Nitrosation-modulating effect of ascorbate in a model dynamic system of coexisting nitric oxide and superoxide

Volatile N-nitrosamines in Spanish commercial meat products and in fermented sausages prepared with different ingoing amounts of nitrate and nitrite

Spanish commercial dry fermented sausages and dry hams, manufactured with and without nitrate and/or nitrite have been screened for volatile N-nitrosamine (VNA) content. VNAs have been also quantified in experimental fermented sausages prepared with known ingoing amounts of curing salts. Solid phase microextraction followed by tandem quadrupole gas chromatography/mass spectrometry (GC-QQQ-MS) analysis allowed the identification and quantification of 8 VNAs, 5 of which were detected in the samples. The highest concentration of VNAs found in the commercial products was 5.4 μg/kg. The most frequently detected VNAs were N-nitrosodiphenylamine and N-nitrosopyrrolidine. Principal component analysis and cluster analysis did not show correlation between the content of VNAs and the use of nitrate/nitrite in the formula. In the experimental sausages N-nitrosodiphenylamine and N-nitrosopyrrolidine were only detected (0.55 μg/kg total concentration) when 150 mg/kg of both nitrate and nitrite were added to the formula without any antioxidant. The levels of VNAs detected in this study are similar to those reported in the literature in different fermented meat products and dry hams.

Protective effect of vitamin C on DNA damage in surgery-induced cognitive dysfunction in APP/PS1 mice

Postoperative cognitive impairment is more likely to occur in elderly patients and in those with neurodegenerative diseases. The mechanisms underlying this impairment include neuroinflammation and oxidative stress. The increase in reactive oxygen species during oxidative stress causes cellular and molecular injury to neurons, including DNA damage, which aggravate brain dysfunction. Vitamin C has antioxidant effects and improves cognitive function in patients with Alzheimer's disease. However, it is unclear whether it can ameliorate surgery-induced cognitive impairment by inhibiting oxidative stress. In this study, 6-month-old mice overexpressing mutant amyloid precursor protein and presenilin-1 (APP/PS1) were subjected to laparotomy. The open field and fear conditioning tests were used to assess cognitive function. Mice that underwent surgery showed cognitive impairment without changes in spontaneous locomotor activity. Oxidative stress, DNA damage and inflammatory mediators were increased in the hippocampus after surgery. The expression levels of non-homologous end-joining DNA repair-associated proteins, including Ku heterodimer, DNA-dependent protein kinase catalytic subunit, X-ray repair cross complementing 4 (XRCC4) and XRCC4-like factor, were increased after surgery. Vitamin C pretreatment effectively attenuated cognitive dysfunction induced by surgery and reduced oxidative stress and DNA damage. Our findings suggest that DNA damage plays an important role in surgery-induced cognitive dysfunction, and that vitamin C pretreatment may have therapeutic potential as a preventative approach for the cognitive impairment.

A vitamina C na esquizofrenia apresenta benefício? Estudo preliminar com análise comportamental em ratos

RESUMO Objetivo O objetivo deste estudo foi analisar em ratos modelos de esquizofrenia, induzidos pela administração de cetamina, a possibilidade dos efeitos benéficos do ácido ascórbico na esquizofrenia, por meio do teste comportamental. Métodos O estudo preliminar foi simples-cego e randomizado. Foi realizado o protocolo de psicose por cetamina em 24 ratos Wistar submetidos posteriormente à análise comportamental. No primeiro grupo, foram administradas: água e cetamina; no segundo: ácido ascórbico e cetamina; no terceiro: antipsicótico, ácido ascórbico e cetamina; e no quarto: antipsicótico, água e cetamina. A análise comportamental foi feita por meio do Open Field Test, considerado o método-padrão para avaliar comportamento em modelos animais de esquizofrenia. A análise estatística foi realizada pelo software IBM-SPSS, por meio dos Modelos Lineares Generalizados. Resultados O tratamento em monoterapia de haloperidol (Média Quadrante: 44,5 ± 15,8; IC: 13,54-75,46/Média Centro: 2,67 ± 0,67; IC: 1,63-4,35) e aquele em conjunto com a vitamina C (Média Quadrante: 38,67 ± 15,8; IC: 7,71-69,52/Média Centro: 2,00 ± 0,58; IC: 1,14-3,52) demonstraram benefícios nos ratos modelos de esquizofrenia induzidos por cetamina (Média Quadrante: 108,5 ± 15,8; IC: 77,54-139,46/Média Centro: 11,33 ± 1,37; IC: 8,94-14,37) (p < 0,001). O tratamento isolado com a vitamina C não apresentou resultado significante (Média Quadrante: 62,00 ± 15,8; IC: 31,04-92,96/Média Centro: 7,00 ± 1,08; IC: 5,17-9,47). Conclusão A associação de antipsicótico e vitamina C e somente o antipsicótico demonstraram efeito terapêutico em relação aos controles. A vitamina C isolada não apresentou benefício.

Vitamin C (Ascorbate) and Redox Topics in Cancer

Significance: Vitamin C (ascorbate), in regard to its effectiveness against malignancies, has had a controversial history in cancer treatment. It has been shown that in vitro and in vivo anticancer efficacy of ascorbate relies on its pro-oxidant effect mainly from an increased generation of reactive oxygen species (ROS). A growing understanding of its anticancer activities and pharmacokinetic properties has prompted scientists to re-evaluate the significance of ascorbate in cancer treatment. Recent Advances: A recent resurge in ascorbate research emerged after discovering that, at high doses, ascorbate preferentially kills Kirsten-Ras (K-ras)- and B-raf oncogene (BRAF)-mutant cancer cells. In addition, some of the main hallmarks of cancer cells, such as redox homeostasis and oxygen-sensing regulation (through inhibition of hypoxia-inducible factor-1 alpha [HIF-1α] activity), are affected by vitamin C. Critical Issues: Currently, there is no clear consensus from the literature in regard to the beneficial effects of antioxidants. Results from both human and animal studies provide no clear evidence about the benefit of antioxidant treatment in preventing or suppressing cancer development. Since pro-oxidants may affect both normal and tumor cells, the extremely low toxicity of ascorbate represents a main advantage. This guarantees the safe inclusion of ascorbate in clinical protocols to treat cancer patients. Future Directions: Current research could focus on elucidating the wide array of reactions between ascorbate and reactive species, namely ROS, reactive nitrogen species as well as reactive sulfide species, and their intracellular molecular targets. Unraveling these mechanisms could allow researchers to assess what could be the optimal combination of ascorbate with standard treatments.

Organosilica colloids as nitric oxide carriers: Pharmacokinetics and biocompatibility

Nitric oxide (NO) is a potential therapeutic agent for various diseases. However, it is challenging to deliver this unstable, free-radical gaseous molecule in the body. Various nanoparticle-based drug delivery systems have been investigated as promising NO carriers without detailed characterization of their biological fate. The purpose of this study is to investigate the pharmacokinetics and biocompatibility of organosilica-based NO-delivering nanocarriers. Two distinct NO nanoformulations, namely NO-SiNP-1 and NO-SiNP-2, were prepared from a thiol-functionalized organosilane using nanoprecipitation and direct aqueous synthesis, respectively. During the preparation, the thiol group was converted to S-nitrosothiol (SNO) under a nitrosation condition. The final products contain SNO-loaded organosilica particles of similar sizes (~130 nm), but of different morphologies and surface charges (between the two formulations). In the in vitro release kinetics study, NO-SiNP-1 exhibited a much slower NO release rate than NO-SiNP-2 (by 5-fold); therefore, the former is considered as a slow NO releaser, and the latter a fast NO releaser. However, in the rat pharmacokinetic study (IV bolus of 50 μmol/kg), NO-SiNP-1 was rapidly eliminated from the blood (within 20 min); in contrast, NO-SiNP-2 was slowly eliminated with an extended circulation time of 12 h for plasma SNO, along with markedly higher plasma levels of nitrite and nitrate. The two formulations are generally biocompatible. In conclusion, the paper presents contrast biological fates of two organosilica colloidal formulations for nitric oxide delivery.

How does ascorbate improve endothelial dysfunction? - A computational analysis

Low levels of ascorbate (Asc) are observed in cardiovascular and neurovascular diseases. Asc has therapeutic potential for the treatment of endothelial dysfunction, which is characterized by a reduction in nitric oxide (NO) bioavailability and increased oxidative stress in the vasculature. However, the potential mechanisms remain poorly understood for the Asc mitigation of endothelial dysfunction. In this study, we developed an endothelial cell based computational model integrating endothelial cell nitric oxide synthase (eNOS) biochemical pathway with downstream reactions and interactions of oxidative stress, tetrahydrobiopterin (BH4) synthesis and biopterin ratio ([BH4]/[TBP]), Asc and glutathione (GSH). We quantitatively analyzed three Asc mediated mechanisms that are reported to improve/maintain endothelial cell function. The mechanisms include the reduction of •BH3 to BH4, direct scavenging of superoxide (O2•-) and peroxynitrite (ONOO-) and increasing eNOS activity. The model predicted that Asc at 0.1-100 μM concentrations improved endothelial cell NO production, total biopterin and biopterin ratio in a dose dependent manner and the extent of cellular oxidative stress. Asc increased BH4 availability and restored eNOS coupling under oxidative stress conditions. Asc at concentrations of 1-10 mM reduced O2•- and ONOO- levels and could act as an antioxidant. We predicted that glutathione peroxidase and peroxiredoxin in combination with GSH and Asc can restore eNOS coupling and NO production under oxidative stress conditions. Asc supplementation may be used as an effective therapeutic strategy when BH4 levels are depleted. This study provides detailed understanding of the mechanism responsible and the optimal cellular Asc levels for improvement in endothelial dysfunction.

Does Vitamin C Influence Neurodegenerative Diseases and Psychiatric Disorders?

Vitamin C (Vit C) is considered to be a vital antioxidant molecule in the brain. Intracellular Vit C helps maintain integrity and function of several processes in the central nervous system (CNS), including neuronal maturation and differentiation, myelin formation, synthesis of catecholamine, modulation of neurotransmission and antioxidant protection. The importance of Vit C for CNS function has been proven by the fact that targeted deletion of the sodium-vitamin C co-transporter in mice results in widespread cerebral hemorrhage and death on post-natal day one. Since neurological diseases are characterized by increased free radical generation and the highest concentrations of Vit C in the body are found in the brain and neuroendocrine tissues, it is suggested that Vit C may change the course of neurological diseases and display potential therapeutic roles. The aim of this review is to update the current state of knowledge of the role of vitamin C on neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis and amyotrophic sclerosis, as well as psychiatric disorders including depression, anxiety and schizophrenia. The particular attention is attributed to understanding of the mechanisms underlying possible therapeutic properties of ascorbic acid in the presented disorders.

Nitroxidative chemistry interferes with fluorescent probe chemistry: implications for nitric oxide detection using 2,3-diaminonaphthalene

Simultaneous production of nitric oxide (NO) and superoxide generates peroxynitrite and causes nitroxidative stress. The fluorometric method for NO detection is based on the formation of a fluorescent product from the reaction of a nonfluorescent probe molecule with NO-derived nitrosating species. Here, we present an example of how nitroxidative chemistry could interact with fluorescent probe chemistry. 2,3-Naphthotriazole (NAT) is the NO-derived fluorescent product of 2,3-diaminonaphthalene (DAN), a commonly used NO-detecting molecule. We show that NO/superoxide cogeneration, and particularly peroxynitrite, mediates the chemical decomposition of NAT. Moreover, the extent of NAT decomposition depends on the relative fluxes of NO and superoxide; the maximum effect being reached at almost equivalent generation rates for both radicals. The rate constant for the reaction of NAT with peroxynitrite was determined to be 2.2×10(3)M(-1)s(-1). Further, various peroxynitrite scavengers were shown to effectively inhibit NO/superoxide- and peroxynitrite-mediated decomposition of NAT. Taken together, the present study suggests that the interference of a fluorometric NO assay can be originated from the interaction between the final fluorescent product and the formed reactive nitrogen and oxygen species.

Ascorbate improves circulation in postural tachycardia syndrome

Low flow postural tachycardia syndrome (LFP) is associated with vasoconstriction, reduced cardiac output, increased plasma angiotensin II, reduced bioavailable nitric oxide (NO), and oxidative stress. We tested whether ascorbate would improve cutaneous NO and reduce vasoconstriction when delivered systemically. We used local cutaneous heating to 42°C and laser Doppler flowmetry to assess NO-dependent conductance (%CVC(max)) to sodium ascorbate and the systemic hemodynamic response to ascorbic acid in 11 LFP patients and in 8 control subjects (aged 23 ± 2 yr). We perfused intradermal microdialysis catheters with sodium ascorbate (10 mM) or Ringer solution. Predrug heat response was reduced in LFP, particularly the NO-dependent plateau phase (56 ± 6 vs. 88 ± 7%CVC(max)). Ascorbate increased baseline skin flow in LFP and control subjects and increased the LFP plateau response (82 ± 6 vs. 92 ± 6 control). Systemic infusion experiments used Finometer and ModelFlow to estimate relative cardiac index (CI) and forearm and calf venous occlusion plethysmography to estimate blood flows, peripheral arterial and venous resistances, and capacitance before and after infusing ascorbic acid. CI increased 40% after ascorbate as did peripheral flows. Peripheral resistances were increased (nearly double control) and decreased by nearly 50% after ascorbate. Calf capacitance and venous resistance were decreased compared with control but normalized with ascorbate. These data provide experimental support for the concept that oxidative stress and reduced NO possibly contribute to vasoconstriction and venoconstriction of LFP.