Counteracting role of nuclear factor erythroid 2-related factor 2 pathway in Alzheimer's disease

Mechanistic insights on TLR-4 mediated inflammatory pathway in neurodegenerative diseases

Neurodegenerative diseases (NDDs) pose a significant issue in healthcare, needing a thorough knowledge of their complex molecular mechanisms. A diverse set of cell signaling mediators and their interactions play critical roles in neuroinflammation. The release of pro-inflammatory mediators in response to neural dysfunction is detrimental to normal cell survival. Moreover, the important role of nuclear factor-κB (NF-κB) in the central nervous system through Toll-like receptor (TLR) activation has been well established. Therefore, through a comprehensive review of current research and experimentation, this investigation elucidates the interactions between novel pharmacological agents (TLR-4/NF-κB inhibitors) and neurodegeneration encompassing Alzheimer's, Parkinson's, Huntington's disease, amyotrophic lateral sclerosis and stroke. Insights garnered from this exploration underscore the potential of TLR-4 as a therapeutic target. Through the revelation of these insights, our aim is to establish a foundation for the development of enhanced and focused therapeutic approaches in the continuous endeavor to combat neurodegeneration. This review thus serves as a roadmap, guiding future research endeavors toward innovative strategies for combatting the complex interplay between TLR-4 signaling and NDDs.

E3 ligases and DUBs target ferroptosis: A potential therapeutic strategy for neurodegenerative diseases

Ferroptosis is a form of cell death mediated by iron and lipid peroxidation (LPO). Recent studies have provided compelling evidence to support the involvement of ferroptosis in the pathogenesis of various neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD), Parkinson's disease (PD). Therefore, understanding the mechanisms that regulate ferroptosis in NDDs may improve disease management. Ferroptosis is regulated by multiple mechanisms, and different degradation pathways, including autophagy and the ubiquitinproteasome system (UPS), orchestrate the complex ferroptosis response by directly or indirectly regulating iron accumulation or lipid peroxidation. Ubiquitination plays a crucial role as a protein posttranslational modification in driving ferroptosis. Notably, E3 ubiquitin ligases (E3s) and deubiquitinating enzymes (DUBs) are key enzymes in the ubiquitin system, and their dysregulation is closely linked to the progression of NDDs. A growing body of evidence highlights the role of ubiquitin system enzymes in regulating ferroptosis sensitivity. However, reports on the interaction between ferroptosis and ubiquitin signaling in NDDs are scarce. In this review, we first provide a brief overview of the biological processes and roles of the UPS, summarize the core molecular mechanisms and potential biological functions of ferroptosis, and explore the pathophysiological relevance and therapeutic implications of ferroptosis in NDDs. In addition, reviewing the roles of E3s and DUBs in regulating ferroptosis in NDDs aims to provide new insights and strategies for the treatment of NDDs. These include E3- and DUB-targeted drugs and ferroptosis inhibitors, which can be used to prevent and ameliorate the progression of NDDs.

Effect of total flavonoids of Dracocephalum moldavica L. On neuroinflammation in Alzheimer's disease model amyloid-β (Aβ1-42)-peptide-induced astrocyte activation

One of the main pathological features noted in Alzheimer's disease (AD) is the presence of plagues of aggregated β-amyloid (Aβ1-42)-peptides. Excess deposition of amyloid-β oligomers (AβO) are known to promote neuroinflammation. Sequentially, following neuroinflammation astrocytes become activated with cellular characteristics to initiate activated astrocytes. The purpose of this study was to determine whether total flavonoids derived from Dracocephalum moldavica L. (TFDM) inhibited Aβ1-42-induced damage attributed to activated C8-D1A astrocytes. Western blotting and ELISA were used to determine the expression of glial fibrillary acidic protein (GFAP), and complement C3 to establish the activation status of astrocytes following induction from exposure to Aβ1-42. Data demonstrated that stimulation of C8-D1A astrocytes by treatment with 40 μM Aβ1-42 for 24 hr produced significant elevation in protein expression and protein levels of acidic protein (GFAP) and complement C3 accompanied by increased expression and levels of inflammatory cytokines. Treatment with TFDM or the clinically employed drug donepezil in AD therapy reduced production of inflammatory cytokines, and toxicity initiated following activation of C8-D1A astrocytes following exposure to Aβ1-42. Therefore, TFDM similar to donepezil inhibited inflammatory secretion in reactive astrocytes, suggesting that TFDM may be considered as a potential compound to be utilized in AD therapy.

Cucurbitacin B attenuates osteoarthritis development by inhibiting NLRP3 inflammasome activation and pyroptosis through activating Nrf2/HO-1 pathway

Osteoarthritis (OA) is a complicated joint disorder characterized by inflammation that causes joint destruction. Cucurbitacin B (CuB) is a naturally occurring triterpenoid compound derived from plants in the Cucurbitaceae family. The aim of this study is to investigate the potential role and mechanisms of CuB in a mouse model of OA. This study identified the key targets and potential pathways of CuB through network pharmacology analysis. In vivo and in vitro studies confirmed the potential mechanisms of CuB in OA. Through network pharmacology, 54 potential targets for CuB in treating OA were identified. The therapeutic potential of CuB is associated with the nod-like receptor pyrin domain 3 (NLRP3) inflammasome and pyroptosis. Molecular docking results indicate a strong binding affinity of CuB to nuclear factor erythroid 2-related factor 2 (Nrf2) and p65. In vitro experiments demonstrate that CuB effectively inhibits the expression of pro-inflammatory factors induced by interleukin-1β (IL-1β), including cyclooxygenase-2, inducible nitric oxide synthase, IL-1β, and IL-18. CuB inhibits the degradation of type II collagen and aggrecan in the extracellular matrix (ECM), as well as the expression of matrix metalloproteinase-13 and a disintegrin and metalloproteinase with thrombospondin motifs-5. CuB protects cells by activating the Nrf2/hemeoxygenase-1 (HO-1) pathway and inhibiting nuclear factor-κB (NF-κB)/NLRP3 inflammasome-mediated pyroptosis. Moreover, in vivo experiments show that CuB can slow down cartilage degradation in an OA mouse model. CuB effectively prevents the progression of OA by inhibiting inflammation in chondrocytes and ECM degradation. This action is further mediated through the activation of the Nrf2/HO-1 pathway to inhibit NF-κB/NLRP3 inflammasome activation. Thus, CuB is a potential therapeutic agent for OA.

Integrating Multi-omics Data for Alzheimer's Disease to Explore Its Biomarkers Via the Hypergraph-Regularized Joint Deep Semi-Non-Negative Matrix Factorization Algorithm

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder. Its etiology may be associated with genetic, environmental, and lifestyle factors. With the advancement of technology, the integration of genomics, transcriptomics, and imaging data related to AD allows simultaneous exploration of molecular information at different levels and their interaction within the organism. This paper proposes a hypergraph-regularized joint deep semi-non-negative matrix factorization (HR-JDSNMF) algorithm to integrate positron emission tomography (PET), single-nucleotide polymorphism (SNP), and gene expression data for AD. The method employs matrix factorization techniques to nonlinearly decompose the original data at multiple layers, extracting deep features from different omics data, and utilizes hypergraph mining to uncover high-order correlations among the three types of data. Experimental results demonstrate that this approach outperforms several matrix factorization-based algorithms and effectively identifies multi-omics biomarkers for AD. Additionally, single-cell RNA sequencing (scRNA-seq) data for AD were collected, and genes within significant modules were used to categorize different types of cell clusters into high and low-risk cell groups. Finally, the study extensively explores the differences in differentiation and communication between these two cell types. The multi-omics biomarkers unearthed in this study can serve as valuable references for the clinical diagnosis and drug target discovery for AD. The realization of the algorithm in this paper code is available at https://github.com/ShubingKong/HR-JDSNMF .

Sirtuin dysregulation in Parkinson's disease: Implications of acetylation and deacetylation processes

Parkinson's disease (PD) is a progressive neurodegenerative condition that primarily affects motor function and is caused by a gradual decline of dopaminergic neurons in the brain's substantia pars compacta (Snpc) region. Multiple molecular pathways are involved in the pathogenesis, which results in impaired cellular functions and neuronal degeneration. However, the role of sirtuins, a type of NAD+-dependent deacetylase, in the pathogenesis of Parkinson's disease has recently been investigated. Sirtuins are essential for preserving cellular homeostasis because they control a number of biological processes, such as metabolism, apoptosis, and DNA repair. This review shed lights on the dysregulation of sirtuin activity in PD, highlighting the role that acetylation and deacetylation processes play in the development of the disease. Key regulators of protein acetylation, sirtuins have been found to be involved in the aberrant acetylation of vital substrates linked to PD pathology when their balance is out of balance. The hallmark characteristics of PD such as neuroinflammation, oxidative stress, and mitochondrial dysfunction have all been linked to the dysregulation of sirtuin expression and activity. Furthermore, we have also explored how the modulators of sirtuins can be a promising therapeutic intervention in the treatment of PD.

The Effect of High-Altitude Hypoxia on Neuropsychiatric Functions

Liu, Bo, Minlan Yuan, Mei Yang, Hongru Zhu, and Wei Zhang. The effect of high-altitude hypoxia on neuropsychiatric functions. High Alt Med Biol. 25:26-41, 2024. Background: In recent years, there has been a growing popularity in engaging in activities at high altitudes, such as hiking and work. However, these high-altitude environments pose risks of hypoxia, which can lead to various acute or chronic cerebral diseases. These conditions include common neurological diseases such as acute mountain sickness (AMS), high-altitude cerebral edema, and altitude-related cerebrovascular diseases, as well as psychiatric disorders such as anxiety, depression, and psychosis. However, reviews of altitude-related neuropsychiatric conditions and their potential mechanisms are rare. Methods: We conducted searches on PubMed and Google Scholar, exploring existing literature encompassing preclinical and clinical studies. Our aim was to summarize the prevalent neuropsychiatric diseases induced by altitude hypoxia, the potential pathophysiological mechanisms, as well as the available pharmacological and nonpharmacological strategies for prevention and intervention. Results: The development of altitude-related cerebral diseases may arise from various pathogenic processes, including neurovascular alterations associated with hypoxia, cytotoxic responses, activation of reactive oxygen species, and dysregulation of the expression of hypoxia inducible factor-1 and nuclear factor erythroid 2-related factor 2. Furthermore, the interplay between hypoxia-induced neurological and psychiatric changes is believed to play a role in the progression of brain damage. Conclusions: While there is some evidence pointing to pathophysiological changes in hypoxia-induced brain damage, the precise mechanisms responsible for neuropsychiatric alterations remain elusive. Currently, the range of prevention and intervention strategies available is primarily focused on addressing AMS, with a preference for prevention rather than treatment.

TFR1 knockdown alleviates iron overload and mitochondrial dysfunction during neural differentiation of Alzheimer's disease-derived induced pluripotent stem cells by interacting with GSK3B

Iron metabolism disorders are implicated in the pathogenesis of Alzheimer's disease (AD). It was previously reported that transferrin receptor (TFR1) expression was upregulated in AD mouse model. However, the precise biological functions of TFR1 in AD progression remains unclear. Herein, we observed a gradual increase in TFR1 protein expression during the differentiation of AD patient-derived induced pluripotent stem cells (AD-iPS). TFR1 knockdown inhibited the protein expression of ferritin and ferritin heavy chain 1 (FTH1), enhanced the expression of ferroportin 1 (FPN1), and decreased intracellular levels of total iron, labile iron, and reactive oxygen species (ROS). Moreover, TFR1 knockdown improved mitochondrial membrane potential (MMP), increased adenosine triphosphate (ATP) content, downregulated mitochondrial fission proteins, and upregulated mitochondrial fusion proteins. TFR1 knockdown alleviated iron overload and mitochondrial dysfunction in neural cells differentiated from AD-iPS, while TFR1 overexpression showed the opposite results. Additionally, TFR1interacted with glycogen synthase kinase 3 beta (GSK3B) and promoted GSK3B expression. GSK3B overexpression reversed the inhibitory effects of TFR1 knockdown on iron overload and mitochondrial dysfunction in AD-iPS differentiated neural cells. In conclusion, TFR1 knockdown alleviated iron overload and mitochondrial dysfunction in neural cells differentiated from AD-iPS by promoting GSK3B expression. Our findings provide a potential therapeutic target for the treatment of AD.

Wnt signalling pathways as mediators of neuroprotective mechanisms: therapeutic implications in stroke

A stroke is a complicated neurological illness that occurs when there is a disruption in the blood flow to the brain. This disruption results in the damage of neurons, which then leads to functional abnormalities. The Wnt signalling pathway, which is already well-known for its important function in development and tissue homeostasis, has recently been recognised as a critical factor in the pathophysiology of stroke. Recent studies have shown the Wnt pathway's roles in stroke-related events. The complex-interactions between the Wnt pathway and stroke emphasising the pathway's contributions to neuro-protection and synaptic plasticity. The Wnt pathway's influence on neuro-genesis and synaptic plasticity underscores its potential for driving stroke recovery and rehabilitation strategies. The current review discusses about the Wnt signalling pathway in brain pathophysiology and stroke with special emphasis on the various pathways involved in the positive and negative modulation of Wnt pathway namely Phosphoinositide 3-kinase (PI3-K), Glycogen synthase kinase-3β (GSK-3β), Mitogen-activated protein kinase (MAPK) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathway.

The Hypoxia Response Pathway: A Potential Intervention Target in Parkinson's Disease?

Parkinson's disease (PD) is a progressive neurodegenerative disorder for which only symptomatic treatments are available. Both preclinical and clinical studies suggest that moderate hypoxia induces evolutionarily conserved adaptive mechanisms that enhance neuronal viability and survival. Therefore, targeting the hypoxia response pathway might provide neuroprotection by ameliorating the deleterious effects of mitochondrial dysfunction and oxidative stress, which underlie neurodegeneration in PD. Here, we review experimental studies regarding the link between PD pathophysiology and neurophysiological adaptations to hypoxia. We highlight the mechanistic differences between the rescuing effects of chronic hypoxia in neurodegeneration and short-term moderate hypoxia to improve neuronal resilience, termed "hypoxic conditioning". Moreover, we interpret these preclinical observations regarding the pharmacological targeting of the hypoxia response pathway. Finally, we discuss controversies with respect to the differential effects of hypoxia response pathway activation across the PD spectrum, as well as intervention dosing in hypoxic conditioning and potential harmful effects of such interventions. We recommend that initial clinical studies in PD should focus on the safety, physiological responses, and mechanisms of hypoxic conditioning, as well as on repurposing of existing pharmacological compounds. © 2023 International Parkinson and Movement Disorder Society.

Targeting protein kinases for the treatment of Alzheimer's disease: Recent progress and future perspectives

Alzheimer's disease (AD) is a serious neurodegenerative disease characterized by memory impairment, mental retardation, impaired motor balance, loss of self-care and even death. Among the complex and diverse pathological changes in AD, protein kinases are deeply involved in abnormal phosphorylation of Tau proteins to form intracellular neuronal fiber tangles, neuronal loss, extracellular β-amyloid (Aβ) deposits to form amyloid plaques, and synaptic disturbances. As a disease of the elderly, the growing geriatric population is directly driving the market demand for AD therapeutics, and protein kinases are potential targets for the future fight against AD. This perspective provides an in-depth look at the role of the major protein kinases (GSK-3β, CDK5, p38 MAPK, ERK1/2, and JNK3) in the pathogenesis of AD. At the same time, the development of different protein kinase inhibitors and the current state of clinical advancement are also outlined.

Major Depressive Disorder and Gut Microbiota: Role of Physical Exercise

Major depressive disorder (MDD) has a high prevalence and is a major contributor to the global burden of disease. This psychiatric disorder results from a complex interaction between environmental and genetic factors. In recent years, the role of the gut microbiota in brain health has received particular attention, and compelling evidence has shown that patients suffering from depression have gut dysbiosis. Several studies have reported that gut dysbiosis-induced inflammation may cause and/or contribute to the development of depression through dysregulation of the gut-brain axis. Indeed, as a consequence of gut dysbiosis, neuroinflammatory alterations caused by microglial activation together with impairments in neuroplasticity may contribute to the development of depressive symptoms. The modulation of the gut microbiota has been recognized as a potential therapeutic strategy for the management of MMD. In this regard, physical exercise has been shown to positively change microbiota composition and diversity, and this can underlie, at least in part, its antidepressant effects. Given this, the present review will explore the relationship between physical exercise, gut microbiota and depression, with an emphasis on the potential of physical exercise as a non-invasive strategy for modulating the gut microbiota and, through this, regulating the gut-brain axis and alleviating MDD-related symptoms.

Amyloid β-Oligomers Inhibit the Nuclear Ca2+ Signals and the Neuroprotective Gene Expression Induced by Gabazine in Hippocampal Neurons

Hippocampal neuronal activity generates dendritic and somatic Ca2+ signals, which, depending on stimulus intensity, rapidly propagate to the nucleus and induce the expression of transcription factors and genes with crucial roles in cognitive functions. Soluble amyloid-beta oligomers (AβOs), the main synaptotoxins engaged in the pathogenesis of Alzheimer's disease, generate aberrant Ca2+ signals in primary hippocampal neurons, increase their oxidative tone and disrupt structural plasticity. Here, we explored the effects of sub-lethal AβOs concentrations on activity-generated nuclear Ca2+ signals and on the Ca2+-dependent expression of neuroprotective genes. To induce neuronal activity, neuron-enriched primary hippocampal cultures were treated with the GABAA receptor blocker gabazine (GBZ), and nuclear Ca2+ signals were measured in AβOs-treated or control neurons transfected with a genetically encoded nuclear Ca2+ sensor. Incubation (6 h) with AβOs significantly reduced the nuclear Ca2+ signals and the enhanced phosphorylation of cyclic AMP response element-binding protein (CREB) induced by GBZ. Likewise, incubation (6 h) with AβOs significantly reduced the GBZ-induced increases in the mRNA levels of neuronal Per-Arnt-Sim domain protein 4 (Npas4), brain-derived neurotrophic factor (BDNF), ryanodine receptor type-2 (RyR2), and the antioxidant enzyme NADPH-quinone oxidoreductase (Nqo1). Based on these findings we propose that AβOs, by inhibiting the generation of activity-induced nuclear Ca2+ signals, disrupt key neuroprotective gene expression pathways required for hippocampal-dependent learning and memory processes.

N-methylpiperazinyl and piperdinylalkyl-O-chalcone derivatives as potential polyfunctional agents against Alzheimer's disease: Design, synthesis and biological evaluation

The series of N-methylpiperazinyl and piperdinylalkyl-O-chalcone derivatives as potential polyfuctional agents against Alzheimer's disease that have been designed, synthesized and then evaluated biologically using in vitro assays for the inhibition of acetylcholinesterase (AChE) activity, AGEs, and free radical formation. The majority of synthesized compounds inhibited AChE & AGEs with additional free radical scavenging activities at nanomolar concentrations. Among these, compound 5k was found to have potent AChE inhibitory activity (IC50  = 11.6 nM), superior than the reference compound donepezil (15.68 nM) along with the good anti-AGEs and free radical formation effect. Its potency was justified by docking studies that revealed its dual binding characteristic with both catalytic active site and peripheral anionic site of AChE, simultaneously. Furthermore, the in vivo evaluation of 5k against streptozotocin (STZ)-induced dementia in rats also showed improvement of memory functions (Morris water maze test) in animals. Also, 5k inhibited STZ-inudced brain AChE activity and oxidative stress which further strengthen the observed in vitro effects. The stability of the ligand-protein complex was then analyzed using a simulation-based interaction protocol. The results revealed that these N-methylpiperazinyl and piperdinylalkyl-O-chalcone derivatives could be considered for potential polyfunctional anti-Alzheimer's molecules.

Anti-Wrinkling Effect of 3,4,5-tri-O-caffeoylquinic Acid from the Roots of Nymphoides peltata through MAPK/AP-1, NF-κB, and Nrf2 Signaling in UVB-Irradiated HaCaT Cells

Nymphoides peltata has been widely used pharmacologically in traditional Chinese medicine to treat heat strangury and polyuria. The aim of this study was to isolate the bioactive components from N. peltata and evaluate their potential use as antioxidant and anti-wrinkle agents. Phytochemical investigation of the methanolic extract of N. peltata roots led to the isolation of 15 compounds (1-15), which were structurally determined as α-spinasterol (1), 3-O-β-D-glucopyranosyl-oleanolic acid 28-O-β-D-glucuronopyranoside (2), 4-hydroxybenzoic acid (3), protocatechuic acid (4), vanillic acid (5), p-coumaric acid (6), caffeic acid (7), ferulic acid (8), neochlorogenic acid (neo-CQA) (9), chlorogenic acid (CQA) (10), cryptochlorogenic acid (crypto-CQA) (11), isochlorogenic acid B (3,4-DCQA) (12), isochlorogenic acid A (3,5-DCQA) (13), isochlorogenic acid C (4,5-DCQA) (14), and 3,4,5-tri-O-caffeoylquinic acid (TCQA) (15). Of these 15 compounds, compound 2 was a new oleanane saponin, the chemical structure of which was characterized by 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data and high-resolution electrospray ionization mass spectrometry (HRESIMS), as well as chemical reaction. Biological evaluation of the isolated compounds revealed that 3,4,5-tri-O-caffeoylquinic acid (TCQA) significantly improved Nrf2 levels in an Nrf2-ARE reporter HaCaT cell screening assay. TCQA was found to potently inhibit the Nrf2/HO-1 pathway and to possess strong anti-wrinkle activity by modulating the MAPK/NF-κB/AP-1 signaling pathway and thus inhibiting MMP-1 synthesis in HaCaT cells exposed to UVB. Our results suggest that TCQA isolated from N. peltata might be useful for developing effective antioxidant and anti-wrinkle agents.

Impact of GSM-EMW exposure on the markers of oxidative stress in fetal rat liver

The current study investigated the effects of 24 h/day prenatal exposure to global system for mobile communication electromagnetic fields (GSM-EMFs), 900 MHZ-induced electromagnetic radiation (EMR), on oxidative stress (OS) status, apoptotic, and inflammatory changes in liver of rats during their fetal development period. Fifty-two Sprague-Dawley pregnant rats were equally divided into control and exposed groups. Whole embryos were removed at 7.5 dpc (days post coitus), while liver tissues were extracted from embryos at 11.5, 15.5, and 19.5 dpc. For exposed animals, results showed an increased OS reflected by high levels of malondialdehyde (MDA), a decrease in cytosolic superoxide dismutase (cytoSOD) activity, in mitochondrial superoxide dismutase (mitoSOD) levels and catalase (CAT) mRNA expression but also in hepatic nuclear factor erythroïd 2-related Factor 2 (Nrf-2), protein kinase B (Akt1), and intercellular adhesion molecule-1 (ICAM-1) mRNA expression at 15.5 dpc. Moreover, GSM-EMR exposure was shown to significantly decrease mitoSOD and CAT activities at almost all studied ages. Thus, rat embryos may be protected by their mothers from OS, apoptotic, and pro-inflammatory responses till a sensitive developmental stage, during a continuous prenatal EMR exposure. This protection could be then created from the embryos themselves.

The Regulatory Effects of JAK2/STAT3 on Spermatogenesis and the Redox Keap1/Nrf2 Axis in an Animal Model of Testicular Ischemia Reperfusion Injury

The male reproductive system requires the pleiotropic activity of JAK/STAT to maintain its function, especially spermatogenesis. The study aims to investigate the effect of JAK2 signaling on the expression of the Keap1/Nrf2 axis, spermatogenesis, and the Sertoli cells (Sc) junctions in an animal model of testicular ischemia reperfusion injury (tIRI). Testes subjected to tIRI exhibited increased JAK2/STAT3 activity associated with spermatogenic arrest and reduced expression of the Sc junctions. In addition, there was an increased protein expression of Keap1 and decreased Nrf2., which was coupled with the downregulation of gene expression of antioxidant enzymes. Reduced SOD and CAT activities were accompanied by increased lipid peroxidation and protein carbonylation during tIRI. Increased caspase 9 activity and Bax/Bcl2 ratio indicated initiation of apoptosis. Inhibition of JAK2 activity by AG490 maintained the integrity of spermatogenesis and SC junctions, normalized the expression of the Keap1/Nrf2 axis and its downstream antioxidant enzymes, and prevented germ cell apoptosis. The results further emphasized the regulatory role of JAK2/STAT3 on spermatogenesis, Keap1/Nrf2 signaling, and maintenance of the testicular redox balance to combat testicular dysfunction and male infertility.

Jian-Yan-Ling capsules ameliorate cognitive impairment in mice with D-galactose-induced senescence and inhibit the oxidation-induced apoptosis of HT22 hippocampal cells by regulating the Nrf2-HO1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The Jian-Yan-Ling (JYL) capsule is a famous anti-aging Chinese patent medicine. It is applied mainly to delay senescence to improve cognition in aging individuals. However, the action mechanisms of JYL for improving cognition have not been determined.

AIM OF THE STUDY

We will evaluate the effect of the JYL capsule at improving the cognition of aging mice by improving oxidative stress in the hippocampus and exploring its action mechanism.

MATERIALS AND METHODS

A senescence mouse model was developed via intraperitoneal injection of D-galactose. The effect of the JYL capsule at improving the learning and memory abilities of mice was evaluated using the Morris water maze and novel object recognition tests. The apotosis of model mice hippocampus' were determined by TUNEL analysis. The antioxidant capacity of the JYL capsule was evaluated by determining the activities of antioxidant enzymes and expressions of oxidative products. The regulation of the Nrf2/HO-1 signaling pathway of the JYL capsule was evaluated by determining the expressions of related proteins via western blotting analysis. In vitro, H₂O₂-treated mouse hippocampal HT22 cells were used to evaluate the antioxidant capacity of JYL-containing rat serum by determining the cell viability, apoptotic level and expressions of related proteins.

RESULTS

JYL capsules enhanced the learning and memory abilities of model mice according to behavioral tests. The results of TUNEL analysis showed that the JYL capsule ameliorated hippocampal apoptosis in model mice. JYL capsules also exerted significant antioxidant capacity by increasing the activities of antioxidant enzymes while decreasing the levels of oxidative products both in the hippocampus and serum. The regulation of Nrf2/HO-1 pathway might contribute to the antioxidant function. In vitro, JYL-containing rat serum protected HT22 cells from H₂O₂ induced oxidative stress. The apoptosis of HT22 cells was also attenuated by regulating the caspase and Nrf2/HO-1 signaling pathways.

CONCLUSIONS

The amelioration of neuronal oxidative stress of hippocampus might contribute to the D-galactose-induced cognition impairment of senescence mice. These findings provide evidence for the application of JYL capsules to enhance cognition in aging individuals.

Glutathione S-transferase gene diversity and their regulation by Nrf2 in Chinese mitten crab (Eriocheir sinensis) during nitrite stress

Eriocheir sinensis is one of the most important economic aquatic products in China. However, nitrite pollution has become a serious threat to the healthy culture of E. sinensis. Glutathione S-transferase (GST) is an important phase II detoxification enzyme, which plays a leading role in the cellular detoxification of exogenous substances. In this study, we obtained 15 GST genes (designated as EsGST1-15) from E. sinensis, and their expression and regulation in E. sinensis under nitrite stress were studied. EsGST1-15 belonged to different GST subclasses. EsGST1, EsGST2, EsGST3, EsGST4, and EsGST5 belonged to Delta-class GSTs; EsGST6 and EsGST7 are Theta-class GSTs; EsGST8 is a mGST-3-class GST; EsGST9 belonged to mGST-1-class GSTs; EsGST10 and EsGST11 belonged to Sigma-class GSTs; EsGST12, EsGST13, and EsGST14 are Mu-class GSTs; EsGST15 is a Kappa-class GST. Tissue distribution experiments showed that EsGSTs were widely distributed in all detected tissues. The expression level of EsGST1-15 was significantly increased in the hepatopancreas under nitrite stress, indicating that EsGSTs were involved in the detoxification of E. sinensis under nitrite stress. Nuclear factor-erythroid 2 related factor 2 (Nrf2) is a transcription factor that can activate the expression of detoxification enzyme. We detected the expression of EsGST1-15 after interfering with EsNrf2 in the hepatopancreas of E. sinensis with or without nitrite stress. Results showed that EsGST1-15 were all regulated by EsNrf2 with or without nitrite stress. Our study provides new information about the diversity, expression, and regulation of GSTs in E. sinensis under nitrite stress.

Neuroprotective effect of tangeretin against chromium-induced acute brain injury in rats: targeting Nrf2 signaling pathway, inflammatory mediators, and apoptosis

Potassium dichromate (PD) is an environmental xenobiotic commonly recognized as teratogenic, carcinogenic, and mutagenic in animals and humans. The present study was conducted to investigate the role of tangeretin (TNG) as a neuro-protective drug against PD-induced brain injury in rats. Thirty-two male adult Wistar rats were blindly divided into four groups (8 rats/group). The first group received saline intranasally (i.n.). The second group received a single dose of PD (2 mg/kg, i.n.). The third group received TNG (50 mg/kg; orally), for 14 days followed by i.n. of PD on the last day of the experiment. The fourth group received TNG (100 mg/kg; orally) for 14 days followed by i.n. of PD on the last day of the experiment. Behavioral indices were evaluated 18 h after PD administration. Neuro-biochemical indices and histopathological studies were evaluated 24 h after PD administration. Results of the present study revealed that rats intoxicated with PD induced- oxidative stress and inflammation via an increase in malondialdehyde (MDA) and a decrease in nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway and glutathione(GSH) levels with an increase in brain contents of tumor necrosis factor-alpha (TNF-α) and interleukin (IL-6). Pre-treatment with TNG (100 mg/kg; orally) ameliorated behavior, cholinergic activities, and oxidative stress and decreased the elevated levels of pro-inflammatory mediators; TNF-α and IL-6 with a decrease in brain content of chromium residues detected by Plasma-Optical Emission Spectrometer. Also, the histopathological picture of the brain was improved significantly in rats that received TNG (100 mg/kg). Additionally, TNG decreased caspase-3 expression in the brain of PD rats. In conclusion, TNG possesses a significant neuroprotective role against PD-induced acute brain injury via modulating the Nrf2 signaling pathway and quenching the release of inflammatory mediators and apoptosis in rats.

QbD-based fabrication of transferrin-anchored nanocarriers for targeted drug delivery to macrophages and colon cells for mucosal inflammation healing

Colon mucosal inflammation attracts a plethora of immune cells with overexpressed surface receptors. Colon drug targeting can be aided by exploiting overexpressed cell surface receptors which improve drug site retention for an extended period. We developed Tofacitinib citrate (Tofa) loaded transferrin anchored PLGA nanocarriers (Tofa-P/tfr NCs) via the quality by design (QbD) approach for specific binding to the transferrin receptor (TFR-1/CD71) overexpressed on macrophages and colon epithelial cells. Nanocarriers were produced using a modified emulsion-evaporation method with a protein adsorption technique. The QbD-risk assessment method was adopted to screen the variables impacting the quality of nanocarriers, which were then optimized using the 3³ Box-Behnken design of experiment (DOE). The obtained nanocarriers have the desired physicochemical properties, drug entrapment, tfr adsorption, stability, mucoadhesion, and sustained drug release pattern at pH 7.4 (colon pH). In vitro cell-based studies confirmed the cellular biocompatibility and considerable uptake of nanocarriers by colon and macrophage cells; the uptake was diminished by anti-CD71/TFR1 antibodies. Tofa-P/tfr NCs demonstrated good colon targeting potential in the dextran sulfate sodium (DSS) induced ulcerative colitis (UC) model. In vivo therapeutic efficacy against UC was established through restored morphological and histopathological scores, vascular integrity, antioxidant levels, hematological parameters, pro-inflammatory cytokine/marker levels, and microbial indices. Tofa-P/tfr NCs shut down the elevated STAT-1 and TFR-1 levels, demonstrating the enhanced efficacy of the encapsulated drug. Thus, the QbD-driven approach successfully developed Tofa-P/tfr NCs with good potential to mitigate mucosal inflammation by targeting colon and macrophage surface receptors.

Brain-Derived Neurotrophic Factor: A Novel Dynamically Regulated Therapeutic Modulator in Neurological Disorders

The growth factor brain-derived neurotrophic factor (BDNF), and its receptor tropomyosin-related kinase receptor type B (TrkB) play an active role in numerous areas of the adult brain, where they regulate the neuronal activity, function, and survival. Upregulation and downregulation of BDNF expression are critical for the physiology of neuronal circuits and functioning in the brain. Loss of BDNF function has been reported in the brains of patients with neurodegenerative or psychiatric disorders. This article reviews the BDNF gene structure, transport, secretion, expression and functions in the brain. This article also implicates BDNF in several brain-related disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, major depressive disorder, schizophrenia, epilepsy and bipolar disorder.

Ellagic acid activates the Keap1-Nrf2-ARE signaling pathway in improving Parkinson's disease: A review

Parkinson's disease (PD) is a familiar neurodegenerative disease, accompanied by motor retardation, static tremor, memory decline and dementia. Heredity, environment, age and oxidative stress have been suggested as key factors in the instigation of PD. The Keap1-Nrf2-ARE signaling is one of the most significant anti- oxidative stress (OS) pathways. The Keap1 is a negative regulator of the Nrf2. The Keap1-Nrf2-ARE pathway can induce cell oxidation resistance and reduce nerve injury to treat neurodegenerative diseases. Ellagic acid (EA) can inhibit the Keap1 to accumulate the Nrf2 in the nucleus, and act on the ARE to produce target proteins, which in turn may alleviate the impact of OS on neuronal cells of PD. This review analyzes the structure and physiological role of EA, along with the structure, composition and functions of the Keap1-Nrf2-ARE signaling pathway. We further expound on the mechanism of ellagic acid in its activation of the Keap1-Nrf2-ARE signaling pathway, as well as the relationship between EA in impairing the TLR4/Myd88/NF-κB and Nrf2 pathways. Ellagic acid has the potentiality of improving PD by activating the Keap1-Nrf2-ARE signaling pathway and scavenging free radicals.

Natural Products Targeting Hsp90 for a Concurrent Strategy in Glioblastoma and Neurodegeneration

Glioblastoma multiforme (GBM) is one of the most common aggressive, resistant, and invasive primary brain tumors that share neurodegenerative actions, resembling many neurodegenerative diseases. Although multiple conventional approaches, including chemoradiation, are more frequent in GBM therapy, these approaches are ineffective in extending the mean survival rate and are associated with various side effects, including neurodegeneration. This review proposes an alternative strategy for managing GBM and neurodegeneration by targeting heat shock protein 90 (Hsp90). Hsp90 is a well-known molecular chaperone that plays essential roles in maintaining and stabilizing protein folding to degradation in protein homeostasis and modulates signaling in cancer and neurodegeneration by regulating many client protein substrates. The therapeutic benefits of Hsp90 inhibition are well-known for several malignancies, and recent evidence highlights that Hsp90 inhibitors potentially inhibit the aggressiveness of GBM, increasing the sensitivity of conventional treatment and providing neuroprotection in various neurodegenerative diseases. Herein, the overview of Hsp90 modulation in GBM and neurodegeneration progress has been discussed with a summary of recent outcomes on Hsp90 inhibition in various GBM models and neurodegeneration. Particular emphasis is also given to natural Hsp90 inhibitors that have been evidenced to show dual protection in both GBM and neurodegeneration.

Neuroprotective effect of the Nrf2/ARE/miRNA145-5p signaling pathway in the early phase of spinal cord injury

AIMS

Spinal cord injury (SCI) is a debilitating neurological condition often associated with chronic neuroinflammation and redox imbalance. Oxidative stress is one of the main hallmark of secondary injury of SCI which is tightly regulated by nuclear factor E2-related factor 2/antioxidant response element (Nrf2/ARE) signaling. In this study, we aimed at investigating the interplay between inflammation-related miRNAs and the Nrf2 pathway in animal model of SCI.

MATERIALS AND METHODS

The expression of selected four validated miRNA-target pairs (miRNA223-3p, miRNA155-5p, miRNA145-5p, and miRNA124-3p) was examined at different time points (6 h, 12 h, 1 day, 3 day and 7 day) after SCI. Further, using GFAP-specific kelch-like ECH-associated protein 1 deletion (Keap1-/-) and whole-body Nrf2-/- knockout mice, we investigated the potential interplay between each miRNA and the Keap1/Nrf2 signaling system.

KEY FINDINGS

The expression of all miRNAs except miRNA155-5p significantly increased 24 h after SCI and decreased after 7 days. Interestingly, Keap1-/- mice only showed significant increase in the miRNA145-5p after 24 h SCI compared to the WT group. In addition, Keap1-/- mice showed significant decrease in CXCL10/12 (CXCL12 increased in Nrf2-/- mice), and TNF-α, and an increase in Mn-SOD and NQO-1 (Mn-SOD and NQO-1 decreased in Nrf2-/- mice) compared to WT mice.

SIGNIFICANCE

Our results suggest that astrocytic hyperactivation of Nrf2 exert neuroprotective effects at least in part through the upregulation of miRNA145-5p, a negative regulator of astrocyte proliferation, and induction of ARE in early phase of SCI. Further studies are needed to investigate the potential interplay between Nrf2 and miRNA145-5p in neuroinflammatory condition.

lncRNA GAS5 Induces Cell Apoptosis in Acute Myeloid Leukemia by Targeting Nrf2

Objective

This study is aimed at investigating the molecular mechanism of lncRNA GAS5-induced cell apoptosis in acute myeloid leukemia (AML) by targeting Nrf2.

Methods

The RNA interfering technique was utilized to silence THP-1 in AML cell line, and lncRNA GAS5 expression in cell line was determined by real-time PCR. EdU experiment and flow cytometry were used to detect the apoptosis and proliferation ability of cells in different groups. PD-L1, STAT3, AKT, and MMP9 expressions were determined by Western blot.

Results

The si-RNA significantly inhibited the expression of lncRNA GAS5 in THP-1 cells. Compared with the si-NC group, the difference in cell apoptosis between lncRNA GAS5 and Nrf2 groups was significant (P < 0.05). Compared with the lncRNA GAS5 group, the number of apoptotic cells in the lncRNA GAS5+Nrf2 group significantly reduced (P < 0.05). Compared with the si-NC group, the differences in the levels of four proteins between lncRNA GAS5 and Nrf2 groups were significant (P < 0.05). In lncRNA GAS5+Nrf2 and lncRNA GAS5 groups, PD-L1 expression increased, while the expression of STAT3, AKT, and MMP9 decreased.

Conclusion

In AML cells, lncRNA GAS5 with Nrf2 could regulate the proliferation and apoptosis of AML cells. lncRNA GAS5 inhibited Nrf2 expression, regulated cell apoptosis and proliferation, and further inhibited the progression of AML disease.

Signal pathways in the treatment of Alzheimer's disease with traditional Chinese medicine

AIM OF THE REVIEW

This study aimed to reveal the classical signal pathways and important potential targets of traditional Chinese medicine (TCM) for treating Alzheimer's disease (AD), and provide support for further investigation on TCM and its active ingredients.

MATERIALS AND METHODS

Literature survey was conducted using PubMed, Web of Science, Google Scholar, CNKI, and other databases, with "Alzheimer's disease," "traditional Chinese medicine," "medicinal herb," "Chinese herb," and "natural plant" as the primary keywords.

RESULTS

TCM could modulate signal pathways related to AD pathological progression, including NF-κB, Nrf2, JAK/STAT, ubiquitin-proteasome pathway, autophagy-lysosome pathway-related AMPK/mTOR, GSK-3/mTOR, and PI3K/Akt/mTOR, as well as SIRT1 and PPARα pathway. It could regulate crosstalk between pathways through a multitarget, thus maintaining chronic inflammatory interaction balance, inhibiting oxidative stress damage, regulating ubiquitin-proteasome system function, modulating autophagy, and eventually improving cognitive impairment in patients with AD.

CONCLUSION

TCM could be multilevel, multitargeted, and multifaceted to prevent and treat AD. In-depth research on the prevention and treatment of AD with TCM could provide new ideas for exploring the pathogenesis of AD and developing new anti-AD drugs.

Wheatgrass extract imparts neuroprotective actions against scopolamine-induced amnesia in mice

The rich and diverse phytoconstituents of wheatgrass have established it as a natural antioxidant and detoxifying agent. The anti-inflammatory potential of wheatgrass has been studied extensively. However, the neuroprotective potential of wheatgrass has not been studied in depth. In this study, we investigated the neuroprotective response of wheatgrass against age-related scopolamine-induced amnesia in mice. Scopolamine is an established anticholinergic drug that demonstrates the behavioural and molecular characteristics of Alzheimer's disease. In the current study, wheatgrass extracts (prepared from 5 and 7 day old plantlets) were administered to scopolamine-induced memory deficit mice. The Morris water maze (MWM) and Y-maze tests demonstrated that wheatgrass treatment improves the behavior and simultaneously enhances the memory of amnesic mice. We further evaluated the expression of neuroinflammation related genes and proteins in the hippocampal region of mice. Wheatgrass significantly upregulated the mRNA and protein expression of neuroprotective markers such as BDNF and CREB in scopolamine-induced mice. Simultaneously, wheatgrass also downregulated the expression of inflammatory markers such as TNF-α and tau genes in these mice. The treatment of scopolamine-induced memory impaired mice with wheatgrass resulted in an elevation in the level of the phosphorylated form of ERK and Akt proteins. Wheatgrass treatment of mice also regulated the phosphorylation of tau protein and simultaneously prevented its aggregation in the hippocampal region of the brain. Overall, this study suggests the therapeutic potential of wheatgrass in the treatment of age-related memory impairment, possibly through the involvement of ERK/Akt-CREB-BDNF pathway and concomitantly ameliorating the tau-related pathogenesis.

Chronic vitamin D3 supplementation alleviates cognition impairment via inhibition of oxidative stress regulated by PI3K/AKT/Nrf2 in APP/PS1 transgenic mice

Oxidative stress plays essential role in the pathogenesis of Alzheimer's disease, and vitamin D₃ (VD₃) is a nutrient with neuroprotective and antioxidant activities. The present study aimed to confirm the neuroprotective effect and the ameliorative effect of cortical oxidative stress of VD₃ in APP/PS1 transgenic mice. APP/PS1 mice were treated with VD₃ for 20 weeks. After treatment, Morris Water Maze test was used to evaluate cognitive level. Western blotting was used to determine APP, p-tau, tau and PI3K/AKT/Nrf2 pathway-related protein expression levels. Immunohistochemical staining was performed to determine the levels of β amyloid peptide (Aβ) deposition. Enzyme linked immunosorbent assay was used to determine the 25(OH)D₃ levels and oxidative stress status. Our results showed that treatment with VD₃ ameliorated behavioral deficits of APP/PS1 mice. In addition, the administration of VD₃ significantly increased the cortical 25(OH)D₃ levels, while reducing the levels of cortical Aβ deposition and decreasing the expression levels of cortical APP, tau and p-tau in APP/PS1 mice. Moreover, VD₃ protected the cortex against oxidative stress by enhancing the levels of superoxide dismutase, glutathione and total antioxidant capacity, and downregulating the malondialdehyde levels. Furthermore, VD₃ clearly activated the PI3K/AKT/Nrf2 pathway, thereby elevating the expression levels of HO1 and NQO1. We concluded that VD₃ improved cognitive function and cortical Alzheimer-like pathology of APP/PS1 mice, which may be related to the inhibition of oxidative stress via activation the PI3K/AKT/Nrf2 pathway.

Salidroside attenuates neuronal ferroptosis by activating the Nrf2/HO1 signaling pathway in Aβ1-42-induced Alzheimer's disease mice and glutamate-injured HT22 cells

Background

Alzheimer’s disease (AD) is a neurodegenerative disease. Ferroptosis plays a critical role in neurodegenerative diseases. Nuclear factor E2-related factor 2 (Nrf2) is considered an important factor in ferroptosis. Studies have demonstrated that salidroside has a potential therapeutic effect on AD. The intrinsic effect of salidroside on ferroptosis is unclear. The purpose of this study was to investigate the protective effects and pharmacological mechanisms of salidroside on alleviating neuronal ferroptosis in Aβ₁₋₄₂-induced AD mice and glutamate-injured HT22 cells.

Methods

HT22 cells were injured by glutamate (Glu), HT22 cells transfected with siRNA Nrf2, and Aβ₁₋₄₂-induced WT and Nrf2^−/−AD mice were treated with salidroside. The mitochondria ultrastructure, intracellular Fe²⁺, reactive oxygen species, mitochondrial membrane potential, and lipid peroxidation of HT22 cells were detected. Malondialdehyde, reduced glutathione, oxidized glutathione disulfide, and superoxide dismutase were measured. The novel object recognition test, Y-maze, and open field test were used to investigate the protective effects of salidroside on Aβ₁₋₄₂-induced WT and Nrf2^−/−AD mice. The protein expressions of PTGS2, GPX4, Nrf2, and HO1 in the hippocampus were investigated by Western blot.

Results

Salidroside increased the cell viability and the level of MMP of Glu-injured HT22 cells, reduced the level of lipid peroxidation and ROS, and increased GPX4 and SLC7A11 protein expressions. These changes were not observed in siRNA Nrf2 transfected HT22 cells. Salidroside improved the ultrastructural changes in mitochondria of HT22 cells and Aβ₁₋₄₂-induced AD mice, but not in Aβ₁₋₄₂-induced Nrf2^−/−AD mice. Salidroside increased protein expression levels of GPX4, HO1, and NQO1 and decreased protein expression of PTGS2 in Aβ₁₋₄₂-induced AD mice but not in Aβ₁₋₄₂-induced Nrf2^−/−AD mice.

Conclusions

Salidroside plays a neuroprotective role by inhibiting neuronal ferroptosis in Aβ₁₋₄₂-induced AD mice and Glu-injured HT22 cells, and its mechanism is related to activation of the Nrf2/HO1 signaling pathway.

Graphical Abstract

Novel Flavan-3,4-diol vernicidin B from Toxicodendron Vernicifluum (Anacardiaceae) as potent antioxidant via IL-6/Nrf2 cross-talks pathways

BACKGROUND

Oxidative stress is considered to be a pathological factor of various neurodegenerative diseases. Studies have confirmed the antioxidant activity of T. vernicifluum. However, the main active components responsible for antioxidant activity remain unknown.

OBJECTIVE

The aim of this study is to explore the activities of vernicidin B on oxidative stress injury induced by H₂O₂ in SH-SY5Y cells, and the underlying mechanism of vernicidin B in oxidative stress-related neurological diseases is further discussed.

METHODS

Various separation methods were used to isolate and identify the compounds in an EtOAc extract of T. vernicifluum. The structures of the isolates were clarified by HR-TOF-MS and 1D/2D NMR data and compared with findings in previous literature. The MTT assay was used to evaluate the potential antioxidant activity of the isolated flavonoids. The apoptosis rate, mitochondrial reactive oxygen species (ROS) level and mitochondrial potential were measured by flow cytometry and fluorescence microscope. The levels of related proteins were detected by Western blotting.

RESULTS

Four new flavan-3,4-diols (1-4, vernicidins A-D) and 11 known flavonoids (5-15) were purified from the EtOAc extract of T. vernicifluum. Among these compounds, vernicidin B showed the most promising potential for protecting SH-SY5Y cells from H₂O₂-induced oxidative stress. Moreover, pretreatment with vernicidin B decreased ROS production and mitochondrial membrane potential and significantly attenuated H₂O₂-induced apoptosis in a dose-dependent manner. Mechanistically, the antioxidant stress activities of vernicidin B were confirmed to be related to the IL-6/Nrf2 cross-talks pathway and its downstream pathways, including PI3K/Akt/mToR-Gsk3β, JAK2/STAT3 and MAPKs.

CONCLUSIONS

Our findings suggested that vernicidin B can improve the oxidative stress injury induced by H₂O₂ through IL-6/Nrf2 cross-talks pathway, indicating that it may be a potential candidate drug for the treatment of oxidative stress-related neurodegenerative diseases.

α-Lipoic Acid, an Organosulfur Biomolecule a Novel Therapeutic Agent for Neurodegenerative Disorders: An Mechanistic Perspective

Lipoic acid (α-LA) (1,2-dithiolane3-pentanoic acid (C₈H₁₄O₂S₂) is also called thioctic acid with an oxidized (disulfide, LA) and a reduced (di-thiol: dihydro-lipoic acid, DHLA) form of LA. α-LA is a potent anti-oxidative agent that has a significant potential to treat neurodegenerative disorders. α-LA is both hydrophilic and hydrophobic in nature. It is widely distributed in plants and animals in cellular membranes and in the cytosol, which is responsible for LA's action in both the cytosol and plasma membrane. A systematic literature review of Bentham, Scopus, PubMed, Medline, and EMBASE (Elsevier) databases was carried out to understand the Nature and mechanistic interventions of the α-Lipoic acid for central nervous system diseases. Moreover, α-LA readily crosses the blood-brain barrier, which is a significant factor for CNS activities. The mechanisms of α-LA reduction are highly tissue-specific. α-LA produces its neuroprotective effect by inhibiting reactive oxygen species formation and neuronal damage, modulating protein levels, and promoting neurotransmitters and anti-oxidant levels. Hence, the execution of α-LA as a therapeutic ingredient in the therapy of neurodegenerative disorders is promising. Finally, based on evidence, it can be concluded that α-LA can prevent diseases related to the nervous system.

Alzheimer’s Disease: An Update and Insights Into Pathophysiology

Alzheimer’s disease (AD) is an irreversible brain disorder associated with slow, progressive loss of brain functions mostly in older people. The disease processes start years before the symptoms are manifested at which point most therapies may not be as effective. In the hippocampus, the key proteins involved in the JAK2/STAT3 signaling pathway, such as p-JAK2-Tyr1007 and p-STAT3-Tyr705 were found to be elevated in various models of AD. In addition to neurons, glial cells such as astrocytes also play a crucial role in the progression of AD. Without having a significant effect on tau and amyloid pathologies, the JAK2/STAT3 pathway in reactive astrocytes exhibits a behavioral impact in the experimental models of AD. Cholinergic atrophy in AD has been traced to a trophic failure in the NGF metabolic pathway, which is essential for the survival and maintenance of basal forebrain cholinergic neurons (BFCN). In AD, there is an alteration in the conversion of the proNGF to mature NGF (mNGF), in addition to an increase in degradation of the biologically active mNGF. Thus, the application of exogenous mNGF in experimental studies was shown to improve the recovery of atrophic BFCN. Furthermore, it is now coming to light that the FGF7/FGFR2/PI3K/Akt signaling pathway mediated by microRNA-107 is also involved in AD pathogenesis. Vascular dysfunction has long been associated with cognitive decline and increased risk of AD. Vascular risk factors are associated with higher tau and cerebral beta-amyloid (Aβ) burden, while synergistically acting with Aβ to induce cognitive decline. The apolipoprotein E4 polymorphism is not just one of the vascular risk factors, but also the most prevalent genetic risk factor of AD. More recently, the research focus on AD shifted toward metabolisms of various neurotransmitters, major and minor nutrients, thus giving rise to metabolomics, the most important “omics” tool for the diagnosis and prognosis of neurodegenerative diseases based on an individual’s metabolome. This review will therefore proffer a better understanding of novel signaling pathways associated with neural and glial mechanisms involved in AD, elaborate potential links between vascular dysfunction and AD, and recent developments in “omics”-based biomarkers in AD.

Kynurenine Metabolism and Alzheimer's Disease: The Potential Targets and Approaches

L-tryptophan, an essential amino acid, regulates protein homeostasis and plays a role in neurotransmitter-mediated physiological events. It also influences age-associated neurological alterations and neurodegenerative changes. The metabolism of tryptophan is carried majorly through the kynurenine route, leading to the production of several pharmacologically active enzymes, substrates, and metabolites. These metabolites and enzymes influence a variety of physiological and pathological outcomes of the majority of systems, including endocrine, haemopoietic, gastrointestinal, immunomodulatory, inflammatory, bioenergetic metabolism, and neuronal functions. An extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the kynurenine metabolites that influence cellular redox potential, immunoregulatory mechanisms, inflammatory pathways, cell survival channels, and cellular communication in close association with several neurodegenerative changes. The imbalanced state of kynurenine pathways has found a close association to several pathological disorders, including HIV infections, cancer, autoimmune disorders, neurodegenerative and neurological disorders including Parkinson's disease, epilepsy and has found special attention in Alzheimer's disease (AD). Kynurenine pathway (KP) is intricately linked to AD pathogenesis owing to the influence of kynurenine metabolites on excitotoxic neurotransmission, oxidative stress, uptake of neurotransmitters, and modulation of neuroinflammation, amyloid aggregation, microtubule disruption, and their ability to induce a state of dysbiosis. Pharmacological modulation of KP pathways has shown encouraging results, indicating that it may be a viable and explorable target for the therapy of AD.

Therapeutic benefits of flavonoids against neuroinflammation: a systematic review

Flavonoids are an important class of natural polyphenolic compounds reported to exert beneficial effects in cardiovascular and metabolic diseases, cancer, autoimmune and neurological disorders. Flavonoids possess potential antioxidant, anti-inflammatory, antiapoptotic and immuno-modulation properties. Intriguingly, the importance of flavonoids in different neurological disorders is gaining more attention due to the safety, better pharmacokinetic profile and blood-brain barrier penetration, cost-effectiveness and readiness for clinical uses/trials. Many in vitro and in vivo research studies have established the neuroprotective mechanism of flavonoids in the central nervous system (CNS) diseases. The present review summarizes the benefits of various classes of flavonoids (flavones, flavonols, flavanones, anthocyanidins, isoflavones, flavanols), chemical nature, classification, their occurrence and distribution, pharmacokinetics and bioavailability. The manuscript also presents available evidences relating to the role of flavonoids in regulating key signaling pathways such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway, mitogen-activated protein kinase (MAPK) pathway, Janus kinase and signal transducer and activator of transcription proteins (JAK/STAT) pathway, Toll-like receptors (TLR) pathway, nuclear factor erythroid 2-related factor 2 (Nrf2) pathway and cAMP response element-binding protein (CREB) pathway involved in neuroinflammation associated with major neurological disorders. Literature search was conducted using electronic databases like Google Scholar, Scopus, PubMed central, Springer search and Web of science. Chemical structures used in the present analysis were drawn using Chemdraw Professional 15.0 software. This collective information provides comprehensive knowledge on disease pathways and therapeutic benefits of flavonoids in neurological disorders, druggability and future scope for research.

Saikosaponin-D Mitigates Oxidation in SH-SY5Y Cells Stimulated by Glutamate Through Activation of Nrf2 Pathway: Involvement of PI3K

Alzheimer's disease (AD) is a typical neurodegenerative disease. Well-established studies have shown an elevated level of ROS (reactive oxygen species) that induces oxidative stress in AD. Saikosaponin-D exhibited significant therapeutic effects on neurodegenerative diseases. However, its in-depth molecular mechanisms against neurotoxicity remain not fully uncovered. Herein, the possible protective effects of saikosaponin-D on glutamate-induced neurotoxicity in SH-SY5Y cells and the underlying mechanism were elucidated. Saikosaponin-D pretreatment could ameliorate glutamate-induced cytotoxicity according to MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and depress apoptosis according to Hoechst 33,342 staining and Annexin V-FITC/PI double staining in SH-SY5Y cells. Additionally, saikosaponin-D administration suppressed oxidative stress in response to glutamate indicated by diminished intracellular ROS formation and reduced MDA (malondialdehyde) content in SH-SY5Y cells. These phenomena, appeared to correlate with the recovered cellular antioxidant enzyme activities and inducted HO-1 (heme oxygenase-1) expression accompanying the nuclear translocation of Nrf2 conduct by saikosaponin-D preconditioning which had been altered by glutamate, were correlated with its neuroprotective. Furthermore, addition of LY294002, a selective inhibitor of PI3K (phosphatidylinositol 3 kinase), blocked saikosaponin-D-caused Nrf2 nuclear translocation and reversed the protection of saikosaponin-D against glutamate in SH-SY5Y cells. Moreover, saikosaponin-D exhibited antioxidant potential with high free radical-scavenging activity as confirmed by a DPPH (2,2-diphenyl-1-picrylhydrazyl) and TEAC (Trolox equivalent antioxidant capacity) in a cell-free system in vitro. Taken together, our results indicated that saikosaponin-D enhanced cellular antioxidant capacity through not only intrinsic free radical-scavenging activity but also induction of endogenous antioxidant enzyme activities and HO-1 expression mediated, at least in part, by activating PI3K and subsequently Nrf2 nuclear translocation, thereby protecting the SH-SY5Y cells from glutamate-induced oxidative cytotoxicity. In concert, these data raise the possibility that saikosaponin-D may be an attractive candidate for prevention and treatment of AD and other diseases related to oxidation in the future.

Neuropeptides: Potential neuroprotective agents in ischemic injury

AIM

Ischemic damage to the brain is linked to an increased rate of morbidity and mortality worldwide. In certain parts of the world, it remains a leading cause of mortality and the primary cause of long-term impairment. Ischemic injury is exacerbated when particular neuropeptides are removed, or their function in the brain is blocked, whereas supplying such neuropeptides lowers ischemic harm. Here, we have discussed the role of neuropeptides in ischemic injury.

MATERIALS & METHODS

Numerous neuropeptides had their overexpression following cerebral ischemia. Neuropeptides such as NPY, CGRP, CART, SP, BK, PACAP, oxytocin, nociception, neurotensin and opioid peptides act as transmitters, documented in several "in vivo" and "in vitro" studies. Neuropeptides provide neuroprotection by activating the survival pathways or inhibiting the death pathways, i.e., MAPK, BDNF, Nitric Oxide, PI3k/Akt and NF-κB.

KEY FINDINGS

Neuropeptides have numerous beneficial effects in ischemic models, including antiapoptotic, anti-inflammatory, and antioxidant actions that provide a powerful protective impact in neurons when combined. These innovative therapeutic substances have the potential to treat ischemia injury due to their pleiotropic modes of action.

SIGNIFICANCE

This review emphasizes the neuroprotective role of neuropeptides in ischemic injury via modulation of various signalling pathways i.e., MAPK, BDNF, Nitric Oxide, PI3k/Akt and NF-κB.

Nuclear Factor Erythroid-2-Related Factor 2 Signaling in the Neuropathophysiology of Inherited Metabolic Disorders

Inherited metabolic disorders (IMDs) are rare genetic conditions that affect multiple organs, predominantly the central nervous system. Since treatment for a large number of IMDs is limited, there is an urgent need to find novel therapeutical targets. Nuclear factor erythroid-2-related factor 2 (Nrf2) is a transcription factor that has a key role in controlling the intracellular redox environment by regulating the expression of antioxidant enzymes and several important genes related to redox homeostasis. Considering that oxidative stress along with antioxidant system alterations is a mechanism involved in the neuropathophysiology of many IMDs, this review focuses on the current knowledge about Nrf2 signaling dysregulation observed in this group of disorders characterized by neurological dysfunction. We review here Nrf2 signaling alterations observed in X-linked adrenoleukodystrophy, glutaric acidemia type I, hyperhomocysteinemia, and Friedreich’s ataxia. Additionally, beneficial effects of different Nrf2 activators are shown, identifying a promising target for treatment of patients with these disorders. We expect that this article stimulates research into the investigation of Nrf2 pathway involvement in IMDs and the use of potential pharmacological modulators of this transcription factor to counteract oxidative stress and exert neuroprotection.

Umuhengerin Neuroprotective Effects in Streptozotocin-Induced Alzheimer's Disease Mouse Model via Targeting Nrf2 and NF-Kβ Signaling Cascades

Alzheimer’s disease (AD) is the most common type of dementia and is characterized by advanced cognitive deterioration, deposition of Aβ (amyloid-beta), and the formation of neurofibrillary tangles. Administration of streptozotocin (STZ) via the intracerebroventricular (ICV) route is a reliable model resembling sporadic AD (SAD) associated neuropathological changes. The present study was undertaken to explore the neuroprotective effects of the methoxy flavonoid, umuhengerin, in an STZ-induced SAD mouse model as a potential therapy for AD. Mice were injected once with STZ (3 mg/kg, ICV), followed by daily administration of umuhengerin (orally, 30 mg/kg) or the positive control donepezil (orally, 2.5 mg/kg) for 21 days. The pharmacological activity of umuhengerin was assessed through estimation of oxidative stress and inflammatory markers via mouse ELISA kits, Western blot analysis, and brain histopathological examination. Morris water maze test was also conducted to investigate umuhengerin-induced cognitive enhancement. The results showed that umuhengerin attenuated STZ-produced neuroinflammation and oxidative stress with a notable rise in the expression of Nrf2 (nuclear factor erythroid 2-related factor 2). In contrast, it downregulated Keap-1 (Kelch-like ECH associated protein 1), as well as elevated brain contents of GSH (reduced glutathione) and HO-1 (heme oxygenase-1). STZ-injected animals receiving umuhengerin showed marked downregulation of the nuclear factor kappa beta (NF-Kβp65) and noticeable increment in the expression of its inhibitor kappa beta alpha protein (IKβα), as well as prominent reduction in malondialdehyde (MDA), H₂O₂ (hydrogen peroxide), and TNF-α (tumor-necrosis factor-alpha) contents. Β-secretase protein expression and acetylcholinesterase (AchE) activity were also diminished upon umuhengerin injection in the STZ group, leading to decreased Aβ formation and cognitive improvement, respectively. In conclusion, umuhengerin neuroprotective effects were comparable to the standard drug donepezil; thus, it could be an alternative approach for AD management.

Pharmacological modulation of cytokines correlating neuroinflammatory cascades in epileptogenesis

Epileptic seizure-induced brain injuries include activation of neuroimmune response with activation of microglia, astrocytes cells releasing neurotoxic inflammatory mediators underlies the pathophysiology of epilepsy. A wide spectrum of neuroinflammatory pathways is involved in neurodegeneration along with elevated levels of inflammatory mediators indicating the neuroinflammation in the epileptic brain. Therefore, the neuroimmune response is commonly observed in the epileptic brain, indicating elevated cytokine levels, providing an understanding of the neuroinflammatory mechanism contributing to seizures recurrence. Clinical and experimental-based evidence suggested the elevated levels of cytokines responsible for neuronal excitation and blood-brain barrier (BBB) dysfunctioning causing the drug resistance in epilepsy. Therefore, the understanding of the pathogenesis of neuroinflammation in epilepsy, including migration of microglial cells releasing the inflammatory cytokines indicating the correlation of elevated levels of inflammatory mediators (interleukin-1beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) triggering the generation or recurrence of seizures. The current review summarized the knowledge regarding elevated inflammatory mediators as immunomodulatory response correlating multiple neuroinflammatory NF-kB, RIPK, MAPK, ERK, JNK, JAK-STAT signaling cascades in epileptogenesis. Further selective targeting of inflammatory mediators provides beneficial therapeutic strategies for epilepsy.

Pharmacological Modulation of Ubiquitin-Proteasome Pathways in Oncogenic Signaling

The ubiquitin-proteasome pathway (UPP) is involved in regulating several biological functions, including cell cycle control, apoptosis, DNA damage response, and apoptosis. It is widely known for its role in degrading abnormal protein substrates and maintaining physiological body functions via ubiquitinating enzymes (E1, E2, E3) and the proteasome. Therefore, aberrant expression in these enzymes results in an altered biological process, including transduction signaling for cell death and survival, resulting in cancer. In this review, an overview of profuse enzymes involved as a pro-oncogenic or progressive growth factor in tumors with their downstream signaling pathways has been discussed. A systematic literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on modulation of ubiquitin-proteasome pathways in oncogenic signaling. Various in vitro, in vivo studies demonstrating the involvement of ubiquitin-proteasome systems in varied types of cancers and the downstream signaling pathways involved are also discussed in the current review. Several inhibitors of E1, E2, E3, deubiquitinase enzymes and proteasome have been applied for treating cancer. Some of these drugs have exhibited successful outcomes in in vivo studies on different cancer types, so clinical trials are going on for these inhibitors. This review mainly focuses on certain ubiquitin-proteasome enzymes involved in developing cancers and certain enzymes that can be targeted to treat cancer.

Fatal attraction - The role of hypoxia when alpha-synuclein gets intimate with mitochondria

Alpha-synuclein aggregation and mitochondrial dysfunction are main pathological hallmarks of Parkinson's disease (PD) and several other neurodegenerative diseases, collectively known as synucleinopathies. However, increasing evidence suggests that they may not be sufficient to cause PD. Here we propose the role of hypoxia as a missing link that connects the complex interplay between alpha-synuclein biochemistry and pathology, mitochondrial dysfunctions and neurodegeneration in PD. We review the partly conflicting literature on alpha-synuclein binding to membranes and mitochondria and its impact on mitochondrial functions. From there, we focus on adverse changes in cellular environments, revolving around hypoxic stress, that may trigger or facilitate PD progression. Inter-dependent structural re-arrangements of mitochondrial membranes, including increased cytoplasmic exposure of mitochondrial cardiolipins and changes in alpha-synuclein localization and conformation are discussed consequences of such conditions. Enhancing cellular resilience could be an integral part of future combination-based therapies of PD. This may be achieved by boosting the capacity of cellular and specifically mitochondrial processes to regulate and adapt to altered proteostasis, redox, and inflammatory conditions and by inducing protective molecular and tissue re-modelling.

Apoptotic Pathways and Alzheimer's Disease: Probing Therapeutic Potential

Apoptosis is an intrinsic biochemical, cellular process that regulates cell death and is crucial for cell survival, cellular homeostasis, and maintaining the optimum functional status. Apoptosis in a predetermined and programmed manner regulates several molecular events, including cell turnover, embryonic development, and immune system functions but may be the exclusive contributor to several disorders, including neurodegenerative manifestations, when it functions in an aberrant and disorganized manner. Alzheimer's disease (AD) is a fatal, chronic neurodegenerative disorder where apoptosis has a compelling and divergent role. The well-characterized pathological features of AD, including extracellular plaques of amyloid-beta, intracellular hyperphosphorylated tangles of tau protein (NFTs), inflammation, mitochondrial dysfunction, oxidative stress, and excitotoxic cell death, also instigate an abnormal apoptotic cascade in susceptible brain regions (cerebral cortex, hippocampus). The apoptotic players in these regions affect cellular organelles (mitochondria and endoplasmic reticulum), interact with trophic factors, and several pathways, including PI3K/AKT, JNK, MAPK, mTOR signalling. This dysregulated apoptotic cascade end with an abnormal neuronal loss which is a primary event that may precede the other events of AD progression and correlates well with the degree of dementia. The present review provides insight into the diverse and versatile apoptotic mechanisms that are indispensable for neuronal survival and constitute an integral part of the pathological progression of AD. Identification of potential targets (restoring apoptotic and antiapoptotic balance, caspases, TRADD, RIPK1, FADD, TNFα, etc.) may be valuable and advantageous to decide the fate of neurons and to develop potential therapeutics for treatment of AD.

Peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ): Molecular Effects and Its Importance as a Novel Therapeutic Target for Cerebral Ischemic Injury

Cerebral ischemic injury is a leading cause of death and long-term disability throughout the world. Peroxisome proliferator-activated receptor gamma (PPAR-ɣ) is a ligand-activated nuclear transcription factor that is a member of the PPAR family. PPAR-ɣ has been shown in several in vitro and in vivo models to prevent post-ischemic inflammation and neuronal damage by negatively controlling the expression of genes modulated by cerebral ischemic injury, indicating a neuroprotective effect during cerebral ischemic injury. A extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the mechanistic role of Peroxisome proliferator activated receptor gamma and its modulation in Cerebral ischemic injury. PPAR-ɣ can interact with specific DNA response elements to control gene transcription and expression when triggered by its ligand. It regulates lipid metabolism, improves insulin sensitivity, modulates antitumor mechanisms, reduces oxidative stress, and inhibits inflammation. This review article provides insights on the current state of research into the neuroprotective effects of PPAR-ɣ in cerebral ischemic injury, as well as the cellular and molecular mechanisms by which these effects are modulated, such as inhibition of inflammation, reduction of oxidative stress, suppression of pro-apoptotic production, modulation of transcription factors, and restoration of injured tissue through neurogenesis and angiogenesis.

Insights into the Mechanism of the Therapeutic Potential of Herbal Monoamine Oxidase Inhibitors in Neurological Diseases

Monoamine oxidase (MAO) is an enzyme that catalyzes the deamination of monoamines and other proteins. MAO's hyperactivation results in the massive generation of reactive oxygen species, which leads to a variety of neurological diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and depression-like disorders. Although synthetic MAO inhibitors are clinically available, they are associated with side effects such as hepatotoxicity, cheese reaction, hypertensive crisis, and so on, necessitating the investigation of alternative MAO inhibitors from a natural source with a safe profile. Herbal medications have a significant impact on the prevention of many diseases; additionally, they have fewer side effects and serve as a precursor for drug development. This review discusses the potential of herbal MAO inhibitors as well as their associated mechanism of action, with an aim to foster future research on herbal MAO inhibitors as potential treatment for neurological diseases.

Hypoxia and brain aging: Neurodegeneration or neuroprotection?

The absolute reliance of the mammalian brain on oxygen to generate ATP renders it acutely vulnerable to hypoxia, whether at high altitude or in clinical settings of anemia or pulmonary disease. Hypoxia is pivotal to the pathogeneses of myriad neurological disorders, including Alzheimer's, Parkinson's and other age-related neurodegenerative diseases. Conversely, reduced environmental oxygen, e.g. sojourns or residing at high altitudes, may impart favorable effects on aging and mortality. Moreover, controlled hypoxia exposure may represent a treatment strategy for age-related neurological disorders. This review discusses evidence of hypoxia's beneficial vs. detrimental impacts on the aging brain and the molecular mechanisms that mediate these divergent effects. It draws upon an extensive literature search on the effects of hypoxia/altitude on brain aging, and detailed analysis of all identified studies directly comparing brain responses to hypoxia in young vs. aged humans or rodents. Special attention is directed toward the risks vs. benefits of hypoxia exposure to the elderly, and potential therapeutic applications of hypoxia for neurodegenerative diseases. Finally, important questions for future research are discussed.

Neuroprotective effects of aucubin on hydrogen peroxide-induced toxicity in human neuroblastoma SH-SY5Y cells via the Nrf2/HO-1 pathway

BACKGROUND

When redox balance is lost in the brain, oxidative stress can cause serious damage that leads to neuronal loss, in congruence with neurodegenerative diseases. Aucubin (AU) is an iridoid glycoside and that is one of the active constituents of Eucommia ulmoides, has many pharmacological effects such as anti-inflammation, anti-liver fibrosis, and anti-atherosclerosis.

PURPOSE

The present study aimed to evaluate the inhibitory effects of AU on cell oxidative stress against hydrogen peroxide (H₂O₂)-induced injury in SH-SY5Y cells in vitro.

METHODS

SH-SY5Y cells were simultaneously treated with AU and H₂O₂ for 24 h. Cell viability was measured by CCK-8. Additionally, mitochondrial membrane depolarization, reactive oxygen species (ROS) generation, and cell apoptosis were measured by flow cytometry.

RESULTS

The results showed that AU can significantly increase the H₂O₂-induced cell viability and the mitochondrial membrane potential, decrease the ROS generation, malondialdehyde (MDA), and increase glutathione (GSH) contents and the superoxide dismutase (SOD) activity. We also found that H₂O₂ stimulated the production of nitric oxide (NO), which could be reduced by treatment with AU through inhibiting the inducible nitric oxide synthase (iNOS) protein expression. In H₂O₂-induced SH-SY5Y cells, the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) content and cell apoptosis were significantly reduced by AU treatment through nuclear factor E2-related factor 2/hemo oxygenase-1 (Nrf2/HO-1) activation, inhibiting the expression of p-NF-κB/NF-κB and down-regulating MAPK and Bcl-2/Bax pathways.

CONCLUSION

These results indicate that AU can reduce inflammation and oxidative stress through the NF-κB, Nrf2/HO-1, and MAPK pathways.

Mechanistic insights and perspectives involved in neuroprotective action of quercetin

Neurodegenerative diseases (NDDs) are the primary cause of disabilities in the elderly people. Growing evidence indicates that oxidative stress, mitochondrial dysfunction, neuroinflammation and apoptosis are associated with aging and the basis of most neurodegenerative disorders. Quercetin is a flavonoid with significant pharmacological effects and promising therapeutic potential. It is widely distributed among plants and typically found in daily diets mainly in fruits and vegetables. It shows a number of biological properties connected to its antioxidant activity. Neuroprotection by quercetin has been reported in many in vitro as well as in in vivo studies. However, the exact mechanism of action is still mystery and similarly there are a number of hypothesis exploring the mechanism of neuroprotection. Quercetin enhances neuronal longevity and neurogenesis by modulating and inhibiting wide number of pathways. This review assesses the food sources of quercetin, its pharmacokinetic profile, structure activity relationship and its pathophysiological role in various NDDs and it also provides a synopsis of the literature exploring the relationship between quercetin and various downstream signalling pathways modulated by quercetin for neuroprotection for eg. nuclear factor erythroid 2-related factor 2 (Nrf2), Paraoxonase-2 (PON2), c-Jun N-terminal kinase (JNK), Tumour Necrosis Factor alpha (TNF-α), Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha (PGC-1α), Sirtuins, Mitogen-activated protein kinases (MAPKs) signalling cascades, CREB (Cyclic AMP response element binding protein) and Phosphoinositide 3- kinase(PI3K/Akt). Therefore, the aim of the present review was to elaborate on the cellular and molecular mechanisms of the quercetin involved in the protection against NDDs.

Dysbiosis and Alzheimer's Disease: A Role for Chronic Stress?

Alzheimer’s disease (AD) is an incurable, neuropsychiatric, pathological condition that deteriorates the worth of geriatric lives. AD is characterized by aggregated senile amyloid plaques, neurofibrillary tangles, neuronal loss, gliosis, oxidative stress, neurotransmitter dysfunction, and bioenergetic deficits. The changes in GIT composition and harmony have been recognized as a decisive and interesting player in neuronal pathologies including AD. Microbiota control and influence the oxidoreductase status, inflammation, immune system, and the endocrine system through which it may have an impact on the cognitive domain. The altered and malfunctioned state of microbiota is associated with minor infections to complicated illnesses that include psychosis and neurodegeneration, and several studies show that microbiota regulates neuronal plasticity and neuronal development. The altered state of microbiota (dysbiosis) may affect behavior, stress response, and cognitive functions. Chronic stress-mediated pathological progression also has a well-defined role that intermingles at various physiological levels and directly impacts the pathological advancement of AD. Chronic stress-modulated alterations affect the well-established pathological markers of AD but also affect the gut–brain axis through the mediation of various downstream signaling mechanisms that modulate the microbial commensals of GIT. The extensive literature reports that chronic stressors affect the composition, metabolic activities, and physiological role of microbiota in various capacities. The present manuscript aims to elucidate mechanistic pathways through which stress induces dysbiosis, which in turn escalates the neuropathological cascade of AD. The stress–dysbiosis axis appears a feasible zone of work in the direction of treatment of AD.

Amyloid toxicity in a Drosophila Alzheimer's model is ameliorated by autophagy activation

Alzheimer's disease (AD) is the prevailing form of dementia. Protein degradation and antioxidant pathways have a critical role in preventing the accumulation of protein aggregation; thus, failure of proteostasis in neurons along with redox imbalance mark AD. Herein, we exploited an AD Drosophila model expressing human amyloid precursor (hAPP) and beta-secretase 1 (hBACE1) proteins, to better understand the role of proteostatic or antioxidant pathways in AD. Ubiquitous expression of hAPP, hBACE1 in flies caused more severe degenerative phenotypes versus neuronal targeted expression; it also, suppressed proteasome activity, increased oxidative stress and significantly enhanced stress-sensitivity. Overexpression of Prosβ5 proteasomal subunit or Nrf2 transcription factor in AD Drosophila flies partially restored proteasomal activity but did not rescue hAPP, hBACE1 induced neurodegeneration. On the other hand, expression of autophagy-related Atg8a in AD flies decelerated neurodegeneration, increased stress-resistance, and improved flies' health-/lifespan. Overall, our data suggest that the noxious effects of amyloid-beta aggregates can be alleviated by enhanced autophagy, thus dietary or pharmacological interventions that target autophagy should be considered in AD therapeutic approaches.