Statins inhibit reoxygenation-induced cardiomyocyte apoptosis: Role for glycogen synthase kinase 3β and transcription factor β-catenin

Background. - Statins may improve left ventricular remodeling after myocardial infarction. We tested whether statins inhibit cardiomyocyte apoptosis through glycogen synthase kinase 3β (GSK3β) inactivation and evaluated activation of downstream transcription factors. Methods/results. - Mevastatin and pravastatin activated serine/threonine kinase Akt in neonatal cardiomyocytes dose and time dependently with maximal activation at 15 min/10 μM. Caspase-3 activity was induced 2.73 ± 0.29-fold by 6 h of hypoxia followed by 18 h of reoxygenation. Pravastatin added at the beginning of the reoxygenation period reduced caspase-3 activation to 1.26 ± 0.06-fold compared to control cells (P < 0.001). Similar results were obtained for mevastatin (decreased to 1.98 ± 0.45-fold, P < 0.05). TUNEL staining of neonatal cardiomyocytes after 24 h reoxygenation and 4′,6′- diamidino-2-phenylindole staining of adult rat cardiomyocytes after 6 h H ₂O ₂ showed reduced cardiomyocyte apoptosis in the presence of statin. Analysis of signaling pathways downstream of Akt revealed phosphorylation of GSK3β. Transcription factor cAMP-responsive element binding (CREB) protein showed weak phosphorylation at serine 133; transcription factor NF-κB was not significantly activated after statin treatment as evaluated by EMSA. The GSK3β target protein β-catenin was stabilized at 3 h after statin treatment both in neonatal as well as adult rat cardiomyocytes. Transfection with constitutive active GSK3βS9A sensitized neonatal cardiomyocytes to hypoxia/reoxygenation-induced apoptosis as measured by annexin V/propidium iodide staining. Furthermore, myocardial protein extracts of mice revealed GSK3β inactivation after administration of pravastatin intraperitoneally. Conclusions. - Statins inhibit cardiomyocyte apoptosis in association with GSK3β inactivation. Inactivation of GSK3β leads to stabilization of β-catenin in cardiomyocytes.