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Biochemical and Molecular Actions of Nutrients

N-Acetylcysteine, Vitamin C and Vitamin E Diminish Homocysteine Thiolactone-Induced Apoptosis in Human Promyeloid HL-60 Cells¹

Department of Nutrition and Food Sciences, Fu-Jen University, Hsin-Chuang, Taiwan, ROC

²To whom correspondence should be addressed. E-mail: rweifen{at}mails.fju.edu.tw.

We showed previously that homocysteine thiolactone (HcyT) is a potent inducer of apoptosis in HL-60 cells. In the present study, the role of some radical scavengers (N-acetylcysteine, vitamin C, vitamin E and folate) on the reduction of HcyT-induced apoptosis was investigated. Preincubation of HcyT-treated HL-60 cells with vitamin C (Vit C; 100 µmol/L) or vitamin E (Vit E; 100 µmol/L) for 2 h significantly reduced the proportion of apoptotic cells with hypodiploid DNA contents or with membrane phosphatidylserine exposure, and attenuated the apoptotic DNA fragmentation. Preincubation of cells with N-acetylcysteine (NAC; 5 mmol/L) for 2 h significantly reduced HcyT-promoted apoptosis measured by membrane phosphatidylserine exposure only. The reduction of HcyT-induced apoptosis by NAC, Vit C or Vit E occurred simultaneously with a significant decrease in intracellular H₂O₂ levels and reduced caspase-3 enzymatic activity. In contrast, folate had no H₂O₂ scavenging capacity and did not suppress caspase-3 activity 6 h after HcyT treatment, although folate exhibited antioxidant behavior toward superoxide anions, hydroxyl radicals and peroxynitrite. Preincubation of cells with folate (10 µmol/L) for 3 d did not affect the extent of HcyT-promoted apoptotic damage. Taken together, our findings suggest that antioxidant pretreatment with NAC, Vit C or Vit E exerts more beneficial effects than folate on reducing apoptotic cell damage induced by homocysteine thiolactone.

KEY WORDS: • homocysteine thiolactone • antioxidant • folate • apoptosis • HL-60 cells

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