AIM2 activation mediated by RIPK1/3-dependent mitochondrial DNA release drives Aβ1-40-Induced retinal pigment epithelium injury.

Abstract

Background: The retinal pigment epithelium (RPE) degeneration and subsequent retinal atrophy are hallmarks of age-related macular degeneration (AMD). Amyloid-beta (Aβ), the primary component of amyloid plaques in Alzheimer's disease (AD), is also present within drusen and is considered a critical factor contributing to RPE degeneration in AMD. Recent findings indicate that Aβ-induced inflammation plays a role in RPE degeneration. The aim of this study was to explore the molecular players and the precise mechanisms involved in this process, particularly the potential role of the absent in melanoma 2 (AIM2)-like receptors (ALRs) inflammasome.

Methods: An animal model of Aβ_1-40-induced RPE injury was established. Fundus photography, electrophysiology and hematoxylin-eosin staining were used to evaluate the morphological and functional RPE damage. Transcriptome sequencing was used to detect the differentially expressed genes between Aβ_1-40 group and control group. The transcriptional and protein expression levels of AIM2 pathway and RIPK family members were detected. Adeno-associated virus vector 2/2 (AAV2/2)-shAIM2 was constructed to knockdown AIM2 expression in mice RPE cells. Aβ_1-40-treated ARPE-19 cells and hRPE cells were employed to analyze the regulatory effects of RIPK family on mitochondrial DNA (mtDNA) release and AIM2 pathway activation.

Results: Aβ induces RPE damage through stimulation of AIM2 inflammasome and augmentation of caspase-1 and interleukin-1β (IL-1β). Knocking down AIM2 inhibits the release of inflammatory cytokines and alleviates the degeneration of the retina and RPE. Simultaneously, Aβ triggers the activation of RIPK1/RIPK3 kinases, as manifested by heightened protein expression and phosphorylation. Inhibiting RIPK1/RIPK3 phosphorylation dampens AIM2 inflammasome activity and curtails IL-1β secretion. Mechanistically, RIPK1/RIPK3 inhibition attenuates Aβ-induced Drp1(S616) hyperphosphorylation, consequently reducing mitochondrial fission and the efflux of mitochondrial DNA (mtDNA) into the cytosol. The diminished mtDNA release is responsible for attenuated AIM2 activation and subsequent inactivation of the stimulator of interferon genes (STING)/nuclear factor-kappa-B (NF-κB) signaling cascade.

Conclusions: Our study is the first to validate AIM2's contribution in Aβ-induced RPE pathology and underscore the significance of the RIPK1/RIPK3-induced mtDNA release in modulating inflammatory responses, shedding light on the underlying mechanisms and potential therapeutics of AMD.