Citrus peel has long been used in traditional medicine in Asia to treat common cold, dyspepsia, cough, and phlegm. Narirutin-a flavanone-7-O-glycoside-is the major flavonoid in citrus peel, and has anti-oxidative, anti-allergic, and anti-inflammatory activities. However, the anti-inflammatory mechanism of narirutin has not been fully elucidated. This study is aimed to investigate the effects of narirutin on the Nod-like receptor protein 3 (NLRP3)-mediated inflammatory response in vitro and in vivo, and determine the underlying mechanism. THP-1 differentiated macrophages and bone marrow-derived macrophages (BMDMs) were used for in vitro experiments, while dextran sulfate sodium (DSS)-induced colitis and alum-induced peritonitis mouse models were constructed to test inflammation in vivo. Narirutin suppressed secretion of interleukin (IL)-1β and pyroptosis in lipopolysaccharide (LPS)/ATP-stimulated macrophages. Narirutin decreased the expression of NLRP3 and IL-1β in the LPS-priming step through inhibition of NF-κB, MAPK and PI3K /AKT signaling pathways. Narirutin inhibited NLRP3-ASC interaction to suppress NLRP3 inflammasome assembly. Furthermore, oral administration of narirutin (300 mg/kg) alleviated inflammation symptoms in mice with peritonitis and colitis. These results suggest that narirutin exerts its anti-inflammatory activity by suppressing NLRP3 inflammasome activation via inhibition of the NLRP3 inflammasome priming processes and NLRP3-ASC interaction in macrophages.
Keywords: DSS-induced colitis; NLRP3 inflammasome; alum-induced peritonitis; citrus peel; inflammation; narirutin.
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