Does this mean iron IS .. intricately .. involved .. in the introduction of disease / parasites ..
INTO .. man .. ?
Exp Parasitol. 2003 Oct;105(2):111-20. Related Articles, Links
Tritrichomonas foetus: the role played by iron during parasite interaction with epithelial cells.
Melo-Braga MB, Da Rocha-Azevedo B, Silva-Filho FC.
UFRJ-Instituto de Biofisica Carlos Chagas Filho, CCS-Bloco G, G-0-44, 21949-900, Rio de
Janeiro, Brazil.
The aim of this work was to investigate the role played by iron during interaction of Tritrichomonas
foetus with cultured epithelial cells. We have observed that the growth rate of T. foetus is
influenced by the amount of iron available into culture medium. When organisms maintained for 24h in
iron-depleted medium were transferred to an iron-rich one, many protozoan cells exhibited a
cytokinesis blockage. Parasites maintained in iron-depleted medium exhibited a significant increase
in cytoadhesion when compared with both controls and parasites that had been cultured in medium in
which iron was replaced. T. foetus collected from iron-depleted medium also exhibited a reduction in
its ability to destroy epithelial cell monolayers and a reduction in the activity of several
cysteine proteases. Taken together, the results presented here demonstrate that iron may be an
extracellular signal, which seems to modulate the ability of T. foetus to interact with host
epithelial cells. Index descriptions and Abbreviations: Tritrichomonas foetus; parasitic protozoa;
iron; HeLa cells; cytoadhesion; cytotoxicity; cysteine proteases; l-trans-epoxysuccinylleucylamido-(4-
guanidino) butane E-64; EDTA, ethylenediaminetetraacetic acid; FCS, fetal calf serum; Hepes, N-2-hydroxyethylpiperazine-
[Formula: see text] -2-ethanesulfonic acid; PAGE, polyacrylamide gel electrophoresis; PBS, phosphate-
buffered saline; PFOR, pyruvate:ferredoxin oxidoreductase; PMSF, phenylmethylsulphonyl fluoride;
RPMI, Roswell Park Memorial Institute medium; SDS, sodium dodecyl sulfate; SOD, superoxide
dismutase; TLCK, N-alpha-p-tosyl-l-lisine chloromethyl ketone
PMID: 14969688 [PubMed - in process]
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Exp Parasitol. 1996 Jul;83(2):216-28. Related Articles, Links
Tritrichomonas foetus: iron acquisition from lactoferrin and transferrin.
Tachezy J, Kulda J, Bahnikova I, Suchan P, Razga J, Schrevel J.
Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic.
Acquisition of iron from lactoferrin and transferrin by a parasitic protozoon Tritrichomonas foetus
has been studied in vitro. Specific, time-dependent, and saturable binding of iodinated ligands to
the outer membrane of T. foetus at 4 degrees C was demonstrated for 125I-labeled lactoferrin only.
About 1.7 x 10(5) binding sites of a single class with Kd approximately equal to 3.6 microM was
estimated by means of Scatchard analysis. Internalization of the bound lactoferrin was observed at
37 degrees C. The cell-associated radioactivity after 30 min incubation of the parasite with 125I-
lactoferrin at 37 degrees C was about 3.5-fold higher than the amount bound at 4 degrees C. The
majority of internalized 125I-lactoferrin was released within 15 min of cell reincubation at 37
degrees C in the presence of a 100-fold excess of nonlabeled lactoferrin. Released lactoferrin
displayed unchanged mobility on autoradiography. In contrast to lactoferrin, binding of 125I-
transferrin was nonspecific and did not display saturable kinetics. The growth of T. foetus in iron-
restricted media was stimulated by both lactoferrin and transferrin. The ability of the cells to
remove and accumulate iron from both proteins was therefore examined using 59Fe-saturated
lactoferrin and transferrin. It was found that trichomonads acquired a comparable amount of iron
from both lactoferrin and transferrin during 60 min incubation at 37 degrees C (495 and 577 pmole
Fe/mg of protein, respectively). The pH of the assay medium (PBS) decreased from pH
7.4 to 5.6 after incubation with trichomonads. At this pH, marked release of iron from transferrin
(up to 47%) but not from lactoferrin (4%) was determined in cell-free media. These results
indicate that T. foetus is able to utilize both lactoferrin and transferrin to cover its iron
requirements. However, mechanisms of iron acquisition from these host proteins appear to be
different. Specific binding and internalization of lactoferrin suggests the possible involvement
of receptor-mediated endocytosis in the acquisition of lactoferrin-bound iron, while retrieval of
iron from transferrin may depend on the extracellular release of iron from this ligand.
PMID: 8682190 [PubMed - indexed for MEDLINE]
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