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. 2025 Nov 14.
doi: 10.1111/bph.70253. Online ahead of print.

Mitochondrial Ca2+ overload is a pivotal risk factor for lethal ventricular arrhythmias due to the oxidation of mitochondrial respirasome and energetic failure

Felipe de Jesús Salazar-Ramírez  1   2 , Luis Alberto Luévano-Martínez  1   2   3 , Abraham Méndez-Fernández  1   2 , Judith Bernal-Ramírez  1   2   3 , Carolina A Morales-Ochoa  1   2 , Christian Silva-Platas  1   2 , Alfredo Cabrera-Orefice  4 , Ana C Murrieta  5 , José Luis Velasco-Bolom  3 , Gricelda Mendiola-Garza  1   2 , Flavio Contreras-Torres  3   5 , Guillermo Torre-Amione  1   3   6 , Ernesto A Aiello  7 , Gerardo García-Rivas  1   3   8
Affiliations

Mitochondrial Ca2+ overload is a pivotal risk factor for lethal ventricular arrhythmias due to the oxidation of mitochondrial respirasome and energetic failure

Felipe de Jesús Salazar-Ramírez et al. Br J Pharmacol. .

Abstract

Background and purpose: Ventricular arrhythmias are a leading cause of death among patients with cardiovascular diseases and are associated with elevated levels of catecholamines. Mitochondrial Ca2+ transport is essential for initiating an adrenergic response. However, continuous stimulation might lead to mitochondrial Ca2+ overload and dysfunction within cardiac tissue. This study investigates the role of mitochondrial Ca2+ in lethal arrhythmogenesis and the effects of its modulation.

Experimental approach: Male C57BL/6 mice were administered either Ru360 (oxo-bridged dinuclear ruthenium ammine complex) a potent and selective mitochondrial Ca2+ transport inhibitor, or normal saline via intravenous injection. A baseline electrocardiogram (ECG) was recorded, followed by subcutaneous administration of isoprenaline. The ECG was monitored for an additional 20 min, after which cardiomyocytes and mitochondria were isolated for further characterization studies.

Key results: Isoprenaline administration led to ventricular tachycardia and fibrillation, but Ru360 pretreatment successfully prevented these arrhythmias. Mitochondria from isoprenaline-treated hearts showed higher Ca2+ content, indicating overload that compromised mitochondrial function and membrane integrity, evidenced by decreased respiratory control, reduced Ca2+ retention capacity and diminished membrane potential. Isoprenaline also increased oxidative stress, illustrated by elevated peroxide production, electron leak and acute oxidative modifications, and erratic cellular Ca2+ dynamics. This mitochondrial dysfunction correlated with a decreased respirasome activity, but not a difference in respirasome abundance quantified by complexome profiling, which was prevented by Ru360 pretreatment.

Conclusion: Mitochondrial Ca2+ overload significantly contributes to arrhythmias by disrupting respirasome function and increasing oxidative stress, impairing cellular Ca2+ dynamics. Modulating mitochondrial Ca2+ transport might be a promising strategy for developing innovative antiarrhythmic therapies.

Keywords: arrhythmia; calcium; mitochondria; respirasome.

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