RESUMO
According to the prediction of the International Diabetes Federation, global diabetes mellitus (DM) patients will reach 783.2 million in 2045. The increasing incidence of DM has led to a global epidemic of diabetic retinopathy (DR). DR is a common microvascular complication of DM, which has a significant impact on the vision of working-age people and is one of the main causes of blindness worldwide. Substantial research has highlighted that microangiopathy and chronic low-grade inflammation are widespread in the retina of DR. Meanwhile, with the introduction of the gut-retina axis, it has also been found that DR is associated with gut microecological disorders. The disordered structure of the GM and the destruction of the gut barrier result in the release of abnormal GM flora metabolites into the blood circulation. In addition, this process induced alterations in the expression of various cytokines and proteins, which further modulate the inflammatory microenvironment, vascular damage, oxidative stress, and immune levels within the retina. Such alterations led to the development of DR. In this review, we discuss the corresponding alterations in the structure of the GM flora and its metabolites in DR, with a more detailed focus on the mechanism of gut microecology in DR. Finally, we summarize the potential therapeutic approaches of DM/DR, mainly regulating the disturbed gut microecology to restore the homeostatic level, to provide a new perspective on the prevention, monitoring, and treatment of DR.
RESUMO
We aimed to explore the effect of N-retinylidene-N-retinylethanolamine (A2E) on the uptake and release of calcium in lysosomes and mitochondria by establishing a model of human retinal pigment epithelial (RPE) cell injury induced by exposure to blue light. Primary human RPE cells were cultured from passages 4 to 6 and exposed to blue light at an intensity of 2000 ± 500 lux for 6 hours. After blue light exposure, the culture was maintained for 24 hours. A2E at a final concentration of 25 µM was added to the culture 2 hours before light exposure, and nifedipine at a final concentration of 10-4 M was added 1 hour before light exposure. The levels of Ca2+ in the cytosol (CaTM/2AM), mitochondria (Rhod/2AM), and lysosomes (LysoTracker Red and Fluo-3/AM) were determined. In order to measure the calcium levels in the different organelles, RPE were imaged using a laser scanning confocal microscope. Moreover, changes in the mitochondrial membrane potential were detected by flow cytometry analysis of JC-1-stained cells. The obtained results revealed that blue light illumination increased the calcium fluorescence intensity in the cytoplasm, mitochondria, and lysosomes of human RPE cells when compared with the control cells (P < 0.05). After A2E treatment, the fluorescence intensity of the calcium in the cytoplasm was further increased (P < 0.05), while that in the mitochondria and lysosomes decreased (P < 0.05). In addition, we observed that nifedipine reduced the fluorescence intensity of calcium in the RPE cells. Our results also showed that the mitochondrial membrane potential in the RPE treated with blue light and A2E was lower than that in the control, blue light, and A2E-treated cells (P < 0.05). Blue light increased calcium levels in the cytoplasm, lysosomes, and mitochondria of RPE cells. A2E damages the lysosomal and mitochondrial membranes, resulting in calcium release into the cytoplasm. Finally, our results demonstrated that both blue light and A2E treatments reduced mitochondrial membrane potential, increasing cytosolic Ca2+ levels, which can contribute to the activation of RPE death.
