Validation and kinetic of enzymatic method for the detection of organophosphate insecticides based on cholinesterase inhibition

Amorphous Selenium Nanoparticles Improve Vascular Function in Rats With Chronic Isocarbophos Poisoning via Inhibiting the Apoptosis of Vascular Endothelial Cells

AIM

This study aimed to investigate the preventive effect and possible mechanism of amorphous selenium nanoparticles (A-SeQDs) on isocarbophos induced vascular dysfunction.

METHODS

A-SeQDs was made by auto redox decomposition of selenosulfate precursor. Male rats were given isocarbophos (0.5 mg/kg/2 days) by intragastric administration for 16 weeks to induce vascular dysfunction. During the course, A-SeQDs (50 mg/kg/day) was added to the water from week 5. Then, the rats were killed to observe and test the influence of A-SeQDs on the vascular dysfunction induced by isocarbophos. Finally, human umbilical vein endothelial cells (HUVECs) were treated with 10% DMEM of isocarbophos (100 μM) for 5 days to detect the related indexes. Before the use of isocarbophos treatment, different drugs were given.

RESULTS

A-SeQDs could reduce total carbon dioxide, MDA, VCAM-1, ICAM-1, IL-1, and IL-6 while increasing oxygen saturation, NO content, and SOD activity in rats. A-SeQDs also resulted in relatively normal vascular morphology, and the expression of sodium hydrogen exchanger 1 (NHE1) and caspase-3 decreased in rats. Furthermore, in HUVECs treated with isocarbophos, A-SeQDs maintained mitochondrial membrane potential, inhibited the cleaved caspase-3 expression, and released cytochrome c from mitochondria to cytosol.

CONCLUSION

A-SeQDs can inhibit the apoptosis of HUVECs through the mitochondrial pathway, and effectively treat the impairment of vascular endothelial function caused by isocarbophos, which is NHE1-dependent.

Optimization of reaction time for detection of organophosphorus pesticides by enzymatic inhibition assay and mathematical modeling of enzyme inhibition

Enzyme inhibition assay was used as a biomarker for detection of organophosphates pesticides in food and environmental samples. The aim of the present study was to optimize the time of enzyme-inhibitor reaction for quantitative determination of fenitrothion organophosphate based on cholinesterase inhibition. The results showed that this method provides a time-efficient, best linearity and simple assay. The effect of reaction time on the linearity relationship of the noncompetitive inhibition equation was studied. The best linearity of the assay was found at an optimum reaction time of 3.0 min, with coefficient of determination r ² of 0.9972, in the range of inhibitor concentrations from 0.016 to 2.0 μg mL^-1. The enzyme inhibition reached a plateau at 5 min by addition of pesticide in vitro and then the inhibited enzyme reactivate spontaneously and approached steady state at 20 min. A theoretical kinetic model to explain the effect of reaction time on the enzyme inhibition by addition of pesticide in vitro was derived. The higher values of coefficient of determination r ² for the predicted model and error functions of the minimum deviations suggest that this model can be used to represent the experimental data and explain the plasma cholinesterase inhibition by fenitrothion pesticide.