Knockdown of Butyrylcholinesterase but Not Inhibition by Chlorpyrifos Alters Early Differentiation Mechanisms in Human Neural Stem Cells.

Angela Tiethof,Jason Richardson,Ronald Hart

doi:10.3390/toxics6030052

Abstract

Butyrylcholinesterase (BChE) is the evolutionary counterpart to acetylcholinesterase (AChE). Both are expressed early in nervous system development prior to cholinergic synapse formation. The organophosphate pesticide chlorpyrifos (CPF) primarily exerts toxicity through the inhibition of AChE, which results in excess cholinergic stimulation at the synapse. We hypothesized that the inhibition of AChE and BChE by CPF may impair early neurogenesis in neural stem cells (NSCs). To model neurodevelopment in vitro, we used human NSCs derived from induced pluripotent stem cells (iPSCs) with a focus on the initial differentiation mechanisms. Over the six days of NSC differentiation, the BChE activity and mRNA expression significantly increased, while the AChE activity and expression remained unchanged. The CPF treatment (10 μM) caused 82% and 92% inhibition of AChE and BChE, respectively. The CPF exposure had no effect on the cell viability or the expression of the differentiation markers HES5, DCX, or MAP2. However, the shRNA-knockdown of the BChE expression resulted in the decreased or delayed expression of the transcription factors HES5 and HES3. BChE may have a role in the differentiation of NSCs independent of, or in addition to, its enzymatic activity.

Highlights

Chlorpyrifos (CPF) is a widely used organophosphorus class pesticide
neural stem cells (NSCs), produce neurons glia, we examined the cultures differentiated for much longer periods of time for the production of and glia, we examined the cultures differentiated for much longer periods of time for the production mature neuronal morphologies and markers
We established an induced pluripotent stem cells (iPSCs)-derived NSC human cell culture model of early neuronal differentiation as a model for testing neurotoxicity in a human neural progenitor. This system was used to probe the developmental neurotoxicity (DNT) of CPF and to assess the function of BChE early in neurogenesis

Summary

Introduction

Chlorpyrifos (CPF) is a widely used organophosphorus class pesticide. Because of concerns relating to neurodevelopmental toxicity, the residential and public pest management use of CPF has been eliminated [1]. Epidemiological studies have suggested that CPF exposure is correlated with adverse neurodevelopmental effects involving cognition, behavior, and fetal growth [2,3,4]. Animal studies have evaluated the developmental neurotoxicity (DNT) of CPF using endpoints, including motor activity, cognition, emotion/anxiety, and social interaction [5,6,7,8,9,10]. The daily administration of 5 mg/kg of CPF to pregnant mice between gestation days (GD) 7.5–11.5 resulted in morphological changes, including the thinning of the CA1 and CA3

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