Anti-Inflammatory Mechanisms of the Annexin A1 Protein and Its Mimetic Peptide Ac2-26 in In Vivo and In Vitro Models of Ocular Inflammation

Abstract

Annexin A1 (AnxA1) is a protein that displays potent anti-inflammatory properties, but its expression in eye tissue and its role on ocular inflammatory diseases have been poorly studied. Here, we investigated the mechanism of action and potential uses of AnxA1 and its mimetic peptide (Ac2-26) in the endotoxin-induced uveitis (EIU) rodent model and in human retinal pigmented epithelium (ARPE-19) cells activated by lipopolysaccharide. In rats, analysis of EIU untreated for 24 and 48 h, EIU treated with topical applications or with a single subcutaneous injection of Ac2-26 revealed the anti-inflammatory actions of Ac2-26 on leukocyte infiltration and on the release of inflammatory mediators, while the systemic administration of Boc2, a formylated peptide receptor (fpr) antagonist, abrogated the peptide protective effects. Moreover, AnxA1-/- mice showed exacerbated EIU compared with wild-type animals. Immunohistochemical studies of ocular tissue showed a specific AnxA1 post-translational modification in EIU and indicated that the fpr2 receptor mediated the anti-inflammatory actions of AnxA1. In vitro studies confirmed the roles of AnxA1 and fpr2 and the protective effects of Ac2-26 on the release of chemical mediators in ARPE-19 cells. Molecular analysis of nuclear transcription factor kB (NF-kB) translocation and interleukin (IL)-6, IL-8 and cyclooxygenase-2 gene expression indicated that protective effects of AnxA1 occur independently of the NF-kB signaling pathway and possibly in a post-transcriptional manner. Together our data highlight the role of AnxA1 in ocular inflammation, especially uveitis, and point out the employment of AnxA1 or its mimetic peptide Ac2-26 as therapeutic approaches. (AU)