Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The clinical efficacy of hydroxyurea (HU) in the treatment of sickle cell anemia has mainly been attributed to increased levels of fetal hemoglobin (HbF), which reduces the tendency for sickle hemoglobin to polymerize, thereby reducing the frequency of the vaso-occlusive phenomena associated with the disease. However, benefits from HU treatment in patients have been reported in advance of increased HbF levels. Thus, it has been suggested that other hydroxyurea-dependent mechanisms may, in part, account for its clinical efficacy. We have previously demonstrated that HU is metabolized in rats to release nitric oxide and, therefore, postulated the same to occur in humans. However, to our knowledge, evidence of nitric oxide production from HU metabolism in humans has yet to be demonstrated. Here we report that oral administration of HU for the treatment of sickle cell anemia produced detectable nitrosyl hemoglobin. The nitrosyl hemoglobin complex could be detected as early as 30 min after administration and persisted up to 4 h. Our observations support the hypothesis that the ability of HU to ease the vaso-occlusive phenomena may, in part, be attributed to vasodilation and/or decreased platelet activation induced by HU-derived nitric oxide well in advance of increased HbF levels.
Mol Pharmacol 1999 Jun
PMID:Detection of nitrosyl hemoglobin in venous blood in the treatment of sickle cell anemia with hydroxyurea. 1034 41

Our current strategy for gene therapy of sickle cell anemia involves retroviral vectors capable of transducing "designer" globin genes that code for novel anti-sickling globins (while resisting digestion by a ribozyme), coupled with the expression of a hammerhead ribozyme that can selectively cleave the human beta s mRNA. In this report, we have tested in vivo an anti-beta s hammerhead ribozyme embedded within a cDNA coding for the luciferase reporter gene driven by the human beta-globin promoter and hyper-sensitive sites 3 and 4 of the locus control region. We have created mice transgenic for this luciferase-ribozyme construct and bred the ribozyme transgene into mice that were already transgenic for the human beta s gene. We then measured expression of the beta s transgene at the protein and RNA levels by HPLC and primer extension. The presence of the ribozyme was associated with a statistically significant reduction in the level of beta s mRNA in spleen stress reticulocytes (from 60.5 +/- 4.1% to 52.9 +/- 4.2%) and in the percentage of beta s globin chains in very young mice (from 44.5 +/- 0.6% to 40.8 +/- 0.7%). These results demonstrate that it is possible to decrease the concentration of beta s chains and mRNA with the help of a hammerhead ribozyme. While the enormous amount of globin mRNA in reticulocytes is a challenge for ribozyme technology, the exquisite dependence of the delay time for formation of Hb S nuclei on the concentration of Hb S in red blood cells suggests that even a modest reduction in Hb S concentration would have therapeutic value.
Blood Cells Mol Dis 1999 Apr
PMID:Anti-beta s-ribozyme reduces beta s mRNA levels in transgenic mice: potential application to the gene therapy of sickle cell anemia. 1038 93

Thrombosis is a major complication of human hemolytic anemias such as sickle cell disease, thalassemia, and severe hereditary spherocytosis (HS). Mice with severe HS and severe hereditary elliptocytosis (HE) also suffer from thrombosis, with incidences ranging from 15 and 22% in beta-spectrin- and ankyrin-deficient mice, respectively, to 85 to 100% in alpha-spectrin-deficient and band 3 knockout mice. A contributing factor to thrombosis could be loss of phospholipid asymmetry of the mutant red blood cells (RBCs), with concomitant exposure of the aminophospholipid phosphatidylserine (PS). Increased PS exposure occurs in RBCs from sickle cell and thalassemia patients and in RBCs from band 3-deficient mice. To determine if increased PS exposure correlates with thrombotic risk in HS and HE mice with ankyrin, beta-spectrin, and alpha-spectrin deficiencies, measurements of FITC-labeled annexin V binding to externalized PS on RBCs were performed. PS exposure is elevated in all mice with HS and HE, but the percentage of RBCs with exposed PS does not correlate with thrombotic risk in these mice.
Blood Cells Mol Dis 2000 Feb
PMID:Erythroid phosphatidyl serine exposure is not predictive of thrombotic risk in mice with hemolytic anemia. 1077 78

Interspecies hybrid HbS (alpha(2)(P)beta(2)(S)), has been assembled in vitro from pig alpha-globin and human beta(S)-chain. The alpha(2)(P)beta(2)(S) retains normal tetrameric structure (alpha(2)beta(2)) of human Hb and an O(2) affinity comparable to that of HbS in 50 mM Hepes buffer; but, its O(2) affinity is slightly higher than that of HbS in the presence of allosteric effectors (chloride, DPG and phosphate). The (1)H-NMR spectroscopy detected distinct differences between the heme environments and alpha(1)beta(1) interfaces of pig Hb and HbS, while their alpha(1)beta(2) interfaces appear very similar. The interspecies hybrid alpha(2)(H)beta(2)(P) resembles pig Hb; the pig beta-chain dictated the conformation of the heme environment of the human alpha-subunit, and to the alpha(1)beta(1) interfaces of the hybrid. In the alpha(2)(P)beta(2)(S) hybrid, beta(S)-chain dictated the conformation of human heme environment to the pig alpha-chain in the hybrid; but the conformation of alpha(1)beta(1) interface of this hybrid is close to, but not identical to that of HbS. On the other hand, the alpha(1)beta(2) interface conformation is identical to that of HbS. More important, the alpha(2)(P)beta(2)(S) does not polymerize when deoxygenated; pig alpha-chain completely neutralizes the beta(S)-chain dependent polymerization. The polymerization inhibitory propensity of pig alpha-chain is higher when it is present in the cis alpha(P)beta(S) dimer relative to that in a trans alpha(P)beta(A) dimer. The semisynthetically generated chimeric pig-human and human-pig alpha-chains by exchanging the alpha(1-30) segments of human and pig alpha-chains have established that the sequence differences of pig alpha(31-141) segment can also completely neutralize the polymerization. Comparison of the electrostatic potential energy landscape of the alpha-chain surfaces of HbS and alpha(2)(P)beta(2)(S) suggests that the differences in electrostatic potential energy surfaces on the alpha-chain of alpha(2)(P)beta(2)(S) relative to that in HbS, particularly the ones involving CD region, E-helix and EF-corner of pig alpha-chain are responsible for the polymerization neutralization activity. The pig and human-pig chimeric alpha-chains can serve as blueprints for the design of a new generation of variants of alpha-chain(s) suitable for the gene therapy of sickle cell disease.
J Mol Biol 2000 Jul 28
PMID:Interspecies hybrid HbS: complete neutralization of Val6(beta)-dependent polymerization of human beta-chain by pig alpha-chains. 1090 76

Recent reports have demonstrated that trans-splicing ribozymes can be employed to repair mutant RNAs. One key factor that influences RNA repair efficiency is the accessibility of the substrate RNA for ribozyme binding, which is complicated by the fact that RNAs may assume multiple conformations and have proteins bound to them in vivo. Here we describe a strategy to map accessible sites on sickle beta-globin (beta(s)-globin) transcripts in vitro and in vivo and to use this information to enhance RNA repair efficiency. Two sites upstream of the sickle mutation were identified as accessible in some fraction of the beta-globin RNA by mapping with a ribozyme library and the accessibility of those sites was assessed by in vitro cleavage analyses. Ribozymes targeting either site could only convert a certain fraction of the beta(s)-globin RNA to product but not drive the reaction to completion. However, cleavage and splicing reactions were driven further toward completion when the two ribozymes were both added to the reactions, suggesting that the substrate RNA is present in multiple conformations in vitro. These two ribozymes were each able to repair beta(s)-globin transcripts in erythrocyte precursors derived from peripheral blood from individuals with sickle cell disease. Moreover, the relative accessibility of the targeted sites in vivo is as predicted by mapping and in vitro analyses. These results demonstrate that this novel RNA mapping strategy represents an effective means to determine the accessible regions of target RNAs and that combinations of trans-splicing ribozymes can be employed to enhance RNA repair efficiency of clinically relevant transcripts such as beta(s)-globin RNA.
Mol Ther 2000 Sep
PMID:Enhancing RNA repair efficiency by combining trans-splicing ribozymes that recognize different accessible sites on a target RNA. 1098 55

Increased expression of fetal hemoglobin can ameliorate the clinical severity of sickle cell disease. Whereas temporary induction of fetal hemoglobin can be achieved by pharmacologic therapy, gene transfer resulting in high-level expression of the fetal gamma-globin gene may provide a permanent cure for sickle cell disease. We had previously developed a high-titer, genetically stable retroviral vector in which the human gamma-globin gene was linked to HS-40, the major regulatory element of the human alpha-globin gene cluster. Based on experience in transgenic mice, the truncated promoter of the gamma-globin gene of this vector should be active in adult erythroid cells. Our earlier studies demonstrated that this retroviral vector can give rise to high-level expression of the human gamma-globin gene in murine erythroleukemia (MEL) cells. We have now utilized this vector to transduce murine bone marrow cells that were transplanted into W/W(v) recipient mice. Analysis of transduction of murine BFU-e's in vitro and peripheral blood cells from transplanted mice in vivo demonstrated efficient transfer of the human gamma-globin gene. However, in contrast to the high level of expression of the human gamma-globin gene of this vector in MEL cells, the gene was completely silent in vivo in all transplanted mice. These observations confirm that all the necessary regulatory elements responsible for the developmental stage-specific expression of the human gamma-globin gene reside in its proximal sequences. They also emphasize the differences between gene regulation in MEL cells, transgenic mice, and retroviral gene transfer vectors. For this form of globin gene therapy to succeed, the proximal regulatory elements of the human gamma-globin gene may have to be replaced with different regulatory elements that allow the expression of the gamma-globin coding sequences in adult red cells in vivo.
Blood Cells Mol Dis 2000 Dec
PMID:In vivo silencing of the human gamma-globin gene in murine erythroid cells following retroviral transduction. 1135 53

The intracellular concentration of Hb S is an important determinant of the kinetic of polymer formation and cell sickling. A variable fraction of dense, dehydrated erythrocytes with high Hb S concentration is seen in the blood of patients with sickle cell disease; these dense cells play an important role in the pathophysiology of the vasoocclusive events of sickle cell disease, due to their higher tendency to polymerize and sickle. Sickle cell dehydration is due to loss of K+, Cl-, and water: the two major determinant pathways of dehydration of sickle erythrocytes are the Ca2+-activated K+ channel (IK1 or Gardos channel) and the K-Cl cotransport (KCC). Specific inhibitors of these pathways being tested in patients with sickle cell disease are Mg2+ pidolate, which inhibits KCC by increasing the sickle cell content of Mg2+, and clotrimazole and derivatives of clotrimazole metabolites, which specifically block the Gardos channel. An inhibitor of Cl- conductance has been shown to reduce dehydration in a transgenic mouse model of sickle cell disease but has not been tested in humans. If clinical efficacy and benefit are demonstrated, an inhibitor of cell dehydration could be used in patients as a single agent or in combination with existing therapies, such as hydroxyurea.
Blood Cells Mol Dis
PMID:Therapeutic strategies for prevention of sickle cell dehydration. 1135 64

There are many examples of O2-sensitive solute transport in vertebrate red cells. The response is selective, specific, and conserved across the entire vertebrate spectrum. A number of possible physiological roles have been proposed, but abnormal responses to O2 may also be important pathologically. Significant alterations in O2 dependence of red cell cation transport are observed in sickle cell disease (and also following exposure to oxidants) and probably contribute to its pathophysiology. In this paper, we review some of the features of O2-sensitive solute transporters in red cells and possible reasons for the abnormal response in sickle cells. Our aim is to identify specific, novel pharmacological inhibitors of these abnormal pathways and thereby ameliorate the disease.
Blood Cells Mol Dis
PMID:Oxygen-sensitive cation transport in sickle cells. 1135 70

The intracellular homeostasis is controlled by different membrane transporters. Organic cation transporters function primarily in the elimination of cationic drugs, endogenous amines, and other xenobiotics in tissues such as the kidney, intestine, and liver. Among these molecules, carnitine is an endogenous amine which is an essential cofactor for mitochondrial beta-oxidation. Recently, a new family of transporters, named OCT (organic cation transporters) has been described. In this minireview, we present the recent knowledge about OCT and focus on carnitine transport, more particularly by the OCTN2. The importance of this sodium-dependent carnitine cotransporter, OCTN2, comes from various recently reported mutations in the gene which give rise to the primary systemic carnitine deficiency (SCD; OMIM 212140). The SCD is an autosomal recessive disorder of fatty acid oxidation characterized by skeletal myopathy, progressive cardiomyopathy, hypoglycemia and hyperammonemia. Most of the OCTN2 mutations identified in humans with SCD result in loss of carnitine transport function. Identifying these mutations will allow an easy targeting of the SCD syndrome. The characteristics of the juvenile visceral steatosis (jvs) mouse, an animal model of SCD showing similar symptoms as humans having this genetic disorder, are also described. These mice have a mutation in the gene encoding the mouse carnitine transporter octn2. Although various OCTN carnitine transporters have been identified and functionally characterized, their membrane localization and regulation are still unknown and must be investigated. This knowledge will also help in designing new drugs that regulate carnitine transport activity.
Mol Genet Metab 2001 Aug
PMID:Carnitine transport by organic cation transporters and systemic carnitine deficiency. 1150 10

Embryos found to be abnormal during preimplantation genetic diagnosis are discarded or analyzed to confirm the diagnosis. The destruction of affected embryos is ethically unacceptable to some couples. We developed a preembryonic genetic diagnosis, that uses sequential first and second polar body removal, followed by oocyte freezing at the pronuclear stage. This was applied in a patient at risk of having a child with sickle cell disease, who suffered hyper-stimulation syndrome. Fourteen oocytes were obtained and tested for the maternal sickle cell allele by PCR analysis of the first and second polar body. Immediately after procedure of polar body removal, the pronuclear-stage oocytes were frozen. Six mutation-free oocytes detected by polar body analysis were then thawed, allowed to cleave, and transferred in the two consecutive clinical cycles, both resulting in clinical pregnancies, one of which resulted in birth of a healthy child. The oocytes predicted to contain abnormal beta-globin gene were not further cultured, to avoid formation and discard of the affected embryos. The results demonstrate feasibility of preembryonic diagnosis for single gene disorders, avoiding the establishment and destruction of mutant embryos.
Mol Cell Endocrinol 2001 Oct 22
PMID:Preembryonic diagnosis for sickle cell disease. 1157 27


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>