Huber-Lang Markus, Younkin Ellen M, Sarma J Vidya, Riedemann Niels, McGuire Stephanie R, Lu Kristina T, Kunkel Robin, Younger John G, Zetoune Firas S, Ward Peter A
Department of Pathology, University of Michigan Medical School, Ann Arbor 48109, USA.
Am J Pathol. 2002 Nov;161(5):1849-59. doi: 10.1016/S0002-9440(10)64461-6.
The complement activation product, C5a, is a powerful phlogistic factor. Using antibodies to detect human or rat C5a, incubation at pH 7.4 of human blood neutrophils or rat alveolar macrophages (AMs) with C5 in the presence of phorbol 12-myristate 13-acetate (PMA) led to generation of C5a. Rat AMs activated with lipopolysaccharide also generated C5a from C5. With activated neutrophils, extensive cleavage of C5 occurred, whereas activated macrophages had much more selective proteolytic activity for C5. Peripheral blood human or rat mononuclear cells and rat alveolar epithelial cells when stimulated with phorbol ester all failed to demonstrate an ability to cleave C5, suggesting a specificity of C5 cleavage by phagocytic cells. With rat AMs, C5a generation was time-dependent and was blocked if AMs were pretreated with inhibitors of transcription or protein synthesis (actinomycin D or cycloheximide). Similar treatment of activated human polymorphonuclear leukocytes only partially reduced C5a generation after addition of C5. C5a generated by activated AMs was biologically (chemotactically) active. This generation was sensitive to serine protease inhibitors but not to other classes of inhibitors. These data indicate that phagocytic cells, especially lung macrophages, can generate C5a from C5. In the context of the lung, this may represent an important C5a-generating pathway that is independent of the plasma complement system.
补体激活产物C5a是一种强大的炎症因子。使用抗体检测人或大鼠的C5a，在pH 7.4条件下，将人血中性粒细胞或大鼠肺泡巨噬细胞（AMs）与C5在佛波酯12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）存在的情况下孵育，会导致C5a的产生。用脂多糖激活的大鼠AMs也能从C5产生C5a。对于激活的中性粒细胞，C5会发生广泛的裂解，而激活的巨噬细胞对C5具有更具选择性的蛋白水解活性。外周血人或大鼠单核细胞以及大鼠肺泡上皮细胞在用佛波酯刺激时均未能表现出裂解C5的能力，这表明吞噬细胞裂解C5具有特异性。对于大鼠AMs，C5a的产生是时间依赖性的，如果AMs用转录或蛋白质合成抑制剂（放线菌素D或环己酰亚胺）预处理，则C5a的产生会被阻断。对激活的人多形核白细胞进行类似处理，在添加C5后仅部分降低C5a的产生。激活的AMs产生的C5a具有生物学（趋化性）活性。这种产生对丝氨酸蛋白酶抑制剂敏感，但对其他类别的抑制剂不敏感。这些数据表明，吞噬细胞，尤其是肺巨噬细胞，可以从C5产生C5a。在肺的环境中，这可能代表了一条独立于血浆补体系统的重要C5a产生途径。
