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Epac1 promotes mitochondrial dysfunction and cardiomyocyte death during persistent lipid overload

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Bergonnier, Dorian | Laudette, Marion | Sainte-Marie, Yannis | Lezoualc’h, Frank

Edité par CCSD -

International audience. IntroductionEPAC1 is a key effector of cAMP and contributes to cardiac remodelling and dysfunction. We recently showed that EPAC1 localizes in the mitochondria and is upregulated in the myocardium of obese patients.The aim of the present study is to determine the role of mitochondrial EPAC1 in cardiomyocyte lipotoxicity.MethodsExperiments were carried out in either isolated neonatal rat ventricular myocytes (NRVM) or adult murine ventricular cardiomyocytes (AMVC), pretreated or not with palmitate (PA, 150 μM, 2h), a toxic fatty acid (FA). We used the seahorse technology to evaluate oxygen consumption rate (OCR) in AMVC isolated from WT or Epac1-/- mice. Mitochondrial ROS production and membrane potential were determined using respectively MitoSOX and JC-1 probe, in WT or Epac1-/- AMVC. Mitochondrial ROS quantification, caspase 3 activity, or LDH release were also measured in NRVM expressing either Epac1WT or an Epac1 mutant deleted for Epac1 putative mitochondrial-targeting sequence (Epac1Δ2–37).ResultsWe found that PA (500 μM) induced cardiomyocyte death was blocked by CE3F4 (20 μM), a selective Epac1 inhibitor. In addition, a selective soluble adenylyl cyclase (sAC) inhibitor, KH7 (20 μM), blocked cAMP accumulation in response to palmitate and significantly reduced palmitate-induced cardiomyocyte AMVC in a manner similar to CE3F4. While chronic exposure to PA reduced maximal mitochondrial respiration in WT AMVC, Epac1-/-AMVC were resistant to this effect. We also found that PA-induced increase in mitochondrial ROS content in WT AMVC but not in Epac1-/-AMVC. Accordingly, pharmacological inhibition of Epac1 with CE3F4 prevented PA-induced loss of mitochondrial membrane potential in WT AMVC. Finally, we showed that NRVM transfected with Epac1Δ2–37 exhibited less mitochondrial ROS production and caspase 3 activation compared to those transfected with Epac1WT.ConclusionOur data demonstrate that PA leads to sAC activation, cAMP production and EPAC1 activation which subsequently promotes mitochondrial dysfunction and cardiomyocyte death.

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