PROJECT SUMMARY/ABSTRACT The objectives of this K08 proposal are to foster the development of critical scientific and professional skills that will allow the candidate, Dr. Mona Alotaibi, to advance toward her goal of becoming an independent investigator; and to investigate the role of metabolic dysregulations and bioactive molecular markers of endothelial dysfunction in modulating pulmonary arterial hypertension (PAH) progression in human studies and experimental models. This will be achieved through a comprehensive training plan and extensive laboratory experience and course work, which will provide Dr. Alotaibi additional expertise in experimental design, laboratory procedures, large data handling and laboratory leadership skills. Pulmonary arterial hypertension is a rare but life-threatening condition, that if left untreated leads to right ventricular failure and death. Despite advances in therapeutics, PAH mortality and morbidity remains unacceptably high, motivating efforts to identify circulating biomarkers and mechanistic targets that could improve tailored treatment approaches and outcomes. Central to PAH pathobiology is endothelial dysfunction governed by imbalance between endothelial derived relaxing and contracting factors. These factors include circulating small bioactive lipid mediators, eicosanoids known to exhibit vasoactive properties including vasocontraction or vasodilation in context dependent matter. Sensitive methods for comprehensively detecting and quantifying distinct eicosanoid species have been limited with prior studies in PAH focusing mainly on cyclooxygenase pathway. We have shown that distinct lipoxygenase (LOX)-eicosanoid dysregulations exist in animal models with severe pulmonary hypertension and these metabolites associated with mortality and worse clinical outcomes in human. The overall goal of this proposal is to utilize our newly developed mass spectrometry approaches together with comprehensive, complementary study design that include human biosamples, PH murine models and cell culture experiments to provide an unprecedented view into the role and mechanism of LOX-eicosanoid derangements in PAH. We hypothesize that endothelial LOX intermediates play an important role in the development and progression of PAH through sustained pulmonary vasoconstriction and concentric pulmonary vascular remodeling, and particularly via activation of mechano- sensitive and receptor-operated cation channels in both pulmonary arterial smooth muscle and endothelial cells. We will test this hypothesis in three Specific Aims: 1) To determine the relation of LOX-derived eicosanoids with PAH disease progression and outcomes; 2) To examine whether LOX-HETEs induce spontaneous PAH or enhance PH in animal models; 3) To examine whether LOX-HETEs activate or upregulate mechanosensitive, or receptor operated cation channels in pulmonary arterial vasculature. Successful implementation of these Specific Aims will provide a rigorous training program for Dr. Alotaibi, laying the groundwork for R01 submission, and will allow us to answer a fundamentally important question about the role of LOX-eicosanoids as specific biomarkers for disease risk and target for future interventions.

PROJECT NARRATIVE Despite advances in the diagnosis and treatment of pulmonary arterial hypertension, morbidity and mortality remain unacceptably high. To improve our currently limited understanding of how complex bioactive metabolite pathways interact to promote or prevent pulmonary hypertension, we will study upstream mediators of endothelial dysfunction in relation to disease risk and progression, in comprehensive study design. These studies can identify novel pathogenic and prognostic biomarkers and future therapeutic interventions.