A BCL-2 ANTISENSE OLIGONUCLEOTIDE INCREASES LPHA-AMINO-3-HYDROXY-5-METHYLISOXAZOLE-4-PROPIONIC ACID (AMPA) TOXICITY IN CORTICAL CULTURES

Both lpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) re ceptor-mediated neurotroxicity and the induction of death-regulatory g enes have been implicated in the pathophysiology of delayed ischemic n euronal injury. To assess the role of the antiapoptotic gene Bcl-2 in the modulation of AMPA toxicity, me exposed neuron-enriched cultures f rom rat cerebral cortex to AMPA, in the absence or presence of an anti sense oligodeoxynucleotide (ODN) directed against Bcl-2. AMPA produced concentration-dependent toxicity detected by a decrease in fluorescen ce of the redox indicator Alamar blue and by an increase in lactic aci d dehydrogenase release. This effect was accompanied by the induction of Bcl-2 protein expression, with maximal induction at 100 mu M AMPA. A phosphorothioate antisense ODN against Bcl-2 reduced the AMPA-stimul ated induction of Bcl-2 protein levels, detected by western blotting, by about 70%. In the presence of the antisense ODN, but not sense or s crambled ODNs, the toxicity of 100 mu M AMPA was increased by about 60 %. These findings suggest that induction of Bcl-2 expression by AMPA m ay have a protective role to limit AMPA receptor-mediated neuronal dam age and that modifying Bcl-2 expression could have therapeutic potenti al in ischemia.