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.

ABSTRACT

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.