Effect of tacrine-3-caffeic acid, a novel multifunctional anti-Alzheimer's dimer, against oxidative-stress-induced cell death in HT22 hippocampal neurons: involvement of Nrf2/HO-1 pathway

Water extract of moschus alleviates erastin-induced ferroptosis by regulating the Keap1/Nrf2 pathway in HT22 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Moschus, first described in the Shennong's Classic of the Materia medicine, is a scarce and precious animal medicine. Modern pharmacological researches have suggested that Moschus has neuroprotective actions, and its mechanism is related to anti-inflammatory, antioxidant, and anti-apoptosis effects. Ferroptosis is one of the major pathologies of Alzheimer's disease (AD) and is widely implicated in the pathogenesis and progression of AD. Although previous studies have suggested that Moschus possesses neuroprotective effect, whether Moschus could mitigate neuronal damages by inhibiting the onset of ferroptosis is unknown in model cells of AD.

AIM OF THE STUDY

The aim of study was to explore the water extract of Moschus (WEM) on ferroptosis caused by erastin and the potential mechanism.

MATERIALS AND METHODS

Erastin was used to stimulate HT22 cells to form ferroptosis model to evaluate the anti-ferroptosis effect of WEM by cell counting kit-8 and lactic dehydrogenase (LDH) tests. The malondialdehyde (MDA) and glutathione (GSH) kits are used for detection of MDA and GSH levels, and 2',7'-dichlorofluorescein diacetate and C11 BODIPY 581/591 fluorescence probe are used for evaluation of reactive oxygen species (ROS) and lipid peroxide (LOOH) levels. And Western blot was used to test nuclear factor erythroid 2-related factor 2 (Nrf2), Kelch-like ECH-associated protein 1 (Keap1), heme oxygenase-1 (HO-1), and ferroptosis associated proteins including glutathione peroxidase 4 (GPX4), cystine/glutamate antiporter subunit (SLC7A11), ferritin heavy chain 1 (FTH1), ferroportin1 (FPN1), transferrin receptor (TFRC). In addition, the Nrf2 inhibitor ML385 was applied to verify whether WEM prevents erastin-induced ferroptosis by activating the Keap1/Nrf2 pathway.

RESULTS

After WEM treatment, erastin-induced HT22 cell survival was significantly elevated, the accumulation of intracellular MDA, ROS, and LOOH were significantly reduced, the level of GSH and expressions of ferroptosis inhibitors GPX4 and SLC7A11 were significantly increased, and iron metabolism-related proteins TFRC, FPN1, and FTH1 were regulated. These effects of WEM are implemented by activating the Keap1/Nrf2 pathway.

CONCLUSIONS

This study demonstrated that WEM could perform neuroprotective effects by alleviating ferroptosis, verified that WEM treatment of AD can be mediated by the Keap1/Nrf2 pathway, and provided theoretical support for the application of WEM in the treatment of AD.

Activation of Atg7-dependent autophagy by a novel inhibitor of the Keap1-Nrf2 protein-protein interaction from Penthorum chinense Pursh. attenuates 6-hydroxydopamine-induced ferroptosis in zebrafish and dopaminergic neurons

The death of dopaminergic neurons is a dominant factor during the occurrence and development of Parkinson's disease (PD). Previous studies demonstrated that ferroptosis is implicated in the death of dopaminergic neurons. Besides, polyphenols have been proven to be effective in preventing the death of dopaminergic neurons. This work aims to explore the neuroprotective effect and mechanism of thonningianin A (Th A), a polyphenolic compound in natural plant foods, against 6-hydroxydopamine (6-OHDA)-induced ferroptosis in dopaminergic cells. The results of molecular docking and other binding assays collectively demonstrated that Th A can strongly target the Kelch domain of Keap1. Th A treatment significantly facilitated the nuclear factor erythroid 2-like 2 (Nrf2) nuclear translocation and subsequently increased the heme oxygenase-1 (HO-1) protein level through inhibiting the protein-protein interaction (PPI) of Keap1 and Nrf2. Compared with the nomifensine (Nomi) treatment, Th A had a more potent protective effect on 6-OHDA-induced ferroptosis during PD pathology in zebrafish, which was associated with assuaging the reduction of the total swimming distance, glutathione (GSH) depletion, iron accumulation, lipid peroxidation, and aggregation of α-synuclein (α-syn). Furthermore, Th A also exhibited a strong protective effect against 6-OHDA-induced ferroptosis in vitro in the human neuroblastoma cell line SH-SY5Y. Th A degraded Keap1 protein through activating Atg7-dependent autophagy. Additionally, Th A treatment facilitated the degradation of Keap1 protein by promoting the interaction between p62/SQSTM1 (sequestosome 1, hereafter referred to as p62) and Keap1. Taken together, our findings indicated that Th A protects dopaminergic cells against 6-OHDA-induced ferroptosis through activating the Nrf2-based cytoprotective system, thus enabling a potential application of Keap1-Nrf2 PPI inhibitors in the restraint of ferroptosis and treatment of PD.

Biosynthesis of a water solubility-enhanced succinyl glucoside derivative of luteolin and its neuroprotective effect

The natural flavonoids luteolin and luteoloside have anti-bacterial, anti-inflammatory, anti-oxidant, anti-tumour, hypolipidemic, cholesterol lowering and neuroprotective effects, but their poor water solubility limits their application in industrial production and the pharmaceutical industry. In this study, luteolin-7-O-β-(6″-O-succinyl)-d-glucoside, a new compound that was prepared by succinyl glycosylation of luteolin by the organic solvent tolerant bacterium Bacillus amyloliquefaciens FJ18 in an 8.0% DMSO (v/v) system, was obtained and identified. Its greater water solubility (2293 times that of luteolin and 12 232 times that of luteoloside) provides the solution to the application problems of luteolin and luteoloside. The conversion rate of luteolin (1.0 g l^-1 ) was almost 100% at 24 h, while the yield of luteolin-7-O-β-(6″-O-succinyl)-d-glucoside reached 76.2%. In experiments involving the oxygen glucose deprivation/reoxygenation injury model of mouse hippocampal neuron cells, the cell viability was significantly improved with luteolin-7-O-β-(6″-O-succinyl)-d-glucoside dosing, and the expressions of the anti-oxidant enzyme HO-1 in the nucleus increased, providing a neuroprotective effect for ischemic cerebral cells. The availability of biosynthetic luteolin-7-O-β-(6″-O-succinyl)-d-glucoside, which is expected to replace luteolin and luteoloside, would effectively expand the clinical application value of luteolin derivatives.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Emodin ameliorates antioxidant capacity and exerts neuroprotective effect via PKM2-mediated Nrf2 transactivation

Pyruvate kinase M2 (PKM2) is overexpressed in neuronal cells. However, there are few studies on the involvement of PKM2 modulators in neurodegenerative diseases. Emodin, a dominating anthraquinone derivative extracting from the rhizome of rhubarb, has received expanding consideration due to its pharmacological properties. Our data reveal that emodin could resist hydrogen peroxide- or 6-hydroxydopamine-mediated mitochondrial fission and apoptosis in PC12 cells (a neuron-like rat pheochromocytoma cell line). Notably, emodin at nontoxic concentrations significantly inhibits PKM2 activity and promotes dissociation of tetrameric PKM2 into dimers in cells. The PKM2 dimerization enhances the interaction of PKM2 and NFE2-related factor 2 (Nrf2), which further triggers the activation of the Nrf2/ARE pathway to upregulate a panel of cytoprotective genes. Modulating the PKM2/Nrf2/ARE axis by emodin unveils a novel mechanism for understanding the pharmacological functions of emodin. Our findings indicate that emodin is a potential candidate for the treatment of oxidative stress-related neurodegenerative disorders.

Cynaropicrin Induces Cell Cycle Arrest and Apoptosis by Inhibiting PKM2 to Cause DNA Damage and Mitochondrial Fission in A549 Cells

Metabolic reprogramming is critical for tumorigenesis. Pyruvate kinase M2 (PKM2) is overexpressed in lung carcinoma cells and plays a critical role in the Warburg effect, making the enzyme a research hotspot for anticancer drug development. Cynaropicrin (CYN), a natural sesquiterpene lactone compound from artichoke, has received increasing consideration due to its consumable esteem and pharmacological properties. Our data reveal that CYN not only inhibited the purified PKM2 activity but also decreased the cellular PKM2 expression in A549 cells. The inhibition of PKM2 leads to the upregulation of p53 and the downregulation of the DNA repair enzyme poly (ADP-ribose) polymerase (PARP), and subsequently causes the cell cycle arrest. Additionally, CYN inhibits the interaction of PKM2 and Nrf2, resulting in the impairment of cellular antioxidant capacity, induction of oxidative stress, and mitochondrial damages. Overexpression of PKM2 attenuates the CYN-induced DNA damage, mitochondrial fission, and cell viability. Thus, targeting PKM2 provides an original mechanism for understanding the pharmacological impact of CYN and assists in the further development of CYN as an anticancer agent.

Dihydroactinidiolide regulates Nrf2/HO-1 expression and inhibits caspase-3/Bax pathway to protect SH-SY5Y human neuroblastoma cells from oxidative stress induced neuronal apoptosis

Alzheimer's disease (AD) etiology has been studied for a long time and it is found to be multifaceted involving the accumulation of amyloid β and tau protein. Oxidative stress is an early event in AD associated neurodegeneration provoking neuronal death through mitochondrial dysfunction and activation of caspase-3. Therefore we tested the efficacy of dihydroactinidiolide (DHAc), a monoterpene lactone against the oxidative load involved in AD like pathological conditions induced by sodium dithionite, glutamate, amyloid β and colchicine in SH-SY5Y cells. Some of the indicators of neurotoxicity like acetylcholinesterase activity, intracellular reactive oxygen species (ROS), nitrite content, lipid peroxidation, protein carbonylation, nuclear and membrane damage were found to be significantly high in the toxicant treated cells when compared to the control cells while DHAc pretreatment significantly restored the toxicant induced neuronal damage signatures. Caspase-3 activity was found to be increased in the toxicant treated cells while DHAc significantly reduced it. Western blotting and RT-PCR revealed that DHAc significantly increased anti-apoptotic Bcl-2 expression and mRNA levels of Nrf2 and HO-1. Therefore DHAc was found to protect SH-SY5Y cells from neurotoxicant induced oxidative stress and apoptosis by regulating cellular antioxidant defenses and apoptosis related genes.

Merging the Multi-Target Effects of Phytochemicals in Neurodegeneration: From Oxidative Stress to Protein Aggregation and Inflammation

Wide experimental evidence has been provided in the last decade concerning the neuroprotective effects of phytochemicals in a variety of neurodegenerative disorders. Generally, the neuroprotective effects of bioactive compounds belonging to different phytochemical classes are attributed to antioxidant, anti-aggregation, and anti-inflammatory activity along with the restoration of mitochondrial homeostasis and targeting alterations of cell-clearing systems. Far from being independent, these multi-target effects represent interconnected events that are commonly implicated in the pathogenesis of most neurodegenerative diseases, independently of etiology, nosography, and the specific misfolded proteins being involved. Nonetheless, the increasing amount of data applying to a variety of neurodegenerative disorders joined with the multiple effects exerted by the wide variety of plant-derived neuroprotective agents may rather confound the reader. The present review is an attempt to provide a general guideline about the most relevant mechanisms through which naturally occurring agents may counteract neurodegeneration. With such an aim, we focus on some popular phytochemical classes and bioactive compounds as representative examples to design a sort of main highway aimed at deciphering the most relevant protective mechanisms which make phytochemicals potentially useful in counteracting neurodegeneration. In this frame, we emphasize the potential role of the cell-clearing machinery as a kernel in the antioxidant, anti-aggregation, anti-inflammatory, and mitochondrial protecting effects of phytochemicals.

Dietary docosahexaenoic acid inhibits neurodegeneration and prevents stroke

Stroke severely impairs quality of life and has a high mortality rate. On the other hand, dietary docosahexaenoic acid (DHA) prevents neuronal damage. In this review, we describe the effects of dietary DHA on ischemic stroke-associated neuronal damage and its role in stroke prevention. Recent epidemiological studies have been conducted to analyze stroke prevention through DHA intake. The effects of dietary intake and supply of DHA to neuronal cells, DHA-mediated inhibition of neuronal damage, and its mechanism, including the effects of the DHA metabolite, neuroprotectin D1 (NPD1), were investigated. These studies revealed that DHA intake was associated with a reduced risk of stroke. Moreover, studies have shown that DHA intake may reduce stroke mortality rates. DHA, which is abundant in fish oil, passes through the blood-brain barrier to accumulate as a constituent of phospholipids in the cell membranes of neuronal cells and astrocytes. Astrocytes supply DHA to neuronal cells, and neuronal DHA, in turn, activates Akt and Raf-1 to prevent neuronal death or damage. Therefore, DHA indirectly prevents neuronal damage. Furthermore, NDP1 blocks neuronal apoptosis. DHA, together with NPD1, may block neuronal damage and prevent stroke. The inhibitory effect on neuronal damage is achieved through the antioxidant (via inducing the Nrf2/HO-1 system) and anti-inflammatory effects (via promoting JNK/AP-1 signaling) of DHA.

Possible involvement of NMDA receptor in the anxiolytic-like effect of caffeic acid in mice model of maternal separation stress

Background and aim

Anxiety disorders are one of the most common psychiatric disorders worldwide. Common anti-anxiety medications are associated with several side effects. Caffeic acid (CA) is a phenolic compound with several pharmacological effects. The aim of this study was to investigate the anxiolytic-like effect of CA in maternally separated (MS) mice focusing on the possible involvement of the NMDA receptor.

Materials and methods

In this study, we used the MS paradigm (as a valid animal model of anxiety) in male mice and examined their anxiety-like behavior in postnatal day (PND) 45. The animals were divided into 12 experimental groups. Mice treated with CA alone and in combination with the NMDA receptor agonist/antagonist and then using open field (OFT) and elevated plus maze (EPM) anxiety-like behavior was assessed. Finally, the expression of NMDA receptor subtypes was assessed in the hippocampus using RT- PCR.

Results

Finding showed that CA exerted anxiolytic –like effects in the OFT and EPM tests. We showed that administration of effective dose of NMDA significantly reversed the anxiolytic-like effect of effective dose of CA and co-administration of ketamine (a NMDA receptor antagonist) significantly potentiated the effect of sub-effective dose of CA. Furthermore, ketamine enhanced the CA-reducing effect on NMDA receptors in the MS mice.

Conclusion

Our finding demonstrated that, probably at least, NMDA receptors are involved in the anxiety-like properties of CA in MS mice.

Activation of p62-Keap1-Nrf2 Pathway Protects 6-Hydroxydopamine-Induced Ferroptosis in Dopaminergic Cells

Parkinson's disease (PD) is a common neurodegenerative disorder primarily caused by the death of dopaminergic neurons in the substantia nigra pars compacta (SNpc). However, the manner of death of dopaminergic neurons remains indistinct. Ferroptosis is a form of cell death involving in the iron-dependent accumulation of glutathione depletion and lipid peroxide. Besides, previous studies indicated that ferroptosis might be involved in the death of dopaminergic neurons. In this study, we aim to explore the protective effect of the p62-Keap1-Nrf2 pathway against 6-hydroxydopamine (6-OHDA)-induced ferroptosis in dopaminergic cells. Firstly, our results demonstrated that 6-OHDA-induced ferroptosis could be observed in vivo zebrafish and in vitro human dopaminergic cell line (SH-SY5Y cells) model. Moreover, ferroptosis induced by 6-OHDA mitigates in SH-SY5Y cells upon ferrostatin-1 (Fer, an inhibitor of ferroptosis) treatment via upregulating the protein expression of glutathione peroxidase 4 (GPX4). Then, we found that high p62/SQSTM1 (p62) expression could protect SH-SY5Y cells against ferroptosis through promoting Nrf2 nuclear transfer and upregulating the expression of the antioxidant protein heme oxygenase-1 (HO-1). Ultimately, high p62 expression activates the Nrf2/HO-1 signaling pathway through binding to Kelch-like ECH-associated protein 1 (Keap1). Collectively, the activation of the p62-Keap1-Nrf2 pathway prevents 6-OHDA-induced ferroptosis in SH-SY5Y cells, targeting this pathway in combination with a pharmacological inhibitor of ferroptosis can be a potential approach for PD therapy.

Docosahexaenoic Acid Protects Traumatic Brain Injury by Regulating NOX2 Generation via Nrf2 Signaling Pathway

Docosahexaenoic acid (DHA) is verified to have neuroprotective effects on traumatic brain injury (TBI) rats by activating Nrf2 signaling pathway, but the role of NOX2 in this effect has not been illuminated. So this study explored the role of NOX2 in TBI models treated with DHA, aiming to complete the mechanism of DHA. TBI rat models were constructed with or without DHA treatment, and H2O2-induced hippocampal neurons were pretreated with DHA alone or in combination with Nrf2 inhibitor brusatol. The neurological function, cognitive ability, and cerebral edema degree of rats were assessed. The apoptosis rate and viability of cells was measured. The generation of NOX2, Nrf2, HO-1 and NQO-1 expression levels, and ROS content in hippocampal CA1 region and hippocampal neurons were detected. DHA could not only improve the neurological function, brain edema and cognitive ability in TBI rats, but also decrease effectively the contents of NOX2 and ROS in hippocampal CA1 region and hippocampal neurons. DHA promoted the nuclear transposition of Nrf2 and the expression levels of HO-1 and NQO-1 in hippocampal CA1 region and hippocampal neurons. On the contrary, Nrf2 inhibitor brusatol inhibited the nuclear transposition of Nrf2 and the expression levels of HO-1 and NQO-1 in hippocampal neurons, promoted the generation of ROS and NOX2, and accelerated cell apoptosis. Both in vivo and in vitro experiments demonstrated that DHA treated TBI by reducing NOX2 generation that might function on Nrf2 signaling pathway, providing a potential evidence for its clinical application.

Hydrogen Sulfide Inhibits Homocysteine-Induced Neuronal Senescence by Up-Regulation of SIRT1

Homocysteine (Hcy) accelerates neuronal senescence and induces age-related neurodegenerative diseases. Silence signal regulating factor 1 (SIRT1) prolongs lifespan and takes neuroprotective effects. We have previously demonstrated that hydrogen sulfide (H₂S) prevents Hcy-induced apoptosis of neuronal cells and has neuroprotective effect. In the present work, we aimed to investigate whether H₂S protects HT22 cells against Hcy-induced neuronal senescence and whether SIRT1 mediates this role of H₂S. We found that Hcy induced cellular senescence in HT22 cells, as determined by β-galactosidase staining, expressions of P16^INK4a, P21^CIPL, and trypan blue Staining, which are the markers of cellular senescence. However, sodium hydrosulfide (NaHS, the donor of H₂S) significantly reversed Hcy-induced cellular senescence. Interestingly, NaHS not only up-regulated the expression of SIRT1 in HT22 cells but also reversed Hcy-downregulated the expression of SIRT1 in HT22 cells. Furthermore, we found that pretreatment with Sirtinol (an inhibitor of SIRT1) markedly reversed the protection of NaHS against Hcy-induced HT22 cells senescence and apoptosis. Our findings illustrated that H₂S protects HT22 cells against Hcy-induced senescence by up-regulating SIRT1.

Protective Effects of miR-126 Specifically Regulates Nrf2 Through Ischemic Postconditioning on Renal Ischemia/Reperfusion Injury in Mice

The protective effects of ischemic postconditioning on renal ischemia/reperfusion injury in mice and the role of miR-126 and Nrf2 signaling pathway in the process were the focus of this study. Mice were classified into 5 groups: sham-operation, I/R6h, I/R24h, postconditioning (POC), and miR-126 agomir. Serum creatinine, renal histopathology changes, and oxidative stress were examined. The expression of miR-126 and Nrf2 were detected. We also treated NRK52E cells with hypoxia reoxygenation. The I/R group showed significant renal injury and increased generation of oxidative stress. However, the severity of renal injury and oxidative stress were markedly attenuated in the POC group. MiR-126 was downregulated, and Nrf2 was upregulated in NRK52E cells subjected to hypoxia/reoxygenation (H/R) and in mouse kidneys subjected to POC. Oxidative stress was higher and Nrf2 was lower in the mouse miR-126 agomir group; apoptosis were higher in H/R-treated NRK52E cells transfected with Nrf2 siRNA and lower in anti-miR-126. These findings demonstrate that after renal ischemic postconditioning, miR-126 inhibits oxidative stress by inducing Nrf2 and suppresses injury.

Pioglitazone Attenuates Lipopolysaccharide-Induced Oxidative Stress, Dopaminergic Neuronal Loss and Neurobehavioral Impairment by Activating Nrf2/ARE/HO-1

The aim of the present study was to examine the neuroprotective potential of pioglitazone via activation of Nrf2/ARE-dependent HO-1 signaling pathway in chronic neuroinflammation and progressive neurodegeneration mouse model induced by lipopolysaccharide (LPS). After assessing spatial memory, anxiety and motor-coordination, TH+ neurons in substantia nigra (SN) were counted. The oxidative stress marker carbonyl protein levels and HO-1 enzyme activity were also evaluated. RT-qPCR was conducted to detect HO-1, Nrf2 and NF-κp65 mRNA expression levels and Nrf2 transcriptional activation of antioxidant response element (ARE) of HO-1 was investigated. Pioglitazone ameliorated LPS-induced dopaminergic neuronal loss, as well as mitigated neurobehavioral impairments. It enhanced Nrf2 mRNA expression, and augmented Nrf2/ARE-dependent HO-1 pathway activation by amplifying HO-1 mRNA expression. Moreover, it induced a significant decrease in NF-κB p65 mRNA expression, while reducing carbonyl protein levels and restoring the HO-1 enzyme activity. Interestingly, LPS induced Nrf2/antioxidant response element (ARE) of HO-1 activation, ultimately resulting in slight enhanced HO-1 mRNA expression. However, LPS elicited decrease in HO-1 enzyme activity. Zinc protoporphyrin-IX (ZnPPIX) administrated with pioglitazone abolished its effects in the LPS mouse model. The study results demonstrate that coordinated activation of Nrf2/ARE-dependent HO-1 pathway defense mechanism by the PPARγ agonist pioglitazone mediated its neuroprotective effects.

Reasonably activating Nrf2: A long-term, effective and controllable strategy for neurodegenerative diseases

Neurodegenerative diseases are a variety of debilitating and fatal disorder in central nervous system (CNS). Besides targeting neuronal activity by influencing neurotransmitters or their corresponding receptors, modulating the underlying processes that lead to cell death, such as oxidative stress and mitochondrial dysfunction, should also be emphasized as an assistant strategy for neurodegeneration therapy. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) has been closely verified to be related to anti-inflammation and oxidative stress, rationally regulating its belonging pathway and activating Nrf2 is emphasized to be a potential treatment approach. There have existed multiple Nrf2 activators with different mechanisms and diverse structures, but those applied for neuro-disorders are still limited. On the basis of research arrangement and compound summary, we put forward the limitations of existing Nrf2 activators for neurodegenerative diseases and their future developing directions in enhancing the blood-brain barrier permeability to make Nrf2 activators function in CNS and designing Nrf2-based multi-target-directed ligands to affect multiple nodes in pathology of neurodegenerative diseases.

Neuroprotective Effect of Swertiamain on Cerebral Ischemia/Reperfusion Injury by Inducing the Nrf2 Protective Pathway

Oxidative stress plays a vital role in the development of cerebral ischemic/reperfusion (I/R). Targeting oxidative stress is proposed to be an effective strategy to treat cerebral I/R injury. Gentiana macrophylla Pall is reported to have a potential protective effect against stroke. Swertiamarin (Swe), an active secoiridoid glycoside compound isolated from Gentiana macrophylla Pall, has been reported to possess antioxidative potential. This study is to explore whether Swe could prevent brain from I/R injury, and the related mechanisms of oxidative stress are also elucidated using mice middle cerebral artery occlusion (MCAO) model and primary hippocampal neurons oxygen-glucose deprivation/reperfusion (OGD/R) model. Swe (25, 100, or 400 mg/kg) was pretreated intraperitoneally for 7 days until establishment of the MCAO model, while hippocampal neurons were maintained in Swe (0.1, 1, or 10 μM) in the entire process of reoxygenation. The results indicated that Swe pretreatment markedly decreased infarct volume, apoptotic neurons, and oxidative damage and promoted neurologic recovery in vivo. It also decreased reactive oxygen species (ROS) and increased cell viability in vitro. Western blot analyses and immunofluorescence staining demonstrated that Swe pretreatment promoted Nrf2 nuclear translocation from Keap1-Nrf2 complex and enhanced the expressions of NAD(P)H: quinone oxidoreductase-1 (NQO1) and heme oxygenase-1 (HO-1) both in vivo and in vitro, while the expressions could be reversed by a Nrf2 inhibitor. The binding mode of Keap1 with Swe was also proposed by covalent molecular docking. Collectively, Swe could be considered as a promising protective agent against cerebral I/R injury through suppressing oxidative stress by activation of the Nrf2 protective pathway.

Heme oxygenase-1 prevents heart against myocardial infarction by attenuating ischemic injury-induced cardiomyocytes senescence

Background

Cellular senescence is a stable cell-cycle arrest induced by telomere shortening and various types of cellular stress including oxidative stress, oncogene activation, DNA damage etc. Heme oxygenase-1 (HO-1) is an inducible stress-response protein that plays antioxidant and anti-apoptotic effects. However, the role and underlying mechanisms of HO-1 in cellular senescence in heart are largely unknown.

Methods

Echocardiography was employed to detect the effect of HO-1 on heart function in adult mice with myocardial infarction (MI) and aged mice. The senescence markers, p53, p16 and LaminB, were analyzed by western blot. The immunofluorescence and immunohistochemical staining were applied to analyze the expression level of p16. SA-β-Gal staining showed the level of cardiomyocyte senescence.

Findings

We found that hemin significantly induced the expression of HO-1, which notably suppressed cardiomyocyte senescence containing the secretion of senescence-associated secretory phenotype. Further studies showed that systemic HO-1 transgenic overexpression improved heart function by inhibiting aging-induced extracellular matrix deposition and fibrogenesis. More importantly, treatment of hemin improved heart function in MI mice. Furthermore, forced expression of HO-1 blunted cardiomyocyte senescence in natural aged mice and in primary cultured neonatal mouse cardiomyocytes.

Interpretation

Our study revealed that HO-1 improved heart function and attenuated cardiomyocyte senescence triggered by ischemic injury and aging. In addition, HO-1 induction alleviated H₂O₂-induced cardiomyocyte senescence. Finally, our study suggested a novel mechanism of HO-1 to play cardioprotective effect.

Fund

This study was supported by the National Natural Science Foundation of China (81770284 to Hongli Shan); and the National Natural Science Foundation of China (81673425, 81872863 to Yuhong Zhou). The National Natural Science Foundation of China (81473213 to Chaoqian Xu). National Key R&D Program of China (2017YFC1307403 to Baofeng Yang), National Natural Science Foundation of China (81730012 to Baofeng Yang).

Taurine Have Neuroprotective Activity against Oxidative Damage-Induced HT22 Cell Death through Heme Oxygenase-1 Pathway

Glutamate-induced oxidative neurotoxicity plays a part role in neuronal degeneration on the disorders of central nervous system (CNS). The expression of heme oxygenase (HO)-1 mediated by Inducible nuclear factor-E2-related factor 2 (Nrf2) functions as an anti-oxidants that is able to play an important role in the pathogenesis of several neuronal disorders. In the present study, taurine showed the inhibitory effect against reactive oxygen species (ROS) induction and protective effects against neurotoxicity induced by glutamate- and H2O2 through induction of HO-1 expression in HT22 cells. Moreover, taurine promoted the Nrf2 nuclear translocation in HT22 cells. We also verified the oxidative stress-mediated cell death of HT22 cells was significantly repressed by taurine, using tin protoporphyrin (SnPP) as an HO activity inhibitor. In addition, we found that treatment of the cells with p38 inhibitor (SB203580) suppressed taurine-induced HO-1 expression and cytoprotection, but inhibitors of c-Jun NH2 terminal kinase (JNK) (SP600125) or extracellular signal regulated kinase (ERK) (PD98059) did not. These results suggest that taurine improves the resistance against oxidative damages induced by glutamate in HT22 cells via the p38/Nrf2-dependent HO-1 expression. Our results demonstrated the potential application of taurine as a therapeutic agent for neurodegenerative diseases.

Neuroprotective Effects of Taraxacum officinale Wigg. Extract on Glutamate-Induced Oxidative Stress in HT22 Cells via HO-1/Nrf2 Pathways

Oxidative stress-mediated neuron damage is considered an important contributor to the pathogenesis and development of neurodegenerative diseases. Taraxacum officinale has been reported to possess antioxidant activities. However, whether it can protect neurons against oxidative damage and the underlying molecular mechanisms have not been fully determined. In the present study, we examined the neuroprotective effects of ethanol extracts of this plant (ETOW) on glutamate-induced oxidative stress in HT22 cells. Both cell viability and reactive oxygen species (ROS) assays showed that ETOW effectively attenuated glutamate-induced cytotoxicity and ROS generation. Furthermore, our results revealed that ETOW increased the expression of heme oxygenase-1 (HO-1) and promoted the nuclear translocation of nuclear factor erythroid 2-related factor-2 (Nrf2). The inhibitory effects of ETOW on glutamate-stimulated cell toxicity and ROS production were partially reversed by tin protoporphyrin (SnPP), an HO activity inhibitor. Taken together, these results demonstrate that ETOW can protect HT22 cells against glutamate-induced oxidative damage by inducing the Nrf2/HO-1 pathways. Our study supports the idea that Taraxacum officinale Wigg. is a promising agent for preventing neurodegenerative diseases.

Multiple mechanisms of dimethyl fumarate in amyloid β-induced neurotoxicity in human neuronal cells

Alzheimer disease (AD) is characterized by a complex heterogeneity of pathological changes, and any therapeutic approach categorically requires a multi-targeted way. It has been demonstrated that together with the hallmarks of the disease such as neurofibrillary tangles and senile plaques, oxidative and inflammatory stress covered an important role. Dimethyl fumarate (DMF) is an orally bioavailable methyl ester of fumaric acid and activator of Nrf2 with potential neuroprotective and immunomodulating activities. Therefore, the aim of the present work was to evaluate the potential beneficial effects of DMF, compared with its active metabolite monomethyl fumarate (MMF) (both at 30 μM) in an in vitro Alzheimer's model using SH-SY5Y human neuroblastoma cell lines stimulated with amyloid-beta (Aβ). Moreover, the effect of DMF, compared with MMF, was evaluate by an ex vivo model using organotypic hippocampal slice cultures stimulated with Aβ1-42 (1 μg/ml), to better understand its action in a pathological setting. In both models, DMF pre-treatment (30 μM) preserved cellular viability from Aβ stimulation, reducing tau hyper-phosphorylation, much more efficiently then MMF (30 μM). Moreover, DMF was able to induce an activation of manganese superoxide dismutase (MnSOD) and heme-oxygenase-1 (HO-1), decreasing the severity of oxidative stress. Our results showed important multi-protective effects of DMF pre-treatment from Aβ stimulation both in in vitro and ex vivo models, highlighting an Nrf2/NF-κB-dependent mechanism, which could provide a valuable support to the therapies for neurodegenerative diseases today.

The Neuroprotective Effect of Dimethyl Fumarate in an MPTP-Mouse Model of Parkinson's Disease: Involvement of Reactive Oxygen Species/Nuclear Factor-κB/Nuclear Transcription Factor Related to NF-E2

AIM

Oxidative stress plays a key role in Parkinson disease (PD), and nuclear transcription factor related to NF-E2 (Nrf-2) is involved in neuroprotection against PD. The aim of the present study was to investigate a role for nuclear factor-κB (NF-κB)/Nrf-2 in the neurotherapeutic action of dimethyl fumarate (DMF) in a mouse model of PD and in vitro in SHSY-5Y cells.

RESULTS

Daily oral gavage of DMF (10, 30, and 100 mg/kg) significantly reduced neuronal cell degeneration of the dopaminergic tract and behavioral impairments induced by four injections of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Moreover, treatment with DMF prevented dopamine depletion, increased tyrosine hydroxylase and dopamine transporter activities, and also reduced the number of α-synuclein-positive neurons. Furthermore, DMF treatment upregulated the Nrf-2 pathway, increased NeuN⁺/Nrf-2⁺ cell number in the striatum, induced activation of manganese superoxide dismutase and heme oxygenase-1, and regulated glutathione levels. Moreover, DMF reduced interleukin 1 levels, cyclooxygenase 2 activity, and nitrotyrosine neuronal nitrite oxide synthase expression. This treatment also modulated microglia activation, restored nerve growth factor levels, and preserved microtubule-associated protein 2 alterations. The protective effects of DMF treatment, via Nrf-2, were confirmed in in vitro studies, through inhibition of Nrf-2 by trigonelline.

INNOVATION

These findings demonstrate that DMF, both in a mouse model of PD and in vitro, provides, via regulation of the NF-κB/Nrf-2 pathway, novel cytoprotective modalities that further augment the natural antioxidant response in neurodegenerative and inflammatory disease models.

CONCLUSION

These results support the thesis that DMF may constitute a promising therapeutic target for the treatment of PD. Antioxid. Redox Signal. 27, 453-471.

Neuroprotective Activity of Cerebrosides from Typhonium giganteum by Regulating Caspase-3 and Bax/Bcl-2 Signaling Pathways in PC12 Cells

An investigation of the potential neuroprotective natural product constituents of the rhizomes of Typhonium giganteum led to the isolation of two new cerebrosides, typhonosides E (1) and F (2), along with 11 known analogues (3-13). The structures of compounds 1 and 2 were elucidated by spectroscopic data interpretation. The activity of these compounds against glutamate-induced cell apoptosis was investigated in PC12 cells. All compounds exhibited such activity, which was related to the length of the fatty acyl chain. Among them, longan cerebroside II (11), with the longest fatty acyl chain, showed the most potent protective effect in PC12 cells from glutamate injury, with an EC₅₀ value of 2.5 μM. Moreover, at the molecular level, longan cerebroside II (11) downregulated the expression of caspase-9, caspase-3, and Bax, upregulated the expression of Bcl-2, and decreased the level of cytosolic cytochrome c in a concentration-dependent manner.

The toxic effects and possible mechanisms of Brusatol on mouse oocytes

Brusatol is a natural quassinoid that shows a potential therapeutic use in cancer models by the inhibition of Nuclear factor erythroid 2-related factor 2 (Nrf2) and is capable of inducing a variety of biological effects. The effects of Brusatol on oocyte meiosis has not been addressed. In this study, we investigated the impact of Brusatol treatment on mouse oocyte maturation and its possible mechanism. Our data demonstrated that Brusatol treatment disrupted oocyte maturation and spindle/chromosome organization by modulating Nrf2-Cyclin B1 pathway, as the influence of Brusatol was compensated by the addition of Nrf2 activation plasmid, and the mRNA and protein levels of Cyclin B1 were severely reduced in oocytes following Nrf2 decline. In summary, our data support a model that Brusatol, through the inhibition of Nrf2, modulate Cyclin B1 levels, consequently disturbing proper spindle assembly and chromosome condensation in meiotic oocytes.

The Nrf2-ARE pathway is associated with Schisandrin b attenuating benzo(a)pyrene-Induced HTR cells damages in vitro

As is ubiquitous in the environmental sources, benzo(a)pyrene (BaP) has been reported to induce reprotoxicity in previous studies. Toxicity to trophoblast cells may be one key factor, but evidences were absent. We speculated that BaP can induce cytotoxicity in human trophoblast HTR-8/SVneo (HTR) cells, and Schisandrin B (Sch B) as a potential protector can inhibit the cytotoxicity. MTS assay identified that BaP induced HTR cells death while Sch B played a cytoprotective role. And after Nrf2 interference, the ability of Sch B-induced cytoprotection was declined. Furthermore, PCR, western blot, ELISA, and SOD assays were found that Sch B significantly increased the mRNA and protein expression of Nrf2, HO1, NQO1, and SOD in the Nrf2-ARE pathway, and the extents of increase were declined after Nrf2 interference. These results demonstrated that the Nrf2-ARE pathway plays an important role in Sch B attenuating BaP-induced HTR cells damages in vitro. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1439-1449, 2016.

MEF2D Mediates the Neuroprotective Effect of Methylene Blue Against Glutamate-Induced Oxidative Damage in HT22 Hippocampal Cells

Methylene blue (MB) can ameliorate behavioral, neurochemical, and neuropathological impairments in animal models of acute and chronic neurodegenerative disorders, but the underlying mechanism remains unclear. Myocyte enhancer factor 2 (MEF2D) is known to promote neuronal survival in several models, and several survival and death signals converge on MEF2D and regulate its activity. Here, we investigated the role of MEF2D in the neuroprotective effect of MB against glutamate-induced toxicity in HT22 neuronal cells. Our results showed that MB, event at less than 100 nM, improved the viability of HT22 cells exposed to 2 mM glutamate. MB attenuated the mitochondrial impairment and quenches the reactive oxygen species (ROS) induced by glutamate. Surprisingly, MB at 50-200 nM did not affect the Nrf2/HO-1 pathway, an important endogenous anti-oxidative system. Further study showed that MB increased the transcription and translation of MEF2D. In addition, MB upregulated the expression of mitochondrial NADH dehydrogenase 6 (ND6) in a MEF2D-dependent manner. Knockdown of MEF2D abolished both MB-medicated increase of ND6 and MB-induced neuroprotection against glutamate-induced toxicity. Moreover, we showed that MB promoted Akt function activity, suppressed GSK-3β activity, and increased MEF2D level in hippocampus of mice and HT22 cells. These findings for the first time demonstrate that MB protects HT22 neuronal cells against glutamate-induced cell death partially via the regulation of MEF2D-associated survival pathway.

Nrf2 as molecular target for polyphenols: A novel therapeutic strategy in diabetic retinopathy

Diabetic retinopathy is a microvascular complication of diabetes that is considered one of the leading causes of blindness among adults. More than 4.4 million people suffer from this disorder throughout the world. Growing evidence suggests that oxidative stress plays a crucial role in the pathophysiology of diabetic retinopathy. Nuclear factor erythroid 2-related factor 2 (Nrf2), a redox sensitive transcription factor, plays an essential protective role in regulating the physiological response to oxidative and electrophilic stress via regulation of multiple genes encoding antioxidant proteins and phase II detoxifying enzymes. Many studies suggest that dozens of natural compounds, including polyphenols, can supress oxidative stress and inflammation through targeting Nrf2 and consequently activating the antioxidant response element-related cytoprotective genes. Therefore, Nrf2 may provide a new therapeutic target for treatment of diabetic retinopathy. In the present article, we will focus on the role of Nrf2 in diabetic retinopathy and the ability of polyphenols to target Nrf2 as a therapeutic strategy.

Polydatin Protects Bone Marrow Stem Cells against Oxidative Injury: Involvement of Nrf 2/ARE Pathways

Polydatin, a glucoside of resveratrol, has been reported to possess potent antioxidative effects. In the present study, we aimed to investigate the effects of polydatin in bone marrow-derived mesenchymal stem cells (BMSCs) death caused by hydrogen peroxide (H₂O₂), imitating the microenvironment surrounding transplanted cells in the injured spinal cord in vitro. In our study, MTT results showed that polydatin effectively prevented the decrease of cell viability caused by H₂O₂. Hochest 33258, Annexin V-PI, and Western blot assay showed H₂O₂-induced apoptosis in BMSCs, which was attenuated by polydatin. Further studies indicated that polydatin significantly protects BMSCs against apoptosis due to its antioxidative effects and the regulation of Nrf 2/ARE pathway. Taken together, our results indicate that polydatin could be used in combination with BMSCs for the treatment of spinal cord injury by improving the cell survival and oxidative stress microenvironments.

Involvement of the Nrf2/HO-1 signaling pathway in sulfuretin-induced protection against amyloid beta25-35 neurotoxicity

Sulfuretin, one of the major flavonoid glycosides found in the stem bark of Albizzia julibrissin and heartwood of Rhus verniciflua, is a known anti-oxidant. We previously demonstrated that sulfuretin inhibits neuronal death via reactive oxygen species (ROS)-dependent mechanisms in human SH-SY5Y cells, although other relevant mechanisms of action of this compound remain largely uncharacterized. As part of our ongoing exploration of the pharmacological actions of sulfuretin, we studied the neuroprotective effects of sulfuretin against amyloid beta (Aβ)-induced neurotoxicity in human SH-SY5Y and primary hippocampal neuron cells and investigated the possible mechanisms involved. Specifically, we found in the present study that sulfuretin significantly attenuates the decrease in cell viability, release of lactate dehydrogenase, and accumulation of ROS associated with Aβ25-35-induced neurotoxicity in neuronal cells. Furthermore, sulfuretin stimulated the activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a downstream target of phosphatidylinositol 3-kinases (PI3K)/Akt. We demonstrated that sulfuretin induces the expression of heme oxygenase-1 (HO-1), an anti-oxidant response gene. Notably, we found that the neuroprotective effects of sulfuretin were diminished by an Nrf2 small interfering RNA (siRNA), the HO-1 inhibitor zinc protoporphyrin IX (ZnPP), as well as the PI3K/Akt inhibitor LY294002. Taken together, these results indicated that sulfuretin protects neuronal cells from Aβ25-35-induced neurotoxicity through activation of Nrf/HO-1 and PI3K/Akt signaling pathways. Our results also indicate that sulfuretin-induced induction of Nrf2-dependent HO-1 expression via the PI3K/Akt signaling pathway has preventive and/or therapeutic potential for the management of Alzheimer's disease.

Sequential Upregulation of Superoxide Dismutase 2 and Heme Oxygenase 1 by tert-Butylhydroquinone Protects Mitochondria during Oxidative Stress

Oxidative stress is linked to mitochondrial dysfunction in aging and neurodegenerative conditions. The transcription factor nuclear factor E2-related factor 2 (Nrf2)-antioxidant response element (ARE) regulates intracellular antioxidative capacity to combat oxidative stress. We examined the effect of tert-butylhydroquinone (tBHQ), an Nrf2-ARE signaling pathway inducer, on mitochondrial function during oxidative challenge in neurons. tBHQ prevented glutamate-induced cytotoxicity in an HT-22 neuronal cell line even with an 8-hour exposure delay. tBHQ blocked glutamate-induced intracellular reactive oxygen species (ROS) and mitochondrial superoxide accumulation. It also protected mitochondrial function under glutamate toxicity, including maintaining mitochondrial membrane potential, mitochondrial Ca(2+) hemostasis, and mitochondrial respiration. Glutamate-activated, mitochondria-mediated apoptosis was inhibited by tBHQ as well. In rat primary cortical neurons, tBHQ protected cells from both glutamate and buthionine sulfoximine toxicity. We found that tBHQ scavenged ROS and induced a rapid upregulation of superoxide dismutase 2 (SOD2) expression and a delayed upregulation of heme oxygenase 1 (HO-1) expression. In HT-22 cells with a knockdown of SOD2 expression, delayed treatment with tBHQ failed to prevent glutamate-induced cell death. Briefly, tBHQ rescues mitochondrial function by sequentially increasing SOD2 and HO-1 expression during glutamate-mediated oxidative stress. This study is the first to demonstrate the role of tBHQ in preserving mitochondrial function during oxidative challenge and provides a clinically relevant argument for using tBHQ against acute neuron-compromising conditions.

Eriodictyol Attenuates β-Amyloid 25-35 Peptide-Induced Oxidative Cell Death in Primary Cultured Neurons by Activation of Nrf2

Oxidative stress plays an important role in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD). Eriodictyol, a flavonoid isolated from the Chinese herb Dracocephalum rupestre, has long been established as an antioxidant. The present study was designed to investigate the effect of eriodictyol on β-amyloid 25-35 peptide (Aβ25-35)-induced oxidative cell death in primary neurons and to explore the role of the nuclear factor erythroid-2-related factor 2/antioxidant response element (Nrf2/ARE) pathway in this process. For this purpose, primary cultures of cortical neurons were exposed to 15 μM Aβ25-35 in the absence or presence of eriodictyol (20, 40 and 80 μM). The results revealed that Aβ25-35-induced cytotoxicity and apoptotic characteristics such as activation of JNK/p38 apoptotic signaling pathway were effectively attenuated by eriodictyol pretreatment. Eriodictyol treatment also resulted in an increase in Nrf2 protein levels and subsequent activation of ARE pathway genes in primary cultured neurons. The protective effects of eriodictyol were attenuated by RNA interference-mediated knockdown of Nrf2 expression. Taken together, these results clearly demonstrate that eriodictyol protects neurons against Aβ25-35-induced cell death partially through Nrf2/ARE signaling pathway, which further supports that eriodictyol might be a promising novel therapeutic agent for AD.

Ammonia-induced oxidative damage in neurons is prevented by resveratrol and lipoic acid with participation of heme oxygenase 1

Ammonia is a metabolite that, at high concentrations, is implicated in neurological disorders, such as hepatic encephalopathy (HE), which is associated with acute or chronic liver failure. Astrocytes are considered the primary target of ammonia toxicity in the central nervous system (CNS) because glutamine synthetase (GS), responsible for ammonia metabolism in CNS, is an astrocytic enzyme. Thus, neuronal dysfunction has been associated as secondary to astrocytic impairment. However, we demonstrated that ammonia can induce direct effects on neuronal cells. The cell viability was decreased by ammonia in SH-SY5Y cells and cerebellar granule neurons. In addition, ammonia induced increased reactive oxygen species (ROS) production and decreased GSH intracellular content, the main antioxidant in CNS. As ammonia neurotoxicity is strongly associated with oxidative stress, we also investigated the potential neuroprotective roles of the antioxidants, resveratrol (RSV) and lipoic acid (LA), against ammonia toxicity in cerebellar granule neurons. RSV and LA were able to prevent the oxidative damage induced by ammonia, maintaining the levels of ROS production and GSH close to basal values. Both antioxidants also decreased ROS production and increased GSH content under basal conditions (in the absence of ammonia). Moreover, we showed that heme oxygenase 1 (HO1), a protein associated with protection against stress conditions, is involved in the beneficial effects of RSV and LA in cerebellar granule neurons. Thus, this study reinforces the neuroprotective effects of RSV and LA. Although more studies in vivo are required, RSV and LA could represent interesting therapeutic strategies for the management of HE.

Brusatol inhibits the response of cultured beta-cells to pro-inflammatory cytokines in vitro

Brusatol is a natural terpenoid that is capable of inducing a variety of biological effects. We presently report that this substance dramatically improves beta-cell survival when exposed to pro-inflammatory cytokines (IL-1β and IFNγ) in vitro. This was observed in insulin producing rat (RIN-5AH), mouse (βTC6) and human (EndoC-βH1) beta-cell lines. Brusatol prevented beta-cell oxidative stress in response to cytokines and counteracted induction of iNOS on the protein level. Brusatol, however, block neither the cytokine-induced increase of iNOS mRNA, nor NF-κB activation, suggesting that inhibition of iNOS protein expression relies on posttranscriptional mechanism. This indicates that brusatol acts via a novel protective pathway, which may represent a more promising way of improving beta-cell function and survival.

Dimethyl fumarate attenuates 6-OHDA-induced neurotoxicity in SH-SY5Y cells and in animal model of Parkinson's disease by enhancing Nrf2 activity

Oxidative stress is central to the pathology of several neurodegenerative diseases, including Parkinson's disease (PD), and therapeutics designed to enhance antioxidant potential could have clinical value. In this study, we investigated whether dimethyl fumarate (DMF) has therapeutic effects in cellular and animal model of PD, and explore the role of nuclear transcription factor related to NF-E2 (Nrf2) in this process. Treatment of animals and dopaminergic SH-SY5Y cells with DMF resulted in increased nuclear levels of active Nrf2, with subsequent upregulation of antioxidant target genes. The cytotoxicity of 6-hydroxydopamine (6-OHDA) was reduced by pre-treatment with DMF in SH-SY5Y cells. The increase in the reactive oxygen species caused by 6-OHDA treatment was also attenuated by DMF in SH-SY5Y cells. The neuroprotective effects of DMF against 6-OHDA neurotoxicity were dependent on Nrf2, since treatment with Nrf2 siRNA failed to block against 6-OHDA neurotoxicity and induce Nrf2-dependent cytoprotective genes in SH-SY5Y cells. In vivo, DMF oral administration was shown to upregulate mRNA and protein levels of Nrf2 and Nrf2-regulated cytoprotective genes, attenuate 6-OHDA induced striatal oxidative stress and inflammation in C57BL/6 mice. Moreover, DMF ameliorated dopaminergic neurotoxicity in 6-OHDA-induced PD animal models as evidenced by amelioration of locomotor dysfunction, loss in striatal dopamine, and reductions in dopaminergic neurons in the substantia nigra and striatum. Taken together, these data strongly suggest that DMF may be beneficial for the treatment of neurodegenerative diseases like PD.