Diosgenin glucoside provides neuroprotection by regulating microglial M1 polarization

The selective suppression of inflammatory factors in activated microglia, rather than totally inhibiting their activation, might be an effective means of slowing the progression of certain neurodegenerative diseases. Diosgenin glucoside (Dios) is a saponin compound extracted from Tritulus terrestris L. We found that Dios suppressed the synthesis of molecules that promote inflammation (M1 markers, such as NO, IL-6, and TNF-α) in rat microglia and BV-2 cells induced with lipopolysaccharides (LPS). In contrast, Dios had no effects on the cellular production of anti-inflammatory factors (M2 markers, such as IL-10, IL-1Rα and CD206) in LPS and IL-4 treated microglia. Dios repressed IκB-α, ERK MAPK and p38 MAPK phosphorylation, but did not affect JNK in LPS-activated microglia. We also found that conditioned medium obtained from cultures of BV-2 cells incubated with Dios plus LPS was markedly less neurotoxic than conditioned medium obtained from cultures of BV-2 cells incubated with LPS alone. In conclusion, this study demonstrated that Dios can selectively suppress the production/expression of pro-inflammatory M1 markers by activated microglia, without affecting M2 markers, and might provide neuroprotection by regulating microglial M1 polarization. Our results suggest that Dios can be used in treatment of various neuroinflammatory diseases mediated by microglia.