Synergistic effect of anemia and red blood cells transfusion on inflammation and lung injury

Anemia and resultant red blood cell transfusion may be associated with adverse long-term clinical outcomes. To investigate the mechanism(s) responsible, we profiled inflammatory biomarkers and circulating levels of the bioactive lysophospholipid mediator sphingosine-1-phosphate (S1P) in control and anemic mice with or without LPS-induced systemic inflammation. Acute anemia or lipopolysaccharide (LPS) challenge alone triggered an increase of circulating levels of the inflammatory markers IL-6 and keratinocyte-derived chemokine (CXCL1/KC). Moreover, administration of LPS to anemic mice reduced circulating S1P levels and augmented lung injury and pulmonary vascular permeability. Transfusion of aged, but not fresh, red blood cells (RBCs) worsened pulmonary vascular leak. S1P levels decline markedly during storage of mouse RBCs. Loading stored murine RBCs with S1P prior to transfusion partially attenuated anemia-associated acute pulmonary vascular leak. Taken together, our results indicate that anemia and systemic inflammation can alter the S1P buffering capacity of RBCs, suggesting possible strategies for alleviating transfusion-related lung injury in clinical practice.