Mason J C, Lidington E A, Yarwood H, Lublin D M, Haskard D O
The BHF Cardiovascular Medicine Unit, Imperial College School of Science, Technology, and Medicine, Hammersmith Hospital, London, UK.
Arthritis Rheum. 2001 Jan;44(1):138-50. doi: 10.1002/1529-0131(200101)44:1<138::AID-ANR18>3.0.CO;2-G.
Decay-accelerating factor (DAF) is a widely expressed, multifunctional cell surface protein involved in complement regulation and cell signaling. Previous studies have demonstrated that endothelial cell (EC) DAF is up-regulated by tumor necrosis factor alpha and inhibits complement binding. Because vascular endothelial growth factor (VEGF) is cytoprotective to endothelium and is expressed at sites of chronic inflammation, we hypothesized that VEGF may induce DAF expression during inflammatory angiogenesis.
Human umbilical vein and dermal microvascular EC were isolated using routine procedures, and the regulation and function of DAF, as well as other complement-regulatory proteins (membrane cofactor protein and CD59), were analyzed following stimulation with VEGF.
Incubation of large- or small-vessel EC with VEGF led to increased expression of DAF, with maximal expression after 48-72 hours of stimulation. This effect depended on the activation of protein kinase C (PKC) and required increased steady-state messenger RNA levels and de novo protein synthesis. Although VEGF-induced EC proliferation was inhibited by both p38 and p42/44 mitogen-activated protein kinase (MAPK) antagonists, DAF up-regulation in response to VEGF was only sensitive to inhibition of p38 MAPK. VEGF-stimulated EC showed a 60% reduction in C3 deposition following complement activation, and this resulted in a marked reduction in complement-mediated EC lysis. These protective effects were abolished by anti-DAF monoclonal antibody 1H4.
This study confirms the importance of PKC for the regulation of DAF expression by EC and reveals VEGF to be a physiologic agonist for this pathway. The up-regulation of DAF expression by VEGF may represent an important mechanism for the protection of EC from complement-mediated injury during angiogenesis in inflammatory rheumatic diseases.
衰变加速因子（DAF）是一种广泛表达的多功能细胞表面蛋白，参与补体调节和细胞信号传导。先前的研究表明，肿瘤坏死因子α可上调内皮细胞（EC）中的DAF，并抑制补体结合。由于血管内皮生长因子（VEGF）对内皮具有细胞保护作用，且在慢性炎症部位表达，我们推测VEGF可能在炎症性血管生成过程中诱导DAF表达。
采用常规方法分离人脐静脉和真皮微血管内皮细胞，在用VEGF刺激后，分析DAF以及其他补体调节蛋白（膜辅助因子蛋白和CD59）的调节和功能。
用VEGF孵育大血管或小血管内皮细胞会导致DAF表达增加，刺激48 - 72小时后表达达到最大值。这种效应依赖于蛋白激酶C（PKC）的激活，需要增加稳态信使核糖核酸水平和从头合成蛋白质。虽然p38和p42/44丝裂原活化蛋白激酶（MAPK）拮抗剂均抑制VEGF诱导的内皮细胞增殖，但VEGF诱导的DAF上调仅对p38 MAPK的抑制敏感。VEGF刺激的内皮细胞在补体激活后C3沉积减少60%，这导致补体介导的内皮细胞溶解显著减少。这些保护作用被抗DAF单克隆抗体1H4消除。
本研究证实了PKC对内皮细胞调节DAF表达的重要性，并揭示VEGF是该途径的生理激动剂。VEGF上调DAF表达可能是炎症性风湿疾病血管生成过程中内皮细胞免受补体介导损伤的重要机制。
