QKI-SIRT1正反馈环路在巨噬细胞M2极化中的作用及其异常与肥胖相关肾病的关系研究

Anomalous polarization of macrophage and its mediated inflammatory response are play an important role in obesity-related glomerulopathy (ORG). With the support of the NSFC, we have revealed that during the macrophage polarization towards to M2,the expression of QKI, especially the QKI expression without acetylation increases. Increased QKI expression can promote M2 polorization and negatively regulate the inflammatory response. Further study revealed that the reason for QKI increase is the acetylation reduced. Increased QKI expression could induce the expression of SIRT1, which in turn deacetylates the QKI. Thus, SIRT1 and QKI form a positive feedback loop. In addition, this feedback loop could negatively regulate the NFκB signal pathway by deacetylating or posttranscriptionally targeting related molecules in this pathway, and thus involve in the M2 polarization. Under the obesity condition, the QKI-SIRT1 feedback loop is blocked due to decreased QKI expression, and thus results in the deficiency of the M2 polarization. In this project, we would clarify the positive feedback loop between QKI and SIRT1 and their role in the inflammatory regulation by using gene gain of function or loss of function analysis. Then, we would analyze the putative role of AMPK, an essential regulator in metabolism and obesity, in the regulation of the QKI-SIRT feedback loop, especially its defect in the obesity model. Finally, we will reveal the effects of the QKI-SIRT feedback loop due to deficiency of AMPK on macrophage and obesity. The proposed study will reveal a novel function of QKI in macrophage polarization and its role in ORG.

巨噬细胞M1异常极化及其介导的炎症反应是肥胖相关肾病的重要机制。在前一个国科金的资助下，我们发现巨噬细胞向M2极化时RNA结合蛋白QKI表达增加， 表达增加的QKI可以促进M2极化、抑制炎症反应。进一步分析发现M2极化过程中QKI乙酰化水平降低是其表达增加的重要原因，而QKI能够增强SIRT1的表达，后者进一步抑制QKI的乙酰化，二者形成正反馈；该正反馈通过调节NFκB信号通路相关分子的表达和修饰，发挥抗炎作用，促进M2极化。肥胖过程中，由于AMPK等的活性发生改变，导致该反馈环路丧失；该通路的异常导致巨噬细胞M2极化降低，而M1极化增强，加剧炎症，促进肥胖相关肾病的发生。本项目拟首先明确QKI-SIRT1形成正反馈的机制和抗炎功能；在此基础上，探讨肥胖条件下代谢相关信号AMPK通路异常对上述正反馈的影响及机制；最后，明确上述调控对巨噬细胞功能的影响及其在肥胖相关肾病发病中的作用。

肾纤维化是肥胖相关性肾病等多种慢性肾脏病发展的最终归途，目前其机制研究多集中在细胞外基质是如何产生的。然而，病理状态下，细胞外基质的降解减少是否参与肾纤维化过程？大量堆积的细胞外基质在破坏正常肾组织结构的同时，是否还异常调控肾组织细胞，加重肾纤维化进程？. 在本项目支持下，该课题组研究发现，QKI-β-catenin/HGF网络调控巨噬细胞活化，促进细胞外基质降解，抑制肾纤维化发生发展。病理状态下，QKI-β-catenin/HGF网络调控缺失，导致巨噬细胞功能异常，uPA、tPA生成减少，水解细胞外基质能力减弱，细胞外基质异常堆积，形成促纤维化Niche样微环境。细胞外基质糖蛋白Tenascin C（TNC）是促纤维化Niche的重要组分。体内、体外研究发现，TNC主要由间质活化的成纤维细胞分泌，其形成的促纤维化Niche能够反作用于间质成纤维细胞，促进其增殖和活化；若抑制TNC的表达，干预促纤维化Niche的形成，则有效抑制成纤维细胞增殖和活化，抑制肾纤维化发生发展。. 通过本项目研究，我们深入探讨了肾组织微环境改变在介导慢性肾病引起的肾纤维化发生发展中的重要作用。恢复体内QKI-β-catenin/HGF网络信号对巨噬细胞功能的调控，抑制肾纤维化Niche的形成，维持肾组织微环境稳态，是有效抑制肾纤维化发生发展的重要手段。此外，在本项目中建立的细胞、组织来源的细胞外基质骨架的分离方法，以及基于细胞外基质骨架的细胞体外三维培养技术，为后续组织微环境的体外研究提供了新的手段，为抗纤维化药物筛选建立了更有效的平台。