Vitamin C function in the brain: vital role of the ascorbate transporter SVCT2

Distinctive Neurochemistry in Alzheimer's Disease via 7 T In Vivo Magnetic Resonance Spectroscopy

This study's objective was to increase understanding of biological mechanisms underlying clinical Alzheimer's disease (AD) by noninvasively measuring an expanded neurochemical profile and exploring how well this advanced technology distinguishes AD from cognitively normal controls. We measured concentrations of 14 neurochemicals using ultra-high field (7 T) ultra-short echo time (8 ms) magnetic resonance spectroscopy (MRS) in 16 participants with mild to moderate clinical AD and 33 age- and gender-matched control participants. MRS was localized to the posterior cingulate cortex (PCC), a region known to be impacted by AD, and the occipital cortex (OCC), a control region. Participants with AD were recruited from dementia specialty clinics. Concentration of the antioxidant ascorbate was higher (p < 0.0007) in both brain regions. Concentrations of the glial marker myo-inositol and the choline-containing compounds involved in membrane turnover were higher (p≤0.0004) in PCC of participants with AD. Ascorbate and myo-inositol concentrations were strongly associated, especially in the PCC. Random forests, using the 14 neurochemicals in the two regions, distinguished participants with AD from controls: same-sample sensitivity and specificity were 88% and 97%, respectively, though out-of-sample-values would be lower. Ultra-high field ultra-short echo time MRS identified the co-occurrence of elevated ascorbate and myo-inositol in the PCC as markers that distinguish participants with mild to moderate AD from controls. While elevated myo-inositol may be a surrogate marker of neuroinflammation, the unexpected elevation of the antioxidant ascorbate may reflect infiltration of ascorbate-rich leukocytes.

Neuroprotective effects of antioxidants in the management of neurodegenerative disorders: A literature review

It is proven that oxidative stress has a pivotal role in the process of neurodegeneration. The use of antioxidants is an attractive method to prevent the incidence of neurodegenerative diseases. We searched major databases (PubMed, Medline, and Google Scholar) using the keywords of neurodegeneration, oxidative stress, and antioxidant for both review and original studies, which have reported the various beneficial effects of antioxidants. About 70 studies were identified for this review. Among various antioxidants, nine antioxidants with the most applications in research investigations were selected and the major findings concerning their protective effects were reviewed. It is concluded that antioxidants can modify and readjust the oxidative stress in the biological milieu, elicit neuroprotective effects, and positively impact the management of neurodegenerative processes.

Therapeutic hypothermia effectively reduces elevated extracellular ascorbate concentrations caused by acute spinal cord injury

In recent years, systemic hypothermia has taken the spotlight for its use in spinal cord injury (SCI) research fields, but detailed molecular mechanisms are still not fully understood. In this study, we use an online-electrochemical system (OECS) to in vivo continuously monitor the ascorbate of the rats' spinal cord. We find that the basal level of ascorbate in rat spinal cord is 1.85 ± 0.88 μmol L^-1 (n = 20). It increased immediately after SCI and reached 2.36 ± 0.65 μmol L^-1 (164.90% ± 7.99% of the basal level) (n = 5) at 60 min after the injury. The SCI-induced extracellular ascorbate increase is obviously attenuated by therapeutic hypothermia (28 °C) after injury and ascorbate returns to 3.01 ± 0.59 μmol L^-1 (100.24% ± 5.02% of the basal level) (n = 5), at 60 min after SCI. These results substantially manifest that the OECS for ascorbate detection could be employed as a platform for understanding the pathological changes during spinal cord injury. This study provides experimental evidence for the essential roles of ascorbate in SCI which could serve as a biomarker for SCI. Our findings also raise the possibility that therapeutic hypothermia can effectively exert neuroprotection in the acute phase of SCI.

Development and In Vitro Evaluation of Linear PEI-Shelled Heparin/Berberine Nanoparticles in Human Osteosarcoma U-2 OS Cells

Berberine (BBR), a natural isoquinoline alkaloid derived from Chinese herbs, exerts many biological effects, including antiviral, antimicrobial, antidiarrhea, anti-inflammatory, and antitumor effects. In this study, a novel berberine nanoparticle (NP) consisting of heparin (HP) and BBR with or without being shelled with linear polyethyleneimine (LPEI) was developed to enhance its antitumor activity on osteosarcoma U-2 OS cells. With varying ratios of HP to BBR, HP/BBR NPs had a size ranging from 218.4 ± 3.9 to 282.0 ± 5.1 nm and zeta potential from -35.7 ± 0.4 to -51.9 ± 1.8 mV. After shelling with LPEI, the resultant NPs (HP/BBR/LPEI) possessed a size ranging from 226.3 ± 3.0 to 405.7 ± 85.2 nm and zeta potential from -46.5 ± 0.3 to -35.6 ± 0.5 mV; the encapsulation rate of BBR was close to 80%. The release profiles of both NPs were revealed to be slower than that of BBR solution. Results also showed that BBR and its two derived NPs reduced the viability of U-2 OS cells, and BBR NPs increased the cellular uptake of BBR. Cells were arrested at the G₁ phase when treated individually with BBR and the two NPs (HP/BBR and HP/BBR/LPEI) and DNA condensation was induced. In addition, BBR and BBR NPs reduced the expression of mouse double minute 2 homolog (MDM2) but increased that of p53, and BBR NPs enhanced apoptotic effects. In short, heparin-based nanoparticles could be potential carriers for osteosarcoma treatment.

Kinetic Modeling of pH-Dependent Oxidation of Dopamine by Iron and Its Relevance to Parkinson's Disease

Parkinson's disease is the second most common neurodegenerative disease. While age is the most significant risk factor, the exact cause of this disease and the most effective approaches to mitigation remain unclear. It has long been proposed that dopamine may play a role in the pathology of Parkinson's disease in view of its ability to generate both protein-modifying quinones such as aminochrome and reactive oxygen species, especially in the presence of pathological iron accumulation in the primary site of neuron loss. Given the clinically measured acidosis of post-mortem Parkinson's disease brain tissue, the interaction between dopamine and iron was investigated over a pH range of 7.4 to 6.5 with emphasis on the accumulation of toxic quinones and generation of reactive oxygen species. Our results show that the presence of iron accelerates the formation of aminochrome with ferrous iron (Fe[II]) being more efficient in this regard than ferric iron (Fe[III]). Our results further suggest that a reduced aminochrome rearrangement rate coupled with an enhanced turnover rate of Fe[II] as a result of brain tissue acidosis could result in aminochrome accumulation within cells. Additionally, under these conditions, the enhanced redox cycling of iron in the presence of dopamine aggravates oxidative stress as a result of the production of damaging reactive species, including hydroxyl radicals.

Ascorbic acid therapy: A potential strategy against comorbid depression-like behavior in streptozotocin-nicotinamide-induced diabetic rats

This study examined the potency and efficacy of ascorbic acid (AA) in the management of depression-like behavior in diabetic rats. Diabetes mellitus was induced by single intraperitoneal injections of nicotinamide (120 mg/kg) and streptozotocin (65 mg/kg) administered 15 min apart. Diabetic (blood glucose ≥250 mg/dL) rats were subjected to intermittent foot-shocks to induce comorbid depression. Seven groups of diabetes comorbid depressed rats received vehicle (1 mL/kg) or AA (10, 25, 50, 100, 200, or 400 mg/kg) orally for eleven days. Three control groups namely- nondiabetic, diabetic, and depressed rats received the vehicles only. The potency (ED₅₀) and efficacy (E_max) of AA against immobility period, hypercorticosteronemia, adrenal hyperplasia, hyperglycemia, hypoinsulinemia, oxidative stress, and inflammatory response were estimated. AA administration caused a dose-dependent decrease (P < 0.05) in immobility period with maximum inhibition of 69% (efficacy) at 200 mg/kg and ED₅₀ of 14 mg/kg (potency). AA at 200 mg/kg produced the maximal reduction in hypercorticosteronemia (55.1%) and adrenal hyperplasia (52.6%) with ED₅₀ of 9.8 and 14.4 mg/kg, respectively. AA at 400 mg/kg produced the maximal reduction in hyperglycemia (35.5%), hypoinsulinemia (32.7%), and lipid peroxidation (82%) with ED₅₀ of 18.6, 13.7, and 20.7 mg/kg, respectively. Moreover, AA at 400 mg/kg produced the maximal increase in SOD content (83%), CAT activity (77.9%), and IL-10 level (63%) with ED₅₀ of 21.5, 21, and 21 mg/kg, respectively. In conclusion, the present results suggest that AA has therapeutic potential against diabetes comorbid depression but better regulation of hyperglycemia and hypoinsulinemia is required to achieve maximal benefits.

Vitamin C prevents hypothyroidism associated neuronal damage in the hippocampus of neonatal and juvenile rats: A stereological study

Hypothyroidism causes an imbalance in antioxidant and pro-oxidants criteria in the brain and enhances the concentration of reactive oxygen species (ROS), and neuronal damage has been observed following an excessive ROS. The main purpose of this study was to examine the preventive effect of vitamin C on hypothyroidism associated neuronal damage in the hippocampus of neonatal and juvenile rats. Pregnant rats after delivery of their pups were randomly divided into four groups and treated with (1) normal drinking water as a control group, (2) Propylthiouracil (PTU) 0.005% added to drinking water, (3-, 4) PTU + Vit C 10 mg/ kg and PTU + Vit C 100 mg/ kg to drinking water. Treatment was carried out during rat's lactation period until to the postnatal day (PND) 60. To assess the histological and stereological changes that occur in this study, brains of 5 male pups were extracted. The number of dark neurons and apoptotic cells in the hippocampal sub-regions of PTU group was significantly greater than the control group's hippocampal sub-regions. In addition, hypothyroidism induced a reduction in the hippocampal volume and increased the numerical density and the total amount of dark neurons. The vitamin C only dose of 100 mg/kg significantly reduced the number of dark neurons and apoptotic cells (P < 0.01) and considerably weakened the influence of hypothyroidism on the volume reduction of the hippocampus (P < 0.05). The current study suggested that vitamin C administration has a possibility to prevent hippocampal neuronal damage caused by neonatal and juvenile hypothyroidism in rats.

Diet Quality for Sodium and Vegetables Mediate Effects of Whole Food Diets on 8-Week Changes in Stress Load

Very little is known about how whole food diets, such as those based on the Dietary Guidelines for Americans (DGA), influence psychological stress and physiological stress load. To better understand the effects of whole food diets on stress, we examined in a randomized control trial the effects of a DGA-based diet on markers of psychological and physiological stress. A randomized, double-blind, controlled 8-week intervention was conducted in overweight and obese women randomly assigned to one of two diet groups: a diet based on the 2010 DGA or a diet based on a Typical American Diet (TAD). The Perceived Stress Scale and allostatic load were used to assess stress load. Eight-week change in perceived stress did not significantly (p = 0.45) differ between the DGA (+0.53 ± 0.99) and TAD (-0.57 ± 0.99) groups. Likewise, 8-week change in allostatic load did not significantly (p = 0.79) differ between the two diet intervention groups (DGA: +0.001 ± 0.26 vs. TAD: +0.105 ± 0.28). However, we did find strong inverse associations between 8-week change in stress and intervention-based improvements in diet quality (lower sodium and higher vegetable consumption). When statistically accounting for these inverse associations, we found that perceived stress and allostatic load were higher (p < 0.04) in the DGA group. These findings suggest that improvements in dietary vegetable and sodium intake mediated effects of the diet intervention on psychological and physiological stress load. That is, adopting and adhering to a diet of higher quality (DGA) for 8 weeks may have been generally more stressful in the absence of improvements in vegetable or sodium consumption. This study provides further evidence for the mental health benefits of maximizing vegetable and minimizing sodium consumption.

Neuroprotective Natural Molecules, From Food to Brain

The prevalence of neurodegenerative disorders is increasing; however, an effective neuroprotective treatment is still remaining. Nutrition plays an important role in neuroprotection as recently shown by epidemiological and biochemical studies which identified food components as promising therapeutic agents. Neuroprotection includes mechanisms such as activation of specific receptors, changes in enzymatic neuronal activity, and synthesis and secretion of different bioactive molecules. All these mechanisms are focused on preventing neuronal damage and alleviating the consequences of massive cell loss. Some neuropathological disorders selectively affect to particular neuronal populations, thus is important to know their neurochemical and anatomical properties in order to design effective therapies. Although the design of such treatments would be specific to neuronal groups sensible to damage, the effect would have an impact in the whole nervous system. The difficult overcoming of the blood brain barrier has hampered the development of efficient therapies for prevention or protection. This structure is a physical, enzymatic, and influx barrier that efficiently protects the brain from exogenous molecules. Therefore, the development of new strategies, like nanocarriers, that help to promote the access of neuroprotective molecules to the brain, is needed for providing more effective therapies for the disorders of the central nervous system (CNS). In order both to trace the success of these nanoplatforms on the release of the bioactive cargo in the CNS and determinate the concentration at trace levels of targets biomolecules by analytical chemistry and concretely separation instrumental techniques, constitute an essential tool. Currently, these techniques are used for the determination and identification of natural neuroprotective molecules in complex matrixes at different concentration levels. Separation techniques such as chromatography and capillary electrophoresis (CE), using optical and/or mass spectrometry (MS) detectors, provide multiples combinations for the quantitative and qualitative analysis at basal levels or higher concentrations of bioactive analytes in biological samples. Bearing this in mind, the development of food neuroprotective molecules as brain therapeutic agents is a complex task that requires the intimate collaboration and engagement of different disciplines for a successful outcome. In this sense, this work reviews the new advances achieved in the area toward a better understanding of the current state of the art and highlights promising approaches for brain neuroprotection.

Conjugation to Ascorbic Acid Enhances Brain Availability of Losartan Carboxylic Acid and Protects Against Parkinsonism in Rats

Identification of renin-angiotensin system in the interplay of hypertension and neurodegeneration has paved the way for the repurposing of antihypertensive drugs against Parkinsonism. Losartan carboxylic acid (LCA), the potent AT1 blocker metabolite of losartan, suffers from poor bioavailability and brain access. Since ascorbate transporters have earlier shown enough flexibility as carriers, we have conjugated losartan carboxylic acid to ascorbic acid with the aim of achieving higher oral/brain availability. Ester of LCA and ascorbic acid (FED) was developed keeping in view the substrate specificity of ascorbate transporters. Oral/brain bioavailability was assessed using in vivo pharmacokinetic model. Effect on central nervous system (CNS) and protection against Parkinsonism was evaluated using in vivo models. FED enhanced bioavailability of LCA. The higher brain availability of LCA enabled CNS protection as evident from the increase in locomotor activity, improved motor coordination, and protection against drug-induced catatonia. In conclusion, FED offers an approach to repurpose LCA against Parkinsonism. This can encourage further investigation to simultaneously address hypertension and neurodegeneration.

Microwave characterization of low-molecular-weight antioxidant specific biomarkers

Antioxidants play a crucial role in the life sciences, as the regulators of biochemical reactions. We studied the dielectric properties of the low-molecular weight antioxidant specific biomarkers sodium ascorbate and glutathione in solutions of different concentrations. The biomarkers are multifunctional metabolites relevant to the reactive oxygen species (ROS) scavenging system of cells. The newly developed high-Q microwave whispering-gallery-mode (WGM) dielectric resonator based technique was applied. The technique allows investigation of liquids of nanoliter volumes filled in microfluidic channel within several milliseconds. The revealed peculiarities in the dependence of permittivity on concentrations of the sodium ascorbate and glutathione solutions are explained by differences in relaxation times and loses introduced by molecules of different shapes. We suggest that this novel approach offers the potential for the detection and characterization of ROS-relevant biomarkers with millisecond-time resolution.

Vitamin C Promotes Astrocyte Differentiation Through DNA Hydroxymethylation

Previous studies have reported that vitamin C (VC) promotes neural stem/precursor cell (NSC) differentiation toward dopamine (DA) neurons via DNA hydroxymethylation-induced transcriptional activation of DA neuron-specific genes. To further understand the VC effects on NSC differentiation, we profiled the transcriptome and DNA methylome/hydroxymethylome using high-throughput sequencing. Interestingly, RNA sequencing analyses have shown that, in addition to DA neuronal genes, astrocytic genes Gfap, Slc1a3, and S100a16 were also upregulated in NSC cultures differentiated with VC treatment. Consistently, enhanced GFAP+ astrocytic yields were manifested in the differentiated cultures with VC treatment, collectively indicating that VC promotes astrocytic differentiation. In genome-wide hydroxymethylome analyses, VC treatment induces enrichment of DNA hydroxymethylation (5-hydroxymethyl cytosine; 5hmC) near the consensus binding motifs of nuclear factor I (NFI). Furthermore, we showed that VC significantly enhanced recruitment of NFI and STAT3, key transcription factors for astrogenesis, in the 5hmC-enriched regions of the astrocyte-specific genes. These findings suggest that VC play important roles in astrocytogenesis during brain development. Stem Cells 2018;36:1578-1588.

Altered glutamate clearance in ascorbate deficient mice increases seizure susceptibility and contributes to cognitive impairment in APP/PSEN1 mice

Ascorbate (vitamin C) is critical as a first line of defense antioxidant within the brain, and specifically within the synapse. Ascorbate is released by astrocytes during glutamate clearance and disruption of this exchange mechanism may be critical in mediating glutamate toxicity within the synapse. This is likely even more critical in neurodegenerative disorders with associated excitotoxicity and seizures, in particular Alzheimer's disease, in which ascorbate levels are often low. Using Gulo^-/- mice that are dependent on dietary ascorbate, we established that low brain ascorbate increased sensitivity to kainic acid as measured via behavioral observations, electroencephalography (EEG) measurements, and altered regulation of several glutamatergic system genes. Kainic acid-induced immobility was improved in wild-type mice following treatment with ceftriaxone, which upregulates glutamate transporter GLT-1. The same effect was not observed in ascorbate-deficient mice in which sufficient ascorbate is not available for release. A single, mild seizure event was sufficient to disrupt performance in the water maze in low-ascorbate mice and in APP_SWE/PSEN1_dE9 mice. Together, the data support the critical role of brain ascorbate in maintaining protection during glutamatergic hyperexcitation events, including seizures. The study further supports a role for mild, subclinical seizures in cognitive decline in Alzheimer's disease.

Vitamin C to Improve Organ Dysfunction in Cardiac Surgery Patients-Review and Pragmatic Approach

The pleiotropic biochemical and antioxidant functions of vitamin C have sparked recent interest in its application in intensive care. Vitamin C protects important organ systems (cardiovascular, neurologic and renal systems) during inflammation and oxidative stress. It also influences coagulation and inflammation; its application might prevent organ damage. The current evidence of vitamin C's effect on pathophysiological reactions during various acute stress events (such as sepsis, shock, trauma, burn and ischemia-reperfusion injury) questions whether the application of vitamin C might be especially beneficial for cardiac surgery patients who are routinely exposed to ischemia/reperfusion and subsequent inflammation, systematically affecting different organ systems. This review covers current knowledge about the role of vitamin C in cardiac surgery patients with focus on its influence on organ dysfunctions. The relationships between vitamin C and clinical health outcomes are reviewed with special emphasis on its application in cardiac surgery. Additionally, this review pragmatically discusses evidence on the administration of vitamin C in every day clinical practice, tackling the issues of safety, monitoring, dosage, and appropriate application strategy.

A review of micronutrients in sepsis: the role of thiamine, l-carnitine, vitamin C, selenium and vitamin D

Sepsis is defined as the dysregulated host response to an infection resulting in life-threatening organ dysfunction. The metabolic demand from inefficiencies in anaerobic metabolism, mitochondrial and cellular dysfunction, increased cellular turnover, and free-radical damage result in the increased focus of micronutrients in sepsis as they play a pivotal role in these processes. In the present review, we will evaluate the potential role of micronutrients in sepsis, specifically, thiamine, l-carnitine, vitamin C, Se and vitamin D. Each micronutrient will be reviewed in a similar fashion, discussing its major role in normal physiology, suspected role in sepsis, use as a biomarker, discussion of the major basic science and human studies, and conclusion statement. Based on the current available data, we conclude that thiamine may be considered in all septic patients at risk for thiamine deficiency and l-carnitine and vitamin C to those in septic shock. Clinical trials are currently underway which may provide greater insight into the role of micronutrients in sepsis and validate standard utilisation.

Potential Mechanisms of Action for Vitamin C in Cancer: Reviewing the Evidence

Whether vitamin C (ascorbate) has a role to play as an anti-cancer agent has been debated for decades. Ascorbate has been used by cancer patients in an unregulated environment, either as a dietary supplement or in pharmacological doses administered by infusion, with numerous reports of clinical benefit, but in the absence of rigorous clinical trial data. The design of appropriate clinical trials has been hindered by a lack of understanding of the mechanism(s) of action that would inform the choice of effective dose, timing of administration and likely responsive cancer models. More recently, expanded understanding of the biological activities of ascorbate has led to a number of plausible hypotheses for mechanisms of anti-cancer activity. Prominent among these are the generation of significant quantities of hydrogen peroxide by the autoxidation of supra-physiological concentrations of ascorbate and stimulation of the 2-oxoglutarate-dependent dioxygenase family of enzymes (2-OGDDs) that have a cofactor requirement for ascorbate. Hydrogen peroxide generation is postulated to generate oxidative stress that preferentially targets cancer cells. The 2-OGDDs include the hydroxylases that regulate the hypoxic response, a major driver of tumor survival, angiogenesis, stem cell phenotype and metastasis, and the epigenetic histone and DNA demethylases. The latter are of particular interest, with recent studies suggesting a promising role for ascorbate in the regulation of the ten-eleven translocase (TET) DNA demethylases in hematological cancers. Support for these proposed mechanisms has come from many in vitro studies, and xenograft animal models have consistently shown an anti-cancer effect of ascorbate administration. However, decisive evidence for any particular mechanism(s) of action is not yet available from an in vivo setting. With a number of early phase clinical trials currently underway, evidence for potential mechanism(s) of action is required to inform the most appropriate study design and choice of cancer model. Hopefully such information will result in sound clinical data that will avert adding any further controversy to this already contentious debate.

Ascorbic acid metabolism and functions: A comparison of plants and mammals

Ascorbic acid is synthesised by eukaryotes, the known exceptions being primates and some other animal groups which have lost functional gulonolactone oxidase. Prokaryotes do not synthesise ascorbate and do not need an ascorbate supply, so the functions that are essential for mammals and plants are not required or are substituted by other compounds. The ability of ascorbate to donate electrons enables it to act as a free radical scavenger and to reduce higher oxidation states of iron to Fe²⁺. These reactions are the basis of its biological activity along with the relative stability of the resulting resonance stabilised monodehydroascorbate radical. The importance of these properties is emphasised by the evolution of at least three biosynthetic pathways and production of an ascorbate analogue, erythroascorbate, by fungi. The iron reducing activity of ascorbate maintains the reactive centre Fe²⁺ of 2-oxoglutarate-dependent dioxygenases (2-ODDs) thus preventing inactivation. These enzymes have diverse functions and, recently, the possibility that ascorbate status in mammals could influence 2-ODDs involved in histone and DNA demethylation thereby influencing stem cell differentiation and cancer has been uncovered. Ascorbate is involved in iron uptake and transport in plants and animals. While the above biochemical functions are shared between mammals and plants, ascorbate peroxidase (APX) is an enzyme family limited to plants and photosynthetic protists. It provides these organisms with increased capacity to remove H₂O₂ produced by photosynthetic electron transport and photorespiration. The Fe reducing activity of ascorbate enables hydroxyl radical production (pro-oxidant effect) and the reactivity of dehydroascorbate (DHA) and reaction of its degradation products with proteins (dehydroascorbylation and glycation) is potentially damaging. Ascorbate status influences gene expression in plants and mammals but at present there is little evidence that it acts as a specific signalling molecule. It most likely acts indirectly by influencing the redox state of thiols and 2-ODD activity. However, the possibility that dehydroascorbylation is a regulatory post-translational protein modification could be explored.

Early Life Vitamin C Deficiency Does Not Alter Morphology of Hippocampal CA1 Pyramidal Neurons or Markers of Synaptic Plasticity in a Guinea Pig Model

Approximately 15% of the Western world population, including pregnant women and their children, is characterized as vitamin C (vitC) deficient. In guinea pigs, early life vitC deficiency causes spatial memory deficits, decreased hippocampal volume and neuron numbers, in otherwise clinically healthy animals. We hypothesized that vitC deficiency leads to decreased brain-derived neurotrophic factor and synaptic plasticity markers in selected brain areas (frontal cortex, hippocampus and striatum) and cause morphological changes in cornu ammonis 1 pyramidal neurons of the hippocampus either through a direct effect or indirectly by increased oxidative stress. Fifty-seven female guinea pigs were allocated to three groups receiving either 1390, 100 or 0–50 mg vitC/kg feed for 11 weeks. Dietary vitC levels were reflected in the plasma, cortical and adrenal gland levels, however, redox imbalance was only present in the adrenal glands allowing for the investigation of a direct influence of vitC deficiency on the chosen parameters in the brain. Synaptic plasticity markers were not affected in the investigated brain areas and no differences in isolated pyramidal neuron morphology was recorded. Based on our findings, it appears that vitC deficiency may primarily elicit impaired neuronal function through increased levels of oxidative stress.

Ascorbic acid increases SVCT2 localization at the plasma membrane by accelerating its trafficking from early secretory compartments and through the endocytic-recycling pathway

Ascorbic acid (Asc) is an antioxidant molecule essential for physiological functions. The concentration of extracellular Asc increases during synaptic transmission and renal reabsorption. These phenomena induce an increase of the Sodium-dependent-Vitamin-C-transporter 2 (SVCT2) at plasma membrane (PM) localization, as we previously demonstrated in neuronal and non-neuronal cells. Hence, the aim of this study was to evaluate intracellular SVCT2 trafficking kinetics in response to Asc. We observed two peaks of SVCT2 localization and function at the PM (at 5-10 min, "acute response", and 30-60 min, "post-acute response") when cells were incubated with Asc. We defined that the post-acute response was dependent on SVCT2 located in early secretory compartments, and its trafficking was abolished with Tunicamycin and Brefeldin A treatment. Moreover, using the RUSH system to retain and synchronize cargo secretion through the secretory pathway we demonstrated that the post-acute response increases SVCT2 trafficking kinetics from the ER to the PM suggesting the retention of SVCT2 at the early secretory pathway when Asc is absent. However, these observations do not explain the increased SVCT2 levels at the PM during the "acute" response, suggesting the involvement of a faster mechanism in close proximity with the PM. To investigate the possible role of endosomal compartments, we tested the effect of endocytosis inhibition. Expression of dominant-negative (DN) versions of the GTPase-dynamin II and clathrin-accessory protein AP180 showed a significant increase in SVCT2 levels at the PM. Moreover, expression of Rab11-DN, a GTPase implicated in cargo protein recycling from endosomes to the PM showed a similar outcome, strongly indicating that Asc impacts SVCT2 trafficking during the acute response. Therefore, our results revealed two mechanisms by which Asc modulates SVCT2 levels at the PM, one at the early secretory pathway and another at the endocytic compartments. We propose that these two mechanisms have key protective implications in the homeostasis of metabolically active and specialized tissues.

Impact of a Specific Amino Acid Composition with Micronutrients on Well-Being in Subjects with Chronic Psychological Stress and Exhaustion Conditions: A Pilot Study

Chronic work-life stress leads to dysfunction of the hypothalamus–pituitary–adrenal axis, the autonomic nervous system, and the serotonergic system, with resultant impairment of overall well-being. Aim of the study was to improve perceived stress by a specific amino acid composition with micronutrients in the verum versus placebo group. A total of 59 participants (18–65 years) with self-reported perceived chronic stress and exhaustion conditions participated in this randomized, double-blind, placebo-controlled study. The Perceived Stress Questionnaire (PSQ₃₀), amino acid profile, anthropometric, clinical, blood, urine parameters, and dietary intake were assessed. After 12 weeks, the verum group achieved significantly greater improvements in the total PSQ₃₀ score compared with the placebo group. In the verum group, serum taurine concentration, folic acid concentration, urinary magnesium excretion, and the ratio of l-tryptophan to the sum of competing amino acids rose significantly. In the placebo group, serum concentrations of serotonin, protein, and magnesium decreased significantly, whereas the cardiometabolic risk parameters body weight, body mass index, waist circumference, and waist-to-height ratio increased significantly. Compared with placebo, the verum supplementation resulted in a higher improvement in perceived stress. Beneficial effects on the serotonergic system and preventive effects on magnesium homeostasis and some cardiometabolic risk factors were supposed. Additional effects might be caused by the optimized food intake.

Preventive and Therapeutic Potential of Vitamin C in Mental Disorders

In this review, we summarize the involvement of vitamin C in mental disorders by presenting available evidence on its pharmacological effects in animal models as well as in clinical studies. Vitamin C, especially its reduced form, has gained interest for its multiple functions in various tissues and organs, including central nervous system (CNS). Vitamin C protects the neuron against oxidative stress, alleviates inflammation, regulates the neurotransmission, affects neuronal development and controls epigenetic function. All of these processes are closely associated with psychopathology. In the past few decades, scientists have revealed that the deficiency of vitamin C may lead to motor deficit, cognitive impairment and aberrant behaviors, whereas supplement of vitamin C has a potential preventive and therapeutic effect on mental illness, such as major depressive disorder (MDD), schizophrenia, anxiety and Alzheimer's disease (AD). Although several studies support a possible role of vitamin C against mental disorders, more researches are essential to accelerate the knowledge and investigate the mechanism in this field.

Amperometric Self-Referencing Ceramic Based Microelectrode Arrays for D-Serine Detection

D-serine is the major D-amino acid in the mammalian central nervous system. As the dominant co-agonist of the endogenous synaptic NMDA receptor, D-serine plays a role in synaptic plasticity, learning, and memory. Alterations in D-serine are linked to neuropsychiatric disorders including schizophrenia. Thus, it is of increasing interest to monitor the concentration of D-serine in vivo as a relevant player in dynamic neuron-glia network activity. Here we present a procedure for amperometric detection of D-serine with self-referencing ceramic-based microelectrode arrays (MEAs) coated with D-amino acid oxidase from the yeast Rhodotorulagracilis (RgDAAO). We demonstrate in vitro D-serine recordings with a mean sensitivity of 8.61 ± 0.83 pA/µM to D-serine, a limit of detection (LOD) of 0.17 ± 0.01 µM, and a selectivity ratio of 80:1 or greater for D-serine over ascorbic acid (mean ± SEM; n = 12) that can be used for freely moving studies.

Treatment with ascorbic acid and α-tocopherol modulates oxidative-stress markers in the spinal cord of rats with neuropathic pain

Vitamin E (vit. E) and vitamin C (vit. C) are antioxidants that inhibit nociception. The effect of these vitamins on oxidative-stress markers in the spinal cord of rats with chronic constriction injury (CCI) of the sciatic nerve is unknown. This study investigated the effect of intraperitoneal administration of vit. E (15 mg·kg-1·day-1) and vit. C (30 mg·kg-1·day-1), given alone or in combination, on spinal cord oxidative-stress markers in CCI rats. Adult male Wistar rats weighing 200-250 g were divided equally into the following groups: Naive (rats did not undergo surgical manipulation); Sham (rats in which all surgical procedures involved in CCI were used except the ligature), and CCI (rats in which four ligatures were tied loosely around the right common sciatic nerve), which received injections of vitamins or vehicle (saline containing 1% Tween 80) for 3 or 10 days (n=6/each group). The vitamins prevented the reduction in total thiol content and the increase in superoxide-anion generation that were found in vehicle-treated CCI rats. While nitric-oxide metabolites increased in vehicle-treated CCI rats 3 days after surgery, these metabolites did not show significant changes in vitamin-treated CCI rats. In all rats, total antioxidant capacity and hydrogen-peroxide levels did not change significantly. Lipid hydroperoxides increased 25% only in vehicle-treated CCI rats. These changes may contribute to vit. C- and vit. E-induced antinociception, because scavenging reactive oxygen species seems to help normalize the spinal cord oxidative status altered by pain.

Affinity resins as new tools for identifying target proteins of ascorbic acid

l-Ascorbic acid (AA) has diverse physiological functions, but little is known about the functional mechanisms of AA. In this study, we synthesized two types of affinity resin on which AA is immobilized in a stable form to identify new AA-targeted proteins, which can provide important clues for elucidating unknown functional mechanisms of AA. To our knowledge, an affinity resin on which AA as a ligand is immobilized has not been prepared, because AA is very unstable and rapidly degraded in an aqueous solution. By using the affinity resins, cytochrome c (cyt c) was identified as an AA-targeted protein, and we showed that oxidized cyt c exhibits specific affinity for AA. These results suggest that two kinds of AA-affinity resin can be powerful tools to identify new target proteins of AA.

Natural Medicines for Psychotic Disorders: A Systematic Review

Patients with psychotic disorders regularly use natural medicines, although it is unclear whether these are effective and safe. The aim of this study was to provide an overview of evidence for improved outcomes by natural medicines. A systematic literature search was performed through Medline, PsycINFO, CINAHL, and Cochrane until May 2015. In 110 randomized controlled trials, evidence was found for glycine, sarcosine, N-acetylcysteine, some Chinese and ayurvedic herbs, ginkgo biloba, estradiol, and vitamin B6 to improve psychotic symptoms when added to antipsychotics. Ginkgo biloba and vitamin B6 seemed to reduce tardive dyskinesia and akathisia. Results on other compounds were negative or inconclusive. All natural agents, except reserpine, were well tolerated. Most study samples were small, study periods were generally short, and most results need replication. However, there is some evidence for beneficial effects of certain natural medicines.

Combination Therapy with Sulfasalazine and Valproic Acid Promotes Human Glioblastoma Cell Death Through Imbalance of the Intracellular Oxidative Response

Glioblastoma (GBM) is the most common and aggressive malignant primary brain tumor and still lacks effective therapeutic strategies. It has already been shown that old drugs like sulfasalazine (SAS) and valproic acid (VPA) present antitumoral activities in glioma cell lines. SAS has also been associated with a decrease of intracellular glutathione (GSH) levels through a potent inhibition of xc- glutamate/cystine exchanger leading to an antioxidant deprotection. In the same way, VPA was recently identified as a histone deacetylase (HDAT) inhibitor capable of activating tumor suppression genes. As both drugs are widely used in clinical practice and their profile of adverse effects is well known, the aim of our study was to investigate the effects of the combined treatment with SAS and VPA in GBM cell lines. We observed that both drugs were able to reduce cell viability in a dose-dependent manner and the combined treatment potentiated these effects. Combined treatment also increased cell death and inhibited proliferation of GBM cells, while having no effect on human and rat cultured astrocytes. Also, we observed high protein expression of the catalytic subunit of xc- in all the examined GBM cell lines, and treatment with SAS blocked its activity and decreased intracellular GSH levels. Noteworthy, SAS but not VPA was also able to reduce the [¹⁴C]-ascorbate uptake. Together, these data indicate that SAS and VPA exhibit a substantial effect on GBM cell's death related to an intracellular oxidative response imbalance, making this combination of drugs a promising therapeutic strategy.

Vitamin transporters in mice brain with aging

Its high metabolic rate and high polyunsaturated fatty acid content make the brain very sensitive to oxidative damage. In the brain, neuronal metabolism occurs at a very high rate and generates considerable amounts of reactive oxygen species and free radicals, which accumulate inside neurons, leading to altered cellular homeostasis and integrity and eventually irreversible damage and cell death. A misbalance in redox metabolism and the subsequent neurodegeneration increase throughout the course of normal aging, leading to several age-related changes in learning and memory as well as motor functions. The neuroprotective function of antioxidants is crucial to maintain good brain homeostasis and adequate neuronal functions. Vitamins E and C are two important antioxidants that are taken up by brain cells via the specific carriers αTTP and SVCT2, respectively. The aim of this study was to use immunohistochemistry to determine the distribution pattern of these vitamin transporters in the brain in a mouse model that shows fewer signs of brain aging and a higher resistance to oxidative damage. Both carriers were distributed widely throughout the entire brain in a pattern that remained similar in 4-, 12-, 18- and 24-month-old mice. In general, αTTP and SVCT2 were located in the same regions, but they seemed to have complementary distribution patterns. Double-labeled cell bodies were detected only in the inferior colliculus, entorhinal cortex, dorsal subiculum, and several cortical areas. In addition, the presence of αTTP and SVCT2 in neurons was analyzed using double immunohistochemistry for NeuN and the results showed that αTTP but not SVCT2 was present in Bergmann's glia. The presence of these transporters in brain regions implicated in learning, memory and motor control provides an anatomical basis that may explain the higher resistance of this animal model to brain oxidative stress, which is associated with better motor performance and learning abilities in old age.

The effect of vitamin C and iron on dopamine-mediated free radical generation: implications to Parkinson's disease

While the application of Asc alone may aggravate the progression of PD in view of the possible peroxidation of Asc bound Fe(ii), a combination therapy of Asc and strong clinically appropriate iron chelator would appear to be a promising direction for the treatment of PD as a result of the enhanced iron chelation and attenuation in oxidative stress and toxicity induced by DA derived quinones.

Novel chelators based on adamantane-derived semicarbazones and hydrazones that target multiple hallmarks of Alzheimer's disease

Novel adamantane-derived semicarbazones and hydrazones show multi-functional activity as potential therapeutics for Alzheimer's disease.

The brains of bats foraging at wastewater treatment works accumulate arsenic, and have low non-enzymatic antioxidant capacities

Increasing rates of urbanisation cause ubiquitous infrastructures that remove anthropogenic contaminants - particularly Wastewater Treatment Works (WWTWs) - to become stressed, and hence pollute surrounding water systems. Neoromicia nana bats are suitable models to study the effects of pollution in these environments because they exploit abundant pollutant-tolerant chironomid midges that breed at WWTWs, and consequently accumulate metals such as iron, copper and zinc in their livers and kidneys. If these metals persist in their circulatory systems, and cross the blood brain barrier (BBB) they can have adverse effects on critical functions such as flight and echolocation. The aim of this study was to investigate the potential neurological effects on N. nana foraging at WWTWs versus bats at reference sites in Durban, South Africa. Our objectives were to 1) compare trace metal levels in brain and hair samples (as a proxy for circulating metals) between N. nana foraging at WWTWs and reference sites to determine if excess metals pass through the BBB via the circulatory system; and 2) compare biomarkers of neuron function (acetylcholinesterase activity), protection (antioxidant capacity), DNA integrity (DNA fragmentation), lipid integrity (lipid peroxidation) and cell viability (caspase-3 activity) between N. nana foraging at WWTW and reference sites. We found a significantly higher concentration of arsenic in hair (p < 0.05) and brain tissue (p < 0.1) of WWTW bats compared to bats at reference sites. By contrast, acetylcholinesterase activity did not differ in bats among sites and there was no evidence of significant differences in lipid peroxidation, compromised DNA integrity or apoptosis in the brains between WWTW bats and reference site bats. However, total antioxidant capacity was significantly lower in brains of WWTW bats than bats at reference sites suggesting that antioxidant protection may be compromised. Long-term exposure to environmental pollutants at WWTWs may therefore affect cellular processes and protection mechanisms in brains of N. nana bats. It may also affect other mechanisms and functions in the brain such as mitochondrial efficiency and other neurotransmitters but that remains to be tested.

Evidence for the involvement of opioid system in the antidepressant-like effect of ascorbic acid

Considering the involvement of the opioid system in major depressive disorder (MDD), mainly concerning refractory MDD, and the evidence that ascorbic acid may exert a beneficial effect for the treatment of this disorder, this study investigated the involvement of the opioid system in the antidepressant-like effect of ascorbic acid in the tail suspension test (TST). Treatment of Swiss mice with the non-selective opioid receptor antagonist naloxone (1 mg/kg, i.p.) prevented the reduced immobility time caused by ascorbic acid (1 mg/kg, p.o.) in the TST. Additionally, administration of the selective μ1-opioid receptor antagonist, naloxonazine (10 mg/kg, i.p.), also abolished the antidepressant-like action of the same dose of ascorbic acid in the TST. We also investigated the possible relationship between the opioid system and NMDA receptors in the mechanism of action of ascorbic acid or ketamine (0.1 mg/kg, i.p.) in the TST. Treatment of mice with naloxone (1 mg/kg, i.p.) blocked the synergistic antidepressant-like effect of ascorbic acid (0.1 mg/kg. p.o.) and MK-801 (0.001 mg/kg, p.o., a non-competitive NMDA receptor antagonist) in the TST. Combined administration of ketamine and MK-801 induced a synergistic antidepressant-like action, and naloxone partially abolished this effect. Our results indicate that the antidepressant-like effect of ascorbic acid in the TST appears to be dependent on the activation of the opioid system, especially μ1-opioid receptors, which might be an indirect consequence of NMDA receptor inhibition elicited by ascorbic acid administration.

Fatty Acids, Antioxidants and Physical Activity in Brain Aging

Polyunsaturated fatty acids and antioxidants are important mediators in the central nervous system. Lipid derivatives may control the production of proinflammatory agents and regulate NF-κB activity, microglial activation, and fatty acid oxidation; on the other hand, antioxidants, such as glutathione and ascorbate, have been shown to signal through transmitter receptors and protect against acute and chronic oxidative stress, modulating the activity of different signaling pathways. Several authors have investigated the role of these nutrients in the brains of the young and the aged in degenerative diseases such as Alzheimer’s and Parkinson’s, and during brain aging due to adiposity- and physical inactivity-mediated metabolic disturbances, chronic inflammation, and oxidative stress. Through a literature review, we aimed to highlight recent data on the role of adiposity, fatty acids, antioxidants, and physical inactivity in the pathophysiology of the brain and in the molecular mechanisms of senescence. Data indicate the complexity and necessity of endogenous/dietary antioxidants for the maintenance of redox status and the control of neuroglial signaling under stress. Recent studies also indicate that omega-3 and -6 fatty acids act in a competitive manner to generate mediators for energy metabolism, influencing feeding behavior, neural plasticity, and memory during aging. Finding pharmacological or dietary resources that mitigate or prevent neurodegenerative affections continues to be a great challenge and requires additional effort from researchers, clinicians, and nutritionists in the field.

Impact of diet-derived signaling molecules on human cognition: exploring the food-brain axis

The processes that define mammalian physiology evolved millions of years ago in response to ancient signaling molecules, most of which were acquired by ingestion and digestion. In this way, evolution inextricably linked diet to all major physiological systems including the nervous system. The importance of diet in neurological development is well documented, although the mechanisms by which diet-derived signaling molecules (DSMs) affect cognition are poorly understood. Studies on the positive impact of nutritive and non-nutritive bioactive molecules on brain function are encouraging but lack the statistical power needed to demonstrate strong positive associations. Establishing associations between DSMs and cognitive functions like mood, memory and learning are made even more difficult by the lack of robust phenotypic markers that can be used to accurately and reproducibly measure the effects of DSMs. Lastly, it is now apparent that processes like neurogenesis and neuroplasticity are embedded within layers of interlocked signaling pathways and gene regulatory networks. Within these interdependent pathways and networks, the various transducers of DSMs are used combinatorially to produce those emergent adaptive gene expression responses needed for stimulus-induced neurogenesis and neuroplasticity. Taken together, it appears that cognition is encoded genomically and modified by epigenetics and epitranscriptomics to produce complex transcriptional programs that are exquisitely sensitive to signaling molecules from the environment. Models for how DSMs mediate the interplay between the environment and various neuronal processes are discussed in the context of the food-brain axis.

Preventive and therapeutic potential of ascorbic acid in neurodegenerative diseases

In this review, we summarize the involvement of ascorbic acid in neurodegenerative diseases by presenting available evidence on the behavioral and biochemical effects of this compound in animal models of neurodegeneration as well as the use of ascorbic acid as a therapeutic approach to alleviate neurodegenerative progression in clinical studies. Ascorbate, a reduced form of vitamin C, has gained interest for its multiple functions and mechanisms of action, contributing to the homeostasis of normal tissues and organs as well as to tissue regeneration. In the brain, ascorbate exerts neuromodulatory functions and scavenges reactive oxygen species generated during synaptic activity and neuronal metabolism. These are important properties as redox imbalance and abnormal protein aggregation constitute central mechanisms implicated in the pathogenesis of neurodegenerative diseases, including Alzheimer's, Parkinson's, and Huntington's diseases, multiple sclerosis, and amyotrophic lateral sclerosis. Indeed, several studies have indicated an association between low serum ascorbate concentrations and neurodegeneration. Moreover, ascorbic acid is a suitable candidate for supplying either antioxidant defense or modulation of neuronal and astrocytic metabolism under neurodegenerative conditions. Ascorbic acid acts mainly by decreasing oxidative stress and reducing the formation of protein aggregates, which may contribute to the reduction of cognitive and/or motor impairments observed in neurodegenerative processes. Although several studies support a possible role of ascorbic acid administration against neurodegeneration, more researches are essential to substantiate the existing results and accelerate the knowledge in this field.

Vitamin C-Induced Epigenetic Modifications in Donor NSCs Establish Midbrain Marker Expressions Critical for Cell-Based Therapy in Parkinson's Disease

Cultured neural stem/precursor cells (NSCs) are regarded as a potential systematic cell source to treat Parkinson's disease (PD). However, the therapeutic potential of these cultured NSCs is lost during culturing. Here, we show that treatment of vitamin C (VC) enhances generation of authentic midbrain-type dopamine (mDA) neurons with improved survival and functions from ventral midbrain (VM)-derived NSCs. VC acted by upregulating a series of mDA neuron-specific developmental and phenotype genes via removal of DNA methylation and repressive histone code (H3K9m3, H3K27m3) at associated gene promoter regions. Notably, the epigenetic changes induced by transient VC treatment were sustained long after VC withdrawal. Accordingly, transplantation of VC-treated NSCs resulted in improved behavioral restoration, along with enriched DA neuron engraftment, which faithfully expressed midbrain-specific markers in PD model rats. These results indicate that VC treatment to donor NSCs could be a simple, efficient, and safe therapeutic strategy for PD in the future.

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Vitamin C (VC) potentiates therapeutic capacity of donor NSCs to treat PD

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Long-lasting epigenetic activation of VM-specific genes underlies the VC effects

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The VC effects enhanced mDA neuron engraftment

Induction of cellular and molecular Immunomodulatory pathways by vitamin E and vitamin C

INTRODUCTION

Vitamins E and C are well known small molecules that have been used to maintain health for decades. Recent studies of the cellular and molecular pathways leading to immunomodulation by these molecules have been of interest, as have their anti-oxidant properties and signal transduction pathways for curing or improving infectious diseases and cancer. Areas covered: Herein, the authors provide a definition and the structural classification of vitamins E and C and how these molecules influence cellular function. The studies include in vitro, ex vivo and in vivo studies in animal models as well as clinical trials. The authors give particular focus to the scientifically factual and putative roles of these molecules in innate and adaptive immunomodulation and prevention or cure of diseases. Expert opinion: The antioxidant properties of vitamins E and C are well studied. However, whether there is a link between their antioxidant and immunomodulation properties is unclear. In addition, there is a strong, albeit putative, prevailing notion that vitamin C can prevent or cure infectious diseases or cancer. Presently, while there is proven evidence that vitamin E possesses immunomodulatory properties that may play a positive role in disease outcomes, this evidence is less available for vitamin C.

Peripheral Vitamin C Levels in Alzheimer's Disease: A Cross-Sectional Study

We previously reported lower lymphocyte vitamin C levels in individuals with type 2 diabetes mellitus and in individuals with severe Parkinson's disease. Oxidative stress has been proposed to play a key role in the progression of Alzheimer's disease. Thus, the objective of this study was to investigate the association between peripheral levels of vitamin C and the progression of cognitive dysfunction in Alzheimer's disease. Fifty individuals with Alzheimer's disease being treated at Shizuoka General Hospital were consecutively enrolled in this study from December 2009 to March 2015 (76.0±9.7 y of age [mean±SD]; 32 men and 18 women; Mini-Mental State Examination Japanese version (MMSE-J) score range, 8-27). Plasma and lymphocyte vitamin C levels in fasting blood samples were measured. The association between the MMSE-J scores and vitamin C levels was estimated using Spearman's rank correlation coefficient (ρ) and the criteria defined by Swinscow. Spearman's ρ for the relationship between peripheral vitamin C levels and the MMSE-J score was ρ=0.17 for plasma vitamin C and ρ=0.26 for lymphocyte vitamin C. Thus, the associations were relatively weak based on the criteria. In contrast with type 2 diabetes mellitus and Parkinson's disease, lymphocyte vitamin C levels in the peripheral blood may not directly reflect the progression of cognitive dysfunction in Alzheimer's disease. Additional longitudinal studies are needed to evaluate the clinical importance of changes of peripheral vitamin C status in Alzheimer's disease.

Efficient Reduction of Vertebrate Cytoglobins by the Cytochrome b5/Cytochrome b5 Reductase/NADH System

Cytoglobin is a heme-containing protein ubiquitous in mammalian tissues. Unlike the evolutionarily related proteins hemoglobin and myoglobin, cytoglobin shows a six-coordinated heme binding, with the heme iron coordinated by two histidine side chains. Cytoglobin is involved in cytoprotection pathways through yet undefined mechanisms, and it has recently been demonstrated that cytoglobin has redox signaling properties via nitric oxide (NO) and nitrite metabolism. The reduced, ferrous cytoglobin can bind oxygen and will react with NO in a dioxygenation reaction to form nitrate, which dampens NO signaling. When deoxygenated, cytoglobin can bind nitrite and reduce it to NO. This oxidoreductase activity could be catalytic if an effective reduction system exists to regenerate the reduced heme species. The nature of the physiological cytoglobin reducing system is unknown, although it has been proposed that ascorbate and cytochrome b₅ could fulfill this role. Here we describe that physiological concentrations of cytochrome b₅ and cytochrome b₅ reductase can reduce human and fish cytoglobins at rates up to 250-fold higher than those reported for their known physiological substrates, hemoglobin and myoglobin, and up to 100-fold faster than 5 mM ascorbate. These data suggest that the cytochrome b₅/cytochrome b₅ reductase system is a viable reductant for cytoglobin in vivo, allowing for catalytic oxidoreductase activity.

Exploring the potential of natural and synthetic neuroprotective steroids against neurodegenerative disorders: A literature review

Neurodegeneration is a complex process, which leads to progressive brain damage due to loss of neurons. Despite exhaustive research, the cause of neuronal loss in various degenerative disorders is not entirely understood. Neuroprotective steroids constitute an important line of attack, which could play a major role against the common mechanisms associated with various neurodegenerative disorders like Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Natural endogenous steroids induce the neuroprotection by protecting the nerve cells from neuronal injury through multiple mechanisms, therefore the structural modifications of the endogenous steroids could be helpful in the generation of new therapeutically useful neuroprotective agents. The review article will keep the readers apprised of the detailed description of natural as well as synthetic neuroprotective steroids from the medicinal chemistry point of view, which would be helpful in drug discovery efforts aimed toward neurodegenerative diseases.

Ascorbic Acid to Manage Psychiatric Disorders

Ascorbate has critical roles in the central nervous system (CNS); it is a neuromodulator of glutamatergic, cholinergic, dopaminergic, and γ-aminobutyric acid (GABA)-ergic neurotransmission, provides support and structure to neurons, and participates in processes such as differentiation, maturation, and survival of neurons. Over the past decade, antioxidant properties of ascorbate have been extensively characterized and now it is known that this compound is highly concentrated in the brain and neuroendocrine tissues. All this information raised the hypothesis that ascorbate may be involved in neurological disorders. Indeed, the biological mechanisms of ascorbate in health and disease and its involvement in homeostasis of the CNS have been the subject of extensive research. In particular, evidence for an association of this vitamin with schizophrenia, major depressive disorder, and bipolar disorder has been provided. Considering that conventional pharmacotherapy for the treatment of these neuropathologies has important limitations, this review aims to explore basic and human studies that implicate ascorbic acid as a potential therapeutic strategy. Possible mechanisms involved in the beneficial effects of ascorbic acid for the management of psychiatric disorders are also discussed.