DNA damage-induced [Zn(2+)](i) transients: correlation with cell cycle arrest and apoptosis in lymphoma cells.
Reactive changes in free intracellular zinc cation concentration ([Zn(2+)](i)) were monitored, using the fluorescent probe Zinquin, in human lymphoma cells exposed to the DNA-damaging agent VP-16. Two-photon excitation microscopy showed that Zinquin-Zn(2+) forms complexes in cytoplasmic vesicles. [Zn(2+)](i) increased in both p53(wt) (wild type) and p53(mut) (mutant) cells after exposure to low drug doses. In p53(mut) cells noncompetent for DNA damage-induced apoptosis, elevated [Zn(2+)](i) was maintained at higher drug doses, unlike competent p53(wt) cells that showed a collapse of the transient before apoptosis. In p53(wt) cells, the [Zn(2+)](i) rise paralleled an increase in p53 and bax-to-bcl-2 ratio but preceded an increase in p21(WAF1), active cell cycle arrest in G(2), or nuclear fragmentation. Reducing [Zn(2+)](i), using N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine, caused rapid apoptosis in both p53(wt) and p53(mut) cells, although cotreatment with VP-16 exacerbated apoptosis only in p53(wt) cells. This may reflect changed thresholds for proapoptotic caspase-3 activation in competent cells. We conclude that the DNA damage-induced transient is p53-independent up to a damage threshold, beyond which competent cells reduce [Zn(2+)](i) before apoptosis. Early stress responses in p53(wt) cells take place in an environment of enhanced Zn(2+) availability.
Smith
Paul J
PJ
Department of Pathology, University of Wales, College of Medicine, Health Park, Cardiff, United Kingdom. smithpj2@cf.ac.uk
Wiltshire
Marie
M
Davies
Sharon
S
Chin
Suet-Feung
SF
Campbell
Anthony K
AK
Errington
Rachel J
RJ
D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage / Q000502:physiology*; D005029:Ethylenediamines / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005456:Fluorescent Dyes; D006801:Humans; D008223:Lymphoma / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D009994:Osmolar Concentration; D015363:Quinolones; D013347:Subcellular Fractions / Q000378:metabolism; D014105:Tosyl Compounds; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D015032:Zinc / Q000378:metabolism*
D002614:Chelating Agents; D005029:Ethylenediamines; D005456:Fluorescent Dyes; D019384:Nucleic Acid Synthesis Inhibitors; D015363:Quinolones; D014105:Tosyl Compounds; D016159:Tumor Suppressor Protein p53; D005047:Etoposide; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine; C084731:zinquin