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

Toxic and carcinogenic effects of parenteral and percutaneous ATP and its iron complex

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.

Free radical scavengers: chemical concepts and clinical relevance

Free radicals are involved in the pathology of many CNS disorders, like Parkinson's disease, Alzheimer's disease, or stroke. This discovery lead to the development of many radical scavengers for the clinical treatment of neurodegenerative diseases. In this review, the different chemical concepts for free radical scavenging will be discussed: nitrons, thiols, iron chelators, phenols, and catechols. Especially catechols, like the naturally occurring flavonols, the synthetic drug nitecapone, or the endogenous catacholamines and their metabolites, are of great interest, as they combine iron chelating with radical scavenging activity. We present data on the radical scvenging activity of dopamine and apomorphine, which prevent lipid peroxidation in rat brain mitochondria and protect PC12 cells against H2O2-toxicity.

Effects of low-molecular-weight aluminum complexes on brain tissue calcium homeostasis

The in vitro effects of low-molecular-weight aluminum complexes (citrate, lactate, and ATP complex) on the Ca2+ uptake and aluminum-induced lipid peroxidation of brain tissue show that the modification of the calcium homeostasis is determined by the nature of the ligand and that there is no correlation between the aluminum-induced lipid peroxidation and the Ca2+ uptake. The same characteristics have been shown by a similar study performed with Ehrlich carcinoma cells. The electrophoretic analyses of the aluminum lactate-albumin and aluminum lactate-ATP interactions indicate an aluminum transfer from the lactate to the albumin and ATP ligands. The increased Ca2+ uptake when ATP is present in the incubation medium with aluminum citrate and aluminum lactate corroborates the suggested mediator role of ATP in cellular calcium homeostasis modification induced by iron.

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 Alzheimer's and Parkinson's diseases, in whose etiology the implication of aluminum and iron has been suggested.