Diazinon oxon affects the differentiation of mouse N2a neuroblastoma cells

The aim of this study was to assess the neurotoxicity of diazinon oxon (DZO), a major in vivo metabolite of the phosphorothionate insecticide diazinon (DZ), on differentiating mouse N2a neuroblastoma cells. When used at concentrations of 1, 5 and 10 μM, DZO did not cause cell death but it impaired the outgrowth of axon-like processes after 24 h. Densitometric scanning of Western blots of lysates of N2a cells revealed that exposure to 5 or 10 μM DZO for 24 h increased the expression of phosphorylated neurofilament heavy chain (NFH) compared to controls, while there was no significant change in total NFH. By contrast, treatment of N2a cells with 1–10 μM DZO resulted in marked reductions in the expression of the axon growth-associated protein GAP-43. DZO-treated cells also showed an increased expression of the heat shock protein HSP-70 compared to controls. The above biochemical changes were not temporally related to inhibition of acetylcholinesterase (AChE). These data suggest that biologically relevant, subcytotoxic levels of DZO may exert neurotoxic effects on differentiating cells and that the mechanisms involved are different from those attributed to its parent compound.     

Protective role of dietary Spirulina platensis against diazinon-induced Oxidative damage in Nile tilapia; Oreochromis niloticus

The current study was performed to investigate the ameliorating effect of dietary supplementation of 0.5 and 1% Spiurolina platensis (SP) diet against the sub-acute toxicity of diazinon (DZN) 0.28 mg/L in Nile tilapia. At the end of experiment after 28 days, hepatic and renal damage markers (aspartate transaminase, alanine transaminase, alkaline phosphatase, urea, uric acid and creatinine), serum biochemical parameters (total proteins, albumin, cholesterol and glucose) and tissue antioxidant status (superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione and malondialdehyde) were detesrmined. The results of the current study revealed significant improvement in hepatic and renal damage markers after SP supplementation in fish exposed to DZN toxicity. Moreover, SP improved serum biochemical markers through increasing serum albumin and globulins with a significant decrease in serum glucose and cholesterol. In addition, liver, kidneys and gills antioxidant status showed a significant improvement after SP supplemented to fish exposed to DZN where a significant increase in tissue antioxidant activity were observed with a significant decline in lipid peroxidation levels. It can be concluded that, SP supplementation attenuated the toxic effect of DZN toxicity in Nile tilapia through improving liver and kidney functions with a significant enhancement of tissue antioxidant status.     

Diazinon impairs bioenergetics and induces membrane permeability transition on mitochondria isolated from rat liver

ABSTRACT

Diazinon (DZN) is a broad-spectrum insecticide extensively used to control pests in crops and animals. Several investigators demonstrated that DZN produced tissue toxicity especially to the liver. In addition, the mitochondrion was implicated in DZN-induced toxicity, but the precise role of this organelle remains to be determined. The aim of this study was thus to examine the effects of DZN (50 to 150 μM) on the bioenergetics and mitochondrial permeability transition (MPT) associated processes in isolated rat liver mitochondria. DZN inhibited state-3 respiration in mitochondria energized with glutamate plus malate, substrates of complex I, and succinate, substrate of complex II of the respiratory chain and decreased the mitochondrial membrane potential resulting in inhibition of ATP synthesis. MPT was estimated by the extent of mitochondrial swelling, in the presence of 10 µM Ca²⁺. DZN elicited MPT in a concentration-dependent manner, via a mechanism sensitive to cyclosporine A, EGTA, ruthenium red and N-ethylmaleimide, which was associated with mitochondrial Ca²⁺ efflux and cytochrome c release. DZN did not result in hydrogen peroxide accumulation or glutathione oxidation, but this insecticide oxidized endogenous NAD(P)H and protein thiol groups. Data suggest the involvement of mitochondria, via apoptosis, in the hepatic cytotoxicity attributed to DZN.     

Diazinon toxicity affects histophysiological and biochemical parameters in rabbits

Diazinon is a widely used pesticide in agriculture. So, the current work aimed to investigate the effects of diazinon exposure on some physiological and biochemical parameters, as well as, histopathological changes and histochemical acetyl-cholinesterase activity (AChE). The red Baladi rabbits were dipped into water (Control Group), diazinon at low concentrations of 0.6 mg diazinon low concentration (DLC) or high concentration of 3mg diazinon high concentration (DHC) dissolved in 1l of water for 10s. Treatment was repeated after 10 days and animals were sacrificed between 0 and 21 days after the second treatment. Blood analysis revealed that Red blood cells (RBC's), hemoglobin (Hb) and plasma total protein (TP) were significantly decreased in both diazinon concentrations (P<0.01), (P<0.05), (P<0.01) respectively. Cholesterol and microsomal protein were increased (P<0.01), while, liver/ body weight and cytochrome P-450 were decreased in both concentrations (P<0.01). Also there was a highly significant effect of concentration X day interaction on all parameters (P<0.01). Histopathological changes of liver, kidney and brain were observed after DHC dipping. Glycogen content was decreased in liver and increased in kidney Bowman's capsule. Furthermore, AChE activity was inhibited in brain tissue, decreased in liver cells, but gradually increased in kidney glomerular cells. Therefore, kidney and brain were highly affected by diazinon exposure compared with the liver. Exposure of animals to diazinon caused extensive changes in physiological, biochemical, and histopathological parameters as well as histochemical AChE. So, contact exposure of diazinon leads to negative response on animal health.     

Pharmacokinetic and pharmacodynamic interaction for a binary mixture of chlorpyrifos and diazinon in the rat

Chlorpyrifos (CPF) and diazinon (DZN) are two commonly used organophosphorus (OP) insecticides and a potential exists for concurrent exposures. The primary neurotoxic effects from OP pesticide exposures result from the inhibition of acetylcholinesterase (AChE). The pharmacokinetic and pharmacodynamic impact of acute binary exposures of rats to CPF and DZN was evaluated in this study. Rats were orally administered CPF, DZN, or a CPF/DZN mixture (0, 15, 30, or 60 mg/kg) and blood (plasma and RBC), and brain were collected at 0, 3, 6, 12, and 24 h postdosing, urine was also collected at 24 h. Chlorpyrifos, DZN, and their respective metabolites, 3,5,6-trichloro-2-pyridinol (TCP) and 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMHP), were quantified in blood and/or urine and cholinesterase (ChE) inhibition was measured in brain, RBC, and plasma. Coexposure to CPF/DZN at the low dose of 15/15 mg/kg did not alter the pharmacokinetics of CPF, DZN, or their metabolites in blood. A high binary dose of 60/60 mg/kg increased the C(max) and AUC and decreased the clearance for both parent compounds, likely due to competition between CPF and DZN for CYP450 metabolism. At lower doses, most likely to be encountered in occupational or environmental exposures, the pharmacokinetics were linear. A dose-dependent inhibition of ChE was noted in tissues for both the single and coexposures, and the extent of inhibition was plasma > RBC > or = brain. The overall relative potency for ChE inhibition was CPF/DZN > CPF > DZN. A comparison of the ChE response at the low binary dose (15/15 mg/kg), where there were no apparent pharmacokinetic interactions, suggested that the overall ChE response was additive. These experiments represent important data concerning the potential pharmacokinetic and pharmacodynamic interactions for pesticide mixtures and will provide needed insight for assessing the potential cumulative risk associated with occupational or environmental exposures to these insecticides.     

Diazinon and diazoxon impair the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons

Evidence from in vivo and epidemiological studies suggests that organophosphorus insecticides (OPs) are developmental neurotoxicants, but possible underlying mechanisms are still unclear. Astrocytes are increasingly recognized for their active role in normal neuronal development. This study sought to investigate whether the widely-used OP diazinon (DZ), and its oxygen metabolite diazoxon (DZO), would affect glial–neuronal interactions as a potential mechanism of developmental neurotoxicity. Specifically, we investigated the effects of DZ and DZO on the ability of astrocytes to foster neurite outgrowth in primary hippocampal neurons. The results show that both DZ and DZO adversely affect astrocyte function, resulting in inhibited neurite outgrowth in hippocampal neurons. This effect appears to be mediated by oxidative stress, as indicated by OP-induced increased reactive oxygen species production in astrocytes and prevention of neurite outgrowth inhibition by antioxidants. The concentrations of OPs were devoid of cytotoxicity, and cause limited acetylcholinesterase inhibition in astrocytes (18 and 25% for DZ and DZO, respectively). Among astrocytic neuritogenic factors, the most important one is the extracellular matrix protein fibronectin. DZ and DZO decreased levels of fibronectin in astrocytes, and this effect was also attenuated by antioxidants. Underscoring the importance of fibronectin in this context, adding exogenous fibronectin to the co-culture system successfully prevented inhibition of neurite outgrowth caused by DZ and DZO. These results indicate that DZ and DZO increase oxidative stress in astrocytes, and this in turn modulates astrocytic fibronectin, leading to impaired neurite outgrowth in hippocampal neurons.     

Acute toxicity and bioaccumulation of pesticide Diazinon in red tilapia (Oreochromis niloticus x Mossambicus albina)

Young red tilapias were exposed for 96 h to each one of 6 concentrations of the pesticide Diazinon in order to determine the pesticide's acute toxicity level. After the ascertaining the lethal concentration (LC50) at 96 h, a level 10 times lower was selected for the bioaccumulation study of the pesticide in male and female specimens exposed for 9 days. The elimination process was carried out for 10 days beginning right after the conclusion of the accumulation process. Analytical procedures were developed and used for the studies of acute toxicity and bioaccumulation of Diazinon in red tilapia. A lethal concentration [LC50 (96 h)] of 3.85 mg/L was found, and steady-state accumulation, at a concentration of 28.45 mg/kg, was reached at 7.72 days. In the elimination process a concentration of 0.29 mg/kg was found in tilapia tissue by the sixth day after the fish were moved to clean water, and it continued to decrease quickly toward nondetectable levels.     

Health Effects of Diazinon on a Family

There is increasing evidence of permanent sequalae from acute organophosphate poisoning. We report on accidental diazinon overexposure with acute organophosphate poisoning through cutaneous absorption and inhalation followed by persistent neurological effects. In addition, we observed skeletal and endocrine effects likely attributable to the diazinon poisoning. A family of seven was exposed to diazinon in June 1999 over a two‐day period. The pesticide company mistakenly used diazinon to heavily spray the inside of the home instead of permethrin. The applicator applied the pesticide over the entire surface of the floor, carpeting, furniture, and clothing in closets to eradicate an infestation of fleas. Acute symptoms in the family members included headaches, nausea, skin irritation, runny nose, and vomiting. The family was first evaluated at 3 months and then 3 years after the acute poisoning. There were persisting neurological symptoms of memory loss, decreased concentration, irritability, and personality changes of varying degrees in all family members. Objective neurological findings of impaired balance, reaction time, color vision, slotted pegboards and trials making were present in the three older children who could be tested. Neuropsychological evaluation revealed evidence of organic brain dysfunction in all seven family members. Bone growth difficulties are present in four of five children. One child has delayed menarche.     

Toxicity Assessment of Diazinon in a Constructed Wetland Using Hyalella azteca

The goal of this study was to examine the use of a constructed wetland to mitigate the ecological impacts of simulated diazinon runoff from agricultural fields into receiving waters, via 48 h aqueous and sediment bioassays using Hyalella azteca. Aqueous animal 48 h survival varied temporally and spatially in conjunction with measured diazinon concentrations. Sediment H. azteca survival varied temporally and spatially in conjunction with measured diazinon concentrations, but less than aqueous exposures, confirming that sediment bound diazinon was less bioavailable than aqueous diazinon.     

Development of a physiologically based pharmacokinetic and pharmacodynamic model to determine dosimetry and cholinesterase inhibition for a binary mixture of chlorpyrifos and diazinon in the rat

Physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) models have been developed for the organophosphorus (OP) insecticides chlorpyrifos (CPF) and diazinon (DZN). It is anticipated that these OPs could interact at a number of important metabolic steps including: CYP450 mediated activation/detoxification, B-esterases [carboxylesterase (CaE), butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE)] or PON-1 (A-esterase) oxon detoxification. We developed a binary PBPK/PD model for CPF, DZN and their metabolites based on previously published models for the individual insecticides. The metabolic interactions (CYP450) between CPF and DZN were evaluated in vitro and suggests that CPF is more substantially metabolized to its oxon metabolite than DZN, which is consistent with observed in vivo potency (CPF>DZN). Each insecticide inhibited the other's in vitro metabolism in a concentration-dependent manner. The PBPK model code used to describe the metabolism of CPF and DZN was modified to reflect the type of CYP450 inhibition kinetics (i.e. competitive vs. non-competitive), while B-esterase metabolism was described as dose-additive, and no PON-1 interactions were assumed between CPF- and DZN-oxon with the enzyme. The binary model was then evaluated against previously published rodent dosimetry and cholinesterase (ChE) inhibition data for the mixture. The PBPK/PD model simulations of the acute oral exposure to single-mixtures (15 mg/kg) vs. binary-mixtures (15+15 mg/kg) of CFP and DZN resulted in no differences in the predicted pharmacokinetics of either the parent OPs or their respective metabolites, while cholinesterase inhibition was reasonably described using the dose-additive model. A binary oral dose of CPF+DZN (60+60 mg/kg) did result in observable changes in the DZN pharmacokinetics where C(max) was more reasonably fit by modifying the absorption parameters. It is anticipated that at low environmentally relevant binary doses, most likely to be encountered in occupational or environmental related exposures, that the pharmacokinetics are expected to be linear, and ChE inhibition dose-additive.