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Am J Physiol Cell Physiol. 2010 Oct;299(4):C750-9. doi: 10.1152/ajpcell.00078.2010. Epub 2010 Jun 30.

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

Author information

1
Department of Medicine and Physiology, Molecular Core in Hypertension and Renal Center of Excellence, Tulane Univ. Health Sciences Center, 1430 Tulane Ave., No. SL39/M720, New Orleans, LA 70112, USA.

Abstract

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

PMID:
20592241
PMCID:
PMC2957270
DOI:
10.1152/ajpcell.00078.2010
[Indexed for MEDLINE]
Free PMC Article

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