Alpha-lipoic acid potently inhibits peroxynitrite-mediated DNA strand breakage and hydroxyl radical formation: implications for the neuroprotective effects of alpha-lipoic acid

• Published in: Molecular and cellular biochemistry 2009-03, Vol.323 (1-2), p.131-138
• Main Authors: Jia, Zhenquan, Zhu, Hong, Vitto, Michael J, Misra, Bhaba R, Li, Yunbo, Misra, Hara P
• Format: Article
• Language: English
• Subjects: Animals; Antioxidants - pharmacology; Biochemistry; Biomedical and Life Sciences; Cardiology; Cytotoxicity; Deoxyribonucleic acid; DNA; DNA Breaks, Double-Stranded - drug effects; DNA damage; Electron Spin Resonance Spectroscopy; Humans; Hydroxyl Radical - metabolism; Hydroxyl radicals; Life Sciences; Medical Biochemistry; Molsidomine - analogs & derivatives; Molsidomine - metabolism; Neurological disorders; Neuroprotective Agents - pharmacology; Nitric Oxide Donors - metabolism; Oncology; Oxidative Stress; Oxygen Consumption; Peroxynitrous Acid - metabolism; Thioctic Acid - pharmacology
• ISSN: 0300-8177; 1573-4919
• DOI: 10.1007/s11010-008-9971-6

Alpha-lipoic acid (LA) has recently been reported to afford protection against neurodegenerative disorders in humans and experimental animals. However, the mechanisms underlying LA-mediated neuroprotection remain an enigma. Because peroxynitrite has been extensively implicated in the pathogenesis of various forms of neurodegenerative disorders, this study was undertaken to investigate the effects of LA in peroxynitrite-induced DNA strand breaks, a critical event leading to peroxynitrite-elicited cytotoxicity. Incubation of φX-174 plasmid DNA with the 3-morpholinosydnonimine (SIN-1), a peroxynitrite generator, led to the formation of both single- and double-stranded DNA breaks in a concentration- and time-dependent fashion. The presence of LA at 100-1,600 μM was found to significantly inhibit SIN-1-induced DNA strand breaks in a concentration-dependent manner. The consumption of oxygen induced by 250 μM SIN-1 was found to be decreased in the presence of high concentrations of LA (400-1,600 μM), indicating that LA at these concentrations may affect the generation of peroxynitrite from auto-oxidation of SIN-1. It is observed that incubation of the plasmid DNA with authentic peroxynitrite resulted in a significant formation of DNA strand breaks, which could also be dramatically inhibited by the presence of LA (100-1,600 μM). EPR spectroscopy in combination with spin-trapping experiments, using 5,5-dimethylpyrroline-N-oxide (DMPO) as spin trap, resulted in the formation of DMPO-hydroxyl radical adduct (DMPO-OH) from authentic peroxynitrite and LA at 50-1,600 μM inhibited the adduct signal. Taken together, these studies demonstrate for the first time that LA can potently inhibit peroxynitrite-mediated DNA strand breakage and hydroxyl radical formation. In view of the critical involvement of peroxynitrite in the pathogenesis of various neurodegenerative diseases, the inhibition of peroxynitrite-mediated DNA damage by LA may be responsible, at least partially, for its neuroprotective activities.