Estradiol reverses TGF-beta1-induced mesangial cell apoptosis by a casein kinase 2-dependent mechanism.
BACKGROUND
The slower rate of progression of chronic renal disease in women than in men is explained in part by the ability of estradiol to reverse the stimulatory effect of transforming growth factor-beta1 (TGF-beta1) on collagen IV synthesis at the level of casein kinase 2 activation. Casein kinase 2 also phosphorylates and activates the pro-apoptotic protein, p53. We hypothesized that estradiol would reverse TGF-beta1-induced mesangial cell apoptosis by antagonizing the stimulatory effects of TGF-beta1 on casein kinase 2 activity, thereby preventing p53 activation.


METHODS
The effects of TGF-beta1 on mesangial cell apoptosis, p53 phosphorylation, Bax and Bcl-2 levels, caspase 9 activity, and cleavage of PARP were examined. The abilities of estradiol and a specific inhibitor of CK2 (5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole) (DRB) to modulate the effects of TGF-beta1 on these processes were also examined.


RESULTS
TGF-beta1 (2 ng/mL), which up-regulates CK2 activity, induces apoptosis in murine mesangial cells together with p53 serine389 phosphorylation, up-regulation of Bax, suppression of Bcl-2, destabilization of mitochondrial permeability transition pores, stimulation of caspase 9 activity and activation of PARP. TGF-beta1-induced p53 activation and all the intermediary steps leading to mesangial cell apoptosis were reversed by estradiol (10-9 mol/L) and by DRB, potent inhibitors of CK2 activity, but not by inhibitors of the p38 MAPK, ERK or JNK signaling cascades. In contrast, TGF-beta1 failed to induce apoptosis in p53 knockout mesangial cells.


CONCLUSIONS
Our data suggest that CK2 mediates the stimulatory effects of TGF-beta1 on mesangial cell apoptosis via a p53-dependent mechanism. The ability of estradiol to reverse TGF-beta1-induced apoptosis may contribute to the protective effects of female gender on the course of chronic renal disease.
Negulescu
Olivia
O
Division of Nephrology, Department of Medicine, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York 10467, USA.
Bognar
Istvan
I
Lei
Jun
J
Devarajan
Prasad
P
Silbiger
Sharon
S
Neugarten
Joel
J
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D047390:Casein Kinase II; D004347:Drug Interactions; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005920:Glomerular Mesangium / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008928:Mitochondria / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012737:Sex Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D004958:Estradiol; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases