Alpha-lipoic acid suppresses 6-hydroxydopamine-induced ROS generation and apoptosis through the stimulation of glutathione synthesis but not by the expression of heme oxygenase-1.
We previously reported that the generation of reactive oxygen species (ROS) is the initial event in cell death induced by 6-hydroxydopamine (6-OHDA), an experimental model of Parkinsonism. Since recent studies suggested the important role of antioxidant activity of alpha-lipoic acid (LA) in the suppression of apoptosis of various types, we studied the effect on 6-OHDA-induced apoptosis of PC12 cells. Biochemical analysis revealed that LA suppressed the 6-OHDA-induced ROS generation, increase of caspase-like activity and chromatin condensation. The suppression of 6-OHDA-induced apoptosis by LA required pre-incubation of PC12 cells with LA for 12-24 h. LA increased the intracellular levels of heme oxygenase-1 (HO-1) and glutathione (GSH) and stimulated the expression of GSH synthesis-related genes such as cystine/glutamate antiporter and gamma-glutamylcysteine synthetase (gamma-GCS). However, Sn-mesoporphyrin IX, an inhibitor of HO-1, did not attenuate the LA-induced suppression of apoptosis. In contrast, buthionine sulfoximine, an inhibitor of gamma-GCS, attenuated the LA-induced suppression of ROS generation and chromatin condensation. In addition, a transcription factor Nrf2, which regulates the expression of antioxidant enzymes such as gamma-GCS, translocated to the nucleus by LA. These results suggested that LA suppressed the 6-OHDA induced-apoptosis by the increase in cellular glutathione through stimulation of the GSH synthesis system but not by the expression of HO-1.
Fujita
Hirofumi
H
Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikatacho, Okayama 700-8558, Japan. fujita00@md.okayama-u.ac.jp
Shiosaka
Masahiko
M
Ogino
Tetsuya
T
Okimura
Yuya
Y
Utsumi
Toshihiko
T
Sato
Eisuke F
EF
Akagi
Reiko
R
Inoue
Masayasu
M
Utsumi
Kozo
K
Sasaki
Junzo
J
D026905:Amino Acid Transport Systems / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000502:physiology; D017920:Antiporters / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D016627:Oxidopamine; D016716:PC12 Cells; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D008063:Thioctic Acid / Q000502:physiology*
D026905:Amino Acid Transport Systems; D000975:Antioxidants; D017920:Antiporters; D017382:Reactive Oxygen Species; D008063:Thioctic Acid; D016627:Oxidopamine; D051547:Heme Oxygenase-1; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione