2630 - Radiation-Induced Disruption of Cardiac Mitochondrial Bioenergetics and Nucleotide Homeostasis in Mice
Presenter(s)
K. Stawarska1,2, A. Kawecka1,2, K. Urbanowicz1, J. Kaminska3,4, M. Posiewnik3, A. Braczko1, W. Michnowska5, B. Kutryb-Zajac1,2, and B. Tomasik2,3; 1Department of Biochemistry, Faculty of Medicine, Medical University of Gdansk, Gdansk, Poland, 2Centre for Experimental Cardiooncology, Medical University of Gdansk, Gdansk, Poland, 3Department of Oncology and Radiotherapy, Medical University of Gdansk, Gdansk, Poland, 4Institute of Experimental Physics, Faculty of Mathematics, Physics and Informatics, University of Gdansk, Gdansk, Poland, 5Department of Cardiology and Heart Electrotherapy, Medical University of Gdansk, Gdansk, Poland
Purpose/Objective(s): Cardiac SBRT for refractory ventricular tachycardia produces rapid anti-arrhythmic effects that precede structural remodeling, suggesting early functional alterations in cardiomyocytes. We investigated the acute and persistent effects of clinically relevant radiation doses on murine cardiac bioenergetics and mitochondrial function to elucidate early mechanistic responses to irradiation.
Materials/Methods: HL-1 murine cardiomyocytes and 200-µm ex vivo left ventricular myocardial slices from C57BL/6J mice were exposed to 10 Gy or 25 Gy irradiation. Control groups underwent identical handling without irradiation. Analyses were performed approximately one hour post-exposure to assess early metabolic responses. Intracellular nucleotides (ATP, ADP, AMP, NAD?) were quantified by ultra-high-performance liquid chromatography. Mitochondrial respiration was evaluated using extracellular flux analysis to determine basal, ATP-linked, and maximal respiration, proton leak, and non-mitochondrial respiration. Cytoskeletal organization and mitochondrial structure were assessed by immunofluorescence, and calcium oscillations were quantified using live-cell fluorescence imaging.
Results: In HL-1 cardiomyocytes, 10 Gy induced acute bioenergetic stress characterized by elevated ADP levels, reduced adenylate energy charge, cytoskeletal disorganization, impaired maximal mitochondrial respiration, and increased calcium oscillation amplitude, consistent with compromised oxidative phosphorylation and excitability changes. In contrast, 25 Gy preserved adenylate energy charge but caused NAD? depletion and paradoxically increased basal and maximal respiratory capacity as well as spare capacity, suggesting a compensatory mitochondrial activation despite redox imbalance. In murine myocardial slices, radiation effects were markedly attenuated. Adenylate energy charge, ATP/ADP ratio, and NAD?/NADH balance remained stable after both doses. Although creatine content was reduced, the phosphocreatine/ATP ratio was preserved, indicating maintained energetic buffering. Notably, 25 Gy selectively increased non-mitochondrial oxygen consumption without affecting basal or maximal mitochondrial respiration, while 10 Gy increased GMP levels, pointing to dose-specific modulation of guanylate metabolism.
Conclusion: Ionizing radiation induces dose- and model-dependent bioenergetic alterations in cardiac cells and tissues, including changes in mitochondrial respiration, nucleotide levels, and redox balance. While 10 Gy exacerbated metabolic disruption, 25 Gy triggered partial recovery, highlighting differential responses across cellular and tissue levels. These metabolic changes may contribute to the immediate effects of cardiac SBRT and potentially to long-term cardiotoxicity. Understanding these molecular responses is essential to optimize the therapeutic window of cardiac radioablation and minimize adverse effects.