The Anti-Inflammatory Effect of Smilax china L. Extract on LPS-Stimulated THP-1 via Downregulation of MAPK and NF-κB Signaling Pathway

BACKGROUND: Traditional Chinese medicine Smilax is the rhizome of liliaceous plant Smilax china L., which is used to treat pelvic inflammatory disease and anxieties. PURPOSE: To investigate the mechanism of anti-inflammatory activity of the extract from Smilax china L. (ES). METHODS: The components of ES were identified by UPLC-QTOF-MS/MS. The anti-inflammatory activities were evaluated in xylene-induced ear oedema and egg white-induced plantar swelling test. Cell viability was examined by CCK-8 assay. The inflammatory mediators, proinflammatory cytokines, and MAPK and NF-κB signals in LPS-stimulated THP-1 cells were determined using ELISA, real-time PCR, and Western blot, respectively. RESULTS: 20 compounds of ES were confirmed by comparing with the reference substance. ES displayed more prominent anti-inflammatory activity than the positive control “Jin Gang Teng” capsule in the in vivo acute inflammatory model. ES suppressed the expression of PGE(2) and 6-Keot-PGF(1)α, and the ratio of IC(50) (COX-1)/IC(50) (COX-2) of ES was 3.15, which indicated that ES could selectively inhibit COX-2. ES dose-dependently (12.5, 25, and 50 mg/L) decreased the production and mRNA levels of proinflammatory cytokines IL-1β, IL-6, and TNF-α. Furthermore, ES significantly decreased LPS-induced phosphorylation of p38, JNK, ERK1/2, and p65, inhibiting the expression of IKKα and the degradation of IκBα. CONCLUSION: The results suggested that ES could selectively inhibit the activity of COX-2, and the anti-inflammatory effect of ES was associated with the inhibition of IL-1β, IL-6, and TNF-α via negative regulation of MAPK and NF-κB signaling pathways in LPS-induced THP-1 cells.