This Article Full Text Full Text (PDF) All Versions of this Article: 117/3/396    most recent CIRCULATIONAHA.107.727073v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Diwan, A. Articles by Dorn, G. W. Search for Related Content PubMed PubMed Citation Articles by Diwan, A. Articles by Dorn, G. W., II Pubmed/NCBI databases Gene GEO Profiles HomoloGene Nucleotide Protein UniGene Related Collections Animal models of human disease Apoptosis Related Article

(Circulation. 2008;117:396-404.)
© 2008 American Heart Association, Inc.

Molecular Cardiology

Nix-Mediated Apoptosis Links Myocardial Fibrosis, Cardiac Remodeling, and Hypertrophy Decompensation

Abhinav Diwan, MD; Janaka Wansapura, PhD; Faisal M. Syed, MD; Scot J. Matkovich, PhD; John N. Lorenz, PhD; Gerald W. Dorn, II, MD

From the Center for Molecular Cardiovascular Research (A.D., F.M.S., S.J.M., G.W.D.), Department of Pediatrics (G.W.D.), and Department of Molecular and Cellular Physiology (J.N.L.), University of Cincinnati; and Imaging Research Center, Department of Radiology, Children’s Hospital Medical Center (J.W.), Cincinnati, Ohio.

Correspondence to Gerald W. Dorn II, MD, Center for Molecular Cardiovascular Research, 231 Albert Sabin Way, ML 0839, Cincinnati, OH 45267-0839. E-mail dorngw{at}ucmail.uc.edu

Received July 10, 2007; accepted November 5, 2007.

Background— Pathological cardiac hypertrophy inevitably remodels, leading to functional decompensation. Although modulation of apoptosis-regulating genes occurs in cardiac hypertrophy, a causal role for programmed cardiomyocyte death in left ventricular (LV) remodeling has not been established.

Methods and Results— We targeted the gene for proapoptotic Nix, which is transcriptionally upregulated in pressure overload and Gq-dependent hypertrophies, in the mouse germ line or specifically in cardiomyocytes (knockout [KO]) and conditionally overexpressed it in the heart (transgenic [TG]). Conditional forced Nix expression acted synergistically with the prohypertrophic Gq transgene to increase cardiomyocyte apoptosis (0.8±0.1% in GqTG versus 7.8±0.6% in GqTG+NixTG; P<0.001), causing lethal cardiomyopathy with LV dilation and depressed systolic function (percent fractional shortening, 39±4 versus 23±4; P=0.042). In the reciprocal experiment, germ-line Nix ablation significantly reduced cardiomyocyte apoptosis (4.8±0.2% in GqTG+NixKO versus 8.4±0.5% in GqTG; P=0.001), which improved percent fractional shortening (43±3% versus 27±3%; P=0.017), attenuated LV remodeling, and largely prevented lethality in the Gq peripartum model of apoptotic cardiomyopathy. Cardiac-specific (Nkx2.5-Cre) Nix KO mice subjected to transverse aortic constriction developed significantly less LV dilation by echocardiography and magnetic resonance imaging, maintained concentric remodeling, and exhibited preserved LV ejection fraction (61±2% in transverse aortic constriction cardiac Nix KO versus 36±6% in transverse aortic constriction wild-type mice; P=0.003) at 9 weeks, with reduced cardiomyocyte apoptosis at day 4 (1.70±0.21% versus 2.73±0.35%; P=0.032).

Conclusions— Nix-induced cardiomyocyte apoptosis is a major determinant of adverse remodeling in pathological hypertrophies, a finding that suggests therapeutic value for apoptosis inhibition to prevent cardiomyopathic decompensation.

---

 

CLINICAL PERSPECTIVE

Related Article:

Clinical Summaries
Circulation 2008 117: 331-332. [Full Text]