Diabetes and high-glucose could upregulate the expression of receptor for activated C kinase 1 in retina

BACKGROUND Diabetic retinopathy (DR) is a major ocular complication of diabetes mellitus, leading to visual impairment. Retinal pigment epithelium (RPE) injury is a key component of the outer blood retinal barrier, and its damage is an important indicator of DR. Receptor for activated C kinase 1 (RACK1) activates protein kinase C-epsilon (PKC-epsilon) to promote the generation of reactive oxygen species (ROS) in RPE cells, leading to apoptosis. Therefore, we hypothesize that the activation of RACK1 under hypoxic/high-glucose conditions may promote RPE cell apoptosis by modulating PKC-epsilon/ROS, thereby disrupting the barrier effect of the outer blood retinal barrier and contributing to the progression of DR. AIM To investigate the role and associated underlying mechanisms of RACK1 in the development of early DR. METHODS In this study, Sprague-Dawley rats and adult RPE cell line-19 (ARPE-19) cells were used as in vivo and in vitro models, respectively, to explore the role of RACK1 in mediating PKC-epsilon in early DR. Furthermore, the impact of RACK1 on apoptosis and barrier function of RPE cells was also investigated in the former model. RESULTS Streptozotocin-induced diabetic rats showed increased apoptosis and up-regulated expression of RACK1 and PKC-epsilon proteins in RPE cells following a prolonged modeling. Similarly, ARPE-19 cells exposed to high glucose and hypoxia displayed elevated mRNA and protein levels of RACK1 and PKC-epsilon, accompanied by an increases in ROS production, apoptosis rate, and monolayer permeability. However, silencing RACK1 significantly downregulated the expression of PKC-epsilon and ROS, reduced cell apoptosis and permeability, and protected barrier function. CONCLUSION RACK1 plays a significant role in the development of early DR and might serve as a potential therapeutic target for DR by regulating RPE apoptosis and barrier function.