Abstract
The aim of the study was to characterize the role of Rac1 GTPase for the mineralocorticoid receptor (MR)-mediated pro-fibrotic remodeling. Transgenic mice with cardiac overexpression of constitutively active Rac1 (RacET) develop an age-dependent phenotype with atrial dilatation, fibrosis, and atrial fibrillation. Expression of MR was similar in RacET and WT mice. The expression of 11β hydroxysteroid dehydrogenase type 2 (11β-HSD2) was age-dependently up-regulated in the atria and the left ventricles of RacET mice on mRNA and protein levels. Statin treatment inhibiting Rac1 geranylgeranylation reduced 11β-HSD2 up-regulation. Samples of human left atrial myocardium showed a positive correlation between Rac1 activity and 11β-HSD2 expression (r = 0.7169). Immunoprecipitation showed enhanced Rac1-bound 11β-HSD2 relative to Rac1 expression in RacET mice that was diminished with statin treatment. Both basal and phorbol 12-myristate 13-acetate (PMA)-induced NADPH oxidase activity were increased in RacET and correlated positively with 11β-HSD2 expression (r = 0.788 and r = 0.843, respectively). In cultured H9c2 cardiomyocytes, Rac1 activation with l-buthionine sulfoximine increased; Rac1 inhibition with NSC23766 decreased 11β-HSD2 mRNA and protein expression. Connective tissue growth factor (CTGF) up-regulation induced by aldosterone was prevented with NSC23766. Cardiomyocyte transfection with 11β-HSD2 siRNA abolished the aldosterone-induced CTGF up-regulation. Aldosterone-stimulated MR nuclear translocation was blocked by the 11β-HSD2 inhibitor carbenoxolone. In cardiac fibroblasts, nuclear MR translocation induced by aldosterone was inhibited with NSC23766 and spironolactone. NSC23766 prevented the aldosterone-induced proliferation and migration of cardiac fibroblasts and the up-regulation of CTGF and fibronectin. In conclusion, Rac1 GTPase regulates 11β-HSD2 expression, MR activation, and MR-mediated pro-fibrotic signaling.
Highlights
The aim of the study was to characterize the role of Rac1 GTPase for the mineralocorticoid receptor (MR)-mediated profibrotic remodeling
We hypothesized that there may be a functional interaction between Rac1 and the MR relevant for the molecular pathways leading to cardiac fibrosis
Because in vitro experiments in cardiomyocytes were performed in the absence of cortisol, the results suggest that 11-HSD2 functionally affects MR signaling independent of its cortisol-inactivating properties, i.e. at the receptor level or through downstream signaling
Summary
The aim of the study was to characterize the role of Rac GTPase for the mineralocorticoid receptor (MR)-mediated profibrotic remodeling. Transgenic mice with cardiac overexpression of constitutively active Rac (RacET) develop an age-dependent phenotype with atrial dilatation, fibrosis, and atrial fibrillation. Samples of human left atrial myocardium showed a positive correlation between Rac activity and 11-HSD2 expression (r ؍0.7169). Immunoprecipitation showed enhanced Rac1-bound 11-HSD2 relative to Rac expression in RacET mice that was diminished with statin treatment. Both basal and phorbol 12-myristate 13-acetate (PMA)induced NADPH oxidase activity were increased in RacET and correlated positively with 11-HSD2 expression (r ؍0.788 and r ؍0.843, respectively). Nuclear MR translocation induced by aldosterone was inhibited with NSC23766 and spironolactone. NSC23766 prevented the aldosterone-induced proliferation and migration of cardiac fibroblasts and the up-regulation of CTGF and fibronectin. We hypothesized that there may be a functional interaction between Rac and the MR relevant for the molecular pathways leading to cardiac fibrosis
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
