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Autophagy attenuates high glucose-induced oxidative injury to lens epithelial cells.

ABSTRACT: PURPOSE:Autophagic dysfunction and abnormal oxidative stress are associated with cataract. The purpose of the present study was to investigate the changes of cellular autophagy and oxidative stress and their association in lens epithelial cells (LECs) upon exposure to high glucose. METHODS:Autophagy and oxidative stress-related changes were detected in streptozotocin-induced Type 1 diabetic mice and normal mouse LECs incubated in high glucose conditions. Rapamycin at a concentration of 100 nm/l or 50 ?M chloroquine was combined for analysis of the relationship between autophagy and oxidative stress. The morphology of LECs during autophagy was observed by transmission electron microscopy. The expressions of autophagy markers (LC3B and p62) were identified, as well as the key factors of oxidative stress (SOD2 and CAT) and mitochondrial reactive oxygen species (ROS) generation. RESULTS:Transmission electron microscopy indicated an altered autophagy activity in diabetic mouse lens tissues with larger autophagosomes and multiple mitochondria. Regarding the expressions, LC3B was elevated, p62 was decreased first and then increased, and SOD2 and CAT were increased before a decrease during 4 months of follow-up in diabetic mice and 72 h of culture under high glucose for mouse LECs. Furthermore, rapamycin promoted the expressions of autophagy markers but alleviated those of oxidative stress markers, whereas chloroquine antagonized autophagy but enhanced oxidative stress by elevating ROS generation in LECs exposed to high glucose. CONCLUSIONS:The changes in autophagy and oxidative stress were fluctuating in the mouse LECs under constant high glucose conditions. Autophagy might attenuate high glucose-induced oxidative injury to LECs.

SUBMITTER: Liu X

PROVIDER: S-EPMC7109002 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Autophagy attenuates high glucose-induced oxidative injury to lens epithelial cells.

Liu Xiaomin X Zhao Xiaowen X Cheng Rong R Huang Yusen Y

Bioscience reports 20200401 4

<h4>Purpose</h4>Autophagic dysfunction and abnormal oxidative stress are associated with cataract. The purpose of the present study was to investigate the changes of cellular autophagy and oxidative stress and their association in lens epithelial cells (LECs) upon exposure to high glucose.<h4>Methods</h4>Autophagy and oxidative stress-related changes were detected in streptozotocin-induced Type 1 diabetic mice and normal mouse LECs incubated in high glucose conditions. Rapamycin at a concentrati ...[more]

PMID: 32186721

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Project description:Thioredoxin (Trx) is an important protein that controls oxidative damage in almost all eukaryotic cells. Trx interaction protein (Txnip) has been reported to negatively regulate the bioavailability of Trx and inhibit its biological function. The E3 ubiquitin ligase ITCH can specifically degrade Txnip via ubiquitination. The apoptosis of human lens epithelial cells (HLECs), which are highly sensitive to redox caused by oxidative stress, is a significant factor for the development of sugar cataract in a high‑glucose environment. However, whether Trx, Txnip and ITCH contribute to the progression of sugar cataracts and the underlying mechanisms remain unknown, and thus, identifying these were the aims of the present study. The present results suggested that the expression levels of Trx, Txnip and ITCH in HLECs cultured with different glucose concentrations were detected by reverse transcription‑quantitative PCR and western blotting, and the apoptotic rate of the cells was detected by flow cytometry and superoxide detection assay. The interaction between ITCH and Txnip was determined by co‑localization immunofluorescence and co‑immunoprecipitation. In addition, a vector and small interfering RNA of ITCH were transfected to overexpress and knockdown ITCH, respectively, to alter the expression of downstream proteins and cell apoptosis. It was found that Txnip was highly expressed in cultured HLECs in high‑glucose environment, and the antioxidative function of Trx was restricted and suppressed, thus promoting apoptosis. The overexpression of ITCH increased the expression of Trx and decreased oxidative stress and apoptosis by decreasing Txnip in cultured HLECs, while downregulation of ITCH significantly decreased the expression of Trx and enhanced oxidative stress and apoptosis. Therefore, the present results indicated that ITCH could regulate the apoptosis of HLECs that were cultured in high‑glucose concentration and that it may be a treatment target for sugar cataract.

Project description:Chronic hyperglycemia causes a progressive decrease of ?-cell function and mass in type 2 diabetic patients. Growing evidence suggests that augment of autophagy may be an effective approach to protect ? cells against various extra-/intracellular stimuli. In this study, we thus investigated whether bone marrow-derived mesenchymal stem cells (BM-MSCs) could ameliorate chronic high glucose (HG)-induced ?-cell injury through modulation of autophagy. Prolonged exposure to HG decreased cell viability, increased cell apoptosis and impaired basal insulin secretion and glucose-stimulated insulin secretion of INS-1 cells, but BM-MSC treatment significantly alleviated these glucotoxic alternations. In addition, western blotting displayed upregulated expression of Beclin1 and LC3-II in INS-1 cells co-cultured with BM-MSCs. Results from immunofluorescence staining and transmission electronic microscope analysis also revealed that BM-MSCs promoted autophagosomes and autolysosomes formation in HG-treated INS-1 cells. However, it should be noted that inhibition of autophagy significantly diminished the protective effects of BM-MSCs on HG-treated INS-1 cells, suggesting that the improvement of ?-cell function and survival induced by BM-MSCs was mediated through autophagy. Furthermore, our results showed that BM-MSCs improved mitochondrial function and reduced reactive oxygen species production in HG-treated INS-1 cells, largely owing to autophagic clearance of impaired mitochondria. In vivo study was performed in rats with type 2 diabetes (T2D). BM-MSC infusion not only ameliorated hyperglycemia, but also promoted restoration of pancreatic ? cells in T2D rats. Meanwhile, BM-MSC infusion upregulated LAMP2 expression and enhanced formation of autophagosomes and autolysosomes, combined with reduced ?-cell apoptosis and increased number of insulin granules. These findings together indicated that BM-MSCs could protect ? cells against chronic HG-induced injury through modulation of autophagy in vitro and in vivo. This study unveiled novel evidence of BM-MSCs as an ideal strategy to enhance autophagy for treatment of T2D mellitus.

Dataset Information

Autophagy attenuates high glucose-induced oxidative injury to lens epithelial cells.

Publications

Autophagy attenuates high glucose-induced oxidative injury to lens epithelial cells.

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