RESUMO
The DNA-damaging agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) causes cardiomyocyte death as a result of energy loss from excessive activation of poly-(ADP) ribose polymerase-1 (PARP-1) resulting in depletion of its substrates nicotinamide adenine dinucleotide (NAD) and ATP. Previously we showed that the chemotherapeutic agent vincristine (VCR) is cardioprotective. Here we tested the hypothesis that VCR inhibits MNNG-induced PARP activation. Adult mouse cardiomyocytes were incubated with 100 micromol/L MNNG with or without concurrent VCR (20 micromol/L) for 2 to 4 hours. Cardiomyocyte survival was measured using the trypan blue exclusion assay. Western blots were used to measure signaling responses. MNNG-induced cardiomyocyte damage was time- and concentration-dependent. MNNG activated PARP-1 and depleted NAD and ATP. VCR completely protected cardiomyocytes from MNNG-induced cell damage and maintained intracellular levels of NAD and ATP. VCR increased phosphorylation of the prosurvival signals Akt, GSK-3beta, Erk1/2, and p70S6 kinase. VCR delayed PARP activation as evidenced by Western blot and by immunofluorescence staining of poly (ADP)-ribose, but without directly inhibiting PARP-1 itself. Known PARP-1 inhibitors also protected cardiomyocytes from MNNG-induced death. Repletion of ATP, NAD, pyruvate, and glutamine had effects similar to PARP-1 inhibitors. We conclude that VCR protects cardiomyocytes from MNNG toxicity by regulating PARP-1 activation, intracellular energy metabolism, and prosurvival signaling.
