Zhu X, Muñoz N M, Kim K P, Sano H, Cho W, Leff A R
Section of Pulmonary and Critical Care Medicine, Department of Medicine, Division of Biological Sciences, University of Chicago, Illinois 60607, USA.
J Immunol. 1999 Sep 15;163(6):3423-9.
We examined the role of cytosolic phospholipase A2 (cPLA2) during human eosinophil adherence to ICAM-1- or VCAM-1-coated plates. IL-5-stimulated eosinophils adhered to ICAM-1 through the beta 2 integrin CD11b/CD18, while nonstimulated eosinophils did not. By contrast, nonstimulated eosinophils adhered to VCAM-1 through the beta 1-integrin VLA-4/CD29. Both IL-5-induced adhesion to ICAM-1 and spontaneous adhesion to VCAM-1 corresponded temporally to cPLA2 phosphorylation, which accompanied enhanced catalytic activity of cPLA2. The structurally unrelated cPLA2 inhibitors, arachidonyl trifluoromethylketone and surfactin, significantly inhibited eosinophil adhesion to ICAM-1 and VCAM-1 in a concentration-dependent manner. Inhibition of secretory PLA2, 5-lipoxygenase, or cyclooxygenase did not affect eosinophil adhesion. Addition of arachidonic acid to eosinophils after cPLA2 inhibition with arachidonyl trifluoromethylketone or surfactin did not reverse the blockade of adhesion to ICAM-1 or VCAM-1. However, CV-6209, a receptor-specific antagonist of platelet-activating factor, inhibited all integrin-mediated adhesion. The activated conformation of CD11b as identified by the mAb, CBRM1/5, as well as quantitative surface CD11b expression were up-regulated after IL-5 stimulation. However, cPLA2 inhibition neither prevented CBRM1/5 expression nor blocked surface Mac-1 up-regulation caused by IL-5. Our data suggest that cPLA2 activation and its catalytic product platelet-activating factor play an essential role in regulating beta 1 and beta 2 integrin-dependent adhesion of eosinophils. This blockade occurs even in the presence of up-regulated eosinophil surface integrin.
我们研究了胞质型磷脂酶A2（cPLA2）在人嗜酸性粒细胞黏附于包被细胞间黏附分子-1（ICAM-1）或血管细胞黏附分子-1（VCAM-1）的平板过程中的作用。白细胞介素-5（IL-5）刺激的嗜酸性粒细胞通过β2整合素CD11b/CD18黏附于ICAM-1，而未受刺激的嗜酸性粒细胞则不黏附。相比之下，未受刺激的嗜酸性粒细胞通过β1整合素VLA-4/CD29黏附于VCAM-1。IL-5诱导的对ICAM-1的黏附和对VCAM-1的自发黏附在时间上均与cPLA2磷酸化相对应，同时伴有cPLA2催化活性增强。结构不相关的cPLA2抑制剂花生四烯酰三氟甲基酮和表面活性素以浓度依赖的方式显著抑制嗜酸性粒细胞对ICAM-1和VCAM-1的黏附。抑制分泌型磷脂酶A2、5-脂氧合酶或环氧化酶并不影响嗜酸性粒细胞的黏附。在用花生四烯酰三氟甲基酮或表面活性素抑制cPLA2后，向嗜酸性粒细胞中添加花生四烯酸并不能逆转对ICAM-1或VCAM-1黏附的阻断。然而，血小板活化因子的受体特异性拮抗剂CV-6209可抑制所有整合素介导的黏附。经单克隆抗体CBRM1/5鉴定的CD11b活化构象以及表面CD11b定量表达在IL-5刺激后上调。然而，抑制cPLA2既不能阻止CBRM1/5表达，也不能阻断IL-5引起的表面Mac-1上调。我们的数据表明，cPLA2活化及其催化产物血小板活化因子在调节嗜酸性粒细胞β1和β2整合素依赖性黏附中起重要作用。即使在嗜酸性粒细胞表面整合素上调的情况下，这种阻断仍会发生。
