The Safe Soluble Compound Dehydroascorbic Acid Inhibits Various Upstream and Downstream Effectors of PI3K and KRAS Signaling Pathways in Undruggable PIK3CA/KRAS-Mutant Colorectal Cancer Stem-Like Cells.

Efforts to develop effective drugs targeting PI3K and KRAS signaling pathways in PIK3CA/KRAS-mutant colorectal cancer stem cells (CRCSCs) remain challenging. Finding safe compounds that can easily enter CRCSCs with the ability to target metastasis-driver gene CXCR4 and pluripotency network genes as key upstream and downstream effectors of both PI3K and KRAS signaling pathways may provide promising results. PIK3CA/KRAS-mutant CRCSCs display high expression of glucose transporters (GLUTs) on their cell membrane and a glycolytic phenotype providing an opportunity to deliver antiglycolytic compounds into these cells via the GLUTs. CRC patients with low levels of vitamin C in their plasma show a shorter survival suggesting the ability of this vitamin at the physiologic levels for caspase-3 activation and apoptosis in CRCSCs. Vitamin C in an oxidized form (L-dehydroascorbic acid; L-DHA) with antiglycolytic activity can be taken up into CRC cells via the GLUTs. This may provide selective toxicity on CRCSCs and affect CXCR4 and stemness markers genes expression in these cells. To this end, we treated PIK3CA/KRAS-mutant LS174T cells with high glycolytic activity as an attractive model for CRCSCs with L-DHA equal to the pharmacological levels of vitamin C in human plasma, after which cell numbers, metabolic activity, proliferation-rate, CXCR4 and pluripotency network genes expression, caspase-3 activity with apoptosis were evaluated. 48 h post-treatment with 100- to 1000 µM L-DHA, cell numbers were decreased and measured to be 70-47% control. L-DHA with selective toxicity on LS174T cells diminished metabolic activity and cell proliferation-rate to 1.4-0.8 (Control OD = 1.5) and 92-54.5% respectively with no toxicity on PBMCs. L-DHA decreased CXCR4, Bmi-1, Sox-2 and Oct-4 expression to 45%, 85%, 45% and 48% control respectively followed by caspase-3 reactivation by 2.5 to 4.9-fold increases and induction of apoptosis ranging from 0.5% to 58.3% for 100- to 1000 µM L-DHA. According to our data, CRC stem-like cells were highly sensitive to L-DHA in in-vitro. L-DHA selectively targeted LS174T cells and successfully reactivated caspase-3 and apoptosis in these cells. CXCR4, stemness marker genes and metabolic activity appear to be promising targets of L-DHA. Our results may provide a new therapeutic approach to target selectively GLUT-overexpressing PIK3CA/KRAS-mutant CRCSCs using L-DHA with no toxicity on normal cells.

Metabolic control by dehydroascorbic acid: Questions and controversies in cancer cells.

For a long time, the effect of vitamin C on cancer cells has been a controversial concept. From Linus Pauling's studies in 1976, it was proposed that ascorbic acid (AA) could selectively kill tumor cells. However, further research suggested that vitamin C has no effect on tumor survival. In the last decade, new and emerging functions for vitamin C have been discovered using the reduced form, AA, and the oxidized form, dehydroascorbic acid (DHA), independently. In this review, we summarized the latest findings related to the effects of DHA on the survival and metabolism of tumor cells. At the same time, we put special emphasis on the bystander effect and the recycling capacity of vitamin C in various cellular models, and how these concepts can affect the experimentation with vitamin C and its therapeutic application in the treatment against cancer.

Expression and/or activity of the SVCT2 ascorbate transporter may be decreased in many aggressive cancers, suggesting potential utility for sodium bicarbonate and dehydroascorbic acid in cancer therapy.

Hypoxia-inducible factor-1 (HIF-1) is a heterodimer transcription factor whose elevated activity in many cancers helps them to survive under hypoxic conditions and enhances their capacity to grow invasively, establish metastases, and survive chemo- or radiotherapy. Optimal intracellular levels of ascorbate suppress the level and transcriptional activity of HIF-1under normoxic or mildly hypoxic conditions by supporting the activity of proly and asparagyl hydroxylases that target HIF-1alpha. High intracellular ascorbate can also work in various ways to down-regulate activation of NF-kappaB which, like HIF-1 is constitutively active in many cancers and promotes aggressive behavior - in part by promoting transcription of HIF-1alpha. Yet recent evidence suggests that, even in the context of adequate ascorbate nutrition, the intracellular ascorbate content of many aggressive cancers may be supoptimal for effective HIF-1 control. This likely reflects low expression or activity of the SVCT2 ascorbate transporter. The expression of SVCT2 in cancers has so far received little study; but the extracellular acidity characteristic of many tumors would be expected to reduce the activity of this transporter, which has a mildly alkaline pH optimum. Unfortunately, since SVCT2 has a high affinity for ascorbate, and its activity is nearly saturated at normal healthy serum levels of this vitamin, increased oral administration of ascorbate would be unlikely to have much impact on the intracellular ascorbate content of tumors. However, cancers in which HIF-1 is active express high levels of glucose transporters such as GLUT-1, and these transporters can promote influx of dehydroascorbic acid (DHA) via facilitated diffusion; once inside the cell, DHA is rapidly reduced to ascorbate, which effectively is "trapped" within the cell. Hence, episodic intravenous infusions of modest doses of DHA may have potential for optimizing the intracellular ascorbate content of cancers, potentially rendering them less aggressive. Indeed, several published studies have concluded that parenteral DHA--sometimes in quite modest doses--can retard the growth of transplanted tumors in rodents. As an alternative or adjunctive strategy, oral administration of sodium bicarbonate, by normalizing the extracellular pH of tumors, has the potential to boost the activity of SCTV2 in tumor cells, thereby promoting increased ascorbate uptake. Indeed, the utility of oral sodium bicarbonate for suppressing metastasis formation in nude mice xenografted with a human breast cancer has been reported. Hence, oral sodium bicarbonate and intravenous DHA may have the potential to blunt the aggressiveness of certain cancers in which suboptimal intracellular ascorbate levels contribute to elevated HIF-1 activity.

The combination of vitamin D3 and dehydroascorbic acid administration attenuates brain damage in focal ischemia.

The aim of this study is to determine the protective effects of vitamin D(3) and dehydroascorbic acid (DHA), a blood-brain barrier transportable form of vitamin C, against ischemia/reperfusion (I/R) injury on a middle cerebral artery occlusion/reperfusion model of brain since reactive oxygen species play an important role in the pathophysiology of I/R injury in brain. In order to examine antioxidant status and lipid peroxidation, we assayed malondialdehyde (MDA) levels as a marker of lipid peroxidation, and reduced glutathione (GSH) and superoxide dismutase (SOD) enzyme activities as free radical scavenging enzymes in cortex and corpus striatum (CS). Wistar albino rats were divided into five equal groups of each consisting of seven rats: control, I/R, I/R + DHA, I/R + vitamin D(3), and I/R + vitamin D(3) + dehydroascorbic acid groups. MDA levels were found to be increased in the I/R group, I/R + DHA, and I/R + vitamin D(3) groups compared with the control group in both cortex and corpus striatum. However, MDA level were found to be significantly decreased in only I/R + vitamin D(3) + DHA group compared with the I/R group in cortex (P < 0.0001). MDA levels were not significantly different in I/R + DHA, and I/R + vitamin D(3) groups compared with the I/R group. GSH and SOD enzyme activities were significantly decreased in I/R, I/R + DHA, and I/R + vitamin D(3) groups compared with the control group in both cortex and corpus striatum (CS) (P < 0.0001). Whereas, both GSH and SOD activity were increased in I/R + vitamin D(3) + DHA group compared with the I/R group in both cortex and CS (P < 0.001 in cortex, P < 0.001 in CS for SOD P < 0.002 in cortex P < 0.03 in CS for GSH). Our results demonstrate that the combination of vitamin D(3) and DHA treatment prevent free radical production and dietary supplementation of vitamin D(3) and DHA which may be useful in the ischemic cerebral vascular diseases.

Dehydroascorbic acid as an anti-cancer agent.

Three discoveries together point the way to a potential treatment for cancer. In 1982, Poydock and colleagues found that dehydroascorbic acid has the remarkable ability to eliminate the aggressive mouse tumours, L1210, P388, Krebs sarcoma, and Ehrlich carcinoma. In 1993, Jakubowski found that cancer cells (but not normal cells) contain measurable quantities of homocysteine thiolactone. Recently, the author found that dehydroascorbic acid reacts with homocysteine thiolactone converting it to the toxic compound, 3-mercaptopropionaldehyde. Taken together, these findings suggest that rapidly-dividing tumour cells make unusually large amounts of homocysteine thiolactone and that administered dehydroascorbic acid enters the cells and converts the thiolactone to mercaptopropionaldehyde which kills the cancer cells. The effectiveness of dehydroascorbic acid might be further increased by combining it with methionine and/or methotrexate to increase the homocysteine concentration in cancer cells.

A cerebroprotective dose of intravenous citrate/sorbitol-stabilized dehydroascorbic acid is correlated with increased cerebral ascorbic acid and inhibited lipid peroxidation after murine reperfused stroke.

OBJECTIVE: Oxidative damage has been implicated in the pathogenesis of cerebral ischemia. We previously demonstrated that exogenously supplied dehydroascorbic acid (DHA), an oxidized, blood-brain barrier transportable form of the antioxidant ascorbic acid (AA), improves outcome after experimental stroke. METHODS: To investigate the neuroprotective effect of DHA therapy, we measured cerebral AA levels using a novel assay, quantified markers of lipid peroxidation, and evaluated infarct volume after reperfused stroke in a murine model. All experiments were performed using a new citrate/sorbitol-stabilized DHA formulation to improve the stability of the compound. RESULTS: Intraparenchymal AA levels declined after cerebral ischemia/reperfusion and were repleted in a dose-dependent fashion by postischemic administration of intravenous DHA (P < 0.01). Repletion of these levels was associated with reductions in cerebral malondialdehyde levels (P < 0.05), which were also elevated after reperfused stroke. DHA repletion of interstitial AA levels and reduction in cerebral lipid peroxidation was associated with dose-dependent reductions in infarct volume (P < 0.05). CONCLUSION: Together, these results indicate that an intravenous cerebroprotective dose of citrate/sorbitol-stabilized DHA is correlated with increased brain ascorbate levels and a suppression of excessive oxidative metabolism.

Dehydroascorbic acid normalizes several markers of oxidative stress and inflammation in acute hyperglycemic focal cerebral ischemia in the rat.

We investigated the effect of dehydroascorbic acid (DHA), the oxidized form of vitamin C which is a superoxide scavenger, on manganese superoxide dismutase (MnSOD), copper-zinc SOD (CuZnSOD), cyclooxygenase-2 (COX-2) and interleukin-1beta (IL-1beta) expression in a rat model of focal cerebral ischemia under normo- and hyperglycemic conditions. Edema formation was also assessed. MnSOD, CuZnSOD, COX-2 and IL-1beta mRNA and protein expression were studied 3 h post-ischemia. No changes were observed in MnSOD and CuZnSOD mRNA expression among the groups. COX-2 and IL-1beta mRNA expression were upregulated by ischemia but were not influenced by the glycemic state. At the protein level, hyperglycemic cerebral ischemia increased MnSOD and CuZnSOD [Bémeur, C., Ste-Marie, L., Desjardins, P., Butterworth, R.F., Vachon, L., Montgomery, J., Hazell, A.S., 2004a. Expression of superoxide dismutase in hyperglycemic focal cerebral ischemia in the rat. Neurochem. Int. 45, 1167-1174] and IL-1beta expression compared to normoglycemic ischemia. COX-2 protein expression was also significantly higher following hyperglycemic ischemia compared to hyperglycemic shams. DHA administration did not change the pattern of COX-2 or IL-1beta mRNA expression, but normalized the increased protein expression following hyperglycemic ischemia. DHA administration also normalized MnSOD and CuZnSOD protein expression to the levels observed in normoglycemic ischemic animals. Edema formation was significantly reduced by DHA administration in hyperglycemic ischemic animals. The DHA-induced post-transcriptional normalization of MnSOD, CuZnSOD, COX-2 and IL-1beta levels and the decreased edema formation suggest that hyperglycemia accelerates superoxide formation and the inflammatory response, thus contributing to early damage in hyperglycemic stroke and strategies to scavenge superoxide should be an important therapeutic avenue.

Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled survey.

One hundred sixty-eight volunteers were randomized to receive a placebo or a vitamin C supplement, two tablets daily, over a 60-day period between November and February. They used a five-point scale to assess their health and recorded any common cold infections and symptoms in a daily diary. Compared with the placebo group, the active-treatment group had significantly fewer colds (37 vs 50, P<.05), fewer days challenged virally (85 vs 178), and a significantly shorter duration of severe symptoms (1.8 vs 3.1 days, P<.03). Consequently, volunteers in the active group were less likely to get a cold and recovered faster if infected. Few side effects occurred with the active treatment, and volunteers reported greatly increased satisfaction with the study supplement compared with any previous form of vitamin C. This well-tolerated vitamin C supplement may prevent the common cold and shorten the duration of symptoms. Volunteers were generally impressed by the protection afforded them during the winter months and the general acceptability of the study medication.

[The antiacidotic and cardioprotective effects of fructose-1,6-diphosphate and dehydroascorbic acid]. / Antiatsidoticheskii i kardioprotektivnyi éffekty fruktozo-1,6-difosfata i degidroaskorbinovoi kisloty.

The antiacidotic and cardioprotective effects of dehydro-L-ascorbic acid and fructose-1,6-diphosphate were compared in experiments of rats. It was found that the both compounds exhibit the antiacidotic effect on the model of metabolic acidosis in the isolated hypoxic heart, decrease the excess-lactate degree, increase ATP level in the myocardium and reduce the size of the necrosis area 4 hours after the modelling of myocardial infarction. The significance of the antiacidotic component in the mechanism of the cardioprotective action of the energy-supplying agents is concluded.

Antiscorbutic effect of dehydro-L-ascorbic acid in vitamin C-deficient guinea pigs.

The antiscorbutic effect of dehydro-L-ascorbic acid (DAsA) was investigated in vitamin C-deficient guinea pigs. Male guinea pigs were fed vitamin C-deficient diets for 16 days to deplete body L-ascorbic acid (AsA) pools and then fed the deficient diet supplemented with DHA and/or AsA intraperitoneally for 14 days. During the repletion period, most of the animals injected with 0.5 mg DAsA/day developed scurvy, their body weights decreased and their mortality rate was higher than that of the other groups injected with 0.5 mg AsA/day or 5 mg DAsA/day. Injecting animals with 0.5 mg AsA/day resulted in the disappearance of the typical scorbutic symptoms and regaining of body weight. These data indicate that DAsA has considerably less antiscorbutic activity than AsA in vitamin C-deficient guinea pigs.