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Dexamethasone stimulates endothelin-1 gene expression in renal collecting duct cells.

ABSTRACT: Aldosterone stimulates the endothelin-1 gene (Edn1) in renal collecting duct (CD) cells by a mechanism involving the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). The goal of the present study was to determine if the synthetic glucocorticoid dexamethasone affected Edn1 gene expression and to characterize GR binding patterns to an element in the Edn1 promoter. Dexamethasone (1?M) induced a 4-fold increase in Edn1 mRNA in mIMCD-3 inner medullary CD cells. Similar results were obtained from cortical collecting duct-derived mpkCCD(c14) cells. RU486 inhibition of GR completely blocked dexamethasone action on Edn1. Similarly, 24h transfection of siRNA against GR reduced Edn1 expression by approximately 50%. However, blockade of MR with either spironolactone or siRNA had little effect on dexamethasone induction of Edn1. Cotransfection of MR and GR siRNAs together had no additive effect compared to GR-siRNA alone. The results indicate that dexamethasone acts on Edn1 exclusively through GR and not MR. DNA affinity purification studies revealed that either dexamethasone or aldosterone resulted in GR binding to the same hormone response element in the Edn1Edn1 promoter. The Edn1 hormone response element contains three important sequence segments. Mutational analysis revealed that one of these segments is particularly important for modulating MR and GR binding to the Edn1 hormone response element.

SUBMITTER: Stow LR

PROVIDER: S-EPMC3303981 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

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Dexamethasone stimulates endothelin-1 gene expression in renal collecting duct cells.

Stow Lisa R LR Voren George E GE Gumz Michelle L ML Wingo Charles S CS Cain Brian D BD

Steroids 20111219 5

Aldosterone stimulates the endothelin-1 gene (Edn1) in renal collecting duct (CD) cells by a mechanism involving the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). The goal of the present study was to determine if the synthetic glucocorticoid dexamethasone affected Edn1 gene expression and to characterize GR binding patterns to an element in the Edn1 promoter. Dexamethasone (1μM) induced a 4-fold increase in Edn1 mRNA in mIMCD-3 inner medullary CD cells. Similar results we ...[more]

PMID: 22209709

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Project description:BackgroundHigh salt intake is associated with both oxidative stress and chronic kidney disease (CKD) progression. Nuclear factor E2-related factor 2 (Nrf2) is a transcriptional factor regulating the antioxidant and detoxifying genes to potently antagonize oxidative stress. This study examined the effect of high salt loading on the expression of Nrf2 in kidney.MethodsMice were treated with acute salt loading, and Nrf2 expression in the kidney was detected by Western blotting and immunostaining. Reactive oxygen species (ROS) levels in the kidney were measured using dihydroethidium (DHE) staining. In vitro, mpkCCD cells were cultured in high osmolality medium by adding sodium chloride (NaCl), sodium gluconate (Na-Glu), choline chloride (Choline-Cl), or mannitol. Then, Nrf2 and its target genes were measured.ResultsNrf2 protein in renal cortex and medulla tissue lysates was significantly downregulated after acute salt loading. Immunofluorescence data showed that Nrf2 was mainly located in collecting duct principal cells evidenced by co-staining of Nrf2 with AQP2. Contrasting to the reduced Nrf2 expression, ROS levels in the kidney were significantly increased after salt loading. In vitro, the Nrf2 protein level was downregulated in mpkCCD cells after NaCl treatment for 24 h. Interestingly, sodium gluconate had a similar effect on downregulating Nrf2 expression as NaCl, whereas neither Choline-Cl nor mannitol changed Nrf2 expression. Meanwhile, the mRNA levels of Nrf2 target genes were downregulated by NaCl and/or sodium gluconate, while some of them were also regulated by Choline-Cl, indicating a more complex regulation of these genes under a high salt condition. Finally, we found that the downregulation of Nrf2 caused by NaCl was not affected by N-acetylcysteine (NAC), spironolactone, or NS-398, suggesting other mechanisms mediating Nrf2 downregulation caused by high salt challenge.ConclusionHigh salt downregulated Nrf2 mainly via a sodium-dependent manner in kidney collecting duct cells, which might contribute to the excessive renal oxidative stress and CKD progression.

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Dexamethasone stimulates endothelin-1 gene expression in renal collecting duct cells.

Publications

Dexamethasone stimulates endothelin-1 gene expression in renal collecting duct cells.

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