The antimicrobial peptide LL-37 induces synthesis and release of cysteinyl leukotrienes from human eosinophils – implications for asthma

Authors

  • J. Sun,

    1. Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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  • B. Dahlén,

    1. The Centre for Allergy Research, Stockholm, Sweden
    2. The Division of Respiratory Medicine and Allergy, Department of Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
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  • B. Agerberth,

    1. Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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    • These two authors contributed equally to this manuscript.
  • J. Z. Haeggström

    Corresponding author
    • Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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    • These two authors contributed equally to this manuscript.

  • Edited by: Hans-Uwe Simon

Correspondence

Jesper Z. Haeggström, MD, PhD, Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden.

Tel.: +46 8 524 87612

Fax: +46 8 736 0439

E-mail: jesper.haeggstrom@ki.se

Abstract

Background

Eosinophils and their products, including leukotrienes and eosinophil cationic protein (ECP), are well-known mediators of inflammation and tissue damage in asthma. The antimicrobial peptide LL-37 exhibits a variety of immunomodulatory activities. However, the role of LL-37 in asthma has not been fully addressed. Here, we aim to investigate the effect of LL-37 on inducing inflammatory mediators in human eosinophils, probe the underlying mechanisms, and search for a clinical correlate.

Methods

Primary eosinophils were isolated from peripheral blood. Leukotriene and ECP levels were measured using EIAs or ELISAs. Activation of leukotriene-synthesizing enzymes and signaling kinases was analyzed by Western blot or immunofluorescent imaging. LL-37/its proform hCAP18 expression was analyzed by Western blot.

Results

LL-37, via formyl peptide receptor-2 (FPR-2), triggered the release of cysteinyl leukotrienes (cys-LTs) from eosinophils. The release was more prominent in cells primed with the eosinophilopoietic cytokine GM-CSF or IL-5 or cells from asthmatic patients. LL-37 stimulates lipid body formation and activates cys-LT-synthesizing enzymes by multiple mechanisms: enhancing cPLA2 activity by pERK1/2-mediated phosphorylation and inducing intracellular translocation and assembly of 5-LO and LTC4S at perinuclear locations and lipid bodies. In addition to cys-LTs, LL-37 enhances ECP release from eosinophils via pERK1/2. The expression of hCAP18 and its release following leukotriene stimulation are significantly higher in eosinophils from asthmatics.

Conclusions

This study identifies LL-37 as an eosinophil-activating peptide that triggers release of inflammatory mediators. The clinical correlation suggests that LL-37/hCAP18 and its signaling pathway represent potential therapeutic targets for this disease.

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