Wu Deng-Pan, Wei Yan-Su, Hou Li-Xiang, Du Yu-Xuan, Yan Qiu-Qing, Liu Ling-Ling, Zhao Yuan-Dan, Yan Ru-Yu, Yu Chao, Zhong Zhen-Guo, Huang Jin-Lan
Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Pharmacy School, Xuzhou Medical University, Xuzhou, 221004, Jiangsu, China.
Xuzhou Ruihu Health Management Consulting Co., Ltd, Xuzhou, 221002, Jiangsu, China.
Alzheimers Res Ther. 2025 Feb 14;17(1):44. doi: 10.1186/s13195-025-01698-7.
Abnormal microglial polarization phenotypes contribute to the pathogenesis of Alzheimer's disease (AD). Circular RNAs (circRNAs) have garnered increasing attention due to their significant roles in human diseases. Although research has demonstrated differential expression of circRNAs in AD, their specific functions in AD pathogenesis remain largely unexplored.
CircRNA microarray was performed to identify differentially expressed circRNAs in the hippocampus of APP/PS1 and WT mice. The stability of circAPP was assessed via RNase R treatment assay. CircAPP downstream targets miR-1906 and chloride intracellular channel 1 (CLIC1) were identified using bioinformatics and proteomics, respectively. RT-PCR assay was conducted to detect the expression of circAPP, miR-1906 and CLIC1. Morris water maze (MWM) test, passive avoidance test and novel object recognition task were used to detect cognitive function of APP/PS1 mice. Microglial M1/M2 polarization and AD pathology were assessed using Western blot, flow cytometry and Golgi staining assays. CLIC1 expression and channel activity were evaluated using Western blot and functional chloride channel assays, respectively. The subcellular location of circAPP was assessed via FISH and RT-PCR assays. RNA pull-down assay was performed to detect the interaction of miR-1906 with circAPP and 3' untranslated region (3'UTR) of CLIC1 mRNA.
In this study, we identified a novel circRNA, named circAPP, that is encoded by amyloid precursor protein (APP) and is implicated in AD. CircAPP is a stable circRNA that was upregulated in Aβ-treated microglial cells and the hippocampus of APP/PS1 mice. Downregulation of circAPP or CLIC1, or overexpression of miR-1906 in microglia modulated microglial M1/M2 polarization in Aβ-treated microglial cells and the hippocampus of APP/PS1 mice, and improved AD pathology and the cognitive function of APP/PS1 mice. Further results revealed that circAPP was mainly distributed in the cytoplasm, and circAPP could regulate CLIC1 expression and channel activity by interacting with miR-1906 and affecting miR-1906 expression, thereby regulating microglial polarization in AD.
Taken together, our study elucidates the regulatory role of circAPP in AD microglial polarization via miR-1906/CLIC1 axis, and suggests that circAPP may act as a critical player in AD pathogenesis and represent a promising therapeutic target for AD.
异常的小胶质细胞极化表型有助于阿尔茨海默病（AD）的发病机制。环状RNA（circRNAs）因其在人类疾病中的重要作用而受到越来越多的关注。尽管研究表明circRNAs在AD中存在差异表达，但其在AD发病机制中的具体功能仍 largely未被探索。
进行circRNA微阵列分析以鉴定APP/PS1和野生型（WT）小鼠海马中差异表达的circRNAs。通过RNase R处理试验评估circAPP的稳定性。分别使用生物信息学和蛋白质组学鉴定circAPP的下游靶标miR-1906和氯离子细胞内通道1（CLIC1）。进行逆转录聚合酶链反应（RT-PCR）试验以检测circAPP、miR-1906和CLIC1的表达。使用莫里斯水迷宫（MWM）试验、被动回避试验和新物体识别任务检测APP/PS1小鼠的认知功能。使用蛋白质免疫印迹法、流式细胞术和高尔基染色试验评估小胶质细胞的M1/M2极化和AD病理学。分别使用蛋白质免疫印迹法和功能性氯离子通道试验评估CLIC1的表达和通道活性。通过荧光原位杂交（FISH）和RT-PCR试验评估circAPP的亚细胞定位。进行RNA下拉试验以检测miR-1906与circAPP以及CLIC1 mRNA的3'非翻译区（3'UTR）之间的相互作用。
在本研究中，我们鉴定了一种新型circRNA，命名为circAPP，它由淀粉样前体蛋白（APP）编码并与AD有关。circAPP是一种稳定的circRNA，在Aβ处理的小胶质细胞和APP/PS1小鼠的海马中上调。在小胶质细胞中下调circAPP或CLIC1，或过表达miR-1906，可调节Aβ处理的小胶质细胞和APP/PS1小鼠海马中的小胶质细胞M1/M2极化，并改善AD病理学和APP/PS1小鼠的认知功能。进一步的结果表明，circAPP主要分布在细胞质中，并且circAPP可以通过与miR-1906相互作用并影响miR-1906的表达来调节CLIC1的表达和通道活性，从而调节AD中的小胶质细胞极化。
综上所述，我们的研究阐明了circAPP通过miR-1906/CLIC1轴在AD小胶质细胞极化中的调节作用，并表明circAPP可能是AD发病机制中的关键参与者，代表了AD的一个有前景的治疗靶点。
