Sevoflurane binds and allosterically blocks integrin lymphocyte function-associated antigen-1.
BACKGROUND
Volatile anesthetics have been shown to modify immune cell functions via several mechanisms, some of which have been only partially elucidated. We demonstrated that isoflurane inhibits primary leukocyte integrin lymphocyte function-associated antigen-1 (LFA-1) by binding to the allosteric cavity critical for conformational activation to its high-affinity form. It remains to be determined whether the allosteric inhibition of LFA-1 by isoflurane can be generalized to other anesthetics such as sevoflurane.


METHODS
The effects of sevoflurane on the ability of LFA-1 to bind to its counter-ligand, intercellular adhesion molecule-1, was studied in leukocytes by flow cytometry. To examine whether sevoflurane acts directly on LFA-1, we measured ligand-binding using beads coated with purified LFA-1 protein. To distinguish between competitive versus allosteric inhibition, we analyzed the effects of sevoflurane on both wild-type and mutant-locked high-affinity LFA-1. One-way analysis of variance was employed for statistical analysis of the data. Nuclear magnetic resonance spectroscopy was used to identify sevoflurane binding site(s).


RESULTS
Sevoflurane at clinically relevant concentrations inhibited the ligand-binding function of LFA-1 in leukocytes as well as in cell-free assays (P<0.05). Sevoflurane blocked wild-type but not locked high-affinity LFA-1, thereby demonstrating an allosteric mode of inhibition. Nuclear magnetic resonance spectroscopy revealed that sevoflurane bound to the allosteric cavity, to which LFA-1 allosteric antagonists and isoflurane also bind.


CONCLUSIONS
This study suggests that sevoflurane also blocks the activation-dependent conformational changes of LFA-1 to the high-affinity form. The allosteric mode of action exemplified by sevoflurane and isoflurane via LFA-1 might represent one of the underlying mechanisms of anesthetic-mediated immunomodulation.
Yuki
Koichi
K
Department of Anesthesiology, Perioperative and Pain Medicine, Children's Hospital Boston, and Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts 02115, USA.
Astrof
Nathan S
NS
Bracken
Clay
C
Soriano
Sulpicio G
SG
Shimaoka
Motomu
M
D000495:Allosteric Site / Q000187:drug effects* / Q000502:physiology*; D018685:Anesthetics, Inhalation; D006801:Humans; D019169:Jurkat Cells; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry* / Q000378:metabolism*; D008738:Methyl Ethers / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D016169:Lymphocyte Function-Associated Antigen-1; D008738:Methyl Ethers; D000077149:Sevoflurane