Progesterone production requires activation of caspase-3 in preovulatory granulosa cells in a serum starvation model.

Granulosa cells proliferate, differentiate, and undergo apoptosis throughout follicular development. Previous studies have demonstrated that stimulation of progesterone production is accompanied by caspase-3 activation. Moreover, we previously reported that arsenic enhanced caspase-3 activity coupled with progesterone production. Inhibition of caspase-3 activity can significantly inhibit progesterone production induced by arsenic or follicle-stimulating hormone (FSH). Here, we report that serum starvation induces caspase-3 activation coupled with augmentation of progesterone production. Serum starvation also increased the levels of cytochrome P450 cholesterol side chain cleavage enzyme (P450scc) and steroidogenic acute regulatory (StAR) protein, both of which may contribute to progesterone synthesis in preovulatory granulosa cells. Inhibition of caspase-3 activity resulted in a decrease in progesterone production. Deactivation of caspase-3 activity by caspase-3 specific inhibitor also resulted in decreases in P450scc and StAR expression, which may partly contribute to the observed decrease in progesterone production. Our study demonstrates for the first time that progesterone production in preovulatory granulosa cells is required for caspase-3 activation in a serum starvation model. Inhibition of caspase-3 activity can result in decreased expression of the steroidogenic proteins P450scc and StAR. Our work provides further details on the relationship between caspase-3 activation and steroidogenesis and indicates that caspase-3 plays a critical role in progesterone production by granulosa cells.

Arsenic induced progesterone production in a caspase-3-dependent manner and changed redox status in preovulatory granulosa cells.

Arsenic contamination is a principal environmental health threat throughout the world. However, little is known about the effect of arsenic on steroidogenesis in granulosa cells (GCs). We found that the treatment of preovulatory GCs with arsenite stimulated progesterone production. A significant increase in serum level of progesterone was observed in female Sprague-Dawley rats following arsenite treatment at a dose of 10 mg/L/rat/day for 7 days. Further experiments demonstrated that arsenite treatment did not change the level of intracellular cyclic AMP (cAMP) or phosphorylated ERK1/2 in preovulatory GCs; however, progesterone production was significantly decreased when cAMP-dependent protein kinase (PKA) or ERK1/2 pathway was inhibited. This implied that the effect of arsenite on progesterone production may require cAMP/PKA and ERK1/2 signaling but not depend on them. Furthermore, we found that arsenite decreased intracellular reactive oxygen species (ROS) but increased the antioxidant glutathione (GSH) levels and mitochondrial membrane potential (ΔΨm) in parallel to the changes in progesterone production. Progesterone antagonist blocked the arsenic-stimulated increase of GSH levels. Arsenite treatment induced caspase-3 activation, although no apoptosis was observed. Inhibition of caspase-3 activity significantly decreased progesterone production stimulated by arsenite or follicle-stimulating hormone (FSH). GSH depletion with buthionine sulfoximine led to cell apoptosis in response to arsenite treatment. Collectively, this study demonstrated for the first time that arsenite stimulates progesterone production through cleaved/active caspase-3-dependent pathway, and the increase of GSH level promoted by progesterone production may protect GCs against apoptosis and maintain the steroidogenesis of GCs in response to arsenite treatment.

Polycomb group proteins are essential for spinal cord development.

Birth defects are the leading cause of infantile mortality, followed by neural tube defects (NTD) and congenital heart defects. Spina bifida and anencephaly are among the most common forms of NTD. NTD etiologies are complex, and are associated with both genetic and environmental factors. Polycomb group proteins are essential for vertebrate development; therefore, the purpose of this study was to determine the role of PcGs in spinal cord morphogenesis in normal and all-trans-retinoic acid (RA)-treated fetal rat models of spina bifida. Pregnant rats were gavage-fed RA, resulting in fetal NTD, and embryos were obtained on day 15.5, 17.5, and 19.5. Western blot and immunohistochemistry were used to reveal PcGs expression in the normal and RA-treated E15.5-19.5 rat sacral cords. Western blot and immunohistochemistry revealed decreased EED, RNF2, SUZ12, and H3K27me3 expression in the normal, E15.5-19.5, rat sacral cords. In addition, the spinal cord of RA-treated rats during embryonic development exhibited altered PcGs protein expression. Administration of excess RA results in NTD. Our results suggest that the Polycomb proteins may be involved in spinal cord development.