Abstract
Sodium arsenite is much more potent than sodium arsenate in producing adverse effects in animals and in cultured cells. Although arsenate may exhibit toxicity as a phosphate analogue, its potency in vivo appears to be enhanced by reduction to arsenite. To understand the relative importance of this reduction, which is critical in evaluating the responsiveness of cell culture models to the different oxidation states and thus to elucidating the mechanism of arsenic action, present work has correlated the extent of reduction with biological activity in human keratinocytes. The results show that at biologically relevant concentrations, arsenate reduction to appreciable levels required several days, helping rationalize a previous empirical observation that it was approximately one-third as potent as arsenite. The relatively low conversion rate also emphasizes a limitation of culture; arsenate was nearly as efficacious as arsenite, but the time required for it to reach maximal effect exceeded ordinary medium change intervals. In keratinocytes, an important role for purine nucleoside phosphorylase in the reduction could not be demonstrated, indicating that another pathway is dominant in this cell type. Methylation of inorganic arsenic, uptake of methylated forms, and their reduction were all very slow. These findings suggest that the reduced methylated forms have only a small contribution to skin carcinogenesis unless they are supplied through the circulation. In parallel experiments, trivalent antimony was similar to arsenite in potency and efficacy, whereas pentavalent antimony was virtually without biological effect. Conversion of antimony in the pentavalent to the trivalent oxidation state was not detectable in keratinocytes. These findings emphasize the importance of intracellular reduction of the metalloids for biological effects.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1624-1631 |
| Number of pages | 8 |
| Journal | Chemical Research in Toxicology |
| Volume | 16 |
| Issue number | 12 |
| DOIs | |
| State | Published - Dec 2003 |
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ASJC Scopus subject areas
- Drug Discovery
- Organic Chemistry
- Chemistry(all)
- Toxicology
- Health, Toxicology and Mutagenesis
Cite this
Biological Activity of Inorganic Arsenic and Antimony Reflects Oxidation State in Cultured Human Keratinocytes. / Patterson, Timothy J.; Ngo, Mai; Aronov, Pavel A.; Reznikova, Tatiana V.; Green, Peter G.; Rice, Robert H.
In: Chemical Research in Toxicology, Vol. 16, No. 12, 12.2003, p. 1624-1631.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Biological Activity of Inorganic Arsenic and Antimony Reflects Oxidation State in Cultured Human Keratinocytes
AU - Patterson, Timothy J.
AU - Ngo, Mai
AU - Aronov, Pavel A.
AU - Reznikova, Tatiana V.
AU - Green, Peter G.
AU - Rice, Robert H.
PY - 2003/12
Y1 - 2003/12
N2 - Sodium arsenite is much more potent than sodium arsenate in producing adverse effects in animals and in cultured cells. Although arsenate may exhibit toxicity as a phosphate analogue, its potency in vivo appears to be enhanced by reduction to arsenite. To understand the relative importance of this reduction, which is critical in evaluating the responsiveness of cell culture models to the different oxidation states and thus to elucidating the mechanism of arsenic action, present work has correlated the extent of reduction with biological activity in human keratinocytes. The results show that at biologically relevant concentrations, arsenate reduction to appreciable levels required several days, helping rationalize a previous empirical observation that it was approximately one-third as potent as arsenite. The relatively low conversion rate also emphasizes a limitation of culture; arsenate was nearly as efficacious as arsenite, but the time required for it to reach maximal effect exceeded ordinary medium change intervals. In keratinocytes, an important role for purine nucleoside phosphorylase in the reduction could not be demonstrated, indicating that another pathway is dominant in this cell type. Methylation of inorganic arsenic, uptake of methylated forms, and their reduction were all very slow. These findings suggest that the reduced methylated forms have only a small contribution to skin carcinogenesis unless they are supplied through the circulation. In parallel experiments, trivalent antimony was similar to arsenite in potency and efficacy, whereas pentavalent antimony was virtually without biological effect. Conversion of antimony in the pentavalent to the trivalent oxidation state was not detectable in keratinocytes. These findings emphasize the importance of intracellular reduction of the metalloids for biological effects.
AB - Sodium arsenite is much more potent than sodium arsenate in producing adverse effects in animals and in cultured cells. Although arsenate may exhibit toxicity as a phosphate analogue, its potency in vivo appears to be enhanced by reduction to arsenite. To understand the relative importance of this reduction, which is critical in evaluating the responsiveness of cell culture models to the different oxidation states and thus to elucidating the mechanism of arsenic action, present work has correlated the extent of reduction with biological activity in human keratinocytes. The results show that at biologically relevant concentrations, arsenate reduction to appreciable levels required several days, helping rationalize a previous empirical observation that it was approximately one-third as potent as arsenite. The relatively low conversion rate also emphasizes a limitation of culture; arsenate was nearly as efficacious as arsenite, but the time required for it to reach maximal effect exceeded ordinary medium change intervals. In keratinocytes, an important role for purine nucleoside phosphorylase in the reduction could not be demonstrated, indicating that another pathway is dominant in this cell type. Methylation of inorganic arsenic, uptake of methylated forms, and their reduction were all very slow. These findings suggest that the reduced methylated forms have only a small contribution to skin carcinogenesis unless they are supplied through the circulation. In parallel experiments, trivalent antimony was similar to arsenite in potency and efficacy, whereas pentavalent antimony was virtually without biological effect. Conversion of antimony in the pentavalent to the trivalent oxidation state was not detectable in keratinocytes. These findings emphasize the importance of intracellular reduction of the metalloids for biological effects.
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UR - http://www.scopus.com/inward/citedby.url?scp=0347629020&partnerID=8YFLogxK
U2 - 10.1021/tx034146y
DO - 10.1021/tx034146y
M3 - Article
C2 - 14680377
AN - SCOPUS:0347629020
VL - 16
SP - 1624
EP - 1631
JO - Chemical Research in Toxicology
JF - Chemical Research in Toxicology
SN - 0893-228X
IS - 12
ER -