Neurotoxicology Research Group, Division of Toxicology, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80.177, NL-3508 TD Utrecht, The Netherlands.
Neurotoxicology Research Group, Division of Toxicology, Institute for Risk Assessment Sciences (IRAS), Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80.177, NL-3508 TD Utrecht, The Netherlands; Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
Neurotoxicology. 2023 Jan;94:35-45. doi: 10.1016/j.neuro.2022.11.002. Epub 2022 Nov 5.
Exposure to organophosphate (OP) insecticides has been related to several adverse health effects, including neurotoxicity. The primary insecticidal mode of action of OP insecticides relies on (irreversible) binding to acetylcholine esterase (AChE), with -oxon metabolites having a much higher potency for AChE inhibition than the parent compounds. However, OP insecticides can also have non-AChE-mediated effects, including changes in gene expression, neuroendocrine effects, disruption of neurite outgrowth and disturbance of the intracellular calcium (Ca) homeostasis. Since Ca is involved in neurotransmission and neuronal development, our research aimed to assess the effects of two widely used OP insecticides, chlorpyrifos (CPF) and diazinon (DZ) and their respective -oxon metabolites, on intracellular Ca homeostasis in human SH-SY5Y cells and rat primary cortical cultures. Furthermore, we assessed the acute and chronic effects of exposure to these compounds on neuronal network maturation and function in rat primary cortical cultures using microelectrode array (MEA) recordings. While inhibition of AChE appears to be the primary mode of action of oxon-metabolites, our data indicate that both parent OP insecticides (CPF and DZ) inhibit depolarization-evoked Ca influx and neuronal activity at concentrations far below their sensitivity for AChE inhibition, indicating that inhibition of voltage-gated calcium channels is a common mode of action of OP insecticides. Notably, parent compounds were more potent than their oxon metabolites, with exposure to diazinon-oxon (DZO) having no effect on both neuronal activity and Ca influx. Human SH-SY5Y cells were more sensitive to OP-induced inhibition of depolarization-evoked Ca influx than rat cortical cells. Acute exposure to OP insecticides had more potent effects on neuronal activity than on Ca influx, suggesting that neuronal activity parameters are especially sensitive to OP exposure. Interestingly, the effects of DZ and chlorpyrifos-oxon (CPO) on neuronal activity lessened after 48 h of exposure, while the potency of CPF did not differ over time. This suggests that neurotoxicity after exposure to different OPs has different effects over time and occurs at levels that are close to human exposure levels. In line with these results, chronic exposure to CPF during 10 days impaired neuronal network development, illustrating the need to investigate possible links between early-life OP exposure and neurodevelopmental disorders in children and highlighting the importance of non-AChE mediated mechanisms of neurotoxicity after OP exposure.
接触有机磷（OP）杀虫剂与多种不良健康影响有关，包括神经毒性。OP 杀虫剂的主要杀虫作用模式依赖于（不可逆）与乙酰胆碱酯酶（AChE）结合，-氧代代谢物对 AChE 的抑制作用比母体化合物高得多。然而，OP 杀虫剂也可能具有非 AChE 介导的作用，包括基因表达的改变、神经内分泌作用、神经突生长的破坏和细胞内钙（Ca）稳态的干扰。由于 Ca 参与神经传递和神经元发育，我们的研究旨在评估两种广泛使用的 OP 杀虫剂，毒死蜱（CPF）和二嗪农（DZ）及其各自的-氧代代谢物，对人 SH-SY5Y 细胞和大鼠原代皮质培养物细胞内 Ca 稳态的影响。此外，我们使用微电极阵列（MEA）记录评估了这些化合物暴露对大鼠原代皮质培养物中神经元网络成熟和功能的急性和慢性影响。虽然 AChE 抑制似乎是氧代代谢物的主要作用模式，但我们的数据表明，两种母体 OP 杀虫剂（CPF 和 DZ）在远远低于其对 AChE 抑制敏感性的浓度下，抑制去极化诱导的 Ca 内流和神经元活性，表明抑制电压门控钙通道是 OP 杀虫剂的共同作用模式。值得注意的是，母体化合物比它们的氧代代谢物更有效，二嗪农-氧代（DZO）暴露对神经元活性和 Ca 内流均没有影响。人 SH-SY5Y 细胞对 OP 诱导的去极化诱导的 Ca 内流抑制比大鼠皮质细胞更敏感。急性暴露于 OP 杀虫剂对神经元活性的影响比 Ca 内流更强，表明神经元活性参数对 OP 暴露特别敏感。有趣的是，DZ 和毒死蜱氧代（CPO）对神经元活性的影响在暴露 48 小时后减弱，而 CPF 的效力在时间上没有差异。这表明不同 OP 暴露后的神经毒性随时间有不同的影响，发生在接近人类暴露水平的水平。与这些结果一致，在 10 天的时间里慢性接触 CPF 会损害神经元网络的发育，这表明需要研究儿童生命早期接触 OP 与神经发育障碍之间可能存在的联系，并强调 OP 暴露后非 AChE 介导的神经毒性机制的重要性。
