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

Persistent organic pollutants and β-cell toxicity: a comprehensive review

Persistent organic pollutants (POPs) are a diverse family of contaminants that show widespread global dispersion and bioaccumulation. Humans are continuously exposed to POPs through diet, air particles, and household and commercial products; POPs are consistently detected in human tissues, including the pancreas. Epidemiological studies show a modest but consistent correlation between exposure to POPs and increased diabetes risk. The goal of this review is to provide an overview of epidemiological evidence and an in-depth evaluation of the in vivo and in vitro evidence that POPs cause β-cell toxicity. We review evidence for six classes of POPs: dioxins, polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), flame retardants, and per- and polyfluoroalkyl substances (PFAS). The available data provide convincing evidence implicating POPs as a contributing factor driving impaired glucose homeostasis, β-cell dysfunction, and altered metabolic and oxidative stress pathways in islets. These findings support epidemiological data showing that POPs increase diabetes risk and emphasize the need to consider the endocrine pancreas in toxicity assessments. Our review also highlights significant gaps in the literature assessing islet-specific endpoints after both in vivo and in vitro POP exposure. In addition, most rodent studies do not consider the impact of biological sex or secondary metabolic stressors in mediating the effects of POPs on glucose homeostasis and β-cell function. We discuss key gaps and limitations that should be assessed in future studies.

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.

Endosulfan induces endothelial inflammation and dysfunction via IRE1α/NF-κB signaling pathway

Cardiovascular diseases are related to vascular endothelial cell injury; our previous studies showed that endosulfan could cause hypercoagulation of blood by inducing endothelial cell injury. To clarify the mechanism of it, we treated human umbilical vein endothelial cells (HUVECs) with 0, 1, 5, and 10 μg/mL endosulfan, while in the inhibition groups, reactive oxygen species (ROS) inhibitor N-acetylcysteine (NAC, 3 mmol) and endoplasmic reticulum (ER) stress inhibitor (STF-083010, 10 μmol) were incubated prior to endosulfan. The results showed that endosulfan could induce inflammatory response and dysfunction by increasing the release of inflammatory cytokines such as interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and adhesion molecules such as vascular cell adhesion molecule 1 (VCAM-1) and endothelin-1 (ET-1), and inducing ROS production in HUVECs. We also found that endosulfan could cause ER damage, remarkably increase the expressions of inositol-requiring enzyme 1α (IRE1α), phosphorylated IRE1α (p-IRE1α), GRP78, XBP1, nuclear factor-kappa B (NF-κB), and phosphorylated NF-κB (p-NF-κB) in HUVECs. The presence of NAC antagonized the ROS production, expressions of IRE1α and p-IRE1α; however, STF-083010 could decrease the expression levels of GRP78, XBP1, NF-κB, and p-NF-κB and attenuate IL-1β, IL-6, TNF-α, VCAM-1, and ET-1 release induced by endosulfan. These results demonstrated that endosulfan-induced endothelial inflammation and dysfunction through the IRE1α/NF-κB signaling pathway may be triggered by oxidative stress. The study provided experimental basis for the correlation between environmental pollutants (endosulfan) and cardiovascular diseases.

A dual mixture of persistent organic pollutants modifies carbohydrate metabolism in the human hepatic cell line HepaRG

Individuals as well as entire ecosystems are exposed to mixtures of Persistent Organic Pollutants (POPs). Previously, we showed, by a non-targeted approach, that the expression of several genes involved in carbohydrate metabolism was almost completely inhibited in the human hepatic cell line HepaRG following exposure to a mixture of the organochlorine insecticide alpha-endosulfan and 2,3,7,8 tetrachlorodibenzo-p-dioxin. In this European HEALS project, which studies the effects of the exposome on human health, we used a Physiologically Based BioKinetic model to compare the concentrations previously used in vitro with in vivo exposures for humans. We investigated the effects of these POPs on the levels of proteins, on glycogen content, glucose production and the oxidation of glucose into CO₂ and correlated them to the expression of genes involved in carbohydrate metabolism as measured by RT-qPCR. Exposure to individual POPs and the mixture decreased the expression of the proteins investigated as well as glucose output (up to 82%), glucose oxidation (up to 29%) and glycogen content (up to 48%). siRNAs that specifically inhibit the expression of several xenobiotic receptors were used to assess receptor involvement in the effects of the POPs. In the HepaRG model, we demonstrate that the effects are mediated by the aryl hydrocarbon receptor and the estrogen receptor alpha, but not the pregnane X receptor or the constitutive androstane receptor. These results provide evidence that exposure to combinations of POPs, acting through different signaling pathways, may affect, more profoundly than single pollutants alone, metabolic pathways such as carbohydrate/energy metabolism and play a potential role in pollutant associated metabolic disorders.

Low-dose endosulfan inhibits proliferation and induces senescence and pro-inflammatory cytokine production in human lymphocytes, preferentially impacting cytotoxic cells

Endosulfan is a DDT-era organochlorine pesticide. Due to past and current environmental contamination, investigation of endosulfan exposure is of current importance. Acute high dose exposure precipitates neural/endocrine system damage, but the effects on the immune system and of lower doses are not well-characterized. Two relatively low concentrations of endosulfan (i.e. 0.1 and 17 µM ENDO) were investigated in an in vitro study using human peripheral blood mononuclear cells (PBMC) to understand effects of relatively low doses (0.1-25.0 µM [≈0.04-10 ppm/40-10,000 ppb]) of ENDO upon normal human T- and B-lymphocytes and NK cells. The study here found that 17 µM ENDO inhibited phytohemagglutinin-M (PHA)-induced human PBMC proliferation. It was also seen that senescence and apoptosis among non-stimulated cells was increased, specifically within CD8 and NK populations, and that CD4:CD8 ratios also were increased. Treatment of non-stimulated PBMC with ENDO led to overall increases in production of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-2, -4, and -6, and decreased production of anti-inflammatory IL-10, suggesting an immunosenescence secretory phenotype. Interestingly, when the cells were pre-stimulated with mitogen (PHA), ENDO became inhibitory against the mitogen-induced proliferation and cytokine formation - with the exception of that of TNFα and IL-6, suggesting differential effects of ENDO on activated cells. Thus, at the organismal level, ENDO might also display differential effects during states of autoimmune disease or chronic viral infection in the exposed host.

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.

Cyp2b-Knockdown Mice Poorly Metabolize Corn Oil and Are Age-Dependent Obese

We previously made a RNAi-based cytochrome P450 2b (Cyp2b)-knockdown (Cyp2b-KD) mouse to determine the in vivo role of the Cyp2b subfamily in xenobiotic detoxification. Further studies reported here indicate a role for Cyp2b in unsaturated fatty-acid (UFA) metabolism and in turn obesity. Mice were treated intraperitoneally (i.p.) with 100 μL corn oil as a carrier or the potent Cyp2b-inducer 3,3',5,5'-Tetrachloro-1,4-bis(pyridyloxy)benzene (TCPOBOP (TC)) dissolved in corn oil. Surprisingly, female Cyp2b-KD mice but not male mice showed increased liver lipid accumulation. Male Cyp2b-KD mice had higher serum triacylglycerols, cholesterol, very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) than wildtype (WT) mice; females had higher cholesterol, LDL, and HDL. Thus, Cyp2b-KD mice are unable to clear a high bolus dose of corn oil, potentially because the Cyp2b-KD mice were unable to metabolize the UFA in the corn oil. Therefore, WT and Cyp2b-KD mice were housed for 35 weeks and necropsies performed to test whether Cyp2b-KD mice develop age onset obesity. Cyp2b-KD mice exhibited a significant increase in body weight caused by an increase in white adipose tissue deposition relative to WT mice. Serum cholesterol, triacylglycerol, LDL, and VLDL were significantly greater in 35-week-old Cyp2b-KD males compared to WT males; only serum triacylglycerol and LDL were higher in females. In conclusion, changes in Cyp2b expression led to perturbation in lipid metabolism and depuration in Cyp2b-KD mice. This suggests that Cyp2b is more than a detoxification enzyme, but also involved in the metabolism of UFA, as Cyp2b-KD mice have increased the body weight, fat deposition, and serum lipids.

Metabolome disruption of pregnant rats and their offspring resulting from repeated exposure to a pesticide mixture representative of environmental contamination in Brittany

The use of pesticides exposes humans to numerous harmful molecules. Exposure in early-life may be responsible for adverse effects in later life. This study aimed to assess the metabolic modifications induced in pregnant rats and their offspring by a pesticide mixture representative of human exposure. Ten pregnant rats were exposed to a mixture of eight pesticides: acetochlor (246 μg/kg bw/d) + bromoxynil (12 μg/kg bw/d) + carbofuran (22.5 μg/kg bw/d) + chlormequat (35 μg/kg bw/d) + ethephon (22.5 μg/kg bw/d) + fenpropimorph (15.5 μg/kg bw/d) + glyphosate (12 μg/kg bw/d) + imidacloprid (12.5 μg/kg bw/d) representing the main environmental pesticide exposure in Brittany (France) in 2004. Another group of 10 pregnant rats served as controls. Females were fed ad libitum from early pregnancy, which is from gestational day (GD) 4 to GD 21. Urine samples were collected at GD 15. At the end of the exposure, mothers and pups were euthanized and blood, liver, and brain samples collected. 1H NMR-based metabolomics and GC-FID analyses were performed and PCA and PLS-DA used to discriminate between control and exposed groups. Metabolites for which the levels were significantly modified were then identified using the Kruskal-Wallis test, and p-values were adjusted for multiple testing correction using the False Discovery Rate. The metabolomics analysis revealed many differences between dams of the two groups, especially in the plasma, liver and brain. The modified metabolites are involved in TCA cycle, energy production and storage, lipid and carbohydrate metabolism, and amino-acid metabolism. These modifications suggest that the pesticide mixture may induce oxidative stress associated with mitochondrial dysfunction and the impairment of glucose and lipid metabolism. These observations may reflect liver dysfunction with increased relative liver weight and total lipid content. Similar findings were observed for glucose and energy metabolism in the liver of the offspring, and oxidative stress was also suggested in the brains of male offspring.

Endosulfan induces cell dysfunction through cycle arrest resulting from DNA damage and DNA damage response signaling pathways

Our previous study showed that endosulfan increases the risk of cardiovascular disease. To identify toxic mechanism of endosulfan, we conducted an animal study for which 32 male Wistar rats were randomly and equally divided into four groups: Control group (corn oil only) and three treatment groups (1, 5 and 10mgkg^-1·d^-1). The results showed that exposure to endosulfan resulted in injury of cardiac tissue with impaired mitochondria integrity and elevated 8-OHdG expression in myocardial cells. Moreover, endosulfan increased the expressions of Fas, FasL, Caspase-8, Cleaved Caspase-8, Caspase-3 and Cleaved Caspase-3 in cardiac tissue. In vitro, human umbilical vein endothelial cells (HUVECs) were treated with different concentrations of endosulfan (1, 6 and 12μgmL^-1) for 24h. An inhibitor for Ataxia Telangiectasia Mutated Protein (ATM) (Ku-55933, 10μM) was added in 12μgmL^-1 group for 2h before exposure to endosulfan. Results showed that endosulfan induced DNA damage and activated DNA damage response signaling pathway (ATM/Chk2 and ATR/Chk1) and consequent cell cycle checkpoint. Furthermore, endosulfan promoted the cell apoptosis through death receptor pathway resulting from oxidative stress. The results provide a new insight for mechanism of endosulfan-induced cardiovascular toxicity which will be helpful in future prevention of cardiovascular diseases induced by endosulfan.

Low, Chronic Exposure to Endosulfan Induces Bioaccumulation and Decreased Carcass Total Fatty Acids in Neotropical Fruit Bats

We investigated the effects of the insecticide endosulfan on energy metabolism and its possible accumulation in fruit bats. Adult male bats (Artibeus lituratus) were exposed for 35 days, when they were offered fruit treated with endosulfan (E) and adhesive spreader (AS) in the following concentrations (g/L): 0.0; 0.0 (Control), 0.0; 0.015 (AS), 1.05; 0.015 (E1), 2.1; 0.015 (E2). Concentrations used were those recommended by the manufacturer for fruit crop application (E1) or twice this value (E2). E1 bats showed decreased plasma glucose concentration. Carcass fatty acids were decreased in E1 and E2 bats. Endosulfan bioaccumulation was observed in both liver and adipose tissues from E1 and E2 bats. These results indicate that the chronic exposure of fruit bats to environmentally relevant concentrations of endosulfan can lead to significant bioaccumulation beyond control and also decreased fatty acid content, which may impair the health of this important seed disperser in neotropical forests.

Chronic exposure to endosulfan induces inflammation in murine colon via β-catenin expression and IL-6 production

Endosulfan (ENDO) is a widely used organochlorine (OC) pesticide and persistent organo-pollutant. Epidemiological studies have shown that high levels of OC exposure were related to colorectal cancer (CRC) incidence. The objectives of the present study were to evaluate histological changes in the colon, as well as in in situ expression of β-catenin and P-selectin, and serum levels of select pro-inflammatory cytokines in mice administered ENDO; there is a relationship between increased serum IL-6 and P-selectin levels in CRC patients and aberrant β-catenin signaling is important in initiation/maintenance of most CRCs. Mice were exposed to ENDO (at dose < LD₅₀) orally once a week for up to 24 weeks, and monitored (inclusive) for a total of 42 weeks. The experiment was comprised of three groups, one that did not receive ENDO (olive oil vehicle), one administered 2 mg ENDO/kg/week and a positive control (for induction of CRC) given a weekly 20 mg 1,2-dimethylhydrazine (DMH)/kg injection. The results indicated that oral administration of ENDO provoked moderate inflammation starting at six weeks, and severe colonic inflammation with an appearance of dysplastic formations (aberrant crypts) in mice treated with ENDO (or DMH) for 12 weeks or longer. Serum IL-6 levels significantly increased starting at six weeks and rose to a peak of 15-fold higher than in controls at 42 weeks; TNFα levels likewise significantly increased, with a later peak (≈four-fold higher than controls) at 30-42 weeks. Immunohistochemical analysis of the colon also showed that expression of β-catenin and P-selectin increased with length of exposure to ENDO. Taken together, the results indicate that continued repeated oral exposure to ENDO induces increased expression of β-catenin and P-selectin, inflammation in the colon, and, ultimately, local tissue dysplasia.

Lipotropes protect against pathogen-aggravated stress and mortality in low dose pesticide-exposed fish

The decline of freshwater fish biodiversity corroborates the trends of unsustainable pesticide usage and increase of disease incidence in the last few decades. Little is known about the role of nonlethal exposure to pesticide, which is not uncommon, and concurrent infection of opportunistic pathogens in species decline. Moreover, preventative measures based on current knowledge of stress biology and an emerging role for epigenetic (especially methylation) dysregulation in toxicity in fish are lacking. We herein report the protective role of lipotropes/methyl donors (like choline, betaine and lecithin) in eliciting primary (endocrine), secondary (cellular and hemato-immunological and histoarchitectural changes) and tertiary (whole animal) stress responses including mortality (50%) in pesticide-exposed (nonlethal dose) and pathogen-challenged fish. The relative survival with betaine and lecithin was 10 and 20 percent higher. This proof of cause-and-effect relation and physiological basis under simulated controlled conditions indicate that sustained stress even due to nonlethal exposure to single pollutant enhances pathogenic infectivity in already nutritionally-stressed fish, which may be a driver for freshwater aquatic species decline in nature. Dietary lipotropes can be used as one of the tools in resurrecting the aquatic species decline.