Cathelicidin LL-37 induces the generation of reactive oxygen species and release of human alpha-defensins from neutrophils.
BACKGROUND
Psoriasis is characterized by epidermal infiltration of neutrophils that destroy invading microorganisms via a potent antimicrobial arsenal of oxidants and antimicrobial agents. In contrast to atopic dermatitis, psoriasis exhibits low levels of skin infections due to the presence of antimicrobial agents, including cathelicidin LL-37. LL-37 kills a broad spectrum of microbes, and activates neutrophil chemotaxis.


OBJECTIVE
To determine whether or not LL-37 could regulate additional neutrophil functions such as production of cytokines/chemokines, reactive oxygen species and release of neutrophil antimicrobial peptides.


METHODS
Human peripheral blood neutrophils were used in this study. The production of interleukin (IL)-8 and release of alpha-defensins were analysed by enzyme-linked immunosorbent assay, and real-time polymerase chain reaction (PCR) was used to quantify alpha-defensin gene expression. Phosphorylation of mitogen-activated protein kinase (MAPK) was determined by Western blotting. The generation of reactive oxygen species was examined using flow cytometry, and intracellular Ca(2+) mobilization was measured using a calcium assay kit.


RESULTS
LL-37 enhanced the production of IL-8 under the control of MAPK p38 and extracellular signal regulated kinase (ERK), as evidenced by the inhibitory effects of p38 and ERK1/2 inhibitors on LL-37-mediated IL-8 production. Furthermore, LL-37 induced phosphorylation of p38 and ERK. We also revealed that LL-37 stimulated the generation of reactive oxygen species dose- and time-dependently, most probably via NADPH oxidase activation and intracellular Ca(2+) mobilization. Finally, LL-37 induced both mRNA expression and protein release of alpha-defensins, known as human neutrophil peptide 1-3.


CONCLUSIONS
Taken together, we suggest that in addition to its microbicidal properties, LL-37 may contribute to innate immunity by enhancing neutrophil host defence functions at inflammation and/or infection sites.
Zheng
Y
Y
Atopy (Allergy) Research Center, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
Niyonsaba
F
F
Ushio
H
H
Nagaoka
I
I
Ikeda
S
S
Okumura
K
K
Ogawa
H
H
D000975:Antioxidants / Q000494:pharmacology; D015153:Blotting, Western; D054804:Cathelicidins / Q000494:pharmacology*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D008297:Male; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism*; D023084:alpha-Defensins / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000975:Antioxidants; D054804:Cathelicidins; D016209:Interleukin-8; D017382:Reactive Oxygen Species; D023084:alpha-Defensins; D048051:p38 Mitogen-Activated Protein Kinases