Biomedical subjects

G A Hair

Publications and source records attributed to G A Hair.

10 recordsLinked to original sources

PubMed1996

Tissue factor expression in human leukemic cells.

Patients with acute leukemia are at increased risk for thrombotic and hemorrhagic complications, particularly those patients with acute promyelocytic leukemia (APL) undergoing induction chemotherapy. These serious complications have been attributed by some authors to the release of tissue factor (TF) procoagulant activity (PCA), particularly during cytotoxic chemotherapy. In previous studies of normal peripheral blood cells, only cells of the monocyte lineage have been found to express TF PCA. Therefore, several questions remain regarding the origin and characterization of the PCA in malignant leukemic cells, particularly those thought to be derived from granulocyte progenitor cells. We utilized a full-length cDNA probe, several monoclonal antibodies (MAbs) and a sensitive one-stage PCA assay to study the expression of TF in the human cell line, HL-60, in human peripheral blood monocytes/macrophages (Mo/Mø) and in highly purified populations of human polymorphonuclear leukocytes (PMN). In the HL-60 cells we detected low but significant levels of TF mRNA and TF antigen (TF:Ag). In unstimulated cells, coordinate increased levels of TF mRNA, TF:Ag and TF PCA expression were noted following phorbol-ester-induced macrophage differentiation of the cells, but a decreased level of TF mRNA with no change in the basal level of TF:Ag expression occurred following retinoic acid-induced granulocyte differentiation of this cell line. Long-term cultures of stimulated mature Mo/Mø demonstrated initial coordinate expression of TF mRNA, TF:Ag and TF PCA, but TF:Ag expression persisted even after 7 days (when TF PCA was undetectable). No TF PCA, TF:Ag or TF mRNA was demonstrated in highly purified populations of human PMN, regardless of culture conditions. Discordant expression of TF mRNA, TF:Ag and TF PCA in HL-60 cells suggests the possibility of novel, post-synthetic mechanisms for the regulation of TF PCA expression, which might be dependent on the phenotypic differentiation level of the cell. Such mechanisms (yet to be defined) might account for the ability of some leukemic cells, which frequently express characteristics of more than one cell line (e.g. monocytes and granulocytes), to express a TF gene product capable of activating blood coagulation.

Antibody Specificity↗

PubMed1995

Recurrent venous thrombosis as the presenting manifestation of acute lymphocytic leukemia: leukemic cell procoagulant activity is not responsible for the hypercoagulable state.

The association of cancer with clinical abnormalities of blood coagulation, including superficial thrombophlebitis, deep vein thrombosis (DVT), and disseminated intravascular coagulation (DIC) is well-known, particularly in patients with solid tumors and acute promyelocytic leukemia (APL). Less commonly appreciated is the potential for the development of venous thromboembolic disease (TED) in patients with acute lymphocytic leukemia (ALL). Multiple mechanisms have been implicated for the activation of coagulation in these patients, with an emphasis on the contribution made by the procoagulant properties of the tumor cells themselves. We present two cases of patients with pre-B cell ALL, both of whom developed recurrent TED as the presenting manifestation of their leukemia and/or heralding relapse. The blast cells from one of the patients were studied for the presence of procoagulant activity (PCA) and by Northern blot analysis for tissue factor (TF) messenger RNA (mRNA). Neither PCA nor TF mRNA could be identified in highly purified populations of the lymphoblast cells. We conclude that recurrent TED can be a manifestation of ALL and that mechanisms other than the release of tumor cell procoagulants should be sought to explain the pathogenesis of thrombosis in some patients.

Adult↗

PubMed1995

Tissue factor expression in human leukocytes and tumor cells.

Tissue factor (TF) exists in a cryptic form [i.e. without procoagulant activity (PCA)] in peripheral blood monocytes and quiescent tissue macrophages but is expressed constitutively in most human tumor cells. Induction and cell surface expression of TF in these cells in vivo is associated with activation of intravascular and extravascular coagulation in patients with a variety of inflammatory or malignant diseases. The regulation of TF synthesis in cells is complex and new information from transfection studies suggests that changes in cellular glycosylation pathways impair cell surface expression of functional TF. Such dysregulation may also characterize the lineage-unfaithful expression of TF in leukemic cells and perhaps explain some of the thrombohemorrhagic complications in patients with acute progranulocytic leukemia. The importance of carbohydrate modification of TF is reviewed.

Acute Disease↗

PubMed1994

In situ characterization of antigenic and functional tissue factor expression in human tumors utilizing monoclonal antibodies and recombinant factor VIIa as probes.

Tissue factor (TF), the primary initiator of blood coagulation in vivo, is expressed in vitro by a variety of cells. Previous efforts to localize TF in tissue and cells have been limited principally to the use of immunological techniques. In the present study, we describe a novel functional probe for TF expression, which can be utilized to localize functional TF in situ in human cells and tissues. This probe, a biotinylated phe-pro-arg-chloro-methyl-ketone-labeled rVIIa (FPR-ck-VIIa), interacts with TF via high-affinity binding sites. The binding of FPR-ck-VIIa, therefore, can be correlated with the ability of TF to activate clotting. In the described studies, TF antigen (TF:Ag) expression was examined immunohistochemically with various TF-specific monoclonal antibodies (MAbs) and was correlated with functional TF expression using our novel TF-binding probe (eg, FPR-ck-VIIa). Initial results indicate that TF:Ag expression correlates with the expression of functional TF (TF:VIIa), and the specificity of both types of probes was confirmed. Parallel antigenic and functional TF expression in situ was demonstrated in various human tumors. We believe this to be the first demonstration of functional TF in situ in human cells and tissues. We suggest that FPR-ck-VIIa should prove a useful reagent for studying the role of TF in the pathogenesis of clotting complications of human disease.

Amino Acid Chloromethyl Ketones↗

PubMed1992

Characterization of human osteoblast and megakaryocyte-derived osteonectin (SPARC).

Osteonectin is an adhesive, cell, and extracellular matrix-binding glycoprotein found primarily in the matrix of bone and in blood platelets in vivo. Osteonectins isolated from these two sources differ with respect to the complexity of their constituent N-linked oligosaccharide. In this study, osteonectin synthesized by bone-forming cells (osteoblasts) and platelet-producing cells (megakaryocytes) in vitro was analyzed to determine if the proteins produced were analogous in terms of glycosylation to those isolated from bone and platelets, respectively. Immunoblot analyses of osteonectin produced by the osteoblast-like cell lines, SaOS-2 and MG-63, indicated that secreted and intracellular forms of the molecule are structurally distinct. Endoglycosidase treatment and immunoblotting of osteonectin secreted from SaOS-2 and MG-63 cells, under serum-deprived conditions, suggested that the molecule possessed a complex type oligosaccharide unlike the high-mannose moiety found on bone matrix-derived osteonectin. Biosynthetic labeling of SaOS-2 cells and human megakaryocytes indicated that both cell types synthesize osteonectin de novo. Electrophoretic and glycosidase sensitivity analyses of [35S]-osteonectin isolated from lysates of metabolically labeled SaOS-2 cells and megakaryocytes indicated that these two cell types synthesize osteonectin molecules that are identical in oligosaccharide structure to the isolated bone and platelet proteins. These data suggest that the intracellular form of the osteonectin molecule is glycosylated differently in SaOS-2 cells and megakaryocytes but that the extracellular form which is secreted from platelets in vivo and osteoblasts in vitro is characterized by the presence of a complex type N-linked oligosaccharide.

Adult↗

PubMed1986

Hyperglycemia-induced activation of human erythrocyte aldose reductase and alterations in kinetic properties.

Incubation of human erythrocytes with varying concentrations of glucose resulted in a several-fold increase in aldose reductase (alditol:NADP+ 1-oxidoreductase, EC 1.1.1.21) activity as determined by the rate of NADPH oxidation and the rate of sorbitol formation. As compared to aldose reductase from human erythrocytes not incubated with glucose (native enzyme), aldose reductase from 30 mM glucose-incubated erythrocytes (activated enzyme) exhibited altered kinetic and inhibition properties. Native enzyme showed biphasic kinetics with substrates (glucose and glyceraldehyde), was strongly inhibited by 15 microM ADP, 1,3-diphosphoglycerate, 2,3-diphosphoglycerate and 3-phosphoglycerate, and aldose reductase inhibitors such as sorbinil and alrestatin. The activated enzyme, on the other hand, exhibited monophasic kinetics, low Km for substrates, was not inhibited by the phosphorylated intermediates, and was less susceptible to inhibition by aldose reductase inhibitors. In erythrocytes of the diabetic subjects, we have found an excellent correlation between aldose reductase activity and plasma glucose levels and have observed that whenever the blood glucose level was higher than 15 mM, all of the erythrocyte aldose reductase was present in the activated form and exhibited properties similar to those observed with aldose reductase obtained from 30 mM glucose-incubated erythrocytes.

Aldehyde Reductase↗

PubMed1986

Activation of human erythrocyte, brain, aorta, muscle, and ocular tissue aldose reductase.

Based upon kinetic, structural, and immunologic properties, we have demonstrated that human tissues have three major forms of aldo-keto reductases: aldose reductase (AR), and aldehyde reductases I (AR I) and II (AR II). The proposed subunit compositions are AR, alpha; AR I, alpha-beta; and AR II, delta. Only AR can effectively reduce glucose to sorbitol. The beta subunits in AR I alter the substrate specificity of AR and prevent conformational changes required for the activation of alpha subunits. Partially purified AR (by DE-52) from human erythrocytes expresses biphasic kinetics with glucose and glyceraldehyde. The enzyme can be activated with glucose + glucose-6-P + NADPH and is strongly inhibited by sorbinil, alrestatin, and quercetrin, and by ADP, 2,3DPG, 1,3DPG, and 3PGA. The activated enzyme expresses monophasic kinetics with substrates (Km glucose less than 1 mmol/L) and is less susceptible to inhibition by synthetic AR inhibitors and phosphorylated intermediates. The enzyme from human brain, aorta, muscle, and ocular tissues was also activated under similar conditions. Erythrocyte enzyme was activated by incubation of blood with 30 to 50 mmol/L glucose. In diabetic subjects with blood sugar levels higher than 250 mg%, almost all the erythrocyte enzyme exists in the activated form. As demonstrated by enzyme-linked immunosorbent assay (ELISA), the increase in AR activity (in vivo and in vitro) was due to the activation of the enzyme and not to the de novo synthesis. In each case, the activation of the enzyme was confirmed by NADPH oxidation and the formation of proportionate amounts of sorbitol.

Aldehyde Reductase↗

PubMed1985

Interrelationships among human aldo-keto reductases: immunochemical, kinetic and structural properties.

We have proposed earlier a three gene loci model to explain the expression of the aldo-keto reductases in human tissues. According to this model, aldose reductase is a monomer of alpha subunits, aldehyde reductase I is a dimer of alpha, beta subunits, and aldehyde reductase II is a monomer of delta subunits. Using immunoaffinity methods, we have isolated the subunits of aldehyde reductase I (alpha and beta) and characterized them by immunocompetition studies. It is observed that the two subunits of aldehyde reductase I are weakly held together in the holoenzyme and can be dissociated under high ionic conditions. Aldose reductase (alpha subunits) was generated from human placenta and liver aldehyde reductase I by ammonium sulfate (80% saturation). The kinetic, structural and immunological properties of the generated aldose reductase are similar to the aldose reductase obtained from the human erythrocytes and bovine lens. The main characteristic of the generated enzyme is the requirement of Li2SO4 (0.4 M) for the expression of maximum enzyme activity, and its Km for glucose is less than 50 mM, whereas the parent enzyme, aldehyde reductase I, is completely inhibited by 0.4 M Li2SO4 and its Km for glucose is more than 200 mM. The beta subunits of aldehyde reductase I did not have enzyme activity but cross-reacted with anti-aldehyde reductase I antiserum. The beta subunits hybridized with the alpha subunits of placenta aldehyde reductase I, and aldose reductase purified from human brain and bovine lens. The hybridized enzyme had the characteristic properties of placenta aldehyde reductase I.

Alcohol Oxidoreductases↗

PubMed1985

Activated and unactivated forms of human erythrocyte aldose reductase.

Aldose reductase (alditol:NADP+ 1-oxidoreductase, EC 1.1.1.21) has been partially purified from human erythrocytes by DEAE-cellulose (DE-52) column chromatography. This enzyme is activated severalfold upon incubation with 10 microM each glucose 6-phosphate, NADPH, and glucose. The activation of the enzyme was confirmed by following the oxidation of NADPH as well as the formation of sorbitol with glucose as substrate. The activated form of aldose reductase exhibited monophasic kinetics with both glyceraldehyde and glucose (Km of glucose = 0.68 mM and Km of glyceraldehyde = 0.096 mM), whereas the native (unactivated) enzyme exhibited biphasic kinetics (Km of glucose = 9.0 and 0.9 mM and Km of glyceraldehyde = 1.1 and 0.14 mM). The unactivated enzyme was strongly inhibited by aldose reductase inhibitors such as sorbinil, alrestatin, and quercetrin, and by phosphorylated intermediates such as ADP, glycerate 3-phosphate, glycerate 1,3-bisphosphate, and glycerate 2,3-trisphosphate. The activated form of the enzyme was less susceptible to inhibition by aldose reductase inhibitors and phosphorylated intermediates.

Aldehyde Reductase↗

PubMed1984

Aldose and aldehyde reductases in human tissues.

Immunochemical characterizations of aldose reductase and aldehyde reductases I and II, partially purified by DEAE-cellulose (DE-52) column chromatography from human tissues, were carried out by immunotitration, using antisera raised against the homogenous preparations of human and bovine lens aldose reductase and human placenta aldehyde reductase I and aldehyde reductase II. Anti-aldose antiserum cross-reacted with aldehyde reductase I, anti-aldehyde reductase I antiserum cross-reacted with aldose reductase and anti-aldehyde reductase II antiserum precipitated aldehyde reductase II, but did not cross-react with aldose reductase or aldehyde reductase I from all the tissues examined. DE-52 elution profiles, substrate specificity and immunochemical characterization indicate that aldose reductase is present in human aorta, brain, erythrocyte and muscle; aldehyde reductase I is present in human kidney, liver and placenta; and aldehyde reductase II is present in human brain, erythrocyte, kidney, liver, lung and placenta. Monospecific anti-alpha and anti-beta antisera were purified from placenta anti-aldehyde reductase I antiserum, using immunoaffinity techniques. Anti-alpha antiserum precipitated both aldehyde reductase I and aldose reductase, whereas anti-beta antibodies cross-reacted with only aldehyde reductase I. Based on these studies, a three gene loci model is proposed to explain the genetic interrelationships among these enzymes. Aldose reductase is a monomer of alpha subunits, aldehyde reductase I is a dimer of alpha and beta subunits and aldehyde reductase II is a monomer of delta subunits.

Aldehyde Oxidoreductases↗