Introduction: During retinal degeneration, the actions of microglia, the resident immune cells of the retina intersect with those of recruited monocytes to regulate neuroinflammation. Activated microglia and monocytes can undergo pyroptosis, a form of programmed cell death, mediated by the nod-like receptor family protein 3 (NLRP3).
NLRP3 driven pyroptosis is inherently inflammatory, characterized by the N-terminal cleavage of gasdermin D (GSDMD) resulting in rapid formation of membrane pores and release of pro-inflammatory cytokines. In this work we have shown that impairing the pore forming capacity of GSDMD thereby impairs pyroptosis, decreasing the release of pro-inflammatory cytokines and overall neuroinflammation. We further investigate the inflammatory profile of GSDMD mutant and KO mice by high-throughput RNA sequencing to develop GSDMD as a novel gene target for treating retinal degenerations.
Methods: Retinal function and health of GSDMD mutant and KO mice was investigated in dim-reared condition and post-exposure to 5 days of photo-oxidative damage. Retinal function and health were examined using electroretinography (ERG), optical coherence tomography (OCT), TUNEL+ assay, IBA-1+ immunohistochemistry and H&E staining. One retina per mouse was excised for RNA extraction followed by high throughput RNA sequencing. Bioinformatics analyses were used to understand differential gene expression and impacted biological pathways in GSDMD mutant mice.
Results: Results from this work strongly support a role for GSDMD in the pathogenesis of retinal degenerations, with GSDMD mutant mice demonstrating preserved retinal function, increased photoreceptor survivability, and decreased number of microglia and infiltrating monocytes compared to WT controls. Results from GSDMD mutant RNA-sequencing also showed reduced neuroinflammation, decrease in pro-inflammatory cytokines and reduced oxidative stress.
Conclusion: Impairing GSDMD function by designing appropriate chemical or genomic inhibitors has high potential for reducing neuroinflammation thereby impairing progression of retinal degenerations, including age-related macular degeneration.