Vol. 305, Issue 2, 502-506, May 2003

Block of Na⁺,K⁺-ATPase and Induction of Hybrid Death by 4-Aminopyridine in Cultured Cortical Neurons

Xue Qing Wang, Ai Ying Xiao, Aizhen Yang, Lori LaRose, Ling Wei and Shan Ping Yu

Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St. Louis, Missouri

K⁺ channel blockers such as 4-aminopyridine (4-AP) can be toxic to neurons; the cellular mechanism underlying the toxicity, however, is obscure. In cultured mouse cortical neurons, we tested the hypothesis that the toxic effect of 4-AP might result from inhibiting the Na⁺,K⁺-ATPase (Na⁺,K⁺-pump) and thereafter induction of a hybrid death of concomitant apoptosis and necrosis. The Na⁺,K⁺-pump activity, monitored as whole-cell membrane currents, was markedly blocked by 4-AP in concentration- and voltage-dependent manners in low millimolar ranges. At similar concentrations, 4-AP induced a neuronal death sensitive to attenuation by the caspase inhibitor Z-VAD-FMK (Z-Val-Ala-Asp(OMe)-fluoromethyl ketone) or Ca²⁺ chelator BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester). Electron microscopy confirmed hybrid ultrastructural features of coexisting apoptotic and necrotic components in same cells. We suggest that 4-AP is a potent antagonist of the Na⁺,K⁺-ATPase and an inducer of the hybrid death of central neurons.