Membrane fluidity and oxygen diffusion in cholesterol-enriched endothelialcells

In this study, we measured the influence of cholesterol rigidification on o xygen permeability in human endothelial cell monolayer membranes (ECs). Cho lesterol-induced membrane rigidification was assessed at different membrane depths by a fluorescence polarization method with diphenyl-hexatriene (DPH ) and 1-(4-trimethylamino)-6-phenylhexatriene (TMA-DPH). Fluorescence quenc hing by oxygen was probed in preferentially labelled membrane with pyrene b utyric acid (PyC4) and pyrene dodecanoic acid (PyC12), as shown with a 3D f luorescence microscope (CellScan(TM) System). With both probes the experime nts revealed a decrease in oxygen diffusion as the cholesterol concentratio n increased in the medium culture (from 3.42 mu M to 17.11 mu M). We showed that very low concentrations of cholesterol (about 1000 times below normal value, 6.2 mM) particularly decrease oxygen levels or diffusion rate in th e middle region of the membrane. In conclusion, these findings prove in a d irect manner that cholesterol significantly affect the endothelial barrier function and molecular oxygen transfer to underlying tissues. Risk factors (cholesterol) directly would contribute to tissue ischemia.