Neuroprotective role of fucoxanthin against cerebral ischemic/reperfusion injury through activation of Nrf2/HO-1 signaling
In the present study, an attempt was made to determine whether administration of fucoxanthin could attenuate cerebral ischemic/reperfusion (I/R) injury and its possible mechanisms using an in vivo middle cerebral artery occlusion (MCAO) model and an in vitro oxygen-glucose deprivation and reoxygenation (OGD/R) model. Fucoxanthin was intragastrically administrated in different doses (30 mg/kg, 60 mg/kg, and 90 mg/kg, respectively) to the rats 1 h before MCAO induction. The neurological function, infarct area and brain water content of rats were then evaluated. Rat cortical neuron were pretreated with different doses of fucoxanthin (5 μM, 10 μM, and 20 μM) and then subjected to OGD/R. Expression levels of proteins in the brain tissues and cultured cells were determined by western blotting. Our results demonstrated that fucoxanthin pretreatment improved the neurologic deficit score, lowered the infarct volume and reduced the expression of apoptosis-associated proteins in brain tissues. In addition, fucoxanthin also suppresses OGD/R-induced apoptosis and ROS accumulation in cultured neurons. Furthermore, we found that fucoxanthin could significantly activate the Nrf2/HO-1 signaling through inducing Nrf2 nuclear translocation with enhanced HO-1 expression, and Nrf2 knockdown obviously abrogated the beneficial role of fucoxanthin in OGD/R-treated neurons. These findings suggested that fucoxanthin could be exploited as a therapeutic target for protecting neurons from cerebral I/R injury.
Photoreceptor Survival Is Regulated by GSTO1-1 in the Degenerating Retina
Glutathione-S-transferase omega 1-1 (GSTO1-1) is a cytosolic glutathione transferase enzyme, involved in glutathionylation, toll-like receptor signaling, and calcium channel regulation. GSTO1-1 dysregulation has been implicated in oxidative stress and inflammation, and contributes to the pathogenesis of several diseases and neurological disorders; however, its role in retinal degenerations is unknown. The aim of this study was to investigate the role of GSTO1-1 in modulating oxidative stress and consequent inflammation in the normal and degenerating retina.
Edaravone Reduces Iron-Mediated Hydrocephalus and Behavioral Disorder in Rat by Activating the Nrf2/HO-1 Pathway
Our previous studies have demonstrated that hemorrhage-derived iron has a key role in causing brain injury after intraventricular hemorrhage (IVH). Based on this finding, we hypothesized that edaravone, a free-radical scavenger, has the potential to alleviate hydrocephalus and neurological deficits post-IVH by suppressing iron-induced oxidative stress. Thus, this study aimed to investigate the efficacy of edaravone for rats with FeCl injection, as well as to explore the related molecular mechanism. An experimental model was established in adult male Sprague-Dawley rats via FeCl injection into the right lateral ventricle. Edaravone or vehicle was administered immediately, 1 day and 2 days after intraventricular injection. Brain water content, magnetic resonance imaging, neurological score, oxidative stress assays, Western blot analysis, and electron microscopy were employed to evaluate brain injury in these rats. Intraventricular injection of FeCl induced brain edema, ventricular dilation, and neurobehavioral disorder in rats. Edaravone treatment significantly attenuated the above symptoms, reduced ependymal cilia and neuron damage, and inhibited oxidative stress (elevated levels of an antioxidant, superoxide dismutase; decreased levels of an oxidant, malondialdehyde). Moreover, edaravone administration effectively activated the Nrf2/HO-1 signaling pathway in rat brain following FeCl injection. These results showed that edaravone treatment alleviated brain edema, ventricular expansion, and neurological disorder after FeCl injection. The possible mechanism is by protecting ependymal cilia and neurons from oxidative stress injury and activating the Nrf2/HO-1 signaling pathway. These results provide further experimental evidence for edaravone application in the treatment of IVH.
Melatonin Upregulates Nuclear Factor Erythroid-2 Related Factor 2 (Nrf2) and Mediates Mitophagy to Protect Against Early Brain Injury After Subarachnoid Hemorrhage
BACKGROUND The aim of this study was to investigate whether melatonin is involved in brain injury following subarachnoid hemorrhage (SAH). MATERIAL AND METHODS An SAH model was established and TUNEL assays were utilized to detect the effect of melatonin on cell apoptosis. Western blot analysis was used to detect the effect of melatonin on expression of autophagic markers and apoptotic factors. Real-time PCR, Western blot analysis, and luciferase assay were performed to study the effect of melatonin on nuclear factor erythroid-2 related factor 2 (NRF2) expression. RESULTS The SAH group displayed a lower neurological score and a higher brain water content, while melatonin treatment increased the neurological score and decreased the brain water content. The administration of melatonin also inhibited the apoptosis of neurons in the brain. In addition, higher Beclin-1 expression and higher conversion ratio from LC3- II to LC3-I were observed in the SAH group. The activation of Beclin-1 and the conversion from LC3-II to LC3-I was further enhanced by melatonin treatment. Furthermore, in the SAH group, the level of Bcl-2 was decreased while the level of Bax and cleaved caspase-3 were increased. However, following melatonin treatment in the SAH group, the level of Bcl-2 was increased while the levels of Bax and cleaved caspase-3 were decreased. CONCLUSIONS Our study indicated that, by increasing the expression of NRF2, the mitophagy induced by melatonin provided protection against brain injury post-SAH.
Newer pharmacological approaches for antioxidant neuroprotection in traumatic brain injury
Reactive oxygen species-induced oxidative damage remains an extensively validated secondary injury mechanism in traumatic brain injury (TBI) as demonstrated by the efficacy of various pharmacological antioxidants agents in decreasing post-traumatic free radical-induced lipid peroxidation (LP) and protein oxidative damage in preclinical TBI models. Based upon strong preclinical efficacy results, two antioxidant agents, the superoxide radical scavenger polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) and the 21-aminosteroid LP inhibitor tirilazad, which inhibits lipid peroxidation, (LP) were evaluated in large phase III trials in moderately- and severely-injured TBI patients. Both failed to improve 6 month survival and neurological recovery. However, in the case of tirilazad, a post hoc analysis revealed that the drug significantly improved survival of male TBI patients who exhibited traumatic subarachnoid hemorrhage (tSAH) that occurs in half of severe TBIs. In addition to reviewing the clinical trial results with PEG-SOD and tirilazad, newer antioxidant approaches which appear to improve neuroprotective efficacy and provide a longer therapeutic window in rodent TBI models will be presented. The first approach involves pharmacological enhancement of the multi-mechanistic Nrf2-antioxidant response element (ARE) pathway. The second involves scavenging of the neurotoxic LP-derived carbonyl compounds 4-hydroxynonenal (4-HNE) and acrolein which are highly damaging to neural protein and stimulate additional free radical generation. A third approach combines mechanistically complimentary antioxidants to interrupt post-TBI oxidative neurodegeneration at multiple points in the secondary injury cascade. These newer strategies appear to decrease variability in the neuroprotective effect which should improve the feasibility of achieving successful translation of antioxidant therapy to TBI patients.
Neuroprotective Effect of Hydrogen Sulfide in Hyperhomocysteinemia Is Mediated Through Antioxidant Action Involving Nrf2
Homocysteine (Hcy) is a sulfur-containing amino acid derived from methionine metabolism. Elevated plasma Hcy levels (> 15 µM) result in a condition called hyperhomocysteinemia (HHcy), which is an independent risk factor in the development of various neurodegenerative disorders. Reactive oxygen species (ROS) produced by auto-oxidation of Hcy have been implicated in HHcy-associated neurological conditions. Hydrogen sulfide (HS) is emerging as a potent neuroprotective and neuromodulator molecule. The present study was aimed to evaluate the ability of NaHS (a source of HS) to attenuate Hcy-induced oxidative stress and altered antioxidant status in animals subjected to HHcy. Impaired cognitive functions assessed by Y-maze and elevated plus maze in Hcy-treated animals were reversed on NaHS administration. Increased levels of ROS, lipid peroxidation, protein carbonyls, and 4-hydroxynonenal (4-HNE)-modified proteins were observed in the cortex and hippocampus of Hcy-treated animals suggesting accentuated oxidative stress. This increase in Hcy-induced oxidative stress was reversed following NaHS supplementation. GSH/GSSG ratio, activity of antioxidant enzymes viz; superoxide dismutase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase were decreased in Hcy-treated animals. NaHS supplementation, on the otherhand, restored redox ratio and activity of antioxidant enzymes in the brains of animals with HHcy. Further, NaHS administration normalized nuclear factor erythroid 2-related factor 2 expression and acetylcholinesterase (AChE) activity in the brain of Hcy-treated animals. Histopathological studies using cresyl violet indicated higher number of pyknotic neurons in the cortex and hippocampus of HHcy animals, which were reversed by NaHS administration. The results clearly demonstrate that NaHS treatment significantly ameliorates Hcy-induced cognitive impairment by attenuating oxidative stress, improving antioxidant status, and modulating AChE activity thereby suggesting potential of HS as a therapeutic molecule.
Na , K -ATPase activity in children with autism spectrum disorder: Searching for the reason(s) of its decrease in blood cells
Na , K -ATPase (NKA) activity, which establishes the sodium and potassium gradient across the cell membrane and is instrumental in the propagation of the nerve impulses, is altered in a number of neurological and neuropsychiatric disorders, including autism spectrum disorders (ASD). In the present work, we examined a wide range of biochemical and cellular parameters in the attempt to understand the reason(s) for the severe decrease in NKA activity in erythrocytes of ASD children that we reported previously. NKA activity in leukocytes was found to be decreased independently from alteration in plasma membrane fluidity. The different subunits were evaluated for gene expression in leukocytes and for protein expression in erythrocytes: small differences in gene expression between ASD and typically developing children were not apparently paralleled by differences in protein expression. Moreover, no gross difference in erythrocyte plasma membrane oxidative modifications was detectable, although oxidative stress in blood samples from ASD children was confirmed by increased expression of NRF2 mRNA. Interestingly, gene expression of some NKA subunits correlated with clinical features. Excess inhibitory metals or ouabain-like activities, which might account for NKA activity decrease, were ruled out. Plasma membrane cholesterol, but not phosphatidylcholine and phosphatidlserine, was slighty decreased in erythrocytes from ASD children. Although no compelling results were obtained, our data suggest that alteration in the erytrocyte lipid moiety or subtle oxidative modifications in NKA structure are likely candidates for the observed decrease in NKA activity. These findings are discussed in the light of the relevance of NKA in ASD. Autism Research 2018. © 2018 The Authors. Autism Research published by International Society for Autism Research and Wiley Periodicals, Inc.
N-glycanase NGLY1 regulates mitochondrial homeostasis and inflammation through NRF1
Mutations in the (N-glycanase 1) gene, encoding an evolutionarily conserved deglycosylation enzyme, are associated with a rare congenital disorder leading to global developmental delay and neurological abnormalities. The molecular mechanism of the NGLY1 disease and its function in tissue and immune homeostasis remain unknown. Here, we find that -deficient human and mouse cells chronically activate cytosolic nucleic acid-sensing pathways, leading to elevated interferon gene signature. We also find that cellular clearance of damaged mitochondria by mitophagy is impaired in the absence of NGLY1, resulting in severely fragmented mitochondria and activation of cGAS-STING as well as MDA5-MAVS pathways. Furthermore, we show that NGLY1 regulates mitochondrial homeostasis through transcriptional factor NRF1. Remarkably, pharmacological activation of a homologous but nonglycosylated transcriptional factor NRF2 restores mitochondrial homeostasis and suppresses immune gene activation in -deficient cells. Together, our findings reveal novel functions of the NGLY1-NRF1 pathway in mitochondrial homeostasis and inflammation and uncover an unexpected therapeutic strategy using pharmacological activators of NRF2 for treating mitochondrial and immune dysregulation.
A novel Nrf2 activator, RS9, attenuates secondary brain injury after intracerebral hemorrhage in sub-acute phase
The poor prognosis of intracranial hemorrhage (ICH) is attributed to secondary brain injury (SBI), which is caused by oxidative stress. Blood components induce reactive oxygen species (ROS) over-production and cause cytotoxicity. We focused on the antioxidant system and investigated nuclear factor-erythroid 2-related factor 2 (Nrf2), which is a transcription factor that controls several antioxidant enzymes. We examined the effects of a novel Nrf2 activator, RS9, on SBI after ICH. ICH was induced by injecting autologous blood collected from the jugular vein (25 µL) into the striatum of mice. RS9 was administrated 0, 24, and 48 h after the induction of ICH. Using the ICH model, we measured brain edema, neurological function, and antioxidant proteins expression. We then investigated the mechanisms responsible for the effects of RS9 in vitro using the SH-SY5Y cell line. We used zinc protoporphyrin (ZnPP), a heme oxygenase-1 (HO-1) inhibitor, to elucidate the relationship between HO-1 expression and cell death in vitro in a hemin injury model. RS9 decreased brain edema, improved neurological deficits, decreased neuronal damage area and up-regulated HO-1 and superoxide dismutase 1(SOD) expressions in the ICH mouse model. RS9 also suppressed neuronal cell death and ROS over-production in vitro. These protective effects were cancelled by the ZnPP co-treatment. Our results suggest that the activation of Nrf2 by RS9 exerts neuroprotective effects that are mediated by the attenuation of oxidative stress, and also that RS9 is an effective therapeutic candidate for the treatment for SBI after ICH.
Cx26 partial loss causes accelerated presbycusis by redox imbalance and dysregulation of Nfr2 pathway
Mutations in GJB2, the gene that encodes connexin 26 (Cx26), are the most common cause of sensorineural hearing impairment. The truncating variant 35delG, which determines a complete loss of Cx26 protein function, is the prevalent GJB2 mutation in several populations. Here, we generated and analyzed Gjb2 mice as a model of heterozygous human carriers of 35delG. Compared to control mice, auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) worsened over time more rapidly in Gjb2 mice, indicating they were affected by accelerated age-related hearing loss (ARHL), or presbycusis. We linked causally the auditory phenotype of Gjb2 mice to apoptosis and oxidative damage in the cochlear duct, reduced release of glutathione from connexin hemichannels, decreased nutrient delivery to the sensory epithelium via cochlear gap junctions and deregulated expression of genes that are under transcriptional control of the nuclear factor erythroid 2-related factor 2 (Nrf2), a pivotal regulator of tolerance to redox stress. Moreover, a statistically significant genome-wide association with two genes (PRKCE and TGFB1) related to the Nrf2 pathway (p-value < 4 × 10) was detected in a very large cohort of 4091 individuals, originating from Europe, Caucasus and Central Asia, with hearing phenotype (including 1076 presbycusis patients and 1290 healthy matched controls). We conclude that (i) elements of the Nrf2 pathway are essential for hearing maintenance and (ii) their dysfunction may play an important role in the etiopathogenesis of human presbycusis.
Dimethyl fumarate-associated transient bone marrow oedema syndrome
Dimethyl fumarate (DMF) is a commonly used and effective treatment for relapsing and remitting multiple sclerosis. Its use results in impairment of the transcription factor nuclear factor erythroid-derived 2 (E2)-related factor (Nrf2), which is involved in both immunomodulation and bone health. DMF has not previously been reported to cause bone marrow complications, though other fumarates including tenofovir have. The mechanism of fumarate-associated bone toxicity remains unclear with altered osteoblastic gene expression and function suggested.
GSK-3β, a double-edged sword in Nrf2 regulation: Implications for neurological dysfunction and disease
In the past decade, it has become evident that glycogen synthase kinase 3β (GSK-3β) modulates the nuclear factor erythroid 2-related factor 2 (Nrf2) oxidative stress response. GSK-3β functions as an inhibitor, both directly in the activation and indirectly in the post-induction of Nrf2. The incidence of oxidative stress in neurological dysfunction and disease has made this signaling pathway an attractive therapeutic target. There is minimal evidence, however, to support a distinctive function for GSK-3β mediated Nrf2 inhibition in nervous system decline, apart from the typical oxidative stress response. In both Alzheimer's disease and brain ischemia, this pathway has been explored for potential benefits on disease etiology and advancement. Presently, it is unclear whether GSK-3β mediated Nrf2 inhibition markedly influences these disease states. Furthermore, the potential that each has unique function in neurodegenerative decline is unsubstantiated.
Trilobatin Protects Against Oxidative Injury in Neuronal PC12 Cells Through Regulating Mitochondrial ROS Homeostasis Mediated by AMPK/Nrf2/Sirt3 Signaling Pathway
Oxidative stress-induced neuronal cell damage is a crucial factor in the pathogenesis of mitochondria-associated neurological diseases. Therefore, elimination of overproduction of mitochondrial reactive oxygen species (mtROS) may be a potential strategy for prevention and treatment of neurological diseases. In the present study, the neuroprotective effects of trilobatin (TLB), a novel small molecule monomer derived from Rehd, and its underlying mechanisms were investigated using hydrogen peroxide (HO)-induced oxidative stress model in a neuron-like PC12 cell. The findings revealed that pre-treatment with TLB dramatically concentration-dependently suppressed HO-induced PC12 cells damage by enhancing cell viability, repressed reduction of mitochondrial membrane potential (MMP) and decreased mtROS overgeneration, thereby deferring cell apoptosis. Further study demonstrated that TLB not only increased the enzymatic activities of glutathione peroxidase (GPx), isocitrate dehydrogenase 2 (IDH2),superoxide dismutase 2 (SOD2) and deacetylation of SOD2, but also activated silent mating-type information regulation 2 homolog 3 (Sirt3) within the mitochondria and thereby upregulating forkheadboxO3a (FoxO3a), which regulated mitochondrial DNA genes, then led to improving complex I activity and adenosine triphosphate (ATP) synthesis. What's more, TLB up-regulated p-adenosine monophosphate-activated protein kinase (AMPK) level, the expression of peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α), and ERRα. Intriguingly, TLB failed to mitigate HO-induced PC12 injury in the presence of the AMPK inhibitor (Compound C), indicating that the beneficial effects of TLB on the regulation of mtROS homeostasis were reliance on AMPK -Sirt3 signaling pathway. Moreover, TLB also facilitated nuclear factor erythroid 2-related factor 2 (Nrf2) and promoted antioxidant gene expression in turn, and knockdown of Nrf2 by siRNA dramatically reduced the neuroprotective effects of TLB. Notably, AMPK inhibitor abolished the activation of Nrf2 and Sirt3, whereas, knockdown of Nrf2 blocked the upregulation of Sirt3, but it did not affect p-AMPK level. In conclusion, our findings demonstrate that TLB protects against oxidative injury in neuronal PC12 cells through regulating mtROS homeostasis in the first time, which is, at least partly, mediated through the AMPK/Nrf2/Sirt3 signaling pathway.
Baicalin provides neuroprotection in traumatic brain injury mice model through Akt/Nrf2 pathway
The neuroprotective effects of Baicalin have been confirmed in several central nervous system (CNS) diseases. However, its possible effect on traumatic brain injury (TBI) model is still not clear. The present study is aimed to investigate the role and the underling mechanisms of 7-D-glucuronic acid-5,6-dihydroxyflavone (Baicalin) on TBI model.
Molecular Mechanisms of Lithium Action: Switching the Light on Multiple Targets for Dementia Using Animal Models
Lithium has long been used for the treatment of psychiatric disorders, due to its robust beneficial effect as a mood stabilizing drug. Lithium's effectiveness for improving neurological function is therefore well-described, stimulating the investigation of its potential use in several neurodegenerative conditions including Alzheimer's (AD), Parkinson's (PD) and Huntington's (HD) diseases. A narrow therapeutic window for these effects, however, has led to concerted efforts to understand the molecular mechanisms of lithium action in the brain, in order to develop more selective treatments that harness its neuroprotective potential whilst limiting contraindications. Animal models have proven pivotal in these studies, with lithium displaying advantageous effects on behavior across species, including worms (), zebrafish (), fruit flies () and rodents. Due to their susceptibility to genetic manipulation, functional genomic analyses in these model organisms have provided evidence for the main molecular determinants of lithium action, including inhibition of inositol monophosphatase (IMPA) and glycogen synthase kinase-3 (GSK-3). Accumulating pre-clinical evidence has indeed provided a basis for research into the therapeutic use of lithium for the treatment of dementia, an area of medical priority due to its increasing global impact and lack of disease-modifying drugs. Although lithium has been extensively described to prevent AD-associated amyloid and tau pathologies, this review article will focus on generic mechanisms by which lithium preserves neuronal function and improves memory in animal models of dementia. Of these, evidence from worms, flies and mice points to GSK-3 as the most robust mediator of lithium's neuro-protective effect, but it's interaction with downstream pathways, including Wnt/β-catenin, CREB/brain-derived neurotrophic factor (BDNF), nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and toll-like receptor 4 (TLR4)/nuclear factor-κB (NFκB), have identified multiple targets for development of drugs which harness lithium's neurogenic, cytoprotective, synaptic maintenance, anti-oxidant, anti-inflammatory and protein homeostasis properties, in addition to more potent and selective GSK-3 inhibitors. Lithium, therefore, has advantages as a multi-functional therapy to combat the complex molecular pathology of dementia. Animal studies will be vital, however, for comparative analyses to determine which of these defense mechanisms are most required to slow-down cognitive decline in dementia, and whether combination therapies can synergize systems to exploit lithium's neuro-protective power while avoiding deleterious toxicity.