Regulatory Mechanisms of Chemokine-induced Eosinophil Adhesion and Transmigration with Pulmonary Microvascular Endothelial Cells

点击翻译按钮获取中文摘要

Eosinophil interaction with endothelial cells via α4β1 integrin/VCAM-1 is considered a key step for selective eosinophil recruitment to the airways of bronchial asthma. It is possible, however, that firm adhesion via this pathway actually inhibits subsequent transendothelial migration. This study was conducted to identify factor (s) that induces eosinophil transmigration across VCAM-1-expressed filter conditions. We first examined the effect of a panel of eosinophil chemoattractants on eosinophil migration across resting or TNF-α + IL-4-treated, hence strongly VCAM-1-expressed, human pulmonary microvascular endothelial cell (HPMEC) monolayers. Eosinophil transmigration by PAF (0.3μM), FMLP (0.1μM), IL-5, GM-CSF (both at 100pM) or IL-8 (10nM) was observed similar degree regardless of the treatment conditions of the HPMEC.Interestingly, C-C chemokines RANTES, eotaxin (both at 30nM), eotaxin-2 (3nM), MCP-3 or MCP-4 (both at 10nM) significantly increased eosinophil migration across VCAM-1-expressed HPMEC when compared with resting HPMEC (p<0.05). To further confirm these findings, eosinophil migration across either recombinant human (rh)-ICAM-1-or rh-VCAM-1-coated filter was also determined. RANTES, eotaxin, eotaxin-2, MCP-3 or MCP-4, but not other chemoattractants, significantly increased eosinophil migration across rh-VCAM-1-coated filters compared with FCS (control)- or rh-ICAM-1-coated filters (p<0.05). RANTES-induced eosinophil migration across rh-ICAM-1- and rh-VCAM-1-coated filters was significantly inhibited by anti-β2 integrin and anti α4 integrin mAb, respectively. These results suggest that eosinophils, which adhered to endothelial cells via α4 integrin/VCAM-1, undergo transmigration efficiently in the presence of C-C chemokines.