Jpn. J. Pharmacol. 84 (3), 334-338 (2000)

Mechanisms of [2,3-Butanedione Bis(Nﾊ⁴-Dimethylthiosemicarbazone)]zinc (Zn-ATSM₂)-Induced Protection of Cultured Hippocampal Neurons Against N-Methyl-D-Aspartate Receptor-Mediated Glutamate Cytotoxicity

Megumi Kubota¹, Yasuhiko Iida², Yasuhiro Magata¹, Youji Kitamura¹, Hideaki Kawashima¹ and Hideo Saji^1,*

¹Department of Patho-functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
²Department of Radioisotope Laboratory, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
*Corresponding author.ﾊﾊFAX: +81-75-753-4568
E-mail: hsaji@pharm.kyoto-u.ac.jp

Abstract: Hyperexcitation of glutamatergic neurons may play a key role in ischemia-related neurodegeneration. Recent studies have suggested that the zinc ion (Zn²⁺), which is present in the central nervous system, has a modulatory role in glutamatergic neuron activity. Zinc ions block glutamate-induced depolarizing currents and neuronal damage by binding with zinc sites on the NMDA subtypes. Therefore, we examined the usefulness of zinc as a therapeutic agent for the prevention of ischemic neuronal damage in the brain. In our previous study, 2,3-butanedione bis(N⁴-dimethylthiosemicarbazonato) zinc complex (Zn-ATSM₂), with high brain uptake, showed significant neuroprotective effects against cerebral ischemia in rats when administered systemically. In this study, to elucidate the mechanism of the neuroprotective effect of Zn-ATSM₂, we first examined its in vitro protective effects against glutamate-, NMDA- and kainite-induced neurotoxicity in primary cultures of hippocampal neurons. Zn-ATSM₂ elicited protective effects against this glutamate- and NMDA-induced neurotoxicity, but did not affect kainite-induced cytotoxicity. In addition, we studied the effects of Zn-ATSM₂ on influx of Ca²⁺, which undergoes modification subsequent to NMDA activation. Zn-ATSM₂ significantly decreased glutamate-induced ⁴⁵Ca²⁺ uptake. Thus, Zn-ATSM₂ protected against glutamate-induced neurotoxicity and its protective effect was, at least in part, due to the blockage of NMDA receptor-mediated Ca²⁺ influx.

Keywords: Zinc, N-Methyl-D-aspartate receptor, Neuroprotection, Hippocampal cell culture, Glutamate