Neuroprotective and neurotrophic effects of long term lithium treatment in mouse brain

Since the worldwide approval of lithium therapy in 1970, lithium has been used for its anti-manic, antidepressant, and anti-suicidal effects. The last decade has witnessed the following discoveries about its neuroprotective and neurotrophic properties, yet the therapeutic mechanisms at the cellular level remain not-fully defined. We have undertaken the present study to determine if chronic lithium treatment, at therapeutically relevant concentrations, exerts neurotrophic/neuroprotective effects in the mouse brain in vivo. For this purpose, 10 months aged mice were fed for 3 months on food pellets contained 1 g (L1 group) or 2 g (L2 group) lithium carbonate/kg, resulting in serum concentrations of 0.4 and 0.8 mM, respectively. The evaluation of lipid peroxidation level and the activities of catalase, superoxide-dismutase and glutathione-peroxidase showed that chronic Li administration, at therapeutic doses doesn’t induce oxidative stress in brain tissue. No changes in the expression levels of molecular chaperones, namely, the HSP70, and HSP90 heat shock proteins and the GRP94 glucose-regulated protein were detected. Moreover, this treatment has caused (1) an increase in the relative brain weight (2) a delay in the age induced cerebral glucose impairment (3) an enhancement of the neurogenesis in hippocampus and enthorinal cortex highlighted by silver impregnation. Under these experimental conditions, no modifications were observed in expression levels of GSK3 and of its downstream target β-catenin proteins. These results suggested that chronic Li administration, at therapeutic doses, has a neuroprotective/neurotrophic properties and its therapeutic mechanism doesn’t implicate GSK3 inactivation.     

Methylmercury distribution, metabolism, and neurotoxicity in the mouse brain

Methylmercury distribution, biotransformation, and neurotoxicity in the brain of male Swiss albino mice were investigated. Mice were orally dosed with [203 Hg]methylmercury chloride (10 mg/kg) for 1 to 9 days. Methylmercury was evenly distributed among the posterior cerebral cortex, subcortex, brain stem, and cerebellum. The The anterior cerebral cortex had a significantly higher methylmercury concentration than the rest of the brain. The distribution of methylmercury's inorganic mercury metabolite was found to be uneven in the brain. The pattern of distribution was cerebellum greater than brain stem greater than subcortex greater than cerebral cortex. The order of the severity of histological damage was cerebral cortex greater than cerebellum greater than subcortex greater than brain stem. There was no correlation between methylmercury distribution in the brain and structural brain damage. However, there was a relationship between the distribution of methylmercury's inorganic mercury metabolite and structural damage in the anterior cerebral cortex (positive correlation) and the anterior subcortex (negative correlation). There was also a positive correlation between the fraction of methylmercury's metabolite of the total mercury present and structural brain damage in the anterior cerebral cortex. This study suggests that biotransformation may have a role in mediating methylmercury neurotoxicity.     

Pregnancy and maternal behavior induce changes in glia, glutamate and its metabolism within the cingulate cortex

An upregulation of the astrocytic proteins GFAP and bFGF within area 2 of the cingulate cortex (Cg2) occurs within 3 hours of parturition in rats. These changes are the result of an interaction between hormonal state and maternal experience and are associated with increased dendritic spine density in this area. Here, we examined whether this upregulation of astrocytic proteins generalized to other glial markers and, in particular those associated with glutamate metabolism. We chose glial markers commonly used to reflect different aspects of glial function: vimentin, like GFAP, is a marker of intermediate filaments; glutamine synthetase (GS), and S-100beta, are used as markers for mature astrocytes and GS has also been used as a specific marker for glutamatergic enzymatic activity. In addition, we examined levels of proteins associated with glutamine synthetase, glutamate, glutamine and two excitatory amino acid transporters found in astrocytes, glt-1 and glast. S100beta immunoreactivity did not vary with reproductive state in either Cg2 or MPOA suggesting no change in the number of mature astrocytes across these conditions. Vimentin-ir did not differ across groups in Cg2, but expression of this protein decreased from Day 1 postpartum onwards in the MPOA. By contrast, GS-ir was increased within 24 h postpartum in Cg2 but not MPOA and similarly to GFAP and bFGF this upregulation of GS resulted from an interaction between hormonal state and maternal experience. Within Cg2, upregulation of GS was not accompanied by changes in the astrocytic glutamatergic transporters, glt-1 and glast, however, an increase in both glutamate and glutamine proteins were observed within the Cg2 of postpartum animals. Together, these changes suggest postpartum upregulation of glutamatergic activity and metabolism within Cg2 that is stimulated by pregnancy hormones and maternal experience.     

Oral administration of royal jelly facilitates mRNA expression of glial cell line-derived neurotrophic factor and neurofilament H in the hippocampus of the adult mouse brain

Royal jelly (RJ) is known to have a variety of biological activities toward various types of cells and tissues of animal models, but nothing is known about its effect on brain functions. Hence, we examined the effect of oral administration of RJ on the mRNA expression of various neurotrophic factors, their receptors, and neural cell markers in the mouse brain. Our results revealed that RJ selectively facilitates the mRNA expression of glial cell line-derived neurotrophic factor (GDNF), a potent neurotrophic factor acting in the brain, and neurofilament H, a specific marker predominantly found in neuronal axons, in the adult mouse hippocampus. These observations suggest that RJ shows neurotrophic effects on the mature brain via stimulation of GDNF production, and that enhanced expression of neurofilament H mRNA is involved in events subsequently caused by GDNF. RJ may play neurotrophic and/or neuroprotective roles in the adult brain through GDNF.     

Abnormal cognition, sleep, EEG and brain metabolism in a novel knock-in Alzheimer mouse, PLB1

Late-stage neuropathological hallmarks of Alzheimer's disease (AD) are β-amyloid (βA) and hyperphosphorylated tau peptides, aggregated into plaques and tangles, respectively. Corresponding phenotypes have been mimicked in existing transgenic mice, however, the translational value of aggressive over-expression has recently been questioned. As controlled gene expression may offer animal models with better predictive validity, we set out to design a transgenic mouse model that circumvents complications arising from pronuclear injection and massive over-expression, by targeted insertion of human mutated amyloid and tau transgenes, under the forebrain- and neurone-specific CaMKIIα promoter, termed PLB1(Double). Crossing with an existing presenilin 1 line resulted in PLB1(Triple) mice. PLB1(Triple) mice presented with stable gene expression and age-related pathology of intra-neuronal amyloid and hyperphosphorylated tau in hippocampus and cortex from 6 months onwards. At this early stage, pre-clinical (18)FDG PET/CT imaging revealed cortical hypometabolism with increased metabolic activity in basal forebrain and ventral midbrain. Quantitative EEG analyses yielded heightened delta power during wakefulness and REM sleep, and time in wakefulness was already reliably enhanced at 6 months of age. These anomalies were paralleled by impairments in long-term and short-term hippocampal plasticity and preceded cognitive deficits in recognition memory, spatial learning, and sleep fragmentation all emerging at ～12 months. These data suggest that prodromal AD phenotypes can be successfully modelled in transgenic mice devoid of fibrillary plaque or tangle development. PLB1(Triple) mice progress from a mild (MCI-like) state to a more comprehensive AD-relevant phenotype, which are accessible using translational tools such as wireless EEG and microPET/CT.     

Accumulation,elimination, release and metabolism of pipecolic acid in the mouse brain following intraventricular injection

Following i.c.v. (intracerebral ventricular) injections ofd,l-[³H]pipecolic acid (PA), it is reabsorbed from the ventricles and redistributed to various brain regions. The highest accumulation is found in three brain regions ipsilateral to the injection site, hippocampus, neocortex, striatum, and in the diencephalon. Following preloading in vivo, the radioactivity is released from hippocampus slices in the perfusion medium after depolarization induced by high K⁺. During perfusion with a Ca⁺⁺ free medium containing EGTA, a significant reduction of release is observed.The radioactivity ofd,l-[³H]PA in the brain shows a more rapid phase of decrease from 0 to 2 hours and a slower phase from 2 to 5 hours. At 5 hours, only 28% radioactivity, represented mainly by PA, is left in the brain. Kidney secretion represents the major route of elimination of the injected PA. The presence of -aminoadipic acid both in brain and urine was observed. Probenecid (200 mg/kg) significantly increases the accumulation of i.c.v. injectedd,l-[³H]PA in brain and kidney. The presence of a regional accumulation of PA in certain brain regions, its metabolism in brain, its enhanced retention following probenecid administration and its Ca⁺⁺ dependent release following high K⁺ stimulation, all constitute indirect evidence for a neuronal localization of this brain endogenous iminoacid.     

Ionic homeostasis and redox metabolism upregulated by 24-epibrassinolide are crucial for mitigating nickel excess in soybean plants,enhancing photosystem II efficiency and biomass

• Nickel (Ni) excess often generates oxidative stress in chloroplasts, causing redox imbalance, membrane damage and negative impacts on biomass. 24-Epibrassinolide (EBR) is a plant growth regulator of great interest to the scientific community because it is a natural molecule extracted from plants, is biodegradable and environmentally friendly. This study aimed to determine whether EBR can improve ionic homeostasis, antioxidant enzymes, PSII efficiency and biomass by evaluating nutritional, physiological, biochemical and morphological responses of soybean plants subjected to Ni excess.
• The experiment used four randomized treatments, with two Ni concentrations (0 and 200 μm Ni, described as –Ni²⁺ and +Ni²⁺, respectively) and two concentrations of EBR (0 and 100 nm EBR, described as –EBR and +EBR, respectively).
• In general, Ni had deleterious effects on chlorophyll fluorescence and gas exchange. In contrast, EBR enhanced the effective quantum yield of PSII photochemistry (15%) and electron transport rate (19%) due to upregulation of SOD, CAT, APX and POX.
• Exogenous EBR application promoted significant increases in biomass, and these results were explained by improved nutrient content and ionic homeostasis, as demonstrated by increased Ca²⁺/Ni²⁺, Mg²⁺/Ni⁺² and Mn²⁺/Ni²⁺ ratios.

     

Expression of the Norrie disease gene (Ndp) in developing and adult mouse eye, ear, and brain

The Norrie disease gene (Ndp) codes for a secreted protein, Norrin, that activates canonical Wnt signaling by binding to its receptor, Frizzled-4. This signaling system is required for normal vascular development in the retina and for vascular survival in the cochlea. In mammals, the pattern of Ndp expression beyond the retina is poorly defined due to the low abundance of Norrin mRNA and protein. Here, we characterize Ndp expression during mouse development by studying a knock-in mouse that carries the coding sequence of human placental alkaline phosphatase (AP) inserted at the Ndp locus (Ndp(AP)). In the CNS, Ndp(AP) expression is apparent by E10.5 and is dynamic and complex. The anatomically delimited regions of Ndp(AP) expression observed prenatally in the CNS are replaced postnatally by widespread expression in astrocytes in the forebrain and midbrain, Bergman glia in the cerebellum, and Müller glia in the retina. In the developing and adult cochlea, Ndp(AP) expression is closely associated with two densely vascularized regions, the stria vascularis and a capillary plexus between the organ of Corti and the spiral ganglion. These observations suggest the possibility that Norrin may have developmental and/or homeostatic functions beyond the retina and cochlea.     

Effects of ATP, Mg2+, and redox agents on the Ca2+ dependence of RyR channels from rat brain cortex

Despite their relevance for neuronal Ca²⁺-induced Ca²⁺ release (CICR), activation by Ca²⁺ of ryanodine receptor (RyR) channels of brain endoplasmic reticulum at the [ATP], [Mg²⁺], and redox conditions present in neurons has not been reported. Here, we studied the effects of varying cis-(cytoplasmic) free ATP concentration ([ATP]), [Mg²⁺], and RyR redox state on the Ca²⁺ dependence of endoplasmic reticulum RyR channels from rat brain cortex. At pCa 4.9 and 0.5 mM adenylylimidodiphosphate (AMP-PNP), increasing free [Mg²⁺] up to 1 mM inhibited vesicular [³H]ryanodine binding; incubation with thimerosal or dithiothreitol decreased or enhanced Mg²⁺ inhibition, respectively. Single RyR channels incorporated into lipid bilayers displayed three different Ca²⁺ dependencies, defined by low, moderate, or high maximal fractional open time (P_o), that depend on RyR redox state, as we have previously reported. In all cases, cis-ATP addition (3 mM) decreased threshold [Ca²⁺] for activation, increased maximal P_o, and shifted channel inhibition to higher [Ca²⁺]. Conversely, at pCa 4.5 and 3 mM ATP, increasing cis-[Mg²⁺] up to 1 mM inhibited low activity channels more than moderate activity channels but barely modified high activity channels. Addition of 0.5 mM free [ATP] plus 0.8 mM free [Mg²⁺] induced a right shift in Ca²⁺ dependence for all channels so that [Ca²⁺] <30 µM activated only high activity channels. These results strongly suggest that channel redox state determines RyR activation by Ca²⁺ at physiological [ATP] and [Mg²⁺]. If RyR behave similarly in living neurons, cellular redox state should affect RyR-mediated CICR. Ca²⁺-induced Ca²⁺ release; Ca²⁺ release channels; endoplasmic reticulum; thimerosal; 2,4-dithiothreitol; ryanodine receptor     

Alternate cadmium exposure differentially affects amino acid metabolism within the hypothalamus, median eminence, striatum and prefrontal cortex of male rats.

This work was designed to analyze the possible changes in glutamate, aspartate and glutamine content induced by cadmium exposure in the hypothalamus, striatum and prefrontal cortex of rats, using an alternate schedule of metal administration. Pubertal-adult differences were also evaluated. In adult control rats, glutamate and aspartate contents in the anterior hypothalamus decreased as compared to pubertal controls. After cadmium administration from day 30 to 60 of life, the content of anterior hypothalamic glutamate and aspartate diminished. In adult control animals, the glutamine content increased in mediobasal hypothalamus as compared to pubertal controls. After cadmium exposure from day 30 to 60 of life, the mediobasal glutamine content increased, and after cadmium treatment from day 60 to 90 of life, the mediobasal aspartate content decreased. In adult control rats the content of glutamine, glutamate and aspartate of the posterior hypothalamus decreased significantly. After cadmium administration in pubertal animals, posterior hypothalamic contents of glutamine, glutamate and aspartate diminished. Cadmium treatment of adult animals caused a decrease in glutamine content, as compared to controls. In adult control rats, only glutamate and aspartate content increased in the prefrontal cortex as compared to the values found in pubertal controls. When cadmium was administered to adult animals, only the aspartate content decreased. In the striatum, cadmium decreased the glutamine and aspartate contents when administered from day 60 to 90 of life. These data suggest that cadmium differentially affects amino acid metabolism in the hypothalamus, striatum and prefrontal cortex. Age-dependent effects of cadmium on these brain areas appeared to have occurred.     

pH, pCO2 and NADP changes during aerobic and anaerobic incubation of the brain cortex of young and adult rats

Wistar rats of both sexes, aged 5 and 90-110 days, bred in the author's department, were used for experiments in which pH, pCO2 and NADP changes induced by incubating brain cortex homogenate (30 min at 37 degrees C) under aerobic and anaerobic conditions were studied. The medium was S?rensen's buffer solution, with succinate as substrate. NADP was assayed by determining glucose-6-phosphate dehydrogenase activity, which is NADP-dependent. The pH and pCO2 were determined with an ABL-2 radiometer (Denmark). The NADP extinction curves showed that the adult rat cortex, with or without substrate, always contained significantly less NADP under anaerobic conditions (the amount of its reduced form increased). In 5-day-old rats, the course of changes in the extinction curves was completely analogous to that for adult rats if the tissue was incubated without substrate; in the presence of substrate, the amount of the oxidized form, i.e. of NADP, decreased and there was no difference between the course of extinction changes under anaerobic and aerobic conditions. Similarly, the pH fell significantly less in 5-day-old rats during anaerobic incubation than in adult rats and was practically no different from the pH changes found during aerobic incubation. In addition, we found that the increase in pCO2 during anaerobic incubation of the brain cortex of 5-day-old rats was very small (also compared with aerobic conditions) whereas the increase in pCO2 under aerobic and anaerobic conditions in adult rats was the same.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of class I, III and IV alcohol dehydrogenase mRNAs in the adult rat, mouse and human brain.

The localization of different classes of alcohol dehydrogenases (ADH) in the brain is of great interest because of their role in both ethanol and retinoic acid metabolism. Conflicting data have been reported in the literature. By Northern blot and enzyme activity analyses only class III ADH has been detected in adult brain specimens, while results from riboprobe in situ hybridization indicate class I as well as class IV ADH expression in different regions of the rat brain. Here we have studied the expression patterns of three ADH classes in adult rat, mouse and human tissues using radioactive oligonucleotide in situ hybridization. Specificity of probes was tested on liver and stomach control tissue, as well as tissue from class IV ADH knock-out mice. Only class III ADH mRNA was found to be expressed in brain tissue of all three investigated species. Particularly high expression levels were found in neurons of the red nucleus in human tissue, while cortical neurons, pyramidal and granule cells of the hippocampus and dopamine neurons of substantia nigra showed moderate expression levels. Purkinje cells of cerebellum were positive for class III ADH mRNA in all species investigated, whereas granular layer neurons were positive only in rodents. The choroid plexus was highly positive for class III ADH, while no specific signal for class I or class IV ADH was detected. Our results thus support the notion that the only ADH expressed in adult mouse, rat and human brain is class III ADH.     

Computational neuroanatomy and co-expression of genes in the adult mouse brain,analysis tools for the Allen Brain Atlas

We review quantitative methods and software developed to analyze genome-scale, brain-wide spatially-mapped gene-expression data. We expose new methods based on the underlying high-dimensional geometry of voxel space and gene space, and on simulations of the distribution of co-expression networks of a given size. We apply them to the Allen Atlas of the adult mouse brain, and to the co-expression network of a set of genes related to nicotine addiction retrieved from the NicSNP database. The computational methods are implemented in BrainGeneExpressionAnalysis (BGEA), a Matlab toolbox available for download.     

An immunofluorescence microscopical study of the neurofilament triplet proteins, vimentin and glial fibrillary acidic protein within the adult rat brain

A collection of antibodies specific to different intermediate filament proteins were applied to frozen sections of adult rat brains. The relative distribution of these proteins was then studied using double label immunofluorescence microscopy. Antibodies specific to each of the neurofilament "triplet" proteins (of approximate molecular weight 68 K, 145 K and 200 K) stained exclusively neuronal structures. The distribution of these three antigens was in general identical, except that certain neurofilament populations such as those in the dendrites and cell bodies of pyramidal cells of the hippocampus and cerebral cortex, contained relatively little if any 200 K protein. Some neurone populations, such as the granule cells of the cerebellar cortex, could not be visualized by neurofilament antibodies, indicating that neurofilaments may not be essential for function of all neurones in vitro. Antibodies to GFA and vimentin stained an entirely different population of processes, none of which stained with any of the neurofilament antibodies. Vimentin antibody stained sheath material around the brain, a monolayer of ependymal cell bodies lining the ventricles, fibrous material associated within the choroid plexus, the walls of blood vessels and capillaries, and the processes of cells in certain regions. GFA antibody stained a second layer of sheath material under the vimentin layer, and numerous processes visible throughout the brain. Some specific populations of GFA-positive processes proved to stain also with vimentin. These included the processes of Golgi "epithelial" cells (Bergmann glial fibres), those of certain astrocytes in bundles of myelinated fibers. In addition, some processes apparently derived from ependymal cells proved to stain for both vimentin and GFA, whilst other could only be reliably visualized by vimentin alone. These results are discussed in terms of the previously described morphological characteristics of the various cell types of the brain.     

Short‐term interleukin‐37 treatment improves vascular endothelial function,endurance exercise capacity,and whole‐body glucose metabolism in old mice

Aging is associated with vascular endothelial dysfunction, reduced exercise tolerance, and impaired whole‐body glucose metabolism. Interleukin‐37 (IL‐37), an anti‐inflammatory cytokine of the interleukin‐1 family, exerts salutary physiological effects in young mice independent of its inflammation‐suppressing properties. Here, we assess the efficacy of IL‐37 treatment for improving physiological function in older age. Old mice (26–28 months) received daily intraperitoneal injections of recombinant human IL‐37 (recIL‐37; 1 µg/200 ml PBS) or vehicle (200 ml PBS) for 10–14 days. Vascular endothelial function (ex vivo carotid artery dilation to increasing doses of acetylcholine, ACh) was enhanced in recIL‐37 vs. vehicle‐treated mice via increased nitric oxide (NO) bioavailability (all p < .05); this effect was accompanied by enhanced ACh‐stimulated NO production and reduced levels of reactive oxygen species in endothelial cells cultured with plasma from IL‐37‐treated animals (p < .05 vs. vehicle plasma). RecIL‐37 treatment increased endurance exercise capacity by 2.4‐fold, which was accompanied by a 2.9‐fold increase in the phosphorylated AMP‐activated kinase (AMPK) to AMPK ratio (i.e., AMPK activation) in quadriceps muscle. RecIL‐37 treatment also improved whole‐body insulin sensitivity and glucose tolerance (p < .05 vs. vehicle). Improvements in physiological function occurred without significant changes in plasma, aortic, and skeletal muscle pro‐inflammatory proteins (under resting conditions), whereas pro‐/anti‐inflammatory IL‐6 was greater in recIL‐37‐treated animals. Plasma metabolomics analysis revealed that recIL‐37 treatment altered metabolites related to pathways involved in NO synthesis (e.g., increased L‐arginine and citrulline/arginine ratio) and fatty acid metabolism (e.g., increased pantothenol and free fatty acids). Our findings provide experimental support for IL‐37 therapy as a novel strategy to improve diverse physiological functions in old age.     

Comparison of turnover rates of proteins of the brain, liver and kidney in mouse in vivo following long term labeling.

Intraperitoneal injection of [14C]tyrosine suspension followed by subcutaneous implantation of a [14C]tyrosine pellet in mice produced a fairly constant specific activity of plasma free tyrosine for 5 days, and for 3-5 days in the tissue free amino acid pool. The specific activity of tyrosine in the tissue (brain, liver, and kidney) free amino acid pool was 75-90% of that in plasma. Incorporation of tyrosine into tissue proteins was followed for 5 days in brain; during this time 33% of tissue proteins were labeled. Incorporation for 68 h in liver and kidney showed labeling of over 70% of the protein of these tissues. These percentages assume a homogeneous tissue free tyrosine pool as the precursor. The rate of incorporation initially was 0.6, 2.8, and 2.0% per h in brain, liver, and kidney protein, respectively. These rates decreased in longer term experiments. The best fit to the incorporation curves was obtained by assuming the following average half-lives for tissue proteins: brain, two compartments, 5.7% with a half-life of 15 h, 94.3% with a half-life of 10 days; liver, a single compartment with a 26-h half-life; kidney, two compartments, 41% with an 18-h half-life, and 59% with a 63-h half-life.