Decreased Cholinergic Tone and Mitochondrial Dysfunction in Heart

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DESCRIPTION (provided by applicant): This research will be done primarily in Brazil at Universidade Federal de Minas Gerais in collaboration with Dr. Silvia Guatimosim, as an extension of Project 3 of NIH Grant number P01 HL67849 (A.R. Marks), 4/1/2006-3/31/2011. Dr. W. Jonathan Lederer is the project leader. The proposed FIRCA project seeks to enable novel real-time imaging and cell biology experiments for an outstanding research group in Brazil headed by Dr. Silvia Guatimosim. The new work will be made possible by using the PI's state-of-the-art facilities at the University of Maryland Center for Biomedical Engineering and Technology to train Dr. Guatimosim and her colleagues in new methods. Broadly the co-investigators will investigate how the cholinergic tone in heart affects Ca2+ signaling in the cardiac myocytes and mitochondrial function. Imaging and biophysical methods will be used along with a novel mouse line (VaChT KDHOM mice) that has reduced expression of the vesicular acetylcholine transporter. This novel mouse line was developed with previous FIRCA funding to Dr. M. Prado and will permit the co-investigators to characterize the consequences of cholinergic hypofunction on heart cell behavior. Provocative preliminary results by Dr. Guatimosim show that the VAChT KDHOM mouse has heart failure including decreased myocardial force, altered ventricular calcium handling and molecular remodeling (Lara et al., Molecular & Cellular Biology, 2010 in press), including altered mitochondrial biology and enzyme levels and increased production of reactive oxygen species (ROS) (see Preliminary Results). Much of this dysfunction was reversed by treatment with a cholinesterase inhibitor (pyridostigmine). Since mitochondria are considered the powerhouse of the cell, the central hypothesis of this FIRCA project is that alterations in mitochondrial dynamics contribute to cardiac malfunction in VAChT mutant mice. To test this hypothesis, we will measure mitochondrial dynamics in patch-clamped ventricular myocytes from VAChT mutants by using a combination of real-time imaging of mitochondrial Ca2+ levels and membrane potential ([Ca2+]mito )The functional data obtained by real-time imaging will provide an integrated understanding of mitochondria' s role on heart disease caused by reduced cholinergic tone. This FIRCA proposal will provide the means to build new research capabilities at the Universidade Federal de Minas Gerais site for the simultaneous patch-clamp and real-time imaging of mitochondria, and to incorporate these state-of-the-art techniques into Dr. Guatimosim's research. Dr. Lederer will provide training in Baltimore for Dr. Guatimosim and her co-workers and on-site instruction in Brazil. PUBLIC HEALTH RELEVANCE: Heart dysfunction is one of leading causes of human morbidity and mortality world-wide. The proposed research examines the surprising finding by the investigators that changes in the balance of the nervous system have profound consequences for heart function. This dysfunction occurs in heart failure and appears to target cellular processes that affect both contraction and the heart rhythm; therefore, the investigators seek to understand the molecular mechanisms of this process and thereby enable new therapies for both heart failure and "sudden cardiac death".