Red ginseng polysaccharide promotes ferroptosis in gastric cancer cells by inhibiting PI3K/Akt pathway through down-regulation of AQP3

OBJECTIVE

This study aims to investigate the effect of red ginseng polysaccharide (RGP) on gastric cancer (GC) development and explore its mechanism.

METHODS

GC cell lines AGS were treated with varying concentrations of RGP (50, 100, and 200 μg/mL). AGS cells treated with 200 μg/mL RGP were transfected with aquaporin 3 (AQP3) overexpression vector. Cell proliferation, viability, and apoptosis were evaluated by MTT, colony formation assay, and flow cytometry, respectively. Real-time quantitative reverse transcription PCR (qRT-PCR) was used to detect the expression of AQP3. The levels of Fe2+, malondialdehyde, and lactate dehydrogenase were measured using their respective detection kits, and the reactive oxygen species levels was determined by probe 2',7'-dichlorodihydrofluorescein diacetate. The expression of ferroptosis-related protein and PI3K/Akt pathway-related protein were assessed by western blot. In vivo experiments in nude mice were performed and the mice were divided into four groups (n = 5/group) which gavage administrated with 150 mg/kg normal saline, and 75, 150, 300 mg/kg RGP, respectively. Their tumor weight and volume were recorded.

RESULTS

RGP treatment effectively inhibited the proliferation and viability of AGS cells in a dosage-dependent manner and induced apoptosis. It induced ferroptosis in AGS cells, as well as inhibiting the expression of PI3K/Akt-related proteins. AQP3 overexpression could reversed the effect of RGP treatment on ferroptosis. Confirmatory in vivo experiments showed that RGP could reduce the growth of implanted tumor, with increased RGP concentration resulting in greater tumor inhibitory effects.

CONCLUSION

RGP might have therapeutic potential against GC, effectively inhibiting the proliferation and viability of AGS cells.

Vigor King mitigates spermatogenic disorders caused by environmental estrogen zearalenone exposure

Zearalenone (ZEN) has been shown to cause reproductive damage by inducing oxidative stress. Astaxanthin and L-carnitine are widely used to alleviate oxidative stress and promote sperm maturation. However, it remains uncertain whether they are effective in mitigating spermatogenesis disorders induced by ZEN. This study aimed to investigate the therapeutic efficacy and potential mechanisms of Vigor King (Vig), a compound preparation primarily consisting of astaxanthin and L-carnitine, in alleviating ZEN-induced spermatogenesis disorders. In the experiment, mice received continuous oral gavage of ZEN (80 μg/kg) for 35 days, accompanied by a rescue strategy with Vig (200 mg/kg). The results showed that Vig effectively reduced the negative impact on semen quality and improved the structural and functional abnormalities of the seminiferous epithelium caused by ZEN. Additionally, the accumulation of reactive oxygen species (ROS), DNA double-strand breaks, apoptosis, and autophagy abnormalities were all significantly ameliorated. Intriguingly, the GSK3β-dependent BTRC-NRF2 signaling pathway was found to play an important role in this process. Furthermore, testing of offspring indicated that Vig could extend its protective effects to the next generation, effectively combating the transgenerational toxic effects of ZEN. In summary, our research suggests that Vig supplementation holds considerable promise in alleviating spermatogenesis disorders induced by zearalenone.

Silencing CK19 regulates ferroptosis by affecting the expression of GPX4 and ACSL4 in oral squamous cell carcinoma in vivo and in vitro

To analyze the mechanism of how interfering with the cytokeratin 19 (CK19) pathway via the ferroptosis pathway affects tumor biological behaviors in the process of oral squamous cell carcinoma (OSCC) development. TCGA was used to analyze the expression of CK19 in pan-cancer and head and neck squamous cell carcinoma (HNSC) and to explore the ferroptosis-related genes related to HNSC. The effect of silencing CK19 on the migration ability of HSC-4 cells was verified by wound healing and migration assay. HSC-4 cells with silencing of CK19 and tumor-bearing nude mouse model were constructed. RT-qPCR, immunofluorescence and western blot were used to analyze the expression of ferroptosis-related genes. CK19 is highly expressed in human OSCC and nude mice. The migration ability of cells in the CK19-silenced group was lower than that of the control group. In vivo and in vitro, CK19 was negatively correlated with the expression of ACSL4 and positively correlated with the expression of GPX4. Compared with the control group, GPX4 expression was down-regulated and ACSL4 expression was up-regulated in the CK19-silenced group. Silencing CK19 also increased intracellular Fe2+ content and MDA content. Silencing CK19 can affect the expression of GPX4 and ACSL4 to regulate ferroptosis and at the same time increase the content of MDA, Fe2+ and ROS levels, thereby activating the regulation of ferroptosis pathway in the development of OSCC.

Biomarkers of NRF2 signalling: Current status and future challenges

The cytoprotective transcription factor NRF2 regulates the expression of several hundred genes in mammalian cells and is a promising therapeutic target in a number of diseases associated with oxidative stress and inflammation. Hence, an ability to monitor basal and inducible NRF2 signalling is vital for mechanistic understanding in translational studies. Due to some caveats related to the direct measurement of NRF2 levels, the modulation of NRF2 activity is typically determined by measuring changes in the expression of one or more of its target genes and/or the associated protein products. However, there is a lack of consensus regarding the most relevant set of these genes/proteins that best represents NRF2 activity across cell types and species. We present the findings of a comprehensive literature search that according to stringent criteria identifies GCLC, GCLM, HMOX1, NQO1, SRXN1 and TXNRD1 as a robust panel of markers that are directly regulated by NRF2 in multiple cell and tissue types. We assess the relevance of these markers in clinically accessible biofluids and highlight future challenges in the development and use of NRF2 biomarkers in humans.

Novel Peptides from Sturgeon Ovarian Protein Hydrolysates Prevent Oxidative Stress-Induced Dysfunction in Osteoblast Cells: Purification, Identification, and Characterization

This study aimed to explore antioxidant peptides derived from sturgeon (Acipenser schrenckii) ovaries that exhibit antiosteoporotic effects in oxidative-induced MC3T3-E1 cells. The F3-15 component obtained from sturgeon ovarian protein hydrolysates (SOPHs) via gel filtration and RP-HPLC significantly increased the cell survival rate (from 49.38 ± 2.88 to 76.26 ± 2.09%). Two putative antioxidant-acting peptides, FDWDRL (FL6) and FEGPPFKF (FF8), were screened from the F3-15 faction via liquid chromatography-tandem mass spectrometry (LC-MS/MS) and through prediction by computer simulations. Molecular docking results indicated that the possible antioxidant mechanisms of FL6 and FF8 involved blocking the active site of human myeloperoxidase (hMPO). The in vitro tests showed that FL6 and FF8 were equally adept at reducing intracellular ROS levels, increasing the activity of antioxidant enzymes, and protecting cells from oxidative injuries by inhibiting the mitogen-activated protein kinase (MAPK) pathway and activating the phosphoinositide-3 kinase (PI3K)/protein kinase B (AKT)/glycogen synthase kinase-3β (GSK-3β) signaling pathway. Moreover, both peptides could increase differentiation and mineralization abilities in oxidatively damaged MC3T3-E1 cells. Furthermore, FF8 exhibited high resistance to pepsin and trypsin, showcasing potential for practical applications.

Lipid Peroxidation-Related Redox Signaling in Osteosarcoma

Oxidative stress and lipid peroxidation play important roles in numerous physiological and pathological processes, while the bioactive products of lipid peroxidation, lipid hydroperoxides and reactive aldehydes, act as important mediators of redox signaling in normal and malignant cells. Many types of cancer, including osteosarcoma, express altered redox signaling pathways. Such redox signaling pathways protect cancer cells from the cytotoxic effects of oxidative stress, thus supporting malignant transformation, and eventually from cytotoxic anticancer therapies associated with oxidative stress. In this review, we aim to explore the status of lipid peroxidation in osteosarcoma and highlight the involvement of lipid peroxidation products in redox signaling pathways, including the involvement of lipid peroxidation in osteosarcoma therapies.

Insights into the mechanism of transcription factors in Pb2+-induced apoptosis

The health risks associated with exposure to heavy metals, such as Pb2+, are increasingly concerning the public. Pb2+ can cause significant harm to the human body through oxidative stress, autophagy, inflammation, and DNA damage, disrupting cellular homeostasis and ultimately leading to cell death. Among these mechanisms, apoptosis is considered crucial. It has been confirmed that transcription factors play a central role as mediators during the apoptosis process. Interestingly, these transcription factors have different effects on apoptosis depending on the concentration and duration of Pb2+ exposure. In this article, we systematically summarize the significant roles of several transcription factors in Pb2+-induced apoptosis. This information provides insights into therapeutic strategies and prognostic biomarkers for diseases related to Pb2+ exposure.

Ambient particulate matter exposure induces ferroptosis in hippocampal cells through the GSK3B/Nrf2/GPX4 pathway

Epidemiological studies have established a robust correlation between exposure to ambient particulate matter (PM) and various neurological disorders, with dysregulation of intracellular redox processes and cell death being key mechanisms involved. Ferroptosis, a cell death form characterized by iron-dependent lipid peroxidation and disruption of antioxidant defenses, may be involved in the neurotoxic effects of PM exposure. However, the relationship between PM-induced neurotoxicity and ferroptosis in nerve cells remains to be elucidated. In this study, we utilized a rat model (exposed to PM at a dose of 10 mg/kg body weight per day for 4 weeks) and an HT-22 cell model (exposed to PM at concentrations of 50, 100, and 200 μg/mL for 24 h) to investigate the potential induction of ferroptosis by PM exposure. Furthermore, RNA sequencing analysis was employed to identify hub genes that potentially contribute to the process of ferroptosis, which was subsequently validated through in vivo and in vitro experiments. The results revealed that PM exposure increased MDA content and Fe2+ levels, and decreased SOD activity and GSH/GSSG ratio in rat hippocampal and HT-22 cells. Through RNA sequencing analysis, bioinformatics analysis, and RT-qPCR experiments, we identified GSK3B as a possible hub gene involved in ferroptosis. Subsequent investigations demonstrated that PM exposure increased GSK3B levels and decreased Nrf2, and GPX4 levels in vivo and in vitro. Furthermore, treatment with LY2090314, a specific inhibitor of GSK3B, was found to mitigate the PM-induced elevation of MDA and ROS and restore SOD activity and GSH/GSSG ratio. The LY2090314 treatment promoted the upregulation of Nrf2 and GPX4 and facilitated the nuclear translocation of Nrf2 in HT-22 cells. Moreover, treatment with LY2090314 resulted in the upregulation of Nrf2 and GPX4, along with the facilitation of nuclear translocation of Nrf2. This study suggested that PM-induced ferroptosis in hippocampal cells may be via the GSK3B/Nrf2/GPX4 pathway.

Protective effects of triptolide against oxidative stress in retinal pigment epithelium cells via the PI3K/AKT/Nrf2 pathway: a network pharmacological method and experimental validation

PURPOSE

Among aging adults, age-related macular degeneration (AMD), is a prevalent cause of blindness. Nevertheless, its progression may be halted by antioxidation in retinal pigment epithelium (RPE). The primary effective constituent of Tripterygium wilfordii Hook. F., triptolide (TP), has demonstrated anti-inflammatory, antiproliferative, and antioxidant properties. The mechanics of the protective effect of triptolide against the oxidative damage in retinal pigment epithelial (RPE) were assessed in this study.

METHODS

ARPE-19 cells were pretreated with TP, and then exposed to sodium iodate (SI). First, cell viability was assessed using CCK-8. Subsequently, we measured indicators for cell oxidation including reactive oxygen species (ROS), catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA). Then, we used network pharmacological analysis and molecular docking to explore the signaling pathway of TP. Last, we used western blot, ELISA, and immunofluorescence assays to clarify the potential mechanistic pathways.

RESULTS

The network pharmacology data suggested that TP may inhibit AMD by regulating the PI3K/Akt signaling pathway. Experimental results showed that the potential mechanism is that it regulates the PI3K/Akt pathway and promotes Nrf2 phosphorylation and activation, thereby raising the level of antioxidant factors (HO-1, NQO1) and reducing the generation of ROS, which inhibit oxidative damage.

CONCLUSION

Our findings suggested that the effect of TP on SI-exposed RPE cells principally relies on the regulation of oxidative stress through the PI3K/Akt/Nrf2 signaling pathway.

Signaling and transcriptional dynamics underlying early adaptation to oncogenic BRAF inhibition

A major contributor to poor sensitivity to anti-cancer kinase inhibitor therapy is drug-induced cellular adaptation, whereby remodeling of signaling and gene regulatory networks permits a drug-tolerant phenotype. Here, we resolve the scale and kinetics of critical subcellular events following oncogenic kinase inhibition and preceding cell cycle re-entry, using mass spectrometry-based phosphoproteomics and RNA sequencing to capture molecular snapshots within the first minutes, hours, and days of BRAF kinase inhibitor exposure in a human BRAF -mutant melanoma model of adaptive therapy resistance. By enriching specific phospho-motifs associated with mitogenic kinase activity, we monitored the dynamics of thousands of growth- and survival-related protein phosphorylation events under oncogenic BRAF inhibition and drug removal. We observed early and sustained inhibition of the BRAF-ERK axis, gradual downregulation of canonical cell cycle-dependent signals, and three distinct and reversible phase transitions toward quiescence. Statistical inference of kinetically-defined signaling and transcriptional modules revealed a concerted response to oncogenic BRAF inhibition and a dominant compensatory induction of SRC family kinase (SFK) signaling, which we found to be at least partially driven by accumulation of reactive oxygen species via impaired redox homeostasis. This induction sensitized cells to co-treatment with an SFK inhibitor across a panel of patient-derived melanoma cell lines and in an orthotopic mouse xenograft model, underscoring the translational potential for measuring the early temporal dynamics of signaling and transcriptional networks under therapeutic challenge.

GSK3β: A ray of hope for the treatment of diabetic kidney disease

Diabetic kidney disease (DKD), a major microvascular complication of diabetes, is characterized by its complex pathogenesis, high risk of chronic renal failure, and lack of effective diagnosis and treatment methods. GSK3β (glycogen synthase kinase 3β), a highly conserved threonine/serine kinase, was found to activate glycogen synthase. As a key molecule of the glucose metabolism pathway, GSK3β participates in a variety of cellular activities and plays a pivotal role in multiple diseases. However, these effects are not only mediated by affecting glucose metabolism. This review elaborates on the role of GSK3β in DKD and its damage mechanism in different intrinsic renal cells. GSK3β is also a biomarker indicating the progression of DKD. Finally, the protective effects of GSK3β inhibitors on DKD are also discussed.

The Hypoxia Response Pathway: A Potential Intervention Target in Parkinson's Disease?

Parkinson's disease (PD) is a progressive neurodegenerative disorder for which only symptomatic treatments are available. Both preclinical and clinical studies suggest that moderate hypoxia induces evolutionarily conserved adaptive mechanisms that enhance neuronal viability and survival. Therefore, targeting the hypoxia response pathway might provide neuroprotection by ameliorating the deleterious effects of mitochondrial dysfunction and oxidative stress, which underlie neurodegeneration in PD. Here, we review experimental studies regarding the link between PD pathophysiology and neurophysiological adaptations to hypoxia. We highlight the mechanistic differences between the rescuing effects of chronic hypoxia in neurodegeneration and short-term moderate hypoxia to improve neuronal resilience, termed "hypoxic conditioning". Moreover, we interpret these preclinical observations regarding the pharmacological targeting of the hypoxia response pathway. Finally, we discuss controversies with respect to the differential effects of hypoxia response pathway activation across the PD spectrum, as well as intervention dosing in hypoxic conditioning and potential harmful effects of such interventions. We recommend that initial clinical studies in PD should focus on the safety, physiological responses, and mechanisms of hypoxic conditioning, as well as on repurposing of existing pharmacological compounds. © 2023 International Parkinson and Movement Disorder Society.

Silva H, P. de Carvalho R, Ventura ALM, Calaza KC, Silveira MS, Kubrusly RCC, de Melo Reis RA. The Healthy and Diseased Retina Seen through Neuron-Glia Interactions

The retina is the sensory tissue responsible for the first stages of visual processing, with a conserved anatomy and functional architecture among vertebrates. To date, retinal eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, glaucoma, and others, affect nearly 170 million people worldwide, resulting in vision loss and blindness. To tackle retinal disorders, the developing retina has been explored as a versatile model to study intercellular signaling, as it presents a broad neurochemical repertoire that has been approached in the last decades in terms of signaling and diseases. Retina, dissociated and arranged as typical cultures, as mixed or neuron- and glia-enriched, and/or organized as neurospheres and/or as organoids, are valuable to understand both neuronal and glial compartments, which have contributed to revealing roles and mechanisms between transmitter systems as well as antioxidants, trophic factors, and extracellular matrix proteins. Overall, contributions in understanding neurogenesis, tissue development, differentiation, connectivity, plasticity, and cell death are widely described. A complete access to the genome of several vertebrates, as well as the recent transcriptome at the single cell level at different stages of development, also anticipates future advances in providing cues to target blinding diseases or retinal dysfunctions.

Xiao-Ban-Xia decoction mitigates cisplatin-induced emesis via restoring PINK1/Parkin mediated mitophagy deficiency in a rat pica model

ETHNOPHARMACOLOGICAL RELEVANCE

As a traditional Chinese anti-emetic formula, Xiao-Ban-Xia decoction (XBXD) was recorded in Golden Chamber, and has promising anti-emetic effect on chemotherapy-induced nausea and vomiting (CINV).

AIM OF THE STUDY

This study aimed to determine whether the underlying mechanism of XBXD against CINV is correlated to the restoration of cisplatin-induced PINK1/Parkin mediated mitophagy deficiency and mitigation of gastrointestinal inflammation.

MATERIALS AND METHODS

The rat pica model was established by intraperitoneal injection of cisplatin 6 mg/kg. The daily kaolin consumption, food intake and body weight were recorded every 24 h. The pathological damage of gastric antrum and ileum were observed by hematoxylin-eosin staining. The levels of serum reactive oxygen species (ROS), interleukin-1β (IL-1β) and interleukin-1β (IL-18) were detected by ELISA. The expression of microtubule-associated protein 1 light chain 3 (LC3) in gastric antrum and ileum was detected by Immunofluorescence staining. The levels of LC3II, P62/SQSTM1, PTEN-induced putative protein kinases (PINK1), E3 ubiquitin ligase (Parkin), AMP-dependent protein kinases (AMPK), phosphorylated AMPK (p-AMPK), nuclear factor erythroid 2-related factor (Nrf2) and kelch like ECH Associated Protein 1 (Keap1) in gastric antrum and ileum were assayed by western blotting.

RESULTS

At 24 h and 72 h following cisplatin challenge, XBXD inhibited cisplatin-induced elevation of kaolin consumption, and improved the daily food intake and body weight loss in rats. Cisplatin-induced gastrointestinal histopathological damages were alleviated, and serum levels of ROS, IL-1β and IL-18 increases were mitigated following XBXD treatments. In gastric antrum and ileum, XBXD activated AMPK-Nrf2 signaling pathway and restored cisplatin-induced PINK1/Parkin mediated mitophagy deficiency.

CONCLUSIONS

XBXD significantly ameliorated CINV in a cisplatin-induced rat pica model. The underlying anti-emetic mechanism of XBXD might be related to the activation of AMPK-Nrf2 signaling pathway and the restoration of cisplatin-induced PINK1/Parkin-mediated mitophagy deficiency in the gastrointestinal tract.

The lack of homology domain and leucine rich repeat protein phosphatase 2 ameliorates visual impairment in rats with diabetic retinopathy through regulation of the AKT-GSK-3β-Nrf2 signal cascade

Pleckstrin homology domain and leucine rich repeat protein phosphatase 2 (PHLPP2) is an emerging player in diverse disorders. Our previous findings have documented that reducing PHLPP2 levels in cultured retinal ganglion cells protects against cellular damage caused by high glucose, indicating a possible link between PHLPP2 and diabetic retinopathy (DR). The present work was dedicated to the investigation of PHLPP2 in DR through in vivo experiments with rat models induced by intraperitoneal injection of streptozotocin. Compared to normal rats, the retinas of rats with DR exhibited a notable increase in the level of PHLPP2. The reduction of PHLPP2 levels in the retina was achieved by the intravitreal administration of adeno-associated viruses expressing specific shRNA targeting PHLPP2. Decreasing the expression of PHLPP2 ameliorated visual function impairment and improved the pathological changes of retina in DR rats. Moreover, decreasing the expression of PHLPP2 repressed the apoptosis, oxidative stress and proinflammatory response in the retinas of rats with DR. Reduction of PHLPP2 levels led to an increase in the levels of phosphorylated AKT and glycogen synthase kinase-3β (GSK-3β). Decreasing the expression of PHLPP2 resulted in increased activation of nuclear factor erythroid 2-related factor 2 (Nrf2), which was reversed by suppressing AKT. Notably, the protective effect of reducing PHLPP2 on DR was eliminated when Nrf2 was restrained. These observations show that the down-regulation of PHLPP2 has protective effects on DR by preserving the structure and function of the retina by regulating the AKT-GSK-3β-Nrf2 signal cascade. Therefore, targeting PHLPP2 may hold promise in the treatment of DR.

Transcription Factor NRF2 in Shaping Myeloid Cell Differentiation and Function

NFE2-related factor 2 (NRF2) is a master transcription factor (TF) that coordinates key cellular homeostatic processes including antioxidative responses, autophagy, proteostasis, and metabolism. The emerging evidence underscores its significant role in modulating inflammatory and immune processes. This chapter delves into the role of NRF2 in myeloid cell differentiation and function and its implication in myeloid cell-driven diseases. In macrophages, NRF2 modulates cytokine production, phagocytosis, pathogen clearance, and metabolic adaptations. In dendritic cells (DCs), it affects maturation, cytokine production, and antigen presentation capabilities, while in neutrophils, NRF2 is involved in activation, migration, cytokine production, and NETosis. The discussion extends to how NRF2's regulatory actions pertain to a wide array of diseases, such as sepsis, various infectious diseases, cancer, wound healing, atherosclerosis, hemolytic conditions, pulmonary disorders, hemorrhagic events, and autoimmune diseases. The activation of NRF2 typically reduces inflammation, thereby modifying disease outcomes. This highlights the therapeutic potential of NRF2 modulation in treating myeloid cell-driven pathologies.

The novel β-TrCP protein isoform hidden in circular RNA confers trastuzumab resistance in HER2-positive breast cancer

Trastuzumab notably improves the outcome of human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients, however, resistance to trastuzumab remains a major hurdle to clinical treatment. In the present study, we identify a circular RNA intimately linked to trastuzumab resistance. circ-β-TrCP, derived from the back-splicing of β-TrCP exon 7 and 13, confers trastuzumab resistance by regulating NRF2-mediated antioxidant pathway in a KEAP1-independent manner. Concretely, circ-β-TrCP encodes a novel truncated 343-amino acid peptide located in the nucleus, referred as β-TrCP-343aa, which competitively binds to NRF2, blocks SCFβ-TrCP-mediated NRF2 proteasomal degradation, and this protective effect of β-TrCP-343aa on NRF2 protein requires GSK3 activity. Subsequently, the elevated NRF2 transcriptionally upregulates a cohort of antioxidant genes, giving rise to trastuzumab resistance. Moreover, the translation ability of circ-β-TrCP is inhibited by eIF3j under both basal and oxidative stress conditions, and eIF3j is transcriptionally repressed by NRF2, thus forming a positive feedback circuit between β-TrCP-343aa and NRF2, expediting trastuzumab resistance. Collectively, our data demonstrate that circ-β-TrCP-encoded β-TrCP protein isoform drives HER2-targeted therapy resistance in a NRF2-dependent manner, which provides potential therapeutic targets for overcoming trastuzumab resistance.

Regulation of NRF2 by Phosphoinositides and Small Heat Shock Proteins

Reactive oxygen species (ROS) are generated by aerobic metabolism, and their deleterious effects are buffered by the cellular antioxidant response, which prevents oxidative stress. The nuclear factor erythroid 2-related factor 2 (NRF2) is a master transcriptional regulator of the antioxidant response. Basal levels of NRF2 are kept low by ubiquitin-dependent degradation of NRF2 by E3 ligases, including the Kelch-like ECH-associated protein 1 (KEAP1). Here, we show that the stability and function of NRF2 is regulated by the type I phosphatidylinositol phosphate kinase g (PIPKIg), which binds NRF2 and transfers its product phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P 2 ) to NRF2. PtdIns(4,5)P 2 binding recruits the small heat shock protein HSP27 to the complex. Silencing PIPKIg or HSP27 destabilizes NRF2, reduces expression of its target gene HO-1, and sensitizes cells to oxidative stress. These data demonstrate an unexpected role of phosphoinositides and HSP27 in regulating NRF2 and point to PIPKIg and HSP27 as drug targets to destabilize NRF2 in cancer.

In brief

Phosphoinositides are coupled to NRF2 by PIPKIγ, and HSP27 is recruited and stabilizes NRF2, promoting stress-resistance.

Overview on the Polyphenol Avenanthramide in Oats (Avena sativa Linn.) as Regulators of PI3K Signaling in the Management of Neurodegenerative Diseases

Avenanthramides (Avns) and their derivatives, a group of polyphenolic compounds found abundantly in oats (Avena sativa Linn.), have emerged as promising candidates for neuroprotection due to their immense antioxidant, anti-inflammatory, and anti-apoptotic properties. Neurodegenerative diseases (NDDs), characterized by the progressive degeneration of neurons, present a significant global health burden with limited therapeutic options. The phosphoinositide 3-kinase (PI3K) signaling pathway plays a crucial role in cell survival, growth, and metabolism, making it an attractive target for therapeutic intervention. The dysregulation of PI3K signaling has been implicated in the pathogenesis of various NDDs including Alzheimer's and Parkinson's disease. Avns have been shown to modulate PI3K/AKT signaling, leading to increased neuronal survival, reduced oxidative stress, and improved cognitive function. This review explores the potential of Avn polyphenols as modulators of the PI3K signaling pathway, focusing on their beneficial effects against NDDs. Further, we outline the need for clinical exploration to elucidate the specific mechanisms of Avn action on the PI3K/AKT pathway and its potential interactions with other signaling cascades involved in neurodegeneration. Based on the available literature, using relevant keywords from Google Scholar, PubMed, Scopus, Science Direct, and Web of Science, our review emphasizes the potential of using Avns as a therapeutic strategy for NDDs and warrants further investigation and clinical exploration.

AMPK-Mediated Phosphorylation of Nrf2 at S374/S408/S433 Favors Its βTrCP2-Mediated Degradation in KEAP1-Deficient Cells

Nrf2 is a transcription factor facilitating cells' resilience against redox and various other forms of stress. In the absence of stressors, KEAP1 and/or βTrCP mediate the ubiquitination of Nrf2 and prevent Nrf2-dependent gene expression and detoxification. AMPK regulates cellular energy homeostasis and redox balance. Previous studies indicated a potential Nrf2-AMPK cooperativity. In line with this, our lab had previously identified three AMPK-dependent phosphorylation sites (S374/408/433) in Nrf2. Given their localization in or near the Neh6 domain, known to regulate βTrCP-mediated degradation, we examined whether they may influence the βTrCP-driven degradation of Nrf2. By employing expression plasmids for WT and triple mutant (TM)-Nrf2 (Nrf2S374/408/433→A), (co)immunoprecipitation, proximity ligation, protein half-life, knockdown, ubiquitination experiments, and qPCR in Keap1-null mouse embryonic fibroblasts, we show that TM-Nrf2S→A374/408/433 had enhanced stability due to impeded interaction with βTrCP2 and reduced ubiquitination in comparison to WT-Nrf2. In addition, TM-Nrf2 elicited higher expression of the Nrf2 target gene Gclc, potentiated in the presence of a pharmacological AMPK activator. Overall, we propose that AMPK-dependent phospho-sites of Nrf2 can favor its βTrCP2-mediated degradation and dampen the extent of Nrf2 target gene expression. Therefore, targeting AMPK might be able to diminish Nrf2-mediated responses in cells with overactive Nrf2 due to KEAP1 deficiency.

The deubiquitylating enzyme USP35 restricts regulated cell death to promote survival of renal clear cell carcinoma

The ubiquitin-proteasome system governs a wide spectrum of cellular events and offers therapeutic opportunities for pharmacological intervention in cancer treatment. Renal clear cell carcinoma represents the predominant histological subtype and accounts for the majority of cancer death related to kidney malignancies. Through a systematic survey in the association of human ubiquitin-specific proteases with patient prognosis of renal clear cell carcinoma and subsequent phenotypic validation, we uncovered the tumor-promoting role of USP35. Biochemical characterizations confirmed the stabilizing effects of USP35 towards multiple members of the IAP family in an enzymatic activity-dependent manner. USP35 silencing led to reduced expression levels of IAP proteins, which were accompanied with increased cellular apoptosis. Further transcriptomic analysis revealed that USP35 knockdown affected the expression levels of NRF2 downstream transcripts, which were conferred by compromised NRF2 abundance. USP35 functions to maintain NRF2 levels by catalyzing its deubiquitylation and thus antagonizing degradation. NRF2 reduction imposed by USP35 silencing rendered renal clear cell carcinoma cells increased sensitivity to ferroptosis induction. Finally, induced USP35 knockdown markedly attenuated xenograft formation of renal clear cell carcinoma in nude mice. Hence, our findings reveal a number of USP35 substrates and uncover the protecting roles of USP35 against both apoptosis and ferroptosis in renal clear cell carcinoma.

Identification of NRF2 Activation as a Prognostic Biomarker in T-Cell Acute Lymphoblastic Leukaemia

The standard-of-care treatment of T-cell acute lymphoblastic leukaemia (T-ALL) with chemotherapy usually achieves reasonable rates of initial complete response. However, patients who relapse or do not respond to conventional therapy show dismal outcomes, with cure rates below 10% and limited therapeutic options. To ameliorate the clinical management of these patients, it is urgent to identify biomarkers able to predict their outcomes. In this work, we investigate whether NRF2 activation constitutes a biomarker with prognostic value in T-ALL. Using transcriptomic, genomic, and clinical data, we found that T-ALL patients with high NFE2L2 levels had shorter overall survival. Our results demonstrate that the PI3K-AKT-mTOR pathway is involved in the oncogenic signalling induced by NRF2 in T-ALL. Furthermore, T-ALL patients with high NFE2L2 levels displayed genetic programs of drug resistance that may be provided by NRF2-induced biosynthesis of glutathione. Altogether, our results indicate that high levels of NFE2L2 may be a predictive biomarker of poor treatment response in T-ALL patients, which would explain the poor prognosis associated with these patients. This enhanced understanding of NRF2 biology in T-ALL may allow a more refined stratification of patients and the proposal of targeted therapies, with the ultimate goal of improving the outcome of relapsed/refractory T-ALL patients.

GSK-3β-dependent Nrf2 antioxidant response modulates ferroptosis of lens epithelial cells in age-related cataract

Oxidative stress-induced lens epithelial cells (LECs) death plays a pivotal role in age-related cataract (ARC) with severe visual impairment, in which ferroptosis is gradually receiving numerous attention resulting from lipid peroxide accumulation and reactive oxygen species (ROS) overproduction. However, the essential pathogenic factors and the targeted medical strategies still remain skeptical and indistinct. In this work, by transmission electron microscopy (TEM) analysis, the major pathological courses in the LECs of ARC patients have been identified as ferroptosis, which was manifested with remarkable mitochondrial alterations, and similar results were found in aged mice (24-month-old). Furthermore, the primary pathological processes in the NaIO3-induced mice and HLE-B3 cell model have also been verified to be ferroptosis with an irreplaceable function of Nrf2, proved by the increased sensitivity to ferroptosis when Nrf2 was blocked in Nrf2-KO mice and si-Nrf2-treated HLE-B3 cells. Importantly, it has been found that an increased expression of GSK-3β was indicated in low-Nrf2-expressed tissues and cells. Subsequently, the contributions of abnormal GSK-3β expression to NaIO3-induced mice and HLE-B3 cell model were further evaluated, inhibition of GSK-3β utilizing SB216763 significantly alleviated LECs ferroptosis with less iron accumulation and ROS generation, as well as reversed expression alterations of ferroptosis markers, including GPX4, SLC7A11, SLC40A1, FTH1 and TfR1, in vitro and in vivo. Collectively, our findings conclude that targeting GSK-3β/Nrf2 balance might be a promising therapeutic strategy to mitigate LECs ferroptosis and thus probably delay the pathogenesis and development of ARC.

Butyrate dictates ferroptosis sensitivity through FFAR2-mTOR signaling

Evidence shows that short-chain fatty acids (SCFAs) play an important role in health maintenance and disease development. In particular, butyrate is known to induce apoptosis and autophagy. However, it remains largely unclear whether butyrate can regulate cell ferroptosis, and the mechanism by which has not been studied. In this study, we found that RAS-selective lethal compound 3 (RSL3)- and erastin-induced cell ferroptosis were enhanced by sodium butyrate (NaB). With regard to the underlying mechanism, our results showed that NaB promoted ferroptosis by inducing lipid ROS production via downregulating the expression of solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4). Moreover, the FFAR2-AKT-NRF2 axis and FFAR2-mTORC1 axis accounts for the NaB-mediated downregulation of SLC7A11 and GPX4, respectively, in a cAMP-PKA-dependent manner. Functionally, we found that NaB can inhibit tumor growth and the inhibitory effect could be eliminated by administrating MHY1485 (mTORC1 activator) and Ferr-1 (ferroptosis inhibitor). Altogether, in vivo results suggest that NaB treatment is correlated to the mTOR-dependent ferroptosis and consequent tumor growth through xenografts and colitis-associated colorectal tumorigenesis, implicating the potential clinical applications of NaB for future colorectal cancer treatments. Based on all these findings, we have proposed a regulatory mechanism via which butyrate inhibits the mTOR pathway to control ferroptosis and consequent tumorigenesis.

Loss of pleckstrin homology domain and leucine-rich repeat protein phosphatase 2 has protective effects on high glucose-injured retinal ganglion cells via the effect on the Akt-GSK-3β-Nrf2 pathway

OBJECTIVE

Pleckstrin homology domain and leucine-rich repeat protein phosphatase 2 (PHLPP2) is linked to various pathological states. However, whether PHLPP2 mediates diabetic retinopathy is unaddressed. This work explored the biological function of PHLPP2 in modulating high glucose (HG)-elicited damage of retinal ganglion cells (RGCs), an in vitro model for studying diabetic retinopathy.

METHODS

Mouse RGCs were treated with HG to establish a cell model. PHLPP2 was silenced by transfecting specific shRNAs targeting PHLPP2. RT-qPCR, immunoblotting, CCK-8 assay, flow cytometry, TUNEL assay, and ELISA were carried out.

RESULTS

Significant increases in PHLPP2 levels were observed in cultured RGCs exposed to HG. The severe damages evoked by HG to RGCs were remarkably weakened in PHLPP2-silenced RGCs, including improved cell survival, attenuated cell apoptosis, repressed oxidative stress, and prohibited proinflammatory response. The silencing of PHLPP2 strengthened the activation of Nrf2 in HG-treated RGCs via modulation of the Akt-GSK-3β axis. Interruption of the Akt-GSK-3β axis reversed PHLPP2-silencing-elicited Nrf2 activation. The protective effects of PHLPP2 silencing on HG-induced injury of RGCs were diminished by Nrf2 inhibition.

CONCLUSIONS

The loss of PHLPP2 was beneficial for HG-injured RGCs through the effect on the Akt-GSK-3β-Nrf2 pathway. This work suggests a possible role of PHLPP2 in diabetic retinopathy.

Reactive Oxygen Species and NRF2 Signaling, Friends or Foes in Cancer?

The imbalance between reactive oxygen species (ROS) production and clearance causes oxidative stress and ROS, which play a central role in regulating cell and tissue physiology and pathology. Contingent upon concentration, ROS influence cancer development in contradictory ways, either stimulating cancer survival and growth or causing cell death. Cells developed evolutionarily conserved programs to sense and adapt redox the fluctuations to regulate ROS as either signaling molecules or toxic insults. The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2)-KEAP1 system is the master regulator of cellular redox and metabolic homeostasis. NRF2 has Janus-like roles in carcinogenesis and cancer development. Short-term NRF2 activation suppresses tissue injury, inflammation, and cancer initiation. However, cancer cells often exhibit constitutive NRF2 activation due to genetic mutations or oncogenic signaling, conferring advantages for cancer cells' survival and growth. Emerging evidence suggests that NRF2 hyperactivation, as an adaptive cancer phenotype under stressful tumor environments, regulates all hallmarks of cancer. In this review, we summarized the source of ROS, regulation of ROS signaling, and cellular sensors for ROS and oxygen (O₂), we reviewed recent progress on the regulation of ROS generation and NRF2 signaling with a focus on the new functions of NRF2 in cancer development that reach beyond what we originally envisioned, including regulation of cancer metabolism, autophagy, macropinocytosis, unfolded protein response, proteostasis, and circadian rhythm, which, together with anti-oxidant and drug detoxification enzymes, contributes to cancer development, metastasis, and anticancer therapy resistance.

C1q/tumor necrosis factor-related protein-6 exerts protective effects on myocardial ischemia-reperfusion injury through the modulation of the Akt-GSK-3β-Nrf2 signaling cascade

C1q/tumor necrosis factor-related protein-6 (CTRP6) is a multifunctional protein that plays a pivotal role in diverse physiological and pathological processes. To date, whether CTRP6 has a role in myocardial ischemia-reperfusion (I/R) injury remains unexplored. This work aimed to investigate the potential role and mechanism of CTRP6 in myocardial I/R injury through in vitro and in vivo experiments. CTRP6 expression was downregulated in hypoxia/reoxygenation (H/R)-treated cardiomyocytes. The apoptosis, oxidative stress, and inflammation in the H/R-treated cardiomyocytes were markedly alleviated by CTRP6 overexpression or exacerbated by CTRP6 silencing. Notably, the overexpression of CTRP6 remarkably ameliorated the myocardial injury, infarction area, cardiac apoptosis, oxidative stress, and inflammation in mice with myocardial I/R injury in vivo. Further investigation revealed that CTRP6 overexpression enhanced the activation of Nrf2 in the H/R-treated cardiomyocytes and the myocardium tissue of mice with myocardial I/R injury. CTRP6 overexpression increased the phosphorylated level of Akt and GSK-3β, and the inhibition of Akt abolished CTRP6-overexpression-elicited Nrf2 activation in the H/R-treated cardiomyocytes. Additionally, the inhibition of Akt or Nrf2 abolished the protective effects of CTRP6 overexpression on the H/R-treated cardiomyocytes. Altogether, CTRP6 had protective effects on myocardial I/R injury via the effects on the Akt-GSK-3β-Nrf2 signaling cascade. Our work recommends CTRP6 as a novel cardioprotective target for the treatment of myocardial I/R injury.

Stress Activated MAP Kinases and Cyclin-Dependent Kinase 5 Mediate Nuclear Translocation of Nrf2 via Hsp90α-Pin1-Dynein Motor Transport Machinery

Non-lethal low levels of oxidative stress leads to rapid activation of the transcription factor nuclear factor-E2-related factor 2 (Nrf2), which upregulates the expression of genes important for detoxification, glutathione synthesis, and defense against oxidative damage. Stress-activated MAP kinases p38, ERK, and JNK cooperate in the efficient nuclear accumulation of Nrf2 in a cell-type-dependent manner. Activation of p38 induces membrane trafficking of a glutathione sensor neutral sphingomyelinase 2, which generates ceramide upon depletion of cellular glutathione. We previously proposed that caveolin-1 in lipid rafts provides a signaling hub for the phosphorylation of Nrf2 by ceramide-activated PKCζ and casein kinase 2 to stabilize Nrf2 and mask a nuclear export signal. We further propose a mechanism of facilitated Nrf2 nuclear translocation by ERK and JNK. ERK and JNK phosphorylation of Nrf2 induces the association of prolyl cis/trans isomerase Pin1, which specifically recognizes phosphorylated serine or threonine immediately preceding a proline residue. Pin1-induced structural changes allow importin-α5 to associate with Nrf2. Pin1 is a co-chaperone of Hsp90α and mediates the association of the Nrf2-Pin1-Hsp90α complex with the dynein motor complex, which is involved in transporting the signaling complex to the nucleus along microtubules. In addition to ERK and JNK, cyclin-dependent kinase 5 could phosphorylate Nrf2 and mediate the transport of Nrf2 to the nucleus via the Pin1-Hsp90α system. Some other ERK target proteins, such as pyruvate kinase M2 and hypoxia-inducible transcription factor-1, are also transported to the nucleus via the Pin1-Hsp90α system to modulate gene expression and energy metabolism. Notably, as malignant tumors often express enhanced Pin1-Hsp90α signaling pathways, this provides a potential therapeutic target for tumors.

Sirt6 mediates antioxidative functions by increasing Nrf2 abundance

Oxidative stress caused by excess ROS often leads to cellular macromolecule damage and eventually causes various biological catastrophes. Sirt6, a member of the mammalian homolog family of yeast Sir2 NAD⁺-dependent histone deacetylases, regulates multiple biological processes. Sirt6 exerts antioxidative functions by enhancing DNA repair and DNA end resection. In our study, we found that Sirt6 expression was induced by H₂O₂ and paraquat (PQ) in cells. When exposed to PQ, the Sirt6^+/- C57BL/6 mice showed more serious liver damage and lower survival rate than the Sirt6^+/+ mice. The Nrf2 protein levels and the mRNA levels of its target genes in mouse tissues were decreased by Sirt6 deficiency, and Sirt6 overexpression increased the Nrf2 protein content. Moreover, the endogenous H₂O₂ levels were increased in the tissues of Sirt6-deficient mice and were decreased in Sirt6 overexpression cells. Then, we found that Nrf2 was degraded faster in the Sirt6-deficient mouse embryonic fibroblasts (MEFs) than in the wild type MEFs and that Sirt6 enhanced the protein accumulation of Nrf2 in the nucleus. Lastly, we found that Sirt6 interacted with Nrf2 in co-IP and GST pull-down assays and that Sirt6 overexpression decreased the binding of Nrf2 to Keap1. Taken together, the results of the present study suggest that Sirt6 exerts antioxidative functions by increasing the Nrf2 protein level via Keap1-mediated regulation.

Nrf2 Regulates the Expression of CYP2D6 by Inhibiting the Activity of Krüppel-Like Factor 9 (KLF9)

AIMS

The aim of the present study is to gain insight into the biology of Parkinson's disease (PD) and cancer to drive translational advances enabling more effective prevention and/or potential treatments.

BACKGROUND

The expression of Cytochrome P450 2D6 (CYP2D6) is correlated with various diseases such as PD and cancer; therefore, exploring its regulatory mechanism at transcriptional levels is of interest. NF-E2-related factor 2 (Nrf2) has been known to be responsible for regulating phase II and phase III drug-metabolizing genes.

OBJECTIVES

The objectives of this study are to investigate the transcriptional regulation of CYP2D6 by Nrf2 and to analyze its role in PD and cancer.

METHODS

Nrf2 was transiently expressed in human hepatoma Hep3B cells, and the expression of CYP2D6 was examined by RT-qPCR. The promoter activity of CYP2D6 and the DNA binding of Nrf2 were examined by luciferase and ChIP assay, respectively. We then investigated the expression and correlation of Nrf2 and CYP2D6 in the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) datasets.

RESULTS

In the present study, we demonstrated that Nrf2 down-regulated CYP2D6 mRNA expression in hepatoma Hep3B cells. Mechanistically, Nrf2 binds to the antioxidant responsive element (ARE) in the proximity of krüppel- like factor 9 (KLF9)-binding site within the -550/+51 of CYP2D6 promoter. The inhibition and activation of Nrf2 enhanced and suppressed KLF9 effects on CYP2D6 expression, respectively. The expression levels of Nrf2 and CYP2D6 were upregulated and downregulated in the PD patient GEO datasets compared to the healthy control tissues, and Nrf2 was negatively correlated with CYP2D6. In liver cancer patients, decreased CYP2D6 levels were apparent and associated with a lower probability of survival.

CONCLUSION

Our work revealed the inhibitory role of Nrf2 in regulating CYP2D6 expression. Moreover, Nrf2- dependent regulation of CYP2D6 can be used as a prognostic factor and therapeutic strategy in PD and liver cancer.

Nrf2 Activation: Involvement in Central Nervous System Traumatic Injuries. A Promising Therapeutic Target of Natural Compounds

Central nervous system (CNS) trauma, such as traumatic brain injury (TBI) and spinal cord injury (SCI), represents an increasingly important health burden in view of the preventability of most injuries and the complex and expensive medical care that they necessitate. These injuries are characterized by different signs of neurodegeneration, such as oxidative stress, mitochondrial dysfunction, and neuronal apoptosis. Cumulative evidence suggests that the transcriptional factor nuclear factor erythroid 2-related factor 2 (Nrf2) plays a crucial defensive role in regulating the antioxidant response. It has been demonstrated that several natural compounds are able to activate Nrf2, mediating its antioxidant response. Some of these compounds have been tested in experimental models of SCI and TBI, showing different neuroprotective properties. In this review, an overview of the preclinical studies that highlight the positive effects of natural bioactive compounds in SCI and TBI experimental models through the activation of the Nrf2 pathway has been provided. Interestingly, several natural compounds can activate Nrf2 through multiple pathways, inducing a strong antioxidant response against CNS trauma. Therefore, some of these compounds could represent promising therapeutic strategies for these pathological conditions.

The role of Nrf2 in periodontal disease by regulating lipid peroxidation, inflammation and apoptosis

Nuclear factor E2-related factor 2(Nrf2) is a transcription factor that mainly regulates oxidative stress in the body. It initiates the expression of several downstream antioxidants, anti-inflammatory proteins and detoxification enzymes through the Kelch-like ECH-associating protein 1 (Keap1) -nuclear factor E2-related factor 2(Nrf2) -antioxidant response element (ARE) signaling pathway. Its anti-apoptosis, anti-oxidative stress and anti-inflammatory effects have gradually become the focus of periodontal disease research in recent years. In this paper, the structure and function of Nrf2 pathway and its mechanism of action in the treatment of periodontitis in recent years were analyzed and summarized, so as to further clarify the relationship between Nrf2 pathway and oxidative stress in the occurrence and development of periodontitis, and to provide ideas for the development of new treatment drugs targeting Nrf2 pathway.

BP5 alleviates endotoxemia-induced acute lung injury by activating Nrf2 via dual regulation of the Keap1-Nrf2 interaction and the Akt (Ser473)/GSK3β (Ser9)/Fyn pathway

Oxidative stress and inflammation play a crucial role in the pathogenesis of acute lung injury (ALI). Previously, pentapeptide bursopentin (BP5, Cys-Lys-Arg-Val-Tyr) was reported to possess significant antioxidant activity and inhibit lipopolysaccharides (LPS)-induced NF-κB activation in vitro, whereas little is known about its effects in vivo. In this study, we explored the effects of BP5 on endotoxemia-induced ALI in mice and the underlying molecular mechanisms. Our studies revealed that BP5 markedly improved survival and effectively alleviated lung injury by reducing overoxidation and excessive inflammatory response in endotoxemia mice. In LPS-stimulated mouse primary macrophages and RAW 264.7 cells, BP5 also exhibited antioxidant and anti-inflammatory properties by enhancing Nrf2 activation. Importantly, these beneficial effects were abolished by Nrf2 knockdown. To further elucidate the underlying mechanisms, we performed localized surface plasmon resonance (LSPR) assays, molecular docking, together with cell-based studies, and found that BP5 inhibited the Keap1-Nrf2 interaction to promote Nrf2 nuclear translocation and activation. Moreover, BP5-induced Nrf2 activation was shown to be accompanied by an increase in the phosphorylation of Akt (at Ser473) and GSK3β (at Ser9), and a decrease in Fyn nuclear accumulation both in vitro and in vivo. Pharmacologically inhibiting phosphorylation of Akt and GSK3β obviously enhanced Fyn nuclear accumulation in RAW 264.7 cells, which partially attenuated the promoting effect of BP5 on Nrf2 nuclear accumulation and activation. Furthermore, In Nrf2^-/- mice, the protective effects of BP5 on the endotoxemia-induced ALI in WT mice were largely vanished. Our findings indicated that BP5 effectively protected endotoxemia-induced ALI against oxidative stress and inflammatory response, which are largely dependent on activation of the Nrf2 pathway. Underlying mechanisms include dual regulation of the Keap-Nrf2 interaction and the Akt (Ser473)/GSK3β (Ser9)/Fyn pathway.

Mechanisms underlying Nrf2 nuclear translocation by non-lethal levels of hydrogen peroxide: p38 MAPK-dependent neutral sphingomyelinase2 membrane trafficking and ceramide/PKCζ/CK2 signaling

Hydrogen peroxide is an aerobic metabolite playing a central role in redox signaling and oxidative stress. H₂O₂ could activate redox sensitive transcription factors, such as Nrf2, AP-1 and NF-κB by different manners. In some cells, treatment with non-lethal levels of H₂O₂ induces rapid activation of Nrf2, which upregulates expression of a set of genes involved in glutathione (GSH) synthesis and defenses against oxidative damage. It depends on two steps, the rapid translational activation of Nrf2 and facilitation of Nrf2 nuclear translocation. We review the molecular mechanisms by which H₂O₂ induces nuclear translocation of Nrf2 in cultured cells by highlighting the role of neutral sphingomyelinase 2 (nSMase2), a GSH sensor. H₂O₂ enters cells through aquaporin channels in the plasma membrane and is rapidly reduced to H₂O by GSH peroxidases to consume cellular GSH, resulting in nSMase2 activation to generate ceramide. H₂O₂ also activates p38 MAP kinase, which enhances transfer of nSMase2 from perinuclear regions to plasma membrane lipid rafts to accelerate ceramide generation. Low levels of ceramide activate PKCζ, which then activates casein kinase 2 (CK2). These protein kinases are able to phosphorylate Nrf2 to stabilize and activate it. Notably, Nrf2 also binds to caveolin-1 (Cav1), which protects Nrf2 from Keap1-mediated degradation and limits Nrf2 nuclear translocation. We propose that Cav1serves as a signaling hub for the control of H₂O₂-mediated phosphorylation of Nrf2 by kinases, which results in release of Nrf2 from Cav1 to facilitate nuclear translocation. In summary, H₂O₂ induces GSH depletion which is recovered by Nrf2 activation dependent on p38/nSMase2/ceramide signaling.

Nrf2 induces malignant transformation of hepatic progenitor cells by inducing β-catenin expression

The Nrf2 signaling pathway prevents cancer initiation, but genetic mutations that activate this pathway are found in various types of cancer. The molecular mechanisms underlying this Janus-headed character are still not understood. Here, we show that sustained Nrf2 activation induces proliferation and dedifferentiation of a Wnt-responsive perivenular hepatic progenitor cell population, transforming them into metastatic cancer cells. The neoplastic lesions display many histological features known from human hepatoblastoma. We describe an Nrf2-induced upregulation of β-catenin expression and its activation as the underlying mechanism for the observed malignant transformation. Thus, we have identified the Nrf2–β-catenin axis promoting proliferation of hepatic stem cells and triggering tumorigenesis. These findings support the concept that different functional levels of Nrf2 control both the protection against various toxins as well as liver regeneration by activating hepatic stem cells. Activation of the hepatic stem cell compartment confers the observation that unbridled Nrf2 activation may trigger tumorigenesis.

Molecular Mechanisms of the Neuroprotective Effect of Methylene Blue

Methylene blue (MB) is the first fully synthetic compound that had found its way into medicine over 120 years ago as a treatment against malaria. MB has been approved for the treatment of methemoglobinemia, but there are premises for its repurposing as a neuroprotective agent based on the efficacy of this compound demonstrated in the models of Alzheimer's, Parkinson's, and Huntington's diseases, traumatic brain injury, amyotrophic lateral sclerosis, depressive disorders, etc. However, the goal of this review was not so much to focus on the therapeutic effects of MB in the treatment of various neurodegeneration diseases, but to delve into the mechanisms of direct or indirect effect of this drug on the signaling pathways. MB can act as an alternative electron carrier in the mitochondrial respiratory chain in the case of dysfunctional electron transport chain. It also displays the anti-inflammatory and anti-apoptotic effects, inhibits monoamine oxidase (MAO) and nitric oxide synthase (NOS), activates signaling pathways involved in the mitochondrial pool renewal (mitochondrial biogenesis and autophagy), and prevents aggregation of misfolded proteins. Comprehensive understanding of all aspects of direct and indirect influence of MB, and not just some of its effects, can help in further research of this compound, including its clinical applications.

The Role of Nrf2 in Pulmonary Fibrosis: Molecular Mechanisms and Treatment Approaches

Pulmonary fibrosis is a chronic, progressive, incurable interstitial lung disease with high mortality after diagnosis and remains a global public health problem. Despite advances and breakthroughs in understanding the pathogenesis of pulmonary fibrosis, there are still no effective methods for the prevention and treatment of pulmonary fibrosis. The existing treatment options are imperfect, expensive, and have considerable limitations in effectiveness and safety. Hence, there is an urgent need to find novel therapeutic targets. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a central regulator of cellular antioxidative responses, inflammation, and restoration of redox balance. Accumulating reports reveal that Nrf2 activators exhibit potent antifibrosis effects and significantly attenuate pulmonary fibrosis in vivo and in vitro. This review summarizes the current Nrf2-related knowledge about the regulatory mechanism and potential therapies in the process of pulmonary fibrosis. Nrf2 orchestrates the activation of multiple protective genes that target inflammation, oxidative stress, fibroblast–myofibroblast differentiation (FMD), and epithelial–mesenchymal transition (EMT), and the mechanisms involve Nrf2 and its downstream antioxidant, Nrf2/HO−1/NQO1, Nrf2/NOX4, and Nrf2/GSH signaling pathway. We hope to indicate potential for Nrf2 system as a therapeutic target for pulmonary fibrosis.

Sulforaphane inhibits angiotensin II-induced cardiomyocyte apoptosis by acetylation modification of Nrf2

Oxidative stress is the central cause of angiotensin II (Ang II)-induced myocardial injury, and nuclear factor erythroid 2-related factor (Nrf2) is the core molecule of the anti-oxidant defense system. We have previously demonstrated that sulforaphane (SFN) can prevent Ang II-induced myocardial injury by activating Nrf2; however, the underlying molecular mechanism is still unclear. This study aimed to evaluate whether SFN prevents Ang II-induced cardiomyocyte apoptosis through acetylation modification of <i>Nrf2</i>. Wild-type and <i>Nrf2</i> knockdown embryonic rat cardiomyocytes (H9C2) were exposed to Ang II to induce apoptosis, oxidative stress, and inflammatory responses. SFN treatment significantly reduced Ang II-induced cardiomyocyte apoptosis, inflammation and oxidative stress. Activation of Nrf2 played a critical role in preventing cardiomyocyte apoptosis. After Nrf2 was knockdown, the anti-inflammatory, antioxidant stress of SFN were eliminated. Furthermore, Nrf2 activation by SFN was closely related to the decreased activity of histone deacetylases (HDACs) and increased histone-3 (H3) acetylation levels in <i>Nrf2</i> promoter region. These findings confirm that Nrf2 plays a key role in SFN preventing Ang II-induced cardiomyocyte apoptosis. SFN activates Nrf2 by inhibiting HDACs expression and activation.

Nonalcoholic steatohepatitis and mechanisms by which it is ameliorated by activation of the CNC-bZIP transcription factor Nrf2

Non-alcoholic steatohepatitis (NASH) represents a global health concern. It is characterised by fatty liver, hepatocyte cell death and inflammation, which are associated with lipotoxicity, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, iron overload and oxidative stress. NF-E2 p45-related factor 2 (Nrf2) is a transcription factor that combats oxidative stress. Remarkably, Nrf2 is downregulated during the development of NASH, which probably accelerates disease, whereas in pre-clinical studies the upregulation of Nrf2 inhibits NASH. We now review the scientific literature that proposes Nrf2 downregulation during NASH involves its increased ubiquitylation and proteasomal degradation, mediated by Kelch-like ECH-associated protein 1 (Keap1) and/or β-transducin repeat-containing protein (β-TrCP) and/or HMG-CoA reductase degradation protein 1 (Hrd1, also called synoviolin (SYVN1)). Additionally, downregulation of Nrf2-mediated transcription during NASH may involve diminished recruitment of coactivators by Nrf2, due to increased levels of activating transcription factor 3 (ATF3) and nuclear factor-kappaB (NF-κB) p65, or competition for promoter binding due to upregulation of BTB and CNC homology 1 (Bach1). Many processes that downregulate Nrf2 are triggered by transforming growth factor-beta (TGF-β), with oxidative stress amplifying its signalling. Oxidative stress may also increase suppression of Nrf2 by β-TrCP through facilitating formation of the DSGIS-containing phosphodegron in Nrf2 by glycogen synthase kinase-3. In animal models, knockout of Nrf2 increases susceptibility to NASH, while pharmacological activation of Nrf2 by inducing agents that target Keap1 inhibits development of NASH. These inducing agents probably counter Nrf2 downregulation affected by β-TrCP, Hrd1/SYVN1, ATF3, NF-κB p65 and Bach1, by suppressing oxidative stress. Activation of Nrf2 is also likely to inhibit NASH by ameliorating lipotoxicity, inflammation, ER stress and iron overload. Crucially, pharmacological activation of Nrf2 in mice in which NASH has already been established supresses liver steatosis and inflammation. There is therefore compelling evidence that pharmacological activation of Nrf2 provides a comprehensive multipronged strategy to treat NASH.

Lignans from Eucommia ulmoides Oliver leaves exhibit neuroprotective effects via activation of the PI3K/Akt/GSK-3β/Nrf2 signaling pathways in H2O2-treated PC-12 cells

BACKGROUND

Neuronal apoptosis and oxidative stress have the most crucial influence on neurodegenerative diseases, including Parkinson's disease. Rat adrenal pheochromocytoma cells (PC-12) induced by H₂O₂ are one of the primary in vitro models of Parkinson's disease (PD) . Previous studies have found that E ulmoides leaf extract exerts good neuroprotective activity and has the potential to treat neurodegenerative diseases. However, the molecular pathways involved in the neuroprotective effects of its primary leaf component, lignans, have not yet been well elucidated yet.

PURPOSE

This study aimed to evaluate the neuroprotective effects of lignans in E. ulmoides leaves and to explore the underlying mechanism.

METHODS

Cell viability was measured using the CCK-8 assay. Apoptosis was assessed by calcein/PI staining. The release levels of ROS and LDH were assessed using a commercial assay kit. The enzyme activities of SOD and GPx were measured using kits. The establishment of the compound-target-pathway-disease network was performed using a database and computer software. Antioxidant proteins (HO-1, NQO-1, and Cat) and related regulatory proteins (Nrf2, GSK-3β, p-GSK 3β (Ser 9), Akt, p-Akt (Tyr326), PI3K) were detected by western blotting. Apoptosis in the zebrafish head was assessed using acridine orange (AO) staining.

RESULTS

In the present study, 12 lignans were isolated and characterized from E. ulmoides leaves, including a new compound, (-)-7‑epi-pinoresinol mr1 (1). Compounds 1-12 exerted neuroprotective effects in H₂O₂-treated PC-12 cells by increasing cell viability, improving the enzyme activity of SOD and GPx, and reducing levels of ROS and LDH. Compared to the positive control group (25 μM hesperetin), cell viability in response to 25 μM compound 1 (78.0 ± 0.8%) was highest, but its relative percent LDH release (20.1 ± 2.5%) was the lowest; 25 μM compound 4 resulted in the lowest ROS release levels (101.7 ± 2.6%) and highest SOD enzyme activity (35.9 ± 4.2 U/mg), and the GPx enzyme activity of 25 μM compound 1 was strongest (197.6 ± 0.6 U/mg). Next, the potential targets (PI3K, GSK-3β) of the test compounds' antioxidant activity were identified using pharmacological network analysis. Using DAVID software for pharmacological network analysis, potential targets (PI3K, GSK-3β, and SOD2) of 12 lignans were identified. Based on the initial screening results, biological experiments confirmed that diepoxylignans 1, 2, and 4 exerted significant neuroprotection by regulating the PI3K/AKT/GSK-3β/Nrf2 signaling pathways, increasing protein expression of HO-1, NQO-1, and CAT, and enhancing the antioxidant enzyme activity of SOD and GPx.

CONCLUSION

Our experiments first propose that the diepoxylignans from E. ulmoides leaves exert neuroprotective effects via activation of the PI3K/Akt/GSK-3β/Nrf2 signaling pathway. These findings further indicate that lignans could be the primary components of E. ulmoides Oliver as agents for the prevention and treatment of neurodegenerative diseases. Collectively, Eucommia ulmoides leaves with important research value may be a potential candidate for traditional Chinese medicine for treating oxidative stress-related neurodegenerative diseases.

Sipeimine ameliorates PM2.5-induced lung injury by inhibiting ferroptosis via the PI3K/Akt/Nrf2 pathway: A network pharmacology approach

Fine particulate matter (PM2.5) exposure can cause lung injury and a large number of respiratory diseases. Sipeimine is a steroidal alkaloid isolated from Fritillaria roylei which has been associated with anti-inflammatory, antitussive and antiasthmatic properties. In this study, we explored the potential effects of sipeimine against PM2.5-induced lung injury in Sprague Dawley rats. Sipeimine alleviated lung injury caused by PM2.5 and decreased pulmonary edema, inflammation and the levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the bronchoalveolar lavage fluid. In addition, sipeimine upregulated the glutathione (GSH) expression and downregulated the expression of 4-hydroxynonenal (4-HNE), tissue iron and malondialdehyde (MDA). The downregulation of proteins involved in ferroptosis, including nuclear factor E2-related factor 2 (Nrf2), glutathione peroxidase 4 (GPX4), heme oxygenase-1 (HO-1) and solute carrier family 7 member 11 (SLC7A11) was reversed by sipeimine. The administration of RSL3, a potent ferroptosis-triggering agent, blocked the effects of sipeimine. Using network pharmacology, we found that the effects of sipeimine were presumably mediated through the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. A PI3K inhibitor (LY294002) blocked the PI3K/Akt signaling pathway and reversed the effects of sipeimine. Overall, this study suggested that the protective effect of sipeimine against PM2.5-induced lung injury was mainly mediated through the PI3K/Akt pathway, ultimately leading to a reduction in ferroptosis.

Protective Effects of Liquiritigenin against Cisplatin-Induced Nephrotoxicity via NRF2/SIRT3-Mediated Improvement of Mitochondrial Function

Acute kidney injury (AKI) induced by cisplatin (CP), a first-line anticancer drug for chemotherapy, is common. To date, there is an urgent need to find effective treatments to reduce the nephrotoxicity caused by CP. Meanwhile, the restoration of mitochondrial dysfunction shows potential to be used as an adjunct to conventional therapeutic strategies. This study found that liquiritigenin can ameliorate mitochondrial dysfunction and acute kidney injury induced by CP in mice. The intraperitoneal injection of 15 mg/kg body weight liquiritigenin for 2 days markedly protected against CP-induced mitochondrial dysfunction, restored renal tubule and mitochondrial morphology, decreased blood Scr and BUN levels, and decreased cell apoptosis. Furthermore, the elevated expression of SIRT3 induced by liquiritigenin, which can be upregulated by NRF2, was confirmed in vivo and in vitro. The underlying protective mechanisms of liquiritigenin in CP-induced nephrotoxicity were then investigated. Molecular docking results showed that liquiritigenin has potent binding activities to KEAP1, GSK-3β and HRD1. Further results showed that liquiritigenin induced the nuclear translocation of NRF2 and increased the levels of mitochondrial bioenergetics-related protein such as PGC-1α, and TFAM, which are related to NRF2 activity and mitochondrial biogenesis. In addition, liquiritigenin was found to possibly reverse the decrease in BCL2/BAX ratio induced by CP in live cultured renal tubule epithelial cells. Collectively, these results indicated that liquiritigenin could be used as a potential nephroprotective agent to protect against cisplatin-induced acute kidney injury in a NRF2-dependent manner by improving mitochondria function.

Recent Advances in the Role of Nuclear Factor Erythroid-2-Related Factor 2 in Spinal Cord Injury: Regulatory Mechanisms and Therapeutic Options

Nuclear factor erythroid-2-related factor 2 (Nrf2) is a pleiotropic transcription factor, and it has been documented that it can induce defense mechanisms both oxidative stress and inflammatory injury. At present, more and more evidences show that the Nrf2 signaling pathway is a key pharmacological target for the treatment of spinal cord injury (SCI), and activating the Nrf2 signaling pathway can effectively treat the inflammatory injury and oxidative stress after SCI. This article firstly introduces the biological studies of the Nrf2 pathway. Meanwhile, it is more powerful to explain that activating the Nrf2 signaling pathway can effectively treat SCI by deeply exploring the relationship between Nrf2 and oxidative stress, inflammatory injury, and SCI. In addition, several potential drugs for the treatment of SCI by promoting Nrf2 activation and Nrf2-dependent gene expression are reviewed. And some other treatment strategies of SCI by modulating the Nrf2 pathway are also summarized. It will provide new ideas and directions for the treatment of SCI.

Cardiac NF-κB Acetylation Increases While Nrf2-Related Gene Expression and Mitochondrial Activity Are Impaired during the Progression of Diabetes in UCD-T2DM Rats

The onset of type II diabetes increases the heart’s susceptibility to oxidative damage because of the associated inflammation and diminished antioxidant response. Transcription factor NF-κB initiates inflammation while Nrf2 controls antioxidant defense. Current evidence suggests crosstalk between these transcription factors that may become dysregulated during type II diabetes mellitus (T2DM) manifestation. The objective of this study was to examine the dynamic changes that occur in both transcription factors and target genes during the progression of T2DM in the heart. Novel UC Davis T2DM (UCD-T2DM) rats at the following states were utilized: (1) lean, control Sprague-Dawley (SD; n = 7), (2) insulin-resistant pre-diabetic UCD-T2DM (Pre; n = 9), (3) 2-week recently diabetic UCD-T2DM (2Wk; n = 9), (4) 3-month diabetic UCD-T2DM (3Mo; n = 14), and (5) 6-month diabetic UCD-T2DM (6Mo; n = 9). NF-κB acetylation increased 2-fold in 3Mo and 6Mo diabetic animals compared to SD and Pre animals. Nox4 protein increased 4-fold by 6Mo compared to SD. Nrf2 translocation increased 82% in Pre compared to SD but fell 47% in 6Mo animals. GCLM protein fell 35% in 6Mo animals compared to Pre. Hmox1 mRNA decreased 45% in 6Mo animals compared to SD. These data suggest that during the progression of T2DM, NF-κB related genes increase while Nrf2 genes are suppressed or unchanged, perpetuating inflammation and a lesser ability to handle an oxidant burden altering the heart’s redox state. Collectively, these changes likely contribute to the diabetes-associated cardiovascular complications.

Targeting NRF2 in Type 2 diabetes mellitus and depression: Efficacy of natural and synthetic compounds

Evidence supports a strong bidirectional association between depression and Type 2 diabetes mellitus (T2DM). The harmful impact of oxidative stress and chronic inflammation on the development of both disorders is widely accepted. Nuclear factor erythroid 2-related factor 2 (NRF2) is a pertinent target in disease management owing to its reputation as the master regulator of antioxidant responses. NRF2 influences the expression of various cytoprotective phase 2 antioxidant genes, which is hampered in both depression and T2DM. Through interaction and crosstalk with several signaling pathways, NRF2 endeavors to contain the widespread oxidative damage and persistent inflammation involved in the pathophysiology of depression and T2DM. NRF2 promotes the neuroprotective and insulin-sensitizing properties of its upstream and downstream targets, thereby interrupting and preventing disease advancement. Standard antidepressant and antidiabetic drugs may be powerful against these disorders, but unfortunately, they come bearing distressing side effects. Therefore, exploiting the therapeutic potential of NRF2 activators presents an exciting opportunity to manage such bidirectional and comorbid conditions.

Recent Advances in Understanding Nrf2 Agonism and Its Potential Clinical Application to Metabolic and Inflammatory Diseases

Oxidative stress is a major component of cell damage and cell fat, and as such, it occupies a central position in the pathogenesis of metabolic disease. Nuclear factor-erythroid-derived 2-related factor 2 (Nrf2), a key transcription factor that coordinates expression of genes encoding antioxidant and detoxifying enzymes, is regulated primarily by Kelch-like ECH-associated protein 1 (Keap1). However, involvement of the Keap1–Nrf2 pathway in tissue and organism homeostasis goes far beyond protection from cellular stress. In this review, we focus on evidence for Nrf2 pathway dysfunction during development of several metabolic/inflammatory disorders, including diabetes and diabetic complications, obesity, inflammatory bowel disease, and autoimmune diseases. We also review the beneficial role of current molecular Nrf2 agonists and summarize their use in ongoing clinical trials. We conclude that Nrf2 is a promising target for regulation of numerous diseases associated with oxidative stress and inflammation. However, more studies are needed to explore the role of Nrf2 in the pathogenesis of metabolic/inflammatory diseases and to review safety implications before therapeutic use in clinical practice.

A non-catalytic scaffolding activity of hexokinase 2 contributes to EMT and metastasis

Hexokinase 2 (HK2), which catalyzes the first committed step in glucose metabolism, is induced in cancer cells. HK2's role in tumorigenesis has been attributed to its glucose kinase activity. Here, we describe a kinase independent HK2 activity, which contributes to metastasis. HK2 binds and sequesters glycogen synthase kinase 3 (GSK3) and acts as a scaffold forming a ternary complex with the regulatory subunit of protein kinase A (PRKAR1a) and GSK3β to facilitate GSK3β phosphorylation and inhibition by PKA. Thus, HK2 functions as an A-kinase anchoring protein (AKAP). Phosphorylation by GSK3β targets proteins for degradation. Consistently, HK2 increases the level and stability of GSK3 targets, MCL1, NRF2, and particularly SNAIL. In addition to GSK3 inhibition, HK2 kinase activity mediates SNAIL glycosylation, which prohibits its phosphorylation by GSK3. Finally, in mouse models of breast cancer metastasis, HK2 deficiency decreases SNAIL protein levels and inhibits SNAIL-mediated epithelial mesenchymal transition and metastasis.