title: Designed azolopyridinium salts block protective antigen pores in vitro and protect cells from anthrax toxin.
abstract: BACKGROUND
  Several intracellular acting bacterial protein toxins of the AB-type, which are known to enter cells by endocytosis, are shown to produce channels. This holds true for protective antigen (PA), the binding component of the tripartite anthrax-toxin of Bacillus anthracis. Evidence has been presented that translocation of the enzymatic components of anthrax-toxin across the endosomal membrane of target cells and channel formation by the heptameric/octameric PA63 binding/translocation component are related phenomena. Chloroquine and some 4-aminoquinolones, known as potent drugs against Plasmodium falciparium infection of humans, block efficiently the PA63-channel in a dose dependent way.
  
  
  RESULTS
  Here we demonstrate that related positively charged heterocyclic azolopyridinium salts block the PA63-channel in the µM range, when both, inhibitor and PA63 are added to the same side of the membrane, the cis-side, which corresponds to the lumen of acidified endosomal vesicles of target cells. Noise-analysis allowed the study of the kinetics of the plug formation by the heterocycles. In vivo experiments using J774A.1 macrophages demonstrated that the inhibitors of PA63-channel function also efficiently block intoxication of the cells by the combination lethal factor and PA63 in the same concentration range as they block the channels in vitro.
  
  
  CONCLUSIONS
  These results strongly argue in favor of a transport of lethal factor through the PA63-channel and suggest that the heterocycles used in this study could represent attractive candidates for development of novel therapeutic strategies against anthrax.
authors.affiliation: Rudolf-Virchow-Center, DFG-Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Beitzinger
authors.forename: Anika
authors.initials: A
authors.lastname: Bronnhuber
authors.forename: Kerstin
authors.initials: K
authors.lastname: Duscha
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Riedl
authors.forename: Markus
authors.initials: M
authors.lastname: Huber-Lang
authors.forename: Roland
authors.initials: R
authors.lastname: Benz
authors.forename: György
authors.initials: G
authors.lastname: Hajós
authors.forename: Holger
authors.initials: H
authors.lastname: Barth
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000942:Antigens, Bacterial / Q000502:physiology; D001408:Bacillus anthracis / Q000276:immunology*; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology*; D008051:Lipid Bilayers; D008564:Membrane Potentials; D051379:Mice; D008954:Models, Biological; D011485:Protein Binding; D021381:Protein Transport; D011725:Pyridines / Q000494:pharmacology*; D017186:Titrimetry; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; C586069:HA 1363; C586070:HA 1495; C586071:HA 1568; D007093:Imidazoles; D008051:Lipid Bilayers; D011725:Pyridines; D014409:Tumor Necrosis Factor-alpha; C030325:anthrax toxin