Intracellular hydrogen peroxide produced by 6-hydroxydopamine is a trigger for nigral dopaminergic degeneration of rats via rapid influx of extracellular Zn2

Beneficial effect of Juncus effusus extract powder enriched with dehydroeffusol on the cognitive and dexterous performance of elderly people: A randomized, double-blind, placebo-controlled, parallel-group study

On the basis of the evidence that dehydroeffusol prevents human amyloid-β-induced memory deficit and neurodegeneration in mice, here we tested the effect of a Juncus effusus extract powder enriched with dehydroeffusol on the cognitive and dexterous performance of elderly people. A randomized, double-blind, placebo-controlled, parallel-group study was conducted in 41 participants (averaged age: 69 years) randomly divided into test and placebo groups who received a test tablet and a placebo tablet, respectively, once a day for 24 weeks. Changes in cognitive function were assessed using the Five-Cog test 24 weeks after the start of intake. The task scores of the test group were significantly higher in the clue recall and clock-drawing tasks than in the placebo group, suggesting that intake of J. effusus extract powder may improve the cognitive function of elderly people. Moreover, the task score of the test group was significantly higher for the assembly task in the dexterity test than the placebo group, suggesting that intake of J. effusus extract powder may improve the dexterous movement of elderly people. No adverse events were clinically observed during the study. The present study first suggests that intake of J. effusus extract powder enriched with dehydroeffusol is of benefit to the cognitive and dexterous performance of elderly people.

Robust In Vitro Models for Studying Parkinson's Disease? LUHMES Cells and SH-SH5Y Cells

As our population ages, there is an increased unmet clinical need surrounding neurodegenerative diseases such as Parkinson's disease (PD). To tackle this ever-increasing problem, we must ensure that the cell models that we use to develop therapeutics in vitro are robust, reliable, and replicable. In this study, we compared SH-SY5Y cells with LUHMES cells in response to 6-Hydroxydopamine (6OHDA) and 1-Methyl-4-phenylpyridinium (MPP+), two common Parkinson's insults used in in vitro analysis. Both these cell types have apparent dopaminergic phenotypes, which could aid us in understanding their potential in this race to novel therapies. The LUHMES cells showed consistent dopaminergic (DA) expression through tyrosine hydroxylase (TH) positivity, alongside depleted ATP levels and elevated reactive oxygen species (ROS) production, whereas the SH-SH5Y cells displayed resilience to both chemical insults, raising questions about their utility in accurately modelling PD pathology. Further electrophysiological analysis revealed comparable firing rates and ion channel signalling between both cell types; however, LUHMES cells demonstrated stronger calcium signalling responses, further supporting their use as a more robust PD model. While SH-SY5Y cells showed some adaptability in vitro, their inconsistent DA phenotype and limited response to chemical insults limit their suitability for advanced research, suggesting that LUHMES cells should and must take their place as a hallmark in Parkinson's disease research.

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.

The Role of Zinc in the Development of Vascular Dementia and Parkinson's Disease and the Potential of Carnosine as Their Therapeutic Agent

Synaptic zinc ions (Zn2+) play an important role in the development of vascular dementia (VD) and Parkinson's disease (PD). In this article, we reviewed the current comprehension of the Zn2+-induced neurotoxicity that leads to the pathogenesis of these neuronal diseases. Zn2+-induced neurotoxicity was investigated by using immortalised hypothalamic neurons (GT1-7 cells). This cell line is useful for the development of a rapid and convenient screening system for investigating Zn2+-induced neurotoxicity. GT1-7 cells were also used to search for substances that prevent Zn2+-induced neurotoxicity. Among the tested substances was a protective substance in the extract of Japanese eel (Anguilla japonica), and we determined its structure to be like carnosine (β-alanylhistidine). Carnosine may be a therapeutic drug for VD and PD. Furthermore, we reviewed the molecular mechanisms that involve the role of carnosine as an endogenous protector and its protective effect against Zn2+-induced cytotoxicity and discussed the prospects for the future therapeutic applications of this dipeptide for neurodegenerative diseases and dementia.

Non-coding RNAs as potential therapeutic targets for receptor tyrosine kinase signaling in solid tumors: current status and future directions

This review article presents an in-depth analysis of the current state of research on receptor tyrosine kinase regulatory non-coding RNAs (RTK-RNAs) in solid tumors. RTK-RNAs belong to a class of non-coding RNAs (nc-RNAs) responsible for regulating the expression and activity of receptor tyrosine kinases (RTKs), which play a critical role in cancer development and progression. The article explores the molecular mechanisms through which RTK-RNAs modulate RTK signaling pathways and highlights recent advancements in the field. This include the identification of potential new RTK-RNAs and development of therapeutic strategies targeting RTK-RNAs. While the review discusses promising results from a variety of studies, encompassing in vitro, in vivo, and clinical investigations, it is important to acknowledge the challenges and limitations associated with targeting RTK-RNAs for therapeutic applications. Further studies involving various cancer cell lines, animal models, and ultimately, patients are necessary to validate the efficacy of targeting RTK-RNAs. The specificity of ncRNAs in targeting cellular pathways grants them tremendous potential, but careful consideration is required to minimize off-target effects, the article additionally discusses the potential clinical applications of RTK-RNAs as biomarkers for cancer diagnosis, prognosis, and treatment. In essence, by providing a comprehensive overview of the current understanding of RTK-RNAs in solid tumors, this review emphasizes their potential as therapeutic targets for cancer while acknowledging the associated challenges and limitations.

Reactive oxygen species produced by Zn2+ influx after exposure to AMPA, but not NMDA and their capturing effect on nigral dopaminergic protection

Glutamate excitotoxicity is involved in dopaminergic degeneration in the substantia nigra pars compacta (SNpc). Here we compared vulnerability to neurodegeneration after exposure to NMDA and AMPA. Apomorphine-induced movement disorder and dopaminergic degeneration in the SNpc, which are associated with Parkinson's syndrome, were induced after injection of AMPA into the SNpc of rats, but not after injection of NMDA. Co-injection of 1-naphthyl acetyl spermine (NASPM), a selective blocker of Ca²⁺- and Zn²⁺-permeable GluR2-lacking AMPA receptors rescued dopaminergic degeneration and increase in intracellular Zn²⁺ by AMPA. Furthermore, we tested the effect of capturing reactive oxygen species (ROS) produced by Zn²⁺ on neuroprotection in vivo. The levels of ROS, which were determined by HYDROP, a membrane-permeable H₂O₂ fluorescence probe and Aminophenyl Fluorescein (APF), a fluorescence probe for hydroxyl radical and peroxynitrite, were increased after injection of AMPA, but not after co-injection of CaEDTA, an extracellular Zn²⁺ chelator, suggesting that increase in Zn²⁺ influx by AMPA elevates the levels of intracellular ROS. AMPA-mediated dopaminergic degeneration was completely rescued by co-injection of either HYDROP or APF. The present study indicates that neurotoxic signaling of the influx of extracellular Zn²⁺ through Zn²⁺-permeable GluR2-lacking AMPA receptors is converted to ROS production and that capturing the ROS completely protects dopaminergic degeneration after exposure to AMPA, but not NMDA. It is likely that regulation of the conversion from Zn²⁺ influx into ROS production plays a key role to preventing Parkinson's syndrome.

[Brain Function and Pathophysiology Focused on Zn2+ Dynamics]

The basal levels of intracellular Zn²⁺ and extracellular Zn²⁺ are in the range of ～100 pM and ～10 nM, respectively, in the brain. Extracellular Zn²⁺ dynamics is involved in both cognitive performance and neurodegeneration. The bidirectional actions are linked with extracellular glutamate and amyloid-β_1-42 (Aβ_1-42). Intracellular Zn²⁺ signaling via extracellular glutamate is required for learning and memory, while intracellular Zn²⁺ dysregulation induces cognitive decline. Furthermore, human Aβ_1-42, a causative peptide in Alzheimer's disease pathogenesis captures extracellular Zn²⁺ and readily taken up into hippocampal neurons followed by intracellular Zn²⁺ dysregulation. Aβ_1-42-mediated intracellular Zn²⁺ dysregulation is accelerated with aging, because extracellular Zn²⁺ is age-relatedly increased, resulting in Aβ_1-42-induced cognitive decline and neurodegeneration with aging. On the other hand, metallothioneins, zinc-binding proteins can capture Zn²⁺ released from intracellular Zn-Aβ_1-42 complexes and serve for intracellular Zn²⁺-buffering to maintain intracellular Zn²⁺ homeostasis. This review summarizes Zn²⁺ function and its neurotoxicity in the brain, and also the potential defense strategy via metallothioneins against Aβ_1-42-induced pathogenesis.

Paraquat-induced intracellular Zn2+ dysregulation causes dopaminergic degeneration in the substantia nigra, but not in the striatum

Parkinson's disease is characterized by a selective death of nigrostriatal dopaminergic neurons, while the difference in the vulnerability to the death between the substantia nigra pars compacta (SNpc) and the striatum is poorly understood. Here we tested the difference focused on paraquat (PQ)-induced intracellular Zn²⁺ toxicity via extracellular glutamate accumulation. When PQ was locally injected into the SNpc and the striatum, dopaminergic degeneration was observed in the SNpc, but not in the striatum. Intracellular hydrogen peroxide (H₂O₂) produced by PQ was increased in both the SNpc and the striatum. In contrast, extracellular glutamate accumulation was observed only in the SNpc and rescued in the presence of N-(p-amylcinnamoyl)anthranilic acid (ACA), a blocker of the transient receptor potential melastatin 2 (TRPM2) cation channels. PQ increased intracellular Zn²⁺ level in the SNpc, but not in the striatum. The increase was rescued by 1-naphthyl acetyl spermine (NASPM), a selective blocker of Ca²⁺- and Zn²⁺-permeable GluR2-lacking AMPA receptors. PQ-induced dopaminergic degeneration in the SNpc was rescued by ACA, NASPM, and GBR, a dopamine reuptake inhibitor. The present study indicates intracellular H₂O₂ produced by PQ, which is taken up through dopamine transporters, is retrogradely transported to presynaptic glutamatergic terminals, activates TRPM2 channels, accumulates glutamate in the extracellular compartment, and induces intracellular Zn²⁺ dysregulation via Ca²⁺- and Zn²⁺-permeable GluR2-lacking AMPA receptor activation, resulting in dopaminergic degeneration in the SNpc. However, H₂O₂ signaling is not the case in the striatum. Paraquat-induced Zn²⁺ dysregulation plays a key role for neurodegeneration in the SNpc, but not in the striatum.