A recessive PRDM13 mutation results in congenital hypogonadotropic hypogonadism and cerebellar hypoplasia

The positive regulatory (PR) domain containing 13 (PRDM13) putative chromatin modifier and transcriptional regulator functions downstream of the transcription factor PTF1A, which controls GABAergic fate in the spinal cord and neurogenesis in the hypothalamus. Here, we report a recessive syndrome associated with PRDM13 mutation. Patients exhibited intellectual disability, ataxia with cerebellar hypoplasia, scoliosis, and delayed puberty with congenital hypogonadotropic hypogonadism (CHH). Expression studies revealed Prdm13/PRDM13 transcripts in the developing hypothalamus and cerebellum in mouse and human. An analysis of hypothalamus and cerebellum development in mice homozygous for a Prdm13 mutant allele revealed a significant reduction in the number of Kisspeptin (Kiss1) neurons in the hypothalamus and PAX2+ progenitors emerging from the cerebellar ventricular zone. The latter was accompanied by ectopic expression of the glutamatergic lineage marker TLX3. Prdm13-deficient mice displayed cerebellar hypoplasia and normal gonadal structure, but delayed pubertal onset. Together, these findings identify PRDM13 as a critical regulator of GABAergic cell fate in the cerebellum and of hypothalamic kisspeptin neuron development, providing a mechanistic explanation for the cooccurrence of CHH and cerebellar hypoplasia in this syndrome. To our knowledge, this is the first evidence linking disrupted PRDM13-mediated regulation of Kiss1 neurons to CHH in humans.

High Expression of Nicotinamide N-Methyltransferase in Patients with Sporadic Alzheimer's Disease

We have previously shown that the expression of nicotinamide N-methyltransferase (NNMT) is significantly increased in the brains of patients who have died of Parkinson's disease (PD). In this study, we have compared the expression of NNMT in post-mortem medial temporal lobe, hippocampus and cerebellum of 10 Alzheimer's disease (AD) and 9 non-disease control subjects using a combination of quantitative Western blotting, immunohistochemistry and dual-label confocal microscopy coupled with quantitative analysis of colocalisation. NNMT was detected as a single protein of 29 kDa in both AD and non-disease control brains, which was significantly increased in AD medial temporal lobe compared to non-disease controls (7.5-fold, P < 0.026). There was no significant difference in expression in the cerebellum (P = 0.91). NNMT expression in AD medial temporal lobe and hippocampus was present in cholinergic neurones with no glial localisation. Cell-type expression was identical in both non-disease control and AD tissues. These results are the first to show, in a proof-of-concept study using a small patient cohort, that NNMT protein expression is increased in the AD brain and is present in neurones which degenerate in AD. These results suggest that the elevation of NNMT may be a common feature of many neurodegenerative diseases. Confirmation of this overexpression using a larger AD patient cohort will drive the future development of NNMT-targetting therapeutics which may slow or stop the disease pathogenesis, in contrast to current therapies which solely address AD symptoms.

Aggravation of autism-like behavior in BTBR T+tf/J mice by environmental pollutant, di-(2-ethylhexyl) phthalate: Role of nuclear factor erythroid 2-related factor 2 and oxidative enzymes in innate immune cells and cerebellum

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder which manifests itself in early childhood and is distinguished by recurring behavioral patterns, and dysfunction in social/communication skills. Ubiquitous environmental pollutant, di-2-ethylhexyl phthalate (DEHP) is one of the most frequently used plasticizers in various industrial products, e.g. vinyl flooring, plastic toys, and medical appliances. DEHP gets easily released into the environment and leads to human exposure through various routes. DEHP has been described to be linked with oxidative stress in various organs in animal/human studies. Increased concentration of DEHP has also been detected in ASD children which indicates an association between phthalates exposure and ASD. However, effect of DEHP on autism-like behavior has not been investigated previously. Therefore, this study probed the effect of DEHP on autism-like behavior (marble burying, self-grooming and sociability) and innate immune cells (dendritic cells/neutrophils)/cerebellar oxidant-antioxidant balance (NFkB, iNOS, NADPH oxidase, nitrotyrosine, lipid peroxides, Nrf2, SOD, GPx) in BTBR and C57 mice. Our data show that DEHP treatment causes worsening of autism-like behavior in BTBR mice which is associated with enhancement of oxidative stress in innate immune cells and cerebellum with concomitant lack of antioxidant protection. DEHP also causes oxidative stress in C57 mice in both innate immune cells and cerebellar compartment, however there is Nrf2-mediated induction of enzymatic antioxidants which protects them from upregulated oxidative stress. This proposes the notion that ubiquitous environmental pollutants such as DEHP may be involved in the pathogenesis/progression of ASD through dysregulation of antioxidant-antioxidant balance in innate immune cells and cerebellum.

Ablation of polyamine catabolic enzymes provokes Purkinje cell damage, neuroinflammation, and severe ataxia

BACKGROUND

Polyamine catabolism plays a key role in maintaining intracellular polyamine pools, yet its physiological significance is largely unexplored. Here, we report that the disruption of polyamine catabolism leads to severe cerebellar damage and ataxia, demonstrating the fundamental role of polyamine catabolism in the maintenance of cerebellar function and integrity.

METHODS

Mice with simultaneous deletion of the two principal polyamine catabolic enzymes, spermine oxidase and spermidine/spermine N1-acetyltransferase (Smox/Sat1-dKO), were generated by the crossbreeding of Smox-KO (Smox-/-) and Sat1-KO (Sat1-/-) animals. Development and progression of tissue injury was monitored using imaging, behavioral, and molecular analyses.

RESULTS

Smox/Sat1-dKO mice are normal at birth, but develop progressive cerebellar damage and ataxia. The cerebellar injury in Smox/Sat1-dKO mice is associated with Purkinje cell loss and gliosis, leading to neuroinflammation and white matter demyelination during the latter stages of the injury. The onset of tissue damage in Smox/Sat1-dKO mice is not solely dependent on changes in polyamine levels as cerebellar injury was highly selective. RNA-seq analysis and confirmatory studies revealed clear decreases in the expression of Purkinje cell-associated proteins and significant increases in the expression of transglutaminases and markers of neurodegenerative microgliosis and astrocytosis. Further, the α-Synuclein expression, aggregation, and polyamination levels were significantly increased in the cerebellum of Smox/Sat1-dKO mice. Finally, there were clear roles of transglutaminase-2 (TGM2) in the cerebellar pathologies manifest in Smox/Sat1-dKO mice, as pharmacological inhibition of transglutaminases reduced the severity of ataxia and cerebellar injury in Smox/Sat1-dKO mice.

CONCLUSIONS

These results indicate that the disruption of polyamine catabolism, via coordinated alterations in tissue polyamine levels, elevated transglutaminase activity and increased expression, polyamination, and aggregation of α-Synuclein, leads to severe cerebellar damage and ataxia. These studies indicate that polyamine catabolism is necessary to Purkinje cell survival, and for sustaining the functional integrity of the cerebellum.

Sex differences in the brain expression of steroidogenic molecules under basal conditions and after gonadectomy

The brain is a steroidogenic tissue. It expresses key molecules involved in the synthesis and metabolism of neuroactive steroids, such as steroidogenic acute regulatory protein (StAR), translocator protein 18 kDa (TSPO), cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), 3β-hydroxysteroid dehydrogenases (3β-HSD), 5α-reductases (5α-R) and 3α-hydroxysteroid oxidoreductases (3α-HSOR). Previous studies have shown that the levels of brain steroids are different in male and female rats under basal conditions and after gonadectomy. In the present study, we assessed gene expression of key neurosteroidogenic molecules in the cerebral cortex and cerebellum of gonadally intact and gonadectomised adult male and female rats. In the cerebellum, the basal mRNA levels of StAR and 3α-HSOR were significantly higher in females than in males. By contrast, the mRNA levels of TSPO and 5α-R were significantly higher in males. In the cerebral cortex, all neurosteroidogenic molecules analysed showed similar mRNA levels in males and females. Gonadectomy increased the expression of 5α-R in the brain of both sexes, although it affected the brain expression of StAR, TSPO, P450scc and 3α-HSOR in females only and with regional differences. Although protein levels were not investigated in the present study, our findings indicate that mRNA expression of steroidogenic molecules in the adult rat brain is sexually dimorphic and presents regional specificity, both under basal conditions and after gonadectomy. Thus, local steroidogenesis may contribute to the reported sex and regional differences in the levels of brain neuroactive steroids and may be involved in the generation of sex differences in the adult brain function.

Cerebral inducible nitric oxide synthase protein expression in microglia, astrocytes and neurons in Trypanosoma brucei brucei-infected rats

To study the anatomo-biochemical substrates of brain inflammatory processes, Wistar male rats were infected with Trypanosoma brucei brucei. With this reproducible animal model of human African trypanosomiasis, brain cells (astrocytes, microglial cells, neurons) expressing the inducible nitric oxide synthase (iNOS) enzyme were revealed. Immunohistochemistry was achieved for each control and infected animal through eight coronal brain sections taken along the caudorostral axis of the brain (brainstem, cerebellum, diencephalon and telencephalon). Specific markers of astrocytes (anti-glial fibrillary acidic protein), microglial cells (anti-integrin alpha M) or neurons (anti-Neuronal Nuclei) were employed. The iNOS staining was present in neurons, astrocytes and microglial cells, but not in oligodendrocytes. Stained astrocytes and microglial cells resided mainly near the third cavity in the rostral part of brainstem (periaqueductal gray), diencephalon (thalamus and hypothalamus) and basal telencephalon. Stained neurons were scarce in basal telencephalon, contrasting with numerous iNOS-positive neuroglial cells. Contrarily, in dorsal telencephalon (neocortex and hippocampus), iNOS-positive neurons were plentiful, contrasting with the marked paucity of labelled neuroglial (astrocytes and microglial) cells. The dual distribution between iNOS-labelled neuroglial cells and iNOS-labelled neurons is a feature that has never been described before. Functionalities attached to such a divergent distribution are discussed.

Mutation in NADPH oxidase 3 (NOX3) impairs SHH signaling and increases cerebellar neural stem/progenitor cell proliferation

Abnormalities in cerebellar structure and function may cause ataxia, a neurological dysfunction of motor coordination. In the course of the present study, we characterized a mutant mouse lineage with an ataxia-like phenotype. We localized the mutation on chromosome 17 and mapped it to position 1534 of the Nox3 gene, resulting in p.Asn64Tyr change. The primary defect observed in Nox3^eqlb mice was increased proliferation of cerebellar granule cell precursors (GCPs). cDNA microarray comparing Nox3^eqlb and BALB/c neonatal cerebellum revealed changes in the expression of genes involved in the control of cell proliferation. Nox3^eqlb GCPs and NSC produce higher amounts of reactive oxygen species (ROS) and upregulate the expression of SHH target genes, such as Gli1-3 and Ccnd1 (CyclinD1). We hypothesize that this new mutation is responsible for an increase in proliferation via stimulation of the SHH pathway. We suggest this mutant mouse lineage as a new model to investigate the role of ROS in neuronal precursor cell proliferation.

Loss of tubulin deglutamylase CCP1 causes infantile-onset neurodegeneration

A set of glutamylases and deglutamylases controls levels of tubulin polyglutamylation, a prominent post-translational modification of neuronal microtubules. Defective tubulin polyglutamylation was first linked to neurodegeneration in the Purkinje cell degeneration (pcd) mouse, which lacks deglutamylase CCP1, displays massive cerebellar atrophy, and accumulates abnormally glutamylated tubulin in degenerating neurons. We found biallelic rare and damaging variants in the gene encoding CCP1 in 13 individuals with infantile-onset neurodegeneration and confirmed the absence of functional CCP1 along with dysregulated tubulin polyglutamylation. The human disease mainly affected the cerebellum, spinal motor neurons, and peripheral nerves. We also demonstrate previously unrecognized peripheral nerve and spinal motor neuron degeneration in pcd mice, which thus recapitulated key features of the human disease. Our findings link human neurodegeneration to tubulin polyglutamylation, entailing this post-translational modification as a potential target for drug development for neurodegenerative disorders.

RNA m6A methylation participates in regulation of postnatal development of the mouse cerebellum

BACKGROUND

N6-methyladenosine (m6A) is an important epitranscriptomic mark with high abundance in the brain. Recently, it has been found to be involved in the regulation of memory formation and mammalian cortical neurogenesis. However, while it is now established that m6A methylation occurs in a spatially restricted manner, its functions in specific brain regions still await elucidation.

RESULTS

We identify widespread and dynamic RNA m6A methylation in the developing mouse cerebellum and further uncover distinct features of continuous and temporal-specific m6A methylation across the four postnatal developmental processes. Temporal-specific m6A peaks from P7 to P60 exhibit remarkable changes in their distribution patterns along the mRNA transcripts. We also show spatiotemporal-specific expression of m6A writers METTL3, METTL14, and WTAP and erasers ALKBH5 and FTO in the mouse cerebellum. Ectopic expression of METTL3 mediated by lentivirus infection leads to disorganized structure of both Purkinje and glial cells. In addition, under hypobaric hypoxia exposure, Alkbh5-deletion causes abnormal cell proliferation and differentiation in the cerebellum through disturbing the balance of RNA m6A methylation in different cell fate determination genes. Notably, nuclear export of the hypermethylated RNAs is enhanced in the cerebellum of Alkbh5-deficient mice exposed to hypobaric hypoxia.

CONCLUSIONS

Together, our findings provide strong evidence that RNA m6A methylation is controlled in a precise spatiotemporal manner and participates in the regulation of postnatal development of the mouse cerebellum.

Mitochondrial PITRM1 peptidase loss-of-function in childhood cerebellar atrophy

OBJECTIVE

To identify the genetic basis of a childhood-onset syndrome of variable severity characterised by progressive spinocerebellar ataxia, mental retardation, psychotic episodes and cerebellar atrophy.

METHODS

Identification of the underlying mutations by whole exome and whole genome sequencing. Consequences were examined in patients' cells and in yeast.

RESULTS

Two brothers from a consanguineous Palestinian family presented with progressive spinocerebellar ataxia, mental retardation and psychotic episodes. Serial brain imaging showed severe progressive cerebellar atrophy. Whole exome sequencing revealed a novel mutation: pitrilysin metallopeptidase 1 (PITRM1) c.2795C>T, p.T931M, homozygous in the affected children and resulting in 95% reduction in PITRM1 protein. Whole genome sequencing revealed a chromosome X structural rearrangement that also segregated with the disease. Independently, two siblings from a second Palestinian family presented with similar, somewhat milder symptoms and the same PITRM1 mutation on a shared haplotype. PITRM1T931M carrier frequency was 0.027 (3/110) in the village of the first family evaluated, and 0/300 among Palestinians from other locales. PITRM1 is a mitochondrial matrix enzyme that degrades 10-65 amino acid oligopeptides, including the mitochondrial fraction of amyloid-beta peptide. Analysis of peptide cleavage activity by the PITRM1T931M protein revealed a significant decrease in the degradation capacity specifically of peptides ≥40 amino acids.

CONCLUSION

PITRM1T931M results in childhood-onset recessive cerebellar pathology. Severity of PITRM1-related disease may be affected by the degree of impairment in cleavage of mitochondrial long peptides. Disruption and deletion of X linked regulatory segments may also contribute to severity.

n-Butylidenephthalide exhibits protection against neurotoxicity through regulation of tryptophan 2, 3 dioxygenase in spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 or Machado-Joseph disease (SCA3/MJD) is characterized by the repetition of a CAG codon in the ataxin-3 gene (ATXN3), which leads to the formation of an elongated mutant ATXN3 protein that can neither be denatured nor undergo proteolysis in the normal manner. This abnormal proteolysis leads to the accumulation of cleaved fragments, which have been identified as toxic and further they act as a seed for more aggregate formation, thereby increasing toxicity in neuronal cells. To date, there have been few studies or treatment strategies that have focused on controlling toxic fragment formation. The aim of this study is to develop a potential treatment strategy for addressing the complications of toxic fragment formation and to provide an alternative treatment strategy for SCA3. Our preliminary data on anti-aggregation and toxic fragment formation using an HEK (human embryonic kidney cells) 293T-84Q-eGFP (green fluorescent protein) cell model identified n-butylidenephthalide (n-BP) as a potential drug treatment for SCA3. n-BP decreased toxic fragment formation in both SCA3 cell and animal models. Moreover, results showed that n-BP can improve gait, motor coordination, and activity in SCA3 mice. To comprehend the molecular basis behind the control of toxic fragment formation, we used microarray analysis to identify tryptophan metabolism as a major player in controlling the fate of mutant ATXN3 aggregates. We also demonstrated that n-BP functions by regulating the early part of the kynurenine pathway through the downregulation of tryptophan 2, 3-dioxygenase (TDO2), which decreases the downstream neurotoxic product, quinolinic acid (QA). In addition, through the control of TDO2, n-BP also decreases active calpain levels, an important enzyme involved in the proteolysis of mutant ATXN3, thereby decreasing toxic fragment formation and associated neurotoxicity. Collectively, these findings indicate a correlation between n-BP, TDO2, QA, calpain, and toxic fragment formation. Thus, this study contributes to a better understanding of the molecular interactions involved in SCA3, and provides a novel potential treatment strategy for this neurodegenerative disease.

Histone deacetylase inhibition reduces hypothyroidism-induced neurodevelopmental defects in rats

Thyroid hormone (TH) through its receptor (TRα/β) influences spatio-temporal regulation of its target gene repertoire during brain development. Though hypothyroidism in WT rodent models of perinatal hypothyroidism severely impairs neurodevelopment, its effect on TRα/β knockout mice is less severe. An explanation to this paradox is attributed to a possible repressive action of unliganded TRs during development. Since unliganded TRs suppress gene expression through the recruitment of histone deacetylase (HDACs) via co-repressor complexes, we tested whether pharmacological inhibition of HDACs may prevent the effects of hypothyroidism on brain development. Using valproate, an HDAC inhibitor, we show that HDAC inhibition significantly blocks the deleterious effects of hypothyroidism on rat cerebellum, evident by recovery of TH target genes like Bdnf, Pcp2 and Mbp as well as improved dendritic structure of cerebellar Purkinje neurons. Together with this, HDAC inhibition also rescues hypothyroidism-induced motor and cognitive defects. This study therefore provides an insight into the role of HDACs in TH insufficiency during neurodevelopment and their inhibition as a possible therapeutics for treatment.

Regulation of neuronal morphogenesis and positioning by ubiquitin-specific proteases in the cerebellum

Ubiquitin signaling mechanisms play fundamental roles in the cell-intrinsic control of neuronal morphogenesis and connectivity in the brain. However, whereas specific ubiquitin ligases have been implicated in key steps of neural circuit assembly, the roles of ubiquitin-specific proteases (USPs) in the establishment of neuronal connectivity have remained unexplored. Here, we report a comprehensive analysis of USP family members in granule neuron morphogenesis and positioning in the rodent cerebellum. We identify a set of 32 USPs that are expressed in granule neurons. We also characterize the subcellular localization of the 32 USPs in granule neurons using a library of expression plasmids encoding GFP-USPs. In RNAi screens of the 32 neuronally expressed USPs, we uncover novel functions for USP1, USP4, and USP20 in the morphogenesis of granule neuron dendrites and axons and we identify a requirement for USP30 and USP33 in granule neuron migration in the rodent cerebellar cortex in vivo. These studies reveal that specific USPs with distinct spatial localizations harbor key functions in the control of neuronal morphogenesis and positioning in the mammalian cerebellum, with important implications for our understanding of the cell-intrinsic mechanisms that govern neural circuit assembly in the brain.

[Simultaneous demonstration of glutamate decarboxylase and synaptophysin in paraffin sections of rat cerebellum]

The article presents highly reproducible and inexpensive protocol for simultaneous demonstration of glutamate decarboxylase (GAD67), the key enzyme of gamma-aminobutyric acid (GABA) synthesis and synaptophysin (SYP), a marker protein of synaptic vesicles using confocal laser microscopy. In the cerebellar cortex, GAD labels Purkinje cells and pinceaux in their basal parts and is unevenly distributed in the neuropil of molecular and granular layers. SYP clearly marks the contours of large dendrites of Purkinje cells in molecular layer, while in the granular layers it labels parts of cerebellar glomeruli--the terminals of the mossy fibers. GAD-immunopositive structures (GABA-ergic axons of stellate cells--Golgi cells) are often located at periphery of the glomeruli. In the peripheral zone of the glomeruli, colocalization of GAD- and SYP-immunopositive structures was observed, suggesting the presence of GABA-ergic synapses in this zone.

[The effects of dexamethasone and hypoxia on the content of active caspase-3 in the cerebellum and the behavior of neonatal rats]

Synthetic glucocorticoid dexamethasone decreased locomotor activity of neonatal rats 120 h after administration. Behavioral changes were associated with an increase in the content of active caspase-3 in the cerebellum. We found that expression of this apoptotic protease was similar to the control value when dexamethasone action was combined to hypoxic treatment to rats; however, the locomotor activity decreased to the hormone action did not recovered. We found that proapoptotic action of dexamethasone was blocked by hypoxic treatment; however, it was not sufficient for prevention of the effect of hormone on behavior.

Activity of trypsin-like enzymes and gelatinases in rats with doxorubicin cardiomyopathy

Activity of trypsin-like enzymes (ATLE) and gelatinases A and B were studied in the blood plasma and extracts from cardiac muscle, cerebral cortex and cerebellum of rats with cardiomyopathy caused by anthracycline antibiotic doxorubicin against the background of preventive application of corvitin and α-ketoglutarate. ATLE significantly increased in blood plasma and extracts from cerebral cortex but decreased in extracts from cardiac muscle and cerebellum in doxorubicin cardiomyopathy (DCMP). In addition, a significant increase of activity of both gelatinases in plasma and tissue extracts was observed. Preventive administration of corvitin and α-ketoglutarate resulted in differently directed changes of activity of the above mentioned enzymes in heart and brain tissues. Obtained data confirm the hypothesis about activation of proteolysis under the influence of anthracycline antibiotics and testify to selective effect of corvitin and α-ketoglutarate on ATLE and gelatinases.

Effect of swainsonine in Oxytropis kansuensis on Golgi α-mannosidase II expression in the brain tissues of Sprague-Dawley rats

The purpose of this study was to observe the effects of swainsonine in Oxytropis kansuensis on the expression of Golgi α-mannosidase II (MAN2A1) in the brain tissues of Sprague-Dawley (SD) rats. Twenty-four SD rats were randomly divided into four groups (experimental groups I, II, and III and a control group) of six animals each. The rats were penned as groups and fed feeds containing either 15% (swainsonine content = 0.003%), 30% (swainsonine content = 0.006%), or 45% (swainsonine content = 0.009%) O. kansuensis for experimental groups I-III, respectively, or complete feed for the control group. One hundred and nineteen days after poisoning, all rats showed neurological disorders at different degrees, which were considered to be successful establishment of a chronic poisoning model of O. kansuensis. Rats were sacrificed, and MAN2A1 expression of brain tissues was detected by immunohistochemistry and RT-PCR. The results showed that MAN2A1 was either not expressed or lowly expressed in the molecular layer of the cerebral cortex and hippocampal layers, but was found to be highly expressed in other areas of the brain. MAN2A1 expression decreased in the cerebrum and cerebellum in experimental groups when compared to the control group, whereas the expression of MAN2A1 mRNA was inhibited in cerebral and cerebellar tissues by O. kansuensis. These results indicated that O. kansuensis treatment could reduce the expression of MAN2A1 in brain tissues of SD rats.

Roles of carbonic anhydrase 8 in neuronal cells and zebrafish

BACKGROUND

Carbonic anhydrase 8 (CA8) is an isozyme of α-carbonic anhydrases (CAs). Previous studies showed that CA8 can be detected in human adult brain, with more intense expression in the cerebellum. Single mutations in CA8 were reported to cause novel syndromes like ataxia, mild mental retardation or the predisposition to quadrupedal gait.

METHODS

In the present study, we examine the functions of CA8 in neuronal cell lines, mouse cerebellar granule neurons and zebrafish.

RESULTS AND CONCLUSIONS

We demonstrated that overexpression of CA8 in neuronal cells significantly decreased cell death under staurosporine treatment. Moreover, CA8 overexpression significantly increased cell migration and invasion ability in neuronal cells and in mouse cerebellar granule neurons, implicating that CA8 may be involved in neuron motility and oncogenesis. By using zebrafish as an animal model, motor reflection of 3dpf zebrafish embryos was significantly affected after the down-regulation of CA8 through ca8 morpholino.

CONCLUSIONS

We concluded that CA8 overexpression desensitizes neuronal cells to STS induced apoptotic stress and increases cell migration and invasion ability in neuronal cells. In addition, down-regulated CA8 decreases neuron mobility in neuronal cells and leads to abnormal calcium release in cerebellar granule neurons. Knockdown of the ca8 gene results in an abnormal movement pattern in zebrafish.

GENERAL SIGNIFICANCE

Our findings provide evidence to support that the impaired protective function of CA8 contributes to human neuropathology, and to suggest that zebrafish can be used as an animal model to study the biological functions of human CA8 in vivo.

Acute liver failure in rats activates glutamine-glutamate cycle but declines antioxidant enzymes to induce oxidative stress in cerebral cortex and cerebellum

Background and Purpose

Liver dysfunction led hyperammonemia (HA) causes a nervous system disorder; hepatic encephalopathy (HE). In the brain, ammonia induced glutamate-excitotoxicity and oxidative stress are considered to play important roles in the pathogenesis of HE. The brain ammonia metabolism and antioxidant enzymes constitute the main components of this mechanism; however, need to be defined in a suitable animal model. This study was aimed to examine this aspect in the rats with acute liver failure (ALF).

Methods

ALF in the rats was induced by intraperitoneal administration of 300 mg thioacetamide/Kg. b.w up to 2 days. Glutamine synthetase (GS) and glutaminase (GA), the two brain ammonia metabolizing enzymes vis a vis ammonia and glutamate levels and profiles of all the antioxidant enzymes vis a vis oxidative stress markers were measured in the cerebral cortex and cerebellum of the control and the ALF rats.

Results

The ALF rats showed significantly increased levels of ammonia in the blood (HA) but little changes in the cortex and cerebellum. This was consistent with the activation of the GS-GA cycle and static levels of glutamate in these brain regions. However, significantly increased levels of lipid peroxidation and protein carbonyl contents were consistent with the reduced levels of all the antioxidant enzymes in both the brain regions of these ALF rats.

Conclusion

ALF activates the GS-GA cycle to metabolize excess ammonia and thereby, maintains static levels of ammonia and glutamate in the cerebral cortex and cerebellum. Moreover, ALF induces oxidative stress by reducing the levels of all the antioxidant enzymes which is likely to play important role, independent of glutamate levels, in the pathogenesis of acute HE.

[A role of glutamate decarboxylase in Alzheimer's disease]

OBJECTIVE

To evaluate the levels of the main GABA synthetic enzyme, glutamate decarboxylase (represented by two isoforms, GAD65 and GAD67) in the cerebellum cortex of patients with Alzheimer's disease (AD) and mentally healthy subjects.

MATERIALS AND METHODS

Samples of the cerebellum cortex from 13 mentally healthy subjects (the control group) and 13 patients with AD were studied. Samples obtained after autopsy were frozen and stored at -80 °C. The groups are matched by sex, age, postmortem interval and cause of death. Protein extracts from cerebellum tissues were obtained after removing of nuclei and cell debris by centrifugation and treatment of the obtained fractions with detergent (SDS). Relative amounts of GAD65 and GAD67 were determined using SDS-PAAG-electrophoresis with the following semi-quantitative ECL-Western-immunoblotting with chemiluminescence detection.

RESULTS

The amounts of both isoenzymes (GAD65 and GAD67) were significantly reduced in AD samples.

CONCLUSION

The decreased amount of both glutamate decarboxylase isoenzymes suggests the decreased synthesis of neurotransmitter and basic GABA pools that indicates insufficient functioning of the GABA system in the cerebellar cortex of AD patients.

Abortive cell cycle events in the brains of scrapie-infected hamsters with remarkable decreases of PLK3/Cdc25C and increases of PLK1/cyclin B1

Polo-like kinases (PLKs) consist of a family of kinases which play critical roles during multiple stages of cell cycle progression. Increase of PLK1 and decrease of PLK3 are associated with the developments and metastases of many types of human malignant tumors; however, the situations of PLKs in prion diseases are less understood. Using Western blots and immunohistochemical and immunofluorescent assays, marked increase of PLK1 and decrease of PLK3 were observed in the brains of scrapie strain 263K-infected hamsters, presenting obviously a time-dependent phenomenon along with disease progression. Similar alterations of PLKs were also detected in a scrapie infectious cell line SMB-S15. Both PLK1 and PLK3 were observed in neurons by confocal microscopy. Accompanying with the changes of PLKs in the brains of 263K-infected hamsters, Cdc25C and its phosphorylated forms (p-Cdc25C-Ser198 and p-Cdc25C-Ser216) were significantly down-regulated, whereas Cyclin B1 and PCNA were obviously up-regulated, while phospho-histone H3 remained almost unchanged. Moreover, exposure of the cytotoxic peptide PrP106-126 on the primary cultured cortical neuron cells induced similar changes of cellular PLKs and some cell cycle-related proteins, such as Cdc25C and its phosphorylated forms, phospho-histone H3. Those results illustrate obviously aberrant expressions of cell cycle regulatory proteins in the prion-infected neurons, which may lead to the cell cycle arrest at M phase. Possibly due to the ill-regulation of some key cell cycle events during prion infection, together with the fact that neurons are unable to complete mitosis, the cell cycle reentry in prion-infected neurons is definitely abortive, which may lead to neuron apoptosis and neuron degeneration.

Fatty acid synthase as a factor required for exercise-induced cognitive enhancement and dentate gyrus cellular proliferation

Voluntary running is a robust inducer of adult hippocampal neurogenesis. Given that fatty acid synthase (FASN), the key enzyme for de novo fatty acid biosynthesis, is critically involved in proliferation of embryonic and adult neural stem cells, we hypothesized that FASN could mediate both exercise-induced cell proliferation in the subgranular zone (SGZ) of the dentate gyrus (DG) and enhancement of spatial learning and memory. In 20 week-old male mice, voluntary running-induced hippocampal-specific upregulation of FASN was accompanied also by hippocampal-specific accumulation of palmitate and stearate saturated fatty acids. In experiments addressing the functional role of FASN in our experimental model, chronic intracerebroventricular (i.c.v.) microinfusions of C75, an irreversible FASN inhibitor, and significantly impaired exercise-mediated improvements in spatial learning and memory in the Barnes maze. Unlike the vehicle-injected mice, the C75 group adopted a non-spatial serial escape strategy and displayed delayed escape latencies during acquisition and memory tests. Furthermore, pharmacologic blockade of FASN function with C75 resulted in a significant reduction, compared to vehicle treated controls, of the number of proliferative cells in the DG of running mice as measured by immunoreactive to Ki-67 in the SGZ. Taken together, our data suggest that FASN plays an important role in exercise-mediated cognitive enhancement, which might be associated to its role in modulating exercise-induced stimulation of neurogenesis.

The effects of pre-weaning undernutrition on the expression levels of free radical deactivating enzymes in the mouse brain

A mild degree of undernutrition brought about by restricting the amount of food in the diet is known to alter the life span of an animal. It has been hypothesised that this may be related to the effects of undernutrition on an animals anti-oxidant defense system. We have therefore, used real-time PCR (rt-PCR) techniques to determine the levels of mRNA expression for manganese superoxide dismutase (MnSOD), copper/zinc superoxide dismutase (Cu/ZnSOD), glutathione peroxidase 1 (GPx 1) and catalase in the brains of Quackenbush mice undernourished from conception until 21-post-natal days of age. It was found that 21- and 61-day-old undernourished mice had a deficit in the expression of Cu/ZnSOD in both the cerebellum and forebrain regions compared to age-matched controls. The expression of MnSOD was found to be greater in the cerebellum, but not the forebrain region, of 21-day-old undernourished mice. There were no significant differences in the expression of GPx 1 and catalase between control and undernourished or previously undernourished mice. Our results confirm that undernutrition during the early life of a mouse may disrupt some of the enzymes involved in the anti-oxidant defense systems.

Sonic hedgehog-induced histone deacetylase activation is required for cerebellar granule precursor hyperplasia in medulloblastoma

Medulloblastoma, the most common pediatric brain tumor, is thought to arise from deregulated proliferation of cerebellar granule precursor (CGP) cells. Sonic hedgehog (Shh) is the primary mitogen that regulates proliferation of CGP cells during the early stages of postnatal cerebellum development. Aberrant activation of Shh signaling during this time has been associated with hyperplasia of CGP cells and eventually may lead to the development of medulloblastoma. The molecular targets of Shh signaling involved in medulloblastoma formation are still not well-understood. Here, we show that Shh regulates sustained activation of histone deacetylases (HDACs) and that this activity is required for continued proliferation of CGP cells. Suppression of HDAC activity not only blocked the Shh-induced CGP proliferation in primary cell cultures, but also ameliorated aberrant CGP proliferation at the external germinal layer (EGL) in a medulloblastoma mouse model. Increased levels of mRNA and protein of several HDAC family members were found in medulloblastoma compared to wild type cerebellum suggesting that HDAC activity is required for the survival/progression of tumor cells. The identification of a role of HDACs in the early steps of medulloblastoma formation suggests there may be a therapeutic potential for HDAC inhibitors in this disease.

Gli2 acetylation at lysine 757 regulates hedgehog-dependent transcriptional output by preventing its promoter occupancy

The morphogenic Hedgehog (Hh) signaling regulates postnatal cerebellar development and its aberrant activation leads to medulloblastoma. The transcription factors Gli1 and Gli2 are the activators of Hh pathway and their function is finely controlled by different covalent modifications, such as phosphorylation and ubiquitination. We show here that Gli2 is endogenously acetylated and that this modification represents a key regulatory step for Hedgehog signaling. The histone acetyltransferase (HAT) coactivator p300, but not other HATs, acetylates Gli2 at the conserved lysine K757 thus inhibiting Hh target gene expression. By generating a specific anti acetyl-Gli2(Lys757) antisera we demonstrated that Gli2 acetylation is readily detectable at endogenous levels and is attenuated by Hh agonists. Moreover, Gli2 K757R mutant activity is higher than wild type Gli2 and is no longer enhanced by Hh agonists, indicating that acetylation represents an additional level of control for signal dependent activation. Consistently, in sections of developing mouse cerebella Gli2 acetylation correlates with the activation status of Hedgehog signaling. Mechanistically, acetylation at K757 prevents Gli2 entry into chromatin. Together, these data illustrate a novel mechanism of regulation of the Hh signaling whereby, in concert with Gli1, Gli2 acetylation functions as a key transcriptional checkpoint in the control of morphogen-dependent processes.

Expression of tryptophan 2,3-dioxygenase and production of kynurenine pathway metabolites in triple transgenic mice and human Alzheimer's disease brain

To assess the role of the kynurenine pathway in the pathology of Alzheimer's disease (AD), the expression and localization of key components of the kynurenine pathway including the key regulatory enzyme tryptophan 2,3 dioxygenase (TDO), and the metabolites tryptophan, kynurenine, kynurenic acid, quinolinic acid and picolinic acid were assessed in different brain regions of triple transgenic AD mice. The expression and cell distribution of TDO and quinolinic acid, and their co-localization with neurofibrillary tangles and senile β amyloid deposition were also determined in hippocampal sections from human AD brains. The expression of TDO mRNA was significantly increased in the cerebellum of AD mouse brain. Immunohistochemistry demonstrated that the density of TDO immuno-positive cells was significantly higher in the AD mice. The production of the excitotoxin quinolinic acid strongly increased in the hippocampus in a progressive and age-dependent manner in AD mice. Significantly higher TDO and indoleamine 2,3 dioxygenase 1 immunoreactivity was observed in the hippocampus of AD patients. Furthermore, TDO co-localizes with quinolinic acid, neurofibrillary tangles-tau and amyloid deposits in the hippocampus of AD. These results show that the kynurenine pathway is over-activated in AD mice. This is the first report demonstrating that TDO is highly expressed in the brains of AD mice and in AD patients, suggesting that TDO-mediated activation of the kynurenine pathway could be involved in neurofibrillary tangles formation and associated with senile plaque. Our study adds to the evidence that the kynurenine pathway may play important roles in the neurodegenerative processes of AD.

The type II cGMP dependent protein kinase regulates GluA1 levels at the plasma membrane of developing cerebellar granule cells

Trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is regulated by specific interactions with other proteins and by post-translational mechanisms, such as phosphorylation. We have found that the type II cGMP-dependent protein kinase (cGKII) phosphorylates GluA1 (formerly GluR1) at S845, augmenting the surface expression of AMPARs at both synaptic and extrasynaptic sites. Activation of cGKII by 8-Br-cGMP enhances the surface expression of GluA1, whereas its inhibition or suppression effectively diminished the expression of this protein at the cell surface. In granule cells, NMDA receptor activation (NMDAR) stimulates nitric oxide and cGMP production, which in turn activates cGKII and induces the phosphorylation of GluA1, promoting its accumulation in the plasma membrane. GluA1 is mainly incorporated into calcium permeable AMPARs as exposure to 8-Br-cGMP or NMDA activation enhanced AMPA-elicited calcium responses that are sensitive to NASPM inhibition. We summarize evidence for an increase of calcium permeable AMPA receptors downstream of NMDA receptor activation that might be relevant for granule cell development and plasticity.

Is oxidative stress in mice brain regions diminished by 2-[(2,6-dichlorobenzylidene)amino]-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile?

2-[(2,6-Dichlorobenzylidene)amino]-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile, 5TIO1, is a new 2-aminothiophene derivative with promising pharmacological activities. The aim of this study was to evaluate its antioxidant activity in different areas of mice central nervous system. Male Swiss adult mice were intraperitoneally treated with Tween 80 dissolved in 0.9% saline (control group) and 5TIO1 (0.1, 1, and 10 mg kg(-1)). Brain homogenates-hippocampus, striatum, frontal cortex, and cerebellum-were obtained after 24 h of observation. Superoxide dismutase and catalase activities, lipid peroxidation and nitrite content were measured using spectrophotometrical methods. To clarify the 5TIO1's mechanism on oxidative stress, western blot analysis of superoxide dismutase and catalase was also performed. 5TIO1 decreased lipid peroxidation and nitrite content in all brain areas and increased the antioxidant enzymatic activities, specially, in cerebellum. The data of Western blot analysis did not demonstrate evidence of the upregulation of these enzymes after the administration of this compound. Our findings strongly support that 5TIO1 can protect the brain against neuronal damages regularly observed during neuropathologies.

Dab2IP GTPase activating protein regulates dendrite development and synapse number in cerebellum

DOC-2/DAB-2 interacting protein (Dab2IP) is a GTPase activating protein that binds to Disabled-1, a cytosolic adapter protein involved in Reelin signaling and brain development. Dab2IP regulates PI3K-AKT signaling and is associated with metastatic prostate cancer, abdominal aortic aneurysms and coronary heart disease. To date, the physiological function of Dab2IP in the nervous system, where it is highly expressed, is relatively unknown. In this study, we generated a mouse model with a targeted disruption of Dab2IP using a retrovirus gene trap strategy. Unlike reeler mice, Dab2IP knock-down mice did not exhibit severe ataxia or cerebellar hypoplasia. However, Dab2IP deficiency produced a number of cerebellar abnormalities such as a delay in the development of Purkinje cell (PC) dendrites, a decrease in the parallel fiber synaptic marker VGluT1, and an increase in the climbing fiber synaptic marker VGluT2. These findings demonstrate for the first time that Dab2IP plays an important role in dendrite development and regulates the number of synapses in the cerebellum.

Pontocerebellar hypoplasia type 6 caused by mutations in RARS2: definition of the clinical spectrum and molecular findings in five patients

Recessive mutations in the mitochondrial arginyl-transfer RNA synthetase (RARS2) gene have been associated with early onset encephalopathy with signs of oxidative phosphorylation defects classified as pontocerebellar hypoplasia 6. We describe clinical, neuroimaging and molecular features on five patients from three unrelated families who displayed mutations in RARS2. All patients rapidly developed a neonatal or early-infantile epileptic encephalopathy with intractable seizures. The long-term follow-up revealed a virtual absence of psychomotor development, progressive microcephaly, and feeding difficulties. Mitochondrial respiratory chain enzymes in muscle and fibroblasts were normal in two. Blood and CSF lactate was abnormally elevated in all five patients at early stages while appearing only occasionally abnormal with the progression of the disease. Cerebellar vermis hypoplasia with normal aspect of the cerebral and cerebellar hemispheres appeared within the first months of life at brain MRI. In three patients follow-up neuroimaging revealed a progressive pontocerebellar and cerebral cortical atrophy. Molecular investigations of RARS2 disclosed the c.25A>G/p.I9V and the c.1586+3A>T in family A, the c.734G>A/p.R245Q and the c.1406G>A/p.R469H in family B, and the c.721T>A/p.W241R and c.35A>G/p.Q12R in family C. Functional complementation studies in Saccharomyces cerevisiae showed that mutation MSR1-R531H (equivalent to human p.R469H) abolished respiration whereas the MSR1-R306Q strain (corresponding to p.R245Q) displayed a reduced growth on non-fermentable YPG medium. Although mutations functionally disrupted yeast we found a relatively well preserved arginine aminoacylation of mitochondrial tRNA. Clinical and neuroimaging findings are important clues to raise suspicion and to reach diagnostic accuracy for RARS2 mutations considering that biochemical abnormalities may be absent in muscle biopsy.

Cerebellar abnormalities in mice lacking type 3 deiodinase and partial reversal of phenotype by deletion of thyroid hormone receptor α1

Thyroid hormone serves many functions throughout brain development, but the mechanisms that control the timing of its actions in specific brain regions are poorly understood. In the cerebellum, thyroid hormone controls formation of the transient external germinal layer, which contains proliferative granule cell precursors, subsequent granule cell migration, and cerebellar foliation. We report that the thyroid hormone-inactivating type 3 deiodinase (encoded by Dio3) is expressed in the mouse cerebellum at embryonic and neonatal stages, suggesting a need to protect cerebellar tissues from premature stimulation by thyroid hormone. Dio3(-/-) mice displayed reduced foliation, accelerated disappearance of the external germinal layer, and premature expansion of the molecular layer at juvenile ages. Furthermore, Dio3(-/-) mice exhibited locomotor behavioral abnormalities and impaired ability in descending a vertical pole. To ascertain that these phenotypes resulted from inappropriate exposure to thyroid hormone, thyroid hormone receptor α1 (TRα1) was removed from Dio3(-/-) mice, which substantially corrected the cerebellar and behavioral phenotypes. Deletion of TRα1 did not correct the previously reported small thyroid gland or deafness in Dio3(-/-) mice, indicating that Dio3 controls the activation of specific receptor isoforms in different tissues. These findings suggest that type 3 deiodinase constrains the timing of thyroid hormone action during cerebellar development.

[Glutaminase in the cerebellum of patients with Alzheimer's disease: a postmortem brain study]

Phosphate activated glutaminase (PAG) was quantified in human cerebellar cortex extracts in 13 patients with Alzheimer's disease (AD) and 13 controls by Western immunoblotting using antibody to C-terminus of PAG kidney isoform. The majority of samples from the AD group contained less amount of PAG in comparison with control samples. Although medians in these groups were slightly different (21 and 28 arbitrary units in AD patients and controls, respectively), the Mann Whitney U-test demonstrated a significant between-group difference (U= 28.5, Z= -2.87, p=0.004). Since the both groups were matched for gender, age and postmortem interval, the difference in the PAG level was probably due to the presence of AD. The alteration in the PAG level observed in the cerebellum of patients with AD results in the disturbance of probably not only glutamate metabolism but also many other pathways involving PAG and leads to crucial consequences, particularly, to neurodegeneration.

N-terminal cleavage of the mitochondrial fusion GTPase OPA1 occurs via a caspase-independent mechanism in cerebellar granule neurons exposed to oxidative or nitrosative stress

Neuronal cell death via apoptosis or necrosis underlies several devastating neurodegenerative diseases associated with aging. Mitochondrial dysfunction resulting from oxidative or nitrosative stress often acts as an initiating stimulus for intrinsic apoptosis or necrosis. These events frequently occur in conjunction with imbalances in the mitochondrial fission and fusion equilibrium, although the cause and effect relationships remain elusive. Here, we demonstrate in primary rat cerebellar granule neurons (CGNs) that oxidative or nitrosative stress induces an N-terminal cleavage of optic atrophy-1 (OPA1), a dynamin-like GTPase that regulates mitochondrial fusion and maintenance of cristae architecture. This cleavage event is indistinguishable from the N-terminal cleavage of OPA1 observed in CGNs undergoing caspase-mediated apoptosis (Loucks et al., 2009) and results in removal of a key lysine residue (K301) within the GTPase domain. OPA1 cleavage in CGNs occurs coincident with extensive mitochondrial fragmentation, disruption of the microtubule network, and cell death. In contrast to OPA1 cleavage induced in CGNs by removing depolarizing extracellular potassium (5K apoptotic conditions), oxidative or nitrosative stress-induced OPA1 cleavage caused by complex I inhibition or nitric oxide, respectively, is caspase-independent. N-terminal cleavage of OPA1 is also observed in vivo in aged rat and mouse midbrain and hippocampal tissues. We conclude that N-terminal cleavage and subsequent inactivation of OPA1 may be a contributing factor in the neuronal cell death processes underlying neurodegenerative diseases, particularly those associated with aging. Furthermore, these data suggest that OPA1 cleavage is a likely convergence point for mitochondrial dysfunction and imbalances in mitochondrial fission and fusion induced by oxidative or nitrosative stress.

Intermittent hypoxia conditioning protects mitochondrial cytochrome c oxidase of rat cerebellum from ethanol withdrawal stress

Intermittent hypoxia (IH) conditioning minimizes neurocognitive impairment and stabilizes brain mitochondrial integrity during ethanol withdrawal (EW) in rats, but the mitoprotective mechanism is unclear. We investigated whether IH conditioning protects a key mitochondrial enzyme, cytochrome c oxidase (COX), from EW stress by inhibiting mitochondrially directed apoptotic pathways involving cytochrome c, Bax, or phosphor-P38 (pP38). Male rats completed two cycles of a 4-wk ethanol diet (6.5%) and 3 wk of EW. An IH program consisting of 5-10 bouts of 5-8 min of mild hypoxia (9.5-10% inspired O(2)) and 4 min of reoxygenation for 20 consecutive days began 3 days before the first EW period. For some animals, vitamin E replaced IH conditioning to test the contributions of antioxidant mechanisms to IH's mitoprotection. During the second EW, cerebellar-related motor function was evaluated by measuring latency of fall from a rotating rod (Rotarod test). After the second EW, COX activity in cerebellar mitochondria was measured by spectrophotometry, and COX, cytochrome c, Bax, and pP38 content were analyzed by immunoblot. Mitochondrial protein oxidation was detected by measuring carbonyl contents and by immunochemistry. Earlier IH conditioning prevented motor impairment, COX inactivation, depletion of COX subunit 4, protein carbonylation, and P38 phosphorylation during EW. IH did not prevent cytochrome c depletion during EW, and Bax content was unaffected by EW ± IH. Vitamin E treatment recapitulated IH protection of COX, and P38 inhibition attenuated protein oxidation during EW. Thus IH protects COX and improves cerebellar function during EW by limiting P38-dependent oxidative damage.

Prenatal hypoxic-ischemic insult changes the distribution and number of NADPH-diaphorase cells in the cerebellum

Astrogliosis, oligodendroglial death and motor deficits have been observed in the offspring of female rats that had their uterine arteries clamped at the 18^th gestational day. Since nitric oxide has important roles in several inflammatory and developmental events, here we evaluated NADPH-diaphorase (NADPH-d) distribution in the cerebellum of rats submitted to this hypoxia-ischemia (HI) model. At postnatal (P) day 9, Purkinje cells of SHAM and non-manipulated (NM) animals showed NADPH-d+ labeling both in the cell body and dendritic arborization in folia 1 to 8, while HI animals presented a weaker labeling in both cellular structures. NADPH-d+ labeling in the molecular (ML), and in both the external and internal granular layer, was unaffected by HI at this age. At P23, labeling in Purkinje cells was absent in all three groups. Ectopic NADPH-d+ cells in the ML of folia 1 to 4 and folium 10 were present exclusively in HI animals. This labeling pattern was maintained up to P90 in folium 10. In the cerebellar white matter (WM), at P9 and P23, microglial (ED1+) NADPH-d+ cells, were observed in all groups. At P23, only HI animals presented NADPH-d labeling in the cell body and processes of reactive astrocytes (GFAP+). At P9 and P23, the number of NADPH-d+ cells in the WM was higher in HI animals than in SHAM and NM ones. At P45 and at P90 no NADPH-d+ cells were observed in the WM of the three groups. Our results indicate that HI insults lead to long-lasting alterations in nitric oxide synthase expression in the cerebellum. Such alterations in cerebellar differentiation might explain, at least in part, the motor deficits that are commonly observed in this model.

An essential role for p38 MAPK in cerebellar granule neuron precursor proliferation

Development of the cerebellum occurs postnatally and is marked by a rapid proliferation of cerebellar granule neuron precursors (CGNPs). CGNPs are the cells of origin for SHH-driven medulloblastoma, the most common malignant brain tumor in children. Here, we investigated the role of ERK, JNK, and p38 mitogen-activated protein kinases in CGNP proliferation. We found high levels of p38α in proliferating CGNPs. Concomitantly, members of the p38 pathway, such as ASK1, MKK3 and ATF-2, were also elevated. Inhibition of the Shh pathway or CGNP proliferation blunts p38α levels, irrespective of Shh treatment. Strikingly, p38α levels were high in vivo in the external granule layer of the postnatal cerebellum, Shh-dependent mouse medulloblastomas and human medulloblastomas of the SHH subtype. Finally, knocking down p38α by short hairpin RNA-carrying lentiviruses as well as the pharmacologically inhibiting of its kinase activity caused a marked decrease in CGNP proliferation, underscoring its requirement for Shh-dependent proliferation in CGNPs. The inhibition of p38α also caused a decrease in Gli1 and N-myc transcript levels, consistent with reduced proliferation. These findings suggest p38 inhibition as a potential way to increase the efficacy of treatments available for malignancies associated with deregulated SHH signaling, such as basal cell carcinoma and medulloblastoma.

Ethnic differences in tissue creatine kinase activity: an observational study

Background

Serum creatine kinase (CK) levels are reported to be around 70% higher in healthy black people, as compared to white people (median value 88 IU/L in white vs 149 IU/L in black people). As serum CK in healthy people is thought to occur from a proportional leak from normal tissues, we hypothesized that the black population subgroup has a generalized higher CK activity in tissues.

Methodology/Principal Findings

We compared CK activity spectrophotometrically in tissues with high and fluctuating energy demands including cerebrum, cerebellum, heart, renal artery, and skeletal muscle, obtained post-mortem in black and white men. Based on serum values, we conservatively estimated to find a 50% greater CK activity in black people compared with white people, and calculated a need for 10 subjects of one gender in each group to detect this difference. We used mixed linear regression models to assess the possible influence of ethnicity on CK activity in different tissues, with ethnicity as a fixed categorical subject factor, and CK of different tissues clustered within one person as the repeated effect response variable. We collected post-mortem tissue samples from 17 white and 10 black males, mean age 62 y (SE 4). Mean tissue CK activity was 76% higher in tissues from black people (estimated marginal means 107.2 [95% CI, 76.7 to 137.7] mU/mg protein in white, versus 188.6 [148.8 to 228.4] in black people, p = 0.002).

Conclusion

We found evidence that black people have higher CK activity in all tissues with high and fluctuating energy demands studied. This finding may help explain the higher serum CK levels found in this population subgroup. Furthermore, our data imply that there are differences in CK-dependent ATP buffer capacity in tissue between the black and the white population subgroup, which may become apparent with high energy demands.

Protective role of Cynodon dactylon in ameliorating the aluminium-induced neurotoxicity in rat brain regions

Cynodon dactylon (Poaceae) is a creeping grass used as a traditional ayurvedic medicine in India. Aluminium-induced neurotoxicity is well known and different salts of aluminium have been reported to accelerate damage to biomolecules like lipids, proteins and nucleic acids. The objective of the present study was to investigate whether the aqueous extract of C. dactylon (AECD) could potentially prevent aluminium-induced neurotoxicity in the cerebral cortex, hippocampus and cerebellum of the rat brain. Male albino rats were administered with AlCl(3) at a dose of 4.2 mg/kg/day i.p. for 4 weeks. Experimental rats were given C. dactylon extract in two different doses of 300 mg and 750 mg/keg/day orally 1 h prior to the AlCl(3) administration for 4 weeks. At the end of the experiments, antioxidant status and activities of ATPases in cerebral cortex, hippocampus and cerebellum of rat brain were measured. Aluminium administration significantly decreased the level of GSH and the activities of SOD, GPx, GST, Na(+)/K(+) ATPase, and Mg(2+) ATPase and increased the level of lipid peroxidation (LPO) in all the brain regions when compared with control rats. Pre-treatment with AECD at a dose of 750 mg/kg b.w increased the antioxidant status and activities of membrane-bound enzymes (Na(+)/K(+) ATPase and Mg(2+) ATPase) and also decreased the level of LPO significantly, when compared with aluminium-induced rats. The results of this study indicated that AECD has potential to protect the various brain regions from aluminium-induced neurotoxicity.

Differential effects of ethanol on c-jun N-terminal kinase, 14-3-3 proteins, and Bax in postnatal day 4 and postnatal day 7 rat cerebellum

These studies investigated ethanol effects on upstream cellular elements and interactions which contribute to Bax-related apoptosis in neonatal rat cerebellum at ages of peak ethanol sensitivity (postnatal day 4 [P4]), compared to later ages of relative resistance (P7). Analyses were made of basal levels of the pro-apoptotic c-jun N-terminal kinase (JNK), Bax, and the 14-3-3 anchoring proteins, as well as the responsiveness of these substances to ethanol at P4 versus P7. Dimerization of Bax with 14-3-3 was also investigated at the two ages following ethanol treatment, a process which sequesters Bax in the cytosol, thus inhibiting its mitochondrial translocation and disruption of the mitochondrial membrane potential. Cultured cerebellar granule cells were used to examine the protective potential of JNK inhibition on ethanol-mediated cell death. Basal levels of JNK were significantly higher at P4 than P7, but no differences in the other proteins were found. Activated JNK, and cytosolic and mitochondrially-translocated Bax were increased in P4 but not P7 animals following ethanol exposure, while protective 14-3-3 proteins were increased only at P7. Ethanol treatment resulted in decreases in Bax:14-3-3 heterodimers at P4, but not at P7. Inhibition of JNK activity in vitro provided partial protection against ethanol neurotoxicity. Thus, differential temporal vulnerability to ethanol in this CNS region correlates with differences in both levels of apoptosis-related substances (e.g., JNK), and differential cellular responsiveness, favoring apoptosis at the most sensitive age and survival at the resistant age. The upstream elements contributing to this vulnerability can be targets for future therapeutic strategies.

Improvement of cerebellum redox states and cholinergic functions contribute to the beneficial effects of silymarin against manganese-induced neurotoxicity

Manganese (Mn) is a potent neurotoxin involved in the initiation and progression of various cognitive disorders. Oxidative stress is reported as one of accepted mechanisms of Mn toxicity. The present study was designed to explore the effects of silymarin, a natural antioxidant, in attenuating the toxicity induced by Mn in rat cerebellum. In this investigation, rats were treated orally with MnCl₂ (20 mg/ml) for 30 days, subsets of these animals were treated intraperitoneally daily with silymarin (100 mg/kg) along with respective controls. Mn exposure caused a marked oxidative stress in cerebellum as indicated by a significant decrease in the activities of enzymatic antioxidants like superoxide dismutase, catalase and glutathione peroxidase and in the levels of non-enzymatic antioxidants like reduced glutathione (GSH), total thiols and vitamin C. Conversely an increase was obtained in lipid and protein markers such as thiobarbituric reactive acid substances, lipid hydroperoxide and protein carbonyl products contents. A significant increase in acetylcholinesterase and a decrease in Na⁺/K⁺-ATPase activities were also shown, with a substantial rise in the expression of acetylcholinesterase and inducible nitric oxide synthase (iNOS), and nitric oxide levels. The potential effect of SIL to prevent Mn induced neurotoxicity was also reflected by histopathological observations. Rats exposed to Mn showed a reduced number and morphological alterations of cerebellar Purkinje cells. These phenomenons were completely reversed by SIL co-treatment. We concluded that silymarin may protect against Mn-induced oxidative stress in cerebellum by inhibiting both lipid and protein oxidation and by activating acetylcholinesterase and inducible nitric oxide synthase (iNOS) gene expression.

Angiotensin III stimulates ERK1/2 mitogen-activated protein kinases and astrocyte growth in cultured rat astrocytes

Angiotensin (Ang) III is a biologically active metabolite of Ang II with similar effects and receptor binding properties as Ang II. Most Ang III studies delineate physiological effects of the peptide but, the intracellular pathways leading to the actions are unknown and are a focus of these studies. We investigated in cultured brainstem and cerebellum rat astrocytes whether Ang III stimulates ERK1/2 mitogen activated protein (MAP) kinases and astrocyte growth. Ang III significantly stimulated ERK1/2 MAP kinases in a dose- and time-dependent manner. The maximal stimulation occurred with 100 nM Ang III (2.8±0.3 and 2.3±0.1-fold over basal, in brainstem and cerebellum astrocytes, respectively). This stimulation occurred as early as 1 min, and was sustained for at least 15 min. Moreover, inhibition of the ERK1/2 MAP kinase pathway by 10 μM PD98059 attenuated Ang III-induced ERK1/2 phosphorylation. Ang III induction of ERK1/2 occurred via stimulation of the Ang AT(1) receptor since pretreatment with 10 μM Losartan, a selective AT(1) receptor blocker, prevented Ang III-induced ERK1/2 phosphorylation. The selective AT(2) Ang receptor blocker PD123319 was ineffective. Comparable to Ang II, Ang III also stimulated astrocyte growth in a concentration-dependent manner, an effect that occurred via activation of the AT(1) receptor as well. These findings suggest that Ang III has similar effects as Ang II in astrocytes since it rapidly stimulates the phosphorylation of the ERK1/2 MAP kinases and induces astrocyte proliferation through activation of the AT(1) receptor. These studies are important in establishing signaling pathways for Ang III and provide validation of the central role of Ang III.

Activation of caspase-3 and c-Jun NH2-terminal kinase signaling pathways involving heroin-induced neuronal apoptosis

Heroin has been shown to cause spongiform leukoencephalopathy (SLE) in heroin addicts. In this study, we found that heroin could induce apoptosis of primary cultured cerebellar granule cells (CGC) and c-Jun N-terminal kinase (JNK) pathway is activated during CGCs apoptosis. Inhibiting JNK with a specific inhibitor, SP600125, reduced the levels of c-Jun phosphorylation and caspase-3 activation. We also showed that use the JNK inhibitor SP600125, caspase inhibitor z-VAD, or use SP600125 and z-VAD together significantly suppressed cell death induced by heroin. These results indicate that JNK pathway is an important mediator of the neurotoxic effects of heroin and inhibiting JNK activity may represent a new and effective strategy to treat heroin-induced SLE.

Age-related protective effect of deprenyl on changes in the levels of diagnostic marker enzymes and antioxidant defense enzymes activities in cerebellar tissue in Wistar rats

Antioxidants are free radical scavengers and protect living organisms against oxidative damage to tissues. Experimental evidence implicates oxygen-derived free radicals as important causative agents of aging and the present study was designed to evaluate the age-related effects of deprenyl on the antioxidant defense in the cerebellum of male Wistar rats. Experimental rats of three age groups (6, 12, and 18 months old) were administered with liquid deprenyl (2 mg/kg body weight/day for a period of 15 days i.p) and levels of diagnostic marker enzymes (alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase and creatine phosphokinase) in plasma, lipid peroxides, reduced glutathione and activities of glutathione-dependent antioxidant enzymes (glutathione peroxidase and glutathione-S-transferase) and antiperoxidative enzymes (catalase and superoxide dismutase) in the cerebellar tissue were determined. Intraperitonial administration of deprenyl (2 mg/kg body weight/day for a period of 15 days) significantly (p < 0.05) attenuated the age-related alterations noted in the levels of diagnostic marker enzymes plasma of experimental animals. Deprenyl also exerted an antioxidant effect against aging process by hindering lipid peroxidation to an extent. Moderate rise in the levels of reduced glutathione and activities of glutathione-dependent antioxidant enzymes and antiperoxidative enzymes was also observed. The results of the present investigation indicated that the protective potential of deprenyl was probably due to the increase of the activity of the free radical scavenging enzymes or to a counteraction of free radicals by its antioxidant nature or to a strengthening of neuronal membrane by its membrane-stabilizing action. Histopathological observations also confirmed the protective effect of deprenyl against the age-related aberrations in rat cerebellum. These data on the effect of deprenyl on parameters of normal aging provides new additional information concerning the anti-aging potential of deprenyl.

Altered levels and distribution of amyloid precursor protein and its processing enzymes in Niemann-Pick type C1-deficient mouse brains

Niemann-Pick type C (NPC) disease is an autosomal recessive neurodegenerative disorder characterized by intracellular accumulation of cholesterol and glycosphingolipids in many tissues including the brain. The disease is caused by mutations of either NPC1 or NPC2 gene and is accompanied by a severe loss of neurons in the cerebellum, but not in the hippocampus. NPC pathology exhibits some similarities with Alzheimer's disease, including increased levels of amyloid beta (Abeta)-related peptides in vulnerable brain regions, but very little is known about the expression of amyloid precursor protein (APP) or APP secretases in NPC disease. In this article, we evaluated age-related alterations in the level/distribution of APP and its processing enzymes, beta- and gamma-secretases, in the hippocampus and cerebellum of Npc1(-/-) mice, a well-established model of NPC pathology. Our results show that levels and expression of APP and beta-secretase are elevated in the cerebellum prior to changes in the hippocampus, whereas gamma-secretase components are enhanced in both brain regions at the same time in Npc1(-/-) mice. Interestingly, a subset of reactive astrocytes in Npc1(-/-) mouse brains expresses high levels of APP as well as beta- and gamma-secretase components. Additionally, the activity of beta-secretase is enhanced in both the hippocampus and cerebellum of Npc1(-/-) mice at all ages, while the level of C-terminal APP fragments is increased in the cerebellum of 10-week-old Npc1(-/-) mice. These results, taken together, suggest that increased level and processing of APP may be associated with the development of pathology and/or degenerative events observed in Npc1(-/-) mouse brains.

Aromatase expression in the cerebellum of the dog infected with canine distemper virus

Aromatase is the enzyme that catalyzes the biosynthesis of estrogens. It is implicated in neuroprotection.The present study investigated aromatase expression in the cerebellum of dogs infected with canine distemper virus (CDV), a disease characterized by demyelination in the white matter of the cerebellum. The presence of CDV infection was confirmed on the basis of histopathology and immunohistochemical localization of CDV antigen in glial cells of the white matter.The number of aromatase immunoreactive astrocytes were significantly (p < 0.05) higher in CDV-infected dogs compared to control dogs. The results suggest that astrocytes respond to invasion and persistence of CDV by means of increased estrogen production.The results also suggest that the high level of estrogen expression is maintained similarly throughout all stages of the disease since the number of aromatase immunoreactive astrocytes did not vary during the different stages of CDV infection.

Inhibition of lindane-induced toxicity using alpha-lipoic acid and vitamin E in the brain of Mus musculus

In the present investigation, we have used adenosine triphosphatase (ATPase) activity as biochemical test of toxic action of lindane that was explained by lipid peroxidation model. Study was also undertaken to ascertain the potential protective role of alpha-lipoic acid (ALA) and vitamin E on the same parameters. Highly acute dose of lindane, i.e., 40 mg/kg bw for 18 h exposure, was used for creating lesions in brain. Lipid peroxidation was measured in terms of glutathione peroxidase and thio barbituric acid-reacting substances (TBARS). Various brain regions under investigation were cerebellum and pons-medulla oblongata. Healthy, male, Swiss mice (7-8 weeks old) were allocated into four groups. First group was control, second group was treated with lindane, third group was treated purely with antioxidants, and fourth group received both antioxidants and lindane treatment. Results revealed the significant difference (at 1% and 5% in all groups) in all studied parameters from control. Increased TBARS level in second group suggests that lindane enhances the production of free radicals in studied brain regions. Antioxidants under test are efficient remedy for neurotoxicity caused by lindane. We conclude that lindane manifests toxic effects on brain ATPase and enhances lipid peroxidation. ALA and vitamin E in combination may provide protection against lindane-induced acute toxicity.

Neonatal organophosphorus pesticide exposure alters the developmental trajectory of cell-signaling cascades controlling metabolism: differential effects of diazinon and parathion

BACKGROUND

Organophosphorus pesticides (OPs) are developmental neurotoxicants but also produce lasting effects on metabolism.

OBJECTIVES/METHODS

We administered diazinon (DZN) or parathion (PRT) to rats on postnatal days 14 at doses straddling the threshold for systemic signs of exposure and assessed the effects on hepatic and cardiac cell signaling mediated through the adenylyl cyclase (AC) cascade.

RESULTS

In the liver, DZN elicited global sensitization, characterized by parallel up-regulation of AC activity itself and of the responses to stimulants acting at beta-adrenergic receptors, glucagon receptors, or G-proteins. The effects intensified over the course from adolescence to adulthood. In contrast, PRT elicited up-regulation in adolescence that waned by adulthood. Superimposed on these general patterns were effects on glucagon receptor coupling to AC and on responses mediated through the Gi inhibitory protein. The effects on the liver were more substantial than those in the heart, which displayed only transient effects of DZN on AC function in adolescence and no significant effects of PRT. Furthermore, the hepatic effects were greater in magnitude than those in a brain region (cerebellum) that shares similar AC cascade elements.

CONCLUSIONS

These findings indicate that OPs alter the trajectory of hepatic cell signaling in a manner consistent with the observed emergence of prediabetes-like metabolic dysfunction. Notably, the various OPs differ in their net impact on peripheral AC signaling, making it unlikely that the effects on signaling reflect their shared property as cholinesterase inhibitors.

Effect of natural polyphenols, pycnogenol® on superoxide dismutase and nitric oxide synthase in diabetic rats

The work is focused on clarifying the impact of diabetes and natural plant polyphenols contained in Pycnogenol® (PYC) on the activity and synthesis of Cu/Zn-SOD and synthesis of nNOS and eNOS in the cerebellum and cerebral cortex in rats with induced diabetes. Rats included in the study (n=38) were divided into three groups: the controls (C), (n=7), untreated diabetics (D) (n=19) and diabetic rats treated with PYC (DP) (n=12). Diabetes significantly decreased synthesis, as well as the activity of Cu/Zn-SOD in both studied parts of the brain. PYC significantly increased the synthesis of Cu/Zn-SOD but had no effect on its activity. Diabetes also reduced the synthesis of nNOS in cerebral cortex and administered PYC elevated its amount to the level of controls. In the cerebellum, diabetes does not affect the synthesis of nNOS and PYC reduces synthesis of NOS. Diabetes as well as PYC had no influence on the synthesis of eNOS in both, the cerebellum and cerebral cortex. PYC modulated level of Cu/Zn-SOD and nNOS in cerebellum and cerebral cortex of diabetic rats, but in a different way.

[The forms of acetyl-cholinesterase molecule. Part I: the research of sole presence of globular G1 monomer in rat cerebellum]

The sole presence--without the rest of molecule forms--of G1 monomer form was sought in the homogenate of rat cerebellum with vertical slab technique with the help of polyacrylamid gel electrophoresis. As a result we got the monomer form in the case of 7 day rat, without the presence of the rest of the forms. In case of older and adult rats the rest of the forms have already evolved, so the dimer and tetramer forms are also present.

Patterned neuroprotection in the Inpp4a(wbl) mutant mouse cerebellum correlates with the expression of Eaat4

The weeble mutant mouse has a frame shift mutation in inositol polyphosphate 4-phosphatase type I (Inpp4a). The phenotype is characterized by an early onset cerebellar ataxia and neurodegeneration, especially apparent in the Purkinje cells. Purkinje cell loss is a common pathological finding in many human and mouse ataxic disorders. Here we show that in the Inpp4a^wbl mutant, Purkinje cells are lost in a specific temporal and spatial pattern. Loss occurs early in postnatal development; however, prior to the appearance of climbing fibers in the developing molecular layer, the mutant has a normal complement of Purkinje cells and they are properly positioned. Degeneration and reactive gliosis are present at postnatal day 5 and progress rapidly in a defined pattern of patches; however, Inpp4a is expressed uniformly across Purkinje cells. In late stage mutants, patches of surviving Purkinje cells appear remarkably normal with the exception that the climbing fibers have been excessively eliminated. Surviving Purkinje cells express Eaat4, a glutamate transporter that is differentially expressed in subsets of Purkinje cells during development and into adult stages. Prior to Purkinje cell loss, reactive gliosis and dendritic atrophy can be seen in Eaat4 negative stripes. Our data suggest that Purkinje cell loss in the Inpp4a^wbl mutant is due to glutamate excitotoxicity initiated by the climbing fiber, and that Eaat4 may exert a protective effect.