Interleukin-1β Increases Baseline Expression and Secretion of Interleukin-6 by Human Uveal Melanocytes In Vitro via the p38 MAPK/NF-κB Pathway

Abstract

Melanocyte is the major cell component in the uvea. Interleukin (IL)-6 is a proinflammatory cytokine. The authors studied the expression of IL-6 in cultured human uveal melanocytes (UMs) and their modulation by IL-1β and explored the relevant signal pathways. Conditioned media and cells were collected from UMs cultured in medium with and without serum and were stimulated by IL-1β. IL-6 protein and transcript were measured using an ELISA kit and RT-PCR, respectively. NF-κB in nuclear extracts and phosphorylated p38 MAPK, ERK, and JNK in cells cultured with and without IL-1β were measured by ELISA kits. Inhibitors of p38 (SB203580), ERK (UO1026), JNK (SP600125), and NF-κB (BAY11-7082) were added to the cultures to evaluate their effects. Low levels of IL-6 protein were detected in the conditioned medium in UMs cultured without serum. The addition of serum increased the secretion of IL-6. IL-1β (0.1-10 ng/mL) increased IL-6 transcript and protein levels in a dose- and time-dependent manner up to sixfold, accompanied by a significant increase of NF-κB in nuclear extracts and phosphorylated p38 MAPK in cell lysates. NF-κB and p38 inhibitors alone decreased, whereas a combination of these two inhibitors completely abolished the IL-1β-induced expression of IL-6. This is the first report on the expression and secretion of IL-6 by UMs. IL-1β augments IL-6 production from the melanocytes. The data suggest that UMs may play a role in the pathogenesis of ocular inflammatory and autoimmune diseases.