Effect of Sarsasapogenin on Lipopolysaccharide-induced BV2 Microglial Subtype M1/M2 Polarization and Sarsasapogenin’s Anti-inflammatory Activity
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Abstract:
In this study, the effect of sarsasapogenin (SAR) on the polarization of BV2 microglia from M1 to M2 subtypes induced by lipopolysaccharide as well as the mechanism underlying SAR’s anti-inflammatory activity were investigated. The MTT method was used to evaluate the effect of SAR on the cell viability of microglia. The release of NO was measured by the Griess method. The expressions of TNFα, IL1β, IL6, and IL10 in the cell culture supernatants were measured by the ELISA. The immunocytochemistry method was used to detect the primary microglia M1 and M2 phenotypes, and the expression levels of p65, p38 and PPARγ in microglia. The results showed that SAR (0.01~1 μmol/L) had no effect on the cell viability of BV2 microglia under normal conditions and in LPS (100 ng/mL)-induced inflammatory state, however, high doses of SAR (10 and 25 μmol/L) showed certain cytotoxic effects. Compared with the normal group, LPS-treated model group exhibited an increased level of released NO (by 22.64%), upregulated expressions of TNFα, IL1β and IL6 (by 25.5%, 13.28%, and 48.21%, respectively), downregulated expression of IL10 (by 14.97%), and significantly increased levels of Cox2 positive and Ym1/2 negative expressed M1 microglia. Furthermore, the phosphorylation levels of p38 and p65 were 2.80 times and 1.86 times, respectively, that of the normal group, while the expression of PPARγ decreased by 73.90% in the LPS-treated group. Compared with the LPS model group, the treatment with SAR (0.1 and 1 μmol/L) inhibited the release of NO and secretion of TNFα, IL1β and IL6, and promoted LPS-induced polarization of microglia to M2 phenotype, decreased significantly the phosphorylation of p38 and p65, and up-regulated the PPARγ expression. The mechanisms underlying SAR’s anti-inflammatory function were attributed to the inhibition of the phosphorylation of p65 and p38 via the activation of PPARγ, promotion of the polarization of microglia from M1 to M2 subtype, and reduction of the expression of inflammatory cytokines and release of NO.
