Perinatal fenvalerate exposure: behavioral and endocrinology changes in male rats

Late gestational exposure to fenvalerate impacts ovarian reserve in neonatal mice via YTHDF2-mediated P-body assembly

Fenvalerate (FEN), a type II pyrethroid pesticide, finds extensive application in agriculture, graziery and public spaces for pest control, resulting in severe environmental pollution. As an environmental endocrine disruptor with estrogen-like activity, exposure to FEN exhibited adverse effects on ovarian functions. Additionally, the presence of the metabolite of FEN in women's urine shows a positive association with the risk of primary ovarian insufficiency (POI). In mammals, the primordial follicle pool established during the early life serves as a reservoir for storing all available oocytes throughout the female reproductive life. The initial size of the primordial follicle pool and the rate of its depletion affect the occurrence of POI. Nevertheless, there is very limited research about the impact of FEN exposure on primordial folliculogenesis. In this study, pregnant mice were orally administrated with 0.2, 2.0 and 20.0 mg/kg FEN from 16.5 to 18.5 days post-coitus (dpc). Ovaries exposed to FEN exhibited the presence of large germ-cell cysts that persist on 1 days post-parturition (1 dpp), followed by a significant reduction in the total number of oocytes in pups on 5 dpp. Moreover, the levels of m6A-RNA and its associated proteins METTL3 and YTHDF2 were significantly increased in the ovaries exposed to FEN. The increased YTHDF2 promoted the assembly of the cytoplasmic processing bodies (P-body) in the oocytes, accompanied with altered expression of transcripts. Additionally, when YTHDF2 was knocked-down in fetal ovary cultures, the primordial folliculogenesis disrupted by FEN exposure was effectively restored. Further, the female offspring exposed to FEN displayed ovarian dysfunctions reminiscent of POI in early adulthood, characterized by decreases in ovarian coefficient and female hormone levels. Therefore, the present study revealed that exposure to FEN during late pregnancy disrupted primordial folliculogenesis by YTHDF2-mediated P-body assembly, causing enduring adverse effects on female fertility.

Effects of pyrethroids on brain development and behavior: Deltamethrin

Deltamethrin (DLM) is a Type II pyrethroid pesticide widely used in agriculture, homes, public spaces, and medicine. Epidemiological studies report that increased pyrethroid exposure during development is associated with neurobehavioral disorders. This raises concern about the safety of these chemicals for children. Few animal studies have explored the long-term effects of developmental exposure to DLM on the brain. Here we review the CNS effects of pyrethroids, with emphasis on DLM. Current data on behavioral and cognitive effects after developmental exposure are emphasized. Although, the acute mechanisms of action of DLM are known, how these translate to long-term effects is only beginning to be understood. But existing data clearly show there are lasting effects on locomotor activity, acoustic startle, learning and memory, apoptosis, and dopamine in mice and rats after early exposure. The most consistent neurochemical findings are reductions in the dopamine transporter and the dopamine D1 receptor. The data show that DLM is developmentally neurotoxic but more research on its mechanisms of long-term effects is needed.

Pyrethroid based pesticides - chemical and biological aspects

Human and animal welfare primarily depends on the availability of food and surrounding environment. Over a century and half, the quest to identify agents that can enhance food production and protection from vector borne diseases resulted in the identification and use of a variety of pesticides, of which the pyrethroid based ones emerged as the best choice. Pesticides while improved the quality of life, on the other hand caused enormous health risks. Because of their percolation into drinking water and food chain and usage in domestic settings, humans unintentionally get exposed to the pesticides on a daily basis. The health hazards of almost all known pesticides at a variety of doses and exposure times are reported. This review provides a comprehensive summation on the historical, epidemiological, chemical and biological (physiological, biochemical and molecular) aspects of pyrethroid based insecticides. An overview of the available knowledge suggests that the synthetic pyrethroids vary in their chemical and toxic nature and pose health hazards that range from simple nausea to cancers. Despite large number of reports, studies that focused on identifying the health hazards using doses that are equivalent or relevant to human exposure are lacking. It is high time such studies are conducted to provide concrete evidence on the hazards of consuming pesticide contaminated food. Policy decisions to decrease the residual levels of pesticides in agricultural products and also to encourage organic farming is suggested.

Estimating household exposure to pyrethroids and the relative contribution of inhalation pathway in a sample of Japanese children

Several synthetic pyrethroids are suspected to have carcinogenicity or reproductive toxicity. However, there is little knowledge about indoor air pollution in residences or the extent of intake by the residents of the newly developed pyrethroids, transfluthrin, profluthrin, and metofluthrin, although they have been widely used indoors as mosquito repellents and mothproof repellents in recent years. In the present study, the household exposure to pyrethroids through all exposure pathways and the contribution of inhalation pathway in Japanese children were examined by measuring urinary pyrethroid metabolites in the children and the airborne pyrethroids in their residences. Urine excreted first after waking up was collected from subjects aged 6 to 15 years (n = 132), and airborne pyrethroids were sampled in the subjects' bedrooms for 24 h. Nineteen pyrethroids and their nine urinary metabolites were measured. Their daily intakes estimated were as follows (median, ng/kg b.w./d): bifenthrin, 56; transfluthrin, 22; metofluthrin, 11; profluthrin, 0.86. The contribution rates of the amounts absorbed by inhalation to the amounts absorbed via all of the exposure pathways while at home tended to decrease in the following order: profluthrin (median 15%) ≈ transfluthrin (14%) > metofluthrin (1%) > bifenthrin (0.1%). Transfluthrin was considered to be the most notable pyrethroid as an indoor air pollutant. Our study demonstrated widespread exposure to transfluthrin, metofluthrin, profluthrin, and bifenthrin in a sample of Japanese children.

Gut Microbiota: A Key Factor in the Host Health Effects Induced by Pesticide Exposure?

In the past few decades, a large number of pesticides have been widely used for plant protection. Pesticides may enter non-target organisms through multiple ways and bring potential health risks. There is a dense and diverse microbial community in the intestines of mammals, which is called the gut microbiota. The gut microbiota and its metabolites play vital roles in maintaining the health of the host. Interestingly, many studies have shown that exposure to multiple pesticides could affect the gut microbiota of the host. However, the roles of gut microbiota and its related metabolites in the host health effects induced by pesticide exposure of non-target organisms need further study. We reviewed the relationships between pesticide exposure and host health effects as well as between the gut microbiota and host health effects. Importantly, we reviewed the latest research on the gut microbiota and its metabolites in the host health effects induced by pesticide exposure.

A metabolomic study on the gender-dependent effects of maternal exposure to fenvalerate on neurodevelopment in offspring mice

BACKGROUND

The general population is widely exposed to fenvalerate. However, the effects of maternal exposure to fenvalerate on neurodevelopment in offspring and the underlying metabolic mechanism are largely unknown.

METHODS

Pregnant mice were exposed to fenvalerate for 11 consecutive days. The forced swimming test (FST) was performed in 35 day-old offspring to investigate the effects of fenvalerate on neurobehavioral responses. Blood serum free T4 and free T3 concentrations were measured using commercial ELISA. Blood and thyroid samples were used for metabolomic analyses with UPLC Q-Exactive. The expression levels of neurotransmitter metaolite receptors were determined in the frontal cortex of offspring using real-time PCR.

RESULTS

The immobility time, free T4 and free T3, and expression levels of Htr1a and Htr2a were statistically changed in offspring male mice. Metabolomic analysis revealed that the pentose phosphate pathway, starch and sucrose metabolism, glutamic acid metabolism were the key changed pathways in the blood, and thiamine metabolism was the key changed pathway in the thyroid.

CONCLUSION

Prenatal exposure to fenvalerate affected neurodevelopment in male offspring mice both via the changed abundances of metabolites involved in glycolysis related metabolism and medium-chain fatty acid metabolism, and the changes in 5-HT receptor expression.

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.

Mate choice, sexual selection, and endocrine-disrupting chemicals

Humans have disproportionately affected the habitat and survival of species through environmental contamination. Important among these anthropogenic influences is the proliferation of organic chemicals, some of which perturb hormone systems, the latter referred to as endocrine-disrupting chemicals (EDCs). EDCs are widespread in the environment and affect all levels of reproduction, including development of reproductive organs, hormone release and regulation through the life cycle, the development of secondary sexual characteristics, and the maturation and maintenance of adult physiology and behavior. However, what is not well-known is how the confluence of EDC actions on the manifestation of morphological and behavioral sexual traits influences mate choice, a process that requires the reciprocal evaluation of and/or acceptance of a sexual partner. Moreover, the outcomes of EDC-induced perturbations are likely to influence sexual selection; yet this has rarely been directly tested. Here, we provide background on the development and manifestation of sexual traits, reproductive competence, and the neurobiology of sexual behavior, and evidence for their perturbation by EDCs. Selection acts on individuals, with the consequences manifest in populations, and we discuss the implications for EDC contamination of these processes, and the future of species.

Quizalofop-P-ethyl exposure increases estrogen axis activity in male and slightly decreases estrogen axis activity in female zebrafish (Danio rerio)

The herbicide Quizalofop-P-ethyl (QpE) exerts toxic effects in fish, but limited information is currently available on its effects on the endocrine system. In the current study, adult zebrafish (Danio rerio) were exposed to different concentrations (0, 2, 20, 200μg/L) of QpE for 30days. In males, QpE exposure significantly increased plasma estradiol (E2) and vitellogenin (VTG) levels, concomitant with up-regulation of hepatic esr1 and vtg gene expression. In females, plasma sex hormone levels and VTG concentrations were not altered significantly, but an increased expression of hepatic esr1 in addition to decreased expression of hepatic vtg, esr2a and esr2b was observed. Marked histological lesions were also observed in the gonads of both males and females. Moreover, QpE exposure significantly increased transcriptional profiles of some genes in the HPG axis and liver in males, while the majority of these genes were down-regulated in females. Docking studies showed QpE forming stable interactions with the ligand-binding domain (LBD) of zebrafish ESR1 and ESR2a, suggesting QpE may bind to estrogen receptors (ESRs). This study for the first time reveals QpE as an endocrine-disrupting chemical (EDC) disrupting the zebrafish endocrine system in a sex-specific manner, whereby it increases estrogen axis activity in males and slightly decreases estrogen axis activity in females, which may be accounted for by QpE regulating steroidogenesis and/or activating ESR(s).

Paternal fenvalerate exposure influences reproductive functions in the offspring

Fenvalerate (Fen), a synthetic pyrethroid insecticide, has been shown to have adverse effects on male reproductive system. Thus, the aim of the present study was to elucidate whether these adverse effects are passed from exposed male mice to their offspring. Adult male mice received Fen (10 mg/kg) daily for 30 days and mated with untreated females to produce offspring. Fenvalerate significantly changed the methylation status of angiotensin I-converting enzyme (Ace), forkhead box O3 (Foxo3a), huntingtin-associated protein 1 (Hap1), nuclear receptor subfamily 3 (Nr3c2), promyelocytic leukemia (Pml), and Prostaglandin F2 receptor negative regulator (Ptgfrn) genes in paternal mice sperm genomic DNA. Further, Fen significantly increased sperm abnormalities; serum testosterone and estradiol-17ß level in adult male (F0) and their male offspring (F1). Further, paternal Fen treatment significantly increased the length of estrous cycle, serum estradiol-17ß concentration in estrus, and progesterone levels in diestrus in female offspring (F1). These findings suggest that adverse effects of paternal Fen exposure on reproductive functions can be seen not only in treated males (F0) but also in their offsprings.

Pesticide exposure and neurodevelopmental outcomes: review of the epidemiologic and animal studies

Assessment of whether pesticide exposure is associated with neurodevelopmental outcomes in children can best be addressed with a systematic review of both the human and animal peer-reviewed literature. This review analyzed epidemiologic studies testing the hypothesis that exposure to pesticides during pregnancy and/or early childhood is associated with neurodevelopmental outcomes in children. Studies that directly queried pesticide exposure (e.g., via questionnaire or interview) or measured pesticide or metabolite levels in biological specimens from study participants (e.g., blood, urine, etc.) or their immediate environment (e.g., personal air monitoring, home dust samples, etc.) were eligible for inclusion. Consistency, strength of association, and dose response were key elements of the framework utilized for evaluating epidemiologic studies. As a whole, the epidemiologic studies did not strongly implicate any particular pesticide as being causally related to adverse neurodevelopmental outcomes in infants and children. A few associations were unique for a health outcome and specific pesticide, and alternative hypotheses could not be ruled out. Our survey of the in vivo peer-reviewed published mammalian literature focused on effects of the specific active ingredient of pesticides on functional neurodevelopmental endpoints (i.e., behavior, neuropharmacology and neuropathology). In most cases, effects were noted at dose levels within the same order of magnitude or higher compared to the point of departure used for chronic risk assessments in the United States. Thus, although the published animal studies may have characterized potential neurodevelopmental outcomes using endpoints not required by guideline studies, the effects were generally observed at or above effect levels measured in repeated-dose toxicology studies submitted to the U.S. Environmental Protection Agency (EPA). Suggestions for improved exposure assessment in epidemiology studies and more effective and tiered approaches in animal testing are discussed.

Effects of pubertal fenvalerate exposure on testosterone and estradiol synthesis and the expression of androgen and estrogen receptors in the developing brain

Fenvalerate is a potential endocrine disruptor. Several studies have demonstrated that fenvalerate disrupts testosterone (T) synthesis in testes. T and estradiol (E(2)) are de novo synthesized in the developing brain. Thus, the aim of the present study was to investigate the effects of pubertal fenvalerate exposure on the synthesis of T and E(2) and the expression of androgen receptor (AR) and estrogen receptors (ERs) in cerebral cortex. CD-1 mice were orally administered daily with either vehicle or fenvalerate (7.5 or 30 mg/kg) from postnatal day (PND) 28 to PND56. The level of T and E(2) in cerebral cortex was significantly decreased in males exposed to fenvalerate. In agreement with the decrease in T and E(2) syntheses, the expression of 17β-HSD, a key enzyme for T synthesis, was significantly reduced in cerebral cortex of fenvalerate-exposed males. Conversely, in females, the expression of 17β-HSD in cerebral cortex was mildly up-regulated by fenvalerate and the level of T and E(2) was mildly increased. Pubertal fenvalerate exposure had no effect on the expression of StAR, P450(17α) and P450scc, the key enzymes for T synthesis, and P450 aromatase, the key enzyme for E(2) synthesis, in cerebral cortex of males and females. Interestingly, the expression of AR in cerebral cortex was up-regulated in male and female mice exposed to fenvalerate, whereas pubertal fenvalerate exposure did not affect the level of ERα and ERβ in cerebral cortex. Taken together, these results suggest that pubertal fenvalerate exposure disrupts T and E(2) synthesis and the expression of AR in cerebral cortex. These changes of steroid status in the developing brain might be deleterious for neurobehavioral development.

Pubertal and early adult exposure to fenvalerate disrupts steroidogenesis and spermatogenesis in mice at adulthood

Fenvalerate, a pyrethroid insecticide used worldwide, has been shown to have a potentially adverse effect on male reproduction. Our earlier study showed that maternal fenvalerate exposure during lactation impaired testicular development in male offspring. In this study, we investigated the effects of pubertal and early adult exposure to fenvalerate on steroidogenesis and spermatogenesis in mice. Male mice were administered fenvalerate (60 mg/kg) by gavage daily from postnatal day 35 (PND35) to PND63. Results showed that sperm count was significantly decreased in fenvalerate-treated mice. In addition, fenvalerate markedly decreased the layers of spermatogenic cells, disturbed the array of spermatogenic cells and increased the number of apoptotic cells in testes. The adverse effects of fenvalerate on male reproduction seemed to be associated with a decrease in serum and testicular testosterone (T). Although pubertal and early adult exposure to fenvalerate had little effect on the number of Leydig cells in testes, mRNA and protein levels of testicular T biosynthetic enzymes including P450(17alpha) and P450scc were significantly downregulated in fenvalerate-treated mice. In conclusion, pubertal and early adult fenvalerate exposure induces a deleterious effect on steroidogenesis and spermatogenesis in adulthood. The decreased testicular T synthesis partially contributes to fenvalerate-induced impairment on spermatogenesis.

An endocrine-disrupting chemical, fenvalerate, induces cell cycle progression and collagen type I expression in human uterine leiomyoma and myometrial cells

Fenvalerate (Fen), widely used for its high insecticidal potency and low mammalian toxicity, is classified as an endocrine-disrupting chemical. Recently, Fen has received great attention for its adverse effects on human reproductive health. In this study, we found that Fen (10 microM) had a stimulatory effect on the growth of both cell lines at 24 h compared with controls by MTS (p < 0.01) and BrdU (p < 0.01) assays in hormonally responsive uterine leiomyoma (UtLM) cells and normal uterine smooth muscle cells (UtSMC). Flow cytometry results showed that Fen enhanced the escape of cells from the G(0)-G(1) checkpoint and promoted progression of both cell types into the S phase. An Annexin V assay showed that Fen had an anti-apoptotic effect on both cell types. By Real-time PCR, we found that collagen I mRNA expression increased (p < 0.05) in Fen-treated cells compared to controls, although it was greater in UtLM tumor cells. Accordingly, Fen increased (p < 0.05) collagen I protein levels in both cell lysate and supernatant when compared to controls. To further test the mechanism of Fen's effects, transactivation and competitive binding assays were done. The results showed Fen did not significantly stimulate luciferase activity at concentrations of 0.1 microM, 1.0 microM or 10.0 microM in either of the cell types. Competitive binding assays revealed that the affinity of Fen binding to estrogen receptors (ERs) was non-detectable compared to E(2). Our data show that Fen can stimulate the growth of both UtLM cells and UtSMC, which involves a combination of enhanced cell cycle progression and inhibition of apoptosis. Also this compound can increase collagen I expression, at both mRNA and protein levels. Interestingly, the ER is less likely involved in either the hyperplasia or extracellular matrix (ECM) overproduction induced by Fen. Our results indicate that Fen exposure could be considered a novel risk factor for uterine fibroids through molecular mechanisms that do not directly involve the ERs.

Effects of gestational and lactational fenvalerate exposure on immune and reproductive systems of male rats

The aim of this study was to determine the consequent reproductive developmental and immunotoxic effects due to exposure to fenvalerate during pregnancy and lactation in male offspring of maternal-treated rats. Pregnant rats were treated daily by oral gavage with 40 or 80 mg/kg of fenvalerate or corn oil (vehicle, control), from d 12 of pregnancy to d 21 of lactation. Immune and reproductive developmental effects were assessed in male offspring at postnatal days (PND) 40 (peripuberty), 60 (postpuberty), and 90 (sexual maturity). Treatment with the higher dose (80 mg/kg) resulted in convulsive behavior, hyperexcitability, and mortality in 45% of the dams. Fenvalerate was detected in the fetus due to placental transfer, as well as in pups due to breast-milk ingestion, persisting in male offspring until PND 40 even though pesticide treatment was terminated on PND 20. However, fenvalerate did not produce marked alterations in age of testicular descent to the scrotum and prepucial separation, parameters indicative of puberty initiation. In contrast, at puberty, there was a reduction in testicular weight and sperm production in male offspring of maternal-treated rats. At adulthood, the sperm counts and fertility did not differ between control and treated groups. Testosterone levels were not changed at any time during reproductive development. Similarly, no apparent exposure-related effects were detected in the histological structures of the lymphohematopoietic system. Data indicate that fenvalerate, in this experimental model, interfered with initial development of the male reproductive system, but that these effects on sperm production or fertility did not persist into adulthood. There was no apparent evidence that fenvalerate altered testosterone levels or produced a disruption in male endocrine functions.

Fenvalerate, a pyrethroid insecticide, adversely affects sperm production and storage in male rats

The aim of this study was to investigate the potential estrogenic activity of fenvalerate by examining reproductive and fertility capabilities in Wistar rats. Adult male animals were treated for 30 d with 20 or 40 mg/kg/d fenvalerate or corn oil (vehicle) by oral gavage. Further, a possible estrogenic activity of fenvalerate (0.4, 1, 4, 8, or 40 mg/kg) was tested after a 3-d treatment of immature female rats using the uterotrophic assay. Exposure to the higher dose of fenvalerate was toxic to testis and epididymis as shown by a decrease in the absolute weights and sperm counts in both organs. Although the sperm counts were reduced, the fertility and sexual behavior were similar in control rats and rats treated with 40 mg/kg pesticide. Fenvalerate did not exert estrogenic activity in vivo at the tested doses. Data suggest that fenvalerate treatment in this study failed to compromise fertility, possibly due to enhanced reproductive capacity in rodents compared to humans.

Effects of fenvalerate and cypermethrin on rat sperm motility patterns in vitro as measured by computer-assisted sperm analysis

Fenvalerate and cypermethrin were reported to impair male reproductive function, inducing significant reductions in epididymal sperm count. Further, fenvalerate was shown to reduce sperm motility. However, it is not clear whether fenvalerate and cypermethrin might impact sperm motility directly or indirectly by affecting spermatogenesis via interaction with androgens or their receptors. In this study, sperm suspensions were treated with fenvalerate and cypermethrin, respectively, at various concentrations (0, 1, 4, 16, or 64 micromol/L) for various times (1, 2, or 4 h). The motility parameters of sperm treated with these two insecticides were analyzed with a computer-assisted sperm analysis (CASA) system. The differential effects of fenvalerate and cypermethrin on rat sperm motility patterns in vitro were also compared. Our study revealed that fenvalerate and cypermethrin reduced sperm motility in vitro in a concentration- and time-dependent manner. Cypermethrin exerted a greater effect on sperm motility in comparison to fenvalerate. These results provided evidence that fenvalerate and cypermethrin directly influence mature rat sperm motility.

Efficient testing strategies for evaluation of xenobiotics with neuroendocrine activity

Maturation of neuroendocrine regulations is an extremely complex process made up of several stages, that can be permanently affected by any exogenous substances able to interfere with the hormonal signalling at various levels. The Endocrine Disrupting Chemicals (EDCs) are a heterogeneous group of xenobiotics with potential endocrine activities which have been identified as priority risk factors in toxicological research. The present review is aimed at suggesting a number of endocrine and behavioural endpoints to be used in experimental studies to: (i) characterize more thoroughly the functional effects of developmental exposure to agents known to act as endocrine disruptors and (ii) unmask possible interferences with the maturation of the hypothalamus-hypophysis-gonad/thyroid (HHG/Th) axis by different class of xenobiotics not considered as EDCs. A combined testing strategy, considering both markers of endocrine/hormonal maturation and behavioural endpoints under hormonal control in laboratory rodents, may evidence even subtle perturbations of the neuroendocrine homeostasis, that often go undetected.

Effects of permethrin given before mating on the behavior of F1-generation in mice

Permethrin, a type I synthetic pyrethroid insecticide, was evaluated through assessment of the behavioral development of F1 progeny of mice. Groups each of 30 male and 30 female ICR (CD-1) mice, as F0-generation, were given 0, 4.9, 9.8, and 19.6 mg/kg/d permethrin by gavage for 4 weeks before mating. Behavioral endpoints of motor reflexes, motor coordination, and activity were evaluated in F1 progeny. Clinical signs of toxicity including salivation, hyperactivity, and liquid feces which attributed to permethrin were observed in the F0-mice treated with 9.8 and 19.6 mg/kg/d. Reduction of body weight became evident only during gestation and lactation periods for the middle and high dose groups. Significant differences in the development of reflexes, swimming ability, and open field activity were evident in the offspring for the 9.8 and 19.6 mg/kg/d dose groups compared to the control group. These results show that permethrin at dose levels of 9.8 and 19.6 mg/kg/d can induce a significant risk to the offspring following treatment of F0-mice before mating. The NOEL obtained in this study for the effects of permethrin on the development of the F1-progeny is 4.9 mg/kg/d.

Behavioral and endocrine changes induced by perinatal fenvalerate exposure in female rats

Pyrethroid insecticides have recently been linked to endocrine disruption. Endocrine disrupting chemicals have been defined as exogenous agents that interfere with the synthesis, secretion, binding, action, or elimination of natural hormones in the body. Previous research conducted in our laboratory suggests that perinatal exposure to fenvalerate, a type-II pyrethroid, interferes with brain sexual organization in male pups, probably acting on a critical perinatal hormone-related period. In the present study we investigate the effects of maternal exposure to fenvalerate (FV) during the prenatal and postnatal periods of sexual brain organization of female offspring. Behavioral (open-field, stereotyped and sexual behaviors), physical (sexual maturation, body and uterine weights), and neuroendocrine (estrous cycle and gonadal hormone levels ) parameters were assessed. Results show that 1) sexual maturation was delayed, albeit body weight was unchanged until adulthood; 2) there was a reduction in sexual behavior; 3) the estrous cycle was abnormal, and the uterine weight at different phases of the estrous cycle was modified; 4) gonadal hormone levels in the plasma were not affected, neither was stereotypy nor open-field behaviors. These results were attributed to an anti-estrogenic effect of perinatal exposure to FV during the critical periods of female brain sexual organization.

Developmental neurotoxicity of pyrethroid insecticides: critical review and future research needs

Pyrethroid insecticides have been used for more than 40 years and account for 25% of the worldwide insecticide market. Although their acute neurotoxicity to adults has been well characterized, information regarding the potential developmental neurotoxicity of this class of compounds is limited. There is a large age dependence to the acute toxicity of pyrethroids in which neonatal rats are at least an order of magnitude more sensitive than adults to two pyrethroids. There is no information on age-dependent toxicity for most pyrethroids. In the present review we examine the scientific data related to potential for age-dependent and developmental neurotoxicity of pyrethroids. As a basis for understanding this neurotoxicity, we discuss the heterogeneity and ontogeny of voltage-sensitive sodium channels, a primary neuronal target of pyrethroids. We also summarize 22 studies of the developmental neurotoxicity of pyrethroids and review the strengths and limitations of these studies. These studies examined numerous end points, with changes in motor activity and muscarinic acetylcholine receptor density the most common. Many of the developmental neurotoxicity studies suffer from inadequate study design, problematic statistical analyses, use of formulated products, and/or inadequate controls. These factors confound interpretation of results. To better understand the potential for developmental exposure to pyrethroids to cause neurotoxicity, additional, well-designed and well-executed developmental neurotoxicity studies are needed. These studies should employ state-of-the-science methods to promote a greater understanding of the mode of action of pyrethroids in the developing nervous system.

Product studies and laser flash photolysis of direct and 2,4,6-triphenylpyrylium-zeolite Y photocatalyzed degradation of fenvalerate

Direct irradiation of fenvalerate (FV) in aqueous solution (4 x 10(-3) M) gives rise to 2,3-diarylisohexanitrile through the homolytic CO-CH(i-Pr) bond cleavage, followed by a rapid decarboxylation of the primary carbonyloxy radical, and radical recombination. The unusual exclusive formation of the cross combination product suggests that the persistent free radical effect is operative in this system and controls product formation. Spectroscopic evidence of the intermediacy of benzylic radicals decaying in microsecond time scale has been obtained by laser flash photolysis. These studies also reveal a remarkable attenuation of radical reactivity toward oxygen resulting from cyano substitution at the radical center. TPY photocatalyzed degradation of FV also leads to decarboxylation products accompanied by oxidative mineralization (38%). The TPY-photocatalyzed degradation can occur through two operating mechanisms involving the generation of OH(*) radicals and/or FV(*+) radical cations. Evidence for the latter intermediate has been obtained by laser flash photolysis in acetonitrile solution (detection of TP(*) radical) and by the quenching by FV of the emission from the TPY solid.

Reproductive effects of deltamethrin on male offspring of rats exposed during pregnancy and lactation

The effects of low doses of deltamethrin administered to female rats on the reproductive system of male offspring were examined. The dams (n=10-12/group) were treated daily by oral gavage with 0, 1.0, 2.0, and 4.0 mg deltamethrin/kg from day 1 of pregnancy to day 21 of lactation. Maternal and reproductive outcome data and male sexual development landmarks were assessed. Fertility, sexual behavior, and a large number of reproductive endpoints, such as organ weights, sperm evaluations, testosterone concentration, and testicular histology were examined on adult male offsprings. No signs of maternal toxicity were detected at the dose levels tested. Significantly adverse effects were only seen on testicular and epididymal absolute weights and the diameter of seminiferous tubules in the group treated with the highest dose of deltamethrin (4.0 mg/kg). The results indicate that in utero and lactational exposure to deltamethrin may induce subtle changes in reproductive behavior and physiology of male offspring rats at dose levels that do not cause maternal toxicity.

Steroidogenic alterations in testes and sera of rats exposed to formulated Fenvalerate by inhalation

Fenvalerate (Fen) is a synthetic pyrethroid, which is commonly used for destroying a variety of insect pests damaging several vegetable, fruit, and cotton crops. This insecticide is also used to mitigate household insects like flies, cockroaches, mosquitoes, and so forth. Human beings are exposed to formulated Fen preparations mostly by inhalation during spraying in fields for crop protection, for control of household insects, and also during handling and packaging at manufacturing plants. Limited online information is available regarding toxic effects of formulated Fen exposure on mammalian reproductive system. The present study has been undertaken to investigate male reproductive toxic effects of a formulated preparation of Fen (20% EC) particularly in relation to steroidogenic alterations in testes and sera of rats exposed by nose-only inhalation for (4 hours/day and five days a week) for three months. The results indicate significant reduction in the weight of testes, epididymal sperm counts, and sperm motility, along with decrease in marker testicular enzymes for testosterone biosynthesis viz. 17-beta-hydroxy steroid dehydrogenase (17-beta-HSD) and glucose-6-phosphate dehydrogenase (G6PDH), leading to net decrease in serum testosterone concentration in group of rats exposed to one-fifth LC50 of Fen (20% EC) by inhalation (4 hours/day, five days a week) subchronically for three months. These results for the first time indicate the role of testosterone in Fen (20% EC)-induced male reproductive toxicity of rats subchronically exposed by inhalation probably due to neuroendocrine-mediated phenomenon and hormone-disrupting property of the insecticide.

Effects of perinatal exposure to flutamide on sex hormones and androgen-dependent organs in F1 male rats

Flutamide, which has antiandrogenic properties, was administered to pregnant rats, and effects on male offspring were examined. Crj: CD (SD) IGS (SPF) females were administered flutamide (0.15, 0.6, 2.5, 10.0, 100 mg/kg, p.o.) from gestation Day 14 to post parturition Day 3. The number of pups, body weights, clinical features, anogenital distance (AGD), nipple retention, testicular descent, and urogenital malformation in F1 males were examined. Hormone measurement, necropsy and histopathological examination were carried out at post-neonatal Day 4 (PND 4) and PND 60. Sperm analysis was also carried out at PND 60. Decrease in body weight was seen in the 100 mg/kg group and the AGD was decreased at 2.5 mg/kg and above. Retention of nipples, hypospadia, vaginal pouches, penis malformation, unilateral ectopic testis, and decrease of organ weights (prostate, seminal vesicles, levator ani muscle plus bulbocavernosus muscle, testis) were observed at 10 mg/kg and above. Testicular testosterone (T) was increased significantly with 100 mg/kg at PND 4 and tendencies for increase were observed in serum T, LH and FSH at 10 mg/kg and more at the same time point. In contrast, elevated levels of LH and FSH were seen with 100 mg/kg at PND 60. Histopathological examination revealed defects or hypoplastic changes of genital organs (> or = 10 mg/kg), squamous metaplasia (10 mg/kg) or mucification (100 mg/kg) of the urethral diverticulum epithelium and inflammation of genital organs (100 mg/kg). Though only undescended testes lacked spermatogenesis at 10 mg/kg, atrophic change of seminiferous tubules and azoospermia were observed in the 100 mg/kg group, despite testicular descent. Perinatal administration of flutamide affected F1 male rats at 2.5 mg/kg and above. In addition to urogenital malformation, 100 mg/kg flutamide caused high LH and FSH levels at PND 60. This study indicates that the most sensitive parameter is AGD, whereby reduction was observed at 2.5 mg/kg. A clear no-effect level (NOEL: 0.6 mg/kg) was obtained in this perinatal study of an antiandrogenic chemical.

Effects of prenatal exposure to deltamethrin on forced swimming behavior, motor activity, and striatal dopamine levels in male and female rats

The effects of prenatal exposure of rat pups to 0.08 mg/kg deltamethrin (DTM) on physical, reflex and behavioral developmental parameters, on forced swimming and open-field behaviors, and on striatal monoamine levels at 60 days of age were observed. Maternal and offspring body weight, physical and reflex development were unaffected by the exposure to the pesticide. At 21 days of age, open-field locomotion frequency and immobility duration of male and female offspring were not different between control and exposed animals. However, male rearing frequency was increased in experimental animals. A decreased immobility latency to float and in general activity after the swimming test in male offspring was observed at adult age; no interference was detected in the float duration during the swimming test. In addition, these animals presented higher striatal 3,4-dihydroxyphenylacetic acid (DOPAC) levels without modification in dopamine (DA) levels and an increased DOPAC/DA ratio. These data indicate a higher activity of the dopaminergic system in these animals. Noradrenaline (NA) levels were increased, while MHPG levels were not detectable in the system studied. Serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) levels, as well as the homovanillic acid (HVA)/DA ratio, were not modified by the exposure to the pesticide. No changes were observed in swimming and open-field behaviors nor were there any changes in striatal monoamines or their metabolites in the female experimental group. In relation to the pesticide formula, the present data showing that prenatal exposure to DTM alters latency to float and the activity of striatal dopaminergic system might reflect a persistent effect of the pesticide on animal motor activity, mainly in males. On the other hand, the decrease in general activity observed in experimental male rats suggests higher levels of emotionality induced by previous exposure to the swimming behavior test in relation to control animals. Data gathered in the present study may be important for the assessment of the safety of pyrethroid insecticides.