Linking mitochondrial dysfunction to inflammation during the progression of atrophic age-related macular degeneration

Abstract

Purpose : Mitochondrial dysfunction can trigger inflammatory changes in many age-related diseases, including AMD. The upregulated AKT2 signaling in RPE cells from human AMD donors triggers inflammation as well as lysosomal/autophagy, and mitochondrial/redox abnormalities. This study aims to explore the impact of dysregulated mitochondrial biogenesis on inflammation and oxidative stress in AKT2-overexpressing RPE cells. By utilizing an AKT2 inhibitor and P110 (a mitochondrial fission inhibitor), the study seeks to mitigate AKT2-induced disruptions in mitochondrial function and subsequently inflammation and oxidative stress induction. Understanding these mechanisms holds promise for unveiling novel therapeutic strategies addressing the inflammatory and mitochondrial impacts on AMD.

Methods : WT and Akt2 KI (RPE-specific knockin of Akt2 that shows an atrophic AMD-like phenotype with age) mice were used. 4 and 10-month-old WT and Akt2 KI mice (mice develop an AMD-like phenotype by 10 months) were used to isolate RPE cells whereas 10-month-old mice were used as donors for culturing RPE explants with or without Akt2 inhibitor (CCT128930; 1 μM) or mitochondrial fission inhibitor (P110; 1 μM) for 24 h. The levels of mitochondrial fission/fusion (Drp1, Mfn2), mitochondrial biogenesis (PGC-1α), oxidative stress (SOD2, CAT), and inflammatory (cGAS, STING) markers were evaluated by western blot. ELISA was performed to ascertain the level of IL-1β.

Results : Akt2 KI RPE cells showed increased expression of the mitochondrial fission protein Drp1 as well as reduced levels of PGC-1α (major regulator of mitochondrial biogenesis) and the mitochondrial fusion protein Mfn2 compared to WT, indicating increased mitochondrial fragmentation and decreased biogenesis. Pro-inflammatory mediators like cGAS, STING, and IL-1β and oxidative stress mediators like SOD2 and CAT were elevated in Akt2 KI RPE cells, compared to WT, indicating pro-inflammatory changes and oxidative stress. Furthermore, treatment with CCT128930 or P110 rescued the levels of these inflammatory and mitochondrial proteins in Akt2 KI RPE explants, compared to untreated explants.

Conclusions : Our study reveals that targeting AKT2 or the mitochondrial fission process could mitigate downstream activation of inflammation and oxidative stress in RPE cells. This study provides novel evidence for the importance of AKT2 and mitochondrial fission in AMD.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.