Aldolase C-positive cerebellar Purkinje cells are resistant to delayed death after cerebral trauma and AMPA-mediated excitotoxicity

Loss of Flocculus Purkinje Cell Firing Precision Leads to Impaired Gaze Stabilization in a Mouse Model of Spinocerebellar Ataxia Type 6 (SCA6)

Spinocerebellar Ataxia Type 6 (SCA6) is a mid-life onset neurodegenerative disease characterized by progressive ataxia, dysarthria, and eye movement impairment. This autosomal dominant disease is caused by the expansion of a CAG repeat tract in the CACNA1A gene that encodes the α1A subunit of the P/Q type voltage-gated Ca²⁺ channel. Mouse models of SCA6 demonstrate impaired locomotive function and reduced firing precision of cerebellar Purkinje in the anterior vermis. Here, to further assess deficits in other cerebellar-dependent behaviors, we characterized the oculomotor phenotype of a knock-in mouse model with hyper-expanded polyQ repeats (SCA6^84Q). We found a reduction in the efficacy of the vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) in SCA6 mutant mice, without a change in phase, compared to their litter-matched controls. Additionally, VOR motor learning was significantly impaired in SCA6^84Q mice. Given that the floccular lobe of the cerebellum plays a vital role in the generation of OKR and VOR calibration and motor learning, we investigated the firing behavior and morphology of floccular cerebellar Purkinje cells. Overall, we found a reduction in the firing precision of floccular lobe Purkinje cells but no morphological difference between SCA6^84Q and wild-type mice. Taken together, our findings establish that gaze stabilization and motor learning are impaired in SCA6^84Q mice and suggest that altered cerebellar output contributes to these deficits.

The Cerebellar Cortex

The cerebellar cortex is an important system for relating neural circuits and learning. Its promise reflects the longstanding idea that it contains simple, repeated circuit modules with only a few cell types and a single plasticity mechanism that mediates learning according to classical Marr-Albus models. However, emerging data have revealed surprising diversity in neuron types, synaptic connections, and plasticity mechanisms, both locally and regionally within the cerebellar cortex. In light of these findings, it is not surprising that attempts to generate a holistic model of cerebellar learning across different behaviors have not been successful. While the cerebellum remains an ideal system for linking neuronal function with behavior, it is necessary to update the cerebellar circuit framework to achieve its great promise. In this review, we highlight recent advances in our understanding of cerebellar-cortical cell types, synaptic connections, signaling mechanisms, and forms of plasticity that enrich cerebellar processing.

Isoquercitrin Upregulates Aldolase C Through Nrf2 to Ameliorate OGD/R-Induced Damage in SH-SY5Y Cells

Isoquercitrin (ISO), an extract from Chinese traditional herb, exhibits potent neuroprotective roles in various disease models. However, its role in stroke is not fully understood. We established oxygen-glucose deprivation and reoxygenation (OGD/R) model in SH-SY5Y cell to study the roles of ISO in stroke. In the experiment, the changes of LDH level and cell viability (MTT) were analyzed. Apoptotic cells stained with anti-Annexin V antibody and propidium iodide (PI) were detected by flow cytometry. The mRNA and protein level of aldolase C (ALDOC) and nuclear factor erythroid 2-related factor (Nrf2) was determined by real-time quantitative polymerase chain reaction (qPCR) and Western blotting assay, respectively. The localization of Nrf2 was investigated by immunofluorescent assay. OGD/R reduced cell viability via inducing cell apoptosis, while ISO treatment reduced the level of apoptosis in OGD/R-treated SH-SY5Y cells ISO rescued OGD/R-treated cells. Mechanistically, the expression of Nrf2 and ALDOC was upregulated upon ISO treatment, while knockdown of ALDOC diminished the activation of autophagy and hence inhibited ISO-mediated protective activity. We further demonstrated that ISO enhanced ALDOC transcription by promoting nuclear translocation of Nrf2, and suppression of Nrf2 decreased the expression of ALDOC. Our data revealed that ISO exhibited neuroprotective activity in OGD/R model through Nrf2-ALDOC-autopagy axis and highlighted the potential application of ISO in stroke treatment.

Proteomics analysis of protein biomarkers in Astragalus membranaceus- and Astragaloside IV-treated brain tissues in ischemia-reperfusion injured rats

Background and aim

Astragalus membranaceus (AM) is a major Chinese herb used in the treatment of stroke. Astragaloside IV (AS)is a component of AM. This study investigated the effects of AM on the protein expression through proteomics analysis in ischemia-reperfusion injured Sprague Dawley rats.

Experimental procedure

An animal model of ischemia-reperfusion injury by occlusion of the right middle cerebral artery for 90 min followed by reperfusion for 24 h. The rats were intraperitoneally injected with AM or AS three times at 30 min, 1 day, and 2 days prior to the occlusion of the cerebral blood flow.

Results

Aldolase C was overexpressed in the cortex, and Dihydrolipoamide dehydrogenase and Triose-phosphate isomerase were overexpressed in the hippocampus.

Conclusion

Pretreatment with AM or AS can induce the overexpression of Aldolase C in the cerebral cortex and that of Dihydrolipoamide dehydrogenase and Triose-phosphate isomerase in the hippocampus, suggesting that both AM and AS may act as neuroprotectors through regulating the expression of Aldolase C, Dihydrolipoamide dehydrogenase and Triose-phosphate isomerase. However, the underlying neuroprotective mechanisms need more studies.

The Relationship Between Zebrin Expression and Cerebellar Functions: Insights From Neuroimaging Studies

The cerebellum has long been known to play an important role in motor and balance control, and accumulating evidence has revealed that it is also involved in multiple cognitive functions. However, the evidence from neuroimaging studies and clinical observations is not well-integrated at the anatomical or molecular level. The goal of this review is to summarize and link different aspects of the cerebellum, including molecular patterning, functional topography images, and clinical cerebellar disorders. More specifically, we explored the potential relationships between the cerebrocerebellar connections and the expression of particular molecules and, in particular, zebrin stripe (a Purkinje cell-specific antibody molecular marker, which is a glycolytic enzyme expressed in cerebellar Purkinje cells). We hypothesized that the zebrin patterns contribute to cerebellar functional maps—especially when cerebrocerebellar circuit changes exist in cerebellar-related diseases. The zebrin stripe receives input from climbing fibers and project to different parts of the cerebral cortex through its cerebrocerebellar connection. Since zebrin-positive cerebellar Purkinje cells are resistant to excitotoxicity and cell injury while zebrin-negative zones are more prone to damage, we suggest that motor control dysfunction symptoms such as ataxia and dysmetria present earlier and are easier to observe than non-ataxia symptoms due to zebrin-negative cell damage by cerebrocerebellar connections. In summary, we emphasize that the molecular zebrin patterns provide the basis for a new viewpoint from which to investigate cerebellar functions and clinico-neuroanatomic correlations.

Specific regions of the brain are capable of fructose metabolism

High fructose consumption in the Western diet correlates with disease states such as obesity and metabolic syndrome complications, including type II diabetes, chronic kidney disease, and non-alcoholic fatty acid liver disease. Liver and kidneys are responsible for metabolism of 40-60% of ingested fructose, while the physiological fate of the remaining fructose remains poorly understood. The primary metabolic pathway for fructose includes the fructose-transporting solute-like carrier transport proteins 2a (SLC2a or GLUT), including GLUT5 and GLUT9, ketohexokinase (KHK), and aldolase. Bioinformatic analysis of gene expression encoding these proteins (glut5, glut9, khk, and aldoC, respectively) identifies other organs capable of this fructose metabolism. This analysis predicts brain, lymphoreticular tissue, placenta, and reproductive tissues as possible additional organs for fructose metabolism. While expression of these genes is highest in liver, the brain is predicted to have expression levels of these genes similar to kidney. RNA in situ hybridization of coronal slices of adult mouse brains validate the in silico expression of glut5, glut9, khk, and aldoC, and show expression across many regions of the brain, with the most notable expression in the cerebellum, hippocampus, cortex, and olfactory bulb. Dissected samples of these brain regions show KHK and aldolase enzyme activity 5-10 times the concentration of that in liver. Furthermore, rates of fructose oxidation in these brain regions are 15-150 times that of liver slices, confirming the bioinformatics prediction and in situ hybridization data. This suggests that previously unappreciated regions across the brain can use fructose, in addition to glucose, for energy production.

Proteomic Analysis of the Effect of Korean Red Ginseng in the Striatum of a Parkinson's Disease Mouse Model

Recent studies have shown that Korean Red Ginseng (KRG) suppresses dopaminergic neuronal death in the brain of a Parkinson's disease (PD) mouse model, but the mechanism is still elusive. Using a 2-dimensional electrophoresis technique, we investigated whether KRG can restore the changes in protein expressions in the striatum (ST) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-injected mice. Male C57BL/6 mice (9 weeks old) were injected with 20 mg/kg MPTP intraperitoneally four times at 2-h intervals. KRG (100 mg/kg) was orally administered once a day for 3 days from one hour after the first MPTP injection. Two hours after the third KRG administration a pole test was performed to evaluate motor function, after which the brains were immediately harvested. Survival of dopaminergic neurons in the nigrostriatal pathway and protein expression in the ST were measured by immunohistochemistry and 2-dimensional electrophoresis. KRG suppressed MPTP-induced behavioral dysfunction and neuronal death in the nigrostriatal pathway. Moreover, 30 proteins changed by MPTP and KRG in the ST were identified and shown to be related to glycolysis/gluconeogenesis and neurodegenerative diseases including Alzheimer's disease and PD. KRG has neuroprotective effects against MPTP toxicity and alleviates protein expression profiles related to enhancing energy metabolism in the ST of MPTP-treated mice.

Modulatory roles of glycolytic enzymes in cell death

Cancer cells depend on an altered energy metabolism characterized by increased rates of both glycolysis and glutaminolysis. Accordingly, corresponding key metabolic enzymes are overexpressed or hyperactivated. As a result, this newly acquired metabolic profile determines most other cancer hallmarks including resistance to cell death. Recent findings highlighted metabolic enzymes as direct modulators of cell death pathways. Conversely, key mediators of cell death mechanisms are emerging as new binding partners of glycolytic actors; moreover, there is evidence that metabolic regulators re-localize to specific subcellular compartments or organelles to modulate various types of cell demise. The final outcome is the resistance against cell death programs. Current findings give a new meaning to metabolic pathways and allow understanding how they affect cancer-specific pathological alterations. Furthermore, they shed light on potentially targetable functions of metabolic actors to restore susceptibility of cancer cells to death. Here, we discuss an emerging interplay between cell metabolism and cell death, focusing on interactions that may offer new options of targeted therapies in cancer treatment involving more specifically hexokinases and glyceraldehyde-3-phosphate dehydrogenase.

A novel anti-aldolase C antibody specifically interacts with residues 85-102 of the protein

Aldolase C is a brain-specific glycolytic isozyme whose complete repertoire of functions are obscure. This lack of knowledge can be addressed using molecular tools that discriminate the protein from the homologous, ubiquitous paralog aldolase A. The anti-aldolase C antibodies currently available are polyclonal and not highly specific. We obtained the novel monoclonal antibody 9F against human aldolase C, characterized its isoform specificity and tested its performance. First, we investigated the specificity of 9F for aldolase C. Then, using bioinformatic tools coupled to molecular cloning and chemical synthesis approaches, we produced truncated human aldolase C fragments, and assessed 9F binding to these fragments by western blot and ELISA assays. This strategy revealed that residues 85–102 harbor the epitope-containing region recognized by 9F. The efficiency of 9F was demonstrated also for immunoprecipitation assays. Finally, surface plasmon resonance revealed that the protein has a high affinity toward the epitope-containing peptide. Taken together, our findings show that epitope recognition is sequence-driven and is independent of the three-dimensional structure. In conclusion, given its specific molecular interaction, 9F is a novel and powerful tool to investigate aldolase C’s functions in the brain.

Effects of intermittent binge alcohol exposure on long-term motor function in young rats

Ethanol has well described acute effects on motor function, and chronic alcoholism can damage the cerebellum, which is associated with motor coordination, as well as motor learning. Binge drinking is common among preadolescents and adolescents, and this type of ethanol exposure may lead to long-term nervous system damage. In the current study, we analyzed the effects of periadolsecent/adolescent ethanol exposure on motor function in both male and female Sprague-Dawley rats. To simulate binge drinking, animals received an intraperitoneal injection of 25% (v/v) ethanol (3 g/kg) on postnatal days (PND) 25, 26, 29, 30, 33, 34, 37 and 38. On PND 42 and PND 61 animals were tested on their ability to traverse both square and round beams. There were no significant differences in the time to traverse the beams, or the amount of foot slips, between treated and untreated animals. On PND 48 and PND 62, animals were tested using a horizontal ladder walking apparatus. On PND 48 there were no differences in the ability of treated and untreated animals to traverse the ladder. On PND 62, there were no differences in the time to traverse the ladder, but ethanol treated animals had more foot slips than controls. On PND 43, we conducted footprint analysis of control and treated animals, which included measurements of stride length, paw overlap, and angle of foot placement. There was a significant difference in the angle of foot placement between treated and control animals, and this finding was significant for both male and female animals. There was also a significant overall difference in paw overlap between treatment groups. Although this effect was manifested in male animals there was no significant difference in females. These findings suggest that adolescent ethanol exposure can produce long-lasting effects on motor coordination, and that overall, effects are similar in males and females. In a second set of experiments, male rats received i.p. ethanol (3 g/kg) for 7 days (P31-37) or 4 days (P31,33,35,37). No significant differences were detected by footprint analysis when compared to control animals. However, ethanol treated animals had significantly less cerebellar Purkinje cells at 3 weeks after the last ethanol exposure. Altered motor function suggests a possible neurodegenerative effect in the cerebellum initiated by adolescent ethanol exposure, and may depend on the extent of exposure during the preadolescent and/or adolescent brain periods.

Comparative analyses of Purkinje cell gene expression profiles reveal shared molecular abnormalities in models of different polyglutamine diseases

Polyglutamine (PolyQ) diseases have common features that include progressive selective neurodegeneration and the formation of protein aggregates. There is growing evidence to suggest that critical nuclear events lead to transcriptional alterations in PolyQ diseases such as spinocerebellar ataxia type 7 (SCA7) and Huntington's disease (HD), conditions which share a cerebellar degenerative phenotype. Taking advantage of laser capture microdissection technique, we compared the Purkinje cell (PC) gene expression profiles of two transgenic polyQ mouse models (HD: R6/2; SCA7: P7E) by microarray analysis that was validated by real time quantitative PCR. A large number of transcriptional alterations were detected in the R6/2 transgenic model of HD. Similar decreases in the same mRNAs, such as phospholipase C, β 3, purkinje cell protein 2 (Pcp2) and aldolase C, were found in both models. A decrease in aldolase C and phospholipase C, β 3, may lead to an increase in the vulnerability of PCs to excitotoxic events. Furthermore, downregulation of mRNAs mediated by the Pcp2-promoter is common in both models. Thus, our data reveal shared molecular abnormalities in different polyQ disorders.

Proteome profiling of spinal cord and dorsal root ganglia in rats with trinitrobenzene sulfonic acid-induced colitis

AIM: To investigate proteomic changes in spinal cord and dorsal root ganglia (DRG) of rats with trinitrobenzene sulfonic acid (TNBS)-induced colitis.

METHODS: The colonic myeloperoxidase (MPO) activity and tumor necrosis factor-α (TNF-α) level were determined. A two-dimensional electrophoresis (2-DE)-based proteomic technique was used to profile the global protein expression changes in the DRG and spinal cord of the rats with acute colitis induced by intra-colonic injection of TNBS.

RESULTS: TNBS group showed significantly elevated colonic MPO activity and increased TNF-α level. The proteins derived from lumbosacral enlargement of the spinal cord and DRG were resolved by 2-DE; and 26 and 19 proteins that displayed significantly different expression levels in the DRG and spinal cord were identified respectively. Altered proteins were found to be involved in a number of biological functions, such as inflammation/immunity, cell signaling, redox regulation, sulfate transport and cellular metabolism. The overexpression of the protein similar to potassium channel tetramerisation domain containing protein 12 (Kctd 12) and low expression of proteasome subunit α type-1 (psma) were validated by Western blotting analysis.

CONCLUSION: TNBS-induced colitis has a profound impact on protein profiling in the nervous system. This result helps understand the neurological pathogenesis of inflammatory bowel disease.

Protein tyrosine nitration of aldolase in mast cells: a plausible pathway in nitric oxide-mediated regulation of mast cell function

NO is a short-lived free radical that plays a critical role in the regulation of cellular signaling. Mast cell (MC)-derived NO and exogenous NO regulate MC activities, including the inhibition of MC degranulation. At a molecular level, NO acts to modify protein structure and function through several mechanisms, including protein tyrosine nitration. To begin to elucidate the molecular mechanisms underlying the effects of NO in MCs, we investigated protein tyrosine nitration in human MC lines HMC-1 and LAD2 treated with the NO donor S-nitrosoglutathione. Using two-dimensional gel Western blot analysis with an anti-nitrotyrosine Ab, together with mass spectrometry, we identified aldolase A, an enzyme of the glycolytic pathway, as a target for tyrosine nitration in MCs. The nitration of aldolase A was associated with a reduction in the maximum velocity of aldolase in HMC-1 and LAD2. Nuclear magnetic resonance analysis showed that despite these changes in the activity of a critical enzyme in glycolysis, there was no significant change in total cellular ATP content, although the AMP/ATP ratio was altered. Elevated levels of lactate and pyruvate suggested that S-nitrosoglutathione treatment enhanced glycolysis. Reduced aldolase activity was associated with increased intracellular levels of its substrate, fructose 1,6-bisphosphate. Interestingly, fructose 1,6-bisphosphate inhibited IgE-mediated MC degranulation in LAD2 cells. Thus, for the first time we report evidence of protein tyrosine nitration in human MC lines and identify aldolase A as a prominent target. This posttranslational nitration of aldolase A may be an important pathway that regulates MC phenotype and function.

Reduced size of the dendritic tree does not protect Purkinje cells from excitotoxic death

Purkinje cell loss by excitotoxic damage is a typical finding in many cerebellar diseases. One important aspect of this high sensitivity of Purkinje cells to excitotoxic death might be the enormous size of their dendritic tree, with a high load of excitatory glutamate receptors. We have studied whether reduction in the size of the dendritic tree might confer resistance against excitotoxic death to Purkinje cells. We have grown Purkinje cells in organotypic cerebellar slice cultures under chronic activation of metabotropic glutamate receptors or of protein kinase C. Both treatments strongly reduced dendritic tree size. After this treatment, cells were exposed to the glutamate receptor agonist AMPA, which has a strong excitotoxic effect on Purkinje cells. We found that Purkinje cells with small dendritic trees were as sensitive to AMPA exposure as untreated control cells with large dendritic trees. Immunostaining against vesicular glutamate transporter 1 revealed that the small dendritic trees were densely covered by glutamatergic terminals. Our results indicate that the expansion of the dendritic tree and the total number of AMPA receptors per neuron do not play a major role in determining the susceptibility of Purkinje cells to excitotoxic death.

The Nm23-H1 metastasis suppressor as a translational target

Nm23 was the first of what has become a field of over 20 known metastasis suppressor genes (MSGs). Since the discovery of Nm23 in 1988, a variety of mechanisms have been attributed to its activity, including a histidine kinase activity, binding of other proteins to regulate metastatic formation, and altered gene expression downstream of Nm23. Here, we will review current efforts to translate the previous work done on this MSG into the clinic, including high-dose medroxyprogesterone acetate (MPA), which has been shown to upregulate Nm23 expression. In addition, we will detail a new potential target downstream of Nm23. LPA1 is one of a group of known cell surface receptors for lysophosphatidic acid (LPA), which has been shown to be inversely correlated with Nm23 expression. A specific LPA1 antagonist could conceivably mimic the effects of Nm23 by downregulating the activity of the LPA1 pathway, which would be of considerable interest for potential clinical use.

Altered gene and protein expression by Nm23-H1 in metastasis suppression

Metastasis suppressor genes (MSG) are characterized by their ability to inhibit the formation of metastasis, while not affecting the growth of the primary tumor in vivo. Nm23-H1, the first MSG to be characterized, has been shown to alter both gene and protein expression in cancer cells. Recently, microarray expression profiling revealed that Nm23-H1 downregulated EDG2, which encodes for a lysophosphatidic acid (LPA) receptor. Reintroduction of EDG2 into cells that express Nm23-H1 overcame the metastasis suppressive ability of Nm23-H1 in both in vivo pulmonary colonization and spontaneous metastasis assays. In addition, isotope capture affinity tag (ICAT) proteomic analysis was performed to identify differentially expressed proteins not accounted for by microarray analysis. ICAT identified several differentially regulated proteins, including GEMIN5, a protein involved in differential mRNA splicing. The contribution of alternative mRNA splicing to cancer and cancer metastasis is poorly defined. It is possible that Nm23-H1, through the regulation of RNA processing proteins, may play a role in proteome stability.

Models of traumatic cerebellar injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide. Studies of human TBI demonstrate that the cerebellum is sometimes affected even when the initial mechanical insult is directed to the cerebral cortex. Some of the components of TBI, including ataxia, postural instability, tremor, impairments in balance and fine motor skills, and even cognitive deficits, may be attributed in part to cerebellar damage. Animal models of TBI have begun to explore the vulnerability of the cerebellum. In this paper, we review the clinical presentation, pathogenesis, and putative mechanisms underlying cerebellar damage with an emphasis on experimental models that have been used to further elucidate this poorly understood but important aspect of TBI. Animal models of indirect (supratentorial) trauma to the cerebellum, including fluid percussion, controlled cortical impact, weight drop impact acceleration, and rotational acceleration injuries, are considered. In addition, we describe models that produce direct trauma to the cerebellum as well as those that reproduce specific components of TBI including axotomy, stab injury, in vitro stretch injury, and excitotoxicity. Overall, these models reveal robust characteristics of cerebellar damage including regionally specific Purkinje cell injury or loss, activation of glia in a distinct spatial pattern, and traumatic axonal injury. Further research is needed to better understand the mechanisms underlying the pathogenesis of cerebellar trauma, and the experimental models discussed here offer an important first step toward achieving that objective.

Cerebellar pathology and motor deficits in the palmitoyl protein thioesterase 1-deficient mouse

Infantile neuronal ceroid lipofuscinosis (INCL, Infantile Batten Disease) is an inherited, neurodegenerative lysosomal storage disorder. INCL is the result of a CLN1 gene mutation leading to a deficiency in palmitoyl protein thioesterase 1 (PPT1) activity. Studies in the forebrain demonstrate the PPT1-deficient mouse (PPT1-/-) mimics the clinical symptoms and underlying pathology of INCL; however, little is known about changes in cerebellar function or pathology. In this study, we demonstrate Purkinje cell loss beginning at 3 months, which correlates with changes in rotarod performance. Concurrently, we observed an early stage reactive gliosis and a primary pathology in astrocytes, including changes in S100beta and GLAST expression. Conversely, there was a late stage granule cell loss, microglial activation, and demyelination. This study suggests that neuronal-glial interactions are the core pathology in the PPT1-/- cerebellum. In addition, these data identify potential endpoints for use in future efficacy studies for the treatment of INCL.

Clinical-translational approaches to the Nm23-H1 metastasis suppressor

Nm23-H1 significantly reduces metastasis without effects on primary tumor size and was the first discovered metastasis suppressor gene. At least three mechanisms are thought to contribute to the metastasis-suppressive effect of Nm23-H1: (a) its histidine kinase activity toward ATP-citrate lyase, aldolase C, and the kinase suppressor of ras, with the last inactivating mitogen-activated protein kinase signaling; (b) binding proteins that titer out "free" Nm23-H1 and inhibit its ability to suppress metastasis; and (c) altered gene expression downstream of Nm23-H1, particularly an inverse association with the lysophosphatidic acid receptor endothelial differentiation gene-28 (EDG2). Most metastasis suppressor genes, including Nm23-H1, affect metastatic colonization, which is the outgrowth of tumor cells in distant locations; therefore, they are of high translational interest. A phase II trial is ongoing to test the hypothesis that a compound, high-dose medroxyprogesterone acetate (MPA), used as an unconventional gluocorticoid, will stimulate breast cancer cells to reexpress Nm23-H1 and limit subsequent metastatic colonization.