Abstract 15705: Disordered Excitation Contraction Coupling as the Basis for Arrhythmogenic and Negative Inotropic Effects of Acute Ethanol Exposure
Rationale: Ethanol (EtOH) acutely has negative inotropic and arrhythmogenic effects, but the mechanisms for this are largely unknown. We speculated that EtOH could have acute effects on cardiomyocyte Ca2+-handling, potentially by inducing reactive oxygen species (ROS) production via NOX2.
Methods: Isolated human (atrial and failing ventricular) and murine cardiomyocytes were preincubated for 30 min and then superfused with either control solution (CTRL) or solution containing EtOH. Confocal microscopy was used to assess SR Ca2+-leak and epifluorescence microscopy to investigate global Ca2+-handling. Also, human atrial muscle strip experiments were performed. ROS generation was assessed using CM-H2DCFDA fluorescence.
Results: EtOH induced servere SR Ca2+-leak in both human (6.91±0.44 Ca2+-sparks/100μm/s vs 3.30±0.36 in CTRL, n≥122) and murine cardiomyocytes. This effect of EtOH was completely abolished in NOX2 knockout mice, suggesting ROS as the reason for the leak. And in fact, CM-H2DCFDA showed increased ROS generation upon EtOH (by 160±9%, n≥35). Also, spontaneous arrhythmogenic Ca2+-waves occurred much more frequently in EtOH treated cells (14.1% vs 2.9% of cells, n≥69). Moreover, cardiomyocyte contractility was impaired by EtOH in a dose-dependent manner (EtOH 1‰: 92±7% vs 3‰: 80±6% vs 6‰: 79±5% of CTRL, n≥29). Hysteresis-loops for Ca2+-fluorescence and sarcomere-length suggests that impaired myofilament Ca2+-sensitivity also contributes to negative inotropic effects of EtOH (slope -0.068±0.014 vs -0.189±0.037 in CTRL, n>7). Both SERCA2a and NCX function were significantly enhanced upon EtOH, thus compensating for the increased SR Ca2+-leak with respect to diastolic Ca2+-levels. Human cardiac muscle strips confirmed the acute negative inotropic (-45±7% contractility, n=10 vs n=10) effects of EtOH also in intact tissue.
Conclusion: We show for the first time that EtOH acutely induces SR Ca2+-leak. The mechanism for this appears to be induction of ROS-production by EtOH via NOX2. This provides a mechanism for the arrhythmogenic effects of EtOH. Furthermore, we show that the acute negative inotropic effects of EtOH can be explained by a combination of reduced systolic Ca2+-release and reduced myofilament Ca2+-sensitivity.
Author Disclosures: J. Mustroph: None. S. Pabel: None. S. Lebek: None. M. Drzymalski: None. T. He: None. L. Schöberl: None. C. Sag: None. S. Wagner: None. S.T. Sossalla: None. L.S. Maier: None. S. Neef: None.
- © 2016 by American Heart Association, Inc.