Conjugates of desferrioxamine and aromatic amines improve markers of iron-dependent neurotoxicity.

Alzheimer's Disease (AD) is a complex neurodegenerative disorder associated in some instances with dyshomeostasis of redox-active metal ions, such as copper and iron. In this work, we investigated whether the conjugation of various aromatic amines would improve the pharmacological efficacy of the iron chelator desferrioxamine (DFO). Conjugates of DFO with aniline (DFOANI), benzosulfanylamide (DFOBAN), 2-naphthalenamine (DFONAF) and 6-quinolinamine (DFOQUN) were obtained and their properties examined. DFOQUN had good chelating activity, promoted a significant increase in the inhibition of ß-amyloid peptide aggregation when compared to DFO, and also inhibited acetylcholinesterase (AChE) activity both in vitro and in vivo (Caenorhabditis elegans). These data indicate that the covalent conjugation of a strong iron chelator to an AChE inhibitor offers a powerful approach for the amelioration of iron-induced neurotoxicity symptoms.

Increased serum iron in preeclamptic women is likely due to low hepcidin levels.

The role of hepcidin in iron homeostasis in preeclamptic pregnant women is unclear. To test the hypothesis that increased serum iron in women diagnosed with preeclampsia results from decreased production of hepcidin, we performed an observational case-control study in which serum hepcidin concentration, dietary iron intake, hematological indices, iron status, liver function, and inflammatory markers in 18 preeclamptic women and 18 healthy normotensive pregnant women of similar age range were evaluated. Iron intake was established via a food frequency questionnaire, whereas hematological indices, iron status, liver function, and inflammatory markers were assessed using standard protocols. Hematocrit was significantly higher (P = .031) in the preeclamptic group compared with the control, whereas erythropoietin level was significantly lower (P = .003). The pronounced inflammatory status of preeclamptic women was confirmed by significantly higher concentrations of interleukin-6 (P = .001), tumor necrosis factor-α (P < .001), and ferritin (P < .001). Nonetheless, the preeclamptic group exhibited significantly higher serum iron (P = .012) and transferrin saturation (P = .006), and these alterations were accompanied by lower hepcidin levels (P = .047). No significant correlations between hepcidin concentration and iron status parameters were observed in either group. However, a positive and significant correlation between hepcidin concentration and C-reactive protein was observed in the preeclamptic group (r = 0.474; P = .047). We conclude that high serum iron in preeclamptic women is likely caused by low production of hepcidin, thus supporting the hypothesis originally stated.

Triphenylphosphonium-desferrioxamine as a candidate mitochondrial iron chelator.

Cell-impermeant iron chelator desferrioxamine (DFO) can have access to organelles if appended to suitable vectors. Mitochondria are important targets for the treatment of iron overload-related neurodegenerative diseases. Triphenylphosphonium (TPP) is a delocalized lipophilic cation used to ferry molecules to mitochondria. Here we report the synthesis and characterization of the conjugate TPP-DFO as a mitochondrial iron chelator. TPP-DFO maintained both a high affinity for iron and the antioxidant activity when compared to parent DFO. TPP-DFO was less toxic than TPP alone to A2780 cells (IC50 = 135.60 ± 1.08 and 4.34 ± 1.06 µmol L-1, respectively) and its native fluorescence was used to assess its mitochondrial localization (Rr = +0.56). These results suggest that TPP-DFO could be an interesting alternative for the treatment of mitochondrial iron overload e.g. in Friedreich's ataxia.

Mitochondria-penetrating peptides conjugated to desferrioxamine as chelators for mitochondrial labile iron.

Desferrioxamine (DFO) is a bacterial siderophore with a high affinity for iron, but low cell penetration. As part of our ongoing project focused on DFO-conjugates, we synthesized, purified, characterized and studied new mtDFOs (DFO conjugated to the Mitochondria Penetrating Peptides TAT49-57, 1A, SS02 and SS20) using a succinic linker. These new conjugates retained their strong iron binding ability and antioxidant capacity. They were relatively non toxic to A2780 cells (IC50 40-100 µM) and had good mitochondrial localization (Rr +0.45 -+0.68) as observed when labeled with carboxy-tetramethylrhodamine (TAMRA) In general, mtDFO caused only modest levels of mitochondrial DNA (mtDNA) damage. DFO-SS02 retained the antioxidant ability of the parent peptide, shown by the inhibition of mitochondrial superoxide formation. None of the compounds displayed cell cycle arrest or enhanced apoptosis. Taken together, these results indicate that mtDFO could be promising compounds for amelioration of the disease symptoms of iron overload in mitochondria.

Talarazines A-E: Noncytotoxic Iron(III) Chelators from an Australian Mud Dauber Wasp-Associated Fungus, Talaromyces sp. (CMB-W045).

Chemical analysis of an Australian mud dauber wasp-associated fungus, Talaromyces sp. (CMB-W045), yielded five new coprogen siderophores, talarazines A-E (1-5), together with dimerumic acid (6), desferricoprogen (7), and elutherazine B (8). Structures inclusive of absolute configuration were assigned on the basis of detailed spectroscopic analysis and application of the C3 Marfey's method. We report on the noncytotoxic Fe(III) chelation properties of 1-8 and demonstrate that biosynthesis is regulated by available Fe(III) in culture media. We demonstrate a magnetic nanoparticule approach to extracting high-affinity Fe(III) binding metabolites (i.e., 8) from complex extracts.

Deferasirox-TAT(47-57) peptide conjugate as a water soluble, bifunctional iron chelator with potential use in neuromedicine.

Deferasirox (DFX), an orally active and clinically approved iron chelator, is being used extensively for the treatment of iron overload. However, its water insolubility makes it cumbersome for practical use. In addition to this, the low efficacy of DFX to remove brain iron prompted us to synthesize and evaluate a DFX-TAT(47-57) peptide conjugate for its iron chelation properties and permeability across RBE4 cell line, an in vitro model of the blood-brain barrier. The water-soluble conjugate was able to remove labile iron from buffered solution as well as from iron overloaded sera, and the permeability of DFX-TAT(47-57) conjugate into RBE4 cells was not affected compared to parent deferasirox. The iron bound conjugate was also able to translocate through the cell membrane.

New PKS-NRPS tetramic acids and pyridinone from an Australian marine-derived fungus, Chaunopycnis sp.

Chemical analysis of a marine-derived fungus, Chaunopycnis sp. (CMB-MF028), isolated from the inner tissue of a pulmonate false limpet Siphonaria sp., collected from rock surfaces in the intertidal zone of Moora Park, Shorncliffe, Queensland, yielded the tetramic acid F-14329 (1) and new analogues, chaunolidines A-C (2-4), together with the new pyridinone chaunolidone A (5), and pyridoxatin (6). Structures inclusive of absolute configurations were assigned to 1-6 on the basis of detailed spectroscopic analysis, X-ray crystallography, electronic circular dichroism (ECD), biosynthetic considerations and chemical interconversion. Chaunolidine C (4) exhibits modest Gram-positive antibacterial activity (IC50 5-10 µM), while chaunolidone A (5) is a selective and potent inhibitor (IC50 0.09 µM) of human non-small cell lung carcinoma cells (NCI-H460). Tetramic acids 1-4 form metal chelates with Fe(III), Al(III), Cu(II), Mg(II) and Zn(II).

Self-assembled penetratin-deferasirox micelles as potential carriers for hydrophobic drug delivery.

There has been a growing interest in the use of micelles with nanofiber geometry as nanocarriers for hydrophobic drugs. Here we show that the conjugate of penetratin, a cell-penetrating peptide (CPP) with blood-brain barrier (BBB) permeability, and deferasirox (DFX), a hydrophobic iron chelator, self-assembles to form micelles at a very low concentration (∼15 mg/L). The critical micelle concentration (CMC) was determined, and the micelles were used for solubilizing curcumin, a hydrophobic anti-neurodegenerative drug, for successful delivery across RBE4 cells, a BBB model. Transmission Electron Microscope images of the curcumin-loaded micelles confirmed the formation of nanofibers. These results indicate the potential of CPP-drug conjugates for use as nanocarriers.

Enhancement of hematoporphyrin IX potential for photodynamic therapy by entrapment in silica nanospheres.

The entrapment of hematoporphyrin IX (Hp IX) in silica by means of a microemulsion resulted in silica spheres of 33 ± 6 nm. The small size, narrow size distribution and lack of aggregation maintain Hp IX silica nanospheres stable in aqueous solutions for long periods and permit a detailed study of the entrapped drug by different techniques. Hp IX entrapped in the silica matrix is accessed by oxygen and upon irradiation generates singlet oxygen which diffuses very efficiently to the outside solution. The Hp IX entrapped in the silica matrix is also reached by iron(II) ions, which causes quenching of the porphyrin fluorescence emission. The silica matrix also provides extra protection to the photosensitizer against interaction with BSA and ascorbic acid, which are known to cause suppression of singlet oxygen generation by the Hp IX free in solution. Therefore, the incorporation of Hp IX molecules into silica nanospheres increased the potential of the photosensitizer to perform photodynamic therapy.

Labile plasma iron generation after intravenous iron is time-dependent and transitory in patients undergoing chronic hemodialysis.

Iron supplementation in hemodialysis patients is fundamental to erythropoiesis, but may cause harmful effects. We measured oxidative stress using labile plasma iron (LPI) after parenteral iron replacement in chronic hemodialysis patients. Intravenous iron saccharate (100 mg) was administered in patients undergoing chronic hemodialysis (N = 20). LPI was measured by an oxidant-sensitive fluorescent probe at the beginning of dialysis session (T0), at 10 min (T1), 20 min (T2), and 30 min (T3) after the infusion of iron and at the subsequent session; P < 0.05 was significant. The LPI values were significantly raised according to the time of administration and were transitory: -0.02 +/- 0.20 micromol/L at the beginning of the first session, 0.01 +/- 0.26 micromol/L at T0, 0.03 +/- 0.23 micromol/L at T1, 0.09 +/- 0.28 micromol/L at T2, 0.18 +/- 0.52 micromol/L at T3, and -0.02 +/- 0.16 micromol/L (P = 0.001 to 0.041) at the beginning of the second session. The LPI level in patients without iron supplementation was -0.06 +/- 0.16 micromol/L. Correlations of LPI according to time were T1, T2, and T3 vs. serum iron (P = 0.01, P = 0.007, and P = 0.0025, respectively), and T2 and T3 vs. transferrin saturation (P = 0.001 and P = 0.0003, respectively). LPI generation after intravenous saccharate administration is time-dependent and transitorily detected during hemodialysis. The LPI increment had a positive correlation to iron and transferrin saturation.

Antimicrobial activity of ethylenediaminedisuccinate metal complexes.

It is shown that metal complexes of the biodegradable ligand ethylenediaminedisuccinic acid (edds) present antimicrobial activity towards fungi and bacteria. [Cd(edds)], in particular, is more toxic than free Cd2+ to Aspergillus niger, behaving as a 'Trojan Horse' in the facilitated delivery of the toxic metal into the fungus.

Labile plasma iron in iron overload: redox activity and susceptibility to chelation.

Plasma non-transferrin-bound-iron (NTBI) is believed to be responsible for catalyzing the formation of reactive radicals in the circulation of iron overloaded subjects, resulting in accumulation of oxidation products. We assessed the redox active component of NTBI in the plasma of healthy and beta-thalassemic patients. The labile plasma iron (LPI) was determined with the fluorogenic dihydrorhodamine 123 by monitoring the generation of reactive radicals prompted by ascorbate but blocked by iron chelators. The assay was LPI specific since it was generated by physiologic concentrations of ascorbate, involved no sample manipulation, and was blocked by iron chelators that bind iron selectively. LPI, essentially absent from sera of healthy individuals, was present in those of beta-thalassemia patients at levels (1-16 microM) that correlated significantly with those of NTBI measured as mobilizer-dependent chelatable iron or desferrioxamine chelatable iron. Oral treatment of patients with deferiprone (L1) raised plasma NTBI due to iron mobilization but did not lead to LPI appearance, indicating that L1-chelated iron in plasma was not redox active. Moreover, oral L1 treatment eliminated LPI in patients. The approach enabled the assessment of LPI susceptibility to in vivo or in vitro chelation and the potential of LPI to cause tissue damage, as found in iron overload conditions.

A review of fluorescence methods for assessing labile iron in cells and biological fluids.

A variety of biochemical, pharmacological, and toxicological properties have been attributed to labile forms of iron that are associated with cells or with biological fluids. Unlike the major fraction of bioiron which is protein bound, the labile bioiron is chelatable and therefore amenable for detection by metal-sensing devices that are coupled to chelation moieties. The present review deals with the detection of various labile forms of iron present in living cells and in fluids of biological interest, in health and disease. The main focus of the review is on the design and application of fluorescent probes as analytical tools for assessing labile iron and iron transport mechanisms and the efficiency of iron chelators in solution and in cellular systems.