NRF2 as a Therapeutic Target in Neurodegenerative Diseases

An Overview of Registered Clinical Trials on Glucosinolates and Human Health: The Current Situation

Epidemiological studies suggest a potential role of glucosinolates (GSLs) and isothiocyanates on human health. However, evidence from intervention studies, due to heterogeneity in features of study design, duration, participants, food or food components administered, and outcomes analyzed, is still insufficient. The current review aims to provide an overview of the trials on GSLs and GSL-rich foods registered over the last 20 years with the intention to summarize the main topics and results, but also the existing gaps that still need to be covered. Studies were collected by using ClinicalTrials.gov and the International Standard Randomized Controlled Trial Number (ISRCTN) registry. A total of 87 registered trials were identified with which most of them were performed by using extracts or pure compounds (n = 60) while few were conducted with GSL-rich foods (n = 27). In detail, sulforaphane was the most investigated compound, while broccoli was the most frequent food tested in the trials. The majority of the studies assessed the health effects of GSLs focusing on outcomes related to cancer and cognitive function, even if the current findings are not univocal. Emerging topics also included the study of GSLs and gut microbiota interaction and impact on skin health. Further attention was also drawn to the bioavailability of GSLs and/or derivatives from foods, extracts, and single compounds by also considering the contribution of the different genetic polymorphisms. In conclusion, although considerable efforts have been made to study GSLs and GSL-rich foods, further studies are necessary to provide evidence-based research and to corroborate the findings obtained. The interindividual response due to genetic polymorphisms should be further investigated in order to explore the contribution to the overall beneficial effect.

Blood-Brain Barrier Dysfunction in CNS Disorders and Putative Therapeutic Targets: An Overview

The blood-brain barrier (BBB) is a fundamental component of the central nervous system (CNS). Its functional and structural integrity is vital to maintain the homeostasis of the brain microenvironment by controlling the passage of substances and regulating the trafficking of immune cells between the blood and the brain. The BBB is primarily composed of highly specialized microvascular endothelial cells. These cells’ special features and physiological properties are acquired and maintained through the concerted effort of hemodynamic and cellular cues from the surrounding environment. This complex multicellular system, comprising endothelial cells, astrocytes, pericytes, and neurons, is known as the neurovascular unit (NVU). The BBB strictly controls the transport of nutrients and metabolites into brain parenchyma through a tightly regulated transport system while limiting the access of potentially harmful substances via efflux transcytosis and metabolic mechanisms. Not surprisingly, a disruption of the BBB has been associated with the onset and/or progression of major neurological disorders. Although the association between disease and BBB disruption is clear, its nature is not always evident, specifically with regard to whether an impaired BBB function results from the pathological condition or whether the BBB damage is the primary pathogenic factor prodromal to the onset of the disease. In either case, repairing the barrier could be a viable option for treating and/or reducing the effects of CNS disorders. In this review, we describe the fundamental structure and function of the BBB in both healthy and altered/diseased conditions. Additionally, we provide an overview of the potential therapeutic targets that could be leveraged to restore the integrity of the BBB concomitant to the treatment of these brain disorders.

17β-Estradiol Abrogates Oxidative Stress and Neuroinflammation after Cortical Stab Wound Injury

Disruptions in brain energy metabolism, oxidative damage, and neuroinflammation are commonly seen in traumatic brain injury (TBI). Microglial activation is the hallmark of neuroinflammation. After brain injury, microglia also act as a double-edged sword with distinctive phenotypic changes. Therefore, therapeutic applications to potentiate microglia towards pro-inflammatory response following brain injury have become the focus of attention in recent years. Here, in the current study, we investigated the hypothesis that 17β-estradiol could rescue the mouse brain against apoptotic cell death and neurodegeneration by suppressing deleterious proinflammatory response probably by abrogating metabolic stress and oxidative damage after brain injury. Male C57BL/6N mice were used to establish a cortical stab wound injury (SWI) model. Immediately after brain injury, the mice were treated with 17β-estradiol (10 mg/kg, once every day via i.p. injection) for one week. Immunoblotting and immunohistochemical analysis was performed to examine the cortical and hippocampal brain regions. For the evaluation of reactive oxygen species (ROS), reduced glutathione (GSH), and oxidized glutathione (GSSG), we used specific kits. Our findings revealed that 17β-estradiol treatment significantly alleviated SWI-induced energy dyshomeostasis and oxidative stress by increasing the activity of phospho-AMPK (Thr172) and by regulating the expression of an antioxidant gene (Nrf2) and cytoprotective enzymes (HO-1 and GSH) to mitigate ROS. Importantly, 17β-estradiol treatment downregulated gliosis and proinflammatory markers (iNOS and CD64) while significantly augmenting an anti-inflammatory response as evidenced by the robust expression of TGF-β and IGF-1 after brain injury. The treatment with 17β-estradiol also reduced inflammatory mediators (Tnf-α, IL-1β, and COX-2) in the injured mouse. Moreover, 17β-estradiol administration rescued p53-associated apoptotic cell death in the SWI model by regulating the expression of Bcl-2 family proteins (Bax and Bcl-2) and caspase-3 activation. Finally, SWI + 17β-estradiol-treated mice illustrated reduced brain lesion volume and enhanced neurotrophic effect and the expression of synaptic proteins. These findings suggest that 17β-estradiol is an effective therapy against the brain secondary injury-induced pathological cascade following trauma, although further studies may be conducted to explore the exact mechanisms.

Anti-Oxidative, Anti-Inflammatory and Anti-Apoptotic Effects of Flavonols: Targeting Nrf2, NF-κB and p53 Pathways in Neurodegeneration

Neurodegenerative diseases are one of the leading causes of disability and death worldwide. Intracellular transduction pathways that end in the activation of specific transcription factors are highly implicated in the onset and progression of pathological changes related to neurodegeneration, of which those related to oxidative stress (OS) and neuroinflammation are particularly important. Here, we provide a brief overview of the key concepts related to OS- and neuroinflammation-mediated neuropathological changes in neurodegeneration, together with the role of transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB). This review is focused on the transcription factor p53 that coordinates the cellular response to diverse genotoxic stimuli, determining neuronal death or survival. As current pharmacological options in the treatment of neurodegenerative disease are only symptomatic, many research efforts are aimed at uncovering efficient disease-modifying agents. Natural polyphenolic compounds demonstrate powerful anti-oxidative, anti-inflammatory and anti-apoptotic effects, partially acting as modulators of signaling pathways. Herein, we review the current understanding of the therapeutic potential and limitations of flavonols in neuroprotection, with emphasis on their anti-oxidative, anti-inflammatory and anti-apoptotic effects along the Nrf2, NF-κB and p53 pathways. A better understanding of cellular and molecular mechanisms of their action may pave the way toward new treatments.

Brain-Protective Mechanisms of Transcription Factor NRF2: Toward a Common Strategy for Neurodegenerative Diseases

Neurodegenerative diseases are characterized by the loss of homeostatic functions that control redox and energy metabolism, neuroinflammation, and proteostasis. The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) is a master controller of these functions, and its overall activity is compromised during aging and in these diseases. However, NRF2 can be activated pharmacologically and is now being considered a common therapeutic target. Many gaps still exist in our knowledge of the specific role that NRF2 plays in specialized brain cell functions or how these cells respond to the hallmarks of these diseases. This review discusses the relevance of NRF2 to several hallmark features of neurodegenerative diseases and the current status of pharmacological activators that might pass through the blood-brain barrier and provide a disease-modifying effect. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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

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

A Targeted Nanosystem for Detection of Inflammatory Diseases via Fluorescent/Optoacoustic Imaging and Therapy via Modulating Nrf2/NF-κB Pathways

Inflammatory diseases are sometimes devastating and notoriously difficult to treat. Precisely modulating inflammatory signaling pathways is a promising approach for treating inflammatory diseases. Herein, a multifunctional nanosystem is developed for active targeting, activatable imaging and on-demand therapy against inflammatory diseases through modulating inflammatory pathways. A chromophore-drug dyad (QBS-FIS) is synthesized by linking a chromophore and a Nrf2 (nuclear factor E2-related factor) activator fisetin through boronate bond which serves as fluorescence quencher and ROS (reactive oxygen species)-responsive linker. QBS-FIS molecules form nanoparticles in water and are coated with macrophage cell membrane to ensure active targeting toward inflammation site. To further improve therapeutic efficacy, a NF-kB (nuclear-factor kappa-light-chain-enhancer of activated B cells) inhibitor thalidomide is co-encapsulated to afford the nanosystem (QBS-FIS&Thd@MM). Upon administration into mice, the nanosystem migrates to inflammatory site and pathological ROS therein cleaves the boronate bonds, thereby activating the chromophore for imaging liver/kidney inflammatory diseases for disease diagnosis and recovery evaluation via fluorescence and optoacoustic imaging as well as releasing the active drugs for treating acute liver inflammation through activating Nrf2 pathway and inhibiting NF-kB pathway. The 3D multispectral optoacoustic tomography imaging is applied to precisely locate the inflammatory foci in a spatiotemporal manner.

Cognitive impairment in obese rat model: role of glial cells

BACKGROUND

Obesity is a worldwide problem. Some studies revealed that it leads to deterioration of the cognitive function, regardless of age.

AIM OF THE STUDY

explore the effect of obesity on cognitive function in a rat model of obesity highlighting the role of glial cells.

MATERIALS AND METHODS

twenty adult male albino rats were assigned to two groups: group I: consumed normal diet, group II: consumed high-fat diet. Body Mass Index (BMI), serum glucose, insulin, HOMA IR and lipid profile were measured. Also, hippocampal expression of Brain derived neurotrophic factor (Bdnf), synapsin, Ionized calcium binding adaptor molecule 1 (Iba), nuclear factor erythroid -related factor 2 (Nrf2), Myelin basic protein (Mbp) were measured by real-time polymerase chain reaction. The Morris Water Maze is a test used to assess spatial learning and memory capacities of rats.

RESULTS

There was a high significant increase in lipid profile, serum glucose, insulin serum levels and HOMA-IR in obese groups with impaired Morris water maze performance compared to control group. There was a significant downregulation in hippocampal Bdnf and synapsin mRNA expression. In addition to decrease in Mbp mRNA expression (P < 0.001). This could be explained by oxidative stress through significant downregulation of Nrf2 mRNA, and inflammation observed in significant upregulation Iba mRNA gene expression in the obese group.

CONCLUSION

Many factors contribute to obesity associated cognitive impairment. In our study, we figured out the crucial roles of glial cells including microglial activation and oligodendrocytes affection with other underlying mechanisms including oxidative stress and hippocampal inflammation.

Pre- and Early Post-treatment With Arthrospira platensis (Spirulina) Extract Impedes Lipopolysaccharide-triggered Neuroinflammation in Microglia

Background: Uncontrolled neuroinflammation and microglia activation lead to cellular and tissue damage contributing to neurodegenerative and neurological disorders. Spirulina (Arthrospira platensis (Nordstedt) Gomont, or Spirulina platensis), a blue-green microalga, which belongs to the class of cyanobacteria, has been studied for its numerous health benefits, which include anti-inflammatory properties, among others. Furthermore, in vivo studies have highlighted neuroprotective effects of Spirulina from neuroinflammatory insults in different brain areas. However, the mechanisms underlying the anti-inflammatory effect of the microalga are not completely understood. In this study we examined the effect of pre- and post-treatment with an acetone extract of Spirulina (E1) in an in vitro model of LPS-induced microglia activation.

Methods: The effect of E1 on the release of IL-1β and TNF-α, expression of iNOS, nuclear factor erythroid 2–related factor 2 (Nrf2), and heme oxygenase-1 (HO-1), and the activation of NF-κB was investigated in primary microglia by ELISA, real-time PCR, and immunofluorescence.

Results: Pre- and early post-treatment with non-cytotoxic concentrations of E1 down-regulated the release of IL-1β and TNF-α, and the over-expression of iNOS induced by LPS. E1 also significantly blocked the LPS-induced nuclear translocation of NF-κB p65 subunit, and upregulated gene and protein levels of Nrf2, as well as gene expression of HO-1.

Conclusions: These results indicate that the extract of Spirulina can be useful in the control of microglia activation and neuroinflammatory processes. This evidence can support future in vivo studies to test pre- and post-treatment effects of the acetone extract from Spirulina.

Resveratrol as an Adjunctive Therapy for Excessive Oxidative Stress in Aging COVID-19 Patients

The coronavirus disease 2019 (COVID-19) pandemic continues to burden healthcare systems worldwide. COVID-19 symptoms are highly heterogeneous, and the patient may be asymptomatic or may present with mild to severe or fatal symptoms. Factors, such as age, sex, and comorbidities, are key determinants of illness severity and progression. Aging is accompanied by multiple deficiencies in interferon production by dendritic cells or macrophages in response to viral infections, resulting in dysregulation of inflammatory immune responses and excess oxidative stress. Age-related dysregulation of immune function may cause a more obvious pathophysiological response to SARS-CoV-2 infection in elderly patients and may accelerate the risk of biological aging, even after recovery. For more favorable treatment outcomes, inhibiting viral replication and dampening inflammatory and oxidative responses before induction of an overt cytokine storm is crucial. Resveratrol is a potent antioxidant with antiviral activity. Herein, we describe the reasons for impaired interferon production, owing to aging, and the impact of aging on innate and adaptive immune responses to infection, which leads to inflammation distress and immunosuppression, thereby causing fulminant disease. Additionally, the molecular mechanism by which resveratrol could reverse a state of excessive basal inflammatory and oxidative stress and low antiviral immunity is discussed.

An Overview of the Nrf2/ARE Pathway and Its Role in Neurodegenerative Diseases

Nrf2 is a basic region leucine-zipper transcription factor that plays a pivotal role in the coordinated gene expression of antioxidant and detoxifying enzymes, promoting cell survival in adverse environmental or defective metabolic conditions. After synthesis, Nrf2 is arrested in the cytoplasm by the Kelch-like ECH-associated protein 1 suppressor (Keap1) leading Nrf2 to ubiquitin-dependent degradation. One Nrf2 activation mechanism relies on disconnection from the Keap1 homodimer through the oxidation of cysteine at specific sites of Keap1. Free Nrf2 enters the nucleus, dimerizes with small musculoaponeurotic fibrosarcoma proteins (sMafs), and binds to the antioxidant response element (ARE) sequence of the target genes. Since oxidative stress, next to neuroinflammation and mitochondrial dysfunction, is one of the hallmarks of neurodegenerative pathologies, a molecular intervention into Nrf2/ARE signaling and the enhancement of the transcriptional activity of particular genes are targets for prevention or delaying the onset of age-related and inherited neurogenerative diseases. In this study, we review evidence for the Nrf2/ARE-driven pathway dysfunctions leading to various neurological pathologies, such as Alzheimer’s, Parkinson’s, and Huntington’s diseases, as well as amyotrophic lateral sclerosis, and the beneficial role of natural and synthetic molecules that are able to interact with Nrf2 to enhance its protective efficacy.

Caffeoylquinic acids: chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity

Caffeoylquinic acids (CQAs) are specialized plant metabolites we encounter in our daily life. Humans consume CQAs in mg-to-gram quantities through dietary consumption of plant products. CQAs are considered beneficial for human health, mainly due to their anti-inflammatory and antioxidant properties. Recently, new biosynthetic pathways via a peroxidase-type p-coumaric acid 3-hydroxylase enzyme were discovered. More recently, a new GDSL lipase-like enzyme able to transform monoCQAs into diCQA was identified in Ipomoea batatas. CQAs were recently linked to memory improvement; they seem to be strong indirect antioxidants via Nrf2 activation. However, there is a prevalent confusion in the designation and nomenclature of different CQA isomers. Such inconsistencies are critical and complicate bioactivity assessment since different isomers differ in bioactivity and potency. A detailed explanation regarding the origin of such confusion is provided, and a recommendation to unify nomenclature is suggested. Furthermore, for studies on CQA bioactivity, plant-based laboratory animal diets contain CQAs, which makes it difficult to include proper control groups for comparison. Therefore, a synthetic diet free of CQAs is advised to avoid interferences since some CQAs may produce bioactivity even at nanomolar levels. Biotransformation of CQAs by gut microbiota, the discovery of new enzymatic biosynthetic and metabolic pathways, dietary assessment, and assessment of biological properties with potential for drug development are areas of active, ongoing research. This review is focused on the chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity recently reported for mono-, di-, tri-, and tetraCQAs.

Role of Oxidative Damage in Alzheimer's Disease and Neurodegeneration: From Pathogenic Mechanisms to Biomarker Discovery

Alzheimer’s disease (AD) is a neurodegenerative disorder accounting for over 50% of all dementia patients and representing a leading cause of death worldwide for the global ageing population. The lack of effective treatments for overt AD urges the discovery of biomarkers for early diagnosis, i.e., in subjects with mild cognitive impairment (MCI) or prodromal AD. The brain is exposed to oxidative stress as levels of reactive oxygen species (ROS) are increased, whereas cellular antioxidant defenses are decreased. Increased ROS levels can damage cellular structures or molecules, leading to protein, lipid, DNA, or RNA oxidation. Oxidative damage is involved in the molecular mechanisms which link the accumulation of amyloid-β and neurofibrillary tangles, containing hyperphosphorylated tau, to microglia response. In this scenario, microglia are thought to play a crucial role not only in the early events of AD pathogenesis but also in the progression of the disease. This review will focus on oxidative damage products as possible peripheral biomarkers in AD and in the preclinical phases of the disease. Particular attention will be paid to biological fluids such as blood, CSF, urine, and saliva, and potential future use of molecules contained in such body fluids for early differential diagnosis and monitoring the disease course. We will also review the role of oxidative damage and microglia in the pathogenesis of AD and, more broadly, in neurodegeneration.

Insulin-like growth factor II prevents oxidative and neuronal damage in cellular and mice models of Parkinson's disease

Oxidative distress and mitochondrial dysfunction, are key factors involved in the pathophysiology of Parkinson's disease (PD). The pleiotropic hormone insulin-like growth factor II (IGF-II) has shown neuroprotective and antioxidant effects in some neurodegenerative diseases. In this work, we demonstrate the protective effect of IGF-II against the damage induced by 1-methyl-4-phenylpyridinium (MPP+) in neuronal dopaminergic cell cultures and a mouse model of progressive PD. In the neuronal model, IGF-II counteracts the oxidative distress produced by MPP + protecting dopaminergic neurons. Improved mitochondrial function, increased nuclear factor (erythroid-derived 2)-like2 (NRF2) nuclear translocation along with NRF2-dependent upregulation of antioxidative enzymes, and modulation of mammalian target of rapamycin (mTOR) signalling pathway were identified as mechanisms leading to neuroprotection and the survival of dopaminergic cells. The neuroprotective effect of IGF-II against MPP + -neurotoxicity on dopaminergic neurons depends on the specific IGF-II receptor (IGF-IIr). In the mouse model, IGF-II prevents behavioural dysfunction and dopaminergic nigrostriatal pathway degeneration and mitigates neuroinflammation induced by MPP+. Our work demonstrates that hampering oxidative stress and normalising mitochondrial function through the interaction of IGF-II with its specific IGF-IIr are neuroprotective in both neuronal and mouse models. Thus, the modulation of the IGF-II/IGF-IIr signalling pathway may be a useful therapeutic approach for the prevention and treatment of PD.

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IGF-II hampers oxidative damage and promotes survival in a cellular model of PD.

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IGF-II avoids mitochondrial damage in dopaminergic cells in a model of PD.

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IGF-II receptor mediates the neuroprotective effect of IGF-II in a cellular model of PD.

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IGF-II prevents nigrostriatal degeneration and inflammation in a mice model of PD.

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IGF-II prevents behavioural dysfunction in a mice model of PD.

Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: Efficacy, mechanisms of action, and factors influencing inter-individual response

The pathophysiology of psychiatric and neurodegenerative disorders is complex and multifactorial. Polyphenols possess a range of potentially beneficial mechanisms of action that relate to the implicated pathways in psychiatric and neurodegenerative disorders. The aim of this review is to highlight the emerging clinical trial and preclinical efficacy data regarding the role of polyphenols in mental and brain health, elucidate novel mechanisms of action including the gut microbiome and gene expression, and discuss the factors that may be responsible for the mixed clinical results; namely, the role of interindividual differences in treatment response and the potentially pro-oxidant effects of some polyphenols. Further clarification as part of larger, well conducted randomized controlled trials that incorporate precision medicine methods are required to inform clinical efficacy and optimal dosing regimens.

Apomorphine Reduces A53T α-Synuclein-Induced Microglial Reactivity Through Activation of NRF2 Signalling Pathway

The chiral molecule, apomorphine, is currently used for the treatment of Parkinson’s disease (PD). As a potent dopamine receptor agonist, this lipophilic compound is especially effective for treating motor fluctuations in advanced PD patients. In addition to its receptor-mediated actions, apomorphine has also antioxidant and free radical scavenger activities. Neuroinflammation, oxidative stress, and microglia reactivity have emerged as central players in PD. Thus, modulating microglia activation in PD may be a valid therapeutic strategy. We previously reported that murine microglia are strongly activated upon exposure to A53T mutant α-synuclein. The present study was designed to investigate whether apomorphine enantiomers could modulate this A53T-induced microglial activation. Taken together, the results provided evidence that apomorphine enantiomers decrease A53T-induced microgliosis, through the activation of the NRF2 signalling pathway, leading to a lower pro-inflammatory state and restoring the phagocytic activity. Suppressing NRF2 recruitment (trigonelline exposure) or silencing specifically Nfe2l2 gene (siRNA treatment) abolished or strongly decreased the anti-inflammatory activity of apomorphine. In conclusion, apomorphine, which is already used in PD patients to mimic dopamine activity, may also be suitable to decrease α-synuclein-induced microglial reactivity.

Conditioned Medium of Adipose-Derived Mesenchymal Stem Cells as a Promising Candidate to Protect High Glucose-Induced Injury in Cultured C28I2 Chondrocytes

Purpose: The aim of this study was to evaluate the protective effect of conditioned medium derived from human adipose mesenchymal stem cells (CM-hADSCs) on C28I2 chondrocytes against oxidative stress and mitochondrial apoptosis induced by high glucose (HG).

Methods: C28I2 cells were pre-treated with CM-hADSCs for 24 hours followed by HG exposure (75 mM) for 48 hours. MTT assay was used to assess the cell viability. Reactive oxygen species (ROS) and lipid peroxidation were determined by 2,7-dichlorofluorescein diacetate (DCFHDA) and thiobarbituric acid reactive substances (TBARS) assays, respectively. Expressions of glutathione peroxidase 3 (GPX 3), heme oxygenase-1 (HO-1), and NAD(P)H quinone dehydrogenase 1 (NQO1) were analyzed by RT-PCR. Finally, western blot analysis was used to measure Bax, Bcl-2, cleaved caspase-3, and Nrf-2 expression at protein levels.

Results: CM-hADSCs pretreatment mitigated the cytotoxic effect of HG on C28I2 viability. Treatment also markedly reduced the levels of ROS, lipid peroxidation, and augmented the expression of HO-1, NQO1, and GPx3 genes in HG-exposed group. CM-ADSCs enhanced Nrf-2 protein expression and reduced mitochondrial apoptosis through reducing Bax/Bcl-2 ratio and Caspase-3 activation.

Conclusion: MSCs, probably through its paracrine effects, declined the deleterious effect of HG on chondrocytes. Hence, therapies based on MSCs secretomes appear to be a promising therapeutic approaches to prevent joint complications in diabetic patients.

Activation of Nrf2 by methylene blue is associated with the neuroprotection against MPP+ induced toxicity via ameliorating oxidative stress and mitochondrial dysfunction

The neuropathological hallmark of Parkinson's disease (PD) is the preferential loss of dopaminergic neurons in the substantia nigra and presence of Lewy bodies in the dying neurons. Though specific molecular mechanisms for the neurodegeneration remains to be clarified, mitochondrial dysfunction and increased oxidative stress are major players associated with PD pathogenesis and these pathogenic mechanisms can be reproduced in cells and animals by application of various neurotoxins such as MPP⁺. In this study, we attempted to determine the neuroprotective effects of methylene blue (MB) against 1-methyl-4-phenylpyridinium (MPP⁺)-induced neurotoxicity, and to elucidate its action mechanism. We observed that MB attenuated MPP⁺-induced apoptotic cell death in SH-SY5Y cells and the mescencephalic dopaminergic neurons. In addition, MB protected the cells against MPP⁺-induced oxidative stress and mitochondrial dysfunction as evidenced by restoration of mitochondrial complex I activity and ATP levels, and attenuation of oxidative stress. Moreover, we demonstrated that MB induced antioxidant molecules, and activated Nrf2 pathway through AKT activation. These results indicate that MB protects the neurons from MPP⁺-induced toxicity through activation of antioxidant system, thereby reducing the oxidative stress and mitochondrial impairment, implying the potential use of MB in the treatment of neurodegenerative diseases such as PD.

Benincasa hispida alleviates amyloid pathology by inhibition of Keap1/Nrf2-axis: Emphasis on oxidative and inflammatory stress involved in Alzheimer's disease model

OBJECTIVES

Alzheimer's disease is a progressive neurodegenerative disorder with cognitive and memory impairment. Benincasa hispida is being used in the treatment of various neurological diseases in Ayurveda system of medicine. The objective of the study was to investigate the effect of Benincasa hispida fruit extract in the Alzheimer's disease rats.

METHODS

Benincasa hispida fruits extract was administered orally for 16 weeks at doses of 250 and 500-mg/kg/day. The cognitive deficits were examined by behavioural tests like Morris water maze test, Y-maze and rota-rod test. Biochemical and neurochemical analysis of Acetylcholine, dopamine, serotonin levels and anti-oxidant, anti-inflammatory markers were evaluated and the mRNA expression of Keap/Nrf2 axis was analysed by RT-PCR.

RESULTS

Aluminum chloride (AlCl₃) induction altered the behavioural profile and produced significant alterations in the cortical and hippocampal regions of the brain and the treatment with Benincasa hispida extract at doses of 250-mg/kg/day (p<0.05) and 500mg/kg/day (p<0.05) alleviated the acetylcholine, dopamine and serotonin neurotransmitter levels. The antioxidant enzyme markers such as superoxide dismutase (SOD), Catalase (CAT), glutathione (GSH) were increased and the oxidative stress marker malondialdehyde(MDA) was decreased. The inflammatory cytokine levels of TNF-α, IL-1β were decreased in Alzheimer's disease induced rats. We further estimated Keap/Nrf2/HO-1 genes these anti-oxidant genes were upregulated(p < 0.001) in treatment groups. Further, the neuroprotective activity of Benincasa was further confirmed by histopathological studies of hippocampal CA3 fields.

CONCLUSIONS

The findings of the current study indicates Benincasa hispida as a possible neuroprotective alternative for Alzheimer's disease.

Contribution of the Nrf2 Pathway on Oxidative Damage and Mitochondrial Failure in Parkinson and Alzheimer's Disease

The increase in human life expectancy has become a challenge to reduce the deleterious consequences of aging. Nowadays, an increasing number of the population suffer from age-associated neurodegenerative diseases including Parkinson's disease (PD) and Alzheimer's disease (AD). These disorders present different signs of neurodegeneration such as mitochondrial dysfunction, inflammation, and oxidative stress. Accumulative evidence suggests that the transcriptional factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) plays a vital defensive role orchestrating the antioxidant response in the brain. Nrf2 activation promotes the expression of several antioxidant enzymes that exert cytoprotective effects against oxidative damage and mitochondrial impairment. In this context, several studies have proposed a role of Nrf2 in the pathogenesis of PD and AD. Thus, we consider it important to summarize the ongoing literature related to the effects of the Nrf2 pathway in the context of these diseases. Therefore, in this review, we discuss the mechanisms involved in Nrf2 activity and its connection with mitochondria, energy supply, and antioxidant response in the brain. Furthermore, we will lead our discussion to identify the participation of the Nrf2 pathway in mitochondrial impairment and neurodegeneration present in PD and AD. Finally, we will discuss the therapeutic effects that the Nrf2 pathway activation could have on the cognitive impairment, neurodegeneration, and mitochondrial failure present in PD and AD.

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.

Divulging the Intricacies of Crosstalk Between NF-Kb and Nrf2-Keap1 Pathway in Neurological Complications of COVID-19

The severity of COVID-19 infection is surging day by day. With the cases increasing daily, it is becoming more and more essential to understand the pathogenic mechanisms underlying the severity of the disease. It is now well known that the infection manifests itself primarily as respiratory, but the involvement of the other organ systems has now been documented in many studies. SARS-CoV-2 can invade the nervous system by a multitude of proposed mechanisms that have been discussed in this review. NF-κB and Nrf2 are transcription factors that regulate genes responsible for inflammatory and anti-oxidant response respectively. Specific focus in this review has been given to NF-κB and Nrf2 pathways that are involved in the cytokine storm and oxidative stress that are the hallmarks of COVID-19. As the immune injury is an important mechanism of neuro-invasion and neuroinflammation, there is the possible involvement of these two pathways in the neurological complications. The crosstalk mechanisms of these signaling pathways have also been discussed. Immuno-modulators both synthetic and natural are promising candidates in catering to the pathologies targeted in the aforementioned pathways.

Mitoprotective Effects of Centella asiatica (L.) Urb.: Anti-Inflammatory and Neuroprotective Opportunities in Neurodegenerative Disease

Natural products remain a crucial source of drug discovery for accessible and affordable solutions for healthy aging. Centella asiatica (L.) Urb. (CA) is an important medicinal plant with a wide range of ethnomedicinal uses. Past in vivo and in vitro studies have shown that the plant extract and its key components, such as asiatic acid, asiaticoside, madecassic acid and madecassoside, exhibit a range of anti-inflammatory, neuroprotective, and cognitive benefits mechanistically linked to mitoprotective and antioxidant properties of the plant. Mitochondrial dysfunction and oxidative stress are key drivers of aging and neurodegenerative disease, including Alzheimer’s disease and Parkinson’s disease. Here we appraise the growing body of evidence that the mitoprotective and antioxidative effects of CA may potentially be harnessed for the treatment of brain aging and neurodegenerative disease.

Activation of kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2/antioxidant response element pathway by curcumin enhances the anti-oxidative capacity of corneal endothelial cells

Fuchs endothelial corneal dystrophy is one of the most common indications for corneal transplantation, and impaired anti-oxidative function is observed in corneal endothelial cells (CECs). Curcumin is well-known for its anti-oxidative property; but, no study has examined the effect of curcumin on anti-oxidative therapeutic roles in corneal endothelial disease. In our experiments, oxidative stress 0.25 mM tert-butyl hydroperoxide for 2 h was induced in immortalized human CECs pretreated with curcumin. Cell behavior and viability, reactive oxygen species production, and the protein expression of the kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2(Nrf2)/antioxidant response element (ARE) pathway were examined; the Keap1/Nrf2/ARE pathway is crucial anti-oxidative pathway of curcumin. The results showed that pretreatment with 12.5 μM curcumin significantly reduced the ROS production and improved the survival of CECs under oxidative stress. In addition, curcumin pretreatment significantly increased the expression of nuclear Nrf2, and the productions of superoxide dismutase 1 and heme oxygenase-1, which were the target anti-oxidative enzymes of the Keap1/Nrf2/ARE pathway. Our findings showed that curcumin enhanced the growth and differentiation of CECs under oxidative stress. The activation of Keap1/Nrf2/ARE pathway by curcumin was crucial for CECs to improve their anti-oxidative capacity.

NXP031 Improves Cognitive Impairment in a Chronic Cerebral Hypoperfusion-Induced Vascular Dementia Rat Model through Nrf2 Signaling

Vascular dementia (VaD) is a progressive cognitive impairment caused by a reduced blood supply to the brain. Chronic cerebral hypoperfusion (CCH) is one cause of VaD; it induces oxidative stress, neuroinflammation, and blood-brain barrier (BBB) disruption, damaging several brain regions. Vitamin C plays a vital role in preventing oxidative stress-related diseases induced by reactive oxygen species, but it is easily oxidized and loses its antioxidant activity. To overcome this weakness, we have developed a vitamin C/DNA aptamer complex (NXP031) that increases vitamin C's antioxidant efficacy. Aptamers are short single-stranded nucleic acid polymers (DNA or RNA) that can interact with their corresponding target with high affinity. We established an animal model of VaD by permanent bilateral common carotid artery occlusion (BCCAO) in 12 week old Wistar rats. Twelve weeks after BCCAO, we injected NXP031 into the rats intraperitoneally for two weeks at moderate (200 mg/4 mg/kg) and high concentrations (200 mg/20 mg/kg). NXP031 administration alleviates cognitive impairment, microglial activity, and oxidative stress after CCH. NXP031 increased the expression of basal lamina (laminin), endothelial cell (RECA-1, PECAM-1), and pericyte (PDGFRβ); these markers maintain the BBB integrity. We found that NXP031 administration activated the Nrf2-ARE pathway and increased the expression of SOD-1 and GSTO1/2. These results suggest that this new aptamer complex, NXP031, could be a therapeutic intervention in CCH-induced VaD.

Sesamin Activates Nrf2/Cnc-Dependent Transcription in the Absence of Oxidative Stress in Drosophila Adult Brains

Sesamin, a major lignin in sesame seeds, possesses health-promoting properties. Sesamin feeding suppresses several aging-related phenotypes such as age-dependent accumulation of damaged proteins in the muscles and neuronal loss in the brains of Drosophila adults with high levels of reactive oxygen species. Sesamin promotes the transcription of several genes that are responsible for oxidative stress, although the underlying mechanism remains unclear. Here, we aimed to demonstrate that sesamin mediates its action through activation of a transcription factor, Nrf2 (Cnc in Drosophila), essential for anti-aging oxidative stress response. Nrf2/Cnc activation was determined using the antioxidant response element, Green Fluorescence Protein reporter, that can monitor Nrf2/Cnc-dependent transcription. We observed strong fluorescence in the entire bodies, particularly in the abdomens and brains, of adult flies fed sesamin. Interestingly, Nrf2/Cnc was strongly activated in neuronal cells, especially in several neuron types, including glutamatergic and cholinergic, and some dopaminergic and/or serotonergic neurons but not in GABAergic neurons or the mushroom bodies of flies fed sesamin. These results indicate that the anti-aging effects of sesamin are exerted via activation of Nrf2/Cnc-dependent transcription to circumvent oxidative stress accumulation in several types of neurons of adult brains. Sesamin could be explored as a potential dietary supplement for preventing neurodegeneration associated with accumulation of oxidative stress.

Oxidative stress sensing and response in neural stem cell fate

Neural stem/progenitor cells (NSPCs) contribute to the physiological cellular turnover of the adult brain and make up its regenerative potential. It is thus essential to understand how different factors influence their proliferation and differentiation to gain better insight into potential therapeutic targets in neurodegenerative diseases and traumatic brain injuries. Recent evidences indicate the roles of redox stress sensing and coping mechanisms in mediating the balance between NSPC self-renewal and differentiation. Such mechanisms involve direct cysteine modification, signaling and metabolic reprogramming, epigenetic alterations and transcription changes leading to adaptive responses like autophagy. Here, we discuss emerging findings on the involvement of redox sensors and effectors and their mechanisms in influencing changes in cellular redox potential and NSPC fate.

17-β Estradiol Rescued Immature Rat Brain against Glutamate-Induced Oxidative Stress and Neurodegeneration via Regulating Nrf2/HO-1 and MAP-Kinase Signaling Pathway

Dysregulated glutamate signaling, leading to neuronal excitotoxicity and death, has been associated with neurodegenerative pathologies. 17β-estradiol (E2) is a human steroid hormone having a role in reproduction, sexual maturation, brain health and biological activities. The study aimed to explain the neuroprotective role of E2 against glutamate-induced ROS production, MAP kinase-dependent neuroinflammation, synaptic dysfunction and neurodegeneration in the cortex and hippocampus of postnatal day 7 rat brain. Biochemical and immunofluorescence analyses were applied. Our results showed that a single subcutaneous injection of glutamate (10 mg/kg) induced brain oxidative stress after 4 h by disturbing the homeostasis of glutathione (GSH) and revealed an upsurge in ROS and LPO levels and downregulated the expression of Nrf2 and HO-1 antioxidant protein. The glutamate-exposed P7 pups illustrated increased phosphorylation of stress-activated c-Jun N-terminal kinase (JNK) and p38 kinase (p38) and downregulated expression of P-Erk1/2. This was accompanied by pathological neuroinflammation as revealed by enhanced gliosis with upregulated expression of GFAP and Iba-1, and the activation of proinflammatory cytokines (TNF-α) in glutamate-injected P7 pups. Moreover, exogenous glutamate also reduced the expression of synaptic markers (PSD-95, SYP) and induced apoptotic neurodegeneration in the cortical and hippocampal regions by dysregulating the expression of Bax, Bcl-2 and caspase-3 in the developing rat brain. On the contrary, co-treatment of E2 (10 mg/kg) with glutamate significantly abrogated brain neuroinflammation, neurodegeneration and synapse loss by alleviating brain oxidative stress by upregulating the Nrf2/HO-1 antioxidant pathway and by deactivating pro-apoptotic P-JNK/P-p38 and activation of pro-survival P-Erk1/2 MAP kinase pathways. In brief, the data demonstrate the neuroprotective role of E2 against glutamate excitotoxicity-induced neurodegeneration. The study also encourages future studies investigating if E2 may be a potent neuroprotective and neurotherapeutic agent in different neurodegenerative diseases.

Repurposing of Anti-Diabetic Agents as a New Opportunity to Alleviate Cognitive Impairment in Neurodegenerative and Neuropsychiatric Disorders

Cognitive impairment is a shared abnormality between type 2 diabetes mellitus (T2DM) and many neurodegenerative and neuropsychiatric disorders, such as Alzheimer’s disease (AD) and schizophrenia. Emerging evidence suggests that brain insulin resistance plays a significant role in cognitive deficits, which provides the possibility of anti-diabetic agents repositioning to alleviate cognitive deficits. Both preclinical and clinical studies have evaluated the potential cognitive enhancement effects of anti-diabetic agents targeting the insulin pathway. Repurposing of anti-diabetic agents is considered to be promising for cognitive deficits prevention or control in these neurodegenerative and neuropsychiatric disorders. This article reviewed the possible relationship between brain insulin resistance and cognitive deficits. In addition, promising therapeutic interventions, especially current advances in anti-diabetic agents targeting the insulin pathway to alleviate cognitive impairment in AD and schizophrenia were also summarized.

C60 Fullerene Reduces 3-Nitropropionic Acid-Induced Oxidative Stress Disorders and Mitochondrial Dysfunction in Rats by Modulation of p53, Bcl-2 and Nrf2 Targeted Proteins

C₆₀ fullerene as a potent free radical scavenger and antioxidant could be a beneficial means for neurodegenerative disease prevention or cure. The aim of the study was to define the effects of C₆₀ administration on mitochondrial dysfunction and oxidative stress disorders in a 3-nitropropionic acid (3-NPA)-induced rat model of Huntington’s disease. Animals received 3-NPA (30 mg/kg i.p.) once a day for 3 consecutive days. C₆₀ was applied at a dose of 0.5 mg/kg of body weight, i.p. daily over 5 days before (C₆₀ pre-treatment) and after 3-NPA exposure (C₆₀ post-treatment). Oxidative stress biomarkers, the activity of respiratory chain enzymes, the level of antioxidant defense, and pro- and antiapoptotic markers were analyzed in the brain and skeletal muscle mitochondria. The nuclear and cytosol Nrf2 protein expression, protein level of MnSOD, γ-glutamate-cysteine ligase (γ-GCLC), and glutathione-S-transferase (GSTP) as Nrf2 targets were evaluated. Our results indicated that C₆₀ can prevent 3-NPA-induced mitochondrial dysfunction through the restoring of mitochondrial complexes’ enzyme activity, ROS scavenging, modulating of pro/antioxidant balance and GSH/GSSG ratio, as well as inhibition of mitochondria-dependent apoptosis through the limitation of p53 mitochondrial translocation and increase in Bcl-2 protein expression. C₆₀ improved mitochondrial protection by strengthening the endogenous glutathione system via glutathione biosynthesis by up-regulating Nrf2 nuclear accumulation as well as GCLC and GSTP protein level.

Heterocyclic Compounds: Pharmacology of Pyrazole Analogs From Rational Structural Considerations

Low quality of life and life-threatening conditions often demand pharmacological screening of lead compounds. A spectrum of pharmacological activities has been attributed to pyrazole analogs. The substitution, replacement, or removal of functional groups on a pyrazole ring appears consistent with diverse molecular interactions, efficacy, and potency of these analogs. This mini-review explores cytotoxic, cytoprotective, antinociceptive, anti-inflammatory, and antidepressant activities of some pyrazole analogs to advance structure-related pharmacological profiles and rational design of new analogs. Numerous interactions of these derivatives at their targets could impact future research considerations and prospects while offering opportunities for optimizing therapeutic activity with fewer adverse effects.

β-Asarone Ameliorates β-Amyloid-Induced Neurotoxicity in PC12 Cells by Activating P13K/Akt/Nrf2 Signaling Pathway

Accumulation of β-amyloid (Aβ) causes oxidative stress, which is the major pathological mechanism in Alzheimer's disease (AD). β-asarone could reduce Aβ-induced oxidative stress and neuronal damage, but the molecular mechanism remains elusive. In this study, we used an Aβ-stimulated PC12 cell model to explore the neuroprotective effects and potential mechanisms of β-asarone. The results showed that β-asarone could improve cell viability and weaken cell damage and apoptosis. β-asarone could also decrease the level of ROS and MDA; increase the level of SOD, CAT, and GSH-PX; and ameliorate the mitochondrial membrane potential. Furthermore, β-asarone could promote the expression of Nrf2 and HO-1 by upregulating the level of PI3K/Akt phosphorylation. In conclusion, β-asarone could exert neuroprotective effects by modulating the P13K/Akt/Nrf2 signaling pathway. β-asarone might be a promising therapy for AD.

Cell Death via Lipid Peroxidation and Protein Aggregation Diseases

Lipid peroxidation of cellular membranes is a complicated cellular event, and it is both the cause and result of various diseases, such as ischemia-reperfusion injury, neurodegenerative diseases, and atherosclerosis. Lipid peroxidation causes non-apoptotic cell death, which is associated with cell fate determination: survival or cell death. During the radical chain reaction of lipid peroxidation, various oxidized lipid products accumulate in cells, followed by organelle dysfunction and the induction of non-apoptotic cell death. Highly reactive oxidized products from unsaturated fatty acids are detected under pathological conditions. Pathological protein aggregation is the general cause of these diseases. The cellular response to misfolded proteins is well-known as the unfolded protein response (UPR) and it is partially concomitant with the response to lipid peroxidation. Moreover, the association between protein aggregation and non-apoptotic cell death by lipid peroxidation is attracting attention. The link between lipid peroxidation and protein aggregation is a matter of concern in biomedical fields. Here, we focus on lethal protein aggregation in non-apoptotic cell death via lipid peroxidation. We reviewed the roles of protein aggregation in the initiation and execution of non-apoptotic cell death. We also considered the relationship between protein aggregation and oxidized lipid production. We provide an overview of non-apoptotic cell death with a focus on lipid peroxidation for therapeutic targeting during protein aggregation diseases.

Challenges and Limitations of Targeting the Keap1-Nrf2 Pathway for Neurotherapeutics: Bach1 De-Repression to the Rescue

The Keap1-Nrf2 signaling axis is a validated and promising target for cellular defense and survival pathways. This minireview discusses the potential off-target effects and their impact on future drug development originating from Keap1-targeting small molecules that function as displacement activators of the redox-sensitive transcription factor Nrf2. We argue that small-molecule displacement activators, similarly to electrophiles, will release both Nrf2 and other Keap1 client proteins from the ubiquitin ligase complex. This non-specificity is likely unavoidable and may result in off-target effects during Nrf2 activation by targeting Keap1. The small molecule displacement activators may also target Kelch domains in proteins other than Keap1, causing additional off-target effects unless designed to ensure specificity for the Kelch domain only in Keap1. A potentially promising and alternative therapeutic approach to overcome this non-specificity emerging from targeting Keap1 is to inhibit the Nrf2 repressor Bach1 for constitutive activation of the Nrf2 pathway and bypass the Keap1-Nrf2 complex.

Dietary Nutrients and Prevention of Alzheimer's disease

Alzheimer's disease is an irrevocable, progressive brain disorder that gradually destroys memory and cognitive skills. One of the extensively studied method of preventing Alzheimer's disease (AD) disease progression is by providing nutritional diet. Several reports have shown that intake of nutritional elements as huperzine A, ursolic acid, vitamins etc. can directly influence pathogenesis of AD. Surprisingly, occurrence of metabolic disorders due to unhealthy diet has been known to be a major environmental causes for AD. It has been noted that AD disease severity can be controlled by supplementing dietary supplements containing huge amounts of health-promoting ingredients. These elements promote cell health, regeneration, and the anti-aging process that specifically interrupt the pathogenic pathways in AD development. Fortunately, incorporating changes in the nutritional content is inexpensive, easy, acceptable, safe, effective, and in most cases free from major adverse events. Many nutritional phytoconstituents such as flavonoids, alkaloids, and terpenoids are still being evaluated in the hope of identifying a successful therapy for AD. This review discusses the therapeutical potential of several key nutrients that have been researched for treating AD treatment and the method of their neuroprotective intervention.

Direct Keap1-kelch inhibitors as potential drug candidates for oxidative stress-orchestrated diseases: A review on In silico perspective

The recent outcry in the search for direct keap1 inhibitors requires a quicker and more effective drug discovery process which is an inherent property of the Computer Aided Drug Discovery (CADD) to bring drug candidates into the clinic for patient's use. This Keap1 (negative regulator of ARE master activator) is emerging as a therapeutic strategy to combat oxidative stress-orchestrated diseases. The advances in computer algorithm and compound databases require that we highlight the functionalities that this technology possesses that can be exploited to target Keap1-Nrf2 PPI. Therefore, in this review, we uncover the in silico approaches that had been exploited towards the identification of keap1 inhibition in the light of appropriate fitting with relevant amino acid residues, we found 3 and 16 other compounds that perfectly fit keap1 kelch pocket/domain. Our goal is to harness the parameters that could orchestrate keap1 surface druggability by utilizing hotspot regions for virtual fragment screening and identification of hotspot residues.

The Nrf2 pathway in psychiatric disorders: pathophysiological role and potential targeting

Introduction: All psychiatric disorders exhibit excitotoxicity, mitochondrial dysfunction, inflammation, oxidative stress, and neural damage as their common characteristic. The endogenous nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway is implicated in the defense mechanism against oxidative stress and has a significant role in psychiatric disorders.Areas covered: We explore the role of Nrf2 pathway and its modulators in psychiatric disorders. The literature was searched utilizing various databases such as Embase, Medline, Web of Science, Pub-Med, and Google Scholar from 2010 to 2020. The search included research articles, clinical reports, systematic reviews, and meta-analyses.Expert opinion: Environmental factors and genetic predisposition can be a trigger for the development of psychiatric disorders. Nrf2 downregulates certain inflammatory pathways and upregulates various antioxidant enzymes to maintain a balance. However, its intricate balance with NF-Kβ (Nuclear factor kappa light chain enhancer of activated B cells) and its crosstalk with the transcription factor Nrf2 is critical in severe oxidative stress. Several Nrf2 modulators are now in clinical trials and can help reduce oxidative stress and neuroinflammation. There are immense potential opportunities for these modulators to become a novel therapeutic option.

Antioxidant and Neuroprotective Activity of Extra Virgin Olive Oil Extracts Obtained from Quercetano Cultivar Trees Grown in Different Areas of the Tuscany Region (Italy)

Neurodegenerative diseases are driven by several mechanisms such as inflammation, abnormal protein aggregation, excitotoxicity, mitochondrial dysfunction and oxidative stress. So far, no therapeutic strategies are available for neurodegenerative diseases and in recent years the research is focusing on bioactive molecules present in food. In particular, extra-virgin olive oil (EVOO) phenols have been associated to neuroprotection. In this study, we investigated the potential antioxidant and neuroprotective activity of two different EVOO extracts obtained from Quercetano cultivar trees grown in two different areas (plain and hill) of the Tuscany region (Italy). The different geographical origin of the orchards influenced phenol composition. Plain extract presented a higher content of phenyl ethyl alcohols, cinnammic acids, oleacein, oleocanthal and flavones; meanwhile, hill extract was richer in lignans. Hill extract was more effective in protecting differentiated SH-SY5Y cells from peroxide stress thanks to a marked upregulation of the antioxidant enzymes heme oxygenase 1, NADPH quinone oxidoreductase 1, thioredoxin Reductase 1 and glutathione reductase. Proteomic analysis revealed that hill extract plays a role in the regulation of proteins involved in neuronal plasticity and activation of neurotrophic factors such as BDNF. In conclusion, these data demonstrate that EVOOs can have important neuroprotective activities, but these effects are strictly related to their specific phenol composition.

Walnut-Derived Peptide Activates PINK1 via the NRF2/KEAP1/HO-1 Pathway, Promotes Mitophagy, and Alleviates Learning and Memory Impairments in a Mice Model

Mitophagy has a pivotal protective function in the pathogenesis of neurological disorders. However, the mechanism of its modulation remains elusive, especially in PINK1-mediated mitophagy. Here, we investigated the neuroprotective effects of a walnut-derived peptide, YVLLPSPK, against scopolamine-induced cognitive deficits in mice and explored the underlying PINK1-mediated mitophagy mechanisms in H₂O₂-treated HT-22 cells. Using the Morris water maze, we showed that YVLLPSPK relieved the cognitive deficiency by alleviating oxidative stress. Mitochondrial morphology was observed in mice hippocampal tissues using transmission electron microscopy (TEM). Both Western blot and immunofluorescence analysis illustrated YVLLPSPK promoted the expression of mitophagy-related proteins and activated the NRF2/KEAP1/HO-1 pathway. Subsequently, an NRF2 inhibitor (ML385) was used to verify the contribution of the YVLLPSPK-regulated NRF2/KEAP1/HO-1 pathway in PINK1-mediated mitophagy in H₂O₂-treated HT-22 cells. These data suggested that YVLLPSPK improved learning and memory in scopolamine-induced cognitive-impaired mice through a mechanism associated with PINK1-mediated mitophagy via the NRF2/KEAP1/HO-1 pathway.

Interplay between bioenergetics and oxidative stress at normal brain aging. Aging as a result of increasing disbalance in the system oxidative stress-energy provision

At normal aging, the brain exhibits signs of compromised bioenergetic and increased levels of products of interaction between reactive oxygen/nitrogen species (ROS/RNS) and brain constituents. Under normal conditions, steady-state levels of ATP and ROS/RNS fluctuate in certain ranges providing basis for stable homeostasis. However, from time to time these parameters leave a "comfort zone," and at adulthood, organisms are able to cope with these challenges efficiently, whereas at aging, efficiency of the systems maintaining homeostasis declines. That is very true for the brain due to high ATP demands which are mainly covered by mitochondrial oxidative phosphorylation. Such active oxidative metabolism gives rise to intensive ROS generation as side products. The situation is worsened by high brain level of polyunsaturated fatty acids which are substrates for ROS/RNS attack and production of lipid peroxides. In this review, organization of energetic metabolism in the brain with a focus on its interplay with ROS at aging is discussed. The working hypothesis on aging as a disbalance between oxidative stress and energy provision as a reason for brain aging is proposed. From this point of view, normal age-related physiological decline in the brain functions results from increased disbalance between decrease in capability of the brain to control constantly increased incapability to maintain ROS levels and produce ATP due to amplification of vicious cycles intensification of oxidative stress <----> impairment of energy provision.

Human INCL fibroblasts display abnormal mitochondrial and lysosomal networks and heightened susceptibility to ROS-induced cell death

Infantile Neuronal Ceroid Lipofuscinosis (INCL) is a pediatric neurodegenerative disorder characterized by progressive retinal and central nervous system deterioration during infancy. This lysosomal storage disorder results from a deficiency in the Palmitoyl Protein Thioesterase 1 (PPT1) enzyme—a lysosomal hydrolase which cleaves fatty acid chains such as palmitate from lipid-modified proteins. In the absence of PPT1 activity, these proteins fail to be degraded, leading to the accumulation of autofluorescence storage material in the lysosome. The underlying molecular mechanisms leading to INCL pathology remain poorly understood. A role for oxidative stress has been postulated, yet little evidence has been reported to support this possibility. Here we present a comprehensive cellular characterization of human PPT1-deficient fibroblast cells harboring Met1Ile and Tyr247His compound heterozygous mutations. We detected autofluorescence storage material and observed distinct organellar abnormalities of the lysosomal and mitochondrial structures, which supported previous postulations about the role of ER, mitochondria and oxidative stress in INCL. An increase in the number of lysosomal structures was found in INCL patient fibroblasts, which suggested an upregulation of lysosomal biogenesis, and an association with endoplasmic reticulum stress response. The mitochondrial network also displayed abnormal spherical punctate morphology instead of normal elongated tubules with extensive branching, supporting the involvement of mitochondrial and oxidative stress in INCL cell death. Autofluorescence accumulation and lysosomal pathologies can be mitigated in the presence of conditioned wild type media suggesting that a partial restoration via passive introduction of the enzyme into the cellular environment may be possible. We also demonstrated, for the first time, that human INCL fibroblasts have a heightened susceptibility to exogenous reactive oxygen species (ROS)-induced cell death, which suggested an elevated basal level of endogenous ROS in the mutant cell. Collectively, these findings support the role of intracellular organellar networks in INCL pathology, possibly due to oxidative stress.

Counteracting Effects of Glutathione on the Glutamate-Driven Excitation/Inhibition Imbalance in First-Episode Schizophrenia: A 7T MRS and Dynamic Causal Modeling Study

Oxidative stress plays a key role in the pathophysiology of schizophrenia. While free radicals produced by glutamatergic excess and oxidative metabolism have damaging effects on brain tissue, antioxidants such as glutathione (GSH) counteract these effects. The interaction between glutamate (GLU) and GSH is centered on N-Methyl-D-aspartate (NMDA) receptors. GSH levels increase during glutamate-mediated excitatory neuronal activity, which serves as a checkpoint to protect neurons from oxidative damage and reduce excitatory overdrive. We studied the possible influence of GSH on the glutamate-mediated dysconnectivity in 19 first-episode schizophrenia (FES) patients and 20 healthy control (HC) subjects. Using ultra-high field (7 Tesla) magnetic resonance spectroscopy (MRS) and resting state functional magnetic resonance imaging (fMRI), we measured GSH and GLU levels in the dorsal anterior cingulate cortex (dACC) and blood-oxygenation level-dependent activity in both the dACC and the anterior insula (AI). Using spectral dynamic causal modeling, we found that when compared to HCs, in FES patients inhibitory activity within the dACC decreased with GLU levels whereas inhibitory activity in both the dACC and AI increased with GSH levels. Our model explains how higher levels of GSH can reverse the downstream pathophysiological effects of a hyperglutamatergic state in FES. This provides an initial insight into the possible mechanistic effect of antioxidant system on the excitatory overdrive in the salience network (dACC-AI).

Gene therapy-mediated enhancement of protective protein expression for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is the leading form of dementia but lacks curative treatments. Current understanding of AD aetiology attributes the development of the disease to the misfolding of two proteins; amyloid-β (Aβ) and hyperphosphorylated tau, with their pathological accumulation leading to concomitant oxidative stress, neuroinflammation, and neuronal death. These processes are regulated at multiple levels to maintain homeostasis and avert disease. However, many of the relevant regulatory proteins appear to be downregulated in the AD-afflicted brain. Enhancement/restoration of these 'protective' proteins, therefore, represents an attractive therapeutic avenue. Gene therapy is a desirable means of achieving this because it is not associated with the side-effects linked to systemic protein administration, and sustained protein expression virtually eliminates compliance issues. The current article represents a focused and succinct review of the better established 'protective' protein targets for gene therapy enhancement/restoration rather than being designed as an exhaustive review incorporating less validated protein subjects. In addition, we will discuss how the risks associated with uncontrolled or irreversible gene expression might be mitigated through combining neuronal-specific promoters, inducible expression systems and localised injections. Whilst many of the gene therapy targets reviewed herein are yet to enter clinical trials, preclinical testing has thus far demonstrated encouraging potential for the gene therapy-based treatment of AD.

Peripheral Blood NRF2 Expression as a Biomarker in Human Health and Disease

Nuclear factor erythroid 2-related factor 2 (NRF2), a transcription factor which plays a critical role in maintenance of cellular redox, has been identified as a therapeutic target in a number of human diseases. Several reports have demonstrated beneficial effects of NRF2 manipulation in animal models of disease, and one NRF2-activating drug, dimethyl fumarate, is already approved for the treatment of multiple sclerosis. However, drug discovery is slowed due to a dearth of biomarkers which can inform target engagement and magnitude and duration of action. Peripheral blood mononuclear cells (PBMCs) are an accessible, minimally-invasive source of biomarkers which can be readily assayed and objectively monitored as a surrogate endpoint of NRF2 activation in clinical trials. We undertook a review of the literature on PBMC NRF2 measurements in human studies to explore its role as a suitable biomarker in various contexts of health and disease. It is clear that NRF2 and its target genes can be readily assayed from PBMCs in multiple disease contexts and may track with disease progression. Further work needs to be undertaken to evaluate its stability but should be considered as an exploratory marker in clinical trials targeting NRF2 activation.

Carnosic acid protects against ferroptosis in PC12 cells exposed to erastin through activation of Nrf2 pathway

AIMS

Ferroptosis is involved in the pathogenesis of spinal cord injury (SCI). Carnosic acid (CA) is a natural phenolic diterpene, which possesses diversiform activities. However, whether the protective effect of CA on SCI is partly due to inhibition of ferroptosis was seldom investigated. Therefore, the objective of this study aimed to investigate the role of CA on ferroptosis in PC12 cells and the underlying mechanisms.

MAIN METHODS

Cell viability, malondialdehyde (MDA) contents, glutathione (GSH) levels, and iron levels were detected to identify the construction of ferroptosis model in PC12 cell induced by erastin. The safe concentrations of CA on PC12 cells were measured via cell counting kit-8 (CCK-8) assays. Then, cellular MDA contents, GSH levels, iron levels, reactive species (RS) generation, and mitochondrial morphology were tested to determine the influence of CA on ferroptosis in erastin-treated PC12 cells. In addition, Western blot and RT-qPCR were utilized to detecteddetect the ferroptosis-related genes and proteins expression levels.

KEY FINDINGS

Our study indicated that treatment with CA could reversed the increased MDA, iron, and RS levels, as well as the decreased GSH levels in erastin-treated PC12 cells. The protective effect of CA could be blocked by ML385. The inhibitory effect of CA on ferroptosis probably was partially governed by activation of Nrf2 to regulate the GSH synthesis and metabolism and cellular iron homeostasis.

SIGNIFICANCE

CA can inhibit ferroptosis in PC12 cells induced by erastin via activating Nrf2 pathway, indicating that CA could lead to neuroprotective effect by restraining the occurrence of ferroptosis.

Exopolysaccharide Isolated from Lactobacillus plantarum L-14 Has Anti-Inflammatory Effects via the Toll-Like Receptor 4 Pathway in LPS-Induced RAW 264.7 Cells

Inflammation is a biological response of the immune system to defend the body from negative stimulation. However, the excessive inflammatory response can damage host tissues and pose serious threats. Exopolysaccharide (EPS), one of the postbiotics, is secreted from lactic acid bacteria. Although many studies have described the beneficial effects of EPS, such as its anti-inflammatory and anti-oxidant effects, its underlying mechanisms have remained to be poorly understood. Thus, we identified that EPS obtained from Lactobacillus plantarum L-14 was a homogeneous polysaccharide primarily comprised of glucose. To examine these anti-inflammatory effects, an inflammatory response was induced by lipopolysaccharide (LPS) administration to mouse macrophage RAW 264.7 cells that were pretreated with EPS. The anti-inflammatory effects of EPS were identified by analyzing the changes within inflammatory markers at the molecular level. We demonstrate here that EPS suppressed proinflammatory mediators, such as cyclooxygenase-2, interleukin-6, tumor necrosis factor-α, and interleukin-1β, and downregulated the expression of an inducible nitric oxide synthase known to lead to oxidative stress. It was also confirmed that EPS had anti-inflammatory effects by blocking the interaction of LPS with Toll-like receptor 4 (TLR4), as demonstrated by using the known TLR4 inhibitor TAK-242. In addition, we found that EPS itself could suppress the expression of TLR4. Consequently, our data suggest that EPS can be a potential target for the development of natural product-derived medicine for treating inflammatory diseases related to TLR4.

Inhalable Nanoparticles/Microparticles of an AMPK and Nrf2 Activator for Targeted Pulmonary Drug Delivery as Dry Powder Inhalers

Metformin is an activator of the AMPK and Nrf2 pathways which are important in the pathology of several complex pulmonary diseases with unmet medical needs. Organic solution advanced spray drying in the absence of water in closed-mode was used to design and develop respirable dry powders. Following comprehensive characterization, the influence of physicochemical properties was correlated with performance as aerosols using inertial impaction and three different human dry powder inhaler (DPI) devices varying in device properties. In vitro cell assays were conducted to test safety in 2D human pulmonary cell lines and in 3D small airway epithelia comprising primary cells at the air-liquid interface (ALI). In addition, in vitro transepithelial electrical resistance (TEER) was carried out. Metformin remained crystalline following advanced spray drying under these conditions. All SD powders consisted of nanoparticles/microparticles in the solid state. In vitro aerosol dispersion performance showed high aerosolization for all SD metformin powders with all DPI devices tested. High emitted dose for all powders with all three DPI devices was measured. Differences in other aerosol performance parameters and the interplay between the properties of different formulations produced at specific pump rates and the three different DPI devices were correlated with spray drying pump rate and device properties. Safety over a wide metformin dose range was also demonstrated in vitro. Aerosol delivery of metformin nanoparticles/microparticles has the potential to be a new "first-in-class" therapeutic for the treatment of a number of pulmonary diseases including pulmonary vascular diseases such as pulmonary hypertension.

Repeat RNA expansion disorders of the nervous system: post-transcriptional mechanisms and therapeutic strategies

Dozens of incurable neurological disorders result from expansion of short repeat sequences in both coding and non-coding regions of the transcriptome. Short repeat expansions underlie microsatellite repeat expansion (MRE) disorders including myotonic dystrophy (DM1, CUG_50–3,500 in DMPK; DM2, CCTG_75–11,000 in ZNF9), fragile X tremor ataxia syndrome (FXTAS, CGG_50–200 in FMR1), spinal bulbar muscular atrophy (SBMA, CAG_40–55 in AR), Huntington’s disease (HD, CAG_36–121 in HTT), C9ORF72-amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD and C9-ALS/FTD, GGGGCC in C9ORF72), and many others, like ataxias. Recent research has highlighted several mechanisms that may contribute to pathology in this heterogeneous class of neurological MRE disorders – bidirectional transcription, intranuclear RNA foci, and repeat associated non-AUG (RAN) translation – which are the subject of this review. Additionally, many MRE disorders share similar underlying molecular pathologies that have been recently targeted in experimental and preclinical contexts. We discuss the therapeutic potential of versatile therapeutic strategies that may selectively target disrupted RNA-based processes and may be readily adaptable for the treatment of multiple MRE disorders. Collectively, the strategies under consideration for treatment of multiple MRE disorders include reducing levels of toxic RNA, preventing RNA foci formation, and eliminating the downstream cellular toxicity associated with peptide repeats produced by RAN translation. While treatments are still lacking for the majority of MRE disorders, several promising therapeutic strategies have emerged and will be evaluated within this review.