Glycosaminoglycans inhibit the antibacterial activity of LL-37 in biological fluids.
OBJECTIVE
The antibacterial activity of antimicrobial peptides is influenced by various factors such as salt content, pH and the presence of proteins. In this study, we explored the antibacterial action of the human cathelicidin LL-37 in physiologically relevant conditions, i.e. various human wound fluids, human plasma fractions and serum.


METHODS
Radial diffusion assays using Staphylococcus aureus and Escherichia coli were employed for the study of antibacterial effects of LL-37 in the presence of 12 different wound fluids, citrate-, heparin- or EDTA-plasma, or human serum. Glycosaminoglycan content of wound fluids was determined by an Alcian Blue-binding assay. Protein content of wound fluids was measured by the Bradford method. A slot-binding assay was used to study the effects of inhibitors on the interaction between LL-37 and glycosaminoglycans.


RESULTS
Five of twelve wound fluids derived from acute wounds showed marked inhibitory effects on the antibacterial action of LL-37. The inhibition was significantly correlated with high glycosaminoglycan content in wound fluid. Analogous to these findings, heparin-plasma strongly inhibited the antibacterial effect of LL-37. The interaction between LL-37 and glycosaminoglycans was abrogated by the cationic polymers DEAE-dextran and chitosan, yielding increased activity of LL-37.


CONCLUSIONS
Glycosaminoglycan-rich biological fluids inhibit the antibacterial effects of LL-37. Furthermore, polycations that bind to glycosaminoglycans increase the antibacterial activities of endogenous antimicrobial peptides in glycosaminoglycan-containing biological fluids.
Barańska-Rybak
W
W
Department of Dermatology, Venereology and Allergology, Medical University of Gdańsk, Debinki 7 Street, 80-288 Gdańsk, Poland.
Sonesson
A
A
Nowicki
R
R
Schmidtchen
A
A
D000900:Anti-Bacterial Agents / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D000925:Anticoagulants / Q000097:blood; D023181:Antimicrobial Cationic Peptides / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D001826:Body Fluids / Q000382:microbiology; D054804:Cathelicidins; D004926:Escherichia coli / Q000187:drug effects; D006025:Glycosaminoglycans / Q000032:analysis / Q000494:pharmacology*; D006493:Heparin / Q000097:blood; D008826:Microbial Sensitivity Tests; D010949:Plasma / Q000382:microbiology; D011485:Protein Binding; D013211:Staphylococcus aureus / Q000187:drug effects; D014947:Wounds and Injuries / Q000378:metabolism
D000900:Anti-Bacterial Agents; D000925:Anticoagulants; D023181:Antimicrobial Cationic Peptides; D054804:Cathelicidins; D006025:Glycosaminoglycans; D006493:Heparin