Resolution of ST-segment elevation after streptokinase therapy in anterior versus inferior wall myocardial infarction

CXCL10/CXCR3 signaling mediates inhibitory action by interferon-gamma on CRF-stimulated adrenocorticotropic hormone (ACTH) release

Secretion of hormones by the anterior pituitary gland can be stimulated or inhibited by paracrine factors that are produced during inflammatory reactions. The inflammation cytokine interferon-gamma (IFN-γ) is known to inhibit corticotropin-releasing factor (CRF)-stimulated adrenocorticotropin (ACTH) release but its signaling mechanism is not yet known. Using rat anterior pituitary, we previously demonstrated that the CXC chemokine ligand 10 (CXCL10), known as interferon-γ (IFN-γ) inducible protein 10 kDa, is expressed in dendritic cell-like S100β protein-positive (DC-like S100β-positive) cells and that its receptor CXCR3 is expressed in ACTH-producing cells. DC-like S100β-positive cells are a subpopulation of folliculo-stellate cells in the anterior pituitary. In the present study, we examine whether CXCL10/CXCR3 signaling between DC-like S100β-positive cells and ACTH-producing cells mediates inhibition of CRF-activated ACTH-release by IFN-γ, using a CXCR3 antagonist in the primary pituitary cell culture. We found that IFN-γ up-regulated Cxcl10 expression via JAK/STAT signaling and proopiomelanocortin (Pomc) expression, while we reconfirmed that IFN-γ inhibits CRF-stimulated ACTH-release. Next, we used a CXCR3 agonist in primary culture to analyze whether CXCL10 induces Pomc-expression and ACTH-release using a CXCR3 agonist in the primary culture. The CXCR3 agonist significantly stimulated Pomc-expression and inhibited CRF-induced ACTH-release, while ACTH-release in the absence of CRF did not change. Thus, the present study leads us to an assumption that CXCL10/CXCR3 signaling mediates inhibition of the CRF-stimulated ACTH-release by IFN-γ. Our findings bring us to an assumption that CXCL10 from DC-like S100β-positive cells acts as a local modulator of ACTH-release during inflammation.

Expression of chemokine CXCL10 in dendritic-cell-like S100β-positive cells in rat anterior pituitary gland

Chemokines are mostly small secreted polypeptides whose signals are mediated by seven trans-membrane G-protein-coupled receptors. Their functions include the control of leukocytes and the intercellular mediation of cell migration, proliferation, and adhesion in several tissues. We have previously revealed that the CXC chemokine ligand 12 (CXCL12) and its receptor 4 (CXCR4) are expressed in the anterior pituitary gland, and that the CXCL12/CXCR4 axis evokes the migration and interconnection of S100β-protein-positive cells (S100β-positive cells), which do not produce classical anterior pituitary hormones. However, little is known of the cells producing the other CXCLs and CXCRs or of their characteristics in the anterior pituitary. We therefore examined whether CXCLs and CXCRs occurred in the rat anterior pituitary lobe. We used reverse transcription plus the polymerase chain reaction to analyze the expression of Cxcl and Cxcr and identified the cells that expressed Cxcl by in situ hybridization. Transcripts of Cxcl10 and its receptor (Cxcr3 and toll-like receptor 4, Tlr4) were clearly detected: cells expressing Cxcl10 and Tlr4 were identified amongst S100β-positive cells and those expressing Cxcr3 amongst adrenocorticotropic hormone (ACTH)-producing cells. We also investigated Cxcl10 expression in subpopulations of S100β-positive cells. We separated cultured S100β-positive cells into the round-type (dendritic-cell-like) and process-type (astrocyte- or epithelial-cell-like) by their adherent activity to laminin, a component of the extracellular matrix; CXCL10 was expressed only in round-type S100β-positive cells. Thus, CXCL10 produced by a subpopulation of S100β-positive cells probably exerts an autocrine/paracrine effect on S100β-positive cells and ACTH-producing cells in the anterior lobe.

Resolution of ST-segment elevation after thrombolytic therapy in elderly patients with acute myocardial infarction

We examined the resolution of ST-segment elevation after thrombolytic therapy in elderly versus younger patients with acute myocardial infarction. Electrocardiograms were recorded before, on completion of, and on day 1 and day 2 post-thrombolytic therapy (streptokinase or tissue thromboplastin activator) in 36 patients older than 65 years and 36 patients younger than 65 years. There was no significant different in the pre-thrombolytic ST-segment elevation per lead in both elderly and younger patients (3.7 +/- 0.7 versus 3.5 +/- 0.8 mm; P = NS). On completion of thrombolytic therapy, both groups demonstrated resolution of ST-segment elevation and, although the ST-segment elevation per lead was higher in elderly patients (3.0 +/- 0.9 versus 2.5 +/- 0.9 mm; P = 0.008), the percentage resolution per lead was not significantly different (19% versus 29%; P = NS). On day 1 post-thrombolytic therapy, there was further resolution of ST-segment elevation in both groups, but at this point, the percentage resolution per lead was significantly less in the elderly than in the younger patients (51% versus 66%; P = 0.03), and the ST-segment elevation per lead remained higher in elderly patients (1.8 +/- 1.0 versus 1.2 +/- 0.6 mm; P = 0.0009). On day 2 post-thrombolytic therapy, although there was further resolution of ST-segment elevation in both groups, the percentage resolution per lead remained significantly less (68% versus 80%; P = 0.05) and ST-segment elevation per lead remained significantly higher in elderly patients (1.2 +/- 0.7 versus 0.7 +/- 0.4 mm; P = 0.0002). Resolution of ST-segment elevation after thrombolytic therapy was less marked in elderly patients, indicating a reduced response to thrombolytic therapy in this patient population.

Early resolution of ST-segment elevation correlates with myocardial salvage assessed by Tc-99m sestamibi scintigraphy in patients with acute myocardial infarction after mechanical or thrombolytic reperfusion therapy

BACKGROUND

Early resolution of ST-segment elevation is an indicator of final infarct size and clinical outcomes. Whether this correlation is an expression of initial infarct characteristics or degree of myocardial salvage achieved with reperfusion therapy is unclear.

METHODS AND RESULTS

We prospectively included 243 patients with acute myocardial infarction (AMI) treated with either coronary stenting (122 patients) or thrombolysis (121 patients). Serial 12-lead electrocardiograms (ECG) were performed at baseline and 90 minutes after initiation of therapy. ST-segment resolution was defined as complete (> or =70%), partial (<70% to 30%), or no resolution (<30%). Paired technetium-99m sestamibi scintigraphic studies were performed to calculate the initial perfusion defect, final infarct size, and the proportion of initial defect salvaged with reperfusion (salvage index). ST-segment resolution correlated significantly with salvage index (P=0.008), final infarct size (P<0.001), and 6-month mortality (P=0.03). In the groups with complete, partial, and no resolution, salvage index was 0.54+/-0.32, 0.39+/-0.36, and 0.33+/-0.60; final infarct size was 12.5+/-12.0%, 20.0+/-13.9%, and 22.7+/-19.4% of the left ventricle; 6-month mortality was 2.4%, 6.2%, and 12.8%, respectively. After adjustment for baseline characteristics, ST-segment resolution was the second strongest predictor of salvage index (P=0.007) after the type of reperfusion, stenting, or thrombolysis (P=0.001); it was greater after stenting than after thrombolysis (P<0.001).

CONCLUSION

Early resolution of ST-segment elevation in surface ECG correlates with myocardial salvage as assessed by scintigraphy in patients with AMI after reperfusion therapy. These data provide an explanation for the favorable prognostic value of the ST-segment resolution and support the use of this parameter to compare the efficacy of different reperfusion strategies.