Remote Ischemic Conditioning Prevents Lung and Liver Injury After Hemorrhagic Shock/Resuscitation Potential Role of a Humoral Plasma Factor

Objective: To evaluate the efficacy of remote ischemic conditioning (RIC) on organ protection after hemorrhagic shock/resuscitation (S/R) in a murine model. Background: Ischemia/reperfusion resulting from S/R contributes to multiple organ dysfunction in trauma patients. We hypothesized that RIC before shock (remote ischemic preconditioning), during shock (remote ischemic "PER" conditioning), or during resuscitation (remote ischemic "POST" conditioning) could confer organ protection. We also tested the effect of ischemic conditioned plasma on neutrophil migration in vivo using transgenic zebrafish models. Methods: C57Bl/6 mice were subjected to S/R with or without hindlimb RIC. Serum levels of alanine aminotransferase and tumor necrosis factor-alpha, and liver tumor necrosis factor-alpha and interleukin 1 beta mRNA were evaluated. In some experiments, lung protein leakage, cytokines, and myeloperoxidase activity were investigated. Plasma from mice subjected to RIC was microinjected into zebrafish, and neutrophil migration was assessed after tailfin transection or copper sulfate treatment. Results: In mice subjected to S/R, remote ischemic preconditioning, remote ischemic "PER" conditioning, and remote ischemic "POST" conditioning each significantly reduced serum alanine aminotransferase and liver mRNA expression of tumor necrosis factor-alpha and interleukin 1 beta and improved liver histology compared with control S/R mice. Lung injury and inflammation were also significantly reduced in mice treated with remote ischemic preconditioning. Zebrafish injected with plasma or dialyzed plasma (fraction > 14 kDa) from ischemic conditioned mice had reduced neutrophil migration toward sites of injury compared with zebrafish injected with control plasma. Conclusions: RIC protects against S/R-induced organ injury, in part, through a humoral factor(s), which alters neutrophil function. The beneficial effects of RIC, performed during the S/R phase of care, suggest a role for its application early in the posttrauma period.