Cytochrome P-450scc activity and substrate supply in human placental trophoblasts

Placenta: an organ with high energy requirements

Placenta is a unique organ, without which the very phenomenon of human pregnancy is impossible. Semiallogeneous nature, localization of the placenta, complex and heterogeneous cellular composition determines its complex and multifaceted role in the course of physiological pregnancy, indicates the importance of studying this organ in a number of reproductive pathologies. The purpose of this review was to analyze the literature sources illustrating the importance of energydependent processes in placental metabolism and to determine the molecular basis of placental energy conversion. Publications of foreign and Russian authors from PubMed database and scientific electronic library eLIBRARY.ru were used when writing the review. The review highlights the main functions of the placenta: transport and synthetic functions in terms of their place in the structure of energy expenditure of the organ. The systems by which the transport of ions and gases from maternal blood through the placental barrier is performed, are considered. The role of the placenta in the synthesis of steroid hormones and glucocorticoids is detailed. The main bioenergetic systems are also considered: placental glucose metabolism, the functional activity of mitochondria and the creatine kinase system of the placenta. These data allow us to put the placenta on a par with other organs with high energy requirements (brain, transverse striated skeletal muscles, heart, kidneys, liver), which are most susceptible to metabolic disorders. Maintaining a balance between expenditure and synthesis of macroergic compounds in the placenta is critical for an adequate course of physiological pregnancy, and imbalances can lead to such pathologies as fetal retardation syndrome or preeclampsia. Further study of placental energy supply systems seems important for understanding the mechanisms of intrauterine development disorders and developing their pathogenetic treatment.

Underestimated reactions and regulation patterns of adrenal cytochromes P450

Although cytochrome P450 (CYP) systems including the adrenal ones are being investigated since many years, there are still reactions and regulation patterns that have been underestimated ever since. This review discusses neglected ones to bring them into the focus of investigators working in the field. Novel substrates and reactions described for adrenal CYPs recently point to the fact that different from what has been believed for many years, adrenal CYPs are less selective than previously thought. The conversion of steroid sulfates, intermediates of steroid biosynthesis as well as of exogenous compounds are being discussed here in more detail and consequences for further studies are drawn. Furthermore, it was shown that protein-protein interactions may have an important effect not only on the activity of adrenal CYPs, but also on the product pattern of the reactions. It was found that, as expected, the stoichiometry of CYP:redox partner plays an important role for tuning the activity. In addition, competition between different CYPs for the redox partner and for electrons and possible alterations by mutants in the efficiency of electron transfer play an important role for the activity and product pattern. Moreover, the influence of phosphorylation and small charged molecules like natural polyamines on the activity of adrenal systems has been demonstrated in-vitro indicating a possible regulation of adrenal CYP reactions by affecting redox partner recognition and binding affinity. Finally, an effect of the genetic background on the consequences of mutations in adrenal CYPs found in patients was suggested from corresponding in-vitro studies indicating that a different genetic background might be able to significantly affect the activity of a CYP mutant.

Expression and regulation of cholesterol sulfotransferase (SULT2B1b) in human endometrium

OBJECTIVE

To investigate the hormonal regulation of SULT2B1b in human endometrium.

DESIGN

In vitro study with human endometrial tissues and cultured human endometrial cells.

SETTING

University hospital.

PATIENT(S)

Thirty-seven women undergoing hysterectomy for benign disease.

INTERVENTION(S)

Human endometrial tissues were collected for in situ hybridization. Culture medium of human endometrial epithelial cells (EECs) was collected for determination of secretion of cholesterol sulfate (CS). Total RNAs were extracted from human endometrial tissues and cultured cells for real-time reverse transcriptase-polymerase chain reaction (RT-PCR).

MAIN OUTCOME MEASURE(S)

The expression of SULT2B1b mRNA in human endometrial tissues and cultured cells.

RESULT(S)

In situ hybridization studies and real-time RT-PCR showed that the amount of SULT2B1b mRNA in human endometrial tissues was significantly higher during the midluteal phase than during other phases of the menstrual cycle. The secretion of CS from EECs was confirmed using [(35)S]-phosphoadenosine phosphosulfate. The expression of SULT2B1b mRNA was induced by cAMP or P in human endometrial stromal cells (ESCs), whereas it was induced by cAMP or relaxin in EECs. The induction of SULT2B1b mRNA by P or relaxin was abolished by the specific protein kinase A (PKA) inhibitor, Rp-adenosine 3',5' cyclic monophosphothioate (Rp-cAMPS).

CONCLUSION(S)

The expression of SULT2B1b mRNA in ESCs is induced by P and that in EECs is induced by relaxin via the cAMP pathway.

Inhibitory effects of cholesterol sulfate on progesterone production in human granulosa-like tumor cell line, KGN

Cholesterol sulfate (CS) is a component of cell membranes that plays a role in stabilizing the cell membrane. We previously reported that CS increased in the endometrium during implantation, suggesting that CS plays an important role in reproduction. It has been reported that CS regulates progesterone and pregnenolone production in the placenta, adrenal glands and ovary. The regulatory mechanisms of steroid hormone production by CS, however, are still unknown. In the present study, we investigated the effect of CS on the expression of progesterone production-related genes in KGN cells, derived from human granulosa-like tumor. KGN cells were cultured with CS (10 muM) or cholesterol (10 muM) in the presence of 8-bromo-cAMP (1 mM). Progesterone levels in the culture media were measured by enzyme linked fluorescent assay at 24 h after treatment of CS and cAMP. Total RNAs were extracted for quantitative real time RT-PCR with specific primer of StAR protein, P450scc, HSD3B2, ferredoxin and ferredoxin reductase. Whole cell lysates were extracted for western blot analysis with antibody for StAR protein. Progesterone concentration in the culture medium increased to 38-fold by treatment of cAMP. CS significantly reduced progesterone concentration by 30% compared with those of cAMP treatment (p<0.05), while cholesterol did not change the progesterone concentration. CS treatment down-regulated the expression of StAR mRNA and P450scc mRNA was to 54% and 60%, respectively (p<0.05). Western blot analysis revealed that the amount of StAR protein was also reduced by CS treatment. The expression of HSD3B2 mRNA was up-regulated to 3.4-fold by treatment of cAMP. The expression of ferredoxin and ferredoxin reductase mRNA was not affected by CS treatment. These data implied that CS has an inhibitory effect on progesterone production by regulating the expression of StAR and P450scc gene expression.

Endocrine cell lines from the placenta

Cell-lines derived from human placenta and chorion have been used extensively to model the endocrine functions of human trophoblast. In general terms, the endocrine functions of the primary cells and tissues are at least partially replicated within the cell-lines, suggesting that they may be used as appropriate models. There are, however, two major provisos that compromise this generalisation. Firstly, the endocrine function of placenta represents a complex interaction between cytotrophoblast, syncytiotrophoblast and multiple regulators, so a single cell population digested from the normal environment is unlikely to represent this. Secondly, the characterisation of primary trophoblast populations and of cell-lines is incomplete, complicating the assignment of functions to trophoblast populations. Despite these difficulties, useful information has been obtained from the available cell-lines, regardless of whether they have arisen spontaneously, been transformed in vitro, or derived from cancers in vivo.