17 beta-Hydroxysteroid dehydrogenase type 2 expression and enzyme activity in the human gastrointestinal tract.

The 17 beta-hydroxysteroid dehydrogenases (17 beta HSDs) play an important role in the regulation of intracellular levels of biologically active sex steroid hormones in various human tissues. To date, eight distinctive 17 beta HSD enzymes have been cloned and characterized in humans. Among these isoenzymes, 17 beta HSD type 2 (17 beta HSD2) catalyses the conversion of testosterone into androstenedione and/or oestradiol into oestrone in various tissues, and it has thus been suggested to be involved in the biological inactivation of these sex steroids. The human gastrointestinal tract and liver are considered as the principle sites of inactivation and metabolism of various forms of orally administered sex steroids. We therefore examined 17 beta HSD2 expression and activity in human adult non-pathological gastrointestinal tract in order to clarify further the biological significance of this enzyme. A total of 80 specimens (40 from males and 40 from females) of normal oesophageal, stomach, duodenal, ileal, colonic and rectal tissues were examined for immunohistochemistry. Altogether, 17 tissue specimens were used for enzyme assay, and eight for RNA analysis. 17 beta HSD2 activity was detected in the stomach, duodenum, ileum, colon and rectum. 17 beta HSD2 mRNA was most abundant in the small intestine. 17 beta HSD2 immunoreactivity was localized almost exclusively to the absorptive epithelium, which may be involved in the inactivation of excessive endogenous and exogenous active sex steroids. Results from the present study thus suggest that the human gastrointestinal tract is an important sex steroid metabolizing organ in humans.

Bone phenotype of the aromatase deficient mouse.

Estrogens are important for normal bone growth and metabolism. The mechanisms are incompletely understood. Thus, we have undertaken characterization of the skeletal phenotype of aromatase (ArKO) deficient mice. No abnormalities have been noted in skeletal patterning in newborns. Adult ArKO mice show decreased femur length and decreased peak Bone Mineral Density (BMD) with accelerated bone loss by 7 months of age in females. Magnetic resonance microscopy (MR) and microCT (microCT) imaging disclosed decreased cancellous connectivity and reduced cancellous bone volume in ArKO females. Bone formation rate (BFR) is increased in ArKO females and decreased in ArKO males. Estradiol therapy reverses these changes. This anabolic effect of estradiol in the male skeleton is supported by 18-F- Positron Emission Tomography (PET) imaging, which clearly demonstrates decreased spinal uptake, but marked increase after estradiol therapy. Serum IGF-1 levels are high in young female ArKO mice but low in young ArKO males. The reduced BMD in ArKO females, despite the presence of elevated serum IGF 1, suggests that other mechanism(s) are operative. There is increased B-cell lymphopoiesis in adult female ArKO bone marrow cells. These results show that ArKO mice show the effects of estrogen deficiency on bone growth, mass, metabolism, microarchitecture and the hematopoietic microenvironment.

11Beta-hydroxysteroid dehydrogenase type II and mineralocorticoid receptor in human placenta.

In mineralocorticoid target organs, 11beta-hydroxysteroid dehydrogenase type II (11beta-HSD2) confers specificity on the mineralocorticoid receptor (MR) by converting biologically active glucocorticoids to inactive metabolites. Placental 11beta-HSD2 is also thought to protect the fetus from high levels of circulating maternal glucocorticoid. In this study, we examined the immunoreactivity of 11beta-HSD2 and MR in human placenta from 5 weeks gestation to full term using immunohistochemistry, 11beta-HSD2 messenger RNA (mRNA) expression using Northern blot analysis, and MR mRNA expression using RT-PCR analysis. Marked 11beta-HSD2 immunoreactivity was detected in placental syncytiotrophoblasts at all gestational stages. MR immunoreactivity was moderately detected in syncytiotrophoblasts, some cytotrophoblasts, and interstitial cells of the villous core. Marked mRNA expression of 11beta-HSD2 was detected in placenta by Northern analysis. RT-PCR analysis of MR in placental tissues showed an amplified product consistent in length with the primers selected. These results suggest that placental 11beta-HSD2 is involved in not only regulating the passage of maternal active glucocorticoids into the fetal circulation but also in regulation of maternal-fetal electrolyte and water transport in the placenta, as in other mineralocorticoid target organs.

17beta-hydroxysteroid dehydrogenase type 1 and 2 expression in the human fetus.

The present study investigates the expression patterns of 17beta-hydroxysteroid dehydrogenase (17betaHSD) isozymes in human fetal tissues to understand how estrogenic activity is regulated in the human fetus. Using enzyme assay, high 17betaHSD activity was detected in the placenta and liver, and low levels of 17betaHSD activity were also present in the gastrointestinal tract and kidney. After Northern blot analysis, we detected the messenger ribonucleic acid for 17betaHSD type 1 (17betaHSD1) only in the placenta, whereas that for 17betaHSD type 2 (17betaHSD2) was detected in the placenta, liver, gastrointestinal tract, and urinary tract at 20 gestational weeks. In RT-PCR analysis of the messenger ribonucleic acid transcripts, 17betaHSD 1 was predominantly expressed in the placenta, brain, heart, lung, and adrenal, whereas 17betaHSD2 expression was predominantly detected in the liver, gastrointestinal tract, and kidney. In addition, we detected 17betaHSD2 immunoreactive protein in surface epithelial cells of the stomach, absorptive epithelial cells of the small intestine and colon, hepatocytes of the liver, and interstitial cells surrounding the urinary tubules of the renal medulla. 17betaHSD2 in these tissues may be functioning in the prevention of in utero exposure of the fetus to excessive estradiol from the maternal circulation and amniotic fluids.

Urocortin and corticotropin-releasing factor receptor expression in the human colonic mucosa.

Urocortin is a newly identified member of the CRF neuropeptide family. Urocortin has been found to bind with high affinity to CRF receptors. The present study investigated urocortin and CRF receptor expression in human colonic mucosa. Non-pathologic sections of adult colorectal tissues were obtained from patients with colorectal cancer at surgery. Urocortin expression was examined using immunohistochemistry and messenger (m) RNA in situ hybridization. Isolated lamina propria mononuclear cells (LPMC) and epithelial cells were also analyzed by flow cytometry for the characterization of urocortin-positive cells, and by RT-PCR for detection of urocortin, CRF, and CRF receptor mRNA. Urocortin peptide distribution at various stages of human development (n = 35, from 11 weeks of gestation to 6 years of age) was examined by immunohistochemistry using surgical and autopsy specimens. Immunoreactive urocortin and urocortin mRNA were predominantly detected in lamina propria macrophages. Urocortin peptide expression was detected from as early as three months of age, but not before birth or in neonates. Urocortin, CRF receptor type 1 and type 2 alpha mRNA were detected in LPMC. CRF receptor type 2 beta mRNA, a minor isoform in human tissues, was also detected in LPMC, but at lower levels. Urocortin is locally synthesized in lamina propria macrophages and may act on lamina propria inflammatory cells as an autocrine/paracrine regulator of the mucosal immune system. The appearance of urocortin after birth indicates that the exposure to dietary intake and/or luminal bacteria after birth may contribute to the initiation of urocortin expression in human gastrointestinal tract mucosa.

11Beta-hydroxysteroid dehydrogenase type 2 and mineralocorticoid receptor in human fetal development.

11Beta-Hydroxysteroid dehydrogenase type II (11betaHSD2) confers specificity on the mineralocorticoid receptor (MR) by converting biologically active glucocorticoids to inactive 11-keto metabolites. The biological significance of 11betaHSD2 activity during fetal development is currently being explored, but the temporal and spatial distributions of the enzyme and receptor have not been examined. We therefore examined their distributions during various stages of human fetal development using immunohistochemistry. Both 11betaHSD2 and MR immunoreactivity were detected in the distal convoluted and collecting tubules of the kidney from early in gestation. Fetal skin, intermediate layer of the epidermis, peridermal cells, and hair follicles were positive for both 11betaHSD2 and MR. Weak 11betaHSD2 and MR immunoreactivity was detected in the superficial ciliated epithelium of the esophagus, the deep layer of gastric epithelial cells, and the superficial epithelium of the small intestine. Columnar epithelium in the terminal bronchiolar budding component of fetal lung and tracheal and bronchial ciliated epithelium were also positive for MR and 11betaHSD2 from early gestation. Colonic epithelium and pancreatic exocrine duct cells, which demonstrated marked immunoreactivity of both MR and 11betaHSD2 in the adult, did not express MR and 11betaHSD2 until very late in gestation. These results imply that mineralocorticoid action in the upper fetal gastrointestinal tract, kidney, skin, and lung is facilitated by 11betaHSD2 and is involved in water and electrolyte transport between fetus and amniotic fluid as well as fetal urine production.

11 beta-hydroxysteroid dehydrogenase type II in human colon: a new marker of fetal development and differentiation in neoplasms.

The colon plays an important role in water and electrolyte homeostasis and is a major target tissue for aldosterone. 11 beta-Hydroxysteroid dehydrogenase type II enzyme (11 beta HSD2) confers specificity to the non-selective mineralocorticoid receptor by inactivating glucocorticoids, thus allowing binding by mineralocorticoids. Using immunohisto/cytochemistry and Northern blot analysis, we examined 11 beta-HSD2 expression in human fetal colon (23 cases ranging in age from 15 to 40 weeks gestation), neonatal colon (2 cases, 6 and 12 months old), normal adult colon (15), adenoma (35), adenocarcinoma (34) and the human colonic epithelial cell line T84, in the presence or absence of sodium butyrate, to study the correlation between enzyme expression and cellular or neoplastic differentiation. In fetal colon, weak 11 beta-HSD2 immunoreactivity was detectable in superficial epithelium from 25 weeks gestation, but normal adult levels were apparent only after 40 weeks gestation, suggesting that fully developed aldosterone induced electrolyte transport can occur only at late gestational stages. In adult normal colon, superficial absorptive cells at the top of crypts were strongly positive for 11 beta-HSD2, whereas immunoreactivity was weak in adenomas and carcinomas, and the pattern of localization varied among patients. Northern blot analysis performed on 4 cases of adenocarcinoma also demonstrated lower levels of mRNA than autologous non-neoplastic colonic mucosa. In carcinomas, 11 beta-HSD2 immunoreactivity was more frequently detected in differentiated structures, such as those forming glandular or tubular structures. Studies with T84 cells showed that expression of 11 beta-HSD2 was markedly enhanced with the addition of sodium butyrate, a well known inducer of cell differentiation in colonic epithelia. These results suggest that the expression of 11 beta-HSD2 is associated with differentiation or maturation in human colonic epithelia and that the enzyme may serve as a useful marker in development and disease.

11Beta-hydroxysteroid dehydrogenase type 2 in human lung: possible regulator of mineralocorticoid action.

11Beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) catalyzes the conversion of cortisol to biologically inactive cortisone and is thought to confer specificity on mineralocorticoid receptors (MR). Cortisol is a prerequisite for surfactant synthesis and fetal lung maturation. Recently, expression of 11betaHSD2 was demonstrated in human fetal lung, but its localization and possible biological roles remain unknown. Therefore, in this study, we examined immunohistochemical localization of 11betaHSD2, MR, and glucocorticoid receptor (GR) in nonpathological human lungs from fetus to adult (8 weeks gestation to 55 yr of age; n = 40) retrieved from pathology files. Both 11betaHSD2 and MR immunoreactivities were detected in airway epithelia, from bronchiole to trachea and in fetal and neonatal ciliated collecting duct cells of tracheal and bronchial glands, but were undetectable in alveoli. On the other hand, GR was detected in all cell types. These results indicate that 11betaHSD2 colocalizes with MR in human airway epithelia and suggest that 11betaHSD2 play an important role in pulmonary mineralocorticoid activity such as sodium and fluid transport.

Colocalization of 11 beta-hydroxysteroid dehydrogenase type II and mineralocorticoid receptor in human epithelia.

The enzyme 11 beta-hydroxysteroid dehydrogenase type II (11 beta HSD2) has been shown to confer specificity on mineralocorticoid receptors (MR) by inactivating glucocorticoids. In the present study we examined the colocalization of 11 beta HSD2 and MR in various exocrine and secretory glands by immunostaining of serial mirror tissue sections with subsequent computerized image analysis. Both 11 beta HSD2 and MR proteins were expressed in the same cells in the distal convoluted tubules, Henle's loop, and collecting tubules of the kidney and the absorptive epithelia of duodenum, jejunum, ileum, colon, and excretory ducts of anal and esophageal glands. Significantly, 11 beta HSD2 and MR immunoreactivity also colocalized in the respiratory tract, in collecting ducts of the tracheal and bronchial glands, ciliated bronchial epithelial cells, and type II alveolar epithelial cells, suggesting important and unexpected roles for mineralocorticoids in the lung. In the skin, 11 beta HSD2 and MR were present only in excretory ducts of eccrine sweat glands, but not in sebaceous or apocrine glands. In eccrine glands, MR immunoreactivity was present in the basal cells of excretory ducts, while 11 beta HSD2 immunoreactivity was localized in the luminal cells. Neither 11 beta HSD2 nor MR proteins were expressed in the lacrimal gland, prostate, bile ducts, gall bladder, urinary bladder, urethra, or ureter. These results indicate that 11 beta HSD2 protein colocalizes with MR protein in the great majority of sodium-transporting epithelia involved in serous secretion and supports the proposal that 11 beta HSD2 is a pivotal determinant of mineralocorticoid receptor occupancy in man. Furthermore, our demonstration of colocalization in discrete areas of the lung suggests that mineralocorticoid agonists or antagonists, and/or inhibitors of 11 beta HSD2, may have unexpected applications in respiratory disease.