who provided up to 4-11 urine samples over one year. The detection rates of four urinary pyrethroid biomarkers, 3-phenoxybenzoic acid (3PBA), 4-fluoro-3-phenoxybenzoic acid (4F-3PBA), trans-2,2-(dichloro)-2-dimethylvinylcyclopropane carboxylic acid (trans-DCCA) and cis-2,2-(dichloro)-2-dimethylvinylcyclopropane carboxylic acid (cis-DCCA) were 100%, 8%, 69% and 44%, respectively. The intraclass correlation coefficient (ICC) estimates for 3PBA indicated poor reproducibility (<0.15) in the spot urine samples of young-aged adults over a week, month and year. Log-transformed 3PBA used the least number of random spot urine samples (≥4) per person, which would provide a reliable biomarker estimate (ICC≥0.40) over a year. As the predictors of the top 33% yearly average 3PBA concentrations, the sensitivity and specificity of 3PBA ranged from 0.25 to 0.89, 0.58 to 0.96, respectively. Based on the results of this study, we recommend at least 4 urine samples collected 3 months apart for prospective assessment of pyrethroid exposure in the epidemiological studies to estimate exposure-response relationships between pyrethroids and health outcomes with relative long-term exposure periods.

Effect of oral administration of a mixture of pyrethroids at doses relevant to human exposure on the general and male reproductive physiology in the rat

Studies on the effects of unintentional intake of pyrethroid pesticides that are akin to actual human exposure settings are very rare. Such an exposure is primarily by consuming the food products as routine diet that contain residual levels of pyrethroids. In this study, rats were orally administered for 15 months with a mixture of pyrethroids at a dose that is one-fifth (high dose; HD) or one-twenty fifth (low dose; LD) of the residual levels commonly present in the average amount of rice and vegetables consumed by Indian population. Lipid profile, kidney and liver function were assessed. Lipid peroxidation, nitric oxide, antioxidant enzyme activities and histopathological changes were analyzed in the liver, lung, kidney, pancreas, testes, caput, cauda and prostate. The effect on the male reproductive system as a function of sperm count, enzyme activity of 3β-HSD and 17β-HSD and the expression profile of genes involved in spermatogenesis, steroidogenesis, genetic reprogramming and apoptosis of male gametes were evaluated. Significant increase in the relative organ weight, perturbations in the activities of antioxidant enzymes, lipid profile and liver function were observed in both LD and HD groups. Damage to the anatomical architecture was evident in all the tissues due to pyrethroid toxicity. Exposure to LD and HD of pyrethroid mixture resulted in decreased sperm count, activities of 3β-HSD and 17β-HSD, impaired capacitation and acrosome reaction and perturbations in the expression of genes that govern male gamete production. Results of our study indicate that exposure to pyrethroids for longer durations even at doses that are far below the residual levels present in the food consumed will result in severe damage to general physiological processes as well as reproductive function.

Pyrethroids Toxicity to Male Reproductive System and Offspring as a Function of Oxidative Stress Induction: Rodent Studies

Pyrethroids may be related to male reproductive system damage. However, the results of many previous studies are contradictory and uncertain. Therefore, a systematic review and a meta-analysis were performed to assess the relationship between pyrethroid exposure and male reproductive system damage. A total of 72 articles were identified, among which 57 were selected for meta-analysis, and 15 were selected for qualitative analysis. Pyrethroid exposure affected sperm count (SMD= -2.0424; 95% CI, -2.4699 to -1.6149), sperm motility (SMD=-3.606; 95% CI, -4.5172 to -2.6948), sperm morphology (SMD=2.686; 95% CI, 1.9744 to 3.3976), testis weight (SMD=-1.1591; 95% CI, -1.6145 to -0.7038), epididymal weight (SMD=-1.1576; 95% CI, -1.7455 to -0.5697), and serum testosterone level (SMD=-1.9194; 95% CI, -2.4589 to -1.3798) in the studies of rats. We found that gestational and lactational exposure to pyrethroids can reduce sperm count (SMD=1.8469; 95% CI, -2.9010 to -0.7927), sperm motility (SMD=-2.7151; 95% CI, -3.9574 to -1.4728), testis weight (SMD=-1.4361; 95% CI, -1.8873 to -0.9848), and epididymal weight (SMD=-0.6639; 95% CI, -0.9544 to -0.3733) of F1 offspring. Exposure to pyrethroids can increase malondialdehyde (SMD=3.3451; 95% CI 1.9914 to 4.6988) oxide in testes and can reduce the activities of glutathione (SMD=-2.075; 95% CI -3.0651 to -1.0848), superoxide dismutase (SMD=-2.4856; 95% CI -3.9612 to -1.0100), and catalase (SMD=-2.7564; 95% CI -3.9788 to -1.5340). Pyrethroid exposure and oxidative stress could damage male sperm quality. Gestational and lactational pyrethroid exposure affects the reproductive system of F1 offspring.

The association of bisphenol A exposure with premature ovarian insufficiency: a case-control study

BACKGROUND

A few epidemiological investigations and animal studies have demonstrated that bisphenol A (BPA) may affect female reproductive health. However, no epidemiologic study has investigated the relationship between BPA exposure and the risk of premature ovarian insufficiency (POI).

METHODS

In this case-control study, urinary concentrations of BPA and serum levels of reproductive hormone were measured. Associations between BPA concentrations and the risk of POI and POI-related hormone levels were estimated.

RESULTS

Among BPA quartiles, no obvious association was found between BPA levels and the risk of POI (p = 0.603). Although the adjusted odds ratio (OR) of POI was slightly increased for participants in the highest BPA concentration quartile, the association was not statistically significant (OR = 1.282, 95% confidence interval [CI] 0.615-2.049 for the highest vs. lowest quartile, p = 0.508). Although follicle stimulating hormone (FSH) and anti-Mullerian hormone (AMH) levels showed no tendency of an association with BPA (p = 0.941 and p = 0.876 for FSH and AMH, respectively), the highest quartile of luteinizing hormone was significantly positively associated with BPA levels (OR = 1.333, 95% CI 0.986-1.803, p = 0.042).

CONCLUSIONS

The urinary concentrations of BPA determined in this study were consistent with the range of exposure currently observed in Chinese women. However, BPA exposure at a relatively low level is not associated with POI in Chinese women. Further epidemiological studies are needed to confirm our findings.

A case-control study of arsenic exposure with the risk of primary ovarian insufficiency in women

Arsenic, a well-known toxic metalloid, is ubiquitously existed in environment. Arsenic exposure has been associated with female reproductive health. However, a potential association between arsenic exposure and primary ovarian insufficiency (POI) in women has not been recognized yet. In this case-control study, a total of 169 POI cases and 209 healthy controls were recruited to determine urinary concentrations of arsenic and serum levels of reproductive hormones (follicle-stimulating hormone (FSH), luteinizing hormone (LH), anti-Mullerian hormone (AMH) and estradiol). The median concentration of urinary arsenic in cases (21.5 μg/L, 28.0 μg/g for creatinine adjustment) was significantly higher than that of controls (13.8 μg/L, 19.3 μg/g for creatinine adjustment). Urinary arsenic concentrations were significantly positively associated with the risk of POI (adjusted odds ratio (OR) = 2.66, 95% CI: 1.43-4.95 for the highest vs lowest tertile of arsenic, p = 0.002; p for trend = 0.004). We also assessed the associations between arsenic exposure and reproductive hormones that are important for ovarian functions. FSH and LH levels were positively associated with urinary arsenic, whereas AMH and estradiol levels were negatively correlated with this element. This study provided evidence that arsenic exposure could be the potential risk factor for POI in women.

Exposure to polycyclic aromatic hydrocarbons and risk for premature ovarian failure and reproductive hormones imbalance

Polycyclic aromatic hydrocarbons (PAHs) are a typical class of persistent organic pollutants that is ubiquitous worldwide. Previous animal studies suggested that PAHs had adverse effects on female reproduction. However, the human data regarding relationship of PAHs exposure with women reproductive health, such as ovarian dysfunction, are scarce. In this case-control study, the associations of serum levels of PAHs with the risk of premature ovarian failure (POF) and reproductive hormones in Chinese women were investigated, with recruiting 157 POF patients and 217 healthy women. The serum levels of 12 types of PAHs, as well as reproductive hormones, including follicle-stimulating hormone, luteinizing hormone and anti-mullerian hormone, were determined. In the logistic regression models, most individual PAH congeners showed significantly positive correlations with the risk of POF (p < 0.05), except for fluorine and pyrene. Benzo(a)pyrene (BaP), as the most carcinogenic PAH congener, was observed to be significantly positively associated with the risk of POF. After adjustment for age, body mass index, educational levels and household income, per one-unit increase in the log-transformed BaP concentration was significantly correlated with 2.191-fold increased risk of POF (OR = 2.191, 95%CI: 1.634-2.938, p < 0.05). To the best of our knowledge, this is the first study to report an association between internal exposure levels of PAHs and the increased risk of POF in women.

Effects and mechanisms of pyrethroids on male reproductive system

Synthetic pyrethroids are used as insecticides in agriculture and a variety of household applications worldwide. Pyrethroids are widely distributed in all environmental compartments and the general populations are exposed to pyrethroids through various routes. Pyrethroids have been identified as endocrine-disrupting chemicals (EDCs) which are responsible for the male reproductive impairments. The data confirm pyrethroids cause male reproductive damages. The insecticides exert the toxic effects on male reproductive system through various complex mechanisms including antagonizing androgen receptor (AR), inhibiting steroid synthesis, affecting the hypothalamic-pituitary-gonadal (HPG) axis, acting as estrogen receptor (ER) modulators and inducing oxidative stress. The mechanisms of male reproductive toxicity of pyrethroids involve multiple targets and pathways. The review will provide further insight into pyrethroid-induced male reproductive toxicity and mechanisms, which is crucial to preserve male reproductive health.

The potential endocrine disruption of pesticide transformation products (TPs): The blind spot of pesticide risk assessment

The ecological and health risk assessment of environmental pesticide residues have attracted ever-growing attention; however, their transformation products (TPs) have seldom been considered. Herein, we examined the endocrine-disrupting effects of 4 widely used pesticides as pyriproxyfen (Pyr), malathion (ML), benalaxyl (BX), and fenoxaprop-ethyl (FE), together with their 21 TPs through in vitro and in silico approaches, and found approximately 50% of the TPs exhibited stronger endocrine-disrupting effects than their corresponding parent compounds. Specifically, Pyr and 9 TPs (five TPs of Pyr, one of ML, one of BX, and two of FE) exhibited estrogen-disrupting effects, which were also confirmed by results of E-screen and pS2 expression assays, and molecular docking showed that certain hydroxylated TPs could well mimic the binding mode of estrogen with ERα. Meanwhile, two TPs of Pyr, ML and its TP demonstrated weak glucocorticoid antagonistic activities partially contributed by hydrogen bonds. We also discovered that in H295R cells, all the endocrine disruptors increased hormone secretion and the related gene expression levels. Conclusively, since an increasing number of pesticide TPs have been being detected in various environmental media, a more comprehensive understanding of the ecological risk of pesticide TPs is imperative for risk assessments more extensively and regulatory policy-making on pesticide restriction in the future.

Urinary levels of phthalate metabolites in women associated with risk of premature ovarian failure and reproductive hormones

Phthalates, a class of high production-volume chemicals widely used as plasticizers, have been shown to impair ovarian functions in female animals, but epidemiological evidence is very limited. In this case-control study, the associations between phthalate exposure and premature ovarian failure (POF) in women were assessed. A total of 173 POF cases and 246 control women were recruited in Zhejiang, China. The urinary concentrations of 8 phthalate metabolites and the serum levels of ovary-related hormones were determined. Mono-isobutyl phthalate (MiBP) was the metabolite with the highest median concentration of 27.23 μg/g of creatinine in the whole group. Compared with the lowest quartile, higher urinary concentrations of MiBP were significantly associated with increased odds of POF (OR = 1.38, 95% CI: 0.73-2.61 for the fourth quartile; p for trend = 0.01). The estradiol/FSH ratio, a marker of ovarian function, in control women was significantly negatively associated with the urinary concentrations of most tested phthalate metabolites. Our results suggest that exposure to some phthalates may impair ovarian function and increase the odds of POF in women.

Glucocorticoid and mineralocorticoid receptors and corticosteroid homeostasis are potential targets for endocrine-disrupting chemicals

Endocrine-disrupting chemicals (EDCs) have received significant concern, since they ubiquitously exist in the environment and are able to induce adverse health effects on human and wildlife. Increasing evidence shows that the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), members of the steroid receptor subfamily, are potential targets for EDCs. GR and MR mediate the actions of glucocorticoids and mineralocorticoids, respectively, which are two main classes of corticosteroids involved in many physiological processes. The effects of EDCs on the homeostasis of these two classes of corticosteroids have also gained more attention recently. This review summarized the effects of environmental GR/MR ligands on receptor activity, and disruption of corticosteroid homeostasis. More than 130 chemicals classified into 7 main categories were reviewed, including metals, metalloids, pesticides, bisphenol analogues, flame retardants, other industrial chemicals and pharmaceuticals. The mechanisms by which EDCs interfere with GR/MR activity are primarily involved in ligand-receptor binding, nuclear translocation of the receptor complex, DNA-receptor binding, and changes in the expression of endogenous GR/MR genes. Besides directly interfering with receptors, enzyme-catalyzed synthesis and prereceptor regulation pathways of corticosteroids are also important targets for EDCs. The collected evidence suggests that corticosteroids and their receptors should be considered as potential targets for safety assessment of EDCs. The recognition of relevant xenobiotics and their underlying mechanisms of action is still a challenge in this emerging field of research.

Polychlorinated Biphenyl Quinone Promotes Macrophage-Derived Foam Cell Formation

Polychlorinated biphenyls (PCBs) are organic environmental pollutants that are accused of various toxic effects. PCB exposure is widely believed to be associated with atherosclerosis, but the underlying mechanisms are unclear. Although PCBs are easily metabolized, there is rarely information on the effects of their metabolites on atherosclerosis. Currently, we evaluate the effect of 2,3,5-trichloro-6-phenyl-[1,4]-benzoquinone (PCB29-pQ) on the critical phase of atherosclerosis development, that is, the formation of macrophage-derived foam cells. We exposed Ox-LDL-induced RAW264.7 cells to 2.5 μM and 5 μM PCB29-pQ. Varieties of evidence have demonstrated that PCB29-pQ promotes foam cell formation and develops proinflammatory cascade and cell necroptosis. In detail, we observed that PCB29-pQ increased levels of total cholesterol (TC), free cholesterol (FC), triglyceride (TG), and cholesteryl ester (CE) by increasing the cholesterol influx and reducing the cholesterol efflux. Moreover, we found that PCB29-pQ induced inflammatory cytokines, such as tumor necrosis factor (TNF-α), interleukin 6 (IL-6), and IL-1β, released by activating the mitogen-activated protein kinase (MAPK)-nuclear factor kappa B (NF-κB) inflammatory pathway. In addition, we demonstrated that PCB29-pQ induced cell necroptosis via receptor interacting protein kinases 1 and 3 (RIPK1/3) and a mixed-lineage kinase domain-like (MLKL) pathway. Finally, the overproduction of reactive oxygen species (ROS) by PCB29-pQ played significant roles in these processes, which could be reversed with an antioxidant. Overall, our results indicated that PCB29-pQ promoted the macrophage formation of foam cells, inflammation, and cell necroptosis.

In vitro assessment of corticosteroid effects of eight chiral herbicides

Information regarding the enantioselective endocrine disruption of chiral herbicides is scarce. This study assessed the disrupting effects of eight typical chiral herbicides on corticosteroids (including glucocorticoids and mineralocorticoids). Enantioselectivity of eight chiral herbicides were evaluated for their agonistic/antagonistic effects on glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) with CHOK1 cell line using reporter gene assay. Their influence on the production of corticosteroids were further investigated in H295R cell line using enzyme-linked immunosorbent assay (ELISA). None of the racemates or enantiomers of eight chiral herbicides exhibited GR or MR agonistic activity at non-cytotoxic concentrations. However, rac-propisochlor and S-imazamox antagonized cortisol-induced transactivation of GR by 21.79% and 38.73% at the concentration of 1.0 × 10^-7 M and 1.0 × 10^-6 M, respectively, and R-napropamide remarkably attenuated aldosterone-induced MR transactivation by 68.78% at 1.0 × 10^-6 M. The secretion of cortisol was significantly restrained after treated with 1.0 × 10^-6 M rac-propisochlor and rac-/R-napropamide at the concentration of 1.0 × 10^-6 M by 26.49%, 30.10% and 35.27%, respectively, while this glucocorticoid was remarkably induced by 1.0 × 10^-5 M rac-diclofop-methyl and its two enantiomers at the concentration of 1.0 × 10^-5 M by 75.60%, 100.1% and 68.78%, respectively. Exposure to rac-propisochlor (1.0 × 10^-6 M), S-diclofop-methyl (1.0 × 10^-5 M) or rac-/S-/R- acetochlor (1.0 × 10^-6 M) and rac-/S-/R-lactofen (1.0 × 10^-6 M) inhibited the secretion of aldosterone by approximately 40%. Our findings suggested that chiral herbicides disrupted corticosteroid homeostasis in an enantioselective way. Therefore, more comprehensive screening is required to better understand the ecological and health risks of chiral pesticides.