title: High glucose-induced hypertrophy of mesangial cells is reversed by connexin43 overexpression via PTEN/Akt/mTOR signaling.
abstract: BACKGROUND
  Hypertrophy of glomerular mesangial cells (GMC) is one of the earliest pathological abnormalities in diabetic nephropathy, which correlates with eventual glomerulosclerosis. We have previously proved that this hypertrophy is mediated by downregulation of connexin43 (Cx43) and dysfunction of gap junctional intercellular communication, but the mechanism involved is still unclear. This study aims to investigate whether PTEN/Akt/mammalian target of rapamycin (mTOR) was involved as the downstream molecular signaling of Cx43 in regulating high glucose-induced GMC hypertrophy.
  
  
  METHODS
  GMC were isolated from male Wistar rats at the age of 3 months. Gene transfer technique was used to upregulate Cx43 in GMC, which was validated by western blot and immunofluorescent staining. Forward scatter of flow cytometry and total protein/cell number were examined to testify GMC hypertrophy induced by high glucose (30 mM) and the influence of Cx43 overexpression; western blot was performed to demonstrate the changes of Cx43 and signal protein level and flow cytometry and MTT test were carried out to check cell cycle and proliferation rate, respectively.
  
  
  RESULTS
  GMC exposed to a high concentration of glucose presented decreased Cx43, inhibited PTEN, triggered Akt phosphorylation and activated downstream mTOR, leading to stagnancy of cell cycle, decline of proliferation rate and occurrence of hypertrophy. Cx43 overexpression could prevent PTEN inhibition, Akt and mTOR phosphorylation, resulting in restoration of cell cycle and proliferation ability and reversion of GMC hypertrophy. GMC with Cx43 inhibition showed similar PTEN/Akt/mTOR change as stimulated by high glucose.
  
  
  CONCLUSIONS
  PTEN/Akt/mTOR signaling stimulated by high concentration of glucose is regulated by Cx43 overexpression, which unveils part of the molecular mechanism of Cx43 in regulating hyperglycemia-induced hypertrophy.
authors.affiliation: Department of Nephrology, Kidney Institute and Key Lab of Chinese PLA, Chinese PLA General Hospital, Beijing, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.forename: Xiao
authors.initials: X
authors.lastname: Hu
authors.forename: Guang-Yan
authors.initials: GY
authors.lastname: Cai
authors.forename: Yang
authors.initials: Y
authors.lastname: Lv
authors.forename: Li
authors.initials: L
authors.lastname: Zhuo
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Gao
authors.forename: Shao-Yuan
authors.initials: SY
authors.lastname: Cui
authors.forename: Zhe
authors.initials: Z
authors.lastname: Feng
authors.forename: Bo
authors.initials: B
authors.lastname: Fu
authors.forename: Xiang-Mei
authors.initials: XM
authors.lastname: Chen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D005920:Glomerular Mesangium / Q000378:metabolism / Q000473:pathology; D005947:Glucose / Q000378:metabolism*; D006943:Hyperglycemia / Q000150:complications*; D006984:Hypertrophy / Q000209:etiology* / Q000378:metabolism / Q000517:prevention & control*; D008297:Male; D050527:Mesangial Cells; D051059:PTEN Phosphohydrolase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D018031:Connexin 43; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C546845:mTOR protein, rat; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D051059:PTEN Phosphohydrolase; C487216:Pten protein, rat; D005947:Glucose