title: Potential of host defense peptide prodrugs as neutrophil elastase-dependent anti-infective agents for cystic fibrosis.
abstract: Host defense peptides (HDPs) are short antimicrobial peptides of the innate immune system. Deficiencies in HDPs contribute to enhanced susceptibility to infections, e.g., in cystic fibrosis (CF). Exogenous HDPs can compensate for these deficiencies, but their development as antimicrobials is limited by cytotoxicity. Three HDP prodrugs were designed so their net positive charge is masked by a promoiety containing a substrate for the enzyme neutrophil elastase (NE). This approach can confine activation to sites with high NE levels. Enzyme-labile peptides were synthesized, and their activation was investigated using purified NE. Susceptibilities of Pseudomonas aeruginosa to parent and prodrug peptides in the presence and absence of NE-rich CF human bronchoalveolar lavage (BAL) fluid and different NaCl concentrations were compared. The effect of the HDP promoiety on cytotoxicity was determined with cystic fibrosis bronchial epithelial (CFBE41o-) cells. NE in CF BAL fluids activated the HDP prodrugs, restoring bactericidal activity against reference and clinical isolates of P. aeruginosa. However, activation also required the addition of 300 mM NaCl. Under these conditions, the bactericidal activity levels of the HDP prodrugs differed, with pro-P18 demonstrating the greatest activity (90% to 100% of that of the parent, P18, at 6.25 μg/ml). Cytotoxic effects on CFBE41o- cells were reduced by the addition of the promoiety to HDPs. We demonstrate here for the first time the selective activation of novel HDP prodrugs by a host disease-associated enzyme at in vivo concentrations of the CF lung. This approach may lead to the development of novel therapeutic agents with low toxicity that are active under the challenging conditions of the CF lung.
authors.affiliation: Centre for Synthesis and Chemical Biology, Department of Pharmaceutical and Medicinal Chemistry, Royal College of Surgeons in Ireland, Dublin, Ireland.
authors.forename: Eanna
authors.initials: E
authors.lastname: Forde
authors.forename: Hilary
authors.initials: H
authors.lastname: Humphreys
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Greene
authors.forename: Deirdre
authors.initials: D
authors.lastname: Fitzgerald-Hughes
authors.forename: Marc
authors.initials: M
authors.lastname: Devocelle
mesh_terms: D000595:Amino Acid Sequence; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D018920:Coculture Techniques; D003550:Cystic Fibrosis / Q000201:enzymology / Q000382:microbiology / Q000473:pathology; D006801:Humans; D019272:Leukocyte Elastase / Q000378:metabolism*; D008168:Lung / Q000201:enzymology / Q000382:microbiology / Q000473:pathology; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D061251:Primary Cell Culture; D011355:Prodrugs / Q000138:chemical synthesis / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development; D012965:Sodium Chloride / Q000378:metabolism; D023084:alpha-Defensins / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D011355:Prodrugs; D023084:alpha-Defensins; D012965:Sodium Chloride; D019272:Leukocyte Elastase