The Renal Pathogenicity of anti-DNA Antibodies

描述（由申请人提供）：双链（ds）DNA抗体不仅对系统性红斑狼疮（SLE）具有高度特异性，而且还直接参与狼疮性肾炎（LN）的发病机制，LN是一种主要的疾病表现。然而，尽管抗dsDNA抗体和肾炎之间的明确关联，抗DNA抗体导致肾损伤的机制尚未最终确定。LN可以通过抗DNA抗体与沉积在肾小球基底膜（GBM）上的核小体抗原结合而原位形成免疫复合物来启动。或者，抗DNA抗体可能不是由于与核抗原结合而是通过与交叉反应性肾靶结合而致病。在该基金资助的最初阶段，我们发现致病性鼠抗DNA抗体与系膜细胞（MC）β-辅肌动蛋白结合，并且在狼疮小鼠的血清和肾脏洗脱液中存在高滴度的抗β-辅肌动蛋白抗体。此外，我们还报道了SLE患者血清中与MC结合的抗-β-辅肌动蛋白抗体的高滴度，并且与LN的存在和活动密切相关。最后，结合MC β辅肌动蛋白的致病性抗体通过Fc依赖性和非依赖性机制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脂质运载蛋白（NGAL，脂质运载蛋白-2）。我们推测，肾细胞中致肾炎抗体诱导的基因调控是LN发病机制的重要贡献者，通过与细胞表面受体结合和Toll样受体（TLR）家族的额外受体参与介导，血清和/或尿液中NGAL水平可能反映了致肾炎抗体诱导的肾损伤程度。我们建议继续我们的研究，以了解肾脏的致病性抗DNA抗体。具体而言，我们将： I）研究β-辅肌动蛋白的特异性在确定抗体致肾性中的重要性以及病原性抗体结合对β-辅肌动蛋白结构和细胞功能的影响; II）研究肾细胞中直接基因调节的机制，包括Fc受体和TLR信号传导途径;和 III）确定NGAL是否是致肾炎抗体损伤肾细胞的可靠标志物，NGAL上调是否在SLE肾病的发病机制中起作用，以及NGAL的血清和/或尿液水平是否可用作狼疮肾炎的生物标志物。 公共卫生相关性：肾脏炎症或肾炎是系统性红斑狼疮患者常见且危险的疾病表现。虽然已知狼疮患者的抗DNA抗体会导致肾炎，但它们实际上是如何导致肾损伤的尚不清楚。我们建议研究抗DNA抗体如何诱导肾损伤，以确定更有效的治疗新方法，并发现新的血清或尿液诊断标志物，以改善狼疮患者的临床护理。

DESCRIPTION (provided by applicant): 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) (-actinin, and that high titers of anti-(-actinin antibodies were present in the serum and kidney eluates of lupus mice. Furthermore, we reported that in human SLE serum anti-(-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 (-actinin directly modulated inflammatory gene expression including cytokines and neutrophil gelatinase associated lipocalin (NGAL, lipocalin-2), 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 (-actinin in determining antibody nephritogenicity and the effects of binding by pathogenic antibodies on (-actinin structure and cellular 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. Public Health Relevance: Inflammation of the kidney, or nephritis, is a common and dangerous manifestation of disease in patients with systemic lupus erythematosus. While it is known that in lupus patients antibodies against DNA contribute to nephritis, how they actually cause kidney damage is not yet clear. We propose to study how anti-DNA antibodies induce kidney injury in an attempt to identify new approaches for more effective treatment, and discover novel serum or urine diagnostic markers that will improve the clinical care of lupus patients.