Quercetin Inhibits AQP1 Translocation in High-Glucose-Cultured SRA01/04 Cells Through PI3K/Akt/mTOR Pathway

Abstract

Objective: The study aimed to investigate the effects of quercetin on Aquaporin 1 (AQP1) translocation in high glucose condition and made an attempt to clarify the underlying mechanisms and provide new ideas for the treatment of diabetic cataract (DC).

Methods: The human lens epithelial line SRA01/04 cells were divided into groups mentioned below: normal glucose, high glucose with a specific time (0 h, 2 h, 4 h, 8 h, 12 h, 24 h), high glucose plus the phosphoinositide 3-kinase (PI3K) inhibitor LY294002, high glucose plus the mammalian target of rapamycin (mTOR) inhibitor rapamycin, and high glucose plus quercetin with different doses (2 μmol/L, 4 μmol/L and 8 μmol/L). The western blotting assay was used to detect the protein kinase B (Akt), phosphorylated protein kinase B (p-Akt), mammalian target of rapamycin (m- TOR), phosphorylated mammalian target of rapamycin (p-mTOR) and AQP1. Real-time polymerase chain reaction (RT-PCR) was used to detect the expression of AQP1. A Membrane and Cytosol Protein Extraction Kit was applied to separate membrane proteins. Immunofluorescence assay was performed to evaluate the expression and location of AQP1. The effect of quercetin on the expression of AQP1 and PI3K/Akt/mTOR signaling was detected.

Results: AQP1 protein was found to be significantly increased in 24 hour when exposed to high glucose condition (P<0.01). LY294002 and rapamycin inhibited PI3K/Akt/mTOR and AQP1 expression (P<0.01), preventing the change of AQP1 location in the SRA01/04 plasma membrane (P<0.01). This effect was further proved by immunofluorescence. In different doses of quercetin groups (2 μmol/L, 4 μmol/L and 8 μmol/L), the phosphorylation of mTOR and Akt were decreased and AQP1 in the membrane was changed compared with high glucose group (P<0.01).

Conclusion: Quercetin significantly decreased the AQP1 elevation and prevented the change of AQP1 location through inhibiting the activation of the PI3K/Akt/mTOR signaling in high-glucose-- cultured SRA01/04 cells, which might have the preventable and inhibitory effects on the early development of diabetic cataract. The specific pathophysiological role of quercetin still needs to be verified.

Keywords: Akt; PI3K; Quercetin; SRA01/04 cells; aquaporin-1; diabetic cataract.; mTOR; translocation.