Tussilagonone-induced Nrf2 pathway activation protects HepG2 cells from oxidative injury

Composition of Polygonatum zanlanscianense Pamp. Steam and Leaf Phenolic Extract and Its Protective Mechanism on t-BHP-Induced Oxidative Damage of HepG2 Cells

Plant phenolic compounds have attracted considerable attention because of their health benefits. This study aimed to investigate the composition and antioxidant activity of phenol extracts from Polygonatum zanlanscianense Pamp. steam and leaf (PPP). The FTIR, UPLC-Q-Obtrip-MS, and HPLC-DAD methods were used to analyze the composition of PPP, and 20 phenolic compounds were preliminarily identified. Among them, the contents of hyperin, astragalin, and diosmetin levels were the highest. Treatment with PPP can significantly reduce t-BHP-induced cell damage in HepG2 cells, reactive oxygen species (ROS) accumulation, and malondialdehyde (MDA) content. Meanwhile, the superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione peroxidase (GSH-Px) activities can be increased. Moreover, PPP enhanced Nrf2 expression, which was consistent with that of heme oxygenase-1 (HO-1), glutamate-cysteine ligase catalytic subunit (GCLC), and NAD(P)H quinone oxidoreductase-1 (NQO1), whereas the expression of Keap1, the Nrf2 inhibitor, was decreased. All findings indicate that PPP can serve as a natural bioactive substance for preventing oxidative stress.

Surfactant-Mediated Ultrasonic-Assisted Extraction and Purification of Antioxidants from Chaenomeles speciosa (Sweet) Nakai for Chemical- and Cell-Based Antioxidant Capacity Evaluation

In this study, a surfactant-mediated ultrasonic-assisted process was used for the first time to produce an antioxidant-enriched extract from Chaenomeles speciosa (Sweet) Nakai (C. speciosa, a popular fruit grown widely in the temperate regions of China). Ultrasonic treatment at 51 °C and 200 W for 30 min with sodium dodecyl sulfate as the surfactant led to a phenolic yield of 32.42 mg/g from dried C. speciosa powder, based on single-factor experiments, the Plackett-Burman design and the Box-Behnken design. The phenolic content increased from 6.5% (the crude extract) to 57% (the purified extract) after the purification, using LSA-900C macroporous resin. Both the crude and purified extracts exhibited a significant total reducing power and DPPH/ABTS scavenging abilities, with the purified extract being more potent. The purified extract exerted significant antioxidant actions in the tert-butyl hydroperoxide-stimulated HepG2 cells, e.g., increasing the activities of superoxide dismutase and catalase, while decreasing the reactive oxygen species and malondialdehyde levels, through the regulation of the genes and proteins of the Nrf2/Keap1 signaling pathway. Therefore, the extract from C. speciosa is a desirable antioxidant agent for the oxidative damage of the body to meet the rising demand for natural therapeutics.

The ethanol extract of flower buds of Tussilago farfara L. attenuates cigarette smoke-induced lung inflammation through regulating NLRP3 inflammasome, Nrf2, and NF-κB

ETHNOPHARMACOLOGICAL RELEVANCE

The flower buds of Tussilago farfara L. (Abbreviated as FTF) were widely used in traditional Chinese medicine (TCM) to treat respiratory diseases, including asthma, dry throat, great thirst, turbid saliva, stinky pus, and coughs caused by various causes.

AIM OF STUDY

The aim of study is to explore the efficiency of FTF in vitro and in vivo for the treatment of lung inflammation, and to illustrate the possible mechanisms of FTF in treating inflammation-related respiratory diseases targeting NOD-like receptor 3 (NLRP3) inflammasome, nuclear factor erythroid 2-related factor 2 (Nrf2), and nuclear transcription factor-κB (NF-κB).

METHODS

Lung inflammation model in vivo was induced by exposure of mice to cigarette smoke (CS) for two weeks. The levels of superoxide dismutase (SOD), malondialdehyde (MDA), inflammatory factors, and histology in lung tissues were investigated in presence or absence of ethanol extract of the flower buds of T. farfara L. (FTF-EtOH). In the cell-based models, nitric oxide (NO) assay, flow cytometry assay, enzyme-linked immunosorbent assay (Elisa), and glutathione (GSH) assay were used to explore the anti-inflammatory and anti-oxidant effects of FTF-EtOH. Possible anti-inflammatory mechanisms of FTF targeting NLRP3 inflammasome, Nrf2, and NF-κB have been determined using western blot, quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR), immunofluorescence assay, nuclear and cytoplasmic extraction, and ubiqutination assay.

RESULTS

FTF-EtOH suppressed CS-induced overproduction of inflammatory factors [e.g., tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β)], and upregulation of the content of intracellular MDA in the lung homogenate of mice. In cell-based models, FTF-EtOH reduced the lipopolysaccharide (LPS)-induced overproduction of inflammatory factors, and attenuated the CS extract-induced overgeneration of reactive oxygen species (ROS). Furthermore, FTF-EtOH up-regulated Nrf2 and its downstream genes through enhancing the stability of Nrf2 protein, and inhibited the activation of NF-κB and NLRP3 inflammasome, which have been confirmed by detecting the protein levels in the mouse model.

CONCLUSIONS

FTF-EtOH effectively attenuated lung inflammation in vitro and in vivo. The protection of FTF-EtOH against inflammation was produced by activation of Nrf2 and inhibitions of NF-κB and NLRP3 inflammasome. These datas definitely support the ethnopharmacological use of FTF as an anti-inflammatory drug for treating respiratory diseases in TCM.

Generation of potent Nrf2 activators via tuning the electrophilicity and steric hindrance of vinyl sulfones for neuroprotection

Oxidative stress is constantly involved in the etiopathogenesis of an ever-widening range of neurodegenerative diseases. As a consequence, effective repression of cellular oxidative stress to a redox homeostatic condition is a promising and feasible strategy to treat, or at least retard the progression of, such disorders. Nrf2, a primary orchestrator of cellular antioxidant response machine, is responsible for detoxifying and compensating for deleterious oxidative stress via transcriptional activation of a diverse array of antioxidant biomolecules. In the framework of our persistent interest in disclosing small molecules that interfere with cellular redox-regulating machinery, we report herein the synthesis, optimization, and biological assessment of 47 vinyl sulfone scaffold-bearing small molecules, most of which exhibit robust neuroprotective effect against H₂O₂-mediated lesions to PC12 cells. After initial screening, the most potent neuroprotective compounds 9b and 9c with marginal cytotoxicity were selected for the follow-up studies. Our results demonstrate that their neuroprotective effects are attributed to the up-regulation of a panel of antioxidant genes and corresponding gene products. Further mechanistic studies indicate that Nrf2 is indispensable for the cellular performances of 9b and 9c, arising from the fact that silence of Nrf2 gene drastically nullifies their protective action. Taken together, 9b and 9c discovered in this work merit further development as neuroprotective candidates for the treatment of oxidative stress-mediated pathological conditions.

Protective effect of coumarin-pi against t-BHP-induced hepatotoxicity by upregulating antioxidant enzymes via enhanced Nrf2 signaling

Coumarin-pi, a new coumarin derivative isolated from the mushroom Paxillus involutus, has antioxidative activity, but the underlying mechanism against intracellular oxidative stress is still unclear. This study investigated its cytoprotective effects and the antioxidative mechanism in tert-butyl hydroperoxide (t-BHP)-induced HepG2 cells. The results demonstrated that coumarin-pi suppressed t-BHP-stimulated cytotoxicity, cell apoptosis, and generation of reactive oxygen species (ROS). Additionally, coumarin-pi promoted nuclear factor erythroid 2-related factor 2 (Nrf2) expression and upregulated the protein expression of antioxidantenzymes, including heme oxygenase-1 (HO-1), NAD(P)H: quinone oxidase (NQO1), glutamyl cysteine ligase catalytic subunit (GCLC), and glutamate-cysteine ligase regulatory subunit (GCLM). After coumarin-pi treatment, transcriptome sequencing and bioinformatic analysis revealed that 256 genes were differentially expressed; interestingly, only 20 genes were downregulated, and the rest of the genes were upregulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional annotation were used to identify changes in metabolic pathways. Collectively, the results presented in this study indicate that coumarin-pi has a protective effect against t-BHP-induced cellular damage and oxidative stress.

A Sesquiterpenoid from Farfarae Flos Induces Apoptosis of MDA-MB-231 Human Breast Cancer Cells through Inhibition of JAK-STAT3 Signaling

Triple-negative breast cancers (TNBCs) are hard-to-treat breast tumors with poor prognosis, which need to be treated by chemotherapy. Signal transducer and activator of transcription 3 (STAT3) is a transcription factor involved in proliferation, metastasis, and invasion of cancer cells. Therefore, research on searching for promising compounds with metabolism that suppress phosphorylation or transcription of STAT3 in TNBC cells is important. Farfarae Flos is well known as a traditional medicine for treating inflammation. However, few studies have shown that sesquiterpenoids from Farfarae Flos have an anticancer effect. In this study, efficient separation methods and an MTT assay were conducted to isolate an anticancer compound from Farfarae Flos against TNBC MDA-MB-231 cells. Here, 7β-(3-Ethyl-cis-crotonoyloxy)-1α-(2-methylbutyryloxy)-3,14-dehydro-Z-notonipetranone (ECN), a compound isolated from Farfarae Flos showed a potent cytotoxic effect on MDA-MB-231 cells. ECN inhibited JAK–STAT3 signaling and suppressed the expression of STAT3 target genes. In addition, ECN induced apoptosis through both extrinsic and intrinsic pathways. Furthermore, we investigated that ECN inhibited the growth of tumors by intraperitoneal administration in mice injected with MDA-MB-231 cells. Therefore, ECN can be an effective chemotherapeutic agent for breast cancer treatment.

Physalin A regulates the Nrf2 pathway through ERK and p38 for induction of detoxifying enzymes

Background

Physalin A isolated from Physalis alkekengi var. franchetii has been known to have many pharmacological properties. However, its effect through the Nrf2 pathway has not yet been elucidated. In the present study, we determined the effects of physalin A on cancer chemoprevention via the Nrf2 pathway.

Methods

Experiments were performed in Hepa-1c1c7 and HepG2 cells. The quinone reductase (QR) activity assay was used to assess the activity of physalin A and other compounds isolated from P. alkekengi. The antioxidant response element (ARE) reporter assay was used to determine physalin A induced transcription of Nrf2 target genes, whereas the oligonucleotide pull-down assay was used to investigate Nrf2 binding to the AREs post physalin A treatment. Real-time PCR and western blotting were performed to determine the expression of Nrf2 target genes. Immunocytochemistry was used to determine Nrf2 localization after treatment with physalin A. Kinase inhibitors were used to test the involvement of Nrf2-targeting kinases and the role of ERK and p38 phosphorylation was confirmed using western blotting.

Results

Physalin A significantly induced QR activity. As an upstream effector of QR, Nrf2 induced genes containing the ARE, which encode various antioxidants and detoxification enzymes. We observed that physalin A increased the expression of Nrf2 and its target genes in HepG2 cells. Moreover, we observed that physalin A-induced Nrf2 activation was regulated by ERK and p38 kinase in HepG2 cells.

Conclusions

Taken together, we showed that physalin A increased detoxifying enzyme expression via activation of Nrf2 and its target genes. These results imply that physalin A could be a potential chemopreventive agent for liver diseases, as well as cancer.

Neuroprotection against 6-OHDA toxicity in PC12 cells and mice through the Nrf2 pathway by a sesquiterpenoid from Tussilago farfara

Oxidative stress plays a key role in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Therefore, the nuclear factor-E2-related factor 2 (Nrf2), a key regulator of the antioxidative response, is considered to be important as a therapeutic target for neurodegenerative diseases. We investigated the underlying mechanism of Nrf2-mediated neuroprotective effects against oxidative stress in the PC12 cell line by 7β-(3-ethyl-cis-crotonoyloxy)-1α-(2-methylbutyryloxy)-3,14-dehydro-Z-notonipetranone (ECN), one of the sesquiterpenoids in Farfarae Flos. Pretreatment of PC12 cells with ECN had a protective effect against hydrogen peroxide (H₂O₂)- or 6-hydroxydopamine (6-OHDA)-induced cytotoxicity. ECN upregulated the ARE-luciferase activity and induced the mRNA expression of Nrf2 and antioxidant enzyme heme oxygenase-1 (HO-1). Knockdown of Nrf2 by small, interfering RNA (siRNA) abrogated the upregulation of HO-1, indicating that ECN had induced HO-1 via the Nrf2 pathway. Pretreatment with the thiol reducing agents, N-acetylcysteine (NAC) or dithiothreitol (DTT), attenuated Nrf2 activation and HO-1 expression. However, the non-thiol reducing antioxidant, Trolox, failed to inhibit HO-1 induction by ECN. These results suggest that ECN may directly interact with Kelch-like ECH-associated protein 1 (Keap1) and modify critical cysteine thiols present in the proteins responsible for Nrf2-mediated upregulation of HO-1. In a 6-OHDA-induced mouse model of PD, administration of ECN ameliorated motor impairments and dopaminergic neuronal damage. Taken together, ECN exerts neuroprotective effects by activating the Nrf2/HO-1 signaling pathway in both PC12 cells and mice. Thus, ECN, as an Nrf2 activator, could be an attractive therapeutic candidate for the neuroprotection or treatment of neurodegenerative diseases.

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ECN protects PC12 cells against H₂O₂- or 6-OHDA-induced cell damage.

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ECN increases HO-1 expression via the nuclear translocation and ARE binding of Nrf2.

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Activation of the Nrf2/HO-1 pathway contributes to the protective properties of ECN.

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ECN ameliorates 6-OHDA-induced motor impairments in mice.

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ECN prevents 6-OHDA-induced loss of dopaminergic neurons in the mouse brain.