Endothelial cell-secreted MIF reduces pericyte contractility and enhances neutrophil extravasation

Abstract

Dysregulated neutrophil extravasation contributes to the pathogenesis ofmany inflammatory disorders. Pericytes (PCs) have been implicated in the regulation of neutrophil transmigration, and previous work demonstrates that endothelial cell (EC)-derived signals reduce PCbarrier function; however, the signalingmechanisms are unknown. Here, we demonstrate a novel role for EC-derived macrophage migration inhibitory factor (MIF) in inhibiting PC contractility and facilitating neutrophil transmigration. With the use of micro-ELISAs, RNA sequencing, quantitative PCR, and flow cytometry, we found that ECs secrete MIF, and PCs upregulate CD74 in response to TNF-α. We demonstrate that EC-derived MIF decreases PC contractility on 2-dimensional silicone substrates via reduction of phosphorylated myosin light chain.With the use of an in vitro microvascularmodel of thehumanEC-PCbarrier,wedemonstrate thatMIFdecreases thePCbarrier tohumanneutrophil transmigrationby increasing intercellular PC gap formation. For the first time, an EC-specific MIF knockout mouse was used to investigate the effects of selective deletion of ECMIF. In amodel of acute lung injury, selective deletion of ECMIF decreases neutrophil infiltration to the bronchoalveolar lavage and tissue and simultaneously decreases PC relaxation by increasing myosin light-chain phosphorylation. We conclude that paracrine signals from EC via MIF decrease PC contraction and enhance PC-regulated neutrophil transmigration.