BACKGROUND: Polymorphonuclear neutrophil (PMN) sequestration in the lung is a hallmark of acute respiratory distress syndrome (ARDS). We have shown that 25% Albumin (A25) resuscitation attenuates lung injury after hemorrhagic shock and lipopolysaccharide (LPS) exposure by reducing lung leukosequestration. We hypothesize that this protective property is mediated by alteration of neutrophil-endothelial cell adhesive interactions. MATERIALS AND METHODS: A 2-hit rodent model of shock resuscitation was used. CD11b and L-selectin were measured using flow cytometry in rat and human neutrophils ex vivo. Intercellular adhesion molecule-1 (ICAM-1) levels were measured by Northern blot and immunohistochemistry. RESULTS: Resuscitation with A25 attenuated the increase in PMN CD11b expression in Ringer's lactate (RL) resuscitated animals at end resuscitation and at 4-hour post-LPS. While PMN L-selectin levels remained stable in RL treated animals, A25 resuscitation resulted in a significant decrease in surface L-selectin expression at 4-hour post-LPS. ICAM-1 lung endothelial cell mRNA, was increased in RL resuscitated animals, however reduced with A25 use by 51%. The LPS induced ICAM-1 endothelial cell protein expression was also prevented with A25 resuscitation. Antioxidant property of albumin was shown to play a critical role in altering CD11b expression. CONCLUSIONS: The A25 exerts its lung-protective activity at various levels including altering the interaction between neutrophils and endothelial cells via suppressed expression of adhesion molecules. These findings suggest a novel role for A25 as an anti-inflammatory agent in PMN-mediated diseases such as ARDS.
BACKGROUND: Polymorphonuclear neutrophil (PMN) sequestration in the lung is a hallmark of acute respiratory distress syndrome (ARDS). We have shown that 25% Albumin (A25) resuscitation attenuates lung injury after hemorrhagic shock and lipopolysaccharide (LPS) exposure by reducing lung leukosequestration. We hypothesize that this protective property is mediated by alteration of neutrophil-endothelial cell adhesive interactions. MATERIALS AND METHODS: A 2-hit rodent model of shock resuscitation was used. CD11b and L-selectin were measured using flow cytometry in rat and human neutrophils ex vivo. Intercellular adhesion molecule-1 (ICAM-1) levels were measured by Northern blot and immunohistochemistry. RESULTS: Resuscitation with A25 attenuated the increase in PMN CD11b expression in Ringer's lactate (RL) resuscitated animals at end resuscitation and at 4-hour post-LPS. While PMN L-selectin levels remained stable in RL treated animals, A25 resuscitation resulted in a significant decrease in surface L-selectin expression at 4-hour post-LPS. ICAM-1 lung endothelial cell mRNA, was increased in RL resuscitated animals, however reduced with A25 use by 51%. The LPS induced ICAM-1 endothelial cell protein expression was also prevented with A25 resuscitation. Antioxidant property of albumin was shown to play a critical role in altering CD11b expression. CONCLUSIONS: The A25 exerts its lung-protective activity at various levels including altering the interaction between neutrophils and endothelial cells via suppressed expression of adhesion molecules. These findings suggest a novel role for A25 as an anti-inflammatory agent in PMN-mediated diseases such as ARDS.