Safety and efficacy evaluation of halicin as an effective drug for inhibiting intestinal infections.

Halicin, the first antibacterial agent discovered by artificial intelligence, exerts broad-spectrum antibacterial effects and has a unique structure. Our study found that halicin had a good inhibitory effect on clinical isolates of drug-resistant strains and Clostridium perfringens (C. perfringens). The safety of halicin was evaluated by acute oral toxicity, genotoxicity and subchronic toxicity studies. The results of acute toxicity test indicated that halicin, as a low-toxicity compound, had an LD50 of 2018.3 mg/kg. The results of sperm malformation, bone marrow chromosome aberration and cell micronucleus tests showed that halicin had no obvious genotoxicity. However, the results of the 90-day subchronic toxicity test indicated that the test rats exhibited weight loss and slight renal inflammation at a high dose of 201.8 mg/kg. Teratogenicity of zebrafish embryos showed that halicin had no significant teratogenicity. Analysis of intestinal microbiota showed that halicin had a significant effect on the intestinal microbial composition, but caused a faster recovery. Furthermore, drug metabolism experiments showed that halicin was poorly absorbed and quickly eliminated in vivo. Our study found that halicin had a good therapeutic effect on intestinal infection model of C. perfringens. These results show the feasibility of developing oral halicin as a clinical candidate drug for treating intestinal infections.

G-Clamp Heterocycle Modification Containing Interstrand Photo-Cross-Linker to Capture Intracellular MicroRNA Targets.

MicroRNAs (miRNAs) play indispensable roles in post-transcriptional gene regulation. The identification of target mRNAs is essential for dissecting the recognition basis, dynamics, and regulatory mechanism of miRNA-mRNA interactions. However, the lack of an unbiased method for detecting weak miRNA-mRNA interactions remains a long-standing obstacle for miRNA research. Here, we develop and provide proof-of-concept evidence demonstrating a chemical G-clamp-enhanced photo-cross-linking strategy for covalent capture of intracellular miRNA targets in different cell lines. This approach relies on an aryl-diazirine-G-clamp-modified-nucleoside (ARAGON) miRNA probe containing an alkynyl group that improves the thermal stability of miRNA-target mRNA duplex molecules and can rapidly cross-link with the complementary strand upon UV 365 nm activation, enhancing the transient capture of mRNA targets. After validating the accuracy and binding properties of ARAGON-based miRNA probes through the successful enrichment for the known targets of miR-106a, miR-21, and miR-101, we then extend ARAGON's application to screen for previously unknown targets of different miRNAs in various cell lines. Ultimately, results in this study uncover GAB1 as a target of miR-101 in H1299 lung cancer cells and show that miR-101 silencing of GAB1 can promote apoptosis in H1299 cells, suggesting an oncogenic mechanism of GAB1. This study thus provides a powerful and versatile tool for enhanced screening of global miRNA targets in cells to facilitate investigations of miRNA functions in fundamental cellular processes and disease pathogenesis.

Design and Synthesis of Pleuromutilin Derivatives as Antibacterial Agents Using Quantitative Structure-Activity Relationship Model.

The quantitative structure-activity relationship (QSAR) is one of the most popular methods for the virtual screening of new drug leads and optimization. Herein, we collected a dataset of 955 MIC values of pleuromutilin derivatives to construct a 2D-QSAR model with an accuracy of 80% and a 3D-QSAR model with a non-cross-validated correlation coefficient (r2) of 0.9836 and a cross-validated correlation coefficient (q2) of 0.7986. Based on the obtained QSAR models, we designed and synthesized pleuromutilin compounds 1 and 2 with thiol-functionalized side chains. Compound 1 displayed the highest antimicrobial activity against both Staphylococcus aureus ATCC 29213 (S. aureus) and Methicillin-resistant Staphylococcus aureus (MRSA), with minimum inhibitory concentrations (MICs) < 0.0625 µg/mL. These experimental results confirmed that the 2D and 3D-QSAR models displayed a high accuracy of the prediction function for the discovery of lead compounds from pleuromutilin derivatives.

GLORI for absolute quantification of transcriptome-wide m6A at single-base resolution.

N6-methyladenosine (m6A) is the most abundant posttranscriptional chemical modification in mRNA, involved in regulating various physiological and pathological processes throughout mRNA metabolism. Recently, we developed GLORI, a sequencing method that enables the production of a globally absolute-quantitative m6A map at single-base resolution. Our technique utilizes the glyoxal- and nitrite-based chemical reaction, which selectively deaminates unmethylated adenosines while leaving m6A intact. The RNA library can then be prepared using a modified library construction protocol from enhanced UV crosslinking and immunoprecipitation (eCLIP) or commercial kits. Here we provide a detailed protocol for proper RNA sample handling and provide further guidelines for the use of a tailored bioinformatics pipeline (GLORI-tools) for subsequent data analysis. Compared with current methods, this new method is both exceptionally sensitive and robust, capable of identifying ~80,000 m6A sites with 50 Gb sequencing data in mammalian cells. It also provides a quantitative readout for m6A sites at single-base resolution. We hope the technique will provide a precise and unbiased tool for investigating m6A biology across various fields. Basic expertise in molecular biology and knowledge of bioinformatics are required for the protocol. The entire procedure can be completed within a week, with the library construction process taking ~4 d.

The Effect of Polymer Blends on the In Vitro Release/Degradation and Pharmacokinetics of Moxidectin-Loaded PLGA Microspheres.

To investigate the effect of polymer blends on the in vitro release/degradation and pharmacokinetics of moxidectin-loaded PLGA microspheres (MOX-MS), four formulations (F1, F2, F3 and F4) were prepared using the O/W emulsion solvent evaporation method by blending high (75/25, 75 kDa) and low (50/50, 23 kDa) molecular weight PLGA with different ratios. The addition of low-molecular-weight PLGA did not change the release mechanism of microspheres, but sped up the drug release of microspheres and drastically shortened the lag phase. The in vitro degradation results show that the release of microspheres consisted of a combination of pore diffusion and erosion, and especially autocatalysis played an important role in this process. Furthermore, an accelerated release method was also developed to reduce the period for drug release testing within one month. The pharmacokinetic results demonstrated that MOX-MS could be released for at least 60 days with only a slight blood drug concentration fluctuation. In particular, F3 displayed the highest AUC and plasma concentration (AUC0-t = 596.53 ng/mL·d, Cave (day 30-day 60) = 8.84 ng/mL), making it the optimal formulation. Overall, these results indicate that using polymer blends could easily adjust hydrophobic drug release from microspheres and notably reduce the lag phase of microspheres.

Synthesis and evaluation of novel pleuromutilin derivatives targeting the 50S ribosomal subunit for antibacterial ability.

Multidrug-resistant bacteria, particularly methicillin-resistant Staphylococcus aureus, have become a major global public health concern. Therefore, developing new antibiotics that do not possess cross-resistance for the currently available antibiotics is critical. Herein, we synthesized a novel class of pleuromutilin derivatives containing substituted triazine with improved antibacterial activity. Among these derivatives, 6d, which contains 4-dimethylamino-1,3,5-triazine in the side chain of pleuromutilin, exhibited highly promising antimicrobial activity and mitigated antibiotic resistance. The high antibacterial potency of 6d was further supported by docking model analysis and green fluorescent protein inhibition assay. Additionally, cytotoxicity and acute oral toxicity evaluation and in vivo mouse systemic infection experiments revealed that 6d possessed tolerable toxicity and promising therapeutic efficacy.

Anti-methicillin-resistant Staphylococcus aureus activity and safety evaluation of 14-O-[(5-ethoxycarbonyl-4,6-dimethylpyrimidine-2-yl) thioacetyl] mutilin (EDT).

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have threated the public health worldwide, which emphasizes the urgent need for new drugs with novel mechanism of actions. 14-O-[(5-ethoxycarbonyl-4,6-dimethylpyrimidine-2-yl) thioacetyl] mutilin (EDT) is a pleuromutilin compound with high activity against several Gram-positive bacteria in vitro and in vivo. This study aimed to verifying the potential anti-MRSA activity and evaluating the safety of EDT. In in vitro antibacterial activity assays, EDT exhibited potent antibacterial activity against MRSA isolated from clinic (minimum inhibitory concentration = 0.0313-0.125 µg/mL), increased post-antibiotic effect (PAE) values and limited potential for the development of resistance. Docking model and green fluorescent protein (GFP) inhibition assay further elucidated the higher antibacterial activities of EDT via mechanism of action. In safety evaluation, EDT exhibited low cytotoxic effect and acute oral toxicity in mice and avoided to significantly increase the number of revertant colonies of six tested strains in the Ames study. Furthermore, EDT displayed a moderate inhibitory effect on CYP3A4 and moderate stability in mouse and human liver microsomes, providing a promising agent for the development of new antimicrobial candidate.

Novel pyridinium cationic pleuromutilin analogues overcoming bacterial multidrug resistance.

A series of pyridinium cation-substituted pleuromutilin analogues were designed, synthesized and evaluated for their antibacterial activities in vitro and in vivo. Most derivatives showed potent antibacterial activities, especially e4 that displayed the highest antibacterial activity against multi-drug resistant bacteria and was subjected to time-kill kinetics, resistance studies, cytotoxicity and molecular docking assays. Molecular docking results, scanning electron microscopy and o-nitrophenyl-ß-galactopyranoside tests showed that e4 not only inhibited bacterial protein synthesis but also disrupted bacterial cell walls. Compound e4 showed an ED50 of 5.68 mg/kg against multi-drug resistant Staphylococcus aureus in infected mice model. In in vivo and in vitro toxicity tests, e4 showed low toxic effects with an LD50 of 879 mg/kg to mice. These results suggest that compound e4 may be considered as a new therapeutic candidate for bacterial infections.

Antibiotic resistance and drug modification: Synthesis, characterization and bioactivity of newly modified potent pleuromutilin derivatives with a substituted piperazine moiety.

Antibiotic-resistant bacteria pose a major global public health concern, owing to the lack of effective antibacterial drugs. Consequently, the discovery and development of innovative antibacterial drug classes with unique mechanisms of action are urgently needed. In this study, we designed, synthesised, and tested a series of novel pleuromutilin derivatives with piperazine linker substituted by amino acids moieties to determine their antibacterial properties. Most synthesized compounds exhibited potent activities against Staphylococcus aureus (S. aureus), methicillin-resistant S. aureus (MRSA), and methicillin-resistant Staphylococcus epidermidis. Compound 6l, the most potent antibacterial agent created in this study, displayed a rapid bactericidal activity against MRSA, Klebsiella pneumoniae and S. aureus cfr N12. Moreover, pharmacokinetics study of compound 6l exhibited good PK performance with a low in vivo clearance (CL = 1965 mL/h/kg) and a suitable half-life (T1/2 = 11.614 ± 5.123 h). Molecular docking experiments revealed the binding model of compound 6l to the unmethylated A2503 of peptidyl transferase centre of 23S rRNA. Interaction pattern of 6l with cfr-mediated ribosomes revealed by molecular dynamics. Moreover in vivo mouse systemic infection experiments with compound 6l revealed its effectiveness against MRSA and S. aureus cfr N12 with the ED50 of 11.08 mg/kg and 14.63 mg/kg body weight, respectively.

Absolute quantification of single-base m6A methylation in the mammalian transcriptome using GLORI.

N6-methyladenosine (m6A) is the most abundant RNA modification in mammalian cells and the best-studied epitranscriptomic mark. Despite the development of various tools to map m6A, a transcriptome-wide method that enables absolute quantification of m6A at single-base resolution is lacking. Here we use glyoxal and nitrite-mediated deamination of unmethylated adenosines (GLORI) to develop an absolute m6A quantification method that is conceptually similar to bisulfite-sequencing-based quantification of DNA 5-methylcytosine. We apply GLORI to quantify the m6A methylomes of mouse and human cells and reveal clustered m6A modifications with differential distribution and stoichiometry. In addition, we characterize m6A dynamics under stress and examine the quantitative landscape of m6A modification in gene expression regulation. GLORI is an unbiased, convenient method for the absolute quantification of the m6A methylome.

Efficacy of the Antimalarial MMV390048 against Babesia Infection Reveals Phosphatidylinositol 4-Kinase as a Druggable Target for Babesiosis.

The present study aimed to evaluate the anti-Babesia effect of MMV390048, a drug that inhibits Plasmodium by targeting the phosphatidylinositol 4-kinase (PI4K). The half inhibitory concentration (IC50) of MMV390048 against the in vitro growth of Babesia gibsoni was 6.9 ± 0.9 µM. In immunocompetent mice, oral treatment with MMV390048 at a concentration of 20 mg/kg effectively inhibited the growth of B. microti (Peabody mjr strain). The peak parasitemia in the control group was 30.5%, whereas the peak parasitemia in the MMV390048-treated group was 3.4%. Meanwhile, MMV390048 also showed inhibition on the growth of B. rodhaini (Australia strain), a highly pathogenic rodent Babesia species. All MMV390048-treated mice survived, whereas the mice in control group died within 10 days postinfection (DPI). The first 7-day administration of MMV390048 in B. microti-infected, severe combined immunodeficiency (SCID) mice delayed the rise of parasitemia by 26 days. Subsequently, a second 7-day administration was given upon recurrence. At 52 DPI, a parasite relapse (in 1 out of 5 mice) and a mutation in the B. microti PI4K L746S, a MMV390048 resistance-related gene, were detected. Although the radical cure of B. microti infection in immunocompromised host SCID mice was not achieved, results from this study showed that MMV390048 has excellent inhibitory effects on Babesia parasites, revealing a new treatment strategy for babesiosis: targeting the B. microti PI4K.

Mutual effects of Shewanella putrefaciens-montmorillonite and their impact on uranium immobilization.

This study investigated the immobilization behavior of U(VI) by the mixture of Shewanella putrefaciens (S. putrefaciens) and montmorillonite with batch experiment. The relevant mechanisms were discussed based on the experimental results and characterizations. It was found that the immobilization of U(VI) by S. putrefaciens-montmorillonite was inhibited at pH < 7.0 and enhanced at pH > 7.0. The inhibition effect was due to the aggregation and coverage between S. putrefaciens and montmorillonite, whereas the association of microbial dissolvable organic matters (DOM) on montmorillonite could promote immobilization of U(VI). The evidences of X-photoelectron spectroscopy (XPS) and density functional theory (DFT) simulation confirmed that the carboxyl-, hydroxyl-, nitrogen-based DOM do have the ability to interacted with U(VI). This work highlights a comprehensive and overlook perspective to understand the immobilization behavior of U(VI) in environmental organo-minerals.

Discovery of novel pleuromutilin derivatives as potent antibacterial agents.

Novel pleuromutilin derivatives with 3,4-dihydropyrimidin and pyrimidine moieties were designed, synthesized, and evaluated for their antibacterial activities. Most of the synthesized derivatives, especially the compounds bearing the pyrimidine moieties, exhibited potent antibacterial activities against methicillin-resistant Staphylococcus aureus BNCC 337371 (MRSA-337371), Staphylococcus aureus ATCC 25923 (S. aureus-25923) and methicillin-resistant Staphylococcus epidermidis ATCC 51625 (MRSE-51625). Compounds 5a, 5g and 5h exerted the excellent antibacterial activities and selected to evaluate their bacterial killing kinetics. Compound 5h displayed the highest antibacterial activities with bacteriostatic activities against MRSA and further evaluated its efficacy in mouse systemic infection. The results showed that compound 5h exhibited potent in vivo antibacterial effects to significantly improve the survival rate of mice (ED50 = 16.14 mg/kg), reduce the bacterial load and alleviate the pathological changes in the lungs of the affected mice. Furthermore, molecular docking studies revealed that the selected compounds successfully localized in the pocket of 50S ribosomal subunit and the formed hydrogen bonds were the main interaction.

Nano zero valent iron encapsulated in graphene oxide for reducing uranium.

Nano zero-valent iron (Fe0) has been widely used to remove Uranium (U(VI)). In order to enhance the performance of Fe0 toward U(VI) removal, the Fe0 was assembled into graphene oxide (GO) sheets via 3-aminopropyl triethoxysilane (APTES) as Fe0/APTES-GO composites. The Fe0/APTES-GO composites were triumphantly prepared, characterized and analyzed by means of Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) together with Energy Dispersive Spectrometer (EDS), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). SEM and TEM-EDS results manifested that Fe0 particles were encapsulated into rolled-up GO, which greatly improved the stability of Fe0. Batch experiment showed that only a small amount of Fe2+ was leached in the first two leaching cycles of Fe0/APTES-GO composites. The removal capacity of Fe0/APTES-GO composites was up to 1357.99 mg/g at pH = 4.1 and T = 50 °C, which was mainly attributed to the reducing activity of Fe0 and an abundance of functional groups (i.e., -COOH, C-OH and -OH) on the Fe0/APTES-GO composites. The electrostatic potential (ESP) from the calculation also supported that U(VI) tended to be reduced at the back side of the GO-Fe0 cluster.

Cytochrome P450 inhibition potential and initial genotoxic evaluation of 14-O-[(4,6-diaminopyrimidine-2-yl)thioacetyl] mutilin.

14-O-[(4,6-Diaminopyrimidine-2-yl)thioacetyl] mutilin (DPTM) is a promising drug candidate with excellent antibacterial activity against Gram-positive bacteria. The present study was designed to characterize its Cytochrome P450 (CYP) enzymes inhibition activities and the genotoxicity with the standard Ames test. We determined the inhibitory effects of DPTM on CYP1A2, CYP2D1/6, CYP2E1, CYP2C11/9 and CYP3A/4 in rat liver microsomes (RLMs) and in human liver microsomes (HLMs). The mRNA expressions of the above CYP isoforms and their transcriptional regulators were also evaluated using the Hep G2 cell model. The results showed DPTM exhibited a moderate inhibitory potential against CYP3A/4 (IC50 values of 10 ± 2 and 8 ± 2 µM, respectively) and weak against the other CYP enzymes based on their IC50 values. Compared to the control, CYP isoforms and their transcriptional regulators mRNA expressions significantly increased when the Hep G2 cells were treated with DPTM for a certain period of time. In the Ames test, Salmonella strains TA97, TA98, TA100, TA102 and TA1535 were treated with or without the metabolic activation (S9). Analysis showed the average number of revertant colonies per plate was less in double in the groups treated with DPTM than that in the negative control plate and showed no dose-related increase.

Novel pleuromutilin derivatives with substituted 6-methylpyrimidine: Design, synthesis and antibacterial evaluation.

A series of novel pleuromutilin derivatives with substituted 6-methylpyrimidine moieties was designed, synthesized, and evaluated for their antibacterial activities. Most of the tested compounds exhibited potent antibacterial activities against Staphylococcus aureus ATCC 25923 (S. aureus-25923), methicillin-resistant Staphylococcus epidermidis ATCC 51625 (MRSE-51625), methicillin-resistant Staphylococcus aureus BNCC 337371 (MRSA-337371), Streptococcus dysgalactiae (S. dysgalactiae) and Streptococcus agalactiae (S. agalactiae). Compounds 5c and 5g were the most active and displayed bacteriostatic activities against MRSA. In vivo mouse systemic infection experiment showed that 5c significantly improved the survival rate of mice (ED50 = 18.02 mg/kg), reduced the bacterial load and alleviated the pathological changes in the lungs of the affected mice.

A Validated HPLC-MS/MS Assay for 14-O-[(4,6-Diaminopyrimidine-2-yl)thioacetyl] Mutilin in Biological Samples and Its Pharmacokinetic, Distribution and Excretion via Urine and Feces in Rats.

14-O-[(4,6-Diaminopyrimidine-2-yl)thioacetyl] mutilin (DPTM), a novel pleuromutilin candidate with a substituted pyrimidine moiety, has been confirmed to possess excellent antibacterial activity against Gram-positive bacteria. To illustrate the pharmacokinetic profile after intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) administrations with DPTM, as well as tissue distribution and excretion via urine and feces in vivo, a specific, sensitive and robust HPLC-MS/MS method was first developed to determine DPTM in rat plasma, various tissues, urine and feces. The plasma, tissues, urine and feces samples were treated by protein precipitation with acetonitrile using tiamulin fumarate as an internal standard (IS). This method which was achieved on an HPLC system detector equipped with an ESI interface, was sensitive with 5 ng/mL as the lower limit of detection and exhibited good linearity (R² > 0.9900) in the range of 5⁻4000 ng/mL for plasma, various tissues, urine and feces, as well as intra-day precision, inter-day precision and accuracy. The matrix effects ranged from 94.2 to 109.7% with RSD ≤ 9.4% and the mean extraction recoveries ranged from 95.4 to 109.5% in plasma, tissue homogenates, urine and feces (RSD ≤ 9.9). After i.v., i.m. and p.o. administrations, DPTM was rapidly absorbed and metabolized in rats with the half-life (t1/2) of 1.70⁻1.86, 3.23⁻3.49 and 4.38⁻4.70 for 10, 25 and 75 mg/kg doses, respectively. The tissue distribution showed that DPTM was diffused into all the tested tissues, especially into the intestine and lung. Excretion via urine and feces studies demonstrated that DPTM was mainly excreted by feces after administration.

A new pleuromutilin candidate with potent antibacterial activity against Pasteurella multocida.

This study assessed the antimicrobial activity of 14-O-[(4,6-Diaminopyrimidine-2-yl) thioacetyl] mutilin (DPTM), a novel pleuromutilin candidate with a substituted pyrimidine moiety, against Pasteurella multocida. Minimum Inhibitory Concentration (MIC), Oxford Cup assay, and time-kill experiments were used to measure the activity of DPTM against P. multocida serotype A in vitro. We observed that DPTM was potent against Pasteurella multocida serotype A with the MIC value of 0.781 µg/mL. The mean inhibition-zone diameters of DPTM (50, 25, and 12.5 µg/mL) were 29.4, 24.2 and 20.1 mm, respectively. Time-kill experiments showed that the drug caused a rapid decline in the number of bacteria compared with the initial inoculum at 4 h and killed 94.6% of the bacteria during 24 h. Furthermore, DPTM activity was also assessed in a lung infection model challenged with 4.0 × 109 CFU/mL P. multocida serotype A. The results showed that DPTM significantly reduced mortality rate and bacterial load, and alleviated the pathological changes of lung. The antibacterial effect of DPTM found in this study suggested that it was useful in the prevention or control of pneumonia caused by P. multocida.

Synthesis and antibacterial activities of novel pleuromutilin derivatives.

Pleuromutilin derivatives 4a-h, 5a-g, and 6a-d were synthesized and characterized by IR, 1 H NMR, and 13 C NMR. All synthetic compounds were screened for their in vitro antibacterial activity against Staphylococcus aureus (ATCC 25923), methicillin-resistant S. aureus (MRSA, ATCC 43300), Pasteurella multocida (CVCC 408), Escherichia coli (ATCC 25922), and Salmonella typhimurium (ATCC 14028). Most compounds with quaternary amine showed higher antibacterial activities against both Gram-positive and Gram-negative bacteria strains. Among the screened compounds, compound 5a bearing an N,N,N-trimethyl group at the C-14 side chain of pleuromutilin was found to be the most active agent. Furthermore, preliminary molecular docking was performed to predict the binding interaction of the compounds in the binding pocket.

Determination of a New Pleuromutilin Derivative in Broiler Chicken Plasma by RP-HPLC-UV and Its Application to a Pharmacokinetic Study.

A simple, sensitive and reproducible high-performance liquid chromatography method was developed and validated for the determination of 14-O-[(2-amino-1,3,4-thiadiazol-5-yl) thioacetyl] mutilin (ATTM), a new synthesized pleuromutilin derivative with potent antibacterial activity, in broiler chicken plasma after a single intravenous (i.v.), intramuscular (i.m.) or oral (p.o.) administration. Satisfactory separation was achieved on a ZORBAX Ecliplus C18 column (250 × 4.6, 5 µm) with UV detection at 279 nm, using a mobile phase comprising acetonitrile and ultrapure water (50:50, v/v). The elution was isocratic at ambient temperature with a flow rate of 1.0 mL/min. The method exhibited good linearity (R2 > 0.999) over the assayed concentration range (0.12-120.00 µg/mL) and demonstrated good intra- and inter-day precision and accuracy. The method was validated and successfully applied to the pharmacokinetic study of ATTM in chicken plasma after i.v. and p.o. administration.