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Altered Hepatic Gene Expression Profiles Associated with Myocardial Ischemia

ABSTRACT: Background–Acute coronary syndrome (ACS) is sometimes accompanied by accelerated coagulability, lipid metabolism, and inflammatory responses, which are not attributable to the cardiac events alone. We hypothesized that the liver plays a pivotal role in the pathophysiology of ACS. We simultaneously analyzed the gene expression profiles of the liver and heart during acute myocardial ischemia in mice. Methods and Results–Mice were divided into three treatment groups: sham-operation, ischemia-reperfusion (I/R), and myocardial infarction. Mice with liver I/R were included as additional controls. Marked changes in hepatic gene expression were observed after 24 hours, despite the lack of histological changes in the liver. Genes related to tissue remodeling, adhesion molecules, and morphogenesis were significantly upregulated in the livers of mice with myocardial I/R or infarction, but not in those with liver I/R. Myocardial ischemia, but not changes in the hemodynamic state, was postulated to significantly alter hepatic gene expression. Moreover, detailed analysis of the signaling pathway suggested the presence of humoral factors that intervened between the heart and liver. To address these points, we utilized isolated primary hepatocytes and showed that osteopontin released from the heart actually altered the signaling pathways of primary hepatocytes to those observed in the livers of mice under myocardial ischemia. Moreover, osteopontin stimulated primary hepatocytes to secrete vascular endothelial growth factor-A, which is important for tissue remodeling. Conclusions– Hepatic gene expression is potentially regulated by cardiac humoral factors under myocardial ischemia. These results provide new insights into the pathophysiology of ACS.

ORGANISM(S): Mus musculus

PROVIDER: GSE14843 | GEO | 2009/11/12

SECONDARY ACCESSION(S): PRJNA112115

REPOSITORIES: GEO

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Project description:Background: Ischemic preconditioning (IPC), i.e., brief periods of ischemia, protect the heart from subsequent prolonged ischemic injury, and reduces infarction size. Myocardial stunning refers to transient loss of contractility in the heart after myocardial ischemia that recovers without causing permanent damage. The relationship between IPC and myocardial stunning remains incompletely understood. Purpose: The primary aim of this study was to examine the effects of IPC on the relationship between ischemia duration, stunning, and infarct size in an ischemia-reperfusion injury model. The secondary aim of the study was to examine to which extent the phosphoproteomic changes induced by IPC relate to myocardial contractile function. Methods: Rats were subjected to different durations of left anterior descending artery (LAD) occlusion, with or without preceding IPC. Echocardiograms were acquired at 4 and 48 hours to assess cardiac contraction in the affected myocardial segment. Reversible akinesia was defined as the presence of myocardial akinesia at 4 hours that resolved by 48 hours; and was considered to represent myocardial stunning. Infarction size was evaluated using triphenyl tetrazolium chloride staining. Phosphoproteomic analysis was performed in heart tissue from preconditioned and non-preconditioned animals using nano-liquid chromatography-mass spectrometry. Results: Reversible akinesia was observed in a majority of the rats that were subjected to IPC and subsequently exposed to ischemia of 13.5 or 15 minutes of ischemia (83.3% [n/N] and 66.6% [n/N] respectively). Among rats without IPC, who were exposed to either 10, 11, 12 or 13.5 minutes of ischemia, reversible akinesia was observed in 0% (n/N), 17% (2/12), 0% (n/N) and 0% (n/N) of rats (p<0.001). Phosphoproteomic analysis revealed significant differential regulation of 809 phosphopeptides between IPC and non-IPC groups, with significant associations with the sarcomere, Z-disc, and actin binding. Conclusion: Our study shows that IPC preferentially induces changes in phosphosites of proteins involved in myocardial contraction, and both increases the incidence of reversible post-ischemic myocardial stunning after ischemia-reperfusion injury and reduces infarction size.

Project description:Disruption of peripheral circadian rhyme pathways dominantly leads to metabolic disorders. Studies on circadian rhythm proteins in the heart indicated a role for Clock or Per2 in cardiac metabolism. In fact, Per2-/- mice have larger infarct sizes with a deficient lactate production during myocardial ischemia. To test the hypothesis that cardiac Per2 represents an important regulator of cardiac metabolism during myocardial ischemia, we performed lactate measurements during reperfusion in Per1-/-, Per2-/- or wildtype mice followed by gene array studies using various ischemia-reperfusion protocols comparing wildtype and Per2-/- mice. Lactate measurements in whole blood confirmed a dominant role of Per2 for lactate production during myocardial ischemia. Surprisingly, high-throughput gene array analysis of eight different conditions on one 24-microarray plate revealed dominantly lipid metabolism as differentially regulated pathway in wildtype mice when compared to Per2-/-. In all treatment groups, the enzyme enoyl-CoA hydratase, which is essential in fatty acid beta-oxidation, was regulated in wildtype animals only. Studies using nuclear magnet resonance imaging (NMRI) confirmed altered fatty acid populations with higher mono-unsaturated fatty acid levels in hearts from Per2-/- mice. Unexpectedly, studies on gene regulation during reperfusion revealed solely pro inflammatory genes as differentially regulated 'Per2-genes'. Subsequent studies on inflammatory markers showed increasing IL6 or TNFa levels during reperfusion in Per2-/- mice. In summary, these studies reveal a novel role of cardiac Per2 for fatty acid metabolism or inflammation during myocardial ischemia and reperfusion. We pursued studies on Per2 dependent gene expression during myocardial ischemia or reperfusion to understand its impact on cardiac metabolism. We designed different ischemia and reperfusion protocols and performed a high-throughput expression profiling of 24 samples at a time using an industry-standard whole mouse gene array (Affymetrix, Mouse Gene 2.1 ST 24-Array). To understand differential gene regulation during different conditions we performed 1) 30 minutes of ischemia without reperfusion, 2) ischemic preconditioning (IP, 4 x 5 minutes ischemia and reperfusion), as known cardioprotective mechanism, and 3) 30 minutes of ischemia followed by 60 minutes of reperfusion. Based on three arrays per condition the total number of arrays was 24, which we analyzed at the same time on a multi plate array to avoid inter-array variations. Quality analysis using Partek Genomics Suite 6.6 revealed high confidence in the quality of the microarray data and all samples met 'Quality Assurance/Quality Control' (QA/QC) criteria.

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Altered Hepatic Gene Expression Profiles Associated with Myocardial Ischemia

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