DNA damage in homocystinuria: 8-oxo-, 8-dihydro-2'-deoxyguanosine levels in cystathionine-ß-synthase deficient patients and the in vitro protective effect of N-acetyl­L­cysteine

Introduction: Homocysteine (Hcy) tissue accumulation occurs in a metabolic disease characterized biochemically by cystathionine ß-synthase (CBS) deficiency and clinically by mental retardation, vascular problems, and skeletal abnormalities. Previous studies indicate the occurrence of DNA damage secondary to hyperhomocysteinemia and it was observed that DNA damage occurs in leukocytes from CBS-deficient patients. This study aimed to investigate whether an oxidative mechanism could be involved in DNA damage previously found and investigated the in vitro effect of N-acety-L-cysteine (NAC) on DNA damage caused by high Hcy levels. Methods: We evaluated a biomarker of oxidative DNA damage in the urine of CBS­deficient patients, as well as the in vitro effect of NAC on DNA damage caused by high levels of Hcy. Moreover, a biomarker of lipid oxidative damage was also measured in urine of CBS deficient patients. Results: There was an increase in parameters of DNA (8-oxo-7,8-dihydro-2'- deoxyguanosine) and lipid (15-F2t-isoprostanes levels) oxidative damage in CBS-deficient patients when compared to controls. In addition, a significant positive correlation was found between 15-F2t-isoprostanes levels and total Hcy concentrations. Besides, an in vitro protective effect of NAC at concentrations of 1 and 5 mM was observed on DNA damage caused by Hcy 50 µM and 200 µM. Additionally, we showed a decrease in sulfhydryl content in plasma from CBS-deficient patients when compared to controls. Discussion: These results demonstrated that DNA damage occurs by an oxidative mechanism in CBS deficiency together with lipid oxidative damage, highlighting the NAC beneficial action upon DNA oxidative process, contributing with a new treatment perspective of the patients affected by classic homocystinuria.

Does phototherapy induce an oxidative stress in preterm neonates?

Of this study was to investigate whether phototherapy leads to oxidative stress in preterm newborns. Lipid peroxidation products as indicated by the thiobarbituric acid reacting substances [TBARS] in blood and urinary 8-Hydroxydeoxyguanosine [8-OHdG] as a protein peroxidation product in urine were assessed before and after exposure to phototherapy. Meanwhile, antioxidant activity in terms of plasma vitamin E and erythrocyte-glutathione peroxidase [GSH-PX] was assessed. The study group enrolled 24 preterm infants with physiological hyperbilirubinemia categorized according to the used modality of phototherapy into single and double phototherapy groups. Their mean gestational age was 31.22 +/- 2.63 weeks, and birth weight was 2.175 +/- 0.86 kg. Blood samples were collected immediately before and after 72 hours of phototherapy. Samples were analyzed for total serum bilirubin [TSB], serum albumin, blood TBARS, plasma vitamin E and erythrocyte-GSH-PX. Urine samples were collected before and after phototherapy for analysis of 8-OHdG. Levels of blood TBARS, Urine 8-OHdG were significantly elevated after phototherapy while plasma vitamin E and erythrocyte GSH-PX did not significantly change. Blood TBARS showed a negative correlation to TSB before phototherapy. The percent increase in serum TBARS or Urine 8-OHdG after phototherapy did not significantly correlate to gestational age or birth weight. Phototherapy induces oxidative stress in preterm neonates with unconjugated hyperbilirubinemia, regardless of their birth weight or gestational age. In face of this stress, antioxidant defense may be inadequate, requiring vitamin E supplementation. No significant photo-oxidant hazard is added in proceeding with double phototherapy in neonates under single phototherapy