Exploration of BAY 11-7082 as a Potential Antibiotic

Perturbation of Pseudomonas aeruginosa peptidoglycan recycling by anti-folates and design of a dual-action inhibitor

Peptidoglycan (PG) is an important bacterial macromolecule that confers cell shape and structural integrity, and is a key antibiotic target. Its synthesis and turnover are carefully coordinated with other cellular processes and pathways. Despite established connections between the biosynthesis of PG and the outer membrane, or PG and DNA replication, links between PG and folate metabolism remain comparatively unexplored. Folate is an essential cofactor for bacterial growth and is required for the synthesis of many important metabolites. Here we show that inhibition of folate synthesis in the important Gram-negative pathogen Pseudomonas aeruginosa has downstream effects on PG metabolism and integrity that can manifest as the formation of a subpopulation of round cells that can undergo explosive lysis. Folate inhibitors potentiated β-lactams by perturbation of PG recycling, reducing expression of the AmpC β-lactamase. Supporting this mechanism, folate inhibitors also synergized with fosfomycin, an inhibitor of MurA, the first committed step in PG synthesis that can be bypassed by PG recycling. These insights led to the design of a dual-active inhibitor that overcomes NDM-1 metallo-β lactamase-mediated meropenem resistance and synergizes with the folate inhibitor, trimethoprim. We show that folate and PG metabolism are intimately connected, and targeting this connection can overcome antibiotic resistance in Gram-negative pathogens.

IMPORTANCE

To combat the alarming global increase in superbugs amid the simultaneous scarcity of new drugs, we can create synergistic combinations of currently available antibiotics or chimeric molecules with dual activities, to minimize resistance. Here we show that older anti-folate drugs synergize with specific cell wall biosynthesis inhibitors to kill the priority pathogen, Pseudomonas aeruginosa. Anti-folate drugs caused a dose-dependent loss of rod cell shape followed by explosive lysis, and synergized with β-lactams that target D,D-carboxypeptidases required to tailor the cell wall. Anti-folates impaired cell wall recycling and subsequent downstream expression of the chromosomally encoded β-lactamase, AmpC, which normally destroys β-lactam antibiotics. Building on the anti-folate-like scaffold of a metallo-β-lactamase inhibitor, we created a new molecule, MLLB-2201, that potentiates β-lactams and anti-folates and restores meropenem activity against metallo-β-lactamase-expressing Escherichia coli. These strategies are useful ways to tackle the ongoing rise in dangerous bacterial pathogens.

Importin α inhibitors act against the differentiated stages of apicomplexan parasites Plasmodium falciparum and Toxoplasma gondii

BACKGROUND

Nuclear import, dependent on the transporter importin α (IMPα), is a drug target for apicomplexan parasites Plasmodium falciparum and Toxoplasma gondii. Indeed, a panel of small molecule inhibit interactions between IMPα and nuclear localization signals (NLSs) in vitro and the growth of rapidly dividing stages (P. falciparum blood stages and T. gondii tachyzoites) in culture.

OBJECTIVES

As new drugs targeting multiple life cycle stages of both parasites are required, the panel of IMPα inhibitors was tested for their ability to inhibit nuclear transport in the rapidly dividing stages and the maturation of differentiated stages (P. falciparum gametocytes and T. gondii bradyzoites).

METHODS

Using biophysical assays, Bay 11-7082, a Bay 11-7085 structural analogue, was tested for inhibition of IMPα:NLS interactions. The effect of the panel of inhibitors on the nuclear localization of reporter proteins was analysed in both parasites using transfections and microscopy. Also, using microscopy, the effect of inhibitors on differentiated stages of both parasites was tested.

RESULTS

Bay 11-7085 can inhibit nuclear transport in tachyzoites, while GW5074 and Caffeic Acid Phenethyl Ester (CAPE) can inhibit nuclear transport in the blood stages. Interestingly, CAPE can strongly inhibit gametocyte maturation, and Bay 11-7082 and Bay 11-7085 weakly inhibit bradyzoite differentiation.

CONCLUSIONS

As differentiation of gametocytes and bradyzoites is dependent on the activation of gene expression triggered by the nuclear translocation of transcription factors, our work provides a 'proof of concept' that targeting nuclear import is a viable strategy for the development of therapeutics against multiple stages of apicomplexan parasites, some of which are recalcitrant to existing drugs.

UBE2N: Hope on the Cancer Front, How to Inhibit This Promising Target Prospect?

UBE2N protein belongs to the UE2s family and plays a crucial role in DNA repair, making it an exciting target for the development of innovative anticancer therapies. With the aim of discovering UBE2N inhibitors (UBE2Ni), this perspective seeks to review and provide elements to guide the design of new compounds. We propose a chemoinformatic structural analysis of the protein and its areas of interaction with its different partners. While covalent UBE2Ni are the most advanced molecules in their development, noncovalent inhibitors offer significant advantages that could overcome the limitations of covalent ones, particularly in terms of selectivity. Lastly, to obtain a drug candidate, early assessment of the druggability of compounds is essential in a hit to lead process. For existing UBE2Ni, a critical challenge lies in their pharmacokinetic properties and will obviously have to be considered as early as possible to hope for an application in human therapy.

The Role and the Regulation of NLRP3 Inflammasome in Irritable Bowel Syndrome: A Narrative Review

Irritable bowel syndrome (IBS) is a chronic disorder of the gastrointestinal tract. Its pathogenesis involves multiple factors, including visceral hypersensitivity and immune activation. NLRP3 inflammasome is part of the nucleotide-binding oligomerization domain-like receptor (NLR) family, a crucial component of the innate immune system. Preclinical studies have demonstrated that inhibiting NLRP3 reduces visceral sensitivity and IBS symptoms, like abdominal pain, and diarrhea, suggesting that targeting the NLRP3 might represent a novel therapeutic approach for IBS. This review aims to assess the NLRP3 inhibitors (tranilast, β-hydroxybutyrate, Chang-Kang-fang, paeoniflorin, coptisine, BAY 11-7082, and Bifidobacterium longum), highlighting the signaling pathways, and their potential role in IBS symptoms management was assessed. Although premature, knowledge of the action of synthetic small molecules, phytochemicals, organic compounds, and probiotics might make NLRP3 a new therapeutic target in the quiver of physicians' therapeutic choices for IBS symptoms management.

War and peace: exploring microbial defence systems as a source of new antimicrobial therapies

The WHO has compiled a list of pathogens that urgently require new antibiotics in response to the rising reports of antibiotic resistance and a diminished supply of new antibiotics. At the top of this list is fluoroquinolone-resistant Salmonella typhi, fluoroquinolone-resistant Shigella spp. and vancomycin-resistant Enterococcus faecium. Although these problems have been covered in great detail by other contemporary reviews, there are still some fundamental gaps in the translation of current knowledge of the infectious process and the molecular ecology of antibiotic production into a sustainable protocol for the treatment of pathogenic diseases. Therefore, in this narrative review we briefly discuss newly approved antimicrobial drugs (since 2014) that could help to alleviate the burden of multiresistant pathogens listed on the WHO priority list. Being conscious that such treatments may eventually run the risk of future cycles of resistance, we also discuss how new understandings in the molecular ecology of antibiotic production and the disease process can be harnessed to create a more sustainable solution for the treatment of pathogenic diseases.

Covalent Inhibitors of S100A4 Block the Formation of a Pro-Metastasis Non-Muscle Myosin 2A Complex

The S100 protein family functions as protein-protein interaction adaptors regulated by Ca2+ binding. Formation of various S100 complexes plays a central role in cell functions, from calcium homeostasis to cell signaling, and is implicated in cell growth, migration, and tumorigenesis. We established a suite of biochemical and cellular assays for small molecule screening based on known S100 protein-protein interactions. From 25 human S100 proteins, we focused our attention on S100A4 because of its well-established role in cancer progression and metastasizes by interacting with nonmuscle myosin II (NMII). We identified several potent and selective inhibitors of this interaction and established the covalent nature of binding, confirmed by mass spectrometry and crystal structures. 5b showed on-target activity in cells and inhibition of cancer cell migration. The identified S100A4 inhibitors can serve as a basis for the discovery of new cancer drugs operating via a novel mode of action.

Targeting bacterial nickel transport with aspergillomarasmine A suppresses virulence-associated Ni-dependent enzymes

Microbial Ni2+ homeostasis underpins the virulence of several clinical pathogens. Ni2+ is an essential cofactor in urease and [NiFe]-hydrogenases involved in colonization and persistence. Many microbes produce metallophores to sequester metals necessary for their metabolism and starve competing neighboring organisms. The fungal metallophore aspergillomarasmine A (AMA) shows narrow specificity for Zn2+, Ni2+, and Co2+. Here, we show that this specificity allows AMA to block the uptake of Ni2+ and attenuate bacterial Ni-dependent enzymes, offering a potential strategy for reducing virulence. Bacterial exposure to AMA perturbs H2 metabolism, ureolysis, struvite crystallization, and biofilm formation and shows efficacy in a Galleria mellonella animal infection model. The inhibition of Ni-dependent enzymes was aided by Zn2+, which complexes with AMA and competes with the native nickelophore for the uptake of Ni2+. Biochemical analyses demonstrated high-affinity binding of AMA-metal complexes to NikA, the periplasmic substrate-binding protein of the Ni2+ uptake system. Structural examination of NikA in complex with Ni-AMA revealed that the coordination geometry of Ni-AMA mimics the native ligand, Ni-(L-His)2, providing a structural basis for binding AMA-metal complexes. Structure-activity relationship studies of AMA identified regions of the molecule that improve NikA affinity and offer potential routes for further developing this compound as an anti-virulence agent.

The vinyl sulfone motif as a structural unit for novel drug design and discovery

INTRODUCTION

Vinyl sulfones are a special sulfur-containing structural unit that have attracted considerable attention, owing to their important role in serving as key structural motifs of various biologically active compounds as well as serving as versatile building blocks for organic transformations. The synthetic strategy of vinyl sulfone derivatives has been substantially upgraded over the past 30 years, and the wide application of this functional group in drug design and discovery has been promoted.

AREA COVERED

In this review, the authors review the application of vinyl sulfones in drug discovery and select optimized compounds which might have significant impact or potential inspiration for drug design.

EXPERT OPINION

Vinyl sulfones have been reported to target various macromolecular targets via non-covalent or covalent interactions, including multiple kinases, tubulin, cysteine protease, transcription factor, and so on. Thus, it has been significantly applied as a privileged scaffold in the design of anticancer, anti-infective, anti-inflammatory, and neuroprotective agents. However, much work remains to be done to improve the drug-like properties, such as chemical and metabolic stability, ADME, and toxicity. Besides, the chemical space of vinyl sulfones needs to be expanded, including but not limited to the design of constrained endocyclic and exocyclic vinyl sulfones.

Central metabolism is a key player in E. coli biofilm stimulation by sub-MIC antibiotics

Exposure of Escherichia coli to sub-inhibitory antibiotics stimulates biofilm formation through poorly characterized mechanisms. Using a high-throughput Congo Red binding assay to report on biofilm matrix production, we screened ~4000 E. coli K12 deletion mutants for deficiencies in this biofilm stimulation response. We screened using three different antibiotics to identify core components of the biofilm stimulation response. Mutants lacking acnA, nuoE, or lpdA failed to respond to sub-MIC cefixime and novobiocin, implicating central metabolism and aerobic respiration in biofilm stimulation. These genes are members of the ArcA/B regulon-controlled by a respiration-sensitive two-component system. Mutants of arcA and arcB had a 'pre-activated' phenotype, where biofilm formation was already high relative to wild type in vehicle control conditions, and failed to increase further with the addition of sub-MIC cefixime. Using a tetrazolium dye and an in vivo NADH sensor, we showed spatial co-localization of increased metabolic activity with sub-lethal concentrations of the bactericidal antibiotics cefixime and novobiocin. Supporting a role for respiratory stress, the biofilm stimulation response to cefixime and novobiocin was inhibited when nitrate was provided as an alternative electron acceptor. Deletion of a gene encoding part of the machinery for respiring nitrate abolished its ameliorating effects, and nitrate respiration increased during growth with sub-MIC cefixime. Finally, in probing the generalizability of biofilm stimulation, we found that the stimulation response to translation inhibitors, unlike other antibiotic classes, was minimally affected by nitrate supplementation, suggesting that targeting the ribosome stimulates biofilm formation in distinct ways. By characterizing the biofilm stimulation response to sub-MIC antibiotics at a systems level, we identified multiple avenues for design of therapeutics that impair bacterial stress management.

Role of the NLRP3 inflammasome in gynecological disease

The NLR family pyrin domain containing 3 (NLRP3) inflammasome is involved in the innate immune system and is a three-part macromolecular complex comprising the NLRP3 protein, apoptosis-associated speck-like protein containing a CARD (ASC) and the cysteine protease pro-caspase-1. When the NLRP3 inflammasome is activated, it can produce interleukin (IL)- 1β and IL-18 and eventually lead to inflammatory cell pyroptosis. Related studies have demonstrated that the NLRP3 inflammasome can induce an immune response and is related to the occurrence and development of gynecological diseases, such as endometriosis, polycystic ovary syndrome and breast cancer. NLRP3 inflammasome inhibitors are beneficial for maintaining cellular homeostasis and tissue health and have been found effective in targeting some gynecological diseases. However, excessive inhibitor concentrations have been found to cause adverse effects. Therefore, proper control of NLRP3 inflammasome activity is critical. This paper summarizes the structure and function of the NLRP3 inflammasome and highlights the therapeutic potential of targeting it in gynecological diseases, such as endometriosis, polycystic ovary syndrome and breast cancer The application of NLRP3 inflammasome inhibitors is also discussed.

Utilization of Existing Human Kinase Inhibitors as Scaffolds in the Development of New Antimicrobials

The prevalence and continuing expansion of drug resistance, both in clinical and community settings represents a major challenge for current antimicrobial therapy. The different approaches for addressing this challenge include (1) identification of novel antibacterials by repurposing of existing drugs originally that historically target host proteins; and (2) effect target switching through modification of existing antimicrobials. The focus of this manuscript is on these drug discovery strategies, with utility for development of new antimicrobials with different modes of action.

Pyroptosis in renal inflammation and fibrosis: current knowledge and clinical significance

Pyroptosis is a novel inflammatory form of regulated cell death (RCD), characterized by cell swelling, membrane rupture, and pro-inflammatory effects. It is recognized as a potent inflammatory response required for maintaining organismal homeostasis. However, excessive and persistent pyroptosis contributes to severe inflammatory responses and accelerates the progression of numerous inflammation-related disorders. In pyroptosis, activated inflammasomes cleave gasdermins (GSDMs) and generate membrane holes, releasing interleukin (IL)-1β/18, ultimately causing pyroptotic cell death. Mechanistically, pyroptosis is categorized into caspase-1-mediated classical pyroptotic pathway and caspase-4/5/11-mediated non-classical pyroptotic pathway. Renal fibrosis is a kidney disease characterized by the loss of structural and functional units, the proliferation of fibroblasts and myofibroblasts, and extracellular matrix (ECM) accumulation, which leads to interstitial fibrosis of the kidney tubules. Histologically, renal fibrosis is the terminal stage of chronic inflammatory kidney disease. Although there is a multitude of newly discovered information regarding pyroptosis, the regulatory roles of pyroptosis involved in renal fibrosis still need to be fully comprehended, and how to improve clinical outcomes remains obscure. Hence, this review systematically summarizes the novel findings regarding the role of pyroptosis in the pathogenesis of renal fibrosis and discusses potential biomarkers and drugs for anti-fibrotic therapeutic strategies.