TUMOR-NECROSIS-FACTOR ALPHA-INDUCED DNA-DEGRADATION CORRELATES WITH SPHINGOSINE CONTENT OF NUCLEUS AND PEROXIDE CONTENT OF DNA

Tumor necrosis factor alpha (alpha-TNF) is known to induce DNA fragmen tation, which in turn results in programmed cell death (apoptosis), To reveal the in vivo mechanism of this effect, the dynamics of liver DN A fragmentation has been studied in mice following intraperitoneal adm inistration of recombinant human alpha-TNF (10 or 40 mu g per animal). The number of single and double strand breaks was determined electrop horetically; the disruption of hydrogen bonds (characteristic of secon dary structure defects) was followed using the kinetic formaldehyde me thod. The accumulation of peroxides in DNA and the activity of sphingo myelinase and the content of sphingosine in liver cell nuclei were als o determined. Sphingomyelinase activation and sphingosine accumulation occurred concurrently with DNA degradation. Intraperitoneal administr ation of alpha-TNF resulted in dose-dependent accumulation of peroxide s (which are believed to contribute to nucleic acid damage) in DNA pre parations isolated from the animals. The role of sphingomyelin cycle p roducts and peroxidation processes in DNA fragmentation induced in viv o by alpha-TNF are discussed.