CA1 LTP Attenuated by Corticosterone is Canceled by Effusol via Rescuing Intracellular Zn2+ Dysregulation

Insight into brain metallothioneins from bidirectional Zn2+ signaling in synaptic dynamics

The basal levels as the labile Zn2+ pools in the extracellular and intracellular compartments are in the range of ∼10 nM and ∼100 pM, respectively. The influx of extracellular Zn2+ is used for memory via cognitive activity and is regulated for synaptic plasticity, a cellular mechanism of memory. When Zn2+ influx into neurons excessively occurs, however, it becomes a critical trigger for cognitive decline and neurodegeneration, resulting in acute and chronic pathogenesis. Aging, a biological process, generally accelerates vulnerability to neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). The basal level of extracellular Zn2+ is age relatedly increased in the rat hippocampus, and the influx of extracellular Zn2+ contributes to accelerating vulnerability to the AD and PD pathogenesis in experimental animals with aging. Metallothioneins (MTs) are Zn2+-binding proteins for cellular Zn2+ homeostasis and involved in not only supplying functional Zn2+ required for cognitive activity, but also capturing excess (toxic) Zn2+ involved in cognitive decline and neurodegeneration. Therefore, it is estimated that regulation of MT synthesis is involved in both neuronal activity and neuroprotection. The present report provides recent knowledge regarding the protective/preventive potential of MT synthesis against not only normal aging but also the AD and PD pathogenesis in experimental animals, focused on MT function in bidirectional Zn2+ signaling in synaptic dynamics.

Dehydroeffusol Pprevents Amyloid β1-42-mediated Hippocampal Neurodegeneration via Reducing Intracellular Zn2+ Toxicity

Dehydroeffusol, a phenanthrene isolated from Juncus effusus, is a Chinese medicine. To explore an efficacy of dehydroeffusol administration for prevention and cure of Alzheimer's disease, here we examined the effect of dehydroeffusol on amyloid β_1-42 (Aβ_1-42)-mediated hippocampal neurodegeneration. Dehydroeffusol (15 mg/kg body weight) was orally administered to mice once a day for 6 days and then human Aβ_1-42 was injected intracerebroventricularly followed by oral administration for 12 days. Neurodegeneration in the dentate granule cell layer, which was determined 2 weeks after Aβ_1-42 injection, was rescued by dehydroeffusol administration. Aβ staining (uptake) was not reduced in the dentate granule cell layer by pre-administration of dehydroeffusol for 6 days, while increase in intracellular Zn²⁺ induced with Aβ_1-42 was reduced, suggesting that pre-administration of dehydroeffusol prior to Aβ_1-42 injection is effective for Aβ_1-42-mediated neurodegeneration that was linked with intracellular Zn²⁺ toxicity. As a matter of fact, pre-administration of dehydroeffusol rescued Aβ_1-42-mediated neurodegeneration. Interestingly, pre-administration of dehydroeffusol increased synthesis of metallothioneins, intracellular Zn²⁺-binding proteins, in the dentate granule cell layer, which can capture Zn²⁺ from Zn-Aβ_1-42 complexes. The present study indicates that pre-administration of dehydroeffusol protects Aβ_1-42-mediated neurodegeneration in the hippocampus by reducing intracellular Zn²⁺ toxicity, which is linked with induced synthesis of metallothioneins. Dehydroeffusol, a novel inducer of metallothioneins, may protect Aβ_1-42-induced pathogenesis in Alzheimer's disease.

Changes in Hippocampal Plasticity in Depression and Therapeutic Approaches Influencing These Changes

Depression is a common neurological disease that seriously affects human health. There are many hypotheses about the pathogenesis of depression, and the most widely recognized and applied is the monoamine hypothesis. However, no hypothesis can fully explain the pathogenesis of depression. At present, the brain-derived neurotrophic factor (BDNF) and neurogenesis hypotheses have highlighted the important role of plasticity in depression. The plasticity of neurons and glial cells plays a vital role in the transmission and integration of signals in the central nervous system. Plasticity is the adaptive change in the nervous system in response to changes in external signals. The hippocampus is an important anatomical area associated with depression. Studies have shown that some antidepressants can treat depression by changing the plasticity of the hippocampus. Furthermore, caloric restriction has also been shown to affect antidepressant and hippocampal plasticity changes. In this review, we summarize the latest research, focusing on changes in the plasticity of hippocampal neurons and glial cells in depression and the role of BDNF in the changes in hippocampal plasticity in depression, as well as caloric restriction and mitochondrial plasticity. This review may contribute to the development of antidepressant drugs and elucidating the mechanism of depression.

Dehydroeffusol Rescues Amyloid β25-35-Induced Spatial Working Memory Deficit

Amyloid β (Aβ) peptides produced from the amyloid precursor protein, a transmembrane protein, are neurotoxic and blocking the neurotoxicity may lead to prevention of Alzheimer's disease (AD). Here we tested whether Aβ_25-35-induced cognitive decline is rescued by treatment with dehydroeffusol, a phenanthrene isolated from Chinese medicine Juncus effusus. Dehydroeffusol (5 ~ 15 mg/kg body weight) was orally administered to mice for 6 days and Aβ_25-35 (2 mM) was injected at the rate of 1 μl/min for 3 min into the lateral ventricle. Y-maze test was performed after dehydroeffusol administration for 12 days. Aβ_25-35 impaired learning and memory in the test, while the impairment was dose-dependently rescued by dehydroeffusol administration. The present study indicates that treatment with dehydroeffusol is effective for rescuing Aβ_25-35-induced cognitive decline.