The β 2 -adrenergic receptor agonist formoterol attenuates necrosis and apoptosis in the rat myocardium under experimental stress-induced cardiac injury

Currently, there is no effective therapy for takotsubo syndrome (stress-induced cardiac injury in humans) in the clinics. It has previously been shown that β -adrenergic receptor (β -AR) agonist formoterol reduces cardiomyocyte injury in experimental takotsubo syndrome. The aim of this study was to investigate whether formoterol prevents apoptosis and necrosis of cardiomyocytes and endothelial cells in stress-induced cardiomyopathy. Stress-induced cardiac injury was induced by immobilization of rats for 2, 6, and 24 hours. The myocardium of stressed rats showed a reduction in contractility and histological manifestations of cardiomyocyte damage: karyopyknosis, perinuclear edema of cardiomyocytes and endothelial cells, and microcirculation disturbances augmented with extended exposure to stress. In addition, apoptosis of endothelial cells was detected 6 hours after the onset of stress and peaked at 24 hours. Apoptosis of cardiomyocytes significantly gained only after 24 hours of stress exposure. These morphological alterations were associated with increased levels of serum creatine kinase-MB, syndecan-1, and thrombomodulin after 24 hours of stress. Administration of β -AR agonist formoterol (50 μg/kg) four times during 24-hour stress exposure led to the improvement in myocardial inotropy, decrease in the severity of histological signatures, reduction in the number of TUNEL-positive cardiomyocytes, serum creatine kinase-MB, syndecan-1, and thrombomodulin levels. Present data suggest that apoptosis and necrosis of cardiomyocytes and necrosis of endothelial cells in stress-induced cardiac injury can be mitigated by activation of the β -AR. However, formoterol did not eliminate completely cardiomyocyte apoptosis, histological alterations, or endothelium injury markers under stress.