RTN1A介导的内质网应激在“缺血再灌注”导致急性肾损伤向慢性肾脏病进展中的作用和机制研究

Acute kidney injury (AKI) is increasingly recognized as a major risk factor for progression to chronic kidney disease (CKD). Severity, duration, and frequency of AKI appear to be important predictors of poor patient outcomes. However, the factors governing AKI to CKD progression are poorly understood, and no specific biomarkers have been identified to distinguish progression after AKI from progression of underlying CKD or how they might interact. Ischemia–reperfusion injury (IRI) is a pathological process that may lead to acute tubulointerstitial injury and subsequent chronic dysfunction in AKI patients. IRI may be followed by a repair process that can restore normal morphology and function in case of moderate damage, but when incomplete leads to permanent damage, progressive fibrosis and CKD. . Studies have shown an important role of endoplasmic reticulum (ER) stress in AKI. We recently reported a novel gene, RTN1A, is a key mediator for ER stress and kidney cell injury and had a critical role in kidney diseases. We conducted microarray analysis in the kidneys of HIV-associated nephropathy mice and found RTN1A is a highly upregulated gene associated with the progression of kidney injury. The expression of RTN1A is increased in murine models of CKD and correlates inversely with renal function of patients with diabetic nephropathy (DN). RTN1A is verified to be involved in ER stress signaling and mediates high glucose or albumin-induced ER stress and apoptosis in kidney cells. We also performed kidney disease models in RTN1A transgenic mice and found reduction of RTN1A attenuates injury in DN and unilateral ureteral obstruction (UUO) murine models. More recently, we demonstrated that increased expression of RTN1A was associated with the severity of kidney injury in AKI patients and with progression to CKD. Using an inducible tubular cell-specific knockdown mouse model for RTN1A, we show that the reduction of RTN1A expression during the initial stage of AKI attenuated ER stress and kidney cell injury in early stages and renal fibrosis development in later stages in models of folic acid nephropathy. . Based on our previous research work, in the present study we’ll first determine the effect of duration and frequency of repeat episodes for the progression of AKI in an animal model of ischemia reperfusion injury. We like to examine the dynamic change of RTN1A and ER stress markers in the development of AKI and its progression to CKD. The combined use of functional markers such as changes in serum creatinine and BUN; novel AKI tubular injury markers such as KIM-1, N-GAL; and ER stress markers like RTN1A, CHOP, XBP-1s, will be important to distinguish early injury of AKI, evaluate disease severity and provide a predictive insight as to the long-term consequences of AKI. Secondly, in RTN1A transgenic mice with conditioned ischemic reperfusion AKI model, we will study whether the alteration of RTN1A expression in tubular cell contributes to the progression and renal outcomes in these mice. Finally, we will determine the mechanism by which RTN1A mediates ER stress activation and the role of RTN1A in ischemia reperfusion induced tubular cell injury in vitro. Together, we hypothesis that therapeutic targeting of RTN1A may be novel strategies to promote adaptive renal repair and to minimize progressive fibrosis and disease progression after acute renal injury.

急性肾损伤（AKI）的远期预后不容乐观，缺血再灌注损伤（IRI）是 AKI向慢性肾脏病（CKD）进展的重要危险因素，但发病机制尚不清楚。课题组前期发现内质网应激（ER stress）相关新基因RTN1A与肾脏疾病关系密切，RTN1A介导的ER stress促进急性间质性肾炎和糖尿病肾病时肾脏细胞的损伤和凋亡，与疾病进展相关。本项目在既往系列研究基础上，通过IRI小鼠模型模拟AKI自然病程，探讨“缺血时间”和“打击频次”对AKI病程转归的影响；研究ER stress反应在AKI向CKD进展中的变化特点，探索敏感生物预警标志物；联合传统生化指标和新型肾小管损伤标志物检测，优化AKI诊断模型；进一步通过RTN1A基因工程小鼠和体外实验，阐明RTN1A对ER stress的调控机制及其在IRI导致的肾小管损伤和AKI向CKD进程中的重要作用，为改善AKI预后、把握有效治疗时机和干预靶点提供新思路。

急性肾损伤（AKI）发生后病程的进展和转归是近年来肾脏病领域研究的热点，不少研究发现部分AKI患者经积极治疗却仍无法使肾功能完全逆转，最终进展至慢性肾脏疾病（CKD），造成肾脏不可逆性损伤，但对于AKI向CKD病程转化的危险因素以及确切发病机制仍不清楚，同时目前也缺乏敏感和特异的生物预警标志物。本项目针对上述当前AKI研究领域的瓶颈，就此开展了一系列体内、体外和临床研究，并取得了突出的研究成果。首先，我们采用缺血再灌注损伤（IRI）诱导小鼠AKI的发生，通过改变IRI缺血时间和打击频次，构建了具有不同肾脏预后的“可逆型”、“进展型”、“加速进展型”AKI动物模型，揭示了AKI向CKD进展的危险因素，并为后续机制学研究和未来相关研究提供了动物模型基础和充分的立论依据。在此基础上，我们研究内质网应激在AKI向CKD进程中的作用机制，发现RTN1A/PERK/ATF通路参与AKI慢性化进程。同时，我们以Wnt5a非经典通路为切入点，聚焦于Wnt5a/CD146/JNK通路与AKI向CKD进程的关系，通过体外调控实验和体内动物模型验证，揭示IRI诱导的急性缺氧通过Wnt5a/CD146介导的炎症机制促进肾小管上皮急性损伤和慢性化进程，继而导致AKI向CKD的进展。此外，基于机制学研究，我们发现新型肾小管上皮损伤标志物NGAL与AKI疾病转归密切相关，我们结合全球新冠疫情背景，同步开展了探索新冠患者AKI不良预后的临床转化研究，构建了以NGAL水平和胸部CT影像为基础的风险预测模型，为新冠肺炎患者AKI的个体化风险评估和疾病防控提供了有效的新方法。本研究揭示了肾脏缺血时间和IRI打击频次与AKI向CKD进展密切相关，阐明了内质网应激和炎症机制在IRI诱导的肾小管慢性损伤和纤维化中的重要作用，并发现了预警AKI进展和转归的敏感生物标志物，这对我们临床改善AKI预后、把握有效治疗时机和干预靶点提供了崭新思路。

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