SUMMARY/ABSTRACT
Heart failure (HF) remains a major health problem and significant mortality in the United States. While defects in
mitochondrial function are strongly implicated in the pathophysiology of HF, no mitochondrial-targeted therapy
has been successful in the clinic to date, indicating that we still do not possess sufficient understanding of the
mechanisms connecting mitochondrial dysfunction and HF development. Normal mitochondrial functions rely on
maintaining the inner membrane potential (¿¿m). In the cardiomyocyte (CM), ¿¿m perturbations not only directly
affect ATP production, but also influence a variety of signaling pathways that modulate redox balance, Ca2+
homeostasis, and mitochondrial quality control. However, to what extent and how the loss of CM ¿¿m alone
impairs cardiac energetics, contractility, and electrical activity (i.e., hallmarks of HF) remains poorly defined. This
is due, in part, to a lack of methods for effectively and selectively manipulating CM mitochondria in the in vivo
setting. Existing pharmacological approaches to depolarize ¿¿m lack both cell (CM versus non-CM) and organ
(cardiac versus non-cardiac) specificity. To overcome this technical barrier, we developed an innovative
mitochondrial-targeted luminoptogenetic (termed mLumOpto) technology and demonstrated that it can induce
dynamic, selective CM ¿¿m depolarization both in vitro and in vivo, with luciferase-luciferin pair-emitted
intracellular bioluminescent illumination. The primary goal of this proposal is to utilize the mLumOpto technology
to directly induce CM-specific ¿¿m depolarization in intact hearts, and delineate the acute (i.e. <24 hours) and
chronic (i.e. 2 weeks) impacts on cardiac functions. Our hypothesis is that CM-specific ¿¿m depolarization alone
is sufficient to induce adverse cardiac remodeling and HF development, which will be tested with the following
Specific Aims. Specific Aim 1 will fully characterize mLumOpto-mediated ¿¿m depolarization in isolated adult
CMs (ACMs) in vitro, and establish luciferin dose dependency. How the mLumOpto-mediated ¿¿m depolarization
acutely and chronically impacts ACM function and health, respectively, will be dissected. Specific Aim 2 will
determine the acute effect of CM-specific ¿¿m depolarization in intact hearts. First, mLumOpto-mediated in vivo
CM-specific ¿¿m depolarization will be determined. Then, the acute effects of CM ¿¿m depolarization on cardiac
metabolism, pump function, and electrophysiology in intact hearts will be examined both ex vivo and in vivo.
Specific Aim 3 will delineate the chronic effects of moderate CM ¿¿m depolarization on cardiac remodeling (at
gravimetric, histologic, biochemical, electrophysiological, and molecular levels) that lead to contractile
dysfunction and HF development. The reversibility of CM ¿¿m depolarization-induced HF will also be examined.
Successful completion of this research will lead to not only an innovative technology for dynamic control of CM
mitochondria in freely-moving animals, but also new findings that will lead us to novel avenues for the
development and translation of future mitochondrial-targeted HF therapies.