IL-33 signaling as a target to reduce ventilator-induced lung inflammation

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PROJECT SUMMARY/ABSTRACT Since being heralded into clinical practice by the Danish polio epidemic of 1952, positive pressure mechanical ventilation has saved countless lives and enabled the safe practice of surgery under general anesthesia. In recent years, however, it has become clear that mechanical ventilation itself can injure the lung by initiating and propagating an inflammatory process termed ventilator-induced lung injury (VILI). Whereas VILI was initially mainly considered an aggravating factor for critically ill patients with acute respiratory distress syndrome, new evidence suggests that it can occur also in subjects with uninjured lungs undergoing ventilation for other reasons, for example while receiving general anesthesia. The long-term goal of this research is to dissect the mechanisms of VILI and identify strategies to ameliorate it. The proposed studies align with this goal because they investigate a novel role for the IL-33/ST2 signaling pathway by addressing the overarching hypothesis that IL-33 is an upstream pathogenetic effector of VILI through its effect on NF-κB mediated inflammation. This hypothesis will be tested through three closely knit specific aims. Aim 1 will establish the role of IL-33 in VILI by demonstrating that its expression increases with tidal volume, that it parallels the response of established VILI cytokines and NF-κB, and that IL-33 deletion blunts such response. Aim 2 builds on aim 1 by probing the efficacy of IL-33 scavenging with IL-33 decoy receptors as an approach for interrupting IL-33/ST2/NF-κB signaling and decreasing inflammation in VILI. This aim will leverage a novel biologic with high affinity for IL-33 (“IL-33 trap”) that preliminary data suggest could have therapeutic potential. The IL-33 trap will be compared with the more traditional approach of anti-ST2 receptor blocking antibodies. Aim 3 flows from aims 1 and 2 as it will determine for how long the activation of NF-κB triggered by release of mechano- sensitive cytokines like IL-33 persists after ventilation ceases, thus rendering the lung vulnerable to other insults, as are those that can occur in the postoperative period. A distinctive feature that permeates all three aims of this project is the application of a unique molecular imaging method based on positron emission tomography (PET) of NF-κB transcriptional activity to measure the effect of IL-33/ST2 signaling on downstream cytokine expression in vivo, noninvasively, repeatedly and with high spatial resolution. It is expected that the combination of clinically relevant murine ventilation model, novel VILI effector (IL-33, aim 1), therapeutic biologic (IL-33 trap, aim 2), and translational perspective (aim 3), will make the proposed experiments uniquely poised to yield fundamental new knowledge on the pathogenesis of VILI and on potential preventative and therapeutic strategies.