Cooperation of Rel family members in regulating Aβ1-40-mediated pro-inflammatory cytokine secretion by retinal pigment epithelial cells

Amyloid-beta (Aβ) is a hallmark component of age-related macular degeneration (AMD), which induces secretion of pro-inflammatory cytokines from retinal pigment epithelium (RPE). Previous studies have shown that p50/RelA (p65), a member of NF-κB family, is an essential pro-inflammatory transcription factor responding to Aβ1-40 stimulation, but few focused on the other two Rel transcription factor members - RelB and c-Rel - and their role in Aβ1-40-mediated inflammation. It was reported that RelA, RelB and c-Rel are also implicated in various NF-κB-mediated inflammatory diseases. Therefore, we infer that Aβ1-40-mediated inflammation targets not only the classical inflammation regulator, RelA, but also RelB and c-Rel. In this study, we demonstrate that intravitreally injected Aβ1-40 mice develop AMD-like pathologic changes, coupled with Rel protein (RelA, RelB and c-Rel) synthesis and nuclear translocation. To focus on the interaction mechanism of Rel proteins, we found that RelB and c-Rel formed a heterodimer with RelA in mice model. We also found that c-Rel silencing decreased the levels of Aβ1-40-dependent RelA expression, indicating that RelB and c-Rel may interact with RelA as coactivator and c-Rel is required to activate the expression of RelA. Moreover, Rel protein silencing decreased the expression of distinct pro-inflammatory cytokines. Together, we demonstrate that besides RelA, RelB and c-Rel can also be activated by Aβ1-40, all of which mediate pro-inflammatory cytokine transcription and RPE damage. Our findings imply that RPE-mediated inflammation under the stimulation of Aβ1-40 is multi-targeted and RelA, RelB and c-Rel proteins may be the new targets of anti-inflammatory agents.