The studies outlined in this proposal will elucidate the mechanistic connections between oxidative injury and altered glutamine metabolism and how these processes directly contribute to the pathogenesis of pulmonary arterial hypertension (PAH). I have over 13 years'experience in free radical biology, lipid biochemistry, and the chemistry of oxygen metabolism. In my more recent work conducted as part of my postdoctoral studies and that forms the foundation for the science in this proposal, I have investigated the contribution of altered molecular and cellular metabolism to the pathogenesis of pulmonary arterial hypertension in cell culture and animal models as well as in human subjects with disease. In addition to my research experience, I am trained and board certified in Internal Medicine and have completed my clinical training in Pulmonary and Critical Care Medicine. My long-term career goal is to continue as an academic physician-scientist conducting basic and translational research into the role of BMP signaling in metabolic control and the role of altered metabolism in complex diseases such as pulmonary hypertension. The scientific investigations and training proposed in this application will prepare me to continue my career as an independent researcher and clinician. Vanderbilt is the ideal place to conduct the proposed studies and to execute my career development plan. International leaders in their respective fields teach the structured coursework outlined in the proposal. The Pulmonary and Critical Care division is rated in the top 10 in the country, and the Department of Medicine is one of the top ranked medicine departments in the country for NIH funding. Vanderbilt is recognized as one of the premier institutions for the study of the genetics and molecular pathogenesis of pulmonary vascular diseases and pulmonary arterial hypertension. My mentor, Dr. James West, has extensive experience in molecular biology and transgenic animal models of pulmonary vascular disease, and I meet on a daily basis with investigators who have defined pulmonary hypertension research over the last 20 years and who continue to do so. The division, department, and university all have a strong track record of fostering the careers of physician-scientists to become independent leaders in their fields through the commitment of resources, the availability of a rich scientific environment, and an emphasis on mentorship. Pulmonary arterial hypertension is a devastating, progressive, fatal disease of the pulmonary vasculature that has no cure. There are no diseases modifying agents that even slow the progression of PAH significantly, largely because the underlying molecular pathogenesis is incompletely understood. Enhanced proliferation, defective apoptosis, and oxidative injury in pulmonary microvascular endothelial cells (PMVEC) cause resistance in the pulmonary vasculature inexorably to rise. The ultimate cause of death is failure of the right ventricle in the face of an increased pressure load. Emerging data indicate that the molecular pathophysiology of PAH is characterized by markedly altered energy metabolism affecting multiple metabolic pathways. Efforts to target the metabolic abnormalities in PAH have been fruitful in preclinical studies and may offer the first truly disease-modifying therapies. However, the extent of the metabolic abnormalities has been incompletely defined in PAH. Our laboratory has found that the metabolic reprogramming in PAH is characterized by simultaneous alterations in multiple interconnected metabolic pathways, including significant reprogramming of the Krebs cycle. Specifically, we have found that BMPR2 mutations that cause PAH in patients and in animal models of disease cause a profound shift to use of glutamine as a fuel source. This shift is associated with increased oxidative stress, increased normoxic activation of hypoxia-inducible factor (HIF), and increased activity of the Krebs cycle enzyme isocitrate dehydrogenase (IDH). Our hypothesis is that decreased BMPR2 function leads to increased production of reactive oxygen species (ROS), which drives HIF activation, increased IDH activity, and increased glutamine metabolism. This, in turn, results in increased PMVEC proliferation and resistance to apoptosis, which are the phenotypes that drive development of PAH. Demonstrating that the ROS/HIF/IDH axis drives the development of PAH via altered glutamine metabolism would have immediate translation potential, as each step in this pathway would be a novel drug target. Moreover, these studies would establish a paradigm for the exploration of relevant signaling pathways in PAH (e.g., BMPR2 signaling) as fundamental regulators of cellular metabolism and for exploring these signaling and metabolic pathways in other complex diseases.
Pulmonary arterial hypertension is a progressive, fatal, and incurable disease of the blood vessels in the lungs that results in death from increasing resistance to blood flow ultimately causing heart failure. None of the currently approved drugs are disease-modifying, in part because the mechanisms that cause the disease are incompletely understood. Using cell culture and animal models of human pulmonary arterial hypertension, this project will define a novel mechanism that changes how cells burn fuel for energy in a way that drives the development of pulmonary arterial hypertension.