Downregulation of superoxide dismutase activity and gene expression in cultured rat brain astrocytes after incubation with vitamin C.
Reactive oxygen species have been linked with neuropathological changes in the central nervous system. Epidemiological studies supported the beneficial effect of supplementation of antioxidants. Superoxide dismutase (SOD) is an endogenous enzyme which can scavenge reactive oxygen species. This study investigated the effect of supplementation with ascorbic acid (vitamin C) on the changes of SOD in cultured neurological cells. Rat brain astrocytes (RBA-1 cells) were incubated with vitamin C and divided into four groups: a control group (without vitamin C) and three treatment groups with vitamin C at 40, 80, and 160 micromol/l. After short-term (2 days) and long-term (7 days) incubation, SOD activity, SOD mRNA level by Northern blotting, and SOD protein amounts by Western blotting were measured. After 2 days of incubation, vitamin C resulted in a decrease in the activity of SOD in a concentration-dependent manner (Mn-SOD from 14.8 +/- 1.2 to 13.2 +/- 0.5 U/mg protein and Cu/Zn-SOD from 64.8 +/- 1.2 to 51.7 +/- 0.9 U/mg protein; p < 0.05), and vitamin C also attenuated the Cu/Zn-SOD mRNA level from 100 to 86.3 +/- 6.7%; p < 0.01), whereas the protein amounts of these two SODs remained unchanged. After 7 days of incubation with vitamin C, the SOD activity of RBA-1 cells decreased significantly (Mn-SOD from 14.9 +/- 0.3 to 11.8 +/- 0.3 U/mg protein and Cu/Zn SOD from 61.8 +/- 1.8 to 54.6 +/- 0.9 U/mg protein; p < 0.01), and the mRNA level was also attenuated (Mn-SOD from 100 to 86.8 +/- 8.7% and Cu/Zn-SOD from 100 to 84.7 +/- 4.8%; p < 0.01). These results suggest that 2 and 7 days of incubation with relatively high concentrations of vitamin C may downregulate activity and gene expression of SOD in cultured RBA-1 cells.
Kao
Pai-Feng
PF
Department of Medicine, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan.
Lee
Wen-Sen
WS
Liu
Ju-Chi
JC
Chan
Paul
P
Tsai
Jen-Chen
JC
Hsu
Yung-Ho
YH
Chang
Wen-Yin
WY
Cheng
Tzu-Hurng
TH
Liao
Shue-Sen
SS
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D001253:Astrocytes / Q000187:drug effects*; D002478:Cells, Cultured; D003470:Culture Media; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D015870:Gene Expression; D066298:In Vitro Techniques; D051381:Rats; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D013997:Time Factors
D003470:Culture Media; D013482:Superoxide Dismutase; D001205:Ascorbic Acid