Diseño y optimización de nuevos péptidos antimicrobianos contra bacterias gram-negativas
- Autores: Daniel Sandín García
- Directores de la Tesis: Marc Torrent Burgas (dir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2023
- Idioma: español
- Tribunal Calificador de la Tesis: Jaume Farrés Vicén (presid.), Sira Defaus Fornaguera (secret.), Salvatore Di Maro (voc.)
- Programa de doctorado: Programa de Doctorado en Bioquímica, Biología Molecular y Biomedicina por la Universidad Autónoma de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The emergence of new microbial drug resistances has conferred increasing harm to human health every year, of which multi-drug resistance is exceptionally problematic. Antimicrobial peptides (AMPs) are a bundle of molecules originating from all eukaryotic and prokaryotic kingdoms that show extraordinary activities not only against bacteria, as many studies have demonstrated their efficacy against virus, parasites, and tumors as well. Regarding their antibacterial activity, they are one of the most promising molecules to help conventional antibiotics to overcome drug-resistant bacteria. Their capacity for bacterial membrane disruption makes them ideal treatments to take the lead against the conventional ones already available, with incipient activity exhaustion, or to be used as coadjuvants to conventional treatments.
The purpose of the different studies performed for this thesis was to improve the understanding on the mode of action of AMPs, to discover new candidates against bacterial pathogens, and to improve the features of already discovered AMPs. During the study, the development of tolerance to several well-known peptides was evaluated. The results suggest that bacteria develop tolerance after several cycles of peptide application by lag. This tolerance appears to affect the use of conventional antibiotics depending on the mechanism of action, possibly affecting single and combinatorial therapies. The mutational landscape found in the evolved strains was varied, affecting different pathways. Some mechanisms were affected, as demonstrated in tolerance studies performed with conventional antibiotics.
In addition to this conceptual study, there are the de novo discovery and improvement of AMPs. A battery of peptides from heparin-binding proteins were synthetized. This peptide discovery was performed from a structural rational design point of view. The disaccharide core of gram-negative lipid A resembled that of heparin. Hence, sequences from heparin-binding proteins with antimicrobial activity may bind to this bacterial compound. The results obtained matched well with the hypothesis, which states that peptides are highly active against gram-negative bacteria but not much against gram-positive strains. High affinities to heparin and LPS binding were obtained from the designed peptides. We also found structural refolding in the presence of these molecules. Finally, the hECP30 peptide with origin in human RNase 3 was rationally modified at usual protease points with non-natural and synthetic residues substitutions to improve its stability. The last modifications offered more than 40-fold increase in human serum stability. Moreover, we found a similar activity in most stable analogs and toxicity reduction.
These findings provide interesting insights into the new ways of conducting basic research on AMP behavior and antibiotics. The projects focused on drug development in addition to introducing new promising antimicrobial agents, opening the scope to innovative approaches for the development of antimicrobial drugs.
