Abstract
Purpose :
RPE dedifferentiation and mesenchymal transition (EMT) is central to numerous degenerative ocular diseases including proliferative vitreoretinopathy and AMD. Loss of cell contact inhibition and exposure to pro-EMT stimuli such as TGF-β have been proposed as the main mechanisms for promoting EMT in RPE. We have previously shown that metabolic dysfunction is sufficient to induce EMT in RPE. Here, we examined the effect of EMT induction on RPE metabolism and evaluated the therapeutic potential of metabolism-targeting drugs.
Methods :
To induce EMT, matured ARPE-19 cells were exposed to 0.2 nM TGFβ1 for up to 72 hrs. Gene expression analysis was performed by quantitative PCR. Mitochondrial and glycolytic functions were assessed by high-resolution respirometry to measure of OCR and ECAR, respectively. Glycolysis was blocked with 5 mM 2-Deoxy-D-glucose (2DG). To promote mitochondrial oxidative phosphorylation (OXPHOS), cells were treated with 10µM ZLN005. ARPE-19 proliferation was assayed by fluorometric quantification of DNA content (CyQuant). ARPE-19 migration and contractility were assessed 24 and 48 hrs post-TGFβ1 using the scratch and collagen gel contraction assays, respectively.
Results :
High-resolution respirometry reveals that TGFβ1 stimulation of RPE triggers a rapid metabolic shift with increased glycolytic activity (ECARmax= 11.8 vs. 15.5 mpH/min, p<0.05) and suppression of mitochondrial respiration (OCRmax= 1.5 vs. 0.2 pmol/min, p<0.001). This metabolic reprogramming is associated with induction of the glycolysis-promoting enzyme, PFKFB3 (1 vs. 1.5, p<0.001) and repression of genes related to mitochondrial function (PGC-1α: 1 vs 0.07, p<0.0001; PPARα: 1 vs. 0.75, p<0.05; TFAM: 1 vs 0.79, p<0.01). Glycolysis inhibition with 2DG or OXPHOS induction with ZNL005 efficiently protects RPE against TGFβ1-induced EMT as shown by reduced migration (2DG= 34% inh., p<0.01; ZLN= 71% inh., p<0.0001) and contractility (2DG= 17.2% inh., p<0.0001; ZLN= 33.4% inh., p<0.0001). ZLN005 shows superior anti-EMT effects compared to 2DG in all end-points assayed including proliferation (2DG= 8% inh. vs. ZLN= 52.4% inh., p<0.001).
Conclusions :
These results indicate that TGFβ-activation of RPE triggers a profound metabolic shift that drives EMT. Pharmaceutical modulation of RPE metabolism represents a novel strategy for preventing EMT of RPE.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.