AUTHOR=Cont Denisa , Harm Stephan , Schildböck Claudia , Kolm Claudia , Kirschner Alexander K. T. , Farnleitner Andreas H. , Pilecky Matthias , Zottl Jennifer , Hartmann Jens , Weber Viktoria 

TITLE=The neutralizing effect of heparin on blood-derived antimicrobial compounds: impact on antibacterial activity and inflammatory response

JOURNAL=Frontiers in Immunology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2024.1373255

DOI=10.3389/fimmu.2024.1373255

ISSN=1664-3224

ABSTRACT=<p>Acting through a combination of direct and indirect pathogen clearance mechanisms, blood-derived antimicrobial compounds (AMCs) play a pivotal role in innate immunity, safeguarding the host against invading microorganisms. Besides their antimicrobial activity, some AMCs can neutralize endotoxins, preventing their interaction with immune cells and avoiding an excessive inflammatory response. In this study, we aimed to investigate the influence of unfractionated heparin, a polyanionic drug clinically used as anticoagulant, on the endotoxin-neutralizing and antibacterial activity of blood-derived AMCs. Serum samples from healthy donors were pre-incubated with increasing concentrations of heparin for different time periods and tested against pathogenic bacteria (<italic>Acinetobacter baumannii</italic>, <italic>Enterococcus faecium</italic>, <italic>Escherichia coli</italic>, <italic>Klebsiella pneumoniae</italic>, <italic>Pseudomonas aeruginosa</italic>, <italic>Staphylococcus aureus</italic>) and endotoxins from <italic>E. coli</italic>, <italic>K. pneumonia</italic>e, and <italic>P. aeruginosa</italic>. Heparin dose-dependently decreased the activity of blood-derived AMCs. Consequently, pre-incubation with heparin led to increased activity of LPS and higher values of the pro-inflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6). Accordingly, higher concentrations of <italic>A. baumannii</italic>, <italic>E. coli</italic>, <italic>K. pneumoniae</italic>, and <italic>P. aeruginosa</italic> were observed as well. These findings underscore the neutralizing effect of unfractionated heparin on blood-derived AMCs <italic>in vitro</italic> and may lead to alternative affinity techniques for isolating and characterizing novel AMCs with the potential for clinical translation.</p>