Neutrophil antimicrobial defense against Staphylococcus aureus is mediated by phagolysosomal but not extracellular trap-associated cathelicidin

Abstract

Neutrophils kill invading pathogens by AMPs, including cathelicidins, ROS, and NETs. The human pathogen Staphylococcus aureus exhibits enhanced resistance to neutrophil AMPs, including the murine cathelicidin CRAMP, in part, as a result of alanylation of teichoic acids by the dlt operon. In this study, we took advantage of the hypersusceptible phenotype of S. aureus DeltadltA against cationic AMPs to study the impact of the murine cathelicidin CRAMP on staphylococcal killing and to identify its key site of action in murine neutrophils. We demonstrate that CRAMP remained intracellular during PMN exudation from blood and was secreted upon PMA stimulation. We show first evidence that CRAMP was recruited to phagolysosomes in infected neutrophils and exhibited intracellular activity against S. aureus. Later in infection, neutrophils produced NETs, and immunofluorescence revealed association of CRAMP with S. aureus in NETs, which similarly killed S. aureus wt and DeltadltA, indicating that CRAMP activity was reduced when associated with NETs. Indeed, the presence of DNA reduced the antimicrobial activity of CRAMP, and CRAMP localization in response to S. aureus was independent of the NADPH oxidase, whereas killing was partially dependent on a functional NADPH oxidase. Our study indicates that neutrophils use CRAMP in a timed and locally coordinated manner in defense against S. aureus.

Afa/Dr Diffusely Adhering Escherichia coli Strain C1845 Induces Neutrophil Extracellular Traps That Kill Bacteria and Damage Human Enterocyte-Like Cells

“…Some bacteria, such as Mycobacterium tuberculosis, cannot be killed by NETs (44), but a variety of other pathogens are very sensitive to killing by high local concentrations of antimicrobial components such as proteases and histones from NETs (9,26,52). In addition to elastase, MPO, and defensins, other mediators recently implicated in netosis include the LL-37 cathelicidin against S. flexneri (23) and Staphylococcus aureus (33) and calprotectin against Candida albicans (52). Nucleus-derived histones also play a role in pathogen killing by NETs, notably, during Leishmania amazonensis infection (31).…”

Toxicity and antibacterial assessment of chitosan-coated silver nanoparticles on human pathogens and macrophage cells

“…46 Previous studies have shown that latex beads and antimicrobial peptides target the macrophage phagosomes, resulting in increased maturation of phagosomes 46 and intracellular killing of S. aureus, 47 respectively. The authors also observed active uptake of PI-labeled CS-AgNPs by macrophages.…”

Cancers predispose neutrophils to release extracellular DNA traps that contribute to cancer-associated thrombosis

“…No increase was observed in the tumor-bearing mice treated with vehicle or in the tumor-free mice treated with LPS, suggesting a stronger effect of LPS on chromatin release in the tumor-bearing mice. To assess whether DNA originated from NETs, we evaluated the presence of cathelicidin-related antimicrobial peptide (CRAMP), the murine homolog of human cathelicidin, a protein highly expressed in neutrophils and shown to be associated with NETs (29), and H3Cit in the plasma. Whereas a small increase in CRAMP was observed in the plasma of LPS-treated tumor-free mice, a higher level was observed in the plasma of LPS-treated tumor-bearing mice (Fig.…”