title: Cationic polyamines inhibit anthrax lethal factor protease.
abstract: BACKGROUND
  Anthrax is a human disease that results from infection by the bacteria, Bacillus anthracis and has recently been used as a bioterrorist agent. Historically, this disease was associated with Bacillus spore exposure from wool or animal carcasses. While current vaccine approaches (targeted against the protective antigen) are effective for prophylaxis, multiple doses must be injected. Common antibiotics that block the germination process are effective but must be administered early in the infection cycle. In addition, new therapeutics are needed to specifically target the proteolytic activity of lethal factor (LF) associated with this bacterial infection.
  
  
  RESULTS
  Using a fluorescence-based assay to identify and characterize inhibitors of anthrax lethal factor protease activity, we identified several chemically-distinct classes of inhibitory molecules including polyamines, aminoglycosides and cationic peptides. In these studies, spermine was demonstrated for the first time to inhibit anthrax LF with a Ki value of 0.9 +/- 0.09 microM (mean +/- SEM; n = 3). Additional linear polyamines were also active as LF inhibitors with lower potencies.
  
  
  CONCLUSIONS
  Based upon the studies reported herein, we chose linear polyamines related to spermine as potential lead optimization candidates and additional testing in cell-based models where cell penetration could be studied. During our screening process, we reproducibly demonstrated that the potencies of certain compounds, including neomycin but not neamine or spermine, were different depending upon the presence or absence of nucleic acids. Differential sensitivity to the presence/absence of nucleic acids may be an additional point to consider when comparing various classes of active compounds for lead optimization.
authors.affiliation: Hawaii Biotech, Inc,, 99-193 Aiea Heights Dr,, Aiea, HI 96701, USA. mgoldman@hawaii.edu
authors.forename: Mark Evan
authors.initials: ME
authors.lastname: Goldman
authors.forename: Lynne
authors.initials: L
authors.lastname: Cregar
authors.forename: Dominique
authors.initials: D
authors.lastname: Nguyen
authors.forename: Ondrej
authors.initials: O
authors.lastname: Simo
authors.forename: Sean
authors.initials: S
authors.lastname: O'Malley
authors.forename: Tom
authors.initials: T
authors.lastname: Humphreys
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology; D000818:Animals; D000942:Antigens, Bacterial; D001408:Bacillus anthracis / Q000201:enzymology*; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors*; D002412:Cations; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical; D045683:Furin / Q000037:antagonists & inhibitors; D007700:Kinetics; D008264:Macrophages / Q000382:microbiology / Q000473:pathology; D051379:Mice; D011073:Polyamines / Q000494:pharmacology*; D013379:Substrate Specificity
chemical_list: D000617:Aminoglycosides; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D002412:Cations; D011073:Polyamines; C030325:anthrax toxin; D004247:DNA; D045683:Furin