Wu W.-C.,Kaoshiung Medical University Hospital |
Wu W.-C.,Kaoshiung Medical University |
Hu D.-N.,New York Medical College |
Gao H.-X.,Yeshiva University |
And 4 more authors.
Purpose: To study the effect of subtoxic levels of hydrogen peroxide (H2O2) on the expression and release of interleukin-6 (IL-6) by cultured retinal pigment epithelial (RPE) cells and to explore the relevant signal pathways. Methods: Cultured human RPE cells were stimulated with various subtoxic concentrations of H2O2 for different periods. Conditioned medium and cells were collected. IL-6 in the medium and IL-6 mRNA in the collected cells were measured using an IL-6 enzyme-linked immunosorbent assay kit and reverse transcriptase polymerase chain reaction, respectively. Nuclear factor-kappaB (NF-κB) in nuclear extracts and phosphorylated p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinases (JNK) in cells cultured with and without H2O2 were measured by NF-κB and MAPK enzyme-linked immunosorbent assay kits. Inhibitors of p38 (SB203580), ERK (UO1026), JNK (SP600125), and NF-κB (BAY11-7082) were added to the cultures before the addition of H2O2 to test their effects. Results: Subtoxic levels of H2O2 (100 μM and less) increased the IL-6 mRNA level and the release of IL-6 protein by the cultured human RPE cells in a dose- and time-dependent manner. This was accompanied by an increase of NF-κB in nuclear extracts and phosphorylated p38 MAPK, ERK, and JNK in cell lysates, particularly in the p38 and NF-κB. The NF-κB inhibitor decreased the H2O2-induced expression of IL-6. The p38 inhibitor, but not the ERK or JNK inhibitor, completely abolished H2O2-induced expression of IL-6 by RPE cells. The p38 inhibitor also abolished the increase of NF- κB in nuclear extracts in cells treated with H2O2. Conclusions: H2O2 stimulated the production of IL-6, a key factor in the modulation of immune responses, inflammatory processes, and the occurrence of autoimmune diseases, which recently has been documented to be increased in age-related macular degeneration (AMD). This may be a molecular linkage for the oxidative stress and inflammatory/autoimmune reactions in AMD and may provide a novel target for the treatment of AMD. © 2010 Molecular Vision. Source