Poly-L-Lysine compacts DNA, kills bacteria, and improves protease inhibition in cystic fibrosis sputum.
BACKGROUND
Neutrophil serine proteases in cystic fibrosis (CF) lung secretions partially resist inhibition by natural and exogenous inhibitors, mostly because DNA impairs their control. Cationic polypeptides display the property of condensing DNA and retain antimicrobial properties. We hypothesized that DNA condensation by cationic polypeptides in CF sputum would result in a better control of CF inflammation and infection.


OBJECTIVE
We examined whether poly-L-lysine would compact DNA in CF lung secretions and liquefy CF sputum, improve the control of extracellular proteases by exogenous inhibitors, and whether it displays antibacterial properties toward CF-associated bacteria.


METHODS
We used fluorogenic methods to measure proteolytic activities and inhibition by protease inhibitors in whole sputum homogenates from patients with CF before and after treatment with poly-L-lysine. Antibacterial properties of poly-L-lysine were measured in bacterial cultures and in whole CF sputum. Poly-L-lysine toxicity was evaluated after aerosolization by histologic analysis, flow cytometry, and quantification of proinflammatory cytokines.


RESULTS
Poly-L-lysine compacts CF sputum DNA, generating a liquid phase that improves ciliary beating frequency at the lung epithelial surface, and allows the control of neutrophil elastase and cathepsin G by their natural inhibitors. It retains antimicrobial properties against Pseudomonas aeruginosa and Staphylococcus aureus at doses that induce no inflammation in the mouse lung after aerosol administration.


CONCLUSIONS
Poly-L-lysine may be an alternative to dornase-α to liquefy sputum with added benefits because it helps natural inhibitors to better control the deleterious effects of extracellularly released neutrophil serine proteases and has the ability to kill bacteria in CF sputum.
1 INSERM UMR-1100, Tours, France.
Alice V
AV
Dubois
Patrick
P
Midoux
Delphine
D
Gras
Mustapha
M
Si-Tahar
Déborah
D
Bréa
Sylvie
S
Attucci
Mustapha-Kamel
MK
Khelloufi
Reuben
R
Ramphal
Patrice
P
Diot
Francis
F
Gauthier
Virginie
V
Hervé
D000328:Adult; D000368:Aged; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D056649:Cathepsin G / Q000187:drug effects / Q000378:metabolism; D003550:Cystic Fibrosis / Q000188:drug therapy* / Q000378:metabolism; D004247:DNA / Q000187:drug effects* / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D019272:Leukocyte Elastase / Q000187:drug effects / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000378:metabolism; D008239:Lysine / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008875:Middle Aged; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D010447:Peptide Hydrolases / Q000187:drug effects* / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013183:Sputum / Q000187:drug effects* / Q000378:metabolism; D013211:Staphylococcus aureus / Q000187:drug effects
D000900:Anti-Bacterial Agents; D004247:DNA; D010447:Peptide Hydrolases; D056649:Cathepsin G; D019272:Leukocyte Elastase; D008239:Lysine