Glutathione transferase isoenzyme patterns in the rat ovary

Glutathione and its related enzymes in the gonad of Nile Tilapia (Oreochromis niloticus)

Glutathione (GSH) concentration, the activity of its metabolizing enzymes, glutathione transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), and the antioxidant enzyme catalase (CAT) in O. niloticus ovary and testis were examined. GSH concentration of O. niloticus testis exhibited high concentration (129 ± 21 nmol/g tissue) compared with GSH concentration (49.2 ± 8.3 nmol/g tissue) in the ovary. GST, GPx, GR, and CAT activities of O. niloticus testis exhibited high values compared with their corresponding values in ovary homogenates. However, protein concentration in ovary homogenates exhibited higher values (175 ± 40.6 mg) compared with testis homogenates (27.1 ± 3.7 mg). O. niloticus ovary was less effective in excretion of xenobiotices compared with the testis, where its function is mainly in increasing the protein content of the eggs; however, in O. niloticus testis, the glutathione cycle operated in accelerated way in the direction of reduced GSH production in order to protect the maturation stages in a save way. A simple reproducible procedure for the purification of GST from O. niloticus ovary was established. The enzymes proved to be homogenous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and its molecular weight was calculated to be 25.1 kDa. GST of O. niloticus ovary exhibited maximum activity at pH 7.5. The Michaelis-Menten constant (K(m)) of the purified ovary GST for GSH and CDNB was 0.076 mM and 1.0 mM, respectively. Cibacron blue was the most potent inhibitor of ovary GST activity (IC50 value, concentration of inhibitor that will give 50% inhibition, equal 0.002 μM). The specific activity of GST toward different electrophilic substrates was determined. GST activity toward benzyl isothiocyanate was the highest compared with phenethyl isothiocyanate and allyl isothiocyanate.

Effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE47) on the enzymes of phase I (CYP2B1/2) and phase II (SULT1A and COMT) metabolism, and differences in the action of parent BDE-47 and its hydroxylated metabolites, 5-OH-BDE-47 and 6-OH-BDE47, on steroid secretion by luteal cells

In this study we determined the effects of BDE-47 on the expression and activity of phase I (CYP2B1/2) and phase II (SULT1A and COMT) enzymes, and assessed the actions of BDE-47 and its metabolites on luteal steroidogenesis. Luteal cells collected during early (ELP), middle (MLP) and late (LLP) luteal phase were exposed to BDE-47 (0.5, 25, and 50ng/ml) or metabolites (2.5, 5 and 25ng/ml). BDE-47 decreased CYP2B1/2 activity and expression but had no effect on SULT1A or COMT. BDE-47 exerted a stimulatory action on estrogen secretion in MLP and an inhibitory in LLP, but had no effect on progesterone secretion. 5-OH-BDE-47 and 6-OH-BDE-47 decreased progesterone, but had no effect on estrogen secretion.

CONCLUSIONS

The inhibitory effect of BDE-47 on CYP2B1/2 suggests the possibility of BDE-47 accumulation in the corpus luteum; by affecting steroid secretion and steroidogenesis enzymes, BDE-47 and its metabolites can be responsible for shortening luteal phase.

Protection from cyclophosphamide-induced ovarian damage with bone marrow-derived mesenchymal stem cells during puberty

OBJECTIVE

In female cancer survivors, the accelerated loss of primordial follicles may lead to premature ovarian failure. We investigated the protective effects of bone marrow derived mesenchymal stem cells (BMMSC) and gonadotropin releasing hormone analogue (GnRHa) against chemotherapeutic-induced ovarian toxicity in a rat model.

MATERIAL AND METHODS

Forty-eight Wistar albino female rats were divided into four groups. Group 1 was composed of rats that were given 200 mg/kg cyclophosphamide injection for each cycle (two cycles for each rat). Both cyclophosphamide and 0.4 µg GnRHa were administered to Group 2. Cyclophosphamide and 4 million/kg BMMSC were administered to Group 3. Cyclophosphamide, GnRHa, and BMMSC were administered to Group 4. Germ cell apoptosis, DNA fragmentation and primordial follicular count were investigated with Cleave Caspase-9 and TUNEL analysis. The presence of the SRY gene on the Y chromosome in the ovary of the recipient female rats was checked with PCR.

RESULTS

Immunohistochemical staining (IHS) of Caspase-9 and TUNEL was higher in Group 1 than in Group 3 (p < 0.05). Similarly, Group 4 had higher values than Group 3 (p < 0.05). The presence of the SRY gene was detected in Groups 3 and 4 with the PCR analysis. The mean primordal follicle count was lowest in Group 1 and the mean primordial follicle counts were higher in Groups 2 and 3 than in Group 1. The difference between Group 1 and Group 4 was not significant.

CONCLUSION

BMMSC therapy was found to be protective from germ cell apoptosis and DNA damage when it was used with chemotherapy regimens including alkylating agents.

A comparative study on oxidative and antioxidative markers of serum and follicular fluid in GnRH agonist and antagonist cycles

OBJECTIVE

To determine whether concentrations of oxidative stress markers of follicular fluid and serum are different in GnRH agonist protocol from GnRH antagonist protocol.

MATERIAL AND METHOD

This was a cross-sectional study. Eighty-four women undergoing controlled ovarian stimulation with either GnRH agonist (n = 39) or GnRH antagonist protocols (n = 45) for IVF/ICSI treatment were assigned by a physician. Blood was obtained at the time of oocyte retrieval, and follicular fluid (FF) from the mature follicles of each ovary was centrifuged and frozen until analysis. Malondialdehyde (MDA), nitric oxide (NO), protein carbonyl (PC), hydroxyl proline (OH-P), sodium oxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidase (GSH-Px), adenosine deaminase (ADA) and xanthine oxidase (XO) were assessed in the serum and follicular fluid of each participants.

RESULTS

The mean serum concentrations of GSH-Px, GSH and MDA were lower in the GnRH antagonist group compared to GnRH agonist group, but mean serum SOD was higher in the GnRH antagonist group. The mean follicular SOD, ADA and NO were higher in GnRH antagonist group than GnRH agonist group. The IVF/ICSI outcomes were similar in both groups.

CONCLUSION(S)

GnRH antagonist protocol is associated with increased oxidative stress. The relation of GnRH analogues with oxidative stress and its implication in follicular growth needs to be addressed in further studies.

Ovarian metabolism of xenobiotics

At birth, the mammalian ovary contains a finite number of primordial follicles, which once depleted, cannot be replaced. Xenobiotic exposures can destroy primordial follicles resulting in premature ovarian failure and, consequently, early entry into menopause. A number of chemical classes can induce premature ovarian failure, including environmental, chemotherapeutic and industrial exposures. While our knowledge on the mechanistic events that occur in the ovary with chemical exposures is increasing, our understanding of the ovary's capacity to metabolize such compounds is less established. This review will focus on three chemicals for which information on ovarian metabolism is known: trichloroethylene, 7,12-dimethylbenz[a]anthracene and 4-vinylcyclohexene. The current state of understanding of ovarian bioactivation and detoxification processes for each will be described.

Ovarian preservation by GnRH agonists during chemotherapy: a meta-analysis

PURPOSE

Treatment with cyclophosphamide (CYC) confers up to a 40% risk of ovarian failure in women of reproductive age. The use of GnRH agonists (GnRHa) to preserve ovarian function has been investigated in several small studies. We performed a systematic review of studies examining whether a GnRHa administered during chemotherapy is protective of ovarian function and fertility.

METHODS

We searched the English-language literature (1966-April 2007) using MEDLINE and meeting abstracts and included studies that reported an association between GnRHa and ovarian preservation in women receiving chemotherapy. Studies without a control group were excluded. Ovarian preservation was defined as the resumption of menstrual cycles and a premenopausal follicle-stimulating hormone (FSH) after chemotherapy. Fertility was determined by a woman's ability to become pregnant. We estimated the summary relative risk (RR) and associated 95% confidence intervals (95% CI) using a random-effects model.

RESULTS

Nine studies included 366 women. Three studies included women with autoimmune disease receiving CYC; six included women with hematologic malignancy receiving combination chemotherapy. In total, 178 women were treated with GnRHa during chemotherapy, 93% of whom maintained ovarian function. Of the 188 women not treated with GnRHa, 48% maintained ovarian function. The use of a GnRHa during chemotherapy was associated with a 68% increase in the rate of preserved ovarian function compared with women not receiving a GnRHa (summary RR = 1.68, 95% CI 1.34-2.1). Among the GnRHa-treated women, 22% achieved pregnancy following treatment compared with 14% of women without GnRHa therapy (summary RR = 1.65, CI 1.03-2.6).

CONCLUSIONS

Based on the available studies, GnRHa appear to improve ovarian function and the ability to achieve pregnancy following chemotherapy. Several randomized trials are underway to define the role and mechanism of GnRHa in ovarian function preservation. In the meantime, premenopausal women facing chemotherapy should be counseled about ovarian preservation options, including the use of GnRHa therapy.

Reduction in rat oocyte fertilizability mediated by S-(1, 2-dichlorovinyl)-L-cysteine: a trichloroethylene metabolite produced by the glutathione conjugation pathway

Trichloroethylene (TCE), a commonly used industrial degreasing solvent and environmental toxicant, reduces rat oocyte fertilizability by an incompletely understood mechanism. Previous evidence implicated cytochrome P450 dependent oxidation of TCE. The current study investigated a second pathway, glutathione conjugation using S-(1,2-dichlorovinyl)-L-cysteine (DCVC), a mutagenic and cytotoxic TCE-metabolite. In vitro exposure of oocytes and in vivo exposure of females to DCVC significantly reduced oocyte fertilizability (63% vs. 26%; p < 0.005 and 60% vs. 36%; p < 0.005, respectively). Reduced fertilizability of oocytes following in vivo TCE exposure may be mediated partially by the glutathione conjugation pathway.

Ovarian gene expression is stable after exposure to trichloroethylene

Exposure of female rats to trichloroethylene (TCE), an environmental toxicant commonly found in ground and surface waters throughout the United States, reduces the fertilizability of oocytes produced by these females compared with oocytes from control females. Localization of cytochrome P450 2E1 and glutathione s-transferase alpha, TCE-metabolizing enzymes, in the ovary suggests TCE metabolism occurs in the ovary. The production of bioactive TCE metabolites in the ovary may alter female reproductive function by altering ovarian gene transcription and/or protein expression and function. The purpose of the present study was to examine ovarian gene transcription after exposure of female rats to 0.45% TCE (v/v) in 3% Tween. Control rats received 3% Tween. Microarray analysis after 1 and 5 days of exposure indicated ovarian gene transcription was maintained during TCE exposure with the possible exception of a very few genes. Although conclusions for these few genes were ambiguous from the microarray analysis due to the minimal but statistically significant reductions, quantitative real time RT-PCR (qRT-PCR) analysis indicated expression of these genes was unaltered after TCE exposure. Protein analysis confirmed qRT-PCR results. This study suggests TCE-induced reductions in oocyte fertilizability are independent of currently detectable alterations in ovarian gene expression.

Absence of conclusive evidence for the safety and efficacy of gonadotropin-releasing hormone analogue treatment in protecting against chemotherapy-induced gonadal injury

Every year, an increasing number of women with malignant and nonmalignant diseases is successfully treated with cytotoxic chemotherapy and/or radiotherapy. Many of these patients suffer from infertility and gonadal failure as a result of these treatments. At present, these patients may resort to assisted-reproduction techniques to protect their future childbearing potential before the implementation of cytotoxic therapy. While embryo cryopreservation is an established technology, oocyte and ovarian tissue freezing techniques are still investigational. Nevertheless both of these techniques have resulted in live births. Apart from assisted-reproduction techniques, it has been extensively debated whether administration of gonadotropin-releasing hormone (GnRH) analogues in conjunction with chemotherapy can protect ovarian reserve against cytotoxic insult. In this manuscript, we debate the rationale for the effectiveness of GnRH analogue coadministration in preservation of fertility by reviewing the literature, and provide preliminary data to support our views.

High expression of bovine alpha glutathione S-transferase (GSTA1, GSTA2) subunits is mainly associated with steroidogenically active cells and regulated by gonadotropins in bovine ovarian follicles

We have previously shown that a major group of 28-30 kDa proteins decreases after the LH surge in bovine granulosa cells (GC). In the present study, we have characterized two proteins in this group in search of factors that may intervene in folliculogenesis and oocyte maturation. Polyclonal antibodies raised against 28 kDa or 29 kDa bovine GC proteins were used to screen a complementary DNA (cDNA) expression library. This resulted in the characterization of two isoenzyme subunits for alpha class glutathione S-transferase, named bGSTA1 and bGSTA2. Both bGSTA1 (25.4 kDa, pI 8.9; 791 bp cDNA; GenBank Accession No. BTU49179) and bGSTA2 (25.6 kDa, pI 7.2; 959 bp cDNA; GenBank Accession No. AF027386) have 222 amino acids. The deduced amino acid sequences were compared and showed 82% (bGSTA1) and 74% (bGSTA2) identity to human GSTA1, whereas bGSTA1 and bGSTA2 are 81% identical to each other. The bGSTA2 represents a novel GSTA subunit because it harbors a specific 16 amino acid sequence not found in any other species and GST classes. Northern blots showed that bGSTA1 and bGSTA2 are coexpressed and are tissue specific with single transcripts of 1.2 kb and 1.4 kb, respectively for bGSTA1 and bGSTA2. The messenger RNA (mRNA) were detected in GC, corpus luteum, adrenal gland, testis, liver, lung, thyroid, kidney and cotyledon, and the relative abundance of their mRNA varied. Ratios of bGSTA1/bGSTA2 mRNA vary between tisssues, indicating that expression of these genes is controlled differently. Immunohistochemistry observations revealed that expression of GSTA is cell specific, being associated with GC and theca cells, small luteal cells, Leydig cells, hepatocytes, adrenal cortex, specific chromaffin cells in the adrenal medulla, renal proximal convoluted tubular cells, and Clara cells in the bronchioles. Studies in vivo showed that levels of mRNA for bGSTA1 were elevated in follicular wall of preovulatory follicles before hCG treatment, but decreased by 77% 12 h after hCG injection. However, in FSH stimulated preovulatory follicles, the decrease in mRNA for both GSTAs was only 21% at 24 h following hCG injection. We concluded that bGSTA1 and bGSTA2 expression is tissue- and cell-specific, is associated with steroidogenically active cells, and is hormonally regulated by gonadotropins in the bovine ovarian follicle.

Expression of glutathione transferase isoenzymes in the porcine ovary in relationship to follicular maturation and luteinization

The expression of different isoenzymes of glutathione transferase (GST), i.e. the cytosolic subunits GSTA1/A2, A3, A4, A5, M1/2, M2 and P1, T2, and the microsomal GST in follicles of different sizes and in corpora lutea from porcine ovary, was investigated by Western blotting. No immunoreactivity was obtained with anti-rat GSTT2 or anti-rat microsomal GST polyclonal antibodies. In contrast, GSTA1/A2, A3, A4, A5, M1/2, M2 and P1 are all expressed in the cytosol from porcine ovaries. In general, the highest levels of these GST isoenzymes were present in the cytosol from corpora lutea, in agreement with measurements of activity towards 1-chloro-2,4-dinitrobenzene. Immunoreactivity with anti-rat GSTP1 was only obtained with follicles. The cytosolic GSTs from follicles and corpora lutea were affinity purified on glutathione-Sepharose and separated by reversed-phase high-performance liquid chromatography in order to quantitate the different subunits. A peak corresponding to the class pi subunit was present in follicles. This peak was also seen with corpora lutea, although at very low level. There were four peaks containing class mu subunits. The remaining peaks were concluded to contain the class alpha subunits, except for two peaks which are suggested to contain proteins other than GSTs. The levels of the different subunits were quantitated on the basis of the areas under the peaks and the relative amounts in follicles of different sizes and in corpora lutea corresponded well with the Western blot analysis.

Characterization of the UDP-glucuronosyltransferase isoenzyme expressed in rat ovary and its regulation by gonadotropins

Earlier studies have demonstrated that phenol UDP-glucuronosyltransferase (UGT) activity is up-regulated by pregnant mare's serum gonadotropin (PMSG) in rat ovary, but not liver. This phenomenon was investigated in more detail in the present study. Ovaries and livers of immature rats, rats synchronized with respect to their preovulatory and corpus luteal phases by treatment with PMSG, and mature rats hyperstimulated with PMSG were compared. Under all of these conditions, only one immunoreactive band of UGT, shown to be phenol UGT, was detected in the rat ovary. The effects of oestradiol, progesterone and/or human chorionic gonadotropin (hCG) on the level of phenol UGT in immature rat ovary were also examined. Partial up-regulation was caused by progesterone or oestradiol, together with hCG, whereas progesterone or oestradiol alone had no up-regulating effect. Follicle-stimulating hormone also seemed to be required for the up-regulation in ovaries enriched in corpus luteum. The present findings demonstrate that progesterone is involved in the regulation of phenol UGT in rat ovary by gonadotropins. Regulation by both progesterone and oestradiol was dependent on induction of ovulation and steroidogenesis by luteinizing hormone.