Human dermal microvascular endothelial cells express inducible nitric oxide synthase in vitro

Stimulation of inducible nitric oxide synthase with subsequent release of n itric oxide in large amounts may play a critical part either in host defens e reactions or in the pathophysiology of the inflammatory response syndrome leading to septic shock. The aim of the present study was to investigate w hether human dermal microvascular endothelial cells exhibit the typical cha racteristics of an inducible nitric oxide synthase expressing cell. A stron g effect on inducible nitric oxide synthase gene expression could be detect ed when the cells were coincubated with the proinflammatory cytokines inter feron-gamma and tumor necrosis factor-alpha with inducible nitric oxide syn thase cDNA concentrations averaging 11.7 +/- 0.6 amol per mu g total RNA at 24 h, and 25.0 +/- 1.4 amol per mu g total RNA at 48 h, respectively. Intr acellular staining with an antibody recognizing inducible nitric oxide synt hase protein and subsequent analysis by flow cytometry revealed a 4-fold in crease of inducible nitric oxide synthase protein in human dermal microvasc ular endothelial cells treated with interferon-gamma/tumor necrosis factor- alpha. This was accompanied by a significant elevation in nitrite/nitrate c oncentrations in the cell-free culture supernatants, Our results indicate t hat human dermal microvascular endothelial cells are provided with an induc ible nitric oxide synthase system and can be regarded as an appropriate cel l model for investigating inducible nitric oxide synthase gene expression a nd nitric oxide properties in microvascular endothelial cells.