The endothelium-derived hyperpolarizing factor, H2O2, promotes metal-ion efflux in aortic endothelial cells:: Elemental mapping by a hard X-ray microprobe

Hydrogen peroxide (H2O2) is a physiologic oxidant implicated in vascular cell signaling, although little is known about the biochemical consequences of its reaction with endothelial cells. Submicrometer-resolution hard X-ray elemental mapping of cultured porcine aortic endothelial cells (PAEC) has provided data on the global changes for intracellular elemental density within PAEC and indicates an efflux of metal ions and phosphorus from the cytoplasm after H2O2 treatment. The synchrotron-radiation-induced X-ray emission experiments (SRIXE) show that H2O2-treated cells are irregularly shaped and exhibit blebbing indicative of increased permeability due to the damaged membrane. The SRIXE results suggest that H2O2-induced damage is largely restricted to the cell membrane as judged by the changes to membrane and cytoplasmic components rather than the cell nucleus. The SRIXE data also provide a mechanism for cell detoxification as the metal-ion efflux resulting from the initial H2O2-mediated changes to cell membrane potentially limits intracellular metal-mediated redox processes through Fenton-like chemistry. They may also explain the increased levels of these ions in atherosclerotic plaques, regardless of whether they are involved in plaque formation. Finally, the SRIXE data support the notion that cultured endothelial cells exposed to H2O2 respond with enhanced cellular metal-ion efflux into the extracellular space.