Mineralocorticoid modulation of cardiac ryanodine receptor activity is associated with downregulation of FK506-binding proteins.
BACKGROUND
The mineralocorticoid pathway is involved in cardiac arrhythmias associated with heart failure through mechanisms that are incompletely understood. Defective regulation of the cardiac ryanodine receptor (RyR) is an important cause of the initiation of arrhythmias. Here, we examined whether the aldosterone pathway might modulate RyR function.


RESULTS
Using the whole-cell patch clamp method, we observed an increase in the occurrence of delayed afterdepolarizations during action potential recordings in isolated adult rat ventricular myocytes exposed for 48 hours to aldosterone 100 nmol/L, in freshly isolated myocytes from transgenic mice with human mineralocorticoid receptor expression in the heart, and in wild-type littermates treated with aldosterone. Sarcoplasmic reticulum Ca(2+) load and RyR expression were not altered; however, RyR activity, visualized in situ by confocal microscopy, was increased in all cells, as evidenced by an increased occurrence and redistribution to long-lasting and broader populations of spontaneous Ca(2+) sparks. These changes were associated with downregulation of FK506-binding proteins (FKBP12 and 12.6), regulatory proteins of the RyR macromolecular complex.


CONCLUSIONS
We suggest that in addition to modulation of Ca(2+) influx, overstimulation of the cardiac mineralocorticoid pathway in the heart might be a major upstream factor for aberrant Ca(2+) release during diastole, which contributes to cardiac arrhythmia in heart failure.
Gómez
Ana María
AM
INSERM, U637, Université Montpellier, France.
Rueda
Angélica
A
Sainte-Marie
Yannis
Y
Pereira
Laetitia
L
Zissimopoulos
Spyros
S
Zhu
Xinsheng
X
Schaub
Roxane
R
Perrier
Emeline
E
Perrier
Romain
R
Latouche
Céline
C
Richard
Sylvain
S
Picot
Marie-Christine
MC
Jaisser
Frederic
F
Lai
F Anthony
FA
Valdivia
Héctor H
HH
Benitah
Jean-Pierre
JP
D000450:Aldosterone / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism* / Q000503:physiopathology; D020013:Calcium Signaling / Q000502:physiology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000502:physiology; D006333:Heart Failure / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008901:Mineralocorticoids / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018161:Receptors, Mineralocorticoid / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases; D022021:Tacrolimus Binding Proteins / Q000378:metabolism*
D008901:Mineralocorticoids; D018161:Receptors, Mineralocorticoid; D019837:Ryanodine Receptor Calcium Release Channel; D000450:Aldosterone; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D022021:Tacrolimus Binding Proteins; C403484:tacrolimus binding protein 1B