Mitochondria are the powerhouse of eukaryotic cells such as cardiomyocytes. Besides their role in free energy transduction, they are responsible for maintaining intracellular ionic homeostasis (e.g., Ca2+, Na+, Mg2+, H+, K+) and handling toxic byproducts of energy metabolism (e.g., ROS). Consequently, functional defects in these processes can lead to mitochondrial dysfunction, cell death, and pathogene- sis of several diseases. A quantitative understanding of regulation of mitochondrial function through the kinetics of mitochondrial cation transport and buffering and ROS generation and scavenging will be cru- cial in developing a systems-based, engineering understanding of mitochondrial, cellular, whole-organ, and whole-organism function and associated disease processes. The overall goal of this collaborative proposal is therefore to quantify the biophysics and chemical kinetics associated with mitochondrial handling of pH, cations, and ROS in cardiomyocytes and to understand how they individually and col- lectively influence mitochondrial function. We hypothesize that cations selectively inhibit or activate specific cation channels and exchangers to regulate trans-matrix fluxes and intra-matrix concentrations of these cations. Furthermore, the intra-matrix free concentrations of cations (e.g., Ca2+) are governed by a dynamic buffering mechanism due to dynamic binding of the cations with phosphates (ATP, ADP, PI) and substrates (TCA cycle intermediates) during transient respiration, which in turn regulate mito- chondrial function, including the rate of ROS generation. Pathophysiological and chronic alterations in these mechanisms can lead to mitochondrial dysfunction and cellular injury. These hypotheses will be tested through an iterative process between experimental measurements and computational modeling of mitochondrial bioenergetics and electrophysiology (changes in trans-matrix cation concentrations and fluxes, NADH and FAD redox states, membrane potential, respiration, and ROS production with normal and abnormal perturbations in extra-matrix cation concentrations) in both isolated cardiac mito- chondria and isolated intact hearts, with the refinement of both the experimental design and computa- tional model as the research unfolds. The model will provide the basis for improving the experimental design and specific hypotheses;in turn, the experimental data will provide the basis to refine and ex- tend the model. By the use of this integrative approach we will also be able to understand regulation of ROS production during ischemia and reperfusion (I/R). Recovery of cardiac function after I/R is critically dependent on rapid recovery of mitochondrial function to restore ATP production, which prevents de- rangement of cytosolic and mitochondrial cation homeostasis and avoid cellular injury or death. The proposed combined approach represents a novel strategy in understanding the integrated function of cardiomyocytes under physiological and pathophysiological conditions.
Relevance of the research to public health: The process of combined computational modeling with experimental measurements of mitochondrial bioenergetics and electrophysiology provides an iterative process to formulate and quantitatively test complex hypotheses regarding regulation of mitochondrial function in health and disease. The proposed research examines the inter-relationships between the kinetics of mitochondrial bioenergetics, electrophysiology, cation and ROS handling, and the dynamic regulation of mitochondrial and cellular function in the heart in health and disease. These studies will provide a novel and rational mechanistic approach for the identification of new therapeutic targets and the development of new therapies (e.g., cation channel blockers or openers) to alleviate mitochondrial dysfunction and preserve cellular viability.
|Blomeyer, Christoph A; Bazil, Jason N; Stowe, David F et al. (2016) Mg(2+) differentially regulates two modes of mitochondrial Ca(2+) uptake in isolated cardiac mitochondria: implications for mitochondrial Ca(2+) sequestration. J Bioenerg Biomembr 48:175-88|
|Ranji, Mahsa; Motlagh, Mohammad Masoudi; Salehpour, Fahimeh et al. (2016) Optical Cryoimaging Reveals a Heterogeneous Distribution of Mitochondrial Redox State in ex vivo Guinea Pig Hearts and Its Alteration During Ischemia and Reperfusion. IEEE J Transl Eng Health Med 4:1800210|
|Pannala, Venkat R; Dash, Ranjan K (2015) Mechanistic characterization of the thioredoxin system in the removal of hydrogen peroxide. Free Radic Biol Med 78:42-55|
|van Brussel, Marco; van Oorschot, Joep W M; Schmitz, Joep P J et al. (2015) Muscle Metabolic Responses During Dynamic In-Magnet Exercise Testing: A Pilot Study in Children with an Idiopathic Inflammatory Myopathy. Acad Radiol 22:1443-8|
|Agarwal, Bhawana; Stowe, David F; Dash, Ranjan K et al. (2014) Mitochondrial targets for volatile anesthetics against cardiac ischemia-reperfusion injury. Front Physiol 5:341|
|Bazil, Jason N; Pannala, Venkat R; Dash, Ranjan K et al. (2014) Determining the origins of superoxide and hydrogen peroxide in the mammalian NADH:ubiquinone oxidoreductase. Free Radic Biol Med 77:121-9|
|Agarwal, Bhawana; Dash, Ranjan K; Stowe, David F et al. (2014) Isoflurane modulates cardiac mitochondrial bioenergetics by selectively attenuating respiratory complexes. Biochim Biophys Acta 1837:354-65|
|Yang, Meiying; Stowe, David F; Udoh, Kenechukwu B et al. (2014) Reversible blockade of complex I or inhibition of PKC? reduces activation and mitochondria translocation of p66Shc to preserve cardiac function after ischemia. PLoS One 9:e113534|
|Nabbi, Raha; Gadicherla, Ashish K; Kersten, Judy R et al. (2014) Genetically determined mitochondrial preservation and cardioprotection against myocardial ischemia-reperfusion injury in a consomic rat model. Physiol Genomics 46:169-76|
|Tewari, Shivendra G; Camara, Amadou K S; Stowe, David F et al. (2014) Computational analysis of Ca2+ dynamics in isolated cardiac mitochondria predicts two distinct modes of Ca2+ uptake. J Physiol 592:1917-30|
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