title: Myocardial mineralocorticoid receptor activation by stretching and its functional consequences.
abstract: Myocardial stretch triggers an angiotensin II-dependent autocrine/paracrine loop of intracellular signals, leading to reactive oxygen species-mediated activation of redox-sensitive kinases. Based on pharmacological strategies, we previously proposed that mineralocorticoid receptor (MR) is necessary for this stretch-triggered mechanism. Now, we aimed to test the role of MR after stretch by using a molecular approach to avoid secondary effects of pharmacological MR blockers. Small hairpin interference RNA capable of specifically knocking down the MR was incorporated into a lentiviral vector (l-shMR) and injected into the left ventricular wall of Wistar rats. The same vector but expressing a nonsilencing sequence (scramble) was used as control. Lentivirus propagation through the left ventricle was evidenced by confocal microscopy. Myocardial MR expression, stretch-triggered activation of redox-sensitive kinases (ERK1/2-p90(RSK)), the consequent Na(+)/H(+) exchanger-mediated changes in pHi (HEPES-buffer), and its mechanical counterpart, the slow force response, were evaluated. Furthermore, reactive oxygen species production in response to a low concentration of angiotensin II (1.0 nmol/L) or an equipotent concentration of epidermal growth factor (0.1 μg/mL) was compared in myocardial tissue slices from both groups. Compared with scramble, animals transduced with l-shMR showed (1) reduced cardiac MR expression, (2) cancellation of angiotensin II-induced reactive oxygen species production but preservation of epidermal growth factor-induced reactive oxygen species production, (3) cancellation of stretch-triggered increase in ERK1/2-p90(RSK) phosphorylation, (4) lack of stretch-induced Na(+)/H(+) exchanger activation, and (5) abolishment of the slow force response. Our results provide strong evidence that MR activation occurs after myocardial stretch and is a key factor to promote redox-sensitive kinase activation and their downstream consequences.
authors.affiliation: Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, UNLP, 60 y 120, 1900 La Plata, Argentina. cicmes@me.com.
authors.forename: Romina G
authors.initials: RG
authors.lastname: Díaz
authors.forename: Néstor G
authors.initials: NG
authors.lastname: Pérez
authors.forename: Patricio E
authors.initials: PE
authors.lastname: Morgan
authors.forename: María C
authors.initials: MC
authors.lastname: Villa-Abrille
authors.forename: Claudia I
authors.initials: CI
authors.lastname: Caldiz
authors.forename: Mariela B
authors.initials: MB
authors.lastname: Nolly
authors.forename: Enrique L
authors.initials: EL
authors.lastname: Portiansky
authors.forename: Irene L
authors.initials: IL
authors.lastname: Ennis
authors.forename: Horacio E
authors.initials: HE
authors.lastname: Cingolani
mesh_terms: D000818:Animals; D005822:Genetic Vectors; D006321:Heart / Q000502:physiology; D016086:Lentivirus; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D018161:Receptors, Mineralocorticoid / Q000378:metabolism*; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D018161:Receptors, Mineralocorticoid; C452850:Slc9a1 protein, rat; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers
keywords: Na+/H+ exchanger; mineralocorticoid receptors; myocardial stretch