Abstract Body (Do not enter title and authors here): Atherosclerosis, a complex process involving chronic systemic inflammation, endothelial dysfunction, retention of lipoproteins, plaque formation in large and medium-sized arteries, is one of the most common causes of morbidity and mortality. Octacosanol, a very long chain saturated (C28) aliphatic alcohol is a major active ingredient in the Policosanol, which is extracted from plants like sugar cane and wheat germ. Policosanol has been proposed as dietary supplement for obesity and for lowering serum lipids. Previous animal studies have shown that both Policosanol and Octacosanol can significantly ameliorate formation of atherosclerotic lesions. To further explore the possible mechanism of Octacosanol on the formation of atherosclerosis, we examined the anti-inflammatory effects of Octacosanol on HAEC treated with LPS at 100ng/ml FBS-free cell culture medium. LPS treatment significantly enhanced human monocyte (THP1) adherence to HAEC cells in time-dependent and dose-dependent style, but Octacosanol at 1.25 or 2.5 µM markedly blocked the adhesion of THP1 to HAEC. ELISA showed that LPS can significantly increase the expression of pro-inflammatory cytokines and adhesion molecules by HAEC at 100ng/ml within 4 hours. LPS stimulated more than 3-fold the release of IL-6, IL-8, MCP-1 at 4 hours. By flow cytometry and ELISA, LPS markedly increased the expression of PE-Selectin and VCAM-1. Pretreatment of HAEC with Octacosanol (1.25µM or 2.5µM) significantly reduced the release of inflammatory cytokines, such as MCP-1(p<0.01), IL-6 (p<0.001) and IL-8(P<0.001)> It also inhibited the expression of PE-selectin(p<0.001) and VCAM-1(P<0.001). By QRT-PCR analysis, Octacosanol reduced the transcription of TRAF-6, MYD88 which are associated with LPS triggered TLR-4 involved pro-inflammatory pathway. Confocal imaging analysis of HAEC cells also confirmed Octacosanol the inhibition of the expression of PE-Selectin and VCAM-1 and VE-Cadherin, leading to the maintenance of cell membrane integrity and underlying ECM and the prevention of THP1 cell adherence. A test of HAEC cell membrane permeability using fluorescent intensity of FITC-Dextran (40kD) showed that Octacosanol can significantly improve cell integrity to damage induced by LPS at 100ng/ml for 4 hours. In summary, Octacosanol appears to have multiple potential beneficial functions related to endothelial cell integrity, which could explain its anti-atherogenic properties observed in animal studies.