Incorporation of oxysterols modulates signal transduction in caveolae

Oxysterols, like 7βhidroxycholesterol, are generated by oxidative modifications to cholesterol molecules and are present in high levels in the atherosclerotic plaque. Since cholesterol is the main component of caveolae, we hypothesized that oxysterol could be incorporated to these domains, interfering with the signaling networks that use this pathway. HUVECs were exposed to 7βhidroxycholesterol (10μg/mL) for different times. Its incorporation to caveolae was detected using mass spectroscopy and activity of signaling pathways present in these domains: endothelial nitric oxide synthase (eNOS), CD40/CD40L, fibroblast growth factor receptor (FGFr), using quantitative PCR and immunoblots. 7βhidroxycholesterol, in physiological concentrations, was incorporated to caveolae more prominently than to other plasma membrane domains. This phenomenon caused a difficulty in eNOS release from caveolin, impairing its function. The CD40 receptor presented a stronger incorporation to caveolae and FGFr maintained a longer activation when cells were exposed to 7βhidroxycholesterol. These oxysterol effects were not related to its action in inflammatory mediators, like cytokines, or nuclear receptors, like PPAR or LXR. Therefore we conclude that 7βhidroxycholesterol incorporation in caveolae domains may interfere with signaling pathways known to be involved in atherogenesis or in plaque rupture.