Echinatin protects from ischemic brain injury by attenuating NLRP3-related neuroinflammation

Background: Microglia-mediated neuroinflammation is the major contributor to the secondary brain injury of ischemic stroke. NLRP3 is one of the major components of ischemia-induced microglial activation. Echinatin, a chalcone found in licorice, was reported to have the activity of anti-inflammation and antioxidant. However, the relative study of echinatin in microglia or ischemic stroke is still unclear. Methods: We intravenously injected echinatin or vehicle into adult ischemic male C57/BL6J mice induced by 60min transient middle cerebral artery occlusion (tMCAO). The intraperitoneal injection was performed 4.5 h after reperfusion and then daily for 2 more days. Infarct size, blood brain barrier (BBB) leakage, neurobehavioral tests, and microglial-mediated inflammatory reaction were examined to assess the outcomes of echinatin treatment. LPS and LPS/ATP stimulation on primary microglia were used to explore the underlying anti-inflammatory mechanism of echinatin. Results: Echinatin treatment efficiently decreased the infarct size, alleviated blood brain barrier (BBB) damage, suppressed microglial activation, reduced the production of inflammatory factors (e.g., IL-1 beta, IL-6, IL-18, TNF-alpha, iNOS, COX2), and relieved post-stroke neurological defects in tMCAO mice. Mechanistically, we found that echinatin could suppress the NLRP3 assembly and reduce the production of inflammatory mediators independently of NF-kappa B and monoamine oxidase (MAO). Conclusion: Based on our study, we have identified echinatin as a promising therapeutic strategy for the treatment of ischemic stroke.