Abstract
Purpose :
Ischemia-induced retinopathy is one of the leading causes of irreversible blindness. Overactivated retinal myeloid cells are a crucial driving force of pathological angiogenesis and inflammation in ischemic retinopathy. The cyclic GMP-AMP (cGAMP) synthase (cGAS) and stimulator of interferon genes (STING) pathway is a key regulator of myeloid cell activation. This study investigated both the functions and regulatory mechanisms of cGAS-STING signaling in oxygen-induced retinopathy (OIR).
Methods :
WT C57BL/6J mice and Sting-/- mice were used for OIR. Retinal neovascular and avascular areas were quantified in isolectin-stained retinal flat mounts. Retinal leukocyte adhesion was measured by perfusion labeling with concanavalin A lectin. Retinal myeloid cells were isolated from retinas using CD11b+ MACS microbeads. The cGAS, STING, peroxisome proliferator-activated receptor α (PPARα), and autophagy markers were measured using Western blot analysis. Surface and activation markers of retinal myeloid cells were measured by flow cytometry.
Results :
The protein levels of cGAS-STING signaling were markedly upregulated in retinal CD11b+ cells of OIR mice. Sting knockout (KO) alleviated pathologies of OIR, including retinal neovascular areas, avascular areas, and leukostasis. Sting KO reduced the percentages of active M1 (IL1β+) and M2 (CD163) myeloid cells in OIR retinas. In addition, we found that PPARα was downregulated in retinal CD11b+ cells of the OIR model. Pparα-/- mice showed higher cGAS-STING levels in retinal CD11b+ cells compared to those in WT mice. PPARα agonists suppressed cGAS-STING signaling in the OIR retinas and mitigated the pathologies of OIR. In primary retinal microglial cells, the cGAS-STING levels were decreased in cells with starvation-induced autophagy and increased when autophagy was blocked by chloroquine. Pparα-/- retinal microglial cells showed defective autophagy and increased protein levels of cGAS-STING. Induction of autophagy decreased cGAS-STING levels in Pparα-/- retinal microglial cells.
Conclusions :
Overactivation of cGAS-STING signaling in retinal myeloid cells plays a pathogenic role in ischemic retinopathy. PPARα inhibits the overactivated cGAS-STING signaling via the modulation of autophagy.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.