Effect of FTY720-phosphate on the expression of inflammation-associated molecules in astrocytes in vitro.

FTY720 is a new oral immunomodulatory therapy for the treatment of multiple sclerosis (MS). There is strong evidence that FTY720 has direct effects on brain resident cells such as astrocytes acting via sphingosine­1­phosphate (S1P) receptors. In the present study, the mRNA expression of S1P receptors as well as selected cytokines, chemokines and growth factors were investigated in primary murine astrocytes under inflammatory conditions in the presence or absence of the phosphorylated form of FTY720 (FTY720­P). Following stimulation with either the pro­inflammatory cytokine tumor necrosis factor­α (TNF­α) or with bacterial lipopolysaccharide, there was an increased expression of the receptors S1P1 and S1P3, the cytokines and chemokines interleukin (IL)­1ß, chemokine (C­C­motif) ligand 2 (CCL­2), CCL­20 and chemokine (C­X­C­motif) ligand 12 as well as the growth factors insulin­like growth factor­1, ciliary neurotrophic factor and glial cell line­derived neurotrophic factor (GDNF). FTY720­P led to an increased expression of IL­1ß and GDNF at distinct time points following co­stimulation with TNF­α compared with TNF­α treatment alone. However, the presence of FTY720­P did not have any further significant effects on the expression of S1P receptors, cytokines or growth factors, suggesting that the regulation of these target genes in astrocytes is not likely to be a major mechanism underlying the effect of FTY720­P in diseases such as MS.

A pivotal role of nonmuscle myosin II during microglial activation.

Microglia are resident macrophages in the central nervous system (CNS) and the primary cells that contribute to CNS inflammation in many pathological conditions. Upon any signs of brain damage, microglia become activated and undergo tremendous cellular reorganization to adopt appropriate phenotypes. They migrate to lesion areas, accumulate, phagocytose cells or cellular debris, and produce a large array of inflammatory mediators like cytokines, chemokines, reactive oxygen species, and other mediators. To cope with the extreme cellular rearrangements during activation, microglia have to be highly dynamic. One major component of the cytoskeleton in nonmuscle cells is nonmuscle myosin II (NM II). This study was aimed to examine the functional role of NM II in resting and activated microglia. Using immunohistochemistry, we demonstrate strong expression of NM II isoform B (NM IIB) in microglia during cuprizone-induced demyelination as well as in cultured microglia. Treatment with the NM II inhibitor blebbistatin prevented the morphological shaping of microglial cells, led to functional deficits during chemokine-directed migration and phagocytosis, induced NM IIB redistribution, and affected actin microfilament patterning. In addition, inhibition of NM II led to an attenuated release of nitric oxide (NO), while TNFα secretion was not altered. In conclusion, we propose a pivotal role of NM II in cytoskeleton organization during microglial activation. This is of great importance to understand the mechanisms of microglial action in inflammatory CNS diseases.

Effects of murine and human bone marrow-derived mesenchymal stem cells on cuprizone induced demyelination.

For the treatment of patients with multiple sclerosis there are no regenerative approaches to enhance remyelination. Mesenchymal stem cells (MSC) have been proposed to exert such regenerative functions. Intravenous administration of human MSC reduced the clinical severity of experimental autoimmune encephalomyelitis (EAE), an animal model mimicking some aspects of multiple sclerosis. However, it is not clear if this effect was achieved by systemic immunomodulation or if there is an active neuroregeneration in the central nervous system (CNS). In order to investigate remyelination and regeneration in the CNS we analysed the effects of intravenously and intranasally applied murine and human bone marrow-derived MSC on cuprizone induced demyelination, a toxic animal model which allows analysis of remyelination without the influence of the peripheral immune system. In contrast to EAE no effects of MSC on de- and remyelination and glial cell reactions were found. In addition, neither murine nor human MSC entered the lesions in the CNS in this toxic model. In conclusion, MSC are not directed into CNS lesions in the cuprizone model where the blood-brain-barrier is intact and thus cannot provide support for regenerative processes.