Putative histidine kinase inhibitors with antibacterial effect against multi-drug resistant clinical isolates identified by in vitro and in silico screens

Novel antibacterials are urgently needed to address the growing problem of bacterial resistance to conventional antibiotics. Two-component systems (TCS) are widely used by bacteria to regulate gene expression in response to various environmental stimuli and physiological stress and have been previously proposed as promising antibacterial targets. TCS consist of a sensor histidine kinase (HK) and an effector response regulator. The HK component contains a highly conserved ATP-binding site that is considered to be a promising target for broad-spectrum antibacterial drugs. Here, we describe the identification of putative HK autophosphorylation inhibitors following two independent experimental approaches: in vitro fragment-based screen via differential scanning fluorimetry and in silico structure-based screening, each followed up by the exploration of analogue compounds as identified by ligand-based similarity searches. Nine of the tested compounds showed antibacterial effect against multi-drug resistant clinical isolates of bacterial pathogens and include three novel scaffolds, which have not been explored so far in other antibacterial compounds. Overall, putative HK autophosphorylation inhibitors were found that together provide a promising starting point for further optimization as antibacterials

Physicochemical-guided design of cathelicidin-derived peptides generates membrane active variants with therapeutic potential.

The spread of multi-drug resistance and the slow pace at which antibiotics come onto the market are undermining our ability to treat human infections, leading to high mortality rates. Aiming to overcome this global crisis, antimicrobial peptides are considered promising alternatives to counter bacterial infections with multi-drug resistant bacteria. The cathelicidins comprise a well-studied class of AMPs whose members have been used as model molecules for sequence modifications, aiming at enhanced biological activities and stability, along with reduced toxic effects on mammalian cells. Here, we describe the antimicrobial activities, modes of action and structural characterization of two novel cathelicidin-like peptides, named BotrAMP14 and CrotAMP14, which were re-designed from snake batroxicidin and crotalicidin, respectively. BotrAMP14 and CrotAMP14 showed broad-spectrum antibacterial activity against susceptible microorganisms and clinical isolates with minimal inhibitory concentrations ranging from 2-35.1 μM. Moreover, both peptides had low cytotoxicity against Caco-2 cells in vitro. In addition, in vivo toxicity against Galleria mellonella moth larvae revealed that both peptides led to>76% larval survival after 144 h. Microscopy studies suggest that BotrAMP14 and CrotAMP14 destabilize E. coli membranes. Furthermore, circular dichroism and molecular dynamics simulations indicate that, in a membrane-like environment, both peptides adopt α-helical structures that interact with bilayer phospholipids through hydrogen bonds and electrostatic interaction. Thus, we concluded that BotrAMP14 and CrotAMP14 are helical membrane active peptides, with similar antibacterial properties but lower cytotoxicity than the larger parent peptides batroxicidin and crotalicidin, having advantages for drug development strategies

Repurposing Hsp90 inhibitors as antimicrobials targeting two-component systems identifies compounds leading to loss of bacterial membrane integrity

19 páginas, 7 figuras, 2 tablasThe discovery of antimicrobials with novel mechanisms of action is crucial to tackle the foreseen global health crisis due to antimicrobial resistance. Bacterial two-component signaling systems (TCSs) are attractive targets for the discovery of novel antibacterial agents. TCS-encoding genes are found in all bacterial genomes and typically consist of a sensor histidine kinase (HK) and a response regulator. Due to the conserved Bergerat fold in the ATP-binding domain of the TCS HK and the human chaperone Hsp90, there has been much interest in repurposing inhibitors of Hsp90 as antibacterial compounds. In this study, we explore the chemical space of the known Hsp90 inhibitor scaffold 3,4-diphenylpyrazole (DPP), building on previous literature to further understand their potential for HK inhibition. Six DPP analogs inhibited HK autophosphorylation in vitro and had good antimicrobial activity against Gram-positive bacteria. However, mechanistic studies showed that their antimicrobial activity was related to damage of bacterial membranes. In addition, DPP analogs were cytotoxic to human embryonic kidney cell lines and induced the cell arrest phenotype shown for other Hsp90 inhibitors. We conclude that these DPP structures can be further optimized as specific disruptors of bacterial membranes providing binding to Hsp90 and cytotoxicity are lowered. Moreover, the X-ray crystal structure of resorcinol, a substructure of the DPP derivatives, bound to the HK CheA represents a promising starting point for the fragment-based design of novel HK inhibitors. Importance: The discovery of novel antimicrobials is of paramount importance in tackling the imminent global health crisis of antimicrobial resistance. The discovery of novel antimicrobials with novel mechanisms of actions, e.g., targeting bacterial two-component signaling systems, is crucial to bypass existing resistance mechanisms and stimulate pharmaceutical innovations. Here, we explore the possible repurposing of compounds developed in cancer research as inhibitors of two-component systems and investigate their off-target effects such as bacterial membrane disruption and toxicity. These results highlight compounds that are promising for further development of novel bacterial membrane disruptors and two-component system inhibitors.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement number 765147 and grants PID2019-108541GB-I00 from the Spanish Government (Ministry of Science and Innovation) and PROMETEO/2020/012 by the Valencian Government to A.M. We also thank the Utrecht Medical Centre (UMC) group from prof. Rob Willems for providing the enterococci.Peer reviewe

Broadening the antibacterial spectrum of histidine kinase autophosphorylation inhibitors via the use of epsilon-poly-L-lysine capped mesoporous silica-based nanoparticles

[EN] Two-component systems (TCS) regulate diverse processes such as virulence, stress responses, metabolism and antibiotic resistance in bacteria but are absent in humans, making them promising targets for novel antibacterials. By incorporating recently described TCS histidine kinase autophosphorylation inhibitors (HKAIs) into epsilon-poly-L-lysine capped nanoparticles (NPs) we could overcome the Gram negative (Gr(-)) permeability barrier for the HKAIs. The observed bactericidal activity against Gr(-) bacteria was shown to be due to the enhanced delivery and internalization of the HKAIs and not an inhibitory or synergistic effect of the NPs. The NPs had no adverse effects on mammalian cell viability or the immune function of macrophages in vitro and showed no signs of toxicity to zebrafish larvae in vivo. These results show that HKAIs are promising antibacterials for both Gr(-) and Gr + pathogens and that NPs are a safe drug delivery technology that can enhance the selectivity and efficacy of HKAIs against bacteria. (C) 2016 Elsevier Inc. All rights reserved.This work was funded by FP7 ITN STARS-Scientific Training in Antimicrobial Research Strategies (Contract No. PITN-GA-2009-238490, J.M.W., A.M.), H2020 MSCA IF (AND-659121, N.V.), grant BIO2013-42619-P from the Ministerio de Economia y Competitividad (A.M.), grant from the Spanish Government (Project MAT2015-64139-C4-1-R,N. M., J.R.M, R.M.M.), and a grant from Generalitat Valenciana (Project PROMETEOII/2014/047, N.M.). and Prometeo II/2014/029, A.M.).Velikova, N.; Mas Font, N.; Miguel-Romero, L.; Polo, L.; Stolte, E.; Zaccaria, E.; Cao, R.... (2017). Broadening the antibacterial spectrum of histidine kinase autophosphorylation inhibitors via the use of epsilon-poly-L-lysine capped mesoporous silica-based nanoparticles. Nanomedicine Nanotechnology Biology and Medicine. 13(2):569-581. https://doi.org/10.1016/j.nano.2016.09.011S56958113

An acidic model pro-peptide affects the secondary structure, membrane interactions and antimicrobial activity of a crotalicidin fragment

In order to study how acidic pro-peptides inhibit the antimicrobial activity of antimicrobial peptides, we introduce a simple model system, consisting of a 19 amino-acid long antimicrobial peptide, and an N-terminally attached, 10 amino-acid long acidic model pro-peptide. The antimicrobial peptide is a fragment of the crotalicidin peptide, a member of the cathelidin family, from rattlesnake venom. The model pro-peptide is a deca (glutamic acid). Attachment of the model pro-peptide only leads to a moderately large reduction in the binding to- and induced leakage of model liposomes, while the antimicrobial activity of the crotalicidin fragment is completely inhibited by attaching the model pro-peptide. Attaching the pro-peptide induces a conformational change to a more helical conformation, while there are no signs of intra- or intermolecular peptide complexation. We conclude that inhibition of antimicrobial activity by the model pro-peptide might be related to a conformational change induced by the pro-peptide domain, and that additional effects beyond induced changes in membrane activity must also be involved.</p

Evaluation of Galleria mellonella larvae for studying the virulence of Streptococcus suis

Background: Streptococcus suis is an encapsulated Gram-positive bacterium and the leading cause of sepsis and meningitis in young pigs, resulting in considerable economic losses in the porcine industry. S. suis is considered an emerging zoonotic agent with increasing numbers of human cases over the last years. In the environment, both avirulent and virulent strains occur in pigs, with no evidence for consistent adapatation of virulent strains to the human host. Currently, there is an urgent need for a convenient, reliable and standardised animal model to rapidly assess S. suis virulence. Wax moth (Galleria mellonella) larvae have successfully been used in human and animal infectious disease studies. Here, we developed G. mellonella larvae as a model to assess virulence of S. suis strains. Results: Fourteen isolates of S. suis belonging to different serotypes killed G. mellonella larvae in a dose-dependent manner. Larvae infected with the virulent serotype 2 strain, S. suis S3881/S10, were rescued by antibiotic therapy. Crucially, the observed virulence of the different serotypes and mutants was in agreement with virulence observed in piglets (Sus scrofa) and the zebrafish larval infection model. Infection with heat-inactivated bacteria or bacteria-free culture supernatants showed that in most cases live bacteria are needed to cause mortality in G. mellonella. Conclusions: The G. mellonella model is simple, cost-efficient, and raises less ethical issues than experiments on vertebrates and reduces infrastructure requirements. Furthermore, it allows experiments to be performed at the host temperature (37 °C). The results reported here, indicate that the G. mellonella model may aid our understanding of veterinary microbial pathogens such as the emerging zoonotic pathogen S. suis and generate hypotheses for testing in the target animal host. Ultimately, this might lead to the timely introduction of new effective remedies for infectious diseases. Last but not least, use of the G. mellonella infection model to study S. suis virulence adheres to the principles of replacement, reduction and refinement (3Rs) and can potentially reduce the number of vertebrates used for experimental infection studies

Additional file 1: Figure S1. of Evaluation of Galleria mellonella larvae for studying the virulence of Streptococcus suis

LD50s of tested strains. Figure S2. Infection with S. suis triggers melanisation in G. mellonella larvae. Figure S3. Effect of cell-free supernatant and heat-inactivated inocula on G. mellonella larvae survivial. Table S1. LD50s of tested strains. (DOC 2250 kb)

Inhibidores de la histidina quinasa con actividad antibacteriana

The present invention relates to a group of compounds of formula (I) and (II) with autophosphorylation inhibition activity and antibacterial activity against different Gram bacterla Staphylococcus aureus and Staphyloccus epidermidis among others, and to the use of said compounds for the manufacturing of antibiotics.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Wageningen Universiteit, Inhibox LimitedA3 Informe de búsqueda internaciona

Histidine kinase inhibitors with antibacterial activity

Inhibidores de la histidina guinasa con actividad antibacteriana. La presente invención se refiere a un grupo de compuestos con actividad inhibidora de la autofosforilación y actividad antibacteriana frente a diferentes bacterias como Staphylococcus aureus y Staphylococcus epidermidis entre otras, y al uso de dichos compuestos para la fabricación de antibióticos.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Wageningen Universiteit, Inhibox LimitedA2 Solicitud de patente sin informe sobre el estado de la técnic