The Secreted Ly6/uPAR-Related Protein 1 (Slurp1) Modulates Corneal Angiogenic Inflammation Via NF-κB Signaling

Purpose: Previously we demonstrated that the secreted Ly-6/uPAR related protein 1 (SLURP1), abundantly expressed in the corneal epithelium (CE) and secreted into the tear fluid, serves as an antiangiogenic molecule. Here we describe the Slurp1-null (Slurp1X−/−) mouse corneal response to silver nitrate (AgNO3) cautery. Methods: Five days after AgNO3 cautery, we compared the wild-type (WT) and Slurp1X−/− mouse (1) corneal neovascularization (CNV) and immune cell influx by whole-mount immunofluorescent staining for CD31 and CD45, (2) macrophage and neutrophil infiltration by flow cytometry, and (3) gene expression by quantitative RT-PCR. Quantitative RT-PCR, immunofluorescent staining, and immunoblots were employed to evaluate the expression, phosphorylation status, and subcellular localization of NF-κB pathway components. Results: Unlike the WT, the Slurp1X−/− corneas displayed denser CNV in response to AgNO3 cautery, with more infiltrating macrophages and neutrophils and greater upregulation of the transcripts encoding VEGFA, MMP2, IL-1b, and vimentin. At 2, 7, and 10 days after AgNO3 cautery, Slurp1 expression was significantly downregulated in the WT corneas. Compared with the WT, naive Slurp1X−/− CE displayed increased phosphorylation of IKK(a/b), elevated phosphorylation of IκB with decreased amounts of total IκB, and higher phosphorylation of NF-κB, suggesting that NF-κB signaling is constitutively active in naive Slurp1X−/− corneas. Conclusions: Enhanced angiogenic inflammation in AgNO3 cauterized Slurp1X−/− corneas and constitutively active status of NF-κB signaling in the absence of Slurp1 suggest that Slurp1 modulates corneal angiogenic inflammation via NF-κB signaling.