Figure 4. Effects of nuclear factor factor-kappaB and mitogen-activated protein kinase inhibitors on the hydrogen peroxide-induced production of interleukin-6 by retinal pigment epithelium cells. Retinal pigment epithelium (RPE) cells (ARPE-19) were plated into 24-well plates. After 24 h incubation, various mitogen-activated protein kinase (MAPK) and nuclear factor-kappaB (NF-κB) inhibitors were added to the medium separately, including BAY11–7082 (NF-κB inhibitor), UO1026 (extracellular signal-regulated kinases inhibitor), SP600125 (c-Jun N-terminal kinase inhibitor) and SB203580 (p38 MAPK inhibitor, all from Calbiochem) at a final concentration of 10 µM with the exception of BAY11–7082 (5 µM). After 30 min, 100 µM hydrogen peroxide (H₂O₂) was added to the medium. Cells cultured without H₂O₂ were used as negative controls. Cells cultured with H₂O₂ but without inhibitors were used as positive controls. After 24 h incubation, the culture medium was collected and the IL-6 levels were measured with the human IL-6 Quantikine ELISA kit and expressed as pg/ml (mean±standard deviation in triplicate tests). *0.01< p<0.05, **p<0.01, compared with the positive controls (cells cultured with H₂O₂ but without inhibitors).