Rüdiger C. Braun-Dullaeus

Ephrin-A1/EphA4-mediated adhesion of monocytes to endothelial cells

The Eph receptors represent the largest family of receptor tyrosine kinases. Both Eph receptors and their ephrin ligands are cell-surface proteins, and they typically mediate cell-to-cell communication by interacting at sites of intercellular contact. The major aim of the present study was to investigate the involvement of EphA4-ephrin-A1 interaction in monocyte adhesion to endothelial cells, as this process is a crucial step during the initiation and progression of the atherosclerotic plaque. Immunohistochemical analysis of human atherosclerotic plaques revealed expression of EphA4 receptor and ephrin-A1 ligand in major cell types within the plaque. Short-time stimulation of endothelial cells with the soluble ligand ephrin-A1 leads to a fourfold increase in adhesion of human monocytes to endothelial cells. In addition, ephrin-A1 further increases monocyte adhesion to already inflamed endothelial cells. EphrinA1 mediates its effect on monocyte adhesion via the activated receptor EphA4. This ephrinA1/EphA4 induced process involves the activation of the Rho signaling pathway and does not require active transcription. Rho activation downstream of EphA4 leads to increased polymerization of actin filaments in endothelial cells. This process was shown to be crucial for the proadhesive effect of ephrin-A1. The results of the present study show that ephrin-A1-induced EphA4 forward signaling promotes monocyte adhesion to endothelial cells via activation of RhoA and subsequent stress-fiber formation by a non-transcriptional mechanism.

Regulation of the HIF-system in human macrophages--differential regulation of HIF-α subunits under sustained hypoxia.

Macrophages are often associated to pathophysiological processes and were found at hypoxic areas. However, cell adaption greatly depends on hypoxia-inducible factors (HIF). Activation of these transcription factors is induced by heterodimerization of an α-(HIF-1α, -2α, -3α) and HIF-1β subunit. The main regulatory pathway is represented by α-subunit stability. Beside, little is known about the exact mechanisms of fine-tuning in Hif-regulation. The present study characterizes the hypoxia-induced regulation of HIF-1α and -2α in human macrophages. The hypoxic increase of both subunits is initially mediated by protein stabilization. Sustained hypoxia caused a distinct regulation of HIF-1α and -2α. The striking increase of HIF-2α protein expression was contrasted by a dramatic decrease of HIF-1α. The long-term downregulation of HIF-1α is due to downregulation of its mRNA. This decrease was accompanied by increased expression of ahif, a natural cis-antisense transcript of HIF-1α. The ahif-transcript was strongly inducible by hypoxia and rapidly degraded under reoxygenation. Using an adenoviral overexpression and siRNA silencing approach revealed that the targeted regulation of ahif is mediated by the HIF-system itself. Furthermore it could be shown that ahif indeed is able to modulate the hypoxic expression of HIF-1α and influences the expression of the HIF-target gene Enolase-2. Taken together, this study characterizes a new regulation process of the HIF-transcription factor-system in human macrophages under hypoxia. For the first time evidence is provided that ahif is regulated by the HIF-system and influences HIF-1α expression in primary human macrophages.

Reversible clopidogrel resistance due to right ventricular myocardial infarction: risk factor of recurrent stent thrombosis?

A 63-year-old male Patient was admitted to the intensive care unit due to acute inferior myocardial infarction with right ventricular dysfunction. He received a loading dose of clopidogrel (600xa0mg) and aspirin (500xa0mg) and was immediately revascularized by reopening of the proximal right coronary artery (RCA) and implantation of a bare metal stent. After primary successful intervention the patient suffered from thoracic pain on day 5 of admission. The ECG indicated reinfarction. The proximal RCA was again re-opended by PTCA alone. The following day the patient suffered again from thoracic pain with ST-elevation in the inferior leads, this time complicated by additional total AV-blockade. The angiography showed another time a thrombotic occlusion of the initially implanted stent. He received another intervention with implantation of additional two baremetal stents, an aortic counter-pulsation and a temporary two-chamber pace maker. Tirofiban was administered for 24xa0h and the IABP was withdrawn after 60xa0h. The patient was discharged on Aspirin 300xa0mg/d, Clopidogrel 150xa0mg/d and Enoxaparin 40xa0mg/d. Six weeks later the patient demonstrated an improved right ventricular function (TAPSE 18xa0mm), liver enzymes were normal, and inhibition of platelet aggregation by clopidogrel (150xa0mg/d) was sufficient. In conclusion this implies that the reversible “clopidogrel-resistance” might have been due to congestion and reduced metabolism due to right ventricular infarction.

Uncoupled eNOS annihilates neuregulin-1β-induced cardioprotection: a novel mechanism in pharmacological postconditioning in myocardial infarction.

Myocardial infarct size can be limited by pharmacological postconditioning (pPC) with cardioprotective agents. Cardioprotective effects of neuregulin-1β (NRG) via activation of protein kinase B (Akt) and downstream pathways like endothelial nitric oxide synthase (eNOS) have been postulated based on results from cell culture experiments. The purpose of this study was to investigate if eNOS may be involved in pPC with NRG. NRG application in an ex vivo mouse model (C57Bl6) of ischemia–reperfusion injury was analyzed. Unexpectedly, the infarct size increased when NRG was infused starting 5xa0min prior to reperfusion, even though protective Akt and GSK3β phosphorylation were enhanced. In eNOS deficient mice, however, NRG significantly reduced the infarct size. Co-infusion of NRG and l-arginine (Arg) lead to a reduction in infarct size in wild type animals. Electron paramagnetic resonance measurements revealed that NRG treatment prior to reperfusion leads to an enhanced release of reactive oxygen species compared to controls and this effect is blunted by co-infusion of Arg. This study documents the cardioprotective mechanisms of NRG signaling to be mediated by GSK3β inactivation. This is the first study to show that this protection fails in situations with dysfunctional eNOS. In eNOS deficient mice NRG exerts its protective effect via the GSK3β pathway, suggesting that the eNOS can limit cardioprotection. As dysfunctional eNOS has been described in cardiovascular risk factors like diabetes, hypertension, and hypercholesterolemia these findings can help to explain lack of postconditioning performance in models of cardiovascular co-morbidities.

In situ postconditioning with neuregulin-1β is mediated by a PI3K/Akt-dependent pathway.

BACKGROUNDnThe myocardial infarct size can be reduced by pharmacological postconditioning using cardioprotective agents. Neuregulin-1β is a potential candidate, but previous studies in an isolated heart model of ischemia and reperfusion displayed controversial results. An in situ model of ischemia/reperfusion was used to clarify whether the remote application of neuregulin-1β can reduce the reperfusion injury. A second aim was to evaluate, if the effects are specific for reperfused tissue or if this is a general antiapoptotic effect. In addition, the contributing molecular mechanisms were investigated.nnnMETHODSnIn an open chest model, mouse hearts were subjected to a regional ischemia (45-minute) using ligature of the left anterior descending artery. Neuregulin-1β (80 ng/kg) was given using an intraperitoneal bolus injection 5 minutes before reopening of the ligature followed by a 30-minute reperfusion.nnnRESULTSnRemote application of recombinant neuregulin-1β protected the heart from reperfusion injury without influencing hemodynamics. This beneficial effect specifically targets reperfusion injury. In contrast, nonreperfused needle trauma was not reduced by neuregulin-1β when applied remotely. Pharmacological blocking experiments and enzyme activation analysis using Western blot analysis revealed a crucial involvement of the antiapoptotic reperfusion injury salvage kinase cascade. In contrast, contribution of the survivor activating factor enhancement pathways to this early cardioprotection was not observed.nnnCONCLUSIONSnRemote application of neuregulin-1β protects hearts from early reperfusion injury by activation of the reperfusion injury salvage kinase pathway without relevant effects on intracardiac pressures in myocardial infarction. Besides its potential pharmacological application, neuregulin-1β might act as an endogenously produced mediator in remote postconditioning.

[19-year-old asthma patient with pronounced eosinophilia and acute coronary syndrome].

Diagnosis of Churg-Strauss syndrome should be considered in young asthmatics with fatigue and eosinophilia. On the base of the etiopathology of a 19-year old man, who was initially admitted because of dyspnoea, fever and acute chest pain, we show that eosinophilia gives an important hint for further diagnostic and is the key trend parameter. Histologically an eosinophilic myocarditis could be shown in the myocardial biopsy. High dose prednisolone induced a clear improvement in symptoms, with decrease of the inflammatory signs and the eosinophilia and a clear improvement of the left ventricular function.ZusammenfassungDas Churg-Strauss-Syndrom sollte bei einer unspezifischen Symptomatik junger Asthmatiker mit ausgeprägter Eosinophilie in Betracht gezogen werden. Anhand des Krankheitsverlaufs eines 19-jährigen Patienten, welcher sich mit zunehmender Dyspnoe, Fieber und akuten linksthorakalen Schmerzen vorstellte, wird aufgezeigt, dass die Eosinophilie den entscheidenden Hinweis für die weiterführende Diagnostik gibt und den entscheidenden Verlaufsparameter darstellt. Histologisch konnte in der Myokardbiopsie eine eosinophile Myokarditis nachgewiesen werden. Unter einer hoch dosierten Prednisolontherapie zeigten sich eine deutliche Beschwerdebesserung mit Regredienz der Entzündungszeichen und der Eosinophilie sowie eine signifikante Besserung der linksventrikulären Funktion.AbstractDiagnosis of Churg-Strauss syndrome should be considered in young asthmatics with fatigue and eosinophilia. On the base of the etiopathology of a 19-year old man, who was initially admitted because of dyspnoea, fever and acute chest pain, we show that eosinophilia gives an important hint for further diagnostic and is the key trend parameter. Histologically an eosinophilic myocarditis could be shown in the myocardial biopsy. High dose prednisolone induced a clear improvement in symptoms, with decrease of the inflammatory signs and the eosinophilia and a clear improvement of the left ventricular function.

19-jähriger Asthmatiker mit ausgeprägter Eosinophilie und akutem Koronarsyndrom

Diagnosis of Churg-Strauss syndrome should be considered in young asthmatics with fatigue and eosinophilia. On the base of the etiopathology of a 19-year old man, who was initially admitted because of dyspnoea, fever and acute chest pain, we show that eosinophilia gives an important hint for further diagnostic and is the key trend parameter. Histologically an eosinophilic myocarditis could be shown in the myocardial biopsy. High dose prednisolone induced a clear improvement in symptoms, with decrease of the inflammatory signs and the eosinophilia and a clear improvement of the left ventricular function.ZusammenfassungDas Churg-Strauss-Syndrom sollte bei einer unspezifischen Symptomatik junger Asthmatiker mit ausgeprägter Eosinophilie in Betracht gezogen werden. Anhand des Krankheitsverlaufs eines 19-jährigen Patienten, welcher sich mit zunehmender Dyspnoe, Fieber und akuten linksthorakalen Schmerzen vorstellte, wird aufgezeigt, dass die Eosinophilie den entscheidenden Hinweis für die weiterführende Diagnostik gibt und den entscheidenden Verlaufsparameter darstellt. Histologisch konnte in der Myokardbiopsie eine eosinophile Myokarditis nachgewiesen werden. Unter einer hoch dosierten Prednisolontherapie zeigten sich eine deutliche Beschwerdebesserung mit Regredienz der Entzündungszeichen und der Eosinophilie sowie eine signifikante Besserung der linksventrikulären Funktion.AbstractDiagnosis of Churg-Strauss syndrome should be considered in young asthmatics with fatigue and eosinophilia. On the base of the etiopathology of a 19-year old man, who was initially admitted because of dyspnoea, fever and acute chest pain, we show that eosinophilia gives an important hint for further diagnostic and is the key trend parameter. Histologically an eosinophilic myocarditis could be shown in the myocardial biopsy. High dose prednisolone induced a clear improvement in symptoms, with decrease of the inflammatory signs and the eosinophilia and a clear improvement of the left ventricular function.

19-jähriger Asthmatiker mit ausgeprägter Eosinophilie und akutem Koronarsyndrom@@@19-year-old asthma patient with pronounced eosinophilia and acute coronary syndrome

Diagnosis of Churg-Strauss syndrome should be considered in young asthmatics with fatigue and eosinophilia. On the base of the etiopathology of a 19-year old man, who was initially admitted because of dyspnoea, fever and acute chest pain, we show that eosinophilia gives an important hint for further diagnostic and is the key trend parameter. Histologically an eosinophilic myocarditis could be shown in the myocardial biopsy. High dose prednisolone induced a clear improvement in symptoms, with decrease of the inflammatory signs and the eosinophilia and a clear improvement of the left ventricular function.ZusammenfassungDas Churg-Strauss-Syndrom sollte bei einer unspezifischen Symptomatik junger Asthmatiker mit ausgeprägter Eosinophilie in Betracht gezogen werden. Anhand des Krankheitsverlaufs eines 19-jährigen Patienten, welcher sich mit zunehmender Dyspnoe, Fieber und akuten linksthorakalen Schmerzen vorstellte, wird aufgezeigt, dass die Eosinophilie den entscheidenden Hinweis für die weiterführende Diagnostik gibt und den entscheidenden Verlaufsparameter darstellt. Histologisch konnte in der Myokardbiopsie eine eosinophile Myokarditis nachgewiesen werden. Unter einer hoch dosierten Prednisolontherapie zeigten sich eine deutliche Beschwerdebesserung mit Regredienz der Entzündungszeichen und der Eosinophilie sowie eine signifikante Besserung der linksventrikulären Funktion.AbstractDiagnosis of Churg-Strauss syndrome should be considered in young asthmatics with fatigue and eosinophilia. On the base of the etiopathology of a 19-year old man, who was initially admitted because of dyspnoea, fever and acute chest pain, we show that eosinophilia gives an important hint for further diagnostic and is the key trend parameter. Histologically an eosinophilic myocarditis could be shown in the myocardial biopsy. High dose prednisolone induced a clear improvement in symptoms, with decrease of the inflammatory signs and the eosinophilia and a clear improvement of the left ventricular function.