The Role of the STING/Type I IFN Signaling Pathway in Age-Related Macular Degeneration(AMD)

Abstract

Purpose : Geographic atrophy(GA), an advanced form of age-related macular degeneration(AMD), is characterized by degeneration of the photoreceptors and retinal pigment epithelium(RPE). Prior evidence has implicated senescent retinal cells contribute to the pathogenesis of AMD. Increased activation of cyclic GMP–AMP synthase(cGAS)/ stimulator of interferon genes(STING)/Type I Interferon pathway has been reported in GA patients. However, the role of Type-I IFNβ in chronic retinal degeneration remains elusive. This study aims to investigate the role of STING/IFNβ in chronic retinal degeneration and cellular senescence contributing to the pathogenesis of GA.

Methods : STING protein expression in postmortem eyes with various stages of AMD was measured by immunohistochemistry. Luminex was used to determine the IFNβ production in response to STING agonists in primary human RPEs. To elucidate the role of IFNβ in chronic retinal degeneration in vivo, AAV2-CAG-IFNβ(1x10^9 GC/eye, n=12) was used for chronic(20 weeks) expression of IFNβ in the eyes of C57BL/6J mice via intravitreal injection and AAV2-CAG-Null(1x10^9 GC/eye, n= 12) was injected as a control. Optical coherence tomography(OCT) and fluorescein angiography(FA) imaging were performed to monitor leakage and retinal degeneration. Senescence-associated(SA) β-galactosidase assay and immunohistochemistry were used to analyze the retinal cellular senescence and RPE degeneration.

Results : STING protein expression increased in the RPE of AMD patients. In primary human RPEs, STING agonists led to dose-dependent IFNβ production. In the mouse model, an increase of retinal degeneration was observed in AAV2-CAG-IFNβ injected eyes by OCT and fundus imaging, but not in AAV2-CAG-Null injected eyes. AAV2-CAG-IFNβ injected mouse eyes showed a reduction of RPE65 and CRALBP expression and developed degenerated RPEs with features remarkably similar to GA patients. Furthermore, β-galactosidase and p16INK4a positive retinal cells were upregulated in the murine eyes injected with AAV2-CAG-IFNβ, but not in the AAV2-CAG-Null eyes.

Conclusions : STING activation in RPE occurs in postmortem eyes with all stages of AMD. STING agonists drive IFNβ secretion in primary human RPEs. In the murine model, chronic IFNβ expression by AAV2 increases retinal cell senescence and contributes to RPE degeneration. These results suggest that cGAS/STING induced IFNβ may contribute to the pathogenesis of AMD.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.