Vitamin C is taken up by human T cells via sodium-dependent vitamin C transporter 2 (SVCT2) and exerts inhibitory effects on the activation of these cells in vitro / 대한해부학회지

Vitamin C is an essential micronutrient that affects immune responses. T cells are one of the main players in acquired immunity and have been reported to be influenced by in vivo vitamin C supplementation. Yet, the way by which T cells uptake vitamin C and what direct effects vitamin C exerts on the cells are not known. To elucidate, we isolated human peripheral blood T cells and analyzed the expression of sodium-dependent vitamin C transporters (SVCT). T cells were activated in vitro in the absence or presence of vitamin C, before or after activation. As results, human T cells expressed SVCT2, but not SVCT1, and the expression level increased following activation. Vitamin C added in the culture media generally did not affect T-cell behaviors following activation, such as proliferation, apoptosis, expression of CD25 and CD69, and interleukin 2 secretion, regardless whether it was added before or after activation. However, exceptionally, high concentration vitamin C, when it was added before activation, but not after activation, did exert toxic effects on cell activation with respect to the above-mentioned parameters. In conclusion, we showed the expression of SVCT2 in human T cells for the first time. Vitamin C exerted toxic effects, at least in vitro, when the concentration was high and when it was given before activation. These toxic effects are not thought to be via anti-oxidant effects of vitamin C.

Vitamin C and oxidative stress in the seminiferous epithelium

In this article, we focus on the fundamental role of vitamin C transporters for the normal delivery of vitamin C to germ cells in the adluminal compartment of seminiferous tubules. We argue that the redox status within spermatozoa or in semen is partly responsible for the etiology of infertility. In this context, antioxidant defence plays a critical role in male fertility. Vitamin C, a micronutrient required for a wide variety of metabolic functions, has long been associated with male reproduction. Two systems for vitamin C transport have been described in mammals. Facilitative hexose transporters (GLUTs), with 14 known isoforms to date, GLUT1-GLUT14, transport the oxidized form of vitamin C (dehydroascorbic acid) into the cells. Sodium ascorbic acid co-transporters (SVCTs), SVCT1 and SVCT2 transport the reduced form of vitamin C (ascorbic acid). Sertoli cells control germ cell proliferation and differentiation through cell-cell communication and form the blood-testis barrier. Because the blood-testis barrier limits direct access of molecules from the plasma into the adluminal compartment of the seminiferous tubule, one important question is the method by which germ cells obtain vitamin C. Some interesting results have thrown light on this matter. Expression of SVCT2 and some isoforms of GLUT transporters in the testis have previously been described. Our group has demonstrated that Sertoli cells express functionally active vitamin C transporters. Kinetic characteristics were described for both transport systems (SVCT and GLUT systems). Sertoli cells are able to transport both forms of vitamin C. These findings are extremely relevant, because Sertoli cells may control the amount of vitamin C in the adluminal compartment, as well as regulating the availability of this metabolite throughout spermatogenesis.

Expression of Sodium-dependent Vitamin C Transporter in Rat Dermal Fibroblasts / 대한피부과학회지

BACKGROUND: Vitamin C is one of the most typical types of water-soluble antioxidants that exerts a variety of biochemical actions on a living body. It acts on the skin by promoting wound healing, preventing skin aging, and inhibiting skin cancer. It also works not only as an antioxidant, protecting the skin from UV radiation but also as an anti-inflammatory agent. It reinforces immunity as well. Recent studies proved the whitening effect of vitamin C, and it can be instilled into the skin by way of iontophoresis. When vitamin C is transported in vivo it is either by simple diffusion or by a transporter. Only a small amount is transported by simple diffusion and the transporter is responsible for most of the vitamin C transport. This study was designed to evaluate the presence of sodium dependent vitamin C transporter (SVCT) and to identify which factor controls its expression. METHODS: Expressions of SVCT 1 and 2 mRNA in the rats' dermal fibroblast were measured by RT-PCR at 3, 6, 12, 24, and 48 hours. RESULTS: The results were used to compare the expression levels of SVCT-1 and SVCT-2 when treated with TGF-beta, estradiol, and retinoic acid. Estradiol showed the highest level of expression of SVCT-1 and SVCT-2. The next highest was TGF-beta, followed by retinoic acid. CONCLUSION: SVCT-1 and SVCT-2 were found to be expressed in the rats' dermal fibroblasts, and exposure to estradiol, TGF-beta and retinoic acid resulted in a higher degree of their expression.