title: Inflammatory macrophages induce Nrf2 transcription factor-dependent proteasome activity in colonic NCM460 cells and thereby confer anti-apoptotic protection.
abstract: Adaptation of epithelial cells to persistent oxidative stress plays an important role in inflammation-associated carcinogenesis. This adaptation process involves activation of Nrf2 (nuclear factor-E2-related factor-2), which has been recently shown to contribute to carcinogenesis through the induction of proteasomal gene expression and proteasome activity. To verify this possible link between inflammation, oxidative stress, and Nrf2-dependent proteasome activation, we explored the impact of inflammatory (M1) macrophages on the human colon epithelial cell line NCM460. Transwell cocultures with macrophages differentiated from granulocyte monocyte-colony-stimulating factor-treated monocytes led to an increased activity of Nrf2 in NCM460 cells along with an elevated proteasome activity. This higher proteasome activity resulted from Nrf2-dependent induction of proteasomal gene expression, as shown for the 19 and 20 S subunit proteins S5a and α5, respectively. These effects of macrophage coculture were preceded by an increase of reactive oxygen species in cocultured NCM460 cells and could be blocked by catalase or by the reactive oxygen species scavenger Tiron, whereas transient treatment of NCM460 cells with H(2)O(2) similarly led to Nrf2-dependent proteasome activation. Through the Nrf2-dependent increase of proteasomal gene expression and proteasome activity, the sensitivity of NCM460 cells to tumor necrosis factor-related apoptosis-inducing ligand- or irinotecan-induced apoptosis declined. These findings indicate that inflammatory conditions such as the presence of M1 macrophages and the resulting oxidative stress are involved in the Nrf2-dependent gain of proteasome activity in epithelial cells, e.g. colonocytes, giving rise of greater resistance to apoptosis. This mechanism might contribute to inflammation-associated carcinogenesis, e.g. of the colon.
authors: Department of Internal Medicine I, Laboratory of Molecular Gastroenterology & Hepatology, Universitätsklinikum Schleswig Holstein-Campus Kiel, Kiel, Germany.
authors: Susanne
authors: S
authors: Sebens
authors: Iris
authors: I
authors: Bauer
authors: Claudia
authors: C
authors: Geismann
authors: Evelin
authors: E
authors: Grage-Griebenow
authors: Stefan
authors: S
authors: Ehlers
authors: Marie-Luise
authors: ML
authors: Kruse
authors: Alexander
authors: A
authors: Arlt
authors: Heiner
authors: H
authors: Schäfer
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D002166:Camptothecin / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D018920:Coculture Techniques; D003106:Colon / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D000077146:Irinotecan; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology
chemical_list: D051267:NF-E2-Related Factor 2; D017382:Reactive Oxygen Species; D053221:TNF-Related Apoptosis-Inducing Ligand; D000077146:Irinotecan; D046988:Proteasome Endopeptidase Complex; D002166:Camptothecin