The role of natural products in revealing NRF2 function

Gaudichaudione H ameliorates liver fibrosis and inflammation by targeting NRF2 signaling pathway

Gaudichaudione H (GH) is a natural small molecular compound isolated from Garcinia oligantha Merr. (Clusiaceae). Being an uncommon rare caged polyprenylated xanthone, the potential pharmacological functions of GH remain to be fully elucidated currently. In this study, we primarily focused on identifying potential bioavailable targets and elucidating related therapeutic actions. Herein, the network pharmacology analysis, metabolomics analysis and genome-wide mRNA transcription assay were performed firstly to predict the major pharmacological action and potential targets of GH. To confirm the hypothesis, gene knockout model was created using CRISPR/Cas9 method. The pharmacological action of GH was evaluated in vitro and in vivo. Firstly, our results of network pharmacology analysis and omics assay indicated that GH significantly activated NRF2 signaling pathway, and the function could be associated with liver disease treatment. Then, the pharmacological action of GH was evaluated in vitro and in vivo. The treatment with GH significantly increased the protein levels of NRF2 and promoted the transcription of NRF2 downstream genes. Further analysis suggested that GH regulated NRF2 through an autophagy-mediated non-canonical mechanism. Additionally, the administration of GH effectively protected the liver from carbon tetrachloride (CCl4)-induced liver fibrosis and inflammation, which depended on the activation of NRF2 in hepatic stellate cells and inflammatory cells respectively. Collectively, our findings underscore the potential therapeutic effect of GH on alleviating hepatic fibrosis and inflammation through the augmentation of NRF2 signaling pathway, providing a promising avenue for the treatment of liver fibrosis and inflammation in clinical settings.

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

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

NRF2 Suppression Enhances the Susceptibility of Pancreatic Cancer Cells, Miapaca-2 to Paclitaxel

Pancreatic cancer is one of the most deadly diseases, with a very high metastasis and low survival rate. High levels of NRF2 have been detected in numerous malignancies, including head, neck, lung, and colon cancers, promoting the expansion and survival of cancer cells and chemical resistance to stressful conditions and affecting the response to treatment. To evaluate the possibility that modulation of NRF2 expression could be effective in treating pancreatic cancer cells, we explored the effect of knockdown of the NRF2 gene by NRF2-specific siRNA and its influence in combination with paclitaxel on pancreatic cancer cells. Miapaca-2 cell line, due to the high expression of the NRF2 gene, was selected for this study. Then, Miapaca-2 cells in different groups were treated with NRF2 siRNA and paclitaxel separately and in combination. After that, cell viability was measured by MTT assay and apoptosis induction by Annexin V-FITC/PI staining test. Cell cycle and autophagy were examined by flow cytometry, and cell migration was assessed by wound-healing assay. Finally, the expression of genes involved in apoptosis, Bax, Caspase-3, Caspase-9, and genes related to migration pathway, MMP-2, and MMP-9 in different groups were measured using qRT-PCR. Combined use of NRF2-specific siRNA with paclitaxel significantly reduced NRF2 gene expression in pancreatic cancer cells. NRF2 siRNA transfection significantly reduced cell viability. In addition, paclitaxel combination therapy with NRF2 siRNA strengthens the anti-tumor effects, such as inhibiting cell migration and provoking apoptosis, and autophagy and the cell cycle arrest in the G2 phase. NRF2 suppression augmented the expression of Bax, Caspase-3, and Caspase-9 genes and lowered the expression of Bcl-2, MMP-2, and MMP-9 genes, which play crucial roles in the pathways of apoptosis and cell migration, respectively. NRF2 siRNA enhances the susceptibility of Miapaca-2 cells to paclitaxel in pancreatic cancer cells. Thereby, suppressing NRF2 in combination with paclitaxel can be a new and efficacious treatment approach in treating pancreatic cancer.

Oxidised rice bran oil induced oxidative stress and apoptosis in IPEC-J2 cells via the Nrf2 signalling pathway

Rice bran oil is a type of rice oil made by leaching or pressing during rice processing and has a high absorption rate after consumption. When oxidative rancidity occurs, it may cause oxidative stress (OS) and affect intestinal function. Meanwhile, the toxic effects of oxidised rice bran oil have been less well studied in pigs. Therefore, the IPEC-J2 cells model was chosen to explore the regulatory mechanisms of oxidised rice bran oil on OS and apoptosis. Oxidised rice bran oil extract treatment (OR) significantly decreased the viability of IPEC-J2 cells. The results showed that OR significantly elevated apoptosis and reactive oxygen species levels and promoted the expression of pro-apoptotic gene Caspase-3 messenger RNA levels. The activation of Nrf2 signalling pathway by OR decreased the cellular antioxidant capacity. This was further evidenced by the expression of kelch-like ECH-associated protein 1, heme oxygenase 1, NADH: quinone oxidoreductase 1, superoxide dismutase 2 and heat shock 70 kDa protein genes and proteins were all downregulated. In conclusion, our results suggested that oxidised rice bran oil induced damage in IPEC-J2 cells through the Nrf2 signalling pathway.

Mitochondrial mechanisms in Cerebral Ischemia-Reperfusion Injury: Unravelling the intricacies

Cerebral ischemic stroke is a major contributor to physical impairments and premature death worldwide. The available reperfusion therapies for stroke in the form of mechanical thrombectomy and intravenous thrombolysis increase the risk of cerebral ischemia-reperfusion (I-R) injury due to sudden restoration of blood supply to the ischemic region. The injury is manifested by hemorrhagic transformation, worsening of neurological impairments, cerebral edema, and progression to infarction in surviving patients. A complex network of multiple pathological processes has been known to be involved in the pathogenesis of I-R injury. Primarily, 3 major contributors namely oxidative stress, neuroinflammation, and mitochondrial failure have been well studied in I-R injury. A transcription factor, Nrf2 (Nuclear factor erythroid 2-related factor 2) plays a crucial defensive role in resisting the deleterious effects of I-R injury and potentiating the cellular protective mechanisms. In this review, we delve into the critical function of mitochondria and Nrf2 in the context of cerebral I-R injury. We summarized how oxidative stress, neuroinflammation, and mitochondrial anomaly contribute to the pathophysiology of I-R injury and further elaborated the role of Nrf2 as a pivotal guardian of cellular integrity. The review further highlighted Nrf2 as a putative therapeutic target for mitochondrial dysfunction in cerebral I-R injury management.

The role of Nrf2 signaling pathways in nerve damage repair

The protein, Nuclear factor-E2-related factor 2 (Nrf2), is a transitory protein that acts as a transcription factor and is involved in the regulation of many cytoprotective genes linked to xenobiotic metabolism and antioxidant responses. Based on the existing clinical and experimental data, it can be inferred that neurodegenerative diseases are characterized by an excessive presence of markers of oxidative stress (OS) and a reduced presence of antioxidant defense systems in both the brain and peripheral tissues. The presence of imbalances in the homeostasis between oxidants and antioxidants has been recognized as a substantial factor in the pathogenesis of neurodegenerative disorders. The dysregulations include several cellular processes such as mitochondrial failure, protein misfolding, and neuroinflammation. These dysregulations all contribute to the disruption of proteostasis in neuronal cells, leading to their eventual mortality. A noteworthy component of Nrf2, as shown by recent research undertaken over the last decade, is to its role in the development of resistance to OS. Nrf2 plays a pivotal role in regulating systems that defend against OS. Extant research offers substantiation for the protective and defensive roles of Nrf2 in the context of neurodegenerative diseases. The purpose of this study is to provide a comprehensive analysis of the influence of Nrf2 on OS and its function in regulating antioxidant defense systems within the realm of neurodegenerative diseases. Furthermore, we evaluate the most recent academic inquiries and empirical evidence about the beneficial and potential role of certain Nrf2 activator compounds within the realm of therapeutic interventions.

Stretch Causes cffDNA and HMGB1-Mediated Inflammation and Cellular Stress in Human Fetal Membranes

Danger-associated molecular patterns (DAMPs) are elevated within the amniotic cavity, and their increases correlate with advancing gestational age, chorioamnionitis, and labor. Although the specific triggers for their release in utero remain unclear, it is thought that they may contribute to the initiation of parturition by influencing cellular stress mechanisms that make the fetal membranes (FMs) more susceptible to rupture. DAMPs induce inflammation in many different tissue types. Indeed, they precipitate the subsequent release of several proinflammatory cytokines that are known to be key for the weakening of FMs. Previously, we have shown that in vitro stretch of human amnion epithelial cells (hAECs) induces a cellular stress response that increases high-mobility group box-1 (HMGB1) secretion. We have also shown that cell-free fetal DNA (cffDNA) induces a cytokine response in FM explants that is fetal sex-specific. Therefore, the aim of this work was to further investigate the link between stretch and the DAMPs HMGB1 and cffDNA in the FM. These data show that stretch increases the level of cffDNA released from hAECs. It also confirms the importance of the sex of the fetus by demonstrating that female cffDNA induced more cellular stress than male fetuses. Our data treating hAECs and human amnion mesenchymal cells with HMGB1 show that it has a differential effect on the ability of the cells of the amnion to upregulate the proinflammatory cytokines and propagate a proinflammatory signal through the FM that may weaken it. Finally, our data show that sulforaphane (SFN), a potent activator of Nrf2, is able to mitigate the proinflammatory effects of stretch by decreasing the levels of HMGB1 release and ROS generation after stretch and modulating the increase of key cytokines after cell stress. HMGB1 and cffDNA are two of the few DAMPs that are known to induce cytokine release and matrix metalloproteinase (MMP) activation in the FMs; thus, these data support the general thesis that they can function as potential central players in the normal mechanisms of FM weakening during the normal distension of this tissue at the end of a normal pregnancy.

Linagliptin ameliorates tacrolimus-induced renal injury: role of Nrf2/HO-1 and HIF-1α/CTGF/PAI-1

BACKGROUND

Tacrolimus (TAC) is a frequently used immunosuppressive medication in organ transplantation. However, its nephrotoxic impact limits its long-term usage. This study aims to investigate the effect of linagliptin (Lina) on TAC-induced renal injury and its underlying mechanisms.

METHODS AND RESULTS

Thirty-two Sprague Dawley rats were treated with TAC (1.5 mg/kg/day, subcutaneously) and/or Lina (5 mg/kg/day, orally) for 4 weeks. Histological examination was conducted, and serum and urinary biomarkers were measured to assess kidney function and integrity. Furthermore, ELISA, Western blot analysis and immunohistochemical assay were employed to determine signaling molecules of oxidative stress, profibrogenic, hypoxic, and apoptotic proteins. Tacrolimus caused renal dysfunction and histological deterioration evidenced by increased serum creatinine, blood urea nitrogen (BUN), urinary cystatin C, and decreased serum albumin as well as elevated tubular injury and interstitial fibrosis scores. Additionally, TAC significantly increased the expression of collagen type-1, alpha-smooth muscle actin (α-SMA), plasminogen activator inhibitor-1 (PAI-1), and transforming growth factor-beta1 (TGF-β1) renal content. Moreover, TAC decreased the expression of nuclear factor erythroid-2-related factor2 (Nrf2), heme oxygenase 1 (HO-1), and mitochondrial superoxide dismutase (SOD2). In addition, TAC increased protein expression of hypoxia-inducible factor1-alpha (HIF-1α), connective tissue growth factor (CTGF), inducible nitric oxide synthase (iNOS), 8-hydroxy-2-deoxyguanosine (8-OHdG), as well as nitric oxide (NO), 4-hydroxynonenal, caspase-3 and Bax renal contents. Furthermore, TAC decreased Bcl-2 renal contents. The Lina administration markedly attenuated these alterations.

CONCLUSION

Lina ameliorated TAC-induced kidney injury through modulation of oxidative stress, hypoxia, and apoptosis related proteins.

Aldo-keto reductase-7A2 protects against atorvastatin-induced hepatotoxicity via Nrf2 activation

Atorvastatin (ATO), as a cholesterol-lowering drug, was the world's best-selling drug in the early 2000s. However, ATO overdose-induced liver or muscle injury is a threat to many patients, which restricts its application. Previous studies suggest that ATO overdose is accompanied with ROS accumulation and increased lipid peroxidation, which are the leading causes of ATO-induced liver damage. This study is, therefore, carried out to investigate the roles of anti-oxidant pathways and enzymes in protection against ATO-induced hepatotoxicity. Here we show that in ATO-challenged HepG2 cells, the expression levels of transcription factor NFE2L2/Nrf2 (nuclear factor erythroid 2 p45-related factor 2) are significantly upregulated. When Nrf2 is pharmacologically inhibited or genetically inactivated, ATO-induced cytotoxicity is significantly aggravated. Aldo-keto reductase-7A (AKR7A) enzymes, transcriptionally regulated by Nrf2, are important for bioactivation and biodetoxification. Here, we reveal that in response to ATO exposure, mRNA levels of human AKR7A2 are significantly upregulated in HepG2 cells. Furthermore, knockdown of AKR7A2 exacerbates ATO-induced hepatotoxicity, suggesting that AKR7A2 is essential for cellular adaptive response to ATO-induced cell damage. In addition, overexpression of AKR7A2 in HepG2 cells can significantly mitigate ATO-induced cytotoxicity and this process is Nrf2-dependent. Taken together, these findings indicate that Nrf2-mediated AKR7A2 is responsive to high concentrations of ATO and contributes to protection against ATO-induced hepatotoxicity, making it a good candidate for mitigating ATO-induced side effects.

Natural products as non-covalent and covalent modulators of the KEAP1/NRF2 pathway exerting antioxidant effects

By controlling several antioxidant and detoxifying genes at the transcriptional level, including NAD(P)H quinone oxidoreductase 1 (NQO1), multidrug resistance-associated proteins (MRPs), UDP-glucuronosyltransferase (UGT), glutamate-cysteine ligase catalytic (GCLC) and modifier (GCLM) subunits, glutathione S-transferase (GST), sulfiredoxin1 (SRXN1), and heme-oxygenase-1 (HMOX1), the KEAP1/NRF2 pathway plays a crucial role in the oxidative stress response. Accordingly, the discovery of modulators of this pathway, activating cellular signaling through NRF2, and targeting the antioxidant response element (ARE) genes is pivotal for the development of effective antioxidant agents. In this context, natural products could represent promising drug candidates for supplementation to provide antioxidant capacity to human cells. In recent decades, by coupling in silico and experimental methods, several natural products have been characterized to exert antioxidant effects by targeting the KEAP1/NRF2 pathway. In this review article, we analyze several natural products that were investigated experimentally and in silico for their ability to modulate KEAP1/NRF2 by non-covalent and covalent mechanisms. These latter represent the two main sections of this article. For each class of inhibitors, we reviewed their antioxidant effects and potential therapeutic applications, and where possible, we analyzed the structure-activity relationship (SAR). Moreover, the main computational techniques used for the most promising identified compounds are detailed in this survey, providing an updated view on the development of natural products as antioxidant agents.

PSMD12 promotes non-small cell lung cancer progression through activating the Nrf2/TrxR1 pathway

BACKGROUND

Non-small cell lung cancer (NSCLC) contributes to the vast majority of cancer-related deaths. Proteasome 26S subunit, non-ATPase 12 (PSMD12), a subunit of 26S proteasome complex, is known to play the tumor-promoting role in several types of cancer but its function in NSCLC remains elusive.

OBJECTIVE

To explore the role and underlying mechanisms of PSMD12 in NSCLC.

METHODS

The PSMD12 expression in human normal lung epithelial cell line (BEAS-2B) and four NSCLC cell lines (A549, NCI-H1299, NCI-H1975, Calu-1) were determined by qRT-PCR and western blot. Malignant phenotypes of NSCLC cells were detected by CCK-8, EdU staining, immunofluorescence staining for E-cadherin, flow cytometry, and Transwell assays to assess cell viability, proliferation, epithelial-mesenchymal transition (EMT), apoptosis, migration and invasion. Dual luciferase assay was used to verify the regulatory role of transcription factor on the promoter.

RESULTS

We identified the upregulation of PSMD12 in NSCLC tissues based on the GEO datasets, which further verified in NSCLC and BEAS-2B cell lines. PSMD12 knockdown significantly suppressed malignant behaviors of NSCLC cells, including cell growth, invasion, and migration, while PSMD12 overexpression presented the opposite effects. Interestingly, we found that PSMD12 upregulated the tumor-promoting factor TrxR1 mRNA expression. For its potential mechanisms, we demonstrated that PSMD12 elevated transcription factor Nrf2 protein level and promoted Nrf2 nuclear translocation. And Nrf2 further increased TrxR1 promoter activity and enhanced TrxR1 transcription. Meanwhile, we proved that TrxR1 overexpression erased the inhibitory effect of PSMD12 knockdown.

CONCLUSION

PSMD12 promotes NSCLC progression by activating the Nrf2/TrxR1 pathway, providing a novel prognostic and therapeutic target for NSCLC treatment.

Role of Natural Compounds Modulating Heme Catabolic Pathway in Gut, Liver, Cardiovascular, and Brain Diseases

The crucial physiological process of heme breakdown yields biliverdin (BV) and bilirubin (BR) as byproducts. BV, BR, and the enzymes involved in their production (the "yellow players-YP") are increasingly documented as endogenous modulators of human health. Mildly elevated serum bilirubin concentration has been correlated with a reduced risk of multiple chronic pro-oxidant and pro-inflammatory diseases, especially in the elderly. BR and BV per se have been demonstrated to protect against neurodegenerative diseases, in which heme oxygenase (HMOX), the main enzyme in the production of pigments, is almost always altered. HMOX upregulation has been interpreted as a tentative defense against the ongoing pathologic mechanisms. With the demonstration that multiple cells possess YP, their propensity to be modulated, and their broad spectrum of activity on multiple signaling pathways, the YP have assumed the role of an adjustable system that can promote health in adults. Based on that, there is an ongoing effort to induce their activity as a therapeutic option, and natural compounds are an attractive alternative to the goal, possibly requiring only minimal changes in the life style. We review the most recent evidence of the potential of natural compounds in targeting the YP in the context of the most common pathologic condition of adult and elderly life.

Protective effects of natural compounds against paraquat-induced pulmonary toxicity: the role of the Nrf2/ARE signaling pathway

Paraquat (PQ) is a toxic herbicide to humans. Once absorbed, it accumulates in the lungs. PQ has been well documented that the generation of reactive oxygen species (ROS) is the main mechanism of its toxicity. Oxidative damage of PQ in lungs is represented as generation of cytotoxic and fibrotic mediators, interruption of epithelial and endothelial barriers, and inflammatory cell infiltration. No effective treatment for PQ toxicity is currently available. Several studies have shown that natural compounds (NCs) have the potential to alleviate PQ-induced pulmonary toxicity, due to their antioxidant and anti-inflammatory effects. NCs function as protective agents through stimulation of nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathways. Elevation of Nrf2 levels leads to the expression of its downstream enzymes such as SOD, CAT, and HO-1. The hypothesized role of the Nrf2/ARE signaling pathway as the protective mechanism of NCs against PQ-induced pulmonary toxicity is reviewed.

Roles of NRF2 in DNA damage repair

PURPOSE

The transcription factor NF-E2-related factor 2 (NRF2) is a master regulator widely involved in essential cellular functions such as DNA repair. By clarifying the upstream and downstream links of NRF2 to DNA damage repair, we hope that attention will be drawn to the utilization of NRF2 as a target for cancer therapy.

METHODS

Query and summarize relevant literature on the role of NRF2 in direct repair, BER, NER, MMR, HR, and NHEJ in pubmed. Make pictures of Roles of NRF2 in DNA Damage Repair and tables of antioxidant response elements (AREs) of DNA repair genes. Analyze the mutation frequency of NFE2L2 in different types of cancer using cBioPortal online tools. By using TCGA, GTEx and GO databases, analyze the correlation between NFE2L2 mutations and DNA repair systems as well as the degree of changes in DNA repair systems as malignant tumors progress.

RESULTS

NRF2 plays roles in maintaining the integrity of the genome by repairing DNA damage, regulating the cell cycle, and acting as an antioxidant. And, it possibly plays roles in double stranded break (DSB) pathway selection following ionizing radiation (IR) damage. Whether pathways such as RNA modification, ncRNA, and protein post-translational modification affect the regulation of NRF2 on DNA repair is still to be determined. The overall mutation frequency of the NFE2L2 gene in esophageal carcinoma, lung cancer, and penile cancer is the highest. Genes (50 of 58) that are negatively correlated with clinical staging are positively correlated with NFE2L2 mutations or NFE2L2 expression levels.

CONCLUSION

NRF2 participates in a variety of DNA repair pathways and plays important roles in maintaining genome stability. NRF2 is a potential target for cancer treatment.

Triterpenoids from the roots of Sanguisorba officinalis and their Nrf2 stimulation activity

Thirteen undescribed ursane-type triterpenoids, named as sangosides A-M (1-13), including two nor-ursanes, one split ring-ursane and ten ursanes, along with thirty-six known triterpenoids (14-49) were isolated and identified from the roots of Sanguisorba officinalis (Rosaceae). Their structures and absolute configurations were elucidated through spectroscopic data, single-crystal X-ray crystallography and electronic circular dichroism analysis. Their Nrf2 activation activity was evaluated in 293 T cells in vitro. Compounds 2, 5-7, 9-13, 19, 25, 26, 28-39, 41 and 46 showed significant Nrf2 agonistic effects compared with the control group at 25 μM, their cytotoxicity and dose-effect relationship were further studied in a dose-dependent manner. Their structure-activity relationships analysis suggested that the pentacyclic triterpenoids (10, 11, 30-34 and 41) contains two pairs of double bonds on the C & E rings and the ursane-type triterpenoids (25 and 26) with a carbonyl to C-2 and a hydroxyl group at C-3 all showed a considerably Nrf2 activation activity. These results suggested that S. officinalis was worthy of further investigation to find small molecule Nrf2 activators and facilitate their utilization as natural antioxidants.

Sanguisorba officinalis L. promotes diabetic wound healing in rats through inflammation response mediated by macrophage

Sanguisorba officinalis L., a traditional Chinese medicine, is frequently used to treat burns and scalds. But even so, it is unknown whether S. officinalis L. can accelerate diabetic wounds (DW) healing. Here, to bridge the gap, we employed in vivo and in vitro evaluations to assess the positive effect of S. officinalis L. ethanol extract (ESO) on DW. Results demonstrated that ESO dramatically improved the DW healing rate. With ESO treatment, the inappropriately elevated levels of IL6, IL1β and TNFα in DW were reduced, while the expression of IL10 was increased, indicating that the abnormal inflammation in DW was also under control. Moreover, the abnormally elevated expression of CD86 was significantly inhibited and the expression of CD206 was significantly up-regulated following treatment with ESO. The global level of NF-κB protein was not affected by ESO treatment, but it suppressed the expression of phosphorylated NF-κB and prevented its nuclear entry. In addition, in RAW264.7 cells activated with lipopolysaccharide (LPS), the expression of NLRP3, Caspase1 and IL1β were significantly diminished following ESO treatment. In conclusion, ESO was proved to be a promising treatment for DW healing due to its potential to accelerate the healing process by suppressing the inflammatory response. This was achieved by increasing the ratio of M2 to M1 polarization through blocking the NF-κB/NLRP3 signaling pathway.

Liquiritigenin Confers Liver Protection by Enhancing NRF2 Signaling through Both Canonical and Non-canonical Signaling Pathways

Oxidative stress plays a critical role in drug-induced liver injury. In recent years, liquiritigenin (LQ), a natural flavonoid distributed in Glycyrrhizae Radix et Rhizoma (Gan Cao), shows protective effects against oxidative hepatotoxicity. However, the underlying mechanism remains unclear. In this study, we mainly investigated the role of NRF2, a core transcription factor in oxidative stress, in LQ-induced hepatoprotection. Our results indicated that the function of LQ to eliminate reactive oxygen species in liver cells was dependent on NRF2 activation. Both a canonical signaling pathway and a non-canonical signaling pathway are involved in LQ-induced NRF2 activation. LQ induced NRF2 activation in a KEAP1-C151-dependent manner partially. Meanwhile, LQ led to the blockage of autophagic flux and upregulation of p62, which competitively bound with KEAP1 and conferred NRF2 activation in a KEAP1-C151-independent manner. Totally, our study reveals a novel molecular mechanism underlying the hepatoprotection of LQ, providing a new insight into the pathogenesis and therapeutic strategy of oxidative liver injury.

A Comparative Analysis of Chemical Constituents and Antioxidant Effects of Dendrobium fimbriatum Hook Fractions with Different Polarities

The aim of this study was to investigate the chemical composition and antioxidant capacity of various polar fractions obtained from Dendrobium fimbriatum Hook (DH). First, a 90% ethanol-aqueous extract of DH (CF) was subjected to sequential fractionation using different organic solvents, resulting in the isolation of a methylene chloride fraction (DF), an ethyl acetate fraction (EF), an n-butanol fraction (BF), and a remaining water fraction (WF) after condensation. Additionally, the CF was also subjected to column chromatography via a D101 macroreticular resin column, eluted with ethanol-aqueous solution to yield six fractions (0%, 20%, 40%, 60%, 80%, and 100%). UPLC-Q-Exactive Orbitrap-MS/MS analysis identified a total of 47 chemical compounds from these polar fractions, including fatty acids, amino acids, phenolic acids, flavonoids, organic heterocyclic molecules, and aromatic compounds. Moreover, DF, EF, and the 60%, 80%, and 100% ethanol-aqueous fractions had higher total phenol content (TPC) and total flavonoid content (TFC) values and greater 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS-) and 1,1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging abilities. In H2O2-induced HepG2 cells, the aforementioned fractions could increase the activities of antioxidative enzymes NAD(P)H: quinone oxidoreductase 1 (NQO1), superoxide dismutase (SOD), heme oxygenase-1 (HO-1) and catalase (CAT), stimulate glutathione (GSH) synthesis by increasing the activities of glutamic acid cysteine ligase (GCL) and glutathione synthetase (GS), regulate GSH metabolism by increasing glutathione peroxidase (GSH-Px) and glutathione reductase (GR) activities, and reduce levels of reactive oxygen species (ROS) and malondialdehyde (MDA). Furthermore, the antioxidative stress effect of the DH fractions was found to be positively correlated with the activation of nuclear factor-erythroid 2-related factor 2 (Nrf2) protein and the presence of antioxidative chemical constituents. In conclusion, this study highlights the efficacy of both liquid-liquid extraction and macroporous resin purification techniques in the enrichment of bioactive compounds from natural food resources. The comprehensive analysis of chemical constituents and antioxidant effects of different polar fractions from Dendrobium fimbriatum Hook contributes to the understanding of its potential application in functional foods and nutraceuticals.

Tetramethylpyrazine ameliorates endotoxin-induced acute lung injury by relieving Golgi stress via the Nrf2/HO-1 signaling pathway

PURPOSE

Endotoxin-induced acute lung injury (ALI) is a severe disease caused by an imbalanced host response to infection. It is necessary to explore novel mechanisms for the treatment of endotoxin-induced ALI. In endotoxin-induced ALI, tetramethylpyrazine (TMP) provides protection through anti-inflammatory, anti-apoptosis, and anti-pyroptosis effects. However, the mechanism of action of TMP in endotoxin-induced ALI remains unclear. Here, we aimed to determine whether TMP can protect the lungs by inhibiting Golgi stress via the Nrf2/HO-1 pathway.

METHODS AND RESULTS

Using lipopolysaccharide (LPS)-stimulated C57BL/6J mice and MLE12 alveolar epithelial cells, we observed that TMP pretreatment attenuated endotoxin-induced ALI. LPS + TMP group showed lesser lung pathological damage and a lower rate of apoptotic lung cells than LPS group. Moreover, LPS + TMP group also showed decreased levels of inflammatory factors and oxidative stress damage than LPS group (P < 0.05). Additionally, LPS + TMP group presented reduced Golgi stress by increasing the Golgi matrix protein 130 (GM130), Golgi apparatus Ca2+/Mn2+ ATPases (ATP2C1), and Golgin97 expression while decreasing the Golgi phosphoprotein 3 (GOLPH3) expression than LPS group (P < 0.05). Furthermore, TMP pretreatment promoted Nrf2 and HO-1 expression (P < 0.05). Nrf2-knockout mice or Nrf2 siRNA-transfected MLE12 cells were pretreated with TMP to explore how the Nrf2/HO-1 pathway affected TMP-mediated Golgi stress in endotoxin-induced ALI models. We observed that Nrf2 gene silencing partially reversed the alleviating effect of Golgi stress and the pulmonary protective effect of TMP.

CONCLUSION

Our findings showed that TMP therapy reduced endotoxin-induced ALI by suppressing Golgi stress via the Nrf2/HO-1 signaling pathway in vivo and in vitro.

Medicinal Chemistry Insights into the Development of Small-Molecule Kelch-Like ECH-Associated Protein 1-Nuclear Factor Erythroid 2-Related Factor 2 (Keap1-Nrf2) Protein-Protein Interaction Inhibitors

Oxidative stress has been implicated in a wide range of pathological conditions. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) exerts a central role in regulating the cellular defense system against oxidative and electrophilic insults. Nonelectrophilic inhibition of the protein-protein interaction (PPI) between Kelch-like ECH-associated protein 1 (Keap1) and Nrf2 has become a promising approach to activate Nrf2. Recently, multiple drug discovery strategies have facilitated the development of small-molecule Keap1-Nrf2 PPI inhibitors with potent activity and favorable drug-like properties. In this Perspective, we summarize the latest progress of small-molecule Keap1-Nrf2 PPI inhibitors from medicinal chemistry insights and discuss future prospects and challenges in this field.

Roles of Oxidative Stress and Nrf2 Signaling in Pathogenic and Non-Pathogenic Cells: A Possible General Mechanism of Resistance to Therapy

The coordinating role of nuclear factor erythroid-2-related factor 2 (Nrf2) in cellular function is undeniable. Evidence indicates that this transcription factor exerts massive regulatory functions in multiple signaling pathways concerning redox homeostasis and xenobiotics, macromolecules, and iron metabolism. Being the master regulator of antioxidant system, Nrf2 controls cellular fate, influencing cell proliferation, differentiation, apoptosis, resistance to therapy, and senescence processes, as well as infection disease success. Because Nrf2 is the key coordinator of cell defence mechanisms, dysregulation of its signaling has been associated with carcinogenic phenomena and infectious and age-related diseases. Deregulation of this cytoprotective system may also interfere with immune response. Oxidative burst, one of the main microbicidal mechanisms, could be impaired during the initial phagocytosis of pathogens, which could lead to the successful establishment of infection and promote susceptibility to infectious diseases. There is still a knowledge gap to fill regarding the molecular mechanisms by which Nrf2 orchestrates such complex networks involving multiple pathways. This review describes the role of Nrf2 in non-pathogenic and pathogenic cells.

A scientometrics and visualization analysis of oxidative stress modulator Nrf2 in cancer profiles its characteristics and reveals its association with immune response

Background

Nrf2, an essential and fascinating transcription factor, enjoys a dual property in the occurrence and development of inflammation and cancer. For over two decades, numerous studies regarding Nrf2 in cancer have been reported, whereas there is still a lack of a scientometrics and visualization analysis of Nrf2 in cancer. Hence, a scientometric study regarding the oxidative stress modulator Nrf2 was implemented.

Methods

After the quality screening, we defined 7168 relevant studies from 2000 to 2021. CiteSpace, VOSviewer, R software, and GraphPad Prism were used for the following scientometric study and visualization analysis, including field profiles, research hotspots, and future predictions.

Results

The total number of publications and citations are 1058 and 54,690, respectively. After polynomial fitting curve analysis, two prediction functions of the annual publication number (y = 3.3909x² - 13585x + 1 E+07) and citation number (185.45x² - 743669x + 7 E+08) were generated. After scientometric analysis, we found that Biochemistry Molecular Biology correlates with Nrf2 in cancer highly, and Free Radical Biology and Medicine is a good choice for submitting Nrf2-related manuscripts. The current research hotspots of Nrf2 in cancer mainly focus on cancer therapy and its cellular and molecular mechanisms. "antioxidant response element (87.5)", "gene expression (43.98)", "antioxidant responsive element (21.14)", "chemoprevention (20.05)", "carcinogenesis (19.2)", "cancer chemoprevention (18.45)", "free radical (17.15)", "response element (14.17)", and "chemopreventive agent (14.04)" are important for cancer therapy study. In addition, "glutathione-S-transferase (47)", "keap1 (15.39)", and "heme oxygenase 1 gene (24.35)" are important for inflammation and cell fate study. More interestingly, by performing an "InfoMap" algorithm, the thematic map showed that the "immune response" is essential to oxidative stress modulator Nrf2 but not well developed, indicating it deserves further exploration.

Conclusion

This study revealed field profiles, research hotspots, and future directions of oxidative stress modulator Nrf2 in inflammation and cancer research, and our findings will offer a vigorous roadmap for further studies in this field.

Drug-induced oxidative stress in cancer treatments: Angel or devil?

Oxidative stress (OS), defined as redox imbalance in favor of oxidant burden, is one of the most significant biological events in cancer progression. Cancer cells generally represent a higher oxidant level, which suggests a dual therapeutic strategy by regulating redox status (i.e., pro-oxidant therapy and/or antioxidant therapy). Indeed, pro-oxidant therapy exhibits a great anti-cancer capability, attributing to a higher oxidant accumulation within cancer cells, whereas antioxidant therapy to restore redox homeostasis has been claimed to fail in several clinical practices. Targeting the redox vulnerability of cancer cells by pro-oxidants capable of generating excessive reactive oxygen species (ROS) has surfaced as an important anti-cancer strategy. However, multiple adverse effects caused by the indiscriminate attacks of uncontrolled drug-induced OS on normal tissues and the drug-tolerant capacity of some certain cancer cells greatly limit their further applications. Herein, we review several representative oxidative anti-cancer drugs and summarize their side effects on normal tissues and organs, emphasizing that seeking a balance between pro-oxidant therapy and oxidative damage is of great value in exploiting next-generation OS-based anti-cancer chemotherapeutics.

Ferroptosis-modulating small molecules for targeting drug-resistant cancer: Challenges and opportunities in manipulating redox signaling

Ferroptosis is an iron-dependent cell death program that is characterized by excessive lipid peroxidation. Triggering ferroptosis has been proposed as a promising strategy to fight cancer and overcome drug resistance in antitumor therapy. Understanding the molecular interactions and structural features of ferroptosis-inducing compounds might therefore open the door to efficient pharmacological strategies against aggressive, metastatic, and therapy-resistant cancer. We here summarize the molecular mechanisms and structural requirements of ferroptosis-inducing small molecules that target central players in ferroptosis. Focus is placed on (i) glutathione peroxidase (GPX) 4, the only GPX isoenzyme that detoxifies complex membrane-bound lipid hydroperoxides, (ii) the cystine/glutamate antiporter system Xc - that is central for glutathione regeneration, (iii) the redox-protective transcription factor nuclear factor erythroid 2-related factor (NRF2), and (iv) GPX4 repression in combination with induced heme degradation via heme oxygenase-1. We deduce common features for efficient ferroptotic activity and highlight challenges in drug development. Moreover, we critically discuss the potential of natural products as ferroptosis-inducing lead structures and provide a comprehensive overview of structurally diverse biogenic and bioinspired small molecules that trigger ferroptosis via iron oxidation, inhibition of the thioredoxin/thioredoxin reductase system or less defined modes of action.

Sulforaphane Inhibits Foam Cell Formation and Atherosclerosis via Mechanisms Involving the Modulation of Macrophage Cholesterol Transport and the Related Phenotype

Sulforaphane (SFN), an isothiocyanate, is one of the major dietary phytochemicals found in cruciferous vegetables. Many studies suggest that SFN can protect against cancer and cardiometabolic diseases. Despite the proposed systemic and local vascular protective mechanisms, SFN's potential to inhibit atherogenesis by targeting macrophages remains unknown. In this study, in high fat diet fed ApoE-deficient (ApoE^-/-) mice, oral SFN treatment improved dyslipidemia and inhibited atherosclerotic plaque formation and the unstable phenotype, as demonstrated by reductions in the lesion areas in both the aortic sinus and whole aorta, percentages of necrotic cores, vascular macrophage infiltration and reactive oxygen species (ROS) generation. In THP-1-derived macrophages, preadministration SFN alleviated oxidized low-density lipoprotein (ox-LDL)-induced lipid accumulation, oxidative stress and mitochondrial injury. Moreover, a functional study revealed that peritoneal macrophages isolated from SFN-treated mice exhibited attenuated cholesterol influx and enhanced apolipoprotein A-I (apoA-I)- and high-density lipoprotein (HDL)-mediated cholesterol efflux. Mechanistic analysis revealed that SFN supplementation induced both intralesional and intraperitoneal macrophage phenotypic switching toward high expression of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and ATP-binding cassette subfamily A/G member 1 (ABCA1/G1) and low expression of peroxisome proliferator-activated receptor γ (PPARγ) and cluster of differentiation 36 (CD36), which was further validated by the aortic protein expression. These results suggest that the regulation of macrophages' cholesterol transport and accumulation may be mainly responsible for SFN's potential atheroprotective properties, and the regulatory mechanisms might involve upregulating ABCA1/G1 and downregulating CD36 via the modulation of PPARγ and Nrf2.

Activation of Nrf2 pathway as a protective mechanism against oxidative stress-induced diseases: Potential of astaxanthin

Astaxanthin, a red-orange liposoluble carotenoid, has been the centre of considerable attention in recent years for its numerous biological activities, notably its potent antioxidant activity. It is reported that astaxanthin elicits these biological activities via a number of cellular pathways. The Nrf2/Keap1 pathway is a major regulator of the antioxidant defence system of cells; it modulates the expression of a plethora of genes related to redox homeostasis as well as cellular detoxification. The pathway has received lots of attention as a prospective therapeutic target for diseases related to oxidative stress and aging. Several reports have shown that the pathway is inducible by many natural compounds. This present work reviews the Nrf2/Keap1 pathway, its regulation and involvement in diseases, provides a brief overview of naturally occurring compounds as activators of the pathway as well as discusses the effect of astaxanthin on the pathway.

Inaugurating a novel adjuvant therapy in urological cancers: Ferroptosis

Ferroptosis, a distinctive form of programmed cell death, is involved in numerous diseases with specific characteristics, including certain cell morphology, functions, biochemistry, and genetics, that differ from other forms of programmed cell death, such as apoptosis. Many studies have explored ferroptosis and its associated mechanisms, drugs, and clinical applications in diseases such as kidney injury, stroke, ischemia-reperfusion injury, and prostate cancer. In this review, we summarize the regulatory mechanisms of some ferroptosis inducers, such as enzalutamide and erastin. These are current research focuses and have already been studied extensively. In summary, this review focuses on the use of ferroptosis induction as a therapeutic strategy for treating tumors of the urinary system.

Antioxidants attenuate mitochondrial oxidative damage through the Nrf2 pathway: A promising therapeutic strategy for stroke

Stroke represents one of the leading causes of disability and death worldwide. Reactive oxygen species overproduction-induced oxidative stress in mitochondria results in mitochondrial DNA damage, mitochondrial autophagy (mitophagy), inflammation, and apoptosis during the pathologic progression of stroke. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator that induces the transcription of a wide range of antioxidant genes to attenuate mitochondrial oxidative stress. Different antioxidative compounds, including polyphenols, mitochondrial antioxidants, triterpenoids, and others, have been shown to be able to activate Nrf2 and, thus, exert neuroprotective effects on stroke by ameliorating mitochondrial oxidative damage. In this review, we briefly discussed the role of mitochondrial oxidative stress in the pathophysiology of stroke and focused on the protective effects of antioxidative compounds through attenuating mitochondrial oxidative damage by activating Nrf2 in stroke. In conclusion, these antioxidants may represent novel therapeutic strategies against stroke.

Decreased autophagosome biogenesis, reduced NRF2, and enhanced ferroptotic cell death are underlying molecular mechanisms of non-alcoholic fatty liver disease

BACKGROUND AND AIMS

Caloric excess and sedentary lifestyles have led to an epidemic of obesity, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD). The objective of this study was to investigate the mechanisms underlying high fat diet (HFD)-induced NAFLD, and to explore NRF2 activation as a strategy to alleviate NAFLD.

APPROACH AND RESULTS

Herein, we demonstrated that high fat diet (HFD) induced lipid peroxidation and ferroptosis, both of which could be alleviated by NRF2 upregulation. Mechanistically, HFD suppressed autophagosome biogenesis through AMPK- and AKT-mediated mTOR activation and decreased ATG7, resulting in KEAP1 stabilization and decreased NRF2 levels in mouse liver. Furthermore, ATG7 is required for HFD-induced NRF2 downregulation, as ATG7 deletion in Cre-inducible ATG7 knockout mice decreased NRF2 levels and enhanced ferroptosis, which was not further exacerbated by HFD. This finding was recapitulated in mouse hepatocytes, which showed a similar phenotype upon treatment with saturated fatty acids (SFAs) but not monounsaturated fatty acids (MUFAs). Finally, NRF2 activation blocked fatty acid (FA)-mediated NRF2 downregulation, lipid peroxidation, and ferroptosis. Importantly, the HFD-induced alterations were also observed in human fatty liver tissue samples.

CONCLUSIONS

HFD-mediated autophagy inhibition, NRF2 suppression, and ferroptosis promotion are important molecular mechanisms of obesity-driven metabolic diseases. NRF2 activation counteracts HFD-mediated NRF2 suppression and ferroptotic cell death. In addition, SFA vs. MUFA regulation of NRF2 may underlie their harmful vs. beneficial effects. Our study reveals NRF2 as a key player in the development and progression of fatty liver disease and that NRF2 activation could serve as a potential therapeutic strategy.

Fermented Angelica sinensis activates Nrf2 signaling and modulates the gut microbiota composition and metabolism to attenuate D-gal induced liver aging

Aging is an inevitable physiological process associated with an imbalance in the oxidative defense system. Angelica sinensis, a kind of traditional Chinese medicine (TCM), has anti-oxidant effects and has been considered as a potential supplement in anti-aging treatment. Nevertheless, it has the disadvantages of slow efficacy and long duration of treatment. Fermentation, as an efficient biotechnological approach, is beneficial for improving the nutritional capacity of the material. Fermented TCMs are considered to be more effective. In this study, fermented Angelica sinensis (FAS) and non-fermented Angelica sinensis (NFAS) were used to investigate changes in the chemical constituents. Furthermore, the improvement effect of FAS on D-galactose-induced aging in mice and the potential mechanisms were explored. The results revealed that FAS and NFAS had different constituents under the influence of fermentation, such as 3-phenyllactic acid, L-5-hydroxytryptophan, taxifolin and methyl gallate. These elevated constituents of FAS might help increase the ability of FAS to improve aging. The aging model was established by intraperitoneal injection of D-galactose (2.5 g kg^-1 day^-1) for 44 days, and FAS (3 g kg^-1 day^-1) was administered daily by oral gavage after 2 weeks of induction with D-galactose. FAS was observed to significantly ameliorate changes associated with liver aging, such as reduction of MDA, AGEs and 8-OHdG. The contents of pro-inflammatory cytokines containing TNF-α, IL-1β and IL-6 were significantly suppressed in the FAS group. In addition, FAS activated Nrf2 signaling better than NFAS, improved the expression of Nrf2, HO-1, NQO1, GCLC, GCLM and GSS, and further increased the activities of SOD, CAT and other antioxidant enzymes in the liver. Simultaneously, it had a certain repair effect on the liver tissues of mice. The intestinal microbiota analysis showed that FAS could regulate the microbiota imbalance caused by aging, increase the ratio of Firmicutes/Bacteroidetes by 95% and improve the relative abundance of beneficial bacteria related to Nrf2 signaling, such as Lactobacillus. Besides, fecal metabolite analysis identified uric acid as an evidential metabolite, suggesting that FAS participates in purine metabolism to improve aging. Therefore, the regulation of intestinal microbiota and metabolism may be one of the important mechanisms of FAS in alleviating hepatic oxidative stress via the gut-liver axis. The results of this study could provide information for the future development of postbiotic products that may have beneficial effects on the prevention or treatment of aging.

The Role of Nrf2 in Relieving Cerebral Ischemia-Reperfusion Injury

Ischemic stroke includes two related pathological damage processes: brain injury caused by primary ischemia and secondary ischemia reperfusion (I/R) injury. I/R injury has become a worldwide health problem. Unfortunately, there is still a lack of satisfactory drugs for ameliorating cerebral I/R damage. Nrf2 is a vital endogenous antioxidant protein, which combines with Keap1 to maintain a dormant state under physiological conditions. When pathological changes such as I/R occurs, Nrf2 dissociates from Keap1 and activates the expression of downstream antioxidant proteins to exert a protective effect. Recent research have shown that the activated Nrf2 not only effectively inhibits oxidative stress, but also performs the ability to repair the function of compromised mitochondria, alleviate endoplasmic reticulum stress, eliminate inflammatory response, reduce blood-brain barrier permeability, inhibit neuronal apoptosis, enhance the neural network remolding, thereby exerting significant protective effects in alleviating the injuries caused by cell oxygen-glucose deprivation, or animal cerebral I/R. However, no definite clinical application report demonstrated the efficacy of Nrf2 activators in the treatment of cerebral I/R. Therefore, further efforts are needed to elaborate the role of Nrf2 activators in the treatment of cerebral I/R. Here, we reviewed the possible mechanisms underlying its potential pharmacological benefits in alleviating cerebral I/R injury, so as to provide a theoretical basis for studying its mechanism and developing Nrf2 activators.

An updated patent review of Nrf2 activators (2020-present)

INTRODUCTION

The nuclear factor erythroid 2-related factor 2 (Nrf2) is a pivotal transcription factor that controls the expression of numerous cytoprotective genes and regulates cellular defense system against oxidative insults. Thus, activating the Nrf2 pathway is a promising strategy for the treatment of various chronic diseases characterized by oxidative stress.

AREAS COVERED

This review first discusses the biological effects of Nrf2 and the regulatory mechanism of Kelch-like ECH-associated protein 1-Nrf2-antioxidant response element (Keap1-Nrf2-ARE) pathway. Then, Nrf2 activators (2020-present) are summarized based on the mechanism of action. The case studies consist of chemical structures, biological activities, structural optimization, and clinical development.

EXPERT OPINION

Extensive efforts have been devoted to developing novel Nrf2 activators with improved potency and drug-like properties. These Nrf2 activators have exhibited beneficial effects in in vitro and in vivo models of oxidative stress-related chronic diseases. However, some specific problems, such as target selectivity and brain blood barrier (BBB) permeability, still need to be addressed in the future.

Astragaloside IV alleviates 1-deoxysphinganine-induced mitochondrial dysfunction during the progression of chronic kidney disease through p62-Nrf2 antioxidant pathway

Introduction: Chronic kidney disease (CKD) can lead to significant elevation of 1-deoxysphingolipids (1-deoxySL). The increase of 1-deoxySL in turn can result in mitochondrial damage and oxidative stress, which can cause further progression of CKD. Methods: This study assessed the therapeutic effect of Astragaloside IV (AST) against 1-deoxySL-induced cytotoxicity in vitro and in rats with CKD. HK-2 cells were exposed to 1-deoxysphinganine (doxSA) or doxSA + AST. doxSA-induced mitochondrial dysfunction and oxidative stress were evaluated by immunostaining, real-time PCR, oxidative stress sensor, and transmission electron microscopy. The potential effects of AST on kidney damage were evaluated in a rat 5/6 nephrectomy (5/6 Nx) model of CKD. Results: The findings of in vitro experiments showed that doxSA induced mitochondrial damage, oxidative stress, and apoptosis. AST markedly reduced the level of mitochondrial reactive oxygen species, lowered apoptosis, and improved mitochondrial function. In addition, exposure to AST significantly induced the phosphorylation of p62 and the nuclear translocation of Nrf2 as well as its downstream anti-oxidant genes. p62 knock-down fully abolished Nrf2 nuclear translocation in cells after AST treatment. However, p62 knock-down did not affect TBHQ-induced Nrf2 nuclear translocation, indicating that AST can ameliorate doxSA-induced oxidative stress through modulation of p62 phosphorylation and Nrf2 nuclear translocation. Conclusion: The findings indicate that AST can activate Nrf2 antioxidant pathway in a p62 dependent manner. The anti-oxidative stress effect and the further mitochondrial protective effect of AST represent a promising therapeutic strategy for the progression of CKD.

A General Signal Pathway to Regulate Multiple Detoxification Genes Drives the Evolution of Helicoverpa armigera Adaptation to Xenobiotics

The study of insect adaptation to the defensive metabolites of host plants and various kinds of insecticides in order to acquire resistance is a hot topic in the pest-control field, but the mechanism is still unclear. In our study, we found that a general signal pathway exists in H. armigera which can regulate multiple P450s, GSTs and UGTs genes to help insects decrease their susceptibility to xenobiotics. Knockdown of HaNrf2 and HaAhR expression could significantly increase the toxicity of xenobiotics to H. armigera, and simultaneously decrease the gene expression of P450s, GSTs and UGTs which are related to the xenobiotic metabolism and synthesis of insect hormone pathways. Then, we used EMSA and dual luciferase assay to verify that a crosstalk exists between AhR and Nrf2 to regulate multiple P450s, GSTs and UGTs genes to mediate H. armigera susceptibility to plant allelochemicals and insecticides. The detoxification genes' expression network which can be regulated by Nrf2 and AhR is still unknown, and there were also no reports about the crosstalk between AhR and Nrf2 that exist in insects and can regulate multiple detoxification genes' expression. Our results provide a new general signaling pathway to reveal the adaptive mechanism of insects to xenobiotics and provides further insight into designing effective pest-management strategies to avoid the overuse of insecticides.

Brusatol sensitizes endometrial hyperplasia and cancer to progestin by suppressing NRF2-TET1-AKR1C1-mediated progestin metabolism

Progestin resistance is the main obstacle for the conservative therapy to maintain fertility in women with endometrial cancer. Brusatol was identified as an inhibitor of the NRF2 pathway; however, its impact on progestin resistance and the underlying mechanism remains unclear. Here, we found that brusatol sensitized endometrial cancer to progestin by suppressing NRF2-TET1-AKR1C1-mediated progestin metabolism. Brusatol transcriptionally suppressed AKR1C1 via modifying the hydroxymethylation status in its promoter region through TET1 inhibition. Suppression of AKR1C1 by brusatol resulted in decreased progesterone catabolism and maintained potent progesterone to inhibit endometrial cancer growth. This inhibition pattern has also been found in the established xenograft mouse and organoid models. Aberrant overexpression of AKR1C1 was found in paired endometrial hyperplasia and cancer samples from the same individuals with progestin resistance, whereas attenuated or loss of AKR1C1 was observed in post-treatment samples with well progestin response as compared with paired pre-treatment tissues. Our findings suggest that AKR1C1 expression pattern may serve as an important biomarker of progestin resistance in endometrial cancer.

Swinhoeic acid from Potentilla fragarioides ameliorates high glucose-induced oxidative stress and accumulation of ECM in mesangial cells via Keap1-dependent activation of Nrf2

OBJECTIVES

Diabetic nephropathy (DN) is one of the most common microvascular complications of diabetes mellitus. Oxidative stress resulting from high glucose promotes accumulation of ECM and development of DN. Activation of Nrf2 could attenuate oxidative stress and following accumulation of ECM. To find novel therapy for DN, we explored the effects of swinhoeic acid from Potentilla fragarioides on mesangial cells under high glucose and underlying mechanisms.

METHODS

CCK-8 and BrdU incorporation assays for survival of mesangial cells gave the concentration of swinhoeic acid in following investigations. ROS, MDA, SOD and CAT were determined. And ECM proteins and their upstream regulators TGF-β₁ and CTGF were detected using ELISA assays. Activation of Nrf2 was explored by immunofluorescence staining together with luciferase reporter assay. To demonstrate the role of Nrf2 activation, siRNA interference was performed. And co-immunoprecipitation assay was used to elucidate swinhoeic acid affects the interaction between Keap1 and Nrf2.

RESULTS

Swinhoeic acid at 10 and 20 μM attenuated oxidative stress and accumulation of ECM in mesangial cells under high glucose. Itactivated Nrf2 in a Keap1-dependent manner, which was involved in its effects.

CONCLUSION

Swinhoeic acid ameliorates oxidative stress and accumulation of ECM resulting from high glucose in mesangial cells via activating Nrf2 in Keap1-dependent manner.

Z-REX uncovers a bifurcation in function of Keap1 paralogs

Studying electrophile signaling is marred by difficulties in parsing changes in pathway flux attributable to on-target, vis-à-vis off-target, modifications. By combining bolus dosing, knockdown, and Z-REX-a tool investigating on-target/on-pathway electrophile signaling, we document that electrophile labeling of one zebrafish-Keap1-paralog (zKeap1b) stimulates Nrf2- driven antioxidant response (AR) signaling (like the human-ortholog). Conversely, zKeap1a is a dominant-negative regulator of electrophile-promoted Nrf2-signaling, and itself is nonpermissive for electrophile-induced Nrf2-upregulation. This behavior is recapitulated in human cells: (1) zKeap1b-expressing cells are permissive for augmented AR-signaling through reduced zKeap1b-Nrf2 binding following whole-cell electrophile treatment; (2) zKeap1a-expressing cells are non-permissive for AR-upregulation, as zKeap1a-Nrf2 binding capacity remains unaltered upon whole-cell electrophile exposure; (3) 1:1 ZKeap1a:zKeap1b-co-expressing cells show no Nrf2-release from the Keap1-complex following whole-cell electrophile administration, rendering these cells unable to upregulate AR. We identified a zKeap1a-specific point-mutation (C273I) responsible for zKeap1a's behavior during electrophilic stress. Human-Keap1(C273I), of known diminished Nrf2-regulatory capacity, dominantly muted electrophile-induced Nrf2-signaling. These studies highlight divergent and interdependent electrophile signaling behaviors, despite conserved electrophile sensing.

Lysionotin Induces Ferroptosis to Suppress Development of Colorectal Cancer via Promoting Nrf2 Degradation

Extensive use of substances derived from natural sources has been documented in the treatment of colorectal cancer (CRC). Lysionotin (Lys) is a flavonoid present in the flowers and leaves of Gesneriaceae family plants. Despite its various pharmacological properties, which include neuroprotective, pro, antimalarial, and anticancer effects, the therapeutic advantages of Lys for CRC remain uncertain. In this present study, we demonstrated that Lys treatment successfully inhibited cell proliferation, migration, and invasion in HCT116 and SW480 CRC cells in vitro. Intriguingly, significant ferroptosis and reactive oxygen species (ROS) accumulation in CRC cells were induced by Lys treatment, whereas antagonism of ferroptosis by Liproxstatin-1 (Lip1) pretreatment retarded the anti-CRC effects of Lys. In addition, Lys reduced the amount of Nrf2 protein in CRC cells by increasing the rate at which it is degraded. Overexpression of Nrf2 rescued Lys reduced ferroptosis, suggesting the Nrf2 signaling is a crucial determinant of whether Lys induces ferroptosis in CRC cells. We also revealed that Lys suppressed tumor growth in vivo without obvious adverse effects on the main organs of mice. In conclusion, our results discovered that Lys treatment induced ferroptosis to exert antitumor effects in HCT116 and SW480 CRC cells by modulating Nrf2 signaling, providing a potential therapeutic approach for the prevention of colorectal cancer.

BACH1-Hemoxygenase-1 axis regulates cellular energetics and survival following sepsis

Sepsis is a complex disease due to dysregulated host response to infection. Oxidative stress and mitochondrial dysfunction leading to metabolic dysregulation are among the hallmarks of sepsis. The transcription factor NRF2 (Nuclear Factor E2-related factor2) is a master regulator of the oxidative stress response, and the NRF2 mediated antioxidant response is negatively regulated by BTB and CNC homology 1 (BACH1) protein. This study tested whether Bach1 deletion improves organ function and survival following polymicrobial sepsis induced by cecal ligation and puncture (CLP). We observed enhanced post-CLP survival in Bach1-/- mice with a concomitantly increased liver HO-1 expression, reduced liver injury and oxidative stress, and attenuated systemic and tissue inflammation. After sepsis induction, the liver mitochondrial function was better preserved in Bach1-/- mice. Furthermore, BACH1 deficiency improved liver and lung blood flow in septic mice, as measured by SPECT/CT. RNA-seq analysis identified 44 genes significantly altered in Bach1-/- mice after sepsis, including HMOX1 and several genes in lipid metabolism. Inhibiting HO-1 activity by Zinc Protoporphyrin-9 worsened organ function in Bach1-/- mice following sepsis. We demonstrate that mitochondrial bioenergetics, organ function, and survival following experimental sepsis were improved in Bach1-/- mice through the HO-1-dependent mechanism and conclude that BACH1 is a therapeutic target in sepsis.

Quercetin Attenuates Quinocetone-Induced Cell Apoptosis In Vitro by Activating the P38/Nrf2/HO-1 Pathway and Inhibiting the ROS/Mitochondrial Apoptotic Pathway

Quinocetone (QCT), a member of the quinoxaline 1,4-di-N-oxides (QdNOs) family, can cause genotoxicity and hepatotoxicity, however, the precise molecular mechanisms of QCT are unclear. This present study investigated the protective effect of quercetin on QCT-induced cytotoxicity and the underlying molecular mechanisms in human L02 and HepG2 cells. The results showed that quercetin treatment (at 7.5–30 μM) significantly improved QCT-induced cytotoxicity and oxidative damage in human L02 and HepG2 cells. Meanwhile, quercetin treatment at 30 μM significantly inhibited QCT-induced loss of mitochondrial membrane potential, an increase in the expression of the CytC protein and the Bax/Bcl-2 ratio, and an increase in caspases-9 and -3 activity, and finally improved cell apoptosis. Quercetin pretreatment promoted the expression of the phosphorylation of p38, Nrf2, and HO-1 proteins. Pharmacological inhibition of p38 significantly inhibited quercetin-mediated activation of the Nrf2/HO-1 pathway. Consistently, pharmacological inhibitions of the Nrf2 or p38 pathways both promoted QCT-induced cytotoxicity and partly abolished the protective effects of quercetin. In conclusion, for the first time, our results reveal that quercetin could improve QCT-induced cytotoxicity and apoptosis by activating the p38/Nrf2/HO-1 pathway and inhibiting the ROS/mitochondrial apoptotic pathway. Our study highlights that quercetin may be a promising candidate for preventing QdNOs-induced cytotoxicity in humans or animals.

The Emerging Role of Immune Cells and Targeted Therapeutic Strategies in Diabetic Wounds Healing

Poor wound healing in individuals with diabetes has long plagued clinicians, and immune cells play key roles in the inflammation, proliferation and remodeling that occur in wound healing. When skin integrity is damaged, immune cells migrate to the wound bed through the actions of chemokines and jointly restore tissue homeostasis and barrier function by exerting their respective biological functions. An imbalance of immune cells often leads to ineffective and disordered inflammatory responses. Due to the maladjusted microenvironment, the wound is unable to smoothly transition to the proliferation and remodeling stage, causing it to develop into a chronic refractory wound. However, chronic refractory wounds consistently lead to negative outcomes, such as long treatment cycles, high hospitalization rates, high medical costs, high disability rates, high mortality rates, and many adverse consequences. Therefore, strategies that promote the rational distribution and coordinated development of immune cells during wound healing are very important for the treatment of diabetic wounds (DW). Here, we explored the following aspects by performing a literature review: 1) the current situation of DW and an introduction to the biological functions of immune cells; 2) the role of immune cells in DW; and 3) existing (or undeveloped) therapies targeting immune cells to promote wound healing to provide new ideas for basic research, clinical treatment and nursing of DW.

Maackiain protects against sepsis via activating AMPK/Nrf2/HO-1 pathway

Sepsis is a life-threatening medical condition caused by infection-triggered aberrant immune responses, leading to host tissue and organ injury. Despite advances in medical interventions, the mortality rate for septic shock remains high. Recent studies highlight the role of oxidative stress in the occurrence and development of sepsis, providing a potential therapeutic target for preventing sepsis-associated organ injury. In this study, we showed that Maackiain, a natural compound isolated from Sophora flavescens, exerted a protective role in a cecal ligation and puncture (CLP)-induced murine model of sepsis. Maackiain treatment reduced organ injury, and mitigated systematic inflammation and oxidative stress in septic mice. Maackiain also reduced the levels of inflammatory cytokines and reactive oxygen species (ROS) in RAW264.7 macrophage cells stimulated with lipopolysaccharide (LPS). We further demonstrated that Maackiain initiated activation of nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway in RAW264.7 cells in an AMP-activated protein kinase (AMPK)-dependent way. Moreover, inhibition of AMPK/Nrf2 axis abrogated the anti-inflammatory and anti-oxidant effects of Maackiain both in vitro and in vivo. Collectively, our study indicates that Maackiain treatment inhibits inflammatory response and oxidative stress via activation of AMPK/Nrf2/HO-1 pathway, thus exerting a protective effect against sepsis, providing an alternative option for sepsis prevention.

Naringin alleviates acetaminophen-induced acute liver injury by activating Nrf2 via CHAC2 upregulation

Severe acetaminophen (APAP)-induced hepatic damage is the second most common cause for hepatic transplantation. Clinically, hepatic damage caused by APAP is treated using N-acetyl-L-cysteine, which can induce numerous side effects. Naringin, a bioflavonoid abundant in grapefruit and other citrus fruits, displays marked antiinflammatory and antioxidant activities. Herein, we aimed to investigate the potential mechanism underlying naringin-mediated protection against APAP-induced acute hepatotoxicity. We observed that naringin afforded protection against APAP-induced acute liver failure in mice. Importantly, pretreatment with naringin before APAP administration further increased antioxidant enzyme expression, inhibited the production of proinflammatory cytokines, and activated apoptotic pathways. Furthermore, we observed that the protective effect was associated with the upregulation of cation transport regulator-like protein 2 (CHAC2) and nuclear factor erythroid derived-2-related factor 2 (Nrf2). Notably, CHAC2 knockdown inhibited Nrf2 activation and naringin-mediated antioxidant, antiinflammatory, and antiapoptotic effects in APAP-induced liver injury. Likewise, si-Nrf2 blocked the protective effect of naringin against APAP-induced liver injury. Collectively, our results indicate that naringin may be a potent CHAC2 activator, alleviating APAP-induced hepatitis via CHAC2-mediated activation of the Nrf2 pathway. These data provide new insights into mechanisms through which CHAC2 regulates APAP-induced liver injury by targeting Nrf2, which should be considered a novel therapeutic target.

Stretch Causes Cell Stress and the Downregulation of Nrf2 in Primary Amnion Cells

Nuclear-factor-E2-related factor 2 (Nrf2) is a key transcription factor for the regulation of cellular responses to cellular stress and inflammation, and its expression is significantly lower after spontaneous term labor in human fetal membranes. Pathological induction of inflammation can lead to adverse pregnancy outcomes such as pre-eclampsia, preterm labor, and fetal death. As stretch forces are known to act upon the fetal membranes in utero, we aimed to ascertain the effect of stretch on Nrf2 to increase our understanding of the role of this stimulus on cells of the amnion at term. Our results indicated a significant reduction in Nrf2 expression in stretched isolated human amnion epithelial cells (hAECs) that could be rescued with sulforaphane treatment. Downregulation of Nrf2 as a result of stretch was accompanied with activation of proinflammatory nuclear factor-kB (NF-kB) and increases in LDH activity, ROS, and HMGB1. This work supports stretch as a key modulator of cellular stress and inflammation in the fetal membranes. Our results showed that the modulation of the antioxidant response pathway in the fetal membranes through Nrf2 activation may be a viable approach to improve outcomes in pregnancy.

Dietary Phytochemicals Targeting Nrf2 to Enhance the Radiosensitivity of Cancer

Nowadays, cancer has become the second leading cause of death worldwide. Radiotherapy (RT) is the mainstay in management of carcinoma; however, overcoming radioresistance remains a great challenge to successfully treat cancer. Nrf2 is a key transcription factor that is responsible for maintaining cellular redox homeostasis. Activation of Nrf2 signaling pathway could upregulate multifarious antioxidant and detoxifying enzymes, further scavenging excessive reactive oxygen species (ROS). Despite its cytoprotective roles in normal cells, it could also alleviate oxidative stress and DNA damage caused by RT in cancer cells, thus promoting cancer cell survival. Accumulating evidence indicates that overactivation of Nrf2 is associated with radioresistance; therefore, targeting Nrf2 is a promising strategy to enhance radiosensitivity. Dietary phytochemicals coming from natural products are characterized by low cost, low toxicity, and general availability. Numerous phytochemicals are reported to regulate Nrf2 and intensify the killing capability of RT through diverse mechanisms, including promoting oxidative stress, proapoptosis, and proautophagy as well as inhibiting Nrf2-mediated cytoprotective genes expression. This review summarizes recent advances in radiosensitizing effects of dietary phytochemicals by targeting Nrf2 and discusses the underlying mechanisms, including N6-methyladenosine (m6A) modification of Nrf2 mediated by phytochemicals in cancer.

Anti-Inflammatory Activity of Monosubstituted Xestoquinone Analogues from the Marine Sponge Neopetrosia compacta

Chronic inflammation is recognized as a contributor to multiple chronic diseases, such as cancer, cardiovascular, and autoimmune disorders. Here, a natural products-initiated discovery of anti-inflammatory agents from marine sponges was undertaken. From the screening of 231 crude extracts, a total of 30 extracts showed anti-inflammatory activity with no direct cytotoxic effects at 50 μg/mL on RAW 264.7 (ATCC®TIB-71™) murine macrophage cells stimulated with 1 μg/mL lipopolysaccharide (LPS). Bioactivity-guided purification of the anti-inflammatory extract from the sponge Neopetrosia compacta led to the isolation of xestoquinone (1), adociaquinone B (2), adociaquinone A (3), 14-hydroxymethylxestoquinone (4), 15-hydroxymethylxestoquinone (5), and an inseparable 2:1 mixture of 14-methoxyxestoquinone and 15-methoxyxestoquinone (6). Compounds 1–6 caused a concentration-dependent reduction of nitric oxide (NO) production in LPS-stimulated RAW 264.7 cells, with 4–6 having low micromolar IC50 and acceptable selectivity index. Gene expression analysis using qRT-PCR showed that 1, 5, and 6 downregulated Il1b and Nos2 expression by 2.1- to 14.8-fold relative to the solvent control at 10 μM. Xestoquinone (1) and monosubstituted analogues (4–6), but not the disubstituted adociaquinones (2 and 3), caused Nrf2 activation in a luciferase reporter MCF7 stable cells. Compounds 5 and 6 caused a modest increase in Nqo1 gene expression at 10 μM. The anti-inflammatory activity of xestoquinone (1) and monosubstituted analogues (4–6) may, in part, be mediated by Nrf2 activation, leading to attenuation of inflammatory mediators such as IL-1β and NOS2.