Macrophage-derived chemokine (CCL22) is a novel mediator of lung inflammation following hemorrhage and resuscitation.

Resuscitation of patients after hemorrhage often results in pulmonary inflammation and places them at risk for the development of acute respiratory distress syndrome. Our previous data indicate that macrophage-derived chemokine (MDC/CCL22) is elevated after resuscitation, but its direct role in this inflammatory response is unknown. Macrophage-derived chemokine signaling through the C-C chemokine receptor type 4 (CCR4) is implicated in other pulmonary proinflammatory conditions, leading us to hypothesize that MDC may also play a role in the pathogenesis of lung inflammation following hemorrhage and resuscitation. To test this, C57BL/6 mice underwent pressure-controlled hemorrhage followed by resuscitation with lactated Ringer's solution. Pulmonary inflammation and inflammatory cell recruitment were analyzed with histological staining, and serum- and tissue-level cytokines were measured by enzyme-linked immunosorbent assay. Pulmonary inflammation and cell recruitment following hemorrhage and resuscitation were associated with systemic MDC levels. Inhibition of MDC via injection of a specific neutralizing antibody prior to hemorrhage and resuscitation significantly reduced pulmonary levels of the chemotactic cytokines keratinocyte-derived chemokine and macrophage inflammatory proteins 2 and 1α, as well as inflammatory cell recruitment to the lungs. Intravenous administration of recombinant MDC prior to resuscitation augmented pulmonary inflammation and cell recruitment. Histological evaluation revealed the expression of CCR4 within the bronchial epithelium, and in vitro treatment of activated bronchial epithelial cells with MDC resulted in production and secretion of neutrophil chemokines. The present study identifies MDC as a novel mediator of lung inflammation after hemorrhage and resuscitation. Macrophage-derived chemokine neutralization may provide a therapeutic strategy to mitigate this inflammatory response.