Development of multidrug resistance type I P-glycoprotein function during in vitro maturation of porcine oocyte

Transcriptional downregulation of ABC transporters is related to follicular degeneration after vitrification and in vitro culture of ovine ovarian tissue

ATP-binding cassette (ABC) transporters perform multiple functions in reproductive tissues. During ovarian tissue vitrification, the plasma membrane has important functions in the influx or efflux of water, and substances such as cryoprotectants and channel proteins that are required in this process. Thus, the present study aimed to verify the relative abundance of mRNA transcript of ABC transporters ABCB1, ABCG2, and MRP2 after vitrification and in vitro culture (IVC) of ovine ovarian tissue. For this study, the ovarian cortex fragments were proportioned into four groups as fresh control, vitrified control, fresh culture, and vitrified culture groups. After vitrification and in vitro culture, the ovarian tissue was evaluated using morphological procedures. Further, relative abundance of ABCB1, ABCG2, and MRP2 transporter mRNA transcripts in the ovarian cortex subjected to aforementioned treatment conditions were evaluated using qPCR. Our results showed a negative association between degenerated follicles and mRNA transcript abundances of ABCB1 and ABCG2. In addition, the percentage of growing follicles in the ovine ovarian cortex after vitrification was similar to that of the fresh control tissue without in vitro culture. The in vitro culture of fresh and vitrified tissue however, showed a significant decrease in the percentage of growing follicles. To the best of our knowledge, we believe that our data for the first time has studied the relative abundances of ABCB1 and ABCG2 mRNA transcripts in the ovine ovarian cortex. In addition, alterations of these protein channels may be indicative of a deleterious effect of osmotic stress on follicular survival during vitrification. Furthermore, these effects were detectable only after the IVC of the ovarian tissues. Nonetheless, further studies are required to investigate the functions of ABC transporters in ovine folliculogenesis, especially after in vitro culture of ovarian tissue.

Multidrug Resistance Protein 1 Deficiency Promotes Doxorubicin-Induced Ovarian Toxicity in Female Mice

Multidrug resistance protein 1 (MDR1), a phase III drug transporter that exports substrates out of cells, has been discovered in both cancerous and normal tissues. The over expression of MDR1 in cancer cells contributes to multiple drug resistance, whereas the MDR1 in normal tissues protects them from chemical-induced toxicity. Currently, the role of MDR1 in the ovary has not been entirely understood. Our objective is to determine the function of MDR1 in protecting against chemotherapy-induced ovarian toxicity. Using both the in vivo transgenic mouse model and in vitro follicle culture model, we investigated the expression of MDR1 in the ovary, the effect of MDR1 deficiency on doxorubicin (DOX)-induced ovarian toxicity, and the ovarian steroid hormonal regulation of MDR1. Results showed that the MDR1 was expressed in the ovarian epithelial cells, stroma cells, theca cell layers, endothelial cells, and luteal cells. The lack of MDR1 did not affect female ovarian function and fertility; however, its deficiency significantly exacerbated the DOX-induced ovarian toxicity in both in vivo and in vitro models. The MDR1 showed significantly higher expression levels in the ovaries at estrus and metestrus stages than those at proestrus and diestrus stages. However, this dynamic expression pattern was not regulated by the ovarian steroid hormones of estrogen (E2) and progesterone (P4) but correlated to the number and status of corpus luteum. In conclusion, our study demonstrates that the lack of MDR1 promotes DOX-induced ovarian toxicity, suggesting the critical role of MDR1 in protecting female ovarian functions during chemotherapy.

Toxicity of beauvericin on porcine oocyte maturation and preimplantation embryo development

Beauvericin (BEA) is one of many toxins produced by Fusarium species that contaminate feed materials. The aim of this study was to assess its effects on porcine oocyte maturation and preimplantation embryo development. Cumulus-oocyte-complexes and developing embryos were exposed to BEA and cultured until the blastocyst stage. Cumulus cells, oocytes and embryos were examined for viability, progesterone synthesis, multidrug resistance protein (MDR1), ATP content and gene expression related to MDR1 function, oxidative phosphorylation, steroidogenesis and apoptosis. BEA was toxic in embryos, oocytes and cumulus cells at concentrations exceeding 0.5μM, and embryos were most vulnerable after the four-cell stage. Since BEA exerted different effects in embryos, oocytes and cumulus cells, the toxic mechanism is suggested to involve different pathways. Currently there are no consistent data on adverse effects of BEA in pig farms.

Multidrug-resistant transport activity protects oocytes from chemotherapeutic agents and changes during oocyte maturation

OBJECTIVE

To determine the multidrug-resistant transporter (MDR) activity in oocytes and their potential role in oocyte susceptibility to chemotherapy.

DESIGN

Experimental laboratory study.

SETTING

University and academic center for reproductive medicine.

SUBJECT(S)

Women with eggs retrieved for intracytoplasmic sperm injection cycles and adult female FVBN and B6C3F1 mouse strains.

INTERVENTION(S)

Inhibition of MDR activity in oocytes.

MAIN OUTCOME MEASURE(S)

Efflux activity of MDRs with the use of quantitative fluorescent dye efflux, and oocyte cell death when exposed to chemotherapy.

RESULT(S)

Oocytes effluxed fluorescent reporters, and this activity was significantly reduced in the presence of the MDR inhibitor PSC 833. Geminal vesicle oocytes were more efficient at efflux than metaphase 2 oocytes. Human oocytes exposed to cyclophosphamide and PSC 833 showed cell death with the use of two different viability assays compared with control samples and those exposed to cyclophosphamide alone. Immunoblots detected MDR-1 in all oocytes, with the greatest accumulation in the geminal vesicle stage.

CONCLUSION(S)

Oocytes have a vast repertoire of active MDRs. The implications of this study are that these protective mechanisms are important during oogenesis and that these activities change with maturation, increasing susceptibility to toxicants. Future directions may exploit the up-regulation of these transporters during gonadotoxic therapy.

Retrovirus-mediated multidrug resistance gene (MDR1) overexpression inhibits chemotherapy-induced toxicity of granulosa cells

OBJECTIVE

To protect granulosa cells from chemotherapy-induced toxicity by retrovirus-mediated multidrug resistance (MDR1) gene transfection.

DESIGN

Laboratory study.

SETTING

Academic research laboratory in a university hospital.

PATIENT(S)

None.

INTERVENTION(S)

KK15 immortalized murine granulosa cell line transiently transduced with sf91m3 retrovirus vector carrying MDR1 complementary DNA that encodes P-glycoprtoein (P-gp); transduced cells selected with colchicine and treated with doxorubicin or paclitaxel for 24-72 hours; expression and function of MDR1 and the messenger RNA (mRNA) expression of selected steroidogenesis enzymes evaluated by flow cytometry, cell viability assays, Western blot, and reverse-transcriptase polymerase chain reaction (RT-PCR).

MAIN OUTCOME MEASURE(S)

Viability of sf91m3-transduced KK15 cells after treatment with doxorubicin and paclitaxel.

RESULT(S)

The sf91m3-transduced KK15 demonstrated high expression of biologically active MDR1, as shown by flow cytometry analysis and immunoblotting using P-gp monoclonal antibody and Rhodamine 123 efflux assays. The sf91m3-transduced KK15 exhibited statistically significant resistance to toxicity of 10 μM paclitaxel. The MDR1-transduced KK15 cells were also protected from doxorubicin toxicity (10 nM to 2.5 μM), as shown by cell viability assay. Both flow cytometry and cell viability assays showed that the protection of KK15 from doxorubicin toxicity was lost at 5 μM of doxorubicin; equivalent to 500 times LD50. The sf91m3-transduced KK15 showed normal mRNA expression of a panel of selected steroidogenesis enzymes.

CONCLUSION(S)

Retroviral gene delivery of human MDR1 inhibited chemotherapy-induced granulosa cell toxicity and offered chemoprotection in an in vitro model.

Progesterone-dependent and -independent expression of the multidrug resistance type I gene in porcine granulosa cells

A primary role of plasma membrane P-glycoprotein (P-gp), encoded by multidrug resistance type I (MDR1), is to protect against naturally occurring xenotoxics. Progesterone (P(4)) profoundly influences MDR1 expression in granulosa cells and luteal cells. Here, P(4) regulation of MDR1 expression was investigated in porcine granulosa cells using the P(4)-mediated promoter activity assay and a P4 receptor (PR) antagonist (RU-486). The promoter activity was measured chronologically for 48 h in cells transfected with the PR response element-containing pGL3. LH could stimulate the promoter activity through endogenous P4, with a maximum activity at 5 h. MDR1 mRNA level was highly maintained at 24-36 h. Conversely, exogenous P4 prolonged the promoter activity to further 10 h, and the high level of MDR1 mRNA was maintained even at 48 h. RU-486 completely inhibited the promoter activity, but the level of MDR1 mRNA rapidly increased in the presence of RU-486. The granulosa cells may become susceptible to RU-486 as a xenotoxic to rapidly express MDR1 for protection against it. These results indicate that MDR1 is expressed in porcine granulosa cells through P4-dependent and -independent regulations.

Progesterone regulation of the expression and function of multidrug resistance type I in porcine granulosa cells

P-glycoprotein (P-gp) coded with the multidrug resistance type I (MDR1) is expressed in various normal tissues including ovaries and may function as detoxification and steroid transport. The present study was performed to analyze the expression and function of MDR1 in granulosa cells stimulated with FSH, LH, estradiol-17beta (E) and progesterone (P). The granulosa cells isolated from porcine ovarian follicles were cultured for 24h in a serum-supplemented medium, and then cultured for 48h with the hormones in a serum-free culture medium. MDR1 was highly expressed in large follicles and induced in cultured granulosa cells stimulated with LH as revealed by RT-PCR. Highly expressed MDR1 resulted in the increased P-gp activity. However, FSH had no effect. P significantly increased the MDR1 expression and P-gp activity in the cells stimulated with LH, whereas E had no stimulatory effect. Aminoglutethimide suppressed the MDR1 expression and P-gp activity, but which were completely restored by P. These results indicate that P participates in MDR1 expression and P-gp function of granulosa cells.