Organophosphorus diisopropylfluorophosphate (DFP) intoxication in zebrafish larvae causes behavioral defects, neuronal hyperexcitation and neuronal death

Olivier Bar,Alexandre Igert,Alexandre Brenet,Nadia Soussi-Yanicostas,Nicolas Taudon,Nina Dupuis,Gregory Dal-Bo,Constantin Yanicostas,Dominique Saurat,Rahma Hassan-Abdi,Julie Somkhit,Florian Nachon,Christiane Romain

doi:10.1038/s41598-020-76056-8

Olivier Bar, Alexandre Igert + Show 11 more

Open Access

https://doi.org/10.1038/s41598-020-76056-8

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Abstract

With millions of intoxications each year and over 200,000 deaths, organophosphorus (OP) compounds are an important public health issue worldwide. OP poisoning induces cholinergic syndrome, with respiratory distress, hypertension, and neuron damage that may lead to epileptic seizures and permanent cognitive deficits. Existing countermeasures are lifesaving but do not prevent long-lasting neuronal comorbidities, emphasizing the urgent need for animal models to better understand OP neurotoxicity and identify novel antidotes. Here, using diisopropylfluorophosphate (DFP), a prototypic and moderately toxic OP, combined with zebrafish larvae, we first showed that DFP poisoning caused major acetylcholinesterase inhibition, resulting in paralysis and CNS neuron hyperactivation, as indicated by increased neuronal calcium transients and overexpression of the immediate early genes fosab, junBa, npas4b, and atf3. In addition to these epileptiform seizure-like events, DFP-exposed larvae showed increased neuronal apoptosis, which were both partially alleviated by diazepam treatment, suggesting a causal link between neuronal hyperexcitation and cell death. Last, DFP poisoning induced an altered balance of glutamatergic/GABAergic synaptic activity with increased NR2B-NMDA receptor accumulation combined with decreased GAD65/67 and gephyrin protein accumulation. The zebrafish DFP model presented here thus provides important novel insights into the pathophysiology of OP intoxication, making it a promising model to identify novel antidotes.

Highlights

Organophosphorus (OP) compounds comprise highly poisonous substances widely used as chemical pesticides and as warfare agents
We checked that DFP was not hydrolyzed during the 6 h incubation time and results showed that DFP diluted in fish water (FW) was almost stable with an average loss of 2% per hour, approximately (Fig. 1c)
Because of the widespread use of organophosphorus (OP) compounds for agricultural purposes and the lack of fully effective countermeasures, OP poisoning remains a major public health issue worldwide, with several million intoxications and over 200,000 deaths reported each y ear[37,38], emphasizing the need for fully efficient antidotes to alleviate OP toxicity. To help fill this gap, we used the possibilities offered by zebrafish larvae and developed a vertebrate model of OP poisoning to investigate the consequences of OP exposure on neuronal functions and neuronal network activity

Summary

Introduction

Organophosphorus (OP) compounds comprise highly poisonous substances widely used as chemical pesticides and as warfare agents. Psychomotor deficits, emphasizing the need for new, more potent antidotes To meet this need, an animal model of OP poisoning that would faithfully reproduce the consequences of OP intoxication in humans and be amenable to drug screening would help achieve a better understanding of the pathophysiology of OP poisoning and identify therapeutic entities counteracting the harmful effects of these compounds. Previous studies in rodents have shown that acute DFP poisoning causes potent AChE inhibition, inducing epileptic seizures, neuronal death, memory impairment and neuroinflammation[9,23]. The zebrafish model of DFP poisoning faithfully reproduces the neuronal deficits observed in both humans and rodents exposed to DFP, and provides interesting new insights into the neurotoxicity of OP agents, making it a promising tool to identify novel, more potent antidotes

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