1,721,005 research outputs found
PHARMACOLOGICAL CHARACTERIZATION OF THE SIGNAL TRANSDUCTION PATHWAYS MODULATED BY A3 RECEPTORS IN CANCER CELLS: POSSIBLE TARGETS FOR THERAPEUTIC INTERVENTION.
No full textAdenosine is an ubiquitous autacoid that modulates a variety of cellular functions through
occupancy of four cell surface G-protein-coupled receptors, named A1, A2A, A2B and A3. In
particular, adenosine was found to exert its effects on cell proliferation, clone formation ability, UV
resistance, and cell death mainly through the A3 subtype, which is highly expressed in tumor cells.
Adenosine also plays a role in the promotion of angiogenesis.
In this thesis I have characterized the signal transduction pathways modulated in hypoxia by A3
adenosine receptors in two different human tumor models: the colon cancer HT29 and the
melanoma A375 cell lines. I have performed the study in hypoxia, present in most solid tumors,
which shifts the cellular phenotype toward an increase in adenosine. Furthermore, hypoxic tumor
cells are resistant to conventional chemiotherapy and radiotherapy. I have investigated the
modulation of hypoxia-inducible factor-1 (HIF-1) through adenosine via its receptor subtypes.
HIF-1 is a transcription factor that functions as a master regulator of oxygen homeostasis. HIF-1 is
a heterodimer composed of an inducibly expressed HIF-1α subunit and a constitutively expressed
HIF-1β one. In normoxia, HIF-1α is rapidly degraded by the ubiquitin proteasome system, whereas
exposure to hypoxic conditions prevents its degradation. I have studied the signaling pathways
modulated by A3 receptors which involved Akt, MEK, and p38 MAPK.
I have demonstrated that adenosine increased in hypoxic colon carcinoma cells HIF-1α and vascular
endothelial growth factor (VEGF) through the A3 receptor stimulation. Furthermore, the stimulation
of A2B receptor increased interleukin-8 (IL-8) expression. Pretreatment of cells with caffeine, which
is a methylxanthine antagonist of adenosine receptors, significantly reduced adenosine-induced
VEGF promoter activity and VEGF and IL-8 expression. The kinases have a key role in A3 receptor
ability to enhance HIF-1α and VEGF protein expression. Moreover, Akt, ERK 1/2, and p38 MAPK
are required for the IL-8 expression increase induced by A2B receptor activation.
Then, I have examined the modulation of IL-8, VEGF and HIF-1 by the DNA-damaging agents
etoposide and doxorubicin, and I have analyzed the influence of the adenosinergic signaling on the
chemotherapeutic drug effects. I have demonstrated that A2B receptor blockade can impair IL-8
production, whereas blocking A3 receptors, it is possible to further decrease VEGF secretion in
melanoma cells treated with etoposide and doxorubicin. The response to adenosine was generated at
the cell surface because the inhibition of A3 receptor expression, by using small interfering RNA,
abolished nucleoside effects. Exposure of melanoma cells to the chemotherapeutic drugs resulted in
the increase of p38, Akt and ERK1/2 phosphorylation levels. Moreover, etoposide and doxorubicin
strongly inhibited HIF-1α protein expression. The A2B receptor antagonist MRE 2029F20 attenuated
the increase in p38, Akt and ERK1/2 phosphorylation levels induced by the chemotherapeutic
drugs, and when used alone it reduced p38, Akt and ERK1/2 phosphorylation basal levels. The A3
receptor antagonist MRE 3008F20 alone reduced HIF-1α protein, and in combination with the
chemotherapeutic drugs further decreased HIF-1α protein accumulation. Therefore, the results of
this thesis provide evidence of how human tumor growth may be influenced through the
adenosinergic system and how the adenosine receptors modulation may be useful for refining the
use of chemotherapeutic drugs to treat human cancer more effectively
Regulation of Second Messenger Systems and Intracellular Pathways.
No full textThe A3 adenosine receptor is a G protein-coupled receptor linked to classical second messenger pathways such as those for cAMP production and phospholipase C. In addition, the receptor couples to mitogen-activated protein kinases (MAPK) and to the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway which could give it a role in cell growth, survival, death and differentiation. Interestingly, the A3 receptor has recently been linked to the hypoxia-inducible factor 1 (HIF-1), the main transcription factor regulating the cellular responses to hypoxia. The focus of this chapter centres on downstream mediators of A3 adenosine receptor signaling
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Increase of VEGF and Fibronectin expression and ultrastructural alterations of intercellular junctions in a swab negative patient after SARS-COV-2 infection
No full textBackground: SARS-CoV-2 infection has been responsible of COrona VIrus Disease (COVID-19) pandemia and can cause a variety of symptoms including gastrointestinal disorders, abdominal pain and liver injury. The host receptor for SARS-CoV-2, ACE2, is expressed in gut and SARS-CoV-2 infection could induce vascular damage and immune system dysregulation, creating an inflammatory and hypercoagulable state, as widely described at the lung level. Case presentation: This work presents the case of a middle-aged Caucasian man admitted to the Hospital Emergency Department from the University Hospital of Ferrara (Italy), complaining of pain in the upper and middle region of the abdomen. The patient tested negative to the nose-oropharyngeal swab for SARS-CoV-2 four weeks after recovering from viral infection. The patient required resection of a segment of ileum and an ulcer of the bowel wall was recognized and sampled. Previous published results had confirmed the presence of the SARS-CoV-2 nucleocapsid protein, an increased human leukocyte antigen (HLA-G) and an altered morphology of microvilli in the ulcerated ileum of the patient when compared to the non-ulcerated ileum. The present study sought to deepen the consequences of SARS-CoV-2 infection. To this end, we evaluated the expression and co-expression of Vascular Endothelial Growth Factor (VEGF) and Fibronectin by immunohistochemical techniques. VEGF immunohistochemical expression was higher in the ulcer than in the control ileum sample and the non-ulcerated ileum areas and co-expressed with the SPIKE protein. Fibronectin staining was lower in control sample than in non-ulcerated and ulcerated ileum. Electron microscopy analysis showed alterations of the integrity of the intestinal barrier in the ulcerated area when compared to the non-ulcerated ileum or to the control sample. Conclusions: Although the patient was tested negative to nose-oropharyngeal swab for SARS-CoV-2, the SPIKE protein was detected in his terminal ileum, especially in the ulcerated areas. The presence of the viral protein was also associated with an increase of VEGF and Fibronectin. In addition to vascular changes, the SARS-CoV-2 infection altered the junctional apparatus among epithelial cells, making the tissue even more fragile and thus susceptible to the entry of pathogens and the development of further infections
The Complexity of the Tumor Microenvironment and Its Role in Acute Lymphoblastic Leukemia: Implications for Therapies
No full textThe microenvironment that surrounds a tumor, in addition to the tumor itself, plays an important role in the onset of resistance to molecularly targeted therapies. Cancer cells and their microenvironment interact closely between them by means of a molecular communication that mutually influences their biological characteristics and behavior. Leukemia cells regulate the recruitment, activation and program of the cells of the surrounding microenvironment, including those of the immune system. Studies on the interactions between the bone marrow (BM) microenvironment and Acute Lymphoblastic Leukemia (ALL) cells have opened a scenario of potential therapeutic targets which include cytokines and their receptors, signal transduction networks, and hypoxia-related proteins. Hypoxia also enhances the formation of new blood vessels, and several studies show how angiogenesis could have a key role in the pathogenesis of ALL. Knowledge of the molecular mechanisms underlying tumor-microenvironment communication and angiogenesis could contribute to the early diagnosis of leukemia and to personalized molecular therapies. This article is part of a Special Issue entitled: Innovative Multi-Disciplinary Approaches for Precision Studies in Leukemia edited by Sandra Marmiroli (University of Modena and Reggio Emilia, Modena, Italy) and Xu Huang (University of Glasgow, Glasgow, United Kingdom)
Binding thermodynamics at the human cannabinoid CB1 and CB2 receptors
No full textThe thermodynamic parameters ΔG°, ΔH° and ΔS° of the binding equilibrium of agonists and antagonists at cannabinoid CB1 and CB2 receptors were determined by means of affinity measurements at different temperatures and van't Hoff plots were constructed. Affinity constants were measured on CHO cells transfected with the human CB1 and CB2 receptors by inhibition assays of the binding of the cannabinoid receptor agonist [3H]-CP-55,940. van't Hoff plots were linear for agonists and antagonists in the temperature range 0-30 °C. The thermodynamic parameters for CB1 receptors fall in the ranges 17 ≤ ΔH° ≤ 59 kJ/mol and 213 ≤ ΔS° ≤ 361 kJ/mol for agonists and -52 ≤ ΔH° ≤ -26 kJ/mol and -12 ≤ ΔS° ≤ 38 kJ/mol for antagonists. The thermodynamic parameters for CB2 receptors fall in the ranges 27 ≤ ΔH° ≤ 48 kJ/mol and 234 ≤ ΔS° ≤ 300 kJ/mol for agonists and -19 ≤ ΔH° ≤ -17 kJ/mol and 43 ≤ ΔS° ≤ 74 kJ/mol for antagonists. Collectively, these data show that agonist binding is always totally entropy-driven while antagonist binding is enthalpy and entropy-driven, indicating that CB1 and CB2 receptors are thermodynamically discriminated. These data could give new details on the nature of the forces driving the CB1 and CB2 binding at a molecular level. Enthalpy, entropy, free energy and binding affinity for each ligand to its receptor can all be assessed and therefore the optimal binding profile discovered. Carrying out these binding investigations as early as possible in the discovery process increases the probability that a lead compound will become a successful pharmaceutical compound
Optical tissue clearing associated with 3D imaging: application in preclinical and clinical studies
No full textUnderstanding the inner morphology of intact tissues is one of the most competitive challenges in modern biology. Since the beginning of the twentieth century, optical tissue clearing (OTC) has provided solutions for volumetric imaging, allowing the microscopic visualization of thick sections of tissue, organoids, up to whole organs and organisms (for example, mouse or rat). Recently, tissue clearing has also been introduced in clinical settings to achieve a more accurate diagnosis with the support of 3D imaging. This review aims to give an overview of the most recent developments in OTC and 3D imaging and to illustrate their role in the field of medical diagnosis, with a specific focus on clinical applications. GRAPHICAL ABSTRACT: [Image: see text
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Physical training interventions for children and teenagers affected by acute lymphoblastic leukemia and related treatment impairments
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