A role for the circadian clock protein Per1 in the regulation of aldosterone levels and renal Na+ retention

A role for the circadian clock protein Per1 in the regulation of the NaCl co-transporter (NCC) and the with-no-lysine kinase (WNK) cascade in mouse distal convoluted tubule cells

It has been well established that blood pressure and renal function undergo circadian fluctuations. We have demonstrated that the circadian protein Per1 regulates multiple genes involved in sodium transport in the collecting duct of the kidney. However, the role of Per1 in other parts of the nephron has not been investigated. The distal convoluted tubule (DCT) plays a critical role in renal sodium reabsorption. Sodium is reabsorbed in this segment through the actions of the NaCl co-transporter (NCC), which is regulated by the with-no-lysine kinases (WNKs). The goal of this study was to test if Per1 regulates sodium transport in the DCT through modulation of NCC and the WNK kinases, WNK1 and WNK4. Pharmacological blockade of nuclear Per1 entry resulted in decreased mRNA expression of NCC and WNK1 but increased expression of WNK4 in the renal cortex of mice. These findings were confirmed by using Per1 siRNA and pharmacological blockade of Per1 nuclear entry in mDCT15 cells, a model of the mouse distal convoluted tubule. Transcriptional regulation was demonstrated by changes in short lived heterogeneous nuclear RNA. Chromatin immunoprecipitation experiments demonstrated interaction of Per1 and CLOCK with the promoters of NCC, WNK1, and WNK4. This interaction was modulated by blockade of Per1 nuclear entry. Importantly, NCC protein expression and NCC activity, as measured by thiazide-sensitive, chloride-dependent (22)Na uptake, were decreased upon pharmacological inhibition of Per1 nuclear entry. Taken together, these data demonstrate a role for Per1 in the transcriptional regulation of NCC, WNK1, and WNK4.

Progress in the identification of responsible genes and molecular mechanisms in primary aldosteronism

Aldosterone, the mineralocorticoid hormone, plays an important role in blood regulation. Autonomous secretion of aldosterone is known as primary aldosteronism (PA), the most common cause of secondary hypertension. PA comprises a group of heterogenous disorders which makes their classification and management challenging. With the advent of the genomic era several germline and somatic mutations have been identified that are involved in the pathogenesis of primary aldosteronism. This article will review our current knowledge of the genetic mechanisms of familial hyperaldosterism, somatic mutations in genes encoding electrolyte channels and other potential genetic mechanisms implicated in the dysregulation of aldosterone production from in vitro and animal models. There is potential for novel targeted therapies and diagnosis for subsets of patient. The challenges to achieve them are highlighted in this review.