Objective: Propranolol is used to treat several cardiovascular diseases; however, toxic doses of propranolol cause severe myocardial depression and cardiac arrest. The aim of this study was to examine the effects of lipid emulsion (LE) on cardiotoxicity induced by toxic doses of propranolol in H9C2 rat cardiomyoblast cell line and to elucidate the underlying mechanism.
Methods: The experimental groups comprised control, propranolol alone, esmolol alone, or LE followed by propranolol or esmolol treatment, and reactive oxygen species (ROS) inhibitor N-acetyl-L-cysteine (NAC) followed by propranolol treatment. The effects of propranolol, esmolol, NAC, and LE, alone or in combination, on cell viability, apoptosis, and ROS production were examined. Additionally, we investigated the effect of LE on propranolol concentration.
Results: LE and NAC reversed the inhibition of cell viability induced by propranolol (p < .001). However, LE had no effect on the inhibition of cell viability caused by esmolol. The LE inhibited propranolol-induced expressions of cleaved caspase-3 (p < .001), caspase-9 (p < .001), and Bax (p < .01), but not caspase-8. NAC inhibited the propranolol-induced expression of cleaved caspase-3. LE inhibited propranolol-induced early apoptosis, but had no effect on late apoptosis. Additionally, LE inhibited the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells generated by propranolol. It attenuated propranolol-induced ROS production. However, it had no effect on propranolol concentration.
Conclusion: LE inhibits early apoptosis caused by a toxic dose of propranolol by suppressing the intrinsic apoptotic pathway, via direct inhibition of ROS production.
Keywords: N-acetyl-L-cysteine; apoptosis; lipid emulsion; propranolol; reactive oxygen species.