title: Effect of beta-sitosterol on transforming growth factor-beta-1 expression and translocation protein kinase C alpha in human prostate stromal cells in vitro.
abstract: BACKGROUND
  Today, plant extracts are widely used in the treatment of benign prostatic hyperplasia (BPH). However, the complete mode of action of the active substance, beta-sitosterol, is under investigation. The purpose of this study was to investigate the effect of beta-sitosterol on the expression of transforming growth factor beta 1 (TGF-beta1) and the activity of protein kinase C alpha (PKC-alpha) in primary prostate stromal cell cultures in vitro.
  
  
  METHODS
  Tissue samples for primary cell cultures were obtained from patients undergoing transurethral resection of the prostate (TURP). TGF-beta1 levels in stromal cell conditioned media following a culture with beta-sitosterol were detected in a TGF-beta1 specific ELISA assay. Following different incubation periods with beta-sitosterol, cells were lysed and fractionated into a Triton-soluble membrane fraction and a cytosol fraction. PKC-alpha protein was detected using immunoblot analysis.
  
  
  RESULTS
  Beta-sitosterol was able to induce the expression and secretion of TGF-beta1 significantly between 1.26- and 1.86-fold compared to a cholesterol and the nonsupplemented control in 6 of 8 individual cultures. The total amount of secreted TGF-beta1 varied in cells from different patients. Based on its presence in both membrane fraction and cytosol, PKC-alpha appeared to be constitutively expressed in stromal cells. In the absence of beta-sitosterol PKC-alpha was predominantly found in its membrane-associated active form. Following a culture with beta-sitosterol, a translocation of PKC-alpha from the membrane to the cytosol was observed. This effect was specific for beta-sitosterol as compared to cholesterol.
  
  
  CONCLUSIONS
  This study describes the effect of beta-sitosterol on the expression of a multifunctional growth factor (TGF-beta1) and the activity of PKC-alpha membrane in stromal cells of the human prostate in vitro.
authors.affiliation: Wissenschaftliches Labor der Urologischen Klinik der Ruhr-Universität Bochum, Deutschland. Annette.Kassen@ruhr-uni-bochum.de
authors.forename: A
authors.initials: A
authors.lastname: Kassen
authors.forename: R
authors.initials: R
authors.lastname: Berges
authors.forename: T
authors.initials: T
authors.lastname: Senge
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D011467:Prostate / Q000166:cytology* / Q000201:enzymology*; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D012855:Sitosterols / Q000494:pharmacology*; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*
chemical_list: D007527:Isoenzymes; D012855:Sitosterols; D016212:Transforming Growth Factor beta; C025473:gamma-sitosterol; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha