title: Oxidative Stress-Activated NHE1 Is Involved in High Glucose-Induced Apoptosis in Renal Tubular Epithelial Cells.
abstract: OBJECTIVE
  Diabetic nephropathy (DN) is a prevalent chronic microvascular complication of diabetes mellitus involving disturbances in electrolytes and the acid-base balance caused by a disorder of glucose metabolism. NHE1 is a Na⁺/H⁺ exchanger responsible for keeping intracellular pH (pHi) balance and cell growth. Our study aimed to investigate roles of NHE1 in high glucose (HG)-induced apoptosis in renal tubular epithelial cells.
  
  
  METHODS
  Renal epithelial tubular cell line HK-2 was cultured in medium containing 5 mM or 30 mM glucose. Then, cell apoptosis, oxidative stress, NHE1 expression, and pHi were evaluated. NHE1 siRNA and inhibitor were used to evaluate its role in cell apoptosis.
  
  
  RESULTS
  HG significantly increased cell apoptosis and the production of reactive oxygen species (ROS) and 8-OHdG (p<0.05). Meanwhile, we found that HG induced the expression of NHE1 and increased the pHi from 7.0 to 7.6 after 48 h of incubation. However, inhibiting NHE1 using its specific siRNA or antagonist DMA markedly reduced cell apoptosis stimulated by HG. In addition, suppressing cellular oxidative stress using antioxidants, such as glutathione and N-acetyl cysteine, significantly reduced the production of ROS, accompanied by a decrease in NHE1. We also found that activated cyclic GMP-Dependent Protein Kinase Type I (PKG) signaling promoted the production of ROS, which contributed to the regulation of NHE1 functions.
  
  
  CONCLUSIONS
  Our study indicated that HG activates PKG signaling and elevates the production of ROS, which was responsible for the induction of NHE1 expression and dysfunction, as well as subsequent cell apoptosis, in renal tubular epithelial cells.
authors.affiliation: Department of Nephrology, Tianjin Union Medicine Center, Tianjin, China.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Nephrology, Tianjin Union Medicine Center, Tianjin, China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Department of Rehabilitation, Tangdu Hospital, Fourth Military Medical University, Xi'an, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.affiliation: Department of Cardiology, Tianjin Union Medicine Center, Tianjin, China. chunjiezhaocjz@163.com.
authors.forename: Chunjie
authors.initials: C
authors.lastname: Zhao
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D027682:Cation Transport Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D007684:Kidney Tubules / Q000166:cytology*; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D027682:Cation Transport Proteins; D017382:Reactive Oxygen Species; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D005978:Glutathione; D005947:Glucose
keywords: NHE1; PKG; diabetic nephropathy; oxidative stress