title: Volatile anesthetics, not intravenous anesthetic propofol bind to and attenuate the activation of platelet receptor integrin αIIbβ3.
abstract: BACKGROUND
  In clinical reports, the usage of isoflurane and sevoflurane was associated with more surgical field bleeding in endoscopic sinus surgeries as compared to propofol. The activation of platelet receptor αIIbβ3 is a crucial event for platelet aggregation and clot stability. Here we studied the effect of isoflurane, sevoflurane, and propofol on the activation of αIIbβ3.
  
  
  METHODS
  The effect of anesthetics on the activation of αIIbβ3 was probed using the activation sensitive antibody PAC-1 in both cell-based (platelets and αIIbβ3 transfectants) and cell-free assays. The binding sites of isoflurane on αIIbβ3 were explored using photoactivatable isoflurane (azi-isoflurane). The functional implication of revealed isoflurane binding sites were studied using alanine-scanning mutagenesis.
  
  
  RESULTS
  Isoflurane and sevoflurane diminished the binding of PAC-1 to wild-type αIIbβ3 transfectants, but not to the high-affinity mutant, β3-N305T. Both anesthetics also impaired PAC-1 binding in a cell-free assay. In contrast, propofol did not affect the activation of αIIbβ3. Residues adducted by azi-isoflurane were near the calcium binding site (an important regulatory site termed SyMBS) just outside of the ligand binding site. The mutagenesis experiments demonstrated that these adducted residues were important in regulating integrin activation.
  
  
  CONCLUSIONS
  Isoflurane and sevoflurane, but not propofol, impaired the activation of αIIbβ3. Azi-isoflurane binds to the regulatory site of integrin αIIbβ3, thereby suggesting that isoflurane blocks ligand binding of αIIbβ3 in not a competitive, but an allosteric manner.
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts, United States of America. yuki.koichi@gmail.com
authors.forename: Koichi
authors.initials: K
authors.lastname: Yuki
authors.forename: Weiming
authors.initials: W
authors.lastname: Bu
authors.forename: Motomu
authors.initials: M
authors.lastname: Shimaoka
authors.forename: Roderic
authors.initials: R
authors.lastname: Eckenhoff
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D018685:Anesthetics, Inhalation / Q000737:chemistry / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D007530:Isoflurane / Q000737:chemistry / Q000494:pharmacology*; D008738:Methyl Ethers / Q000737:chemistry / Q000494:pharmacology*; D008969:Molecular Sequence Data; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D015742:Propofol / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D008738:Methyl Ethers; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D000077149:Sevoflurane; D007530:Isoflurane; D015742:Propofol