A therapy with miglustat, 2-hydroxypropyl-ß-cyclodextrin and allopregnanolone restores splenic cholesterol homeostasis in Niemann-pick disease type C1.

BACKGROUND: Niemann-Pick disease type C1 (NPC1) is an autosomal-recessive lipid-storage disorder with an estimated minimal incidence of 1/120,000 live births. Besides other neuronal and visceral symptoms, NPC1 patients develop spleen dysfunction, isolated spleno- or hepatosplenomegaly and infections. The mechanisms of splenomegaly and alterations of lipid metabolism-related genes in NPC1 disease are still poorly understood. METHODS: Here, we used an NPC1 mouse model to study a splenoprotective effect of a treatment with miglustat, 2-hydroxypropyl-ß-cyclodextrin and allopregnanolone and showed that this treatment has a positive effect on spleen morphology and lipid metabolism. RESULTS: Disease progress can be halted and blocked at the molecular level. Mutant Npc1 (Npc1-/-) mice showed increased spleen weight and increased lipid accumulation that could be avoided by our treatment. Also, FACS analyses showed that the increased number of splenic myeloid cells in Npc1-/- mice was normalized by the treatment. Treated Npc1-/- mice showed decreased numbers of cytotoxic T cells and increased numbers of T helper cells. CONCLUSIONS: In summary, the treatment promotes normal spleen morphology, stabilization of lipid homeostasis and blocking of inflammation, but alters the composition of T cell subtypes.

Transcription factor Yin-Yang 2 alters neuronal outgrowth in vitro.

The Yin-Yang 2 (YY2) protein is the most recently described member of the family of YY transcription factors. Despite its high structural and functional homology with the well-characterized YY1, less is known about its role in biological processes. In previous studies, we have found differential yy2 mRNA expression levels in various cell types of the murine brain. To investigate the functional implication of yy2 in neurons, we have examined the influence of altered cellular yy2 concentrations during neuronal differentiation. Our results indicate that both the up- and down-regulation of yy2 significantly impairs the outgrowth of the major neurite of primary hippocampal neurons and the numbers of neuronal processes in proximate extensions. Moreover, enhanced expression of wild-type yy2 results in increased cell death, whereas elevated expression levels of a yy2 DNA-binding mutant have no effect on cell viability. Therefore, stringent regulation of the cellular yy2 content might be needed to ensure proper neurite outgrowth and cell vitality.

Studying Axonal Outgrowth and Regeneration of the Corticospinal Tract in Organotypic Slice Cultures.

Studies of axonal outgrowth and regeneration after spinal cord injury are hampered by the complexity of the events involved. Here, we present a simple and improved in vitro approach to investigate outgrowth, regeneration of the corticospinal tract, and intrinsic parenchymal responses. We prepared organotypic co-cultures using explants from the motor cortex of postnatal donor mice ubiquitously expressing green fluorescent protein and cervical spinal cord from wild type pups of the same age. Our data show that: a) motor-cortical outgrowth is already detectable after 1 d in culture and is source specific; b) treatment with neurotrophin-3 and C3 transferase from Clostridium botulinum significantly enhances axonal outgrowth during the course of cultivation; c) outgrowing axons form synaptic connections, as demonstrated by immunohistochemistry and calcium imaging; and d) migrating cells of motor-cortical origin can be reliably identified without previous tracing and are mostly neural precursors that survive and mature in the spinal cord parenchyma. Thus, our model is suitable for screening for candidate substances that enhance outgrowth and regeneration of the corticospinal tract and for studying the role of endogenous neural precursors after lesion induction.

Developmental expression profile of the YY2 gene in mice.

BACKGROUND: The transcription factor Yin Yang 2 (YY2) shares a structural and functional highly homologue DNA-binding domain with the ubiquitously expressed YY1 protein, which has been implicated in regulating fundamental biological processes. However, the biological relevance of YY2 has not been identified yet. RESULTS: Towards the understanding of YY2 biology, we analyzed in detail the expression pattern of yy2 in various organs during embryonic and postnatal mouse development till adulthood. Thereby, a constant yy2 level was detected in heart and lung tissue, whereas in different brain regions yy2 expression was dynamically regulated. Interestingly, in any analyzed tissue neither the homologue yy1 nor the mbtps2 gene showed changes in mRNA expression levels like yy2, although the intronless yy2 gene is located within the mbtps2 locus.Furthermore, we detected yy1, yy2, and mbtps2 mRNA in primary mouse neurons, microglia cells, and astrocytes. In comparison to yy2 and mbtps2, yy1 revealed the highest expression level in all cell types. Again, only yy2 showed significantly altered gene expression levels among the cell types. Higher yy2 expression levels were detected in microglia cells and astrocytes than in primary neurons. CONCLUSION: Yy2 expression in the heart and lung is constitutively expressed during embryogenesis and in adult mice. For the first time, developmental changes of yy2 transcription became obvious in various areas of the brain. This suggests that yy2 is involved in developmental gene regulation.

The brain selenoproteome: priorities in the hierarchy and different levels of selenium homeostasis in the brain of selenium-deficient rats.

The application of radionuclides for the localization of essential trace elements in vivo and the characterization of their binding proteins is a story of intermittently made improvements of the techniques used for their detection. In this study we present the use of neutron activation analysis and different autoradiographic imaging methods including real-time digital autoradiography to reveal new insights in the hierarchy of selenium homeostasis. Selenoproteins containing the essential trace element selenium play important roles in the CNS. Although the CNS does not show the highest selenium concentration in the case of selenium-sufficient supply in comparison with other organs, it shows a high priority for selenium uptake and retention in the case of dietary selenium deficiency. To characterize the hierarchy of selenium supply in the brain, in vivo radiotracer labeling with (75)Se in rats with different selenium status was combined with autoradiographic detection of (75)Se in brain tissue sections and (75)Se-labeled selenoproteins after protein separation by two-dimensional gel electrophoresis. This study demonstrates significant differences in the uptake of (75)Se into the brain of rats with different selenium status. A brain region-specific uptake pattern of the radiotracer (75)Se in selenium-deficient rats could be revealed and the CSF was identified as a key part of the brain selenium homeostasis.

The role of selenite on microglial migration.

Oxidative brain damage, such as excitotoxicity and stroke, leads to primary neuronal destruction. The primary damage is further potentiated by macrophages and microglial cells, which are attracted and invade into the zone of damage resulting in secondary neuronal death. Since the essential trace element selenium has anti-inflammatory properties, we analyzed the effects of selenium on these inflammatory cells. Here, we show that the essential trace element selenium abrogates the stress-induced migration of microglial cells. Thus, the antimigratory effects of selenium may attenuate the secondary cell death cascade by preventing microglial invasion.

Selenium and brain function: a poorly recognized liaison.

Molecular biology has recently contributed significantly to the recognition of selenium (Se)2 and Se-dependent enzymes as modulators of brain function. Increased oxidative stress has been proposed as a pathomechanism in neurodegenerative diseases including, among others, Parkinson's disease, stroke, and epilepsy. Glutathione peroxidases (GPx), thioredoxin reductases, and one methionine-sulfoxide-reductase are selenium-dependent enzymes involved in antioxidant defense and intracellular redox regulation and modulation. Selenium depletion in animals is associated with decreased activities of Se-dependent enzymes and leads to enhanced cell loss in models of neurodegenerative disease. Genetic inactivation of cellular GPx increases the sensitivity towards neurotoxins and brain ischemia. Conversely, increased GPx activity as a result of increased Se supply or overexpression ameliorates the outcome in the same models of disease. Genetic inactivation of selenoprotein P leads to a marked reduction of brain Se content, which has not been achieved by dietary Se depletion, and to a movement disorder and spontaneous seizures. Here we review the role of Se for the brain under physiological as well as pathophysiological conditions and highlight recent findings which open new vistas on an old essential trace element.

Molecular actions of selenium in the brain: neuroprotective mechanisms of an essential trace element.

In addition to acting as an essential nutrient for the immune system and overall body function, it is apparent that selenium also plays a critical role in the operation of the nervous system. Selenium itself is a constituent of selenoproteins, which are primarily involved in antioxidant function and redox status. However, apart from its covalent incorporation into these proteins, selenium also performs neuroprotective actions independent of translational processes. Furthermore, low selenium intake has detrimental effects on proper brain function, such as epileptic episodes and neuronal cell death, which have, in turn, been shown to be mitigated by higher selenium levels. Understanding the mechanisms of selenium action will be crucial to determining its potential as a preventive and therapeutic agent against excitatory brain damage.

Selenium deficiency increases susceptibility to glutamate-induced excitotoxicity.

Excitotoxic brain lesions, such as stroke and epilepsy, lead to increasing destruction of neurons hours after the insult. The deadly cascade of events involves detrimental actions by free radicals and the activation of proapoptotic transcription factors, which finally result in neuronal destruction. Here, we provide direct evidence that the nutritionally essential trace element selenium has a pivotal role in neuronal susceptibility to excitotoxic lesions. First, we observed in neuronal cell cultures that addition of selenium in the form of selenite within the physiological range protects against excitotoxic insults and even attenuates primary damage. The neuroprotective effect of selenium is not directly mediated via antioxidative effects of selenite but requires de novo protein synthesis. Gel shift analysis demonstrates that this effect is connected to the inhibition of glutamate-induced NF-kappaB and AP-1 activation. Furthermore, we provide evidence that selenium deficiency in vivo results in a massive increase in susceptibility to kainate-induced seizures and cell loss. These findings indicate the importance of selenium for prevention and therapy of excitotoxic brain damage.