Cyanidin 3-O-glucopyranoside protects and rescues SH-SY5Y cells against amyloid-beta peptide-induced toxicity

Aβ Oligomer Toxicity-Reducing Therapy for the Prevention of Alzheimer's Disease: Importance of the Nrf2 and PPARγ Pathways

Recent studies have revealed that soluble amyloid-β oligomers (AβOs) play a pathogenetic role in Alzheimer's disease (AD). Indeed, AβOs induce neurotoxic and synaptotoxic effects and are also critically involved in neuroinflammation. Oxidative stress appears to be a crucial event underlying these pathological effects of AβOs. From a therapeutic standpoint, new drugs for AD designed to remove AβOs or inhibit the formation of AβOs are currently being developed. However, it is also worth considering strategies for preventing AβO toxicity itself. In particular, small molecules with AβO toxicity-reducing activity have potential as drug candidates. Among such small molecules, those that can enhance Nrf2 and/or PPARγ activity can effectively inhibit AβO toxicity. In this review, I summarize studies on the small molecules that counteract AβO toxicity and are capable of activating Nrf2 and/or PPARγ. I also discuss how these interrelated pathways are involved in the mechanisms by which these small molecules prevent AβO-induced neurotoxicity and neuroinflammation. I propose that AβO toxicity-reducing therapy, designated ATR-T, could be a beneficial, complementary strategy for the prevention and treatment of AD.

Development and Evaluation of Solid Lipid Nanoparticles for the Clearance of Aβ in Alzheimer's Disease

Aggregation of Amyloid-β (Aβ) leads to the formation and deposition of neurofibrillary tangles and plaques which is the main pathological hallmark of Alzheimer's disease (AD). The bioavailability of the drugs and their capability to cross the BBB plays a crucial role in the therapeutics of AD. The present study evaluates the Memantine Hydrochloride (MeHCl) and Tramiprosate (TMPS) loaded solid lipid nanoparticles (SLNs) for the clearance of Aβ on SHSY5Y cells in rat hippocampus. Molecular docking and in vitro Aβ fibrillation were used to ensure the binding of drugs to Aβ. The in vitro cell viability study showed that the M + T SLNs showed enhanced neuroprotection against SHSY5Y cells than the pure drugs (M + T PD) in presence of Aβ (80.35µM ± 0.455 µM) at a 3:1 molar ratio. The Box-Behnken Design (BBD) was employed to optimize the SLNs and the optimized M + T SLNs were further characterized by %drug entrapment efficiency (99.24 ± 3.24 of MeHCl and 89.99 ± 0.95 of TMPS), particle size (159.9 ± 0.569 nm), PDI (0.149 ± 0.08), Zeta potential (-6.4 ± 0.948 mV), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and in vitro drug release. The TEM & AFM analysis showed irregularly spherical morphology. In vitro release of SLNs was noted up to 48 h; whereas the pure drugs released completely within 3 hrs. M + T SLNs revealed an improved pharmacokinetic profile and a 4-fold increase in drug concentration in the brain when compared to the pure drug. Behavioral tests showed enhanced spatial memory and histological studies confirmed reduced Aβ plaques in rat hippocampus. Furthermore, the levels of Aβ decreased in AlCl₃-induced AD. Thus, all these noted results established that the M + T SLNs provide enhanced neuroprotective effects when compared to pure and individual drugs and can be a promising therapeutic strategy for the management of AD.

Comparative Transcriptome Analysis of the Expression of Antioxidant and Immunity Genes in the Spleen of a Cyanidin 3-O-Glucoside-Treated Alzheimer's Mouse Model

Cyanidin 3-O-glucoside (C3G) is a well-known antioxidant found as a dietary anthocyanin in different fruits and vegetables. It has protective and therapeutic effects on various diseases. It can reduce neuronal death from amyloid-beta (Aβ)-induced toxicity and promote the inhibition of Aβ fibrillization. Antioxidant and immune modulation might play a critical role in the properties of C3G against Alzheimer's disease (AD) and other diseases. However, limited studies have been performed on the mechanism involved in the effect of C3G through transcriptome analysis. Thus, the objective of this study was to perform comparative transcriptome analysis of the spleen to determine gene expression profiles of wild-type mice (C57BL/6J Jms), an Alzheimer's mouse model (APPswe/PS1dE9 mice), and a C3G-treated Alzheimer's mouse model. Differentially expressed antioxidant, immune-related, and AD pathways genes were identified in the treated group. The validation of gene expression data via RT-PCR studies further supported the current findings. Six important antioxidant genes (S100a8, S100a9, Prdx2, Hp, Mpst, and Prxl2a) and a high number of immune-related genes were found to be upregulated in the treatment groups, suggesting the possible antioxidant and immunomodulatory mechanisms of C3G, respectively. Further studies are strongly recommended to elucidate the precise role of these essential genes and optimize the therapeutic function of C3G in AD and other disease conditions.

Role of natural plant products against Alzheimer's disease

Alzheimer's disease (AD) is one of the major neurodegenerative disorder. Deposition of amyloid fibrils and tau protein are associated with various pathological symptoms. Currently limited medication is available for AD treatment. Most of the drugs are basically cholinesterase inhibitors and associated with various side effects. Natural plant products have shown potential as a therapeutic agent for the treatment of AD symptoms. Variety of secondary metabolites like flavonoids, tannins, terpenoids, alkaloids and phenols are used to reduce the progression of the disease. Plant products have less or no side effect and are easily available. The present review gives a detailed account of the potential of natural plant products against the AD symptoms.

Potential therapeutic effects of cyanidin-3-O-glucoside on rheumatoid arthritis by relieving inhibition of CD38+ NK cells on Treg cell differentiation

Background

CD38+ NK cells are overabundant in rheumatoid arthritis (RA). Cyanidin-3-O-glucoside (C3G) is an inhibitor of CD38. This study investigated the pathogenic role of CD38+ NK cells and the effect of C3G on RA.

Methods

Rats with bovine type II collagen-induced arthritis (CIA) were injected with C3G. RA synovial fibroblasts (RASFs) or mononuclear cells (MNCs) were cultured with C3G. MNCs were also cocultured with CD38+ NK cells following C3G pretreatment.

Results

C3G injection significantly alleviated CIA. C3G also significantly increased the level of interleukin (IL)-10 and the regulatory T (Treg) cell proportion, and it decreased the interleukin (IL)-6 and interferon (IFN)-γ levels and CD38+ NK cell proportion in rat peripheral blood and synovial fluid. Additionally, C3G significantly increased RASF apoptosis and decreased RASF proliferation and IL-6 production in the culture medium. Furthermore, C3G stimulated MNCs to increase IL-2 and IL-10 production and the Treg cell proportion, and it caused MNCs to decrease IL-6 and IFN-γ production and the CD38+ NK cell proportion. Although CD38+ NK cells significantly decreased the Treg cell proportion and IL-10 level in MNCs, CD38+ NK cells that had been pretreated with C3G increased the proportion of Treg cells and IL-10 levels and decreased the IL-6 and IFN-γ levels in the coculture. In CD38+ NK cells, C3G significantly increased Sirtuin 6 (Sirt6) expression and the tumor necrosis factor (TNF)-α level, and it decreased natural killer group 2D (NKG2D) expression and the IFN-γ level. However, when CD38+ NK cells were treated with Sirt6 siRNA, C3G did not change the NKG2D expression, the TNF-α level sharply decreased, and the IFN-γ level increased. When MNCs were cocultured with C3G-pretreated CD38+ NK cells in the presence of TNF-α and an anti-IFN-γ antibody, the IL-10+ Treg cell proportion significantly increased. When MNCs were cocultured with C3G-pretreated CD38+ NK cells in the presence of IFN-γ and an anti-TNF-α antibody, the IL-10+ Treg cell proportion sharply decreased. When CIA rats were injected with both C3G and the Sirt6 inhibitor OSS_128167, the rats exhibited joint inflammation and a low Treg cell proportion, but the CD38+ NK proportion was still low.

Conclusion

C3G has therapeutic effects on CIA and RA. C3G decreased the proportion of CD38+ cells, RASF proliferation, and proinflammatory cytokine secretion, and it increased the Treg cell proportion. C3G also elevated Sirt6 expression to suppress NKG2D expression, increase TNF-α secretion, and decrease IFN-γ secretion in CD38+ NK cells, which stimulates MNCs to differentiate into Treg cells. This study also demonstrates that the inhibition of Treg cell differentiation in MNCs by CD38+ NK cells is a potential cause of the immune imbalance in RA and CIA.

An Exploration of the Oryza sativa L. Cyanidin-3-glucoside on the Cognitive Function in Older Adults with Subjective Memory Impairment

OBJECTIVE

Cyanidin-3-glucoside (C3G), is a component of anthocyanin, have been considered to positively influence cognition and be beneficial for the prevention and treatment of dementia. We aimed to assess the safety and efficacy of cyanidin-3-glucoside-rich Oryza sativa L. (black rice) extract on cognitive function.

METHODS

A 12-weeks double-blind randomized, placebo controlled trial assessed safety and cognitive outcomes in participants with subjective memory impairment (n=48) following consumption of 6 black rice extract capsules or a placebo. Cognitive function was assessed using the ADAS-cog and the CERAD-K. Subjective memory impairment also assessed. Safety was assessed by hematologic blood test, urine analysis, and participant reports of adverse events.

RESULTS

There was significant improvement on subjective memory in intervention group. There was no statistically significant difference in objective cognitive outcomes following 12 weeks of consuming black rice extract. ADAS-cog scores, however, trended toward improvement in the intervention group compared to the placebo group. There was no adverse event.

CONCLUSION

Although significant improvement in objective cognitive function was not proved, we found that C3G-rich Oryza sativa L. extract improves subjective memory in this study. Therefore the results may be informative of the possible effectiveness of the C3G-rich Oryza sativa L. on cognitive function.

PQM130, a Novel Feruloyl-Donepezil Hybrid Compound, Effectively Ameliorates the Cognitive Impairments and Pathology in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most frequent type of dementia in older people. The complex nature of AD calls for the development of multitarget agents addressing key pathogenic processes. Donepezil, an acetylcholinesterase inhibitor, is a first-line acetylcholinesterase inhibitor used for the treatment of AD. Although several studies have demonstrated the symptomatic efficacy of donepezil treatment in AD patients, the possible effects of donepezil on the AD process are not yet known. In this study, a novel feruloyl-donepezil hybrid compound (PQM130) was synthesized and evaluated as a multitarget drug candidate against the neurotoxicity induced by Aβ1-42 oligomer (AβO) injection in mice. Interestingly, PQM130 had already shown anti-inflammatory activity in different in vivo models and neuroprotective activity in human neuronal cells. The intracerebroventricular (i.c.v.) injection of AβO in mice caused the increase of memory impairment, oxidative stress, neurodegeneration, and neuroinflammation. Instead, PQM130 (0.5-1 mg/kg) treatment after the i.c.v. AβO injection reduced oxidative damage and neuroinflammation and induced cell survival and protein synthesis through the modulation of glycogen synthase kinase 3β (GSK3β) and extracellular signal-regulated kinases (ERK1/2). Moreover, PQM130 increased brain plasticity and protected mice against the decline in spatial cognition. Even more interesting is that PQM130 modulated different pathways compared to donepezil, and it is much more effective in counteracting AβO damage. Therefore, our findings highlighted that PQM130 is a potent multi-functional agent against AD and could act as a promising neuroprotective compound for anti-AD drug development.

Callistephin enhances the protective effects of isoflurane on microglial injury through downregulation of inflammation and apoptosis

Microglia are the major immune cells in the central nervous system. Microglial activation can be beneficial or detrimental depending on the stimuli and the physiopathological environment. Microglial activation is involved in a variety of neurodegenerative disorders. Different anesthetic agents have exhibited diverse effects on microglial activation and the engulfment process. The anthocyanin callistephin has been demonstrated to have antioxidant and anti‑inflammatory properties, and these were assessed in the present study, with a focus on its effect on microglial activation. Mouse microglial cells C8‑4B were treated with 100 ng/µl lipopolysaccharide (LPS) and 1 ng/µl interferon‑γ. Cells were subsequently treated with 2% isoflurane, 100 µM callistephin or both. LPS promoted apoptosis in C8‑B4 cells, and this was reduced following treatment with isoflurane and callistephin. LPS‑treated C8‑B4 cells also exhibited enhanced production of reactive oxygen species and nitric oxide, excessive engulfment and increased caspase 3/7 activity. These detrimental alterations were suppressed following co‑treatment with isoflurane and callistephin. LPS‑induced apoptosis was facilitated via the expression of B‑cell lymphoma‑2 like 1 and poly (ADP‑ribose) polymerase, which were subsequently restored following treatment with isoflurane and callistephin. Callistephin was demonstrated to be involved in the modulation of inducible nitric oxide synthase, cytochrome c oxidase subunit 2, tumor necrosis factor‑α and nuclear factor‑κ B. Callistephin enhanced the protective effects of isoflurane by modulating engulfment and apoptosis in C8‑B4 cells. The potential underlying mechanism was identified to be the suppression of p38 phosphorylation. The present study thus suggested that the negative effects on microglial activity induced by LPS were ameliorated following treatment with callistephin, which also enhanced the effects of isoflurane. Callistephin may therefore constitute a candidate drug agent that may target inflammatory and growth regulatory signaling pathways, thus ameliorating certain aspects of neurodegenerative diseases.

Vildagliptine protects SH-SY5Y human neuron-like cells from Aβ 1-42 induced toxicity, in vitro

The amyloid β (Aβ) toxic fibrils is thought to play a central role in the onset and progression of Alzheimer's disease (AD) because of it is a main formation of senile plaques. Diabetic patients are more vulnerable to caught Alzheimer's disease. Vildagliptine, a novel anti diabetic agent, has been reported to exert protective effects on AD rat models in restricted study. We aimed to investigate any protective effects of vildagliptine against Aβ fibrils on SH-SY5Y cell line. Vildagliptine decreased PSEN1 and PSEN2 mRNA levels which enroll Aβ production. In addition, vildagliptin was downregulated caspase-3 and caspase-9 expression levels which were evoked by Aβ. Also we confirmed cellular viability with real time cell analyzer and MTT assay. Our data exposed that vildagliptine has lowering effect on GSK3β and Tau phosphorylation. However we did not get protective effect of vildagliptine against Aβ toxicity on mitochondrial membrane potential. These results indicate that vildagliptine exerts a protective effect against Aβ by decreasing apoptosis related proteins, lowering GSK3β and Tau phosphorylation levels in addition to expression of PSEN1 and PSEN2 mRNA downregulation effect.

Cyanidin-3-glucoside inhibits amyloid β25-35-induced neuronal cell death in cultured rat hippocampal neurons

Increasing evidence implicates changes in [Ca²⁺]_i and oxidative stress as causative factors in amyloid beta (Aβ)-induced neuronal cell death. Cyanidin-3-glucoside (C3G), a component of anthocyanin, has been reported to protect against glutamate-induced neuronal cell death by inhibiting Ca²⁺ and Zn²⁺ signaling. The present study aimed to determine whether C3G exerts a protective effect against Aβ_25–35-induced neuronal cell death in cultured rat hippocampal neurons from embryonic day 17 fetal Sprague-Dawley rats using MTT assay for cell survival, and caspase-3 assay and digital imaging methods for Ca²⁺, Zn²⁺, MMP and ROS. Treatment with Aβ_25–35 (20 µM) for 48 h induced neuronal cell death in cultured rat pure hippocampal neurons. Treatment with C3G for 48 h significantly increased cell survival. Pretreatment with C3G for 30 min significantly inhibited Aβ_25–35-induced [Zn²⁺]_i increases as well as [Ca²⁺]_i increases in the cultured rat hippocampal neurons. C3G also significantly inhibited Aβ_25–35-induced mitochondrial depolarization. C3G also blocked the Aβ_25–35-induced formation of ROS. In addition, C3G significantly inhibited the Aβ_25–35-induced activation of caspase-3. These results suggest that cyanidin-3-glucoside protects against amyloid β-induced neuronal cell death by reducing multiple apoptotic signals.

Neuroprotective Effect of Caffeic Acid Phenethyl Ester in A Mouse Model of Alzheimer's Disease Involves Nrf2/HO-1 Pathway

Alzheimer's disease (AD) is a progressive pathology, where dementia symptoms gradually worsen over a number of years. The hallmarks of AD, such as amyloid β-peptide (Aβ) in senile plaque and neurofibrillary tangles, are strongly intertwined with oxidative stress, which is considered one of the common effectors of the cascade of degenerative events. The endogenous nuclear factor erythroid 2-related factor 2 (Nrf2) is the "master regulator" of the antioxidant response and it is known as an indicator and regulator of oxidative stress. The present study aimed to determine the potential neuroprotective activity of caffeic acid phenethyl ester (CAPE), a polyphenolic compound abundant in honeybee, against the neurotoxicity of Aβ_1-42 oligomers (AβO) in mice. An intracerebroventricular (i.c.v.) injection of AβO into the mouse brain triggered increased reactive oxygen species levels, neurodegeneration, neuroinflammation, and memory impairment. In contrast, the intraperitoneal administration of CAPE (10 mg/kg) after i.c.v. AβO-injection counteracted oxidative stress accompanied by an induction of Nrf2 and heme oxygenase-1 via the modulation of glycogen synthase kinase 3β in the hippocampus of mice. Additionally, CAPE treatment decreased AβO-induced neuronal apoptosis and neuroinflammation, and improved learning and memory, protecting mice against the decline in spatial cognition. Our findings demonstrate that CAPE could potentially be considered as a promising neuroprotective agent against progressive neurodegenerative diseases such as AD.

Protective Effects of 6-(Methylsulfinyl)hexyl Isothiocyanate on Aβ1-42-Induced Cognitive Deficit, Oxidative Stress, Inflammation, and Apoptosis in Mice

Alzheimer's disease (AD) is the most common form of dementia among older people. Although soluble amyloid species are recognized triggers of the disease, no therapeutic approach is able to stop it. 6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC) is a major bioactive compound in Wasabia japonica, which is a typical Japanese pungent spice. Recently, in vivo and in vitro studies demonstrated that 6-MSITC has several biological properties. The aim of the present study was to investigate the neuroprotective activity of 6-MSITC in a murine AD model, induced by intracerebroventricular injection of β-amyloid oligomers (Aβ1-42O). The treatment with 6-MSITC started 1 h after the surgery for the next 10 days. Behavioral analysis showed that 6-MSITC ameliorated Aβ1-42O-induced memory impairments. The decrease of glutathione levels and increase of reactive oxygen species in hippocampal tissues following Aβ1-42O injection were reduced by 6-MSITC. Moreover, activation of caspases, increase of inflammatory factors, and phosphorylation of ERK and GSK3 were inhibited by 6-MSITC. These results highlighted an interesting neuroprotective activity of 6-MSITC, which was able to restore a physiological oxidative status, interfere positively with Nrf2-pathway, decrease apoptosis and neuroinflammation and contribute to behavioral recovery. Taken together, these findings demonstrated that 6-MSITC could be a promising complement for AD therapy.

Role of Plant-Derived Flavonoids and Their Mechanism in Attenuation of Alzheimer's and Parkinson's Diseases: An Update of Recent Data

Neurodegeneration is a progressive loss of neuronal cells in certain regions of the brain. Most of the neurodegenerative disorders (NDDs) share the communal characteristic such as damage or reduction of various cell types typically including astrocytes and microglial activity. Several compounds are being trialed to treat NDDs but they possess solitary symptomatic advantages along with copious side effects. The finding of more enthralling and captivating compounds to suspend and standstill the pathology of NDDs will be considered as a hallmark of present times. Phytochemicals possess the potential to alternate the synthetic line of therapy against NDDs. The present review explores the potential efficacy of plant-derived flavonoids against most common NDDs including Alzheimer's disease (AD) and Parkinson's disease (PD). Flavonoids are biologically active phytochemicals which possess potential pharmacological effects, including antiviral, anti-allergic, antiplatelet, anti-inflammatory, anti-tumor, anti-apoptotic and anti-oxidant effects and are able to attenuate the pathology of various NDDs through down-regulating the nitric oxide (NO) production, by reducing the tumor necrosis factor-α (TNF-α), by reducing the excitotoxicity of superoxide as well as acting as tyrosine kinase (TK) and monoamine oxidase (MAO) inhibiting enzyme.

Design, synthesis and pharmacological evaluation of N-benzyl-piperidinyl-aryl-acylhydrazone derivatives as donepezil hybrids: Discovery of novel multi-target anti-alzheimer prototype drug candidates

A new series of sixteen multifunctional N-benzyl-piperidine-aryl-acylhydrazones hybrid derivatives was synthesized and evaluated for multi-target activities related to Alzheimer's disease (AD). The molecular hybridization approach was based on the combination, in a single molecule, of the pharmacophoric N-benzyl-piperidine subunit of donepezil, the substituted hydroxy-piperidine fragment of the AChE inhibitor LASSBio-767, and an acylhydrazone linker, a privileged structure present in a number of synthetic aryl- and aryl-acylhydrazone derivatives with significant AChE and anti-inflammatory activities. Among them, compounds 4c, 4d, 4g and 4j presented the best AChE inhibitory activities, but only compounds 4c and 4g exhibited concurrent anti-inflammatory activity in vitro and in vivo, against amyloid beta oligomer (AβO) induced neuroinflammation. Compound 4c also showed the best in vitro and in vivo neuroprotective effects against AβO-induced neurodegeneration. In addition, compound 4c showed a similar binding mode to donepezil in both acetylated and free forms of AChE enzyme in molecular docking studies and did not show relevant toxic effects on in vitro and in vivo assays, with good predicted ADME parameters in silico. Overall, all these results highlighted compound 4c as a promising and innovative multi-target drug prototype candidate for AD treatment.

Bridging Type 2 Diabetes and Alzheimer's Disease: Assembling the Puzzle Pieces in the Quest for the Molecules With Therapeutic and Preventive Potential

Type 2 diabetes (T2D) and Alzheimer's disease (AD) are two age-related amyloid diseases that affect millions of people worldwide. Broadly supported by epidemiological data, the higher incidence of AD among type 2 diabetic patients led to the recognition of T2D as a tangible risk factor for the development of AD. Indeed, there is now growing evidence on brain structural and functional abnormalities arising from brain insulin resistance and deficiency, ultimately highlighting the need for new approaches capable of preventing the development of AD in type 2 diabetic patients. This review provides an update on overlapping pathophysiological mechanisms and pathways in T2D and AD, such as amyloidogenic events, oxidative stress, endothelial dysfunction, aberrant enzymatic activity, and even shared genetic background. These events will be presented as puzzle pieces put together, thus establishing potential therapeutic targets for drug discovery and development against T2D and diabetes-induced cognitive decline-a heavyweight contributor to the increasing incidence of dementia in developed countries. Hoping to pave the way in this direction, we will present some of the most promising and well-studied drug leads with potential against both pathologies, including their respective bioactivity reports, mechanisms of action, and structure-activity relationships.

Chemical basis for the disparate neuroprotective effects of the anthocyanins, callistephin and kuromanin, against nitrosative stress

Oxidative and nitrosative stress are major factors in neuronal cell death underlying neurodegenerative disease. Thus, supplementation of antioxidant defenses may be an effective therapeutic strategy for diseases such as amyotrophic lateral sclerosis, Parkinson's disease, and Alzheimer's disease. In this regard, treatment with nutraceutical antioxidants has garnered increasing attention; however, the differential neuroprotective effects of structurally similar nutraceuticals, which may affect their suitability as therapeutic agents, has not been directly examined. In this study we compare the ability of two anthocyanins, callistephin (pelargonidin-3-O-glucoside) and kuromanin (cyanidin-3-O-glucoside) to protect cerebellar granule neurons from damage induced by either oxidative or nitrosative stress. These anthocyanins differ by the presence of a single hydroxyl group on the B-ring of kuromanin, forming a catechol moiety. While both compounds protected neurons from oxidative stress induced by glutamate excitotoxicity, a stark contrast was observed under conditions of nitrosative stress. Only kuromanin displayed the capacity to defend neurons from nitric oxide (NO)-induced apoptosis. This protective effect was blocked by addition of Cu, Zn-superoxide dismutase, indicating that the neuroprotective mechanism is superoxide dependent. Based on these observations, we suggest a unique mechanism by which slight structural variances, specifically the absence or presence of a catechol moiety, lend kuromanin the unique ability to generate superoxide, which acts as a scavenger of NO. These findings indicate that kuromanin and compounds that share similar chemical characteristics may be more effective therapeutic agents for treating neurodegenerative diseases than callistephin and related (non-catechol) compounds.

Protocatechuic Acid: Inhibition of Fibril Formation, Destabilization of Preformed Fibrils of Amyloid-β and α-Synuclein, and Neuroprotection

Protocatechuic acid (PCA) is the major metabolite of the anthocyanin known as cyanidin 3-glucoside. It is found in plasma and tissues, such as the brain, heart, liver, and kidneys, following consumption of a rich source of this flavonoid. The abnormal pathological assembly of amyloid-β (Aβ) and α-synuclein (αS) is an underlying mechanism involved in the formation of amyloid plaques and Lewy bodies in the brain, which are responsible for neuropathology symptoms in Alzheimer's (AD) and Parkinson's diseases (PD), respectively. This research was performed to evaluate the protective effects of PCA, by establishing its potential role in inhibiting aggregation and fibril destabilization of Aβ and αS proteins. It has been found that PCA inhibits the aggregation of Aβ and αS and destabilizes their preformed fibrils. These results were confirmed by TEM images, electrophoresis, and immunoblotting experiments. Furthermore, PCA prevents the death of PC12 cells triggered by Aβ- and αS-induced toxicity.

Early effects of Aβ1-42 oligomers injection in mice: Involvement of PI3K/Akt/GSK3 and MAPK/ERK1/2 pathways

Neuronal and synaptic loss are the best pathological correlates for memory decline in Alzheimer's disease (AD). Soluble beta-amyloid oligomers (AβO) are considered to putatively play a crucial role in the early synapse loss and cognitive impairment observed in AD. Evidence suggests that oxidative stress and apoptosis are involved in the mechanism of Aβ-induced neurotoxicity and AD pathogenesis. This study aimed to explore the molecular mechanisms that contribute to the early memory deficits induced by intracerebroventricular injection of AβO in mice. Ten days after a single AβO injection memory impairments were observed, as measured by Morris water maze and novel object recognition tests. Cognitive decline was associated with increased oxidative stress, caspase-9 activation, and decreased hippocampal synaptophysin immunoreactivity. Furthermore, GSH levels were significantly higher in AβO-injected mice than in sham mice, showing that a protective mechanism might develop due to oxidative stress. Additionally, AβO-induced toxicity was aligned with an increment of the activation of Akt and ERK1/2, and reduced activity of GSK3. These findings suggest that AβO injection triggers a cascade of events that mimic the key neuropathological hallmarks of AD. Aβ acute injection helps to better understand how this peptide impairs specific signaling pathways leading to synaptic and memory dysfunctions. Thus, this model is a valid tool for investigating AD and may suggest a new way to develop neuroprotective therapies at such early stages of the disease.

Cyanidin-3-glucoside inhibits glutamate-induced Zn2+ signaling and neuronal cell death in cultured rat hippocampal neurons by inhibiting Ca2+-induced mitochondrial depolarization and formation of reactive oxygen species

Cyanidin-3-glucoside (C3G), a member of the anthocyanin family, is a potent natural antioxidant. However, effects of C3G on glutamate-induced [Zn(2+)]i increase and neuronal cell death remain unknown. We studied the effects of C3G on glutamate-induced [Zn(2+)]i increase and cell death in cultured rat hippocampal neurons from embryonic day 17 maternal Sprague-Dawley rats using digital imaging methods for Zn(2+), Ca(2+), reactive oxygen species (ROS), mitochondrial membrane potential and a MTT assay for cell survival. Treatment with glutamate (100 µM) for 7 min induces reproducible [Zn(2+)]i increase at 35 min interval in cultured rat hippocampal neurons. The intracellular Zn(2+)-chelator TPEN markedly blocked glutamate-induced [Zn(2+)]i increase, but the extracellular Zn(2+) chelator CaEDTA did not affect glutamate-induced [Zn(2+)]i increase. C3G inhibited the glutamate-induced [Zn(2+)]i response in a concentration-dependent manner (IC50 of 14.1 ± 1.1 µg/ml). C3G also significantly inhibited glutamate-induced [Ca(2+)]i increase. Two antioxidants such as Trolox and DTT significantly inhibited the glutamate-induced [Zn(2+)]i response, but they did not affect the [Ca(2+)]i responses. C3G blocked glutamate-induced formation of ROS. Trolox and DTT also inhibited the formation of ROS. C3G significantly inhibited glutamate-induced mitochondrial depolarization. However, TPEN, Trolox and DTT did not affect the mitochondrial depolarization. C3G, Trolox and DTT attenuated glutamate-induced neuronal cell death in cultured rat hippocampal neurons, respectively. Taken together, all these results suggest that cyanidin-3-glucoside inhibits glutamate-induced [Zn(2+)]i increase through a release of Zn(2+) from intracellular sources in cultured rat hippocampal neurons by inhibiting Ca(2+)-induced mitochondrial depolarization and formation of ROS, which is involved in neuroprotection against glutamate-induced cell death.

Protective effects of anthocyanins against amyloid beta-induced neurotoxicity in vivo and in vitro

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders in recent world, characterized by increased production of amyloid beta in the nervous system with an ultimate effect of apoptotic neurodegeneration. This study was aimed to investigate the neuroprotective effect of black soybean anthocyanins in a neurodegenerative model of amyloid beta 1-42 (Aβ1-42). Aβ1-42 was treated to HT22 cell lines or adult male rats via intra-cerebro-ventricular injection to induce neurotoxicity in these experimental models. Anthocyanins were treated 0.2 mg/kg in case of cell lines or 4 mg/kg intragastrically to adult rats to protect against Aβ-induced neurodegeneration. Assay for cell viability, mitochondrial membrane potential (Ψm), intracellular free Ca(2+) and apoptotic cells (fluoro-jade B and TUNEL) were performed in vitro while western blot analyses were performed to the hippocampal proteins of adult rats. Our results showed that Aβ1-42 treatment reduced cell viability, disturbed the Ψm and Ca(2+) homeostasis in and out of the cell, and increased neuronal apoptosis. Treatment with anthocyanins for 12 hr retained the cell viability, normalized Ψm and Ca(2+) level, and decreased the neuronal cell death. In accordance, anthocyanins reversed Aβ-induced effect on protein expression of mitochondrial apoptotic pathway (Bax, cytochrome C, caspase-9 and caspase-3) and major Alzheimer's markers i.e. Aβ, APP, P-tau and BACE-1. Overall, our results showed that anthocyanins are potential candidates to treat neurodegenerative disorders like AD.

Neuroprotective effect of purple rice extract and its constituent against amyloid beta-induced neuronal cell death in SK-N-SH cells

This study evaluated the protective effects of purple rice (Oryza sativa L.) extract (PRE) and its major constituent, cyanidin, and their underlying mechanisms against Aβ 25-35-induced neuronal cell death in SK-N-SH cells. Aβ 25-35-induced neuronal toxicity is characterized by decrease in cell viability, the release of lactate dehydrogenase (LDH), decrease superoxide dismutase (SOD) activity, increase in reactive oxygen species (ROS) production, morphological alteration, and activation of mitochondrial death pathway. Pretreatment with PRE and cyanidin significantly attenuated Aβ 25-35-induced loss of cell viability, apoptosis, and increase in ROS and RNS production in a dose-dependent manner. In addition, PRE and cyanidin also helped to bring about the downregulation of the expression of Bax, cytochrome c, cleavage caspase-9, and cleavage caspase-3 proteins, and the upregulation of the Bcl-XL protein in cascade. Therefore, it is evident that PRE and its major constituent, cyanidin, were successful in protecting from the cytotoxic effect of Aβ 25-35 through attenuation ROS and RNS production and modulation of mitochondrial death pathway in SK-N-SH cells. This result suggests that PRE and its major constituent, cyanidin, might be beneficial as potential therapeutic agents in preventing neurodegenerative diseases.

Cyanidin-3-glucoside Inhibits ATP-induced Intracellular Free Ca(2+) Concentration, ROS Formation and Mitochondrial Depolarization in PC12 Cells

Flavonoids have an ability to suppress various ion channels. We determined whether one of flavonoids, cyanidin-3-glucoside, affects adenosine 5'-triphosphate (ATP)-induced calcium signaling using digital imaging methods for intracellular free Ca(2+) concentration ([Ca(2+)]i), reactive oxygen species (ROS) and mitochondrial membrane potential in PC12 cells. Treatment with ATP (100µM) for 90 sec induced [Ca(2+)]i increases in PC12 cells. Pretreatment with cyanidin-3-glucoside (1µ g/ml to 100µg/ml) for 30 min inhibited the ATP-induced [Ca(2+)]i increases in a concentration-dependent manner (IC50=15.3µg/ml). Pretreatment with cyanidin-3-glucoside (15µg/ml) for 30 min significantly inhibited the ATP-induced [Ca(2+)]i responses following removal of extracellular Ca(2+) or depletion of intracellular [Ca(2+)]i stores. Cyanidin-3-glucoside also significantly inhibited the relatively specific P2X2 receptor agonist 2-MeSATP-induced [Ca(2+)]i responses. Cyanidin-3-glucoside significantly inhibited the thapsigargin or ATP-induced store-operated calcium entry. Cyanidin-3-glucoside significantly inhibited the ATP-induced [Ca(2+)]i responses in the presence of nimodipine and ω-conotoxin. Cyanidin-3-glucoside also significantly inhibited KCl (50 mM)-induced [Ca(2+)]i increases. Cyanidin-3-glucoside significantly inhibited ATP-induced mitochondrial depolarization. The intracellular Ca(2+) chelator BAPTA-AM or the mitochondrial Ca(2+) uniporter inhibitor RU360 blocked the ATP-induced mitochondrial depolarization in the presence of cyanidin-3-glucoside. Cyanidin-3-glucoside blocked ATP-induced formation of ROS. BAPTA-AM further decreased the formation of ROS in the presence of cyanidin-3-glucoside. All these results suggest that cyanidin-3-glucoside inhibits ATP-induced calcium signaling in PC12 cells by inhibiting multiple pathways which are the influx of extracellular Ca(2+) through the nimodipine and ω-conotoxin-sensitive and -insensitive pathways and the release of Ca(2+) from intracellular stores. In addition, cyanidin-3-glucoside inhibits ATP-induced formation of ROS by inhibiting Ca(2+)-induced mitochondrial depolarization.

Caffeoylquinic acid-rich purple sweet potato extract, with or without anthocyanin, imparts neuroprotection and contributes to the improvement of spatial learning and memory of SAMP8 mouse

The effects of caffeoylquinic acid (CQA)-rich purple sweet potato (PSP) extract, with (PSPEa) or without (PSPEb) anthocyanin, on the improvement of spatial learning and memory of senescence-accelerated prone mouse strain (SAMP) 8 was determined. SAMP8 was treated with 20 mg/kg/day of PSPEa or PSPEb for 30 days. The effect on spatial learning and memory and the molecular mechanism of this effect were determined in vivo (SAMP8) and in vitro (SH-SY5Y cells). PSPEa or PSPEb reduced the escape latency time of SAMP8 by 17.0 ± 8.0 and 14.2 ± 5.8 s (P < 0.01), respectively. PSPEa administration induced an overexpression of antioxidant-, energy metabolism-, and neuronal plasticity-related proteins in the brain of SAMP8. Additionally, PSPEa and PSPEb increased the cell viability by 141.6 and 133% as compared to Aβ1-42-treated cells. These findings suggest that PSP rich in CQA derivatives with or without anthocyanidine had a neuroprotective effect on mouse brain and can improve the spatial learning and memory of SAMP8.

Protective effect of cyanidin 3-O-glucoside on beta-amyloid peptide-induced cognitive impairment in rats

Alzheimer's disease (AD) is a neurodegenerative disorder that results in cognitive impairment. It has been proposed that deposits of beta-amyloid (Aβ) form the cores of the plaque and, subsequently, induce the activation of GSK-3β and the hyperphosphorylation of tau, resulting in cognitive impairment. Oxidative stress has been proposed to be an important factor in the pathogenesis of AD. Cyanidin 3-O-glucoside (Cy3G) is a neuroprotective antioxidant. However, the effects of Cy3G on cognition are unclear. In this paper, we show that Cy3G is protective against the Aβ-induced impairment of learning and memory, but has no effect on normal learning and memory. Moreover, we found that Gy3G attenuated the Aβ-induced tau hyperphosphorylation and GSK-3β hyperactivation observed in AD. Taken together, these results demonstrated that Cy3G can rescue the cognitive impairments that are induced by Aβ via the modulation of GSK-3β/tau, suggesting a potential therapeutic role of Cy3G in AD.

Chronic cyanidin-3-glucoside administration improves short-term spatial recognition memory but not passive avoidance learning and memory in streptozotocin-diabetic rats

This research study was conducted to evaluate the efficacy of chronic cyanidin-3-glucoside (C3G) on alleviation of learning and memory deficits in diabetic rats as a result of the observed antidiabetic and antioxidant activity of C3G. Male Wistar rats were divided into control, diabetic, C3G-treated-control and -diabetic groups. The C3G was administered i.p. at a dose of 10 mg/kg on alternate days for eight weeks. For evaluation of learning and memory, initial latency (IL) and step-through latency (STL) were determined at the end of study using passive avoidance test. Meanwhile, spatial recognition memory was assessed as alternation in the Y-maze task. Oxidative stress markers in brain tissue were also measured. It was found that the alternation score of the diabetic rats was lower than that of control (p < 0.01) and C3G-treated diabetic rats showed a higher alternation score as compared to diabetic group (p < 0.05). Diabetic rats also developed a significant impairment in retention and recall in passive avoidance test (p < 0.01) and C3G treatment of diabetic rats did not produce any significant improvement. Meanwhile, increased level of malondialdehyde (MDA) in diabetic rats was significantly reduced following C3G treatment (p < 0.05). Taken together, chronic C3G could improve short-term spatial recognition memory disturbance in the Y-maze test but not retention and recall capability in passive avoidance test in STZ-diabetic rats.

Cyanidin-3-glucoside ameliorates ethanol neurotoxicity in the developing brain

Ethanol exposure induces neurodegeneration in the developing central nervous system (CNS). Fetal alcohol spectrum disorders (FASD) are caused by ethanol exposure during pregnancy and are the most common nonhereditary cause of mental retardation. It is important to identify agents that provide neuroprotection against ethanol neurotoxicity. Multiple mechanisms have been proposed for ethanol-induced neurodegeneration, and oxidative stress is one of the most important mechanisms. Recent evidence indicates that glycogen synthase kinase 3β (GSK3β) is a potential mediator of ethanol-mediated neuronal death. Cyanidin-3-glucoside (C3G), a member of the anthocyanin family, is a potent natural antioxidant. Our previous study suggested that C3G inhibited GSK3β activity in neurons. Using a third trimester equivalent mouse model of ethanol exposure, we tested the hypothesis that C3G can ameliorate ethanol-induced neuronal death in the developing brain. Intraperitoneal injection of C3G reduced ethanol-meditated caspase-3 activation, neurodegeneration, and microglial activation in the cerebral cortex of 7-day-old mice. C3G blocked ethanol-mediated GSK3β activation by inducing phosphorylation at serine 9 while reducing the phosphorylation at tyrosine 216. C3G also inhibited ethanol-stimulated expression of malondialdehyde (MDA) and p47phox, indicating that C3G alleviated ethanol-induced oxidative stress. These results provide important insight into the therapeutic potential of C3G.

Protective effects of anthocyanins against amyloid β-peptide-induced damage in neuro-2A cells

Alzheimer's disease is neuropathologically characterized by amyloid β-protein (Aβ) deposition, resulting in neurotoxicity. Herein, we focused on the prevention of anthocyanins from amyloid-mediated neurodysfunction. The data demonstrated that combined exposure of Aβ(1-40) and Aβ(25-35) to Neuro-2A cells resulted in reactive oxygen species (ROS) production and perturbation of calcium homeostasis. The expressions of LXRα, ApoE, ABCA1, and seladin-1 genes were significantly down-regulated upon Aβ challenge. β-Secretase, the rate-limiting enzyme that catalyzes amyloid precursor protein transform to Aβ, was up-regulated by Aβ treatment. For the duration of Aβ stimulation, malvidin (Mal) or oenin (Oen; malvidin-3-O-glucoside) was added, and the protective effects were observed. Mal and Oen showed protective effects against Aβ-induced neurotoxicity through blocking ROS formation, preserving Ca(2+) homeostasis, and preventing Aβ-mediated perturbation of certain genes involved in Aβ metabolism and cellular defense. The present study implicates anthocyanin as a potential therapeutic candidate for the prevention of amyloid-mediated neurodysfunction.

Targeting NADPH oxidase and phospholipases A2 in Alzheimer's disease

Alzheimer's disease (AD) is marked by an increase in the production of extracellular beta amyloid plaques and intracellular neurofibrillary tangles associated with a decline in brain function. Increases in oxidative stress are regarded as an early sign of AD pathophysiology, although the source of reactive oxygen species (ROS) and the mechanism(s) whereby beta amyloid peptides (Abeta) impact oxidative stress have not been adequately investigated. Recent studies provide strong evidence for the involvement of NADPH oxidase and its downstream oxidative signaling pathways in the toxic effects elicited by Abeta. ROS produced by NADPH oxidase activate multiple signaling pathways leading to neuronal excitotoxicity and glial cell-mediated inflammation. This review describes recent studies demonstrating the neurotoxic effects of Abeta in conjunction with ROS produced by NADPH oxidase and the downstream pathways leading to activation of cytosolic phospholipase A(2) (PLA(2)) and secretory PLA(2). In addition, this review also describes recent studies using botanical antioxidants to protect against oxidative damage associated with AD. Investigating the metabolic and signaling pathways involving Abeta NADPH oxidase and PLA(2) can help understand the mechanisms underlying the neurodegenerative effects of oxidative stress in AD. This information should provide new therapeutic approaches for prevention of this debilitating disease.

Anthocyanins: are they beneficial in treating ethanol neurotoxicity?

Heavy alcohol exposure produces profound damage to the developing central nervous system (CNS) as well as the adult brain. Children with fetal alcohol spectrum disorders (FASD) have a variety of cognitive, behavioral, and neurological impairments. FASD currently represents the leading cause of mental retardation. Excessive alcohol consumption is associated with Wernicke-Korsakoff syndrome (WKS) and neurodegeneration in the adult brain. Although the cellular/molecular mechanism underlying ethanol's neurotoxicity has not been fully understood, it is generally believed that oxidative stress plays an important role. Identification of neuroprotective agents that can ameliorate ethanol neurotoxicity is an important step for developing preventive/therapeutic strategies. Targeting ethanol-induced oxidative stress using natural antioxidants is an attractive approach. Anthocyanins, a large subgroup of flavonoids present in many vegetables and fruits, are safe and potent antioxidants. They exhibit diverse potential health benefits including cardioprotection, anti-atherosclerotic activity, anti-cancer, anti-diabetic, and anti-inflammation properties. Anthocyanins can cross the blood-brain barrier and distribute in the CNS. Recent studies indicate that anthocyanins represent novel neuroprotective agents and may be beneficial in ameliorating ethanol neurotoxicity. In this review, we discuss the evidence and potential of anthocyanins in alleviating ethanol-induced damage to the CNS. Furthermore, we discuss possible underlying mechanisms as well as future research approaches necessary to establish the therapeutic role of anthocyanins.