PROGRAM SUMMARYMechanical ventilation a life-saving intervention in critically ill patients with respiratory failure due to acute respiratory distress syndrome (ARDS) also creates excessive mechanical stress that augments lung injury asyndrome known as ventilator-induced lung injury (VILI). The pathobiology of VILI and ARDS share many inflammatory features including increases in lung vascular permeability due to loss of endothelial cell (EC) barrier integrity. Insights into VILI pathobiology have been incremental with no viable therapies realized. This PPGintensely focuses on increasing our understanding of: i) the transcription factors that relay the effects of excessive mechanical stress; ii) the molecular signaling pathways that lead to EC injury including initial activation ofa mechanosensitive Ca2+-regulatory receptor transient receptor potential cation channel subfamily V member 4(TRPV4); iii) post translational modifications (PTMs) that influence key signaling pathways involved in VILI responses; iv) genetic and epigenetic influences in key target genes involved in VILI responses; and v) noveltherapeutic strategies for VILI. The key novel genes that comprise the focus of each Project were identified byour genomicintensive approaches and selected for their capacity to contribute to a spectrum of VILI responses from VILI-induced lung inflammation increased vascular permeability and injury (Projects #1 and #2); toVILI resolution with restoration of lung vascular barrier integrity (Project #3). These strategies are integratedacross our three PPG projects and represent the thematic underpinnings of this PPG. Studies will be conducted by an outstanding group of gifted and interactive translational scientists. Project #1 will examine the NF-B-dependent mechanisms (including protein nitration) by which VILI downregulates expression of SOX18 a critical lung vascular barrier-protective transcription factor (TF) and the key tight junction protein claudin 5. Theinfluence of the mechanosensitive receptor TRPV4 on mitochondrial ROS and mechanical stress-associatedTFs such as HIF2 will be explored. Project #2 will extend novel insights regarding the critical role of secretedextracellular NAMPT (eNAMPT) a nicotinamide phosphoribosyltransferase in VILI and ARDS. Excessive mechanical stress induces NAMPT expression and eNAMPT ligates TLR4 (Toll-like receptor 4) to induce NF-Bsignaling and inflammatory lung injury. Project #2 will interrogate novel mechanisms of NAMPT secretion theinfluence of NAMPT/TLR4 SNPs and NAMPT and TLR4 as therapeutic targets. Project #3 will interrogate genetic and epigenetic regulation of mechanical stress-mediated sphingosine 1-phosphate receptor expression(S1PR1 S1PR3) and the role of VILI-induced nitration of Rac1 and RhoA GTPases in lung vascular barrierregulation. The synergy derived from the interaction between individual Projects as well as with our scientificCores with enviable expertise in molecular biology (B) genetic epidemiology (B) pre-clinical models of disease (C) and protein chemistry & Biophyics (D) will advance our programmatic approaches and promote thedevelopment of novel individualized therapies to attenuate VILI especially in populations at risk for ARDS.