Pivotal role of choline metabolites in remyelination.

Neuroprotective approaches for central nervous system regeneration have not been successful in clinical practice so far and compounds that enhance remyelination are still not available for patients with multiple sclerosis. The objective of this study was to determine potential regenerative effects of the substance cytidine-5'-diphospho (CDP)-choline in two different murine animal models of multiple sclerosis. The effects of exogenously applied CDP-choline were tested in murine myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis. In addition, the cuprizone-induced mouse model of de- and remyelination was used to specifically test the hypothesis that CDP-choline directly increases remyelination. We found that CDP-choline ameliorated the disease course of experimental autoimmune encephalomyelitis and exerted beneficial effects on myelin, oligodendrocytes and axons. After cuprizone-induced demyelination, CDP-choline effectively enhanced myelin regeneration and reversed motor coordination deficits. The increased remyelination arose from an increase in the numbers of proliferating oligodendrocyte precursor cells and oligodendrocytes. Further in vitro studies suggest that this process is regulated by protein kinase C. We thus identified a new mechanism to enhance central nervous system remyelination via the choline pathway. Due to its regenerative action combined with an excellent safety profile, CDP-choline could become a promising substance for patients with multiple sclerosis as an add-on therapy.

Spatial and temporal profiles of growth factor expression during CNS demyelination reveal the dynamics of repair priming.

Demyelination is the cause of disability in various neurological disorders. It is therefore crucial to understand the molecular regulation of oligodendrocytes, the myelin forming cells in the CNS. Growth factors are known to be essential for the development and maintenance of oligodendrocytes and are involved in the regulation of glial responses in various pathological conditions. We employed the well established murine cuprizone model of toxic demyelination to analyze the expression of 13 growth factors in the CNS during de- and remyelination. The temporal mRNA expression profile during demyelination and the subsequent remyelination were analyzed separately in the corpus callosum and cerebral cortex using laser microdissection and real-time PCR techniques. During demyelination a similar pattern of growth factor mRNA expression was observed in both areas with a strong up-regulation of NRG1 and GDNF and a slight increase of CNTF in the first week of cuprizone treatment. HGF, FGF-2, LIF, IGF-I, and TGF-ß1 were up-regulated mainly during peak demyelination. In contrast, during remyelination there were regional differences in growth factor mRNA expression levels. GDNF, CNTF, HGF, FGF-2, and BDNF were elevated in the corpus callosum but not in the cortex, suggesting tissue differences in the molecular regulation of remyelination in the white and grey matter. To clarify the cellular source we isolated microglia from the cuprizone lesions. GDNF, IGF-1, and FGF mRNA were detected in the microglial fraction with a temporal pattern corresponding to that from whole tissue PCR. In addition, immunohistochemical analysis revealed IGF-1 protein expression also in the reactive astrocytes. CNTF was located in astrocytes. This study identified seven different temporal expression patterns for growth factors in white and grey matter and demonstrated the importance of early tissue priming and exact orchestration of different steps during callosal and cortical de- and remyelination.

Lipopolysaccharide delays demyelination and promotes oligodendrocyte precursor proliferation in the central nervous system.

Systemic infection can influence the course in many diseases of the central nervous system (CNS) such as multiple sclerosis (MS), yet the relationship between infection outside the CNS and potential damage and/or protection within the CNS is still not understood. Activation of microglia is a characteristic feature of most CNS autoimmune disorders, including MS, and both protective and degenerative functions of microglia have been proposed. Hence, we analyzed the effects of a systemic inflammatory reaction induced by peripheral treatment with lipopolysaccharide (LPS) on microglial reaction and cuprizone induced de- and remyelination. We found that LPS administration delayed demyelination, which was linked with inhibition of microglial proliferation and reduced numbers of activated microglia. The phenotype of microglia changed as an increase of Toll-like receptor 4 was found. During remyelination, LPS treatment delayed the onset of myelin protein re-expression, but later there was a beneficial effect via an increase of proliferating oligodendrocyte precursor cells (OPC) and mature oligodendrocytes. Moreover, the expression of ciliary neurotrophic factor was increased in response to LPS, a growth factor known to mediate OPC proliferation. Additional experiments showed that the time window to induce LPS effects was limited and associated with the presence of microglia. In conclusion, LPS delayed demyelination and caused beneficial effects on remyelination via increasing the proliferation of OPC. These differences seem to be an effect of LPS induced microglial modulation and indicate that exposure to certain infectious agents within a given time window may be beneficial in promoting tissue repair.

CCL5 induces a pro-inflammatory profile in microglia in vitro.

The chemokine receptors CCR1, CCR2, CCR3, CCR5, and CXCR2 have been found to be expressed on microglia in many neurodegenerative diseases, such as multiple sclerosis and Alzheimer's disease. There is emerging evidence that chemokines, besides chemoattraction, might directly modulate reactive profiles of microglia. To address this hypothesis we have investigated the effects of CCL2, CCL3, CCL5, and CXCL1 on cytokine and growth factor production, NO synthesis, and phagocytosis in non-stimulated and lipopolysaccharide-stimulated primary rat microglia. The respective receptors CCR1, CCR5, and CXCR2 were shown to be functionally expressed on microglia. All tested chemokines stimulated chemotaxis whereas only CCL5 increased NO secretion and attenuated IL-10 as well as IGF-1 production in activated microglia. Based on these findings we propose that besides its chemoattractant function CCL5 has a modulatory effect on activated microglia.

Glatiramer acetate modulates TNF-α and IL-10 secretion in microglia and promotes their phagocytic activity.

Glatiramer acetate (GA) is an approved immunomodulating agent for the treatment of relapsing-remitting multiple sclerosis. Its mode of action is attributed to a T helper cell-type 1 (Th1) to Th2 cytokine shift in T cells. Th2-type GA-reactive T cells migrate into the brain and act suppressive at the sites of inflammation. However, there is increasing evidence that the effect of GA is not confined to T cells. It inhibits broadly the activation of monocytes and induces peritoneal macrophages and monocytes to differentiate into a type 2 antigen-presenting cell (APC) secreting anti-inflammatory cytokines. Thus, we examined whether GA has also direct effects on microglia cells which are involved in modifying/directing the local microenvironment in the central nervous system. Primary rat microglia were purified and cultured under standard conditions. Griess reaction was used to measure one of the stable end products of nitric oxide (NO), nitrite. Tumor necrosis factor (TNF)-alpha and interleukin-10 (IL-10) were measured in the cell culture supernatants using ELISA. Phagocytosis was quantified with a FACS-based assay. Our experiments show that GA directly modulates microglia cells. It promotes the phagocytic activity and increases the secretion of IL-10 while it decreases that of TNFα. In contrast, there was no effect on NO production. GA induces a type 2 APC differentiation of microglia suggesting a general effect on myeloid monocytic cells. Using microglia we report for the first time that GA promotes phagocytosis which could play an important role in removal of debris.

Effects of fumaric acids on cuprizone induced central nervous system de- and remyelination in the mouse.

BACKGROUND: Fumaric acid esters (FAE) are a group of compounds which are currently under investigation as an oral treatment for relapsing-remitting multiple sclerosis. One of the suggested modes of action is the potential of FAE to exert a neuroprotective effect. METHODOLOGY/PRINCIPAL FINDINGS: We have investigated the impact of monomethylfumarate (MMF) and dimethylfumaric acid (DMF) on de- and remyelination using the toxic cuprizone model where the blood-brain-barrier remains intact and only scattered T-cells and peripheral macrophages are found in the central nervous system (CNS), thus excluding the influence of immunomodulatory effects on peripheral immune cells. FAE showed marginally accelerated remyelination in the corpus callosum compared to controls. However, we found no differences for demyelination and glial reactions in vivo and no cytoprotective effect on oligodendroglial cells in vitro. In contrast, DMF had a significant inhibitory effect on lipopolysaccharide (LPS) induced nitric oxide burst in microglia and induced apoptosis in peripheral blood mononuclear cells (PBMC). CONCLUSIONS: These results contribute to the understanding of the mechanism of action of fumaric acids. Our data suggest that fumarates have no or only little direct protective effects on oligodendrocytes in this toxic model and may act rather indirectly via the modulation of immune cells.

Beneficial effects of minocycline on cuprizone induced cortical demyelination.

In this study, we investigated the potential of minocycline to influence cuprizone induced demyelination in the grey and white matter. To induce demyelination C57BL/6 mice were fed with cuprizone for up to 6 weeks and were analysed at different timepoints (week 0, 4, 5, 6). Mice treated with minocycline had less demyelination of the cortex and corpus callosum compared with sham treated animals. In the cortex decreased numbers of activated and proliferating microglia were found after 6 weeks of cuprizone feeding, while there were no significant effects for microglial infiltration of the corpus callosum. In addition to the beneficial effects on demyelination, minocycline prevented from motor coordination disturbance as shown in the beam walking test. For astrogliosis and the numbers of OPC and oligodendrocytes no treatment effects were found. In summary, minocycline treatment diminished the course of demyelination in the grey and white matter and prevented disturbances in motor coordination.

Cerebellar cortical demyelination in the murine cuprizone model.

In multiple sclerosis, demyelination occurs beside the white-matter structures and in the cerebral and cerebellar cortex. We have previously shown that, in the cuprizone model, demyelination is present not only in the corpus callosum but also in the cerebral cortex. Here, we have performed a detailed analysis of the dynamics of de- and remyelination in the cerebellar cortex and white matter at nine timepoints in two cerebellar regions. To induce demyelination, C57BL/6 mice were fed with 0.2% cuprizone for 12 weeks followed by a recovery of 8 weeks. Both cortex and white-matter structures were significantly demyelinated after 12 weeks of cuprizone feeding. Remyelination occurred after withdrawal of cuprizone but was less prominent in the more caudal cerebellar region. Microglia infiltration was prominent in all analyzed cerebellar areas, preceding demyelination by approximately 2-4 weeks, and was delayed in the more caudal cerebellar region. Astrogliosis was also seen but did not reach the extent observed in the cerebrum. In summary, cuprizone feeding provides an excellent model for the investigation of de- and remyelination processes in the cerebellar cortex and white matter. Furthermore, demyelination, microglia and astrocyte changes were different in the cerebellum as compared with the cerebrum, indicating region-dependent pathomechanisms.

Regional differences between grey and white matter in cuprizone induced demyelination.

Cuprizone feeding is a commonly used model to study experimental de- and remyelination, with the corpus callosum being the most frequently investigated white matter tract. We have previously shown that demyelination is also extensive in the cerebral cortex in the cuprizone model. In the current study, we have performed a detailed analysis of the dynamics of demyelination in the cortex in comparison to the corpus callosum. Prominent and almost complete demyelination in the corpus callosum was observed after 4.5-5 weeks of 0.2% cuprizone feeding, whereas complete cortical demyelination was only observed after 6 weeks of cuprizone feeding. Interestingly, remyelination in the corpus callosum occurred even before the termination of cuprizone administration. Accumulation of microglia in the corpus callosum started as early as week 3 reaching its maximum at week 4.5 and was still significantly elevated at week 6 of cuprizone treatment. Within the cortex only a few scattered activated microglial cells were found. Furthermore, the intensity of astrogliosis, accumulation of oligodendrocyte progenitor cells and nestin positive cells differed between the two areas investigated. The time course and dynamics of demyelination differ in the corpus callosum and in the cortex, suggesting different underlying pathomechanisms.

Demyelination of the hippocampus is prominent in the cuprizone model.

In multiple sclerosis demyelination not only affects the white matter, but also the grey matter of the brain. We have previously reported that in the murine cuprizone model for demyelination lesions occur in addition to the corpus callosum also in the neocortex and hippocampus. In the current study, we provide a detailed characterization of hippocampal demyelination in the cuprizone model. Male C57BL/6 mice were challenged with 0.2% cuprizone for 6 weeks. Defined structures within the hippocampus were investigated at week 0 (control), 3, 4, 4.5, 5, 5.5, and 6. Demyelination affected all hippocampal structures analyzed and was complete after 6 weeks of cuprizone treatment. Between the distinct hippocampal structures the temporal pattern of demyelination varied considerably. Furthermore, infiltration of activated microglia as well as astrogliosis was detected. In summary, cuprizone feeding provides a useful model for studying demyelination processes in the mouse hippocampus.

TSPY expression is variably altered in transgenic mice with testicular feminization.

TSPY (testis-specific protein, Y-encoded) genes are expressed in premeiotic germ cells and round spermatids. The topology and timing of TSPY expression, and also its homology to members of the TTSN-family, suggest that TSPY is a proliferation factor for germ cells. There is also evidence for a role of TSPY in the aetiology of testis cancer. TSPY is a candidate for GBY, the elusive gonadoblastoma locus on the human Y chromosome, which is thought to predispose dysgenetic gonads of 46, XY sex-reversed females to develop gonadoblastoma. We have previously generated a TSPY transgenic mouse line (Tg(TSPY)9Jshm) that carries approximately 50 copies of the human TSPY gene on the mouse Y chromosome. In order to elucidate TSPY expression under complete androgen insensitivity and to investigate a possible role of TSPY in gonadal tumorigenesis, we have now generated sex-reversed TSPY transgenic Ar(Tfm) mice hemizygous for the X-linked testicular feminization mutation (Ar(Tfm)). We can show that the TSPY transcript is aberrantly spliced in the testes of TSPY-Ar(Tfm) mice, and that TSPY expression is upregulated by androgen insensitivity in some but not all animals. TSPY transgenic mice showed significantly increased testes weights. In one TSPY transgenic Ar(Tfm) animal, spermatogenesis proceeded beyond meiotic prophase. No tumors of germ cell origin were found in the testes of TSPY-Ar(Tfm) mice. Five out of 46 TSPY transgenic Ar(Tfm) mice, and 3 out of 31 age-related NMRI-Ar(Tfm) controls developed Leydig cell tumors, whereas none of the age-matched Ar(Tfm) mice (n=44) on a wild type background were affected by Leydig cell tumorigenesis.

UBD, a downstream element of FOXP3, allows the identification of LGALS3, a new marker of human regulatory T cells.

Here, we report the identification of the ubiquitin-like gene UBD as a downstream element of FOXP3 in human activated regulatory CD4(+)CD25(hi) T cells (T(reg)). Retroviral transduction of UBD in human allo-reactive effector CD4(+) T helper (T(h)) cells upregulates CD25 and mediates downregulation of IL4 and IL5 expression similar to overexpression of FOXP3. Moreover, UBD impairs T(h) cell proliferation without upregulation of FOXP3 and impairs calcium mobilization. In the presence of ionomycin, overexpression of UBD in T(h) cells leads to the induction of IL1R2 that resemble FOXP3-transduced T(h) cells and naturally derived T(reg) cells. A comparison of the transcriptome of FOXP3- and UBD-transduced T(h) cells with T(reg) cells allowed the identification of the gene LGALS3. However, high levels of LGALS3 protein expression were observed only in human CD4(+)CD25(hi) derived T(reg) cells and FOXP3-transduced T(h) cells, whereas little was induced in UBD-transduced T(h) cells. Thus, UBD contributes to the anergic phenotype of human regulatory T cells and acts downstream in FOXP3 induced regulatory signaling pathways, including regulation of LGALS3 expression. High levels of LGALS3 expression represent a FOXP3-signature of human antigen-stimulated CD4(+)CD25(hi) derived regulatory T cells.