Regulation of NF-E2-related factor 2 signaling for cancer chemoprevention: antioxidant coupled with antiinflammatory

NRF2 inhibitors: Recent progress, future design and therapeutic potential

Nuclear factor erythroid 2-related factor 2 (NRF2) is a crucial transcription factor involved in oxidative stress response, which controls the expression of various cytoprotective genes. Recent research has indicated that constitutively activated NRF2 can enhance patients' resistance to chemotherapy drugs, resulting in unfavorable prognosis. Therefore, the development of NRF2 inhibitors has emerged as a promising approach for overcoming drug resistance in cancer treatment. However, there are limited reports and reviews focusing on NRF2 inhibitors. This review aims to provide a comprehensive analysis of the structure and regulation of the NRF2 signaling pathway, followed by a comprehensive review of reported NRF2 inhibitors. Moreover, the current design strategies and future prospects of NRF2 inhibitors will be discussed, aiming to establish a foundation for the development of more effective NRF2 inhibitors.

Ocotillol Derivatives Mitigate Retinal Ischemia-Reperfusion Injury by Regulating the Keap1/Nrf2/ARE Signaling Pathway

Retinal ischemia-reperfusion (RIR) injury can lead to various retinal diseases. Oxidative stress is considered an important pathological event in RIR injury. Here, we designed and synthesized 34 ocotillol derivatives, then examined their antioxidant and anti-inflammatory capacities; we found that compounds 7 (C24-R) and 8 (C24-S) were most active. To enhance their water solubility, sustained release, and biocompatibility, compounds 7 and 8 were encapsulated into liposomes for in vivo activity and mechanistic studies. In vivo studies indicated that compounds 7 and 8 protected normal retinal structure and physiological function after RIR injury, reversed damage to retinal ganglion cells, and the S-configuration exhibited significantly stronger activity compared with the R-configuration. Mechanistic studies showed that compound 8 exerted a therapeutic effect on RIR injury by activating the Keap1/Nrf2/ARE signaling pathway; compound 7 did not influence this pathway. We also demonstrated that differential isomerization at the C-24 position influenced protection against RIR injury.

Equol: a metabolite of gut microbiota with potential antitumor effects

An increasing number of studies have shown that the consumption of soybeans and soybeans products is beneficial to human health, and the biological activity of soy products may be attributed to the presence of Soy Isoflavones (SI) in soybeans. In the intestinal tracts of humans and animals, certain specific bacteria can metabolize soy isoflavones into equol. Equol has a similar chemical structure to endogenous estradiol in the human body, which can bind with estrogen receptors and exert weak estrogen effects. Therefore, equol plays an important role in the occurrence and development of a variety of hormone-dependent malignancies such as breast cancer and prostate cancer. Despite the numerous health benefits of equol for humans, only 30-50% of the population can metabolize soy isoflavones into equol, with individual variation in gut microbiota being the main reason. This article provides an overview of the relevant gut microbiota involved in the synthesis of equol and its anti-tumor effects in various types of cancer. It also summarizes the molecular mechanisms underlying its anti-tumor properties, aiming to provide a more reliable theoretical basis for the rational utilization of equol in the field of cancer treatment.

An Update on Potential Molecular Biomarkers of Dietary Phytochemicals Targeting Lung Cancer Interception and Prevention

Since ancient times, dietary phytochemicals are known for their medicinal properties. They are broadly classified into polyphenols, terpenoids, alkaloids, phytosterols, and organosulfur compounds. Currently, there is considerable interest in their potential health effects against various diseases, including lung cancer. Lung cancer is the leading cause of cancer deaths with an average of five-year survival rate of lung cancer patients limited to just 14%. Identifying potential early molecular biomarkers of pre-malignant lung cancer cells may provide a strong basis to develop early cancer detection and interception methods. In this review, we will discuss molecular changes, including genetic alterations, inflammation, signal transduction pathways, redox imbalance, epigenetic and proteomic signatures associated with initiation and progression of lung carcinoma. We will also highlight molecular targets of phytochemicals during lung cancer development. These targets mainly consist of cellular signaling pathways, epigenetic regulators and metabolic reprogramming. With growing interest in natural products research, translation of these compounds into new cancer prevention approaches to medical care will be urgently needed. In this context, we will also discuss the overall pharmacokinetic challenges of phytochemicals in translating to humans. Lastly, we will discuss clinical trials of phytochemicals in lung cancer patients.

Sulforaphane prevents LPS-induced inflammation by regulating the Nrf2-mediated autophagy pathway in goat mammary epithelial cells and a mouse model of mastitis

BACKGROUND

Mastitis not only deteriorates the composition or quality of milk, but also damages the health and productivity of dairy goats. Sulforaphane (SFN) is a phytochemical isothiocyanate compound with various pharmacological effects such as anti-oxidant and anti-inflammatory. However, the effect of SFN on mastitis has yet to be elucidated. This study aimed to explore the anti-oxidant and anti-inflammatory effects and potential molecular mechanisms of SFN in lipopolysaccharide (LPS)-induced primary goat mammary epithelial cells (GMECs) and a mouse model of mastitis.

RESULTS

In vitro, SFN downregulated the mRNA expression of inflammatory factors (tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6), inhibited the protein expression of inflammatory mediators (cyclooxygenase-2 (COX2), and inducible nitric oxide synthase (iNOS)) while suppressing nuclear factor kappa-B (NF-κB) activation in LPS-induced GMECs. Additionally, SFN exhibited an antioxidant effect by increasing Nrf2 expression and nuclear translocation, up-regulating antioxidant enzymes expression, and decreasing LPS-induced reactive oxygen species (ROS) production in GMECs. Furthermore, SFN pretreatment promoted the autophagy pathway, which was dependent on the increased Nrf2 level, and contributed significantly to the improved LPS-induced oxidative stress and inflammatory response. In vivo, SFN effectively alleviated histopathological lesions, suppressed the expression of inflammatory factors, enhanced immunohistochemistry staining of Nrf2, and amplified of LC3 puncta LPS-induced mastitis in mice. Mechanically, the in vitro and in vivo study showed that the anti-inflammatory and anti-oxidative stress effects of SFN were mediated by the Nrf2-mediated autophagy pathway in GMECs and a mouse model of mastitis.

CONCLUSIONS

These results indicate that the natural compound SFN has a preventive effect on LPS-induced inflammation through by regulating the Nrf2-mediated autophagy pathway in primary goat mammary epithelial cells and a mouse model of mastitis, which may improve prevention strategies for mastitis in dairy goats.

Inflammatory stimulus worsens the effects of UV-A exposure on J774 cells

UV-A radiation affects skin homeostasis by promoting oxidative distress. Endogenous photosensitizers in the dermis and epidermis of human skin absorb UV-A radiation forming excited states (singlet and triplet) and reactive oxygen species (ROS) producing oxidized compounds that trigger biological responses. The activation of NF-kB induces the expression of pro-inflammatory cytokines and can intensify the generation of ROS. However, there is no studies evaluating the cross talks between inflammatory stimulus and UV-A exposure on the levels of redox misbalance and inflammation. In here, we evaluated the effects of UV-A exposure on J774 macrophage cells previously challenged with LPS in terms of oxidative distress, release of pro-inflammatory cytokines, and activation of regulated cell death pathways. Our results showed that LPS potentiates the dose-dependent UV-A-induced oxidative distress and cytokine release, in addition to amplifying the regulated (autophagy and apoptosis) and non-regulated (necrosis) mechanisms of cell death, indicating that a previous inflammatory stimulus potentiates UV-A-induced cell damage. We discuss these results in terms of the current-available skin care strategies.

Sulforaphane Suppresses H2O2-Induced Oxidative Stress and Apoptosis via the Activation of AMPK/NFE2L2 Signaling Pathway in Goat Mammary Epithelial Cells

Oxidative stress in high-yielding dairy goats adversely affects lactation length, milk quality, and the economics of dairy products. During the lactation period, goat mammary epithelial cells (GMECs) are often in a state of disordered metabolic homeostasis primarily caused by the overproduction of reactive oxygen species (ROS). Sulforaphane (SFN), an electrophilic compound that is enriched in broccoli, is a promising antioxidant agent for future potential clinical applications. The objective of the present study was to investigate the function of SFN on hydrogen peroxide (H₂O₂)-induced oxidative damage in primary GMECs and the underlying molecular mechanisms. Isolated GMECs in triplicate were pretreated with SFN (1.25, 2.5, and 5 μM) for 24 h in the absence or presence of H₂O₂ (400 μM) for 24 h. The results showed that SFN effectively enhanced superoxide dismutase (SOD) activity, elevated the ratio of glutathione (GSH)/glutathione oxidized (GSSG), and reduced H₂O₂-induced ROS and malondialdehyde (MDA) production and cell apoptosis. Mechanically, SFN-induced nuclear factor erythroid 2-related factor 2 (NRF2/NFE2L2) translocation to the nucleus through the activation of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway coupled with inhibition of the caspase apoptotic pathway. In addition, GMECs were transfected with NFE2L2 small interfering RNA (NFE2L2 siRNA) for 48 h and/or treated with SFN (5 μM) for 24 h before being exposed to H₂O₂ (400 μM) for 24 h. We found that knockdown of NFE2L2 by siRNA abrogated the preventive effect of SFN on H₂O₂-induced ROS overproduction and apoptosis. Taken together, sulforaphane suppressed H₂O₂-induced oxidative stress and apoptosis via the activation of the AMPK/NFE2L2 signaling pathway in primary GMECs.

DNA Methylome and Transcriptome Study of Triterpenoid CDDO in TPA-Mediated Skin Carcinogenesis Model

Overexposure to ultraviolet radiation and environmental carcinogens drive skin cancer development through redox imbalance and gene mutation. Antioxidants such as triterpenoids have exhibited anti-oxidative and anti-inflammatory potentials to alleviate skin carcinogenesis. This study investigated the methylome and transcriptome altered by tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) or TPA with 2-cyano 2,3-dioxoolean-1,9-dien-28-oic acid (CDDO). The results show that CDDO blocks TPA-induced transformation dose dependently. Several differential expressed genes (DEGs) involved in skin cell transformation, while counteracted by CDDO, were revealed by differential expression analysis including Lyl1, Lad1, and Dennd2d. In CpG methylomic profiles, the differentially methylated regions (DMRs) in the promoter region altered by TPA while showing the opposite methylation status in the CDDO treatment group were identified. The correlation between DNA methylation and RNA expression has been established and DMRs showing inverse correlation were further studied as potential therapeutic targets. From the CpG methylome and transcriptome results, CDDO significantly restored gene expression of NAD(P)H:quinone oxidoreductase 1 (Nqo1) inhibited by TPA by decreasing their promoter CpG methylation. Ingenuity Pathways Analysis (IPA) shows that CDDO neutralized the effect of TPA through modulating cell cycles, cell migration, and inflammatory and immune response regulatory pathways. Notably, Tumor Necrosis Factor Receptor 2 (TNFR2) signaling was significantly downregulated by CDDO potentially contributing to prevention of TPA-induced cell transformation. Overall, incorporating the transcriptome, CpG methylome, and signaling pathway network, we reveal potential therapeutic targets and pathways by which CDDO could reverse TPA-induced carcinogenesis. The results could be useful for future human study and targets development for skin cancer.

Nrf2 Modulation in Breast Cancer

Reactive oxygen species (ROS) are identified to control the expression and activity of various essential signaling intermediates involved in cellular proliferation, apoptosis, and differentiation. Indeed, ROS represents a double-edged sword in supporting cell survival and death. Many common pathological processes, including various cancer types and neurodegenerative diseases, are inflammation and oxidative stress triggers, or even initiate them. Keap1-Nrf2 is a master antioxidant pathway in cytoprotective mechanisms through Nrf2 target gene expression. Activation of the Nfr2 pathway benefits cells in the early stages and reduces the level of ROS. In contrast, hyperactivation of Keap1-Nrf2 creates a context that supports the survival of both healthy and cancerous cells, defending them against oxidative stress, chemotherapeutic drugs, and radiotherapy. Considering the dual role of Nrf2 in suppressing or expanding cancer cells, determining its inhibitory/stimulatory position and targeting can represent an impressive role in cancer treatment. This review focused on Nrf2 modulators and their roles in sensitizing breast cancer cells to chemo/radiotherapy agents.

Pharmaceutical and nutraceutical potential of natural bioactive pigment: astaxanthin

Astaxanthin (3,3'-dihydroxy-β,β-carotene-4,4'-dione) is an orange-red, lipophilic keto-carotenoid pigment. It is majorly found in marine ecosystems particularly in aquatic animals such as salmon, shrimp, trout, krill, crayfish, and so on. It is also synthesized in microalgae Heamatococcus pluvialis, Chlorococcum, Chlorella zofingiensis, red yeast Phaffia rhodozyma and bacterium Paracoccus carotinifaciens. Some aquatic and terrestrial creatures regarded as a primary and secondary sources of the astaxanthin producing and accumulating it through their metabolic pathways. Astaxanthin is the powerful antioxidant, nutritional supplement as well as promising therapeutic compound, observed to have activities against different ravaging diseases and disorders. Researchers have reported remarkable bioactivities of astaxanthin against major non-communicable chronic diseases such as cardiovascular diseases, cancer, diabetes, neurodegenerative, and immune disorders. The current review discusses some structural aspects of astaxanthin. It further elaborates its multiple potencies such as antioxidant, anti-inflammatory, anti-proliferative, anti-cancer, anti-obese, anti-diabetic, anti-ageing, anti-TB, anti-viral, anti-COVID 19, neuro-protective, nephro-protective, and fertility-enhancing properties. These potencies make it a more precious entity in the preventions as well as treatments of prevalent systematic diseases and/or disorders. Also, the review is acknowledging and documenting its powerful bioactivities in relation with the pharmaceutical as well as nutraceutical applicability.

Oxidative Stress Induced by High Salt Diet—Possible Implications for Development and Clinical Manifestation of Cutaneous Inflammation and Endothelial Dysfunction in Psoriasis vulgaris

Although oxidative stress is recognized as an important effector mechanism of the immune system, uncontrolled formation of reactive oxygen and nitrogen species promotes excessive tissue damage and leads to disease development. In view of this, increased dietary salt intake has been found to damage redox systems in the vessel wall, resulting in endothelial dysfunction associated with NO uncoupling, inflammation, vascular wall remodeling and, eventually, atherosclerosis. Several studies have reported increased systemic oxidative stress accompanied by reduced antioxidant capacity following a high salt diet. In addition, vigorous ionic effects on the immune mechanisms, such as (trans)differentiation of T lymphocytes are emerging, which together with the evidence of NaCl accumulation in certain tissues warrants a re-examination of the data derived from in vitro research, in which the ionic influence was excluded. Psoriasis vulgaris (PV), as a primarily Th17-driven inflammatory skin disease with proven inflammation-induced accumulation of sodium chloride in the skin, merits our interest in the role of oxidative stress in the pathogenesis of PV, as well as in the possible beneficial effects that could be achieved through modulation of dietary salt intake and antioxidant supplementation.

HIF-1α and Nrf2 regulates hypoxia induced overexpression of DDAH1 through promoter activation in prostate cancer

Dimethylarginine dimethylaminohydrolase-1 (DDAH1) is overexpressed in prostate cancer (PCa) and promotes PCa progression in in vivo through the ADMA-NO pathway by degrading nitric oxide synthase (NOS) inhibitors such as asymmetric dimethylarginine (ADMA) and monomethylamine arginine (L-NMMA). In this study, we investigated the molecular mechanism involved in the overexpression of DDAH1 in PCa and examined its potential role as a therapeutic target. We observed that DDAH1expression is elevated in PCa (PC3, LNCaP, and DU145) cell lines under hypoxia. ChIP and reporter assay results confirmed that DDAH1 expression is positively regulated by HIF-1α through directly binding to the hypoxia response elements (HRE) located within the promoter region between - 1242/- 1238 upstream of its transcription start site (TSS). Under hypoxia, HIF-1α is translocated into the nucleus and activates its target gene expression in PC3 cells. Interestingly, in the event of HIF-1α inhibition or siRNA-mediated knockdown, an alternative transcription factor Nrf2 promotes DDAH1 expression through antioxidant response elements (AREs) on its promoter. ChIP assay results showed that Nrf2 binds to AREs located between -1016 / -1008 bp from the TSS of DDAH1. Furthermore, knockdown of PCa therapeutic target HSP90, an essential co-factor for both HIF-1α and Nrf2 causes attenuation of hypoxia induced DDAH1 overexpression in PCa cells. These results demonstrate that hypoxia induced upregulation of DDAH1 expression is positively regulated by HIF-1α and Nrf2 in association with HSP90. Therefore, targeting tumor angiogenesis promoting DDAH1 along with standard androgen receptor (AR) targeted therapy may offer an effective strategy to prevent PCa progression.

Exploring the Mangrove Fruit: From the Phytochemicals to Functional Food Development and the Current Progress in the Middle East

Nowadays, the logarithmic production of existing well-known food materials is unable to keep up with the demand caused by the exponential growth of the human population in terms of the equality of access to food materials. Famous local food materials with treasury properties such as mangrove fruits are an excellent source to be listed as emerging food candidates with ethnomedicinal properties. Thus, this study reviews the nutrition content of several edible mangrove fruits and the innovation to improve the fruit into a highly economic food product. Within the mangrove fruit, the levels of primary metabolites such as carbohydrates, protein, and fat are acceptable for daily intake. The mangrove fruits, seeds, and endophytic fungi are rich in phenolic compounds, limonoids, and their derivatives as the compounds present a multitude of bioactivities such as antimicrobial, anticancer, and antioxidant. In the intermediary process, the flour of mangrove fruit stands as a supplementation for the existing flour with antidiabetic or antioxidant properties. The mangrove fruit is successfully transformed into many processed food products. However, limited fruits from species such as Bruguiera gymnorrhiza, Rhizophora mucronata, Sonneratia caseolaris, and Avicennia marina are commonly upgraded into traditional food, though many more species demonstrate ethnomedicinal properties. In the Middle East, A. marina is the dominant species, and the study of the phytochemicals and fruit development is limited. Therefore, studies on the development of mangrove fruits to functional for other mangrove species are demanding. The locally accepted mangrove fruit is coveted as an alternate food material to support the sustainable development goal of eliminating world hunger in sustainable ways.

Taify Pomegranate Juice (TPJ) Abrogates Acrylamide-Induced Oxidative Stress Through the Regulation of Antioxidant Activity, Inflammation, and Apoptosis-Associated Genes

Acrylamide (ACR) has various effects on biological systems, including oxidative stress and its associated metabolic disorders. Previous research reports that plants growing at high altitude have a different profile of antioxidants. In the current report, the Taify pomegranate juice (TPJ) of the Taify pomegranate growing at the Taif region (high altitude), Saudi Arabia, was investigated for its protective activity from ACR-induced oxidative stress. Rats were treated with ACR, TPJ, or TPJ+ACR, and various assays, including blood chemistry, liver function biomarkers, gene expression of endogenous antioxidant enzymes, oxidative stress regulatory genes, inflammation biomarkers, and apoptosis, were estimated using biochemical, real-time PCR, histopathological, and immunohistochemical analysis. TPJ showed a protective function of ACR-induced alteration of AST, ALT, GGT, urea, total proteins, albumin, MDA, and NO. It also increased the level of the endogenous antioxidative enzymes, including SOD, catalase, and GSH. It showed anti-inflammatory activity by reduction the TNF-α, IL-6 secretion and the enhancing of IL-10 levels. At the gene expression level, TPJ upregulated the expression of endogenous antioxidant genes (SOD and catalase) and of antioxidant-regulating genes Nrf2 and HO-1; downregulated the expression of inflammatory genes TGF-β1, COX2, and the apoptotic gene caspase-3; and upregulated the expression of antiapoptotic gene Bcl2. At the histological level, TPJ showed a protective effect from the ACR-induced hepatic histological damage. Results of this study conclude that TPJ has a protective effect from ACR-induced oxidative stress and its associated metabolic alterations through its antioxidant and anti-inflammatory activities.

Nrf2/Keap1/ARE signaling: Towards specific regulation

The Nrf2 transcription factor governs the expression of hundreds genes involved in cell defense against oxidative stress, the hallmark of numerous diseases such as neurodegenerative, cardiovascular, some viral pathologies, diabetes and others. The main route for Nrf2 activity regulation is via interactions with the Keap1 protein. Under the normoxia the Keap1 binds the Nrf2 and targets it to the proteasomal degradation, while the Keap1 is regenerated. Upon oxidative stress the interactions between Nrf2 and Keap1 are interrupted and the Nrf2 activates the transcription of the protective genes. Currently, the Nrf2 system activation is considered as a powerful cytoprotective strategy for treatment of different pathologies, which pathogenesis relies on oxidative stress including viral diseases of pivotal importance such as COVID-19. The implementation of this strategy is accomplished mainly through the inactivation of the Keap1 "guardian" function. Two approaches are now developing: the Keap1 modification via electrophilic agents, which leads to the Nrf2 release, and direct interruption of the Nrf2:Keap1 protein-protein interactions (PPI). Because of theirs chemical structure, the Nrf2 electrophilic inducers could non-specifically interact with others cellular proteins leading to undesired effects. Whereas the non-electrophilic inhibitors of the Nrf2:Keap1 PPI could be more specific, thereby widening the therapeutic window.

Nfe2l2 Regulates Metabolic Rewiring and Epigenetic Reprogramming in Mediating Cancer Protective Effect by Fucoxanthin

Fucoxanthin (FX) is a carotenoid with many pharmaceutical properties due to its antioxidant/anti-inflammatory and epigenetic effects. NFE2L2 is involved in the defense against oxidative stress/inflammation-mediated diseases, like anticancer effects elicited by phytochemicals including FX. However, the role of FX and NFE2L2 in metabolic rewiring, epigenomic reprogramming, and transcriptomic network in blocking pro-tumorigenic signaling and eliciting cancer-protective effects remains unknown. Herein, we utilized multi-omics approaches to evaluate the role of NFE2L2 and the impact of FX on tumor promoter TPA-induced skin cell transformation. FX blocked TPA-induced ROS and oxidized GSSG/reduced GSH in Nfe2l2wild-type(WT) but not Nfe2l2-knockdown (KD) cells. Both Nfe2l2 KD and TPA altered cellular metabolisms and metabolites which are tightly coupled to epigenetic machinery. The suppressive effects of FX on TPA-enhancedSAM/SAH was abrogated by Nfe2l2 KD indicating Nfe2l2 plays a critical role in FX-mediated metabolic rewiring and its potential consequences on epigenetic reprogramming. Epigenomic CpG methyl-seq revealed that FX attenuated TPA-induced differentially methylated regions (DMRs) of Uhrf1 and Dnmt1 genes. Transcriptomic RNA-seq showed that FX abrogated TPA-induced differentially expressed genes (DEGs) of Nfe2l2-related genes Nqo1, Ho1, and Keap1. Associative analysis of DEGs and DMRs identified that the mRNA expressions of Uhrf1 and Dnmt1 were correlated with the promoter CpG methylation status. Chromatin immunoprecipitation assay showed that FX restored Uhrf1 expression by regulating H3K27Me3 enrichment in the promoter region. In this context, FX/Nfe2l2's redox signaling drives metabolic rewiring causing epigenetic and transcriptomic reprogramming potentially contributing to the protection of TPA-induced JB6 cellular transformation skin cancer model. Graphical abstract.

Cell-Based Assays to Identify Modulators of Nrf2/ARE Pathway

The nuclear factor erythroid 2-related factor (Nrf2) and antioxidant response element (ARE) signaling pathway play an important role in the amelioration of cellular oxidative stress. Thus, assays that detect this pathway can be useful for identifying chemicals that induce or inhibit oxidative stress signaling. This chapter is to describe two cell-based Nrf2/ARE assays in a quantitative high-throughput screening (HTS) format to test a large collection of chemicals for oxidative stress induction ability. The assay descriptions involve cell handling, assay preparation, instrument usage, and assay procedure.

p62 functions as a signal hub in metal carcinogenesis

A number of metals are toxic and carcinogenic to humans. Reactive oxygen species (ROS) play an important role in metal carcinogenesis. Oxidative stress acts as the converging point among various stressors with ROS being the main intracellular signal transducer. In metal-transformed cells, persistent expression of p62 and erythroid 2-related factor 2 (Nrf2) result in apoptosis resistance, angiogenesis, inflammatory microenvironment, and metabolic reprogramming, contributing to overall mechanism of metal carcinogenesis. Autophagy, a conserved intracellular process, maintains cellular homeostasis by facilitating the turnover of protein aggregates, cellular debris, and damaged organelles. In addition to being a substrate of autophagy, p62 is also a crucial molecule in a myriad of cellular functions and in molecular events, which include oxidative stress, inflammation, apoptosis, cell proliferation, metabolic reprogramming, that modulate cell survival and tumor growth. The multiple functions of p62 are appreciated by its ability to interact with several key components involved in various oncogenic pathways. This review summarizes the current knowledge and progress in studies of p62 and metal carcinogenesis with emphasis on oncogenic pathways related to oxidative stress, inflammation, apoptosis, and metabolic reprogramming.

Exploring the Protective and Reparative Mechanisms of G. lucidum Polysaccharides Against H2O2-Induced Oxidative Stress in Human Skin Fibroblasts

BACKGROUND

Ganoderma lucidum (G. lucidum) is one of China's traditional medicinal materials. G. lucidum polysaccharide has a wide range of promising pharmacological applications. However, there are many kinds of G. lucidum and they contain different kinds of polysaccharides. The biological mechanism through which Ganoderma lucidum polysaccharides (GLP) is able to protect human skin fibroblasts (HSFs) from H2O2-induced oxidative damage is still unclear.

METHODS

Six polysaccharides were obtained from G. lucidum to evaluate their free radical scavenging ability (DPPH free radical, ABTS free radical, hydroxyl-free radical, superoxide anion-free radical) in vitro, and their protective and reparative effects on oxidative damage induced by H2O2 in human skin fibroblasts. One polysaccharide was selected to detect oxidative damage markers and gene expression in the Keap1-Nrf2/ARE signaling pathway in HSFs.

RESULTS

All six polysaccharides showed the ability to scavenge free radicals and enhance the tolerance of human skin fibroblasts to H2O2 damage. Among them, GLP1 was selected and separated into two components (GLP1I and GLP1II). The results showed that GLP1, GLP1I and GLPII could significantly reduce the levels of reactive oxygen species (ROS) and malondialdehyde (MDA). The protective effect of GLP1II was stronger than that of positive control vitamin C. In addition, GLP1, GLP1I and GLP1II could significantly increase the levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). And GLP1I works best in both ways. Meanwhile, Nrf2, a key regulator of keAP1-NRF2/ARE signaling pathway, was activated, while Keap1, a negative regulator, was inhibited, thus promoting the expression of downstream antioxidant enzyme genes (GSTs, GCLs, Nqo1, and Ho-1).

CONCLUSION

The results showed that GLP could protect human skin fibroblasts from oxidative damage caused by H2O2 peroxide by enhancing enzyme activity and activating Keap1-Nrf2/ARE signaling pathway. GLP will act as a natural antioxidant to protect the skin from oxidative stress damage.

A Novel Nrf2 Pathway Inhibitor Sensitizes Keap1-Mutant Lung Cancer Cells to Chemotherapy

The nuclear factor erythroid-2-related factor 2 (Nrf2)-Keap1-ARE pathway, a master regulator of oxidative stress, has emerged as a promising target for cancer therapy. Mutations in NFE2L2, KEAP1, and related genes have been found in many human cancers, especially lung cancer. These mutations lead to constitutive activation of the Nrf2 pathway, which promotes proliferation of cancer cells and their resistance to chemotherapies. Small molecules that inhibit the Nrf2 pathway are needed to arrest tumor growth and overcome chemoresistance in Nrf2-addicted cancers. Here, we identified a novel small molecule, MSU38225, which can suppress Nrf2 pathway activity. MSU38225 downregulates Nrf2 transcriptional activity and decreases the expression of Nrf2 downstream targets, including NQO1, GCLC, GCLM, AKR1C2, and UGT1A6. MSU38225 strikingly decreases the protein level of Nrf2, which can be blocked by the proteasome inhibitor MG132. Ubiquitination of Nrf2 is enhanced following treatment with MSU38225. By inhibiting production of antioxidants, MSU38225 increases the level of reactive oxygen species (ROS) when cells are stimulated with tert-butyl hydroperoxide (tBHP). MSU38225 also inhibits the growth of human lung cancer cells in both two-dimensional cell culture and soft agar. Cancer cells addicted to Nrf2 are more susceptible to MSU38225 for suppression of cell proliferation. MSU38225 also sensitizes human lung cancer cells to chemotherapies both in vitro and in vivo Our results suggest that MSU38225 is a novel Nrf2 pathway inhibitor that could potentially serve as an adjuvant therapy to enhance the response to chemotherapies in patients with lung cancer.

Antioxidant properties of anthocyanins and their mechanism of action in atherosclerosis

Atherosclerosis develops due to lipid accumulation in the arterial wall and sclerosis as result of increased hyperlipidemia, oxidative stress, lipid oxidation, and protein oxidation. However, improving antioxidant status through diet may prevent the progression of atherosclerotic cardiovascular disease. It is believed that polyphenol-rich plants contribute to the inverse relationship between fruit and vegetable intake and chronic disease. Anthocyanins are flavonoid polyphenols with antioxidant properties that have been associated with reduced risk of cardiovascular disease. The consumption of anthocyanins increases total antioxidant capacity, antioxidant defense enzymes, and HDL antioxidant properties by several measures in preclinical and clinical populations. Anthocyanins appear to impart antioxidant actions via direct antioxidant properties, as well as indirectly via inducing intracellular Nrf2 activation and antioxidant gene expression. These actions counter oxidative stress and inflammatory signaling in cells present in atherosclerotic plaques, including macrophages and endothelial cells. Overall, anthocyanins may protect against atherosclerosis and cardiovascular disease through their effects on cellular antioxidant status, oxidative stress, and inflammation; however, their underlying mechanisms of action appear to be complex and require further elucidation.

Inflammation and Alzheimer's Disease: Mechanisms and Therapeutic Implications by Natural Products

Alzheimer's disease (AD) is a neurodegenerative disorder with no clear causative event making the disease difficult to diagnose and treat. The pathological hallmarks of AD include amyloid plaques, neurofibrillary tangles, and widespread neuronal loss. Amyloid-beta has been extensively studied and targeted to develop an effective disease-modifying therapy, but the success rate in clinical practice is minimal. Recently, neuroinflammation has been focused on as the event in AD progression to be targeted for therapies. Various mechanistic pathways including cytokines and chemokines, complement system, oxidative stress, and cyclooxygenase pathways are linked to neuroinflammation in the AD brain. Many cells including microglia, astrocytes, and oligodendrocytes work together to protect the brain from injury. This review is focused to better understand the AD inflammatory and immunoregulatory processes to develop novel anti-inflammatory drugs to slow down the progression of AD.

Protective Effects of Fucoxanthin Dampen Pathogen-Associated Molecular Pattern (PAMP) Lipopolysaccharide-Induced Inflammatory Action and Elevated Intraocular Pressure by Activating Nrf2 Signaling and Generating Reactive Oxygen Species

Inflammation and oxidative stress are closely related processes in the pathogenesis of various ocular diseases. Uveitis is a disorder of the uvea and ocular tissues that causes extreme pain, decreases visual acuity, and can eventually lead to blindness. The pharmacological functions of fucoxanthin, isolated from brown algae, induce a variety of therapeutic effects such as oxidative stress reduction and repression of inflammation reactions. However, the specific anti-inflammatory effects of fucoxanthin on pathogen-associated molecular pattern (PAMP) lipopolysaccharide-induced uveitis have yet to be extensively described. Therefore, the aim of present study was to investigate the anti-inflammatory effects of fucoxanthin on uveitis in rats. The results showed that fucoxanthin effectively enhanced the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) in ocular tissues. Furthermore, fucoxanthin significantly increased the ocular activities of superoxide dismutase and decreased the levels of malondialdehyde stimulated by PAMP-induced uveitis. Ocular hypertension and the levels of inflammatory cells and proinflammatory cytokine tumor necrosis factor-alpha in the aqueous humor were alleviated with fucoxanthin treatment. Consequently, compared to the observed effects in lipopolysaccharide groups, fucoxanthin treatment significantly preserved iris sphincter innervation and pupillary function. Additionally, PAMP-induced corneal endothelial disruption was significantly inhibited by fucoxanthin treatment. Overall, these findings suggest that fucoxanthin may protect against inflammation from PAMP-induced uveitis by promoting the Nrf2 pathway and inhibiting oxidative stress.

Nrf2/Keap1-Pathway Activation and Reduced Susceptibility to Chemotherapy Treatment by Acidification in Esophageal Adenocarcinoma Cells

Simple Summary

Inflammation caused by acidic reflux contributes to disease progression in Barrett’s esophagus. Little is known, whether esophageal cancer cells are influenced by acidic reflux and whether reflux influences cancer cell physiology, targeting the Nrf2/Kepa1- and the NFκB-pathway. The understanding mechanisms of the acidic susceptibility in cells from advanced stages of Barrett’s esophagus will provide further evidence, whether it should be prevented during chemotherapy for EAC treatment.

Abstract

Chronic acid reflux causes cellular damage and inflammation in the lower esophagus. Due to these irritating insults, the squamous epithelium is replaced by metaplastic epithelium, which is a risk factor for the development of esophageal adenocarcinoma (EAC). In this study, we investigated the acid susceptibility in a Barrett’s cell culture in vitro model, using six cell lines, derived from squamous epithelium (EPC1 and EPC2), metaplasia (CP-A), dysplasia (CP-B), and EAC (OE33 and OE19) cells. Cells exposed to acidic pH showed a decreased viability dependent on time, pH, and progression status in the Barrett’s sequence, with the highest acid susceptibility in the squamous epithelium (EPC1 and EPC2), and the lowest in EAC cells. Acid pulsing was accompanied with an activation of the Nrf2/Keap1- and the NFκB-pathway, resulting in an increased expression of HO1—independent of the cellular context. OE33 showed a decreased responsiveness towards 5-FU, when the cells were grown in acidic conditions (pH 6 and pH 5.5). Our findings suggest a strong damage of squamous epithelium by gastroesophageal reflux, while Barrett’s dysplasia and EAC cells apparently exert acid-protective features, which lead to a cellular resistance against acid reflux.

Common and Novel Markers for Measuring Inflammation and Oxidative Stress Ex Vivo in Research and Clinical Practice-Which to Use Regarding Disease Outcomes?

Many chronic conditions such as cancer, chronic obstructive pulmonary disease, type-2 diabetes, obesity, peripheral/coronary artery disease and auto-immune diseases are associated with low-grade inflammation. Closely related to inflammation is oxidative stress (OS), which can be either causal or secondary to inflammation. While a low level of OS is physiological, chronically increased OS is deleterious. Therefore, valid biomarkers of these signalling pathways may enable detection and following progression of OS/inflammation as well as to evaluate treatment efficacy. Such biomarkers should be stable and obtainable through non-invasive methods and their determination should be affordable and easy. The most frequently used inflammatory markers include acute-phase proteins, essentially CRP, serum amyloid A, fibrinogen and procalcitonin, and cytokines, predominantly TNFα, interleukins 1β, 6, 8, 10 and 12 and their receptors and IFNγ. Some cytokines appear to be disease-specific. Conversely, OS-being ubiquitous-and its biomarkers appear less disease or tissue-specific. These include lipid peroxidation products, e.g., F2-isoprostanes and malondialdehyde, DNA breakdown products (e.g., 8-OH-dG), protein adducts (e.g., carbonylated proteins), or antioxidant status. More novel markers include also -omics related ones, as well as non-invasive, questionnaire-based measures, such as the dietary inflammatory-index (DII), but their link to biological responses may be variable. Nevertheless, many of these markers have been clearly related to a number of diseases. However, their use in clinical practice is often limited, due to lacking analytical or clinical validation, or technical challenges. In this review, we strive to highlight frequently employed and useful markers of inflammation-related OS, including novel promising markers.

Perspectives on the Clinical Development of NRF2-Targeting Drugs

The transcription factor NRF2 (nuclear factor erythroid 2-related factor 2) triggers homeostatic responses against a plethora of environmental or endogenous deviations in redox metabolism, inflammation, proteostasis, etc. Therefore, pharmacological activation of NRF2 is a promising therapeutic strategy for several chronic diseases that are underlined by low-grade oxidative inflammation and dysregulation of redox metabolism, such as neurodegenerative, cardiovascular, and metabolic diseases. While NRF2 activation is useful in inhibiting carcinogenesis, its inhibition is needed in constituted tumors where NRF2 provides a survival advantage in the challenging tumor niche. This review describes the electrophilic and non-electrophilic NRF2 activators with clinical projection in various chronic diseases. We also analyze the status of NRF2 inhibitors, which are for the moment in a proof-of-concept stage. Advanced in silico screening and medicinal chemistry are expected to provide new or repurposing small molecules with increased potential for fostering the development of targeted NRF2 modulators. The nuclear factor erythroid 2 (NFE2)-related factor 2 (NRF2) is rapidly degraded by proteasomes under a basal condition in a Keap1-dependent manner. ROS oxidatively modifies Keap1 to release NRF2 and allow its nuclear translocation. Here it binds to the antioxidant response element to regulate gene transcription. An alternative mechanism controlling NRF2 stability is glycogen synthase kinase 3 (GSK-3)-induced phosphorylation. Indicated in blue are NRF2-activating and NRF2-inhibiting drugs.

Loss-of-function mutations in KEAP1 drive lung cancer progression via KEAP1/NRF2 pathway activation

BACKGROUND AND PURPOSE

Targeted therapy and immunotherapy have led to dramatic change in the treatment of lung cancer, however, the overall 5-year survival rate of lung cancer patients is still suboptimal. It is important to exploit new potential of molecularly targeted therapies. High-frequency somatic mutations in KEAP1/NRF2 (27.9%) have been identified in lung squamous cell carcinoma. In this research, we explored the role of KEAP1 somatic mutations in the development of LSCC and whether a nuclear factor erythroid 2-related factor 2(NRF2) inhibitor be potential to target lung cancer carrying KEAP1/NRF2 mutations.

METHODS

Lung cancer cell lines A549 and H460 with loss-of-function mutations in KEAP1 stably transfected with wild-type (WT) KEAP1 or somatic mutations in KEAP1 were used to investigate the functions of somatic mutations in KEAP1. Flow cytometry, plate clone formation experiments, and scratch tests were used to examine reactive oxygen species, proliferation, and migration of these cell lines.

RESULTS

The expression of NRF2 and its target genes increased, and tumor cell proliferation, migration, and tumor growth were accelerated in A549 and H460 cells stably transfected with KEAP1 mutants compared to control cells with a loss-of-function KEAP1 mutation and stably transfected with WT KEAP1 in both in vitro and in vivo studies. The proliferation of A549 cell line trasfected with the R320Q KEAP1 mutant was inhibited more apparent than that of the A549 cell line trasfected with WT KEAP1 after treatment with NRF2 inhibitor ML385.

CONCLUSION

Somatic mutations of KEAP1 identified from patients with LSCC likely promote tumorigenesis mediated by activation of the KEAP1/NRF2 antioxidant stress response pathway. NRF2 inhibition with ML385 could inhibit the proliferation of tumor cells with KEAP1 mutation. Video abstract.

Obtusaquinone: A Cysteine-Modifying Compound That Targets Keap1 for Degradation

We have previously identified the natural product obtusaquinone (OBT) as a potent antineoplastic agent with promising in vivo activity in glioblastoma and breast cancer through the activation of oxidative stress; however, the molecular properties of this compound remained elusive. We used a multidisciplinary approach comprising medicinal chemistry, quantitative mass spectrometry-based proteomics, functional studies in cancer cells, and pharmacokinetic analysis, as well as mouse xenograft models to develop and validate novel OBT analogs and characterize the molecular mechanism of action of OBT. We show here that OBT binds to cysteine residues with a particular affinity to cysteine-rich Keap1, a member of the CUL3 ubiquitin ligase complex. This binding promotes an overall stress response and results in ubiquitination and proteasomal degradation of Keap1 and downstream activation of the Nrf2 pathway. Using positron emission tomography (PET) imaging with the PET-tracer 2-[¹⁸F]fluoro-2-deoxy-d-glucose (FDG), we confirm that OBT is able to penetrate the brain and functionally target brain tumors. Finally, we show that an OBT analog with improved pharmacological properties, including enhanced potency, stability, and solubility, retains the antineoplastic properties in a xenograft mouse model.

Astaxanthin anticancer effects are mediated through multiple molecular mechanisms: A systematic review

During the latest decades, the interest on the effectiveness of natural compounds and their impact on human health constantly increased, especially on those demonstrating to be effective on cancer. Molecules coming from nature are currently used in chemotherapy like Taxol, Vincristine or Vinblastine, and several other natural substances have been showed to be active in reducing cancer cell progression and migration. Among them, astaxanthin, a xanthophyll red colored carotenoid, displayed different biological activities including, antinflammatory, antioxidant, proapoptotic, and anticancer effects. It can induce apoptosis through downregulation of antiapoptotic protein (Bcl-2, p-Bad, and survivin) expression and upregulation of proapoptotic ones (Bax/Bad and PARP). Thanks to these mechanisms, it can exert anticancer effects towards colorectal cancer, melanoma, or gastric carcinoma cell lines. Moreover, it possesses antiproliferative activity in many experimental models and enhances the effectiveness of conventional chemotherapic drugs on tumor cells underling its potential future use. This review provides an overview of the current knowledge on the anticancer potential of astaxanthin by modulating several molecular targets. While it has been clearly demonstrated its multitarget activity in the prevention and regression of malignant cells in in vitro or in preclinical investigations, further clinical studies are needed to assess its real potential as anticancer in humans.

Recent progress in the development of small molecule Nrf2 activators: a patent review (2017-present)

Introduction: The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is the first line of defense against a plethora of environmental or endogenous deviations in redox metabolism, proteostasis, inflammation, etc. Therefore, pharmacological activation of Nrf2 is a potential therapeutic approach for several diseases related to oxidative stress and inflammation, such as cancer, cardiovascular, and neurodegenerative diseases.Areas covered: The authors first describe the biological function of Nrf2 and the molecular regulatory mechanism of Keap1-Nrf2-ARE ((Kelch-like ECH-Associating protein 1)-Nrf2-(antioxidant response element)). Then, they review recent progress of covalent activators and non-covalent Keap1-Nrf2 protein-protein interaction (PPI) inhibitors from patents and publications in 2017-present, consisting of new chemical molecules, structure optimization of reported activators and progress in preclinical or clinical trials.Expert opinion: Despite significant achievements in the development of Nrf2 activators, the selectivity is the primary consideration. Due to reacting with redox-sensitive cysteines in proteins except for Keap1, electrophilic activators often exhibit off-target effects. For Keap1-Nrf2 PPI inhibitors, how to enhance in vivo efficacy and/or penetrate blood-brain barrier (BBB) to reach central nervous system (CNS) is also challenging. Fragment-based drug discovery (FBDD), carboxylic acid bioisosteric replacement and prodrug approach might be used to circumvent this challenge. Moreover, the possibility of cancer risk caused by Nrf2 activation needs to be considered carefully.

Sulfiredoxin as a Potential Therapeutic Target for Advanced and Metastatic Prostate Cancer

The incidence of prostate cancer (PCa) is increasing, and it is currently the second most frequent cause of death by cancer in men. Despite advancements in cancer therapies, new therapeutic approaches are still needed for treatment-refractory advanced metastatic PCa. Cross-species analysis presents a robust strategy for the discovery of new potential therapeutic targets. This strategy involves the integration of genomic data from genetically engineered mouse models (GEMMs) and human PCa datasets. Considering the role of antioxidant pathways in tumor initiation and progression, we searched oxidative stress-related genes for a potential therapeutic target for PCa. First, we analyzed RNA-sequencing data from Pb-Cre4; Pten^f/f mice and discovered an increase in sulfiredoxin (Srxn1) mRNA expression in high-grade prostatic intraepithelial neoplasia (PIN), well-differentiated adenocarcinoma (medium-stage tumors), and poor-differentiated adenocarcinoma (advanced-stage prostate tumors). The increase of SRXN1 protein expression was confirmed by immunohistochemistry in mouse prostate tumor paraffin samples. Analyses of human databases and prostate tissue microarrays demonstrated that SRXN1 is overexpressed in a subset of high-grade prostate tumors and correlates with aggressive PCa with worse prognosis and decreased survival. Analyses in vitro showed that SRXN1 expression is also higher in most PCa cell lines compared to normal cell lines. Furthermore, siRNA-mediated downregulation of SRXN1 led to decreased viability of PCa cells LNCaP. In conclusion, we identified the antioxidant enzyme SRXN1 as a potential therapeutic target for PCa. Our results suggest that the use of specific SRXN1 inhibitors may be an effective strategy for the adjuvant treatment of castration-resistant PCa with SRXN1 overexpression.

Dietary lycopene alters the expression of antioxidant enzymes and modulates the blood lipid profile of pigs

Lycopene has the highest antioxidant activity among carotenoids due to its high number of conjugated double bonds; thus, it can be used in pig diets to look for improvements in growth performance and health status, eliminating or preventing the formation of free radicals. Therefore, the aim of the present study was to investigate the effects of dietary lycopene on the growth performance, the gene expression of antioxidant enzymes and blood lipid profile of finishing pigs. In total, 40 barrows and 40 gilts (Piétrain × Landrace × Large White) were used, averaging 75.04 ± 1.6 kg of initial bodyweight. Pigs were distributed in a 2 × 5 factorial arrangement, consisting of two genders (male and female) and five dietary levels of lycopene (0, 12.5, 25.0, 37.5 and 50.0 mg/kg of diet) supplemented for 28 days. It was observed that gilts presented with average daily feed intake (P = 0.001) being lower and the gain:feed ratio (P = 0.001) higher than for barrows. Increasing dietary lycopene concentration provided a linear decrease in the gene expression of the enzymes superoxide dismutase (SOD1; P = 0.018) and catalase (P = 0.001) in the liver of gilts. The gilts showed a lower gene expression than did barrows for SOD1 gene (P = 0.001) receiving 50.0 mg lycopene/kg of diet and for catalase gene (P = 0.001) receiving of 0, 12.5 and 50.0 mg lycopene/kg of diet. Glutathione peroxidase showed a lower expression (P = 0.001) for gilts than for barrows. Total cholesterol, low-density lipoprotein (LDL) and LDL:high-density lipoprotein (HDL) ratio decreased (P = 0.001) as lycopene concentration increased in the diet. Increasing dietary lycopene in pig diets improved the lipid profile of the blood plasma, providing an increase in the concentration of high-density lipoprotein (HDL; P = 0.001). Gilts had greater plasma concentrations of urea (P = 0.001) and triglycerides (P = 0.001) and lower concentrations of HDL (P = 0.001), LDL (P = 0.001) and a lower LDL:HDL ratio (P = 0.004) than did barrows. Dietary lycopene up to 50 mg/kg does not affect the growth performance of pigs, acting as a potent modulator of the lipid profile and also reducing the plasma concentrations of total cholesterol and low-density lipoproteins, while increasing the high-density lipoproteins. In addition, lycopene also reduces the gene expression of superoxide dismutase and catalase enzymes in the liver of gilts.

Mechanisms of Herbal Nephroprotection in diabetes mellitus

Diabetic nephropathy (DN) is a leading cause of kidney morbidity. Despite the multilayered complexity of the mechanisms involved in the pathogenesis of DN, the conventional treatment is limited to just a few drug classes fraught with the risk of adverse events, including the progression of renal dysfunction. Phytoceuticals offer a promising alternative as they act on the many-sidedness of DN pathophysiology, multitargeting its intricacies. This paper offers a review of the mechanisms underlying the protective action of these phytoagents, including boosting the antioxidant capabilities, suppression of inflammation, averting the proliferative and sclerosing/fibrosing events. The pathogenesis of DN is viewed as a continuum going from the original offense, high glucose, through the noxious products it generates (advanced glycation end-products, products of oxidative and nitrosative stress) and the signaling chains consequently brought into action, to the harmful mediators of inflammation, sclerosis, and proliferation that eventually lead to DN, despite the countervailing attempts of the protective mechanisms. Special attention was given to the various pathways involved, pointing out the ability of the phytoagents to hinder the deleterious ones (especially those leading to, driven by, or associated with TGF-β activation, SREBP, Smad, MAPK, PKC, NF-κB, NLRP3 inflammasome, and caspase), to promote the protective ones (PPAR-α, PPAR-γ, EP4/Gs/AC/cAMP, Nrf2, AMPK, and SIRT1), and to favorably modulate those with potentially dual effect (PI3K/Akt). Many phytomedicines have emerged as potentially useful out of in vitro and in vivo studies, but the scarcity of human trials seriously undermines their usage in the current clinical practice-an issue that stringently needs to be addressed.

Anthocyanin Delphinidin Prevents Neoplastic Transformation of Mouse Skin JB6 P+ Cells: Epigenetic Re-activation of Nrf2-ARE Pathway

Redox imbalance is a major contributor to the pathogenesis of melanoma and nonmelanoma skin cancer. Activation of the nuclear factor E2-related factor 2 (Nrf2) antioxidant responsive element (ARE) pathway is an intrinsic defense mechanism against oxidative stress. Flavonoids such as anthocyanidins, which are found abundantly in fruits and vegetables, have been shown to activate Nrf2. However, the epigenetic and genetic mechanisms by which anthocyanidins modulate the Nrf2-ARE pathway remain poorly understood in the context of skin cancer. In this study, delphinidin, one of the most potent and abundant anthocyanidins in berries, significantly inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced neoplastic cell transformation in mouse epidermal JB6 P+ cells by 69.4 to 99.4%. The mechanism was elucidated based on observations of increased ARE-driven luciferase activity and elevated mRNA and protein expression of Nrf2 downstream genes, such as heme oxygenase-1 (Ho-1), in JB6 P+ cells. Activation of the Nrf2-ARE pathway was correlated with demethylation of 15 CpG sites in the mouse Nrf2 promoter region between nt - 1226 and - 863 from the transcription start site. The reduced CpG methylation ratio in the Nrf2 promoter region was consistent with observed decreases in the protein expression of DNA methyltransferases 1 (DNMT1), DNMT3a, and class I/II histone deacetylases (HDACs). Overall, our results suggest that delphinidin, an epigenetic demethylating agent of the Nrf2 promoter, can activate the Nrf2-ARE pathway, which can be applied as a potential skin cancer chemopreventive agent.

Pelargonidin reduces the TPA induced transformation of mouse epidermal cells -potential involvement of Nrf2 promoter demethylation

Pelargonidin, a well-known natural anthocyanidin found in berries strawberries, blueberries, red radishes and other natural foods, has been found to possess health beneficial effects including anti-cancer effect. Herein, we investigated the effect of pelargonidin on cellular transformation in mouse skin epidermal JB6 (JB6 P+) cells induced by tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Pelargonidin treatment significantly decreased colony formation and suppressed cell viability of JB6 P+ cells. Pelargonidin also induced the anti-oxidant response element (ARE)-luciferase activation in HepG2-C8 cells overexpressing the ARE-luciferase reporter. Knockdown of nuclear factor E2-related factor 2 (Nrf2) in shNrf2 JB6 P+ cells enhanced TPA-induced colony formation and attenuated pelargonidin's blocking effect. Pelargonidin reduced the protein levels of genes encoding methyltransferases (DNMTs) and histone deacetylases (HDACs). Importantly, pelargonidin decreased the DNA methylation in the Nrf2 promoter region of JB6 P+ cells and increased Nrf2 downstream target genes expression, such as NAD(P)H/quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1), involved in cellular protection. In summary, our results showed that pelargonidin blocks TPA-induced cell transformation. The possible molecular mechanisms of its potential anti-cancer effects against neoplastic transformation may be attributed to its activation of Nrf2-ARE signaling pathway and its cytoprotective effect.

Astragaloside IV ameliorates high glucose-induced HK-2 cell apoptosis and oxidative stress by regulating the Nrf2/ARE signaling pathway

Diabetic nephropathy (DN) has become the major cause of end-stage renal disease increasing the mortality risk of diabetes. Research has demonstrated that the oxidative damage and apoptosis of renal tubular cells is present during DN. Astragaloside IV (AS-IV) has been widely used for the treatment of many diseases, however, the role and mechanism by which AS-IV may ameliorate high glucose-induced apoptosis and oxidative stress of the human proximal tubular cell line HK-2 remains largely unknown. The present study investigated the effect of AS-IV on high glucose-induced apoptosis and oxidative stress in HK-2 cells. Cell viability, apoptosis and protein expression were detected by Trypan blue staining, Cell Counting Kit-8 assay, terminal deoxynucleotidyl transferase 2′-deoxyuridine-5′-triphosphate nick-end labelling, flow cytometry and western blot analyses. In addition, enzymatic activities, including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and lipid peroxide (LPO), were measured with the corresponding detection kits. DCFH-DA assay and flow cytometry were performed to detect the production of reactive oxygen species (ROS). Western blot analysis and reverse transcription-quantitative polymerase chain reaction were conducted to evaluate protein and mRNA expressions of the nuclear factor erythroid 2 like 2 (Nrf2)/antioxidant response element (ARE) signaling pathway. The results demonstrated that AS-IV significantly enhanced HK-2 cell viability induced by high glucose in a dose-dependent manner. In addition, AS-IV notably inhibited HK-2 cell apoptosis stimulated by high glucose, which may be associated with inhibition of BCL2 associated X protein, Cleaved-caspase-3 and Cleaved-caspase-9, expression and the promotion of Bcl-2. AS-IV significantly increased the activities of antioxidant enzymes SOD, GSH-Px and CAT, and decreased the high-glucose-induced ROS production in HK-2 cells, in a dose-dependent manner. Finally, it was determined that AS-IV regulated the Nrf2/ARE signaling pathway and inhibited the expression of liver-type fatty acid binding protein. In conclusion, these findings may provide evidence that AS-IV has a potential role for the treatment of DN.

5-(3,4-Difluorophenyl)-3-(6-methylpyridin-3-yl)-1,2,4-oxadiazole (DDO-7263), a novel Nrf2 activator targeting brain tissue, protects against MPTP-induced subacute Parkinson's disease in mice by inhibiting the NLRP3 inflammasome and protects PC12 cells against oxidative stress

Parkinson's disease (PD) is the second most common aging-related neurodegenerative disease worldwide. Oxidative stress and neuroinflammation are critical events in the degeneration of dopaminergic neurons in PD. In this study, we found that DDO-7263, a novel Nrf2-ARE activator reported by us, has ideal therapeutic effects on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease in mice. DDO-7263 improved the behavioral abnormalities induced by MPTP in mice, significantly attenuated chemically induced dopaminergic neuron loss of tyrosine hydroxylase (TH) in the substantia nigra (SN) and striatum of the mouse brain and inhibited the secretion of inflammatory factors. In addition, DDO-7263 protected PC12 neurons from H₂O₂-induced oxidative damage. The neuroprotective effects of DDO-7263 were confirmed both in vitro and in vivo models. Further studies showed that the neuroprotective effect of DDO-7263 was mediated by the activation of Nrf2-ARE signaling pathway and the inhibition of NLRP3 inflammasome activation. DDO-7263 induced NLRP3 inflammasome inhibition is dependent on Nrf2 activation. This conclusion was also verified in THP-1-derived macrophages (THP-Ms). DDO-7263 significantly inhibited NLRP3 activation, cleaved caspase-1 production and IL-1β protein expression in ATP-LPS-exposed THP-Ms cells. The pharmacokinetic parameters and tissue distribution results indicated that DDO-7263 has a brain tissue targeting function. All these lines of evidence show that DDO-7263 has ideal therapeutic effects on neurodegenerative diseases such as PD.

CpG methyl-seq and RNA-seq epigenomic and transcriptomic studies on the preventive effects of Moringa isothiocyanate in mouse epidermal JB6 cells induced by the tumor promoter TPA

Epigenetic mechanisms play an important role in the early stages of carcinogenesis. Moringa isothiocyanate (MIC-1) is a major bioactive component derived from Moringa oleifera that has considerable antioxidant and anti-inflammatory effects. However, how MIC-1 influences epigenomic alterations in TPA-mediated JB6 cell carcinogenic transformation has not been evaluated. In this study, DNA and RNA isolated from TPA-induced JB6 cells in the presence or absence of MIC-1 were subjected to DNA Methyl-seq and RNA-seq to identify differentially methylated regions (DMRs) and differentially expressed genes (DEGs), respectively. When JB6 cells were challenged with TPA alone, there was a significant alteration of DEGs and DMRs; importantly, MIC-1 treatment reversed the patterns of some of the DEGs and DMRs. Transcriptome and CpG methylome profiling was performed in Ingenuity® Pathway Analysis (IPA) software to analyze the altered signaling pathways. Several anti-inflammatory responses, antioxidative stress-related pathways, and anticancer-related pathways were identified to be affected by MIC-1. These pathways included NF-kB, IL-1, LPS/IL-1-mediated inhibition of RXR function, Nrf2-mediated oxidative stress response, p53, and PTEN signaling pathways. Examination of correlations between transcriptomic and CpG methylome profiles yielded a small subset of genes, including the cancer-related genes Tmpt, Tubb3, and Muc2; the GTPases Gchfr and Igtp; and the cell cycle-related gene Cdc7. Taken together, our results show the potential contributions of epigenomic changes in DNA CpG methylation to gene expression to molecular pathways active in TPA-induced JB6 cells and demonstrate that MIC-1 can reverse these changes, supporting the potential preventive/treatment effects of MIC-1 against skin carcinogenesis.

Moringa Isothiocyanate Activates Nrf2: Potential Role in Diabetic Nephropathy

Moringa isothiocyanate (MIC-1) is the main active isothiocyanate found in Moringa oleifera, a plant consumed as diet and traditional herbal medicine. Compared to sulforaphane (SFN), MICs are less studied and most work have focused on its anti-inflammatory activity. The purpose of this study is to better understand the Nrf2-ARE antioxidant activity of MIC-1 and its potential in diabetic nephropathy. MIC-1 showed little toxicity from 1.25-5 μM. MIC-1 activated Nrf2-ARE at similar levels to SFN. MIC-1 also increased gene expression of downstream Nrf2 genes NQO1, HO-1, and GCLC. Protein expression of HO-1 and GCLC was elevated in MIC-1-treated cells versus control. MIC-1 suppressed pro-inflammatory cytokines in LPS-stimulated macrophages. MIC-1 reduced levels of reactive oxygen species in high glucose (HG)-treated human renal proximal tubule HK-2 cells. RNA-seq was performed to examine the transcriptome in HK-2 cells exposed to HG with or without MIC-1. Ingenuity Pathway Analysis (IPA) of RNA-seq on HK-2 cells exposed to HG identified TGFβ1 and NQO1 regulation as potentially impacted and treatment of HG-exposed HK-2 cells with MIC-1 reversed the gene expression of these two pathways. Results implicate that the transcriptional regulator TGFβ1 signaling is activated by HG and that MIC-1 can inhibit HG-stimulated TGFβ1 activation. In summary, MIC-1 activates Nrf2-ARE signaling, increases expression of Nrf2 target genes, and suppresses inflammation, while also reducing oxidative stress and possibly TGFβ1 signaling in high glucose induced renal cells. Taken together, it appears that one potential therapeutic strategy for managing DN and is currently under development in clinic is Nrf2 activation.

Contribution of Nrf2 Modulation to the Mechanism of Action of Analgesic and Anti-inflammatory Drugs in Pre-clinical and Clinical Stages

Despite the progress that has occurred in recent years in the development of therapies to treat painful and inflammatory diseases, there is still a need for effective and potent analgesics and anti-inflammatory drugs. It has long been known that several types of antioxidants also possess analgesic and anti-inflammatory properties, indicating a strong relationship between inflammation and oxidative stress. Understanding the underlying mechanisms of action of anti-inflammatory and analgesic drugs, as well as essential targets in disease physiopathology, is essential to the development of novel therapeutic strategies. The Nuclear factor-2 erythroid related factor-2 (Nrf2) is a transcription factor that regulates cellular redox status through endogenous antioxidant systems with simultaneous anti-inflammatory activity. This review summarizes the molecular mechanisms and pharmacological actions screened that link analgesic, anti-inflammatory, natural products, and other therapies to Nrf2 as a regulatory system based on emerging evidences from experimental disease models and new clinical trial data.

Expression Levels of microRNAs miR-93 and miR-200a in Pancreatic Adenocarcinoma with Special Reference to Differentiation and Relapse-Free Survival

OBJECTIVES

Protein levels of the transcription factor nuclear factor erythroid-derived 2-like 2 (Nrf2) and its inhibitor Kelch-like ECH-associated protein 1 (Keap1) have been proposed as prognostic factors in pancreatic ductal adenocarcinomas (PDACs). These cellular redox-state-regulating enzymes are targeted by several microRNAs, including miR-93 and miR-200a.

METHODS

We assessed mRNA levels of Nrf2 and Keap1 and tissue expression of miR-93 and miR-200a in 51 patients with surgically treated PDAC. Expression levels were separately measured in malignant cells and adjacent benign cells.

RESULTS

Keap1 and Nrf2 mRNA expression levels in cancer cells were lower than in adjacent benign tissue (Wilcoxon's test; p = 0.0015 and p = 0.000032, respectively). Conversely, miR-93 expression was higher in cancer cells than in adjacent benign tissue (p = 0.00082). Low levels of miR-93 and miR-200a in cancer cells were associated with poorer differentiation (p = 0.004 and p = 0.002, respectively). In univariate survival analysis, benign-tissue levels of miR-200a above the median predicted better relapse-free survival (RFS) (p = 0.045).

CONCLUSIONS

High miR-93 and miR-200a levels in cancer cells of PDAC were associated with better differentiation, and miR-200a expression in benign tissue with excellent RFS. Keap1 and Nrf2 mRNA levels showed prominent down-regulation in cancerous versus benign tissue, but they were not associated with disease aggressiveness or outcome.

Identification of an Unfavorable Immune Signature in Advanced Lung Tumors from Nrf2-Deficient Mice

AIMS

Activation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway in normal cells inhibits carcinogenesis, whereas constitutive activation of Nrf2 in cancer cells promotes tumor growth and chemoresistance. However, the effects of Nrf2 activation in immune cells during lung carcinogenesis are poorly defined and could either promote or inhibit cancer growth. Our studies were designed to evaluate tumor burden and identify immune cell populations in the lungs of Nrf2 knockout (KO) versus wild-type (WT) mice challenged with vinyl carbamate.

RESULTS

Nrf2 KO mice developed lung tumors earlier than the WT mice and exhibited more and larger tumors over time, even at late stages. T cell populations were lower in the lungs of Nrf2 KO mice, whereas tumor-promoting macrophages and myeloid-derived suppressor cells were elevated in the lungs and spleen, respectively, of Nrf2 KO mice relative to WT mice. Moreover, 34 immune response genes were significantly upregulated in tumors from Nrf2 KO mice, especially a series of cytokines (Cxcl1, Csf1, Ccl9, Cxcl12, etc.) and major histocompatibility complex antigens that promote tumor growth.

INNOVATION

Our studies discovered a novel immune signature, characterized by the infiltration of tumor-promoting immune cells, elevated cytokines, and increased expression of immune response genes in the lungs and tumors of Nrf2 KO mice. A complementary profile was also found in lung cancer patients, supporting the clinical significance of our findings.

CONCLUSION

Overall, our results confirmed a protective role for Nrf2 in late-stage carcinogenesis and, unexpectedly, suggest that activation of Nrf2 in immune cells may be advantageous for preventing or treating lung cancer. Antioxid. Redox Signal.

Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2) Inhibition: An Emerging Strategy in Cancer Therapy

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a pleiotropic transcription factor, especially for its complex and dual effects in cancer. With the continuous growing research, new regulatory modes and new functions of Nrf2 and tumor-promoting effects of Nrf2 in malignant transformed tumors have become increasingly clear. Accumulating evidence has established that Nrf2 contributes to the whole process of pathogenesis, progression, metastasis, and prognosis of cancer, and Nrf2 could be a promising target in cancer therapy. However, the development of Nrf2 inhibitor is still limited. In this perspective, we will briefly describe the biological function and modulating network of Nrf2, stress its oncogenic role, and point out possible ways to inhibit Nrf2, as well as summarize the reported Nrf2 inhibitors.

Exposure to formaldehyde and diisononyl phthalate exacerbate neuroinflammation through NF-κB activation in a mouse asthma model

Diisononyl phthalate (DINP) and formaldehyde both are associated with asthma and allergies. However, it is unclear about the adverse effect of DINP and formaldehyde exposure on the brain for asthma patients. Here, we determined the effect of DINP and/or formaldehyde exposure on neuroinflammation in brain by a murine asthma model and investigated the underlying mechanisms. Mice were exposed to formaldehyde and/or DINP and sensitization with ovalbumin. The results show that exposure to formaldehyde and/or DINP not only exacerbated allergic asthma-like symptoms, but also promoted neuroinflammation in brain. The incrassation of the airway wall and exacerbation of neuroinflammation were more obviously when mice were subjected to a combined exposure to DINP and formaldehyde. Exposure to DINP and/or formaldehyde enhances oxidative stress and the activation of NF-κB in the prefrontal cortex of mouse asthma model. Exposure to DINP and/or formaldehyde also induced an increase in IL-1β, IL-17, and NGF. Blocking oxidative stress by administering melatonin or inhibiting NF-κB activation by treatment with Dehydroxymethylepoxyquinomicin effectively prevented increasing the levels IL-1β, IL-17 and nerve growth factor. The data indicated that DINP and/or formaldehyde exposure promoted neuroinflammation in the brain through enhanced oxidative stress and activation of NF-κB in a mouse asthma model.

Chrysin suppresses proliferation, migration, and invasion in glioblastoma cell lines via mediating the ERK/Nrf2 signaling pathway

Background

Chrysin, an active natural bioflavonoid, has been proven to protect against carcinogenesis. However, the role of chrysin in glioblastoma and the potential molecular mechanisms remain to be elucidated. In our previous study, we found that nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) is highly expressed in a variety of glioblastoma cell lines associated with the mitogen-activated protein kinase (MAPK) pathway. The aim of this study was to evaluate the antitumor effects of chrysin in glioblastoma cells and how chrysin is related to the MAPK/Nrf2 signaling pathway.

Methods

A Cell Counting Kit-8 assay and a plate colony formation assay were performed to evaluate cell proliferation. Cell migration ability was tested by a wound-healing assay. Transwell migration and Matrigel invasion assay were used to test the migration and invasion potential of cells. Nrf2 was knocked down by shRNA transfection. Protein expression was determined by Western blotting and immunofluorescence staining. The in vivo anticancer effect was measured using tumor xenografts in nude mice.

Results

Chrysin inhibited the proliferation, migration, and invasion capacity of glioblastoma cells in dose- and time-dependent manners. Mechanistically, chrysin deactivated the Nrf2 signaling pathway by decreasing the translocation of Nrf2 into the nucleus and suppressing the expression of hemeoxygenase-1 (HO-1) and NAD(P)H quinine oxidoreductase-1, meanwhile, Nrf2 shRNA attenuated the anticancer activity of chrysin. Furthermore, chrysin downregulated the protein expression of p-extracellular signal-regulated kinase 1 and 2 (ERK1/2), but did not significantly affect p-JNK and p-P38 expression levels. However, the downregulated level of Nrf2 and the antitumor effect of chrysin in glioblastoma cell lines were partially abrogated by the ERK1/2 signaling inhibitor (U0126). Finally, chrysin inhibited tumor growth in U87 xenografts.

Conclusion

Our results show that chrysin exerts anticancer activity in glioblastoma cell lines possibly via the ERK/Nrf2 signaling pathway and indicate the potential application of chrysin as a natural sensitizer in chemotherapy.

Fucoxanthin Elicits Epigenetic Modifications, Nrf2 Activation and Blocking Transformation in Mouse Skin JB6 P+ Cells

Nuclear factor erythroid-2-related factor-2 (Nrf2 or NFE2L2) is a master regulator of the anti-oxidative stress response, which is involved in the defense against many oxidative stress/inflammation-mediated diseases, including anticancer effects elicited by an increasing number of natural products. Our previous studies showed that the epigenetic modification of the Nrf2 gene plays a key role in restoring the expression of Nrf2. In this study, we aimed to investigate the epigenetic regulation of Nrf2 by astaxanthin (AST) and fucoxanthin (FX), carotenoids which are abundant in microalgae and seaweeds, in mouse skin epidermal JB6 P+ cells. FX induced the anti-oxidant response element (ARE)-luciferase and upregulated the mRNA and protein levels of Nrf2 and Nrf2 downstream genes in HepG2-C8 cells overexpressing the ARE-luciferase reporter. Both FX and AST decreased colony formation in 12-Otetradecanoylphorbol-13-acetate (TPA)-induced transformation of JB6 P+ cells. FX decreased the methylation of the Nrf2 promoter region in the JB6 P+ cells by the bisulfite conversion and pyrosequencing. Both FX and AST significantly reduced DNA methyltransferase (DNMT) activity but did not affect histone deacetylase (HDAC) activity in JB6 P+ cells. In summary, our results show that FX activates the Nrf2 signaling pathway, induces the epigenetic demethylation of CpG sites in Nrf2 and blocks the TPA-induced transformation of JB6 P+ cells, indicating the potential health-promoting effects of FX in skin cancer prevention.

Dual Roles of Oxidative Stress in Metal Carcinogenesis

It has been well established that environmental and occupational exposure to heavy metal causes cancer in several organs. Although the exact mechanism of heavy metal carcinogenesis remains elusive, metal-generated reactive oxygen species (ROS) are essential. ROS can play two roles in metal carcinogenesis; two stages in the process of metal carcinogenesis differ in the amounts of ROS activating a dual redox-mediated mechanism. In the early stage of metal carcinogenesis, ROS acts in an oncogenic role. However, in the late stage of metal carcinogenesis, ROS plays an antioncogenic role. Similarly, NF-E2-related factor 2 (Nrf2) also has two different roles, which makes it a key molecule for separating metal carcinogenesis into two different stages. In the early stage, inducible Nrf2 fights against elevated ROS to decrease cell transformation by its antioxidant protection property. In the late stage, constitutively activated Nrf2 manipulates reduced ROS to perform a comfortable environment for apoptosis resistance through an oncogenic role. Interestingly, a cunning carcinogenic mechanism takes advantage of the dual role of Nrf2 to implement the dual role of ROS through a series of redox adaption mechanisms. In this review, we discuss the paradox in the rationales behind the two opposite ROS roles and focus on their potential pharmacological application. The dual role of ROS represents a 'double-edged sword' with many possible novel ROS-mediated strategies in cancer therapy in metal carcinogenesis.