Suppression of homeostatic gene expression and increased expression of metabolism-related genes are early features of glaucoma in optic nerve head microglia

Abstract

Background: Glaucoma is the leading cause of irreversible vision loss. Ocular hypertension is a major risk factor for glaucoma and recent work has demonstrated critical early neuroinflammatory insults occur in the optic nerve head following ocular hypertension. Microglia and infiltrating monocytes are likely candidates to drive these neuroinflammatory insults. However, the exact molecular identity / transcriptomic profile of microglia early following ocular hypertensive insults is unknown. Methods:To elucidate the molecular identity of microglia during early glaucoma pathogenesis, we performed RNA-sequencing of microglia mRNA from the optic nerve head of a genetic mouse model of glaucoma (DBA/2J) at a time point following ocular hypertensive insults, but preceding detectable neurodegeneration (with microglia identified as being CD45 lo /CD11b + /CD11c -). Transcriptomic profiles were compared to other published optic nerve head datasets to assess the contribution of microglia to the signatures discovered in these published data. Furthermore, RNAsequencing was performed on optic nerve head microglia from mice treated with radiation therapy, a potent therapy preventing neuroinflammatory insults.Results: Transcriptomic profiling of optic nerve head microglia mRNA identifies early metabolic priming with marked changes to mitochondria-derived RNA expression, and changes to phagocytosis, inflammatory, and sensome pathways. Comparative analysis of these data with data from previously published whole optic nerve head tissue or monocyte-only samples from DBA/2J mice demonstrate that many of the neuroinflammatory signatures in these data sets arise from infiltrating monocytes and not reactive microglia. Finally, radiation therapy of DBA/2J mice potently abolishes these microglia metabolic transcriptomic changes at the same time points. Conclusions:Microglia become metabolically primed early in glaucoma pathogenesis with suppression of homeostatic regulation including phagocytosis, inflammatory, and sensome pathways. These changes are largely prevented by radiation therapy. Neuroinflammatory signatures in DBA/2J glaucoma likely arise from infiltrating monocytes and not from activated or proliferative microglia at this early time point. In addition, our data provide a unique resource for the community to help drive further hypothesis generation and testing. (Figure 3D-F) showed that radiation treatment affects phagocytosis, metabolism, mitochondria, and inflammation related genes, all pathways altered in microglia (see above). There were 579 genes altered by radiation that overlapped with changes in glaucoma (D2 vs. D2-Gpnmb + comparison). For 578 of these genes, radiation treatment corrected the disease-related change (Figure 3G). Dcbld2 was the single gene DE downregulated in both datasets. Dcbld2 encodes the endothelial and smooth muscle cell-derived neuropilin-like protein (ESDN) which is upregulated in endothelial cells following vascular injury (53). Its deletion or downregulation impairs retinal angiogenesis (54) and ...

GLP-1R agonist NLY01 reduces retinal inflammation, astrocyte reactivity, and retinal ganglion cell death secondary to ocular hypertension

“…Recently published transcriptomic data from the DBA/2J mouse model of glaucoma suggested that early inflammation is driven by infiltrating macrophages (CD11b+ CD11c+), while resident microglia (CD11b+ CD11c) initially adopt an anti-inflammatory gene expression pattern (Tribble et al, 2019). Our results support this conclusion, by demonstrating IL-1α, TNF-α, and C1q upregulation by CD11b+ CD11c+ cells before CD11b+ CD11c-cells.…”

“…However, recent work in the DBA/2J mouse model of glaucoma demonstrated that resident retinal microglia (CD11b+ CD11c-) adopted an anti-inflammatory state early on in their response to eIOP. The authors suggested that CD11b+ CD11c+ cells, a population enriched with infiltrating macrophages, contributed to early eIOP-induced inflammation (Tribble et al, 2019). We compared the expression of Il1a, Tnf, and C1qa between CD11b+ CD11c-(predominantly microglia) and CD11b+ CD11c+ (predominantly macrophages) cells isolated from microbeadinjected eyes.…”

GLP-1 Receptor Agonist NLY01 Reduces Retinal Inflammation and Neuron Death Secondary to Ocular Hypertension

“…Recent work in the DBA/2J mouse model of glaucoma has further refined our understanding of CD11b + cell subpopulations. In the DBA/2J mouse model, early inflammation is driven by CD11b + CD11c + cells while CD11b + CD11c − cells adopt a largely anti-inflammatory pattern of gene expression ( Tribble et al, 2019 ). We isolated CD11b + CD11c + and CD11b + CD11c − cells ( Figure S3A ) and measured Tmem119 mRNA levels in both populations ( Figure S3B ), a marker of resident microglia ( Bennett et al, 2016 ).…”