Prevention of glutamate neurotoxicity in cultured neurons by 3,4-dihydro-6-hydroxy-7-methoxy-2,2-dimethyl-1(2H)-benzopyran (CR-6), a scavenger of nitric oxide

Glutamate neurotoxicity in cerebellar neurons in culture is mediated by exc essive production of nitric oxide (NO). We anticipated that 3,4-dihydro 6-h ydroxy-7-methoxy-2,2-dimethyl-1(2H) -benzopyran (CR-6) could act as a scave nger of NO since it contains a position (C-5) highly activated towards nitr ation reaction. The aim of this work was to assess whether CR-6 acts as an NO scavenger and prevents glutamate neurotoxicity in cultures of cerebellar neurons. It was shown that CR-6 reduced, in a dose-dependent manner, gluta mate-induced formation of cGMP (EC50 approximate to 15 mu M) and prevented glutamate neurotoxicity. The protection was approximate to 50% at 3-10 mu M and nearly complete at 100 mu M. CR-6 did not prevent glutamate-induced ac tivation of NO synthase, but interfered with the glutamate-NO-cGMP pathway at a later step. CR-6 reduced the formation of cGMP induced by S-nitroso-N- acetylpenicillamine (SNAP), an NO-generating agent, indicating that CR-6 ac ts as a scavenger of NO in cultured neurons. This was further supported by experiments showing that in neurons treated with CR-6 and glutamate, the 5- nitro derivative of CR-6 was formed, as determined by GC-MS analyses. Moreo ver, in vitro incubation of CR-6 with SNAP also produced the 5-nitroderivat ive, thus confirming that CR-6 directly reacts with NO. The results reporte d indicate that CR-6 acts as an NO scavenger in neurons and prevents glutam ate neurotoxicity. (C) 1999 EIsevier Science Inc.