暴露于环境污染物和诱导芳香烃受体(AhR)表达的内源性代谢物已被认为会影响认知发展,尤其是在男生中,也是运动功能。由于目前的知识是基于流行病学和动物研究,需要体外模型来更好地了解这些化合物在分子水平上对人类神经系统的影响。这里,我们研究了AhR通路组分在人运动神经元中的表达以及它们如何被AhR配体调节。从人诱导多能干细胞(hiPSC)产生的运动神经元在分子水平上和通过电生理学表征。AhR靶基因的mRNA水平,CYP1A1和CYP1B1(细胞色素P4501A1/1B1),用AhR配体处理后,在hiPSC和分化的神经元中监测AhR信号传导成分,2,3,7,8,-四氯二苯并-对二恶英(TCDD),L-犬尿氨酸(L-Kyn),和犬尿烯酸(KA),通过RT-qPCR。还评估了用AhR配体处理的神经元中AhR细胞定位和CYP1A1活性的变化。我们生成的神经元表达运动神经元特异性标记,并且具有功能性。CYP1B1、AhR核转位物(ARNT1和ARNT2)和AhR阻遏物(AhRR)的转录水平随神经元分化而改变,在神经元中显著高于hiPSC。相比之下,神经元中的CYP1A1和AhR转录物水平略低于hiPSC。对TCDD治疗的反应在hiPSC和神经元中不同,只有后者表现出显著的CYP1A1上调。相比之下,TCDD轻微上调hiPSC中CYP1B1mRNA,而是在神经元中下调它。不同AhR配体对神经元AhR及其一些靶基因的影响比较表明L-Kyn和KA,但不是TCDD,调节AhR表达并不同地影响CYP1A1和CYP1B1表达。最后,虽然TCDD不会显著影响AhR转录水平,它诱导AhR蛋白易位到细胞核并增加CYP1A1活性。这与L-Kyn和KA相反,既不影响也不减少,分别,CYP1A1活性。AhR信号通路各组分的表达受神经元分化的调控,并受TCDD的不同影响,这表明多能干细胞对这种毒素的敏感性可能低于神经元。至关重要的是,AhR信号受到人类运动神经元中TCDD和其他AhR配体的不同影响,表明它们可以为评估环境污染物的影响提供有价值的工具。
Exposure to environmental pollutants and endogenous metabolites that induce aryl hydrocarbon receptor (AhR) expression has been suggested to affect cognitive development and, particularly in boys, also motor function. As current knowledge is based on epidemiological and animal studies, in vitro models are needed to better understand the effects of these compounds in the human nervous system at the molecular level. Here, we investigated expression of AhR pathway components and how they are regulated by AhR ligands in human motor neurons. Motor neurons generated from human induced pluripotent stem cells (hiPSCs) were characterized at the molecular level and by electrophysiology. mRNA levels of AhR target genes, CYP1A1 and CYP1B1 (cytochromes P450 1A1/1B1), and AhR signaling components were monitored in hiPSCs and in differentiated neurons following treatment with AhR ligands, 2,3,7,8,-tetrachlodibenzo-p-dioxin (TCDD), L-kynurenine (L-Kyn), and kynurenic acid (
KA), by RT-qPCR. Changes in AhR cellular localization and CYP1A1 activity in neurons treated with AhR ligands were also assessed. The neurons we generated express motor neuron-specific markers and are functional. Transcript levels of CYP1B1, AhR nuclear translocators (ARNT1 and ARNT2) and the AhR repressor (AhRR) change with neuronal differentiation, being significantly higher in neurons than hiPSCs. In contrast, CYP1A1 and AhR transcript levels are slightly lower in neurons than in hiPSCs. The response to TCDD treatment differs in hiPSCs and neurons, with only the latter showing significant CYP1A1 up-regulation. In contrast, TCDD slightly up-regulates CYP1B1 mRNA in hiPSCs, but downregulates it in neurons. Comparison of the effects of different AhR ligands on AhR and some of its target genes in neurons shows that L-Kyn and
KA, but not TCDD, regulate AhR expression and differently affect CYP1A1 and CYP1B1 expression. Finally, although TCDD does not significantly affect AhR transcript levels, it induces AhR protein translocation to the nucleus and increases CYP1A1 activity. This is in contrast to L-Kyn and
KA, which either do not affect or reduce, respectively, CYP1A1 activity. Expression of components of the AhR signaling pathway are regulated with neuronal differentiation and are differently affected by TCDD, suggesting that pluripotent stem cells might be less sensitive to this toxin than neurons. Crucially, AhR signaling is affected differently by TCDD and other AhR ligands in human motor neurons, suggesting that they can provide a valuable tool for assessing the impact of environmental pollutants.