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 μM 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.
Highlights
Cataract occurs two to five times more frequently in patients with diabetes than nondiabetic populations [1,2]
We demonstrated that the lens epithelial cell (LEC) continuously exposed to a high concentration of glucose could induce dysregulation of autophagy and oxidative stress, which may help to improve our knowledge of the pathogenesis of Diabetic cataract (DC)
The finding of the blocking effects of rapamycin on autophagy inhibition in and oxidant damage to LECs might provide a new clue for the pathogenesis and therapy of cataract caused mainly by high glucose (HG)
Summary
Cataract occurs two to five times more frequently in patients with diabetes than nondiabetic populations [1,2]. Diabetic cataract (DC), one of the major ocular complications of hyperglycemia, often develops in earlier age of diabetic patients and progresses fast [3,4]. Approximately a quarter of patients with late-onset diabetes will undergo cataract surgery within 10 years [2]. Lens epithelial cells (LECs), as the major tissue participating in nutrition and ions transportation, metabolism, and detoxification during lens development [5], contribute greatly to transparency of the lens [6]. Autophagosomal–lysosomal pathway is critically important for maintaining lens transparency in clearing the degradation of LEC proteins and organelles.
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