title: Microcystin-LR induced DNA damage in human peripheral blood lymphocytes.
abstract: Human exposure to microcystins, which are produced by freshwater cyanobacterial species, is of growing concern due to increasing appearance of cyanobacterial blooms as a consequence of global warming and increasing water eutrophication. Although microcystins are considered to be liver-specific, there is evidence that they may also affect other tissues. These substances have been shown to induce DNA damage in vitro and in vivo, but the mechanisms of their genotoxic activity remain unclear. In human peripheral blood lymphocytes (HPBLs) exposure to non-cytotoxic concentrations (0, 0.1, 1 and 10μg/ml) of microcystin-LR (MCLR) induced a dose- and time-dependent increase in DNA damage, as measured with the comet assay. Digestion of DNA from MCLR-treated HPBLs with purified formamidopyrimidine-DNA glycosylase (Fpg) displayed a greater number of DNA strand-breaks than non-digested DNA, confirming the evidence that MCLR induces oxidative DNA damage. With the cytokinesis-block micronucleus assay no statistically significant induction of micronuclei, nucleoplasmic bridges and nuclear buds was observed after a 24-h exposure to MCLR. At the molecular level, no changes in the expression of selected genes involved in the cellular response to DNA damage and oxidative stress were observed after a 4-h exposure to MCLR (1μg/ml). After 24h, DNA damage-responsive genes (p53, mdm2, gadd45a, cdkn1a), a gene involved in apoptosis (bax) and oxidative stress-responsive genes (cat, gpx1, sod1, gsr, gclc) were up-regulated. These results provide strong support that MCLR is an indirectly genotoxic agent, acting via induction of oxidative stress, and that lymphocytes are also the target of microcystin-induced toxicity.
authors: National Institute of Biology, Department for Genetic Toxicology and Cancer Biology, Ljubljana, Slovenia. bojana.zegura@nib.si
authors: B
authors: B
authors: Zegura
authors: G
authors: G
authors: Gajski
authors: A
authors: A
authors: Straser
authors: V
authors: V
authors: Garaj-Vrhovac
authors: M
authors: M
authors: Filipič
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000187:drug effects; D001427:Bacterial Toxins / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D020869:Gene Expression Profiling; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects*; D008297:Male; D008387:Marine Toxins; D052998:Microcystins / Q000633:toxicity*; D015162:Micronucleus Tests; D009153:Mutagens / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D001427:Bacterial Toxins; D008387:Marine Toxins; D052998:Microcystins; D009153:Mutagens; D012333:RNA, Messenger; C057862:cyanoginosin LR