Leopold J. Anghileri

Natural polyphenols-iron interaction: its biological importance.

The iron-binding capacity of different fractions of natural polyphenols extracts was determined by chromatographic and electrophoretic methods. Their effects on iron-induced calcium homeostasis changes in liver tissue suspension showed that mate tea and green tea extracts provoke a very significant inhibition of the iron effects, whereas it is much less significant with red wine extract. The biological importance of this phenomenon is discussed.

Changes in calcium uptake by liver induced by ferric lactate

In vitro and in vivo Ca(2+)-uptake by the liver is increased by ferric lactate. In vitro albumin and deferoxamine inhibit ferric lactate effects. Electrophoresis demonstrates the binding of ferric lactate to albumin. In vivo, ferric lactate induces a significant increase of Ca(2+)-uptake by liver, with a maximum of 2.9 nmol/g against 0.66 nmol/g for control livers (P less than 0.005) between 5 and 24 h after administration. This uptake modification is reversible, while the amount of iron (measured as 59Fe taken up) remains constant throughout the experiment. The affinity of ferric lactate for protein and the iron mass-dependence of Ca(2+)-uptake increase support for the hypothesis of a ferric lactate-cell membrane interaction rather than an iron-catalyzed cell injury by lipid peroxidation as the major event leading to an increased Ca(2+)-uptake.

TOXIC AND CARCINOGENIC EFFECTS OF PARENTERAL AND PERCUTANEOUS ATP AND ITS IRON COMPLEX

ABSTRACT The long term effects of percutaneous, subcutaneous and intraperitoneal administration of sodium–ATP (NaATP) and ferric iron–ATP (FeATP) were studied on an animal model. Both compounds induce a generalized lymphoadenitis which in the case of FeATP led to lymphomas. The analytical study of the involved target tissues showed intracellular composition changes that result from the impairment of the cell membrane permeability. The morbidity and mortality rate were higher with FeATP which seems to be the result of two different, in intensity and duration, interactions with the cell plasma membrane. The influence of the changes in cellular calcium homeostasis, and its relationship with carcinogenesis and immuno response are discussed.

ATP in Cellular Calcium-Overload by Trivalent Metal Ions

Extracellular Ca2+-influx induced by trivalent metal ions (Fe3+, Al3+, Cr3+, In3+, Ga3+, and La3+) in Ehrlich carcinoma cells is enhanced by ATP. This action seems to be related to the high coordination capacity of the ATP ligand that inhibits the polymerization of the solvated cations taking place at physiological pH, and consequently permits their biological activity. A general relationship between induced lipid peroxidation and increased calcium uptake was not found. These results emphasize the ATP role in the toxicity of trivalent metals, and its possible involvement, via cellular calcium overload, in a neurodegenerative process, such as Alzheimers and Parkinsons diseases, in whose etiology the implication of aluminum and iron has been suggested.

In vivo distribution of ferric-ATP complex

SummaryAt physiological pH, ferric-ATP complex presents ionic characteristics unlike those of ferric lactate. Its rapid diffusion into the tissues, and its reactivity which is not impaired by polymerization seem responsible for its toxicity. In comparison with ferric lactate, after parenteral administration there is a much higher spleen, lung, kidney and bone accumulation. After oral administration, on the other hand, the values are lower. ATP hydrolysis by the stomach’s pH, and the subsequent iron insolubilisation as phosphate could be the reason for this behaviour.

The role of ATP as a mediator in the action of iron complexes on cellular calcium homeostasis

The effects of the interaction between low molecular weight iron complexes (citrate, lactate, and ATP complexes) with ATP and proteins, on the modification of Ehrlich carcinoma cell calcium homeostasis have been studied. In that modification the ferric-ATP complex shows much higher activity than the others. Sodium ATP, by iron translocation from citrate and lactate, increases their activity. This phenomenon implicates ATP as a mediator on the cellular activity of the complexes. Proteins, particularly ferritin, appear to moderately reduce their activity, whereas glutathione and ascorbic acid, acting as lipid peroxidation-inhibitors, show only a slight reduction of the iron complex’s effects on cellular calcium uptake.

On the mechanism of soft tissue calcification induced by complexed iron

The interaction of ferric lactate with Ehrlich carcinoma ascites cells induces a modification of Ca(2+)-uptake which is in direct relationship with the iron mass bound to the cells. Competitive binding of iron by deferoxamine indicates that only a part of the bound iron penetrates the cell, and that to trigger a Ca(2+)-influx this intracellular iron must be over a threshold concentration. The experimental finding that ferric lactate transfers its iron to albumin and to ATP suggests that in the Ca(2+)-uptake modification it works through its iron transfer which provokes the inhibition of the cell calcium homeostasis regulatory systems (Ca(2+)-channels, intracellular Ca(2+)-binding sites and Ca(2+)-pump ATPase). The involvement of ATP in the action of ferric lactate seems related to a higher stability of the complex, and to a larger availability of active iron able to perform the inhibitory process.

Effects of albumin and adenosine phosphates on iron transfer from ferric lactate

Ferric lactate is known to modify Ca2+ uptake by the cells. To enlighten the role of protein and ATP in this phenomenon, iron transfer from ferric lactate to albumin and adenosine polyphosphates was determined by electrophoresis. The order of iron affinity was ATP>ADP>AMP for the polyphosphates, and albumin does not compete for iron binding with the polyphosphates. The iron transfer to ATP was also observed in vivo by adsorption chromatography of the adenosine polyphosphates fraction from blood plasma of mice injected with ferric lactate plus ATP. In vitro iron and calcium uptake by Ehrlich ascites tumor cells showed that albumin and ATP decreased iron uptake, whereas calcium incorporation is diminished by albumin but augmented by ATP. This difference might be explained by albumin binding of ferric lactate that is inhibited from reaching cell structures, whereas ATP, known to be an inhibitor of iron polimerization, facilitates it.

In vivo behaviour of low molecular weight iron complexes

SummaryThe in vivo distribution in mice of ferric citrate, ferric β-glycerophosphate and ferric lactate complexes has been studied. There is a relationship between the59Fe uptake by various tissues and the physicochemical characteristics of the complexes. Ferric lactate seems a useful preparation for iron deficiency therapy.

Molecular exchange of metal ions and tissular calcium overload

In vitro and in vivo, mouse tissues assayed for 45Ca2+ uptake have shown that ATP increases the Ca2+ take-up in the presence of lactates of iron and aluminum, but this effect is absent with the citrates. The in vitro metal ion exchange with ATP has been demonstrated by electrophoresis and by chromatography. It is considered the cause of the increased capacity of ATP to modify the cellular effects of lactates. The in vitro modifications of Ca2+ uptake by lactates when in the presence of ATP are much more important than those of citrate. In general, aluminum compounds show a higher Ca2+ uptake and, coincidentally, they have shown a higher carcinogenic capacity than iron ATP.