Zinc Inhibits Amyloid beta Production from Alzheimer's Amyloid Precursor Protein in SH-SY5Y Cells

ABSTRACT

Zinc released from excited glutamatergic neurons accelerates amyloid beta (A beta) aggregation, underscoring the therapeutic potential of zinc chelation for the treatment of Alzheimer's disease (AD). Zinc can also alter A beta concentration by affecting its degradation. In order to elucidate the possible role of zinc influx in secretase-processed A beta production, SH-SY5Y cells stably expressing amyloid precursor protein (APP) were treated with pyrrolidine dithiocarbamate (PDTC), a zinc ionophore, and the resultant changes in APP processing were examined. PDTC decreased A beta40 and A beta42 concentrations in culture media bathing APP-expressing SH-SY5Y cells. Measuring the levels of a series of C-terminal APP fragments generated by enzymatic cutting at different APP-cleavage sites showed that both beta- and alpha-cleavage of APP were inhibited by zinc influx. PDTC also interfered with the maturation of APP. PDTC, however, paradoxically increased the intracellular levels of A beta40. These results indicate that inhibition of secretase-mediated APP cleavage accounts -at least in part- for zinc inhibition of A beta secretion.