RESUMO
Antibiotics with new mechanisms of action are urgently required to combat the growing health threat posed by resistant pathogenic microorganisms. We synthesized a family of peptidomimetic antibiotics based on the antimicrobial peptide protegrin I. Several rounds of optimization gave a lead compound that was active in the nanomolar range against Gram-negative Pseudomonas spp., but was largely inactive against other Gram-negative and Gram-positive bacteria. Biochemical and genetic studies showed that the peptidomimetics had a non-membrane-lytic mechanism of action and identified a homolog of the beta-barrel protein LptD (Imp/OstA), which functions in outer-membrane biogenesis, as a cellular target. The peptidomimetic showed potent antimicrobial activity in a mouse septicemia infection model. Drug-resistant strains of Pseudomonas are a serious health problem, so this family of antibiotics may have important therapeutic applications.
Assuntos
Antibacterianos/farmacologia , Proteínas da Membrana Bacteriana Externa/metabolismo , Membrana Celular/metabolismo , Peptídeos/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/metabolismo , Animais , Antibacterianos/síntese química , Antibacterianos/metabolismo , Peptídeos Catiônicos Antimicrobianos/química , Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/genética , Desenho de Fármacos , Farmacorresistência Bacteriana/genética , Genes Bacterianos , Lipopolissacarídeos/metabolismo , Camundongos , Testes de Sensibilidade Microbiana , Mimetismo Molecular , Mutação , Biblioteca de Peptídeos , Peptídeos/síntese química , Peptídeos/química , Peptídeos/metabolismo , Estrutura Terciária de Proteína , Infecções por Pseudomonas/tratamento farmacológico , Infecções por Pseudomonas/microbiologia , Pseudomonas aeruginosa/crescimento & desenvolvimento , Pseudomonas aeruginosa/ultraestrutura , Sepse/tratamento farmacológico , Sepse/microbiologiaRESUMO
The properties and structure-activity relationships (SAR) of a macrocyclic analogue of porcine protegrin I (PG-I) have been investigated. The lead compound, having the sequence cyclo-(-Leu-Arg-Leu-Lys-Lys-Arg-Arg-Trp-Lys-Tyr-Arg-Val-d-Pro-Pro-), shows antimicrobial activity against Gram-positive and -negative bacteria, but a much lower haemolytic activity and a much reduced ability to induce dye release from phosphatidylcholine/phosphatidylglycerol liposomes, when compared to PG-I. The enantiomeric form of the lead peptide shows comparable antimicrobial activity, a property shared with other cationic antimicrobial peptides acting on cell membranes. SAR studies involving the synthesis and biological profiling of over 100 single site substituted analogues, showed that the antimicrobial activity was tolerant to a large number of the substitutions tested. Some analogues showed slightly improved antimicrobial activities (2-4-fold lowering of MICs), whereas other substitutions caused large increases in haemolytic activity on human red blood cells.