PubMed Health⌕ Search

Biomedical subjects

F Viñals

Publications and source records attributed to F Viñals.

At least 19 recordsLinked to original sources
PubMed2006

Fetal atrioventricular valve junction in normal fetuses and in fetuses with complete atrioventricular septal defect assessed by 4D volume rendering.

OBJECTIVES: To assess the feasibility and clinical potential of 4D volume rendering of the atrioventricular (AV) valve junction, to standardize the acquisition method, and to display the AV valve junction morphology in normal fetuses and in those with a complete atrioventricular septal defect (AVSD). METHODS: We performed sonography in 40 normal fetuses and 10 fetuses with complete AVSD, and volume datasets were acquired from apical and lateral four-chamber views. The render box was placed systematically. First, it included the AV valves, with the reference dot at the level of the crux of the heart. Then, it included the papillary muscles, with the reference dot in the interventricular septum at the level of the distal opening of the tricuspid valve leaflet. RESULTS: Volume acquisition and rendering were technically possible in all cases. Volume rendering of the left ventricle showed the position of the anterolateral and posteromedial papillary muscles in 36/40 normal fetuses (90%). At the level of the right ventricle, the septal, anterior and posterior papillary muscles were visualized in 33/40 normal fetuses (82%). In cases of complete AVSD, the AV valve has five leaflets, with anterosuperior and posteroinferior bridging leaflets straddling the septa. The morphology of the anterosuperior bridging leaflets and the abnormal position of the papillary muscles could be displayed in all cases. CONCLUSIONS: Our study suggests that some of the components of the AV junction can be reconstructed easily from sonographic volumes acquired from an apical or lateral four-chamber view. This new technique may have a role in obtaining views that are not easily accessible by standard sonography, enabling a rapid complementary assessment of normal and abnormal intracardiac anatomy.

Adult↗
PubMed2006

Simple approach to prenatal diagnosis of transposition of the great arteries.

OBJECTIVE: To analyze the most relevant anomalies, seen in a sequential segmental transverse views approach to imaging the fetal heart, that provide clues to the diagnosis of complete transposition of the great arteries (TGA). METHODS: We reviewed retrospectively all the cases of isolated TGA diagnosed in our center or submitted for a second opinion through the spatio-temporal image correlation (STIC) telemedicine (TELE-STIC) program. Only transverse cardiac sweeps were obtained. Digital video clips and STIC volumes were reviewed. The abnormal features on four-chamber, five-chamber, three-vessel (3V) and three vessels and trachea (3VT) views were analyzed. RESULTS: The study population consisted of eight fetuses with TGA with normal extracardiac anatomy. The gestational age ranged from 13 to 32 (mean, 23) weeks. The maternal age ranged from 25 to 42 (mean, 32) years. A normal four-chamber view was seen in seven cases. Only one case demonstrated a significant ventricular septal defect. At the level of the five-chamber view a straight course arterial vessel arose from the left ventricle with lateral branches in all fetuses. In the 3V view, the ascending aorta was seen reaching more anteriorly than was the pulmonary artery in six cases. At the level of the 3VT view, two vessels (transverse aortic arch and superior vena cava) rather than three were seen in all cases. CONCLUSION: Our proposed sequential segmental approach to imaging the fetal heart apparently allows, in five-chamber and 3VT views, clear and confident signs to be detected that aid diagnosis of TGA.

Adult↗
PubMed2005

Prenatal diagnosis of congenital heart disease using four-dimensional spatio-temporal image correlation (STIC) telemedicine via an Internet link: a pilot study.

OBJECTIVE: To assess whether the spatio-temporal image correlation (STIC) acquisition technique can be taught to a general obstetrician by e-mail; whether STIC volume datasets can be transmitted over the Internet; and whether STIC volume datasets analyzed offline at a remote setting can be used to confirm or exclude major cardiac defects (TELE-STIC). METHODS: This was a prospective study involving 50 pregnant women with gestational ages ranging between 20 and 36 weeks. These patients were selected by two general obstetricians (operators) working in geographically remote areas of Chile. Although both obstetricians were users of equipment capable of four-dimensional (4D) ultrasound with STIC, they lacked skill in the performance of fetal cardiac examination. A dedicated web disk was created to upload the acquired volume datasets using an Internet broadband connection. Offline analysis was performed by a single investigator experienced in fetal echocardiography (the administrator). RESULTS: A telemedicine link via the Internet was possible in all cases. Seventy-seven volume datasets were sent to the web server. A complete cardiac examination according to set criteria was achieved by the administrator in 86% of the cases scanned by one operator and 95% of the cases scanned by the other operator. Three patients had cardiac defects confirmed postnatally, two fetuses had extracardiac anomalies and one fetus had a suspected cardiac defect unconfirmed by second-opinion TELE-STIC. There were two isolated major congenital heart defects. Both patients were given advice by e-mail and teleconference using a web camera about the likely outcome and benefits of scheduling in utero transport to a tertiary care center. CONCLUSIONS: STIC volumes can be obtained by operators inexperienced in fetal echocardiography, transmitted via the Internet, and their analysis enables recognition of most of the structures and views necessary to assess fetal cardiac anatomy. The preliminary use of TELE-STIC allowed us to demonstrate that some intracardiac anomalies can be ruled out and others confirmed, allowing perinatal management to be tailored accordingly.

Chile↗
PubMed2005

The fetal cerebellar vermis: anatomy and biometric assessment using volume contrast imaging in the C-plane (VCI-C).

OBJECTIVES: To describe the normal appearance and study the biometry of the fetal cerebellar vermis by three-dimensional (3D) volume contrast imaging in the coronal (C-) plane (VCI-C). METHODS: A total of 203 normally developed fetuses were examined prospectively at 18-33 weeks' gestation. At the level of the view used to measure the transverse cerebellar diameter (TCD), a VCI-C plane was displayed to examine, using a transabdominal probe, the fetal mid-saggital vermis. The volumes acquired were stored for later review and measurement of the anteroposterior (AP) diameter, craniocaudal (CC) diameter and surface area of the cerebellar vermis. Each dataset was evaluated by two independent observers. Measurements as a function of gestational age (GA), biparietal diameter (BPD), head circumference (HC) and TCD were expressed by regression equations. Interobserver variability was evaluated. Nomograms were produced. In order to validate the use of VCI in fetal biometry, datasets from 57 patients were selected arbitrarily for comparison of their VCI-C measurements with those from mid-sagittal sections of a stored 3D multiplanar examination. Intraclass correlation was used to evaluate the agreement between these measurements. RESULTS: The mean maternal age was 32 years. We were able to measure mid-sagittal CC diameter, mid-sagittal AP diameter and cerebellar vermis surface area in all fetuses. Interobserver variability analysis showed no significant differences between the two observers (P > 0.05). Measurements of the cerebellar vermis (AP diameter, CC diameter and surface area) correlated linearly with GA, BPD, HC and TCD (r > or = 0.82, P < 0.0001). CC and AP diameters estimated from the mid-sagittal section of the multiplanar measurements were significantly correlated with VCI-C measurements (r = 0.96, P < 0.00001 and r = 0.95, P < 0.00001, respectively). CONCLUSIONS: VCI-C is a valuable tool, allowing intrauterine assessment of the normal appearance of the fetal cerebellar vermis. The nomograms developed in this study should enable accurate evaluation of the cerebellar vermis.

Adolescent↗
PubMed2004

A novel muscle DNA-binding activity in the GLUT1 promoter.

GLUT1 glucose transporters are highly expressed in proliferating and transformed cells and serum and cAMP or the transcription factor Sp1 induce GLUT1 gene transcription. Here we identified a cis element situated at -46/-37 (MG1E - muscle-specific GLUT1 element) to which muscle-specific nuclear factors bind, and the DNA-protein complexes showed electrophoretic mobility of 41 and 32 kDa. MyoD over-expression induced the generation of MG1E-protein complexes characteristic of myoblast cells. MG1E does not bind any known factors defined in databases. Mutation of the MG1E sequence impaired transcriptional activity of the GLUT1 promoter specifically in skeletal or cardiac muscle cells. The transcriptional activity of the GLUT1 promoter induced by either Sp1, cAMP or serum was markedly reduced when MG1E was inactivated. We propose that the MG1E sequence permits the binding of muscle-specific nuclear factors and a maximal transcriptional activity in muscle cells in response to Sp1, cAMP or serum.

Animals↗
PubMed2003

Induction of the Sry-related factor SOX6 contributes to bone morphogenetic protein-2-induced chondroblastic differentiation of C3H10T1/2 cells.

Chondrogenesis leads to the formation of mature cartilage and generates initial skeletal elements that serve as templates for endochondral bone formation. Bone morphogenetic proteins (BMPs) are involved in several developmental and organogenetic processes and have been identified as key regulators in chondrogenesis. In the present study we sought to determine the transcriptional mechanisms contributing to the induction of chondrogenic markers by BMP-2. Time-course studies with BMP-2-stimulated C3H10T1/2 cells showed a dose-dependent appearance of Alcian-blue-positive material and up-regulated expression of type-II collagen mRNA. This last effect required new protein synthesis because addition of cycloheximide completely blocked the induction of type-II collagen mRNA. A region encompassing the chondrocyte-specific enhancer, localized in intron I of type-II collagen alpha1 chain (Col2a1) gene, is sufficient to confer BMP-2-dependent transcriptional induction of type-II collagen gene expression. Analysis of the expression levels of chondrogenic Sry-type high-mobility group (HMG) box proteins (SOX) transcription factors demonstrated a time-dependent induction of Sox6 expression by BMP-2 that correlated with the appearance of BMP-2- induced protein complexes bound to the chondrocyte-specific enhancer. Preincubation of nuclear extracts with SOX6 and SOX9 antibodies markedly reduced the intensity of these bands. Forced expression of SOX6 mimicked the BMP-2 effect, whereas coexpression of SOX9 promoted a synergistic interaction between both factors in transcription from the chondrocyte-specific enhancer. Moreover, overexpression of a SOX6 mutated form, devoid of its high-mobility group domain, was sufficient to prevent transcriptional induction of the chondrocyte-specific enhancer by BMP-2. Taken together, these results indicate that SOX6 is an important downstream mediator of BMP-2 signaling in chondrogenesis.

Animals↗
PubMed2003

The role of the three vessels and trachea view (3VT) in the diagnosis of congenital heart defects.

OBJECTIVE: To analyse the anomalies seen at the three vessels and trachea (3VT) view in fetuses with antenatally diagnosed congenital heart disease (CHD), specifically in defects involving the upper mediastinum, including the outflow tracts and/or arteries. METHODS: Seventy-four consecutive fetuses of singleton pregnancies with antenatally diagnosed structural heart defects were initially included in the study. We selected those in which there was an anomaly seen on the 3VT view and classified them into groups: abnormalities detected on the upper mediastinum (abnormal vessel size, alignment, arrangement and number), abnormal location of the transverse aortic arch in relation to the trachea, and abnormal functional behavior of the arterial vessels (reversed flow and turbulent flow) detected using color Doppler. The abnormalities detected were confirmed postnatally by a pediatric cardiologist, echocardiography and/or autopsy. RESULTS: Thirty-four of the 74 fetuses showed an abnormal 3VT view that could be classified into one of the groups. We classified the lesions according to the most evident abnormal finding during the examination. Gestational age ranged from 17 to 39 (mean, 30) weeks. Abnormal vessel size was found in 20 of the 74 fetuses, abnormal vessel alignment was found in two fetuses, and abnormal vessel arrangement in three fetuses. Two vessels instead of three were found in five fetuses and four vessels were found in two fetuses. Abnormal visualization of the trachea, between the pulmonary artery and the transverse arch, occurred in one fetus with isolated right aortic arch. We found reversed flow in the transverse aortic arch in three fetuses with aortic atresia and in two fetuses with severe coarctation of the aorta. Reversed flow in the pulmonary trunk was seen in a fetus with pulmonary atresia and double outlet right ventricle. Turbulent flow was found in two fetuses with outflow tract stenosis. CONCLUSION: Our study, descriptive in nature, demonstrates that the 3VT view is a reliable method with which to determine abnormalities in the upper mediastinum. It proved to be efficient in identifying an important group of critical heart defects involving the outflow tracts and the aortic arch. It also provided important clues to the diagnosis of minor anomalies considered as markers of other CHD. We believe that use of the 3VT view should become routine in screening for CHD.

Aorta, Thoracic↗
PubMed2003

Spatio-temporal image correlation (STIC): a new tool for the prenatal screening of congenital heart defects.

OBJECTIVE: To assess the feasibility and capability of STIC acquisition, performed by a general obstetrician performing antenatal ultrasound, to visualize fetal cardiac structures in women undergoing routine obstetric ultrasound examination, in order to obtain information to confirm normality of the fetal heart during intrauterine life. METHODS: This was a prospective study of one hundred fetuses with echocardiographically confirmed normal hearts and no extracardiac anomalies with gestational ages ranging between 18 and 37 weeks. A general obstetrician was invited to acquire the STIC volumes. The four-chamber view was obtained as a starting point. A standard 7.5-s acquisition time and 30 degrees angle of acquisition were used and the resulting STIC was stored for later offline analysis by a fetal echocardiologist. For each patient, the stored STIC data were first evaluated by sweeping from the initial acquisition plane, in the caudal direction and then cranially, zooming, slowing or stopping the cardiac motion to visualize views and structures. If a structure or view was rated as inadequate or not identifiable, a multiplanar three-dimensional (3D) examination of the STIC volume was taken in order to try to visualize it adequately. The rates obtained using just the STIC sweeps were compared independently, and then the 3D multiplanar study was added. RESULTS: STIC acquisition was possible in all cases. The mean time required for STIC acquisition was 7.5 min. A complete cardiac examination according to the set criteria was achieved in 94.2% (95% confidence interval (CI), 90-99) of cases. We obtained a 94.2% success rate of visualizing different structures and views of the fetal heart using the STIC sweep alone (95% CI, 90-99) and 96.2% adding 3D multiplanar examination (95% CI, 92-100). CONCLUSION: STIC acquisition of the fetal heart is feasible with high success rates in visualization of the principal connections. The STIC data acquired by a general obstetrician can subsequently be used by a fetal echocardiologist for prenatal confirmation of normal cardiac structure or exclusion of major cardiac malformations.

Echocardiography, Three-Dimensional↗
PubMed2002

Active, phosphorylation-dependent MAP kinases, MAPK/ERK, SAPK/JNK and p38, and specific transcription factor substrates are differentially expressed following systemic administration of kainic acid to the adult rat.

Excitotoxicity is considered a major cell death inductor in neurodegeneration. Yet the mechanisms involved in cell death and cell survival following excitotoxic insults are poorly understood. Expression of active, phosphorylation-dependent mitogen-activated extracellular signal-regulated kinases (MAPK/ERKs), stress-activated c-Jun N-terminal kinases (SAPK/JNKs) and p38 kinases, as well as their putative active, phosphorylation-dependent specific transcriptional factor substrates CREB, Elk-1, ATF-2, c-Myc and c-Jun, has been examined following systemic administration of kainic acid (KA) at convulsant doses to rats. Increased phosphorylated MAPK (MAPK(P)) immunoreactivity has been found at 3 and 6 h in the vulnerable regions entorhinal cortex and CA3, in which neurons are committed to die, as well as in sensitive regions dentate gyrus and gyrus cinguli, in which neurons will survive. JNK(P) has been observed in the entorhinal cortex and dentate gyrus, and p38(P) immunoreactivity occurs in the entorhinal cortex. Strong c-Myc(P) expression parallels MAPK(P) immunoreactivity in the entorhinal cortex, CA3, dentate gyrus and gyrus cinguli, showing that enhanced c-Myc(P) expression does not preclude cell death or cell survival. Selective decrease of CREB(P) immunoreactivity in entorhinal cortex and CA3 indicates CREB(P) reduction associated with cell death. Strong c-Jun(P) immunoreactivity has been found in the entorhinal cortex, CA3 and dentate gyrus, thus suggesting that regulation of two opposing cellular programs (cell death or cell survival) of c-Jun(P) depends on c-Jun interactions with other factors. Interestingly, ATF-2(P), and to a lesser extent Elk-1(P), is selectively increased in the dentate gyrus. These results suggest ATF-2(P) involvement in cell survival of dentate gyrus granule cells. The present results demonstrate activation of specific MAPK pathways in association with either cell death or cell survival triggered by KA. Furthermore, increased Ras activation, as seen with p21 Ras activation assay, indicates a crucial role for Ras in activating MAP kinases following excitotoxic insult.

Activating Transcription Factor 2↗
PubMed2002

Prenatal detection of ductal-dependent congenital heart disease: how can things be made easier?

OBJECTIVE: To improve the detection of ductal dependence in fetuses with severe anomalies of the outflow tracts by observing, with directional power Doppler, reverse flow through the aortic arch or ductus arteriosus in a transverse view of the upper mediastinum. METHODS: A slight cranial move of the ultrasound beam from the three-vessel view allows the transverse view of the aortic arch and ductus arteriosus to be visualized simultaneously. This view is orthogonal to the fetal body axis and parallel to the plane of the four-chamber view. In normal fetuses, directional power Doppler interrogation at this level identifies forward flow in both oblique vessels. RESULTS: We examined 43 fetuses with cardiac defects. In five of the cases, there was reversed flow in the aortic arch or ductus arteriosus in addition to severe anomalies of the outflow tracts, including four with hypoplastic left ventricle and one with pulmonary atresia. CONCLUSIONS: Prenatal detection of reversed flow in the aortic arch or ductus arteriosus is associated with complex congenital heart disease with major diminution of forward flow to the corresponding great vessels.

Aorta, Thoracic↗
PubMed2001

Growth factor-stimulated protein synthesis is inhibited by sodium orthovanadate.

The study of intracellular signaling pathways has been aided by the use of sodium orthovanadate, a cell-permeable inhibitor of tyrosine phosphatases. However, long-term addition of sodium orthovanadate is often cytotoxic. In this study we demonstrate that the growth factor-mediated increase in the rate of protein synthesis was inhibited by sodium orthovanadate. This effect of sodium orthovanadate was dose-dependent, with an IC50 of 40 microM and maximal inhibition obtained at 100 microM. As a consequence, the fetal bovine serum-mediated induction of the immediate-early genes, c-Fos and MKP-1, at the protein level was inhibited by orthovanadate. Orthovanadate's ability to attenuate protein synthesis was partially reversible, and was no longer evident when the agent was added 6 h after addition of growth factor to cells. Analysis of several elements of signaling pathways which are known to regulate protein synthesis in a positive manner (p42/p44 MAPK, AKT and p70 S6K stimulation, and hyperphosphorylation of PHAS-I) were not inhibited but rather were stimulated by orthovanadate. Thus, sodium orthovanadate is a potent inhibitor of growth factor-stimulated protein synthesis independent of p42/p44 MAPK or PI3K-p70 S6K activation.

Animals↗
PubMed2001

Phosphorylated map kinase (ERK1, ERK2) expression is associated with early tau deposition in neurones and glial cells, but not with increased nuclear DNA vulnerability and cell death, in Alzheimer disease, Pick's disease, progressive supranuclear palsy and corticobasal degeneration.

Abnormal tau phosphorylation and deposition in neurones and glial cells is one of the major features in taupathies. The present study examines the involvement of the Ras/MEK/ERK pathway of tau phosphorylation in Alzheimer disease (AD), Pick's disease (PiD), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), by Western blotting, single and double-labelling immunohistochemistry, and p21Ras activation assay. Since this pathway is also activated in several paradigms of cell death and cell survival, activated ERK expression is also analysed with double-labelling immunohistochemistry and in situ end-labelling of nuclear DNA fragmentation to visualise activated ERK in cells with increased nuclear DNA vulnerability. The MEK1 antibody recognises one band of 45 kD that identifies phosphorylation-independent MEK1, whose expression levels are not modified in diseased brains. The ERK antibody recognises one band of 42 kD corresponding to the molecular weight of phosphorylation-independent ERK2; the expression levels, as well as the immunoreactivity of ERK in individual cells, is not changed in AD, PiD, PSP and CBD. The antibody MAPK-P distinguishes two bands of 44 kD and 42 kD that detect phosphorylated ERK1 and ERK2. MAPK-P expression levels, as seen with Western blotting, are markedly increased in AD, PiD, PSP and CBD. Moreover, immunohistochemistry discloses granular precipitates in the cytoplasm of neurones in AD, mainly in a subpopulation of neurones exhibiting early tau deposition, whereas neurones with developed neurofibrillary tangles are less commonly immunostained. MAPK-P also decorates neurones with Pick bodies in PiD, early tau deposition in neurones in PSP and CBD, and cortical achromatic neurones in CBD. In addition, strong MAPK-P immunoreactivity is found in large numbers of tau-positive glial cells in PSP and CBD, as seen with double-labelling immunohistochemistry. Yet no co-localisation of enhanced phosphorylated ERK immunoreactivity and nuclear DNA fragmentation is found in AD, PiD, PSP and CBD. Finally, activated Ras expression levels are increased in AD cases when compared with controls. These results demonstrate increased phosphorylated (active) ERK expression in association with early tau deposition in neurones and glial cells in taupathies, and suggest activated Ras as the upstream activator of the MEK/ERK pathway of tau phosphorylation in AD.

Aged↗
PubMed2001

Transforming growth factor beta1 (TGF-beta1) promotes endothelial cell survival during in vitro angiogenesis via an autocrine mechanism implicating TGF-alpha signaling.

Mouse capillary endothelial cells (1G11 cell line) embedded in type I collagen gels undergo in vitro angiogenesis. Cells rapidly reorganize and form capillary-like structures when stimulated with serum. Transforming growth factor beta1 (TGF-beta1) alone can substitute for serum and induce cell survival and tubular network formation. This TGF-beta1-mediated angiogenic activity depends on phosphatidylinositol 3-kinase (PI3K) and p42/p44 mitogen-activated protein kinase (MAPK) signaling. We showed that specific inhibitors of either pathway (wortmannin, LY-294002, and PD-98059) all suppressed TGF-beta1-induced angiogenesis mainly by compromising cell survival. We established that TGF-beta1 stimulated the expression of TGF-alpha mRNA and protein, the tyrosine phosphorylation of a 170-kDa membrane protein representing the epidermal growth factor (EGF) receptor, and the delayed activation of PI3K/Akt and p42/p44 MAPK. Moreover, we showed that all these TGF-beta1-mediated signaling events, including tubular network formation, were suppressed by incubating TGF-beta1-stimulated endothelial cells with a soluble form of an EGF receptor (ErbB-1) or tyrphostin AG1478, a specific blocker of EGF receptor tyrosine kinase. Finally, addition of TGF-alpha alone poorly stimulated angiogenesis; however, by reducing cell death, it strongly potentiated the action of TGF-beta1. We therefore propose that TGF-beta1 promotes angiogenesis at least in part via the autocrine secretion of TGF-alpha, a cell survival growth factor, activating PI3K/Akt and p42/p44 MAPK.

Androstadienes↗
PubMed2000

Signaling angiogenesis via p42/p44 MAP kinase and hypoxia.

Angiogenesis is associated with a number of pathological situations. In this study, we have focused our attention on the role of p42/p44 MAP (mitogen-activated protein) kinases and hypoxia in the control of angiogenesis. We demonstrate that p42/p44 MAP kinases play a pivotal role in angiogenesis by exerting a determinant action at three levels: i) persistent activation of p42/p44 MAP kinases abrogates apoptosis; ii) p42/p44 MAP kinase activity is critical for controlling proliferation and growth arrest of confluent endothelial cells; and iii) p42/p44 MAP kinases promote VEGF (vascular endothelial growth factor) expression by activating its transcription via recruitment of the AP-2/Sp1 (activator protein-2) complex on the proximal region (-88/-66) of the VEGF promoter and by direct phosphorylation of hypoxia-inducible factor 1 alpha (HIF-1 alpha). HIF-1 alpha plays a crucial role in the control of HIF-1 activity, which mediates hypoxia-induced VEGF expression. We show that oxygen-regulated HIF-1 alpha protein levels are not affected by intracellular localization (nucleus versus cytoplasm). Finally, we propose a model which suggests an autoregulatory feedback mechanism controlling HIF-1 alpha and therefore HIF-1-dependent gene expression.

Animals↗
PubMed2000

Signaling angiogenesis via p42/p44 MAP kinase cascade.

Vascular endothelial growth factor (VEGF), a potent agonist secreted by virtually all cells, controls migration and division of vascular endothelial cells. Disruption of one VEGF allele in mice has revealed a dramatic lethal effect in early embryogenesis, suggesting a key role in vasculogenesis. We analyzed the regulation of VEGF mRNA in normal and transformed CCL39 fibroblasts and then dissected the VEGF promoter to identify the signaling pathway(s) controlling the activation of this promoter in response to growth factors, oncogenes, and hypoxic stress. We demonstrated that the p42/p44 MAP kinase signaling cascade controls VEGF expression at least at two levels. In normoxic conditions, MAPKs activate the VEGF promoter at the proximal (-88/-66) region where Sp-1/AP-2 factors bind. Activation of p42/p44 MAPKs is sufficient to turn on VEGF mRNA. At low O2 tension, hypoxia inducible factor-1 alpha (HIF-1 alpha), a limiting factor rapidly stabilized and phosphorylated, plays a key role in the expression of several genes including VEGF. We demonstrated that p42/p44MAPKs stoichiometrically phosphorylate HIF-1 alpha in vitro and that HIF-1-dependent VEGF gene expression is strongly enhanced by the exclusive activation of p42/p44MAPKs. Finally, we demonstrated that the regulation of p42/p44MAPK activity is critical for controlling proliferation and growth arrest of vascular endothelial cells at confluency. These results point to at least three major targets of angiogenesis where p42/p44 MAP kinases exert a determinant action.

Animals↗
PubMed1999

GLUT1 glucose transporter gene transcription is repressed by Sp3. Evidence for a regulatory role of Sp3 during myogenesis.

GLUT1 glucose transporters are highly expressed in proliferating and transformed cells as well as in tissues during fetal life. However, the mechanisms that regulate GLUT1 gene expression remain largely unknown. Here, we demonstrate that Sp3 proteins bind to the GLUT1 proximal promoter gene and inhibit transcriptional activity in muscle and non-muscle cells. Two different Sp3 translational products (110 and 74 kDa) derived from differential translational initiation were detected in nuclear extracts from myoblast cells, and both Sp3 protein species inhibited GLUT1 gene transcriptional activity. The inhibitory effect of Sp3 was dominant over the stimulatory effect of Sp1 on transcriptional activity of GLUT1 gene. Furthermore, abolition of Sp3 binding to the proximal promoter of GLUT1 gene completely blocked the response to Sp3. We provide evidence that the expression of Sp3 protein is subject to regulation in muscle cells and that this is likely to control GLUT1. Thus, Sp3 protein was up-regulated in the absence of changes in Sp1 early after the induction of IGF-II-dependent myogenesis. Furthermore, forced over-expression of MyoD caused an enhancement in the cellular Sp3/Sp1 ratio which was concomitant to a reduced GLUT1 expression. Later during myogenesis, Sp3 expression was substantial whereas Sp1 was markedly down-regulated. In summary, we provide direct evidence that the transcription factor Sp3 represses gene expression in non-muscle and muscle cells and this is likely to operate in fetal heart by binding to the GLUT1 gene promoter. This is the first description of a repressor of GLUT1 gene transcription. Furthermore, we propose that variations in the ratio of Sp3 versus Sp1 regulate GLUT1 promoter activity and this is crucial in the down-regulation of GLUT1 associated to myogenesis.

Animals↗
PubMed1999

p70 S6 kinase-mediated protein synthesis is a critical step for vascular endothelial cell proliferation.

In this work, we analyzed the role of the PI3K-p70 S6 kinase (S6K) signaling cascade in the stimulation of endothelial cell proliferation. We found that inhibitors of the p42/p44 MAPK pathway (PD98059) and the PI3K-p70 S6K pathway (wortmannin, Ly294002, and rapamycin) all block thymidine incorporation stimulated by fetal calf serum in the resting mouse endothelial cell line 1G11. The action of rapamycin can be generalized, since it completely inhibits the mitogenic effect of fetal calf serum in primary endothelial cell cultures (human umbilical vein endothelial cells) and another established capillary endothelial cell line (LIBE cells). The inhibitory effect of rapamycin is only observed when the inhibitor is added at the early stages of G(0)-G(1) progression, suggesting an inhibitory action early in G(1). Rapamycin completely inhibits growth factor stimulation of protein synthesis, which perfectly correlates with the inhibition of cell proliferation. In accordance with its inhibitory action on protein synthesis, activation of cyclin D1 and p21 proteins by growth factors is also blocked by preincubation with rapamycin. Expression of a p70 S6K mutant partially resistant to rapamycin reverses the inhibitory effect of the drug on DNA synthesis, indicating that rapamycin action is via p70 S6K. Thus, in vascular endothelial cells, activation of protein synthesis via p70 S6K is an essential step for cell cycle progression in response to growth factors.

Animals↗