The effect of 17β-estradiol on IL-6 secretion and NF-κB DNA-binding activity in human retinal pigment epithelial cells

Toll-like receptors (TLRs) and inflammatory cascades participate in the pathology of age-related macular degeneration (AMD). The effect of estrogens on the development of AMD is poorly understood, although many studies indicate that these compounds can modulate inflammatory responses. In this study, we investigated the regulatory role of TLR agonists and 17β-estradiol (E2) on IL-6 expression and NF-κB DNA-binding activity in human retinal pigment epithelial cells (ARPE-19). The inflammatory response of ARPE-19 cells to various TLR agonists, e.g. Pam, zymosan, flagellin, SLTA and lipopolysaccharide (LPS) exposures were examined via the secretion of IL-6 cytokine as analyzed by ELISA. In addition, the IL-6 responses to the estrogen-receptor agonist, E2, and to the estrogen-receptor antagonist ICI 182.780 as well as to the NF-κB inhibitor helenalin were compared. The DNA-binding activity of NF-κB transcription factor of nuclear cell extracts was analyzed by the gel mobility shift assay (EMSA). TLR4 gene expression was studied by quantitave PCR. The TLR4 agonist, LPS, caused a clear IL-6 response that was attenuated by E2 in ARPE-19-cells. The anti-inflammatory properties of E2 were mediated through estrogen receptors and were associated with decreased NF-κB DNA-binding activity. The level of TLR4 gene expression was not affected by LPS exposure. Our results indicate that IL-6 expression is regulated through NF-κB transcription factor and stereoid-receptor signalling pathways in ARPE-19 cells.