Fumonisin blunts nitric oxide-induced and nitroprusside-induced cardiomyocyte death

The objective of this study was to determine whether nitric oxide (NO)-induced cell death in cardiomyocytes was operative through de novo synthesis of ceramide by determining whether the ceramide synthase inhibitor fumonisin blocked NO-mediated cell death. Neonatal mouse cardiomyocytes in culture were pretreated with fumonisin B1 (FB1). FB1 is a competitive inhibitor of sphinganine N-acyl transferase, also known as ceramide synthase (EC 2.3.1.24). Cell viability was assessed by the (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, which is based on the ability of viable cells to reduce MTT. Treatment with the NO donor nitroso-glutathione (NO-GSH) for 24h produced a significant (p<0.05) concentration-dependent reduction in OD(570) or an increase in cell death. Sodium nitroprusside (SNP) treatment for 24h produced a significant (p<0.001) concentration-dependent reduction in OD(570) and an increase in cardiomyocyte cell death but the effects of SNP were greater than those of NO-GSH. FB1 significantly (p<0.05) reduced cell death induced by either SNP or NO-GSH. The SNP (0.1mM) increase in cell death of 36.9+/-2.8% was significantly (p<0.05) reduced to 24.7+/-1.8% by FB1 (10 microM). The effect of FB1 was not mediated through inhibition of the cell death effects of H(2)O(2), which is produced by SNP, as FB1 did not prevent H(2)O(2)-induced cell death. Confirmation of the ability of ceramide to produce cell death was demonstrated by the cell-permeable ceramide analogue, C(2)-ceramide (100 and 200 microM), which induced, respectively, 23.4+/-11.3 and 78.0+/-3.7% increases in cell death. The cell death effects of SNP and NO-GSH are likely independent of cGMP signal transduction pathways, which are activated by either SNP or NO-GSH, as there was no significant concentration-dependent change in cardiomyocyte viability after treatment with the cell-permeable analogue dibutyryl-GMP. These data show that FB1 blunts SNP- and NO-induced cardiomyocyte death and raise the novel possibility of preventing some of SNP- or NO-induced cardiomyocyte cell death by ceramide synthase inhibition.