Hydrogen peroxide induces mRNA for tumour necrosis factor alpha in human endothelial cells

Reactive oxygen intermediates are important mediators of inflammation. We investigated if hydrogen peroxide (H2O2) induces tumour necrosis factor alpha (TNFalpha) expression in cultured human cells from umbilical vein endothelium (HUVEC), aortic smooth muscle cells (SMC), peripheral blood mononuclear cells (PBMC), or the cell line Mono Mac 6. Cultures were stimulated with 200 micromol/L H2O2 for 15 min. After 4 h cells were harvested, mRNA extracted, and amplified by semiquantitative reverse transcription polymerase chain reaction (RT-PCR) with histone (H3) as reference gene. In HUVECs, mRNA for TNFalpha increased with a factor of 4 after stimulation (p < 0.001), in PBMC with a factor of 2 (p < 0.05), while mRNA from SMC and Mono Mac 6 did not increase significantly. Cellular TNFalpha protein in HUVECs was measured with flow cytometry (FACS) before and 6, 12, and 24 h after stimulation. TNFalpha protein was detectable in small, but reproducible amounts 12 h after stimulation, and increased further after 24 h. However, no secretion of TNFalpha was detected by ELISA. FACS analysis of the passaged HUVEC cultures did not reveal any contamination with non-endothelial cells. In conclusion, H2O2 induces TNFalpha mRNA in HUVECs and PBMC. In HUVECs an increase of intracellular TNFalpha protein was also detected, indicating that endothelial cells can produce small amounts of TNFalpha.