TRANSIENT G2M ARREST AND SUBSEQUENT RELEASE OF APOPTOTIC AND MITOTIC CELLS IN VANADYL(4)-PREPULSED HUMAN CHANG LIVER-CELLS

The relationship between cell cycling and apoptosis/ programmed cell d eath has been perceived as either checkpoint arrests or mitotic aberra tion where common pathways between mitosis and apoptosis seem suggeste d. We show here evidence implicating both perceptions of cell cycle in volvement. The process was initiated by hydroxyl free radicals (OH) g enerated intracellularly from internalized vanadyl(4). Intranuclear se questration of vanadyl(4) was verified by nuclear microscopy. Resultan t high oxidative reactivity in the nucleus was shown by the redox indi cator methylene blue, suggesting direct oxidative damage to genomic DN A. Oxidative stress was further enhanced by depletion of glutathione w hich is the main cellular reducing agent. Genomic degradation and frag mentation was confirmed by flow cytometric evaluation of terminal deox ynucleotidyl transferase (TdT)-mediated 3'OH end-labelling (TUNEL) of DNA nicks, and cell cycle DNA profiling demonstrating sub-G1 (sub-SN) accumulation. With DNA degradation, there was a G2M transient with hyp erdiploid right-shifting, consistent with G2 arrest. G2 arrest was sub sequently 'released' with abolition of G2M and all other cell cycle ph ases except for a solitary sub-G1 (apoptotic) peak, The cytological pr ofile of this 'release' phenomenon was initially marked by the appeara nce of clusters of mitotic and apoptotic cells, At later stages, the c ell population was composed exclusively of nuclear ghosts, apoptotic c ells, mitotic cells, and mitotic cells with both chromosomes and apopt otic condensations. Concurrent and conjoint expression of cell death a nd cell division as the exclusive process of an entire cell population refuted the notion of mutual exclusivity between life and death. Zn2, an endonuclease inhibitor, abolished all observed cytological and DN A profile changes.