Search

G. Taimor, K.-D. Schlüter, K. Frischkopf, M. Flesch, S. Rosenkranz and H. M. Piper. Autocrine Regulation of TGF βExpression in Adult Cardiomyocytes. Journal of Molecular and Cellular Cardiology(1999)31, 2127–2136. As shown before, TGF βacts in an autocrine manner on the induction of hypertrophic responsiveness to β-adrenoceptor stimulation in cultured ventricular cardiomyocytes of adult rat. We now investigated how TGF βexpression and activation is regulated in these cultures and how β-adrenoceptor stimulation influences TGF β-mRNA expression. It was found that freshly isolated cardiomyocytes secrete latent TGF βin the culture medium. Supplementation of the cultures with 20% FCS resulted in activation of the secreted TGFβto 4.1±0.2 ng/ml active TGF βafter 6 days. Presence of the protease inhibitor aprotinin (50μg/ml) reduced TGF βactivity by 44±5% (n=5, P<0.05). In cultures supplemented with 5% FCS, TGF βwas not activated. Active TGF βdownregulated its mRNA-expression: after 6 days TGF β1-mRNA was reduced to 55.1±11.0%, TGFβ2-mRNA to 30.1±16.5%, and TGF β3-mRNA to 0.3±0.4% in 20% FCS-cultures as compared to their expression in freshly isolated cells (n=4, P<0.05). TGFβ-mRNA expression did not change in cultures without active TGF β. Isoprenaline (1 μm) increased TGF β1-mRNA only in cultures which had been pre-exposed to active TGF β. This effect was also seen when hearts from normal mice were compared with hearts from transgenic mice overexpressing TGFβ1: only in hearts from transgenic animals perfusion with isoprenaline increased TGFβ1-mRNA. In conclusion, isolated cardiomyocytes release latent TGF β, which is activated by external proteases. Active TGF βdownregulates its own mRNA expression. Preexposure to TGF βis necessary for a β-adrenoceptor-mediated increase in TGF β1-mRNA in cardiomyocytes.

Objective To determine if end-stage dilated cardiomyopathy (DCM) is associated with the presence of Lyme disease causing spirochete Borrelia burgdorferi in the myocardium, we used nested polymerase chain reaction to detect B burgdorferi DNA in myocardial samples from explanted hearts of patients with end-stage DCM. Patients originated from endemic areas for Lyme disease (Bavaria, Lower Saxony, Germany). Methods and Results This was a retrospective study. Polymerase chain reaction was used to detect the specific B burgdorferi recombinant outer surface protein A (OspA) gene in myocardial tissue from 68 patients with end-stage DCM who had undergone heart transplantation. The clinical history of Lyme disease, the presence of Borrelia burgdorferi OspA, and antibodies against OspA in myocardial tissue and serum were investigated. B burgdorferi DNA was not detected in any of the 68 human hearts. Immunoglobulin G antibodies against specific B burgdorferi antigens were observed in 3 (12.5%) of 24 patients. In contrast, 4 hearts from rats experimentally infected with B burgdorferi were all positive for OspA DNA as measured by polymerase chain reaction. Conclusion Our data show that cardiac myocytes of hearts obtained from subjects with end-stage DCM did not contain B burgdorferi DNA as investigated by polymerase chain reaction. However, B burgdorferi shows a high affinity for myocardial tissue as shown by the animal studies, indicating that myocardial infections are nevertheless possible. (Am Heart J 1999;138:269-72.)

We studied the feasibility of T cell depletion of bone marrow for transplantation in preventing acute graftversus-host disease GVHD in patients having a high risk of acute GVHD.

Thirty-two patients with acute leukemia, chronic granulocytic leukemia, or multiple myeloma received a T lymphocyte-depleted HLA-identical marrow. After being treated with pan-T monoclonal antibodies (MoAbs) and one round of baby rabbit complement, the mean percentage of T cell depletion was 94% +/- 4%. The number of residual viable T cell infused to the patient was 0.99 +/- 0.65 X 10(6) per kg body weight. The patients were conditioned with fractionated total body irradiation (TBI) (12 Gy) preceding high doses of cyclophosphamide (120 mg/kg). Methotrexate was used as an additional immunosuppressant in the first ten patients. For the following 22 patients no posttransplant immunoprophylaxis was administered. Eight patients died within three months due to complications related to transplantation. Engraftment was achieved in all evaluable patients, and no patient has a late graft failure. The proof of total chimerism was established in 24 patients. Twenty-four of 27 evaluable patients (88%) did not have an acute graft- v-host disease (GVHD) greater than grade 0 to 1. Two patients had a grade 2 (skin only), and one patient had a grade 4 acute GVHD (the latter had only 80% of T cell depletion). A medullary relapse occurred in 11 patients (nine of them had previously been defined as “high risk leukemia”). Our data suggest that it may not be necessary to deplete nearly all T cells to prevent acute GVHD in recipients of HLA-identical marrow.

Abnormalities in intracellular Ca2+ handling play a crucial role in the pathogenesis of heart failure. The reduced capacity of failing human myocardium to restore low resting Ca2+ levels during diastole has been explained by the impairment of Ca2+ uptake into the sarcoplasmic reticulum (SR) via the SR Ca2+ATPase. It is unclear whether Ca2+ATPase function, protein levels, and mRNA steady-state levels correspond to one other, and whether the cause of heart failure, namely idiopathic dilated or ischemic cardiomyopathy, produces different changes. The present study examined SR Ca2+ATPase activity and both mRNA and protein levels of SR Ca2+ATPase, phospholamban, and Gia2 in left ventricular myocardium from eight nonfailing hearts, from eight hearts of patients with idiopathic dilated cardiomyopathy (DCM), and from six hearts from patients with ischemic cardiomyopathy (ICM). Compared to nonfailing myocardium, the activity of the SR Ca2+ATPase was significantly reduced in failing myocardium from patients with DCM (36%, P<0.01) and from patients with ICM (37%, P<0.001). Significantly lower levels of SR Ca2+ATPase mRNA levels (55% and -56%, P<0.001 for DCM and ICM, respectively) and phospholamban mRNA (45%, P<0.001 for DCM; 31%, P<0.05 for ICM) were observed in failing than in nonfailing myocardium. In contrast, no significant changes were observed at the level of proteins. Gia2 mRNA and protein levels were both significantly increased in failing mycocardium. There were no differences between idiopathic dilated and ischemic cardiomyopathy concerning the examined parameter. It is concluded that reduced SR Ca2+ATPase activity contributes to an altered intracellular Ca2+ handling by the SR in both dilated and ischemic cardiomyopathic hearts. However, changes in SR Ca2+ATPase and phospholamban steady-state protein levels do not contribute to these alterations. The dissociation between protein and mRNA levels provides evidence for a posttranscriptional or posttranslational regulation of these proteins. The observed alterations are not dependent on the underlying cause of end-stage heart failure.

Human myocardial angiotensin II receptors and the angiotensin AT"1 and AT"2 receptor subtypes were characterised using the partial angiotensin II receptor agonist [^1^2^5I][Sar^1,IIe^8]angiotensin II and the selective antagonists losartan (2-n-butyl-4-chloro-5-hydroxymethyl-1-[2'((1H-tetrazol-5-yl)biphenyl-4-yI)-methyl]imidazole) and PD 123177 (1-[(4-amino-3-methylphenyl)methyl]-5-(diphenyl-acetyl)-4,5,6,7-tetrahydro-1H-imidazol[4,5-c]pyridine-6-car@?ylic acid). The density of angiotensin II receptors was higher in atrial than in ventricular myocardium. Angiotensin AT"2 receptors were predominant in atria and ventricles (80-85% of total angiotensin II receptors). Only in isolated, electrically driven atrial trabeculae but not in ventricular preparations, angiotensin II did produce a concentration-dependent positive inotropic effect, which was antagonized exclusively by the angiotensin AT"1 receptor antagonist losartan and which amounted to about 20% of the positive inotropic effect of mihinone and isoprenaline. The application of the angiotensin-converting enzyme inhibitors captopril, enalaprilat and ramiprilat had no inotropic effect in either tissue. It is concluded that angiotensin AT"1 receptors exclusively mediate direct positive inotropic effects in atrial myocardium. Since angiotensin-converting enzyme inhibitors do not produce any inotropic effect, tonic regulation of basal force of contraction by angiotensin II does not occur.