Failed Downregulation of Circulating MicroRNA-155 in the Early Phase after ST Elevation Myocardial Infarction Is Associated with Adverse Left Ventricular Remodeling.

BACKGROUND: MicroRNA are noncoding RNA that have a significant role in both inflammatory and cardiovascular diseases. AIMS: We aimed to assess whether the inflammation-related microRNA-155 is associated with the development of adverse left ventricular (LV) remodeling following ST elevation myocardial infarction (STEMI). METHODS: Peripheral blood samples were collected in the inflammatory (day 2), proliferative (day 5), and maturation phases (6 months) after STEMI (n = 20). Granulocytes, monocytes, and lymphocytes were enumerated with flow cytometry. The changes in LV volumes were assessed with 3-D echocardiography on day 1 and after 6 months. Adverse remodeling was defined as a >20% increase in end-diastolic volume. Healthy subjects were recruited as controls. RESULTS: MicroRNA-155 measured on day 5 correlated positively with the relative change in end-diastolic volume (ρ = 0.490, p = 0.028). MicroRNA-155 (day 5) was significantly higher in patients with compared to patients without adverse LV remodeling. The expression level was similar in healthy subjects (n = 8) and in patients with LV remodeling. There was a positive correlation between microRNA-155 and the amount of monocytes (day 5, ρ = 0.463, p = 0.046). CONCLUSION: Impaired downregulation of microRNA-155 during the second phase of the post- STEMI inflammatory response is a determinant of the development of adverse LV remodeling.

Altered expression of monocyte and dendritic cell membrane-associated antigens following coronary angiography.

INTRODUCTION: Coronary angiography is able to induce a systemic inflammatory response. We hypothesised that this procedure may affect monocyte and dendritic cell count and membrane-associated antigen expression. METHODS: Blood samples were obtained before and immediately after coronary angiography in twenty patients with stable angina pectoris. Cell enumeration and antigen expression levels were evaluated by flow cytometry. Plasma levels of soluble CD14 and interleukin-6 were quantified by ELISA. RESULTS: The absolute and relative numbers of circulating monocytes (Mon1, Mon2 and Mon3 subsets) and dendritic cells (myeloid and plasmacytoid subsets) were not significantly different pre-versus post-angiography. Expression of CD14 on Mon1 and Mon2 decreased significantly by 12.01% (P = 0.002) and 13.01% (P=0.012), respectively. CD16 expression on Mon2 (+10.53%; P=0.017) and Mon3 (+12.58%; P<0.001) increased. CD45 expressed by monocytic and dendritic cells was lowered (-5.80% and P = 0.001, -11.49% and P < 0.001, respectively). The level of plasma IL-6 decreased significantly (P = 0.002). The reduction in sCD14 was not significant (P = 0.054). CONCLUSION: Coronary angiography leads to changes in surface expression of CD14, CD16 and CD45. These findings underline the importance of blood collection prior to the angiographic procedure when aiming to study the functional analysis of monocyte and dendritic cell numbers by flow cytometry.

The cellular immune system in the post-myocardial infarction repair process.

Growing evidence indicates that overactivation and prolongation of the inflammatory response after acute myocardial infarction (AMI) result in worse left ventricular remodelling, dysfunction and progression to heart failure. This post-AMI inflammatory response is characterised by the critical involvement of cells from both the innate and adaptive immune systems. In this review paper, we aim to summarise and discuss the emergence of immune cells in the bloodstream and myocardium after AMI in men and mice. Subset composition, phenotypes, and kinetics of immune cells are considered. In addition, the relation with post-MI cardiac remodelling, function and outcome is reported. Increased knowledge of immune components, the mechanisms and interactions by which these cells contribute to myocardial damage and repair following AMI may help to close the gaps that limit improvement of treatments of those who survive the acute infarction.