Stimulation of 11β-HSD1 expression by IL-1β via a C/EBP binding site in human fetal lung fibroblasts

Inhibition of 11β-HSD1 Expression by Insulin in Skin: Impact for Diabetic Wound Healing

Chronic, non-healing wounds impose a great burden on patients, professionals and health care systems worldwide. Diabetes mellitus (DM) and obesity are globally highly prevalent metabolic disorders and increase the risk for developing chronic wounds. Glucocorticoids (GCs) are endogenous stress hormones that exert profound effects on inflammation and repair systems. 11-beta-hydroxysteroid dehydrogenase 1 (11β-HSD1) is the key enzyme which controls local GC availability in target tissues such as skin. Since treatment with GCs has detrimental side effects on skin integrity, causing atrophy and delayed wound healing, we asked whether the dysregulated expression of 11β-HSD1 and consequently local GC levels in skin contribute to delayed wound healing in obese, diabetic db/db mice. We found increased expression of 11β-HSD1 during disturbed wound healing and in the healthy skin of obese, diabetic db/db mice. Cell analysis revealed increased expression of 11β-HSD1 in fibroblasts, myeloid cells and dermal white adipose tissue from db/db mice, while expression in keratinocytes was unaffected. Among diabetes- and obesity-related factors, insulin and insulin-like growth factor 1 down-regulated 11β-HSD1 expression in fibroblasts and myeloid cells, while glucose, fatty acids, TNF-α and IL-1β did not affect it. Insulin exerted its inhibitory effect on 11β-HSD1 expression by activating PI3-kinase/Akt-signalling. Consequently, the inhibitory effect of insulin is attenuated in fibroblasts from insulin-resistant db/db mice. We conclude that insulin resistance in obesity and diabetes prevents the down-regulation of 11β-HSD1, leading to elevated endogenous GC levels in diabetic skin, which could contribute to impaired wound healing in patients with DM.

Decreased 11β-hydroxysteroid dehydrogenase 1 in lungs of steroid receptor coactivator (Src)-1/-2 double-deficient fetal mice is caused by impaired glucocorticoid and cytokine signaling

Our previous research revealed that steroid receptor coactivators (Src)-1 and -2 serve a critical cooperative role in production of parturition signals, surfactant protein A and platelet-activating factor, by the developing mouse fetal lung (MFL). To identify the global landscape of genes in MFL affected by Src-1/-2 double-deficiency, we conducted RNA-seq analysis of lungs from 18.5 days post-coitum (dpc) Src-1^-/- /-2^-/- (dKO) vs. WT fetuses. One of the genes most highly downregulated (~4.8 fold) in Src-1/-2 dKO fetal lungs encodes 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which catalyzes conversion of inactive 11-dehydrocorticosterone to the glucocorticoid receptor (GR) ligand, corticosterone. Glucocorticoids were reported to upregulate 11β-HSD1 expression in various cell types via induction of C/EBP transcription factors. We observed that C/ebpα and C/ebpβ mRNA and protein were markedly reduced in Src-1/-2 double-deficient (Src-1/-2^d/d ) fetal lungs, compared to WT. Moreover, glucocorticoid induction of 11β-hsd1, C/ebpα and C/ebpβ in cultured MFL epithelial cells was prevented by the SRC family inhibitor, SI-2. Cytokines also contribute to the induction of 11β-HSD1. Expression of IL-1β and TNFα, which dramatically increased toward term in lungs of WT fetuses, was markedly reduced in Src-1/-2^d/d fetal lungs. Our collective findings suggest that impaired lung development and surfactant synthesis in Src-1/-2^d/d fetuses are likely caused, in part, by decreased GR and cytokine induction of C/EBP and NF-κB transcription factors. This results in reduced 11β-HSD1 expression and glucocorticoid signaling within the fetal lung, causing a break in the glucocorticoid-induced positive feedforward loop.

The upregulation of 11β-HSD1 in ovarian granulosa cells by cortisol and interleukin-1β in polycystic ovary syndrome

Our previous study have demonstrated the elevated cortisol concentration in the follicular fluid (FF) contributed to the insulin resistance of the granulosa cells (GCs) in PCOS, but the complicated cortisol generation mechanisms are still unknown. 11β-hydroxysteroid type 1(11β-HSD1) mainly functions as reductase in intact cells, converting cortisone to cortisol. Cortisol and IL-1β are known to induce 11β-HSD1 in number of tissues, but few results were obtained in ovarian GCs In this study, FF and GCs from PCOS and non-PCOS patients were collected to study the interaction of cortisol and IL-1β in 11β-HSD1 expression. The ELISA and qRT-PCR revealed that the cortisol and IL-1β concentration in FF and 11β-HSD1 abundance in GCs were elevated in PCOS patients. By using cultured GCs in vitro, we demonstrated that both cortisol and IL-1β could stimulate 11β-HSD1 expression. The induction of 11β-HSD1 by IL-1β was further inducted by cortisol, whereas the induction of IL-1β and IL-6 expression by IL-1β was completely inhibited by cortisol. In conclusion, cortisol and IL-1β preformed a synergistically upregulation of 11β-HSD1 expression in GCs, contributing to the accumulation of cortisol in FF of PCOS patients. This may lead to the metabolic disorders of the ovary.

A heretical view: rather than a solely placental protective function, placental 11β hydroxysteroid dehydrogenase 2 also provides substrate for fetal peripheral cortisol synthesis in obese pregnant ewes

Exposure to glucocorticoid levels higher than appropriate for current developmental stages induces offspring metabolic dysfunction. Overfed/obese (OB) ewes and their fetuses display elevated blood cortisol, while fetal Adrenocorticotropic hormone (ACTH) remains unchanged. We hypothesized that OB pregnancies would show increased placental 11β hydroxysteroid dehydrogenase 2 (11β-HSD2) that converts maternal cortisol to fetal cortisone as it crosses the placenta and increased 11β-HSD system components responsible for peripheral tissue cortisol production, providing a mechanism for ACTH-independent increase in circulating fetal cortisol. Control ewes ate 100% National Research Council recommendations (CON) and OB ewes ate 150% CON diet from 60 days before conception until necropsy at day 135 gestation. At necropsy, maternal jugular and umbilical venous blood, fetal liver, perirenal fat, and cotyledonary tissues were harvested. Maternal plasma cortisol and fetal cortisol and cortisone were measured. Fetal liver, perirenal fat, cotyledonary 11β-HSD1, hexose-6-phosphate dehydrogenase (H6PD), and 11β-HSD2 protein abundance were determined by Western blot. Maternal plasma cortisol, fetal plasma cortisol, and cortisone were higher in OB vs. CON (p < 0.01). 11β-HSD2 protein was greater (p < 0.05) in OB cotyledonary tissue than CON. 11β-HSD1 abundance increased (p < 0.05) in OB vs. CON fetal liver and perirenal fat. Fetal H6PD, an 11β-HSD1 cofactor, also increased (p < 0.05) in OB vs. CON perirenal fat and tended to be elevated in OB liver (p < 0.10). Our data provide evidence for increased 11β-HSD system components responsible for peripheral tissue cortisol production in fetal liver and adipose tissue, thereby providing a mechanism for an ACTH-independent increase in circulating fetal cortisol in OB fetuses.

Involvement of STAT3 in the synergistic induction of 11β-HSD1 by SAA1 and cortisol in human amnion fibroblasts

PROBLEM

Cortisol, which is regenerated from biologically inactive cortisone by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in human fetal membranes, may play an important role in human parturition. Recently, we have demonstrated that human fetal membranes are capable of de novo synthesis of serum amyloid A1 (SAA1), an acute-phase protein of inflammation, and SAA1 may be engaged in multiple actions associated with human parturition. It remains to be determined whether SAA1 can interact with cortisol in the regulation of 11β-HSD1 in the fetal membranes.

METHOD OF STUDY

In the current study, we examined the regulation of 11β-HSD1 expression by SAA1, and the interaction between SAA1 and cortisol in the regulation of 11β-HSD1 expression in primary human amnion fibroblasts and amnion tissue.

RESULTS

Either SAA1 or cortisol induced 11β-HSD1 expression in a concentration-dependent manner. Combination of SAA1 and cortisol synergistically enhanced 11β-HSD1 expression. Mechanism studies revealed that SAA1 and cortisol induced the phosphorylation of the transcription factor STAT3 in a sequential order with the induction by SAA1 preceding the induction by cortisol. Furthermore, the induction of 11β-HSD1 expression by either SAA1 or cortisol or combination of SAA1 and cortisol was blocked by STAT3 inhibition with its antagonist S3I-201 or siRNA-mediated knockdown.

CONCLUSION

This study has demonstrated that SAA1 and cortisol can reinforce each other in the induction of 11β-HSD1 expression through sequential phosphorylation of STAT3. The synergistic enhancement of 11β-HSD1 expression by SAA1 and cortisol may lead to excessive cortisol accumulation in the fetal membranes at parturition.

Glucocorticoids and Bone: Consequences of Endogenous and Exogenous Excess and Replacement Therapy

Osteoporosis associated with long-term glucocorticoid therapy remains a common and serious bone disease. Additionally, in recent years it has become clear that more subtle states of endogenous glucocorticoid excess may have a major impact on bone health. Adverse effects can be seen with mild systemic glucocorticoid excess, but there is also evidence of tissue-specific regulation of glucocorticoid action within bone as a mechanism of disease. This review article examines (1) the role of endogenous glucocorticoids in normal bone physiology, (2) the skeletal effects of endogenous glucocorticoid excess in the context of endocrine conditions such as Cushing disease/syndrome and autonomous cortisol secretion (subclinical Cushing syndrome), and (3) the actions of therapeutic (exogenous) glucocorticoids on bone. We review the extent to which the effect of glucocorticoids on bone is influenced by variations in tissue metabolizing enzymes and glucocorticoid receptor expression and sensitivity. We consider how the effects of therapeutic glucocorticoids on bone are complicated by the effects of the underlying inflammatory disease being treated. We also examine the impact that glucocorticoid replacement regimens have on bone in the context of primary and secondary adrenal insufficiency. We conclude that even subtle excess of endogenous or moderate doses of therapeutic glucocorticoids are detrimental to bone. However, in patients with inflammatory disorders there is a complex interplay between glucocorticoid treatment and underlying inflammation, with the underlying condition frequently representing the major component underpinning bone damage.

11β-HSD1 in Human Fetal Membranes as a Potential Therapeutic Target for Preterm Birth

Human parturition is a complex process involving interactions between the myometrium and signals derived from the placenta, fetal membranes, and fetus. Signals originating from fetal membranes are crucial components that trigger parturition, which is clearly illustrated by the labor-initiating consequence of membrane rupture. It has been recognized for a long time that among fetal tissues in late gestation the fetal membranes possess the highest capacity for cortisol regeneration by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). However, the exact role of this unique feature remains a mystery. Accumulating evidence indicates that this extra-adrenal source of cortisol may serve as an upstream signal for critical events in human parturition, including enhanced prostaglandin and estrogen synthesis as well as extracellular matrix remodeling. This may explain why such high capacity for cortisol regeneration develops in human fetal membranes at late gestation. Therefore, inhibition of 11β-HSD1 may provide a potential therapeutic target for prevention of preterm birth. This review summarizes the current understanding of the functional role of cortisol regeneration by 11β-HSD1 in human fetal membranes.

Comparing human and macaque placental transcriptomes to disentangle preterm birth pathology from gestational age effects

INTRODUCTION

A major issue in the transcriptomic study of spontaneous preterm birth (sPTB) in humans is the inability to collect healthy control tissue at the same gestational age (GA) to compare with pathologic preterm tissue. Thus, gene expression differences identified after the standard comparison of sPTB and term tissues necessarily reflect differences in both sPTB pathology and GA. One potential solution is to use GA-matched controls from a closely related species to tease apart genes that are dysregulated during sPTB from genes that are expressed differently as a result of GA effects.

METHODS

To disentangle genes whose expression levels are associated with sPTB pathology from those linked to GA, we compared RNA sequencing data from human preterm placentas, human term placentas, and rhesus macaque placentas at 80% completed gestation (serving as healthy non-human primate GA-matched controls). We first compared sPTB and term human placental transcriptomes to identify significantly differentially expressed genes. We then overlaid the results of the comparison between human sPTB and macaque placental transcriptomes to identify sPTB-specific candidates. Finally, we overlaid the results of the comparison between human term and macaque placental transcriptomes to identify GA-specific candidates.

RESULTS

Examination of relative expression for all human genes with macaque orthologs identified 267 candidate genes that were significantly differentially expressed between preterm and term human placentas. 29 genes were identified as sPTB-specific candidates and 37 as GA-specific candidates. Altogether, the 267 differentially expressed genes were significantly enriched for a variety of developmental, metabolic, reproductive, immune, and inflammatory functions. Although there were no notable differences between the functions of the 29 sPTB-specific and 37 GA-specific candidate genes, many of these candidates have been previously shown to be dysregulated in diverse pregnancy-associated pathologies.

DISCUSSION

By comparing human sPTB and term transcriptomes with GA-matched control transcriptomes from a closely related species, this study disentangled the confounding effects of sPTB pathology and GA, leading to the identification of 29 promising sPTB-specific candidate genes and 37 genes potentially related to GA effects. The apparent similarity in functions of the sPTB and GA candidates may suggest that the effects of sPTB and GA do not correspond to biologically distinct processes. Alternatively, it may reflect the poor state of knowledge of the transcriptional landscape underlying placental development and disease.

Stabilization of ATF5 by TAK1-Nemo-like kinase critically regulates the interleukin-1β-stimulated C/EBP signaling pathway

Interleukin-1β (IL-1β) is a key proinflammatory cytokine that initiates several signaling cascades, including those involving CCAAT/enhancer binding proteins (C/EBPs). The mechanism by which IL-1β propagates a signal that activates C/EBP has remained elusive. Nemo-like kinase (NLK) is a mitogen-activated protein kinase (MAPK)-like kinase associated with many pathways and phenotypes that are not yet well understood. Using a luciferase reporter screen, we found that IL-1β-induced C/EBP activation was positively regulated by NLK. Overexpression of NLK activated C/EBP and potentiated IL-1β-triggered C/EBP activation, whereas knockdown or knockout of NLK had the opposite effect. NLK interacted with activating transcription factor 5 (ATF5) and inhibited the proteasome-dependent degradation of ATF5 in a kinase-independent manner. Consistently, NLK deficiency resulted in decreased levels of ATF5. NLK cooperated with ATF5 to activate C/EBP, whereas NLK could not activate C/EBP upon knockdown of ATF5. Moreover, TAK1, a downstream effector of IL-1β that acts upstream of NLK, mimicked the ability of NLK to stabilize ATF5 and activate C/EBP. Thus, our findings reveal the TAK1-NLK pathway as a novel regulator of basal or IL-1β-triggered C/EBP activation though stabilization of ATF5.

Mineralocorticoid effects in the late gestation ovine fetal lung

This study was designed to determine the effects of corticosteroids at MR in the late‐gestation fetal lung. Since both the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) are expressed at relatively high levels in the fetal lung, endogenous corticosteroids may act at MR as well as GR in the preterm fetal lung. The GR agonist, betamethasone, the MR agonist, aldosterone, or both were infused intravenously for 48 h in ovine fetuses of approximately 130 days gestation. Effects on airway pressures during stepwise inflation of the in situ lung, expression of ENaC alpha (SCNN1A), ENaC beta (SCNN1B), and Na,K ATPase (ATP1A1), and elastin and collagen content were determined after the infusions. We found that aldosterone significantly reduced the airway pressure measured during the initial step in inflation of the lung, although aldosterone had no overall effect on lung compliance, nor did aldosterone induce expression of ENaCα, ENaCβ or Na,K ATPaseα1. Betamethasone significantly increased expression of the epithelial sodium channel (ENaC) subunit mRNAs, and collagen and elastin content in the lungs, although this dose of betamethasone also had no effect on lung compliance. There was no synergy between effects of the MR and GR agonists. Transcriptomic analysis suggested that although aldosterone did not alter genes in pathways related to epithelial sodium transport, aldosterone did alter genes in pathways involved in cell proliferation in the lungs. The results are consistent with corticosteroid‐induced fluid reabsorption at birth through GR rather than MR, but suggest that MR facilitates lung maturation, and may contribute to inflation with the first breaths via mechanisms distinct from known aldosterone effects in other epithelia.

Infusion of the mineralocorticoid receptor agonist, aldosterone, to the ovine fetus resulted in reduced airway pressures with initial lung inflation. However, aldosterone did not alter lung surfactant or epithelial sodium transport genes which are classical MR gene targets. Transcriptomic analysis revealed an aldosterone effect on genes related to cell cycle, suggesting that MR have a role distinct form that of GR in the maturing lung.

Proinflammatory cytokine induction of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in human adipocytes is mediated by MEK, C/EBPβ, and NF-κB/RelA

CONTEXT

Levels of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which regenerates active glucocorticoids, are selectively elevated in adipose tissue in human obesity and metabolic syndrome, both conditions associated with chronic low-grade inflammation. 11β-HSD1 expression is induced by proinflammatory cytokines in a variety of cell types, including in human adipocytes differentiated in vitro.

OBJECTIVE

Our objective was to determine the mechanisms by which proinflammatory cytokines induce 11β-HSD1 in human adipocytes.

RESULTS

The proinflammatory cytokines IL-1α (10 ng/mL) and TNFα (20 ng/mL) increased 11β-HSD1 mRNA levels in human primary adipocyte fractions and Simpson-Golabi-Behmel syndrome (SGBS) adipocytes (P<.001). Inhibition of the MAPK/ERK kinase (MEK) attenuated CCAAT/enhancer binding protein (C/EBP) β phosphorylation at Thr235 and IL-1α/TNFα induction of 11β-HSD1 (P≤.007). The small interfering RNA-mediated knockdown of C/EBPβ and nuclear factor (NF)-κB/RelA or inhibition of NF-κB/RelA also attenuated cytokine induction of 11β-HSD1 (P≤.001). Moreover, induction of 11β-HSD1 by IL-1α in SGBS cells was associated with nuclear localization of C/EBPβ and NF-κB/RelA. Chromatin immunoprecipitation experiments showed C/EBPβ and NF-κB/RelA located to the 11β-HSD1 promoter in human adipose tissue. Treatment of adipocyte fractions or SGBS adipocytes with metformin or acetylsalicylic acid, which target C/EBPβ and NF-κB/RelA signaling, attenuated the IL-1α induction of 11β-HSD1 (P≤.002).

CONCLUSIONS

Increased proinflammatory signaling in inflamed adipose tissue may mediate elevated 11β-HSD1 expression at this site via MEK, C/EBPβ, and NF-κB/RelA. These molecules/signaling pathways are, therefore, potential targets for drugs, including metformin and acetylsalicylic acid, to prevent/decreased up-regulation of 11β-HSD1 in human obese/metabolic syndrome adipose tissue.

Glucocorticoid metabolism in the developing lung: adrenal-like synthesis pathway

Glucocorticoids (GCs) are essential to normal lung development. They participate in the regulation of important developmental events including morphological changes, and lung maturation leading to the surge of surfactant synthesis by type II epithelial cells. Antenatal GC is administered to mothers at risk of premature delivery to reduce the risk of respiratory distress syndrome (RDS). Sex differences were reported in RDS, in the efficiency of antenatal GC treatment independently of surfactant levels, and in surfactant lipid synthesis. Type II epithelial cell maturation is regulated by epithelial-fibroblast cell-cell communication and involves paracrine factors secreted by fibroblasts under the stimulatory effect of GC. This positive action of GC can be inhibited by androgens through the androgen receptor (AR) present in fibroblasts. In fact, lung development is regulated not only by GC and androgens but also by GC and androgen metabolisms within the developing lung. We recently reviewed the metabolism of androgens in the fetal lung [45]. Here, we review multiple aspects of GC metabolism in the developing lung including inactivation and re-activation by 11β-HSDs, synthesis from the adrenal-like synthesis pathway expressed within the lung and the putative role of CRH and ACTH originating from lung in the regulation of this pathway. This article is part of a Special Issue entitled 'Pregnancy and Steroids'.

11β-hydroxysteroid dehydrogenases: intracellular gate-keepers of tissue glucocorticoid action

Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.

Pro-inflammatory cytokine induction of 11β-hydroxysteroid dehydrogenase type 1 in A549 cells requires phosphorylation of C/EBPβ at Thr235

11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) converts inert glucocorticoids into active forms, thereby increasing intracellular glucocorticoid levels, important to restrain acute inflammation. 11β-HSD1 is induced by pro-inflammatory cytokines in a variety of cells. Here, we show 11β-HSD1 expression in human A549 epithelial cells is increased by pro-inflammatory cytokines (IL-1α/TNFα) via the P2 promoter of the HSD11B1 gene. Inhibition of p38 MAPK attenuated the pro-inflammatory cytokine induction of mRNA encoding 11β-HSD1 as well as that encoding C/EBPβ. IL-1α/TNFα-induced phosphorylation of C/EBPβ at Thr235 was also attenuated by p38 MAPK inhibition suggesting involvement of a p38 MAPK-C/EBPβ pathway. siRNA-mediated knock-down of C/EBPβ and NF-κB/RelA implicated both transcription factors in the IL-1α/TNFα induction of HSD11B1 mRNA. Transient transfections of HSD11B1 promoter-reporter constructs identified the proximal region of the P2 promoter of HSD11B1 as essential for this induction. IL-1α increased binding of C/EBPβ to the HSD11B1 P2 promoter, but this was not observed for NF-κB/RelA, suggesting indirect regulation by NF-κB/RelA. Ectopic expression of mutant chicken C/EBPβ constructs unable to undergo phosphorylation at the threonine equivalent to Thr235 attenuated the IL-1α-induction of HSD11B1, whereas mimicking constitutive phosphorylation of Thr235 (by mutation to aspartate) increased basal expression of HSD11B1 mRNA without affecting IL-1α-induced levels. These data clearly demonstrate a role for both C/EBPβ and NF-κB/RelA in the pro-inflammatory cytokine induction of HSD11B1 in human epithelial cells and show that p38 MAPK-induced phosphorylation of C/EBPβ at Thr235 is critical in this.

Changing glucocorticoid action: 11β-hydroxysteroid dehydrogenase type 1 in acute and chronic inflammation

Since the discovery of cortisone in the 1940s and its early success in treatment of rheumatoid arthritis, glucocorticoids have remained the mainstay of anti-inflammatory therapies. However, cortisone itself is intrinsically inert. To be effective, it requires conversion to cortisol, the active glucocorticoid, by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Despite the identification of 11β-HSD in liver in 1953 (which we now know to be 11β-HSD1), its physiological role has been little explored until recently. Over the past decade, however, it has become apparent that 11β-HSD1 plays an important role in shaping endogenous glucocorticoid action. Acute inflammation is more severe with 11β-HSD1-deficiency or inhibition, yet in some inflammatory settings such as obesity or diabetes, 11β-HSD1-deficiency/inhibition is beneficial, reducing inflammation. Current evidence suggests both beneficial and detrimental effects may result from 11β-HSD1 inhibition in chronic inflammatory disease. Here we review recent evidence pertaining to the role of 11β-HSD1 in inflammation. This article is part of a Special Issue entitled 'CSR 2013'.

11β-Hydroxysteroid dehydrogenase 1 inhibition attenuates collagen-induced arthritis

11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1) plays an important role in inflammation. However, the role of 11β-HSD1 in rheumatoid arthritis (RA) remains unknown. The purpose of this study was to evaluate the therapeutic effects of a selective 11β-HSD1 inhibitor BVT-2733 in collagen-induced arthritis (CIA) and its underlying mechanisms. CIA mice were treated with BVT-2733 (100 mg/kg, orally) or vehicle twice daily for 2 weeks. Arthritis score and joint histology were investigated. The levels of pro-inflammatory cytokines as well as anti-type II collagen antibody (anti-CII) were detected by ELISA. Western blot analysis was used to assess the activation of NF-κB and NLRP1 inflammasome in joint tissues and in human RA synovial cells. BVT-2733 treatment attenuated the arthritis severity and anti-CII level in CIA mice. BVT-2733 also decreased the levels of serum TNF-α, IL-1β, IL-6 and IL-17. BVT-2733 treatment also significantly reduced synovial inflammation and joint destruction. NF-κB activation and NLRP1 inflammasome assembly were also inhibited in arthritic joints and human RA synovial cells. In conclusion, BVT-2733 exhibits an anti-inflammatory effect on CIA. This protective effect is, at least partly, mediated by inhibition of the NF-κB and NLRP1 inflammasome signaling pathways. 11β-HSD1 inhibition may represent a potential therapeutic target for RA patients.

Stable conditional expression and effect of C/ebpβ-LIP in adipocytes using the pSLIK system

Murine 3T3-L1 adipocytes are widely used as a cellular model of obesity. However, whereas transfection of 3T3-L1 preadipocytes is straightforward, ectopic gene expression in mature 3T3-L1 adipocytes has proved challenging. Here, we used the pSLIK vector system to generate stable doxycycline-inducible expression of the liver-enriched inhibitor protein isoform of CCAAT/enhancer binding protein β (C/ebpβ (Cebpb)) (C/EBPβ-LIP) in fully differentiated 3T3-L1 adipocytes. Because overexpression of C/ebpβ-LIP impairs adipocyte differentiation, the C/ebpβ-LIP construct was first integrated in 3T3-L1 preadipocytes but expression was induced only when adipocytes were fully differentiated. Increased C/EBPβ-LIP in mature adipocytes down-regulated C/ebpβ target genes including 11β-hydroxysteroid dehydrogenase type 1, phosphoenolpyruvate carboxykinase and fatty acid binding protein 4 but had no effect on asparagine synthetase, demonstrating that transcriptional down-regulation by C/ebpβ-LIP in 3T3-L1 adipocytes is not a general effect. Importantly, these genes were modulated in a similar manner in adipose tissue of mice with genetically increased C/ebpβ-LIP levels. The use of the pSLIK system to conditionally express transgenes in 3T3-L1 cells could be a valuable tool to dissect adipocyte physiology.

Attenuation of inhibitory prostaglandin E2 signaling in human lung fibroblasts is mediated by phosphodiesterase 4

The etiology of chronic obstructive pulmonary disease (COPD) is complex and involves an aberrant inflammatory response. Prostaglandin (PG)E2 is elevated in COPD, is a key modulator of lung fibroblast functions, and may influence COPD progression. Most studies evaluating the effects of PGE2 on lung fibroblasts have used acute exposures. The current study evaluated whether longer-term exposure would induce attenuation of PGE2 signaling as part of an autoregulatory pathway. Human fetal lung fibroblasts were pretreated with PGE2 for 24 hours, and migration and cAMP accumulation in response to acute stimulation with PGE2 were assessed. Fibroblasts from adults with and without COPD were pretreated, and migration was assessed. PGE2 pretreatment attenuated subsequent PGE2-mediated inhibition of chemotaxis and cAMP stimulation. This attenuation was predominantly due to an increase in phosphodiesterase (PDE)4-mediated degradation of cAMP rather than to decreased activation of PGE2 receptors (receptor desensitization). Albuterol- and iloprost-mediated signaling were also attenuated after PGE2 pretreatment, suggesting that activation of PDE4 was able to broadly modulate multiple cAMP-coupled pathways. Lung fibroblasts from adult control subjects pretreated with PGE2 also developed attenuation of PGE2-mediated inhibition of chemotaxis. In contrast, fibroblasts obtained from patients with COPD maintained inhibitory PGE2 signaling after PGE2 pretreatment. These data identify a PDE4-mediated attenuation of PGE2 inhibitory signaling in normal fibroblasts that appears to be altered in COPD fibroblasts. These alterations may contribute to COPD pathogenesis and could provide novel therapeutic targets.

Regulation of adipocyte 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) by CCAAT/enhancer-binding protein (C/EBP) β isoforms, LIP and LAP

11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyses intracellular regeneration of active glucocorticoids, notably in liver and adipose tissue. 11β-HSD1 is increased selectively in adipose tissue in human obesity, a change implicated in the pathogenesis of metabolic syndrome. With high fat (HF)-feeding, adipose tissue 11β-HSD1 is down-regulated in mice, plausibly to counteract metabolic disease. Transcription of 11β-HSD1 is directly regulated by members of the CCAAT/enhancer binding protein (C/EBP) family. Here we show that while total C/EBPβ in adipose tissue is unaltered by HF diet, the ratio of the C/EBPβ isoforms liver-enriched inhibitor protein (LIP) and liver-enriched activator protein (LAP) (C/EBPβ-LIP:LAP) is increased in subcutaneous adipose. This may cause changes in 11β-HSD1 expression since genetically modified C/EBPβ^(+/L) mice, with increased C/EBPβ-LIP:LAP ratio, have decreased subcutaneous adipose 11β-HSD1 mRNA levels, whereas C/EBPβ^ΔuORF mice, with decreased C/EBPβ-LIP:LAP ratio, show increased subcutaneous adipose 11β-HSD1. C/EBPβ-LIP:LAP ratio is regulated by endoplasmic reticulum (ER) stress and mTOR signalling, both of which are altered in obesity. In 3T3-L1 adipocytes, 11β-HSD1 mRNA levels were down-regulated following induction of ER stress by tunicamycin but were up-regulated following inhibition of mTOR by rapamycin. These data point to a central role for C/EBPβ and its processing to LIP and LAP in transcriptional regulation of 11β-HSD1 in adipose tissue. Down-regulation of 11β-HSD1 by increased C/EBPβ-LIP:LAP in adipocytes may be part of a nutrient-sensing mechanism counteracting nutritional stress generated by HF diet.

The emerging role of C/EBPs in glucocorticoid signaling: lessons from the lung

Glucocorticoids (GCs) have been successfully used in the treatment of inflammatory diseases for decades. However, there is a relative GC resistance in several inflammatory lung disorders, such as chronic obstructive pulmonary disease (COPD), but still the mechanism(s) behind this unresponsiveness remains unknown. Interaction between transcription factors and the GC receptor contribute to GC effects but may also provide mechanisms explaining steroid resistance. CCAAT/enhancer-binding protein (C/EBP) transcription factors are important regulators of pulmonary gene expression and have been implicated in inflammatory lung diseases such as asthma, pulmonary fibrosis, cystic fibrosis, sarcoidosis, and COPD. In addition, several studies have indicated a role for C/EBPs in mediating GC effects. In this review, we discuss the different mechanisms of GC action as well as the function of the lung-enriched members of the C/EBP transcription factor family. We also summarize the current knowledge of the role of C/EBP transcription factors in mediating the effects of GCs, with emphasis on pulmonary effects, and their potential role in mediating GC resistance.

[Progress of transcription factor CCAAT enhancer binding protein β]

CCAAT enhancer binding protein β (C/EBP β) belongs to CCAAT enhancer binding protein (C/EBP) family, which is a subfamily of basic leucine zipper (bZIP) protein family. C/EBP family plays important roles in many processes such as cell differentiation, metabolism, and development. In this paper, the structure, expression regulation, and function of C/EBP β were reviewed.

The anti-inflammatory and immunosuppressive effects of glucocorticoids, recent developments and mechanistic insights

Since the discovery of glucocorticoids in the 1940s and the recognition of their anti-inflammatory effects, they have been amongst the most widely used and effective treatments to control inflammatory and autoimmune diseases. However, their clinical efficacy is compromised by the metabolic effects of long-term treatment, which include osteoporosis, hypertension, dyslipidaemia and insulin resistance/type 2 diabetes mellitus. In recent years, a great deal of effort has been invested in identifying compounds that separate the beneficial anti-inflammatory effects from the adverse metabolic effects of glucocorticoids, with limited effect. It is clear that for these efforts to be effective, a greater understanding is required of the mechanisms by which glucocorticoids exert their anti-inflammatory and immunosuppressive actions. Recent research is shedding new light on some of these mechanisms and has produced some surprising new findings. Some of these recent developments are reviewed here.