Superoxide release from interleukin-1β-stimulated human vascular cells: in situ electrochemical measurement

Release of superoxide anion by cultured vascular cells was investigated with the use of selective microelectrodes. Local concentration of superoxide anion (O2•−) was followed by differential pulse amperometry on a carbon microfiber at 0.1 V/SCE. The oxidation current allows O2•− detection in the 10−8 M concentration range without interference of the other major oxygen species. Interleukin-1β-stimulated O2•− release that progressively increased to reach local concentrations at the cell membrane level of 76 ± 11 nm 40–60 min after stimulation in human cord vein endothelial cells, and 131 ± 18 nm 1–2 h after stimulation in internal mammary artery smooth muscle cells. In the two types of cells, the O2•− oxidation signal was suppressed in the presence of superoxide dismutase. Spontaneous O2•− release from unstimulated cells was undetectable. These results demonstrate that selective microelectrodes allow direct and real-time monitoring of local O2•− released from vascular endothelial as well as from smooth muscle cells submitted to an inflammatory stimulus.