Globotriaosylsphingosine induces oxidative DNA damage in cultured kidney cells.

Fabry disease (FD) is a lysosomal disorder caused by mutations leading to a deficient activity α-galactosidase A with progressive and systemic accumulation of its substrates. Substrates deposition is related to tissue damage in FD, but the underlying molecular mechanisms remain not completely understood. DNA damage has been associated with disease progression in chronic diseases and was recently described in high levels in Fabry patients. Once renal complications are major morbidity causes in FD, we investigated the effects of the latest biomarker for FD - globotriaosylsphingosine (lyso-Gb3) in a cultured renal lineage - human embryonic kidney cells (HEK-293 T) - on DNA damage. In concentrations found in Fabry patients, lyso-Gb3 induced DNA damage (by alkaline comet assay) with oxidative origin in purines and pyrimidines (by comet assay with endonucleases). These data provide new information about a deleterious effect of lyso-Gb3 and could be useful to studies looking for new therapeutic strategies to FD.

Biomolecules damage and redox status abnormalities in Fabry patients before and during enzyme replacement therapy.

Fabry disease (FD) is caused by deficient activity of the lysosomal enzyme α-galactosidase A. Its substrates, mainly globotriaosylceramide (Gb3), accumulate and seem to induce other pathophysiological findings of FD. Once enzyme replacement therapy (ERT) is not completely efficient on preventing disease progress in FD patients, elucidating the underlying mechanisms in FD pathophysiology is essential to the development of additional therapeutic strategies. We investigated 58 Fabry patients (23 male and 35 female) subdivided into two groups (at diagnosis and during long-term ERT) and compared them to healthy individuals. Fabry patients at diagnosis presented altered glutathione (GSH) metabolism (higher GSH levels, lower glutathione peroxidase - GPx - and normal glutathione reductase - GR - activities), higher lipid peroxidation levels (thiobarbituric acid reactive species - TBARS - and malondialdehyde - MDA), nitric oxide (NO(.)) equivalents and urinary Gb3. Fabry patients on ERT presented GSH metabolism similar to controls, although lipid peroxidation and urinary levels of NO(.) equivalents remained higher whereas Gb3 levels were lower than at diagnosis but still higher than controls. These data demonstrated that redox impairment occurs in Fabry patients before and after ERT, probably as a consequence of Gb3 accumulation, providing targets to future therapy approaches using antioxidants in combination with ERT in FD.

DNA damage in Fabry patients: An investigation of oxidative damage and repair.

Fabry disease (FD) is a lysosomal storage disorder associated with loss of activity of the enzyme α-galactosidase A. In addition to accumulation of α-galactosidase A substrates, other mechanisms may be involved in FD pathophysiology, such as inflammation and oxidative stress. Higher levels of oxidative damage to proteins and lipids in Fabry patients were previously reported. However, DNA damage by oxidative species in FD has not yet been studied. We investigated basal DNA damage, oxidative DNA damage, DNA repair capacity, and reactive species generation in Fabry patients and controls. To measure oxidative damage to purines and pyrimidines, the alkaline version of the comet assay was used with two endonucleases, formamidopyrimidine DNA-glycosylase (FPG) and endonuclease III (EndoIII). To evaluate DNA repair, a challenge assay with hydrogen peroxide was performed. Patients presented significantly higher levels of basal DNA damage and oxidative damage to purines. Oxidative DNA damage was induced in both DNA bases by H2O2 in patients. Fabry patients presented efficient DNA repair in both assays (with and without endonucleases) as well as significantly higher levels of oxidative species (measured by dichlorofluorescein content). Even if DNA repair be induced in Fabry patients (as a consequence of continuous exposure to oxidative species), the repair is not sufficient to reduce DNA damage to control levels.

Hyperprolinemia induces DNA, protein and lipid damage in blood of rats: antioxidant protection.

The present study investigated the effects of hyperprolinemia on oxidative damage to biomolecules (protein, lipids and DNA) and the antioxidant status in blood of rats. The influence of the antioxidants on the effects elicited by proline was also examined. Wistar rats received two daily injections of proline and/or vitamin E plus C (6th-28th day of life) and were killed 12h after the last injection. Results showed that hyperprolinemia induced a significant oxidative damage to proteins, lipids and DNA demonstrated by increased carbonyl content, malondialdehyde levels and a greater damage index in comet assay, respectively. The concomitant antioxidants administration to proline treatment completely prevented oxidative damage to proteins, but partially prevented lipids and DNA damage. We also observed that the non-enzymatic antioxidant potential was decreased by proline treatment and partially prevented by antioxidant supplementation. The plasma levels of vitamins E and C significantly increased in rats treated exogenously with these vitamins but, interestingly, when proline was administered concomitantly with vitamin E plus C, the levels of these vitamins were similar to those found in plasma of control and proline rats. Our findings suggest that hyperprolinemia promotes oxidative damage to the three major classes of macromolecules in blood of rats. These effects were accomplished by decrease in non-enzymatic antioxidant potential and decrease in vitamins administered exogenously, which significantly decreased oxidative damage to biomolecules studied. These data suggest that antioxidants may be an effective adjuvant therapeutic to limit oxidative damage caused by proline.

Homocysteine contribution to DNA damage in cystathionine ß-synthase-deficient patients.

High blood levels of homocysteine (Hcy) are found in patients affected by homocystinuria, a genetic disorder caused by deficiency of cystathionine ß-synthase (CBS) activity, as well as in nutritional deficiencies (vitamin B12 or folate) and in abnormal renal function. We previously demonstrated that lipid and protein oxidative damage is increased and the antioxidant defenses diminished in plasma of CBS-deficient patients, indicating that oxidative stress is involved in the pathophysiology of this disease. In the present work, we extended these investigations by evaluating DNA damage through the comet assay in peripheral leukocytes from CBS-deficient patients, as well as by analyzing of the in vitro effect of Hcy on DNA damage in white blood cells. We verified that DNA damage was significantly higher in the CBS-deficient patients under treatment based on a protein-restricted diet and pyridoxine, folic acid, betaine and vitamin B12 supplementation, when compared to controls. Furthermore, the in vitro study showed a concentration-dependent effect of Hcy inducing DNA damage. Taken together, the present data indicate that DNA damage occurs in treated CBS-deficient patients, possibly due to high Hcy levels.

Protein and lipid damage in maple syrup urine disease patients: l-carnitine effect.

Maple syrup urine disease (MSUD) is an inborn error of metabolism biochemically characterized by elevated levels of the branched chain amino acids (BCAA) leucine, isoleucine, valine and the corresponding branched-chain α-keto acids. This disorder is clinically characterized by ketoacidosis, seizures, coma, psychomotor delay and mental retardation whose pathophysiology is not completely understood. Recent studies have shown that oxidative stress may be involved in neuropathology of MSUD. l-Carnitine (l-Car) plays a central role in the cellular energy metabolism because it transports long-chain fatty acids for oxidation and ATP generation. In recent years many studies have demonstrated the antioxidant role of this compound. In this work, we investigated the effect of BCAA-restricted diet supplemented or not with l-Car on lipid peroxidation and in protein oxidation in MSUD patients. We found a significant increase of malondialdehyde and of carbonyl content in plasma of MSUD patients under BCAA-restricted diet compared to controls. Furthermore, patients under BCAA-restricted diet plus l-Car supplementation presented a marked reduction of malondialdehyde content in relation to controls, reducing the lipid peroxidation. In addition, free l-Car concentrations were negatively correlated with malondialdehyde levels. Our data show that l-Car may have an antioxidant effect, protecting against the lipid peroxidation and this could represent an additional therapeutic approach to the patients affected by MSUD.

Experimental evidence of oxidative stress in plasma of homocystinuric patients: a possible role for homocysteine.

Homocystinuria is an inherited disorder biochemically characterized by high urinary excretion of homocystine and increased levels of homocysteine (Hcy) and methionine in biological fluids. Affected patients usually have a variety of clinical and pathologic manifestations. Previous experimental data have shown a relationship between Hcy and oxidative stress, although very little was reported on this process in patients with homocystinuria. Therefore, in the present study we evaluated parameters of oxidative stress, namely carbonyl formation, malondialdehyde (MDA) levels, sulfhydryl content and total antioxidant status (TAS) in patients with homocystinuria at diagnosis and under treatment with a protein restricted diet supplemented by pyridoxine, folate, betaine, and vitamin B(12). We also correlated plasma Hcy and methionine concentrations with the oxidative stress parameters examined. We found a significant increase of MDA levels and carbonyl formation, as well as a reduction of sulfhydryl groups and TAS in plasma of homocystinuric patients at diagnosis relatively to healthy individuals (controls). We also verified that Hcy levels were negatively correlated with sulfhydryl content and positively with MDA levels. Furthermore, patients under treatment presented a significant reduction of the content of MDA, Hcy and methionine concentrations relatively to patients at diagnosis. Taken together, the present data indicate that lipid and protein oxidative damages are increased and the antioxidant defenses diminished in plasma of homocystinuric patients, probably due to increased reactive species elicited by Hcy. It is therefore presumed that oxidative stress participates at least in part in the pathogenesis of homocystinuria.

Simvastatin treatment prevents oxidative damage to DNA in whole blood leukocytes of dyslipidemic type 2 diabetic patients.

Type 2 diabetes (T2D) is associated with increased oxidative stress as indicated by elevated levels of lipid peroxidation and protein oxidation products. Since reactive oxygen species (ROS) can cause damage to biological macromolecules including DNA, this study investigated oxidative damage to DNA using the alkaline (pH > 13) comet assay in peripheral whole blood leukocytes sampled from 15 dyslipidemic T2D patients treated with simvastatin (20 mg/day), 15 dyslipidemic T2D patients not treated with simvastatin, 20 non-dyslipidemic T2D patients, and 20 healthy individuals (controls). Our results showed a greater DNA migration in terms of damage index (DI) (p < 0.01) in the dyslipidemic T2D patients not treated with statin (DI = 67.70 +/- 10.89) when compared to the dyslipidemic T2D patients under statin treatment (DI = 47.56 +/- 7.02), non-dyslipidemic T2D patients (DI = 52.25 +/- 9.14), and controls (DI = 13.20 +/- 6.40). Plasma malondialdehyde (MDA) and C-reactive protein (CRP) levels were also increased and total antioxidant reactivity (TAR) and paraoxonase activity (PON1) decreased in non-dyslipidemic T2D patients and dyslipidemic T2D non-treated with simvastatin. We also found that DI was inversely correlated with TAR (r = -0.61, p < 0.05) and PON1 (r = -0.67, p < 0.01). In addition, there was a significant positive correlation between DI and CRP (r = 0.80, p < 0.01). Our results therefore indicate that simvastatin treatment plays a protective role on oxidative damage to DNA in dyslipidemic T2D patients probably reflecting a general decrease in oxidative stress in these patients.

Apolipoprotein, C-reactive protein and oxidative stress parameters in dyslipidemic type 2 diabetic patients treated or not with simvastatin.

BACKGROUND AND AIMS: Oxidative stress is considered an important factor in the development of diabetic complications that causes a variety of changes such as oxidative modification of membrane lipids, nucleic acids and cellular proteins. Dyslipidemia is frequently associated with diabetes and cardiovascular disease. In this context, the objective of this study was to evaluate oxidative modifications of plasma proteins and lipids in non dyslipidemic type 2 diabetic (T2D) patients, in dyslipidemic T2D patients treated or not with simvastatin and in healthy subjects to investigate whether treatment with low doses of simvastatin plays a protective role on the lipid and protein oxidative damage in these patients. METHODS: We determined oxidative damage of plasma proteins by carbonyl assay and total thiol group determination. We also characterized the membrane damage in terms of lipid peroxidation by measuring malonaldehyde (MDA) in nondyslipidemic T2D patients, dyslipidemic T2D patients treated with simvastatin (20 mg/day), dyslipidemic T2D patients not treated with simvastatin and in healthy age-matched control subjects. RESULTS: Our results showed that dyslipidemic T2D patients not treated with simvastatin had significantly higher plasma protein carbonyl groups and MDA when compared to dyslipidemic T2D patients treated with simvastatin and control group. Thiol concentrations from dyslipidemic T2D patients not treated with simvastatin were significantly lower than treated patients and controls. It was verified that the thiols groups were inversely correlated with apolipoprotein B and positively correlated with apolipoprotein A-I. CONCLUSIONS: These results demonstrated that treatment with low doses of simvastatin can minimize the protein and lipid oxidative damage in dyslipidemic T2D patients.