A selective inhibitor of N8-acetylspermidine deacetylation in mice and hela cells without effects on histone deacetylation

Abstract

The inhibitory effects of 7-[ N-(3-aminopropyl)amino]heptan-2-one (APAH) on N 8-acetylspermidine deacetylation were studied. In in vitro studies, APAH produced inhibition (apparent K i of 0.18 μ m) of N 8-acetylspermidine deacetylation by the 100,000 g supernatant fraction of rat liver. This apparent K i was 60-fold less than the apparent K m (11 μ m) for deacetylation of the substrate, N 8-acetylspermidine, suggesting that APAH could be a potent, effective inhibitor in vivo. APAH was administered to mice by intraperitoneal injection at a dose of 200 mg/kg, and polyamine and acetylpolyamine levels in liver and spleen were measured. In tissues of control mice, N 8-acetylspermidine was not detectable but increased to detectable levels 30–360 min after APAH treatment. These data are consistent with inhibition of the deacetylase by APAH. Increases in putrescine and N 1-acetylspermidine levels occurred in liver after APAH treatment with increases in N 1-acetylspermidine levels observed in spleen. In HeLa cells, a significant increase in N 8-acetylspermidine was observed following 24 h exposure to 10 μ m APAH while no change occurred in the acetylation level of HeLa cell histones. In contrast, 24 h exposure to 10 m m sodium butyrate produced no change in N 8-acetylspermidine levels and an increase in the acetylation level of histones H4 and H2B. These results suggest that APAH has a relatively selective inhibitory effect on N 8-acetylspermidine but not histone deacetylation. This is the first report of significant levels of N 8-acetylspermidine in animal tissues and of the effects of in vivo inhibition of N 8-acetylspermidine deacetylase.