Studying the effects of the combined action of proline-rich peptides of human saliva with antimicrobial proteins and peptides

Rationale. The substances that make up mixed saliva are active against bacteria, viruses and fungi. Among them, various cationic antimicrobial peptides (AMP) are distinguished: alpha- and beta-defensins, cathelicidins, histatins, but their concentration is relatively low. On the other hand, the fraction of proline-rich proteins (PRPs) and peptides that are the product of their proteolysis, the functions of which currently remain poorly studied and unclear, is widely represented in saliva.
The study of the antimicrobial activity of PBPs, in particular when they act together with AMPs, and deciphering the molecular cellular basis for the protective functions of proline-rich peptides is an urgent task in medicine and biology. The data obtained will help to understand the mechanisms of anti-infective protection of the oral cavity with the participation of the innate immune system, and will also make it possible in the future to create drugs based on human and animal PRP.
Target. Study of the individual antibacterial effect of salivary PRP, their combined effect with the antimicrobial proteins lactoferrin and lysozyme, as well as with one of the most significant endogenous protective peptides - cathelicidin LL-37 on the formation of bacterial biofilms.
Materials and methods. Human lactoferrin and egg lysozyme were used in this work. The minimum inhibitory concentrations of peptides against gram-negative and gram-positive bacteria were assessed using the method of serial dilutions in a liquid nutrient medium. Using serial checkerboard dilutions, it was shown that PRP can enhance the antibacterial activity of innate immune peptides present in the oral cavity. The ability of combinations of cationic proline-enriched peptides with cathelicidin LL-37 to prevent the formation of bacterial biofilms was studied.
Results. In the presence of proline-rich peptides, the antimicrobial activity of some AMP and proteins present in saliva against planktonic bacteria increases. When PBP is combined with LL-37, an increase in inhibition of the formation of bacterial biofilms is observed.
Conclusion. As a result of the study, it was shown that the analyzed cationic proline-rich peptides of human saliva exhibit anti-inflammatory effects, which suggests their significant role in the regulation of inflammatory processes in the oral cavity, as well as their participation in restorative processes.