Abstract
To understand the role of intracellular zinc ion (Zn(2+)) dysregulation in mediating age-related neurodegenerative changes, particularly neurotoxicity resulting from the generation of excessive neurotoxic amyloid-β (Aβ) peptides, this study aimed to investigate whether N, N, N', N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), a Zn(2+)-specific chelator, could attenuate Aβ(25-35)-induced neurotoxicity and the underlying electrophysiological mechanism. We used the 3-(4, 5-dimethyl-thiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay to measure the viability of hippocampal neurons and performed single-cell confocal imaging to detect the concentration of Zn(2+) in these neurons. Furthermore, we used the whole-cell patch-clamp technique to detect the evoked repetitive action potential (APs), the voltage-gated sodium and potassium (K(+)) channels of primary hippocampal neurons. The analysis showed that TPEN attenuated Aβ(25-35)-induced neuronal death, reversed the Aβ(25-35)-induced increase in intracellular Zn(2+) concentration and the frequency of APs, inhibited the increase in the maximum current density of voltage-activated sodium channel currents induced by Aβ(25-35), relieved the Aβ(25-35)-induced decrease in the peak amplitude of transient outward K(+) currents (I(A)) and outward-delayed rectifier K(+) currents (I(DR)) at different membrane potentials, and suppressed the steady-state activation and inactivation curves of I(A) shifted toward the hyperpolarization direction caused by Aβ(25-35). These results suggest that Aβ(25-35)-induced neuronal damage correlated with Zn(2+) dysregulation mediated the electrophysiological changes in the voltage-gated sodium and K(+) channels. Moreover, Zn(2+)-specific chelator-TPEN attenuated Aβ(25-35)-induced neuronal damage by recovering the intracellular Zn(2+) concentration.