The Renal Pathogenicity of anti-DNA Antibodies

描述(申请人提供)：抗双链(DS)DNA抗体不仅对系统性红斑狼疮(SLE)具有高度特异性，而且与狼疮性肾炎(LN)的发病直接相关，LN是一种主要的疾病表现。然而，尽管抗dsDNA抗体与肾炎之间存在明显的联系，但抗dsDNA抗体促进肾损害的机制尚未确定。LN可能是通过抗DNA抗体与沉积在肾小球基底膜(GBM)上的核小体抗原结合，在原位形成免疫复合物而启动的。或者，抗DNA抗体可能不是通过与核抗原结合而致病的，而是通过与交叉反应的肾脏靶点结合而致病的。在这项资助的最初阶段，我们发现致病的小鼠抗DNA抗体与系膜细胞(MC)(-Actinin)结合，在狼疮小鼠的血清和肾脏洗脱液中存在高滴度的抗(-Actinin抗体)。此外，我们还报道，在人类SLE血清中，与MC结合的抗(-Actinin)抗体也以高滴度存在，并与LN的存在和活动密切相关。最后，与MC(-Actinin)结合的致病抗体通过Fc依赖和独立的机制直接调节炎症基因的表达，包括细胞因子和中性粒细胞明胶酶相关的Lipocalin-2。我们推测肾小球肾炎抗体诱导的基因调控是LN发病的重要因素，它通过与细胞表面受体结合和与Toll样受体(TLR)家族的额外受体结合而发挥作用，血和/或尿NGAL水平可能反映肾小球肾炎抗体引起的肾脏损伤程度。我们建议继续我们的研究，以了解抗DNA抗体的肾脏致病性。具体来说，我们会： I)研究(-肌动蛋白)的特异性在确定抗体肾源性中的重要性，以及致病抗体结合对(-肌动蛋白结构和细胞功能的影响； Ii)研究肾脏细胞的直接基因调控机制，包括Fc受体和TLR信号通路；以及 Iii)确定NGAL是否是肾性抗体对肾脏细胞损伤的可靠标志物，NGAL上调是否在SLE肾病的发病机制中起作用，以及血清和/或尿液NGAL水平是否可作为狼疮性肾炎的生物标志物。 公共卫生相关性：肾脏炎症，或称肾炎，是系统性红斑狼疮患者常见且危险的疾病表现。虽然众所周知，在狼疮患者中，抗DNA抗体有助于肾炎，但它们实际上是如何导致肾脏损害的尚不清楚。我们建议研究抗DNA抗体是如何导致肾脏损伤的，以期找到更有效的治疗方法，并发现新的血清或尿液诊断标记物，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.