title: Change of MAX interactor 1 expression in an anti-Thy1 nephritis model and its effect on mesangial cell proliferation.
abstract: OBJECTIVE
  During the disease process of mesangial proliferative glomerulonephritis, the expression of various factors that influence mesangial proliferation is altered. MAX interactor 1 (Mxi1) antagonizes the transcription factor Myc and is believed to be a tumor suppressor. However, no studies have investigated its effect on mesangial cell proliferation.
  
  
  METHODS
  To investigate the effect of Mxi1 on renal mesangial cell proliferation, we established a classic rat anti-Thy1 mesangial proliferative glomerulonephritis model. Mesangial proliferation was estimated by immunohistochemical analysis of Ki67. Mxi1 expression at each time point was assessed by real-time RT-PCR and Western blot analyses. Furthermore, we altered the expression level of Mxi1 by a plasmid and siRNA to detect its effect on rat mesangial cell proliferation in vitro.
  
  
  RESULTS
  Mxi1 expression decreased significantly during the proliferative period of anti-Thy1 nephritis model and then gradually increased as proliferation declined, indicating that Mxi1 may be linked to mesangial cell proliferation. Upregulation of Mxi1 expression via plasmid transfection in vitro reduced the expression of the positive-acting cell cycle regulatory proteins cyclin B1, cyclin D1, cyclin E, CDC2 and CDK2; significantly reduced mesangial cell proliferation; reduced the percentage of S phase cells; and increased the percentage of G2/M phase cells. Inhibition of Mxi1 expression by siRNA in vitro produced the opposite effects: increased expression of cyclin B1, cyclin D1, cyclin E, CDC2 and CDK2; markedly increased cell proliferation; higher percentage of S phase cells; and dramatically lower percentage of G2/M phase cells. Transcription factor c-myc protein expression showed no obvious difference after Mxi1 plasmid and siRNA transfection. The expressions of cell cycle regulatory proteins mentioned above were negative correlated with Mxi1 expression in anti-Thy1 nephritis model.
  
  
  CONCLUSIONS
  These results suggest that Mxi1 expression levels were inversely correlated with proliferation in anti-Thy1 nephritis rats and it may influence cell cycle progression and thus the rate of mesangial cell proliferation by regulating the expression of c-myc target cell cycle regulatory proteins.
authors.affiliation: Department of Nephrology, Institute of Nephrology & Key Laboratory of PLA, Chinese PLA General Hospital, Beijing, China.
authors.forename: Xiaoluan
authors.initials: X
authors.lastname: Liu
authors.forename: Yang
authors.initials: Y
authors.lastname: Lv
authors.forename: Yuansheng
authors.initials: Y
authors.lastname: Xie
authors.forename: Quan
authors.initials: Q
authors.lastname: Hong
authors.forename: Guangyan
authors.initials: G
authors.lastname: Cai
authors.forename: Shujia
authors.initials: S
authors.lastname: Zhang
authors.forename: Wen
authors.initials: W
authors.lastname: Liu
authors.forename: Xiangmei
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000633:toxicity; D051792:Basic Helix-Loop-Helix Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016203:CDC2 Protein Kinase / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D049109:Cell Proliferation; D056744:Cyclin B1 / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D004195:Disease Models, Animal; D016195:G2 Phase; D005921:Glomerulonephritis / Q000378:metabolism* / Q000473:pathology; D008297:Male; D050527:Mesangial Cells / Q000166:cytology / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016196:S Phase; D018800:Thy-1 Antigens / Q000276:immunology; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000906:Antibodies; D051792:Basic Helix-Loop-Helix Proteins; D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D056744:Cyclin B1; D019938:Cyclin D1; D019927:Cyclin E; D051357:Cyclin-Dependent Kinase 2; D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D018800:Thy-1 Antigens; D025521:Tumor Suppressor Proteins; C512789:Mxi1 protein, rat