Injury to adult human dermal microvascular endothelial cells in vitro

Adult human dermal microvascular endothelial cells maintained in culture for four to eight passages after isolation were injured by activated human neutrophils but were not injured by unstimulated cells. Injury was cytotoxic as indicated by release of 51Cr from prelabeled cells. Injury was partially inhibited with catalase, dimethylthiourea, and deferoxamine, but was not blocked by superoxide dismutase. Injury was enhanced following pretreatment with iron bound to the membrane-permeable chelator 8-hydroxyquinoline, while neither iron alone nor the chelator by itself enhanced injury. These data suggest that injury results from the generation of hydrogen peroxide by the activated neutrophils and its conversion to hydroxyl radical through an iron-dependent mechanism. These cells appear to be similar to human umbilical vein endothelial cells (HUVEC) in sensitivity to oxidant-induced injury. However, unlike HUVEC, these cells do not show the age-dependent decrease in sensitivity to killing by activated neutrophils that is a characteristic feature of HUVEC. Nor do they show the same increase in spontaneous lysis as a function of age that is characteristic of HUVEC.