OBJECTIVE: Cucurbitacin E (CuE), a triterpenoid compound isolated from Cucurbitaceae plants, possesses a wide range of biological activities including anti-inflammatory properties. The present study aimed to investigate the anti-inflammatory effect of CuE and the underlying mechanism of action. METHODS: The anti-inflammatory effect of CuE was evaluated in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Cell proliferation was assessed using a modified MTT assay. Cell cycle distribution was analyzed by propidium iodide staining. The actin cytoskeleton was examined by immunofluorescent staining. The expression of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta was determined by intracellular cytokine staining. G-actin level and nuclear factor (NF)-kappaB nuclear translocation were detected by immunoblotting. RESULTS: CuE inhibited cell proliferation and induced cell cycle arrest at G2/M phase in RAW 264.7 cells. CuE also suppressed LPS-induced cell spreading and pseudopodia formation. These effects were associated with decreased G-actin level and severe actin aggregation. Moreover, CuE significantly inhibited both TNF-alpha and IL-1beta production in LPS-stimulated RAW 264.7 cells. This was likely mediated by suppressing LPS-induced nuclear translocation of NF-kappaB, a critical transcription factor responsible for pro-inflammatory cytokine expression. CONCLUSION: CuE displayed anti-inflammatory effects through suppression of NF-kappaB nuclear translocation leading to a decreased expression of TNF-alpha and IL-1beta in LPS-stimulated RAW 264.7 cells.