Abstract
Purpose :
Activation of the innate immune cGAS-STING signaling has been detected in retinal pigment epithelium (RPE) of Geographic atrophy (GA) patients, but the regulatory basis is largely unexplored. We have recently shown that transcriptional inert heterochromatin is required for RPE survival. Here, we investigate heterochromatin-mediated regulation of cGAS-STING, and determine the therapeutic potential of methotrexate (MTX), a newly identified heterochromatin-promoting drug and also a commonly used anti-inflammatory agent, in an experimental mouse model of GA.
Methods :
In silico analysis was performed to determine the expression of cGAS and STING in dry AMD patients. GA mouse model was established by I.P. injection of sodium iodate. Chaetocin (0.25mg/kg), a heterochromatin inhibitor, or MTX (1mg/kg) was I.P. injected daily for 3 days after SI injection. Fundus photography and immunohistofluorescent analysis determined RPE morphology. Protein cytokine array, western blot and qRT-PCR analysis detected the activation of cGAS-STING pathway. ChIP assay determined the occupancy of heterochromatin on cGAS and STING upon MTX treatment.
Results :
cGAS and STING are upregulated in RPE of GA patients and an experimental GA-like mouse model. Disruption of heterochromatin induces cGAS, STING and the downstream proinflammatory factors expression. Systemic application of MTX inhibits inflammatory gene expression in both RPE and retina, attenuates RPE degeneration and immune cell accumulation/activation. MTX promotes heterochromatin formation and thus epigenetically silencing of cGAS and STING.
Conclusions :
Together, we demonstrated the anti-inflammatory function of MTX in a GA-like mouse model and revealed a novel mechanism that MTX suppresses cGAS and STING expression through promoting heterochromatin-mediated silencing. This study may provide new treatment strategy for GA.
This is a 2021 ARVO Annual Meeting abstract.