Microglia are highly specialized resident macrophages in the central nervous system that play a pivotal role in modulating neuroinflammation. Microglial plasticity is essential for their function, allowing them to polarize into proinflammatory M1-like or anti-inflammatory M2-like phenotypes. However, the mechanisms driving M1 and M2 microglial induction during retinal degeneration remain largely unexplored. In addition, drugs that regulate retinal microglial polarity have not been fully investigated. The synthetic glucocorticoid triamcinolone acetonide (TA) is widely utilized in ophthalmology clinics for its anti-inflammatory properties. Here, we investigated microglial polarity in a light-induced retinal degeneration mouse model, along with the effects and mechanisms of intravitreal injection of TA on microglial polarity, retinal inflammation, and visual function following light damage (LD). Our findings demonstrated that LD induced a pro-inflammatory M1 microglial signature, with levels of M1 marker proteins in the retina increasing in a time-dependent manner following LD. Intravitreal TA treatment mitigated LD-induced retinal inflammation, photoreceptor death, and retinal blood vessel leakage, and preserved retinal responsiveness to light stimuli. Mechanistically, TA suppressed the proinflammatory microglial phenotype while promoting the anti-inflammatory phenotype by activating the signal transducer and activator of transcription 6/arginase1 (STAT6/Arg1) signaling pathway. These results reveal a new mechanism by which TA protects the retina from LD by shifting microglia toward an anti-inflammatory state through the STAT6/Arg1 axis.
Keywords: Age-related macular degeneration; Glucocorticoid; High-content analysis; Inflammation; Microglia/macrophage polarization; Retinal degeneration; Retinitis pigmentosa.
© 2024. The Author(s).