Endothelial pro‐coagulant responses in acid‐induced lung injury

The mechanisms underlying the development of procoagulant conditions in lung vasculature during acute lung injury (ALI) remain inadequately understood. To address this issue, we instilled HCl ( pH 1.2, 2 ml/kg) intra‐tracheally in isolated perfused lungs of strain‐matched wild type (WT) and reactive oxygen species (ROS)‐incompetent, gp91phox −/− mice. After 2 h, clearing the pulmonary vasculature with ice‐cold buffer, we perfused chilled collagenase (1000 units/ml) and trypsin (3 ml). The venous outflow contained ~10 6 cells that we surface‐labeled, using fluorophore‐conjugated mAbs against tissue factor (TF) and the endothelial marker, von Willebrand factor (vWf). WT lungs were perfused with WT blood (WT/WT), or with blood from gp91phox −/− mice (WT/gp91). By flow cytometry, we selected for endothelial cells, denoted as vWf+ cells. Then in the vWf+ cells, we selected those that were TF+. Acid instillation increased endothelial expressions of TF more than two fold in WT/WT (n=3; P<0.05). By contrast in WT/gp91, the increase was blunted ~70% (n=3; P<0.05), indicating that the effect was ROS dependent. We conclude that following acid instillation in mouse lungs, increased ROS production caused increases in lung endothelial TF expression. Since TF initiates coagulation, our finding provides evidence that the procoagulant phenotype is established early in the course of acid‐induced ALI (HL36024).