Miriana da Silva Machado

Trabectedin and its C-subunit modified analogue PM01183 attenuate nucleotide excision repair and show activity toward platinum-resistant cells

PM01183 is a novel marine-derived covalent DNA binder in clinical development. PM01183 is structurally similar to trabectedin (yondelis, ecteinascidin-743) except for the C subunit, and this modification is accompanied by different pharmacokinetics in cancer patients. We here characterize the interaction of PM01183 with the nucleotide excision repair (NER) pathway in comparison with trabectedin. Our results show for the first time that although neither PM01183 nor trabectedin is repaired by NER, both compounds are able to interfere with the NER machinery thereby attenuating the repair of specific NER substrates. We further show that the NER activity is increased in 3 of 4 cellular models with acquired resistance to cisplatin or oxaliplatin, confirming the involvement of NER in the resistance to platinum derivatives. Importantly, both PM01183 and trabectedin show unchanged or even enhanced activity toward all 4 cisplatin- and oxaliplatin-resistant cell lines. We finally show that combinations of PM01183 and cisplatin were mostly synergistic toward both parental and cisplatin-resistant ovarian carcinoma cells as indicated by Chou and Talalay analysis. These data show that the C subunit of trabectedin can be subjected to at least some structural modifications without loss of activity or NER interaction. While PM01183 and trabectedin appear functionally similar in cellular models, it is likely that the differences in pharmacokinetics may allow different dosing and scheduling of PM01183 in the clinic that could lead to novel and/or increased antitumor activity. Taken together, our results provide a mechanistic basis to support clinical trials of PM01183 alone or in combination with cisplatin. Mol Cancer Ther; 10(8); 1481–9. ©2011 AACR.

Evaluation of the cytotoxic and antimutagenic effects of biflorin, an antitumor 1,4 o-naphthoquinone isolated from Capraria biflora L

Biflorin is a natural quinone isolated from Capraria biflora L. Previous studies demonstrated that biflorin inhibits in vitro and in vivo tumor cell growth and presents potent antioxidant activity. In this paper, we report concentration-dependent cytotoxic, genotoxic, antimutagenic, and protective effects of biflorin on Salmonella tiphymurium, yeast Saccharomyces cerevisiae, and V79 mammalian cells, using different approaches. In the Salmonella/microsome assay, biflorin was not mutagenic to TA97a TA98, TA100, and TA102 strains. However, biflorin was able to induce cytotoxicity in haploid S. cerevisiae cells in stationary and exponential phase growth. In diploid yeast cells, biflorin did not induce significant mutagenic and recombinogenic effects at the employed concentration range. In addition, the pre-treatment with biflorin prevented the mutagenic and recombinogenic events induced by hydrogen peroxide (H2O2) in S. cerevisiae. In V79 mammalian cells, biflorin was cytotoxic at higher concentrations. Moreover, at low concentrations biflorin pre-treatment protected against H2O2-induced oxidative damage by reducing lipid peroxidation and DNA damage as evaluated by normal and modified comet assay using DNA glycosylases. Our results suggest that biflorin cellular effects are concentration dependent. At lower concentrations, biflorin has significant antioxidant and protective effects against the cytotoxicity, genotoxicity, mutagenicity, and intracellular lipid peroxidation induced by H2O2 in yeast and mammalian cells, which can be attributed to its hydroxyl radical-scavenging property. However, at higher concentrations, biflorin is cytotoxic and genotoxic.

Piplartine induces genotoxicity in eukaryotic but not in prokaryotic model systems.

Piplartine {5,6-dihydro-1-[(2E)-1-oxo-3-(3,4,5-trimethoxyphenyl)-2-propen-1-yl]-2(1H)-pyridinone} is an alkamide present in Piper species that exhibits promising anticancer properties. It was previously shown that piplartine is mutagenic in yeast and cultured mammalian cells. This study was performed to increase the knowledge on the mutagenic potential of piplartine using the Salmonella/microsome assay, V79 cell micronucleus and chromosome aberration assays, and mouse bone-marrow micronucleus tests. Piplartine was isolated from the roots of Piper tuberculatum. This extracted compound was unable to induce a mutagenic response in any Salmonella typhimurium strain either in the presence or absence of metabolic activation. Piplartine showed mutagenic effects in V79 cells, as there was an increased frequency of aberrant cells and micronuclei formation. In addition, piplartine administered at 50mg/kg did not induce micronucleus formation in vivo, but a dose of 100mg/kg induced an increase in the levels of micronucleus polychromatic erythrocytes (MNPCEs). Overall, these results provide further support that piplartine induces in vivo and in vitro mutagenicity in eukaryotic models.

Titanium dioxide nanoparticles induce genotoxicity but not mutagenicity in golden mussel Limnoperna fortunei

The widespread use of titanium dioxide nanoparticles (TiO2-NP) in consumer products is the cause of its appearance in wastewater and effluents, reaching the aquatic environment. The evaluation of the biological impact of TiO2-NP and the need to understand its ecotoxicological impact to the aquatic ecosystem are of major concern. Bivalve mollusks may represent a target group for nanoparticle toxicity. Limnoperna fortunei (golden mussel), a freshwater bivalve organism that has been employed in biomonitoring environmental conditions. Comet assay, micronucleus test and oxidative damage to lipids and proteins were performed after the golden mussel was exposed to TiO2-NP (1, 5, 10 and 50μgmL(-1)). The results demonstrate that TiO2-NP can damage the DNA of haemocytes after 2h of exposure and the genotoxic activity significantly increased after 4h exposure to TiO2-NP, at all the TiO2-NP concentrations. TiO2-NP was ineffective in causing mutagenicity in the haemolymph cells of golden mussel. The increase in the lipid peroxidation levels and carbonyl proteins after the exposure to TiO2-NP indicates the induction of oxidative stress at 2h exposure with similar results to all TiO2-NP concentrations, but these effects did not occur at 4h exposure. These results demonstrated that, although TiO2-NP is not mutagenic to golden mussel, it does induce DNA damage and oxidative stress in these organisms.

Cytotoxicity and genotoxicity of orthodontic bands with or without silver soldered joints.

Stainless steel bands, with or without silver soldered joints, are routinely used in orthodontics. However, little is known about the toxic biological effects of these appliances. The aims of this study were to evaluate the cytotoxic, cytostatic, genotoxic and DNA damage-inducing effects of non-soldered bands (NSB) and silver soldered bands (SSB) on the HepG2 and HOK cell lines and to quantify the amount of ions released by the bands. The 24-h metallic eluates of NSBs and SSBs were quantified by atomic absorption spectrophotometry. An MTT reduction assay was performed to evaluate the cytotoxicity, alkaline and modified comet assays were employed to measure genotoxicity and oxidative DNA damage effects, and cytokinesis-block micronucleus cytome (CBMN-Cyt) assays were used to verify DNA damage, cytostasis and cytotoxicity. Ag, Cd, Cr, Cu and Zn were detected in SSB medium samples, and Fe and Ni were detected in both the SSB and NSB medium samples. The SSB group induced stronger cytotoxic effects than the NSB group in both evaluated cell lines. NSB and SSB induced genotoxicity as evaluated by comet assays; stronger effects were observed in the SSB group. Both groups induced similar increases in the number of oxidative DNA lesions, as detected by the FPG and Endo III enzymes. Nucleoplasmic bridges, biomarkers of DNA misrepair and/or telomere end fusions, were significantly elevated in the SSB group. The SSB eluates showed higher amounts of Ni and Fe than NSB, and all the quantified ions were detected in SSB eluates, including Cd. The SSB eluates were more cytotoxic and genotoxic than the NSB samples. Based on these results, we propose that other brands, materials and techniques should be further investigated for the future manufacture of orthodontic appliances.

Cytotoxicity and genotoxicity induced by coal and coal fly ash particles samples in V79 cells

AbstractExposure to coal and coal ashes can cause harmful effects in in vitro and in vivo systems, mainly by the induction of oxidative damage. The aim of this work was to assess cytotoxic and genotoxic effects using the V79 cell line treated with coal and coal fly ash particles derived from a coal power plant located in Santa Catarina, Brazil. Two coal samples (COAL11 and COAL16) and two coal fly ash samples (CFA11 and CFA16) were included in this study. COAL16 was co-firing with a mixture of fuel oil and diesel oil. The comet assay data showed that exposure of V79 cells to coal and coal fly ash particles induced primary DNA lesions. Application of lesion-specific endonucleases (FPG and ENDO III) demonstrated increased DNA effects indicating the presence of high amounts of oxidative DNA lesions. The cytokinesis-block micronucleus cytome assay analysis showed that exposure of V79 cells to high concentrations of coal and coal fly ash particles induced cytotoxic effects (apoptosis and necrosis) and chromosomal instability (nucleoplasmic bridges, nuclear buds, and micronucleus (MN) formation). These results may be associated with compounds contained in the surface of the particles as hazardous elements, ultrafine/nanoparticles, and polycyclic aromatic hydrocarbons (PAHs) which were detected in the samples. Graphical abstractᅟ

Origanum majorana Essential Oil Lacks Mutagenic Activity in the Salmonella/Microsome and Micronucleus Assays

The present study aimed to investigate the in vitro mutagenic activity of Origanum majorana essential oil. The most abundant compounds identified by GC-MS were γ-terpinene (25.73%), α-terpinene (17.35%), terpinen-4-ol (17.24%), and sabinene (10.8%). Mutagenicity was evaluated by the Salmonella/microsome test using the preincubation procedure on TA98, TA97a, TA100, TA102, and TA1535 Salmonella typhimurium strains, in the absence or in the presence of metabolic activation. Cytotoxicity was detected at concentrations higher than 0.04 μL/plate in the absence of S9 mix and higher than 0.08 μL/plate in the presence of S9 mix and no gene mutation increase was observed. For the in vitro mammalian cell micronucleus test, V79 Chinese hamster lung fibroblasts were used. Cytotoxicity was only observed at concentrations higher than or equal to 0.05 μg/mL. Moreover, when tested in noncytotoxic concentrations, O. majorana essential oil was not able to induce chromosome mutation. The results from this study therefore suggest that O. majorana essential oil is not mutagenic at the concentrations tested in the Salmonella/microsome and micronucleus assays.