Cardiac response to beta-adrenergic stimulation is partially dependent on mitochondrial calcium uniporter activity

FERNÁNDEZ-SADA E; SILVA-PLATAS C; VILLEGAS CA; RIVERO SL; WILLIS BC; GARCÍA N; GARZA JR; OROPEZA-ALMAZÁN Y; VALVERDE CA; MAZZOCCHI G; ZAZUETA C; TORRE-AMIONE G; GARCÍA-RIVAS G

BRITISH JOURNAL OF PHARMACOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 171 p. 4207 - 4221

0007-1188

Background and Purpose Despite the importance of mitochondrial Ca2+ to metabolic regulation and cell physiology, little is known about the mechanisms that regulate Ca2+ entry into the mitochondria. Accordingly, we established a system to determine the role of the mitochondrial Ca2+ uniporter in an isolated heart model, at baseline and during increased workload due to β-adrenergic stimulation. Experimental approach Cardiac contractility, oxygen consumption and intracellular Ca2+ transients were measured in ex vivo-perfused murine hearts. Ru360 and spermine were used to modify mitochondrial Ca2+ uniporter activity. Changes in mitochondrial Ca2+ content and energetic phosphate metabolites levels were determined. Key Results The addition of Ru360, a selective inhibitor of mitochondrial Ca2+ uniporter, induced progressively and sustained negative inotropic effects that were dose-dependent with an EC50 of 7 μM. Treatment with spermine, a uniporter agonist, showed a positive inotropic effect that was blocked by Ru360. Inotropic stimulation with isoproterenol elevated oxygen consumption (2.7-fold), Ca2+-dependent activation of pyruvate dehydrogenase (5-fold), and mitochondrial Ca2+ content (2.5-fold). However, in Ru360-treated hearts, this parameter was attenuated. In addition, Ru360-decreased β-adrenergic stimulation did not have an effect on intracellular Ca2+ handling and protein kinase A and Ca2+/calmodulin-dependent protein kinase signaling. Conclusions and Implications We identified that mitochondrial Ca2+ uniporter inhibition results in lower β-adrenergic response, uncoupling between workload, and production of energetic metabolites. Our results support the hypothesis that coupling between workload and energy supply is partially dependent on mitochondrial Ca2+ uniporter activity.