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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Tom