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The American Journal of Physiology - Cell Physiology
Year: 2010  |  Volume: 299  |  Issue: 4  |  Page No.: 750 - 759

Tumor necrosis factor-{alpha} suppresses angiotensinogen expression through formation of a p50/p50 homodimer in human renal proximal tubular cells

R Satou, K Miyata, A Katsurada, L. G Navar and H. Kobori    

Abstract:

Angiotensinogen (AGT) expression in renal proximal tubular cells (RPTCs) and intrarenal tumor necrosis factor- (TNF-) levels are increased in hypertension and renal diseases However, the contribution of TNF- to AGT expression in RPTCs has not been established. Therefore, the objective of the present study was to determine influence of TNF- on AGT expression in RPTCs. Human kidney-2 (HK-2) cells, immortalized human RPTCs, were treated with several concentrations of TNF- up to 24 h. AGT mRNA and protein expression were evaluated by RT-PCR and ELISA, respectively. Activation of nuclear factor-B (NF-B) by TNF- was evaluated by Western blot analysis, immunocytochemistry, and electrophoretic mobility shift assay (EMSA). TNF- suppressed AGT mRNA expression in a dose- and time-dependent manner. Maximum AGT mRNA reduction was caused by 40 ng/ml of TNF- (0.52 ± 0.09, ratio to control, at 24 h) and at 24 h (0.66 ± 0.05, ratio to control, by 10 ng/ml TNF-). TNF- reduced AGT protein accumulation in the medium between 8 and 24 h (0.62 ± 0.13 by 40 ng/ml TNF-, ratio to control). TNF- activated and induced translocalization of p50 and p65, which are NF-B subunits. Elevated formation of p50/p65 and p50/p50 dimers by TNF- were observed by EMSA and supershift assay. Gene silencing of p50, but not p65, attenuated the effect of TNF- on reduction of AGT expression in RPTCs. These results indicate that TNF- suppresses AGT expression through p50/p50 homodimer formation in human RPTCs, suggesting a possible counteracting mechanism that limits excessive intrarenal AGT production.

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