Guanosine prevents nitroxidative stress and recovers mitochondrial membrane potential disruption in hippocampal slices subjected to oxygen/glucose deprivation.

Guanosine, the endogenous guanine nucleoside, prevents cellular death induced by ischemic events and is a promising neuroprotective agent. During an ischemic event, nitric oxide has been reported to either cause or prevent cell death. Our aim was to evaluate the neuroprotective effects of guanosine against oxidative damage in hippocampal slices subjected to an in vitro ischemia model, the oxygen/glucose deprivation (OGD) protocol. We also assessed the participation of nitric oxide synthase (NOS) enzymes activity on the neuroprotection promoted by guanosine. Here, we showed that guanosine prevented the increase in ROS, nitric oxide, and peroxynitrite production induced by OGD. Moreover, guanosine prevented the loss of mitochondrial membrane potential in hippocampal slices subjected to OGD. Guanosine did not present an antioxidant effect per se. The protective effects of guanosine were mimicked by inhibition of neuronal NOS, but not of inducible NOS. The neuroprotective effect of guanosine may involve activation of cellular mechanisms that prevent the increase in nitric oxide production, possibly via neuronal NOS.

A Novel Diselenide-Probucol-Analogue Protects Against Methylmercury-Induced Toxicity in HT22 Cells by Upregulating Peroxide Detoxification Systems: a Comparison with Diphenyl Diselenide.

Methylmercury (MeHg) is a ubiquitous environmental neurotoxicant whose mechanisms of action involve oxidation of endogenous nucleophilic groups (mainly thiols and selenols), depletion of antioxidant defenses, and disruption of neurotransmitter homeostasis. Diphenyl diselenide-(PhSe)2-a model diaryl diselenide, has been reported to display significant protective effects against MeHg-induced neurotoxicity under both in vitro and in vivo experimental conditions. In this study, we compared the protective effects of (PhSe)2 with those of RC513 (4,4'-diselanediylbis(2,6-di-tert-butylphenol), a novel diselenide-probucol-analog) against MeHg-induced toxicity in the neuronal (hippocampal) cell line HT22. Although both (PhSe)2 and RC513 significantly mitigated MeHg- and tert-butylhydroperoxide (t-BuOOH)-cytotoxicity, the probucol analog exhibited superior protective effects, which were observed earlier and at lower concentrations compared to (PhSe)2. RC513 treatment (at either 0.5 µM or 2 µM) significantly increased glutathione peroxidase (GPx) activity, which has been reported to counteract MeHg-toxicity. (PhSe)2 was also able to increase GPx activity, but only at 2 µM. Although both compounds increased the Gpx1 transcripts at 6 h after treatments, only RC513 was able to increase mRNA levels of Prx2, Prx3, Prx5, and Txn2, which are also involved in peroxide detoxification. RC513 (at 2 µM) significantly increased GPx-1 protein expression in HT22 cells, although (PhSe)2 displayed a minor (nonsignificant) effect in this parameter. In agreement, RC513 induced a faster and superior capability to cope with exogenously-added peroxide (t-BuOOH). In summary, when compared to the prototypical organic diaryl diselenide [(PhSe)2], RC513 displayed superior protective properties against MeHg-toxicity in vitro; this was paralleled by a more pronounced upregulation of defenses related to detoxification of peroxides, which are well-known MeHg-derived intermediate oxidant species.

Norbixin, a natural dye that improves serum lipid profile in rabbits and prevents LDL oxidation.

We hypothesized that norbixin, which is a carotenoid used as an orange/red natural food coloring additive, has anti-atherogenic properties. An in vitro oxidation assay with human LDL and a rabbit model of atherosclerosis were used to test this hypothesis. Norbixin inhibited the oxidation of isolated human LDL in a concentration-dependent manner. In the in vivo assay, rabbits were fed with a regular chow (control) or an atherogenic diet (0.5% cholesterol) alone or supplemented with norbixin (10, 30 or 100 mg/kg b.w.) for 60 days. Norbixin supplementation (30 and 100 mg/kg b.w.) increased HDL levels and reduced triglyceride levels and the atherogenic index of rabbits. This effect was associated with the decrease of serum levels of oxidized LDL, oxidized LDL antibodies and aortic tissue levels of lipid and protein oxidation in the atherogenic rabbits supplemented with norbixin. Atherogenic diet increased enzymatic (superoxide dismutase, catalase, glutathione reductase, and thioredoxin reductase-1) and non-enzymatic (non-protein thiol groups content) antioxidant defense systems in the aortic tissue but reduced the activity of paraoxonase-1 in the serum. All these changes were prevented by norbixin supplementation (10, 30 and 100 mg/kg b.w.). These results suggest that norbixin has atheroprotective potential by improving serum lipid profile and preventing oxidative modifications of circulating LDL and aortic tissue. Norbixin may, therefore, be beneficial in the control of atherosclerosis risk factors and can be further investigated as a candidate to be used not only as a functional food ingredient but also for therapeutic applications and in the nutraceutical industry.

Metabolic activity in cryopreserved and grafted ovarian tissue using high-resolution respirometry.

Cryopreservation of ovarian tissue followed by transplantation represents a strategy to restore ovarian function and fertility. Stress from cryopreservation-thawing processes can lead to alterations and/or damage to mitochondrial structure and functionality. High resolution respirometry and histological analysis were used to evaluate the effect of cryopreservation and transplantation on ovarian tissue. Four different conditions were performed: Fresh non-transplanted tissue, Fresh transplanted tissue, Cryopreserved non-transplanted tissue and Cryopreserved transplanted tissue. All groups were able to respond to the substrates-uncoupler-inhibitor protocol. We found a dramatic decrease in general oxygen consumption in hemi-ovaries submitted to cryopreservation and/or transplantation. The effect of cryopreservation on mitochondrial metabolism was less intense than effect of transplantation, since the transplantation affected all of the mitochondrial states. A total of 2644 follicles were analyzed. Of these, 2198 were classified as morphologically normal. The percentage of morphologically normal follicles was significantly lower in the Cryopreserved transplanted group when compared to the Cryopreserved non-transplanted group and the Fresh transplanted group (p-value < 0.05). Despite decreased follicular viability and mitochondrial activity, the cryopreservation followed by transplantation of ovarian tissue proved feasible for attempts to restore ovarian function.

Short-term high-fat diet induces cognitive decline, aggression, and anxiety-like behavior in adult zebrafish.

Obesity is a global health problem with high prevalence and defined by a high body mass index (BMI). Several comorbidities affecting the central nervous system (CNS) are associated with obesity (e.g., neurodegenerative diseases, cognitive deficit, and psychobehavioral disturbs). The zebrafish (Danio rerio) has been considered a suitable model organism to investigate the neurobehavioral features of various human diseases. Here, we verify the impact of a high-fat diet (HFD) on the CNS by specifically assessing the effects of short-term HFD on anxiety-like responses, aggression, social preference, and memory, which are essential behaviors for survival and reproduction. Animals were separated in three experimental groups. The standard diet group (SD) received 7.5 mg/fish of dry food, while HFD groups received 5 mg/fish dry food plus 7.5 (HFD-7.5) or 15 mg/fish (HFD-15) of chicken egg yolk daily. Dietary fat content (w/w) was approximately 6.5%, 16.9%, and 21.1%, respectively. We performed behavioral tests and morphometric analyses after two weeks of HFD. In comparison to SD animals, HFD groups showed typical obesogenic responses with increases in BMI, abdominal length, and body weight. HFD individuals also showed increased aggression and anxiety-like behaviors in the mirror-induced aggression and novel tank diving tests, respectively. Interestingly, HFD did not change the social preference behavior, mean swimming speed or spontaneous activity levels, while the HFD-15 group showed cognitive deficits in the inhibitory avoidance test. Collectively, this "proof-of-concept" study is the first report to characterize the effects of short-term HFD on different behavioral domains of zebrafish with high degree of face validity. Moreover, our data reinforce the growing utility of zebrafish to explore the neurobehavioral basis of obesity, providing clinically translatable data, complementing the existing rodent models and supporting future mechanistic studies.

Proanthocyanidin-rich fraction from Croton celtidifolius Baill confers neuroprotection in the intranasal 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine rat model of Parkinson's disease.

We have recently demonstrated that rodents treated intranasally with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) suffered impairments in olfactory, cognitive and motor functions associated with time-dependent disruption of dopaminergic neurotransmission in different brain structures conceivably analogous to those observed during different stages of Parkinson's disease (PD). On the other hand, the proanthocyanidin-rich fraction (PRF) obtained from the bark of Croton celtidifolius Baill (Euphorbiaceae), a tree frequently found in the Atlantic forest in south Brazil, has been described to have several neurobiological activities including antioxidant and anti-inflammatory properties, which may be of interest in the treatment of PD. The present data indicated that the pretreatment with PRF (10 mg/kg, i.p.) during five consecutive days was able to prevent mitochondrial complex-I inhibition in the striatum and olfactory bulb, as well as a decrease of the enzyme tyrosine hydroxylase expression in the olfactory bulb and substantia nigra of rats infused with a single intranasal administration of MPTP (1 mg/nostril). Moreover, pretreatment with PRF was found to attenuate the short-term social memory deficits, depressive-like behavior and reduction of locomotor activity observed at different periods after intranasal MPTP administration in rats. Altogether, the present findings provide strong evidence that PRF from C. celtidifolius may represent a promising therapeutic tool in PD, thus being able to prevent both motor and non-motor early symptoms of PD, together with its neuroprotective potential.

Mitochondrial NAD(P)+ Transhydrogenase is Unevenly Distributed in Different Brain Regions, and its Loss Causes Depressive-like Behavior and Motor Dysfunction in Mice.

NAD(P)+ transhydrogenase (NNT) links redox states of the mitochondrial NAD(H) and NADP(H) via a reaction coupled to proton-motive force across the inner mitochondrial membrane. NNT is believed to be ubiquitously present in mammalian cells, but its expression may vary substantially in different tissues. The present study investigated the tissue distribution and possible roles of NNT in the mouse brain. The pons exhibited high NNT expression/activity, and immunohistochemistry revealed intense NNT labeling in neurons from brainstem nuclei. In some of these regions, neuronal NNT labeling was strongly colocalized with enzymes involved in the biosynthesis of 5-hydroxytryptamine (5-HT) and nitric oxide (NO), which directly or indirectly require NADPH. Behavioral tests were performed in mice lacking NNT activity (Nnt-/-, mice carrying the mutated NntC57BL/6J allele from the C57BL/6J strain) and the Nnt+/+ controls. Our data demonstrated that aged Nnt-/- mice (18-20 months old), but not adult mice (3-4 months old), showed an increased immobility time in the tail suspension test that was reversed by fluoxetine treatment, providing evidence of depressive-like behavior in these mice. Aged Nnt-/- mice also exhibited behavioral changes and impaired locomotor activity in the open field and rotarod tests. Despite the colocalization between NNT and NO synthase, the S-nitrosation and cGMP levels were independent of the Nnt genotype. Taken together, our results indicated that NNT is unevenly distributed throughout the brain and associated with 5-THergic and NOergic neurons. The lack of NNT led to alterations in brain functions related to mood and motor behavior/performance in aged mice.

The effect of voluntary wheel running on the antioxidant status is dependent on sociability conditions.

Voluntary wheel running is widely used as a physical activity (PA) model in rodents, but most studies investigate the beneficial effects of this intervention in socially isolated mice. Social isolation stress (SIS) is associated with vulnerability to oxidative stress and reduced mitochondrial activity. Thus, the aim of this study was to investigate the effects of free access to a running wheel for 21 days on the various markers of the cellular redox/antioxidant status as well as mitochondrial function of mice subjected to SIS or maintained in groups of 3 in the homecage. SIS increased thiobarbituric acid reactive substance (TBARS) levels in the cerebral cortex, and PA intervention was not able to reverse such alteration. PA reduced TBARS levels in the liver of grouped mice and gastrocnemius of socially isolated mice. PA increased nonprotein thiol (NPSH) levels in the cerebral cortex of grouped mice. Furthermore, socially isolated mice presented lower glutathione peroxidase (GPx) activity in the cerebellum and gastrocnemius, and glutathione reductase (GR) activity in the cerebral cortex and liver. By contrast, SIS induced higher GPx activity in the cerebral cortex and heart. PA reduced GPx (cerebral cortex) and GR (cerebral cortex and liver) activities of socially isolated mice. SIS caused higher activity of mitochondrial complexes I and II in the cerebral cortex, and the PA paradigm was not able to alter this effect. Interestingly, the PA produced antidepressant-like effect at both SIS and control groups. In conclusion, the results showed the influence of SIS for the effects of PA on the antioxidant status, but not on the mitochondrial function and emotionality.

High Cholesterol Diet Exacerbates Blood-Brain Barrier Disruption in LDLr-/- Mice: Impact on Cognitive Function.

BACKGROUND: Evidence has revealed an association between familial hypercholesterolemia and cognitive impairment. In this regard, a connection between cognitive deficits and hippocampal blood-brain barrier (BBB) breakdown was found in low-density lipoprotein receptor knockout mice (LDLr-/-), a mouse model of familial hypercholesterolemia. OBJECTIVE: Herein we investigated the impact of a hypercholesterolemic diet on cognition and BBB function in C57BL/6 wild-type and LDLr-/-mice. METHODS: Animals were fed with normal or high cholesterol diets for 30 days. Thus, wild-type and LDLr-/-mice were submitted to memory paradigms. Additionally, BBB integrity was evaluated in the mice's prefrontal cortices and hippocampi. RESULTS: A tenfold elevation in plasma cholesterol levels of LDLr-/-mice was observed after a hypercholesterolemic diet, while in wild-type mice, the hypercholesterolemic diet exposure increased plasma cholesterol levels only moderately and did not induce cognitive impairment. LDLr-/-mice presented memory impairment regardless of the diet. We observed BBB disruption as an increased permeability to sodium fluorescein in the prefrontal cortices and hippocampi and a decrease on hippocampal claudin-5 and occludin mRNA levels in both wild-type and LDLr-/-mice treated with a hypercholesterolemic diet. The LDLr-/-mice fed with a regular diet already presented BBB dysfunction. The BBB-increased leakage in the hippocampi of LDLr-/-mice was related to high microvessel content and intense astrogliosis, which did not occur in the control mice. CONCLUSION: Therefore, LDLr-/-mice seem to be more susceptible to cognitive impairments and BBB damage induced by exposure to a high cholesterol diet. Finally, BBB disruption appears to be a relevant event in hypercholesterolemia-induced brain alterations.

LDL Receptor Deficiency Does not Alter Brain Amyloid-ß Levels but Causes an Exacerbation of Apoptosis.

Familial hypercholesterolemia (FH) is a genetic disorder caused by dysfunction of low density lipoprotein receptors (LDLr), resulting in elevated plasma cholesterol levels. FH patients frequently exhibit cognitive impairment, a finding recapitulated in LDLr deficient mice (LDLr-/-), an animal model of FH. In addition, LDLr-/- mice are more vulnerable to the deleterious memory impact of amyloid-ß (Aß), a peptide linked to Alzheimer's disease. Here, we investigated whether the expression of proteins involved in Aß metabolism are altered in the brains of adult or middle-aged LDLr-/- mice. After spatial memory assessment, Aß levels and gene expression of LDLr related-protein 1, proteins involved in Aß synthesis, and apoptosis-related proteins were evaluated in prefrontal cortex and hippocampus. Moreover, the location and cell-specificity of apoptosis signals were evaluated. LDLr-/- mice presented memory impairment, which was more severe in middle-aged animals. Memory deficit in LDLr-/- mice was not associated with altered expression of proteins involved in Aß processing or changes in Aß levels in either hippocampus or prefrontal cortex. We further found that the expression of Bcl-2 was reduced while the expression of Bax was increased in both prefrontal cortex and hippocampus in 3- and 14-month-old LDLr-/-mice Finally, LDLr-/- mice presented increased immunoreactivity for activated caspase-3 in the prefrontal cortex and hippocampus. The activation of caspase 3 was predominantly associated with neurons in LDLr-/- mice. Cognitive impairment in LDLr-/- mice is thus accompanied by an exacerbation of neuronal apoptosis in brain regions related to memory formation, but not by changes in Aß processing or levels.

Impaired adult hippocampal neurogenesis in a mouse model of familial hypercholesterolemia: A role for the LDL receptor and cholesterol metabolism in adult neural precursor cells.

OBJECTIVE: In familial hypercholesterolemia (FH), mutations in the low-density lipoprotein (LDL) receptor (LDLr) gene result in increased plasma LDL cholesterol. Clinical and preclinical studies have revealed an association between FH and hippocampus-related memory and mood impairment. We here asked whether hippocampal pathology in FH might be a consequence of compromised adult hippocampal neurogenesis. METHODS: We evaluated hippocampus-dependent behavior and neurogenesis in adult C57BL/6JRj and LDLr-/- mice. We investigated the effects of elevated cholesterol and the function of LDLr in neural precursor cells (NPC) isolated from adult C57BL/6JRj mice in vitro. RESULTS: Behavioral tests revealed that adult LDLr-/- mice showed reduced performance in a dentate gyrus (DG)-dependent metric change task. This phenotype was accompanied by a reduction in cell proliferation and adult neurogenesis in the DG of LDLr-/- mice, suggesting a potential direct impact of LDLr mutation on NPC. Exposure of NPC to LDL as well as LDLr gene knockdown reduced proliferation and disrupted transcriptional activity of genes involved in endogenous cholesterol synthesis and metabolism. The LDL treatment also induced an increase in intracellular lipid storage. Functional analysis of differentially expressed genes revealed parallel modulation of distinct regulatory networks upon LDL treatment and LDLr knockdown. CONCLUSIONS: Together, these results suggest that high LDL levels and a loss of LDLr function, which are characteristic to individuals with FH, might contribute to a disease-related impairment in adult hippocampal neurogenesis and, consequently, cognitive functions.

Plasmatic vitamin C in nontreated hepatitis C patients is negatively associated with aspartate aminotransferase.

OBJECTIVES: To evaluate the possible relationship between aminotransferases levels and markers of oxidative stress in chronic hepatitis C patients. DESIGN AND METHODS: Patients without treatment for hepatitis were divided in to group I (15-39 U/L); group II (41-76 U/L) and group III (81-311 U/L) of activity alanine aminotransferase (ALT). Blood markers of oxidative stress [catalase (CAT), glutathione peroxidase (GPx), thiobarbituric acid-reactive species (TBARS), nonprotein and protein thiol (NP-SH and P-SH) groups and vitamin C] were determined. RESULTS: P-SH and NP-SH levels, TBARS, GPx and CAT were not different between groups. Vitamin C was significantly decreased in groups II (P=0.03) and III (P=0.001) when compared with group I and correlated negatively with aspartate aminotransferase (AST; r=-0.29, P=0.042). CONCLUSION: Vitamin C levels were negatively associated with AST, suggesting that vitamin C could be an additional indicator of hepatitis C severity.

Hypercholesterolemia impairs contextual fear conditioning memory formation in female mice: evidence for cholinergic dysfunction.

The present study evaluated the effects of hypercholesterolemia in response to conditioned aversive stimuli in mice. Specifically, (a) young (3 months old) and aged (24 months old) female C57Bl/6 mice were fed daily for 4 weeks with a standard rodent diet or an enriched cholesterol diet (ECD) and then subjected to the contextual fear conditioning test. In another experimental set, 3-month-old C576Bl/6 female mice, fed daily during the 4 weeks with the standard rodent diet or ECD, were subjected to the contextual fear conditioning test and received vehicle or scopolamine (0.37 mg/kg; intraperitoneally) immediately after the training session. (b) 12-month-old C576Bl/6 and low-density lipoprotein receptor knockout mice (LDLr) female mice were subjected to the contextual fear conditioning test. In another experimental set, they were subjected to the contextual fear conditioning test and received vehicle or donepezil (3.0 mg/kg; intraperitoneally) immediately after the training session. The present results show that (a) the ECD specifically impaired retrieval of contextual fear memory in aged mice; (b) an ineffective dose of scopolamine impaired fear memory consolidation in young mice fed the ECD; (c) LDLr mice presented impaired contextual fear memory retrieval; and (d) boosting cholinergic neurotransmission with a single donepezil administration at the consolidation window led to improved fear memory consolidation in LDLr mice. These findings suggest that high levels of cholesterol induced by either an ECD or a genetic deletion of LDLr decreased freezing behavior on the contextual fear conditioning test, which seemed to involve dysfunction of the cholinergic system.

Syzygium cumini leaf extract inhibits LDL oxidation, but does not protect the liproprotein from glycation.

ETNOPHARMACOLOGICAL RELEVANCE: Syzygium cumini (L.) Skeels is a plant widely used in folk medicine to treat diabetes mellitus (DM). The tea from its leaves is frequently used by diabetics for lowering hyperglycemia. There is a close relationship between DM and atherosclerosis, a chronic immuno-inflammatory disease, were the early stages encompass oxidative and glycative modifications in the structure of low density lipoprotein (LDL). AIM OF THIS STUDY: To investigate the potential protective effects of aqueous-leaf extract from Syzygium cumini (S.cExt) against CuSO4-induced oxidation and methylglyoxal (MG)-induced glycation of human LDL in vitro. MATERIALS AND METHODS: LDL oxidative changes were evaluated by measuring conjugated dienes (CD) formation, thiobarbituric acid reactive substances (TBARS) levels, quenching of tryptophan (Trp) fluorescence and structural modifications in LDL particle. In LDL glycated by MG (glyLDL), we determined the levels of fluorescent advanced glycation end products (AGEs) and mobility by agarose gel electrophoresis. RESULTS: S.cExt blocked oxidative events induced by CuSO4 in human LDL, plasma and serum. Fourier transform infrared spectroscopy (FT-IR) revealed that specific regions of apoB100 were oxidized by CuSO4 in human LDL and that S.cExt reduced these oxidations. Unlike, the increased AGEs levels and eletrophoretic mobility observed in LDL MG-glycated were not modified by S.cExt. CONCLUSION: The findings herein indicate that S.cExt could be tested in atherogenesis models as potential protective agent against LDL oxidation.

Antidepressant effects of creatine on amyloid ß1-40-treated mice: The role of GSK-3ß/Nrf2 pathway.

Alzheimer's disease (AD) is characterized by progressive synaptic dysfunction and neuronal lost in specific brain areas including hippocampus, resulting in memory/learning deficits and cognitive impairments. In addition, non-cognitive symptoms are reported in AD patients, such as anxiety, apathy and depressed mood. The current antidepressant drugs present reduced efficacy to improve depressive symptoms in AD patients. Here, we investigated the ability of creatine, a compound with neuroprotective and antidepressant properties, to counteract amyloid ß1-40 peptide-induced depressive-like behavior in mice. Moreover, we addressed the participation of the intracellular signaling pathway mediated by glycogen synthase kinase-3ß (GSK-3ß)/nuclear factor erythroid-2-related factor 2 (Nrf2) in the creatine effects. Aß1-40 administration (400 pmol/mouse, i.c.v.) increased the immobility time in the tail suspension test and decreased the grooming time and increased latency to grooming in the splash test, indicative of depressive-like behavior. These impairments were attenuated by creatine (0.01 and 10 mg/kg, p.o.) and fluoxetine (10 mg/kg, p.o., positive control). No significant alterations on locomotor performance were observed in the open field. Aß1-40 administration did not alter hippocampal phospho-GSK-3ß (Ser9)/total GSK-3ß, total GSK-3ß and heme oxygenase-1 (HO-1) immunocontents. However, Aß1-40-infused mice treated with creatine (0.01 mg/kg) presented increased phosphorylation of GSK-3ß(Ser9) and HO-1 immunocontent in the hippocampus. Fluoxetine per se increased GSK-3ß(Ser9) phosphorylation, but did not alter HO-1 levels. In addition, Aß1-40 administration increased hippocampal glutathione (GSH) levels as well as glutathione reductase (GR) and thioredoxin reductase (TrxR) activities, and these effects were abolished by creatine and fluoxetine. This study provides the first evidence of the antidepressive-like effects of creatine in Aß1-40-treated mice, which were accompanied by hippocampal inhibition of GSK-3ß and modulation of antioxidant defenses. These findings indicate the potential of creatine for the treatment of depression associated with AD.

Brain-Defective Insulin Signaling Is Associated to Late Cognitive Impairment in Post-Septic Mice.

Sepsis survivors frequently develop late cognitive impairment. Because little is known on the mechanisms of post-septic memory deficits, there are no current effective approaches to prevent or treat such symptoms. Here, we subjected mice to severe sepsis induced by cecal ligation and puncture (CLP) and evaluated the sepsis-surviving animals in the open field, novel object recognition (NOR), and step-down inhibitory avoidance (IA) task at different times after surgery. Post-septic mice (30 days post-surgery) failed in the NOR and IA tests but exhibited normal performance when re-evaluated 45 days after surgery. Cognitive impairment in post-septic mice was accompanied by reduced hippocampal levels of proteins involved in synaptic plasticity, including synaptophysin, cAMP response element-binding protein (CREB), CREB phosphorylated at serine residue 133 (CREBpSer133), and GluA1 phosphorylated at serine residue 845 (GluA1pSer845). Expression of tumor necrosis factor α (TNF-α) was increased and brain insulin signaling was disrupted, as indicated by increased hippocampal IRS-1 phosphorylation at serine 636 (IRS-1pSer636) and decreased phosphorylation of IRS-1 at tyrosine 465 (IRS-1pTyr465), in the hippocampus 30 days after CLP. Phosphorylation of Akt at serine 473 (AktpSer473) and of GSK3 at serine 9 (GSK3ßpSer9) were also decreased in hippocampi of post-septic animals, further indicating that brain insulin signaling is disrupted by sepsis. We then treated post-septic mice with liraglutide, a GLP-1 receptor agonist with insulinotropic activity, or TDZD-8, a GSK3ß inhibitor, which rescued NOR memory. In conclusion, these results establish that hippocampal inflammation and disrupted insulin signaling are induced by sepsis and are linked to late memory impairment in sepsis survivors.

Organoselenium compounds as mimics of selenoproteins and thiol modifier agents.

Selenium is an essential trace element for animals and its role in the chemistry of life relies on a unique functional group: the selenol (-SeH) group. The selenol group participates in critical redox reactions. The antioxidant enzymes glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) exemplify important selenoproteins. The selenol group shares several chemical properties with the thiol group (-SH), but it is much more reactive than the sulfur analogue. The substitution of S by Se has been exploited in organic synthesis for a long time, but in the last 4 decades the re-discovery of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) and the demonstration that it has antioxidant and therapeutic properties has renovated interest in the field. The ability of ebselen to mimic the reaction catalyzed by GPx has been viewed as the most important molecular mechanism of action of this class of compound. The term GPx-like or thiol peroxidase-like reaction was previously coined in the field and it is now accepted as the most important chemical attribute of organoselenium compounds. Here, we will critically review the literature on the capacity of organoselenium compounds to mimic selenoproteins (particularly GPx) and discuss some of the bottlenecks in the field. Although the GPx-like activity of organoselenium compounds contributes to their pharmacological effects, the superestimation of the GPx-like activity has to be questioned. The ability of these compounds to oxidize the thiol groups of proteins (the thiol modifier effects of organoselenium compounds) and to spare selenoproteins from inactivation by soft-electrophiles (MeHg+, Hg2+, Cd2+, etc.) might be more relevant for the explanation of their pharmacological effects than their GPx-like activity. In our view, the exploitation of the thiol modifier properties of organoselenium compounds can be harnessed more rationally than the use of low mass molecular structures to mimic the activity of high mass macromolecules that have been shaped by millions to billions of years of evolution.

MPP+-Lesioned Mice: an Experimental Model of Motor, Emotional, Memory/Learning, and Striatal Neurochemical Dysfunctions.

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces motor and nonmotor dysfunctions resembling Parkinson's disease (PD); however, studies investigating the effects of 1-methyl-4-phenylpyridinium (MPP+), an active oxidative product of MPTP, are scarce. This study investigated the behavioral and striatal neurochemical changes (related to oxidative damage, glial markers, and neurotrophic factors) 24 h after intracerebroventricular administration of MPP+ (1.8-18 µg/mouse) in C57BL6 mice. MPP+ administration at high dose (18 µg/mouse) altered motor parameters, since it increased the latency to leave the first quadrant and reduced crossing, rearing, and grooming responses in the open-field test and decreased rotarod latency time. MPP+ administration at low dose (1.8 µg/mouse) caused specific nonmotor dysfunctions as it produced a depressive-like effect in the forced swim test and tail suspension test, loss of motivational and self-care behavior in the splash test, anxiety-like effect in the elevated plus maze test, and short-term memory deficit in the step-down inhibitory avoidance task, without altering ambulation. MPP+ at doses of 1.8-18 µg/mouse increased tyrosine hydroxylase (TH) immunocontent and at 18 µg/mouse increased α-synuclein and decreased parkin immunocontent. The astrocytic calcium-binding protein S100B and glial fibrillary acidic protein (GFAP)/S100B ratio was decreased following MPP+ administration (18 µg/mouse). At this highest dose, MPP+ increased the ionized calcium-binding adapter molecule 1 (Iba-1) immunocontent, suggesting microglial activation. Also, MPP+ at a dose of 18 µg/mouse increased thiobarbituric acid reactive substances (TBARS) and glutathione (GSH) levels and increased glutathione peroxidase (GPx) and hemeoxygenase-1 (HO-1) immunocontent, suggesting a significant role for oxidative stress in the MPP+-induced striatal damage. MPP+ (18 µg/mouse) also increased striatal fibroblast growth factor 2 (FGF-2) and brain-derived neurotrophic factor (BDNF) levels. Moreover, MPP+ decreased tropomyosin receptor kinase B (TrkB) immunocontent. Finally, MPP+ (1.8-18 µg/mouse) increased serum corticosterone levels and did not alter acetylcholinesterase (AChE) activity in the striatum but increased it in cerebral cortex and hippocampus. Collectively, these results indicate that MPP+ administration at low doses may be used as a model of emotional and memory/learning behavioral deficit related to PD and that MPP+ administration at high dose could be useful for analysis of striatal dysfunctions associated with motor deficits in PD.

Ethanol inhibits δ-aminolevulinate dehydratase and glutathione peroxidase activities in mice liver: Protective effects of ebselen and N-acetylcysteine.

Changes in sulfhydryl status have been shown to be involved with the ethanol-induced hepatotoxicity. In addition, evidence shows the importance of replenishing thiols in patients with alcoholic liver disease. This study was undertaken to examine the possible beneficial effects of the individual and simultaneous treatments with two antioxidant drugs (N-acetylcysteine and ebselen) against ethanol-induced changes in thiol status, as well as on the activities of δ-aminolevulinate dehydratase (δ-ALA-D) and glutathione peroxidase (GPx) in mice liver. Daily ethanol administrations (3g ethanol/kg, by gavage) decreased liver nonprotein thiols (NPSH) concentration after 30 days of treatment and N-acetylcysteine (300mg/kg once a day, i.p.) or ebselen (5mg/kg once a day, subcutaneously) treatment restored this variable to control levels. However, additive beneficial effects concerning NPSH levels were not observed after the simultaneous administration with both drugs. While liver GPx and δ-ALA-D activities were inhibited by ethanol exposure and these inhibitions were significantly blunted by N-acetylcysteine or ebselen treatment, the simultaneous administration with both drugs did not show additive beneficial effects in relation to the enzymes' activities. NPSH levels were positively correlated with GPx and δ-ALA-D activities. The results presented herein show that ebselen and N-acetylcysteine alone are able to restore ethanol-induced thiols as well as the inhibition of hepatic enzymes whose catalytic functions depend on their thiol (δ-ALA-D) and selenol (GPx) groups.