Steroid receptor coactivators 1 and 2 mediate fetal-to-maternal signaling that initiates parturition.

The precise mechanisms that lead to parturition are incompletely defined. Surfactant protein-A (SP-A), which is secreted by fetal lungs into amniotic fluid (AF) near term, likely provides a signal for parturition; however, SP-A-deficient mice have only a relatively modest delay (~12 hours) in parturition, suggesting additional factors. Here, we evaluated the contribution of steroid receptor coactivators 1 and 2 (SRC-1 and SRC-2), which upregulate SP-A transcription, to the parturition process. As mice lacking both SRC-1 and SRC-2 die at birth due to respiratory distress, we crossed double-heterozygous males and females. Parturition was severely delayed (~38 hours) in heterozygous dams harboring SRC-1/-2-deficient embryos. These mothers exhibited decreased myometrial NF-κB activation, PGF2α, and expression of contraction-associated genes; impaired luteolysis; and elevated circulating progesterone. These manifestations also occurred in WT females bearing SRC-1/-2 double-deficient embryos, indicating that a fetal-specific defect delayed labor. SP-A, as well as the enzyme lysophosphatidylcholine acyltransferase-1 (LPCAT1), required for synthesis of surfactant dipalmitoylphosphatidylcholine, and the proinflammatory glycerophospholipid platelet-activating factor (PAF) were markedly reduced in SRC-1/-2-deficient fetal lungs near term. Injection of PAF or SP-A into AF at 17.5 days post coitum enhanced uterine NF-κB activation and contractile gene expression, promoted luteolysis, and rescued delayed parturition in SRC-1/-2-deficient embryo-bearing dams. These findings reveal that fetal lungs produce signals to initiate labor when mature and that SRC-1/-2-dependent production of SP-A and PAF is crucial for this process.

Cell-intrinsic regulation of murine dendritic cell function and survival by prereceptor amplification of glucocorticoid.

Although the inhibitory effects of therapeutic glucocorticoids (GCs) on dendritic cells (DCs) are well established, the roles of endogenous GCs in DC homeostasis are less clear. A critical element regulating endogenous GC concentrations involves local conversion of inactive substrates to active 11-hydroxyglucocorticoids, a reduction reaction catalyzed within the endoplasmic reticulum by an enzyme complex containing 11ß-hydroxysteroid dehydrogenase type 1 (11ßHSD1) and hexose-6-phosphate dehydrogenase (H6PDH). In this study, we found that this GC amplification pathway operates both constitutively and maximally in steady state murine DC populations and is unaffected by additional inflammatory stimuli. Under physiologic conditions, 11ßHSD1-H6PDH increases the sensitivity of plasmacytoid DCs (pDCs) to GC-induced apoptosis and restricts the survival of this population through a cell-intrinsic mechanism. Upon CpG activation, the effects of enzyme activity are overridden, with pDCs becoming resistant to GCs and fully competent to release type I interferon. CD8α(+) DCs are also highly proficient in amplifying GC levels, leading to impaired maturation following toll-like receptor-mediated signaling. Indeed, pharmacologic inhibition of 11ßHSD1 synergized with CpG to enhance specific T-cell responses following vaccination targeted to CD8α(+) DCs. In conclusion, amplification of endogenous GCs is a critical cell-autonomous mechanism for regulating the survival and functions of DCs in vivo.

11ß-Hydroxysteroid dehydrogenase blockade prevents age-induced skin structure and function defects.

Glucocorticoid (GC) excess adversely affects skin integrity, inducing thinning and impaired wound healing. Aged skin, particularly that which has been photo-exposed, shares a similar phenotype. Previously, we demonstrated age-induced expression of the GC-activating enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) in cultured human dermal fibroblasts (HDFs). Here, we determined 11ß-HSD1 levels in human skin biopsies from young and older volunteers and examined the aged 11ß-HSD1 KO mouse skin phenotype. 11ß-HSD1 activity was elevated in aged human and mouse skin and in PE compared with donor-matched photo-protected human biopsies. Age-induced dermal atrophy with deranged collagen structural organization was prevented in 11ß-HSD1 KO mice, which also exhibited increased collagen density. We found that treatment of HDFs with physiological concentrations of cortisol inhibited rate-limiting steps in collagen biosynthesis and processing. Furthermore, topical 11ß-HSD1 inhibitor treatment accelerated healing of full-thickness mouse dorsal wounds, with improved healing also observed in aged 11ß-HSD1 KO mice. These findings suggest that elevated 11ß-HSD1 activity in aging skin leads to increased local GC generation, which may account for adverse changes occurring in the elderly, and 11ß-HSD1 inhibitors may be useful in the treatment of age-associated impairments in dermal integrity and wound healing.

Synovial DKK1 expression is regulated by local glucocorticoid metabolism in inflammatory arthritis.

INTRODUCTION: Inflammatory arthritis is associated with increased bone resorption and suppressed bone formation. The Wnt antagonist dickkopf-1 (DKK1) is secreted by synovial fibroblasts in response to inflammation and this protein has been proposed to be a master regulator of bone remodelling in inflammatory arthritis. Local glucocorticoid production is also significantly increased during joint inflammation. Therefore, we investigated how locally derived glucocorticoids and inflammatory cytokines regulate DKK1 synthesis in synovial fibroblasts during inflammatory arthritis. METHODS: We examined expression and regulation of DKK1 in primary cultures of human synovial fibroblasts isolated from patients with inflammatory arthritis. The effect of TNFα, IL-1ß and glucocorticoids on DKK1 mRNA and protein expression was examined by real-time PCR and ELISA. The ability of inflammatory cytokine-induced expression of the glucocorticoid-activating enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) to sensitise fibroblasts to endogenous glucocorticoids was explored. Global expression of Wnt signalling and target genes in response to TNFα and glucocorticoids was assessed using a custom array. RESULTS: DKK1 expression in human synovial fibroblasts was directly regulated by glucocorticoids but not proinflammatory cytokines. Glucocorticoids, but not TNFα, regulated expression of multiple Wnt agonists and antagonists in favour of inhibition of Wnt signalling. However, TNFα and IL-1ß indirectly stimulated DKK1 production through increased expression of 11ß-HSD1. CONCLUSIONS: These results demonstrate that in rheumatoid arthritis synovial fibroblasts, DKK1 expression is directly regulated by glucocorticoids rather than TNFα. Consequently, the links between synovial inflammation, altered Wnt signalling and bone remodelling are not direct but are dependent on local activation of endogenous glucocorticoids.

Lack of significant metabolic abnormalities in mice with liver-specific disruption of 11ß-hydroxysteroid dehydrogenase type 1.

Glucocorticoids (GC) are implicated in the development of metabolic syndrome, and patients with GC excess share many clinical features, such as central obesity and glucose intolerance. In patients with obesity or type 2 diabetes, systemic GC concentrations seem to be invariably normal. Tissue GC concentrations determined by the hypothalamic-pituitary-adrenal (HPA) axis and local cortisol (corticosterone in mice) regeneration from cortisone (11-dehydrocorticosterone in mice) by the 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) enzyme, principally expressed in the liver. Transgenic mice have demonstrated the importance of 11ß-HSD1 in mediating aspects of the metabolic syndrome, as well as HPA axis control. In order to address the primacy of hepatic 11ß-HSD1 in regulating metabolism and the HPA axis, we have generated liver-specific 11ß-HSD1 knockout (LKO) mice, assessed biomarkers of GC metabolism, and examined responses to high-fat feeding. LKO mice were able to regenerate cortisol from cortisone to 40% of control and had no discernible difference in a urinary metabolite marker of 11ß-HSD1 activity. Although circulating corticosterone was unaltered, adrenal size was increased, indicative of chronic HPA stimulation. There was a mild improvement in glucose tolerance but with insulin sensitivity largely unaffected. Adiposity and body weight were unaffected as were aspects of hepatic lipid homeostasis, triglyceride accumulation, and serum lipids. Additionally, no changes in the expression of genes involved in glucose or lipid homeostasis were observed. Liver-specific deletion of 11ß-HSD1 reduces corticosterone regeneration and may be important for setting aspects of HPA axis tone, without impacting upon urinary steroid metabolite profile. These discordant data have significant implications for the use of these biomarkers of 11ß-HSD1 activity in clinical studies. The paucity of metabolic abnormalities in LKO points to important compensatory effects by HPA activation and to a crucial role of extrahepatic 11ß-HSD1 expression, highlighting the contribution of cross talk between GC target tissues in determining metabolic phenotype.

Inflammatory regulation of glucocorticoid metabolism in mesenchymal stromal cells.

OBJECTIVE: Tissue glucocorticoid (GC) levels are regulated by the GC-activating enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1). This enzyme is expressed in cells and tissues arising from mesenchymal stromal cells. Proinflammatory cytokines dramatically increase expression of 11ß-HSD1 in stromal cells, an effect that has been implicated in inflammatory arthritis, osteoporosis, obesity, and myopathy. Additionally, GCs act synergistically with proinflammatory cytokines to further increase enzyme expression. The present study was undertaken to investigate the mechanisms underlying this regulation. METHODS: Gene reporter analysis, rapid amplification of complementary DNA ends (RACE), chemical inhibition experiments, and genetic disruption of intracellular signaling pathways in mouse embryonic fibroblasts (MEFs) were used to define the molecular mechanisms underlying the regulation of 11ß-HSD1 expression. RESULTS: Gene reporter, RACE, and chemical inhibitor studies demonstrated that the increase in 11ß-HSD1 expression with tumor necrosis factor α (TNFα)/interleukin-1ß (IL-1ß) occurred via the proximal HSD11B1 gene promoter and depended on NF-κB signaling. These findings were confirmed using MEFs with targeted disruption of NF-κB signaling, in which RelA (p65) deletion prevented TNFα/IL-1ß induction of 11ß-HSD1. GC treatment did not prevent TNFα-induced NF-κB nuclear translocation. The synergistic enhancement of TNFα-induced 11ß-HSD1 expression with GCs was reproduced by specific inhibitors of p38 MAPK. Inhibitor and gene deletion studies indicated that the effects of GCs on p38 MAPK activity occurred primarily through induction of dual-specificity phosphatase 1 expression. CONCLUSION: The mechanism by which stromal cell expression of 11ß-HSD1 is regulated is novel and distinct from that in other tissues. These findings open new opportunities for development of therapeutic interventions aimed at inhibiting or stimulating local GC levels in cells of mesenchymal stromal lineage during inflammation.

Glucocorticoid-induced apoptosis in human decidua: a novel role for 11beta-hydroxysteroid dehydrogenase in late gestation.

Glucocorticoids play a fundamental role in the endocrinology of pregnancy but excess glucocorticoids in utero may lead to abnormalities of fetal growth. Protection against fetal exposure to cortisol is provided by the enzyme 11beta-hydroxysteroid dehydrogenase 2 (11beta-HSD2) located in the human placental trophoblast. By contrast, relatively little is known concerning the function of glucocorticoid-activating 11beta-HSD1, which is strongly expressed within human maternal decidua. To address this we have assessed: i) changes in decidual 11beta-HSD1 expression across gestation and ii) the functional role of glucocorticoids in decidua. Human decidua was collected from women undergoing surgical termination of pregnancy in first (n = 32) and second (n = 10) trimesters, and elective caesarean sections in the third trimester (n = 9). Analysis of mRNA for 11beta-HSD1 by real-time RT-PCR showed increased expression in second (9.3-fold, P < 0.01) and third (210-fold, P < 0.001) trimesters. Studies using primary cultures of decidual cells also revealed higher levels of cortisol generation in the third trimester. Changes in decidual 11beta-HSD1 with gestation were paralleled by increased expression of the apoptosis markers caspase-3 and annexin-V, particularly in cluster designation (CD)10(-VE) non-stromal cells (20-fold in third trimester relative to first trimester). Apoptosis was also readily induced in primary cultures of third trimester decidual cells when treated with cortisol, cortisone, or dexamethasone (all 100 nM for 24 h). The effect of cortisone but not cortisol or dexamethasone was blocked by an 11beta-HSD inhibitor confirming the functional significance of endogenous cortisol generation. These data show that autocrine metabolism of glucocorticoids is an important facet of the feto-placental unit in late gestation and we propose that a possible effect of this is to stimulate programmed cell death in human decidua.

Differential expression, function and response to inflammatory stimuli of 11beta-hydroxysteroid dehydrogenase type 1 in human fibroblasts: a mechanism for tissue-specific regulation of inflammation.

Stromal cells such as fibroblasts play an important role in defining tissue-specific responses during the resolution of inflammation. We hypothesized that this involves tissue-specific regulation of glucocorticoids, mediated via differential regulation of the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). Expression, activity and function of 11beta-HSD1 was assessed in matched fibroblasts derived from various tissues (synovium, bone marrow and skin) obtained from patients with rheumatoid arthritis or osteoarthritis. 11beta-HSD1 was expressed in fibroblasts from all tissues but mRNA levels and enzyme activity were higher in synovial fibroblasts (2-fold and 13-fold higher mRNA levels in dermal and synovial fibroblasts, respectively, relative to bone marrow). Expression and activity of the enzyme increased in all fibroblasts following treatment with tumour necrosis factor-alpha or IL-1beta (bone marrow: 8-fold and 37-fold, respectively, compared to vehicle; dermal fibroblasts: 4-fold and 14-fold; synovial fibroblasts: 7-fold and 31-fold; all P < 0.01 compared with vehicle). Treatment with IL-4 or interferon-gamma was without effect, and there was no difference in 11beta-HSD1 expression between fibroblasts (from any site) obtained from patients with rheumatoid arthritis or osteoarthritis. In the presence of 100 nmol/l cortisone, IL-6 production--a characteristic feature of synovial derived fibroblasts--was significantly reduced in synovial but not dermal or bone marrow fibroblasts. This was prevented by co-treatment with an 11beta-HSD inhibitor, emphasizing the potential for autocrine activation of glucocorticoids in synovial fibroblasts. These data indicate that differences in fibroblast-derived glucocorticoid production (via the enzyme 11beta-HSD1) between cells from distinct anatomical locations may play a key role in the predeliction of certain tissues to develop persistent inflammation.

Late-onset apparent mineralocorticoid excess caused by novel compound heterozygous mutations in the HSD11B2 gene.

Mutations in the gene encoding 11beta-hydroxysteroid dehydrogenase type 2, 11beta-HSD2 (HSD11B2), explain the molecular basis for the syndrome of apparent mineralocorticoid excess (AME), characterized by severe hypertension and hypokalemic alkalosis. Cortisol is the offending mineralocorticoid in AME, as the result of a lack of 11beta-HSD2-mediated cortisol to cortisone inactivation. In this study, we describe mutations in the HSD11B2 gene in 3 additional AME kindreds in which probands presented in adult life, with milder phenotypes including the original seminal case reported by Stewart and Edwards. Genetic analysis of the HSD11B2 gene revealed that all probands were compound heterozygotes, for a total of 7 novel coding and noncoding mutations. Of the 7 mutations detected, 6 were investigated for their effects on gene expression and enzyme activity by the use of mutant cDNA and minigene constructs transfected into HEK 293 cells. Four missense mutations resulted in enzymes with varying degrees of activity, all <10% of wild type. A further 2 mutations generated incorrectly spliced mRNA and predicted severely truncated, inactive enzyme. The mothers of 2 probands heterozygous for missense mutations have presented with a phenotype indistinguishable from "essential" hypertension. These genetic and biochemical data emphasize the heterogeneous nature of AME and the effects that heterozygosity at the HSD11B2 locus can have on blood pressure in later life.

Osteoblastic 11beta-hydroxysteroid dehydrogenase type 1 activity increases with age and glucocorticoid exposure.

The risk of glucocorticoid-induced osteoporosis increases substantially with age but there is considerable individual variation. In recent studies we have shown that the effects of glucocorticoids on bone are dependent on autocrine actions of the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1); expression of 11beta-HSD1 in osteoblasts (OBs) facilitates local synthesis of active glucocorticoids with consequent effects on osteoblastic proliferation and differentiation. Using primary cultures of human OBs, we have now characterized the age-specific variation in osteoblastic 11beta-HSD1 and defined enzyme kinetics and regulation using natural and therapeutic glucocorticoids. 11beta-HSD1 reductase activity (cortisone to cortisol conversion) was recognized in all OB cultures and correlated positively with age (r = 0.58 with all cultures, p < 0.01, and n = 18; r = 0.87 with calcaneal-derived cultures, p < 0.001, and n = 14). Glucocorticoid treatment caused a time- and dose-dependent increase in 11beta-HSD1 activity over control (e.g., dexamethasone [DEX; 1 microM], 2.6-fold +/- 0.5 (mean +/- SE), p < 0.001, and n = 16; cortisol (100 nM), 1.7-fold +/- 0.1, p < 0.05, and n = 14). Similar increases in 11beta-HSD1 mRNA expression were indicated using real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) analyses (3.5-fold with DEX, p < 0.01; 2.5-fold with cortisol, p < 0.05). The capacity of 11beta-HSD1 to metabolize the synthetic glucocorticoids prednisone and prednisolone was investigated in human OBs (hOBs) and fetal kidney-293 cells stably transfected with human 11beta-HSD1 cDNA. Transfected cells and hOBs were able to interconvert prednisone and prednisolone with reaction kinetics indistinguishable from those for cortisone and cortisol. To assess the in vivo availability of substrates for osteoblastic 11beta-HSD1, plasma cortisone and prednisone levels were measured in normal males before and after oral prednisolone (5 mg). The 9:00 a.m. serum cortisone levels were 110 +/- 5 nmol/liter and prednisone levels peaked at 78 +/- 23 nmol/liter 120 minutes after administration of prednisolone. Thus, therapeutic use of steroids increases substrate availability for 11beta-HSD1 in bone. These studies indicate that activation of glucocorticoids at an autocrine level within bone is likely to play an important role in the age-related decrease in bone formation and increased risk of glucocorticoid-induced osteoporosis.

Prereceptor regulation of glucocorticoid action by 11beta-hydroxysteroid dehydrogenase: a novel determinant of cell proliferation.

Isozymes of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) act at a prereceptor level to regulate the tissue-specific availability of active glucocorticoids. To examine the effect of this on cell proliferation and differentiation, we have developed transfectant variants of a rat osteosarcoma cell line that express cDNA for 11beta-HSD1 (ROS 17/2.8beta1) or 11beta-HSD2 (ROS 17/2.8beta2). ROS 17/2.8beta1 showed net conversion of cortisone to cortisol whereas ROS 17/2.8beta2 showed only inactivation of cortisol to cortisone. There was no significant difference in glucocorticoid receptor (GR) expression between the different clones. However, in proliferation and differentiation studies, ROS 17/2.8beta2 cells were completely resistant to cortisol. In contrast, ROS 17/2.8beta1 were sensitive to both cortisone and cortisol. Expression of 11beta-HSD1 decreased cell proliferation whereas 11beta-HSD2 increased proliferation. These responses appear to be due to metabolism of endogenous serum glucocorticoids; proliferation of ROS 17/2.8beta1 decreased further with exogenous cortisone or cortisol whereas ROS 17/2.8beta2 were resistant to both compounds. The pro-proliferative effects of 11beta-HSD2 were abrogated by 18beta-glycyrrhetinic acid, an 11beta-HSD inhibitor, and in cells transfected with cDNA encoding inactive 11beta-HSD2. Data indicate that differential regulation of 11beta-HSD1 and 2 (rather than GR expression) is a key determinant of cell proliferation. Dysregulated expression of 11beta-HSD2 may be a novel feature of tumorigenesis.