Endoplasmic reticulum stress and inflammation: Mechanisms and implications in diabetic retinopathy

The endoplasmic reticulum (ER) is the primary cellular compartment where proteins are synthesized and modified before they can be transported to their destination. Dysfunction of the ER impairs protein homeostasis and leads to the accumulation of misfolded/unfolded proteins in the ER, or ER stress. While it has long been recognized that ER stress is a major cause of conformational disorders, such as Alzheimer's disease, Huntington's disease, certain types of cancer, and type 2 diabetes, recent evidence suggests that ER stress is also implicated in many chronic inflammatory diseases. These diseases include irritable bowel syndrome, atherosclerosis, diabetic complications, and many others. Diabetic retinopathy is a common microvascular complication of diabetes, characterized by chronic inflammation, progressive damage to retinal vascular and neuronal cells, vascular leakage, and abnormal blood vessel growth (neovascularization). In this review, we discuss the role and mechanisms of ER stress in retinal inflammation and vascular damage in diabetic retinopathy.