Endogenous regulators of inflammation in liver ischemia/reperfusion

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 DESCRIPTION (provided by applicant): Thorough understanding of the pathophysiology of liver ischemia reperfusion (I/R) is vital as it is commonly encountered clinically during elective liver surgical procedures, solid organ transplantation, trauma, and hypovolemic shock. Although the distal events involved in the inflammatory response resulting in liver damage after I/R injury has been well-studied, the proximal events dictating the propagation of the inflammatory response and further tissue damage is poorly understood. This proposal focuses on a group of endogenous damage-associated molecular pattern (DAMP) molecules that emanate from the cell nucleus during infection and injury to initiate the activation of innate inflammatory responses. Our recent findings demonstrate that nuclear DAMPs are involved in neutrophil biology, namely neutrophil extracellular trap (NET) formation, in the setting of liver I/R. IL-33, novel member of the IL-1 family associated with chromatin in the nucleus, can act as a DAMP when released following liver I/R to stimulate NET formation. In addition to the presence of nuclear histones, we have also identified a novel requirement of intracellular high mobility group box-1 (HMGB1) protein in the ability of neutrophils to form NETs. Importantly, targeting NETs ameliorates the hepatic as well as systemic I/R-induced injury in mice. Thus, we propose that nuclear DAMPs (such as IL-33, histones, and HMGB1) mediate NET formation and subsequent organ injury following liver I/R. These mechanisms will also be validated in clinical outcomes of patients undergoing liver resection. In Aim 1, we will determine the role of IL-33 in NET formation and inflammatory signaling during ischemic liver injury. Aim 2 will identify the intracellular roles of HMGB1 in regulating neutrophil formation of NETs. In Aim 3, we will establish the mechanisms of NET-mediated local and systemic organ injury following liver I/R. These studies will serve as a basis for developing both a more comprehensive understanding of how DAMPs mediate both harmful and adaptive responses during non-infectious inflammation, and should prove useful in the design of novel therapies, broadly applicable, to minimize tissue damage in a variety of clinical settings.