P.D.L. Lima

Genotoxic and cytotoxic effects of manganese chloride in cultured human lymphocytes treated in different phases of cell cycle

Manganese (Mn) has a natural occurrence and is necessary during the initial periods of the development. However, in high concentrations, Mn can be related to neurodegenerative disorders. The aim of the present study was to evaluate the mutagenic potential of manganese chloride (MnCl2.4H2O). Comet assay and chromosome aberrations analysis were applied to determine the DNA-damaging and clastogenic effects of MnCl2.4H2O. Cultured human lymphocytes were treated with 15, 20 and 25 microM manganese chloride during the G1, G1/S, S (pulses of 1 and 6h), and G2 phases of the cell cycle. All tested concentrations were cytotoxic and reduced significantly the mitotic index in G1, G1/S and S (1 and 6h) treatments, while in G2 treatment only the higher concentrations (20 and 25 microM) showed cytotoxic effects. Clastogenicity and DNA damage were found only in treatments with the highest concentration (25 microM). Chromosome aberrations were found exclusively in the G2 phase of the cell cycle. The absence of polyploidy in mitosis, suggests that manganese does not affect the formation of the mitotic spindle with the concentrations tested. The genotoxicity found in G2 phase and in the comet assay can be related to the short time of treatment in both cases.

Cytotoxic and genotoxic monitoring of sickle cell anaemia patients treated with hydroxyurea

Very satisfactory results have been obtained with the treatment of sickle cell anaemia with hydroxyurea (HU), an antineoplastic drug. This is because it significantly increases the levels of foetal haemoglobin. Nevertheless, inadequate dosages or prolonged treatment with this pharmaceutical can provoke cytotoxicity or genotoxicity, increasing the risk of neoplasia. We monitored patients under treatment with HU for possible mutagenic effects, through cytogenetic tests (mitotic index and chromosome aberrations) for one year. Checking at two-month intervals, the cytotoxic effect was not evident. There was no evidence of genotoxicity under the conditions of our experiment. However individuals treated with HU should be constantly monitored, as an absence of genotoxicity could be transitory; the mitotic index should also be observed, as an indicator of cytotoxicity.

Lymphocyte proliferation stimulated by activated human macrophages treated with Canova

INTRODUCTION Canova (CA) is a homeopathic medication with immunomodulatory properties, recommended for patients with a depressed immune system. CA has been reported to increase in leukocyte numbers, cellular differentiation and reduction in tumor size. AIM AND METHOD Since CA may stimulate lymphocyte differentiation, proliferation, and/or survival, the aim of the present study was to compare the mitotic index (MI) of phytohemagglutinin-stimulated human lymphocytes cultured in a medium supplemented with human macrophages activated by CA, with lymphocytes cultured in a medium without CA-treated macrophages. RESULTS In this study, the MI of lymphocyte cultured received the medium containing CA-stimulated macrophages showed a higher proliferation index (p<0.01) than the lymphocytes cultured in a medium without CA-treated macrophages. Our results suggest that CA treatment, in addition to activating macrophages, indirectly induces lymphocyte proliferation and has potential as a new adjuvant therapeutic approach.

Genotoxic and cytotoxic effects of iron sulfate in cultured human lymphocytes treated in different phases of cell cycle

Iron (Fe) is a common chemical element that is essential for organisms as a co-factor in oxygen transport, but that in high amounts presents a significant risk of neurodegenerative disorders. The objective of this study was to evaluate the mutagenic potential of iron sulfate. The comet assay and chromosome aberration (CA) analysis were applied to determine the DNA-damaging and clastogenic effects of iron sulfate. Human lymphocytes were treated in the quiescent phase for the comet assay and proliferative phase during the G1, G1/S, S (pulses of 1 and 6 h), and G2 phases of the cell cycle for CA analysis, with 1.25, 2.5 and 5 microg/mL concentrations of FeSO(4).7H2O. All tested concentrations were cytotoxic and reduced significantly the mitotic index (MI) in all phases of the cell cycle. They also induced CA in G1, G1/S and S (pulses of 1 and 6 h) phases. Iron sulfate also induced polyploidy in cells treated during G1. In the comet assay, this metal did not induce significant DNA damage. Our results show that Fe causes alteration and inhibition of DNA synthesis only in proliferative cells, which explain the concomitant occurrence of mutagenicity and cytotoxicity, respectively, in the lymphocytes studied.

Mutagenicity of hydroxyurea in lymphocytes from patients with sickle cell disease

Abstract Hydroxyurea is commonly used in the treatment of myeloproliferative diseases and in patients with sickle celldisease (SCD). The use of this antineoplastic agent in patients with SCD is justified because of the drug’s ability toincrease fetal hemoglobin levels, thereby decreasing the severity of SCD. However, high doses or prolongedtreatment with hydroxyurea can be cytotoxic or genotoxic for these patients, with an increased risk of developingacute leukemia. This danger can be avoided by monitoring the lymphocytes of patients treated with hydroxyurea.Cytogenetic tests are important endpoints for monitoring the physiological effects of physical and chemical agents,includingdrugs.Inthiswork,weassessedthegenotoxicityofhydroxyureainshort-termculturesoflymphocytesfromSCD patients. Hydroxyurea was not cytotoxic or genotoxic at the concentrations tested in the G2 phase of the cellcycle. These results support the use of hydroxyurea in the treatment of SCD, although further work is necessary tounderstand the effects of this drug in vivo.

Organic effects of associating paclitaxel with a lipid-based nanoparticle system on a nonhuman primate, Cebus apella

Lipid-based nanoparticle systems have been used as vehicles for chemotherapeutic agents in experimental cancer treatments. Those systems have generally been credited with attenuating the severe toxicity of chemotherapeutic agents. This study aimed to investigate the effects of associating paclitaxel (PTX) with a lipid-based nanoparticle system on a nonhuman primate, Cebus apella, documenting the toxicity as measured by serum biochemistry, which is a detailed analysis of blood and tissue. Eighteen C. apella were studied: three animals were treated with cholesterol-rich nanoemulsion (LDE) only, without PTX, administered intravenously every 3 weeks, during six treatment cycles; six animals were treated with PTX associated with LDE at the same administration scheme, three with lower (175 mg/m2) and three with higher (250 mg/m2) PTX doses; and six animals were treated with commercial PTX, three with the lower and three with the higher doses. In the LDE-PTX group, no clinical toxicity appeared, and the weight–food consumption curve was similar to that of the controls. Two animals treated with commercial PTX presented weight loss, nausea and vomiting, diarrhea, skin flaking, 70% loss of body hair, and decreased physical activity. The use of LDE as a carrier at both lower and higher doses reduced the toxicity of the drug in this species, which is closely related to human subjects. This was observed not only by clinical, biochemical, and hematological profiles but also by the histopathological analysis. The results of this study support the assumption that lipid-based nanoparticle systems used as drug carriers can serve as valuable tools to decrease the toxicity and increase the safety of chemotherapeutic agents.

Inhibitory effect of pisosterol on human glioblastoma cell lines with C-MYC amplification

Despite the remarkable progress in the characterization of the molecular pathogenesis of glioblastoma multiforme (GBM), these tumors remain incurable and, in most cases, refractory to aggressive cytotoxic treatments. We conducted a morphological and cytogenetic study in two GBM cell lines (U343 and AHOL1), before and after treatment with pisosterol (at 0.5, 1.0 and 1.8 µg ml−1), a triterpene isolated from the fungus Pisolithus tinctorius. No significant alteration was observed in the morphology and frequency of chromosomal abnormalities in the cell lines analyzed after treatment with pisosterol. Using fluorescence in situ hybridization analysis with a locus‐specific probe for C‐MYC showed that 72% of U343 and 65% of AHOL1 cells contained more than two alleles of C‐MYC before treatment. After treatment, no effects were detected at lower concentrations of pisosterol (0.5 and 1.0 µg ml−1). However, at 1.8 µg ml−1 of pisosterol, only 33% of U343 cells and 15% of AHOL1 cells presented more than two fluorescent signals, suggesting that pisosterol blocks the cells with gene amplification. Cells that do not show a high degree of C‐MYC gene amplification have a less aggressive and invasive behavior and are easy targets for chemotherapy. Therefore, further studies are needed to examine the use of pisosterol in combination with conventional anti‐cancer therapy. Copyright

Evaluation of Genotoxic Effects of Xenobiotics in Fishes Using Comet Assay—A Review

Comet assay is a useful tool on the evaluation of DNA damage, and it can estimate the genetic risk followed by xenobiotic exposures. This technique has been extensively used to detect DNA lesions in a large number of tissues because its application requires viable cells that are not necessarily mitotically active. It has been recognized that the use of aquatic organisms as sentinels is of fundamental importance on environmental biomonitoring studies, and the DNA strand breaks in these organisms are fast and sensible indicators of pollutant exposure. Additionally, these bioassays detect single or associated toxic effects of these contaminants and reduce the influence of different environmental variability. The current literature presents a large number of in vitro and in vivo analyses using Comet Assay with fishes from Brazilian fauna; however, the use of endemic species is preferential considering the importance of standardization of the methodology that is employed to detect the DNA damage.

Genotoxic effects of white fluorescent light on human lymphocytes in vitro.

Sources of light beams such as white fluorescent light, are present in our daily life to meet the needs of life in the modern world. This study was conducted with the objective of determining the possible genotoxic, cytotoxic and aneugenic effects caused by this agent in different stages of the cell cycle (G0/early G1, S, and late G2), using different cytogenetic parameters (sister chromatid exchanges--SCE, chromosome aberrations--CA, and detection of aneugenic effects) in lymphocytes from temporary cultures of human peripheral blood. WFL showed a genotoxic effect in vitro, expressed by an increase in the frequency of SCEs, regardless of the cell cycle stage. However, no increase in the frequency of CAs was observed. In addition, disturbances in cell cycle kinetics and chromosomal segregation were also observed. Taken together, such data may contribute to a better understanding and a different management in the use of phototherapy for some pathological conditions.