Mechanistic Studies Research Articles

Endothelin-1 down-regulates nuclear factor erythroid 2-related factor-2 and contributes to perivascular adipose tissue dysfunction in obesity.

Perivascular adipose tissue (PVAT) negatively regulates vascular muscle contraction. However, in the context of obesity, the PVAT releases vasoconstrictor substances that detrimentally affect vascular function. A pivotal player in this scenario is the peptide endothelin-1 (ET-1), which induces oxidative stress and disrupts vascular function. The present study postulates that obesity augments ET-1 production in the PVAT, decreases the function of the nuclear factor erythroid 2-related factor-2 (Nrf2) transcription factor, further increasing reactive oxygen species (ROS) generation, culminating in PVAT dysfunction. Male C57BL/6 mice were fed either a standard or a high-fat diet for 16 weeks. Mice were also treated with saline or a daily dose of 100 mg·kg-1 of the ETA and ETB receptor antagonist Bosentan, for 7 days. Vascular function was evaluated in thoracic aortic rings, with and without PVAT. Mechanistic studies utilized PVAT from all groups and cultured WT-1 mouse brown adipocytes. PVAT from obese mice exhibited increased ET-1 production, increased ECE1 and ETA gene expression, loss of the anticontractile effect, as well as increased ROS production, decreased Nrf2 activity, and downregulated expression of Nrf2-targeted antioxidant genes. PVAT of obese mice also exhibited increased expression of Tyr216-phosphorylated-GSK3β and KEAP1, but not BACH1 - negative Nrf2 regulators. Bosentan treatment reversed all these effects. Similarly, ET-1 increased ROS generation and decreased Nrf2 activity in brown adipocytes, events mitigated by BQ123 (ETA receptor antagonist). These findings place ET-1 as a major contributor to PVAT dysfunction in obesity and highlight that pharmacological control of ET-1 effects restores PVAT's cardiovascular protective role.

Ammonium-Binding Bifunctional Aza-Crown Ether Catalysts for Substrate-Selective Hydroxyl Functionalization.

Herein, we describe a new bifunctional macrocyclic catalyst that employs multiple weak noncovalent interactions to enable substrate-selective O-silylation of ammonium alcohols over more reactive aliphatic alcohols with up to >20:1 substrate selectivity. Our catalytic strategy merges (i) the use of crown ethers as ammonium-binding receptors and (ii) the exploitation of N-methyl imidazole as a catalytic motif. Our collective mechanistic studies reveal the importance of receptor size, conformational preorganization, and the number of hydrogen-bonding acceptor units needed to achieve high selectivity within the macrocyclic binding pocket.

Photochemistry of 2-(2-formylphenyloxy)acetic acid derivatives: synthesis of hydroxychromanones and benzofuranones.

Photochemical transformations of small molecules, such as ortho-substituted benzaldehydes, in the absence of a photocatalyst are significantly underexplored and may reveal unexpected outcomes. In the present paper, we showed that 2-(2-formylphenoxy)acetic acid and its esters undergo photocyclization into chromanone and benzofuranone derivatives under 365 nm irradiation. The reaction occurs exclusively in dimethyl sulfoxide and can be used to efficiently obtain hydroxychromanones in good yields (27-91%). A detailed mechanistic study revealed the clue of the divergent phototransformation with various products.

Site- and Enantioselective Homobenzylic C(sp3)-H Borylation via Dehydrogenation of Alkyl Chains.

A one-pot, dehydrogenation-based Ir/Co/Cu triple catalysis has been developed for formal asymmetric borylation of homobenzylic C(sp3)-H bonds, furnishing enantioenriched organoboronates with a β-stereocenter directly from simple arylalkanes. Mechanistic studies indicate that the Ir catalyst is responsible for dehydrogenation of arylalkanes to 1-arylalkenes, followed by Cu-catalyzed regio- and enantioselective protoboration of (E)-arylalkenes; the introduction of Co-catalyzed stereoisomerization of the (Z)-alkenes to (E)-isomers was found to have a beneficial effect on the productivity and enantioselectivity.

A Versatile Method for Site-Specific Chemical Installation of Aromatic Posttranslational Modification Analogs into Proteins.

Posttranslational modifications (PTMs) of proteins play central roles in regulating the protein structure, interactome, and functions. A notable modification site is the aromatic side chain of Tyr, which undergoes modifications such as phosphorylation and nitration. Despite the biological and physiological importance of Tyr-PTMs, our current understanding of the mechanisms by which these modifications contribute to human health and disease remains incomplete. This knowledge gap arises from the absence of natural amino acids that can mimic these PTMs and the lack of synthetic tools for the site-specific introduction of aromatic PTMs into proteins. Herein, we describe a facile method for the site-specific chemical installation of aromatic PTMs into proteins through palladium-mediated S-C(sp2) bond formation under ambient conditions. We demonstrate the incorporation of novel PTMs such as Tyr-nitration and phosphorylation analogs to synthetic and recombinantly expressed Cys-containing peptides and proteins within minutes and in good yields. To demonstrate the versatility of our approach, we employed it to prepare 10 site-specifically modified proteins, including nitrated and phosphorylated analogs of Myc and Max proteins. Furthermore, we prepared a focused library of site-specifically nitrated and phosphorylated α-synuclein (α-Syn) protein, which enabled, for the first time, deciphering the role of these competing modifications in regulating α-Syn conformation aggregation in vitro. Our strategy offers advantages over synthetic or semisynthetic approaches, as it enables rapid and selective transfer of rarely explored aromatic PTMs into recombinant proteins, thus facilitating the generation of novel libraries of homogeneous posttranslationally modified proteins for biomarker discovery, mechanistic studies, and drug discovery.

Oxidative Aminotrifluoromethylation of 1,4-Naphthoquinone.

A strategy for convenient and precise oxidative aminotrifluoromethylation of 1,4-naphthoquinone with the Togni reagent and amines has been demonstrated via a radical process. This method allows efficient access for the preparation of a wide range of CF3-functionalized 1,4-naphthoquinones under mild conditions, and its application in late-stage modification of drug molecules is achieved. Mechanistic studies indicate that 1,4-naphthoquinone serves as both a substrate and a catalyst and that the Togni reagent plays a dual role of a substrate and an oxidant. As a result, the title reaction can take place in the dark without external catalysts and oxidants.

Ru(II)-Catalyzed Decarboxylative (4 + 2)-Annulation of Benzoic Acids and Benzamides with Propargyl Cyclic Carbonates.

Propargyl cyclic carbonates have emerged as versatile precursors in synthetic chemistry. However, their reactivity has so far been limited to transition metal-catalyzed substitution and cyclization reactions. Herein, we illustrate the successful employment of propargyl cyclic carbonates as coupling partners in Ru(II)-catalyzed C-H annulation of benzoic acids and benzamides. This approach allowed us to access a broad range of biologically relevant isocoumarin and isoquinolinone derivatives in good to excellent yields, utilizing bench-stable and easily accessible precursors. Preliminary mechanistic studies indicated that the C-H metalation step is both reversible and rate-determining in the reaction pathway. Furthermore, the utility of the developed methodology has been illustrated by scale-up and postfunctionalization experiments.

α’‐Selective Selenium‐catalyzed Allylic C−H Amination of Enol Derivatives

AbstractA transition metal‐free Se‐catalyzed C−H amination protocol for α’‐amination of enol derivatives has been developed. This reaction can be used to functionalize a wide variety of oxygen‐ and halogen‐substituted alkenes spanning a vast range of nucleophilicities, giving α’‐aminated enol derivatives with high regioselectivity. Amination of E/Z mixtures of alkenes proceeds stereoconvergently to give the (Z)‐enol derivatives exclusively. Mechanistic studies revealed that the relative reactivity and α’‐regioselectivity of these transformations is determined by substantial resonance donation to the heteroatom‐bound carbon in the transition state. These products participate in traditional reactions of enol derivatives, allowing for efficient functionalization of both α‐ and α’‐positions from a single enol derivative with high diastereocontrol.

NDR1 mediates PD-L1 deubiquitination to promote prostate cancer immune escape via USP10.

Prostate cancer (PCa) is one of the most common male genitourinary system malignancies. Despite the significant benefits of anti-PD-L1 immune checkpoint inhibitor therapy in other cancers, the reasons for its poor therapeutic efficacy in prostate cancer (PCa) remain unclear.NDR1 plays an important role in innate immunity, but its role in tumor immunity and immunotherapy has not been investigated. The role of NDR1 in the immune microenvironment of PCa and the related mechanisms are unknown. Here, we found a positive correlation between NDR1 and PD-L1 expression in PCa. NDR1 significantly inhibits CD8 + T cell infiltration and function, thereby promoting immune escape in prostate cancer.More importantly, NDR1 inhibition significantly enhanced CD8 + T cell activation, which enhanced the therapeutic effect of anti-PD-L1. Mechanistic studies revealed that NDR1 inhibits ubiquitination-mediated PD-L1 degradation via the deubiquitinase USP10, upregulates PD-L1, and promotes PCa immune escape. Thus, our study suggests a unique PD-L1 regulatory mechanism underlying PCa immunotherapy failure. The significance of NDR1 in PCa immune escape and its mechanism of action were clarified, and combined NDR1/PD-L1 inhibition was suggested as an approach to boost PCa immunotherapy effectiveness.

Synthesis and Evaluation of Novel 1-Methyl-1H-pyrazol-5-amine Derivatives with Disulfide Moieties as Potential Antimicrobial Agents.

Sulfur-containing compounds have diverse biological functions and are crucial in crop protection chemistry. In this study, a series of novel 1-methyl-1H-pyrazol-5-amine derivatives incorporating disulfide moieties were synthesized and evaluated for their antimicrobial properties. In vitro bioassays demonstrated that compound 7f displayed potent antifungal activity against Valsa mali, with an EC50 value of 0.64 mg/L, outperforming allicin (EC50 = 26.0 mg/L) but lower than tebuconazole (EC50 = 0.33 mg/L). In vivo experiments confirmed that compound 7f could effectively inhibit V. mali infection on apples at a concentration of 100 mg/L, similar to the positive control tebuconazole. Mechanistic studies revealed that compound 7f could induce hyphal shrinkage and collapse, trigger intracellular reactive oxygen species accumulation, modulate antioxidant enzyme activities, initiate lipid peroxidation, and ultimately cause irreversible oxidative damage to the cells of V. mali. Additionally, compound 7b exhibited notable antibacterial activity, particularly against Pseudomonas syringae pv. actinidiae, with a MIC90 value of 1.56 mg/L, surpassing the positive controls allicin, bismerthiazol, and streptomycin sulfate. These findings suggest that 1-methyl-1H-pyrazol-5-amine derivatives containing disulfide moieties hold promise as potent candidates for the development of novel antimicrobial agents.

A study of Antibiotics and Neem-Chirata Extracts in clinical trials of Salmonella typhi

The purpose of this study is to provide light on the possible benefits that Neem and Chirata may have over conventional antibiotics on the market. Investigations into the length of therapy and dose selection, as well as detailed examinations of safety profiles, will be used to attain this goal. As part of the therapeutic care of Salmonella typhi infections, an investigation of the efficacy of a number of medicinal and botanical extracts, including Neem and Chirata, is described. An in-depth investigation of the efficacy and safety of a number of different drugs, with a specific emphasis on how they affect S. typhi, is the purpose of this study. After it has been carried out, mechanistic study will assist in shedding light on the particular antibacterial processes that these drugs utilize. The abstract provides a concise summary of the aims of the study, which include evaluating the overall outcomes of clinical trials, comparing these interventions to standard treatments, investigating the synergistic benefits of combination therapy, monitoring the growth of antibiotic resistance, and evaluating the efficacy of combination therapy. And last, the abstract provides a concise analysis of the objectives of the clinical research as well as the possible future contributions that these investigations might make to the treatment of infectious diseases. This is accomplished by providing a synopsis of all the significant and substantial aspects of the clinical trials that are being taken into consideration.

Organic Bases as the Organic Electron Donors (OED) Promoted Reductive Coupling of Diarylhalomethanes: Halogens Controlled Construction of Tetraarylethylenes and Tetraarylethanes.

Using the organic base as the organic electron donors, the reductive coupling of diaryhalomethanes was smoothly achieved under transition-metal-free reaction conditions, giving a series of synthetically important tetraarylethylenes and tetraarylethanes in high yields. The mechanistic study revealed that the organic bases acting as the electron donor initiated the generation of a radical intermediate, realizing the construction of tetraarylethylene and tetraarylethane skeletons.

Selective Protein Degradation through Tetrazine Ligation of Genetically Incorporated Unnatural Amino Acids.

Small molecule-responsive tags for targeted protein degradation are valuable tools for fundamental research and drug target validation. Here, we show that genetically incorporated unnatural amino acids bearing a strained alkene or alkyne functionality can act as a minimalist tag for targeted protein degradation. Specifically, we observed the degradation of strained alkene- or alkyne-containing kinases and E2 ubiquitin-conjugating enzymes upon treatment with hydrophobic tetrazine conjugates. The extent of the induced protein degradation depends on the identity of the target protein, unnatural amino acid, and tetrazine conjugate, as well as the site of the unnatural amino acid in the target protein. Mechanistic studies revealed proteins undergo proteasomal degradation after tetrazine tethering, and the identity of tetrazine conjugates influences the dependence of ubiquitination on protein degradation. This work provides an alternative approach for targeted protein degradation and mechanistic insight, facilitating the future development of more effective targeted protein degradation strategies.

Rongalite/iodine-mediated C(sp3)-H bond oximation and thiomethylation reaction of methyl ketones using copper nitrate as the [NO] reagent: synthesis of thiohydroximic acids.

In this work, a highly efficient rongalite/iodine-mediated oxime formation reaction for the preparation of thiohydroximic acids from methyl ketones by employing copper nitrate as the [NO] reagent has been developed. Notably, copper nitrate participated as both a catalyst and the mild oximation reagent in the transformation. This reaction is highly efficient and facile, with a broad substrate scope, especially for fused ring skeleton substrates, heterocyclic skeleton substrates, and acetyl-substituted natural products. Mechanistic studies revealed that copper nitrate might be converted into a NO2 radical or the NO2 radical dimeric forms as an ion-pair equivalent to participate in the transformation.

Natural STAT3 Inhibitors for Cancer Treatment: A Comprehensive Literature Review.

Cancer is one of the leading causes of mortality and morbidity worldwide, affecting millions of people physically and financially every year. Over time, many anticancer treatments have been proposed and studied, including synthetic compound consumption, surgical procedures, or grueling chemotherapy. Although these treatments have improved the daily life quality of patients and increased their survival rate and life expectancy, they have also shown significant drawbacks, including staggering costs, multiple side effects, and difficulty in compliance and adherence to treatment. Therefore, natural compounds have been considered a possible key to overcoming these problems in recent years, and thorough research has been done to assess their effectiveness. In these studies, scientists have discovered a meaningful interaction between several natural materials and signal transducer and activator of transcription 3 molecules. STAT3 is a transcriptional protein that is vital for cell growth and survival. Mechanistic studies have established that activated STAT3 can increase cancer cell proliferation and invasion while reducing anticancer immunity. Thus, inhibiting STAT3 signaling by natural compounds has become one of the favorite research topics and an attractive target for developing novel cancer treatments. In the present article, we intend to comprehensively review the latest knowledge about the effects of various organic compounds on inhibiting the STAT3 signaling pathway to cure different cancer diseases.

Serum leptin and adiponectin function as indicators of allergic sensitization in pediatric adenotonsillar hypertrophy.

Obesity is commonly linked to both adenotonsillar hypertrophy (ATH) and allergic disorders, in which the roles of adipokines are not fully illuminated. This study aims to investigate the levels of leptin and adiponectin and their associations with allergic sensitization in pediatric ATH. Serum levels of specific immunoglobulin E (IgE), leptin and adiponectin were quantified in 35 controls and 111 ATH children, in which 54 were non-atopic and 57 were atopic. Spearman's correlation analysis and polynomial linear trend test were conducted. The odds ratios and 95% confidence intervals were calculated by binary logistic regression after multivariable adjustment. The serum level of leptin and leptin/adiponectin (L/A) ratio was significantly increased in children with ATH. An increase in leptin level and L/A ratio and a decrease in adiponectin level were observed in atopic children compared with non-atopic children. Among ATH children, the level of adiponectin was negatively while L/A ratio was positively correlated with specific IgE. After multivariable adjustment, leptin was significantly associated with increased risk of atopy to D. pteronyssinus and D. farina, and adiponectin was significantly associated with decreased risk of atopy to willow and mugwort. Leptin was associated with higher odds while adiponectin was associated with lower odds of overall atopy. Besides, significant multiplicative interactions of obesity with leptin and adiponectin on atopy were observed respectively. Leptin and adiponectin were both associated with allergic sensitization and function differently in pediatric ATH. Mechanistic studies are needed to elucidate the involvement of adipokines in allergic sensitization of pediatric ATH.

Strengthened Ozone Adsorption through Positive Electric Field-Induced Charge Migration on Various TiO2 Crystal Surfaces: A Mechanistic and Theoretical Study

This study investigates the enhancement of ozone adsorption on diverse TiO2 crystal interfaces through an innovative electrochemical modulation approach. The research focuses on the effects of applied electric field strength and reaction sites on ozone interfacial adsorption energies for Ti/Anatase TiO2 (0 0 1) and Ti/Rutile TiO2 (1 1 0) interfaces. The findings reveal that positive electric fields significantly enhance ozone adsorption on both interfaces, with adsorption energies increasing by up to 18% for Ti/Anatase TiO2 (0 0 1) and 15% for Ti/Rutile TiO2 (1 1 0). Notably, double water molecule sites (≡(H2O)2) play a crucial role in this enhancement process. The study demonstrates that the applied electric field alters the charge distribution at the TiO2 catalytic interface, thereby increasing interfacial charge density and promoting charge migration to ozone. Furthermore, this process leads to enhanced overlap and hybridization between ≡(H2O)2 sites and the s and p orbitals of ozone molecules, resulting in the formation of chemical bonds with lower Fermi levels. These comprehensive results demonstrate the broad applicability of the electrochemical interfacial ozone adsorption enhancement method across different crystal types and surfaces. Consequently, this study provides essential data to support the advancement of greener and more energy-efficient heterogeneous catalytic ozonation processes, potentially contributing to significant improvements in ozone-based water treatment technologies

Ginger (Zingiber officinale Roscoe; Family: Zingiberaceae) in Non-Alcoholic Fatty Liver Disease: Review on the Existing Scientific Evidence and Way Forward

Abstract: Non-alcoholic fatty liver disease (NAFLD) is today the most prevalent hepatic disorder in the world. Although many pharmaceutical agents have been investigated for their potential to prevent or treat NAFLD, currently, there is no standard treatment to manage this ailment. Reports indicate that ginger and its phytochemicals gingerol and zingerone are effective in mitigating NAFLD in experimental study models. Furthermore, randomised control trials have demonstrated that ginger is also effective in preventing NAFLD in both adults and children. Mechanistic studies suggest that ginger mediates these beneficial effects by activating many pathways, such as reducing free radicals, dyslipidemia, and hepatic fat deposition. Concomitantly, ginger also increases antioxidant enzyme levels and insulin-sensitive effects, and all these pharmacological actions provide beneficial outcomes. In this review, the evidence from experimental and clinical trials has been emphasised. In addition, an attempt has been made to identify the gaps for future study to address for the benefit of the medical, pharmaceutical, nutraceutical, and agricultural businesses.

Sleeve Gastrectomy Protects Against Hypertension in Rats due to Changes in the Gut Microbiome

IntroductionSleeve gastrectomy (SG), results in improvement in hypertension. We have previously published that rodent SG improves hypertension independent of weight loss associated with unique shifts in the gut microbiome. We tested if the gut microbiome directly improves blood pressure by performing fecal material transfer (FMT) from post-SG rats to surgery-naïve animals. MethodsWe performed SG or Sham surgery in male, Zucker rats (n = 6-7) with obesity. Stool was collected postop from surgical donors for treatment of recipient rats. Three nonsurgical groups received daily, oral consumption of SG stool, sham stool, or vehicle alone (Nutella) for 10 wk (n = 7-8). FMT treatment was assessed for effects on body weight, food intake, oral glucose tolerance, and blood pressure. Genomic DNA of stool from donor and recipient groups were sequenced by 16S ribosomal RNA and analyzed for diversity, abundance, and importance. ResultsTen weeks of SG-FMT treatment significantly lowered systolic blood pressures in surgery-naïve, recipient rats compared to vehicle treatment alone (126.8 ± 13.3 mmHg versus 151.8 ± 12.2 mmHg, P = 0.001). SG-FMT treatment also significantly altered beta diversity metrics compared to Sham-FMT and vehicle treatment. In random forest analysis, amplicon sequence variant level significantly predicted FMT group, P = 0.01. ConclusionsWe have found a direct link between gut microbial changes after SG and regulation of blood pressure. Future mechanistic studies are required to learn what specific gut microbial changes are required to induce improvements in obesity-associated hypertension and translation to clinical, metabolic surgery.

Multi-molar absorption of CO2 by a novel dual-functionalized ionic liquid solution: Experimental and DFT mechanistic study

Viscosity and absorption capacity are the main indexes to evaluate functionalized ionic liquids. Based on the precise design strategy of both anion and cation absorption, a dual-functionalized protic IL diethylenetriamine methylurea ([DETAH][MEUR]) for trapping CO2 was successfully synthesized. The absorption and regeneration properties of the ILs solution were tested, and the changes in the physical properties of ILs before and after CO2 absorption were compared. The experimental results showed that the [DETAH][MEUR] solution had relatively low viscosity, excellent absorption property with 2.05 mol CO2/mol IL at 40 °C and 0.5 mol/L concentration, and its regeneration efficiencies still kept above 90.09 % after five cycles. In addition, the mechanism of the absorption reaction was explored by combining Fourier transform infrared (FT-IR) spectroscopy, carbon nuclear magnetic resonance (13C NMR) spectroscopy, and density functional theory (DFT) calculation methods. It shows that in [DETAH][MEUR] solution, the N atom losing proton (-NH) in the anion is the main absorption site, and the primary amine (-NH2) in the protonated cation [DETAH]+ of secondary amine is used as an auxiliary cooperative trapping CO2. Hopefully, this work can provide a new way for the research and development of green CO2 absorbents.