Sofalcone, a gastroprotective drug, covalently binds to KEAP1 to activate Nrf2 resulting in anti-colitic activity

Research progress on the role and inhibitors of Keap1 signaling pathway in inflammation

Inflammation is a protective mechanism against endogenous and exogenous pathogens. It is a typical feature of numerous chronic diseases and their complications. Keap1 is an essential target in oxidative stress and inflammatory diseases. Among them, the Keap1-Nrf2-ARE pathway (including Keap1-Nrf2-HO-1) is the most significant pathway of Keap1 targets, which participates in the control of inflammation in multiple organs (including renal inflammation, lung inflammation, liver inflammation, neuroinflammation, etc.). Identifying new Keap1 inhibitors is crucial for new drug discovery. However, most drugs have specificity issues as they covalently bind to cysteine residues of Keap1, causing off-target effects. Therefore, direct inhibition of Keap1-Nrf2 PPIs is a new research idea. Through non-electrophilic and non-covalent binding, its inhibitors have better specificity and ability to activate Nrf2, and targeting therapy against Keap1-Nrf2 PPIs has become a new method for drug development in chronic diseases. This review summarizes the members and downstream genes of the Keap1-related pathway and their roles in inflammatory disease models. In addition, we summarize all the research progress of anti-inflammatory drugs targeting Keap1 from 2010 to 2024, mainly describing their biological functions, molecular mechanisms of action, and therapeutic roles in inflammatory diseases.

The role of Keap1-Nrf2 signaling pathway in the treatment of respiratory diseases and the research progress on targeted drugs

Lungs are exposed to external oxidants from the environment as in harmful particles and smog, causing oxidative stress in the lungs and consequently respiratory ailment. The NF-E2-related factor 2 (Nrf2) is the one with transcriptional regulatory function, while its related protein Kelch-like ECH-associated protein 1 (Keap1) inhibits Nrf2 activity. Together, they form the Keap1-Nrf2 pathway, which regulates the body's defense against oxidative stress. This pathway has been shown to maintain cellular homeostasis during oxidative stressing, inflammation, oncogenesis, and apoptosis by coordinating the expression of cytoprotective genes and making it a potential therapeutic target for respiratory diseases. This paper summarizes this point in detail in Chapter 2. In addition, this article summarizes the current drug development and clinical research progress related to the Keap1-Nrf2 signaling pathway, with a focus on the potential of Nrf2 agonists in treating respiratory diseases. Overall, the article reviews the regulatory mechanisms of the Keap1-Nrf2 signaling pathway in respiratory diseases and the progress of targeted drug research, aiming to provide new insights for treatment.

Sofalcone attenuates neurodegeneration in MPTP-induced mouse model of Parkinson's disease by inhibiting oxidative stress and neuroinflammation

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by oxidative stress and neuroinflammation. Sofalcone (SFC), a chalcone derivative known for its antioxidative and anti-inflammatory properties, is widely used clinically as a gastric mucosa protective agent. However, its therapeutic potential in PD remains to be fully explored. In this study, we investigated the neuroprotective effects of SFC in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model.

METHODS AND RESULTS

We found that SFC ameliorated MPTP-induced motor impairments in mice, as assessed by the rotarod and wire tests. Moreover, SFC administration prevented the loss of dopaminergic neurons and striatal degeneration induced by MPTP. Subsequent investigations revealed that SFC reversed MPTP-induced downregulation of NRF2, reduced elevated levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and increased total antioxidant capacity (TAOC). Furthermore, SFC suppressed MPTP-induced activation of microglia and astrocytes, downregulated the pro-inflammatory cytokine TNF-α, and upregulated the anti-inflammatory cytokine IL-4. Additionally, SFC ameliorated the MPTP-induced downregulation of phosphorylation of Akt at Ser473.

CONCLUSIONS

This study provides evidence for the neuroprotective effects of SFC, highlighting its antioxidative and anti-inflammatory properties and its role in Akt activation in the PD model. These findings underscore SFC's potential as a promising therapeutic candidate for PD, warranting further clinical investigation.

Significance of Chalcone Scaffolds in Medicinal Chemistry

Chalcone is a simple naturally occurring α,β-unsaturated ketone with biological importance, which can also be easily synthesized in laboratories by reaction between two aromatic scaffolds. In plants, chalcones occur as polyphenolic compounds of different frameworks which are bioactive molecules that have been in traditional medicinal practice for many years. Chalcone-based lead molecules have been developed, possessing varied potentials such as antimicrobial, antiviral, anti-inflammatory, anticancer, anti-oxidant, antidiabetic, antihyperurecemic, and anti-ulcer effects. Chalcones contribute considerable fragments to give important heterocyclic molecules with therapeutic utilities targeting various diseases. These characteristic features have made chalcone a topic of interest among researchers and have attracted investigations into this widely applicable structure. This review highlights the extensive exploration carried out on the synthesis, biotransformations, chemical reactions, hybridization, and pharmacological potentials of chalcones, and aims to provide an extensive, thorough, and critical review of their importance, with emphasis on their properties, chemistry, and biomedical applications to boost future investigations into this potential scaffold in medicinal chemistry.

Examining the Scope of Deriving β-Aryl Enones from Enol Silanes as Ketone Equivalents via Pd(II)-Mediated Sequential Dehydrosilylation and Arylation

Silyl enol ethers were examined as a masked source of saturated ketones to derive β-aryl enones and their derivatives by dehydrosilylation to generate enones in situ and subsequent oxidative arylation with arylboronic acids as transmetallation coupling partners using relayed Pd(II) catalysis in one pot under base-free conditions. Oxygen was found to be an efficient and green oxidant to enable both dehydrosilylation of enol silanes and arylation. Additionally, arylation conditions can be custom-designed to take advantage of aryl halides as an alternative source of arylating agents. The preparative scope was investigated with 35 examples (up to 95% yield), and mechanistic studies implied a cationic Pd(II)-based catalytic system.

Novel Hydrogen Sulfide Hybrid Derivatives of Keap1-Nrf2 Protein-Protein Interaction Inhibitor Alleviate Inflammation and Oxidative Stress in Acute Experimental Colitis

Ulcerative colitis (UC) is an idiopathic inflammatory disease of unknown etiology possibly associated with intestinal inflammation and oxidative stress. Molecular hybridization by combining two drug fragments to achieve a common pharmacological goal represents a novel strategy. The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway provides an effective defense mechanism for UC therapy, and hydrogen sulfide (H₂S) shows similar and relevant biological functions as well. In this work, a series of hybrid derivatives were synthesized by connecting an inhibitor of Keap1-Nrf2 protein-protein interaction with two well-established H₂S-donor moieties, respectively, via an ester linker, to find a drug candidate more effective for the UC treatment. Subsequently, the cytoprotective effects of hybrids derivatives were investigated, and DDO-1901 was identified as a candidate showing the best efficacy and used for further investigation on therapeutic effect on dextran sulfate sodium (DSS)-induced colitis in vitro and in vivo. Experimental results indicated that DDO-1901 could effectively alleviate DSS-induced colitis by improving the defense against oxidative stress and reducing inflammation, more potent than parent drugs. Compared with either drug alone, such molecular hybridization may offer an attractive strategy for the treatment of multifactorial inflammatory disease.

Radiolabeled Chalcone Derivatives as Potential Radiotracers for β-Amyloid Plaques Imaging

Natural products often provide a pool of pharmacologically relevant precursors for the development of various drug-related molecules. In this review, the research performed on some radiolabeled chalcone derivatives characterized by the presence of the α-β unsaturated carbonyl functional group as potential radiotracers for the imaging of β-amyloids plaques will be summarized. Chalcones' structural modifications and chemical approaches which allow their radiolabeling with the most common SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography) radionuclides will be described, as well as the state of the art regarding their in vitro binding affinity and in vivo biodistribution and pharmacokinetics in preclinical studies. Moreover, an explanation of the rationale behind their potential utilization as probes for Alzheimer's disease in nuclear medicine applications will be provided.

Chalcones and Gastrointestinal Cancers: Experimental Evidence

Colorectal (CRC) and gastric cancers (GC) are the most common digestive tract cancers with a high incidence rate worldwide. The current treatment including surgery, chemotherapy or radiotherapy has several limitations such as drug toxicity, cancer recurrence or drug resistance and thus it is a great challenge to discover an effective and safe therapy for CRC and GC. In the last decade, numerous phytochemicals and their synthetic analogs have attracted attention due to their anticancer effect and low organ toxicity. Chalcones, plant-derived polyphenols, received marked attention due to their biological activities as well as for relatively easy structural manipulation and synthesis of new chalcone derivatives. In this study, we discuss the mechanisms by which chalcones in both in vitro and in vivo conditions suppress cancer cell proliferation or cancer formation.

Terminators or Guardians? Design, Synthesis, and Cytotoxicity Profiling of Chalcone-Sulfonamide Hybrids

With a "less is more" philosophy, a series of 15 chalcone-sulfonamide hybrids were designed anticipating synergistic anticancer activity. The aromatic sulfonamide moiety was included as a known direct inhibitor of carbonic anhydrase IX activity through its zinc chelating property. The chalcone moiety was incorporated as an electrophilic stressor to indirectly inhibit carbonic anhydrase IX cellular activity. Screening by the Developmental Therapeutics Program of the National Cancer Institute, NCI-60, revealed that 12 derivatives were potent inhibitors of cancer cell growth in multiple cell lines and were promoted to the five-dose screen. The cancer cell growth inhibition profile indicated sub- to two-digit micromolar potency (GI₅₀ down to 0.3 μM and LC₅₀ as low as 4 μM) against colorectal carcinoma cells, in particular. Unexpectedly, most compounds demonstrated low to moderate potency as direct inhibitors of carbonic anhydrase catalytic activity in vitro, with 4d being the most potent, having an average Ki value of 4 μM. Compound 4j showed ca. six-fold selectivity to carbonic anhydrase IX over the other tested isoforms in vitro. Cytotoxicity of both 4d and 4j in live HCT116, U251, and LOX IMVI cells under hypoxic conditions confirmed their targeting of carbonic anhydrase activity. Elevation of oxidative cellular stress was stipulated from the increase in Nrf2 and ROS levels in 4j-treated colorectal carcinoma, HCT116, cells compared to the control. Compound 4j arrested the cell cycle of HCT116 cells at the G1/S phase. In addition, both 4d and 4j showed up to 50-fold cancer cell selectivity compared to the non-cancerous HEK293T cells. Accordingly, this study presents 4d and 4j being new, synthetically accessible, simplistically designed derivatives as potential candidates to be further developed as anticancer therapeutics.

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.

A three-step pathway from (2-aminophenyl)chalcones to novel styrylquinoline-chalcone hybrids: synthesis and spectroscopic and structural characterization of three examples

Three new styrylquinoline-chalcone hybrids have been synthesized using a three-step pathway starting with Friedländer cyclocondensation between (2-aminophenyl)chalcones and acetone to give 2-methyl-4-styrylquinolines, followed by selective oxidation to the 2-formyl analogues, and finally Claisen-Schmidt condensation between the formyl intermediates and 1-acetylnaphthalene. All intermediates and the final products have been fully characterized by IR and 1H/13C NMR spectroscopy, and by high-resolution mass spectrometry, and the three products have been characterized by single-crystal X-ray diffraction. The molecular conformations of (E)-3-{4-[(E)-2-phenylethenyl]quinolin-2-yl}-1-(naphthalen-1-yl)prop-2-en-1-one, C30H21NO, (IVa), and (E)-3-{4-[(E)-2-(4-fluorophenyl)ethenyl]quinolin-2-yl}-1-(naphthalen-1-yl)prop-2-en-1-one, C30H20FNO, (IVb), are very similar. In each compound, the molecules are linked into a three-dimensional array by hydrogen bonds, of the C-H...O and C-H...N types in (IVa), and of the C-H...O and C-H...π types in (IVb), and by two independent π-π stacking interactions. By contrast, the conformation of the chalcone unit in (E)-3-{4-[(E)-2-(2-chlorophenyl)ethenyl]quinolin-2-yl}-1-(naphthalen-1-yl)prop-2-en-1-one, C30H20ClNO, (IVc), differs from those in (IVa) and (IVb). There are only weak hydrogen bonds in the structure of (IVc), but a single rather weak π-π stacking interaction links the molecules into chains. Comparisons are made with some related structures.

N-Acetylserotonin is an oxidation-responsive activator of Nrf2 ameliorating colitis in rats

N-Acetylserotonin (NAS) is an intermediate in the melatonin biosynthetic pathway. We investigated the anti-inflammatory activity of NAS by focusing on its chemical feature oxidizable to an electrophile. NAS was readily oxidized by reaction with HOCl, an oxidant produced in the inflammatory state. HOCl-reacted NAS (Oxi-NAS), but not NAS, activated the anti-inflammatory nuclear factor erythroid 2-related factor 2 (Nrf2)-heme oxygenase (HO)-1 pathway in cells. Chromatographic and mass analyses demonstrated that Oxi-NAS was the iminoquinone form of NAS and could react with N-acetylcysteine possessing a nucleophilic thiol to form a covalent adduct. Oxi-NAS bound to Kelch-like ECH-associated protein 1, resulting in Nrf2 dissociation. Moreover, rectally administered NAS increased the levels of nuclear Nrf2 and HO-1 proteins in the inflamed colon of rats. Simultaneously, NAS was converted to Oxi-NAS in the inflamed colon. Rectal NAS mitigated colonic damage and inflammation. The anticolitic effects were significantly compromised by the coadministration of an HO-1 inhibitor.

Orchestrating a β-Hydride Elimination Pathway in Palladium(II)-Catalyzed Arylation/Alkenylation of Cyclopropanols Using Organoboron Reagents

The scope of chemoselective β-hydride elimination in the context of arylation/alkenylation of homoenolates from cyclopropanol precursors using organoboronic reagents as transmetalation coupling partners was examined. The reaction optimization paradigm revealed a simple ligand-free Pd(II) catalytic system to be most efficient under open air conditions. The preparative scope, which was investigated with 48 examples, supported the applicability of this reaction to a wide range of substrates tolerating a variety of functional groups while delivering β-substituted enone and dienone derivatives in 62-95% yields.

The discovery of novel antitrypanosomal 4-phenyl-6-(pyridin-3-yl)pyrimidines

Human African trypanosomiasis, or sleeping sickness, is a neglected tropical disease caused by Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense which seriously affects human health in Africa. Current therapies present limitations in their application, parasite resistance, or require further clinical investigation for wider use. Our work herein describes the design and syntheses of novel antitrypanosomal 4-phenyl-6-(pyridin-3-yl)pyrimidines, with compound 13, the 4-(2-methoxyphenyl)-6-(pyridine-3-yl)pyrimidin-2-amine demonstrating an IC₅₀ value of 0.38 μM and a promising off-target ADME-Tox profile in vitro. In silico molecular target investigations showed rhodesain to be a putative candidate, supported by STD and WaterLOGSY NMR experiments, however, in vitro evaluation of compound 13 against rhodesain exhibited low experimental inhibition. Therefore, our reported library of drug-like pyrimidines present promising scaffolds for further antikinetoplastid drug development for both phenotypic and target-based drug discovery.

Design, synthesis, and evaluation of amphiphilic sofalcone derivatives as potent Gram-positive antibacterial agents

New antimicrobial agents are urgently needed to overcome drug-resistant bacterial infections. Here we describe the design, synthesis and evaluation of a new class of amphiphilic sofalcone compounds as antimicrobial peptidomimetics. The most promising compound 14, bearing two arginine residues, showed poor hemolytic activity, low cytotoxicity, and excellent antimicrobial activity against Gram-positive bacteria, including MRSA. Compound 14, had good stability in various salt conditions, killed bacteria rapidly by directly disrupting bacterial cell membranes and was slow at developing bacterial resistance. Additionally, compound 14 exhibited effective in vivo efficacy in the murine model of bacterial keratitis caused by Staphylococcus aureus ATCC29213. Our studies suggested that compound 14 possessed promising potential to be used as a novel antimicrobial agent to combat drug-resistant Gram-positive bacteria.

Potential Applications of NRF2 Modulators in Cancer Therapy

The nuclear factor erythroid 2-related factor 2 (NRF2)-Kelch-like ECH-associated protein 1 (KEAP1) regulatory pathway plays an essential role in protecting cells and tissues from oxidative, electrophilic, and xenobiotic stress. By controlling the transactivation of over 500 cytoprotective genes, the NRF2 transcription factor has been implicated in the physiopathology of several human diseases, including cancer. In this respect, accumulating evidence indicates that NRF2 can act as a double-edged sword, being able to mediate tumor suppressive or pro-oncogenic functions, depending on the specific biological context of its activation. Thus, a better understanding of the mechanisms that control NRF2 functions and the most appropriate context of its activation is a prerequisite for the development of effective therapeutic strategies based on NRF2 modulation. In line of principle, the controlled activation of NRF2 might reduce the risk of cancer initiation and development in normal cells by scavenging reactive-oxygen species (ROS) and by preventing genomic instability through decreased DNA damage. In contrast however, already transformed cells with constitutive or prolonged activation of NRF2 signaling might represent a major clinical hurdle and exhibit an aggressive phenotype characterized by therapy resistance and unfavorable prognosis, requiring the use of NRF2 inhibitors. In this review, we will focus on the dual roles of the NRF2-KEAP1 pathway in cancer promotion and inhibition, describing the mechanisms of its activation and potential therapeutic strategies based on the use of context-specific modulation of NRF2.