title: Ursolic acid improves podocyte injury caused by high glucose.
abstract: BACKGROUND
  Autophagy plays an important role in the maintenance of podocyte homeostasis. Reduced autophagy may result in limited renal cell function during exposure to high glucose conditions. In this study we investigated the effects of ursolic acid (UA) on autophagy and podocyte injury, which were induced by high glucose.
  
  
  METHODS
  Conditionally immortalized murine podocytes were cultured in media supplemented with high glucose and the effects of the PI3K inhibitor LY294002 and UA on protein expression were determined. miR-21 expression was detected by real-time RT-PCR. Activation of the PTEN-PI3K/Akt/mTOR pathway, expression of autophagy-related proteins and expression of podocyte marker proteins were determined by western blot. Immunofluorescence was used to monitor the accumulation of LC3 puncta. Autophagosomes were also observed by transmission electron microscopy.
  
  
  RESULTS
  During exposure to high glucose conditions, the normal level of autophagy was reduced in podocytes, and this defective autophagy induced podocyte injury. Increased miR-21 expression, decreased PTEN expression and abnormal activation of the PI3K/Akt/mTOR pathway were observed in cells that were cultured in high glucose conditions. UA and LY294002 reduced podocyte injury through the restoration of defective autophagy. Our data suggest that UA inhibits miR-21 expression and increases PTEN expression, which in turn inhibits Akt and mTOR and restores normal levels of autophagy.
  
  
  CONCLUSIONS
  Our data suggest that podocyte injury is associated with reduced levels of autophagy during exposure to high glucose conditions, UA attenuated podocyte injury via an increase in autophagy through miR-21 inhibition and PTEN expression, which inhibit the abnormal activation of the PI3K/Akt/mTOR pathway.
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Qiuling
authors.initials: Q
authors.lastname: Fan
authors.affiliation: Department of Gastroenterology, First Hospital of China Medical University, Shenyang, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Xinxing
authors.initials: X
authors.lastname: Lu
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yue
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Cao
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Department of Nephrology, First Hospital of China Medical University, Shenyang 110001, China.
authors.forename: Lining
authors.initials: L
authors.lastname: Wang
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects*; D005947:Glucose / Q000633:toxicity*; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D050199:Podocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects; D013549:Sweetening Agents / Q000633:toxicity; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology*; D000097245:Ursolic Acid
chemical_list: D000890:Anti-Infective Agents; D005947:Glucose; D035683:MicroRNAs; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D013549:Sweetening Agents; D058570:TOR Serine-Threonine Kinases; D014315:Triterpenes; D000097245:Ursolic Acid; C531950:MIRN21 microRNA, mouse; C546843:mTOR protein, mouse; C487757:Pten protein, mouse
keywords: autophagy; high glucose; miR-21; podocyte; ursolic acid