β-adrenoceptor blockers protect against staurosporine-induced apoptosis in SH-SY5Y neuroblastoma cells

The β-adrenoceptor blockers exhibit a well-characterized anti-apoptotic property in the heart and kidney while less is known about the effect of this class of drugs on neuronal apoptosis. We studied the effects of three β-adrenoceptor blockers propranolol (1-(isoproplyamino)-3-(naphthalene-1-yloxy)propan-2-ol), atenolol (2-[4-[2-hydroxy-3-(1-methylethylamino)propoxyl]phenyl]ehanamide), and ICI 118551 (1-[2,3-(dihydro-7-methyl-1H-iden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol), against staurosporine-induced apoptosis in SH-SY5Y human neuroblastoma cells. Staurosporine increased caspase 3-like activity, DNA fragmentation, PARP cleavage, and the number of TUNEL positive cells consistent with the induction of apoptosis. Propranolol and ICI 118551, but not atenolol, demonstrated a concentration-dependent inhibition of caspase 3-like activity. Propranolol and ICI 118551 directly inhibited the enzymatic activity of recombinant caspase 9 while atenolol did not; however, none of the β-adrenoceptor blockers that were examined directly blocked caspases 2 or 3 activity. In isolated mitochondria, propranolol and ICI 118551 inhibited staurosporine-induced cytochrome c release while atenolol did not. We conclude that propranolol and ICI 118551 protect SH-SY5Y cells against staurosporine-induced apoptosis through a dual action on the mitochondria and on caspase 9 in a cell type and an apoptotic paradigm where the conventional inhibitors of mitochondrial permeability transition such as cyclosporin A and bongkrekic acid demonstrate no protection.