miR-200a regulates Nrf2 activation by targeting Keap1 mRNA in breast cancer cells

Positive and Negative Regulation of Ferroptosis and Its Role in Maintaining Metabolic and Redox Homeostasis

Ferroptosis is a recently recognized regulated form of cell death characterized by accumulation of lipid-based reactive oxygen species (ROS), particularly lipid hydroperoxides and loss of activity of the lipid repair enzyme glutathione peroxidase 4 (GPX4). This iron-dependent form of cell death is morphologically, biochemically, and also genetically discrete from other regulated cell death processes, which include autophagy, apoptosis, necrosis, and necroptosis. Ferroptosis is defined by three hallmarks, defined as the loss of lipid peroxide repair capacity by GPX4, the bioavailability of redox-active iron, and oxidation of polyunsaturated fatty acid- (PUFA-) containing phospholipids. Experimentally, it can be induced by many compounds (e.g., erastin, Ras-selective lethal small-molecule 3, and buthionine sulfoximine) and also can be pharmacologically inhibited by iron chelators (e.g., deferoxamine and deferoxamine mesylate) and lipid peroxidation inhibitors (e.g., ferrostatin and liproxstatin). The sensitivity of a cell towards ferroptotic cell death is tightly associated with the metabolism of amino acid, iron, and polyunsaturated fatty acid metabolism, and also with the biosynthesis of glutathione, phospholipids, NADPH, and coenzyme Q10. Ferroptosis sensitivity is also governed by many regulatory proteins, which also link ferroptosis to the function of key tumour suppressor pathways. In this review, we highlight the discovery of ferroptosis, the mechanism of ferroptosis regulation, and its association with other cellular metabolic processes.

Advances in Understanding Mitochondrial MicroRNAs (mitomiRs) on the Pathogenesis of Triple-Negative Breast Cancer (TNBC)

Triple-negative breast cancer (TNBC) is characterized by poor outcome and the most challenging breast cancer type to treat worldwide. TNBC manifests distinct profile of mitochondrial functions, which dictates reprogrammed metabolism, fosters tumor progression, and notably serves as therapeutic targets. Mitochondrial microRNAs (mitomiRs) are a group of microRNAs that critically modulate mitochondrial homeostasis. By a pathway-centric manner, mitomiRs tightly orchestrate metabolic reprogramming, redox status, cell apoptosis, mitochondrial dynamics, mitophagy, mitochondrial DNA (mtDNA) maintenance, and calcium balance, leading to an emerging field of study in various cancer types, including TNBC. We herein review the recent insights into the roles and mechanism of mitomiRs in TNBC and highlight its clinical value in diagnosis and prognosis as well as vital advances on therapeutics of preclinical and clinical studies.

Pharmacological Targeting of Heme Oxygenase-1 in Osteoarthritis

Osteoarthritis (OA) is a common aging-associated disease that clinically manifests as joint pain, mobility limitations, and compromised quality of life. Today, OA treatment is limited to pain management and joint arthroplasty at the later stages of disease progression. OA pathogenesis is predominantly mediated by oxidative damage to joint cartilage extracellular matrix and local cells such as chondrocytes, osteoclasts, osteoblasts, and synovial fibroblasts. Under normal conditions, cells prevent the accumulation of reactive oxygen species (ROS) under oxidatively stressful conditions through their adaptive cytoprotective mechanisms. Heme oxygenase-1 (HO-1) is an iron-dependent cytoprotective enzyme that functions as the inducible form of HO. HO-1 and its metabolites carbon monoxide and biliverdin contribute towards the maintenance of redox homeostasis. HO-1 expression is primarily regulated at the transcriptional level through transcriptional factor nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), specificity protein 1 (Sp1), transcriptional repressor BTB-and-CNC homology 1 (Bach1), and epigenetic regulation. Several studies report that HO-1 expression can be regulated using various antioxidative factors and chemical compounds, suggesting therapeutic implications in OA pathogenesis as well as in the wider context of joint disease. Here, we review the protective role of HO-1 in OA with a focus on the regulatory mechanisms that mediate HO-1 activity.

Heme Oxgenase-1, a Cardinal Modulator of Regulated Cell Death and Inflammation

Heme oxygenase catalyzes the rate-limiting step in heme degradation in order to generate biliverdin, carbon monoxide (CO), and iron. The inducible form of the enzyme, heme oxygenase-1 (HO-1), exerts a central role in cellular protection. The substrate, heme, is a potent pro-oxidant that can accelerate inflammatory injury and promote cell death. HO-1 has been implicated as a key mediator of inflammatory cell and tissue injury, as validated in preclinical models of acute lung injury and sepsis. A large body of work has also implicated HO-1 as a cytoprotective molecule against various forms of cell death, including necrosis, apoptosis and newly recognized regulated cell death (RCD) programs such as necroptosis, pyroptosis, and ferroptosis. While the antiapoptotic potential of HO-1 and its reaction product CO in apoptosis regulation has been extensively characterized, relatively fewer studies have explored the regulatory role of HO-1 in other forms of necrotic and inflammatory RCD (i.e., pyroptosis, necroptosis and ferroptosis). HO-1 may provide anti-inflammatory protection in necroptosis or pyroptosis. In contrast, in ferroptosis, HO-1 may play a pro-death role via enhancing iron release. HO-1 has also been implicated in co-regulation of autophagy, a cellular homeostatic program for catabolic recycling of proteins and organelles. While autophagy is primarily associated with cell survival, its occurrence can coincide with RCD programs. This review will summarize the roles of HO-1 and its reaction products in co-regulating RCD and autophagy programs, with its implication for both protective and detrimental tissue responses, with emphasis on how these impact HO-1 as a candidate therapeutic target in disease.

Fumonisin B1 alters global m6A RNA methylation and epigenetically regulates Keap1-Nrf2 signaling in human hepatoma (HepG2) cells

FB₁ is a common contaminant of cereal grains that affects human and animal health. It has become increasingly evident that epigenetic changes are implicated in FB₁ toxicity. N6-methyladenosine (m6A), the most abundant post-transcriptional RNA modification, is influenced by fluctuations in redox status. Since oxidative stress is a characteristic of FB₁ exposure, we determined if there is cross-talk between oxidative stress and m6A in FB₁-exposed HepG2 cells. Briefly, HepG2 cells were treated with FB₁ (0, 5, 50, 100, 200 µM; 24 h) and ROS, LDH and m6A levels were quantified. qPCR was used to determine the expression of m6A modulators, Nrf2, Keap1 and miR-27b, while western blotting was used to quantify Keap1 and Nrf2 protein expression. Methylation status of Keap1 and Nrf2 promoters was assessed and RNA immunoprecipitation quantified m6A-Keap1 and m6A-Nrf2 levels. FB₁ induced accumulation of intracellular ROS (p ≤ 0.001) and LDH leakage (p ≤ 0.001). Elevated m6A levels (p ≤ 0.05) were accompanied by an increase in m6A "writers" [METLL3 (p ≤ 0.01) and METLL14 (p ≤ 0.01)], and "readers" [YTHDF1 (p ≤ 0.01), YTHDF2 (p ≤ 0.01), YTHDF3 (p ≤ 0.001) and YTHDC2 (p ≤ 0.01)] and a decrease in m6A "erasers" [ALKBH5 (p ≤ 0.001) and FTO (p ≤ 0.001)]. Hypermethylation and hypomethylation occurred at Keap1 (p ≤ 0.001) and Nrf2 (p ≤ 0.001) promoters, respectively. MiR-27b was reduced (p ≤ 0.001); however, m6A-Keap1 (p ≤ 0.05) and m6A-Nrf2 (p ≤ 0.01) levels were upregulated. This resulted in the ultimate decrease in Keap1 (p ≤ 0.001) and increase in Nrf2 (p ≤ 0.001) expression. Our findings reveal that m6A RNA methylation can be modified by exposure to FB₁, and a cross-talk between m6A and redox regulators does occur.

Potential role of specific microRNAs in the regulation of thermal stress response in livestock

Thermal stress is known to have harmful effects on livestock productivity and can cause livestock enterprises considerable financial loss. These effects may be aggravated by climate change. Stress responses to nonspecific systemic actions lead to perturbation of molecular pathways in the organism. The molecular response is regulated in a dynamic and synchronized manner that assurances robustness and flexibility for the restoration of functional and structural homeostasis in stressed cells and tissues. MicroRNAs (miRNAs) are micro molecules of small non-coding RNA that control gene expression at the post-transcriptional level. Recently, various studies have discovered precise types of miRNA that regulate cellular machinery and homeostasis under various types of stress, suggesting a significant role of miRNA in thermal stress responses in animals. The miRNAs revealed in this paper could serve as promising candidates and biomarkers for heat stress and could be used as potential pharmacological targets for mitigating the consequences of thermal stress. Stress miRNA pathways may be associated with thermal stress, which offers some potential approaches to combat the negative impacts of thermal stress in livestock. The review provides new data that can assist the elucidation of the miRNA mechanisms that mediate animals' responses to thermal stress.

Effects of triclosan on the RedoximiRs/Sirtuin/Nrf2/ARE signaling pathway in mosquitofish (Gambusia affinis)

Triclosan (TCS) has been widely used in daily life for its broad-spectrum antibacterial property and subsequently detected frequently in aquatic waterborne. Environmental relevant concentrations of TCS in water (ng-μg/L) may pose potential unexpected impact on non-target aquatic organisms. In the present work, we investigated the transcriptional responses of Nrf2 as well as its downstream genes, sirtuins and redox-sensitive microRNAs (RedoximiRs) in livers of the small freshwater fish mosquitofish (Gambusia affinis) which were exposed to environmental relevant concentrations of TCS (0.05 μg/L, 0.5 μg/L and 5 μg/L for 24 h and 168 h). Results showed there were similar up-regulations in Nrf2 and its target genes (e. g. NQO1, CAT and SOD) at transcriptional, enzymatic and protein levels, reflecting oxidative stress of TCS to mosquitofish. Meanwhile, up-regulations of Sirt1, Sirt2 and down-regulations of miR-34b, miR-200b-5p and miR-21 could modulate antioxidant system via the Nrf2/ARE signaling pathway by the post-transcriptional regulations. Some oxidative stress-related biomarkers displayed in concentration-dependent manners (e. g. NQO1 mRNA, CAT mRNA) and/or time-dependent manners (e. g. GSH contents). This study indicated that the RedoximiRs/Sirtuin/Nrf2/ARE signaling pathway played a crucial role in mosquitofish exposed to TCS, and there might be potentially profound effects for TCS on the aquatic ecological safety.

Oxidative Stress and Cancer Development: Are Noncoding RNAs the Missing Links?

Significance: It is now clear that genetic changes underlie the basis of cancer, and alterations in functions of multiple genes are responsible for the process of tumorigenesis. Besides the classical genes that are usually implicated in cancer, the role of noncoding RNAs (ncRNAs) and reactive oxygen species (ROS) as independent entitites has also been investigated. Recent Advances: The microRNAs and long noncoding RNAs (lncRNAs), two main classes of ncRNAs, are known to regulate many aspects of tumor development. ROS, generated during oxidative stress and pathological conditions, are known to regulate every step of tumor development. Conversely, oxidative stress and ROS producing agents can suppress tumor development. The malignant cells normally produce high levels of ROS compared with normal cells. The interaction between ROS and ncRNAs regulates the expression of multiple genes and pathways implicated in cancer, suggesting a unique mechanistic relationship among ncRNA-ROS-cancer. The mechanistic relationship has been reported in hepatocellular carcinoma, glioma, and malignancies of blood, breast, colorectum, esophagus, kidney, lung, mouth, ovary, pancreas, prostate, and stomach. The ncRNA-ROS regulate several cancer-related cell signaling pathways, namely, protein kinase B (AKT), epidermal growth factor receptor (EGFR), forkhead box O3 (FOXO3), kelch-like ECH-associated protein 1 (Keap1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), nuclear factor erythroid 2-related factor 2 (Nrf2), p53, phosphatase and tensin homologue (PTEN), and wingless-related integration site (Wnt)/glycogen synthase kinase-3 beta (GSK3β). Critical Issues: To date, most of the reports about ncRNA-oxidative stress-carcinogenesis relationships are based on cell lines. The mechanistic basis for this relationship has not been completely elucidated. Future Directions: Attempts should be made to explore the association of lncRNAs with ROS. The significance of the ncRNA-oxidative stress-carcinogenesis interplay should also be explored through studies in animal models.

The Keap1/Nrf2 Signaling Pathway in the Thyroid-2020 Update

The thyroid gland has a special relationship with oxidative stress. On the one hand, like all other tissues, it must defend itself against reactive oxygen species (ROS). On the other hand, unlike most other tissues, it must also produce reactive oxygen species in order to synthesize its hormones that contribute to the homeostasis of other tissues. The thyroid must therefore also rely on antioxidant defense systems to maintain its own homeostasis in the face of continuous self-exposure to ROS. One of the main endogenous antioxidant systems is the pathway centered on the transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) and its cytoplasmic inhibitor Kelch-like ECH-associated protein 1 (Keap1). Over the last few years, multiple links have emerged between the Keap1/Nrf2 pathway and thyroid physiology, as well as various thyroid pathologies, including autoimmunity, goiter, hypothyroidism, hyperthyroidism, and cancer. In the present mini-review, we summarize recent studies shedding new light into the roles of Keap1/Nrf2 signaling in the thyroid.

Nuclear Factor Erythroid 2-Related Factor 2 in Regulating Cancer Metabolism

Significance: Nuclear factor erythroid 2 (NFE2)-related factor 2 (NFE2L2, or NRF2) is a transcription factor predominantly affecting the expression of antioxidant genes. NRF2 plays a significant role in the control of redox balance, which is crucial in cancer cells. NRF2 activation regulates numerous cancer hallmarks, including metabolism, cancer stem cell characteristics, tumor aggressiveness, invasion, and metastasis formation. We review the molecular characteristics of the NRF2 pathway and discuss its interactions with the cancer hallmarks previously listed. Recent Advances: The noncanonical activation of NRF2 was recently discovered, and members of this pathway are involved in carcinogenesis. Further, cancer-related changes (e.g., metabolic flexibility) that support cancer progression were found to be redox- and NRF2 dependent. Critical Issues: NRF2 undergoes Janus-faced behavior in cancers. The pro- or antineoplastic effects of NRF2 are context dependent and essentially based on the specific molecular characteristics of the cancer in question. Therefore, systematic investigation of NRF2 signaling is necessary to clarify its role in cancer etiology. The biggest challenge in the NRF2 field is to determine which cancers can be targeted for better clinical outcomes. Further, large-scale genomic and transcriptomic studies are missing to correlate the clinical outcome with the activity of the NRF2 system. Future Directions: To exploit NRF2 in a clinical setting in the future, the druggable members of the NRF2 pathway should be identified. In addition, it will be important to study how the modulation of the NRF2 system interferes with cytostatic drugs and their combinations.

Antioxidant defense mechanisms and its dysfunctional regulation in the mitochondrial disease, Friedreich's ataxia

Redox stress is associated with the pathogenesis of a wide variety of disease states. This can be amplified potentially through redox active iron deposits in oxidatively active organelles such as the mitochondrion. There are a number of disease states, including Friedreich's ataxia (FA) and sideroblastic anemia, where iron metabolism is dysregulated and leads to mitochondrial iron accumulation. Considering FA, which is due to the decreased expression of the mitochondrial protein, frataxin, this iron accumulation does not occur within protective storage proteins such as mitochondrial ferritin. Instead, it forms unbound biomineral aggregates composed of high spin iron(III), phosphorous and sulfur, which probably contributes to the observed redox stress. There is also a dysregulated response to the ensuing redox assault, as the master regulator of oxidative stress, nuclear factor erythroid 2-related factor-2 (Nrf2), demonstrates marked down-regulation. The dysfunctional response of Nrf2 in FA is due to multiple mechanisms including: (1) up-regulation of Keap1 that is involved in Nrf2 degradation; (2) activation of the nuclear Nrf2 export/degradation machinery via glycogen synthase kinase-3β (Gsk3β) signaling; and (3) inhibited nuclear translocation of Nrf2. More recently, increased microRNA (miRNA) 144 expression has been demonstrated to down-regulate Nrf2 in several disease states, including an animal model of FA. Other miRNAs have also demonstrated to be dysregulated upon frataxin depletion in vivo in humans and animal models of FA. Collectively, frataxin depletion results in multiple, complex responses that lead to detrimental redox effects that could contribute to the mechanisms involved in the pathogenesis of FA.

Primary Amine Modified Gold Nanodots Regulate Macrophage Function and Antioxidant Response: Potential Therapeutics Targeting of Nrf2

BACKGROUND

Gold nanoparticles with high biocompatibility and immunomodulatory properties have potential applications in the development of new diagnostic and therapeutic strategies for nanomedicine. Nanoparticles targeting macrophages can manipulate or control immunological diseases. This study assessed the activity of dendrimer-encapsulated gold nanodots (AuNDs) with three surface modifications [ie, outfacing groups with primary amine (AuNDs-NH2), hydroxyl (AuNDs-OH), and quaternary ammonium ions (AuNDs-CH3)] regulated macrophage function and antioxidant response through Nrf2-dependent pathway.

METHODS

AuNDs were prepared and characterized. Intracellular distribution of AuNDs in human macrophages was observed through confocal microscopy. The activity of AuNDs was evaluated using macrophage functions and antioxidant response in the human macrophage cell line THP-1.

RESULTS

AuNDs-NH2 and AuNDs-CH3, but not AuNDs-OH, drove the obvious Nrf2-antioxidant response element pathway in THP-1 cells. Of the three, AuNDs-NH2 considerably increased mRNA levels and antioxidant activities of heme oxygenase 1 and NAD(P)H quinone dehydrogenase 1 in THP-1 cells. IL-6 mRNA and protein expression was mediated through Nrf2 activation in AuNDs-NH2-treated macrophages. Furthermore, Nrf2 activation by AuNDs-NH2 increased the phagocytic ability of THP-1 macrophages.

CONCLUSION

AuNDs-NH2 had immunomodulatory activities in macrophages. The findings of the present work suggested that AuNDs have potential effects against chronic inflammatory diseases via the Nrf2 pathway.

Epigenetic Regulation of NRF2/KEAP1 by Phytochemicals

Epigenetics has provided a new dimension to our understanding of nuclear factor erythroid 2–related factor 2/Kelch-like ECH-associated protein 1 (human NRF2/KEAP1 and murine Nrf2/Keap1) signaling. Unlike the genetic changes affecting DNA sequence, the reversible nature of epigenetic alterations provides an attractive avenue for cancer interception. Thus, targeting epigenetic mechanisms in the corresponding signaling networks represents an enticing strategy for therapeutic intervention with dietary phytochemicals acting at transcriptional, post-transcriptional, and post-translational levels. This regulation involves the interplay of histone modifications and DNA methylation states in the human NFE2L2/KEAP1 and murine Nfe2l2/Keap1 genes, acetylation of lysine residues in NRF2 and Nrf2, interaction with bromodomain and extraterminal domain (BET) acetyl “reader” proteins, and non-coding RNAs such as microRNA (miRNA) and long non-coding RNA (lncRNA). Phytochemicals documented to modulate NRF2 signaling act by reversing hypermethylated states in the CpG islands of NFE2L2 or Nfe2l2, via the inhibition of DNA methyltransferases (DNMTs) and histone deacetylases (HDACs), through the induction of ten-eleven translocation (TET) enzymes, or by inducing miRNA to target the 3′-UTR of the corresponding mRNA transcripts. To date, fewer than twenty phytochemicals have been reported as NRF2 epigenetic modifiers, including curcumin, sulforaphane, resveratrol, reserpine, and ursolic acid. This opens avenues for exploring additional dietary phytochemicals that regulate the human epigenome, and the potential for novel strategies to target NRF2 signaling with a view to beneficial interception of cancer and other chronic diseases.

Beyond repression of Nrf2: An update on Keap1

Nrf2 (NFE2L2 - nuclear factor (erythroid-derived 2)-like 2) is a transcription factor, which is repressed by interaction with a redox-sensitive protein Keap1 (Kelch-like ECH-associated protein 1). Deregulation of Nrf2 transcriptional activity has been described in the pathogenesis of multiple diseases, and the Nrf2/Keap1 axis has emerged as a crucial modulator of cellular homeostasis. Whereas the significance of Nrf2 in the modulation of biological processes has been well established and broadly discussed in detail, the focus on Keap1 rarely goes beyond the regulation of Nrf2 activity and redox sensing. However, recent studies and scrutinized analysis of available data point to Keap1 as an intriguing and potent regulator of cellular function. This review aims to shed more light on Keap1 structure, interactome, regulation and non-canonical functions, thereby enhancing its significance in cell biology. We also intend to highlight the impact of balance between Keap1 and Nrf2 in the maintenance of cellular homeostasis.

Treatment of dilated cardiomyopathy in a mouse model of Friedreich's ataxia using N-acetylcysteine and identification of alterations in microRNA expression that could be involved in its pathogenesis

Deficient expression of the mitochondrial protein, frataxin, leads to a deadly cardiomyopathy. Our laboratory reported the master regulator of oxidative stress, nuclear factor erythroid 2-related factor-2 (Nrf2), demonstrates marked down-regulation after frataxin deletion in the heart. This was due, in part, to a pronounced increase in Keap1. To assess if this can be therapeutically targeted, cells were incubated with N-acetylcysteine (NAC), or buthionine sulfoximine (BSO), which increases or decreases glutathione (GSH), respectively, or the NRF2-inducer, sulforaphane (SFN). While SFN significantly (p < 0.05) induced NRF2, KEAP1 and BACH1, NAC attenuated SFN-induced NRF2, KEAP1 and BACH1. The down-regulation of KEAP1 by NAC was of interest, as Keap1 is markedly increased in the MCK conditional frataxin knockout (MCK KO) mouse model and this could lead to the decreased Nrf2 levels. Considering this, MCK KO mice were treated with i.p. NAC (500- or 1500-mg/kg, 5 days/week for 5-weeks) and demonstrated slightly less (p > 0.05) body weight loss versus the vehicle-treated KO. However, NAC did not rescue the cardiomyopathy. To additionally examine the dys-regulation of Nrf2 upon frataxin deletion, studies assessed the role of microRNA (miRNA) in this process. In MCK KO mice, miR-144 was up-regulated, which down-regulates Nrf2. Furthermore, miRNA screening in MCK KO mice demonstrated 23 miRNAs from 756 screened were significantly (p < 0.05) altered in KOs versus WT littermates. Of these, miR-21*, miR-34c*, and miR-200c, demonstrated marked alterations, with functional clustering analysis showing they regulate genes linked to cardiac hypertrophy, cardiomyopathy, and oxidative stress, respectively.

Natural Nrf2 Modulators for Skin Protection

Since the discovery of antioxidant responsive elements (ARE), which are commonly found in the promoter of the Phase II metabolism/antioxidant enzymes, and nuclear factor erythroid 2-related factor 2 (Nrf2), the transcription factor that binds to ARE, the study conducted in this field has expanded remarkably over the decades, and the Nrf2-mediated pathway is now recognized to occupy a central position in cell defense mechanisms. Induction of the Phase II metabolism/antioxidant enzymes through direct activation of Nrf2 can be a promising strategy for preventing degenerative diseases in general, but a dark side of this strategy should be considered, as Nrf2 activation can enhance the survival of cancer cells. In this review, we discuss the historical discovery of Nrf2 and the regulatory mechanism of the Nrf2-mediated pathway, focusing on the interacting proteins and post-translational modifications. In addition, we discuss the latest studies that examined various natural Nrf2 modulators for the protective roles in the skin, in consideration of their dermatological and cosmetic applications. Studies are reviewed in the order of time of research as much as possible, to help understand how and why such studies were conducted under the circumstances of that time. We hope that this review can serve as a steppingstone in conducting more advanced research by providing a scientific basis for researchers newly entering this field.

Revisiting cancer hallmarks: insights from the interplay between oxidative stress and non-coding RNAs

Cancer is one of the most common disease worldwide, with complex changes and certain traits which have been described as “The Hallmarks of Cancer.” Despite increasing studies on in-depth investigation of these hallmarks, the molecular mechanisms associated with tumorigenesis have still not yet been fully defined. Recently, accumulating evidence supports the observation that microRNAs and long noncoding RNAs (lncRNAs), two main classes of noncoding RNAs (ncRNAs), regulate most cancer hallmarks through their binding with DNA, RNA or proteins, or encoding small peptides. Reactive oxygen species (ROS), the byproducts generated during metabolic processes, are known to regulate every step of tumorigenesis by acting as second messengers in cancer cells. The disturbance in ROS homeostasis leads to a specific pathological state termed “oxidative stress”, which plays essential roles in regulation of cancer progression. In addition, the interplay between oxidative stress and ncRNAs is found to regulate the expression of multiple genes and the activation of several signaling pathways involved in cancer hallmarks, revealing a potential mechanistic relationship involving ncRNAs, oxidative stress and cancer. In this review, we provide evidence that shows the essential role of ncRNAs and the interplay between oxidative stress and ncRNAs in regulating cancer hallmarks, which may expand our understanding of ncRNAs in the cancer development from the new perspective.

Fusaric acid-induced epigenetic modulation of hepatic H3K9me3 triggers apoptosis in vitro and in vivo

Aim: To determine the effect of the food-borne mycotoxin, fusaric acid (FA) on miR-200a, SUV39H1-mediated H3K9me3, genome integrity and apoptosis in human liver (HepG2) cells and C57BL/6 mice livers. Materials & methods: MiR-200a, Sirt1, SUV39H1-mediated H3K9me3, genome integrity and apoptosis was measured in HepG2 cells and C57BL/6 mice livers using qPCR, western blot, DNA electrophoresis and luminometry. Results: FA: upregulated miR-200a and decreased Sirt1 expression in HepG2 cells and mice livers; decreased expression of SUV39H1 and KDM4B, thus decreasing H3K9me3 and increasing H3K9me1; increased cell mortality via apoptosis. Conclusion: FA induced apoptosis by upregulating miR-200a and decreasing SUV39H1-mediated H3K9me3 in HepG2 cells and mice livers.

Molecular Mechanisms Underlying Hepatocellular Carcinoma Induction by Aberrant NRF2 Activation-Mediated Transcription Networks: Interaction of NRF2-KEAP1 Controls the Fate of Hepatocarcinogenesis

NF-E2-related factor 2 (NRF2) is a basic leucine zipper transcription factor, a master regulator of redox homeostasis regulating a variety of genes for antioxidant and detoxification enzymes. NRF2 was, therefore, initially thought to protect the liver from oxidative stress. Recent studies, however, have revealed that mutations in NRF2 cause aberrant accumulation of NRF2 in the nucleus and exert the upregulation of NRF2 target genes. Moreover, among all molecular changes in hepatocellular carcinoma (HCC), NRF2 activation has been revealed as a more prominent pathway contributing to the progression of precancerous lesions to malignancy. Nevertheless, how its activation leads to poor prognosis in HCC patients remains unclear. In this review, we provide an overview of how aberrant activation of NRF2 triggers HCC development. We also summarize the emerging roles of other NRF family members in liver cancer development.

Evaluation of the Diagnostic and Predicative Values of 8-Iso-Prostaglandin F2α as a Biomarker of Breast Cancer

BACKGROUND

Breast cancer (BC) is a commonly reported cancer that is widely prevalent among women. Its early detection improves patient survival and results in better outcomes. For diagnosis and follow-up care, tumor markers are one of the feasible investigations to be ordered. 8-Iso-prostaglandin F2α (8-iso-PGF2α) serves as a serum marker reflecting oxidative stress and subsequent damaging of DNA. In the present study, we aimed to evaluate both diagnostic and predictive values of 8-iso-PGF2α in BC patients.

MATERIALS AND METHODS

Serum levels of 8-iso-PGF2α were assessed for 66 women with benign breast tumors and 65 women who had malignant BC. To compare the patients who had breast tumors with healthy individuals, 63 women free of breast diseases were selected as controls.

RESULTS

The serum level of 8-iso-PGF2α in the BC patients (57.92 pg/mL) was significantly higher compared to those with benign tumors (18.89 pg/mL) (p < 0.001). In addition, individuals with no breast diseases had less 8-iso-PGF2α (4.02 pg/mL) compared to those who had developed a tumor (p < 0.001). Serum 8-iso-PGF2α was found to be positively correlated with both carcinoembryonic antigen (r = 0.74, p < 0.001) and cancer antigen 15-3 (r = 0.80, p < 0.001). Furthermore, serum 8-iso-PGF2α showed high diagnostic performance in BC (AUC = 0.999, sensitivity = 100%, specificity = 99.2% at a cutoff value of 36.18 pg/mL).

CONCLUSIONS

Our study found that the high level of serum 8-iso-PGF2α helps to provide a non-invasive indicator to detect BC. Future work with a larger sample size and various phases of BC can confirm the current results which provide insights into the early detection of cancer.

Crosstalk between noncoding RNAs and ferroptosis: new dawn for overcoming cancer progression

Cancer progression including proliferation, metastasis, and chemoresistance has become a serious hindrance to cancer therapy. This phenomenon mainly derives from the innate insensitive or acquired resistance of cancer cells to apoptosis. Ferroptosis is a newly discovered mechanism of programmed cell death characterized by peroxidation of the lipid membrane induced by reactive oxygen species. Ferroptosis has been confirmed to eliminate cancer cells in an apoptosis-independent manner, however, the specific regulatory mechanism of ferroptosis is still unknown. The use of ferroptosis for overcoming cancer progression is limited. Noncoding RNAs have been found to play an important roles in cancer. They regulate gene expression to affect biological processes of cancer cells such as proliferation, cell cycle, and cell death. Thus far, the functions of ncRNAs in ferroptosis of cancer cells have been examined, and the specific mechanisms by which noncoding RNAs regulate ferroptosis have been partially discovered. However, there is no summary of ferroptosis associated noncoding RNAs and their functions in different cancer types. In this review, we discuss the roles of ferroptosis-associated noncoding RNAs in detail. Moreover, future work regarding the interaction between noncoding RNAs and ferroptosis is proposed, the possible obstacles are predicted and associated solutions are put forward. This review will deepen our understanding of the relationship between noncoding RNAs and ferroptosis, and provide new insights in targeting noncoding RNAs in ferroptosis associated therapeutic strategies.

Epigenetic repression of miR-17 contributed to di(2-ethylhexyl) phthalate-triggered insulin resistance by targeting Keap1-Nrf2/miR-200a axis in skeletal muscle

Rationale: Skeletal muscle insulin resistance is detectable before type 2 diabetes is diagnosed. Exposure to di(2-ethylhexyl) phthalate (DEHP), a typical environmental endocrine-disrupting chemical, is a novel risk factor for insulin resistance and type 2 diabetes. This study aimed to explore insulin signaling regulatory pathway in skeletal muscle of the DEHP-induced insulin-resistant mice and to investigate potential therapeutic strategies for treating insulin resistance.

Methods: C57BL/6J male mice were exposed to 2 mg/kg/day DEHP for 15 weeks. Whole-body glucose homeostasis, oxidative stress and deregulated miRNA-mediated molecular transduction in skeletal muscle were examined. microRNA (miRNA) interventions based on lentiviruses and adeno-associated viruses 9 (AAV9) were performed.

Results: Dnmt3a-dependent promoter methylation and lncRNA Malat1-related sponge functions cooperatively downregulated miR-17 in DEHP-exposed skeletal muscle cells. DEHP suppressed miR-17 to disrupt the Keap1-Nrf2 redox system and to activate oxidative stress-responsive Txnip in skeletal muscle. Oxidative stress upregulated miR-200a, which directly targets the 3'UTR of Insr and Irs1, leading to hindered insulin signaling and impaired insulin-dependent glucose uptake in skeletal muscle, ultimately promoting the development of insulin resistance. AAV9-induced overexpression of miR-17 and lentivirus-mediated silencing of miR-200a in skeletal muscle ameliorated whole-body insulin resistance in DEHP-exposed mice.

Conclusions: The miR-17/Keap1-Nrf2/miR-200a axis contributed to DEHP-induced insulin resistance. miR-17 is a positive regulator, whereas miR-200a is a negative regulator of insulin signaling in skeletal muscle, and both miRNAs have the potential to become therapeutic targets for preventing and treating insulin resistance or type 2 diabetes.

Protective role of NRF2 in macrovascular complications of diabetes

Macrovascular complications develop in over a half of the diabetic individuals, resulting in high morbidity and mortality. This poses a severe threat to public health and a heavy burden to social economy. It is therefore important to develop effective approaches to prevent or slow down the pathogenesis and progression of macrovascular complications of diabetes (MCD). Oxidative stress is a major contributor to MCD. Nuclear factor (erythroid‐derived 2)‐like 2 (NRF2) governs cellular antioxidant defence system by activating the transcription of various antioxidant genes, combating diabetes‐induced oxidative stress. Accumulating experimental evidence has demonstrated that NRF2 activation protects against MCD. Structural inhibition of Kelch‐like ECH‐associated protein 1 (KEAP1) is a canonical way to activate NRF2. More recently, novel approaches, such as activation of the Nfe2l2 gene transcription, decreasing KEAP1 protein level by microRNA‐induced degradation of Keap1 mRNA, prevention of proteasomal degradation of NRF2 protein and modulation of other upstream regulators of NRF2, have emerged in prevention of MCD. This review provides a brief introduction of the pathophysiology of MCD and the role of oxidative stress in the pathogenesis of MCD. By reviewing previous work on the activation of NRF2 in MCD, we summarize strategies to activate NRF2, providing clues for future intervention of MCD. Controversies over NRF2 activation and future perspectives are also provided in this review.

Programmed Death Ligand-1 (PD-L1) Regulated by NRF-2/MicroRNA-1 Regulatory Axis Enhances Drug Resistance and Promotes Tumorigenic Properties in Sorafenib-Resistant Hepatoma Cells

Sorafenib, a multityrosine kinase inhibitor, is a standard treatment for advanced hepatocellular carcinoma (HCC), but the clinical response to sorafenib is seriously limited by drug resistance. Programmed death ligand-1 (PD-L1) is one of the most important inhibitory molecules involved in tumor immune evasion. Recently, it has been reported that PD-L1 could play crucial roles in drug resistance of many kinds of cancers. However, the expression, function, and regulation of PD-L1 in sorafenib-resistant hepatoma cells remain unclear. In this study, we reported that PD-L1 was overexpressed in sorafenib-resistant hepatoma cells, and shRNA-mediated PD-L1 depletion attenuated drug resistance and suppressed the migration, invasion, colony formation, and tumorigenesis in sorafenib-resistant hepatoma cells in vitro and in vivo. Mechanistic investigations indicated that loss of microRNA-1 (miR-1), a tumor-suppressive microRNA, contributed to the PD-L1 upregulation in sorafenib-resistant hepatoma cells, and PD-L1 was a direct regulatory target of miR-1. Further study revealed that an oncogenic transcriptional factor, nuclear factor E2-related factor 2 (NRF-2), was induced in sorafenib-resistant hepatoma cells and inhibited expression of miR-1 in vitro. From molecular mechanism insight back to the functional verification, we eventually demonstrated that miR-1 executed its tumor-suppressive effects on drug resistance and other malignant properties in sorafenib-resistant hepatoma cells partially by PD-L1 inhibition in vitro and in vivo. In conclusion, our data suggested that a NRF-2/miR-1/PD-L1 regulatory axis contributed to the development and maintenance of drug resistance and other tumorigenic properties in sorafenib-resistant hepatoma cells and provided a potential therapeutic target for overcoming sorafenib resistance in HCC.

MicroRNAs in the regulation of cellular redox status and its implications in myocardial ischemia-reperfusion injury

MicroRNAs (miRNAs) are small RNAs that do not encode for proteins and play key roles in the regulation of gene expression. miRNAs are involved in a comprehensive range of biological processes such as cell cycle control, apoptosis, and several developmental and physiological processes. Oxidative stress can affect the expression levels of multiple miRNAs and, conversely, miRNAs may regulate the expression of redox sensors, alter critical components of the cellular antioxidants, interact with the proteasome, and affect DNA repair systems. The number of publications identifying redox-sensitive miRNAs has increased significantly over the last few years, and some miRNA targets such as Nrf2, SIRT1 and NF-κB have been identified. The complex interplay between miRNAs and ROS is discussed together with their role in myocardial ischemia-reperfusion injury and the potential use of circulating miRNAs as biomarkers of myocardial infarction. Detailed knowledge of redox-sensitive miRNAs is needed to be able to effectively use individual compounds or sets of miRNA-modulating compounds to improve the health-related outcomes associated with different diseases.

The Molecular Mechanisms Regulating the KEAP1-NRF2 Pathway

The KEAP1-NRF2 pathway is the principal protective response to oxidative and electrophilic stresses. Under homeostatic conditions, KEAP1 forms part of an E3 ubiquitin ligase, which tightly regulates the activity of the transcription factor NRF2 by targeting it for ubiquitination and proteasome-dependent degradation. In response to stress, an intricate molecular mechanism facilitated by sensor cysteines within KEAP1 allows NRF2 to escape ubiquitination, accumulate within the cell, and translocate to the nucleus, where it can promote its antioxidant transcription program. Recent advances have revealed that KEAP1 contains multiple stress sensors and inactivation modalities, which together allow diverse cellular inputs, from oxidative stress and cellular metabolites to dysregulated autophagy, to regulate NRF2 activity. This integration of the KEAP1-NRF2 system into multiple cellular signaling and metabolic pathways places NRF2 activation as a critical regulatory node in many disease phenotypes and suggests that the pharmaceutical modulation of NRF2's cytoprotective activity will be beneficial for human health in a broad range of noncommunicable diseases.

When Oxidative Stress Meets Epigenetics: Implications in Cancer Development

Cancer is one of the leading causes of death worldwide and it can affect any part of the organism. It arises as a consequence of the genetic and epigenetic changes that lead to the uncontrolled growth of the cells. The epigenetic machinery can regulate gene expression without altering the DNA sequence, and it comprises methylation of the DNA, histones modifications, and non-coding RNAs. Alterations of these gene-expression regulatory elements can be produced by an imbalance of the intracellular environment, such as the one derived by oxidative stress, to promote cancer development, progression, and resistance to chemotherapeutic treatments. Here we review the current literature on the effect of oxidative stress in the epigenetic machinery, especially over the largely unknown ncRNAs and its consequences toward cancer development and progression.

Epigenetics/epigenomics of triterpenoids in cancer prevention and in health

Triterpenoids are a powerful group of phytochemicals derived from plant foods and herbs. Many reports have shown that they possess chemopreventive and chemotherapeutic effects not only in cell lines and animal models but also in clinical trials. Because epigenetic changes could potentially occur in the early stages of carcinogenesis preceding genetic mutations, epigenetics are considered promising targets in early interventions against cancer using epigenetic bioactive substances. The biological properties of triterpenoids in cancer prevention and in health have multiple mechanisms, including antioxidant and anti-inflammatory activities, cell cycle regulation, as well as epigenetic/epigenomic regulation. In this review, we will discuss and summarize the latest advances in the study of the pharmacological effects of triterpenoids in cancer chemoprevention and in health, including the epigenetic machinery.

Crosstalk of MicroRNAs and Oxidative Stress in the Pathogenesis of Cancer

Oxidative stress refers to an imbalance between reactive oxygen species (ROS) generation and body's capability to detoxify the reactive mediators or to fix the relating damage. MicroRNAs are considered to be important mediators that play essential roles in the regulation of diverse aspects of carcinogenesis. Growing studies have demonstrated that the ROS can regulate microRNA biogenesis and expression mainly through modulating biogenesis course, transcription factors, and epigenetic changes. On the other hand, microRNAs may in turn modulate the redox signaling pathways, altering their integrity, stability, and functionality, thus contributing to the pathogenesis of multiple diseases. Both ROS and microRNAs have been identified to be important regulators and potential therapeutic targets in cancers. However, the information about the interplay between oxidative stress and microRNA regulation is still limited. The present review is aimed at summarizing the current understanding of molecular crosstalk between microRNAs and the generation of ROS in the pathogenesis of cancer.

Upregulation of microRNA-200a in bone marrow mesenchymal stem cells enhances the repair of spinal cord injury in rats by reducing oxidative stress and regulating Keap1/Nrf2 pathway

Spinal cord injury (SCI) is a common disease with high incidence, disability rate and treatment cost. microRNA (miR)-200a is reported to inhibit Keap1 to activate Nrf2 signaling. This study aimed to explore the effects of lentivirus-mediated miR-200a gene-modified bone marrow mesenchymal stem cells (BMSCs) transplantation on the repair of SCI in a rat model. BMSCs were isolated from the bone marrow of Sprague-Dawley rats. MiR-200a targeting to Keap1 was identified by luciferase reporter gene assay. The expressions of Keap1, nuclear factor erythroid 2-related factor 2 (Nrf2), NAD(P)H-dependent quinone oxidoreductase 1 (NQO-1), heme oxygenase-1 (HO-1) and glutamate-cysteine ligase catalytic subunit (GCLC) were detected by Western blotting in SCI rats. The locomotor capacity of the rats was evaluated using the Basso, Beattie, and Bresnahan scale. The levels of malondialdehyde (MDA), activities of superoxide dismutase (SOD), and catalase (CAT) were measured. miR-200a inhibited Keap-1 3' UTR activity in BMSCs. Transplantation of BMSCs with overexpression of miR-200a or si-Keap1 increased locomotor function recovery of rats after SCI, while decreased MDA level, increased SOD, CAT activities, and Nrf2 expression together with its downstream HO-1, NQO1, GCLC protein expressions in SCI rat. These results indicated that overexpressed miR-200a in BMSCs promoted SCI repair, which may be through regulating antioxidative signaling pathway.

A Splice Variant of NCOR2, BQ323636.1, Confers Chemoresistance in Breast Cancer by Altering the Activity of NRF2

Breast cancer is the most common type of female cancer. Reactive oxygen species (ROS) are vital in regulating signaling pathways that control cell survival and cell proliferation. Chemotherapeutic drugs such as anthracyclines induce cell death via ROS induction. Chemoresistance development is associated with adaptive response to oxidative stress. NRF2 is the main regulator of cytoprotective response to oxidative stress. NRF2 can enhance cell growth, antioxidant expression, and chemoresistance by providing growth advantage for malignant cells. Previously, we identified BQ323636.1 (BQ), a novel splice variant of nuclear co-repressor NCOR2, which can robustly predict tamoxifen resistance in primary breast cancer. In this study, we found that BQ was overexpressed in epirubicin-resistant cells and demonstrated that BQ overexpression could reduce the levels of epirubicin-induced ROS and confer epirubicin resistance. In vivo analysis using tissue microarray of primary breast cancer showed direct correlation between BQ expression and chemoresistance. In vitro experiments showed BQ could modulate NRF2 transcriptional activity and upregulate antioxidants. Luciferase reporter assays showed that although NCOR2 repressed the transcriptional activity of NRF2, the presence of BQ reduced this repressive activity. Co-immunoprecipitation confirmed that NCOR2 could bind to NRF2 and that this interaction was compromised by BQ overexpression, leading to increased transcriptional activity in NRF2. Our findings suggest BQ can regulate the NRF2 signaling pathway via interference with NCOR2 suppressive activity and reveals a novel role for BQ as a modulator of chemoresistance in breast cancer.

Keap1-targeting microRNA-941 protects endometrial cells from oxygen and glucose deprivation-re-oxygenation via activation of Nrf2 signaling

BACKGROUND

Mimicking ischemia-reperfusion injury, oxygen and glucose deprivation (OGD)-re-oxygenation (OGDR) applied to endometrial cells produces significant oxidative stress and programmed necrosis, which can be inhibited by nuclear-factor-E2-related factor 2 (Nrf2) signaling. MicroRNA (miRNA)-induced repression of Keap1, a Nrf2 suppressor protein that facilitates Nrf2 degradation, is novel strategy to activate Nrf2 cascade.

METHODS

MicroRNA-941 (miR-941) was exogenously expressed in HESC and primary human endometrial cells, and the Nrf2 pathway examined by Western blotting and real-time quantitative PCR analysis. The endometrial cells were treated with OGDR, cell programmed necrosis and apoptosis were tested.

RESULTS

MiR-941 is a novel Keap1-targeting miRNA that regulates Nrf2 activity. In T-HESC cells and primary human endometrial cells, ectopic overexpression of miR-941 suppressed Keap1 3'-UTR (untranslated region) expression and downregulated its mRNA/protein expression, leading to activation of the Nrf2 cascade. Conversely, inhibition of miR-941 elevated Keap1 expression and activity in endometrial cells, resulting in suppression of Nrf2 activation. MiR-941 overexpression in endometrial cells attenuated OGDR-induced oxidative stress and programmed necrosis, whereas miR-941 inhibition enhanced oxidative stress and programmed necrosis. MiR-941 overexpression and inhibition were completely ineffective in Keap1-/Nrf2-KO T-HESC cells (using CRISPR/Cas9 strategy). Restoring Keap1 expression, using an UTR-depleted Keap1 construct, abolished miR-941-induced anti-OGDR activity in T-HESC cells. Thus Keap1-Nrf2 cascade activation is required for miR-941-induced endometrial cell protection.

CONCLUSIONS

Targeting Keap1 by miR-941 activates Nrf2 cascade to protect human endometrial cells from OGDR-induced oxidative stress and programmed necrosis. Video Abstract.

The function of miR-200 family in oxidative stress response evoked in cancer chemotherapy and radiotherapy

Since the beginning of the discovery of microRNAs (miRs), these molecules have attracted highly progressive attention due to their powerful regulatory roles in a broad spectrum of biological processes, including proliferation, differentiation, apoptosis and carcinogenesis. With regard to carcinogenesis, the miRs regulatory potency has been associated with cancer onset, progression, metastasis, diagnosis and therapeutic response. In this review we discuss the impact of miR-200 family on drug resistance development during anti-cancer therapy. Developing resistance to chemotherapeutic drugs as well as radiotherapy are major clinical obstacles in the successful therapeutic strategies to cancer treatment. Acquired cancer chemoresistance is a multifactorial phenomenon involving such factors as tumor type, tumor stage, cellular reactive oxygen species (ROS) level or ROS-responsive miRs profile. ROS level could influence the miRs expression level, which changes the cellular profile of the content of miRs. Such significant changes in the cellular miRs profile generate subsequent biological effects through the regulation of their target genes. This review outlines the interactions between ROS and miR-200 family in different kinds of cancers in response to chemotherapy.

MicroRNA Targeting Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Cancer

Significance: Reactive oxygen species (ROS) production occurs primarily in the mitochondria as a by-product of cellular metabolism. ROS are also produced by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases in response to growth factors and cytokines by normal physiological signaling pathways. NADPH oxidase, a member of NADPH oxidase (NOX) family, utilizes molecular oxygen (O₂) to generate ROS such as hydrogen peroxide and superoxide. Imbalance between ROS production and its elimination is known to be the major cause of various human diseases. NOX family proteins are exclusively involved in ROS production, which makes them attractive target(s) for the treatment of ROS-mediated diseases including cancer. Recent Advances: Molecules such as Keap1/nuclear factor erythroid 2-related factor 2 (Nrf2), N-methyl-d-aspartic acid (NMDA) receptors, nuclear factor-kappaB, KRAS, kallistatin, gene associated with retinoic-interferon-induced mortality-19, and deregulated metabolic pathways are involved in ROS production in association with NADPH oxidase. Critical Issues: Therapeutic strategies targeting NADPH oxidases in ROS-driven cancers are not very effective due to its complex regulatory circuit. Tumor suppressor microRNAs (miRNAs) viz. miR-34a, miR-137, miR-99a, and miR-21a-3p targeting NADPH oxidases are predominantly downregulated in ROS-driven cancers. miRNAs also regulate other cellular machineries such as Keap1/Nrf2 pathway and NMDA receptors involved in ROS production and consequently drug resistance. Here, we discuss the structure, function, and metabolic role of NADPH oxidase, NOX family protein-protein interaction, their association with other pathways, and NADPH oxidase alteration by miRNAs. Moreover, we also discuss and summarize studies on NADPH oxidase associated with various malignancies and their therapeutic implications. Future Directions: Targeting NADPH oxidases through miRNAs appears to be a promising strategy for the treatment of ROS-driven cancer.

Role of diets and exercise in ameliorating obesity-related hepatic steatosis: Insights at the microRNA-dependent thyroid hormone synthesis and action

AIMS

The present study was designed to compare the effects of a low-fat diet (LF), calorie restriction (CR), quercetin (Que) and exercise (Ex) on hepatic steatosis in a high-fat (HF) diet-induced obesity prone (OP) model in the perspective of microRNA (miR)-dependent thyroid hormone (TH) synthesis and action.

MAIN METHODS

Male C57BL/6J mice were administered a HF diet for 10 weeks to induce OP phenotype and then divided into 5 groups, HF diet (OP-HF), LF diet (OP-LF), 70% CR (OP-CR), 0.05% Que (OP-Que) and a treadmill exercise regimen (OP-Ex); one additional group fed LF diet served as control (LF). 7 weeks later, serum indexes, metabolic alterations, redox status and histological appearance in the thyroid and liver, and TH related miRs with their targets expressions were determined.

KEY FINDINGS

No significance on T3 levels was observed among the six groups. LF, CR, Que and Ex significantly ameliorated HF-induced hepatic steatosis to varying degrees, inhibited T4 production via differentially elevating miR-339, miR-383 and miR-146b to decrease NIS expression and regulating miR-200a/Nrf2 to maintain redox status in the thyroid. Furthermore, these four interventions differentially and significantly decreased miR-383 and miR-146b to elevate TRb and DIO1 expression, and subsequent TH responsive lipid metabolism genes regulation. Among them, the effects of CR on hepatic steatosis were the most prominent.

SIGNIFICANCE

Our data indicated that amelioration of hepatic steatosis by LF, CR, Que and Ex resulted in many shared, but also many differential changes in the miR-dependent TH production and action.

Small molecular Nrf2 inhibitors as chemosensitizers for cancer therapy

The basic leucine zipper transcription factor Nrf2 is the primary regulator of cellular oxidative stress. Activation of Nrf2 is regarded as a potential preventive and therapeutic strategy. However, aberrant hyperactivation of Nrf2 is found in a variety of cancers and promotes cancer progression and metastasis. Moreover, constitutive activation of Nrf2 confers cancer cells resistance to chemo- and radio-therapy. Thus, inhibiting Nrf2 could be a new therapeutic strategy for cancer. With the aim of accelerating the discovery and development of novel Nrf2 inhibitors, we summarize the biological and pathological functions of Nrf2 in cancer. Furthermore, the recent studies of small molecular Nrf2 inhibitors and potential Nrf2 inhibitory mechanisms are also summarized in this review.

Cullin 3 and Its Role in Tumorigenesis

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

Action of trichostatin A on Alzheimer's disease-like pathological changes in SH-SY5Y neuroblastoma cells

The histone deacetylase inhibitor, trichostatin A, is used to treat Alzheimer's disease and can improve learning and memory but its underlying mechanism of action is unknown. To determine whether the therapeutic effect of trichostatin A on Alzheimer's disease is associated with the nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like epichlorohydrin-related protein-1 (Keap1) signaling pathway, amyloid β-peptide 25-35 (Aβ_25-35) was used to induce Alzheimer's disease-like pathological changes in SH-SY5Y neuroblastoma cells. Cells were then treated with trichostatin A. The effects of trichostatin A on the expression of Keap1 and Nrf2 were detected by real-time quantitative polymerase chain reaction, western blot assays and immunofluorescence. Total antioxidant capacity and autophagy activity were evaluated by total antioxidant capacity assay kit and light chain 3-I/II levels, respectively. We found that trichostatin A increased cell viability and Nrf2 expression, and decreased Keap1 expression in SH-SY5Y cells. Furthermore, trichostatin A increased the expression of Nrf2-related target genes, such as superoxide dismutase, NAD(P)H quinone dehydrogenase 1 and glutathione S-transferase, thereby increasing the total antioxidant capacity of SH-SY5Y cells and inhibiting amyloid β-peptide-induced autophagy. Knockdown of Keap1 in SH-SY5Y cells further increased trichostatin A-induced Nrf2 expression. These results indicate that the therapeutic effect of trichostatin A on Alzheimer's disease is associated with the Keap1-Nrf2 pathway. The mechanism for this action may be that trichostatin A increases cell viability and the antioxidant capacity of SH-SY5Y cells by alleviating Keap1-mediated inhibition Nrf2 signaling, thereby alleviating amyloid β-peptide-induced cell damage.

Targeting miRNAs by histone deacetylase inhibitors (HDACi): Rationalizing epigenetics-based therapies for breast cancer

MicroRNAs (miRNAs) belong to a group of short RNA molecules of ~22 nucleotides that play a significant role in the regulation of gene expression through post-transcriptional regulatory mechanisms. They can directly interact with their target mRNA molecules and induce target gene silencing. Many investigations over the past decade have revealed the involvement of different miRNAs in essential biological events. The expression of a considerable number of miRNAs is tightly regulated through epigenetic events such as histone modifications and DNA methylation. Notably, irregularities in these epigenetic events are associated with aberrant expression of miRNAs in a range of diseases including cancer. Impaired epigenetic events associated with aberrant expression of miRNAs can be pharmacologically modified using chromatin modifying drugs. Numerous pre-clinical and clinical data demonstrate that histone deacetylase inhibitors (HDACi) can re-establish the expression of aberrantly expressed miRNAs in a range of cancer types, rationalizing miRNAs as potential drug targets. This review highlights evidence from investigations assessing the effects of different classes of HDACi on miRNA expression in breast cancer (BC).

The Role of Nrf2 Activity in Cancer Development and Progression

Nrf2 is a transcription factor that stimulates the expression of genes which have antioxidant response element-like sequences in their promoter. Nrf2 is a cellular protector, and this principle applies to both normal cells and malignant cells. While healthy cells are protected from DNA damage induced by reactive oxygen species, malignant cells are defended against chemo- or radiotherapy. Through our literature search, we found that Nrf2 activates several oncogenes unrelated to the antioxidant activity, such as Matrix metallopeptidase 9 (MMP-9), B-cell lymphoma 2 (BCL-2), B-cell lymphoma-extra large (BCL-xL), Tumour Necrosis Factor α (TNF-α), and Vascular endothelial growth factor A (VEGF-A). We also did a brief analysis of The Cancer Genome Atlas (TCGA) data of lung adenocarcinoma concerning the effects of radiation therapy and found that the therapy-induced Nrf2 activation is not universal. For instance, in the case of recurrent disease and radiotherapy, we observed that, for the majority of Nrf2-targeted genes, there is no change in expression level. This proves that the universal, axiomatic rationale that Nrf2 is activated as a response to chemo- and radiation therapy is wrong, and that each scenario should be carefully evaluated with the help of Nrf2-targeted genes. Moreover, there were nine genes involved in lipid peroxidation, which showed underexpression in the case of new radiation therapy: ADH1A, ALDH3A1, ALDH3A2, ADH1B, GPX2, ADH1C, ALDH6A1, AKR1C3, and NQO1. This may relate to the fact that, while some studies reported the co-activation of Nrf2 and other oncogenic signaling pathways such as Phosphoinositide 3-kinases (PI3K), mitogen-activated protein kinase (MAPK), and Notch1, other reported the inverse correlation between Nrf2 and the tumor-promoter Transcription Factor (TF), Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Lastly, Nrf2 establishes its activity through interactions at multiple levels with various microRNAs. MiR-155, miR-144, miR-28, miR-365-1, miR-93, miR-153, miR-27a, miR-142, miR-29-b1, miR-340, and miR-34a, either through direct repression of Nrf2 messenger RNA (mRNA) in a Kelch-like ECH-associated protein 1 (Keap1)-independent manner or by enhancing the Keap1 cellular level, inhibit the Nrf2 activity. Keap1–Nrf2 interaction leads to the repression of miR-181c, which is involved in the Nuclear factor kappa light chain enhancer of activated B cells (NF-κB) signaling pathway. Nrf2’s role in cancer prevention, diagnosis, prognosis, and therapy is still in its infancy, and the future strategic planning of Nrf2-based oncological approaches should also consider the complex interaction between Nrf2 and its various activators and inhibitors.

Differentially expressed microRNAs in exosomes of patients with breast cancer revealed by next‑generation sequencing

MicroRNAs (miRNAs/miRs) in exosomes play crucial roles in the onset, progression and metastasis of cancer by regulating the stability of target mRNAs or by inhibiting translation. In the present study, differentially expressed miRNAs were identified in exosomes of 27 breast cancer patients and 3 healthy controls using RNA sequencing. The differentially expressed microRNAs were selected by bioinformatic analysis. Subjects were followed up for 2 years and exosomal miRNA profiles were compared between patients with and without recurrence of breast cancer. A total of 30 complementary DNA libraries were constructed and sequenced and 1,835 miRNAs were detected. There were no significant differences in the expression of miRNAs between the basal-like, human epidermal growth factor receptor-2⁺, luminal A, luminal B and healthy control (HC) groups. A total of 54 differentially expressed miRNAs were identified in triple-negative breast cancer (TNBC) patients vs. HCs, including 20 upregulated and 34 downregulated miRNAs. The results of the reverse transcription-quantitative PCR were consistent with this. Receiver operating characteristic curve analyses indicated that miR-150-5p [area under the curve (AUC)=0.705, upregulated], miR-576-3p (AUC=0.691, upregulated), miR-4665-5p (AUC=0.681, upregulated) were able to distinguish breast cancer patients with recurrence from those without recurrence. In conclusion, the present results indicated differences in miRNA expression profiles between patients with TNBC and healthy controls. Certain exosomal miRNAs were indicated to have promising predictive value as biomarkers for distinguishing breast cancer with recurrence from non-recurrence, which may be utilized for preventive strategies.

Targeting Keap1 by miR-626 protects retinal pigment epithelium cells from oxidative injury by activating Nrf2 signaling

Activation of the NF-E2-related factor 2 (Nrf2) cascade can offer significant protection against oxidative stress in retinal pigment epithelium (RPE) cells. Here, we identified a novel kelch-like ECH-associated protein 1 (Keap1)-targeting microRNA, microRNA-626 (miR-626) that activates Nrf2 signaling. In ARPE-19 cells and primary human RPE cells, ectopic overexpression of miR-626 targeting the 3'-UTR (3'-untranslated region) of Keap1 downregulated its expression, promoting Nrf2 protein stabilization and nuclear translocation, leading to expression of ARE-dependent genes (HO1, NOQ1 and GCLC). Functional studies showed that miR-626 protected RPE cells from hydrogen peroxide (H₂O₂)-induced oxidative injury. Conversely, miR-626 inhibition induced Keap1 upregulation and Nrf2 cascade inhibition, exacerbating oxidative injury in RPE cells. Further studies demonstrated that miR-626 was ineffective in Keap1-knockout or Nrf2-knockout RPE cells. Importantly, miR-626 also activated Keap1-Nrf2 signaling cascade in human lens epithelial cells (HLECs) and primary human retinal ganglion cells (RGCs), providing protection from H₂O₂. At last, we show that plasma miR-626 levels are significantly downregulated in age-related macular degeneration (AMD) patients than those in the healthy donors. We conclude that targeting Keap1 by miR-626 protects RPE cells and other ophthalmic cells from oxidative injury via activation of Nrf2 signaling cascade.

The Yin-Yang Regulation of Reactive Oxygen Species and MicroRNAs in Cancer

Reactive oxygen species (ROS) are highly reactive oxygen-containing chemical species formed as a by-product of normal aerobic respiration and also from a number of other cellular enzymatic reactions. ROS function as key mediators of cellular signaling pathways involved in proliferation, survival, apoptosis, and immune response. However, elevated and sustained ROS production promotes tumor initiation by inducing DNA damage or mutation and activates oncogenic signaling pathways to promote cancer progression. Recent studies have shown that ROS can facilitate carcinogenesis by controlling microRNA (miRNA) expression through regulating miRNA biogenesis, transcription, and epigenetic modifications. Likewise, miRNAs have been shown to control cellular ROS homeostasis by regulating the expression of proteins involved in ROS production and elimination. In this review, we summarized the significance of ROS in cancer initiation, progression, and the regulatory crosstalk between ROS and miRNAs in cancer.

MicroRNA and Oxidative Stress Interplay in the Context of Breast Cancer Pathogenesis

Oxidative stress is a pathological condition determined by a disturbance in reactive oxygen species (ROS) homeostasis. Depending on the entity of the perturbation, normal cells can either restore equilibrium or activate pathways of cell death. On the contrary, cancer cells exploit this phenomenon to sustain a proliferative and aggressive phenotype. In fact, ROS overproduction or their reduced disposal influence all hallmarks of cancer, from genome instability to cell metabolism, angiogenesis, invasion and metastasis. A persistent state of oxidative stress can even initiate tumorigenesis. MicroRNAs (miRNAs) are small non coding RNAs with regulatory functions, which expression has been extensively proven to be dysregulated in cancer. Intuitively, miRNA transcription and biogenesis are affected by the oxidative status of the cell and, in some instances, they participate in defining it. Indeed, it is widely reported the role of miRNAs in regulating numerous factors involved in the ROS signaling pathways. Given that miRNA function and modulation relies on cell type or tumor, in order to delineate a clearer and more exhaustive picture, in this review we present a comprehensive overview of the literature concerning how miRNAs and ROS signaling interplay affects breast cancer progression.

Epigenetic Drugs for Cancer and microRNAs: A Focus on Histone Deacetylase Inhibitors

Over recent decades, it has become clear that epigenetic abnormalities are involved in the hallmarks of cancer. Histone modifications, such as acetylation, play a crucial role in cancer development and progression, by regulating gene expression, such as for oncogenes or tumor suppressor genes. Therefore, histone deacetylase inhibitors (HDACi) have recently shown efficacy against both hematological and solid cancers. Designed to target histone deacetylases (HDAC), these drugs can modify the expression pattern of numerous genes including those coding for micro-RNAs (miRNA). miRNAs are small non-coding RNAs that regulate gene expression by targeting messenger RNA. Current research has found that miRNAs from a tumor can be investigated in the tumor itself, as well as in patient body fluids. In this review, we summarized current knowledge about HDAC and HDACi in several cancers, and described their impact on miRNA expression. We discuss briefly how circulating miRNAs may be used as biomarkers of HDACi response and used to investigate response to treatment.

Targeting epigenetic modifications as a potential therapeutic option for diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of visual impairment in adults of working age (20-65 years) in developed countries. The metabolic memory phenomena (persistent effect of a glycemic insult even after retrieved) associated with it has increased the risk of developing the complication even after the termination of the glycemic insult. Hence, the need for finding early diagnosis and treatment options has been of great concern. Epigenetic modifications which generally occur during the beginning stages of the disease are responsible for the metabolic memory effect. Therefore, the therapy based on the reversal of the associated epigenetic mechanism can bring new insight in the area of early diagnosis and treatment mechanism. This review discusses the diabetic retinopathy, its pathogenesis, current treatment options, need of finding novel treatment options, and different epigenetic alterations associated with DR. However, the main focus is emphasized on various epigenetic modifications particularly DNA methylation which are responsible for the initiation and progression of diabetic retinopathy and the use of different epigenetic inhibitors as a novel therapeutic option for DR.

MicroRNA Networks Modulate Oxidative Stress in Cancer

Imbalanced regulation of reactive oxygen species (ROS) and antioxidant factors in cells is known as "oxidative stress (OS)". OS regulates key cellular physiological responses through signal transduction, transcription factors and noncoding RNAs (ncRNAs). Increasing evidence indicates that continued OS can cause chronic inflammation, which in turn contributes to cardiovascular and neurological diseases and cancer development. MicroRNAs (miRNAs) are small ncRNAs that produce functional 18-25-nucleotide RNA molecules that play critical roles in the regulation of target gene expression by binding to complementary regions of the mRNA and regulating mRNA degradation or inhibiting translation. Furthermore, miRNAs function as either tumor suppressors or oncogenes in cancer. Dysregulated miRNAs reportedly modulate cancer hallmarks such as metastasis, angiogenesis, apoptosis and tumor growth. Notably, miRNAs are involved in ROS production or ROS-mediated function. Accordingly, investigating the interaction between ROS and miRNAs has become an important endeavor that is expected to aid in the development of effective treatment/prevention strategies for cancer. This review provides a summary of the essential properties and functional roles of known miRNAs associated with OS in cancers.

Curcumin protects against methylmercury-induced cytotoxicity in primary rat astrocytes by activating the Nrf2/ARE pathway independently of PKCδ

Methylmercury (MeHg) is a ubiquitous environmental toxicant that leads to long-lasting neurological deficits in animals and humans. Curcumin, a polyphenol obtained from the rhizome of turmeric, has well-known antioxidant functions. Here, we evaluated curcumin's efficacy in mitigating MeHg-induced cytotoxicity and further investigated the underlying mechanism of this neuroprotection in primary rat astrocytes. Pretreatment with curcumin (2, 5, 10 and 20 μM for 3, 6, 12 or 24 h) protected against MeHg-induced (5 μM for 6 h) cell death in a time and dose-dependent manner. Curcumin (2, 5, 10 or 20 μM) pretreatment for 12 h significantly ameliorated the MeHg-induced astrocyte injury and oxidative stress, as evidenced by morphological alterations, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) generation, and glutathione (GSH) and catalase (CAT) levels. Moreover, curcumin pretreatment increased Nrf2 nuclear translocation and downstream enzyme expression, heme oxygenase-1 (HO-1) and NADPH quinone reductase-1 (NQO1). Knockdown of Nrf2 with siRNA attenuated the protective effect of curcumin against MeHg-induced cell death. However, both the pan-protein kinase C (PKC) inhibitor, Ro 31-8220, and the selective PKCδ inhibitor, rottlerin, failed to suppress the curcumin-activated Nrf2/Antioxidant Response Element(ARE) pathway and attenuate the protection exerted by curcumin. Taken together, these findings confirm that curcumin protects against MeHg-induced neurotoxicity by activating the Nrf2/ARE pathway and this protection is independent of PKCδ activation. More studies are needed to understand the mechanisms of curcumin cytoprotection.