Abstract
Purpose :
Retinitis pigmentosa (RP) is a group of inherited retinal dystrophies caused by mutations in genes that are typically expressed by rods, which results in initial death of rods followed by cones. Although a number of gene mutations associated with RP have been identified, the molecular mechanisms underlying this family of incurable condition remains unknown. Recently, purinergic signaling has been implicated in the progression of retinal degeneration. This study aimed to investigate the role of the P2X4 receptor (P2X4-R) in microglia activation and to evaluate the effects of P2X4-R inhibition on neuroinflammation and photoreceptor (PR) death in RP.
Methods :
Pharmacological blockade of the P2X4-R was performed by administering duloxetine hydrochloride to rd10 mice. To achieve specific retinal microglia P2X4-R inhibition, we subretinally injected an AAV-Cre vector driven by a CX3CR1 promoter into rd10/P2X4-Rfl/fl mice to knockdown microglial P2X4-R. Immunohistochemistry and qPCR were used to validate microglial P2X4-R inhibition and to examine its effects on PR integrity and neuroinflammation in rd10 mouse. ERG and optokinetic tracking were used to assess PR function and visual performance in microglial P2X4-R-deficient- and untreated rd10 mice.
Results :
Microglial P2X4-R expression was elevated in PR death and contributed to the loss of visual function in the rd10 retina. Pharmacological inhibition and genetic ablation of microglial P2X4-R in P25 rd10 mice significantly increased ONL thickness (by 21.52 ± 1.758µm, p<0.0001 and 19.53 ± 6.656µm, p=0.017) and cone IS/OS length (by 5.272 ± 0.4880µm, p<0.0001 and 8.368 ± 1.281µm, p<0.0001). Improved ERG scotopic (AAV-Cre=43.61±3.81µV vs. control=8.52±1.40µV, p<0.0001) and photopic (AAV-Cre =23.07±3.06µV vs. control=9.08±1.22µV, p=0.02) a-wave amplitudes and optokinetic responses (AAV-Cre=0.46±0.01 cycles/degree vs. control=0.38±0.0006 cycles/degree, p<0.0001) in microglial P2X4-R-depleted rd10 mice corroborated our histological findings, indicating that inhibition of microglial P2X4-R ameliorated PR degeneration in rd10 retina.
Conclusions :
This study suggested a key role for microglial P2X4-R in mediating neuroinflammation and contributing to PR death in RP. Microglial P2X4-R is a potential therapeutic target in preventing PR degeneration in retinal dystrophy.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.