Translational toxicological research: investigating and preventing acute lung injury in organophosphorus insecticide poisoning

A rat model of organophosphate-induced status epilepticus and the beneficial effects of EP2 receptor inhibition

This review describes an adult rat model of status epilepticus (SE) induced by diisopropyl fluorophosphate (DFP), and the beneficial outcomes of transient inhibition of the prostaglandin-E2 receptor EP2 with a small molecule antagonist, delayed by 2-4 h after SE onset. Administration of six doses of the selective EP2 antagonist TG6-10-1 over a 2-3 day period accelerates functional recovery, attenuates hippocampal neurodegeneration, neuroinflammation, gliosis and blood-brain barrier leakage, and prevents long-term cognitive deficits without blocking SE itself or altering acute seizure characteristics. This work has provided important information regarding organophosphate-induced seizure related pathologies in adults and revealed the effectiveness of delayed EP2 inhibition to combat these pathologies.

Xuebijing injection induces anti-inflammatory-like effects and downregulates the expression of TLR4 and NF-κB in lung injury caused by dichlorvos poisoning

BACKGROUND

The mechanism in lung injury caused by acute organophosphate pesticide poisoning (AOPP) and an effective treatment remains unclear. We aim to clarify how the inflammatory lung injury caused by AOPP might be modulated by Xuebijing (XBJ) injection.

METHODS

AOPP-induced lung injury model was induced by dichlorvos (DDVP) subcutaneous administration in rats and XBJ injection was administered by intraperitoneal injection after DDVP challenge. The effects of XBJ injection were assessed by lung histopathological analysis and lung injury scores, lung wet-to-dry weight ratios (WDR) and oxygenation, differential immune cell count in bronchoalveolar lavage fluid (BALF), IL-6 and TNF-α levels in blood, the levels of TLR4 and NF-κB proteins in lung tissue and blood acetylcholinesterase (AChE) activity.

RESULTS

DDVP administration resulted in damage of lung histopathology and lower PaO2/FiO2 ratios (P < 0.05), which were notably attenuated by XBJ injection (P < 0.05). Total cell, macrophage, and neutrophils count in BALF and TNF-α and IL-6 levels in blood were significantly increased after DDVP exposure (P < 0.05), which were notably ameliorated by XBJ injection (P < 0.05). TLR4 and NF-κB protein in lung tissue expression after DDVP challenge were markedly increased (P < 0.05), and they were substantially downregulated by XBJ injection (P < 0.05). In addition, blood AChE activity was significantly decreased by DDVP administration (P < 0.05), however, there was no significant improvement after XBJ injection.

CONCLUSION

XBJ injection prevents DDVP poisoning induced lung injury by attenuating the inflammatory response. The protective effect appears to be mediated through downregulation of the TLR4 and NF-κB expression.

High Dose of Pralidoxime Reverses Paraoxon-Induced Respiratory Toxicity in Mice

Objective

The efficiency of pralidoxime in the treatment of human organophosphates poisoning is still unclear. In a rat model, we showed that pralidoxime induced a complete but concentration-dependent reversal of paraoxon-induced respiratory toxicity. The aim of this study was to assess the efficiency of pralidoxime in a species other than rats.

Methods

A dose of diethylparaoxon corresponding to 50% of the median lethal dose was administered subcutaneously to male F1B6D2 mice. Ascending single pralidoxime doses of 10, 50-100 and 150 mg kg^-1 were administered intramuscularly 30 min after diethylparaoxon administration. Ventilation at rest was assessed using whole-body plethysmography and mice temperature was assessed using infrared telemetry. Results are expressed as mean±SE. Statistical analysis used non-parametric tests.

Results

From 30 to 150 min post-injection, diethylparaoxon induced clinical symptoms and a decrease in respiratory frequency, which resulted from an increase in expiratory and inspiratory times associated with an increase in the tidal volume. In the 10-, 50- and 100-mg kg^-1 pralidoxime groups, there was a trend towards a non-significant improvement of paraoxon-induced respiratory toxicity. The 150 mg kg^-1 dose of pralidoxime induced a significant reversal of all respiratory parameters.

Conclusion

In the present study, a toxic but non-lethal model of diethylparaoxon in awake, unrestrained mice was observed. By administering an equipotent dose of diethylparaoxon to rats, a 150 mg kg^-1 dose of pralidoxime administered alone completely reversed diethylparaoxon-induced respiratory toxicity in mice. The dose dependency of reversal suggests that further studies are needed for assessing plasma concentrations of pralidoxime resulting in reversal of toxicity.

Pulmonary innate inflammatory responses to agricultural occupational contaminants

Agricultural workers are exposed to many contaminants and suffer from respiratory and other symptoms. Dusts, gases, microbial products and pesticide residues from farms have been linked to effects on the health of agricultural workers. Growing sets of data from in vitro and in vivo models demonstrate the role of the innate immune system, especially Toll-like receptor 4 (TLR4) and TLR9, in lung inflammation induced following exposure to contaminants in agricultural environments. Interestingly, inflammation and lung function changes appear to be discordant indicating the complexity of inflammatory responses to exposures. Whereas the recent development of rodent models and exposure systems have yielded valuable data, we need new systems to examine the combined effects of multiple contaminants in order to increase our understanding of farm-exposure-induced negative health effects.

Mitigation of diazinon-induced cardiovascular and renal dysfunction by gallic acid

Studies of the link between environmental pollutants and cardiovascular dysfunction, neglected for decades, have recently provided new insights into the pathology and consequences of these killers. In this study, rats were divided into four groups, each containing 10 rats. The rats in group one served as controls and were administered normal saline, whereas the rats in group two were orally gavaged with 3 mg/kg of diazinon (DZN) alone for twenty one consecutive days. The rats in groups 3 and 4 were administered respective 60 mg/kg and 120 mg/kg gallic acid (GA) in addition to DZN for twenty one consecutive days. Exposure of rats to diazinon significantly (p<0.05) reduced the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and reduced glutathione (GSH) content. Malondialdehyde, hydrogen peroxide (H2O2) and nitric oxide (NO) contents were also significantly (p<0.05) elevated following DZN exposure. DZN further caused a significant (p<0.05) decrease of heart rate and QT interval prolongation. Hematologic analysis revealed significant reduction (p<0.05) in packed cell volume (PCV), hemoglobin concentration (Hb), red blood cell (RBC) count, and total white blood cell count of rats administered only DZN. Observations in this study suggest a modulatory role of gallic acid in diazinon-induced anemia and associated cardiovascular dysfunction in rats. Treatment with gallic acid reversed the oxidative stress markers studied, increased the antioxidant defence system and reduced deleterious effects on hematological parameters in rats. Pathologic findings of the heart and kidney were also found to be lessened.