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Analysis of cardiac gene expression in response to isoproterenol-induced heart failure (part 2)

ABSTRACT: Myoglobin knockout mice (myo-/-) adapt to the loss of myoglobin by the activation of a variety of compensatory mechanisms on the structural and functional level. In order to analyze to what extent myo-/- mice would tolerate cardiac stress we used the model of chronic isoproterenol application to induce cardiac hypertrophy in myo-/- mice and wild type (WT) controls. After 14 d of isoproterenol infusion cardiac hypertrophy in WT and myo-/- mice reached a similar level. WT mice developed lung oedema and left ventricular dilatation indicating the development of heart failure. In contrast, myo-/- mice displayed conserved cardiac function and no signs of heart failure. Analysis of the cardiac gene expression profile using 40 k mouse oligonucleotide arrays showed that isoproterenol affected the expression of 180 genes in WT but only 92 genes of myo-/- hearts. Only 40 of these genes were regulated in WT and myo-/- hearts. Whereas in WT hearts a prononced induction of genes of the extracellular matrix occurred suggesting a higher level of remodelling, in myo-/- hearts genes of carbon metabolism and genes linked to inhibition of apoptosis and muscular repair were altered. Interestingly, a subset of genes which was altered in myo-/- mice already under basal conditions was differentially expressed in WT hearts under isoproterenol treatment. In summary, our data show, that the genetic background (WT, myo-/-) has a major impact on cardiac gene expression even in the context of an aggressive hypertrophy model such as chronic isoproterenol stimulation. Keywords: gene expression profiling of isoproterenol induced heart failure in WT and myo-/- mice

ORGANISM(S): Mus musculus

PROVIDER: GSE16246 | GEO | 2010/05/31

SECONDARY ACCESSION(S): PRJNA115183

REPOSITORIES: GEO

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Project description:Muscle ring finger-1 (MuRF1) is a muscle-specific protein implicated in the regulation of cardiac myocyte size and contractility. MuRF2, a closely related family member, redundantly interacts with protein substrates, and hetero-dimerizes with MuRF1. Mice lacking either MuRF1 or MuRF2 are phenotypically normal whereas mice lacking both proteins develop a spontaneous cardiac and skeletal muscle hypertrophy indicating cooperative control of muscle mass by MuRF1 and MuRF2. In order to identify the role that MuRF1 plays in regulating cardiac hypertrophy in vivo, we created transgenic mice expressing increased amounts of cardiac MuRF1. Adult MuRF1 transgenic (Tg+) hearts exhibited a non-progressive thinning of the left ventricular wall and a concomitant decrease in cardiac function. Experimental induction of cardiac hypertrophy by trans-aortic constriction (TAC) induced rapid failure of MuRF1 Tg+ hearts. Microarray analysis identified that the levels of genes associated with metabolism (and in particular mitochondrial processes) were significantly altered in MuRF1 Tg+ hearts, both at baseline and during the development of cardiac hypertrophy. Surprisingly, ATP levels in MuRF1 Tg+ mice did not differ from wild type mice despite the depressed contractility following TAC. To explain this discrepancy between the ongoing heart failure and maintained ATP levels in MuRF1 Tg+ hearts, we compared the level and activity of creatine kinase (CK) between wild type and MuRF1 Tg+ hearts. Although mCK and CK-M/B protein levels were unaffected in MuRF1 Tg+ hearts, total CK activity was significantly inhibited. We conclude that MuRF1’s inhibition of CK activity leads to increased susceptibility to heart failure following TAC, demonstrating for the first time that MuRF1 regulates cardiac energetics in vivo. Keywords: Genetic modification, physiological manipulation. Three-condition experiment, MuRF1 Tg+ vs. WT mice. Biological replicates: 4 WT baseline, 3 MuRF1 Tg+ baseline, cardiac overpressure hypertrophy induced by trans-aortic banding at 1 week (3 WT, 3 MurF Tg) and 4 weeks (3 WT, 3 MurF Tg), hearts harvested. One replicate per array.

Project description:Aims: We investigate sex differences and the role of oestrogen receptor beta (ERbeta) in a mouse model of pressure overload-induced myocardial hypertrophy. Methods and results: We performed transverse aortic constriction (TAC) or sham surgery in male and female wild-type (WT) and ER knockout (ERbeta-/-) C57Bl6 mice. All mice were characterised by echocardiography and haemodynamic measurements and were sacrificed nine weeks after surgery. Left ventricular (LV) samples were analysed by microarray profiling, real-time RT-PCR and histology. After nine weeks, WT males showed more hypertrophy and heart failure signs than WT females. Notably, WT females developed a concentric form of hypertrophy, while males developed eccentric hypertrophy. These sex differences were abolished in ERbeta-/- mice. ERbeta deletion augmented the TAC-induced increase in cardiomyocyte diameter in both sexes. Gene expression profiling revealed that male WT hearts had a stronger induction of matrix-related genes and a stronger repression of mitochondrial genes than female hearts. ERbeta-/- mice exhibited a different transcriptome. Induction of pro-apoptotic genes after TAC occurred in ERbeta-/- mice of both sexes with a stronger expression in ERbeta-/- males. Histological analysis revealed, that cardiac fibrosis was more pronounced in male WT TAC than in female mice. This was abolished in ERbeta-/- mice. Apoptosis was significantly induced in both sexes of ERbeta-/- TAC mice, but it was most prominent in males. Conclusion: Female sex offers protection against ventricular chamber dilation in the TAC model. Both the female sex and ER attenuate the development of fibrosis and apoptosis; thus slowing the progression to heart failure. The influence of sex (male/female) and estrogen receptor beta expression (ERbeta knockout/wildtype) on cardiac hypertrophy (transverse aortic constriction/sham operated) was investigated. The left ventricular transcriptome of four individual mice for each combination of the three factors (sex, genotype, surgery) was detected with Affymetrix RAE 430 2.0 GeneChip arrays.

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Analysis of cardiac gene expression in response to isoproterenol-induced heart failure (part 2)

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