The lipophilic zinc chelator DP-b99 prevents zinc induced neuronal death

Abstract

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 β-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.