Developmental neurotoxicity targeting hepatic and cardiac sympathetic innervation: effects of organophosphates are distinct from those of glucocorticoids

A comprehensive review on chlorpyrifos toxicity with special reference to endocrine disruption: Evidence of mechanisms, exposures and mitigation strategies

Chlorpyrifos (CPF) is a broad-spectrum chlorinated organophosphate (OP) pesticide used for the control of a variety of insects and pathogens in crops, fruits, vegetables, as well as households, and various other locations. The toxicity of CPF has been associated with neurological dysfunctions, endocrine disruption, and cardiovascular diseases (CVDs). It can also induce developmental and behavioral anomalies, hematological malignancies, genotoxicity, histopathological aberrations, immunotoxicity, and oxidative stress as evidenced by animal modeling. Moreover, eye irritation and dermatological defects are also reported due to CPF toxicity. The mechanism of action of CPF involves blocking the active sites of the enzyme, acetylcholinesterase (AChE), thereby producing adverse nervous system effects. Although CPF has low persistence in the body, its active metabolites, 3,5,6-trichloro-2-pyridinol (TCP), and chlorpyrifos-oxon (CPO) are comparatively more persistent, albeit equally toxic, and thus produce serious health complications. The present review has been compiled taking into account the work related to CPF toxicity and provides a brief compilation of CPF-induced defects in animals and humans, emphasizing the abnormalities leading to endocrine disruption, neurotoxicity, reproductive carcinogenesis, and disruptive mammary gland functionality. Moreover, the clinical signs and symptoms associated with the CPF exposure along with the possible pharmacological treatment are reported in this treatise. Additionally, the effect of food processing methods in reducing CPF residues from different agricultural commodities and dietary interventions to curtail the toxicity of CPF has also been discussed.

Cluster analysis profiling of behaviors in zebrafish larvae treated with antidepressants and pesticides

Antidepressants are used by a substantial number of women in their childbearing years. Treatment may continue during pregnancy, since untreated depression poses a risk to the mother and child. However, many antidepressants readily pass through the placental barrier to reach the fetus or may be ingested by the newborn via breastmilk. Little is known about the effects of antidepressants on brain development and subsequent behavior in young children. In the current study, we used zebrafish as a model system to examine the neurodevelopmental effects of three commonly prescribed antidepressants, sertraline, duloxetine and bupropion. Zebrafish were exposed to these antidepressants during development and were examined for changes in larval avoidance behavior, activity, social behaviors, and anxiety-related behaviors. The results show that antidepressants commonly affect larval swim speeds and resting, and differentially affect other behaviors depending upon the exposure period. Using cluster analysis profiling, we compared the obtained results to previous reports on behavioral defects induced by organophosphate pesticides. We found that the behavioral profiles induced by antidepressants and pesticides overlap, indicating a common mechanism of action. We conclude that developmental antidepressant exposures lead to specific behavioral changes in zebrafish larvae. At present, it is not known if antidepressants have similar effects in human development.

Metabolic Effects of a Chronic Dietary Exposure to a Low-Dose Pesticide Cocktail in Mice: Sexual Dimorphism and Role of the Constitutive Androstane Receptor

BACKGROUND

Epidemiological evidence suggests a link between pesticide exposure and the development of metabolic diseases. However, most experimental studies have evaluated the metabolic effects of pesticides using individual molecules, often at nonrelevant doses or in combination with other risk factors such as high-fat diets.

OBJECTIVES

We aimed to evaluate, in mice, the metabolic consequences of chronic dietary exposure to a pesticide mixture at nontoxic doses, relevant to consumers' risk assessment.

METHODS

A mixture of six pesticides commonly used in France, i.e., boscalid, captan, chlorpyrifos, thiofanate, thiacloprid, and ziram, was incorporated in a standard chow at doses exposing mice to the tolerable daily intake (TDI) of each pesticide. Wild-type (WT) and constitutive androstane receptor-deficient (CAR-/-) male and female mice were exposed for 52 wk. We assessed metabolic parameters [body weight (BW), food and water consumption, glucose tolerance, urinary metabolome] throughout the experiment. At the end of the experiment, we evaluated liver metabolism (histology, transcriptomics, metabolomics, lipidomics) and pesticide detoxification using liquid chromatography-mass spectrometry (LC-MS).

RESULTS

Compared to those fed control chow, WT male mice fed pesticide chow had greater BW gain and more adiposity. Moreover, these WT males fed pesticide chow exhibited characteristics of hepatic steatosis and glucose intolerance, which were not observed in those fed control chow. WT exposed female mice exhibited fasting hyperglycemia, higher reduced glutathione (GSH):oxidized glutathione (GSSG) liver ratio and perturbations of gut microbiota-related urinary metabolites compared to WT mice fed control chow. When we performed these experiments on CAR-/- mice, pesticide-exposed CAR-/- males did not exhibit BW gain or changes in glucose metabolism compared to the CAR-/- males fed control chow. Moreover, CAR-/- females fed pesticide chow exhibited pesticide toxicity with higher BWs and mortality rate compared to the CAR-/- females fed control chow.

CONCLUSIONS

To our knowledge, we are the first to demonstrate a sexually dimorphic obesogenic and diabetogenic effect of chronic dietary exposure to a common mixture of pesticides at TDI levels, and to provide evidence for a partial role for CAR in an in vivo mouse model. This raises questions about the relevance of TDI for individual pesticides when present in a mixture. https://doi.org/10.1289/EHP2877.

Chlorpyrifos and malathion have opposite effects on behaviors and brain size that are not correlated to changes in AChE activity

Organophosphates, a type of neurotoxicant pesticide, are used globally for the treatment of pests on croplands and are therefore found in a large number of conventional foods. These pesticides are harmful and potentially deadly if ingested or inhaled in large quantities by causing a significant reduction in acetylcholinesterase (AChE) activity in the central and peripheral nervous system. However, much less is known about the effects of exposure to small quantities of the pesticides on neural systems and behavior during development. In the current study we used zebrafish larvae in order to determine the effects of two of the most widely used organophosphates, chlorpyrifos and malathion, on zebrafish behavior and AChE activity. Embryos and larvae were exposed to the organophosphates during different time points in development and then tested at 5 days post-fertilization for behavioral, neurodevelopmental and AChE abnormalities. The results of the study indicate that chlorpyrifos and malathion cause opposing behaviors in the larvae such as swim speed (hypoactivity vs. hyperactivity) and rest. Additionally, the pesticides affect only certain behaviors, such as thigmotaxis, during specific time points in development that are unrelated to changes in AChE activity. Larvae treated with malathion but not chlorpyrifos also had significantly smaller forebrain and hindbrain regions compared to controls by 5 days post-fertilization. We conclude that exposure to very low concentrations of organophosphate pesticides during development cause abnormalities in behavior and brain size.

Indigenous children living nearby plantations with chlorpyrifos-treated bags have elevated 3,5,6-trichloro-2-pyridinol (TCPy) urinary concentrations

BACKGROUND

The US Environmental Protection Agency voluntary phased-out residential use of chlorpyrifos in 2001. In contrast, in Costa Rica, chlorpyrifos-treated bags are increasingly used to protect banana and plantain fruits from insects and to fulfill product standards, even in populated areas.

OBJECTIVES

To evaluate children's exposure to chlorpyrifos in villages situated nearby banana plantations and plantain farms in Costa Rica.

METHODS

The study targeted two villages with use of chlorpyrifos-treated bags in nearby banana plantations and plantain farms and one village with mainly organic production. For 140 children from these villages, mostly indigenous Ngäbe and Bribri, parent-interviews and urine samples (n=207) were obtained. Urinary 3,5,6-trichloro-2-pyridinol (TCPy) levels were measured as a biomarker for chlorpyrifos exposure. In the banana and plantain village also environmental contamination to chlorpyrifos was explored.

RESULTS

Children from the banana and plantain villages had statistically significant higher urinary TCPy concentrations than children from the referent village; 2.6 and 2.2 versus 1.3μg/g creatinine, respectively. Chlorpyrifos was detected in 30% of the environmental samples as well as in 92% of the hand/foot wash samples. For more than half of the children their estimated intake exceeded the US EPA chronic population adjusted dose. For some, the acute population adjusted dose and the chronic reference dose were also exceeded.

CONCLUSIONS

Our results suggest that children living nearby plantations with chlorpyrifos-treated bags are exposed to chlorpyrifos levels that may affect their health. Interventions to reduce chlorpyrifos exposure are likely to improve children's health and environment in banana and plantain growing regions.

Effects of Banana Plantation Pesticides on the Immune Response of Lepidopteran Larvae and Their Parasitoid Natural Enemies

Basic research on the insect immune response has progressed dramatically within the last two decades, showing that immunity is one of the most effective defenses against foreign invaders. As such, it is important to understand the causes of variation in this response. Here, we investigate the effects of pesticides used in Costa Rican banana plantations on the immune response of the lepidopteran larva, Caligo memnon (Brassolinae). In addition, we performed a parasitism survey of the banana plantations and surrounding forests to provide a broader assessment of pesticide effects on parasitoid populations. All caterpillars for the immune assay were collected from two banana plantations and brought to La Selva Biology Station for immune challenge. Individuals were fed leaves from the plantations (pesticide) or leaves from La Selva (pesticide-free), then immune challenged with injected sephadex beads. We found that individuals feeding on pesticide leaves had significantly lower bead melanization compared to individuals feeding on pesticide-free leaves. Nonetheless, the parasitism survey showed that caterpillars from the banana plantations had lower parasitism rates compared to caterpillars from the La Selva forest. This study adds to the growing body of evidence documenting negative effects of pesticides on the insect immune response and on adult parasitoids, and underscores the need for more research at the intersection between ecological entomology and immunology.

Hypothermia down-regulates the LPS-induced norepinephrine (NE) release in ischaemic human heart cells

Hypothermia has been widely acknowledged as the fundamental component of myocardial protection during cardiac operations. In this work, we studied in human atrial tissue the effect of the common hypothermic protection used in cardiac surgery, and we assessed this effect by comparing catecholamine release among normoxic, ischaemic, and inflammatory conditions. Our results provide the first evidence that lipopolysaccharide treatment results in an extremely dramatic and significant increase in the resting norepinephrine release under ischaemic conditions that can be normalised by hypothermia. These findings demonstrate that inflammatory conditions increase the temperature sensitivity of the norepinephrine transporter in human cardiac tissue. When the possible pharmacological interventions are taken into consideration, the results presented here provide new insight into the protection against ischaemia/reperfusion injury during cardiac surgery.