Synthesis of piperlongumine analogues and discovery of nuclear factor erythroid 2-related factor 2 (Nrf2) activators as potential neuroprotective agents

Hydroxygenkwanin exerts a neuroprotective effect by activating the Nrf2/ARE signaling pathway

High levels of reactive oxygen species (ROS) have been associated with the progression of neurodegenerative diseases such as Alzheimer's disease. The activation of the NFE2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway may restore the neuron's redox balance and provide a therapeutic impact. Hydroxygenkwanin (HGK), a dominant flavone from Genkwa Flos, has received expanding attention due to its medicinal activities. Our investigation results demonstrated the ability of HGK to protect the PC12 cells from oxidative damage caused by an excessive hydrogen peroxide load. HGK also showed the ability to upregulate a panel of endogenous antioxidant proteins. Further investigations have demonstrated that the neuroprotection mechanism of HGK is dependent on the activation of the Nrf2/ARE signaling pathway. Activating the Nrf2/ARE pathway by HGK reveals a novel mechanism for understanding the pharmacological functions of HGK. These findings suggest that HGK could be considered for further development as an oxidative stress-related neurological pathologies potential therapeutic drug.

Targeting thioredoxin reductase by eupalinilide B promotes apoptosis of colorectal cancer cells in vitro and in vivo

Aberrant activation of thioredoxin reductase (TrxR) is correlated with tumor occurrence and progression, suggesting that TrxR inhibitors can be used as antitumor agents. In this study, we evaluated the anticancer efficacy of eupalinilides B on colorectal cancer cells. Eupalinilides B primarily targeted the conserved selenocysteine 498 residues in TrxR. Besides, it inhibited the enzyme activity in an irreversible manner. After eupalinilides B was used to pharmacologically inhibit TrxR, reactive oxygen species accumulated, and the intracellular redox balance was broken, finally causing oxidative stress-induced tumor cell apoptosis. Significantly, eupalinilides B treatment inhibited in vivo tumor growth. Targeting TrxR by eupalinilides B reveals the new mechanism underlying eupalinilides B and provides insight in developing eupalinilides B as the candidate antitumor chemotherapeutic agent for the treatment of cancer.

N-Cinnamoylpyrrole-derived alkaloids from the genus Piper as promising agents for ischemic stroke by targeting eEF1A1

BACKGROUND

Ischemic stroke (IS) is a serious cerebrovascular disease characterized by significantly elevated mortality and disability rates, and the treatments available for this disease are limited. Neuroinflammation and oxidative stress are deemed the major causes of cerebral ischemic injury. N-Cinnamoylpyrrole alkaloids form a small group of natural products from the genus Piper and have not been extensively analyzed pharmacologically. Thus, identifying the effect and mechanism of N-cinnamoylpyrrole-derived alkaloids on IS is worthwhile.

PURPOSE

The present research aimed to explore the antineuroinflammatory and antioxidative stress effects of N-cinnamoylpyrrole-derived alkaloids isolated from the genus Piper and to explain the effects and mechanism on IS.

METHODS

N-cinnamoylpyrrole-derived alkaloids were isolated from Piper boehmeriaefolium var. tonkinense and Piper sarmentosum and identified by various chromatographic methods. Lipopolysaccharide (LPS)-induced BV-2 microglia and a mouse model intracerebroventricularly injected with LPS were used to evaluate the antineuroinflammatory and antioxidative stress effects. Oxygen‒glucose deprivation/reperfusion (OGD/R) and transient middle cerebral artery occlusion (tMCAO) models were used to evaluate the effect of PB-1 on IS. To elucidate the fundamental mechanism, the functional target of PB-1 was identified by affinity-based protein profiling (ABPP) strategy and verified by cellular thermal shift assay (CETSA), drug affinity responsive target stability (DARTS), and circular dichroism (CD) analyses. The effect of PB-1 on the NF-κB and NRF2 signaling pathways was subsequently evaluated via western blotting and immunofluorescence staining.

RESULTS

The results showed that N-cinnamoylpyrrole-derived alkaloids significantly affected neuroinflammation and oxidative stress. The representative compound, PB-1 not only inhibited neuroinflammation and oxidative stress induced by LPS or OGD/R insult, but also alleviated cerebral ischemic injury induced by tMCAO. Further molecular mechanism research found that PB-1 promoted antineuroinflammatory and antioxidative stress activities via the NF-κB and NRF2 signaling pathways by targeting eEF1A1.

CONCLUSION

Our research initially unveiled that the therapeutic impact of PB-1 on cerebral ischemic injury might rely on its ability to target eEF1A1, leading to antineuroinflammatory and antioxidative stress effects. The novel discovery highlights eEF1A1 as a potential target for IS treatment and shows that PB-1, as a lead compound that targets eEF1A1, may be a promising therapeutic agent for IS.

Protective effect of colchicine on albumin glycation and cellular oxidative stress: Insights into diabetic cardiomyopathy

The present work elucidates the role of colchicine (COL) on albumin glycation and cellular oxidative stress in diabetic cardiomyopathy (DCM). Human serum albumin (HSA) was glycated with methylglyoxal in the presence of COL (2.5, 3.75, and 5 µM), whereas positive and negative control samples were maintained separately. The effects of COL on HSA glycation, structural and functional modifications in glycated HSA were analyzed using different spectroscopical and fluorescence techniques. Increased fructosamine, carbonyl, and pentosidine formation in glycated HSA samples were inhibited in the presence of COL. Structural conformation of HSA and glycated HSA samples was examined by field emission scanning electron microscopy, circular dichroism, Fourier transform infrared, and proton nuclear magnetic resonance analyses, where COL maintained both secondary and tertiary structures of HSA against glycation. Functional marker assays included ABTS•+ radical scavenging and total antioxidant activities, advanced oxidative protein product formation, and turbidimetry, which showed preserved functional properties of glycated HSA in COL-containing samples. Afterward, rat cardiomyoblast (H9c2 cell line) was treated with glycated HSA-COL complex (400 μg/mL) for examining various cellular antioxidants (nitric oxide, catalase, superoxide dismutase, and glutathione) and detoxification enzymes (aldose reductase, glyoxalase I, and II) levels. All three concentrations of COL exhibited effective anti-glycation properties, enhanced cellular antioxidant levels, and detoxification enzyme activities. The report comprehensively analyzes the potential anti-glycation and properties of COL during its initial assessment.

Dimethyl fumarate improves cognitive impairment and neuroinflammation in mice with Alzheimer's disease

BACKGROUND

Neuroinflammation substantially contributes to the pathology of Alzheimer's disease (AD), the most common form of dementia. Studies have reported that nuclear factor erythroid 2-related factor 2 (Nrf2) attenuates neuroinflammation in the mouse models of neurodegenerative diseases, however, the detailed mechanism remains unclear.

METHODS

The effects of dimethyl fumarate (DMF), a clinically used drug to activate the Nrf2 pathway, on neuroinflammation were analyzed in primary astrocytes and AppNL-G-F (App-KI) mice. The cognitive function and behavior of DMF-administrated App-KI mice were evaluated. For the gene expression analysis, microglia and astrocytes were directly isolated from the mouse cerebral cortex by magnetic-activated cell sorting, followed by quantitative PCR.

RESULTS

DMF treatment activated some Nrf2 target genes and inhibited the expression of proinflammatory markers in primary astrocytes. Moreover, chronic oral administration of DMF attenuated neuroinflammation, particularly in astrocytes, and reversed cognitive dysfunction presumably by activating the Nrf2-dependent pathway in App-KI mice. Furthermore, DMF administration inhibited the expression of STAT3/C3 and C3 receptor in astrocytes and microglia isolated from App-KI mice, respectively, suggesting that the astrocyte-microglia crosstalk is involved in neuroinflammation in mice with AD.

CONCLUSION

The activation of astrocytic Nrf2 signaling confers neuroprotection in mice with AD by controlling neuroinflammation, particularly by regulating astrocytic C3-STAT3 signaling. Furthermore, our study has implications for the repositioning of DMF as a drug for AD treatment.

The protective effect of PL 1-3 on D-galactose-induced aging mice

The aging population has become an issue that cannot be ignored, and research on aging is receiving increasing attention. PL 1-3 possesses diverse pharmacological properties including anti-oxidative stress, inhibits inflammatory responses and anti-apoptosis. This study showed that PL 1-3 could protect mice, especially the brain, against the aging caused by D-galactose (D-gal). D-gal could cause oxidative stress, inflammation, apoptosis and tissue pathological injury and so on in aging mice. The treatment of PL 1-3 could increase the anti-oxidative stress ability in the serum, liver, kidney and brain of aging mice, via increasing the total antioxidant capacity and the levels of anti-oxidative defense enzymes (superoxide dismutase, glutathione peroxidase, and catalase), and reducing the end product of lipid peroxidation (malondialdehyde). In the brain, in addition to the enhanced anti-oxidative stress via upregulating the level of the nuclear factor erythroid 2-related factor 2 and heme oxygenase 1, PL 1-3 could improve the dysfunction of the cholinergic system via reducing the active of acetylcholinesterase so as to increase the level of acetylcholine, increase the anti-inflammatory and anti-apoptosis activities via downregulating the expressions of pro-inflammatory cytokines (interleukin-6 and tumor necrosis factor-α) and pro-apoptosis proteins (Bcl-2 associated X protein and Caspase-3) in the D-gal-induced aging mice, to enhance the anti-aging ability via upregulating the expression of sirtuin 1 and downregulating the expressions of p53, p21, and p16. Besides, PL 1-3 could reverse the liver, kidney and spleen damages induced by D-gal in aging mice. These results suggested that PL 1-3 may be developed as an anti-aging drug for the prevention and intervention of age-related diseases.

Senolytic and senomorphic secondary metabolites as therapeutic agents in Drosophila melanogaster models of Parkinson's disease

Drosophila melanogaster is a valuable model organism for a wide range of biological exploration. The well-known advantages of D. melanogaster include its relatively simple biology, the ease with which it is genetically modified, the relatively low financial and time costs associated with their short gestation and life cycles, and the large number of offspring they produce per generation. D. melanogaster has facilitated the discovery of many significant insights into the pathology of Parkinson's disease (PD) and has served as an excellent preclinical model of PD-related therapeutic discovery. In this review, we provide an overview of the major D. melanogaster models of PD, each of which provide unique insights into PD-relevant pathology and therapeutic targets. These models are discussed in the context of their past, current, and future potential use for studying the utility of secondary metabolites as therapeutic agents in PD. Over the last decade, senolytics have garnered an exponential interest in their ability to mitigate a broad spectrum of diseases, including PD. Therefore, an emphasis is placed on the senolytic and senomorphic properties of secondary metabolites. It is expected that D. melanogaster will continue to be critical in the effort to understand and improve treatment of PD, including their involvement in translational studies focused on secondary metabolites.

Recent Progresses in the Catalytic Stereoselective Dearomatization of Pyridines

1,2- and 1,4-dihydropyridines and N-substituted 2-pyridones are very important structural motifs due to their synthetic versatility and vast presence in a variety of alkaloids and bioactive molecules. In this article, we gather and summarize the catalytic and stereoselective synthesis of partially hydrogenated pyridines and pyridones via the dearomative reactions of pyridine derivatives up to mid-2023. The material is fundamentally organized according to the type of reactivity (electrophilic/nucleophilic) of the pyridine nucleus. The material is further sub-divided taking into account the nucleophilic species when dealing with electrophilic pyridines and considering the reactivity manifold of pyridine derivatives behaving as nucleophiles at the nitrogen site. The latter more recent approach allows for an unconventional entry to chiral N-substituted 2- and 4-pyridones in non-racemic form.

Evaluation of the Antiparasitic and Antifungal Activities of Synthetic Piperlongumine-Type Cinnamide Derivatives: Booster Effect by Halogen Substituents

A series of synthetic N-acylpyrrolidone and -piperidone derivatives of the natural alkaloid piperlongumine were prepared and tested for their activities against Leishmania major and Toxoplasma gondii parasites. Replacement of one of the aryl meta-methoxy groups by halogens such as chlorine, bromine and iodine led to distinctly increased antiparasitic activities. For instance, the new bromo- and iodo-substituted compounds 3 b/c and 4 b/c showed strong activity against L. major promastigotes (IC50 =4.5-5.8 μM). Their activities against L. major amastigotes were moderate. In addition, the new compounds 3 b, 3 c, and 4 a-c exhibited high activity against T. gondii parasites (IC50 =2.0-3.5 μM) with considerable selectivities when taking their effects on non-malignant Vero cells into account. Notable antitrypanosomal activity against Trypanosoma brucei was also found for 4 b. Antifungal activity against Madurella mycetomatis was observed for compound 4 c at higher doses. Quantitative structure-activity relationship (QSAR) studies were carried out, and docking calculations of test compounds bound to tubulin revealed binding differences between the 2-pyrrolidone and 2-piperidone derivatives. Microtubules-destabilizing effects were observed for 4 b in T. b. brucei cells.

Alkaloids as Natural NRF2 Inhibitors: Chemoprevention and Cytotoxic Action in Cancer

Being a controller of cytoprotective actions, inflammation, and mitochondrial function through participating in the regulation of multiple genes in response to stress-inducing endogenous or exogenous stressors, the transcription factor Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) is considered the main cellular defense mechanism to maintain redox balance at cellular and tissue level. While a transient activation of NRF2 protects normal cells under oxidative stress, the hyperactivation of NRF2 in cancer cells may help them to survive and to adapt under oxidative stress. This can be detrimental and related to cancer progression and chemotherapy resistance. Therefore, inhibition of NRF2 activity may be an effective approach for sensitizing cancer cells to anticancer therapy. In this review, we examine alkaloids as NRF2 inhibitors from natural origin, their effects on cancer therapy, and/or as sensitizers of cancer cells to anticancer chemotherapeutics, and their potential clinical applications. Alkaloids, as inhibitor of the NRF2/KEAP1 signaling pathway, can have direct (berberine, evodiamine, and diterpenic aconitine types of alkaloids) or indirect (trigonelline) therapeutic/preventive effects. The network linking alkaloid action with oxidative stress and NRF2 modulation may result in an increased NRF2 synthesis, nuclear translocation, as well in a downstream impact on the synthesis of endogenous antioxidants, effects strongly presumed to be the mechanism of action of alkaloids in inducing cancer cell death or promoting sensitivity of cancer cells to chemotherapeutic agents. In this regard, the identification of additional alkaloids targeting the NRF2 pathway is desirable and the information arising from clinical trials will reveal the potential of these compounds as a promising target for anticancer therapy.

Naphthalimide Fluorescent Skeleton for Facile and Accurate Quantification of Glutathione

Glutathione (GSH), the most prevalent nonprotein thiol in biological systems, acts as both an antioxidant to manipulate intracellular redox homeostasis and a nucleophile to detoxify xenobiotics. The fluctuation of GSH is closely related to the pathogenesis of diverse diseases. This work reports the construction of a nucleophilic aromatic substitution-type probe library based on the naphthalimide skeleton. After an initial evaluation, the compound R13 was identified as a highly efficient GSH fluorescent probe. Further studies demonstrate that R13 could readily quantify GSH in cells and tissues via a straightforward fluorometric assay with a comparable accuracy to the results from the HPLC. We then used R13 to quantify the content of GSH in mouse livers after X-ray irradiation, revealing that irradiation-induced oxidative stress leads to the increase of oxidized GSH (GSSG) and depletion of GSH. In addition, probe R13 was also applied to investigate the alteration of the GSH level in the Parkinson's mouse brains, showing a decrease of GSH and an increase of GSSG in Parkinson's mouse brains. The convenience of the probe in quantifying GSH in biological samples facilitates further understanding of the fluctuation of the GSH/GSSG ratio in diseases.

6-Shogaol as a Novel Thioredoxin Reductase Inhibitor Induces Oxidative-Stress-Mediated Apoptosis in HeLa Cells

Inhibition of thioredoxin reductase (TrxR) is a crucial strategy for the discovery of antineoplastic drugs. 6-Shogaol (6-S), a primary bioactive compound in ginger, has high anticancer activity. However, its potential mechanism of action has not been thoroughly investigated. In this study, we demonstrated for the first time that 6-S, a novel TrxR inhibitor, promoted oxidative-stress-mediated apoptosis in HeLa cells. The other two constituents of ginger, 6-gingerol (6-G) and 6-dehydrogingerduone (6-DG), have a similar structure to 6-S but fail to kill HeLa cells at low concentrations. 6-Shogaol specifically inhibits purified TrxR1 activity by targeting selenocysteine residues. It also induced apoptosis and was more cytotoxic to HeLa cells than normal cells. The molecular mechanism of 6-S-mediated apoptosis involves TrxR inhibition, followed by an outburst of reactive oxygen species (ROS) production. Furthermore, TrxR knockdown enhanced the cytotoxic sensitivity of 6-S cells, highlighting the physiological significance of targeting TrxR by 6-S. Our findings show that targeting TrxR by 6-S reveals a new mechanism underlying the biological activity of 6-S and provides meaningful insights into its action in cancer therapeutics.

Catalytic Access to Chiral δ-Lactams via Nucleophilic Dearomatization of Pyridine Derivatives

Nitrogen-bearing rings are common features in the molecular structures of modern drugs, with chiral δ-lactams being an important subclass due to their known pharmacological properties. Catalytic dearomatization of preactivated pyridinium ion derivatives emerged as a powerful method for the rapid construction of chiral N-heterocycles. However, direct catalytic dearomatization of simple pyridine derivatives are scarce and methodologies yielding chiral δ-lactams are yet to be developed. Herein, we describe an enantioselective C4-dearomatization of methoxypyridine derivatives for the preparation of functionalised enantioenriched δ-lactams using chiral copper catalysis. Experimental ¹³ C kinetic isotope effects and density functional theory calculations shed light on the reaction mechanism and the origin of enantioselectivity.

Dual Antioxidant DH-217 Mitigated Cerebral Ischemia-Reperfusion Injury by Targeting IKKβ/Nrf2/HO-1 Signal Axis

Antioxidants represent a potential therapy for cerebral ischemia-reperfusion injury (CIRI). Compounds which exhibit both direct and indirect antioxidative activity may potentially exert improved effects. Hence, we aimed to assess whether the dual antioxidant DH-217, a derivative of DHAP clinically used to treat coronary heart disease, can reduce oxidative stress damage and elucidate the underlying mechanism. Hydrogen peroxide (H₂O₂)-induced and Middle Cerebral Artery Occlusion (MCAO)-induced damages were used to imitate oxidative stress. The antioxidation of DH-217 was determined by MTT, ROS, colony and DPPH assay. Besides, immunofluorescence, Real-Time PCR Analyses, western blotting and si-RNA/Plasmid-induced protein expression were used for mechanism validation. DPPH scavenging assay evidenced DH-217 was a well free radical scavenger. Cell survival assay also showed that DH-217 had a significant cytoprotection through direct and indirect clearance mechanisms. Further, it clearly inhibited oxidative stress-induced IkappaB kinase beta (IKKβ) phosphorylation and increased heme oxygenase-1 (HO-1) expression. Significantly, these antioxidant beneficial effects were reversed by HO-1 inhibitor, si-nuclear erythroid 2-related factor 2 (Nrf2) and IKKβ plasmid. Meanwhile, DH-217 had a good neuroprotective effect on CIRI rats. The dual antioxidant DH-217 has potential reference value for drug development of CIRI. Furthermore, inhibition of IKKβ phosphorylation and activation of Nrf2/HO-1 could be a promising antioxidant pathway. Dual antioxidant DH-217 not only has the ability of directly scavenging ROS, but also can clear it by targeting IKKβ/Nrf2/HO-1 signal axis. Inhibition of IKKβ phosphorylation and activation of Nrf2/HO-1 may be a promising antioxidant pathway for CIRI.

Oxidative N-Heterocyclic Carbene Catalysis

N-Heterocyclic carbene (NHC) catalysis is a by now consolidated organocatalytic platform for a number of synthetic (asymmetric) transformations via diverse reaction modes/intermediates. In addition to the typical umpolung processes involving acyl anion/homoenolate equivalent species, implementation of protocols under oxidative conditions greatly expands the possibilities of this methodology. Oxidative NHC-catalysis allows for oxidative and oxygenative transformations through specific manipulations of Breslow-type species depending upon the oxidant used (external oxidant or O₂ /air), the derived NHC-bound intermediates paving the way to non-umpolung processes through activation of carbon atoms and heteroatoms. This review is intended to update the state of the art in oxidative NHC-catalyzed reactions that appeared in the literature from 2014 to present, with a strong focus to crucial intermediates and their mechanistic implications.

Engineering piperlongumine-inspired analogs as Nrf2-dependent neuroprotectors against oxidative damage by an electrophilicity-based strategy

Oxidative stress contributes significantly to the development of neurodegenerative diseases, thus developing nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent neuroprotectors is highly required for either prevention or treatment of these diseases. This work highlights an electrophilicity-based strategy that allows finding more active Nrf2-dependent neuroprotectors than natural piperlongumine (PL). Electrophilic modification was applied on both the exocylic and endocyclic Michael acceptors of PL, which includes placement of an electron-withdrawing trifluoromethyl group on its aromatic ring in the ortho, meta, or para position to the exocyclic olefin, and further introduction of an electron-withdrawing α-chlorine on its lactam ring. From a panel of PL analogs, we identified PLCl-4CF₃, characterized by the presence of p-trifluoromethyl group and α-chlorine, to be significantly superior to the parent PL in protecting PC12 cells from oxidative damage induced by 6-hydroxydopamine hydrochloride. Mechanistic studies reveal that the increased electrophilicity of PLCl-4CF₃ in its two Michael acceptors allows its ability to covalently modify Cys-151 at Keap1, facilitating inhibition against Nrf2 ubiquitination, translocation of Nrf2 into the nucleus, induction of phase 2 enzymes and final protection of PC12 cells from oxidative damage.

The design and synthesis of benzylpiperazine-based edaravone derivatives and their neuroprotective activities

New edaravone derivatives containing a benzylpiperazine moiety are designed and synthesized. The structures are characterized by 1H NMR, 13C NMR, and high-resolution mass spectrometry. The potential neuroprotective activities of the target compounds are evaluated in differentiated rat pheochromocytoma cells (PC12 cells) and in mice subjected to acute cerebral ischemia. Most of the target compounds showed neuroprotective activities both in vivo and in vitro, especially 1-(4-(4-fluorobenzyl) piperazin-1-yl)-2-(4-(5-hydroxy-3-methyl-1 H-pyrazol-1-yl)phenoxy)ethanone and 1-(4-(4-nitrobenzyl)piperazin-1-yl)-2-(4-(5-hydroxy-3-methyl-1 H-pyrazol-1-yl)phenoxy)ethanone, which displayed significant protective effects on cell viability against damage caused by H2O2, and remarkably prolonged the survival time of mice subjected to acute cerebral ischemia and decreased the mortality rate at all doses. These compounds represent lead compounds for the further discovery of neuroprotective agents for treating cerebral ischemic stroke. Molecular docking studies and basic structure–activity relationships are also presented.

Hispolon alleviates oxidative damage by stimulating the Nrf2 signaling pathway in PC12 cells

Natural products derived from the daily diet are garnering increasing attention for neurodegenerative disease (ND) treatment. Hispolon (His), a small molecule from Phellinus linteus, has been reported to have various pharmacological activities. Here, we evaluated its protective effect on a neuron-like rat pheochromocytoma cell line (PC12). Results showed that His could restore cell death induced by oxidative damage. Nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2) plays a significant role in maintaining cellular redox homeostasis. After treatment with His, some Nrf2-governed antioxidant genes were upregulated in a dose-dependent manner. However, the protective effect of His on PC12 cells was easily terminated by Nrf2 knockdown, demonstrating that Nrf2 is a critical component in this cytoprotective process. Taken together, our study showed that His was not only an effective activator of Nrf2 but also a promising candidate for ND treatment.

Hinokitiol functions as a ferroptosis inhibitor to confer neuroprotection

The intrinsic link of ferroptosis to neurodegeneration, such as Parkinson's disease and Alzheimer's disease, has set promises to apply ferroptosis inhibitors for treatment of neurodegenerative disorders. Herein, we report that the natural small molecule hinokitiol (Hino) functions as a potent ferroptosis inhibitor to rescue neuronal damages in vitro and in vivo. The action mechanisms of Hino involve chelating irons and activating cytoprotective transcription factor Nrf2 to upregulate the antioxidant genes including solute carrier family 7 member 11, glutathione peroxidase 4 and Heme oxygenase-1. In vivo studies demonstrate that Hino rescues the deficits of locomotor activity and neurodevelopment in zebrafishes. In addition, Hino shows the efficient blood-brain barrier permeability in mice, supporting the application of Hino for brain disorders. Paclitaxel is one of the most widely used broad-spectrum antineoplastic agents. However, its neurotoxic side effect is a severe concern. We demonstrate that the neurotoxicity of paclitaxel is ferroptosis-related and Hino also alleviates the paclitaxel-induced neurotoxicity without compromising its cytotoxicity to cancer cells. Hino also salvages the neurobehavioral impairment by paclitaxel in zebrafishes. Collectively, the discovery of Hino as a novel ferroptosis inhibitor and disclosure of its action mechanisms establish a foundation for the further development of Hino as a neuroprotective agent.

A multi-target directed ligands strategy for the treatment of Alzheimer's disease: Dimethyl fumarate plus Tranilast modified Dithiocarbate as AChE inhibitor and Nrf2 activator

Alzheimer's disease (AD) possessed intricate pathogenesis. Currently, multi-targeted drugs were considered to have the potential to against AD by simultaneously triggering molecules in functionally complementary pathways. Hence, a series of molecules based on the pharmacophoric features of Dimethyl fumarate, Tranilast, and Dithiocarbate were designed and synthesized. These compounds showed significant AChE inhibitory activity in vitro. Among them, compound 4c₂ displayed the mighty inhibitory activity to hAChE (IC₅₀ = 0.053 μM) and held the ability to cross the BBB. Kinetic study and molecular docking pointed out that 4c₂ bound well into the active sites of hAChE, forming steady and sturdy interactions with key residues in hAChE. Additionally, 4c₂ as an Nrf2 activator could promote the nuclear translocation of Nrf2 protein and induce the expressions of Nrf2-dependent enzymes HO-1, NQO1, and GPX4. Moreover, 4c₂ rescued BV-2 cells from H₂O₂-induced injury and inhibited ROS accumulation. For the anti-neuroinflammatory potential of 4c₂, we observed that 4c₂ could lower the levels of pro-inflammatory cytokines (NO, IL-6 and TNF-α) and suppressed the expressions of iNOS and COX-2. In particular, 4c₂ was well tolerated in mice (2500 mg/kg, p.o.) and efficaciously recovered the memory impairment in a Scopolamine-induced mouse model. Overall, these results highlighted that 4c₂ was a promising multi-targeted agent for treating AD.

Piperlongumine as a Neuro-Protectant in Chemotherapy Induced Cognitive Impairment

Advances in the early diagnosis and treatment have led to increases in breast cancer survivorship. Survivors report cognitive impairment symptoms such as loss of concentration and learning and memory deficits which significantly reduce the patient's quality of life. Additional therapies are needed to prevent these side effects and, the precise mechanisms of action responsible are not fully elucidated. However, increasing evidence points toward the use of neuroprotective compounds with antioxidants and anti-inflammatory properties as tools for conserving learning and memory. Here, we examine the ability of piperlongumine (PL), an alkaloid known to have anti-inflammatory and antioxidant effects, to play a neuroprotective role in 16-week-old female C57BL/6J mice treated with a common breast cancer regimen of doxorubicin, cyclophosphamide, and docetaxel (TAC). During social memory testing, TAC-treated mice exhibited impairment, while TAC/PL co-treated mice did not exhibit measurable social memory deficits. Proteomics analysis showed ERK1/2 signaling is involved in TAC and TAC/PL co-treatment. Reduced Nrf2 mRNA expression was also observed. mRNA levels of Gria2 were increased in TAC treated mice and reduced in TAC/PL co-treated mice. In this study, PL protects against social memory impairment when co-administered with TAC via multifactorial mechanisms involving oxidative stress and synaptic plasticity.

Imidazolylacetophenone oxime-based multifunctional neuroprotective agents: Discovery and structure-activity relationships

Alzheimer's disease (AD) possesses a complex pathogenetic mechanism. Nowadays, multitarget agents are considered to have potential in effectively treating AD via triggering molecules in functionally complementary pathways at the same time. Here, based on the screening (∼1400 compounds) against neuroinflammation, an imidazolylacetophenone oxime ether (IOE) was discovered as a novel hit. In order to obtain SARs, a series of imidazolylacetophenone oxime derivatives were constructed, and their C=N bonds were confirmed as the Z configuration by single crystals. These derivatives exhibited potential multifunctional neuroprotective effects including anti-neuroinflammatory, antioxidative damage, metal-chelating, inhibition of acetylcholinesterase (AChE) properties. Among these derivatives, compound 12i displayed the most potent inhibitory activity against nitric oxide (NO) production with EC₅₀ value of 0.57 μM 12i can dose-dependently suppress the expression of iNOS and COX-2 but not change the expression of HO-1 protein. Moreover, 12i exhibited evidently neuroprotective effects on H₂O₂-induced PC12 cells damage and ferroptosis without cytotoxicity at 10 μM, as well as selectively metal chelating properties via chelating Cu²⁺. In addition, 12i showed a mixed-type inhibitory effect on AChE in vitro. The structure-activity relationships (SARs) analysis indicated that dioxolane groups on benzene ring and rigid oxime ester can improve the activity. Parallel artificial membrane permeation assay (PAMPA) also verified that 12i can overcome the blood-brain barrier (BBB). Overall, this is the first report on imidazolylacetophenone oxime-based multifunctional neuroprotective effects, suggesting that this type of compounds might be novel multifunctional agents against AD.

Emodin ameliorates antioxidant capacity and exerts neuroprotective effect via PKM2-mediated Nrf2 transactivation

Pyruvate kinase M2 (PKM2) is overexpressed in neuronal cells. However, there are few studies on the involvement of PKM2 modulators in neurodegenerative diseases. Emodin, a dominating anthraquinone derivative extracting from the rhizome of rhubarb, has received expanding consideration due to its pharmacological properties. Our data reveal that emodin could resist hydrogen peroxide- or 6-hydroxydopamine-mediated mitochondrial fission and apoptosis in PC12 cells (a neuron-like rat pheochromocytoma cell line). Notably, emodin at nontoxic concentrations significantly inhibits PKM2 activity and promotes dissociation of tetrameric PKM2 into dimers in cells. The PKM2 dimerization enhances the interaction of PKM2 and NFE2-related factor 2 (Nrf2), which further triggers the activation of the Nrf2/ARE pathway to upregulate a panel of cytoprotective genes. Modulating the PKM2/Nrf2/ARE axis by emodin unveils a novel mechanism for understanding the pharmacological functions of emodin. Our findings indicate that emodin is a potential candidate for the treatment of oxidative stress-related neurodegenerative disorders.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

Meta-substituted piperlongumine derivatives attenuate inflammation in both RAW264.7 macrophages and a mouse model of colitis

Piperlongumine (PL) has been showed to have multiple pharmacological activities. In this study, we reported the synthesis of three series of PL derivatives, and evaluation of their anti-inflammatory effects in both lipopolysaccharide (LPS)-induced Raw264.7 macrophages and a dextran sulfate sodium (DSS)-induced mouse model of colitis. Our results presented that two meta-substituent containing derivatives 1-3 and 1-6, in which γ-butyrolactam replaced α,β-unsaturated δ-valerolactam ring of PL, displayed low cytotoxicity and effective anti-inflammatory activity. Molecular docking also showed that the meta-substituted derivative, compared with the corresponding ortho- or para-substituted derivative, had significant interactions with the amino acid residues of CD14, which was the core receptors recognizing LPS. In vitro and in vivo studies, 1-3 and 1-6 could inhibit the expression of pro-inflammatory cytokines, and the excessive production of reactive nitrogen species and reactive oxygen species. Oral administration of 100 mg/kg/day of 1-3 or 1-6 alleviated the severity of clinical symptoms of colitis in mice, and significantly reduced the colonic tissue damage to protect the colonic tissue from the DSS-induced colitis. These results suggested that meta-substituted derivatives 1-3 and 1-6 were potential anti-inflammatory agents, which may lead to future pharmaceutical development.

Cynaropicrin Induces Cell Cycle Arrest and Apoptosis by Inhibiting PKM2 to Cause DNA Damage and Mitochondrial Fission in A549 Cells

Metabolic reprogramming is critical for tumorigenesis. Pyruvate kinase M2 (PKM2) is overexpressed in lung carcinoma cells and plays a critical role in the Warburg effect, making the enzyme a research hotspot for anticancer drug development. Cynaropicrin (CYN), a natural sesquiterpene lactone compound from artichoke, has received increasing consideration due to its consumable esteem and pharmacological properties. Our data reveal that CYN not only inhibited the purified PKM2 activity but also decreased the cellular PKM2 expression in A549 cells. The inhibition of PKM2 leads to the upregulation of p53 and the downregulation of the DNA repair enzyme poly (ADP-ribose) polymerase (PARP), and subsequently causes the cell cycle arrest. Additionally, CYN inhibits the interaction of PKM2 and Nrf2, resulting in the impairment of cellular antioxidant capacity, induction of oxidative stress, and mitochondrial damages. Overexpression of PKM2 attenuates the CYN-induced DNA damage, mitochondrial fission, and cell viability. Thus, targeting PKM2 provides an original mechanism for understanding the pharmacological impact of CYN and assists in the further development of CYN as an anticancer agent.

Hydroxycinnamic Acid Amide Dimers from Goji Berry and Their Potential Anti-AD Activity

Three undescribed hydroxycinnamic acid amide dimers 1-3 were isolated and identified from an extract of Goji berry. Their molecular structures were elucidated based on NMR, MS, and IR spectra analysis. Compounds 1-3 were hydroxycinnamic acid amide dimers, which possess a cyclic butane moiety formed by head-to-head connection. These compounds at 25 μM showed the disaggregation potency on the copper-mediated Aβ_1-42 aggregation ranging from 27.3±3.2 to 31.0±2.9 %. This study provides new information on the antiaging traditional usage of goji berry.

Inhibition of Thioredoxin Reductase by Santamarine Conferring Anticancer Effect in HeLa Cells

Natural products frequently have unique physiological activities and new action mechanisms due to their structural diversity and novelty, and are an important source for innovative drugs and lead compounds. We present herein that natural product santamarine targeted thioredoxin reductase (TrxR) to weaken its antioxidative function in cells, accompanied by accumulation of high levels of reactive oxygen species (ROS), and finally induced a new mechanism of tumor cell oxidative stress-mediated apoptosis. TrxR knockdown or overexpression cell lines were employed to further evaluate the cytotoxicity of santamarine regulated by TrxR, demonstrated that TrxR played a key role in the physiological effect of santamarine on cells. Santamarine targeting TrxR reveals its previously unrecognized mechanism of antitumor and provides a basis for the further development of santamarine as a potential cancer therapeutic agent.

Overview of piperlongumine analogues and their therapeutic potential

Natural products have long been an important source for discovery of new drugs to treat human diseases. Piperlongumine (PL) is an amide alkaloid isolated from Piper longum L. (long piper) and other piper plants and has received widespread attention because of its diverse biological activities. A large number of PL derivatives have been designed, synthesized and assessed in many pharmacological functions, including antiplatelet aggregation, neuroprotective activities, anti-diabetic activities, anti-inflammatory activities, anti-senolytic activities, immune activities, and antitumor activities. Among them, the anti-tumor effects and application of PL and its derivatives are most extensively studied. We herein summarize the development of PL derivatives, the structure and activity relationships (SARs), and their therapeutic potential on the treatments of various diseases, especially against cancer. We also discussed the challenges and future directions associated with PL and its derivatives in these indications.

Activation of Cellular Antioxidant Defense System by Naturally Occurring Dibenzopyrone Derivatives Confers Neuroprotection against Oxidative Insults

Seven dibenzopyrone phenolic derivatives, i.e., alternariol (1), alternariol 5-O-methyl ether (2), altenusin B (3), dehydroaltenusin (4), altenuene (5), altenusin (6), and alterlactone (7), were isolated from endophytic fungi Alternaria alternata extract, and these compounds' structures were elucidated based on various spectroscopic data. Compound 3, a diphenic acid derivative, was determined as a new compound. In this study, compounds 3, 4, 6, and 7 displayed remarkable neuroprotective effects against oxidative injuries by acting as potent activators of nuclear factor-erythroid derived 2-like 2 (Nrf2) in PC12 cells. A mechanistic study indicated that these compounds induced the nuclear accumulation of Nrf2, promoted the expression of Nrf2-governed cytoprotective genes, and increased the cellular antioxidant capacity. More importantly, genetic silence of Nrf2 expression deprived the observed cytoprotection, highlighting the important role of Nrf2 in the protection of these compounds.

Inhibition of the NRF2/KEAP1 Axis: A Promising Therapeutic Strategy to Alter Redox Balance of Cancer Cells

Significance: The nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (NRF2/KEAP1) pathway is a crucial and highly conserved defensive system that is required to maintain or restore the intracellular homeostasis in response to oxidative, electrophilic, and other types of stress conditions. The tight control of NRF2 function is maintained by a complex network of biological interactions between positive and negative regulators that ultimately ensure context-specific activation, culminating in the NRF2-driven transcription of cytoprotective genes. Recent Advances: Recent studies indicate that deregulated NRF2 activation is a frequent event in malignant tumors, wherein it is associated with metabolic reprogramming, increased antioxidant capacity, chemoresistance, and poor clinical outcome. On the other hand, the growing interest in the modulation of the cancer cells' redox balance identified NRF2 as an ideal therapeutic target. Critical Issues: For this reason, many efforts have been made to identify potent and selective NRF2 inhibitors that might be used as single agents or adjuvants of anticancer drugs with redox disrupting properties. Despite the lack of specific NRF2 inhibitors still represents a major clinical hurdle, the researchers have exploited alternative strategies to disrupt NRF2 signaling at different levels of its biological activation. Future Directions: Given its dualistic role in tumor initiation and progression, the identification of the appropriate biological context of NRF2 activation and the specific clinicopathological features of patients cohorts wherein its inactivation is expected to have clinical benefits, will represent a major goal in the field of cancer research. In this review, we will briefly describe the structure and function of the NRF2/ KEAP1 system and some of the most promising NRF2 inhibitors, with a particular emphasis on natural compounds and drug repurposing. Antioxid. Redox Signal. 34, 1428-1483.

Piperlongumine attenuates oxidative stress, inflammatory, and apoptosis through modulating the GLUT-2/4 and AKT signaling pathway in streptozotocin-induced diabetic rats

The current study was done to measure the role of piperlongumine (PL) on hyperglycemia interrelated oxidative stress-mediated inflammation and apoptosis, inflammatory stress, and the diabetic insulin receptor substrate 2 (IRS2), protein kinase B (AKT), and glucose transporter 2 (GLUT-2)/4 signaling pathway in streptozotocin (STZ)-persuaded diabetic animals. Diabetes was initiated in experimental animals via a single dose intraperitoneal inoculation of STZ. Diabetic rats revealed an augmented blood-glucose level with drastically diminished plasma-insulin status. The functions of antioxidants were diminished with enhanced lipid peroxidation, conjugated dienes, and protein carbonyls noticed in diabetic rats'  plasma and pancreatic tissues. An elevation of nuclear factor-κB (NF-κB), tumor necrosis factor-α, and interleukin-6 proteins was noticed in pancreatic tissues as well as IRS2, AKT, GLUT-2, and GLUT-4 marker expressions were quantified in the hepatic tissue of control and diabetic rats. Oral administration of PL for 30 days drastically lowered glucose and higher insulin status in STZ-induced diabetic rats. Impressively, PL oral supplementation considerably restored the antioxidant levels and reduced inflammation and diabetic marker expressions in STZ-diabetic rats. These results were supported through a histological study. Moreover, PL also augmented the level of B-cell lymphoma 2 and diminished the level of Bcl-2-associated X protein in STZ-treated rat's hepatic tissues. Thus, we concluded that PL excellently rescued pancreatic β cells through mitigating hyperglycemia via dynamic insulin secretion, activating antioxidants, and inhibiting inflammation and apoptosis in the pancreatic and hepatic tissue of diabetic rats.

Trimethoxycinnamates and Their Cholinesterase Inhibitory Activity

A series of twelve nature-inspired 3,4,5-trimethoxycinnamates were prepared and characterized. All compounds, including the starting 3,4,5-trimethoxycinnamic acid, were tested for their ability to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in vitro; the selectivity index (SI) was also determined. 2-Fluororophenyl (2E)-3-(3,4,5-trimethoxyphenyl)-prop-2-enoate demonstrated the highest SI (1.71) in favor of BChE inhibition. 2-Chlorophenyl (2E)-3-(3,4,5-trimethoxyphenyl)prop-2-enoate showed the highest AChE-inhibiting (IC50 = 46.18 µM) as well as BChE-inhibiting (IC50 = 32.46 µM) activity with an SI of 1.42. The mechanism of action of the most potent compound was determined by the Lineweaver–Burk plot as a mixed type of inhibition. An in vitro cell viability assay confirmed the insignificant cytotoxicity of the discussed compounds on the two cell lines. Trends between structure, physicochemical properties and activity were discussed.

Natural Molecules Targeting Thioredoxin System and Their Therapeutic Potential

Significance: Thioredoxin (Trx) and thioredoxin reductase are two core members of the Trx system. The system bridges the gap between the universal reducing equivalent NADPH and various biological molecules and plays an essential role in maintaining cellular redox homeostasis and regulating multiple cellular redox signaling pathways. Recent Advance: In recent years, the Trx system has been well documented as an important regulator of many diseases, especially tumorigenesis. Thus, the development of potential therapeutic molecules targeting the system is of great significance for disease treatment. Critical Issues: We herein first discuss the physiological functions of the Trx system and the role that the Trx system plays in various diseases. Then, we focus on the introduction of natural small molecules with potential therapeutic applications, especially the anticancer activity, and review their mechanisms of pharmacological actions via interfering with the Trx system. Finally, we further discuss several natural molecules that harbor therapeutic potential and have entered different clinical trials. Future Directions: Further studies on the functions of the Trx system in multiple diseases will not only improve our understanding of the pathogenesis of many human disorders but also help develop novel therapeutic strategies against these diseases. Antioxid. Redox Signal. 34, 1083-1107.

Twin drug design, synthesis and evaluation of diosgenin derivatives as multitargeted agents for the treatment of vascular dementia

A novel series of multitargeted molecules were designed and synthesized by combining the pharmacological role of cholinesterase inhibitor and antioxidant of steroid as potential ligands for the treatment of Vascular Dementia (VD). The oxygen-glucose deprivation (OGD) model was used to evaluate these molecules, among which the most potent compound ML5 showed the highest activity. Firstly, ML5 showed appropriate inhibition of cholinesterases (ChEs) at orally 15 mg/kg in vivo. The further test revealed that ML5 promoted the nuclear translocation of Nrf2. Furthermore, ML5 has significant neuroprotective effect in vivo model of bilateral common carotid artery occlusion (BCCAO), significantly increasing the expression of Nrf2 protein in the cerebral cortex. In the molecular docking research, we predicted the ML5 combined with hAChE and Keap1. Finally, compound ML5 displayed normal oral absorption and it was nontoxic at 500 mg/kg, po, dose. We can draw the conclusion that ML5 could be considered as a new potential compound for VD treatment.

Synthesis and evaluation of multi-target-directed ligands with BACE-1 inhibitory and Nrf2 agonist activities as potential agents against Alzheimer's disease

Cumulative evidence suggests that β-amyloid and oxidative stress are closely related with each other and play key roles in the process of Alzheimer's disease (AD). Multitarget regulation of both pathways might represent a promising therapeutic strategy. Here, a series of selenium-containing compounds based on ebselen and verubecestat were designed and synthesized. Biological evaluation showed that 13f exhibited good BACE-1 inhibitory activity (IC₅₀ = 1.06 μΜ) and potent GPx-like activity (ν₀ = 183.0 μM min^-1). Aβ production experiment indicated that 13f could reduce the secretion of Aβ1-40 in HEK APPswe 293T cells. Moreover, 13f exerted a cytoprotective effect against the H₂O₂ or 6-OHDA caused cell damage via alleviation of intracellular ROS, mitochondrial dysfunction, Ca²⁺ overload and cell apoptosis. The mechanism studies indicated that 13f exhibited cytoprotective effect by activating the Keap1-Nrf2-ARE pathway and stimulating downstream anti-oxidant protein including HO-1, NQO1, TrxR1, GCLC, and GCLM. In addition, 13f significantly reduced the production of NO and IL-6 induced by LPS in BV2 cells, which confirmed its anti-inflammatory activity as a Nrf2 activator. The BBB permeation assay predicted that 13f was able to cross the BBB. In summary, 13f might be a promising multi-target-directed ligand for the treatment of AD.

Design, synthesis, and biological evaluation of diosgenin-indole derivatives as dual-functional agents for the treatment of Alzheimer's disease

The complex pathogenesis of Alzheimer's disease (AD) has become a major obstacle in its treatment. An effective approach is to develop multifunctional agents that simultaneously target multiple pathological processes. Here, a series of diosgenin-indole compounds were designed, synthesized and evaluated for their neuroprotective effects against H₂O₂ (hydrogen peroxide), 6-OHDA (6-hydroxydopamine) and Aβ (beta amyloid) damages. Preliminary structure-activities relationship revealed that the introduction of indole fragment and electron-donating group at C-5 on ring indole could be beneficial for neuroprotective activities. Results indicated that compound 5b was the most promising candidate against cellular damage induced by H₂O₂ (52.9 ± 1.9%), 6-OHDA (38.4 ± 2.4%) and Aβ_1-42 (54.4 ± 2.7%). Molecular docking study suggested the affinity for 5b bound to Aβ_1-42 was -40.59 kcal/mol, which revealed the strong binding affinity of 5b to Aβ_1-42. The predicted values of brain/blood partition coefficient (-0.733) and polar surface area (85.118 Å²) indicated the favorable abilities of BBB permeation and absorption of 5b. In addition, 5b significantly decreased ROS (reactive oxygen species) production induced by H₂O₂. In the following in vivo experiment, 5b obviously attenuated memory and learning impairments of Aβ-injected mice. In summary, compound 5b could be considered as a promising dual-functional neuroprotective agent against AD.

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.

Identification and optimization of piperlongumine analogues as potential antioxidant and anti-inflammatory agents via activation of Nrf2

Oxidative stress and inflammation are significant risk factors for neurodegenerative disease. The Keap1-Nrf2-ARE pathway is one of the most promising defensive systems against oxidative stress. Here, dozens of piperlongumine analogues were designed, synthesized, and tested on PC12 cells to examine neuroprotective effects against H2O2 and 6-OHDA induced damage. Among them, 6d was found to be able to alleviate the accumulation of ROS, inhibit the production of NO and downregulate the level of IL-6, which indicated its potential antioxidant and anti-inflammatory activity. Further studies proved that 6d could activate Nrf2 signaling pathway, induce the translocation of Nrf2 from cell cytosol to nucleus and upregulate the related phase II antioxidant enzymes including NQO1, HO-1, GCLC, GCLM and TrxR1. These results confirmed that 6d exerted antioxidant and anti-inflammatory activities by activating Nrf2 signaling pathway. Moreover, the parallel artificial membrane permeability assay indicated that 6d can cross the blood-brain barrier. In general, 6d is promising for further development as a therapeutic drug against oxidative stress and inflammation related neurodegenerative disorders.

Nrf2: a dark horse in Alzheimer's disease treatment

Alzheimer's disease (AD), an age-dependent neurodegenerative disorder, is the main cause of dementia. Common hallmarks of AD include the amyloid β-peptide (Aβ) aggregation, high levels of hyperphosphorylated tau protein (p-tau) and failure in redox homeostasis. To date, all proposed drugs affecting Aβ and/or p-tau have been failed in clinical trials. A decline in the expression of the transcription factor Nrf2 (nuclear factor-erythroid 2-p45 derived factor 2) and its driven genes (NQO1, HO-1, and GCLC), and alteration of the Nrf2-related pathways have been observed in AD brains. Nrf2 plays a critical role in maintaining cellular redox homeostasis and regulating inflammation response. Nrf2 activation also provides cytoprotection against increasing pathologies including neurodegenerative diseases. These lines of evidence imply that Nrf2 activation may be a novel AD treatment option. Interestingly, recent studies have also demonstrated that Nrf2 interferes with several key pathogenic processes in AD including Aβ and p-tau pathways. The current review aims to provide insights into the role of Nrf2 in AD. Also, we discuss the progress and challenges regarding the Nrf2 activators for AD treatment.

Generation of potent Nrf2 activators via tuning the electrophilicity and steric hindrance of vinyl sulfones for neuroprotection

Oxidative stress is constantly involved in the etiopathogenesis of an ever-widening range of neurodegenerative diseases. As a consequence, effective repression of cellular oxidative stress to a redox homeostatic condition is a promising and feasible strategy to treat, or at least retard the progression of, such disorders. Nrf2, a primary orchestrator of cellular antioxidant response machine, is responsible for detoxifying and compensating for deleterious oxidative stress via transcriptional activation of a diverse array of antioxidant biomolecules. In the framework of our persistent interest in disclosing small molecules that interfere with cellular redox-regulating machinery, we report herein the synthesis, optimization, and biological assessment of 47 vinyl sulfone scaffold-bearing small molecules, most of which exhibit robust neuroprotective effect against H₂O₂-mediated lesions to PC12 cells. After initial screening, the most potent neuroprotective compounds 9b and 9c with marginal cytotoxicity were selected for the follow-up studies. Our results demonstrate that their neuroprotective effects are attributed to the up-regulation of a panel of antioxidant genes and corresponding gene products. Further mechanistic studies indicate that Nrf2 is indispensable for the cellular performances of 9b and 9c, arising from the fact that silence of Nrf2 gene drastically nullifies their protective action. Taken together, 9b and 9c discovered in this work merit further development as neuroprotective candidates for the treatment of oxidative stress-mediated pathological conditions.

The potential role of the 5,6-dihydropyridin-2(1H)-one unit of piperlongumine on the anticancer activity

Piperlongumine (PL), a potent anticancer agent from the plant long pepper (Piper longum), contains the 5,6-dihydropyridin-2(1H)-one heterocyclic scaffold and cinnamoyl unit. In this paper, we synthesized a series of PL analogs and evaluated their cytotoxicity against cancer cells for the sake of exploring which pharmacophore plays a more potent role in enhancing the anticancer activities of PL. These results illustrated that the position effect, not the electronic effect, of substituents plays a certain role in the cytotoxicity of PL and its analogs. More important, the 5,6-dihydropyridin-2(1H)-one unit, a potent pharmacophore in enhancing the antiproliferative activities of PL, could react with cysteamine and lead to ROS generation, and then bring about the occurrence of ROS-induced downstream events, followed by cell cycle arrest and apoptosis. This work suggests that introducing a lactam unit containing Michael acceptors may be a potent strategy to enhancing the anticancer activity of 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.

Synthesis and Spectroscopic Analysis of Piperine- and Piperlongumine-Inspired Natural Product Scaffolds and Their Molecular Docking with IL-1β and NF-κB Proteins

Inspired by the remarkable bioactivities exhibited by the natural products, piperine and piperlongumine, we synthesised eight natural product-inspired analogues to further investigate their structures. For the first time, we confirmed the structure of the key cyclised dihydropyrazolecarbothioamide piperine analogues including the use of two-dimensional (2D) 15N-based spectroscopy nuclear magnetic resonance (NMR) spectroscopy. Prior investigations demonstrated promising results from these scaffolds for the inhibition of inflammatory response via downregulation of the IL-1β and NF-κB pathway. However, the molecular interaction of these molecules with their protein targets remains unknown. Ab initio calculations revealed the electronic density function map of the molecules, showing the effects of structural modification in the electronic structure. Finally, molecular interactions between the synthesized molecules and the proteins IL-1β and NF-κB were achieved. Docking results showed that all the analogues interact in the DNA binding site of NF-κB with higher affinity compared to the natural products and, with the exception of 9a and 9b, have higher affinity than the natural products for the binding site of IL-1β. Specificity for the molecular recognition of 3a, 3c and 9b with IL-1β through cation-π interactions was determined. These results revealed 3a, 3c, 4a, 4c and 10 as the most promising molecules to be evaluated as IL-1β and NF-κB inhibitors.