Effects of bifenthrin on sex differentiation in Japanese Medaka (Oryzias latipes)

A systematic review of the evaluation of endocrine-disrupting chemicals in the Japanese medaka (Oryzias latipes) fish

Japanese medaka (Oryzias latipes) is an acceptable small laboratory fish model for the evaluation and assessment of endocrine-disrupting chemicals (EDCs) found in the environment. In this research, we used this fish as a potential tool for the identification of EDCs that have a significant impact on human health. We conducted an electronic search in PubMed (http://www.ncbi.nlm.nih.gov/pubmed) and Google Scholar (https://scholar.google.com/) using the search terms, Japanese medaka, Oryzias latipes, and endocrine disruptions, and sorted 205 articles consisting of 128 chemicals that showed potential effects on estrogen-androgen-thyroid-steroidogenesis (EATS) pathways of Japanese medaka. From these chemicals, 14 compounds, namely, 17β-estradiol (E2), ethinylestradiol (EE2), tamoxifen (TAM), 11-ketotestosterone (11-KT), 17β-trenbolone (TRB), flutamide (FLU), vinclozolin (VIN), triiodothyronine (T3), perfluorooctanoic acid (PFOA), tetrabromobisphenol A (TBBPA), terephthalic acid (TPA), trifloxystrobin (TRF), ketoconazole (KTC), and prochloraz (PCZ), were selected as references and used for the identification of apical endpoints within the EATS modalities. Among these endpoints, during classification, priorities are given to sex reversal (masculinization of females and feminization of males), gonad histology (testis-ova or ovotestis), secondary sex characteristics (anal fin papillae of males), plasma and liver vitellogenin (VTG) contents in males, swim bladder inflation during larval development, hepatic vitellogenin (vtg) and choriogenin (chg) genes in the liver of males, and several genes, including estrogen-androgen-thyroid receptors in the hypothalamus-pituitary-gonad/thyroid axis (HPG/T). After reviewing 205 articles, we identified 108 (52.68%), 46 (22.43%), 19 (9.26%), 22 (17.18%), and 26 (12.68%) papers that represented studies on estrogen endocrine disruptors (EEDs), androgen endocrine disruptors (AEDs), thyroid endocrine disruptors (TEDs), and/or steroidogenesis modulators (MOS), respectively. Most importantly, among 128 EDCs, 32 (25%), 22 (17.18%), 15 (11.8%), and 14 (10.93%) chemicals were classified as EEDs, AEDs, TEDs, and MOS, respectively. We also identified 43 (33.59%) chemicals as high-priority candidates for tier 2 tests, and 13 chemicals (10.15%) show enough potential to be considered EDCs without any further tier-based studies. Although our literature search was unable to identify the EATS targets of 45 chemicals (35%) studied in 60 (29.26%) of the 205 articles, our approach has sufficient potential to further move the laboratory-based research data on Japanese medaka for applications in regulatory risk assessments in humans.

Accounting for transgenerational effects of toxicant exposure in population models alters the predicted long-term population status

Acute environmental stressors such as short-term exposure to pollutants can have lasting effects on organisms, potentially impacting future generations. Parental exposure to toxicants can result in changes to the epigenome (e.g., DNA methylation) that are passed down to subsequent, unexposed generations. However, it is difficult to gauge the cumulative population-scale impacts of epigenetic effects from laboratory experiments alone. Here, we developed a size- and age-structured delay-coordinate population model to evaluate the long-term consequences of epigenetic modifications on population sustainability. The model emulated changes in growth, mortality, and fecundity in the F0, F1, and F2 generations observed in experiments in which larval Menidia beryllina were exposed to environmentally relevant concentrations of bifenthrin (Bif), ethinylestradiol (EE2), levonorgestrel (LV), or trenbolone (TB) in the parent generation (F0) and reared in clean water up to the F2 generation. Our analysis suggests potentially dramatic population-level effects of repeated, chronic exposures of early-life stage fish that are not captured by models not accounting for those effects. Simulated exposures led to substantial declines in population abundance (LV and Bif) or near-extinction (EE2 and TB) with the exact trajectory and timeline of population decline dependent on the combination of F0, F1, and F2 effects produced by each compound. Even acute one-time exposures of each compound led to declines and recovery over multiple years due to lagged epigenetic effects. These results demonstrate the potential for environmentally relevant concentrations of commonly used compounds to impact the population dynamics and sustainability of an ecologically relevant species and model organism.

Pyrethroid bioaccumulation in wild fish linked to geographic distribution and feeding habit

The accumulation of pyrethroid insecticides in aquatic food webs has attracted increased research attention. Fish are key species in aquatic food webs, directly connecting invertebrates and human consumption. However, little is known about the bioaccumulation of pyrethroids in wild fish species. In this study, 19 species of wild fish were collected from 11 sites in the Pearl River, China, and the levels of seven pyrethroids in the fish were determined. Linear mixed-effects models were applied to estimate the means of pyrethroid concentrations, in which sample site and fish species were set as random effects. The concentrations of Σ₇ pyrethroids in fish ranged from 4.99 to 50.82 ng/g. Permethrin and bifenthrin were present at the highest concentration (8.89 ± 1.47 ng/g) and frequency (100%) in fish muscle, respectively. The composition patterns of pyrethroids varied in fish organs. Fish species contributed a higher proportion of the variance than geographic distribution (28.6% vs. 26.4%). The pyrethroids in carnivorous fish (23.5 ± 2.9 ng/g) were significantly higher than in omnivorous (14.6 ± 1.9 ng/g) and phytophagous fish (16.0 ± 4.7 ng/g). To our knowledge, this is the first report examining the effect of feeding habits on pyrethroid bioaccumulation in wild fish. The results can provide evidence for the risk of pyrethroid pollution in aquatic ecosystems.

Stage Dependent Enantioselective Metabolism of Bifenthrin in Embryos of Zebrafish (Danio rerio) and Japanese Medaka (Oryzias latipes)

Bifenthrin (BF) is a widely used pyrethroid that has been frequently detected in surface waters. Previous studies indicated that BF had antiestrogenic activity in zebrafish embryos but estrogenic activity in posthatch fish. To determine whether age-related differences in metabolism contribute to the endocrine effects in developing fish, embryos from zebrafish and Japanese medaka were exposed to BF before and after liver development. Since the commercial mixture of BF is an isomer-enriched product containing two enantiomers (1R-cis-BF and 1S-cis-BF), enantioselective metabolism was also evaluated. The estrogenic metabolite, 4-hydroxybifenthrin (4-OH-BF) was identified in zebrafish embryos, and formation was higher in animals after liver development (>48 hpf). Treatments with β-glucuronidase indicated that 4-OH-BF underwent conjugation in embryos. Formation was reduced by cotreatment of the cytochrome P450 (CYP450) inhibitor, ketoconazole. Formation of 4-OH-BF was greater when treated with 1R-cis-BF compared to the S-enantiomer. However, metabolites were not observed in medaka embryos. These data indicate enantioselective oxidation of BF to an estrogenic metabolite occurs in zebrafish embryos and, since it is increased after liver development, may partially explain estrogenic activity observed in older animals. The lack of activity in medaka suggests species-specific effects with BF metabolism and may influence risk assessment strategies in wildlife.

Influence of bifentrin, a pyrethriod pesticide, on human colorectal HCT-116 cells attributed to alterations in oxidative stress involving mitochondrial apoptotic processes

The widespread use of pesticides is beneficial for food production; however, there are numerous adverse consequences reported in the ecosystem and humans associated with exposure to these contaminants. The pyrethriod bifenthrin (BIF) is utilized for (1) maintenance, growth, and storage of agricultural products; (2) control of internal and external parasites of farm animals; and (3) eradication of insects threatening public health. Numerous data are available regarding environmental and ecological impact of pyrethriods on the central and peripheral nervous systems; however few studies focused on non-target tissues especially in humans. Therefore, the aim of this investigation was to determine the potential cytotoxic effects of BIF on a non-target tissue using human colorectal HCT-116 cells as a model. Data demonstrated that BIF reduced cell viability and disrupted mitochondrial functions which were accompanied by increased reactive oxygen species (ROS) levels indicating the presence of oxidative stress. BIF produced a significant elevation in levels of malondialdehyde (MDA) supporting the role of oxidative stress in pesticide-mediated toxicity. Concomitantly, a fall of mitochondrial transmembrane potential (Δψ), consequently producing perturbation of fluidity as well as excitability of cellular membranes was noted. Our results also indicated that BIF induced a rise in DNA damage as evidenced by the comet assay. An increase in mitogen-activated protein kinases (MAPKs), JNK (N-terminal Kinase), p38, and ERK (extracellular-signal-regulated kinase) suggested an apoptotic effect. Data thus indicated that BIF-induced cytotoxicity in human colorectal HCT-116 cells was associated with oxidative stress, mitochondrial dysfunction, and apoptosis.

Method validation for bifenthrin emulsifiable concentrate and uncertainty calculation using gas chromatographic approach

Background

Bifenthrin is the third-generation synthetic pyrethroid insecticide having an effective control on the pest of cotton, vegetable, and fruits. This study is focused on the validation of the test procedure for the quantitative determination of bifenthrin contents in the emulsifiable concentrate and measurement of uncertainty. The purpose of this validation procedure is to demonstrate that it is suitable for the intended use. This was determined by gas chromatography with a flame ionization detector (FID). The estimation was carried out on Shimadzu GC equipped with TRB-5 (95% dimethyl, 5% diphenyl polysiloxane) column using a nitrogen carrier gas.

Results

Different parameters of validation (precision, accuracy, linearity, specificity, selectivity, and robustness) were executed. All steps of method validation were performed, and its uncertainty is determined. The method is simple, selective, accurate, precise, cost-effective, and suitable. The validation parameters are based on harmonized guidelines on the validation of the analytical test method.

Conclusions

Pesticide formulation bodies can use this method for the qualitative and quantitative determination of bifenthrin different formulations. These data verify that the method is validated, and all results are in an acceptable limit. The method is developed on GC. Moreover, the analysis time is also short as compared to that of HPLC. The developed method is simple reliable and has a realistic approach.