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Biomedical subjects

Fernando A González

Publications and source records attributed to Fernando A González.

At least 19 recordsLinked to original sources
PubMed2007

P2Y2 receptors induced cell surface redistribution of alpha(v) integrin is required for activation of ERK 1/2 in U937 cells.

Nucleotides released from cells due to stress, injury or inflammation, induce mitogenic effects in monocytes via activation of P2Y(2) nucleotide receptors (P2Y(2)Rs). Here we show that P2Y(2) nucleotide receptors in U937 monocytic cells regulate the activation of extracellular signal-regulated kinases 1 and 2 (ERK 1/2) by inducing the clustering of alpha(v) integrins. The activation of phosphatidylinositol 3-kinase by P2Y(2)R ligands was required for alpha(v) clustering, suggesting a means whereby two different classes of receptors communicate to induce mitogenic responses in monocytic cells. P2Y(2)R-induced alpha(v) clustering was also associated with a flattened phenotype of the U937 cells, consistent with the role of the P2Y(2)R in regulating early events in cell migration.

Calcium↗
PubMed2006

First Spanish case of thalassemia major due to a compound heterozygosity for the IVS-II-848 (C --> A) and codon 39 (C --> T) mutations of the beta-globin gene.

This report describes the first case in Spain of a severe form of beta-thalassemia (thal) due to a compound heterozygosity for the IVS-II-848 (C --> A) and the nonsense codon 39 (C --> T) mutations. Five members of a family from Cadiz (southern Spain) were studied. The proband was an 8-year-old girl diagnosed as anemic at the age of 13 months. Her father had the codon 39 (C --> T) mutation and her mother the C --> A change at nucleotide (nt) 848 of IVS-II. Haplotype analysis showed that the proband was a compound heterozygote for haplotypes I [+ --> + +] and VII [+ --> +]. This is the first description in Spain of the IVS-II-848 (C --> A) mutation. It appears, from restriction fragment length polymorphism (RFLP) analysis, that this mutation has a different origin in the various populations, where it was found. This observation shows that in this case the association of a beta(0)- and a beta(+)-thal mutation does not lead to a thalassemia intermedia but to a severe thalassemia with very low hemoglobin (Hb) levels. From a therapeutic point of view, early introduction of a transfusion regimen may improve the clinical picture of these children, allowing for better development and growth.

Adolescent↗
PubMed2006

Hb La Coruña [beta38(C4)Thr-->Ile]: a new hemoglobin variant leading to familial polycythemia.

Hb La Coruña [beta38(C4)Thr --> Ile] is a new hemoglobin (Hb) variant that has an increased oxygen affinity. Clinically, this Hb leads to erythrocytosis. Hb La Coruña is an electrophoretically silent variant that can be detected by reversed phase high performance liquid chromatography (HPLC) and characterized by DNA sequencing. The patient was a 22-year-old Spanish male whose family lived in La Coruña, in the northwest of Spain. His mother was also a carrier.

Adult↗
PubMed2005

P2Y2 nucleotide receptors enhance alpha-secretase-dependent amyloid precursor protein processing.

The amyloid precursor protein (APP) is proteolytically processed by beta- and gamma-secretases to release amyloid beta, the main component in senile plaques found in the brains of patients with Alzheimer disease. Alternatively, APP can be cleaved within the amyloid beta domain by alpha-secretase releasing the non-amyloidogenic product sAPP alpha, which has been shown to have neuroprotective properties. Several G protein-coupled receptors are known to activate alpha-secretase-dependent processing of APP; however, the role of G protein-coupled nucleotide receptors in APP processing has not been investigated. Here it is demonstrated that activation of the G protein-coupled P2Y2 receptor (P2Y2R) subtype expressed in human 1321N1 astrocytoma cells enhanced the release of sAPP alpha in a time- and dose-dependent manner. P2Y2 R-mediated sAPP alpha release was dependent on extracellular calcium but was not affected by 1,2-bis(2-aminophenoxy)ethane-N,N,N,-trimethylammonium salt, an intracellular calcium chelator, indicating that P2Y2R-stimulated intracellular calcium mobilization was not involved. Inhibition of protein kinase C (PKC) with GF109203 or by PKC down-regulation with phorbol ester pre-treatment had no effect on UTP-stimulated sAPP alpha release, indicating a PKC-independent mechanism. U0126, an inhibitor of the mitogen-activated protein kinase pathway, partially inhibited sAPPalpha release by UTP, whereas inhibitors of Src-dependent epidermal growth factor receptor transactivation by P2Y2Rs had no effect. The metalloprotease inhibitors phenanthroline and TAPI-2 and the furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone also diminished UTP-induced sAPP alpha release. Furthermore, small interfering RNA silencing of an endogenous adamalysin, ADAM10 or ADAM17/TACE, partially suppressed P2Y2R-activated sAPP alpha release, whereas treatment of cells with both ADAM10 and ADAM17/TACE small interfering RNAs completely abolished UTP-activated sAPP alpha release. These results may contribute to an understanding of the non-amyloidogenic processing of APP.

ADAM Proteins↗
PubMed2005

Synthesis of a novel series of 2-methylsulfanyl fatty acids and their toxicity on the human K-562 and U-937 leukemia cell lines.

The hitherto unknown 2-methylsulfanyldecanoic acid and 2-methylsulfanyldodecanoic acid were synthesized from methyl decanoate and methyl dodecanoate, respectively, through the reaction of lithium diisopropylamide and dimethyldisulfide in THF followed by saponification with potassium hydroxide in ethanol. Both alpha-methylsulfanylated FA were cytotoxic to the human chronic myelogenous leukemia K-562 and the human histiocytic lymphoma U-937 cell lines with EC50 values in the 200-300 microM range, which makes them more cytotoxic to these cell lines than decanoic and/or dodecanoic acid. The cytotoxicity of the studied FA toward K-562 followed the order 2-SCH3-12:0 > 2-SCH3-10:0 > 10:0 > 12:0 > 2-OCH3-12:0, whereas toward U-937 the cytotoxicity was 2-SCH3-10:0 > 2-SCH3-12:0 > 12:0 > 10:0 > 2-OCH3-12:0. These results indicate that the alpha-methylsulfanyl substitution increases the cytotoxicity of the C10 and C12 FA toward the studied leukemia cell lines.

Amsacrine↗
PubMed2005

The first case of Hb E-Saskatoon associated with Hb Lepore-Baltimore found in Spain.

Hb E-Saskatoon [beta22(B4)Glu-->Lys] does not cause any clinical symptoms in the heterozygous state. The homozygous state shows moderate phenotype expression. It has also been detected in association with beta-thalassemia. We present the first case of Hb E-Saskatoon associated with Hb Lepore-Baltimore. This unusual combination of mutations does not aggravate the clinical picture, as only microcytosis and hypochromia have been observed. Hb E-Saskatoon can only be correctly characterized by ion exchange high performance liquid chromatography (HPLC) or by DNA sequencing.

Adult↗
PubMed2005

Phospholipase A2 in astrocytes: responses to oxidative stress, inflammation, and G protein-coupled receptor agonists.

Astrocytes comprise the major cell type in the central nervous system (CNS) and they are essential for support of neuronal functions by providing nutrients and regulating cell-to-cell communication. Astrocytes also are immune-like cells that become reactive in response to neuronal injury. Phospholipases A2 (PLA2) are a family of ubiquitous enzymes that degrade membrane phospholipids and produce lipid mediators for regulating cellular functions. Three major classes of PLA2 are expressed in astrocytes: group IV calcium-dependent cytosolic PLA2 (cPLA2), group VI calcium-independent PLA2 (iPLA2), and group II secretory PLA2(sPLA2). Upregulation of PLA2 in reactive astrocytes has been shown to occur in a number of neurodegenerative diseases, including stroke and Alzheimer's disease. This review focuses on describing the effects of oxidative stress, inflammation, and activation of G protein-coupled receptors on PLA2 activation, arachidonic acid (AA) release, and production of prostanoids in astrocytes.

Animals↗
PubMed2005

Mechanisms for inhibition of P2 receptors signaling in neural cells.

Trophic factors are required to ensure neuronal viability and regeneration after neural injury. Although abundant information is available on the factors that cause the activation of astrocytes, little is known about the molecular mechanisms underlying the regulation of this process. Nucleotides released into the extracellular space from injured or dying neural cells can activate astrocytes via P2 nucleotide receptors. After a brief historical review and update of novel P2 receptor antagonists, this article focuses on recent advancements toward understanding molecular mechanisms that regulate G protein-coupled P2Y receptor signaling. Among P2Y receptor subtypes, the heptahelical P2Y2 nucleotide receptor interacts with vitronectin receptors via an RGD sequence in the first extracellular loop, and this interaction is required for effective signal transduction to activate mitogen-activated protein kinases ERK1/2, to mobilize intracellular calcium stores via activation of phospholipase C, protein kinase C isoforms, and to activate focal adhesion kinase and other signaling events. Ligation of vitronectin receptors with specific antibodies caused an inhibition of P2Y2 receptor-induced ERK1/2 and p38 phosphorylation and P2Y2 receptor-induced cytoskeleton rearrangement and DNA synthesis. Structure-function studies have identified agonist-induced phosphorylation of the C-terminus of the P2Y2 receptor, an important mechanism for receptor desensitization. Understanding selective mechanisms for regulating P2Y2 receptor signaling could provide novel targets for therapeutic strategies in the management of brain injury, synaptogenesis, and neurological disorders.

Animals↗
PubMed2005

Molecular determinants of P2Y2 nucleotide receptor function: implications for proliferative and inflammatory pathways in astrocytes.

In the mammalian nervous system, P2 nucleotide receptors mediate neurotransmission, release of proinflammatory cytokines, and reactive astrogliosis. Extracellular nucleotides activate multiple P2 receptors in neurons and glial cells, including G protein-coupled P2Y receptors and P2X receptors, which are ligand-gated ion channels. In glial cells, the P2Y2 receptor subtype, distinguished by its ability to be equipotently activated by ATP and UTP, is coupled to pro-inflammatory signaling pathways. In situ hybridization studies with rodent brain slices indicate that P2Y2 receptors are expressed primarily in the hippocampus and cerebellum. Astrocytes express several P2 receptor subtypes, including P2Y2 receptors whose activation stimulates cell proliferation and migration. P2Y2 receptors, via an RGD (Arg-Gly-Asp) motif in their first extracellular loop, bind to alphavbeta3/beta5 integrins, whereupon P2Y2 receptor activation stimulates integrin signaling pathways that regulate cytoskeletal reorganization and cell motility. The C-terminus of the P2Y2 receptor contains two Src-homology-3 (SH3)-binding domains that upon receptor activation, promote association with Src and transactivation of growth factor receptors. Together, our results indicate that P2Y2 receptors complex with both integrins and growth factor receptors to activate multiple signaling pathways. Thus, P2Y2 receptors present novel targets to control reactive astrogliosis in neurodegenerative diseases.

Amino Acid Sequence↗
PubMed2004

[Hemoglobin Korle-Bu [beta73(E17)Asp ->Asn]. First cases described in Spain].

BACKGROUND AND OBJECTIVE: Hemoblobin Korle-Bu [beta73(E17)Asp->Asn], also known as hemoglobin GACCRA, is frequent in African colour population. The interest of this work has been confirmed that hemoglobin Korle-Bu is a structural variant which mutation is located in the CD73 (GAT->AAT) of the exon 2 of beta gene and that this characterises has been made in the first cases found in Spanish population. Where to be carrier of African hemoglobins is less frequent. PATIENTS AND METHOD: Two unrelated families (4 subjects) from the same geographical area were studied because all of them shown an abnormal hemoglobin during a screening program of hemoglobinopathies in blood donors. Electrophoretic methods and ion exchange HPLC studied this hemoglobin. Globin chains are studied by reverse phase HPLC. Automatic sequencing carried out the molecular study. RESULTS: In the electrophoretic study and by ion exchange HPLC was observed an abnormal hemoglobin. The study of globin chains by reverse phase HPLC revealed the presence of three peaks betaX, betaA y alpha. In all the cases, the P50 was increased. The molecular study by sequencing revealed the substitution GAT->AAT in the codon 73 of beta gene globin. This variant of haemoglobin is named hemoglobin Korle-Bu [beta73(E17)Asp->Asn]. CONCLUSIONS: This hemoglobin variant becomes important when it is associated with hemoglobin S or C because, although it is not associated with a clinical picture severe, when this hemoglobin is associated with another kind of alterations of hemoglobin molecule (thalassemias or hemoglobinopathies) the clinical could be more severe. So, it is important its genetic characterization for the diagnoses of the serious forms.

Female↗
PubMed2004

The P2Y2 nucleotide receptor mediates vascular cell adhesion molecule-1 expression through interaction with VEGF receptor-2 (KDR/Flk-1).

UTP stimulates the expression of pro-inflammatory vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells through activation of the P2Y(2) nucleotide receptor P2Y(2)R. Here, we demonstrated that activation of the P2Y(2)R induced rapid tyrosine phosphorylation of vascular endothelial growth factor receptor (VEGFR)-2 in human coronary artery endothelial cells (HCAEC). RNA interference targeting VEGFR-2 or inhibition of VEGFR-2 tyrosine kinase activity abolishes P2Y(2)R-mediated VCAM-1 expression. Furthermore, VEGFR-2 and the P2Y(2)R co-localize upon UTP stimulation. Deletion or mutation of two Src homology-3-binding sites in the C-terminal tail of the P2Y(2)R or inhibition of Src kinase activity abolished the P2Y(2)R-mediated transactivation of VEGFR-2 and subsequently inhibited UTP-induced VCAM-1 expression. Moreover, activation of VEGFR-2 by UTP leads to the phosphorylation of Vav2, a guanine nucleotide exchange factor for Rho family GTPases. Using a binding assay to measure the activity of the small GTPases Rho, we found that stimulation of HCAEC by UTP increased the activity of RhoA and Rac1 (but not Cdc42). Significantly, a dominant negative form of RhoA inhibited P2Y(2)R-mediated VCAM-1 expression, whereas expression of dominant negative forms of Cdc42 and Rac1 had no effect. These data indicate a novel mechanism whereby a nucleotide receptor transactivates a receptor tyrosine kinase to generate an inflammatory response associated with atherosclerosis.

Amino Acid Sequence↗
PubMed2004

P2Y receptors activate neuroprotective mechanisms in astrocytic cells.

Mechanical or ischemic trauma to the CNS causes the release of nucleotides and other neurotransmitters into the extracellular space. Nucleotides can activate nucleotide receptors that modulate the expression of genes implicated in cellular adaptive responses. In this investigation, we used human 1321N1 astrocytoma cells expressing a recombinant P2Y2 receptor to assess the role of this receptor in the regulation of anti-apoptotic (bcl-2 and bcl-xl) and pro-apoptotic (bax) gene expression. Acute treatment with the P2Y2 receptor agonist UTP up-regulated bcl-2 and bcl-xl, and down-regulated bax, gene expression. Activation of P2Y2 receptors was also coupled to the phosphorylation of cyclic AMP responsive element binding protein that positively regulates bcl-2 and bcl-xl gene expression. Cyclic AMP responsive element decoy oligonucleotides markedly attenuated the UTP-induced increase in bcl-2 and bcl-xl mRNA levels. Activation of P2Y2 receptors induced the phosphorylation of the pro-apoptotic factor Bad and caused a reduction in bax/bcl-2 mRNA expression ratio. All these signaling pathways are known to be involved in cell survival mechanisms. Using cDNA microarray analysis and RT-PCR, P2Y2 receptors were found to up-regulate the expression of genes for neurotrophins, neuropeptides and growth factors including nerve growth factor 2; neurotrophin 3; glia-derived neurite-promoting factor, as well as extracellular matrix proteins CD44 and fibronectin precursor--genes known to regulate neuroprotection. Consistent with this observation, conditioned media from UTP-treated 1321N1 cells expressing P2Y2 receptors stimulated the outgrowth of neurites in PC-12 cells. Taken together, our results suggest an important novel role for the P2Y2 receptor in survival and neuroprotective mechanisms under pathological conditions.

Animals↗
PubMed2003

Src homology 3 binding sites in the P2Y2 nucleotide receptor interact with Src and regulate activities of Src, proline-rich tyrosine kinase 2, and growth factor receptors.

Many G protein-coupled receptors activate growth factor receptors, although the mechanisms controlling this transactivation are unclear. We have identified two proline-rich, SH3 binding sites (PXXP) in the carboxyl-terminal tail of the human P2Y(2) nucleotide receptor that directly associate with the tyrosine kinase Src in protein binding assays. Furthermore, Src co-precipitated with the P2Y(2) receptor in 1321N1 astrocytoma cells stimulated with the P2Y(2) receptor agonist UTP. A mutant P2Y(2) receptor lacking the PXXP motifs was found to stimulate calcium mobilization and serine/threonine phosphorylation of the Erk1/2 mitogen-activated protein kinases, like the wild-type receptor, but was defective in its ability to stimulate tyrosine phosphorylation of Src and Src-dependent tyrosine phosphorylation of the proline-rich tyrosine kinase 2, epidermal growth factor receptor (EGFR), and platelet-derived growth factor receptor. Dual immunofluorescence labeling of the P2Y(2) receptor and the EGFR indicated that UTP caused an increase in the co-localization of these receptors in the plasma membrane that was prevented by the Src inhibitor PP2. Together, these data suggest that agonist-induced binding of Src to the SH3 binding sites in the P2Y(2) receptor facilitates Src activation, which recruits the EGFR into a protein complex with the P2Y(2) receptor and allows Src to efficiently phosphorylate the EGFR.

Amino Acid Sequence↗
PubMed2003

The P2Y2 nucleotide receptor mediates UTP-induced vascular cell adhesion molecule-1 expression in coronary artery endothelial cells.

P2Y2 receptor up-regulation and activation induces intimal hyperplasia and monocyte/macrophage infiltration in the collared rabbit carotid artery model of vascular injury, suggesting a potential role for P2Y2 receptors in monocyte recruitment by vascular endothelium. In this study, we addressed the hypothesis that activation of P2Y2 receptors by extracellular nucleotides modulates the expression of adhesion molecules on vascular endothelial cells that are important for monocyte recruitment. Results indicated that the equipotent P2Y2 receptor agonists UTP or ATP (1-100 microm) stimulated the expression of vascular cell adhesion molecule-1 (VCAM-1) in human coronary artery endothelial cells (HCAEC) in a time- and dose-dependent manner. P2Y2 antisense oligonucleotides inhibited VCAM-1 expression induced by UTP but not by tumor necrosis factor-alpha. Furthermore, UTP induced VCAM-1 expression in human 1321N1 astrocytoma cell transfectants expressing the recombinant P2Y2 receptor, whereas vector-transfected control cells did not respond to UTP. The effect of UTP on VCAM-1 expression in HCAEC was prevented by depletion of intracellular calcium stores with thapsigargin or by inhibition of p38 mitogen-activated protein kinase or Rho kinase, but was not affected by inhibitors of the mitogen-activated protein/extracellular signal-regulated kinase pathway (i.e. MEK1/2). Consistent with a role for VCAM-1 in the recruitment of monocytes, UTP or ATP increased the adherence of monocytic U937 cells to HCAEC, an effect that was inhibited by anti-VCAM-1 antibodies. These findings suggest a novel role for the P2Y2 receptor in the p38- and Rho kinase-dependent expression of VCAM-1 that mediates the recruitment of monocytes by vascular endothelium associated with the development of atherosclerosis.

Cells, Cultured↗
PubMed2003

The first total synthesis of the marine fatty acid (+/-)-2-methoxy-13-methyltetradecanoic acid: a cytotoxic fatty acid to leukemia cells.

The recently discovered marine fatty acid (+/-)-2-methoxy-13-methyltetradecanoic acid was synthesized for the first time in six steps (26% overall yield) starting from commercially available methyl 12-methyltridecanoate. The synthetic approach provided enough material to corroborate the structure of the acid, which was recently identified in the sponge Amphimedon complanata from Aguadilla, Puerto Rico, and to test its cytotoxicity to three leukemia cell lines. The key step in the synthesis was the addition of trimethylsilyl cyanide to 12-methyltridecanal under triethylamine catalysis. Nuclear magnetic resonance data are provided for the first time for this methoxylated fatty acid and the synthetic approach utilized is of general applicability since it can be used in the synthesis of other methyl-branched 2-methoxylated fatty acids. We also report that the acid (+/-)-2-methoxy-13-methyltetradecanoic acid is cytotoxic to human chronic myelogenous leukemia K-562 (EC50=238 microM), histiocytic lymphoma U-937 (EC50=250 microM), and promielocytic leukemia HL-60 (EC50=476 microM) in RPMI 1640 medium.

Animals↗
PubMed2003

P2X7 nucleotide receptor activation enhances IFN gamma-induced type II nitric oxide synthase activity in BV-2 microglial cells.

Under normal and pathological conditions, brain cells release nucleotides that regulate a wide range of cellular responses due to activation of P2 nucleotide receptors. In this study, the effect of extracellular nucleotides on IFN gamma-induced NO release in murine BV-2 microglial cells was investigated. BV-2 cells expressed mRNA for metabotropic P2Y and ionotropic P2X receptors. Among the P2 receptor agonists tested, ATP, ADP, 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP), and 2-methylthio-ATP (2-MeSATP), but not UTP, enhanced IFN gamma-induced iNOS expression and NO production, suggesting that the uridine nucleotide receptors P2Y2 and P2Y6 are not involved in this response. U0126, an antagonist for MEK1/2, a kinase that phosphorylates the extracellular signal-regulated kinases ERK1/2, decreased IFN gamma-induced NO production. BzATP, a potent P2X7 receptor agonist, was more effective than ATP, ADP, or 2-MeSATP at enhancing IFN gamma-induced ERK1/2 phosphorylation. Consistent with activation of the P2X7 receptor, periodate-oxidized ATP, a P2X7 receptor antagonist, and suramin, a non-specific P2 receptor antagonist, inhibited the effect of ATP or BzATP on IFN gamma-induced NO production, whereas pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), an antagonist of several P2X receptor subtypes, was ineffective. These results suggest that activation of P2X7 receptors may contribute to inflammatory responses in microglial cells seen in neurodegenerative diseases.

Adenosine Diphosphate↗