Ascorbic acid attenuates scopolamine-induced spatial learning deficits in the water maze

Effects of thymoquinone on scopolamine-induced spatial and echoic memory changes through regulation of lipid peroxidation and cholinergic impairment

Thymoquinone (TMQ), one of the main components active of Nigella sativa, shows very useful biomedical properties. Evidence suggests that cholinergic dysfunction and oxidative stress play role in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD). In the present study, we investigated the anti-amnestic effect of TMQ in scopolamine-induced animal model of AD. Wistar rats were randomly divided into four groups; Sham(SH), TMQ-treated(TMQ), scopolamine-treated(SCO) and scopolamine+TMQ-treated(SCO_TMQ) groups. TMQ (20 mg/kg) prepared in corn oil was administered intraperitoneally (i.p.) 1-h before experiments. Scopolamine (1 mg/kg) dissolved in 0.9% physiological saline was administered intraperitoneally (i.p.). We recorded mismatch negativity (MMN) response as an electrophysiological correlate of echoic memory. Object location memory (OLM) and Y-maze alternation tests were carried out to assess spatial memory. Then, the brain homogenates content of thiobarbituric-acid-reactive-substances (TBARS), 4-Hydroxy-2-nonenal (4-HNE) and acetylcholine (ACh)/acetylcholine (AChE) activity were biochemically determined. In the scopolamine-treated rats, TMQ was found to significantly improve the discrimination and spontaneous alteration levels in the OLM and Y-maze tests, respectively. Furthermore, TMQ significantly mitigated the scopolamine-induced attenuation of MMN and related theta responses. Moreover, scopolamine treatment increased TBARS/4-HNE level and decreased ACh level in the brain, and TMQ was able to significantly prevent these effects. AChE activity was increased in the SCO group; this effect was significantly attenuated by TMQ. TMQ diminished the lipid peroxidation and cholinergic dysfunction in the scopolamine-induced AD rat model which all reflected in improving the MMN/theta response and spatial memory. This may implement TMQ as an adjuvant therapeutic strategy in ameliorating AD.

Effect of Sanguisorba minor on scopolamine-induced memory loss in rat: involvement of oxidative stress and acetylcholinesterase

Sanguisorba minor (S. minor) has neuroprotective and antioxidant activities. However, its potential benefits in ameliorating learning and memory functions have been explored in no studies up to now. So, in the current study, rats were treated with S. minor hydro-ethanolic extract (50, 100, and 200 mg/kg, intraperitoneal (i.p.)) as well as rivastigmine (0.5 mg/kg, i.p.) for 21 consecutive days. Thereafter, their behavioral performance was assessed using Morris water maze (MWM) and passive avoidance (PA) tasks. Notably, 30 min before conducting the tasks, scopolamine was injected. Finally, the biochemical assessments were done using the brain tissue. The extract characterization was performed by liquid chromatography-mass spectrometry, which confirmed the presence of quercetin, myricetin, kaempferol, catechin, ellagic acid, and gallic acid derivatives. In the MWM test, the extract reduced both escape latency and the travelled distance, compared to the scopolamine group. Moreover, in the PA test, the latency to enter the dark chamber significantly increased by the extract, compared to the scopolamine group (p < 0.05-p < 0.001). Notably, the beneficial effects of S. minor on cognitive performance of the scopolamine-treated rats appeared to be similar or even better than rivastigmine in behavior performance. Similar to rivastigmine, it was observed that the extract attenuated both AChE activity and oxidative injury in the brain as evidenced by the increased antioxidant enzymes and total thiol content; however, it decreased malondialdehyde level (p < 0.05-p < 0.001). In conclusion, the results suggested the effectiveness of S. minor in preventing cognitive dysfunction induced by scopolamine. Accordingly, these protective effects might be produced by the regulation of cholinergic activity and oxidative stress. S. minor could be considered as a potential alternative therapy in cognition disorders.

Resveratrol protects against inorganic arsenic-induced oxidative damage and cytoarchitectural alterations in female mouse hippocampus

Prolonged inorganic arsenic (iAs) exposure is widely associated with brain damage particularly in the hippocampus via oxidative and apoptotic pathways. Resveratrol (RES) has gained considerable attention because of its benefits to human health. However, its neuroprotective potential against iAs-induced toxicity in CA1 region of hippocampus remains unexplored. Therefore, we investigated the neuroprotective efficacy of RES against arsenic trioxide (As₂O₃)-induced adverse effects on neuronal morphology, apoptotic markers and oxidative stress parameters in mouse CA1 region (hippocampus). Adult female Swiss albino mice of reproductive maturity were orally exposed to either As₂O₃ (2 and 4 mg/kg bw) alone or in combination with RES (40 mg/kg bw) for a period of 45 days. After animal sacrifice on day 46, the perfusion fixed brain samples were used for the observation of neuronal morphology and studying the morphometric features. While the freshly dissected hippocampi were processed for biochemical estimation of oxidative stress markers and western blotting of apoptosis-associated proteins. Chronic iAs exposure led to significant decrease in Stratum Pyramidale layer thickness along with reduction in cell density and area of Pyramidal neurons in contrast to the controls. Biochemical analysis showed reduced hippocampal GSH content but no change in total nitrite (NO) levels following iAs exposure. Western blotting showed apparent changes in the expression levels of Bax and Bcl-2 proteins following iAs exposure, however the change was statistically insignificant. Contrastingly, iAs +RES co-treatment exhibited substantial reversal in morphological and biochemical observations. Together, these findings provide preliminary evidence of neuroprotective role of RES on structural and biochemical alterations pertaining to mouse hippocampus following chronic iAs exposure.

Bergapten Improves Scopolamine-Induced Memory Impairment in Mice via Cholinergic and Antioxidative Mechanisms

Bergapten is a furanocoumarin naturally occurring in the Apiaceae family and it is a well-known photosensitizing agent used in photochemotherapy. In this study, we investigated the influence of bergapten on cognitive function and mechanism underlying these effects in scopolamine-induced memory impairment in male Swiss mice. The passive avoidance test was used to evaluate the efficiency of memory acquisition and consolidation. The results demonstrated that both single and repeated administration of bergapten improved not only the acquisition but also consolidation of memory. The behavioral tests showed that bergapten prevented memory impairment induced by administration of scopolamine. Observed effects may result from the inhibition of acetylcholinesterase activity in the hippocampus and prefrontal cortex. Also, bergapten caused significant anti-oxidative effects. These new findings provide pharmacological and biochemical support for the development of the coumarin’s potential in cognitive deficits.

The role of vitamin C in stress-related disorders

Stress-related disorders, such as depression and anxiety, present marked deficits in behavioral and cognitive functions related to reward. These are highly prevalent disabling conditions with high social and economic costs. Furthermore, a significant percentage of affected individuals cannot benefit from clinical intervention, opening space for new treatments. Although the literature data have reported limited and variable results regarding oxidative stress-related endpoints in stress-related disorders, the possible neuroprotective effect of antioxidant compounds, such as ascorbic acid (vitamin C), emerges as a possible therapy strategy for psychiatric diseases. Here, we briefly present background information on biological activity of ascorbic acid, particularly functions related to the CNS homeostasis. Additionaly, we reviewed the available information on the role of ascorbic acid in stress-related diseases, focusing on supplementation and depletion studies. The vitamin C deficiency is widely associated to stress-related diseases. Although the efficacy of this vitamin in anxiety spectrum disorders is less stablished, several studies showed that ascorbic acid supplementation produces antidepressant effect and improves mood. Interestingly, the modulation of monoaminergic and glutamatergic neurotransmitter systems is postulated as pivotal target for the antidepressant and anxiolytic effects of this vitamin. Given that ascorbic acid supplementation produces fast therapeutic response with low toxicity and high tolerance, it can be considered as a putative candidate for the treatment of mood and anxiety disorders, especially those that are refractory to current treatments. Herein, the literature was reviewed considering the potential use of ascorbic acid as an adjuvant in the treatment of anxiety and depression.

The Effects of Ripe Pistachio Hulls Hydroalcoholic Extract and Aerobic Training on Learning and Memory in Streptozotocin-induced Diabetic Male Rats

Introduction:

Diabetes mellitus has harmful effects on body functions, such as learning and memory. According to the role of exercise and medicinal plants on body health, the purpose of this study was to survey the effect of combined aerobic training and the use of Ripe Pistachio Hulls (RPH) hydro-alcoholic extract on learning and memory in streptozotocin-induced diabetic male rats.

Methods:

In this experimental study, 42 male Wistar rats weighing 250–280 g were used in 6 groups with an equal number of 7 rats in each one. Streptozotocin (STZ) (50 mg / kg)was used to induce diabetes, and the test protocol was applied for 8 weeks. Passive avoidance memory was assessed using a step-through passive avoidance apparatus (shuttle box). SPSS software was used to analyze the data and P<0.05 was significant.

Results:

The results showed that step-through latency in the acquisition trial (STLa) was not significantly different among groups. Step-through latency in retrieval (STLr 24) test significantly reduced and time spent in The Dark Compartment (TDC) decreased in treated groups compared with the diabetic control groups (P<0.001). Also, there was no significant difference between the STZ and saline diabetic groups.

Conclusion:

The findings of this study revealed that the RPH hydro-alcoholic extract and aerobic exercise could improve passive avoidance memory in streptozotocin diabetic rats. Meanwhile, they might be an adjuvant therapy combined with other traditional medicine.

Glutathione in Brain: Overview of Its Conformations, Functions, Biochemical Characteristics, Quantitation and Potential Therapeutic Role in Brain Disorders

Glutathione (GSH) is an important antioxidant found abundantly and synthesized intracellularly in the cytosol in a tightly regulated fashion. It has diverse physiological functions, including protection against reactive oxygen species and nitrogen species, antioxidant defense as well as maintenance of cellular thiol status. The human brain due to the high oxygen consumption is extremely susceptible to the generation of reactive oxygen species. GSH plays a paramount role in brain antioxidant defense, maintaining redox homeostasis. The depletion of brain GSH has also been observed from both autopsies as well as in vivo MRS studies with aging and varied neurological disorders (Alzheimer's disease, Parkinson's disease, etc.). Therefore, GSH enrichment using supplementation is a promising avenue in the therapeutic development for these neurological disorders. This review will enrich the information on the importance of GSH synthesis, metabolism, functions, compartmentation and inter-organ transport, structural conformations and its quantitation via different techniques. The transportation of GSH in the brain via different interventional routes and its potential role in the development of therapeutic strategies for various brain disorders is also addressed. Very recent study found significant improvement of behavioral deficits including cognitive decline, depressive-like behaviors, in APP (NL-G-F/NL-G-FG-) mice due to oral GSH administration. This animal model study put an emergent need to complete GSH supplementation trial in MCI and AD patients for cognitive improvement as proposed earlier.

Cell-free hemoglobin augments acute kidney injury during experimental sepsis

Acute kidney injury is a common complication of severe sepsis and contributes to high mortality. The molecular mechanisms of acute kidney injury during sepsis are not fully understood. Because hemoproteins, including myoglobin and hemoglobin, are known to mediate kidney injury during rhabdomyolysis, we hypothesized that cell-free hemoglobin (CFH) would exacerbate acute kidney injury during sepsis. Sepsis was induced in mice by intraperitoneal injection of cecal slurry (CS). To mimic elevated levels of CFH observed during human sepsis, mice also received a retroorbital injection of CFH or dextrose control. Four groups of mice were analyzed: sham treated (sham), CFH alone, CS alone, and CS + CFH. The addition of CFH to CS reduced 48-h survival compared with CS alone (67% vs. 97%, P = 0.001) and increased the severity of illness. After 24 and 48 h, CS + CFH mice had a reduced glomerular filtration rate from baseline, whereas sham, CFH, and CS mice maintained baseline glomerular filtration rate. Biomarkers of acute kidney injury, neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1), were markedly elevated in CS+CFH compared with CS (8-fold for NGAL and 2.4-fold for KIM-1, P < 0.002 for each) after 48 h. Histological examination showed a trend toward increased tubular injury in CS + CFH-exposed kidneys compared with CS-exposed kidneys. However, there were similar levels of renal oxidative injury and apoptosis in the CS + CFH group compared with the CS group. Kidney levels of multiple proinflammatory cytokines were similar between CS and CS + CFH groups. Human renal tubule cells (HK-2) exposed to CFH demonstrated increased cytotoxicity. Together, these results show that CFH exacerbates acute kidney injury in a mouse model of experimental sepsis, potentially through increased renal tubular injury.

Neurobiology of vitamin C: Expanding the focus from antioxidant to endogenous neuromodulator

Ascorbic acid (AA) is a water-soluble vitamin (C) found in all bodily organs. Most mammals synthesize it, humans are required to eat it, but all mammals need it for healthy functioning. AA reaches its highest concentration in the brain where both neurons and glia rely on tightly regulated uptake from blood via the glucose transport system and sodium-coupled active transport to accumulate and maintain AA at millimolar levels. As a prototype antioxidant, AA is not only neuroprotective, but also functions as a cofactor in redox-coupled reactions essential for the synthesis of neurotransmitters (e.g., dopamine and norepinephrine) and paracrine lipid mediators (e.g., epoxiecoisatrienoic acids) as well as the epigenetic regulation of DNA. Although redox capacity led to the promotion of AA in high doses as potential treatment for various neuropathological and psychiatric conditions, ample evidence has not supported this therapeutic strategy. Here, we focus on some long-neglected aspects of AA neurobiology, including its modulatory role in synaptic transmission as demonstrated by the long-established link between release of endogenous AA in brain extracellular fluid and the clearance of glutamate, an excitatory amino acid. Evidence that this link can be disrupted in animal models of Huntington´s disease is revealing opportunities for new research pathways and therapeutic applications (e.g., epilepsy and pain management). In fact, we suggest that improved understanding of the regulation of endogenous AA and its interaction with key brain neurotransmitter systems, rather than administration of AA in excess, should be the target of future brain-based therapies.

Neuroprotective Activity of Evolvulus alsinoides & Centella asiatica Ethanolic Extracts in Scopolamine-Induced Amnesia in Swiss Albino Mice

AIM

To carry out the comparative nootropic, neuroprotective potentials of two medicinal plant species.

MATERIAL AND METHODS

For neuroprotective activity; behavior models (elevated plus maze & morris water maze), in vivo antioxidant (superoxide dismutase, catalase, lipid peroxidation & reduced glutathione), inflammatory markers (IL-1β, IL-6 & TNF-α) and acetylcholine esterase (AChE) assessment procedures followed at different dosages i.e. 250 & 500 mg/kg of Evolvulus alsinoides and Centella asiatica ethanolic extracts. At the end of the study, it was performed histopathological analysis of the following organs: brain, heart, liver, and kidney.

RESULTS

In oral administration of different doses of ethanolic extracts of both medicinal plants i.e. Sco + EEA 250 = 2.49 ± 0.29 , Sco + EEA 500 = 2.67 ± 0.36, Sco + ECA 250 = 2.33 ± 0.17, Sco + ECA 500 = 2.77 ± 0.21, Sco + EEA + ECA 250 = 2.61 ± 0.32 and Sco + EEA + ECA 500 = 2.79 ± 0.16 U/mg of protein respectively against the scopolamine induced group Sco (control) = 5.51 ± 0.35 U/mg of protein extracts shows neuroprotective and nootropic activity with reducing AChE level in the brain homogenate of swiss albino mice.

CONCLUSION

Since the E. alsinoides & C. asiatica are already used in traditional Indian medicine as the neuroprotective agent and also found promising effects over inflammatory diseases, wound healing, and immunomodulatory activity. The neuroprotective effect of both plants extracts attributed to inhibition of AChE activity and improve the spatial memory formation.

Oxidative Stress Levels in the Brain Are Determined by Post-Mortem Interval and Ante-Mortem Vitamin C State but Not Alzheimer's Disease Status

The current study highlighted several changes in measures of oxidative stress and antioxidant status that take place in the mouse brain over the course of 24 h post-mortem. Ascorbic acid (vitamin C) and glutathione both decreased significantly in cortex in as little as 2 h and malondialdehyde levels increased. Further change from baseline was observed up to 24 h, including carbonyl and sulfhydryl formation. The greatest changes were observed in brains that began with low ascorbic acid levels (gulo^{&minus;/&minus;} mice) compared to wild-type or 5XFAD mice. Cortical samples from nine Alzheimer&rsquo;s Disease cases and five controls were also assayed under the same conditions. Post mortem intervals ranged from 6 to 47 h and all samples had low ascorbic acid levels at time of measurement. Malondialdehyde levels were lower in Alzheimer&rsquo;s Disease cases. Despite a strong positive correlation between ascorbic acid and glutathione levels, no other correlations among oxidative stress measures or post mortem interval were observed. Together the data suggest that molecular changes occurring within the first hours of death may mask differences between patient groups. Care must be taken interpreting studies in human brain tissue where ante-mortem nutrient status is not known to avoid bias or confounding of results.

Comparison of Memory Impairment and Oxidative Stress Following Single or Repeated Doses Administration of Scopolamine in Rat Hippocampus

Introduction

Scopolamine, a muscarinic cholinergic receptor antagonist, is widely used to induce memory impairment in experimental animals. The present study aims to compare memory impairment and oxidative stress following single and repeated doses administration of scopolamine.

Methods

A group of rats received a single shot of scopolamine in different doses (0.5, 1, or 3 mg/kg, IP) 24 hours after the passive avoidance training. Then the memory retrieval test was performed 30 minutes and 7 days after the injection. In the other experiment, rats received similar doses of scopolamine for 7 consecutive days, 24 hours after the training session. Then the memory retrieval test was performed 30 minutes and 7 days after the last injection. Acetylcholinesterase (AChE) activity and lipid peroxidation were measured in their hippocampus tissue, too.

Results

Scopolamine administered in repeated doses caused more impairment in memory function compared to single dose injection based on the evaluation 30 minutes after injection. Moreover, the memory impairment persisted for 7 days only in repeated doses treated groups. Increase in acetylcholinesterase activity and lipid peroxidation in both groups was observed 30 minutes after scopolamine administration. These abnormal increases persisted for 7 days only in repeated doses treated groups. Increased AChE activity and lipid peroxidation was well correlated with behavioral deficit. Also AChE activity was well associated with lipid peroxidation.

Conclusion

The results of present study showed that repeated administration of scopolamine induced results in memory impairment. This effect can be due to long-lasting oxidative stress which may damage the hippocampus tissue.

The effects of vitamin C on hypothyroidism-associated learning and memory impairment in juvenile rats

In this study the effects of Vitamin C (Vit C) on hypothyroidism-associated learning and memory impairment in juvenile rats was investigated. The pregnant rats were kept in separate cages. After delivery, they were randomly divided into six groups and treated: (1) Control; (2) Propylthiouracil (PTU) which 0.005% PTU in their drinking; (3-5) Propylthiouracil- Vit C groups; besides PTU, dams in these groups received 10, 100 and 500 mg/kg Vit C respectively, (6) one group as a positive control; the intact rats received an effective dose, 100 mg/kg Vit. C. After delivery, the pups were continued to receive the experimental treatments in their drinking water up to 56th day of their life. Ten male offspring of each group were randomly selected and tested in the Morris water maze (MWM) and passive avoidance (PA) which were started at 63th day (one week after stopping of the treatments). Brains were then removed for biochemical measurements. PTU increased time latency and traveled distance during 5 days in MWM while, reduced the spent time in target quadrant in MWM and step-trough latency (STL) in PA. PTU decreased thiol content, superoxide dismutase (SOD) and catalase (CAT) activities in the brain while, increased molondialdehyde (MDA). In MWM test, 10, 100 and 500 mg/kg Vit C reduced time latency and traveled distance without affecting the traveling speed during 5 days. All doses of Vit C increased the spent time in target quadrant in probe trail of MWM and also increased STL in PA test. Vit C increased thiol, SOD and CAT in the brain tissues while, reduced MDA. Results of present study confirmed the beneficial effects of Vit C on learning and memory. It also demonstrated that Vit C has protective effects on hypothyroidism-associated learning and memory impairment in juvenile rats which might be elucidated by the antioxidative effects.

Selenium attenuates apoptosis, inflammation and oxidative stress in the blood and brain of aged rats with scopolamine-induced dementia

A potent antioxidant, selenium might modulate dementia-induced progression of brain and blood oxidative and apoptotic injuries. The present study explores whether selenium protects against experimental dementia (scopolamine, SCOP)-induced brain, and blood oxidative stress, apoptosis levels, and cytokine production in rats. Thirty-two rats were equally divided into four groups. The first group was used as an untreated control. The second group was treated with SCOP to induce dementia. The third and fourth groups received 1.5 mg/kg selenium (sodium selenite) and SCOP + selenium, respectively. Dementia was induced in the second and forth groups by intraperitoneal SCOP (1 mg/kg) administration. Brain, plasma, and erythrocyte lipid peroxidation levels as well as plasma TNF-α, interleukin (IL)-1β, and IL-4 levels were high in the SCOP group though they were low in selenium treatments. Selenium and selenium + SCOP treatments increased the lowered glutathione peroxidase activity, reduced glutathione, vitamins A and E concentrations in the brain, erythrocytes and plasma of the SCOP group. Apoptotic value expressions as active caspase-3, procaspase-9, and PARP were also increased by SCOP, while they were decreased by selenium and selenium + SCOP treatments. In conclusion, selenium induced protective effects against experimental dementia-induced brain, and blood oxidative injuries and apoptosis through regulation of cytokine production, vitamin E, glutathione concentrations, and glutathione peroxidase activity.

Oxidative stress, serotonergic changes and decreased ultrasonic vocalizations in a mouse model of Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome is an inherited monogenic disorder in which mutations to the 7-dehydrocholesterol (7-DHC) reductase (Dhcr7) gene lead to deficits in cholesterol synthesis. As a result, many patients suffer from gross physiological and neurological deficits. The purpose of this study was to identify a potential abnormal behavioral phenotype in a compound mutant mouse model for Smith-Lemli-Opitz disease (Dhcr7 ^Δ3-5/T93M ) to further validate the model and to provide potential targets for future therapeutic interventions. We also sought to identify some of the underlying changes in brain function that may be responsible for behavioral differences among groups. The Dhcr7 compound mutant mice were smaller than their single mutant littermates. Both single and compound heterozygous mice made fewer ultrasonic vocalizations when separated from the dam, which may suggest a communication deficit in these animals. Striking increases of the highly oxidizable 7-DHC were observed in the compound mutant mice. 7-Dehydrocholesterol is the precursor to cholesterol and builds up because of decreased function of the mutated Dhcr7 enzyme. Additionally, several differences were noted in the serotonergic system including increased expression of the serotonin transporter and increased uptake of serotonin by isolated synaptosomes. We propose that changes to the oxidative environment during development can have a significant impact on the development of serotonergic function and that this contributes to behavioral differences observed in the mutant mice.

Reversal of high fat diet-induced obesity improves glucose tolerance, inflammatory response, β-amyloid accumulation and cognitive decline in the APP/PSEN1 mouse model of Alzheimer's disease

This study assessed the extent to which high fat diet (HFD)-induced β-amyloid accumulation and cognitive decline in APP/PSEN1 mice are reversible through control of fat intake. Ten months of HFD (60% calories from fat) led to significant deficits in a 2-trial Y maze task, and nest building assay, and decreased voluntary locomotor activity. The HFD induced an inflammatory response, indicated by increased expression of several inflammatory markers. Substituting a low fat diet led to pronounced weight loss and correction of glucose intolerance, decreases in the inflammatory response, and improved performance on behavioral tasks in both wild-type and APP/PSEN1 transgenic mice. Insoluble β-amyloid levels, and extent of tau phosphorylation were also lower following dietary reversal in APP/PSEN1 mice compared to high fat-fed animals, indicating that the inflammatory response may have contributed to key pathogenic pathways in the Alzheimer's disease model. The data suggest that weight loss can be a vital strategy for cognitive protection, but also highlight potential mechanisms for intervention when sustained weight loss is not possible.

The influence of vitamins E and C and exercise on brain aging

Age-related declines in motor and cognitive function have been associated with increases in oxidative stress. Accordingly, interventions capable of reducing the oxidative burden would be capable of preventing or reducing functional declines occurring during aging. Popular interventions such as antioxidant intake and moderate exercise are often recommended to attain healthy aging and have the capacity to alter redox burden. This review is intended to summarize the outcomes of antioxidant supplementation (more specifically of vitamins C and E) and exercise training on motor and cognitive declines during aging, and on measures of oxidative stress. Additionally, we will address whether co-implementation of these two types of interventions can potentially further their individual benefits. Together, these studies highlight the importance of using translationally-relevant parameters for interventions and to study their combined outcomes on healthy brain aging.

Selected Micronutrients in Cognitive Decline Prevention and Therapy

Population aging is a worldwide demographic trend. Consequently, the prevalence of chronic age-related conditions such as clinically diagnosed neurological diseases, cognitive decline, and dementia will significantly increase in the near future. The important role of diets and healthy lifestyle as preventative of neurodegenerative diseases is widely accepted nowadays, and it may provide preventive strategies in very early, non-symptomatic phases of dementia well, especially because there are still no effective treatments for it. In this article, we review the known effects of selected micronutrients on the aging brain and we propose strategies for dietary improvements.

Hippocampal memory enhancing activity of pine needle extract against scopolamine-induced amnesia in a mouse model

We evaluated the neuropharmacological effects of 30% ethanolic pine needle extract (PNE) on memory impairment caused by scopolamine injection in mice hippocampus. Mice were orally pretreated with PNE (25, 50, and 100 mg/kg) or tacrine (10 mg/kg) for 7 days, and scopolamine (2 mg/kg) was injected intraperitoneally, 30 min before the Morris water maze task on first day. To evaluate memory function, the Morris water maze task was performed for 5 days consecutively. Scopolamine increased the escape latency and cumulative path-length but decreases the time spent in target quadrant, which were ameliorated by pretreatment with PNE. Oxidant-antioxidant balance, acetylcholinesterase activity, neurogenesis and their connecting pathway were abnormally altered by scopolamine in hippocampus and/or sera, while those alterations were recovered by pretreatment with PNE. As lipid peroxidation, 4HNE-positive stained cells were ameliorated in hippocampus pretreated with PNE. Pretreatment with PNE increased the proliferating cells and immature neurons against hippocampal neurogenesis suppressed by scopolamine, which was confirmed by ki67- and DCX-positive stained cells. The expression of brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element-binding protein (pCREB) in both protein and gene were facilitated by PNE pretreatment. These findings suggest that PNE could be a potent neuropharmacological drug against amnesia, and its possible mechanism might be modulating cholinergic activity via CREB-BDNF pathway.

Vitamin C deficiency in the brain impairs cognition, increases amyloid accumulation and deposition, and oxidative stress in APP/PSEN1 and normally aging mice

Subclinical vitamin C deficiency is widespread in many populations, but its role in both Alzheimer's disease and normal aging is understudied. In the present study, we decreased brain vitamin C in the APPSWE/PSEN1deltaE9 mouse model of Alzheimer's disease by crossing APP/PSEN1(+) bigenic mice with SVCT2(+/-) heterozygous knockout mice, which have lower numbers of the sodium-dependent vitamin C transporter required for neuronal vitamin C transport. SVCT2(+/-) mice performed less well on the rotarod task at both 5 and 12 months of age compared to littermates. SVCT2(+/-) and APP/PSEN1(+) mice and the combination genotype SVCT2(+/-)APP/PSEN1(+) were also impaired on multiple tests of cognitive ability (olfactory memory task, Y-maze alternation, conditioned fear, Morris water maze). In younger mice, both low vitamin C (SVCT2(+/-)) and APP/PSEN1 mutations increased brain cortex oxidative stress (malondialdehyde, protein carbonyls, F2-isoprostanes) and decreased total glutathione compared to wild-type controls. SVCT2(+/-) mice also had increased amounts of both soluble and insoluble Aβ1-42 and a higher Aβ1-42/1-40 ratio. By 14 months of age, oxidative stress levels were similar among groups, but there were more amyloid-β plaque deposits in both hippocampus and cortex of SVCT2(+/-)APP/PSEN1(+) mice compared to APP/PSEN1(+) mice with normal brain vitamin C. These data suggest that even moderate intracellular vitamin C deficiency plays an important role in accelerating amyloid pathogenesis, particularly during early stages of disease development, and that these effects are likely modulated by oxidative stress pathways.

Does vitamin C deficiency affect cognitive development and function?

Vitamin C is a pivotal antioxidant in the brain and has been reported to have numerous functions, including reactive oxygen species scavenging, neuromodulation, and involvement in angiogenesis. Absence of vitamin C in the brain has been shown to be detrimental to survival in newborn SVCT2(−/−) mice and perinatal deficiency have shown to reduce hippocampal volume and neuron number and cause decreased spatial cognition in guinea pigs, suggesting that maternal vitamin C deficiency could have severe consequences for the offspring. Furthermore, vitamin C deficiency has been proposed to play a role in age-related cognitive decline and in stroke risk and severity. The present review discusses the available literature on effects of vitamin C deficiency on the developing and aging brain with particular focus on in vivo experimentation and clinical studies.

Ethanol extract of Astragali Radix and Salviae Miltiorrhizae Radix, Myelophil, exerts anti-amnesic effect in a mouse model of scopolamine-induced memory deficits

ETHNOPHARMACOLOGICAL RELEVANCE

Myelophil, a combination of extracts taken from Astragali Radix and Salviae Miltiorrhizae Radix, is a traditional Chinese medicine used for the treatment of chronic fatigue-associated disorders. Here we examined the ability of Myelophil to alleviate memory impairment in a mouse model. We aimed to investigate whether Myelophil has the pharmacological effects on memory deficits associated with brain dysfunctions using an animal model.

MATERIALS AND METHODS

Ten week-old male C57BL/6N mice were pretreated with Myelophil (50, 100, or 200 mg/kg), or tacrine (10 mg/kg) for 7 days, and then intraperitoneally injected with scopolamine (1 mg/kg). Memory-related behaviors were evaluated using the Morris water maze for 5 days. Levels of biomarkers of oxidative stress, antioxidant activity, acetylcholinesterase (AChE) activity, and extracellular signal-regulated kinase (ERK) were measured in brain tissues.

RESULTS

Scopolamine treatment increased the escape latency time and shortened time spent in the target quadrant; these effects were ameliorated by pretreatment with Myelophil. Scopolamine-induced changes in reactive oxygen species (ROS), malondialehyde (MDA), and AChE activity were significantly attenuated in mice pretreated with Myelophil. Recovery of antioxidant capacities, including total glutathione (GSH) content, and the activities of GSH-reductase, GSH-S-transferase, and catalase was also evident in Myelophil-treated mice. The strongest effects were seen for ERK and muscarinic acetylcholine receptor 1 (mAChR1) at both the protein and gene expression levels, with significant amelioration of expression levels in the Myelophil pretreatment group.

CONCLUSIONS

These results suggest that Myelophil confers anti-amnesic properties in a mouse model of memory impairment, driven in part by the modulation of cholinergic activity.

Intravenous ascorbate improves spatial memory in middle-aged APP/PSEN1 and wild type mice

The present study investigated the effects of a single intravenous (i.v.) dose of Vitamin C (ascorbate, ASC) on spatial memory in APP/PSEN1 mice, an Alzheimer's disease model. First, we confirmed the uptake time course in ASC-depleted gulo (-/-) mice, which cannot synthesize ASC. Differential tissue uptake was seen based on ASC transporter distribution. Liver (SVCT1 and SVCT2) ASC was elevated at 30, 60 and 120 min post-treatment (125 mg/kg, i.v.), whereas spleen (SVCT2) ASC increased at 60 and 120 min. There was no detectable change in cortical (SVCT2 at choroid plexus, and neurons) ASC within the 2-h interval, although the cortex preferentially retained ASC. APP/PSEN1 and wild type (WT) mice at three ages (3, 9, or 20 months) were treated with ASC (125 mg/kg, i.v.) or saline 45 min before testing on the Modified Y-maze, a two-trial task of spatial memory. Memory declined with age and ASC treatment improved performance in 9-month-old APP/PSEN1 and WT mice. APP/PSEN1 mice displayed no behavioral impairment relative to WT controls. Although dopamine and metabolite DOPAC decreased in the nucleus accumbens with age, and improved spatial memory was correlated with increased dopamine in saline treated mice, acute ASC treatment did not alter monoamine levels in the nucleus accumbens. These data show that the Modified Y-maze is sensitive to age-related deficits, but not additional memory deficits due to amyloid pathology in APP/PSEN1 mice. They also suggest improvements in short-term spatial memory were not due to changes in the neuropathological features of AD or monoamine signaling.

The ameliorative effect of ascorbic acid and Ginkgo biloba on learning and memory deficits associated with fluoride exposure

Chronic exposure to fluoride causes dental and skeletal fluorosis. Fluoride exposure is also detrimental to soft tissues and organs. The present study aimed at evaluation of the effect of Ginkgo biloba and ascorbic acid on learning and memory deficits caused by fluoride exposure. Male Wistar rats were divided into five groups (n=6). Group 1 control. Groups 2 to 5 received 100 ppm of sodium fluoride over 30 days. Groups 3, 4 and 5 were further treated for 15 days receiving respectively 1% gum acacia solution, 100 mg/kg body weight ascorbic acid, and 100mg/kg body weight Ginkgo biloba extract. After 45 days, all animals were subjected to behavioural tests. The results showed that fluoride affected learning and memory. Fluoride causes oxidative stress and neurodegeneration, thereby affecting learning and memory. Ascorbic acid and Ginkgo biloba were found to augment the reversal of learning and memory deficits caused by fluoride ingestion.

Protective effect of ascorbic acid and Ginkgo biloba against learning and memory deficits caused by fluoride

Fluoride is present in the ground water, World Health Organization permitted level of fluoride in the ground water is 0.5 ppm. Tooth pastes, mouth washes, tea and sea fish are the sources of fluoride. Exposure to these multiple sources results in several adverse effects in addition to the fluorosis. The present study aimed to test the effect of vitamin C and Ginkgo biloba against the behavioural deficits caused by fluoride. Rats were divided into five groups with six animals in each group ( n = 6). Control group received ordinary tap water with 0.5 ppm of fluoride, the remaining groups received 100 ppm of fluoride for 30 days prior to fluoride exposure. Two groups of animals received 100 mg/kg body weight of vitamin C and G. biloba for 15 days prior to fluoride exposure. After 45 days, behavioural studies (T-Maze, passive avoidance) were conducted on the experimental animals. The results of the present study showed no behavioural deficits in the control group of animals however, the rats that received fluoride water exhibited impairment in their spatial learning and memory deficits. The deficits are not marked in the vitamin C and G. biloba groups. To conclude chronic exposure to high levels of fluoride causes severe impairment in the spatial learning and memory, these deficits can be ameliorated with the vitamin C and G. biloba.

Pomegranate supplementation improves affective and motor behavior in mice after radiation exposure

Currently, NASA has plans for extended space travel, and previous research indicates that space radiation can have negative effects on cognitive skills as well as physical and mental health. With long-term space travel, astronauts will be exposed to greater radiation levels. Research shows that an antioxidant-enriched diet may offer some protection against the cellular effects of radiation and may provide significant neuroprotection from the effects of radiation-induced cognitive and behavioral skill deficits. Ninety-six C57BL/6 mice (48 pomegranate fed and 48 control) were irradiated with proton radiation (2 Gy), and two-month postradiation behaviors were assessed using a battery of behavioral tests to measure cognitive and motor functions. Proton irradiation was associated with depression-like behaviors in the tail suspension test, but this effect was ameliorated by the pomegranate diet. Males, in general, displayed worse coordination and balance than females on the rotarod task, and the pomegranate diet ameliorated this effect. Overall, it appears that proton irradiation, which may be encountered in space, may induce a different pattern of behavioral deficits in males than females and that a pomegranate diet may confer protection against some of those effects.

Combined vitamin C and E deficiency induces motor defects in gulo(-/-)/SVCT2(+/-) mice

OBJECTIVES

Key antioxidants, vitamins C and E, are necessary for normal brain development and neuronal function. In this study, we depleted both of these vitamins in two mouse models to determine if oxidative stress due to combined vitamin C and E dietary deficiency altered their neurological phenotype. The first model lacked both alleles for the Gulonolactone oxidase gene (Gulo(-/-)) and therefore was unable synthesize vitamin C. To obtain an additional cellular deficiency of vitamin C, the second model also lacked one allele for the cellular vitamin C transporter gene (Gulo(-/-)/SVCT2(+/-)).

METHODS

The experimental treatment was 16 weeks of vitamin E deprivation followed by 3 weeks of vitamin C deprivation. Mice were assessed for motor coordination deficits, vitamin levels, and oxidative stress biomarkers.

RESULTS

In the first model, defects in motor performance were more apparent in both vitamin C-deficient groups (VE+VC-, VE-VC-) compared to vitamin C-supplemented groups (VE+VC+, VE-VC+) regardless of vitamin E level. Analysis of brain cortex and liver confirmed decreases of at least 80% for each vitamin in mice on deficient diets. Vitamin E deficiency doubled oxidative stress biomarkers (F2-isoprostanes and malondialdehyde). In the second model, Gulo(-/-)/SVCT2(+/-) mice on the doubly deficient diets showed deficits in locomotor activity, Rota-rod performance, and other motor tasks, with no concomitant change in anxiety or spatial memory.

DISCUSSION

Vitamin E deficiency alone caused a modest oxidative stress in brain that did not affect motor performance. Adding a cellular deficit in vitamin C to dietary deprivation of both vitamins significantly impaired motor performance.

Behavioral and monoamine changes following severe vitamin C deficiency

Severe vitamin C deficiency (ascorbic acid; AA) was induced in gulo-/- mice incapable of synthesizing their own AA. A number of behavioral measures were studied before and during the deprivation period, including a scorbutic period, during which weight loss was observed in the mice. Mice were then resuscitated with AA supplements. During the scorbutic period, gulo-/- mice showed decreased voluntary locomotor activity, diminished physical strength, and increased preference for a highly palatable sucrose reward. These behaviors all returned to control levels following resuscitation. Altered trial times in subordinate mice in the tube test for social dominance in the AA-deprived mice persisted following resuscitation and may signify a depressive-like behavior in these mice. Biochemical analyses were undertaken following a second deprivation period. AA deficiency was accompanied by decreased blood glucose levels, oxidative damage to lipids and proteins in the cortex, and decreases in dopamine and serotonin metabolites in both the cortex and striatum. Given the reasonably high proportions of the population that do not consume sufficient AA in the diet, these data have important implications for physical and psychological function in the general population.

Subtle biobehavioral effects produced by paternal cocaine exposure

Despite the increased prevalence of cocaine use and abuse in males when compared with females, possible effects of paternal cocaine exposure on biobehavioral development have received little attention. We therefore exposed male mice to cocaine (20 mg/kg, i.p.) or vehicle for 10 weeks and then used those mice as sires. We then behaviorally phenotyped the F1 offspring to assess the consequences of paternal cocaine exposure on brain function. We report the presence of a subtle but significant increase in immobility in the tail suspension test, a measure of behavioral depression, following paternal cocaine. Body weight was also significantly decreased in paternal cocaine-exposed offspring. Other aspects of neurobehavioral function, including locomotor activity, anxiety, and learning and memory, were not affected by paternal cocaine history. These data suggest alterations in brain systems and/or circuitry underlying mood regulation in the offspring of cocaine-using fathers. Synapse 2012. © 2012 Wiley Periodicals, Inc.

Increased expression of SVCT2 in a new mouse model raises ascorbic acid in tissues and protects against paraquat-induced oxidative damage in lung

A new transgenic mouse model for global increases in the Sodium Dependent Vitamin C transporter 2 (SVCT2) has been generated. The SVCT2-Tg mouse shows increased SVCT2 mRNA levels in all organs tested and correspondingly increased ascorbic acid (ASC) levels in all organs except liver. The extent of the increase in transporter mRNA expression differed among mice and among organs. The increased ASC levels did not have any adverse effects on behavior in the SVCT2-Tg mice, which did not differ from wild-type mice on tests of locomotor activity, anxiety, sensorimotor or cognitive ability. High levels of SVCT2 and ASC were found in the kidneys of SVCT2-Tg mice and urinary albumin excretion was lower in these mice than in wild-types. No gross pathological changes were noted in kidneys from SVCT2-Tg mice. SVCT2 immunoreactivity was detected in both SVCT2 and wild-type mice, and a stronger signal was seen in tubules than in glomeruli. Six treatments with Paraquat (3x10 and 3x15 mg/kg i.p.) were used to induce oxidative stress in mice. SVCT2-Tg mice showed a clear attenuation of Paraquat-induced oxidative stress in lung, as measured by F(2)-isoprostanes. Paraquat also decreased SVCT2 mRNA signal in liver, lung and kidney in SVCT2-Tg mice.

Ascorbic acid, cognitive function, and Alzheimer's disease: a current review and future direction

This narrative review appraises the human and animal studies implicating ascorbic acid (AA) in normal cognitive function and Alzheimer's disease. A research framework for how nutrition affects brain aging is proposed with emphasis on AA intake, status, metabolism, and transport into brain tissue. A final synopsis highlights areas for future research regarding AA nourishment and healthy brain aging.

Scopolamine administration modulates muscarinic, nicotinic and NMDA receptor systems

Studies on the effect of scopolamine on memory are abundant but so far only regulation of the muscarinic receptor (M1) has been reported. We hypothesized that levels of other cholinergic brain receptors as the nicotinic receptors and the N-methyl-D-aspartate (NMDA) receptor, known to be involved in memory formation, would be modified by scopolamine administration.

C57BL/6J mice were used for the experiments and divided into four groups. Two groups were given scopolamine 1 mg/kg i.p. (the first group was trained and the second group untrained) in the multiple T-maze (MTM), a paradigm for evaluation of spatial memory. Likewise, vehicle-treated mice were trained or untrained thus serving as controls. Hippocampal levels of M1, nicotinic receptor alpha 4 (Nic4) and 7 (Nic7) and subunit NR1containing complexes were determined by immunoblotting on blue native gel electrophoresis.

Vehicle-treated trained mice learned the task and showed memory retrieval on day 8, while scopolamine-treatment led to significant impairment of performance in the MTM. At the day of retrieval, hippocampal levels for M1, Nic7 and NR1 were higher in the scopolamine treated groups than in vehicle-treated groups.

The concerted action, i.e. the pattern of four brain receptor complexes regulated by the anticholinergic compound scopolamine, is shown. Insight into probable action mechanisms of scopolamine at the brain receptor complex level in the hippocampus is provided. Scopolamine treatment is a standard approach to test cognitive enhancers and other psychoactive compounds in pharmacological studies and therefore knowledge on mechanisms is of pivotal interest.

Neuronal and vascular oxidative stress in Alzheimer's disease

The brain is a highly metabolically active organ producing large amounts of reactive oxygen species (ROS). These ROS are kept in check by an elaborate network of antioxidants. Although ROS are necessary for signaling and synaptic plasticity, their uncontrolled levels cause oxidation of essential macromolecules such as membrane lipids, nucleic acids, enzymes and cytoskeletal proteins. Indeed, overproduction of ROS and/or failure of the antioxidant network lead to neuronal oxidative stress, a condition associated with not only aging but also Alzheimer's disease (AD). However, the specific source of excessive ROS production has not yet been identified. On one hand, amyloid beta (Aβ) has been extensively shown to act as an oxidant molecule. On the other hand, oxidative stress has been shown to precede and exacerbate Aβ pathology. This review will address the involvement of oxidative stress in the context of neuronal as well as vascular dysfunction associated with AD.

Reactive oxygen species in the regulation of synaptic plasticity and memory

The brain is a metabolically active organ exhibiting high oxygen consumption and robust production of reactive oxygen species (ROS). The large amounts of ROS are kept in check by an elaborate network of antioxidants, which sometimes fail and lead to neuronal oxidative stress. Thus, ROS are typically categorized as neurotoxic molecules and typically exert their detrimental effects via oxidation of essential macromolecules such as enzymes and cytoskeletal proteins. Most importantly, excessive ROS are associated with decreased performance in cognitive function. However, at physiological concentrations, ROS are involved in functional changes necessary for synaptic plasticity and hence, for normal cognitive function. The fine line of role reversal of ROS from good molecules to bad molecules is far from being fully understood. This review focuses on identifying the multiple sources of ROS in the mammalian nervous system and on presenting evidence for the critical and essential role of ROS in synaptic plasticity and memory. The review also shows that the inability to restrain either age- or pathology-related increases in ROS levels leads to opposite, detrimental effects that are involved in impairments in synaptic plasticity and memory function.

Ascorbic acid prevents oxidant-induced increases in endothelial permeability

Oxidative stress acutely increases the permeability of the vascular endothelium to large molecules that would not otherwise cross the barrier. Ascorbic acid is an antioxidant that tightens the endothelial permeability barrier, so we tested whether it might also prevent the increase in endothelial permeability due to cellular oxidative stress. Treatment of EA.hy926 endothelial cells cultured on filter inserts with H(2) O(2) , menadione, and buthionine sulfoximine increased endothelial permeability to radiolabeled inulin. Short-term ascorbate loading of the cells to what are likely physiologic concentrations of the vitamin by treating them with dehydroascorbate prevented the increase in endothelial permeability due to these agents. The nonphysiologic antioxidants dithiothreitol and tempol also prevented increases in endothelial barrier permeability induced by the agents. These results suggest that oxidative stress induced directly by oxidants or indirectly by glutathione depletion impairs endothelial barrier function and that intracellular ascorbate may serve to prevent this effect.

Prolonged treatment with vitamins C and E separately and together decreases anxiety-related open-field behavior and acoustic startle in hooded rats

Adult male and female hooded rats (about 110 days old) consumed vitamins C and E separately and combined together in their drinking water and were assessed for anxiety approximately 50 and then 80 days later in an open field and an acoustic startle apparatus. They were tested when 160+ days old, and then again at 190+ days. For both testing ages combined, the vitamins and their combination increased open-field ambulation and occupancy of the four center squares of the apparatus, while also accordingly decreasing occupancy of the four corners. Treatment with vitamins C and E separately and combined together also decreased acoustic startle amplitude. While there were several significant overall sex and testing age differences, there was no evidence that the vitamin treatment effects were dependent on the operation of either variable. There was also no evidence of synergism between vitamins C and E in their effects. It was suggested that decreases in anxiety produced by the vitamins may have arisen from their antioxidant properties, attenuation of cortisol activity or some as yet undetermined effects on anxiety-related brain structures and neurotransmitters.

High dietary fat and cholesterol exacerbates chronic vitamin C deficiency in guinea pigs

Vitamin C deficiency – or hypovitaminosis C defined as a plasma concentration below 23 μm – is estimated to affect hundreds of millions of people in the Western world, in particular subpopulations of low socio-economic status that tend to eat diets of poor nutritional value. Recent studies by us have shown that vitamin C deficiency may result in impaired brain development. Thus, the aim of the present study was to investigate if a poor diet high in fat and cholesterol affects the vitamin C status of guinea pigs kept on either sufficient or deficient levels of dietary ascorbate (Asc) for up to 6 months with particular emphasis on the brain. The present results show that a high-fat and cholesterol diet significantly decreased the vitamin C concentrations in the brain, irrespective of the vitamin C status of the animal (P < 0·001). The brain Asc oxidation ratio only depended on vitamin C status (P < 0·0001) and not on the dietary lipid content. In plasma, the levels of Asc significantly decreased when vitamin C in the diet was low or when the fat/cholesterol content was high (P < 0·0001 for both). The Asc oxidation ratio increased both with low vitamin C and with high fat and cholesterol content (P < 0·0001 for both). We show here for the first time that vitamin C homoeostasis of brain is affected by a diet rich in fat and cholesterol. The present findings suggest that this type of diet increases the turnover of Asc; hence, individuals consuming high-lipid diets may be at increased risk of vitamin C deficiency.

Low vitamin C and increased oxidative stress and cell death in mice that lack the sodium-dependent vitamin C transporter SVCT2

The sodium-dependent vitamin C transporter (SVCT2) is responsible for the transport of vitamin C into cells in multiple organs, from either the blood or the cerebrospinal fluid. Mice null for SVCT2 (SVCT2(-/-)) do not survive past birth but the cause of death has not yet been ascertained. After mating of SVCT2(+/-) males and SVCT2(+/-) females, fewer SVCT2(-/-) and SVCT2(+/-) progeny were observed than would be expected according to Mendelian ratios. Vitamin C levels in SVCT2(-/-), SVCT2(+/-), and SVCT2(+/+) were genotype-dependent. SVCT2(-/-) fetuses had significantly lower vitamin C levels than littermates in placenta, cortex, and lung, but not in liver (the site of vitamin C synthesis). Low vitamin C levels in placenta and cortex were associated with elevations in several markers of oxidative stress: malondialdehyde, isoketals, F(2)-isoprostanes, and F(4)-neuroprostanes. Oxidative stress was not elevated in fetal SVCT2(-/-) lung tissue despite low vitamin C levels. In addition to the expected severe hemorrhage in cortex, we also found hemorrhage in the brain stem, which was accompanied by cell loss. We found evidence of increased apoptosis in SVCT2(-/-) mice and disruption of the basement membrane in fetal brain. Together these data show that SVCT2 is critical for maintaining vitamin C levels in fetal and placental tissues and that the lack of SVCT2, and the resulting low vitamin C levels, results in fetal death and, in SVCT2(-/-) mice that survive the gestation period, in oxidative stress and cell death.

Low ascorbic acid and increased oxidative stress in gulo(-/-) mice during development

Vitamin C (ascorbic acid, AA) depletion during prenatal and postnatal development can lead to oxidative stress in the developing brain and other organs. Such damage may lead to irreversible effects on later brain function. We studied the relationship between AA deficiency and oxidative stress during development in gulonolactone oxidase (gulo) knockout mice that are unable to synthesize their own ascorbic acid. Heterozygous gulo(+/-) mice can synthesize AA and typically have similar tissue levels to wild-type mice. Gulo(+/-) dams were mated with gulo(+/-) males to provide offspring of each possible genotype. Overall, embryonic day 20 (E20) and postnatal day 1 (P1) pups were protected against oxidative stress by sufficient AA transfer during pregnancy. On postnatal day 10 (P10) AA levels were dramatically lower in liver and cerebellum in gulo(-/-) mice and malondialdehyde (MDA) levels were significantly increased. In postnatal day 18 pups (P18) AA levels decreased further in gulo(-/-) mice and oxidative stress was observed in the accompanying elevations in MDA in liver, and F(2)-isoprostanes in cortex. Further, total glutathione levels were higher in gulo(-/-) mice in cortex, cerebellum and liver, indicating that a compensatory antioxidant system was activated. These data show a direct relationship between AA level and oxidative stress in the gulo(-/-) mice. They reinforce the critical role of ascorbic acid in preventing oxidative stress in the developing brain in animals that, like humans, cannot synthesize their own AA.

Vitamin C distribution and retention in the mouse brain

Vitamin C (VC) is a crucial antioxidant in the brain. To assess whether different brain regions vary in their sensitivity to oxidative stress induced by VC depletion, we used the gulonolactone oxidase (gulo) knockout mouse. This mouse, like humans, cannot synthesize VC and thus its tissue VC levels can be varied by dietary VC intake. Gulo knockout mice were fed drinking water containing standard (0.33g/L), low (0.033g/L) or zero (0g/L) VC supplementation levels. After 4weeks, mice were sacrificed and different brain regions removed for assay of VC and malondialdehyde, a marker of lipid peroxidation. Compared to age-matched wild-type controls, the cerebellum, olfactory bulbs and frontal cortex had the highest VC content, whereas the pons and spinal chord had the lowest. However, in mice that did not receive VC, area differences were no longer significant as all values trended towards zero. Malondialdehyde increased in the cortex as VC supplementation was decreased. The same changes were not observed in the cerebellum or pons, suggesting that cortex is more susceptible to oxidative damage from low VC. These results suggest enhanced susceptibility of the cortex to oxidative stress induced by low VC compared to other brain regions.