Interactive toxicity of chlorpyrifos and parathion in neonatal rats: Role of esterases in exposure sequence-dependent toxicity

Effects of chlorothalonil, prochloraz and the combination on intestinal barrier function and glucolipid metabolism in the liver of mice

Chlorothalonil (CHL) and procymidone (PRO) are fungicides that exhibit low toxicity and are widely used in many countries. And both fungicides are frequently detected in the food chain. However, the health risk posed by these fungicides is still unclear. Here, 8-week-old male C57BL/6 mice were orally treated with CHL (10, 50 mg/kg/day), PRO (20, 100 mg/kg/day) and CHL+PRO (5+10, 25+50 mg/kg/day) by dietary supplementation for 10 weeks. Hepatic pathological analysis showed that exposure to CHL, PRO and CHL+PRO could cause liver injury. The glucose, triglyceride (TG) levels and the related gene expression to glucolipid metabolism changed significantly. The significantly reduced acylcarnitine levels demonstrated that CHL, PRO and CHL+PRO exposure inhibited fatty acids (FAs) β-oxidation. In addition, CHL and PRO altered the structure of the gut microbiota and destroyed the integrity of the intestinal barrier function. In particular, AF12, Odoribacter, Prevotella and Lactobacillus were highly correlated with carnitine. The results showed that CHL, PRO and CHL+PRO exposure might inhibit FAs β-oxidation by decreasing cystic fibrosis transmembrane conductance regulator (CFTR)-mediated ion transport, indicating that these fungicides disturbed intestinal barrier function associated with glucolipid metabolism disorder. Here, the data also indicated that there was an additive effect between CHL and PRO in mice.

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.

Japanese quail acute exposure to methamidophos: experimental design, lethal, sub-lethal effects and cholinesterase biochemical and histochemical expression

We exposed the Japanese quail (Coturnix coturnix japonica) to the organophosphate methamidophos using acute oral test. Mortality and sub-lethal effects were recorded in accordance to internationally accepted protocols. In addition cholinesterases were biochemically estimated in tissues of the quail: brain, liver and plasma. Furthermore, brain, liver and duodenum cryostat sections were processed for cholinesterase histochemistry using various substrates and inhibitors. Mortalities occurred mainly in the first 1-2h following application. Sub-lethal effects, such as ataxia, ruffled feathers, tremor, salivation and reduced or no reaction to external stimuli were observed. Biochemical analysis in the brain, liver and plasma indicates a strong cholinesterase dependent inhibition with respect to mortality and sub-lethal effects of the quail. The histochemical staining also indicated a strong cholinesterase inhibition in the organs examined and the analysis of the stained sections allowed for an estimation and interpretation of the intoxication effects of methamidophos, in combination with tissue morphology visible by Haematoxylin and Eosin staining. We conclude that the use of biochemistry and histochemistry for the biomarker cholinesterase, may constitute a significantly novel approach for understanding the results obtained by the acute oral test employed in order to assess the effects of methamidophos and other chemicals known to inhibit this very important nervous system enzyme.

Degradation mechanisms of phoxim in river water

Degradation of phoxim in river water was fully explored in this paper. Effects of pH, temperature, and photoirradiation on the degradation were investigated in detail. The results indicated that the degradation was characterized by a first-order process; UV irradiation and the increase of pH and temperature substantially accelerated the degradation. To fully characterize the degradation mechanism, HPLC-MS/MS was utilized to identify the degradation intermediates. Five intermediates were identified as phoxom, phoxom dimer, O,O,O',O'-tetraethyldithiopyrophosphate, O,O,O'-triethyl-O'-2-hydroxyethyldisulfinylpyrophosphate, and O,O,O'-triethyl-O'-2-hydroxyethyldithiopyrophosphate. On the basis of the results of the intermediate analysis, the degradation pathways of phoxim under the present experimental conditions were proposed. Through conversion of a thiophosphoryl into a phosphoryl group, some phoxim was converted to phoxom, most of which further formed dimer. Another portion of phoxim transformed to O,O,O',O'-tetraethyldithiopyrophosphate via nucleophilic substitution and photolysis. Thereafter, O,O,O',O'-tetraethyldithiopyrophosphate underwent hydroxylation to form O,O,O'-triethyl-O'-2-hydroxyethyldithiopyrophosphate or sulfur oxidation first and then hydroxylation to produce O,O,O'-triethyl-O'-2-hydroxyethyldisulfinylpyrophosphate. The understanding of phoxim's degradation mechanism in this study will be critical to its safety assessment and increase the understanding of the fate of phoxim in environment water.

Exposure of neonatal rats to parathion elicits sex-selective impairment of acetylcholine systems in brain regions during adolescence and adulthood

BACKGROUND

Organophosphates elicit developmental neurotoxicity through multiple mechanisms other than their shared property as cholinesterase inhibitors. Accordingly, these agents may differ in their effects on specific brain circuits.

OBJECTIVES

We gave parathion to neonatal rats [postnatal days (PNDs) 1-4], at daily doses of 0.1 or 0.2 mg/kg, spanning the threshold for barely detectable cholinesterase inhibition and systemic effects.

METHODS

We assessed neurochemical indices related to the function of acetylcholine (ACh) synapses (choline acetyltransferase, presynaptic high-affinity choline transporter, nicotinic cholinergic receptors) in brain regions comprising all the major ACh projections, with determinations carried out from adolescence to adulthood (PNDs 30, 60, and 100).

RESULTS

Parathion exposure elicited lasting alterations in ACh markers in the frontal/parietal cortex, temporal/occipital cortex, midbrain, hippocampus, and striatum. In cerebrocortical areas, midbrain, and hippocampus, effects in males were generally greater than in females, whereas in the striatum, females were targeted preferentially. Superimposed on this general pattern, the cerebrocortical effects showed a nonmonotonic dose-response relationship, with regression of the defects at the higher parathion dose; this relationship has been seen also after comparable treatments with chlorpyrifos and diazinon and likely represents the involvement of cholinesterase-related actions that mask or offset the effects of lower doses.

CONCLUSIONS

Neonatal exposure to parathion, at doses straddling the threshold for cholinesterase inhibition, compromises indices of ACh synaptic function in adolescence and adulthood. Differences between the effects of parathion compared with chlorpyrifos or diazinon and the non-monotonic dose-effect relationships reinforce the conclusion that various organophosphates diverge in their effects on neurodevelopment, unrelated to their anticholinesterase actions.

Lipotoxic effects of triacylglycerols in J774.2 macrophages

OBJECTIVE

Triacylglycerols (TGs) are being considered as an independent risk factor in atherosclerosis and metabolic syndrome, acting by dysregulation of the TG/high-density lipoprotein axis. Accumulation of lipids in subendothelial space attracts macrophages, leading to atherosclerotic plaque formation and increased plaque instability due to formation of foam cells and macrophage death. The aim of this study was to evaluate lipotoxic effects in macrophages caused by TG uptake.

METHODS

J774.2 macrophages were exposed to soybean or olive oil-based lipid emulsions as a source of TGs (1 mg/mL) in a presence or absence of lipase inhibitor paraoxon (20 microM) or to bovine serum albumin-complexed palmitic (150 microM), linoleic (600 microM), and oleic (600 microM) fatty acids.

RESULTS

The results demonstrated accumulation of TGs, G1/S arrest, and cell death with necrotic morphologic features after exposure to TG emulsions. These effects were prevented by treatment with an antioxidant N-acetyl-cysteine (0.5 mM). Paraoxon inhibited intracellular TG degradation but did not prevent lipotoxicity and cell death. Olive oil TG triggered macrophage death in a manner similar to soybean oil. Treatment of the macrophages with free fatty acid, mainly with palmitic acid, showed a reactive oxygen species-independent cell death pathway, which was different from that of TG and was not prevented by N-acetyl-cysteine.

CONCLUSION

This study shows a direct lipotoxic pathway for TG molecules in macrophages, which is not associated with degradation of TG molecule to free fatty acids. This study for the first time can explain at a cellular level how TGs as an independent risk factor aggravate atherosclerotic outcomes.