Amelioration of nitroglycerin-induced migraine in mice via Wuzhuyu decoction: Inhibition of the MZF1/PGK1 pathway and activation of NRF2 antioxidant response.

ETHNOPHARMACOLOGICAL RELEVANCE: Migraine, a chronic and intricate disorder, manifests as recurrent episodic headaches accompanied by various neurological symptoms. Wuzhuyu Decoction (WZYD) is a traditional Chinese medical formula with promising effects in treating migraines; however, its underlying mechanisms have not yet been clarified. AIM OF STUDY: The study aimed to evaluate WZYD's effectiveness in migraine treatment and investigate the potential mechanism of WZYD's effects on migraine and oxidative stress. MATERIALS AND METHODS: Behavior tests and immunofluorescence assay for the intensity of migraine markers to assess the migraine-relieving effect of WZYD after chronic migraine model induced by nitroglycerin in mice. The impacts of WZYD on oxidative stress-related markers, including reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), nuclear factor erythroid 2-related factor 2 (NRF2), heme oxygenase 1 (HO1), and NAD (P)H quinone oxidoreductase 1 (NQO1) in brain tissue were examined. In addition, protein expression or mRNA levels of the MZF1/PGK1 were detected using Western blot or PCR, respectively. Finally, the MZF1 overexpression vector was constructed to the higher level of MZF1. The MZF1/PGK1 signaling pathway expression was evaluated by markers of oxidative stress including NRF2 and others in this series of experiments. RESULTS: Through murine model experimentation, we observed that WZYD effectively alleviates migraine symptoms, signifying its therapeutic efficacy. Mechanistically, WZYD emerges as a potent activator of the NRF2, acting as a robust defense against oxidative stress. In vitro investigations demonstrated that WZYD combats oxidative stress and curbs cell apoptosis induced by these detrimental conditions. Furthermore, by suppressing the transcriptional expression of PGK1, an influential player in the NRF2 pathway, WZYD effectively activates NRF2 signaling. Intriguingly, we have identified MZF1 as the mediator orchestrating the regulation of the PGK1/NRF2 pathway by WZYD. CONCLUSION: The study confirms the effectiveness of WZYD in alleviating migraine symptoms. Mechanistically, WZYD activated the NRF2 signaling pathway; moreover, the action of WZYD involved the down-regulation of PGK1 mediated by MZF1, which promoted the activation of the NRF2 pathway. This study advances our understanding of the intricate mechanisms driving WZYD's efficacy, paving the way for novel treatments in migraine management.

Isolation and Purification of Harpagogenin as an Nrf2-ARE Activator from the Tubers of Chinese Artichoke (Stachys sieboldii).

Chinese artichoke tuber (Stachys sieboldii Miq.) is used as an herbal medicine as well as edible food. This study examined the effect of the Chinese artichoke extracts on the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway that induces the expression of antioxidant enzymes to explore its novel characteristics. Hot water extracts exhibited relatively high ARE activity. ARE activity was observed in two fractions when the hot water extracts were separated in the presence of trifluoroacetic acid using HPLC. Conversely, the highly active fraction disappeared when the hot water extracts were separated in the absence of trifluoroacetic acid. These results indicate that acidic degradation produces active ingredients. The structural analysis of the two active fractions identified harpagide, which is an iridoid glucoside, and harpagogenin. In vitro experiments revealed that harpagide was converted into harpagogenin under acidic conditions and that harpagogenin, but not harpagide, had potent ARE activity. Therefore, this study identified harpagogenin, which is an acid hydrolysate of harpagide, as an ARE activator and suggests that Nrf2-ARE pathway activation by Chinese artichoke contributes to the antioxidative effect.

Triggers for the Nrf2/ARE Signaling Pathway and Its Nutritional Regulation: Potential Therapeutic Applications of Ulcerative Colitis.

Ulcerative colitis (UC), which affects millions of people worldwide, is characterized by extensive colonic injury involving mucosal and submucosal layers of the colon. Nuclear factor E2-related factor 2 (Nrf2) plays a critical role in cellular protection against oxidant-induced stress. Antioxidant response element (ARE) is the binding site recognized by Nrf2 and leads to the expression of phase II detoxifying enzymes and antioxidant proteins. The Nrf2/ARE system is a key factor for preventing and resolving tissue injury and inflammation in disease conditions such as UC. Researchers have proposed that both Keap1-dependent and Keap1-independent cascades contribute positive effects on activation of the Nrf2/ARE pathway. In this review, we summarize the present knowledge on mechanisms controlling the activation process. We will further review nutritional compounds that can modulate activation of the Nrf2/ARE pathway and may be used as potential therapeutic application of UC. These comprehensive data will help us to better understand the Nrf2/ARE signaling pathway and promote its effective application in response to common diseases induced by oxidative stress and inflammation.

Bach1 derepression is neuroprotective in a mouse model of Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder characterized by the loss of nigrostriatal dopaminergic neurons. Mounting evidence suggests that Nrf2 is a promising target for neuroprotective interventions in PD. However, electrophilic chemical properties of the canonical Nrf2-based drugs cause irreversible alkylation of cysteine residues on cellular proteins resulting in side effects. Bach1 is a known transcriptional repressor of the Nrf2 pathway. We report that Bach1 levels are up-regulated in PD postmortem brains and preclinical models. Bach1 knockout (KO) mice were protected against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic neurotoxicity and associated oxidative damage and neuroinflammation. Functional genomic analysis demonstrated that the neuroprotective effects in Bach1 KO mice was due to up-regulation of Bach1-targeted pathways that are associated with both Nrf2-dependent antioxidant response element (ARE) and Nrf2-independent non-ARE genes. Using a proprietary translational technology platform, a drug library screen identified a substituted benzimidazole as a Bach1 inhibitor that was validated as a nonelectrophile. Oral administration of the Bach1 inhibitor attenuated MPTP neurotoxicity in pre- and posttreatment paradigms. Bach1 inhibitor-induced neuroprotection was associated with the up-regulation of Bach1-targeted pathways in concurrence with the results from Bach1 KO mice. Our results suggest that genetic deletion as well as pharmacologic inhibition of Bach1 by a nonelectrophilic inhibitor is a promising therapeutic approach for PD.

Increasing the Power of Polyphenols through Nanoencapsulation for Adjuvant Therapy against Cardiovascular Diseases.

Polyphenols play a therapeutic role in vascular diseases, acting in inherent illness-associate conditions such as inflammation, diabetes, dyslipidemia, hypertension, and oxidative stress, as demonstrated by clinical trials and epidemiological surveys. The main polyphenol cardioprotective mechanisms rely on increased nitric oxide, decreased asymmetric dimethylarginine levels, upregulation of genes encoding antioxidant enzymes via the Nrf2-ARE pathway and anti-inflammatory action through the redox-sensitive transcription factor NF-κB and PPAR-γ receptor. However, poor polyphenol bioavailability and extensive metabolization restrict their applicability. Polyphenols carried by nanoparticles circumvent these limitations providing controlled release and better solubility, chemical protection, and target achievement. Nano-encapsulate polyphenols loaded in food grade polymers and lipids appear to be safe, gaining resistance in the enteric route for intestinal absorption, in which the mucoadhesiveness ensures their increased uptake, achieving high systemic levels in non-metabolized forms. Nano-capsules confer a gradual release to these compounds, as well as longer half-lives and cell and whole organism permanence, reinforcing their effectiveness, as demonstrated in pre-clinical trials, enabling their application as an adjuvant therapy against cardiovascular diseases. Polyphenol entrapment in nanoparticles should be encouraged in nutraceutical manufacturing for the fortification of foods and beverages. This study discusses pre-clinical trials evaluating how nano-encapsulate polyphenols following oral administration can aid in cardiovascular performance.

Direct and Indirect Antioxidant Effects of Selected Plant Phenolics in Cell-Based Assays.

Background: Oxidative stress is a key factor in the pathophysiology of many diseases. This study aimed to verify the antioxidant activity of selected plant phenolics in cell-based assays and determine their direct or indirect effects. Methods: The cellular antioxidant assay (CAA) assay was employed for direct scavenging assays. In the indirect approach, the influence of each test substance on the gene and protein expression and activity of selected antioxidant enzymes was observed. One assay also dealt with activation of the Nrf2-ARE pathway. The overall effect of each compound was measured using a glucose oxidative stress protection assay. Results: Among the test compounds, acteoside showed the highest direct scavenging activity and no effect on the expression of antioxidant enzymes. It increased only the activity of catalase. Diplacone was less active in direct antioxidant assays but positively affected enzyme expression and catalase activity. Morusin showed no antioxidant activity in the CAA assay. Similarly, pomiferin had only mild antioxidant activity and proved rather cytotoxic. Conclusions: Of the four selected phenolics, only acteoside and diplacone demonstrated antioxidant effects in cell-based assays.

Oat polyphenol avenanthramide-2c confers protection from oxidative stress by regulating the Nrf2-ARE signaling pathway in PC12 cells.

Accumulating evidence has demonstrated that cellular antioxidant systems play essential roles in retarding oxidative stress-related diseases, such as Parkinson's disease. Because nuclear factor erythroid 2-related factor 2 (Nrf2) is a chief regulator of cellular antioxidant systems, small molecules with Nrf2-activating ability may be promising neuroprotective agents. Avenanthramide-2c (Aven-2c), avenanthramide-2f (Aven-2f) and avenanthramide-2p (Aven-2p) are the most abundant avenanthramides in oats, and they have been documented to possess multiple pharmacological benefits. In this work, we synthesized these three compounds and evaluated their cytoprotective effect against oxidative stress-induced PC12 cell injuries. Aven-2c displayed the best protective potency among them. Aven-2c conferred protection on PC12 cells by scavenging free radicals and activating the Nrf2-ARE signaling pathway. Pretreatment of PC12 cells with Aven-2c efficiently enhanced Nrf2 nuclear accumulation and evoked the expression of a set of cytoprotective molecules. The mechanistic study also supports that Nrf2 activation is the molecular basis for the cellular action of Aven-2c. Collectively, this study demonstrates that Aven-2c is a potent Nrf2 agonist, shedding light on the potential usage of Aven-2c in the treatment of neuroprotective diseases.

Dehydroabietic acid improves nonalcoholic fatty liver disease through activating the Keap1/Nrf2-ARE signaling pathway to reduce ferroptosis.

The accumulation of iron-dependent lipid peroxides is one of the important causes of NAFLD. The purpose of this study is to explore the effect of dehydroabietic acid (DA) on ferroptosis in nonalcoholic fatty liver disease (NAFLD) mice and its possible mechanisms. DA improved NAFLD and reduced triglycerides (TG), total cholesterol (TC), and lipid peroxidation level and inhibited ferroptosis in the liver of HFD-induced mice. DA binds with Keap1 to form 3 stable hydrogen bonds at VAL512 and LEU557 and increased nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elemen (ARE) luciferase activity. DA promoted the expression downstream of Nrf2 such as heme oxygenase-1 (HO-1), glutathione (GSH) and its peroxidase 4 (GPX4), so as to eliminate the accumulation of reactive oxygen species (ROS) and reduce lipid peroxides malondialdehyde (MDA) in the liver. DA inhibited ferroptosis and increased the expression of key genes such as ferroptosis suppressor protein 1 (FSP1) in vitro and vivo. In all, DA may bind with Keap1, activate Nrf2-ARE, induce its target gene expression, inhibit ROS accumulation and lipid peroxidation, and reduce HFD-induced NAFLD.

Unfolding Nrf2 in diabetes mellitus.

In spite of much awareness, diabetes mellitus continues to remain one of major reasons for mortality and morbidity rate all over the globe. Free radicals cause oxidative stress which is responsible for causing diabetes. The recent advancements in elucidation of ARE/keap1/Nrf2 pathway can help in better understanding of diabetes mellitus. Various clinical trials and animal studies have shown the promising effect of Nrf2 pathway in reversing diabetes by counteracting with the oxidative stress produced. The gene is known to dissociate from Keap1 on coming in contact with such stresses to show preventive and prognosis effect. The Nrf2 gene has been marked as a molecular player in dealing with wide intracellular as well as extracellular cellular interactions in different diseases. The regulation of this gene gives some transcription factor that contain antioxidant response elements (ARE) in their promoter region and thus are responsible for encoding certain proteins involved in regulation of metabolic and detoxifying enzymes.

Astragaloside IV, a saponin from Astragalus membranaceus var. mongholicus, induces expressions of heme recycle proteins via signaling of Nrf2/ARE in cultured macrophages.

ETHNOPHARMACOLOGICAL RELEVANCE: In traditional Chinese medicine (TCM) theory, "Qi" is classified as energetic essence supporting the life activities in human. "Blood" is categorized as nourishing essence and circulating in the body. "Blood" and "Qi" have an intimate relationship. Astragali Radix (AR; root of Astragalus membranaceus (Fisch.) Bge. Var. mongholicus (Bge.) Hsiao) has a broad spectrum of application for "Qi-Blood" enrichment. Astragaloside IV, a major saponin in AR, has therapeutic functions in erythropoietic, cardiovascular and immune systems. However, the efficacy of astragaloside IV in erythrophagocytosis has not been elucidated. AIM OF THE STUDY: The possible functions of astragaloside IV in heme iron recycling during erythrophagocytosis in cultured macrophage were elucidated. METHODS: The translational and transcriptional expressions of heme recycling enzymes were determined after incubating of astragaloside IV for 24 h in cultured macrophage. RESULTS: In astragaloside IV-treated macrophage, the expressions, both RNA and protein levels, of regulators of heme recycling, e.g. heme oxygenase-1 (HO-1), ferroportin (FPN), biliverdin reductase A and B (BVRA, BVRB), were markedly induced in dose-dependent manners. In parallel, the transcriptional activity of antioxidant response element, cloned within an expression vector as pARE-Luc and transfected in cultured macrophages, was markedly induced after a challenge with astragaloside IV in a dose-dependent manner. Moreover, the translocation of Nrf2, a transcriptional factor in regulating expression of heme recycling protein, was induced by astragaloside IV, leading to an enrichment at nucleus fraction. CONCLUSION: Astragaloside IV shed lights in enhancing the expression of heme recycle proteins via Nrf2/ARE signaling pathway.

Potential neuroprotection of wheat alkylresorcinols in hippocampal neurons via Nrf2/ARE pathway.

5-n-Alkylresorcinols (ARs) are abundant in wheat bran and potentially antioxidative, although the neuroprotective mechanism is not fully understood. The neuroprotective effect of wheat bran ARs on H2O2-induced neuronal cells and the relationship between neuroprotection and the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant-response element (ARE) pathway were investigated in this study. Seven homologs were identified in the purified ARs by high-performance liquid chromatography-tandem mass spectrometry. Pretreatment with 80 µg mL-1 ARs alleviated 23% HT22 cell death and the up-regulation of intracellular reactive oxygen species level and malondialdehyde under H2O2 stimulation. The neuroprotection effect was proved by the increase in the Nrf2 nuclear location and up-regulation of mRNA and protein expressions of heme oxygenase-1, NAD(P)H quinone dehydrogenase 1, glutamate-cysteine ligase catalytic subunit, and glutamate-cysteine ligase modifier subunit l. Wheat bran ARs displayed a neuroprotective function, possibly by promoting the endogenous antioxidant defense system. ARs may be regarded as a functional food ingredient for preventing neurodegenerative diseases in the future.

Attenuation of Nrf2/Keap1/ARE in Alzheimer's Disease by Plant Secondary Metabolites: A Mechanistic Review.

Alzheimer's disease (AD) is a progressive neuronal/cognitional dysfunction, leading to disability and death. Despite advances in revealing the pathophysiological mechanisms behind AD, no effective treatment has yet been provided. It urges the need for finding novel multi-target agents in combating the complex dysregulated mechanisms in AD. Amongst the dysregulated pathophysiological pathways in AD, oxidative stress seems to play a critical role in the pathogenesis progression of AD, with a dominant role of nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein-1 (Keap1)/antioxidant responsive elements (ARE) pathway. In the present study, a comprehensive review was conducted using the existing electronic databases, including PubMed, Medline, Web of Science, and Scopus, as well as related articles in the field. Nrf2/Keap1/ARE has shown to be the upstream orchestrate of oxidative pathways, which also ameliorates various inflammatory and apoptotic pathways. So, developing multi-target agents with higher efficacy and lower side effects could pave the road in the prevention/management of AD. The plant kingdom is now a great source of natural secondary metabolites in targeting Nrf2/Keap1/ARE. Among natural entities, phenolic compounds, alkaloids, terpene/terpenoids, carotenoids, sulfur-compounds, as well as some other miscellaneous plant-derived compounds have shown promising future accordingly. Prevailing evidence has shown that activating Nrf2/ARE and downstream antioxidant enzymes, as well as inhibiting Keap1 could play hopeful roles in overcoming AD. The current review highlights the neuroprotective effects of plant secondary metabolites through targeting Nrf2/Keap1/ARE and downstream interconnected mediators in combating AD.

Chemical Space Charting of Different Parts of Inula nervosa Wall.: Upregulation of Expression of Nrf2 and Correlated Antioxidants Enzymes.

The edible and medicinal part of Inula nervosa Wall. (Xiaoheiyao) is confined to its root without sufficient phytochemical and biological investigation. In this study, the secondary metabolites of root, stem, leaf, and flower of I. nervosa Wall. were visualized using Global Natural Products Social Molecular Networking (GNPS), MolNetEnhancer, XCMS(xcmsonline.scripps.edu) analysis, and `ili mapping based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) data to reveal their chemical differences. Among the 11 kinds of chemical repertoires annotated by MolNetEnhancer and 16 hits against the GNPS library, 10-isobutyryloxy-8,9-epoxythymol isobutyrate (1) was revealed as the most dominant and responsible marker between the roots and the other parts. Moreover, a battery of unique MS features as well as differential markers were discovered from different parts of the plant. The chemical differences contribute to the bioactivity differences, which presented in the 2,2-diphenyl-1-picryl-hydrazyl (DPPH)assay and H2O2-insulted HepG2 cells and were in significant correlations with the contents of 1. real-time reverse transcription polymerase chain reaction (RT-PCR)results demonstrated that I. nervosa Wall. extracts upregulated the mRNA expression of nuclear factor E2-related factor 2(Nrf2), heme oxygenase 1(HO-1), NAD(P)H quinone dehydrogenase 1 (NQO1), manganese superoxide dismutase (MnSOD), and glutamate-cysteine ligase catalytic subunit (GCLC) actors involved in antioxidative response in H2O2-challenged HepG2 cells. These findings support the roots of I. nervosa Wall. as active parts of Xiaoheiyao, and also indicate the potential antioxidant activities of other parts.

[Effect and mechanism of moxibustion on oxidative stress injury in rats with Parkinson's disease by activating Nrf2/ARE pathway].

OBJECTIVE: To observe the effect of moxibustion on oxidative stress injury of nigrostriatal system in rats with Parkinson's disease (PD) based on nuclear factor erythroid 2-related factor (Nrf2)/antioxidant response element (ARE) pathway, and to explore its mechanism. METHODS: A total of 48 SD rats were randomized into a blank group, a sham-operation group, a model group and a moxibustion group, 12 rats in each group. Unilateral two-point injection with 6-hydroxydopamine (6-OHDA) was adopted in the model group and the moxibustion group to establish the PD model; the operation manipulation in the sham-operation group was the same as the model group and the moxibustion group, and the same volume of 0.9% sodium chloride solutions was given by unilateral two-point injection. Moxibustion was adopted at "Baihui" (GV 20) and "Sishencong" (EX-HN 1) in the moxibustion group for 20 min, once a day, 6 times a week for 6 weeks. No intervention was given in the other 3 groups. Morphology of right mesencephalon substantia nigra was observed by HE staining, the expression of tyrosine hydroxylase (TH) in right mesencephalon substantia nigra was detected by immunohistochemistry method, the expression of reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), and glutathione peroxidase (GSH-Px) in corpus striatum was detected by colorimetry method, and the expression of Nrf2 and heme oxygenase-1 (HO-1) proteins was detected by Western blot in the 4 groups. RESULTS: Clear tissue structure and complete dopaminergic neurons of right mesencephalon substantia nigra were observed in the blank group and the sham-operation group; unclear tissue structure, decreased and swelling dopaminergic neurons were observed in the model group; compared with the model group, more neurons were observed and the swelling of cyton was reduced in the moxibustion group. Compared with the sham-operation group, the expression of TH in right mesencephalon substantia nigra was decreased in the model group (P<0.01); compared with the model group, the expression of TH in right mesencephalon substantia nigra was increased in the moxibustion group (P<0.05). Compared with the sham-operation group, the expression of ROS, MDA was increased (P<0.01), the expression of GSH, GSH-Px, Nrf2 and HO-1 was decreased in the model group (P<0.01, P<0.05); compared with the model group, the expression of ROS, MDA was decreased (P<0.05, P<0.01), the expression of GSH, GSH-Px, Nrf2 and HO-1 was increased in the moxibustion group (P<0.05, P<0.01). CONCLUSION: Moxibustion can alleviate oxidative stress injury of nigrostriatal system in rats with Parkinson's disease by activating the Nrf2/ARE pathway, and protect the dopamine neurons.

Bioassay-Guided Separation of Centipeda minima Using Comprehensive Linear Gradient Centrifugal Partition Chromatography.

A comprehensive linear gradient solvent system for centrifugal partition chromatography (CPC) was developed for the bioassay-guided isolation of natural compounds. The gradient solvent system consisted of three different ternary biphasic solvents types: n-hexane-acetonitrile-water (10:2:8, v/v), ethyl acetate-acetonitrile-water (10:2:8, v/v), and water-saturated n-butanol-acetonitrile-water (10:2:8, v/v). The lower phase of the n-hexane-acetonitrile-water (10:2:8, v/v) was used as the stationary phase, while its upper phase, as well as ethyl acetate-acetonitrile-water (10:2:8), and water-saturated n-butanol-acetonitrile-water (10:2:8, v/v) were pumped to generate a linear gradient elution, increasing the mobile phase polarity. We used the gradient CPC to identify antioxidant response elements (AREs), inducing compounds from Centipeda minima, using an ARE-luciferase assay in HepG2 cells, which led to the purification of the active molecules 3-methoxyquercetin and brevilin A. The developed CPC solvent systems allow the separation and isolation of compounds with a wide polarity range, allowing active molecule identification in the complex crude extract of natural products.

Antifatigue effects of anshenyizhi compound in acute excise-treated mouse via modulation of AMPK/PGC-1α-related energy metabolism and Nrf2/ARE-mediated oxidative stress.

The anshenyizhi compound (AC), a mixture from Chinese medicine herbs, has numerous biological effects. In the present study, the acute exercise-treated mice model was established to explore the antifatigue properties of AC and its underlying mechanisms. AC increased exercise endurance in the weight-loaded forced swimming test and rota-rod test. The antifatigue properties of AC were closely correlated with enhancing the body's exercise endurance by increasing the levels of cyanmethemoglobin, testosterone/corticosterone, and creatine kinase, while decreasing the levels of lactic acid, lactate dehydrogenase, and blood urea nitrogen in serum. Moreover, our results confirmed the antioxidant ability of AC by improving the activities of superoxide dismutase while reducing reactive oxygen species and malondialdehyde levels in serum. The AC also improved the storage of glycogen by increasing the levels of succinate dehydrogenase, and malate dehydrogenase in liver and muscle. Additionally, AC displayed the antifatigue and antiapoptosis effects via regulating Nrf2-mediated oxidative stress, AMPK-related glucose metabolism, and p53 pathways. Our experimental results first provided a support that AC had effects on antifatigue through regulating AMPK/PGC-1α-related energy metabolism and Nrf2/ARE-mediated oxidative stress. Consequently, AC could be developed into a new functional food supplement for the prevention and treatment of diseases related to fatigue in the future.

Luteolin prevents liver from tunicamycin-induced endoplasmic reticulum stress via nuclear factor erythroid 2-related factor 2-dependent sestrin 2 induction.

Endoplasmic reticulum (ER) stress designates a cellular response to the accumulation of misfolded proteins, which is related to disease progression in the liver. Luteolin (3',4',5,7-tetrahydroxyflavone) is a phytochemical found frequently in medicinal herbs. Although luteolin has been reported to possess the therapeutic potential to prevent diverse stage of liver diseases, its role in hepatic ER stress has not been established. Thus, the present study aimed to determine the role of luteolin in tunicamycin (Tm)-induced ER stress, and to identify the relevant mechanisms involved in its hepatoprotective effects. In hepatocyte-derived cells and primary hepatocytes, luteolin significantly decreased Tm- or thapsigargin-mediated C/EBP homologous protein (CHOP) expression. In addition, luteolin reduced the activation of three canonical signaling pathways related to the unfolded protein response, and decreased mRNA levels of glucose-regulated protein 78, ER DNA J domain-containing protein 4, and asparagine synthetase. Luteolin also significantly upregulated sestrin 2 (SESN2), and luteolin-mediated CHOP inhibition was blocked in SESN2 (+/-) cells. Moreover, luteolin resulted in phosphorylation of nuclear factor erythroid 2-related factor 2 (Nrf2), as well as increased nuclear Nrf2 expression. Deletion of the antioxidant response element in the human SESN2 promoter inhibited increased luciferase activation by luteolin, suggesting that Nrf2 is a critical transcription factor for luteolin-dependent SESN2 expression. In a Tm-mediated liver injury model, luteolin decreased serum alanine aminotransferase and aspartate aminotransferase activities, prevented degenerative changes and apoptosis of hepatocytes, and inhibited CHOP and glucose-regulated protein 78 expression in hepatic tissues. Therefore, luteolin may be an effective phytochemical to manage ER stress-related liver injury.

α-Sens: The improved ARE-Nrf2-based sensitization screening assay using normalized transcriptional activity.

Two non-animal test methods, KeratinoSens™ and LuSens, have been approved by the Organization of Economic Cooperation and Development (OECD) test guidelines for evaluating the sensitization potential of chemicals, and been positioned as a method for appraising key event (KE)-2, namely, the keratinocyte response component of the Adverse Outcome Pathway (AOP) in sensitization process. However, these two methods require separate cytotoxicity tests to determine the concentrations to be tested in the main test. Therefore, we developed a simple and highly accurate KE-2 test method named α-Sens that uses the dual luciferase assay system and attempted a further application of luciferase-based determination of cell viability to calculate the normalized Antioxidant response element (ARE)-mediated transcriptional activity, named normalized ARE Activity (nAA), to evaluate the sensitizing potential of chemicals. A cell line carrying the ARE-inducible Firefly luciferase reporter gene and Thymidine kinase (TK) promoter-driven Renilla luciferase gene was established and used for the α-Sens. A total of 28 chemicals, consisting of 19 skin sensitizers and nine non-skin sensitizers were tested by this assay system. The α-Sens yielded an accuracy (%), sensitivity (%), and specificity (%) against corresponding values for local lymph node assay of 96.4 %, 95.0 %, and 100 %, respectively, and for human data of 100 % for all. The α-Sens gave clear positive results for phenyl benzoate and eugenol, chemicals for which KeratinoSens™ or LuSens yielded false-negative results, using a new parameter. Our results suggest that better prediction capacity could be achieved by using nAA as a classifier compared to other existing KE-2 test methods. In conclusion, the α-Sens is promising as a simple and highly accurate in vitro skin sensitization test method for evaluation of KE-2.

Nrf2/ARE pathway activation is involved in negatively regulating heat-induced apoptosis in non-small cell lung cancer cells.

Hyperthermia, particularly in combination with chemoradiotherapy, is widely used to treat various cancers. However, hyperthermia treatment is often insufficient due to thermo-tolerance. To date, the detailed mechanism underlying thermo-tolerance has not been clarified. The nuclear factor erythroid 2-related factor 2 (Nrf2)/ antioxidant response element (ARE) pathway is an important cellular cytoprotective defense system that is activated by various stresses. In this study, using immunocytochemistry and western blot analysis, we demonstrated that heat stress induced Nrf2/ARE activation through the nuclear translocation of Nrf2 in non-small cell lung cancer cells. Luciferase activity was also increased. Additionally, antioxidant enzymes were increased through Nrf2 activation after heat stress. Transfection of lung cancer cells with siRNA directed against Nrf2 increased heat cytotoxicity and cell apoptosis. Heat stress could induce reactive oxygen species (ROS) accumulation, while the antioxidant NAC obviously reduced cell apoptosis ratio, indicating that heat stress induced cell apoptosis in a ROS-dependent manner. Knockdown of Nrf2 led to an abnormal elevation of ROS, and the antioxidant NAC could increase Nrf2 activation, indicating that ROS and Nrf2 act within a negative feedback loop. Taken together, these results demonstrated that Nrf2 pathway is important for maintaining resistance to heat stress, and we postulated that Nrf2 may represent a potential therapeutic target for hyperthermia in lung cancer.

Obesity and NRF2-mediated cytoprotection: Where is the missing link?

The expanding dimensions of the global health crisis of overweight population has defined the term "globesity". Among the most common pathological conditions connected with excessive adiposity are hyperglycemia, insulin resistance, dyslipidemia and hypertension which result in chronic non-communicable diseases (NCD) such as metabolic syndrome (MetS), type 2 diabetes (T2D), and nonalchoholic steatohepatitis (NASH). The contribution of inflammatory-immune reactions in obesity and its related co-morbidities is unequivocal. Increased levels of free fatty acids (FFA), reactive oxygen species (ROS) and reactive nitrogen species (RNS) overloads the homeostatic system resulting in pro-inflammatory adipokines secretion, immune-activation and chronic inflammation in obesity. The cellular mechanisms of defense against oxidative stress are orchestrated by the transcription factor nuclear factor erythroid 2 p45-related factor 2 (NRF2). Excessive oxidative stress in the cell activates NRF2 which upregulates genes encoding major cytoprotective enzymes such as NAD(P)H:quinone oxidoreductase 1 (NQO1), heme oxygenase 1 (HO1), and glutathione S-transferases (GST). The present review aims to clarify the interconnections between chronic inflammation, oxidative overload and NRF2-mediated cytoprotection as potential therapeutic approach in obesity.