Tumour necrosis factor-alpha gene expression and production in human umbilical arterial endothelial cells

Endothelial cells act as an interface between the blood and tissues, and are known to be involved in inflammatory processes. These cells are responsive to and produce different cytokines. Tumour necrosis factor-alpha (TNF-alpha) not only is one of the most important inflammatory peptides, but also can be induced by lipopolysaccharide (LPS). The focus of the present study was on TNF-alpha gene expression and production in human umbilical arterial endothelial cells (HUAEC), including the kinetics of this process. Interleukin-1alpha (IL-1alpha), LPS and TNF-alpha, which are all known to be elevated in septic shock, were used as stimulators at concentrations commonly found in patients with sepsis. Through the use of reverse transcriptase/PCR, immunohistochemical reactions and ELISA techniques, we showed that, in HUAEC, all three stimuli were able to induce gene expression and production of TNF-alpha. Furthermore, this induction by IL-1alpha, LPS and TNF-alpha occurred in a time- and concentration-dependent manner in these cells. TNF-alpha expression and production was induced by all three agents at concentrations commonly found in patients with sepsis. TNF-alpha mRNA was observed within 30 min regardless of the stimulus used, but the levels peaked at different times. Since it is well established that TNF-alpha is able to induce the synthesis of IL-1alpha in endothelial cells and, as shown in the present study, TNF-alpha and IL-1alpha are themselves able to induce the synthesis of TNF-alpha in endothelial cells, an autocrine potentiation of cytokine release in sepsis can be proposed. This situation could lead to a locally acting 'vicious cycle' which, when considered in addition to the known ability of TNF-alpha to induce apoptosis, could mean that various organs will be damaged, a condition associated with sepsis. Thus these results provide further evidence for the important role played by the endothelium in inflammation.