Esculetin improves cognitive impairments induced by transient cerebral ischaemia and reperfusion in mice via regulation of mitochondrial fragmentation and mitophagy
Mitochondrial dynamics regulate mitochondrial autophagy (mitophagy) and apoptosis, which are important events for the quality control of mitochondria and mitochondrial-associated diseases. Esculetin (ESC) is a natural coumarin that exhibits inspiring biological activities in a variety of animal models, but its neuroprotective effects on cerebral ischaemia have not been clearly elucidated. In this paper, we demonstrated the effects of ESC on transient cerebral ischaemia and reperfusion injury induced in a mouse model and examined the possible underlying mechanisms by investigating mitochondrial fragmentation-regulated mitochondrial autophagy and apoptosis. The experimental results showed that ESC treatment alleviated neurological defects and improved cognitive impairments in transient bilateral common carotid artery occlusion (tBCCAO)-treated mice. Further mechanism studies showed that tBCCAO induced mitochondrial oxidative stress injuries and triggered mitochondrial fragmentation, which were evident by the elevated levels of malondialdehyde and mitochondrial dynamin-related protein 1 (Drp1) and the downregulated activities of superoxide dismutase and nuclear transcription factor E2-related factor 2 (Nrf2). ESC treatment significantly alleviated tBCCAO-induced mitochondrial stress and mitochondrial fragmentation. Moreover, mitophagy and mitochondrial apoptosis were stimulated in response to the mitochondrial oxidative stress in the hippocampus of tBCCAO-treated mice, and ESC treatment regulated the expression of mitophagy-related factors, including Bnip3, Beclin1, Pink1, and parkin, the LC-3 II/I ratio, and apoptosis-related factors, including p53, Bax, and caspase 3. Taken together, our results suggest that ESC treatment regulated hippocampal mitophagy and mitochondrial apoptosis triggered by mitochondrial stress via the mediation of mitochondrial fragmentation during transient cerebral ischaemia and reperfusion injury, which provides insight into the potential of ESC for further therapeutic implications.
Influences of urinary kallidinogenase on neuronal apoptosis in cerebral infarction rats through Nrf2/ARE oxidative stress pathway
To investigate the influences of urinary kallidinogenase on neuronal apoptosis in rats with cerebral infarction through the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) oxidative stress pathway.
Isoliquiritigenin attenuates lipopolysaccharide-induced cognitive impairment through antioxidant and anti-inflammatory activity
Oxidative stress and neuroinflammation are central pathogenic mechanisms common to many neurological diseases. Isoliquiritigenin (ISL) is a flavonoid in licorice with multiple pharmacological properties, including anti-inflammatory activity, and has demonstrated protective efficacy against acute neural injury. However, potential actions against cognitive impairments have not been examined extensively. We established a rat model of cognitive impairment by intracerebroventricular injection of lipopolysaccharide (LPS), and examined the effects of ISL pretreatment on cognitive function, hippocampal injury, and hippocampal expression of various synaptic proteins, antioxidant enzymes, pro-inflammatory cytokines, and signaling factors controlling anti-oxidant and pro-inflammatory responses.
Nomilin protects against cerebral ischemia-reperfusion induced neurological deficits and blood-brain barrier disruption via the Nrf2 pathway
Oxidative stress is considered to play an important role in the cerebral ischemia-reperfusion injury. The nuclear transcription factor erythroid-2-related factor 2 (Nrf2)/NAD(P)H dehydrogenase [quinone] 1 (NQO1) pathway has been considered as a potential target for neuroprotection in cerebral ischemia-reperfusion injury. Nomilin (NOM) is a limonoid compound obtained from the extracts of citrus fruits. The purpose of our study was to determine whether NOM could exert beneficial effects in cerebral ischemia-reperfusion rats. Firstly, NOM treatment significantly mitigated cell death and decreased lactate dehydrogenase (LDH) release and ROS production in SH-SY5Y cells induced by oxygen-glucose deprivation (OGD), which was almost abolished by Nrf2 knockdown. Secondly, NOM improved infarct area, brain edema and neurological deficits in an experimental stroke rat model via middle cerebral artery occlusion (MCAO). Furthermore, NOM attenuated blood-brain barrier (BBB) disruption in MCAO rats, which might be associated with alleviating the loss of tight junction proteins, including ZO-1 and occludin-5. Further results revealed that NOM treatment effectively mitigated oxidative stress and facilitated the expressions of Nrf2 and NQO1, which might confirm that the loss of tight junction proteins in the microvasculature was likely mediated by oxidative stress. In conclusion, our study provided evidence that the protective effects of NOM in cerebral ischemia-reperfusion rats were related to the Nrf2/NQO1 pathway.
Edaravone attenuates traumatic brain injury through anti-inflammatory and anti-oxidative modulation
Traumatic brain injury (TBI) is among the leading causes of irreversible neurological damage and death worldwide. The aim of the present study was to investigate whether edaravone (EDA) had a neuroprotective effect on TBI as well as to identify the potential mechanism. Results demonstrated that EDA suppressed inflammatory and oxidative responses in mice following TBI. This was evidenced by a reduction in glutathione peroxidase, interleukin 6, tumor necrosis factor-α and hydrogen peroxide levels, in addition to an increase in hemeoxygenase-1, quinone oxidoreductase 1 and superoxide dismutase levels, thereby mitigating neurofunctional deficits, cell apoptosis and structural damage. EDA prevented the transfer of NF-κB protein from the cytoplasm to the nucleus, whilst promoting the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) protein in mice following TBI. These results indicated that EDA exerted neuroprotective effects, including impeding neurofunctional deficits, cell apoptosis and structural damage, in mice with TBI, potentially via suppression of NF-κB-mediated inflammatory activation and promotion of the Nrf2 antioxidant pathway.
Tert-butylhydroquinone enhanced angiogenesis and astrocyte activation by activating nuclear factor-E2-related factor 2/heme oxygenase-1 after focal cerebral ischemia in mice
Angiogenesis after cerebral ischemia plays a pivotal role in neurological recovery and represents a therapeutic target. The angiogenic effect of nuclear factor E2-related factor 2 (Nrf2) was identified in recent years. However, the effects of tert-butylhydroquinone, an Nrf2 inducer, on angiogenesis and astrocyte activation after stroke remain unclear. In this study, we investigated whether tert-butylhydroquinone enhanced angiogenesis and astrocyte activation through Nrf2 pathway. Wild-type (Nrf2) and Nrf2-deficient (Nrf2) mice were subjected to permanent distal middle cerebral artery occlusion (dMCAO). We established 6 experimental groups (sham Nrf2 group, vehicle Nrf2 group, tBHQ Nrf2 group; sham Nrf2 group, vehicle Nrf2 group, and tBHQ Nrf2 group). The infarct volume, neurological function, microvessel density (MVD), astrocytic endfeet covered ratio and the expression of Nrf2, HO-1 and VEGF in the ischemic brain were measured at different time points. Compared with that observed in the vehicle Nrf2 group, tBHQ significantly reduced the infarct volume, enhanced post-stroke angiogenesis and astrocytic endfeet covered ratio in the peri-infarct area. The Nrf2/HO-1/VEGF pathway was activated by tBHQ in the angiogenesis process. However, in Nrf2 mice, Nrf2 deficiency blocked the effects of tBHQ on angiogenesis process and neurological recovery as well as abolished the mediation of proangiogenic factors. These results suggested that tBHQ enhanced angiogenesis and astrocyte activation through activating Nrf2 pathway after cerebral ischemia.
Lipoamide Ameliorates Oxidative Stress via Induction of Nrf2/ARE Signaling Pathway in PC12 Cells
The mechanisms underlying neurodegenerative diseases are not fully understood yet. However, an increasing amount of evidence has suggested that these disorders are related to oxidative stress. We reported herein that lipoamide (LM), a neutral amide derivative of lipoic acid (LA), could resist oxidative stress-mediated neuronal cell damage. LM is more potent than LA in alleviating hydrogen peroxide- or 6-hydroxydopamine-induced PC12 cell injury. Our results reveal that LM promotes the nuclear accumulation of NFE2-related factor 2 (Nrf2), following with the activation of expression of Nrf2-governed antioxidant and detoxifying enzymes. Notably, silencing Nrf2 gene annuls the protection of LM, which demonstrates that Nrf2 is engaged in this cytoprotection. Our findings suggest that LM might be used as a potential therapeutic candidate for oxidative stress-related neurological disorders.
Curcumin protects against methylmercury-induced cytotoxicity in primary rat astrocytes by activating the Nrf2/ARE pathway independently of PKCδ
Methylmercury (MeHg) is a ubiquitous environmental toxicant that leads to long-lasting neurological deficits in animals and humans. Curcumin, a polyphenol obtained from the rhizome of turmeric, has well-known antioxidant functions. Here, we evaluated curcumin's efficacy in mitigating MeHg-induced cytotoxicity and further investigated the underlying mechanism of this neuroprotection in primary rat astrocytes. Pretreatment with curcumin (2, 5, 10 and 20 μM for 3, 6, 12 or 24 h) protected against MeHg-induced (5 μM for 6 h) cell death in a time and dose-dependent manner. Curcumin (2, 5, 10 or 20 μM) pretreatment for 12 h significantly ameliorated the MeHg-induced astrocyte injury and oxidative stress, as evidenced by morphological alterations, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) generation, and glutathione (GSH) and catalase (CAT) levels. Moreover, curcumin pretreatment increased Nrf2 nuclear translocation and downstream enzyme expression, heme oxygenase-1 (HO-1) and NADPH quinone reductase-1 (NQO1). Knockdown of Nrf2 with siRNA attenuated the protective effect of curcumin against MeHg-induced cell death. However, both the pan-protein kinase C (PKC) inhibitor, Ro 31-8220, and the selective PKCδ inhibitor, rottlerin, failed to suppress the curcumin-activated Nrf2/Antioxidant Response Element(ARE) pathway and attenuate the protection exerted by curcumin. Taken together, these findings confirm that curcumin protects against MeHg-induced neurotoxicity by activating the Nrf2/ARE pathway and this protection is independent of PKCδ activation. More studies are needed to understand the mechanisms of curcumin cytoprotection.
Cerebrovascular and Neurological Disorders: Protective Role of NRF2
Cellular defense mechanisms, intracellular signaling, and physiological functions are regulated by electrophiles and reactive oxygen species (ROS). Recent works strongly considered imbalanced ROS and electrophile overabundance as the leading cause of cellular and tissue damage, whereas oxidative stress (OS) plays a crucial role for the onset and progression of major cerebrovascular and neurodegenerative pathologies. These include Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), stroke, and aging. Nuclear factor erythroid 2-related factor (NRF2) is the major modulator of the xenobiotic-activated receptor (XAR) and is accountable for activating the antioxidative response elements (ARE)-pathway modulating the detoxification and antioxidative responses of the cells. NRF2 activity, however, is also implicated in carcinogenesis protection, stem cells regulation, anti-inflammation, anti-aging, and so forth. Herein, we briefly describe the NRF2-ARE pathway and provide a review analysis of its functioning and system integration as well as its role in major CNS disorders. We also discuss NRF2-based therapeutic approaches for the treatment of neurodegenerative and cerebrovascular disorders.
Simvastatin alleviates inflammation and oxidative stress in rats with cerebral hemorrhage through Nrf2-ARE signaling pathway
To investigate the regulatory effects of simvastatin on the inflammation and oxidative stress in rats with cerebral hemorrhage through the nuclear factor E2-related factor 2-antioxidant response element (Nrf2-ARE) signaling pathway.
Histone deacetylase 6 interference protects mice against experimental stroke-induced brain injury via activating Nrf2/HO-1 pathway
Cerebral stroke is a fatal disease with increasing incidence. The study was to investigate the role and mechanism of Histone deacetylase 6 (HDAC6) on experimental stroke-induced brain injury. The recombinant shRNA-HDAC6 or scramble shRNA lentivirus was transfected to ICR mice. Then, the ischemia/reperfusion injury (I/RI) mice were constructed using middle cerebral artery occlusion (MCAO) method. Brain TTC staining was used to determine infarct areas. Serum levels of oxidative stress-related factors were detected by enzyme linked immunosorbnent assay (ELISA). Realtime-qPCR (RT-qPCR) and Western blot were used to respectively detect mRNA and protein levels. HDAC6 was up-regulated in brain I/RI mice (MCAO group), and down-regulated again in MCAO mice transfected with shRNA-HDAC6 (MCAO + shRNA group). The infarct area of the MCAO mice was increased, neurological scores were higher, and serum protein levels of 3-NT, 4-HNE and 8-OHdG were higher. HDAC6 interference attenuated above effects. Though protein levels of Nrf2 and HO-1 in cytoplasm increased slightly in MCAO group, they increased significantly by HDAC6 interference. The protein levels of Nrf2 in cytoblast decreased significantly in MCAO group, and increased markedly by HDAC6 interference. HDAC6 interference protected mice against experimental stroke-induced brain injury via Nrf2/HO-1 pathway.
Pyrethroid exposure and neurotoxicity: a mechanistic approach
Pyrethroids are a class of synthetic insecticides that are used widely in and around households to control the pest. Concerns about exposure to this group of pesticides are now mainly related to their neurotoxicity and nigrostriatal dopaminergic neurodegeneration seen in Parkinson's disease. The main neurotoxic mechanisms include oxidative stress, inflammation, neuronal cell loss, and mitochondrial dysfunction. The main neurodegeneration targets are ion channels. However, other receptors, enzymes, and several signalling pathways can also participate in disorders induced by pyrethroids. The aim of this review is to elucidate the main mechanisms involved in neurotoxicity caused by pyrethroids deltamethrin, permethrin, and cypermethrin. We also review common targets and pathways of Parkinson's disease therapy, including Nrf2, Nurr1, and PPARγ, and how they are affected by exposure to pyrethroids. We conclude with possibilities to be addressed by future research of novel methods of protection against neurological disorders caused by pesticides that may also find their use in the management/treatment of Parkinson's disease.
The neuroprotective mechanisms and effects of sulforaphane
Sulforaphane (SFN) is a phytochemical found in cruciferous vegetables. It has been shown to have many protective effects against many diseases, including multiple types of cancer. SFN is a potent activator of the nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant response element (ARE) genetic pathway. Upregulation of Nrf2-ARE increases the availability of multiple antioxidants. A substantial amount of preclinical research regarding the ability of SFN to protect the nervous system from many diseases and toxins has been done, but only a few small human trials have been completed. Preclinical data suggest that SFN protects the nervous system through multiple mechanisms and may help reduce the risk of many diseases and reduce the burden of symptoms in existing conditions. This review focuses on the literature regarding the protective effects of SFN on the nervous system. A discussion of neuroprotective mechanisms is followed by a discussion of the protective effects elicited by SFN administration in a multitude of neurological diseases and toxin exposures. SFN is a promising neuroprotective phytochemical which needs further human trials to evaluate its efficacy in preventing and decreasing the burden of many neurological diseases.
TTB Protects Astrocytes Against Oxygen-Glucose Deprivation/Reoxygenation-Induced Injury Activation of Nrf2/HO-1 Signaling Pathway
Neonatal hypoxic/ischemic encephalopathy (NHIE) is a severe condition that leads to death or neurological disability in newborns. The underlying pathological mechanisms are unclear, and developing the target neuroprotective strategies are urgent. 2,7,2'-trihydroxy-4,4'7'-trimethoxy-1,1'-biphenanthrene (TTB) is a natural product isolated from (D. Don) Makino and (Thunb.) Lindl. TTB has demonstrated potent cytotoxic activity against stomach (HGC-27) and colon (HT-29) cancer cell lines. However, none of the studies have addressed the effects of TTB in NHIE. In the present study, an oxygen-glucose deprivation/reoxygenation (OGD/R)-induced astrocyte injury model was established to investigate the effect of TTB and its potential mechanisms. Our results showed that TTB alleviated the OGD/R-induced reactive oxygen species increase and the intracellular antioxidant capacity of superoxide dismutase activity decrease. Moreover, TTB potentially prolonged the activation state of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway and maintained the protection against oxidative stress in OGD/R-induced astrocytes by inducing the nuclear translocation and up-regulation of Nrf2 along with the enhanced expression of the downstream target gene HO-1. Furthermore, TTB treatment diminished the accumulation of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) expression induced by OGD/R. We also found TTB-treated astrocytes reversed the inhibition of OGD/R on neurite growth of neurons by the astrocyte-neuron coculture system. In conclusion, TTB inhibited the OGD/R-induced astrocyte oxidative stress at least partially through the inhibition of HIF-1α and VEGF the Nrf2/HO-1 signaling pathway.
Melatonin Prevents Mice Cortical Astrocytes From Hemin-Induced Toxicity Through Activating PKCα/Nrf2/HO-1 Signaling
Secondary injuries mediated by oxidative stress lead to deterioration of neurological functions after intracerebral hemorrhage (ICH). Cortical astrocytes are among the most important cells in the central nervous system (CNS), and play key roles in maintaining redox homeostasis by providing oxidative stress defense. Hemin is a product of hemoglobin degradation, which has strong toxicity and can induce reactive oxygen species (ROS). Melatonin (Mel) and its metabolites are well tolerated without toxicity, prevent tissue damage as well as effectively assist in scavenging free radicals. We evaluated the hemin neurotoxicity to astrocytes and the resistance of Mel-treated astrocytes to hemin neurotoxicity. And we found Mel induced PKCα phosphorylation (p-PKC), nuclear translocation of Nrf2 in astrocytes, and upregulation of HO-1, which contributed to the reduction of ROS accumulation and cell apoptosis. Nrf2 and HO1 protein expression upregulated by Mel were decreased after administration of PKC inhibitor, Ro 31-8220 (Ro 31). Luzindole (Luz), a melatonin receptor inhibitor, suppressed p-PKCα, HO-1, and Nrf2 expression upregulated by Mel and increased cell apoptosis rate. The upregulation of HO-1 induced by Mel was depressed by knocking down Nrf2 expression by siRNA, which also decreased the resistance of astrocytes to toxicity of hemin. Mel activates astrocytes through PKCα/Nrf2/HO-1 signaling pathway to acquire resistance to toxicity of hemin and resist from oxidative stress and apoptosis. The positive effect of Mel on PKCα/Nrf2/HO-1 signaling pathway may become a new target for neuroprotection after intracerebral hemorrhage.