Human choroid plexus papilloma cells efficiently transport glucose and vitamin C

Abstract

In vitro and in vivo studies suggest that the basolateral membrane of choroid plexus cells, which is in contact with blood vessels, is involved in the uptake of the reduced form of vitamin C, ascorbic acid (AA), through the sodium-vitamin C cotransporter, (SVCT2). Moreover, very low levels of vitamin C were observed in the brains of SVCT2-null mice. The oxidized form of vitamin C, dehydroascorbic acid (DHA), is incorporated through the facilitative glucose transporters (GLUTs). In this study, the contribution of SVCT2 and GLUT1 to vitamin C uptake in human choroid plexus papilloma (HCPP) cells in culture was examined. Both the functional activity and the kinetic parameters of GLUT1 and SVCT2 in cells isolated from HCPP were observed. Finally, DHA uptake by GLUT1 in choroid plexus cells was assessed in the presence of phorbol-12-myristate-13-acetate (PMA)-activated human neutrophils. A marked increase in vitamin C uptake by choroid plexus cells was observed that was associated with superoxide generation and vitamin C oxidation (bystander effect). Thus, vitamin C can be incorporated by epithelial choroid plexus papilloma cells using the basolateral polarization of SVCT2 and GLUT1. This mechanism may be amplified with neutrophil infiltration (inflammation) of choroid plexus tumors.

A fluorophore-conjugated ascorbic acid functions for the visualization of sodium vitamin C transporters in living cells

“…22,29,30 In this experiment, we added 100 nM PMA to HEK-293T cells to induce an up-regulated SVCT expression, and then extracted the cytoplasmic proteins to conduct a Western blot experiment. Aer exposure with PMA, the expression of SVCT2 greatly increased.…”

SVCT2 transporter expression is post‐natally induced in cortical neurons and its function is regulated by its short isoform

“…Both sodium-vitamin C cotransporters (SVCTs) mediate high-affinity L-AA transport in a Na + -dependent manner, which is necessary for vitamin C uptake by many tissues. In the adult brain, SVCT2 is expressed not only in neurons, specialized hypothalamic ependymal cells and choroid plexus cells (Garcia et al 2005;Mun et al 2006;Ulloa et al 2013) but also in neurogenic niche progenitor cells (Pastor et al 2013). In fetal rat brain, SVCT2 is highly expressed in the cortex and cerebellum (Caprile et al 2009), and we have used kinetic analyses of AA uptake to demonstrate the presence of SVCT2-like proteins in cortical and cerebellar neurons (Caprile et al 2009).…”

Vitamin C Transporters, Recycling and the Bystander Effect in the Nervous System: SVCT2 versus Gluts

“…However, a strong reaction in the basolateral region was observed in a few regions of the plexus [57]. Due to the difficulties in obtaining normal human choroid plexus cells, further studies utilized resected human choroid plexus papilloma cells obtained from a 16–year-old male [58]. These cells maintain the characteristics of choroid plexus cells as well as the structure of the tissue within the brain.…”

“…In addition to analyzing SVCT2 localization, the effect of sodium dependence and temperature on these cells was also analyzed. In the absence of sodium, AA incorporation was greatly reduced and was even more significant when performed at 37°C [58]. It must also be mentioned that the mechanisms by which AA enters the brain from choroid plexus cells remains to be elucidated.…”