The complement system plays an important role in the pathogenesis of rheumatoid arthritis (RA). Besides driving lectin pathway (LP) activation, the mannan-binding lectin (MBL)-associated serine proteases (MASPs) also play a key role in regulating the alternative pathway (AP). We evaluated the effects of N-acetylgalactosamine (GalNAc)-conjugated MASP-1 and MASP-2 duplexes in vitro and in mice with and without arthritis to examine whether knockdown of MASP-1 and MASP-2 expression affects the development of arthritis. GalNAc-siRNAs for MASP-1 and MASP-2 demonstrated robust silencing of MASP-1 or MASP-2 at pM concentrations in vitro. To evaluate the impact of silencing in arthritic mice, we used the collagen antibody-induced arthritis (CAIA) mouse model of RA. Mice were injected a 10 mg/kg dose of GalNAc-siRNAs 3x s.q. prior to the induction of CAIA. Liver gene expression was examined using qRT-PCR, and protein levels were confirmed in the circulation by sandwich immunoassays and Western blot. At day 10, CAIA mice separately treated with MASP-1 and MASP-2 duplexes had a specific reduction in expression of liver MASP-1 (70–95%, p < 0.05) and MASP-2 (90%, p < 0.05) mRNA, respectively. MASP-1-siRNA treatment resulted in a 95% reduction in levels of MASP-1 protein in circulation with no effect on MASP-2 levels and clinical disease activity (CDA). In mice injected with MASP-2 duplex, there was a significant (p < 0.05) 90% decrease in ex vivo C4b deposition on mannan, with nearly complete elimination of MASP-2 in the circulation. MASP-2 silencing initially significantly decreased CDA by 60% but subsequently changed to a 40% decrease vs. control. Unexpectedly, GalNAc-siRNA-mediated knockdown of MASP-1 and MASP-2 revealed a marked effect of these proteins on the transcription of FD under normal physiological conditions, whereas LPS-induced inflammatory conditions reversed this effect on FD levels. LPS is recognized by Toll-like receptor 4 (TLR4), we found MBL not only binds to TLR4 an interaction with a K_d of 907 nM but also upregulated FD expression in differentiated adipocytes. We show that MASP-2 knockdown impairs the development of RA and that the interrelationship between proteins of the LP and the AP may extend to the transcriptional modulation of the FD gene.

补体系统在类风湿关节炎（RA）的发病机理中起重要作用。除了驱动凝集素途径（LP）激活外，甘露聚糖结合凝集素（MBL）相关的丝氨酸蛋白酶（MASP）在调节替代途径（AP）中也起着关键作用。我们评估了N-乙酰半乳糖胺（GalNAc）结合的MASP-1和MASP-2双链体的作用体外并在患有和不患有关节炎的小鼠中检查MASP-1和MASP-2表达的敲低是否会影响关节炎的发展。MASP-1和MASP-2的GalNAc-siRNA在pM浓度下显示出MASP-1或MASP-2的强大沉默体外。为了评估沉默对关节炎小鼠的影响，我们使用了胶原蛋白抗体诱导的关节炎（CAIA）RA小鼠模型。在诱导CAIA之前，向小鼠注射3×sq的10mg / kg剂量的GalNAc-siRNA。使用qRT-PCR检查肝基因表达，并通过三明治免疫测定和Western印迹确认循环中的蛋白质水平。在第10天，分别用MASP-1和MASP-2双链体处理的CAIA小鼠肝脏MASP-1的表达有特异性降低（70-95％，p <0.05）和MASP-2（90％， p<0.05）mRNA。MASP-1-siRNA处理可使循环中的MASP-1蛋白水平降低95％，而对MASP-2水平和临床疾病活性（CDA）无影响。在注射MASP-2双链体的小鼠中，p <0.05）减少90％ 离体C4b沉积在甘露聚糖上，几乎完全消除了循环中的MASP-2。MASP-2沉默最初使CDA显着降低了60％，但随后变为与对照相比降低了40％。出乎意料的是，在正常生理条件下，GalNAc-siRNA介导的MASP-1和MASP-2的敲低揭示了这些蛋白对FD转录的显着影响，而LPS诱导的炎症条件则逆转了这种对FD水平的影响。LPS被Toll样受体4（TLR4）识别，我们发现MBL不仅与TLR4结合，而且与K _d相互作用907 nM的表达，但在分化的脂肪细胞中FD表达也上调。我们表明，MASP-2敲低损害了RA的发展，LP和AP的蛋白质之间的相互关系可能延伸到FD基因的转录调控。