Ongoing Research on the Role of Gintonin in the Management of Neurodegenerative Disorders

Emerging Pro-neurogenic Therapeutic Strategies for Neurodegenerative Diseases: A Review of Pre-clinical and Clinical Research

The neuroscience community has largely accepted the notion that functional neurons can be generated from neural stem cells in the adult brain, especially in two brain regions: the subventricular zone of the lateral ventricles and the subgranular zone in the dentate gyrus of the hippocampus. However, impaired neurogenesis has been observed in some neurodegenerative diseases, particularly in Alzheimer's, Parkinson's, and Huntington's diseases, and also in Lewy Body dementia. Therefore, restoration of neurogenic function in neurodegenerative diseases emerges as a potential therapeutic strategy to counteract, or at least delay, disease progression. Considering this, the present study summarizes the different neuronal niches, provides a collection of the therapeutic potential of different pro-neurogenic strategies in pre-clinical and clinical research, providing details about their possible modes of action, to guide future research and clinical practice.

Atypical formations of gintonin lysophosphatidic acids as new materials and their beneficial effects on degenerative diseases

Fresh ginseng is prone to spoilage due to its high moisture content. For long-term storage, most fresh ginsengs are dried to white ginseng (WG) or steamed for hours at high temperature/pressure and dried to form Korean Red ginseng (KRG). They are further processed for ginseng products when subjected to hot water extraction/concentration under pressure. These WG or KRG preparation processes affect ginsenoside compositions and also other ginseng components, probably during treatments like steaming and drying, to form diverse bioactive phospholipids. It is known that ginseng contains high amounts of gintonin lysophosphatidic acids (LPAs). LPAs are simple lipid-derived growth factors in animals and humans and act as exogenous ligands of six GTP-binding-protein coupled LPA receptor subtypes. LPAs play diverse roles ranging from brain development to hair growth in animals and humans. LPA-mediated signaling pathways involve various GTP-binding proteins to regulate downstream pathways like [Ca2+]i transient induction. Recent studies have shown that gintonin exhibits anti-Alzheimer's disease and anti-arthritis effects in vitro and in vivo mediated by gintonin LPAs, the active ingredients of gintonin, a ginseng-derived neurotrophin. However, little is known about how gintonin LPAs are formed in high amounts in ginseng compared to other herbs. This review introduces atypical or non-enzymatic pathways under the conversion of ginseng phospholipids into gintonin LPAs during steaming and extraction/concentration processes, which exert beneficial effects against degenerative diseases, including Alzheimer's disease and arthritis in animals and humans via LPA receptors.

Neuroprotective evaluation of diospyrin against drug-induced Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease linked to memory impairment. A current investigation was performed to assess the neuroprotective effect of Diospyrin, a novel therapeutic agent, for the curing of Alzheimer's disease. For this purpose, in-vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory assays and antioxidant studies were conducted, whereas in-vivo studies involved different behavioral animal models tests such as elevated plus maze (EPM), morris water maze (MWM) and paddling Y-maze test. Results of the in-vitro analysis showed IC50 values of 95 μg/mL for AChE and 110 μg/mL for BChE as compared to the standard drug donepezil (IC50: 95 & 85 μg/mL, respectively). DPPH antioxidant assay showed a maximum of 72.85% inhibition (IC50: 139.74 μg/mL) of DPPH-free radicals at the highest concentration of 1000 μg/mL as compared to the ascorbic acid (IC50: 13.72 μg/mL). Moreover, the in-vivo analysis revealed that diospyrin treatment demonstrated gradual betterment in memory and enhanced motor functionality. On the other hand, the computational analysis also showed that the diospyrin had exceptional binding affinities for both AChE and BChE enzymes. In the net shell, it may be deduced that our compound diospyrin could be a valuable drug candidate in managing neurodegenerative disorders like AD.

Social avoidance and altered hypothalamic-pituitary-adrenal axis in a mouse model of anxious depression: The role of LPA1 receptor

Anxious depression is a prevalent disease with devastating consequences. Despite the lack of knowledge about the neurobiological basis of this subtype of depression, recently our group has identified a relationship between the LPA1 receptor, one of the six characterized G protein-coupled receptors (LPA1-6) for lysophosphatidic acid, with a mixed depressive-anxiety phenotype. Dysfunctional social behaviors, which have been related to increased activation of the hypothalamus-pituitary-adrenal (HPA) axis, are key symptoms of depression and are even more prominent in patients with comorbid anxiety and depressive disorders. Social behavior and HPA functioning were assessed in animals lacking the LPA1 receptor. For these purposes, we first examined social behaviors in wild-type and LPA1 receptor-null mice. In addition, a dexamethasone (DEX) suppression test was carried out. maLPA1-null mice exhibited social avoidance, a blunted response to DEX administration and an impaired circadian rhythm of corticosterone levels, which are features that are consistently dysregulated in many mental illnesses including anxious depression. Here, we have strengthened the previous experimental evidence for maLPA1-null mice to represent a good animal model of anxious depression, providing an opportunity to explore new therapeutic targets for the treatment of mood disorders, particularly this subtype of depression.

Caffeic Acid, a Polyphenolic Micronutrient Rescues Mice Brains against Aβ-Induced Neurodegeneration and Memory Impairment

Oxidative stress plays an important role in cognitive dysfunctions and is seen in neurodegeneration and Alzheimer's disease (AD). It has been reported that the polyphenolic compound caffeic acid possesses strong neuroprotective and antioxidant effects. The current study was conducted to investigate the therapeutic potential of caffeic acid against amyloid beta (Aβ_1-42)-induced oxidative stress and memory impairments. Aβ_1-42 (5 μL/5 min/mouse) was administered intracerebroventricularly (ICV) into wild-type adult mice to induce AD-like pathological changes. Caffeic acid was administered orally at 50 mg/kg/day for two weeks to AD mice. Y-maze and Morris water maze (MWM) behavior tests were conducted to assess memory and cognitive abilities. Western blot and immunofluorescence analyses were used for the biochemical analyses. The behavioral results indicated that caffeic acid administration improved spatial learning, memory, and cognitive abilities in AD mice. Reactive oxygen species (ROS) and lipid peroxidation (LPO) assays were performed and showed that the levels of ROS and LPO were markedly reduced in the caffeic acid-treated mice, as compared to Aβ-induced AD mice brains. Moreover, the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were regulated with the administration of caffeic acid, compared to the Aβ-injected mice. Next, we checked the expression of ionized calcium-binding adaptor molecule 1 (Iba-1), glial fibrillary acidic proteins (GFAP), and other inflammatory markers in the experimental mice, which suggested enhanced expression of these markers in AD mice brains, and were reduced with caffeic acid treatment. Furthermore, caffeic acid enhanced synaptic markers in the AD mice model. Additionally, caffeic acid treatment also decreased Aβ and BACE-1 expression in the Aβ-induced AD mice model.

Zinc Ortho Methyl Carbonodithioate Improved Pre and Post-Synapse Memory Impairment via SIRT1/p-JNK Pathway against Scopolamine in Adult Mice

Alzheimer's disease (AD) is globally recognized as a prominent cause of dementia for which efficient treatment is still lacking. New candidate compounds that are biologically potent are regularly tested. We, therefore, hypothesized to study the neuroprotective potential of Zinc Ortho Methyl Carbonodithioate (thereafter called ZOMEC) against Scopolamine (SCOP) induced Alzheimer's disease (AD) model using adult albino mice. We post-administered ZOMEC (30 mg/Kg) into two group of mice for three weeks on daily basis that received either 0.9% saline or SCOP (1 mg/Kg) for initial two weeks. The other two groups of mice received 0.9% saline and SCOP (1 mg/Kg) respectively. After memory related behavioral analysis the brain homogenates were evaluated for the antioxidant potential of ZOMEC and multiple protein markers were examined through western blotting. Our results provide enough evidences that ZOMEC decrease oxidative stress by increasing catalase (CAT) and glutathione S transferase (GST) and decreasing the lipid peroxidation (LPO). The SIRT1 and pre and post synaptic marker proteins, synaptophysin (SYP) as well as post synaptic density protein (PSD-95) expression were also enhanced upon ZOMEC treatment. Furthermore, memory impairment was rescued and ZOMEC appreciably abrogated the Aβ accumulation, BACE1 expression C and the p-JNK pathway. The inflammatory protein markers, NF-kβ and IL-1β in ZOMEC treated mice were also comparable with control group. The predicted interaction of ZOMEC with SIRT1 was further confirmed by molecular docking. These findings thus provide initial reports on efficacy of ZOMEC in SCOP induced AD model.

Gintonin Isolated from Ginseng Inhibits the Epithelial-Mesenchymal Transition Induced by TGF-β in A549 Lung Cancer Cells

Epithelial-to-mesenchymal transition (EM transition) is a process wherein epithelial cells lose their intrinsic characteristics and cell-cell junctions and differentiate into a mesenchymal phenotype. EM transition is an important feature of cancer invasion and metastasis. In this study, we aimed to investigate the inhibitory effect of gintonin (GT), an ingredient of ginseng, on EM transition using A549 cells. The proliferation of A549 cells was enhanced following treatment with 50, 75, and 100 μg/mL of GT. GT affected EM transition-induced gene and protein expression, specifically that of vimentin (Vim), N-cadherin (N-cad), zinc finger E-box-binding homeobox 1, and Twist in A549 cells. Furthermore, the transforming growth factor beta 1 (TGF-β1)-induced phosphorylation of Smad2 and Smad3 was suppressed by GT treatment. Immunofluorescence staining also showed that GT treatment decreased the TGF-β1-induced expression of Vim and N-cad in A549 cells. Therefore, GT may be used to suppress cancer cell metastasis via maintenance of the cell-cell junction's integrity. However, further studies are required to pave the way for its translation into clinical application in cancer therapeutics.

Efforts Towards Repurposing of Antioxidant Drugs and Active Compounds for Multiple Sclerosis Control

Multiple Sclerosis (MS) is a degenerative disorder of the central nervous system (CNS) with complicated etiology that has not been clearly analyzed until nowadays. Apart from anti-inflammatory, immune modulatory and symptomatic treatments, which are the main tools towards MS control, antioxidant molecules may be of interest. Oxidative stress is a key condition implicated in the disease progression. Reactive species production is associated with immune cell activation in the brain as well as in the periphery, accounting for demyelinating and axonal disruptive processes. This review refers to research articles, of the last decade. It describes biological evaluation of antioxidant drugs, and molecules with pharmaceutical interest, which are not designed for MS treatment, however they seem to have potency against MS. Their antioxidant effect is accompanied, in most of the cases, by anti-inflammatory, immune-modulatory and neuroprotective properties. Compounds with such characteristics are expected to be beneficial in the treatment of MS, alone or as complementary therapy, improving some clinical and mechanistic aspects of the disease. This review also summarizes some of the pathobiological characteristics of MS, as well as the role of oxidative stress and inflammation in the progression of neurodegeneration. It presents known drugs and bioactive compounds with antioxidant, and in many cases, pleiotropic activity that have been tested for their efficacy in MS progression or the experimentally induced MS. Antioxidants may offer reduction or prevention of the disease symptoms and progression. Thus, their results may, combined with already applied treatments, be beneficial for the development of new molecules or the repurposing of drugs and supplements that are used with other indication so far.

The Emerging Landscape of Natural Small-molecule Therapeutics for Huntington's Disease

Huntington's disease (HD) is a rare and fatal neurodegenerative disorder with no diseasemodifying therapeutics. HD is characterized by extensive neuronal loss and is caused by the inherited expansion of the huntingtin (HTT) gene that encodes a toxic mutant HTT (mHTT) protein having expanded polyglutamine (polyQ) residues. Current HD therapeutics only offer symptomatic relief. In fact, Food and Drug Administration (FDA) approved two synthetic small-molecule VMAT2 inhibitors, tetrabenazine (1) and deutetrabenazine (2), for managing HD chorea and various other diseases in clinical trials. Therefore, the landscape of drug discovery programs for HD is evolving to discover disease- modifying HD therapeutics. Likewise, numerous natural products are being evaluated at different stages of clinical development and have shown the potential to ameliorate HD pathology. The inherent anti-inflammatory and antioxidant properties of natural products mitigate the mHTT-induced oxidative stress and neuroinflammation, improve mitochondrial functions, and augment the anti-apoptotic and pro-autophagic mechanisms for increased survival of neurons in HD. In this review, we have discussed HD pathogenesis and summarized the anti-HD clinical and pre-clinical natural products, focusing on their therapeutic effects and neuroprotective mechanism/s.

GSK-3β-mediated regulation of Nrf2/HO-1 signaling as a new therapeutic approach in the treatment of movement disorders

Movement disorders are neurological conditions characterized by involuntary motor movements, such as dystonia, ataxia, chorea myoclonus, tremors, Huntington's disease (HD), and Parkinson's disease (PD). It is classified into two categories: hypokinetic and hyperkinetic movements. Globally, movement disorders are a major cause of death. The pathophysiological process is initiated by excessive ROS generation, mitochondrial dysfunction, neuroinflammation, and neurotransmitters imbalance that lead to motor dysfunction in PD and HD patients. Several endogenous targets including Nrf2 maintain oxidative balance in the body. Activation of Nrf2 signaling is regulated by the enzyme glycogen synthase kinase (GSK-3β). In the cytoplasm, inhibition of GSK-3β regulates cellular proliferation, homeostasis, and apoptotic process by stimulating the nuclear factor erythroid 2 (Nrf2) pathway which is involved in the elevation of the cellular antioxidant enzymes which controls the ROS generation. The activation of Nrf2 increases the expression of antioxidant response elements (ARE), such as (Hemeoxygenase-1) HO-1, which decreases excessive cellular stress, mitochondrial dysfunction, apoptosis, and neuronal degeneration, which is the major cause of motor dysfunction. The present review explores the GSK-3β-mediated neuroprotection in various movement disorders through the Nrf2/HO-1 antioxidant pathway. This review provides a link between GSK-3β and the Nrf2/HO-1 signaling pathway in the treatment of PD and HD. In addition to that it highlights various GSK-3β inhibitors and the Nrf2/HO-1 activators, which exert robust neuroprotection against motor disorders. Therefore, the present review will help in the discovery of new therapy for PD and HD patients.

Pharmacological Inhibition of Spleen Tyrosine Kinase Suppressed Neuroinflammation and Cognitive Dysfunction in LPS-Induced Neurodegeneration Model

Tyrosine-protein kinase (Syk) plays a potential role in neuroinflammation and adaptive immune responses in several neurodegenerative conditions. Seeing the significant role of Syk in the pathophysiology of neurodegeneration, several pharmacological inhibitors have been developed. One of the known inhibitors of Syk is BAY61-3606, which has shown efficacies in Alzheimer’s disease (AD) through regulating amyloid production. However, little is known about its efficacies in neuroinflammation and neurodegeneration. Our finding showed that Syk expression was up-regulated by lipopolysaccharide (LPS)-dependent manner, and BAY61-3606 significantly suppressed the activated microglia (ionized calcium-binding adaptor molecule 1 [Iba-1]) and the inflammatory cytokines (tumor necrosis factor-alpha [TNF-α], interleukin 1-beta [IL-1β], IL-6) and other inflammatory mediators (nuclear factor kappa B [NF-κB], cyclooxygenase-2 [Cox-2], and inducible nitric axide synthase [iNOS]) in the lipopolysaccharide (LPS)-treated in vivo and in vitro models. Moreover, BAY61-3606 significantly reduced microglia-mediated neuronal cell death by regulating the expression of Cytochrome C and Bim (B-cell lymphoma 2 [BCL-2] interacting mediator of cell death) in the LPS-treated mice brain and HT22 cells. Furthermore, the expression of synaptic markers, synaptosomal-associated protein, 25 kDa (SNAP25), synaptophysin (Syp), and postsynaptic density protein-95 (PSD95) in LPS-challenged mice showed that BAY61-3606 significantly recovered the synaptic markers. Finally, we have analyzed the effects of BAY61-3606 against memory and cognitive dysfunctions in the LPS injected mice. The Y-maze test and Passive avoidance test suggested that BAY61-3606 significantly protected against LPS-induced cognitive and memory dysfunctions. The current findings not only highlight the mechanisms of Syk in the pathophysiology of neuro-inflammation, but also support the therapeutic efficacy of BAY61-3606 in the management of neurodegeneration.

Melatonin as a Potential Regulator of Oxidative Stress, and Neuroinflammation: Mechanisms and Implications for the Management of Brain Injury-Induced Neurodegeneration

This review covers the preclinical and clinical literature supporting the role of melatonin in the management of brain injury-induced oxidative stress, neuroinflammation, and neurodegeneration, and reviews the past and current therapeutic strategies. Traumatic brain injury (TBI) is a neurodegenerative condition, unpredictably and potentially progressing into chronic neurodegeneration, with permanent cognitive, neurologic, and motor dysfunction, having no standard therapies. Due to its complex and multi-faceted nature, the TBI has highly heterogeneous pathophysiology, characterized by the highest mortality and disability worldwide. Mounting evidence suggests that the TBI induces oxidative and nitrosative stress, which is involved in the progression of chronic and acute neurodegenerative diseases. Defenses against such conditions are mostly dependent on the usage of antioxidant compounds, the majority of whom are ingested as nutraceuticals or as dietary supplements. A large amount of literature is available regarding the efficacy of antioxidant compounds to counteract the TBI-associated damage in animal and cellular models of the TBI and several clinical studies. Collectively, the studies have suggested that TBI induces oxidative stress, by suppressing the endogenous antioxidant system, such as nuclear factor erythroid 2–related factor-2 (Nrf-2) increasing the lipid peroxidation and elevation of oxidative damage. Moreover, elevated oxidative stress may induce neuroinflammation by activating the microglial cells, releasing and activating the inflammatory cytokines and inflammatory mediators, and energy dyshomeostasis. Thus, melatonin has shown regulatory effects against the TBI-induced autophagic dysfunction, regulation of mitogen-activated protein kinases, such as ERK, activation of the NLRP-3 inflammasome, and release of the inflammatory cytokines. The collective findings strongly suggest that melatonin may regulate TBI-induced neurodegeneration, although further studies should be conducted to better facilitate future therapeutic windows.

Cycloastragenol, a Triterpenoid Saponin, Regulates Oxidative Stress, Neurotrophic Dysfunctions, Neuroinflammation and Apoptotic Cell Death in Neurodegenerative Conditions

Here, we have unveiled the effects of cycloastragenol against Aβ (Amyloid-beta)-induced oxidative stress, neurogenic dysfunction, activated mitogen-activated protein (MAP) kinases, and mitochondrial apoptosis in an Aβ-induced mouse model of Alzheimer's disease (AD). The Aβ-induced mouse model was developed by the stereotaxic injection of amyloid-beta (5 μg/mouse/intracerebroventricular), and cycloastragenol was given at a dose of 20 mg/kg/day/p.o for 6 weeks daily. For the biochemical analysis, we used immunofluorescence and Western blotting. Our findings showed that the injection of Aβ elevated oxidative stress and reduced the expression of neurogenic markers, as shown by the reduced expression of brain-derived neurotrophic factor (BDNF) and the phosphorylation of its specific receptor tropomyosin receptor kinase B (p-TrKB). In addition, there was a marked reduction in the expression of NeuN (neuronal nuclear protein) in the Aβ-injected mice brains (cortex and hippocampus). Interestingly, the expression of Nrf2 (nuclear factor erythroid 2-related factor 2), HO-1 (heme oxygenase-1), p-TrKB, BDNF, and NeuN was markedly enhanced in the Aβ + Cycloastragenol co-treated mice brains. We have also evaluated the expressions of MAP kinases such as phospho c-Jun-N-terminal kinase (p-JNK), p-38, and phospho-extracellular signal-related kinase (ERK1/2) in the experimental groups, which suggested that the expression of p-JNK, p-P-38, and p-Erk were significantly upregulated in the Aβ-injected mice brains; interestingly, these markers were downregulated in the Aβ + Cycloastragenol co-treated mice brains. We also checked the expression of activated microglia and inflammatory cytokines, which showed that cycloastragenol reduced the activated microglia and inflammatory cytokines. Moreover, we evaluated the effects of cycloastragenol against mitochondrial apoptosis and memory dysfunctions in the experimental groups. The findings showed significant regulatory effects against apoptosis and memory dysfunction as revealed by the Morris water maze (MWM) test. Collectively, the findings suggested that cycloastragenol regulates oxidative stress, neurotrophic processes, neuroinflammation, apoptotic cell death, and memory impairment in the mouse model of AD.

Weighted gene co-expression network analysis identifies specific modules and hub genes related to Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. This study aims to screen specific modules and key genes related to PD.

METHODS

Gene expression profile data GSE6613 and GSE22491 were downloaded from the Gene Expression Omnibus database. The significantly differentially expressed genes (DEGs) in different datasets were screened, followed by gene ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The Weighted Gene Co-expression Network Analysis (WGCNA) was used to screen disease-related modules that are significantly stable across datasets. The protein-protein interaction network was constructed using the DEGs in the stable module obtained and preservation modules. Finally, the hub genes directly related to PD were screened.

RESULTS

A total of 179 DEGs with the same significant difference direction were screened. The enrichment analysis of GO and KEGG pathways showed that 20 significantly related GO biological processes and 9 KEGG signaling pathways were screened. A total of three highly conservative modules were detected in the WGCNA network. Finally, three significant PD-related KEGG pathways screened from the Comparative Toxicogenomics Database were identified, including neuroactive ligand-receptor interaction (CRHR2, CTSG, GRIN1, GRIN2D, LPAR4 and P2RX3), amyotrophic lateral sclerosis (BCL2, GRIN1 and GRIN2D) and alcoholism (CAMKK2, GRIN1, GRIN2D and SLC18A2). Key genes, such as SLC18A2, GRIN1 and GRIN2D, may be potential candidate genes for PD progression.

CONCLUSIONS

Our findings indicate that SLC18A2, GRIN1 and GRIN2D may play an important role in the pathogenesis of PD.

Deciphering the Potential Neuroprotective Effects of Luteolin against Aβ1-42-Induced Alzheimer's Disease

The current study was undertaken to unveil the protective effects of Luteolin, a natural flavonoid, against amyloid-beta (Aβ₁–₄₂)-induced neuroinflammation, amyloidogenesis, and synaptic dysfunction in mice. For the development of an AD mouse model, amyloid-beta (Aβ₁–₄₂, 5 μL/5 min/mouse) oligomers were injected intracerebroventricularly (i.c.v.) into mice’s brain by using a stereotaxic frame. After that, the mice were treated with Luteolin for two weeks at a dose of 80 mg/kg/day. To monitor the biochemical changes, we conducted western blotting and immunofluorescence analysis. According to our findings, the infusion of amyloid-beta activated c-Jun N-terminal kinases (p-JNK), p38 mitogen-activated protein kinases, glial fibrillary acidic protein (GFAP), and ionized calcium adaptor molecule 1 (Iba-1) in the cortex and hippocampus of the experimental mice; these changes were significantly inhibited in Aβ₁–₄₂ + Luteolin-treated mice. Likewise, we also checked the expression of inflammatory markers, such as p-nuclear factor-kB p65 (p-NF-kB p65 (Ser536), tissue necrosis factor (TNF-α), and Interleukin1-β (IL-1β), in Aβ₁–₄₂-injected mice brain, which was attenuated in Aβ₁–₄₂ + Luteolin-treated mice brains. Further, we investigated the expression of pro- and anti-apoptotic cell death markers such as Bax, Bcl-2, Caspase-3, and Cox-2, which was significantly reduced in Aβ₁–₄₂ + Lut-treated mice brains compared to the brains of the Aβ-injected group. The results also indicated that with the administration of Aβ₁–₄₂, the expression levels of β-site amyloid precursor protein cleaving enzyme (BACE-1) and amyloid-beta (Aβ₁–₄₂) were significantly enhanced, while they were reduced in Aβ₁–₄₂ + Luteolin-treated mice. We also checked the expression of synaptic markers such as PSD-95 and SNAP-25, which was significantly enhanced in Aβ₁–₄₂ + Lut-treated mice. To unveil the underlying factors responsible for the protective effects of Luteolin against AD, we used a specific JNK inhibitor, which suggested that Luteolin reduced Aβ-associated neuroinflammation and neurodegeneration via inhibition of JNK. Collectively, our results indicate that Luteolin could serve as a novel therapeutic agent against AD-like pathological changes in mice.

Antioxidative and Anti-inflammatory Effects of Kojic Acid in Aβ-Induced Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a common cause of dementia that is clinically characterized by the loss of memory and cognitive functions. Currently, there is no specific cure for the management of AD, although natural compounds are showing promising therapeutic potentials because of their safety and easy availability. Herein, we evaluated the neuroprotective properties of kojic acid (KA) in an AD mouse model. Intracerebroventricular injection (i.c.v) of Aβ_1-42 (5 μL/5 min/mouse) into wild-type adult mice induced AD-like pathological changes in the mouse hippocampus by increasing oxidative stress and neuroinflammation, affecting memory and cognitive functions. Interestingly, oral treatment of kojic acid (50 mg/kg/mouse for 3 weeks) reversed the AD pathology by reducing the expression of amyloid-beta (Aβ) and beta-site amyloid precursor protein cleaving enzyme1 (BACE-1). Moreover, kojic acid reduced oxidative stress by enhancing the expression of nuclear factor erythroid-related factor 2 (Nrf2) and heme oxygenase 1 (HO1). Also, kojic acid reduced the lipid peroxidation and reactive oxygen species in the Aβ + kojic acid co-treated mice brains. Moreover, kojic acid decreased neuroinflammation by inhibiting Toll-like receptor 4, phosphorylated nuclear factor-κB, tumor necrosis factor-alpha, interleukin 1-beta (TLR-4, p-NFκB, TNFα, and IL-1β, respectively), and glial cells. Furthermore, kojic acid enhanced synaptic markers (SNAP-23, SYN, and PSD-95) and memory functions in AD model mice. Additionally, kojic acid treatment also decreased Aβ expression, oxidative stress, and neuroinflammation in vitro in HT-22 mouse hippocampal cells. To the best of our knowledge, this is the first study to show the neuroprotective effects of kojic acid against an AD mouse model. Our findings could serve as a favorable and alternative strategy for the discovery of novel drugs to treat AD-related neurodegenerative conditions.

Role of Plant-Derived Natural Compounds in Experimental Autoimmune Encephalomyelitis: A Review of the Treatment Potential and Development Strategy

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system that is mainly mediated by pathological T-cells. Experimental autoimmune encephalomyelitis (EAE) is a well-known animal model of MS that is used to study the underlying mechanism and offers a theoretical basis for developing a novel therapy for MS. Good therapeutic effects have been observed after the administration of natural compounds and their derivatives as treatments for EAE. However, there has been a severe lag in the research and development of drug mechanisms related to MS. This review examines natural products that have the potential to effectively treat MS. The relevant data were consulted in order to elucidate the regulated mechanisms acting upon EAE by the flavonoids, glycosides, and triterpenoids derived from natural products. In addition, novel technologies such as network pharmacology, molecular docking, and high-throughput screening have been gradually applied in natural product development. The information provided herein can help improve targeting and timeliness for determining the specific mechanisms involved in natural medicine treatment and lay a foundation for further study.

Neuroprotective Potentials of Panax Ginseng Against Alzheimer's Disease: A Review of Preclinical and Clinical Evidences

Alzheimer's disease (AD), a neurodegenerative disorder, is a major health concern in the increasingly aged population worldwide. Currently, no clinically effective drug can halt the progression of AD. Panax ginseng C.A. Mey. is a well-known medicinal plant that contains ginsenosides, gintonin, and other components and has neuroprotective effects against a series of pathological cascades in AD, including beta-amyloid formation, neuroinflammation, oxidative stress, and mitochondrial dysfunction. In this review, we summarize the effects and mechanisms of these major components and formulas containing P. ginseng in neuronal cells and animal models. Moreover, clinical findings regarding the prevention and treatment of AD with P. ginseng or its formulas are discussed. This review can provide new insights into the possible use of ginseng in the prevention and treatment of AD.

Guiding the Patterned Growth of Neuronal Axons and Dendrites Using Anisotropic Micropillar Scaffolds

The patterning of axonal and dendritic growth is an important topic in neural tissue engineering and critical for generating directed neuronal networks in vitro. Evidence shows that artificial micro/nanotopography can better mimic the environment for neuronal growth in vivo. However, the potential mechanisms by which neurons interact with true three dimensional (3D) topographical cues and form directional networks are unclear. Herein, 3D micropillar scaffolds are designed to guide the growth of neural stem cells and hippocampal neurons in vitro. Discontinuous and anisotropic micropillars are fabricated by femtosecond direct laser writing to form patterned scaffolds with various spacings and heights, which are found to affect the branching and orientation of axons and dendrites. Interestingly, axons and dendrites tend to grow on an array of 3D micropillar scaffolds of the same height and form functionally connected neuronal networks, as reflected by synchronous neuronal activity visualized by calcium imaging. This method may represent a promising tool for studying neuron behavior and directed neuronal networks in a 3D environment.

Oral Administration of Gintonin Protects the Brains of Mice against Aβ-Induced Alzheimer Disease Pathology: Antioxidant and Anti-Inflammatory Effects

The study was aimed at analyzing the protective effects of gintonin in an amyloid beta- (Aβ-) induced Alzheimer's disease (AD) mouse model. For the development of the Aβ-induced AD mouse model, the amyloid-β (Aβ 1-42) peptide was stereotaxically injected into the brains of mice. Subsequently, gintonin was administered at a dose of 100 mg/kg/day/per oral (p.o) for four weeks daily, and its effects were evaluated by using western blotting, fluorescence analysis of brain sections, biochemical tests, and memory-related behavioral evaluations. To elucidate the effects of gintonin at the mechanistic level, the activation of endogenous antioxidant mechanisms, as well as the activation of astrocytes, microglia, and proinflammatory mediators such as nuclear factor erythroid 2-related factor 2 (NRF-2) and heme oxygenase-1 (HO-1), was evaluated. In addition, microglial cells (BV-2 cells) were used to analyze the effects of gintonin on microglial activation and signaling mechanisms. Collectively, the results suggested that gintonin reduced elevated oxidative stress by improving the expression of NRF-2 and HO-1 and thereby reducing the generation of reactive oxygen species (ROS) and lipid peroxidation (LPO). Moreover, gintonin significantly suppressed activated microglial cells and inflammatory mediators in the brains of Aβ-injected mice. Our findings also indicated improved synaptic and memory functions in the brains of Aβ-injected mice after treatment with gintonin. These results suggest that gintonin may be effective for relieving AD symptoms by regulating oxidative stress and inflammatory processes in a mouse model of AD. Collectively, the findings of this preclinical study highlight and endorse the potential, multitargeted protective effects of gintonin against AD-associated oxidative damage, neuroinflammation, cognitive impairment, and neurodegeneration.

Pathology, Risk Factors, and Oxidative Damage Related to Type 2 Diabetes-Mediated Alzheimer's Disease and the Rescuing Effects of the Potent Antioxidant Anthocyanin

The pathology and neurodegeneration in type 2 diabetes- (T2D-) mediated Alzheimer's disease (AD) have been reported in several studies. Despite the lack of information regarding the basic underlying mechanisms involved in the development of T2D-mediated AD, some common features of the two conditions have been reported, such as brain atrophy, reduced cerebral glucose metabolism, and insulin resistance. T2D phenotypes such as glucose dyshomeostasis, insulin resistance, impaired insulin signaling, and systemic inflammatory cytokines have been shown to be involved in the progression of AD pathology by increasing amyloid-beta accumulation, tau hyperphosphorylation, and overall neuroinflammation. Similarly, oxidative stress, mitochondrial dysfunction, and the generation of advanced glycation end products (AGEs) and their receptor (RAGE) as a result of chronic hyperglycemia may serve as critical links between diabetes and AD. The natural dietary polyflavonoid anthocyanin enhances insulin sensitivity, attenuates insulin resistance at the level of the target tissues, inhibits free fatty acid oxidation, and abrogates the release of peripheral inflammatory cytokines in obese (prediabetic) individuals, which are responsible for insulin resistance, systemic hyperglycemia, systemic inflammation, brain metabolism dyshomeostasis, amyloid-beta accumulation, and neuroinflammatory responses. In this review, we have shown that obesity may induce T2D-mediated AD and assessed the recent therapeutic advances, especially the use of anthocyanin, against T2D-mediated AD pathology. Taken together, the findings of current studies may help elucidate a new approach for the prevention and treatment of T2D-mediated AD by using the polyflavonoid anthocyanin.

Fisetin Rescues the Mice Brains Against D-Galactose-Induced Oxidative Stress, Neuroinflammation and Memory Impairment

Herein, we have evaluated the protective potentials of Fisetin against d-galactose-induced oxidative stress, neuroinflammation, and memory impairment in mice. d-galactose (D-gal) causes neurological impairment by inducing reactive oxygen species (ROS), neuroinflammation, and synaptic dysfunction, whereas fisetin (Fis) is a natural flavonoid having potential antioxidant effects, and has been used against different models of neurodegenerative diseases. Here, the normal mice were injected with D-gal (100 mg/kg/day for 60 days) and fisetin (20 mg/kg/day for 30 days). To elucidate the protective effects of fisetin against d-galactose induced oxidative stress-mediated neuroinflammation, we conducted western blotting, biochemical, behavioral, and immunofluorescence analyses. According to our findings, D-gal induced oxidative stress, neuroinflammation, synaptic dysfunctions, and cognitive impairment. Conversely, Fisetin prevented the D-gal-mediated ROS accumulation, by regulating the endogenous anti-oxidant mechanisms, such as Sirt1/Nrf2 signaling, suppressed the activated p-JNK/NF-kB pathway, and its downstream targets, such as inflammatory cytokines. Hence, our results together with the previous reports suggest that Fisetin may be beneficial in age-related neurological disorders.

Chinese nutraceuticals and physical activity; their role in neurodegenerative tauopathies

The onset of neurodegenerative disease has not only been a major cause of scientific worry, but of economic burden to the health system. This condition has been further attributed to mis-stability, deletion or mutation of tau protein, causing the onset of Corticobasal degeneration, Pick's diseases, Progressive supranuclear palsy, Argyrophilic grains disease, Alzheimer's diseases etc. as scientifically renowned. This is mainly related to dysregulation of translational machinery, upregulation of proinflammatory cytokines and inhibition of several essential cascades such as ERK signaling cascade, GSK3β, CREB, and PKA/PKB (Akt) signaling cascades that enhances protein processing, normal protein folding, cognitive function, and microtubule associated tau stability. Administration of some nutrients and/or bioactive compounds has a high tendency to impede tau mediated inflammation at neuronal level. Furthermore, prevention and neutralization of protein misfolding through modulation of microtubule tau stability and prevention of protein misfolding is by virtue few of the numerous beneficial effects of physical activity. Of utmost important in this study is the exploration of promising bioactivities of nutraceuticals found in china and the ameliorating potential of physical activity on tauopathies, while highlighting animal and in vitro studies that have been investigated for comprehensive understanding of its potential and an insight into the effects on human highly probable to tau mediated neurodegeneration.

Antioxidant and Neuroprotective Effects of Caffeine against Alzheimer's and Parkinson's Disease: Insight into the Role of Nrf-2 and A2AR Signaling

This paper reviews the results of studies conducted on the role of caffeine in the management of different neurological disorders, such as Parkinson's disease (PD) and Alzheimer's disease (AD). To highlight the potential role of caffeine in managing different neurodegenerative diseases, we identified studies by searching PubMed, Web of Science, and Google Scholar by scrutinizing the lists of pertinent publications. According to the collected overall findings, caffeine may reduce the elevated oxidative stress; inhibit the activation of adenosine A2A, thereby regulating the accumulation of Aβ; reduce the hyperphosphorylation of tau; and reduce the accumulation of misfolded proteins, such as α-synuclein, in Alzheimer's and Parkinson's diseases. The studies have suggested that caffeine has promising protective effects against different neurodegenerative diseases and that these effects may be used to tackle the neurological diseases and/or their consequences. Here, we review the ongoing research on the role of caffeine in the management of different neurodegenerative disorders, focusing on AD and PD. The current findings suggest that caffeine produces potent antioxidant, inflammatory, and anti-apoptotic effects against different models of neurodegenerative disease, including AD, PD, and other neurodegenerative disorders. Caffeine has shown strong antagonistic effects against the adenosine A2A receptor, which is a microglial receptor, and strong agonistic effects against nuclear-related factor-2 (Nrf-2), thereby regulating the cellular homeostasis at the brain by reducing oxidative stress, neuroinflammation, regulating the accumulation of α-synuclein in PD and tau hyperphosphorylation, amyloidogenesis, and synaptic deficits in AD, which are the cardinal features of these neurodegenerative diseases.

Antioxidant and Anti-Inflammatory Effects of Citrus Flavonoid Hesperetin: Special Focus on Neurological Disorders

Neurodegenerative disorders have emerged as a serious health issue in the current era. The most common neurodegenerative disorders are Alzheimer's disease (AD), Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis (ALS). These diseases involve progressive impairment of neurodegeneration and memory impairment. A wide range of compounds have been identified as potential neuroprotective agents against different models of neurodegeneration both in vivo and in vitro. Hesperetin, a flavanone class of citrus flavonoid, is a derivative of hesperidin found in citrus fruits such as oranges, grapes, and lemons. It has been extensively reported that hesperetin exerts neuroprotective effects in experimental models of neurodegenerative diseases. In this systematic review, we have compiled all the studies conducted on hesperetin in both in vivo and in vitro models of neurodegeneration. Here, we have used an approach to lessen the bias in each study, providing a least biased, broad understanding of findings and impartial conclusions of the strength of evidence and the reliability of findings. In this review, we collected different papers from a wide range of journals describing the beneficial effects of hesperetin on animal models of neurodegeneration. Our results demonstrated consistent neuroprotective effects of hesperetin against different models of neurodegeneration. In addition, we have summarized its underlying mechanisms. This study provides the foundations for future studies and recommendations of further mechanistic approaches to conduct preclinical studies on hesperetin in different models.