The Renal Pathogenicity of Anti-DNA Antibodies

抗双链DNA抗体不仅对系统性红斑狼疮具有高度特异性， (SLE)但也直接参与了狼疮性肾炎（LN）的发病机制， 表现。然而，尽管抗dsDNA抗体和肾炎之间存在明确的联系， 抗DNA抗体导致肾损伤的机制尚未得到结论性的证实。 测定LN可通过抗DNA结合原位形成免疫复合物而启动 沉积在肾小球基底膜（GBM）上的核小体抗原的抗体。 或者，抗DNA抗体可能不是由于与核抗原结合而是由于与核抗原结合而具有致病性。 而是通过与交叉反应性肾靶结合。在这项资助的最初阶段，我们发现， 致病性鼠抗-DNA抗体与系膜细胞（MC）α-辅肌动蛋白结合，且抗-α-辅肌动蛋白的最高滴度 辅肌动蛋白抗体存在于狼疮小鼠的血清和肾脏洗脱液中。此外，我们报告说， 在人SLE血清中，与MC结合的抗α辅肌动蛋白抗体也以高滴度存在， 与LN的存在和活动密切相关。最后，与MC结合的致病性抗体 α-辅肌动蛋白直接调节炎性基因表达，包括细胞因子和中性粒细胞明胶酶 相关的脂质运载蛋白（NGAL，脂质运载蛋白），通过Fc依赖性和非依赖性机制。我们假设 肾细胞中由致肾炎抗体诱导的基因调节是导致肾功能衰竭的重要因素。 LN的发病机制，通过与细胞表面受体的结合和额外的 来自Toll样受体（TLR）家族的受体，并且血清和/或尿NGAL水平可以反映 致肾炎抗体引起的肾损伤程度。我们建议继续研究， 了解抗DNA抗体的肾脏致病性。具体而言，我们将： I）研究α-辅肌动蛋白的特异性在确定抗体致肾炎性中的重要性和其作用 病原性抗体结合对α-辅肌动蛋白结构和功能的影响; II）研究肾细胞中直接基因调节的机制，包括Fc受体和TLR 信号通路;以及 III）确定NGAL是否是致肾炎抗体损伤肾细胞的可靠标志物， 上调有助于SLE肾病的发病机制，以及血清和/或尿液水平 NGAL的表达可作为狼疮性肾炎的生物标志物。

Antibodies to double stranded (ds) DNA are not only highly specific for systemic lupus erythematosus (SLE), but are also directly involved in the pathogenesis of lupus nephritis (LN), a major disease manifestation. However, despite the clear association between anti-dsDNA antibodies and nephritis, the mechanisms by which anti-DNA antibodies contribute to renal damage have yet to be conclusively determined. LN may be initiated by formation of immune complexes in situ, via binding of anti-DNA antibodies to nucleosomal antigens deposited on the glomerular basement membrane (GBM). Alternatively, anti-DNA antibodies may be pathogenic not by virtue of binding to nuclear antigens, but rather via binding to cross reactive renal targets. In the initial period of funding for this grant, we found that pathogenic murine anti-DNA antibodies bind to mesangial cell (MC) a-actinin, and that high titers of anti-a- actinin antibodies were present in the serum and kidney eluates of lupus mice. Furthermore, we reported that in human SLE serum anti-a-actinin antibodies that bound to MC were present in high titers as well, and were closely associated with the presence and activity of LN. Finally, pathogenic antibodies binding to MC a-actinin directly modulated inflammatory gene expression including cytokines and neutrophil gelatinase associated lipocalin (NGAL, lipocalin), via Fc-dependent and independent mechanisms. We hypothesize that gene regulation induced by nephritogenic antibodies in kidney cells is an important contributor to the pathogenesis of LN, mediated by binding to cell surface receptors and engagement of an additional receptor from the Toll-like receptor (TLR) family, and that serum and/or urinary levels of NGAL may reflect the degree of renal injury induced by nephritogenic antibodies. We propose to continue our studies to understand the renal pathogenicity of anti-DNA antibodies. Specifically we will: I) Study the importance of specificity for a-actinin in determining antibody nephritogenicity and the effects of binding by pathogenic antibodies on a-actinin structure and function; II) Investigate the mechanisms of direct gene modulation in kidney cells, including Fc receptor and TLR signaling pathways; and III) Determine if NGAL is a reliable marker for injury of kidney cells by nephritogenic antibodies, is NGAL upregulation instrumental in the pathogenesis of SLE renal disease, and whether serum and/or urine levels of NGAL may be useful as a biomarker for lupus nephritis.