Influence of microRNAs on iNOS expression in postmortem human infarction hearts.

MicroRNAs (miRNAs) are important post-transcriptional regulators in several diseases, including cancer, immunologic and cardiovascular diseases. A growing list of miRNAs are dysregulated in cardiac arrhythmias, contractility diseases, myocardial infarction (MI), sudden cardiac death (SCD), chronic heart failure and hypertrophy. However, the exact regulatory pathways, through which miRNAs exert their effects are often unclear. In this study, we measured the expression patterns of miR-21, miR-939 and miR-30e in postmortem human MI. The aim of the study was to examine the influence of these miRNAs on cardiac inducible nitric oxide synthase (iNOS) mRNA levels. We measured iNOS mRNA and miRNA expression patterns by means of qPCR. Further we used correlation analyses to determine causality between miRNA expression and cardiac iNOS levels. iNOS mRNA, miR-21, miR-939 and miR-30e were significantly upregulated in infarcted and non-infarcted regions of postmortem human MI hearts in comparison to healthy controls. While miR-21 and miR-939 showed their strongest expression in infarcted regions, miR-30e peaked in the non-infarcted myocardium. Further, we found a significant correlation between miR-939 and iNOS expression levels in controls and infarcted regions. The results indicate, that miR-939 is a regulator of cardiac iNOS expression. However, a massive iNOS activation might exceed the capability of miR-939 to keep its expression in balance. miR-21 and miR-30e do not seem to influence cardiac iNOS levels in MI. Further studies are needed to evaluate downstream targets of these miRNAs and their signaling pathways to clarify their role in human MI.

Suitable biomarkers for post-mortem differentiation of cardiac death causes: Quantitative analysis of miR-1, miR-133a and miR-26a in heart tissue and whole blood.

Cardiovascular diseases are the most common causes of death worldwide. Cardiac death can occur as reaction to myocardial infarction (MI). A diagnostic challenge arises for sudden unexpected death (SUD) cases with structural abnormalities (SA) or without any structural abnormalities (without SA). Therefore, the identification of reliable biomarkers to differentiate cardiac cases from each other is necessary. In the current study, the potential of different microRNAs (miRNAs) as biomarkers in tissue and blood samples of cardiac death cases was analyzed. Blood and tissue samples of 24 MI, 21 SUD and 5 control (C) cases were collected during autopsy. Testing for significance and receiver operating characteristic analysis (ROC) were performed. The results show that miR-1, miR-133a and miR-26a possess a high diagnostic power to discriminate between different cardiac death causes in whole blood and in tissue.

iNOS expressing macrophages co-localize with nitrotyrosine staining after myocardial infarction in humans.

Introduction: Inducible nitric oxide synthase (iNOS) produces micromolar amounts of nitric oxide (NO) upon the right stimuli, whose further reactions can lead to oxidative stress. In murine models of myocardial infarction (MI), iNOS is known to be expressed in infiltrating macrophages, which at early onset enter the infarcted zone and are associated with inflammation. In contrast cardiac tissue resident macrophages are thought to enhance regeneration of tissue injury and re-establish homeostasis. Both detrimental and beneficial effects of iNOS have been described, still the role of iNOS in MI is not fully understood. Our aim was to examine cell expression patterns of iNOS and nitrotyrosine (NT) production in human MI. Material and Methods: We examined in postmortem human MI hearts the iNOS mRNA expression by means of qPCR. Further we performed immunohistochemical stainings for cell type identification. Afterwards a distance analysis between iNOS and NT was carried out to determine causality between iNOS and NT production. Results: iNOS mRNA expression was significantly increased in infarcted regions of human MI hearts and iNOS protein expression was detected in resident macrophages in infarcted human hearts as well as in controls hearts, being higher in resident macrophages in MI hearts compared to control. Furthermore in MI and in healthy human hearts cells showing signs of NT production peaked within 10-15 µm proximity of iNOS+ cells. Discussion: These results indicate that, unexpectedly, resident macrophages are the main source of iNOS expression in postmortem human MI hearts. The peak of NT positive cells within 10-15 µm of iNOS+ cells suggest an iNOS dependent level of NT and therefore iNOS dependent oxidative stress. Our results contribute to understanding the role of iNOS in human MI.

Changes in gene expression patterns in postmortem human myocardial infarction.

In murine models, the expression of inducible nitric oxide synthase (iNOS) in myocardial infarction (MI) has been reported to be the result of tissue injury and inflammation. In the present study, mRNA expression of iNOS, hypoxia-inducible factor-1α (HIF-1α), and vascular endothelial growth factor (VEGF) was investigated in postmortem human infarction hearts. Since HIF-1α is the inducible subunit of the transcription factor HIF-1, which regulates transcription of iNOS and VEGF, the interrelation between the three genes was observed, to examine the molecular processes during the emergence of MI. iNOS and VEGF mRNAs were found to be significantly upregulated in the affected regions of MI hearts in comparison to healthy controls. Upregulation of HIF-1α was also present but not significant. Correlation analysis of the three genes indicated a stronger and significant correlation between HIF-1α and iNOS mRNAs than between HIF-1α and VEGF. The results of the study revealed differences in the expression patterns of HIF-1 downstream targets. The stronger transcription of iNOS by HIF-1 in the affected regions of MI hearts may represent a pathological process, since no correlation of iNOS and HIF-1α mRNA was found in non-affected areas of MI hearts. Oxidative stress is considered to cause molecular changes in MI, leading to increased iNOS expression. Therefore, it may also represent a forensic marker for detection of early changes in heart tissue.

Increased inducible nitric oxide synthase (iNOS) expression in human myocardial infarction.

Increased inducible nitric oxide synthase (iNOS) expression has been reported in heart failure, cardiomyopathies, and arteriosclerosis. iNOS is expressed in the heart upon inflammatory stimuli and produces excessive amounts of nitric oxide (NO). The overproduction of NO is cytotoxic and involved in cardiovascular diseases. Furthermore, iNOS produces superoxide anion which proceeds with NO to the harmful oxidant peroxynitrite, causing oxidative stress in the heart. The aim of the study was to gain new insights into the role of iNOS in human myocardial infarction (MI) and its contribution to oxidative stress in the heart. Furthermore, we investigated the unaffected myocardium of the infarction hearts, to study if iNOS expression is increased, probably as an indicator for oxidative stress. Our results show a significant increase (p = 0.013) of the iNOS expression in the affected regions of MI hearts (n = 9) in comparison with healthy control hearts (n = 4). In the unaffected regions of MI hearts, an increase in the iNOS expression in some samples was found as well. Our study demonstrated the direct detection of iNOS mRNA in human myocardial tissue. The balance between beneficial and deleterious effects of iNOS may be particularly influenced by the presence or absence of concurrent oxidative stress.