Aims:Urotensin Ⅱ (Ull) is the most potent vasoactive peptide identified to date.Serum urotensin Ⅱ levels elevated in non-dipper hypertensive patients.Human urotensin Ⅱ promotes hypertension.Moreover,increased levels of urotensin Ⅱ levels are correlated with carotid atherosclerosis in essential hypertensive patients.Atherosclerosis is an inflammatory process associated with several pathophysiological reactions within the vascular wall.The events involved in early atherosclerosis is vascular dysfunction or injury and monocyte recruitment.UII had a chemoattractant effect on cultured monocytes.It is well established that luekotriene B4(LTB4) is a potent chemoattractant, facilitating leucocyte adhesion and recruitment.LTB4 is a metabolite of arachidonic acid through the 5-Lipoxygenase(5-LO) pathway.The aim of this study was to explore the potential role for Ull in 5-LO expression and to investigate the molecular mechanisms of 5-LO expression in UII-stimulated RAW264.7 macrophages.