Abstract
INTRODUCTION: Large-volume packed red blood cell (pRBC) transfusion is associated with lung injury and worsened outcomes. Amitriptyline reduces lung injury and inflammation in a murine sepsis model. We hypothesized that red cell microparticles (MP) activate endothelial cells, leading to lung injury and that treatment with amitriptyline would blunt the inflammatory response MPs through inhibition of acid sphingomyelinase (ASM). METHODS: Murine pRBCs were obtained from C57Bl/6 mice and stored in AS3 for 14 d. The MPs were isolated from pRBCs by serial centrifugation. Mouse lung endothelial cells (MLECs) were pretreated with amitriptyline (0, 2.5, 25, 27 μM, n = 5) for 30 min prior to MP treatment. Chemokine secretion and adhesion molecule shedding was assessed. ASM activity was measured from cell lysates. RESULTS: MPs increased the secretion of chemokines and shedding of adhesion molecules in MLECs at both four and 24 h. Amitriptyline treatment of MLECs decreased ASM activity in the setting of MPs. Amitriptyline pretreatment decreased the secretion of chemokines and shedding of adhesion molecules in response to MPs at 4 h but did not decrease adhesion molecule shedding at 24 h CONCLUSIONS: Endothelial cell treatment with MPs induces secretion of chemokines responsible for chemotaxis (keratinocyte chemoattractant, regulated upon activation normal T cell expressed and presumably secreted, and G-granulocyte colony-stimulating factor) as well as many downstream proinflammatory effects (interleukin-6). Additionally, MPs induce adhesion molecule shedding (vascular cell adhesion molecule-1, intracellular adhesion molecule-1, P-selectin, and E-selectin), which has been shown to be associated with endothelial cell activation. Amitriptyline pretreatment decreases MLEC inflammatory response and ASM activity is decreased. These data suggest that ASM inhibition in MLECs is a potential strategy to blunt the inflammatory response to the red blood cell storage lesion.