Oestradiol potentiates the effects of certain pyrethroid compounds in the MCF7 human breast carcinoma cell line

GPR39-mediated ERK1/2 signaling reduces permethrin-induced proliferation of estrogen receptor α-negative cells

Certain insecticides are known to have estrogenic effects by activating estrogen receptors through genomic transcription. This has led researchers to associate specific insecticide use with an increased breast cancer risk. However, it is unclear if estrogen receptor-dependent pathways are the only way in which these compounds induce carcinogenic effects. The objective of this study was to determine the impact of the pyrethroid insecticide permethrin on the growth of estrogen receptor negative breast cancer cells MDA-MB-231. Using tandem mass spectrometric techniques, the effect of permethrin on cellular protein expression was investigated, and gene ontology and pathway function enrichment analyses were performed on the deregulated proteins. Finally, molecular docking simulations of permethrin with the candidate target protein was performed and the functionality of the protein was confirmed through gene knockdown experiments. Our findings demonstrate that exposure to 10-40 μM permethrin for 48 h enhanced cell proliferation and cell cycle progression in MDA-MB-231. We observed deregulated expression in 83 upregulated proteins and 34 downregulated proteins due to permethrin exposure. These deregulated proteins are primarily linked to transmembrane signaling and chemical carcinogenesis. Molecular docking simulations revealed that the overexpressed transmembrane signaling protein, G protein-coupled receptor 39 (GPR39), has the potential to bind to permethrin. Knockdown of GPR39 partially impeded permethrin-induced cellular proliferation and altered the expression of proliferation marker protein PCNA and cell cycle-associated protein cyclin D1 via the ERK1/2 signaling pathway. These findings offer novel evidence for permethrin as an environmental breast cancer risk factor, displaying its potential to impact breast cancer cell proliferation via an estrogen receptor-independent pathway.

Comparative analysis of two methodological approaches to the study of endocrine disruptor alpha-cypermethrin reproductive toxicity

At present, one of the main threats to humanity is undoubtedly endocrine disruptors (ED), since they directly disrupt the processes of ensuring homeostasis, which are identical to the very essence of the concept of health, considered in valeology as the ability to maintain age-appropriate stability in conditions of sharp changes in quantitative and qualitative parameters of the triune flow of sensory, verbal and structural information. Pesticides can disrupt the physiological functioning of many endocrine chains, including the endocrine mechanisms that ensure reproductive health. The study aimed to compare the results of our studies of alpha-cypermethrin reproductive toxicity in the test system for studying gonadotoxic activity with data obtained in the test system "Three Generation Reproduction Study". The studies were performed on male and female Wistar Han rats with two generic samples of alpha-cypermethrin from different manufacturers at doses of 0.2, 1.0 and 3.0 mg/kg body weight. The exposure lasted 11 (males) and 10 (females) weeks. During the last two weeks of exposure the state of the estrous cycle, duration and frequency of each stage in females was studied. After the end of treatment functional parameters of the state of the gonads in males and the ability of animals to reproduce were examined. In males, the total sperm count, the absolute and relative number of motile germ cells, and the number of pathologically altered forms were evaluated. The results of the study showed that exposure of male and female Wistar Han rats to alpha-cypermethrin at doses of 0.2–3.0 mg/kg during gametogenesis had a toxic effect on the reproductive system characterized by impaired gonadal and reproductive functions. In our studies, alpha-cypermethrin was found to have reproductive toxicity (reduced number of corpora luteum and live fetuses, increased absolute and relative postimplantation death, reduced average weight of fetuses and litters) and endocrine-disruptive effect, having a pronounced antiandrogenic effect on males. Obvious signs of endocrine reproductive disorders (changes in testis and epididymis weight, deterioration in semen parameters, altered length of separate stages of the estrous cycle) were observed in both females and males. However, studies in a test system of three-generations did not reveal a reproductive and endocrine-disruptive effect of cypermethrin, the toxicity of which was recognized as equivalent to the toxicity of alpha-cypermethrin. The obtained results showed higher sensitivity, informative and diagnostic significance of the methods for studying gonadotoxicity than the methodology of reproductive toxicity studies in the test system “Three Generation Reproduction Study”.

Assessment of genotoxicity of pyrethrin in cultured human lymphocytes

Pyrethrin is an insecticide that is obtained from the Chrysanthemum flower (Pyrethrum). In this study, we examined the genotoxic effects of pyrethrin on cultured human lymphocytes using sister chromatid exchanges (SCEs) and 8-hydroxy deoxyguanosine (8-OHdG) assays. Cultures were treated with different concentrations of pyrethrin (25, 50, and 100 μg/mL), which was dissolved in in dimethyl sulfoxide (DMSO). The results showed that treatment of cultured lymphocytes with pyrethrin at 50 μg/mL and 100 μg/mL induced significant elevation in SCEs (p < 0.05). In addition, the 100 μg/mL concentration significantly affected both mitotic and proliferative indices (p < 0.05). Finally, pyrethrin induced significant elevation in the oxidative stress marker 8-OHdG in a dose-dependent manner (p < 0.001). In conclusion, the results suggest that pyrethrin is genotoxic as measured by two independent assays on genetic toxicity.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead

Low-dose exposures to common environmental chemicals that are deemed safe individually may be combining to instigate carcinogenesis, thereby contributing to the incidence of cancer. This risk may be overlooked by current regulatory practices and needs to be vigorously investigated.

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety ‘Mode of Action’ framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.

Cancer incidence among pesticide applicators exposed to permethrin in the Agricultural Health Study

BACKGROUND

Permethrin is a synthetic pyrethroid insecticide widely used in agriculture, in public health, and in many U.S. homes and gardens.

OBJECTIVE

In this study we evaluated the incidence of cancer among pesticide applicators exposed to permethrin in the Agricultural Health Study (AHS).

METHODS

A total of 49,093 pesticide applicators were included in this analysis of the AHS, a prospective cohort study of licensed pesticide applicators in Iowa and North Carolina. Detailed information on pesticide exposure and lifestyle factors was obtained from self-administered questionnaires completed in 1993-1997. Average length of follow-up since applicator enrollment in the cohort was 9.14 years. We used two permethrin exposure metrics: a) lifetime days applicators personally mixed or applied permethrin and b) intensity-weighted lifetime days (lifetime days weighted by estimated intensity of exposure). We used Poisson regression analysis to estimate relative risks (RRs) and 95% confidence intervals (CIs) for malignancies by tertiles of exposure.

RESULTS

We found no associations between permethrin and all malignant neoplasms combined, or between permethrin and melanoma, non-Hodgkin lymphoma, leukemia, or cancers of the colon, rectum, lung, or prostate. We found elevated and statistically significant risks for multiple myeloma in the highest tertiles of both lifetime exposure-days (RR = 5.72; 95% CI, 2.76-11.87) and intensity-weighted lifetime exposure-days (RR = 5.01; 95% CI, 2.41-10.42), compared with applicators reporting they never used permethrin; these results are based on only 15 exposed cases. These findings were similar across a variety of alternative exposure metrics, exposure categories, and reference groups.

CONCLUSIONS

This study found no association with most cancers analyzed. Although the suggested association with multiple myeloma was based on a small number of cases, it warrants further evaluation.

The in vitro genotoxic effects of a commercial formulation of alpha-cypermethrin in human peripheral blood lymphocytes

alpha-Cypermethrin, a highly active pyrethroid insecticide, is effective against a wide range of insects encountered in agriculture and animal husbandry. The potential genotoxicity of a commercial formulation of alpha-cypermethrin (Fastac 100 EC, containing 10% alpha-cypermethrin as the active ingredient) on human peripheral lymphocytes was examined in vitro by sister chromatid exchange (SCE), chromosomal aberrations (CAs), and micronucleus (MN) tests. The human lymphocytes were treated with 5, 10, 15, and 20 microg/ml of alpha-cypermethrin for 24- and 48-hr. alpha-Cypermethrin induced SCEs and CAs significantly at all concentrations and treatment times and MN formation was significantly induced at 5 and 10 microg/ml of alpha-cypermethrin when compared with both the control and solvent control. Binuclear cells could not be detected sufficiently in the highest two concentration of alpha-cypermethrin (15 and 20 microg/ml) for both the 24- and 48-hr treatment times. alpha-Cypermethrin decreased the proliferation index (PI) at three high concentrations (10, 15, and 20 microg/ml) for both treatment periods as compared with the control groups. In addition, alpha-cypermethrin reduced both the mitotic index (MI) and nuclear division index (NDI) significantly at all concentrations for two treatment periods. The PI and MI were reduced by alpha-cypermethrin in a concentration-dependent manner during both treatment times. In general, alpha-cypermethrin showed higher cytotoxic and cytostatic effects than positive control (MMC) at the two highest concentrations for the 24- and 48-hr treatment periods. The present study is the first to report the genotoxic and cytotoxic effects of commercial formulation of alpha-cypermethrin in peripheral blood lymphocytes.

The attribution of urban and suburban children's exposure to synthetic pyrethroid insecticides: a longitudinal assessment

Despite the widespread use of synthetic pyrethroid insecticides that led to common exposure in the population, very few studies have been conducted to quantitatively assess human, particularly, children's, long-term exposures to pyrethroid insecticides. The objective of the Children Pesticide Exposure Study - Washington (CPES-WA) was to establish the longitudinal exposure profiles for pyrethroid insecticides in a cohort of children living in an urban and suburban community using urinary pyrethroid metabolites as exposure biomarkers. The results from this analysis will allow us to examine potential risk factors in relation to the elevated pyrethroid insecticide exposure in children. A total of 23 children, aged 3-11 years, who only consumed conventional diets were enrolled in this 1-year study. We provided organic food items to children for 5 consecutive days in the summer and fall sampling seasons. We measured urinary metabolites for the synthetic pyrethroid insecticides in urine samples that were collected twice daily during each of the four sampling seasons. 3-phenoxybenzoic acid was frequently detected in the urine samples with mean and median daily volume-weighted average levels of 1.5 and 1.2 microg/l, followed by trans-2,2-(dichloro)-2-dimethylvinylcyclopropane carboxylic acid (1.4 and 1.0 microg/l) and cis-2,2-(dichloro)-2-dimethylvinylcyclopropane carboxylic acid (0.5 microg/l, and non-detected). When we took into account season, age, sex, diet, and self-reported residential use of pyrethroid insecticides in a linear mixed-effects model, the results suggested that the combination of the use of pyrethroid insecticides in the household, dietary intake, and seasonal differences play a significant role in predicting children's exposure to synthetic pyrethroid insecticides. We found CPES-WA children were continuously exposed to pyrethroid insecticides through their diets all year long, and this chronic exposure pattern was periodically modified by episodes of relatively high exposures from residential uses. Future research should be devoted to enhancing our understanding of the complexity of pyrethroid insecticide exposure patterns.

High-throughput automated luminescent magnetic particle-based immunoassay to monitor human exposure to pyrethroid insecticides

We have developed a sensitive, automated, competitive chemiluminescent immunoassay for the detection of 3-phenoxybenzoic acid (3-PBA), a metabolite common to many pyrethroid insecticides. The system uses a competitive hapten-protein conjugate that has been labeled with an acridinium ester as the chemiluminescent probe and secondary antibody-coated paramagnetic particles for the separation. After the immunoassay reagents and samples are combined for the competitive incubation step, a fully automated system is used to load the postincubation mixture into a delivery cuvette, facilitating the subsequent magnetic separation of the immunocomplex and the measurement of chemiluminescent signal for quantification. The immunoassay format described here supports the requirement for high throughput necessary for monitoring large numbers of samples in population-based studies. The optimized immunoassay was more sensitive than the conventional enzyme immunoassay in buffer (IC(50) = 0.1 and 2 microg/L, respectively). The mixed-mode solid-phase extraction used for sample preparation to reduce possible urinary matrix effects allowed the accurate measurement of 3-PBA levels as low as 1 microg/L. The automated chemiluminescent immunoassay described here is sensitive, simple to use, and more rapid than the previously reported standard microplate assay.

A longitudinal approach to assessing urban and suburban children's exposure to pyrethroid pesticides

We conducted a longitudinal study to assess the exposure of 23 elementary school-age children to pyrethroid pesticides, using urinary pyrethroid metabolites as exposure biomarkers. We substituted most of the children's conventional diets with organic food items for 5 consecutive days and collected two daily spot urine samples, first morning and before bedtime voids, throughout the 15-day study period. We analyzed urine samples for five common pyrethroid metabolites. We found an association between the parents' self-reported pyrethroid use in the residential environment and elevated pyrethroid metabolite levels found in their children's urine. Children were also exposed to pyrethroids through their conventional diets, although the magnitude was smaller than for the residential exposure. Children's ages appear to be significantly associated with pyrethroids exposure, which is likely attributed to the use of pyrethroids around the premises or in the facilities where older children engaged in the outdoor activities. We conclude that residential pesticide use represents the most important risk factor for children's exposure to pyrethroid insecticides. Because of the wide use of pyrethroids in the United States, the findings of this study are important for both children's pesticide exposure assessment and environmental public health.