Effect of tumor necrosis factor-α on intracellular Staphylococcus aureus in vascular endothelial cells

Abstract

Although tumor necrosis factor-α (TNF-α) is an important host factor against intracellular bacteria, little is known about the effect of TNF-α on the persistence of intracellular Staphylococcus aureus in vascular endothelial cells. It was investigated whether recombinant human TNF-α influences the survival of intracellular S. aureus (ATCC 29213) in human umbilical vein endothelial cells (HUVEC) under a condition with an antistaphylococcal agent, and its mechanism. The HUVECs were incubated with TNF-α, oxacillin, or both in 24-well plates for up to 48 h following internalization of S. aureus (106 CFU well-1) into HUVECs for 1 h. TNF-α (1 ng mL-1) significantly reduced the number of intracellular S. aureus in HUVECs, and TNF-α plus oxacillin eliminated more intracellular S. aureus in HUVEC than oxacillin alone. The LDH viability assay and quantification of apoptosis using photometric enzyme-immunoassay showed that TNF-α preferentially induced cell death and apoptosis of HUVECs infected with S. aureus compared with noninfected HUVECs. These results indicate that TNF-α helps antistaphylococcal antibiotics to eliminate intracellular S. aureus in vascular endothelial cells, partly because TNF-α preferentially induces apoptosis of endothelial cells infected by S. aureus. © 2008 Federation of European Microbiological Societies.