Structure of the Keap1:Nrf2 interface provides mechanistic insight into Nrf2 signaling

Exploring the Potential of Black Soldier Fly Larval Proteins as Bioactive Peptide Sources through in Silico Gastrointestinal Proteolysis: A Cheminformatic Investigation

Despite their potential as a protein source for human consumption, the health benefits of black soldier fly larvae (BSFL) proteins following human gastrointestinal (GI) digestion are poorly understood. This computational study explored the potential of BSFL proteins to release health-promoting peptides after human GI digestion. Twenty-six proteins were virtually proteolyzed with GI proteases. The resultant peptides were screened for high GI absorption and non-toxicity. Shortlisted peptides were searched against the BIOPEP-UWM and Scopus databases to identify their bioactivities. The potential of the peptides as inhibitors of myeloperoxidase (MPO), NADPH oxidase (NOX), and xanthine oxidase (XO), as well as a disruptor of Keap1–Nrf2 protein–protein interaction, were predicted using molecular docking and dynamics simulation. Our results revealed that about 95% of the 5218 fragments generated from the proteolysis of BSFL proteins came from muscle proteins. Dipeptides comprised the largest group (about 25%) of fragments arising from each muscular protein. Screening of 1994 di- and tripeptides using SwissADME and STopTox tools revealed 65 unique sequences with high GI absorption and non-toxicity. A search of the databases identified 16 antioxidant peptides, 14 anti-angiotensin-converting enzyme peptides, and 17 anti-dipeptidyl peptidase IV peptides among these sequences. Results from molecular docking and dynamic simulation suggest that the dipeptide DF has the potential to inhibit Keap1–Nrf2 interaction and interact with MPO within a short time frame, whereas the dipeptide TF shows promise as an XO inhibitor. BSFL peptides were likely weak NOX inhibitors. Our in silico results suggest that upon GI digestion, BSFL proteins may yield high-GI-absorbed and non-toxic peptides with potential health benefits. This study is the first to investigate the bioactivity of peptides liberated from BSFL proteins following human GI digestion. Our findings provide a basis for further investigations into the potential use of BSFL proteins as a functional food ingredient with significant health benefits.

From In Silico to a Cellular Model: Molecular Docking Approach to Evaluate Antioxidant Bioactive Peptides

The increasing need to counteract the redox imbalance in chronic diseases leads to focusing research on compounds with antioxidant activity. Among natural molecules with health-promoting effects on many body functions, bioactive peptides are gaining interest. They are protein fragments of 2–20 amino acids that can be released by various mechanisms, such as gastrointestinal digestion, food processing and microbial fermentation. Recent studies report the effects of bioactive peptides in the cellular environment, and there is evidence that these compounds can exert their action by modulating specific pathways. This review focuses on the newest approaches to the structure–function correlation of the antioxidant bioactive peptides, considering their molecular mechanism, by evaluating the activation of specific signaling pathways that are linked to antioxidant systems. The correlation between the results of in silico molecular docking analysis and the effects in a cellular model was highlighted. This knowledge is fundamental in order to propose the use of bioactive peptides as ingredients in functional foods or nutraceuticals.

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.

Herpes Simplex Virus 1-Induced Ferroptosis Contributes to Viral Encephalitis

Herpes simplex virus 1 (HSV-1) is a DNA virus belonging to the family Herpesviridae. HSV-1 infection causes severe neurological disease in the central nervous system (CNS), including encephalitis. Ferroptosis is a nonapoptotic form of programmed cell death that contributes to different neurological inflammatory diseases. However, whether HSV-1 induces ferroptosis in the CNS and the role of ferroptosis in viral pathogenesis remain unclear. Here, we demonstrate that HSV-1 induces ferroptosis, as hallmarks of ferroptosis, including Fe²⁺ overload, reactive oxygen species (ROS) accumulation, glutathione (GSH) depletion, lipid peroxidation, and mitochondrion shrinkage, are observed in HSV-1-infected cultured human astrocytes, microglia cells, and murine brains. Moreover, HSV-1 infection enhances the E3 ubiquitin ligase Keap1 (Kelch-like ECH-related protein 1)-mediated ubiquitination and degradation of nuclear factor E2-related factor 2 (Nrf2), a transcription factor that regulates the expression of antioxidative genes, thereby disturbing cellular redox homeostasis and promoting ferroptosis. Furthermore, HSV-1-induced ferroptosis is tightly associated with the process of viral encephalitis in a mouse model, and the ferroptosis-activated upregulation of prostaglandin-endoperoxide synthase 2 (PTGS2) and prostaglandin E₂ (PGE₂) plays an important role in HSV-1-caused inflammation and encephalitis. Importantly, the inhibition of ferroptosis by a ferroptosis inhibitor or a proteasome inhibitor to suppress Nrf2 degradation effectively alleviated HSV-1 encephalitis. Together, our findings demonstrate the interaction between HSV-1 infection and ferroptosis and provide novel insights into the pathogenesis of HSV-1 encephalitis. IMPORTANCE Ferroptosis is a nonapoptotic form of programmed cell death that contributes to different neurological inflammatory diseases. However, whether HSV-1 induces ferroptosis in the CNS and the role of ferroptosis in viral pathogenesis remain unclear. In the current study, we demonstrate that HSV-1 infection induces ferroptosis, as Fe²⁺ overload, ROS accumulation, GSH depletion, lipid peroxidation, and mitochondrion shrinkage, all of which are hallmarks of ferroptosis, are observed in human cultured astrocytes, microglia cells, and murine brains infected with HSV-1. Moreover, HSV-1 infection enhances Keap1-dependent Nrf2 ubiquitination and degradation, which results in substantial reductions in the expression levels of antiferroptotic genes downstream of Nrf2, thereby disturbing cellular redox homeostasis and promoting ferroptosis. Furthermore, HSV-1-induced ferroptosis is tightly associated with the process of viral encephalitis in a mouse model, and the ferroptosis-activated upregulation of PTGS2 and PGE₂ plays an important role in HSV-1-caused inflammation and encephalitis. Importantly, the inhibition of ferroptosis by either a ferroptosis inhibitor or a proteasome inhibitor to suppress HSV-1-induced Nrf2 degradation effectively alleviates HSV-1-caused neuro-damage and inflammation in infected mice. Overall, our findings uncover the interaction between HSV-1 infection and ferroptosis, shed novel light on the physiological impacts of ferroptosis on the pathogenesis of HSV-1 infection and encephalitis, and provide a promising therapeutic strategy to treat this important infectious disease with a worldwide distribution.

Bioactive Peptides from Skipjack Tuna Cardiac Arterial Bulbs (II): Protective Function on UVB-Irradiated HaCaT Cells through Antioxidant and Anti-Apoptotic Mechanisms

The aim of this study was to investigate the protective function and mechanism of TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) from skipjack tuna cardiac arterial bulbs on skin photoaging using UVB-irradiated HaCaT cell model. The present results indicated that TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) had significant cytoprotective effect on UVB-irradiated HaCaT cells (p < 0.001). Hoechst 33342 staining showed that apoptosis of UV-irradiated HaCaT cells could be significantly reduced by the treatment of TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM); JC-1 staining showed that TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) could protect HaCaT cells from apoptosis by restoring mitochondrial membrane potential (MMP); Furthermore, TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) could significantly down-regulate the ratio of Bax/Bcl-2 and reduce the expression level of the apoptosis-executing protein Caspase-3 by decreasing the expression of protein Caspase-8 and Caspase-9 (p < 0.05). The action mechanism indicated that TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) could up-regulate the expression levels of Nrf2, NQO1 and HO-1 (p < 0.05), which further increased the activity of downstream proteases (SOD, CAT and GSH-Px), and scavenged reactive oxygen species (ROS) and decreased the intracellular levels of malondialdehyde (MDA). In addition, molecular docking indicated that TCP3 (PKK) and TCP6 (YEGGD) could competitively inhibit the Nrf2 binding site because they can occupy the connection site of Nrf2 by binding to the Kelch domain of Keap1 protein. TCP9 (GPGLM) was inferred to be non-competitive inhibition because it could not bind to the active site of the Kelch domain of Keap1 protein. In summary, the antioxidant peptides TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) from cardiac arterial bulbs of skipjack tuna can effectively protect HaCaT cells from UVB-irradiated damage and can be used in the development of healthy and cosmetic products to treat diseases caused by UV radiation.

Thioredoxin Signaling Pathways in Cancer

Significance: Thioredoxin (Trx) is a powerful antioxidant that reduces protein disulfides to maintain redox stability in cells and is involved in regulating multiple redox-dependent signaling pathways. Recent Advance: The current accumulation of findings suggests that Trx participates in signaling pathways that interact with various proteins to manipulate their dynamic regulation of structure and function. These network pathways are critical for cancer pathogenesis and therapy. Promising clinical advances have been presented by most anticancer agents targeting such signaling pathways. Critical Issues: We herein link the signaling pathways regulated by the Trx system to potential cancer therapeutic opportunities, focusing on the coordination and strengths of the Trx signaling pathways in apoptosis, ferroptosis, immunomodulation, and drug resistance. We also provide a mechanistic network for the exploitation of therapeutic small molecules targeting the Trx signaling pathways. Future Directions: As research data accumulate, future complex networks of Trx-related signaling pathways will gain in detail. In-depth exploration and establishment of these signaling pathways, including Trx upstream and downstream regulatory proteins, will be critical to advancing novel cancer therapeutics. Antioxid. Redox Signal. 38, 403-424.

Antioxidant and Anti-inflammatory Activity of Sea Cucumber (Holothuria scabra) Active Compounds against KEAP1 and iNOS Protein

Oxidative stress and inflammation have a role in the development of various diseases. Oxidative stress and inflammation are associated with many proteins, including Kelch ECH associating protein 1 (KEAP1) and inducible nitric oxide synthase (iNOS) proteins. The active compounds contained in Holothuria scabra have antioxidant and anti-inflammatory properties. This study aimed to evaluate the antioxidant and anti-inflammatory activity of sea cucumber's active compounds by targeting KEAP1 and iNOS proteins. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) scavenging activity of H. scabra extract were measured spectrophotometrically. The 3-dimensional (3D) structures of sea cucumber's active compounds and proteins were obtained from the PubChem and Research Collaboratory for Structural Bioinformatics Protein Data Bank (RCSB PDB) databases. Molecular docking was performed using AutoDock Vina software. Molecular dynamics simulations were carried out using Yet Another Scientific Artificial Reality Application (YASARA) software with environmental parameters according to the cell's physiological conditions. The membrane permeability test was performed using the PerMM web server. The methanol extract of H. scabra had a weak antioxidant activity against DPPH and strong activity against NO radical. Scabraside and holothurinoside G had the most negative binding affinity values when interacting with the active site of KEAP1 and iNOS proteins. Molecular dynamics simulations also showed that both compounds were stable when interacting with KEAP1 and iNOS. However, scabraside and holothurinoside G were difficult to penetrate the cell plasma membrane, which is seen from the high energy transfer value in the lipid acyl chain region of phospholipids. Scabraside and holothurinoside G are predicted to act as antioxidants and anti-inflammations, but in their implementation to in vitro and in vivo study, it is necessary to have liposomes or nanoparticles, or other delivery methods to help these 2 compounds enter the cell.

Briarane-type diterpenoids, the inhibitors of osteoclast formation by interrupting Keap1-Nrf2 interaction and activating Nrf2 pathway

Chemoinformatic and bioassay-guided fractionation of a gorgonian coral Junceella juncea resulted in the isolation of 45 briarane-type diterpenoids, of which 16 new analogues were characterized. Their structures were identified by extensive analyses of the spectroscopic data. Most isolated briaranes showed significant inhibition against the receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast differentiation in bone marrow-derived macrophages cells (BMMs). Praelolide, one of the active analogues, significantly activates nuclear factor erythroid-2-related factor 2 (Nrf2) nucleus translocation, induces the expression of Nrf2-targeted genes, suppresses reactive oxygen species (ROS) production, abrogates the activation of downstream mitogen-activated protein kinase (MAPK)/nuclear factor-κB (NFκB) signaling, and subsequently attenuates osteoclast differentiation. Mechanically, praelolide interacts with Kelch-like ECH-associated protein 1 (Keap1) protein by non-covalent interaction to interrupt the interaction between Keap1 and Nrf2 and thereby to activate the Nrf2 signaling pathway. In addition, praelolide rescues the bone loss in prednisone-induced zebrafish. The present study provided praelolide as a new natural scaffold to remedy osteoclastogenic bone disease.

Comparative in silico and in vitro study of the stability and biological activity of an octapeptide from microalgae Isochrysis zhanjiangensis and its truncated short peptide

In this study, the structural characteristics and active sites of the octapeptide (IIAVEAGC), the pentapeptide (IIAVE) and tripeptide (AGC) were studied in silica and in vitro.

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.

NRF2 in dermo-cosmetic: From scientific knowledge to skin care products

The skin is the organ that is most susceptible to the impact of the exposome. Located at the interface with the external environment, it protects internal organs through the barrier function of the epidermis. It must adapt to the consequences of the harmful effects of solar radiation, the various chemical constituents of atmospheric pollution, and wounds associated with mechanical damage: oxidation, cytotoxicity, inflammation, and so forth. In this biological context, a capacity to adapt to the various stresses caused by the exposome is essential; otherwise, more or less serious conditions may develop accelerated aging, pigmentation disorders, atopy, psoriasis, and skin cancers. Nrf2-controlled pathways play a key role at this level. Nrf2 is a transcription factor that controls genes involved in oxidative stress protection and detoxification of chemicals. Its involvement in UV protection, reduction of inflammation in processes associated with healing, epidermal differentiation for barrier function, and hair regrowth, has been demonstrated. The modulation of Nrf2 in the skin may therefore constitute a skin protection or care strategy for certain dermatological stresses and disorders initiated or aggravated by the exposome. Nrf2 inducers can act through different modes of action. Keap1-dependent mechanisms include modification of the cysteine residues of Keap1 by (pro)electrophiles or prooxidants, and disruption of the Keap1-Nrf2 complex. Indirect mechanisms are suggested for numerous phytochemicals, acting on upstream pathways, or via hormesis. While developing novel and safe Nrf2 modulators for skin care may be challenging, new avenues can arise from natural compounds-based molecular modeling and emerging concepts such as epigenetic regulation.

Jatamansinol from Nardostachys jatamansi: a multi-targeted neuroprotective agent for Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial progressive and irreversible neurodegenerative disorder characterized by severe memory impairment and cognitive disability in the middle and old-aged human population. There are no proven drugs for AD treatment and prevention. In Ayurveda, medhya plants are used to prepare Rasayana, and its consumption improves memory and cognition. Nardostachys jatamansi (D.Don) DC is a medhya plant used in traditional medicine to treat neurological disorders, and its unique pyranocoumarins can be a potential drug candidate for AD. Given its traditional claims, this study aims to find the multi-target potential efficacy of the ligands (drug molecules) against the AD from N. jatamansi pyranocoumarins using computational drug discovery techniques. Drug likeliness analysis confirms that pyranocoumarins of N. jatamansi, such as seselin, jatamansinol, jatamansine, jatamansinone, and dihydrojatamansin are probable drug candidates for AD. Molecular docking, molecular dynamic simulations, and Molecular Mechanics/Generalized Born Surface Area (MM-GBSA) analysis confirm that dihydrojatamansin inhibits acetylcholinesterase (AChE), and jatamansinol inhibits butyrylcholinesterase (BuChE), glycogen synthase kinase 3β (GSK3β), and kelch-like ECH-associating protein 1 (Keap1) AD therapeutic targets. Therefore, this study provides potential multi-target inhibitors that would further validate experimental studies, leading to new treatments for AD.Communicated by Ramaswamy H. Sarma.

KEAP1-NRF2 protein-protein interaction inhibitors: Design, pharmacological properties and therapeutic potential

The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) is considered the master regulator of the phase II antioxidant response. It controls a plethora of cytoprotective genes related to oxidative stress, inflammation, and protein homeostasis, among other processes. Activation of these pathways has been described in numerous pathologies including cancer, cardiovascular, respiratory, renal, digestive, metabolic, autoimmune, and neurodegenerative diseases. Considering the increasing interest of discovering novel NRF2 activators due to its clinical application, initial efforts were devoted to the development of electrophilic drugs able to induce NRF2 nuclear accumulation by targeting its natural repressor protein Kelch-like ECH-associated protein 1 (KEAP1) through covalent modifications on cysteine residues. However, off-target effects of these drugs prompted the development of an innovative strategy, the search of KEAP1-NRF2 protein-protein interaction (PPI) inhibitors. These innovative activators are proposed to target NRF2 in a more selective way, leading to potentially improved drugs with the application for a variety of diseases that are currently under investigation. In this review, we summarize known KEAP1-NRF2 PPI inhibitors to date and the bases of their design highlighting the most important features of their respective interactions. We also discuss the preclinical pharmacological properties described for the most promising compounds.

Synthesis, antioxidant, in silico and computational investigation of 2,5-dihydroxyacetophenone derived chloro-substituted hydroxychalcones, hydroxyflavanones and hydroxyflavindogenides

An imbalance between reactive oxygen species (ROS) and their elimination by antioxidants damages the cell and infect whole organism. The biological defence system against oxidative stress injury is Kelch-like ECH associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elements (ARE) pathways. Antioxidants activate the Nrf2-ARE-Keap1 pathway and suppress the oxidative stress. Flavonoids are well known medicinal compounds inheriting antioxidant efficacy and wide spectrum of pharmacological activities. The study is aimed to synthesise, characterize and evaluate pharmacological activities of synthesized chloro-derivatives of flavonoids. Chloro-derivatives of flavonoids were synthesized and characterized by IR, ¹H NMR and ¹³C NMR. Antioxidant potential of each synthesized compound was evaluated and then subjected to molecular docking with Keap1 (PDB ID: 2FLU) for the activation of Nrf2 and computational studies were performed by using DFT approach. Among the synthesized compounds compound 1a exhibited lower IC₅₀ value. While docking and computational studies infer that compound 3c is a good Nrf2 activator and radical scavenger with highest docking score and lower energy gaps and IP values compared to references. Hence, it might be considered for further molecular studies for the treatment of inflammatory diseases through Nrf2-ARE-Keap1 pathway. Communicated by Ramaswamy H. Sarma.HighlightsChloro-substituted hydroxychalcones, hydroxyflavanones and hydroxyflavindogenides were synthesized.Antioxidant potential was accessed, compound 1a exhibited good antioxidant potential.In silico study was performed with Keap1, compound 3c have shown highest docking score with Keap1.DFT approach was used to explore the structure activity relationship.

Nrf2 and Oxidative Stress: A General Overview of Mechanisms and Implications in Human Disease

Organisms are continually exposed to exogenous and endogenous sources of reactive oxygen species (ROS) and other oxidants that have both beneficial and deleterious effects on the cell. ROS have important roles in a wide range of physiological processes; however, high ROS levels are associated with oxidative stress and disease progression. Oxidative stress has been implicated in nearly all major human diseases, from neurogenerative diseases and neuropsychiatric disorders to cardiovascular disease, diabetes, and cancer. Antioxidant defence systems have evolved as a means of protection against oxidative stress, with the transcription factor Nrf2 as the key regulator. Nrf2 is responsible for regulating an extensive panel of antioxidant enzymes involved in the detoxification and elimination of oxidative stress and has been extensively studied in the disease contexts. This review aims to provide the reader with a general overview of oxidative stress and Nrf2, including basic mechanisms of Nrf2 activation and regulation, and implications in various major human diseases.

Targeting NRF2-KEAP1 axis by Omega-3 fatty acids and their derivatives: Emerging opportunities against aging and diseases

The transcription factor NRF2 and its endogenous inhibitor KEAP1 play a crucial role in the maintenance of cellular redox homeostasis by regulating the gene expression of diverse networks of antioxidant, anti-inflammatory, and detoxification enzymes. Therefore, activation of NRF2 provides cytoprotection against numerous pathologies, including age-related diseases. An age-associated loss of NRF2 function may be a key driving force behind the aging phenotype. Recently, numerous NRF2 inducers have been identified and some of them are promising candidates to restore NRF2 transcriptional activity during aging. Emerging evidence indicates that omega-3 (n-3) polyunsaturated fatty acids (PUFAs) and their electrophilic derivatives may trigger a protective response via NRF2 activation, rescuing or maintaining cellular redox homeostasis. In this review, we provide an overview of the NRF2-KEAP1 system and its dysregulation in aging cells. We also summarize current studies on the modulatory role of n-3 PUFAs as potential agents to prevent multiple chronic diseases and restore the age-related impairment of NRF2 function.

Lycopene Alleviates Chronic Stress-Induced Liver Injury by Inhibiting Oxidative Stress-Mediated Endoplasmic Reticulum Stress Pathway Apoptosis in Rats

The liver is the major organ of metabolism and is extremely vulnerable to chronic stress. Lycopene (LYC) is a natural carotenoid with potent antioxidant and chronic disease potential. However, whether LYC protects against chronic restraint stress (CRS)-induced liver injury and the underlying mechanisms remain unclear. In this study, rats were restrained for 21 days for 6 h per day, with or without gavage of LYC (10 mg/kg). Serum ALT (85.99 ± 4.07 U/L) and AST (181.78 ± 7.35 U/L) and scores of liver injury were significantly increased in the CRS group. LYC significantly promoted the nuclear translocation of Nrf2, elevated the expression of antioxidant genes, and attenuated reactive oxygen radicals (ROS) levels within the liver. Cellular thermal shift assay (CETSA) and molecular docking results indicated that LYC competitively binds to Keap1 with the lowest molecule affinity of -9.0 kcal/mol. Moreover, LYC significantly relieved the hepatic endoplasmic reticulum swelling and decreased the expression of endoplasmic reticulum stress (ERS) hallmarks like GRP78, CHOP, and cleaved caspase-12. Meanwhile, LYC also mitigated CRS-induced hepatocyte apoptosis. Interestingly, every other day, the intraperitoneal injection of the Nrf2 inhibitor brusatol (0.4 mg/kg) significantly counteracted the protective effect of LYC. In conclusion, LYC protects against CRS-induced liver injury by activating the Nrf2 signaling pathway, scavenging ROS, and further attenuating ERS-associated apoptosis pathways.

A novel anti-atherosclerotic mechanism of quercetin: Competitive binding to KEAP1 via Arg483 to inhibit macrophage pyroptosis

Natural antioxidants represented by quercetin have been documented to be effective against atherosclerosis. However, the related mechanisms remain largely unclear. In this study, we identified a novel anti-atherosclerotic mechanism of quercetin inhibiting macrophage pyroptosis by activating NRF2 through binding to the Arg483 site of KEAP1 competitively. In ApoE-/- mice fed with high fat diet, quercetin administration attenuated atherosclerosis progression by reducing oxidative stress level and suppressing macrophage pyroptosis. At the cellular level, quercetin suppressed THP-1 macrophage pyroptosis induced by ox-LDL, demonstrated by inhibiting NLRP3 inflammasome activation and reducing ROS level, while these effects were reversed by the specific NRF2 inhibitor (ML385). Mechanistically, quercetin promoted NRF2 to dissociate from KEAP1, enhanced NRF2 nuclear translocation as well as transcription of downstream antioxidant protein. Molecular docking results suggested that quercetin could bind with KEAP1 at Arg415 and Arg483. In order to verify the binding sites, KEAP1 mutated at Arg415 and Arg483 to Ser (R415S and R483S) was transfected into THP-1 macrophages, and the anti-pyroptotic effect of quercetin was abrogated by Arg483 mutation, but not Arg415 mutation. Furthermore, after administration of adeno associated viral vector (AAV) with AAV-KEAP1-R483S, the anti-atherosclerotic effects of quercetin were almost abolished in ApoE-/- mice. These findings proved quercetins suppressed macrophage pyroptosis by targeting KEAP1/NRF2 interaction, and provided reliable data on the underlying mechanism of natural antioxidants to protect against atherosclerosis.

Exploring the target scope of KEAP1 E3 ligase-based PROTACs

Targeted protein degradation (TPD) uses small molecules to recruit E3 ubiquitin ligases into the proximity of proteins of interest, inducing ubiquitination-dependent degradation. A major bottleneck in the TPD field is the lack of accessible E3 ligase ligands for developing degraders. To expand the E3 ligase toolbox, we sought to convert the Kelch-like ECH-associated protein 1 (KEAP1) inhibitor KI696 into a recruitment handle for several targets. While we were able to generate KEAP1-recruiting degraders of BET family and murine focal adhesion kinase (FAK), we discovered that the target scope of KEAP1 was narrow, as targets easily degraded using a cereblon (CRBN)-recruiting degrader were refractory to KEAP1-mediated degradation. Linking the KEAP1-binding ligand to a CRBN-binding ligand resulted in a molecule that induced degradation of KEAP1 but not CRBN. In sum, we characterize tool compounds to explore KEAP1-mediated ubiquitination and delineate the challenges of exploiting new E3 ligases for generating bivalent degraders.

Oxidative Stress Amelioration of Novel Peptides Extracted from Enzymatic Hydrolysates of Chinese Pecan Cake

Pecan (Carya cathayensis) is an important economic crop, and its hydrolyzed peptides have been evidenced to reduce the effect of oxidative stress due to their antioxidant capacity. Hence, the protocols of ultrafiltration and gel filtration chromatography were established to obtain bioactive peptides from by-products of C. cathayensis (pecan cake). As measured by DPPH/ABTS radical scavenging, the peptides with less molecular weight (MW) possess higher antioxidant capacity. PCPH-III (MW < 3 kDa) presented higher radical scavenging capacity than PCPH-II (3 kDa < MW < 10 kDa) and PCPH-I (MW > 10 kDa) measured by DPPH (IC50: 111.0 μg/ mL) and measured by ABTs (IC50: 402.9 μg/mL). The secondary structure and amino acid composition varied by their MW, in which PCPH-II contained more α-helices (26.71%) and β-sheets (36.96%), PCPH-III contained higher ratios of β-turns (36.87%), while the composition of different secondary of PCPH-I was even 25 ± 5.76%. The variation trend of α-helix and random experienced slightly varied from PCPH-I to PCPH-II, while significantly decreased from PCPH-II to PCPH-III. The increasing antioxidant capacity is followed by the content of proline, and PCPH-III had the highest composition (8.03%). With regard to the six peptides identified by LC-MS/MS, two of them (VYGYADK and VLFSNY) showed stronger antioxidant capacity than others. In silico molecular docking demonstrated their combining abilities with a transcription factor Kelch-like ECH-associated protein 1 (Keap1) and speculated that they inhibit oxidative stress through activating the Keap1-Nrf2-ARE pathway. Meanwhile, increased activity of SOD and CAT—antioxidant markers—were found in H2O2-induced cells. The residue of tyrosine was demonstrated to contribute the most antioxidant capacity of VYGYADK and its position affected less. This study provided a novel peptide screening and by-product utilization process that can be applied in natural product developments.

Current strategies and progress for targeting the "undruggable" transcription factors

Transcription factors (TFs) specifically bind to DNA, recruit cofactor proteins and modulate target gene expression, rendering them essential roles in the regulation of numerous biological processes. Meanwhile, mutated or dysregulated TFs are involved in a variety of human diseases. As multiple signaling pathways ultimately converge at TFs, targeting these TFs directly may prove to be more specific and cause fewer side effects, than targeting the upfront conventional targets in these pathways. All these features together endue TFs with great potential and high selectivity as therapeutic drug targets. However, TFs have been historically considered "undruggable", mainly due to their lack of structural information, especially about the appropriate ligand-binding sites and protein-protein interactions, leading to relatively limited choices in the TF-targeting drug design. In this review, we summarize the recent progress of TF-targeting drugs and highlight certain strategies used for targeting TFs, with a number of representative drugs that have been approved or in the clinical trials as examples. Various approaches in targeting TFs directly or indirectly have been developed. Common direct strategies include aiming at defined binding pockets, proteolysis-targeting chimaera (PROTAC), and mutant protein reactivation. In contrast, the indirect ones comprise inhibition of protein-protein interactions between TF and other proteins, blockade of TF expression, targeting the post-translational modifications, and targeting the TF-DNA interactions. With more comprehensive structural information about TFs revealed by the powerful cryo-electron microscopy technology and predicted by machine-learning algorithms, plus more efficient compound screening platforms and a deeper understanding of TF-disease relationships, the development of TF-targeting drugs will certainly be accelerated in the near future.

Nrf2 Pathway and Autophagy Crosstalk: New Insights into Therapeutic Strategies for Ischemic Cerebral Vascular Diseases

Cerebrovascular disease is highly prevalent and has a complex etiology and variable pathophysiological activities. It thus poses a serious threat to human life and health. Currently, pathophysiological research on cerebrovascular diseases is gradually improving, and oxidative stress and autophagy have been identified as important pathophysiological activities that are gradually attracting increasing attention. Many studies have found some effects of oxidative stress and autophagy on cerebrovascular diseases, and studies on the crosstalk between the two in cerebrovascular diseases have made modest progress. However, further, more detailed studies are needed to determine the specific mechanisms. This review discusses nuclear factor erythroid 2-related factor 2 (Nrf2) molecules, which are closely associated with oxidative stress and autophagy, and the crosstalk between them, with the aim of providing clues for studying the two important pathophysiological changes and their crosstalk in cerebrovascular diseases as well as exploring new target treatments.

Pharmacological characterization of a novel peptide inhibitor of the Keap1-Nrf2 protein-protein interaction

LAS200813 is a novel bicyclic lipopeptide that activates Nrf2 by binding to Keap1, thereby antagonising the Keap1-Nrf2 protein-protein interaction. In this work we report the pharmacological characterization of LAS200813 in Nrf2-dependent translational preclinical models. LAS200813 binds to Keap1 with high affinity (IC₅₀: 0.73 nM) and is able to induce the translocation of Nrf2 to the nucleus. Furthermore, LAS200813 increases the expression of Nrf2 target genes in human bronchial epithelial cells (EC₅₀ of 96 and 70 nM for srxn1 and nqo1, respectively). Similarly, the intratracheal administration of LAS200813 to rats increases the expression of Nrf2-dependent genes in lung tissue, an effect that lasts for a few hours. Moreover, in cells exposed to cigarette smoke, LAS200813 shows an antioxidant effect by increasing the production of glutathione and prevents cellular apoptosis. In conclusion, the results described herein demonstrate that LAS200813 is a potent non-electrophilic Nrf2-activating peptide designed to be administered by inhaled route which may be a potential therapeutic strategy for respiratory diseases driven by oxidative stress.

Role of Nuclear Factor Erythroid 2 (Nrf2) in the Recovery of Long COVID-19 Using Natural Antioxidants: A Systematic Review

Coronavirus disease 2019 (COVID-19) is an infectious disease with approximately 517 million confirmed cases, with the average number of cases revealing that patients recover immediately without hospitalization. However, several other cases found that patients still experience various symptoms after 3–12 weeks, which is known as a long COVID syndrome. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can activate nuclear factor kappa beta (NF-κβ) and unbind the nuclear factor erythroid 2-related factor 2 (Nrf2) with Kelch-like ECH-associated protein 1 (Keap1), causing inhibition of Nrf2, which has an important role in antioxidant response and redox homeostasis. Disrupting the Keap1–Nrf2 pathway enhances Nrf2 activity, and has been identified as a vital approach for the prevention of oxidative stress and inflammation. Hence, natural antioxidants from various sources have been identified as a promising strategy to prevent oxidative stress, which plays a role in reducing the long COVID-19 symptoms. Oxygen-rich natural antioxidant compounds provide an effective Nrf2 activation effect that interact with the conserved amino acid residues in the Keap1-binding pocket, such as Ser602, Ser363, Ser508, and Ser555. In this review, the benefits of various natural antioxidant compounds that can modulate the Nrf2 signaling pathway, which is critical in reducing and curing long COVID-19, are highlighted and discussed.

Antiaging function of Chinese pond turtle (Chinemys reevesii) peptide through activation of the Nrf2/Keap1 signaling pathway and its structure-activity relationship

Chinese pond turtle is a traditional nourishing food with high nutritional value and bioactivity and has been considered a dietary remedy for prolonging the lifespan since ancient times. However, only limited information about their effects on longevity is available. This study was performed to assess the antioxidant activities and antiaging potential of Chinese pond turtle peptide (CPTP) using Drosophila melanogaster model and uncover the possible mechanisms underlying the beneficial effects. CPTP exhibited excellent antioxidant capability in vitro with IC₅₀ values of 3.31, 1.93, and 9.52 mg/ml for 1,1-diphenyl-2-pycryl-hydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazo-line-6-sulfonic acid) diammonium salt (ABTS), and hydroxyl radical scavenging, respectively. In vivo, 0.8% of CPTP significantly extended the mean and median lifespan of female flies by 7.66 and 7.85%, followed by enhanced resistance to oxidative and heat stress. Besides, CPTP remarkably increased the antioxidant enzyme activities and diminished the peroxide product accumulation. Furthermore, CPTP upregulated the relative mRNA expression of antioxidant-related genes, including nuclear factor-erythroid-2-like 2 (Nrf2) and its downstream target genes, while downregulated the expression of Kelch-like ECH-associated protein 1 (Keap1). Taken together, CPTP displayed promising potential in both antioxidant and antiaging effects on flies by targeting the Nrf2/Keap1 pathway. Further peptide sequence determination revealed that 89.23% of peptides from the identified sequences in CPTP could exert potential inhibitory effects on Keap1. Among these peptides, ten representative peptide sequences could actively interact with the binding sites of Keap1-Nrf2 interaction through hydrogen bonds, van der Walls, hydrophobic interactions, and electrostatic interactions. Conclusively, CPTP could be utilized as health-promoting bioactive peptide with antioxidant and antiaging capacities.

Signal amplification in the KEAP1-NRF2-ARE antioxidant response pathway

The KEAP1-NRF2-ARE signaling pathway plays a central role in mediating the adaptive cellular stress response to oxidative and electrophilic chemicals. This canonical pathway has been extensively studied and reviewed in the past two decades, but rarely was it looked at from a quantitative signaling perspective. Signal amplification, i.e., ultrasensitivity, is crucially important for robust induction of antioxidant genes to appropriate levels that can adequately counteract the stresses. In this review article, we examined a number of well-known molecular events in the KEAP1-NRF2-ARE pathway from a quantitative perspective with a focus on how signal amplification can be achieved. We illustrated, by using a series of mathematical models, that redox-regulated protein sequestration, stabilization, translation, nuclear trafficking, DNA promoter binding, and transcriptional induction - which are embedded in the molecular network comprising KEAP1, NRF2, sMaf, p62, and BACH1 - may generate highly ultrasensitive NRF2 activation and antioxidant gene induction. The emergence and degree of ultrasensitivity depend on the strengths of protein-protein and protein-DNA interaction and protein abundances. A unique, quantitative understanding of signal amplification in the KEAP1-NRF2-ARE pathway will help to identify sensitive targets for the prevention and therapeutics of oxidative stress-related diseases and develop quantitative adverse outcome pathway models to facilitate the health risk assessment of oxidative chemicals.

Virtual Screening Expands the Non-Natural Amino Acid Palette for Peptide Optimization

Peptides are an important modality in drug discovery. While current peptide optimization focuses predominantly on the small number of natural and commercially available non-natural amino acids, the chemical spaces available for small molecule drug discovery are in the billions of molecules. In the present study, we describe the development of a large virtual library of readily synthesizable non-natural amino acids that can power the virtual screening protocols and aid in peptide optimization. To that end, we enumerated nearly 380 thousand amino acids and demonstrated their vast chemical diversity compared to the 20 natural and commercial residues. Furthermore, we selected a diverse ten thousand amino acid subset to validate our virtual screening workflow on the Keap1-Neh2 complex model system. Through in silico mutations of Neh2 peptide residues to those from the virtual library, our docking-based protocol identified a number of possible solutions with a significantly higher predicted affinity toward the Keap1 protein. This protocol demonstrates that the non-natural amino acid chemical space can be massively extended and virtually screened with a reasonable computational cost.

The Role of Organosulfur Compounds as Nrf2 Activators and Their Antioxidant Effects

Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling has become a key pathway for cellular regulation against oxidative stress and inflammation, and therefore an attractive therapeutic target. Several organosulfur compounds are reportedly activators of the Nrf2 pathway. Organosulfur compounds constitute an important class of therapeutic agents in medicinal chemistry due to their ability to participate in biosynthesis, metabolism, cellular functions, and protection of cells from oxidative damage. Sulfur has distinctive chemical properties such as a large number of oxidation states and versatility of reactions that promote fundamental biological reactions and redox biochemistry. The presence of sulfur is responsible for the peculiar features of organosulfur compounds which have been utilized against oxidative stress-mediated diseases. Nrf2 activation being a key therapeutic strategy for oxidative stress is closely tied to sulfur-based chemistry since the ability of compounds to react with sulfhydryl (-SH) groups is a common property of Nrf2 inducers. Although some individual organosulfur compounds have been reported as Nrf2 activators, there are no papers with a collective analysis of these Nrf2-activating organosulfur compounds which may help to broaden the knowledge of their therapeutic potentials and motivate further research. In line with this fact, for the first time, this review article provides collective and comprehensive information on Nrf2-activating organosulfur compounds and their therapeutic effects against oxidative stress, thereby enriching the chemical and pharmacological diversity of Nrf2 activators.

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.

Phenyl Bis-Sulfonamide Keap1-Nrf2 Protein-Protein Interaction Inhibitors with an Alternative Binding Mode

Inhibitors of Kelch-like ECH-associated protein 1 (Keap1) increase the activity of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) by stalling its ubiquitination and degradation. This enhances the expression of genes encoding proteins involved in drug detoxification, redox homeostasis, and mitochondrial function. Nrf2 activation offers a potential therapeutic approach for conditions including Alzheimer's and Parkinson's diseases, vascular inflammation, and chronic obstructive airway disease. Non-electrophilic Keap1-Nrf2 protein-protein interaction (PPI) inhibitors may have improved toxicity profiles and different pharmacological properties to cysteine-reactive electrophilic inhibitors. Here, we describe and characterize a series of phenyl bis-sulfonamide PPI inhibitors that bind to Keap1 at submicromolar concentrations. Structural studies reveal that the compounds bind to Keap1 in a distinct "peptidomimetic" conformation that resembles the Keap1-Nrf2 ETGE peptide complex. This is different to other small molecule Keap1-Nrf2 PPI inhibitors, including bicyclic aryl bis-sulfonamides, offering a starting point for new design approaches to Keap1 inhibitors.

Neuroprotective Effects and Therapeutic Potential of the Citrus Flavonoid Hesperetin in Neurodegenerative Diseases

Neurodegenerative disorders affect more than fifty million Americans each year and represent serious health threats as the population ages. Neuroinflammation and oxidative stress are critical in the onset, progression, and pathogenesis of neurodegenerative diseases such as Alzheimer’s (AD), Parkinson’s (PD), and amyotrophic lateral sclerosis (ALS). A wide range of natural compounds has been investigated because of their antioxidant, anti-inflammatory, and neuroprotective properties. The citrus flavonoid hesperetin (HPT), an aglycone of hesperidin found in oranges, mandarins, and lemons, has been extensively reported to exert neuroprotective effects in experimental models of neurogenerative diseases. This review has compiled multiple studies on HPT in both in vivo and in vitro models to study neurodegeneration. We focused on the modulatory effects of hesperetin on the release of cellular anti-inflammatory and antioxidative stress mediators. Additionally, this review discusses the hesperetin effect in maintaining the levels of microRNA (miRNA) and modulating autophagy as it relates to hesperetin’s protective mechanisms against neurodegeneration. Moreover, this review is focused on providing experimental data for hesperetin’s potential as a neuroprotective compound and discusses reported evidence that HPT crosses the blood–brain barrier. In summary, this review shows the evidence available in the literature to indicate the efficacy of hesperetin in delaying the onset of neurodegenerative diseases.

In-silico validation of novel therapeutic activities of withaferin a using molecular docking and dynamics studies

Withaferin A is a bioactive molecule of W. somnifera. We access its efficacy against various target proteins associated with Cancer, Type-II Diabetes and hypercholesterolemia using molecular docking. Although it's efficacy against some of these targets have been reported earlier, we validate each mechanism in order to report the most appropriate mechanism of action. We explain the anti-cancer activity of Withaferin A by inhibition of Mortalin (mtHsp70) and Nrf2 protein with binding energies -8.85 kcal/mol and -12.59 kcal/mol respectively. Similarly, the anti-diabetic activity could be explained by inhibition of alpha and betα-glucosidase with binding energies -6.44 and -4.43 kcal/mol respectively and the cholesterol reduction could be explained by its ability to inhibition of NPC1 and SRB1 with binding energies -5.73 and -7.16 kcal/mol respectively. The molecular dynamics of the apoprotein and the protein-ligand complex simulated for the best targets of each activity namely Nrf2 protein for anti-cancer, α-glucosidase for anti-diabetic and SR-B1 for anti-hypercholesterolemia activity indicated the formation of stable complexes due to low RMSD deviations, low RMSF fluctuations and low RG values after the docking simulation. Finally, an ADME + T (Adsorption, distribution, metabolism, excretion and toxicity) prediction on Withaferin A showed that it obeyed all the Lipinsky's rules and qualified the drug-like criteria. All these results validate that Withaferin A possess potential anti-cancer, anti-diabetic and cholesterol reducing properties. This is the first report that indicates the possibility of Withaferin A binding and inhibiting SR-B1 as a mechanism of its anti-hypercholesterolemia activity.

Nrf2 Activation Protects Against Organic Dust and Hydrogen Sulfide Exposure Induced Epithelial Barrier Loss and K. pneumoniae Invasion

Agriculture workers report various respiratory symptoms owing to occupational exposure to organic dust (OD) and various gases. Previously, we demonstrated that pre-exposure to hydrogen sulfide (H₂S) alters the host response to OD and induces oxidative stress. Nrf2 is a master-regulator of host antioxidant response and exposures to toxicants is known to reduce Nrf2 activity. The OD exposure-induced lung inflammation is known to increase susceptibility to a secondary microbial infection. We tested the hypothesis that repeated exposure to OD or H₂S leads to loss of Nrf2, loss of epithelial cell integrity and that activation of Nrf2 rescues this epithelial barrier dysfunction. Primary normal human bronchial epithelial (NHBE) cells or mouse precision cut-lung slices (PCLS) were treated with media, swine confinement facility organic dust extract (ODE) or H₂S or ODE+H₂S for one or five days. Cells were also pretreated with vehicle control (DMSO) or RTA-408, a Nrf2 activator. Acute exposure to H₂S and ODE+H₂S altered the cell morphology, decreased the viability as per the MTT assay, and reduced the Nrf2 expression as well as increased the keap1 levels in NHBE cells. Repeated exposure to ODE or H₂S or ODE+H₂S induced oxidative stress and cytokine production, decreased tight junction protein occludin and cytoskeletal protein ezrin expression, disrupted epithelial integrity and resulted in increased Klebsiella pneumoniae invasion. RTA-408 (pharmacological activator of Nrf2) activated Nrf2 by decreasing keap1 levels and reduced ODE+H₂S-induced changes including reversing loss of barrier integrity, inflammatory cytokine production and microbial invasion in PCLS but not in NHBE cell model. We conclude that Nrf2 activation has a partial protective function against ODE and H₂S.

Structure-guided discovery of antioxidant peptides bounded to the Keap1 receptor as hunter for potential dietary antioxidants

Human health can be damaged by free radicals, and antioxidant peptides are excellent radical scavengers. Antioxidant tripeptides data set based on 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulofnic acid) (ABTS) assay was created, 9 types of descriptors were integrated and 4 quantitative structure-activity relationship (QSAR) models were constructed in this study. Several structural factors influencing the activity of antioxidant tripeptides and the dominant amino acids at each position of tripeptides were revealed by the optimal model. Ten food-derived tripeptides with higher activity were selected for synthesis and activity determination. Molecular docking results demonstrated that these tripeptides were stably bound to the Keap1 receptor, further elucidating the antioxidant mechanism. It was known from the simulation of gastrointestinal digestion experiments that the model results possessed a guiding effect on the selection of proteins with high antioxidant activity. The performance of the model was proved to be robust after validation.

Sequence and structural variations determining the recruitment of WNK kinases to the KLHL3 E3 ligase

The BTB-Kelch protein KLHL3 is a Cullin3-dependent E3 ligase that mediates the ubiquitin-dependent degradation of kinases WNK1-4 to control blood pressure and cell volume. A crystal structure of KLHL3 has defined its binding to an acidic degron motif containing a PXXP sequence that is strictly conserved in WNK1, WNK2 and WNK4. Mutations in the second proline abrograte the interaction causing the hypertension syndrome pseudohypoaldosteronism type II. WNK3 shows a diverged degron motif containing four amino acid substitutions that remove the PXXP motif raising questions as to the mechanism of its binding. To understand this atypical interaction, we determined the crystal structure of the KLHL3 Kelch domain in complex with a WNK3 peptide. The electron density enabled the complete 11-mer WNK-family degron motif to be traced for the first time revealing several conserved features not captured in previous work, including additional salt bridge and hydrogen bond interactions. Overall, the WNK3 peptide adopted a conserved binding pose except for a subtle shift to accommodate bulkier amino acid substitutions at the binding interface. At the centre, the second proline was substituted by WNK3 Thr541, providing a unique phosphorylatable residue among the WNK-family degrons. Fluorescence polarisation and structural modelling experiments revealed that its phosphorylation would abrogate the KLHL3 interaction similarly to hypertension-causing mutations. Together, these data reveal how the KLHL3 Kelch domain can accommodate the binding of multiple WNK isoforms and highlight a potential regulatory mechanism for the recruitment of WNK3.

Quality control of protein complex composition

Eukaryotic cells possess hundreds of protein complexes that contain multiple subunits and must be formed at the correct time and place during development. Despite specific assembly pathways, cells frequently encounter complexes with missing or aberrant subunits that can disrupt important signaling events. Cells, therefore, employ several ubiquitin-dependent quality control pathways that can prevent, correct, or degrade flawed complexes. In this review, we will discuss our emerging understanding of such quality control of protein complex composition.

Ellagic acid inhibits proinflammatory intermediary manufacture by suppressing NF-κB/Akt, VEGF and activating Nrf-2/Caspase-3 signaling pathways in rat testicular damage: a new way for testicular damage cure and in silico approach

Ellagic acid (EA) has protective effect on testicular damage and this natural compound decreases oxidative damage. The present study aims to examine the preventive effect of ellagic acid (EA) against carbon tetrachloride (CCl₄)-induced testicular tissue damage in rats. In testicular tissue, tumor necrosis factor-α (TNF-α), Nuclear factor erythroid-2 related factor 2 (Nrf-2), B-cell lymphoma-2 (Bcl-2), vascular endothelial growth factor (VEGF), Nuclear factor-kappa B (NF-κB), cysteine aspartic proteases (caspase-3) and protein kinase B (Akt) synthesis levels were analyzed by western blot method, reactive oxygen species (ROS) was measured by malondialdehyde (MDA) levels, Glutathione (GSH) level and catalase (CAT) by spectrophotometer. As a result, in comparison with the CCl₄ group, caspase-3 and Nrf-2 protein synthesis levels increased in EA + CCl₄ group, however, VEGF, Bcl-2, NF-κB, TNF-α and Akt protein synthesis levels decreased, EA application raised GSH levels and CAT activity, reduced MDA levels. In this study, in silico tools were applied to confirm the activity of EA against the cancer with macromolecules such as the above mentioned transcription factors. EA, turned out to show significant activity similarly to some cocrystal ligands, particularly against cancer. These results points out that EA can be used as a testicular damage cure drug in future.

Perillyl alcohol attenuates rheumatoid arthritis via regulating TLR4/NF-κB and Keap1/Nrf2 signaling pathways: A comprehensive study onin-vitro and in-vivo experimental models

BACKGROUND

Rheumatoid arthritis is a chronic and idiopathic autoimmune disorder. Perillyl alcohol (POH) is a monoterpene which can be extracted from widely available essential oils and is known for its strong anti-inflammatory and anti-oxidant properties.

HYPOTHESIS/PURPOSE

Recent studies have been proven that inhibitors of farnesyltransferase enzyme showed significant anti-arthritic activity. POH is one such natural molecule having anti-inflammatory and anti-oxidant properties by inhibiting farnesyltransferase enzyme which further down regulates NF-κB and Nrf2 via Ras/Raf/MAPK pathway. Also, the effect of POH against rheumatoid arthritis is not known yet. Hence, the present research was intended to assess the anti-arthritic potential of POH in-vitro and in-vivo.

METHODS

The in-vitro effects of POH on RAW 264.7 cells stimulated with LPS 1 µg/ml were investigated to its potential therapeutic effects. CFA 100 µl was intradermally administered to rats for the induction of arthritis. POH 100 mg/kg and 200 mg/kg administered topically from day 1 to day 28. Paw volumes measured, radiography analysis, anti-oxidant status, Gene expression studies, western blot analysis and histological analysis were performed to check the effects of POH.

RESULTS

Our in-vitro findings suggested that POH inhibits inflammation by suppressing reactive oxygen species (ROS), NF-кB and Nrf2 signaling axis. Besides this, POH also rescinded the nitrate levels, pro-inflammatory cytokine levels like IL-1β, IL-6 and TNF-α also PGE2 and COX-2 levels induced by LPS in murine macrophages. Additionally, our in-vivo results revealed that POH conscientiously alleviated CFA induced inflammation by restoring arthritis index, body weight, nitrosative, lipid peroxidation assays. Macroscopically through measuring paw volumes and X-ray, it was evidenced that POH has decreased inflammation and bone erosion. Not only in-vitro but also in-vivo, POH has abridged cytokine levels IL-1β, IL-6, and TNF-α. Histopathological evaluation presented POH treatment alleviated joint inflammation, pannus formation, and bone erosion significantly. Moreover, POH suppressed the protein expression of NF-кB, COX-2, iNOS and improved Nrf2, and SOD2 levels in paw tissues estimated by western blotting.

CONCLUSION

POH was effective in ameliorating LPS stimulation mediated oxidative stress and pro-inflammatory cytokines in RAW 264.7 cells in-vitro and FCA induced arthritis in rats in-vivo through its anti-inflammatory effects via regulating TLR4/NF-κB and Keap1/Nrf2 signaling pathways..

In vivo, in vitro and in silico anticancer investigation of fullerene C60 on DMBA induced breast cancer in rats

AIMS

The aim of the study was to determine the protective and therapeutic effect of fullerene C₆₀ nanoparticle on DMBA-induced breast cancer in rats.

MAIN METHODS

In vitro cell viability was determined by the WST-1 test. In vivo analysis was performed in female Wistar Albino rats. The expression of caspase-3, Bcl-2, Nrf-2, NF-κB, TNF-α, COX-2, p53, IL-6, IL-1α ve p38α (MAPK) proteins were assessed by western blotting. Furthermore, malondialdehyde (MDA), glutathione (GSH), catalase activity (CAT), total protein levels and DNA damage were investigated. In addition, tissues were evaluated by histopathologically. In in silico analysis, the binding affinities of the fullerene C₆₀ nanoparticle to transcription factors such as caspase-3, Bcl-2, Nrf-2, NF-κB, TNF-α, COX-2, VEGF and Akt were demonstrated by molecular docking.

KEY FINDINGS

Treatment of MCF-7 cells at various concentrations of fullerene C₆₀ (0.1 to 100 mg/ml) inhibited cell viability in a dose dependent manner. Fullerene C₆₀ treated rats exhibited considerable increase in the level of caspase-3 while decrease in the level of pro-survival protein Bcl-2. Bcl-2, NF-κB, TNF-α, COX-2, IL-6, IL-1α and p38α (MAPK) protein expression levels and malondialdehyde (MDA) levels were decreased in the C₆₀ + DMBA groups compared to the DMBA group. It was observed that caspase-3, Nrf-2 and p53 protein expression levels, glutathione (GSH) level, catalase activities (CAT) and total protein levels increased significantly which was further confirmed through the resulting DNA fragmentation.

SIGNIFICANCE

In silico assays, fullerene C₆₀ has been observed to have similar affinity to some crystal ligands, especially against cancer.

Nrf2/Keap1/ARE signaling: Towards specific regulation

The Nrf2 transcription factor governs the expression of hundreds genes involved in cell defense against oxidative stress, the hallmark of numerous diseases such as neurodegenerative, cardiovascular, some viral pathologies, diabetes and others. The main route for Nrf2 activity regulation is via interactions with the Keap1 protein. Under the normoxia the Keap1 binds the Nrf2 and targets it to the proteasomal degradation, while the Keap1 is regenerated. Upon oxidative stress the interactions between Nrf2 and Keap1 are interrupted and the Nrf2 activates the transcription of the protective genes. Currently, the Nrf2 system activation is considered as a powerful cytoprotective strategy for treatment of different pathologies, which pathogenesis relies on oxidative stress including viral diseases of pivotal importance such as COVID-19. The implementation of this strategy is accomplished mainly through the inactivation of the Keap1 "guardian" function. Two approaches are now developing: the Keap1 modification via electrophilic agents, which leads to the Nrf2 release, and direct interruption of the Nrf2:Keap1 protein-protein interactions (PPI). Because of theirs chemical structure, the Nrf2 electrophilic inducers could non-specifically interact with others cellular proteins leading to undesired effects. Whereas the non-electrophilic inhibitors of the Nrf2:Keap1 PPI could be more specific, thereby widening the therapeutic window.

How Cells Deal with the Fluctuating Environment: Autophagy Regulation under Stress in Yeast and Mammalian Systems

Eukaryotic cells frequently experience fluctuations of the external and internal environments, such as changes in nutrient, energy and oxygen sources, and protein folding status, which, after reaching a particular threshold, become a type of stress. Cells develop several ways to deal with these various types of stress to maintain homeostasis and survival. Among the cellular survival mechanisms, autophagy is one of the most critical ways to mediate metabolic adaptation and clearance of damaged organelles. Autophagy is maintained at a basal level under normal growing conditions and gets stimulated by stress through different but connected mechanisms. In this review, we summarize the advances in understanding the autophagy regulation mechanisms under multiple types of stress including nutrient, energy, oxidative, and ER stress in both yeast and mammalian systems.

Nrf2 Regulation by Curcumin: Molecular Aspects for Therapeutic Prospects

Nuclear factor erythroid 2 p45-related factor (2Nrf2) is an essential leucine zipper protein (bZIP) that is primarily located in the cytoplasm under physiological conditions. Nrf2 principally modulates endogenous defense in response to oxidative stress in the brain.In this regard, Nrf2 translocates into the nucleus and heterodimerizes with the tiny Maf or Jun proteins. It then attaches to certain DNA locations in the nucleus, such as electrophile response elements (EpRE) or antioxidant response elements (ARE), to start the transcription of cytoprotective genes. Many neoplasms have been shown to have over activated Nrf2, strongly suggesting that it is responsible for tumors with a poor prognosis. Exactly like curcumin, Zinc-curcumin Zn (II)-curc compound has been shown to induce Nrf2 activation. In the cancer cell lines analyzed, Zinc-curcumin Zn (II)-curc compound can also display anticancer effects via diverse molecular mechanisms, including markedly increasing heme oxygenase-1 (HO-1) p62/SQSTM1 and the Nrf2 protein levels along with its targets. It also strikingly decreases the levels of Nrf2 inhibitor, Kelch-like ECH-associated protein 1 (Keap1) protein.As a result, the crosstalk between p62/SQSTM1 and Nrf2 could be used to improve cancer patient response to treatments. The interconnected anti-inflammatory and antioxidative properties of curcumin resulted from its modulatory effects on Nrf2 signaling pathway have been shown to improve insulin resistance. Curcumin exerts its anti-inflammatory impact through suppressing metabolic reactions and proteins such as Keap1 that provoke inflammation and oxidation. A rational amount of curcumin-activated antioxidant Nrf2 HO-1 and Nrf2-Keap1 pathways and upregulated the modifier subunit of glutamate-cysteine ligase involved in the production of the intracellular antioxidant glutathione. Enhanced expression of glutamate-cysteine ligase, a modifier subunit (GLCM), inhibited transcription of glutamate-cysteine ligase, a catalytic subunit (GCLC). A variety of in vivo, in vitro and clinical studies has been done so far to confirm the protective role of curcumin via Nrf2 regulation. This manuscript is designed to provide a comprehensive review on the molecular aspects of curcumin and its derivatives/analogs via regulation of Nrf2 regulation.

Flavonoids Seen through the Energy Perspective

In all life forms, opposing forces provide the energy that flows through networks in an organism, which fuels life. In this concept, health is the ability of an organism to maintain the balance between these opposing forces, which creates resilience, and a deranged flow of energy is the basis for diseases. Treatment should focus on adjusting the deranged flow of energy, e.g., by the redox modulating activity of antioxidants. A major group of antioxidants is formed by flavonoids, a group of polyphenolic compounds abundantly present in our diet. The objective here is to review how the redox modulation by flavonoids fits in the various concepts on the mode of action of bioactive compounds, so we can 'see' where there is overlap and where the missing links are. Based on this fundament, we should choose our research path aiming to 'understand' the redox modulating profile of specific flavonoids, so we can ultimately rationally apply the redox modulating power of flavonoids to improve our health.

Computational Screening for the Anticancer Potential of Seed-Derived Antioxidant Peptides: A Cheminformatic Approach

Some seed-derived antioxidant peptides are known to regulate cellular modulators of ROS production, including those proposed to be promising targets of anticancer therapy. Nevertheless, research in this direction is relatively slow owing to the inevitable time-consuming nature of wet-lab experimentations. To help expedite such explorations, we performed structure-based virtual screening on seed-derived antioxidant peptides in the literature for anticancer potential. The ability of the peptides to interact with myeloperoxidase, xanthine oxidase, Keap1, and p47^phox was examined. We generated a virtual library of 677 peptides based on a database and literature search. Screening for anticancer potential, non-toxicity, non-allergenicity, non-hemolyticity narrowed down the collection to five candidates. Molecular docking found LYSPH as the most promising in targeting myeloperoxidase, xanthine oxidase, and Keap1, whereas PSYLNTPLL was the best candidate to bind stably to key residues in p47^phox. Stability of the four peptide-target complexes was supported by molecular dynamics simulation. LYSPH and PSYLNTPLL were predicted to have cell- and blood-brain barrier penetrating potential, although intolerant to gastrointestinal digestion. Computational alanine scanning found tyrosine residues in both peptides as crucial to stable binding to the targets. Overall, LYSPH and PSYLNTPLL are two potential anticancer peptides that deserve deeper exploration in future.

SH-29 and SK-119 Attenuates Air-Pollution Induced Damage by Activating Nrf2 in HaCaT Cells

Air pollution has been repeatedly linked to numerous health-related disorders, including skin sensitization, oxidative imbalance, premature extrinsic aging, skin inflammation, and increased cancer prevalence. Nrf2 is a key player in the endogenous protective mechanism of the skin. We hypothesized that pharmacological activation of Nrf2 might reduce the deleterious action of diesel particulate matter (DPM), evaluated in HaCaT cells. SK-119, a recently synthesized pharmacological agent as well as 2,2′-((1E,1′E)-(1,4-phenylenebis(azaneylylidene))bis(methaneylylidene))bis(benzene-1,3,5-triol) (SH-29) were first evaluated in silico, suggesting a potent Nrf2 activation capacity that was validated in vitro. In addition, both compounds were able to attenuate key pathways underlying DPM damage, including cytosolic and mitochondrial reactive oxygen species (ROS) generation, tested by DC-FDA and MitoSOX fluorescent dye, respectively. This effect was independent of the low direct scavenging ability of the compounds. In addition, both SK-119 and SH-29 were able to reduce DPM-induced IL-8 hypersecretion in pharmacologically relevant concentrations. Lastly, the safety of both compounds was evaluated and demonstrated in the ex vivo human skin organ culture model. Collectively, these results suggest that Nrf2 activation by SK-119 and SH-29 can revert the deleterious action of air pollution.

Nutrigenetic reprogramming of oxidative stress

Retinal disorders such as retinitis pigmentosa, age-related retinal degeneration, oxygen-induced retinopathy, and ischemia-reperfusion injury cause debilitating and irreversible vision loss. While the exact mechanisms underlying these conditions remain unclear, there has been a growing body of evidence demonstrating the pathological contributions of oxidative stress across different cell types within the eye. Nuclear factor erythroid-2-related factor (Nrf2), a transcriptional activator of antioxidative genes, and its regulator Kelch-like ECH-associated protein 1 (Keap1) have emerged as promising therapeutic targets. The purpose of this review is to understand the protective role of the Nrf2-Keap1 pathway in different retinal tissues and shed light on the complex mechanisms underlying these processes. In the photoreceptors, we highlight that Nrf2 preserves their survival and function by maintaining oxidation homeostasis. In the retinal pigment epithelium, Nrf2 similarly plays a critical role in oxidative stabilization but also maintains mitochondrial motility and autophagy-related lipid metabolic processes. In endothelial cells, Nrf2 seems to promote proper vascularization and revascularization through concurrent activation of antioxidative and angiogenic factors as well as inhibition of inflammatory cytokines. Finally, Nrf2 protects retinal ganglion cells against apoptotic cell death. Importantly, we show that Nrf2-mediated protection of the various retinal tissues corresponds to a preservation of functional vision. Altogether, this review underscores the potential of the Nrf2-Keap1 pathway as a powerful tool against retinal degeneration. Key insights into this elegant oxidative defense mechanism may ultimately pave the path toward a universal therapy for various inherited and environmental retinal disorders.