ATP in cellular calcium-overload by trivalent metal ions

Lanthanum nanoparticles to target the brain: proof of biodistribution and biocompatibility with adjuvant therapies

Aim: To determine the biodistribution of lanthanum (III) oxide (La₂O₃) nanoparticle (NP) therapy to the brain and its biocompatibility with radiation therapy (RT) and chemotherapy (CT). Materials & methods: Healthy balb/c nude mice were administered 4 weekly doses of La₂O₃ NP therapy via tail vein injection. Organ weights and lanthanum concentrations were evaluated. Results: La₂O₃ NP penetrated the brain. Concentrations were found to peak in the brain at 24 h after injection and persisted at 8 weeks after injection. Neither RT nor CT affected biodistribution. No adverse events or safety concerns in other organs were noted. Conclusion: La₂O₃ NP can reach the brain to target neurological disease and is biocompatible with RT and CT in a biological system.

Knockdown of STIM1 inhibits 6-hydroxydopamine-induced oxidative stress through attenuating calcium-dependent ER stress and mitochondrial dysfunction in undifferentiated PC12 cells

Stromal interaction molecule (STIM) proteins are parts of elaborate eukaryotic Ca(2+) signaling systems and are considered to be important players in regulating neuronal Ca(2+) homeostasis under normal ageing and pathological conditions. Here, we investigated the potential role of STIM1 in 6-hydroxydopamine (6-OHDA)-induced toxicity in undifferentiated PC12 cell lines. Cells exposed to 6-OHDA demonstrated alterations in the generation of reactive oxygen species (ROS) in a Ca(2+)-dependent manner. Downregulation of STIM1 expression by specific small interfering RNA (siRNA) attenuated apoptotic cell death, reduced intracellular ROS production, and partially prevented the impaired endogenous antioxidant enzyme activities after 6-OHDA treatment. Furthermore, STIM1 knockdown significantly attenuated 6-OHDA-induced intracellular Ca(2+) overload by inhibiting endogenous store-operated calcium entry (SOCE). The effect of STIM1 siNRA on SOCE was related to orai1 and L-type Ca(2+) channels, but not to transient receptor potential canonical type 1 (TRPC1) channel. In addition, silencing of STIM1 increased the Ca(2+) buffering capacity of the endoplasmic reticulum (ER) in 6-OHDA-injured cells. ER vacuoles formed from the destruction of ER structural integrity and activation of ER-related apoptotic factors (CHOP and Caspase-12) were partially prevented by STIM1 knockdown. Moreover, STIM1 knockdown attenuated 6-OHDA-induced mitochondrial Ca(2+) uptake and mitochondrial dysfunction, including the collapse of mitochondrial membrane potential (MMP) and the decrease of ATP generation. Taken together, our data provide the first evidence that inhibition of STIM1-meditated intracellular Ca(2+) dyshomeostasis protects undifferentiated PC12 cells against 6-OHDA toxicity and indicate that STIM1 may be responsible for neuronal oxidative stress induced by ER stress and mitochondrial dysfunction in PD.

The effect of pyrophosphate, tripolyphosphate and ATP on the rate of the Fenton reaction

It has been recently reported that pyrophosphate, tri-polyphosphate, ATP and analogous ligands considerably decrease the yield of hydroxyl radicals by the Fenton reaction under conditions where [H(2)O(2)]>>[Fe(II)L(n)]. It was suggested that this effect is due to the slowing down of the Fenton reaction by these ligands. This suggestion seemed surprising as polyphosphate ligands stabilize Fe(III). Indeed, a kinetic study points out that these ligands accelerate the rate of the Fenton reaction by several orders of magnitude. Thus it is suggested that the effect of the ligands on the yield of the hydroxyl radicals is due to the stabilization of the Fe(III) complexes which slows down, or inhibits, their reduction by the radicals formed in the system and thus decreases the overall yield of hydroxyl radicals.

The paradoxical immuno-response of adenosine triphosphate effects

The actual research on the paradoxical effects of ATP to obtain to optimal conditions of the immune response against certain pathologies. The ATP Paradox, after its interaction with iron or aluminum, which have shown important effects on carcinogenesis, suggests its implication in pathological systems in which overcalcification may play a role.

Characterization and elucidation of coordination requirements of adenine nucleotides complexes with Fe(II) ions

In spite of the significant role of iron ions-nucleotide complexes in living cells, these complexes have been studied only to a limited extent. Therefore, we fully characterized the ATP:Fe(II) complex including stoichiometry, geometry, stability constants, and dependence of Fe(II)-coordination on pH. A 1:1 stoichiometry was established for the ATP:Fe(II) complex based on volumetric titrations, UV and SEM/EDX measurements. The coordination sites of ferrous ions in the complex with ATP, established by 1H-, 31P-, and 15N-NMR, involve the adenine N7 as well as P(alpha), P(beta), and P(gamma). Coordination sites remain the same within the pH range of 3.1-8.3. By applying fluorescence monitored Fe(II)-titration, we established a logK value of 5.13 for the Fe(ATP)2- complex, and 2.31 for the Fe(HATP)-complex. Ferrous complexes of ADP3- and AMP2- were less stable (log K 4.43 and 1.68, respectively). The proposed major structure for the Fe(ATP)2- complex is the 'open' structure. In the minor 'closed' structure N7 nitrogen is probably coordinated with Fe(II) through a bridging water molecule. The electronic and stereochemical requirements for Fe(II)-coordination with ATP4- were probed using a series of modified-phosphate or modified-adenine ATP analogues. We concluded that: Fe(II) coordinates solely with the phosphate-oxygen atom, and not with sulfur, amine, or borane in the cases of phosphate-modified analogues of ATP; a high electron density on N7 and an anti conformation of the adenine-nucleotide are required for enhanced stability of ATP analogues:Fe(II) complexes as compared to ATP complexes (up to more than 100-fold); there are no stereochemical preferences for Fe(II)-coordination with either Rp or Sp isomers of ATP-alpha-S or ATP-alpha-BH3 analogues.

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.

A unifying hypothesis of Alzheimer's disease. III. Risk factors

Normal ageing and Alzheimer's disease (AD) have many features in common and, in many respects, both conditions only differ by quantitative criteria. A variety of genetic, medical and environmental factors modulate the ageing-related processes leading the brain into the devastation of AD. In accordance with the concept that AD is a metabolic disease, these risk factors deteriorate the homeostasis of the Ca(2+)-energy-redox triangle and disrupt the cerebral reserve capacity under metabolic stress. The major genetic risk factors (APP and presenilin mutations, Down's syndrome, apolipoprotein E4) are associated with a compromise of the homeostatic triangle. The pathophysiological processes leading to this vulnerability remain elusive at present, while mitochondrial mutations can be plausibly integrated into the metabolic scenario. The metabolic leitmotif is particularly evident with medical risk factors which are associated with an impaired cerebral perfusion, such as cerebrovascular diseases including stroke, cardiovascular diseases, hypo- and hypertension. Traumatic brain injury represents another example due to the persistent metabolic stress following the acute event. Thyroid diseases have detrimental sequela for cerebral metabolism as well. Furthermore, major depression and presumably chronic stress endanger susceptible brain areas mediated by a host of hormonal imbalances, particularly the HPA-axis dysregulation. Sociocultural and lifestyle factors like education, physical activity, diet and smoking may also modulate the individual risk affecting both reserve capacity and vulnerability. The pathophysiological relevance of trace metals, including aluminum and iron, is highly controversial; at any rate, they may adversely affect cellular defences, antioxidant competence in particular. The relative contribution of these factors, however, is as individual as the pattern of the factors. In familial AD, the genetic factors clearly drive the sequence of events. A strong interaction of fat metabolism and apoE polymorphism is suggested by intercultural epidemiological findings. In cultures, less plagued by the 'blessings' of the 'cafeteria diet-sedentary' Western lifestyle, apoE4 appears to be not a risk factor for AD. This intriguing evidence suggests that, analogous to cardiovascular diseases, apoE4 requires a hyperlipidaemic lifestyle to manifest as AD risk factor. Overall, the etiology of AD is a key paradigm for a gene-environment interaction. Copyright 2000 John Wiley & Sons, Ltd.