title: Brain protection at the blood-cerebrospinal fluid interface involves a glutathione-dependent metabolic barrier mechanism.
abstract: The choroid plexuses (CPs) form a protective interface between the blood and the ventricular cerebrospinal fluid (CSF). To probe into the pathways by which CPs provide brain protection, we sought to evaluate the efficiency of glutathione conjugation in this barrier as a mechanism to prevent the entry of blood-borne electrophilic, potentially toxic compounds into the CSF, and we investigated the fate of the resulting metabolites. Rat CPs, as well as human CPs from both fetal and adult brains, displayed high glutathione-S-transferase activities. Using an in vitro model of the blood-CSF barrier consisting of choroidal epithelial cells cultured in a two-chambered device, we showed that glutathione conjugation can efficiently prevent the entry of 1-chloro-2,4-dinitrobenzene (CDNB) into the CSF, a model for electrophilic compounds. The duration of this enzymatic protection was set by the concentration of CDNB to which the epithelium was exposed, and this barrier effect was impaired only on severe epithelial intracellular glutathione and cysteine depletion. The conjugate was excreted from the choroidal cells in a polarized manner, mostly at the blood-facing membrane, via a high-capacity transport process, which is not a rate-limiting step in this detoxification pathway, and which may involve transporters of the ATP-binding cassette c(Abcc) and/or solute carrier 21 (Slc21) families. Supplying the choroidal epithelium at the blood-facing membrane with a therapeutically relevant concentration of N-acetylcysteine sustained this neuroprotective effect. Thus, glutathione conjugation at the CP epithelium coupled with the basolateral efflux of the resulting metabolites form an efficient blood-CSF enzymatic barrier, which can be enhanced by pharmacologically increasing glutathione synthesis within the epithelial cells.
authors.affiliation: Unité INSERM 433, IFR 19, Université Claude Bermard, Faculté de Médecine RTH Laennec, Lyon, France. ghersi-egea@lyon.inserm.fr
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Ghersi-Egea
authors.forename: Nathalie
authors.initials: N
authors.lastname: Strazielle
authors.forename: Audrey
authors.initials: A
authors.lastname: Murat
authors.forename: Anne
authors.initials: A
authors.lastname: Jouvet
authors.forename: Annie
authors.initials: A
authors.lastname: Buénerd
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Belin
mesh_terms: D000111:Acetylcysteine / Q000378:metabolism; D000818:Animals; D001812:Blood-Brain Barrier / Q000502:physiology*; D002555:Cerebrospinal Fluid / Q000502:physiology*; D002831:Choroid Plexus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000378:metabolism; D004137:Dinitrochlorobenzene / Q000493:pharmacokinetics / Q000633:toxicity; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005978:Glutathione / Q000502:physiology*; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007509:Irritants / Q000493:pharmacokinetics / Q000633:toxicity; D009419:Nerve Tissue Proteins / Q000378:metabolism; D018696:Neuroprotective Agents; D010539:Permeability; D012313:RNA / Q000096:biosynthesis / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D004137:Dinitrochlorobenzene; D007509:Irritants; D009419:Nerve Tissue Proteins; D018696:Neuroprotective Agents; D012313:RNA; D005982:Glutathione Transferase; D005978:Glutathione; D003545:Cysteine; D000111:Acetylcysteine