The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Yoshihiro Ito - One of the best experts on this subject based on the ideXlab platform.
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In vitro selection of Hemin-binding catalytic RNA
Bioorganic & medicinal chemistry letters, 2009Co-Authors: Mingzhe Liu, Takuma Kagahara, Hiroshi Abe, Yoshihiro ItoAbstract:Abstract Catalytic RNAs with peroxidase activity were obtained by the in vitro selection of RNA aptamer-binding Hemin. One of the RNA aptamers selected showed binding affinity to Hemin with a dissociation constant of 0.8 μM and exhibited high peroxidase activity by forming a complex with Hemin. The catalytic efficiency of the RNA–Hemin complex was 10-fold higher than that of Hemin alone.
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In vitro selection of RNA aptamer to Hemin
Nucleic Acids Symposium Series, 2008Co-Authors: Mingzhe Liu, Takuma Kagahara, Hiroshi Abe, Yoshihiro ItoAbstract:A new RNA aptamer-binding Hemin was synthesized by the in vitro selection (SELEX) method. A pool of 103 bases single strand DNAs containing a randomized sequence of 59 bases was synthesized. The pool was incubated with Hemin on Hemin-immobilized affinity column. Bound RNAs were eluted off with Hemin solution and amplified by PCR. After 3 rounds of selection process, the selected RNAs were cloned and sequenced. Some RNA aptamers, which have affinity to Hemin, was selected.
Caroline A. Genco - One of the best experts on this subject based on the ideXlab platform.
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Regulation of Hemin and Iron Transport in Porphyromonas Gingivalis
Advances in dental research, 1995Co-Authors: Caroline A. GencoAbstract:As with other pathogens, a requirement for the in vivo growth of Porphyromonas gingivalis is that the organism must be capable of obtaining iron from the host. The ability to utilize Hemin and Hemin-containing compounds for nutritional iron has been documented for several pathogenic bacteria, including P. gingivalis; however, the mechanisms involved in Hemin uptake are poorly defined. I have determined that P. gingivalis transports the entire Hemin moiety into the cell by an energy-dependent mechanism and that the binding and accumulation of Hemin are induced by growth of cultures in the presence of Hemin. A model of Hemin transport in P. gingivalis consistent with these results is presented. I have also found that, in P. gingivalis, Hemin regulates the expression of several putative virulence factors; this in turn results in the increased virulence potential of P. gingivalis as assessed in an animal model. Regulation of Hemin-responsive genes in P. gingivalis may occur by a negative regulator, as has bee...
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Binding and accumulation of Hemin in Neisseria gonorrhoeae.
Infection and immunity, 1995Co-Authors: Pragnya Jasvantrai Desai, R Nzeribe, Caroline A. GencoAbstract:The ability to utilize Hemin and Hemin-containing compounds for nutritional iron (Fe) uptake has been documented for several pathogenic bacteria. Neisseria gonorrhoeae can utilize free Hemin as a source of Fe for growth; however, little is known concerning the mechanisms involved in Hemin transport. In this study we have characterized the binding and accumulation of Hemin by N. gonorrhoeae and defined the specificity of the gonococcal Hemin receptor. N. gonorrhoeae F62 was grown in a chemically defined medium containing the iron chelator Desferal, and Hemin transport was initiated by the addition of [59Fe]Hemin (4.0 or 8.0 microM; specific activity, 7.0 Ci/mol). 59Fe uptake from radiolabeled Hemin by N. gonorrhoeae was energy dependent, and 59Fe was shown to accumulate in the cell at a constant rate during logarithmic growth. However, we observed a decrease in the uptake of 59Fe from radiolabeled Hemin when inorganic iron was present in the growth medium. Binding of 59Fe from radiolabeled Hemin was inhibited by the addition of either cold Hemin, hematoporphyrin, or hemoglobin, but not by ferric citrate. Although [14C]Hemin was found to support the growth of N. gonorrhoeae, we did not detect the uptake of 14C from radiolabeled Hemin. Extraction of the gonococcal periplasmic ferric binding protein (Fbp) from cultures grown with [59Fe]Hemin indicated that a majority of the 59Fe was associated with the Fbp. Taken together, the results presented here indicate that Hemin binds to a gonococcal outer membrane receptor through the protoporphyrin portion of the molecule and that following binding, iron is removed and transported into the cell, where it is associated with the gonococcal periplasmic ferric binding protein, Fbp.
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Characterization of a Tn4351-generated Hemin uptake mutant of Porphyromonas gingivalis: evidence for the coordinate regulation of virulence factors by Hemin.
Infection and immunity, 1995Co-Authors: Caroline A. Genco, Waltena Simpson, R Y Forng, Mariam Egal, B M OdusanyaAbstract:The ability of Porphyromonas gingivalis to acquire iron in the iron-limited environment of the host is crucial to the colonization of this organism. We report here on the isolation and characterization of a transpositional insertion mutant of P. gingivalis A7436 (designated MSM-3) which is defective in the utilization and transport of Hemin. P. gingivalis MSM-3 was selected on the basis of its nonpigmented phenotype on anaerobic blood agar following mutagenesis with the Bacteroides fragilis transposon Tn4351. P. gingivalis MSM-3 grew poorly when supplied with Hemin as a sole source of iron; however, growth was observed with hemoglobin or inorganic iron. P. gingivalis MSM-3 grown in either Hemin-replete or Hemin-depleted conditions bound and transported less [14C]Hemin or [59Fe]Hemin than did the parent strain. At 4 h, P. gingivalis MSM-3 grown in Hemin-replete conditions transported only 10,000 pmol of Hemin per mg of protein, or 14% of the amount transported by P. gingivalis A7436. Unlike P. gingivalis A7436, Hemin binding and transport by P. gingivalis MSM-3 were not tightly regulated by Hemin or iron. Examination of P. gingivalis MSM-3 cultures by electron microscopy revealed an overproduction of membrane vesicles, and determination of the dry weight of purified vesicles indicated that P. gingivalis MSM-3 produced twice as much membrane vesicles as did strain A7436. Extracellular vesicles isolated from P. gingivalis MSM-3 also were found to express increased hemolytic and trypsin-like protease activities compared with the parent strain. When inoculated into subcutaneous chambers implanted in mice, P. gingivalis MSM-3 was highly infectious and more invasive than the parent strain, as indicated by secondary lesion formation and death. Taken together, these results indicate that the decreased transport of Hemin by P. gingivalis MSM-3 results in the increased expression of several virulence factors which may be coordinately regulated by Hemin.
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Binding and accumulation of Hemin in Porphyromonas gingivalis are induced by Hemin.
Infection and immunity, 1994Co-Authors: Caroline A. Genco, B M Odusanya, G BrownAbstract:Although Hemin is an essential nutrient for the black-pigmented oral bacterium Porphyromonas gingivalis, the mechanisms involved in Hemin binding and uptake are poorly defined. In this study, we have examined the binding of Hemin and Congo red (CR) to P. gingivalis whole cells and have defined the conditions for maximal binding. Additionally, the accumulation of Hemin by P. gingivalis under growing conditions has been characterized. P. gingivalis A7436 was grown under Hemin- or iron-deplete conditions (basal medium [BM] or Schaedler broth with dipyridyl [SBD]) or under Hemin- or iron-replete conditions (BM with Hemin [BMH] or Schaedler broth [SB]), and Hemin and CR binding were assessed spectrophotometrically. Binding of Hemin by P. gingivalis whole cells was rapid and was observed in samples obtained from cells grown under Hemin- and iron-replete and Hemin-deplete conditions but was not observed in cells grown under iron limitation. We also found that P. gingivalis whole cells bound more Hemin when grown in BMH or SB than cells grown in BM or SBD. Binding of CR by P. gingivalis A7436 was also enhanced when cells were grown in the presence of Hemin or when cells were incubated with Hemin prior to CR binding. Hemin binding and accumulation were also assessed using [14C]Hemin and [59Fe]Hemin under growing conditions. Both [14C]Hemin and [59Fe]Hemin were accumulated by P. gingivalis, indicating that iron and the porphyrin ring were taken into the cell. Binding and accumulation of Hemin under growing conditions were also induced by growth of P. gingivalis in Hemin-replete media. Hemin accumulation was inhibited by the addition of KCN to P. gingivalis cultures, indicating that active transport was required for Hemin uptake. [14C]Hemin binding and accumulation were also inhibited by the addition of either cold Hemin or protoporphyrin IX. Taken together, these results indicate that P. gingivalis transports the entire Hemin moiety into the cell and that the binding and accumulation of Hemin are induced by growth of cultures in the presence of Hemin.
Mingzhe Liu - One of the best experts on this subject based on the ideXlab platform.
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In vitro selection of Hemin-binding catalytic RNA
Bioorganic & medicinal chemistry letters, 2009Co-Authors: Mingzhe Liu, Takuma Kagahara, Hiroshi Abe, Yoshihiro ItoAbstract:Abstract Catalytic RNAs with peroxidase activity were obtained by the in vitro selection of RNA aptamer-binding Hemin. One of the RNA aptamers selected showed binding affinity to Hemin with a dissociation constant of 0.8 μM and exhibited high peroxidase activity by forming a complex with Hemin. The catalytic efficiency of the RNA–Hemin complex was 10-fold higher than that of Hemin alone.
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In vitro selection of RNA aptamer to Hemin
Nucleic Acids Symposium Series, 2008Co-Authors: Mingzhe Liu, Takuma Kagahara, Hiroshi Abe, Yoshihiro ItoAbstract:A new RNA aptamer-binding Hemin was synthesized by the in vitro selection (SELEX) method. A pool of 103 bases single strand DNAs containing a randomized sequence of 59 bases was synthesized. The pool was incubated with Hemin on Hemin-immobilized affinity column. Bound RNAs were eluted off with Hemin solution and amplified by PCR. After 3 rounds of selection process, the selected RNAs were cloned and sequenced. Some RNA aptamers, which have affinity to Hemin, was selected.
Arnold Stern - One of the best experts on this subject based on the ideXlab platform.
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Inhibition of Hemin-induced hemolysis by desferrioxamine: binding of Hemin to red cell membranes and the effects of alteration of membrane sulfhydryl groups.
Biochimica et biophysica acta, 1992Co-Authors: Stephen Gene Sullivan, Erol Baysal, Arnold SternAbstract:Hemin binds to red cell membranes during Hemin-induced hemolysis but the precise mechanism of hemolysis has not been characterized. Desferrioxamine (DFO), an iron chelator, inhibited Hemin-induced hemolysis. DFO partially prevented Hemin binding to red cell membranes and partially removed previously bound Hemin. Glutathione, an intracellular sulfhydryl compound, also inhibited Hemin-induced hemolysis but was only about one tenth as potent as DFO. Decrease of membrane sulfhydryl groups by treatment of cells with either N-ethylmaleimide (NEM) or diamide (azodicarboxylic acid bis [dimethylamide]) enhanced Hemin-induced hemolysis. Enhancement of Hemin-induced hemolysis by NEM and diamide and inhibition of hemolysis by DFO were independent with no evidence of synergism or interference between the two processes. Red cell membranes were saturated with Hemin at approximately 75 nmol per mg protein. DFO decreased the Hemin saturation level to 25 nmol per mg protein. In the presence of DFO, Hemin was bound as the DFO-Hemin complex since membranes preferentially removed DFO-Hemin complexes from mixtures of complexed and free Hemin while free DFO was not bound by the membranes. Access to the inner surface of the membrane was required for binding of the DFO-Hemin complex since DFO completely prevented Hemin binding in intact cells but not in cells undergoing hemolysis or red cell ghosts. Approximately 50 x 10(6) molecules of Hemin were bound to the membrane of one red cell following Hemin-induced hemolysis.
Glenda M. Bishop - One of the best experts on this subject based on the ideXlab platform.
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Phenanthrolines Protect Astrocytes from Hemin Without Chelating Iron
Neurochemical research, 2014Co-Authors: Jessica E. Owen, Glenda M. Bishop, Stephen R. RobinsonAbstract:Hemin, the degradation product of hemoglobin, contributes to the neurodegeneration that occurs in the weeks following a hemorrhagic stroke. The breakdown of Hemin in cells releases redox-active iron that can facilitate the production of toxic hydroxyl radicals. The present study used 3-week old primary cultures of mouse astrocytes to compare the toxicity of 33 μM Hemin in the presence of the iron chelator 1,10-phenanthroline or its non-chelating analogue, 4,7-phenanthroline. This concentration of Hemin killed approximately 75 % of astrocytes within 24 h. Both isoforms of phenanthroline significantly decreased the toxicity of Hemin, with the non-chelating analogue providing complete protection at concentrations of 33 μM and above. The decrease in toxicity was associated with less cellular accumulation of Hemin. Approximately 90 % of the Hemin accumulated was not degraded, irrespective of treatment condition. These observations indicate that chelatable iron is not the cause of Hemin toxicity. Cell-free experiments demonstrated that Hemin can inactivate a molar excess of hydrogen peroxide (H2O2), and that the rate of inactivation is halved in the presence of either isoform of phenanthroline. We conclude that phenanthrolines may protect astrocytes by limiting Hemin uptake and by impairing the capacity of intact Hemin to interact with endogenous H2O2.
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Uptake, metabolism and toxicity of Hemin in cultured neurons.
Neurochemistry international, 2011Co-Authors: Theresa Ngoc Thu Dang, Stephen R. Robinson, Ralf Dringen, Glenda M. BishopAbstract:Following hemorrhagic stroke, red blood cells lyse and release neurotoxic Hemin into the interstitial space. The present study investigates whether neurons can accumulate and metabolize Hemin. We demonstrate that cultured neurons express the heme carrier protein 1 (HCP1), and that this transporter appears to contribute to the time- and concentration-dependent accumulation of Hemin by neurons. Although exposure of neurons to Hemin stimulates the synthesis of the iron storage protein ferritin, approximately 80% of the Hemin accumulated by neurons remains intact. Within 24 h of incubation, substantial neurotoxicity was observed that was not attenuated by the cell permeable, selective ferrous iron chelator, 1,10-phenanthroline. These results demonstrate that while neurons efficiently accumulate Hemin they slowly degrade it, and they support the conclusion that intact Hemin is more neurotoxic than the iron released from the breakdown of Hemin. Further investigations are required to determine the basis of this neurotoxicity.
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Hemin toxicity a preventable source of brain damage following hemorrhagic stroke
Redox Report, 2009Co-Authors: Stephen R. Robinson, Theresa Ngoc Thu Dang, Ralf Dringen, Glenda M. BishopAbstract:Hemorrhagic stroke is a common cause of permanent brain damage, with a significant amount of the damage occurring in the weeks following a stroke. This secondary damage is partly due to the toxic effects of Hemin, a breakdown product of hemoglobin. The serum proteins hemopexin and albumin can bind Hemin, but these natural defenses are insufficient to cope with the extremely high amounts of Hemin (10 mM) that can potentially be liberated from hemoglobin in a hematoma. The present review discusses how Hemin gets into brain cells, and examines the multiple routes through which Hemin can be toxic. These include the release of redox-active iron, the depletion of cellular stores of NADPH and glutathione, the production of superoxide and hydroxyl radicals, and the peroxidation of membrane lipids. Important gaps are revealed in contemporary knowledge about the metabolism of Hemin by brain cells, particularly regarding how Hemin interacts with hydrogen peroxide. Strategies currently being developed for the reduction of Hemin toxicity after hemorrhagic stroke include chelation therapy, antioxidant therapy and the modulation of heme oxygenase activity. Future strategies may be directed at preventing the uptake of Hemin into brain cells to limit the opportunity for toxic interactions.