Inducible Knock-Down of the Mineralocorticoid Receptor in Mice Disturbs Regulation of the Renin-Angiotensin-Aldosterone System and Attenuates Heart Failure Induced by Pressure Overload

Abstract

Mineralocorticoid receptor (MR) inactivation in mice results in early postnatal lethality. Therefore we generated mice in which MR expression can be silenced during adulthood by administration of doxycycline (Dox). Using a lentiviral approach, we obtained two lines of transgenic mice harboring a construct that allows for regulatable MR inactivation by RNAi and concomitant expression of eGFP. MR mRNA levels in heart and kidney of inducible MR knock-down mice were unaltered in the absence of Dox, confirming the tightness of the system. In contrast, two weeks after Dox administration MR expression was significantly diminished in a variety of tissues. In the kidney, this resulted in lower mRNA levels of selected target genes, which was accompanied by strongly increased serum aldosterone and plasma renin levels as well as by elevated sodium excretion. In the healthy heart, gene expression and the amount of collagen were unchanged despite MR levels being significantly reduced. After transverse aortic constriction, however, cardiac hypertrophy and progressive heart failure were attenuated by MR silencing, fibrosis was unaffected and mRNA levels of a subset of genes reduced. Taken together, we believe that this mouse model is a useful tool to investigate the role of the MR in pathophysiological processes.

Deletion of the Mineralocorticoid Receptor in Myeloid Cells Attenuates Central Nervous System Autoimmunity

“…Lysates were prepared from BMDM in denaturating sample buffer containing a protease inhibitor cocktail (RIPA with NP40, NA 3 VO 4 , and Na 3 MoO 4 ) and heated at 95°C for 5 min ( 22 ). 15 µg proteins were separated on a 7.5% SDS-PAGE gel, transferred to a nitrocellulose membrane (Amersham, Braunschweig, Germany) and stained with a rabbit anti-MR or a rabbit anti-ERK antibody (both 1:1,000, Santa Cruz, Heidelberg, Germany).…”

“…It is generally assumed that the major physiological role of the MR is the regulation of the salt-water balance and various cardiac functions. For example, an ubiquitous inactivation of the MR or its conditional ablation in kidney or cardiomyocytes altered the control of sodium reabsorption and blood pressure, and partially protected from cardiac failure ( 19 – 22 ). Furthermore, specific deletion of the MR in myeloid cells was also found to protect against cardiac hypertrophy, fibrosis, and heart failure, suggesting that the MR in immune cells is more important than previously supposed ( 9 ).…”

Mineralocorticoid Receptor Deficiency in T Cells Attenuates Pressure Overload–Induced Cardiac Hypertrophy and Dysfunction Through Modulating T-Cell Activation

“…Although functions of MR in several other cell types have been elucidated in pathologic cardiac hypertrophy and heart failure, [15][16][17]19,[36][37][38] the roles of MR in T cells have not been illuminated. Through this study, we demonstrated that eplerenone and TMRKO attenuated POL-induced cardiac remodeling and dysfunction in parallel with attenuated cardiac inflammation, as well as decreased T-cell accumulation and activation in the heart.…”

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: Mineralocorticoid receptor null mice: informing cell-type-specific roles

“…Most transgenic rats survived to adulthood providing a rodent model of pseudo-hyperaldosteronism that could be assessed in future studies. A more elegant RNAi-based MR knockdown transgenic model has been recently created by the same group using a doxycycline induced MRshRNA approach in mice (Montes-Cobos et al 2015). This transgenic model used the Tet-repressor to block expression of an MRshRNA transgene that would only become active when adult mice were treated with doxycycline.…”