Abstract
Purpose :
The G-protein coupled receptor 81 (GPR81) is a lactate receptor expressed in tissues with high energy demands, and has been shown to regulate cerebral blood flow. Previous work showed delayed inner retinal vascular development in neonatal Gpr81-/- mice, but no long-term effects on vasculature in adult retinas. Here, we examined the effect of Gpr81 deletion on blood-retinal barrier (BRB) integrity in adult mice.
Methods :
Gpr81+/+ and Gpr81-/- mice (3 mo.) were used. Retinal flatmounts were immunostained for CD31. Retinal vascular integrity was assessed by measuring retinal leakage of FITC-albumin following tail-vein injection; albumin extravasation was confirmed by immunoblotting in neural retina. Expression of genes in the Wnt signaling pathway and paracellular/transcellular BRB function was analyzed by qPCR. Transcriptomic analysis (RNA-seq) was done on Gpr81+/+ and Gpr81-/- retinas. Bioinformatics analyses (Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG)) were performed on differentially expressed genes.
Results :
Large retinal arteries showed increased vascular beading in Gpr81-/- retinas, with no difference in capillary morphology. Extravasation of mouse IgG in Gpr81-/- retinas was not detected; however, fluorescein angiography showed retinal leakage of FITC-albumin, and was confirmed by immunoblotting in neural retina. Gpr81-/- retinas showed upregulation of PLVAP (~3x), Sox17 (~15x), and Wnt3 (~5x), and downregulation of Ndp (~2x) and Wnt7 (~10x) (p<0.05). RNA-seq yielded 1021 genes that were differentially expressed; 355 upregulated and 666 downregulated in Gpr81-/- retinas. GO analysis showed downregulation of cell adhesion molecule binding (p<0.0025) and cell-cell adhesion mediator activity in Gpr81-/- retinas (p<0.0005). The most statistically significant pathway downregulated by KEGG analysis was the tight junction pathway (p<0.0025).
Conclusions :
Our data suggest a possible role of GPR81 in regulating BRB integrity in adult mice. Ongoing studies examine the participation of GPR81 in BRB formation in neonatal mice, and investigate GPR81 agonism as a treatment for pathologic BRB breakdown.
This is a 2020 ARVO Annual Meeting abstract.