title: Stereoselectivity of isoflurane in adhesion molecule leukocyte function-associated antigen-1.
abstract: BACKGROUND
  Isoflurane in clinical use is a racemate of S- and R-isoflurane. Previous studies have demonstrated that the effects of S-isoflurane on relevant anesthetic targets might be modestly stronger (less than 2-fold) than R-isoflurane. The X-ray crystallographic structure of the immunological target, leukocyte function-associated antigen-1 (LFA-1) with racemic isoflurane suggested that only S-isoflurane bound specifically to this protein. If so, the use of specific isoflurane enantiomers may have advantage in the surgical settings where a wide range of inflammatory responses is expected to occur. Here, we have further tested the hypothesis that isoflurane enantioselectivity is apparent in solution binding and functional studies.
  
  
  METHODS
  First, binding of isoflurane enantiomers to LFA-1 was studied using 1-aminoanthracene (1-AMA) displacement assays. The binding site of each enantiomer on LFA-1 was studied using the docking program GLIDE. Functional studies employed the flow-cytometry based ICAM binding assay.
  
  
  RESULTS
  Both enantiomers decreased 1-AMA fluorescence signal (at 520 nm), indicating that both competed with 1-AMA and bound to the αL I domain. The docking simulation demonstrated that both enantiomers bound to the LFA-1 "lovastatin site." ICAM binding assays showed that S-isoflurane inhibited more potently than R-isoflurane, consistent with the result of 1-AMA competition assay.
  
  
  CONCLUSIONS
  In contrast with the x-ray crystallography, both enantiomers bound to and inhibited LFA-1. S-isoflurane showed slight preference over R-isoflurane.
authors.affiliation: Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Weiming
authors.initials: W
authors.lastname: Bu
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts, United States of America; Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Luis M
authors.initials: LM
authors.lastname: Pereira
authors.affiliation: Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Roderic G
authors.initials: RG
authors.lastname: Eckenhoff
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts, United States of America; Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Koichi
authors.initials: K
authors.lastname: Yuki
mesh_terms: D000873:Anthracenes / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D057809:HEK293 Cells; D006801:Humans; D007530:Isoflurane / Q000737:chemistry / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D062105:Molecular Docking Simulation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D013237:Stereoisomerism
chemical_list: D000873:Anthracenes; D016169:Lymphocyte Function-Associated Antigen-1; D011994:Recombinant Proteins; C049062:1-aminoanthracene; D007530:Isoflurane