In vitro evaluation of physiologically relevant concentrations of teriflunomide on activation and proliferation of primary rodent microglia.

BACKGROUND: Teriflunomide, an inhibitor of dihydroorotate dehydrogenase, is thought to ameliorate multiple sclerosis by reducing activation-induced proliferation of lymphocytes, which is highly dependent on de novo pyrimidine synthesis. Nevertheless, its immunomodulatory effects on resident glial cells in the central nervous system are only poorly understood. METHODS: In this study, we employed physiologically relevant concentrations of teriflunomide and investigated its effects on survival, proliferation, activation, and function of primary rat microglia in vitro. RESULTS: We demonstrate that teriflunomide had no cytotoxic effect on microglia and had only a minor impact on microglial activation. In a concentration- and time-dependent manner, teriflunomide significantly downregulated surface expression of the co-stimulatory molecule CD86. Furthermore, in the highest concentration applied (5 µM), it slightly increased the expression of interleukin-10 in microglia in response to lipopolysaccharide. Treatment with low concentrations of teriflunomide (0.25-1 µM) did not have any impact on the activation or proliferation of microglia. At 5 µM concentration of teriflunomide, we observed a reduction of approximately 30 % in proliferation of microglia in mixed glial cell cultures. CONCLUSIONS: Taken together, our in vitro findings suggest that at higher concentrations, teriflunomide potentially exerts its effects by reducing microglial proliferation and not by modulating the M1-/M2-like cell differentiation of primary rat microglia. Thus, teriflunomide has no major impact on the plasticity of microglia; however, the anti-proliferative and minimal anti-inflammatory effects might be clinically relevant for immune modulation in the treatment of neuroinflammatory CNS diseases such as multiple sclerosis.

The Effect of Stereotactic Injections on Demyelination and Remyelination: a Study in the Cuprizone Model.

Remyelination is the natural repair mechanism in demyelinating disorders of the central nervous system (CNS) such as multiple sclerosis. Several animal models have been used to study demyelination and remyelination. Among toxic animal models, oral administration of the toxin cuprizone leads to white and gray matter demyelination. In contrast, focal demyelination models include the stereotactic application of a toxin such as lysolecithin or ethidium bromide. The injection procedure generates a local disruption of the blood-brain barrier (BBB) and might thus trigger a local inflammatory reaction and consequently may influence demyelination and remyelination. In order to study such consequences, we applied stereotactic injections in the cuprizone model where demyelination and remyelination are mediated independent of this procedure. Immunohistochemistry was performed to detect the presence of lymphocytes and activated glial cells in the injection area. Blood protein stainings were used to assess the integrity of the BBB and myelin staining to evaluate demyelination and remyelination processes. Stereotactic injection led to a local disruption of the BBB as shown by local extravasation of blood proteins. Along the injection canal, T and B lymphocytes could be detected and there was a tendency of a higher microgliosis and astrocytosis. However, these changes did not influence demyelination and remyelination processes at the site of injection, in the corpus callosum, or in the cerebral cortex. Our results suggest that a local stereotactic injection has no major impact on CNS demyelination and remyelination.

Different morphology of amyloid fibrils originating from agitated and non-agitated conditions.

In vitro amyloid formation has been suggested to be a common property of any polypeptide chain depending on particular environmental conditions although in vivo amyloid fibril formation can be promoted by point mutations or triplet expansions. Here, we explored the influence of agitation on fibril formation of amyloidogenic alanine segments fused to Cold Shock Protein B (CspB) of Bacillus subtilis. While without agitation fibril formation was clearly dependent on the presence of an amyloidogenic alanine segment, fibril formation was independent of the amyloidogenic segment under agitation. Agitation even led to fibrillation of native CspB lacking the amyloidogenic segment. Furthermore, agitation not only influenced the kinetics of fibril formation, but also resulted in completely different fibril morphologies. These results indicate that experimental conditions can alter the region that undergoes a conformational change during in vitro fibrillation. Moreover, the data show that deductions from in vitro assays on in vivo fibril formation mechanisms are afflicted with a certain degree of uncertainty and therefore need to be cautiously discussed.