title: Mice with cardiomyocyte-specific disruption of the endothelin-1 gene are resistant to hyperthyroid cardiac hypertrophy.
abstract: Endothelin 1 (ET-1), a potent vasoconstrictor peptide expressed by endothelium, is also produced in the heart in response to a variety of stresses. It induces hypertrophy in cultured cardiac myocytes but only at concentrations far greater than those found in plasma. We tested whether ET-1 generated by cardiac myocytes in vivo is a local signal for cardiac hypertrophy. To avoid the perinatal lethality seen in systemic ET-1-null mice, we used the Cre/loxP system to generate mice with cardiac myocyte-specific disruption of the ET-1 gene. We used the alpha-myosin heavy chain promoter to drive expression of Cre and were able to obtain 75% reduction in ET-1 mRNA in cardiac myocytes isolated from these mice at baseline and after stimulation, in vivo, for 24 h with tri-iodothyronine (T3). Necropsy measurements of cardiac mass indexed for body weight showed a 57% reduction in cardiac hypertrophy in response to 16 days of exogenous T3 in mice homozygous for the disrupted ET-1 allele compared to siblings with an intact ET-1 gene. Moreover, in vivo MRI showed only a 3% increase in left ventricular mass indexed for body weight in mice with the disrupted allele after 3 weeks of T3 treatment versus a 27% increase in mice with an intact ET-1 gene. A reduced hypertrophic response was confirmed by planimetry of cardiac myocytes. We conclude that ET-1, produced locally by cardiac myocytes, and acting in a paracrine/autocrine manner, is an important signal for myocardial hypertrophy that facilitates the response to thyroid hormone.
authors.affiliation: Department of Internal Medicine, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. ralph.shohet@utsouthwestern.edu
authors.forename: Ralph V
authors.initials: RV
authors.lastname: Shohet
authors.forename: Yaz Y
authors.initials: YY
authors.lastname: Kisanuki
authors.forename: Xiao-Song
authors.initials: XS
authors.lastname: Zhao
authors.forename: Zakir
authors.initials: Z
authors.lastname: Siddiquee
authors.forename: Fatima
authors.initials: F
authors.lastname: Franco
authors.forename: Masashi
authors.initials: M
authors.lastname: Yanagisawa
mesh_terms: D000375:Aging; D000483:Alleles; D000818:Animals; D006332:Cardiomegaly / Q000139:chemically induced / Q000235:genetics*; D019332:Endothelin-1 / Q000172:deficiency* / Q000235:genetics*; D005260:Female; D017353:Gene Deletion; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006980:Hyperthyroidism / Q000235:genetics*; D019426:Integrases / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D009928:Organ Specificity; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D014284:Triiodothyronine / Q000494:pharmacology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D012333:RNA, Messenger; D014764:Viral Proteins; D014284:Triiodothyronine; C045073:Cre recombinase; D019426:Integrases