Silymarin in Silybum marianum ameliorated acute lethal sepsis in mice by targeting caspase-11 noncanonical inflammasome in macrophages.

Abstract

ETHNOPHARMACOLOGICAL RELEVANCE: Silymarin, a flavonolignan complex derived from Silybum marianum, has been widely used in traditional medicine, particularly for liver-related disorders. AIM OF THE STUDY: Although silymarin has recognized anti-inflammatory activity, its role in regulating inflammation driven by the noncanonical caspase-11 inflammasome has not been clarified. This study investigated whether silymarin suppresses caspase-11 inflammasome-mediated inflammatory responses in macrophages and in a mouse model of acute septic shock. MATERIALS AND METHODS: In vivo, an acute lethal sepsis model was established by intraperitoneal LPS administration in mice. The therapeutic effects of silymarin were determined by assessing survival, murine sepsis scores, serum cytokines, and lactate dehydrogenase (LDH) release. In vitro, J774A.1 macrophages were primed with Pam3CSK4 and then transfected with LPS to activate the caspase-11 inflammasome. The inhibitory effects of Silymarin were evaluated using MTT and LDH assays, flow cytometry, fluorescence imaging, ELISA, qPCR, and Western blotting. RESULTS: Silymarin treatment markedly improved survival, reduced murine sepsis scores, and lowered circulating LDH and pro-inflammatory cytokines in septic mice, without notable adverse effects. In cultured macrophages, silymarin prevented pyroptosis induced by caspase-11 inflammasome activation and suppressed the release of cytokines, nitric oxide (NO), and inflammatory enzyme, NOS2. Mechanistic analysis revealed that silymarin suppressed caspase-11 autocleavage and subsequent activation of gasdermin D (GSDMD) by preventing formation of N-GSDMD fragments, while leaving LPS-caspase-11 binding unaffected. CONCLUSION: These findings demonstrate that silymarin mitigates inflammation through inhibition of caspase-11 noncanonical inflammasome activity in both macrophages and septic mice, suggesting its potential as a traditional meidcine for inflammatory conditions.