Endothelial cell activation leads to neutrophil transmigration as supported by the sequential roles of ICAM-2, JAM-A, and PECAM-1

Abstract

Abstract Leukocyte transmigration is mediated by endothelial cell (EC) junctional molecules, but the associated mechanisms remain unclear. Here we investigate how intercellular adhesion molecule-2 (ICAM-2), junctional adhesion molecule-A (JAM-A), and platelet endothelial cell adhesion molecule (PECAM-1) mediate neutrophil transmigration in a stimulus-dependent manner (eg, as induced by interleukin-1β [IL-1β] but not tumor necrosis factor-α [TNF-α]), and demonstrate their ability to act in sequence. Using a cell-transfer technique, transmigration responses of wild-type and TNF-α p55/p75 receptor-deficient leukocytes (TNFR−/−) through mouse cremasteric venules were quantified by fluorescence intravital microscopy. Whereas wild-type leukocytes showed a normal transmigration response to TNF-α in ICAM-2−/−, JAM-A−/−, and PECAM-1−/− recipient mice, TNFR−/− leukocytes exhibited a reduced transmigration response. Hence, when the ability of TNF-α to directly stimulate neutrophils is blocked, TNF-α–induced neutrophil transmigration is rendered dependent on ICAM-2, JAM-A, and PECAM-1, suggesting that the stimulus-dependent role of these molecules is governed by the target cell being activated. Furthermore, analysis of the site of arrest of neutrophils in inflamed tissues from ICAM-2−/−, JAM-A−/−, and PECAM-1−/− mice demonstrated that these molecules act sequentially to mediate transmigration. Collectively, the findings provide novel insights into the mechanisms of action of key molecules implicated in leukocyte transmigration.