Increase in intracellular free/bound NAD[P]H as a cause of Cd-induced oxidative stress in the HepG(2) cells.
The present study shows the use of confocal autofluorescence spectroscopy coupled with the time-resolved fluorescence decay analysis to measure changes in FAD/NAD[P]H and free/bound NAD[P]H in HepG(2) cells at 0.5, 1.5, 3 and 4.5h after exposure to cadmium chloride (Cd). These changes were compared to changes in GSSG/GSH and production of reactive oxygen radicals (ROS) production. The results demonstrated that both FAD/NAD[P]H and GSSG/GSH increased significantly upon exposure to Cd. The change in GSSG/GSH occurred as early as 1.5h after treatment while the change in FAD/NAD[P]H did not occur until 3h after exposure. Production of ROS was also increased at 1.5h. The ratio of free/bound NAD[P]H was studied. It was demonstrated that free/bound NAD[P]H increased significantly as early as 0.5h and remained elevated until 4.5h after treatment with Cd. The present study provides novel data to show that changes in NAD[P]H metabolism precedes the increase in ROS production and cellular oxidative stress (increase GSSG/GSH, FAD/NAD[P]H). It is suggested that Cd causes a release of NAD[P]H, an important cofactor for electron transfer, from its normal protein binding sites. This may result in a disruption of the activity of the enzyme and proteins, and may lead to the subsequent toxic events.
Yang
M S
MS
Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong, China. msyang@hkbu.edu.hk
Li
D
D
Lin
T
T
Zheng
J J
JJ
Zheng
W
W
Qu
J Y
JY
D001665:Binding Sites / Q000187:drug effects; D019256:Cadmium Chloride / Q000633:toxicity*; D045744:Cell Line, Tumor; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism*; D005978:Glutathione / Q000187:drug effects / Q000378:metabolism; D019803:Glutathione Disulfide / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D009249:NADP / Q000187:drug effects* / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D011485:Protein Binding / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D017382:Reactive Oxygen Species; D005182:Flavin-Adenine Dinucleotide; D009249:NADP; D005978:Glutathione; D019256:Cadmium Chloride; D019803:Glutathione Disulfide