Kalra V K, Shen Y, Sultana C, Rattan V
Department of Biochemistry and Molecular Biology, University of Southern California School of Medicine, Los Angeles 90033, USA.
Am J Physiol. 1996 Nov;271(5 Pt 2):H2025-34. doi: 10.1152/ajpheart.1996.271.5.H2025.
Polymorphonuclear neutrophils (PMN) adhere to the vascular endothelium under hypoxic conditions, causing microvascular injury. The molecular mechanism of hypoxia-induced adhesion of PMN to and diapedesis through the vascular endothelium is poorly understood. We examined the effects of hypoxia on the transendothelial migration of monocytes. Exposure of human umbilical vein endothelial cells (HUVEC) cultured in Transwell chambers under low oxygen tension (3% O2 compared with 21% O2) resulted in an increased rate of migration of both monocyte-like HL-60 cells and human peripheral blood monocytes. Migration was inhibited by addition of an antibody to platelet endothelial cell adhesion molecule-1 (PECAM-1), a protein kinase C (PKC) inhibitor, or a platelet-activating factor (PAF)-receptor antagonist. In HUVEC, hypoxic conditions (1, 3, 5, and 14% O2) increased the phosphorylation of PECAM-1. The extent of phosphorylation of PECAM-1 was inversely related to the concentration of oxygen to which HUVEC were exposed. Hypoxia-induced phosphorylation of PECAM-1 was inhibited by either a PKC inhibitor or a PAF-receptor antagonist, indicating the involvement of hypoxia-induced release of PAF in both PKC activation and the concomitant phosphorylation of PECAM-1. These results were substantiated by the findings that treatment of HUVEC with 100 nM PAF under normoxic conditions augmented 11.8-fold the phosphorylation of PECAM-1 and twofold increase in the transendothelial migration of monocyte-like HL-60 cells. We conclude that PAF, produced by cultured endothelial cells in response to hypoxia, acts in an autocrine fashion to activate PKC, causing PECAM-1 phosphorylation and thus the transendothelial migration of monocytes.
多形核中性粒细胞（PMN）在缺氧条件下会黏附于血管内皮，导致微血管损伤。目前对缺氧诱导PMN黏附并穿过血管内皮进行渗出的分子机制了解甚少。我们研究了缺氧对单核细胞跨内皮迁移的影响。在低氧张力（3% O₂，与21% O₂相比）条件下，培养于Transwell小室中的人脐静脉内皮细胞（HUVEC）暴露后，单核细胞样HL-60细胞和人外周血单核细胞的迁移速率均增加。添加血小板内皮细胞黏附分子-1（PECAM-1）抗体、蛋白激酶C（PKC）抑制剂或血小板活化因子（PAF）受体拮抗剂可抑制迁移。在HUVEC中，缺氧条件（1%、3%、5%和14% O₂）会增加PECAM-1的磷酸化。PECAM-1的磷酸化程度与HUVEC暴露的氧浓度呈负相关。PKC抑制剂或PAF受体拮抗剂均可抑制缺氧诱导的PECAM-1磷酸化，表明缺氧诱导的PAF释放参与了PKC激活以及随之而来的PECAM-1磷酸化过程。在常氧条件下用100 nM PAF处理HUVEC，使PECAM-1磷酸化增加11.8倍，单核细胞样HL-60细胞的跨内皮迁移增加两倍，这些结果证实了上述发现。我们得出结论，培养的内皮细胞在缺氧时产生的PAF以自分泌方式激活PKC，导致PECAM-1磷酸化，进而引起单核细胞的跨内皮迁移。
