Overexpression of the serotonin 5-HT2B receptor in heart leads to abnormal mitochondrial function and cardiac hypertrophy.
BACKGROUND
Identification of factors regulating myocardial structure and function is important to understand the pathogenesis of heart disease. We previously reported that 5-HT2B receptor ablation in mice leads to dilated cardiomyopathy. In this study, we investigated the pathological consequence of overexpressing 5-HT2B receptors in heart in vivo.


RESULTS
We have generated transgenic mice overexpressing the Gq-coupled 5-HT2B receptor specifically in heart. We found that overexpression of 5-HT2B receptor in heart leads to ventricular hypertrophy as the result of increased cell number and size. Increased atrial natriuretic peptide and myosin heavy chain expression demonstrated activation of the molecular program for cardiac hypertrophy. Echocardiographic analysis indicated the presence of thickened ventricular free wall without alteration of the systolic function, showing that transgenic mice have compensated hypertrophy. Electron microscopic analysis revealed structural abnormalities including mitochondrial proliferation, as also manifested by histological staining. Transgenic mouse heart displayed a specific reduction in the expression levels of the adenine nucleotide translocator associated to increase in the succinate dehydrogenase and cytochrome C oxidase mitochondrial activities.


CONCLUSIONS
Our results constitute the first genetic evidence that overexpression of the 5-HT2B receptor in the heart leads to compensated hypertrophic cardiomyopathy associated with proliferation of the mitochondria. This observation suggests a role for mitochondria in the hypertrophic signaling that is regulated by serotonin. These transgenic mice provide a new genetic model for hypertrophic heart disease.
Nebigil
Canan G
CG
Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS, INSERM, Université de Strasbourg, Illkirch, France.
Jaffré
Fabrice
F
Messaddeq
Nadia
N
Hickel
Pierre
P
Monassier
Laurent
L
Launay
Jean-Marie
JM
Maroteaux
Luc
L
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D006332:Cardiomegaly / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D002452:Cell Count; D048429:Cell Size; D004195:Disease Models, Animal; D004452:Echocardiography; D003576:Electron Transport Complex IV / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D015870:Gene Expression; D006352:Heart Ventricles / Q000473:pathology; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000473:pathology; D018995:Myosin Heavy Chains / Q000378:metabolism; D009928:Organ Specificity; D044403:Receptor, Serotonin, 5-HT2B; D011985:Receptors, Serotonin / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction; D013385:Succinate Dehydrogenase / Q000378:metabolism
D044403:Receptor, Serotonin, 5-HT2B; D011985:Receptors, Serotonin; D009320:Atrial Natriuretic Factor; D000226:Mitochondrial ADP, ATP Translocases; D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV; D018995:Myosin Heavy Chains; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins