Epigenetics Reactivation of Nrf2 in Prostate TRAMP C1 Cells by Curcumin Analogue FN1

Epigenetics of Dietary Phytochemicals in Cancer Prevention: Fact or Fiction

ABSTRACT

Cancer development takes 10 to 50 years, and epigenetics plays an important role. Recent evidence suggests that ~80% of human cancers are linked to environmental factors impinging upon genetics/epigenetics. Because advanced metastasized cancers are resistant to radiation/chemotherapeutic drugs, cancer prevention by relatively nontoxic "epigenetic modifiers" will be logical. Many dietary phytochemicals possess powerful antioxidant and anti-inflammatory properties that are hallmarks of cancer prevention. Dietary phytochemicals can regulate gene expression of the cellular genome via epigenetic mechanisms. In this review, we will summarize preclinical studies that demonstrate epigenetic mechanisms of dietary phytochemicals in skin, colorectal, and prostate cancer prevention. Key examples of the importance of epigenetic regulation in carcinogenesis include hypermethylation of the NRF2 promoter region in cancer cells, resulting in inhibition of NRF2-ARE signaling. Many dietary phytochemicals demethylate NRF2 promoter region and restore NRF2 signaling. Phytochemicals can also inhibit inflammatory responses via hypermethylation of inflammation-relevant genes to block gene expression. Altogether, dietary phytochemicals are excellent candidates for cancer prevention due to their low toxicity, potent antioxidant and anti-inflammatory properties, and powerful epigenetic effects in reversing procarcinogenic events.

Effects of curcumin and ursolic acid in prostate cancer: A systematic review

The major barriers to phytonutrients in prostate cancer therapy are non-specific mechanisms and bioavailability issues. Studies have pointed to a synergistic combination of curcumin (CURC) and ursolic acid (UA). We investigate this combination using a systematic review process to assess the most likely mechanistic pathway and human testing in prostate cancer. We used the PRISMA statement to screen titles, abstracts, and the full texts of relevant articles and performed a descriptive analysis of the literature reviewed for study inclusion and consensus of the manuscript. The most common molecular and cellular pathway from articles reporting on the pathways and effects of CURC (n = 173) in prostate cancer was NF-κB (n = 25, 14.5%). The most common molecular and cellular pathway from articles reporting on the pathways and effects of UA (n = 24) in prostate cancer was caspase 3/caspase 9 (n = 10, 41.6%). The three most common molecular and cellular pathway from articles reporting on the pathways and effects of both CURC and UA (n = 193) in prostate cancer was NF-κB (n = 28, 14.2%), Akt (n = 22, 11.2%), and androgen (n = 19, 9.6%). Therefore, we have identified the potential synergistic target pathways of curcumin and ursolic acid to involve NF-κB, Akt, androgen receptors, and apoptosis pathways. Our review highlights the limited human studies and specific effects in prostate cancer.

Mechanism insights of curcumin and its analogues in cancer: An update

Cancer is the world's second leading cause of mortality and one of the major public health problems. Cancer incidence and mortality rates remain high despite the great advancements in existing therapeutic, diagnostic, and preventive approaches. Therefore, a quest for less toxic and more efficient anti-cancer strategies is still at the forefront of the current research. Traditionally important, curcumin commonly known as a wonder molecule has received considerable attention as an anti-cancer, anti-inflammatory, and antioxidant candidate. However, limited water solubility and low bioavailability restrict its extensive utility in different pathological states. The investigators are making consistent efforts to develop newer strategies to overcome its limitations by designing different analogues with better pharmacokinetic and pharmacodynamic properties. The present review highlights the recent updates on curcumin and its analogues with special emphasis on various mechanistic pathways involved in anti-cancer activity. In addition, the structure-activity relationship of curcumin analogues has also been precisely discussed. This article will also provide key information for the design and development of newer curcumin analogues with desired pharmacokinetic and pharmacodynamic profiles and will provide in depth understanding of molecular pathways involved in the anti-cancer activities.

NRF2 modulation in TRAMP mice: an in vivo model of prostate cancer

BACKGROUND

Prostate cancer (PCa) is one of the most common cancers worldwide and oxidative stress is involved in its occurrence, development and progression. In fact, in transgenic adenocarcinoma of mouse prostate (TRAMP) mice, prostate cancer onset is associated with the methylation of the first five CpG in the nuclear factor erythroid 2-related factor 2 (NRF2) promoter, a key regulator of oxidative stress response, leading to its downregulation and accumulation of reactive oxygen species (ROS). It has been demonstrated that both natural and synthetic compounds can reactivate NRF2 expression inhibiting the methylation status of its promoter by downregulation of DNA methyltransferases (DNMTs) and histone deacetylases (HDACs). Interestingly, NRF2 re-expression significantly reduced prostate cancer onset in TRAMP mice highlighting an important role of NRF2 in prostate tumorigenesis.

METHODS AND RESULTS

We analysed the current literature regarding the role of natural and synthetic compounds in modulating NRF2 pathway in TRAMP mice, an in vivo model of prostate cancer, to give an overview on prostate carcinogenesis and its possible prevention.

CONCLUSION

We can conclude that specific natural and synthetic compounds can downregulate DNMTs and/or HDACs inhibiting the methylation status of NRF2 promoter, then reactivating the expression of NRF2 protecting normal prostatic cells from ROS damage and tumorigenesis.

NRF2: A crucial regulator for mitochondrial metabolic shift and prostate cancer progression

Metabolic alterations are a common survival mechanism for prostate cancer progression and therapy resistance. Oxidative stress in the cellular and tumor microenvironment dictates metabolic switching in the cancer cells to adopt, prosper and escape therapeutic stress. Therefore, regulation of oxidative stress in tumor cells and in the tumor-microenvironment may enhance the action of conventional anticancer therapies. NRF2 is the master regulator for oxidative stress management. However, the overall oxidative stress varies with PCa clinical stage, metabolic state and therapy used for the cancer. In agreement, the blanket use of NRF2 inducers or inhibitors along with anticancer therapies cause adverse effects in some preclinical cancer models. In this review, we have summarized the levels of oxidative stress, metabolic preferences and NRF2 activity in the different stages of prostate cancer. We also propose condition specific ways to use NRF2 inducers or inhibitors along with conventional prostate cancer therapies. The significance of this review is not only to provide a detailed understanding of the mechanism of action of NRF2 to regulate oxidative stress-mediated metabolic switching by prostate cancer cells to escape the radiation, chemo, or hormonal therapies, and to grow aggressively, but also to provide a potential therapeutic method to control aggressive prostate cancer growth by stage specific proper use of NRF2 regulators.

Application of ARE-reporter systems in drug discovery and safety assessment

The human body is continuously exposed to xenobiotics and internal or external oxidants. The health risk assessment of exogenous chemicals remains a complex and challenging issue. Alternative toxicological test methods have become an essential strategy for health risk assessment. As a core regulator of constitutive and inducible expression of antioxidant response element (ARE)-dependent genes, nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in maintaining cellular redox homeostasis. Consistent with the properties of Nrf2-mediated antioxidant response, Nrf2-ARE activity is a direct indicator of oxidative stress and thus has been used to identify and characterize oxidative stressors and redox modulators. To screen and distinguish chemicals or environmental insults that affect the cellular antioxidant activity and/or induce oxidative stress, various in vitro cell models expressing distinct ARE reporters with high-throughput and high-content properties have been developed. These ARE-reporter systems are currently widely applied in drug discovery and safety assessment. In the present review, we provide an overview of the basic structures and applications of various ARE-reporter systems employed for discovering Nrf2-ARE modulators and characterizing oxidative stressors.

Nrf2 antioxidant pathway and apoptosis induction and inhibition of NF-κB-mediated inflammatory response in human prostate cancer PC3 cells by Brassica oleracea var. acephala: An in vitro study

BACKGROUND

Brassica oleracea var. acephala is a good source of health-promoting biologically active compounds like phenolics, vitamins, and glucosinolates.

METHODS AND RESULTS

This in vitro research was conducted to evaluate the apoptotic, antioxidant, anti-inflammatory, and antiproliferative properties of ethanolic extract of Brassica oleracea var. acephala (EEBO) in PC3 prostate cancer cells. The LC-MS/MS technique was applied to identify the biomolecules of EEBO. The MTT assay was used to evaluate the cytotoxic effects of EEBO on PC3 cells. Moreover, qRT-PCR was used to examine the expression levels of Nrf2, NQO1, HO-1, NF-κB, TNF-α, IL-6, BAX, and BCL-2 in PC3 cell line. MMP was predicted by Rhodamine 123 staining, and release of cytochrome c was detected by an ELISA kit. Further, apoptosis was quantified by DNA fragmentation assay. The Western blotting method was used to detect the protein expression levels, and The DPPH assay was applied to determine the antioxidant effect of EEBO. The formula and structure of 19 biomolecules were predicted by LC-MS/MS. EEBO exhibited scavenging activity for DPPH. The MTT test showed EEBO reduced the viability of PC3 cells. The mRNA and protein levels of NRF2 pathway genes and BAX were increased, but those of the NF-κB pathway genes and BCL-2 were decreased in the EEBO-treated cells. Moreover, EEBO led to the diminution of MMP and enhanced the release of cytochrome c and DNA fragmentation, which resulted in apoptosis.

CONCLUSIONS

Molecular changes due to the anticancer impact of EEBO on PC3 were involved in the induction of Nrf2 antioxidant pathway and apoptosis and inhibition of inflammation.

Regulation of ferroptosis by noncoding RNAs: a novel promise treatment in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a highly prevalent tumor that requires extensive research. Ferroptosis is a unique cell death modality driven by iron-dependent phospholipid peroxidation manifested as an accumulation of lipid-reactive oxygen species. With further understanding of noncoding RNAs (ncRNAs), numerous studies have demonstrated an important regulatory role of ncRNAs in ESCC through ferroptosis, including microRNAs, long ncRNAs, and circular RNAs. These ncRNAs influence the expression of the target gene to regulate ESCC progression by involving the ferroptosis signaling pathway. However, the specific regulatory mechanism of ncRNAs on ferroptosis in ESCC remains largely unknown. This review summarized the current knowledge on the relation between ferroptosis regulators, such as glutathione synthesis/metabolism, Keap1/Nfr2, and p53, by ncRNAs and ESCC. This review also proposed the possible therapeutic approaches for ncRNAs targeting ferroptosis in ESCC. This is the latest and most effective summary of recent research achievements of ncRNAs on ferroptosis in ESCC. These ncRNAs based on ferroptosis merit further investigation in preclinical research of ESCC.

Nrf2 Regulation by Curcumin: Molecular Aspects for Therapeutic Prospects

Nuclear factor erythroid 2 p45-related factor (2Nrf2) is an essential leucine zipper protein (bZIP) that is primarily located in the cytoplasm under physiological conditions. Nrf2 principally modulates endogenous defense in response to oxidative stress in the brain.In this regard, Nrf2 translocates into the nucleus and heterodimerizes with the tiny Maf or Jun proteins. It then attaches to certain DNA locations in the nucleus, such as electrophile response elements (EpRE) or antioxidant response elements (ARE), to start the transcription of cytoprotective genes. Many neoplasms have been shown to have over activated Nrf2, strongly suggesting that it is responsible for tumors with a poor prognosis. Exactly like curcumin, Zinc-curcumin Zn (II)-curc compound has been shown to induce Nrf2 activation. In the cancer cell lines analyzed, Zinc-curcumin Zn (II)-curc compound can also display anticancer effects via diverse molecular mechanisms, including markedly increasing heme oxygenase-1 (HO-1) p62/SQSTM1 and the Nrf2 protein levels along with its targets. It also strikingly decreases the levels of Nrf2 inhibitor, Kelch-like ECH-associated protein 1 (Keap1) protein.As a result, the crosstalk between p62/SQSTM1 and Nrf2 could be used to improve cancer patient response to treatments. The interconnected anti-inflammatory and antioxidative properties of curcumin resulted from its modulatory effects on Nrf2 signaling pathway have been shown to improve insulin resistance. Curcumin exerts its anti-inflammatory impact through suppressing metabolic reactions and proteins such as Keap1 that provoke inflammation and oxidation. A rational amount of curcumin-activated antioxidant Nrf2 HO-1 and Nrf2-Keap1 pathways and upregulated the modifier subunit of glutamate-cysteine ligase involved in the production of the intracellular antioxidant glutathione. Enhanced expression of glutamate-cysteine ligase, a modifier subunit (GLCM), inhibited transcription of glutamate-cysteine ligase, a catalytic subunit (GCLC). A variety of in vivo, in vitro and clinical studies has been done so far to confirm the protective role of curcumin via Nrf2 regulation. This manuscript is designed to provide a comprehensive review on the molecular aspects of curcumin and its derivatives/analogs via regulation of Nrf2 regulation.

Bioactive Compounds in Oxidative Stress-Mediated Diseases: Targeting the NRF2/ARE Signaling Pathway and Epigenetic Regulation

Oxidative stress is a pathological condition occurring due to an imbalance between the oxidants and antioxidant defense systems in the body. Nuclear factor E2-related factor 2 (NRF2), encoded by the gene NFE2L2, is the master regulator of phase II antioxidant enzymes that protect against oxidative stress and inflammation. NRF2/ARE signaling has been considered as a promising target against oxidative stress-mediated diseases like diabetes, fibrosis, neurotoxicity, and cancer. The consumption of dietary phytochemicals acts as an effective modulator of NRF2/ARE in various acute and chronic diseases. In the present review, we discussed the role of NRF2 in diabetes, Alzheimer's disease (AD), Parkinson's disease (PD), cancer, and atherosclerosis. Additionally, we discussed the phytochemicals like curcumin, quercetin, resveratrol, epigallocatechin gallate, apigenin, sulforaphane, and ursolic acid that have effectively modified NRF2 signaling and prevented various diseases in both in vitro and in vivo models. Based on the literature, it is clear that dietary phytochemicals can prevent diseases by (1) blocking oxidative stress-inhibiting inflammatory mediators through inhibiting Keap1 or activating Nrf2 expression and its downstream targets in the nucleus, including HO-1, SOD, and CAT; (2) regulating NRF2 signaling by various kinases like GSK3beta, PI3/AKT, and MAPK; and (3) modifying epigenetic modulation, such as methylation, at the NRF2 promoter region; however, further investigation into other upstream signaling molecules like NRF2 and the effect of phytochemicals on them still need to be investigated in the near future.

Current insights into epigenetics, noncoding RNA interactome and clinical pharmacokinetics of dietary polyphenols in cancer chemoprevention

Several studies have reported the health-beneficial effects of dietary phytochemicals, namely polyphenols, to prevent various diseases, including cancer. Polyphenols, like (-)-epigallocatechin-3-gallate (EGCG) from green tea, curcumin from turmeric, and ellagic acid from pomegranate are known to act by modulating antioxidant, anti-inflammatory and apoptotic signal transduction pathways in the tumor milieu. The evolving literature underscores the role of epigenetic regulation of genes associated with cancer by these polyphenols, primarily via non-coding RNAs (ncRNAs), such as microRNAs (miRNA) and long noncoding RNA (lncRNA). However, there is little clarity on the exact role(s) played by these ncRNAs and their interactions with other ncRNAs, or with their protein targets, in response to modulation by these dietary polyphenols. Here, we review ncRNA interactions and functional networks of the complex ncRNA interactome with their targets in preclinical studies along with the role of epigenetics as well as key aspects of pharmacokinetics and phytochemistry of dietary polyphenols. We also summarize the current state of clinical trials with these dietary polyphenols. Taken together, this synthetic review provides insights into the molecular aspects underlying the anticancer chemopreventive effects of dietary polyphenols as well as summarizes data on novel biomarkers modulated by these polyphenols for preventive or therapeutic purposes in various types of cancer.

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.

Role of long non-coding RNAs on the regulation of Nrf2 in chronic diseases

Studies have identified dysregulated long non-coding RNA (lncRNA) in several diseases at transcriptional, translational, and post-translational levels. Although our mechanistic knowledge on the regulation of lncRNAs is still limited, one of the mechanisms of action attributed is binding and regulating transcription factors, thus controlling gene expression and protein function. One such transcription factor is nuclear factor erythroid 2-related factor 2 (Nrf2), which plays a critical biological role in maintaining cellular homeostasis at multiple levels in physiological and pathophysiological conditions. The levels of Nrf2 were found to be down-regulated in many chronic diseases, signifying that Nrf2 can be a key therapeutic target. Few lncRNAs like lncRNA ROR, ENSMUST00000125413, lncRNA ODRUL, Nrf2-lncRNA have been associated with the Nrf2 signaling pathway in response to various stimuli, including stress. This review discusses the regulation of Nrf2 in different responses and the potential role of specific lncRNA in modulating its transcriptional activities. This review further helps to enhance our knowledge on the regulatory role of the critical antioxidant transcription factor, Nrf2.

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.

Epigenetics of Muscle- and Brain-Specific Expression of KLHL Family Genes

KLHL and the related KBTBD genes encode components of the Cullin-E3 ubiquitin ligase complex and typically target tissue-specific proteins for degradation, thereby affecting differentiation, homeostasis, metabolism, cell signaling, and the oxidative stress response. Despite their importance in cell function and disease (especially, KLHL40, KLHL41, KBTBD13, KEAP1, and ENC1), previous studies of epigenetic factors that affect transcription were predominantly limited to promoter DNA methylation. Using diverse tissue and cell culture whole-genome profiles, we examined 17 KLHL or KBTBD genes preferentially expressed in skeletal muscle or brain to identify tissue-specific enhancer and promoter chromatin, open chromatin (DNaseI hypersensitivity), and DNA hypomethylation. Sixteen of the 17 genes displayed muscle- or brain-specific enhancer chromatin in their gene bodies, and most exhibited specific intergenic enhancer chromatin as well. Seven genes were embedded in super-enhancers (particularly strong, tissue-specific clusters of enhancers). The enhancer chromatin regions typically displayed foci of DNA hypomethylation at peaks of open chromatin. In addition, we found evidence for an intragenic enhancer in one gene upregulating expression of its neighboring gene, specifically for KLHL40/HHATL and KLHL38/FBXO32 gene pairs. Many KLHL/KBTBD genes had tissue-specific promoter chromatin at their 5' ends, but surprisingly, two (KBTBD11 and KLHL31) had constitutively unmethylated promoter chromatin in their 3' exons that overlaps a retrotransposed KLHL gene. Our findings demonstrate the importance of expanding epigenetic analyses beyond the 5' ends of genes in studies of normal and abnormal gene regulation.

Protective effects of natural compounds against oxidative stress in ischemic diseases and cancers via activating the Nrf2 signaling pathway: A mini review

Oxidative stress, an imbalance between reactive oxygen species and antioxidants, has been seen in the pathological states of many disorders such as ischemic diseases and cancers. Many natural compounds (NCs) have long been recognized to ameliorate oxidative stress due to their inherent antioxidant activities. The modulation of oxidative stress by NCs via activating the Nrf2 signaling pathway is summarized in the review. Three NCs, ursolic acid, betulinic acid, and curcumin, and the mechanisms of their cytoprotective effects are investigated in myocardial ischemia, cerebral ischemia, skin cancer, and prostate cancer. To promote the therapeutic performance of NCs with poor water solubility, the formulation approach, such as the nano drug delivery system, is elaborated as well in this review.

Roles of Nrf2 in Liver Diseases: Molecular, Pharmacological, and Epigenetic Aspects

Liver diseases represent a critical health problem with 2 million deaths worldwide per year, mainly due to cirrhosis and its complications. Oxidative stress plays an important role in the development of liver diseases. In order to maintain an adequate homeostasis, there must be a balance between free radicals and antioxidant mediators. Nuclear factor erythroid 2-related factor (Nrf2) and its negative regulator Kelch-like ECH-associated protein 1 (Keap1) comprise a defense mechanism against oxidative stress damage, and growing evidence considers this signaling pathway as a key pharmacological target for the treatment of liver diseases. In this review, we provide detailed and updated evidence regarding Nrf2 and its involvement in the development of the main liver diseases such as alcoholic liver damage, viral hepatitis, steatosis, steatohepatitis, cholestatic damage, and liver cancer. The molecular and cellular mechanisms of Nrf2 cellular signaling are elaborated, along with key and relevant antioxidant drugs, and mechanisms on how Keap1/Nrf2 modulation can positively affect the therapeutic response are described. Finally, exciting recent findings about epigenetic modifications and their link with regulation of Keap1/Nrf2 signaling are outlined.

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.

A pilot study of the effect of curcumin on epigenetic changes and DNA damage among patients with non-alcoholic fatty liver disease: A randomized, double-blind, placebo-controlled, clinical trial

BACKGROUND

The enhancement of oxidative stress in non-alcoholic fatty liver disease (NAFLD) patients may cause mutation in DNA by deamination of cytosine to 5-hydroxyuracil or uracil. This study aimed to discover the effects of curcumin on NAFLD progress, DNA damage caused by oxidative stress, and promoter methylation of mismatch repair enzymes.

MATERIAL AND METHODS

in this study, 54 NAFLD patients were randomly devided into two groups, according to a double blind parallel design either phytosomal curcumin (250 mg/day) or placebo for 8 weeks. Fasting blood samples and anthropometric measures were taken twice, once at the baseline and once at the end of the study. Promoter methylation and 8-hydroxy-2' -deoxyguanosine (8-OHdG) concentration as DNA damage mediator were measured by restriction enzymes and enzyme-linked immunosorbent assay, respectively.

RESULT

Analysis was performed on 44 patients. According to our between groups analysis, curcumin significantly reduced the methylation in MutL homolog 1 (MLH1) and MutS homolog 2 (MSH2) promoter regions. The within-group comparison revealed that anthropometric variables significantly decreased. However, the result of the between groups comparison indicated no significant changes in the anthropometric variables except for BMI. Liver enzymes and 8-OHdG did not significantly change at the end of the study, neither in curcumin group nor in placebo group.

CONCLUSION

Curcumin might be able to reduce the risk of mismatch base pair in DNA among the NAFLD patients. However, it did not change the DNA damage mediator and liver enzymes. For confirming these results, more studies with longer duration, more numbers of examined genes, higher dose of curcumin, and larger sample size are required.

Curcumin upregulates the Nrf2 system by repressing inflammatory signaling-mediated Keap1 expression in insulin-resistant conditions

Both oxidative stress and inflammation contribute to the development of insulin resistance (IR). Curcumin (Cur) not only has an anti-inflammatory effect but also has an antioxidative stress effect via the activation of NF-E2-related factor 2 (Nrf2). Since there is close cross-communication between inflammation and oxidative stress, we examined whether Cur could modulate Nrf2 function via its anti-inflammatory ability and investigated its underlying mechanism. In this study, we show that Cur inhibits inflammatory signaling and Kelch-like ECH-associated protein 1 (Keap1) expression, which is accompanied by the activation of the Nrf2 system. We further identified that the proinflammatory cytokine tumor necrosis factor alpha (TNFα) could stimulate Keap1 synthesis and increase Nrf2 polyubiquitination, but these effects could be significantly inhibited by Cur treatment. This study demonstrates that Cur-induced Nrf2 activation occurs through the inhibition of inflammatory signaling-mediated upregulation of Keap1, contributing to its beneficial effects on redox homeostasis and insulin sensitivity.

Luteolin promotes apoptotic cell death via upregulation of Nrf2 expression by DNA demethylase and the interaction of Nrf2 with p53 in human colon cancer cells

Luteolin, a dietary flavone, modulates various signaling pathways involved in carcinogenesis. In this study, we investigated the molecular mechanism that underlies the apoptotic effects of luteolin mediated by DNA demethylation of the nuclear factor erythroid 2-related factor 2 (Nrf2) promoter and the interaction of Nrf2 and p53, a tumor suppressor, in human colon cancer cells. Luteolin increased the expression of apoptosis-related proteins and antioxidant enzymes. In DNA methylation, luteolin inhibited the expression of DNA methyltransferases, a transcription repressor, and increased the expression and activity of ten-eleven translocation (TET) DNA demethylases, a transcription activator. Methyl-specific polymerase chain reaction and bisulfite genomic sequencing indicated that luteolin decreased the methylation of the Nrf2 promoter region, which corresponded to the increased mRNA expression of Nrf2. In addition, luteolin increased TET1 binding to the Nrf2 promoter, as determined using a chromatin immunoprecipitation (ChIP) assay. TET1 knockdown decreased the percentages of luteolin-treated cells in sub-G₁ phase and cells with fragmented nuclei. Furthermore, complex formation between p53 and Nrf2 was involved in the apoptotic effects of luteolin. These results provide insight into the mechanism that underlies the anticancer effects of luteolin on colon cancer, which involve the upregulation of Nrf2 and its interaction with the tumor suppressor.

A molecule found in fruits, vegetables and herbs helps kill colon cancer cells by activating a master regulator of detoxifying enzymes. Jin Won Hyun from Jeju National University School of Medicine in South Korea and colleagues treated human colon cancer cells with luteolin, a molecule that occurs naturally in many food plants. They showed that luteolin increased the levels of proteins involved in cell death and antioxidant responses by causing DNA-modifying enzymes to strip suppressive chemical markers off the gene encoding Nrf2, a protein that regulates antioxidant effects. Nrf2 levels subsequently increased and the protein interacted with the tumor suppressor p53 to facilitate destruction of the colon cancer cells. The findings offer a mechanistic basis for using luteolin to help prevent and treat cancer.

Luteolin Shifts Oxaliplatin-Induced Cell Cycle Arrest at G₀/G₁ to Apoptosis in HCT116 Human Colorectal Carcinoma Cells

Certain antioxidative flavonoids are known to activate nuclear factor E2-related factor 2 (Nrf2), a transcription factor that regulates cellular antioxidants and detoxifying response and is reportedly highly activated in many types of cancers. Few studies on the potential undesired effects of flavonoid intake during chemotherapy have been conducted, yet Nrf2 activators could favor cancer cell survival by attenuating chemotherapeutic efficiency. This study aimed to examine if luteolin, an Nrf2 activator, hinders chemotherapeutic activity of oxaliplatin, a potent anticancer agent for colorectal cancer, in HCT116 cells. Luteolin treatment strongly increased the transcriptional activity of the antioxidant response element in HCT116 cells and induced the protein expression of heme oxygenase-1, which were indicative of its Nrf2-inducing potential. Intriguingly, 25 μM luteolin reduced cell viability through apoptotic induction, which was intensified in p53-expressing cells while 1 μM oxaliplatin caused cell cycle arrest at G₀/G₁-phase via the p53/p21-dependent mechanism. Moreover, luteolin treatment was found to reduce oxaliplatin-treated p53-null cell viability and colony counts further, thereby demonstrating an additional effect of luteolin in the killing of human colorectal tumor HCT116 cells not expressing functional p53 protein. The findings suggest that luteolin can induce p53-mediated apoptosis regardless of oxaliplatin treatment and may eliminate oxaliplatin-resistant p53-null colorectal cells.

Nuclear transcription factor Nrf2 suppresses prostate cancer cells growth and migration through upregulating ferroportin

VTo investigate the effect of nuclear transcription factor Nrf2 on the transcription of Ferroportin (FPN) in prostate cancer cells, and the regulation mechanisms of FPN on cell viability, migration and apoptosis of prostate cancer cells.Empty vectors, pEGFPC1-Nrf2, pEGFPC1-FPN, Si-FPN and Si-Nrf2 were transfected into prostate cancer cell line PC3. The expression of mRNA and protein were measured by real time-PCR (RT-PCR) and western blot. Cell viability, migration, cycle and apoptosis were tested by CCK-8 assay, wound healing and flow cytometry, respectively. The interaction between FPN and Nrf2 was confirmed by chromatin immunoprecipitation (CHIP) assay.The viability, migration and mitosis of PC3 cells could be repressed by over-expressed FPN, with decreased intracellular ferritin. The CHIP assay demonstrated that Nrf2 is one transcription factor of FPN and promotes its transcription. With the increase of Nrf2 in PC3 cells, the viability, migration ability and concentration of ferritin were suppressed, while the apoptosis rate was increased. The above effects were counteracted by down-regulating FPN.FPN could inhibit the prostate cancer cell viability, migration and mitosis, which is also related to a decrease of intracellular ferritin content. In conclusion, Nrf2 suppresses prostate cancer cells viability, migration, and mitosis through upregulating FPN.

Sulforaphane epigenetically demethylates the CpG sites of the miR-9-3 promoter and reactivates miR-9-3 expression in human lung cancer A549 cells

Increasing evidence suggests that epigenetic aberrations contribute to the development and progression of cancers such as lung cancer. The promoter region of miR-9-3 was recently found to be hypermethylated in lung cancer, resulting in down-regulation of miR-9-3 and poor patient prognosis. Sulforaphane (SFN), a natural compound that is obtained from cruciferous vegetables, has potent anticancer activities. In this study, we aimed to investigate the effect of SFN on restoring the miR-9-3 level in lung cancer A549 cells through epigenetic regulation. DNA methylation of the miR-9-3 promoter was examined using bisulfite genomic sequencing and methylated DNA immunoprecipitation analysis. The expression levels of miR-9-3 and several epigenetic modifying enzymes were measured using quantitative real-time polymerase chain reaction and Western blotting, respectively. The transcriptional activity of the miR-9-3 promoter was evaluated by patch methylation, and histone modifications were analyzed using chromatin immunoprecipitation (ChIP) assays. We found that CpG methylation was reduced in the miR-9-3 promoter and that miR-9-3 expression was increased after 5 days of treatment with SFN. In vitro methylation analysis showed that the methylated recombinant construct exhibited lower luciferase reporter activity than the unmethylated counterpart. ChIP assays revealed that SFN treatment increased H3K4me1 enrichment at the miR-9-3 promoter. Furthermore, SFN treatment attenuated enzymatic DNMT activity and DNMT3a, HDAC1, HDAC3, HDAC6 and CDH1 protein expression. Taken together, these findings indicate that SFN may exert its chemopreventive effects partly through epigenetic demethylation and restoration of miR-9-3.

Correction to: In Vitro-In Vivo Dose Response of Ursolic Acid, Sulforaphane, PEITC, and Curcumin in Cancer Prevention

The citation of the author name "Ah-Ng Tony Kong" in PubMed is not the author's preference. Instead of "Kong AT", the author prefers "Kong AN".

The triterpenoid corosolic acid blocks transformation and epigenetically reactivates Nrf2 in TRAMP-C1 prostate cells

Corosolic acid (CRA) is found in various plants and has been used as a health food supplement worldwide. Although it has been reported that CRA exhibits significant anticancer activity, the effect of this compound on prostate cancer remains unknown. In this study, we investigated the effect of CRA on cellular transformation and the reactivation of nuclear factor erythroid 2-related factor 2 (Nrf2) through epigenetic regulation in TRAMP-C1 prostate cells. Specifically, we found that CRA inhibited anchorage-independent growth of prostate cancer TRAMP-C1 cells but not Nrf2 knockout prostate cancer TRAMP-C1 cells. Moreover, CRA induced mRNA and protein expression of Nrf2, heme oxygenase-1 (HO-1) and NAD(P)H Quinone Oxidoreductase 1 (NQO1). Bisulfite genomic sequencing and methylated DNA immunoprecipitation results revealed that CRA treatment decreased the level of methylation of the first five CpG sites of the Nrf2 promoter. Histone modification was analyzed using a chromatin immunoprecipitation (ChIP) assay, which revealed that CRA treatment increased the acetylation of histone H3 lysine 27 (H3K27ac) while decreasing the trimethylation of histone H3 lysine 27 (H3K27me3) in the promoter region of Nrf2. Furthermore, CRA treatment attenuated the protein expression of DNA methyltransferases (DNMTs) and histone deacetylases (HDACs). These findings indicate that CRA has a significant anticancer effect in TRAMP-C1 cells, which could be partly attributed to epigenetics including its ability to epigenetically restore the expression of Nrf2.

Curcumin Derivative Epigenetically Reactivates Nrf2 Antioxidative Stress Signaling in Mouse Prostate Cancer TRAMP C1 Cells

The carcinogenesis of prostate cancer (PCa) in TRAMP model is highly correlated with hypermethylation in the promoter region of Nrf2 and the accompanying reduced transcription of Nrf2 and its regulated detoxifying genes. We aimed to investigate the effects of (3E,5E)-3,5-bis-(3,4,5-trimethoxybenzylidene)-tetrahydro-thiopyran-4-one (F10) and (3E,5E)-3,5-bis-(3,4,5-trimethoxy-benzylidene)-tetrahydropyran-4-one (E10), two synthetic curcumin derivatives, on restoring Nrf2 activity in TRAMP C1 cells. HepG2-C8 cells transfected with an antioxidant-response element (ARE)-luciferase vector were treated with F10, E10, curcumin, and sulforaphane (SFN) to compare their effects on Nrf2-ARE pathways. We performed real-time quantitative PCR and Western blotting to investigate the effects of F10 and E10 on Nrf2, correlated phase II detoxification genes. We also measured expression and activity of DNMTand HDAC enzymes. Enrichment of H3K27me3 on the promoter region of Nrf2 was explored with a chromatin immunoprecipitation (ChIP) assay. Methylation of the CpG region in Nrf2 promoter was doubly examined by bisulfite genomic sequencing (BGS) and methylation DNA immunoprecipitation (MeDIP). Compared with curcumin and SFN, F10 is more potent in activating Nrf2-ARE pathways. Both F10 and E10 enhanced level of Nrf2 and the correlated phase II detoxifying genes. BGS and MeDIP assays indicated that F10 but not E10 hypomethylated the Nrf2 promoter. F10 also downregulated the protein level of DNMT1, DNMT3a, DNMT3b, HDAC1, HDAC4, and HDAC7 and the activity of DNMTs and HDACs. F10 but not E10 effectively reduced the accumulation of H3k27me3 on the promoter of Nrf2. F10 and E10 can activate the Nrf2-ARE pathway and increase the level of Nrf2 and correlated phase II detoxification genes. The reactivation effect on Nrf2 by F10 in TRAMP C1 may come from demethylation, decrease of HDACs, and inhibition of H3k27me3 accumulation.

Targeting oncogenic transcription factors by polyphenols: A novel approach for cancer therapy

Inflammation is one of the major causative factor of cancer and chronic inflammation is involved in all the major steps of cancer initiation, progression metastasis and drug resistance. The molecular mechanism of inflammation driven cancer is the complex interplay between oncogenic and tumor suppressive transcription factors which include FOXM1, NF-kB, STAT3, Wnt/β- Catenin, HIF-1α, NRF2, androgen and estrogen receptors. Several products derived from natural sources modulate the expression and activity of multiple transcription factors in various tumor models as evident from studies conducted in cell lines, pre-clinical models and clinical samples. Further combination of these natural products along with currently approved cancer therapies added an additional advantage and they considered as promising targets for prevention and treatment of inflammation and cancer. In this review we discuss the application of multi-targeting natural products by analyzing the literature and future directions for their plausible applications in drug discovery.

In Vitro-In Vivo Dose Response of Ursolic Acid, Sulforaphane, PEITC, and Curcumin in Cancer Prevention

According to the National Center of Health Statistics, cancer was the culprit of nearly 600,000 deaths in 2016 in the USA. It is by far one of the most heterogeneous diseases to treat. Treatment for metastasized cancers remains a challenge despite modern diagnostics and treatment regimens. For this reason, alternative approaches are needed. Chemoprevention using dietary phytochemicals such as triterpenoids, isothiocyanates, and curcumin in the prevention of initiation and/or progression of cancer poses a promising alternative strategy. However, significant challenges exist in the extrapolation of in vitro cell culture data to in vivo efficacy in animal models and to humans. In this review, the dose at which these phytochemicals elicit a response in vitro and in vivo of a multitude of cellular signaling pathways will be reviewed highlighting Nrf2-mediated antioxidative stress, anti-inflammation, epigenetics, cytoprotection, differentiation, and growth inhibition. The in vitro-in vivo dose response of phytochemicals can vary due, in part, to the cell line/animal model used, the assay system of the biomarker used for the readout, chemical structure of the functional analog of the phytochemical, and the source of compounds used for the treatment study. While the dose response varies across different experimental designs, the chemopreventive efficacy appears to remain and demonstrate the therapeutic potential of triterpenoids, isothiocyanates, and curcumin in cancer prevention and in health in general.

Protection against oxidative stress mediated by the Nrf2/Keap1 axis is impaired in Primary Biliary Cholangitis

In response to oxidative stress, nuclear factor (erythroid-derived 2)-like2 (Nrf2) induces expression of cytoprotective genes. The Nrf2 pathway is controlled by microRNAs and Kelch-like ECH-associated protein1 (Keap1). Nrf2 is stabilized when Keap1 is degraded through the autophagy pathway in a p62-dependent manner. The inhibition of autophagy causes protein accumulation, and Keap1 is inactivated by binding to p62. We investigated the role of the Nrf2/Keap1 axis in the amelioration of oxidative stress in primary biliary cholangitis (PBC). Liver specimens from patients with PBC, with (n = 24) or without cirrhosis (n = 14), and from controls (n = 16) were used for molecular analyses. We found that Nrf2 protein levels were elevated in PBC compared to controls, but Nrf2 gene expression was significantly reduced in cirrhotic PBC. Nrf2 target gene products, HO-1 and GCLC proteins, were reduced compared to controls and reduction of Nrf2 gene expression was associated with elevated levels of microRNA-132 and microRNA-34a. Both Keap1 and p62 protein levels were substantially increased in PBC compared to controls. PBC was associated with reduced Nrf2 expression and autophagy deterioration and these impairments were more advanced in patients with cirrhosis. Aberrant Nrf2/Keap1 system integrity may affect self-defence mechanisms against oxidative stress in PBC.

Dietary Phytochemicals and Cancer Chemoprevention: A Perspective on Oxidative Stress, Inflammation, and Epigenetics

Oxidative stress occurs when cellular reactive oxygen species levels exceed the self-antioxidant capacity of the body. Oxidative stress induces many pathological changes, including inflammation and cancer. Chronic inflammation is believed to be strongly associated with the major stages of carcinogenesis. The nuclear factor erythroid 2-related factor 2 (Nrf2) pathway plays a crucial role in regulating oxidative stress and inflammation by manipulating key antioxidant and detoxification enzyme genes via the antioxidant response element. Many dietary phytochemicals with cancer chemopreventive properties, such as polyphenols, isothiocyanates, and triterpenoids, exert antioxidant and anti-inflammatory functions by activating the Nrf2 pathway. Furthermore, epigenetic changes, including DNA methylation, histone post-translational modifications, and miRNA-mediated post-transcriptional alterations, also lead to various carcinogenesis processes by suppressing cancer repressor gene transcription. Using epigenetic research tools, including next-generation sequencing technologies, many dietary phytochemicals are shown to modify and reverse aberrant epigenetic/epigenome changes, potentially leading to cancer prevention/treatment. Thus, the beneficial effects of dietary phytochemicals on cancer development warrant further investigation to provide additional impetus for clinical translational studies.

A Subpopulation of the K562 Cells Are Killed by Curcumin Treatment after G2/M Arrest and Mitotic Catastrophe

Curcumin is extensively investigated as a good chemo-preventive agent in the development of many cancers and particularly in leukemia, including treatment of chronic myelogenous leukemia and it has been proposed as an adjuvant for leukemia therapies. Human chronic myeloid leukemia cells (K562), were treated with 20 μM of curcumin, and we found that a subpopulation of these cells were arrested and accumulate in the G2/M phase of the cell cycle. Characterization of this cell subpopulation showed that the arrested cells presented nuclear morphology changes resembling those described for mitotic catastrophe. Mitotic cells displayed abnormal chromatin organization, collapse of the mitotic spindle and abnormal chromosome segregation. Then, these cells died in an apoptosis dependent manner and showed diminution in the protein levels of BCL-2 and XIAP. Moreover, our results shown that a transient activation of the nuclear factor κB (NFκB) occurred early in these cells, but decreased after 6 h of the treatment, explaining in part the diminution of the anti-apoptotic proteins. Additionally, P73 was translocated to the cell nuclei, because the expression of the C/EBPα, a cognate repressor of the P73 gene, was decreased, suggesting that apoptosis is trigger by elevation of P73 protein levels acting in concert with the diminution of the two anti-apoptotic molecules. In summary, curcumin treatment might produce a P73-dependent apoptotic cell death in chronic myelogenous leukemia cells (K562), which was triggered by mitotic catastrophe, due to sustained BAX and survivin expression and impairment of the anti-apoptotic proteins BCL-2 and XIAP.

Preconditioning by Low Dose LPS Prevents Subsequent LPS-Induced Severe Liver Injury via Nrf2 Activation in Mice

BACKGROUND

Sepsis is a syndrome triggered by endotoxin lipopolysaccharide (LPS) during bacterial infection. Sepsis sometimes recurs, with the second sepsis giving rise to a different phenotype because of disease modification by the preceding sepsis. Such a protective modification is called a preconditioning (PC) effect. PC is an endogenous protective mechanism by which sublethal damage confers tolerance to a subsequent lethal load. Oxidative stress is one of the important pathogenetic mechanisms that occur in sepsis. The nuclear factor erythroid 2 (NF-E2)-related factor-2 (Nrf2) system is a key regulatory transcription factor that protects organs and cells against oxidative stress and may be associated with the PC effect in repeated sepsis.

METHODS

The effect of PC induced by low-dose LPS on survival rate and liver injury against subsequent high-dose LPS stimulation was examined using a mouse model of sepsis. In order to understand the detailed mechanism(s) involved in the PC effect within the liver, gene expression array was performed. As a candidate mechanism of PC, the activation of the Nrf2 system was analyzed using Nrf2 reporter mice. Furthermore, the induction of heme oxygenase-1 (HO-1), one of the main targets of Nrf2, in the liver was examined by immunoblotting and immunohistochemistry. The PC effect on liver injury induced by LPS was further examined using Nrf2-deficient mice.

RESULTS

PC by LPS (1.7 or 5.0 mg/kg body weight, intraperitoneally) increased the survival rate of mice and decreased liver injury in response to a subsequent injection of a lethal level of LPS (20 mg/kg body weight). DNA array revealed that the gene ontology term "antioxidant activity" as one of the candidate mechanisms of the PC effect by LPS. In Nrf2 reporter mice, PC immediately and intensely enhanced luminescence that indicated Nrf2 activation after subsequent LPS injection. The induction of HO-1 by LPS was also enhanced by preceding PC, and its induction was observed mainly in Kupffer cells of the liver. In Nrf2-deficient mice, the induction of HO-1 in Kupffer cells and the hepatoprotective effect of PC were decreased as compared with wild-type mice.

CONCLUSION

Our results suggest that activation of the Nrf2 system is, at least in part, one of the mechanisms of a PC effect in the mouse liver in the case of repeated LPS stimulation.