Diabetic retinopathy (DR) is a neurovascular complication of diabetes. As a crucial player in the retinal physiology, Müller cells are affected in DR, impairments of Müller cell function lead to retinal malfunctions. Therefore, searching for approaches to mitigate diabetes-induced injury in Müller cells is imperative for delaying DR. Peroxiredoxin 4 (PRDX4), an important endoplasmic reticulum (ER)-resident antioxidant, was explored in this study for its potential protective role against DR. Streptozotocin-induced mouse model of diabetes and high glucose (HG)-induced Müller cells were utilized to assess the impact of PRDX4. Compared with WT mice, PRDX4 knockout exacerbated retinal neurodegeneration, reactive gliosis, cell apoptosis, ER stress, oxidative stress, and mitochondrial dysfunction in diabetic retinas. Knockdown of PRDX4 aggravated HG-induced reactive gliosis, apoptosis, ER stress, oxidative stress, and mitochondrial dysfunction in Müller cells. Conversely, PRDX4 overexpression in Müller cells protected against HG-induced cell damage. Mechanistically, PRDX4 promoted the degradation of dipeptidyl peptidase-4, which is associated with DR in type 1 diabetics, thereby alleviating HG-stimulated Müller cell abnormalities. Our study indicated that PRDX4 is a crucial protective regulator in DR progression via destabilization of dipeptidyl peptidase-4 protein and suggested that enhancement of PRDX4 level may represent a promising approach for treating DR.

To detect the effect of connective tissue growth factor (CTGF) on the apoptosis in the diabetic retina with small interfering RNAs (siRNA) targeting CTGF. A total of 60 rats were divided into 6 groups including control group, diabetic 4, 8, 12, 16 weeks groups, and interference group. Diabetic rats were induced by intraperitoneal streptozotocin (STZ). Retinas were obtained from control, diabetic rats and diabetic rats of interference group treated by intravitreal injection of CTGFsiRNA to suppress the expression of CTGF mRNA. Retinal cells apoptosis was detected by Tunnel staining and mRNA expression of CTGF was analyzed by RT-PCR. The levels of CTGF and the apoptosis in the retinas of diabetic rats were significantly higher than those in the controls. Apoptosis occurred at 4 weeks after a diabetic model being set up, became serious with the diabetes developing, while CTGF elevated at 8 weeks. The apoptosis cell counts increased to 25.8cells/mm2 at 24weeks of diabetes. SiRNA-mediated inhibition of CTGF mRNA resulted in a significant decrease in apoptosis. Significant correlations were found between CTGF and apoptosis in the retina. It was suggested that CTGF might be involved in retinal cells apoptosis which is a characteristic of early diabetic retina. SiRNA targeting CTGF seems to have the advantage of ameliorating retinal cells apoptosis.

Background The mechanism for ultraviolet A (UVA) involvement in age-related macular degeneration (AMD) is unclear. We examined the levels of autophagy-related proteins and ubiquitination of cell proteins after acute UVA exposure and determined whether UVA causes AMD by affecting autophagy in retinal pigment epithelium (RPE) cells. Methods Western blotting was used to determine the level of Beclin-1, LC3, and p62 in ARPE-19 cells exposed to UVA. Co-immunoprecipitation was used to detect the ubiquitination of proteins in cells. Cell viability was determined with a CGD1 assay. Results UVA irradiation increased the level of LC3 and the conversion of LC3-I to LC3-II in ARPE-19 cells within 24 h, inhibition of autophagy by NH4CL reversed the effect of UVA, and suppression of proteasomes by Epoxomicin (EPO) did not enhance the effect of UVA. UVA irradiation did not affect the level of Beclin-1. UVA up-regulated the expression of p62 and the ubiquitination of proteins in cells, especially k63-linked ubiquitination. ARPE-19 cells were lost in a short- time under exposure to UVA. Conclusion UVA induces autophagy in ARPE-19 cells in a short period, and promotes protein degradation through the autophagy pathway. However, acute UVA irradiation leads to cell death. Therefore, while acute UVA irradiation cannot cause protein degeneration by impairing autophagy in RPE cells, it is still a risk factor for AMD occurrence due to its effect on reducing cells.

Diabetic retinopathy (DR) is a common microvascular complication that leads to vision loss in patients with diabetes. The SLC12A2/SLC12A4 inhibitor, bumetanide, has been reported to alleviate hypoxia-induced retinopathy. It was hypothesized that it may exert the same effect in DR. DR cell types and SLC12A2/SLC12A4 expression at the cell level were analyzed using single cell RNA-sequencing (scRNA-seq) data. Next, cell [high glucose (HG) stimulation] and animal (mice injected with streptozotocin) DR models were constructed. The protective effects and possible mechanisms of bumetanide and SLC12A2 were investigated through a series of experiments, including Cell Counting Kit-8, TUNEL, Transwell, tube formation, ELISA, immunofluorescence staining, western blot and reverse transcription-quantitative PCR assays. Bumetanide reduced HG-induced cell apoptosis by suppressing the expression of SLC12A2 and SLC12A4. Second, scRNA-seq analysis revealed that SLC12A2 was predominantly expressed in endothelial cells, which are the main targets of hyperglycemic damage. Endothelial cell-related markers were involved in angiogenesis and adhesion molecule-related pathways. Third, in HG-stimulated cells, SLC12A2 knockdown efficiently reduced the inflammatory response and angiogenesis, while maintaining endothelial barrier integrity. This protective process involved reduced release of inflammatory factors (IL-1β and IL-6) and growth factors (vascular endothelial growth factor), suppression of adhesion molecule expression (VCAM1, ICAM1, E-Selectin and P-Selectin), activation of tight junction protein (ZO-1), and decreased matrix metalloproteinases (MMP2 and MMP9). Furthermore, SLC12A2 deficiency ameliorated DR progression in streptozotocin-induced diabetic mice by improving retinal thickness and pathological changes. The present study elucidates the crucial role of bumetanide in DR treatment and suggests that targeting SLC12A2 may represent a novel therapeutic strategy for the prevention of DR.