Astragaloside IV attenuates lead acetate-induced inhibition of neurite outgrowth through activation of Akt-dependent Nrf2 pathway in vitro

Astragaloside IV attenuates high glucose-induced NF-κB-mediated inflammation through activation of PI3K/AKT-ERK-dependent Nrf2/ARE signaling pathway in glomerular mesangial cells

Inflammation is a key contributor to diabetic kidney disease pathogenesis, including reactive oxidation stress (ROS)-mediated nuclear factor-κB (NF-κB) signaling pathway. In this study, we examined the effect of Astragaloside IV (AS-IV) on anti-inflammatory and anti-oxidative properties under high glucose (HG) condition and the potential mechanism in glomerular mesangial cells (GMCs). We showed that AS-IV concentration-dependently reduced GMCs proliferation, restrained ROS release and hydrogen peroxide content, and suppressed pro-inflammatory cytokines as well as pro-fibrotic factors expression, which were associated with the inhibition of NF-κB and nuclear factor-erythroid 2-related factor 2 (Nrf2) signaling activation. Accordingly, both NF-κB overexpression by using RNA plasmid and Nrf2 gene silencing by using RNA interference weakened the ability of AS-IV to ameliorate HG-induced oxidative stress, inflammation, and cell proliferation. Furthermore, phosphatidylinositide 3-kinases (PI3K)/serine/threonine protein kinase (Akt) and extracellular regulated protein kinases (ERK) signaling pathway regulated the process of AS-IV-induced Nrf2 activation and antioxidant capacity, which evidenced by using PI3K inhibitor LY294002 or ERK inhibitor PD98059 that largely abolished the AS-IV efficacy. Taken together, these results indicated that AS-IV protected against HG-induced GMCs damage by inhibiting ROS/NF-kB-induced increases of inflammatory cytokines, fibrosis biomarkers, and cell proliferation via up-regulation of Nrf2-dependent antioxidant enzyme expression, which were mediated by PI3K/Akt and ERK signaling pathway activation.

Different Effects and Mechanisms of Selenium Compounds in Improving Pathology in Alzheimer’s Disease

Owing to the strong antioxidant capacity of selenium (Se) in vivo, a variety of Se compounds have been shown to have great potential for improving the main pathologies and cognitive impairment in Alzheimer’s disease (AD) models. However, the differences in the anti-AD effects and mechanisms of different Se compounds are still unclear. Theoretically, the absorption and metabolism of different forms of Se in the body vary, which directly determines the diversification of downstream regulatory pathways. In this study, low doses of Se-methylselenocysteine (SMC), selenomethionine (SeM), or sodium selenate (SeNa) were administered to triple transgenic AD (3× Tg-AD) mice for short time periods. AD pathology, activities of selenoenzymes, and metabolic profiles in the brain were studied to explore the similarities and differences in the anti-AD effects and mechanisms of the three Se compounds. We found that all of these Se compounds significantly increased Se levels and antioxidant capacity, regulated amino acid metabolism, and ameliorated synaptic deficits, thus improving the cognitive capacity of AD mice. Importantly, SMC preferentially increased the expression and activity of thioredoxin reductase and reduced tau phosphorylation by inhibiting glycogen synthase kinase-3 beta (GSK-3β) activity. Glutathione peroxidase 1 (GPx1), the selenoenzyme most affected by SeM, decreased amyloid beta production and improved mitochondrial function. SeNa improved methionine sulfoxide reductase B1 (MsrB1) expression, reflected in AD pathology as promoting the expression of synaptic proteins and restoring synaptic deficits. Herein, we reveal the differences and mechanisms by which different Se compounds improve multiple pathologies of AD and provide novel insights into the targeted administration of Se-containing drugs in the treatment of AD.

Treatment with astragaloside IV reduced blood glucose, regulated blood lipids, and protected liver function in diabetic rats

Objectives

To investigate the effects of astragaloside IV on blood glucose, blood lipids, and liver function in diabetic rats.

Methods

Fifty diabetic rats were randomly placed into five groups (n = 10 each): the diabetes mellitus (DM) group received intragastric saline, the metformin hydrochloride group received intragastric metformin hydrochloride, and the astragaloside-30, -60, and -120 groups received intragastric astragaloside 30 mg/kg, 60 mg/kg, and 120 mg/kg for 28 days, respectively. Ten non-diabetic rats received intragastric saline as controls.

Results

Relative to the DM group, fasting blood glucose, triglyceride, total cholesterol, serum alanine transaminase, and serum aspartate aminotransferase levels decreased in the astragaloside-60 and astragaloside-120 groups; serum alkaline phosphatase decreased solely in the astragaloside-120 group. Serum superoxide dismutase (SOD), glutathione (GSH-Px), and catalase (CAT) levels were elevated, while maleic dialdehyde (MDA) decreased in the astragaloside-120 group, relative to the DM group. Relative to the DM group, the liver index and liver cell apoptosis rate were reduced, while histopathological changes in liver tissue were ameliorated in the astragaloside groups; moreover, liver tissue SOD, GSH-Px, and CAT levels were increased, while liver tissue MDA was reduced.

Conclusions

Astragaloside IV can lower blood glucose, regulate blood lipids, and protect liver function in diabetic rats.

Downregulation of glob1 suppresses pathogenesis of human neuronal tauopathies in Drosophila by regulating tau phosphorylation and ROS generation

Human tauopathies represent a group of neurodegenerative disorders, characterized by abnormal hyperphosphorylation and aggregation of tau protein, which ultimately cause neurodegeneration. The aberrant tau hyperphosphorylation is mostly attributed to the kinases/phosphatases imbalance, which is majorly contributed by the generation of reactive oxygen species (ROS). Globin(s) represent a well-conserved group of proteins which are involved in O₂ management, regulation of cellular ROS in different cell types. Similarly, Drosophila globin1 (a homologue of human globin) with its known roles in oxygen management and development of nervous system exhibits striking similarities with the mammalian neuroglobin. Several recent evidences support the hypothesis that neuroglobins are associated with Alzheimer's disease pathogenesis. We herein noted that targeted expression of human-tau induces the cellular level of Glob1 protein in Drosophila tauopathy models. Subsequently, RNAi mediated restored level of Glob1 restricts the pathogenic effect of human-tau by minimizing its hyperphosphorylation via GSK-3β/p-Akt and p-JNK pathways. In addition, it also activates the Nrf2-keap1-ARE cascade to stabilize the tau-mediated increased level of ROS. These two parallel cellular events provide a significant rescue against human tau-mediated neurotoxicity in the fly models. For the first time we report a direct involvement of an oxygen sensing globin gene in tau etiology. In view of the fact that human genome encodes for the multiple Globin proteins including a nervous system specific neuroglobin; and therefore, our findings may pave the way to investigate if the conserved oxygen sensing globin gene(s) can be exploited in devising novel therapeutic strategies against tauopathies.

Nephroprotective effect of gastrodin against lead-induced oxidative stress and inflammation in mice by the GSH, Trx, Nrf2 antioxidant system, and the HMGB1 pathway

Gastrodin (GAS), the main phenolic glycoside derivative from Gastrodiaelata Blume, has several bio-activities. However, the molecular mechanisms of these protective actions currently remain unclear. This study aimed to investigate the mechanisms of GAS on lead (Pb)-induced oxidative stress and inflammation in the kidneys and primary kidney mesangial cells. Results indicated that GAS improved Pb-induced renal dysfunction and morphological changes in mice. GAS ameliorated Pb-induced inflammation in kidneys by reducing the TNF-α and IL-6 levels. GAS inhibited Pb-induced oxidative stress by regulating the glutathione, thioredoxin (Trx), and Nrf2 antioxidant systems. Furthermore, GAS supplementation increased the activation of SOD, GPx, HO-1, and NQO1 in the kidneys. GAS decreased the expression levels of HMGB1, TLR4, RAGE, MyD88, and NF-κB. These results were further confirmed in primary kidney mesangial cells. Collectively, this study demonstrated that GAS alleviated Pb-induced kidney oxidative stress and inflammation by regulating the antioxidant systems and the Nrf2 signaling pathway. Highlights Gastrodin ameliorated Pb-induced kidney injury in mice.Gastrodin inhibited oxidative stress and inflammation in kidneys.Gastrodin activated the GSH, Trx and Nrf2 antioxidant system in kidneys.Gastrodin inhibited the activities of HMGB1. RAGE, TLR4, and MyD88.

Astragaloside IV-induced Nrf2 nuclear translocation ameliorates lead-related cognitive impairments in mice

Recently, oxidative stress is a common denominator in the pathogenesis of metal-induced neurotoxicity. Thus, antioxidant therapy is considered as a promising strategy for treating lead-related cognitive impairment. Here, we tested the hypothesis that astragaloside IV (AS-IV) ameliorates lead-associated cognitive deficits through Nrf2-dependent antioxidant mechanisms. Male Nrf2-KO and WT mice received drinking water with 2000 ppm lead and/or AS-IV by gavage for 8 weeks starting at 4 weeks of age. Morris water maze test and biochemical assays were employed to study cognition-enhancing and antioxidant effects of AS-IV. The signaling pathways involved were analyzed using RT-PCR and western blot technology. Significantly, AS-IV attenuated Morris water maze-based cognitive impairment in lead-intoxicated mice. Importantly, cognition-enhancing effect of AS-IV was lost in Nrf2-KO mice. In parallel, AS-IV suppressed lead acetate (PbAc)-induced oxidative stress, as measured by MDA. Mechanistically, AS-IV can up-regulate the expressions of the GCLc and HO-1 at the level of transcription and translation, but not SOD, TrxR activity, GCLm, Trx1, and NQO1 expression. Interestingly, AS-IV induced accumulation of Nrf2 in the nucleus, whereas Nrf2 mRNA levels were unchanged. Furthermore, AS-IV treatment resulted in elevated levels of phosphorylated Akt (active form) and phosphorylated GSK-3β (inactive forms) but decreased level of phosphorylated Fyn. Collectively, our findings indicate that AS-IV may target Nrf2 to attenuate lead-triggered oxidative stress and subsequent cognitive impairments, suggesting that AS-IV is a potential candidate for the treatment of lead-associated cognitive diseases.

Antagonistic effects of IL-17 and Astragaloside IV on cortical neurogenesis and cognitive behavior after stroke in adult mice through Akt/GSK-3β pathway

We aimed to investigate the exact effect of IL-17 on regulating neural stem cells (NSCs) stemness and adult neurogenesis in ischemic cortex after stroke, how Astragaloside IV(As-IV) regulated IL-17 expression and the underlying mechanism. Photochemical brain ischemia model was established and IL-17 protein expression was observed at different time after stroke in WT mice. At 3 days after stroke, when IL-17 expression peaked, IL-17 knock out (KO) mice were used to observe cell proliferation and neurogenesis in ischemic cortex. Then, As-IV was administered intravenously to assess cell apoptosis, proliferation, neurogenesis, and cognitive deficits by immunochemistry staining, western blots, and animal behavior tests in WT mice. Furthermore, IL-17 KO mice and As-IV were used simultaneously to evaluate the mechanism of cell apoptosis and proliferation after stroke in vivo. Besides, in vitro, As-IV and recombinant mouse IL-17A was administered, respectively, into NSCs culture, and then their diameters, viable cell proliferation and pathway relevant protein was assessed. The results showed knocking out IL-17 contributed to regulating PI3K/Akt pathway, promoting NSCs proliferation, and neurogenesis after ischemic stroke. Moreover, As-IV treatment helped inhibit neural apoptosis, promote the neurogenesis and eventually relieve mice anxiety after stroke. Unsurprisingly, IL-17 protein expression could be downregulated by As-IV in vivo and in vitro and they exerted antagonistic effect on neurogenesis by regulating Akt/GSK-3β pathway, with significant regulation for apoptosis. In conclusion, IL-17 exerts negative effect on promoting NSCs proliferation, neurogenesis and cognitive deficits after ischemic stroke, which could be reversed by As-IV.

Astragaloside IV and ferulic acid synergistically promote neurite outgrowth through Nrf2 activation

Recently, nuclear factor (erythroid-derived 2)-like 2 (Nrf2) have nuclear localization and nuclear exclusion signals and shuttle between the cytoplasm and the nucleus. Thus, we hypothesised that astragaloside IV (AS-IV) induction nuclear import of Nrf2 and ferulic acid (FA) inhibition nuclear export of Nrf2 contribute to synergistic antioxidant effects of combination of FA and AS-IV (FA/AS-IV). Here, we have demonstrated that FA/AS-IV enhances neurite outgrowth of PC12 cells challenged with lead acetate (PbAc) via antioxidant properties in a synergistic manner. Concomitantly, FA/AS-IV significantly promotes Nrf2 activation and induces "phase-II'' enzymes during PbAc toxicity, compared with either FA or AS-IV alone. Interestingly, FA but not AS-IV activates the extracellular signal-regulated kinases 1 and 2 (ERK1/2), leading to an increase in both de novo synthesis of Nrf2 and nuclear import of Nrf2. Simultaneously, AS-IV but not FA suppresses Fyn phosphorylation via Akt-mediated inhibition of GSK-3β, which inhibited nuclear export of Nrf2. Importantly, dual activation of both ERK1/2 and Akt by FA/AS-IV in PC12 cells challenged with PbAc is mediated by independent mechanisms, which are supported by pharmacological inhibitors. Collectively, these results support the notion that the FA/AS-IV may be promising in therapy for lead developmental neurotoxicity. This combination deserves further study in vivo.

Astragaloside IV reduces neuronal apoptosis and parthanatos in ischemic injury by preserving mitochondrial hexokinase-II

Cerebral ischemia induces neuronal cell death in different ways and mitochondrial dysfunction is an important cause. Astragaloside IV (AIV) is a natural saponin abandent in Astragalus membranaceus and this study aims to find if AIV protects neuronal survival via preserving mitochondrial hexokinase-II (HK-II). Glutamate stimulation induced HK-II dissociation from mitochondria and impaired mitochondrial function, indicated by the opening of the mitochondrial permeability transition pore, the collapse of mitochondrial membrane potential and reduced mitochondrial oxygen consumption ratio in neurons. Accompanied with apoptosis, oxidative DNA damage, PAR formation and nuclear translocation of apoptosis inducing factor (AIF) indicated the presence of parthanatos. AIV activated Akt and protected mitochondrial HK-II via promoting the binding of Akt to HK-II and protected hexokinase activity with improved glycolysis. As a consequence of preserved mitochondrial HK-II, AIV reduced the release of pro-apoptotic proteins and AIF, resultantly protected neurons from apoptosis and parthanatos. Moreover, the neuroprotective effects of AIV were also reproduced in mice subjected to middle cerebral artery occlusion to support the findings in vitro. Together, these results showed that glutamate excitotoxicity impaired mitochondrial HK-II and simultaneously induced apoptosis and parthanatos owing to mitochondrial dysfunction. AIV activated Akt to promote HK-II binding to mitochondria, and the structural and functional integrity of mitochondria contributed to protecting neurons from apoptosis and DNA damage. These findings address the important role of mitochondrial HK-II in neuronal protection.

Essential Role of Keap1-Nrf2 Signaling in Mood Disorders: Overview and Future Perspective

Depression is one of the most common mood disorders with a high rate of relapse. Accumulating evidence suggests that the transcription factor Kelch-like erythroid cell-derived protein with CNC homology (ECH)-associated protein 1 (Keap1)-Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) system plays a key role in inflammation which is involved in depression. Preclinical studies demonstrated that the protein expressions of Keap1 and Nrf2 in the prefrontal cortex (PFC), CA3 and dentate gyrus (DG) of hippocampus in mice with depression-like phenotype were lower than control mice. In the learned helplessness paradigm, the protein levels of Keap1 and Nrf2 in the PFC and DG of hippocampus from rats with depression-like phenotype were also lower than control and resilient rats. Furthermore, rodents with depression-like phenotype have higher levels of pro-inflammatory cytokines. Interestingly, Nrf2 knock-out (KO) mice exhibit depression-like phenotype, and higher serum levels of pro-inflammatory cytokines compared with wild-type mice. Furthermore, Nrf2 KO mice have lower expression of brain-derived neurotrophic factor (BDNF) in the PFC, and CA3 and DG of hippocampus compared to wild-type mice. 7,8-Dihydroxyflavone, a TrkB agonist, showed antidepressant effects in Nrf2 KO mice, by stimulating BDNF-TrkB in the PFC, CA3, and DG. Pretreatment with sulforaphane, a naturally occurring Nrf2 activator, prevented depression-like phenotype in mice after inflammation, or chronic social defeat stress. Interestingly, dietary intake of 0.1% glucoraphanin (a precursor of sulforaphane) containing food during juvenile and adolescent stages of mice could prevent depression-like phenotype in adulthood after chronic social defeat stress. Moreover, the protein expressions of Keap1 and Nrf2 in the parietal cortex from major depressive disorder and bipolar disorder were lower than controls. These findings suggest that Keap1-Nrf2 system plays a key role in the stress resilience which is involved in the pathophysiology of mood disorders. It is, therefore, possible that dietary intake of cruciferous vegetables including glucoraphanin (or SFN) may prevent or minimize relapse from remission, induced by stress and/or inflammation in depressed patients. In the review, the author would like to discuss the role of Keap1-Nrf2 system in mood disorders.

Dihydromyricetin Inhibits Lead-Induced Cognitive Impairments and Inflammation by the Adenosine 5'-Monophosphate-Activated Protein Kinase Pathway in Mice

Dihydromyricetin (DHM), a natural flavonoid derived from the medicinal and edible plant Ampelopsis grossedentata, exhibits antioxidant, antiapoptosis, antitumor, and anti-inflammatory bioactivities. This study evaluated the effects of DHM on Pb-induced neurotoxicity and explored the underlying mechanisms. DHM significantly ameliorated behavioral impairments of Pb-induced mice. It decreased the levels of lipid peroxidation and protein carbonyl and increased the activities of superoxide dismutase and catalase in the brains. DHM suppressed Pb-induced apoptosis, as indicated by the decreased levels of Bax and cleaved caspase-3. DHM also decreased inflammatory cytokines in the brains of Pb-treated mice. DHM decreased amyloid-beta (Aβ) level and nuclear factor-κB nuclear translocation. Moreover, DHM induced the adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation and inhibited the activation of p38, Toll-like receptor 4, myeloid differentiation factor 88, and glycogen synthase kinase-3. Collectively, this is the first report indicating that DHM could improve Pb-induced cognitive functional impairment by preventing oxidative stress, apoptosis, and inflammation and that the protective effect was mediated partly through the AMPK pathway.

Rosmarinic acid attenuates β-amyloid-induced oxidative stress via Akt/GSK-3β/Fyn-mediated Nrf2 activation in PC12 cells

Oxidative stress is an important pathogenic factor in Alzheimer's disease (AD). Recently, nuclear factor E2-related factor 2 (Nrf2) has emerged as a master regulator for the endogenous antioxidant response, and thus represents an attractive therapeutic target against AD. The aim of this study is to test the hypothesis that rosmarinic acid (RosA) attenuates amyloid-β (Aβ)-evoked oxidative stress through activating Nrf2-inducible cellular antioxidant defense system. Here, we reported that RosA attenuated Aβ-induced cellular reactive oxygen species (ROS) generation and lipid hydroperoxides (LPO). Interestingly, knockdown of Nrf2 by plasmid-based short hairpin RNA (shRNA) abrogated, at least in part, RosA-mediated neuroprotection in Aβ-challenged PC12 cells. Mechanistically, RosA enhanced the nuclear translocation of Nrf2 and binding to antioxidant response element (ARE) core element but did not induced Nrf2 transcription. Simultaneously, RosA induced a set of Nrf2 downstream target genes encoding phase-II antioxidant enzymes. Furthermore, RosA enhanced protein kinase B (Akt) phosphorylation, glycogen synthase kinase-3β (GSK-3β) phosphorylation at Ser9, and Fyn phosphorylation. Noteworthy, pharmacological inhibition or gene knockdown studies demonstrated that Akt locate upstream of GSK-3β and regulate Nrf2 through Fyn in the context of PC12 cells pre-incubated with RosA following exposed to Aβ. Conversely, the antioxidant effects of RosA could be blocked by Akt inhibitors LY294002, GSK-3β inhibitor LiCl, Nrf2 shRNA, or Fyn shRNA in Aβ-challenged PC12 cells. Consequently, the antioxidant effects of RosA are mediated predominantly by Akt/GSK-3β/Fyn pathway through increased activity of Nrf2. These results suggest, although do not prove, that RosA can be a promising candidate for neuroprotective treatment of AD.

Rapamycin Confers Neuroprotection against Colistin-Induced Oxidative Stress, Mitochondria Dysfunction, and Apoptosis through the Activation of Autophagy and mTOR/Akt/CREB Signaling Pathways

Our previous studies showed that colistin-induced neurotoxicity involves apoptosis and oxidative damage. The present study demonstrates a neuroprotective effect of rapamycin against colistin-induced neurotoxicity in vitro and in vivo. In a mouse model, colistin treatment (18 mg/kg/d; 14 days) produced marked neuronal mitochondria damage in the cerebral cortex and increased activation of caspase-9 and -3. Rapamycin cotreatment (2.5 mg/kg/d) effectively reduced this neurotoxic effect. In an in vitro mouse neuroblastoma-2a (N2a) cell culture model, rapamycin pretreatment (500 nM) reduced colistin (200 μM) induced cell death from ∼50% to 72%. Moreover, rapamycin showed a marked neuroprotective effect in the N2a cells by decreasing intracellular reactive oxygen species (ROS) production and by up-regulating the activities of the anti-ROS enzymes superoxide dismutase and catalase and recovering glutathione (GSH) levels to normal. Moreover, rapamycin pretreatment protected against colistin-induced mitochondrial dysfunction, caspase activation, and subsequent apoptosis by up-regulating autophagy and activating the Akt/CREB, NGF, and Nrf2 pathways, while inhibiting p53 signaling. Taken together, this is the first study to demonstrate that rapamycin protects against colistin-induced neurotoxicity by activating autophagy, inhibiting oxidative stress, mitochondria dysfunction, and apoptosis. Our data highlight that regulating autophagy to rescue neurons from apoptosis may become a new targeted therapy to relieve the adverse neurotoxic effects associated with colistin therapy.

Klotho protects the heart from hyperglycemia-induced injury by inactivating ROS and NF-κB-mediated inflammation both in vitro and in vivo

Cardiac inflammation and oxidative stress play a key role in the pathogenesis of diabetic cardiomyopathy (DCM). The anti-aging protein Klotho has been found to protect cells from inflammation and oxidative stress. The current study aimed to explore the cardioprotective effects of Klotho on DCM and the underlying mechanisms. H9c2 cells and neonatal cardiomyocytes were incubated with 33mM glucose in the presence or absence of Klotho. Klotho pretreatment effectively inhibited high glucose-induced inflammation, ROS generation, apoptosis, mitochondrial dysfunction, fibrosis and hypertrophy in both H9c2 cells and neonatal cardiomyocytes. In STZ-induced type 1 diabetic mice, intraperitoneal injection of Klotho at 0.01mg/kg per 48h for 3months completely suppressed cardiac inflammatory cytokines and oxidative stress and prevented cardiac cell death and remodeling, which subsequently improved cardiac dysfunction without affecting hyperglycemia. This study revealed that Klotho may exert its protective effects by augmenting nuclear factor erythroid 2-related factor 2 (Nrf2) expression and inactivating nuclear factor κB (NF-κB) activation both in vitro and in vivo. Thus, this work demonstrated for the first time that the anti-aging protein Klotho may be a potential therapeutic agent to treat DCM by inhibiting oxidative stress and inflammation. We also demonstrated the critical roles of the Nrf2 and NF-κB pathways in diabetes-stimulated cardiac injuries and indicated that they may be key therapeutic targets for diabetic complications.