Letters to the Editor pubs.acs.org/crt
Methylmercury Absorption and Human Intestinal Caco‑2 Cells
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Notes
o the Editor: In their informative and interesting article about intestinal methylmercury absorption in an experimental study on human intestinal epithelial Caco-2 cells, Vasquez et al.1 in the Discussion section state that “However, highly lipophilic compounds such as CH3Hg tend to accumulate significantly within the cell, and this in turn can complicate the establishment of correlations between in vivo and in vitro studies.”1 They claimed that methylmercury (CH3Hg+) has a cell-specific lipophilic characteristic that enables methylmercury to cross the membranes of intestinal cells, and this chemical property was constantly repeated throughout their article.1 To dispel any confusion regarding the biochemical profile of monomethylmercury (CH3Hg+), we would like to share our experience in analytical chemistry of organic mercury compounds (CH3Hg+). Closely related to the electronegativity of the monomethylmercury cation (CH3Hg+), we think that it is reasonable for a biochemist to at least consider the possibility of a water-soluble instead of lipophilic character of methylmercury, as previously reported.2,3 Chemically speaking, methylmercury in human tissue is expected to be present as water-soluble complexes, especially in liver cells4,5 (i.e., reduced glutathione−methylmercury complexes, thiolbased proteins, sulfhydryl-containing ligands, such as cysteine, and amino acids), and there is no tissue disposition in body fat. We believe that a clear distinction between a hydrophilic and lipophilic pathway of monomethylmercury is of paramount importance in determining the differential toxicity in humans.
The authors declare no competing financial interest.
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REFERENCES
(1) Vazquez, M., Velez, D., and Devesa, V. (2014) In vitro characterization of the intestinal absorption of methylmercury using a Caco-2 cell model. Chem. Res. Toxicol. 27, 254−264. (2) Guzzi, G., and Pigatto, P. D. (2005) More on methyl mercury. Toxicol. Appl. Pharmacol. 206, 94. (3) Suzuki, T., Imura, N., Clarkson, T. W., and Rochester International Conference in Environmental Toxicity (1991) Advances in Mercury Toxicology, Plenum Press, New York. (4) Ballatori, N., and Clarkson, T. W. (1985) Biliary secretion of glutathione and of glutathione-metal complexes. Fundam. Appl. Toxicol. 5, 816−831. (5) Goyer, R. A., and Clarkson, T. W. (2001) Toxic Effects of Metals, in Casarett & Doull’s Toxicology: The Basic of Poisons (Klaassen, C. D., Ed.) pp 822−826, McGraw-Hill Medical Pub. Division, New York.
Gianpaolo Guzzi*,† Maria T. Bardella‡,⊥ Paolo D. Pigatto§ Luca Elli‡,⊥ †
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Italian Association for Metals and Biocompatibility Research, A.I.R.M.E.B., Via A. Banfi, 4, Milan 20122, Italy ‡ Centre for the Prevention and Diagnosis of Celiac Disease, IRCCS Maggiore Hospital, Mangiagalli and R. Elena Policlinico Foundation, University of Milan, Via Festa del Perdono, 7, 20122 Milan, Italy § Department of Bioscience for Health, Dermatological Clinic, IRCCS Galeazzi Hospital, University of Milan, Via R. Galeazzi, 4, 20161 Milan, Italy
AUTHOR INFORMATION
Corresponding Author
*Italian Association for Metals and Biocompatibility Research, A.I.R.M.E.B. (not-for-profit organization), Via A. Banfi, 4 20122 Milan, Italy. Tel: +11-39-02-782 561. Fax: +11-39-02-367 355 40. E-mail:
[email protected]. Present Address ⊥
(M.T.B. and L.E.) Center for the Prevention and Diagnosis of Celiac Disease, Gastroenterology and Endoscopy Unit, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Via F. Sforza 35, 20122 Milan, Italy. © 2014 American Chemical Society
Published: May 21, 2014 941
dx.doi.org/10.1021/tx5000848 | Chem. Res. Toxicol. 2014, 27, 941−941
