Are you T de Jager?

Claim your profile

Publications (4)11.28 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In contrast to the vasculature, it remains unclear whether oestrogens also directly affect the myocardium. In this study, we addressed basic questions regarding oestrogen effects on the myocardium, including specificity, pathophysiological relevance and potential clinical implications, with a special focus on interactions between oestrogen and angiotensin-converting enzyme (ACE) inhibitors in an established in-vivo model of cardiac hypertrophy. Female spontaneously hypertensive rats (SHR) were ovarectomized (OVX) or sham-operated and treated with 17beta-oestradiol (2 microg/kg per day subcutaneously), the oestrogen receptor antagonist ZM-182780 (250 microg/kg per day subcutaneously) and the ACE-inhibitor moexipril (10 mg/kg per day orally) alone or in combination for 3 months. Hormone replacement restored physiological oestradiol serum levels and prevented uterus atrophy. Whereas moexipril alone was ineffective in OVX rats, substitution of oestradiol restored the beneficial effect of moexipril on systolic blood pressure (-30 +/- 5 mmHg) and relative heart weight (-11 +/- 3%) in OVX rats. Oestradiol upregulated alpha-myosin heavy chain (MHC) mRNA (+37 +/- 7%) and protein expression (+43 +/- 6%) in spite of increased blood pressure in OVX rats. Simultaneous treatment with oestradiol plus moexipril most effectively shifted the ratio of alpha-/beta-MHC mRNA and protein expression towards alpha-MHC in OVX animals. Oestradiol (10 nmol/l) also upregulated alpha-MHC mRNA and protein in cultured cardiac myocytes. The oestrogen receptor antagonist ZM-182780 significantly inhibited the observed oestrogen effects. Oestrogen replacement is permissive for the beneficial effects of ACE-inhibition in female SHR rats. Oestrogen effects on the myocardium in vivo are specific (i.e. oestrogen receptor mediated) because they are inhibited by a pure oestrogen receptor antagonist and occur at physiological hormone levels.
    Journal of Hypertension 06/2002; 20(5):1001-6. · 4.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have previously shown that estrogen effects in the heart include direct hormone effects on the myocardium. In a recent study we found that one beneficial effect of estradiol on the myocardium is the inhibition of apoptosis in cardiac myocytes. This effect was associated with a reduction of NF-kappaB activity. In the present study we have analyzed the functional mechanism of NF-kappaB inhibition in the myocardium by estrogen receptors-alpha and -beta. Despite the previous finding that 17-beta-estradiol (10 nM) inhibited the staurosporine-induced binding of p65/p50 NF-kappaB complexes to their cognate DNA elements in cultured rat cardiac myocytes, myocyte extracts showed no change in expression or cellular localization of p65, p50, and IkappaB upon staurosporine or estradiol treatment. Addition of either estrogen receptor-alpha or estrogen receptor-beta as recombinant protein was sufficient to inhibit staurosporine-dependent p65/p50 DNA binding in cardiac myocytes. 17-beta-Estradiol inhibits staurosporine-induced p65/p50 DNA binding associated with apoptotic cell death of cardiac myocytes via estrogen receptors-alpha and -beta. This is not associated with changes in p65, p50 and IkappaB expression or subcellular localization. Thus, inhibition of NF-kappaB activity by estrogenic compounds might inhibit NF-kappaB dependent gene expression such as pro-inflammatory cytokines in the myocardium.
    Biochemical and Biophysical Research Communications 10/2001; 286(5):1153-7. · 2.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have previously shown that the myocardium is a target tissue for estrogen. Here, we have identified rapid non-nuclear estrogen effects on the expression of the early growth response gene-1 (Egr-1) in cardiomyocytes. Egr-1 mRNA and protein were rapidly and strongly induced by estrogen in an estrogen receptor-dependent manner via the extracellular signal-regulated kinase, ERK1/2. A promoter analysis study of a 1.2-kilobase Egr-1 promoter fragment revealed that the serum response elements (SREs) but not the estrogen response elements or AP-1 sites are responsible for Egr-1 induction by estrogen, identifying a novel mechanism of estrogen receptor-dependent gene activation in the myocardium. Both estrogen receptor-alpha and -beta induced the Egr-1 promoter via the SREs as well as an artificial promoter consisting of only five SREs in cardiomyocytes. Electrophoretic mobility shift assays showed that a protein complex containing serum response factor or an antigenically related protein was recruited to the SREs by estrogen treatment of primary cardiomyocytes. The recruitment of the protein complex was inhibited by the specific estrogen receptor antagonist ICI 182,780 as well as the MEK inhibitor PD 98059. Taken together, these results identify SREs as important promoter control elements for an estrogen receptor-dependent mechanism of gene activation in the myocardium.
    Journal of Biological Chemistry 08/2001; 276(30):27873-80. · 4.65 Impact Factor
  • Source
    Tertia ¬de¬ Jager
    [Show abstract] [Hide abstract]
    ABSTRACT: Cardiovascular disease is the leading cause of mortality in both men and women in the Western world. Earlier observations have pointed out that pre-menopausal women have a lower risk of developing cardiovascular disease than age-matched men, with an increase in risk after the onset of menopause. This observation has directed the attention to estrogen as a potential protective factor in the heart. So far the focus of research and clinical studies has been the vascular system, leaving the current knowledge on the role of estrogen in the myocardium itself rather scarce. Functional estrogen receptor-alpha as well as -beta have recently been identified in the myocardium, making the myocardium an estrogen target organ. The focus of this thesis was 1) to investigate the role of estrogen and estrogen receptors in modulating myocardial gene expression both in vivo in an animal model for cardiac hypertrophy (spontaneously hypertensive rats; SHR), as well as in vitro in isolated neonatal cardiomyocytes, 2) to investigate the mechanisms of the rapid induction of an estrogen target gene, the early growth response gene-1 (Egr-1) and 3) to initiate the search for novel estrogen target genes in the myocardium. 1) The effects of estrogen on the expression of one of the major myocardial specific contractile proteins, the alpha-myosin heavy chain (alpha-MHC) have been investigated. In ovarectomised animals treated either with 17beta-estradiol alone or in combination with a specific estrogen receptor antagonist, ICI 182780, it was shown that both alpha-MHC mRNA and protein were upregulated by estrogen in an estrogen receptor specific manner. The in vivo results were confirmed in vitro in isolated neonatal cardiomyocytes which showed that estrogen has a direct action on the myocardium potent enough to upregulate the expression of alpha-MHC. Furthermore it was shown that the alpha-MHC promoter is induced by estrogen in an estrogen receptor-dependent manner and first investigations into the mechanisms involved in this upregulation identified Egr-1 as a potential transcription factor which, upon induction by estrogen, drives the expression of the alpha-MHC promoter. 2) Previously it was shown that Egr-1 is rapidly induced by estrogen in an estrogen receptor-dependent manner which was mediated via 5 serum response elements (SREs) in the promoter region and surprisingly not via the estrogen response elements (EREs). In this study it was shown that estrogen-treatment of cardiomyocytes resulted in the recruitment of serum response factor (SRF), or an antigenically related protein, to the SREs in the Egr-1 promoter, which was specifically inhibited by the estrogen receptor antagonist ICI 182780. Transfection experiments showed that estrogen induced a heterologous promoter consisting only of 5 tandem repeats of the c-fos SRE in an ER-dependent manner, which identified SREs as promoter elements able to confer an estrogen response to target genes. 3) Potentially new target genes regulated by estrogen in vivo were analysed using hearts of ovarectomised animals as well as ovarectomised animals treated with estrogen. Analyses of cDNA microarray filters containing 1250 known genes identified 24 genes that were modified by estrogen in vivo. Among these genes, some might have potentially important functions in the heart and further analyses of these genes will create a more global picture of the role and function of estrogen in the myocardium. Taken together, the results showed that estrogen does have a direct action on the myocardium both by regulating the expression of myocardial specific genes in vivo, as well as exerting rapid non-nuclear effects in cardiac myocytes. It was shown that SREs in the promoter region of genes can confer an estrogen response to genes identifying SREs as important elements in regulation of genes by estrogen. Furthermore, 24 potentially new estrogen targets were identified in the myocardium, contributing to the general understanding of estrogen action in the myocardium. Kardiovaskuläre Erkrankungen gehören zu den häufigsten Todesursachen in westlichen Ländern. Vor den Wechseljahren besteht für Frauen ein geringeres Risiko, Herzerkrankungen zu entwickeln als für gleichaltrige Männer. Nach dem Eintritt der Menopause sind diese geschlechtsspezifischen Unterschiede aufgehoben, da sich das Risiko bei Frauen erhöht. Dies deutet darauf hin, dass Östrogene kardioprotektiv wirken. Bislang konzentrierten sich sowohl Forschung als auch klinische Studien hauptsächlich auf das vaskuläre System, so dass wenig über die Rolle von Östrogenen im Myokard bekannt ist. Zwar wurde gezeigt, dass funktionelle Östrogenrezeptoren (alpha- und beta-Form) in Herzmuskelzellen exprimiert werden, ihre genaue Funktion im Myokard ist jedoch noch ungeklärt. Dies lieferte den Ansatzpunkt für die vorliegende Arbeit, die sich mit der Rolle von Östrogenen im Myokard beschäftigte. Dazu wurde 1) der Einfluss der Östrogene auf die Genexpression im Myokard sowohl in vivo mit Hilfe eines Tiermodells für Herzhypertrophie, der spontan hypertensiven Ratte (SHR), als auch in vitro an isolierten neonatalen Kardiomyozyten untersucht. 2) Weiterhin wurde der Mechanismus der schnellen Geninduktion durch Östrogene mit Hilfe eines bereits identifizierten östrogenresponsiven Gens, dem ?Early growth response gene-1? (Egr-1), analysiert. 3) Gleichzeitig wurden erste Versuche zur Identifizierung bislang unbekannter Östrogenzielgene im Myokard eingeleitet. 1) Die Beeinflussung der myokardiale Genexpression wurde an Hand eines myokardial spezifischen kontraktilen Proteins, der alpha-Myosinschwerkette (alpha-MHC), untersucht. Östrogensubstitution in ovarektomierten Ratten induzierte alpha-MHC sowohl auf mRNA- als auch auf Protein-Ebene in einer spezifisch durch Östrogenrezeptoren vermittelten Weise. In isolierten Kardiomyozyten konnten diese in vivo Ergebnisse bestätigt werden, indem gezeigt wurde, dass Östrogene direkt auf die Herzmuskelzellen wirken und die alpha-MHC-Expression induzieren. Weiterhin wurde die Östrogenrezeptor-abhängige Induktion des alpha-MHC-Promotors durch Östrogene nachgewiesen. Untersuchungen zu dem Mechanismus dieser Induktion identifizierten Egr-1 als potentiellen Transkriptionsfaktor, der durch Östrogene induziert wird und so die alpha-MHC-Induktion vermittelt. 2) Es wurde bereits in einer früheren Arbeit nachgewiesen, dass Egr-1 durch Östrogene in Kardiomyozyten induziert wird. Diese schnelle Induktion wird durch serumresponsive Elemente (SREs), nicht aber durch die östrogenresponsiven Elemente (EREs) im Egr-1 Promotor vermittelt. Zur Untersuchung des Mechanismus dieser schnellen Induktion konnte in der vorliegenden Arbeit gezeigt werden, dass Östrogenbehandlung die Bindung von SRF (serum response factor) an die SREs im Egr-1 Promoter auslöst. Ebenso wurde ein künstlicher Promotor aus 5 SREs des c-fos Promotors durch Östrogene induziert. Diese Induktion fand in einer spezifisch Östrogenrezeptor-vermittelten Weise statt. Damit konnten SREs neben EREs und AP-1 als Promoterelemente identifiziert werden, die eine wichtige Rolle bei der östrogenabhängigen Induktion von Zielgenen spielen. 3) Ein Ansatz zur Identifizierung neuer potentieller Östrogenzielgene im Myokard wurde etabliert. Mit Hilfe der Microarray-Technik wurde die Genexpression in Herzen von ovarektomierten, östrogenbehandelten Tieren mit unbehandelten Tieren verglichen. Durch die Verwendung von cDNA Mikroarray-Membranen mit 1250 cDNAs bekannter Rattengene wurden 24 Gene identifiziert, deren Expression möglicherweise durch Östrogene im Herzen beeinflusst werden könnte. Im Rahmen dieser Arbeit ist es somit gelungen zu zeigen, dass Östrogene eine direkte Wirkung auf das Myokard haben, indem sie die Expression des wichtigen kontraktilen Proteins a-MHC beeinflussen. Daneben vermitteln Östrogene auch schnelle nicht-genomische Geninduktionen via SREs. Zusätzlich wurden 24 potentiell neue Östrogenzielgene im Myokard identifiziert, was zu dem allgemeinen Verständnis der Östrogenwirkung im Myokard beiträgt.