© 2000 by European Society of Cardiology
Copyright © 2000, European Society of Cardiology
Expression of secreted frizzled related proteins 3 and 4 in human ventricular myocardium correlates with apoptosis related gene expression
aMolecular Biology Group, Medical Faculty of Martin-Luther-University Halle-Wittenberg, Magdeburger Strasse 18, 06097 Halle/Saale, Germany
bInstitute of Pathophysiology, Medical Faculty of Martin-Luther-University, Halle-Wittenberg, Germany
cClinic for Cardiac and Thoracic Surgery, Medical Faculty of Martin-Luther-University, Halle-Wittenberg, Germany
* Corresponding author. Tel.: +49-345-557-1460; fax: +49-345-557-4421 heike.schumann{at}medizin.uni-halle.de
Objective: Overload-induced heart failure is associated with myocyte apoptosis induced by unknown mechanisms. Wnt genes encode secreted signaling molecules that bind to frizzled receptors and stabilize cytosolic β-catenin which is translocated into the nucleus, acts as transcriptional activator and imparts an apoptosis resistant phenotype. This signaling pathway is antagonized by secreted frizzled related proteins (sFRPs) which modulate apoptosis susceptibility in cell culture models. On the basis of these considerations, the present investigation compares myocardial mRNA expression of sFRPs and the level of soluble β-catenin in tissue samples from nonfailing and failing hearts. Methods: Nonischemic transmural samples from human failing left ventricles and from nonfailing donor ventricles were used in the present study. The mRNA concentration of the Wnt-antagonists sFRP 1–4 were determined by quantitative reverse transcription polymerase chain reaction (RT-PCR). The myocardial localization of sFRP 3 and 4 expression was investigated using in situ RT-PCR. The pool of soluble β-catenin was quantified by Western blot analysis of protein extracts. Results: The mRNA levels of proapoptotic sFRPs 3 and 4 but not of sFRP 1 and 2 were elevated in failing ventricles compared to donor hearts. There was no significant difference between patients suffering from a dilated cardiomyopathy or a coronary heart disease. sFRPs 3 and 4 were expressed in cardiomyocytes and their expression correlated with the mRNA expression of the proapoptotic Fas/Fas-antagonist ratio, but inversely with the mRNA levels of the antiapoptotic bcl-xL. The size of the pool of 0.1% Triton soluble β-catenin tended to decrease in myocardial samples with high sFRP 3 and 4 expression levels. Conclusions: The results support the hypothesis that in failing human myocardium the Wnt/β-catenin pathway is attenuated by enhanced expression of two endogenous Wnt-antagonists. This might contribute to an apoptosis susceptible phenotype of overloaded human myocardium.
KEYWORDS Apoptosis; Cell communication; Heart failure; Receptors
1 Present address: Clinic for Cardiothoracic Surgery, University Clinic of Kantonspital Basel, Basel, Switzerland.
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