Role of CYP27A1 in progesterone metabolism in vitro and in vivo.

In the kidney, progesterone is inactivated to 20alpha-dihydro-progesterone (20alpha-DH-progesterone) to protect the mineralocorticoid receptor from progesterone excess. In an attempt to clone the enzyme with 20alpha-hydroxysteroid activity using expression cloning in CHOP cells and a human kidney expression library, serendipitously cDNA encoding CYP27A1 was isolated. Overexpression of CYP27A1 in CHOP cells decreased progesterone conversion to 20alpha-DH-progesterone in a dose-dependent manner, an effect enhanced by cotransfection with adrenodoxin and adrenodoxin reductase. Incubation of CHOP cells with 27-hydroxycholesterol, a product of CYP27A1, increased the ratio of progesterone to 20alpha-DH-progesterone in a concentration-dependent manner, indicating that the effect of CYP27A1 overexpression was mediated by 27-hydroxycholesterol. To analyze whether these observations are relevant in vivo, progesterone and 20alpha-DH-progesterone were measured by gas chromatography-mass spectometry in 24-h urine of CYP27A1 gene knockout (ko) mice and their control wild-type and heterozygote littermates. In CYP27A1 ko mice, urinary progesterone concentrations were decreased, 20alpha-DH-progesterone increased, and the progesterone-to-20alpha-DH-progesterone ratio decreased threefold (P < 0.001). Thus CYP27A1 modulates progesterone concentrations. The underlying mechanism is inhibition of 20alpha-hydroxysteroid dehydrogenase by 27-hydroxycholesterol.

Hexose-6-phosphate dehydrogenase and 11beta-hydroxysteroid dehydrogenase-1 tissue distribution in the rat.

Intracellular concentrations of the glucocorticoids cortisol and corticosterone are modulated by the enzymes 11beta-hydroxysteroid dehydrogenase (11beta-HSD) 1 and 2. 11beta-HSD1 is a reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent microsomal reductase that converts the inactive glucocorticoids cortisone and 11-dehydrocorticosterone to their active forms, cortisol and corticosterone. Hexose-6-phosphate dehydrogenase (H6PDH) is an enzyme that generates NADPH from oxidized NADP (NADP(+)) within the endoplasmic reticulum. In the absence of NADPH or H6PDH to regenerate NADPH, 11beta-HSD1 acts as a dehydrogenase and inactivates glucocorticoids, as does 11beta-HSD2. A monoclonal antibody against H6PDH was produced to study the possibility that 11beta-HSD1 in the absence of H6PDH may be responsible for hydroxysteroid dehydrogenase activity in tissues that do not express significant amounts of 11beta-HSD2. H6PDH and 11beta-HSD1 expression was surveyed in a variety of rat tissues by real-time RT-PCR, Western blot analysis, and immunohistochemistry. H6PDH was found in a wide variety of tissues, with the greatest concentrations in the liver, kidney, and Leydig cells. Although the brain as a whole did not express significant amounts of H6PDH, some neurons were clearly immunoreactive by immunohistochemistry. H6PDH was amply expressed in most tissues examined in which 11beta-HSD1 was also expressed, with the notable exception of the renal interstitial cells, in which dehydrogenase activity by 11beta-HSD1 probably moderates activation of the glucocorticoid receptor because rat renal interstitial cells do not have significant amounts of mineralocorticoid receptors. This antibody against the H6PDH should prove useful for further studies of enzyme activity requiring NADPH generation within the endoplasmic reticulum.

11-Beta hydroxysteroid dehydrogenase type 2 in human adult and fetal lung and its regulation by sex steroids.

11-Beta hydroxysteroid dehydrogenase type 2 (HSD2) oxidizes the biologically active glucocorticoid (GC), cortisol, to inactive cortisone. We characterized HSD2 gene expression and activity in human adult and fetal lung tissues and in cultured fetal lung explants, and examined the potential regulation of HSD2 in the fetal lung by sex steroids. Human adult lung, fetal lung, and cultured fetal lung explant tissues contained similar amounts of HSD2 mRNA. However, higher levels of HSD2 protein were detected in human fetal lung tissue than in adult lung, with expression being restricted to a subset of epithelial cells in the fetal lung tissue. Differentiated fetal lung explants maintained in culture expressed higher levels of HSD2 protein and enzymatic activity than undifferentiated fetal lung tissues. Finally, HSD2 protein levels were decreased in male, but not female, fetal lung explants treated with 17-beta estradiol. In contrast, 5-alpha dihydrotestosterone did not significantly affect HSD2 levels. These data indicate that HSD2 protein and activity levels increase in parallel with the differentiation of alveolar type II epithelial cells in vitro, and that HSD2 protein levels are regulated by 17-beta estradiol in male fetal lung tissue.

Altered activity of 11beta-hydroxysteroid dehydrogenase types 1 and 2 in skeletal muscle confers metabolic protection in subjects with type 2 diabetes.

CONTEXT: There is little information regarding the regulation of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes in skeletal muscle in the setting of type 2 diabetes. OBJECTIVE: Our objective was to investigate whether there is differential mRNA expression and enzyme activity of 11beta-HSD1 and 11beta-HSD2 in the skeletal muscle of diabetic subjects compared with controls at baseline and in response to dexamethasone. DESIGN: Participants underwent muscle biopsy of vastus lateralis at baseline and after dexamethasone. SETTING: The study took place at a university teaching hospital. PARTICIPANTS: Twelve subjects with type 2 diabetes and 12 age- and sex-matched controls participated. INTERVENTION: Subjects were given oral dexamethasone, 4 mg/d for 4 d. MAIN OUTCOME MEASURES: We assessed 11beta-HSD1, 11beta-HSD2, and H6PDH mRNA levels by quantitative RT-PCR and enzyme activity by percent conversion of [(3)H]cortisone and [(3)H]cortisol, respectively. RESULTS: At baseline, mRNA levels were similar in diabetic and control subjects for 11beta-HSD1, 11beta-HSD2, and H6PDH. 11beta-HSD1 activity was reduced in diabetic subjects (percent conversion of [(3)H]cortisone to [(3)H]cortisol was 11.4 +/- 2.5% vs. 18.5 +/- 2.2%; P = 0.041), and 11beta-HSD2 enzyme activity was higher in diabetic subjects (percent conversion of [(3)H]cortisone to [(3)H]cortisol was 17.2 +/- 2.6% vs. 9.2 +/- 1.3%; P = 0.012). After dexamethasone, 11beta-HSD1 mRNA increased in both groups (P < 0.001), whereas 11beta-HSD2 mRNA decreased (P = 0.002). 11beta-HSD1 activity increased in diabetic subjects (P = 0.021) but not in controls, whereas 11beta-HSD2 activity did not change in either group. At baseline, there was a significant negative correlation between 11beta-HSD1 and 11beta-HSD2 enzyme activity (r = -0.463; P = 0.026). CONCLUSIONS: The activities of skeletal muscle 11beta-HSD1 and 11beta-HSD2 are altered in diabetes, which together may reduce intracellular cortisol generation, potentially conferring metabolic protection.

Reduction of glucocorticoid receptor ligand binding by the 11-beta hydroxysteroid dehydrogenase type 2 inhibitor, Thiram.

Endogenous and synthetic glucocorticoids (GCs), such as cortisol and dexamethasone (Dex), modulate airway inflammation, regulate the production of surfactant by lung epithelial cells, and influence fetal lung maturation. The 11-beta hydroxysteroid dehydrogenase type 2 (HSD2) enzyme catalyzes the oxidation of bioactive cortisol and Dex to their 11-keto metabolites. Thiram (tetramethylthiuram disulfide) specifically inhibits HSD2 activity by oxidizing cysteine residues located in the cofactor binding domain of the enzyme. During studies performed to define a potential role for HSD2 in modulating GC action in human lung epithelial cells, we observed that exposure of intact human lung epithelial cells (NCI-H441) to 50 microM Thiram significantly attenuated the down-stream effects of Dex (100 nM) on the expression of two GC-sensitive genes, pulmonary surfactant proteins A and B. This observation appeared to be inconsistent with simple inhibition of HSD2 activity. Although Thiram inhibited HSD2 oxidase activity in a dose-dependent manner without affecting HSD2 protein expression, Thiram also reduced specific binding of [3H]-Dex to the glucocorticoid receptor (GR). Pre-treatment of cells with 1 mM dithiothreitol (DTT), a thiol-reducing agent, completely blocked the inhibitory effect of Thiram on ligand binding. These results are suggestive that Thiram may alter the ligand-binding domain of the GR by oxidizing critical thiol-containing amino acid residues. Taken collectively, these data demonstrate that attenuated down-stream GC signaling, via decreased binding of ligand to the GR, is a novel cellular effect of Thiram exposure in human lung epithelial cells.

Arginine vasopressin stimulates 11beta-hydroxysteroid dehydrogenase type 2 expression in the mineralocorticosteroid target cells.

11Beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) deficiency causes sodium retention and severe hypertension by allowing glucocorticoids access to the non-selective mineralocorticosteroid receptor. Understanding regulation of the HSD11B2 gene is thus of fundamental importance in hypertension research. A number of studies have suggested that second messenger pathways may be important in this regard. In the present study we show that HSD11B2 expression in human renal epithelial P58 cells is regulated at the mRNA and protein level, and that protein kinases A (PKA) and C (PKC) are involved in this process. PKA stimulation resulted in almost two-fold increase while PKC activation in almost two-fold decrease in the HSD11B2 mRNA and protein level. Western blot analysis revealed a dimeric form of 11beta-HSD2 of about 80kDa. Arginine vasopressin (AVP), acting through the AVP2 receptor, as well as 11beta-HSD2 substrates, corticosterone and dexamethasone, up-regulate HSD11B2 expression, suggesting their role as possible factors affecting blood pressure. We show that the activators of the PKA pathway induce, while activators of PKC pathway repress the expression of HSD11B2 in human renal epithelial cells. AVP, acting via the PKA pathway, might be a physiological stimulator of the HSD11B2 expression. The 11beta-HSD2 substrates, both natural (corticosterone) and synthetic (dexamethasone), might protect the mineralocorticosteroid-target cells against cortisol excess.

11Beta-hydroxysteroid dehydrogenase type 2 and the regulation of surfactant protein A by dexamethasone metabolites.

Glucocorticoid (GC) metabolism by the 11beta-hydroxysteroid dehydrogenase (HSD) system is an important prereceptor regulator of GC action. The HSD enzymes catalyze the interconversion of the endogenous, biologically active GC cortisol and its inactive 11-dehydro metabolite cortisone. The role of the HSD enzymes in the metabolism of synthetic GCs, such as dexamethasone (Dex), is more complex. The human lung is a classic GC-sensitive organ; however, the roles of the HSD enzymes (HSD1 and HSD2) in the human lung are poorly understood. In the present study, we examined the expression of the HSD enzymes in human adult and fetal lung tissues and the human lung epithelial cell line NCI-H441. We observed that human adult and fetal lung tissues, as well as H441 cells, express HSD2 protein and that it is upregulated by Dex (10(-7) M). By contrast, HSD1 protein was undetectable. We also show that the Dex-mediated regulation of surfactant protein A is attenuated by inhibition of HSD2 activity. Furthermore, we demonstrate that unlike the inactive, 11-dehydro metabolite of cortisol (i.e., cortisone), the 11-dehydro metabolite of Dex, 11-dehydro-Dex, competes for binding to the GC receptor (GR) in human lung epithelial cells and retains GR agonist activity. Together, these data suggest that differences exist in the biological activities of the metabolites of cortisol and Dex.

Inflammatory mediators down-regulate 11beta-hydroxysteroid dehydrogenase type 2 in a human lung epithelial cell line BEAS-2B and the rat lung.

In the lung, anti-inflammatory actions of glucocorticoids would be determined by 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), the microsomal enzyme responsible for the breakdown of bio-active glucocorticoids. However, regulation of 11beta-HSD2 under inflammatory conditions such as acute lung injury is not well understood. In the present study, we examined whether inflammatory substances would influence the activity and mRNA expression of 11beta-HSD2 in the lung. In a human bronchial epithelial cell line BEAS-2B, endotoxin inhibited 11beta-HSD2 enzyme activity in a dose-dependent manner over 48 h with a significant decrease in the mRNA expression. Likewise, tumor necrosis factor (TNF)-alpha inhibited both activity and mRNA expression of 11beta-HSD2. The TNF-alpha-dependent decrease in the enzyme activity was completely blocked by anti-TNF-alpha antibody, while antibody alone showed no significant influence on the enzyme activity. An nitric oxide donor (NO) sodium nitropusside or a cGMP analog 8-br-cGMP caused moderate but significant decreases in both activity and mRNA expression of 11beta-HSD2. Importantly, treatment of rats with endotoxin significantly decreased both activity and mRNA expression of 11beta-HSD2 in the lung tissue. We conclude that lung inflammation reduces local glucocorticoid breakdown and augments glucocorticoid action in the lung by down-regulating 11beta-HSD2 via multiple mechanisms.

Aldosterone enhances 11beta-hydroxysteroid dehydrogenase type 2 expression in colonic epithelial cells in vivo.

OBJECTIVE: [corrected] 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) metabolizes glucocorticoids, thus enabling aldosterone to bind to the mineralocorticoid receptor. However, little is known about the regulatory mechanism of epithelial 11beta-HSD2 expression in the gut. MATERIALS AND METHODS: Sprague-Dawley rats were maintained on a sodium-depleted diet or subjected to continuous aldosterone infusion for 4 weeks. Plasma aldosterone and arginine-vasopressin (AVP) levels were measured by radioimmunoassay. Expression of 11beta-HSD2 in colonic epithelia was evaluated by Northern blotting and immunohistochemistry. T84 and Caco2 cells were stimulated with aldosterone, dexamethasone and AVP alone or in combination, and 11beta-HSD2 mRNA was measured by quantitative reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Sodium-depleted and aldosterone-infused rats showed an increase of plasma aldosterone and AVP. Both treatments resulted in induction of 11beta-HSD2 in the colonic epithelia at mRNA and protein levels. Positive immunoreactivity was detected in the cytoplasm of the surface epithelia in control rats. In contrast, epithelial cells in the crypt also showed immunoreactivity for 11beta-HSD2 in the proximal colon of dietary sodium-depleted and aldosterone-infused rats. Induction of 11beta-HSD2 mRNA was observed when T84 cells were stimulated with corticosteroids plus AVP. CONCLUSIONS: Aldosterone has a pivotal role by increasing expression of 11beta-HSD2 in epithelial cells of the colon. AVP may act as a synergistic hormone in aldosterone-mediated 11beta-HSD2 induction.

Demethylation using the epigenetic modifier, 5-azacytidine, increases the efficiency of transient transfection of macrophages.

This study was aimed at developing a method for high-efficiency transient transfection of macrophages. Seven methods were evaluated for transient transfection of murine macrophage RAW 264.7 cells. The highest transfection efficiency was achieved with DEAE-dextran, although the proportion of cells expressing the reporter gene did not exceed 20%. It was subsequently found that the cytomegalovirus plasmid promoter in these cells becomes methylated. When cells were treated with the methylation inhibitor 5-azacytidine, methylation of the plasmid promoter was abolished and a dose-dependent stimulation of reporter gene expression was observed with expression achieved in more than 80% of cells. Treatment of cells with 5-azacytidine also caused increased efficiency of transfection of macrophages with plasmids driven by RSV, SV40, and EF-1alpha promoters and transient transfection of human HepG2 cells. Inhibition of methylation also increased the amount and activity of sterol 27-hydroxylase (CYP27A1) detected in RAW 264.7 cells transfected with a CYP27A1 expression plasmid. Treatment of cells with 5-azacytidine alone did not affect either cholesterol efflux from nontransfected cells or expression of ABCA1 and CYP27A1. However, transfection with CYP27A1 led to a 2- to 4-fold increase of cholesterol efflux. We conclude that treatment with 5-azacytidine can be used for high-efficiency transient transfection of macrophages.

Contribution of protein kinase A and protein kinase C signalling pathways to the regulation of HSD11B2 expression and proliferation of MCF-7 cells.

Contribution of the protein kinase A (PKA) and protein kinase C (PKC) signalling pathways to the regulation of 11beta-hydroxysteroid dehydrogenase type II (HSD11B2) gene expression was investigated in human breast cancer cell line MCF-7. Treatment of the cells with an adenylyl cyclase activator, forskolin, known to stimulate the PKA pathway, resulted in an increase in HSD11B2 mRNA content. Semi-quantitative RT-PCR revealed attenuation of the effect of forskolin by phorbol ester, tetradecanoyl phorbol acetate (TPA), an activator of the PKC pathway. It was also demonstrated that specific inhibitors significantly reduced the effect of activators of the two pathways. Stimulation of the PKA pathway did not affect, whereas stimulation of the PKC pathway significantly reduced MCF-7 cell proliferation in a time-dependent manner. A cell growth inhibitor, dexamethasone, at high concentrations, caused a 40% decrease in proliferation of MCF-7 cells and this effect was abolished under conditions of increased HSD11B2 expression. It was concluded that in MCF-7 cells, stimulation of the PKA signal transduction pathway results in the induction of HSD11B2 expression and that this effect is markedly reduced by activation of the PKC pathway. Activation of the PKC pathway also resulted in inhibition of cell proliferation, while activation of the PKA pathway abolished the antiproliferative effect of dexamethasone. These effects might be due to oxidation of dexamethasone by the PKA-inducible HSD11B2.

Aromatase-deficient (ArKO) mice have reduced blood pressure and baroreflex sensitivity.

Aromatase-deficient (ArKO) mice are deficient in estrogens due to deletion of the aromatase gene. We hypothesized that there may be changes in the cardiovascular system of ArKO mice because of evidence linking estrogens with improved cardiovascular outcomes and the induction of the glucocorticoid-metabolizing enzyme, 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2), gene in the kidney, which is important for the regulation of blood pressure (BP). BP and baroreflex sensitivity (BRS) in female conscious ArKO mice were compared with those in age- and weight-matched wild-type (WT) mice. Power spectral analysis was used to determine cardiovascular variability and BRS. Although systolic BP was similar in the two groups, diastolic and mean BPs were lower in the ArKO mice (-6.3 +/- 1.9 and -4.6 +/- 2.1 mm Hg, respectively). Heart rate (HR) was greater in the ArKO mice (+36 +/- 6 beats/min). The mean BP in WT mice was 105 mm Hg, and the HR was 481 beats/min. In the autonomic frequency range, BP variability was 74% greater, and HR variability was only 26% that in WT mice. The BRS of ArKO mice was 46% of the value observed in WT mice. 11betaHSD2 levels were unaltered in ArKO mice, except in the kidney, where they were only 10% of WT levels. Estradiol administration to ArKO mice restored renal 11betaHSD2 to WT levels. The results show that ArKO mice have lower diastolic BP, but increased BP variability, perhaps due to an impaired BRS. Thus, aromatase activity is critical for normal autonomic control of the heart and, hence, for reducing the deleterious effects of high BP variability.

Expression of caveolin-1 enhances cholesterol efflux in hepatic cells.

HepG2 cells were stably transfected with human caveolin-1 (HepG2/cav cells). Transfection resulted in expression of caveolin-1 mRNA, a high abundance of caveolin-1 protein, and the formation of caveolae on the plasma membrane. Cholesterol efflux from HepG2/cav cells was 280 and 45% higher than that from parent HepG2 cells when human plasma and human apoA-I, respectively, were used as acceptors. The difference in efflux was eliminated by treatment of cells with progesterone. There was no difference in cholesterol efflux to cyclodextrin. Cholesterol efflux from plasma membrane vesicles was similar for the two cell types. Transfection led to a 40% increase in the amount of plasma membrane cholesterol in cholesterol-rich domains (caveolae and/or rafts) and a 67% increase in the rate of cholesterol trafficking from intracellular compartments to these domains. Cholesterol biosynthesis in HepG2/cav cells was increased by 2-fold, and cholesterol esterification was reduced by 50% compared with parent HepG2 cells. The proliferation rate of transfected cells was significantly lower than that of non-transfected cells. Transfection did not affect expression of ABCA1 or the abundance of ABCA1 protein, but decreased secretion of apoA-I. We conclude that overexpression of caveolin-1 in hepatic cells stimulates cholesterol efflux by enhancing transfer of cholesterol to cholesterol-rich domains in the plasma membrane.

Sympathetic augmentation in hypertension: role of nerve firing, norepinephrine reuptake, and Angiotensin neuromodulation.

There is growing evidence that essential hypertension is commonly neurogenic and is initiated and sustained by sympathetic nervous system overactivity. Potential mechanisms include increased central sympathetic outflow, altered norepinephrine (NE) neuronal reuptake, diminished arterial baroreflex dampening of sympathetic nerve traffic, and sympathetic neuromodulation by angiotensin II. To address this issue, we used microneurography and radiotracer dilution methodology to measure regional sympathetic activity in 22 hypertensive patients and 11 normotensive control subjects. The NE transport inhibitor desipramine was infused to directly assess the potential role of impaired neuronal NE reuptake. To evaluate possible angiotensin sympathetic neuromodulation, the relation of arterial and coronary sinus plasma concentrations of angiotensin II to sympathetic activity was investigated. Hypertensive patients displayed increased muscle sympathetic nerve activity and elevated total systemic, cardiac, and renal NE spillover. Cardiac neuronal NE reuptake was decreased in hypertensive subjects. In response to desipramine, both the reduction of fractional transcardiac 3[H]NE extraction and the increase in cardiac NE spillover were less pronounced in hypertensive patients. DNA sequencing analysis of the NE transporter gene revealed no mutations that could account for reduced transporter activity. Arterial baroreflex control of sympathetic nerve traffic was not diminished in hypertensive subjects. Angiotensin II plasma concentrations were similar in both groups and were not related to indexes of sympathetic activation. Increased rates of sympathetic nerve firing and reduced neuronal NE reuptake both contribute to sympathetic activation in hypertension, whereas a role for dampened arterial baroreflex restraint on sympathetic nerve traffic and a peripheral neuromodulating influence of angiotensin II appear to be excluded.

Transgenic expression of 11beta-hydroxysteroid dehydrogenase type 2 in osteoblasts reveals an anabolic role for endogenous glucocorticoids in bone.

Glucocorticoid excess leads to bone loss, primarily by decreasing bone formation. However, a variety of in vitro models show that glucocorticoids can promote osteogenesis. To elucidate the role of endogenous glucocorticoids in bone metabolism, we developed transgenic (TG) mice in which a 2.3-kb Col1a1 promoter fragment drives 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) expression in mature osteoblasts. 11beta-HSD2 should metabolically inactivate endogenous glucocorticoids in the targeted cells, thereby reducing glucocorticoid signaling. The inhibitory effect of 300 nm hydrocortisone on percent collagen synthesis was blunted in TG calvariae, demonstrating that the transgene was active. Collagen synthesis rates were lower in TG calvarial organ cultures compared with wild-type. Trabecular bone parameters measured by microcomputed tomography were reduced in L3 vertebrae, but not femurs, of 7- and 24-wk-old TG females. These changes were also not seen in males. In addition, histomorphometry showed that osteoid surface was increased in TG female vertebrae, suggesting that mineralization may be impaired. Our data demonstrate that endogenous glucocorticoid signaling is required for normal vertebral trabecular bone volume and architecture in female mice.

Localization of 11beta-hydroxysteroid dehydrogenase types 1 and 2 in the male reproductive tract.

The action of glucocorticoids in target tissues is dependent on the local expression of glucocorticoid receptors and two 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes, 11beta-HSD1 and 11beta-HSD2, which interconvert active and inactive glucocorticoids. This study examined expression of the 11beta-HSD enzymes in the male reproductive tract of the adult rat. 11beta-HSD1 was immunolocalized to the apical region of principal epithelial cells of the caput epididymis, with the less numerous clear cells devoid of signal. Epididymal 11beta-HSD1 expression was confirmed by Western blot analysis, with immunoreactive species identified at 34 kDa (the expected size for 11beta-HSD1) and at approximately 48 kDa. 11beta-HSD bioactivity was readily detectable in the epididymis, with 11-oxoreductase activity clearly the favored reaction (as observed in liver), consistent with 11beta-HSD1 expression. The epithelium of the vas deferens, seminal vesicle, and penile urethra were also immunopositive for 11beta-HSD1, as were smooth muscle cells of the vas deferens and penile blood vessels. 11beta-HSD2 was also immunolocalized to the epididymal epithelium, but its distribution was complementary to that of 11beta-HSD1 (i.e. clear cells showing intense 11beta-HSD2 staining but principal cells devoid of signal). 11beta-HSD2 was also present in the corpora cavernosa of the penis but not in other tissues. In conclusion, the differential expression of 11beta-HSD1 and 11beta-HSD2 throughout the male reproductive tract suggests that these enzymes locally modulate glucocorticoid and mineralocorticoid actions, particularly in the epididymis and penile vasculature.

17 beta-hydroxysteroid dehydrogenase type XI localizes to human steroidogenic cells.

We searched expressed sequence tag databases with conserved domains of the short-chain alcohol dehydrogenase superfamily and identified another isoform of 17 beta-hydroxysteroid dehydrogenase, 17 beta HSDXI. This enzyme converts 5 alpha-androstane-3 alpha, 17 beta-diol to androsterone. The substrate has been implicated in supporting gestation and modulating gamma-aminobutyric acid receptor activity. 17 beta HSDXI is colinear with human retinal short-chain dehydrogenase/reductase retSDR2, a protein with no known biological activity (accession no. AAF06939). Of the proteins with known function, 17 beta HSDXI is most closely related to the retinol-metabolizing enzyme retSDR1, with which it has 30% identity. There is a polymorphic stretch of 15 adenosines in the 5' untranslated region of the cDNA sequence and a silent polymorphism at C719T. A 17 beta HSDXI construct with a stretch of 20 adenosines was found to produce significantly more enzyme activity than constructs containing 15 or less adenosines (43% vs. 26%, P < 0.005). The C719T polymorphism is present in 15% of genomic DNA samples. Northern blot analysis showed high levels of 17 beta HSDXI expression in the pancreas, kidney, liver, lung, adrenal, ovary, and heart. Immunohistochemical staining for 17 beta HSDXI is strong in steroidogenic cells such as syncytiotrophoblasts, sebaceous gland, Leydig cells, and granulosa cells of the dominant follicle and corpus luteum. In the adrenal 17 beta HSDXI, staining colocalized with the distribution of 17 alpha-hydroxylase but was stronger in the mid to outer cortex. 17 beta HSDXI was also found in the fetus and increased after birth. Liver parenchymal cells and epithelium of the endometrium and small intestine also stained. Regulation studies in mouse Y1 cells showed that cAMP down-regulates 17 beta HSDXI enzymatic activity (40% vs. 32%, P < 0.05) and reduces gene expression to undetectable levels. All-trans-retinoic acid did not affect 17 beta HSDXI expression or activity, but addition of the retinoid together with cAMP significantly decreased activity over cAMP alone (32% vs. 23%, P < 0.05). Cloning and sequencing of the 17 beta HSDXI promoter identified the potential nuclear receptor steroidogenic factor-1 half-site TCCAAGGCCGG, and a cluster of three other potential steroidogenic factor-1 half-sites were found in the distal part of intron 1. Collectively, these results suggest a role for 17 beta HSDXI in androgen metabolism during steroidogenesis and a possible role in nonsteroidogenic tissues including paracrine modulation of 5 alpha-androstane-3 alpha, 17 beta-diol levels. 17 beta HSDXI could act by metabolizing compounds that stimulate steroid synthesis and/or by generating metabolites that inhibit it.

Expression of sterol 27-hydroxylase (CYP27A1) enhances cholesterol efflux.

Cholesterol efflux from CHOP cells transfected with sterol 27-hydroxylase (CYP27A1) was compared with non-transfected and mock-transfected cells. Transfection caused expression of CYP27A1, formation of 27-hydroxycholesterol, and inhibition of cholesterol biosynthesis. Transfection enhanced cholesterol efflux to apolipoprotein A-I or human plasma by 2-3-fold but did not affect the efflux in the absence of acceptor. The analysis of released sterols revealed that 27-hydroxycholesterol represented only a small proportion of sterols, most of which was non-oxidized cholesterol. Time course and dose dependence studies showed that expression of CYP27A1 in CHOP cells mostly affected the efflux of the "fast" cholesterol pool, and relatively more cholesterol was released with low concentrations of an acceptor. Preincubation of non-transfected cells with exogenous 27-hydroxycholesterol (10(-9) and 10(-7) m) led to the stimulation of cholesterol efflux by 24-60%. Expression of CYP27A1 in CHOP cells did not affect ABCA1 expression and abundance of ABCA1 protein. Thus, introduction of CYP27A1 into cells stimulates cholesterol efflux and therefore may increase protection against atherosclerosis.

Clinical relevance of airway 11beta-hydroxysteroid dehydrogenase type II enzyme in asthma.

11beta-hydroxysteroid dehydrogenases (11beta-HSD) are responsible for the conversion of bioactive glucocorticoids to and from inactive metabolites. 11beta-HSD2 is generally considered a high-affinity inactivator of natural glucocorticoids, although its activity with synthetic compounds in vivo is unknown. Inhaled corticosteroids (ICS) remain the primary antiinflammatory agents for treating asthma, but little is known about their metabolism in the lung. The aims of this study were to determine whether the 11beta-HSD2 enzyme can be localized to human airway tissue and whether differential expression of this enzyme relates to asthma severity and ICS needs. We studied airway biopsy specimens from 22 asthmatic subjects, in two groups: (1) a group not treated with ICS (n = 7); and (2) a group treated with ICS (range: 200 to 1,500 microg/d; n = 15). A control population consisted of nine nonasthmatic subjects. Immunostaining was done with an immunopurified antibody to human 11beta-HSD2. Immunoreactivity was generally localized to the endothelium of vessels in the lamina propria and to airway epithelium both in asthmatic patients and nonasthmatic controls. There was a statistically significant inverse relationship between the ICS dose required for effective treatment and the extent of epithelial 11beta-HSD2 staining (r = -0.44; p = 0.04). This is consistent with 11beta-HSD2 acting as an oxidoreductase that regenerates rather than inactivates ICS. This study suggests that glucocorticoid sensitivity in the lung is not determined by ICS breakdown, but may be related to 11beta-HSD2 sustaining the activation of synthetic glucocorticoids.