Diabetic retinopathy (DR) is a retinal disease caused by metabolic disorders of glucose tolerance that can lead to irreversible blindness if not adequately treated. Retinal pigment epithelial cell (RPEC) dysfunction contributes to the pathogenesis of DR. In the present study the anti-inflammatory effect of curcumin (CUR) was investigated in RPECs damaged by high glucose levels. RPEC treated with 30 mmol/l glucose was regarded as high glucose group, and cells treated with 24.4 mmol/l mannitol was set as equivalent osmolarity group. Cell Counting Kit-8 assay was used to measure RPEC viability, the expression of phosphorylated (p)-AKT and p-mammalian target of rapamycin (mTOR) were assessed by western blot, and secretion of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β in the culture medium was measured by ELISA. Intracellular reactive oxygen species (ROS) levels were measured by laser scanning confocal microscope. The present data indicated that, compared with mannitol treatment, high glucose treatment reduced RPEC viability, increased TNF-α, IL-6 and IL-1β secretion, increased ROS formation and promoted phosphorylation of AKT and mTOR. The antioxidant N-acetylcysteine, the phosphoinositide 3-kinase (PI3K)/AKT inhibitor LY294002 and the mTOR inhibitor rapamycin ameliorated the effects of high glucose. In addition, pretreatment with 10 µmol/l CUR reduced secretion levels of TNF-α, IL-6 and IL-1β, ROS formation and phosphorylation of AKT and mTOR. In conclusion, CUR inhibited high glucose-induced inflammatory injury in RPECs by interfering with the ROS/PI3K/AKT/mTOR signaling pathway. The present study may reveal the molecular mechanism of CUR inhibition effects to high glucose-induced inflammatory injury in RPEC.

Age-related macular degeneration (AMD) is the most common cause of blindness and visual impairment in the elderly. 1 AMD is characterized by accumulation of yellow crystal deposits and loss of central vision due to degenerative changes in the macula. The integrity of the retina is strongly related to retinal pigment epithelial cells, which maintain the local extracellular environment. Morphological and functional abnormalities of these cells can lead to AMD. 2 Inflammation and apoptosis also play central roles in the pathophysiology of AMD. 3,4 Determining appropriate treatment for AMD is an important endeavour to increase patient quality of life.MicroRNAs (miRs) are a class of noncoding RNAs that can inhibit or degrade genetic targets by binding to their 3ʹ untranslated regions (UTRs). MiRs play integral roles in numerous disease processes, including oxidase stress, inflammation, and apoptosis. 5 For AbstractAge-related macular degeneration (AMD) is a major reason of blindness in the elderly.MicroRNAs are implicated in various pathological processes, including inflammation and apoptosis. In this study, we aim to investigate the biological functions of miR- 21-3p in inflammation and apoptosis caused by lipopolysaccharide (LPS) in humanretinal pigment epithelial (ARPE-19) cells. The miR-21-3p inhibitor and mimic were transfected into ARPE-19 cells for 48 hours, followed by exposed to LPS (10 μg/mL) for 24 hours. The mRNA and protein expression of IL-6 and MCP-1 were measured using real-time PCR (RT-PCR) and enzyme-linked immunosorbent assays. Cell viability, apoptosis, caspase 3 activity, cleaved caspase-3 and cleaved-PARP protein levels were detected to evaluate the effects of miR-21-3p on apoptosis. Additionally, the target relationship between miR-21-3p and regulator of G-protein signalling 4 (RGS4) was verified by dual luciferase reporter assay. RT-PCR analysis demonstrated that LPS induced miR-21-3p expression. Inhibition of miR-21-3p reduced the mRNA and protein levels of IL-6 and MCP-1. Apoptosis, caspase-3 activity, and cleaved-caspase 3 and cleaved PARP protein levels were repressed by the miR-21-3p inhibitor.However, overexpression of miR-21-3p showed the opposite results. Furthermore, we identified that miR-21-3p directly targeted the 3ʹ untranslated region of RGS4.MiR-21-3p negatively regulated the expression of RGS4 both in mRNA and protein levels. Silencing RGS4 reduced the anti-inflammatory and anti-apoptotic effects of miR-21-3p inhibitor. Our results revealed that miR-21-3p inhibition targeted RGS4 to attenuate inflammatory responses and apoptosis caused by LPS in ARPE-19 cells. K E Y W O R D Sapoptosis, inflammation, MiR-21-3p, RGS4

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