Metallothionein synthesis increased by Ninjin-yoei-to, a Kampo medicine protects neuronal death and memory loss after exposure to amyloid ß1-42.

BACKGROUND: It is possible that increased synthesis of metallothioneins (MTs), Zn2+-binding proteins is linked with the protective effect of Ninjin-yoei-to (NYT) on Zn2+ toxicity ferried by amyloid ß1-42 (Aß1-42). METHODS: Judging from the biological half-life (18-20 h) of MTs, the effective period of newly synthesized MT on capturing Zn2+ is estimated to be approximately 2 days. In the present paper, a diet containing 3% NYT was administered to mice for 2 days and then Aß1-42 was injected into the lateral ventricle of mice. RESULTS: MT level in the dentate granule cell layer was elevated 2 days after administration of NYT diet, while the administration reduced intracellular Zn2+ level increased 1 h after Aß1-42 injection, resulting in rescuing neuronal death in the dentate granule cell layer, which was observed 14 days after Aß1-42 injection. Furthermore, Pre-administration of NYT diet rescued object recognition memory loss via affected perforant pathway long-term potentiation after local injection of Aß1-42 into the dentate granule cell layer of rats. CONCLUSION: The present study indicates that pre-administration of NYT diet for 2 days increases synthesis of MTs, which reduces intracellular Zn2+ toxicity ferried by extracellular Aß1-42, resulting in protecting neuronal death in the dentate gyrus and memory loss after exposure to Aß1-42.

Preventive effect of Ninjin-yoei-to, a Kampo medicine, on amyloid ß1-42-induced neurodegeneration via intracellular Zn2+ toxicity in the dentate gyrus.

Ninjin-yoei-to (NYT), a Kampo medicine, has ameliorative effects on cognitive dysfunction via enhancing cholinergic neuron activity. To explore an efficacy of NYT administration for prevention and cure of Alzheimer's disease, here we examined the effect of NYT on amyloid ß1-42 (Aß1-42)-induced neurodegeneration in the dentate gyrus. A diet containing 3% NYT was administered to mice for 2 weeks and human Aß1-42 was intracerebroventricularly injected. Neurodegeneration in the dentate granule cell layer of the hippocampus, which was determined 2 weeks after the injection, was rescued by administration of the diet for 4 weeks. Aß staining (uptake) was not modified in the dentate granule cell layer by pre-administration of the diet for 2 weeks, while Aß1-42-induced increase in intracellular Zn2+ was reduced, suggesting that pre-administration of NYT prior to Aß injection is effective for reducing Aß1-42-induced Zn2+ toxicity in the dentate gyrus. As a matter of fact, Aß1-42-induced neurodegeneration in the dentate gyrus was rescued by pre-administration of NYT. Interestingly, the level of metallothioneins, intracellular Zn2+-binding proteins, which can capture Zn2+ from Zn-Aß1-42 complexes, was elevated in the dentate granule cell layer by pre-administration of NYT. The present study suggests that pre-administration of NYT prevents Aß1-42-mediated neurodegeneration in the dentate gyurs by induced synthesis of metallothioneins, which reduces intracellular Zn2+ toxicity induced by Aß1-42.