Genotoxicity of Microcystin-LR inIn VitroandIn VivoExperimental Models

Abstract

Microcystin-LR (MCLR) is a cyanobacterial toxin known for its acute hepatotoxicity. Despite being recognized as tumour promoter, its genotoxicity is far from being completely clarified, particularly in organs other than liver. In this work, we used the comet and/or the micronucleus (MN) assays to study the genotoxicity of MCLR in kidney- (Vero-E6) and liver-derived (HepG2) cell lines and in blood cells from MCLR-exposed mice. MCLR treatment (5 and 20 μM) caused a significant induction in the MN frequency in both cell lines and, interestingly, a similar positive effect was observed in mouse reticulocytes (37.5 μg MCLR/kg, i.p. route). Moreover, the FISH-based analysis of the MN content (HepG2 cells) suggested that MCLR induces both chromosome breaks and loss. On the other hand, the comet assay results were negative in Vero-E6 cells and in mouse leukocytes, with the exception of a transient increase in the level of DNA damage 30 minutes after mice exposure. Overall, the present findings contributed to increase the weight of evidence in favour of MCLR genotoxicity, based on its capacity to induce permanent genetic damage either in vitro or in vivo. Moreover, they suggest a clastogenic and aneugenic mode of action that might underlie a carcinogenic effect.

Mechanisms of Microcystin-induced Cytotoxicity and Apoptosis

“…Molecular analysis of the TK mutants revealed that MC-LR specifically induced loss of heterozygosity (LOH) at the TK locus, but not point mutations or other small structural changes. Dias et al [84] also reported that MC-LR treatment caused a significant induction of micronuclei in both HepG2 and Vero-E6 cells in vitro. Similarly, a positive effect was also observed in reticulocytes of mice i.p.…”

“…MC-LR. Moreover, the fluorescence in situ hybridization (FISH) analysis of the MN content (HepG2 cells) suggested that MC-LR induces both chromosome breaks and loss [84]. Significantly elevated MN frequency was also observed in bone marrow cells of MC-LR-treated mice [85].…”

The Biochemical Alteration and Dna Damage in Rats (Rattus Rattus) After Chronic Intraperitoneally Injection to Purified Microcystin-Lr From Anabaena Circinalis

“…The comet length was positively correlated with the level of DNA breakage in cell because the distribution the comet was heterogeneous [19]. The highest value of the markers of DNA damage would be increased with increasing the toxicant dose this may be due to insufficient produce of antioxidant defense systems to scavenge the ROS that is generated by MC-LR which lead to finding their way across nuclear membrane indicating DNA strand breakage [42][43][44][45][46].…”

Microcystin-LR Induced Immunotoxicity in Mammals

“…Previous results from the comet assay in mice leukocytes have shown that MC-LR (37.5 μ g/kg bw/day, i.p.) induced a 2-fold transient increase in the level of DNA breaks after 30 min exposure [ 15 ]. In vivo studies by Kujbida et al suggested that topical application of MC-LR (1000 nM) for 4 hours to male rats caused an improvement of the number of rolling and adhered leukocytes in the endothelium of postcapillary mesenteric venules [ 16 ].…”