The Alternative Pathway of Complement: A Potential Contributor to Adverse Outcomes in CKD

项目总结 慢性肾脏疾病(CKD)是发病率的强大媒介，也是因以下原因而死亡的独立预测因子 心血管疾病(CVD)。具体地说，肾小球滤过率(GFR)降低是一个强有力的预测指标 不利的结果。在此应用程序中，我们提出因子D(Fd)的累积，它由 肾脏，并激活补体的替代途径(AP)，代表获得性失调 AP继而促进CVD和CKD的进展。我们比较了慢性肾脏病患者和健康人的蛋白质组 控制。我们观察到的最强信号是AP通路的组成部分。CKD患者有 循环中微粒(脱落的亚微米级膜泡)中的FD水平显著升高 来自细胞对激活或损伤的反应)和较高水平的血浆中的Ba值(Ba值是AP的生物标记物 激活)。FD激活AP，导致包括BA在内的补体片段的产生。系数H(FH) 是AP的主要抑制剂，但CKD与FH水平的差异无关。我们的活体数据 这表明，即使FD中的微小增量，如果没有足够的FH水平的对抗，也会导致系统性AP 激活。此外，我们还发现慢性肾脏病患者的血钙水平升高，且与肱动脉血钙水平呈正相关。 血流介导的扩张和蛋白尿是内皮功能障碍的两个指标。因此，增加的 FD(如观察到CKD中GFR减少)将CKD与全身性AP调节失调联系在一起，这可能是一种 CKD患者CVD和CKD进展的重要机制。补体中的遗传变异 调控基因也可能影响AP的激活，并可能参与CVD和CKD进展的风险 慢性肾脏病患者。我们的团队已经确定了几种常见的CFH基因多态性，这些基因与 功能性AP激活。因此，我们的总体假设是CKD患者会出现获得性失衡。 在FD和FH之间(高FD/FH比率)导致AP失调(即激活)，从而使 AP是CKD患者CVD、CKD进展和死亡的预测指标。其次，我们假设每个人 有AP遗传倾向的人在AP环境中最容易受到AP失调的影响 对CKD的研究。为了验证我们的假设，我们建议使用来自两个临床试验的样本：退伍军人事务部 糖尿病肾病(VA NETHRON-D)和收缩压干预试验(Sprint)。在……里面 目标1，如果CKD与AP激活独立相关，并确定高FD/FH比率是否预测AP 慢性肾脏病中的激活。在目标2a和2b中，我们将检查血浆中的BA是否独立地预测CVD或CKD CKD患者的进展情况。在目标3中，我们将确定CKD受试者是否具有最高程度的 与程度最低的AP相比，AP的CFH和其他基因的遗传变异使AP的激活更加丰富 AP的激活。拟议的实验将帮助我们了解AP背后的机制 CKD中的调节失调，并可能在这一高危患者群体中定义新的治疗靶点。

PROJECT SUMMARY Chronic kidney disease (CKD) is a powerful mediator of morbidity and an independent predictor of death due to cardiovascular disease (CVD). Specifically, reduced glomerular filtration rate (GFR) is a powerful predictor of adverse outcomes. In this application we propose that the accumulation of Factor D (FD), which is filtered by the kidney and activates the alternative pathway (AP) of complement, represents an acquired dysregulation in the AP which then contributes to CVD and CKD progression. We compared the proteome of CKD patients to healthy controls. The strongest signal we observed was for components of the AP pathway. CKD patients had significantly higher levels of FD in circulating microparticles (sub-micrometer membrane vesicles that are shed from cells in response to activation or injury) and higher levels of Ba in the plasma (Ba is a biomarker of AP activation). FD activates the AP resulting in the generation of complement fragments including Ba. Factor H (FH) is the main inhibitor of the AP, but CKD was not associated with differences in the levels of FH. Our in vivo data indicate that even small increments in FD, if unopposed by adequate levels of FH, result in systemic AP activation. Furthermore, we found that plasma Ba levels are elevated in CKD and correlate with brachial artery flow-mediated dilation and with albuminuria, two indicators of endothelial dysfunction. Thus, increased levels of FD (as observed with reduced GFR in CKD) links CKD with systemic AP dysregulation, which may be an important mechanism of CVD and CKD progression in patients with CKD. Genetic variants in complement regulatory genes may also affect AP activation and may contribute to the risk of CVD and CKD progression in patients with CKD. Our group has identified several common CFH gene polymorphisms that associate with functional AP activation. Thus, our overall hypothesis is that CKD patients develop an acquired imbalance between FD and FH (high FD/FH ratio) leading to AP dysregulation (i.e., activation) such that biomarkers of the AP are predictive of CVD, CKD progression, and death in CKD. Secondarily, we hypothesize that individuals with a genetic propensity towards AP dysregulation will be the most susceptible to AP dysregulation in the setting of CKD. To test our hypothesis, we propose to utilize samples from two clinical trials: Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) and the Systolic Blood Pressure Interventional Trial (SPRINT). In aim 1, if CKD is independently associated with AP activation and determine if high FD/FH ratio predicts AP activation in CKD. In aims 2a and 2b we will examine whether plasma Ba independently predicts CVD or CKD progression in CKD patients, respectively. In aim 3, we will determine if CKD subjects with the highest degree of AP activation are enriched for genetic variants in CFH and other genes of the AP vs those with the lowest degree of AP activation. The proposed experiments will help us understand the mechanisms that underlie AP dysregulation in CKD and may define new therapeutic targets in this high-risk patient population.