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

RpUGT344J7 is involved in the reproduction switch of Rhopalosiphum padi with holocyclic life cycle

Many aphid species exhibit both cyclical parthenogenesis (CP) and the obligate parthenogenesis (OP) life history, which are genetically determined. In CP aphid lineages, the parthenogenetic individuals can switch from asexual to sexual reproduction quickly in response to environmental factors such as changes in photoperiod and temperature. However, the OP aphid lineages do not undergo sexual reproduction under any conditions. So far, mechanisms underlying the reproduction switch in CP aphids have not been fully elucidated. Rhopalosiphum padi, a serious worldwide insect pest of wheat, has both CP and OP lineages. Uridine diphosphate-glycosyltransferases (UGTs) are enzymes that participate in the metabolic detoxification of xenobiotics. Here, we identified 43 RpUGT genes from R. padi genome and transcriptome sequences, and found that: (1) the UGT content of the CP lineage was significantly higher than that in the OP lineage at the key time points when CP lineage mainly produce virginoparae, gynoparae, and males under inducing condition, while there were no significant difference under normal conditions; (2) RpUGT344J7 gene was highly expressed during the time points when CP lineages produce gynopara and males; (3) the critical time points for CP lineages to produce virginoparaee, gynoparae, and males were affected when the CP lineages were injected with dsRpUGT344J7; (4) the knockdown of RpUGT344J7 caused a significant reduction in the total number of virginoparae, gynoparae, and males in the offspring under inducing condition. The findings contribute to our understanding of the molecular mechanisms underlying the quick shift from asexual to sexual reproduction in aphid species.

The impact of bisphenol S on bovine granulosa and theca cells

Bisphenol S (BPS) is an endocrine-disrupting chemical with multiple potential mechanisms of action, including as an oestrogen receptor agonist. BPS is increasingly used in plastics and thermal receipts as a substitute for bisphenol A, which has been phased out due to concerns about human health implications. The ability of BPS to alter female reproductive function in mammals has not been widely studied, despite the importance of normal hormone signalling for female reproduction. The aim of this study was to investigate how BPS (in a wide range of doses, including very low doses) affects granulosa cell and theca cell steroid hormone production and cell viability in the bovine. Granulosa cell oestradiol production was stimulated when cells were exposed to 100 μM BPS under basal conditions, but there was no effect of BPS when cells were stimulated with follicle-stimulating hormone (FSH). Additionally, there was no effect of BPS on granulosa cell progesterone production or cell viability under basal or FSH-stimulated conditions. BPS did not affect theca cell androstenedione or progesterone production, or theca cell viability under basal or luteinizing hormone-stimulated conditions. This study suggests for the first time that BPS may alter oestradiol production by bovine granulosa cells, albeit at a concentration that is unlikely to be physiologically relevant. Further studies are needed to determine the effects of BPS on the bovine oocyte and on other functions of follicular cells.

Regulation of uridine diphosphate-glucuronosyltransferase 2B15 expression during ovulation in the rat

Uridine diphosphate-glucuronosyltransferase 2B15 (UGT2B15) conjugates 5α-androstane-3α, 17β-diol (3α-diol) to 3α-diol glucuronide (3α-diol G) in steroid target tissues. The present study investigated the regulation of UGT2B15 expression during the ovulatory process in the rat. Real-time PCR analysis revealed that treatment of immature rats with equine chorionic gonadotropin followed by human chorionic gonadotropin transiently stimulated UGT2B15 gene expression in granulosa cells of preovulatory follicles within 6 h. The progesterone receptor antagonist RU486 suppressed the gonadotropin-induced UGT2B15 expression. The expression of UGT2B15 and the levels of 3α-diol G were transiently increased by luteinizing hormone (LH) treatment in cultured preovulatory follicles. The LH-stimulated UGT2B15 mRNA level in cultured preovulatory follicles was inhibited by inhibitors of adenylyl cyclase, phosphoinositide 3-kinase and mitogen-activated protein kinase. Furthermore, a vitamin D receptor agonist (calcitriol) suppressed the LH-stimulated UGT2B15 expression in a dose-dependent manner. Taken together, these results indicate that gonadotropins transiently stimulate UGT2B15 expression and activity in preovulatory follicles, and UGT2B15 mRNA levels are regulated by the progesterone receptor and vitamin D receptor.

Effect of gender, pregnancy and exposure conditions on metabolism and distribution of zearalenone in rats

The mycotoxin zearalenone (ZEA) is produced by a variety of Fusarium fungi and contaminates numerous cereals, fruits and vegetables. Interacting with the oestrogen receptors, ZEA and reduced metabolites zearalenols (ZOLs) cause hormonal effects in animals, such as abnormalities in the development of the reproductive tract and mammary gland in female offspring. Limited information is available on the pharmacokinetics of ZEA and its metabolites, particularly in pregnant females, foetuses and newborns. Our study was conducted to characterise the tissue distribution and metabolism of ZEA in male and female rats in various physiological states (virgin female, pregnant female) and exposure conditions (subcutaneous versus oral exposure, single versus repeated exposure to 1 mg/kg ZEA). Respective placental and mammary transfer to foetuses and newborns was evaluated. In all states and exposure conditions, α-ZOL and the glucuronides of ZEA and α-ZOL were the predominant metabolites, mostly concentrated in the intestine, the liver and the urine. Toxins were very low or undetectable in most of the tissues 24 h after ZEA exposure, except in foetal livers. Absorption and intestinal glucuronidation of ZEA were higher in males than females. α-ZOL concentration was significantly higher in the intestine and liver of males and pregnant females, compared to virgin females. ZEA and all its metabolites easily crossed the placental barrier and transferred into the milk. ZEA was metabolised in the foetal and neonatal stages, glucuronides being the main form detected in all organs. Metabolite elimination was slower in foetal tissues than in maternal tissues. All toxin concentrations in the foetal and neonatal tissues strongly increased in cases of repeated maternal exposure. A better knowledge of the metabolism and transfer of ZEA in foetuses and newborns will help to evaluate the health risk that such endocrine disruptors represent in these stages.

Detailed analytical subcellular fractionation of non-pregnant porcine corpus luteum reveals peroxisomes of normal size and significant UDP-glucuronosyltransferase activity in the high-speed supernatant

A detailed subfractionation of the non-pregnant porcine corpus luteum (CL) was performed employing differential centrifugation. Marker enzyme assays (i.e., lactate dehydrogenase for the cytosol, NADPH-cytochrome P450 reductase for the endoplasmatic reticulum, catalase (CAT) for peroxisomes, glutamate dehydrogenase for the mitochondrial matrix and acid phosphatase for lysosomes) in all subfractions obtained exhibited a pattern of distribution similar to that observed with rat liver. These subfractions should be useful in connection with many types of future studies. In disagreement with previous biochemical and morphological studies, peroxisomes (identified on the basis of catalase activity and by Western blotting of catalase and of the major peroxisomal membrane protein (PMP-70)) sedimented together with mitochondria (i.e., at 5000 x g(av) for 10 min) and not in the post-mitochondrial fraction prepared at 30,000 x g(av) for 20 min by Peterson and Stevensson. No other classical peroxisomal enzymes were detectable in the porcine ovary, raising questions concerning the function of peroxisomes in this organ. Furthermore, UDP-glucuronosyltransferase (UGT), generally considered to be an integral membrane protein anchored in the endoplasmatic reticulum, was recovered in both the cytosolic (i.e., the supernatant after centrifugation at 50,000 x g(av) for 1h) and the microsomal fraction of the porcine corpus luteum, even upon further centrifugation of the former. In contrast, UGT sediments exclusively in the microsomal fraction upon subfractionation of the liver and ovary from rat.

Follicle-stimulating hormone, testosterone, and hypoxia differentially regulate UDP-glucuronosyltransferase 1 isoforms expression in rat sertoli and peritubular myoid cells

Uridine diphosphoglucuronosyltransferases (UGTs) are detoxifying enzymes responsible for the metabolism of endogenous and xenobiotics compounds. UGT isoforms are widely distributed in rat tissues showing a constitutive and inducible gene expression. However, little information is available concerning UGTs expression in testis. The UGT1A1, UGT1A2, and UGT1B1 mRNAs expression in whole rat testis, in Sertoli and peritubular myoid cells in basal conditions, and after hormonal and hypoxic stimulation were investigated by reverse transcriptase-polymerase chain reaction (RT-PCR). Constitutive expression of each UGT1 isoform was present in rat testis with higher levels of UGT1A2. UGT transcripts were also detected in Sertoli and peritubular myoid cells. After FSH stimulation, Sertoli cells showed an increase in UGT1B1 mRNA expression, whereas the levels of UGT1A1 and UGT1A2 resulted unmodified. The main effect induced by testosterone was a decrease of UGT1B1 mRNA expression in peritubular myoid cells, whereas in Sertoli cells an increase in UGT1A1 and UGT1B1 was observed. In hypoxic conditions, a reduction in UGTs mRNA levels was detected in both cell types. These findings suggest that rat UGT1 isoforms are regulated in testis by hormonal and environmental factors. Thus, it was speculated that alterations in UGTs expression and/or activity may be involved in the pathogenesis of testis injury.

In situ hybridization studies of UDP-glucuronosyltransferase UGT1A6 expression in rat testis and brain

UDP-glucuronosyltransferases (UGTs), in addition to their role in overall pharmacokinetics, play important roles in local protection of cells against toxins and in the control of endogenous receptor ligands. UGT1A6, which conjugates planar phenols, appears to be expressed in many organs, but information on cell-specific expression in these organs is controversial or absent. Therefore, a non-isotopic in situ hybridization method was developed and applied to localize UGT1A6 expression in rat testis and brain. It was found that UGT1A6 is expressed in Sertoli cells and spermatogonia of rat testis and in brain neurons, in particular in hippocampal pyramidal cells and Purkinje cells of the cerebellum.

Conjugation of 1-naphthol in primary cell cultures of rat ovarian cells

The present study concerns conjugation of 1-naphthol in primary cultures of rat ovarian cells. Two phase II enzymes catalyzing conjugation, i.e. phenol sulfotransferase (P-SULT) and phenol UDP-glucuronosyltransferase (P-UGT), were measured using 1-naphthol as substrate. The rates of conjugation by the different cell types of the rat ovary were the same at low concentrations and short incubation times. However, after 20 h of incubation the rate of conjugation in cells isolated from ovaries enriched in corpora lutea (CL) exceeded the rate in cells isolated from ovaries enriched in preovulatory follicles. In addition, when the granulosa cells were removed from the preovulatory follicles, the rate of conjugation was 1.7-fold higher, i.e. in the theca/stroma cells. When the cells were incubated with 1-[14C]naphthol and conjugates were subsequently separated by thin-layer chromatography, naphthyl glucuronide was the only conjugate observed. Pentachlorophenol (PCP), a commonly used inhibitor of P-SULT, inhibited 1-naphthol conjugation 50% in cell cultures, as well as in microsomal preparations. alpha-Naphthoflavone (ANF) and ellipticine (ELP), both cytochrome P450 (CYP) inhibitors, affected the conjugation of 1-naphthol in different ways; ANF did not affect P-UGT activity in microsomal preparations, but inhibited 1-naphthol conjugation in cell cultures by as much as 90%. On the other hand, ELP inhibited the conjugation of 1-naphthol up to 99% in the cell cultures, but only 75% in microsomal fractions. Testosterone (TST) and estradiol inhibited this activity approximately equal 50% in both of these experimental systems. Clomiphene citrate (CLF), a drug used to induce ovulation and demonstrating both estrogenic and antiestrogenic effects, did not influence the conjugation of 1-naphthol significantly in the cell cultures. The present findings demonstrate that P-UGT is by far the major enzyme conjugating 1-naphthol in the rat ovary and that commonly used inhibitors of P-SULT and CYPs also inhibit P-UGT activity, either directly or via other mechanisms.