Acetylbritannilactone suppresses lipopolysaccharide-induced vascular smooth muscle cell inflammatory response

To investigate the mechanism of action by which a new anti-inflammatory active compound, 1-O-acetylbritannilactone (ABL) isolated from Inula britannica-F., inhibits inflammatory responses in vascular smooth muscle cells (VSMCs). Enzyme immunoassay was used to measure the levels of prostandin E(2) (PGE(2)) production. Immunocytochemistry staining and Western blot analysis were performed to detect the nuclear translocation of nuclear factor-kappaB (NF-kappaB) p65 and the expression of IkappaB-alpha, pIkappaB-alpha and cyclooxygenase-2 (COX-2). Electrophoretic mobility shift assays (EMSA) were used to detect DNA-binding activity of NF-kappaB in VSMCs. ABL (5, 10, 20 micrommol/l) had several concentration-dependent effects, including inhibition of lipopolysaccharide (LPS)-induced PGE(2) production and COX-2 expression, and blockade of NF-kappaB activation and translocation. These effects were owing to reductions in IkappaB-alpha phosphorylation and degradation induced by LPS. In addition, ABL directly inhibited the binding of active NF-kappaB to specific DNA cis-element. These results indicate that ABL is a potent inhibitor of LPS-stimulated VSMC inflammatory responses through blockade of NF-kappaB activity and inhibition of inflammatory gene COX-2 expression.