TY - JOUR
T1 - Complementary biological and computational approaches identify distinct mechanisms of chlorpyrifos versus chlorpyrifos-oxon-induced dopaminergic neurotoxicity
AU - Sammi, Shreesh Raj
AU - Syeda, Tauqeerunnisa
AU - Conrow, Kendra D.
AU - Leung, Maxwell C.K.
AU - Cannon, Jason R.
N1 - Publisher Copyright:
© The Author(s) 2022. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
PY - 2023/1/31
Y1 - 2023/1/31
N2 - Organophosphate (OP) pesticides are widely used in agriculture. While acute cholinergic toxicity has been extensively studied, chronic effects on other neurons are less understood. Here, we demonstrated that the OP pesticide chlorpyrifos (CPF) and its oxon metabolite are dopaminergic neurotoxicants in Caenorhabditis elegans. CPF treatment led to inhibition of mitochondrial complex II, II + III, and V in rat liver mitochondria, while CPF-oxon did not (complex II + III and IV inhibition observed only at high doses). While the effect on C. elegans cholinergic behavior was mostly reversible with toxicant washout, dopamine-associated deficits persisted, suggesting dopaminergic neurotoxicity was irreversible. CPF reduced the mitochondrial content in a dose-dependent manner and the fat modulatory genes cyp-35A2 and cyp-35A3 were found to have a key role in CPF neurotoxicity. These findings were consistent with in vitro effects of CPF and CPF-oxon on nuclear receptor signaling and fatty acid/steroid metabolism observed in ToxCast assays. Two-way hierarchical analysis revealed in vitro effects on estrogen receptor, pregnane X receptor, and peroxisome proliferator-activated receptor gamma pathways as well as neurotoxicity of CPF, malathion, and diazinon, whereas these effects were not detected in malaoxon and diazoxon. Taken together, our study suggests that mitochondrial toxicity and metabolic effects of CPF, but not CPF-oxon, have a key role of CPF neurotoxicity in the low-dose, chronic exposure. Further mechanistic studies are needed to examine mitochondria as a common target for all OP pesticide parent compounds, because this has important implications on cumulative pesticide risk assessment.
AB - Organophosphate (OP) pesticides are widely used in agriculture. While acute cholinergic toxicity has been extensively studied, chronic effects on other neurons are less understood. Here, we demonstrated that the OP pesticide chlorpyrifos (CPF) and its oxon metabolite are dopaminergic neurotoxicants in Caenorhabditis elegans. CPF treatment led to inhibition of mitochondrial complex II, II + III, and V in rat liver mitochondria, while CPF-oxon did not (complex II + III and IV inhibition observed only at high doses). While the effect on C. elegans cholinergic behavior was mostly reversible with toxicant washout, dopamine-associated deficits persisted, suggesting dopaminergic neurotoxicity was irreversible. CPF reduced the mitochondrial content in a dose-dependent manner and the fat modulatory genes cyp-35A2 and cyp-35A3 were found to have a key role in CPF neurotoxicity. These findings were consistent with in vitro effects of CPF and CPF-oxon on nuclear receptor signaling and fatty acid/steroid metabolism observed in ToxCast assays. Two-way hierarchical analysis revealed in vitro effects on estrogen receptor, pregnane X receptor, and peroxisome proliferator-activated receptor gamma pathways as well as neurotoxicity of CPF, malathion, and diazinon, whereas these effects were not detected in malaoxon and diazoxon. Taken together, our study suggests that mitochondrial toxicity and metabolic effects of CPF, but not CPF-oxon, have a key role of CPF neurotoxicity in the low-dose, chronic exposure. Further mechanistic studies are needed to examine mitochondria as a common target for all OP pesticide parent compounds, because this has important implications on cumulative pesticide risk assessment.
KW - chlorpyrifos
KW - dopamine
KW - neurotoxicity
KW - organophosphate
KW - oxon
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U2 - 10.1093/toxsci/kfac114
DO - 10.1093/toxsci/kfac114
M3 - Article
C2 - 36269219
AN - SCOPUS:85147143522
SN - 1096-6080
VL - 191
SP - 163
EP - 178
JO - Toxicological Sciences
JF - Toxicological Sciences
IS - 1
ER -