The effect of chelating agents on iron mobilization in Chang cell cultures.
The investigation of chelating agents with potential therapeutic value in patients with transfusional iron overload has been facilitated by the use of Chang cell cultures. These cells have been incubated with [59Fe]transferrin for 22 hr, following which most of the intracellular radioiron is found in the cytosol, distributed between a ferritin and a nonferritin form. Iron release from the cells depends on transferrin saturation in the medium, but when transferrin is 100% saturated, which normally does not allow iron release, desferrioxamine, 2,3-dihydroxybenzoic acid, rhodotorulic acid, cholythydroxamic acid, and tropolone all promote the mobilization of ferritin iron and its release from cells. They are effective to an approximately equal degree. The incubation of [59Fe]transferrin with tropolone in vitro at a molar ratio of 1:500 results in the transfer of most of the labeled iron to the chelator, reflecting the exceptionally high binding constant of this compound. How far these phenomena relate to therapeutic potentially remains to be seen. (+info)
Studies of the binding of different iron donors to human serum transferrin and isolation of iron-binding fragments from the N- and C-terminal regions of the protein.
1. Trypsin digestion of human serum transferrin partially saturated with iron(III)-nitrilotriacetate at pH 5.5 or pH 8.5 produces a carbohydrate-containing iron-binding fragment of mol.wt. 43000. 2. When iron(III) citrate, FeCl3, iron (III) ascorabate and (NH4)2SO4,FeSO4 are used as iron donors to saturate the protein partially, at pH8.5, proteolytic digestion yields a fragment of mol.wt. 36000 that lacks carbohydrate. 3. The two fragments differ in their antigenic structures, amino acid compositions and peptide 'maps'. 4. The fragment with mol.wt. 36000 was assigned to the N-terminal region of the protein and the other to the C-terminal region. 5. The distribution of iron in human serum transferrin partially saturated with various iron donors was examined by electrophoresis in urea/polyacrylamide gels and the two possible monoferric forms were unequivocally identified. 6. The site designated A on human serum transferrin [Harris (1977) Biochemistry 16, 560--564] was assigned to the C-terminal region of the protein and the B site to the N-terminal region. 7. The distribution of iron on transferrin in human plasma was determined. (+info)
Role of iron in Nramp1-mediated inhibition of mycobacterial growth.
Innate resistance to mycobacterial growth is mediated by a gene, Nramp1. We have previously reported that Nramp1 mRNA from macrophages of Mycobacterium bovis BCG-resistant (Bcgr) mice is more stable than Nramp1 mRNA from macrophages of BCG-susceptible (Bcgs) mice. Based on these observations and on reports that show that the closely related Nramp2 gene is a metal ion transporter, we evaluated the effect of iron on the growth of Mycobacterium avium within macrophages as well as on the stability of Nramp1 mRNA. The addition of iron to macrophages from Bcgs mice resulted in a stimulation of mycobacterial growth. In contrast, iron increased the capacity of macrophages from Bcgr mice to control the growth of M. avium. When we treated recombinant gamma interferon (IFN-gamma)-activated macrophages with iron, we found that iron abrogated the growth inhibitory effect of IFN-gamma-activated macrophages from Bcgs mice but that it did not affect the capacity of macrophages from Bcgr mice to control microbial growth. A more detailed examination of the effect of iron on microbial growth showed that the addition of small quantities of iron to resident macrophages from Bcgr mice stimulated antimicrobial activity within a very narrow dose range. The effect of iron on the growth inhibitory activity of macrophages from Bcgr mice was abrogated by the addition of catalase or mannitol to the culture medium. These results are consistent with an Fe(II)-mediated stimulation of the Fenton/Haber-Weiss reaction and hydroxyl radical-mediated inhibition of mycobacterial growth. (+info)
Characterization of Moraxella (Branhamella) catarrhalis lbpB, lbpA, and lactoferrin receptor orf3 isogenic mutants.
Pathogenic members of the family Neisseriaceae produce specific receptors to acquire iron from their host's lactoferrin and transferrin. Recently, putative Moraxella catarrhalis lactoferrin receptor genes and a third open reading frame (lbpB, lbpA, and orf3) were cloned and sequenced. We describe the preliminary characterization of isogenic mutants deficient in LbpB, LbpA, or Orf3 protein. (+info)
Chemical and immunochemical measurement of total iron-binding capacity compared.
Radiometric, colorimetric, and two immunochemical methods for measuring total iron-binding capacity are compared. We evaluated the procedures on the basis of precision, applicability to a pediatric population, and accuracy as assessed by analytical recovery of purified transferrin. The immunoephelometric assay for transferrin provides significant advantages over the other methods examined. (+info)
Changes in haematological parameters and iron metabolism associated with a 1600 kilometre ultramarathon.
OBJECTIVE: To investigate haematological variations and iron related changes in the serum of participants in a 1600 kilometre ultramarathon run. PARTICIPANTS: Seven male and two female participants in a 1600 km foot race. METHODS: Blood samples were obtained from the participants before, after four and 11 days of running, and at the end of the event. Samples were analysed by standard methods for haemoglobin, packed cell volume, total red cell count, mean red cell volume, mean red cell haemoglobin, total white cell count and differential, platelets, reticulocytes, iron, ferritin, total iron binding capacity, percentage transferrin saturation, haptoglobin, and bilirubin and corrected for changes in plasma volume. RESULTS: The following variables decreased during the event (p < 0.05): haemoglobin, packed cell volume, mean red cell volume, percentage lymphocytes, percentage monocytes, serum iron, total iron binding capacity, and percentage transferrin saturation. Increases (p < 0.05) were found in plasma volume, total red cell count (day 4 only), total white cell count, percentage and absolute numbers of neutrophils and reticulocytes, absolute numbers of lymphocytes and monocytes (day 4 only), absolute numbers of eosinophils (day 11 and race end), absolute numbers of basophils (race end only), platelets, ferritin, haptoglobin, and bilirubin (day 4 only). CONCLUSION: Ultramarathon running is associated with a wide range of changes in haematological parameters, many of which are related to the normal acute phase response to injury. These should not be confused with indicators of disease. (+info)
Coronary heart disease and iron status: meta-analyses of prospective studies.
BACKGROUND: Studies of iron status and coronary heart disease (CHD) have yielded conflicting results. In a systematic review ("meta-analysis"), we quantitatively assessed epidemiological associations reported in prospective studies. METHODS AND RESULTS: Studies were identified by computer-assisted searches of the published literature, scanning of relevant reference lists, hand searching of relevant journals, and discussions with relevant authors. The following was abstracted: size and type of cohort, mean age, mean duration of follow-up, assay methods, degree of adjustment for confounders, and relationship of CHD risk to the baseline assay results. Twelve studies were identified, involving a total of 7800 CHD cases, with several reporting on >1 marker of iron status. For serum ferritin, with 570 CHD cases in 5 studies, comparison of individuals with baseline values >/=200 versus <200 microg/L yielded a combined risk ratio of 1.0 (95% CI, 0.8 to 1.3). For transferrin saturation, with 6194 CHD cases in 5 studies, comparison of individuals in the top third with those in the bottom third of the baseline measurements yielded a combined risk ratio of 0.9 (95% CI, 0.7 to 1.1). Comparisons of individuals in top and bottom thirds of baseline measurements also yielded nonsignificant risk ratios in combined analyses of studies involving total iron-binding capacity (combined risk ratio, 1.0; 95% CI, 0.7 to 1.5), serum iron (0.8; 95% CI, 0.7 to 1.0), and total dietary iron (0.8; 95% CI, 0.7 to 1.1). CONCLUSIONS: Published prospective studies do not provide good evidence to support the existence of strong epidemiological associations between iron status and CHD. (+info)
The binding of human lactoferrin to mouse peritoneal cells.
Human iron-saturated Lf (FeLf), which was labeled with 125I or 50Fe, was found to combine with the membrane of mouse peritoneal cells (MPC) which consisted of 70% macrophages. The following experimental data suggested the involvement of a specific receptor. (a) The binding of FeLf to MPC reached a saturation point. (b) The binding of radioactive FeLf was inhibited by preincubating the cells with cold FeLf but not with human Tf, human aggregated and nonaggregated IgG, or beef heart cytochrome c (c) Succinylation and carbamylation of FeLf resulted in a loss of its inhibiting activity on the binding of radioactive FeLf. Removal of neuraminic acid from FeLf increased its inhibitory activity. (d) The ability of apoLf to inhibit the binding of FeLf to MPC was significantly lower than that of FeLf. The existence of a Lf receptor capable of concentrating Lf released from neutrophils on the membrane of macrophages could explain the apparent blockade of the release of iron from the reticuloendothelial system, which accounts for the hyposideremia of inflammation. A receptor for FeLf was also found on mouse peritoneal lymphocytes. The affinity constant of FeLf for both lymphocytes and macrophages was 0.9 X 12(6) liter/mol. Howerver, macrophages bound three times more FeLf molecules (20 X 10(6)) per cell than did lymphocytes (7 X 10(6)). (+info)