Sodium vitamin C cotransporter SVCT2 is expressed in hypothalamic glial cells.
Kinetic analysis of vitamin C uptake demonstrated that different specialized cells take up ascorbic acid through sodium-vitamin C cotransporters. Recently, two different isoforms of sodium-vitamin C cotransporters (SVCT1/SLC23A1 and SVCT2/SLC23A2) have been cloned. SVCT2 was detected mainly in choroidal plexus cells and neurons; however, there is no evidence of SVCT2 expression in glial and endothelial cells of the brain. Certain brain locations, including the hippocampus and hypothalamus, consistently show higher ascorbic acid values compared with other structures within the central nervous system. However, molecular and kinetic analysis addressing the expression of SVCT transporters in cells isolated from these specific areas of the brain had not been done. The hypothalamic glial cells, or tanycytes, are specialized ependymal cells that bridge the cerebrospinal fluid with different neurons of the region. Our hypothesis postulates that SVCT2 is expressed selectively in tanycytes, where it is involved in the uptake of the reduced form of vitamin C (ascorbic acid), thereby concentrating this vitamin in the hypothalamic area. In situ hybridization and optic and ultrastructural immunocytochemistry showed that the transporter SVCT2 is highly expressed in the apical membranes of mouse hypothalamic tanycytes. A newly developed primary culture of mouse hypothalamic tanycytes was used to confirm the expression and function of the SVCT2 isoform in these cells. The results demonstrate that tanycytes express a high-affinity transporter for vitamin C. Thus, the vitamin C uptake mechanisms present in the hypothalamic glial cells may perform a neuroprotective role concentrating vitamin C in this specific area of the brain.
García
María De Los Angeles
Mde L
Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile.
Salazar
Katherine
K
Millán
Carola
C
Rodríguez
Federico
F
Montecinos
Hernán
H
Caprile
Teresa
T
Silva
Carmen
C
Cortes
Christian
C
Reinicke
Karin
K
Vera
Juan Carlos
JC
Aguayo
Luis G
LG
Olate
Juan
J
Molina
Benedicto
B
Nualart
Francisco
F
D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism* / Q000493:pharmacokinetics; D001693:Biological Transport, Active / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D002555:Cerebrospinal Fluid / Q000378:metabolism; D019610:Cytoprotection / Q000502:physiology; D004805:Ependyma / Q000378:metabolism* / Q000648:ultrastructure; D007031:Hypothalamus / Q000378:metabolism* / Q000648:ultrastructure; D017403:In Situ Hybridization; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D009457:Neuroglia / Q000378:metabolism* / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D029363:Organic Anion Transporters, Sodium-Dependent / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D020542:Third Ventricle / Q000378:metabolism / Q000648:ultrastructure
D029363:Organic Anion Transporters, Sodium-Dependent; D020033:Protein Isoforms; D012333:RNA, Messenger; C555164:Slc23a1 protein, mouse; C555165:Slc23a2 protein, mouse; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters; D001205:Ascorbic Acid