title: Effect of Poria cocos on hypertonic stress-induced water channel expression and apoptosis in renal collecting duct cells.
abstract: BACKGROUND
  A major physiological role of the kidney is to regulate body water and urine concentration. Aquaporin-2 (AQP2), a family of water channels, plays an important role in the urinary concentrating process and regulation of water balance in the kidney. The dried sclerotia of Poria cocos Wolf has been known to have a diuretic effect and used for the treatment of chronic edema and nephrosis.
  
  
  OBJECTIVE
  This study was conducted to evaluate the inhibitory effect of the sclerotia of Poria cocos (WPC) on hypertonic stress-induced AQP2 expression and apoptosis in inner medullary collecting duct cell lines (IMCD-3).
  
  
  METHODS
  Hypertonic stress was induced by 175mM NaCl. Inhibitory effect of WPC on hypertonic stress-induced AQP2 expression and apoptosis were determined by western blot, RT-PCR, and immunofluorescence.
  
  
  RESULTS
  Hypertonic stress (175mM NaCl) increased in the levels of AQP2 expression by hypertonicity in IMCD-3 cells. WPC attenuated the hypertonicity-induced increase in protein and mRNA levels of AQP2 in a concentration-dependent manner. Pretreatment with WPC attenuated hypertonicity-induced cell death. Hypertonicity increased serum- and glucocorticoid-inducible protein kinase (Sgk1) phosphorylation, however, WPC attenuated the hypertonicity-induced Sgk1 activation. Tonicity-responsive enhancer binding protein (TonEBP) mRNA was also recovered by WPC under hypertonic stress. Pretreatment with WPC presented the similar effect of PKA inhibitor which decreased hypertonic stress-induced AQP2 expression. Hypertonicity increased cAMP levels and the changes were blocked by WPC. On the other hand, hypertonic stress-induced Bax or caspase-3 expression was decreased by WPC, resulting in anti-apoptotic effect.
  
  
  CONCLUSIONS
  These results provided evidence that the beneficial effect of WPC in water balance against in vitro hypertonic stress of renal collecting ducts. In addition, WPC exhibits anti-apoptotic property response to hypertonic stress. Thus, these data suggests that WPC has benefit for the therapeutic approach to the inhibition of renal disorder.
authors.affiliation: Department of Oriental Medicine and Professional Graduate School of Oriental Medicine, Wonkwang University, Iksan 570-749, Republic of Korea; Hanbang Body-fluid Research Center, Wonkwang University, Iksan 570-749, Republic of Korea.
authors.forename: So Min
authors.initials: SM
authors.lastname: Lee
authors.forename: Yun Jung
authors.initials: YJ
authors.lastname: Lee
authors.forename: Jung Joo
authors.initials: JJ
authors.lastname: Yoon
authors.forename: Dae Gill
authors.initials: DG
authors.lastname: Kang
authors.forename: Ho Sub
authors.initials: HS
authors.lastname: Lee
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051399:Aquaporin 2 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004232:Diuretics / Q000302:isolation & purification / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005455:Fluorescent Antibody Technique; D017874:Immediate-Early Proteins / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D009997:Osmotic Pressure; D010766:Phosphorylation; D055441:Poria / Q000737:chemistry; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012462:Saline Solution, Hypertonic / Q000633:toxicity*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D051399:Aquaporin 2; D053148:Caspase 3; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D004232:Diuretics; D017874:Immediate-Early Proteins; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D012462:Saline Solution, Hypertonic; D014157:Transcription Factors; D051028:bcl-2-Associated X Protein; D000099184:Serum-Glucocorticoid Regulated Kinases; C496024:Aqp2 protein, mouse; C494827:Bax protein, mouse; C492200:Nfat5 protein, mouse; C505409:Casp3 protein, mouse