Abstract
Millions of people globally are exposed to the proven human carcinogen arsenic at unacceptable levels in drinking water. In contrast, arsenic is a poor rodent carcinogen, requiring >100-fold higher doses for tumor induction, which may be explained by toxicokinetic differences between humans and mice. The human ATP-binding cassette subfamily C (ABCC) transporter hABCC4 mediates the cellular efflux of a diverse array of metabolites, including the glutathione (GSH) conjugate of the highly toxic monomethylarsonous acid (MMAIII), monomethylarsenic diglutathione [MMA(GS)2], and the major human urinary arsenic metabolite dimethylarsinic acid (DMAV). Our objective was to determine if mouse Abcc4 (mAbcc4) protected against and/or transported the same arsenic species as hABCC4. The anti-ABCC4 antibody M4I-10 epitope was first mapped to an octapeptide (411HVQDFTA418F) present in both hABCC4 and mAbcc4, enabling quantification of relative amounts of hABCC4/mAbcc4. mAbcc4 expressed in human embryonic kidney (HEK)293 cells did not protect against any of the six arsenic species tested [arsenite, arsenate, MMAIII, monomethylarsonic acid, dimethylarsinous acid, or DMAV], despite displaying remarkable resistance against the antimetabolite 6-mercaptopurine (>9-fold higher than hABCC4). Furthermore, mAbcc4-enriched membrane vesicles prepared from transfected HEK293 cells did not transport MMA(GS)2 or DMAV despite a >3-fold higher transport activity than hABCC4-enriched vesicles for the prototypic substrate 17β-estradiol-17-(β-D-glucuronide). Abcc4(+/+) mouse embryonic fibroblasts (MEFs) were ∼3-fold more resistant to arsenate than Abcc4(–/–) MEFs; however, further characterization indicated that this was not mAbcc4 mediated. Thus, under the conditions tested, arsenicals are not transported by mAbcc4, and differences between the substrate selectivity of hABCC4 and mAbcc4 seem likely to contribute to arsenic toxicokinetic differences between human and mouse.
SIGNIFICANCE STATEMENT Toxicokinetics of the carcinogen arsenic differ among animal species. Arsenic methylation is known to contribute to this, whereas arsenic transporters have not been considered. Human ATP-binding cassette subfamily C member 4 (hABCC4) is a high-affinity transporter of toxicologically important arsenic metabolites. Here we used multiple approaches to demonstrate that mouse Abcc4 does not protect cells against or transport any arsenic species tested. Thus, differences between hABCC4 and mAbcc4 substrate selectivity likely contribute to differences in human and mouse arsenic toxicokinetics.
Footnotes
- Received August 9, 2024.
- Accepted September 10, 2024.
This work was supported by the Canadian Institutes of Health Research [Grant MOP-272075] (to E.M.L.), [Grant MOP-106513] (to S.P.C.C.), and [Grant PJT-159547] (to E.M.L.); by American Lebanese Syrian Associated Charities (ALSAC) (to J.D.S.); and by National Institutes of Health National Cancer Institute [Grant P30 CA021765], [Grant R01 CA194057], [Grant R01 CA21865], and [Grant R01 CA96832] (to J.D.S.); M.B. was supported by an Alberta Cancer Foundation Cancer Research Postdoctoral Fellowship award. X.C.L. holds the Canada Research Chair in Bioanalytical Technology and Environmental Health.
No author has an actual or perceived conflict of interest with the contents of this article.
↵1Current affiliation: Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
↵2Current affiliation: Department of Pharmacology and Toxicology, University of Louisville, Louisville, Kentucky.
↵
This article has supplemental material available at dmd.aspetjournals.org.
- Copyright © 2024 by The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|
