Glucocorticoids stimulate p21CIP1 in mesangial cells and in anti-GBM glomerulonephritis

Abstract

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 p21CIP1 promoter-CAT construct to mesangial cells using an electroporation method. We also examined whether glucocorticoids stimulate the expression of p21CIP1 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 p21CIP1 promoter 4.5-fold. Deletion analysis of the p21CIP1 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 p21CIP1 promoter activity requires the presence of the C/EBPα DNA binding site in the GRE of the p21CIP1 promoter and C/EBPα 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 p21CIP1 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 p21CIP1 not only in vitro but also in vivo. Our observations provide new insights into the molecular mechanisms of glucocorticoid action in glomerulonephritis. © 2001 Elsevier Science Ltd. All rights reserved.