Sakarya Serhan, Rifat Salahaldin, Zhou Jie, Bannerman Douglas D, Stamatos Nicholas M, Cross Alan S, Goldblum Simeon E
Department of Medicine, Division of Infectious Diseases, University of Maryland School of Medicine Baltimore, MD 21201, USA.
Glycobiology. 2004 Jun;14(6):481-94. doi: 10.1093/glycob/cwh065. Epub 2004 Mar 24.
The amount of sialic acid on the surface of the neutrophil (PMN) influences its ability to interact with other cells. PMN activation with various stimuli mobilizes intracellular sialidase to the plasma membrane, where it cleaves sialic acid from cell surfaces. Because enhanced PMN adherence, spreading, deformability, and motility each are associated with surface desialylation and are critical to PMN diapedesis, we studied the role of sialic acid on PMN adhesion to and migration across pulmonary vascular endothelial cell (EC) monolayers in vitro. Neuraminidase treatment of either PMN or EC increased adhesion and migration in a dose-dependent manner. Neuraminidase treatment of both PMNs and ECs increased PMN adhesion to EC more than treatment of either PMNs or ECs alone. Moreover, neuraminidase treatment of ECs did not change surface expression of adhesion molecules or release of IL-8 and IL-6. Inhibition of endogenous sialidase by either cross-protective antineuraminidase antibodies (45.5% inhibition) or competitive inhibition with pseudo-substrate (41.2% inhibition) decreased PMN adhesion to ECs; the inhibitable sialidase activity appeared to be associated with activated PMNs. Finally, EC monolayers preincubated with activated PMNs became hyperadhesive for subsequently added resting PMNs, and this hyperadhesive state was mediated through endogenous PMN sialidase activity. Blocking anti-E-selectin, anti-CD54 and anti-CD18 antibodies decreased PMN adhesion to tumor necrosis factor-activated ECs but not to PMN-treated ECs. These data implicate desialylation as a novel mechanism through which PMN-EC adhesion can be regulated independent of de novo protein synthesis or altered adhesion molecule expression. The ability of activated PMNs, through endogenous sialidase activity, to render the EC surface hyperadherent for unstimulated PMNs may provide for rapid amplification of the PMN-mediated host response.
中性粒细胞（PMN）表面唾液酸的含量会影响其与其他细胞相互作用的能力。用各种刺激物激活PMN会促使细胞内唾液酸酶转移至质膜，在质膜处它会从细胞表面裂解唾液酸。由于增强的PMN黏附、铺展、变形能力和运动能力均与表面去唾液酸化相关，且对PMN穿壁迁移至关重要，因此我们研究了唾液酸在体外PMN黏附于肺血管内皮细胞（EC）单层并穿越该单层细胞迁移过程中的作用。用神经氨酸酶处理PMN或EC均可使黏附及迁移呈剂量依赖性增加。同时用神经氨酸酶处理PMN和EC比单独处理PMN或EC更能增加PMN对EC的黏附。此外，用神经氨酸酶处理EC并不会改变黏附分子的表面表达或IL-8和IL-6的释放。用交叉保护性抗神经氨酸酶抗体（抑制率45.5%）或用假底物进行竞争性抑制（抑制率41.2%）来抑制内源性唾液酸酶，会降低PMN对EC的黏附；可被抑制的唾液酸酶活性似乎与活化的PMN相关。最后，用活化的PMN预孵育的EC单层对随后添加的静息PMN变得具有高黏附性，且这种高黏附状态是通过内源性PMN唾液酸酶活性介导的。阻断抗E-选择素、抗CD54和抗CD18抗体可降低PMN对肿瘤坏死因子激活的EC的黏附，但对经PMN处理的EC则无此作用。这些数据表明去唾液酸化是一种新机制，通过该机制可独立于从头合成蛋白质或改变黏附分子表达来调节PMN-EC黏附。活化的PMN通过内源性唾液酸酶活性使EC表面对未刺激的PMN具有高黏附性的能力，可能有助于PMN介导的宿主反应的快速放大。
