title: Identification and potency of cyclodextrin-lipid inhibitors of Staphylococcus aureus α-toxin.
abstract: OBJECTIVE
  Staphylococcus aureus, a leading cause of bacterial keratitis, secretes α-toxin, a cytotoxin active on the corneal epithelium. This study describes the production and testing of chemical inhibitors of α-toxin action.
  
  
  METHODS
  Purified α-toxin was titered by its ability to lyse rabbit erythrocytes in buffered saline (PBS). To prepare potential toxin inhibitors, each of 18 lipids was incorporated into a complex with methyl-β-cyclodextrin (MβCD) or hydroxypropyl-β-cyclodextrin (HPβCD). Serial dilutions of each lipid-cyclodextrin (CD-lipid) complex were mixed with α-toxin prior to the addition of rabbit erythrocytes. Select CD-lipid complexes were mixed with 12 hemolytic units (HU) α-toxin and injected into the rabbit corneal stroma so the resulting corneal erosions could be measured at 4 and 8 hours post-injection (PI). Eyes injected with toxin alone, MβCD, or HPβCD alone served as controls.
  
  
  RESULTS
  Neither form of CD alone inhibited α-toxin. Of the 36 complexes prepared, 6 lipid-CD complexes were found to inhibit >100 HU of α-toxin. Four lipid complexes able to inhibit >200 HU of α-toxin were tested in toxin-injected corneas; at 4 and 8 hours PI, the complexes of cholesterol or lanosterol with MβCD and squalene or desmosterol with HPβCD caused a significant reduction in the corneal erosion size as compared to eyes injected with α-toxin alone (P ≤ 0.05).
  
  
  CONCLUSIONS
  Specific lipid inclusion complexes with either MβCD or HPβCD demonstrated a significant inhibition of α-toxin in both in vitro and in vivo assays. Changes in either the cyclodextrin or lipid of a complex affected the inhibitory activity.
authors: Department of Microbiology, University of Mississippi Medical Center, Jackson, MS 39216, USA.
authors: Anastasia C
authors: AC
authors: Weeks
authors: Charles L
authors: CL
authors: Balzli
authors: Armando
authors: A
authors: Caballero
authors: Aihua
authors: A
authors: Tang
authors: Richard
authors: R
authors: O'Callaghan
mesh_terms: D000073738:2-Hydroxypropyl-beta-cyclodextrin; D000818:Animals; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors* / Q000633:toxicity; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D015941:Complement Hemolytic Activity Assay; D003315:Cornea / Q000187:drug effects*; D006460:Hemolysin Proteins / Q000037:antagonists & inhibitors* / Q000633:toxicity; D008055:Lipids / Q000737:chemistry / Q000494:pharmacology*; D011817:Rabbits; D013047:Specific Pathogen-Free Organisms; D047392:beta-Cyclodextrins / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D008055:Lipids; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; C021091:staphylococcal alpha-toxin; D000073738:2-Hydroxypropyl-beta-cyclodextrin