Division of Rheumatology, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA.
Division of Rheumatology, Hackensack University Medical Center, Hackensack, NJ, USA.
Semin Arthritis Rheum. 2023 Dec;63:152263. doi: 10.1016/j.semarthrit.2023.152263. Epub 2023 Sep 27.
Intrarenal complement activation has been implicated in the pathogenesis of tubulointerstitial fibrosis in lupus nephritis (LN) based on prior animal studies. The assembly of the membrane attack complex (MAC) by complement C5b to C9 on the cell membrane leads to cytotoxic pores and cell lysis, while CD59 inhibits MAC formation by preventing C9 from joining the complex. We hypothesize that complement activation and imbalance between complement activation and inhibition, as defined by increased production of individual complement components and uncontrolled MAC activation relative to CD59 inhibition, are associated with interstitial fibrosis and tubular atrophy (IFTA) in LN and correlate with the key mediators of kidney fibrosis- transforming growth factor receptors beta (TGFRβ), platelet-derived growth factor beta (PDGFβ) and platelet-derived growth factor receptor beta (PDGFRβ).
We included urine samples from 46 adults and pediatric biopsy-proven lupus nephritis patients who underwent clinically indicated kidney biopsies between 2010 and 2019. We compared individual urinary complement components and the urinary C9-to-CD59 ratio between LN patients with moderate/severe IFTA and none/mild IFTA. IFTA was defined as none/mild (<25% of interstitium affected) versus moderate/severe (≥ 25% of interstitium affected). Proteomics analysis was performed using mass spectrometry (Orbitrap Fusion Lumos, Thermo Scientific) and processed by the Proteome Discoverer. Urinary complement proteins enriched in LN patients with moderate/severe IFTA were correlated with serum creatinine, TGFβR1, TGFβR2, PDGFβ, and PDGFRβ.
Of the 46 LN patients included in the study, 41 (89.1%) were women, 20 (43.5%) self-identified as Hispanic or Latino, and 26 (56.5%) self-identified as Black or African American. Ten of the 46 (21.7%) LN patients had moderate/severe IFTA on kidney biopsy. LN patients with moderate/severe IFTA had an increased urinary C9-to-CD59 ratio [median 0.91 (0.83-1.05) vs 0.81 (0.76-0.91), p=0.01]. Urinary C3 and CFI levels in LN patients with moderate/severe IFTA were higher compared to those with none/mild IFTA [C3 median (IQR) 24.4(23.5-25.5) vs. 20.2 (18.5-22.2), p= 0.02], [CFI medium (IQR) 28.8 (21.8-30.6) vs. 20.4 (18.5-22.9), p=0.01]. Complement C9, CD59, C3 and CFI correlated with TGFβR1, PDGFβ, and PDGFRβ, while C9, CD59 and C3 correlated with TGFβR2.
This study is one of the first to compare the urinary complement profile in LN patients with moderate/severe IFTA and none/mild IFTA in human tissues. This study identified C3, CFI, and C9-to-CD59 ratio as potential markers of tubulointerstitial fibrosis in LN.
基于先前的动物研究，补体在狼疮肾炎（LN）肾小管间质纤维化的发病机制中起作用。补体 C5b 至 C9 在细胞膜上组装成膜攻击复合物（MAC），导致细胞毒性孔和细胞裂解，而 CD59 通过阻止 C9 加入复合物来抑制 MAC 的形成。我们假设补体的激活以及补体激活与抑制之间的失衡与 LN 中的间质纤维化和肾小管萎缩（IFTA）有关，并与肾脏纤维化的关键介质 - 转化生长因子受体β（TGFRβ）、血小板衍生生长因子β（PDGFβ）和血小板衍生生长因子受体β（PDGFRβ）相关。
我们纳入了 46 名成人和儿科经活检证实的狼疮肾炎患者的尿液样本，这些患者在 2010 年至 2019 年期间接受了临床指征的肾活检。我们比较了 LN 患者中中度/重度 IFTA 和无/轻度 IFTA 患者的尿液中单个补体成分和 C9 与 CD59 的比值。IFTA 定义为无/轻度（<25%的间质受累）与中度/重度（≥25%的间质受累）。使用质谱法（Orbitrap Fusion Lumos，Thermo Scientific）进行蛋白质组学分析，并由 Proteome Discoverer 进行处理。LN 患者中中度/重度 IFTA 中富集的尿液补体蛋白与血清肌酐、TGFβR1、TGFβR2、PDGFβ 和 PDGFRβ 相关。
在纳入研究的 46 名 LN 患者中，41 名（89.1%）为女性，20 名（43.5%）自我认定为西班牙裔或拉丁裔，26 名（56.5%）自我认定为黑人和非裔美国人。46 名 LN 患者中有 10 名（21.7%）出现中度/重度 IFTA。中度/重度 IFTA 的 LN 患者的尿液 C9 与 CD59 比值升高[中位数 0.91（0.83-1.05）比 0.81（0.76-0.91），p=0.01]。与无/轻度 IFTA 相比，中度/重度 IFTA 的 LN 患者尿液 C3 和 CFI 水平更高[C3 中位数（IQR）24.4（23.5-25.5）比 20.2（18.5-22.2），p=0.02]，[CFI 中位数（IQR）28.8（21.8-30.6）比 20.4（18.5-22.9），p=0.01]。补体 C9、CD59、C3 和 CFI 与 TGFβR1、PDGFβ 和 PDGFRβ 相关，而 C9、CD59 和 C3 与 TGFβR2 相关。
这项研究是首次在人类组织中比较 LN 患者中中度/重度 IFTA 和无/轻度 IFTA 的尿液补体谱的研究之一。本研究发现 C3、CFI 和 C9 与 CD59 的比值可作为 LN 肾小管间质纤维化的潜在标志物。
