Abstract
Purpose :
Diabetic retinopathy (DR) is the leading cause of vision loss globally-age adults. Glucose-6-phosphate dehydrogenase (G6PD) is a cytoplasmatic enzyme that plays a critical role in intracellular antioxidant defense by producing NAPDH through the oxidative pentose phosphate pathway (oxPPP). Hence, the present study investigates whether G6PD overexpression protects the retina from diabetic damage by enhancing antioxidant function in the murine model of DR.
Methods :
G6PD-transgenic (GT) and C57BL6 wild-type (WT-D) mice were induced to develop DR by intraperitoneal injection of streptozotocin (60 mg/kg) for five consecutive days; WT mice without STZ injection (WT-C) serve as baseline controls. The mice were examined for fundus and retinal structure by spectral domain-optical coherence tomography (SD-OCT) under a MICRON IV fundoscopic system. Retinal vasculatures were stained with Alexa Fluor 594-conjugated isolectin B4 on the whole retina flat-mounts(WRFM). Western blots (WB) and IFC examined the protein expression level and tissue distribution. Intracellular ROS levels was detected with a H2DCFDA fluorescent probe. Mitochondria ROS level was evaluated with MitosoxRed.
Results :
Fundoscopy showed that the diabetic WT mice have a more severe abnormal fundus than the GT mice, as compared to the normal fundus of the non-diabetic WT-C mice. OCT imaging analysis revealed that the total retinal thickness of the diabetic WT mice was significantly reduced the diabetic G6PD-tg mice than WT-D (242.9± 0.041, 240.3±0.41, and 234.3±0.47µM and similar pattern was found in ONL and RNFL+GC (65.2, and 25.3µM,GT and WT-D). The WRFM indicates increased vascular leakage and abnormal microvasculature in WT-D compared to WT-C. Inversely, GT mice had significantly less retinal microvascular leakage compared to WT-D. Loss of PDGFRβ (+) pericytes was observed in retinal vasculatures of diabetic mice. PDGFRβ protein expression levels were decreased in the retinal of WT-D mice compared to WT-C, while G6PD overexpression in the GT mice prevented the diabetic-induced PDGFRβ protein degradation. Studies on the mechanisms and mitochondria's function in relation to diabetic retinopathy are still ongoing.
Conclusions :
This reults demonstrated that G6PD overexpression protects the retina from diabetic damage, including loss of microvascular structure and pericytes. Modulation of G6PD controlled oxPPP would be a potential tool in the treatment of DR.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.