Aim Magnesium lithospermate B (MLB) is the most abundant hydrophilic active component of Salvia miltiorrhiza Radix, a traditional Chinese herbal medicine mainly used to treat cardiovascular diseases.Studies have shown that endothelial activation contributes to the pathophysiology of cardiovascular diseases such as atherosclerosis, diabetic vasculopathy, heart failure and hypertension.In the present study, the effects of MLB on endothelial activation were investigated.Lipopolysaccharide (LPS) 1 mg · L1 was employed to induce endothelial activation,which was determined by relative gene expression and endothelial adhesion assay.Results showed that pretreatment with MLB attenuated LPSinduced ICAM1, VCAM1 and TNFc upregulation in human dermal microvascular endothelial cells (HMEC1) in dosedependent manner, which contributed to the reduction of THP1 adhesion to HMEC1.Furthermore, it was revealed that 100 μmol · L1 MLB significantly decreased the nuclear translocation of NFκB p65, a critical transcription factor in LPSinduced inflammatory response, through the inhibition of IκBαdegradation.Besides, the transcriptional activity of NFκB p65 was also inhibited by the pretreatment of MLB.Moreover, MLB pretreatment considerably inhibited LPSinduced p38 phosphorylation, which at least partly contributed to the reduction of ICAM1 expression.In conclusion, these findings suggest that MLB inhibits LPSinduced nuclear translocation and transcripitional activity of NFκB, thus attenuates the increased expression of adhesion molecules and inflammatory factors, protects endothelial cells from LPSinduced activation.