BACKGROUNDIn beta-thalassaemia syndromes, decreased or impaired biosynthesis of beta-globin leads to accumulation of unpaired alpha-globin chains. Moreover, the iron overload in beta-thalassaemia patients generates oxygen-free radicals and peroxidative tissue injury. The aim of this study was to detect and correlate iron overload parameters with the oxidative stress and the antioxidant capability in beta-thalassaemia patients.DESIGNSerum iron, transferrin saturation, serum ferritin, nontransferrin-bound iron (NTBI), levels of serum free and total (free + bound) malondialdehyde (MDA) and total peroxyl radical-trapping antioxidant parameter (TRAP) were evaluated in 21 regularly transfused beta-thalassaemia major (TM) patients, 13 untransfused beta-thalassaemia intermedia (TI) patients and 17 healthy controls. Blood from the TM patients was drawn 48 h after the last desferoxamine (20-40 mg kg(-1)) infusion and just before transfusion.RESULTSFree and total MDA and NTBI levels were higher in the TM patients than in the TI. In the TM patients the free MDA levels correlated positively with serum iron (r = +0.3, P = 0.0006), whereas the total MDA correlated positively with NTBI (r = +0.45, P = 0.037). However, a negative correlation was observed between TRAP and NTBI (r = -0.4, P = 0.0006). In the TI patients there was no significant correlation between free or total MDA and TRAP or NTBI.CONCLUSIONSOur results confirm the peroxidative status generated by iron overload in thalassaemia patients and highlight the rapid formation of marked amounts of free MDA despite the chelation therapy in TM patients.

Malondialdehyde (MDA), a compound derived from lipid peroxidation and from eicosanoid biosynthesis, exists in biological matrices both in the free form and bound to SH and/or NH2 groups of various biomolecules (1). Although other compounds (isoprostanes) have been proposed as more reliable indicators of oxidative damage (2), MDA is still widely used in clinical chemistry laboratories to monitor oxidative stress (3). Several methods have been developed to evaluate MDA in biological samples (1)(4), but the different analytical conditions used and the lack of a suitable internal standard have led to large discrepancies in measurements even at physiologic MDA concentrations in human plasma (5). We (6) recently reported a “reference method” for free and total plasma MDA quantification, as the phenylpyrazole derivative, by isotope-dilution gas chromatography–mass spectrometry (ID-GC-MS) with dideuterated MDA (d2-MDA) as internal standard. This method, used for clinical MDA detection (7)(8)(9), offers the possibility of validating other proposed internal standards that differ from MDA in structure, stability, and reactivity. Unfortunately, the major limitations of d2-MDA include its difficult synthesis (10) and that it is detectable only by GC-MS, a method not always available in clinical laboratories. A compound that appears to be more suitable as an internal standard is methyl malondialdehyde (MMDA) because it is structurally close to MDA, is absent from biological matrices, is easily obtainable from a commercial compound, and is detectable by common methods such as HPLC, GC, and capillary electrophoresis. MMDA was first evaluated as an internal standard for MDA determinations by Bull and Marnett (11), who unfortunately experienced difficulties in resolving the underivatized MDA and MMDA by HPLC. Recently, Claeson et al. (12) reported the use of MMDA as an internal standard for measurement of MDA in rat brain by capillary electrophoresis, …

BACKGROUND:Oxidative stress is present in cardiovascular diseases (CVDs), and hyperhomocysteinemia, an independent risk factor for these diseases, may play a role by inducing production of oxygen free radicals.METHODS:To evaluate the possible role of homocysteine (Hcy) in inducing oxidative stress in coronary artery disease (CAD), plasma Hcy was measured in 68 consecutive cardiovascular patients, and plasma malondialdehyde (MDA), both free and total (free + bound), was measured in 40 patients with CAD (18 with chronic stable angina and 22 with unstable angina). As controls, we tested 70 healthy volunteers. Hcy was measured by an immunoenzymatic method and MDA, an index of lipid peroxidation, by gas chromatography-mass spectrometry.RESULTS:Plasma Hcy concentrations were significantly higher in cardiovascular patients than in controls (10.2 vs 8.9 micromol/L; P <0.0002), with no significant difference between values in the stable and unstable angina subgroups. Similarly, total MDA was significantly higher in the CAD group than in the controls (2.6 vs 1.3 micromol/L; P <0.00001), again with no significant difference between stable and unstable angina patients. By contrast, free MDA, which was significantly higher in the CAD patients than the controls (0.4 vs 0.2 micromol/L; P < 0.00001), was also significantly higher in the unstable than in the stable angina group (0.5 vs 0.3 micromol/L; P <0.03). However, no correlation was observed among Hcy and free and total MDA.CONCLUSIONS:Our findings show that a moderate increase of Hcy is associated with CVD but that Hcy at the detected values cannot be considered completely responsible for oxidative damage. That lipid peroxidation is involved in CAD is shown by our observation of significantly increased plasma free and total MDA concentrations compared with controls. Moreover, free MDA values discriminated between unstable and chronic stable angina, and could thus represent a new diagnostic tool.

Studies have been made on the possible involvement of malondialdehyde (MDA) and (E)-4-hydroxynon-2-enal (HNE), two terminal compounds of lipid peroxidation, in modifying xanthine oxidoreductase activity through interaction with the oxidase (XO) and/or dehydrogenase (XDH) forms. The effect of the two aldehydes on XO (reversible, XO(rev), and irreversible, XO(irr)) and XDH was studied using xanthine oxidase from milk and xanthine oxidoreductase partially purified from rat liver. The incubation of milk xanthine oxidase with these aldehydes resulted in the inactivation of the enzyme following pseudo-first-order kinetics: enzyme activity was completely abolished by MDA (0.5-4 mM), while residual activity (5% of the starting value) associated with an XO(irr) form was always observed when the enzyme was incubated in the presence of HNE (0.5-4 mM). The addition of glutathione to the incubation mixtures prevented enzyme inactivation by HNE. The study on the xanthine oxidoreductase partially purified from rat liver showed that MDA decreases the total enzyme activity, acting only with the XO forms. On the contrary HNE leaves the same level of total activity but causes the conversion of XDH into an XO(irr) form.