The Epidermal Growth Factor Receptor Is Involved in Angiotensin II But Not Aldosterone/Salt-Induced Cardiac Remodelling

Experimental and clinical studies have shown that aldosterone/mineralocorticoid receptor (MR) activation has deleterious effects in the cardiovascular system; however, the signalling pathways involved in the pathophysiological effects of aldosterone/MR in vivo are not fully understood. Several in vitro studies suggest that Epidermal Growth Factor Receptor (EGFR) plays a role in the cardiovascular effects of aldosterone. This hypothesis remains to be demonstrated in vivo. To investigate this question, we analyzed the molecular and functional consequences of aldosterone exposure in a transgenic mouse model with constitutive cardiomyocyte-specific overexpression of a mutant EGFR acting as a dominant negative protein (DN-EGFR). As previously reported, Angiotensin II-mediated cardiac remodelling was prevented in DN-EGFR mice. However, when chronic MR activation was induced by aldosterone-salt-uninephrectomy, cardiac hypertrophy was similar between control littermates and DN-EGFR. In the same way, mRNA expression of markers of cardiac remodelling such as ANF, BNF or β-Myosin Heavy Chain as well as Collagen 1a and 3a was similarly induced in DN-EGFR mice and their CT littermates. Our findings confirm the role of EGFR in AngII mediated cardiac hypertrophy, and highlight that EGFR is not involved in vivo in the damaging effects of aldosterone on cardiac function and remodelling

Cardiomyopathy and Response to Enzyme Replacement Therapy in a Male Mouse Model for Fabry Disease

Fabry disease is an X-linked disorder of glycosphingolipid metabolism that results in progressive accumulation of neutral glycosphingolipids, (predominately globotriaosylceramide; GL-3) in lysosomes, as well as other cellular compartments and the extracellular space. Our aim was to characterize the cardiac phenotype of male knock-out mice that are deficient in alpha-galactosidase A activity, as a model for Fabry disease and test the efficacy of Enzyme Replacement Therapy with agalsidase-beta. Male mice (3–4 months of age) were characterized with awake blood pressure and heart rate measurements, cardiac echocardiography and electrocardiography measurements under light anesthesia, histological studies and molecular studies with real-time polymerase chain reaction. The Fabry knock-out mouse has bradycardia and lower blood pressure than control wild type (CB7BL/6J) mice. In Fabry knock-out mice, the cardiomyopathy associated mild hypertrophy at echography with normal systolic LV function and mild diastolic dysfunction. Premature atrial contractions were more frequent in without conduction defect. Heart weight normalized to tibial length was increased in Fabry knock-out mice. Ascending aorta dilatation was observed. Molecular studies were consistent with early stages of cardiac remodeling. A single dose of agalsidase-beta (3 mg/kg) did not affect the LV hypertrophy, function or heart rate, but did improve the mRNA signals of early cardiac remodeling. In conclusion, the alpha-galactosidase A deficient mice at 3 to 4 months of age have cardiac and vascular alterations similar to that described in early clinical stage of Fabry disease in children and adolescents. Enzyme replacement therapy affects cardiac molecular remodeling after a single dose

Cardiac phenotype of CT and DN-EGFR mice after two weeks of Angiotensin II or aldosterone (NAS) treatment.

<p><b>A:</b> Heart weight to tibia length ratio of CT and DN-EGFR mice under basal conditions or after two weeks of Angiotensin II infusion. Values are means ± SEM, n = 3–6 mice per group. *p<0.05, Angiotensin II-treated mice <i>versus</i> corresponding Sham. <b>B:</b> Cardiac ANF mRNA expression of CT and DN-EGFR mice under basal conditions or after two weeks of Angiotensin II infusion. Values are expressed relative to those for UBC ± SEM, n = 3–6 mice per condition. *p<0.05, Angiotensin II <i>versus</i> corresponding Sham. <b>C:</b> Heart weight to tibia length ratio of CT and DN-EGFR mice under basal conditions or after two weeks of Nephrectomy-Aldo-Salt treatment (NAS). Values are means ± SEM, n = 5–6 mice per group. *p<0.05, NAS-treated mice <i>versus</i> corresponding Sham. <b>D:</b> Cardiac ANF mRNA expression of CT and DN-EGFR mice under basal conditions or after two weeks of NAS treatment. Values are expressed relative to those for UBC ± SEM, n = 5–6 mice per condition. *p<0.05, NAS <i>versus</i> corresponding Sham.</p

Echocardiographic data of DN-EGFR or CT mice after 4 weeks of Nephrectomy-Aldo-Salt treatment (NAS).

<p>LA: left atrium; LV EDD: left ventricle end diastolic diameter; BW: body weight; EF: ejection fraction; Vcfc: velocity shortening of circumferential fibers; Sa, Spw: maximal systolic velocity of the mitral annulus and posterior wall; IVRT: isovolumic relaxation time; Ea and Epw: maximal diastolic velocity of the mitral annulus and the posterior wall; E: maximal velocity of the LV inflow.</p><p>*p<0.05 <i>versus</i> CT-Sham.</p

General characteristics of CT and DN-EGFR mice after 2 or 4 weeks of aldosterone (NAS) treatment.

<p>BW: body weight; TL: tibia length; KW: kidney weight; SBP: Systolic Blood Pressure.</p><p>*p<0.05 <i>vs</i> corresponding Sham.</p

Cardiac phenotype of CT and DN-EGFR mice after 4 weeks of aldosterone (NAS) treatment.

<p><b>A</b>- Heart weight to tibia length ratio of CT and DN-EGFR mice under basal conditions or after 4 weeks of NAS treatment. Values are means ± SEM, n = 3–5 mice per group. *p<0.05, NAS <i>versus</i> corresponding Sham. <b>B:</b> Cardiac ANF mRNA expression of CT and DN-EGFR mice under basal conditions or after 4 weeks of NAS. Values are expressed relative to those for UBC ± SEM, n = 3–5 mice per condition. *p<0.05, NAS <i>versus</i> corresponding Sham. <b>C–E:</b> Cardiac BNF and βMHC (C) , Col1A and Col3A (D) and Mmp9 (E) mRNA expression of CT and DN-EGFR mice under basal conditions or after 4 weeks of NAS. Values are expressed relative to those for UBC ± SEM, n = 3–5 mice per condition. *p<0.05, NAS <i>versus</i> corresponding Sham. <b>F:</b> Interstitial cardiac fibrosis quantification. Cardiac fibrosis in CT and DN-EGFR mice under basal conditions or after 4 weeks of NAS. Values are expressed as arbitrary units. n = 3–5 mice per condition.</p

Echocardiographic data of DN-EGFR or CT mice after 2 weeks of aldosterone treatment (NAS).

<p>LA: left atrium; LV EDD: left ventricle end diastolic diameter; BW: body weight; EF: ejection fraction; Vcfc: velocity shortening of circumferential fibers; Sa, Spw: maximal systolic velocity of the mitral annulus and posterior wall; IVRT: isovolumic relaxation time; Ea and Epw: maximal diastolic velocity of the mitral annulus and the posterior wall; E: maximal velocity of the LV inflow.</p><p>*p<0.05 <i>versus</i> CT-Sham.</p

Primers sequences.

<p>Primers sequences.</p