title: All-trans retinoic acid inhibits mesangial cell proliferation by up-regulating p21Waf1/Cip1 and p27Kip1 and down-regulating Skp2.
abstract: BACKGROUND
  The aim of this study was to examine effects of all-trans retinoic acid (ATRA) on rat mesangial cell proliferation, apoptosis and underlying mechanisms.
  
  
  METHODS
  Cultured HBZY-1 rat mesangial cells received the following treatments: group 1: controls (DMSO); group 2: TGF-beta(1) (10 µg/L); groups 3-5: ATRA (0.1, 1.0 and 10 µmol/L) + TGF-beta(1) (10 µg/L). After treatments, the cells were studied by CCK-8 assay, cell cycle assay and TUNEL staining. p21(Waf1/Cip1), p27(Kip1) and Skp2 mRNA levels were measured by real-time PCR. p21(Waf1/Cip1), p27(Kip1) and Skp2 protein levels were detected by Western blot. The localization of p21(Waf1/Cip1) and p27(Kip1) proteins was observed by immunofluorescence and confocal microscopy.
  
  
  RESULTS
  Compared with controls, TGF-beta(1) significantly enhanced proliferation and inhibited apoptosis of mesangial cells. ATRA dose-dependently reversed both TGF-beta(1)-induced decreases in p21(Waf1/Cip1) mRNA and protein levels and p27(Kip1) protein level and increases in Skp2 mRNA and protein levels, and inhibited TGF-beta(1)-induced proliferation through G(1) arrest. Meanwhile, after ATRA treatments, p21(Waf1/Cip1) and p27(Kip1) proteins mainly localized in the nucleus, and their concentrations in cytoplasm decreased.
  
  
  CONCLUSIONS
  ATRA inhibited TGF-beta(1)-induced mesangial cell proliferation by up-regulating p21(Waf1/Cip1) mRNA and protein levels, and p27(Kip1) protein level, and down-regulating Skp2 mRNA and protein levels, but it had no significant effect on apoptosis in rat mesangial cells.
authors.affiliation: Department of Nephrology, Affiliated Hospital of Nantong University, Nantong, Jiangsu Province, PR China.
authors.forename: Baofeng
authors.initials: B
authors.lastname: Su
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Chen
authors.forename: Chonghui
authors.initials: C
authors.lastname: Zhong
authors.forename: Naifeng
authors.initials: N
authors.lastname: Guo
authors.forename: Jianghong
authors.initials: J
authors.lastname: He
authors.forename: Yaping
authors.initials: Y
authors.lastname: Fan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects; D020287:In Situ Nick-End Labeling; D050527:Mesangial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018613:Microscopy, Confocal; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D015854:Up-Regulation
chemical_list: C493958:Cdkn1a protein, rat; C493962:Cdkn1b protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D012333:RNA, Messenger; D044786:S-Phase Kinase-Associated Proteins; D053773:Transforming Growth Factor beta1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D014212:Tretinoin