Zinc plays a key pathophysiological role in major
neurological disorders as well as diabetes, while being essential for the activity of numerous
zinc binding proteins. A major challenge in chelation based
therapy must take into consideration these apparently conflicting effects of
zinc. One approach is to limit the activity of the
chelator to regions and levels of
zinc pathology, making normal
zinc-dependent processes invisible to the
chelator. Combining fluorescent
zinc imaging with cytotoxicity assays we studied the
zinc chelation efficacy and
neuroprotective effect of the lipophilic divalent transition
metal chelator DP-b99 (1,2-Bis(2-amino-phenoxy)
ethane-N,N,N',N'-tetraacetic
acid-N-N'-di[2-(octyloxy)ethyl
ester],-N,N'-disodium
salt). The affinity of
DP-b99 to Zn(2+) and Ca(2+)
ions is moderate in water and enhanced significantly in the
lipid milieu. Application of
DP-b99 to MIN6 beta-cells that were preloaded with
zinc was followed by a decrease in fluorescence of the intracellular Zn(2+) sensitive
dye, ZnAF-2DA, to resting levels. Preloading of MIN6 cells with
DP-b99 was also effective in attenuating subsequent cellular
zinc rise. Concentration-dependence analysis of
zinc accumulation indicated that
DP-b99 acts as a
zinc chelator with moderate affinity.
DP-b99 preapplication attenuated both Zn(2+) and Ca(2+) rise in neuronal cultures and also Zn(2+) rise in brain slices. Finally,
DP-b99 attenuated Zn(2+)-induced neuronal death. Our results indicate that
DP-b99 is effective in attenuating Zn(2+) and Ca(2+) surges and protecting neurons against a toxic Zn(2+)-rise. This may underlie the efficacy of
DP-b99 in
stroke treatment.