Slit2/Robo4 signaling pathway modulates endothelial hyper-permeability in a two-event in vitro model of transfusion-related acute lung injury.

Transfusion-related acute lung injury (TRALI) remains the leading cause of transfusion-related mortality. Endothelium semipermeable barrier function plays a critical role in the pathophysiology of transfusion-related acute lung injury (TRALI). Recently, Roundabout protein 4 (Robo4), interaction with its ligand Slit 2, was appreciated as a modulator of endothelial permeability and integrity. However, not much is known about the role of Slit2/Robo4 signaling pathway in the pathophysiology of TRALI. In this study, the TRALI model was performed by the "two-event" model of polymorphonuclear neutrophils (PMN)-mediated pulmonary microvascular endothelial cells (PMVECs) damage. We investigated the expression of Slit2/Robo4 and VE-cadherin and examined the pulmonary endothelial hyper-permeability in TRALI model. We found that the expression of Slit2/Robo4 and VE-cadherin were significantly decreased in a time-dependent manner, whereas the PMVECs permeability was gradually increased over time in TRALI model. Moreover, the treatment with Slit2-N, an active fragment of Slit2, increased the expression of Slit2/Robo4 and VE-cadherin to protect PMVECs from PMN-mediated pulmonary endothelial hyper-permeability. These results indicate that targeting Slit2/Robo4 signaling pathway may modulate the permeability as well as protect the integrity of endothelial barrier. In addition, Slit2-N appears to be a promising candidate for developing novel therapies against TRALI.