Isotope-Coded On-Tissue Derivatization for Quantitative Mass Spectrometry Imaging of Short-Chain Fatty Acids in Biological Tissues.

Short-chain fatty acids (SCFAs), as the main metabolites of gut microbiota, are recognized as crucial players in the host's inflammatory response and metabolic disease. Imaging the spatial distributions and calculating the accurate contents of SCFAs in the heterogeneous intestinal tissue are critical to reveal their biological functions. Here, we develop an isotope-coded on-tissue derivatization method combined with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to map the spatial expressions of SCFAs in the colon tissue based on pair-labeled N,N,N-trimethyl-2-(piperazin-1-yl)ethan-1-aminium iodide (TMPA) and D3-TMPA. A noticeable increase in the MALDI-MSI sensitivity of SCFAs was achieved after on-tissue derivatization, which enables the visualization of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, hydroxy acetic acid, and hydroxy propionic acid in the colon tissue. Moreover, the introduction of D3-TMPA-tagged SCFAs as internal standards can significantly reduce quantitation deviation from the matrix effects, ensuring the quantitative MALDI-MSI of SCFAs. We further used this method to characterize the spatial alterations of SCFAs in the colon tissues of mice with enterocolitis. The development of this strategy provides a reliable approach to image the spatial expressions of SCFAs in tissues and paves an insight way to study the roles of SCFAs in the gut microbiota and disease.

pH and Proton Sensor GPR65 Determine Susceptibility to Atopic Dermatitis.

pH sensing by GPR65 regulates various inflammatory conditions, but its role in skin remains unknown. In this study, we performed a phenome-wide association study and report that the T allele of GPR65-intronic single-nucleotide polymorphism rs8005161, which reduces GPR65 signaling, showed a significant association with atopic dermatitis, in addition to inflammatory bowel diseases and asthma, as previously reported. Consistent with this genetic association in humans, we show that deficiency of GPR65 in mice resulted in markedly exacerbated disease in the MC903 experimental model of atopic dermatitis. Deficiency of GPR65 also increased neutrophil migration in vitro. Moreover, GPR65 deficiency in mice resulted in higher expression of the inflammatory cytokine TNF-α by T cells. In humans, CD4+ T cells from rs8005161 heterozygous individuals expressed higher levels of TNF-α after PMA/ionomycin stimulation, particularly under pH 6 conditions. pH sensing by GPR65 appears to be important for regulating the pathogenesis of atopic dermatitis.

A Host-Guest Interaction-Based and Metal-Organic Gel-Based Biosensor with Aggregation-Induced Electrochemiluminescence Enhancement for Methyltransferase Assay.

Metal-organic gels (MOGs) are new soft materials with the characteristics of high colloidal stability, superb luminescence properties, and facile synthesis. Herein, we develop for the first time a host-guest interaction-based and MOG-based biosensor with aggregation-induced electrochemiluminescence (ECL) enhancement for M.SssI methyltransferase (M.SssI MTase) assay. This biosensor employs a MOG as the luminophor and potassium persulfate as the coreactant, and the formation of the Ag-MOG from the aggregation of silver nanoclusters can induce significant ECL enhancement. Two complementary single-stranded DNAs (ssDNAs, i.e., biotinylated DNA-1 and Fc-labeled DNA-2) that contain specific recognition sequence 5'-CCGG-3' can form a double-stranded DNA (dsDNA) probe. In the absence of M.SssI MTase, the dsDNA probe will be digested by restriction endonuclease HpaII, leading to the release of Fc from magnetic beads (MBs). The ß-CD can specifically recognize the released Fc through guest-host interaction, resulting in the quenching of an ECL signal. In contrast, the presence of M.SssI MTase enables the formation of fully methylated dsDNA, which cannot be cleaved by HpaII, making Fc remain on the MB surface and consequently generating an improved ECL signal. This biosensor can specifically detect M.SssI MTase with a linear range of 0.05-100 U mL-1 and a limit of detection of 3.5 × 10-3 U mL-1, and it enables accurate detection of M.SssI MTase in human serum. In addition, it can be used for inhibitor screening, with wide applications in drug discovery and disease diagnosis.

Screening of Xanthine Oxidase Inhibitors by Liquid Crystal-Based Assay Assisted with Enzyme Catalysis-Induced Aptamer Release.

Small-molecule drugs play an important role in the treatment of various diseases. The screening of enzyme inhibitors is one of the most important means in developing therapeutic drugs. Herein, we demonstrate a liquid crystal (LC)-based screening assay assisted with enzyme catalysis-induced aptamer release for screening xanthine oxidase (XOD) inhibitors. The oxidation of xanthine by XOD prevents the specific binding of xanthine and its aptamer, which induces a bright image of LCs. However, when XOD is inhibited, xanthine specifically binds to the aptamer. Correspondingly, LCs display a dark image. Three compounds are identified as potent XOD inhibitors by screening a small library of triazole derivatives using this method. Molecular docking verifies the occupation of the active site by the inhibitor, which also exhibits excellent biocompatibility to HEK293 cells and HeLa cells. This strategy takes advantages of the unique aptamer-target binding, specific enzymatic reaction, and simple LC-based screening assay, which allows high-throughput and label-free screening of inhibitors with high sensitivity and remarkable accuracy. Overall, this study provides a competent and promising approach to facilitate the screening of enzyme inhibitors using the LC-based assay assisted with the enzyme catalysis-induced aptamer release.

Single-Sided Competitive Axial Coordination of G-Quadruplex/Hemin as Molecular Switch for Imaging Intracellular Nitric Oxide.

Axial coordination is a crucial biological process to regulate biomolecules' functions in natural enzymes. However, it is a great challenge to determine the single or dual axial interaction between the metal center of enzymes and the ligand. In this work, a controllable axial coordination system was developed based on G-quadruplex/hemin complex by designing a series of fluorescent derivatives. The mechanism on axial coordination of G-quadruplex/hemin with coumarin-imidazole ligands was proposed to be single-sided, and led to fluorescence quenching of ligands. Upon addition of nitric oxide, the fluorescence of ligands was recovered through competitive axial coordination, providing a "signal on" strategy for signal transduction. More significantly, the fluorescent imaging of intracellular nitric oxide was achieved after conjugating with gold nanoparticles. Also, the proposed protocol provided a smart strategy to monitor the relationship between nitric oxide and p53 protein activity in living cells.

Surface Decorated Porphyrinic Nanoscale Metal-Organic Framework for Photodynamic Therapy.

Nanocrystallization of organic molecular photosensitizers (PSs) by means of NMOF platforms has been demonstrated to be a promising approach to build up highly efficient PDT therapeutics. We report herein a new UiO-66 type of NMOF-based PS (UiO-66-TPP-SH), which is generated from UiO-66 NMOF and S-ethylthiol ester monosubstituted metal free porphyrin (TPP-SH) via a facile postsynthetic approach under mild conditions. The obtained NMOF (size less than 150 nm) with surface-decorated porphyrinic PS can not only retain MOF crystallinity, structural feature, and size, but also exhibit highly efficient singlet oxygen generation. Compared to the interior-located porphyrinic NMOF, UiO-66-TPP-SH shows significantly higher photodynamic activity and more efficient PDT tumor treatment.

Species-habitat associations in an old-growth temperate forest in northeastern China.

BACKGROUND: Species coexistence mechanisms and maintenance of biodiversity have long been considered important components of community ecology research. As one of the important mechanisms, species coexistence theory based on niche differentiation has received attention in past years. Thus, topography, through the formation of habitat heterogeneity, affects species distributions and coexistence. A 30-ha dynamic plot of mixed broadleaved-Korean pine (Pinus koraiensis) forest is located in the Heilongjiang Fenglin National Nature Reserve. We examined species-habitat associations using the torus-translation method. We aim to understand the habitat associations of different species, life forms (shrubs, trees), and shade tolerance (light-demanding, midtolerant, shade-tolerant) across life stages (sapling, juvenile and mature), providing further evidence for the role of niche theory in temperate forests. RESULTS: Of the 33 species we tested, 28 species (84.8%) were at least significantly associated with one habitat type. Positive associations were more frequent in the valley and slope (shady and sunny) and less frequent on the ridge. Thirty-four significant positive associations with the five habitats were detected at three life stages (11, 11 and 12 at the sapling stage, juvenile stage, and mature stage, respectively). The trees were positively associated with the valley, and the shrubs were positively associated with sunny and ridge. The majority of species' habitat preferences shifted among different life stages; the exceptions were Corylus mandshurica, Maackia amurensis, Quercus mongolica, Picea jezoensis and Acer ukurunduense, which had consistent associations with the same habitat at all stages. The midtolerant trees and midtolerant shrubs were positively correlated with sunny across the three life stages. CONCLUSIONS: Most species show habitat preferences in the plot. These results indicate that niche theory plays an important role in species coexistence. Most species have no consistent association with habitat at different life stages.

Folate receptor-targeted and cathepsin B-activatable nanoprobe for in situ therapeutic monitoring of photosensitive cell death.

The integration of diagnostic and therapeutic functions in a single system holds great promise to enhance the theranostic efficacy and prevent the under- or overtreatment. Herein, a folate receptor-targeted and cathepsin B-activatable nanoprobe is designed for background-free cancer imaging and selective therapy. The nanoprobe is prepared by noncovalently assembling phospholipid-poly(ethylene oxide) modified folate and photosensitizer-labeled peptide on the surface of graphene oxide. After selective uptake of the nanoprobe into lysosome of cancer cells via folate receptor-mediated endocytosis, the peptide can be cleaved to release the photosensitizer in the presence of cancer-associated cathepsin B, which leads to 18-fold fluorescence enhancement for cancer discrimination and specific detection of intracellular cathepsin B. Under irradiation, the released photosensitizer induces the formation of cytotoxic singlet oxygen for triggering photosensitive lysosomal cell death. After lysosomal destruction, the lighted photosensitizer diffuses from lysosome into cytoplasm, which provides a visible method for in situ monitoring of therapeutic efficacy. The nanoprobe exhibits negligible dark toxicity and high phototoxicity with the cell mortality rate of 0.06% and 72.1%, respectively, and the latter is specific to folate receptor-positive cancer cells. Therefore, this work provides a simple but powerful protocol with great potential in precise cancer imaging, therapy, and therapeutic monitoring.

A peptide nucleic acid-functionalized carbon nitride nanosheet as a probe for in situ monitoring of intracellular microRNA.

A novel probe for recognition of both cancer cells and intracellular microRNA (miRNA) is designed by functionalizing a carbon nitride nanosheet (f-CNNS) with a Cy5-labeled peptide nucleic acid (Cy5-PNA) and folate. The interaction between Cy5-PNA and CNNS quenches the fluorescence of Cy5, and the presence of folate endows the probe with good specificity to folate acceptor overexpressed cells. The probe can be specifically taken up by cancer cells with an incubation step. Upon the recognition of the PNA to complementary miRNA, the hybridization product is released from the CNNS surface, which leads to the fluorescence recovery and provides a specific method for sensing of miRNA. Thus, this probe can be used for cell-specific intracellular miRNA sensing with a confocal microscope. Using miRNA-18a as a target model, the dynamic changes of its expression level inside living cells can be monitored with the proposed method. This method possesses promising applications in the study of miRNA related bioprocesses and biomedicine.

Strand displacement activated peroxidase activity of hemin for fluorescent DNA sensing.

To efficiently regulate the catalytic activity of the peroxidase mimic hemin, this work designs a double-stranded DNA probe containing an intermolecular dimer of hemin, whose peroxidase activity can be activated by a DNA strand displacement reaction. The double-stranded probe is prepared by annealing two strands of hemin labelled DNA oligonucleotides. Using the fluorescent oxidation product of tyramine by H2O2 as a tracing molecule, the low peroxidase activity of the hemin dimer ensures a low fluorescence background. The strand displacement reaction of the target DNA dissociates the hemin dimer and thus significantly increases the catalytic activity of hemin to produce a large amount of dityramine for fluorescence signal readout. Based on the strand displacement regulated peroxidase activity, a simple and sensitive homogeneous fluorescent DNA sensing method is proposed. The detection can conveniently be carried out in a 96-well plate within 20 min with a detection limit of 0.18 nM. This method shows high specificity, which can effectively distinguish single-base mismatched DNA from perfectly matched target DNA. The DNA strand displacement regulated catalytic activity of hemin has promising application in the determination of various DNA analytes.

Tannic acid and carboxymethyl chitosan-based multi-functional double-layered hydrogel with pH-stimulated response behavior for smart real-time infection monitoring and wound treatment.

The dramatic increase of drug-resistant pathogenic bacteria has seriously effect on human health, appealing the needs of developing theranostic platforms with stimuli-responsive materials to realize the accurate bacterial diagnostics and therapeutics. Herein, a tannic acid and carboxymethyl chitosan-based multifunctional ZIF-90@i-PPOPs-phenol red double-layered hydrogel with stimuli-responsiveness and antibacterial activity was fabricated. The inner layer hydrogel (ZIF-90@i-PPOPs-based TFC hydrogels) was fabricated based on ZIF-90@i-PPOPs, integrate tannic acid and carboxymethyl chitosan linked by formylphenylboronic acid (FPBA), which exhibited outstanding injectable, biodegradability and antibacterial activity. The outer layer hydrogel (PR@PAM hydrogels) were constructed from polyacrylamide (PAM) and pH indicator phenol red, owning porous structure and excellent tissue adhesion. Due to the weakly acidic microenvironment within wound, the inner-layer hydrogel was stimulus-responsively decomposed, resulting in the accurate delivery of the positively charged ZIF-90@i-PPOPs to the lesion site to capture and kill bacteria by enhanced Zn2+ and ROS release. Meantime, the outer-layer hydrogel could real-timely monitor the pH changes to evaluate the wound recovery status. These double-layered hydrogels possessed precisely pH monitoring capacity, excellent antibacterial ability and negligible side effect to normal tissue in vivo, implying the high potential of the suggested hydrogels as theranostic platform for antibacterial treatment.

Indole-3-acetic acid ameliorates dextran sulfate sodium-induced colitis via the ERK signaling pathway.

Microbiota-derived catabolism of nutrients is closely related to ulcerative colitis (UC). The level of indole-3-acetic acid (IAA), a microbiota-dependent metabolite of tryptophan, was decreased significantly in the feces of UC patients. Thus supplementation with IAA could be a potential therapeutic method for ameliorating colitis. In this work, the protective effect of supplementation with IAA on dextran sulfate sodium (DSS)-induced colitis was evaluated, and the underlying mechanism was elucidated. The results indicated that the administration of IAA significantly relieved DSS-induced weight loss, reduced the disease activity index (DAI), restored colon length, alleviated intestinal injury, and improved the intestinal tight junction barrier. Furthermore, IAA inhibited intestinal inflammation by reducing the expression of proinflammatory cytokines and promoting the production of IL-10 and TGF-ß1. In addition, the ERK signaling pathway is an important mediator of various physiological processes including inflammatory responses and is closely associated with the expression of IL-10. Notably, IAA treatment induced the activation of extracellular signal-regulated kinase (ERK), which is involved in the progression of colitis, while the ERK inhibitor U0126 attenuated the beneficial effects of IAA. In summary, IAA could attenuate the clinical symptoms of colitis, and the ERK signaling pathway was involved in the underlying mechanism. Supplementation with IAA could be a potential option for preventing or ameliorating UC.

Fluorescence quenching of carbon nitride nanosheet through its interaction with DNA for versatile fluorescence sensing.

This work investigates the interaction of carbon nitride nanosheet (CNNS), a recently developed two-dimensional nanomaterial, with DNA and its fluorescence quenching mechanism on fluorophore labeled single-stranded DNA probes. The static quenching through the photoinduced electron transfer (PET) from the excited fluorophore to the conductive band of CNNS is identified. Utilizing the affinity change of CNNS to DNA probes upon their recognition to targets and the PET-based fluorescence quenching effect, a universal sensing strategy is proposed for design of several homogeneous fluorescence detection methods with short assay time and high sensitivity. This strategy is versatile and can be combined with different amplification tools for quick fluorescence sensing of DNA and extensive DNA related analytes such as metal cations, small molecules, and proteins. As examples, two simple fluorescence detection methods for DNA and Hg(2+), one facile detection method coupled with Exo III-mediated target recycling for sensitive DNA analysis, and a ratiometric fluorescence protocol for DNA detection are proposed. This work provides an avenue for understanding the interaction between two-dimensional nanomaterials and biomolecules and designing novel sensing strategies for extending the applications of nanomaterials in bioanalysis.

Construction of palladium porphyrins and triptycene photo-activated nanomaterial for enhanced colorimetric detection and inactivation of bacteria.

In the face of increasing bacterial resistance, design of high-performing and dual-functional nanomaterials to satisfy the requirements for both detecting and eradicating bacteria is of immense importance, but still remains a great challenge. Herein, a hierarchically three-dimensional (3D) porous organic frameworks (PdPPOPHBTT) was rationally designed and fabricated for the first time to realize ideal simultaneous detection and eradication of bacteria. PdPPOPHBTT covalently integrated palladium 5,10,15,20-tetrakis-(4'-bromophenyl) porphyrin (PdTBrPP, an excellent photosensitizer) with 2,3,6,7,12,13-hexabromotriptycene (HBTT, a 3D building module). The resulting material had outstanding NIR absorption, narrow bad gap and robust singlet oxygen (1O2) production capacity, which is responsible for the sensitive detection and effective removal of bacteria. We successfully realized the colorimetric detection of S. aureus and the efficient removal of S. aureus and E. coli. The first-principles calculations found at the highly activated 1O2 derived from the 3D conjugated periodic structures and ample palladium adsorption site in PdPPOPHBTT. The bacterial infection wound model revealed that PdPPOPHBTT possesses good disinfection ability and negligible side effect to normal tissue in vivo. This finding provides an innovative strategy for designing individual porous organic polymer (POPs) with multi-function and also broaden the applications of POPs as powerful nonantibiotic type of antimicrobials.

A metalloporphyrin and hydantoin functionalized nanozyme with synergistically enhanced bacterial inhibition.

An elaborate design of multimodal antibacterial agents has been revealed to be a promising strategy to address bacterial resistance, originating from the abuse of antibiotics. In this work, we have developed a positively charged and porous material, FePPOPHydantoin, as a disinfectant via introducing 1,3-dibromo-5,5-dimethylhydantoin (Hydantoin) and porphyrin iron units into a polymer framework. The extended π conjugated networks of FePPOPHydantoin endowed the material with strong near-infrared (NIR) absorption, high density of surface catalytic active centers, superior stability, and reproducibility. FePPOPHydantoin exhibits high peroxidase mimetic and photo-Fenton activity, which can catalyze the biologically allowable maximum concentrations of hydrogen peroxide (100 µM) to produce a vast amount of hydroxyl radicals. Simultaneously, the effective electrostatic interaction between the positively charged FePPOPHydantoin and the negatively charged bacteria facilitates the binding of FePPOPHydantoin on the bacterial membrane, restricting bacteria within the destruction range of hydroxyl radicals and thus making the bacteria more vulnerable. Finally, further close contact between bacteria and Hydantoin units in FePPOPHydantoin gave the material an antibacterial efficiency of over 99.999%. Compared with chemical therapy, photo-Fenton therapy, or peroxidase catalytic therapy alone, FePPOPHydantoin had a noteworthy multi-amplified antibacterial efficiency. Furthermore, FePPOPHydantoin exhibited good biocompatibility and negligible cytotoxicity. The in vivo antibacterial therapy on the Staphylococcus aureus (S. aureus) infected mouse wound model clearly proved the effectiveness of FePPOPHydantoin for fighting bacterial infections. This work highlights opportunities for the design of nanozymes with enhanced bacteriostatic activity, providing a new avenue for the construction of novel antibiotics.

Indole acetylated high-amylose maize starch: Synthesis, characterization and application for amelioration of colitis.

Tryptophan metabolites such as indole-3-acetic acid (IAA) are critical for gut health, through their binding to the aryl hydrocarbon receptor (AhR), and may be useful for treatment of gastrointestinal diseases. Delivery of IAA to the colon is necessary, and one strategy is use of esterified starches which get digested in the colon by gut microbes. High amylose maize starch (HAMS) resists digestion in the upper gastrointestinal tract and is fermented by gut microbiota to release short-chain fatty acids (SCFAs), which are also beneficial to intestinal homeostasis. IAA esterified to HAMS (HAMSIAA) was synthesized with different degrees of substitution (DSs) by controlling the ratio of IAA vs HAMS. Successful incorporation of indole acetyl group was verified by NMR and FTIR spectra. XRD revealed that the crystalline type of HAMSIAA changed from B to V-type. SEM showed the destroyed surface of the starch granules. HAMSIAA with DS ~ 0.3 effectively increased IAA in the colon, to levels unachievable by oral IAA delivery. HAMSIAA increased pathways downstream of AhR activation, including CYP1A1 mRNA expression and IL-22 protein levels, and greatly improved DSS-induced colitis. HAMSIAA could serve as an ideal means for colon-targeted delivery of IAA and a promising nutraceutical for amelioration of inflammatory conditions.

Neutrophil subsets and their differential roles in viral respiratory diseases.

Neutrophils play significant roles in immune homeostasis and as neutralizers of microbial infections. Recent evidence further suggests heterogeneity of neutrophil developmental and activation states that exert specialized effector functions during inflammatory disease conditions. Neutrophils can play multiple roles during viral infections, secreting inflammatory mediators and cytokines that contribute significantly to host defense and pathogenicity. However, their roles in viral immunity are not well understood. In this review, we present an overview of neutrophil heterogeneity and its impact on the course and severity of viral respiratory infectious diseases. We focus on the evidence demonstrating the crucial roles neutrophils play in the immune response toward respiratory infections, using influenza as a model. We further extend the understanding of neutrophil function with the studies pertaining to COVID-19 disease and its neutrophil-associated pathologies. Finally, we discuss the relevance of these results for future therapeutic options through targeting and regulating neutrophil-specific responses.

Propionate Ameliorates Alcohol-Induced Liver Injury in Mice via the Gut-Liver Axis: Focus on the Improvement of Intestinal Permeability.

Alcohol-related liver disease (ALD) is a major cause of chronic liver disease worldwide with limited therapeutic options. Here, we first revealed the promising beneficial effect of gut microbiota-derived propionate on alcoholic liver injury in mice. This effect was dependent on the modulation of homeostasis of the gut-liver axis, especially the improvement of intestinal permeability. Dietary supplementation with propionate protected against ethanol-induced loss of hepatic function and hepatic steatosis in mice. Meanwhile, propionate treatment attenuated intestinal epithelial barrier dysfunction, restored the expression of intestinal mucus layer components, suppressed intestinal inflammation, and altered intestinal microbiota dysbiosis, which inhibited the intestinal hyperpermeability and subsequently reduced lipopolysaccharide leakage in ALD mice. Furthermore, as a consequence of endotoxemia amelioration, the liver inflammation-related TLR4-NF-κB pathway was inhibited. Collectively, our results suggested that propionate supplementation may be a promising option for the prevention and treatment of ALD.

Bis{1-[(4-methyl-phen-yl)imino-meth-yl]-2-naphtho-lato-κN,O}nickel(II).

In the title complex, [Ni(C(18)H(14)NO)(2)], the Ni(II) ion lies on an inversion center and is coordinated in a slightly distorted square-planar environment. The 1-[(4-methyl-phen-yl)imino-meth-yl]-2-naphtho-late ligands are coordinated in a trans arrangement with respect to the N and O atoms. In the symmetry-unique ligand, the dihedral angle between the naphthalene ring system and the benzene ring of the methyl-phenyl group is 49.03 (7)°.