Substrate regulation of ascorbate transport activity in astrocytes

Wilson, John X.; Jaworski, Ewa; Kulaga, A. E.; Dixon, S. Jeffrey

doi:10.1007/bf00965751

Cited by 30 publications

(14 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, at least part of the up-regulation of the SVCT2 protein and function when the cells are put in culture could be due to changes in intracellular ascorbate, with low concentrations inducing the SVCT2 and high concentrations suppressing it. Wilson and colleagues have previously shown that culture in high concentrations of ascorbate suppresses ascorbate transport in primary cultures of cerebral astrocytes (Wilson et al, 1990), which supports the notion that ascorbate can regulate its own transporter. …”

mentioning

confidence: 66%

Development of ascorbate transporters in brain cortical capillary endothelial cells in culture

Qiao

May

2008

Brain Research

View full text Add to dashboard Cite

Ascorbic acid in its reduced form is not transported across the capillary endothelial cell blood-brain barrier. This is thought to be due to absence of the SVCT2, a specific transporter for ascorbate. To assess this directly we prepared primary cultures of mouse cortical microvascular endothelial cells. When still in the capillaries, these cells did not express the SVCT2 protein as assessed by immunocytochemistry and by immunoblotting. However, during several days in culture, they developed SVCT2 expression and showed ascorbate transport rates comparable to those in immortalized endothelial cell lines. SVCT2 expression was inversely proportional to cell density, was enhanced by culture at low physiologic plasma ascorbate concentrations, was inhibited by ascorbate concentrations expected in the brain interstitium, and was stimulated by cobalt ions. Expression of the SVCT2 was associated with ascorbate-dependent maturation and release of type IV collagen by the cells in culture. Although the SVCT2 is induced by culture of cortical capillary endothelial cells, its absence in vivo remains perplexing, given the need for intracellular ascorbate to facilitate type IV collagen maturation and release by endothelial cells. SectionStructural Organization of the Brain Keywords SVCT2; ascorbate transport; cobalt, collagen; cortical capillary endothelial cells Vitamin C, or ascorbic acid, is an important antioxidant and enzyme co-factor in the central nervous system, where it has several functions, including antioxidant protection (Rice2000), peptide amidation (Eipper et al., 1983), myelin formation (Eldridge et al., 1987), enhancement of synaptic activity (Qiu et al., 2007), and protection against glutamate toxicity (Rebec et al., 1994). In contrast to other organs, however, very little ascorbate appears to enter the brain directly across capillary endothelial cells forming the blood-brain barrier (BBB). Rather, the vitamin is transported from the blood into the cerebrospinal fluid through the choroid plexus (Agus et al., 1997;Spector1977) and by specialized cells lining the third ventricle . Plasma concentrations of ascorbate are 30-60 µM, and these are increased to 200-400 µM in the cerebrospinal fluid through this mechanism (Reiber et al., 1993;Spector et al., 1973). Transport of ascorbate into neurons further increases the gradient, since neurons contain *Corresponding author: Dr. James May, 7465 Medical Research Building IV, Vanderbilt University School of Medicine, Nashville, TN 37232-0475. Tel. (615) 936-1653; Fax: (615) 936-1667. E-mail: james.may@vanderbilt.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal d...

show abstract

mentioning

confidence: 66%

Development of ascorbate transporters in brain cortical capillary endothelial cells in culture

Qiao

May

2008

Brain Research

View full text Add to dashboard Cite

show abstract

“…However, the rate of ascorbate uptake was significantly lower for the artery rings than for the cultured cells. Ascorbate loading of astrocytes has been shown to decrease their subsequent ascorbate uptake [33]. Therefore, one would expect a low rate of ascorbate uptake in the artery rings which already contained a very high concentration of unlabeled ascorbate.…”

Section: Discussionmentioning

confidence: 99%

Ascorbate Transport in Pig Coronary Artery Smooth Muscle: Na<sup>+</sup> Removal and Oxidative Stress Increase Loss of Accumulated Cellular Ascorbate

et al. 2000

Self Cite

View full text Add to dashboard Cite

Pig deendothelialized coronary artery rings and smooth muscle cells cultured from them accumulated ascorbate from medium containing Na⁺. The accumulated material was determined to be ascorbate using high-performance liquid chromatography. We further characterized ascorbate uptake in the cultured cells. The data fitted best with a Hill coefficient of 1 for ascorbate (K_asc = 22 ± 2 μM) and 2 for Na⁺ (K_Na = 84 ± 10 mM). The anion transport inhibitors sulfinpyrazone and 4,4′-diisothiocyanatostilbene-2,2′-disulfonate (DIDS) inhibited the uptake. Transferring cultured cells loaded with ¹⁴C-ascorbate into an ascorbate-free solution resulted in a biphasic loss of radioactivity – an initial sulfinpyrazone-insensitive faster phase and a late sulfinpyrazone-sensitive slower phase. Transferring loaded cells into a Na⁺-free medium increased the loss in the initial phase in a sulfinpyrazone-sensitive manner, suggesting that the ascorbate transporter is bidirectional. Including peroxide or superoxide in the solution increased the loss of radioactivity. Thus, ascorbate accumulated in coronary artery smooth muscle cells by a Na⁺-dependent transporter was lost in an ascorbate-free solution, and the loss was increased by removing Na⁺ from the medium or by oxidative stress.

show abstract

“…There are only a limited number of studies which have looked at the ability of analogues of ascorbic acid to either inhibit uptake, when on the same side of the membrane, or stimulate transport, when on the opposite side (so called cis-inhibition-trans-stimulation). Published reports indicate that the process seems to be fairly specific to ascorbic acid with pre-incubation in the absence of the vitamin enhancing uptake (Wilson et al 1990). There is still controversy as to whether glucose is able to compete with ascorbic acid transport and, therefore, inhibit its available at https://www.cambridge.org/core/terms.…”

Section: Mechanisms Of Vitamin C Transportmentioning

confidence: 99%

The transport of vitamin C and effects of disease

Schorah

1992

Proc. Nutr. Soc.

View full text Add to dashboard Cite

It has been known for a number of years that high concentrations of vitamin C (ascorbic acid + dehydroascorbic acid) occur in some cells, but it is only recently that we have begun to discover how high the levels are and also that the vitamin seems to be secreted onto epithelial surfaces (Table 1). If we assume that such concentrations and secretions are needed for the appropriate biological activity of the vitamin, it follows that transport of vitamin C will be required in order to sustain normal metabolic functions. Further, if transport is central to the metabolism of vitamin C, any defect in the process could lead to the development of disease.

show abstract

Substrate regulation of ascorbate transport activity in astrocytes

Cited by 30 publications

References 51 publications

Development of ascorbate transporters in brain cortical capillary endothelial cells in culture

Development of ascorbate transporters in brain cortical capillary endothelial cells in culture

Ascorbate Transport in Pig Coronary Artery Smooth Muscle: Na<sup>+</sup> Removal and Oxidative Stress Increase Loss of Accumulated Cellular Ascorbate

The transport of vitamin C and effects of disease

Contact Info

Product

Resources

About