[Correlation of DNA degradation, induced by tumor necrosis factor-alpha, with accumulation of sphingosine in the nucleus and peroxides in DNA].

The tumour necrosis factor alpha (TNF-alpha) initiates DNA degradation in many types of cells, eventually resulting in a programmed cell death (apoptosis). In order to study the mechanism of TNF-alpha action in vivo, the dynamics of mouse liver DNA fragmentation was examined after intraperitoneal administration of recombinant hTNF-alpha (10 and 40 micrograms per animal). The number of single-strand (SSB) and double-strand (DSB) breaks was determined electrophoretically and interruption of hydrogen bonds (secondary structure defects SSD) were studied by the kinetic formaldehyde method. In parallel experiments the accumulation of peroxide products in DNA, the activity of sphingomyelinase and the content of sphingosine in liver cell nuclei were measured. Sphingomyelinase activation and sphingosine accumulation in the nuclei were found to coincide in time with the maximal values of DNA degradation parameters (SSB, DBS and SSD). TNF-alpha caused a dose-dependent accumulation in DNA peroxide products which seem to lead to the DNA damages. The role of sphingomyelin cycle products and peroxidation in DNA fragmentation induced by TNF-alpha in vivo is discussed.