Loss of Response Gene to Complement 32 (RGC-32) in Diabetic Mouse Retina Is Involved in Retinopathy Development

Abstract

Diabetic retinopathy (DR) is a severe and recurrent microvascular complication in diabetes. The multifunctional response gene to complement 32 (RGC-32) is involved in the regulation of cell cycle, proliferation, and apoptosis. To investigate the role of RGC-32 in the development of DR, we used human retinal microvascular endothelial cells under high-glucose conditions and type 2 diabetes (T2D) mice (+Leprdb/ + Leprdb, db/db). The results showed that RGC-32 expression increased moderately in human retinal endothelial cells under hyperglycemic conditions. Histopathology and RGC-32 expression showed no significant changes between T2D and control mice retina at 16 and 24 weeks of age. However, RGC-32 expression was significantly decreased in T2D mouse retina compared to the control group at 32 weeks of age, which develop features of the early clinical stages of DR, namely reduced retinal thickness and increased ganglion cell death. Moreover, immunohistochemistry showed that RGC-32 was predominantly expressed in the photoreceptor inner segments of control mice, while the expression was dramatically lowered in the T2D retinas. Furthermore, we found that the level of anti-apoptotic protein Bcl-2 was decreased (approximately 2-fold) with a concomitant increase in cleaved caspase-3 (approximately 3-fold) in T2D retina compared to control. In summary, RGC-32 may lose its expression in T2D retina with features of DR, suggesting that it plays a critical role in DR pathogenesis.

Increased Expression of Ecto-NOX Disulfide-thiol Exchanger 1 (ENOX1) in Diabetic Mice Retina and its Involvement in Diabetic Retinopathy Development

“…Previous studies have suggested that diabetes-induced structural and functional alterations in photoreceptors may play a role in DR pathogenesis (15,28). Such retinal abnormalities have also been reported in other studies in db/db mice over 8-24 weeks of diabetes (29,30) and our previous study at 32 weeks of age (15).…”

“…The retinal cells were treated with normal (5 mM of D-glucose) or high concentration of Dglucose (25 mM) or osmotic control L-glucose (25 mM) for 48 h. The results showed that the expression levels of ENOX1 slightly increased in cells treated with high concentration of D-glucose compared to cells treated with normal glucose condition, but no significant difference was observed in both cell types ( Figure 1B). db/db T2D mice at 32 weeks of age exhibited features of the early clinical stages of DR, as reported previously (15). We then compared the protein expression levels of ENOX1 in the retina of T2D and of non-diabetic control mice at 32 weeks of age (Figure 2A).…”

“…Human retinal microvascular endothelial cells (HRECs) purchased from Cell Biologics Inc (Cell Biologics, Inc., Chicago, IL, USA) and human retinal pigment epithelial cells (HRPEpiCs) purchased from ScienCell Research Laboratories (ScienCell Research Laboratories, Carlsbad, CA, USA) were used for in vitro experiments. HRECs were maintained in tissue culture flasks precoated with a gelatin-based solution and incubated in complete human endothelial medium (Cell Biologics, Inc., Chicago IL, USA) (15). HRPEpiCs were maintained in tissue culture flasks pre-coated with poly-L-lysine overnight and grown in a complete medium consisting of a mixture of epithelial culture medium containing 2% fetal bovine serum, epithelial cell growth supplement, and penicillin/streptomycin solution (ScienCell Research Laboratories, Carlsbad, CA, USA).…”

“…T2D mice (BKS.Cg-Dock7 m +/+Lepr db /JNarl, abbreviation db/db), and their non-diabetic littermates (control mice, abbreviation +/+) were obtained from the National Laboratory Animal Center (Taipei, Taiwan) (16,17). Six male mice per group were grown for 32 weeks during the experiment (15). All the mice were housed under a 12 hour light/dark condition with free access to water and food.…”

Oncogenic gene RGC‐32 is a direct target of miR‐26b and facilitates tongue squamous cell carcinoma aggressiveness through EMT and PI3K/AKT signalling

“…[8][9][10][11] Extensive researches have shown that RGC-32 induces cell proliferation, differentiation, invasion, migration, epithelial-mesenchymal transition (EMT) occurrence and metabolism. [12][13][14][15][16] A considerable amount of literatures have been published on regulatory effects of RGC-32 in a variety of non-cancerous diseases, concerning vascular diseases, [17][18][19] Alzheimer's Disease, 20 obesity, 21 diabetic retinopathy, 22 autoimmune encephalomyelitis, 23 renal ischemia reperfusion injury, 24 preeclampsia 25 and other non-tumour diseases. In addition to its mediating role in non-cancer, essential roles of it were identified to facilitate the progressions of numerous malignancies, namely ovarian cancer, 26,27 colon cancer, 28,29 prostate cancer, 30 lung cancer, 31,32 breast carcinoma 33 and pancreatic cancer.…”