A Curcumin Derivative That Inhibits Vinyl Carbamate-Induced Lung Carcinogenesis via Activation of the Nrf2 Protective Response

Carbamate compounds induced toxic effects by affecting Nrf2 signaling pathways

Carbamate (CBs) is a class of insecticides which is being known as an important cause of intentional or accidental poisoning. CBs, cause carbamylation of acetylcholinesterase at neuronal synapses and neuromuscular junction. Exposure to CBs through skin contact, inhalation, or ingestion can result in significant cholinergic toxicity. This is due to the elevation of acetylcholine levels at ganglionic synapses found in both the sympathetic and parasympathetic nervous systems, as well as muscarinic receptors located in target organs of the parasympathetic nervous system, nicotinic receptors situated in skeletal muscle tissue, and the central nervous system. The association between human illnesses and environmental exposures to CBs have been extensively studied in several studies. Although CBs-triggered toxicity leads to overproduction of reactive oxygen species (ROS), the detailed association between the toxicity under CBs exposure and NFE2-related factor 2 (Nrf2) signaling pathways has not been completely clarified. In this review we aimed to summarize the latest findings on the functional interrelationship between carbamates compounds and Nrf2 signaling.

Promotion of transcription factor EB-dependent autophagic process by curcumin alleviates arsenic-caused lung oxidative stress and inflammation in mice

Arsenic is a human carcinogen widely distributed in the environment, and arsenic exposure from drinking water has received widespread attention as a global public health problem. Curcumin is a natural bioactive substance with high efficiency and low toxicity extracted from turmeric, which has a variety of biological properties such as antioxidation, anti-inflammation, anticancer, and immuno-modulatory activities. Curcumin is widely used in daily life as a food additive and dietary supplement. However, its protective effects in lung injuries by chronic arsenic exposure orally remain unexplored. In this study, curcumin treatment not only significantly accelerated arsenic elimination and improved lung tissue morphology, but also decreased arsenic-generated ROS by activating Nrf2 and its down-stream antioxidants. Further, curcumin alleviated inflammatory changes in mice exposed to arsenic for 6 and 12 weeks, as manifested by lung MPO levels, total protein and cellular levels in bronchoalveolar lavage fluid (BALF), serum IL-4 levels, and MAPK/NF-κB expression in lung tissue. Notably, our study also confirmed that curcumin could promote the expression and nuclear translocation of the transcription factor EB (TFEB), as well as activate TFEB-regulated autophagy in lung tissue of arsenic-treated mice, accompanied by inhibition of the AKT-mTOR signaling pathway. Overall, our study here suggests that natural bioactive compound curcumin could alleviate arsenic-induced pulmonary oxidative stress and inflammation in vivo, which is closely related to enhanced TFEB activity and induction of the autophagic process.

Unleashing the Potential of Nrf2: A Novel Therapeutic Target for Pulmonary Vascular Remodeling

Pulmonary vascular remodeling, characterized by the thickening of all three layers of the blood vessel wall, plays a central role in the pathogenesis of pulmonary hypertension (PH). Despite the approval of several drugs for PH treatment, their long-term therapeutic effect remains unsatisfactory, as they mainly focus on vasodilation rather than addressing vascular remodeling. Therefore, there is an urgent need for novel therapeutic targets in the treatment of PH. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a vital transcription factor that regulates endogenous antioxidant defense and emerges as a novel regulator of pulmonary vascular remodeling. Growing evidence has suggested an involvement of Nrf2 and its downstream transcriptional target in the process of pulmonary vascular remodeling. Pharmacologically targeting Nrf2 has demonstrated beneficial effects in various diseases, and several Nrf2 inducers are currently undergoing clinical trials. However, the exact potential and mechanism of Nrf2 as a therapeutic target in PH remain unknown. Thus, this review article aims to comprehensively explore the role and mechanism of Nrf2 in pulmonary vascular remodeling associated with PH. Additionally, we provide a summary of Nrf2 inducers that have shown therapeutic potential in addressing the underlying vascular remodeling processes in PH. Although Nrf2-related therapies hold great promise, further research is necessary before their clinical implementation can be fully realized.

Electrophile versus oxidant modification of cysteine residues: Kinetics as a key driver of protein modification

Humans have widespread exposure to both oxidants, and soft electrophilic compounds such as alpha,beta-unsaturated aldehydes and quinones. Electrophilic motifs are commonly found in a drugs, industrial chemicals, pollutants and are also generated via oxidant-mediated degradation of biomolecules including lipids (e.g. formation of 4-hydroxynonenal, 4-hydroxyhexenal, prostaglandin J2). All of these classes of compounds react efficiently with Cys residues, and the particularly the thiolate anion, with this resulting in Cys modification via either oxidation or adduct formation. This can result in deleterious or beneficial effects, that are either reversible (e.g. in cell signalling) or irreversible (damaging). For example, acrolein is a well-established toxin, whereas dimethylfumarate is used in the treatment of multiple sclerosis and psoriasis. This short review discusses the targets of alpha,beta-unsaturated aldehydes, and particularly two prototypic cases, acrolein and dimethylfumarate, and the factors that control the selectivity and kinetics of reaction of these species. Comparison is made between the reactivity of oxidants versus soft electrophiles. These rate constants indicate that electrophiles can be significant thiol modifying agents in some situations, as they have rate constants similar to or greater than species such as H₂O₂, can be present at higher concentrations, and are less efficiently removed by protective systems when compared to H₂O₂. They may also induce similar or higher levels of modification than highly reactive oxidants, due to the very low concentrations of oxidants formed in most in vivo situations.

Role of Nuclear Factor Erythroid 2 (Nrf2) in the Recovery of Long COVID-19 Using Natural Antioxidants: A Systematic Review

Coronavirus disease 2019 (COVID-19) is an infectious disease with approximately 517 million confirmed cases, with the average number of cases revealing that patients recover immediately without hospitalization. However, several other cases found that patients still experience various symptoms after 3–12 weeks, which is known as a long COVID syndrome. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can activate nuclear factor kappa beta (NF-κβ) and unbind the nuclear factor erythroid 2-related factor 2 (Nrf2) with Kelch-like ECH-associated protein 1 (Keap1), causing inhibition of Nrf2, which has an important role in antioxidant response and redox homeostasis. Disrupting the Keap1–Nrf2 pathway enhances Nrf2 activity, and has been identified as a vital approach for the prevention of oxidative stress and inflammation. Hence, natural antioxidants from various sources have been identified as a promising strategy to prevent oxidative stress, which plays a role in reducing the long COVID-19 symptoms. Oxygen-rich natural antioxidant compounds provide an effective Nrf2 activation effect that interact with the conserved amino acid residues in the Keap1-binding pocket, such as Ser602, Ser363, Ser508, and Ser555. In this review, the benefits of various natural antioxidant compounds that can modulate the Nrf2 signaling pathway, which is critical in reducing and curing long COVID-19, are highlighted and discussed.

Cisplatin Chemotherapy and Cochlear Damage: Otoprotective and Chemosensitization Properties of Polyphenols

Significance: Cisplatin is an important component of treatment regimens for different cancers. Notwithstanding that therapeutic success often results from partial efficacy or stabilizing the disease, chemotherapy failure is driven by resistance to drug treatment and occurrence of side effects, such as progressive irreversible ototoxicity. Cisplatin's side effects, including ototoxicity, are often dose limiting. Recent Advances: Cisplatin ototoxicity results from several mechanisms, including redox imbalance caused by reactive oxygen species production and lipid peroxidation, activation of inflammation, and p53 and its downstream pathways that culminate in apoptosis. Considerable efforts in research have targeted development of molecular interventions that can be concurrently administered with cisplatin or other chemotherapies to reduce side effect toxicities while preserving or enhancing the antineoplastic effects. Evidence from studies has indicated some polyphenols, such as curcumin, can help to regulate redox signaling and inflammatory effects. Furthermore, polyphenols can exert opposing effects in different types of tissues, that is, normal cells undergoing stressful conditions versus cancer cells. Critical Issues: This review article summarizes evidence of curcumin antioxidant effect against cisplatin-induced ototoxicity that is converted to a pro-oxidant activity in cisplatin-treated cancer cells, thus providing an ideal chemosensitivity combined with otoprotection. Polyphenols can modulate the adaptive responses to stress in the cisplatin-exposed cochlea. These adaptive effects can result from the interaction/cross talk between the cell's defenses, inflammatory molecules, and the key signaling molecules of signal transducers and activators of transcription 3 (STAT-3), nuclear factor κ-B (NF-κB), p53, and nuclear factor erythroid 2-related factor 2 (Nrf-2). Future Directions: We provide molecular evidence for alternative strategies for chemotherapy with cisplatin addressing the otoprotection and chemosensitization properties of polyphenols. Antioxid. Redox Signal. 36, 1229-1245.

Genetic and epigenetic regulation of the NRF2-KEAP1 pathway in human lung cancer

Electrophilic and oxidative stress is caused when homeostatic mechanisms are disrupted. A major defense mechanism involves the activation of the nuclear factor erythroid 2-related factor 2 (NRF2) transcription factor encoded by the NFE2L2 gene, which can accelerate the detoxification of electrophilic carcinogens and prevent cancer and on the other hand in certain exposure contexts may exacerbate the carcinogenic process. NRF2-target genes activated under these conditions can be used as biomarkers of stress signalling, while activation of NRF2 can also reveal the epigenetic mechanisms that modulate NFE2L2 expression. Epigenetic mechanisms that regulate NFE2L2 and the gene for its adaptor protein KEAP1 include DNA methylation, histone modifications and microRNA. Understanding the activation of the NRF2-KEAP1 signalling pathway in human lung cancer, its epigenetic regulation and its role in oncogenesis is the subject of this review.

Targeting Autophagy with Natural Products as a Potential Therapeutic Approach for Cancer

Macro-autophagy (autophagy) is a highly conserved eukaryotic intracellular process of self-digestion caused by lysosomes on demand, which is upregulated as a survival strategy upon exposure to various stressors, such as metabolic insults, cytotoxic drugs, and alcohol abuse. Paradoxically, autophagy dysfunction also contributes to cancer and aging. It is well known that regulating autophagy by targeting specific regulatory molecules in its machinery can modulate multiple disease processes. Therefore, autophagy represents a significant pharmacological target for drug development and therapeutic interventions in various diseases, including cancers. According to the framework of autophagy, the suppression or induction of autophagy can exert therapeutic properties through the promotion of cell death or cell survival, which are the two main events targeted by cancer therapies. Remarkably, natural products have attracted attention in the anticancer drug discovery field, because they are biologically friendly and have potential therapeutic effects. In this review, we summarize the up-to-date knowledge regarding natural products that can modulate autophagy in various cancers. These findings will provide a new position to exploit more natural compounds as potential novel anticancer drugs and will lead to a better understanding of molecular pathways by targeting the various autophagy stages of upcoming cancer therapeutics.

Modulation of cigarette smoke extract-induced human bronchial epithelial damage by eucalyptol and curcumin

Smoking is one of the most important leading death cause worldwide. From a toxicological perspective, cigarette smoke serves hazards especially for the human being exposed to passive smoke. Over the last decades, the effects of natural compounds on smoking-mediated respiratory diseases such as COPD, asthma, and lung cancer have been under investigation, as well as the mechanistic aspects of disease progression. In the present study, the protective mechanism of eucalyptol (EUC), curcumin (CUR), and their combination on BEAS-2B cells were investigated in vitro to understand their impact on cell death, oxidative cell injury, and inflammatory response induced by 3R4F reference cigarette extract (CSE). According to the present findings, EUC, CUR, and their combination improved cell viability, attenuated CSE-induced apoptosis, and LC3B expression. Further, CSE-induced oxidative damage and inflammatory response in human bronchial epithelial cells were remarkably reduced by the combination treatment through modification of enzymatic antioxidant activity, GSH, MDA, and intracellular ROS levels as well as nitrite and IL-6 levels. In addition, nuclear translocation of Nrf2, a regulatory protein involved in the indirect antioxidant response, was remarkably up-regulated with the combination pre-treatment. In conclusion, EUC and CUR in combination might be a potential therapeutic against smoking-induced lung diseases through antioxidant and inflammatory pathways and results represent valuable background for future in vivo pulmonary toxicity studies.

Comparison of COVID-19 and Lung Cancer via Reactive Oxygen Species Signaling

COVID-19 and lung cancer are two severe pulmonary diseases that cause millions of deaths globally each year. Understanding the dysregulated signaling pathways between them can benefit treating the related patients. Recent studies suggest the critical role of reactive oxygen species (ROS) in both diseases, indicating an interplay between them. Here we reviewed references showing that ROS and ROS-associated signaling pathways, specifically via NRF2, HIF-1, and Nf-κB pathways, may bridge mutual impact between COVID-19 and lung cancer. As expected, typical ROS-associated inflammation pathways (HIF-1 and Nf-κB) are activated in both diseases. The activation of both pathways in immune cells leads to an overloading immune response and exacerbates inflammation in COVID-19. In lung cancer, HIF-1 activation facilitates immune escape, while Nf-κB activation in T cells suppresses tumor growth. However, the altered NRF2 pathway show opposite trends between them, NRF2 pathways exert immunosuppressive effects in both diseases, as it represses the immune response in COVID-19 patients while facilitates the immune escape of tumor cells. Furthermore, we summarized the therapeutic targets (e.g., phytochemicals) on these ROS pathways. In sum, our review focus on the understanding of ROS Signaling in COVID-19 and lung cancer, showing that modulating ROS signaling pathways may alleviate the potentially mutual impacts between COVID-19 and lung cancer patients.

Curcumin Activates the Nrf2 Pathway and Induces Cellular Protection Against Oxidative Injury

Curcumin is a naturally occurring polyphenol that is isolated from the rhizome of Curcuma longa (turmeric). This medicinal compound has different biological activities, including antioxidant, antibacterial, antineoplastic, and anti-inflammatory. It also has therapeutic effects on neurodegenerative disorders, renal disorders, and diabetes mellitus. Curcumin is safe and well-tolerated at high concentrations without inducing toxicity. It seems that curcumin is capable of targeting the Nrf2 signaling pathway in protecting the cells against oxidative damage. Besides, this strategy is advantageous in cancer therapy. Accumulating data demonstrates that curcumin applies four distinct ways to stimulate the Nrf2 signaling pathway, including inhibition of Keap1, affecting the upstream mediators of Nrf2, influencing the expression of Nrf2 and target genes, and finally, improving the nuclear translocation of Nrf2. In the present review, the effects of curcumin on the Nrf2 signaling pathway to exert its therapeutic and biological activities has been discussed.

Structure-Activity Relationship (SAR) and in vitro Predictions of Mutagenic and Carcinogenic Activities of Ixodicidal Ethyl-Carbamates

Ethyl-4-bromophenyl-carbamate (LQM 919) and Ethyl-4-chlorophenyl-carbamate (LQM 996) are compounds that inhibit egg-laying and hatching of tick larvae that are resistant to conventional ixodicides. The structure-activity relationship (SAR) to get the endpoint predictions of mutagenicity and carcinogenicity of the LQM 919 and LQM 996 was performed and the absence of mutagenicity was confirmed by Ames test. SAR analysis show no structural alerts indicating the ability of ethyl-carbamates to bind biomolecules or estrogen receptors. Endpoint of mutagenicity with and without metabolic activation showed that the ethyl-carbamates were negative (p <0.05) for mutagenicity induction in strains TA97, TA98, TA102, TA1535, TA1537 and TA1538 of Salmonella typhimurium. Pre-incubation with different ethyl-carbamate concentrations did not increase the number of spontaneously reverting colonies; moreover, the compounds did not induce a concentration-dependent increase in the number of reverting colonies in any of the strains used. This confirmed the absence of mutagenic activity in this test system. Exogenous metabolic activation did not modify these observations; suggesting that no metabolites with mutagenic activity were present. The endpoint of carcinogenicity in rats were negative for LQM 919 (p <0.05,) and LQM 996 (p <0.001). The results of the present study strongly suggest that ethyl-carbamates do not represent a risk for cancer in mammals.

Activation of Nrf2 signaling pathway by natural and synthetic chalcones: a therapeutic road map for oxidative stress

Introduction:Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway plays a key role in diverse gene expressions responsible for protection against oxidative stress and xenobiotics. Chalcones with a common chemical scaffold of 1,3-diaryl-2- propen-1-one, are abundantly present in nature with a wide variety of pharmacological properties. This review will discuss the interactions of natural and synthetic chalcones with Nrf2 signaling.Areas covered:Chalcones are reportedly found to activate Nrf2 signaling pathway, expression of Nrf2-regulated antioxidant genes, induce cytoprotective proteins and upregulate multidrug resistance-associated proteins. Chalcones being soft electrophiles are less prone to hostile off-target effects and unlikely to induce carcinogenicity and mutagenicity. Furthermore, their low toxicity, structural diversity, feasibility in structural reorganization and the presence of α,β-unsaturated carbonyl group which makes them suitable drug candidates targeting Nrf2-dependent diseases.Expert opinion:Nrf2-Keap1 signaling pathway plays a central role in redox signaling. However, available therapeutic agents for Nrf2 activation have limited practical applications due to their associated risks, relatively low efficacy and bioavailability. The designing and fabrication of new chemical entities with chalcone scaffold-based Michael acceptor mechanism should be aimed as potential therapeutic Nrf2 activators to target oxidative stress and inflammation-mediated diseases such as atherosclerosis, Parkinson's disease and many more.

Thymoquinone: A Tie-Breaker in SARS-CoV2-Infected Cancer Patients?

Since the beginning of the SARS-CoV-2(severe acute respiratory syndrome-coronavirus-2) pandemic, arace to develop a vaccine has been initiated, considering the massive and rather significant economic and healthcare hits that this virus has caused. The pathophysiology occurring following COVID-19(coronavirus disease-2019) infection has givenhints regarding the supportive and symptomatic treatments to establish for patients, as no specific anti-SARS-CoV-2 is available yet. Patient symptoms vary greatly and range from mild symptoms to severe fatal complications. Supportive treatments include antipyretics, antiviral therapies, different combinations of broad-spectrum antibiotics, hydroxychloroquine and plasma transfusion. Unfortunately, cancer patients are at higher risk of viral infection and more likely to develop serious complications due to their immunocompromised state, the fact that they are already administering multiple medications, as well as combined comorbidity compared to the general population. It may seem impossible to find a drug that possesses both potent antiviral and anticancer effects specifically against COVID-19 infection and its complications and the existing malignancy, respectively. Thymoquinone (TQ) is the most pharmacologically active ingredient in Nigella sativa seeds (black seeds); it is reported to have anticancer, anti-inflammatory and antioxidant effects in various settings. In this review, we will discuss the multiple effects of TQ specifically against COVID-19, its beneficial effects against COVID-19 pathophysiology and multiple-organ complications, its use as an adjuvant for supportive COVID-19 therapy and cancer therapy, and finally, its anticancer effects.

Antiviral and immunomodulatory activity of curcumin: A case for prophylactic therapy for COVID-19

Coronavirus disease-19 (COVID-19), a devastating respiratory illness caused by SARS-associated coronavirus-2 (SARS-CoV-2), has already affected over 64 million people and caused 1.48 million deaths, just 12 months from the first diagnosis. COVID-19 patients develop serious complications, including severe pneumonia, acute respiratory distress syndrome (ARDS), and or multiorgan failure due to exaggerated host immune response following infection. Currently, drugs that were effective against SARS-CoV are being repurposed for SARS-CoV-2. During this public health emergency, food nutraceuticals could be promising prophylactic therapeutics for COVID-19. Curcumin, a bioactive compound in turmeric, exerts diverse pharmacological activities and is widely used in foods and traditional medicines. This review presents several lines of evidence, which suggest curcumin as a promising prophylactic, therapeutic candidate for COVID-19. First, curcumin exerts antiviral activity against many types of enveloped viruses, including SARS-CoV-2, by multiple mechanisms: direct interaction with viral membrane proteins; disruption of the viral envelope; inhibition of viral proteases; induce host antiviral responses. Second, curcumin protects from lethal pneumonia and ARDS via targeting NF-κB, inflammasome, IL-6 trans signal, and HMGB1 pathways. Third, curcumin is safe and well-tolerated in both healthy and diseased human subjects. In conclusion, accumulated evidence indicates that curcumin may be a potential prophylactic therapeutic for COVID-19 in the clinic and public health settings.

Antibacterial activity of a new monocarbonyl analog of curcumin MAC 4 is associated with divisome disruption

Curcumin (CUR) is a symmetrical dicarbonyl compound with antibacterial activity. On the other hand, pharmacokinetic and chemical stability limitations hinder its therapeutic application. Monocarbonyl analogs of curcumin (MACs) have been shown to overcome these barriers. We synthesized and investigated the antibacterial activity of a series of unsymmetrical MACs derived from acetone against Mycobacterium tuberculosis and Gram-negative and Gram-positive species. Phenolic MACs 4, 6 and 8 showed a broad spectrum and potent activity, mainly against M. tuberculosis, Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus (MRSA), with MIC (minimum inhibitory concentration) values ranging from 0.9 to 15.6 µg/mL. The investigation regarding toxicity on human lung cells (MRC-5 and A549 lines) revealed MAC 4 was more selective than MACs 6 and 8, with SI (selectivity index) values ranging from 5.4 to 15.6. In addition, MAC 4 did not demonstrate genotoxic effects on A549 cells and it was more stable than CUR in phosphate buffer (pH 7.4) for 24 h at 37 °C. Fluorescence and phase contrast microscopies indicated that MAC 4 has the ability to disrupt the divisome of Bacillus subtilis without damaging its cytoplasmic membrane. However, biochemical investigations demonstrated that MAC 4 did not affect the GTPase activity of B. subtilis FtsZ, which is the main constituent of the bacterial divisome. These results corroborated that MAC 4 is a promising antitubercular and antibacterial agent.

Anti-Viral Potential and Modulation of Nrf2 by Curcumin: Pharmacological Implications

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential transcription factor that maintains the cell's redox balance state and reduces inflammation in different adverse stresses. Under the oxidative stress, Nrf2 is separated from Kelch-like ECH-associated protein 1 (Keap1), which is a key sensor of oxidative stress, translocated to the nucleus, interacts with the antioxidant response element (ARE) in the target gene, and then activates the transcriptional pathway to ameliorate the cellular redox condition. Curcumin is a yellow polyphenolic curcuminoid from Curcuma longa (turmeric) that has revealed a broad spectrum of bioactivities, including antioxidant, anti-inflammatory, anti-tumor, and anti-viral activities. Curcumin significantly increases the nuclear expression levels and promotes the biological effects of Nrf2 via the interaction with Cys151 in Keap1, which makes it a marvelous therapeutic candidate against a broad range of oxidative stress-related diseases, including type 2 diabetes (T2D), neurodegenerative diseases (NDs), cardiovascular diseases (CVDs), cancers, viral infections, and more recently SARS-CoV-2. Currently, the multifactorial property of the diseases and lack of adequate medical treatment, especially in viral diseases, result in developing new strategies to finding potential drugs. Curcumin potentially opens up new views as possible Nrf2 activator. However, its low bioavailability that is due to low solubility and low stability in the physiological conditions is a significant challenge in the field of its efficient and effective utilization in medicinal purposes. In this review, we summarized recent studies on the potential effect of curcumin to activate Nrf2 as the design of potential drugs for a viral infection like SARS-Cov2 and acute and chronic inflammation diseases in order to improve the cells' protection.

NRF2 and the Ambiguous Consequences of Its Activation during Initiation and the Subsequent Stages of Tumourigenesis

NF-E2 p45-related factor 2 (NRF2, encoded in the human by NFE2L2) mediates short-term adaptation to thiol-reactive stressors. In normal cells, activation of NRF2 by a thiol-reactive stressor helps prevent, for a limited period of time, the initiation of cancer by chemical carcinogens through induction of genes encoding drug-metabolising enzymes. However, in many tumour types, NRF2 is permanently upregulated. In such cases, its overexpressed target genes support the promotion and progression of cancer by suppressing oxidative stress, because they constitutively increase the capacity to scavenge reactive oxygen species (ROS), and they support cell proliferation by increasing ribonucleotide synthesis, serine biosynthesis and autophagy. Herein, we describe cancer chemoprevention and the discovery of the essential role played by NRF2 in orchestrating protection against chemical carcinogenesis. We similarly describe the discoveries of somatic mutations in NFE2L2 and the gene encoding the principal NRF2 repressor, Kelch-like ECH-associated protein 1 (KEAP1) along with that encoding a component of the E3 ubiquitin-ligase complex Cullin 3 (CUL3), which result in permanent activation of NRF2, and the recognition that such mutations occur frequently in many types of cancer. Notably, mutations in NFE2L2, KEAP1 and CUL3 that cause persistent upregulation of NRF2 often co-exist with mutations that activate KRAS and the PI3K-PKB/Akt pathway, suggesting NRF2 supports growth of tumours in which KRAS or PKB/Akt are hyperactive. Besides somatic mutations, NRF2 activation in human tumours can occur by other means, such as alternative splicing that results in a NRF2 protein which lacks the KEAP1-binding domain or overexpression of other KEAP1-binding partners that compete with NRF2. Lastly, as NRF2 upregulation is associated with resistance to cancer chemotherapy and radiotherapy, we describe strategies that might be employed to suppress growth and overcome drug resistance in tumours with overactive NRF2.

Small molecules regulating reactive oxygen species homeostasis for cancer therapy

Elevated intracellular reactive oxygen species (ROS) and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. Compared with normal cells, cancer cells exhibit increased ROS to maintain their malignant phenotypes and are more dependent on the "redox adaptation" mechanism. Thus, there are two apparently contradictory but virtually complementary therapeutic strategies for the regulation of ROS to prevent or treat cancer. The first strategy, that is, chemoprevention, is to prevent or reduce intracellular ROS either by suppressing ROS production pathways or by employing antioxidants to enhance ROS clearance, which protects normal cells from malignant transformation and inhibits the early stage of tumorigenesis. The second strategy is the ROS-mediated anticancer therapy, which stimulates intracellular ROS to a toxicity threshold to activate ROS-induced cell death pathways. Therefore, targeting the regulation of intracellular ROS-related pathways by small-molecule candidates is considered to be a promising treatment for tumors. We herein first briefly introduce the source and regulation of ROS, and then focus on small molecules that regulate ROS-related pathways and show efficacy in cancer therapy from the perspective of pharmacophores. Finally, we discuss several challenges in developing cancer therapeutic agents based on ROS regulation and propose the direction of future development.

Lysosomal Reacidification Ameliorates Vinyl Carbamate-Induced Toxicity and Disruption on Lysosomal pH

Ethyl carbamate (EC) is a carcinogen toxicant, commonly found in fermented foods and beverages. The carcinogenic and toxic possibility of EC is thought to be related to its metabolite vinyl carbamate (VC). However, we found interesting mechanisms underlying VC-induced toxicity in this study, which were greatly different from EC. We first conducted a simple synthesis procedure for VC and found that VC possessed higher toxicity but failed to regulate levels of reactive oxygen species, glutathione, and autophagy. Notably, VC treatment resulted in upregulation of lysosomal pH, which was responsible for its cytotoxicity. Cyclic adenosine monophosphate (cAMP) pretreatment could enhance restoration of lysosomal acidity and ameliorate VC-induced damage. Inhibition of protein kinase A and cystic fibrosis transmembrane conductance regulator can block cAMP-induced cytoprotection. Together, our results provided the evidence for novel mechanisms of toxicity and possible protection method under VC exposure, which might give new perspectives on the study of EC-induced toxicity.

Current Landscape of NRF2 Biomarkers in Clinical Trials

The transcription factor NF-E2 p45-related factor 2 (NRF2; encoded by NFE2L2) plays a critical role in the maintenance of cellular redox and metabolic homeostasis, as well as the regulation of inflammation and cellular detoxication pathways. The contribution of the NRF2 pathway to organismal homeostasis is seen in many studies using cell lines and animal models, raising intense attention towards targeting its clinical promise. Over the last three decades, an expanding number of clinical studies have examined NRF2 inducers targeting an ever-widening range of diseases. Full understanding of the pharmacokinetic and pharmacodynamic properties of drug candidates rely partly on the identification, validation, and use of biomarkers to optimize clinical applications. This review focuses on results from clinical trials with four agents known to target NRF2 signaling in preclinical studies (dimethyl fumarate, bardoxolone methyl, oltipraz, and sulforaphane), and evaluates the successes and limitations of biomarkers focused on expression of NRF2 target genes and others, inflammation and oxidative stress biomarkers, carcinogen metabolism and adduct biomarkers in unavoidably exposed populations, and targeted and untargeted metabolomics. While no biomarkers excel at defining pharmacodynamic actions in this setting, it is clear that these four lead clinical compounds do touch the NRF2 pathway in humans.

Versatile role of curcumin and its derivatives in lung cancer therapy

Lung cancer is a main cause of death all over the world with a high incidence rate. Metastasis into neighboring and distant tissues as well as resistance of cancer cells to chemotherapy demand novel strategies in lung cancer therapy. Curcumin is a naturally occurring nutraceutical compound derived from Curcuma longa (turmeric) that has great pharmacological effects, such as anti-inflammatory, neuroprotective, and antidiabetic. The excellent antitumor activity of curcumin has led to its extensive application in the treatment of various cancers. In the present review, we describe the antitumor activity of curcumin against lung cancer. Curcumin affects different molecular pathways such as vascular endothelial growth factors, nuclear factor-κB (NF-κB), mammalian target of rapamycin, PI3/Akt, microRNAs, and long noncoding RNAs in treatment of lung cancer. Curcumin also can induce autophagy, apoptosis, and cell cycle arrest to reduce the viability and proliferation of lung cancer cells. Notably, curcumin supplementation sensitizes cancer cells to chemotherapy and enhances chemotherapy-mediated apoptosis. Curcumin can elevate the efficacy of radiotherapy in lung cancer therapy by targeting various signaling pathways, such as epidermal growth factor receptor and NF-κB. Curcumin-loaded nanocarriers enhance the bioavailability, cellular uptake, and antitumor activity of curcumin. The aforementioned effects are comprehensively discussed in the current review to further direct studies for applying curcumin in lung cancer therapy.

The role of natural products in revealing NRF2 function

Covering: up to 2020The transcription factor NRF2 is one of the body's major defense mechanisms, driving transcription of >300 antioxidant response element (ARE)-regulated genes that are involved in many critical cellular processes including redox regulation, proteostasis, xenobiotic detoxification, and primary metabolism. The transcription factor NRF2 and natural products have an intimately entwined history, as the discovery of NRF2 and much of its rich biology were revealed using natural products both intentionally and unintentionally. In addition, in the last decade a more sinister aspect of NRF2 biology has been revealed. NRF2 is normally present at very low cellular levels and only activated when needed, however, it has been recently revealed that chronic, high levels of NRF2 can lead to diseases such as diabetes and cancer, and may play a role in other diseases. Again, this "dark side" of NRF2 was revealed and studied largely using a natural product, the quassinoid, brusatol. In the present review, we provide an overview of NRF2 structure and function to orient the general reader, we will discuss the history of NRF2 and NRF2-activating compounds and the biology these have revealed, and we will delve into the dark side of NRF2 and contemporary issues related to the dark side biology and the role of natural products in dissecting this biology.

4β-Hydroxywithanolide E from Goldenberry (Whole Fruits of Physalis peruviana L.) as a Promising Agent against Chronic Obstructive Pulmonary Disease

Environmental toxicant- and oxidant-induced [e.g., cigarette smoke (CS)] respiratory oxidative stress and inflammatory response play a vital role in the onset and progression of COPD. The nuclear factor erythroid 2-related factor 2 (Nrf2) represents an important mechanism for regulating intracellular oxidative stress and inflammatory response and is a promising target for developing agents against COPD. Herein, a bioactivity-guided purification of goldenberry (whole fruits of Physalis peruviana L.) led to the isolation of a novel and potent Nrf2 activator 4β-hydroxywithanolide E (4β-HWE). Our study indicated that (i) 4β-HWE activated the Nrf2-mediated defensive response through interrupting Nrf2-Keap1 protein-protein interaction (PPI) via modification of Cys151 and Cys288 cysteine residues in Keap1 and accordingly suppressing the ubiquitination of Nrf2. (ii) 4β-HWE enhanced intracellular antioxidant capacity and inhibited oxidative stress in normal human lung epithelial Beas-2B cells and wild-type AB zebrafish. (iii) 4β-HWE blocked LPS-stimulated inflammatory response and inhibited LPS-stimulated NF-κB activation in RAW 264.7 murine macrophages. (iv) 4β-HWE effectively suppressed oxidative stress and inflammatory response in a CS-induced mice model of pulmonary injury. Collectively, these results display the feasibility of using 4β-HWE to prevent or alleviate the pathological progression of COPD and suggest that 4β-HWE is a candidate or a leading molecule against COPD.

Cullin 3 and Its Role in Tumorigenesis

Cullin 3 (Cul3) family of ubiquitin ligases comprises three components, the RING finger protein RBX1, the Cul3 scaffold, and a Bric-a-brac/Tramtrack/Broad complex (BTB) protein. The BTB protein serves as a bridge to connect Cul3 to substrate and is functionally equivalent to the combination of substrate adaptor and linker in other Cullin complexes. Human genome encodes for ~180 BTB proteins, implying a broad spectrum of ubiquitination signals and substrate repertoire. Accordingly, Cul3 ubiquitin ligases are involved in diverse cellular processes, including cell division, differentiation, cytoskeleton remodeling, stress responses, and nerve cell functions. Emerging evidence has pointed to the prominent role of Cul3 ubiquitin ligases in cancer. This chapter will describe recent advances on the roles of Cul3 E3 ligase complexes in regulating various cancer hallmarks and therapeutic responses and the mutation/dysregulation of Cul3 substrate adaptors in cancer. In particular, we will focus on several extensively studied substrate adaptors, such as Keap1, SPOP, KLHL20, and LZTR1, and will also discuss other recently identified Cul3 adaptors with oncogenic or tumor-suppressive functions. We conclude that Cul3 ubiquitin ligases represent master regulators of human malignancies and highlight the importance of developing modulating agents for oncogenic/tumor-suppressive Cul3 E3 ligase complexes to prevent or intervene tumorigenesis.

Quantification of 1D, a novel derivative of curcumin with potential antitumor activity, in rat plasma by liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study in rats

CONTEXT

1 D is a novel derivative of curcumin and shows very promising antitumor activities in various cancer cell lines.

OBJECTIVE

To characterize its preclinical pharmacokinetic profiles, a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of 1 D in rat plasma.

MATERIALS AND METHODS

An aliquot of 50 μL plasma sample was processed by protein precipitation with methanol. Chromatographic separation was accomplished on a Zorbax Eclipse Plus C₁₈ column (2.1 mm × 50 mm, 1.8 μm) with a gradient elution system (water/0.1% formic acid and methanol). Detection was performed by multiple reaction monitoring (MRM) mode using electrospray ionization in the positive ion mode. The optimized fragmentation transition for 1 D was m/z 491.2 → 361.2.

RESULTS

The method was linear over the concentration range of 5-1000 ng/mL. The intra- and inter-day precisions were less than 9.8% and the accuracy was within ± 14.5%. The mean recovery of 1 D ranged from 102.5 to 105.9%. No matrix effects and significant sample loss during sample processing were observed. The validated method has been successfully applied to a pharmacokinetic study in rats after intravenous administration of 1 D. Non-compartmental pharmacokinetic parameters, including half-life (t_1/2), apparent volume of distribution (V_z), clearance (CL_z), and area under the concentration-time curve (AUC_(0-t)) were 4.92 h, 46.56 L/kg, 6.33 L/h/kg, and 806.70 μg/L/h, respectively.

DISCUSSION AND CONCLUSIONS

Results demonstrated that 1 D displayed favourable pharmacokinetic properties for further in vivo pharmacologic evaluation, which could be facilitated by the validated LC-MS/MS method.

Non-covalent NRF2 Activation Confers Greater Cellular Protection than Covalent Activation

The transcription factor NRF2 confers cellular protection by maintaining cellular redox homeostasis and proteostasis. Basal NRF2 levels are normally low due to KEAP1-mediated ubiquitylation and subsequent proteasomal degradation. KEAP1, a substrate adaptor protein of a KEAP1-CUL3-RBX1 E3 ubiquitin ligase complex, contains a critical cysteine (C151) that is modified by electrophiles or oxidants, resulting in inactivation of the E3 ligase and inhibition of NRF2 degradation. Currently, nearly all NRF2 inducers are electrophilic molecules that possess unwanted off-target effects due to their reactive nature. Here, we report a group of NRF2 inducers, ent-kaurane diterpenoid geopyxins, with and without C151 reactive electrophilic moieties. Among 16 geopyxins, geopyxin F, a non-electrophilic NRF2 activator, showed enhanced cellular protection relative to an electrophilic NRF2 activator, geopyxin C. To our knowledge, this is the first detailed structure-activity relationship study of covalent versus non-covalent NRF2 activators, showing the promise of non-covalent NRF2 activators as potential therapeutic compounds.

The E-Cadherin and N-Cadherin Switch in Epithelial-to-Mesenchymal Transition: Signaling, Therapeutic Implications, and Challenges

Epithelial-to-Mesenchymal Transition (EMT) has been shown to be crucial in tumorigenesis where the EMT program enhances metastasis, chemoresistance and tumor stemness. Due to its emerging role as a pivotal driver of tumorigenesis, targeting EMT is of great therapeutic interest in counteracting metastasis and chemoresistance in cancer patients. The hallmark of EMT is the upregulation of N-cadherin followed by the downregulation of E-cadherin, and this process is regulated by a complex network of signaling pathways and transcription factors. In this review, we summarized the recent understanding of the roles of E- and N-cadherins in cancer invasion and metastasis as well as the crosstalk with other signaling pathways involved in EMT. We also highlighted a few natural compounds with potential anti-EMT property and outlined the future directions in the development of novel intervention in human cancer treatments. We have reviewed 287 published papers related to this topic and identified some of the challenges faced in translating the discovery work from bench to bedside.

Novel diterpenoid-type activators of the Keap1/Nrf2/ARE signaling pathway and their regulation of redox homeostasis

Oxidative stress is involved in the onset and progression of many human diseases. Activators of the Keap1/Nrf2/ARE pathway effectively inhibit the progression of oxidative stress-induced diseases. Herein, a small library of diterpenoids was established by means of phytochemical isolation, and chemical modification on naturally occurring molecules. The diterpenoids were subjected to a NAD(P)H: quinone reductase (QR) assay to evaluate its potential inhibition against oxidative stress. Sixteen diterpenoids were found to be novel potential activators of Nrf2-mediated defensive response. Of which, an isopimarane-type diterpenoid, sphaeropsidin A (SA), was identified as a potent activator of the Keap1/Nrf2/ARE pathway, and displayed approximately 5-folds potency than that of sulforaphane (SF). SA activated Nrf2 and its downstream cytoprotective genes through enhancing the stabilization of Nrf2 in a process involving PI3K, PKC, and PERK, as well as potentially interrupting Nrf2-Keap1 protein-protein interaction. In addition, SA conferred protection against sodium arsenite [As(III)]- and cigarette smoke extract (CSE)-induced redox imbalance and cytotoxicity in human lung epithelial cells, as wells as inhibited metronidazole (MTZ)-induced oxidative insult in Tg (krt4: NTR-hKikGR)^cy17 transgenic zebrafish and lipopolysaccharide (LPS)-induced oxidative damage in wild-type AB zebrafish. These results imply that SA is a lead compound for therapeutic agent against oxidative stress-induced diseases, and diterpenoid is a good resource for discovering drug candidates and leads of antioxidant therapy.

Botrysphin D attenuates arsenic-induced oxidative stress in human lung epithelial cells via activating Nrf2/ARE signaling pathways

Oxidative stress is one of the main pathogenesis for many human diseases. Nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway plays a key role in regulating intracellular antioxidant responses, and thus activation of Nrf2/ARE signaling pathway is a potential chemopreventive or therapeutic strategy to treat diseases caused by oxidative damage. In the present study, we have found that treatment of Beas-2B cells with botrysphins D (BD) attenuated sodium arsenite [As (III)]-induced cell death and apoptosis. Meanwhile, BD was able to upregulate protein levels of Nrf2 and its downstream genes NQO1 and γ-GCS through inducing Nrf2 nuclear translocation, enhancing protein stability, and inhibiting ubiquitination. It was also found that BD-induced activation of the Nrf2/ARE pathway was regulated by PI3K, MEK1/2, PKC, and PERK kinases. Collectively, BD is a novel activator of Nrf2/ARE pathway, and is verified to be a potential preventive agent against oxidative stress-induced damage in human lung tissues.

Determination and pharmacokinetic study of isothiouronium-modified pyrimidine-substituted curcumin analog (1G), a novel antitumor agent, in rat plasma by liquid chromatography-tandem mass spectrometry

1G, a novel derivative of curcumin, exhibits promising anticancer activities in various cancer cell lines. To support its further pharmacological studies, a liquid chromatography-tandem mass spectrometry method was developed and validated in accordance with FDA's Guidance. After extraction by protein precipitation, analytes were separated by a 4.5 min gradient elution (water/0.1% formic acid and methanol) on a reverse-phase C₁₈ column at 40 °C. The multiple reaction monitoring mode was used for quantification on a triple quadrupole mass spectrometer with positive ionization. The assay was linear over the concentration range of 5-1000 ng/mL with a correlation coefficient (r) greater than 0.99. Values of intra- and inter-day precision and accuracy were satisfactory, i.e. <10.1% for precision and within ± 14.5% for accuracy. No obvious matrix effect was observed. Recovery of the analyte was higher than 95.3%. 1G was stable during the whole analytic process. The validated method was successfully applied to the pharmacokinetic study of 1G after intravenous and intraperitoneal administration in rats. Favorable pharmacokinetic profiles were demonstrated, including good abdominal absorption (F = 62.58%), moderate clearance and high extravascular distribution. Results indicated that as a novel antitumor agent, 1G exhibited acceptable pharmacokinetic properties for further in vivo pharmacologic evaluation.

Lignan and flavonoid support the prevention of cinnamon against oxidative stress related diseases

BACKGROUND

Oxidative stress contributes to the pathogenesis of many human diseases. Cinnamon is a worldwide used spice, dietary supplement and traditional medicine, and is used for the therapy of oxidative stress related diseases. A well-established concept is that the functions of cinnamon preventing oxidative stress-induced diseases are attributed to the occurrence of cinnamaldehyde and its analogues.

HYPOTHESIS

In our continuous searching of natural molecules with antioxidant capacity, we have found that cinnamaldehyde and its analogues in cinnamon are weak inhibitors of oxidative stress, and thus we speculate that there are novel and/or potent molecules inhibiting oxidative stress in cinnamon.

STUDY DESIGN AND METHODS

A systemic phytochemical investigation of cinnamon using column chromatography was performed to identify the chemical constituents of cinnamon, and then their capacity of inhibiting oxidative stress and action of mechanism targeting Nrf2 pathway were investigated using diverse bioassay, including NAD(P)H: quinone reductase (QR) assay, immunoblot analysis, luciferase reporter gene assay, immunofluorescence and flow cytometry.

RESULTS

Cinnamon improved the intracellular antioxidant capacity. A systemic phytochemical investigation of cinnamon gave the isolation of twenty-two chemical ingredients. The purified constituents were tested for their potential inhibitory effects against oxidative stress. Besides cinnamaldehyde analogues, a lignan pinoresinol (PRO) and a flavonol (-)-(2R,3R)-5,7-dimethoxy-3', 4'-methylenedioxy-flavan-3-ol (MFO) were firstly identified to be inhibitors of oxidative stress. Further study indicated that PRO and MFO activated Nrf2-mediated antioxidant response, and protected human lung epithelial cells against sodium arsenite [As(III)]-induced oxidative insults.

CONCLUSION

The lignan PRO and the flavonoid MFO are two novel Nrf2 activators protecting tissues against oxidative insults, and these two constituents support the application of cinnamon as an agent against oxidative stress related diseases.

Proanthocyanidins Protect against β-Hydroxybutyrate-Induced Oxidative Damage in Bovine Endometrial Cells

Metabolic diseases, such as ketosis, are closely associated with decreased reproductive performance (such as delayed estrus and decreased pregnancy rate) in dairy cows. The change of β-hydroxybutyrate (BHBA) concentration in dairy cattle is an important mechanism leading to ketosis, and its blood concentration in ketotic cows is always significantly higher than in nonketotic cows. Many studies indicated that BHBA can induce oxidative damage in liver and other organs. Proanthocyanidins (PCs) have gained substantial attention in the last decade as strong antioxidative substances. This study aimed to demonstrate a protective effect of PCs against BHBA-induced oxidative stress damage in bovine endometrial (BEND) cells by activating the nuclear erythroid2-related factor2 (Nrf2) signaling pathway. Our research show that PCs could significantly increase activities of catalase (CAT) and glutathione peroxidase (GSH-PX), glutathione (GSH) content, and antioxidant capacity (T-AOC), while significantly decreasing malondialdehyde (MDA) content in BEND cells. Both mRNA and protein expression levels of Nrf2 were significantly increased in BEND cells, and glutamate–cysteine ligase catalytic subunit (GCLC), heme oxygenase 1 (HO-1), manganese superoxide dismutase (Mn-SOD), and NAD(P)Hquinone dehydrogenase 1 (NQO-1) were also significantly increased. These results indicate that PCs can antagonize BHBA-induced oxidative damage by activating the Nrf2 signaling pathway to exert an antioxidant effect.

Role of Nrf2 and Its Activators in Respiratory Diseases

Transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is a major regulator of antioxidant response element- (ARE-) driven cytoprotective protein expression. The activation of Nrf2 signaling plays an essential role in preventing cells and tissues from injury induced by oxidative stress. Under the unstressed conditions, natural inhibitor of Nrf2, Kelch-like ECH-associated protein 1 (Keap1), traps Nrf2 in the cytoplasm and promotes the degradation of Nrf2 by the 26S proteasome. Nevertheless, stresses including highly oxidative microenvironments, impair the ability of Keap1 to target Nrf2 for ubiquitination and degradation, and induce newly synthesized Nrf2 to translocate to the nucleus to bind with ARE. Due to constant exposure to external environments, including diverse pollutants and other oxidants, the redox balance maintained by Nrf2 is fairly important to the airways. To date, researchers have discovered that Nrf2 deletion results in high susceptibility and severity of insults in various models of respiratory diseases, including bronchopulmonary dysplasia (BPD), respiratory infections, acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), asthma, idiopathic pulmonary fibrosis (IPF), and lung cancer. Conversely, Nrf2 activation confers protective effects on these lung disorders. In the present review, we summarize Nrf2 involvement in the pathogenesis of the above respiratory diseases that have been identified by experimental models and human studies and describe the protective effects of Nrf2 inducers on these diseases.

Curcumin Inhibits Lipopolysaccharide-Induced Mucin 5AC Hypersecretion and Airway Inflammation via Nuclear Factor Erythroid 2-Related Factor 2

Background:

Excess mucus production is an important pathophysiological feature of chronic inflammatory airway diseases. Effective therapies are currently lacking. The aim of the study was to evaluate the effects of curcumin (CUR) on lipopolysaccharide (LPS)-induced mucus secretion and inflammation, and explored the underlying mechanism in vivo and in vitro.

Methods:

For the in vitro study, human bronchial epithelial (NCI-H292) cells were pretreated with CUR or vehicle for 30 min, and then exposed to LPS for 24 h. Next, nuclear factor erythroid 2-related factor 2 (Nrf2) was knocked down with Nrf2 small interfering RNA (siRNA) to confirm the specific role of Nrf2 in mucin regulation of CUR in NCI-H292 cells. In vivo, C57BL/6 mice were randomly assigned to three groups (n = 7 for each group): control group, LPS group, and LPS + CUR group. Mice in LPS and LPS + CUR group were injected with saline or CUR (50 mg/kg) intraperitoneally 2 h before intratracheal instillation with LPS (100 μg/ml) for 7 days. Cell lysate and lung tissue were obtained to measured Mucin 5AC (MUC5AC) and Nrf2 mRNA and protein expression by a real-time polymerase chain reaction and Western blotting. Bronchoalveolar lavage fluid (BALF) was collected to enumerate total cells and neutrophils. Histopathological changes of the lung were observed. Data were analyzed by one-way analysis of variance. Student's t-test was used when two groups were compared.

Results:

CUR significantly decreased the expression of MUC5AC mRNA and protein in NCI-H292 cells exposed to LPS. This effect was dose dependent (2.424 ± 0.318 vs. 7.169 ± 1.785, t = 4.534, and 1.060 ± 0.197 vs. 2.340 ± 0.209, t = 7.716; both P < 0.05, respectively) and accompanied by increased mRNA and protein expression of Nrf2 (1.952 ± 0.340 vs. 1.142 ± 0.176, t = −3.661, and 2.010 ± 0.209 vs. 1.089 ± 0.132, t = −6.453; both P < 0.05, respectively). Furthermore, knockdown of Nrf2 with siRNA increased MUC5AC mRNA expression by 47.7%, compared with levels observed in the siRNA-negative group (6.845 ± 1.478 vs. 3.391 ± 0.517, t = −3.821, P < 0.05). Knockdown of Nrf2 with siRNA also markedly increased MUC5AC protein expression in NCI-H292 cells. CUR also significantly decreased LPS-induced mRNA and protein expression of MUC5AC in mouse lung (1.672 ± 0.721 vs. 5.961 ± 2.452, t = 2.906, and 0.480 ± 0.191 vs. 2.290 ± 0.834, t = 3.665, respectively; both P < 0.05). Alcian blue/periodic acid-Schiff staining also showed that CUR suppressed mucin production. Compared with the LPS group, the numbers of inflammatory cells (247 ± 30 vs. 334 ± 24, t = 3.901, P < 0.05) and neutrophils (185 ± 22 vs. 246 ± 20, t = 3.566, P < 0.05) in BALF decreased in the LPS + CUR group, as well as reduced inflammatory cell infiltration in lung tissue.

Conclusion:

CUR inhibits LPS-induced airway mucus hypersecretion and inflammation through activation of Nrf2 possibly.

Discovery of natural flavonoids as activators of Nrf2-mediated defense system: Structure-activity relationship and inhibition of intracellular oxidative insults

Continuous overproduction of reactive oxygen species (ROS), termed as oxidative stress, plays a crucial role in the onset and progression of many human diseases. Activation of nuclear transcription factor erythroid 2-related factor (Nrf2) by small molecules could eliminate ROS, and thus block the pathogenesis of oxidative stress-induced diseases. In this study, a natural flavonoid library was established and tested for their potential Nrf2 inducing effects. Based on QR inducing effect of flavonoids, their structure-activity relationship (SAR) on Nrf2 induction was summarized, and twenty flavonoids were firstly identified to be potential activators of Nrf2-mediated defensive response. Then, 7-O-methylbiochanin A (7-MBA) was further investigated for its capability on the Nrf2 activation and prevention against oxidative insults in human lung epithelial cells. Further studies indicated that 7-MBA activated Nrf2 signaling pathway and protected human lung epithelial Beas-2B cells against sodium arsenite [As(III)]-induced cytotoxicity in an Nrf2-dependent manner. Activation of Nrf2 by 7-MBA upregulated intracellular antioxidant capacity, which was produced by enhancement of Nrf2 stabilization, blockage of Nrf2 ubiquitination, as well as Nrf2 phosphorylation by mitogen-activated protein kinase (MAPK), protein kinase C (PKC), protein kinase R-like endoplasmic reticulum kinase (PERK), and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). Taken together, 7-MBA is a novel isoflavone-type Nrf2 activator displaying potential preventive effect against oxidative damages in human lung epithelial cells.

NRF2 and the Hallmarks of Cancer

The transcription factor NRF2 is the master regulator of the cellular antioxidant response. Though recognized originally as a target of chemopreventive compounds that help prevent cancer and other maladies, accumulating evidence has established the NRF2 pathway as a driver of cancer progression, metastasis, and resistance to therapy. Recent studies have identified new functions for NRF2 in the regulation of metabolism and other essential cellular functions, establishing NRF2 as a truly pleiotropic transcription factor. In this review, we explore the roles of NRF2 in the hallmarks of cancer, indicating both tumor suppressive and tumor-promoting effects.

Verapamil Inhibits TRESK (K2P18.1) Current in Trigeminal Ganglion Neurons Independently of the Blockade of Ca2+ Influx

Tandem pore domain weak inward rectifier potassium channel (TWIK)-related spinal cord K⁺ (TRESK; K_2P18.1) channel is the only member of the two-pore domain K⁺ (K_2P) channel family that is activated by an increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) and linked to migraines. This study was performed to identify the effect of verapamil, which is an L-type Ca²⁺ channel blocker and a prophylaxis for migraines, on the TRESK channel in trigeminal ganglion (TG) neurons, as well as in a heterologous system. Single-channel and whole-cell currents were recorded in TG neurons and HEK-293 cells transfected with mTRESK using patch-clamping techniques. In TG neurons, changes in [Ca²⁺]_i were measured using the fluo-3-AM Ca²⁺ indicator. Verapamil, nifedipine, and NiCl₂ inhibited the whole-cell currents in HEK-293 cells overexpressing mTRESK with IC₅₀ values of 5.2, 54.3, and >100 μM, respectively. The inhibitory effect of verapamil on TRESK channel was also observed in excised patches. In TG neurons, verapamil (10 μM) inhibited TRESK channel activity by approximately 76%. The TRESK channel activity was not dependent on the presence of extracellular Ca²⁺. In addition, the inhibitory effect of verapamil on the TRESK channel remained despite the absence of extracellular Ca²⁺. These findings show that verapamil inhibits the TRESK current independently of the blockade of Ca²⁺ influx in TG neurons. Verapamil will be able to exert its pharmacological effects by modulating TRESK, as well as Ca²⁺ influx, in TG neurons in vitro. We suggest that verapamil could be used as an inhibitor for identifying TRESK channel in TG neurons.

Camptosorus sibiricus rupr aqueous extract prevents lung tumorigenesis via dual effects against ROS and DNA damage

ETHNOPHARMACOLOGICAL RELEVANCE

Camptosorus sibiricus Rupr (CSR) is a widely used herbal medicine with antivasculitis, antitrauma, and antitumor effects. However, the effect of CSR aqueous extract on B[a]P-initiated tumorigenesis and the underlying mechanism remain unclear. Moreover, the compounds in CSR aqueous extract need to be identified and structurally characterized.

AIM OF THE STUDY

We aim to investigate the chemopreventive effect of CSR and the underlying molecular mechanism.

MATERIALS AND METHODS

A B[a]P-stimulated normal cell model (BEAS.2B) and lung adenocarcinoma animal model were established on A/J mice. In B[a]P-treated BEAS.2B cells, the protective effects of CSR aqueous extract on B[a]P-induced DNA damage and ROS production were evaluated through flow cytometry, Western blot, real-time quantitative PCR, single-cell gel electrophoresis, and immunofluorescence. Moreover, a model of B[a]P-initiated lung adenocarcinoma was established on A/J mice to determine the chemopreventive effect of CSR in vivo. The underlying mechanism was analyzed via immunohistochemistry and microscopy. Furthermore, the new compounds in CSR aqueous extract were isolated and structurally characterized using IR, HR-ESI-MS, and 1D and 2D NMR spectroscopy.

RESULTS

CSR effectively suppressed ROS production by re-activating Nrf2-mediated reductases HO-1 and NQO-1. Simultaneously, CSR attenuated the DNA damage of BEAS.2B cells in the presence of B[a]P. Moreover, CSR at 1.5 and 3 g/kg significantly suppressed tumorigenesis with tumor inhibition ratios of 36.65% and 65.80%, respectively. The tumor volume, tumor size, and multiplicity of B[a]P-induced lung adenocarcinoma were effectively decreased by CSR in vivo. After extracting and identifying the compounds in CSR aqueous extract, three new triterpene saponins were isolated and characterized structurally.

CONCLUSIONS

CSR aqueous extract prevents lung tumorigenesis by exerting dual effects against ROS and DNA damage, suggesting that CSR is a novel and effective agent for B[a]P-induced carcinogenesis. Moreover, by isolating and structurally characterizing three new triterpene saponins, our study further standardized the quality of CSR aqueous extract, which could widen CSR clinical applications.

Therapeutic Potential of Salviae Miltiorrhizae Radix et Rhizoma against Human Diseases Based on Activation of Nrf2-Mediated Antioxidant Defense System: Bioactive Constituents and Mechanism of Action

Oxidative stress plays a central role in the pathogenesis of many human diseases. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor regulating the intracellular antioxidant response and is an emerging target for the prevention and therapy of oxidative stress-related diseases. Salviae Miltiorrhizae Radix et Rhizoma (SMRR) is a traditional Chinese medicine (TCM) and is commonly used for the therapy of cardiac cerebral diseases. Cumulative evidences indicated that the extract of SMRR and its constituents, represented by lipophilic diterpenoid quinones and hydrophilic phenolic acids, were capable of activating Nrf2 and inhibiting oxidative stress. These bioactive constituents demonstrated a therapeutic potential against human diseases, exemplified by cardiovascular diseases, neurodegenerative diseases, diabetes, nephropathy, and inflammation, based on the induction of Nrf2-mediated antioxidant response and the inhibition of oxidative stress. In the present review, we introduced the SMRR and Nrf2 signaling pathway, summarized the constituents with an Nrf2-inducing effect isolated from SMRR, and discussed the molecular mechanism and pharmacological functions of the SMRR extract and its constituents.

Ingredients from Litsea garrettii as Potential Preventive Agents against Oxidative Insult and Inflammatory Response

Oxidative stress and inflammation undoubtedly contribute to the pathogenesis of many human diseases. The nuclear transcription factor erythroid 2-related factor (Nrf2) and the nuclear factor κB (NF-κB) play central roles in regulation of oxidative stress and inflammation and thus are targets for developing agents against oxidative stress- and inflammation-related diseases. Our previous study indicated that the EtOH extract of Litsea garrettii protected human bronchial epithelial cells against oxidative insult via the activation of Nrf2. In the present study, a systemic phytochemical investigation of L. garrettii led to the isolation of twenty-one chemical ingredients, which were further evaluated for their inhibitions on oxidative stress and inflammation using NAD(P)H:quinone reductase (QR) assay and nitric oxide (NO) production assay. Of these ingredients, 3-methoxy-5-pentyl-phenol (MPP, 5) was identified as an Nrf2 activator and an NF-κB inhibitor. Further studies demonstrated the following: (i) MPP upregulated the protein levels of Nrf2, NAD(P)H:quinone oxidoreductase 1 (NQO1), and glutamate-cysteine ligase regulatory subunit (GCLM); enhanced the nuclear translocation and stabilization of Nrf2; and inhibited arsenic [As(III)]-induced oxidative insult in normal human lung epithelial Beas-2B cells. And (ii) MPP suppressed the nuclear translocation of NF-κB p65 subunit; inhibited the lipopolysaccharide- (LPS-) stimulated increases of NF-κB p65 subunit, COX-2, iNOS, TNF-α, and IL-1β; and blocked the LPS-induced biodegrade of IκB-α in RAW 264.7 murine macrophages. Taken together, MPP displayed potential preventive effects against inflammation- and oxidative stress-related diseases.

Phytosome complex of curcumin as complementary therapy of advanced pancreatic cancer improves safety and efficacy of gemcitabine: Results of a prospective phase II trial

A large body of biomedical evidence indicates that activation of Nrf2 by curcumin increases the nucleophilic tone and damps inflammation cumulatively supporting the malignant phenotype. Conversely, genetic analyses suggest a possible oncogenic nature of constitutive Nrf2 activation since an increased nucleophilic tone is alleged increasing chemoresistance of cancer cells. Aiming to contribute to solve this paradox, this study addressed the issue of safety and efficacy of curcumin as complementary therapy of gemcitabine on pancreatic cancer. This was a single centre, single arm prospective phase II trial. Patients received gemcitabine and Meriva^®, a patented preparation of curcumin complexed with phospholipids. Primary endpoint was response rate, secondary endpoints were progression free survival, overall survival, tolerability and quality of life. Analysis of inflammatory biomarkers was also carried out. Fifty-two consecutive patients were enrolled. Forty-four (13 locally advanced and 31 metastatic) were suitable for primary endpoint evaluation. Median age was 66 years (range 42-87); 42 patients had Eastern Cooperative Oncology Group performance status 0-1. The median number of treatment cycle was 4.5 (range 2-14). We observed 27.3% of response rate and 34.1% of cases with stable disease, totalizing a disease control rate of 61.4%. The median progression free survival and overall survival were 8.4 and 10.2 months, respectively. Higher IL-6 and sCD40L levels before treatment were associated to a worse overall survival (p < 0.01). Increases in sCD40L levels after 1 cycle of chemotherapy were associated with a reduced response to the therapy. Grade 3/4 toxicity was observed (neutropenia, 38.6%; anemia, 6.8%). There were no significant changes in quality of life during therapy. In conclusion, the complementary therapy to gemcitabine with phytosome complex of curcumin is not only safe but also efficiently translate in a good response rate in first line therapy of advanced pancreatic cancer.

Dihydromyricetin promotes autophagy and apoptosis through ROS-STAT3 signaling in head and neck squamous cell carcinoma

Chemotherapy is an effective weapon in the battle against cancer, but numerous cancer patients are either not sensitive to chemotherapy or develop drug resistance to current chemotherapy regimens. Therefore, an effective chemotherapy mechanism that enhances tumor sensitivity to chemotherapeutics is urgently needed. The aim of the present study was to determine the antitumor activity of dihydromyricetin (DHM) on head and neck squamous cell carcinoma (HNSCC) and its underlying mechanisms. We demonstrated that DHM can markedly induce apoptotic cell death and autophagy in HNSCC cells. Meanwhile, increased autophagy inhibited apoptosis. Pharmacological or genetic inhibition of autophagy further sensitized the HNSCC cells to DHM-induced apoptosis. Mechanistic analysis showed that the antitumor of DHM may be due to the activation phosphorylation of signal transducer and activator of transcription 3 (p-STAT3), which contributed to autophagy. Importantly, DHM triggered reactive oxygen species (ROS) generation in the HNSCC cells and the levels of ROS decreased with N-acetyl-cysteine (NAC), a ROS scavenger. Moreover, NAC abrogated the effects of DHM on STAT3-dependent autophagy. Overall, the following critical issues were observed: first, DHM increased the p-STAT3-dependent autophagy by generating ROS-signaling pathways in head and neck squamous cell carcinoma. Second, inhibiting autophagy could enhance DHM-induced apoptosis in head and neck squamous cell carcinoma.

Nrf2 at the heart of oxidative stress and cardiac protection

The NFE2L2 gene encodes the transcription factor Nrf2 best known for regulating the expression of antioxidant and detoxification genes. Gene knockout approaches have demonstrated its universal cytoprotective features. While Nrf2 has been the topic of intensive research in cancer biology since its discovery in 1994, understanding the role of Nrf2 in cardiovascular disease has just begun. The literature concerning Nrf2 in experimental models of atherosclerosis, ischemia, reperfusion, cardiac hypertrophy, heart failure, and diabetes supports its cardiac protective character. In addition to antioxidant and detoxification genes, Nrf2 has been found to regulate genes participating in cell signaling, transcription, anabolic metabolism, autophagy, cell proliferation, extracellular matrix remodeling, and organ development, suggesting that Nrf2 governs damage resistance as well as wound repair and tissue remodeling. A long list of small molecules, most derived from natural products, have been characterized as Nrf2 inducers. These compounds disrupt Keap1-mediated Nrf2 ubquitination, thereby prohibiting proteasomal degradation and allowing Nrf2 protein to accumulate and translocate to the nucleus, where Nrf2 interacts with sMaf to bind to ARE in the promoter of genes. Recently alternative mechanisms driving Nrf2 protein increase have been revealed, including removal of Keap1 by autophagy due to p62/SQSTM1 binding, inhibition of βTrCP or Synoviolin/Hrd1-mediated ubiquitination of Nrf2, and de novo Nrf2 protein translation. We review here a large volume of literature reporting historical and recent discoveries about the function and regulation of Nrf2 gene. Multiple lines of evidence presented here support the potential of dialing up the Nrf2 pathway for cardiac protection in the clinic.

Recent advances in understanding NRF2 as a druggable target: development of pro-electrophilic and non-covalent NRF2 activators to overcome systemic side effects of electrophilic drugs like dimethyl fumarate

Dimethyl fumarate (DMF) is an electrophilic compound previously called BG-12 and marketed under the name Tecfidera ^®. It was approved in 2013 by the US Food and Drug Administration and the European Medicines Agency for the treatment of relapsing multiple sclerosis. One mechanism of action of DMF is stimulation of the nuclear factor erythroid 2-related factor 2 (NRF2) transcriptional pathway that induces anti-oxidant and anti-inflammatory phase II enzymes to prevent chronic neurodegeneration. However, electrophiles such as DMF also produce severe systemic side effects, in part due to non-specific S-alkylation of cysteine thiols and resulting depletion of glutathione. This mini-review presents the present status and future strategy for NRF2 activators designed to avoid these side effects. Two modes of chemical reaction leading to NRF2 activation are considered here. The first mode is S-alkylation (covalent reaction) of thiols in Kelch-like ECH-associated protein 1 (KEAP1), which interacts with NRF2. The second mechanism involves non-covalent pharmacological inhibition of protein-protein interactions, in particular domain-specific interaction between NRF2 and KEAP1 or other repressor proteins involved in this transcriptional pathway. There have been significant advances in drug development using both of these mechanisms that can potentially avoid the systemic side effects of electrophilic compounds. In the first case concerning covalent reaction with KEAP1, monomethyl fumarate and monoethyl fumarate appear to represent safer derivatives of DMF. In a second approach, pro-electrophilic drugs, such as carnosic acid from the herb Rosmarinus officinalis, can be used as a safe pro-drug of an electrophilic compound. Concerning non-covalent activation of NRF2, drugs are being developed that interfere with the direct interaction of KEAP1-NRF2 or inhibit BTB domain and CNC homolog 1 (BACH1), which is a transcriptional repressor of the promoter where NRF2 binds.

Activation of anti-oxidant Nrf2 signaling by enone analogues of curcumin

Inflammation and oxidative stress are common in many chronic diseases. Targeting signaling pathways that contribute to these conditions may have therapeutic potential. The transcription factor Nrf2 is a major regulator of phase II detoxification and anti-oxidant genes as well as anti-inflammatory and neuroprotective genes. Nrf2 is widespread in the CNS and is recognized as an important regulator of brain inflammation. The natural product curcumin exhibits numerous biological activities including ability to induce the expression of Nrf2-dependent phase II and anti-oxidant enzymes. Curcumin has been examined in a number of clinical studies with limited success, mainly owing to limited bioavailability and rapid metabolism. Enone analogues of curcumin were examined with an Nrf2 reporter assay to identify Nrf2 activators. Analogues were separated into groups with a 7-carbon dienone spacer, as found in curcumin; a 5-carbon enone spacer with and without a ring; and a 3-carbon enone spacer. Activators of Nrf2 were found in all three groups, many of which were more active than curcumin. Dose-response studies demonstrated that a range of substituents on the aromatic rings of these enones influenced not only the sensitivity to activation, reflected in EC₅₀ values, but also the extent of activation, which suggests that multiple mechanisms are involved in the activation of Nrf2 by these analogues.