Staphylococcal enterotoxin A-induced injury of human lung endothelial cells and IL-8 accumulation are mediated by TNF-alpha.

Staphylococcal enterotoxin A (SEA), a superantigen produced by some strains of Staphylococcus aureus, causes a variety of clinical manifestations ranging from food poisoning to shock. S. aureus can also be associated with the development of acute respiratory distress syndrome, and SEA has been shown to cause an inflammatory reaction in the lung. Therefore, we examined possible interactions between SEA, PBMCs, polymorphonuclear cells (PMNs), and normal human lung microvascular endothelial cells (HMVEC-L), as well as the role of these interactions on the secretion of IL-8. Injury to HMVEC-L, as measured by the release of 51Cr, increased significantly when HMVEC-L were incubated with SEA and PBMCs. IL-8 was secreted by both PBMCs and HMVEC-L. The accumulation of IL-8 in the culture medium of HMVEC-L was increased by SEA in a dose-dependent manner and was directly related to the number of PBMCs present. Although neither anti-human IL-8 nor IL-1 mAb inhibited HMVEC-L cytotoxicity, anti-human TNF-alpha mAb inhibited both the cytotoxicity and IL-8 accumulation completely. When HMVEC-L were incubated with supernatants from SEA-treated PBMCs, HMVEC-L cytotoxicity was comparable with HMVEC-L incubated with SEA and PBMCs at the same time. Although high concentrations of purified PMNs induced HMVEC-L lysis in a dose-dependent manner, the effect of PMNs was not changed in the presence of SEA. These findings suggest that TNF-alpha secreted by SEA-stimulated PBMCs plays a leading role in HMVEC-L injury.