Journal Article

Expression of glutathione <i>S</i>-transferases (GSTs) in human colon cells and inducibility of GSTM2 by butyrate

Miriam Nannette Ebert, Annett Klinder, Wilbert H.M. Peters, Anja Schäferhenrich, Wolfgang Sendt, Johannes Scheele and Beatrice Louise Pool-Zobel

in Carcinogenesis

Volume 24, issue 10, pages 1637-1644
Published in print October 2003 | ISSN: 0143-3334
Published online October 2003 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgg122
Expression of glutathione S-transferases (GSTs) in human colon cells and inducibility of GSTM2 by butyrate

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The glutathione S-transferases (GSTs) are a multigene family of enzymes largely involved in the detoxification of chemicals. In animals, enhanced expression is mediated by products of gut fermentation. Of these, butyrate induces GSTP1 protein expression and GST activity in the human colon tumor cell line HT29. The aim of the following investigations was to further elucidate butyrate-modulated induction of additional colonic GSTs in HT29 and to determine baseline expression in non-transformed cells, isolated from human colorectal tissue. We measured five GST protein subunits (GSTA1/2—composed of GST A1-1, A1-2 and A2-2—GSTM1, GSTM2, GSTP1, GSTT1) by western blot, GST activity using 1-chloro-2,4-dinitrobenzene as substrate and GSTM2 mRNA expression with RT–PCR. GSTP1, followed by GSTT1, were major subunits in all colon cells. Cells isolated from colon tissue were identified to be colonocytes and colon fibroblasts, both of which also expressed substantial levels of GSTM1 and GSTM2. The inter-individual variation of GST subunits in coloncytes of 15 individuals was marked, with total GST protein per 106 cells differing by more than a factor of four. In HT29, butyrate significantly enhanced GSTA1/2 (3.5-fold), GSTM2 (not detectable in controls), GSTP1 (1.5-fold) and GST activity (1.4-fold), but not GSTM1 or GSTT1. GSTM2 mRNA expression was significantly induced after 24 (≈14-fold) and 72 h treatment (≈8-fold). In colon fibroblasts, butyrate (4 mM, 72 h) also induced GSTM2 protein (1.7-fold) and GST activity (1.4-fold). Colonocytes were too short lived to be used for inducibility studies. In conclusion, GSTs are expressed with high inter-individual variability in human colonocytes. This points to large differences in cellular susceptibility to xenobiotics. However, butyrate, an important luminal component produced from fermentation of dietary fibers, is an efficient inducer of GSTs and especially of GSTM2. This indicates that butyrate may act chemoprotectively by increasing detoxification capabilities in the colon mucosa.

Keywords: GAPDH, glycerinealdehyde-3-phosphate-dehydrogenase; GST, glutathione S-transferase; HBSS, Hanks balanced salt solution; PCR, polymerase chain reaction; RT–PCR, reverse transcriptase–PCR

Journal Article.  6210 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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