Accumulation of lipid peroxidation‐derived DNA lesions in iron‐overloaded thalassemic mouse livers: Comparison with levels in the lymphocytes of thalassemia patients

Abstract

In thalassemia patients, iron overload can stimulate lipid peroxidation (LPO), thereby generating miscoding DNA adducts. Adducted DNA was measured in the lymphocytes of b-Thal/Hb E patients and healthy controls and in the organs of thalassemic mice. edA, edC and M 1 dG residues were quantified by 32 P-postlabeling-TLC/ HPLC. M 1 dG levels in lymphocyte DNA from patients were 4 times as high as in controls, while the increase in edA and edC was not significant. Adducted DNA accumulated in the liver of thalassemic mice having >2.7 mg Fe/g tissue dry weight; DNA adducts and iron were highly correlated. edA was not specifically generated in certain mouse liver cell types as revealed by immunohistochemical staining. We found elevated LPO-induced DNA damage in the liver of thalassemic mouse and in lymphocytes, implicating that massive DNA damage occurs in the liver of thalassemia patients. We conclude that promutagenic LPO-derived DNA lesions are involved in the onset of hepatocellular carcinoma in these patients. ' 2009 UICC Key words: iron overload; lipid peroxidation; thalassemia; etheno-DNA adducts Iron overload, one of the major causes of morbidity and mortality in thalassemia patients, results from multiple, life-long transfusions and enhanced iron absorption as a response to increased erythropoiesis. [1][2][3] Iron overload in these patients is indicated by significantly increased levels of serum ferritin, saturated transferrin (the iron carrier protein) 4 and iron deposition in many organs. 5,6 Administration of the iron chelators, desferrioxamine and deferiprone, is commonly used in therapy. These drugs can cause serious side effects and are expensive. For desferrioxamine, a special infusion equipment is needed and, therefore, not all patients can benefit from iron-chelating therapy. In addition, patients who receive iron chelators still encounter a milder or shorter period of iron overload. As a result of iron overload, high levels of plasma iron in the form of nontransferrin bound iron (NTBI) can be found in both transfusion-dependent and transfusion-independent thalassemia patients. 7 NTBI plays a crucial role in the production of hydroxyl radicals (HO • ) in vivo that occurs through the biological Fenton-type and Haber-Weiss reactions. The resulting hydroxyl radicals can induce oxidative stress and, as a consequence, damage of cellular nucleic acids, proteins, lipids and carbohydrates, which in turn can potentiate tissue damage. 8 Previous studies demonstrated increased oxidative stress in thalassemia patients, including increased antioxidant enzyme activities and decreased nonenzymatic antioxidants. 9-12 Moreover, increase in modified DNA bases such as 8-oxodG, resulting from direct attack of hydroxyl radical to DNA, 13 increase in ortho-and meta-tyrosine, which are products of hydroxyl radical attack on phenylalanine, 14 and increase in lipid peroxidation (LPO) products, such as malondialdehyde (MDA) 10 and F 2 -isoprostane, 15 have been reported.LPO end-products such as 4-hydroxy-2-nonenal (HNE) and 1...

Lyn regulates inflammatory responses in Klebsiella pneumoniae infection via the p38/NF‐κB pathway

“…Remarkably, many bacteria also have oxidation-sensing mechanisms to respond to and counteract the oxidation-mediated host response [34]. Our results also showed that lipid peroxidation increased markedly in some Kp-infected organs of lyn −/− mice as compared with those of WT mice [19]. …”

“…Increased MPO in these major organs suggests that oxidative stress may have resulted from systemic spread of the invading Kp bacteria. As increased oxidation can also cause tissue injury by oxidative degraded lipids, we used a thiobarbituric acid-reactive substrate assay to detect lipid peroxidation in the lung, liver, spleen, and kidney tissue [19]. To our no surprise, lipid peroxidation significantly increased in the organs of lyn −/− mice compared with that of WT mice (Fig.…”

Lack of correlation between non-labile iron parameters, total carbonyl and malondialdehyde in major thalassemia

“…However, the direct correlation between iron status parameters and MDA or total carbonyl is not well examined; in the present study, this correlation was statistically analyzed. However, some researches mentioned that excess iron concentration can stimulate lipid peroxidation (27) which is a well-defined mechanism of cellular damage in animals. Increased levels of erythrocyte free reactive iron and lipid peroxidation end product are associated with low erythrocyte glutathione level.…”

“…(27) However, studies have indicated that no direct association between serum iron parameters and MDA and total carbonyl concentrations is indicated. In one study, the strongest predictor of increased MDA in patients with thalassemia is liver iron concentration.…”

Foxo3 gene expression and oxidative status in beta-thalassemia minor subjects

“…Al-Hakeim et al reported no statistically significant correlation between iron status parameters and MDA or total carbonyl in patients with β-thalassemia major 22 . Excessive iron concentrations can stimulate lipid peroxidation in thalassemia mouse models, which resemble thalassemia patients receiving blood transfusions, 23 however these studies have indicated no direct association between serum iron parameters and MDA 22, 23. Instead, the strongest predictor of increased MDA in patients with severe thalassemia would be the liver iron concentration 24 …”