Transcription factor Egr-1 regulates glomerular mesangial cell proliferation.
Increase of glomerular mesangial cells (MCs) is a prominent histopathological finding in many types of glomerulonephritis. We have shown previously that expression of the zinc-finger transcription factor, early growth response gene-1 (egr-1), is closely correlated with the proliferation of cultured MCs. To elucidate whether Egr-1 is required for MC proliferation, we inhibited serum-induced Egr-1 expression by phosphothioate-modified antisense oligonucleotides (ODNs). Uptake of antisense ODNs into MCs was demonstrated, and five different egr-1 antisense ODNs were tested for their impact on serum-induced egr-1 mRNA and protein levels and on MC growth. The most potent egr-1 antisense ODN inhibited serum-induced egr-1 mRNA by 68%, protein induction by 58%, and MC replication as measured by [3H]thymidine uptake and cell counts by 78 and 46%, respectively. The effects of antisense ODNs on MC growth correlated closely with their ability to inhibit Egr-1 protein. ODNs acted in a dose-dependent manner, the minimal effective concentration being 1 microM. Control ODNs had no significant effects. In addition, antisense ODNs against egr-1 potently inhibited endothelin-1-induced Egr-1 expression and MC growth. Heparin, a known inhibitor of MC growth, suppressed serum-induced [3H]thymidine uptake by 39% and egr-1 mRNA expression by 44%. We conclude that Egr-1 is an essential part of the mitogenic signal transduction cascade in cultured MCs.
Hofer
G
G
Medizinische Klinik IV der Universität Erlangen-Nürnberg, Nephrologische Forschungslabors, Loschgestrasse 8, 91054 Erlangen, Germany.
Grimmer
C
C
Sukhatme
V P
VP
Sterzel
R B
RB
Rupprecht
H D
HD
D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D051766:Early Growth Response Protein 1; D005920:Glomerular Mesangium / Q000166:cytology*; D006493:Heparin / Q000494:pharmacology; D017874:Immediate-Early Proteins; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D051381:Rats; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D016376:Oligonucleotides, Antisense; D014157:Transcription Factors; D006493:Heparin