Synthesis and biological evaluation of indane-based fluorescent probes for detection of amyloid-ß aggregates in Alzheimer's disease.

In this article, the development of fluorescent imaging probes for the detection of Alzheimer's disease (AD)-associated protein aggregates is described. Indane derivatives with a donor-π-acceptor (D-π-A) structure were designed and synthesized. The probes were evaluated for their ability to bind to ß-amyloid (Aß) protein aggregates, which are a key pathological hallmark of AD. The results showed that several probes exhibited significant changes in fluorescence intensity at wavelengths greater than 600 nm when they were bound to Aß aggregates compared to the Aß monomeric form. Among the tested probes, four D-π-A type indane derivatives showed promising binding selectivity to Aß aggregates over non-specific proteins such as bovine serum albumin (BSA). The molecular docking study showed that our compounds were appropriately located along the Aß fibril axis through the hydrophobic tunnel structure. Further analysis revealed that the most active compound having dimethylaminopyridyl group as an election donor and dicyano group as an electron acceptor could effectively stain Aß plaques in brain tissue samples from AD transgenic mice. These findings suggest that our indane-based compounds have the potential to serve as fluorescent probes for the detection and monitoring of Aß aggregation in AD.

Visible-Light-Induced DDQ-Catalyzed Fluorocarbamoylation Using CF3SO2Na and Oxygen.

The synthesis of carbamoyl fluorides via visible-light induced DDQ catalysis of secondary amines is described. This protocol employs sodium trifluorosulfinate and molecular oxygen for the in situ generation of carbonyl difluoride, which is reacted with amines to afford the corresponding carbamoyl fluorides efficiently. Moreover, carbamoyl fluorides are easily transformed to synthetically useful carbonyl compounds under mild reaction conditions.

Correction: Kim et al. Mito-TIPTP Increases Mitochondrial Function by Repressing the Rubicon-p22phox Interaction in Colitis-Induced Mice. Antioxidants 2021, 10, 1954.

In the original publication [...].

Novel potent blockers for TWIK-1/TREK-1 heterodimers as potential antidepressants.

TREK-1 (TWIK-related potassium channel-1) is a subunit of the two-pore domain potassium (K2p) channel and is widely expressed in the brain. TREK-1 knockout mice were shown to have antidepressant-like effects, providing evidence for the channel's potential as a therapeutic target. However, currently there is no good pharmacological inhibitor specifically targeting TREK-1 containing K2p channels that also displays similar antidepressant-like effects. Here, we sought to find selective and potent inhibitors for TREK-1 related dimers both in vitro and in vivo. We synthesized and evaluated 2-hydroxy-3-phenoxypropyl piperidine derivatives yielding a library from which many TREK-1 targeting candidates emerged. Among these, hydroxyl-phenyl- (2a), piperidino- (2g), and pyrrolidino- (2h) piperidinyl substituted compounds showed high potencies to TREK-1 homodimers with significant antidepressant-like effects in forced swim test and tail suspension test. Interestingly, these compounds were found to have high potencies to TWIK-1/TREK-1 heterodimers. Contrastingly, difluoropiperidinyl-4-fluorophenoxy (3e) and 4-hydroxyphenyl-piperidinyl-4-fluorophenoxy (3j) compounds had high potencies to TREK-1 homodimer but lower potency to TWIK-1/TREK-1 heterodimers without significant antidepressant-like effects. We observed positive correlation between inhibition potency to TWIK-1/TREK-1 and immobility time, and no correlation between inhibition potency to TREK-1 homodimer and immobility time. This was consistent with molecular docking simulations of selected compounds to TREK-1 homodimeric and TWIK-1/TREK-1 heterodimeric models. Existing antidepressant fluoxetine was also found to potently inhibit TWIK-1/TREK-1 heterodimers. Our study reveals novel potent TWIK-1/TREK-1 inhibitors 2a, 2g, and 2h as potential antidepressants and suggest that the TWIK-1/TREK-1 heterodimer could be a potential novel molecular therapeutic target for antidepressants.

DS86760016, a Leucyl-tRNA Synthetase Inhibitor, Is Active against Mycobacterium abscessus.

Benzoxaboroles are a new class of leucyl-tRNA synthetase inhibitors. Epetraborole, a benzoxaborole, is a clinical candidate developed for Gram-negative infections and has been confirmed to exhibit favorable activity against a well known pulmonary pathogen, Mycobacterium abscessus. However, according to ClinicalTrials.gov, in 2017, a clinical phase II study on the use of epetraborole to treat complicated urinary tract and intra-abdominal infections was terminated due to the rapid emergence of drug resistance during treatment. Nevertheless, epetraborole is in clinical development for nontuberculous mycobacteria (NTM) disease especially for Mycobacterium avium complex-related pulmonary disease (MAC-PD). DS86760016, an epetraborole analog, was further demonstrated to have an improved pharmacokinetic profile, lower plasma clearance, longer plasma half-life, and higher renal excretion than epetraborole in animal models. In this study, DS86760016 was found to be similarly active against M. abscessus in vitro, intracellularly, and in zebrafish infection models with a low mutation frequency. These results expand the diversity of druggable compounds as new benzoxaborole-based candidates for treating M. abscessus diseases.

Dynamic Nuclear Polarization of Selectively 29Si-Enriched Core@shell Silica Nanoparticles.

29Si silica nanoparticles (SiO2 NPs) are promising magnetic resonance imaging (MRI) probes that possess advantageous properties for in vivo applications, including suitable biocompatibility, tailorable properties, and high water dispersibility. Dynamic nuclear polarization (DNP) is used to enhance 29Si MR signals via enhanced nuclear spin alignment; to date, there has been limited success employing DNP for SiO2 NPs due to the lack of endogenous electronic defects that are required for the process. To create opportunities for SiO2-based 29Si MRI probes, we synthesized variously featured SiO2 NPs with selective 29Si isotope enrichment on homogeneous and core@shell structures (shell thickness: 10 nm, core size: 40 nm), and identified the critical factors for optimal DNP signal enhancement as well as the effective hyperpolarization depth when using an exogenous radical. Based on the synthetic design, this critical factor is the proportion of 29Si in the shell layer regardless of core enrichment. Furthermore, the effective depth of hyperpolarization is less than 10 nm between the surface and core, which demonstrates an approximately 40% elongated diffusion length for the shell-enriched NPs compared to the natural abundance NPs. This improved regulation of surface properties facilitates the development of isotopically enriched SiO2 NPs as hyperpolarized contrast agents for in vivo MRI.

Stereoselective synthesis of 1,6-diazecanes by a tandem aza-Prins type dimerization and cyclization process.

We report the stereocontrolled synthesis of 1,6-diazecanes via a tandem aza-Prins type reaction of N-acyliminium ions with allylsilanes. It involves an aza-Prins type dimerization and cyclization in a single-step operation. This reaction represents the first example of 10-membered N-heterocycle synthesis using an aza-Prins reaction. Also, the interesting formation of an unusual tetracyclic compound through further cyclization of 1,6-diazecane and bicyclic compounds by the intramolecular cyclization of linear allylsilane are described. This tandem aza-Prins protocol provides a new synthetic strategy for the direct synthesis of medium-sized nitrogen heterocycles.

Hyperpolarized 29Si magnetic resonance spectroscopy of selectively radical-embedded silica nanoparticles.

The embedding of radicals at different locations within core@shell silica nanoparticles contributes to enhanced polarization capability and can be self-polarized without adding external radicals. With grafting the radical source homogenously inside of the nanoparticles, a significant 29Si hyperpolarization signal enhancement of 49.4 was obtained.

Stereoselective Synthesis of Benzo[a]quinolizidines via Aerobic DDQ-Catalyzed Allylation and Reductive Cyclization.

Stereoselective synthesis of C4-substituted benzo[a]quinolizidines via redox-controlled catalytic C-C-bond-forming reactions was carried out. Aerobic DDQ-catalyzed allylation of N-Cbz tetrahydroisoquinolines efficiently provided α-allylated products 5, which were transformed to enones 6 via cross-metathesis reactions using the second-generation Hoveyda-Grubbs catalyst. Palladium-catalyzed hydrogenation of 6 prompted alkene reduction, protecting group removal, and intramolecular reductive amination in one step to afford the desired benzo[a]quinolizidines 7 as single diastereomers.

Zero Energy Heating of Solvent with Network-Structured Solar-Thermal Material: Eco-Friendly Palladium Catalysis of the Suzuki Reaction.

Solar-thermal materials absorb sunlight and convert it into heat, which is released into the surrounding medium. Utilization of solar energy for solvent heating can be a potential method of eco-friendly organic reactions. However, to date, significant heating of the entire volume of a solvent by 1 sun illumination has not been reported. In the present work, a network structure of solar-thermal materials has been proposed for zero energy heating of a solvent under 1 sun illumination. A network-structured solar-thermal material with an additional catalytic function was fabricated by sputtering palladium into a melamine sponge. The nanocrystalline palladium-decorated melamine sponge (Pd-sponge) has excellent sunlight absorption properties in the entire wavelength range that enable efficient solar-thermal conversion. The Pd-sponge can reduce heat loss to the surroundings by effectively blocking thermal radiation from the heated solvent. The temperature of the reaction solution with the ethanol-water mixture filled in the Pd-sponge increased from 23 to 59 °C under 1 sun illumination. The elevated temperature of the reaction solutions by solar-thermal conversion successfully accelerated the heterogeneous Pd-catalyzed Suzuki coupling reactions with high conversions. Easy and low-energy-consuming multicycle use of the solar-thermal and catalytic properties of the Pd-sponge has also been demonstrated.

One-pot bifunctionalization of silica nanoparticles conjugated with bioorthogonal linkers: application in dual-modal imaging.

Covalent surface modification of silica nanoparticles (SNPs) offers great potential for the development of multimodal nanomaterials for biomedical applications. Herein, we report the synthesis of covalently conjugated bifunctional SNPs and their application to in vivo multimodal imaging. Bis(methallyl)silane 15 with cyclopropene and maleimide, designed as a stable bifunctional linker, was efficiently synthesized by traceless Staudiger ligation, and subsequently introduced onto the surface of monodispersed SNPs via Sc(OTf)3-catalyzed siloxane formation. The bifunctional linker-grafted SNP 20 underwent both thiol-conjugated addition and tetrazine cycloaddition in one pot. Finally, positron emission tomography/computed tomography and fluorescence imaging study of dual functional SNP [125I]28 labeled with NIR dye and 125I isotope showed a prolonged circulation in mice, which is conducive to the systemic delivery of therapeutics.

Discovery of Mycobacterium tuberculosis Rv3364c-Derived Small Molecules as Potential Therapeutic Agents to Target SNX9 for Sepsis.

The serine protease inhibitor Rv3364c of Mycobacterium tuberculosis (MTB) is highly expressed in cells during MTB exposure. In this study, we showed that the 12WLVSKF17 motif of Rv3364c interacts with the BAR domain of SNX9 and inhibits endosome trafficking to interact with p47phox, thereby suppressing TLR4 inflammatory signaling in macrophages. Derived from the structure of this Rv3364c peptide motif, 2,4-diamino-6-(4-tert-butylphenyl)-1,3,5-trazine, DATPT as a 12WLVSKF17 peptide-mimetic small molecule has been identified. DATPT can block the SNX9-p47phox interaction in the endosome and suppress reactive oxygen species and inflammatory cytokine production; it demonstrated significant therapeutic effects in a mouse model of cecal ligation and puncture-induced sepsis. DATPT has considerably improved potency, with an IC50 500-fold (in vitro) or 2000-fold (in vivo) lower than that of the 12WLVSKF17 peptide. Furthermore, DATPT shows potent antibacterial activities by reduction in ATP production and leakage of intracellular ATP out of bacteria. These results provide evidence for peptide-derived small molecule DATPT with anti-inflammatory and antibacterial functions for the treatment of sepsis.

Mito-TIPTP Increases Mitochondrial Function by Repressing the Rubicon-p22phox Interaction in Colitis-Induced Mice.

The run/cysteine-rich-domain-containing Beclin1-interacting autophagy protein (Rubicon) is essential for the regulation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase by interacting with p22phox to trigger the production of reactive oxygen species (ROS) in immune cells. In a previous study, we demonstrated that the interaction of Rubicon with p22phox increases cellular ROS levels. The correlation between Rubicon and mitochondrial ROS (mtROS) is poorly understood. Here, we report that Rubicon interacts with p22phox in the outer mitochondrial membrane in macrophages and patients with human ulcerative colitis. Upon lipopolysaccharide (LPS) activation, the binding of Rubicon to p22phox was elevated, and increased not only cellular ROS levels but also mtROS, with an impairment of mitochondrial complex III and mitochondrial biogenesis in macrophages. Furthermore, increased Rubicon decreases mitochondrial metabolic flux in macrophages. Mito-TIPTP, which is a p22phox inhibitor containing a mitochondrial translocation signal, enhances mitochondrial function by inhibiting the association between Rubicon and p22phox in LPS-primed bone-marrow-derived macrophages (BMDMs) treated with adenosine triphosphate (ATP) or dextran sulfate sodium (DSS). Remarkably, Mito-TIPTP exhibited a therapeutic effect by decreasing mtROS in DSS-induced acute or chronic colitis mouse models. Thus, our findings suggest that Mito-TIPTP is a potential therapeutic agent for colitis by inhibiting the interaction between Rubicon and p22phox to recover mitochondrial function.

29Si Isotope-Enriched Silicon Nanoparticles for an Efficient Hyperpolarized Magnetic Resonance Imaging Probe.

Silicon particles have garnered attention as promising biomedical probes for hyperpolarized 29Si magnetic resonance imaging and spectroscopy. However, due to the limited levels of hyperpolarization for nanosized silicon particles, microscale silicon particles have primarily been the focus of dynamic nuclear polarization (DNP) applications, including in vivo magnetic resonance imaging (MRI). To address these current challenges, we developed a facile synthetic method for partially 29Si-enriched porous silicon nanoparticles (NPs) (160 nm) and examined their usability in hyperpolarized 29Si MRI agents with enhanced signals in spectroscopy and imaging. Hyperpolarization characteristics, such as the build-up constant, the depolarization time (T1), and the overall enhancement of the 29Si-enriched silicon NPs (10 and 15%), were thoroughly investigated and compared with those of a naturally abundant NP (4.7%). During optimal DNP conditions, the 15% enriched silicon NPs showed more than 16-fold higher enhancements─far beyond the enrichment ratio─than the naturally abundant sample, further improving the signal-to-noise ratio in in vivo 29Si MRI. The 29Si-enriched porous silicon NPs used in this work are potentially capable to serve as drug-delivery vehicles in addition to hyperpolarized 29Si in vivo, further enabling their potential future applicability as a theragnostic platform.

Modulation of SETDB1 activity by APQ ameliorates heterochromatin condensation, motor function, and neuropathology in a Huntington's disease mouse model.

The present study describes evaluation of epigenetic regulation by a small molecule as the therapeutic potential for treatment of Huntington's disease (HD). We identified 5-allyloxy-2-(pyrrolidin-1-yl)quinoline (APQ) as a novel SETDB1/ESET inhibitor using a combined in silico and in vitro cell based screening system. APQ reduced SETDB1 activity and H3K9me3 levels in a HD cell line model. In particular, not only APQ reduced H3K9me3 levels in the striatum but it also improved motor function and neuropathological symptoms such as neuronal size and activity in HD transgenic (YAC128) mice with minimal toxicity. Using H3K9me3-ChIP and genome-wide sequencing, we also confirmed that APQ modulates H3K9me3-landscaped epigenomes in YAC128 mice. These data provide that APQ, a novel small molecule SETDB1 inhibitor, coordinates H3K9me-dependent heterochromatin remodelling and can be an epigenetic drug for treating HD, leading with hope in clinical trials of HD.

Cell-penetrating peptide-conjugated lipid/polymer hybrid nanovesicles for endoplasmic reticulum-targeting intracellular delivery.

The endoplasmic reticulum (ER) apparatus is a part of the secretory pathway that transports proteins to the plasma membrane through vesicle trafficking, enabling post-translational modification of the newly synthesized proteins. Several diseases such as inflammation, neurodegenerative disorder, and bipolar disorder are closely associated with dysfunction of the ER stress response. Herein, we present an ER-targeting, intracellular delivery approach that utilized cell-penetrating peptide (CPP)-conjugated lipid/polymer hybrid nanovehicles (LPNVs). For this, we patched Penetratin, a type of CPP, onto the LPNVs with vesicular membranes formulated with poly(ethylene oxide)-b-poly(ε-caprolactone)-b-poly(ethylene oxide) (PEO-b-PCL-b-PEO) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). We found that the Penetratin-conjugated LPNV (LPNVPnt) was readily taken up by cells and showed specific ER-targeting ability, which was comparable to that of LPNVs conjugated with other types of CPPs. Moreover, we observed that remarkable lysosomal escape of the LPNVs occurred due to effective pH buffering with the aid of PEO-b-PCL-b-PEO. These results highlighted that our LPNVPnt system could pave the way for the development of an elaborate drug delivery technology for ER-targeting at the intracellular level.

Performance of a novel fluorogenic probe assay for the detection of extended-spectrum-ß-lactamase or plasmid AmpC ß-lactamase-producing Enterobacterales directly from simulated blood culture bottles.

Resistance to third generation cephalosporins is widely disseminated in Enterobacteriaceae mainly because of extended-spectrum-ß-lactamases (ESBL), plasmid AmpC ß-lactamases (PABL), and hyper-production of chromosomal AmpC ß-lactamases. Here, we evaluated the performance of rapid test using novel fluorogenic probe assay in simulated blood cultures and compared the results with the phenol red assay using a total of 172 characterized isolates (39 ESBL producers, 13 PABL producers, and 120 susceptible isolates). We prepared a pellet by centrifugation and washing, which can also be used for identification with MALDI-TOF directly from positive blood cultures. After that, we mixed the pellet with fluorogenic probe and measured the fluorescent signal using fluorometer. The fluorogenic probe assay showed higher sensitivity than the phenol red assay (96.2% vs. 71.2%, p < .0001) in 172 simulated blood culture bottles especially in detecting PABL (84.6% vs. 0%, p = .0026) and the turnaround time was 1.5 h. This fluorogenic probe assay, combined with the direct identification of pathogens, could be very useful for rapid identification of isolates and detecting cephalosporin resistance caused by ESBL and PABL directly from positive blood cultures.

Identification of highly potent and selective inhibitor, TIPTP, of the p22phox-Rubicon axis as a therapeutic agent for rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease linked to oxidative stress, which is associated with significant morbidity. The NADPH oxidase complex (NOX) produces reactive oxygen species (ROS) that are among the key markers for determining RA's pathophysiology. Therefore, understanding ROS-regulated molecular pathways and their interaction is necessary for developing novel therapeutic approaches for RA. Here, by combining mouse genetics and biochemistry with clinical tissue analysis, we reveal that in vivo Rubicon interacts with the p22phox subunit of NOX, which is necessary for increased ROS-mediated RA pathogenesis. Furthermore, we developed a series of new aryl propanamide derivatives consisting of tetrahydroindazole and thiadiazole as p22phox inhibitors and selected 2-(tetrahydroindazolyl)phenoxy-N-(thiadiazolyl)propanamide 2 (TIPTP, M.W. 437.44), which showed considerably improved potency, reaching an IC50 value up to 100-fold lower than an inhibitor that we previously synthesized reported N8 peptide-mimetic small molecule (blocking p22phox-Rubicon interaction). Notably, TIPTP treatment showed significant therapeutic effects a mouse model for RA. Furthermore, TIPTP had anti-inflammatory effects ex vivo in monocytes from healthy individuals and synovial fluid cells from RA patients. These findings may have clinical applications for the development of TIPTP as a small molecule inhibitor of the p22phox-Rubicon axis for the treatment of ROS-driven diseases such as RA.

Development of carbapenem-based fluorogenic probes for the clinical screening of carbapenemase-producing bacteria.

This report describes the synthesis of a library of fluorogenic carbapenemase substrates consisting of carbapenem derivatives, fluorescence dyes, and active cleavable linkers and their evaluation for specifically detecting carbapenemase-producing organisms (CPOs). We synthesized a series of compounds having three different types of linkers such as benzyl ether, carbamate, and amine using hydroxymethyl carbapenem 7a and hydroxyallyl carbapenem 7b as key intermediates. Probe 1b exhibited high stability and a prompt turn-on fluorescence signal upon hydrolysis by carbapenemases. In particular, the screening of clinical samples indicated that the probe 1b exhibited excellent selectivity to the CPOs over other ß-lactamases or non-carbapenemase producing bacteria, which may be of clinical use for the rapid and accurate detection of CPOs for timely diagnosis and treatment.

Performance of a Novel Fluorogenic Assay for Detection of Carbapenemase-Producing Enterobacteriaceae from Bacterial Colonies and Directly from Positive Blood Cultures.

Rapid and accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) is critical for appropriate treatment and infection control. We compared a rapid fluorogenic assay using a carbapenem-based fluorogenic probe with other phenotypic assays: modified carbapenem inactivation method (mCIM), Carba NP test (CNP), and carbapenemase inhibition test (CIT). A total of 217 characterized isolates of Enterobacteriaceae were included as follows: 63 CPE; 48 non-carbapenemase-producing carbapenem-resistant Enterobacteriaceae (non-CP-CRE); 53 extended-spectrum ß-lactamase producers; and 53 third-generation-cephalosporin-susceptible isolates. The fluorogenic assay using bacterial colonies (Fluore-C) was conducted by lysing the isolates followed by centrifugation and mixing the supernatant with fluorogenic probe. In addition, for the fluorogenic assay using spiked blood culture bottles (Fluore-Direct), pellets were obtained via the saponin preparation method, which can directly identify the pathogens using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The fluorescence signal was measured over 50 min using a fluorometer. The fluorescent signal of CPE was significantly higher than that of non-CPE in both Fluore-C (median relative fluorescence units [RFU] [range], 5,814 [240 to 32,009] versus 804 [36 to 2,480], respectively; P < 0.0001) and Fluore-Direct (median RFU [range], 10,355 [1,689 to 31,463] versus 1,068 [428 to 2,155], respectively; P < 0.0001) tests. Overall, positive and negative percent agreements of Fluore-C, mCIM, CNP, CIT, and Fluore-Direct were 100% and 98.7%, 98.3% and 97.5%, 88.1% and 100%, 96.4% and 98.7%, and 98.3% and 98.1%, respectively. The relatively lower positive percent agreement (PPA) of CNP was mainly observed in OXA-type CPE. The fluorogenic assay showed excellent performance with bacterial colonies and also directly from positive blood cultures. We included many non-CP-CRE isolates for strict evaluation. The fluorogenic assay will be a useful tool for clinical microbiology laboratories.