NeuroDiderot, Inserm, Université Paris Cité, F-75019 Paris, France.
Int J Mol Sci. 2022 Jul 26;23(15):8240. doi: 10.3390/ijms23158240.
Organophosphate (OP) compounds include highly toxic chemicals widely used both as pesticides and as warfare nerve agents. Existing countermeasures are lifesaving, but do not alleviate all long-term neurological sequelae, making OP poisoning a public health concern worldwide and the search for fully efficient antidotes an urgent need. OPs cause irreversible acetylcholinesterase (AChE) inhibition, inducing the so-called cholinergic syndrome characterized by peripheral manifestations and seizures associated with permanent psychomotor deficits. Besides immediate neurotoxicity, recent data have also identified neuroinflammation and microglia activation as two processes that likely play an important, albeit poorly understood, role in the physiopathology of OP intoxication and its long-term consequences. To gain insight into the response of microglia to OP poisoning, we used a previously described model of diisopropylfluorophosphate (DFP) intoxication of zebrafish larvae. This model reproduces almost all the defects seen in poisoned humans and preclinical models, including AChE inhibition, neuronal epileptiform hyperexcitation, and increased neuronal death. Here, we investigated in vivo the consequences of acute DFP exposure on microglia morphology and behaviour, and on the expression of a set of pro- and anti-inflammatory cytokines. We also used a genetic method of microglial ablation to evaluate the role in the OP-induced neuropathology. We first showed that DFP intoxication rapidly induced deep microglial phenotypic remodelling resembling that seen in M1-type activated macrophages and characterized by an amoeboid morphology, reduced branching, and increased mobility. DFP intoxication also caused massive expression of genes encoding pro-inflammatory cytokines , , , and to a lesser extent, immuno-modulatory cytokine , suggesting complex microglial reprogramming that included neuroinflammatory activities. Finally, microglia-depleted larvae were instrumental in showing that microglia were major actors in DFP-induced neuroinflammation and, more importantly, that OP-induced neuronal hyperactivation was markedly reduced in larvae fully devoid of microglia. DFP poisoning rapidly triggered massive microglia-mediated neuroinflammation, probably as a result of DFP-induced neuronal hyperexcitation, which in turn further exacerbated neuronal activation. Microglia are thus a relevant therapeutic target, and identifying substances reducing microglial activation could add efficacy to existing OP antidote cocktails.
有机磷 (OP) 化合物包括高度有毒的化学物质，广泛用作农药和战争神经毒剂。现有的解毒剂虽然能救命，但不能缓解所有的长期神经后遗症，因此 OP 中毒成为全世界的公共卫生关注点，寻找完全有效的解毒剂成为当务之急。OP 会导致乙酰胆碱酯酶（AChE）不可逆抑制，引发所谓的胆碱能综合征，其特征为外周表现和与永久性精神运动缺陷相关的癫痫发作。除了即刻神经毒性外，最近的数据还表明神经炎症和小胶质细胞激活是两个可能在 OP 中毒及其长期后果的病理生理学中发挥重要但理解不足的作用的过程。为了深入了解小胶质细胞对 OP 中毒的反应，我们使用了先前描述的斑马鱼幼虫二异丙基氟磷酸酯 (DFP) 中毒模型。该模型再现了几乎所有在中毒人类和临床前模型中观察到的缺陷，包括 AChE 抑制、神经元癫痫样过度兴奋和神经元死亡增加。在这里，我们研究了急性 DFP 暴露对小胶质细胞形态和行为以及一组促炎和抗炎细胞因子表达的影响。我们还使用了小胶质细胞消融的遗传方法来评估其在 OP 诱导的神经病变中的作用。我们首先表明，DFP 中毒会迅速诱导小胶质细胞表型重塑，类似于 M1 型激活的巨噬细胞，并表现为阿米巴样形态、分支减少和迁移能力增强。DFP 中毒还导致编码促炎细胞因子的基因大量表达， 、 、 ，以及免疫调节细胞因子的表达程度较低 ，表明小胶质细胞发生了复杂的重编程，其中包括神经炎症活动。最后，小胶质细胞耗竭的幼虫对于证明小胶质细胞是 DFP 诱导的神经炎症的主要因素非常重要，更重要的是，完全缺乏小胶质细胞的幼虫中，DFP 诱导的神经元过度兴奋明显减少。DFP 中毒会迅速引发大量小胶质细胞介导的神经炎症，可能是由于 DFP 诱导的神经元过度兴奋，而神经元过度兴奋又进一步加剧了神经元的激活。因此，小胶质细胞是一个有意义的治疗靶点，确定能减少小胶质细胞激活的物质可能会提高现有 OP 解毒剂鸡尾酒的疗效。
