metallothionein and oxalylglycine

A positive-feedback mechanism between hypoxia-inducible factor 1 alpha (HIF-1α) and metallothioneins (MTs) has been identified in different diseases. Both proteins have been independently proposed in the pathogenesis of inflammatory bowel disease (IBD); however, their relation has never been studied in the gut. In this study, we investigated the interaction between HIF-1α and MTs in colonic epithelial cells and during experimental colitis. Dimethyloxalylglycine (DMOG) was used to subject colonocytes to hydroxylase inhibition and HIF-1α stabilization in three experimental models (in vitro, in vivo and ex vivo). Small interfering RNA targeting HIF-1α (siRNA-HIF) and MT (siRNA-MT) together with zinc-mediated MT induction were used to study the interaction between HIF-1α and MT in HT29 cells. Acute colitis was induced in C57BL/6 mice using dextran sulphate sodium. MT expression and HIF-1α protein levels were measured using quantitative real-time PCR and ELISA, respectively. Vascular endothelial growth factor (VEGF) expression was quantified as an indirect measure of HIF-1 transcriptional activity. DMOG down-regulated MT expression in HT29 cells, in freshly isolated human colonocytes and in colonocytes isolated from mice treated with DMOG (p<0.05). SiRNA-HIF-treated cells displayed significant higher basal MT levels (p<0.05) and an attenuated MT down-regulation after DMOG treatment. In turn, HIF-1α stabilization was significantly lower in zinc-treated control cells, displaying high MT levels, compared to siRNA-MT cells treated with DMOG (p<0.05). In the course of experimental colitis, MT and VEGF mRNA expression were inversely related. MTs were induced in the acute phase and down-regulated during recovery. Opposing results were observed for VEGF expression levels (p<0.05). The present study underscores the inverse relation between HIF-1α and MT expression in colonocytes and during experimental colitis. The manipulation of MTs may represent a novel therapeutic strategy for patients suffering from IBD.

Topics: Amino Acids, Dicarboxylic; Animals; Colitis; Colon; Down-Regulation; HT29 Cells; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Inflammatory Bowel Diseases; Metallothionein; Mice; Mice, Inbred C57BL; Models, Animal; RNA, Small Interfering; Vascular Endothelial Growth Factor A; Zinc

Hypoxia-inducible factor 1 (HIF-1) is a hypoxia-induced transcription factor that regulates gene expression in critical pathways involved in tumour growth and metastasis. Metallothionein (MT) is a group of small molecular weight cysteine-rich proteins with a broad variety of functions. The present study aimed to analyse the prognostic impact of HIF-1alpha and MT expression in colorectal cancer and to evaluate a possible link of combined HIF-1alpha and MT expression with colorectal cancer progression.. We investigated the relationship of HIF-1alpha and MT with each other and clinicopathological parameters including proliferative activity (Ki67) and apoptosis (terminal desoxyribonucleotide transferase-mediated dUTP nick-end labelling) using immunohistochemistry.. HIF-1alpha expression was identified as an independent prognostic parameter in multivariate survival analysis and characterised an aggressive cancer phenotype. In addition, HIF-1alpha was significantly linked to an increased expression of MT.. HIF-1alpha expression qualified as an independent prognostic and characterised an aggressive cancer phenotype associated with an increased expression of MT. Our study suggests that MT can be added to the complex biological pathways induced by hypoxia in human cancer tissue.

Topics: Amino Acids, Dicarboxylic; Apoptosis; Cell Line, Tumor; Cell Proliferation; Colorectal Neoplasms; Epithelial Cells; Female; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Immunohistochemistry; Kaplan-Meier Estimate; Male; Metallothionein; Phenotype; Reactive Oxygen Species; Staining and Labeling