title: Blood-brain barrier transport pathways for cytoprotective thiols.
abstract: The purpose of this study is to further define transport pathways for biological thiols by blood-brain barrier (BBB) endothelial cells, as a means of identifying endogenous cytoprotective mechanisms and potential therapeutic protocols for oxidative injury. Similar low-affininty, high-capacity passive carriers for glutathione (GSH) were observed at both the luminal (blood-facing) and abluminal (brain-facing) plasma membranes of BBB endothelial cells. These carriers are voltage dependent, favoring outward movement of intact peptide across both membrane domains, including efflux at the luminal plasmalemma where γ-glutamyl transpeptidase is located. Although present at both cell surfaces, the carriers are distributed unequally, with more appearing in the abluminal membrane. By contrast, high-affinity, low-capacity sodium-dependent GSH cotransport (Na-GSH) is observed only at the abluminal membrane, indicative of an inwardly directed active peptide carrier at the brain-facing plasma membrane. Treatment of cultured BBB endothelial cells with the GSH precursor γ-glutamyl-cysteine reduces cell damage under conditions simulating ischemia and reperfusion. These findings are consistent with the presence of (1) a typical γ-glutamyl cycle at the luminal membrane of BBB endothelial cells, (2) a significant efflux pathway at the abluminal membrane allowing passive movement of BBB GSH into brain extracellular fluid, (3) a Na-dependent, brain-to-blood pathway for transcellular transport of GSH, and (4) a mechanism for cytoprotection by γ-glutamyl cysteine, under conditions of ischemia and reperfusion.
authors.affiliation: 1Department of Physiology and Biophysics and 2Medicine, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, North Chicago, IL; and 3Department of Medicine, Christ Hospital and Medical Center, Oak Lawn, IL.
authors.forename: Darryl R
authors.initials: DR
authors.lastname: Peterson
authors.forename: Ernest J
authors.initials: EJ
authors.lastname: Sukowski
authors.forename: Demetrios
authors.initials: D
authors.lastname: Zikos
mesh_terms: D001692:Biological Transport; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D019610:Cytoprotection / Q000502:physiology*; D004151:Dipeptides / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D007511:Ischemia / Q000503:physiopathology; D015427:Reperfusion Injury / Q000503:physiopathology; D012964:Sodium / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D005723:gamma-Glutamyltransferase / Q000378:metabolism
chemical_list: D004151:Dipeptides; D013438:Sulfhydryl Compounds; D012964:Sodium; D005723:gamma-Glutamyltransferase; D005978:Glutathione; C017341:gamma-glutamylcysteine