RESUMO
We have previously shown that daily exposure to the environmental pollutant 3-methylcholanthrene (3MC) alters the ovarian function by affecting follicle growth and ovulation. To extend our findings, the aims of this work were to study the effects of daily and non-daily exposure to 3MC on oocyte morphology and integrity and the meiosis process. To this end, immature female rats were daily (0.1-1.0 mg/kg) and non-daily (0.1 mg/kg, three times a week) exposed to 3MC and/or α-naphthoflavone (αNF) (80 mg/kg) for 19 and 20 days, respectively. The latter was used to study its ability to prevent the 3MC action. Follicular growth was examined by histology, apoptosis by in situ cell death detection, oocyte integrity by morphological parameters and fluorescent dyes, and the meiotic spindle by immunostaining. Compared with controls (C), and in a dose-dependent manner, all 3MC-treated rats showed i) increased presence of apoptotic cells in antral follicles and decreased percentage of healthy oocytes, ii) increased oocyte area, perimeter and perivitelline space and decreased thickness of the zona pellucida, and ii) increased percentage of oocytes with abnormal meiotic spindle. In addition, the non-daily dose of 3MC caused DNA damage in oocytes, but not in blood or bone marrow cells. All 3MC-induced changes were prevented with the co-treatment with αNF. These results suggest that low doses of 3MC severely disrupt the ovarian function and that germ cells seem to be more sensitive to this environmental pollutant than other cells such as peripheral blood and bone marrow cells.
Assuntos
Benzoflavonas/toxicidade , Metilcolantreno/toxicidade , Oócitos/efeitos dos fármacos , Folículo Ovariano/efeitos dos fármacos , Animais , Apoptose/efeitos dos fármacos , Benzoflavonas/administração & dosagem , Células da Medula Óssea/efeitos dos fármacos , Dano ao DNA/efeitos dos fármacos , Relação Dose-Resposta a Droga , Poluentes Ambientais/administração & dosagem , Poluentes Ambientais/toxicidade , Feminino , Meiose/efeitos dos fármacos , Metilcolantreno/administração & dosagem , Oócitos/citologia , Ratos , Ratos Sprague-DawleyRESUMO
Human papilloma viruses 16 and 18 express E6 and E7 oncoproteins. E6 activates and redirects E6-associated protein (E6AP), an E3 ubiquitin ligase. E6AP interacts with Ube2l3, an E2 ubiquitin conjugating enzyme protein (also known as UbcH7), to promote p53 ubiquitination and degradation by the 26S proteasome. Therefore, blocking E6-mediated p53 degradation might be an alternative treatment for cervical cancer. In addition, activation of the aryl hydrocarbon receptor (AHR) induces Ube2l3 expression, resulting in p53 ubiquitination and degradation. The aim of the present study was to determine whether inhibition of AHR in HeLa cells resulted in an increase in p53 and apoptosis along with a decrease in cell proliferation. The results demonstrate that two AHR antagonists, α-naphthoflavone (α-NF) and resveratrol, decreased cell proliferation, arrested cells in the gap 1/synthesis (G1/S) phases, and increased p53 levels and apoptosis. However, knocking out the Ahr gene did not abrogate the effects of α-NF and resveratrol. Moreover, Ahr-null cells presented similar cell proliferation rates and apoptosis levels when compared to control HeLa cells. Taken together, the results indicate that α-NF's and resveratrol's cytostatic and cytotoxic actions, respectively, occur through an AHR-independent mechanism, and that AHR is not required for HeLa cell proliferation.
Assuntos
Apoptose/efeitos dos fármacos , Benzoflavonas/toxicidade , Proliferação de Células/efeitos dos fármacos , Receptores de Hidrocarboneto Arílico/metabolismo , Estilbenos/toxicidade , Sistemas CRISPR-Cas/genética , Pontos de Checagem da Fase G1 do Ciclo Celular/efeitos dos fármacos , Células HeLa , Humanos , Microscopia Confocal , Receptores de Hidrocarboneto Arílico/antagonistas & inibidores , Receptores de Hidrocarboneto Arílico/genética , Resveratrol , Proteína Supressora de Tumor p53/metabolismoRESUMO
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor and the first protein involved in a variety of physiological and toxicological processes, including those of xenobiotic metabolizing enzymes. AhR has been found in the ovary of many species and seems to mediate the ovarian toxicity of many environmental contaminants, which are AhR ligands. However, the role of AhR in the ovarian function is unknown. Therefore, the aim of this work was to study the action of α-naphthoflavone (αNF), known to be an AhR antagonist, on both follicular growth and ovulation. Immature Sprague-Dawley rats were daily injected intraperitoneally with αNF (0.1-80 mg/kg) or vehicle for 12 days, and primed with gonadotrophins (eCG/hCG) to induce follicular growth and ovulation. Ovaries were obtained 20 h after hCG administration. By means of immunohistochemistry, we found that the numbers of primordial, primary and antral follicles were increased in rats treated with 80 mg/kg αNF and that there were no differences with other doses. Likewise, the ovarian weight and the ovulation rate, measured by both number of oocytes within oviducts and corpora lutea in ovarian sections, were increased when the rats received either 1 or 10mg/kg daily. Although further studies are necessary to know the mechanism of action of αNF, it is possible that the different ovarian processes can be differentially responsive to the presence of different levels of αNF, and that the same or different endogenous AhR ligands can be involved in these ovarian processes in a cell type-dependent manner.