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

项目摘要 慢性肾脏疾病（CKD）是一种发病率的强有力的媒介，也是由于肾脏疾病导致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因子， 不良后果。在本申请中，我们提出因子D（FD）的累积，其由 肾脏并激活补体的旁路途径（AP），代表了肾脏中的获得性失调。 AP会导致心血管疾病和慢性肾病进展。我们比较了CKD患者和健康人的蛋白质组， 对照我们观察到的最强信号是AP通路的组分。CKD患者有 循环微粒（脱落的亚微米膜囊泡）中FD水平显著更高 从细胞响应激活或损伤）和血浆中较高水平的Ba（Ba是AP的生物标志物 激活）。FD激活AP，导致产生包括Ba的补体片段。因子H（FH） 是AP的主要抑制剂，但CKD与FH水平的差异无关。我们的体内数据 表明即使FD的小增量，如果没有足够水平的FH的对抗，也会导致系统性AP activation.此外，我们发现CKD患者血浆Ba水平升高，并与肱动脉收缩压相关， 血流介导的扩张和蛋白尿，内皮功能障碍的两个指标。因此， FD（观察到CKD患者GFR降低）将CKD与全身性AP失调联系起来，这可能是一种慢性肾脏病的发病机制。 CKD患者CVD和CKD进展的重要机制。补体中的遗传变异 调节基因也可能影响AP激活，并可能导致CVD和CKD进展的风险。 CKD患者。我们的小组已经确定了几个常见的CFH基因多态性， 功能性AP激活。因此，我们的总体假设是，CKD患者发展为获得性失衡， FD和FH之间（高FD/FH比率）导致AP失调（即，活化），使得所述细胞的生物标志物 AP可预测CVD、CKD进展和CKD死亡。其次，我们假设个人 具有AP失调遗传倾向的患者将最易受AP失调的影响 的CKD。为了验证我们的假设，我们建议利用两个临床试验的样本：退伍军人事务部 糖尿病肾病（VA NEPHRON-D）和收缩压干预试验（SPRINT）。在 目的1，如果CKD与AP激活独立相关，并确定高FD/FH比值是否预测AP CKD中的激活。在目标2a和2b中，我们将研究血浆Ba是否独立预测CVD或CKD CKD患者的进展。在目标3中，我们将确定是否有最高程度的CKD受试者， AP激活富集CFH和AP的其他基因的遗传变异，与那些程度最低的基因相比， AP激活。拟议的实验将帮助我们了解AP的潜在机制 这可能是慢性肾脏病的一个新的治疗靶点，并可能在这一高风险患者人群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.