Desferrioxamine, effect

Desferrioxamine reduces the incidence of heart and liver disease in thalassemia patients. In patients for whom desferrioxamine effectively controls iron overload, there is a 91% rate of cardiac disease-free survival after 15 years of therapy.7 There are negative effects of desferrioxamine treatment for example, too high a dose stunts a child s growth. 

Gower, J., Healing, G. and Green, C.J. (1989c). Measurement by HPLC of desferrioxamine-avaUable iron in rabbit kidneys to assess the effect of ischaemia on the distribution of iron within the total pool. Free Rad. Res. Commun. 5, 291-299. 

Gower, J.D., Ambrose, I.J., Manek, S., Bright, P.S., Dobbin, P.S., Hider, R.C., Goddard, J.G., Thomiley, M.S. and Green, C.J. (1993). The effect of a synthetic hexadentate iron chelator (CP130) and desferrioxamine on rabbit kidneys exposed to cold and warm ischaemia. Agents Actions 40, 96-105. 

Gastric mucosal injury induced by non-steroidal antiinflammatory drugs such as aspirin and indomethacin has also been extensively studied, again with somewhat conflicting results. Several studies have shown a protective effect of SOD, catalase, hydroxyurea and desferrioxamine (Takeuchi et al., 1991a Vaananen et al., 1991 Naito et al., 1992). Del Soldato etal. (1985) also found aminopy-rine, thiourea and its derivative, MK 447, and SAZ to be protective. Allopurinol has been shown to be both protective (Takeuchi etal., 1991a) and ineffective (Vaananen etal., 1991). 

Treatment with iron chelators and a-tocopherol protect against lipid p>eroxidation and hepatocellular injury in iron-overloaded rats (Sharma etal., 1990). When hepatocytes are isolated from rats, which have been pretreated with a-tocopherol, there is a significant reduction in iron-induced lipid peroxidation and improvement in cell viability in vitro (Poli et al., 1985). Similar effects were seen when hepatocytes were incubated with iron chelators (Bacon and Britton, 1990). Treatment of moderately, but not heavily, iron-loaded rats with desferrioxamine in vivo inhibits the pro-oxidant activity of hepatic ultrafiltrates (Britton et al., 1990b). 

Another factor that relates complex stability and siderophore architecture is the chelate effect. The chelate effect is represented by an increase in complex stability for a multidentate ligand when compared to complexes with homologous donor atoms of lower denticity. The effect can be observed when comparing the stability of complexes of mono-hydroxamate ligands to their tris-hydroxamate analogs, such as ferrichrome (6) or desferrioxamine B (4). However, the increase in stability alone is not sufficient to explain the preponderance of hexadentate siderophores over tetradentate or bidentate siderophores in nature, and the chelate effect is not observed to a great extent in some siderophore structures (10,22,50,51). 

Chelators of iron, which are now widely applied for the treatment of patients with thalassemia and other pathologies associated with iron overload, are the intravenous chelator desferal (desferrioxamine) and oral chelator deferiprone (LI) (Figure 19.23, see also Chapter 31). Desferrioxamine (DFO) belongs to a class of natural compounds called siderophores produced by microorganisms. The antioxidant activity of DFO has been studied and compared with that of synthetic hydroxypyrid-4-nones (LI) and classic antioxidants (vitamin E). It is known that chronic iron overload in humans is associated with hepatocellular damage. Therefore, Morel et al. [370] studied the antioxidant effects of DFO, another siderophore pyoverdin, and hydroxypyrid-4-ones on lipid peroxidation in primary hepatocyte culture. These authors found that the efficacy of chelators to inhibit iron-stimulated lipid peroxidation in hepatocytes decreased in the range of DFO > hydroxypyrid-4-ones > pyoverdin. It seems that other siderophores are also less effective inhibitors of lipid peroxidation than DFO [371],... 

As in the case of other cardiovascular diseases, the possibility of antioxidant treatment of diabetes mellitus has been studied in both animal models and diabetic patients. The treatment of streptozotocin-induced diabetic rats with a-lipoic acid reduced superoxide production by aorta and superoxide and peroxynitrite formation by arterioles providing circulation to the region of the sciatic nerve, suppressed lipid peroxidation in serum, and improved lens glutathione level [131]. In contrast, hydroxyethyl starch desferrioxamine had no effect on the markers of oxidative stress in diabetic rats. Lipoic acid also suppressed hyperglycemia and mitochondrial superoxide generation in hearts of glucose-treated rats [132],... 

The most successful up-to-date treatment of thalassemic patients is chelating therapy, which is based on patient s lifetime application of iron chelators. Removal of excess iron is supposed to be effective route for suppressing free radical-mediated damage. There is a great number of studies showing successful treatment of thalassemic patients with intravenous chelator desferal (desferrioxamine) and oral chelator deferiprone (LI). Biochemical studies show the efficacy of both chelators in removal of excess iron. For example, the incubation of thalassemic erythrocytes with 0.5 mmol 1 1 LI during 6h resulted in 96% removal of membrane-free iron [392], It was demonstrated that LI is able to remove pathologic deposits of... 

Fe(III) displacement of Al(III), Ga(III), or In(III) from their respective complexes with these tripodal ligands, have been determined. The M(III)-by-Fe(III) displacement processes are controlled by the ease of dissociation of Al(III), Ga(III), or In(III) Fe(III) may in turn be displaced from these complexes by edta (removal from the two non-equivalent sites gives rise to an appropriate kinetic pattern) (343). Kinetics and mechanism of a catalytic chloride ion effect on the dissociation of model siderophore-hydroxamate iron(III) complexes chloride and, to lesser extents, bromide and nitrate, catalyze ligand dissociation through transient coordination of the added anion to the iron (344). A catechol derivative of desferrioxamine has been found to remove iron from transferrin about 100 times faster than desferrioxamine itself it forms a significantly more stable product with Fe3+ (345). 

A study investigating the consequences of diesel exhaust particles in human airway epithelial cells also concluded that any effects of these particles occurred after their endocytosis. However, organic components rather than the metals on the surface of the particles were considered to be responsible for subsequent events. Thus, treatment with the iron chelator desferrioxamine had no inhibitory effect on the secretion of the inflammatory cytokines interleukin-8,... 

The choice of iron chelators on the basis of both molecular and cellular criteria was discussed in 2003 (374). One 2005 review is concerned with the design of orally active iron chelators (375), another considers the prospects for effective clinical use of several hydro-x5rpyridinones, dealing with novel species such as the 1-allyl compound as well as with the established deferiprone (LI) and desferrioxamine (Desferal, DFO) (376). A review dated 2006 deals with relevance of iron mobilization from both transferrin and other iron-containing proteins by LI to the treatment of various anemias and other iron-overload conditions (377). Two 2007 reviews concentrate on LI, as the only hydroxypyridinone in general clinical use. One author concludes that, on balance, LI is to be preferred to DFO. This conclusion is on the grounds that, despite the not infrequent occurrence of minor side effects, the incidence of serious side effects... 

An order of effectiveness has been established and a mechanism proposed for the removal of iron from ferritin by several 3-hydroxy-4-pyridinone chelators. The removal of iron from ferritin is, as one would expect, considerably slower than from calcein or doxorubicin (cf. above) or from transferrin. Rate constants are between 1.5 x 10 s and 7.5 x 10 s for removal of iron from ferritin by a series of hexadentate ligands each consisting of three substituted A-hydroxypyrimidinone or A-hydroxypyrazinone units, the rate decreasing with increasing substituent bulk. The slowest rate approximates to that for removal of iron from ferritin by desferrioxamine. The influence of chirality on the kinetic barrier provides insight into the detailed mechanism of removal in these systems.Slow removal of iron from ferritin by chelators should be contrasted with rapid reductive removal. ... 

There is a considerable difference in the antimalarial action of desferrioxamine B (DFO) and the hydrophobic chelators based on ferrichrome analogs. While the former is limited to mature forms in the life cycle of P. falciparum (trophozoites and schizonts), the latter effects to a greater extent early developing stages (ring). Therefore, studies explored... 

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