Mild Hyperhomocysteinemia Causes Anxiety-like Behavior and Brain Hyperactivity in Rodents: Are ATPase and Excitotoxicity by NMDA Receptor Overstimulation Involved in this Effect?

Mild hyperhomocysteinemia is a risk factor for psychiatric and neurodegenerative diseases, whose mechanisms between them are not well-known. In the present study, we evaluated the emotional behavior and neurochemical pathways (ATPases, glutamate homeostasis, and cell viability) in amygdala and prefrontal cortex rats subjected to mild hyperhomocysteinemia (in vivo studies). The ex vivo effect of homocysteine on ATPases and redox status, as well as on NMDAR antagonism by MK-801 in same structures slices were also performed. Wistar male rats received a subcutaneous injection of 0.03 µmol Homocysteine/g of body weight or saline, twice a day from 30 to 60th-67th days of life. Hyperhomocysteinemia increased anxiety-like behavior and tended to alter locomotion/exploration of rats, whereas sucrose preference and forced swimming tests were not altered. Glutamate uptake was not changed, but the activities of glutamine synthetase and ATPases were increased. Cell viability was not altered. Ex vivo studies (slices) showed that homocysteine altered ATPases and redox status and that MK801, an NMDAR antagonist, protected amygdala (partially) and prefrontal cortex (totally) effects. Taken together, data showed that mild hyperhomocysteinemia impairs the emotional behavior, which may be associated with changes in ATPase and glutamate homeostasis, including glutamine synthetase and NMDAR overstimulation that could lead to excitotoxicity. These findings may be associated with the homocysteine risk factor on psychiatric disorders development and neurodegeneration.

Hypermethioninemia induces memory deficits and morphological changes in hippocampus of young rats: implications on pathogenesis.

The aim of this study was to investigate the effect of the chronic administration of methionine (Met) and/or its metabolite, methionine sulfoxide (MetO), on the behavior and neurochemical parameters of young rats. Rats were treated with saline (control), Met (0.2-0.4 g/kg), MetO (0.05-0.1 g/kg), and/or a combination of Met + MetO, subcutaneously twice a day from postnatal day 6 (P6) to P28. The results showed that Met, MetO, and Met + MetO impaired short-term and spatial memories (P < 0.05), reduced rearing and grooming (P < 0.05), but did not alter locomotor activity (P > 0.05). Acetylcholinesterase activity was increased in the cerebral cortex, hippocampus, and striatum following Met and/or MetO (P < 0.05) treatment, while Na+, K+-ATPase activity was reduced in the hippocampus (P < 0.05). There was an increase in the level of thiobarbituric acid reactive substances (TBARS) in the cerebral cortex in Met-, MetO-, and Met + MetO-treated rats (P < 0.05). Met and/or MetO treatment reduced superoxide dismutase, catalase, and glutathione peroxidase activity, total thiol content, and nitrite levels, and increased reactive oxygen species and TBARS levels in the hippocampus and striatum (P < 0.05). Hippocampal brain-derived neurotrophic factor was reduced by MetO and Met + MetO compared with the control group. The number of NeuN-positive cells was decreased in the CA3 in Met + MetO group and in the dentate gyrus in the Met, MetO, and Met + MetO groups compared to control group (P < 0.05). Taken together, these findings further increase our understanding of changes in the brain in hypermethioninemia by elucidating behavioral alterations, biological mechanisms, and the vulnerability of brain function to high concentrations of Met and MetO.

P2X7 receptor deletion attenuates oxidative stress and liver damage in sepsis.

Sepsis is a severe disease characterized by an uncontrolled systemic inflammation and consequent organ dysfunction generated in response to an infection. Extracellular ATP acting through the P2X7 receptor induces the maturation and release of pro-inflammatory cytokines (i.e., IL-1ß) and the production of reactive nitrogen and oxygen species that lead to oxidative tissue damage. Here, we investigated the role of the P2X7 receptor in inflammation, oxidative stress, and liver injury in sepsis. Sepsis was induced by cecal ligation and puncture (CLP) in wild-type (WT) and P2X7 knockout (P2X7-/-) mice. The oxidative stress in the liver of septic mice was assessed by 2',7'-dichlorofluorescein oxidation reaction (DCF), thiobarbituric acid-reactive substances (TBARS), and nitrite levels dosage. The status of the endogenous defense system was evaluated through catalase (CAT) and superoxide dismutase (SOD) activities. The inflammation was assessed histologically and by determining the expression of inflammatory cytokines and chemokines by RT-qPCR. We observed an increase in the reactive species and lipid peroxidation in the liver of septic WT mice, but not in the liver from P2X7-/- animals. We found an imbalance SOD/CAT ratio, also only WT septic animals. The number of inflammatory cells and the gene expression of IL-1 ß, IL-6, TNF-α, IL-10, CXCL1, and CXCL2 were higher in the liver of WT septic mice in comparison to P2X7-/- septic animals. In summary, our results suggest that the P2X7 receptor might be a therapeutic target to limit oxidative stress damage and liver injury during sepsis.

Chronic mild Hyperhomocysteinemia impairs energy metabolism, promotes DNA damage and induces a Nrf2 response to oxidative stress in rats brain.

Homocysteine (HCY) has been linked to oxidative stress and varied metabolic changes that are dependent on its concentration and affected tissues. In the present study we evaluate parameters of energy metabolism [succinate dehydrogenase (SDH), complex II and IV (cytochrome c oxidase), and ATP levels] and oxidative stress [DCFH oxidation, nitrite levels, antioxidant enzymes and lipid, protein and DNA damages, as well as nuclear factor erythroid 2-related (Nrf2) protein abundance] in amygdala and prefrontal cortex of HCY-treated rats. Wistar male rats were treated with a subcutaneous injection of HCY (0.03 µmol/g of body weight) from the 30th to 60th post-natal day, twice a day, to induce mild hyperhomocysteinemia (HHCY). The rats were euthanatized without anesthesia at 12 h after the last injection, and amygdala and prefrontal cortex were dissected for biochemical analyses. In the amygdala, mild HHCY increased activities of SDH and complex II and decreased complex IV and ATP level, as well as increased antioxidant enzymes activities (glutathione peroxidase and superoxide dismutase), nitrite levels, DNA damage, and Nrf 2 protein abundance. In the prefrontal cortex, mild HHCY did not alter energy metabolism, but increased glutathione peroxidase, catalase and DNA damage. Other analyzed parameters were not altered by HCY-treatment. Our findings suggested that chronic mild HHCY changes each brain structure, particularly and specifically. These changes may be associated with the mechanisms by which chronic mild HHCY has been linked to the risk factor of fear, mood disorders and depression, as well as in neurodegenerative diseases.

Pregnancy swimming causes short- and long-term neuroprotection against hypoxia-ischemia in very immature rats.

BackgroundHypoxia-ischemia (HI) is a major cause of neurological damage in preterm newborn. Swimming during pregnancy alters the offspring's brain development. We tested the effects of swimming during pregnancy in the very immature rat brain.MethodsFemale Wistar rats (n=12) were assigned to the sedentary (SE, n=6) or the swimming (SW, n=6) group. From gestational day 0 (GD0) to GD21 the rats in the SW group were made to swim for 20 min/day. HI on postnatal day (PND) 3 rats caused sensorimotor and cognitive impairments. Animals were distributed into SE sham (SESH), sedentary HIP3 (SEHI), swimming sham (SWSH), and swimming HIP3 (SWHI) groups. At PND4 and PND5, Na+/K+-ATPase activity and brain-derived neurotrophic factor (BDNF) levels were assessed. During lactation and adulthood, neurological reflexes, sensorimotor, anxiety-related, and cognitive evaluations were made, followed by histological assessment at PND60.ResultsAt early stages, swimming caused an increase in hippocampal BDNF levels and in the maintenance of Na+/K+-ATPase function in the SWHI group. The SWHI group showed smaller lesions and the preservation of white matter tracts. SEHI animals showed a delay in reflex maturation, which was reverted in the SWHI group. HIP3 induced spatial memory deficits and hypomyelination in SEHI rats, which was reverted in the SWHI group.ConclusionSwimming during pregnancy neuroprotected the brains against HI in very immature neonatal rats.

Effect of physical exercise on changes in activities of creatine kinase, cytochrome c oxidase and ATP levels caused by ovariectomy.

The reduction in the secretion of ovarian hormones, principally estrogen, is a consequence of menopause. Estrogens act primarily as female sex hormones, but also exert effects on different physiological systems including the central nervous system. The treatment normally used to reduce the symptoms of menopause is the hormone therapy, which seems to be effective in treating symptoms, but it may be responsible for adverse effects. Based on this, there is an increasing demand for alternative therapies that minimize signs and symptoms of menopause. In the present study we investigated the effect of ovariectomy and/or physical exercise on the activities of energy metabolism enzymes, such as creatine kinase (cytosolic and mitochondrial fractions), pyruvate kinase, succinate dehydrogenase, complex II, cytochrome c oxidase, as well as on ATP levels in the hippocampus of adult rats. Adult female Wistar rats with 90 days of age were subjected to ovariectomy (an animal model widely used to mimic the postmenopausal changes). Thirty days after the procedure, the rats were submitted to the exercise protocol, which was performed three times a week for 30 days. Twelve hours after the last training session, the rats were decapitated for subsequent biochemical analyzes. Results showed that ovariectomy did not affect the activities of pyruvate kinase, succinate dehydrogenase and complex II, but decreased the activities of creatine kinase (cytosolic and mitochondrial fractions) and cytochrome c oxidase. ATP levels were also reduced. Exercise did not produce the expected results since it was only able to partially reverse the activity of creatine kinase cytosolic fraction. The results of this study suggest that estrogen deficiency, which occurs as a result of ovariectomy, affects generation systems and energy homeostasis, reducing ATP levels in hippocampus of adult female rats.

Mild hyperhomocysteinemia reduces the activity and immunocontent, but does not alter the gene expression, of catalytic α subunits of cerebral Na+,K+-ATPase.

Na(+),K(+)-ATPase is a membrane protein which plays a key role in the maintenance of ion homeostasis that is necessary to neuronal excitability, secondary transport and neurotransmitter uptake. Mild hyperhomocysteinemia leads to several clinical manifestations and particularly cerebral diseases; however, little is known about the mechanisms of homocysteine on cerebral Na(+),K(+)-ATPase. In the present study, we investigated the effect of mild hyperhomocysteinemia on the activity, the immunocontent of catalytic subunits (α1, α2, and α3) and the gene expression of this enzyme. We used the experimental model of mild hyperhomocysteinemia that was induced by homocysteine administration (0.03 µmol/g of body weight) twice a day, from the 30th to the 60th postpartum day. Controls received saline in the same volumes. Results showed that mild hyperhomocysteinemia significantly decreased the activity and the immunocontent of the α 1 and α 2 subunits of the Na(+),K(+)-ATPase in cerebral cortex and hippocampus of adult rats. On the other hand, we did not observe any change in levels of Na(+),K(+)-ATPase mRNA transcripts in such cerebral structures of rats after chronic exposure to homocysteine. The present findings support that the homocysteine modulates the Na(+),K(+)-ATPase and this could be associated, at least in part, with the risk to the development of cerebral diseases in individuals with mild hyperhomocysteinemia.

Homocysteine induces energy imbalance in rat skeletal muscle: is creatine a protector?

Homocystinuria is a neurometabolic disease caused by a severe deficiency of cystathionine beta-synthase activity, resulting in severe hyperhomocysteinemia. Affected patients present several symptoms including a variable degree of motor dysfunction. In this study, we investigated the effect of chronic hyperhomocysteinemia on the cell viability of the mitochondrion, as well as on some parameters of energy metabolism, such as glucose oxidation and activities of pyruvate kinase, citrate synthase, isocitrate dehydrogenase, malate dehydrogenase, respiratory chain complexes and creatine kinase in gastrocnemius rat skeletal muscle. We also evaluated the effect of creatine on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injections of homocysteine (0.3-0.6 µmol/g body weight) and/or creatine (50 mg/kg body weight) from the 6th to the 28th days of age. The animals were decapitated 12 h after the last injection. Homocysteine decreased the cell viability of the mitochondrion and the activities of pyruvate kinase and creatine kinase. Succinate dehydrogenase was increased other evaluated parameters were not changed by this amino acid. Creatine, when combined with homocysteine, prevented or caused a synergistic effect on some changes provoked by this amino acid. Creatine per se or creatine plus homocysteine altered glucose oxidation. These findings provide insights into the mechanisms by which homocysteine exerts its effects on skeletal muscle function, more studies are needed to elucidate them. Although creatine prevents some alterations caused by homocysteine, it should be used with caution, mainly in healthy individuals because it could change the homeostasis of normal physiological functions.

Sub­chronic administration of lead alters markers of oxidative stress, acetylcholinesterase and Na+K+­ATPase activities in rat brain.

This study investigated the effects of sub­chronic administration of lead (Pb) acetate on thiobarbituric acid reactive substances (TBA­RS), total sulfhydryl content, protein carbonyl content, antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GSH­Px]), acetylcholinesterase (AChE), and Na+K+­ATPase in the cerebral structures of rats. Male Wistar rats aged 60 days were treated with saline (control group) or Pb (treatment group), at various doses, by gavage, once a day for 35 days. The animals were sacrificed twelve hours after the last administration, and the cerebellum, hippocampus and cerebral cortex were removed. The results showed that Pb did not alter the evaluated oxidative stress parameters. Furthermore, Pb (64 and/or 128 mg/kg) altered SOD in the cerebellum, cerebral cortex and hippocampus. Pb (128 mg/kg) altered CAT in the cerebellum and cerebral cortex and GSH­Px in the cerebral cortex. Also, Pb (64 mg/kg and 128 mg/kg) altered GSH­Px in the cerebellum. Moreover, Pb (128 mg/kg) increased AChE in the hippocampus and decreased Na+K+­ATPase in the cerebellum and hippocampus. In conclusion, sub­chronic exposure to Pb (occupational and environmental intoxication) altered antioxidant enzymes, AChE, and Na+K+­ATPase, contributing to cerebral dysfunction.

Intrastriatal Quinolinic Acid Administration Impairs Redox Homeostasis and Induces Inflammatory Changes: Prevention by Kynurenic Acid.

Kynurenic acid (KYNA) and quinolinic acid (QUIN) are metabolites formed in the degradation of tryptophan (Trp). QUIN is a selective NMDA receptor antagonist and may exert neurotoxic effects, whereas KYNA is an agonist of glutamatergic and cholinergic receptors and presents antioxidant properties. KYNA/QUIN ratio is decreased in several central nervous system disorders, but the mechanisms involved are not well elucidated. In the present study, we try to determine the neuroprotective capacity of KYNA on the QUIN effects in redox homeostasis changes (H2DCF oxidation, superoxide dismutase/catalase (SOD/CAT) ratio, glutathione peroxidase (GPx) activity, sulfhydryl content, and nitrite levels), as well as on inflammatory parameters (levels of TNF-α, IL-1ß, and IL-6). KYNA and QUIN effects on the activities of Na+,K+-ATPase and acetylcholinesterase (AChE) were also evaluated. Thirty-day-old male Wistar rats underwent stereotactic surgery and received intrastriatal injections as follows: group 1-control (PBS-injected), group 2-KYNA (100 µM), group 3-QUIN (150 nM), and group 4-KYNA + QUIN (KYNA-injected followed QUIN-injected). Results demonstrated that the KYNA administration was able to prevent the increase in reactive oxygen species, SOD/CAT ratio, and pro-inflammatory cytokines (IL-1ß and IL-6) and the decrease in GPx activity, sulfhydryl content, and nitrite levels caused by QUIN. KYNA was also able to partially prevent the decrease in Na+,K+-ATPase activity and the increase in AChE activity caused by QUIN. This study may help in the elucidation of neuroprotective effects of KYNA against oxidative and inflammatory insults caused by QUIN in the striatum of young male Wistar rats.

Changes in Inflammatory Response, Redox Status and Na+, K+-ATPase Activity in Primary Astrocyte Cultures from Female Wistar Rats Subject to Ovariectomy.

Astrocytes are dynamic glial cells that maintain brain homeostasis, particularly metabolic functions, inflammatory response, and antioxidant defense. Since menopause may be associated with brain dysfunction, in the present study, we evaluated anti- and proinflammatory cytokine release in cortical and hippocampal astrocyte cultures obtained from adult female Wistar rats subjected to ovariectomy, a known experimental model of menopause. We also tested some parameters of metabolic functionality (Na+, K+-ATPase activity) and cellular redox status, such as antioxidant enzyme defenses (superoxide dismutase and catalase) and the intracellular production of reactive oxygen species in this experimental model. Female adult Wistar rats (180 days-age) were assigned to one of the following groups: sham (submitted to surgery without removal of the ovaries) and ovariectomy (submitted to surgery to removal of the ovaries). Thirty days after ovariectomy or sham surgery, we prepared astrocyte cultures from control and ovariectomy surgery animals. Ovariectomized rats presented an increase in pro-inflammatory cytokines (tumor necrosis factor α, interleukins 1ß, 6, and 18) and a decrease in interleukin 10 release, an anti-inflammatory cytokine, in cortical and hippocampal astrocytes, when compared to those obtained from sham group (control). In addition, Na+,K+-ATPase activity decreased in hippocampal astrocytes, but not in cortical astrocyte cultures. In contrast, antioxidant enzymes did not alter in cortical astrocyte cultures, but increased in hippocampal astrocytes. In summary, our findings suggest that ovariectomy is able to induce an inflammatory response in vivo, which could be detected in in vitro astrocytes after approximately 4 weeks.

Vitamin D partially reverses the increase in p-NF-κB/p65 immunocontent and interleukin-6 levels, but not in acetylcholinesterase activity in hippocampus of adult female ovariectomized rats.

The aim of this study was to verify the effects of ovariectomy (OVX) and/or vitamin D supplementation (VIT D) on inflammatory and cholinergic parameters in hippocampus, as well as on serum estradiol and VIT D levels of rats. Ninety-day-old female Wistar rats were randomly divided into four groups: SHAM, OVX, VIT D or OVX + VIT D. Thirty days after OVX, VIT D (500 IU/kg/day) was supplemented by gavage, for 30 days. Approximately 12 h after the last VIT D administration, rats were euthanized and hippocampus and serum were obtained for further analyses. Results showed that OVX rats presented a decrease in estradiol levels when compared to control (SHAM). There was an increase in VIT D levels in the groups submitted to VIT D supplementation. OVX increased the immunocontent of nuclear p-NF-κB/p65, TNF-α and IL-6 levels. VIT D partially reversed the increase in p-NF-κB/p65 immunocontent and IL-6 levels. Regarding cholinergic system, OVX caused an increase in acetylcholinesterase activity without changing acetylcholinesterase and choline acetyltransferase immunocontents. VIT D did not reverse the increase in acetylcholinesterase activity caused by OVX. These results demonstrate that OVX alters inflammatory and cholinergic parameters and that VIT D supplementation, at the dose used, partially reversed the increase in immunocontent of p-NF-Kb/p65 and IL-6 levels, but it was not able to reverse other parameters studied. Our findings may help in the understanding of the brain changes that occurs in post menopause period and open perspectives for futures research involving VIT D therapies.

Chronic Mild Hyperhomocysteinemia Alters Inflammatory and Oxidative/Nitrative Status and Causes Protein/DNA Damage, as well as Ultrastructural Changes in Cerebral Cortex: Is Acetylsalicylic Acid Neuroprotective?

Homocysteine is a sulfur-containing amino acid derived from methionine metabolism. When plasma homocysteine levels exceed 10-15 µM, there is a condition known as hyperhomocysteinemia, which occur as a result of an inborn error of methionine metabolism or by non-genetic causes. Mild hyperhomocysteinemia is considered a risk factor for development of neurodegenerative diseases. The objective of the present study was to evaluate whether acetylsalicylic acid has neuroprotective role on the effect of homocysteine on inflammatory, oxidative/nitrative stress, and morphological parameters in cerebral cortex of rats subjected to chronic mild hyperhomocysteinemia. Wistar male rats received homocysteine (0.03 µmol/g of body weight) by subcutaneous injections twice a day and acetylsalicylic acid (25 mg/Kg of body weight) by intraperitoneal injections once a day from the 30th to the 60th postpartum day. Control rats received vehicle solution in the same volume. Results showed that rats subjected to chronic mild hyperhomocysteinemia significantly increased IL-1ß, IL-6, and acetylcholinesterase activity and reduced nitrite levels. Homocysteine decreased catalase activity and immunocontent and superoxide dismutase activity, caused protein and DNA damage, and altered neurons ultrastructure. Acetylsalicylic acid totally prevented the effect of homocysteine on acetylcholinesterase activity and catalase activity and immunocontent, as well as the ultrastructural changes, and partially prevented alterations on IL-1ß levels, superoxide dismutase activity, sulfhydryl content, and comet assay. Acetylsalicylic acid per se increased DNA damage index. In summary, our findings showed that chronic chemically induced model of mild hyperhomocysteinemia altered some parameters and acetylsalicylic acid administration seemed to be neuroprotective, at least in part, on neurotoxicity of homocysteine.

Vitamin D Supplementation Reverses DNA Damage and Telomeres Shortening Caused by Ovariectomy in Hippocampus of Wistar Rats.

The aim of this study was to investigate the effect of ovariectomy (OVX), a surgical model of menopause, and/or vitamin D (VIT D) supplementation on oxidative status, DNA damage, and telomere length in hippocampus of rats at two ages. Ninety-day-old (adult) or 180-day-old (older) female Wistar rats were divided into four groups: SHAM, OVX, VIT D, and OVX + VIT D. Thirty days after OVX, rats were supplemented with VIT D (500 IU/kg) by gavage, for a period of 30 days. Results showed that OVX altered antioxidant enzymes, increasing the activities of catalase in adult rats and superoxide dismutase in older rats. VIT D per se increased the activities of catalase and superoxide dismutase in older rats, but not in adult rats. VIT D supplementation to OVX (OVX + VIT D) rats did not reverse the effect of OVX on catalase in adult rats, but it partially reversed the increase in superoxide dismutase activity in older rats. OVX increased DNA damage in hippocampus of adult and older rats. VIT D per se reduced DNA damage, and when associated to OVX, it partially reversed this alteration. Additionally, OVX caused a telomere shortening in older rats, and VIT D was able to reverse such effect. Taken together, these results demonstrate that surgical menopause in rats causes hippocampal biochemical changes and VIT D appears, at least in part, to act in a beneficial way.

Neonatal handling impairs intradimensional shift and alters plasticity markers in the medial prefrontal cortex of adult rats.

Stress response can be modulated by neonatal/childhood events. Neonatal handling (NH) is an animal model in which the animals are subjected to brief separations from the dam during the first days of life, and it leads to lower emotionality and behavioral changes in adulthood. The aim of this study was to observe if early events, such as (NH), may program associative learning and behavioral flexibility in adult male rats and if these changes could be related to altered neurochemistry in the medial prefrontal cortex (mPFC). We evaluated proteins related to synaptic plasticity (brain-derived neurotrophic factor [BDNF] and synaptophysin [SYP]) as well as Na+/K+-ATPase activity. Additionally, we evaluated proteins related to the dopaminergic system (tyrosine hydroxylase [TH] and phosphorylated TH [pTH]), since this system appears to be affected in some neonatal interventions. Neonatally handled animals exhibited impairment in simple discrimination and intradimensional shift but not in reversal or compound discrimination; in addition, no alteration in switching from an egocentric spatial to a cued strategy was observed. These effects were accompanied by a decrease in SYP levels and Na+/K+-ATPase activity, suggesting reduced synaptic function. These results indicate that NH increases attention to irrelevant stimuli and/or impairs associative learning, and this is accompanied by neurochemical alterations in the (mPFC).

Severe Hyperhomocysteinemia Decreases Creatine Kinase Activity and Causes Memory Impairment: Neuroprotective Role of Creatine.

In the present study, we investigate the effect of severe hyperhomocysteinemia on biochemical (creatine kinase activity), behavioral (memory tests), and histological assessments (hippocampal volume). A possible neuroprotective role of creatine on hyperhomocysteinemia effects was also evaluated. Severe hyperhomocysteinemia was induced in neonate rats (starting at 6 days of age) by treatment with homocysteine (0.3-0.6 µmol/g body weight) for 23 days. Creatine (50 mg/kg body weight) was administered concomitantly with homocysteine. Controls received saline in the same volumes. Twelve hours after the last injection, the rats were submitted to behavioral tests [(recognition task (NOR)] and inhibitory avoidance (IA)]. Following behavioral assessment, the animals were perfused and decapitated, the brain removed for subsequent morphological analysis of the hippocampus. Another group of animals was used to test creatine kinase activity in hippocampus. The results showed that rats treated with homocysteine decreased (44%) the exploration of the novel object in NOR. In the IA task, homocysteine-treated animals presented decreased latencies to step down the platform in short- (32%) and long-term (18%) testings (3 h and 7 days, respectively), evidencing aversive memory impairment. Hippocampal volume was not altered by homocysteine administration. Hyperhomocysteinemia decreased (45%) creatine kinase activity, and creatine was able to prevent such effect probably by creatine kinase/phosphocreatine/creatine homeostasis, which serves as energy circuit within of the cell. This finding may be associated, at least in part, with memory improvement, suggesting that creatine might represent an effective adjuvant to protect against the effects of high homocysteine plasma levels.

Effects of previous physical exercise to chronic stress on long-term aversive memory and oxidative stress in amygdala and hippocampus of rats.

Since stressful situations are considered risk factors for the development of depression and there are few studies evaluating prevention therapies for this disease, in the present study we evaluated the effect of previous physical exercise in animals subjected to chronic variable stress (CVS), an animal model of depression, on behavior tasks. We also investigated some parameters of oxidative stress and Na+, K+-ATPase activity, immunocontent and gene expression of alpha subunits in amygdala and hippocampus of rats. Young male rats were randomized into four study groups (control, exercised, stressed, exercised+stressed). The animals were subjected to controlled exercise treadmill for 20min,three times a week, for two months prior to submission to the CVS (40days). Results show that CVS impaired performance in inhibitory avoidance at 24h and 7days after training session. CVS induced oxidative stress, increasing reactive species, lipoperoxidation and protein damage, and decreasing the activity of antioxidant enzymes. The activity of Na+, K+-ATPase was decreased, but the immunocontents and gene expression of catalytic subunits were not altered. The previous physical exercise was able to improve performance in inhibitory avoidance at 24h after training; additionally, exercise prevented oxidative damage, but was unable to reverse completely the changes observed on the enzymatic activities. Our findings suggest that physical exercise during the developmental period may protect against aversive memory impairment and brain oxidative damage caused by chronic stress exposure later in life.

Vitamin D3 Reverses the Hippocampal Cytoskeleton Imbalance But Not Memory Deficits Caused by Ovariectomy in Adult Wistar Rats.

The objective of study was to investigate changes caused by ovariectomy (OVX) on aversive and non-aversive memories, as well as on cytoskeleton phosphorylating system and on vitamin D receptor (VDR) immunocontent in hippocampus. The neuroprotective role of vitamin D was also investigated. Ninety-day-old female Wistar rats were divided into four groups: SHAM, OVX, VITAMIN D and OVX + VITAMIN D; 30 days after the OVX, vitamin D supplementation (500 IU/kg), by gavage, for 30 days was started. Results showed that OVX impaired short-term and long-term recognition, and long-term aversive memories. OVX altered hippocampal cytoskeleton phosphorylating system, evidenced by the hyperphosphorylation of glial fibrillary acidic protein (GFAP), low molecular weight neurofilament subunit (NFL), medium molecular weight neurofilament subunit (NFM) and high molecular weight neurofilament subunit (NFH), and increased the immunocontent of c-Jun N-terminal protein kinases (JNK), Ca2+/calmodulin-dependent protein kinase II (PKCaMII) and of the sites phosphorylated lysine-serine-proline (KSP) repeats, Ser55 and Ser57. Vitamin D reversed the effects caused by OVX on cytoskeleton in hippocampus, but it was not able to reverse the effects on memory.

1,25-Dihydroxyvitamin D3 prevents deleterious effects of homocysteine on mitochondrial function and redox status in heart slices.

Because homocysteine (Hcy) is a risk factor for cardiovascular disease, and vitamin D deficiency can contribute to cardiovascular pathologies. In the present study, we tested the hypothesis that Hcy could impair energy metabolism, mitochondrial function, and redox status in heart slices of Wistar rats and that 1,25-dihydroxivitamin D3 (calcitriol) treatment could prevent such effects. Heart slices were first pretreated with 3 different concentrations of calcitriol (50, 100, and 250nmol/L) for 30minutes at 37°C, after which Hcy was added to promote deleterious effects on metabolism. After 1 hour of incubation, the samples were washed, homogenized, and stored at -80°C before analysis. The results showed that Hcy caused changes in energy metabolism (respiratory chain enzymes), mitochondrial function, and cell viability. Homocysteine also induced oxidative stress, increasing lipid peroxidation, reactive oxygen species generation, and protein damage. An imbalance in antioxidant enzymes was also observed. Calcitriol (50nmol/L) reverted the effect of Hcy on the parameters tested, except for the immunocontent of catalase. Both treatments (calcitriol and Hcy) did not alter the vitamin D receptor immunocontent, which combined with the fact that our ex vivo model is acute, suggesting that the beneficial effect of calcitriol occurs directly through antioxidative mechanisms and not via gene expression. In this study, we show that Hcy impairs mitochondrial function and induces changes in the redox status in heart slices, which were reverted by calcitriol. These findings suggest that calcitriol may be a preventive/therapeutic strategy for complications caused by Hcy.

Severe Hyperhomocysteinemia Decreases Respiratory Enzyme and Na(+)-K(+) ATPase Activities, and Leads to Mitochondrial Alterations in Rat Amygdala.

Severe hyperhomocysteinemia is caused by increased plasma levels of homocysteine (Hcy), a methionine derivative, and is associated with cerebral disorders. Creatine supplementation has emerged as an adjuvant to protect against neurodegenerative diseases, due to its potential antioxidant role. Here, we examined the effects of severe hyperhomocysteinemia on brain metabolism, and evaluated a possible neuroprotective role of creatine in hyperhomocysteinemia, by concomitant treatment with Hcy and creatine (50 mg/Kg body weight). Hyperhomocysteinemia was induced in young rats (6-day-old) by treatment with homocysteine (0.3-0.6 µmol/g body weight) for 23 days, and then the following parameters of rat amygdala were evaluated: (1) the activity of the respiratory chain complexes succinate dehydrogenase, complex II and cytochrome c oxidase; (2) mitochondrial mass and membrane potential; (3) the levels of necrosis and apoptosis; and (4) the activity and immunocontent of Na(+),K(+)-ATPase. Hcy treatment decreased the activities of succinate dehydrogenase and cytochrome c oxidase, but did not alter complex II activity. Hcy treatment also increased the number of cells with high mitochondrial mass, high mitochondrial membrane potential, and in late apoptosis. Importantly, creatine administration prevented some of the key effects of Hcy administration on the amygdala. We also observed a decrease in the activity and immunocontent of the α1 subunit of the Na(+),K(+)-ATPase in amygdala after Hcy- treatment. Our findings support the notion that Hcy modulates mitochondrial function and bioenergetics in the brain, as well as Na(+),K(+)-ATPase activity, and suggest that creatine might represent an effective adjuvant to protect against the effects of high Hcy plasma levels.