The host defense peptide LL-37 triggers release of nucleic acids from human mast cells

• Published in: Peptides (New York, N.Y. : 1980) Vol. 109; pp. 39 - 45
• Main Authors: Dahl, Sara, Anders, Emma, Gidlöf, Olof, Svensson, Daniel, Nilsson, Bengt-Olof
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2018
• Subjects: Antimicrobial Cationic Peptides - metabolism; Basic Medicine; Cathelicidin; Cell and Molecular Biology; Cell Line; Cell viability; Cell- och molekylärbiologi; DNA - metabolism; Extracellular trap; Extracellular Traps - metabolism; Host defense peptide (HDP); Humans; Immunity, Innate; Immunologi inom det medicinska området; Immunology in the medical area; Innate immunity; Mast cells; Mast Cells - immunology; Mast Cells - metabolism; Medical and Health Sciences; Medicin och hälsovetenskap; Medicinska och farmaceutiska grundvetenskaper; Cathelicidin; Cell viability; Innate immunity; Mast cells; Extracellular trap; Host defense peptide (HDP)
• ISSN: 0196-9781; 1873-5169; 1873-5169
• DOI: 10.1016/j.peptides.2018.10.001

•LL-37 is internalized by human LAD2 mast cells and detected in cytoplasm and nuclei.•LL-37 reduces cell viability at high (4 and 10 μM) but not low (1 μM) concentrations.•LL-37 promotes release of both nucleic acids and lactate dehydrogenase from mast cells.•LL-37 does not trigger formation of extracellular trap-like structures by mast cells. The human host defense peptide LL-37 possesses antimicrobial activity but also affects host cell function and viability. Mast cells are involved in innate immunity but no data have been presented on effects of LL-37 on human mast cell viability and export of nucleic acids. Here, we demonstrated by immunofluorescence microscopy that synthesized LL-37 was internalized by human LAD2 mast cells and detected both in cytoplasm and nucleus. Treatment with high (4 and 10 μM) but not low (1 μM) concentrations of LL-37 for 4 h reduced cell viability assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Stimulation with 10 μM LL-37 for 4 h enhanced export of nucleic acids, total protein and lactate dehydrogenase (LDH), suggesting that both nuclear and plasma membranes are permeabilized by LL-37. Although LL-37 triggered release of nucleic acids, no extracellular trap-like structures were observed by laser scanning confocal microscopy of cells incubated with the plasma membrane impermeable nucleic acid fluorophore SYTOX-Green, indicating that LL-37 promotes export of nucleic acids but not formation of extracellular traps. On the other hand, phorbol-12-myristate-13-acetate (PMA), which is a well-known inducer of extracellular traps, stimulated export of nucleic acids and also formation of extracellular trap-like structures. However, PMA had no effect on export of either total protein or LDH. Hence, LL-37 and PMA seem to stimulate export of nucleic acids from LAD2 mast cells through different pathways. In conclusion, we demonstrate that LL-37 triggers release of nucleic acids from human mast cells but not the formation of extracellular trap-like structures.