The transcription factor Nrf2 as a new therapeutic target in Parkinson's disease

An Update on the Potential of Tangeretin in the Management of Neuroinflammation-Mediated Neurodegenerative Disorders

Neuroinflammation is the major cause of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. Currently available drugs present relatively low efficacy and are not capable of modifying the course of the disease or delaying its progression. Identifying well-tolerated and brain-penetrant agents of plant origin could fulfil the pressing need for novel treatment techniques for neuroinflammation. Attention has been drawn to a large family of flavonoids in citrus fruits, which may function as strong nutraceuticals in slowing down the development and progression of neuroinflammation. This review is aimed at elucidating and summarizing the effects of the flavonoid tangeretin (TAN) in the management of neuroinflammation-mediated neurodegenerative disorders. A literature survey was performed using various resources, including ScienceDirect, PubMed, Google Scholar, Springer, and Web of Science. The data revealed that TAN exhibited immense neuroprotective effects in addition to its anti-oxidant, anti-diabetic, and peroxisome proliferator-activated receptor-γ agonistic effects. The effects of TAN are mainly mediated through the inhibition of oxidative and inflammatory pathways via regulating multiple signaling pathways, including c-Jun N-terminal kinase, phosphoinositide 3-kinase, mitogen-activated protein kinase, nuclear factor erythroid-2-related factor 2, extracellular-signal-regulated kinase, and CRE-dependent transcription. In conclusion, the citrus flavonoid TAN has the potential to prevent neuronal death mediated by neuroinflammatory pathways and can be developed as an auxiliary therapeutic agent in the management of neurodegenerative disorders.

Ferulic acid grafted into β-cyclodextrin nanosponges ameliorates Paraquat-induced human MRC-5 fibroblast injury

Paraquat (PQ) is a commercially important and effective herbicide in the world. Nevertheless, it has higher toxicity causing acute organ damage and different complications, mainly in the lungs and kidneys. Ferulic acid (FA), 4-hydroxy-3-methoxycinnamic acid imposes multiple pharmacological impacts. No protective effect of FA on PQ poisoning-caused human embryonic lung fibroblast damage has not been reported. Despite their many beneficial effects, FA is characterized by poor water solubility, low bioavailability, and phytochemical instability. To solve the problem, β-cyclodextrin nanosponge (β-CD NSs) was utilized to increase the solubility of FA so that it was grafted into β-CD NSs to establish β-CD@FA NSs. The purpose of this work was to examine for the first time the protective effect of β-CD@FA NS on MRC-5 human lung cells damages induced by PQ poisoning. MTS assay was performed to investigate the viability of MRC-5 cells at different concentrations of FA/β-CD@FA NSs when cells were co-cultured with 0.2 μg/mL PQ. The flow cytometry study was carried out to determine apoptosis. Malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels were detected using appropriate biochemistry kits. Compared with the PQ group, the cell activity, CAT, and SOD levels were significantly increased in the FA and chiefly in β-CD@FA NSs intervention groups, whereas apoptosis and MDA levels were markedly decreased. The inflammatory factors tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), and interleukin 22 (IL-22) were detected. The results demonstrate that β-CD@FA NSs can inhibit PQ-induced cell damage by enhancing antioxidant stress capacity and regulation of inflammatory responses.

Induced oxidative stress and apoptosis by 1-bromopropane in SH-SY5Y cells correlates with inhibition of Nrf2 function

In this study, we established SH-SY5Y human neuroblastoma cells as an in vitro model to investigate whether oxidative stress and the nuclear erythroid-2 related factor 2 (Nrf2) signaling pathway are associated with 1-bromopropane (1-BP) -induced nerve cell injury. We identified that 1-BP exhibited neurotoxicity mainly through oxidant-based processes in SH-SY5Y cells, as reactive oxygen species, malondialdehyde levels, and 8-hydroxy-2' -deoxyguanosine significantly increased, while superoxide dismutase activity decreased. Furthermore, Nrf2 translocation from the cytosol to the nucleus was inhibited, as was downstream protein expression of the Nrf2-regulated genes HO-1 and Bcl-2. Activation of caspase-9 and -3 increased, and apoptosis was observed. Vitamin C alleviated 1-BP-induced apoptosis by decreasing oxidative stress and activating the Nrf2 signaling pathway. Knockdown of Nrf2 in SH-SY5Y cells increased 1-BP-induced reactive oxygen species production and cell apoptosis, and inhibited HO-1 and Bcl-2 protein expression, while overexpression of Nrf2 alleviated these processes. These findings suggest that 1-BP-induced oxidative stress and apoptosis in SH-SY5Y cells are associated with Nrf2 function inhibition.

Curcumin supplementation prevents cisplatin-induced nephrotoxicity: a randomized, double-blinded, and placebo-controlled trial

Background and purpose

Cisplatin-induced nephrotoxicity (CIN) remains the most prevailing unfavorable influence and may affect its clinical usage. This study sought to explore the possible impacts of curcumin on preventing CIN in human subjects.

Clinical design

The investigation was a placebo-controlled, double-blinded, randomized clinical trial conducted on 82 patients receiving nano-curcumin (80 mg twice daily for five days) or an identical placebo with standard nephroprotective modalities against CIN. Data was gathered on patients' demographics, blood, urinary nitrogen, creatinine (Cr) levels, urinary electrolytes, and urine neutrophil gelatinase-associated lipocalin (NGAL) levels in treatment and placebo groups, 24 h and five days after initiating the administration of cisplatin.

Findings/Results

Both investigation groups were alike considering the demographic characteristics and clinical baseline data. Curcumin administration led to a significant improvement in blood-urine nitrogen (BUN). BUN, Cr, glomerular filtration rate (GFR), and the ratio of NGAL-to-Cr considerably altered during the follow-up periods. However, the further alterations in other indices, including urinary sodium, potassium, magnesium, NGAL values, and potassium-to-Cr ratio were not statistically noteworthy. The significant differences in the NGAL-to-Cr ratio between the two groups may indicate the potential protective impact of curcumin supplementation against tubular toxicity. Curcumin management was safe and well-accepted; only insignificant gastrointestinal side effects were reported.

Conclusion and implications

Curcumin supplementation may have the potential to alleviate CIN and urinary electrolyte wasting in cancer patients. Future research investigating the effects of a longer duration of follow-up, a larger participant pool, and a higher dosage of curcumin are recommended.

Edaravone promotes viability of random skin flaps via activating PI3K/Akt/mTOR signalling pathway-mediated enhancement of autophagy

Random skin flap transplantation is a commonly used technique. However, ischemia and ischemia-reperfusion injury always impair its therapeutic effectiveness through acclerating oxidative stress, apoptosis and suppressing angiogenesis. To survive, cells rely on mediating autophagy, DNA repair, immunoregulation to resist these cellular injuries. Thus, mediating autophagy may affect the survival of random skin flaps. The edaravone (EDA), a oxygen radicals scavenger, also possesses autophagy mediator potential, we investigated the effects of EDA on skin flap survival and its autophagy-related mechanisms. In vivo, mice were administered EDA or saline intraperitoneally for 7 days postoperatively. We found that EDA ameliorated the viability of random skin flaps, promoted autophagy and angiogenesis, attenuated apoptosis and oxidative stress. In vitro, mouse umbilical vascular endothelial cells (MUVECs) were administered EDA or 3-methyladenine (3-MA, an autophagy inhibitor) or rapacymin (Rapa, an autophagy activator) at the beginning of oxygen glucose deprivation (OGD). We found that EDA promoted cell viability, activated autophagy, enhanced angiogenesis, alleviated apoptosis and oxidative stress. On one hand, 3-MA reversed the effects of EDA on cell viability, oxidative stress and apoptosis via inhibiting autophagy. On the other hand, Rapa had the similar effects of EDA. Furthermore, EDA-induced autophagy was mediated through downregulating PI3K/Akt/mTOR signalling pathway. The findings showed that EDA ameliorated viability of random skin flaps by promoting angiogenesis, suppressing oxidative stress and apoptosis, which may be mediated by autophagic activation through downregulating PI3K/AKT/mTOR signalling pathway.

Delivery of Transcriptional Factors for Activating Antioxidant Defenses against Inflammatory Bowel Disease

Oxidative stress caused by the overproduction of reactive oxygen species (ROS) plays an important role in inflammatory bowel disease (IBD). It is well-known that the Nrf2-ARE (antioxidative response element) pathway is important in the regulation mechanism of antioxidant defense. Therefore, Nrf2 activation may be an effective therapeutic strategy for IBD. Here, we reported the development of a nucleus-targeted Nrf2 delivery nanoplatform, termed N/LC, that could accumulate in inflamed colonic epithelium, reduce inflammatory responses, and restore epithelium barriers in a murine model of acute colitis. N/LC nanocomposites could quickly escape from lysosomes, so Nrf2 largely accumulated in the nucleus of colonic cells, activated the Nrf2-ARE signaling pathway, further elevated the expression levels of downstream detoxification and antioxidant genes, and protected cells from oxidative damage. These results suggested that N/LC might be a potential nanoplatform for IBD therapy. The study provided the basis for the biomedical applications of Nrf2-based therapeutics in various diseases.

The Role of Nrf2 in Relieving Cerebral Ischemia-Reperfusion Injury

Ischemic stroke includes two related pathological damage processes: brain injury caused by primary ischemia and secondary ischemia reperfusion (I/R) injury. I/R injury has become a worldwide health problem. Unfortunately, there is still a lack of satisfactory drugs for ameliorating cerebral I/R damage. Nrf2 is a vital endogenous antioxidant protein, which combines with Keap1 to maintain a dormant state under physiological conditions. When pathological changes such as I/R occurs, Nrf2 dissociates from Keap1 and activates the expression of downstream antioxidant proteins to exert a protective effect. Recent research have shown that the activated Nrf2 not only effectively inhibits oxidative stress, but also performs the ability to repair the function of compromised mitochondria, alleviate endoplasmic reticulum stress, eliminate inflammatory response, reduce blood-brain barrier permeability, inhibit neuronal apoptosis, enhance the neural network remolding, thereby exerting significant protective effects in alleviating the injuries caused by cell oxygen-glucose deprivation, or animal cerebral I/R. However, no definite clinical application report demonstrated the efficacy of Nrf2 activators in the treatment of cerebral I/R. Therefore, further efforts are needed to elaborate the role of Nrf2 activators in the treatment of cerebral I/R. Here, we reviewed the possible mechanisms underlying its potential pharmacological benefits in alleviating cerebral I/R injury, so as to provide a theoretical basis for studying its mechanism and developing Nrf2 activators.

New Insights into the Gut Microbiota in Neurodegenerative Diseases from the Perspective of Redox Homeostasis

An imbalance between oxidants and antioxidants in the body can lead to oxidative stress, which is one of the major causes of neurodegenerative diseases. The gut microbiota contains trillions of beneficial bacteria that play an important role in maintaining redox homeostasis. In the last decade, the microbiota-gut-brain axis has emerged as a new field that has revolutionized the study of the pathology, diagnosis, and treatment of neurodegenerative diseases. Indeed, a growing number of studies have found that communication between the brain and the gut microbiota can be accomplished through the endocrine, immune, and nervous systems. Importantly, dysregulation of the gut microbiota has been strongly associated with the development of oxidative stress-mediated neurodegenerative diseases. Therefore, a deeper understanding of the relationship between the gut microbiota and redox homeostasis will help explain the pathogenesis of neurodegenerative diseases from a new perspective and provide a theoretical basis for proposing new therapeutic strategies for neurodegenerative diseases. In this review, we will describe the role of oxidative stress and the gut microbiota in neurodegenerative diseases and the underlying mechanisms by which the gut microbiota affects redox homeostasis in the brain, leading to neurodegenerative diseases. In addition, we will discuss the potential applications of maintaining redox homeostasis by modulating the gut microbiota to treat neurodegenerative diseases, which could open the door for new therapeutic approaches to combat neurodegenerative diseases.

Can Berberine Serve as a New Therapy for Parkinson's Disease?

Parkinson's disease (PD) is a neurodegenerative disorder characterized by dopaminergic neurodegeneration and deposition of alpha-synuclein. Mechanisms associated with PD etiology include oxidative stress, apoptosis, autophagy, and abnormalities in neurotransmission, to name a few. Drugs used to treat PD have shown significant limitations in their efficacy. Therefore, recent focus has been placed on the potential of active plant ingredients as alternative, complementary, and efficient treatments. Berberine is an isoquinoline alkaloid that has shown promise as a pharmacological treatment in PD, given its ability to modulate several molecular pathway associated with the disease. Here, we review contemporary knowledge supporting the need to further characterize berberine as a potential treatment for PD.

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

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

The principal molecular mechanisms behind the activation of Keap1/Nrf2/ARE pathway leading to neuroprotective action in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder. PD is associated with the loss of dopaminergic neurons in the substantia nigra pars compacta region of the midbrain. Present therapies for PD provide only symptomatic relief by restoring the dopamine (DA) level. However, they are not disease modifying agents and so they do not delay the disease progression. Alpha-synuclein aggregation, oxidative stress, mitochondrial dysfunction and chronic inflammation are considered to be the major pathological mechanisms mediating neurodegeneration in PD. To resist oxidative stress, the human body has an antioxidant defence mechanism consisting of many antioxidants and cytoprotective genes. The expression of those genes are largely controlled by the Kelch-like ECH-associated protein 1/Nuclear factor - erythroid - 2 - related factor 2/Antioxidant response element (Keap1/Nrf2/ARE) signalling pathway. The transcription factor Nrf2 is activated in response to oxidative or electrophilic stress and protects the cells from oxidative stress and inflammation. Nrf2 has been widely considered as a therapeutic target for neurodegeneration and several drugs are now being tested in clinical trials. Regulation of the Keap1/Nrf2/ARE pathway by small molecules which can act as Nrf2 activators could be effective for treating oxidative stress and neuroinflammation in PD. In this review, we had discussed the principal molecular mechanisms behind the neuroprotective effects of Keap1/Nrf2/ARE pathway in PD. Additionally, we also discussed the small molecules and phytochemicals that could activate the Nrf2 mediated anti-oxidant pathway for neuroprotection in PD.

3-Pyridinylboronic Acid Ameliorates Rotenone-Induced Oxidative Stress Through Nrf2 Target Genes in Zebrafish Embryos

Parkinson's disease (PD) is one of the most common forms of neurodegenerative diseases and research on potential therapeutic agents for PD continues. Rotenone is a neurotoxin that can pass the blood-brain barrier and is used to generate PD models in experimental animals. Boron is a microelement necessary for neural activity in the brain. Antioxidant, non-cytotoxic, anti-genotoxic, anti-carcinogenic effects of boric acid, the salt compound of boron has been reported before. Boronic acids have been approved for treatment by FDA and are included in drug discovery studies and pyridine boronic acids are a subclass of heterocyclic boronic acids used in drug design and discovery as substituted pyridines based on crystal engineering principles. The aim of our study was to determine the effect of 3-pyridinylboronic acid in rotenone-exposed zebrafish embryos, focusing on oxidant-antioxidant parameters and gene expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) target genes gclm, gclc, hmox1a, nqo1, and PD related genes, brain-derived neurotrophic factor, dj1, and tnfα. Zebrafish embryos were exposed to Rotenone (10 μg/l); Low Dose 3-Pyridinylboronic acid (100 μM); High Dose 3-Pyridinylboronic acid (200 μM); Rotenone + Low Dose-3-Pyridinylboronic acid (10 μg/l + 100 μM); Rotenone + High Dose-3-Pyridinylboronic acid (10 μg/l + 200 μM) in well plates for 96 h post-fertilization (hpf). Our study showed for the first time that 3-pyridinylboronic acid, as a novel sub-class of the heterocyclic boronic acid compound, improved locomotor activities, ameliorated oxidant-antioxidant status by decreasing LPO and NO levels, and normalized the expressions of bdnf, dj1, tnf⍺ and Nrf2 target genes hmox1a and nqo1 in rotenone exposed zebrafish embryos. On the other hand, it caused the deterioration of the oxidant-antioxidant balance in the control group through increased lipid peroxidation, nitric oxide levels, and decreased antioxidant enzymes. We believe that these results should be interpreted in the context of the dose-toxicity and benefit-harm relationship of the effects of 3-pyridinylboronic.

Novel Series of Dual NRF2 Inducers and Selective MAO-B Inhibitors for the Treatment of Parkinson’s Disease

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disease. It is characterized by a complex network of physiopathological events where oxidative stress plays a central role among other factors such as neuroinflammation and protein homeostasis. Nuclear factor-erythroid 2 p45-related factor 2 (NRF2) has a multitarget profile itself as it controls a plethora of cellular processes involved in the progression of the disease. In this line, we designed a novel family of 2-(1H-indol-3-yl)ethan-1-amine derivatives as NRF2 inducers with complementary activities. Novel compounds are based on melatonin scaffold and include, among other properties, selective monoamine oxidase B (MAO-B) inhibition activity. Novel multitarget compounds exhibited NRF2 induction activity and MAO-B selective inhibition, combined with anti-inflammatory, antioxidant, and blood–brain barrier permeation properties. Furthermore, they exert neuroprotective properties against oxidative stress toxicity in PD-related in vitro. Hit compound 14 reduced oxidative stress markers and exerted neuroprotection in rat striatal slices exposed to 6-hydroxydopamine or rotenone. In conclusion, we developed a promising family of dual NRF2 inducers and selective MAO-B inhibitors that could serve as a novel therapeutic strategy for PD treatment.

A Perspective on Nrf2 Signaling Pathway for Neuroinflammation: A Potential Therapeutic Target in Alzheimer's and Parkinson's Diseases

Neuroinflammation plays a pivotal role in Alzheimer's disease (AD) and Parkinson's disease (PD), the leading causes of dementia. These neurological disorders are characterized by the accumulation of misfolded proteins such as amyloid-ß (Aß), tau protein and α-synuclein, contributing to mitochondrial fragmentation, oxidative stress, and neuroinflammation. Misfolded proteins activate microglia, which induces neuroinflammation, expression of pro-inflammatory cytokines and subsequently facilitates synaptic damage and neuronal loss. So far, all the proposed drugs were based on the inhibition of protein aggregation and were failed in clinical trials. Therefore, the treatment options of dementia are still a challenging issue. Thus, it is worthwhile to study alternative therapeutic strategies. In this context, there is increasing data on the pivotal role of transcription factor NF- E2 p45-related factor 2 (Nrf2) on the redox homeostasis and anti-inflammatory functions in neurodegenerative disorders. Interestingly, Nrf2 signaling pathway has shown upregulation of antioxidant genes, inhibition of microglia-mediated inflammation, and improved mitochondrial function in neurodegenerative diseases, suggesting Nrf2 activation could be a novel therapeutic approach to target pathogenesis. The present review will examine the correlation between Nrf2 signaling with neuroinflammation in AD and PD.

The potential neuroprotective effect of diosmin in rotenone-induced model of Parkinson's disease in rats

Most treatments for Parkinson's disease (PD) focus on improving the symptoms and the dopaminergic effects; nevertheless, they cannot delay the disease progression. Diosmin (DM), a naturally occurring flavone that is obtained from citrus fruits, has demonstrated anti-apoptotic, anti-inflammatory and antioxidative properties in many diseases. This study aimed to assess the neuroprotective effects of diosmin in rotenone-induced rat model of PD and investigate its potential underlying mechanisms. A preliminary dose-response study was conducted where rats were treated with DM (50,100 and 200 mg/kg, p.o.) concomitantly with rotenone (2 mg/kg, s.c.) for 4 weeks. Catalepsy, motor impairment, spontaneous locomotion, body weight, histological examination and tyrosine hydroxylase (TH) immunoreactivity were evaluated in both the midbrains and striata of rats. Treatment with DM (200 mg/kg) showed the most promising outcome therefore, it was selected for further evaluation of α-synuclein, Bax, Bcl2, nuclear factor kappa B (NF-кB), nuclear factor erythroid 2- related factor 2 (Nrf2), and heme oxygenase-1 (HO-1), in addition to biochemical analysis of tumor necrosis factor-α (TNF-α). Results showed that DM (200 mg/kg, p.o.) prevented rotenone-induced motor impairment, weight reduction and histological damage. Furthermore, it significantly inhibited rotenone-induced decrease in TH expression. These results were correlated with reduction in α-synuclein immunoreactivity, together with improvement of Bax/Bcl2 ratio compared to rotenone group. DM also attenuated rotenone-induced increase in NF-кB expression as well as TNF- α levels. Moreover, DM inhibited rotenone-induced upregulation of Nrf2/HO-1 pathway. Thus, the current study suggests that DM might be a promising candidate for managing the neuropathological course of PD.

Açai Berry Mitigates Parkinson's Disease Progression Showing Dopaminergic Neuroprotection via Nrf2-HO1 Pathways

The current pharmacological treatment for Parkinson's disease (PD) is focused on symptom alleviation rather than disease prevention. In this study, we look at a new strategy to neuroprotection that focuses on nutrition, by a supplementation with Açai berry in an experimental models of PD. Daily orally supplementation with Açai berry dissolved in saline at the dose of 500 mg/kg considerably reduced motor and non-motor symptom and neuronal cell death of the dopaminergic tract induced by 4 injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Furthermore, Açai berry administration reduced α-synuclein aggregation in neurons, enhanced tyrosine hydroxylase and dopamine transporter activities, and avoided dopamine depletion. Moreover, Açai berry administration was able to reduce astrogliosis and microgliosis as well as neuronal death. Its beneficial effects could be due to its bioactive phytochemical components that are able to stimulate nuclear factor erythroid 2-related factor 2 (Nrf2) by counteracting the oxidative stress and neuroinflammation that are the basis of this neurodegenerative disease.

AGE-Rich Bread Crust Extract Boosts Oxidative Stress Interception via Stimulation of the NRF2 Pathway

Advanced glycation end products (AGEs) result from a non-enzymatic reaction of proteins with reactive carbohydrates. Heat-processed food, such as bread, contains high amounts of AGEs. The activation of the NF-κB signaling pathway by bread crust extract (BCE) is well understood. However, it is largely unknown whether NRF2, the master regulator of oxidative stress resistance in mammalian cells, is affected by BCE. We have investigated the molecular mechanisms by which BCE induces antioxidant gene expression in cellular models. Our data showed that soluble extracts from bread crust are capable of stimulating the NRF2 signaling pathway. Furthermore, NRF2 pathway activation was confirmed by microarray and reporter-cell analyses. QRT-PCR measurements and Western blot analyses indicated an induction of antioxidative genes such as HMOX1, GCLM and NQO1 upon BCE treatment. Moreover, BCE pretreated cells had a survival advantage compared to control cells when exposed to oxidative stress. BCE induces phosphorylation of AKT and ERK kinase in EA.hy926 cells. By mass spectrometry, several new, potentially active modifications in BCE were identified. Our findings indicate that BCE activates NRF2-dependent antioxidant gene expression, thus provoking a protection mechanism against oxidative stress-mediated tissue injury. Hence, BCE can be considered as functional food with antioxidative and cardioprotective potential.

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.

Redox Homeostasis and Prospects for Therapeutic Targeting in Neurodegenerative Disorders

Reactive species, such as those of oxygen, nitrogen, and sulfur, are considered part of normal cellular metabolism and play significant roles that can impact several signaling processes in ways that lead to either cellular sustenance, protection, or damage. Cellular redox processes involve a balance in the production of reactive species (RS) and their removal because redox imbalance may facilitate oxidative damage. Physiologically, redox homeostasis is essential for the maintenance of many cellular processes. RS may serve as signaling molecules or cause oxidative cellular damage depending on the delicate equilibrium between RS production and their efficient removal through the use of enzymatic or nonenzymatic cellular mechanisms. Moreover, accumulating evidence suggests that redox imbalance plays a significant role in the progression of several neurodegenerative diseases. For example, studies have shown that redox imbalance in the brain mediates neurodegeneration and alters normal cytoprotective responses to stress. Therefore, this review describes redox homeostasis in neurodegenerative diseases with a focus on Alzheimer's and Parkinson's disease. A clearer understanding of the redox-regulated processes in neurodegenerative disorders may afford opportunities for newer therapeutic strategies.

NRF2 Loss Accentuates Parkinsonian Pathology and Behavioral Dysfunction in Human α-Synuclein Overexpressing Mice

Nuclear factor (erythroid-derived 2)-like 2 (NRF2) is a central regulator of cellular stress responses and its transcriptional activation promotes multiple cellular defense and survival mechanisms. The loss of NRF2 has been shown to increase oxidative and proteotoxic stress, two key pathological features of neurodegenerative disorders such as Parkinson's disease (PD). Moreover, compromised redox homeostasis and protein quality control can cause the accumulation of pathogenic proteins, including alpha-synuclein (α-Syn) which plays a key role in PD. However, despite this link, the precise mechanisms by which NRF2 may regulate PD pathology is not clear. In this study, we generated a humanized mouse model to study the importance of NRF2 in the context of α-Syn-driven neuropathology in PD. Specifically, we developed NRF2 knockout and wild-type mice that overexpress human α-Syn (hα-Syn+/Nrf2-/- and hα-Syn+/Nrf2+/+ respectively) and tested changes in their behavior through nest building, challenging beam, and open field tests at three months of age. Cellular and molecular alterations in α-Syn, including phosphorylation and subsequent oligomerization, as well as changes in oxidative stress, inflammation, and autophagy were also assessed across multiple brain regions. It was observed that although monomeric α-Syn levels did not change, compared to their wild-type counterparts, hα-Syn+/Nrf2-/- mice exhibited increased phosphorylation and oligomerization of α-Syn. This was associated with a loss of tyrosine hydroxylase expressing dopaminergic neurons in the substantia nigra, and more pronounced behavioral deficits reminiscent of early-stage PD, in the hα-Syn+/Nrf2-/- mice. Furthermore, hα-Syn+/Nrf2-/- mice showed significantly amplified oxidative stress, greater expression of inflammatory markers, and signs of increased autophagic burden, especially in the midbrain, striatum and cortical brain regions. These results support an important role for NRF2, early in PD progression. More broadly, it indicates NRF2 biology as fundamental to PD pathogenesis and suggests that targeting NRF2 activation may delay the onset and progression of PD.

Natural Phytochemicals as Novel Therapeutic Strategies to Prevent and Treat Parkinson's Disease: Current Knowledge and Future Perspectives

Parkinson's disease (PD) is the second-most common neurodegenerative chronic disease affecting both cognitive performance and motor functions in aged people. Yet despite the prevalence of this disease, the current therapeutic options for the management of PD can only alleviate motor symptoms. Research has explored novel substances for naturally derived antioxidant phytochemicals with potential therapeutic benefits for PD patients through their neuroprotective mechanism, targeting oxidative stress, neuroinflammation, abnormal protein accumulation, mitochondrial dysfunction, endoplasmic reticulum stress, neurotrophic factor deficit, and apoptosis. The aim of the present study is to perform a comprehensive evaluation of naturally derived antioxidant phytochemicals with neuroprotective or therapeutic activities in PD, focusing on their neuropharmacological mechanisms, including modulation of antioxidant and anti-inflammatory activity, growth factor induction, neurotransmitter activity, direct regulation of mitochondrial apoptotic machinery, prevention of protein aggregation via modulation of protein folding, modification of cell signaling pathways, enhanced systemic immunity, autophagy, and proteasome activity. In addition, we provide data showing the relationship between nuclear factor E2-related factor 2 (Nrf2) and PD is supported by studies demonstrating that antiparkinsonian phytochemicals can activate the Nrf2/antioxidant response element (ARE) signaling pathway and Nrf2-dependent protein expression, preventing cellular oxidative damage and PD. Furthermore, we explore several experimental models that evaluated the potential neuroprotective efficacy of antioxidant phytochemical derivatives for their inhibitory effects on oxidative stress and neuroinflammation in the brain. Finally, we highlight recent developments in the nanodelivery of antioxidant phytochemicals and its neuroprotective application against pathological conditions associated with oxidative stress. In conclusion, naturally derived antioxidant phytochemicals can be considered as future pharmaceutical drug candidates to potentially alleviate symptoms or slow the progression of PD. However, further well-designed clinical studies are required to evaluate the protective and therapeutic benefits of phytochemicals as promising drugs in the management of PD.

CDDO-Im exerts antidepressant-like effects via the Nrf2/ARE pathway in a rat model of post-stroke depression

Increasing evidence suggests that oxidative damage and neuroinflammation play a critical role in the pathogenesis of post-stroke depression (PSD). These pathologic processes are tightly regulated by the NF-E2-related factor 2/antioxidant response element (Nrf2/ARE) signaling pathway. The synthetic triterpenoid, 2-Cyano-3,12-dioxooleana-1,9-dien-28-imidazolide (CDDO-Im), is a potent Nrf2 activator. This study investigated whether CDDO-Im exhibited antidepressant-like activity and elucidated its protective mechanisms in a rat model of PSD, which was produced by middle cerebral artery occlusion (MCAO) followed by 28 days of chronic unpredictable mild stress (CUMS) in conjunction with solitary housing. The results demonstrated that CDDO-Im treatment markedly improved the depressive-like behaviors and reduced neuronal cell loss in the hippocampus, through decreasing the malondialdehyde (MDA) content (indicative of lipid peroxidation), superoxide dismutase (SOD), NF-kB activation, interleukin-6 (IL-6) and interleukin-1b (IL-1β) in PSD rats. CDDO-Im treatment alleviated the oxidative stress and inflammatory response in PSD rats by promoting Nrf2 nuclear import and increasing the protein levels of Nrf2 downstream target genes, including heme oxygenase-1(HOMX1) and, quinone oxidoreductase-1(NQO1).These findings suggested that CDDO-Im treatment exhibited antidepressant-like effects and protected PSD rats from oxidative and inflammatory injury via the Nrf2/ARE pathway. Therefore, CDDO-Im treatment is worthy of further study.

Dietary Restriction and Oxidative Stress: Friends or Enemies?

Significance: It is well established that lifestyle and dietary habits have a tremendous impact on life span, the rate of aging, and the onset/progression of age-related diseases. Specifically, dietary restriction (DR) and other healthy dietary patterns are usually accompanied by physical activity and differ from Western diet that is rich in fat and sugars. Moreover, as the generation of reactive oxidative species is the major causative factor of aging, while DR could modify the level of oxidative stress, it has been proposed that DR increases both survival and longevity. Recent Advances: Despite the documented links between DR, aging, and oxidative stress, many issues remain to be addressed. For instance, the free radical theory of aging is under "re-evaluation," while DR as a golden standard for prolonging life span and ameliorating the effects of aging is also under debate. Critical Issues: This review article pays special attention to highlight the link between DR and oxidative stress in both aging and age-related diseases. We discuss in particular DR's capability to counteract the consequences of oxidative stress and the molecular mechanisms involved in these processes. Future Directions: Although DR is undoubtedly beneficial, several considerations must be taken into account when designing the best dietary intervention. Use of intermittent fasting, daily food reduction, or DR mimetics? Future research should unravel the pros and cons of all these processes. Antioxid. Redox Signal. 34, 421-438.

Generation of potent Nrf2 activators via tuning the electrophilicity and steric hindrance of vinyl sulfones for neuroprotection

Oxidative stress is constantly involved in the etiopathogenesis of an ever-widening range of neurodegenerative diseases. As a consequence, effective repression of cellular oxidative stress to a redox homeostatic condition is a promising and feasible strategy to treat, or at least retard the progression of, such disorders. Nrf2, a primary orchestrator of cellular antioxidant response machine, is responsible for detoxifying and compensating for deleterious oxidative stress via transcriptional activation of a diverse array of antioxidant biomolecules. In the framework of our persistent interest in disclosing small molecules that interfere with cellular redox-regulating machinery, we report herein the synthesis, optimization, and biological assessment of 47 vinyl sulfone scaffold-bearing small molecules, most of which exhibit robust neuroprotective effect against H₂O₂-mediated lesions to PC12 cells. After initial screening, the most potent neuroprotective compounds 9b and 9c with marginal cytotoxicity were selected for the follow-up studies. Our results demonstrate that their neuroprotective effects are attributed to the up-regulation of a panel of antioxidant genes and corresponding gene products. Further mechanistic studies indicate that Nrf2 is indispensable for the cellular performances of 9b and 9c, arising from the fact that silence of Nrf2 gene drastically nullifies their protective action. Taken together, 9b and 9c discovered in this work merit further development as neuroprotective candidates for the treatment of oxidative stress-mediated pathological conditions.

The insect molting hormone 20-hydroxyecdysone protects dopaminergic neurons against MPTP-induced neurotoxicity in a mouse model of Parkinson's disease

20-hydroxyecdysone (20E), a steroidal prohormone, is secreted from the prothoracic glands. While 20E has been shown to have neuroprotective effects in Parkinson's disease (PD) models in vitro, its effects have not yet been examined in vivo. We sought to assess the behavioral and mechanistic effects of 20E on MPTP-induced toxicity in mice. To this end, we used behavioral tests, stereological analyses of dopaminergic neurons by tyrosine hydroxylase immunohistochemistry, and assessments of apoptotic mechanisms, focusing on Nrf2 signaling through Western blotting and ELISA assays. A 20E treatment protected against MPTP-induced motor incoordination, postural imbalance, and bradykinesia, and significantly reduced dopaminergic neuronal loss in the substantia nigra pars compacta (SNpc) and the striatum (ST). It also attenuated dopamine deficiency in the ST, modulated levels of antioxidative enzymes superoxide dismutase, catalase, and glutathione in the SNpc, increased the Bcl-2/Bax ratio, and inhibited cytosolic cytochrome c release and caspase-9, -7, and -3 activity in the SNpc. These results indicated that 20E inhibited the apoptotic cascade. Furthermore, the attenuation of MPTP neurotoxicity was associated with inhibited cleaved-caspase signaling pathways, along with upregulated Nrf2 pathways in the SNpc, suggesting that 20E mitigates MPTP-induced neurotoxicity via mitochondria-mediated apoptosis by modulating anti-oxidative activities. Our results suggest that 20E can inhibit MPTP-induced behavioral and neurotoxic effects in mice. This lays the foundation for further research on 20E as a potential target for therapeutic use.

Protective effects of irigenin against 1-methyl-4-phenylpyridinium-induced neurotoxicity through regulating the Keap1/Nrf2 pathway

The rhizome of Belamcanda chinensis possesses antiinflammatory and antioxidant activities. However, the effect of irigenin, isolated from the rhizome of B. chinensis, on 1-methyl-4-phenylpyridinium (MPP⁺ )-induced neurotoxicity is unknown. MTT assay showed that MPP⁺ exposure dose dependently inhibited the viability of mouse microglia BV-2 cells, whereas irigenin suppressed MPP⁺ -induced viability reduction. The production of nitric oxide, prostaglandin E2, tumor necrosis factor-α and interleukin-6 were increased by MPP⁺ treatment, which were abolished by irigenin treatment. Irigenin-attenuated MPP⁺ -induced increase of malondialdehyde content and activities of superoxide dismutase, catalase and glutathione peroxidase in BV-2 cells. Irigenin treatment also repressed apoptosis, caspase-3/7 activity and Cytochrome C expression in MPP⁺ -challenged BV-2 cells. Interestingly, irigenin activated the Keap1/Nrf2 pathway in MPP⁺ -induced BV-2 cells. Nrf2 knockdown attenuated the effects of irigenin on MPP⁺ -induced viability reduction, inflammation, oxidative stress and apoptosis in BV-2 cells. In conclusion, irigenin alleviated MPP⁺ -induced neurotoxicity in BV-2 cells through regulating the Keap1/Nrf2 pathway.

Tissue distribution, hormonal regulation, ontogeny, diurnal expression, and induction of mouse cystine transporters Slc3a1 and Slc7a9

Slc7a11 (xCT) and Slc3a1 (rBAT) are cystine uptake transporters that maintain intracellular concentrations of cysteine, the rate-limiting amino acid in glutathione synthesis. This study was conducted to first determine the tissue distribution of the two transporters in male and female mice. Because Slc3a1 was the primary cystine transporter in liver, its sex-divergent expression, ontogeny, diurnal rhythm and whether its mRNA expression is altered by transcription factors (AhR, CAR, PXR, PPARα, and Nrf2) was also investigated. Slc7a11 was expressed highest in brain and gonads. Slc3a1 was expressed highest in kidney and intestine, followed by liver. Duodenal and hepatic Slc3a1 was higher in females than males. Hepatic Slc3a1 was high during darkness and low during daytime. Hepatic Scl3a1 was lowest pre-birth, increased to near maximal levels at birth, decreased back to pre-birth levels between Days 3-10, and then returned to peak levels by Day 45. Except for CAR, activation of transcription factors did not increase hepatic mRNA expression of Slc3a1. Chemical activation of CAR significantly induced Slc3a1 1.4-fold in wild-type but not CAR-null mice. Slc3a1 mRNA was higher in livers of AhR- and Nrf2-null mice compared to wild-type mice. High doses of diquat but not acetaminophen induced Slc3a1, suggesting Slc3a1 may respond to oxidative stress but not necessarily to GSH depletion. Overall, Slc7a11 is mainly expressed in brain and gonads, whereas Slc3a1 is mainly expressed in kidney, small intestine and liver, and its hepatic expression is regulated by diurnal rhythm and certain xenobiotic treatments.

Puerarin suppresses MPP+/MPTP-induced oxidative stress through an Nrf2-dependent mechanism

In this study, we hypothesized that anti-parkinsonian effect of puerarin is attributable to its antioxidant properties via Nrf2-dependent glutathione (GSH) biosynthesis mechanism. Experimentally, we found that puerarin attenuated 1-methyl-4-phenylpyridinium (MPP⁺)-induced oxidative stress through elevating biosynthetic capacity of GSH in PC12 cells. Mechanistically, puerarin suppressed Fyn phosphorylation by GSK-3β-dependent mechanism in MPP⁺-challenged PC12 cells. Furthermore, puerarin induced accumulation of Nrf2 in the nucleus via inhibiting its nuclear exclusion. In parallel, puerarin up-regulated antioxidant response element (ARE)-driven catalytic subunits from glutamate cysteine ligase (GCLc) expression at levels of transcription and translation. Most interestingly, pharmacological inhibitor of GSK-3β or Fyn shRNA blocked puerarin-induced Nrf2 activation in MPP⁺-challenged PC12 cells. Concomitantly, puerarin ameliorated motor deficits and inhibited oxidative stress in the ventral midbrain in MPTP-intoxicated wild-type (WT) mice, but failed to attenuate MPTP neurotoxicity and up-regulate GCLc gene in Nrf2-knockout (Nrf2^-/-) mice, suggesting that anti-parkinsonian effect of puerarin was dependent on Nrf2. Additionally, puerarin regulated Fyn and GSK-3β phosphorylation in the ventral midbrain in MPTP-intoxicated WT mice. Collectively, the results of the study provide molecular insights into the potential therapeutic action of puerarin in Parkinson's disease, suggesting that puerarin may be a promising candidate for the treatment of Parkinson's disease.

Antioxidant and Anti-inflammatory Effect of Nrf2 Inducer Dimethyl Fumarate in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) represents debilitating conditions characterized by degeneration of neuronal cells in specific brain areas, causing disability and death in patients. In the pathophysiology of NDs, oxidative stress, apoptosis and neuroinflammation have a key role, as demonstrated by in vivo and in vitro models. Therefore, the use of molecules with antioxidant and anti-inflammatory activities represents a possible strategy for the treatment of NDs. Many studies demonstrated the beneficial effects of fumaric acid esters (FAEs) to counteract neuroinflammation and oxidative stress. Among these molecules, dimethyl fumarate (DMF) showed a valid therapeutic approach to slow down neurodegeneration and relieve symptoms in patients with NDs. DMF is a methyl ester of fumaric acid and acts as modulator of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway as well as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) translocation. Therefore, this review aims to examine the potential beneficial effects of DMF to counteract oxidative stress and inflammation in patients with NDs.

Synthesis of new ferulic/lipoic/comenic acid-melatonin hybrids as antioxidants and Nrf2 activators via Ugi reaction

Aim: Oxidative stress has been implicated in the pathogenesis of many neurodegenerative diseases, and particularly in Alzheimer's disease. Results: This work describes the Ugi multicomponent synthesis, antioxidant power and Nrf2 pathway induction in antioxidant response element cells of (E)-N-(2-((2-(1H-indol-3-yl)ethyl)amino)-2-oxoethyl)-N-(2-(5-(benzyloxy)-1H-indol-3-yl)ethyl)-3-(4-hydroxy-3-methoxyphenyl)acryl amides 8a-d, N-(2-((2-(1H-indol-3-yl)ethyl)amino)-2-oxoethyl)-N-(2-(5-(benzyloxy)-1H-indol-3-yl)ethyl)-5-(1,2-dithiolan-3-yl)pentanamides 8e-h and N-(2-((2-(1H-indol-3-yl)ethyl)amino)-2-oxoethyl)-N-(2-(5-(benzyloxy)-1H-indol-3-yl)ethyl)-5-hydroxy-4-oxo-4H-pyran-2-carboxamides 8i,j. Conclusion: We have identified compounds 8e and 8g, showing a potent antioxidant capacity, a remarkable neuroprotective effect against the cell death induced by H₂O₂ in SH-SY5Y cells, and a performing activation of the Nrf2 signaling pathway, as very interesting new antioxidant agents for pathologies that curse with oxidative stress.

A novel pyrazolo [3,4-d] pyrimidine, KKC080106, activates the Nrf2 pathway and protects nigral dopaminergic neurons

The transcription factor nuclear factor-erythroid 2-related factor-2 (Nrf2) is known to induce neuroprotective and anti-inflammatory effects and is considered to be an excellent molecular target for drugs related to neurodegenerative disease therapy. Nrf2 activators previously tested in clinical trials were electrophilic, causing adverse effects due to non-selective and covalent modification of cellular thiols. In order to circumvent this issue, we constructed and screened a chemical library consisting of 241 pyrazolo [3,4-d] pyrimidine derivatives and discovered a novel, non-electrophilic compound: 1-benzyl-6-(methylthio)-N-(1-phenylethyl)-1H-pyrazolo[3,4-d]pyrimidine-4-amine (KKC080106). KKC080106 was able to activate Nrf2 signaling as it increases the cellular levels of Nrf2, binds to the Nrf2 inhibitor protein Keap1, and causes the accumulation of nuclear Nrf2. We also observed an increase in the expression levels of Nrf2-dependent genes for antioxidative/neuroprotective enzymes in dopaminergic neuronal cells. In addition, in lipopolysaccharide-activated microglia, KKC080106 suppressed the generation of the proinflammatory markers, such as IL-1β, TNF-α, cyclooxygenase-2, inducible nitric oxide synthase, and nitric oxide, and inhibited the phosphorylation of kinases known to be involved in inflammatory signaling, such as IκB kinase, p38, JNK, and ERK. As a drug, KKC080106 exhibited excellent stability against plasma enzymes and a good safety profile, evidenced by no mortality after the administration of 2000 mg/kg body weight, and minimal inhibition of the hERG channel activity. Pharmacokinetic analysis revealed that KKC080106 has good bioavailability and enters the brain after oral and intravenous administration, in both rats and mice. In MPTP-treated mice that received KKC080106 orally, the compound blocked microglial activation, protected the nigral dopaminergic neurons from degeneration, and prevented development of the dopamine deficiency-related motor deficits. These results suggest that KKC080106 has therapeutic potential for neurodegenerative disorders such as Parkinson's disease.

NRF2 Regulation Processes as a Source of Potential Drug Targets against Neurodegenerative Diseases

NRF2 acts by controlling gene expression, being the master regulator of the Phase II antioxidant response, and also being key to the control of neuroinflammation. NRF2 activity is regulated at several levels, including protein degradation by the proteasome, transcription, and post-transcription. The purpose of this review is to offer a concise and critical overview of the main mechanisms of NRF2 regulation and their actual or potential use as targets for the treatment of neurodegenerative diseases.

KEAP1, a cysteine-based sensor and a drug target for the prevention and treatment of chronic disease

Redox imbalance and persistent inflammation are the underlying causes of most chronic diseases. Mammalian cells have evolved elaborate mechanisms for restoring redox homeostasis and resolving acute inflammatory responses. One prominent mechanism is that of inducing the expression of antioxidant, anti-inflammatory and other cytoprotective proteins, while also suppressing the production of pro-inflammatory mediators, through the activation of transcription factor nuclear factor-erythroid 2 p45-related factor 2 (NRF2). At homeostatic conditions, NRF2 is a short-lived protein, which avidly binds to Kelch-like ECH-associated protein 1 (KEAP1). KEAP1 functions as (i) a substrate adaptor for a Cullin 3 (CUL3)-based E3 ubiquitin ligase that targets NRF2 for ubiquitination and proteasomal degradation, and (ii) a cysteine-based sensor for a myriad of physiological and pharmacological NRF2 activators. Here, we review the intricate molecular mechanisms by which KEAP1 senses electrophiles and oxidants. Chemical modification of specific cysteine sensors of KEAP1 results in loss of NRF2-repressor function and alterations in the expression of NRF2-target genes that encode large networks of diverse proteins, which collectively restore redox balance and resolve inflammation, thus ensuring a comprehensive cytoprotection. We focus on the cyclic cyanoenones, the most potent NRF2 activators, some of which are currently in clinical trials for various pathologies characterized by redox imbalance and inflammation.

Synthesis of Dithiolethiones and Identification of Potential Neuroprotective Agents via Activation of Nrf2-Driven Antioxidant Enzymes

Oxidative stress is implicated in the pathogenesis of a wide variety of neurodegenerative disorders, and accordingly, dietary supplement of exogenous antioxidants or/and upregulation of the endogenous antioxidant defense system are promising for therapeutic intervention or chemoprevention of neurodegenerative diseases. Nrf2, a master regulator of the cellular antioxidant machinery, cardinally participates in the transcription of cytoprotective genes against oxidative/electrophilic stresses. Herein, we report the synthesis of 59 structurally diverse dithiolethiones and evaluation of their neuroprotection against 6-hydroxydopamine- or H₂O₂-induced oxidative damages in PC12 cells, a neuron-like rat pheochromocytoma cell line. Initial screening identified compounds 10 and 11 having low cytotoxicity but conferring remarkable protection on PC12 cells from oxidative-mediated damages. Further studies demonstrated that both compounds upregulated a battery of antioxidant genes as well as corresponding genes' products. Significantly, silence of Nrf2 expression abolishes cytoprotection of 10 and 11, indicating targeting Nrf2 activation is pivotal for their cellular functions. Taken together, the two lead compounds discovered here with potent neuroprotective functions against oxidative stress via Nrf2 activation merit further development as therapeutic or chemopreventive candidates for neurodegenerative disorders.

Nrf2 activator via interference of Nrf2-Keap1 interaction has antioxidant and anti-inflammatory properties in Parkinson's disease animal model

Parkinson's disease (PD) is a neurodegenerative disorder characterized by abnormal movement, including slowed movements, shuffling gait, lack of balance, and tremor. Oxidative stress has been shown to play a decisive role in dopaminergic neuronal cell death in PD. The nuclear factor E2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein 1 (Keap1) signaling pathway provides the main defense system against oxidative stress by inducing the expression of antioxidant enzyme genes. Direct interference in the Keap1-Nrf2 protein-protein interaction (PPI) has emerged as an effective strategy for Nrf2 activation. Therefore, we searched for novel Nrf2 activators that can disrupt Nrf2-Keap1 interaction by using a virtual screening approach and identified a potent Nrf2 activator, KKPA4026. KKPA4026 was confirmed to induce the expression of the Nrf2-dependent antioxidant enzymes heme oxygenase-1, glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase regulatory subunit, and NAD(P)H:quinone oxidoreductase 1 in BV-2 cells. Furthermore, KKPA4026 showed anti-inflammatory effects in an Nrf2-dependent manner. In a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD, KKPA4026 effectively attenuated PD-associated behavioral deficits and protected dopaminergic neurons. In summary, we identified KKPA4026 as a novel Nrf2 activator and suggested that Nrf2 activation through interference with the Nrf2-Keap1 interaction may be effective for PD treatment.

Astrocytes autophagy in aging and neurodegenerative disorders

Astrocytes can serve multiple functions in maintaining cellular homeostasis of the central nervous system (CNS), and normal functions for autophagy in astrocytes is considered to have very vital roles in the pathogenesis of aging and neurodegenerative diseases. Autophagy is a major intracellular lysosomal (or its yeast analog, vacuolar) clearance pathways involved in the degradation and recycling of long-lived proteins, oxidatively damaged proteins and dysfunctional organelles by lysosomes. Current evidence has shown that autophagy might influence inflammation, oxidative stress, aging and function of astrocytes. Although the interrelation between autophagy and inflammation, oxidative stress, aging or neurological disorders have been addressed in detail, the influence of astrocytes mediated-autophagy in aging and neurodegenerative disorders has yet to be fully reviewed. In this review, we will summarize the most up-to-date findings and highlight the role of autophagy in astrocytes and link autophagy of astrocytes to aging and neurodegenerative diseases. Due to the prominent roles of astrocytic autophagy in age-related neurodegenerative diseases, we believe that we can provide new suggestions for the treatment of these disorders.

Basic Concepts on the Role of Nuclear Factor Erythroid-Derived 2-Like 2 (Nrf2) in Age-Related Diseases

The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is one of the most important oxidative stress regulator in the human body. Once Nrf2 regulates the expression of a large number of cytoprotective genes, it plays a crucial role in the prevention of several diseases, including age-related disorders. However, the involvement of Nrf2 on these conditions is complex and needs to be clarified. Here, a brief compilation of the Nrf2 enrollment in the pathophysiology of the most common age-related diseases and bring insights for future research on the Nrf2 pathway is described. This review shows a controversial response of this transcriptional factor on the presented diseases. This reinforces the necessity of more studies to investigate modulation strategies for Nrf2, making it a possible therapeutic target in the treatment of age-related disorders.

Therapeutic targeting of the NRF2 and KEAP1 partnership in chronic diseases

The transcription factor NF-E2 p45-related factor 2 (NRF2; encoded by NFE2L2) and its principal negative regulator, the E3 ligase adaptor Kelch-like ECH-associated protein 1 (KEAP1), are critical in the maintenance of redox, metabolic and protein homeostasis, as well as the regulation of inflammation. Thus, NRF2 activation provides cytoprotection against numerous pathologies including chronic diseases of the lung and liver; autoimmune, neurodegenerative and metabolic disorders; and cancer initiation. One NRF2 activator has received clinical approval and several electrophilic modifiers of the cysteine-based sensor KEAP1 and inhibitors of its interaction with NRF2 are now in clinical development. However, challenges regarding target specificity, pharmacodynamic properties, efficacy and safety remain.

Hydralazine Protects Nigrostriatal Dopaminergic Neurons From MPP+ and MPTP Induced Neurotoxicity: Roles of Nrf2-ARE Signaling Pathway

Although the pathogenic mechanisms of Parkinson's disease (PD) remain unclear, ample empirical evidence suggests that oxidative stress is involved in the pathogenesis of this disease. The nuclear factor E2-related factor 2 (Nrf2) is known to activate several antioxidant response element (ARE)-driven antioxidative genes that prevents oxidative stress in vitro and in vivo. Moreover, it was documented that hydralazine is a potent Nrf2 activator. In this study, we tested whether hydralazine can attenuate 1-Methyl-4-phenylpyridinium (MPP⁺) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- induced neurotoxicity in vitro and in vivo by activating Nrf2 and its downstream network of antioxidative genes. We found that treatment with hydralazine attenuated MPP⁺ or H₂O₂-induced loss of cell viability in human neuroblastoma cell line (SH-SY5Y). In addition, hydralazine significantly promoted the nuclear translocation of Nrf2, and upregulated the expression of its downstream antioxidative genes. Further, knockout of Nrf2 abolished the protection conferred by hydralazine on MPP⁺ -induced cell death. Similar findings were observed in vivo. Before, during, and after MPTP 30 mg/kg (i.p.) administration for 7 days, the mice were given hydralazine (Hyd) 51.7 mg/kg per day by oral gavage for 3 weeks. Oral administration of hydralazine ameliorated oxidative stress, MPTP-induced behavioral disorder, and loss of neurons of dopaminergic system in the substantia nigra (SN) and striatum, all of which were attributed to its ability to activate the Nrf2-ARE pathway. Hydralazine increased the migration of Nrf2 to the nucleus in dopaminergic neurons, enhanced the expression of its downstream antioxidative genes. Together, these datasets show that the Nrf2-ARE pathway mediates the protective effects of hydralazine on Parkinson's disease.

Nrf2/ARE Pathway Modulation by Dietary Energy Regulation in Neurological Disorders

Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates the expression of an array of enzymes with important detoxifying and antioxidant functions. Current findings support the role of high levels of oxidative stress in the pathogenesis of neurological disorders. Given the central role played by Nrf2 in counteracting oxidative damage, a number of studies have targeted the modulation of this transcription factor in order to confer neuroprotection. Nrf2 activity is tightly regulated by oxidative stress and energy-based stimuli. Thus, many dietary interventions based on energy intake regulation, such as dietary energy restriction (DER) or high-fat diet (HFD), modulate Nrf2 with consequences for a variety of cellular processes that affect brain health. DER, by either restricting calorie intake or meal frequency, activates Nrf2 thereby triggering its protective effects, whilst HFD inhibit this pathway, thereby exacerbating oxidative stress. Consequently, DER protocols can be valuable strategies in the management of central nervous system (CNS) disorders. Herein, we review current knowledge of the role of Nrf2 signaling in neurological diseases, namely Alzheimer’s disease, Parkinson’s disease, multiple sclerosis and cerebral ischemia, as well as the potential of energy intake regulation in the management of Nrf2 signaling.

Different roles of Nrf2 and NFKB in the antioxidant imbalance produced by esculetin or quercetin on NB4 leukemia cells

Esculetin (6,7-dihydrocoumarin) and the flavonoid quercetin (3,5,7,3',4' pentahydroxyflavone) are compounds that could change the balance of redox homeostasis. NB4 leukemia cells were treated with 25 μM quercetin for 24 h and with esculetin at either 100 or 500 μM for different times. Quercetin increased the levels of pro-inflammatory NFkB p65 in the nucleus correspondingly reducing them in the cytosol. The levels of NFkB p65 decreased in the nucleus at high esculetin concentration treatments for long times (19 h), concomitantly increasing the levels of anti-inflammatory NFkB p50 in the nucleus. This could suggest formation of inhibitory p50 homodimers possibly related with anti-inflammatory response. Lipoxygenase expression was reduced either by esculetin or quercetin. A significant increase of Nrf2 in the nucleus of NB4 cells treated with 100 μM esculetin for 19 h was observed. Quercetin increased the levels of Nrf2 in the cytosol reducing them in the nucleus. Superoxide dismutase expression increased in NB4 cells treated with esculetin in contrast with quercetin. All these data support a relevant differential role for NFkB and Nrf2 in anti-inflammatory and redox response when apoptosis was induced by esculetin or quercetin in human leukemia NB4 cells.

Nicotine and cigarette smoke modulate Nrf2-BDNF-dopaminergic signal and neurobehavioral disorders in adult rat cerebral cortex. Hum Exp Toxicol 2018;37:540-556. [PMID: 28641491 DOI: 10.1177/0960327117698543]

BACKGROUND

Nicotine and cigarette smoking (CS) are associated with addiction behavior, drug-seeking, and abuse. However, the mechanisms that mediate this association especially, the role of brain-derived neurotrophic factor (BDNF), dopamine (DA), and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling in the cerebral cortex, are not fully known. Therefore, we hypothesized that overexpression of BDNF and DA, and suppression of Nrf2 contribute to several pathological and behavioral alterations in adult cerebral cortex. Methodology/Principal Observations: We treated Wistar rats with different doses of oral nicotine and passive CS for 4-week (short-term) and 12-week (long-term) duration, where doses closely mimic the human smoking scenario. Our result showed dose-dependent association of anxiogenic and depressive behavior, and cognitive interference with neurodegeneration and DNA damage in the cerebral cortex upon exposure to nicotine/CS as compared to the control. Further, the results are linked to upregulation of oxidative stress, overexpression of BDNF, DA, and DA marker, tyrosine hydroxylase (TH), with concomitant downregulation of ascorbate and Nrf2 expression in the exposed cerebral cortex when compared with the control.

CONCLUSION/SIGNIFICANCE

Overall, our data strongly suggest that the intervention of DA and BDNF, and depletion of antioxidants are important factors during nicotine/CS-induced cerebral cortex pathological changes leading to neurobehavioral impairments, which could underpin the novel therapeutic approaches targeted at tobacco smoking/nicotine's neuropsychological disorders including cognition and drug addiction.

Microarray Analysis of the Molecular Mechanism Involved in Parkinson's Disease

Purpose

This study aimed to investigate the underlying molecular mechanisms of Parkinson's disease (PD) by bioinformatics.

Methods

Using the microarray dataset GSE72267 from the Gene Expression Omnibus database, which included 40 blood samples from PD patients and 19 matched controls, differentially expressed genes (DEGs) were identified after data preprocessing, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Protein-protein interaction (PPI) network, microRNA- (miRNA-) target regulatory network, and transcription factor- (TF-) target regulatory networks were constructed.

Results

Of 819 DEGs obtained, 359 were upregulated and 460 were downregulated. Two GO terms, “rRNA processing” and “cytoplasm,” and two KEGG pathways, “metabolic pathways” and “TNF signaling pathway,” played roles in PD development. Intercellular adhesion molecule 1 (ICAM1) was the hub node in the PPI network; hsa-miR-7-5p, hsa-miR-433-3p, and hsa-miR-133b participated in PD pathogenesis. Six TFs, including zinc finger and BTB domain-containing 7A, ovo-like transcriptional repressor 1, GATA-binding protein 3, transcription factor dp-1, SMAD family member 1, and quiescin sulfhydryl oxidase 1, were related to PD.

Conclusions

“rRNA processing,” “cytoplasm,” “metabolic pathways,” and “TNF signaling pathway” were key pathways involved in PD. ICAM1, hsa-miR-7-5p, hsa-miR-433-3p, hsa-miR-133b, and the abovementioned six TFs might play important roles in PD development.

Paraquat and MPTP induce neurodegeneration and alteration in the expression profile of microRNAs: the role of transcription factor Nrf2

Both transcription factors (TFs) and microRNAs (miRNAs) can exert a widespread impact on gene expression. In the present study, we investigated the role of Nrf2 in paraquat-induced intracorporeal neurodegeneration and miRNA expression by exposing Nrf2 wild-type and knockout mice to paraquat (PQ) or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Exposure to 10 mg/kg PQ or 30 mg/kg MPTP caused damage to nerve cells in the substantia nigra (SN) in both Nrf2 (+/+) and Nrf2 (−/−) ICR mice, which included cell morphological changes, detectable apoptosis and a significant reduction in the number of dopaminergic (DA) neurons. When mice were exposed to the same PQ dose of 10 mg/kg, significant fewer tyrosine hydroxylase (TH)-positive DA neurons were observed in the Nrf2 (−/−) mice than that in the Nrf2 (+/+) mice. Both Nrf2 deficiency and PQ or MPTP exposure could alter miRNA expression profile in the SN, suggesting the potential involvement of Nrf2 in the PQ-induced or MPTP-induced miRNA expression alteration. The expression of miR-380-3p was altered by the Nrf2-MPTP interaction effect. miR-380-3p/Sp3-mRNA pathway is likely part of the mechanism of MPTP-induced neurodegeneration. Collectively, our results corroborated the protective role of Nrf2 and also demonstrated the essential interaction of Nrf2 with miRNAs in intracorporal neurodegeneration induced by neurotoxicants.

The gene expression regulators Nrf2 and small regulatory RNA molecule miR-380-3p protect nerve cells from damage caused by neurotoxins. Huangyuan Li, at Fujian Medical University, China, and colleagues examined the effects of paraquat and MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine), two chemicals known to induce parkinsonism, in mice lacking Nrf2, a key mediator of antioxidant and anti-inflammatory responses. They found that after MPTP or paraquat exposure, the extent of neuronal loss in the substantia nigra was greater in mice lacking Nrf2 than in wild-type controls. Moreover, Nrf2 deficiency prevented an upregulation of miR-380-3p following MPTP exposure. These findings implicate miR-380-3p in the mechanism through which Nrf2 protects the brain from Parkinson’s disease-related cell death and opens new avenues of investigation for developing more effective neuroprotective therapies.

Nrf2-Inducers Counteract Neurodegeneration in Frataxin-Silenced Motor Neurons: Disclosing New Therapeutic Targets for Friedreich's Ataxia

Oxidative stress is actively involved in Friedreich's Ataxia (FA), thus pharmacological targeting of the antioxidant machinery may have therapeutic value. Here, we analyzed the relevance of the antioxidant phase II response mediated by the transcription factor Nrf2 on frataxin-deficient cultured motor neurons and on fibroblasts of patients. The in vitro treatment of the potent Nrf2 activator sulforaphane increased Nrf2 protein levels and led to the upregulation of phase II antioxidant enzymes. The neuroprotective effects were accompanied by an increase in neurites' number and extension. Sulforaphane (SFN) is a natural compound of many diets and is now being used in clinical trials for other pathologies. Our results provide morphological and biochemical evidence to endorse a neuroprotective strategy that may have therapeutic relevance for FA. The findings of this work reinforce the crucial importance of Nrf2 in FA and provide a rationale for using Nrf2-inducers as pharmacological agents.

The attenuating effects of plumbagin on pro-inflammatory cytokine expression in LPS-activated BV-2 microglial cells

Activated microglial cells produce the pro-inflammatory mediators such as nitric oxide (NO) and cytokines. The excessive release of these mediators can lead to neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD). Inhibition of the release of these pro-inflammatory molecules may prevent or halt the progression of these diseases. Plumbagin (PL), a naphthoquinone compound in the roots of the traditional medicinal plant Plumbago zeylanica L., showed anti-inflammatory effects on macrophages. However, PL effects on activated microglia remain unknown. In the present study, PL has been examined for its anti-inflammatory effect on LPS - activated microglial BV-2 cells. In this study, NO and iNOS expression were investigated in BV-2 microglial cells in the presence of PL or the selective iNOS inhibitor L-N6-(1-iminoethyl) lysine (L-NIL). The results obtained indicate that PL was >30-fold potent than L-NIL in inhibiting NO production with an IC₅₀ of 0.39μM. Our immunofluorescence study confirmed the ability of PL to significantly inhibit iNOS expression in the activated microglia. Furthermore, the extracellular microglial pro-inflammatory cytokine expression in the presence of 2μM of PL was detected, quantified, and validated using cytokine antibody protein arrays and quantitative ELISA. The results obtained showed that PL significantly downregulated the expression of many cytokines including IL-1α, G-CSF, IL-12 p40/p70, MCP-5, MCP-1, and IL-6. In conclusion, PL potency in attenuating multiple pro-inflammatory agents indicates its potential to be used for neurodegenerative diseases.