Abstract 12651: Fine-Tuning of Lung Thrombosis is a Therapeutic Strategy Against Inflammatory Lung Injury

Abstract

Introduction: Lung thrombosis (LT) and endothelial cell (EC) death are positively associated with mortality in sepsis-induced acute lung injury (ALI) patients, but anti-coagulants have failed in clinical trials of sepsis. Hypothesis: We hypothesized that different levels of LT mediate ALI by regulating lung EC viability. Methods: To assess the impact of different levels of LT on ALI, we used murine models of LT and ALI. To explore how LT level might alter lung EC viability and ALI, we assessed survival gene expression by RNA sequencing. To identify the mechanism(s) responsible for changes in ALI after varying levels of LT, we assessed lung EC viability and ALI in mice with cell-specific knockout of different survival genes. Results: In platelet-depleted mice, LT was reduced while ALI was increased. Intra-venous microbeads were then administered to induce LT in a dose-dependent manner, showing that restoration of LT to the level found in platelet-replete mice protected against thrombocytopenia-induced ALI. We next showed in wild type mice, that while excessive increases in LT worsened ALI, induction of a mild level of LT conversely protected against ALI. The opposing impact of diminished or excessive versus mild LT on ALI was associated with changes in lung EC apoptosis. Subsequent studies showed a panel of candidate survival factors were differentially expressed in the lungs of ALI mice with or without mild or excessive LT. Mechanistically, we found that the protective impact of mild LT on ALI is dependent upon hypoxia-inducible factor (HIF) 1α in Tie2-expressing cells. Remarkably, the same mild level of LT retained its protective impact in platelet-depleted and platelet-replete mice even when induced up to 8 hours after sepsis. Conclusions: ALI is enhanced by diminished or excessive LT but suppressed by mild LT through HIF1α. The control of LT represents a therapeutic strategy for the induction of a pro-survival response that protects against inflammatory lung injury.