Effects of organophosphates on precision-cut kidney slices

Organophosphate (OP) poisoning, both accidental and with suicidal intent, is a global medical challenge. While the primary toxicity of these pesticides is based on the inhibition of acetylcholinesterase (AChE), case reports describe patients developing OP-mediated renal insufficiency. We set out to investigate possible pathomechanisms utilizing rat precision-cut kidney slices (PCKS). Depending on the method of investigation, PCKS were observed for a maximum of 10 days. PCKS exposed to OP compounds (malaoxon, malathion, paraoxon, parathion) showed a dose-dependent loss of viability and a reduction of total protein content over the course of 10 days. A concentration of 500 µM OP showed the most differences between OP compounds. After two days of incubation parathion showed a significantly lower level of viability than malathion. The respective effects of paraoxon and malaoxon were not significantly different from the control. However, effects of OP were only observed in concentrations exceeding those that were needed to achieve significant AChE inhibition in rat kidney tissue. In addition, we observed histological changes, without inducing LDH leakage. Overall, results suggest that OP exert effects in kidney tissue, that exceed those expected from the sole inhibition of AChE and vary between compounds. Without signs of necrosis, findings call for studies that address other possible pathomechanisms, including inflammatory response, oxidative stress or activation of apoptosis to further understand the nephrotoxicity of OP compounds. Monitoring oxon concentration over time, we demonstrated reduced enzyme-inhibiting properties in the presence of PCKS, suggesting interactions between OP compound and kidney tissue.

Study of detoxification of methyl parathion by dielectric barrier discharge (DBD) non-thermal plasma at gas-liquid interface：mechanism and bio-toxicity evaluation

Methyl parathion (MP) as an organophosphorus pesticide has been used in the control of agricultural pests and diseases. Due to its high toxicity and persistence in the environment, MP may pose threat to human health when it is released into environmental water. For MP treatment, people have found that oxidative degradation of MP may generate some intermediates which are more toxic than MP itself, such as methyl paraoxon. Herein, we proposed a new method of applying dielectric barrier discharge (DBD) non-thermal plasma technology to treat MP in aqueous solution, and investigated the influences of different gases, pH value, discharge voltage/power, and main active species on the MP removal efficiency. In particular, the safety of DBD treatment was concerned with analysis of the biological toxicity of the byproducts from the DBD oxidation, and the DBD-induced degradation together with the involved mechanism was explored therein. The results showed that the production of toxic intermediates could be effectively suppressed or avoided under certain treatment conditions. As such, this work demonstrates that the proper application of DBD plasma technology with necessary caution can detoxify methyl parathion effectively, and also provides a practical guide for low-temperature plasma application in treatment of various organophosphorus pesticides in agricultural wastewater.

Organophosphorus pesticides exhibit compound specific effects in rat precision-cut lung slices (PCLS): mechanisms involved in airway response, cytotoxicity, inflammatory activation and antioxidative defense

Organophosphorus compound pesticides (OP) are widely used in pest control and might be misused for terrorist attacks. Although acetylcholinesterase (AChE) inhibition is the predominant toxic mechanism, OP may induce pneumonia and formation of lung edema after poisoning and during clinical treatment as life-threatening complication. To investigate the underlying mechanisms, rat precision-cut lung slices (PCLS) were exposed to the OP parathion, malathion and their biotransformation products paraoxon and malaoxon (100–2000 µmol/L). Airway response, metabolic activity, release of LDH, cytokine expression and oxidative stress response were analyzed. A concentration-dependent inhibition of airway relaxation was observed after exposure with the oxon but not with the thion-OP. In contrast, cytotoxic effects were observed for both forms in higher concentrations. Increased cytokine expression was observed after exposure to parathion and paraoxon (IL-6, GM-CSF, MIP-1α) and IL-6 expression was dependent on NFκB activation. Intracellular GSH levels were significantly reduced by all four tested OP but an increase in GSSG and HO-1 expression was predominantly observed after malaoxon exposure. Pretreatment with the antioxidant N-acetylcysteine reduced malaoxon but not paraoxon-induced cytotoxicity. PCLS as a 3D lung model system revealed OP-induced effects depending on the particular OP. The experimental data of this study contribute to a better understanding of OP toxicity on cellular targets and may be a possible explanation for the variety of clinical outcomes induced by different OP.

Cytotoxic and estrogenic activity of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol. Study of marine yeasts as potential toxicity indicators

Chlorpyrifos (CP) is one of the organophosphate insecticides most used worldwide today. Although the main target organ for CP is the nervous system triggering predominantly neurotoxic effects, it has suggested other mechanisms of action as cytotoxicity and endocrine disruption. The risk posed by the pesticide metabolites on non-target organisms is increasingly recognized by regulatory agencies and natural resource managers. In the present study, cytotoxicity and estrogenic activity of CP, and its principal metabolite 3,5,6-trichloro-2-pyridinol (TCP) have been evaluated by in vitro assays, using two mammalian cell lines (HEK293 and N2a), and a recombinant yeast. Results indicate that TCP is more toxic than CP for the two cell lines assayed, being N2a cells more sensitive to both compounds. Both compounds show a similar estrogenic activity being between 2500 and 3000 times less estrogenic than 17β-estradiol. In order to find new toxicity measurement models, yeasts isolated from marine sediments containing CP residues have been tested against CP and TCP by cell viability assay. Of the 12 yeast strains tested, 6 of them showed certain sensitivity, and a concentration-dependent response to the tested compounds, so they could be considered as future models for toxicity tests, although further investigations and proves are necessary.