Activation of Nrf2/ARE pathway alleviates the cognitive deficits in PS1V97L-Tg mouse model of Alzheimer's disease through modulation of oxidative stress
Oxidative stress refers to an imbalance between oxidative and antioxidative systems due to environmental factors. Although oxidative stress is implicated in the pathogenesis of Alzheimer's disease (AD), its precise role is not yet understood. We aimed to investigate the pathogenic mechanisms of the oxidative stress by using in vitro cultured neurons and in vivo AD models of PS1V97L-transgenic (Tg) mice. Our results showed that when oxidative stress became increasingly evident, the endogenous protective pathway of nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) decreased in 10-month-old PS1V97L-Tg mice. Activating the Nrf2/ARE pathway suppressed oxidative stress, decreased amyloid-β (Aβ), and improved the cognitive function of the PS1V97L-Tg mice. In contrast, blocking the Nrf2/ARE pathway augmented oxidative injury and decreased the cell viability of PS1V97L-Tg neurons. Our results highlight the role of the Nrf2/ARE pathway in regulating oxidative stress of the PS1V97L-Tg mice and may indicate a potential therapeutic avenue for AD treatment.
Dimethyloxalylglycine preconditioning enhances protective effects of bone marrow-derived mesenchymal stem cells in Aβ- induced Alzheimer disease
Mesenchymal stem cell (MSC) transplantation therapy has been proposed as a promising approach for the treatment of neurodegenerative disease. Chemical and pharmacological preconditioning before transplantation could optimize the therapeutic properties of transplanted MSCs. In this study, we hypothesized that preconditioning treatment with a prolyl hydroxylase inhibitor, dimethyloxalylglycine (DMOG), will increase MSC efficacy and paracrine effects in an amyloid-β (Aβ)-injected Alzheimer rat model. MSCs were incubated in different concentrations of DMOG for 24 h. Cell viability, migration, and antioxidant capacity was assessed in DMOG-treated and non-treated MSCs before transplantation into Aβ-injected rats. In vitro analysis revealed that DMOG treatment increased cell viability, migration, and expression of CXCR4, CCR2, Nrf2, and HIF-1α in the MSCs. Our in vivo results show that DMOG preconditioning enhances a MSC-mediated rescue of learning and memory function in Aβ-injected rats. Furthermore, we found an increased level of BDNF and total antioxidant capacity in the hippocampus of Aβ-injected rats following transplantation of preconditioned relative to untreated MSCs. Our results suggest that preconditioning MSCs with DMOG before transplantation may enhance the efficacy of stem cell based therapy in neurodegenerative disease.
Artemisia amygdalina Upregulates Nrf2 and Protects Neurons Against Oxidative Stress in Alzheimer Disease
Alzheimer disease is a complex neurodegenerative disorder. It is the common form of dementia in elderly people. The etiology of this disease is multifactorial, pathologically it is accompanied with accumulation of amyloid beta and neurofibrillary tangles. Accumulation of amyloid beta and mitochondrial dysfunction leads to oxidative stress. In this study, neuroprotective effect of Artemisiaamygdalina against HO-induced death was studied in differentiated N2a and SH-SY5Ycells. Cells were treated with HO to induce toxicity which was attenuated by Artemisia amygdalina. The nuclear factor erythroid 2-related factor 2 (Nrf2) is an emerging regulator of cellular resistance to oxidants. It controls the basal and induced expression of antioxidant response element-dependent genes. Further, we demonstrated that Artemisia amygdalina protects neurons through upregulation of Nrf2 pathway. Moreover, reactive oxygen species and mitochondrial membrane potential loss formed by HO was attenuated by Artemisia amygdalina. Thus, Artemisia amygdalina may have the possibility to be a therapeutic agent for Alzheimer disease.
Edaravone reduces Aβ-induced oxidative damage in SH-SY5Y cells by activating the Nrf2/ARE signaling pathway
Edaravone potentially alleviates cognitive deficits in a mouse model of Alzheimer's disease (AD). However, the mechanism of edaravone in suppressing AD progression remains unclear. We aim to investigate the mechanism of edaravone in suppressing oxidative stress-mediated AD progression in vitro.
Protective roles of Amanita caesarea polysaccharides against Alzheimer's disease via Nrf2 pathway
This study explores the neuro-protective effects of Amanita caesarea polysaccharides (ACPS), obtained by 80% alcohol precipitation of water extract and purified using a DEAE-52 cellulose anion exchange column, related to antioxidant activity. A 3-h pre-treatment of ACPS prior to l‑glutamic acid (l‑Glu) co-exposure reversed the decreased cell viability, inhibited apoptosis, suppressed the accumulation of intracellular reactive oxygen species and restored mitochondrial membrane potential in HT22 cells. Compared to l‑Glu-exposed cells, ACPS enhanced the nuclear levels of NF-E2p45-related factor 2 (Nrf2), reduced the cytoplasmic levels of Nrf2 and cytochrome C, suppressed the expression of Kelch-like ECH-associated protein 1, and enhanced the expression of heme oxygenase‑1, superoxide dismutase 1 and cysteine ligase catalytic subunit. In a d‑galactose and aluminum trichloride Alzheimer's disease (AD) mouse model, 42-day administration of ACPS improved the abnormal behaviors. ACPS suppressed the deposition of β‑amyloid peptide in the brain and ameliorated oxidative stress via modulating the levels of related enzymes. ACPS improved the functioning of the central cholinergic system, as indicated by an increase in acetylcholine and choline acetyltransferase concentrations, and reduced acetylcholine esterase levels in the serum, hypothalamus and cerebral cortex. Our data suggest that ACPS may be a promising candidate for the treatment of AD.
Ginsenoside Compound K Regulates Amyloid β via the Nrf2/Keap1 Signaling Pathway in Mice with Scopolamine Hydrobromide-Induced Memory Impairments
The objective of this study was to investigate the neuroprotective and antioxidant effects of ginsenoside compound K (CK) in a model of scopolamine hydrobromide-induced, memory-impaired mice. The role of CK in the regulation of amyloid β (Aβ) and its capacity to activate the Nrf2/Keap1 signaling pathway were also studied due to their translational relevance to Alzheimer's disease. The Morris water maze was used to assess spatial memory functions. Levels of superoxide dismutase, glutathione peroxidase, and malondialdehyde in brain tissues were tested. Cell morphology was detected by hematoxylin and eosin staining and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling assay. Immunohistochemistry and western blotting were used to determine expression levels of Nrf2/Keap1 signaling pathway-related factors and Aβ. Ginsenoside CK was found to enhance memory function, normalize neuronal morphology, decrease neuronal apoptosis, increase superoxide dismutase and glutathione peroxidase levels, reduce malondialdehyde levels, inhibit Aβ expression, and activate the Nrf2/Keap1 signaling pathway in scopolamine-exposed animals. Based on these results, we conclude that CK may improve memory function in scopolamine-injured mice by regulating Aβ aggregation and promoting the transduction of the Nrf2/Keap1 signaling pathway, thereby reducing oxidative damage to neurons and inhibiting neuronal apoptosis. This study suggests that CK may serve as a future preventative agent or treatment for Alzheimer's disease.
Mini-GAGR, an intranasally applied polysaccharide, activates the neuronal Nrf2-mediated antioxidant defense system
Oxidative stress triggers and exacerbates neurodegeneration in Alzheimer's disease (AD). Various antioxidants reduce oxidative stress, but these agents have little efficacy due to poor blood-brain barrier (BBB) permeability. Additionally, single-modal antioxidants are easily overwhelmed by global oxidative stress. Activating nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) and its downstream antioxidant system are considered very effective for reducing global oxidative stress. Thus far, only a few BBB-permeable agents activate the Nrf2-dependent antioxidant system. Here, we discovered a BBB-bypassing Nrf2-activating polysaccharide that may attenuate AD pathogenesis. Mini-GAGR, a 0.7-kDa cleavage product of low-acyl gellan gum, increased the levels and activities of Nrf2-dependent antioxidant enzymes, decreased reactive oxygen species (ROS) under oxidative stress in mouse cortical neurons, and robustly protected mitochondria from oxidative insults. Moreover, mini-GAGR increased the nuclear localization and transcriptional activity of Nrf2 similarly to known Nrf2 activators. Mechanistically, mini-GAGR increased the dissociation of Nrf2 from its inhibitor, Kelch-like ECH-associated protein 1 (Keap1), and induced phosphorylation and nuclear translocation of Nrf2 in a protein kinase C (PKC)- and fibroblast growth factor receptor (FGFR1)-dependent manner. Finally, 20-day intranasal treatment of 3xTg-AD mice with 100 nmol of mini-GAGR increased nuclear p-Nrf2 and growth-associated protein 43 (GAP43) levels in hippocampal neurons, reduced p-tau and β-amyloid (Aβ) peptide-stained neurons, and improved memory. The BBB-bypassing Nrf2-activating polysaccharide reported here may be effective in reducing oxidative stress and neurodegeneration in AD.
Is a Meal without Wine Good for Health?
Hippocrates, the father of medicine, had said: "Wine is a thing wonderfully appropriate to man if, in health as in disease, it is administered with appropriate and just measure according to the individual constitution." Wine has always accompanied humanity, for religion or for health. Christians and Jews need wine for the liturgy. For Plato, wine was an indispensable element in society and the most important in the symposium. In this second part of the banquet, mixed with water, the wine gave the word. If the French paradox made a lot of ink flow; it was the wine that was originally responsible for it. Many researchers have tried to study alcohol and polyphenols in wine, in order to solve the mystery. Beyond its cardiovascular effects, there are also effects on longevity, metabolism, cancer prevention, and neuroprotection, and the list goes on. The purpose of this work is to make an analysis of the current knowledge on the subject. Indeed, if the paradigm of antioxidants is seductive, it is perhaps by their prooxidant effect that the polyphenols act, by an epigenetic process mediated by nrf2. Wine is a preserve of antioxidants for the winter and it is by this property that the wine acts, in an alcoholic solution. A wine without alcohol is pure heresy. Wine is the elixir that by design, over millennials, has acted as a pharmacopeia that enabled man to heal and prosper on the planet. From Alvise Cornaro to Serge Renaud, nutrition was the key to health and longevity, whether the Cretan or Okinawa diet, it is the small dose of alcohol (wine or sake) that allows the bioavailability of polyphenols. Moderate drinking gives a protection for diseases and a longevity potential. In conclusion, let us drink fewer, but drink better, to live older.
Streptocyclinones A and B ameliorate Alzheimer's disease pathological processes in vitro
Alzheimer's disease (AD) is a pathology characterized by the abnormal accumulation of amyloid-beta (Aβ) and hyperphosphorylated tau. Oxidative stress and neuroinflammation are also strongly related to this disease. The ability of two new glycosylated angucyclinones, streptocyclinones A and B (1 and 2), isolated from Streptomyces sp to improve AD hallmarks was evaluated. Compounds were able to protect SH-SY5Y neuroblastoma cells from HO-induced oxidative injury by activating the nuclear factor E2-related factor (Nrf2). Their capacity to modulate neuroinflammation was tested in lipopolysaccharide-activated BV2 microglial cells. Compounds reduced the release of pro-inflammatory factors, inhibited the activation of NFκB and mitogen activated kinases (MAPK), and induced the translocation of Nrf2 to the nucleus of microglial cells. A trans-well co-culture was established to determine the effect of microglia treated with streptocyclinones on the survival of SH-SY5Y cells. The cell viability of neuroblastoma cells increased when the compounds were added to BV2 cells. SH-SY5Y-TMHT441 cells were used to determine the effect of compounds on tau phosphorylation. Both compounds reduced tau hyperphophorylation by targeting MAPK kinases. Moreover, streptocyclinone B (2) was able to inhibit the activity of β-secretase 1 and decrease the release of reactive oxygen species in BV2 cells stimulated with Aβ. With the same co-culture trans-well system, the treatment of Aβ-stimulated microglia with compound 2 augmented the viability of SH-SY5Y-TMHT441 cells. The results presented in this work provide evidences of the multitarget activities displayed by these new Streptomyces compounds, making them good candidates for further studies in the treatment of AD.
The cargo receptor SQSTM1 ameliorates neurofibrillary tangle pathology and spreading through selective targeting of pathological MAPT (microtubule associated protein tau)
Accumulating evidence suggests that misfolded MAPT (microtubule associated protein tau), the main component of neurofibrillary tangles in tauopathies, is subject to degradation by the autophagy-lysosomal pathway. Selective autophagy is a subtype of macroautophagy that requires cargo receptors, such as OPTN (optineurin) or SQSTM1, to recognize specific targets for their sequestration within the autophagosome and their eventual degradation by the lysosome, although their roles in targeting distinct MAPT species have not been fully investigated. Using cargo receptor knockout cell lines and a seeding-based cellular assay in which neurofibrillary tangle pathology can be modeled in vitro, we reveal that while OPTN primarily targets soluble MAPT expressed in physiological conditions, SQSTM1 predominantly degrades insoluble but not soluble mutant MAPT. Endogenous SQSTM1 colocalizes with misfolded and aggregated MAPT species in vitro and in vivo, and both this colocalization and its function in MAPT clearance require both the LC3-interacting region (LIR) motif and also the PB1 self-polymerization domain of SQSTM1. Further, pathogenic MAPT accumulation reduces basal macroautophagy/autophagy in vitro and is associated with a compensatory upregulation of the lysosomal pathway in vivo. Finally, increased expression of SQSTM1 in MAPT transgenic mouse brains ameliorates MAPT pathology and prion-like spreading. Our results uncover distinct properties of selective autophagy receptors in targeting different MAPT species, implicate compromised autophagy as a potential underlying factor in mutant MAPT deposition, and demonstrate a potent and specific role of SQSTM1 in targeted clearance of pathogenic MAPT, through which it blocks neurofibrillary tangle accumulation and pathological spreading. Abbreviations: AAV: adeno-associated virus; AD: Alzheimer disease; ALP: autophagy-lysosomal pathway; ALS: amyotrophic lateral sclerosis; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; FTD: frontotemporal dementias; HD: Huntington disease; HTT: huntingtin; LIR: LC3-interacting region; NBR1: autophagy cargo receptor; NFE2L2/Nrf2: nuclear factor, erythroid derived 2, like 2; NFTs: neurofibrillary tangles; MAPT: microtubule associated protein tau; OPTN: optineurin; p-MAPT: hyperphosphorylated MAPT; PFA: paraformaldehyde; TARDBP/TDP-43: TAR DNA binding protein; TAX1BP1 Tax1: binding protein 1; ThioS: thioflavin-S; UBA: ubiquitin-associated.
Deficiency in the transcription factor NRF2 worsens inflammatory parameters in a mouse model with combined tauopathy and amyloidopathy
Chronic neuroinflammation is a hallmark of the onset and progression of brain proteinopathies such as Alzheimer disease (AD) and it is suspected to participate in the neurodegenerative process. Transcription factor NRF2, a master regulator of redox homeostasis, controls acute inflammation but its relevance in low-grade chronic inflammation of AD is inconclusive due to lack of good mouse models. We have addressed this question in a transgenic mouse that combines amyloidopathy and tauopathy with either wild type (AT-NRF2-WT) or NRF2-deficiency (AT-NRF2-KO). AT-NRF2-WT mice died prematurely, at around 14 months of age, due to motor deficits and a terminal spinal deformity but AT-NRF2-KO mice died roughly 2 months earlier. NRF2-deficiency correlated with exacerbated astrogliosis and microgliosis, as determined by an increase in GFAP, IBA1 and CD11b levels. The immunomodulatory molecule dimethyl fumarate (DMF), a drug already used for the treatment of multiple sclerosis whose main target is accepted to be NRF2, was tested in this preclinical model. Daily oral gavage of DMF during six weeks reduced glial and inflammatory markers and improved cognition and motor complications in the AT-NRF2-WT mice compared with the vehicle-treated animals. This study demonstrates the relevance of the inflammatory response in experimental AD, tightly regulated by NRF2 activity, and provides a new strategy to fight AD.
Heme Oxygenase 1 in the Nervous System: Does It Favor Neuronal Cell Survival or Induce Neurodegeneration?
Heme oxygenase 1 (HO-1) up-regulation is recognized as a pivotal mechanism of cell adaptation to stress. Under control of different transcription factors but with a prominent role played by Nrf2, HO-1 induction is crucial also in nervous system response to damage. However, several lines of evidence have highlighted that HO-1 expression is associated to neuronal damage and neurodegeneration especially in Alzheimer's and Parkinson's diseases. In this review, we summarize the current literature regarding the role of HO-1 in nervous system pointing out different molecular mechanisms possibly responsible for HO-1 up-regulation in nervous system homeostasis and neurodegeneration.
Pyridoxine exerts antioxidant effects in cell model of Alzheimer's disease via the Nrf-2/HO-1 pathway
Pyridoxine is a water- soluble pyridine derivative. The effect of pyridoxine in cell models of Alzheimer's disease (AD), and the potential mechanisms involved, are not fully understood. In this study, the anti-AD effects of pyridoxine were studied in an AD cell model using a combination of techniques viz MTT assay, western blotting and assays for reactive oxygen species (ROS). Assays were also carried out to determine the mechanism underlying the antioxidant effects of pyridoxine. The results obtained revealed that pyridoxine exerted a protective potential against AD, attenuated ROS levels, decreased the expressions of cytoplasmic Nrf2, and upregulated whole-cell HO-1 expression. These results suggest that the anti-AD effect of pyridoxine may be attributed to its anti-oxidant property elicited via stimulation of the Nrf2/HO-1 pathway.
Evaluation of antioxidant and neuroprotective activities of (L.) using the model
(L.) (Fabaceae) is a medicinal plant from tropical Asia. It is known for its marked antioxidant activity, which is attributed to its high phenolic content. The present study aims at testing both the antioxidant and neuroprotective effects of a hydroalcoholic extract from the aerial parts of using the model, which is widely used in this context.
When safeguarding goes wrong: Impact of oxidative stress on protein homeostasis in health and neurodegenerative disorders
Cellular redox status is an established player in many different cellular functions. The buildup of oxidants within the cell is tightly regulated to maintain a balance between the positive and negative outcomes of cellular oxidants. Proteins are highly sensitive to oxidation, since modification can cause widespread unfolding and the formation of toxic aggregates. In response, cells have developed highly regulated systems that contribute to the maintenance of both the global redox status and protein homeostasis at large. Changes to these systems have been found to correlate with aging and age-related disorders, such as neurodegenerative pathologies. This raises intriguing questions as to the source of the imbalance in the redox and protein homeostasis systems, their interconnectivity, and their role in disease progression. Here we focus on the crosstalk between the redox and protein homeostasis systems in neurodegenerative diseases, specifically in Alzheimer's, Parkinson's, and ALS. We elaborate on some of the main players of the stress response systems, including the master regulators of oxidative stress and the heat shock response, Nrf2 and Hsf1, which are essential features of protein folding, and mediators of protein turnover. We illustrate the elegant mechanisms used by these components to provide an immediate response, including protein plasticity controlled by redox-sensing cysteines and the recruitment of naive proteins to the redox homeostasis array that act as chaperons in an ATP-independent manner.