Avtor/Urednik     Žegura, Bojana
Naslov     Vloga reaktivnih kisikovih zvrsti pri genotoksičnem delovanju mikrocistinov
Tip     monografija
Kraj izdaje     Ljubljana
Založnik     Univerza v Ljubljani, Medicinska fakulteta
Leto izdaje     2004
Obseg     str. 147
Jezik     slo
Abstrakt     Microcystins are the most commonly found hepatotoxic cyclic heptapeptides produeed bv different cyanobacterial species such as Microcystis aeruginosa. "I-hey are potent inhibitors of protein phosphatases 1 and 2A, which can result in the disruption of many cellular processes and alteration of the cytoskeletal structures. Microcystins are well known tumor promoters and it was suggested that they might also act as tumor initiators. They have been shown to induce DNA damage in vitro and in vivo, however, the mechanisms of their genotoxic activity remain unclear. In our in vitro study the genotoxicity of MCLR was evaluated on human hepatoma cell line, HepG2 cells, using a single cell gel electrophoresis, also called comet assay. We showed that MCLR at doses that were not cytotoxic (10, 100 and 1000 ng/ml) induced dose and time dependent increase of DNA strand breaks. These DNA strand breaks were transiently present in DNA helix and reached a maximum level after 4 hours of exposure and declined afterwards. We showed that in the presence of DNA repair inhibitors cytosine arabinoside (AraC) and hydroxyurea (HU) together with MCLR DNA strand breaks accumulated after prolonged exposure. These results suggest that DNA strand breaks are intermediates, produced during the cellular repair of MCLR induced DNA damage. Using the modified version of the comet assay we observed that digestion of DNA from MCLR treated HepG2 cells with purified specific DNA enzymes, endonuclease III (endoIII), which recognizes and excises oxidized pyrimidines and formamidopyrimidineDNA glycosylase (fpg), which recognizes and excises oxidized purines and opened ring purines, markedly increased the number of DNA strand breaks, which occurred at sites of oxidised pyrimidines and purines, respectively. (Abstract truncated at 2000 characters).
Deskriptorji     TUMOR CELLS, CULTURED
BACTERIAL TOXINS
CYANOBACTERIA
REACTIVE OXYGEN SPECIES
MUTAGENICITY TESTS
DNA DAMAGE
DNA FRAGMENTATION
DNA REPAIR
ENDONUCLEASES
GAMMA-GLUTAMYL-CYSTEINE SYNTHETASE
GLUTATHIONE
CELL SURVIVAL
APOPTOSIS
LACTATE DEHYDROGENASE
RNA, MESSENGER
POLYMERASE CHAIN REACTION
BASE SEQUENCE