Lothar Jahn

Endothelin-1 and Smooth Muscle Cells Induction of Jun Amino-Terminal Kinase Through an Oxygen Radical–Sensitive Mechanism

Endothelin-1 (ET-1) has been proposed to contribute to atherogenesis and plaque rupture in coronary heart disease through activation of mitogen-activated protein kinases (MAPKs) in smooth muscle cells (SMCs). Reactive oxygen species (ROS) have been shown to be important signal transduction molecules in SMCs. Thus, the present study aimed to assess the role of ROS in ET-1-mediated activation of c-Jun amino-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) 1/2. Rat SMCs were exposed to ET-1 over time at concentrations from 10(-6) to 10(-10) mol/L, and MAPK activity was quantified. Activation of JNK and ERK was observed with a maximum stimulation at 10(-7) mol/L ET-1. JNK and ERK were activated by ET-1 binding to a single receptor (ET-1A) but differed in their downstream mechanisms: only JNK activation was sensitive to the radical scavenger N-acetylcysteine and diphenylene iodonium, an inhibitor of NADPH oxidase, indicating a role for ROS. The downstream MAPK effector and proinflammatory transcription factor, the activator protein-1 complex, was maximally activated 2 hours after the addition of ET-1. It was mainly composed of the JNK substrate c-Jun, and activation was also dependent on ROS formation. We suggest that plaque activation by ET-1 can be mediated through ROS. It can be hypothesized that the clinical benefit of antioxidants in the treatment of atherogenesis may partially depend on neutralization of ET-1-mediated ROS production.

Expression of nitric oxide related enzymes in coronary heart disease

Enzymes involved in the metabolism nitric oxide (NO) and reactive oxygen species (ROS) may play a role for the decreased availability of NO in atherosclerosis. We, therefore, hypothesized that the pattern of gene expression of these enzymes is altered in atherosclerosis. Myocardial tissue from patients with coronary heart disease (CHD) or without CHD (control group) was investigated. The level of enzymes related to NO/ROS metabolism was determined both at mRNA level and protein level by rt-PCR, real-time PCR, and western blot. The expression of NOS1–3 (synthesis of NO), arginase1 (reduction of l-arginine), p22phox (active subunit of NADPH oxidase), GTPCH (rate limiting enzyme for tetrahydrobiopterin), SOD1–3 (scavengers of superoxide anions), PRTMT1–3, and DDAH2 (involved in the metabolism of ADMA) was determined. All enzymes were found to be expressed in human myocardium. NOS isoforms were decreased in CHD in protein level, but only the downregulation of NOS3 expression reached statistical significance. The expression of PRMT1 and PRMT3 was increased. In addition, the expression of DDAH2 was reduced, both theoretically leading to an increase of ADMA concentration. SOD3 was downregulated in tissue from patients with CHD. Taken together, in myocardial tissue from patients with atherosclerosis, the expression of genes increasing ADMA levels is enhanced in contrast to a reduced expression of genes promoting NO synthesis. These results may contribute to the explanation of increased oxidative stress in atherosclerosis on the level of gene expression.

Chemotaxis of the monocyte cell line U937: dependence on cholesterol and early mevalonate pathway products

In the present study we investigated the influence of cholesterol depletion and hydroxymethylglutaryl-coenzyme A reductase (HMG-CoA reductase) inhibition on chemotaxis of the human monocytic cell line U937. Chemotaxis was nearly completely depressed after incubation for 24 h in the absence of lipoproteins. This was accompanied by a significant decrease in cellular cholesterol. Addition of 10 micrograms/ml low density lipoprotein (LDL) for 2 h to the cholesterol-depleted cells restored chemotaxis. Free cholesterol had no effect under these conditions. Inhibition of HMG-CoA reductase by pravastatin (0.01-1.0 mM) for 20 or 72 h also reduced chemotaxis. However, this effect was not accompanied by a decrease in cellular cholesterol when cells were grown in the presence of lipoproteins. The effect of pravastatin could be reversed by the addition of mevalonate. Addition of LDL did not change the response to pravastatin. We propose that the availability of cholesterol plays an important role in cellular chemotaxis. Furthermore, it can be suggested that other products of the mevalonate pathway apart from cholesterol may contribute to the regulation of chemotaxis.

Upregulation of embryonic transcription factors in right ventricular hypertrophy

Abstract.Increased ventricular expression of genes encoding for various structural and contractile proteins has been reported in cardiac hypertrophy. Mechanisms leading to this altered gene expression are only partly understood. Recently, various transcription factors (TF), among them GATA-4, Nkx-2.5/Csx, MEF-2 and the HAND family (eHAND and dHAND), and their role in embryonic cardiac development have been described. These transcription factors are known to have binding sites to promotor regions of many genes known to be regulated in hypertrophy of adult ventricular myocardium.We investigated the temporal and spatial expression pattern of these transcription factors in a rat model of acute pressure-overload of the right ventricle, induced by banding (coarctation) of the pulmonary artery. Expression of GATA-4, Nkx-2.5/Csx, MEF-2 and dHAND protein was found to increase in the right ventricle after the banding procedure as determined by immunohistochemistry and western blotting. A marker of the onset of cardiac hypertrophy was expression of ANP protein. We conclude that TF known to regulate embryonic heart development are involved in the adaptational response of adult ventricular myocardium to pressure overload.

Smoothelin is an indicator of reversible phenotype modulation of smooth muscle cells in balloon-injured rat carotid arteries

Abstract Restenosis is the major obstacle interfering with a successful long-term outcome of balloon angioplasty. Neointima formation following endothelial injury is the result of phenotype modulation and proliferation of smooth muscle cells (SMC). To characterize these time-dependent changes, a rat balloon injury model of carotid artery restenosis was assessed. We applied monoclonal antibodies recognizing desmin, sm-α-actin and smoothelin, a novel marker specific for the differentiated phenotype of SMC.Neointima formation could be seen from day 7 after injury onwards. During early phases, the number of smoothelin-positive cells in the media was decreased compared with uninjured controls. Smoothelin staining was absent in the neointima during formation. Increased levels of smoothelin in both media and neointima were observed at days 28 and 56, correlating with a decrease in proliferation as assessed by Ki-67 antigen staining. No such changes were observed for desmin and sm-α-actin.Following balloon injury, SMC in both the media and the neointima underwent an early, reversible dedifferentiation, followed by proliferation. The novel SMC-specific marker protein smoothelin can be used to monitor this SMC (de)differentiation in neointima and media. These findings support the pivotal role of SMC phenotype modulation in neointima formation and restenosis.

LDL Stimulates Chemotaxis of Human Monocytes Through a Cyclooxygenase-Dependent Pathway

Monocyte migration into the vessel wall is an early step in atherogenesis. Even though a number of chemotactic factors have been identified, the regulation of the chemotactic response is not clearly understood. As the release of arachidonic acid has been implicated in monocyte chemotaxis, we studied the influence of LDL, which can supply this fatty acid to cells, on the chemotactic mobility of monocytes. Migration of human monocytic U937 cells was abolished by a 30-hour incubation in medium containing lipoprotein-depleted 10% fetal calf serum. Thereafter, human VLDL, LDL, acetyl LDL, methyl LDL, HDL, free cholesterol, linoleic acid, oleic acid, or arachidonic acid was added. At the end of varying incubation periods (0.5 to 8 hours), chemotaxis, viability, and cellular cholesterol content were measured. In the same experimental setting we also studied the effects of the pharmacological agents chloroquine, indomethacin, and acetylsalicylic acid on LDL-mediated chemotaxis. Chemotaxis was restored by LDL in a dose- and time-dependent manner starting at concentrations as low as 5 micrograms/mL and at incubations as brief as 30 minutes. The other lipoproteins tested (VLDL, HDL, acetyl LDL, and methyl LDL) as well as free cholesterol had no comparable effect on chemotaxis. Viability and total cholesterol content did not differ among the groups. Simultaneous incubation of cells with chloroquine, indomethacin, and acetylsalicylic acid reduced restitution of chemotaxis by LDL by 71%, 82%, and 68%, respectively. In contrast, the agents had only slight inhibitory effects on the chemotactic mobility of serum-fed control cells. Incubation with linoleic acid showed a 60% restoration of chemotaxis, whereas arachidonic acid stimulated chemotaxis by 140% compared with the positive control. Preincubation of LDL with the monoclonal antibody MB47 directed against LDL resulted in a significantly reduced migratory response. The data suggest a novel cyclooxygenase-dependent regulatory mechanism of chemotaxis by LDL.

Fibrinogen promotes monocyte adhesion via a protein kinase C dependent mechanism

The accumulation of blood monocytes at sites of predilection of the vessel wall is an early cellular event of atherogenesis. Proteins of the vessel wall may facilitate monocyte adhesion and thus promote their recruitment. It has been shown that the relative content of extracellular fibrinogen increases during lesion development, and this study investigated the contribution of immobilized fibrinogen to monocyte adhesion and the underlying mechanism. Freshly isolated human blood monocytes were cultivated in serum-free RPMI 1640 in tissue culture wells precoated with albumin, fibrinogen, or fibrin. After 16 h the plates were washed and adherent cells enumcrated. Immobilized fibrinogen enhanced monocyte adhesion more than 1.9-fold compared to immobilized albumin or fibrin (P<0.05). Concomitant addition of the protein kinase C (PKC) inhibitors staurosporine or H7 suppressed monocyte adherence to immobilized fibrinogen but exerted no significant effect upon adhesion to any other surface tested. Stimulation of monocytes using phorbol myristate acetate resulted in increased binding of monocytes on fibrinogen but not on bovine serum albumin. When PKC activity was reduced through prolonged incubation with PMA for 16h, a significant reduction of monocyte adhesion on fibrinogen was observed. Peptides containing RGD sequences, which have been demonstrated to be ligands for certain integrins, did not inhibit monocyte adhesion. The data suggest that fibrinogen promotes monocyte adhesion in vitro by a PKC-dependent mechanism. PKC appears to be important not only for the initial cell adhesion but also for sustained binding of monocytes to fibrinogen.

Phosphorylation of cytokeratin 8 and 18 in human vascular smooth muscle cells of atherosclerotic lesions and umbilical cord vessels.

Abstract Expression of cytokeratins (CK) is considered a hallmark of the state of epithelial differentiation. CK also occur in certain vascular smooth muscle cells (VSMC), inferring an association with a less differentiated phenotype. Recently, CK posttranslational modification was shown to occur in epithelial cells in stress, mitosis or apoptosis.The aim of this study was to determine potential CK phosphorylation patterns in human VSMC. Tissue samples of normal peripheral and coronary arteries, atherosclerotic lesions and umbilical cord vessels were evaluated by immunofluorescence microscopy applying antibodies specific for cytokeratins 8 and 18, specific cytokeratin phosphorylation sites, Ki-67-antigen as a proliferation marker and nick end labeling (TUNEL) to detect apoptosis.All samples contained cytokeratin-positive VSMC but diverse phosphorylation patterns. The C-terminal serine 431 of cytokeratin 8 (CK8Ser-431) was phosphorylated in the vast majority of CK-expressing VSMC of coronary artery lesions. Only a subset of these cells demonstrated phosphorylation of CK18Ser-33 or, to an even lesser extent, CK8Ser-73. DNA fragmentation occurred predominantly in samples containing cells with phosphorylated CK8Ser-431 domains. In contrast, occluded peripheral lesions exhibited little or no phosphorylation. Neonatal VSMC in umbilical cord vessels contain abundant phosphorylated CK domains, again predominantly CK8Ser-431, but also CK18Ser-33. Again, only single cells were found to be proliferating or to contain DNA fragmentation.Thus, abundant CK phosphorylation in VSMC of atherosclerotic lesions suggests a specific functional response to cell stress and a possible relation to apoptosis.

Cardiac α-actin in smooth muscle cells: detection in umbilical cord vessels and in atherosclerotic lesions

Abstract Phenotypic modulation of smooth muscle cells (SMC) is a key event during the development of atherosclerotic and restenotic lesions. During this process, the composition of the cytoskeleton is substantially altered, with changes predominantly in actin expression reflecting a shift from smooth muscle α-actin to the non-muscle β-isoform. We now demonstrate that yet another actin isoform, cardiac α-actin, is synthesized, de novo, in SMC of various atherosclerotic lesions. Using a highly specific monoclonal antibody against cardiac α-actin, we analyzed and compared the accumulation of this actin isoform in diverse SMC by immunofluorescence microscopy and immunoblotting. As expect, cardiac α-actin was present in human myocardium but not in healthy SMC of adult aorta, coronary arteries, trabeculae of the spleen, colon, stomach or skeletal muscle. Interestingly, the presence of cardiac α-actin was detected in umbilical cord vessels, human myometrium, in atherosclerotic coronary lesions and atherosclerotic lesions from peripheral vascular disease. The distribution of cardiac α-actin often paralleled that of cytokeratins 8 and 18, intermediate filament proteins typically found in dedifferentiated SMC. Taken together, the data presented here illustrate the expression of cardiac α-actin to be limited to either fetal vessels or those vessels or tissue having suffered damage or atrophy, outside its ‘native’ environment in the heart. The demonstration of cardiac α-actin in SMC of umbilical cord vessels and in atherosclerotic lesions but not in apparently healthy vessels supports the notion that SMC in atherosclerotic lesions exhibit a dedifferentiated phenotype.

Kardiomyopathie assoziiert mit unkontrollierter Selbstmedikation anaboler Steroide

Though doping has become increasingly ostracized in the context of professional sports, an enormous number of unrecorded cases must be assumed in semi-professional competitive sports as well as in popular sports. This holds especially true for those forms of sports which are done in order to obtain a well-proportioned, athletic, healthy looking body.    This case report describes a formerly healthy young man who had to be urgently admitted to an intensive care unit due to severe myocardial pump failure. As anamnestic information was insufficient and inadequate, the taking of anabolic steroids in high doses was proven, as their metabolites could be detected by urine analysis. Until now, myocardial contractile dysfunction has persisted for more than twelve months after the initial admission. Though other diagnoses which might have led to this impaired myocardial contractile performance have been excluded, cardiomyopathy associated with the taking of anabolic steroids must be assumed.    Even in non-professional and public sports, a widespread abuse of doping substances exists. Hence, cardiomyopathy associated with the misuse of anabolic steroids has to be considered especially in young, formerly healthy patients. Trotz der zunehmenden Ächtung des Dopings im Spitzensport ist im Breitensport eine hohe Dunkelziffer der Einnahme leistungssteigernder Präparate zu befürchten. Dies trifft vor allem auf solche „Sportarten” zu, die vorrangig dem Ziel dienen, einen wohlproportionierten, athletischen, gesund aussehenden Körper zu erzielen bzw. zu erhalten.    Im vorliegenden Beitrag wird über einen jungen Patienten mit akuter kardialer Dekompensation infolge schwerwiegenden myokardialen Pumpversagens berichtet. Bei unzureichenden anamnestischen Angaben konnte mittels Urinanalyse die hochdosierte Einnahme anaboler Steroide nachgewiesen werden. Die kontraktile Funktionseinschränkung persistiert bislang über einen Nachbeobachtungszeitraum von einem Jahr. Nach Ausschluss anderer, zu myokardialer Dysfunktion führender Pathomechanismen ist eine Anabolika-assoziierte Myokardschädigung anzunehmen.    Auch im nicht-professionellen sportlichen Bereich muss von einem weit verbreiteten Abusus leistungssteigernder Präparate wie anaboler Steroide ausgegangen werden. An die Möglichkeit einer Anabolika-assoziierten Kardiomyopathie sollte deshalb vor allem bei jungen, zuvor leistungsfähigen Patienten gedacht werden.