Oxidative stress-induced KLF4 activates inflammatory response through IL17RA and its downstream targets in retinal pigment epithelial cells

Age-related macular degeneration (AMD) is a leading cause of irreversible blindness worldwide. Oxidative stress (OS), inflammation and genetics are considered the key pathogenic factors contributing to AMD development. Recent evidence shows the pro-inflammatory interleukin 17 (IL17) signaling is activated in AMD patients and promotes disease pathogenesis. However, the interplay between OS and IL17 signaling, and the regulatory mechanism of IL17 pathway are largely unknown. OS-induced retinal pigment epithelial cell (RPE) damage causes both the initial pathogenesis of AMD and secondary degeneration of rods and cones. Healthy RPE is essential for ocular immune privilege, however, damaged RPE cells can activate inflammatory response. In the present study, we identified IL17RA, the principle receptor of IL17 signaling, is one of the most upregulated inflammatory genes in human RPE cells upon OS exposure. The prominent increase of IL17RA was also observed in RPE and retina of an AMD-like mouse model. Knockdown of IL17RA in RPE cells prevented OS-induced RPE cell apoptosis and reduced the inflammatory response in both RPE and macrophages. Furthermore, we found that transcription factor KLF4 directly activates IL17RA expression, therefore, promotes the production of IL1 beta and IL8 in an IL17RA-dependent manner. In addition, the mRNA level of KLF4 isoform 2 was positively correlated with that of IL17RA in AMD patients. Together, our study demonstrates an unrevealed relationship between IL17RA and OS, and a new regulatory mechanism of IL17RA by KLF4 in RPE cells. These findings suggest that inhibition of IL17RA as a new potential therapeutic target for AMD through RPE protection and inflammatory suppression upon OS exposure.