Regulation of blood-retina barrier by placental growth factor

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Project Abstract Diabetic retinopathy (DR) is a common complication of diabetes causing vision loss. Diabetes- induced metabolic abnormality and mitochondrial dysfunction resulting in oxidative stress is a primary pathogenic factor driving DR onset and development. This proposal will complete the two Aims: (1) To elucidate how placental growth factor (PlGF) mediates DR-related pathology by suppressing glucose 6 phosphate dehydrogenase (G6PD) activity and oxidative pentose phosphate pathway (oxPPP) flux. (2) To determine the protective role of G6PD’s antioxidant function via oxPPP in retinal cells against diabetes- induced oxidative injury. More specifically, the PlGF signaling pathway molecules involved in regulating G6PD expression and activity will be uncovered. The new mechanisms by which PlGF mediates diabetes- induced retinal endothelial cell barrier dysfunction and other DR-related pathologies through the metabolic shift from PPP to glycolysis and mitochondrial dysfunction will be elucidated in cell cultures and murine models. G6PD’s protective role in DR will be determined using cell-/tissue-specific G6PD conditional knockout (cKO) and conditional overexpression (cOE) mice, as well as AAV-based G6PD expression vector and small-molecule G6PD activator. Overall, the research is designed to elucidate the regulation and role of the “diabetes-PlGF-G6PD-oxidative stress” signaling cascades in DR pathogenesis. The outcomes will give mechanistic insight into DR pathogenesis in general and PlGF function in particular. Since that PlGF has emerged as a promising target molecule to treat DR and diabetic macular edema (DEM), understanding the underlying mechanism is significant. Given the central role of G6PD-gated oxPPP in regulating redox homeostasis and cell survival under stress conditions, this project will fill a critical knowledge gap regarding whether G6PD’s antioxidant function via oxPPP plays a pivotal role in protecting retinal cells from diabetes-induced oxidative damage and compromised G6PD activity and limited oxPPP flux contribute to DR pathogenesis. To examine metabolic flux and mitochondrial function, quantitative measurements will be applied, including stable labeling tracer [1,2-13C2]glucose, liquid chromatography/mass spectrometry, targeted metabolomics, oxygen consumption rate/extracellular acidification rate. Cutting-edge approaches will be employed to determine G6PD’s protective effect, such as gene silence (shRNA), genetic models (cKO and cOE mouse), CRISPR-Cas9 genome editing, virus- based gene transfer, and pharmaceutical compounds. In summary, this project is innovative because it will elucidate a novel mechanism for PlGF to mediate DR-related pathology by regulating glucose metabolism and provide new insights into the question(s) “why or how are retinal cells become vulnerable to diabetes-induced oxidative stress?”. It will also explore the new approaches to prevent or delay DR and DME development by enhancing antioxidant capacity.