CC chemokines and transmigration of eosinophils in the presence of vascular cell adhesion molecule 1

Abstract

Background: Interaction between eosinophil alpha4 integrin and vascular cell adhesion molecule 1 (VCAM-1) expressed on activated endothelial cells may be a key step in the selective recruitment of eosinophils from the circulation to sites of inflammation.

Objective: To investigate the factor(s) that induces transmigration of eosinophils after firm adhesion via the alpha4 integrin/VCAM-1 pathway.

Methods: We examined the effects of a variety of inflammatory mediators on the migration of eosinophils across recombinant human (rh) intracellular adhesion molecule 1- or rhVCAM-1-coated Transwell filters or VCAM-1-expressing human pulmonary microvascular endothelial cells (HPMECs) that had been stimulated with interleukin 4 (IL-4) and tumor necrosis factor alpha. The number of eosinophils that had transmigrated was evaluated by measuring eosinophil peroxidase activity.

Results: The CC chemokines RANTES (regulated on activation, normal T-cell expressed, and secreted), eotaxin, eotaxin 2, monocyte chemotactic protein 3 (MCP-3), and MCP-4 each increased eosinophil transmigration across rhVCAM-1-coated filters compared with fetal calf serum-blocked or rh intracellular adhesion molecule 1-coated filters (P < .01). On the other hand, platelet-activating factor, C5a, formyl-methionyl-leucil-phenylalanine, granulocyte-macrophage colony-stimulating factor, IL-5, and IL-8 did not enhance migration across rhVCAM-1. The enhancement of migration by RANTES in the presence of rhVCAM-1 was blocked by an anti-alpha4 integrin monoclonal antibody. CC chemokines augmented eosinophil transmigration across VCAM-1-expressing HPMECs compared with resting HPMECs (P < .01). Conversely, the transmigration induced by platelet-activating factor, C5a, formyl-methionyl-leucil-phenylalanine, or IL-8 was not modified by the expression of VCAM-1 on HPMECs.

Conclusions: CC chemokines induce transendothelial migration of eosinophils after interaction between eosinophil alpha4 integrin and endothelial VCAM-1.