Search

• Cuprizone affects inflammatory and myelin gene expression in vivo. • Treatment with etazolate does not restore the level of gene expression upon demyelination. • Spatial memory evaluated by Y-maze is not affected by cuprizone and/or etazolate treatment. • Etazolate improves locomotor function following demyelination. Demyelination is a well-known pathological process in CNS disorders such as multiple sclerosis (MS). It provokes progressive axonal degeneration and functional impairments and no efficient therapy is presently available to combat such insults. Recently, we have shown that etazolate, a pyrazolopyridine compound and an α-secretase activator, was able to promote myelin protection and remyelination after cuprizone (CPZ)-induced acute demyelination in C57Bl/6 mice. In continuation of this work, here we have further investigated the effects of etazolate treatment after acute cuprizone-induced demyelination at the molecular level (expression of myelin genes Plp , Mbp and Mag and inflammatory markers Il-1β, Tnf-α) and at the functional level (locomotor and spatial memory skills) in vivo. To this end, we have employed two protocols which consists of administering etazolate (10 mg/kg/d) for a period of 2 weeks either during (Protocol #1) or after (Protocol #2) 5-weeks of CPZ-induced demyelination. At the molecular level, we observed that CPZ intoxication altered inflammatory and myelin gene expression and it was not restored with either of the etazolate treatment protocols. At the functional level, the locomotor activity was impaired after 3-weeks of CPZ intoxication (Protocol #1) and our data indicates a modest but beneficial effect of etazolate treatment. Spatial memory evaluated was not affected either by CPZ intake or etazolate treatment in both protocols. Altogether, this study shows that the beneficial effect of etazolate upon demyelination does not occur at the gene expression level at the time points studied. Furthermore, our results also highlight the difficulty in revealing functional sequelae following CPZ intoxication. [ABSTRACT FROM AUTHOR]

An increase in central nervous system (CNS) remyelination and a decrease in CNS inflammation are important steps to halt the progression of multiple sclerosis (MS). RNS60 is a bioactive aqueous solution generated by subjecting normal saline to Taylor–Couette–Poiseuille flow under elevated oxygen pressure. Recently we have demonstrated that RNS60 exhibits anti-inflammatory properties. Here, we describe promyelinating property of RNS60. RNS60, but not normal saline (NS), RNS10.3 (TCP-modified saline without excess oxygen) or PNS60 (saline containing excess oxygen without TCP modification), stimulated the expression of myelin-specific genes and proteins (myelin basic protein, MBP; myelin oligodendrocyte glycoprotein, MOG and proteolipid protein, PLP) in primary mouse oligodendroglia and mixed glial cells. While investigating the mechanisms, we found that RNS60 treatment induced the activation of cAMP response element binding protein (CREB) in oligodendrocytes, ultimately leading to the recruitment of CREB to the promoters of myelin-specific genes. Furthermore, activation of type 1A p110β/α, but not type 1B p110γ, phosphatidylinositol-3 (PI-3) kinase by RNS60 together with abrogation of RNS60-mediated activation of CREB and upregulation of myelin genes by LY294002 (a specific inhibitor of PI-3 kinase) suggest that RNS60 upregulates the activation of CREB and the expression of myelin-specific molecules in oligodendrocytes via activation of PI3 kinase. These results highlight a novel promyelinating property of RNS60, which may be of benefit for MS and other demyelinating disorders. [ABSTRACT FROM AUTHOR]

MiR-21 is a microRNA implicated in cancer, development, and cardiovascular diseases and expressed in the central nervous system (CNS), especially after injury. However, the cellular expression of miR-21 in the adult CNS has not been clearly established either in mice or human subjects, while its alteration in psychiatric disorders is unknown. MiR-21 expression was characterized in reporter mice expressing β-galactosidase (LacZ) under the endogenous miR-21 promoter (miR-21/LacZ). Brain co-localization of miR-21/LacZ with specific neural markers was examined by double immunofluorescence in reporter mice, while extent of immunostaining for myelin basic protein and PDGFRα was determined in miR-21 knockout and wild-type mice. Levels of miR-21, and mRNAs of selected miR-21 targets, miR-21 regulator STAT3 and myelin-related proteins were measured by qRT-PCR in the white matter (WM) adjacent to the left postmortem orbitofrontal cortex (OFC) of human subjects with major depressive disorder (MDD), alcoholism, comorbid MDD plus alcoholism (MDA) and non-psychiatric control subjects. MiR-21/LacZ was highly expressed in cell bodies of WM and myelinated portions of gray matter (GM). Labeled cell bodies were identified as oligodendrocytes, while miR-21/LacZ was barely detectable in other cell types. MiR-21, as well as the mRNAs of several myelin-related proteins, were reduced in the WM of subjects with MDD and alcoholism. MiR-21 positively correlated with mRNA of myelin-related proteins and astrocytic GFAP. High expression of miR-21 in adult oligodendrocytes and the correlation of miR-21 decrease with mRNA of some myelin proteins, regulator STAT3, and oligodendrocyte-related transcription factors suggest an involvement of miR-21 in WM alterations in depression and alcoholism. [ABSTRACT FROM AUTHOR]

Aims: Paraquat (PQT), a redox-active herbicide, is a free radical-producing molecule, causing damage particularly to the nervous system; thus, it is employed as an animal model for Parkinson's disease. However, its impact on peripheral nerve demyelination is still unknown. Our aim is to decipher the influence of PQT-induced reactive oxygen species (ROS) production on peripheral myelin. Results: We report that PQT provokes severe locomotor and sensory defects in mice. PQT elicited an oxidative stress in the nerve, resulting in an increase of lipid peroxidation and protein carbonylation, despite the induction of nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent antioxidant defenses. We observed a dramatic disorganization of myelin sheaths in the sciatic nerves, dysregulation of myelin gene expression, and aggregation of myelin proteins, a hallmark of demyelination. PQT altered myelin gene expression via liver X receptor (LXR) signaling, a negative regulator of peripheral myelin gene expression through its dialog with the Wnt/β-catenin pathway. PQT prevented β-catenin binding on myelin gene promoters, resulting in the inhibition of Wnt/β-catenin-dependent myelin gene expression. Wnt pathway activation by LiCl dampened the deleterious effects of PQT. LiCl blocked PQT-induced oxidative stress and reduced Schwann cell death. LiCl+PQT-treated mice had normal sensorimotor behaviors and a usual nerve structure. Innovation: We reveal that PQT damages the sciatic nerve by generating an oxidative stress, dysregulating LXR and Wnt/β-catenin pathways. The activation of Wnt signaling by LiCl reduced the deleterious effects of PQT on the nerve. Conclusion: We demonstrate that PQT instigates peripheral nerve demyelinating neuropathies by enhancing ROS production and deregulating LXR and Wnt pathways. Stimulating Wnt pathway could be a therapeutic strategy for neuropathy treatment. Antioxid. Redox Signal. 27, 168-183. [ABSTRACT FROM AUTHOR]

Nerve injury triggers the conversion of myelin and non-myelin (Remak) Schwann cells to a cell phenotype specialized to promote repair. Distal to damage, these repair Schwann cells provide the necessary signals and spatial cues for the survival of injured neurons, axonal regeneration and target reinnervation. The conversion to repair Schwann cells involves de-differentiation together with alternative differentiation, or activation, a combination that is typical of cell type conversions often referred to as (direct or lineage) reprogramming. Thus, injury-induced Schwann cell reprogramming involves down-regulation of myelin genes combined with activation of a set of repair-supportive features, including up-regulation of trophic factors, elevation of cytokines as part of the innate immune response, myelin clearance by activation of myelin autophagy in Schwann cells and macrophage recruitment, and the formation of regeneration tracks, Bungner's bands, for directing axons to their targets. This repair programme is controlled transcriptionally by mechanisms involving the transcription factor c-Jun, which is rapidly up-regulated in Schwann cells after injury. In the absence of c-Jun, damage results in the formation of a dysfunctional repair cell, neuronal death and failure of functional recovery. c-Jun, although not required for Schwann cell development, is therefore central to the reprogramming of myelin and non-myelin (Remak) Schwann cells to repair cells after injury. In future, the signalling that specifies this cell requires further analysis so that pharmacological tools that boost and maintain the repair Schwann cell phenotype can be developed. [ABSTRACT FROM AUTHOR]

Myelination of Schwann cells (SCs) is critical for the success of peripheral nerve regeneration, and biomaterials that can promote SCs' neurotrophin secretion as scaffolds are beneficial for nerve repair. Here we present a biomaterials-approach, specifically, a highly tunable conductive biodegradable flexible polyurethane by polycondensation of poly(glycerol sebacate) and aniline pentamer, to significantly enhance SCs' myelin gene expression and neurotrophin secretion for peripheral nerve tissue engineering. SCs are cultured on these conductive polymer films, and the biocompatibility of these films and their ability to enhance myelin gene expressions and sustained neurotrophin secretion are successfully demonstrated. The mechanism of SCs' neurotrophin secretion on conductive films is demonstrated by investigating the relationship between intracellular Ca 2+ level and SCs' myelination. Furthermore, the neurite growth and elongation of PC12 cells are induced by adding the neurotrophin medium suspension produced from SCs-laden conductive films. These data suggest that these conductive degradable polyurethanes that enhance SCs' myelin gene expressions and sustained neurotrophin secretion perform great potential for nerve regeneration applications. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome (PRRS) has devastated pig industries worldwide for many years. It is caused by a small RNA virus (PRRSV), which targets almost exclusively pig monocytes or macrophages. In the present study, five SAGE (serial analysis of gene expression) libraries derived from 0 hour mock-infected and 6, 12, 16 and 24 hours PRRSV-infected porcine alveolar macrophages (PAMs) produced a total 643,255 sequenced tags with 91,807 unique tags. Differentially expressed (DE) tags were then detected using the Bayesian framework followed by gene/mRNA assignment, arbitrary selection and manual annotation, which determined 699 DE genes for reactome analysis. The DAVID, KEGG and REACTOME databases assigned 573 of the DE genes into six biological systems, 60 functional categories and 504 pathways. The six systems are: cellular processes, genetic information processing, environmental information processing, metabolism, organismal systems and human diseases as defined by KEGG with modification. Self-organizing map (SOM) analysis further grouped these 699 DE genes into ten clusters, reflecting their expression trends along these five time points. Based on the number one functional category in each system, cell growth and death, transcription processes, signal transductions, energy metabolism, immune system and infectious diseases formed the major reactomes of PAMs responding to PRRSV infection. Our investigation also focused on dominant pathways that had at least 20 DE genes identified, multi-pathway genes that were involved in 10 or more pathways and exclusively-expressed genes that were included in one system. Overall, our present study reported a large set of DE genes, compiled a comprehensive coverage of pathways, and revealed system-based reactomes of PAMs infected with PRRSV. We believe that our reactome data provides new insight into molecular mechanisms involved in host genetic complexity of antiviral activities against PRRSV and lays a strong foundation for vaccine development to control PRRS incidence in pigs. [ABSTRACT FROM AUTHOR]

Abstract: In submammalian animals including chicks, the retina contains oligodendrocytes (OLs), and axons in the optic fiber layer are wrapped with compact myelin within the retina; however, the expression of myelin genes in the chick retina has not been demonstrated yet. In the present study, we examined the expression of three myelin genes (proteolipid protein, PLP; myelin basic protein, MBP; cyclic nucleotide phosphodiesterase, CNP) and PLP in the developing chick retina, in comparison to the localization of Mueller cells. In situ hybridization demonstrated that all three myelin genes began to be expressed at E14 in the chick embryo retina. They are mostly restricted to the ganglion cell layer and the optic fiber layer, with a few exceptions in the inner nuclear layer where Mueller cells reside; however, PLP mRNA+ cells do not express glutamine synthetase, or vice versa. The present results elucidate that myelin genes are expressed only by OLs that are mostly localized in the innermost layer of the developing chick retina. [Copyright &y& Elsevier]

Despite the importance of myelin for the rapid conduction of action potentials, the molecular bases of oligodendrocyte differentiation and central nervous system (CIMS) myelination are still incompletely understood. Recent results have greatly advanced this understanding, identifying new transcriptional regulators of myelin gene expression, elucidating vital roles for microRNAs in controlling myelination, and clarifying the extracellular signaling mechanisms that orchestrate the development of myelin. Studies have also demonstrated an unexpected level of plasticity of myelin in the adult CNS. These recent advances provide new insight into how remyelination may be stimulated in demyelinating disorders such as multiple sclerosis. [ABSTRACT FROM AUTHOR]

The myelin sheath allows axons to conduct action potentials rapidly in the vertebrate nervous system. Axonal signals activate expression of specific transcription factors, including Oct6 and Krox20, that initiate myelination in Schwann cell. Elevation of cyclic adenosine monophosphate (cAMP) can mimic axonal contact in vitro, but the mechanisms that regulate cAMP levels in vivo are unknown. Using mutational analysis in zebrafish, we found that the G protein-coupled receptor Gpr126 is required autonomously in Schwann cells for myelination. In gpr126 mutants, Schwann cells failed to express oct6 and krox20 and were arrested at the promyelinating stage. Elevation of cAMP in gpr126 mutants but not krox20 mutants, could restore myelination. We propose that Gpr126 drives the differentiation of promyelinating Schwann cells by elevating cAMP levels, thereby triggering Oct6 expression and myelination. [ABSTRACT FROM AUTHOR]

The promyelocytic leukemia zinc-finger protein (PLZF) is a transcription factor and c-kit is a receptor tyrosine kinase associated with human disease, particularly in hematopoietic cells. MicroRNAs (miRs) are post-transcriptional regulators of gene expression, and c-kit has been described as a target of miRs-221 and -222 in erythropoiesis. In the present study, we identified c-kit as a target of PLZF in normal and leukemic cells. Particularly, in erythropoietic (E) culture of CD34+ progenitors, PLZF is downregulated, whereas c-kit expression at both the mRNA and protein levels inversely increases during the first days of E differentiation. In functional experiments, PLZF transfection induces c-kit downregulation, inhibits E proliferation and delays differentiation, whereas PLZF knockdown induces opposite effects, independently of miRs-221 and -222 expression. The inverse correlation between PLZF and c-kit expression was found in normal CD34+38+/− hematopoietic progenitor/stem cells and in acute myeloid leukemias of M0/M1 French–American–British subtypes, suggesting that the control of PLZF on c-kit expression may be crucial at the level of the stem cell/progenitor compartment. Altogether, our data indicate a new mechanism of regulation of c-kit expression that involves a transcriptional control by PLZF in CD34+ cells and early erythropoiesis.Oncogene (2009) 28, 2276–2288; doi:10.1038/onc.2009.87; published online 4 May 2009 [ABSTRACT FROM AUTHOR]

Abstract: The mitogen-activated protein kinase organizer 1 (Morg1) has been recently identified as modular scaffold regulating ERK signaling. Morg1 also attenuates expression of the hypoxia-inducible factor-1α (HIF-1α) by activating or stabilizing of prolyl-hydroxylase 3 (PHD3). Here we demonstrate for the first time that Morg1 is expressed in the human brain in neurons, glial cells, and blood vessel walls. Immunohistochemistry, RT real-time PCR and western blotting indicated that Morg1 expression is reduced in human brain tissue with ischemic damage. Moreover, reactive astrocytes in the surrounding brain tissue showed strong Morg1 expression. Since hypoxic adaptation with enhancing HIF-1α expression can engage a genetic program leading to profound sparing of brain tissue and enhanced recovery of function, down-regulation of Morg1 expression in the ischemic brain may be viewed as an intrinsic mechanism to stimulate this response. On the other hand, upregulation of Morg1 in astrocytes surrounding the penumbra may counteract this hypoxic adaptation. [Copyright &y& Elsevier]

Abstract: N-methyl-d-aspartate (NMDA) receptor-induced activation of extracellular signal-related protein kinase (Erk) plays important roles in various neuronal functions including long-term potentiation (LTP). Son of sevenless (Sos) proteins have been implicated in NMDA-induced Erk activation in neurons of young mice. However, contribution of each of the two Sos isoforms, Sos1 and Sos2, has not been clarified. In this study, Sos2 involvement in NMDA-induced Erk activation was examined. We observed no defect in Erk phosphorylation induced by NMDA treatment of cortical neuronal cultures from Sos2−/− newborn mice. Moreover, theta-burst-induced LTP induction in the hippocampus of Sos2−/− mice was also normal. Finally, Erk activation by either depolarization or BDNF treatment was also normal in cultured neurons from Sos2 knockout mice. These results imply that Sos1 is the major regulator of these well-known neuronal Sos functions and suggest that a novel function for Sos2 in neurons remains to be determined. [Copyright &y& Elsevier]

Abstract: We investigated the expression of the semaphorin family member, Sema3D, in the developing dorsal root ganglia of the rat. Sema3D expression was observed in a subpopulation of dorsal root ganglion (DRG) neurons. The expression peaked at E15 and thereafter it declined. The change in Sema3D expression between E13 and E20 was analyzed by comparison to the expression of TrkA, TrkC and Neuropilin-1 by in situ hybridization. The expression pattern of Sema3D in DRG was similar to that of TrkC and was different from that of TrkA or Neuropilin-1. Double immunohistochemical analysis revealed that Sema3D expression was confined to neurons that expressed TrkC and Runx3, which mediate proprioception, but not to nociceptive neurons that express TrkA. Functionally distinct DRG neurons have different projection patterns in the spinal cord, therefore, Sema3D may regulate the axonal navigation of the large diameter DRG neurons. [Copyright &y& Elsevier]

A signal transduction pathway (STP) is a cascade composed of a series of signal transferring steps, which often activate one or more transcription factors (TFs) to control the transcription of target genes. Understanding signaling pathways is important to our understanding of the molecular mechanisms of disease. Many condition-annotated pathways have been deposited in public databases. However, condition-annotated pathways are far from complete, considering the large number of possible conditions. Computational methods to assist in the identification of conditionally activated pathways are greatly needed. In this paper, we propose an efficient method to identify conditionally activated pathway segments starting from the identification of conditionally activated TFs, by incorporating protein-DNA binding data, gene expression data and protein interaction data. Applying our methods on several microarray datasets, we have discovered many significantly activated TFs and their corresponding pathway segments, which are supported by evidence in the literature. [ABSTRACT FROM AUTHOR]

How to combine heterogeneous data sources for reliable prediction of transcriptional regulation is a challenge. Here we present an easy but powerful method to integrate Chromatin immunoprecipitation (ChIP)-chip and knock-out data. Since these two types of data provide complementary (physical and functional) information about transcription, the method combining them is expected to achieve high detection rates and very low false positive rates. We try to seek the optimal integration of these two data using hypergeometric distribution. We evaluate our method on yeast data and compare our predictions with YEASTRACT, high-quality ChIP-chip data, and literature. The results show that even using low-quality ChIP-chip data, our method uncovers more relations than those inferred before from high-quality data. Furthermore our method achieves a low false positive rate. We find experimental and computational evidence in literature for most transcription factor (TF)-gene relations uncovered by our method. [ABSTRACT FROM AUTHOR]

Limited data are available in humans regarding the molecular biology of hibernating myocardium (HM). The aim of this study was to identify gene expression patterns distinctive for human HM. We compared in patients with ischemic left ventricular dysfunction the gene expression profile of myocardial biopsies from HM ( n = 5), as identified by positron emission tomography, with expression profiles of matched biopsies from normally perfused myocardium by using cDNA array analysis. Gene-specific polymerase chain reaction of selected genes and immunohistochemical staining of desmoplakin were used to validate our technical approach. Of 4171 transcripts examined, we identified 86 to be differentially expressed. Compared to normally perfused myocardium, 21 genes showed an increased expression and 65 genes a decreased expression in HM. Functional clustering revealed changes in the expression of genes associated with transcription, protein modification and phosphorylation, regulation of apoptosis, and intercellular communication. Besides the reported upregulation of β-adrenergic receptor kinase-1 in heart failure, we observed new gene expression patterns, such as the upregulation of fas-activated serine/threonine kinase (FAST) or reduced expression of desmoplakin. Downregulation of desmoplakin in cardiomyocytes from HM was also seen on the protein level. Gene expression analysis provided novel insights into the pathophysiological changes of HM. Impaired intercellular communication as suggested by decreased expression of desmoplakin may be an important feature of contractile dysfunction in HM. [ABSTRACT FROM AUTHOR]

An important question in neuropathology involves determining the antigens that are targeted during demyelinating disease. Viral infection of the central nervous system (CNS) leads to T-cell responses that can be protective as well as pathogenic. In the Theiler’s murine encephalomyelitis virus (TMEV) model of demyelination it is known that the immune response to the viral capsid protein 2 (VP2) is critical for disease pathogenesis. This study shows that expressing the whole viral capsid VP2 or the minimal CD8-specific peptide VP2121-130 as “self” leads to a loss of VP2-specific immune responses. Loss of responsiveness is caused by T cell-specific tolerance, as VP2-specific antibodies are generated in response to infection. More importantly, these mice lose the CD8 T-cell response to the immunodominant peptide VP2121-130, which is critical for the development of demyelinating disease. The transgenic mice fail to clear the infection and develop chronic demyelinating disease in the spinal cord white matter. These findings demonstrate that T-cell responses can be removed by transgenic expression and that lack of responsiveness alters viral clearance and CNS pathology. This model will be important for understanding the mechanisms involved in antigen-specific T-cell deletion and the contribution of this response to CNS pathology. [ABSTRACT FROM AUTHOR]

This study identifies novel mechanisms of Hes5 function in developmental myelination. We report here upregulation of myelin gene expression in Hes5−/− mice compared to wild-type siblings and downregulation in overexpressing progenitors. This effect was only partially explained by the ability to regulate the levels of Mash1 and bind to N boxes in myelin promoters, as deletion of the DNA-binding domain of Hes5 did not suppress its inhibitory role on myelin gene expression. Novel mechanisms of Hes5 function in the oligodendrocyte lineage include the regulation of feedback loops with the cell-specific transcriptional activator Sox10. In progenitors with low levels of Sox10, Hes5 further decreases the bioavailability of this protein by transcriptional inhibition and direct sequestration of this activator. Increasing levels of Sox10 in progenitors, in turn, bind to Hes5 and titrate out its inhibitory effect by sequestration and displacement of the repressive complexes from myelin promoters. Thus, Hes5-dependent modulation of myelin gene expression involves old players (i.e. Mash1) and novel mechanisms of transcriptional regulation that include cell-specific regulatory loops with transcriptional activators (i.e. Sox10). [ABSTRACT FROM AUTHOR]

Abstract: Multiple sclerosis (MS) is a chronic autoimmune demyelinating disorder of the central nervous system (CNS) of unknown etiology. Several studies have shown that demyelination in MS is caused by proinflammatory mediators which are released by perivascular infiltrates and/or activated glial cells. To understand if proinflammatory mediators such as IL (interleukin)-1β and TNF (tumor necrosis factor)-α are capable of modulating the expression of myelin-specific genes, we investigated the effect of these cytokines on the expression of myelin basic protein (MBP), 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase), myelin oligodendrocyte glycoprotein (MOG), and proteolipid protein (PLP) in human primary oligodendrocytes. Interestingly, both IL-1β and TNF-α markedly inhibited the expression of MOG, CNPase, and PLP but not MBP, the effect that was blocked by antioxidants such as N-acetylcysteine (NAC) and pyrrolidine dithiocarbamate (PDTC). Consistently, oxidants and prooxidants like H2O2 and diamide also markedly inhibited the expression of MOG, CNPase, and PLP. Furthermore, both IL-1β and TNF-α induced the production of H2O2. Taken together, these studies suggest that proinflammatory cytokines inhibit the expression of myelin genes in human primary oligodendrocytes through the alteration of cellular redox. [Copyright &y& Elsevier]

Recent studies suggest that specific neural basic helix-loop-helix (HLH; i.e., Olig1 and Olig2, Mash1), associated inhibitory HLH (i.e., Id2 and Id4), high-mobility group domain (i.e., Sox10), and homeodomain(i.e., Nkx2.2) transcription factors are involved in oligodendrocyte (OL) lineage specification and progressive stages of maturation including myelination. However, the developmental interplay among these lineage-selective determinants, in a cell- and maturational stage-specific context, has not yet been defined. We show here in vivo and in vitro developmental expression profiles for these distinct classes of transcriptional regulators of OLs. We show that progressive stages of OL lineage maturation are characterized by dynamic changes in the subcellular distribution of these transcription factors and by different permutations of combinatorial transcriptional codes. Transient transfections of these precise combinatorial codes with a luciferase reporter gene driven by the myelin basic protein promoter define how changes in the molecular composition of these transcriptional complexes modulate myelin gene expression. Our overall findings suggest that the dynamic interplay between developmental stage-specific classes of transcriptional activators and associated inhibitory factors orchestrate myelin gene expression during terminal maturation of the mammalian CNS. [ABSTRACT FROM AUTHOR]

In this study, the role of exogenous fatty acids in the regulation of proteolipid protein (PLP) gene expression was investigated using the following model culture system: C6 glioma cells expressing the green-fluorescent protein (eGFP) driven by different segments of PLP promoter. Eicosapentanoic acid (EPA; 20:5 n-3), but not arachidonic acid (AA; 20:4 n-6), induced a significant increase in medium fluorescence intensity (MFI) determined by fluorescence-activated cell sorting (FACS). The induction of PLP promoter was time-dependent showing maximal activity between 24 and 48 h after EPA exposure. PLP promoter activation was dependent on fatty acid concentration, with maximum activation at 200 μM. Northern blot analysis confirmed the fluorescence data in C6 cells incubated with EPA. Furthermore, this treatment increased the adenylyl cyclase-cyclic AMP (cAMP) levels and the mitogen-activated protein kinase (MAPK) activation in C6 cells. PLP promoter activity was inhibited by pre-treatment with H89 (protein kinase A (PKA) inhibitor), but not with PD98059 (MAPK inhibitor), suggesting that EPA stimulates the expression of PLP via cAMP-mediated pathways. [Copyright &y& Elsevier]

: PurposeThe aim of this study was to assess changes in oligodendrocytes (OL), myelin gene expression, and their relationships with late demyelination after irradiation.: Methods and materialsAdult rats were given single doses of 8 or 22 Gy to the cervical spinal cord. Immunohistochemistry for APC or GST-π was used to identify OL. Changes in myelin gene expression were assessed using RT-PCR for proteolipid protein (PLP). Luxol fast blue staining was used to assess demyelination. CNP-βgeo transgenic mice were used to confirm some of the results of the rat model. Cells of the oligodendroglial lineage in these animals express β-galactosidase (β-gal).: ResultsEarly apoptosis of APC, GST-π, and β-galactosidase positive cells was observed in the spinal cord of rats and CNP-βgeo mice. At 24 h after 22 Gy, there was a significant decrease in OL density. Cell density continued to decline thereafter after both 8 and 22 Gy, and a reduction in PLP expression was observed at 4–5 weeks. A further decrease in PLP expression was seen beginning at 18 weeks after 22 Gy only. Demyelination was observed at 19 weeks after 22 Gy.: ConclusionsApoptosis of OL and changes in OL density and PLP gene expression were observed early after both 8 and 22 Gy. This suggests that these early changes are unlikely to be directly related to the late demyelination observed. [Copyright &y& Elsevier]

Abstract: There are no reports that hypothalamus can directly affect the expression of neuron-related genes and immune-related genes in liver. We identified genes of which expression profiles showed significant modulation in rat liver after ventromedial hypothalamic (VMH) lesions. Total RNA was extracted, and differences in the gene expression profiles between rats at day 3 after VMH lesioning and sham-VMH lesioned rats were investigated using DNA microarray analysis. The result revealed that VMH lesions regulated the genes that were involved in functions related to neuronal development and immunofunction in the liver. Real-time PCR also confirmed that gene expression of SULT4A1 was upregulated, but expression of ACSL1 and CISH were downregulated at day 3 after VMH lesions. VMH lesions may change the expression of neuron-related genes and immune-related genes in rat liver. [Copyright &y& Elsevier]

SOX10 is a Sry-related high mobility (HMG)-box transcriptional regulator that promotes differentiation of neural crest precursors into Schwann cells, oligodendrocytes, and melanocytes. Myelin, formed by Schwann cells in the peripheral nervous system, is essential for propagation of nerve impulses. SWI/SNF complexes are ATP dependent chromatin remodeling enzymes that are critical for cellular differentiation. It was recently demonstrated that the BRG1 subunit of SWI/SNF complexes activates SOX10 expression and also interacts with SOX10 to activate expression of OCT6 and KROX20, two transcriptional regulators of Schwann cell differentiation. To determine the requirement for SWI/SNF enzymes in the regulation of genes that encode components of myelin, which are downstream of these transcriptional regulators, we introduced SOX10 into fibroblasts that inducibly express dominant negative versions of the SWI/SNF ATPases, BRM or BRG1. Dominant negative BRM and BRG1 have mutations in the ATP binding site and inhibit gene activation events that require SWI/SNF function. Ectopic expression of SOX10 in cells derived from NIH 3T3 fibroblasts led to the activation of the endogenous Schwann cell specific gene, myelin protein zero (MPZ) and the gene that encodes myelin basic protein (MBP). Thus, SOX10 reprogrammed these cells into myelin gene expressing cells. Ectopic expression of KROX20 was not sufficient for activation of these myelin genes. However, KROX20 together with SOX10 synergistically activated MPZ and MBP expression. Dominant negative BRM and BRG1 abrogated SOX10 mediated activation of MPZ and MBP and synergistic activation of these genes by SOX10 and KROX20. SOX10 was required to recruit BRG1 to the MPZ locus. Similarly, in immortalized Schwann cells, BRG1 recruitment to SOX10 binding sites at the MPZ locus was dependent on SOX10 and expression of dominant negative BRG1 inhibited expression of MPZ and MBP in these cells. Thus, SWI/SNF enzymes cooperate with SOX10 to directly activate genes that encode components of peripheral myelin. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is a chronic autoimmune demyelinating disorder of the central nervous system (CNS) with unknown etiology. Several studies have shown that demyelination in MS is caused by proinflammatory mediators and nitric oxide (NO), which is released by perivascular infiltrates and/or activated glial cells. Both endogenous NO released by microglia and astrocytes; and NO generated from exogenous NO donors are known to induce oligodendrocytes death. However, the molecular mechanism of oligodendroglial death is poorly understood. Here we explore the role of NO in modulating the expression of myelin-specific genes that leads to oligodendroglial death. We investigated the effect of NO on the expression of myelin basic protein (MBP), 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), myelin oligodendrocyte glycoprotein (MOG), and proteolipid protein (PLP) in human primary oligodendrocytes. Combination of IFN-γ and bacterial lipopolysaccharide (LPS) or double stranded RNA in the form of polyIC induced the production of NO and decreased the expression of myelin gene in human fetal mixed glial cultures. Either a scavenger of NO (PTIO) or an inhibitor of inducible nitric oxide synthase (L-NIL) abrogated (LPS+IFN-γ)- and polyIC-mediated suppression of myelin genes in human mixed glial cells. The role of NO was further corroborated by the inhibition of myelin gene expression in purified human oligodendroglia by several NO donors including SNP, NOC-7, SIN-1, and SNAP. This study illustrates a novel biological role of NO in down-regulating the expression of myelin genes preceding the death of oligodendrocytes.