Macrophage Plasticity in Inflammatory Lung Injury

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RESEARCH SUMMARY/ABSTRACT OF PROGRAM The fundamental challenge in treating the hyper-inflammatory state underlying Acute Lung Injury/Acute Respiratory Distress Disorder (ALI/ARDS) is that broad anti-inflammatory interventions could compromise host defense and potentially exacerbate the underlying infectious process that triggered ALI/ARDS. Novel targeted approaches to treat ALI/ARDS thus require an in-depth understanding of the intricate inflammatory mechanisms to reduce the extent of injury and promote the resolution of inflammation as well as the initiation of lung repair without compromising host defense. It is now recognized that macrophages (Mφ) in lungs represent diverse multi-functional cell populations. They have the ability to sense pathogens and danger signals, and their plasticity and diversity allows them to respond in specialized manners to specific niche environments. They are able to change their phenotypes in a chameleon-like manner by activation of specialized transcriptional programs. Thus, they have the remarkable ability to amplify inflammation and also to coordinate resolution of lung inflammatory lung injury and restore homeostasis. Mφ carry out these functions through the release of an array of cytokines, phagocytosis of microbes, efferocytosis of dead cells, and provide the essential inflammatory or reparative signals to nearby cells. The central focus of this program will be to precisely define the roles of distinct macrophage subpopulations in inflammatory lung injury and signaling nodes to harness the plasticity of macrophages and thereby bring about the resolution of lung injury. Project 1 will test the hypothesis that two specific specific ion channels, P2RX7 (Purinergic Receptor 2 subtype X7) and the potassium (K+) efflux channel TWIK2 regulate the plasticity to either promote lung injury or to activate the repair program. Project 2 will test the hypothesis that the transcription factor CREB and its downstream targets are critical regulators of the anti- inflammatory and reparative function of alveolar Mφ. Project 3 will test the hypothesis that endothelial cells lining all lung vessels direct the plasticity of Mφ via modulation of Wnt signaling in Mφ. Project 4 will test the hypothesis that circulating postnatal CX3CR1+ monocytes replenish lung interstitial Mφ during inflammatory injury and can direct the lung tissue repair program. These four Projects are supported and complemented by highly innovative scientific Cores which will provide important optogenetic tools (Synthetic Biology and Optogenetics Core B), super-resolution and intravital imaging (Advanced Imaging Core C), and access to clinical samples as well as single cell transcriptomic analysis of macrophages (Clinical Sampling and Genomics Core D) to unravel the complexities of macrophage biology in lung injury, thus paving the way for much-needed novel therapeutic approaches in ALI/ARDS.