Combined arginine and ascorbic acid treatment induces apoptosis in the hepatoma cell line HA22T/VGH and changes in redox status involving the pentose phosphate pathway and reactive oxygen and nitrogen species.
Arginine is a physiological substrate for nitric oxide synthase to generate nitric oxide (NO), which can influence tumor cell survival, while ascorbic acid is selectively toxic for cancer cells. This study explored the effect of an arginine/ascorbic acid combination on human cancer cell lines. The hepatoma cell line HA22T/VGH was the most sensitive of the tested cells to combination treatment. A combination of 5.74 mM of arginine and 0.57 mM of ascorbic acid induced HA22T/VGH cell death through apoptosis and an increase in levels of reactive oxygen species and NO, as well as its stable products NO(2)(-) and NO(3)(-). The combination also reduced the activity of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and transaldolase in the pentose phosphate pathway, a major mechanism for producing NADPH, resulting in a marked decrease in intracellular NADPH levels. A dramatic decrease in intracellular glutathione (GSH) levels, a decrease in the mitochondrial membrane potential, ATP depletion and release of cytochrome c were also seen. Caspase-9 and caspase-3 were activated, apoptotic protein Bax expression increased and the expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL decreased. These results suggest that this combination induced HA22T/VGH cell death by interfering with redox state regulation by a reduction in pentose phosphate pathway activity and increasing oxidative and nitrosative stress.
Hsieh
Bau-Shan
BS
Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan.
Huang
Li-Wen
LW
Su
Shu-Jem
SJ
Cheng
Hsiao-Ling
HL
Hu
Yu-Chen
YC
Hung
Thu-Ching
TC
Chang
Kee-Lung
KL
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001120:Arginine / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D045304:Cytochromes c / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D009584:Nitrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010427:Pentose Phosphate Pathway / Q000187:drug effects*; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism; D026361:Reactive Nitrogen Species / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014153:Transaldolase / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D001120:Arginine; D010734:Phosphogluconate Dehydrogenase; D014153:Transaldolase; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9; D005978:Glutathione; D009584:Nitrogen; D001205:Ascorbic Acid; D010100:Oxygen