Phosphodiesterase Inhibition Attenuates Stored Blood-Induced Neutrophil Activation: A Novel Adjunct to Blood Transfusion

Abstract

Activated neutrophils play a central role in the pathogenesis of ARDS and multiple organ failure (MOF). Transfusion of packed red blood cells (PRBCs) is an independent risk factor in the development of ARDS and MOF. It has been postulated that factors present in the supernatant of PRBCs activate neutrophils. The magnitude of neutrophil activation is dependent on the age of the stored blood. Our laboratory and others have reported that pentoxifylline (PTX), a nonspecific phosphodiesterase inhibitor, decreases neutrophil activation. We hypothesized that adding PTX to PRBCs would attenuate blood transfusion-induced neutrophil activation. Peripheral blood was obtained from healthy human volunteers. Oxidative burst, CD11b, and CD35 expression were measured by flow cytometry using a whole blood preparation. Whole blood was incubated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) (1 microM) alone and 42-day-old PRBC supernatant + fMLP with or without PTX (2 mmol/L). N-formyl-methionyl-leucyl-phenylalanine alone caused a significant increase in neutrophil oxidative burst (100%). The exposure of whole blood to PRBC supernatants + fMLP led to a 1.3-fold increase in neutrophil oxidative burst as compared with fMLP alone, indicating that PRBC supernatants prime neutrophils for oxidative burst by 75%. More importantly, PTX decreased neutrophil oxidative burst by 114% in supernatant + fMLP-stimulated whole blood (p < 0.001). PTX decreased CD11b expression in both fMLP (p < 0.01) and fMLP+supernatant-stimulated whole blood (p < 0.05). Supernatant from PRBCs did not have an additive effect to fMLP alone on CD11b expression. N-formyl-methionyl-leucyl-phenylalanine-induced CD35 expression was downregulated by PTX. The addition of PRBC supernatant did not increase the already upregulated fMLP-induced CD35 expression. Our results suggest that adding PTX to PRBC supernatant markedly decreases neutrophil activation. The lack of successful treatment strategies to effectively modulate the inflammatory response after blood transfusion indicates the need for novel therapies. Because the deleterious effects of blood transfusion on end-organ injury and MOF are associated with neutrophil activation, the adjunct use of PTX to blood transfusion may have therapeutic potential.