Effect of scutellarin on BV-2 microglial-mediated apoptosis in PC12 cells via JAK2/STAT3 signalling pathway.

Previous studies have shown that scutellarin inhibits the excessive activation of microglia, reduces neuronal apoptosis, and exerts neuroprotective effects. However, whether scutellarin regulates activated microglia-mediated neuronal apoptosis and its mechanisms remains unclear. This study aimed to investigate whether scutellarin can attenuate PC12 cell apoptosis induced by activated microglia via the JAK2/STAT3 signalling pathway. Microglia were cultured in oxygen-glucose deprivation (OGD) medium, which acted as a conditioning medium (CM) to activate PC12 cells, to investigate the expression of apoptosis and JAK2/STAT3 signalling-related proteins. We observed that PC12 cells apoptosis in CM was significantly increased, the expression and fluorescence intensity of the pro-apoptotic protein Bax and apoptosis-related protein cleaved caspase-3 were increased, and expression of the anti-apoptotic protein B-cell lymphoma-2 (Bcl-2) was decreased. Phosphorylation levels and fluorescence intensity of the JAK2/STAT3 signalling pathway-related proteins JAK2 and STAT3 decreased. After treatment with scutellarin, PC12 cells apoptosis as well as cleaved caspase-3 and Bax protein expression and fluorescence intensity decreased. The expression and fluorescence intensity of Bcl-2, phosphorylated JAK2, and STAT3 increased. AG490, a specific inhibitor of the JAK2/STAT3 signalling pathway, was used. Our findings suggest that AG490 attenuates the effects of scutellarin. Our study revealed that scutellarin inhibited OGD-activated microglia-mediated PC12 cells apoptosis which was regulated via the JAK2/STAT3 signalling pathway.

Scutellarin Exerts Anti-Inflammatory Effects in Activated Microglia/Brain Macrophage in Cerebral Ischemia and in Activated BV-2 Microglia Through Regulation of MAPKs Signaling Pathway.

BACKGROUND: Scutellarin, an herbal compound, can effectively suppress the inflammatory response in activated microglia/brain macrophage(AM/BM) in experimentally induced cerebral ischemia; however, the underlying mechanism for this has not been fully clarified. We sought to elucidate if scutellarin would exert its anti-inflammatory effects on AM/BM through the MAPKs pathway. MATERIALS AND METHODS: Western blot and immunofluorescence labeling were used to determine the expression of the MAPKs pathway in AM/BM in rats subjected to middle cerebral artery occlusion (MCAO) also in lipopolysaccharide (LPS)-activated BV-2 microglia in vitro. Furthermore, expression of p-p38 along with that of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta(IL-1ß), and inducible nitric oxide synthase (iNOS) in LPS-activated microglia subjected to pretreatment with p38 inhibitor SB203580, p38 activator sc-201214, scutellarin, or a combination of them was evaluated. FINDINGS: Scutellarin markedly attenuated the expression of p-p38, p-JNK in AM/BM in MCAO rats and in vitro. Conversely, p-ERK1/2 expression level was significantly increased by scutellarin. Meanwhile, scutellarin suppressed the expression of proinflammatory mediators including iNOS, TNF-α, and IL-1ß in AM/BM. More importantly, SB203580 suppressed p-p38 protein expression level in LPS-activated BV-2 microglia that was coupled with decreased expression of proinflammatory mediators (TNF-α, iNOS) in LPS-activated BV-2 microglia. However, p38 activator sc-201214 increased expression of proinflammatory mediators TNF-α, iNOS, and IL-1ß. Interestingly, the decreased expression of both proinflammatory markers by p38 MAPK inhibitor and increased expression of proinflammatory markers by p38 MAPK activator were compatible with that in BV-2-activated microglia pretreated with scutellarin. CONCLUSIONS: The results suggest that scutellarin down-regulates the expression of proinflammatory mediators in AM/BM through suppressing the p-JNK and p-p38 MAPKs. Of note, the anti-inflammatory effect of p38 MAPK inhibitor and scutellarin is comparable. Besides, p38 MAPKs activator reverses the effect of scutellarin. Additionally, scutellarin increases p-ERK1/2 expression that may be neuroprotective.