BACKGROUND/AIMS: To investigate the regulation of LaCl3 on lipopolysaccharides (LPS)-induced pro-inflammatory cytokines and adhesion molecules in human umbilical vein endothelial cells (HUVECs). METHODS: Primary cultured HUVECs were pretreated with 2.5 µM LaCl3 for 30 min followed by 1 µg/ml LPS for 2 h. Pro-inflammatory cytokine and adhesion molecule expressions were determined by real-time RT-PCR and ELISA. NF-κB/p65 nuclear translocation was examined by immunofluorescence and immuno-blot, and its DNA-binding activity was measured by chemiluminescence. Recruitment of NF-κB/p65, Jmjd3, and H3K27me3 to gene promoter regions was determined by ChIP-qPCR. RESULTS: LaCl3 exhibited no cytotoxic effects to primary HUVECs at concentrations ≤ 50 µM. LPS-mediated TNF-α, IL-1β, IL-6, MMP-9, and ICAM-1 production, nuclear translocation, and DNA-binding activity of NF-κB/p65, as well as Jmjd3 expression, were all reduced significantly by LaCl3. Furthermore, LaCl3 treatment significantly impaired LPS-induced enrichment of NF-κB/p65 to the promoter regions of TNF-α, MMP-9, IL-1β, ICAM-1, and IL-6; and of Jmjd3 to the promoter regions of TNF-α, MMP-9, IL-1β, and IL-6. H3K27me3 abundance in the promoter regions of TNF-α and ICAM-1 increased significantly in following LaCl3 treatment. CONCLUSION: LaCl3 inhibits pro-inflammatory cytokine and adhesion molecule expressions induced by LPS in HUVECs. NF-κB and histone demethylase Jmjd3 are involved in this effect.