Brusatol inhibits HIF-1 signaling pathway and suppresses glucose uptake under hypoxic conditions in HCT116 cells

Recent Update of Natural Compounds as HIF-1α Inhibitors in Colorectal Carcinoma

Hypoxia-inducible factor (HIF)-1 is a transcription factor that regulates the expression of target genes associated with oxygen homeostasis under hypoxic conditions, thereby contributing to tumor development and progression. Accumulating evidence has demonstrated that HIF-1α mediates different biological processes, including tumor angiogenesis, metastasis, metabolism, and immune evasion. Thus, overexpression of HIF-1α is strongly associated with poor prognosis in cancer patients. Natural compounds are important sources of anticancer drugs and studies have emphasized the decisive role of these mediators in modulating HIF-1α. Therefore, the pharmacological targeting of HIF-1α has emerged as a novel cancer therapeutic approach in recent years. The novelty of this review is that it summarizes natural products targeting HIF-1α in colorectal cancer that have not been presented earlier. We studied research publications related to the HIF-1α domain in cancer from 2010 to 2024. However, our main focus was to identify a better targeted approach for colorectal carcinoma management. Our review described HIF-1α role in tumor progression, summarizes the natural compounds employed as HIF-1α inhibitors, and discusses their potential in the development of natural compounds as HIF-1α inhibitors for colorectal cancer treatment.

The Janus face of HIF-1α in ischemic stroke and the possible associated pathways

Stroke is the most devastating disease, causing paralysis and eventually death. Many clinical and experimental trials have been done in search of a new safe and efficient medicine; nevertheless, scientists have yet to discover successful remedies that are also free of adverse effects. This is owing to the variability in intensity, localization, medication routes, and each patient's immune system reaction. HIF-1α represents the modern tool employed to treat stroke diseases due to its functions: downstream genes such as glucose metabolism, angiogenesis, erythropoiesis, and cell survival. Its role can be achieved via two downstream EPO and VEGF strongly related to apoptosis and antioxidant processes. Recently, scientists paid more attention to drugs dealing with the HIF-1 pathway. This review focuses on medicines used for ischemia treatment and their potential HIF-1α pathways. Furthermore, we discussed the interaction between HIF-1α and other biological pathways such as oxidative stress; however, a spotlight has been focused on certain potential signalling contributed to the HIF-1α pathway. HIF-1α is an essential regulator of oxygen balance within cells which affects and controls the expression of thousands of genes related to sustaining homeostasis as oxygen levels fluctuate. HIF-1α's role in ischemic stroke strongly depends on the duration and severity of brain damage after onset. HIF-1α remains difficult to investigate, particularly in ischemic stroke, due to alterations in the acute and chronic phases of the disease, as well as discrepancies between the penumbra and ischemic core. This review emphasizes these contrasts and analyzes the future of this intriguing and demanding field.

Hypoxia, oxidative stress, and the interplay of HIFs and NRF2 signaling in cancer

Oxygen is crucial for life and acts as the final electron acceptor in mitochondrial energy production. Cells adapt to varying oxygen levels through intricate response systems. Hypoxia-inducible factors (HIFs), including HIF-1α and HIF-2α, orchestrate the cellular hypoxic response, activating genes to increase the oxygen supply and reduce expenditure. Under conditions of excess oxygen and resulting oxidative stress, nuclear factor erythroid 2-related factor 2 (NRF2) activates hundreds of genes for oxidant removal and adaptive cell survival. Hypoxia and oxidative stress are core hallmarks of solid tumors and activated HIFs and NRF2 play pivotal roles in tumor growth and progression. The complex interplay between hypoxia and oxidative stress within the tumor microenvironment adds another layer of intricacy to the HIF and NRF2 signaling systems. This review aimed to elucidate the dynamic changes and functions of the HIF and NRF2 signaling pathways in response to conditions of hypoxia and oxidative stress, emphasizing their implications within the tumor milieu. Additionally, this review explored the elaborate interplay between HIFs and NRF2, providing insights into the significance of these interactions for the development of novel cancer treatment strategies.

Exploring the mechanism underlying the therapeutic effects of butein in colorectal cancer using network pharmacology and single-cell RNA sequencing data

BACKGROUND

Butein has shown substantial potential as a cancer treatment, but its precise mechanism of action in colorectal cancer (CRC) remains unclear. This study aimed to uncover the underlying mechanisms through which butein operates in CRC and to identify potential biomarkers through a comprehensive investigation.

METHODS

Target genes associated with butein were sourced from SwissTargetPrediction, CTD, BindingDB and TargetNet. Gene expression data from the GSE38026 dataset and the single-cell dataset (GSE222300) were retrieved from the Gene Expression Omnibus database. The activation of disease-related pathways was assessed using Kyoto Encyclopedia of Genes and Genomes, Gene Ontology and differential gene analysis. Disease-associated genes were identified through differential analysis and weighted gene co-expression network analysis (WGCNA). The protein-protein interaction network was utilized to pinpoint potential drug targets. Molecular complex detection (MCODE) analysis was employed to uncover relevant genes influenced by butein within key subgroup networks. Machine learning techniques were applied for the screening of potential biomarkers, with receiver operating characteristic curves used to evaluate their clinical significance. Single-cell analysis was conducted to assess the pharmacological targets of butein in CRC, with validation performed using the external dataset GSE40967.

RESULTS

A total of 232 target genes for butein were identified. Functional enrichment analysis revealed significant enrichment of signaling pathways, including mitogen-activated protein kinase, JAK-STAT and NF-κB, among these genes. Differential analysis, in conjunction with WGCNA, yielded 520 disease-related genes. Subsequently, a disease-drug-gene network consisting of 727 targets was established, and a subnetwork containing 56 crucial genes was extracted. Important pathways such as the FoxO signaling pathway exhibited significant enrichment within these key genes. Machine learning applied to the 56 important genes led to the identification of a potential biomarker, UBE2C. Receiver operating characteristic analysis demonstrated the excellent clinical predictive utility of UBE2C. Single-cell analysis suggested that butein's therapeutic effects might be linked to its influence on epithelial and T cells, with UBE2C expression associated with these cell types. Validation using the external dataset GSE40967 further confirmed the exceptional clinical predictive capability of UBE2C.

CONCLUSION

This study combines network pharmacology with single-cell analysis to unravel the mechanisms underlying butein's effects in CRC. Notably, UBE2C emerged as a promising biomarker with superior clinical efficacy. These research findings contribute significantly to our understanding of specific molecular mechanisms, potentially shaping future clinical practices.

Identification of the Brucea javanica Constituent Brusatol as a EGFR-Tyrosine Kinase Inhibitor in a Cell-Free Assay

Inhibitors of the tyrosine kinase (TK) activity of the epidermal growth factor receptor (EGFR) are routinely used in cancer therapy. However, there is a need to discover a new TK inhibitor. This study evaluated extracts from Brucea javanica and its components for their potential as novel EGFR-TK inhibitors. The cytotoxic effect of a g aqueous extract and its fractions was assessed by MTT assays with A549 lung cancer cells. The two fractions with the highest cytotoxicity were analyzed by LC/MS and 1H NMR. Brusatol was identified as the main constituent of these fractions, and its cytotoxic and pro-apoptotic activities were confirmed in A549 cells. To elucidate the inhibitory activity of brusatol against EGFR-TK, a specific ADP-GloTM kinase assay was used. In this assay, the IC50 value for EGFR-TK inhibition was 333.1 nM. Molecular dynamic simulations and docking experiments were performed to identify the binding pocket of brusatol to be located in the intracellular TK-domain of EGFR. This study demonstrates that brusatol inhibits EGFR-TK and therefore harbors a potential as a new therapeutic drug for the therapy of EGFR-depending cancers.

Quassinoid analogs exert potent antitumor activity via reversible protein biosynthesis inhibition in human colorectal cancer

Cellular protein synthesis is accelerated in human colorectal cancer (CRC), and high expression of protein synthesis regulators in CRC patients is associated with poor prognosis. Thus, inhibition of protein synthesis may be an effective therapeutic strategy for CRC. We previously demonstrated that the quassinoid bruceantinol (BOL) had antitumor activity against CRC. Herein, potent tumor growth suppression (>80%) and STAT3 inhibition was observed in two different mouse models following BOL administration. Loss of body and spleen weight was observed but was eliminated upon nanoparticle encapsulation while maintaining strong antitumor activity. STAT3 siRNA knockdown exhibited modest suppression of cell proliferation. Surprisingly, STAT3 inhibition using a PROTAC degrader (SD-36) had little effect on cancer cell proliferation suggesting the possibility of additional mechanism(s) of action for quassinoids. BOL-resistant (BR) cell lines, HCT116BR and HCA7BR, were equally sensitive to standard CRC therapeutic agents and known STAT3 inhibitors but resistant to homoharringtonine (HHT), a known protein synthesis inhibitor. The ability of quassinoids to inhibit protein synthesis was dependent on the structure of the C15 sidechain. Of note, BOL did not inhibit protein synthesis in normal human colon epithelial cells whereas HHT and napabucasin remained effective in these normal cells. Novel quassinoids were designed, synthesized, and evaluated in pre-clinical CRC models. Treatment with the most potent analog, 5c, resulted in significant inhibition of cell proliferation and protein synthesis at nanomolar concentrations. These quassinoid analogs may represent a novel class of protein synthesis inhibitors for the treatment of human CRC.

Natural Compounds, Optimal Combination of Brusatol and Polydatin Promote Anti-Tumor Effect in Breast Cancer by Targeting Nrf2 Signaling Pathway

Triple-negative breast cancer (TNBC) has been clearly recognized as a heterogeneous tumor with the worst prognosis among the subtypes of breast cancer (BC). The advent and application of current small-molecule drugs for treating TNBC, as well as other novel inhibitors, among others, have made treatment options for TNBC more selective. However, there are still problems, such as poor patient tolerance, large administration doses, high dosing frequency, and toxic side effects, necessitating the development of more efficient and less toxic treatment strategies. High expression of Nrf2, a vital antioxidant transcription factor, often promotes tumor progression, and it is also one of the most effective targets in BC therapy. We found that in MDA-MB-231 cells and SUM159 cells, brusatol (BRU) combined with polydatin (PD) could significantly inhibit cell proliferation in vitro, significantly downregulate the expression of Nrf2 protein as well as the expression of downstream related target genes Heme Oxygenase-1 (HO-1) and NAD(P)H dehydrogenase, quinone 1 (NQO1), and promote reactive oxygen species (ROS) levels to further strengthen the anti-tumor effect. Furthermore, we discovered in our in vivo experiments that by reducing the drug dosage three times, we could significantly reduce tumor cell growth while avoiding toxic side effects, providing a treatment method with greater clinical application value for TNBC treatment.

Brusatol: A potential sensitizing agent for cancer therapy from Brucea javanica

Cancer is currently the most important problem endangering human health. As antitumor drugs have always been the most common methods for treating cancers, searching for new antitumor agents is of great significance. Brusatol, a quassinoid from the seeds of Brucea javanica, exhibits a potent tumor-suppressing effect with improved disease outcome. Studies have shown that brusatol not only shows potential tumor inhibition through multiple pharmacological effects, such as promoting apoptosis and inhibiting metastasis but also exhibits significant synergistic antitumor effects in combination with chemotherapeutic agents and overcoming chemical resistance in a wide range of cancer types. In this paper, the antitumor effects and mechanisms of brusatol were reviewed to provide evidence that brusatol has the exact antitumor efficacy of chemotherapeutic agents and show the potential of brusatol to be developed as a promising antitumor drug.

Effects of altitude on meat quality difference and its relationship with HIF-1α during postmortem maturation of beef

This study investigated the differences in meat quality during postmortem aging of yak meat from different altitudes as well as the relationship between the release of hypoxic factor HIF-1α and meat quality. The results showed that the HIF-1α increased with altitude but during aging process, there was an initial increase before a subsequent decrease (p < .05). Moreover, significant increases were showed in glycolytic potential, a* value, pH, HIF-1α mRNA expression, HIF-1α protein expression and shear force with altitude (p < .05). Additionally, the b* value, L* value, water holding power and MFI decreased significantly (p < .05). HIF-1α was shown, by PLS-DA method analysis, to be the main protein marker for differences in the quality during aging time of meat from three altitude groups. HIF-1α protein expression was high correlated with glycolytic potential, pH value, meat color, tenderness and water holding capacity during postmortem aging. The results demonstrated that HIF-1α is a novel marker protein that influences meat quality in yak from different altitudes and that HIF-1α-mediated glycolytic pathway was key to the meat quality during postmortem aging. PRACTICAL APPLICATIONS: Yak meat has the advantages of high protein, low fat, good amino acid and fatty acid composition, so the nutritional value of yak meat is in line with the current best-selling beef with less fat in domestic and foreign markets. But consumers often think that the meat tenderness of yak meat is worse than that of beef and improving the quality of yak meat was worthy of attention specifically. This study investigated the differences in meat quality during postmortem aging of yak meat at different altitudes and the relationship between hypoxic factor HIF-1α release and meat quality.

Effect of Curcumin on Attenuation of Liver Cirrhosis via Genes/Proteins and Pathways: A System Pharmacology Study

Background: Liver cirrhosis is a life-threatening seqsuel of many chronic liver disorders of varying etiologies. In this study, we investigated protein targets of curcumin in liver cirrhosis based on a bioinformatics approach. Methods: Gene/protein associations with curcumin and liver cirrhosis were probed in drug−gene and gene−diseases databases including STITCH/DGIdb/DisGeNET/OMIM/DISEASES/CTD/Pharos and SwissTargetPrediction. Critical clustering groups (MCODE), hub candidates and critical hub genes in liver cirrhosis were identified, and connections between curcumin and liver cirrhosis-related genes were analyzed via Venn diagram. Interaction of hub genes with curcumin by molecular docking using PyRx-virtual screening tools was performed. Results: MCODE analysis indicated three MCODEs; the cluster (MCODE 1) comprised 79 nodes and 881 edges (score: 22.59). Curcumin database interactions recognized 318 protein targets. Liver cirrhosis genes and curcumin protein targets analysis demonstrated 96 shared proteins, suggesting that curcumin may influence 20 candidate and 13 hub genes, covering 81% of liver cirrhosis critical genes and proteins. Thirteen shared proteins affected oxidative stress regulation, RNA, telomerase activity, cell proliferation, and cell death. Molecular docking analysis showed the affinity of curcumin binding hub genes (Binding affinity: ΔG < −4.9 kcal/mol). Conclusions: Curcumin impacted on several critical liver cirrhosis genes mainly involved in extracellular matrix communication, focal adhesion, and the response to oxidative stress.

Pros and cons of NRF2 activation as adjunctive therapy in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease with an important inflammatory component accompanied by deregulated redox-dependent signaling pathways that are feeding back into inflammation. In this context, we bring into focus the transcription factor NRF2, a master redox regulator that exerts exquisite antioxidant and anti-inflammatory effects. The review does not intend to be exhaustive, but to point out arguments sustaining the rationale for applying an NRF2-directed co-treatment in RA as well as its potential limitations. The involvement of NRF2 in RA is emphasized through an analysis of publicly available transcriptomic data on NRF2 target genes and the findings from NRF2-knockout mice. The impact of NRF2 on concurrent pathologic mechanisms in RA is explained by its crosstalk with major redox-sensitive inflammatory and cell death-related pathways, in the context of the increased survival of pathologic cells in RA. The proposed adjunctive therapy targeted to NRF2 is further sustained by the existence of promising NRF2 activators that are in various stages of drug development. The interference of NRF2 with conventional anti-rheumatic therapies is discussed, including the cytoprotective effects of NRF2 for alleviating drug toxicity. From another perspective, the review presents how NRF2 activation would be decreasing the efficacy of synthetic anti-rheumatic drugs by increasing drug efflux. Future perspectives regarding pharmacologic NRF2 activation in RA are finally proposed.

Puerarin: A Potential Therapeutic for Colon Adenocarcinoma (COAD) Patients Suffering From SARS-CoV-2 Infection

Patients with colonic adenocarcinoma (COAD) are at relatively high risk of SARS-CoV-2 infection. However, there is a lack of medical strategies to treat COVID-19/COAD comorbidity. Puerarin, a natural product, is a known antiviral, antitumor, and immunomodulatory effect. Therefore, we hypothesised that puerarin could be used to treat COVID-19/COAD patients. Based on network pharmacology and bioinformatics analysis, the potential targets and pharmacological mechanisms of puerarin in COVID-19/COAD were identified. By intersecting therapeutic target genes for puerarin, COVID-19-related genes and COAD-related genes, 42 target genes of puerarin that could potentially treat COVID-19/COAD comorbidity were obtained. By using the 42 potential target genes to construct the protein-protein interaction (PPI) network, we obtained five core target genes, namely RELA, BCL2, JUN, FOS, and MAPK1. The results of bioinformatics analysis revealed that puerarin could be able to treat COVID-19/COAD comorbidity through apoptosis, antiviral, antioxidant, NF-κB signaling pathway, MAPK signaling pathway, IL-17 signaling pathway, TNF signaling pathway, and HIF-1 signaling pathway etc. This study found that puerarin has the potential to treat COVID-19/COAD patients and that the therapeutic target genes obtained in the study may provide clues for the treatment of COVID19/COAD comorbidity.

Major Constituents From Brucea javanica and Their Pharmacological Actions

Brucea javanica (Ya-dan-zi in Chinese) is a well-known Chinese herbal medicine, which is traditionally used in Chinese medicine for the treatment of intestinal inflammation, diarrhea, malaria, and cancer. The formulation of the oil (Brucea javanica oil) has been widely used to treat various types of cancer. It has also been found that B. javanica is rich in chemical constituents, including quassinoids, triterpenes, alkaloids and flavonoids. Pharmacological studies have revealed that chemical compounds derived from B. javanica exhibit multiple bioactivities, such as anti-cancer, anti-bacterial, anti-diabetic, and others. This review provides a comprehensive summary on the pharmacological properties of the main chemical constituents presented in B. javanica and their underlying molecular mechanisms. Moreover, the review will also provide scientific references for further research and development of B. javanica and its chemical constituents into novel pharmaceutical products for disease management.

Brusatol modulates diverse cancer hallmarks and signaling pathways as a potential cancer therapeutic

Cancer is a consequence of uncontrolled cell proliferation that is associated with cell-cycle disruption. It is a multifactorial disease that depends on the modulation of numerous oncogenic signaling pathways and targets. Although a battle against cancer has been waged for centuries, this disease remains a major cause of death worldwide. Because of the development of resistance to current anticancer drugs, substantial effort has been focused on discovering more effective agents for tumor therapy. Natural products have powerful prospects as anticancer drugs. Brusatol, a component isolated from the plant Brucea javanica, has been demonstrated to efficiently combat a wide variety of tumors. Extensive studies have indicated that brusatol exhibits anticancer effects by arresting the cell cycle; promoting apoptosis; inducing autophagy; attenuating epithelial-mesenchymal transition; inhibiting migration, invasion and angiogenesis; and increasing chemosensitivity and radiosensitivity. These effects involve various oncogenic signaling pathways, including the MAPK, NF-κB, PI3K/AKT/mTOR, JAK/STAT and Keap1/Nrf2/ARE signaling pathways. This review describes the evidence suggesting that brusatol is a promising drug candidate for cancer therapeutics.

miR-140-5p Attenuates Hypoxia-Induced Breast Cancer Progression by Targeting Nrf2/HO-1 Axis in a Keap1-Independent Mechanism

Hypoxia and oxidative stress significantly contribute to breast cancer (BC) progression. Although hypoxia-inducible factor 1α (Hif-1α) is considered a key effector of the cellular response to hypoxia, nuclear factor erythroid 2-related factor 2 (Nrf2), a master antioxidant transcription factor, is a crucial factor essential for Hif-1α-mediated hypoxic responses. Hence, targeting Nrf2 could provide new treatment strategies for cancer therapy. miRNAs are potential regulators of hypoxia-responsive genes. In a quest to identify novel hypoxia-regulated miRNAs involved in the regulation of Nrf2, we found that miR-140-5p significantly affects the expression of Nrf2 under hypoxia. In our study, miR-140-5p expression is downregulated in BC cells under hypoxic conditions. We have identified Nrf2 as a direct target of miR-140-5p, as confirmed by the luciferase assay. Knockdown of miR-140-5p under normoxic conditions significantly enhanced Nrf2/HO-1 signaling and tumor growth, angiogenesis, migration, and invasion in BC. In contrast, overexpression of miR-140-5p under hypoxic conditions revealed opposite results. Further silencing Nrf2 expression mimicked the miR-140-5p-induced anti-tumor effects. Consistent with the knockdown of miR-140-5p in vitro, mice injected with miR-140-5p-KD cells exhibited dramatically reduced miR-140-5p levels, increased Nrf2 levels, and increased tumor growth. In contrast, tumor growth is potently suppressed in mice injected with miR-140-5p-OE cells. Collectively, the above results demonstrate the importance of the Nrf2/HO-1 axis in cancer progression and, thus, targeting Nrf2 by miR-140-5p could be a better strategy for the treatment of Nrf2-driven breast cancer progression.

The Potential Role of Curcumin in Modulating the Master Antioxidant Pathway in Diabetic Hypoxia-Induced Complications

Oxidative stress is the leading player in the onset and development of various diseases. The Keap1-Nrf2 pathway is a pivotal antioxidant system that preserves the cells' redox balance. It decreases inflammation in which the nuclear trans-localization of Nrf2 as a transcription factor promotes various antioxidant responses in cells. Through some other directions and regulatory proteins, this pathway plays a fundamental role in preventing several diseases and reducing their complications. Regulation of the Nrf2 pathway occurs on transcriptional and post-transcriptional levels, and these regulations play a significant role in its activity. There is a subtle correlation between the Nrf2 pathway and the pivotal signaling pathways, including PI3 kinase/AKT/mTOR, NF-κB and HIF-1 factors. This demonstrates its role in the development of various diseases. Curcumin is a yellow polyphenolic compound from Curcuma longa with multiple bioactivities, including antioxidant, anti-inflammatory, anti-tumor, and anti-viral activities. Since hyperglycemia and increased reactive oxygen species (ROS) are the leading causes of common diabetic complications, reducing the generation of ROS can be a fundamental approach to dealing with these complications. Curcumin can be considered a potential treatment option by creating an efficient therapeutic to counteract ROS and reduce its detrimental effects. This review discusses Nrf2 pathway regulation at different levels and its correlation with other important pathways and proteins in the cell involved in the progression of diabetic complications and targeting these pathways by curcumin.

Inhibition of Nrf2-mediated glucose metabolism by brusatol synergistically sensitizes acute myeloid leukemia to Ara-C

Chemotherapy resistance remains to be the primary barrier to acute myeloid leukemia (AML) treatment failure. Nuclear factor-erythroid 2-related factor 2 (Nrf2) has been well established as a truly pleiotropic transcription factor. Inhibition of Nrf2 function increases the sensitivity of various chemotherapeutics and overcomes chemoresistance effectively. Brusatol (Bru) has been reported to decrease Nrf2 protein expression specifically by ubiquitin degradation of Nrf2. However, it remains elusive whether combination of Brusatol and Cytarabine (Ara-C) elicits a synergistic antitumor effect in AML. Our results demonstrated that combination of Ara-C and Brusatol synergistically exerted remarkable pro-apoptosis effect in HL-60 and THP-1 cells. Mechanistically, synergistic anti-tumor effect of Ara-C/Brusatol in AML cells is mediated by attenuating Nrf2 expression. To our surprise, Nrf2 inhibition by Brusatol causes downregulation of the expression of glycolysis-related proteins and decreased glucose consumption and lactate production, whereas the level of ROS production was unaffected. The activation of Nrf2 by Sulforaphane (SFP) could reverse the chemotherapeutic effect and changes of glycolysis of concomitant of Ara-C with Brusatol in AML cell lines. Additionally, Ara-C/Brusatol co-treatment decreased Glucose-6-phosphate dehydrogenase (G6PD) protein expression and increased the sensitivity of Ara-C. Moreover, the mouse xenograft in vivo experiment confirmed that combining Ara-C with Brusatol exerted stronger antileukemia than Ara-C alone. The efficacy, together with the mechanistic observations, reveals the potential of simultaneously giving these two drugs and provides a rational basis for targeting glucose catabolism in future clinical therapeutic approach.

Role of Nrf2 in Synaptic Plasticity and Memory in Alzheimer's Disease

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important transcription factor that reduces oxidative stress. When reactive oxygen species (ROS) or reactive nitrogen species (RNS) are detected, Nrf2 translocates from the cytoplasm into the nucleus and binds to the antioxidant response element (ARE), which regulates the expression of antioxidant and anti-inflammatory genes. Nrf2 impairments are observed in the majority of neurodegenerative disorders, including Alzheimer’s disease (AD). The classic hallmarks of AD include β-amyloid (Aβ) plaques, and neurofibrillary tangles (NFTs). Oxidative stress is observed early in AD and is a novel therapeutic target for the treatment of AD. The nuclear translocation of Nrf2 is impaired in AD compared to controls. Increased oxidative stress is associated with impaired memory and synaptic plasticity. The administration of Nrf2 activators reverses memory and synaptic plasticity impairments in rodent models of AD. Therefore, Nrf2 activators are a potential novel therapeutic for neurodegenerative disorders including AD.

Evaluation of hepatotoxicity induced by 2-ethylhexyldiphenyl phosphate based on transcriptomics and its potential metabolism pathway in human hepatocytes

Increasing use of organophosphorus flame retardants (OPFRs) has aroused great concern to their uncertain environment risk, especially to human health risk. In our study, hepatotoxicity screening of six aryl-OPFRs, potential hepatotoxicity mechanism of 2-ethylhexyldiphenyl phosphate (EHDPP) using RNA-sequencing and its metabolites were investigated in human hepatocytes (L02). The toxicity results demonstrated that EHDPP should be prioritized for further research with the highest toxicity. Further RNA-seq results through GO and KEGG enrichment analysis indicated that exposure to 10 mg/L of EHDPP significantly affected energy homeostasis, endoplasmic reticulum (ER) stress, apoptosis, cell cycle, and inflammation response in cells. The top 12 hub genes were validated by RT-qPCR and conformed to be mainly related to glycolysis and ER stress, followed by cell cycle and inflammation response. Western blot, apoptosis detection, glycolysis stress test, and cell cycle analysis were further performed to verify the above main pathways. Additionally, it was found in the metabolism experiment that detoxification of EHDPP by phase I and phase II metabolism in cells wasn't significant until 48 h with a metabolic rate of 6.12%. EHDPP was stable and still dominated the induction of toxicity. Overall, this study provided valuable information regarding the toxicity and potential metabolism pathway of EHDPP.

Natural products as potent inhibitors of hypoxia-inducible factor-1α in cancer therapy

Hypoxia is a prominent feature of tumors. Hypoxia-inducible factor-1α (HIF-1α), a major subunit of HIF-1, is overexpressed in hypoxic tumor tissues and activates the transcription of many oncogenes. Accumulating evidence has demonstrated that HIF-1α promotes tumor angiogenesis, metastasis, metabolism, and immune evasion. Natural products are an important source of antitumor drugs and numerous studies have highlighted the crucial role of these agents in modulating HIF-1α. The present review describes the role of HIF-1α in tumor progression, summarizes natural products used as HIF-1α inhibitors, and discusses the potential of developing natural products as HIF-1α inhibitors for the treatment of cancer.

Inhibition of the NRF2/KEAP1 Axis: A Promising Therapeutic Strategy to Alter Redox Balance of Cancer Cells

Significance: The nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (NRF2/KEAP1) pathway is a crucial and highly conserved defensive system that is required to maintain or restore the intracellular homeostasis in response to oxidative, electrophilic, and other types of stress conditions. The tight control of NRF2 function is maintained by a complex network of biological interactions between positive and negative regulators that ultimately ensure context-specific activation, culminating in the NRF2-driven transcription of cytoprotective genes. Recent Advances: Recent studies indicate that deregulated NRF2 activation is a frequent event in malignant tumors, wherein it is associated with metabolic reprogramming, increased antioxidant capacity, chemoresistance, and poor clinical outcome. On the other hand, the growing interest in the modulation of the cancer cells' redox balance identified NRF2 as an ideal therapeutic target. Critical Issues: For this reason, many efforts have been made to identify potent and selective NRF2 inhibitors that might be used as single agents or adjuvants of anticancer drugs with redox disrupting properties. Despite the lack of specific NRF2 inhibitors still represents a major clinical hurdle, the researchers have exploited alternative strategies to disrupt NRF2 signaling at different levels of its biological activation. Future Directions: Given its dualistic role in tumor initiation and progression, the identification of the appropriate biological context of NRF2 activation and the specific clinicopathological features of patients cohorts wherein its inactivation is expected to have clinical benefits, will represent a major goal in the field of cancer research. In this review, we will briefly describe the structure and function of the NRF2/ KEAP1 system and some of the most promising NRF2 inhibitors, with a particular emphasis on natural compounds and drug repurposing. Antioxid. Redox Signal. 34, 1428-1483.

Intermittent hypoxia preconditioning protects WRL68 cells against oxidative injury: Involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1

The protective effect of intermittent hypoxia (IH) preconditioning against oxidative injury in hepatic cells was investigated and the involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1 (NRF-1) was evaluated. The results showed that IH preconditioning protected HepG2 cells against oxygen and glucose deprivation/reperfusion (OGD/Rep)-induced injury and protected WRL68 cells against H₂O₂ or AMA-induced oxidative injury. IH preconditioning up-regulated the protein level of NRF-1, PINK1, Parkin, and LC3 II, promoted the recruitment of the cytosolic Parkin, indicating the initiation of the PINK1/Parkin-mediated mitophagy in WRL68 cells. When NRF-1 was down-regulated by NRF-1 specific shRNA, the protein level of PINK1 and Parkin as well as the mitophagy level were significantly decreased. After IH preconditioning, the protein level of PINK1 and the recruitment of Parkin in CCCP-treated group were significantly higher than that of the control group, indicating the increased mitophagy capacity. And the increased mitophagy capacity induced by IH preconditioning was also reduced by down-regulation of NRF-1. Furthermore, the protective effect of IH preconditioning against H₂O₂-induced oxidative injury in WRL68 cells was inhibited when NRF-1 or PINK1 was down-regulated by specific shRNA. Mitochondrial ROS generation may be responsible for the increased expression of NRF-1 induced by IH preconditioning. In conclusion, the PINK1/Parkin-mediated mitophagy regulated by NRF-1 was involved in IH preconditioning-induced protective effect against oxidative cellular injury in hepatic cells.

NONO-TFE3 fusion promotes aerobic glycolysis and angiogenesis by targeting HIF1A in NONO-TFE3 translocation renal cell carcinoma

BACKGROUND

NONO-TFE3 translocation renal cell carcinoma (tRCC), one of RCCs associated with Xp11.2 translocation/TFE3 gene fusion (Xp11.2 tRCCs), involves an X chromosome inversion between NONO and TFE3 with the characteristics of endonuclear aggregation of NONO-TFE3 fusion protein. Nowadays, the oncogenic mechanisms of NONO-TFE3 fusion have not been fully elucidated.

OBJECTIVE

This study aimed at investigating the mechanism of NONO-TFE3 fusion regulating HIF1A as well as the role of HIF-1α in the progression of NONO-TFE3 tRCC under hypoxia.

METHODS

Immunohistochemistry and Western Blotting assays were performed to profile HIF-1α expression in renal clear cell carcinoma (ccRCC) or in Xp11.2 tRCC. Chromatin immunoprecipitation (ChIP), luciferase reporter assay and real-time quantitative PCR (RT-qPCR) were used to evaluate the regulation of HIF1A expression by NONO-TFE3 fusion. Then, flow cytometry analysis, tube formation assays and cell migration assays were used as well as glucose or lactic acid levels were measured to establish the impact of HIF-1α on the progression of NONO-TFE3 tRCC. Besides, the effect of HIF-1α inhibitor (PX-478) on UOK109 cells was analyzed.

RESULTS

We found that HIF1A was targeting gene of NONO-TFE3 fusion. In UOK109 cells, which were isolated from NONO-TFE3 tRCC samples, NONO-TFE3 fusion promoted aerobic glycolysis and angiogenesis by up-regulating the expression of HIF-1α under hypoxia. Furthermore, inhibition of HIF-1α mediated by PX-478 suppressed the development of NONO-TFE3 tRCC under hypoxia.

CONCLUSION

HIF-1α is a potential target for therapy of NONO-TFE3 tRCC under hypoxia.

Anti-Angiogenic Therapy: Current Challenges and Future Perspectives

Anti-angiogenic therapy is an old method to fight cancer that aims to abolish the nutrient and oxygen supply to the tumor cells through the decrease of the vascular network and the avoidance of new blood vessels formation. Most of the anti-angiogenic agents approved for cancer treatment rely on targeting vascular endothelial growth factor (VEGF) actions, as VEGF signaling is considered the main angiogenesis promotor. In addition to the control of angiogenesis, these drugs can potentiate immune therapy as VEGF also exhibits immunosuppressive functions. Despite the mechanistic rational that strongly supports the benefit of drugs to stop cancer progression, they revealed to be insufficient in most cases. We hypothesize that the rehabilitation of old drugs that interfere with mechanisms of angiogenesis related to tumor microenvironment might represent a promising strategy. In this review, we deepened research on the molecular mechanisms underlying anti-angiogenic strategies and their failure and went further into the alternative mechanisms that impact angiogenesis. We concluded that the combinatory targeting of alternative effectors of angiogenic pathways might be a putative solution for anti-angiogenic therapies.

Network pharmacology unveils spleen-fortifying effect of Codonopsis Radix on different gastric diseases based on theory of “same treatment for different diseases” in traditional Chinese medicine

Objective

Methods

Results

Conclusion

Disruption of Circadian Transcriptome in Lung by Acute Sleep Deprivation

Inadequate sleep prevails in modern society and it impairs the circadian transcriptome. However, to what extent acute sleep deprivation (SD) has impact on the circadian rhythms of peripheral tissues is not clear. Here, we show that in mouse lung, a 10-h acute sleep deprivation can alter the circadian expression of approximately 3,000 genes. We found that circadian rhythm disappears in genes related to metabolism and signaling pathways regulating protein phosphorylation after acute sleep deprivation, while the core circadian regulators do not change much in rhythmicity. Importantly, the strong positive correlation between mean expression and amplitude (E-A correlation) of cycling genes has been validated in both control and sleep deprivation conditions, supporting the energetic cost optimization model of circadian gene expression. Thus, we reveal that acute sleep deprivation leads to a profound change in the circadian gene transcription that influences the biological functions in lung.

Nrf2 mediates hypoxia-inducible HIF1α activation in kidney tubular epithelial cells

Nuclear factor erythroid 2-related factor 2 (Nrf2) and hypoxia-inducible factor-1α (HIF1α) transcription factors protect against ischemic acute kidney injury (AKI) by upregulating metabolic and cytoprotective gene expression. In this study, we tested the hypothesis that Nrf2 is required for HIF1α-mediated hypoxic responses using Nrf2-sufficient (wild-type) and Nrf2-deficient (Nrf2-/-) primary murine renal/kidney tubular epithelial cells (RTECs) and human immortalized tubular epithelial cells (HK2 cells) with HIF1 inhibition and activation. The HIF1 pathway inhibitor digoxin blocked hypoxia-stimulated HIF1α activation and heme oxygenase (HMOX1) expression in HK2 cells. Hypoxia-mimicking cobalt (II) chloride-stimulated HMOX1 expression was significantly lower in Nrf2-/- RTECs than in wild-type counterparts. Similarly, hypoxia-stimulated HIF1α-dependent metabolic gene expression was markedly impaired in Nrf2-/- RTECs. Nrf2 deficiency impaired hypoxia-induced HIF1α stabilization independent of increased prolyl 4-hydroxylase gene expression. We found decreased HIF1α mRNA levels in Nrf2-/- RTECs under both normoxia and hypoxia-reoxygenation conditions. In silico analysis and chromatin immunoprecipitation assays demonstrated Nrf2 binding to the HIF1α promoter in normoxia, but its binding decreased in hypoxia-exposed HK2 cells. However, Nrf2 binding at the HIF1α promoter was enriched following reoxygenation, demonstrating that Nrf2 maintains constitutive HIF1α expression. Consistent with this result, we found decreased levels of Nrf2 in hypoxia and that were restored following reoxygenation. Inhibition of mitochondrial complex I prevented hypoxia-induced Nrf2 downregulation and also increased basal Nrf2 levels. These results demonstrate a crucial role for Nrf2 in optimal HIF1α activation in hypoxia and that mitochondrial signaling downregulates Nrf2 levels in hypoxia, whereas reoxygenation restores it. Nrf2 and HIF1α interact to provide optimal metabolic and cytoprotective responses in ischemic AKI.

Integrated analysis of the responses of a circRNA-miRNA-mRNA ceRNA network to heat stress in rainbow trout (Oncorhynchus mykiss) liver

BACKGROUND

With the intensification of global warming, rainbow trout (Oncorhynchus mykiss) suffer from varying degrees of thermal stimulation, leads to mass mortality, which severely restrict the development of aquaculture. Understanding the molecular regulatory mechanisms of rainbow trout under heat stress is useful to develop approaches to relieve symptoms.

RESULTS

Changes in nonspecific immune parameters revealed that a strong stress response was caused in rainbow trout at 24 °C, so we performed multiple transcriptomic analyses of rainbow trout liver under heat stress (HS, 24 °C) and control conditions (CG, 18 °C). A total of 324 DEcircRNAs, 105 DEmiRNAs, and 1885 DEmRNAs were identified. A ceRNA regulatory network was constructed and a total of 301 circRNA-miRNA and 51 miRNA-mRNA negative correlation pairs were screened, and three regulatory correlation pairs were predicted: novel_circ_003889 - novel-m0674-3p - hsp90ab1, novel_circ_002325 - miR-18-y - HSPA13 and novel_circ_002446 - novel-m0556-3p - hsp70. Some target genes involved in metabolic processes, biological regulation or response to stimulus were highly induced at high temperatures. Several important pathways involved in heat stress were characterized, such as protein processing in the ER, the estrogen signaling pathway, and the HIF-1 signaling pathway.

CONCLUSIONS

These results extend our understanding of the molecular mechanisms of the heat stress response and provide novel insight for the development of strategies that relieve heat stress.

Cartilage Targets of Knee Osteoarthritis Shared by Both Genders

As the leading cause of disability, osteoarthritis (OA) affects people of all ages, sexes, and races. With the increasing understanding of OA, the sex differences have attracted specific attention as the burden of OA is greater in women. There is no doubt that gender-specific OA management has great potential for precision treatment. On the other hand, from the marketing aspect, a medication targeting the OA-responsive biomarker(s) shared by both genders is more favorable for drug development. Thus, in the current study, a published transcriptome dataset of knee articular cartilage was used to compare OA and healthy samples for identifying the genes with the same significantly different expression trend in both males and females. With 128 genes upregulated and 143 genes downregulated in both OA males and females, 9 KEGG pathways have been enriched based on the current knowledge, including 'renal cell carcinoma,' 'ECM-receptor interaction,' 'HIF-1 signaling pathway,' 'MicroRNAs in cancer,' 'focal adhesion,' 'Relaxin signaling pathway,' 'breast cancer,' 'PI3K-Akt signaling pathway,' and 'human papillomavirus infection.' Here, we explore the potential impacts of these clusters in OA. We also analyze the identified 'cell plasma membrane related genes' in-depth to identify the potential chondrocyte cell surface target(s) of OA management.

miR-150-mediated increase in glucose uptake in HIV-infected cells

Replication of HIV-1 inside host cells is dependent on both viral and host factors. MicroRNAs are small noncoding RNAs that regulate protein synthesis. MicroRNAs may control viral replication either by directly targeting the viral genome or indirectly through cellular proteins that are required during the viral lifecycle. HIV infection may, in turn, regulate host microRNA expression to facilitate its propagation inside cells. miR-150 has been reported to be an essential factor involved in T-cell activation and may serve as a biomarker for HIV disease progression. The current study provides valuable insights into the role of miR-150 in HIV infection. We quantified miR-150 expression in HIV-infected Jurkat cells and observed a time-dependent increase in the expression of miR-150. In addition, HIV infection led to an enhanced influx of glucose inside the infected cells, which further increased on overexpression of miR-150. The increased uptake of glucose was due to miR-150-mediated increase in expression of glucose transporter-1 (GLUT1). In an attempt to decipher the mechanism, we identified that HIV Tat protein enhanced the expression of miR-150 which then upregulated GLUT1 in HIV-infected cells. In summary, this study sheds light on the role of miR-150 in HIV infection and paves the way for miR-150 as a novel therapeutic target against HIV-1.

NRF2 regulates the sensitivity of human NSCLC cells to cystine deprivation-induced ferroptosis via FOCAD-FAK signaling pathway

Transcription factor nuclear factor-erythroid 2-like 2 (NRF2) mainly regulates cellular antioxidant response, redox homeostasis and metabolic balance. Our previous study illustrated the translational significance of NRF2-mediated transcriptional repression, and the transcription of FOCAD gene might be negatively regulated by NRF2. However, the detailed mechanism and the related significance remain unclear. In this study, we mainly explored the effect of NRF2-FOCAD signaling pathway on ferroptosis regulation in human non-small-cell lung carcinoma (NSCLC) model. Our results confirmed the negative regulation relationship between NRF2 and FOCAD, which was dependent on NRF2-Replication Protein A1 (RPA1)-Antioxidant Response Elements (ARE) complex. In addition, FOCAD promoted the activity of focal adhesion kinase (FAK), which further enhanced the sensitivity of NSCLC cells to cysteine deprivation-induced ferroptosis via promoting the tricarboxylic acid (TCA) cycle and the activity of Complex I in mitochondrial electron transport chain (ETC). However, FOCAD didn't affect GPX4 inhibition-induced ferroptosis. Moreover, the treatment with the combination of NRF2 inhibitor (brusatol) and erastin showed better therapeutic action against NSCLC in vitro and in vivo than single treatment, and the improved therapeutic function partially depended on the activation of FOCAD-FAK signal. Taken together, our study indicates the close association of NRF2-FOCAD-FAK signaling pathway with cysteine deprivation-induced ferroptosis, and elucidates a novel insight into the ferroptosis-based therapeutic approach for the patients with NSCLC.

Brusatol: A potential anti-tumor quassinoid from Brucea javanica

Brusatol, a triterpene lactone compound mainly from Brucea javanica, sensitizes a broad spectrum of cancer cells. It is known as a specific inhibitor of nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway. In this review, we provide a comprehensive overview on the antitumor effect and molecular mechanisms of brusatol in vitro and in vivo. This review also covers pharmacokinetics studies, modification of dosages forms of brusatol. Increasing evidences have validated the value of brusatol as a chemotherapeutic agent in cancers, which may contribute to drug development and clinical application.

MiR-887 Promotes the Progression of Hepatocellular Carcinoma via Targeting VHL

Background:

MiR-887 has been proved to promote the tumorigenesis in diverse cancers, but its function and downstream mechanism in hepatocellular carcinoma remain obscure.

Methods:

Quantitative real-time polymerase chain reaction was performed to detect the expression levels of miR-887 in hepatocellular carcinoma tissues and cell lines. MiR-887 mimics and miR-887 inhibitor were transfected into Huh7 and MHCC97H to establish miR-887 overexpression or inhibition models. Cell Counting Kit-8 and colony formation experiment were conducted to monitor cell proliferation. Subcutaneous xenotransplanted tumor model and tail vein injection model in mice were also established to further verify the effect of miR-887 on hepatocellular carcinoma in vivo. The targeting relationship between miR-887 and von Hippel-Lindau tumor suppressor (VHL) was determined by quantitative real-time polymerase chain reaction, Western blot, and luciferase reporter gene assay.

Results:

miR-887 expression in hepatocellular carcinoma tissues was significantly upregulated. Compared with the control cells, the proliferation and metastasis of cancer cells were enhanced by miR-887 mimics and suppressed by miR-887 inhibitor. Compared with control mice, the volume and weight of subcutaneous tumors of mice in the miR-887 mimics group were significantly elevated, and the significant increase was found in the occurrence of lung metastasis. Moreover, bioinformatics tools showed that miR-887 and VHL had 2 binding sites. Luciferase activity assay demonstrated that miR-887 can inhibit the luciferase activity of VHL, and miR-887 mimics could reduce the expressions of VHL at both messenger RNA and protein levels to increase hypoxia-inducible factor α expression.

Conclusion:

The upregulation of miR-887 could facilitate the proliferation and metastasis of hepatocellular carcinoma cells via targeting VHL.

Nrf2 Inhibitor, Brusatol in Combination with Trastuzumab Exerts Synergistic Antitumor Activity in HER2-Positive Cancers by Inhibiting Nrf2/HO-1 and HER2-AKT/ERK1/2 Pathways

The HER2-targeting antibody trastuzumab has shown effectiveness in treating HER2-positive breast and gastric cancers; however, its responses are limited. Currently, Nrf2 has been deemed as a key transcription factor in promoting cancer progression and resistance by crosstalk with other proliferative signaling pathways. Brusatol as a novel Nrf2 inhibitor has been deemed as an efficacious and safe drug candidate in cancer therapy. In this study, we firstly reported that brusatol exerted the growth-inhibitory effects on HER2-positive cancer cells by regressing Nrf2/HO-1 and HER2-AKT/ERK1/2 signaling pathways in these cells. More importantly, we found that brusatol synergistically enhanced the antitumor activity of trastuzumab against HER2-positive SK-OV-3 and BT-474 cells, which may be attributed to the inhibition of Nrf2/HO-1 and HER2-AKT/ERK1/2 signaling pathways. Furthermore, the synergistic effects were also observed in BT-474 and SK-OV-3 tumor xenografts. In addition, our results showed that trastuzumab markedly enhanced brusatol-induced ROS accumulation and apoptosis level, which could further explain the synergistic effects. To conclude, the study provided a new insight on exploring Nrf2 inhibition in combination with HER2-targeted trastuzumab as a potential clinical treatment regimen in treating HER2-positive cancers.

Qiliqiangxin Improves Cardiac Function through Regulating Energy Metabolism via HIF-1α-Dependent and Independent Mechanisms in Heart Failure Rats after Acute Myocardial Infarction

The present study is aimed at investigating whether Qiliqiangxin (QL) could regulate myocardial energy metabolism in heart failure rats after acute myocardial infarction (AMI) and further exploring the underlying mechanisms. AMI was established by ligating the left anterior descending coronary artery in adult male SD rats. AMI rats with ejection fraction (EF) < 50% at two weeks after the operation were chosen as heart failure rats for the main study. Rats were randomized into the sham, MI, MI+QL, and MI+QL+2-MeOE2 groups. The results showed that compared with the MI group, QL significantly improved cardiac function, reduced serum NT-proBNP level, and alleviated myocardial fibrosis. QL also increased myocardial capillary density by upregulated protein expressions of vascular endothelial growth factor (VEGF) and CD31 by regulating the HIF-1α/VEGF pathway. Moreover, QL promoted ATP production, glucose uptake, and glycolysis by upregulating HIF-1α and a series of glycolysis-relevant enzymes in a HIF-1α-dependent manner. QL also improved myocardial glucose oxidation enzyme expression and free fatty acid uptake by a HIF-1α-independent pathway. Our results indicate that QL treatment improves cardiac function through regulating glucose uptake, FFA uptake, and key enzymes of energy metabolism via HIF-1α-dependent and independent mechanisms.

Hypoxia preconditioning promotes endurance exercise capacity of mice by activating skeletal muscle Nrf2

Elite endurance athletes are used to train under hypoxic/high-altitude conditions, which can elicit certain stress responses in skeletal muscle and helps to improve their physical performance. Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates cellular redox homeostasis and metabolism in skeletal muscle, playing important roles in adaptation to various stresses. In this study, Nrf2 knockout (KO) and wild-type (WT) mice were preconditioned to 48 h of hypoxia exposure (11.2% oxygen), and the effects of hypoxia preconditioning (HP) on exercise capacity and exercise-induced changes of antioxidant status, energetic metabolism, and mitochondrial adaptation in skeletal muscle were evaluated. Nrf2 knockout (KO) and wild-type (WT) mice were exposed to normoxia or hypoxia for 48 h before taking incremental treadmill exercise to exhaustion under hypoxia. The skeletal muscles were collected immediately after the incremental treadmill exercise to evaluate the impacts of HP and Nrf2 on the exercise-induced changes. The results indicate the absence of Nrf2 did not affect exercise capacity, although the mRNA expression of certain muscular genes involved in antioxidant, glycogen and fatty acid catabolism was decreased in Nrf2 KO mice. However, 48-h HP enhanced exercise capacity in WT mice but not in Nrf2 KO mice, and the exercise capacity of WT mice was significantly higher than that of Nrf2 KO mice. These findings suggest HP promotes exercise capacity of mice with the participation of the Nrf2 signal in skeletal muscle.

NEW & NOTEWORTHY Hypoxia preconditioning (HP) activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signal, which was involved in HP-elicited adaptation responses to hypoxia, oxidative, and metabolic stresses in skeletal muscle. On the other hand, Nrf2 deficiency abolished the enhanced exercise capacity after the 48-h HP. Our results indicate that Nrf2 plays an essential role in the exercise capacity-enhancing effect of HP, possibly by modulating muscular antioxidative responses, the mRNA expression of muscular genes involved in glycogen and fatty acid metabolism, as well as mitochondrial biogenesis, and through the cross talk with AMPK and hypoxia-inducible factor-1α signaling.

Ammonia mediates mitochondrial uncoupling and promotes glycolysis via HIF-1 activation in human breast cancer MDA-MB-231 cells

It has been reported that ammonia produced by glutaminolysis activates the HIF-1 pathway in several types of cancer cells, but the underlying mechanisms remain unclear. In this study, the effects of ammonia on the activation of HIF-1 pathway and glycolysis in MDA-MB-231 breast cancer cells were investigated and the underlying mechanisms involved were elucidated. The results showed that NH₄Cl concentration-dependently increased the protein level of HIF-1α and enhanced the transactivation activity of HIF-1 in MDA-MB-231 cells. In addition, NH₄Cl increased the expression of GluT1 and LDHA and promoted aerobic glycolysis by activating the HIF-1 pathway. Further study revealed that NH₄Cl increased the mitochondrial ROS level and decreased the cellular Fe²⁺ level in MDA-MB-231 cells. Activation of the HIF-1 pathway induced by NH₄Cl was inhibited by addition of the antioxidant NAC or the NADPH oxidase (NOX) inhibitor apocynin, indicating the involvement of the NOX-induced ROS generation. When MDA-MB-231 cells were treated with NH₄Cl, the oxygen consumption of cells increased, followed by the decreased mitochondrial membrane potential and cellular ATP level, indicating the uncoupling of mitochondria. In conclusion, NH₄Cl activated the HIF-1 signaling pathway and promoted aerobic glycolysis in MDA-MB-231 cells, likely through the promotion of mitochondrial ROS release and mitochondrial uncoupling.

Willed‑movement training reduces middle cerebral artery occlusion‑induced motor deficits and improves angiogenesis and survival of cerebral endothelial cells via upregulating hypoxia‑inducible factor‑1α

Willed movement facilitates neurological rehabilitation in patients with stroke. Focal ischaemia is the hallmark of patients after stroke, though the detailed molecular mechanism by which willed movement affects neurological rehabilitation after stroke is not fully understood. The aim of the present study was to dissect the key factors of the hypoxia signaling pathway responsible for the willed movement‑improved rehabilitation. Sprague‑Dawley rats undergoing right middle cerebral artery occlusion (MCAO) surgery were randomly divided into four groups: MCAO alone, willed movement (WM), environmental modification (EM) and common rehabilitation (CR). The neurological behaviour score was assessed, and infarction areas were detected by TTC staining. In addition, angiogenesis‑associated genes (vascular epithelial growth factor, angiogenin‑1, matrix metalloproteinases‑2 and ‑9) and hypoxia inducible factor (HIF)‑1α expression was investigated in cells derived from MCAO, WM, EM and CR groups. Finally, the role of HIF‑1α using HIF‑1α knockdown in HUVECs under hypoxic conditions was evaluated. WM significantly improved neurological behaviour and rehabilitation by increasing the behaviour score and by decreasing the infarction area. In addition, CR, EM and WM raised the expression of angiogenesis‑associated genes and HIF‑1α, thereby promoting in vitro tube formation of primary endothelial cells. Knockdown of HIF‑1α in HUVECs restored the increased expression of angiogenesis‑associated genes to normal levels and inhibited in vitro tube formation of HUVECs. Willed movement most effectively improved the neurological rehabilitation of rats with focal ischaemia through upregulation of HIF‑1α. The present findings provide insight into willed movement‑facilitated rehabilitation and may help treat stroke‑triggered motor deficit and improve angiogenesis of cerebral endothelial cells.

Hypoxia Induces Drug Resistance in Colorectal Cancer through the HIF-1α/miR-338-5p/IL-6 Feedback Loop

Hypoxia is associated with poor prognosis and therapeutic resistance in cancer patients. Accumulating evidence has shown that microRNA (miRNA) plays an important role in the acquired drug resistance in colorectal carcinoma (CRC). However, the role of miRNA in hypoxia-induced CRC drug resistance remains to be elucidated. Here, we identified a hypoxia-triggered feedback loop that involves hypoxia-inducible transcription factor 1α (HIF-1α)-mediated repression of miR-338-5p and confers drug resistance in CRC. In this study, the unbiased miRNA array screening revealed that miR-338-5p is downregulated in both hypoxic CRC cell lines tested. Repression of miR-338-5p was required for hypoxia-induced CRC drug resistance. Furthermore, we identified interleukin-6 (IL-6), which mediates STAT3/Bcl2 activation under hypoxic conditions, as a direct miR-338-5p target. The resulting HIF-1α/miR-338-5p/IL-6 feedback loop was necessary for drug resistance in colon cancer cell lines. Using CRC patient samples, we found miR-338-5p has a negative correlation with HIF-1α and IL-6. Finally, in a xenograft model, overexpressing miR-338-5p in CRC cells and HIF-1α inhibitor PX-478 were able to enhance the sensitivity of CRC to oxaliplatin (OXA) via suppressing the HIF-1α/miR-338-5p/IL-6 feedback loop in vivo. Taken together, our results uncovered an HIF-1α/miR-338-5p/IL-6 feedback circuit that is critical in hypoxia-mediated drug resistance in CRC; targeting each member of this feedback loop could potentially reverse hypoxia-induced drug resistance in CRC.

Potential Applications of NRF2 Inhibitors in Cancer Therapy

The NRF2/KEAP1 pathway represents one of the most important cell defense mechanisms against exogenous or endogenous stressors. Indeed, by increasing the expression of several cytoprotective genes, the transcription factor NRF2 can shelter cells and tissues from multiple sources of damage including xenobiotic, electrophilic, metabolic, and oxidative stress. Importantly, the aberrant activation or accumulation of NRF2, a common event in many tumors, confers a selective advantage to cancer cells and is associated to malignant progression, therapy resistance, and poor prognosis. Hence, in the last years, NRF2 has emerged as a promising target in cancer treatment and many efforts have been made to identify therapeutic strategies aimed at disrupting its prooncogenic role. By summarizing the results from past and recent studies, in this review, we provide an overview concerning the NRF2/KEAP1 pathway, its biological impact in solid and hematologic malignancies, and the molecular mechanisms causing NRF2 hyperactivation in cancer cells. Finally, we also describe some of the most promising therapeutic approaches that have been successfully employed to counteract NRF2 activity in tumors, with a particular emphasis on the development of natural compounds and the adoption of drug repurposing strategies.

LncRNA SNHG1 alleviates OGD induced injury in BMEC via miR-338/HIF-1α axis

BACKGROUND

Brain microvascular endothelial cell (BMEC) is an important therapeutic target for the inhibition of brain vascular dysfunction in ischemic stroke. Expression of long non-coding RNA SNHG1 is reportedly upregulated in BMEC after OGD. The present study aims to investigate the potential roles of SNHG1 in OGD-induced injury in BMEC.

METHODS

Mice primary brain microvascular endothelial cells (BMEC) were cultured under "normal" or "oxygen/glucose-deprived" (OGD) conditions. The expression of SNHG1 and miR-338 after OGD were examined by qPCR. shRNA against SNHG1 was used to knockdown SNHG1 in BMEC. MiR-338-3p mimic and inhibitor were used to change the expression of miR-338 in BMEC. The relationship between SNHG1 and miR-338, and the relationship between miR-338 and HIF-1α were clarified using RNA pull-down and luciferase reporter gene assays, respectively.

RESULTS

SNHG1 and miR-338 were upregulated in OGD induced BMEC. SNHG1 silence aggravated OGD-induced cell apoptosis by down-regulating Bcl-2, HIF-1α and VEGF-A, and upregulating caspase 3 activity and Bax. MiR-338 was upregulated in SNHG1-silenced BMEC. RNA pull-down assays showed that SNHG1 could be directly bound by miR-338. In addition, miR-338 overexpression reduced cell viability in OGD while miR-338 inhibition protected BMEC against OGD-induced injury. Furthermore, luciferase reporter assay showed that HIF-1α was a direct target of miR-338.

CONCLUSIONS

SNHG1 exerted protective effects against OGD induced injury via sponging miR-338, thus upregulating HIF-1α/VEGF-A in BMEC.

Brusatol Enhances the Chemotherapy Efficacy of Gemcitabine in Pancreatic Cancer via the Nrf2 Signalling Pathway

Although gemcitabine is the standard chemotherapy treatment for advanced pancreatic cancer, its benefits are quite limited due to prevalent chemoresistance, and the mechanism underlying gemcitabine chemoresistance remains unclear. Currently, Nrf2 has been deemed as a significant contributor to gemcitabine chemoresistance in pancreatic cancer. Brusatol is a unique inhibitor of the Nrf2 pathway, and in previous studies, we determined that brusatol exhibits the effects of growth inhibition and proapoptosis in pancreatic cancer cells. Due to these data, we speculate that brusatol can reverse gemcitabine-induced Nrf2 activation and propose that it can enhance gemcitabine efficacy in treating pancreatic cancer. In this study, we first proved that brusatol can effectively inhibit the Nrf2 signalling pathway and increase ROS accumulation in pancreatic cancer cells. Next, we demonstrated that brusatol can abrogate gemcitabine-induced Nrf2 activation in pancreatic cancer cells. In addition, we discovered that brusatol potentiates gemcitabine-induced growth inhibition and apoptosis in human pancreatic cancer cells. In nude mice with PANC-1 xenografts, treatment with a combination of brusatol and gemcitabine considerably reduced in vivo tumour growth compared with control treatment or treatment with either brusatol or gemcitabine alone. Immunohistochemical staining also showed that Nrf2 expression levels were reduced in brusatol-treated xenograft tumour tissues. In summary, our results suggest that brusatol is capable of enhancing the antitumour effects of gemcitabine in both pancreatic cancer cells and PANC-1 xenografts via suppressing the Nrf2 pathway.

ROS Modulator Molecules with Therapeutic Potential in Cancers Treatments

Reactive Oxygen Species (ROS) are chemically reactive chemical species containing oxygen. The redox status of a cell is function of the relative concentrations of oxidized and reduced forms of proteins, enzymes, ROS, molecules containing thiol and other factors. In the organism, the redox balance is based on the generation and elimination of ROS produced by endogenous and exogenous sources. All living organisms must maintain their redox equilibrium to survive and proliferate. Enzymatic and molecular pathways control ROS levels tightly but differentially depending on the type of cell. This review is an overview of various molecules that modulate ROS production/detoxification and have a synergistic action with the chemotherapies to kill cancer cells while preserving normal cells to avoid anticancer drugs side effects, allowing a better therapeutic index of the anticancer treatments.

Brusatol-Mediated Inhibition of c-Myc Increases HIF-1α Degradation and Causes Cell Death in Colorectal Cancer under Hypoxia

HIF-1 (hypoxia-inducible factor-1) regulates the expression of ~100 genes involved in angiogenesis, metastasis, tumor growth, chemoresistance and radioresistance, underscoring the growing interest in targeting HIF-1 for cancer control. In the present study, we investigated the molecular mechanisms underlying brusatol-induced HIF-1α degradation and cell death in colorectal cancer under hypoxia (0.5% O₂). Under hypoxia, pretreatment of cancer cells with brusatol increased HIF-1α degradation and cancer cell death in a dose-dependent manner. This effect was mediated by activation of prolyl hydroxylases (PHDs), as evidenced by the block of brusatol-induced HIF-1α degradation and cancer cell death by both pharmacological inhibition and siRNA-mediated knockdown of PHDs. In addition, a ferrous iron chelator (2,2'-bypyridyl) blocked brusatol-induced degradation of HIF-1α and cancer cell death in hypoxia by inhibiting PHD activation. We further found that brusatol inhibited c-Myc expression, and showed that overexpression of c-Myc prevented brusatol-induced degradation of HIF-1α and cancer cell death by increasing mitochondrial ROS production and subsequent ROS-mediated transition of ferrous iron to ferric iron. Consistent with these results, treatment of tumor-bearing mice with brusatol significantly suppressed tumor growth by promoting PHD-mediated HIF-1α degradation. Collectively, our results suggest that brusatol-mediated inhibition of c-Myc/ROS signaling pathway increases HIF-1α degradation by promoting PHD activity and induces cell death in colorectal cancer under hypoxia

Effects of Cobalt Chloride, a Hypoxia-Mimetic Agent, on Autophagy and Atrophy in Skeletal C2C12 Myotubes

Background

Hypoxia-induced autophagy and muscle wasting occur in several environmental and pathological conditions. However, the molecular mechanisms underlying the effects of the hypoxia-mimetic agent CoCl₂ on autophagy and muscle atrophy are still unclear.

Methods

C2C12 myotubes were exposed to increasing concentrations of CoCl₂ for 24 hours. Quantitative RT-PCR, Western blotting, and transmission electron microscopy were performed to confirm autophagy occurs. Autophagy proteins were measured to understand the molecule mechanisms. We also inhibited hypoxic autophagy and examined the changes in myogenin expression, myotubes formation, and apoptosis.

Results

Our results showed that CoCl₂-mimicked hypoxia upregulated the expression of the autophagy-related proteins LC3, HIF-1α, BNIP3, p-AMPKα, and beclin-1, whereas p62 and p-mTOR were downregulated. In addition, the autophagosome could be observed after CoCl₂ induction. The expression of the autophagy-related E3 ligase parkin and the muscle-specific ubiquitin ligase atrogin-1 was increased by CoCl₂. Inhibition of autophagy by 3MA increased myogenin expression and promoted myotubes formation and the percentage of cell death was decreased.

Conclusions

Our results confirmed that CoCl₂-mimicked hypoxia induced autophagy via the HIF-1α/BNIP3/beclin-1 and AMPK/mTOR pathways. Our results also revealed an important link between autophagy and muscle atrophy under hypoxia, which may help to develop new therapeutic strategies for muscle diseases.

Brusatol inhibits growth and induces apoptosis in pancreatic cancer cells via JNK/p38 MAPK/NF-κb/Stat3/Bcl-2 signaling pathway

Brusatol, isolated from brucea, has been proved to exhibit anticancer influence on various kind of human malignancies. However, the role that brusatol plays in pancreatic cancer is seldom known by the public. Through researches brusatol was proved to inhibit growth and induce apoptosis in both PATU-8988 and PANC-1 cells by decreasing the expression level of Bcl-2 and increasing the expression levels of Bax, Cleaved Caspase-3. Then we found the activation of the JNK, p38 MAPK and inactivation of the NF-κb, Stat3 are related with the potential pro-apoptotic signaling pathways. However, SP600125 could not only abrogated the JNK activation caused by brusatol, but also reverse the p38 activation and the decrease of Bcl-2 as SB203580 did. Besides, SP600125 and SB203580 also reversed the inactivation of NF-κb and Stat3. Furthermore, BAY 11-7082 and S3I-201 indeed had the similar effect as brusatol had on the expression of Phospho-Stat3 and Bcl-2. To sum up, we came to a conclusion that in pancreatic cancer, brusatol do inhibit growth and induce apoptosis. And we inferred that brusatol illustrates anticancer attribution via JNK/p38 MAPK/NF-κb/Stat3/Bcl-2 signaling pathway.

Strange Bedfellows: Nuclear Factor, Erythroid 2-Like 2 (Nrf2) and Hypoxia-Inducible Factor 1 (HIF-1) in Tumor Hypoxia

The importance of the tumor microenvironment for cancer progression and therapeutic resistance is an emerging focus of cancer biology. Hypoxia, or low oxygen, is a hallmark of solid tumors that promotes metastasis and represents a significant obstacle to successful cancer therapy. In response to hypoxia, cancer cells activate a transcriptional program that allows them to survive and thrive in this harsh microenvironment. Hypoxia-inducible factor 1 (HIF-1) is considered the main effector of the cellular response to hypoxia, stimulating the transcription of genes involved in promoting angiogenesis and altering cellular metabolism. However, growing evidence suggests that the cellular response to hypoxia is much more complex, involving coordinated signaling through stress response pathways. One key signaling molecule that is activated in response to hypoxia is nuclear factor, erythroid 2 like-2 (Nrf2). Nrf2 is a transcription factor that controls the expression of antioxidant-response genes, allowing the cell to regulate reactive oxygen species. Nrf2 is also activated in various cancer types due to genetic and epigenetic alterations, and is associated with poor survival and resistance to therapy. Emerging evidence suggests that coordinated signaling through Nrf2 and HIF-1 is critical for tumor survival and progression. In this review, we discuss the distinct and overlapping roles of HIF-1 and Nrf2 in the cellular response to hypoxia, with a focus on how targeting Nrf2 could provide novel chemotherapeutic modalities for treating solid tumors.