Permethrin may disrupt testosterone biosynthesis via mitochondrial membrane damage of Leydig cells in adult male mouse

The mollifying effect of Sambucus nigra extract on StAR gene expression, oxidative stress, and apoptosis induced by fenpropathrin in male rats

Fenpropathrin (FNP) is a man-made insecticide of to the pyrethroid class, commonly employed in agricultural and horticultural practices. However, it has a prolonged persistence in the environment. Sambucus nigra, also referred to as SN, is a botanical species recognized for its notable antioxidant characteristics. The objective of this study was to examine if SN extract could mitigate the reproductive toxicity induced by FNP in rats. A total of thirty rats were categorized into six distinct groups: a control group with no treatment, two groups getting SN extract at varying doses, a group receiving FNP, and two groups receiving both FNP and SN extract. The exposure to FNP led to a decline in the number and movement of sperm, lowered levels of testosterone, and reduced the activity of the StAR gene in the FNP group compared to the control group (p < 0.05). In addition, FNP resulted in a significant increase in malondialdehyde levels with a significant drop in GSH content compared to the control group (p < 0.05). Also, a significant increase in the expression of caspase 3. Nevertheless, the administration of SN extract alleviated these effects and reinstated spermatogenesis, thereby bringing the parameters closer to those observed in the control group. The data indicate that FNP can induce testicular harm and infertility, but SN extract can mitigate these detrimental consequences.

Assessing the impact and mechanisms of environmental pollutants (heavy metals and pesticides) on the male reproductive system: a comprehensive review

The escalation of technological advancements, coupled with the increased use of hazardous chemicals, has emerged as a significant concern for human health. Exposure to environmental pollutants like heavy metals and pesticides (insecticides, herbicides and fungicides) is known to significantly contribute to various health problems, particularly affecting reproductive health. Disturbances in reproductive potential and reproductive toxicity in males are particularly worrisome. Existing literature suggests that exposure to these environmental pollutants significantly alters male reproductive parameters. Thus, it is imperative to thoroughly analyze, comprehend, and evaluate their impact on male reproductive toxicity. Oxidative stress and disruptions in redox equilibrium are major factors through which these pollutants induce changes in sperm parameters and affect the reproductive system. Insecticides, fungicides, and herbicides act as endocrine disruptors, interfering with the secretion and function of reproductive hormones such as testosterone and luteinizing hormone (LH), consequently impacting spermatogenesis. Additionally, heavy metals are reported to bio-accumulate in reproductive organs, acting as endocrine disruptors and triggering oxidative stress. The co-operative association of these pollutants can lead to severe damage. In this comprehensive review, we have conducted an in-depth analysis of the impact of these environmental pollutants on the male reproductive system, shedding light on the underlying mechanisms of action.

Endocrine-disrupting chemicals and male reproductive health

Modifiable factors, such as environmental exposures, can impact human fertility. The objective of this review is to summarize the potential effects of exposure to important endocrine-disrupting chemicals on male reproductive health. Most experimental and animal data demonstrate strong evidence for the negative effects of exposure to phenols, phthalates, pesticides, and perfluoroalkyl and polyfluoroalkyl substances on male reproductive health. Although evidence of negative associations in humans was overall strong for phthalates and pesticides, limited and inconclusive relationships were found for the other examined chemical biomarkers. Reasons for the discrepancies in results include but are not limited to, differences in study populations, exposure concentrations, number of samples collected, sample sizes, study design, and residual confounding. Additional studies are needed, particularly for newer phenols and perfluoroalkyl and polyfluoroalkyl substances, given the scarce literature on the topic and increasing exposures over time.

Ameliorative effect of L-carnitine on lambda-cyhalothrin-induced anatomical and reproductive aberrations in albino mice

The objective of this research was to look at how the pesticide lambda-cyhalothrin (LCT) affected the liver, kidney, testis, and ovary of albino mice; and on morphological and skeletal features of the newborn of treated females. The study also aimed to test the ameliorative effects of L-carnitine (LC) against (LCT). Five sets of mice were created, Group 1 acted as the control, while Group 2 received a high dose of LCT, Group 3 received a high dose of LCT + LC, Group 4 received a low dose of LCT that was a residue of in khat (Qat), and Group 5 received a low dose of LCT + LC. The findings revealed that the treated groups' body weights were reduced significantly, whereas the absolute and relative weights of the liver in all groups were statistically decreased insignificantly. There were histopathological changes in the tissues in groups 2 and 4. While the tissues of the ovary and testis showed recovery in groups 3 and 5. When compared to the control group, the values of the seminiferous tubules parameters were statistically significant in the 3 and 5 groups. The newborn had a high dose of pesticides and showed some malformations in the skeleton. However, in group 3 the skeletal malformation was minimized and in-group 5 the skeleton malformations had completely disappeared. It could be concluded that LCT is highly harmful to mouse tissues and caused neonatal malformations, whereas LC has a marked protective effect against LCT.

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.

Key role of mitochondrial mutation Leu107Ser (COX1) in deltamethrin resistance in salmon lice (Lepeophtheirus salmonis)

The pyrethroid deltamethrin (DTM) is used to treat Atlantic salmon (Salmo salar) against salmon louse (Lepeophtheirus salmonis) infestations. However, DTM resistance has evolved in L. salmonis and is currently common in the North Atlantic. This study aimed to re-assess the association between DTM resistance and mitochondrial (mtDNA) mutations demonstrated in previous reports. Among 218 L. salmonis collected in Scotland in 2018–2019, 89.4% showed DTM resistance in bioassays, while 93.6% expressed at least one of four mtDNA single nucleotide polymorphisms (SNPs) previously shown to be resistance associated. Genotyping at further 14 SNP loci allowed to define three resistance-associated mtDNA haplotypes, named 2, 3 and 4, occurring in 72.0%, 14.2% and 7.3% of samples, respectively. L. salmonis strains IoA-02 (haplotype 2) and IoA-10 (haplotype 3) both showed high levels (~ 100-fold) of DTM resistance, which was inherited maternally in crossing experiments. MtDNA haplotypes 2 and 3 differed in genotype for 17 of 18 studied SNPs, but shared one mutation that causes an amino acid change (Leu107Ser) in the cytochrome c oxidase subunit 1 (COX1) and was present in all DTM resistant while lacking in all susceptible parasites. We conclude that Leu107Ser (COX1) is a main genetic determinant of DTM resistance in L. salmonis.

Therapeutic Effects of Ethanolic Extract of Polygonum limbatum meism Against Reproductive Toxicity Induced by Cadmium in Male Guinea Pigs (Cavia porcellus)

This study aimed at evaluating the therapeutic effects of ethanolic extract of Polygonum limbatum meism (EEPLM) on the reproductive parameters of male Guinea pigs exposed to cadmium chloride. Thirty-six male guinea pigs were randomly assigned to six treatment groups (with six animals per group). Group 1 (DW) received distilled water orally; group 2 (Cd), negative control, was treated with cadmium chloride at a dose of 26.25 mg/kg body weight (bw); while group 3 (VitC), positive control, was given 26.25 mg of cadmium chloride/kg bw and 100 mg of vitamin C, and groups 4, 5, and 6 were treated, respectively, with EEPLM at doses of 50, 100, and 200 mg/kg bw in addition to cadmium chloride (26.25 mg/kg bw). After 90 days, all animals were sacrificed, and data related to reproduction, toxicity, and oxidative stress were collected. Results revealed a significant decrease (p < 0.05) of serum levels of creatinine, urea, alanine, and aspartate amino transferases in guinea pigs treated with cadmium chloride and EEPLM compared to the negative control group (Cd). The weight of the bulbo-urethral gland was significantly (p < 0.05) decreased in animals exposed to cadmium chloride and treated with vitamin C or EEPLM compared to the negative control (Cd). Guinea pigs orally receiving cadmium chloride and EEPLM showed significantly (p < 0.05) increased motility, sperm count, spermatozoa with entire plasma membrane, and percentage of normal spermatozoa with reference to the negative control (Cd). The serum level of testosterone increased insignificantly (p > 0.05) in animals given cadmium and EEPLM compared to the negative control (Cd). Animals co-administered cadmium chloride and EEPLM recorded a significantly (p < 0.05) reduced level of MDA, activities of SOD, and total peroxidases compared to the group that received cadmium chloride (Cd) only. In conclusion, cadmium chloride induced reproductive impairments by generating oxidative stress. However, the administration of EEPLM can mitigate these adverse effects due to its antioxidant properties.

Short-term intake of deltamethrin-contaminated fruit, even at low concentrations, induces testicular damage in fruit-eating bats (Artibeus lituratus)

Deltamethrin (DTM) is a pyrethroid insecticide widely used for agricultural purposes. Exposure to DTM has proven to be harmful to humans, but whether low, environmental concentrations of this pesticide also poses a threat to wild mammals is still unknown. In Neotropical areas, bats play important roles in contributing to forest regeneration. We investigated the effects of DTM exposure on the reproductive function of male Neotropical fruit-eating bats (Artibeus lituratus), known for contributing to reforestation through seed dispersal in Neotropical Forests. Bats were assigned to 3 groups: control (fed with papaya); DTM2 (fed with papaya treated with DTM at 0.02 mg/kg) and DTM4 (fed with papaya treated with DTM at 0.04 mg/kg) for seven days. Bats from DTM2 and DTM4 groups showed increased testicular levels of nitric oxide and superoxide dismutase and catalase activities. The germinal epithelium from DTM4 bats showed non-viable cells and cell desquamation, indicating microscopic lesions and Leydig cells atrophy. Our results demonstrate the onset of cell degeneration that may affect the reproductive function in DTM exposed bats.

Reducing the reproductive toxicity activity of Lactiplantibacillus plantarum: a review of mechanisms and prospects

Food pollution can cause a variety of negative effects on human health, especially reproductive toxicity. Common food contaminants include biological contaminants, chemical contaminants, and physical contaminants, among which endocrine disruptors, pesticides, and heavy metals have the greatest reproductive toxicity in chemical contaminants. Humans mainly solve food pollution through three aspects: decreasing the pollution of food raw materials, lowering the pollution in food processing, and reducing the harm to the human body after food pollutants enter the human body. With more and more research on probiotics, not only beneficial effects, but also the ability to reduce the toxicity of food contaminants is found. Thus, microbial treatment has been proved to be a more effective way to deal with food pollution. Recent research shows that several strains of Lactiplantibacillus plantarum can adsorb or degrade some chemical pollutants and relieve inflammation and oxidative stress caused by them. This review summarized the research to explore the possible role of Lactiplantibacillus plantarum in protecting human reproductive ability and maintaining food safety.

Testosterone synthesis in testicular Leydig cells after long-term exposure to a static electric field (SEF)

China's clean energy and resources are mainly located in the west and north while electric load center is concentrated in the middle and east. Thus, these resources and energy need to be converted into electrical energy in situ and transported to electric load center through ultra-high voltage direct current (UHVDC) transmissions. China has built 25,000 km UHVDC transmission lines of 800 kV and 1100 kV, near which the impact of electric field on health has attracted public attention. Previous studies showed that time-varying electromagnetic field exposure could disturb testosterone secretion. To study the effect of non-time-varying electric field caused by direct current transmission lines on testosterone synthesis, male ICR mice were continually (24 h/d) exposed to static electric field of 56.3 ± 1.4 kV/m. Results showed that on the 3^rd day of exposure and on the 7^th day after ceasing the exposure of 28 d, serum testosterone level and testicular oxidative stress indicators didn't change significantly. On the 28^th day of exposure, serum testosterone levels, testicular glutathione peroxidase (GSH-Px) activity, the mRNA and protein levels of testicular StAR, PBR, CYP11A1 decreased significantly, and testicular malondialdehyde (MDA) content increased significantly. Meanwhile, electron-dense edges and vacuolation appeared in lipid droplets of Leydig cells. The gap between inner mitochondrial membrane (IMM) and outer mitochondrial membrane (OMM) enlarged, which would cause the swelling of mitochondria, the rupture and deficiency of mitochondrial membranes. Analysis showed that testicular oxidative stress could induce the damage of mitochondrial structure in Leydig cells, which would decrease the rate of cholesterol transport from cytoplasm to mitochondria. Since cholesterol is the necessary precursor of testosterone synthesis, testosterone synthesis was inhibited. The decrease of the mRNA and protein expression levels of StAR and PBR in testes could diminish the cholesterol transported from OMM to IMM. The decrease of the mRNA and protein expression levels of CYP11A1 could reduce the pregnenolone required in testosterone synthesis and inhibit testosterone synthesis consequently.

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.

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.

Pyroglutamylated RFamide peptide 43: A putative modulator of testicular steroidogenesis

BACKGROUND

We have recently shown that QRFP and its receptor are predominantly expressed in germ cells, Sertoli cells and Leydig cells in mice testes.

OBJECTIVE

The present study investigated the role of QRFP in testicular steroidogenesis in mice.

MATERIALS AND METHODS

Both ex vivo and in vivo experiments were performed. For ex vivo, testicular tissues were cultured with 0, 10, 100 and 1000 nM QRFP, with or without hCG, for 6, 12 and 24 h, and media were used for testosterone assay. The hCG-stimulated testicular tissues were used for immunoblot of SF1, StAR, CYP11A1, 3β- and 17β-HSD. For in vivo, mice received bilateral intratesticular injection of saline or 0.3, 1 and 3nmol QRFP and were killed at 6, 12 and 24 h post-injection. Testosterone in serum was measured at above durations, while qRT-PCR of HMG-CoA synthase 1 and SR-B1 and immunoblot of steroidogenesis-related markers were performed at 24 h post-injection.

RESULTS

Testosterone production under basal and hCG-stimulated conditions increased in a time-dependent manner, and QRFP supplementation to testicular culture caused an increase and a decrease in hormone production. The effect of QRFP on testosterone production under hCG-stimulated culture or in vivo conditions at 6 and 24h was similar. At 6h, testosterone production increased at 10 and 100 nM and also at 0.3 and 1nmol QRFP, while it decreased at 1000 nM and 3 nmol doses. At 24 h, testosterone level decreased at lower concentrations (10 nM and 0.3 nmol) and thereafter increased at middle (100nM and 1nmol) and higher (1000 nM and 3 nmol) concentrations under both hCG-stimulated culture and in vivo.

DISCUSSION AND CONCLUSION

QRFP induced production of testosterone by modulating steroidogenic machinery at optimal doses and durations. Further, findings of in vivo study indicate that QRFP besides directly regulating testicular steroidogenesis may also have modulated other factors which act together in a holistic manner to control steroidogenesis.

Testosterone recuperates deteriorated male fertility in cypermethrin intoxicated rats

The present study investigates the protective effects of testosterone against reproductive toxicity induced by cypermethrin (50 mg/kg body weight) in rats. Significant reduction in the testicular and accessory sex organ weights were observed in cypermethrin-treated rats over controls. Cypermethrin intoxication significantly reduced testicular daily sperm count, epididymal sperm count, sperm motility, sperm viability and HOS-tail coiled sperm accompanied by significant reduction in the activity levels of testicular steroidogenic enzymes such as 3β- and 17β- hydroxysteroid dehydrogenases in rats as compared to controls. Further, qPCR studies indicated that the mRNA expression levels of steroidogenic acute regulatory protein (StAR) significantly decreased in cypermethrin-treated rats over controls. Molecular docking analysis indicated that the binding affinity of cypermethrin (- 11.2 kcal/mol) towards StAR protein was greater as compared to its natural ligand, cholesterol (- 8.2 kcal/mol) suggesting improper cholesterol channeling across the testis. Significant reduction in the circulatory levels of testosterone was also recorded in cypermethrin-exposed rats. An increase in pre- and post-implantation loss was observed in rats cohabited with cypermethrin-treated rats. On the other hand, testosterone (4.16 mg/kg body weight) treatment ameliorated cypermethrin-induced reprotoxic effects in rats. To conclude, cypermethrin-induced deterioration of suppressed reproductive performance in male rats could be linked to its antiandrogenic effects and on the other hand, testosterone-mediated protection of male reproductive health in cypermethrin-treated rats at least in part occurs via restoration of testosterone biosynthesis, spermatogenesis and sperm maturation events.

Impact of environmental contaminants on reproductive health of male domestic ruminants: a review

Environmental contaminants are gaining more attention in the livestock sector lately due to their harmful effects on productivity and fertility of livestock. Recent research indicates that many domestic ruminants are becoming subfertile/infertile due to confounding reasons associated with management. Contaminants like metals, metalloids, herbicides, pesticides, insecticides, chemicals, or natural contaminants are present everywhere in day to day life and are becoming a threat to the livestock. Studies on a broad-spectrum of animals suggest that high doses of acute or low doses of chronic exposure to the contaminants lead to disruption of multi-organs/systems including reproductive function. The lowered reproductive efficiency in animals is attributed to the endocrine disruptor activities of the environmental contaminants on the gonads, affecting gametogenesis and steroidogenesis. In vitro studies on testicular cells and the semen suggest that spermatozoa are more susceptible to damage by environmental contaminants. The quality of the semen happens to be a critical factor in the livestock industry. Contaminants affecting gametogenesis and steroidogenesis may lead to devastating consequences to the livestock reproduction, and thus the production. However, there is a lack of collective data on the effect of such environmental contaminants on the fertility of male domestic ruminants. This review discusses the studies related to the impact of environmental contaminants on male fertility in large (bull and buffalo) and small (sheep and goat) ruminants by focusing on the underlying molecular interactions between the contaminants and gonads.

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

Pyrethroids, a class of ubiquitous insecticides, have been recognized as endocrine-disrupting chemicals (EDCs). A lot of studies have implied the endocrine-disrupting effects of pyrethroids on the hypothalamic-pituitary-gonadal (HPG) axis. However, there are few review articles regarding the effects of pyrethroids on the HPG axis of mammal and human, especially new research progress made in this area. The present review sums up the effects of pyrethroids on the HPG axis-related reproductive outcomes, including epidemiological investigations based on human biomonitoring, animal studies and in vitro tests. Mechanisms have described that the endocrine-disrupting effects of pyrethroids on mammal can be mediated via the interaction with steroid receptors, the direct action on ion channels and signaling molecules. Finally, we summarize the current research gaps and suggest future directions in this topic.

[Reproductive Toxicological Research as Countermeasures to Declining Birth Rate]

Research into reproductive toxicology may lead to one of the countermeasures to the declining birth rate observed in industrialized countries. Some chemicals can pose risks to human reproduction that is a multistage process starting from the development of male and female germ cells to childbirth and the subsequent growth and development of the child. In Japan, the government has amended law enforcement, i.e., the Regulations on Labor Standards for Women, recently to improve protection for pregnant women against reproductive chemical hazards in workplaces. Male workers may also be protected against such hazards if appropriate risk assessment and the following management are performed as required by the Industrial Safety and Health Law. However, it remains a concern that an unexpected adverse outcome due to an unknown reproduction hazard may occur owing to the use of chemicals not listed in the regulations. This is because the toxicity of a large number of chemicals has not been entirely revealed. Moreover, it is often difficult to determine from a Safety Data Sheet for a product of interest whether the chemicals contained in the product do not have reproductive toxicity or the toxicity data are just not available because of lack of pertinent studies. Thus, researchers in the field of occupational and environmental health need to make effort to fill in such data gaps and to raise the awareness among the public the importance of experimental and epidemiological studies. Study designs for investigating subclinical effects, mechanisms of reproductive toxicity, exposure levels, and dose-response relationships to determine environmental standards are also required.

The pyrethroid insecticides permethrin and esfenvalerate do not disrupt testicular steroidogenesis in the rat fetus

The present study investigated the effects of maternal exposure to the widely used pyrethroid insecticides, permethrin and esfenvalerate, on fetal testicular steroidogenesis. Pregnant Sprague-Dawley rats were administered permethrin at doses of 1, 10, 50, or 100 mg/kg/day, or esfenvalerate at 0.1, 1, 7.5 or 15 mg/kg/day, by gavage, from gestation day (GD) 13 to 19. Testicular testosterone production and the expression of several key genes necessary for cholesterol and androgen synthesis and transport were assessed in GD 19 male fetuses. Dams treated with 100 mg/kg/day of permethrin or 15 mg/kg/day of esfenvalerate showed clinical signs of neurotoxicity. The highest dose of esfenvalerate also resulted in reduced maternal body weight gain throughout the treatment period. In the fetal testes, mRNA expressions of HMG-CoA synthase and reductase, SR-B1, StAR, P450scc, 3βHSD, P450 17A1, and 17βHSD were not affected by exposure to either pyrethroid. No significant change was observed in ex vivo testosterone production. In conclusion, in utero exposure to permethrin or esfenvalerate has no effect on the testosterone biosynthesis pathway in the fetal rat testis up to maternal toxic doses.

Protective effect of green tea extract on the deltamethrin-induced toxicity in mice testis: An experimental study

Background

Deltamethrin (DM) is one of the environmental factors that can have destructive effects on the male fertility. Green tea (GT) as a medicinal herb, has antioxidant property.

Objective

The present study investigated the protective role of GT extract in improving the harmful effects of DM on the testis.

Materials and Methods

In this experimental study, 35 adult male mice (25–30 gr) were divided in to five groups (n = 7/each). The control group received only normal saline. Sham received 0.2 ml corn oil. Green tea group received only GT of 150 mg/kg. bw; deltamethrin group received the DM at a dose of 0.6 mg/kg. bw; GT + DM received both GT and DM. The effect of GT was assessed by measuring oxidative stress markers, sperm parameters, histological and immunohistochemical analysis.

Results

The results showed that the count and motility of spermatozoa, testosterone, and Malondialdehyde significantly decreased (p < 0.001) and the abnormal spermatozoa increased (p < 0.001) in DM group compared to control group. Moreover, enhanced caspase-3expression and apoptosis were observed in DM-treated mice compared to control group. Histologically, DM with a degenerative effect on testicular tissue reduced the spermatogenesis progenitor cells. The epithelial height and the diameter of the seminiferous tubules were also reduced in the DM group. Treatment with GT in the DM-treated mice significantly improved these changes.

Conclusion

With these findings, it was concluded that the GT treatment with antioxidant activity and anti-apoptotic property could protect the testicular injury induced by DM.

Antouka Super® induced oxidative stress and reproductive toxicity in male Japanese quail (Coturnix coturnix japonica)

Background

Antouka Super^® (AS), a combination of insecticide (Pirimiphos-methyl 16% and Permethrin 3%), is one of the most widely used pesticides in agriculture, public health, home and garden, with high potential for human and animal exposure.

Objective

The present study was undertaken to evaluate the effect of AS on the serum testosterone, oxidative stress biomarkers, testis histology and fertility of male Japanese quail.

Methods

Thirty-two (32) male Japanese quails twenty-eight (28) days were randomly divided into four groups: C0 (control), T1, T2 and T3, exposed daily (gavage) to 0, 37.5, 56.25 and 75 mg of AS/kg body weight (b.w), respectively, for 49 consecutive days and were analysed for fertility. Control and experimental male quails were cohabited, for two days, with untreated female quails and sperm positive female quail were analysed for paternal-mediated toxicity. After completion of fertility studies quails were sacrificed and analysed for reproductive endpoints.

Results

There was a dose dependent decrease of the relative weight of testis, epididymis and vas deferens. Additionally, testis total proteins and serum testosterone levels were decreased in AS treated quails (p < 0.05). A decrease of sperm motility, viability and concentration per vas deferens, and an increase of sperm anomalies were recorded in AS exposed quails with respect to the controls. The embryonic and post-embryonic mortality rate were significantly (p < 0.05) higher in group T3 (25.00 ± 3.40% and 31.66 ± 10.22% respectively) than in control group (6.25 ± 3.98% and 9.54 ± 3.72% respectively). The superoxide dismutase (SOD), total peroxidase (POD) and catalase activity (CAT) were significantly (p < 0.05) lower treated than control quails, while the level of malondialdehyde (MDA) was significantly (p < 0.05) higher in groups T1, T2 and T3 (13.00 ± 0.96, 23.50 ± 1.35 and 29.08 ± 1.58 nmol/mg tissues respectively) compared to the control one (9.32 ± 0.67nmol/mg tissues). Histopathological examination of the testes of AS treated quails revealed testicular lesions characterized by moderate to severe degenerative changes of seminiferous tubules, incomplete spermatogenesis and depletion in the germ layers of seminiferous tubules in which immature spermatozoa were hardly seen.

Conclusion

From the above study, it can be inferred that AS (56.25 and 75) mg/kg b.w decrease body and relative organ weights and induces testicular lesions. Also, AS increases the level of MDA while it reduces the levels of enzymatic antioxidant biomarkers, serum testosterone and reproductive indices of intoxicated quails and their offspring. However, further work is needed to establish the genetic toxicology and immunohistochemistry of caspase-3 and claudin-1.

Prenatal and postnatal exposure to low levels of permethrin exerts reproductive effects in male mice

Permethrin, a pyrethroid chemical, is widely used as a pesticide because of its rapid insecticidal activity. Although permethrin is considered to exert very low toxicity on mammalian reproductive organs, the effects of early low-level and chronic exposure on adult spermatogenesis are unclear. We exposed mice to environmentally relevant concentrations of permethrin (0, 0.3, and 30ppm) in drinking water during prenatal and postnatal period and examined the effects on the testis in mice offspring when they reached maturity (12 weeks of age). Using methyl green-pyronin staining, we found an abnormal accumulation of RNA in the seminiferous epithelia of mice treated with permethrin; this accumulation may be derived from an enlargement of the residual body. Additionally, permethrin may cause a decline of Sertoli cell functions. Our findings demonstrate that low-level and chronic permethrin exposure during prenatal and postnatal period has distinct effects on male reproductive system in mice.

Pyrethroid Insecticide Cypermethrin Accelerates Pubertal Onset in Male Mice via Disrupting Hypothalamic-Pituitary-Gonadal Axis

Pyrethroids, a class of insecticides that are widely used worldwide, have been identified as endocrine-disrupting chemicals (EDCs). Our recent epidemiological study reported on an association of increased pyrethroids exposure with elevated gonadotropins levels and earlier pubertal development in Chinese boys. In this study, we further investigated the effects of cypermethrin (CP), one of the most ubiquitous pyrethroid insecticides, on hypothalamic-pituitary-gonadal (HPG) axis and pubertal onset in male animal models. Early postnatal exposure to CP at environmentally relevant doses (0.5, 5, and 50 μg/kg CP) significantly accelerated the age of puberty onset in male mice. Administration of CP induced a dose-dependent increase in serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone in male mice. CP did not affect gonadotropin-releasing hormone (GnRH) gene expression in the hypothalamus, but CP at higher concentrations stimulated GnRH pulse frequency. CP could induce the secretion of LH and FSH, as well as the expression of gonadotropin subunit genes [chorionic gonadotropin α (CGα), LHβ, and FSHβ] in pituitary gonadotropes. CP stimulated testosterone production and the expression of steroidogenesis-related genes [steroidogenic acute regulatory (StAR) and Cytochrome p 450, family 11, subfamily A, polypeptide 1 (CYP11A1)] in testicular Leydig cells. The interference with hypothalamic sodium channels as well as calcium channels in pituitary gonadotropes and testicular Leydig cells was responsible for CP-induced HPG axis maturation. Our findings established in animal models provide further evidence for the biological plausibility of pyrethroid exposure as a potentially environmental contributor to earlier puberty in males.

Steroidogenesis in Leydig cells: effects of aging and environmental factors

Serum testosterone (TS) levels decrease with aging in both humans and rodents. Using the rat as a model system, it was found that age-related reductions in serum TS were not due to loss of Leydig cells, but rather to the reduced ability of the Leydig cells to produce TS in response to luteinizing hormone (LH). Detailed analyses of the steroidogenic pathway have suggested that two defects along the pathway, LH-stimulated cAMP production and cholesterol transport to and into the mitochondria, are of particular importance in age-related reductions in TS production. Although the mechanisms involved in these defects are far from certain, increasing oxidative stress appears to play a particularly important role. Interestingly, increased oxidative stress also appears to be involved in the suppressive effects of endocrine disruptors on Leydig cell TS production.

Maternal inheritance of deltamethrin resistance in the salmon louse Lepeophtheirus salmonis (Krøyer) is associated with unique mtDNA haplotypes

Parasitic infections by the salmon louse, Lepeophtheirus salmonis (Krøyer), cause huge economic damage in salmon farming in the northern hemisphere, with combined treatment costs and production losses in 2014 having been estimated at US$ 350 million for Norway (annual production 1.25 million tonnes). The control of L. salmonis relies significantly on medicinal treatments, supplemented by non-pharmacological approaches. However, efficacy losses have been reported for several delousing agents, including the pyrethroid deltamethrin. The aim of the present study was to analyse the genetic basis of deltamethrin resistance in L. salmonis. Deltamethrin median effective concentrations (EC50) were 0.28 μg L-1 in the drug susceptible L. salmonis strain IoA-00 and 40.1 μg L-1 in the pyrethroid resistant strain IoA-02. IoA-00 and IoA-02 were crossed to produce families spanning one parental and three filial generations (P0, F1-F3). In three families derived from P0 crosses between an IoA-00 sire and an IoA-02 dam, 98.8% of F2 parasites (n = 173) were resistant, i.e. remained unaffected after exposure to 2.0 μg L-1 deltamethrin. F3 parasites from these crosses showed a deltamethrin EC50 of 9.66 μg L-1. In two families of the inverse orientation at P0 (IoA-02 sire x IoA-00 dam), 16.7% of F2 parasites were resistant (n = 84), while the deltamethrin EC50 in F3 animals was 0.26 μg L-1. The results revealed a predominantly maternal inheritance of deltamethrin resistance. The 15,947-nt mitochondrial genome was sequenced and compared among six unrelated L. salmonis strains and parasites sampled from wild salmon in 2010. IoA-02 and three further deltamethrin resistant strains, established from isolates originating from different regions of Scotland, showed almost identical mitochondrial haplotypes. In contrast, the mitochondrial genome was variable among susceptible strains and L. salmonis from wild hosts. Deltamethrin caused toxicity and depletion of whole body ATP levels in IoA-00 but not IoA-02 parasites. The maternal inheritance of deltamethrin resistance and its association with mitochondrial haplotypes suggests that pyrethroid toxicity in L. salmonis may involve molecular targets encoded by mitochondrial genes.

Relationships of Pyrethroid Exposure with Gonadotropin Levels and Pubertal Development in Chinese Boys

Although an acceleration of male pubertal development has been observed, precisely which endocrine-disrupting chemicals (EDCs) might contribute to the advancing onset of puberty in boys remains unclear. Here, pyrethroids, a class of widely used insecticides that have been considered as EDCs, are proposed as new environmental risk factors. In this study, 463 boys at the age of 9-16 years old were recruited in Hangzhou, Zhejiang, China. The common metabolites of pyrethroids, 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), as well as gonadotropins, including luteinizing hormone (LH) and follicle-stimulating hormone (FSH), were analyzed in urine samples. Pubertal development was assessed based on Tanner stages and testicular volume (TV). A positive association between 3-PBA and gonadotropins was found (p < 0.001), in which a 10% increase in 3-PBA was associated with a 2.4% and 2.9% increase in LH and FSH, respectively. Higher urinary levels of 3-PBA in boys were associated with 275% and 280% increase in the risk of being genitalia stage 3 (G3) and G4, respectively (p < 0.05). There was a significant (132%) induction in odd of being TV 12-19 mL with increasing 3-PBA concentration compared to being in TV < 4 mL (p < 0.05). For the first time to our knowledge, this work reports on an association of increased pyrethroid exposure with elevated gonadotropins levels and earlier pubertal development in boys.

Effects of oral administration of 2,4-dichlorophenoxyacetic acid (2,4-D) on reproductive parameters in male Wistar rats

The 2,4-dichlorophenoxyacetic acid (2,4-D) is used worldwide in agriculture as a selective herbicide. It has been shown to produce a wide range of adverse effects on the health of both animals and humans from embryotoxicity and teratogenicity to neurotoxicity. In the present study, we have examined the effect of 2,4-D on male reproductive function of rats. Male Wistar rats received daily by force-feeding 100 or 200 mg of 2,4-D/kg body weight for 30 consecutive days. Rats exposed to 100 and 200 mg of 2,4-D/kg showed a significant decrease in body weights only after 24 days of treatment and in relative weights of testis, seminal vesicles and prostate at killing day, when compared with controls. Moreover, a decrease in testosterone and an increase in FSH and LH serum levels were detected in treated rats. Besides, exposure to this herbicide induced pronounced testicular histological alterations with enlarged intracellular spaces, tissue loosening and dramatic loss of gametes in the lumen of the seminiferous tubules. In addition, a decreased motility and a number of epididymal spermatozoa with an increased sperm abnormality rate were found in treated rats in comparison with control. With the highest dose, histological observations of seminal vesicles indicated a considerable decrease of secretions in the lumen, a thinness of the muscle layer surrounding the epithelium with branched mucosal crypts and reduced luminal space. In prostate, the heights of the cells decreased while acinar lumen were enlarged and they lost the typical invaginations. Our results suggest that a subacute treatment of 2,4-D promotes reproductive system toxicity.

Effects of label-dose permethrin administration in yearling beef cattle: I. Bull reproductive function and testicular histopathology

Pyrethroid administration to a wide variety of laboratory animals has been shown to cause detrimental effects on male fertility, including sperm quality, by means of endocrine disruption. The objective of this experiment was to study the effects of a commercial, permethrin-containing pour-on product on reproductive variables and testicular histopathology of yearling beef bulls. Black Angus bulls (n = 60; aged 369 ± 17 days; 511 ± 33 kg; 6.2 ± 0.5 body condition scores) were assigned to either (1) saline control (CON) or (2) permethrin pour-on administered at label dose (PYR). Blood samples were collected, and industry standard breeding soundness examinations (BSE), via electroejaculation, were performed on all bulls at 5 days before and 14 days after treatment. Progressive sperm motility and eosin-nigrosin-stained sperm were analyzed using high-power phase-contrast microscopy. Plasma testosterone concentrations were analyzed via radioimmunoassay. Bulls were slaughtered at 34 days, and one testicle per bull was randomly collected for histologic examination. Change in sperm motility between BSEs was not different because of treatment; sperm morphology however improved across treatments, but PYR bulls had less improvement in percent of head (P < 0.001) sperm abnormalities compared to CON, resulting in less improvement of primary abnormalities (P = 0.04). Nonetheless, morphological differences did not change the overall outcome for satisfactory breeder status. Change in testosterone concentration did not differ because of treatment. Histopathologic examination identified that testicular degeneration and tubule diameter did not differ as a result of treatment. It should be noted, however, that degeneration score (higher score having more degeneration) was positively correlated with primary abnormalities (P < 0.01; r = 0.35) and negatively correlated with normal sperm cells (P < 0.001; r = -0.43). In summary, these data indicate that a single use of permethrin at label dose in yearling Angus bulls results in minimal detrimental effects on sperm morphology but not to a degree that impacts the ability of bulls to pass a standard BSE.

Efficacy of naringenin against permethrin-induced testicular toxicity in rats

Permethrin (PM), a synthetic pyrethroid insecticide, has broad toxicity spectra. We aimed to investigate the effects of PM on the testes of adult albino rats, examine the recovery response and evaluate the efficacy of naringenin (NG) supplementation. Adult male albino rats were randomly assigned to five groups of six each: control, NG (50 mg/kg), PM (70 mg/kg), recovery (after subsequent withdrawal of PM) and NG-PM group. All treatments were given by oral gavage for 6 weeks and another 3 weeks for the recovery group. At the time of sacrifice, each testis was weighed. Biochemical analysis of epididymal sperm count and serum testosterone level was performed. Testes were processed for histological, ultrastructural and c-Kit immunohistochemical study. PM toxicity was evidenced by a highly significant decrease in testicular weight, epididymal sperm count and serum testosterone level compared to control. Furthermore, testicular structure abnormalities and reduced c-Kit immunoreactions were observed. Stoppage of PM in the recovery group partially reversed PM-induced changes. There was a mild decrease in testicular weight and biochemical parameters compared to control. The structure of seminiferous tubules was partially retained. The NG-PM group showed an overall improvement in testicular weight and biochemical alterations which were confirmed by light and electron microscopic examination. In conclusion, PM induced testicular toxicity, which was ameliorated by NG co-administration. However, stoppage of PM exposure was associated with partial recovery.

Effect of in utero exposure to endocrine disruptors on fetal steroidogenesis governed by the pituitary-gonad axis: a study in rats using different ways of administration

The effects of endocrine disruptors on testicular steroidogenesis in fetal rats were investigated in a study involving in utero exposure. In the major part of this study, pregnant rats at gestational day (GD)15 were given a single oral administration of the test substance, and then the expression of the following mRNAs in GD20 fetuses was determined: testicular steroidogenic acute-regulatory protein (StAR), a cholesterol transporter mediating the rate-limiting step of steroidogenesis, a ß-subunit of pituitary luteinizing hormone (LH), and a regulator of gonadal steroidogenesis. Among the substances tested, only di(2-ethylhexyl)phthalate (DEHP) reduced the expression of fetal testicular StAR. The others listed below exhibited little effect on fetal StAR: 2,2',4,4'-tetrabromodiphenylether, tributyltin chloride, atrazine, permethrin, cadmium chloride (Cd), lead acetate (Pb) and methylmercury (CH3HgOH). None of them, including DEHP, lacked the ability to reduce the expression of pituitary LHß mRNA. The present study also examined the potential of metals as modifiers of fetal steroidogenesis by giving them to pregnant dams in drinking water during GD1 and GD20. Under these conditions, Cd and Pb at a low concentration (0.01 ppm) significantly attenuated the fetal testicular expression of StAR mRNA without a concomitant reduction in LHß. No such effect was detected with CH3HgOH even at 1 ppm. These results suggest that: 1) DEHP, Cd and Pb attenuate the fetal production of sex steroids by directly acting on the testis, and 2) chronic treatment during the entire gestational period is more useful than a single administration for determining the hazardous effect of a suspected endocrine disruptor on fetal steroidogenesis.

Enantioselective disruption of the endocrine system by Cis-Bifenthrin in the male mice

Bifenthrin (BF), as a chiral pyrethroid, is widely used to control field and household pests in China. At present, the commercial BF is a mixed compound containing cis isomers (cis-BF) including two enantiomers of 1R-cis-BF and 1S-cis-BF. In the present study, the two individual cis-BF enantiomers were separated by a preparative supercritical fluid chromatography. Then, four week-old adolescent male ICR mice were orally administered 1R-cis-BF and 1S-cis-BF separately daily for 3 weeks at doses of 0, 7.5 and 15 mg/kg/day, respectively. Results showed that the transcription status of some genes involved in cholesterol synthesis and transport as well as testosterone (T) synthesis in the testes were influenced by cis-BF enantiomers. Especially, we observed that the transcription status of key genes on the pathway of T synthesis including cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc) and cytochrome P450 17α-hydroxysteroid dehydrogenase (P45017α)) were selectively altered in the testis of mice when treated with 1S-cis-BF, suggesting that it is the possible reason to explain why the lower serum T concentration in 1S-cis-BF treated group. Taken together, it concluded that both of the cis-BF enantiomers have the endocrine disruption activities, while 1S-cis-BF was higher than 1R-cis-BF in mice when exposed during the puberty. The data was helpful to understand the toxicity of cis-BF in mammals under enantiomeric level.

Downregulation of cytochrome P450scc as an initial adverse effect of adult exposure to diethylstilbestrol on testicular steroidogenesis

Reproductive toxicities and endocrine disruptions caused by chemicals in adult males are still poorly understood. It is our objectives to understand further details of the initial adverse effects leading severe testicular toxicities of a pharmaceutical endocrine disruptor, diethylstilbestrol (DES). Downregulations of both testicular regulatory proteins, such as the steroidogenic acute regulatory protein (StAR) and the peripheral benzodiazepine receptor (PBR), which play important roles in the transport of cholesterol into the mitochondria, and cytochrome P450 mediating the cholesterol side chain cleavage reaction (P450scc), were observed in the rat orally administered DES (340 μg/kg/2 days) for 2 weeks. We found that after only 1 week treatment with DES, the blood and testicular testosterone (TS) levels were drastically decreased without abnormalities of the StAR and PBR; however, the protein and mRNA levels of P450scc were diminished. Decrease in the conversion rate of cholesterol to pregnenolone was delayed in the in vitro assay using the testicular mitochondrial fraction from the rat treated with DES for 1 week. When the precursors in TS biosynthesis containing the testis were identified and determined by liquid chromatography-mass spectrometry analysis, decreased levels of all precursors except cholesterol were observed. In conclusion, suppressed cytochrome P450scc expression in adult male rat was identified as an initial target of DES in testicular steroidogenesis disorder leading reproductive toxicities.

Fenitrothion action at the endocannabinoid system leading to spermatotoxicity in Wistar rats

Organophosphate (OP) compounds as anticholinesterase agents may secondarily act on diverse serine hydrolase targets, revealing unfavorable physiological effects including male reproductive toxicity. The present investigation proposes that fenitrothion (FNT, a major OP compound) acts on the endocannabinoid signaling system in male reproductive organs, thereby leading to spermatotoxicity (sperm deformity, underdevelopment, and reduced motility) in rats. FNT oxon (bioactive metabolite of FNT) preferentially inhibited the fatty acid amide hydrolase (FAAH), an endocannabinoid anandamide (AEA) hydrolase, in the rat cellular membrane preparation from the testis in vitro. Subsequently, male Wistar rats were treated orally with 5 or 10mg/kg FNT for 9 weeks and the subchronic exposure unambiguously deteriorated sperm motility and morphology. The activity-based protein profiling analysis with a phosphonofluoridate fluorescent probe revealed that FAAH was selectively inhibited among the FNT-treated cellular membrane proteome in testis. Intriguingly, testicular AEA (endogenous substrate of FAAH) levels were elevated along with the FAAH inhibition caused by the subchronic exposure. More importantly, linear regression analyses for the FNT-elicited spermatotoxicity reveal a good correlation between the testicular FAAH activity and morphological indices or sperm motility. Accordingly, the present study proposes that the FNT-elicited spermatotoxicity appears to be related to inhibition of FAAH leading to overstimulation of the endocannabinoid signaling system, which plays crucial roles in spermatogenesis and sperm motility acquirement.

Reproductive toxicity and histopathological changes induced by lambda-cyhalothrin in male mice

Lambda-cyhalothrin (LCT) is a widely used broad-spectrum pyrethroid insecticide. Oral LCT administration to adult male mice at 3 doses (0.2, 0.4, and 0.8 mg/kg/day) for 6 weeks caused a significant reduction in the weight of the seminal vesicles. The epididymal sperm count was lower in mice that received at the highest dose than in control mice. However, the proportions of live and motile spermatozoa were reduced at both the medium and the high doses compared with control mice. All doses induced an increase in the number of morphologically abnormal spermatozoa. Histopathological observations of the testes, liver, kidneys, and spleen showed dose-related degenerative damage in LCT-treated mice. The results indicate that LCT has reproductive toxicity, hepatotoxicity, nephrotoxicity, and splenotoxicity in male mice at the tested doses. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 750-762, 2014.

Evaluation of the stereoselective biotransformation of permethrin in human liver microsomes: contributions of cytochrome P450 monooxygenases to the formation of estrogenic metabolites

Permethrin (PM) is a pyrethroid insecticide that exists as 4 enantiomers. Biotransformation of PM to estrogen receptor agonists (3-phenoxybenzyl alcohol (PBOH) and 3-(4'-hydroxyphenoxy)-benzyl alcohol (3,4 PBOH)) has been shown to be stereoselective in other vertebrate species. This study evaluated the biotransformation of PM enantiomers in human liver microsomes and with recombinant CYP3A4 and CYP2C19. PBOH and 3,4 PBOH were the only metabolites detected from in vitro incubations including each of the 4 enantiomers of PM with 1R-trans PM having the most efficient NADPH-catalyzed biotransformation to both metabolites. Coincubation with the CYP inhibitor ketoconazole and time course experiments with liver microsomes and recombinant CYP2C19 and CYP3A4 indicated CYP-catalyzed stereoselective cleavage of the ester followed by 4-hydoxylation to 3,4' PBOH. These data indicate potential dispositional differences may occur with PM enantiomers and a shift in putative molecular targets. While cleavage of pyrethroid esters lead to detoxification of the acute neurological effects, formation of the benzyl alcohol and hydroxylated metabolite may lead to estrogenic responses, since each of these metabolites are estrogen receptor ligands.