Molecular and chemical regulation of the Keap1-Nrf2 signaling pathway

Effect of long-term dietary supplementation with Bacillus subtilis in pigs on meat color and oxidative stability under high‑oxygen packaging

This study aimed to investigate the effects of dietary Bacillus subtilis (B. subtilis) supplementation in pigs on the meat color and oxidative stability of the meat under high‑oxygen packaging. The results showed B. subtilis increased redness (a*) (P < 0.05), accompanied by inhibiting the formation of metmyoglobin (MetMb) of pork, and maintained better meat color during storage. Compared to the control group, dietary B. subtilis supplementation increased the R630/580 value, metmyoglobin-reducing activity (MRA) and the oxygen consumption rate (OCR) of pork (P < 0.05), and the pork had better meat color stability. B. subtilis supplementation also upregulated the expression of Nrf2 and downstream antioxidant enzyme genes (SOD, CAT, and GSH-Px) in the Nrf2-Keap1 signaling pathway and downregulated the expression of the Keap1 (P < 0.05). The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and catalase (CAT) in longissimus thoracis et lumborum (LTL) muscle were increased by B. subtilis while the levels of lipid and protein oxidation were decreased (P < 0.05). All results confirmed that dietary B. subtilis supplementation could effectively maintain the meat color and delay the oxidation of chilled pork compared to the control.

Periplaneta americana Extract Protects Glutamate-Induced Nerve Cell Damage by Inhibiting N-Methyl-D-Aspartate Receptor Activation

Neurocytotoxicity elicited by N-methyl-D-aspartate receptors (NMDAR) is a substantial contributor to neurodegenerative diseases. Our current study expands on the previous findings in which Periplaneta americana (L.) extract (PAS840) was shown to protect PC12 cells from hydrogen peroxide-induced injury. In this investigation, we performed LC-MS/MS and peptidomics analyses on the constituents of PAS840. Considering Alzheimer's disease (AD) as the primary focus, we utilized network pharmacology and molecular-docking techniques to predict PAS840's influence on AD targets. We established a glutamate (Glu)-induced PC12 cell injury model to conduct a comprehensive examination of PAS840's effects on pivotal cellular parameters, including intracellular Ca2+ levels, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, reactive oxygen species (ROS) levels, cell apoptosis rate, mitochondrial membrane potential (MMP) levels, and the expression of key proteins such as NMDAR1, cytochrome c (Cytc), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). The results suggest that PAS840 manifests multi-target actions, robustly attenuating NMDAR activity. It efficaciously suppresses excessive NMDAR1 activation, restricts Ca2+ influx, alleviates oxidative stress, and mitigates inflammation, thereby ameliorating neuronal cell damage. Consequently, it establishes a solid scientific foundation for further exploration of PAS840's potential in addressing neurological diseases.

Vericiguat improves cardiac remodelling and function in rats with doxorubicin-induced cardiomyopathy

PURPOSE

Vericiguat, a soluble guanylate cyclase (sGC) stimulator, has been demonstrated effective in improving prognosis of patients with heart failure with reduced ejection fraction. However, there are limited data concerning the effect of vericiguat in patients with doxorubicin (DOX)-induced cardiomyopathy (DIC). In this study, we investigated the effects of vericiguat on cardiac structure and function in rats with DIC as well as their potential mechanisms of action.

METHODS

DIC rats were established by intraperitoneal injection of DOX (1 mg/kg) twice a week for 6 weeks, followed by intragastric administration of vericiguat 1 mg/kg/day or an equal volume of normal saline for 8 weeks. Cardiac histology and function, circulating levels of amino-terminal pro-B-type natriuretic peptide (NT-proBNP), nitric oxide (NO), and oxidative indices, as well as myocardial cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) signalling, oxidative and apoptosis-associated protein were measured.

RESULTS

Compared with the control group, rats treated with DOX exhibited significantly increased heart size, reduced systolic function and elevated plasma levels of NT-proBNP. Histological findings revealed myocardial cell atrophy, fibrosis and apoptosis. Vericiguat treatment effectively reversed DOX-induced cardiac remodelling and improved systolic function. Mechanistically, Vericiguat attenuated the inhibitory effects of DOX on the myocardial cGMP-PKG axis and nuclear factor erythroid 2-related factor 2 (Nrf2) protein, thereby alleviating oxidative stress and apoptosis.

CONCLUSIONS

Vericiguat improved cardiac remodelling and contractile function in rats with DIC through upregulation of cGMP-PKG signalling and inhibition of oxidative stress and myocardial apoptosis.

Irisin-mediated KEAP1 degradation alleviates oxidative stress and ameliorates pancreatitis

Oxidative stress (OS) injury is pivotal in acute pancreatitis (AP) pathogenesis, contributing to inflammatory cascades. Irisin, a ubiquitous cytokine, exhibits antioxidant properties. However, the role of irisin in AP remains inconclusive. Our study aims to elucidate irisin expression in AP patients and investigate its mechanism of action to propose a novel treatment strategy for AP. Serum irisin levels in 65 AP patients were quantified using an enzyme-linked immunosorbent assay and correlated with disease severity scores. Core genes implicated in AP-related oxidative stress were identified and screened via bioinformatics analysis. The therapeutic efficacy of irisin in AP was confirmed using a murine cerulein-induced AP model. The intrinsic mechanism of irisin's antioxidative stress action was investigated and verified in pancreatic AR42J cells (Supplementary Fig. 1). Common targets shared by irisin and AP were further validated using a molecular docking model which was constructed for virtual docking analysis. This study investigated alterations in redox status in AP and found a significant reduction in serum irisin levels, correlating inversely with AP severity. In a murine AP model, we showed that irisin triggers an antioxidative stress program via the KEAP1 gene; this process helps reestablish redox balance by decreasing the buildup of reactive oxygen species (ROS) and suppressing the secretion of inflammatory mediators within pancreatic tissues Notably, increased KEAP1 expression counteracted the antioxidative effects of irisin. Our findings unveil a novel therapeutic mechanism for AP, wherein irisin inhibits KEAP1 to alleviate OS. Increasing irisin levels in vivo presents a promising strategy for AP treatment.

Unveiling the Complexities: Exploring Mechanisms of Anthracyclineinduced Cardiotoxicity

The coexistence of cancer and heart disease, both prominent causes of illness and death, is further exacerbated by the detrimental impact of chemotherapy. Anthracycline-induced cardiotoxicity is an unfortunate side effect of highly effective therapy in treating different types of cancer; it presents a significant challenge for both clinicians and patients due to the considerable risk of cardiotoxicity. Despite significant progress in understanding these mechanisms, challenges persist in identifying effective preventive and therapeutic strategies, rendering it a subject of continued research even after three decades of intensive global investigation. The molecular targets and signaling pathways explored provide insights for developing targeted therapies, emphasizing the need for continued research to bridge the gap between preclinical understanding and clinical applications. This review provides a comprehensive exploration of the intricate mechanisms underlying anthracycline-induced cardiotoxicity, elucidating the interplay of various signaling pathways leading to adverse cellular events, including cardiotoxicity and death. It highlights the extensive involvement of pathways associated with oxidative stress, inflammation, apoptosis, and cellular stress responses, offering insights into potential and unexplored targets for therapeutic intervention in mitigating anthracycline-induced cardiac complications. A comprehensive understanding of the interplay between anthracyclines and these complexes signaling pathways is crucial for developing strategies to prevent or mitigate the associated cardiotoxicity. Further research is needed to outline the specific contributions of these pathways and identify potential therapeutic targets to improve the safety and efficacy of anthracycline-based cancer treatment. Ultimately, advancements in understanding anthracycline-induced cardiotoxicity mechanisms will facilitate the development of more efficacious preventive and treatment approaches, thereby improving outcomes for cancer patients undergoing anthracycline-based chemotherapy.

Genetic and Functional Changes in Mitochondria in the Pituitary Adenoma: The Pathogenesis and Its Therapy

Pituitary adenoma is a common neoplasm of the pituitary gland. Although most pituitary adenomas are benign, they can pose significant challenges in terms of their consequences and prognosis due to their tendency to invade surrounding tissues and their effects on hormone secretion. The management of pituitary adenomas typically involves surgery, medical therapy, and radiotherapy, each of which has its own limitations. Mitochondria play a crucial role in tumor development and progression by regulating various metabolic processes and signaling pathways within tumor cells and the tumor microenvironment. Multiple studies have indicated that mitochondrial dysfunction is implicated in human pituitary adenomas. Furthermore, several compounds with therapeutic effects on pituitary adenomas have been reported to target mitochondrial function. In this review, we summarize recent studies that highlight the involvement of mitochondrial homeostasis imbalance in the biology of pituitary adenomas. We conclude that mitochondria may represent a promising therapeutic target for the treatment of pituitary adenomas.

Human umbilical cord mesenchymal stem cells protect MC3T3-E1 osteoblasts from dexamethasone-induced apoptosis via induction of the Nrf2-ARE signaling pathway

Objective

To investigate the protective effect human umbilical cord mesenchymal stem cells (hUC-MSCs) have on Dexamethasone (Dex)-induced apoptosis in osteogenesis via the Nrf2-ARE signaling pathway.

Methods

Glucocorticoid-induced osteonecrosis of the femoral head (GC-ONFH) was developed in rats through the administration of lipopolysaccharide and methylprednisolone. The incidence of femoral head necrosis, cavity notch, apoptosis of osteoblasts, and bone density were observed by HE staining, TUNEL staining, and Micro-CT. HUC-MSCs were co-cultured with mouse pre-osteoblast MC3T3-E1. The survival rate of osteoblasts was determined by CCK8, and apoptosis and ROS levels of osteoblasts were determined by flow cytometer. The viability of antioxidant enzymes SOD, GSH-Px, and CAT was analyzed by biochemistry. Nrf2 expression levels and those of its downstream proteins and apoptosis-related proteins were analyzed by Western blotting.

Results

In rats, hUC-MSCs can reduce the rates of empty bone lacuna and osteoblast apoptosis that are induced by glucocorticoids (GCs), while reducing the incidence of GC-ONFH. hUC-MSCs can significantly improve the survival rate and antioxidant SOD, GSH-Px, and CAT activity of MC3T3-E1 cells caused by Dex, and inhibit apoptosis and oxidative stress levels. In addition, hUC-MSCs can up-regulate the expression of osteoblast antioxidant protein Nrf2 and its downstream protein HO-1, NQO-1, GCLC, GCLM, and apoptosis-related protein bcl-2, while also down-regulating the expression of apoptosis-related protein bax, cleaved caspase-3, cleaved caspase-9, and cytochrome C in MC3T3-E1 cells. hUC-MSCs improve the ability of MC3T3-E1 cells to mineralize to osteogenesis. However, the promoting effects of hUC-MSCs were abolished following the blocking of the Nrf2-ARE signaling pathway for osteoblasts.

Conclusion

The results reveal that hUC-MSCs can reduce Dex-induced apoptosis in osteoblasts via the Nrf2-ARE signaling pathway.

Melittin - the main component of bee venom: a promising therapeutic agent for neuroprotection through keap1/Nrf2/HO-1 pathway activation

The Nuclear factor erythroid 2-related factor (Nrf2)/ Heme oxygenase-1 (HO-1) pathway, known for its significant role in regulating innate antioxidant defense mechanisms, is increasingly being recognized for its potential in neuroprotection studies. Derived from bee venom, melittin's neuroprotective effects have raised interest. This study confirmed that melittin specificity upregulated the weakened Nrf2/HO-1 signaling in mice brain. Interestingly, we also revealed melittin's efficient tactic, as it was suggested to first restore redox balance and then gradually stabilized other regulations of the mouse hippocampus. Using a neuro-stress-induced scopolamine model, chromatography and mass spectrometry analysis revealed that melittin crossed the compromised blood-brain barrier and accumulated in the hippocampus, which provided the chance to interact directly to weakened neurons. A wide range of improvements of melittin action were observed from various tests from behavior Morris water maze, Y maze test to immune florescent staining, western blots. As we need to find out what is the focus of melittin action, we conducted a careful observation in mice which showed that: the first signs of changes, in the hippocampus, within 5 h after melittin administration were the restoration of the Nrf2/HO-1 system and suppression of oxidative stress. After this event, from 7 to 12.5 h after administration, a diversity of conditions was all ameliorated: inflammation, apoptosis, neurotrophic factors, cholinergic function, and tissue ATP level. This chain reaction underscores that melittin focus was on redox balance's role, which revived multiple neuronal functions. Evidence of enhancement in the mouse hippocampus led to further exploration with hippocampal cell line HT22 model. Immunofluorescence analysis showed melittin-induced Nrf2 translocation to the nucleus, which would initiating the translation of antioxidant genes like HO-1. Pathway inhibitors pinpointed melittin's direct influence on the Nrf2/HO-1 pathway. 3D docking models and pull-down assays suggested melittin's direct interaction with Keap1, the regulator of the Nrf2/HO-1 pathway. Overall, this study not only highlighted melittin specifically effect on Nrf2/HO-1, thus rebalancing cellular redox, and also showed that this is an effective multi-faceted therapeutic strategy against neurodegeneration.

Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling in heavy metals-induced oxidative stress

Organisms encounter reactive oxidants through intrinsic metabolism and environmental exposure to toxicants. Reactive oxygen and nitrogen species (ROS, RNS) are generally considered detrimental because they induce oxidative stress. In order to combat oxidative stress, a potential modulator of cellular defense nuclear factor erythroid 2-related factor 2 (Nrf2) and its endogenous inhibitor Kelch-like ECH-associated protein 1 (Keap1) operate as a common, genetically preserved intrinsic defense system. There has been a significant increase in the amount of harmful metalloids and metals that individuals are exposed to through their food, water, and air, primarily due to human activities. Many studies have looked at the connection between the emergence of different ailments in humans and ecological exposure to metalloids, i.e., arsenic (As) and metals viz., chromium (Cr), mercury (Hg), cadmium (Cd), cobalt (Co), and lead (Pb). It is known that they can produce ROS in several organs by both direct and indirect means. Studies suggest that Nrf2 signaling is a crucial mechanism in maintaining antioxidant balance and can have two roles, depending on the particular biological setting. From one perspective, Nrf2 is an essential defense mechanism against metal-induced toxicity. Still, it may also operate as a catalyst for metal-induced carcinogenesis in situations involving protracted exposure and persistent activation. Therefore, this review aims to provide an overview of the antioxidant defense mechanism of Nrf2-Keap1 signaling and the interrelation between Nrf2 signaling and the toxic elements.

Regulation of Keap1-Nrf2 signaling in health and diseases

Nuclear factor erythroid 2-related factor 2 (Nrf2) functions as a central regulator in modulating the activities of diverse antioxidant enzymes, maintaining cellular redox balance, and responding to oxidative stress (OS). Kelch-like ECH-associated protein 1 (Keap1) serves as a principal negative modulator in controlling the expression of detoxification and antioxidant genes. It is widely accepted that OS plays a pivotal role in the pathogenesis of various diseases. When OS occurs, leading to inflammatory infiltration of neutrophils, increased secretion of proteases, and the generation of large quantities of reactive oxygen radicals (ROS). These ROS can oxidize or disrupt DNA, lipids, and proteins either directly or indirectly. They also cause gene mutations, lipid peroxidation, and protein denaturation, all of which can result in disease. The Keap1-Nrf2 signaling pathway regulates the balance between oxidants and antioxidants in vivo, maintains the stability of the intracellular environment, and promotes cell growth and repair. However, the antioxidant properties of the Keap1-Nrf2 signaling pathway are reduced in disease. This review overviews the mechanisms of OS generation, the biological properties of Keap1-Nrf2, and the regulatory role of its pathway in health and disease, to explore therapeutic strategies for the Keap1-Nrf2 signaling pathway in different diseases.

A novel crosstalk between Nrf2 and Smad2/3 bridged by two nuanced Keap1 isoforms with their divergent effects on these distinct family transcription factors

The Keap1-Nrf2 signalling to transcriptionally regulate antioxidant response element (ARE)-driven target genes has been accepted as key redox-sensitive pathway governing a vast variety of cellular stresses during healthy survival and disease development. Herein, we identified two nuanced isoforms α and β of Keap1 in HepG2 cells, arising from its first and another in-frame translation starting codons, respectively. In identifying those differential expression genes monitored by Keap1α and/or Keap1β, an unusual interaction of Keap1 with Smad2/3 was discovered by parsing transcriptome sequencing, Keap1-interacting protein profiling and relevant immunoprecipitation data. Further examination validated that Smad2/3 enable physical interaction with Keap1, as well as its isoforms α and β, by both EDGETSD and DLG motifs in the linker regions between their MH1 and MH2 domains, such that the stability of Smad2/3 and transcriptional activity are enhanced with their prolonged half-lives and relevant signalling responses from the cytoplasmic to nuclear compartments. The activation of Smad2/3 by Keap1, Keap1α or Keap1β was much likely contributable to a coordinative or another competitive effect of Nrf2, particularly in distinct Keap1-based cellular responses to its cognate growth factor (i.e. TGF-β1) or redox stress (e.g. stimulated by tBHQ and DTT). Overall, this discovery presents a novel functional bridge crossing the Keap1-Nrf2 redox signalling and the TGF-β1-Smad2/3 pathways so as to coordinately regulate the healthy growth and development.

Redox Homeostasis and Nrf2-Regulated Mechanisms Are Relevant to Male Infertility

Infertility represents a significant global health challenge, affecting more than 12% of couples worldwide, and most cases of infertility are caused by male factors. Several pathological pathways are implicated in male infertility. The main mechanisms involved are driven by the loss of reduction-oxidation (redox) homeostasis and the resulting oxidative damage as well as the chronic inflammatory process. Increased or severe oxidative stress leads to sperm plasma membrane and DNA oxidative damage, dysregulated RNA processing, and telomere destruction. The signaling pathways of these molecular events are also regulated by Nuclear factor-E2-related factor 2 (Nrf2). The causes of male infertility, the role of oxidative stress in male infertility and the Keap1-Nrf2 antioxidant pathway are reviewed. This review highlights the regulatory role of Nrf2 in the balance between oxidants and antioxidants as relevant mechanisms to male fertility. Nrf2 is involved in the regulation of spermatogenesis and sperm quality. Establishing a link between Nrf2 signaling pathways and the regulation of male fertility provides the basis for molecular modulation of inflammatory processes, reactive oxygen species generation, and the antioxidant molecular network, including the Nrf2-regulated antioxidant response, to improve male reproductive outcomes.

Post-translational modifications of Keap1: the state of the art

The Keap1-Nrf2 signaling pathway plays a crucial role in cellular defense against oxidative stress-induced damage. Its activation entails the expression and transcriptional regulation of several proteins involved in detoxification and antioxidation processes within the organism. Keap1, serving as a pivotal transcriptional regulator within this pathway, exerts control over the activity of Nrf2. Various post-translational modifications (PTMs) of Keap1, such as alkylation, glycosylation, glutathiylation, S-sulfhydration, and other modifications, impact the binding affinity between Keap1 and Nrf2. Consequently, this leads to the accumulation of Nrf2 and its translocation to the nucleus, and subsequent activation of downstream antioxidant genes. Given the association between the Keap1-Nrf2 signaling pathway and various diseases such as cancer, neurodegenerative disorders, and diabetes, comprehending the post-translational modification of Keap1 not only deepens our understanding of Nrf2 signaling regulation but also contributes to the identification of novel drug targets and biomarkers. Consequently, this knowledge holds immense importance in the prevention and treatment of diseases induced by oxidative stress.

A redox-based characterization of human immune cell subsets by polychromatic flow cytometry

Cellular redox state determinants are traditionally studied using fluorescent microscopy and immunoblot analysis; however, no procedure has been developed for simultaneous measurement in various immune cell subsets. Here, we present a flow cytometry assay for measuring antioxidant defense systems and reactive oxygen species simultaneously in T, B, and natural killer lymphocytes. We describe steps for preparing and treating peripheral blood mononuclear cells, surface and dye staining, cell fixation/permeabilization, and intracellular staining. We then detail machine standardization, acquisition, and analysis.

Intramuscular vitamin A injection in newborn lambs enhances antioxidant capacity and improves meat quality

Introduction

Vitamin A (VA) and its metabolite, retinoic acid (RA) possess several biological functions. This report investigated whether neonatal intramuscular VA injection affected antioxidative activity and meat quality in longissimus dorsi (LD) muscle of lambs.

Methods

Lambs were injected with 0 (control) or 7,500 IU VA palmitate into the biceps femoris muscle on day 2 after birth. At 3, 12, and 32 weeks of age, blood samples were collected in the jugular vein for serum levels of RA and muscle samples were collected in the biceps femoris for analysis of relative mRNA expression of enzyme contributors to retinoid metabolism. All animals were harvested at 32 weeks of age and muscle samples were collected to explore the role of VA on the meat quality and antioxidant capacity of lambs.

Results and discussion

Our results indicated that VA increased the redness, crude protein, and crude fat (p < 0.05), without affecting moisture, ash, and amino acid composition in LD muscle (p > 0.05). In addition, VA increased catalase (CAT) activity and decreased malondialdehyde (MDA) levels in LD muscle (p < 0.05). Meanwhile, greater levels of CAT and NRF2 mRNA and protein contents with VA treatment were observed in LD muscle (p < 0.05), partly explained by the increased level of RA (p < 0.05). Collectively, our findings indicated that VA injection at birth could improve lamb meat quality by elevating the redness, crude protein, crude fat, and antioxidative capacity in LD muscle of lambs.

Enhancement of porcine in vitro embryonic development through luteolin-mediated activation of the Nrf2/Keap1 signaling pathway

BACKGROUND

Oxidative stress, caused by an imbalance in the production and elimination of intracellular reactive oxygen species (ROS), has been recognized for its detrimental effects on mammalian embryonic development. Luteolin (Lut) has been documented for its protective effects against oxidative stress in various studies. However, its specific role in embryonic development remains unexplored. This study aims to investigate the influence of Lut on porcine embryonic development and to elucidate the underlying mechanism.

RESULTS

After undergoing parthenogenetic activation (PA) or in vitro fertilization, embryos supplemented with 0.5 µmol/L Lut displayed a significant enhancement in cleavage and blastocyst formation rates, with an increase in total cell numbers and a decrease in the apoptosis rate compared to the control. Measurements on D2 and D6 revealed that embryos with Lut supplementation had lower ROS levels and higher glutathione levels compared to the control. Moreover, Lut supplementation significantly augmented mitochondrial content and membrane potential. Intriguingly, activation of the Nrf2/Keap1 signaling pathway was observed in embryos supplemented with Lut, leading to the upregulation of antioxidant-related gene transcription levels. To further validate the relationship between the Nrf2/Keap1 signaling pathway and effects of Lut in porcine embryonic development, we cultured PA embryos in a medium supplemented with brusatol, with or without the inclusion of Lut. The positive effects of Lut on developmental competence were negated by brusatol treatment.

CONCLUSIONS

Our findings indicate that Lut-mediated activation of the Nrf2/Keap1 signaling pathway contributes to the enhanced production of porcine embryos with high developmental competence, and offers insight into the mechanisms regulating early embryonic development.

Oxidative stress in pituitary neuroendocrine tumors: Affecting the tumor microenvironment and becoming a new target for pituitary neuroendocrine tumor therapy

Pituitary adenomas (PAs), or pituitary neuroendocrine tumors (PitNETs), are commonly found in the anterior pituitary gland. Although the majority of PitNETs are benign and stable, several tumors have malignant characteristics. The tumor microenvironment (TME) plays an important role in the process of tumorigenesis and is composed of several types of cells. Various cells in the TME are significantly affected by oxidative stress. It has been reported that immunotherapeutic strategies have good effects in several cancers. However, the clinical potential of immunotherapies in PitNETs has not yet been fully discussed. Oxidative stress can regulate PitNET cells and immune cells in the TME, thus affecting the immune status of the TME of PitNETs. Therefore, modulation of oxidative stress-regulated immune cells using a combination of several agents and the immune system to suppress PitNETs is a promising therapeutic direction. In this review, we systematically analyzed the oxidative stress process within PitNET cells and various immune cells to elucidate the potential value of immunotherapy.

Sodium butyrate enhances titanium nail osseointegration in ovariectomized rats by inhibiting the PKCα/NOX4/ROS/NF-κB pathways

BACKGROUND

Elevated levels of oxidative stress as a consequence of estrogen deficiency serve as a key driver of the onset of osteoporosis (OP). In addition to increasing the risk of bone fractures, OP can reduce the bone volume proximal to titanium nails implanted to treat these osteoporotic fractures, thereby contributing to titanium nail loosening. Sodium butyrate (NaB) is a short-chain fatty acid produced by members of the gut microbiota that exhibits robust antioxidant and anti-inflammatory properties.

METHODS

OP fracture model rats parameters including bone mineral density (BMD), new bone formation, and the number of bonelets around the implanted nail were analyzed via micro-CT scans, H&E staining, and Masson's staining. The protective effects of NaB on such osseointegration and the underlying mechanisms were further studied in vitro using MC3T3-E1 cells treated with carbonyl cyanide m-chlorophenylhydrazone (CCCP) to induce oxidative stress. Techniques including Western immunoblotting, electron microscopy, flow cytometry, alkaline phosphatase (ALP) staining, and osteoblast mineralization assays were employed to probe behaviors such as reactive oxygen species production, mineralization activity, ALP activity, protein expression, and the ability of cells to attach to and survive on titanium plates.

RESULTS

NaB treatment was found to enhance ALP activity, mineralization capacity, and Coll-I, BMP2, and OCN expression levels in CCCP-treated MC3T3-E1 cells, while also suppressing PKC and NF-κB expression and enhancing Nrf2 and HO-1 expression in these cells. NaB further suppressed intracellular ROS production and malondialdehyde levels within the cytosol while enhancing superoxide dismutase activity and lowering the apoptotic death rate. In line with these results, in vivo work revealed an increase in BMD in NaB-treated rats that was associated with enhanced bone formation surrounding titanium nails.

CONCLUSION

These findings indicate that NaB may represent a valuable compound that can be postoperatively administered to aid in treating OP fractures through the enhancement of titanium nail osseointegration.

Impaired NRF2 Inhibits Recovery from Ischemic Reperfusion Injury in the Aging Kidney

Deteriorating kidney function is frequently observed in the elderly population, as well as vulnerability to acute kidney failure, such as ischemic/reperfusion injury (IRI), and inadequate recovery from IRI is one of the mechanisms of kidney dysfunction in the elderly. The potential mediators in the progression of kidney dysfunction in the aging kidney have not yet been clearly revealed. In this study, we investigated the role of nuclear factor erythroid 2-related factor 2 (NRF2), which is an essential regulator of cellular redox homeostasis, in restoring kidney function after IRI in the aging kidney. NRF2 expression decreased significantly in the kidneys of old mice, as well as histologic and functional renal recovery after IRI; 45-min renal pedicle clamping was retarded in old compared with young mice. Persistent renal injury during the recovery phase after IRI was aggravated in NRF2 knockout (KO) mice compared to wild-type mice. Oxidative stress occurred in NRF2 KO old mice during the IRI recovery phase along with decreased expression of mitochondrial OXPHOS-related proteins and a reduction in mitochondrial ATP content. In vitro, hypoxia/reoxygenation (H/R) injury was aggravated in senescent human proximal tubuloepithelial cells after NRF2 restriction using NRF2 siRNA, which also increased the level of oxidative stress and deteriorated mitochondrial dysfunction. Treating the mice with an NRF2 activator, CDDO-Me, alleviated the injury. These results suggest that NRF2 may be a therapeutic target for the aging kidney.

Pharmacological Potential of Betulin as a Multitarget Compound

Betulin is a natural triterpene, usually from birch bark, known for its potential wound-healing properties. Despite having a wide range of pharmacological targets, no studies have proposed betulin as a multitarget compound. Betulin has protective effects against cardiovascular and liver diseases, cancer, diabetes, oxidative stress, and inflammation. It reduces postprandial hyperglycemia by inhibiting α-amylase and α-glucosidase activity, combats tumor cells by inducing apoptosis and inhibiting metastatic proteins, and modulates chronic inflammation by blocking the expression of proinflammatory cytokines via modulation of the NFκB and MAPKs pathways. Given its potential to influence diverse biological networks with high target specificity, it can be hypothesized that betulin may eventually become a new lead for drug development because it can modify a variety of pharmacological targets. The summarized research revealed that the diverse beneficial effects of betulin in various diseases can be attributed, at least in part, to its multitarget anti-inflammatory activity. This review focuses on the natural sources, pharmacokinetics, pharmacological activity of betulin, and the multi-target effects of betulin on signaling pathways such as MAPK, NF-κB, and Nrf2, which are important regulators of the response to oxidative stress and inflammation in the body.

The bridge between cell survival and cell death: reactive oxygen species-mediated cellular stress

As a requirement of aerobic metabolism, regulation of redox homeostasis is indispensable for the continuity of living homeostasis and life. Since the stability of the redox state is necessary for the maintenance of the biological functions of the cells, the balance between the pro-oxidants, especially ROS and the antioxidant capacity is kept in balance in the cells through antioxidant defense systems. The pleiotropic transcription factor, Nrf2, is the master regulator of the antioxidant defense system. Disruption of redox homeostasis leads to oxidative and reductive stress, bringing about multiple pathophysiological conditions. Oxidative stress characterized by high ROS levels causes oxidative damage to biomolecules and cell death, while reductive stress characterized by low ROS levels disrupt physiological cell functions. The fact that ROS, which were initially attributed as harmful products of aerobic metabolism, at the same time function as signal molecules at non-toxic levels and play a role in the adaptive response called mithormesis points out that ROS have a dose-dependent effect on cell fate determination. See also Figure 1(Fig. 1).

The Keap1-Nrf2 signaling pathway regulates antioxidant defenses of Ctenopharyngodon idella induced by bacterial infection

Respiratory burst is a process involving rapid production of reactive oxygen species (ROS) for eliminating invading pathogens. However, excessive ROS production can be fatal to the host organism. The Keap1-Nrf2-ARE (Kelch-like ECH-associated protein 1 [Keap1]; Nuclear factor erythroid-derived 2-like 2 [Nrf2]; Antioxidant responsive element [ARE]) signaling pathway plays an important role in alleviating oxidative stress and preserving cellular homeostasis. However, the role of Keap1 during bacterial infection in fish remains unclear. In this study, we cloned and characterized the Keap1 gene of grass carp (CiKeap1) for the first time. CiKeap1 encodes a 593-amino acid protein of the Keap1b type. The tissue distribution analysis data revealed that the brain contains the highest transcription level of Keap1, followed by the heart and liver. The infection of Aeromonas hydrophila and Staphylococcus aureus obviously modulated the gene transcription and protein expression levels of Keap1, which suggested that the CiKeap1 participates in antibacterial immune responses. Furthermore, in vitro overexpression assays clarified the defensive and regular roles of CiKeap1 in maintaining host redox homeostasis in response to bacterial infection through the Keap1-Nrf2-ARE signaling pathway. In conclusion, the present results provide an expanded perspective on the role of Keap1 in teleost immunology that can guide healthy farming cultivation of grass carp.

Oxazole-4-carboxamide/butylated hydroxytoluene hybrids with GSK-3β inhibitory and neuroprotective activities against Alzheimer's disease

Neuronal cells overexpressing phosphorylated Tau proteins can increase the susceptibility to oxidative stress. Regulation of glycogen synthase-3β (GSK-3β) and reduction of Tau protein hyperphosphorylation, along with alleviation of oxidative stress, may be an effective way to prevent or treat Alzheimer's disease (AD). For this purpose, a series of Oxazole-4-carboxamide/butylated hydroxytoluene hybrids were designed and synthesized to achieve multifunctional effects on AD. The biological evaluation showed that the optimized compound KWLZ-9e displayed potential GSK-3β (IC₅₀ = 0.25 μM) inhibitory activity and neuroprotective capacity. Tau protein inhibition assays showed that KWLZ-9e reduced the expression of GSK-3β and downstream p-Tau in HEK GSK-3β 293T cells. Meanwhile, KWLZ-9e could alleviate H₂O₂-induced ROS damage, mitochondrial membrane potential imbalance, Ca²⁺ influx and apoptosis. Mechanistic studies suggest that KWLZ-9e activates the Keap1-Nrf2-ARE signaling pathway and enhances the expression of downstream oxidative stress proteins including TrxR1, HO-1, NQO1, GCLM to exert cytoprotective effects. We also confirmed that KWLZ-9e could ameliorate learning and memory impairments in vivo model of AD. The multifunctional properties of KWLZ-9e suggest that it is a promising lead for the treatment of AD.

Nrf2 signaling in diabetic nephropathy, cardiomyopathy and neuropathy: Therapeutic targeting, challenges and future prospective

Western lifestyle contributes to an overt increase in the prevalence of metabolic anomalies including diabetes mellitus (DM) and obesity. Prevalence of DM is rapidly growing worldwide, affecting many individuals in both developing and developed countries. DM is correlated with the onset and development of complications with diabetic nephropathy (DN), diabetic cardiomyopathy (DC) and diabetic neuropathy being the most devastating pathological events. On the other hand, Nrf2 is a regulator for redox balance in cells and accounts for activation of antioxidant enzymes. Dysregulation of Nrf2 signaling has been shown in various human diseases such as DM. This review focuses on the role Nrf2 signaling in major diabetic complications and targeting Nrf2 for treatment of this disease. These three complications share similarities including the presence of oxidative stress, inflammation and fibrosis. Onset and development of fibrosis impairs organ function, while oxidative stress and inflammation can evoke damage to cells. Activation of Nrf2 signaling significantly dampens inflammation and oxidative damage, and is beneficial in retarding interstitial fibrosis in diabetic complications. SIRT1 and AMPK are among the predominant pathways to upregulate Nrf2 expression in the amelioration of DN, DC and diabetic neuropathy. Moreover, certain therapeutic agents such as resveratrol and curcumin, among others, have been employed in promoting Nrf2 expression to upregulate HO-1 and other antioxidant enzymes in the combat of oxidative stress in the face of DM.

Modulation of Nrf2/HO-1 by Natural Compounds in Lung Cancer

Oxidative stresses (OSs) are considered a pivotal factor in creating various pathophysiological conditions. Cells have been able to move forward by modulating numerous signaling pathways to moderate the defects of these stresses during their evolution. The company of Kelch-like ECH-associated protein 1 (Keap1) as a molecular sensing element of the oxidative and electrophilic stress and nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) as a master transcriptional regulator of the antioxidant response makes a master cytoprotective antioxidant pathway known as the Keap1/Nrf2 pathway. This pathway is considered a dual-edged sword with beneficial features for both normal and cancer cells by regulating the gene expression of the array of endogenous antioxidant enzymes. Heme oxygenase-1 (HO-1), a critical enzyme in toxic heme removal, is one of the clear state indicators for the duality of this pathway. Therefore, Nrf2/HO-1 axis targeting is known as a novel strategy for cancer treatment. In this review, the molecular mechanism of action of natural antioxidants on lung cancer cells has been investigated by relying on the Nrf2/HO-1 axis.

Role of oxidative stress and inflammation-related signaling pathways in doxorubicin-induced cardiomyopathy

Doxorubicin (DOX) is a powerful and commonly used chemotherapeutic drug, used alone or in combination in a variety of cancers, while it has been found to cause serious cardiac side effects in clinical application. More and more researchers are trying to explore the molecular mechanisms of DOX-induced cardiomyopathy (DIC), in which oxidative stress and inflammation are considered to play a significant role. This review summarizes signaling pathways related to oxidative stress and inflammation in DIC and compounds that exert cardioprotective effects by acting on relevant signaling pathways, including the role of Nrf2/Keap1/ARE, Sirt1/p66Shc, Sirt1/PPAR/PGC-1α signaling pathways and NOS, NOX, Fe²⁺ signaling in oxidative stress, as well as the role of NLRP3/caspase-1/GSDMD, HMGB1/TLR4/MAPKs/NF-κB, mTOR/TFEB/NF-κB pathways in DOX-induced inflammation. Hence, we attempt to explain the mechanisms of DIC in terms of oxidative stress and inflammation, and to provide a theoretical basis or new idea for further drug research on reducing DIC. Video Abstract.

Structural basis of Nrf2 activation by flavonolignans from silymarin

Several properties of silymarin (SM) extract have been attributed to their three major flavonolignans (silybin, silychristin, and silydianin) and their 2,3-dehydro derivatives (2,3-dehydrosilybin, 2,3-dehydrosilychristin, and 2,3-dehydrosilydianin). Experimental findings have suggested that the antioxidative and protective activities of these compounds could be due to their ability to activate nuclear factor erythroid 2-related factor 2 (Nrf2). The mechanism by which SM compounds exert their effect has been suggested to be by disrupting the complex between Nrf2 and Kelch-like ECH-associated protein 1 (Keap1). However, information about the structural and energetic basis of the inhibitory mechanism of SM compounds on the Nrf2-Keap1 pathway is lacking. We evaluated the binding properties of SM compounds because experimental findings have pointed to them as potential activators of Nrf2. Our study combined docking and molecular dynamics (MD) simulations with the Poisson-Boltzmann and generalized Born and surface area (MMPBSA and MMGBSA) methods and quantum mechanics-molecular mechanics (QMMM) calculations to investigate Keap1-ligand interactions. Our results predicted that silybin_A and 2,3-dehydrosilybin bind to Keap1, forming interactions with the same pockets as those observed for the cocrystallized Keap1-Cpd16 complex but with more favorable binding free energies. These findings indicate that both natural compounds are potential activators of Nrf2.

Cytotoxic and Antioxidant Activity of Hypericum perforatum L. Extracts against Human Melanoma Cells from Different Stages of Cancer Progression, Cultured under Normoxia and Hypoxia

Oxidative stress and the hypoxic microenvironment play a key role in the progression of human melanoma, one of the most aggressive skin cancers. The aim of our study was to evaluate the effect of Hypericum perforatum extracts of different origins (both commercially available (HpEx2) and laboratory-prepared from wild grown (HpEx12) and in vitro cultured (HpEx13) plants) and hyperforin salt on WM115 primary and WM266-4 lymph node metastatic human melanoma cells cultured under normoxic and hypoxic conditions. The polyphenol content, radical scavenging activity, and hyperforin concentration were determined in the extracts, while cell viability, apoptosis, ROS production, and expression of NRF2 and HO-1, important oxidative stress-related factors, were analyzed after 24 h of cell stimulation with HpExs and hyperforin salt. We found that cytotoxic, pro-apoptotic and antioxidant effects depend on the extract composition, the stage of melanoma progression, and the oxygen level. Hyperforin salt showed lower activity than H. perforatum extracts. Our study for the first time showed that the anticancer activity of H. perforatum extracts differs in normoxia and hypoxia. Importantly, the composition of extracts of various origins, including in vitro cultured, resulting in their unique properties, may be important in the selection of plants for therapeutic application.

Curdione Relieved Isoproterenol-Induced Myocardial Damage through Inhibiting Oxidative Stress and Apoptosis

Isoproterenol (ISO) is widely used to treat bronchial asthma, cardiogenic or septic shock, complete atrioventricular block, and cardiac arrest. However, it can also cause myocardial damage owing to infarct-like necrosis. Curdione, an extract of the Chinese herb Rhizoma Curcumae, has a variety of pharmacological activities, including cardioprotective effects. In this study, we investigated the protective effects of curdione and its underlying mechanisms in an ISO-induced myocardial injury model. Our results showed that curdione attenuated ISO-induced H9c2 cell proliferation inhibition and lactic dehydrogenase (LDH) release. Curdione ameliorated morphological damage and reduced the ISO-induced elevation of serum creatine kinase-MB isoenzyme (CK-MB) and LDH. Furthermore, curdione inhibited ISO-induced cell apoptosis, modulated the expression of Bcl-2 and Bax proteins, repealed the accumulation of ISO-induced reactive oxygen species (ROS), prevented mitochondrial dysfunction, and activated the Nrf2/SOD1/HO-1 signaling pathway. The above results show that curdione exerts a protective effect against ISO-induced myocardial damage by inhibiting apoptosis and oxidative stress, suggesting that curdione is a potential therapeutic strategy to prevent ISO-induced myocardial damage.

Sulforaphane Delays Intervertebral Disc Degeneration by Alleviating Endoplasmic Reticulum Stress in Nucleus Pulposus Cells via Activating Nrf-2/HO-1

Intervertebral disc degeneration (IVDD) is one of the main causes of low back pain, which brings heavy burdens to individuals and society. The mechanism of IVDD is complex and diverse. One of the important reasons is that the abnormal accumulation of reactive oxygen species (ROS) in nucleus pulposus cells (NPCs) leads to endoplasmic reticulum stress (ERS), which causes increased apoptosis of NPCs. Nuclear factor E2-related factor 2 (Nrf-2) and its downstream antioxidant proteins are key molecular switches for sensing oxidative stress and regulating antioxidant responses in cells. Sulforaphane (SFN), a natural compound derived from Brassicaceae plants, is a Nrf-2 agonist that displays potent antioxidant potential in vitro and in vivo. Here, we used advanced glycation end products (AGEs) to construct an in vitro degeneration model of NPCs, and we found that AGEs elevated ROS level in NPCs and caused severe ERS and apoptosis. While SFN can promote the entry of Nrf-2 into the nucleus and increase the expression level of heme oxygenase 1 (HO-1) in vitro, thus clearing the accumulated ROS in cells and alleviating ERS and cell apoptosis. Moreover, the protection of SFN on NPCs was greatly attenuated after HO-1 was inhibited. We also used AGEs to construct a rat IVDD model. Consistent with the in vitro experiments, SFN could attenuate ERS in NPCs in vivo and delay disc degeneration in rats. This study found that SFN can be used as a new and promising agent for the treatment of IVDD.

Free radicals, antioxidants, nuclear factor-E2-related factor-2 and liver damage

The liver performs various biochemical and molecular functions. Its location as a portal to blood arriving from the intestines makes it susceptible to several insults, leading to diverse pathologies, including alcoholic liver disease, viral infections, nonalcoholic steatohepatitis, and hepatocellular carcinoma, which are causes of death worldwide. Illuminating the molecular mechanism underlying hepatic injury will provide targets to develop new therapeutic strategies to fight liver maladies. In this regard, reactive oxygen species (ROS) are well-recognized mediators of liver damage. ROS induce nuclear factor-κB and the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 inflammasome, which are the main proinflammatory signaling pathways that upregulate several proinflammatory and profibrogenic mediators. Additionally, oxygen-derived free radicals induce hepatic stellate cell activation to produce exacerbated quantities of extracellular matrix proteins, leading to fibrosis, cirrhosis and eventually hepatocellular carcinoma. Exogenous and endogenous antioxidants counteract the harmful effects of ROS, preventing liver necroinflammation and fibrogenesis. Therefore, several researchers have demonstrated that the administration of antioxidants, mainly derived from plants, affords beneficial effects on the liver. Notably, nuclear factor-E2-related factor-2 (Nrf2) is a major factor against oxidative stress in the liver. Increasing evidence has demonstrated that Nrf2 plays an important role in liver necroinflammation and fibrogenesis via the induction of antioxidant response element genes. The use of Nrf2 inducers seems to be an interesting approach to prevent/attenuate hepatic disorders, particularly under conditions where ROS play a causative role.

Natural compound glycyrrhetinic acid protects against doxorubicin-induced cardiotoxicity by activating the Nrf2/HO-1 signaling pathway

BACKGROUND

As one of the most classic antineoplastic agents, doxorubicin (Dox) is extensively used to treat a wide range of cancers. Nevertheless, the clinical outcomes of Dox-based therapies are severely hampered due to the significant cardiotoxicity. Glycyrrhetinic acid (GA) is the major biologically active compound of licorice, one of the most well-known food additives and medicinal plants in the world. We previously demonstrated that GA has the potential capability to protect mice from Dox-induced cardiac injuries. However, the underlying cardioprotective mechanism remains unexplored.

PURPOSE

To investigate the cardioprotective benefits of GA against Dox-induced cardiotoxicity and to elucidate its mechanisms of action.

STUDY DESIGN/METHODS

H9c2 cardiomyoblasts and AC16 cardiomyocytes were used as the cell models in vitro. A transgenic zebrafish model and a 4T1 mouse breast cancer model were applied to explore the cardioprotective effects of GA in vivo.

RESULTS

In vitro, GA inhibited Dox-induced cell death and LDH release in H9c2 and AC16 cells without affecting the anti-cancer effects of Dox. GA significantly alleviated Dox-induced ROS generation, mitochondrial dysfunction, and apoptosis in H9c2 cells. Moreover, GA abolished the expression of pro-apoptotic proteins and restored Nrf2/HO-1 signaling pathway in Dox-treated H9c2 cells. On the contrary, Nrf2 knockdown strongly abrogated the cardioprotective effects of GA on Dox-treated H9c2 cells. In vivo, GA attenuated Dox-induced cardiac dysfunction by restoring stroke volume, cardiac output, and fractional shortening in the transgenic zebrafish embryos. In a 4T1 mouse breast cancer model, GA dramatically prevented body weight loss, attenuated cardiac dysfunction, and prolonged survival rate in Dox-treated mice, without compromising Dox's anti-tumor efficacy. Consistently, GA attenuated oxidative injury, reduced cardiomyocytes apoptosis, and restored the expressions of Nrf2 and HO-1 in Dox-treated mouse hearts.

CONCLUSION

GA protects against Dox-induced cardiotoxicity by suppressing oxidative stress, mitochondrial dysfunction, and apoptosis via upregulating Nrf2/HO-1 signaling pathway. These findings could provide solid evidence to support the further development of GA as a feasible and safe adjuvant to Dox chemotherapy for overcoming Dox-induced cardiotoxicity.

Glycyrrhetinic acid prevents carbapenem-resistant Klebsiella pneumoniae-induced cell injury by inhibiting mitochondrial dysfunction via Nrf-2 pathway

OBJECTIVES

Due to the abuse of antibiotics, the high reoccurrence of drug-resistance strains, such as carbapenem-resistant Klebsiella pneumoniae (CRKP), deteriorates CRKP-infected pneumonia in the clinic, suggesting it is necessary to find new alternatives. Glycyrrhetinic acid (GA), an active ingredient of Yinhuapinggan granule, has antioxidant & anti-inflammatory capacity. Little, however, is known about the effects of GA on CRKP-induced epithelial injury.

METHODS

In this research, we examined the protective effects of GA against pulmonary epithelium damage caused by CRKP infection and potential molecular mechanisms.

RESULTS

Our results noted GA significantly promoted cell survival and reduced pro-inflammatory cytokines production, during CRKP-induced human pulmonary epithelial cell. Mechanically, GA alleviated mitochondrial-damage-induced apoptosis amid CRKP infection by inhibiting mitochondrial damage. Additionally, we found GA inhibited the expression of pro-apoptotic proteins Cyto-c, the Bax, and Caspase-3 while increasing the expression of anti-apoptotic protein Bcl-2. Further exploration found GA could trigger Nrf-2 expression at both gene and protein levels, activating antioxidative proteins to diminish CRKP-induced oxidative stress.

CONCLUSION

Together, our results demonstrated that GA was a promising candidate to alleviate CRKP-infected lung injury as well as a synergist to treat CRKP infection with antibiotics.

Exploring Nrf2 as a therapeutic target in testicular dysfunction

Testicular dysfunction, a major contributory factor to infertility, has received a lot of attention over the recent years. Several studies have linked abnormal sperm function and morphology with an enhanced generation of reactive oxygen species (ROS) and oxidative stress. The nuclear factor erythroid-derived 2 (Nrf2) is a transcriptional response to cellular stresses (intrinsic or extrinsic) that regulates the oxidative status, mitochondrial dysfunction, inflammation, and proteostasis. In this review, the therapeutic role of Nrf2 was explored. To do so, scientific data were retrieved from databases such as Elsevier, Wiley, Web of Science, Springer, PubMed, Taylor and Francis, and Google Scholar using search terms such as "Nrf2" and "testis," "sperm," "testicular function," and "testosterone." It has been noted that Nrf2 influences the physiology and pathology of testicular dysfunction, especially in the spermatogenic process, by regulating cellular resistance to oxidative stress, inflammation, and environmental toxicants. However, numerous compounds serve as activators and inhibitors of testicular Nrf2. Nrf2 activators might play a therapeutic role in the prevention and treatment of testicular dysfunction, while molecules that inhibit Nrf2 might induce dysfunction in testis components. Nrf2 activators protect cells against oxidative damage and activate Nrf2/KEAP1 signaling which promotes its movement to the nucleus, and increased Nrf2 function and expression, along with their downstream antioxidant gene. Nrf2 inhibitors facilitate oxidative stress via interfering with the Nrf2 signal pathway. The Nrf2 activation could serve as a promising therapeutic target for testicular dysfunction. This review explored the effect of Nrf2 on testicular function while highlighting potential activators and inhibitors of Nrf2.

Different Inhibition of Nrf2 by Two Keap1 Isoforms α and β to Shape Malignant Behaviour of Human Hepatocellular Carcinoma

Nrf2 (nuclear factor E2-related factor 2, encoded by Nfe2l2) acts as a master transcriptional regulator in mediating antioxidant, detoxification, and cytoprotective responses against oxidative, electrophilic, and metabolic stress, but also plays a crucial role in cancer metabolism and multiple oncogenic pathways, whereas the redox sensor Keap1 functions as a predominant inhibitor of Nrf2 and, hence, changes in its expression abundance directly affect the Nrf2 stability and transcriptional activity. However, nuanced functional isoforms of Keap1 α and β have rarely been identified to date. Herein, we have established four distinct cell models stably expressing Keap1^-/-, Keap1β(Keap1^Δ1-31), Keap1-Restored, and Keap1α-Restored aiming to gain a better understanding of similarities and differences of two Keap1 isoforms between their distinct regulatory profiles. Our experimental evidence revealed that although Keap1 and its isoforms are still localized in the cytoplasmic compartments, they elicited differential inhibitory effects on Nrf2 and its target HO-1. Furthermore, transcriptome sequencing unraveled that they possess similar but different functions. Such functions were further determined by multiple experiments in vivo (i.e., subcutaneous tumour formation in nude mice) and in vitro (e.g., cell cloning, infection, migration, wound healing, cell cycle, apoptosis, CAT enzymatic activity, and intracellular GSH levels). Of note, the results obtained from tumourigenesis experiments in xenograft model mice were verified based on the prominent changes in the PTEN signaling to the PI3K-AKT-mTOR pathways, in addition to substantially aberrant expression patterns of those typical genes involved in the EMT (epithelial-mesenchymal transition), cell cycle, and apoptosis.

Dual antioxidant activity and the related mechanisms of a novel pentapeptide GLP4 from the fermented mycelia of Ganoderma lingzhi

Oxidative stress causes chronic inflammation, and mediates various diseases. The discovery of antioxidants from natural sources is important to research. Here we identified a novel antioxidant peptide (GLP4) from Ganoderma lingzhi mycelium and investigated its antioxidant type and potential protective mechanisms. Through free radical scavenging assay, active site shielding validation, superoxide dismutase (SOD) activity assay, and lipid peroxidation assay, we demonstrated that GLP4 was a novel protective agent with both direct and indirect antioxidant activities. GLP4 could directly enter human umbilical vein endothelial cells (HUVECs) as an exogenous substance. Meanwhile, GLP4 promoted the nuclear translocation of nuclear factor erythroid-2-related factor 2 (Nrf2) and activated the Nrf2/antioxidant response element (ARE) signaling pathway, exhibiting antioxidant and anti-apoptotic cytoprotective effects on hydrogen peroxide (H₂O₂)-induced HUVECs. Pull-down experiments of GLP4 target proteins, bioinformatics analysis and molecular docking further revealed that GLP4 mediated Nrf2 activation through binding to phosphoglycerate mutase 5 (PGAM5). The results suggested that GLP4 is a novel peptide with dual antioxidant activity and has promising potential as a protective agent in preventing oxidative stress-related diseases.

TRPV1 Modulator Ameliorates Alzheimer-Like Amyloid-β Neuropathology via Akt/Gsk3β-Mediated Nrf2 Activation in the Neuro-2a/APP Cell Model

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder for which there is no effective therapeutic strategy. PcActx peptide from the transcriptome of zoantharian Palythoa caribaeorum has recently been identified and verified as a novel antagonist of transient receptor potential cation channel subfamily V member 1 (TRPV1). In the present study, we further investigated the neuroprotective potential of PcActx peptide and its underlying mechanism of action, in an N2a/APP cell model of AD. Both Western blot and RT-PCR analysis revealed that PcActx peptide markedly inhibited the production of amyloid-related proteins and the expression of BACE1, PSEN1, and PSEN2. Moreover, PcActx peptide notably attenuated the capsaicin-stimulated calcium response and prevented the phosphorylation of CaMKII and CaMKIV (calcium-mediated proteins) in N2a/APP cells. Further investigation indicated that PcActx peptide significantly suppressed ROS generation through Nrf2 activation, followed by enhanced NQO1 and HO-1 levels. In addition, PcActx peptide remarkably improved Akt phosphorylation at Ser 473 (active) and Gsk3β phosphorylation at Ser 9 (inactive), while pharmacological inhibition of the Akt/Gsk3β pathway significantly attenuated PcActx-induced Nrf2 activation and amyloid downregulation. In conclusion, PcActx peptide functions as a TRPV1 modulator of intercellular calcium homeostasis, prevents AD-like amyloid neuropathology via Akt/Gsk3β-mediated Nrf2 activation, and shows promise as an alternative therapeutic agent for AD.

Evaluation of Nrf2/ARE Signaling Pathway in the Presence of Pentoxifylline as a Cryoprotectant in Mouse Spermatogonial Stem Cells

The process of spermatogonial stem cell cryopreservation (SSCs) in young male cancer survivors is associated with increased reactive oxygen species (ROS), DNA fragmentation, apoptosis, decreased cell activity, and finally reduced fertility of SSCs. Therefore, it is necessary to add cryoprotectants to the freezing medium to minimize the injuries associated with cryopreservation. In addition, the Nrf2/ARE pathway is a main cellular pathway that regulates the antioxidant defense system. The purpose of this study was to evaluate the cryoprotective effect of pentoxifylline (PTX) on SSCs after freezing-thawing through the Nrf2/ARE pathway. SSCs extracted from neonatal mice testes were isolated and their purity was measured by flow cytometry with GDNF family receptor alpha-1 (GFRα1) and inhibitor of differentiation 4 (ID4). After culturing, the cells were frozen in different groups for 1 month. After freezing-thawing, cell viability, colonization rate, and intracellular ROS, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) were evaluated. Quantitative real-time polymerase chain reaction and western blotting were done to assess the expression levels of Nrf2, Keap-1, PI3K, and AKT genes and proteins. The survival and colonization rates of SSCs, SOD, and CAT levels, and Nrf2, PI3K, and AKT expression levels were significantly higher in the PTX group compared with the other cryopreservation groups. The Keap-1 expression level and the ROS and MDA production levels also decreased significantly in the PTX group (p-value <0.05). According to our findings, PTX can activate the antioxidant defense through the Nrf2/ARE signaling pathway; therefore, it could be a suitable cryoprotectant candidate for freezing and long-term storage of SSCs in the clinical setting.

Dietary α-lipoic acid supplementation improves postmortem color stability of the lamb muscles through changing muscle fiber types and antioxidative status

This study investigated the effect of dietary α-lipoic acid (600 mg/kg) supplementation on the postmortem color stability of the biceps femoris from lambs. The results showed that dietary α-lipoic acid supplementation increased a* and decreased b* and metmyoglobin (MMb) percentage of the biceps femoris with the time of storage (P < 0.05). The content of malondialdehyde (MDA) reduced with the time of storage after treatment with α-lipoic acid (P < 0.05). α-lipoic acid increased the myoglobin (Mb) content, and myosin heavy chain I (MyHC I) gene expression but decreased glycogen content, lactate dehydrogenase (LDH) activity, and MyHC IIb gene expression (P < 0.05). The T-AOC value, catalase (CAT) activity, and expression of SOD and CAT gene expression increased after α-lipoic acid treatment (P < 0.05). Therefore, dietary α-lipoic acid supplementation improved the meat color by regulating muscle fiber types and inhibited glycolysis. Moreover, α-lipoic acid maintained meat color stability by effectively inhibiting muscle oxidation via enhancing the antioxidant capacity.

Nrf2 signaling activation by a small molecule activator compound 16 inhibits hydrogen peroxide-induced oxidative injury and death in osteoblasts

We explored the potential activity of compound 16 (Cpd16), a novel small molecule Nrf2 activator, in hydrogen peroxide (H₂O₂)-stimulated osteoblasts. In the primary murine/human osteoblasts and MC3T3-E1 murine osteoblastic cells, Cpd16 treatment at micro-molar concentrations caused disassociation of Keap1-Nrf2 and Nrf2 cascade activation. Cpd16 induced stabilization of Nrf2 protein and its nuclear translocation, thereby increasing the antioxidant response elements (ARE) reporter activity and Nrf2 response genes transcription in murine and human osteoblasts. Significantly, Cpd16 mitigated oxidative injury in H₂O₂-stimulited osteoblasts. H₂O₂-provoked apoptosis as well as programmed necrosis in osteoblasts were significantly alleviated by the novel Nrf2 activator. Cpd16-induced Nrf2 activation and osteoblasts protection were stronger than other known Nrf2 activators. Dexamethasone- and nicotine-caused oxidative stress and death in osteoblasts were attenuated by Cpd16 as well. Cpd16-induced osteoblast cytoprotection was abolished by Nrf2 short hairpin RNA or knockout, but was mimicked by Keap1 knockout. Keap1 Cys151S mutation abolished Cpd16-induced Nrf2 cascade activation and osteoblasts protection against H₂O₂. Importantly, weekly Cpd16 administration largely ameliorated trabecular bone loss in ovariectomy mice. Together, Cpd16 alleviates H₂O₂-induced oxidative stress and death in osteoblasts by activating Nrf2 cascade.

An update of Nrf2 activators and inhibitors in cancer prevention/promotion

NF-E2-related factor 2 (Nrf2) protein is a basic-region leucine zipper transcription factor that defends against endogenous or exogenous stressors. By inducing several cytoprotective and detoxifying gene expressions, Nrf2 can increase the sensitivity of the cells to oxidants and electrophiles. Transient Nrf2 activation, by its specific activators, has protective roles against carcinogenesis and cancer development. However, permanent activation of Nrf2 promotes various cancer properties, comprising malignant progression, chemo/radio resistance, and poor patient prognosis. Taken together, these findings suggest that reaching an optimal balance between paradoxical functions of Nrf2 in malignancy may render a selective improvement to identify therapeutic strategies in cancer treatment. In this review, we describe lately discovered Nrf2 inducers and inhibitors, and their chemopreventive and/or anticancer activities.

The Nrf2 pathway signifies one of the most significant cell defense procedures against exogenous or endogenous stressors. Certainly, by increasing the expression of several cytoprotective genes, the transcription factor Nrf2 can shelter cells and tissues from multiple sources of damage including electrophilic, xenobiotic, metabolic, and oxidative stress. Notably, the aberrant activation or accumulation of Nrf2, a common event in many tumors, confers a selective advantage to cancer cells and is connected to malignant progression, therapy resistance, and poor prognosis. Therefore, lately, Nrf2 has arisen as a hopeful target in treatment of cancer, and many struggles have been made to detect therapeutic strategies intended at disrupting its pro-oncogenic role. By summarizing the outcomes from past and recent studies, this review provided an overview concerning the Nrf2 pathway and the molecular mechanisms causing Nrf2 hyperactivation in cancer cells. Finally, this paper also described some of the most promising therapeutic approaches that have been successfully employed to counteract Nrf2 activity in tumors, with a particular emphasis on the development of natural compounds and the adoption of drug repurposing strategies.

mRNA and long non-coding RNA expression profiles of rotator cuff tear patients reveal inflammatory features in long head of biceps tendon

Background

This study aimed to identify the differentially expressed mRNAs and lncRNAs in inflammatory long head of biceps tendon (LHBT) of rotator cuff tear (RCT) patients and further explore the function and potential targets of differentially expressed lncRNAs in biceps tendon pathology.

Methods

Human gene expression microarray was made between 3 inflammatory LHBT samples and 3 normal LHBT samples from RCT patients. GO analysis and KEGG pathway analysis were performed to annotate the function of differentially expressed mRNAs. The real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was admitted to verify their expression. LncRNA-mRNA co-expression network, cis-acting element, trans-acting element and transcription factor (TF) regulation analysis were constructed to predict the potential molecular regulatory mechanisms and targets for LHB tendinitis.

Results

103 differentially expressed lncRNAs and mRNAs, of which 75 were up-regulated and 28 were down-regulated, were detected to be differentially expressed in LHBT. The expressions of 4 most differentially expressed lncRNAs (A2MP1, LOC100996671, COL6A4P, lnc-LRCH1-5) were confirmed by qRT-PCR. GO functional analysis indicated that related lncRNAs and mRNAs were involved in the biological processes of regulation of innate immune response, neutrophil chemotaxis, interleukin-1 cell response and others. KEGG pathway analysis indicated that related lncRNAs and mRNAs were involved in MAPK signaling pathway, NF-kappa B signaling pathway, cAMP signaling pathway and others. TF regulation analysis revealed that COL6A4P2, A2MP1 and LOC100996671 target NFKB2.

Conclusions

LlncRNA-COL6A4P2, A2MP1 and LOC100996671 may regulate the inflammation of LHBT in RCT patients through NFKB2/NF-kappa B signaling pathway, and preliminarily revealed the pathological molecular mechanism of tendinitis of LHBT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01292-y.

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.

Isoquercitrin Attenuates Osteogenic Injury in MC3T3 Osteoblastic Cells and the Zebrafish Model via the Keap1-Nrf2-ARE Pathway

Isoquercitrin (IQ) widely exists in natural products, with a variety of pharmacological activities. In this study, the anti-apoptotic and antioxidative activities of IQ were evaluated. IQ showed protective activity against 2, 2′-azobis [2-methylpropionamidine] dihydrochloride (AAPH)-induced cell damage, as well as a marked reduction in reactive oxygen species (ROS). The evidence of IQ regulating Keap1-Nrf2-ARE and the mitochondrial-mediated Caspase 3 pathway were found in the MC3T3 osteoblastic cell line. Furthermore, IQ significantly decreased ROS production, apoptosis, and lipid peroxidation in AAPH-treated 72 h post-fertilization (hpf) zebrafish, as observed via DCFH-DA, acridine orange (AO), and a 1,3-bis(diphenylphosphino) propane (DPPP) probe, respectively. In AAPH-treated 9 day post-fertilization (dpf) zebrafish, IQ strongly promoted osteogenic development, with increased concentrations by calcein staining, compared with the untreated group. In a molecular docking assay, among all signal proteins, Keap1 showed the strongest affinity with IQ at −8.6 kcal/mol, which might be the reason why IQ regulated the Keap1-Nrf2-ARE pathway in vitro and in vivo. These results indicated that IQ promotes bone development and repairs bone injury, which is valuable for the prevention and treatment of bone diseases.

The Keap1 signaling in the regulation of HSP90 pathway

The Keap1 protein is the master modulator of Nrf2 pathway; moreover, it is the hub of such important processes as cancer, cell stress, inflammation, and chemio- and radio-resistance. That is why Keap1 has become an intriguing pharmacological target. Many recent data show that Keap1 interacts with HSP90 protein. In this study, we use ferulic acid (FA) as antioxidant and anti-inflammatory agent, able to relieve inflammatory response. It is known that treatment with 100 μg of FA can significantly decrease the oxidative stress, so it turns to be useful to study the antioxidant regulation. The RAW 264.7 cells transfected with si-Keap1 and LPS treated are the in vitro model used to study the effects of Keap1 silencing on HSP90 activities and the FA antioxidant modulation. Immunoblot data and qPCR analysis show that Keap1 is involved in HSP90 modulation and on anti-oxidative response. Keap1 silencing affects negatively COX2 activation; in fact western blot and qPCR analysis conducted on RAW 264.7 cells Keap1silenced highlight that LPS treatment does not induce COX2 activation. In addition, the FA anti-oxidative and modulatory effect is abolished in COX2 pathway. The same results are point out using human A549 cell line with an allelic mutation on Keap1 gene, and the protein results are partially inactive. This preliminary study points out that Keap1protein is involved in HSP90 and anti-oxidative pathway regulation.

Ethanol Extract of Chaenomeles sinensis Inhibits the Development of Benign Prostatic Hyperplasia by Exhibiting Anti-oxidant and Anti-inflammatory Effects

Chaenomeles sinensis is known to inhibit the development and progression of many age-related diseases, but the underlying molecular mechanisms are largely unclear. In the present study, we observed that the ethanol extract of Chaenomeles sinensis scavenged 2,2’-diphenylpicrylhydrazyl and 2,2’-azinobis diammonium radicals in vitro. The ethanol extract of Chaenomeles sinensis activated antioxidant response element-luciferase activity and induced expression of NRF2 target genes in HaCaT cells. The ethanol extract of Chaenomeles sinensis also suppressed LPS-induced expression of COX-2 and iNOS proteins, and mRNA expression of TNF-α and IL-2 in RAW264.7 cells. Finally, the ethanol extract of Chaenomeles sinensis significantly suppressed testosterone propionate-induced benign prostatic hyperplasia in mice. Together, our study provides the evidence that the ethanol extract of Chaenomeles sinensis inhibits the development of benign prostatic hyperplasia by exhibiting anti-oxidant and anti-inflammatory effects.

Target Fishing Reveals a Novel Mechanism of 1,2,4-Oxadiazole Derivatives Targeting Rpn6, a Subunit of 26S Proteasome

1,2,4-Oxadiazole derivatives, a class of Nrf2-ARE activators, exert an extensive therapeutic effect on inflammation, cancer, neurodegeneration, and microbial infection. Among these analogues, DDO-7263 is the most potent Nrf2 activator and used as the core structure for bioactive probes to explore the precise mechanism. In this work, we obtained compound 7, a mimic of DDO-7263, and biotin-labeled and fluorescein-based probes, which exhibited homologous biological activities to DDO-7263, including activating Nrf2 and its downstream target genes, anti-oxidative stress, and anti-inflammatory effects. Affinity chromatography and mass analysis techniques revealed Rpn6 as the potential target protein regulating the Nrf2 signaling pathway. In vitro affinity experiments further confirmed that DDO-7263 upregulated Nrf2 through binding to Rpn6 to block the assembly of 26S proteasome and the subsequent degradation of ubiquitinated Nrf2. These results indicated that Rpn6 is a promising candidate target to activate the Nrf2 pathway for protecting cells and tissues from oxidative, electrophilic, and exogenous microbial stimulation.

The principal molecular mechanisms behind the activation of Keap1/Nrf2/ARE pathway leading to neuroprotective action in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder. PD is associated with the loss of dopaminergic neurons in the substantia nigra pars compacta region of the midbrain. Present therapies for PD provide only symptomatic relief by restoring the dopamine (DA) level. However, they are not disease modifying agents and so they do not delay the disease progression. Alpha-synuclein aggregation, oxidative stress, mitochondrial dysfunction and chronic inflammation are considered to be the major pathological mechanisms mediating neurodegeneration in PD. To resist oxidative stress, the human body has an antioxidant defence mechanism consisting of many antioxidants and cytoprotective genes. The expression of those genes are largely controlled by the Kelch-like ECH-associated protein 1/Nuclear factor - erythroid - 2 - related factor 2/Antioxidant response element (Keap1/Nrf2/ARE) signalling pathway. The transcription factor Nrf2 is activated in response to oxidative or electrophilic stress and protects the cells from oxidative stress and inflammation. Nrf2 has been widely considered as a therapeutic target for neurodegeneration and several drugs are now being tested in clinical trials. Regulation of the Keap1/Nrf2/ARE pathway by small molecules which can act as Nrf2 activators could be effective for treating oxidative stress and neuroinflammation in PD. In this review, we had discussed the principal molecular mechanisms behind the neuroprotective effects of Keap1/Nrf2/ARE pathway in PD. Additionally, we also discussed the small molecules and phytochemicals that could activate the Nrf2 mediated anti-oxidant pathway for neuroprotection in PD.

An Insight on the Pathways Involved in Crizotinib and Sunitinib Induced Hepatotoxicity in HepG2 Cells and Animal Model

Both crizotinib and sunitinib, novel orally-active multikinase inhibitors, exhibit antitumor activity and extend the survival of patients with a malignant tumor. However, some patients may suffer liver injury that can further limit the clinical use of these drugs, however the mechanisms underlying hepatotoxicity are still to be elucidated. Thus, our study was designed to use HepG2 cells in vitro and the ICR mice model in vivo to investigate the mechanisms of hepatotoxicity induced by crizotinib and sunitinib. Male ICR mice were treated orally with crizotinib (70 mg/kg/day) or sunitinib (7.5 mg/kg/day) for four weeks. The results demonstrated that crizotinib and sunitinib caused cytotoxicity in HepG2 cells and chronic liver injury in mice, which were associated with oxidative stress, apoptosis and/or necrosis. Crizotinib- and sunitinib-induced oxidative stress was accompanied by increasing reactive oxygen species and malondialdehyde levels and decreasing the activity of superoxide dismutase and glutathione peroxidase. Notably, the activation of the Kelch-like ECH-associated protein-1/Nuclear factor erythroid-2 related factor 2 signaling pathway was involved in the process of oxidative stress, and partially protected against oxidative stress. Crizotinib and sunitinib induced apoptosis via the mitochondrial pathway, which was characterized by decreasing Bcl2/Bax ratio to dissipate the mitochondrial membrane potential, and increasing apoptotic markers levels. Moreover, the pan-caspase inhibitor Z-VAD-FMK improved the cell viability and alleviated liver damage, which further indicated the presence of apoptosis. Taken together, this study demonstrated that crizotinib- and sunitinib-caused oxidative stress and apoptosis finally impaired hepatic function, which was strongly supported by the histopathological lesions and markedly increased levels of serum alanine aminotransferase, alkaline phosphatase and lactate dehydrogenase.