Phospholipid scramblase 1 activity mediates phospholipid alterations leading to an endothelial response following hypoxia and reoxygenation (P1295)

Abstract

Abstract Ischemia, lack of blood flow, and reperfusion, return of blood flow, is a common phenomenon affecting millions of Americans each year. Roughly 30,000 Americans per year experience intestinal ischemia-reperfusion (IR), which is associated with a 70-80% mortality rate. Previous studies of the intestine established a role for innate immune cells and naturally occurring antibodies (Ab) in IR-induced pathology. Furthermore, administration of two monoclonal Ab that recognize phospholipids (PL) or the PL binding protein β2-glycoprotein I (β2-GPI) restores tissue damage in IR-resistant Rag-1-/- mice to wildtype levels. These data indicate involvement of a lipid or lipid-like moiety in mediating IR-induced damage. We hypothesized that PL scramblase 1 (PLSCR1), a protein regulating bilayer asymmetry, is involved in altering the PL of endothelial cells during hypoxia leading to β2-GPI binding and subsequent inflammation. To test our hypothesis, an endothelial cell line, MS1, was subjected to hypoxia (1% O2) followed by reoxygenation as an in vitro model of IR. PLSCR1 transcription, protein expression and activity were assessed. Mass spectrometry detected PL alterations and β2-GPI binding was confirmed by immunohistochemistry. Inflammatory markers including prostaglandins were also evaluated. Our data demonstrate hypoxia and reoxygenation-induced PLSCR1 activity in PL scrambling of endothelial cells. The altered PL arrangement enhances β2-GPI binding and leads to intestinal IR pathology.