Abstract
Purpose :
Reactive macrophages/microglia have been found to actively phagocytose live photoreceptors and release proinflammatory cytokines and chemokines, which can lead to visual impairment. Light damage (LD) is an environmental risk factor to induce retinal degeneration. The bromodomain and extraterminal domain (BET) proteins are epigenetic readers, which promote transcription of proinflammatory factors. Here, we are aimed to determine the effects of dBET6 ,a proteolysis-targeting chimera (PROTAC) molecule that selectively degrades BET through the ubiquitin-proteasome system, on macrophages/microglia reactivity and reactive gliosis in response to LD.
Methods :
To induce the mouse model of light-induced retinal degeneration (LIDR), BLAC/c mice were exposed to 15000 lux white light for 2 h. Mice were subjected to intraperitoneal injections of dBET6 or a vehicle solution, administered 1 hour prior to light exposure and repeated 24 hours after light exposure. A control group (CTRL) was left untreated. Immunofluorescence (IF) staining analysis showed the morphology of microglia in retinal flat mounts and the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was used to determine retinal cell viability. Western blot assay determined the expression patterns of proinflammatory factors.
Results :
We found that LD led to presence of amoeboid-haped macrophages/microglia, characterized by significantly reduced process length and endpoints. IF staining analysis revealed that LD had induced an elevation in the signal of glial fibrillary acidic protein (GFAP), which is a widely used marker of Muller cell and astrocyte reactivity, in the inner plexiform layer and inner nuclear layer. While IF analysis also revealed a reduction in the GFAP signal in mouse retina injected with dBET6. In addition, dBET6 inhibited activation of macrophages/microglia after LD, as evidenced by reduced IBA1 and CD86-positive cells in the retina. WB analysis also indicated that dBET6 suppressed the protein level of CD86, IBA1 and GFAP after LD.
Conclusions :
In summary, we found that dBET6 effectively inhibited LD-induced macrophages/microglia activation and gliosis in the mouse retina. Our results suggest that dBET6 acts as a promising potential drug for the treatment of retinal degeneration.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.