Potency of Michael reaction acceptors as inducers of enzymes that protect against carcinogenesis depends on their reactivity with sulfhydryl groups

Electrophilic metabolites targeting the KEAP1/NRF2 partnership

Numerous electrophilic metabolites are formed during cellular activity, particularly under conditions of oxidative, inflammatory and metabolic stress. Among them are lipid oxidation and nitration products, and compounds derived from amino acid and central carbon metabolism. Here we focus on one cellular target of electrophiles, the Kelch-like ECH associated protein 1 (KEAP1)/nuclear factor erythroid 2 p45-related factor 2 (NRF2) partnership. Many of these reactive compounds modify C151, C273 and/or C288 within KEAP1. Other types of modifications include S-lactoylation of C273, N-succinylation of K131, and formation of methylimidazole intermolecular crosslink between two KEAP1 monomers. Modified KEAP1 relays the initial signal to transcription factor NRF2 and its downstream targets, the ultimate effectors that provide means for detoxification, adaptation and survival. Thus, by non-enzymatically covalently modifying KEAP1, the electrophilic metabolites discussed here serve as chemical signals connecting metabolism with stress responses.

Nrf2/HO-1 as a therapeutic target in renal fibrosis

Chronic kidney disease (CKD) is one of the most prevalent chronic diseases and affects between 10 and 14 % of the world's population. The World Health Organization estimates that by 2040, the disease will be fifth in prevalence. End-stage CKD is characterized by renal fibrosis, which can eventually lead to kidney failure and death. Renal fibrosis develops due to multiple injuries and involves oxidative stress and inflammation. In the human body, nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the expression of antioxidant, anti-inflammatory, and cytoprotective genes, which prevents oxidative stress and inflammation damage. Heme oxygenase (HO-1) is an inducible homolog influenced by heme products and after exposure to cellular stress inducers such as oxidants, inflammatory chemokines/cytokines, and tissue damage as an outcome or downstream of Nrf2 activation. HO-1 is known for its antioxidative properties, which play an important role in regulating oxidative stress. In renal diseases-induced tissue fibrosis and xenobiotics-induced renal fibrosis, Nrf2/HO-1 has been targeted with promising results. This review summarizes these studies and highlights the interesting bioactive compounds that may assist in attenuating renal fibrosis mediated by HO-1 activation. In conclusion, Nrf2/HO-1 signal activation could have a renoprotective effect strategy against CKD caused by oxidative stress, inflammation, and consequent renal fibrosis.

Intestinal polyphenol antioxidant activity involves redox signaling mechanisms facilitated by aquaporin activity

Ascertaining whether dietary polyphenols evoke an antioxidant or prooxidant activity, which translates to a functional role required to maintain intestinal cell homeostasis continues to be an active and controversial area of research for food chemists and biochemists alike. We have proposed that the paradoxical function of polyphenols to autoxidize to generate H2O2 is a required first step in the capacity of some plant phenolics to function as intracellular antioxidants. This is based on the fact that cell redox homeostasis is achieved by a balance between H2O2 formation and subsequent outcomes of antioxidant systems function. Maintaining optimal extracellular and intracellular H2O2 concentrations is required for cell survival, since low levels are important to upregulate endogenous antioxidant capacity; whereas, concentrations that go beyond homeostatic control typically result in an inflammatory response, growth arrest, or eventual cell death. Aquaporins (AQPs) are a family of water channel membrane proteins that facilitate cellular transportation of water and other small molecule-derived solutes, such as H2O2, in all organisms. In the intestine, AQPs act as gatekeepers to regulate intracellular uptake of H2O2, generated from extracellular polyphenol autoxidation, thus enabling an intracellular cell signaling responses to mitigate onset of oxidative stress and intestinal inflammation. In this review, we highlight the potential role of AQPs to control important underlying mechanisms that define downstream regulation of intestinal redox homeostasis, specifically. It has been established that polyphenols that undergo oxidation to the quinone form, resulting in subsequent adduction to a thiol group on Keap1-Nrf2 complex, trigger Nrf2 activation and a cascade of indirect intracellular antioxidant effects. Here, we propose a similar mechanism that involves H2O2 generated from specific dietary polyphenols with a predisposition to undergo autoxidation. The ultimate bioactivity is regulated and expressed by AQP membrane function and thus, by extension, represents expression of an intracellular antioxidant chemoprotection mechanism.

The sub-acute toxicity of kavalactone in rats: a study of the effect of oral doses and the mechanism of toxicity in combination with ethanol

Kava is a herbal supplement and beverage made from the Piper methysticum plant, which is known for its recreational use as a mood enhancer, relaxation, as well as pain relief for centuries. Kava is widely used among alcoholics, but it is dangerous and potentially fatal. The objectives of this study were to examine the sub-acute toxicity effects of different doses of 70% kavalactone (KL) in rats by oral application, as well as to elucidate the mechanisms of toxicity alone and in combination with ethanol (EtOH). The most common side effects observed were abnormal breathing, ataxia, lethargy, loss of appetite, indigestion, and loss of coordination, especially in the 800 mg/kg bw, po bodyweight dosage of kava treatment group alone, and in combination with EtOH. In the sub-acute study, there were dose-related decreases in body weight, feed intake, and water consumption rates. Gross and histopathological findings revealed that the liver was abnormal in color, size, consistency, and the weight significantly increased at a dose of 800 mg/kg bw, po, with KL alone and a greater increase in combination with EtOH. Hepatocellular hypertrophy (HP) and necrosis with Kupffer cells hyperplasia were observed in the periacinar zone of all rats dosed with KL (800 mg/kg bw, po) alone, and extensive changes were observed in combination with EtOH. The periportal (Z1) and mid-zonal (Z2) areas of hepatocytes were less affected as compared to the periacinar zone. These results demonstrate that EtOH exacerbated the sedative and hypnotic activity of KL, and markedly increased toxicity. The histopathological results supported the clinical and biochemical findings and the severity of hepatic damage in a dose-dependent manner.

Thymoquinone effect on the Dictyostelium discoideum model correlates with functional roles for glutathione S-transferases in eukaryotic proliferation, chemotaxis, and development

An increasing body of literature demonstrates the therapeutic relevance of polyphenols in eukaryotic cell and animal model studies. The phase II glutathione S-transferases (GST) show differential responses to thymoquinone, a major bioactive polyphenol constituent of the black seed, Nigella sativa. Beyond antioxidant defense, GSTs may act in non-enzymatic capacities to effect cell cycle, motility, and differentiation. Here, we report the impact of thymoquinone on the life cycle of the eukaryotic model Dictyostelium discoideum and accompanying profiles of its GST-alpha (DdGSTA) enzyme activity and isozyme expression. In silico molecular modeling revealed strong interaction(s) between thymoquinone and DdGSTA2 and DdGSTA3 isozymes that correlated with in vivo, dose-dependent inhibition of cell proliferation of amoebae at 24, 48, and 72hr. Similarly, cytosolic DdGST enzyme activity (CDNB activity) was also responsive to different thymoquinone concentrations. Thymoquinone generally reduced expression of DdGSTA2 and DdGSTA3 isozymes in proliferating cells, however differential expression of the isozymes occurred during starvation. Thymoquinone effectively reduced early-stage aggregation of starved amoeba, accompanied by increased reactive oxygen species and altered expression of tubulin and contact site A (gp80), which resulted in reduced morphogenesis and fruiting body formation. These observations reveal that thymoquinone can impact signaling mechanisms that regulate proliferation and development in D. discoideum.

More than Just Antioxidants: Redox-Active Components and Mechanisms Shaping Redox Signalling Network

The concept of oxidative stress as a condition underlying a multitude of human diseases has led to immense interest in the search for antioxidant-based remedies. The simple and intuitive story of "the bad" reactive oxygen species (ROS) and "the good" antioxidants quickly (and unsurprisingly) lead to the commercial success of products tagged "beneficial to health" based solely on the presence of antioxidants. The commercial success of antioxidants by far preceded the research aimed at understanding the exact redox-related mechanisms that are in control of shaping the states of health and disease. This review describes the redox network formed by the interplay of ROS with cellular molecules and the resulting regulation of processes at the genomic and proteomic levels. Key players of this network are presented, both involved in redox signalling and control of cellular metabolism linked to most, if not all, physiological processes. In particular, this review focuses on the concept of reductive stress, which still remains less well-established compared to oxidative stress.

Trifluoromethylcinnamanilide Michael Acceptors for Treatment of Resistant Bacterial Infections

A series of thirty-two anilides of 3-(trifluoromethyl)cinnamic acid (series 1) and 4-(trifluoromethyl)cinnamic acid (series 2) was prepared by microwave-assisted synthesis. All the compounds were tested against reference strains Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 and resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecalis (VRE). All the compounds were evaluated in vitro against Mycobacterium smegmatis ATCC 700084 and M. marinum CAMP 5644. (2E)-3-[3-(Trifluoromethyl)phenyl]-N-[4-(trifluoromethyl)phenyl]prop-2-enamide (1j), (2E)-N-(3,5-dichlorophenyl)-3-[3-(trifluoromethyl)phenyl]prop-2-enamide (1o) and (2E)-N-[3-(trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)-phenyl]prop-2-enamide (2i), (2E)-N-[3,5-bis(trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)phenyl]-prop-2-enamide (2p) showed antistaphylococcal (MICs/MBCs 0.15-5.57 µM) as well as anti-enterococcal (MICs/MBCs 2.34-44.5 µM) activity. The growth of M. marinum was strongly inhibited by compounds 1j and 2p in a MIC range from 0.29 to 2.34 µM, while all the agents of series 1 showed activity against M. smegnatis (MICs ranged from 9.36 to 51.7 µM). The performed docking study demonstrated the ability of the compounds to bind to the active site of the mycobacterial enzyme InhA. The compounds had a significant effect on the inhibition of bacterial respiration, as demonstrated by the MTT assay. The compounds showed not only bacteriostatic activity but also bactericidal activity. Preliminary in vitro cytotoxicity screening was assessed using the human monocytic leukemia cell line THP-1 and, except for compound 2p, all effective agents did show insignificant cytotoxic effect. Compound 2p is an interesting anti-invasive agent with dual (cytotoxic and antibacterial) activity, while compounds 1j and 1o are the most interesting purely antibacterial compounds within the prepared molecules.

Regulation of nuclear factor erythroid-2-related factor 2 as a potential therapeutic target in intracerebral hemorrhage

Hemorrhagic stroke can be categorized into several subtypes. The most common is intracerebral hemorrhage (ICH), which exhibits significant morbidity and mortality, affecting the lives of millions of people worldwide every year. Brain injury after ICH includes the primary injury that results from direct compression as well as stimulation by the hematoma and secondary brain injury (SBI) that is due to ischemia and hypoxia in the penumbra around the hematoma. A number of recent studies have analyzed the mechanisms producing the oxidative stress and inflammation that develop following hematoma formation and are associated with the ICH induced by the SBI as well as the resulting neurological dysfunction. Nuclear factor erythroid-2-related factor 2 (Nrf2) is a critical component in mediating oxidative stress and anti-inflammatory response. We summarize the pathological mechanisms of ICH focusing on oxidative stress and the regulatory role of Nrf2, and review the mechanisms regulating Nrf2 at the transcriptional and post-transcriptional levels by influencing gene expression levels, protein stability, subcellular localization, and synergistic effects with other transcription factors. We further reviewing the efficacy of several Nrf2 activators in the treatment of ICH in experimental ICH models. Activation of Nrf2 might produce antioxidant, anti-inflammatory, and neuron-protection effects, which could potentially be a focus for developing future treatments and prevention of ICH.

Better detoxifying effect of ripe forsythiae fructus over green forsythiae fructus and the potential mechanisms involving bile acids metabolism and gut microbiota

Forsythiae Fructus (FF), the fruit of Forsythia suspensa (Thunb.) Vahl. (Lianqiao), is one of the most fundamental herbs in Traditional Chinese Medicines (TCM), mainly due to its heat-clearing and detoxifying effects. There are two types of FF, the greenish fruits that start to ripen (GF) and the yellow fruits that are fully ripe (RF), called “Qingqiao” and “Laoqiao” referred to the Chinese Pharmacopoeia, respectively. It undergoes a complex series of changes during the maturation of FF. However, the clinical uses and preparation of phytopharmaceuticals of FF have not been distinguished to date. Moreover, there is limited information on the study of the difference in pharmacological activity between RF and GF. In this study, a rat model of bile duct ligation (BDL)-induced cholestasis was used to compare the differences in their effects. RF was found to have better results than GF in addressing toxic bile acids (BAs) accumulation and related pathological conditions caused by BDL. The underlying mechanism may be related to the interventions of gut microbiota. The results of the present study suggest that the better detoxifying effect of RF than GF may be indirectly exerted through the regulation of gut microbiota and thus the improvement of BAs metabolism.

Identification of the NRF2 transcriptional network as a therapeutic target for trigeminal neuropathic pain

Trigeminal neuralgia, historically dubbed the "suicide disease," is an exceedingly painful neurologic condition characterized by sudden episodes of intense facial pain. Unfortunately, the only U.S. Food and Drug Administration (FDA)-approved medication for trigeminal neuralgia carries substantial side effects, with many patients requiring surgery. Here, we identify the NRF2 transcriptional network as a potential therapeutic target. We report that cerebrospinal fluid from patients with trigeminal neuralgia accumulates reactive oxygen species, several of which directly activate the pain-transducing channel TRPA1. Similar to our patient cohort, a mouse model of trigeminal neuropathic pain also exhibits notable oxidative stress. We discover that stimulating the NRF2 antioxidant transcriptional network is as analgesic as inhibiting TRPA1, in part by reversing the underlying oxidative stress. Using a transcriptome-guided drug discovery strategy, we identify two NRF2 network modulators as potential treatments. One of these candidates, exemestane, is already FDA-approved and may thus be a promising alternative treatment for trigeminal neuropathic pain.

NRF2 and Mitochondrial Function in Cancer and Cancer Stem Cells

The NRF2–KEAP1 system is a fundamental component of the cellular response that controls a great variety of transcriptional targets that are mainly involved in the regulation of redox homeostasis and multiple cytoprotective mechanisms that confer adaptation to the stress conditions. The pleiotropic response orchestrated by NRF2 is particularly relevant in the context of oncogenic activation, wherein this transcription factor acts as a key driver of tumor progression and cancer cells’ resistance to treatment. For this reason, NRF2 has emerged as a promising therapeutic target in cancer cells, stimulating extensive research aimed at the identification of natural, as well as chemical, NRF2 inhibitors. Excitingly, the influence of NRF2 on cancer cells’ biology extends far beyond its mere antioxidant function and rather encompasses a functional crosstalk with the mitochondrial network that can influence crucial aspects of mitochondrial homeostasis, including biogenesis, oxidative phosphorylation, metabolic reprogramming, and mitophagy. In the present review, we summarize the current knowledge of the reciprocal interrelation between NRF2 and mitochondria, with a focus on malignant tumors and cancer stem cells.

The Structure Basis of Phytochemicals as Metabolic Signals for Combating Obesity

The consumption of phytochemicals, bioactive compounds in fruits and vegetables, has been demonstrated to ameliorate obesity and related metabolic symptoms by regulating specific metabolic pathways. This review summarizes the progress made in our understanding of the potential of phytochemicals as metabolic signals: we discuss herein selected molecular mechanisms which are involved in the occurrence of obesity that may be regulated by phytochemicals. The focus of our review highlights the regulation of transcription factors toll like receptor 4 (TLR4), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), the peroxisome proliferator-activated receptors (PPARs), fat mass and obesity-associated protein (FTO) and regulation of microRNAs (miRNA). In this review, the effect of phytochemicals on signaling pathways involved in obesity were discussed on the basis of their chemical structure, suggesting molecular mechanisms for how phytochemicals may impact these signaling pathways. For example, compounds with an isothiocyanate group or an α, β-unsaturated carbonyl group may interact with the TLR4 signaling pathway. Regarding Nrf2, we examine compounds possessing an α, β-unsaturated carbonyl group which binds covalently with the cysteine thiols of Keap1. Additionally, phytochemical activation of PPARs, FTO and miRNAs were summarized. This information may be of value to better understand how specific phytochemicals interact with specific signaling pathways and help guide the development of new drugs to combat obesity and related metabolic diseases.

Rational drug design strategies for the development of promising multi-target directed indole hybrids as Anti-Alzheimer agents

Alzheimer's disease (AD) is a neurological disorder that leads to dementia i.e., progressive memory loss accompanied with worsening of thinking ability of an individual. The cause of AD is not fully understood but it progresses with age where brain cells gradually die over time. According to the World Health Organization (WHO), currently 50 million people worldwide are affected by dementia and 60-70% of the cases belong to AD. Cumulative research over the past few decades have shown that molecules that act at a single target possess limited efficacy since these investigational drugs are not able to act against complex pathologies and thus do not provide permanent cure. Designing of multi-target directed ligands (MTDLs) appears to be more beneficial and a rational approach to treat chronic complex diseases including neurodegenerative diseases. Recently, MTDLs are being extensively researched by the medicinal chemists for the development of drugs for the treatment of various multifactorial diseases. Indole is one of the privileged scaffolds which is considered as an essential mediator between the gut-brain axis because of its neuroprotective, anti-inflammatory, β-amyloid anti-aggregation and antioxidant activities. Herein, we have reviewed the potential of some indole-hybrids acting at multiple targets in the pathogenesis of AD. We have reviewed research articles from the year 2014-2021 from various scientific databases and highlighted the synthetic strategies, mechanisms of neuroprotection, toxicity, structure activity relationships and molecular docking studies of various indole-hybrid derivatives. This literature review of published data on indole derivatives indicated that developing indole hybrids have improved the pharmacokinetic profile with lower toxicity, provided synergistic effect, helped to develop more potent compounds and prevented drug-drug interactions. It is evident that this class of compounds have potential to inhibit multiple enzymes targets involved in the pathogenesis of AD and therefore indole hybrids as MTDLs may play an important role in the development of anti-AD molecules.

Developing dietary curcumin mono-carbonyl piperidinone analogs as Nrf2-dependent cytoprotectors against oxidative damage: Structure-activity relationship and mechanisms

Developing nuclear factor erythroid-2 related factor 2 (Nrf2)-dependent cytoprotectors against oxidative damage is of concern because they can effectively reduce the risk of oxidative stress-related diseases, such as cancer and inflammation. This work was aimed to develop more active Nrf2-dependent cytoprotectors than curcumin, a well-known dietary Nrf2 activator and cancer chemopreventive agent. Herein we designed a panel of curcumin-inspired mono-carbonyl piperidinone analogs differentiated by placing distinct electron-withdrawing and electron-donating groups on its two aromatic rings in the ortho, meta, or para position to the linker of α, β-unsaturated piperidinone. Among these, the ortho-fluorine-substituted CN-2F surfaced as a promising lead molecule, which was significantly superior to the parent curcumin in protecting HepG2 cells from oxidative damage induced by tert-butyl hydroperoxide. Mechanically, by virtue of its Michael receptor units and ortho-substituted mode, CN-2F activated Nrf2 signaling by covalently modifying Cys-151 and Cys-288 residues at Keap1, promoting phosphorylation of JNK, ERK and p38, as well as inhibiting Nrf2 degradation. This work reveals the structural determinants and the activity mechanisms of CN-2F as an Nrf2-dependent cytoprotector, and gives useful information on how to design curcumin-inspired Nrf2 activators and cytoprotectors.

Curcumin Restrains Oxidative Stress of After Intracerebral Hemorrhage in Rat by Activating the Nrf2/HO-1 Pathway

Intracerebral hemorrhage (ICH), a severe hemorrhagic stroke, induces cerebral oxidative stress and severe secondary neurological injury. Curcumin was demonstrated to inhibit oxidative stress in the brain after ICH. However, the pharmacological mechanism needs further research. We used an intrastriatal injection of autologous blood to make the rat ICH model, and then the rat was treated with curcumin (100 mg/kg/day). Modified Neurological Severity Score (mNSS) and corner test results showed that curcumin could significantly promote the neurological recovery of ICH rats. Meanwhile, curcumin could substantially reduce ROS and MDA in the tissues around intracranial hematoma and prevent GSH depletion. To explore the pharmacological molecular mechanism of curcumin, we used HAPI cells and primary rat cortical microglia for in vitro experiments. In vitro, heme-treated cells were used as the cell model of ICH to explore the molecular mechanism of inhibiting oxidative stress by curcumin treatment. The results showed that curcumin significantly inhibited heme-induced oxidative stress, decreased intracellular ROS and MDA, and promoted Nrf2 and its downstream antioxidant gene (HO-1, NQO1, and Gpx4) expression. These results suggest that curcumin inhibits oxidative stress by activating the Nrf2/HO-1 pathway. Here, our results indicate that curcumin can promote the inhibition of oxidative stress in microglia by activating the Nrf2/HO-1 pathway and promoting neurological recovery after ICH, providing a new therapeutic target for clinical treatment of ICH.

Hybrid Catalysts from Copper Biosorbing Bacterial Strains and Their Recycling for Catalytic Application in the Asymmetric Addition Reaction of B2(pin)2 on α,β-Unsaturated Chalcones

The recycling of heavy metal contaminants from wastewater as a source of valuable products perfectly fits with the principles of a Circular Economy system in view of restoring pollutants back into the system endowed with new social and economic benefits. Heavy metals are often present in such a low concentration that it makes the removal efficiency difficult to realize through the conventional physicochemical methods with high selectivity. Biosorption, conversely, by EPSs (extracellular polymeric substances) produced by several bacterial cells’ strains, is gaining a great deal of attention as an economic, efficient and sustainable depolluting process of wastewater from metal cations such as copper. Metal coordination to EPS components was thus deeply investigated by 1H NMR titration experiments. The 1,10–Phenanthroline–copper complex was exploited for quantifying the ability of different strains to sequester copper by a practical UV-Vis spectrophotometric method. The obtained data distinguished Serratia plymuthica strain SC5II as the bacterial strain displaying copper-adsorbing properties higher than any other, with Stenotrophomonas sp. strain 13a resulting in the worst one. Different analytical techniques, i.e., Dynamic Light Scattering (DLS), FT-IR analysis and SEM spectroscopy were thus employed to rationalize these results. Finally, the obtained copper chelates were successfully employed as hybrid catalysts in the asymmetric boron addition to α,β-unsaturated chalcones for the synthesis of valuable pharmaceutical intermediates, thus placing waste management in a new circular perspective.

The Medicinal Chemistry of Chalcones as Anti-Mycobacterium tuberculosis Agents

Abstract:

Tuberculosis (TB), a highly fatal infectious disease, is caused by Mycobacterium tuberculosis (Mtb) that has inflicted mankind for several centuries. In 2019, the staggering number of new cases reached 10 million resulting in 1.2 million deaths. The emergence of multidrug-resistance-Mycobacterium tuberculosis (MDR-TB) and extensively drug-resistant-Mycobacterium tuberculosis (XDR-TB) is a global concern that requires the search for novel, effective, and safer short-term therapies. Nowadays, among the few alternatives available to treat resistant-Mtb strains, the majority have limitations, which include drug-drug interactions, long-term treatment, and chronic induced toxicities. Therefore, it is mandatory to develop new anti-Mtb agents to achieve health policy goals to mitigate the disease by 2035. Among the several bioactive anti-Mtb compounds, chalcones have been described as the privileged scaffold useful for drug design. Overall, this review explores and analyzes 37 chalcones that exhibited anti-Mtb activity described in the literature up to April 2021 with minimum inhibitory concentration (MIC90) values inferior to 20 µM and selective index superior to 10. In addition, the correlation of some properties for most active compounds was evaluated, and the main targets for these compounds were discussed.

Role of Nrf2 in Disease: Novel Molecular Mechanisms and Therapeutic Approaches - Pulmonary Disease/Asthma

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a major transcription factor involved in redox homeostasis and in the response induced by oxidative injury. Nrf2 is present in an inactive state in the cytoplasm of cells. Its activation by internal or external stimuli, such as infections or pollution, leads to the transcription of more than 500 elements through its binding to the antioxidant response element. The lungs are particularly susceptible to factors that generate oxidative stress such as infections, allergens and hyperoxia. Nrf2 has a crucial protective role against these ROS. Oxidative stress and subsequent activation of Nrf2 have been demonstrated in many human respiratory diseases affecting the airways, including asthma and chronic obstructive pulmonary disease (COPD), or the pulmonary parenchyma such as acute respiratory distress syndrome (ARDS) and pulmonary fibrosis. Several compounds, both naturally occurring and synthetic, have been identified as Nrf2 inducers and enhance the activation of Nrf2 and expression of Nrf2-dependent genes. These inducers have proven particularly effective at reducing the severity of the oxidative stress-driven lung injury in various animal models. In humans, these compounds offer promise as potential therapeutic strategies for the management of respiratory pathologies associated with oxidative stress but there is thus far little evidence of efficacy through human trials. The purpose of this review is to summarize the involvement of Nrf2 and its inducers in ARDS, COPD, asthma and lung fibrosis in both human and in experimental models.

Bisretinoids of the Retina: Photo-Oxidation, Iron-Catalyzed Oxidation, and Disease Consequences

The retina and, in particular, retinal pigment epithelial cells are unusual for being encumbered by exposure to visible light, while being oxygen-rich, and also amassing photoreactive molecules. These fluorophores (bisretinoids) are generated as a byproduct of the activity of vitamin A aldehyde-the chromophore necessary for vision. Bisretinoids form in photoreceptor cells due to random reactions of two molecules of vitamin A aldehyde with phosphatidylethanolamine; bisretinoids are subsequently transferred to retinal pigment epithelial (RPE) cells, where they accumulate in the lysosomal compartment with age. Bisretinoids can generate reactive oxygen species by both energy and electron transfer, and they become photo-oxidized and photolyzed in the process. While these fluorescent molecules are accrued by RPE cells of all healthy eyes, they are also implicated in retinal disease.

Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: Efficacy, mechanisms of action, and factors influencing inter-individual response

The pathophysiology of psychiatric and neurodegenerative disorders is complex and multifactorial. Polyphenols possess a range of potentially beneficial mechanisms of action that relate to the implicated pathways in psychiatric and neurodegenerative disorders. The aim of this review is to highlight the emerging clinical trial and preclinical efficacy data regarding the role of polyphenols in mental and brain health, elucidate novel mechanisms of action including the gut microbiome and gene expression, and discuss the factors that may be responsible for the mixed clinical results; namely, the role of interindividual differences in treatment response and the potentially pro-oxidant effects of some polyphenols. Further clarification as part of larger, well conducted randomized controlled trials that incorporate precision medicine methods are required to inform clinical efficacy and optimal dosing regimens.

Reaction of Chalcones with Cellular Thiols. The Effect of the 4-Substitution of Chalcones and Protonation State of the Thiols on the Addition Process. Diastereoselective Thiol Addition

Several biological effects of chalcones have been reported to be associated with their thiol reactivity. In vivo, the reactions can result in the formation of small-molecule or protein thiol adducts. Both types of reactions can play a role in the biological effects of this class of compounds. Progress of the reaction of 4-methyl- and 4-methoxychalcone with glutathione and N-acetylcysteine was studied by the HPLC-UV-VIS method. The reactions were conducted under three different pH conditions. HPLC-MS measurements confirmed the structure of the formed adducts. The chalcones reacted with both thiols under all incubation conditions. The initial rate and composition of the equilibrium mixtures depended on the ratio of the deprotonated form of the thiols. In the reaction of 4-methoxychalcone with N-acetylcysteine under strongly basic conditions, transformation of the kinetic adduct into the thermodynamically more stable one was observed. Addition of S-protonated N-acetylcysteine onto the polar double bonds of the chalcones showed different degrees of diastereoselectivity. Both chalcones showed a Michael-type addition reaction with the ionized and non-ionized forms of the investigated thiols. The initial reactivity of the chalcones and the equilibrium composition of the incubates showed a positive correlation with the degree of ionization of the thiols. Conversions showed systematic differences under each set of conditions. The observed differences can hint at the difference in reported biological actions of 4-methyl- and 4-methoxy-substituted chalcones.

Role of Glutathione in Chalcone Derivative Induced Apoptosis of Brugia malayi and its Possible Therapeutic Implication

PURPOSE

Oxidative stress is an essential component of innate response against microbes. The oxidative impact has a very subtle connection with apoptosis. Our previous work indicated presumptive evidence of apoptosis by the chalcone derivatives against the human lymphatic filarial parasite. Evidence suggests the involvement of glutathione-S-transferase (GST) in the mechanism of action of chalcone drugs. In the present study, we explored the implications of redox status in apoptosis of the parasite by this drug.

RESULTS

Treatment with the representative drug, 4t, significantly decreased GSH level and increased GST activity in the Brugia malayi microfilariae (Mf) in comparison to Mf without 4t treatment. Drug-induced loss of motility of the parasites was reversed by the treatment with GSH (41%) and NAC (19%). A significant fall in rGST activity was observed due to drug addition, which could be reversed by the addition of GSH co-substrate, but not with the re-addition of rGST, indicating a vital role of GSH. In silico study demonstrated a favorable drug-GST enzyme interaction. Oxidative stress was reflected by increased protein carbonylation and intracellular reactive oxygen species level, in the drug-treated parasite. Mitochondrial oxygen consumption was reduced by the drug, which was reversed on the addition of GSH. Mitochondrial dysfunction was confirmed by MTT and cytochrome c assay. Apoptosis was confirmed by the inhibition in PARP activity.

CONCLUSION

We conclude that the depletion of GSH by chalcone with concomitant mitochondrial dysfunction revealed a novel rationale of apoptosis in the parasite. Such a mechanism might have wide therapeutic implications.

HO-1: A new potential therapeutic target to combat osteoporosis

Heme oxygenase-1 (HO-1) exerts a protective effect against cell damage and induces the activity of many enzymes involved in the treatment of many human diseases, including osteoporosis. The increasing prevalence of osteoporosis and the limitations of the current treatments available led to a continuous occurrence of bone loss and osteoporotic fractures, highlighting the need of a better understanding of the mechanism and function of HO-1. Many factors cause osteoporosis, including lack of estrogen, aging, and iron overload, and they either cause the increase in inflammatory factors or the increase in reactive oxygen species to break bone reconstruction balance. Therefore, regulating the production of inflammatory factors and reactive oxygen species may become a strategy for the treatment of osteoporosis. Solid evidence showed that the overexpression of HO-1 compensates high oxidation levels by increasing intracellular antioxidant levels and reduces inflammation by suppressing pro-inflammatory factors. Some extracts can target HO-1 and ameliorate osteoporosis. However, no systematic report is available on therapies targeting HO-1 to combat osteoporosis. Therefore, this review summarizes the biological characteristics of HO-1, and the relationship between inflammatory response and reactive oxygen species production regulated by HO-1 and osteoporosis. The understanding of the role of HO-1 in osteoporosis may provide ideas for a potential clinical treatment and new drugs targeting HO-1.

Anti-inflammatory activity of ortho-trifluoromethoxy-substituted 4-piperidione-containing mono-carbonyl curcumin derivatives in vitro and in vivo

Curcumin was reported as an anti-inflammatory agent. However, curcumin's poor bioavailability limited its clinical utility. Here, thirty ortho-substituted mono-carbonyl curcumin derivatives, containing acetone, cyclopentanone, cyclohexanone or 4-piperidione (NH, N-methyl or N-acrylyl) moieties replacing β-diketone moiety of curcumin, were investigated for anti-inflammatory activity. Two active ortho-trifluoromethoxy-substituted 4-piperidione-containing derivatives 22 and 24 owned good cell uptake ability, and displayed excellent anti-inflammatory activity in both lipopolysaccharide-induced Raw264.7 macrophages and a dextran sulfate sodium (DSS)-induced mouse model of colitis. They inhibited the production of nitric oxide, reactive oxygen species, malonic dialdehyde and cyclooxygenase-2; and the expression of pro-inflammatory cytokines interleukin-1β, tumor necrosis factor-α and myeloperoxidase; the phosphorylation of mitogen-activated protein kinases; and the nucleus translocation of p65. What's more, 22 or 24 oral administered reduced the severity of clinical symptoms of ulcerative colitis (body weight and disease activity index), and reduced obviously DSS-induced colonic pathological damage (the colon length and histopathology analysis). These results suggested that ortho-trifluoromethoxy-substituted 4-piperidione-containing mono-carbonyl curcumin derivatives 22 and 24 were potential anti-inflammatory agents; and offered the important information for design and discovery of more potent anti-inflammatory drug candidates.

Oat polyphenol avenanthramide-2c confers protection from oxidative stress by regulating the Nrf2-ARE signaling pathway in PC12 cells

Accumulating evidence has demonstrated that cellular antioxidant systems play essential roles in retarding oxidative stress-related diseases, such as Parkinson's disease. Because nuclear factor erythroid 2-related factor 2 (Nrf2) is a chief regulator of cellular antioxidant systems, small molecules with Nrf2-activating ability may be promising neuroprotective agents. Avenanthramide-2c (Aven-2c), avenanthramide-2f (Aven-2f) and avenanthramide-2p (Aven-2p) are the most abundant avenanthramides in oats, and they have been documented to possess multiple pharmacological benefits. In this work, we synthesized these three compounds and evaluated their cytoprotective effect against oxidative stress-induced PC12 cell injuries. Aven-2c displayed the best protective potency among them. Aven-2c conferred protection on PC12 cells by scavenging free radicals and activating the Nrf2-ARE signaling pathway. Pretreatment of PC12 cells with Aven-2c efficiently enhanced Nrf2 nuclear accumulation and evoked the expression of a set of cytoprotective molecules. The mechanistic study also supports that Nrf2 activation is the molecular basis for the cellular action of Aven-2c. Collectively, this study demonstrates that Aven-2c is a potent Nrf2 agonist, shedding light on the potential usage of Aven-2c in the treatment of neuroprotective diseases.

Chalcone and its analogs: Therapeutic and diagnostic applications in Alzheimer's disease

Chalcone [(E)-1,3-diphenyl-2-propene-1-one], a small molecule with α, β unsaturated carbonyl group is a precursor or component of many natural flavonoids and isoflavonoids. It is one of the privileged structures in medicinal chemistry. It possesses a wide range of biological activities encouraging many medicinal chemists to study this scaffold for its usefulness to oncology, infectious diseases, virology and neurodegenerative diseases including Alzheimer's disease (AD). Small molecular size, convenient and cost-effective synthesis, and flexibility for modifications to modulate lipophilicity suitable for blood brain barrier (BBB) permeability make chalcones a preferred candidate for their therapeutic and diagnostic potential in AD. This review summarizes and highlights the importance of chalcone and its analogs as single target small therapeutic agents, multi-target directed ligands (MTDLs) as well as molecular imaging agents for AD. The information summarized here will guide many medicinal chemist and researchers involved in drug discovery to consider chalcone as a potential scaffold for the development of anti-AD agents including theranostics.

A comparative theoretical mechanism on simplified flavonoid derivatives and isoxazolone analogous as Michael system inhibitor

Flavonoids are a big class of natural product and have a wide range of biological activities. Some of these applications depend on its antioxidant capacity. Nevertheless, another mechanism can be involved by means of alkylation reaction on α,β-unsaturated carbonyl system. This study aimed to evaluate the antioxidant capacity and the chemical reactivity among simplified flavonoid derivatives and isoxazolone analogous as Michael system by using B3LYP functional and 6-311 g(d,p) basis set. Frontier molecular orbital, ionization potential (IP), spin density contributions, and Fukui index explain the antioxidant capacity and reactivity index on isoxazolone and its related derivatives. The best contribution at β-alkene moiety is related to better reactivity of α,β-unsaturated carbonyl group. A decrease in antioxidant capacity is related to an increase in the chemical reactivity index. The frontier molecular orbitals show that aurone is more reactive than isoxazolone. In accordance with Fukui index, isoxazolone can be better inhibitor as Michael system when compared to flavonoid derivatives. Graphical abstract.

Anti-Viral Potential and Modulation of Nrf2 by Curcumin: Pharmacological Implications

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential transcription factor that maintains the cell's redox balance state and reduces inflammation in different adverse stresses. Under the oxidative stress, Nrf2 is separated from Kelch-like ECH-associated protein 1 (Keap1), which is a key sensor of oxidative stress, translocated to the nucleus, interacts with the antioxidant response element (ARE) in the target gene, and then activates the transcriptional pathway to ameliorate the cellular redox condition. Curcumin is a yellow polyphenolic curcuminoid from Curcuma longa (turmeric) that has revealed a broad spectrum of bioactivities, including antioxidant, anti-inflammatory, anti-tumor, and anti-viral activities. Curcumin significantly increases the nuclear expression levels and promotes the biological effects of Nrf2 via the interaction with Cys151 in Keap1, which makes it a marvelous therapeutic candidate against a broad range of oxidative stress-related diseases, including type 2 diabetes (T2D), neurodegenerative diseases (NDs), cardiovascular diseases (CVDs), cancers, viral infections, and more recently SARS-CoV-2. Currently, the multifactorial property of the diseases and lack of adequate medical treatment, especially in viral diseases, result in developing new strategies to finding potential drugs. Curcumin potentially opens up new views as possible Nrf2 activator. However, its low bioavailability that is due to low solubility and low stability in the physiological conditions is a significant challenge in the field of its efficient and effective utilization in medicinal purposes. In this review, we summarized recent studies on the potential effect of curcumin to activate Nrf2 as the design of potential drugs for a viral infection like SARS-Cov2 and acute and chronic inflammation diseases in order to improve the cells' protection.

5-Arylidene-2-(4-hydroxyphenyl)aminothiazol-4(5H)-ones with selective inhibitory activity against some leukemia cell lines

The data on the pharmacology of 4-thiazolidinones showed that 5-ene-2-(imino)amino-4-thiazolidinones are likely to comprise one of the most promising groups of compounds possessing anticancer properties. A series of 5-arylidene-2-(4-hydroxyphenyl)aminothiazol-4(5H)-ones was designed, synthesized, and studied against 10 leukemia cell lines, including the HL-60, Jurkat, K-562, Dami, KBM-7, and some Ba/F3 cell lines. The structure-activity relationship analysis shows that almost all tested 5-arylidene-2-(4-hydroxyphenyl)aminothiazol-4(5H)-ones were characterized by ІС₅₀ values lower or comparable to that of the control drug chlorambucil. Among the tested compounds, (5Z)-5-(2-methoxybenzylidene)- (12), (5Z)-(2-ethoxybenzylidene)- (21), (5Z)-5-(2-benzyloxybenzylidene)- (25), and (5Z)-5-(2-allyloxybenzylidene)-2-(4-hydroxyphenylamino)thiazol-4(5H)-ones (28) possessed the highest antileukemic activity at submicromolar concentrations (ІС₅₀  = 0.10-0.95 µM).

Cellular Target Proteome in Breast Cancer Cells of an Oplopane Sesquiterpenoid Isolated from Tussilago farfara

Tussilago farfara is a traditional herbal medicine used to treat coughs, bronchitis, and asthma. Its bioactive compounds include sesquiterpenoids with anti-inflammatory, antiproliferative, neuroprotective, and other effects. Biochemical studies have highlighted the mechanisms of action, but the investigations of related molecular pathways have not specified direct molecular targets. Therefore, this study profiled cellular target proteins of a sesquiterpenoid isolated from T. farfara using quantitative chemical proteomics in MDA-MB-231 and MCF-7 human breast cancer cells. Compound 8, 7β-(3'-ethyl-cis-crotonoyloxy)-1α-(2'-methyl butyryloxy)-3,14-dehydro-Z-notonipetranone, exhibited potent antiproliferative activity based on its α,β-unsaturated carbonyl moiety, and its potential cellular target proteins were identified using a compound 8-based clickable probe. Among >200 identified proteins, 17 showed enrichment ratios of >3 in both cell lines, while recombinant 14-3-3 protein zeta and peroxiredoxin-1 were verified using isothermic calorimetry and their alkylation sites. Considering the interaction between the α,β-unsaturated carbonyl moiety of compound 8 and cysteine residues of the proteins, peptides containing Cys25 and Cys94 of 14-3-3 protein zeta and Cys83 of peroxiredoxin-1 were significantly reduced by this sesquiterpene ester. Although the results did not elucidate the effects of compound 8 in breast cancer cells, identification of potential target proteins contributes to enhanced understanding of its antiproliferative and anti-inflammatory effects.

Beyond repression of Nrf2: An update on Keap1

Nrf2 (NFE2L2 - nuclear factor (erythroid-derived 2)-like 2) is a transcription factor, which is repressed by interaction with a redox-sensitive protein Keap1 (Kelch-like ECH-associated protein 1). Deregulation of Nrf2 transcriptional activity has been described in the pathogenesis of multiple diseases, and the Nrf2/Keap1 axis has emerged as a crucial modulator of cellular homeostasis. Whereas the significance of Nrf2 in the modulation of biological processes has been well established and broadly discussed in detail, the focus on Keap1 rarely goes beyond the regulation of Nrf2 activity and redox sensing. However, recent studies and scrutinized analysis of available data point to Keap1 as an intriguing and potent regulator of cellular function. This review aims to shed more light on Keap1 structure, interactome, regulation and non-canonical functions, thereby enhancing its significance in cell biology. We also intend to highlight the impact of balance between Keap1 and Nrf2 in the maintenance of cellular homeostasis.

Molecular targets and anticancer activity of quinoline-chalcone hybrids: literature review

α,β-Unsaturated chalcone moieties and quinoline scaffolds play an important role in medicinal chemistry, especially in the identification and development of potential anticancer agents. The multi-target approach or hybridization is considered as a promising strategy in drug design and discovery. Hybridization may improve the affinity and potency while simultaneously decreasing the resistance and/or side effects. The conjugation of quinolines with chalcones has been a promising approach to the identification of potential anticancer agents. Most of these hybrids showed anticancer activities through the inhibition of tubulin polymerization, different kinases, topoisomerases, or by affecting DNA cleavage activity. Accordingly, this class of compounds can be classified based on their molecular modes of action. In this article, the quinolone-chalcone hybrids with potential anticancer activity have been reviewed. This class of compounds might be helpful for the design, discovery and development of new and potential multi-target anticancer agents or drugs.

Structural basis of the anti-ageing effects of polyphenolics: mitigation of oxidative stress

Ageing, and particularly the onset of age-related diseases, is associated with tissue dysfunction and macromolecular damage, some of which can be attributed to accumulation of oxidative damage. Polyphenolic natural products such as stilbenoids, flavonoids and chalcones have been shown to be effective at ameliorating several age-related phenotypes, including oxidative stress, inflammation, impaired proteostasis and cellular senescence, both in vitro and in vivo. Here we aim to identify the structural basis underlying the pharmacology of polyphenols towards ROS and related biochemical pathways involved in age-related disease. We compile and describe SAR trends across different polyphenol chemotypes including stilbenoids, flavonoids and chalcones, review their different molecular targets and indications, and identify common structural ground between chemotypes and mechanisms of action. In particular, we focus on the structural requirements for the direct scavenging of reactive oxygen/nitrogen species such as radicals as well as coordination of a broader antioxidant response. We further suggest that it is important to consider multiple (rather than single) biological activities when identifying and developing new medicinal chemistry entities with utility in modulating complex biological properties such as cell ageing.

HSF1 inhibition attenuates HIV-1 latency reversal mediated by several candidate LRAs In Vitro and Ex Vivo

HIV-1 latency is a major barrier to cure. Identification of small molecules that destabilize latency and allow immune clearance of infected cells could lead to treatment-free remission. In vitro models of HIV-1 latency involving cell lines or primary cells have been developed for characterization of HIV-1 latency and high-throughput screening for latency-reversing agents (LRAs). We have shown that the majority of LRAs identified to date are relatively ineffective in cells from infected individuals despite activity in model systems. We show here that, for diverse LRAs, latency reversal observed in model systems involves a heat shock factor 1 (HSF1)-mediated stress pathway. Small-molecule inhibition of HSF1 attenuated HIV-1 latency reversal by histone deactylase inhibitors, protein kinase C agonists, and proteasome inhibitors without interfering with the known mechanism of action of these LRAs. However, latency reversal by second mitochondria-derived activator of caspase (SMAC) mimetics was not affected by inhibition of HSF1. In cells from infected individuals, inhibition of HSF1 attenuated latency reversal by phorbol ester+ionomycin but not by anti-CD3+anti-CD28. HSF1 promotes elongation of HIV-1 RNA by recruiting P-TEFb to the HIV-1 long terminal repeat (LTR), and we show that inhibition of HSF1 attenuates the formation of elongated HIV-1 transcripts. We demonstrate that in vitro models of latency have higher levels of the P-TEFb subunit cyclin T1 than primary cells, which may explain why many LRAs are functional in model systems but relatively ineffective in primary cells. Together, these studies provide insights into why particular LRA combinations are effective in reversing latency in cells from infected individuals.

The Molecular Mechanisms Regulating the KEAP1-NRF2 Pathway

The KEAP1-NRF2 pathway is the principal protective response to oxidative and electrophilic stresses. Under homeostatic conditions, KEAP1 forms part of an E3 ubiquitin ligase, which tightly regulates the activity of the transcription factor NRF2 by targeting it for ubiquitination and proteasome-dependent degradation. In response to stress, an intricate molecular mechanism facilitated by sensor cysteines within KEAP1 allows NRF2 to escape ubiquitination, accumulate within the cell, and translocate to the nucleus, where it can promote its antioxidant transcription program. Recent advances have revealed that KEAP1 contains multiple stress sensors and inactivation modalities, which together allow diverse cellular inputs, from oxidative stress and cellular metabolites to dysregulated autophagy, to regulate NRF2 activity. This integration of the KEAP1-NRF2 system into multiple cellular signaling and metabolic pathways places NRF2 activation as a critical regulatory node in many disease phenotypes and suggests that the pharmaceutical modulation of NRF2's cytoprotective activity will be beneficial for human health in a broad range of noncommunicable diseases.

Oxidative Stress in DNA Repeat Expansion Disorders: A Focus on NRF2 Signaling Involvement

DNA repeat expansion disorders are a group of neuromuscular and neurodegenerative diseases that arise from the inheritance of long tracts of nucleotide repetitions, located in the regulatory region, introns, or inside the coding sequence of a gene. Although loss of protein expression and/or the gain of function of its transcribed mRNA or translated product represent the major pathogenic effect of these pathologies, mitochondrial dysfunction and imbalance in redox homeostasis are reported as common features in these disorders, deeply affecting their severity and progression. In this review, we examine the role that the redox imbalance plays in the pathological mechanisms of DNA expansion disorders and the recent advances on antioxidant treatments, particularly focusing on the expression and the activity of the transcription factor NRF2, the main cellular regulator of the antioxidant response.

Cytotoxicity of some synthetic bis(arylidene) derivatives of cyclic ketones towards cisplatin-resistant human ovarian carcinoma cells

Symmetrical α,αʹ-bis(arylidene)ketones were prepared by acid-catalyzed aldol condensations between aliphatic ketones (e.g., cyclopentanone, 4-alkylcyclohexanones, tetrahydropyran-4-one, and tetrahydrothiopyran-4-one) and two equivalents of an aromatic hydroxyaldehyde (e.g., 4-hydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, vanillin, isovanillin, and 3-fluoro-4-hydroxybenzaldehyde). Most of the compounds were cytotoxic towards the cisplatin-resistant human ovarian cancer cell line A2780-CP70 as well as the non-resistant line A2780.

Suppressive effects of dehydrocostus lactone on the toll-like receptor signaling pathways

Toll-like receptors (TLRs) are a group of pattern-recognition receptors (PRRs) that are at the core of innate and adaptive immune responses. TLRs activation triggers the activation of two downstream signaling pathways, the myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent pathways. To evaluate the therapeutic potential of DHL, a natural sesquiterpene lactone derived from Inulahelenium L. and Saussurea lappa, we examined its effect on signal transduction via the TLR signaling pathways. DHL inhibited the activation of nuclear factor-κB (NF-κB) and interferon regulatory factor 3 (IRF3), the representative transcription factors involved in the inflammatory response, induced by TLR agonists, as well as the expression of cyclooxygenase-2 and interferon inducible protein-10. DHL also inhibited the activation of NF-κB and IRF3 induced by the overexpression of downstream signaling components of the TLRs signaling pathways. All results suggest that DHL might become a new therapeutic drug for a variety of inflammatory diseases.

Sulforaphane Protects Cells against Lipopolysaccharide-Stimulated Inflammation in Murine Macrophages

Inflammation is an essential part for the general or innate immune defenses to defend against tissue damage and accelerate the curing process by providing protection against pathogens. Sulforaphane (SFN) is a natural isothiocyanate that has potential properties against inflammation, along with other protective functions. The purpose of this study was to examine the mechanism of its protective effect on lipopolysaccharide (LPS)-induced inflammation in Raw 264.7 macrophages. Here, we compared LPS-challenged macrophages with or without SFN pretreatment. Macrophages were pre-incubated for 6 h with a wide range of concentrations of SFN (0 to 50 µM), and then treated with LPS for 24 h. Nitric oxide (NO) concentration and gene expression of different inflammatory mediators, i.e., interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β, were measured. SFN neither directly reacted with cytokines, nor with NO. To understand the mechanisms, we performed analyses of the expression of regulatory enzyme inducible nitic oxide synthase (iNOS), the transcription factor NF-E2-related factor 2 (Nrf2), and its enzyme heme-oxygenase (HO)-1. Our results revealed that LPS increased significantly the expression of inflammatory cytokines and concentration of NO in non-treated cells. SFN was able to prevent the expression of NO and cytokines through regulating inflammatory enzyme iNOS and activation of Nrf2/HO-1 signal transduction pathway.

New Insights into the Nrf-2/HO-1 Signaling Axis and Its Application in Pediatric Respiratory Diseases

Respiratory diseases are one of the most common pediatric diseases in clinical practice. Their pathogenesis, diagnosis, and treatment are thus worthy of further investigation. The nuclear factor erythroid 2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) signaling axis is a multiple organ protection chain that protects against oxidative stress injury. This signaling axis regulates anti-inflammation and antioxidation by regulating calcium ions, mitochondrial oxidative stress, autophagy, ferroptosis, pyroptosis, apoptosis, alkaliptosis, and clockophagy. This review presents an overview of the role of the Nrf2/HO-1 signaling axis in the pathogenesis of pediatric respiratory diseases and the latest research progress on this subject. Overall, the Nrf2/HO-1 signaling axis has an important clinical value in pediatric respiratory diseases, and its protective effect needs further exploration.

Reasonably activating Nrf2: A long-term, effective and controllable strategy for neurodegenerative diseases

Neurodegenerative diseases are a variety of debilitating and fatal disorder in central nervous system (CNS). Besides targeting neuronal activity by influencing neurotransmitters or their corresponding receptors, modulating the underlying processes that lead to cell death, such as oxidative stress and mitochondrial dysfunction, should also be emphasized as an assistant strategy for neurodegeneration therapy. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) has been closely verified to be related to anti-inflammation and oxidative stress, rationally regulating its belonging pathway and activating Nrf2 is emphasized to be a potential treatment approach. There have existed multiple Nrf2 activators with different mechanisms and diverse structures, but those applied for neuro-disorders are still limited. On the basis of research arrangement and compound summary, we put forward the limitations of existing Nrf2 activators for neurodegenerative diseases and their future developing directions in enhancing the blood-brain barrier permeability to make Nrf2 activators function in CNS and designing Nrf2-based multi-target-directed ligands to affect multiple nodes in pathology of neurodegenerative diseases.

The Therapeutic Effect of Curcumin in Quinolinic Acid-Induced Neurotoxicity in Rats is Associated with BDNF, ERK1/2, Nrf2, and Antioxidant Enzymes

In the present study we investigated the participation of brain-derived neurotropic factor (BDNF) on the activation of the mitogen activated protein kinase (MAPK) protein extracellular signal-regulated kinase-1/2 (ERK1/2) as a mechanism of curcumin (CUR) to provide an antioxidant defense system mediated by the nuclear factor erythroid 2-related factor 2 (Nrf2) in the neurotoxic model induced by quinolinic acid (QUIN). Wistar rats received CUR (400 mg/kg, intragastrically) for 6 days after intrastriatal injection with QUIN (240 nmol). CUR improved the motor deficit and morphological alterations induced by QUIN and restored BDNF, ERK1/2, and Nrf2 levels. CUR treatment avoided the decrease in the protein levels of glutathione peroxidase (GPx), glutathione reductase (GR), γ-glutamylcysteine ligase (γ-GCL), and glutathione (GSH) levels. Only, the QUIN-induced decrease in the GR activity was prevented by CUR treatment. Finally, QUIN increased superoxide dismutase 2 (SOD2) and catalase (CAT) levels, and the γGCL and CAT activities; however, this increase was major in the QUIN+CUR group for γ-GCL, CAT, and SOD activities. These data suggest that the therapeutic effect of CUR could involve BDNF action on the activation of ERK1/2 to induce increased levels of protein and enzyme activity of antioxidant proteins regulated by Nrf2 and GSH levels.