Specific knockout of S1PR1 from astrocytes or pFTY720 treatment reduces the levels of IL1β, IL6 and IL17, which are cytokines increased during the course of EAE [
5]. In agreement, pFTY720 attenuates the levels of cytokines such as IL6, TNFα and IL1β from LPS-activated microglia, in addition to enhancing the levels of brain-derived nerve factor (BDNF) and glial-derived nerve factor (GDNF) [
37]. Treatment of organotypic cerebellar slice cultures with LPC for 2 days also increases the number of both Iba1+ and GFAP+ cells, which subsides after 14 days of LPC treatment, suggesting a temporal effect of LPC on microglia and astrocyte cells numbers [
8]. The treatment of these slice cultures with pFTY720 alone does not appear to alter astrocyte levels [
9], but treatment with pFTY720 after a 2-day exposure to LPC increases the number of Iba1+ and GFAP+ cells, compared to LPC alone [
8]. Importantly, both treatment with pFTY720 at the same time as LPC [
9] and 2 days after LPC [
8] shows increased levels of myelination compared to LPC alone, suggesting that pFTY720 can likely inhibit processes of demyelination and promote events enhancing remyelination. Here, we showed that while BAF312 and pFTY720 modestly attenuate the levels of IL6 from LPS-stimulated mouse astrocytes, they had no observable effect on TNFα/IL17 stimulated human astrocytes. We also found that pFTY720 did not strongly attenuate LPS-induced IL6 in cultured mouse microglia. In contrast, BAF312 attenuated the levels of IL6 levels in organotypic slice cultures treated with LPC, similar to our previous data [
9]. Unlike isolated cell cultures, organotypic slice cultures preserve the brain architecture and also contain immune cells [
9,
38,
39]. Thus, one possible explanation for our findings using cultured astrocytes and microglia, versus organotypic slice cultures, may be the absence or presence of peripheral immune cells, respectively. It remains unclear, however, the number(s) or type(s) of immune cells in these slice cultures that are required to confer a BAF312 effect, if any. A small and undetectable number of immune cells in these slices may indeed be sufficient to trigger a subsequent amplified response by glial cells. The idea that immune cells can induce demyelination and that S1PR drugs can attenuate this response is in line with our previous findings demonstrating that MOG-reactive splenocytes can induce demyelination when added to organotypic slice cultures and their treatment with pFTY720 reverses this effect [
21].