Arginine administration inhibits hippocampal Na+,K+-ATPase activity and impairs retention of an inhibitory avoidance task in rats

Melatonin Successfully Rescues the Hippocampal Molecular Machinery and Enhances Anti-oxidative Activity Following Early-Life Sleep Deprivation Injury

Early-life sleep deprivation (ESD) is a serious condition with severe cognitive sequelae. Considering hippocampus plays an essential role in cognitive regulation, the present study aims to determine whether melatonin, a neuroendocrine beard with significant anti-oxidative activity, would greatly depress the hippocampal oxidative stress, improves the molecular machinery, and consequently exerts the neuro-protective effects following ESD. Male weanling Wistar rats (postnatal day 21) were subjected to ESD for three weeks. During this period, the animals were administered normal saline or melatonin (10 mg/kg) via intraperitoneal injection between 09:00 and 09:30 daily. After three cycles of ESD, the animals were kept under normal sleep/wake cycle until they reached adulthood and were sacrificed. The results indicated that ESD causes long-term effects, such as impairment of ionic distribution, interruption of the expressions of neurotransmitters and receptors, decreases in the levels of several antioxidant enzymes, and impairment of several signaling pathways, which contribute to neuronal death in hippocampal regions. Melatonin administration during ESD prevented these effects. Quantitative evaluation of cells also revealed a higher number of neurons in the melatonin-treated animals when compared with the saline-treated animals. As the hippocampus is critical to cognitive activity, preserving or even improving the hippocampal molecular machinery by melatonin during ESD not only helps us to better understand the underlying mechanisms of ESD-induced neuronal dysfunction, but also the therapeutic use of melatonin to counteract ESD-induced neuronal deficiency.

Modulation of glutamate levels and Na+,K+-ATPase activity contributes to the chrysin memory recovery in hypothyroidism mice

Abnormalities in the thyroid hormones, like in hypothyroidism, are closely related to dementia and Alzheimer's disease demonstrating the main symptom of these disorders: memory deficit. In this study we evaluated the effect of chrysin on deficit spatial and aversive memories and the contribution of glutamatergic, cholinergic pathways and Na⁺, K⁺-ATPase activity on hippocampus and prefrontal cortex in hypothyroid adult female mice C57BL/6. Hypothyroidism was induced by the continuous exposure to 0.1% methimazole (MTZ) in drinking water for 31 days. The exposure to MTZ was associated to low plasma levels of thyroid hormones (TH) compared to the control group on the 32nd. Subsequently, euthyroid and MTZ-induced hypothyroid mice received (intragastrically) either vehicle or chrysin (20 mg/kg) once a day for 28 consecutive days. After treatments mice performed the following behavioral assessments: open-field test (OFT), morris water maze (MWM) and passive avoidance test. Additionally, plasma TH levels were measured again, as well as glutamate levels, Na⁺,K⁺-ATPase and acetylcholinesterase (AChE) activities were analyzed in the hippocampus and prefrontal cortex of mice. Mice with hypothyroidism showed a deficit of spatial and aversive memory and chrysin treatment reversed these deficits. It also reduced the levels of glutamate and decreased Na⁺,K⁺-ATPase activity in both cerebral structures in the hypothyroid mice compared with the euthyroid ones, with the exception of glutamate in the hippocampus, which was a partial reversal. AChE activity was not altered by treatments. Together, our results demonstrate that chrysin normalized hippocampal glutamate levels and Na⁺,K⁺-ATPase activity, which could be involved in the reversal of memory deficit.

Ameliorative effect of boric acid against formaldehyde-induced oxidative stress in A549 cell lines

Formaldehyde (HCHO) is a reactive agent and the most essential common carcinogenic environmental pollutant. The present study investigated the protective and ameliorative effects of boric acid (BA) against formaldehyde-induced oxidative stress in A549 cell lines. The first group served as a control, the second group was treated with only 100 μM formaldehyde, and the third, fourth, and fifth groups were treated with 2.5, 5, and 10 mM BA, respectively. The sixth, seventh, and eighth groups were treated with 2.5, 5, and 10 mM BA plus 100 μM formaldehyde, respectively. In A549 cell lines, formaldehyde treatment significantly decreased cell viability, glutathione level, and enzyme activities of superoxide dismutase and catalase; however, malondialdehyde levels of the cell lysate were found to increase compared with the control group. In addition, formaldehyde treatment did not significantly alter nitric oxide levels. Meanwhile, mRNA expression levels of Tnf-α, NFĸB, and caspase-3 significantly increased but the Bcl-XL level did not show significant alteration by formaldehyde treatment. In contrast, the BA treatment reversed the formaldehyde-induced alteration in A549 cell lines. Consequently, BA exhibited a protective effect in A549 cell line against formaldehyde-induced lipid peroxidation. Furthermore, it ameliorated the antioxidant status and mRNA expression levels of proinflammatory cytokines.

Effects of transcranial photobiomodulation and methylene blue on biochemical and behavioral profiles in mice stress model

The effectiveness of transcranial photobiomodulation (tPBM) and methylene Blue (MB) in treating learning and memory impairments is previously reported. In this study, we investigated the effect of tPBM and MB in combination or alone on unpredictable chronic mild stress (UCMS)-induced learning and memory impairments in mice. Fifty-five male BALB/c mice were randomly allocated to five groups: control, laser sham + normal saline (NS), tPBM + NS, laser sham + MB, and tPBM + MB. All groups except the control underwent UCMS and were treated simultaneously for 4 weeks. Elevated plus maze (EPM) was used to evaluate anxiety-like behaviors. Novel object recognition (NOR) test and Barnes maze tests were used to evaluate learning and memory function. The serum cortisol and brain nitric oxide (NO), reactive oxygen species (ROS), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and superoxide dismutase (SOD) levels were measured by spectrophotometric methods. Behavioral tests revealed that UCMS impaired learning and memory, and treatment with PBM, MB, and their combination reversed these impairments. Levels of NO, ROS, SOD activity in brain, and serum cortisol levels significantly increased while brain GPx activity and total antioxidant capacity significantly decreased in the sham + NS animals when compared with the controls. A significant improvement was observed in treatment groups due to reversion of the aforementioned molecular analysis caused by UCMS when it was compared with control levels. Both tPBM and MB in combination or alone have significant therapeutic effects on learning and memory impairments in UCMS-received animals.

Argininemia as a cause of severe chronic stunting and partial growth hormone deficiency (PGHD): A case report

RATIONALE

Argininemia is an autosomal recessive inherited disorder of the urea cycle. Because of its atypical symptoms in early age, diagnosis can be delayed until the typical chronic manifestations - including spastic diplegia, deterioration in cognitive function, and epilepsy - appear in later childhood.

PATIENT CONCERNS

A Chinese boy initially presented with severe stunting and partial growth hormone deficiency (PGHD) at 3 years old and was initially treated with growth hormone replacement therapy. Seven years later (at 10 years old), he presented with spastic diplegia, cognitive function lesions, epilepsy, and peripheral neuropathy.

DIAGNOSES

Ultimately, the patient was diagnosed with argininemia with homozygous mutation (c.32T>C) of the ARG1 gene at 10 years old. Blood tests showed mildly elevated blood ammonia and creatine kinase, and persistently elevated bilirubin.

INTERVENTIONS

Protein intake was limited to 0.8 g/kg/day, citrulline (150-200 mg [kg d]) was prescribed.

OUTCOMES

The patient's mental state and vomiting had improved after 3 months treatment. At 10 years and 9 month old, his height and weight had reached 121cm and 22kg, respectively, but his spastic diplegia symptoms had not improved.

LESSONS

This case demonstrates that stunting and PGHD that does not respond to growth hormone replacement therapy might hint at inborn errors of metabolism (IEM). IEM should also be considered in patients with persistently elevated bilirubin with or without abnormal liver transaminase, as well as elevated blood ammonia and creatine kinase, in the absence of hepatic disease.

Protective effect against brain tissues oxidative damage as a possible mechanism for beneficial effects of L-arginine on lipopolysaccharide induced memory impairment in rats

L-Arginine (LA) and nitric oxide (NO) have been suggested to have some effects on learning, memory, brain tissues oxidative damage, and neuroinflammation. In this study, protective effect against brain tissues oxidative damage as a possible mechanism for beneficial effects of LA on lipopolysaccharide (LPS) induced memory impairment was investigated. The rats were grouped into and treated by (1) control (saline), (2) LPS (1 mg/kg, IP), (3) LA (200 mg/kg) - LPS (4) LA. In passive avoidance (PA) test, LPS administration shortened the latency to enter the dark compartment in LPS group compared to control (p < .001) which was accompanied with a high level of malondialdehyde (MDA) and NO metabolite concentrations in the hippocampal tissues (p < .001and p < .05, respectively). Pretreatment with LA prolonged the latency in LA-LPS group compared with LPS group (p < .01-.001) and re-stored MDA and NO metabolites in the hippocampal tissues (p < .05). LPS also reduced superoxide dismutase (SOD) and catalase (CAT) activities and thiol content in the hippocampal tissues in LPS group compared to control (p < .05 and p < .001, respectively) which improved by LA when it was administered before LPS in LA-LPS group (p < .05 and p < .001). Finally, the serum TNFα level of LPS group was higher than the control (p < .01) while, in LA-LPS group it was lower than LPS group (p < .01). It seems that the beneficial effects of LA on memory impairment of LPS-treated rats may be due to its protective effects against brain tissues oxidative damage.

Argininic acid alters markers of cellular oxidative damage in vitro: Protective role of antioxidants

We, herein, investigated the in vitro effects of argininic acid on thiobarbituric acid-reactive substances (TBA-RS), total sulfhydryl content and on the activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the blood, kidney and liver of 60-day-old rats. We also verified the influence of the antioxidants (each at 1.0mM) trolox and ascorbic acid, as well as of N^G-nitro-l-arginine methyl ester (L-NAME) at 1.0mM, a nitric oxide synthase inhibitor, on the effects elicited by argininic acid on the parameters tested. The liver, renal cortex and renal medulla were homogenized in 10vol (1:10w/v) of 20mM sodium phosphate buffer, pH 7.4, containing 140mM KCl; and erythrocytes and plasma were prepared from whole blood samples obtained from rats. For in vitro experiments, the samples were pre-incubated for 1h at 37°C in the presence of argininic acid at final concentrations of 0.1, 1.0 and 5.0μM. Control experiments were performed without the addition of argininic acid. Results showed that argininic acid (5.0μM) enhanced CAT and SOD activities and decreased GSH-Px activity in the erythrocytes, increased CAT and decreased GSH-Px activities in the renal cortex and decreased CAT and SOD activities in the renal medulla of 60-day-old rats, as compared to the control group. Antioxidants and/or L-NAME prevented most of the alterations caused by argininic acid on the oxidative stress parameters evaluated. Data suggest that argininic acid alters antioxidant defenses in the blood and kidney of rats; however, in the presence of antioxidants and L-NAME, most of these alterations in oxidative stress were prevented. These findings suggest that oxidative stress may be make an important contribution to the damage caused by argininic acid in hyperargininemic patients and that treatment with antioxidants may be beneficial in this pathology.

The effects of intra-hippocampal L-thyroxine infusion on long-term potentiation and long-term depression: A possible role for the αvβ3 integrin receptor

Although the effects of long-term experimental dysthyroidism on long-term potentiation (LTP) and long-term depression (LTD) have been documented, the relationship between LTP/LTD and acute administration of L-thyroxine (T4) has not been described. Here, we investigated the effects of intra-hippocampal administration of T4 on synaptic plasticity in the dentate gyrus of the hippocampal formation. After a 15-minute baseline recording, LTP and LTD were induced by application of high- and low-frequency stimulation protocols, respectively. Infusions of saline or T4 and tetraiodothyroacetic acid (tetrac), a T4 analog that inhibits binding of iodothyronines to the integrin αvβ3 receptor, either alone or together, were made during the stimulation protocols. The averages of the excitatory postsynaptic potential (EPSP) slopes and population spike (PS) amplitudes, between 55 to 60 minutes, were used as a measure of the LTP/LTD magnitude and were analyzed by two-way univariate ANOVA with T4 and tetrac as between-subjects factors. The input-output curves of the infusion groups were comparable to each other, as shown by the non significant interaction observed between stimulus intensity and infused drug. The magnitude of the LTP in T4-infused rats was significantly lower as compared to saline-infused rats. Both the PS amplitude and the EPSP slope were depressed more markedly with T4 infusion than with saline, tetrac, and T4 + tetrac infusion. Data of this study provide in vivo evidence that T4 can promote LTD over LTP via the integrin αvβ3 receptor, and that the effect of endogenous T4 on this receptor can be suppressed by tetrac in the hippocampus. © 2016 Wiley Periodicals, Inc.

Decreased Prolidase Activity in Patients with Posttraumatic Stress Disorder

OBJECTIVE

Many neurochemical systems have been implicated in the development of Posttraumatic Stress Disorder (PTSD). The prolidase enzyme is a cytosolic exopeptidase that detaches proline or hydroxyproline from the carboxyl terminal position of dipeptides. Prolidase has important biological effects, and to date, its role in the etiology of PTSD has not been studied. In the present study, we aimed to evaluate prolidase activity in patients with PTSD.

METHODS

The study group consisted of patients who were diagnosed with PTSD after the earthquake that occurred in the province of Van in Turkey in 2011 (n=25); the first control group consisted of patients who experienced the earthquake but did not show PTSD symptoms (n=26) and the second control group consisted of patients who have never been exposed to a traumatic event (n=25). Prolidase activities in the patients and the control groups were determined by the ELISA method using commercial kits.

RESULTS

Prolidase activity in the patient group was significantly lower when compared to the control groups. Prolidase activity was also significantly lower in the traumatized healthy subjects compared to the other healthy group (p<0.01).

CONCLUSION

The findings of the present study suggest that the decrease in prolidase activity may have neuroprotective effects in patients with PTSD.

Comprehensive Application of Time-of-flight Secondary Ion Mass Spectrometry (TOF-SIMS) for Ionic Imaging and Bio-energetic Analysis of Club Drug-induced Cognitive Deficiency

Excessive exposure to club drug (GHB) would cause cognitive dysfunction in which impaired hippocampal Ca²⁺-mediated neuroplasticity may correlate with this deficiency. However, the potential changes of in vivo Ca²⁺ together with molecular machinery engaged in GHB-induced cognitive dysfunction has never been reported. This study aims to determine these changes in bio-energetic level through ionic imaging, spectrometric, biochemical, morphological, as well as behavioral approaches. Adolescent rats subjected to GHB were processed for TOF-SIMS, immunohistochemistry, biochemical assay, together with Morris water maze to detect the ionic, molecular, neurochemical, and behavioral changes of GHB-induced cognitive dysfunction, respectively. Extent of oxidative stress and bio-energetics were assessed by levels of lipid peroxidation, Na⁺/K⁺ ATPase, cytochrome oxidase, and [¹⁴C]-2-deoxyglucose activity. Results indicated that in GHB intoxicated rats, decreased Ca²⁺ imaging and reduced NMDAR1, nNOS, and p-CREB reactivities were detected in hippocampus. Depressed Ca²⁺-mediated signaling corresponded well with intense oxidative stress, diminished Na⁺/K⁺ ATPase, reduced COX, and decreased 2-DG activity, which all contributes to the development of cognitive deficiency. As impaired Ca²⁺-mediated signaling and oxidative stress significantly contribute to GHB-induced cognitive dysfunction, delivering agent(s) that improves hippocampal bio-energetics may thus serve as a promising strategy to counteract the club drug-induced cognitive dysfunction emerging in our society nowadays.

The effects of L-arginine on spatial memory and synaptic plasticity impairments induced by lipopolysaccharide

Background:

An important role of nitric oxide (NO) in neuroinflammation has been suggested. It is also suggested that NO has a critical role in learning and memory. Neuro-inflammation induced by lipopolysaccharide (LPS) has been reported that deteriorates learning and memory. The effect of L-arginine (LA) as a precursor of NO on LPS-induced spatial learning and memory and neuronal plasticity impairment was evaluated.

Materials and Methods:

The animals were grouped into: (1) Control, (2) LPS, (3) LA-LPS, and (4) LA. The rats received intraperitoneally LPS (1 mg/kg) 2 h before experiments and LA (200 mg/kg) 30 min before LPS. The animals were examined in Morris water maze (MWM). Long-term potentiation (LTP) from CA₁ area of the hippocampus was also assessed by 100 Hz stimulation in the ipsilateral Schaffer collateral pathway.

Results:

In MWM, time latency and traveled path were higher in LPS group than the control group (P < 0.001) whereas in LA-LPS group they were shorter than LPS group (P < 0.001). The amplitude and slope of field excitatory postsynaptic potential (fEPSP) decreased in LPS group compared to control group (P < 0.05 and P < 0.01) whereas, there was not any significant difference in these parameters between LPS and LA-LPS groups.

Conclusion:

Administration of LPS impaired spatial memory and synaptic plasticity. Although LA ameliorated deleterious effects of LPS on learning of spatial tasks, it could not restore LPS-induced LTP impairment.

Lipopolysaccharide-induced memory impairment in rats is preventable using 7-nitroindazole

Inflammation and oxidative stress have important roles in memory impairment. The effect of 7-nitroindazole (7NI) on lipopolysaccharide (LPS)-induced memory impairment was investigated. Rats were used, divided into four groups that were treated as follows: (1) control (saline); (2) LPS; (3) 7NI-LPS; and (4) 7NI before passive avoidance (PA). In the LPS group, the latency for entering the dark compartment was shorter than in the controls (p < 0.01 and p < 0.001); while in the 7NI-LPS group, it was longer than in the LPS group (p < 0.01 and p < 0.001). Malondialdehyde (MDA) and nitric oxide (NO) metabolite concentrations in the brain tissues of the LPS group were higher than in the controls (p < 0.001 and p < 0.05); while in the 7NI-LPS group, they were lower than in the LPS group (p < 0.001 and p < 0.05, respectively). The thiol content in the brain of the LPS group was lower than in the controls (p < 0.001); while in the 7NI-LPS group, it was higher than in the LPS group (p < 0.001). It is suggested that brain tissue oxidative damage and NO elevation have a role in the deleterious effects of LPS on memory retention that are preventable using 7NI.

Trypanosoma evansi infection impairs memory, increases anxiety behaviour and alters neurochemical parameters in rats

The aim of this study was to investigate neurochemical and enzymatic changes in rats infected with Trypanosoma evansi, and their interference in the cognitive parameters. Behavioural assessment (assessment of cognitive performance), evaluation of cerebral L-[3H]glutamate uptake, acetylcholinesterase (AChE) activity and Ca+2 and Na+, K+-ATPase activity were evaluated at 5 and 30 days post infection (dpi). This study demonstrates a cognitive impairment in rats infected with T. evansi. At 5 dpi memory deficit was demonstrated by an inhibitory avoidance test. With the chronicity of the disease (30 dpi) animals showed anxiety symptoms. It is possible the inhibition of cerebral Na+, K+-ATPase activity, AChE and synaptosomal glutamate uptake are involved in cognitive impairment in infected rats by T. evansi. The understanding of cerebral host–parasite relationship may shed some light on the cryptic symptoms of animals and possibly human infection where patients often present with other central nervous system (CNS) disorders.

Quercetin protects the impairment of memory and anxiogenic-like behavior in rats exposed to cadmium: Possible involvement of the acetylcholinesterase and Na(+),K(+)-ATPase activities

The present study investigated the effects of quercetin in the impairment of memory and anxiogenic-like behavior induced by cadmium (Cd) exposure. We also investigated possible alterations in acetylcholinesterase (AChE), Na(+),K(+)-ATPase and δ-aminolevulinate dehydratase (δ-ALA-D) activities as well as in oxidative stress parameters in the CNS. Rats were exposed to Cd (2.5mg/kg) and quercetin (5, 25 or 50mg/kg) by gavage for 45days. Animals were divided into eight groups (n=10-14): saline/control, saline/Querc 5mg/kg, saline/Querc 25mg/kg, saline/Querc 50mg/kg, Cd/ethanol, Cd/Querc 5mg/kg, Cd/Querc 25mg/kg and Cd/Querc 50mg/kg. Results demonstrated that Cd impaired memory has an anxiogenic effect. Quercetin prevented these harmful effects induced by Cd. AChE activity decreased in the cerebral cortex and hippocampus and increased in the hypothalamus of Cd-exposed rats. The Na(+),K(+)-ATPase activity decreased in the cerebral cortex, hippocampus and hypothalamus of Cd-exposed rats. Quercetin prevented these effects in AChE and Na(+),K(+)-ATPase activities. Reactive oxygen species production, thiobarbituric acid reactive substance levels, protein carbonyl content and double-stranded DNA fractions increased in the cerebral cortex, hippocampus and hypothalamus of Cd-exposed rats. Quercetin totally or partially prevents these effects caused by Cd. Total thiols (T-SHs), reduced glutathione (GSH), and reductase glutathione (GR) activities decreased and glutathione S-transferase (GST) activity increased in Cd exposed rats. Co-treatment with quercetin prevented reduction in T-SH, GSH, and GR activities and the rise of GST activity. The present findings show that quercetin prevents alterations in oxidative stress parameters as well as AChE and Na(+),K(+)-ATPase activities, consequently preventing memory impairment and anxiogenic-like behavior displayed by Cd exposure. These results may contribute to a better understanding of the neuroprotective role of quercetin, emphasizing the influence of this flavonoid in the diet for human health, possibly preventing brain injury associated with Cd intoxication.

Neuroprotective effect of anthocyanins on acetylcholinesterase activity and attenuation of scopolamine-induced amnesia in rats

Anthocyanins are a group of natural phenolic compounds responsible for the color to plants and fruits. These compounds might have beneficial effects on memory and have antioxidant properties. In the present study we have investigated the therapeutic efficacy of anthocyanins in an animal model of cognitive deficits, associated to Alzheimer's disease, induced by scopolamine. We evaluated whether anthocyanins protect the effects caused by SCO on nitrite/nitrate (NOx) levels and Na(+),K(+)-ATPase and Ca(2+)-ATPase and acetylcholinesterase (AChE) activities in the cerebral cortex and hippocampus (of rats. We used 4 different groups of animals: control (CTRL), anthocyanins treated (ANT), scopolamine-challenged (SCO), and scopolamine+anthocyanins (SCO+ANT). After seven days of treatment with ANT (200mgkg(-1); oral), the animals were SCO injected (1mgkg(-1); IP) and were performed the behavior tests, and submitted to euthanasia. A memory deficit was found in SCO group, but ANT treatment prevented this impairment of memory (P<0.05). The ANT treatment per se had an anxiolytic effect. AChE activity was increased in both in cortex and hippocampus of SCO group, this effect was significantly attenuated by ANT (P<0.05). SCO decreased Na(+),K(+)-ATPase and Ca(2+)-ATPase activities in hippocampus, and ANT was able to significantly (P<0.05) prevent these effects. No significant alteration was found on NOx levels among the groups. In conclusion, the ANT is able to regulate cholinergic neurotransmission and restore the Na(+),K(+)-ATPase and Ca(2+)-ATPase activities, and also prevented memory deficits caused by scopolamine administration.

Nitric oxide mediates the beneficial effect of chronic naltrexone on cholestasis-induced memory impairment in male rats

Recent studies suggest an augmentation of endogenous opioids following bile duct ligation (BDL) and their pivotal role in the pathophysiology of cholestasis. In this study, the effect of naltrexone, an opioid receptor antagonist, was determined on cholestasis-induced memory impairment and the possible involvement of nitric oxide (NO) in this effect. Male Albino-Wistar rats were randomized to sham-operated and BDL-operated groups. In each group, animals were treated for up to 28 days with saline; naltrexone (10 mg/kg); naltrexone and N(G)-nitro-L-arginine methyl ester (L-NAME), a nonselective nitric oxide synthase (NOS) inhibitor (3, 10 mg/kg); naltrexone and aminoguanidine, an inducible NOS inhibitor (100 mg/kg); or methylnaltrexone, a peripherally acting opioid receptor antagonist (3 mg/kg, intraperitoneal). Spatial recognition memory was determined in a Y-maze task on the day before surgery and days 7, 14, 21, and 28 after surgery. Memory performance was impaired 14 days after BDL in cholestatic rats and was significantly reversed by chronic treatment with naltrexone at days 14, 21, and 28 after BDL. On day 21 after BDL, chronic L-NAME produced only a nonsignificant decrease in the beneficial effect of naltrexone, whereas on day 28, chronic administration of both L-NAME and aminoguanidine significantly reversed this effect of naltrexone. It is therefore shown in this study that naltrexone improves BDL-induced memory deficit in rats. We conclude that the memory impairment in cholestatic rats might be because of an increase in the level of endogenous opioids and that naltrexone improved the spatial recognition memory by antagonizing opioid receptors. The observation that the procognitive effect of naltrexone is counteracted either by general inhibition of NOS enzymes or by selective inhibition of inducible NOS suggests the nitrergic pathway as a probable mechanism involved in the amelioration of spatial recognition memory by naltrexone in BDL rats.

N-acetylcysteine prevents spatial memory impairment induced by chronic early postnatal glutaric acid and lipopolysaccharide in rat pups

Background and Aims

Glutaric aciduria type I (GA-I) is characterized by accumulation of glutaric acid (GA) and neurological symptoms, such as cognitive impairment. Although this disease is related to oxidative stress and inflammation, it is not known whether these processes facilitate the memory impairment. Our objective was to investigate the performance of rat pups chronically injected with GA and lipopolysaccharide (LPS) in spatial memory test, antioxidant defenses, cytokines levels, Na+, K+-ATPase activity, and hippocampal volume. We also evaluated the effect of N-acetylcysteine (NAC) on theses markers.

Methods

Rat pups were injected with GA (5umol g of body weight-1, subcutaneously; twice per day; from 5th to 28th day of life), and were supplemented with NAC (150mg/kg/day; intragastric gavage; for the same period). LPS (2mg/kg; E.coli 055 B5) or vehicle (saline 0.9%) was injected intraperitoneally, once per day, from 25th to 28th day of life. Oxidative stress and inflammatory biomarkers as well as hippocampal volume were assessed.

Results

GA caused spatial learning deficit in the Barnes maze and LPS potentiated this effect. GA and LPS increased TNF-α and IL-1β levels. The co-administration of these compounds potentiated the increase of IL-1β levels but not TNF-α levels in the hippocampus. GA and LPS increased TBARS (thiobarbituric acid-reactive substance) content, reduced antioxidant defenses and inhibited Na+, K+-ATPase activity. GA and LPS co-administration did not have additive effect on oxidative stress markers and Na+, K+ pump. The hippocampal volume did not change after GA or LPS administration. NAC protected against impairment of spatial learning and increase of cytokines levels. NAC Also protected against inhibition of Na+,K+-ATPase activity and oxidative markers.

Conclusions

These results suggest that inflammatory and oxidative markers may underlie at least in part of the neuropathology of GA-I in this model. Thus, NAC could represent a possible adjuvant therapy in treatment of children with GA-I.

Arginine exposure alters ectonucleotidase activities and morphology of zebrafish larvae (Danio rerio)

Hyperargininemia is an inborn error of metabolism (IEM) characterized by tissue accumulation of arginine (Arg). Mental retardation and other neurological features are common symptoms in hyperargininemic patients. Considering purinergic signaling has a crucial role from the early stages of development and underlying mechanisms of this disease are poorly established, we investigated the effect of Arg administration on locomotor activity, morphological alterations, and extracellular nucleotide hydrolysis in larvae and adult zebrafish. We showed that 0.1 mM Arg was unable to promote changes in locomotor activity. In addition, 7-day-post-fertilization (dpf) larvae treated with Arg demonstrated a decreased body size. Arg exposure (0.1 mM) promoted an increase in ATP, ADP, and AMP hydrolysis when compared to control group. These findings demonstrated that Arg might affect morphological parameters and ectonucleotidase activities in zebrafish larvae, suggesting that purinergic system is a target for neurotoxic effects induced by Arg.

Thyroid hormone's role in regulating brain glucose metabolism and potentially modulating hippocampal cognitive processes

Cognitive performance is dependent on adequate glucose supply to the brain. Insulin, which regulates systemic glucose metabolism, has been recently shown both to regulate hippocampal metabolism and to be a mandatory component of hippocampally-mediated cognitive performance. Thyroid hormones (TH) regulate systemic glucose metabolism and may also be involved in regulation of brain glucose metabolism. Here we review potential mechanisms for such regulation. Importantly, TH imbalance is often encountered in combination with metabolic disorders such as diabetes, and may cause additional metabolic dysregulation and hence worsening of disease states. TH's potential as a regulator of brain glucose metabolism is heightened by interactions with insulin signaling, but there have been relatively few studies on this topic or on the actions of TH in a mature brain. This review discusses evidence for mechanistic links between TH, insulin, cognitive function, and brain glucose metabolism, and reaches the conclusion that TH may modulate memory processes, likely at least in part by modulation of central insulin signaling and glucose metabolism.

Spermidine decreases Na⁺,K⁺-ATPase activity through NMDA receptor and protein kinase G activation in the hippocampus of rats

Spermidine is an endogenous polyamine with a polycationic structure present in the central nervous system of mammals. Spermidine regulates biological processes, such as Ca(2+) influx by glutamatergic N-methyl-d-aspartate receptor (NMDA receptor), which has been associated with nitric oxide synthase (NOS) and cGMP/PKG pathway activation and a decrease of Na(+),K(+)-ATPase activity in rats' cerebral cortex synaptosomes. Na(+),K(+)-ATPase establishes Na(+) and K(+) gradients across membranes of excitable cells and by this means maintains membrane potential and controls intracellular pH and volume. However, it has not been defined whether spermidine modulates Na(+),K(+)-ATPase activity in the hippocampus. In this study we investigated whether spermidine alters Na(+),K(+)-ATPase activity in slices of hippocampus from rats, and possible underlying mechanisms. Hippocampal slices and homogenates were incubated with spermidine (0.05-10 μM) for 30 min. Spermidine (0.5 and 1 μM) decreased Na(+),K(+)-ATPase activity in slices, but not in homogenates. MK-801 (100 and 10 μM), a non-competitive antagonist of NMDA receptor, arcaine (0.5μM), an antagonist of the polyamine binding site at the NMDA receptor, and L-NAME (100μM), a NOS inhibitor, prevented the inhibitory effect of spermidine (0.5 μM). ODQ (10 μM), a guanylate cyclase inhibitor, and KT5823 (2 μM), a protein kinase G inhibitor, also prevented the inhibitory effect of spermidine on Na(+),K(+)-ATPase activity. Spermidine (0.5 and 1.0 μM) increased NO(2) plus NO(3) (NOx) levels in slices, and MK-801 (100 μM) and arcaine (0.5 μM) prevented the effect of spermidine (0.5 μM) on the NOx content. These results suggest that spermidine-induced decrease of Na(+),K(+)-ATPase activity involves NMDA receptor/NOS/cGMP/PKG pathway.

A more accurate profile of Achyrocline satureioides hypocholesterolemic activity

The aim of this study was to investigate the effect of the aqueous extract (AE) of Achyrocline satureioides on serum lipid profile, liver oxidative profile and Na(+),K(+)-ATPase activity of rats submitted to a hyperlipidic diet. The animals were divided into four groups: control (C), AE 10% (A(10)), hyperlipidic (H) and hyperlipidic/AE 10% (HA(10)). In serum, we measured the levels of total cholesterol (TC), high-density lipoprotein, very-low-density lipoprotein, low-density lipoprotein (LDL) and triglyceride (TG). In liver homogenates, we measured the thiobarbituric acid reactive substances, the carbonyl proteins, the non-protein thiols (NPSHs) and the activity of superoxide dismutase, catalase (CAT) and Na(+),K(+)-ATPase. We observed a significant increase in the TC and LDL levels in the H group. A. satureioides prevented these effects, decreased the TG levels in the HA(10) group and increased the NPSH levels in the A(10) and HA(10) groups. The H group showed an increase in the carbonyl protein level and a decrease in CAT and Na(+),K(+)-ATPase activities. With the use of this model, results show that increased levels of lipids are related to a redox imbalance in the liver, which is also related to the inhibition of Na(+),K(+)-ATPase activity, and that chronic administration of the AE of A. satureioides is capable of changing this profile.

Protective effect of antioxidants on blood oxidative stress caused by arginine

In this study, we investigated in vivo and in vitro effect of arginine on parameters of oxidative stress namely thiobarbituric acid-reactive substances (TBA-RS) and total radical-trapping antioxidant parameter (TRAP) in plasma and on the antioxidant enzymes activities catalase (CAT), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) in erythrocytes of rats. Results showed that acute administration reduced TRAP and CAT activity and increased TBA-RS. Furthermore, in vitro studies did not alter oxidative parameters studied. The influence of N(ω)-nitro-L-arginine methyl ester (L-NAME) and antioxidants (α-tocopherol plus ascorbic acid) on the effects elicited by arginine was also studied. In addition, simultaneous injection of L-NAME or treatment with antioxidants prevented the alteration on TRAP, TBA-RS, and CAT activity caused by arginine. Data indicate that oxidative stress induction is probably mediated by the generation of NO and/or ONOO(-) and other free radicals, because L-NAME and these antioxidants prevented these effects caused by arginine.

Protective effect of antioxidants on cerebrum oxidative damage caused by arginine on pyruvate kinase activity

We have demonstrated that acute arginine administration decreases antioxidant defenses and compromises enzymes of respiratory chain in rat brain. In this study we evaluated in vivo and in vitro effect of arginine on pyruvate kinase activity, as well as its effect on an important parameter of oxidative stress namely thiobarbituric acid-reactive substances (TBA-RS) in cerebrum of rats. We also tested the influence of antioxidants, namely alpha -tocopherol plus ascorbic acid on the effects elicited by arginine in order to investigate the possible participation of free radicals on the effects of arginine on these parameters. Results showed that arginine acute administration inhibited pyruvate kinase activity in cerebrum of rats, as well as increased TBA-RS. By the other hand, arginine added to the incubation medium, in vitro studies, did not alter these parameters in rat cerebrum. In addition, pretreatment with antioxidants prevented the reduction of pyruvate kinase activity and the increase of TBA-RS caused by arginine. The data indicate that acute administration of arginine induces lipid peroxidation in rat cerebrum and that the inhibition of pyruvate kinase activity caused by this amino acid was probably mediated by free radicals since antioxidants prevented such effect. It is presumed that these results might be associated, at least in part, with the neuronal dysfunction of patients affected by hyperargininemia. Finally, we suggest that the administration of antioxidants should be considered as an adjuvant therapy to specific diets in hyperargininemia.

Inhibition of CO(2) production from glucose by arginine in brain slices of rats

In the present study we evaluated the in vivo effect of arginine on CO(2) production from glucose in a medium with physiological and high extracellular K(+) concentrations. We also tested the influence of the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), on the effects elicited by arginine in order to investigate the possible participation of NO and/or its derivatives on the effects of arginine on CO(2) production from glucose. Sixty-day-old rats were treated with a single intraperitoneal injection of saline (control; group I), arginine (0.8 g/kg; group II), L-NAME (2.0 mg/kg; group III) or arginine (0.8 g/kg) plus L-NAME (2.0 mg/kg; group IV) and were killed 1 h later. Results showed that arginine administration inhibited CO(2) production from glucose at physiological extracellular K(+) concentration and L-NAME prevented such effect. In contrast, arginine administration had no effect on CO(2) production from glucose at high extracellular K(+) concentration. Based on these data, we also investigated the in vitro effect of arginine on CO(2) production from glucose in a medium with physiological extracellular K(+) concentration in hippocampus slices. Results showed that arginine (0.1-1.5 mM) when added to the incubation medium did not alter CO(2) production from glucose in hippocampus slices of untreated rats. In addition, we also demonstrated that arginine inhibits Na(+), K(+)-ATPase activity. The data indicate that the reduction of CO(2) production by arginine was probably mediated by NO and/or its derivatives, which could act inhibiting the activity of Na(+), K(+)-ATPase. The results suggest that arginine impairs energy metabolism in hippocampus slices of rats.

NTPDase and 5'-nucleotidase activities of synaptosomes from hippocampus of rats subjected to hyperargininemia

ATP is an important excitatory neurotransmitter and adenosine acts as a neuromodulatory structure inhibiting neurotransmitters release in the central nervous system. Since the ecto-nucleotidase cascade that hydrolyzes ATP to adenosine is involved in the control of brain functions and previous studies realized in our laboratory have recently reported that acute administration of Arg decreases the NTPDase and 5'-nucleotidase activities of rat blood serum, in the present study we investigated the effect of arginine administration on NTPDase and 5'-nucleotidase activities by synaptosomes from hippocampus of rats. First, sixty-days-old rats were treated with a single or a triple intraperitoneal injection of arginine (0.8 g/Kg) or an equivalent volume of 0.9% saline solution (control) and were killed 1 h later. Second, rats received an intracerebroventricular injection of 1.5 mM arginine solution or saline (5 microL) and were killed 1 h later. We also tested the in vitro effect of arginine (0.1-1.5 mM) on nucleotide hydrolysis in synaptosomes from rat hippocampus. Results showed that intraperitoneal arginine administration did not alter nucleotide hydrolysis. On the other hand, arginine administered intracerebroventricularly reduced ATP (32%), ADP (30%) and AMP (21%) hydrolysis, respectively. In addition, arginine added to the incubation medium, provoked a decrease on ATP (19%), ADP (17%) and AMP (23%) hydrolysis, respectively. Furthermore, kinetic studies showed that the inhibitory effect of arginine was uncompetitive in relation to ATP, ADP and AMP. In conclusion, according to our results it seems reasonable to postulate that arginine alters the cascade involved in the extracellular degradation of ATP to adenosine.

Arginine administration reduces creatine kinase activity in rat cerebellum

In the present study were evaluated the in vivo effects of arginine administration on creatine kinase (CK) activity in cerebellum of rats. We also tested the influence of antioxidants, namely alpha-tocopherol and ascorbic acid and the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), on the effects elicited by Arg in order to investigate the possible participation of nitric oxide (NO) and/or its derivatives peroxynitrite (ONOO(-)) and other/or free radicals on the effects of arginine on CK activity. Sixty-day-old rats were treated with a single i.p. injection of saline (control, group I), arginine (0.8 g/kg) (group II), L-NAME (2.0 mg/kg or 20.0 mg/kg) (group III) or Arg (0.8 g/kg) plus L-NAME (2.0 mg/kg or 20.0 mg/kg) (group IV) and were killed 1 h later. In another set of experiments, the animals were pretreated for 1 week with daily i.p. administration of saline (control) or alpha-tocopherol (40 mg/kg) and ascorbic acid (100 mg/kg). Twelve hours after the last injection of the antioxidants, the rats received one i.p. injection of arginine (0.8 g/kg) or saline and were killed 1 h later. Results showed that total and cytosolic CK activities were significantly inhibited by arginine administration in cerebellum of rats, in contrast to mitochondrial CK activity which was not affected by this amino acid. Furthermore, simultaneous injection of L-NAME (20.0 mg/kg) and treatment with alpha-tocopherol and ascorbic acid prevented these effects. The data indicate that the reduction of CK activity in cerebellum of rats caused by arginine was probably mediated by NO and/or its derivatives ONOO(-)and other free radicals. Considering the importance of CK for the maintenance of energy homeostasis in the brain, if this enzyme inhibition also occurs in hyperargininemic patients, it is possible that CK inhibition may be one of the mechanisms by which arginine is neurotoxic in hyperargininemia.

Alpha-tocopherol and ascorbic acid administration prevents the impairment of brain energy metabolism of hyperargininemic rats

1. We have previously demonstrated that arginine administration induces oxidative stress and compromises energy metabolism in rat hippocampus. In the present study we initially investigated the influence of pretreatment with alpha-tocopherol and ascorbic acid on the effects produced by arginine on hippocampus energy metabolism. We also tested the effect of acute administration of arginine on various parameters of energy metabolism, namely glucose uptake, lactate release and on the activities of succinate dehydrogenase, complex II and cytochrome c oxidase in rat cerebellum, as well as the influence of pretreatment with alpha-tocopherol and ascorbic acid on the effects elicited by arginine on this structure. 2. Sixty-day-old female Wistar rats were treated with a single i.p. injection of saline (control) or arginine (0.8 g/kg) and were killed 1 h later. In another set of experiments, the animals were pretreated for 1 week with daily i.p. administration of saline (control) or alpha-tocopherol (40 mg/kg) and ascorbic acid (100 mg/kg). Twelve hours after the last injection of the antioxidants the rats received one i.p. injection of arginine (0.8 g/kg) or saline and were killed 1 h later. 3. Results showed that arginine administration significantly increased lactate release and diminished glucose uptake and the activities of succinate dehydrogenase and complex II in rat cerebellum. In contrast, complex IV (cytochrome c oxidase) activity was not changed by this amino acid. Furthermore, pretreatment with alpha-tocopherol and ascorbic acid prevented the impairment of energy metabolism caused by hyperargininemia in cerebellum and hippocampus of rats.

Na+,K(+)-ATPase activity is reduced in hippocampus of rats submitted to an experimental model of depression: effect of chronic lithium treatment and possible involvement in learning deficits

This study was undertaken to verify the effects of chronic stress and lithium treatments on the hippocampal Na+,K(+)-ATPase activity of rats, as well as to investigate the effects of stress interruption and post-stress lithium treatment on this enzyme activity and on spatial memory. Two experiments were carried out; in the first experiment, adult male Wistar rats were divided into two groups: control and submitted to a chronic variate stress paradigm, and subdivided into treated or not with LiCl. After 40 days of treatment, rats were killed, and Na+,K(+)-ATPase activity was determined. In the second experiment, rats were stressed during 40 days, and their performance was evaluated in the Water Maze task. The stressed group was then subdivided into four groups, with continued or interrupted stress treatment and treated or not with lithium for 30 additional days. After a second evaluation of performance in the Water Maze, rats were killed and Na+,K(+)-ATPase activity was also measured. Results showed an impairment in Na+,K(+)-ATPase activity and in Water Maze performance of chronically stressed rats, which were prevented by lithium treatment and reversed by lithium treatment and by stress interruption. These results suggest that the modulation of Na+,K(+)-ATPase activity may be one of the mechanisms of action of lithium in the treatment of mood disorders.

Vitamins E and C pretreatment prevents ovariectomy-induced memory deficits in water maze

We investigated whether the pretreatment with vitamins E (alpha-tocopherol) and C (ascorbic acid) would act on ovariectomy-induced memory deficits in Morris water maze tasks. Adult female Wistar rats were divided into three groups: (1) naive (control), (2) sham (submitted to surgery without removal of ovaries) and (3) ovariectomized. Thirty days after surgery, they were trained in the Morris water maze in order to verify ovariectomy effects both on reference and working memory tasks. Results show that ovariectomized rats presented impairment in spatial navigation in the acquisition phase, as well as in the time spent in target quadrant and in the latency to cross over the location of the platform in test session, when compared to naive and sham groups (controls), in the reference memory task. Ovariectomy did not affect performance in the working memory task. Confirming our hypothesis, ovariectomized rats pretreated for 30 days with vitamins E and C had those impairments prevented. We conclude that ovariectomy significantly impairs spatial reference learning/memory and that pretreatment with vitamins E and C prevents such effect. Assuming this experimental memory impairment might mimic, at least in part, the cognitive deficit sometimes present in the human condition of lack of reproductive hormones, our findings lend support to a novel therapeutic strategy, based on vitamins E and C, to cognitive impairments in post-menopausal women.

L-NAME administration prevents the inhibition of nucleotide hydrolysis by rat blood serum subjected to hyperargininemia

The main objective of the present study was to evaluate the in vivo and in vitro effect of Arg on serum nucleotide hydrolysis. The action of Nomega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase, on the effects produced by Arg was also examined. Sixty-day-old rats were treated with a single or a triple (with an interval of 1 h between each injection) intraperitoneal injection of saline (group I), Arg (0.8 g/kg) (group II), L-NAME (2.0 mg/kg or 20 mg/kg) (group III) or Arg (0.8 g/kg) plus L-NAME (2.0 mg/kg or 20 mg/kg) (group IV) and were killed 1 h later. The present results show that a triple Arg administration decreased ATP, ADP and AMP hydrolysis. Simultaneous injection of L-NAME (20 mg/kg) prevented such effects. Arg in vitro did not alter nucleotide hydrolysis. It is suggested that in vivo Arg administration reduces nucleotide hydrolysis in rat serum, probably through nitric oxide or/and peroxynitrite formation.

Chronic aspartame affects T-maze performance, brain cholinergic receptors and Na+,K+-ATPase in rats

This study demonstrated that chronic aspartame consumption in rats can lead to altered T-maze performance and increased muscarinic cholinergic receptor densities in certain brain regions. Control and treated rats were trained in a T-maze to a particular side and then periodically tested to see how well they retained the learned response. Rats that had received aspartame (250 mg/kg/day) in the drinking water for 3 or 4 months showed a significant increase in time to reach the reward in the T-maze, suggesting a possible effect on memory due to the artificial sweetener. Using [(3)H]quinuclidinyl benzilate (QNB) (1 nM) to label muscarinic cholinergic receptors and atropine (10(-6) M) to determine nonspecific binding in whole-brain preparations, aspartame-treated rats showed a 31% increase in receptor numbers when compared to controls. In aspartame-treated rats, there was a significant increase in muscarinic receptor densities in the frontal cortex, midcortex, posterior cortex, hippocampus, hypothalamus and cerebellum of 80%, 60%, 61%, 65%, 66% and 60%, respectively. The midbrain was the only area where preparations from aspartame-treated rats showed a significant increase in Na(+),K(+)-ATPase activity. It can be concluded from these data that long-term consumption of aspartame can affect T-maze performance in rats and alter receptor densities or enzymes in brain.

Training in inhibitory avoidance causes a reduction of Na+,K+-ATPase activity in rat hippocampus

Compelling evidence has indicated the involvement of Na(+),K(+)-ATPase in the mechanisms of synaptic plasticity. In the present study, we investigated the effect of inhibitory avoidance training on Na(+),K(+)-ATPase activity, at different times after training, in the rat hippocampus. Male adult Wistar rats were trained in a step-down inhibitory avoidance task and compared to those submitted to isolated footshock (0.4 mA) or placed directly onto the platform. Na(+),K(+)-ATPase activity decreased, by 60%, in hippocampus of rats sacrificed immediately after the isolated footshock, as well as immediately (0 min) and 6 h after training; this effect was not present 24 h after training. We also verified that enzyme activity was not altered in rats killed after just being on the platform. These findings suggest that Na(+),K(+)-ATPase activity may be involved in the memory consolidation of step-down inhibitory avoidance in the hippocampus.

Reduction of energy metabolism in rat hippocampus by arginine administration

Hyperargininemia is an inherited metabolic disease biochemically characterized by tissue accumulation of arginine. Mental retardation and other neurological features are common symptoms in hyperargininemic patients. Considering that the underlying mechanisms of brain damage in this disease are poorly established, in this work we investigated the effect of arginine administration to adult Wistar rats on some parameters of energy metabolism (CO(2) production, glucose uptake, lactate release and the activities of succinate dehydrogenase, complexes II and IV of the respiratory chain) in rat hippocampus. The action of L-NAME, an inhibitor of oxide nitric oxide synthase, on the effects produced by arginine was also tested. Sixty-day-old rats were treated with a single intraperitoneal injection of saline (group I, control), arginine (0.8 g/kg) (group II) or arginine (0.8 g/kg) plus L-NAME (2 mg/kg) (group III) and were killed 1 h later. Results showed that arginine administration significantly increased lactate release and diminished CO(2) production, glucose uptake, succinate dehydrogenase and complex II activities. In contrast, complex IV (cytochrome c oxidase) activity was not changed by this amino acid. Furthermore, simultaneous injection of L-NAME prevented some of these effects, except CO(2) production and lactate release. The present data indicate that in vivo arginine administration impairs some parameters of energy metabolism in hippocampus of rats probably through NO formation.