Isoquercetin activates the ERK1/2-Nrf2 pathway and protects against cerebral ischemia-reperfusion injury in vivo and in vitro

Qualitative and quantitative analysis of major components in Abelmoschus manihot flowers treated with different drying methods using UHPLC Q-exactive MS and HPLC-PDA

The flowers of Abelmoschus manihot (L.) Medic are commonly used in clinical practice in China to cure forms of chronic kidney disease. Despite a long history of traditional use, the flowers obtained by different drying technologies have never been fully chemically characterized, and the ranges of constituents between different drying methods have not been comprehensively reported. To establish a quality control and chemical characterization method, a total of 14 batches of samples corresponding to 14 postharvest treatments were studied. Seven flavonoids were quantified using a HPLC-PDA method. The method was validated in terms of linearity (r > 0.999), precision (intra- and inter-day: 0.7-1.4 %), accuracy (99.90-100.7 %), detection limit (0.34-0.46 µg/mL) and quantification limit (1.15-1.52 µg/mL). The contents of total flavonoids in manihot flowers were as follows in descending order: Infrared Drying (50.96 mg/g) > Microwave Drying (41.84 mg/g) ≈ Hot-air Drying (39.58 mg/g) ≈ Fresh (39.35 mg/g) ≈ Primary Drying (38.95 mg/g). Principal component analysis showed that samples processed with Fresh, Primary Drying, and the investigated three modern drying methods were well classified into three domains, indicating an important difference between drying methods. For the purpose of saving the flavonoids contents, infrared drying under 80-100 °C would be most acceptable. Furthermore, using UHPLC Q-Exactive Orbitrap MS data with targeted and non-targeted approaches, 28 compounds were identified in Abelmoschus manihot samples. Flavonoids were the main group of compounds found in Abelmoschus manihot flowers. The study could provide the scientific evidence for the selection and optimization of appropriate drying method for manihot flowers, and also provide the reference for the formation of generic primary drying processing technology for medicinal flowers containing flavonoids.

Kaempferol-3-O-(2″-O-galloyl-β-D-glucopyranoside): a novel neuroprotective agent from Diospryros kaki against cerebral ischemia-induced brain injury

Our previous study demonstrated neuroprotective and therapeutic effects of a standardized flavonoid extract from leaves of Diospyros kaki L.f. (DK) on middle cerebral artery occlusion-and-reperfusion (MCAO/R)-induced brain injury and its underlying mechanisms. This study aimed to clarify flavonoid components responsible for the effects of DK using in vitro and in vivo transient brain ischemic models. Organotypic hippocampal slice cultures (OHSCs) subjected to oxygen- and glucose-deprivation (OGD) were performed to evaluate in vitro neuroprotective activity of DK extract and nine isolated flavonoid components. MCAO/R mice were employed to elucidate in vivo neuroprotective effects of the flavonoid component that exhibited the most potent neuroprotective effect in OHSCs. DK extract and seven flavonoids [quercetin, isoquercetin, hyperoside, quercetin-3-O-(2″-O-galloyl-β-D-galactopyranoside), kaempferol, astragalin, and kaempferol-3-O-(2″-O-galloyl-β-D-glucopyranoside) compound (9)] attenuated OGD-induced neuronal cell damage and compound (9) possessed the most potent neuroprotective activity in OHSCs. The MCAO/R mice showed cerebral infarction, massive weight loss, characteristic neurological symptoms, and deterioration of neuronal cells in the brain. Compound (9) and a reference drugs, edaravone, significantly attenuated these physical and neurological impairments. Compound (9) mitigated the blood-brain barrier dysfunction and the change of glutathione and malondialdehyde content in the MCAO mouse brain. Edaravone suppressed the oxidative stress but did not significantly affect the blood-brain barrier permeability. The present results indicated that compound (9) is a flavonoid constituent of DK with a potent neuroprotective activity against transient ischemia-induced brain damage and this action, at least in part, via preservation of blood-brain barrier integrity and suppression of oxidative stress caused by ischemic insult.

Antidiabetic effects of polyherbal mixture made of Centaurium erythraea, Cichorium intybus and Potentilla erecta

ETHNOPHARMACOLOGICAL RELEVANCE

The polyherbal mixture made of Centaurium erythraea aerial parts and Cichorium intybus roots and Potentilla erecta rhizomes has been used for centuries to treat both the primary and secondary complications of diabetes.

AIM OF THE STUDY

As a continuation of our search for the most effective herbal mixture used as an ethnopharmacological remedy for diabetes, this study aimed to compare the in vitro biological activities of this polyherbal mixture and its individual ingredients, and, most importantly, to validate the ethnopharmacological value of the herbal mixture through evaluation of its phytochemical composition, its potential in vivo toxicity and its effect on diabetes complications.

MATERIALS AND METHODS

Phytochemical analysis was performed using HPLC-UV. Antioxidant activity was estimated via the DPPH test. Potential cytotoxicity/anticytotoxicity was assessed using an in vitro RBCs antihemolytic assay and an in vivo sub-chronic oral toxicity method. Antidiabetic activity was evaluated using an in vitro α-amylase inhibition assay and in vivo using a chemically induced diabetic rat model.

RESULTS

The HPLC-UV analysis revealed the presence of p-hydroxybenzoic acid, p-hydroxybenzoic acid derivative, catechin, five catechin derivatives, epicatechin, isoquercetin, hyperoside, rutin, four quercetin derivatives, caffeic acid, and four caffeic acid derivatives in the polyherbal mixture decoction. Treatment with the decoction has shown no toxic effects. The antioxidant and cytoprotective activities of the polyherbal mixture were higher than the reference's ones. Its antidiabetic activity was high in both in vitro and in vivo studies. Fourteen days of treatment with the decoction (15 g/kg) completely normalized blood glucose levels of diabetic animals, while treatments with insulin and glimepiride only slightly lowered glycemic values. In addition, lipid status of treated animals as well as levels of serum AST, ALT, ALP, creatinine, urea and MDA were completely normalized. In addition, the polyherbal mixture completely restored the histopathological changes of the liver, kidneys and all four Cornu ammonis regions of the hippocampus.

CONCLUSIONS

The polyherbal mixture was effective in the prevention of both primary and secondary diabetic complications such as hyperlipidemia, increased lipid peroxidation, non-alcoholic fatty liver disease, nephropathy and neurodegeneration.

Extracts from Dendropanax morbifera leaves ameliorates cerebral ischemia-induced hippocampal damage by reducing oxidative damage in gerbil

AIM

In this study, we investigated the effects of Dendropanax morbifera extract (DME) on neuroprotection against ischemic damage in gerbils.

METHODS

DME (100 or 300 mg/kg) was orally administered to gerbils for three weeks, and 2 h after the last DME treatment, transient forebrain ischemia in the common carotid arteries was induced for 5 min. The forebrain ischemia-related cognitive impairments were assessed by spontaneous motor activity and passive avoidance test one and four days after ischemia, respectively. In addition, surviving and degenerating neurons were morphologically confirmed by neuronal nuclei immunohistochemical staining and Fluoro-Jade C staining, respectively, four days after ischemia. Changes of glial morphology were visualized by immunohistochemical staining for each marker such as glial fibrillary acidic protein and ionized calcium-binding protein. Oxidative stress was determined by measurements of dihydroethidium, O2· (formation of formazan) and malondialdehyde two days after ischemia. In addition, glutathione redox system such as reduced glutathione, oxidized glutathione levels, glutathione peroxidase, and glutathione reductase activities were measured two days after ischemia.

RESULTS

Spontaneous motor activity monitoring and passive avoidance tests showed that treatment with 300 mg/kg DME, but not 100 mg/kg, significantly alleviated ischemia-induced memory impairments. In addition, approximately 67 % of mature neurons survived and 29.3 % neurons were degenerated in hippocampal CA1 region four days after ischemia, and ischemia-induced morphological changes in astrocytes and microglia were decreased in the CA1 region after 300 mg/kg DME treatment. Furthermore, treatment with 300 mg/kg DME significantly ameliorated ischemia-induced oxidative stress, such as superoxide formation and lipid peroxidation, two days after ischemia. In addition, ischemia-induced reduction of the glutathione redox system in the hippocampus, assessed two days after the ischemia, was ameliorated by treatment with 300 mg/kg DME. These suggest that DME can potentially reduce ischemia-induced neuronal damage through its antioxidant properties.

Isoquercitrin Played a Neuroprotective Role in Rats After Cerebral Ischemia/Reperfusion Through Up-Regulating Neuroglobin and Anti-Oxidative Stress

BACKGROUND

This study aims to investigate whether isoquercitrin (Iso) exerts a neuroprotective role effect after cerebral ischemia-reperfusion (CIR) via up-regulating neuroglobin (Ngb) or reducing oxidative stress.

METHODS

The middle cerebral artery occlusion/reperfusion (MCAO/R) model was constructed using Sprague Dawley rats. First, we divided 40 mice into 5 groups (n = 8): sham, MCAO/R, Low-dosed Iso (5 mg/kg Iso), Mid-dosed Iso (10 mg/kg Iso), and High-dosed Iso (20 mg/kg Iso). Then, 48 rats were separated into 6 groups (n = 8): sham, MCAO/R, Iso, artificial cerebrospinal fluid, Ngb antisense oligodeoxynucleotides (AS-ODNs), and AS-ODNs ± Iso. The effects of Iso on brain tissue injury and oxidative stress were evaluated using hematoxylin-eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, immunofluorescence, western blotting, and real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and reactive oxygen species (ROS) detection.

RESULTS

The neurologic score, infarct volume, histopathology, apoptosis rate, and ROS production were reduced in Iso dose-dependent. The Ngb expression enhanced in Iso dose-dependent. The oxidative stress-related factors SOD, GSH, CAT, Nrf2, HO-1, and HIF-1α levels also increased in Iso dose-dependent, whereas the MDA levels decreased. However, related regulation of Iso on brain tissue damage and oxidative stress were reversed after low expression of Ngb.

CONCLUSION

Isoquercitrin played a neuroprotective role after CIR through up-regulating of Ngb and anti-oxidative stress.

Mechanically demanding eccentric exercise increases nuclear factor erythroid 2-related factor 2 activity in human peripheral blood mononuclear cells

PRE-REGISTRATION NUMBER

osf.io/kz37g.

Upregulation of neuronal progranulin mediates the antinociceptive effect of trimetazidine in paclitaxel-induced peripheral neuropathy: Role of ERK1/2 signaling

Neuronal progranulin (PGRN) overexpression is an endogenous adaptive pain defense following nerve injury. It allows the survival of injured neurons to block enhanced nociceptive responses. Trimetazidine (TMZ) is widely used by cardiac patients as an anti-anginal drug, reflecting its anti-ischemic property. TMZ promotes axonal regeneration of sciatic nerves after crush injury. This study explored the interplay between PGRN and extracellular signal-regulated kinases (ERK1/2) to address mechanisms underlying neuropathic pain alleviation following paclitaxel (PTX) administration. Rats were given four injections of PTX (2 mg/kg, i.p.) every other day. Two days after the last dose, rats received TMZ (25 mg/kg) with or without the ERK inhibitor, PD98059, daily for 21 days. TMZ preserved the integrity of myelinated nerve fibers, as evidenced by an obvious reduction in axonal damage biomarkers. Accordingly, it alleviated PTX-evoked thermal, cold, and mechanical hyperalgesia/allodynia. TMZ also promoted ERK1/2 phosphorylation with a profound upsurge in PGRN content. These effects were associated with a substantial increase in Notch1 receptor gene expression and a prominent anti-inflammatory effect with a marked increase in mRNA expression of secretory leukocyte protease inhibitor. Further, TMZ decreased oxidative stress and caspase-3 activity in the sciatic nerve. Conversely, co-administration of PD98059 completely abolished these beneficial effects. Thus, the robust antinociceptive effect of TMZ is largely attributed to upregulating PGRN and Notch1 receptors via ERK1/2 activation.

Isoquercetin alleviates sleep deprivation dependent hippocampal neurons damage by suppressing NLRP3-induced pyroptosis

Sleep deprivation (SD) leads to memory and cognitive impairment due to damage to the hippocampus. Isoquercetin possesses neuron-protective properties. Our study aimed to investigate the effects of isoquercetin on SD-induced hippocampal neurons damage and the underlying mechanism. Herein, the cognitive competence was evaluated by Morris water maze (MWM) test after SD. The morphology of the hippocampus was observed after Nissl staining. Moreover, the level of NLRP3 was detected by Immunofluorescent staining and western blot. In vitro study, pyroptosis was tested by TUNEL assay and flow cytometry. The levels of pyroptosis-related factors were measured by western blot. The results indicated that isoquercetin improved spatial memory and prevented change of hippocampal neurons of SD mice. Moreover, SD upregulated NLRP3 level, which was downregulated by isoquercetin. Additionally, isoquercetin rescued the increase of pyroptosis and the upregulation of NLRP3, caspase-1, ASC, IL-1β, IL-18, and GSDMD levels induced by LPS. In conclusion, isoquercetin improved learning and cognitive capability of SD mice via suppressing NLRP3-induced pyroptosis of hippocampal neurons cells, suggesting that isoquercetin might be an efficacious drug for memory disorders caused by SD.

Antioxidative effect of dietary flavonoid isoquercitrin on human ovarian granulosa cells HGL5 in vitro

This study aimed to examine the effect of dietary flavonoid isoquercitrin on ovarian granulosa cells using the immortalized human cell line HGL5. Cell viability, survival, apoptosis, release of steroid hormones 17beta-estradiol and progesterone, and human transforming growth factor-beta2 (TGF-beta2) and TGF-beta2 receptor as well as intracellular reactive oxygen species (ROS) generation were investigated after isoquercitrin treatment at the concentration range of 5-100 microg.ml-1. It did not cause any significant change (p>0.05) in cell viability as studied by AlamarBlue assay in comparison to control. No significant change was observed (p>0.05) in the proportion of live, dead and apoptotic cells as revealed by apoptotic assay using flow cytometry. Similarly, the release of 17beta-estradiol, progesterone, TGF-beta2 and its receptor were not affected significantly (p>0.05) by isoquercitrin as detected by ELISA, in comparison to control. Except for the highest concentration of 100 microg.ml-1, which led to oxidative stress, isoquercitrin exhibited antioxidative activity at lower concentration used in the study (5, 10, 25, and 50 microg.ml-1) by hampering the production of intracellular ROS, in comparison to control, as detected by chemiluminescence assay (p<0.05). Findings of the present study indicate an existence of the antioxidative pathway that involves inhibition of intracellular ROS generation by isoquercitrin in human ovarian granulosa cells.

Isoquercitrin Upregulates Aldolase C Through Nrf2 to Ameliorate OGD/R-Induced Damage in SH-SY5Y Cells

Isoquercitrin (ISO), an extract from Chinese traditional herb, exhibits potent neuroprotective roles in various disease models. However, its role in stroke is not fully understood. We established oxygen-glucose deprivation and reoxygenation (OGD/R) model in SH-SY5Y cell to study the roles of ISO in stroke. In the experiment, the changes of LDH level and cell viability (MTT) were analyzed. Apoptotic cells stained with anti-Annexin V antibody and propidium iodide (PI) were detected by flow cytometry. The mRNA and protein level of aldolase C (ALDOC) and nuclear factor erythroid 2-related factor (Nrf2) was determined by real-time quantitative polymerase chain reaction (qPCR) and Western blotting assay, respectively. The localization of Nrf2 was investigated by immunofluorescent assay. OGD/R reduced cell viability via inducing cell apoptosis, while ISO treatment reduced the level of apoptosis in OGD/R-treated SH-SY5Y cells ISO rescued OGD/R-treated cells. Mechanistically, the expression of Nrf2 and ALDOC was upregulated upon ISO treatment, while knockdown of ALDOC diminished the activation of autophagy and hence inhibited ISO-mediated protective activity. We further demonstrated that ISO enhanced ALDOC transcription by promoting nuclear translocation of Nrf2, and suppression of Nrf2 decreased the expression of ALDOC. Our data revealed that ISO exhibited neuroprotective activity in OGD/R model through Nrf2-ALDOC-autopagy axis and highlighted the potential application of ISO in stroke treatment.

Role of Polyphenols as Antioxidant Supplementation in Ischemic Stroke

Stroke is the second most common cause of death globally and the leading cause of death in China. The pathogenesis of cerebral ischemia injury is complex, and oxidative stress plays an important role in the fundamental pathologic progression of cerebral damage in ischemic stroke. Previous studies have preliminarily confirmed that oxidative stress should be a potential therapeutic target and antioxidant as a treatment strategy for ischemic stroke. Emerging experimental studies have demonstrated that polyphenols exert the antioxidant potential to play the neuroprotection role after ischemic stroke. This comprehensive review summarizes antioxidant effects of some polyphenols, which have the most inhibition effects on reactive oxygen species generation and oxidative stress after ischemic stroke.

Synergistic Protection by Isoquercitrin and Quercetin against Glutamate-Induced Oxidative Cell Death in HT22 Cells via Activating Nrf2 and HO-1 Signaling Pathway: Neuroprotective Principles and Mechanisms of Dendropanax morbifera Leaves

Dendropanax morbifera leaves (DML) have long been used as traditional medicine to treat diverse symptoms in Korea. Ethyl acetate-soluble extracts of DML (DMLE) rescued HT22 mouse hippocampal neuronal cells from glutamate (Glu)-induced oxidative cell death; however, the protective compounds and mechanisms remain unknown. Here, we aimed to identify the neuroprotective ingredients and mechanisms of DMLE in the Glu-HT22 cell model. Five antioxidant compounds were isolated from DMLE and characterized as chlorogenic acid, hyperoside, isoquercitrin, quercetin, and rutin by spectroscopic methods. Isoquercitrin and quercetin significantly inhibited Glu-induced oxidative cell death by restoring intracellular reactive oxygen species (ROS) levels and mitochondrial superoxide generation, Ca²⁺ dysregulation, mitochondrial dysfunction, and nuclear translocation of apoptosis-inducing factor. These two compounds significantly increased the expression levels of nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) in the presence or absence of Glu treatment. Combinatorial treatment of the five compounds based on the equivalent concentrations in DMLE showed that significant protection was found only in the cells cotreated with isoquercitrin and quercetin, both of whom showed prominent synergism, as assessed by drug–drug interaction analysis. These findings suggest that isoquercitrin and quercetin are the active principles representing the protective effects of DMLE, and these effects were mediated by the Nrf2/HO-1 pathway.

Polyphenols from Penthorum chinense Pursh. Attenuates high glucose-induced vascular inflammation through directly interacting with Keap1 protein

ETHNOPHARMACOLOGICAL RELEVANCE

Penthorum chinense Pursh is used for promoting diuresis and alleviating "heat"-associated disorders, which were considered to be related to diabetic in Traditional Chinese Medicine (TCM).

AIMS OF THIS STUDY

Here, we aimed to evaluate the ability and underlying mechanism of the ethyl acetate fraction of Penthorum chinense Pursh stems (PSE) to inhibit vascular inflammation in high glucose (HG)-induced human umbilical vein endothelial cells (HUVEC cells).

MATERIALS AND METHODS

HUVEC cells were pre-treated with PSE following HG treatment. The cell viability, mitochondrial membrane potential (MMP), lactate dehydrogenase (LDH) levels, reactive oxygen species (ROS) generation were analyzed. Inflammatory, and antioxidant,-related proteins were analyzed using western blotting. Molecular docking and drug affinity targeting experiments (DARTS) were utilized to analyze and verify the binding of the Keap1 protein and polyphenols of PSE.

RESULTS

HG can significantly increase the activity of lactic dehydrogenase (LDH), destroy the mitochondrial membrane potential (MMP), and promote the generation of reactive oxygen species (ROS), while PSE treatment reversed these changes. Mechanistically, PSE inhibited NF-κB and inflammatory cytokines activation induced by HG through activating the expression of Nrf2 and its downstream antioxidant proteins Heme oxygenase-1 (HO-1), NAD (P)H Quinone Dehydrogenase 1 (NQO1), Glutamate cysteine ligase catalytic subunit (GCLC), Glutamate-cysteine ligase modifier (GCLM). Further study indicated that PSE activated Nrf2 antioxidant pathway mainly by the binding of primary polyphenols from PSE and the Keap1 protein.

CONCLUSION

Taken together, the present data highlight the health benefits of polyphenols from Penthorum chinense Pursh. regarding diabetes, proving it to be an important source of health care products. Besides, binding of the Keap1 protein may be an effective strategy to activate Nrf2 antioxidant pathway and prevent diabetes.

Natural Antioxidants Improve the Vulnerability of Cardiomyocytes and Vascular Endothelial Cells under Stress Conditions: A Focus on Mitochondrial Quality Control

Cardiovascular disease has become one of the main causes of human death. In addition, many cardiovascular diseases are accompanied by a series of irreversible damages that lead to organ and vascular complications. In recent years, the potential therapeutic strategy of natural antioxidants in the treatment of cardiovascular diseases through mitochondrial quality control has received extensive attention. Mitochondria are the main site of energy metabolism in eukaryotic cells, including myocardial and vascular endothelial cells. Mitochondrial quality control processes ensure normal activities of mitochondria and cells by maintaining stable mitochondrial quantity and quality, thus protecting myocardial and endothelial cells against stress. Various stresses can affect mitochondrial morphology and function. Natural antioxidants extracted from plants and natural medicines are becoming increasingly common in the clinical treatment of diseases, especially in the treatment of cardiovascular diseases. Natural antioxidants can effectively protect myocardial and endothelial cells from stress-induced injury by regulating mitochondrial quality control, and their safety and effectiveness have been preliminarily verified. This review summarises the damage mechanisms of various stresses in cardiomyocytes and vascular endothelial cells and the mechanisms of natural antioxidants in improving the vulnerability of these cell types to stress by regulating mitochondrial quality control. This review is aimed at paving the way for novel treatments for cardiovascular diseases and the development of natural antioxidant drugs.

Inhibition of miR-448-3p Attenuates Cerebral Ischemic Injury by Upregulating Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2)

BACKGROUND

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key regulator responsible for oxidative stress in brain injury. This study aimed to investigate the potential mechanism of miR-448-3p and Nrf2 in cerebral ischemia/reperfusion (I/R) injury.

METHODS

In vitro and in vivo cerebral I/R injury models were constructed, and Nrf2 expression levels were detected by qRT-PCR and Western blot. The potential miRNAs for Nrf2 were predicted by bioinformatic analysis. The binding interaction between miR-448-3p and Nrf2 was determined by luciferase reporter assay. The effects of miR-448-3p on neurological deficit, infarct volume, and brain water content in mice were tested. The effects of miR-448-3p on oxidative stress indicators (SOD activity, MDA content, and ROS production) were detected by commercial assay kits. The levels of HO-1 and cleaved caspase-3 were evaluated by Western blot. Cell viability was evaluated by MTT assay, and cell apoptosis was evaluated by TUNEL staining and flow cytometry.

RESULTS

Nrf2 was significantly downregulated and miR-448-3p was upregulated in cerebral I/R injury both in vivo and in vitro. MiR-448-3p downregulation efficiently attenuated brain injury and reduced oxidative stress and apoptosis. MiR-448-3p was identified to act as ceRNA of Nrf2 and negatively regulated Nrf2 expression, which was consistent with the animal studies. In addition, Nrf2 silencing obviously attenuated the neuroprotective effects of miR-448-3p inhibitor in vitro.

CONCLUSION

MiR-448-3p participated in the regulation of cerebral I/R injury via inhibiting Nrf2.

Astragaloside IV Reduces Cerebral Ischemia/Reperfusion-Induced Blood-Brain Barrier Permeability in Rats by Inhibiting ER Stress-Mediated Apoptosis

Background

Previous studies proved that AS-IV could prevent blood-brain barrier (BBB) against an increase in permeability. However, its underlying molecular mechanism has not been enlightened yet. The aim of the study is to reveal the potential protective mechanism of astragaloside IV (AS-IV) on the blood-brain barrier after ischemia-reperfusion.

Methods

In vivo, AS-IV neurological protection was measured by Long's five-point scale and 2,3,5-triphenyltetrazolium chloride staining. AS-IV protection for BBB was observed by Evans blue extravasation technique. Endoplasmic reticulum stress and apoptosis-related protein levels were measured by western blot with AS-IV intervention. In vitro, cell apoptosis was analyzed by western blot and flow cytometry.Endoplasmic reticulum stress-related protein levels were quantified through western blot.

Results

AS-IV treatment could decrease the infarct size in rats' brain and protect the BBB against Evans blue permeating through brain, after ischemia/reperfusion, significantly. Further, ischemia/reperfusion or oxygen-glucose deprivation/reperfusion was found to have an increase in endothelial cell apoptosis proteins, such as Bax, Bcl-2, and caspase-3, and endoplasmic reticulum stress-associated proteins, such as phosphorylated PERK and eIF2α, Bip, and CHOP, which were attenuated by AS-IV treatment.

Conclusions

AS-IV can effectively protect the blood-brain barrier and reduce the area of cerebral infarction via inhibiting endoplasmic reticulum stress-mediated apoptosis in endothelial cells.

Garcinol protects against cerebral ischemia-reperfusion injury in vivo and in vitro by inhibiting inflammation and oxidative stress

Garcinol, a polyisoprenylated benzophenone derivative, is isolated from fruit rind of Garcinia indica. It is known to exert potent anti-inflammatory and anti-oxidative properties. In the present study, we tried to investigate the neuroprotective effects of garcinol on a rat model with middle cerebral artery occlusion/reperfusion (MCAO/R) and a cell model subjected to oxygen glucose deprivation and reperfusion (OGD/R). In vivo, we found that the rats with garcinol treatment showed a lower neurological deficit score and a smaller infarct size compared with the rats with ischemia-reperfusion (I/R) injury alone. We further found that garcinol treatment decreased cerebral I/R-induced inflammatory cytokines and oxidative stress, including inhibiting the production of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α), decreasing the levels of malonaldehyde (MDA) and nitric oxide (NO), and suppressing the decreased superoxide dismutase (SOD) activity. Moreover, the suppression of toll-like receptor (TLR) 4 and nuclear NF-κB (p65) expression by garcinol was found both in vivo and in vitro. In addition, NF-κB activator or TLR4 overexpression was employed to investigate its involvement in the effects of garcinol. The results showed that NF-κB activator or TLR4 overexpression at least in part reversed the anti-inflammatory and anti-oxidative properties of garcinol in vitro. Taken together, the data suggest that garcinol could protect against cerebral I/R injury through attenuating inflammation and oxidative stress, and improving neurological function. The molecular mechanism might be related to its suppression of TLR4/NF-ĸB signal pathway.

Fyn gene silencing reduces oligodendrocytes apoptosis through inhibiting ERK1/2 phosphorylation in epilepsy

This study aimed to investigate the effect of Fyn gene silencing on the apoptosis of oligodendrocytes (OLs) in epileptic model in vitro and the involved mechanism. Primary oligodendrocyte pro-genitor cells (OPCs) were separated from rats and differentiated to OLs. Immunofluorescent labeling showed positive expression of A2B5 in OPCs and Olig2 in OLs, suggesting the successful separation of OPCs and OLs. Three Fyn siRNAs (si-Fyn) and Fyn siRNA negative control (NC) were transfected into OLs. Western blot showed that among three si-Fyn groups, si-Fyn3 caused the lowest Fyn expression, so si-Fyn3 was chosen for following experiment. Cells were divided into four groups: Control, Model, NC and si-Fyn. In the Model group, cells were cultured in Mg-free extracellular fluid for 3 h. The morphology of control cells was normal. However, the migration of neurons, the aggregation of cell bodies and the "grid-like" changes of neural networks were observed in the model cells. OLs apoptosis in various groups was assessed by flow cytometry. Expression of Fyn, ERK1/2 and phosphorylated ERK1/2 (p-ERK1/2) in OLs of various groups was evaluated by western blot. Compared with the Control group, the apoptotic rates, the Fyn expression and p-ERK1/2/ERK1/2 ratio in the Model and NC groups increased significantly (p < .05). However, the apoptotic rate, the Fyn expression and p-ERK1/2/ERK1/2 ratio in the si-Fyn group were remarkably smaller than those in the Model group (p < .05). In conclusion, Fyn gene silencing reduced the apoptosis of OLs through inhibiting the phosphorylation of ERK1/2 in epileptic model.

K-3-Rh Protects Against Cerebral Ischemia/Reperfusion Injury by Anti-Apoptotic Effect Through PI3K-Akt Signaling Pathway in Rat

BACKGROUND/AIMS

Ischemic stroke is the main cause of nerve damage and brain dysfunction, accompanied by strong brain cell apoptosis. This study aimed to investigate the effect of kaempferol-3-O-rhamnoside (K-3-rh) on cerebral ischemia-reperfusion (I/R) injury.

METHODS AND MATERIALS

A rat model of cerebral I/R injury was established. The effects of K-3-rh on cerebral infarction size, brain water content and neurological deficits in rats were evaluated. Apoptosis of ischemic brain cells after mouse I/R was observed by TUNEL staining and flow cytometry. Western blot and qRT-PCR were used to detect the effect of K-3-rh on the expression of apoptosis-related proteins.

RESULTS

K-3-rh can improve the neurological deficit score, reduce the infarct volume and brain water content, and inhibit cell apoptosis. In addition, K-3-rh significantly downregulated the expression of Bax and p53 and upregulated the expression of Bcl-2, and the phosphorylation level of Akt. Blockade of PI3K activity by the PI3K inhibitor wortmannin not only reversed the effects of K-3-rh on infarct volume and brain water content but also reversed the expression level of p-Akt.

CONCLUSION

K-3-rh had obvious neuroprotective effects on brain I/R injury and neuronal apoptosis, and its mechanism may be related to activation of PI3K/Akt signaling pathway.

Theaflavin attenuates cerebral ischemia/reperfusion injury by abolishing miRNA‑128‑3p‑mediated Nrf2 inhibition and reducing oxidative stress

Theaflavin has been proven to own strong antioxidative capacity; however, the molecular mechanism underlying its protective effect against cerebral ischemia-reperfusion (I/R) injury remains unclear. Therefore, the present study was designed to elucidate the neuroprotective effects of theaflavin on cerebral I/R injury and its underlying molecular mechanisms. To investigate the effects of theaflavin on neurological function, neurogenesis, and oxidative stress, experiments were performed using a cerebral I/R injury rat model, and neural stem cells (NSCs) were subjected to oxygen-glucose deprivation and reoxygenation (OGD/R). Further, the expression profiles of miRNA-128-3p and the regulatory function of nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2) were evaluated in these models. We found that theaflavin treatment significantly reduced infarct volume and neuronal injury, and thus improved the impaired memory and learning ability. Furthermore, theaflavin treatment significantly enhanced the increase in NSC proliferation, reduction in the apoptotic rate and inhibition of oxidative stress. Mechanistically, theaflavin targeted miRNA-128-3p and further activated the Nrf2 pathway to reduce oxidative stress. In summary, theaflavin has a strong ability to attenuate cerebral I/R injury through miRNA-128-3p-mediated recovery of the impaired antioxidant defense system, which suggests that it could be a potential drug candidate for ischemic stroke.

Neuroprotective effect of Dictyopteris divaricata extract-capped gold nanoparticles against oxygen and glucose deprivation/reoxygenation

Combination therapy remains a promising approach to ameliorate cerebral ischemia injury. Nevertheless, the primary mechanism of the neuroprotective properties of Dictyopteris divaricata extract-capped gold nanoparticles (DD-GNPs) is not completely understood. DD-GNPs displayed maximum absorption at 525 nm and a diameter of 62.6 ± 1.2 nm, with a zeta potential value of -26.1 ± 0.6 mV. High resolution-transmission electron microscopy confirmed the spherical shape and average diameter (28.01 ± 2.03 nm). Crystalline structure and gold nanoparticle synthesis of DD-GNPs were determined by X-ray powder diffraction, and the presence of elemental gold was confirmed by energy-dispersive X-ray spectroscopy and Fourier transform-infrared spectroscopy. We examined the neuroprotective properties of DD-GNPs and explored their potential mechanisms in human SH-SY5Y neuroblastoma cells treated with oxygen and glucose deprivation/reoxygenation (OGD/R). We found that DD-GNPs inhibited OGD/R-induced release of lactate dehydrogenase (LDH), loss of cell viability, and production of reactive oxygen species. This neuroprotection was accompanied by regulation of apoptosis-related proteins, as indicated by decreased levels of cleaved-caspase-3, cleaved-PARP, cleaved-caspase-9, p53, p21, and Bax, as well as an increased level of Bcl-2. Notably, the neuroprotective effects of DD-GNPs were partially abolished by HO-1, NQO1, Nrf2, and AMPK knockdown. Our results established that DD-GNPs effectively attenuated OGD/R-stimulated neuronal injury, as evidenced by reduced neuronal injury. Even though the accumulating evidence has indicated the low toxicity and minimal side effects of GNPs, experimental clinical trials of DD-GNPs are still limited because of the lack of knowledge regarding the effects of DD-GNPs as neuroprotective agents against neurodegenerative diseases.

Critical Role of Nrf2 in Experimental Ischemic Stroke

Ischemic stroke is one of the leading causes of death and long-term disability worldwide; however, effective clinical approaches are still limited. The transcriptional factor Nrf2 is a master regulator in cellular and organismal defense against endogenous and exogenous stressors by coordinating basal and stress-inducible activation of multiple cytoprotective genes. The Nrf2 network not only tightly controls redox homeostasis but also regulates multiple intermediary metabolic processes. Therefore, targeting Nrf2 has emerged as an attractive therapeutic strategy for the prevention and treatment of CNS diseases including stroke. Here, the current understanding of the Nrf2 regulatory network is critically examined to present evidence for the contribution of Nrf2 pathway in rodent ischemic stroke models. This review outlines the literature for Nrf2 studies in preclinical stroke and focuses on the in vivo evidence for the role of Nrf2 in primary and secondary brain injuries. The dynamic change and functional importance of Nrf2 signaling, as well as Nrf2 targeted intervention, are revealed in permanent, transient, and global cerebral ischemia models. In addition, key considerations, pitfalls, and future potentials for Nrf2 studies in preclinical stroke investigation are discussed.

Uric Acid Protects against Focal Cerebral Ischemia/Reperfusion-Induced Oxidative Stress via Activating Nrf2 and Regulating Neurotrophic Factor Expression

The aim of this study was to investigate whether uric acid (UA) might exert neuroprotection via activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway and regulating neurotrophic factors in the cerebral cortices after transient focal cerebral ischemia/reperfusion (FCI/R) in rats. UA was intravenously injected through the tail vein (16 mg/kg) 30 min after the onset of reperfusion in rats subjected to middle cerebral artery occlusion for 2 h. Neurological deficit score was performed to analyze neurological function at 24 h after reperfusion. Terminal deoxynucleotidyl transferase-mediated dNTP nick end labeling (TUNEL) staining and hematoxylin and eosin (HE) staining were used to detect histological injury of the cerebral cortex. Malondialdehyde (MDA), the carbonyl groups, and 8-hydroxyl-2′-deoxyguanosine (8-OHdG) levels were employed to evaluate oxidative stress. Nrf2 and its downstream antioxidant protein, heme oxygenase- (HO-) 1,were detected by western blot. Nrf2 DNA-binding activity was observed using an ELISA-based measurement. Expressions of BDNF and NGF were analyzed by immunohistochemistry. Our results showed that UA treatment significantly suppressed FCI/R-induced oxidative stress, accompanied by attenuating neuronal damage, which subsequently decreased the infarct volume and neurological deficit. Further, the treatment of UA activated Nrf2 signaling pathway and upregulated BDNF and NGF expression levels. Interestingly, the aforementioned effects of UA were markedly inhibited by administration of brusatol, an inhibitor of Nrf2. Taken together, the antioxidant and neuroprotective effects afforded by UA treatment involved the modulation of Nrf2-mediated oxidative stress and regulation of BDNF and NGF expression levels. Thus, UA treatment could be of interest to prevent FCI/R injury.

Modulation of nuclear factor-κB signaling and reduction of neural tube defects by quercetin-3-glucoside in embryos of diabetic mice

BACKGROUND

Diabetes mellitus in early pregnancy increases the risk of birth defects in infants. Maternal hyperglycemia stimulates the expression of nitric oxide synthase 2, which can be regulated by transcription factors of the nuclear factor-κB family. Increases in reactive nitrogen species generate intracellular stress conditions, including nitrosative, oxidative, and endoplasmic reticulum stresses, and trigger programmed cell death (or apoptosis) in the neural folds, resulting in neural tube defects in the embryo. Inhibiting nitric oxide synthase 2 can reduce neural tube defects; however, the underlying mechanisms require further delineation. Targeting nitric oxide synthase 2 and associated nitrosative stress using naturally occurring phytochemicals is a potential approach to preventing birth defects in diabetic pregnancies.

OBJECTIVE

This study aims to investigate the effect of quercetin-3-glucoside, a naturally occurring polyphenol flavonoid, in reducing maternal diabetes-induced neural tube defects in an animal model, and to delineate the molecular mechanisms underlying quercetin-3-glucoside action in regulating nitric oxide synthase 2 expression.

STUDY DESIGN

Female mice (C57BL/6) were induced to develop diabetes using streptozotocin before pregnancy. Diabetic pregnant mice were administered quercetin-3-glucoside (100 mg/kg) daily via gavage feeding, introduction of drug to the stomach directly via a feeding needle, during neurulation from embryonic day 6.5-9.5. After treatment at embryonic day 10.5, embryos were collected and examined for the presence of neural tube defects and apoptosis in the neural tube. Expression of nitric oxide synthase 2 and superoxide dismutase 1 (an antioxidative enzyme) was quantified using Western blot assay. Nitrosative, oxidative, and endoplasmic reticulum stress conditions were assessed using specific biomarkers. Expression and posttranslational modification of factors in the nuclear factor-κB system were investigated.

RESULTS

Treatment with quercetin-3-glucoside (suspended in water) significantly decreased neural tube defect rate and apoptosis in the embryos of diabetic mice, compared with those in the water-treated diabetic group (3.1% vs. 24.7%; P < .001). Quercetin-3-glucoside decreased the expression of nitric oxide synthase 2 and nitrosative stress (P < .05). It also increased the levels of superoxide dismutase 1 (P < .05), further increasing the antioxidative capacity of the cells. Quercetin-3-glucoside treatment also alleviated of endoplasmic reticulum stress in the embryos of diabetic mice (P < .05). Quercetin-3-glucoside reduced the levels of p65 (P < .05), a member of the nuclear factor-κB transcription factor family, but augmented the levels of the inhibitor of κBα (P < .05), which suppresses p65 nuclear translocation. In association with these changes, the levels of inhibitor of κB kinase-α and inhibitor of κBα phosphorylation were elevated (P < .05).

CONCLUSION

Quercetin-3-glucoside reduces the neural tube defects rate in the embryos of diabetic dams. Quercetin-3-glucoside suppresses nitric oxide synthase 2 and increases superoxide dismutase 1 expression, leading to alleviation of nitrosative, oxidative, and endoplasmic reticulum stress conditions. Quercetin-3-glucoside may regulate the expression of nitric oxide synthase 2 via modulating the nuclear factor-κB transcription regulation system. Quercetin-3-glucoside, a naturally occurring polyphenol that has high bioavailability and low toxicity, is a promising candidate agent to prevent birth defects in diabetic pregnancies.

Up-regulation of HO-1 by Nrf2 activation protects against palmitic acid-induced ROS increase in human neuroblastoma BE(2)-M17 cells

Saturated fatty acids (SFAs) induce reactive oxygen species (ROS) production in neurons. Extracellular signal regulated kinase (ERK)/nuclear factor erythroid-2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) is a ROS response pathway. Therefore, high ROS is always accompanied by increase of HO-1, an anti-oxidative enzyme; but it remains unknown why there is no significant reduction of ROS with the increase of HO-1 in SFAs-treated neurons. We hypothesized that the up-regulation of HO-1 is compensatory for response to fatty acid-induced oxidative stress but not enough to reduce ROS levels. We evaluated the anti-ROS effect of HO-1 and the involved pathway in palmitic acid (PA)-treated human neuroblastoma BE(2)-M17 cells. As expected, PA-induced ROS increase was accompanied by activation of the ERK-Nrf2-HO-1 pathway, as demonstrated by an increase in ERK phosphorylation, Nrf2 phosphorylation and nuclear accumulation, and HO-1 expression at the mRNA and protein levels, in a PA-dose-dependent manner. In contrast, administration of the ROS scavenger NAC significantly reduced the levels of PA-regulated ROS and HO-1 protein. However, the ERK inhibitor U0126 not only reversed the activating effect of PA on the ERK-Nrf2-HO-1 pathway but also aggravated PA-induced ROS. Furthermore, the Nrf2-specific activator NK-252 significantly increased PA-up-regulated HO-1 protein and alleviated PA-induced ROS. Therefore, our results suggest that up-regulation of HO-1 in PA-treated neurons is a compensatory response to ROS increase and that increasing HO-1 expression by Nrf2 activation can prevent the process of ROS production in PA-treated neurons.

Klotho Improves Cardiac Function by Suppressing Reactive Oxygen Species (ROS) Mediated Apoptosis by Modulating Mapks/Nrf2 Signaling in Doxorubicin-Induced Cardiotoxicity

Background

Anthracyclines-induced cardiotoxicity has become one of the major restrictions of their clinical applications. Klotho showed cardioprotective effects. This study aimed to investigate the effects and possible mechanisms of klotho on doxorubicin (DOX)-induced cardiotoxicity.

Material/Methods

Rats and isolated myocytes were exposed to DOX and treated with exogenous klotho. Specific inhibitors and siRNAs silencing MAPKs were also used to treat the animals and/or myocytes. An invasive hemodynamic method was used to determine cardiac functions. Intracellular ROS generation was evaluated by DHE staining. Western blotting was used to determine the phosphorylation levels of JNK, ERK, and p38 MAPKs in plasma extracts and Nrf2 in nuclear extracts. Nuclear translocation of Nrf2 in myocytes was evaluated by immunohistochemistry. Cell apoptosis was evaluated by TUNEL assay and flow cytometry.

Results

Klotho treatment improved DOX-induced cardiac dysfunction in rats. The DOX-induced ROS accumulation and cardiac apoptosis were attenuated by klotho. Impaired phosphorylations of MAPKs, Nrf2 translocation and expression levels of HO1 and Prx1 were also attenuated by klotho treatment. However, the anti-oxidant and anti-apoptotic effects of klotho on DOX-exposed myocardium and myocytes were impaired by both specific inhibitors and siRNAs against MAPKs. Moreover, the recovery effects of klotho on phosphorylations of MAPKs, Nrf2 translocation and expression levels of HO1 and Prx1 were also impaired by specific inhibitors and siRNAs against MAPKs.

Conclusions

By recovering the activation of MAPKs signaling, klotho improved cardiac function loss which was triggered by DOX-induced ROS mediated cardiac apoptosis.

Mild hypothermia protects hippocampal neurons against oxygen-glucose deprivation/reperfusion-induced injury by improving lysosomal function and autophagic flux

Mild hypothermia has been proven to be useful to treat brain ischemia/reperfusion injury. However, the underlying mechanisms have not yet been fully elucidated. The present study was undertaken to determine whether mild hypothermia protects hippocampal neurons against oxygen-glucose deprivation/reperfusion(OGD/R)-induced injury via improving lysosomal function and autophagic flux. The results showed that OGD/R induced the occurrence of autophagy, while the acidic environment inside the lysosomes was altered. The autophagic flux assay with RFP-GFP tf-LC3 was impeded in hippocampal neurons after OGD/R. Mild hypothermia recovered the lysosomal acidic fluorescence and the lysosomal marker protein expression of LAMP2, which decreased after OGD/R.Furthermore, we found that mild hypothermia up-regulated autophagic flux and promoted the fusion of autophagosomes and lysosomes in hippocampal neurons following OGD/R injury, but could be reversed by treatment with chloroquine, which acts as a lysosome inhibitor. We also found that mild hypothermia improved mitochondrial autophagy in hippocampal neurons following OGD/R injury. Finally,we found that chloroquine blocked the protective effects of mild hypothermia against OGD/R-induced cell death and injury. Taken together, the present study indicates that mild hypothermia protects hippocampal neurons against OGD/R-induced injury by improving lysosomal function and autophagic flux.