Sir Run run Hospital, Nanjing Medical University, Nanjing, China.
State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China.
Theranostics. 2021 Aug 11;11(18):8797-8812. doi: 10.7150/thno.61601. eCollection 2021.
Neprilysin (NEP) is a major endogenous catabolic enzyme of amyloid β (Aβ). Previous studies have suggested that increasing NEP expression in animal models of Alzheimer's disease had an ameliorative effect. However, the underlying signaling pathway that regulates NEP expression remains unclear. The aryl hydrocarbon receptor (AhR) is a ligand-activated cytoplasmic receptor and transcription factor. Recent studies have shown that AhR plays essential roles in the central nervous system (CNS), but its physiological and pathological roles in regulating NEP are not entirely known. Western blotting, immunofluorescence, quantitative RT-PCR and enzyme activity assay were used to verify the effects of AhR agonists on NEP in a cell model (N2a) and a mouse model (APP/PS1). Luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay were conducted to investigate the roles of AhR in regulating NEP transcription. Object recognition test and the Morris water maze task were performed to assess the cognitive capacity of the mice. Activating AhR by the endogenous ligand L-Kynurenine (L-KN) or FICZ, or by the exogenous ligand diosmin or indole-3-carbinol (I3C) significantly increases NEP expression and enzyme activity in N2a cells and APP/PS1 mice. We also found that AhR is a direct transcription factor of NEP. Diosmin treatment effectively ameliorated the cognitive disorder and memory deficit of APP/PS1 transgenic mice. By knocking down AhR or using a small molecular inhibitor targeting AhR or NEP, we found that diosmin enhanced Aβ degradation through activated AhR and increased NEP expression. These results indicate a novel pathway for regulating NEP expression in neurons and that AhR may be a potential therapeutic target for the treatment of Alzheimer's disease.
神经肽酶（NEP）是淀粉样β（Aβ）的主要内源性代谢酶。先前的研究表明，在阿尔茨海默病动物模型中增加 NEP 的表达具有改善作用。然而，调节 NEP 表达的潜在信号通路仍不清楚。芳香烃受体（AhR）是一种配体激活的细胞质受体和转录因子。最近的研究表明，AhR 在中枢神经系统（CNS）中发挥重要作用，但它在调节 NEP 方面的生理和病理作用尚不完全清楚。Western 印迹、免疫荧光、定量 RT-PCR 和酶活性测定用于验证 AhR 激动剂对细胞模型（N2a）和小鼠模型（APP/PS1）中 NEP 的影响。荧光素酶报告基因测定和染色质免疫沉淀（ChIP）测定用于研究 AhR 在调节 NEP 转录中的作用。物体识别测试和 Morris 水迷宫任务用于评估小鼠的认知能力。通过内源性配体 L-犬尿氨酸（L-KN）或 FICZ、外源性配体地奥司明或吲哚-3-甲醇（I3C）激活 AhR，可显著增加 N2a 细胞和 APP/PS1 小鼠中的 NEP 表达和酶活性。我们还发现 AhR 是 NEP 的直接转录因子。地奥司明治疗可有效改善 APP/PS1 转基因小鼠的认知障碍和记忆缺陷。通过敲低 AhR 或使用针对 AhR 或 NEP 的小分子抑制剂，我们发现地奥司明通过激活 AhR 增强 Aβ 降解并增加 NEP 表达。这些结果表明，在神经元中调节 NEP 表达的新途径，AhR 可能是治疗阿尔茨海默病的潜在治疗靶点。
