title: Beyond Gap Junction Channel Function: the Expression of Cx43 Contributes to Aldosterone-Induced Mesangial Cell Proliferation via the ERK1/2 and PKC Pathways.
abstract: OBJECTIVE
  This study aimed to explore the precise mechanism and signaling pathways of mesangial cell (MC) proliferation from a new point of view considering Connexin 43 (Cx43).
  
  
  METHODS
  MC proliferation was measured by the incorporation of 3H-thymidine (3H-TdR). Cx43 was over-expressed in MC cells using lipofectamine 2000, and the expression level was tested with reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analyses. The gap junction channel function was explored by Lucifer Yellow scrape loading and dye transfer (SLDT), and the intracellular calcium concentrations ([Ca(2+)]i) were characterized by confocal microscopy on cells loaded with Fura-3/AM.
  
  
  RESULTS
  There was an inverse correlation between Cx43 expression and MC proliferation (P<0.05). SLDT studies revealed that there was no difference in the gap junction channel function between the normal and Aldosterone (Aldo)-stimulated groups (P>0.05). Our data also showed that the mineralcorticoid receptor (MR) antagonist spironolactone, ERK1/2 inhibitor PD98059 and PKC inhibitor GF109203X could attenuate the down-regulation of Cx43 expression in Aldo-induced MC proliferation; however, the PI3K inhibitor LY294002 could block MC proliferation without affecting Cx43 expression at either the mRNA or protein level. In addition, Aldo promoted MC proliferation in parallel with increasing [Ca(2+)]i (P<0.05), suggesting that the classical PKC pathway might be activated.
  
  
  CONCLUSIONS
  Our study provides preliminary evidence that Cx43 is an important regulator of Aldo-promoted MC proliferation. Furthermore, reduced Cx43 expression promoted MC proliferation independent of the gap junction channel function, and this process might be mediated through the ERK1/2- and PKC-dependent pathways.
authors.affiliation: Department of Pediatric Nephrology, the Second Affiliated Hospital of Nanjing Medical University, Nanjing, P. R. China.
authors.forename: Aiqing
authors.initials: A
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Han
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.forename: Shanwen
authors.initials: S
authors.lastname: Li
authors.forename: Weihua
authors.initials: W
authors.lastname: Gan
mesh_terms: D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism; D002450:Cell Communication / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D018031:Connexin 43 / Q000235:genetics* / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D005456:Fluorescent Dyes; D017629:Gap Junctions / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D007211:Indoles / Q000494:pharmacology; D007546:Isoquinolines; D008301:Maleimides / Q000494:pharmacology; D050527:Mesangial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D018161:Receptors, Mineralocorticoid / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013148:Spironolactone / Q000494:pharmacology
chemical_list: D000450:Aldosterone; D001572:Benzofurans; D002118:Calcium; D002867:Chromones; D018031:Connexin 43; D005419:Flavonoids; D005456:Fluorescent Dyes; D007211:Indoles; D007546:Isoquinolines; D008301:Maleimides; D000451:Mineralocorticoid Receptor Antagonists; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D018161:Receptors, Mineralocorticoid; D013148:Spironolactone; C580592:Gja1 protein, rat; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C017475:lucifer yellow; C070515:bisindolylmaleimide I; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one