Inflammation and endothelial dysfunction are key steps in the pathogenesis of atherosclerosis. Octacosanol (C 28 H 58 O, OCT), a very-long-chain saturated aliphatic alcohol (VLCA) with 28 carbons, is the main component of policosanol, a nutraceutical mixture of VLCAs (C20-C34) extracted from plants. Polycosanol in animal models is known to reduce atherosclerosis, but its mechanism of action remains unclear. This study investigates the pathways by which OCT alleviates LPS-induced inflammation in primary human aortic endothelial cells (HAECs). After overnight pretreatment with purified OCT, inflammation in HAECs was induced by lipopolysaccharide (LPS) at 100 ng/ml. The effects of OCT on the levels of pro-inflammatory cytokines, and molecules involved in inflammation signaling pathway, cell adhesion, and cell integrity were examined using quantitative RT-PCR, enzyme-linked immunosorbent assay, flow cytometry, or confocal microscopy in LPS-stimulated HAECs. The group of untreated HAECs was used as a control. OCT pretreatment of HAECs significantly reduced LPS-induced inflammatory responses, decreasing levels of IL-6, IL-8, and MCP-1 mRNA and protein, as well as TLR4, MYD88, TIRAP, TRAF6, and IRAK1 mRNA (p 0.05). In a monocyte adhesion assay, LPS exposure increased human monocytic cells (THP-1) adherence to HAECs, whereas OCT pretreatment suppressed the LPS-induced adhesion of THP-1 to HAECs in a time- and dose-dependent manner, by blocking the mRNA and protein expression of adhesion molecules (VCAM-1, ICAM-1, P- and E-SELECTIN) (p 0.05). OCT also suppressed mRNA and protein levels of CORTACTIN, VINCULIN, and TALIN, and inhibited focal adhesion and lamellipodia formation, cell deformation, and migration in response to LPS (p 0.05). In addition, an endothelial permeability assay revealed that OCT pretreatment also improved endothelial cell integrity after LPS stimulation by preserving both adherens junctions and tight junctions formed by VE-CADHERIN, β -CATENIN, and Zonula Occludens-1 (ZO-1) (p 0.05). In summary, the multiple cytoprotective effects of OCT against LPS-induced inflammation in endothelial cells could contribute to the anti-atherogenic properties of policosanol.
Tang et al. (Wed,) studied this question.