[Show abstract][Hide abstract] ABSTRACT: Recent reports show that ER stress plays an important role in diabetic retinopathy (DR), but ER stress is a complicated process involving a network of signaling pathways and hundreds of factors, What factors involved in DR are not yet understood. We selected 89 ER stress factors from more than 200, A rat diabetes model was established by intraperitoneal injection of streptozotocin (STZ). The expression of 89 ER stress-related factors was found in the retinas of diabetic rats, at both 1- and 3-months after development of diabetes, by quantitative real-time polymerase chain reaction arrays. There were significant changes in expression levels of 13 and 12 ER stress-related factors in the diabetic rat retinas in the first and third month after the development of diabetes, Based on the array results, homocysteine- inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1(HERP), and synoviolin(HRD1) were studied further by immunofluorescence and Western blot. Immunofluorescence and Western blot analyses showed that the expression of HERP was reduced in the retinas of diabetic rats in first and third month. The expression of Hrd1 did not change significantly in the retinas of diabetic rats in the first month but was reduced in the third month.
Preview · Article · Jan 2012 · Experimental Diabetes Research
[Show abstract][Hide abstract] ABSTRACT: 58-kilodalton inhibitor of protein kinase (P58(IPK)) plays an important role in preventing endoplasmic reticulum (ER) stress. It is an interferon-induced kinase that targets the eukaryotic translation initiation factor eukaryotic initiation factor 2 alpha. The aim of this study was to determine the roles of P58(IPK) in protecting against diabetic retinopathy (DR) by inhibiting ER stress-signaling mediators.
A rat diabetic model was established by intraperitoneal injection of streptozotocin. Overexpression of P58(IPK) was achieved by intravitreal injection of purified recombinant adeno-associated virus vector (rAAV2)-P58(IPK) or transfection into rat retinal capillary endothelial cells. Retinal vascular permeability was determined by assessing the Evans Blue retinal leakage. To downregulate the P58(IPK) level in cultured rat retinal capillary endothelial cells, pGIPZ-P58(IPK) RNA interference (P58(IPK)RNAi) was introduced in these cells. Real time reverse transcription (RT)-PCR and western blot analyses were performed to evaluate the mRNA and protein levels of Core/emopamil binding protein (C/EBP) homologous protein (CHOP), vascular endothelial growth factor (VEGF), and tumor necrosis factor-α (TNF-α).
Retinal blood vessel leakage was significantly decreased in rAAV2-P58(IPK)-transfected diabetic rats compared with the control diabetic rats. Both mRNA and protein levels of CHOP, TNF-α, and VEGF in the retina of diabetic rats were remarkably reduced in P58(IPK)-transfected rats. In vitro study further demonstrated that overexpression of P58(IPK) downregulated the expression of CHOP, TNF-α, and VEGF under high glucose conditions, whereas introduction of P58(IPK)RNAi enhanced the expression of CHOP, TNF-α, and VEGF.
These results revealed the protecting role of P58(IPK) against ER stress-mediated DR in diabetic rats, suggesting that P58(IPK) may act as a DR-resistant gene during diabetes.