The objectives of our study were to investigate the possible effect of rosuvastatin in ameliorating high salt and cholesterol diet (HSCD)-induced cognitive impairment and to also investigate its possible action via the Nrf2-ARE pathway.

The aim of the present study was to assess the neuroprotective effects of pinostrobin (PSB), a dietary bioflavonoid, and its underlying mechanisms in neurotoxin-induced PD models. Firstly, PSB could attenuate MPTP-induced loss of dopaminergic neurons and improve behavior deficiency in zebrafish, supporting its potential neuroprotective actions in vivo. Next, PSB could decreased apoptosis and death in the MPP⁺-intoxicated SH-SY5Y cells, evidenced by MTT, LDH, Annexin V-FITC/PI and DNA fragmentation assay. PSB also blocked MPP+-induced apoptotic cascades, including loss of mitochondrial membrane potential, activation of caspase 3, and reduced ratio of Bcl-2/Bax. In addition, PSB suppressed MPP+-induced oxidative stress but increased antioxidant enzymes, evidenced by decrease of ROS generation and lipid peroxidation and up-regulation of GSH-Px, SOD, CAT, GSH/GSSG and NAD/NADH. Further investigations showed that PSB significantly enhanced Nrf2 expression and nuclear accumulation, improved ARE promoter activity and up-regulated expression of HO-1 and GCLC. Furthermore, Nrf2 knockdown via specific Nrf2 siRNA abolished PSB-induced anti-oxidative and anti-apoptotic effects against MPP⁺ insults. Interestingly, we then found that PSB promoted phosphorylation of PI3K/AKT and ERK, and pharmacological inhibition of PI3K/AKT or ERK signaling diminished PSB-induced Nrf2/ARE activation and protective actions. In summary, PSB confers neuroprotection against MPTP/MPP⁺-induced neurotoxicity in Parkinson’s disease models. Promoting activation of Nrf2/ARE signaling contributes to PSB-mediated anti-oxidative and neuroprotective actions, which, in part is mediated by PI3K/AKT and ERK.

Oxidative stress and inflammatory response are well known to be involved in the pathogenesis of acute liver injury. This study was performed to examine the hepatoprotective effect of ginsenoside Rg1 (Rg1) against CCl -induced acute liver injury, and further to elucidate the involvement of Nrf2 signaling pathway in vivo and in vitro. Mice were orally administered Rg1 (15, 30, and 60 mg/kg) or sulforaphane (SFN) once daily for 1 week prior to 750 μL/kg CCl injection. The results showed that Rg1 markedly altered relative liver weights, promoted liver repair, increased the serum level of TP and decreased the serum levels of ALT, AST and ALP. Hepatic oxidative stress was inhibited by Rg1, as evidenced by the decrease in MDA, and increases in GSH, SOD, and CAT in the liver. Further research demonstrated that Rg1 suppressed liver inflammation response through repressing the expression levels of inflammation-related genes including TNF-α, IL-1β, IL-6, COX-2, and iNOS. In addition, Rg1 enhanced antioxidative stress and liver detoxification abilities by up-regulating Nrf2 and its target-genes such as GCLC, GCLM, HO-1, NQO1, Besp, Mrp2, Mrp3, Mrp4, and down-regulating Cyp2e1. However, the changes in Nrf2 target-genes, as well as ameliorative liver histology induced by Rg1 were abrogated by Nrf2 antagonist all-transretinoic acid in vivo and Nrf2 siRNA in vitro. Overall, the findings indicated that Rg1 might be an effective approach for the prevention against acute liver injury by activating Nrf2 signaling pathway.

The current study was designed to investigate the protective effect and possible mechanisms of umbelliferone (Umb) on liver injury in diabetic C57BL/KsJ-db/db mice. Mice were divided into five groups: wide type mice group (WY), C57BL/KsJ-db/db (dbdb) mice group, C57BL/KsJ-db/db mice + Metformin (100 mg/kg) group, C57BL/KsJ-db/db mice + Umb (20, 40 mg/kg) group. Blood glucose regulation was assessed by an oral glucose tolerance test (OGTT). At 28 days after drug administration, blood samples were obtained for the analysis of lipids and enzymes related to hepatic function, including alanine aminotransferase (ALT), aspartate aminotransaminase (AST) and total cholesterol (TC) and triglyceride (TG). Expression levels of inflammatory cytokines (TNF-α, IL-1β and IL-6) and oxidative stress indicators (SOD and MDA) were measured with ELISA assay kit. The expressions of HMGB1, TLR4, Myd88, NF-κB, IκB, Nrf2 and OH-1 proteins were also evaluated by western blotting analysis. The results showed that Umb significantly restored the blood glucose in OGTT, and inhibited the levels of insulin, TG, TC, as well as activities of ALT and AST. Moreover, Umb inhibited diabetic inflammation through down-regulating the expression of HMGB1, TLR4, NF-κB and IκB. In addition, Umb alleviated oxidative damage in the liver by activating Nrf2-mediated signal pathway. These findings demonstrated that Umb exhibited protective effect against diabetic live injury, which may be through inhibiting HMGB1-induced inflammatory response and activating Nrf2-mediated antioxidant.

Oxidative stress has been considered a key causing factor of liver damage induced by a variety of agents, including alcohol, drugs, viral infections, environmental pollutants and dietary components, which in turn results in progression of liver injury, non-alcoholic steatohepatitis, non-alcoholic liver disease, liver fibrosis and cirrhosis. During the past 30 years and even after the major progress in the liver disease management, millions of people worldwide still suffer from an acute or chronic liver condition. Curcumin is one of the most commonly used indigenous molecules endowed by various shielding functionalities that protects the liver. The aim of the present study is to comprehensively review pharmacological effects and molecular mechanisms, as well as clinical evidence, of curcumin as a lead compound in the prevention and treatment of oxidative associated liver diseases. For this purpose, electronic databases including “Scopus,” “PubMed,” “Science Direct” and “Cochrane library” were extensively searched with the keywords “curcumin or curcuminoids” and “hepatoprotective or hepatotoxicity or liver” along with “oxidative or oxidant.” Results showed that curcumin exerts remarkable protective and therapeutic effects of oxidative associated liver diseases through various cellular and molecular mechanisms. Those mechanisms include suppressing the proinflammatory cytokines, lipid perodixation products, PI3K/Akt and hepatic stellate cells activation, as well as ameliorating cellular responses to oxidative stress such as the expression of Nrf2, SOD, CAT, GSH, GPx and GR. Taking together, curcumin itself acts as a free radical scavenger over the activity of different kinds of ROS via its phenolic, β-diketone and methoxy group. Further clinical studies are still needed in order to recognize the structure-activity relationships and molecular mechanisms of curcumin in oxidative associated liver diseases.

Metformin not only regulates energy metabolism, but also involves in many cellular processes. In this study, we investigated the effect of metformin on lipopolysaccharide (LPS)-induced intestinal barrier damage. We found that LPS treatment decreased the expression of tight junction proteins, caused pro-inflammatory response and oxidative stress in intestine. Interestingly, metformin treatments attenuated LPS-induced intestinal barrier damage, inflammation and oxidative stress. We found that metformin improved the expression of intestinal tight junction proteins (ZO1, Occludin and Claudin1) that were reduced by LPS stimulation. Moreover, metformin alleviated LPS-induced NF-κB phosphorylation, promoted Nrf2 nuclear translocation and increased the expression of the antioxidative genes (HO-1 and NQO-1), leading to reduced intestinal ROS content. Mechanistically, we found that metformin protects against LPS-induced intestinal barrier dysfunction by activating AMPK. These results reveal the potential of metformin as an effective therapy for treating intestinal diseases.

A general hallmark of neurological diseases is the loss of redox homeostasis that triggers oxidative damages to biomolecules compromising neuronal function. Under physiological conditions the steady-state concentrations of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are finely regulated for proper cellular functions. Reduced surveillance of endogenous antioxidant defenses and/or increased ROS/RNS production leads to oxidative stress with consequent alteration of physiological processes. Neuronal cells are particularly susceptible to ROS/RNS due to their biochemical composition. Overwhelming evidences indicate that nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-linked pathways are involved in protective mechanisms against oxidative stress by regulating antioxidant and phase II detoxifying genes. As such, Nrf2 deregulation has been linked to both aging and pathogenesis of many human chronic diseases, including neurodegenerative ones such as Parkinson’s disease, Alzheimer’s disease and amyotrophic lateral sclerosis. Nrf2 activity is tightly regulated by a fine balance between positive and negative modulators. A better understanding of the regulatory mechanisms underlying Nrf2 activity could help to develop novel therapeutic interventions to prevent, slow down or possibly reverse various pathological states. To this end, microRNAs (miRs) are attractive candidates because they are linked to intracellular redox status being regulated and, post-transcriptionally, regulating key components of ROS/RNS pathways, including Nrf2.

Fibroblast growth factor 19 (FGF19) has emerged as a crucial cytoprotective regulator that antagonizes cell apoptosis and oxidative stress under adverse conditions. However, whether FGF19 plays a cytoprotective role in preventing myocardial damage during myocardial ischemia/reperfusion injury remains unknown. In this study, we aimed to investigate the potential role of FGF19 in regulating hypoxia/reoxygenation (H/R)-induced injury of cardiomyocytes in vitro. We found that that FGF19 expression was upregulated in response to H/R treatment in cardiomyocytes. Silencing of FGF19 significantly inhibited viability and increased apoptosis and reactive oxygen species (ROS) generation in cardiomyocytes with H/R treatment. In contrast, overexpression of FGF19 improved viability and inhibited apoptosis and ROS generation induced by H/R treatment, showing a cardioprotective effect. Moreover, we found that FGF19 regulated the phosphorylation of glycogen synthase kinase-3β (GSK-3β) and the nuclear translocation of nuclear factor-E2-related factor 2 (Nrf2). In addition, FGF19 promoted the activation of Nrf2-mediated antioxidant response element (ARE) antioxidant signaling. Notably, treatment with a GSK-3β inhibitor significantly abrogated the adverse effects of FGF19 silencing on H/R-induced injury, whereas silencing of Nrf2 partially blocked the FGF19-mediated cardioprotective effect against H/R-induced injury in cardiomyocytes. Taken together, our findings demonstrate that FGF19 alleviates H/R-induced apoptosis and oxidative stress in cardiomyocytes by inhibiting GSK-3β activity and promoting the activation of Nrf2/ARE signaling, providing a potential therapeutic target for prevention of myocardial injury.

Oxidative stress and inflammation are major contributors to diabetes-induced endothelial dysfunction which is the critical first step to the development of diabetic macrovascular complications. Nuclear factor erythroid 2-related factor 2 (NRF2) plays a key role in combating diabetes-induced oxidative stress and inflammation. Sodium butyrate (NaB) is an inhibitor of histone deacetylase (HDAC) and an activator of NRF2. However, NaB’s effect on diabetes-induced aortic injury was unknown. It was also not known whether or to what extent NRF2 is required for both self-defense and NaB’s protection in the diabetic aorta. Additionally, the mechanism by which NaB activates NRF2 was unclear. Therefore, C57BL/6 Nrf2 knockout (KO) and wild type (WT) mice were induced to diabetes by streptozotocin, and were treated in the presence or absence of NaB, for 20 weeks. The KO diabetic mice developed more severe aortic endothelial oxidative stress, inflammation and dysfunction, as compared with the WT diabetic mice. NaB significantly attenuated these effects in the WT, but not the KO, mice. In high glucose-treated aortic endothelial cells, NaB elevated Nrf2 mRNA and protein without facilitating NRF2 nuclear translocation, an effect distinct from that of sulforaphane. NaB inhibited HDAC activity, and increased occupancy of the transcription factor aryl hydrocarbon receptor and the co-activator P300 at the Nrf2 gene promoter. Further, the P300 inhibitor C646 completely abolished NaB’s efficacies. Thus, NRF2 is required for both self-defense and NaB’s protection against diabetes-induced aortic endothelial dysfunction. Other findings suggest that P300 mediates the transcriptional activation of Nrf2 by NaB.

Hypoxia is a key pathological process involved in many cutaneous diseases. Nuclear factor E2-related factor 2 (NRF2) is a central regulator of antioxidant response element (ARE)-dependent transcription and plays a pivotal role in the cellular adaptive response to oxidative stress. Kelch-like ECH-associated protein 1 (KEAP1) is a cullin-3-adapter protein that represses the activity of NRF2 by mediating its ubiquitination and degradation. In the present study, we examined the role of NRF2 signaling pathway in the cytotoxicity induced by cobalt chloride(CoCl), a hypoxia-mimicking agent, in human keratinocyte HaCaT cells with stable knockdown of NRF2 (NRF2-KD) and KEAP1 (KEAP1-KD). Acute CoCl exposure markedly increased the levels of intracellular reactive oxygen species (ROS), and resulted in hypoxic damage and cytotoxicity of HaCaT cells. Stable knockdown of NRF2 dramatically reduced the expression of many antioxidant enzymes and sensitized the cells to acute CoCl-induced oxidative stress and cytotoxicity. In contrast, KEAP1-KD cells observably enhanced the activity of NRF2 and ARE-regulated genes and led to a significant resistance to CoCl-induced cellular damage. In addition, pretreatment of HaCaT cells with tert-butylhydroquinone, a well-known NRF2 activator, protected HaCaT cells from CoCl-induced cellular injury in a NRF2-dependent fashion. Likewise, physical hypoxia-induced cytotoxicity could be significantly ameliorated through NRF2 signaling pathway in HaCaT cells. Together, our results suggest that NRF2 signaling pathway is involved in antioxidant response triggered by CoCl-induced oxidative stress and could protect human keratinocytes against acute CoCl -induced hypoxic cytotoxicity.

Salvianolic acid B (SalB), a natural polyphenolic compound extracted from the herb of Salvia miltiorrhiza, possesses antioxidant and neuroprotective properties and has been shown to be beneficial for diseases that affect vasculature and cognitive function. Here we investigated the protective effects of SalB against subarachnoid hemorrhage (SAH)-induced oxidative damage, and the involvement of underlying molecular mechanisms. In a rat model of SAH, SalB inhibited SAH-induced oxidative damage. The reduction in oxidative damage was associated with suppressed reactive oxygen species generation; decreased lipid peroxidation; and increased glutathione peroxidase, glutathione, and superoxide dismutase activities. Concomitant with the suppressed oxidative stress, SalB significantly reduced neurologic impairment, brain edema, and neural cell apoptosis after SAH. Moreover, SalB dramatically induced nuclear factor-erythroid 2-related factor 2 (Nrf2) nuclear translocation and increased expression of heme oxygenase-1 and NADPH: quinine oxidoreductase-1. In a mouse model of SAH, Nrf2 knockout significantly reversed the antioxidant effects of SalB against SAH. Additionally, SalB activated sirtuin 1 (SIRT1) expression, whereas SIRT1-specific inhibitor sirtinol pretreatment significantly suppressed SalB-induced SIRT1 activation and Nrf2 expression. Sirtinol pretreatment also reversed the antioxidant and neuroprotective effects of SalB. In primary cultured cortical neurons, SalB suppressed oxidative damage, alleviated neuronal degeneration, and improved cell viability. These beneficial effects were associated with activation of the SIRT1 and Nrf2 signaling pathway and were reversed by sirtinol treatment. Taken together, these in vivo and in vitro findings suggest that SalB provides protection against SAH-triggered oxidative damage by upregulating the Nrf2 antioxidant signaling pathway, which may be modulated by SIRT1 activation.

Pogostone (PO), a major component of Pogostemon cablin, displays potent protective effects against lipopolysaccharide-induced acute lung injury (ALI) in mice. This study aimed to investigate the protective effect of PO on TNF-α-induced cell injury in human alveolar epithelial cells in vitro and its underlying mechanism. The cell viability was measured using the MTS method. The cell apoptosis was determined using flow cytometry. The activities of reactive oxygen species (ROS) were detected using a fluorescence microscope. The pro-inflammatory cytokines and antioxidant genes were assessed using reverse transcription-polymerase chain reaction. The protein expression of Kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor-alpha (IκBα), and nuclear factor-kappa B (NF-κB) p65 was analyzed using the Western blot analysis. PO alleviated cell apoptosis and inhibited ROS production. It alleviated TNF-α-induced cell injury, suppressed the levels of inflammatory cytokines [interleukin (IL)-6, IL-1β, and IL-8], and enhanced the expression of antioxidant genes (quinine oxidoreductase 1, glutamate cysteine ligase catalytic subunit, heme oxygenase-1). It increased the expression of Keap1 and promoted the activation of Nrf2. However, the phosphorylation of IκBα and the nuclear expression of NF-κB p65 decreased. The anti-inflammatory and antioxidant effects of PO were abrogated following Nrf2 and NF-κB p65 knockdown. The results indicated a protective effect of PO against TNF-α-induced cell injury in A549 cells by modulating the balance between Nrf2 and NF-κB p65 signaling pathways. They verified PO as a promising anti-inflammatory adjuvant drug for treating ALI.

Chronic exposure to ultraviolet (UV) radiation causes photo-oxidation, which in turn results in the upregulation of matrix metalloproteinases (MMPs) and loss of collagen. Rubus idaeus L. (RI), also called red raspberry, is an important cash crop that contains abundant antioxidant compounds. Sanguiin H-6 and lambertianin C are the major ingredients presented in the extracts. Here, we studied the protective effect of RI on UVB-induced photoaging in normal human dermal fibroblasts (NHDFs). We found that RI notably reduced UVB-induced MMPs secretion and pro-inflammatory mediators production, and significantly suppressed UVB-induced activation of mitogen-activated protein kinase (MAPK), nuclear factor-κβ, as well as activator protein 1. Additionally, treatment of NHDFs with the ERK inhibitor (PD98059) and JNK inhibitor (SP600125) resulted in the reduction of UVB-induced MMP-1 and IL-6 expressions, which demonstrated that the inhibition of MMP-1 and IL-6 by RI is associated with the MAPK pathway. Furthermore, we also found that RI accelerated procollagen type I synthesis by activating the transforming growth factor-β/Smad pathway and enhanced the expression of cytoprotective antioxidants such as heme oxygenase-1 and NHD(P)H quinone oxidoreductase 1 by promoting nuclear factor E2-related factor 2 nuclear transfer. Overall, these findings demonstrated that RI was potentially effective in preventing UVB induced skin photoaging.

The transcription factor Nrf2 is a master regulator of antioxidant and cytoprotective genes, binding to antioxidant response elements (AREs) in their promoter regions. Due to the therapeutic role of the Nrf2/ARE system in oxidative homeostasis, its activation has been investigated in many pre-clinical and clinical trials for common chronic diseases. One of the most promising Nrf2 activators is sulforaphane, the subject of over 50 clinical trials. In this work, we examine the effect of reactive oxygen species (ROS) on sulforaphane’s Nrf2/ARE activation in the non-tumorigenic keratinocyte cell line HaCaT, with the non-arylating oxidizable phenol, 2,5-di-tert-butylhydroquinone (dtBHQ), as the source of ROS. We find that, in combination with 2.5µM sulforaphane, dtBHQ markedly enhances ARE-regulated gene expression, including expression of the cytoprotective proteins aldo-keto reductase family 1 member C1 (AKR1C1) and heme oxygenase-1 (HO-1). Additionally, sulforaphane’s therapeutic window is widened by 12.5µM dtBHQ. Our data suggest that HO generated by dtBHQ oxidation is responsible for these effects, as shown by inclusion of catalase and by co-treatment with sulforaphane and HO. While sulforaphane treatment causes Nrf2 protein to accumulate as expected, interestingly, dtBHQ and HO appear to act on targets downstream of Nrf2 protein accumulation to enhance sulforaphane’s ARE-regulated gene expression. Inclusion of dtBHQ or HO with sulforaphane does not increase Nrf2 protein levels, and catalase has little effect on Nrf2 protein levels in the presence of sulforaphane and dtBHQ. Surprisingly, dtBHQ suppresses Nrf2 protein synthesis. Inclusion of a superoxide dismutase mimetic with sulforaphane and dtBHQ partly rescues Nrf2 suppression and significantly further increases sulforaphane’s efficacy for ARE-reporter expression. Thus, there is a “Dr. Jekyll and Mr. Hyde” effect of ROS: ROS enhance sulforaphane’s ARE-regulated gene expression even as they also inhibit Nrf2 protein synthesis. This unexpected finding reveals the degree to which targets in the ARE pathway downstream of Nrf2 protein accumulation contribute to gene expression. The results presented here provide a model system for significant enhancement of sulforaphane’s potency with small molecule co-treatment.

Intermittent hypoxia (IH)-the hallmark of obstructive sleep apnea (OSA)-increases leukocyte activation, production of NADPH-oxidase dependent reactive oxygen species (ROS) and oxidative stress, affecting endothelial function. However, IH and oxidative stress can also stimulate adaptive-protective mechanisms by inducing the development of Endothelial Cell-Colony Forming Units (EC-CFUs), which are considered as a good surrogate marker for endothelial progenitor cells (EPCs), and likely reflect a reparatory response to vascular damage or tissue ischemia by leukocytes. Blood samples were obtained from 15 healthy consenting volunteers to evaluate the effects of IH and sustained hypoxia (SH) on EC-CFUs development and functions. The variables measured included: their numbers, the area, the proliferative capacity and ROS production. Additionally, NADPH-oxidase, VEGF and nuclear factor-erythroid 2 related factor 2 (Nrf2) expression, as well as their paracrine effects on endothelial tube formation were determined. The involvement of ROS was probed using the anti-oxidant N-acetylcysteine (NAC) and NADPH-oxidase inhibitors apocynin and diphenyl-iodide. Compared to normoxia, IH-dependent increases in EC-CFUs numbers were observed, showing an individual donor-dependent trait. Also, the expression of VEGF and gp91phox, a subunit of NADPH-oxidase, were significantly increased. ROS production and oxidative stress markers were also significantly increased, but Nrf2 expression and colony size were unaffected by IH. Additionally, conditioned media harvested from IH- and SH-treated mature EC-CFUs, significantly increased endothelial tube formation. These effects were markedly attenuated or diminished by the ROS and NADPH-oxidase inhibitors employed. In conclusion, we show here for the first time that IH-associated oxidative stress promotes EC-CFUs’ vascular and paracrine capacities through ROS. However, the large inter-individual variability expressed in EC-CFUs numbers and functions to a given IH stimulus, may represent an individual trait with a potential clinical significance.