Scutellarin regulates the Notch pathway and affects the migration and morphological transformation of activated microglia in experimentally induced cerebral ischemia in rats and in activated BV-2 microglia

Background: Activated microglial cells release an excess of inflammatory mediators after an ischemic stroke. We reported previously that scutellarin effectively suppressed the inflammatory response induced by activated microglia in rats subjected to middle cerebral artery occlusion (MCAO); however, the mechanism via which scutellarin exerts its effects on microglial activation has not been explored. This study aimed to elucidate if scutellarin can regulate the Notch pathway that is linked to microglia activation in MCAO rat, and in lipopolysaccharide (LPS)-induced BV-2 microglia. Along with this, we also investigated some characteristic behavioral responses of activated microglia. Methods: Expression of various members of the Notch pathway, including Notch-1, intracellular Notch receptor domain (NICD), recombining binding protein suppressor of hairless (RBP-JK) and transcription factor hairy and enhancer of split-1 (Hes-1) in activated microglia was assessed by immunofluorescence staining and western blot after experimental MCAO and in vitro LPS activation. The effect of scutellarin on migration of microglia was determined by the transwell chamber assay as well as expression of monocyte chemoattractant protein-1 (MCP-1). The morphological change of microglia induced by scutellarin was detected by F-actin staining and electron microscopy. Results: Scutellarin markedly attenuated the expression of NF-kappa B, Notch-1, NICD, RBP-JK and Hes-1 both in vivo and in activated microglia. It decreased the expression of MCP-1 and microglial migration, but increased the ability of microglia adhesion. Scutellarin also altered the phenotype of microglia by causing rearrangement or reorganization of its cytoskeleton. Conclusions: The results suggest that scutellarin regulates the activation of microglia via the Notch pathway and concurrently induces morphological and functional changes in activated microglia.