Relationship between ascorbyl radical intensity and apoptosis-inducing activity.
Ascorbic acid and its related compounds were compared for their ascorbyl radical intensity and apoptosis-inducing activity. Sodium L-ascorbate, L-ascorbic acid, D-isoascorbic acid, sodium 6-beta-O-galactosyl-L-ascorbate and sodium 5,6-benzylidene-L-ascorbate, at the concentration of 1-10 mM, induced apoptotic cell death characterized by cell shrinkage, nuclear fragmentation and internucleosomal DNA cleavage in human promyelocytic leukemic HL-60 cells. On the other hand, L-ascorbic acid-2-phosphate magnesium salt and L-ascorbic acid 2-sulfate did not induce any of these apoptosis-associated characteristics. ESR measurements revealed that all the active compounds were progressively degraded, producing the ascorbyl radical (g = 2.0064, hfc = 0.17 mT) in culture medium, whereas the inactive compounds were stable and did not produce the ascorbyl radical. Cytotoxicity began to appear when the radical intensity exceeded a certain threshold level. In the presence of N-acetyl-L-cysteine, both ascorbyl radical intensity and apoptosis-inducing activity were significantly reduced. These data suggest the possible involvement of the ascorbyl radical in apoptosis induction by ascorbic acid-related compounds. Exposure of HL-60 cells to ascorbic acid or its active derivatives resulted in the rapid elevation of intracellular Ca2+ concentration, which might serve as the initial signal leading to the cell death pathway.
First Department of Biochemistry, School of Medicine, Showa University, Tokyo, Japan.
H
H
Sakagami
K
K
Satoh
H
H
Ohata
H
H
Takahashi
H
H
Yoshida
M
M
Iida
N
N
Kuribayashi
T
T
Sakagami
K
K
Momose
M
M
Takeda
D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D001597:Benzylidene Compounds / Q000737:chemistry / Q000494:pharmacology*; D053938:DNA Fragmentation; D004273:DNA, Neoplasm / Q000187:drug effects*; D004355:Drug Stability; D005609:Free Radicals / Q000737:chemistry / Q000494:pharmacology; D018922:HL-60 Cells / Q000187:drug effects; D006801:Humans; D013997:Time Factors
D000970:Antineoplastic Agents; D001597:Benzylidene Compounds; D004273:DNA, Neoplasm; D005609:Free Radicals; D001205:Ascorbic Acid; C070680:zilascorb