"Stretch-dependent X-ROS signaling: implications for cardiomyopathy" PI: Benjamin L. Prosser A novel signaling pathway in heart cells, termed X-ROS signaling, links the lengthening of a heart cell during diastole to the generation of reactive oxygen species (ROS) and subcellular Ca2+ signaling (Prosser et al., Science 2011). Discovered and characterized by the PI, X-ROS signaling regulates the release of Ca2+ from sarcoplasmic reticulum stores in heart cells. While X-ROS signaling is a normal physiological mechanism, it is upregulated in disease processes (e.g. Duchenne muscular dystrophy) and can trigger Ca2+-dependent arrhythmias. Using innovative techniques that combine the control of cell length with patch-clamp electrophysiology, the PI will characterize unknown critical biophysical features of this physiological generation of ROS, and investigate the signaling cascade that results. This biophysical characterization in single heart cells will be performed under the guidance of Dr. W.J. Lederer (mentor, University of Maryland), a world leader in cardiac cellular electrophysiology and calcium imaging. Through the adoption of new techniques and training, the PI will next move X-ROS signaling from the cellular level to that of the whole heart. The PI will image ROS and calcium signaling in intact, Langendorff-perfused hearts where diastolic length is modulated by a change in pre-load pressure. These examinations of length- dependent signaling will be conducted in both healthy and diseased hearts, as our recent evidence suggests that hyper-active X-ROS may be linked to calcium-dependent arrhythmia in disease. These studies will be guided by Dr. David Kass (co-mentor, Johns Hopkins School of Medicine), a translational cardiologist who specializes in the role of ROS signaling in cardiomyopathy. As a clinician scientist, Dr. Kass will broaden the perspective and skill set of the PI, which will allow the PI to take a more integrative approach to his work. The PI has assembled an excellent research advisory committee who will provide the training and support to facilitate the proposed studies and the growth of the PI. The PI will remain based at Maryland, but will work under the guidance of both Drs. Lederer and Kass during the entire period of work. Additionally, the PI has access to state-of-the-art equipment, as well as excellent resources for career development at the University of Maryland and at Johns Hopkins. The proposed work and development plan will enable the PI to characterize the physiological and pathophysiological actions of X-ROS signaling from the subcellular to the whole heart level, and will thus enable him to carve his niche as an independent faculty member. The proposed program is part of the PI's long term goal to investigate molecular mechanisms of cardiac function, with a particular focus on ROS and Ca2+ signaling, and to apply this knowledge to clinically relevant conditions.
This proposal will determine how the lengthening of heart cells, such as occurs when the heart fills with blood during diastole, influences the generation of reactive oxygen species. These reactive oxygen species can disrupt normal calcium homeostasis and the electrical rhythm of the heart, which may be particularly important in the context of heart disease.