Abstract
The concept of diabetic retinopathy (DR) has been extended from microvascular disease to neurovascular disease in which microglia activation plays a remarkable role. Fractalkine (FKN)/CX3CR1 is reported to regulate microglia activation in central nervous system diseases. To characterize the effect of FKN on microglia activation in DR, we employed streptozotocin-induced diabetic rats, glyoxal-treated R28 cells and hypoxia-treated BV2 cells to mimic diabetic conditions and explored retinal neuronal apoptosis, reactive oxygen species (ROS), as well as the expressions of FKN, Iba-1, TSPO, NF-κB, Nrf2 and inflammation-related cytokines. The results showed that FKN expression declined with diabetes progression and in glyoxal-treated R28 cells. Compared with normal control, retinal microglia activation and inflammatory factors surged in both diabetic rat retinas and hypoxia-treated microglia, which was largely dampened by FKN. The NF-κB and Nrf2 expressions and intracellular ROS were up-regulated in hypoxia-treated microglia compared with that in normoxia control, and FKN significantly inhibited NF-κB activation, activated Nrf2 pathway and decreased intracellular ROS. In conclusion, the results demonstrated that FKN deactivated microglia via inhibiting NF-κB pathway and activating Nrf2 pathway, thus to reduce the production of inflammation-related cytokines and ROS, and protect the retina from diabetes insult.