Calcium channel blockers inhibit proliferation and matrix production in rat mesangial cells: possible mechanism of suppression of AP-1 and CREB activities.
BACKGROUND
Calcium channel blockers (CCBs) are reported to attenuate the loss of renal function in various glomerulonephritides.


METHODS
To determine the mechanism of action of these drugs, we investigated the effects of CCBs on cell proliferation and extracellular matrix (ECM) production in cultured rat mesangial cells.


RESULTS
While stimulation with 5% fetal calf serum (FCS) increased [(3)H]thymidine and [(3)H]proline incorporation into quiescent mesangial cells, incubation with nifedipine and cilnidipine inhibited the increase in a dose-dependent manner. Northern blot analysis demonstrated that 5% FCS increased the expression of transforming growth factor beta (TGF-beta) and fibronectin (FN) mRNA and that CCBs significantly reduced this induction, indicating that CCBs may reduce ECM production through inhibiting TGF-beta and FN. Since activator protein 1 (AP-1) regulates cell proliferation and TGF-beta expression, we evaluated the AP-1 activity by gel mobility shift analysis. Nuclear extracts of FCS-treated cells showed a strong binding to AP-1-specific oligonucleotides which was suppressed by CCBs, suggesting that these agents may inhibit cell proliferation by suppressing AP-1. CCBs also inhibited the binding activity of cyclic adenosine monophosphate responsive element binding protein which regulates FN gene expression. However, neither CCBs nor FCS affected the NFkappaB activity.


CONCLUSIONS
These results suggest that CCBs may, in part, inhibit the progression of glomerulonephritis through non-hemodynamic actions that include the suppression of mesangial cell proliferation and the production of ECM.
Sugiura
T
T
Department of Internal Medicine and Therapeutics, Osaka University Graduate School of Medicine, Japan.
Imai
E
E
Moriyama
T
T
Horio
M
M
Hori
M
M
D000818:Animals; D000906:Antibodies; D015152:Blotting, Northern; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen / Q000235:genetics; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004095:Dihydropyridines / Q000494:pharmacology; D004586:Electrophoresis; D005109:Extracellular Matrix / Q000378:metabolism*; D005353:Fibronectins / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology*; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000276:immunology / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000032:analysis / Q000276:immunology / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D013936:Thymidine / Q000378:metabolism / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics; D014316:Tritium
D000906:Antibodies; D002121:Calcium Channel Blockers; D017362:Cyclic AMP Response Element-Binding Protein; D004095:Dihydropyridines; D005353:Fibronectins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta; D014316:Tritium; D003094:Collagen; C065927:cilnidipine; D009543:Nifedipine; D013936:Thymidine