A key role for platelet GPVI in neutrophil recruitment, migration and NETosis in the early stages of acute lung injury.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are associated with high morbidity and mortality. Excessive neutrophil infiltration into the pulmonary airspace is the main cause for the acute inflammation and lung injury. Platelets have been implicated in the pathogenesis of ALI/ARDS, but the underlying mechanisms are not fully understood. We here show that the immunoreceptor tyrosine-based activation motif (ITAM)-coupled Ig-like platelet receptor glycoprotein (GP)VI plays a key role in the early phase of pulmonary thrombo-inflammation in a model of lipopolysaccharide (LPS)-induced ALI in mice. In WT control mice, intranasal LPS application triggered severe pulmonary and blood neutrophilia, hypothermia, and increased blood lactate levels. In contrast, Gp6-/- mice as well as anti-GPVI-treated WT mice were markedly protected from pulmonary and systemic compromises and showed no increased pulmonary bleeding. High resolution multicolor microscopy of lung sections and intravital confocal microcopy of the ventilated lung revealed that anti-GPVI treatment resulted in less stable platelet interaction with neutrophils and overall reduced platelet-neutrophil complex (PNC)-formation. Anti-GPVI treatment also reduced neutrophil crawling and adhesion on endothelial cells resulting in reduced neutrophil transmigration and alveolar infiltrates. Remarkably, also neutrophil activation was diminished in anti-GPVI treated animals, associated with strongly reduced formation of platelet/neutrophil clusters and neutrophil extracellular traps (NETs) compared to control. These results establish GPVI as a key mediator of neutrophil recruitment, PNC-formation, and NETosis in experimental ALI. Thus, GPVI inhibition might be a promising strategy to reduce the acute pulmonary inflammation causing ALI/ARDS.