Fig. 5

SLDS inhibits inflammatory cytokine secretion, increases phagocytosis in primary microglia, and promotes primary oligodendrocyte differentiation via M2 polarization. The M1 phenotype was induced using LPS plus IFN-γ, and the M2 phenotype was induced using IL-4 plus IL-13. Vehicle was added to non-treated microglia. a ELISA results indicated that SLDS inhibited the expression of IL-1β, IL-2, IL-6, IL-8, and TNFα in microglial-conditioned media; n = 9–12 per group. b Quantification of fluorescent microsphere intensity; n = 9 per group. c Representative images of microglial phagocytosis detected by fluorescent microspheres. Left scale bar, 10 μm; right scale bar, 5 μm. Phalloidin staining was used to visualize F-actin. d In vitro experiments using the transwell contact-independent system. Microglia seeded in inserts were incubated with vehicle or different SLDS treatment combinations for 48 h, after which the inserts were placed over oligodendrocyte cultures. After 3 days in culture, inserts were changed and fresh 48-h-treated microglia inserts were added. Oligodendrocytes were collected 5 or 7 days after the initial microglial insert addition. Vehicle was added to oligodendrocytes alone (control group) or oligodendrocyte-microglia cocultures (M0 group). e The expression of NG2 and MBP in the oligodendrocytes cocultured with microglia treated with various concentrations of SLDS (and controls). RT-PCR was performed to detect the expression of NG2 and MBP; n = 3 per group. f Representative NG2 (green) and MBP (red) staining in the different groups. Scale bar, 50 μm. DAPI (blue) was used as a nuclear marker. Data are expressed as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, by one-way ANOVA and Tukey’s test