Angiotensin converting enzyme inhibition modulates cardiac fibroblast growth.

in Journal of hypertension (1998), 16(3), 377-84

BACKGROUND: The progression of left ventricular hypertrophy and cardiac fibrosis in hypertensive heart disease is influenced by sex and age. Although angiotensin converting enzyme inhibition has been ... [more ▼]

BACKGROUND: The progression of left ventricular hypertrophy and cardiac fibrosis in hypertensive heart disease is influenced by sex and age. Although angiotensin converting enzyme inhibition has been shown to prevent progression of the disease in postmenopausal women, the interaction of angiotensin II and estrogen in this process before and after the menopause is poorly understood. OBJECTIVE: To investigate the influence of the angiotensin converting enzyme inhibitor moexiprilat on serum, estrogen and angiotensin II-induced cardiac fibroblast growth. METHODS: Neonatal rat cardiac fibroblasts were incubated with 1 and 10% fetal calf serum, 10(-7) mol/l angiotensin II, 10(-9) mol/l estrone, 10(-9) mol/l 17beta-estradiol and 10(-8) mol/l moexiprilat. Proliferation was measured in terms of incorporation of bromodeoxyuridine. Western blot analysis was performed using antibodies directed against the growth-related immediate early genes c-fos and Sp-1. All experiments were performed at least three times. RESULTS: Fetal calf serum stimulated cardiac fibroblast proliferation (1% fetal calf serum 2.0+/-0.028-fold; 10% fetal calf serum 2.7+/-0.028-fold). Angiotensin II and estrone stimulated proliferation of cardiac fibroblasts grown in the absence of fetal calf serum (angiotensin II 4.2+/-0.075-fold; estrone 2.9+/-0.034-fold) and further increased proliferation in the presence of 1% fetal calf serum (angiotensin 11 4.3+/-0.072-fold); estrone 3.8+/-0.045-fold) and 10% fetal calf serum (angiotensin II 4.8+/-0.112-fold; estrone 4.1+/-0.047-fold). Coincubation with moexiprilat specifically inhibited proliferation induced by angiotensin II and estrone but not by serum, and angiotensin II type 1 receptor blockade inhibited angiotensin II-induced but not estrone-induced cell growth. Western blot analysis showed that the expression of c-fos and Sp-1 was induced in a time-dependent fashion by angiotensin II (to maxima of 5.0-fold for c-fos and 3.0-fold for Sp-1) and estrone (15.2-fold for c-fos and 6.2-fold for Sp-1). This effect was completely inhibited by moexiprilat. CONCLUSIONS: Angiotensin converting enzyme inhibition modulates cardiac fibroblast growth induced by angiotensin II and estrone. This mechanism might contribute to the beneficial effects of angiotensin converting enzyme inhibition in postmenopausal patients with hypertensive heart disease. [less ▲]

Cardiac myocytes and fibroblasts contain functional estrogen receptors.

in FEBS letters (1997), 416(1), 107-12

Gender-based differences found in cardiovascular diseases raise the possibility that estrogen may have direct effects on cardiac tissue. Therefore we investigated whether cardiac myocytes and fibroblasts ... [more ▼]

Gender-based differences found in cardiovascular diseases raise the possibility that estrogen may have direct effects on cardiac tissue. Therefore we investigated whether cardiac myocytes and fibroblasts express functional estrogen receptors. Immunofluorescence demonstrated estrogen receptor protein expression in both female and male rat cardiac myocytes and fibroblasts. Nuclear translocation of the estrogen receptor protein was observed after stimulation of cardiomyocytes with 17beta-estradiol (E2). Cells transfected with an estrogen-responsive reporter plasmid showed that treatment with E2 induced a significant increase in reporter activity. Furthermore, E2 induced a significant increase in expression of the estrogen receptors alpha and beta, progesterone receptor and connexin 43 in cardiac myocytes. Cardiac myocytes and fibroblasts contain functional estrogen receptors and estrogen regulates expression of specific cardiac genes. These data suggest that gender-based differences in cardiac diseases may in part be due to direct effects of estrogen on the heart. [less ▲]

Molecular Biology of oncogenes and cardiovascular hypertrophy

in Lindpaintner, K; Ganten, D (Eds.) Molecular Reviews in Cardiovascular Medicine (1996)

Hormonal induction of an immediate-early gene response in myogenic cell lines--a paradigm for heart growth.

in European heart journal (1995), 16 Suppl C

Cardiac hypertrophy is characterized by growth of myocardial cells without proliferation. Many endo- paracrine stimuli such as angiotensin II, endothelin, alpha 1-adrenergic agonists, and insulin have ... [more ▼]

Cardiac hypertrophy is characterized by growth of myocardial cells without proliferation. Many endo- paracrine stimuli such as angiotensin II, endothelin, alpha 1-adrenergic agonists, and insulin have been shown to be able to induce cardiac hypertrophy either in vivo or in vitro. We have used the myoblast model of differentiation and proliferation to determine nuclear signal transduction mechanisms in muscle and (by analogy) cardiac growth. The first nuclear event known to occur when a growth stimulus acts upon a cell is induction of a family of immediate-early genes. Our group focused on the role of one of these genes, the early growth response gene-1 (Egr-1). We have shown that this gene is induced in isolated adult cardiac myocytes in the presence of endothelin. An anti-sense oligonucleotide complementary to the first six codons of the Egr-1 mRNA abolishes the stimulation of protein synthesis induced by endothelin. In the present study we further characterized paracrine growth stimuli in the myogenic cell line Sol8, which was used as a paradigm to further investigate mechanisms of paracrine growth induction. We demonstrated that a variety of candidate endo- paracrine stimuli for the induction of cardiac hypertrophy induced the Egr-1 messenger RNA in the myogenic cell line Sol8. Among these are endothelin, insulin, basic fibroblast growth factor, and platelet-derived growth factor BB (PDGF BB). We conclude: (1) In analogy to the myocardium, these growth factors act upon myoblasts. (2) This line appears to be a suitable model for the molecular characterization of Egr-1 target genes. [less ▲]

Differentiation-specific isoform mRNA expression of the calmodulin-dependent plasma membrane Ca(2+)-ATPase.

in FASEB Journal (1994), 8(6), 428-35

The functional significance of the isoform diversity of the calmodulin-dependent plasma membrane Ca(2+)-ATPase (PMCA) is largely unknown. To determine whether the mRNA synthesis of different isoforms of ... [more ▼]

The functional significance of the isoform diversity of the calmodulin-dependent plasma membrane Ca(2+)-ATPase (PMCA) is largely unknown. To determine whether the mRNA synthesis of different isoforms of the enzyme is regulated in a differentiation-specific manner, we investigated the expression of isoform-specific mRNAs in muscle and neuronal cells during differentiation by reverse transcription PCR. In the rat, the ubiquitous PMCA splicing variants 1b and 4b formed the typical PMCA isoform pattern of L6 myoblasts, the heart-derived cell line H9c2(2-1), two different fibroblast cell lines (FR and NRK-49F), smooth muscle, and endothelial cells. In addition to these two enzymes, novel expression of the splicing variants 1c, 1d, and 4a was induced during myogenic differentiation of L6 and H9c2(2-1) cells. A similar isoform subtype switch could be detected during differentiation of the neuronal PC-12 cells induced by nerve growth factor (NGF). The isoform-specific mRNAs 1c, 1d, and 4a were not expressed in cells other than myocytes and neurons, and therefore may be specific for excitable cells. The mRNA for isoform 1d was heart- and skeletal muscle-specific. To determine whether expression of a differentiation-specific PMCA mRNA pattern is under control of a myogenic determination factor, myogenin was constitutively expressed in rat fibroblasts. These cells converted to multinucleated myotubes, which displayed the PMCA isoform-specific mRNAs 1c, 1d, and 4a, typical of differentiated muscle cells. We conclude that: 1) the distribution of the various PMCA isoform-specific mRNAs and their splicing variants is cell type- and development-specific; 2) expression of the myogenic determination factor myogenin is sufficient to direct alternative splicing generating muscle-specific PMCA mRNA species; and 3) PMCA isoforms and/or splicing variants may play a role in determining functions of terminally differentiated muscle and neuronal cells and possibly during the differentiation process itself. [less ▲]

Induction of immediate-early genes by angiotensin II and endothelin-1 in adult rat cardiomyocytes.

in Journal of hypertension (1993), 11(9), 927-34

OBJECTIVE: Few molecular signals for induction of myocardial hypertrophy have been identified. This study was carried out to investigate the action of angiotensin II and endothelin on the growth- and ... [more ▼]

OBJECTIVE: Few molecular signals for induction of myocardial hypertrophy have been identified. This study was carried out to investigate the action of angiotensin II and endothelin on the growth- and differentiation-related genes Egr-1 (early growth response gene 1) and c-fos in isolated adult rat cardiomyocytes. METHODS: Cardiac myocytes from male Wistar-Kyoto rats were isolated and incubated with angiotensin II and endothelin-1 in Dulbecco's modified Eagle's medium. RNA was isolated and blotted, and densitometric analysis was performed. All experiments were repeated at least three times. RESULTS: Endothelin-1 (10(-7) mmol/l) induced a 20-25-fold rise in Egr-1 messenger RNA within 15 min. This effect was dose-dependent. c-fos was induced 10-20-fold within 15 min with similar dose-response characteristics. Angiotensin II also induced Egr-1 and c-fos with kinetics similar to endothelin but a cofactor from fetal calf serum was needed for full c-fos expression. The protein kinase C activator phorbol 12-myristate 13-acetate also induced Egr-1. CONCLUSIONS: The results identify Egr-1 and c-fos as target genes for the action of endothelin and angiotensin II in the adult myocardium suggesting that induction of the genes may be part of the signal transduction pathway for angiotensin II and endothelin in the myocardium. [less ▲]

Hyperosmotic stress induces immediate-early gene expression in ventricular adult cardiomyocytes.

in Biochemical and biophysical research communications (1993), 194(2), 642-6

Mammalian cells possessing osmosensors have long been described in brain and kidney. The genetic basis of the response to hyperosmotic stress has been well characterized in prokaryotes. In contrast, the ... [more ▼]

Mammalian cells possessing osmosensors have long been described in brain and kidney. The genetic basis of the response to hyperosmotic stress has been well characterized in prokaryotes. In contrast, the genetic response of eukaryotic cells is poorly understood. Therefore we investigated the effect of hypertonic NaCl and sucrose solutions on the transcriptional activation of the immediate-early genes (IEGs) egr-1 and c-fos in isolated ventricular adult rat cardiomyocytes. We observed that even small increases in osmolarity to 315 +/- 5 mosmol/l and 370 +/- 8 mosmol/l by hypertonic NaCl solution resulted in dose-dependent induction of egr-1 (4-and 5-fold) and c-fos (3-and 4-fold), respectively. Hypertonic sucrose solution had the same effect on egr-1 and c-fos mRNA levels while increased sucrose concentration under isotonic conditions had no effect. Cardiomyocytes exposed to hypertonic media did not significantly shrink as shown by a cell length measurement. We conclude that isolated adult cardiomyocytes possess an osmoreceptor mechanism which is able to sense even slight changes in osmolarity and to translate these into a transcriptional response of the myocardial IEG program. [less ▲]

Molecular biology of oncogenes and cardiovascular hypertrophy.

in Journal of hypertension (1992), 10(12), 1447-52

Isolierte Kardiomyozyten - ein Modell zur Aufklaerung der Pathophysiologie der hypertensiven Herzkrankheit - physiologische und erste molekularbiologische Ergebnisse

in Ganten, D (Ed.) Herz-Kreislaufregulation, Organprotektion und Organschaden (1991)

Hypertensive Herzkrankheit - pathophysiologische Grundlaten, Diagnostik und Therapie

in Deutsche Medizinische Wochenschrift (1946) (1990), (39), 1480-1486