The Diuretic Torasemide Does Not Prevent Aldosterone-Mediated Mineralocorticoid Receptor Activation in Cardiomyocytes

Abstract

Aldosterone binds to the mineralocorticoid receptor (MR) and exerts pleiotropic effects beyond enhancing renal sodium reabsorption. Excessive mineralocorticoid signaling is deleterious during the evolution of cardiac failure, as evidenced by the benefits provided by adding MR antagonists (MRA) to standard care in humans. In animal models of cardiovascular diseases, MRA reduce cardiac fibrosis. Interestingly diuretics such as torasemide also appear efficient to improve cardiovascular morbidity and mortality, through several mechanisms. Among them, it has been suggested that torasemide could block aldosterone binding to the MR. To evaluate whether torasemide acts as a MRA in cardiomyocytes, we compared its effects with a classic MRA such as spironolactone. We monitored ligand-induced nuclear translocation of MR-GFP and MR transactivation activity in the cardiac-like cell line H9C2 using a reporter gene assay and known endogenous aldosterone-regulated cardiac genes. Torasemide did not modify MR nuclear translocation. Aldosterone-induced MR transactivation activity was reduced by the MRA spironolactone, not by torasemide. Spironolactone blocked the induction by aldosterone of endogenous MR-responsive genes (Sgk-1, PAI-1, Orosomucoid-1, Rgs-2, Serpina-3, Tenascin-X), while torasemide was ineffective. These results show that torasemide is not an MR antagonist; its association with MRA in heart failure may however be beneficial, through actions on complementary pathways.

Inhibition of aldosterone synthase (CYP11B2) by torasemide prevents atrial fibrosis and atrial fibrillation in mice

“…This finding may be explained by the reported ability of torasemide to reduce trans-cardiac extraction of circulating aldosterone [47] and/or by the direct inhibition of aldosterone synthase activity. The data are in agreement with previous studies reporting that torasemide is not an MR antagonist [41] but reduces the expression of aldosterone synthase and fibrosis in the left ventricles of rats with dilated cardiomyopathy [35,48] as well as the incidence of atrial fibrillation in patients with dilated cardiomyopathy [49]. Importantly and consistently, the regulation e.g.…”

“…CYP11B2 is a mitochondrial cytochrome P450 enzyme which is located in the inner mitochondrial membrane, mainly in the Zona glomerulosa of the adrenal cortex and to a much lesser extend in the myocardium [37][38][39][40]. Here, our data confirm the expression and functional role of CYP11B2 in cardiac myocytes and in cardiac fibroblasts [41]. By binding to epithelial mineralocorticoid receptors (MR), aldosterone plays an important role regulating sodium and water retention as well as potassium secretion.…”

Influence of Torasemide on Electrical Instability of the Heart in Patients With Ischemic Mitral Regurgitation Post Myocardial Infarction

“…Считают, что благоприятные эффекты этого класса препаратов опосредованы именно замедлением прогрессирования фиброза миокарда (Messaoudi S, et al, 2012). Торасемид по сравнению с фуросемидом имеет более длитель-ное время полувыведения, длительное время дей-ствия и большую биодоступность [7]. Антифиброти-ческие эффекты торасемида у пациентов с ХСН могут быть объяснены его способностью влиять на различные этапы синтеза коллагена (подавление активности протеиназы коллагена I типа, уменьше-ние экспрессии лизил-оксидазы, замедление "сши-вания" коллагена) [8].…”

Phosphorylation of Mineralocorticoid Receptor Ligand Binding Domain Impairs Receptor Activation and Has a Dominant Negative Effect over Non-phosphorylated Receptors

“…Generation and use of a functional fluorescent derivative of MR with insertion of YFP after amino acid 147 has been previously described (5,21). A derivative of that construct substituting YFP by three copies of the HA epitope was generated by using AscI sites flanking the YFP sequence and cloning a PCRgenerated 3ϫHA epitope with the same flanking sites.…”

“…Images were collected using a Fluoview 1000 confocal microscope (Olympus, Barcelona, Spain). Kinetic analysis of aldosterone-induced MR nuclear translocation was performed as previously described (21,26). Briefly, cells were transfected with MR-YFP and grown for 48 h in DMEM supplemented with charcoal-stripped FBS.…”