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C T Noguchi

Publications and source records attributed to C T Noguchi.

88 records · Page 5Linked to original sources
PubMed1983

5-Azacytidine increases gamma-globin synthesis and reduces the proportion of dense cells in patients with sickle cell anemia.

We previously demonstrated that 5-azacytidine can selectively increase gamma-globin synthesis in a patient with beta +-thalassemia, prompting us to treat two patients with sickle cell anemia and two additional patients with beta + thalassemia. 5-Azacytidine (2 mg/kg/day) was continuously infused for 7 days with no apparent clinical toxicity. The gamma/beta-globin biosynthetic ratio increased fourfold to sixfold in the bone marrow cells of each patient after treatment and remained elevated for 7-14 additional days. Hypomethylation of DNA near the gamma-globin genes in bone marrow cells was demonstrated 2 days after beginning the 5-azacytidine infusion. The peripheral blood fetal hemoglobin (HbF) level increased from 6.0% to 13.7% in one patient with sickle cell anemia and from 1.6% to 8.9% in the second. Stractan gradient analyses of peripheral blood from patients with sickle cell anemia revealed a marked decrease in the percentage of dense cells (cells that contain increased amounts of HbS polymer when deoxygenated) following treatment. These observations provide an impetus to investigate the effects of repeated courses of 5-azacytidine in a small group of severely ill patients to determine whether this drug may have a role in the treatment of patients with sickle cell anemia and beta-thalassemia.

Adult↗
PubMed1983

DNA methylation and globin gene expression in patients treated with 5-azacytidine.

5-Azacytidine, a cytidine analog, stimulated fetal hemoglobin synthesis in five patients who had either severe beta-thalassemia or sickle cell anemia. After treatment, a reduction in the frequency of methylated cytosine residues was observed at all Hpa II sites examined. Despite causing "global" hypomethylation, 5-azacytidine augmented the synthesis of gamma-globin only. Although gamma-gene hypomethylation and increased gamma-gene expression seem to be linked, hypomethylation near other genes was not sufficient to activate transcription. These data suggest that the gamma genes lie in a unique "preactivational" state responsive to hypomethylation, and that other genes are repressed in bone marrow cells by different mechanisms. DNA hypomethylation and an increased concentration of gamma-mRNA were observed in bone marrow cells 2 days after initiation of treatment, indicating that 5-azacytidine may act directly on differentiated erythroid precursors. This compound probably affects early erythroid progenitors as well, since an increased level of gamma-globin synthesis persists for 1-2 weeks after the drug is stopped. A direct effect on erythroid progenitors was also suggested by in vitro assays: Erythroid colonies derived from progenitor cells obtained on day 2 of treatment produced more Hb F than colonies derived from progenitors obtained before 5-azacytidine was given.

Azacitidine↗
PubMed1983

The effect of phenylalanine derivatives on the solubility of deoxyhemoglobin S. A model class of gelation inhibitors.

Among the class of non-covalent inhibitors of deoxyhemoglobin S gelation, the aromatic amino acids have been shown to be the most effective. We have examined several synthetic chemical modifications of phenylalanine in order to determine the stereospecific constraints for inhibition of gelation by this class of compounds. The phenylalanine derivatives with ring modification by electron-donating groups (NH2, CH3, or OH) inhibited gelation to the same order of magnitude as phenylalanine (10-20% increase in deoxyhemoglobin S solubility at 32 mM). The phenylalanine derivative with the electron-withdrawing group NO2 in the p-position behaved similarly, but the inhibitory effect was eliminated by NO2 in the m- and possibly o-positions. Furthermore, side-chain modifications also eliminated the inhibitory effect. These studies, in conjunction with crystallographic analyses of the binding sites of gelation inhibitors, may provide a rational strategy for finding suitable compounds (whether covalent or non-covalent inhibitors) with appropriate physicochemical and biological properties to pursue as potential therapies with sickle cell disease.

Anemia, Sickle Cell↗
PubMed1982

Molecular and cellular pathogenesis of hemoglobin SC disease.

Solution and cell studies were performed to ascertain why individuals with hemoglobin (Hb) SC have disease whereas those with Hb AS do not. The polymerization of deoxygenated mixtures containing sickle cell Hb (Hb S; alpha 2 beta 2(6)Glu leads to Val) and Hb C (alpha 2 beta 2(6)Glu leads to Lys) was investigated by measurements of delay times and solubilities. In mixtures containing more than 40% Hb S, polymerization takes place by the same mechanism as in solutions of Hb S alone, with no evidence for independent crystallization of Hb C. A detailed comparison of Hb S/Hb C and Hb S/Hb A mixtures with identical concentrations and proportions of Hb S show that there is no significant difference in the tendency of Hb C and Hb A to copolymerize with Hb S. In 50:50 Hb S/Hb C mixtures, polymerization is about 15 times more rapid than in 40:60 Hb S/Hb A mixtures at the same total Hb concentration. Measurements on density-fractionated erythrocytes show that SC cells contain a higher total Hb concentration and a more uniform distribution of reticulocytes compared to normal (AA) or sickle trait (AS) cells. The concentration distribution for C trait (AC) cells is much closer to that of SC cells than to AS or AA cells. It appears, therefore, that the presence of Hb C results in the SC cell beginning its life with an abnormally high Hb concentration. From these findings we conclude that both the larger proportion of Hb S and the higher intracellular Hb concentration contribute to the pathogenesis of Hb SC disease.

Anemia, Sickle Cell↗
PubMed1982

Determination of sickle hemoglobin polymer in SS and AS erythrocytes.

Using 13C nuclear magnetic resonance techniques, we have studied the polymerization of hemoglobin S and intracellular polymerization in SS and AS erythrocytes. For SS erythrocytes, polymer could be detected at high oxygen saturations (greater than 90%) and increased with decreasing oxygen saturation to 70% of the total hemoglobin at complete deoxygenation. These results are consistent with the non-ideal behavior of hemoglobin S at the high intracellular concentration of 34 g/dl. The amount of polymer in AS erythrocytes was also measured as a function of oxygen saturation and is in agreement with the amount of polymer determined for homolysates using ultracentrifuge sedimentation. In general, these results on intracellular gelation are in good agreement with results predicted by cell-free studies extrapolated to the high intracellular hemoglobin concentration (34 g/dl). The significance of the detection of polymer at high oxygen saturation of SS erythrocytes is discussed in terms of morphologic deformation and erythrocyte transit through the circulation. We propose that intracellular polymerization is important in abnormal cell rheology and manifestation of disease.

Anemia, Sickle Cell↗
PubMed1981

Polymerization of hemoglobin in sickle trait erythrocytes and lysates.

We report 13C/1H magnetic double resonance measurements of polymer in sickle trait erythrocytes and direct measurements of solubility on lysates of these cells as a function of oxygen saturation. Polymerized hemoglobin is detected by these two methods only at oxygen saturation values below 60% and increases to 0.4 of the total hemoglobin at complete deoxygenation. These results confirm the validity of the NMR approach in determining values of polymer fraction. We have also found that the thermodynamic theory, that successfully describes gelation in sickle erythrocytes, does not predict the experimental results for sickle trait erythrocytes and must be refined.

Anemia, Sickle Cell↗
PubMed1980

Detection of human ADCC activity using automated flow cytometry.

Using automated flow cytometry techniques we have developed a rapid assay to measure human antibody-dependent cell-mediated cytotoxicity (ADCC). By staining cell cultures for DNA content, chick red blood cell targets can be readily distinguished from human effector cells and ADCC can be measured by changes in their relative proportions. The sensitivity and rapidly of the assay is shown by the finding that at an effector to target ratio of only 2:1, 42% killing can be detected after 1 h incubation.

Antibodies↗
PubMed1980

Determination of deoxyhemoglobin S polymer in sickle erythrocytes upon deoxygenation.

We have used 13C/1H magnetic double-resonance spectroscopy to measure the amount of sickle hemoglobin polymer within sickle erythrocytes as a function of oxygen saturation. We previously showed that the methods of cross-polarization and scalar decoupling could be used to measure accurately the polymer fraction in deoxygenated sickle hemoglobin solutions [Noguchi, C.T., Torchia, D.A. & Schechter, A.N. (1979) Proc. Natl. Acad. Sci. USA 76, 4936-4940]. Our measurements show that the amount of intracellular deoxyhemoglobin S polymer increases monotonically with decreasing oxygen saturation. Polymer can be detected at oxygen saturation values above 90%. This result can be theoretically explained by the excluded volume effect of the oxyhemoglobin S in the cell. The very high total intracellular hemoglobin concentration (34 g/dl) reduces the amount of soluble deoxyhemoglobin S to about 3 g/dl at 90% oxygen saturation. The agreement between theory and experiment indicates that the equilibrium properties of intracellular polymerization can be described by the analyses resulting from studies of concentrated sickle hemoglobin solutions. The curve for polymer formation as a function of oxygen saturation is roughly hyperbolic whereas that for cell sickling is sigmoidal; the difference is most apparent for measurements at pH 7.65. Intracellular polymer formation may in general have a different relationship to oxygen saturation than cell sickling and may be a more meaningful parameter of the pathophysiological process in sickle cell anemia than cell morphology. In addition, measurements of intracellular polymer should be useful in evaluating potential therapeutic agents.

Anemia, Sickle Cell↗
PubMed1979

13C NMR quantitation of polymer in deoxyhemoglobin S gels.

13C/1H magnetic double-resonance spectroscopy has been used to quantitate the amount of polymerized hemoglobin S in deoxygenated gels at 30 degrees C, for samples whose hemoglobin concentration range from 21 to 32 g/dl. Scalar- and dipolar-decoupled spectra and a 13C proton-enhanced dipolar-decoupled spectrum were recorded for each sample as was a scalar-decoupled spectrum for a matching oxyhemoglobin S control. The difference between the oxyhemoglobin S and deoxyhemoglobin S scalar-decoupled spectra was used to determine the polymer fraction, and this value was compared with the polymer fraction determined by using ultracentrifugation sedimentation on the same sample (assuming a two-phase model). The polymer fraction value determined by uncorrected sedimentation averaged 0.15 more than the value obtained from NMR. The discrepancy between the two techniques was largely removed when the analysis of the sedimentation data included a correction for depletion of hemoglobin in the supernatant or sol phase due to sedimentation of free molecules. The best fit to both the sedimentation and NMR data was obtained by using a solubility of deoxyhemoglobin S at 30 degrees C of 17.3 +/- 1 g/dl. These results indicate that the NMR techniques, which do not require separation of the sample into a sol phase and a pellet phase, provide quantitative information about the deoxyhemoglobin S polymer and will be useful for studies of sickle erythrocytes.

Erythrocytes↗
PubMed1978

Inhibition of sickle hemoglobin gelation by amino acids and related compounds.

The effects of amino acids, several aromatic compounds, and peptides on the gelation and solubility of deoxyhemoglobin S have been studied. The aromatic amino acids (tryptophan, phenylalanine, and possibly tyrosine) significantly inhibited the rate of gel formation and increased solubility. The dipeptide L-Thr-L-Phe, the tripeptide L-Lys-L-Phe-L-Phe, and various phenylalanine analogues (hydrocinnamic acid, phenethylamine, benzamine, and amphetamine) also inhibited gelation. However, aromaticity is not a sufficient condition for inhibiting gelation as shown by the fact that several aromatic compounds (acetylsalicylic acid, salicyclic acid, aniline, and phenol) enhanced gelation. Surprisingly, several oligopeptides (betaS1--12, betaS4--8, betaS3--13, and betaS4--10) also enhanced gelation. All of these additives follow the supersaturation relationship that the delay time for gelation is proportional to the ratio of the total hemoglobin concentration to the solubility of deoxyhemoglobin S to the nth power (n approximately 35). A possible mechanism for the action of these inhibitors is considered in terms of a specific site of interaction on the hemoglobin molecule. Although none of these compounds may prove to be efficacious in treatment of sickle cell anemia, they should yield information about the structure and process of formation of the deoxyhemoglobin S gel.

Amino Acids↗
PubMedDate not supplied

Multi-ribozyme targeting of human alpha-globin gene expression.

One approach to gene therapy for the treatment of hemoglobinopathies has been focused on increasing normal globin gene expression. However, because of the high concentration of hemoglobin in the red blood cell (32-34 g/dl), merely introducing the normal globin gene may not be enough to counteract the effect of an abnormal globin. We propose that in addition to strategies to add normal beta- or gamma-globin production to sickle erythrocytes, a decrease in overall hemoglobin concentration would further decrease the polymerization potential and should be considered with other gene therapy approaches. Ribozymes offer the potential to target a selected gene product. A model system has been set up using the human alpha-globin gene for specific gene suppression by ribozymes by cleaving alpha-globin mRNA transcripts. Ribozymes, specifically targeted to five different sites in the 5' portion of human alpha-globin mRNA, have been designed and tested in vitro. Cleavage of 32P-labeled alpha-globin mRNA by these ribozymes has been observed in vitro and the highest level of activity has been found for a multi-ribozyme combining all five ribozymes. The multi-ribozyme gene along with promoters with varying activities in erythroid cells was transfected into human erythroleukemia K562 cells. The multi-ribozyme gene, under the control of human alpha-2-globin promoter alone and combined with the locus control region enhancer, caused a decrease in the level of alpha-globin mRNA of 50-75% compared to the control, determined by RNase protection and by real-time quantitative PCR. The decrease in alpha-globin transcripts has been found to be correlated with expression of the multi-ribozyme in a dose-dependent manner and does not appear to be mediated by an antisense effect. These results suggest that the multi-ribozyme may be useful in gene therapy as an effective suppressor of a specific globin gene.

Antisense Elements (Genetics)↗
PubMedDate not supplied

Pathophysiology of a sickle cell trait mouse model: human alpha(beta)(S) transgenes with one mouse beta-globin allele.

As a potential model for sickle cell trait (AS), we examined mice containing one normal mouse beta-globin allele in combination with a human hemoglobin S (h(alpha)beta(S)) transgene (m(beta)/hS). The mice segregated into two subpopulations containing low and high proportions of hemoglobin S (m(beta)/hS1 and m(beta)/hS2, respectively) that was associated with one or two human h(alpha)beta(S) transgenes. We noted striking kidney pathology (cortical cysts, hyperplastic tubules, and glomerulonephritis), increasing with age and with greater severity in m(beta)/hS1. mBeta/hS2 animals were largely tolerant to 5% O(2) for 1 h, whereas 80% of m(beta)/hS1 mice died, exhibiting acute sequestration of erythrocytes in spleen, liver, and heart. These pathologies appear to result from a decreased oxygen affinity of the hybrid (human alpha/mouse beta) hemoglobins with a mild beta-thalassemia phenotype. Thus, these mouse models of sickle trait seem to manifest their renal pathology and sensitivity to hypoxia by mechanisms related to low tissue oxygen delivery and are different from the human syndrome. Analyses of parameters such as P(50), red cell indices, and genetic background are necessary in establishing potential relevance of any mouse model of the sickle cell syndromes.

Alleles↗
PubMedDate not supplied

Renal pathology in hemizygous sickle cell mice.

Transgenic mice have been developed that express exclusively human sickle cell beta hemoglobin and have major pathological features found in humans with sickle cell disease. These mice provide a unique opportunity to investigate the fundamental mechanisms of this disease and to design new strategies to correct the associated genetic defect(s). We found that in breeding males expressing only adult human alpha-globin and sickle beta-globin (homozygous SS mice) with females containing these transgenes plus one copy of the mouse beta-globin gene (hemizygous SS mice) greater than expected numbers of hemizygous offspring were produced than homozygous mice (carrying no mouse beta-globin gene). These hemizygous mice, expressing the human alpha and sickle beta(s) transgenes in combination with mouse beta+/-, were used for our preliminary studies of their renal pathology. No kidney lesions were found in the control (129/Sv) mice, whereas about 50% of the hemizygous SS mice showed mild-to-severe kidney lesions, including glomerulonephritis, cystic atypical hyperplastic tubules, and general nephropathy. Kidneys of some hemizygous mice were normal or showed minimal nephropathy, yet those of the susceptible phenotype developed a mild-to-more-severe form of renal lesions. The tubular epithelium of kidneys of hemizygous mice of the more affected phenotype exhibited increased expression of inducible nitric oxide synthase with an increased 3-nitrotyrosine in close proximity. There was also a stronger immunostaining for vascular cell adhesion molecule-1 in the interstitial capillary cells as well as the tubular epithelial cells of the renal cortex, compared with normal control mice. The occurrence of a high incidence of renal abnormalities in our hemizygous SS mice suggests that these mice may provide a suitable model to study the pathogenesis of nephropathy resulting from altered blood flow and/or insufficient oxygen delivery.

Anemia, Sickle Cell↗