The calcium sensitizer levosimendan is indicated for the hemodynamic stabilization of patients with acutely decompensated heart failure and has been shown to be protective against reperfusion injury after myocardial infarction. However, affected forms of cell death and underlying signaling pathways remain controversial. Therefore, the aim of this study was to examine the influence of levosimendan preconditioning and postconditioning on anoxia/reoxygenation-induced apoptosis, necrosis, and autophagy in H9c2 myoblasts. To mimic conditions of myocardial ischemia/reperfusion, rat cardiac H9c2 myoblasts were exposed to anoxia/starvation, followed by reoxygenation/refeeding. Apoptosis, necrosis, autophagy, cell viability, survival signaling, and mitochondrial permeability transition pore (mPTP) opening were measured. Both, pharmacological preconditioning and postconditioning with levosimendan were capable to reduce apoptosis as well as necrosis in stressed H9c2 cells. However, preconditioning showed to have the stronger impact compared with postconditioning. Moreover, levosimendan preconditioning increased autophagy, suggesting enhanced repair processes initiated by the early presence of the drug. Underlying mechanisms differ between both interventions: Although both are associated with PI3/Akt activation and reduced mPTP opening, only postconditioning but not preconditioning depended on mKATP activation. This variation might indicate that a pharmacological treatment after the onset of reoxygenation at least in part directly addresses mitochondrial structures for protection. In conclusion, we demonstrate that both pharmacological preconditioning and postconditioning with levosimendan protect anoxia/reoxygenation-stressed cells but differ in the underlying mechanisms. These results are decisive to obtain more insights into the beneficial effects of levosimendan in the treatment of reperfusion-mediated damage.
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