Overall mutational scanning unveils the essential active residues for the mechanistic action of MCR-1.

Polymyxins, including colistin and polymyxin B, serve as crucial last-resort antibiotics for managing infections caused by carbapenem-resistant Enterobacterales (CRE). However, the rapid spread of the mobilized colistin resistance gene (mcr-1) challenged the efficacy of treatment by polymyxins. The mcr-1 gene encoded a transmembrane phosphoethanolamine (PEA) transferase enzyme, MCR-1.

Repurposing cetylpyridinium chloride and domiphen bromide as phosphoethanolamine transferase inhibitor to combat colistin-resistant Enterobacterales.

The emergence of plasmid-encoded colistin resistance mechanisms, MCR-1, a phosphoethanolamine transferase, rendered colistin ineffective as last resort antibiotic against severe infections caused by clinical Gram-negative bacterial pathogens. Through screening FDA-approved drug library, we identified two structurally similar compounds, namely cetylpyridinium chloride (CET) and domiphen bromide (DOM), which potentiated colistin activity in both colistin-resistant and susceptible Enterobacterales. These compounds were found to insert their long carbon chain to a hydrophobic pocket of bacterial phosphoethanolamine transferases including MCR-1, competitively blocking the binding of lipid A tail for substrate recognition and modification, resulting in the increase of bacterial sensitivity to colistin.

Identification of isothiazolones analogues as potent bactericidal agents against antibiotic resistant CRE and MRSA strains.

Carbapenem-resistant Enterobacterales (CRE) has emerged as a worldwide spread nosocomial superbug exhibiting antimicrobial resistance (AMR) to all current antibiotics, leaving limited options for treating its infection. To discovery novel antibiotics against CRE, we designed and synthesized a series of 14 isothiazol-3(2H)-one analogues subjected to antibacterial activity evaluation against Escherichia coli (E. coli) BL21 (NDM-1) and clinical strain E.

A novel ESKAPE-sensitive peptide with enhanced stability and its application in controlling multiple bacterial contaminations in chilled fresh pork.

The co-existence of various pathogenic bacteria on the surface of pork products exacerbates difficulties in food safety control. Developing broad-spectrum and stable antibacterial agents that are not antibiotics is an unmet need. To address this issue, all l-arginine residues of a reported peptide (IIRR)-NH (zp80) were substituted with the corresponding D enantiomers.

C-terminal modification of a de novo designed antimicrobial peptide via capping of macrolactam rings.

In this work, by capping a macrolactam ring at the C-terminus of a de novo-designed peptide, namely zp80, we have constructed a small peptide library via the solid phase peptide synthesis for screening. Eight peptides bearing different aspartic acid-rich macrolactam rings but the same linear (IIRR) unit exhibited improved antibacterial activities, hemolytic activity, and selectivity index. Mechanistic studies revealed that they could destroy the integrity of bacterial envelope, leading to cytoplasm leakage and rapid dissipation of membrane potential.

Flavonoid Monomers as Potent, Nontoxic, and Selective Modulators of the Breast Cancer Resistance Protein (ABCG2).

We synthesize various substituted triazole-containing flavonoids and identify potent, nontoxic, and highly selective BCRP inhibitors. , , and possess -methoxycarbonylbenzyloxy substitution at C-3 of the flavone moiety and substituted triazole at C-4' of the B-ring. They show low toxicity (IC toward L929 > 100 μM), potent BCRP-inhibitory activity (EC = 1-15 nM), and high BCRP selectivity (BCRP selectivity over MRP1 and P-gp > 67-714).

An ornithine-rich dodecapeptide with improved proteolytic stability selectively kills gram-negative food-borne pathogens and its action mode on Escherichia coli O157:H7.

Food-borne pathogenic bacteria are dispersed throughout the entire chain of the food industry. However, many food preservatives are limited by poor biocompatibility such as cumulative poisoning. The antimicrobial peptide is increasingly regarded as a promising preservative in food research due to its high bioactivity and low cytotoxicity.

Investigation of antibiofilm activity, antibacterial activity, and mechanistic studies of an amphiphilic peptide against Acinetobacter baumannii.

Biofilm-producing pathogens, such as Acinetobacter baumannii, have aroused escalating attention. Because these bacteria could secrete mixture with close-knit architecture and complicated components to resist traditional antibiotics. Here, we reported an amphiphilic peptide denoted as zp3 (GIIAGIIIKIKK-NH), which showed favorable bioactivity against Acinetobacter baumannii ATCC 19606 (minimal inhibitory concentration, MIC = 4 μM) and low cytotoxicity to mammalian cells Vero (half maximal inhibitory concentration, IC > 100 μM).

Bioisosteric investigation of ebselen: Synthesis and in vitro characterization of 1,2-benzisothiazol-3(2H)-one derivatives as potent New Delhi metallo-β-lactamase inhibitors.

Carbapenem-resistant Enterobacteriaceae (CRE) producing New Delhi metallo-β-lactamase (NDM-1) cause untreatable bacterial infections, posing a significant threat to human health. In the present study, by employing the concept of bioisosteric replacement of the selenium moiety of ebselen, we have designed, synthesized and characterized a small compound library of 2-substituted 1,2-benzisothiazol-3(2H)-one derivatives and related compounds for evaluating their cytotoxicity and synergistic activity in combination with meropenem against the E. coli Tg1 (NDM-1) strain.

Designed Hexadecapeptides Synergize Glycopeptide Antibiotics Vancomycin and Teicoplanin against Pathogenic via Disruption of Cell Permeability and Potential.

Given the worldwide prevalence of pathogenic drug-resistant bacteria and the slow pace of new antibacterial development, discovering new uses for approved drugs that are outside the scope of the original indication is increasingly becoming an attractive proposition. In this work, seven linear cationic hexadecapeptides were designed, synthesized, and characterized. These amphiphilic peptides are able to transform from the random coil structure in water to α-helix in SDS solution and have only modest bioactivity to limited bacterial strains when used alone.

Hydrophobic substituents on isatin derivatives enhance their inhibition against bacterial peptidoglycan glycosyltransferase activity.

Moenomycin A, the well-known natural product inhibitor of peptidoglycan glycosyltransferase (PGT), is a large amphiphilic molecule of molecular mass of 1583 g/mol and its bioavailablity as a drug is relatively poor. In searching for small-molecule ligands with high inhibition ability targeting the enzyme, we found that the addition of hydrophobic groups to an isatin-based inhibitor of bacterial PGT significantly improves its inhibition against the enzyme, as well as its antibacterial activity. The improvement in enzymatic inhibition can be attributed to a better binding of the small molecule inhibitor to the hydrophobic region of the membrane-bound bacterial cell wall synthesis enzyme and the plasma membrane.

Triazole Bridged Flavonoid Dimers as Potent, Nontoxic, and Highly Selective Breast Cancer Resistance Protein (BCRP/ABCG2) Inhibitors.

The present work describes the syntheses of diverse triazole bridged flavonoid dimers and identifies potent, nontoxic, and highly selective BCRP inhibitors. A homodimer, , with -methoxycarbonylbenzyloxy substitution at C-3 of the flavone moieties and a triazole-containing linker (21 atoms between the two flavones) showed low toxicity (IC toward L929, 3T3, and HFF-1 > 100 μM), potent BCRP-inhibitory activity (EC = 1-2 nM), and high BCRP selectivity (BCRP selectivity over MRP1 and P-gp > 455-909). inhibits BCRP-ATPase activity, blocks the drug efflux activity of BCRP, elevates the intracellular drug accumulation, and finally restores the drug sensitivity of BCRP-overexpressing cells.

Phenol-Soluble-Modulin-Inspired Amphipathic Peptides Have Bactericidal Activity against Multidrug-Resistant Bacteria.

Phenol-soluble modulins (PSMs) are a large family of cytolytic peptide toxins produced by Staphylococcus aureus. Based on their amino acid sequences, we have constructed a small library of cationic isoleucine-rich peptides for antimicrobial evaluation. Relative to the parent PSMs, peptide zp3 (GIIAGIIIKIKK-NH ) was found to possess greatly improved physicochemical properties (soluble in water) and antibacterial activity (MIC=8 μm for E.

Antibacterial activity and mechanism of action of a thiophenyl substituted pyrimidine derivative.

The issue of multidrug resistant bacteria is a worldwide health threat. To develop new antibacterial agents with new mechanisms of action is thus an urgent request to address this antibiotic resistance crisis. In the present study, a new thiophenyl-pyrimidine derivative was prepared and utilized as an effective antibacterial agent against Gram-positive strains.

Boosting the efficacy of anti-MRSA β-lactam antibiotics via an easily accessible, non-cytotoxic and orally bioavailable FtsZ inhibitor.

The rapid emergence of methicillin-resistant Staphylococcus aureus (MRSA) strains has undermined the therapeutic efficacy of existing β-lactam antibiotics (BLAs), prompting an urgent need to discover novel BLAs adjuvants that can potentiate their anti-MRSA activities. In this study, cytotoxicity and antibacterial screening of a focused compound library enabled us to identify a compound, namely 28, which exhibited low cytotoxicity against normal cells and robust in vitro bactericidal synergy with different classes of BLAs against a panel of multidrug-resistant clinical MRSA isolates. A series of biochemical assays and microscopic studies have revealed that compound 28 is likely to interact with the S.

Discovery of Novel Flavonoid Dimers To Reverse Multidrug Resistance Protein 1 (MRP1, ABCC1) Mediated Drug Resistance in Cancers Using a High Throughput Platform with "Click Chemistry".

A 300-member flavonoid dimer library of multidrug resistance-associated protein 1 (MRP1, ABCC1) modulators was rapidly assembled using "click chemistry". Subsequent high-throughput screening has led to the discovery of highly potent (EC ranging from 53 to 298 nM) and safe (selective indexes ranging from >190 to >1887) MRP1 modulators. Some dimers have potency about 6.

Design, synthesis and antibacterial evaluation of 2,4-disubstituted-6-thiophenyl-pyrimidines.

The increasing incidences of multidrug resistant bacterial infections urge the development of novel antibacterial having a new mechanism of action. The small molecule-based inhibitors targeting at the cell division protein FtsZ has been recognized as a promising approach to search for new antibacterial with high potency. In the present study, a series of novel 2,4-disubstituted-6-thiophenyl-pyrimidine derivatives were synthesized and their antibacterial activities against clinically related pathogens were investigated.

Efficient Synthesis of Amine-Linked 2,4,6-Trisubstituted Pyrimidines as a New Class of Bacterial FtsZ Inhibitors.

We have recently identified a new class of filamenting temperature-sensitive mutant Z (FtsZ)-interacting compounds that possess a 2,4,6-trisubstituted pyrimidine-quinuclidine scaffold with moderate antibacterial activity. Employing this scaffold as a molecular template, a compound library of amine-linked 2,4,6-trisubstituted pyrimidines with 99 candidates was successfully established by employing an efficient convergent synthesis designed to explore their structure-activity relationship. The results of minimum inhibitory concentration (MIC) assay against strains and cytotoxicity assay against the mouse L929 cell line identified those compounds with potent antistaphylococcal properties (MIC ranges from 3 to 8 μg/mL) and some extent of cytotoxicity against normal cells (IC ranges from 6 to 27 μM).

Investigation of synergistic antimicrobial effects of the drug combinations of meropenem and 1,2-benzisoselenazol-3(2H)-one derivatives on carbapenem-resistant Enterobacteriaceae producing NDM-1.

The worldwide prevalence of NDM-1-producing bacteria has drastically undermined the clinical efficacy of the last line antibiotic of carbapenems, prompting a need to devise effective strategy to preserve their clinical value. Our previous studies have shown that ebselen can restore the efficacy of meropenem against a laboratory strain that produces NDM-1. Here we report the construction of a focused compound library of 1,2-benzisoselenazol-3(2H)-one derivatives which comprise a total of forty-six candidate compounds.

Modified Penicillin Molecule with Carbapenem-Like Stereochemistry Specifically Inhibits Class C β-Lactamases.

Bacterial β-lactamases readily inactivate most penicillins and cephalosporins by hydrolyzing and "opening" their signature β-lactam ring. In contrast, carbapenems resist hydrolysis by many serine-based class A, C, and D β-lactamases due to their unique stereochemical features. To improve the resistance profile of penicillins, we synthesized a modified penicillin molecule, MPC-1, by "grafting" carbapenem-like stereochemistry onto the penicillin core.

Flavonoid dimers are highly potent killers of multidrug resistant cancer cells overexpressing MRP1.

MRP1 overexpression in multidrug-resistant cancer cells has been shown to be responsible for collateral sensitivity to some flavonoids that stimulate a huge MRP1-mediated GSH efflux. This massive GSH depletion triggers the death of these cancer cells. We describe here that bivalent flavonoid dimers strikingly stimulate such MRP1-mediated GSH efflux and trigger a 50-100 fold more potent cell death than their corresponding monomers.

A New Class of Safe, Potent, and Specific P-gp Modulator: Flavonoid Dimer FD18 Reverses P-gp-Mediated Multidrug Resistance in Human Breast Xenograft in Vivo.

Flavonoid dimer FD18 is a new class of dimeric P-gp modulator that can reverse cancer drug resistance. FD18 is a potent (EC50 = 148 nM for paclitaxel), safe (selective index = 574), and selective P-glycoprotein (P-gp) modulator. FD18 can modulate multidrug resistance toward paclitaxel, vinblastine, vincristine, doxorubicin, daunorubicin, and mitoxantrone in human breast cancer LCC6MDR in vitro.

Ebselen as a potent covalent inhibitor of New Delhi metallo-β-lactamase (NDM-1).

We report the discovery of a promising NDM-1 inhibitor, ebselen, through a cell-based screening approach. Enzymatic kinetic study and ESI-MS analysis suggested that ebselen could bind to NDM-1 by forming a S-Se bond with the Cys(221) residue at the active site, thereby exhibiting a new inhibition mechanism with broad spectrum inhibitory potential.

Structure-based design, synthesis, and biological evaluation of isatin derivatives as potential glycosyltransferase inhibitors.

Peptidoglycan glycosyltransferase (PGT) has been shown to be an important pharmacological target for the inhibition of bacterial cell wall biosynthesis. Structure-based virtual screening of about 3,000,000 commercially available compounds against the crystal structure of the glycosyltransferase (GT) domain of the Staphylococcus aureus penicillin-binding protein 2 (S. aureus PBP2) resulted in identification of an isatin derivative, 2-(3-(2-carbamimidoylhydrazono)-2-oxoindolin-1-yl)-N-(m-tolyl)acetamide (4) as a novel potential GT inhibitor.

Rational design of berberine-based FtsZ inhibitors with broad-spectrum antibacterial activity.

Inhibition of the functional activity of Filamenting temperature-sensitive mutant Z (FtsZ) protein, an essential and highly conserved bacterial cytokinesis protein, is a promising approach for the development of a new class of antibacterial agents. Berberine, a benzylisoquinoline alkaloid widely used in traditional Chinese and native American medicines for its antimicrobial properties, has been recently reported to inhibit FtsZ. Using a combination of in silico structure-based design and in vitro biological assays, 9-phenoxyalkyl berberine derivatives were identified as potent FtsZ inhibitors.