ABSTRACTThis application seeks to address the unmet need for curative therapies in pulmonary arterial hypertension(PAH) a fatal disease with a dismal prognosis. A key feature of the pathobiology of PAH is the profound pulmo-nary vascular remodeling for which new therapeutic strategies are woefully lacking. We successfully employedgenomicintensive approaches to identify nicotinamide phosphoribosyltransferase (NAMPT) as a novel PAHtarget that is robustly upregulated in PBMCs from PAH patients. We also demonstrated markedly increasedNAMPT expression in remodeled vessels from human PAH subjects and in preclinical PAH models (mice andrats) with NAMPT localized to lung endothelial cells (ECs). We further reported that reducing the availability ofsecreted or extracellular NAMPT or eNAMPT (via eNAMPT neutralizing antibodies siRNAs Nampt+/- mice) dra-matically attenuated PAH severity in our preclinical PAH models. To test the hypothesis that NAMPT promotesvascular remodeling during PH development and serves as a novel PAH therapeutic target Specific Aim #1 (SA#1) will further characterize the regulation of NAMPT expression in response to PAH stimuli (PDGF VEGFPHD2 inhibitor endothelin-1) focusing on promoter activity and epigenetic regulation (DNA methylation miR-NAs) and specific transcription factors (HIF-2a STAT5 SOX17) that we have shown to regulate NAMPT tran-scription. SA #2 will mechanistically examine the contribution of extracellular NAMPT (eNAMPT) to vascularremodeling via influences on EC apoptosis and smooth muscle cell (SMC) activation (Ca2+ signaling and prolif-eration). We will specifically focus on the interaction of eNAMPT with Tolllike receptor 4 (TLR4) that we recentlyidentified as the NAMPT receptor and explore eNAMPT-TLR4 mediated NFB transcriptional activities as a novelmechanism by which eNAMPT may influence vascular remodeling. SA #3 will leverage our prior published stud-ies and preliminary data demonstrating that NAMPT 5 promoter polymorphisms (SNPs) alter NAMPT promoteractivity which also confer significantly increased risk for susceptibility and severity in acute respiratory distresssyndrome (ARDS) and will be assessed in PAH. SA #3 studies will determine the influence of NAMPT SNPs ontranscriptional regulation on eNAMPT-TLR4 binding and NFB activation in PAH. Finally SA #4 will define inestablished PAH the therapeutic efficacy of reduced NAMPT expression (conditional EC knockout mice) eN-AMPT elimination (neutralizing antibodies) inhibition of NAMPT enzymatic activity (novel FK-866 analogues)and TLR4 antagonism (novel peptide inhibitors). Supported by intimate involvement of outstanding investigatorsand substantial highly translational published/preliminary data highlighting NAMPT as a novel innate immunitymodulator this application will successfully define NAMPT participation in PAH susceptibility pathobiology andseverity.