Aldosterone is the principal hormonal regulator of sodium homeostasis in vertebrates. It exerts its actions through the mineralocorticoid receptor (MR) that regulates the transcription of specific target genes. In recent years, a number of MR target genes have been identified that are involved in the regulation of the epithelial sodium channel (ENaC), a key modulator of renal sodium absorption. Here we report the identification of cnksr3 as a direct MR target gene that is up-regulated in response to physiological concentrations of aldosterone. The cnksr3 promoter exhibits two functional aldosterone-responsive regions, which were bound by the MR as assessed by chromatin immunoprecipitation (ChIP). In vivo, CNKSR3 was highly expressed in the renal cortical collecting duct (CCD), the prime target segment of aldosterone-regulated sodium retention in the kidney. CCD cell lines stably overexpressing or silencing CNKSR3 were electrophysiologically analyzed and show that CNKSR3 expression correlated with and is required for ENaC-mediated transepithelial sodium transport. In parallel, CNKSR3 expression led to decreased MEK phosphorylation. We conclude that CNKSR3, a homologue of scaffold proteins involved in MAPK pathway regulation, is a direct target of MR and is required for the maintenance of transepithelial sodium transport in the kidney.

Stress has complex effects on hippocampal structure and function, which consequently affects learning and memory. These effects are mediated in part by circulating glucocorticoids (GC) acting via the intracellular GC receptor (GR) and mineralocorticoid receptor (MR). Here, we investigated GC regulation of Krüppel-like factor 9 (KLF9), a transcription factor implicated in neuronal development and plasticity. Injection of corticosterone (CORT) in postnatal d 6 and 30 mice increased Klf9 mRNA and heteronuclear RNA by 1 h in the hippocampal region. Treatment of the mouse hippocampal cell line HT-22 with CORT caused a time- and dose-dependent increase in Klf9 mRNA. The CORT induction of Klf9 was resistant to protein synthesis inhibition, suggesting that Klf9 is a direct CORT-response gene. In support of this hypothesis, we identified two GR/MR response elements (GRE/MRE) located -6.1 and -5.3 kb relative to the transcription start site, and we verified their functionality by enhancer-reporter, gel shift, and chromatin immunoprecipitation assays. The -5.3-kb GRE/MRE is largely conserved across tetrapods, but conserved orthologs of the -6.1-kb GRE/MRE were only detected in therian mammals. GC treatment caused recruitment of the GR, histone hyperacetylation, and nucleosome removal at Klf9 upstream regions. Our findings support a predominant role for GR, with a minor contribution of MR, in the direct regulation of Klf9 acting via two GRE/MRE located in the 5'-flanking region of the gene. KLF9 may play a key role in GC actions on hippocampal development and plasticity.

The mineralocorticoid aldosterone is indispensable for the control of blood pressure and fluid volume in mammals. It acts in large part to increase the abundance and activity of the epithelial Na+ channel (ENaC), which mediates apical Na+ entry in the distal parts of the kidney tubules. Aldosterone acts through the mineralocorticoid receptor to alter the transcription of specific genes, including SGK1 and GILZ1. Recent evidence suggests that these key aldosterone-regulated factors function within a unique multi-protein ENaC-regulatory-complex that governs the net cell surface expression and activity of the channel. Another aldosterone-induced protein, CNK3 (connector enhancer of kinase suppressor of Ras 3), also stimulates ENaC and has all of the features of a scaffolding protein. With these observations in mind, we discuss the possibility that CNK3 coordinates the dynamic assembly of the ENaC-regulatory-complex, and promotes context-appropriate aldosterone signal transduction in the regulation of epithelial Na+ transport.

BACKGROUND Plasma concentrations of the peptides midregional proadrenomedullin (MR-proADM), midregional proatrial natriuretic peptide (MR-proANP), and C-terminal endothelin-1 precursor fragment (CT-proET-1) are increased in various cardiovascular conditions. However, there is limited information about the association and comparative performance of these peptides in peripheral arterial disease (PAD). METHODS The associations of MR-proADM, MR-proANP, and CT-proET-1 plasma concentrations with symptomatic PAD were investigated in the CAVASIC (Cardiovascular Disease in Intermittent Claudication) Study. Study participants were a male cohort of 238 patients with a diagnosis of intermittent claudication (IC) and 245 age- and diabetes-matched controls. Results were compared to those for N-terminal pro-B-type natriuretic peptide (NT-proBNP). RESULTS Each increase of MR-proADM, MR-proANP, and CT-proET-1 by 1 SD was significantly associated with symptomatic PAD: odds ratio (OR) = 1.78 (95% CI, 1.41–2.25, P < 0.001), OR = 1.32 (95% CI, 1.06–1.66, P = 0.014), and OR = 1.80 (95% CI, 1.43–2.28, P < 0.001), respectively. The association remained significant for all 3 markers after additional adjustment for log C-reactive protein, serum creatinine, HDL cholesterol, and current smoking. When one adjusts for log NT-proBNP and excluding individuals with prevalent cardiovascular disease, MR-proADM and CT-proET-1 still predicted symptomatic PAD. Extended adjustment models including MR-proADM or CT-proET-1 showed significantly improved model fits compared to models including classical cardiac risk factors or NT-proBNP and led to significant reclassification (P < 0.05). CONCLUSIONS This study in a male cohort of patients with IC and age- and diabetes-matched controls indicates a significant association of high MR-proADM, MR-proANP, and CT-proET-1 concentrations with PAD. MR-proADM and CT-proET-1 provide additive information in comparison to NT-proBNP. Moreover, MR-proADM and CT-proET-1 significantly predict PAD in those patients and controls free from prevalent CVD.

Background and Purpose— Copeptin levels are increased in patients diagnosed with stroke and other vascular diseases. Copeptin elevation is associated with adverse outcome, predicts re-events in patients with transient ischemic attack and is used in ruling-out acute myocardial infarction. We evaluated whether copeptin can also be used as a diagnostic marker in the prehospital stroke setting. Methods— We prospectively examined patients with suspected stroke on the Stroke Emergency Mobile—an ambulance that is equipped with computed tomography and point-of-care laboratory. A blood sample was taken from patients immediately after arrival. We analyzed copeptin levels in patients with final hospital-based diagnosis of stroke or stroke mimics as well as in vascular or nonvascular patients. In addition, we examined the associations of symptom onset with copeptin levels and the prognostic value of copeptin in patients with stroke. Results— Blood samples of 561 patients were analyzed. No significant differences were seen neither between cerebrovascular (n=383) and other neurological (stroke mimic; n=90) patients ( P =0.15) nor between vascular (n=391) and nonvascular patients (n=170; P =0.57). We could not detect a relationship between copeptin levels and time from onset to blood draw. Three-month survival status was available in 159 patients with ischemic stroke. Copeptin levels in nonsurviving patients (n=8: median [interquartile range], 27.4 [20.2–54.7] pmol/L) were significantly higher than in surviving patients (n=151: median [interquartile range], 11.7 [5.2–30.9] pmol/L; P =0.024). Conclusions— In the prehospital setting, copeptin is neither appropriate to discriminate between stroke and stroke mimic patients nor between vascular and nonvascular patients. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT01382862. The Pre-Hospital Acute Neurological Therapy and Optimization of Medical Care in Stroke Patients study (PHANTOM-S) was registered (NCT01382862). This sub-study was observational and not registered separately, therefore.