The role of sequestosome 1/p62 protein in amyotrophic lateral sclerosis and frontotemporal dementia pathogenesis
Amyotrophic lateral sclerosis and frontotemporal lobar degeneration are multifaceted diseases with genotypic, pathological and clinical overlap. One such overlap is the presence of SQSTM1/p62 mutations. While traditionally mutations manifesting in the ubiquitin-associated domain of p62 were associated with Paget's disease of bone, mutations affecting all functional domains of p62 have now been identified in amyotrophic lateral sclerosis and frontotemporal lobar degeneration patients. p62 is a multifunctional protein that facilitates protein degradation through autophagy and the ubiquitin-proteasome system, and also regulates cell survival via the Nrf2 antioxidant response pathway, the nuclear factor-kappa B signaling pathway and apoptosis. Dysfunction in these signaling and protein degradation pathways have been observed in amyotrophic lateral sclerosis and frontotemporal lobar degeneration, and mutations that affect the role of p62 in these pathways may contribute to disease pathogenesis. In this review we discuss the role of p62 in these pathways, the effects of p62 mutations and the effect of mutations in the p62 modulator TANK-binding kinase 1, in relation to amyotrophic lateral sclerosis-frontotemporal lobar degeneration pathogenesis.
Protective effects of combined treatment with mild hypothermia and edaravone against cerebral ischemia/reperfusion injury via oxidative stress and Nrf2 pathway regulation
Mild hypothermia (MH) and edaravone (EDA) exert neuroprotective effects against cerebral ischemia/reperfusion (I/R) injury through activation of the nuclear factor erythroid 2‑related factor 2 (Nrf2) pathway. However, whether MH and EDA exert synergistic effects against cerebral I/R injury remains unknown. The aim of the present study was to investigate the effects and mechanism of action of MH in combination with EDA in cerebral I/R injury. A rat cerebral I/R injury model was constructed by middle cerebral artery occlusion (MCAO) followed by reperfusion, and the mice were treated by MH, EDA or the inhibitor of the Nrf2 signaling pathway brusatol (Bru). It was observed that mice treated by MCAO had higher neurological deficit scores and oxidative stress levels, and low spatial learning and memory capacity; moreover, the CA1 region of the hippocampi of the mice exhibited reduced neuronal density and viability, and reduced mitochondrial dysfunction. However, MH in combination with EDA reversed the effects of MCAO, which were blocked by Bru injection. The levels of glutathione (GSH), GSH peroxidase, catalase and superoxide dismutase in rat ischemic hemisphere tissues were reduced by Bru. Western blotting demonstrated that the combined treatment with MH and EDA promoted the nuclear localization of Nrf2, and increased the levels of NAD(P)H quinone oxidoreductase and heme oxygenase (HO)‑1. In conclusion, MH combined with EDA exerted synergistic neuroprotective effects against cerebral I/R injury involving changes in the Nrf2/HO‑1 pathway.
Docosahexaenoic Acid Protects Traumatic Brain Injury by Regulating NOX 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 NOX in this effect has not been illuminated. So this study explored the role of NOX in TBI models treated with DHA, aiming to complete the mechanism of DHA. TBI rat models were constructed with or without DHA treatment, and HO-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 NOX, 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 NOX 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 NOX, and accelerated cell apoptosis. Both in vivo and in vitro experiments demonstrated that DHA treated TBI by reducing NOX generation that might function on Nrf2 signaling pathway, providing a potential evidence for its clinical application.
Recombinant CCL17 Enhances Hematoma Resolution and Activation of CCR4/ERK/Nrf2/CD163 Signaling Pathway After Intracerebral Hemorrhage in Mice
Hematoma is a crucial factor leading to poor prognosis after intracerebral hemorrhage (ICH). Promoting microglial phagocytosis to enhance hematoma resolution may be an important therapeutic target for recovery after ICH. C-C chemokine receptor 4 (CCR4) is important for regulating immune balance in the central nervous system. However, whether CCR4 activation can attenuate hematoma after ICH remains unknown. We aimed to evaluate whether CCL17 (a specific ligand of CCR4) treatment can promote hematoma resolution through CCR4/ERK/Nrf2/CD163 pathway after ICH. A total of 261 adult male CD1 mice were used. Mice were subjected to intrastriatal injection of autologous blood to induce ICH and randomly assigned to receive recombinant CCL17 (rCCL17) or vehicle which was administered intranasally at 1 h after ICH. To elucidate the underlying mechanism, C021, a selective inhibitor of CCR4 and ML385 and a selective inhibitor of Nrf2 were administered 1 h prior to ICH induction. Clustered regularly interspaced short palindromic repeats (CRISPR) knockout for CD163 was administered by intracerebroventricular injection at 48 h before ICH. Brain edema, short- and long-term neurobehavior evaluation, hematoma volume, hemoglobin content, western blot, and immunofluorescence staining were performed. Endogenous CCL17, CCR4, and CD163 expression increased and peaked at 72 h after ICH. CCR4 was expressed by microglia. CCR4 activation with rCCL17 significantly improved neurobehavioral scores and reduced hematoma volume and brain edema compared with vehicle. Moreover, rCCL17 treatment significantly promoted phosphorylation of ERK1/2, increased the expression Nrf2, and upregulated CD163 expression after ICH. The protective effects of rCCL17 were abolished by administration of C021, ML385, and CD163 CRISPR knockout. This study demonstrated that CCR4 activation with rCCL17 promoted hematoma resolution by increasing CD163 expression and CCR4/ERK/Nrf2 pathway activation after ICH, thereby reducing brain edema and improving neurological function. Overall, our study suggests that CCR4 activation may be a potential therapeutic strategy to attenuate hematoma in early brain injury after ICH.
Anti-aging Klotho Protects SH-SY5Y Cells Against Amyloid β1-42 Neurotoxicity: Involvement of Wnt1/pCREB/Nrf2/HO-1 Signaling
Alzheimer's disease (AD) is considered a prevalent neurological disorder with a neurodegenerative nature in elderly people. Oxidative stress and neuroinflammation due to amyloid β (Aβ) peptides are strongly involved in AD pathogenesis. Klotho is an anti-aging protein with multiple protective effects that its deficiency is involved in development of age-related disorders. In this study, we investigated the beneficial effect of Klotho pretreatment at different concentrations of 0.5, 1, and 2 nM against Aβ1-42 toxicity at a concentration of 20 μM in human SH-SY5Y neuroblastoma cells. Our findings showed that Klotho could significantly and partially restore cell viability and decrease reactive oxygen species (known as ROS) and improve superoxide dismutase activity (SOD) in addition to reduction of caspase 3 activity and DNA fragmentation following Aβ1-42 challenge. In addition, exogenous Klotho also reduced inflammatory biomarkers consisting of nuclear factor-kB (NF-kB), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) in Aβ-exposed cells. Besides, Klotho caused downregulation of Wnt1 level, upregulation of phosphorylated cyclic AMP response element binding (pCREB), and mRNA levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) with no significant alteration of epsilon isoform of protein kinase C (PKCε) after Aβ toxicity. In summary, Klotho could alleviate apoptosis, oxidative stress, and inflammation in human neuroblastoma cells after Aβ challenge and its beneficial effect is partially exerted through appropriate modulation of Wnt1/pCREB/Nrf2/HO-1 signaling.
Mitochondria and lipid peroxidation in the mechanism of neurodegeneration: Finding ways for prevention
The world's population aging progression renders age-related neurodegenerative diseases to be one of the biggest unsolved problems of modern society. Despite the progress in studying the development of pathology, finding ways for modifying neurodegenerative disorders remains a high priority. One common feature of neurodegenerative diseases is mitochondrial dysfunction and overproduction of reactive oxygen species, resulting in oxidative stress. Although lipid peroxidation is one of the markers for oxidative stress, it also plays an important role in cell physiology, including activation of phospholipases and stimulation of signaling cascades. Excessive lipid peroxidation is a hallmark for most neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and many other neurological conditions. The products of lipid peroxidation have been shown to be the trigger for necrotic, apoptotic, and more specifically for oxidative stress-related, that is, ferroptosis and neuronal cell death. Here we discuss the involvement of lipid peroxidation in the mechanism of neuronal loss and some novel therapeutic directions to oppose it.
Neuroprotective effects of 1-O-hexyl-2,3,5-trimethylhydroquinone on ischaemia/reperfusion-induced neuronal injury by activating the Nrf2/HO-1 pathway
1-O-Hexyl-2,3,5-trimethylhydroquinone (HTHQ), a lipophilic phenolic agent, has an antioxidant activity and reactive oxygen species (ROS) scavenging property. However, the role of HTHQ on cerebral ischaemic/reperfusion (I/R) injury and the underlying mechanisms remain poorly understood. In the present study, we demonstrated that HTHQ treatment ameliorated cerebral I/R injury in vivo, as demonstrated by the decreased infarct volume ration, neurological deficits, oxidative stress and neuronal apoptosis. HTHQ treatment increased the levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream antioxidant protein, haeme oxygenase-1 (HO-1). In addition, HTHQ treatment decreases oxidative stress and neuronal apoptosis of PC12 cells following hypoxia and reperfusion (H/R) in vitro. Moreover, we provided evidence that PC12 cells were more vulnerable to H/R-induced oxidative stress after si-Nrf2 transfection, and the HTHQ-mediated protection was lost in PC12 cells transfected with siNrf2. In conclusion, these results suggested that HTHQ possesses neuroprotective effects against oxidative stress and apoptosis after cerebral I/R injury via activation of the Nrf2/HO-1 pathway.
Nuclear Factor-Erythroid 2-Related Factor 2 (Nrf2) and Mitochondrial Dynamics/Mitophagy in Neurological Diseases
Mitochondria play an essential role in bioenergetics and respiratory functions for cell viability through numerous biochemical processes. To maintain mitochondria quality control and homeostasis, mitochondrial morphologies change rapidly in response to external insults and changes in metabolic status through fusion and fission (so called mitochondrial dynamics). Furthermore, damaged mitochondria are removed via a selective autophagosomal process, referred to as mitophagy. Although mitochondria are one of the sources of reactive oxygen species (ROS), they are themselves vulnerable to oxidative stress. Thus, endogenous antioxidant defense systems play an important role in cell survival under physiological and pathological conditions. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a redox-sensitive transcription factor that maintains redox homeostasis by regulating antioxidant-response element (ARE)-dependent transcription and the expression of antioxidant defense enzymes. Although the Nrf2 system is positively associated with mitochondrial biogenesis and mitochondrial quality control, the relationship between Nrf2 signaling and mitochondrial dynamics/mitophagy has not been sufficiently addressed in the literature. This review article describes recent clinical and experimental observations on the relationship between Nrf2 and mitochondrial dynamics/mitophagy in various neurological diseases.
Sulforaphane alleviates ethanol-mediated central inhibition and reverses chronic stress-induced aggravation of acute alcoholism via targeting Nrf2-regulated catalase expression
Acute ethanol intoxication by excessive drinking is an important cause of alcohol-induced death. Stress exposure has been identified as one risk factor for alcohol abuse. Previous reports indicated that stressors may augment inhibitory effects of alcohol, but the underlying mechanism remains unknown. Here, we reported that chronic unpredictable stress increased the sensitivity to the acute ethanol intoxication in mice via impairing nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-catalase signaling. Nrf2 activity regulates the expression of catalase, a key antioxidant enzyme that mediates ethanol oxidation in the brain. Pharmacological blockade of catalase or Nrf2 activity significantly aggravated acute ethanol intoxication. Sulforaphane, a cruciferous vegetable-derived activator of Nrf2, significantly attenuated acute ethanol intoxication. Furthermore, the stress-induced aggravation of acute alcoholism was rapidly reversed by sulforaphane. Our findings suggest that Nrf2 may function as a novel drug target for the prevention of acute alcoholism, especially in psychiatric patients, by controlling catalase-mediated ethanol oxidation.
Synergistic effect of Aminoguanidine and L-Carnosine against Thioacetamide-induced Hepatic Encephalopathy in rats: Behavioral, Biochemical and Ultra Structural Evidences
Hepatic encephalopathy (HE) depicts the cluster of neurological alterations that occur during acute or chronic hepatic injury. This study was aimed to evaluate the possible synergistic effect between aminoguanidine (AG; 100 mg/kg; p.o.) and l-carnosine (CAR; 100 mg/kg; p.o.) on HE that was induced by thioacetamide (TAA; 100 mg/kg; i.p) thrice weekly for six weeks. Twenty-four hours after the last treatment; behavioral changes, biochemical parameters, histopathological analysis, immunohistochemical and ultrastructural studies were conducted. Combining AG with CAR improved TAA-induced locomotor impairment and motor incoordination evidenced by; reduced locomotor activity and decline in motor skill performance as well as ameliorated cognitive deficits. Moreover, both drugs restored the levels of serum hepatic enzymes as well as serum and brain levels of ammonia. In addition to, the combination significantly modulated hepatic and brain oxidative stress biomarkers, inflammatory cytokines and cleaved caspase-3 expression. Furthermore, they succeeded to activate nuclear erythroid 2-related factor 2 (Nrf2) expression and ameliorate markers of HE including hepatic necrosis and brain astrocyte swelling. This study depicts that combining AG with CAR exerted new intervention for hepatic and brain damage in HE due to their complementary antioxidant, anti-inflammatory effect and hypoammonemic effects via Nrf2/HO-1 activation and NO inhibition.
Inhibition of JNK Alleviates Chronic Hypoperfusion-Related Ischemia Induces Oxidative Stress and Brain Degeneration via Nrf2/HO-1 and NF-B Signaling
Cerebral ischemia is one of the leading causes of neurological disorders. The exact molecular mechanism related to chronic unilateral cerebral ischemia-induced neurodegeneration and memory deficit has not been precisely elucidated. In this study, we examined the effect of chronic ischemia on the induction of oxidative stress and c-Jun N-terminal kinase-associated detrimental effects and unveiled the inhibitory effect of specific JNK inhibitor (SP600125) on JNK-mediated brain degeneration in adult mice. Our behavioral, biochemical, and immunofluorescence studies revealed that chronic ischemic injuries sustained increased levels of oxidative stress-induced active JNK for a long time, whereas SP600125 significantly reduced the elevated level of active JNK and further regulated Nrf2/HO-1 and NF-B signaling, which have been confirmed in vivo. Neuroinflammatory mediators and loss of neuronal cells was significantly reduced with the administration of SP600125. Ischemic brain injury caused synaptic dysfunction and memory impairment in mice. However, these were significantly improved with SP600125. On the whole, these findings suggest that elevated ROS-mediated JNK is a key mediator in chronic ischemic conditions and has a crucial role in neuroinflammation, neurodegeneration, and memory dysfunction. Our findings suggest that chronic oxidative stress associated JNK would be a potential target in time-dependent studies of chronic ischemic conditions induced brain degeneration.
The Potential Value of Targeting Ferroptosis in Early Brain Injury After Acute CNS Disease
Acute central nervous system (CNS) disease is very common and with high mortality. Many basic studies have confirmed the molecular mechanism of early brain injury (EBI) after acute CNS disease. Neuron death and dysfunction are important reasons for the neurological dysfunction in patients with acute CNS disease. Ferroptosis is a nonapoptotic form of cell death, the classical characteristic of which is based on the iron-dependent accumulation of toxic lipid reactive oxygen species. Previous studies have indicated that this mechanism is critical in the cell death events observed in many diseases, including cancer, tumor resistance, Alzheimer's disease, Parkinson's disease, stroke, and intracerebral hemorrhage (ICH). Ferroptosis may also play a very important role in EBI after acute CNS disease. Unresolved issues include the relationship between ferroptosis and other forms of cell death after acute CNS disease, the specific molecular mechanisms of EBI, the strategies to activate or inhibit ferroptosis to achieve desirable attenuation of EBI, and the need to find new molecular markers of ferroptosis that can be used to detect and study this process after acute CNS disease.
Neuroprotective effects of natural compounds on LPS-induced inflammatory responses in microglia
Neuroinflammation is one of the main mechanisms involved in the progression of neurodegeneration. The activation of microglia is the main feature of neuroinflammation, promoting the release of neurotoxic molecules and pro-inflammatory cytokines and resulting in the progressive neuronal cell death. Thus, suppression of the over-activation of microglia using novel pharmacological agents is an attractive issue to alleviate the neuroinflammatory processes associated with neurodegeneration. In recent years, medicinal plants-derived natural compounds have received extensive attention as useful sources of new neuroprotective agents for treating neurological disorders. In this review, we summarized the detailed research progress on the natural compounds derived from medicinal plants with potential anti-inflammatory effects and their molecular mechanisms on modulating the LPS-induced inflammatory responses in microglia. The natural compounds that efficacious in inhibiting the microglia activation include flavonoids, glycosides, phenolics, terpenoids, quinones, alkaloids, lignans, coumarins, chalcone, stilbene and others (biphenyl, phenylpropanoid, oxy carotenoid). They can reduce the expression of neurotoxic mediators (NO, PGE2, iNOS, COX-2) and pro-inflammatory cytokines (IL-6, TNF-α, IL-1β), down-regulate inflammatory markers and prevent neural damage. They exert anti-neuroinflammatory effects by modulating relevant signaling pathways (NF-κB, MAPKs, Nrf2/HO-1, PI3K/Akt, JAK/STAT) as demonstrated by experimental data. The present work reviews the role of microglia activation in neuroinflammation, highlighting the potential anti-inflammatory effects of natural compounds as a promising approach to develop innovative neuroprotective strategy.
Potent Natural Antioxidant Carveol Attenuates MCAO-Stress Induced Oxidative, Neurodegeneration by Regulating the Nrf-2 Pathway
Ischemic stroke is a severe neurological disorder with a high prevalence rate in developed countries. It is characterized by permanent or transient cerebral ischemia and it activates syndrome of pathological events such as membrane depolarization, glutamate excitotoxicity, and intracellular calcium buildup. Carveol is widely employed as anti-inflammatory and antioxidant in traditional Chinese medicine. In the present study, the neuroprotective effects of post-treated carveol were demonstrated against transient middle cerebral artery occlusion (MCAO) induced focal ischemic cerebral injury. Male Sprague Dawley (SD) rats were subjected to two different experimental protocols to determine the dose and effects of carveol, and to demonstrate the underlying role of the nuclear factor E2-related factor (Nrf2) pathway. Our results showed that MCAO induced marked neuronal injury in the ipsilateral cortex and striatum associated with higher inflammatory cytokines expression, along with apoptotic markers such as caspase-3 and the phosphorylated -Jun -terminal kinase (JNK). Furthermore, MCAO induced a marked increase in oxidative stress as evidenced by high lipid peroxidase (LPO) content accompanied by the depressed antioxidant system. Carveol significantly reversed the oxidative stress and downregulated inflammatory cascades by enhancing endogenous antioxidant mechanisms including the Nrf2 gene, which critically regulates the expression of several downstream antioxidants. Further, to determine the possible involvement of Nrf2 in carveol mediated neuroprotection, we antagonized Nrf2 by all- retinoic acid (ATRA), and such treatment abrogated the protective effects of carveol accompanied with exaggerated neuronal toxicity as demonstrated by higher infarction area. The target effects of carveol were further supported by molecular docking analysis of drug-protein interactions. Together, our findings suggest that carveol could activate endogenous master anti-oxidant Nrf2, which further regulates the expression of downstream antioxidants, eventually ameliorating MCAO-induced neuroinflammation and neurodegeneration.
Salvianolic Acid B Improves Postresuscitation Myocardial and Cerebral Outcomes in a Murine Model of Cardiac Arrest: Involvement of Nrf2 Signaling Pathway
Survival and outcome of cardiac arrest (CA) are dismal despite improvements in cardiopulmonary resuscitation (CPR). Salvianolic acid B (Sal B), extracted from Salvia miltiorrhiza, has been investigated for its cardioprotective properties in cardiac remodeling and ischemic heart disease, but less is known about its role in CA. The aim of this study was to learn whether Sal B improves cardiac and neurologic outcomes after CA/CPR in mice. Female C57BL/6 mice were subjected to eight minutes of CA induced by an intravenous injection of potassium chloride (KCl), followed by CPR. After 30 seconds of CPR, mice were blindly randomized to receive either Sal B (20 mg/kg) or vehicle (normal saline) intravenously. Hemodynamic variables and indices of left ventricular function were determined before CA and within three hours after CPR, the early postresuscitation period. Sal B administration resulted in a remarkable decrease in the time required for the return of spontaneous circulation (ROSC) in animals that successfully resuscitated compared to the vehicle-treated mice. Myocardial performance, including cardiac output and left ventricular systolic (dp/dt) and diastolic (dp/dt) function, was clearly ameliorated within three hours of ROSC in the Sal B-treated mice. Moreover, Sal B inhibited CA/CPR-induced cardiomyocyte apoptosis and preserved mitochondrial morphology and function. Mechanistically, Sal B dramatically promoted Nrf2 nuclear translocation through the downregulation of Keap1, which resulted in the expression of antioxidant enzymes, including HO-1 and NQO1, thereby counteracted the oxidative damage in response to CA/CPR. The aforementioned antiapoptotic and antioxidant effects of Sal B were impaired in the setting of gene silencing of Nrf2 with siRNA in vitro model. These improvements were associated with better neurological function and increased survival rate (75% vs. 40%, < 0.05) up to 72 hours postresuscitation. Our findings suggest that the administration of Sal B improved cardiac function and neurological outcomes in a murine model of CA via activating the Nrf2 antioxidant signaling pathway, which may represent a novel therapeutic strategy for the treatment of CA.