An assessment of the developmental, reproductive, and neurotoxicity of endosulfan

Endosulfan induces reproductive & genotoxic effect in male and female Swiss albino mice

BACKGROUND

Toxicity by pesticide has become a global health issue and leaves a harmful impact on human health via various ways. The people exposed to pesticides in the rural population get affected by the harmful effects of it as they enter the human body system through skin, inhalation, oral administration, food chain and many more ways. The present work is designed to study the toxic effect of endosulfan in male (n=30) and female (n=30) Swiss albino mice. Endosulfan was administered by oral gavage (oral administration) method, at the dose of 3.5 mg/Kg body weight daily for period of 3 weeks, 5 weeks and 7 weeks. After the completion of the treatment, the mice were sacrificed and their ovary and testis tissues were dissected out to check the degeneration. The blood was collected for karyotyping, biochemical and hormonal analysis of pesticide induced genotoxicity. After 7 weeks of administration with Endosulfan, various abnormalities were observed in male and female mice.

RESULTS

Treatment with endosulfan at the dose of 3.5 mg/Kg body weight caused a higher degree of degeneration in the reproductive organ of Swiss albino mice . Treatment by this pesticide generated degeneration in long duration of dosage for 3,5 and 7 weeks. Ovaries of endosulfan administered groups showed degenerated germinal epithelium, Graffian follicles and corpus luteum. In testis of endosulfan treated mice, microscopic examination showed that there is significant damage and reduction in the tissue of seminiferous tubules and primordial germ cells. High degree of degeneration caused the disarrangement and deformation of spermatogonia with the decrease in the number of Sertoli cells. Biochemical and hormonal properties was also affected by endosulfan treatment. There was significant 5 folds decrease in the testosterone value of endosulfan in 7 weeks treated mice in comparison to control (p < 0.0001) and similarly there was significant elevation in the estrogen levels found in 7th week endosulfan treated mice. It also influenced the level of free radicals as there was significant decrease (p < 0.0001) in the value in catalase levels in 7 weeks endosulfan treated male and female mice, while significant (p < 0.0001) increase in the values of lipid peroxidation levels as 8 folds and 10 folds in 7 weeks endosulfan treated male and female Swiss albino mice respectively. This study hence speculates that the endosulfan exposed population are at the risk of reproductive health hazards.

CONCLUSIONS

The present study thus concludes that, endosulfan after 7 weeks of exposure caused significant reproductive damage to both male and female Swiss albino mice groups. Moreover, the karyotyping study also correlated the genotoxic damage in the mice.

Investigating open access new approach methods (NAM) to assess biological points of departure: A case study with 4 neurotoxic pesticides

Open access new approach methods (NAM) in the US EPA ToxCast program and NTP Integrated Chemical Environment (ICE) were used to investigate activities of four neurotoxic pesticides: endosulfan, fipronil, propyzamide and carbaryl. Concordance of in vivo regulatory points of departure (POD) adjusted for interspecies extrapolation (AdjPOD) to modelled human Administered Equivalent Dose (AEDHuman) was assessed using 3-compartment or Adult/Fetal PBTK in vitro to in vivo extrapolation. Model inputs were from Tier 1 (High throughput transcriptomics: HTTr, high throughput phenotypic profiling: HTPP) and Tier 2 (single target: ToxCast) assays. HTTr identified gene expression signatures associated with potential neurotoxicity for endosulfan, propyzamide and carbaryl in non-neuronal MCF-7 and HepaRG cells. The HTPP assay in U-2 OS cells detected potent effects on DNA endpoints for endosulfan and carbaryl, and mitochondria with fipronil (propyzamide was inactive). The most potent ToxCast assays were concordant with specific components of each chemical mode of action (MOA). Predictive adult IVIVE models produced fold differences (FD) < 10 between the AEDHuman and the measured in vivo AdjPOD. The 3-compartment model was concordant (i.e., smallest FD) for endosulfan, fipronil and carbaryl, and PBTK was concordant for propyzamide. The most potent AEDHuman predictions for each chemical showed HTTr, HTPP and ToxCast were mainly concordant with in vivo AdjPODs but assays were less concordant with MOAs. This was likely due to the cell types used for testing and/or lack of metabolic capabilities and pathways available in vivo. The Fetal PBTK model had larger FDs than adult models and was less predictive overall.

Pesticides exposure in pregnant Argentinian women: Potential relations with the residence areas and the anthropometric neonate parameters

Intrauterine environment is the first chemical exposure scenario in life, through transplacental transfer. In this study, the aim was to determine concentrations of organochlorine pesticides (OCPs) and selected current use pesticides in the placentas of pregnant women from Argentina. Socio-demographic information, the mother's lifestyle and neonatal characteristics were also analysed and related to pesticides residue concentrations. Thus, 85 placentas were collected at birth, from an area of intensive fruit production for the international market, in Patagonia Argentina. Concentrations of 23 pesticides including, trifluralin (herbicide), the fungicides chlorothalonil and HCB, and the insecticides chlorpyrifos, HCHs, endosulfans, DDTs, chlordanes, heptachlors, drins and metoxichlor, were determined by GC-ECD and GC-MS. Results were first analysed all together and then grouped by their residential settings, in urban and rural groups. Total mean pesticide concentration was 582.6 ± 1034.4 ng/g lw, where DDTs (325.9 ± 950.3 ng/g lw) and chlorpyrifos (188.4 ± 365.4 ng/g lw) showed a high contribution. Pesticide levels found exceeded those reported in low, middle and high income countries from Europe, Asia and Africa. In general, pesticides concentrations were not associated with neonatal anthropometric parameters. When the results were analysed by residence place, significantly higher concentrations of total pesticides and chlorpyrifos (Mann Whitney test p = 0.0003 and p = 0.032, respectively) were observed in placentas collected from mothers living in rural settings compared to urban areas. Rural pregnant women presented the highest pesticide burden (5.9 μg), where DDTs and chlorpyrifos were the major constituents. These results suggested that all pregnant women are highly exposed to complex pesticide mixtures, including banned OCPs and the widely used chlorpyrifos. Based on the pesticide concentrations found, our results warn of possible health impacts from prenatal exposure through transplacental transfer. This is one of the first reports of both chlorpyrifos and chlorothalonil concentrations in placental tissue, and contributes to the knowledge of current pesticide exposure in Argentina.

Protective Effects of Black Tea (<i>Camellia sinensis</i>) Extract on Endosulfan Induced Oxidative Stress, Inflammation and Hepatic Damage in Rats

With the agricultural expansion the use of pesticides is increasing rapidly in developing countries. Endosulfan, an organochlorine insecticide, is a broadspectrum effective compound used in wide variety of agricultural crops but known to generate free radicals in the liver and caused hepatotoxicity. Thus, we considered it necessary to explore the protective effect of black tea extract against endusulfan mediated hepatotoxicity. 18 male albino Wistar rats were divided into 3 groups: Control, endosulfan treated (5mg/kg body weight/day) and endosulfan+black tea extract treated (1ml of 2.5gm%/100gm of body weight/day). After 30 days of treatment period, all the animals were sacrificed, and blood and liver tissue were collected. Serum and tissue cholesterol, serum liver function parameters, liver oxidative stress parameters and serum proinflammatory cytokines were measured. Liver sections were stained with haematoxylene and eosine and histological evaluation was done. Results revealed that endusulfan induces oxidative stress in liver by altering oxidant/antioxidant balance, and causes inflammation resulting into hepatic damage. Black tea extract supplementation shows considerable protection against endosulfan mediated changes in liver. Thus, black tea extract exerts ameliorative effect against endosulfan mediated liver toxicity.

Endocrine disruptors also function as nervous disruptors and can be renamed endocrine and nervous disruptors (ENDs)

Endocrine disruption (ED) and endocrine disruptors (EDs) emerged as scientific concepts in 1995, after numerous chemical pollutants were found to be responsible for reproductive dysfunction. The World Health Organization established in the United Nations Environment Programme a list of materials, plasticizers, pesticides, and various pollutants synthesized from petrochemistry that impact not only reproduction, but also hormonal functions, directly or indirectly. Cells communicate via either chemical or electrical signals transmitted within the endocrine or nervous systems. To investigate whether hormone disruptors may also interfere directly or indirectly with the development or functioning of the nervous system through either a neuroendocrine or a more general mechanism, we examined the scientific literature to ascertain the effects of EDs on the nervous system, specifically in the categories of neurotoxicity, cognition, and behaviour. To date, we demonstrated that all of the 177 EDs identified internationally by WHO are known to have an impact on the nervous system. Furthermore, the precise mechanisms underlying this neurodisruption have also been established. It was previously believed that EDs primarily function via the thyroid. However, this study presents substantial evidence that approximately 80 % of EDs operate via other mechanisms. It thus outlines a novel concept: EDs are also neurodisruptors (NDs) and can be collectively termed endocrine and nervous disruptors (ENDs). Most of ENDs are derived from petroleum residues, and their various mechanisms of action are similar to those of "spam" in electronic communications technologies. Therefore, ENDs can be considered as an instance of spam in a biological context.

Effect of environmental toxicants on neuronal functions

In the last few years, neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) have attracted attention due to their high prevalence worldwide. Environmental factors may be one of the biggest reasons for these diseases related to neuronal dysfunctions. Most of neuronal disorders are strongly associated with pre- and postnatal exposure to environmental toxins released from industries. Some of the neurotoxic metals such as lead, aluminum, mercury, manganese, cadmium, and arsenic as well as some pesticides and metal-based nanoparticles have been involved in AD and PD due to their ability to produce senile/amyloid plaques and NFTs which are the main feature of these neuronal dysfunctions. Exposure to solvents is also majorly responsible for neurodegenerative disorders. The present review highlights the impact of omnipresent heavy metals with some other neurotoxins on human health and how they give rise to neuronal dysfunctions which in turn causes socio-economic consequences due to increasing pollution worldwide. Graphical abstract.

Postnatal exposure to endosulfan affects uterine development and fertility

Endosulfan is an organochlorine pesticide (OCP) used in large-scale agriculture for controlling a variety of insects and mites that attack food and non-food crops. Although endosulfan has been listed in the Stockholm Convention as a persistent organic pollutant to be worldwide banned, it is still in use in some countries. Like other OCPs, endosulfan is bioaccumulative, toxic and persistent in the environment. Human unintentional exposure may occur through air inhalation, dietary, skin contact, as well as, via transplacental route and breast feeding. Due to its lipophilic nature, endosulfan is rapidly absorbed into the gastrointestinal tract and bioaccumulates in the fatty tissues. Similar to other OCPs, endosulfan has been classified as an endocrine disrupting chemical (EDC). Endocrine action of endosulfan on development and reproductive function of males has been extensively discussed; however, endosulfan effects on the female reproductive tract have received less attention. This review provides an overview of: i) the fate and levels of endosulfan in the environment and human population, ii) the potential estrogenic properties of endosulfan in vitro and in vivo, iii) its effects on uterine development, and iv) the long-term effects on female fertility and uterine functional differentiation during early gestation.

Mechanistic Interplay Between Autophagy and Apoptotic Signaling in Endosulfan-Induced Dopaminergic Neurotoxicity: Relevance to the Adverse Outcome Pathway in Pesticide Neurotoxicity

Chronic exposure to pesticides is implicated in the etiopathogenesis of Parkinson's disease (PD). Previously, we showed that dieldrin induces dopaminergic neurotoxicity by activating a cascade of apoptotic signaling pathways in experimental models of PD. Here, we systematically investigated endosulfan's effect on the interplay between apoptosis and autophagy in dopaminergic neuronal cell models of PD. Exposing N27 dopaminergic neuronal cells to endosulfan rapidly induced autophagy, indicated by an increased number of autophagosomes and LC3-II accumulation. Prolonged endosulfan exposure (>9 h) triggered apoptotic signaling, including caspase-2 and -3 activation and protein kinase C delta (PKCδ) proteolytic activation, ultimately leading to cell death, thus demonstrating that autophagy precedes apoptosis during endosulfan neurotoxicity. Furthermore, inhibiting autophagy with wortmannin, a phosphoinositide 3-kinase inhibitor, potentiated endosulfan-induced apoptosis, suggesting that autophagy is an early protective response against endosulfan. Additionally, Beclin-1, a major regulator of autophagy, was cleaved during the initiation of apoptotic cell death, and the cleavage was predominantly mediated by caspase-2. Also, caspase-2 and caspase-3 inhibitors effectively blocked endosulfan-induced apoptotic cell death. CRISPR/Cas9-based stable knockdown of PKCδ significantly attenuated endosulfan-induced caspase-3 activation, indicating that the kinase serves as a regulatory switch for apoptosis. Additional studies in primary mesencephalic neuronal cultures confirmed endosulfan's effect on autophagy and neuronal degeneration. Collectively, our results demonstrate that a functional interplay between autophagy and apoptosis dictate pesticide-induced neurodegenerative processes in dopaminergic neuronal cells. Our study provides insight into cell death mechanisms in environmentally linked neurodegenerative diseases.

Combination of fluoride and endosulfan induced teratogenicity and developmental toxicity in Swiss albino mice exposed during organogenesis

The present investigation was conducted to evaluate the teratogenic and developmental toxicity of fluoride and endosulfan alone and in combination in pregnant Swiss albino mice exposed during the organogenetic period (5-14 days) of gestation. Fluoride (25.1 mg/kg body weight in water) and endosulfan (1.8 mg/kg bw by oral intubation) when administered alone and in combination (fluoride 25.1 mg/kg bw + endosulfan 1.8 mg/kg bw) to pregnant mice caused significant teratogenic effects in developing fetuses. There was no maternal mortality but significant decreases in maternal weight gain and numbers of live fetuses and significant increases in numbers of fetal resorption were recorded in the treated groups. The fetal body weight and litter size also decreased significantly in all treated groups. No external malformations were observed in any of the fetuses. The percent of visceral and skeletal anomalies increased in the fetuses of all treated groups. The fetal malformations observed were internal hydrocephaly, microphthalmia, anophthalmia, pulmonary edema, subcutaneous edema, reduced ossification of skull bones, widened cranial sutures, rib anomalies (short, wavy, partially ossified, or absent ribs), and reduced ossification of phalanges. The occurrence of visceral and skeletal malformations was more severe in the combination group, suggesting additive interaction of fluoride and endosulfan in inducing developmental toxicity in Swiss albino mice.

Neurotoxicity of pesticides

Pesticides are unique environmental contaminants that are specifically introduced into the environment to control pests, often by killing them. Although pesticide application serves many important purposes, including protection against crop loss and against vector-borne diseases, there are significant concerns over the potential toxic effects of pesticides to non-target organisms, including humans. In many cases, the molecular target of a pesticide is shared by non-target species, leading to the potential for untoward effects. Here, we review the history of pesticide usage and the neurotoxicity of selected classes of pesticides, including insecticides, herbicides, and fungicides, to humans and experimental animals. Specific emphasis is given to linkages between exposure to pesticides and risk of neurological disease and dysfunction in humans coupled with mechanistic findings in humans and animal models. Finally, we discuss emerging techniques and strategies to improve translation from animal models to humans.

Effect of neonatal exposure to endosulfan on myometrial adaptation during early pregnancy and labor in rats

Proper myometrial adaptation during gestation is crucial for embryo implantation, pregnancy maintenance and parturition. Previously, we reported that neonatal exposure to endosulfan alters uterine development and induces implantation failures. The present work investigates the effects of endosulfan exposure on myometrial differentiation at the pre-implantation period, and myometrial activation during labor. Newborn female rats were s.c. injected with corn oil (vehicle) or 600 μg/kg/day of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5 and 7. On PND90, the rats were mated to evaluate: i) the myometrial differentiation on gestational day 5 (GD5, pre-implantation period), by assessment myometrial histomorphology, smooth muscle cells (SMCs) proliferation, and expression of proteins involved in myometrial adaptation for embryo implantation (steroid receptors, Wnt7a and Hoxa10); ii) the timing of parturition and myometrial activation during labor by determining the uterine expression of contraction-associated genes (oxytocin receptor, OTXR; prostaglandin F₂α receptor, PTGFR and connexin-43, Cx-43). Endosulfan decreased the thickness of both myometrial layers, with a concomitant decrease in the collagen remodeling. Blood vessels relative area in the interstitial connective tissue between muscle layers was also decreased. Endo600 group showed lower myometrial proliferation in association with a downregulation of Wnt7a and Hoxa10. Although in all females labor occurred on GD23, the exposure to endosulfan altered the timing of parturition, by inducing advancement in the initiation of labor. This alteration was associated with an increased uterine expression of OTXR, PTGFR and Cx-43. In conclusion, neonatal exposure to endosulfan produced long-term effects affecting myometrial adaptation during early pregnancy and labor. These alterations could be associated with the aberrant effects of endosulfan on the implantation process and the timing of parturition.

Relationship between geosorbent properties and field-based partition coefficients for pesticides in surface water and sediments of selected agrarian catchments: Implications for risk assessment

Studies on pesticide behavior, adsorption-likelihood, and bioavailability vis-a-vis geosorbent properties and seasons, are critical for understanding pesticide-fate and risks in pesticide-prone environments. We examined the relationship between geosorbent profiles of sediments (percentage sand, silt, clay, organic carbon content) across seasons and occurrence of pesticide residues in surface water and sediment of agricultural catchments at Owan, Ogbesse and Illushi communities of Edo State, Nigeria. Pesticide concentrations were measured monthly in samples of surface water and sediments across the selected sites for 18-months. Pesticide behavior and sorption-likelihoods were examined using partition coefficients K_d (sediment-water coefficient), K_oc (sediment-water coefficient normalized for organic carbon) and Log K_ow (octane-water coefficient); the relationship between K_d and K_oc was also examined. Results of the principal component analysis (PCA) indicated that pesticide levels in sediment and surface water were positively associated with the rainy season, total organic content (TOC), percentage silt and clay in sediment. Field-derived pesticide partition coefficients (K_d < 100 and log K_oc < 3) indicated that pesticide species were largely mobile and less likely to be retained in sediments by adsorption. As such, pesticides irrespective of solubility would end up in surface water, increasing risks for pelagic biota and humans sourcing river water for domestic use. Values of Log K_ow indicate that organochlorines including DDT, dieldrin, endrin and heptachlor epoxide portend significant bioaccumulation risks to humans and biota across sites. The relationship between K_d and K_oc for each site fitted into a quadratic model; it depicted a biphasic behavior of pesticide adsorption and desorption to sediments revealing that concentration of organic carbon across study sites was a limiting factor determining the extent of pesticide adsorption. This study demonstrates that understanding pesticide mobility using field-based partition coefficients could give a clearer picture of pesticide risks to biota and human populations.

Uterine ERα epigenetic modifications are induced by the endocrine disruptor endosulfan in female rats with impaired fertility

High ERα activity may disrupt the window of uterine receptivity, causing defective implantation. We investigated whether implantation failures prompted by endosulfan are associated with aberrant ERα uterine expression and DNA methylation status during the pre-implantation period. ERα-dependent target genes that play a crucial role in the uterine receptivity for embryo attachment and implantation were also investigated. Newborn female rats received corn oil (vehicle, Control), 6 μg/kg/d of endosulfan (Endo6) or 600 μg/kg/d of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5, and 7. On PND90, females were made pregnant and on gestational day 5 (GD5, pre-implantation period) uterine samples were collected. ERα expression was assessed at protein and mRNA levels by immunohistochemistry and real time RT-PCR, respectively. ERα transcript variants mRNA containing alternative 5'-untranslated regions (5'UTRs) were also evaluated. We searched for predicted transcription factors binding sites in ERα regulatory regions and assessed their methylation status by Methylation-Sensitive Restriction Enzymes-PCR technique (MSRE-PCR). The expression of the ERα-dependent uterine target genes, i.e. mucin-1 (MUC-1), insulin-like growth factor-1 (IGF-1), and leukemia inhibitory factor (LIF), was assessed by real time RT-PCR. Both doses of endosulfan increased the expression of ERα and its transcript variants ERα-OS, ERα-O, ERα-OT and ERα-E1. Moreover, a decreased DNA methylation levels were detected in some ERα regulatory regions, suggesting an epigenetic up-regulation of it transcription. ERα overexpression was associated with an induction of its downstream genes, MUC-1 and IGF-1, suggesting that endosulfan might alter the uterine estrogenic pathway compromising uterine receptivity. These alterations could account, at least in part, for the endosulfan-induced implantation failures.

Alteration of membrane integrity and respiratory function of brain mitochondria in the rats chronically exposed to a low dose of acetamiprid

The pesticides are used in several fields of agriculture and farms to protect crops against harmful insects and herbs. The increased and uncontrolled use of these pollutants is very hazardous for the population health. Consumption of contaminated food matrices with these pesticides could impair the cell integrity and its molecular function. The main aim of this present study was to evaluate the alteration of the integrity of mitochondrial membranes and respiratory chain potential in the brain of rats exposed during 90 days to acetamiprid (AC), organochlorine of the new generation. After oral administration of AC in rats with 3.14 mg/kg of body weight, the results of this current study showed enhance in mitochondrial oxidative stress status by significant decrease of glutathione (GSH) level, glutathione pyroxidase (GPx), and catalase (CAT) activities. On the other hand, there is an increase in the enzymatic activity of the glutathione s-transferase (GST) and superoxide dismutase (SOD); at the same time, the MDA level was also highly increased. Furthermore, evaluation results of brain mitochondrial integrity revealed a significant increase in membrane permeability and mitochondrial swelling in rats exposed chronically to AC. Instead, other results of this present work showed a significant decrease in mitochondrial respiration potent (O₂ consumption) in acetamiprid-treated rats. In conclusion, the long duration exposition of the animals to AC has led to respiratory chain dysfunction, disturbance of matrix oxidative status, and a loss of mitochondrial membranes integrity.

Induction of DNA damage and erroneous repair can explain genomic instability caused by endosulfan

Endosulfan (ES) is an organochlorine pesticide, speculated to be associated with chromosomal abnormalities and diseases in humans. However, very little is known about the mechanism of its genotoxicity. Using in vivo, ex vivo and in vitro model systems, we show that exposure to ES induces reactive oxygen species (ROS) in a concentration and time-dependent manner. The generation of ROS results in DNA double-strand breaks either directly or in a replication-dependent manner, both in mice and human cells. Importantly, ES-induced DNA damage evokes DNA damage response, resulting in elevated levels of classical non-homologous DNA endjoining (NHEJ), the predominant double-strand break repair pathway in higher eukaryotes. Sequence analyses of NHEJ junctions revealed that ES treatment results in extensive processing of broken DNA, culminating in increased and long junctional deletions, thereby favoring erroneous repair. We also find that exposure to ES leads to significant increase in microhomology-mediated end joining (MMEJ), a LIGASE III-dependent alternative repair pathway. Therefore, we demonstrate that ES induces DNA damage and genomic instability, alters DNA damage response thereby promoting erroneous DNA repair.

Isomers and their metabolites of endosulfan induced cytotoxicity and oxidative damage in SH-SY5Y cells

As an organochlorine insecticide, endosulfan has been widely banned or restricted, but it is still largely used in many developing countries. Previous studies have shown multiple adverse health effects of endosulfan. However, the neurotoxicity of endosulfan has not been fully elucidated. In this study, endosulfan isomers (α-/β-endosulfan) and their major metabolites (endosulfan sulfate, endosulfan diol, and endosulfan lactone) were, respectively, exposed to human neuroblastoma SH-SY5Y cells. Results showed that both α-endosulfan and β-endosulfan caused decrease of cell viability and morphological damages in a dose-dependent manner. Their median effective concentrations (EC50s) were respectively 79.6 μM (α-endosulfan) and 50.37 μM (β-endosulfan) for 72 h exposure. EC50s of α/β-endosulfan mixture were lower than that of the single isomer. However, EC50s of its metabolites were higher than that of technical endosulfan. Endosulfan and its metabolites caused increases of reactive oxygen species and the lipid peroxidation, but decrease of superoxide dismutase in a dose-dependent manner. These results indicate that α-endosulfan exhibits higher neurotoxicity than β-endosulfan. Mixture of endosulfan isomers shows stronger cytotoxicity than the single isomer. After endosulfan is degraded, cytotoxicity of its metabolites decreases gradually. The neurotoxicity of endosulfan and its metabolites is closely related to oxidative damage and antioxidative deficit.

Protective effects of testosterone propionate on reproductive toxicity caused by Endosulfan in male mice

To investigate the protective effect of testosterone propionate (TP) on reproductive toxicity caused by endosulfan in male mice, three group experiments were designed: the control group received 0 and 0, the endosulfan group received 0.8 and 0, and the endosulfan + TP group received 0.8 mg/kg/d endosulfan and 10 mg/kg/d TP, respectively. The results showed that TP significantly prevented the declines of concentration and motility rates in sperm, reduced the rate of sperm abnormalities in epididymis; and antagonized the decreases in spermatogenous cell and sperm numbers in testes induced by endosulfan. TP also decreased the numbers of cavities formed, prevented the decreases of plasma testosterone and androgen receptor (AR) mRNA in testicular tissue, alleviated the increase of LH induced by endosulfan. It is likely that TP relieve the reproductive toxicity by reversing the endosulfan-induced decreases in testosterone secretion and AR expression that resulted from the alteration of Leydig cell function.

Integrative genomic and proteomic profiling of human neuroblastoma SH-SY5Y cells reveals signatures of endosulfan exposure

Endosulfan, an organochlorine pesticide, is known to induce multiple disorders/abnormalities including neuro-degenerative disorders in many animal species. However, the molecular mechanism of endosulfan induced neuronal alterations is still not well understood. In the present study, the effect of sub-lethal concentration of endosulfan (3 μM) on human neuroblastoma cells (SH-SY5Y) was investigated using genomic and proteomic approaches. Microarray and 2D-PAGE followed by MALDI-TOF-MS analysis revealed differential expression of 831 transcripts and 16 proteins in exposed cells. A gene ontology enrichment analysis revealed that the differentially expressed genes and proteins were involved in variety of cellular events such as neuronal developmental pathway, immune response, cell differentiation, apoptosis, transmission of nerve impulse, axonogenesis, etc. The present study attempted to explore the possible molecular mechanism of endosulfan induced neuronal alterations in SH-SY5Y cells using an integrated genomic and proteomic approach. Based on the gene and protein profile possible mechanisms underlying endosulfan neurotoxicity were predicted.

Ionotropic GABA receptor antagonism-induced adverse outcome pathways for potential neurotoxicity biomarkers

Antagonism of ionotropic GABA receptors (iGABARs) can occur at three distinct types of receptor binding sites causing chemically induced epileptic seizures. Here we review three adverse outcome pathways, each characterized by a specific molecular initiating event where an antagonist competitively binds to active sites, negatively modulates allosteric sites or noncompetitively blocks ion channel on the iGABAR. This leads to decreased chloride conductance, followed by depolarization of affected neurons, epilepsy-related death and ultimately decreased population. Supporting evidence for causal linkages from the molecular to population levels is presented and differential sensitivity to iGABAR antagonists in different GABA receptors and organisms discussed. Adverse outcome pathways are poised to become important tools for linking mechanism-based biomarkers to regulated outcomes in next-generation risk assessment.

Studies of pesticide residues in tomatoes and cucumbers from Kazakhstan and the associated health risks

The aim of the present study was to assess the level of pesticide residues in vegetables in the Almaty Region of Kazakhstan and to determine the potential health risks associated with the exposures to these pesticides. A total of 82 samples of cucumbers and tomatoes from top agro-based market and greenhouses were analysed using a gas chromatography-micro electron capture detector/nitrogen-phosphorous detector (GC-μECD/NPD), a multiresidue method to analyse 184 different pesticide types. The results indicated that more than half of samples (59 %) contained 29 pesticides, in which 10 are not registered in Kazakhstan, ranging from 0.01 to 0.88 mg kg(-1), and 28 % contained pesticide residues above maximum residue levels (MRLs). The estimated daily intakes (EDIs) ranged from 0.01 % of the acceptable daily intake (ADI) for pyrimethanil to 12.05 % of the ADI for lambda-cyhalothrin. The most critical commodity is triazophos and flusilazole in tomatoes, contributing 70.8 and 42.5 % to the acute hazard index (aHI). The results provided important information on the current pesticide contamination status of two commonly consumed vegetables and pointed an urgent need to control the use of plant protection products applied, especially potentially persistent pesticides, such as endosulfan and dicofol. These results also show that the detected pesticides may be considered a public health problem.

A Comparison of ToxCast Test Results with In Vivo and Other In Vitro Endpoints for Neuro, Endocrine, and Developmental Toxicities: A Case Study Using Endosulfan and Methidathion

INTRODUCTION

The U.S. Environmental Protection Agency's (EPA's) Toxicity Forecaster (ToxCast) is a potential tool for chemical prioritization, hazard identification, and risk assessment. We conducted a case study to compare ToxCast data with endpoints from other in vitro and in vivo studies for two data-rich pesticides: endosulfan and methidathion.

METHODS

ToxCast assays for endocrine disruption, development (zebrafish), and neurotoxicity were qualitatively compared to traditional neurotoxicity, developmental and reproductive toxicity findings. We also used in vitro-in vivo extrapolation to convert half-maximal activity concentrations in active ToxCast assays to rat oral equivalent doses, and quantitatively compared these to the lowest observable effect level (LOEL) from in vivo studies.

RESULTS

Endosulfan was inactive for GABAA R, unlike in vivo; but active with dopamine transporter assays and was neurotoxic in zebrafish as expected. Methidathion was not active for these endpoints in vivo or in vitro. Acetylcholinesterase inhibition was ToxCast-inactive, although both pesticides are inhibitors in vivo. ToxCast results were generally inactive for endosulfan estrogen receptor agonism and androgen receptor antagonism unlike in vivo. Calculated oral equivalent doses for estrogen receptor and androgen receptor pathways and for zebrafish assays for both compounds were generally consistent with in vivo LOELs. Endosulfan showed neurotoxicity and both pesticides showed developmental effects in the zebrafish assays, although methidathion is not developmentally toxic in vivo.

CONCLUSIONS

ToxCast's predictions showed concordance on some endpoints and nonconcordance, consisting mainly of false inactives, in several critical endpoints, likely due to a lack of metabolic activation and limitations in assay design. Zebrafish assays were good predictors of developmental toxicity and neurotoxicity for endosulfan.

Oxidative stress and brain mitochondria swelling induced by endosulfan and protective role of quercetin in rat

The neurological damages resulted by endosulfan poisoning is not completely elucidated, especially in cellular organelles such as mitochondria. In the present study, the pro-oxidant effect of endosulfan on brain mitochondria was first investigated. Gavages of endosulfan into rats at the dose of 2 mg/kg induced oxidative stress in this organelle since it provokes a significant reduction of catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) level. In addition, a significant increase in mitochondria swelling and malondialdehyde (MDA) levels were observed in neuronal mitochondria, indicating clearly an intense peroxidation within mitochondria. Second, the protective effect of quercetin (QE) (10 mg/kg) against endosulfan-induced oxidative stress in mitochondria was also assessed. Indeed, the pretreatment of rats with QE protects brain mitochondria from oxidative stress, lipid peroxidation, and mitochondria swelling induced by endosulfan. The activities of antioxidant enzymes and the mitochondrial content of GSH and MDA were returned to control values. Thus, although endosulfan can have neurotoxic effects in brain rats, this toxicity can be prevented by quercetin.

Reproductive Toxicity of Endosulfan: Implication From Germ Cell Apoptosis Modulated by Mitochondrial Dysfunction and Genotoxic Response Genes in Caenorhabditis elegans

Endosulfan as a new member of persistent organic pollutants has been shown to induce reproductive dysfunction in various animal models. However, the action mechanism of endosulfan-produced reproductive toxicity remains largely unknown. This study was focused on investigating the reproductive toxicity induced by α-endosulfan and clarifying the role of mitochondria and genotoxic response genes in germ cell apoptosis of Caenorhabditis elegans. Our data showed that endosulfan induced a dose-dependent decrease of life span, fecundity, and hatchability, whereas the germ cell apoptosis was dose-dependently increased. The mitochondria membrane potential was disrupted by endosulfan, leading to a significant increase of germ cell apoptosis in mev-1(kn-1) mutant. However, the apoptotic effects of endosulfan were blocked in mutants of cep-1(w40), egl-1(n487), and hus-1(op241), indicating conserved genotoxic response genes played an essential role in endosulfan-induced germ cell apoptosis. Furthermore, exposure to endosulfan induced the accumulation of HUS-1::GFP foci and the germ cell cycle arrest. These findings provided clear evidence that endosulfan caused significant adverse effects on the reproduction system of C. elegans and increased germ cell apoptosis, which was regulated by mitochondrial dysfunction and DNA damage response genes. This study may help to understand the signal transduction pathways involved in endosulfan-induced reproductive toxicity.

Neonatal exposure to low doses of endosulfan induces implantation failure and disrupts uterine functional differentiation at the pre-implantation period in rats

We investigated whether neonatal exposure to low doses of endosulfan affects fertility and uterine functional differentiation at pre-implantation in rats. Newborn female rats received the vehicle, 0.2 µg/kg/d of diethylstilbestrol (DES), 6 µg/kg/d of endosulfan (Endo6) or 600 µg/kg/d of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5, and 7. On PND90, the rats were mated to evaluate their reproductive performance on gestational day (GD) 19 and their ovarian steroid serum levels, endometrial proliferation and implantation-associated proteins on GD5. DES and endosulfan decreased the pregnancy rate and the number of implantation sites. On GD5, DES and endosulfan did not change the serum levels of 17β-estradiol (E2) and progesterone (P); the endometrial proliferation decreased, which was associated with silencing of Hoxa10 in the Endo600-treated rats. Both doses of endosulfan increased the progesterone receptor (PR) expression, whereas the higher dose led additionally to an increase in estrogen receptor alpha (ERα). In the Endo600-treated rats, the down-regulation of Hoxa10 was associated with a deregulation of the steroid receptor coregulators. Alterations in endometrial proliferation and the endocrine pathway of Hoxa10/steroid receptors/coregulators might be the mechanism of endosulfan-induced implantation failure.

Prediction of embryotoxic potential using the ReProGlo stem cell-based Wnt reporter assay

The ReProGlo assay was developed in 2009 to predict embryotoxic potential of drugs and chemicals by use of a stem cell-based in vitro system. It utilizes a luciferase reporter to detect drug-induced alterations in the canonical Wnt/β-catenin signaling pathway, which is involved in regulation of early embryonic development. It allows the simultaneous determination of cell viability and luciferase reporter activity in a high throughput format. The present study was conducted within the framework of the EU ChemScreen-project. It (1) enlarges the original number of test-compounds from 17 to now 80, (2) introduces a new classification scheme and (3) anchors the results against a prediction scheme based on structural features of chemicals. The assay is applicable as stand-alone for priority setting or in a test battery.

Endosulfan induces COX-2 expression via NADPH oxidase and the ROS, MAPK, and Akt pathways

Endosulfan (1,4,5,6,7,7-hexachloro-8,9,10-trinorborn-5-en-2,3-ylenebismet-hylene) is correlated with endocrine disruption, reproductive, and immune dysfunctions. Recently, endosulfan was shown to have an effect on inflammatory pathways, but its influence on cyclooxygenase-2(COX-2) expression is unclear. This study investigated the effects of COX-2 and molecular mechanisms by endosulfan in murine macrophage RAW 264.7 cells. Endosulfan significantly induced COX-2 protein and mRNA levels, as well as COX-2 promoter-driven luciferase activity and the production of prostaglandin E2, a major COX-2 metabolite. Transfection experiments with several human COX-2 promoter constructs revealed that endosulfan activated NF-κB, C/EBP, AP-1, and CREB. Moreover, Akt and mitogen-activated protein kinases (MAPK) were significantly activated by endosulfan. Moreover, endosulfan increased production of the ROS and the ROS-producing NAPDH-oxidase (NOX) family oxidases, NOX2, and NOX3. Endosulfan-induced Akt/MAPK pathways and COX-2 expression were attenuated by DPI, a specific NOX inhibitor, and the ROS scavenger N-acetylcysteine. These results demonstrate that endosulfan induces COX-2 expression via NADPH oxidase, ROS, and Akt/MAPK pathways. These findings provide further insight into the signal transduction pathways involved in the inflammatory effects of endosulfan.

Aberrant cerebellar neurotrophin-3 expression induced by lipopolysaccharide exposure during brain development

Autism is a developmental disorder affecting communication, social interaction, motor skills, and cerebellar structure and functions. Recent studies have indicated that maternal infection during brain development may be one of the risk factors for autism. We have previously demonstrated the abnormal overexpression of neurotrophin-3 (NT-3) in autistic cerebellum. To examine further the potential link between autism and maternal infection, and specifically NT-3 expression in the cerebellum, we used maternal lipopolysaccharide (LPS)-exposed rat model of infection. In group 1, pregnant female rats were exposed to 200 μg/kg body weight LPS delivered subcutaneously from gestational days (G) 10 to G15, and pups were exposed to LPS from postnatal days (P) 5 to P10, whereas in group 2, pups were exposed to the same dose of LPS from P5 to P10. There was no change in body mass of pups and mothers following LPS treatment. Cerebellar NT-3 levels were examined by enzyme-linked immunosorbent assay on P6, P12, and P21. We report here that cerebellar NT-3 levels were elevated in pups of both LPS groups as compared to the controls on P21. Our results suggest that altered neurotrophin levels may affect normal brain development and contribute to autistic pathology.

Evaluation of an alternative in vitro test battery for detecting reproductive toxicants

The application of alternative methods in developmental and reproductive toxicology is challenging in view of the complexity of mechanisms involved. A battery of complementary test systems may provide a better prediction of developmental and reproductive toxicity than single assays. We tested twelve compounds with varying mechanisms of toxic action in an assay battery including 24 CALUX transcriptional activation assays, mouse cardiac embryonic stem cell test, ReProGlo assay, zebrafish embryotoxicity assay, and two CYP17 and two CYP19 activity assays. The battery correctly detected 11/12 compounds tested, with one false negative occurring, which could be explained by the absence of the specific mechanism of action of this compound in the battery. Toxicokinetic modeling revealed that toxic concentrations were in the range expected from in vivo reproductive toxicity data. This study illustrates added value of combining assays that contain complementary biological processes and mechanisms, increasing predictive value of the battery over individual assays.

Specific metabolic fingerprint of a dietary exposure to a very low dose of endosulfan

Like other persistent organochlorine pesticides, endosulfan residues have been detected in foods including fruit, vegetables, and fish. The aim of our study was to assess the impact of a dietary exposure to low doses of endosulfan from foetal development until adult age on metabolic homeostasis in mice and to identify biomarkers of exposure using an ¹H-NMR-based metabonomic approach in various tissues and biofluids. We report in both genders an increase in plasma glucose as well as changes in levels of factors involved in the regulation of liver oxidative stress, confirming the prooxidant activities of this compound. Some metabolic changes were distinct in males and females. For example in plasma, a decrease in lipid LDL and choline content was only observed in female. Lactate levels in males were significantly increased. In conclusion, our results show that metabolic changes in liver could be linked to the onset of pathologies like diabetes and insulin resistance. Moreover from our results it appears that the NMR-based metabonomic approach could be useful for the characterization in plasma of a dietary exposure to low dose of pesticide in human.

Pesticide exposure in children

Pesticides are a collective term for a wide array of chemicals intended to kill unwanted insects, plants, molds, and rodents. Food, water, and treatment in the home, yard, and school are all potential sources of children's exposure. Exposures to pesticides may be overt or subacute, and effects range from acute to chronic toxicity. In 2008, pesticides were the ninth most common substance reported to poison control centers, and approximately 45% of all reports of pesticide poisoning were for children. Organophosphate and carbamate poisoning are perhaps the most widely known acute poisoning syndromes, can be diagnosed by depressed red blood cell cholinesterase levels, and have available antidotal therapy. However, numerous other pesticides that may cause acute toxicity, such as pyrethroid and neonicotinoid insecticides, herbicides, fungicides, and rodenticides, also have specific toxic effects; recognition of these effects may help identify acute exposures. Evidence is increasingly emerging about chronic health implications from both acute and chronic exposure. A growing body of epidemiological evidence demonstrates associations between parental use of pesticides, particularly insecticides, with acute lymphocytic leukemia and brain tumors. Prenatal, household, and occupational exposures (maternal and paternal) appear to be the largest risks. Prospective cohort studies link early-life exposure to organophosphates and organochlorine pesticides (primarily DDT) with adverse effects on neurodevelopment and behavior. Among the findings associated with increased pesticide levels are poorer mental development by using the Bayley index and increased scores on measures assessing pervasive developmental disorder, inattention, and attention-deficit/hyperactivity disorder. Related animal toxicology studies provide supportive biological plausibility for these findings. Additional data suggest that there may also be an association between parental pesticide use and adverse birth outcomes including physical birth defects, low birth weight, and fetal death, although the data are less robust than for cancer and neurodevelopmental effects. Children's exposures to pesticides should be limited as much as possible.

Organochlorine pesticide, endosulfan induced cellular and organismal response in Drosophila melanogaster

The effect of endosulfan (0.02-2.0μgmL(-1)) to Drosophila melanogaster (Oregon R(+)) at the cellular and organismal levels was examined. Third instar larvae of D. melanogaster and the strains transgenic for hsp70, hsp83 and hsp26 were exposed to endosulfan through food for 12-48h to examine the heat shock proteins (hsps), reactive oxygen species (ROS) generation, anti-oxidant stress markers and xenobiotic metabolism enzymes. We observed a concentration- and time-dependent significant induction of only small hsps (hsp23>hsp22) in the exposed organism in concurrence with a significant induction of ROS generation, oxidative stress and xenobiotic metabolism markers. Sub-organismal response was to be propagated towards organismal response, i.e., delay in the emergence of flies and decreased locomotor behaviour. Organisms with diminished locomotion also exhibited significantly lowered acetylcholinesterase activity. A significant positive correlation observed among ROS generation and different cellular endpoints (small hsps, oxidative stress markers, cytochrome P450 activities) in the exposed organism indicate a modulatory role of ROS in endosulfan-mediated cellular toxicity. The study thus suggests that the adverse effects of endosulfan in exposed Drosophila are manifested both at cellular and organismal levels and recommends Drosophila as an alternative animal model for screening the risk caused by environmental chemicals.

Lethal Neurotoxicity Induced by Endosulfan Ingestion

Endosulfan is a highly toxic agricultural pesticide that has been banned in many countries due to its significant neurotoxicity and environmental persistence. Accidental or intentional ingestion by humans induces severe neurological symptoms, which frequently culminate in coma or death. Forensic evaluation of suspected endosulfan toxicity cases can be challenging, given that endosulfan residue may not be detectable in the blood or tissues at the time of death. As such, evaluation of the case history in the context of the reported literature becomes extremely important. Although acute endosulfan toxicity in adults has been well documented, pediatric cases are rare within the literature. Here we present the case of a toddler who accidentally ingested an unknown quantity of endosulfan from an unmarked water bottle on his family farm. The child developed rapid-onset neurological symptoms, including vomiting and seizures, followed by coma. Despite medical intervention, the child was eventually pronounced brain dead and taken off life support. Autopsy revealed massive cerebral edema and its sequelae (sutural diastasis, pituitary necrosis, and dural venous thromboses), and pulmonary thromboemboli. Endosulfan was detected in the bottle from which the child drank. As endosulfan was not detectable in postmortem blood, the cause of death was certified based upon the totality of available information including history, consistency of the case history with the clinical presentation, and the autopsy findings.

Protection by an antioxidant of rotenone-induced neuromotor decline, reactive oxygen species generation and cellular stress in mouse brain

Exposure to environmental toxins, including rotenone, results in central nervous system and systemic toxicity. Rotenone is a widely used pesticide and a mitochondrial complex I (CI) inhibitor. This study reports effectiveness of a synthetic lipoylcarnitine antioxidant compound, lipoylcarnitine methyl ester iodide (PMX-500F), for treatment of chronic rotenone induced neurological deficits in mice. Mice (C57BL/6NTac; two months of age) received oral administration of rotenone (30 mg/kg/day) or vehicle, preceded by intraperitoneal injection of PMX-500F (19 mg/kg) or vehicle for four weeks. In the Rota-rod test, rotenone treatment had no effect (P>0.05); however, PMX-500F treatment improved locomotor coordination and endurance (latency to fall time; P<0.05). For neuromuscular strength (wire hang test), rotenone treated mice showed reduced latency to fall compared to control mice (P<0.05). PMX-500F treatment improved the outcome in both control and rotenone exposed mice (P<0.05). Rotenone administration increased ROS generation in the forebrain and midbrain regions, but not in the cerebellum (P<0.05). Co-treatment with PMX-500F normalized the ROS in forebrain and midbrain regions to that of the control concentrations. In rotenone administered mice, activated stress-activated protein kinase/c-Jun NH2-terminal kinase (pSAPK/JNK) was higher in forebrain and midbrain lysates than in control mice (P<0.05) and treatment with PMX-500F reduced pSAPK/JNK to control levels. The pSAPK/JNK levels in the cerebellum were similar in all four groups (P>0.05). Total SAPK/JNK was not altered by either rotenone or PMX-500F treatment (P>0.05). These results illustrate that an antioxidant, here PMX-500F, provides protection against rotenone induced decline in neuromotor function, reactive oxygen species (ROS) generation and cellular stress.

DDT and Other Chlorinated Insecticides

The use of organochlorine insecticides such as DDT, lindane and cyclodieneshas declined markedly worldwide over the last decades. Most are now banned or not used. At an acute toxicity level they have been relatively safe in use for humans. However, the greatest concerns are their persistence in people, wildlife and the environment due to their slow metabolism. Although their carcinogenicity for humans has not been supported by strong epidemiological evidence, their potential to be modulators of endocrine and immune function at levels remaining in the environment or associated with residual spraying of DDT continue to be of concern. At present, DDT is still allowed by the United Nations for combating malaria, with continual monitoring and assessment where possible. The toxicological consequences of exposure of animals and people to DDT is discussed as well as some analogues and other insecticides such as lindane, dieldrin and chlordecone that, although little used, continue to persist in surroundings and people. Because of circumstances of world health brought about by climate change or human activities that have yet to develop, there may come a time when the importance of some may re-emerge.

Transcriptome analysis provides insights for understanding the adverse effects of endosulfan in Drosophila melanogaster

Indiscriminate use of agrochemicals worldwide, particularly, persistent organic pollutants (POPs), is of concern. Endosulfan, a POP, is used by various developing/developed nations and is known to adversely affect the development and the hormonal profiles of humans and animals. However, little is known about the molecular players/pathways underlying the adverse effects of endosulfan. We therefore analyzed the global gene expression changes and subsequent adverse effects of endosulfan using Drosophila. We used Drosophila melanogaster keeping in view of its well annotated genome and the wealth of genetic/molecular reagents available for this model organism. We exposed third instar larvae of D. melanogaster to endosulfan (2.0 μg mL(-1)) for 24 h and using microarray, we identified differential expression of 256 genes in exposed organisms compared to controls. These genes are associated with cellular processes such as development, stress and immune response and metabolism. Microarray results were validated through quantitative PCR and biochemical assay on a subset of genes/proteins. Taking cues from microarray data, we analyzed the effect of endosulfan on development, emergence and survival of the organism. In exposed organisms, we observed deformities in hind-legs, reminiscent of those observed in higher organisms exposed to endosulfan. In addition, we observed delayed and/or reduced emergence in exposed organisms when compared to their respective controls. Together, our studies not only highlight the adverse effects of endosulfan on the organism but also provide an insight into the possible genetic perturbations underlying these effects, which might have potential implications to higher organisms.

Human health risk assessment of endosulfan. I: Toxicology and hazard identification

Endosulfan is persistent in the environment and toxic to wildlife. Legal mandates necessitate that a risk assessments be performed for endosulfan by the California Department of Pesticide Regulation (CDPR) and the United States Environmental Protection Agency (USEPA). This hazard identification (hazard ID) compared critical no-observed effect levels (NOEL) for acute, subchronic and chronic exposure intervals between the agencies. NOELs were discussed in light of their application to numerous exposure scenarios (occupational, general population and dietary). Only the acute oral NOELs differed between CDPR (0.7 mg/kg/day) and USEPA (1.5 mg/kg/day). Pregnant rabbits were considered by CDPR to be more responsive to low gavage doses of endosulfan than non-pregnant female or male rats in the acute study selected by USEPA. NOELs for other exposure routes and durations were similar between agencies. CDPR and USEPA concurred that a Food Quality Protection Act (FQPA, 1996) Safety Factor is not needed after evaluating all studies including a Developmental Neurotoxicity study. The SF was reduced to 1x. NOELs generated from this hazard ID will be used to calculate the Margins of Exposure for all scenarios and subsequently the risk characterization for endosulfan.