Anna E.O. Fisher

Iron supplements: the quick fix with long-term consequences

Co-supplementation of ferrous salts with vitamin C exacerbates oxidative stress in the gastrointestinal tract leading to ulceration in healthy individuals, exacerbation of chronic gastrointestinal inflammatory diseases and can lead to cancer. Reactive oxygen and nitrogen species (RONS) have been ascribed an important role in oxidative stress. Redox-active metal ions such as Fe(II) and Cu(I) further activate RONS and thus perpetuate their damaging effects. Ascorbic acid can exert a pro-oxidant effect by its interaction with metal ions via a number of established RONS generating systems which are reviewed here. Further studies are required to examine the detrimental effects of nutraceuticals especially in chronic inflammatory conditions which co-present with anaemia.

Therapeutic chelators for the twenty first century: new treatments for iron and copper mediated inflammatory and neurological disorders.

Superoxide, hydrogen peroxide, hydroxyl radicals and peroxynitrite are collectively termed reactive oxygen and nitrogen species (RONS). They have been ascribed an important role in oxidative stress contributing to the progression of inflammatory diseases. RONS generating systems include the inflammatory response, enzymatic pathways and as side products of catabolism. Protective enzymes exist for the regulation of RONS such as superoxide dismutase, catalase and glutathione peroxidase. Furthermore, vitamins play a secondary role in deactivating RONS. The redox active metal ions such as ferrous and cuprous ions are released from the storage proteins ferritin and caeruloplasmin by RONS. Redox active metal ions further activate/generate RONS and thus perpetuate their damaging effects. Here we report recent therapies that focus on intervening in the roles of metal ions in oxidative stress. These include: i) chelators which complex labile metal ions to form antioxidant enzyme mimetics, ii) site-specific RONS scavengers, where dual functionality co-localizes the scavenger and chelation centre to direct scavenging, and iii) redox silencing, metal complexation with concomitant stabilization of the metal ion in the oxidized form to prevent further activation of RONS. The rationale for this new therapeutic approach and recent advances will be presented in this review.

Vitamin C contributes to inflammation via radical generating mechanisms: a cautionary note.

Reactive oxygen and nitrogen species (RONS) have been ascribed an important role in oxidative stress contributing to the progression of inflammatory diseases such as Crohns disease and rheumatoid arthritis. Redox-active metal ions such as Fe(II) and Cu(I) further activate RONS and thus perpetuate their damaging effects. High intake of ascorbic acid exerts a pro-oxidant effect by its interaction with metal ions via a number of established RONS generating systems. Caution should be exerted regarding surplus ascorbic acid intake for patients with chronic inflammatory diseases.

Catalase and superoxide dismutase mimics for the treatment of inflammatory diseases

Abstract Conjugation of a metal ion chelator to aromatic amino acids generates a series of novel metal-binding anti-oxidant enzyme mimics. Our catalytic peptoids are designed to suppress oxidative damage via a number of routes. These include: (i) binding redox-active metal ions that further generate/activate RONS, (ii) removal of hydrogen peroxide by catalase activity, (iii) removal of superoxide by superoxide dismutase activity, and (iv) preventing the formation of hydroxyl radicals and peroxynitrite by removal of their precursors [as in (ii) and (iii)]. Thus, the redox-active metal ions are changed from detrimental RONS producers to beneficial RONS scavengers. In conclusion, we present a series of biomimetic peptoids that (i) bind redox-active metal ions, (ii) detoxify RONS and (iii) have potential therapeutic applications in inflammatory diseases.

Why nutraceuticals do not prevent or treat Alzheimer's disease

A great deal of research has pointed to deleterious roles of metal ions in the development of Alzheimers disease. These include: i) the precipitation and aggregation of amyloid β (Aβ) peptides to form senile plaques and neurofibrillary tangles, and/or ii) the augmentation of oxidative stress by metal ion mediated production and activation of hydrogen peroxide. The growing trend in nutraceutical intake is in part a result of the belief that they postpone the development of dementias such as Alzheimers disease. However, pathogenic events centred on metal ions are expected to be aggravated by frequent nutraceutical intake. Novel therapeutic approaches centred on chelators with specificity for copper and iron ions should be fully explored.

EDTA bis-(methyl tyrosinate): a chelating peptoid peroxynitrite scavenger.

Conjugation of ethylenediaminetetra-acetic acid (EDTA) to methyl tyrosinate generates a chelating peptoid EDTA bis-(methyl tyrosinate), (EBMT). Peroxynitrite-mediated nitration was studied for the free peptoid and its ferric and cupric complexes. The nitration products were monitored by electronic absorption spectroscopy at lambda(max) of 420 nm (mono-nitrated) and 440 nm (di-nitrated). Peak deconvolution was effected by pH manipulation as the mono-nitrated analogue of tyrosine exhibited a bathochromic shift from 365 nm (below its pK(a) of 6.8) to 420 nm. Rates of nitration were: free peptoid <Cu(II) complex <<Fe(III) complex. These results demonstrate the potential of EBMT to act as a radical scavenging chelating peptoid antioxidant.