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play a role during the initial chemotactic response of neutrophils shortly after infection

following vitamin C supplementation, a 20% increase in neutrophil chemotactic activity was observed

also contributes to the phagocytosis and killing of microbes by neutrophils

low levels of vitamin C occurring in high-stress situations

maturation, proliferation, and viability of T cells have all been shown to be upregulated by the presence of normal physiologic concentrations of vitamin C

Vitamin C has been shown to directly affect the number of Igs released from B cells

vitamin C among healthy young adult males showed a significant increase in serum levels of IgA, IgG, and IgM

effects of high-dose vitamin C on cytokine levels in cancer patients, finding decreased amounts of the cytokines Interleukin-1 alpha (IL-1 alpha), IL-2, IL-8, and tumor necrosis factor-alpha (TNF-alpha) after high-dose vitamin C infusion

when vitamin C was supplemented with vitamin E in healthy adults, it increased the production of cytokines IL-1 beta and TNF-alpha

vitamin C acts to modulate the levels of cytokines to prevent them from fluctuating in either direction

vitamin C also acts as an important antioxidant to the cells of the immune system.

human leukocytes, neutrophils, in particular, possess the ability to transport the oxidized form of vitamin C across its membrane to use as a defense mechanism against ROS produced during an immune response

Vitamin C also can recover other endogenous antioxidants in the body such as vitamin E and glutathione, returning them to their active state

vitamin C can decrease the activation of NF-kB

can reduce harmful nitrogen-based compounds such as N-nitrosamines and nitrosamides, both of which are carcinogenic 

subjects taking oral vitamin C supplementation saw a 60% to 90% reduction in oxidative stress compared to a placebo control

subjects infused with vitamin C alone had a 516% increase in glutathione levels compared to subjects not provided the 500 mg daily supplementation

hydroxylating proline and lysine

mature and stabilize the tissue of a healing wound

healing

oral surgery

improved soft tissue regeneration

vitamin C increases the mRNA levels of type I and type III collagen in the human dermis

Studies have demonstrated that those with low levels of vitamin C are at a significantly higher risk of respiratory infection compared to those with normal levels

viral cold duration was reduced by about 8% in adults and 13.5% in children using prophylactic daily doses of 200 mg of oral vitamin C

prophylactically supplementing vitamin C decreases the risk of infection with respiratory viruses such as the common cold

combined with probiotics, oral vitamin C supplementation showed a 33% decrease in the incidence of respiratory tract infections in preschool-age children [

high-dose oral supplementation of vitamin C managed to prevent or reduce symptoms if taken before or just after the onset of cold- or flu-like symptoms

improvements in oxygen saturation and decreased IL-6 levels (a marker of inflammation) in the treatment group compared to the control group

8 g doses of oral vitamin C

there is a negative correlation between age and serum levels of vitamin C

Patients with COVID-19 will likely also experience depletion in serum levels of vitamin C as a direct result of the upregulation of the immune system to combat the infection

Colunga et al. suggested that oral vitamin C can be combined with oral Quercetin, an antiviral flavonoid, to improve Quercetin’s ability to block viral membrane fusion of SARS-CoV-2

high doses of 1-2 g/day of oral vitamin C could prevent other upper respiratory infections

It appears vitamin C supplementation by itself does not provide a striking benefit in preventing COVID-19 infection for those without a deficiency

Hiedra et al. were able to show decreases in inflammatory biomarkers, such as D-dimer and ferritin

some evidence to support that prophylactic use of vitamin C helps reduce the severity of respiratory infection symptoms once a subject has already been infected

oral vitamin C in combination with zinc provided the largest amount of antibody titers 42 days

linear relationship between days of vitamin C therapy and survival duration

other studies were unable to find any definitive improvement concerning therapy with vitamin C

Fowler et al. aimed to see if a high-dose vitamin C infusion would benefit patients affected by ARDS, but they were unable to conclude that vitamin C infusion, compared to a placebo, could decrease vascular inflammation and damage in ARDS

in a sample of 67 COVID-19-positive ICU patients, 82% of them displayed plasma vitamin C levels below 0.4 mg/dL

continuous vitamin C infusion at a rate of 60 mg/kg/day for four days decreased the need for mechanical ventilation and vasopressor use but had no significant effect on overall mortality

Carr et al. suggested that high-dose IV vitamin C is most effective when treating sepsis as septic patients receiving the normal daily recommendations through diet still showed decreased vitamin C levels

High-dose IV vitamin C treatment has also been shown by Kakodkar et al. to decrease syndecan-1, an endothelial glycocalyx that contributes to mortality in septic patients

combined with hydrocortisone and thiamine, septic patients treated with 1.5 g of IV vitamin C every six hours showed a distinct decrease in their SOFA scores and none of the patients treated developed organ failure

combined with hydrocortisone and thiamine, septic patients treated with 1.5 g of IV vitamin C every six hours showed a distinct decrease in their SOFA scores and none of the patients treated developed organ failure

reduced overall mortality

reduced overall mortality

propose the use for high-dose vitamin C to aid in the treatment of septic shock-induced hypotension

treatment of severe sepsis using a high dose (up to 200 mg/kg/day) of IV vitamin C was explored in phase I, a double-blind, randomized, placebo-controlled trial by Fowler et al. [75]. Their findings included a reduction in SOFA scores and decreased vascular injury compared to a placebo control group, all while showing minimal adverse side effects

Maintaining a daily intake of 75 and 100 mg for men and women, respectively, as recommended by the U.S. Institute of Medicine

These results show that targeting the cancer DNA methylome by combining low-dose 5-aza-CdR and vitamin C stimulates the expression of ERVs, the induction of a cell-autonomous immune activation response, and increased apoptosis of cancer cells

The addition of vitamin C to treatment protocols therefore may be a straightforward way to increase the clinical efficacy of such drugs in MDS and leukemia patients

Vitamin C deficiency has been seen previously in patients with multiple types of cancer, including hematological malignancies (35⇓–37). We predict that these patients might receive the most benefits from the combination treatment.

induction of an innate immune response

We therefore measured plasma concentrations of vitamin C in a small number of patients with miscellaneous hematologic malignancies. Strikingly, 58% of patients with hematological neoplasia who were not taking vitamin C supplements had severe vitamin C deficiency (serum concentration <11.4 μM, at which clinical features of scurvy may be manifested) (34), and 33% had vitamin C levels below the normal range

it is possible that vitamin C was oxidized to DHA before it was transported into the cells

Oral administration of vitamin C should be sufficient for the therapeutic strategy, because the concentrations reported in this study would not require i.v. administration.

Vitamin C is an essential nutrient for humans and has been reported to increase IFN levels in human cells upon virus infection

daily treatment with vitamin C alone at physiological concentrations enhanced the expression of viral-defense genes relative to untreated cells

When combined with low-dose 5-aza-CdR, physiological concentrations of vitamin C synergistically inhibited cancer-cell growth and induced apoptosis. Such synergy was associated with increased ERV expression and dsRNA in treated cells. The mechanism of action differs from that of vitamin C at higher doses, which involves its pro-oxidant activity, including GSH inhibition, to generate reactive oxygen species

This activity has been shown to induce DNA damage and to enhance the sensitivities of myeloid malignancies, multiple myeloma, and cutaneous T-cell lymphoma to arsenic trioxide (41⇓⇓–44). It also can increase chemosensitivity of ovarian cancer cells (27) and selectively kill KRAS or BRAF mutant colorectal cancer cells by inhibiting GAPDH

reactive oxygen species

Patients with higher inflammation or tumor burdens, as measured by CRP levels or tumor antigen levels, tend to show lower peak plasma ascorbate levels after IVC.

Patients with metastatic tumors tend to achieve lower post infusion plasma ascorbate levels than those with localized tumors.

Meta-analyses of clinical studies involving cancer and vitamins also conclude that antioxidant supplementation does not interfere with the efficacy of chemotherapeutic regiments

Most of the prostate cancer patients studied, 75±19% (95% confidence), showed reductions in PSA levels during the course of their IVC therapy

Laboratory studies suggest that, at high concentrations, ascorbate does not interfere with chemotherapy or irradiation and may enhance efficacy in some situations

Cameron and Pauling observed fourfold survival times in terminal cancer patients treated with intravenous ascorbate infusions followed by oral supplementation

The inflammatory microenvironment of cancer cells leads to increasing oxidative stress, which apparently depletes vitamin C, resulting in lower plasma ascorbate concentrations in blood samples post IVC infusion. Another explanation for this finding may be that cancers are themselves more metabolically active in their uptake of vitamin C, causing subjects to absorb more of the vitamin, and as a results show lower plasma ascorbate concentrations in blood post IVC infusion.

patients with severely elevated CRP levels attain plasma ascorbate concentrations after IVC infusions that are only 65% of those attained for subjects with normal CRP levels

The finding of decreased plasma ascorbate levels in cancer patients may relate to the molecular structure of ascorbic acid; in particular, the similarity of its oxidized form, dihydroascorbic acid, to glucose

Since tumor have increased requirement for glucose [67], transport of dehydroascorbate into the cancer cells via glucose transport molecules and ascorbate through sodium-dependent transporter may be elevated

Increased accumulation of ascorbic acid in the tumor site was supported by measurements of the level of ascorbic acid in tumors in animal experiments

patients with advanced malignancies may have lower level of ascorbic acid in tissue, creating a higher demand for the vitamin C

IVC therapy appears to reduce CRP levels in cancer patients.

CRP concentrations directly correlate with disease activity in many cases and can contribute to disease progression through a range of pro-inflammatory properties.

Being an exquisitely sensitive marker of systemic inflammation and tissue damage, CRP is very useful in screening for organic disease and monitoring treatment responses

ncreases in CRP concentrations have been associated with poorer prognosis of survival in cancer patients, particularly with advance disease independent of tumor stage

Regarding inflammation, 73±13% of subjects (95% confidence) showed a reduction in CRP levels during therapy. This was an even more dramatic 86±13% (95% confidence) in subjects who started therapy with CRP levels above 10 mg/L

patients treated by IVC with follow-up several year showed that suppression of inflammation in cancer patients by high-dose IVC is feasible and potentially beneficial

Inflammation is a marker of high cancer risk, and poor treatment outcome

The subjects with highly elevated CRP concentrations have a three-fold elevation “all-cause” mortality risk and a twenty-eight fold increase in cancer mortality risk

cancer patients may need higher doses to achieve a given plasma concentration.

patients with lower vitamin C levels may see more distribution of intravenously administered ascorbate into tissues and thus attain less in plasma.

When treating patients with IVC, the first treatment likely serves to replenish depleted tissue stores, if those subjects were vitamin C deficient at the beginning of the treatment. Then, in subsequent treatments, with increasing doses, higher plasma concentrations can be attained. On-going treatments serve to progressively reduce oxidative stress in cancer patients.

large doses given intravenously may result in maximum plasma concentrations of roughly 30 mM, a level that has been shown to be sufficient for preferential cytotoxicity against cancer cells

oral intake of vitamin C exceeded 200 mg administered once daily, it was difficult to increase plasma and tissue concentrations above roughly 200 μM.

whereas the expression of SVCT-2 is ubiquitous

differential sensitivity to VC may result from variations in VC flow into cells, which is dependent on SVCT-2 expression.

high-dose VC significantly impaired both the tumorspheres initiation (Fig. 4d, e) and the growth of established tumorspheres derived from HCC cells (Fig. 4f, g) in a time-dependent and dose-dependent manner.

Hepatocellular carcinoma (HCC)

The antioxidant, N-acetyl-L-cysteine (NAC), preventing VC-induced ROS production (a ROS scavenger), completely restored the viability and colony formation among VC-treated cells

DNA double-strand damage was found following VC treatment

DNA damage was prevented by NAC

Interestingly, the combination of VC and cisplatin was even more effective in reducing tumor growth and weight

Consistent with the in vitro results, stemness-related genes expressions in tumor xenograft were remarkably reduced after VC or VC+cisplatin treatment, whereas conventional cisplatin therapy alone led to the increase of CSCs

VC is one of the numerous common hepatoprotectants.

Interestingly, at extracellular concentrations greater than 1 mM, VC induces strong cytotoxicity to cancer cells including liver cancer cells

we hypothesized that intravenous VC might reduce the risk of recurrence in HCC patients after curative liver resection.

Intriguingly, the 5-year disease-free survival (DFS) for patients who received intravenous VC was 24%, as opposed to 15% for no intravenous VC-treated patients

Median DFS time for VC users was 25.2 vs. 18 months for VC non-users

intravenous VC use is linked to improved DFS in HCC patients.

In this study, based on the elevated expression of SVCT-2, which is responsible for VC uptake, in liver CSCs, we revealed that clinically achievable concentrations of VC preferentially eradicated liver CSCs in vitro and in vivo

Additionally, we found that intravenous VC reduced the risk of post-surgical HCC progression in a retrospective cohort study.

Three hundred thirty-nine participants (55.3%) received 2 g intravenous VC for 4 or more days after initial hepatectomy

As the key protein responsible for VC uptake in the liver, SVCT-2 played crucial roles in regulating the sensitivity to ascorbate-induced cytotoxicity

we also observed that SVCT-2 was highly expressed in human HCC samples and preferentially elevated in liver CSCs

SVCT-2 might serve as a potential CSC marker and therapeutic target in HCC

CSCs play critical roles in regulating tumor initiation, relapse, and chemoresistance

we revealed that VC treatment dramatically reduced the self-renewal ability, expression levels of CSC-associated genes, and percentages of CSCs in HCC, indicating that CSCs were more susceptible to VC-induced cell death

as a drug for eradicating CSCs, VC may represent a promising strategy for treatment of HCC, alone or particularly in combination with chemotherapeutic drugs

In HCC, we found that VC-generated ROS caused genotoxic stress (DNA damage) and metabolic stress (ATP depletion), which further activated the cyclin-dependent kinase inhibitor p21, leading to G2/M phase cell cycle arrest and caspase-dependent apoptosis in HCC cells

we demonstrated a synergistic effect of VC and chemotherapeutic drug cisplatin on killing HCC both in vitro and in vivo

Intravenous VC has also been reported to reduce chemotherapy-associated toxicity of carboplatin and paclitaxel in patients,38 but the specific mechanism needs further investigation

Our retrospective cohort study also showed that intravenous VC use (2 g) was related to the improved DFS in HCC patients after initial hepatectomy

several clinical trials of high-dose intravenous VC have been conducted in patients with advanced cancer and have revealed improved quality of life and prolonged OS

high-dose VC was not toxic to immune cells and major immune cell subpopulations in vivo

high recurrence rate and heterogeneity

tumor progression, metastasis, and chemotherapy-resistance

SVCT-2 was highly expressed in HCC samples in comparison to peri-tumor tissues

high expression (grade 2+/3+) of SVCT-2 was in agreement with poorer overall survival (OS) of HCC patients (Fig. 1c) and more aggressive tumor behavior

SVCT-2 is enriched in liver CSCs

these data suggest that SVCT-2 is preferentially expressed in liver CSCs and is required for the maintenance of liver CSCs.

pharmacologic concentrations of plasma VC higher than 0.3 mM are achievable only from i.v. administration

The viabilities of HCC cells were dramatically decreased after exposure to VC in dose-dependent manner

VC and cisplatin combination further caused cell apoptosis in tumor xenograft

These results verify that VC inhibits tumor growth in HCC PDX models and SVCT-2 expression level is associated with VC response

qPCR and IHC analysis demonstrated that expression levels of CSC-associated genes and percentages of CSCs in PDXs dramatically declined after VC treatment, confirming the inhibitory role of VC in liver CSCs

Our data show that ascorbic acid selectively killed cancer but not normal cells, using concentrations that could only be achieved by i.v. administration

Ascorbate-mediated cell death was due to protein-dependent extracellular H2O2 generation, via ascorbate radical formation from ascorbate as the electron donor. Like glucose, when ascorbate is infused i.v., the resulting pharmacologic concentrations should distribute rapidly in the extracellular water space (42). We showed that such pharmacologic ascorbate concentrations in media, as a surrogate for extracellular fluid, generated ascorbate radical and H2O2. In contrast, the same pharmacologic ascorbate concentrations in whole blood generated little detectable ascorbate radical and no detectable H2O2. These findings can be accounted for by efficient and redundant H2O2 catabolic pathways in whole blood (e.g., catalase and glutathione peroxidase) relative to those in media or extracellular fluid

ascorbic acid administered i.v. in pharmacologic concentrations may serve as a pro-drug for H2O2 delivery to the extracellular milieu

H2O2 generated in blood is normally removed by catalase and glutathione peroxidase within red blood cells, with internal glutathione providing reducing equivalents

The electron source for glutathione is NADPH from the pentose shunt, via glucose-6-phosphate dehydrogenase. If activity of this enzyme is diminished, the predicted outcome is impaired H2O2 removal causing intravascular hemolysis, the observed clinical finding.

Only recently has it been understood that the discordant clinical findings can be explained by previously unrecognized fundamental pharmacokinetics properties of ascorbate

Intracellular transport of ascorbate is tightly controlled in relation to extracellular concentration

Intravenous ascorbate infusion is expected to drastically change extracellular but not intracellular concentrations

For i.v. ascorbate to be clinically useful in killing cancer cells, pharmacologic but not physiologic extracellular concentrations should be effective, independent of intracellular ascorbate concentrations.

It is unknown why ascorbate, via H2O2, killed some cancer cells but not normal cells.

There was no correlation with ascorbate-induced cell death and glutathione, catalase activity, or glutathione peroxidase activity.

H2O2, as the product of pharmacologic ascorbate concentrations, has potential therapeutic uses in addition to cancer treatment, especially in infections

Neutrophils generate H2O2 from superoxide,

i.v. ascorbate is effective in some viral infections

H2O2 is toxic to hepatitis C

Use of ascorbate as an H2O2-delivery system against sensitive pathogens, viral or bacterial, has substantial clinical implications that deserve rapid exploration.

Recent pharmacokinetics studies in men and women show that 10 g of ascorbate given i.v. is expected to produce plasma concentrations of nearly 6 mM, which are >25-fold higher than those concentrations from the same oral dose

As much as a 70-fold difference in plasma concentrations is expected between oral and i.v. administration,

Complementary and alternative medicine practitioners worldwide currently use ascorbate i.v. in some patients, in part because there is no apparent harm

Human Burkitt's lymphoma cells

We first investigated whether ascorbate in pharmacologic concentrations selectively affected the survival of cancer cells by studying nine cancer cell lines

Clinical pharmacokinetics analyses show that pharmacologic concentrations of plasma ascorbate, from 0.3 to 15 mM, are achievable only from i.v. administration

plasma ascorbate concentrations from maximum possible oral doses cannot exceed 0.22 mM because of limited intestinal absorption

For five of the nine cancer cell lines, ascorbate concentrations causing a 50% decrease in cell survival (EC50 values) were less than 5 mM, a concentration easily achievable from i.v. infusion

All tested normal cells were insensitive to 20 mM ascorbate.

Lymphoma cells were selected because of their sensitivity to ascorbate

As ascorbate concentration increased, the pattern of death changed from apoptosis to pyknosis/necrosis, a pattern suggestive of H2O2-mediated cell death

Apoptosis occurred by 6 h after exposure, and cell death by pyknosis was ≈90% at 14 h after exposure

In contrast to lymphoma cells, there was little or no killing of normal lymphocytes and monocytes by ascorbate

Ascorbate is transported into cells as such by sodium-dependent transporters, whereas dehydroascorbic acid is transported into cells by glucose transporters and then immediately reduced internally to ascorbate

Whether or not intracellular ascorbate was preloaded, extracellular ascorbate induced the same amount and type of death.

extracellular ascorbate in pharmacologic concentrations mediates death of lymphoma cells by apoptosis and pyknosis/necrosis, independently of intracellular ascorbate.

H2O2 as the effector species mediating pharmacologic ascorbate-induced cell death

Superoxide dismutase was not protective

Because these data implicated H2O2 in cell killing, we added H2O2 to lymphoma cells and studied death patterns using nuclear staining (19, 28). The death patterns found with exogenous H2O2 exposure were similar to those found with ascorbate

For both ascorbate and H2O2, death changed from apoptosis to pyknosis/necrosis as concentrations increased

Sensitivity to direct exposure to H2O2 was greater in lymphoma cells compared with normal lymphocytes and normal monocytes

There was no association between the EC50 for ascorbate-mediated cell death and intracellular glutathione concentrations, catalase activity, or glutathione peroxidase activity

H2O2 generation was dependent on time, ascorbate concentration, and the presence of trace amounts of serum in media

ascorbate radical is a surrogate marker for H2O2 formation.

whatever H2O2 is generated should be removed by glutathione peroxidase and catalase within red blood cells, because H2O2 is membrane permeable

The data are consistent with the hypothesis that ascorbate in pharmacologic concentrations is a pro-drug for H2O2 generation in the extracellular milieu but not in blood.

The occurrence of one predicted complication, oxalate kidney stones, is controversial

In patients with glucose-6-phosphate dehydrogenase deficiency, i.v. ascorbate is contraindicated because it causes intravascular hemolysis

ascorbate at pharmacologic concentrations in blood is a pro-drug for H2O2 delivery to tissues.

ascorbate, an electron-donor in such reactions, ironically initiates pro-oxidant chemistry and H2O2 formation

data here showed that ascorbate initiated H2O2 formation extracellularly, but H2O2 targets could be either intracellular or extracellular, because H2O2 is membrane permeant

More than 100 patients have been described, presumably without glucose-6-phosphate dehydrogenase deficiency, who received 10 g or more of i.v. ascorbate with no reported adverse effects other than tumor lysis

metabolic activity, oxygen transport, and DNA synthesis

Iron is found in the human body in the form of haemoglobin in red blood cells and growing erythroid cells.

macrophages contain considerable quantities of iron

iron is taken up by the majority of cells in the form of a transferrin (Tf)-Fe(III) complex that binds to the cell surface receptor transferrin receptor 1 (TfR1)

excess iron is retained in the liver cells

the endosomal six transmembrane epithelial antigen of the prostate 3 (STEAP3) reduces Fe(III) (ferric ion) to Fe(II) (ferrous ion), which is subsequently transferred across the endosomal membrane by divalent metal transporter 1 (DMT1)

labile iron pool (LIP)

LIP is toxic to the cells owing to the production of massive amounts of ROS.

DHA is quickly converted to Vit-C within the cell, by interacting with reduced glutathione (GSH) [45,46,47]. NADPH then recycles the oxidized glutathione (glutathione disulfide (GSSG)) and converts it back into GSH

Fe(II) catalyzes the formation of OH• and OH− during the interaction between H2O2 and O2•− (Haber–Weiss reaction)

Ascorbate can efficiently reduce free iron, thus recycling the cellular Fe(II)/Fe(III) to produce more OH• from H2O2 than can be generated during the Fenton reaction, which ultimately leads to lipid, protein, and DNA oxidation

Vit-C-stimulated iron absorption

reduce cellular iron efflux

high-dose Vit-C may elevate cellular LIP concentrations

ascorbate enhanced cancer cell LIP specifically by generating H2O2

Vit-C produces H2O2 extracellularly, which in turn inhibits tumor cells immediately

tumor cells have a need for readily available Fe(II) to survive and proliferate.

Tf has been recognized to sequester most labile Fe(II) in vivo

Asc•− and H2O2 were generated in vivo upon i.v Vit-C administration of around 0.5 g/kg of body weight and that the generation was Vit-C-dose reliant

free irons, especially Fe(II), increase Vit-C autoxidation, leading to H2O2 production

iron metabolism is altered in malignancies

increase in the expression of various iron-intake pathways or the downregulation of iron exporter proteins and storage pathways

Fe(II) ion in breast cancer cells is almost double that in normal breast tissues

macrophages in the cancer microenvironment have been revealed to increase iron shedding

Advanced breast tumor patients had substantially greater Fe(II) levels in their blood than the control groups without the disease

increased the amount of LIP inside the cells through transferrin receptor (TfR)

Warburg effect, or metabolic reprogramming,

Warburg effect is aided by KRAS or BRAF mutations

Vit-C is supplied, it oxidizes to DHA, and then is readily transported by GLUT-1 in mutant cells of KRAS or BRAF competing with glucose [46]. DHA is quickly converted into ascorbate inside the cell by NADPH and GSH [46,107]. This decrease reduces the concentration of cytosolic antioxidants and raises the intracellular ROS amounts

increased ROS inactivates glyceraldehyde 3-phosphate dehydrogenase (GAPDH)

ROS activates poly (ADP-ribose) polymerase (PARP), which depletes NAD+ (a critical co-factor of GAPDH); thus, further reducing the GAPDH associated with a multifaceted metabolic rewiring

Hindering GAPDH can result in an “energy crisis”, due to the decrease in ATP production

high-dose Vit-C recruited metabolites and increased the enzymatic activity in the pentose phosphate pathway (PPP), blocked the tri-carboxylic acid (TCA) cycle, and increased oxygen uptake, disrupting the intracellular metabolic balance and resulting in irreversible cell death, due to an energy crisis

mega-dose Vit-C influences energy metabolism by producing tremendous amounts of H2O2

Due to its great volatility at neutral pH [76], bolus therapy with mega-dose DHA has only transitory effects on tumor cells, both in vitro and in vivo.

pharmacologic ascorbate as a prooxidant drug for therapeutic use.

Recently we reported that pharmacologic ascorbic acid concentrations produced H2O2 concentrations of ≥25 μM, causing cancer cell death in vitro

We found that H2O2 concentrations generated in vivo were those that caused cancer cell death in vitro

When ascorbate was given parenterally, Asc•−, the product of a loss of one electron from ascorbate, was detected preferentially in extracellular fluid compared with blood

Asc•− generation in extracellular fluid depended on the ascorbate dose and the resulting concentrations

With i.v. administration of ascorbate, Asc•− concentrations were as much as 12-fold greater in extracellular fluid compared to blood and approached 250 nM

In blood, such Asc•− concentrations were never produced and were always <50 nM

These data are all consistent with the hypothesis that pharmacologic ascorbate concentrations in vivo serve as a prodrug for selective delivery of H2O2 to the extracellular space

After oral ingestion, control of intracellular and extracellular ascorbate concentrations is mediated by three mechanisms: intestinal absorption, tissue transport, and renal reabsorption

intestinal absorption, or bioavailability, declines at doses >200 mg

corresponding to plasma concentrations of ≈60 μM

at approximately this concentration, the ascorbate tissue transporter SVCT2 approaches Vmax, and tissues appear to be saturated

also at ≈60 μM, renal reabsorption approaches saturation, and excess ascorbate is excreted in urine

Parenteral administration bypasses tight control

When tight control is bypassed, H2O2 forms in the extracellular space

in vivo validation of ascorbate as a prodrug for selective H2O2 formation

Temporarily bypassing tight control with parenteral administration of ascorbate allows H2O2 to form in discrete time periods only, decreasing likelihood of harm, and provides a pharmacologic basis for therapeutic use of i.v. ascorbate

H2O2 formation results in selective cytotoxicity

Tumor cells are killed with exposure to H2O2 for ≤30 min

In vitro, killing is mediated by H2O2 rather than Asc•−

In addition to cancer treatment, another potential therapeutic use is for treatment of infections. H2O2 concentrations of 25–50 μM are bacteriostatic

virally infected cells may also be candidates