Antibacterial cathelicidin peptide CAP11 inhibits the lipopolysaccharide (LPS)-induced suppression of neutrophil apoptosis by blocking the binding of LPS to target cells.
OBJECTIVE
The action of antibacterial cathelicidin CAP11 (cationic antibacterial polypeptide of 11 kDa) on the lipopolysaccharide (LPS)-induced suppression of neutrophil apoptosis was evaluated in vitro.


METHODS
Human neutrophils (10(6) cells/ml) were incubated alone or with mononuclear cells (6 x 10(5) cells/ml) in the presence of LPS (10 ng/ml) and CAP 11 (0.1 approximately 10 microg/ml), and neutrophil apoptosis was determined.


RESULTS
LPS suppressed neutrophil apoptosis, accompanied with the activation of NF-kappaB, phosphorylation of extracellular signal-related protein kinase (ERK), expression of Bcl-XL (an anti-apoptotic protein) and inhibition of caspase 3 activity. Interestingly, CAP11 (> 1 microg/ml) reversed the actions of LPS to trigger these changes, and induced neutrophil apoptosis (p < 0.0001). Moreover, neutralizing antibodies against Mac-1 (CD11b/CD18) and Toll-like receptor (TLR) 4 completely blocked the LPS-induced suppression of neutrophil apoptosis (p < 0.0001), suggesting a major role of Mac-1 and TLR4 in the LPS-mediated neutrophil activation. In addition, LPS activated monocytes to produce proinflammatory cytokines (IL-1beta, TNF-alpha and IL-8) and inhibited neutrophil apoptosis. Importantly, CAP11 (> 1 microg/ml) reduced the cytokine production, thereby inducing neutrophil apoptosis (p < 0.0001). Finally, CAP11 (> 1 microg/ml) strongly suppressed the LPS-binding to neutrophils and monocytes (p < 0.01).


CONCLUSIONS
CAP11 is able to block the LPS-induced survival of neutrophils via the suppression of anti-apoptotic signaling in neutrophils and cytokine production from monocytes by inhibiting the binding of LPS to target cells.
Nagaoka
I
I
Department of Host Defense and Biochemical Research, Juntendo University, School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. nagaokai@med.juntendo.ac.jp
Yomogida
S
S
Tamura
H
H
Hirata
M
M
D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D018920:Coculture Techniques; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis; D016209:Interleukin-8 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors* / Q000276:immunology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D051020:bcl-X Protein
D023181:Antimicrobial Cationic Peptides; C494811:BCL2L1 protein, human; C440609:CAP11 protein, Cavia; D007375:Interleukin-1; D016209:Interleukin-8; D008070:Lipopolysaccharides; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3