Role of steroidogenic acute regulatory protein in adrenal and gonadal steroidogenesis

Congenital lipoid adrenal hyperplasia is an autosomal recessive disorder that is characterized by impaired synthesis of all adrenal and gonadal steroid hormones. In three unrelated individuals with this disorder, steroidogenic acute regulatory protein, which enhances the mitochondrial conversion of cholesterol into pregnenolone, was mutated and nonfunctional, providing genetic evidence that this protein is indispensable normal adrenal and gonadal steroidogenesis.

The role of endozepine in the regulation of steroid synthesis

Endozepine has recently been isolated from various steroid-forming organs. The following article explores the role of endozepine in the regulation of steroid synthesis. Steroid hormone synthesis from cholesterol begins in the inner mitochondrial membrane, where cytochrome P450 converts cholesterol to pregnenolone. Scientists thought that ACTH would stimulate this conversion, but experiments showed no such stimulation. However, addition of aminoglutethimide to block side-chain cleavage caused the expected reaction of ACTH to take place. Next the role of protein synthesis on the actions of ACTH was explored. Then endozepine was isolated from bovine fasciculata based on stimulation of pregnenolone production by freshly prepared mitochondria. After further experimentation it was concluded that endozepine is a peptide with at least two groups of actions: It binds GABAA receptors in the central nervous system, and it increases the mitochondrial synthesis of pregnenolone.

Post-transcriptional regulation of the stanniocalcin gene by calcium

Stanniocalcin (STC) is a Ca(2+)-regulating hormone produced by the corpuscles of Stannius in bony fish. Calcium has been shown to stimulate STC synthesis at multiple levels including the level of gene expression. The purpose of this study was to determine the effects of Ca2+ on STC mRNA stability. The half-life of STC mRNA was measured in primary cultured trout corpuscles of Stannius cells maintained in either normal (1.2 mM) or high (1.9 mM) levels of extracellular calcium and treated with the transcriptional inhibitor alpha-amanitin. In cells maintained in 1.2 mM Ca2+, STC mRNA levels decreased progressively over time with an estimated half-life of approximately 71 h. However, message levels remained unchanged for up to 4 days in cells maintained in 1.9 mM Ca2+, indicating that the transcript had been stabilized in response to Ca2+ stimulation. Blocking transcription prior to exposing cells to high Ca2+ did not alter the stabilizing effects of the cation, indicating that synthesis and processing of the mRNA transcript were not involved in message stabilization. Inhibiting protein synthesis with cycloheximide also had no influence on the stabilizing effects of high calcium. The experiments involving cycloheximide further suggested that the mechanism of mRNA stabilization involved protein-nucleic acid interactions in the cytoplasm, whereby the polysomal complex protected the mRNA from degradation. These data demonstrate that the stimulatory effect of Ca2+ on STC gene expression is due, in part, to mRNA stabilization.

Proteases and the emerging role of protease inhibitors in prohormone processing

Peptide hormones and neurotransmitters constitute a large class of neurohumoral agents that mediate cell-cell communication in neuroendocrine systems. Their biosynthesis requires proteolytic processing of inactive protein precursors into active neuropeptides. Elucidation of the proteolytic components required for prohormone processing is important for identifying key proteases that may control the production of neuropeptides. This article compares the subtilisin-like PC1/3 and PC2 processing enzymes identified through molecular biological approaches, and several candidate processing enzymes identified biochemically, including the 'proopiomelanocortin converting enzyme' (PCE) and the 'prohormone thiol protease' (PTP), as well as others of different classes (aspartyl, cysteine, metallo, and serine proteases). A role for PTP in cellular proenkephalin processing is suggested by blockade of forskolin-stimulated (Met)enkephalin production by Ep453 that is converted intracellularly to E-64c, a selective cysteine protease inhibitor that potently inhibits PTP. A possible role for endogenous protease inhibitors in prohormone processing represents a new aspect of cellular mechanisms that may regulate neuropeptide biosynthesis. Future studies of the enzymology and molecular biology of processing enzymes and endogenous protease inhibitors will be necessary to elucidate mechanisms of prohormone processing.

No mutation in cytochrome P450 side chain cleavage in a patient with congenital lipoid adrenal hyperplasia

Molecular basis of lipoid adrenal hyperplasia (lipoid CAH) in a Japanese patient was investigated. A 46XY Japanese female patient was clinically diagnosed as having lipoid CAH based on her clinical history of adrenal crisis at birth and the low basal concentrations of cortisol, aldosterone, adrenal androgens and testosterone in serum. In vitro studies of testicular mitochondrial enzymes confirmed a specific impairment of cholesterol side chain cleavage (SCC) activity. However, in spite of the virtual reduction of SCC activity, the amounts of immunodetectable P450scc, adrenodoxin reductase, and adrenodoxin in testicular mitochondria were almost same as those of normal testis. Furthermore, the size of each protein was similar to that of normal testis. Enzymatic amplification of the complementary DNA encoding P450scc from the patient's testis RNA and its nucleotide analysis by direct sequencing revealed no mutation. These results indicate that defective P450scc is not the lesion in this patient, confirming a previous report showing no P450scc mutations in patients with lipoid CAH. The exact lesion causing lipoid CAH in this patient is currently unknown.

A human cDNA coding for the Leydig insulin-like peptide (Ley I-L)

cDNA clones for the human Leydig insulin-like peptide (Ley I-L) have been isolated and characterized. The nucleotide sequence of the 743-bp cDNA includes an incomplete 7-bp 5'-noncoding region, an open reading frame of 393 bp, and a 343-bp 3'-noncoding region. By primer extension analysis, the transcription start site was determined as being 14-bp upstream of the translation start site. The underlying gene is expressed in the testis but not in other organs. From the cDNA sequence, it can be deduced that the Ley I-L protein is synthesized as a 131-amino-acid (aa) preproprotein and that it contains a 24-aa signal peptide. Comparison of the pro Ley I-L protein with members of the insulin-like hormone superfamily predicts that the biologically active hormone, after proteolytic processing of the C peptide, consists of a 31-aa long B chain and a 26-aa long A chain, and that it has a molecular weight of 6.25 kDa.

Neuroendocrinoimmunology

Interest in neuroendocrinoimmunology has increased greatly in the last decade. The most important evidence of neuroendocrine-immune system interactions is that spleen, thymus, bone marrow and lymph nodes are innervated by neurons of the autonomic nervous system; changes in brain functions can affect different immune responses; immune and neuroendocrine cells share receptors (e.g., lymphocytes and macrophages have receptors for a vast number of hormones and neuropeptides); hormones and neuropeptides can alter the functional activity of immune system cells; several hormones and neuropeptides can be synthesized by leukocytes; cytokines produced by leukocytes are able to modulate neuroendocrine system activity, behaviour, sleep and thermoregulation. The recent literature on neuroendocrinoimmunology has laid the physiopathological groundwork for a new clinical approach which perceives and treats the patient as a psychic and somatic whole.

[Synthesis, function, and evolutionary origin of secondary metabolites produced by micro-organisms]

The microbial secondary metabolites are compounds with a wide range of chemical structures, produced mainly by actinomycetales and some fungi, usually in the late growth phase. Although a high proportion of this metabolites are antibiotics, there are also examples with pigment, herbicide and surfactant properties. Its function has been correlated to bacterial pathogenicity and cellular differentiation, however, properties dealing with chelation, hormonal and antitumor activities as well as nutritional reserve have been also reported. As in other examples of cellular compounds, the secondary metabolites are produced from low molecular weight precursors. For this purpose, specific biosynthetic pathways are utilized and regulated by processes which generally affect either the activity or the synthesis of the enzymes involved in it. Considering the secondary metabolites apparently are dispensable compounds, there are difficulties to explain their existence from an evolutionary point of view. Explanations to their existence have gone from laboratory artifacts to those conferring them an adaptative value in the past. It seems that they were maintained due to selective advantages to the producer microorganisms and probably, their sometimes complex biosynthetic pathways, have emerged from primary metabolites and evolved later independently by random mutation, amplification and genetic transfer.

The endocrinology of parturition in the mare

The endocrinology of late gestation and parturition in the mare has been described, but unlike other domestic animal species, the factors that initiate parturition in the mare have not been elucidated. In contrast to ruminant species, maternal estrogen and progesterone concentrations do not change markedly, and a well-defined fetal cortisol surge is not observed just prior to parturition in the mare. Parturition is associated with large increases in prostaglandin and oxytocin concentrations, which induce uterine contractions and delivery of the foal. There are many methods of inducing parturition in term mares, but the most popular and safest method is through the administration of low-dose oxytocin.

Hyperandrogenism in polycystic ovary syndrome. Evidence of dysregulation of 11 beta-hydroxysteroid dehydrogenase

BACKGROUND

Hyperandrogenemia is the hallmark of the polycystic ovary syndrome, yet the relative contributions of the adrenal cortex and ovary to the overproduction of androgen remain unclear. To identify possible causes of adrenocortical overactivity, we studied the metabolism of adrenal and ovarian steroid hormones in women with this disorder.

METHODS

We measured 24-hour urinary excretion of steroid hormone metabolites by high-resolution capillary gas chromatography in 65 women with the polycystic ovary syndrome and 45 normal women matched for body-mass index.

RESULTS

After adjustment for body-mass index, the urinary excretion of testosterone and androstenedione metabolites was 1.9 times higher in the women with the syndrome than in the normal women, and the excretion of dehydroepiandosterone metabolites (C19 steroid sulfates) and cortisol metabolites was 1.5 and 1.3 times higher, respectively (P < 0.01 for all comparisons). The affected women also had significantly higher ratios of 11-oxo (oxygenated) metabolites to 11-hydroxy metabolites of cortisol (1.4 times higher, P < 0.001) and of 11-oxo to 11-hydroxy metabolites of corticosterone (1.8 times higher, P < 0.001). In the group with the polycystic ovary syndrome, 55 percent of the nonobese women and 24 percent of the obese women had ratios above the upper limit of normal; the ratios in the obese women did not differ significantly from those in the nonobese women.

CONCLUSIONS

Adrenal secretion of cortisol and androgens is increased in women with the polycystic ovary syndrome. The increases may be explained by dysregulation of 11 beta-hydroxysteroid dehydrogenase causing increased oxidation of cortisol to cortisone, which cannot be accounted for by obesity.

Hepatocyte growth factor/scatter factor is an autocrine factor for human normal bronchial epithelial and lung carcinoma cells

Hepatocyte growth factor (HGF) or scatter factor (SF) has been considered primarily as an endocrine/paracrine factor. We report here that HGF/SF mRNA was expressed by cultured human normal bronchial epithelial cells and many non-small cell lung carcinoma cell lines. Scatter activity was detected in the culture media of these cells, and this activity was inhibited by a neutralizing anti-recombinant human HGF antiserum. Immunostaining confirmed the presence of immunoreactive human HGF-like protein in the cytoplasm of these cultured cells, and in ciliated columnar epithelium of normal human bronchus/bronchioles. The met/HGF/SF receptor of these cultured cells was constitutively phosphorylated on tyrosine residues. A neutralizing anti-recombinant human HGF antiserum decreased the phosphorylation of the receptor, inhibited the proliferation of 45% of the non-small cell lung carcinoma cell lines studied, and stimulated the proliferation of normal bronchial epithelial cells. Altogether, the data demonstrate that HGF/SF and/or HGF-like protein is an autocrine factor for normal and neoplastic human bronchial epithelial cells in culture.

Steroid synthesis by equine conceptuses between days 7 and 14 and endometrial steroid metabolism

The objective of this study was to determine if changes in steroid synthesis occurred in the horse blastocyst about the time of maternal recognition of pregnancy. Embryos collected between days 7.5 and 14.5 were incubated for 8 hr in vitro in HAM's F10 containing radiolabelled pregnenolone. The steroid metabolites in the incubation medium were separated by reverse phase HPLC and the major peaks expressed as a percentage of total metabolites. It was found that there were no major changes in the profile of metabolites throughout the period of study, although there was increased conversion as the conceptuses developed. It was found that the major metabolite produced was 17 alpha-hydroxyprogesterone and not estradiol as expected. A second experiment was conducted to determine if 17 alpha-hydroxyprogesterone was metabolized by endometrial tissue. Endometrial biopsies from anestrous mares and from pregnant and nonpregnant mares at day 11 were incubated with radiolabelled 17 alpha-hydroxyprogesterone, progesterone or pregnenolone. The 17 alpha-hydroxyprogesterone, but not progesterone nor pregnenolone, was converted to a more polar metabolite in all groups. Production of this metabolite was significant greater in the anestrous mares. This metabolite has not been unidentified conclusively. Thus, results of this study show that 17 alpha-hydroxyprogesterone is the major steroid synthesized by the equine blastocyst and that this steroid is further metabolized to an unidentified steroid by the endometrium. These steroids could play a role in conceptus development or maternal recognition of pregnancy.

Steroid production in different parts of malignant and benign ovarian tumors in vitro

Pieces of ovaries and tumors from 45 patients (19 with malignant epithelial tumors, 14 with benign epithelial tumors, and 12 with normal postmenopausal ovaries) were incubated, and the release of steroid hormones from different parts of the tumors and from the contralateral ovaries was measured. Tumor tissue (mainly tumor cells with a small number of stromal cells), tumor base tissue (more stromal cells than tumor cells), and control ovaries were preincubated in oxygenated 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid-minimum essential medium buffer at 37 degrees C for 30 min followed by a 3-h incubation in fresh, oxygenated medium. Progesterone, androstenedione, testosterone, and estradiol were measured in the medium by radioimmunoassay at the end of the incubation period. Malignant tumors released more progesterone and androstenedione than benign tumors or postmenopausal control ovaries. In contrast, benign tumors released more testosterone than malignant tumors or control ovaries. Release of estradiol was low and not significantly different among control ovaries and malignant and benign tumor tissue. Different parts of the tumors differed in steroid hormone release. Tissue samples containing more tumor cells than stromal cells released more progesterone than those with predominantly stromal cells. Thus, malignant tumors had an active steroid secretion. Progesterone was the main steroid released.

Steroid biosynthetic enzymes: 17 beta-hydroxysteroid dehydrogenase

Polyclonal antibodies produced against human placental 17 beta-hydroxysteroid dehydrogenase (17HSD), purified to homogeneity, and the corresponding cDNA for the enzyme were used to study the expression of 17HSD in a number of human tissues using various immunological methods together with RNA hybridization techniques. In addition, two 17HSD genes and their putative regulatory elements were sequenced. Immunoblotting analysis showed that the placental-type enzyme is expressed in granulosa-luteal cells, breast cancer tissue and breast cancer cell lines. An immunologically identical antigen was also detected in normal and carcinomatous human endometrium. The same antiserum, following affinity purification, was used for immunohistochemical studies of the endometrium and breast tissue, whereupon staining of the cytoplasm of the epithelial cells alone was observed. Immunostaining was also present in cultured human granulosa cells and in about half of the endometrial and breast carcinoma specimens investigated. Progesterone induction of the 17HSD enzyme protein was demonstrated in the human endometrium during the secretory phase of the menstrual cycle and in one breast cancer cell line (T-47D) following progestin treatment. There are at least two mRNAs for placental 17HSD (1.3 kb, 2.3 kb). RNA hybridization analysis of various breast cancer cell lines showed that the 1.3 kb mRNA was most closely associated with enzyme protein expression and was also the only form responding to progesterone induction. We conclude that placental-type 17HSD is also expressed in some other human tissues, both steroid-synthesizing and steroid-responding, and that the mRNA and enzyme protein are induced by progesterone. The availability of the sequence of 17HSD genes and surrounding regions allows us to study the sequences responsible for the expression and regulation of 17HSD.

In situ detection and distribution of stanniocalcin mRNA in the corpuscles of Stannius of sockeye salmon, Oncorhynchus nerka

Stanniocalcin (STC) gene expression was examined in the corpuscles of Stannius of sockeye salmon by in situ hybridization. Generally, the STC gene was not expressed uniformly in all cells of the corpuscles of Stannius. However, in cases where gene expression was uniform throughout a gland, it appeared that virtually all cells contained STC mRNA, thereby supporting the 'one cell type' hypothesis for the corpuscles of Stannius. Correlative immunocytochemistry on adjacent tissue sections indicated that cellular levels of stored hormone paralleled the distribution of STC mRNA. Stanniocalcin mRNA was undetectable in numerous other salmon tissues, thereby further supporting the notion that the STC gene is expressed exclusively in the corpuscles of Stannius.

Acute adrenocorticotropin stimulation of postmenopausal cigarette smokers and nonsmokers: effects on steroidogenesis

Cigarette smoking has been associated with elevated levels of A and DHEAS in postmenopausal women. One possible mechanism postulated for this effect is enzymatic blockage by components of cigarette smoke. In this study, acute ACTH stimulation of postmenopausal cigarette smokers did not result in abnormal elevations of precursor steroids. Other possible mechanisms may be operative in vivo to account for the previously reported findings.

Peptide hormone processing in tumours: biogenetic and diagnostic implications

Insight into the biogenesis of peptide hormones has grown explosively by elucidation of gene, mRNA and prohormone structures. In addition, information about prohormone processing enzymes is rapidly accumulating. Prohormones vary in size and organization from poly- to monoprotein structures. According to their structural organization and sequence homology, hormones are grouped in families. Prohormones are processed to bioactive peptides by multiple modifications during the transport from the endoplasmic reticulum to secretory granules. The modifications comprise different proteolytic cleavages and amino acid derivatizations. By constitutive secretion, the processing is less pronounced. The same prohormone may be expressed in several cell types that process the precursor in different ways. Awareness of cell-specific processing patterns is important for understanding the tumour synthesis of peptides and for appropriate diagnosis of peptide-producing tumours. These tumours comprise not only well-known neuroendocrine neoplasias. An increasing number of common carcinomas also expresses peptide hormone genes. However, the translation and post-translational processing in tumours are generally attenuated. Consequently, the expression is often functionally and clinically silent. A new diagnostic tool, processing-independent analysis (PIA), seems promising in quantitation of hormone gene expression at peptide level irrespective of the degree of processing. Studies of progastrin expression and processing in tumours illustrate the diagnostic superiority of PIA.

Chronic somatostatin analog administration in patients with alpha-subunit-secreting pituitary tumors

Glycoprotein hormone-producing (GPH) pituitary adenomas represent approximately 25% of all pituitary tumors. Elevated serum levels of intact GPHs or their free alpha- and beta-subunits have been demonstrated in patients with such tumors, and isolated hypersecretion of alpha-subunit has been reported to occur in 7% of patients. Somatostatin has been shown to decrease GPH subunit levels in cultured adenoma cells in vitro, and somatostatin receptors have been identified on the cell membranes of these tumors. We, therefore, investigated the effect of chronic somatostatin analog administration on hormone production and tumor size in six patients with GPH-producing macroadenomas and elevated serum alpha-subunit levels. Patients initially received native somatostatin as an iv 250-micrograms bolus at 0800 h, followed by a constant infusion of 2 mg over 4 h, and serum alpha-subunit concentrations were measured at 30-min intervals after baseline sampling for a total of 9 h. Patients then received a somatostatin analog, octreotide (100 micrograms, twice daily, sc) for 8 weeks. Serum alpha-subunit levels were determined weekly at 30-min intervals before and for 4 h after the 0800 h octreotide dose. Pituitary magnetic resonance imaging scans and visual field testing were assessed before and after the study. During the 4-h somatostatin infusion, four patients had a significant decrease in alpha-subunit levels (P < 0.05). During the 8-week chronic octreotide administration period, two patients had significant decreases in alpha-subunit levels of 34.6% and 26.7% (P = 0.03 and 0.01, respectively). One of these two patients had a small reduction in tumor size. Two patients whose serum alpha-subunit level did not significantly change while receiving octreotide had a reduction in tumor size or definite improvement in visual field abnormalities. Three patients received a maximum octreotide dose of 250 micrograms, three times daily. In one patient, there was a significant decrease in alpha-subunit levels by 45% (P = 0.0001) in association with a marked improvement in visual field abnormalities. In another such patient, continued administration of octreotide to a maximum dose of 250 micrograms, three times daily, was associated with a marked reduction in tumor size. Of the four patients who demonstrated significant decreases in alpha-subunit concentrations during the initial somatostatin infusion, three patients had a significant reduction in alpha-subunit levels while receiving octreotide. One patient who did not have a decrease in alpha-subunit levels during the somatostatin infusion demonstrated a small decrease in tumor size during higher dose octreotide treatment.(ABSTRACT TRUNCATED AT 400 WORDS)