RESUMO
Increased incidence of infections with multidrug-resistant bacterial strains warrants an intensive search for novel potential antimicrobial agents. Here, an antimicrobial peptide analogue with a cationic/hydrophobic alternating design displaying only moderate activity against Gram-positive pathogens was optimized. Generally, introduction of hydrophobic moieties at the N-terminus resulted in analogues with remarkably increased activity against multidrug-resistant Staphylococcus aureus and Enterococcus faecium. Interestingly, the potency against Escherichia coli strains was unaffected, whereas modification with hydrophobic moieties led to increased activity towards the Gram-negative Acinetobacter baumannii. Despite increased cytotoxicity against murine fibroblasts and human umbilical vein endothelial cells, the optimized peptide analogues exhibited significantly improved cell selectivity. Overall, the most favorable hydrophobic activity-inducing moieties were found to be cyclohexylacetyl and pentafluorophenylacetyl groups, while the presence of a short PEG-like chain had no significant effect on activity. Introduction of cationic moieties conferred no effect or merely a moderate activity-promoting effect to the analogues.
Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Bactérias Gram-Positivas/efeitos dos fármacos , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/farmacologia , Animais , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Células Cultivadas , Eritrócitos/efeitos dos fármacos , Eritrócitos/microbiologia , Eritrócitos/fisiologia , Bactérias Gram-Positivas/fisiologia , Células Endoteliais da Veia Umbilical Humana , Humanos , Camundongos , Testes de Sensibilidade Microbiana/métodos , Células NIH 3T3 , Resultado do TratamentoRESUMO
Proton-coupled oligopeptide transporters (POTs) utilize an electrochemical proton gradient to accumulate peptides in the cytoplasm. Changing the highly conserved active-site Lys117 in the Escherichia coli POT YjdL to glutamine resulted in loss of ligand affinity as well as inability to distinguish between a dipeptide ligand and the corresponding dipeptide amide. The radically changed pH(Bulk) profiles of Lys117Gln and Lys117Arg mutants indicate an important role of Lys117 in facilitating protonation of the transporter; a notion that is supported by the close proximity of Lys117 to the conserved ExxERFxYY POT motif previously shown to be involved in proton translocation. These results point toward a novel dual role of Lys117 in direct or indirect interaction with both proton and peptide.
Assuntos
Proteínas de Escherichia coli/metabolismo , Lisina/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Oligopeptídeos/metabolismo , Prótons , Motivos de Aminoácidos/genética , Sequência de Aminoácidos , Sítios de Ligação/genética , Transporte Biológico/genética , Membrana Celular/metabolismo , Sequência Conservada/genética , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Glutamina/química , Glutamina/genética , Glutamina/metabolismo , Cinética , Lisina/química , Lisina/genética , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/genética , Modelos Moleculares , Dados de Sequência Molecular , Mutação de Sentido Incorreto , Oligopeptídeos/química , Ligação Proteica , Estrutura Terciária de Proteína , Homologia de Sequência de Aminoácidos , Especificidade por SubstratoRESUMO
Infections with multidrug-resistant pathogens are an increasing concern for public health. Recently, subtypes of peptide-peptoid hybrids were demonstrated to display potent activity against multidrug-resistant Gram-negative bacteria. Here, structural variation of these antibacterial peptidomimetics was investigated as a tool for optimizing cell selectivity. A protocol based on dimeric building blocks allowed for efficient synthesis of an array of peptide-peptoid oligomers representing length variation as well as different backbone designs displaying chiral or achiral peptoid residues. Lack of α-chirality in the side chains of the peptoid residues proved to be correlated to reduced cytotoxicity. Furthermore, optimization of the length of these peptidomimetics with an alternating cationic-hydrophobic design was a powerful tool to enhance the selectivity against Gram-negative pathogens over benign mammalian cells. Thus, lead compounds with a high selectivity toward killing of clinically important multidrug-resistant E. coli were identified.
Assuntos
Antibacterianos/farmacologia , Peptídeos Catiônicos Antimicrobianos/química , Peptídeos Catiônicos Antimicrobianos/farmacologia , Antineoplásicos/farmacologia , Proliferação de Células/efeitos dos fármacos , Resistência a Múltiplos Medicamentos/efeitos dos fármacos , Bactérias Gram-Negativas/efeitos dos fármacos , Peptidomiméticos/farmacologia , Dicroísmo Circular , Humanos , Lipossomos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Neoplasias/tratamento farmacológico , Neoplasias/patologia , Peptidomiméticos/química , Relação Estrutura-Atividade , Células Tumorais CultivadasRESUMO
The in vitro activity of a host defense peptidomimetic (HDM-4) was investigated. The compound exhibited an antimicrobial activity profile against a range of Gram-negative bacteria. HDM-4 permeabilized the outer membrane and partly depolarized the inner membrane at its minimal inhibitory concentration (MIC). Moreover, it was demonstrated that HDM-4 was distributed widely in the bacterial cell at lethal concentrations, and that it could bind to DNA. It was confirmed that the multimodal action of HDM-4 resulted in it being less likely to lead to resistance development as compared to single-target antibiotics. HDM-4 exhibited multispecies anti-biofilm activity at sub-MIC levels. Furthermore, HDM-4 modulated the immune response by inducing the release of the chemoattractants interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1), and MCP-3 from human peripheral blood mononuclear cells. In addition, the compound suppressed lipopolysaccharide-mediated inflammation by reducing the release of the pro-inflammatory cytokines IL-6 and tumor necrosis factor-α.
Assuntos
Anti-Infecciosos/metabolismo , Anti-Infecciosos/farmacologia , Peptidomiméticos/metabolismo , Peptidomiméticos/farmacologia , Proteólise , Biofilmes/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , DNA/metabolismo , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/fisiologia , Humanos , Imunomodulação/efeitos dos fármacos , Inflamação/induzido quimicamente , Inflamação/imunologia , Cinética , Lipopolissacarídeos/farmacologia , Estabilidade ProteicaRESUMO
Novel remedies in the battle against multidrug-resistant bacterial strains are urgently needed, and one obvious approach involves antimicrobial peptides and mimics hereof. The impact of α- and ß-peptoid as well as ß(3)-amino acid modifications on the activity profile against ß-lactamase-producing Escherichia coli was assessed by testing an array comprising different types of cationic peptidomimetics obtained by a general monomer-based solid-phase synthesis protocol. Most of the peptidomimetics possessed high to moderate activity toward multidrug-resistant E. coli as opposed to the corresponding inactive peptides. Nevertheless, differences in hemolytic activities indicate that a careful choice of backbone design constitutes a significant parameter in the search for effective cationic antimicrobial peptidomimetics targeting specific bacteria.
