The growth plate sparing effects of the selective glucocorticoid receptor modulator, AL-438

A novel link between chronic inflammation and humanin regulation in children

Objective

Children with inflammatory bowel disease (IBD) often suffer from poor bone growth and impaired bone health. Humanin is a cytoprotective factor expressed in bone and other tissues and we hypothesized that humanin levels are suppressed in conditions of chronic inflammation. To address this, humanin levels were analyzed in serum samples from IBD patients and in ex vivo cultured human growth plate tissue specimens exposed to IBD serum or TNF alone.

Methods

Humanin levels were measured by ELISA in serum from 40 children with IBD and 40 age-matched healthy controls. Growth plate specimens obtained from children undergoing epiphysiodesis surgery were cultured ex vivo for 48 hours while being exposed to IBD serum or TNF alone. The growth plate samples were then processed for immunohistochemistry staining for humanin, PCNA, SOX9 and TRAF2 expression. Dose-response effect of TNF was studied in the human chondrocytic cell line HCS-2/8. Ex vivo cultured fetal rat metatarsal bones were used to investigate the therapeutic effect of humanin.

Results

Serum humanin levels were significantly decreased in children with IBD compared to healthy controls. When human growth plate specimens were cultured with IBD serum, humanin expression was significantly suppressed in the growth plate cartilage. When cultured with TNF alone, the expression of humanin, PCNA, SOX9, and TRAF2 were all significantly decreased in the growth plate cartilage. Interestingly, treatment with the humanin analog HNG prevented TNF-induced bone growth impairment in cultured metatarsal bones.

Conclusion

Our data showing suppressed serum humanin levels in IBD children with poor bone health provides the first evidence for a potential link between chronic inflammation and humanin regulation. Such a link is further supported by the novel finding that serum from IBD patients suppressed humanin expression in ex vivo cultured human growth plates.

Discovery and Optimization of N-Acyl-6-sulfonamide-tetrahydroquinoline Derivatives as Novel Non-Steroidal Selective Glucocorticoid Receptor Modulators

Selective glucocorticoid receptor modulators (SGRMs), which can dissociate the transactivation from the transrepression of the glucocorticoid receptor (GR), are regarded as very promising therapeutics for inflammatory and autoimmune diseases. We previously discovered a SGRM HP-19 based on the passive antagonistic conformation of GR and bioassays. In this study, we further analyzed the dynamic changes of the passive antagonistic state upon the binding of HP-19 and designed and synthesized 62 N-acyl-6-sulfonamide-tetrahydroquinoline derivatives by structural optimization of HP-19. Therein, compound B53 exhibits the best transrepression activity (IC_{50 NF-κB} = 0.009 ± 0.001 μM) comparable with dexamethasone (IC_{50 NF-κB} = 0.005 ± 0.001 μM) and no transactivation activity. B53 can efficiently reduce the expression of inflammatory factors IL-6, IL-1β, TNF-α, and so on and makes a milder adverse effect and is highly specific to GR. Furthermore, B53 is able to significantly relieve dermatitis on a mouse model via oral drug intervention.

A glucocorticoid-receptor agonist ameliorates bleomycin-induced alveolar simplification in newborn rats

BACKGROUND

Glucocorticoids (GCs) are highly effective yet problematic agents against bronchopulmonary dysplasia (BPD). The dimeric trans-activation of GCs induces unfavorable effects, while monomeric trans-repression suppresses inflammation-related genes. Recently, non-steroidal-selective glucocorticoid-receptor agonists and modulators (SEGRAMs) with only the trans-repressive action have been designed.

METHODS

Using a bleomycin (Bleo)-induced alveolar simplification newborn rat model (recapitulating arrested alveolarization during BPD), we evaluated the therapeutic effects of compound-A (CpdA), a SEGRAM. Sprague-Dawley rats were administered Bleo from postnatal day (PD) 0 to 10 and treated with dexamethasone (Dex) or CpdA from PD 0 to 13. The morphological changes and mRNA expression of inflammatory mediators, including interleukin (IL)-1β, C-X-C motif chemokine ligand 1 (CXCL1), and C-C motif chemokine 2 (CCL2) were investigated.

RESULTS

Similar to the effects of Dex, CpdA exerted protective effects on morphological derangements and inhibited macrophage infiltration and production of pro-inflammatory mediators in Bleo-treated animals. The effects of CpdA were probably mediated by GC receptor (GR)-dependent trans-repression, because unlike the Dex-treated group, anti-inflammatory genes specifically induced by GR-dependent trans-activation (such as "glucocorticoid-induced leucine zipper, GILZ") were not upregulated.

CONCLUSIONS

CpdA improved lung inflammation, inhibited the arrest of alveolar maturation, and restored histological and biochemical changes in a Bleo-induced alveolar simplification model.

IMPACT

SEGRAMs have attracted widespread attention because they are expected to not exhibit unfavorable effects of GCs. Compound A, one of the SEGRAMs, improved lung morphometric changes and decreased lung inflammation in a bleomycin-induced arrested alveolarization, a newborn rat model representing one of the main features of BPD pathology. Compound A did not elicit bleomycin-induced poor weight gain, in contrast to dexamethasone treatment. SEGRAMs, including compound A, may be promising candidates for the therapy of BPD with less adverse effects compared with GCs.

Discovery of a novel nonsteroidal selective glucocorticoid receptor modulator by virtual screening and bioassays

Synthetic glucocorticoids (GCs) have been widely used in the treatment of a broad range of inflammatory diseases, but their clinic use is limited by undesired side effects such as metabolic disorders, osteoporosis, skin and muscle atrophies, mood disorders and hypothalamic-pituitary-adrenal (HPA) axis suppression. Selective glucocorticoid receptor modulators (SGRMs) are expected to have promising anti-inflammatory efficacy but with fewer side effects caused by GCs. Here, we reported HT-15, a prospective SGRM discovered by structure-based virtual screening (VS) and bioassays. HT-15 can selectively act on the NF-κB/AP1-mediated transrepression function of glucocorticoid receptor (GR) and repress the expression of pro-inflammation cytokines (i.e., IL-1β, IL-6, COX-2, and CCL-2) as effectively as dexamethasone (Dex). Compared with Dex, HT-15 shows less transactivation potency that is associated with the main adverse effects of synthetic GCs, and no cross activities with other nuclear receptors. Furthermore, HT-15 exhibits very weak inhibition on the ratio of OPG/RANKL. Therefore, it may reduce the side effects induced by normal GCs. The bioactive compound HT-15 can serve as a starting point for the development of novel therapeutics for high dose or long-term anti-inflammatory treatment.

Corticosteroid resistance in asthma: Cellular and molecular mechanisms

Inhaled glucocorticoids (GCs) are drugs widely used as treatment for asthma patients. They prevent the recruitment and activation of lung immune and inflammatory cells and, moreover, have profound effects on airway structural cells to reverse the effects of disease on airway inflammation. GCs bind to a specific receptor, the glucocorticoid receptor (GR), which is a member of the nuclear receptor superfamily and modulates pro- and anti-inflammatory gene transcription through a number of distinct and complementary mechanisms. Targets genes include many pro-inflammatory mediators such as chemokines, cytokines, growth factors and their receptors. Inhaled GCs are very effective for most asthma patients with little, if any, systemic side effects depending upon the dose. However, some patients show poor asthma control even after the administration of high doses of topical or even systemic GCs. Several mechanisms relating to inflammation have been considered to be responsible for the onset of the relative GC resistance observed in these patients. In these patients, the side-effect profile of GCs prevent continued use of high doses and new drugs are needed. Targeting the defective pathways associated with GC function in these patients may also reactivate GC responsiveness.

To Predict Anti-Inflammatory and Immunomodulatory Targets of Guizhi Decoction in Treating Asthma Based on Network Pharmacology, Molecular Docking, and Experimental Validation

Asthma, characterized by the continuous inflammatory response caused by a variety of immune cells, is one of the most common chronic respiratory diseases worldwide. Relevant clinical trials proved that the traditional Chinese medicine formula Guizhi Decoction (GZD) had multitarget and multichannel functions, which might be an effective drug for asthma. However, the effective ingredients and mechanisms of GZD against asthma are still unclear. Therefore, network pharmacology, molecular docking, and cell experiments were performed to explore the antiasthma effects and potential mechanisms of GZD. First, we applied the TCMSP database and literature to obtain the bioactivated ingredients in GZD. SwissTargetPrediction, TCMSP, GeneCards, OMIM, PharmGkb, TTD, DrugBank, and STRING database were used to get core genes. In addition, the key pathways were analyzed by the DAVID database. Molecular docking was used to predict whether the important components could act on the core target proteins directly. Finally, qPCR was carried out to verify the network pharmacology results and the possible mechanisms of GZD in the treatment of asthma. We collected 134 active ingredients in GZD, 959 drug targets, and 3223 disease targets. 431 intersection genes were screened for subsequent analysis. Through GO and KEGG analyses, enriched pathways related to inflammation and immune regulation were presented. Through the qPCR method to verify the role of essential genes, we found that GZD had an excellent anti-inflammatory effect. Direct or indirect inhibition of MAPK and NF-κB pathways might be one of the crucial mechanisms of GZD against asthma. GZD might be a promising potential drug for the treatment of asthma. This article provided a reference for the clinical application of GZD.

A General Introduction to Glucocorticoid Biology

Glucocorticoids (GCs) are steroid hormones widely used for the treatment of inflammation, autoimmune diseases, and cancer. To exert their broad physiological and therapeutic effects, GCs bind to the GC receptor (GR) which belongs to the nuclear receptor superfamily of transcription factors. Despite their success, GCs are hindered by the occurrence of side effects and glucocorticoid resistance (GCR). Increased knowledge on GC and GR biology together with a better understanding of the molecular mechanisms underlying the GC side effects and GCR are necessary for improved GC therapy development. We here provide a general overview on the current insights in GC biology with a focus on GC synthesis, regulation and physiology, role in inflammation inhibition, and on GR function and plasticity. Furthermore, novel and selective therapeutic strategies are proposed based on recently recognized distinct molecular mechanisms of the GR. We will explain the SEDIGRAM concept, which was launched based on our research results.

The Ex Vivo Organ Culture of Bone

The ex vivo organ culture of bone provides many of the advantages of both the whole organism and isolated cell strategies and can deliver valuable insight into the network of processes and activities that are fundamental to bone and cartilage biology. Through maintaining the bone and/or cartilage cells in their native environment, this model system provides the investigator with a powerful experimental protocol to address specific facets of skeletal growth and development. In this chapter, we outline the basic protocols and possible readouts of organ culture models to replicate; (a) linear bone growth (murine metatarsal culture model), (b) bone and cartilage metabolism (murine femoral head culture model), (c) bone response to mechanical stimulation (bovine trabecular core culture model), and (d) bone resorption and formation (murine calvaria culture model).

Animal models to explore the effects of glucocorticoids on skeletal growth and structure

Glucocorticoids (GCs) are effective for the treatment of many chronic conditions, but their use is associated with frequent and wide-ranging adverse effects including osteoporosis and growth retardation. The mechanisms that underlie the undesirable effects of GCs on skeletal development are unclear, and there is no proven effective treatment to combat them. An in vivo model that investigates the development and progression of GC-induced changes in bone is, therefore, important and a well-characterized pre-clinical model is vital for the evaluation of new interventions. Currently, there is no established animal model to investigate GC effects on skeletal development and there are pros and cons to consider with the different protocols used to induce osteoporosis and growth retardation. This review will summarize the literature and highlight the models and techniques employed in experimental studies to date.

Culture of Murine Embryonic Metatarsals: A Physiological Model of Endochondral Ossification

The fundamental process of endochondral ossification is under tight regulation in the healthy individual so as to prevent disturbed development and/or longitudinal bone growth. As such, it is imperative that we further our understanding of the underpinning molecular mechanisms involved in such disorders so as to provide advances towards human and animal patient benefit. The mouse metatarsal organ explant culture is a highly physiological ex vivo model for studying endochondral ossification and bone growth as the growth rate of the bones in culture mimic that observed in vivo. Uniquely, the metatarsal organ culture allows the examination of chondrocytes in different phases of chondrogenesis and maintains cell-cell and cell-matrix interactions, therefore providing conditions closer to the in vivo situation than cells in monolayer or 3D culture. This protocol describes in detail the intricate dissection of embryonic metatarsals from the hind limb of E15 murine embryos and the subsequent analyses that can be performed in order to examine endochondral ossification and longitudinal bone growth.

Growth and the Growth Hormone-Insulin Like Growth Factor 1 Axis in Children With Chronic Inflammation: Current Evidence, Gaps in Knowledge, and Future Directions

Growth failure is frequently encountered in children with chronic inflammatory conditions like juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis. Delayed puberty and attenuated pubertal growth spurt are often seen during adolescence. The underlying inflammatory state mediated by proinflammatory cytokines, prolonged use of glucocorticoid, and suboptimal nutrition contribute to growth failure and pubertal abnormalities. These factors can impair growth by their effects on the GH-IGF axis and also directly at the level of the growth plate via alterations in chondrogenesis and local growth factor signaling. Recent studies on the impact of cytokines and glucocorticoid on the growth plate further advanced our understanding of growth failure in chronic disease and provided a biological rationale of growth promotion. Targeting cytokines using biological therapy may lead to improvement of growth in some of these children, but approximately one-third continue to grow slowly. There is increasing evidence that the use of relatively high-dose recombinant human GH may lead to partial catch-up growth in chronic inflammatory conditions, although long-term follow-up data are currently limited. In this review, we comprehensively review the growth abnormalities in children with juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis, systemic abnormalities of the GH-IGF axis, and growth plate perturbations. We also systematically reviewed all the current published studies of recombinant human GH in these conditions and discussed the role of recombinant human IGF-1.

The Functional co-operativity of Tissue-Nonspecific Alkaline Phosphatase (TNAP) and PHOSPHO1 during initiation of Skeletal Mineralization

Phosphatases are recognised to have important functions in the initiation of skeletal mineralization. Tissue-nonspecific alkaline phosphatase (TNAP) and PHOSPHO1 are indispensable for bone and cartilage mineralization but their functional relationship in the mineralization process remains unclear. In this study, we have used osteoblast and ex-vivo metatarsal cultures to obtain biochemical evidence for co-operativity and cross-talk between PHOSPHO1 and TNAP in the initiation of mineralization. Clones 14 and 24 of the MC3T3-E1 cell line were used in the initial studies. Clone 14 cells expressed high levels of PHOSPHO1 and low levels of TNAP and in the presence of β-glycerol phosphate (BGP) or phosphocholine (P-Cho) as substrates and they mineralized their matrix strongly. In contrast clone 24 cells expressed high levels of TNAP and low levels of PHOSPHO1 and mineralized their matrix poorly. Lentiviral Phospho1 overexpression in clone 24 cells resulted in higher PHOSPHO1 and TNAP protein expression and increased levels of matrix mineralization. To uncouple the roles of PHOSPHO1 and TNAP in promoting matrix mineralization we used PHOSPHO1 (MLS-0263839) and TNAP (MLS-0038949) specific inhibitors, which individually reduced mineralization levels of Phospho1 overexpressing C24 cells, whereas the simultaneous addition of both inhibitors essentially abolished matrix mineralization (85 %; P<0.001). Using metatarsals from E15 mice as a physiological ex vivo model of mineralization, the response to both TNAP and PHOSPHO1 inhibitors appeared to be substrate dependent. Nevertheless, in the presence of BGP, mineralization was reduced by the TNAP inhibitor alone and almost completely eliminated by the co-incubation of both inhibitors. These data suggest critical non-redundant roles for PHOSPHO1 and TNAP during the initiation of osteoblast and chondrocyte mineralization.

Selective glucocorticoid receptor modulation: New directions with non-steroidal scaffolds

Glucocorticoids remain the frontline treatment for inflammatory disorders, yet represent a double-edged sword with beneficial therapeutic actions alongside adverse effects, mainly in metabolic regulation. Considerable efforts were made to improve this balance by attempting to amplify therapeutic beneficial anti-inflammatory actions and to minimize adverse metabolic actions. Most attention has focused on the development of novel compounds favoring the transrepressing actions of the glucocorticoid receptor, assumed to be important for anti-inflammatory actions, over the transactivating actions, assumed to underpin the undesirable actions. These compounds are classified as selective glucocorticoid receptor agonists (SEGRAs) or selective glucocorticoid receptor modulators (SEGRMs). The latter class is able to modulate the activity of a GR agonist and/or may not classically bind the glucocorticoid receptor ligand-binding pocket. SEGRAs and SEGRMs are collectively denominated SEGRAMs (selective glucocorticoid receptor agonists and modulators). Although this transrepression vs transactivation concept proved to be too simplistic, the developed SEGRAMs were helpful in elucidating various molecular actions of the glucocorticoid receptor, but have also raised many novel questions. We discuss lessons learned from recent mechanistic studies of selective glucocorticoid receptor modulators. This is approached by analyzing recent experimental insights in comparison with knowledge obtained using mutant GR research, thus clarifying the current view on the SEGRAM field. These insights also contribute to our understanding of the processes controlling glucocorticoid-mediated side effects as well as glucocorticoid resistance. Our perspective on non-steroidal SEGRAs and SEGRMs considers remaining opportunities to address research gaps in order to harness the potential for more safe and effective glucocorticoid receptor therapies.

Targeting glucocorticoid side effects: selective glucocorticoid receptor modulator or glucocorticoid-induced leucine zipper? A perspective

Glucocorticoids (GCs) are steroid hormones that are necessary for life and important in health and disease. They regulate crucial homeostatic functions, including metabolism, cell growth, and development. Although GCs are regulated by circadian rhythm, increased production is associated with stress. Synthetic GCs are a valuable resource for anti-inflammatory and immunosuppressive therapy. Natural and synthetic GCs transduce signals mainly through GC receptor (GR) activation. Extensive research has explored the downstream targets of the GR, and optimization of GC therapy has required collaborative efforts. One highly promising approach involves new dissociative GR modulators. Because transrepression and transactivation of GR genes induce beneficial and adverse effects, respectively, this approach favors transrepression. Another approach involves the use of GC-dependent genes to generate proteins to mediate therapeutic GC effects. In a third approach, drug discovery is used to identify agents that selectively target GR isoforms to obtain differential gene transcription and effects. In this review, we focus on mechanisms of GR function compatible with the use of dissociative drugs. We highlight GC-induced leucine zipper (GILZ), a gene cloned in our laboratory, as a mediator of GC anti-inflammatory and immunosuppressive effects, to outline our perspective on the future of GC therapy.

Recent research on the growth plate: Impact of inflammatory cytokines on longitudinal bone growth

Children with inflammatory diseases usually display abnormal growth patterns as well as delayed puberty. This is a result of several factors related to the disease itself, such as malnutrition, hypercortisolism, and elevated levels of pro-inflammatory cytokines. These factors in combination with glucocorticoid treatment contribute to growth retardation during chronic inflammation by systemically affecting the major regulator of growth, the GH/IGF1 axis. However, recent studies have also shown evidence of a direct effect of these factors at the growth plate level. In conditions of chronic inflammation, pro-inflammatory cytokines are upregulated and released into the circulation. The most abundant of these, tumor necrosis factor α, interleukin 1β (IL1β), and IL6, are all known to directly act on growth plate cartilage to induce apoptosis and thereby suppress bone growth. Both clinical and experimental studies have shown that growth retardation can partly be rescued when these cytokines are blocked. Therefore, therapy modulating the local actions of these cytokines may be effective for preventing growth failure in patients with chronic inflammatory disorders. In this review, we report the current knowledge of inflammatory cytokines and their role in regulating bone growth.

Differential response of chondrocytes and chondrogenic-induced mesenchymal stem cells to C1-OH tributanoylated N-acetylhexosamines

Articular cartilage has a limited ability to self-repair because of its avascular nature and the low mitotic activity of the residing chondrocytes. There remains a significant need to develop therapeutic strategies to increase the regenerative capacity of cells that could repair cartilage. Multiple cell types, including chondrocytes and mesenchymal stem cells, have roles in articular cartilage regeneration. In this study, we evaluated a platform technology of multiple functionalized hexosamines, namely 3,4,6-O-tributanoylated-N-acetylgalactosamine (3,4,6-O-Bu₃GalNAc), 3,4,6-O-tributanoylated-N-acetylmannosamine (3,4,6-O-Bu₃ManNAc) and 3,4,6-O-Bu₃GlcNAc, with the potential ability to reduce NFκB activity. Exposure of IL-1β-stimulated chondrocytes to the hexosamine analogs resulted in increased expression of ECM molecules and a corresponding improvement in cartilage-specific ECM accumulation. The greatest ECM accumulation was observed with 3,4,6-O-Bu₃GalNAc. In contrast, mesenchymal stem cells (MSCs) exposed to 3,4,6-O-Bu₃GalNAc exhibited a dose dependent decrease in chondrogenic differentation as indicated by decreased ECM accumulation. These studies established the disease modification potential of a hexosamine analog platform on IL-1β-stimulated chondrocytes. We determined that the modified hexosamine with the greatest potential for disease modification is 3,4,6-O-Bu₃GalNAc. This effect was distinctly different with 3,4,6-O-Bu₃GalNAc exposure to chondrogenic-induced MSCs, where a decrease in ECM accumulation and differentiation was observed. Furthermore, these studies suggest that NFκB pathway plays a complex role cartilage repair.

Noncanonical mechanisms to regulate nuclear receptor signaling

Nuclear receptor (NR)-targeted therapies comprise a large class of clinically employed drugs. A number of drugs currently being used against this protein class were designed as structural analogs of the endogenous ligand of these receptors. In recent years, there has been significant interest in developing newer strategies to target NRs, especially those that rely on mechanistic pathways of NR function. Prominent among these are noncanonical means of targeting NRs, which include selective NR modulation, NR coactivator interaction inhibition, inhibition of NR DNA binding, modulation of NR cellular localization, modulation of NR ligand biosynthesis and downregulation of NR levels in target tissues. This article reviews each of these promising emerging strategies for NR drug development and highlights some of most significant successes achieved in using them.

Selective glucocorticoid receptor modulation maintains bone mineral density in mice

Glucocorticoids (GCs) are potent anti-inflammatory drugs, but their use is limited by their adverse effects on the skeleton. Compound A (CpdA) is a novel GC receptor modulator with the potential for an improved risk/benefit profile. We tested the effects of CpdA on bone in a mouse model of GC-induced bone loss. Bone loss was induced in FVB/N mice by implanting slow-release pellets containing either vehicle, prednisolone (PRED) (3.5 mg), or CpdA (3.5 mg). After 4 weeks, mice were killed to examine the effects on the skeleton using quantitative computed tomography, bone histomorphometry, serum markers of bone turnover, and gene expression analysis. To assess the underlying mechanisms, in vitro studies were performed with human bone marrow stromal cells (BMSCs) and murine osteocyte-like cells (MLO-Y4 cells). PRED reduced the total and trabecular bone density in the femur by 9% and 24% and in the spine by 11% and 20%, respectively, whereas CpdA did not influence these parameters. Histomorphometry confirmed these results and further showed that the mineral apposition rate was decreased by PRED whereas the number of osteoclasts was increased. Decreased bone formation was paralleled by a decline in serum procollagen type 1 N-terminal peptide (P1NP), reduced skeletal expression of osteoblast markers, and increased serum levels of the osteoblast inhibitor dickkopf-1 (DKK-1). In addition, serum CTX-1 and the skeletal receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG) ratio were increased by PRED. None of these effects were observed with CpdA. Consistent with the in vivo data, CpdA did not increase the RANKL/OPG ratio in MLO-Y4 cells or the expression of DKK-1 in bone tissue, BMSCs, and osteocytes. Finally, CpdA also failed to transactivate DKK-1 expression in bone tissue, BMSCs, and osteocytes. This study underlines the bone-sparing potential of CpdA and suggests that by preventing increases in the RANKL/OPG ratio or DKK-1 in osteoblast lineage cells, GC-induced bone loss may be ameliorated.

MEPE is a novel regulator of growth plate cartilage mineralization

Matrix extracellular phosphoglycoprotein (MEPE) belongs to the SIBLING protein family which play key roles in biomineralization. Although the growth plates of MEPE-overexpressing mice display severe morphological disruption, the expression and function of MEPE in growth plate matrix mineralization remains largely undefined. Here we show MEPE and its cleavage product, the acidic serine aspartate-rich MEPE-associated motif (ASARM) peptide, to be localised to the hypertrophic zone of the growth plate. We also demonstrate that the phosphorylated (p)ASARM peptide inhibits ATDC5 chondrocyte matrix mineralization. Stable MEPE-overexpressing ATDC5 cells also had significantly reduced matrix mineralization in comparison to the control cells. Interestingly, we show that the addition of the non-phosphorylated (np)ASARM peptide promoted mineralization in the ATDC5 cells. The peptides and the overexpression of MEPE did not affect the differentiation of the ATDC5 cells. For a more physiologically relevant model, we utilized the metatarsal organ culture model. We show the pASARM peptide to inhibit mineralization at two stages of development, as shown by histological and μCT analysis. Like in the ATDC5 cells, the peptides did not affect the differentiation of the metatarsals indicating that the effects seen on mineralization are direct, as is additionally confirmed by no change in alkaline phosphatase activity or mRNA expression. In the metatarsal organ cultures, the pASARM peptide also reduced endothelial cell markers and vascular endothelial growth factor mRNA expression. Taken together these results show MEPE to be an important regulator of growth plate chondrocyte matrix mineralization through its cleavage to an ASARM peptide.

Chondrogenic ATDC5 cells: an optimised model for rapid and physiological matrix mineralisation

The development of chondrogenic cell lines has led to major advances in the understanding of how chondrocyte differentiation is regulated, and has uncovered many signalling pathways and gene regulatory mechanisms required to maintain normal function. ATDC5 cells are a well established in vitro model of endochondral ossification; however, current methods are limited for mineralisation studies. In this study we demonstrate that culturing cells in the presence of ascorbic acid and 10 mM β-glycerophosphate (βGP) significantly increases the rate of extracellular matrix (ECM) synthesis and reduces the time required for mineral deposition to occur to 15 days of culture. Furthermore, the specific expression patterns of Col2a1 and Col10a1 are indicative of ATDC5 chondrogenic differentiation. Fourier transform-infrared spectroscopy analysis and transmission electron microscopy (TEM) showed that the mineral formed by ATDC5 cultures is similar to physiological hydroxyapatite. Additionally, we demonstrated that in cultures with βGP, the presence of alkaline phosphatase (ALP) is required for this mineralisation to occur, further indicating that chondrogenic differentiation is required for ECM mineralisation. Together, these results demonstrate that when cultured in the presence of ascorbic acid and 10 mM βGP, ATDC5 cells undergo chondrogenic differentiation and produce a physiological mineralised ECM from Day 15 of culture onwards. The rapid and novel method for ATDC5 culture described in this study is a major improvement compared with currently published methods and this will prove vital in the pursuit of underpinning the molecular mechanisms responsible for poor linear bone growth observed in a number of chronic diseases such as cystic fibrosis, chronic kidney disease, rheumatological conditions and inflammatory bowel disease.

Selective glucocorticoid receptor agonists for the treatment of inflammatory bowel disease: studies in mice with acute trinitrobenzene sulfonic acid colitis

Despite being a mainstay of inflammatory bowel disease (IBD) therapy, glucocorticoids (GCs) still carry significant risks with respect to unwanted side effects. Alternative drugs with a more favorable risk/benefit ratio than common GCs are thus highly desirable for the management of IBD. New and supposedly selective glucocorticoid receptor (GR) agonists (SEGRAs), with dissociated properties, have been described as promising candidates for circumventing therapeutic problems while still displaying full beneficial anti-inflammatory potency. Here, we report on compound A [CpdA; (2-((4-acetophenyl)-2-chloro-N-methyl)ethylammonium-chloride)] and N-(4-methyl-1-oxo-1H-2,3-benzoxazine-6-yl)-4-(2,3-dihydrobenzofuran-7-yl)-2-hydroxy-2-(trifluoromethyl)-4-methylpentanamide (ZK216348), two GR agonists for the treatment of experimental colitis. Their therapeutic and anti-inflammatory effects were tested in the acute trinitrobenzene sulfonic acid-mediated colitis model in mice against dexamethasone (Dex). In addition to their influence on immunological pathways, a set of possible side effects, including impact on glucose homeostasis, steroid resistance, and induction of apoptosis, was surveyed. Our results showed that, comparable with Dex, treatment with CpdA and ZK216348 reduced the severity of wasting disease, macroscopic and microscopic damage, and colonic inflammation. However, both SEGRAs exhibited no GC-associated diabetogenic effects, hypothalamic pituitary adrenal axis suppression, or development of glucocorticoid resistance. In addition, CpdA and ZK216348 showed fewer transactivating properties and successfully dampened T helper 1 immune response. Unlike ZK216348, the therapeutic benefit of CpdA was lost at higher doses because of toxic apoptotic effects. In conclusion, both SEGRAs acted as potent anti-inflammatory agents with a significantly improved profile compared with classic GCs. Although CpdA revealed a narrow therapeutic window, both GR agonists might be seen as a starting point for a future IBD treatment option.

Dissociation of osteogenic and immunological effects by the selective glucocorticoid receptor agonist, compound A, in human bone marrow stromal cells

Glucocorticoids (GCs) regulate various physiological processes, including bone remodeling. Whereas physiological amounts of GCs are required for proper human osteoblast differentiation, prolonged exposure to GCs leads to substantial bone loss in vivo predominantly by inhibiting osteoblast functions. Compound A (CpdA) is a novel GC receptor modulator with the potential of an improved benefit/risk profile. Here we tested the osteoimmunological effects of CpdA on primary human osteoblasts and their paracrine interactions with osteoclasts. To assess the antiinflammatory potential of CpdA in human bone marrow stromal cell (BMSC)-derived osteoblasts, cells were stimulated with lipopolysaccharide and cytokine expression was determined. Similar to dexamethasone (DEX), CpdA profoundly suppressed lipopolysaccharide-induced TNF-α (-63%), IL-1β (-38%), and IL-6 (-36%) (P < 0.05) mRNA levels. Of note, CpdA failed to induce osteogenic differentiation of BMSCs, whereas DEX and budesonide enhanced matrix mineralization an d increased runt-related transcription factor 2 and alkaline phosphatase mRNA levels up to 5-fold in a dose-dependent manner. Interestingly, each substance promoted cell proliferation by 7-10% and suppressed apoptosis by 25-30% at low concentrations and early differentiation stages, whereas high concentrations (1 μm) suppressed proliferation and stimulated apoptosis in mature osteoblasts. Finally, CpdA did not increase the receptor activator of nuclear factor-κB ligand to osteoprotegerin mRNA ratio as compared with DEX and did not stimulate the formation of osteoclasts in coculture with BMSCs. In summary, CpdA displays dissociated osteogenic and immunological effects in human BMSCs that are distinct from those of conventional GCs. Whether the specific osteoimmunological profile of CpdA translates into a relevant in vivo effect needs to be further explored.

Classic glucocorticoids versus non-steroidal glucocorticoid receptor modulators: survival of the fittest regulator of the immune system?

The search for novel glucocorticoid receptor (GR) modulators with similar anti-inflammatory properties as conventional steroids, but with a reduction in the number or severity of the side effects has been a long-standing goal, and still remains a challenge today. The quest for these so-called 'dissociated GR ligands' is mainly based on the hypothesis that the occurrence of undesirable side effects is mostly associated with GR-mediated transactivation, whereas transrepression of many pro-inflammatory genes (e.g. cytokines and enzymes involved in inflammatory processes) is more involved in GR-mediated anti-inflammatory effects. As glucocorticoids (GCs) can also enhance the transcription of anti-inflammatory genes, the GR-mediated activation-repression dissociation hypothesis has to be nuanced. However, an enhanced selectivity of GR-affected genes, while upholding the desired anti-inflammatory potential, is still believed to contribute to a more beneficial therapeutic profile with fewer side effects. The initial pharmacological focus on steroidal scaffolds as a basis to dissociate the functionalities of GR has, due to a lack of success, recently been shifted to a focus on non-steroidal ligands. The current work reviews recent advances on the characterization of a generation of novel non-steroidal GR ligands.

Assessment of Growth Disturbance in Japanese Children with IBD

In Japan, there is as yet no report on growth retardation in children with IBD. We therefore investigated the cause of growth retardation in Japanese children with IBD. We investigated the height, body weight, serum levels of albumin, IGF-I, CRP, and cytokines, and the amount of corticosteroid administered in children with Crohn's disease (CD, n = 15) and ulcerative colitis (UC, n = 18). Our results suggest that growth retardation is already present before the initial visit in children with CD, and chronic inflammation may be responsible this growth disturbance. Moreover, the amount of PSL used may contribute to growth retardation by decreasing the serum levels of IGF-I in children with IBD.

Selective Glucocorticoid Receptor modulators

The ancient two-faced Roman god Janus is often used as a metaphor to describe the characteristics of the Glucocorticoid Receptor (NR3C1), which exhibits both a beneficial side, that serves to halt inflammation, and a detrimental side responsible for undesirable effects. However, recent developments suggest that the Glucocorticoid Receptor has many more faces with the potential to express a range of different functionalities, depending on factors that include the tissue type, ligand type, receptor variants, cofactor surroundings and target gene promoters. This behavior of the receptor has made the development of safer ligands, that trigger the expression program of only a desirable subset of genes, a real challenge. Thus more knowledge-based fundamental research is needed to ensure the design and development of selective Glucocorticoid Receptor modulators capable of reaching the clinic. Recent advances in the characterization of novel selective Glucocorticoid Receptor modulators, specifically in the context of anti-inflammatory strategies, will be described in this review.

Crosstalk in inflammation: the interplay of glucocorticoid receptor-based mechanisms and kinases and phosphatases

Glucocorticoids (GCs) are steroidal ligands for the GC receptor (GR), which can function as a ligand-activated transcription factor. These steroidal ligands and derivatives thereof are the first line of treatment in a vast array of inflammatory diseases. However, due to the general surge of side effects associated with long-term use of GCs and the potential problem of GC resistance in some patients, the scientific world continues to search for a better understanding of the GC-mediated antiinflammatory mechanisms. The reversible phosphomodification of various mediators in the inflammatory process plays a key role in modulating and fine-tuning the sensitivity, longevity, and intensity of the inflammatory response. As such, the antiinflammatory GCs can modulate the activity and/or expression of various kinases and phosphatases, thus affecting the signaling efficacy toward the propagation of proinflammatory gene expression and proinflammatory gene mRNA stability. Conversely, phosphorylation of GR can affect GR ligand- and DNA-binding affinity, mobility, and cofactor recruitment, culminating in altered transactivation and transrepression capabilities of GR, and consequently leading to a modified antiinflammatory potential. Recently, new roles for kinases and phosphatases have been described in GR-based antiinflammatory mechanisms. Moreover, kinase inhibitors have become increasingly important as antiinflammatory tools, not only for research but also for therapeutic purposes. In light of these developments, we aim to illuminate the integrated interplay between GR signaling and its correlating kinases and phosphatases in the context of the clinically important combat of inflammation, giving attention to implications on GC-mediated side effects and therapy resistance.

Chondrocyte p21(WAF1/CIP1) expression is increased by dexamethasone but does not contribute to dexamethasone-induced growth retardation in vivo

It has been shown that cell cycle genes play an important role in the coordination of chondrocyte proliferation and differentiation. The inhibitory effects of glucocorticoids (GCs) on chondrocyte proliferation are consistent with GCs disrupting cell cycle progression and promoting cell cycle exit. Cyclin-dependent kinase inhibitors (CDKIs) force cells to exit the cell cycle and differentiate, and studies have shown that expression of the CDKI p21(CIP1/WAF1) is increased in terminally differentiated cells. In this study, p21 mRNA and protein expression was increased during chondrocyte differentiation and after exposure to dexamethasone (Dex, 10(-6 )M) in murine chondrogenic ATDC5 cells. In 4-week-old mice lacking a functional p21 gene, Dex caused a reduction in body weight compared to saline control null mice, but this was consistent with the reduction in body weight observed in Dex-treated wild-type littermates. In addition, p21 ablation had no effect on the reduction in width of the growth plate or reduced mineral apposition rate in Dex-treated mice. However, an alteration in growth rate and epiphyseal structure is evident when comparing p21(-/-) and wild-type mice. These findings suggest that p21 does not directly contribute to GC-induced growth retardation in vivo but is involved in the maintenance of the growth plate.

Genetic selection for fast growth generates bone architecture characterised by enhanced periosteal expansion and limited consolidation of the cortices but a diminution in the early responses to mechanical loading

Bone strength is, in part, dependent on a mechanical input that regulates the (re)modelling of skeletal elements to an appropriate size and architecture to resist fracture during habitual use. The rate of longitudinal bone growth in juveniles can also affect fracture incidence in adulthood, suggesting an influence of growth rate on later bone quality. We have compared the effects of fast and slow growth on bone strength and architecture in the tibiotarsi of embryonic and juvenile birds. The loading-related biochemical responses (intracellular G6PD activity and NO release) to mechanical load were also determined. Further, we have analysed the proliferation and differentiation characteristics of primary tibiotarsal osteoblasts from fast and slow-growing strains. We found that bones from chicks with divergent growth rates display equal resistance to applied loads, but weight-correction revealed that the bones from juvenile fast growth birds are weaker, with reduced stiffness and lower resistance to fracture. Primary osteoblasts from slow-growing juvenile birds proliferated more rapidly and had lower alkaline phosphatase activity. Bones from fast-growing embryonic chicks display rapid radial expansion and incomplete osteonal infilling but, importantly, lack mechanical responsiveness. These findings are further evidence that the ability to respond to mechanical inputs is crucial to adapt skeletal architecture to generate a functionally appropriate bone structure and that fast embryonic and juvenile growth rates may predispose bone to particular architectures with increased fragility in the adult.

Minireview: live and let die: molecular effects of glucocorticoids on bone cells

Glucocorticoids (GCs) are efficient drugs that are used to treat various immune-mediated diseases, but their long-term administration is associated with multiple metabolic side effects, including osteoporosis. Molecular analyses of the mechanisms exerted by the GC receptor have resulted in the development of GC receptor agonists that selectively repress or activate GC target genes. This review summarizes the cellular and molecular effects of GCs on bone cells and highlights the critical signaling pathways that may evolve into future therapeutic strategies.

Mechanisms regulating the susceptibility of hematopoietic malignancies to glucocorticoid-induced apoptosis

Glucocorticoids (GCs) are commonly used in the treatment of hematopoietic malignancies owing to their ability to induce apoptosis of these cancerous cells. Whereas some types of lymphoma and leukemia respond well to this drug, others are resistant. Also, GC-resistance gradually develops upon repeated treatments ultimately leading to refractory relapsed disease. Understanding the mechanisms regulating GC-induced apoptosis is therefore uttermost important for designing novel treatment strategies that overcome GC-resistance. This review discusses updated data describing the complex regulation of the cell's susceptibility to apoptosis triggered by GCs. We address both the genomic and nongenomic effects involved in promoting the apoptotic signals as well as the resistance mechanisms opposing these signals. Eventually we address potential strategies of clinical relevance that sensitize GC-resistant lymphoma and leukemia cells to this drug. The major target is the nongenomic signal transduction machinery where the interplay between protein kinases determines the cell fate. Shifting the balance of the kinome towards a state where Glycogen synthase kinase 3alpha (GSK3alpha) is kept active, favors an apoptotic response. Accumulating data show that it is possible to therapeutically modulate GC-resistance in patients, thereby improving the response to GC therapy.

Minireview: latest perspectives on antiinflammatory actions of glucocorticoids

Taking into consideration that glucocorticoid (GC) hormones have been used clinically for over half a century and that more than 20 yr have passed since the cloning of the GC receptor (GR), it is hard to imagine that novel aspects in the molecular mechanism by which GCs mediate their antiinflammatory actions are still being unveiled today. Partly, this is because almost on a daily basis, novel insights arise from parallel fields, e.g. nuclear receptor cofactor and chromatin regulation and their concomitant impact on gene transcription events, eventually leading to a revisitation or refinement of old hypotheses. On the other hand, it does remain striking and puzzling why GCs use different mechanisms in so many different cell types and on many different target genes to elicit an antiinflammatory effect. Meanwhile, the obvious question for the clinic remains: is the separation of GR functionalities through differential ligand design the strategy of choice to avoid most GC-mediated side effects? This minireview aims to highlight some of the latest findings on aspects of the antiinflammatory working mechanisms of GCs.

Nuclear receptor drug discovery

Nuclear receptors (NR) are ligand-activated transcription factors that regulate the activation of a variety of important target genes. There are 48 genes that encode NRs in the human genome, and these receptors now represent one of the most important targets for therapeutic drug development. Successful identification of selective NR modulators has transformed the NR drug discovery strategy from the designing of synthetic compounds that mimic the full function of cognate ligands to developing compounds that selectively modulate the functional activity of an NR in a manner that is distinct from the cognate ligands. Current efforts regarding NR drug development continue to focus on improving the function and tissue selectivity of drug candidates to reduce undesirable side effects. This review focuses on modulators of the glucocorticoid receptor (GR), androgen receptor (AR), and pregnane X receptor (PXR).

Dexamethasone-induced expression of the glucocorticoid response gene lipocalin 2 in chondrocytes

Glucocorticoids (GC) are commonly used anti-inflammatory drugs, but long-term use can result in marked growth retardation in children due to their actions on growth plate chondrocytes. To gain an insight into the mechanisms involved in GC-induced growth retardation, we performed Affymetrix microarray analysis of the murine chondrogenic cell line ATDC5, incubated with 10(-6) M dexamethasone (Dex) for 24 h. Downregulated genes included secreted frizzled-related protein and IGF-I, and upregulated genes included serum/GC-regulated kinase, connective-tissue growth factor, and lipocalin 2. Lipocalin 2 expression increased 40-fold after 24-h Dex treatment. Expression increased further after 48-h (75-fold) and 96-h (84-fold) Dex treatment, and this response was Dex concentration dependent. Lipocalin 2 was immunolocalized to both proliferating and hypertrophic growth plate zones, and its expression was increased by Dex in primary chondrocytes at 6 h (3-fold, P < 0.05). The lipocalin 2 response was blocked by the GC-receptor antagonist RU-486 and was increased further by the protein synthesis blocker cycloheximide. Proliferation in lipocalin 2-overexpressing cells was less than in control cells (49%, P < 0.05), and overexpression caused an increase in collagen type X expression (4-fold, P < 0.05). The effects of lipocalin 2 overexpression on chondrocyte proliferation (64%, P < 0.05) and collagen type X expression (8-fold, P < 0.05) were further exacerbated with the addition of 10(-6) M Dex. This synergistic effect may be explained by a further increase in lipocalin 2 expression with Dex treatment of transfected cells (45%, P < 0.05). These results suggest that lipocalin 2 may mediate Dex effects on chondrocytes and provides a potential novel mechanism for GC-induced growth retardation.

LGD-5552, an antiinflammatory glucocorticoid receptor ligand with reduced side effects, in vivo

Treatment of inflammation is often accomplished through the use of glucocorticoids. However, their use is limited by side effects. We have examined the activity of a novel glucocorticoid receptor ligand that binds the receptor efficiently and strongly represses inflammatory gene expression. This compound has potent antiinflammatory activity in vivo and represses the transcription of the inflammatory cytokine monocyte chemoattractant protein-1 and induces the antiinflammatory cytokine IL-10. The compound demonstrates differential gene regulation, compared with commonly prescribed glucocorticoids, effectively inducing some genes and repressing others in a manner different from the glucocorticoid prednisolone. The separation between the antiinflammatory effects of LGD-5552 and the side effects commonly associated with glucocorticoid treatment suggest that this molecule differs significantly from prednisolone and other steroids and may provide a safer therapeutic window for inflammatory conditions now commonly treated with steroidal glucocorticoids.

The 7th ESPE Growth Plate Working Group symposium--EUROGROP, June 27th 2007, Helsinki, Finland

Longitudinal bone growth occurs within the epiphyseal growth plate, a highly organized biological structure located at the distal ends of the long bones, via endochondral bone formation. This developmentally regulated process is finely tuned through the interaction of circulating systemic hormones and locally produced peptide growth factors, the net result of which is to trigger changes in gene expression by growth plate chondrocytes. These molecular events lead to carefully orchestrated alterations in chondrocyte size, extracellular matrix components, secreted enzymes, growth factors and receptor expression. These events finally result in calcification of the matrix, chondrocyte death, vascular invasion and the completion of endochondral bone formation. Although the past several years have seen important progress in the identification of numerous important factors, which, in a complex and integrated network, control longitudinal bone growth, many of the signaling pathways and their interactions in the growth plate remain poorly understood. The ESPE Growth Plate Working Group (EUROGROP) was established in 2000 with the aim to bring together both basic and clinical European research groups with an interest in the biology and pathology of the growth plate. The 7th EUROGROP Symposium was held as an official ESPE working group of the 46th ESPE Annual Meeting held in Helsinki, Finland, 2007. It enabled researchers from all parts of the world to discuss their ongoing studies and exchange technical information. The program consisted of three lectures and four original papers, all followed by attractive discussions. This report summarizes the data presented and provides some comments on each of the presentations.

Improving growth in children with inflammatory bowel disease

BACKGROUND

Growth in children with inflammatory bowel disease (IBD) is affected through a number of mechanisms; controlling disease activity and supporting poor nutritional status are paramount in these patients. Further understanding of the basic mechanisms by which cytokines influence growth will facilitate the development of therapeutic modalities to improve growth.

CONCLUSIONS

Clinical management that addresses growth and puberty in children with IBD should be a partnership between paediatric gastroenterologists and endocrinologists. Well-designed studies of growth-promoting hormonal treatment may answer questions regarding the efficacy and safety of treating growth retardation in the subgroup of patients who continue to fail to grow despite optimal management of their IBD.

Selective glucocorticoid receptor agonists (SEGRAs): novel ligands with an improved therapeutic index

Glucocorticoids are among the most successful therapies in the treatment of chronic inflammatory and autoimmune diseases. Their efficacy seems to be caused by the interference of the ligand-activated glucocorticoid receptor with many pro-inflammatory pathways via different mechanisms. The ubiquitous expression of the glucocorticoid receptor is a prerequisite for efficacy. Their main drawback, however, is due to their potential to induce adverse effects, in particular upon high dosage and prolonged usage. For the purpose reducing systemic side effects, topical glucocorticoids that act locally have been developed. Nevertheless, undesirable cutaneous effects such as skin atrophy persist from the use of topical glucocorticoids. Therefore a high medical need exists for drugs as effective as glucocorticoids but with a reduced side effect profile. Glucocorticoids function by binding to and activating the glucocorticoid receptor which positively or negatively regulates the expression of specific genes. Several experiments suggest that negative regulation of gene expression by the glucocorticoid receptor accounts for its anti-inflammatory action. This occurs through direct or indirect binding of the receptor to pro-inflammatory transcription factors that are already bound to their regulatory sites. The positive action of the receptor occurs through homodimer binding of the ligand receptor complex to discrete nucleotide sequences and this contributes to some of the adverse effects of the hormone. Glucocorticoid receptor ligands that promote the negative regulatory action of the receptor with reduced positive regulatory function should therefore show an improved therapeutic index. A complete separation of the positive from the negative regulatory activities of the receptor has so far not been possible because of the interdependent nature of the two regulatory processes. Nevertheless, recent understanding of the molecular mechanisms of the GR has triggered several drug discovery programs and these have led to the identification of dissociated GR-ligands. Such selective GR agonists (SEGRAs) are likely to enter clinical testing soon.