Research projects

You are here:

1. High molecular weight kininogen, a novel factor in the regulation of matrix proteinases

Project leader: Elena Kaschina
Coworkers: Dilyara Lauer, Manuela Sommerfeld, Svetlana Slavic, Ulrich Rudolf Kemnitz
Funding: Bayer Schering Pharma
External cooperations: Dr. Christa Thöne-Reineke, CCR Prof. Marjan Boerma, University of Arkansas, USA

Increased activity of matrix metalloproteinases (MMPs), leading to degradation of extracellular matrix components, is considered to play a crucial role in the pathogenesis of cardiovascular diseases such as heart failure and aneurysms. Thereby, a pivotal role has been attributed to MMPs belonging to the subgroup of gelatinases, including MMP-2 (gelatinase A) and MMP-9 (gelatinase B). We previously reported that kininogen-deficient rats are predisposed to develop abdominal aortic aneurysms. Thereby, aneurysm formation was associated with enhanced elastolysis and increased expression of MMPs, thus indicating a role for kininogens in the regulation of MMPs. We investigated whether cleaved high molecular weight kininogen (cleaved HK) affects the regulation of MMPs in primary vascular smooth muscle cells (VSMCs), cultured from the rat aorta. We found that cleaved HK reduced in a concentration dependent manner cytokine-induced release of both MMP-9 and MMP-2 by VSMCs. Furthermore, cytokine-induced MMP-9 mRNA expression was negatively regulated by cleaved HK to almost the same extent. Determination of expression levels of the endogenous inhibitors of MMPs, the TIMPs, revealed that TIMP-1 mRNA expression, already increased as a result of cytokine-stimulation, was further enhanced by cleaved HK. Altogether, these findings indicate that the balance between MMPs and TIMPs was shifted towards less net MMP activity by cleaved HK. Our current investigations are focused on the antioproteolytic effect of kininogen and its domains in primary cardiomyocytes. We found that cleaved HK prevented cytokine-induced release of MMP-9 and reduced gelatinase/collagenase activity of cardiomyocytes. In summary, high molecular weight kininogen is a potential drug target for diseases with excessive extracellular matrix turnover. Further research will be focused on therapeutic effects of kininogen in the models of heart failure and aneurysm formation. (published in Biochemical Pharmacology, 2010)

2. Regulation of cardiac and vascular functions by selective cannabinoid 1 receptor blocker rimonabant

Project leader: Elena Kaschina
Coworkers: Svetlana Slavic, Manuela Sommerfeld, Ulrich Rudolf Kemnitz Funding: Sanofi-Aventis GmbH Deutschland
External cooperations: Prof. Ulrich Kintscher, CCR PD Dr. med. Johannes Baulmann, University of Lübeck Yulia Sharkovska, medical student, AG Prof. Hocher, CCR

The biological effects of endocannabinoids such as anandamide, are mediated by specific G protein-coupled cannabinoid (CB) receptors. The CB1 receptor is present in heart and vascular tissues, fat tissue and liver. CB1 receptor blockade by a selective antagonist rimonabant is known to be beneficial by obesity and metabolic syndrome in humans. Our study aimed to investigate whether cannabinoid-1 receptor blockade may result in heart protection by metabolic syndrome and whether this protection is primary and not dependent from metabolic corrections. We could show that rimonabant improves heart function in Obese Spontaneously Hypertensive Koletsky Rats. In non-obese rats, the effects of CB1-blockade were studied in the model of myocardial infarction (MI), which was induced by permanent ligation of the left coronary artery. Treatment with rimonabant was started one week before MI and continued for 7 days or 6 weeks. Hemodynamic parameters were measured via transthoracic Doppler echocardiography and intracardiac Samba catheter. Arterial function was studied using pulse wave analysis. Cytokines, apoptotic and fibrotic markers were determined in heart tissue. Rimonabant improved systolic left ventricular function, lowered left ventricular end-diastolic pressure and increased heart contractility in the early and late phase after myocardial infarction. Arterial function parameters, such as pulse pressure, augmentation pressure- and index, were decreased in the rimonabant group mostly 6 weeks after MI compared to vehicle. Analysis of locomotor behaviour demonstrated continuously increasing activity of treated rats. Up-regulated IL-1beta-expression and TGF-beta expression in postinfarcted myocardium was ameliorated by rimonabant treatment at both time points, whereas caspase 3 was down-regulated only 7 days after MI. Thus, the cannabinoid-1 receptor antagonist rimonabant continually improves heart function in rats after myocardial infarction. Reduced inflammation in the heart and reduced pulse wave reflection may contribute to cardiac protection by rimonabant. Since rimonabant improved vascular function by decreasing arterial stiffness as well as by diminishing concentration of hydroxyprolin in aorta, our research will be further focused on the role of CB1 receptor in vascular diseases.

3. Aneurysm formation in mild uremia

Project leader: Elena Kaschina
Coworkers: Aleksej Akohov, Manuela Sommerfeld, Ulrich Rudolf Kemnitz Funding: internal
External cooperations: Prof. Harm Peters, CCR, Department of Nephrology Dr. Stephanie Kraemer, Deutsche Institut für Ernährungsforschung

Mild renal failure is known to be an independent risk factor for cardiovascular disease. Mild uremia is followed by fluid overload, inflammation and production of uremic toxins. All these factors may contribute to vascular remodelling. The aim of this study was to investigate the effects of mild uremia on aneurysm size, as well as on matrix remodelling, apoptosis, proteolysis and inflammation and their related gene- and protein expression patterns in the rat. Investigation was performed in a combined model of experimental uremia followed by elastase-induced aneurysm formation. Mild uremia was induced in rats by right uni-nephrectomy and removing 2/3 of the left kidney surgically (5/6 nephrectomy)(NE). 4 weeks later aneurysm (AAA) was induced via continuous infusion of an isolated aortic segment with elastase. One group of NE animals was additionally treated with hydralazine. Aortic diameter and heart function were measured by ultrasound. Aortic tissues, renal functional parameters and serum pro-inflammatory cytokines were investigated. Uremia induced aortic dilatation. Histological analysis revealed an outward aortic remodelling, increased elastin fragmentation, cystic medial degradation, calcification of tunica media and inflammatory infiltrates in the adventitia. After aneurysm induction, aortic diameter was further increased in the NE group as compared to AAA rats without NE. Hydralazine treatment significantly reduced blood pressure but did not influence aortic diameter. Protein expression of NF-kB was strongly (3-fold) up-regulated in aortic tissues from NE rats. MMP2, MMP9, cathepsin D and TGF-beta1 were significantly increased after AAA and further up-regulated in the NE/AAA group. Heart function was also negatively affected by uremia: Ejection fraction and fractional shortening were significantly decreased whereas left ventricular volume was increased in the systole and in the diastole. Alltogether, we could demonstrate that mild uremia induces aortic outward remodeling independently of blood pressure elevation. Activation of NFkB by uremic toxins may contribute to remodelling via inhibition of elastin- and collagen gene transcription.