Hyperglycemia induced down-regulation of renal P-glycoprotein expression

• Published in: European journal of pharmacology 2012-09, Vol.690 (1-3), p.42-50
• Main Authors: Yeh, Szu-Yu, Pan, Huei-Ju, Lin, Chung-Cheng, Kao, Yu-Han, Chen, Yen-Hui, Lin, Chun-Jung
• Format: Article
• Language: English
• Subjects: Animals; antioxidants; ATP-Binding Cassette, Sub-Family B, Member 1 - genetics; ATP-Binding Cassette, Sub-Family B, Member 1 - metabolism; Biological Transport - drug effects; Blood Glucose - metabolism; Body Weight - drug effects; Cell Membrane - drug effects; Cell Membrane - metabolism; Diabetes; Diabetes Complications - blood; Diabetes Complications - genetics; Diabetes Complications - metabolism; Diabetes Complications - pathology; Diabetes Mellitus, Type 1 - complications; Diabetes Mellitus, Type 2 - complications; Digoxin - metabolism; Dogs; Down-Regulation - drug effects; Female; glucose; glutathione; hydrogen peroxide; hyperglycemia; Hyperglycemia - blood; Hyperglycemia - genetics; Hyperglycemia - metabolism; Hyperglycemia - pathology; insulin; Insulin - pharmacology; interleukin-6; Interleukin-6 - pharmacology; Kidney; Kidney - metabolism; Kidney - pathology; kidneys; Madin Darby Canine Kidney Cells; Male; Mice; noninsulin-dependent diabetes mellitus; oxidants; P-glycoprotein; pharmacology; PKC; protein kinase C; Protein Kinase C - metabolism; Reactive oxygen species; Reactive Oxygen Species - metabolism; reverse transcriptase polymerase chain reaction; tumor necrosis factor-alpha; Tumor Necrosis Factor-alpha - pharmacology; Western blotting
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/j.ejphar.2012.06.013

The purpose of this study is to investigate the regulation of P-glycoprotein expression in the kidney under diabetic condition. Renal P-glycoprotein expression was examined in inbred mice with type 1 or type 2 diabetes by Western blotting. The underlying mechanisms of P-glycoprotein regulation were examined in Madin–Darby canine kidney type II (MDCK-II) cells by Western blotting or qRT-PCR. 3H-digoxin uptake was measured for P-glycoprotein activity in cells under various treatments. The results showed that P-glycoprotein expression was lower in kidneys of diabetic mice than in controls. In MDCK-II cells, treatments with insulin or IL-6 did not cause any change in P-glycoprotein expression, whereas TNF-α tended to increase P-glycoprotein expression at a concentration of 1ng/ml. On the other hand, P-glycoprotein expression was reduced under high glucose conditions (450mg/dl), while superoxide production was increased, and the reduction in P-glycoprotein expression was abolished by N-acetylcysteine (an antioxidant) and staurosporine (a nonselective PKC inhibitor). Treatment with oxidizing agents (H2O2, BSO) or PMA (a PKC activator) reduced P-glycoprotein expression. Antioxidant (N-acetylcysteine or glutathione) co-treatment abolished the H2O2-induced and BSO-induced reduction in P-glycoprotein expression, whereas it did not prevent the effect of PMA. The PMA-induced P-glycoprotein down-regulation was prevented by co-treatment of LY333531 (a PKC-β inhibitor). 3H-digoxin levels were higher in MDCK-II cells with high glucose, PMA or H2O2 treatments. In conclusion, P-glycoprotein expression is lower in kidneys of diabetic mice and in MDCK-II cells under high glucose conditions. Hyperglycemia induced reactive oxygen species and activated PKC in MDCK-II cells, leading to the decrease in P-glycoprotein expression.