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Glucocorticoids stimulate p21(CIP1) in mesangial cells and in anti-GBM glomerulonephritis
Y Terada1, T Okado, S Inoshita
1Second Department of Internal Medicine, Tokyo Medical and Dental University, Tokyo, Japan. yterada.kid@tmd.ac.jp
Background:
Glucocorticoids are widely used for the treatment of glomerulonephritis, but the mechanism of cell cycle inhibition by glucocorticoids is poorly understood at a molecular level.
Methods:
The effects of dexamethasone on cell cycle progression were examined in rat mesangial cells. To investigate the mechanisms of cell cycle inhibition by dexamethasone, we transfected the -2.3 kb p21(CIP1) promoter-CAT construct to mesangial cells using an electroporation
Method:
We also examined whether glucocorticoids stimulate the expression of p21(CIP1) and inhibit cell proliferation in glomeruli of anti-glomerular basement membrane (GBM) glomerulonephritis in rats.
Results:
Dexamethasone inhibited 3H-thymidine uptake and the percentages of S and G2/M phases in rat mesangial cells. Dexamethasone stimulated CAT activity of the p21(CIP1) promoter 4.5-fold. Deletion analysis of the p21(CIP1) promoter revealed that the glucocorticoid-responsive region (GRE) is present between -1.4 and -1.1 kb upstream of the transcription initiation site. Dexamethasone inducibility of p21(CIP1) promoter activity requires the presence of the C/EBP alpha DNA binding site in the GRE of the p21(CIP1) promoter and C/EBP alpha protein. Intravenous injection of anti-GBM antibody caused mesangial proliferation, crescent formation, and proteinuria in rats. Ten days of administration of prednisolone (1 mg/kg/day) reduced proteinuria and inhibited mesangial cell proliferation and crescent formation. The glomerular-sieving method revealed that prednisolone increased p21(CIP1) expression in glomeruli.
Conclusion:
These data suggest that the cell cycle arrest of mesangial cells is mediated by a functional link between the glucocorticoid receptor and the transcriptional control of p21(CIP1) not only in vitro but also in vivo. Our observations provide new insights into the molecular mechanisms of glucocorticoid action in glomerulonephritis.
Insights
Glucocorticoids like dexamethasone inhibit mesangial cell proliferation in glomerulonephritis by increasing p21(CIP1) expression. This molecular mechanism involves the glucocorticoid receptor and transcriptional control of p21(CIP1), offering new insights into treatment strategies.
Area of Science:
- Nephrology
- Molecular Biology
- Pharmacology
Background:
- Glucocorticoids are standard treatments for glomerulonephritis.
- The precise molecular mechanisms by which glucocorticoids inhibit cell cycle progression remain unclear.
Purpose of the Study:
- To investigate the molecular mechanisms of glucocorticoid-induced cell cycle inhibition in mesangial cells.
- To determine if glucocorticoids upregulate p21(CIP1) expression and inhibit proliferation in vivo during glomerulonephritis.
Main Methods:
- Dexamethasone's effects on rat mesangial cell cycle progression were assessed.
- The p21(CIP1) promoter activity was analyzed using a reporter construct and deletion analysis.
- Glucocorticoid effects on cell proliferation and p21(CIP1) expression were examined in a rat model of anti-glomerular basement membrane glomerulonephritis.
Main Results:
- Dexamethasone inhibited mesangial cell proliferation and S/G2/M phase progression.
- Dexamethasone significantly increased p21(CIP1) promoter activity, with a critical glucocorticoid-responsive region identified between -1.4 and -1.1 kb.
- The induction of p21(CIP1) promoter activity by dexamethasone was dependent on the C/EBP alpha DNA binding site and protein.
- Prednisolone treatment in rats with glomerulonephritis reduced proteinuria, inhibited mesangial cell proliferation and crescent formation, and increased glomerular p21(CIP1) expression.
Conclusions:
- Glucocorticoid-induced cell cycle arrest in mesangial cells is mediated by a functional link between the glucocorticoid receptor and the transcriptional control of p21(CIP1).
- This mechanism operates both in vitro and in vivo, providing crucial insights into glucocorticoid action in glomerulonephritis.