No abstract

Cellular glutathione levels may exceed vitamin C levels by 10-fold, generating the question about the real antioxidant role that low intracellular concentrations of vitamin C can play in the presence of a vast molar excess of glutathione. We characterized the metabolism of vitamin C and its relationship with glutathione in primary cultures of human endothelial cells oxidatively challenged by treatment with hydrogen peroxide or with activated cells undergoing the respiratory burst, and analyzed the manner in which vitamin C interacts with glutathione to increase the antioxidant capacity of cells. Our data indicate that: (i) endothelial cells express transporters for reduced and oxidized vitamin C and accumulate ascorbic acid with participation of glutathione-dependent dehydroascorbic acid reductases, (ii) although increased intracellular levels of vitamin C or glutathione caused augmented resistance to oxidative stress, 10-times more glutathione than vitamin C was required, (iii) full antioxidant protection required the simultaneous presence of intracellular and extracellular vitamin C at concentrations normally found in vivo, and (iv) intracellular vitamin C cooperated in enhancing glutathione recovery after oxidative challenge thus providing cells with enhanced survival potential, while extracellular vitamin C was recycled through a mechanism involving the simultaneous neutralization of oxidant species. Therefore, in endothelial cells under oxidative challenge, vitamin C functions as an essential cellular antioxidant even in the presence of a vast molar excess of glutathione.Human cells contain two important water soluble antioxidants, vitamin C and the tripeptide glutathione (L-␥-glutamyl-L-cysteinyl-glycine). Vitamin C plays an important physiological role in cells as a reducing agent and antioxidant, free radical scavenger, and enzyme cofactor (1, 2). Glutathione is the most abundant non-protein thiol in mammalian cells and participates in multiple functions central to the physiology of cells, acting as a reducing agent, antioxidant, and free-radical scavenger and is involved in the metabolism and detoxification of xenobiotics, and alterations in GSH levels and metabolism have been associated with different human diseases (3, 4). Glutathione and vitamin C show a strong functional interdependence in vivo. Disruption of glutathione metabolism in vivo in rats and guinea pigs by treatment with buthionine-(SR)-sulfoximine (BSO), 5 a potent and specific glutathione synthesis inhibitor, revealed that the dysfunction and mortality associated with glutathione deficiency can be ameliorated by vitamin C supplementation (3, 5). Inversely, glutathione ester supplementation can protect or delay the effects of a vitamin C-free diet in newborn rats and guinea pigs unable to synthesize vitamin C (3, 6).Although a functional relationship between glutathione and vitamin C has been clearly established in rats and guinea pigs, we know little about how they cooperate in providing human cells with potent antioxidant defense mechan...

In the development of vaccines capable of providing immunity against brucellosis, Cu-Zn superoxide dismutase (SOD) has been demonstrated to be one of the protective immunogens of Brucella abortus. In an earlier study, we provided strong evidence that intramuscular injection with a plasmid DNA carrying the SOD gene (pcDNA-SOD) was able to induce a protective immune response. The present study was designed to characterize T-cell immune responses after an intraspleen (i.s.) vaccination of BALB/c mice with pcDNA-SOD. Animals vaccinated with pcDNA-SOD did not develop SOD-specific antibodies, at least until week 4 after immunization (the end of the experiment), and in vitro stimulation of their splenocytes with either recombinant Cu-Zn SOD or crude Brucella protein induced the secretion of gamma interferon (IFN-␥), but not interleukin-4, and elicited the induction of cytotoxic-T-lymphocyte activity. Upon analyzing the SOD-specific T-cell responses, the pcDNA-SOD vaccination was found to be stimulating both CD4؉ -and CD8 ؉ -T-cell populations. However, only the CD4 ؉ population was able to produce IFN-␥ and only the CD8 ؉ population was able to induce cytotoxic activity. Nevertheless, although i.s. route vaccination induces a significant level of protection in BALB/c mice against challenge with the virulent B. abortus strain 2308, vaccination by the intramuscular route with a similar amount of plasmid DNA does not protect. Based on these results, we conclude that i.s. immunization with pcDNA-SOD vaccine efficiently induced a Th1 type of immune response and a protective response that could be related to IFN-␥ production and cytotoxic activity against infected cells by SOD-specific CD4 ؉ and CD8 ؉ T cells, respectively.Brucellosis is a zoonotic disease that is endemic in some regions of the world. In human populations, the major cause of the disease is Brucella melitensis, but several cases have also been attributed to Brucella abortus, which otherwise primarily affects bovines. Because of the economic losses to the cattle industry caused by B. abortus, as well as because of the zoonotic infections by these bacterial species (8), great efforts are being made to eradicate bovine brucellosis all over the world. In order to achieve this objective, vaccine strains of B. abortus 32) have been used with relatively good results. However, even these vaccine strains are far from ideal, since they present some disadvantages, e.g., causing reactions in humans, inducing abortion in pregnant cattle, and showing a likelihood of changing to a virulent form (33).Brucella is an intracellular pathogen; therefore, cellular immune response is critical in generating protection against infection (42). It is well documented that gamma interferon (IFN-␥) production by CD4 ϩ T cells is essential to the protective response; IFN-␥ activates macrophages by enhancing their ability to kill bacteria (18,20,34,43). It is still unknown if there is a correlation between the degree of in vitro cytotoxic-Tlymphocyte (CTL) activity and in vivo levels of pro...

Since the early studies of William J. McCormick in the 1950s, vitamin C has been proposed as a candidate for the treatment of cancer. A number of reports have shown that pharmacological concentrations of vitamin C selectively kill cancer cells in vitro and decrease the growth rates of a number of human tumor xenografts in immunodeficient mice. However, up to the date there is still doubt regarding this possible therapeutic role of vitamin C in cancer, mainly because high dose administration in cancer patients has not showed a clear antitumor activity. These apparent controversial findings highlight the fact that we lack information on the interactions that occurs between cancer cells and vitamin C, and if these transformed cells can uptake, metabolize and compartmentalize vitamin C like normal human cells do. The role of SVCTs and GLUTs transporters, which uptake the reduced form and the oxidized form of vitamin C, respectively, has been recently highlighted in the context of cancer showing that the relationship between vitamin C and cancer might be more complex than previously thought. In this review, we analyze the state of art of the effect of vitamin C on cancer cells in vitro and in vivo, and relate it to the capacity of cancer cells in acquiring, metabolize and compartmentalize this nutrient, with its implications on the potential therapeutic role of vitamin C in cancer.

Neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD) and Creutzfeldt–Jakob disease (CJD) are brain conditions affecting millions of people worldwide. These diseases are associated with the presence of amyloid-β (Aβ), alpha synuclein (α-Syn) and prion protein (PrP) depositions in the brain, respectively, which lead to synaptic disconnection and subsequent progressive neuronal death. Although considerable progress has been made in elucidating the pathogenesis of these diseases, the specific mechanisms of their origins remain largely unknown. A body of research suggests a potential association between host microbiota, neuroinflammation and dementia, either directly due to bacterial brain invasion because of barrier leakage and production of toxins and inflammation, or indirectly by modulating the immune response. In the present review, we focus on the emerging topics of neuroinflammation and the association between components of the human microbiota and the deposition of Aβ, α-Syn and PrP in the brain. Special focus is given to gut and oral bacteria and biofilms and to the potential mechanisms associating microbiome dysbiosis and toxin production with neurodegeneration. The roles of neuroinflammation, protein misfolding and cellular mediators in membrane damage and increased permeability are also discussed.