Multi‐step DNA cleavage in rat liver nuclei is inhibited by thiol reactive agents

Abstract

DNA fragmentation in isolated rat liver nuclei is a Mg2+-dependent, multi-step process which is potentiated by Ca 2÷ and cleaves the DNA into -> 700, 200-300 and 30-50 kilobase pair (kbp) fragments, prior to internucleosomal cleavage by Ca2÷/ Mg2÷-dependent endonuclease(s). We now show that Cd 2÷, Hg 2÷, dichloroisocoumarin (DCI, a serine protease inhibitor) and N-ethylmaleimide (NEM) block both Mg 2÷ and CaZ+/Mg2+-dependent processes. Inhibition of DNA cleavage produced an increase in the size of the DNA fragments, from mono-/oligonucleosomes to 30-50, 200-300, -> 700 kbp and finally to intact DNA. NEM and DCI inhibition was blocked by dithiothreitol, and it is proposed that a critical thiol(s) is involved in the DNA cleavage reactions which are a feature of the apoptotic process.

Apoptosis, DNA damage and ubiquitin expression in normal and mdx muscle fibers after exercise

“…The observed DNA damage, probably the ildtiation of apoptosis process, was presumably due to an accele~ated muscle metabolism during exercise or to a production o r reactive oxygen species (ROS), facilitated by the increased catecholamine level induced by stress, not compensated by norn tal glutathione cycle and/or normal cellular ROS scavengers. hdeed the recent findings [17] that thiol compounds inhibit e ~donuclease and protect from apoptosis while glucocorticoid hormones, which are produced in stress conditions, facilitate tile DNA fragmentation are able to explain why DSB are prese at in runner muscle mice. Of particular interest is the observation that a real myonecrosis follows the DNA damage observed it muscle after mild exercise only in a few percent of slow-type f bers [18].…”

Fas-mediated apoptosis in mouse hepatocytes involves the processing and activation of caspases

“…Proteases that are unrelated to caspases have also been implicated in apoptosis in numerous cell types, 19,39,[43][44][45][46][47][48][49][50] including hepatocytes 29,[51][52][53][54] and hepatoma cells. 30 Here, we looked at the possibility that non-caspase proteases also contribute to hepatocyte apoptosis following Fas antigen stimulation.…”

Dithiocarbamates and the redox regulation of cell death

“…$To whom correspondence should be addressed. [18]. Acute oxidative stress actually tends to prevent apoptosis, which has recently been reported in the Fas death system [ 191 and which we also have observed (see below).…”