Apoptosis in granulose cells induced by intrafollicular peptide

Effect of FSH receptor-binding inhibitor-8 on FSH-mediated granulosa cell signaling and proliferation

Follicle-stimulating hormone is important for mammalian reproduction. It acts through specific receptors located on the plasma membrane of granulosa cells in ovaries and Sertoli cells in testes. The binding of follicle-stimulating hormone to its receptor activates intracytoplasmic signaling pathways leading to steroidogenesis. These steroids in turn regulate the follicle-stimulating hormone action from the anterior pituitary through exerting negative feedback effect. In addition to steroids, non-steroidal factors secreted by the ovaries are believed to modulate follicle-stimulating hormone action through autocrine/paracrine mode. One such low molecular weight peptide referred to as follicle-stimulating hormone receptor-binding inhibitor-8 purified from human follicular fluid has been extensively studied. Follicle-stimulating hormone receptor-binding inhibitor-8 has been shown to inhibit binding of follicle-stimulating hormone to its receptor. The present article describes the effect of follicle-stimulating hormone receptor-binding inhibitor-8 on follicle-stimulating hormone-induced signaling in rat granulosa cells. Follicle-stimulating hormone receptor-binding inhibitor-8 inhibited the follicle-stimulating hormone-induced cAMP, and the effect was observed to be mediated through the protein kinase A. Further, an inhibitory effect of follicle-stimulating hormone receptor-binding inhibitor-8 on the granulosa cell proliferation was evaluated using COV434 cell line which is derived from the human granulosa cell tumor. The effect of the peptide on the cell cycle analysis showed an increase in apoptotic population and the arrest of G1 phase. These findings suggest that follicle-stimulating hormone receptor-binding inhibitor-8 acts as a follicle-stimulating hormone antagonist and affects the follicle-stimulating hormone-mediated signaling and proliferation in the granulosa cells.

Evaluation of alkyl polyglucoside as an alternative surfactant in the preparation of peptide-loaded nanoparticles

The present study was carried out to evaluate potentials of alkyl polyglucoside (APG) as an alternative surfactant/stabilizer in the preparation of peptide-loaded nanoparticles. hGF(2) (human gel filtration fraction 2) was used as a model peptide and APG based on C(10) fatty alcohol (decyl polylglucoside) was used as a representative surfactant. PLA (poly D,L-lactide) and PLGA (poly D,L-lactide-co-glycolide) based nanoparticles were prepared and the effect of APG on particle size, entrapment efficiency and biological activity was evaluated. At a concentration as low as 0.05% w/v, APG provided an excellent stabilization effect, resulting in nanoparticles with better encapsulation efficiency and particle size well below 450 nm. The effective concentration of APG was found to be much less (10-fold) as compared to PVA. Moreover, APG also showed low residual content as compared to PVA. In-vitro and in-vivo biological activity evaluation confirmed that encapsulated peptide was compatible with APG. These preliminary results suggest that APGs can be used as alternate surfactants for nanoparticle preparation.

Granulosa cell apoptosis induced by a novel FSH binding inhibitory peptide from human ovarian follicular fluid

Pituitary gonadotropins, follicle-stimulating hormone and luteinizing hormone, are the key regulators of ovarian folliculogenesis; these are known to be directly or indirectly modulated by many intraovarian factors. Our group has identified and studied one such novel peptide from human ovarian follicular fluid. Its partial N-terminal eight amino acid sequence has been deduced, referred to as octapeptide (OP). OP induces follicular atresia in mice and interferes with normal ovarian function in non-human primates, this action being similar to the native peptide. Thus, in this study, an attempt has been made to elucidate the mechanism of action of the synthetic OP by studying the pathway of follicular atresia in mouse ovary. Changes in granulosa cells were studied using various apoptotic markers by flow cytometry and immunohistochemistry. An increase in apoptotic cell population in atretic- and peptide-treated groups was observed compared with normal controls. Interestingly, both these groups exhibited differences in the apoptotic pathway. Results showed that the mitochondrial pathway was predominant in the atretic group, whereas the Fas-FasL pathway was predominant in the peptide-treated groups. The ultrastructural study also showed apoptotic changes in the OP-treated and atretic groups; the pattern of apoptosis differed at the subcellular level.

Effect of the human follicle-stimulating hormone-binding inhibitor and its N-terminal fragment on follicle-stimulating hormone-induced progesterone secretion by granulosa cells in vitro

Intrafollicular factors play an important role in folliculogenesis. The follicle-stimulating hormone (FSH)-binding inhibitor (FSHBI), purified by our laboratory from human ovarian follicular fluid, has been shown to suppress ovulation and induce follicular atresia/apoptosis in mice as well as impair fertility in marmosets, the New World monkeys. The octapeptide, a peptide corresponding to the N-terminal region of human FSHBI (hFSHBI), has been synthesized and also shows FSHBI activity in vitro. In the present study, we have attempted to identify the mechanism of action of the peptide in granulosa cell cultures. Rat granulosa cell cultures were treated with varying concentrations of the octapeptide or partially purified hFSHBI (gel chromatography fraction hGF 2) in the presence or absence of human FSH (hFSH) and the amount of progesterone (P;4) secreted in the culture supernatants after 3 h/48 h was estimated. Both hGF2 and the octapeptide failed to alter basal levels as well as 8-bromo cAMP-induced P;4 production, while FSH-induced P 4 secretion was inhibited in a dose-dependent manner. These studies reveal that the octapeptide, a fragment of FSHBI, and the native protein have similar activity in vitro and both compounds alter FSH action at the receptor level upstream of cAMP formation.

Effect of octapeptide: FSH binding inhibitor on cyclicity of bonnet monkeys (Macaca radiata)

BACKGROUND

The gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone play an important role in the development of ovarian follicles, and a number of autocrine/paracrine factors secreted by the ovary are known to directly or indirectly regulate gonadotropin action. The objective of the present study was to elucidate the effect of octapeptide (OP) on cyclicity and hormonal profile of bonnet monkeys, the menstruating Old World primates.

STUDY DESIGN

Our group has purified one such factor from human ovarian follicular fluid, which inhibits the binding of FSH to the granulosa cells. N-terminal eight-amino-acid sequence of this peptide has been deduced, which is referred to as the OP. It has shown an antifertility effect in marmosets, the New World primates. In the present study, the bonnet monkeys were divided into two groups, namely, the treated group (n=5), which was administered with OP (250 mcg/kg body weight/day) intramuscularly during the follicular phase, and the control group (n=6), which was injected with vehicle (saline). Blood was collected every other day, and progesterone levels were estimated by enzyme-linked immunosorbent assay.

RESULTS

Animals in the control group demonstrated normal plasma progesterone levels and exhibited normal cyclicity. On the other hand, in the treated group, progesterone levels decreased by 65.8%, as compared with that in pretreatment cycles. This probably disturbed the cyclicity, thus causing amenorrhea (73.0+/-6.7 days).

Expression of bcl(xs) and c-myc in atretic follicles of mouse ovary

At birth, in the human female, one million follicles are present, out of which only 450 ovulate during the reproductive lifespan while the remainder of the 99.9% follicles degenerate. It is therefore important to understand the regulation of follicular atresia. Immature mice injected with pregnant mare serum gonadotrophin (PMSG) were used as a model for follicular atresia. In this model, we demonstrated by various methods, including the TdT-mediated dUTP nick end labelling (TUNEL) technique, that granulosa cells in atretic follicles undergo apoptosis. In eukaryotic cells, apoptosis is regulated by genes such as bcl(2) and c-myc. Regulation of apoptosis in the ovary by these proteins/genes was studied using the mouse model. bcl(2) is anti-apoptotic; however, bcl(xs), a member of the bcl(2) family, is apoptotic. Immunohistochemical localization of bcl(xs) in the granulosa cells of atretic follicles suggested its role in follicular atresia. Expression of c-myc was studied by in-situ hybridization in the mouse follicular atresia model. In the atretic follicles, expression of c-myc in granulosa cells was observed. Thus our studies indicate that bcl(xs) regulates granulosa cell apoptosis, while c-myc may also play a role in cell death during follicular atresia.