DT-13 ameliorates TNF-α-induced nitric oxide production in the endothelium in vivo and in vitro

The steroidal saponin DT-13 (25(R,S)-ruscogenin-1-O-[β-d-glucopyranosyl-(1 → 2)][β-d-xylopyranosyl-(1 → 3)]-β-d-fucopyranoside), one of the major active compounds of the herb Liriope muscari (Decne.), exhibits significant anti-inflammatory, anti-tumor and cardioprotective effects. This study aimed to explore the protective effect of DT-13 on endothelium through regulating of nitric oxide production induced by Tumor necrosis factor-α (TNF-α). The results demonstrated that DT-13 inhibited inflammatory cell infiltration and thus played a protective effect on endothelial cells in vivo, as shown by hematoxylin-eosin (H&E) staining and immunohistochemical staining. Enzyme-linked immunosorbent assay (ELISA) results demonstrated that DT-13 could suppress the TNF-α-induced upregulation of reactive oxygen species (ROS), tumor necrosis factor receptor (TNFR), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and nitric oxide in vivo dose-dependently and suppressed production of nitric oxide in vitro as shown by DAF-FMDA. Western blotting results indicated that DT-13 could down-regulate phosphorylation of endothelial nitric oxide synthase (eNOS) significantly in TNF-α-induced human umbilical vein endothelial cells (HUVECs). Taken together, we speculate that DT-13 inhibits endothelium vascular inflammation through regulating nitric oxide production and the expression of ROS, TNFR, IL-8, MCP-1, which are associated with inflammation.