Hibiscus sabdariffa leaf polyphenolic extract inhibits LDL oxidation and foam cell formation involving up-regulation of LXRa/ABCA1 pathway

The oxidative modification of low-density lipoprotein (LDL) is involved in the pathogenesis of atherosclerotic lesions through the formation of macrophage-derived foam cells. In the present study, we aimed to investigate the anti-atherosclerotic effect of Hibiscus sabdariffa leaf polyphenolic extract (HLP), which is rich in flavonoid. The inhibitory effect of HLP on oxidation and lipid peroxidation of LDL was defined in vitro. HLP showed potential in reducing foam cell formation and intracellular lipid accumulation in oxidised- LDL (ox-LDL)-induced macrophage J774A.1 cells under non-cytotoxic concentrations. Molecular data showed these influences of HLP might be mediated via liver-X receptor a (LXRa)/ATP-binding cassette transporter A1 (ABCA1) pathway, as demonstrated by the transfection of LXRa siRNA. Our data implied that HLP up-regulated the LXRa/ABCA1 pathway, which in turn led to stimulation of cholesterol removal from macrophages and delay atherosclerosis. These results suggested that HLP potentially could be developed as an anti-atherosclerotic agent.