AMYLOID BETA-PEPTIDE-INDUCED INHIBITION OF MTT REDUCTION IN PC12H ANDC1300 NEUROBLASTOMA-CELLS - EFFECT OF NITROPRUSSIDE

We have investigated the effect of amyloid beta-peptide (A beta) in ra t pheochromocytoma PC12h and murine C1300 neuroblastoma cells by using MTT (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide} reduc tion assay. Exposure of the cells to A beta peptides, A beta 1-40 and its fragment A beta 25-35, induced a concentration-dependent inhibitio n of MTT reduction in both cell lines, and MTT-dependent LDH release d ue to cell lysis in PC12h cells. We also found that sodium nitroprussi de (SNP), a spontaneous nitric oxide (NO) generator, significantly pre vented the inhibition of MTT reduction and MTT-dependent LDH release c aused by A beta peptides at 10-100 mu M, although a high concentration of SNP (greater than or equal to 333 mu M) was remarkably toxic by it self. Since the inhibition of MTT reduction caused by A beta is known as one of the first indicators of its toxicity, these findings suggest that A beta peptides have a toxic effect in these cell lines, and SNP may attenuate the A beta peptide-induced toxicity. In regard the mech anisms of the actions of SNP, hydroxylamine which also generates NO an d 8-Br-cGMP, a membrane-permeable analogue of cyclic GMP (cGMP), faile d to prevent the inhibition of MTT reduction caused by A beta 25-35 in PC12h cells, implying that the effect of SNP may be mediated by the N O-independent pathway. Since potassium ferrocyanide showed a significa nt prevention at 333 mu M although it had toxic effect at this concent ration, it is considered that the ferrocyanide portion of the SNP meta bolite may be partially involved. The cell death induced by other oxid ative insults, such as glutamate and hydrogen peroxide (H2O2), could n ot be attenuated by SNP in both cell lines. Thus, the observed effect of SNP might not be due to its direct antioxidative action. (C) 1998 E lsevier Science Inc.