Cyclooxygenase-2 overexpression inhibits platelet-derived growth factor-induced mesangial cell proliferation through induction of the tumor suppressor gene p53 and the cyclin-dependent kinase inhibitors p21waf-1/cip-1 and p27kip-1.
Cyclooxygenase-2 (COX-2) is an inducible enzyme and serves as a source of paracrine prostaglandin E2 (PGE2) formation in many tissues. In glomerular immune injury COX-2 formation is up-regulated in association with increased mesangial cell growth. To examine whether COX-2 exerts growth modulating effects on glomerular cells, we established two separate COX-2-overexpressing mesangial cell lines (COX-2+) and assessed their proliferative response to the potent mesangial cell growth-promoting factor, platelet-derived growth factor (PDGF). PDGF increased proliferation in mock-transfected cells. In contrast, PDGF did not induce proliferation in COX-2+ cells. Our results also showed that the tumor suppressor protein p53 and the cyclin-dependent kinase inhibitors p21(cip-1) and p27(kip-1) were up-regulated in COX-2+ cells de novo as well as under PDGF-stimulated conditions. To study whether COX-2 products are required for these effects, COX-2+ cells were treated with indomethacin (1 microg/ml) or NS-398 (3 microm). Unexpectedly, both COX inhibitors had no significant effect on cell proliferation, not on the protein levels of p53, p21(cip-1), or p27(kip-1). To evaluate the role of p21(cip-1) and p27(kip-1), COX-2 was overexpressed in mesangial cells derived from p21(cip-1) (p21-/- COX-2+) and p27(kip-1) (p27-/- COX-2+) null mice. In contrast to the wild type COX-2+ cells, p21-/- COX-2+ and p27-/- COX-2+ cells proliferated in response to PDGF. These data suggest that COX-2 inhibits mesangial cell proliferation by a novel mechanism that is independent of prostaglandin synthesis, but involves p53, p21(cip-1), and p27(kip-1).
Zahner
Gunther
G
Department of Medicine, Division of Nephrology and Osteology, University of Hamburg, 20246 Hamburg, Germany. zahner@uke.uni-hamburg.de
Wolf
Gunter
G
Ayoub
Murwan
M
Reinking
Rudiger
R
Panzer
Ulf
U
Shankland
Stuart J
SJ
Stahl
Rolf A K
RA
D000818:Animals; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D002460:Cell Line; D002469:Cell Separation; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D003893:Desmin / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D016158:Genes, p53 / Q000235:genetics; D005920:Glomerular Mesangium / Q000166:cytology / Q000201:enzymology*; D007213:Indomethacin / Q000494:pharmacology; D007527:Isoenzymes / Q000096:biosynthesis*; D008297:Male; D009578:Nitrobenzenes / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D011453:Prostaglandins / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D015533:Transcriptional Activation; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
C493958:Cdkn1a protein, rat; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D003893:Desmin; D007527:Isoenzymes; D009578:Nitrobenzenes; D010982:Platelet-Derived Growth Factor; D011453:Prostaglandins; D013449:Sulfonamides; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D007213:Indomethacin