Factor-H-related protein 1 (FHR1), a promotor of para-inflammation in age-related macular degeneration.

Abstract

Age-related macular degeneration (AMD), a multifactorial type of retinal degeneration represents the most common cause for blindness in elderly. Polymorphisms in complement factor-H increase, while absence of factor-H-related protein-1 (FHR1) decreases the AMD risk, currently explained by their opposing relationship. Here we identify a FHR1-driven pathway fostering chronic cellular inflammation. FHR1 accumulates below the retinal pigment epithelium (RPE) in AMD donor tissue and similarly the murine homolog, muFHR1 is abundant in three AMD-relevant mouse models. These mouse models express the muFHR1 receptor EGF-like module-containing mucin-like hormone receptor 1 (Emr1) on the RPE and on invading mononuclear phagocytes (MP), where both cells form clusters via muFHR1/Emr1. FHR1 ignited EMR2-dependent Ca-signals and gene expression in both human RPE cell line and in vivo where muFHR1 affects Emr1cells (RPE and MP) gene expression shown by RNAseq analysis. As muFHR1 deletion in mice revealed significantly reduced MP invasion and neoangiogenesis in laser-induced choroidal neovascularization, we hypothesize that FHR1 accumulates, stabilizes and activates MP in the stage of RPE degeneration.