Download Innate immune responses to cationic antimicrobial peptides in the lung

CIHR-UBC Strategic Training Program for
Translational Research in Infectious Diseases
Address: D452 – 2733 Heather Pavilion, Vancouver, BC V5Z 3J5
E-mail: [email protected]
Voice: (604) 875-5063 Fax: (604) 875-4013 Website: http://cmdr.ubc.ca/trainingprogram
Research Theme:
Molecular pathogenesis, innate immunity, cell signalling, immunomodulation
Sub-theme:
Innate immune responses to cationic antimicrobial peptides in the lung
Principal Investigator:
Dr. Robert E.W. Hancock, PhD
Telephone:
Fax:
E-mail:
(604) 822-2682
(604) 822-6041
[email protected]
The airway inflammation observed in CF patients is believed to be a result of prior or concurrent infection with
Pseudomonas aeruginosa or other pathogens. However, it has been shown that infants, prior to chronic colonization of
P. aeruginosa have elevated levels of neutrophils, elastase, α1-antiprotease and the pro-inflammatory cytokine, IL-8 in
their lungs1. As well, bronchial epithelial cells from CF patients are not able to secrete IL-10 (an anti-inflammatory
cytokine) but do produce the pro-inflammatory cytokines IL-8 & IL-6. In contrast, healthy controls produce the anti- but
not pro-inflammatory cytokines2. The pathology of CF and the ability of P. aeruginosa to colonize their lungs may be at
least partially due to pre-existing inflammation. In addition there is no question that inflammatory response plays an
important role in late stage CF lung disease.
Cationic antimicrobial peptides have been proposed as a therapeutic option for the treatment of CF. The ability of
peptides to kill P. aeruginosa and other CF pathogens is well established. In addition to their antimicrobial activity, the
ability of these peptides to modulate the inflammatory response may be useful for treatment of the lung infections which
are characteristic of CF. For example, Hancock’s laboratory has demonstrated that peptides, e.g. the human cathelicidin
LL-37, reduce cytokine production induced by lipopolysaccharide, lipoteichoic acid, and noncapped
lipoarabinomannan. They have shown that the peptide protects against endotoxaemia 3 while other labs have
demonstrated that addition of this peptide with high LPS doses attenuates inflammation-induced lung damage4. As well,
they have demonstrated that LL-37 alters the expression of a number of genes (e.g. IL-8Rb, CXCR4, IL-10, etc)
involved in the recruitment and activation of the effector cells of the innate immune response3.
Effector cells of the innate immune response include neutrophils, monocytes and immature dendritic cells. LL-37 has
been demonstrated to have a variety of effects on all these cell types; however, the mechanisms by which it exerts these
effects have not yet been determined. The objective of this research will be to elucidate the initial signalling events that
occur when human blood derived monocytes are exposed to LL-37. This will shed light on how LL-37 induces changes
in transcription of genes involved in the inflammatory response, and is able to block LPS induced cytokine production.
Prelinminary data demonstrates that LL-37 causes dozens of genes to be up-regulated in a lung epithelial cell line within
4 h, and stimulates tyrosine phosphorylation of certain signalling molecules. RNA collected from primary human blood
monocytes will be treated with LL-37 and analysed for transcriptional activity of immediate-early response genes by
DNA arrays and confirmed by reverse-transcriptase PCR (RT-PCR) and Northern blots. Conventional inhibitor studies
will be performed to determine if inhibition of these pathways affects cytokine responses and gene transcription. These
studies will provide insight into the role of LL-37 in the innate immune response and its potential as a novel therapeutic
agent for the treatment of bacterial colonization and inflammation in the CF lung.
Khan et al., Am J Respir Crit Care Med 1995 Sep;152(3):921-6; 2. Stutts et al., Am Rev Respir Dis 1986 Jul;134(1):1721; 3. Scott, Bowdish et al., J Immunol. 2002 Oct 1;169(7):3883-91; 4. Bals et al., Clin Invest 1999 Apr;103(8):1113-7.
Updated: August 2003
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