In the present study, we started out to test whether the follicle-stimulating hormone (FSH)-activated p38 MAPK signaling cascade was involved in the regulation of steroidogenesis in granulosa cells (GCs). GCs were prepared from the ovaries of DES-treated immature rats and cultured in serum-free medium. Treatment of GCs with FSH (50 ng/ml) induced the phosphorylation of p38 MAPK rapidly with the phosphorylation being observed within 5 min and reaching the highest level at 30 min. Such activation was protein kinase A-dependent as indicated by the results using specific inhibitors. FSH stimulated the production of progesterone and estradiol as well as the expression of the steroidogenic acute regulatory protein (StAR) in a time-dependent manner, with a maximum level being observed in the production of progesterone and StAR at 48 h. Moreover, the potent p38 MAPK inhibitor SB203580 (20 µM) augmented FSH-induced progesterone and StAR production, while reduced FSH-induced estradiol production at the same time (P<0·01). RT-PCR data showed that inclusion of SB203580 in the media enhanced FSH-stimulated StAR mRNA production, while decreased the FSH-stimulated P450arom mRNA expression (P<0·05). Immunocytochemical studies showed that FSH treatment together with the inhibition of p38 MAPK activity resulted in a higher expression of StAR in mitochondria than FSH treatment alone. FSH also significantly up-regulated the protein level of LRH-1, a member of the orphan receptor family that activates the expression of P450arom in ovaries and testes. p38 MAPK inactivation down-regulated the basal and FSH-induced LRH-1 expression significantly. The intracellular level of DAX-1, another orphan receptor that inhibits StAR expression, also decreased upon p38 MAPK being inactivated. For the first time, the present study suggests that FSH-activated p38 MAPK signal pathway regulates progesterone and estrogen production in GCs differentially, and that the transcription factors LRH-1 and DAX-1 might play important roles in the process.

Stem cell factor (SCF) is essential for the development of primordial follicles. One of its functions is to prevent oocytes from apoptosis. However, the underlying mechanism remains largely unknown. By using cultured ovaries that are rich in primordial follicles, the anti-apoptotic action of SCF and the potential signal transduction pathways were investigated. The apoptosis was evaluated by means of in situ 3'-end labeling. The expressions of proteins were analyzed with immunohistochemistry and Western blot. The data showed that SCF significantly prevented oocytes from apoptosis in the cultured organs. Addition of a specific pharmacological inhibitor of PI3K abolished the anti-apoptotic action of SCF while that of a MEK inhibitor did not. The phosphorylation of two mitogen activated protein kinases (MAPKs) (p42 and p44) and AKT, the respective substrates of MEK and PI3K, were enhanced by SCF treatment. Not surprisingly, the MAPK activation occurred only in theca cells. The expressions of apoptosis-related gene products, the Bcl-2 family proteins, in response to SCF treatment were also investigated. While SCF up-regulated the expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL, it did the opposite to the pro-apoptotic factor Bax. The PI3K inhibitor reversed the regulation of SCF on Bcl-xL and Bax but not on Bcl-2. Therefore, it seemed that SCF initiated an anti-apoptotic signal starting from its membrane receptor c-kit to Bcl-2 family members through PI3K/AKT and other signaling cascades in the oocytes of primordial follicles.

Herein we demonstrate the synthesis and investigation of organic D-A type fluorophores, named Np-TPA and Np-2TPA, comprising of twisted triphenylamine (TPA) as electron-donor and planar 1,8-naphthalenimide (Np) as electron-acceptor. These...

Follicular development is characterized by both proliferation and differentiation of granulosa cells (GCs) under the control of FSH. However, the cellular mechanism by FSH is not known. Using cultured GCs, we examined whether FSH activated ERK1/2 was involved in the regulation of the proliferation related gene proliferating cell nuclear antigen (PCNA) and steroidogenesis. GCs were obtained from the ovaries of DES treated immature rats and cultured in serum free medium. The results showed that FSH activated ERK1/2 in a time dependent manner, with a peak at 20 min. Such activation was PKA dependent as was inhibited by specific inhibitors. FSH induced PCNA expression in a time dependent manner, with a maximum stimulation at 2 h. Similarly, StAR and steroid levels increased as FSH treatment time extended, with a maximum progesterone and StAR production at 48 h. ERK1/2 inactivation by UO126 inhibited the stimulatory effects of FSH on both PCNA and StAR expression and steroid synthesis in the GCs (p less than 0.01). Immunocytochemical studies further revealed that ERK1/2 inhibition led to a reduction of mitochondrial StAR in the GCs by FSH. These observations suggested that the stimulation of FSH on PCNA expression and steroidogenesis in GCs was mediated at least partially by ERK1/2.