Rinder C S, Rinder H M, Johnson K, Smith M, Lee D L, Tracey J, Polack G, Higgins P, Yeh C G, Smith B R
Department of Laboratory Medicine and Anesthesiology, Yale University School of Medicine, New Haven, CT 06520-8035, USA.
Circulation. 1999 Aug 3;100(5):553-8. doi: 10.1161/01.cir.100.5.553.
We previously demonstrated that inhibiting formation of terminal complement components (C5a and C5b-9) prevents platelet and neutrophil (PMN) but not monocyte activation during simulated extracorporeal circulation (SECC). This study examined whether earlier complement inhibition during SECC, blocking C3a formation, would additionally prevent monocyte activation.
SECC was established by recirculating heparinized whole blood from human volunteers on a membrane oxygenator. CAB-2, a chimeric protein constructed from genes encoding the complement regulatory proteins CD46 and CD55, inactivates the C3/C5 convertases and blocks in vitro generation of C3a, C5a, and C5b-9. CAB-2 was used in 4 experiments at a final concentration of 300 micrograms/mL and 4 experiments at 30 micrograms/mL; 4 control runs used vehicle alone. Samples were assayed for C3a and C5b-9, monocyte activation (CD11b upregulation), PMN activation (CD11b upregulation and elastase release), and platelet activation (P-selectin expression and monocyte-platelet conjugate formation). CAB-2 at both doses significantly inhibited formation of C3a and C5b-9 during SECC. High-dose CAB-2 significantly blocked monocyte and PMN CD11b upregulation and PMN elastase release. CAB-2 also inhibited formation of platelet activation-dependent monocyte-platelet conjugates.
Blockade of complement activation early in the common pathway inhibited monocyte CD11b upregulation during SECC, suggesting that early complement components contribute most to monocyte activation during SECC. As expected, PMN and platelet activation were blocked by terminal complement inhibition. This investigation further elucidates the relation between complement and blood cell activation during simulated cardiopulmonary bypass.
我们之前证明，在模拟体外循环（SECC）期间抑制终末补体成分（C5a和C5b-9）的形成可防止血小板和中性粒细胞（PMN）活化，但不能防止单核细胞活化。本研究探讨在SECC期间更早地抑制补体，即阻断C3a的形成，是否还能防止单核细胞活化。
通过在膜式氧合器上循环人类志愿者的肝素化全血建立SECC。CAB-2是一种由编码补体调节蛋白CD46和CD55的基因构建的嵌合蛋白，可使C3/C5转化酶失活并阻断体外C3a、C5a和C5b-9的生成。在4个实验中使用终浓度为300微克/毫升的CAB-2，在另外4个实验中使用30微克/毫升的CAB-2；4个对照实验仅使用赋形剂。检测样本中的C3a和C5b-9、单核细胞活化（CD11b上调）、PMN活化（CD11b上调和弹性蛋白酶释放）以及血小板活化（P-选择素表达和单核细胞-血小板共轭物形成）。两种剂量的CAB-2均显著抑制SECC期间C3a和C5b-9的形成。高剂量CAB-2显著阻断单核细胞和PMN的CD11b上调以及PMN弹性蛋白酶释放。CAB-2还抑制血小板活化依赖性单核细胞-血小板共轭物的形成。
在补体激活的共同途径早期进行阻断可抑制SECC期间单核细胞CD11b上调，这表明早期补体成分对SECC期间单核细胞活化的贡献最大。正如预期的那样，终末补体抑制可阻断PMN和血小板活化。本研究进一步阐明了模拟体外循环期间补体与血细胞活化之间的关系。
