M-phase specific centrosome-microtubule alterations induced by the fungicide MBC in human granulosa cells

Effects of environmentally relevant concentrations of carbendazim, either alone or combined with benzophenone-3, on testicular development in Xenopus laevis

The fungicide carbendazim (CBZ), widely present in aquatic environments, has been reported to disrupt testicular development in rodents, yet its impacts on amphibians remain poorly understood. Here, we investigated the effects of environmentally-relevant concentrations of CBZ (1, 10, 100 μg/L) on early testicular development in Xenopus laevis following exposure from Nieuwkoop-Faber (NF) stages 45/46 to 52 in Experiment I. While all the concentrations of CBZ inhibited tadpole development, 10 and 100 μg/L CBZ caused retarded testicular development, which was characterized by morphological abnormality, suppressed cell proliferation and reduced germ cells, along with downregulation of testis-biased genes and upregulation of ovary-biased genes in certain concentration groups. Although 1 μg/L CBZ did not lead to significant changes in these testicular parameters, their declining trends are of concern, especially when considering its combined exposure with other contaminants. Thus, we conducted Experiment II to address the combined effects of 1 μg/L CBZ with the UV filter benzophenone-3 (BP-3), which was reported to affect testicular development in X. laevis, on testicular development from stages 45/46 to 66. As expected, we found that co-exposure to 1 μg/L CBZ and 2.28 μg/L BP-3 produced smaller testis size accompanied with fewer germ cells compared to the control, while alone exposure had no significant effects on the two parameters, exhibiting a synergistic effect on testicular development. Besides, their combined exposure also exerted synergistic effects with regard to metamorphic delay, increased liver weight and hepatic histological changes. Our findings emphasize the impacts of environmentally relevant concentrations of CBZ alone or in combination with UV-filters on testicular development, highlighting the ecological risk of these contaminants especially their mixtures for amphibians, which warrants continued attention.

Effects of Environmental Endocrine-Disrupting Chemicals on Female Reproductive Health

Environmental endocrine-disrupting chemicals (EDCs) are xenobiotic compounds that are frequently contacted in daily life. With the species and quantity of substances created and utilized by human beings significantly surpassing the self-purification capacity of nature, a large number of hazardous substances are enriched in the human body through the respiratory tract, digestive tract, and skin. Some of these compounds cause many problems endangering female reproductive health by simulating/antagonizing endogenous hormones or affecting the synthesis, metabolism, and bioavailability of endogenous hormones, including reproductive disorders, fetal birth defects, fetal developmental abnormalities, endocrine and metabolic disorders, and even gynecological malignancies. Therefore, the study of the relationship between environmental EDCs and female reproductive diseases and related mechanisms is of considerable significance to women, children health care, and improve the quality of the population.

Comparative study of genetic activity of chlorambucil's active metabolite steroidal esters: the role of steroidal skeleton on aneugenic potential

p-N,N-bis(2-chloroethyl)aminophenylacetic acid (PHE), a nitrogen mustard analogue and chlorambucil's active metabolite used as chemotherapeutic agent, has been shown that, in addition to its clastogenic activity, induces chromosome delay. In the present study an efford has been made (a) to investigate if the steroidal analogues of PHE (EA-92, EA-97, AK-333, AK-409 and AK-433) exert the same genetic activity as the parent compound, (b) to further analyze the aneugenic activity of nitrogen mustard analogues, (c) to investigate the mechanism by which they exert aneugenic potential and (d) to correlate the genetic activity with chemical structure. For this purpose the Cytokinesis Block Micronucleus (CBMN) assay was conducted in human lymphocytes in vitro and the micronucleus (MN) frequency was determined to investigate their genetic activity. The mechanism of micronucleation was determined in combination with Fluorescence In Situ Hybridization (FISH) using pancentromeric DNA probe. Since one of the mechanisms that chemicals cause aneuploidy is through alterations in the mitotic spindle, we also investigated the effect of the above compounds on the integrity and morphology of the mitotic spindle using double immunofluorescence of beta- and gamma-tubulin in C(2)C(12) mouse cell line. We found that PHE and its steroidal analogues, EA-92, EA-97, AK-333, AK-409 and AK-433, affect cell proliferation in human lymphocytes and C(2)C(12) mouse cells. All studied compounds are capable of inducing chromosome breakage events, as indicated by the enhanced C(-)MN frequencies. The less lipophilic compounds are the most genetically active molecules. PHE and only two of the studied analogues, AK-409 and AK-433, the most hydrophilic ones, showed aneugenic potential, by increasing the frequencies of MN containing a whole chromosome. The aneugenic potential of the above referred analogues is associated with amplification of centrosome number, since they caused high multipolar metaphase frequencies.

Carbendazim inhibits cancer cell proliferation by suppressing microtubule dynamics

Carbendazim (methyl 2-benzimidazolecarbamate) is widely used as a systemic fungicide in human food production and appears to act on fungal tubulin. However, it also inhibits proliferation of human cancer cells, including drug- and multidrug-resistant and p53-deficient cell lines. Because of its promising preclinical anti-tumor activity, it has undergone phase I clinical trials and is under further clinical development. Although it weakly inhibits polymerization of brain microtubules and induces G(2)/M arrest in tumor cells, its mechanism of action in human cells has not been fully elucidated. We examined its mechanism of action in MCF7 human breast cancer cells and found that it inhibits proliferation (IC(50), 10 microM) and half-maximally arrests mitosis at a similar concentration (8 microM), in concert with suppression of microtubule dynamic instability without appreciable microtubule depolymerization. It induces mitotic spindle abnormalities and reduces the metaphase intercentromere distance of sister chromatids, indicating reduction of tension on kinetochores, thus leading to metaphase arrest. With microtubules assembled in vitro from pure tubulin, carbendazim also suppresses dynamic instability, reducing the dynamicity by 50% at 10 microM, with only minimal (21%) reduction of polymer mass. Carbendazim binds to mammalian tubulin (K(d), 42.8 +/- 4.0 microM). Unlike some benzimidazoles that bind to the colchicine site in tubulin, carbendazim neither competes with colchicine nor competes with vinblastine for binding to brain tubulin. Thus, carbendazim binds to an as yet unidentified site in tubulin and inhibits tumor cell proliferation by suppressing the growing and shortening phases of microtubule dynamic instability, thus inducing mitotic arrest.

Aneugenic potential of the nitrogen mustard analogues melphalan, chlorambucil and p-N,N-bis(2-chloroethyl)aminophenylacetic acid in cell cultures in vitro

Melphalan (MEL), chlorambucil (CAB) and p-N,N-bis(2-chloroethyl)aminophenylacetic acid (PHE) are nitrogen mustard analogues, which are clinically used as chemotherapeutic agents. They also exert carcinogenic activity. The aim of this study was to investigate the aneugenic potential of the above drugs and the possible mechanism responsible for this activity. The Cytokinesis Block Micronucleus (CBMN) assay in combination with fluorescence in situ hybridization (FISH) was used in human lymphocyte cultures to evaluate micronucleus (MN) frequency. Pancentromeric probe (alpha-satellite) was applied to identify chromosomes in micronuclei and an X-chromosome specific centromeric probe was used to asses micronucleation and non-disjunction of this chromosome in binucleated cells. The effect of the above compounds on the organization of mitotic apparatus, as a possible target of chemicals with aneugenic potential, was investigated in C(2)C(12) mouse cell line by double immunofluorescence of alpha- and gamma-tubulin. We found that the studied drugs increased MN frequency in a linear dose-dependent manner primarily by chromosome breakage and in a lesser extent by an aneugenic mechanism. Non-disjunction and micronucleation of X-chromosome were also induced. Abnormal metaphase cells were linearly increased with concentration and characterized by abnormal centrosome number. Interphase cells with micronuclei and abnormal centrosome number were also observed. Since nitrogen mustards are highly reactive agents, with low selectivity and form covalent bonds with different nucleophilic sites in proteins and nucleic acids, it is reasonable to consider that one possible pathway for nitrogen mustard analogues to exert their aneugenic activity is through reaction with nucleophilic moieties of proteins or genes that are involved in the duplication and/or separation of centrosomes, resulting in abnormal centrosome number. Based on our results the carcinogenicity of nitrogen mustard analogues studied may be attributed not only to their activity to trigger gene mutation and chromosome breakage, but also to their aneugenic potential. Further studies are warranted to clarify the above two hypotheses.

Effects of carbendazim on rat thyroid, parathyroid, pituitary and adrenal glands and their hormones

The purpose of this study is to determine the effects of low and high dose of carbendazim on the level of certain hormones and endocrine glands (thyroid, parathyroid, adrenal and pituitary glands) of male rats. Carbendazim is a systemic fungicide with activity against a number of plant pathogens. In this study, daily doses of 0, 150, 300 and 600 mg/kg per day carbendazim were applied to male rats by gavage for 15 weeks. At the end of the experiment, T3, T4, TSH, ACTH and GH levels in rat serum were analysed. Thyroid, parathyroid, adrenal and pituitary glands of rats were taken. A significant increase was observed in serum T3 levels of the rats, which were exposed to 300 mg/kg per day carbendazim doses, compared to the serum T3 levels of the control group. There were no differences between the control and carbendazim-treated group of rats regarding serum TSH, T4, ACTH and growth hormone levels. This showed us that carbendazim caused histopathological damages in thyroid, parathyroid and adrenal glands of rats. No changes were observed in pituitary glands of treated rats. These results suggest that a high quantity of subchronic carbendazim exposure affects thyroid, parathyroid and adrenal glands.

Role of mitotic motors, dynein and kinesin, in the induction of abnormal centrosome integrity and multipolar spindles in cultured V79 cells exposed to dimethylarsinic acid

The role of microtubule-based motors in the induction of abnormal centrosome integrity by dimethylarsinic acid (DMAA) was investigated with the use of monastrol, a specific inhibitor of mitotic kinesin, and vanadate, an inhibitor of dynein ATPase. Cytoplasmic dynein co-localized with multiple foci of gamma-tubulin in mitotic cells arrested by DMAA. Disruption of microtubules caused dispersion of dynein while multiple foci of gamma-tubulin were coalesced to a single dot. Vanadate also caused dispersion of dynein, which had been co-localized with multiple foci of gamma-tubulin by DMAA, without affecting spindle organization. However, the dispersion of dynein did not prohibit the induction of abnormal centrosome integrity by DMAA. Inhibition of mitotic kinesin by monastrol resulted in monoastral cells with non-migrated centrosomes in the cell center. Monastrol, when applied to mitotic cells with abnormal centrosome integrity, rapidly reduced the incidence of cells with the centrosome abnormality. Moreover, monastrol completely inhibited reorganization of abnormal centrosomes that had been coalesced to a single dot by microtubule disruption. These results suggest that abnormal centrosome integrity caused by DMAA is not simply due to dispersion of fragments of microtubule-organizing centers, but is dependent on the action of kinesin. In addition, the results suggest that kinesin plays a role not only in the induction of mitotic centrosome abnormality, but also in maintenance.

Carbendazim-induced haematological, biochemical and histopathological changes to the liver and kidney of male rats

Carbendazim is a systemic broad-spectrum fungicide controlling a wide range of pathogens. It is also used as a preservative in paint, textile, papermaking and leather industry, as well as a preservative of fruits. In the present study, carbendazim was administered at 0, 150, 300 and 600 mg/kg per day doses orally to male rats (Rattus rattus) for 15 weeks. At the end of the experiment, blood samples, liver and kidney tissues of each animal were taken. Serum enzyme activities, and haematological and biochemical parameters were analysed. In toxicological tests, 600 mg/kg per day doses of carbendazim caused an increase of albumin, glucose, creatinine and cholesterol levels. Also, at the same doses, white blood cell and lymphocyte counts decreased. However, mean cell hemoglobin and mean cell hemoglobin concentrations increased. Histopathological examinations revealed congestion, an enlargement of the sinusoids, an increase in the number of Kupffer cells, mononuclear cell infiltration and hydropic degeneration in the liver. At the highest doses, congestion, mononuclear cell infiltration, tubular degeneration and fibrosis were observed in the kidney tissue. These results indicate that 300 and 600 mg/kg per day carbendazim affected the liver and kidney tissue and caused some changes on haematological and biochemical parameters of rats.

Structure-effect relationship in the induction of mitotic phase-specific abnormality of centrosome integrity and multipolar spindles by steroidal estrogens and their derivatives in cultured mammalian cells

In order to determine the structure-effect relationship in the induction of centrosome disintegrity (abnormality of gamma-tubulin signals) and multipolar spindles in a cultured fibroblast cell line V79 by steroidal estrogens, the activities of various estrogens and their derivatives were investigated. Induction of centrosome disintegrity by estrogens was specific in cells in the mitotic phase and was not observed in interphase cells. The centrosome disintegrity induced 24 h after exposure to estrogens was accompanied by the appearance of multinucleated cells, but the microtubule network was organized. The rank order of potency of estrogens in inducing mitotic phase-specific centrosome disintegrity and multipolar spindles was as follows: 2-methoxyestradiol>dihydroequilin 3-methyl ether=equilin 3-methyl ether>17alpha-estradiol>17beta-estradiol 3-methyl ether=17beta-estradiol>dihydroequilin>estrone 3-methyl ether. Equilin and estrone were not effective in causing centrosome disintegrity. These results suggest that the 17-hydroxyl group, irrespective of whether it is the sterically alpha or beta form, is necessary for estradiol and dihydroequilin to cause centrosome disintegrity and that O-methylation at the C-3 position was effective for equilin and dihydroequilin in enhancing the centrosome abnormality. 2-Methoxyestradiol was the most potent inducer of the centrosome disintegrity among the tested compounds and caused the induction of multiple signals of gamma-tubulin, including more than five signals.

Induction of centrosome injury, multipolar spindles and multipolar division in cultured V79 cells exposed to dimethylarsinic acid: role for microtubules in centrosome dynamics

Role for microtubules in the induction of multiple microtubule organizing centers (MTOCs) and multipolar spindles by dimethylarsinic acid (DMAA), a methylated derivative of inorganic arsenics, was investigated with respect to the effects of microtubule disruption and reorganization. DMAA induced multiple signals of gamma-tubulin, a well-characterized component of MTOCs in the centrosome, in a manner specific to mitotic cells. The multiple signals of gamma-tubulin were co-localized with multipolar spindles caused by DMAA. Disruption of microtubules by nocodazole (NOZ) suppressed the appearance of centrosome injury caused by DMAA while disorganization of actin microfilaments by cytochalasin D did not. Post-treatment incubation of cells in which multiple signals of gamma-tubulin caused by DMAA had been coalesced to one or two dots by NOZ caused the reappearance of mitotic cells with multiple signals of gamma-tubulin, in conjunction with reorganization of the microtubules. These results suggest a role for microtubules in the dynamic behavior of the mitotic centrosome. DMAA induced aberrant cytokinesis, such as tripolar and quadripolar division, in a concentration-dependent manner. These results, together with the findings of earlier studies, suggest that the centrosome is the primary target for the induction of multipolar spindles by DMAA and the resultant induction of multinucleation and multipolar division.

Behavior of M-phase synchronized blastomeres after nuclear transfer in cattle

M-phase synchronized bovine blastomeres were used to study the effect of nuclear-cytoplasmic synchronization on the developmental potential after nuclear transfer (NT). The capacity of nocodazole and benomyl to reversibly synchronize blastomeres from embryos in M-phase was evaluated. Nocodazole reversibly arrested bovine embryos at the studied stages and induced high rates of M-phases in morulae and compact morulae. In contrast, benomyl was less efficient than nocodazole to synchronize in M-phase. After transfer of an M-phase blastomere, premature chromatin condensation was the prevalent finding 1 hr post-fusion (hpf). Condensed chromosomes non-arranged in the equatorial plate (1-3 hpf) that acquired an organized structure over time (3-7 hpf) were subsequently observed. Anaphase-telophase structures were predominantly recorded at 4-9 hpf. About 50% of the embryos activated at both 3-4 and 6-7 hpf extruded a polar body-like structure 5 hr after activation, but this was not observed in embryos activated immediately after fusion. A significantly lower activation rate was observed for oocytes activated 3-4 hpf compared to those activated 6-7 hpf. However, the ability to undergo first cleavage was significantly lower in the latter group. Reconstructed embryos activated immediately after fusion showed no difference in the rate of activation compared to those activated 6-7 hpf, although the cleavage rate was higher. DNA synthesis was observed at a significantly higher rate in embryos activated both immediately and 3-4 hpf that did not extrude a PB-like structure than in those activated 3-4 hpf that extruded a polar body-like structure. Under the conditions tested M-phase donor cells cannot be properly remodeled after NT in cattle to trigger normal embryonic development. Our observations of chromatin structures together with DNA synthesis suggest that the failure in the development may be due to improper chromatin remodeling of mitotic nuclei after NT, which may result in chromosomal abnormalities incompatible with normal embryo development.

NuMA: a nuclear protein involved in mitotic centrosome function

Nuclear mitotic apparatus protein, NuMA, is an abundant 240 kDa protein with microtubule (MT) binding capacity via its carboxyl terminal region. Structurally, it has been shown to be a double-strand coiled-coil that has a high potential to form filamentous polymers. During interphase, NuMA locates within the nucleus but rapidly redistributes to the separating centrosomes during early mitosis. Xenopus NuMA associates with MT minus end-directed motor cytoplasmic dynein and its motility-activating complex dynactin at mitotic centrosomal regions. This NuMA-motor complex binds the free ends of MTs, converging and tethering spindle MT ends to the poles. A similar scenario appears to be true in higher vertebrates as well. As a mitotic centrosomal component, NuMA is essential for the organization and stabilization of spindle poles from early mitosis until at least the onset of anaphase. The cell cycle-dependent distribution and function of NuMA is regulated by phosphorylation and dephosphorylation, and p34/CDC2 activity is important to the mitotic role of NuMA. This review summarizes data about the structural features and mitotic function of NuMA with particular emphasis on the newly discovered NuMA-motor complex in spindle organization. Furthermore, NuMA may represent a large group of proteins whose mitotic function is sequestered in the nucleus during interphase.

Parathyroid hormone regulates the expression of the nuclear mitotic apparatus protein in the osteoblast-like cells, ROS 17/2.8

The parathyroid hormone (PTH) signaling pathways that effect changes in osteoblast gene expression also alter the organization of the cytoskeletal proteins. PTH regulates the expression of nucleoskeletal proteins, such as nuclear mitotic apparatus protein (NuMA) and topoisomerase II-alpha. NuMA is a structural component of the interphase nucleus and organizes the microtubules of the mitotic spindle during mitogenesis. We propose that PTH-induced alterations in osteoblast cytoarchitecture are accompanied by changes in osteoblast nuclear structure that contribute to changes in gene expression. We used immunofluorescence and confocal microscopy to determine the effect of PTH on the expression and nuclear distribution of NuMA in the rat osteosarcoma cell line, ROS 17/2.8. Cells were treated with PTH or vehicle, then fixed and stained with NuMA antibody. Optical sections of interphase naive cells revealed a diffuse distribution of NuMA, interspersed with speckles, in the central nuclear planes but not in nucleoli. During the metaphase and anaphase, NuMA localized at the mitotic spindle apparatus. The percentage of NuMA-immunopositive ROS 17/2.8 cells decreased with increasing confluence, but serum starvation did not attenuate NuMA expression. Cell density-dependent changes in cytoskeletal organization were observed in these cells. PTH treatment induced changes in cytoskeletal organization and increased the percentage of NuMA-immunopositive ROS 17/2.8 cells. These data suggest that PTH effects changes in osteoblast nuclear architecture by regulating NuMA, and that these alterations may be coupled to cytoskeletal organization.