title: In vitro DNA-damaging effects of intestinal and related tetrapyrroles in human cancer cells.
abstract: Epidemiological studies report a negative association between circulating bilirubin concentrations and the risk for cancer and cardiovascular disease. Structurally related tetrapyrroles also possess in vitro anti-genotoxic activity and may prevent mutation prior to malignancy. Furthermore, few data suggest that tetrapyrroles exert anti-carcinogenic effects via induction of cell cycle arrest and apoptosis. To further investigate whether tetrapyrroles provoke DNA-damage in human cancer cells, they were tested in the single cell gel electrophoresis assay (SCGE). Eight tetrapyrroles (unconjugated bilirubin, bilirubin ditaurate, biliverdin, biliverdin-/bilirubin dimethyl ester, urobilin, stercobilin and protoporphyrin) were added to cultured Caco2 and HepG2 cells and their effects on comet formation (% tail DNA) were assessed. Flow cytometric assessment (apoptosis/necrosis, cell cycle, intracellular radical species generation) assisted in revealing underlying mechanisms of intracellular action. Cells were incubated with tetrapyrroles at concentrations of 0.5, 5 and 17μM for 24h. Addition of 300μM tertiary-butyl hydroperoxide to cells served as a positive control. Tetrapyrrole incubation mostly resulted in increased DNA-damage (comet formation) in Caco2 and HepG2 cells. Tetrapyrroles that are concentrated within the intestine, including protoporphyrin, urobilin and stercobilin, led to significant comet formation in both cell lines, implicating the compounds in inducing DNA-damage and apoptosis in cancer cells found within organs of the digestive system.
authors.affiliation: Department of Nutritional Sciences, Emerging Field Oxidative Stress and DNA Stability, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090 Vienna, Austria. christine.moelzer@univie.ac.at
authors.forename: Christine
authors.initials: C
authors.lastname: Mölzer
authors.forename: Barbara
authors.initials: B
authors.lastname: Pfleger
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Putz
authors.forename: Antonia
authors.initials: A
authors.lastname: Roßmann
authors.forename: Ursula
authors.initials: U
authors.lastname: Schwarz
authors.forename: Marlies
authors.initials: M
authors.lastname: Wallner
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Bulmer
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Wagner
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D001654:Bile Pigments / Q000494:pharmacology; D001663:Bilirubin / Q000031:analogs & derivatives / Q000494:pharmacology; D018938:Caco-2 Cells; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D005434:Flow Cytometry; D056945:Hep G2 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D009369:Neoplasms / Q000235:genetics / Q000473:pathology*; D009994:Osmolar Concentration; D011524:Protoporphyrins / Q000494:pharmacology; D045725:Tetrapyrroles / Q000378:metabolism* / Q000494:pharmacology*; D014557:Urobilin / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D001654:Bile Pigments; D011524:Protoporphyrins; D045725:Tetrapyrroles; C002298:stercobilin; D014557:Urobilin; D001663:Bilirubin