Biomedical subjects

Paola De Paolis

Publications and source records attributed to Paola De Paolis.

10 recordsLinked to original sources

PubMed2006

Cardiac resynchronization therapy increases plasma levels of the endogenous inotrope apelin.

BACKGROUND: Cardiac resynchronization therapy (CRT) has been introduced to treat drug refractory chronic heart failure (CHF). Apelin, the endogenous ligand of the APJ receptor, is under evaluation for its potential role in human CHF pathophysiology. This study aims to assess whether biventricular pacing affects plasma apelin levels in patients with severe CHF. METHODS AND RESULTS: Fourteen patients (9 men, 5 women, mean age 68+/-13 years) undergoing biventricular pace-maker/ICD implantation were studied. Patients underwent baseline clinical and echocardiographic evaluation, and assessment of plasma apelin and NT-proBNP levels. The evaluation was repeated 48 h and 9+/-2 months after device implantation to assess the acute and chronic effects of CRT on apelin and NT-proBNP levels. Eight healthy age- and sex-matched subjects served as controls. In CHF patients, baseline apelin levels were reduced and NT-proBNP increased compared to control subjects (apelin: 0.47+/-0.2 vs. 0.97+/-0.3 ng/mL, p<0.001; NT-proBNP: 2007+/-114 vs. 229+/-72 pmol/L, p<0.001). Short-term evaluation did not reveal any effect of CRT on apelin or NT-proBNP levels. By contrast, at 9+/-2 months follow-up, CRT responders showed left ventricular reverse remodelling and an increase in ejection fraction, together with a significant increase in plasma apelin levels (0.99+/-0.1 vs. 0.47+/-0.2 ng/mL, p<0.001) and decrease in NT-proBNP (938+/-591 vs. 2007+/-114 pmol/L, p<0.05). CONCLUSIONS: Long-term CRT increases plasma levels of the endogenous inotrope apelin in patients with CHF.

Aged↗

PubMed2005

Angiotensin II type 2 receptors contribute to vascular responses in spontaneously hypertensive rats treated with angiotensin II type 1 receptor antagonists.

BACKGROUND: Vasoconstrictive, proliferative and oxidative effects of angiotensin II (Ang II) are mediated by Ang II type 1 (AT1) receptors. The effects of Ang II via the Ang II type 2 (AT2) receptor subtype (AT2R) are less well defined. Growing evidence shows the existence of cross-talk between the Ang II receptor subtypes, which is revealed by AT1R blockade. Hence, under certain conditions, AT2R may act as an antagonistic system with respect to the AT1R. METHODS: The present study was designed to investigate the effects of long-term treatment with the AT1R antagonist losartan on the AT2R-mediated response to Ang II in thoracic aortas isolated from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Untreated animals from both groups were used as controls. The mRNA expression of AT1R and AT2R was measured by reverse transcription-polymerase chain reaction. RESULTS: During contraction in response to norepinephrine, Ang II induced concentration-dependent relaxation only in aortas isolated from SHR chronically treated with losartan (8 weeks; 30 mg/kg/day in drinking water). These relaxations were inhibited by the selective AT2R blocker PD123319, N(G)-nitro-L-arginine methyl ester (L-NAME), and B2receptor antagonist HOE-140. Accordingly, nitric oxide (NO) production was increased by Ang II only in the aortas of treated SHR. After AT1R blockade, AT2R mRNA was significantly increased. These findings demonstrate that, in hypertensive rats, chronic AT1R blockade is associated with an inverted vasomotor response to Ang II via AT2R-mediated NO production. CONCLUSIONS: The losartan-unmasked AT2R-vasorelaxation could significantly contribute to the beneficial hemodynamic effects of AT1R blockade. In view of this, our study highlights the importance of the integrated Ang II receptor network, which may help to define further the mechanisms of the well-established vascular protective effects of AT1R blockers.

Acetylcholine↗

PubMed2004

In the search for stroke genes: a long and winding road.

In spite of a significant improvement in control of numerous predisposing risk factors, stroke remains a major health problem and a common cause of death and disability in our societies. Genetic predisposition to stroke development exists and has been documented in both animal models and in humans. However, a precise definition of genetic factors responsible for common forms of stroke is still lacking, mainly due to its complex nature, the confounding presence of other predisposing risk factors, and the genetic heterogeneity of human populations. In contrast, important breakthroughs have been reached for monogenic forms of stroke, such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). An animal model of stroke, the stroke-prone spontaneously hypertensive rat, has provided valuable information on genetic factors involved in stroke predisposition. Among them, the gene-encoding atrial natriuretic peptide has been identified as a stroke gene in both the stroke-prone spontaneously hypertensive rat and, subsequently, in two different human populations. In particular, structural alterations of the gene are consistently present in diseased individuals, suggesting an important role of mutation-dependent mechanisms in stroke predisposition. Finally, the recent use of intermediate disease phenotypes provides a reductionist approach that may contribute to important accumulating information on genes contributing to cerebrovascular accidents.

Animals↗

PubMed2004

Gene polymorphisms of the renin-angiotensin-aldosterone system and the risk of ischemic stroke: a role of the A1166C/AT1 gene variant.

OBJECTIVE: The role of the renin-angiotensin-aldosterone system (RAAS) genes on predisposition to develop stroke, a multifactorial and polygenic cardiovascular trait, is still under investigation. In the present study we characterized the contributory role of RAAS genes in the susceptibility to develop ischemic stroke in humans. METHODS: Allele and genotype frequencies of RAAS genes were characterized in a population of 215 cases (including only atherothrombotic and lacunar forms) and 236 controls selected in Sardinia, a large Mediterranean island with a well-known segregated population. Statistical analysis was performed in the whole population and, based on a significant interaction between angiotensin II receptor (AT1) genotype and hypertension, was also repeated in the hypertensive subgroup. RESULTS: A significant association of the C1166/AT1 gene allelic variant with stroke was found when assuming a dominant model of transmission [unadjusted odds ratio (OR)=1.5, 95% confidence interval (CI) 1.1-2.2, P=0.024]. The strength of the association became more evident in the subgroup of hypertensive individuals (135 cases and 110 controls). In fact, in this cohort the independent OR for the AT1 gene was 2.1, 95% CI 1.2-3.7, P=0.006 in the dominant model and 2.0, 95% CI 1.3-3.2, P=0.002 in the additive model. No other RAAS gene was identified as a contributor to stroke. CONCLUSIONS: Our findings support a predisposing role of an AT1 gene variant in the development of ischemic stroke. In particular, the AT1 gene variant exerted a major impact on ischemic stroke occurrence in the presence of hypertension.

Aged↗

PubMed2003

High glucose causes upregulation of cyclooxygenase-2 and alters prostanoid profile in human endothelial cells: role of protein kinase C and reactive oxygen species.

BACKGROUND: Prostaglandins generated by cyclooxygenase (COX) have been implicated in hyperglycemia-induced endothelial dysfunction. However, the role of individual COX isoenzymes as well as the molecular mechanisms linking oxidative stress and endothelial dysfunction in diabetes remains to be clarified. METHODS AND RESULTS: Human aortic endothelial cells were exposed to normal (5.5 mmol/L) and high (22.2 mmol/L) glucose. Glucose selectively increased mRNA and protein expression of COX-2. Its upregulation was associated with an increase of thromboxane A2 and a reduction of prostacyclin (PGI2) release. Glucose-induced activation of PKC resulted in the formation of peroxynitrite and tyrosine nitration of PGI2 synthase. NO release was reduced despite 2-fold increase of endothelial NO synthase expression. Phorbol ester caused an increase of COX-2 and endothelial NO synthase expression similar to that elicited by glucose. These effects were prevented by the PKC inhibitor calphostin C. N-acetylcysteine, vitamin C, and calphostin C prevented ROS formation, restored NO release, and reduced colocalization of nitrotyrosine and PGI2 synthase. Expression of p22(phox), a subunit of NAD(P)H oxidase, was increased, and diphenyleneiodonium inhibited ROS formation. By contrast, indomethacin did not affect glucose-induced ROS generation. CONCLUSIONS: Thus, high glucose, via PKC signaling, induces oxidative stress and upregulation of COX-2, resulting in reduced NO availability and altered prostanoid profile.

Cells, Cultured↗

PubMed2003

p300/cAMP-response-element-binding-protein ('CREB')-binding protein (CBP) modulates co-operation between myocyte enhancer factor 2A (MEF2A) and thyroid hormone receptor-retinoid X receptor.

Thyroid hormone receptors (TRs) and members of the myocyte enhancer factor 2 (MEF2) family are involved in the regulation of muscle-specific gene expression during myogenesis. Physical interaction between these two factors is required to synergistically activate gene transcription. p300/cAMP-response-element-binding-protein ('CREB')-binding protein (CBP) interacting with transcription factors is able to increase their activity on target gene promoters. We investigated the role of p300 in regulating the TR-MEF2A complex. To this end, we mapped the regions of these proteins involved in physical interactions and we evaluated the expression of a chloramphenicol acetyltransferase (CAT) reporter gene in U2OS cells under control of the alpha-myosin heavy chain promoter containing the thyroid hormone response element (TRE). Our results suggested a role of p300/CBP in mediating the transactivation effects of the TR-retenoid X receptor (RxR)-MEF2A complex. Our findings showed that the same C-terminal portion of p300 binds the N-terminal domains of both TR and MEF2A, and our in vivo studies demonstrated that TR, MEF2A and p300 form a ternary complex. Moreover, by the use of CAT assays, we demonstrated that adenovirus E1A inhibits activation of transcription by TR-RxR-MEF2A-p300 but not by TR-RxR-MEF2A. Our data suggested that p300 can bind and modulate the activity of TR-RxR-MEF2A at TRE. In addition, it is speculated that p300 might modulate the activity of the TR-RxR-MEF2A complex by recruiting a hypothetical endogenous inhibitor which may act like adenovirus E1A.

Animals↗

PubMed2003

Angiotensin II AT2 receptor subtype: an uprising frontier in cardiovascular disease?

The renin-angiotensin system (RAS) plays a pivotal role in the regulation of fluid, electrolyte balance and blood pressure, and is a modulator of cellular growth and proliferation. Biological actions of RAS are linked to the binding of the effector molecule, angiotensin II (AngII), to specific membrane receptors, mostly the AT1 subtype and, to a lesser extent, other subtypes. Following the identification and characterization of the AT2 subtype receptor, it has been proposed that a complex interaction between AngII and its receptors may play an important role in the effects of RAS. In this paper current information on AngII subtype receptors--their structure, regulation and intracellular signalling--are reviewed, with a particular emphasis on the potential relevance for cardiovascular pathophysiology. In addition, we discuss modulation of expression of the AT2 receptor and its interaction with the AT1 receptor subtype, as well as the potential effects of this receptor on blood pressure regulation. A better understanding of the integrated effects of the AngII subtype receptors may help to elucidate the function of the RAS, as well as their participation in the mechanisms of cardiovascular disease and attendant therapeutic implications.

Animals↗

PubMed2002

Effect of a regulatory mutation on the rat atrial natriuretic peptide gene transcription.

To investigate the functional relevance of a regulatory mutation affecting the enhancer element PEA2 of the rat ANP gene we transfected rat cardiomyocytes and aortic endothelial cells with either the mutant or the wild-type ANP promoter construct (-683 +54) and performed CAT assays both at baseline and in response to Phenylephrine and Angiotensin II. In the myocardial cells we also determined the DNA/nuclear protein interaction through electrophoretic mobility shift assay. These studies showed a significantly lower degree of ANP transcription in the presence of the mutant PEA2 site, thus demonstrating its functional significance and the biological relevance of ANP gene structural alterations.

Animals↗

PubMed2002

Functional cross-talk between angiotensin II and epidermal growth factor receptors in NIH3T3 fibroblasts.

BACKGROUND: The main angiotensin (Ang) II subtype receptors (AT1R and AT2R) are involved in cellular growth processes and exert functionally antagonistic effects. OBJECTIVE: To characterize the mechanisms by which Ang II receptors influence growth, by investigating the interactions between Ang II subtype receptors and epidermal growth factor (EGF) receptors on mitogen-activated protein kinase (MAPK) pathway activation. DESIGN AND METHODS: The experiments were performed using a mouse fibroblast cell line, NIH3T3, by transient co-transfection with rat AT1R or AT2R expression vectors, or both. Extracellular-signal-regulated kinase (ERK)1/2 phosphorylation was analysed by western blot and the ERK activity was evaluated using PathDetect, an in-vivo signal transduction pathway trans-reporting system. Selective Ang II receptor antagonists (losartan for AT1R and PD123319 for AT2R) were used to investigate the contributions of each receptor to the response observed. RESULTS: Our data show that, in this cellular model, both Ang II receptors phosphorylate ERK1/2. However, in the cells expressing AT1R, the EGF-induced MAPK pathway was enhanced in the presence of Ang II in a synergistic fashion. In contrast, a reduction of EGF-induced MAPK activation was observed in the cells expressing AT2R. In cells expressing both Ang II subtype receptors, Ang II promoted an enhancement of EGF-induced MAPK activation. However, in the presence of the AT1R antagonist, losartan, the effect of EGF was reduced. CONCLUSION: These data indicate the existence of an opposite cross-talk of AT1R and AT2R with EGF receptors, and suggest a complex functional interaction between these pathways in the regulation of cellular growth processes.

3T3 Cells↗

PubMed2002

The renin-angiotensin system as a risk factor and therapeutic target for cardiovascular and renal disease.

The renin-angiotensin system (RAS) plays an important homeostatic role in BP regulation, water and salt balance, and tissue growth control under physiologic conditions. On the other hand, a pivotal involvement of the RAS in the pathophysiology of cardiovascular and renal disease is extensively supported by both basic and clinical evidence. In particular, it is today recognized that angiotensin II (AngII), the biologic effector of the RAS, may prompt a number of relevant structural and functional abnormalities through the activation of a complex of cellular effects mostly mediated via its binding with the AT(1) subtype receptors. The key role of these AngII-linked mechanisms of disease is strongly corroborated by large interventional studies. In fact, pharmacologic interference with RAS activity, by both preventing AngII formation with angiotensin-converting enzyme inhibitors or antagonizing its binding to cell membrane receptors by selective antagonists, is associated with highly beneficial outcomes in major disease conditions (hypertension, diabetes, renal failure, heart failure, myocardial infarction, stroke, and others). This article briefly reviews the current views on the biologic organization of RAS evidence supporting a pathogenic role of the RAS activity in promoting cardiac, vascular, and renal disease, and finally provides the basis for considering inhibition of RAS activity a major target for therapeutic interventions in these conditions.

Cardiovascular Diseases↗