Down-regulation Of Steroidogenesis Research Articles

The Effect of Methallibure (ICI Compound 33, 828) on Folliculogenesis and Steroidogenic Potential of Developing Ovary in the Lizard, <i>Calotes versicolor</i> (Daud.)

In vertebrates, it is well established that gonadotropins are crucial for vertebrate ovarian development and its endocrine functions. The current investigation envisages determining how methallibure affects the histoanatomical structure and steroidogenic capacity of the developing ovary of 10-day-old female hatchlings of Calotes versicolor. The eggs were collected from gravid females during the breeding season and incubated at a female-producing temperature of 31.5±0.5 oC till hatching. Hatchlings were fed with live termites. Intraperitoneal injections of 6μg of methallibure in 0.05ml of 0.7% saline were injected into 10-day-old female hatchlings on alternate days for 21 days. The appropriate saline-treated hatchlings served as control. The results reveal that methallibure significantly reduces the number of oocytes (P<0.02) and primordial follicles, decreases their diameter, and increases the number of previtellogenic atretic follicles (P<0.001) with concomitant suppression of the progression of ovarian development when compared with that of baseline control. Three types of atretic follicles were noticed. The histoenzymatic activity of Δ5-3β-hydroxysteroid dehydrogenase in the ooplasm of the follicle and the stromal region showed a decreased intensity. The downregulation of steroidogenesis is probably due to the deprived secretion of gonadal steroids which disturbs the negative feedback mechanism because of the action of the drug at the hypothalamic-hypophyseal-ovarian axis. The present study unveils that methallibure acts as an antigonadotrophic drug altering the synthesis/secretion of gonadotrophin by hypophysis. It is inferred that methallibure induces an anti-gonadotropic effect in the newly hatched hatchlings probably by quenching the pituitary gonadotropins.

P–664 Bone morphogenetic protein–7 (BMP–7) reduces E2 and P4 production of human luteinized granulosa cells by down-regulating the expression of the steroidogenic enzymes StAR and 3B-HSD

Abstract Study question What is the biological role of BMP–7 on the granulosa cells after luteinization? Summary answer BMP–7 down regulates the steroidogenic enzymes and reduces E2 and P4 output of luteinized granulosa cells. What is known already BMP–7 is a member of TGF-B super family that is mainly produced by theca cells in the ovary. It promotes the transition of primordials into primary follicles, and the growth and preantral and antral follicles, and inhibits progesterone (P4) production during FSH-induced growth phase of Graafian follicles (luteinization inhibitor). However, limited data is available regarding the role of this hormone on the molecular luteal characteristics of granulosa cells after ovulation and luteinization processes. We therefore aimed to address this issue in the current study. Study design, size, duration A basic science study on the corpus luteum biology Participants/materials, setting, methods Human luteal granulosa cells were obtained from 10 normo-responder IVF patients undergoing ovarian stimulation with rec-FSH and GnRH antagonist protocol and cultured with recombinant forms of BMP–7, hCG and activin-A for 24h. The presence of cognate receptors for these hormones were validated using RT-PCR. The expression of the steroidogenic enzymes were analyzed with quantitative immunoblotting, real-time RT-PCR and confocal microscopy. E2 and P4 production of the cells were measured using ECLIA method. Main results and the role of chance BMP–7 significantly down-regulated the expression of StAR and 3b-HSD in immunoblotting and confocal images and caused a substantial decrease in P4 production in the luteal GCs in a dose dependent manner. It did not cause any notable change in aromatase expression, however E2 output declined in parallel with P4 due to the reduced expression of StAR, which is the rate limiting enzyme in steroidogenesis. hCG significantly up-regulated StAR and 3b-HSD expression and enhanced P4 output whereas activin-A did the opposite effect. Viability assay with Yo-PRO–1 uptake assay did not reveal any significant differences in the viability of the cells before and after treatment with these hormones. Limitations, reasons for caution In-vitro findings requires validation using in-vivo models. Wider implications of the findings: Reversal of luteinization and down-regulation of steroidogenesis with BMP–7 and other hormones with similar actions warrant further investigation to test their in-vivo effects in order to develop new strategies against ovarian hyperstimulation syndrome (OHSS). Trial registration number Not applicable

Involvement of IGF-I signaling pathway in the regulation of steroidogenesis in mouse Leydig cells treated with fenvalerate

Exposure to fenvalerate has been shown to be associated with decreased steroid hormone production by mouse Leydig tumor cells (MLTC-1) in our previous study and the interference with cAMP–PKA pathway cannot explain this inhibitory effect completely. In this study, the same cell line was used to investigate the potential involvement of insulin-like growth factor I (IGF-I) signaling pathway in the downregulation of steroidogenesis by fenvalerate. Results showed that fenvalerate treatment decreased IGF-I secretion significantly which was consistent with the reduced expression of IGF-I mRNA. Then inhibitors of the two downstream pathways of IGF-I were added to the medium. The addition of LY294002 (inhibitor of phosphatidylinositol (PI)-3-kinase) did not alter the declining trend of progesterone production with increasing dosages of fenvalerate treatment while the addition of UO126 (inhibitor of extracellular signal-regulated kinases 1/2 (ERK1/2)) markedly attenuated this trend, which strongly indicated the possible involvement of pathway ERK1/2. In addition, phosphorylation of ERK1/2 was also suppressed by fenvalerate. The results suggest that the mechanism by which fenvalerate decreased steroid hormone production might involve the impairment of IGF-I signal pathway by attenuating the IGF-I production and ERK1/2 phosphorylation.

Studies of the nature of 17-hydroxyprogesterone hyperresonsiveness to gonadotropin-releasing hormone agonist challenge in functional ovarian hyperandrogenism.

Plasma 17-hydroxyprogesterone (17PROG) hyperresponsiveness to GnRH agonist (nafarelin) testing is typical of polycystic ovary syndrome and other functional ovarian hyperandrogenism (FOH) that does not meet customary criteria for the diagnosis of polycystic ovary syndrome. We have postulated that this results from abnormal regulation of androgen secretion. Whether this dysregulation is the result of a normal physiological response to ovarian hyperstimulation or escape from down-regulation of steroidogenesis is unknown. To distinguish between these possibilities, we have analyzed the ovarian steroid responses to nafarelin for the apparent efficiency of the steroidogenic steps and the apparent dose-response relationships between blood LH and steroid levels. We compared normal women (n = 18) with three groups of hyperandrogenic women (n = 15-19/group): patients with 17PROG hyperresponsiveness with or without elevated LH levels (type 1 and type 2 FOH, respectively) and patients with normal 17PROG responses to nafarelin (nafarelin negative). Subjects were pretreated with dexamethasone to suppress coincidental adrenal contributions to plasma steroid levels. The pattern of steroid secretion was similarly abnormal in both types of FOH, with the high LH group having generally more severe abnormalities in the levels of steroid intermediates. Baseline 17PROG and 17-hydroxypregnenolone and the ratio of 17PROG to androstenedione (AD) were increased (P < 0.05). In addition, the apparent slope of the 17PROG response to LH was significantly increased. Baseline levels of both AD and dehydroepiandrosterone and the AD response to nafarelin were increased, yet the ratio of peak minus baseline (delta) AD/delta 17PROG (another index of 17,20-lyase activity) was subnormal in FOH. The apparent slope of the testosterone (T) response to LH was significantly increased, and indexes of aromatase activity [estradiol (E2)/T and delta estradiol/delta T] were significantly decreased. Nafarelin stimulated plasma E2 in all groups to rise along an apparently similar LH-E2 dose-response slope. We interpret these results as indicating that FOH patients have generalized overactivity of thecal steroidogenesis, but nevertheless compensate so as to maintain a normal dose-response relationship between blood levels of LH and E2. FOH patients, whether they have LH excess or not, seen to form excessive 17PROG and incompletely dampen (down-regulate) thecal cell 17PROG, AD, and T secretion in response to LH stimulation. 17PROG hyperresponsiveness to nafarelin seems to be prominent both because it is formed in excess and because 17,20-lyase efficiency is rate limiting. The T elevation seems to arise mainly from overactive steroidogenesis, but also partly from an additional functional decrease in aromatase efficiency, which is secondary to negative feedback by the substrate-driven tendency toward estrogen excess.(ABSTRACT TRUNCATED AT 400 WORDS)