Short cationic antimicrobial peptides bind to human alpha‐1 acid glycoprotein with no implications for the in vitro bioactivity

Abstract

Several drugs interact with the major plasma proteins serum albumin and alpha-1 acid glycoprotein. Such binding may be either beneficial or disadvantageous from a pharmacokinetic perspective. In the present paper, we investigate the thermodynamics involved in the binding of a series of promising cationic antimicrobial peptides to the alpha-1 acid glycoprotein using isothermal titration calorimetry. The drug-like peptides are able to effectively destroy multiresistant bacterial strains, and members of this peptide class are currently in clinical phase II trials. Similar peptides, in a previous study, have been shown to bind to serum albumin resulting in a 10-fold reduction in the peptides ability to kill bacteria in vitro. Here, it is shown that the peptides also are ligands for alpha-1 glycoprotein with moderate binding affinities. The binding mode is investigated in detail using molecular docking, which maps the interaction to sub-pockets I, II and III of the binding site. Despite this interaction, protein binding is shown to have little or no effect on the ability of the peptides to kill bacteria in vitro, either at normal physiological or acute phase concentrations. The results show that although the peptides interact with the binding pocket of alpha-1 acid glycoprotein, the low stoichiometric binding ratio ensures that the interaction is not an obstacle for further development of these promising peptides as antimicrobial therapies.

Correlation between hemolytic activity, cytotoxicity and systemic in vivo toxicity of synthetic antimicrobial peptides

“…These types of compounds are cationic and amphiphilic, and they are prone to rapidly associate with both major exogenic transport plasma proteins serum albumin and α-1 glycoprotein. Recent studies illustrate that several binding modes are available for short cationic AMPs 41 , 80 , 81 to these carriers. Addition of serum albumin at physiological concentrations to a MIC-experiment effectively resulted in a tenfold reduction in potency illustrating the ability of albumin to soak up lipophilic AMPs 41 and this is a parameter not accounted for in the haemolysis experiment.…”

Very Short and Stable Lactoferricin-Derived Antimicrobial Peptides: Design Principles and Potential Uses

“…The peptides bound with a low stoichiometry (n = 0.1−0.3), ensuring that the peptides maintained their activity in assays incorporating ORM at physiological conditions, implying that ORM would have little effect on the performance of this family of compounds. 33 Inspired by the observed increased metabolic stabilities obtained from the fine-tuning of the peptide sequences, additional studies toward uptake were initiated through studying interactions with the human intestinal peptide transporter hPEPT1 and via passive routes. 34 Such a study not only answers important questions about the likely absorption via hPEPT1 but also provides insight into the mechanism behind substrate specificity and transport of the peptide transporter, as the peptides contain numerous unnatural elements.…”

“…While albumin binding was pronounced, the opposite was seen for ORM with a binding free energy between 6 and 7 kJ/mol. The peptides bound with a low stoichiometry ( n = 0.1–0.3), ensuring that the peptides maintained their activity in assays incorporating ORM at physiological conditions, implying that ORM would have little effect on the performance of this family of compounds …”

Efficient Prevention of Marine Biofilm Formation Employing a Surface-Grafted Repellent Marine Peptide

“…The concept of attaching a surface-active component to generate a bioactive interface has attracted a lot of research studies over recent years. , The lytic mechanism of AMPs has been the main driver to develop surfaces or polymers that kill settling bacteria. While this theory appears to be achievable, the near binary dose–activity relationship of AMPs combined with a need for a high degree of flexibility and rotational freedom to effectively exert its mode of action leads to a multitude of technological and chemical challenges. ,, Parameters such as peptide surface density, spacer length, and peptide attachment orientation have all been shown to play a big role in the performance of surfaces. , In addition, the bioactive lifespan of these surfaces in an in vivo or field situation needs addressing given the propensity of these compounds to associate with plasma proteins − and potentially become covered in cellular debris upon exerting its lytic mechanism. Dathe and co-workers have illustrated the importance of the spacer length for optimal antimicrobial activity for surface-tethered AMPs, , and Costa et al further reported the difference between N and C-terminal surface attachment on the antimicrobial effect of the AMP Dhvar5 .…”