Cross-talk between glucocorticoid receptor and AP-1

Effect of chronic corticosterone administration on acute stress-mediated gene expression in the cortex and hippocampus of male mice

Corticosterone plays an important role in the stress response, physiological regulation, and development of stress-related psychiatric disorders. Although several studies have demonstrated that chronic corticosterone induces anxiety- or depressive-related behaviors in mice, it remains unclear whether chronic corticosterone administration affects gene expression in the brain during the stress response. This study investigated whether chronic corticosterone administration has a significant effect on stress-related gene expression in the brain. Therefore, mice were chronically treated with corticosterone in drinking water and gene expression was analyzed by quantitative PCR (qPCR). Moreover, restraint stress was acutely applied as a novel stressor in mice chronically treated with corticosterone in the cortex and hippocampus. We initially found that chronic corticosterone administration altered glucocorticoid signaling-mediated gene expression, such as FK506 binding protein 5 (Fkbp5) and glucocorticoid-inducible kinase 1 (Sgk1), in the cortex and hippocampus of mice. Next, we found that restraint stress exposure elevated Fkbp5 expression in the vehicle group; however, chronic corticosterone administration occluded further induction of Fkbp5 expression after restraint stress exposure. In addition, pro-inflammatory cytokines tumor necrosis factor α (Tnfa) and interleukin-1β (Il1b) mRNA expression in the cortex and hippocampus were remarkably enhanced by restraint stress in corticosterone-treated mice, but not in the vehicle group. Collectively, our results demonstrated that chronic corticosterone administration modulates glucocorticoid signaling and uncovered the robust induction of pro-inflammatory cytokines after restraint stress exposure in chronically corticosterone-treated mice. These mechanisms may be involved in the molecular basis for the onset of stress-related mental illnesses.

Glucocorticoid receptor action in prostate cancer: the role of transcription factor crosstalk

Prostate cancer is one of the most prevalent malignancies and is primarily driven by aberrant androgen receptor (AR) signaling. While AR-targeted therapies form the cornerstone of prostate cancer treatment, they often inadvertently activate compensatory pathways, leading to therapy resistance. This resistance is frequently mediated through changes in transcription factor (TF) crosstalk, reshaping gene regulatory programs and ultimately weakening treatment efficacy. Consequently, investigating TF interactions has become crucial for understanding the mechanisms driving therapy-resistant cancers. Recent evidence has highlighted the crosstalk between the glucocorticoid receptor (GR) and AR, demonstrating that GR can induce prostate cancer therapy resistance by replacing the inactivated AR, thereby becoming a driver of the disease. In addition to this oncogenic role, GR has also been shown to act as a tumor suppressor in prostate cancer. Owing to this dual role and the widespread use of glucocorticoids as adjuvant therapy, it is essential to understand GR's actions across different stages of prostate cancer development. In this review, we explore the current knowledge of GR in prostate cancer, with a specific focus on its crosstalk with other TFs. GR can directly and indirectly interact with a variety of TFs, and these interactions vary significantly depending on the type of prostate cancer cells. By highlighting these crosstalk interactions, we aim to provide insights that can guide the research and development of new GR-targeted therapies to mitigate its harmful effects in prostate cancer.

Stress-induced Neuroinflammation of the Spinal Cord is Restrained by Cort113176 (Dazucorilant), A Specific Glucocorticoid Receptor Modulator

Glucocorticoids exert antiinflammatory, antiproliferative and immunosupressive effects. Paradoxically they may also enhance inflammation particularly in the nervous system, as shown in Cushing´ syndrome and neurodegenerative disorders of humans and models of human diseases. ."The Wobbler mouse model of amyotrophic lateral sclerosis shows hypercorticoidism and neuroinflammation which subsided by treatment with the glucocorticoid receptor (GR) modulator Dazucorilant (CORT113176). This effect suggests that GR mediates the chronic glucocorticoid unwanted effects. We now tested this hypothesis using a chronic stress model resembling the condition of the Wobbler mouse Male NFR/NFR mice remained as controls or were subjected to a restraining / rotation stress protocol for 3 weeks, with a group of stressed mice receiving CORT113176 also for 3 weeks. We determined the mRNAS or reactive protein for the proinflamatory factors HMGB1, TLR4, NFkB, TNFα, markers of astrogliosis (GFAP, SOX9 and acquaporin 4), of microgliosis (Iba, CD11b, P2RY12 purinergic receptor) as well as serum IL1β and corticosterone. We showed that chronic stress produced high levels of serum corticosterone and IL1β, decreased body and spleen weight, produced microgliosis and astrogliosis and increased proinflammatory mediators. In stressed mice, modulation of the GR with CORT113176 reduced Iba + microgliosis, CD11b and P2RY12 mRNAs, immunoreactive HMGB1 + cells, GFAP + astrogliosis, SOX9 and acquaporin expression and TLR4 and NFkB mRNAs vs. stress-only mice. The effects of CORT113176 indicate that glucocorticoids are probably involved in neuroinflammation. Thus, modulation of the GR would become useful to dampen the inflammatory component of neurodegenerative disorders.

Bisphenol S induces brown adipose tissue whitening and aggravates diet-induced obesity in an estrogen-dependent manner

Bisphenol S (BPS) exposure has been implied epidemiologically to increase obesity risk, but the underlying mechanism is unclear. Here, we propose that BPS exposure at an environmentally relevant dose aggravates diet-induced obesity in female mice by inducing brown adipose tissue (BAT) whitening. We explored the underlying mechanism by which KDM5A-associated demethylation of the trimethylation of lysine 4 on histone H3 (H3K4me3) in thermogenic genes is overactivated in BAT upon BPS exposure, leading to the reduced expression of thermogenic genes. Further studies have suggested that BPS activates KDM5A transcription in BAT by binding to glucocorticoid receptor (GR) in an estrogen-dependent manner. Estrogen-estrogen receptors facilitate the accessibility of the KDM5A gene promoter to BPS-activated GR by recruiting the activator protein 1 (AP-1) complex. These results indicate that BAT is another important target of BPS and that targeting KDM5A-related signals may serve as an approach to counteract the BPS-induced susceptivity to obesity.

Luminal breast cancer identity is determined by loss of glucocorticoid receptor activity

Glucocorticoid receptor (GR) is a transcription factor that plays a crucial role in cancer biology. In this study, we utilized an in silico-designed GR activity signature to demonstrate that GR relates to the proliferative capacity of numerous primary cancer types. In breast cancer, the GR activity status determines luminal subtype identity and has implications for patient outcomes. We reveal that GR engages with estrogen receptor (ER), leading to redistribution of ER on the chromatin. Notably, GR activation leads to upregulation of the ZBTB16 gene, encoding for a transcriptional repressor, which controls growth in ER-positive breast cancer and associates with prognosis in luminal A patients. In relation to ZBTB16's repressive nature, GR activation leads to epigenetic remodeling and loss of histone acetylation at sites proximal to cancer-driving genes. Based on these findings, epigenetic inhibitors reduce viability of ER-positive breast cancer cells that display absence of GR activity. Our findings provide insights into how GR controls ER-positive breast cancer growth and may have implications for patients' prognostication and provide novel therapeutic candidates for breast cancer treatment.

Phosphorylation of glucocorticoid receptor induced by 16-kauren-2-beta-18, 19-triol decreases expression of Melanophilin through JNK signalling

16-kauren-2-beta-18, 19-triol (16-kauren) is a natural diterpenoid substance derived from Asteraceae psiadia punctulata, a small tropical shrub in Africa and Asia, and it can reduce Mlph expression without affecting the expression of Rab27a and MyoVa in melanocytes. Melanophilin (Mlph) is an important linker protein in the melanosome transport process. However, the signal transduction pathway for the regulation of Mlph expression has not been fully established. We examined the mechanism of 16-kauren on Mlph expression. Murine melan-a melanocytes were used for in vitro analysis. Western blot analysis, quantitative real-time polymerase chain reaction, and luciferase assay were performed. The inhibition of Mlph expression by 16-kauren-2β-18,19-triol (16-kauren) occurs through the JNK signal and is reversed following glucocorticoid receptor (GR) activation by dexamethasone (Dex). Especially, 16-kauren activates JNK and c-jun signalling, part of the MAPK pathway, with subsequent Mlph repression. When the JNK signal is weakened by siRNA, the inhibition of Mlph expression by 16-kauren was not seen. JNK activation by 16-kauren induces GR phosphorylation, which leads to Mlph repression. These results demonstrate that 16-kauren regulates Mlph expression through the phosphorylation of GR via the JNK signalling pathway.

Nuclear receptor: Structure and function

Ligand-dependent transcription factors are nuclear receptors (NRs) that regulate various critical cellular processes such as reproduction, metabolism, development, etc. NRs are classified into (subgroup 0 to subgroup 6) seven superfamilies based on ligand-binding characteristics. All NRs share a general domain structure (A/B, C, D, and E) with distinct essential functions. NRs as monomers, homodimers, or heterodimers bind to consensus DNA sequences known as Hormone Response Elements (HREs). Furthermore, nuclear receptor-binding efficiency depends on minor differences in the sequences of HREs, spacing between the two half-sites, and the flanking sequence of the response elements. NRs can trans-activate and repress their target genes. In positively regulated genes, ligand-bound NRs recruit coactivators to activate the target gene expression, and unliganded NRs cause transcriptional repression. On the other hand, NRs repress gene expression by different mechanisms: (i) ligand-dependent transcriptional repression, (ii) ligand-independent transcriptional repression. This chapter will briefly explain NR superfamilies, their structures, molecular mechanism of action and their role in pathophysiological conditions, etc. That could enable the discovery of new receptors and their ligands and may elucidate their roles in various physiological processes. In addition, therapeutic agonists and antagonists would be developed to control the dysregulation of nuclear receptor signaling.

In silico discovery of blood cell macromolecular associations

Background

Physical molecular interactions are the basis of intracellular signalling and gene regulatory networks, and comprehensive, accessible databases are needed for their discovery. Highly correlated transcripts may reflect important functional associations, but identification of such associations from primary data are cumbersome. We have constructed and adapted a user-friendly web application to discover and identify putative macromolecular associations in human peripheral blood based on significant correlations at the transcriptional level.

Methods

The blood transcriptome was characterized by quantification of 17,328 RNA species, including 341 mature microRNAs in 105 clinically well-characterized postmenopausal women. Intercorrelation of detected transcripts signal levels generated a matrix with > 150 million correlations recognizing the human blood RNA interactome. The correlations with calculated adjusted p-values were made easily accessible by a novel web application.

Results

We found that significant transcript correlations within the giant matrix reflect experimentally documented interactions involving select ubiquitous blood relevant transcription factors (CREB1, GATA1, and the glucocorticoid receptor (GR, NR3C1)). Their responsive genes recapitulated up to 91% of these as significant correlations, and were replicated in an independent cohort of 1204 individual blood samples from the Framingham Heart Study. Furthermore, experimentally documented mRNAs/miRNA associations were also reproduced in the matrix, and their predicted functional co-expression described. The blood transcript web application is available at http://app.uio.no/med/klinmed/correlation-browser/blood/index.php and works on all commonly used internet browsers.

Conclusions

Using in silico analyses and a novel web application, we found that correlated blood transcripts across 105 postmenopausal women reflected experimentally proven molecular associations. Furthermore, the associations were reproduced in a much larger and more heterogeneous cohort and should therefore be generally representative. The web application lends itself to be a useful hypothesis generating tool for identification of regulatory mechanisms in complex biological data sets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-022-01077-3.

Transcriptomic profiling of clobetasol propionate-induced immunosuppression in challenged zebrafish embryos

In the ecotoxicological hazard assessment of chemicals, the detection of immunotoxicity is currently neglected. This is mainly due to the complexity of the immune system and the consequent lack of standardized procedures and markers for the comprehensive assessment of immunotoxic modes of action. In this study, we present a new approach applying transcriptome profiling to an immune challenge with a mixture of pathogen-associated molecular patterns (PAMPs) in zebrafish embryos, analyzing differential gene expression during acute infection with and without prior exposure to the immunosuppressive drug clobetasol propionate (CP). While PAMP injection itself triggered biological processes associated with immune activation, some of these genes were more differentially expressed upon prior exposure to CP than by immune induction alone, whereas others showed weaker or no differential regulation in response to the PAMP stimulus. All of these genes responding differently to PAMP after prior CP exposure showed additivity of PAMP- and CP-induced effects, indicating independent regulatory mechanisms. The transcriptomic profiles suggest that CP impaired innate immune induction by attenuating the response of genes involved in antigen processing, TLR signaling, NF-КB signaling, and complement activation. We propose this approach as a powerful method for detecting gene biomarkers for immunosuppressive modes of action, as it was able to identify alternatively regulated processes and pathways in a sublethal, acute infection zebrafish embryo model. This allowed to define biomarker candidates for immune-mediated effects and to comprehensively characterize immunosuppression. Ultimately, this work contributes to the development of molecular biomarker-based environmental hazard assessment of chemicals in the future.

Dexamethasone and Fumaric Acid Ester Conjugate Synergistically Inhibits Inflammation and NF-κB in Macrophages

Macrophage-mediated inflammation drives autoimmune and chronic inflammatory diseases. Treatment with anti-inflammatory agents can be an effective strategy to reduce this inflammation; however, high concentrations of these agents can have immune-dampening and other serious side effects. Synergistic combination of anti-inflammatory agents can mitigate dosing by requiring less drug. Multiple anti-inflammatory agents were evaluated in combination for synergistic inhibition of macrophage inflammation. The most potent synergy was observed between dexamethasone (DXM) and fumaric acid esters (e.g., monomethyl fumarate (MMF)). Furthermore, this combination was found to synergistically inhibit inflammatory nuclear factor κB (NF-κB) transcription factor activity. The optimal ratio for synergy was determined to be 1:1, and DXM and MMF were conjugated by esterification at this molar ratio. The DXM-MMF conjugate displayed improved inhibition of inflammation over the unconjugated combination in both murine and human macrophages. In the treatment of human donor monocyte-derived macrophages, the combination of DXM and MMF significantly inhibited inflammatory gene expression downstream of NF-κB and overall performed better than either agent alone. Further, the DXM-MMF conjugate significantly inhibited expression of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome-associated genes. The potent anti-inflammatory activity of the DXM-MMF conjugate in human macrophages indicates that it may have benefits in the treatment of autoimmune and inflammatory diseases.

Reprogrammed intestinal functions in Astragalus polysaccharide-alleviated osteoporosis: combined analysis of transcriptomics and DNA methylomics demonstrates the significance of the gut-bone axis in treating osteoporosis

Researchers have noted that organ-organ communication between bone and intestine has significant effects on bone health and its related diseases. In this study, we collected colonic epithelial tissue from dexamethasone-induced osteoporotic rats and Astragalus polysaccharide (APS)-alleviated osteoporotic rats and employed transcriptome sequencing to investigate the functional changes that occurred in the intestine. Principal component analysis showed that both dexamethasone (inducer of osteoporosis) and APS reprogrammed the gene expression profile of the intestine. Further analysis identified 496 and 291 differentially expressed genes (DEGs) in osteoporotic and APS-treated osteoporotic rats, respectively. KEGG enrichment analysis of these DEGs demonstrated osteoporosis-induced intestinal dysfunctions that were further modified by APS treatment. Further analysis demonstrated that APS could restore intestinal functions by reversing the expression of 53 DEGs in osteoporotic rats. Recovery of osteoclast differentiation and the calcium signalling pathway might contribute to the improvement of osteoporosis. Moreover, utilizing methylC-capture sequencing (MCC-Seq), we studied the changes in DNA methylation and performed epigenetic analysis of dexamethasone- and APS-induced gene expression changes. In this study, osteoporosis was observed to cause intestinal dysfunction, which is a complication of this disease. More importantly, APS was determined to reprogram intestinal functions to alleviate osteoporosis via the gut-bone axis. Our results support the existence of a gut-bone axis and suggest new therapeutic opportunities for the treatment of osteoporosis via the gut-bone axis.

Insights into mineralocorticoid receptor homodimerization from a combined molecular modeling and bioinformatics study

In vertebrates, the mineralocorticoid receptor (MR) is a steroid-activated nuclear receptor (NR) that plays essential roles in water-electrolyte balance and blood pressure homeostasis. It belongs to the group of oxo-steroidian NRs, together with the glucocorticoid (GR), progesterone (PR), and androgen (AR) receptors. Classically, these oxo-steroidian NRs homodimerize and bind to specific genomic sequences to activate gene expression. NRs are multi-domain proteins, and dimerization is mediated by both the DNA (DBD) and ligand binding domains (LBDs), with the latter thought to provide the largest dimerization interface. However, at the structural level, the dimerization of oxo-steroidian receptors LBDs has remained largely a matter of debate and, despite their sequence homology, there is currently no consensus on a common homodimer assembly across the four receptors, that is, GR, PR, AR, and MR. Here, we examined all available MR LBD crystals using different computational methods (protein common interface database, proteins, interfaces, structures and assemblies, protein-protein interaction prediction by structural matching, and evolutionary protein-protein interface classifier, and the molecular mechanics Poisson-Boltzmann surface area method). A consensus is reached by all methods and singles out an interface mediated by helices H9, H10 and the C-terminal F domain as having characteristics of a biologically relevant assembly. Interestingly, a similar assembly was previously identified for GRα, MR closest homolog. Alternative architectures that were proposed for GRα were not observed for MR. These data call for further experimental investigations of oxo-steroid dimer architectures.

Decreased Colonic Guanylin/Uroguanylin Expression and Dried Stool Property in Mice With Social Defeat Stress

Psychological stress is deeply involved in the pathophysiology of not only mental illness but also functional gastrointestinal disorders. In the present study, we examined the relationship between psychological stress and abnormality of stool properties, focusing on the alteration of plasma glucocorticoid and guanylin (GN)/uroguanylin (UGN) expression in the colon. A murine model of chronic social defeat stress (CSDS) was established by exposing a C57BL/6N intruder mouse to a CD-1 aggressor mouse for 3–5 min. Thereafter the mice were kept in the same cage but separated by a divider for the remainder of the day. This procedure was repeated for 10 consecutive days, and then a social interaction test was performed to evaluate social avoidance. Fresh fecal and blood samples were collected for stool property analysis and measurement of the plasma glucocorticoid level by ELISA. The expression of GN, UGN, and guanylate cyclase 2C in the colonic tissues was examined by real-time RT-PCR and immunohistochemistry. Moreover, Lovo cells were stimulated with dexamethasone, and the expression of GN/UGN mRNA was examined. In the CSDS group, the time spent in the social interaction zone was significantly shorter when the CD-1 aggressor mouse was present than when it was absent. The social interaction ratio was also significantly lower in the CSDS group relative to the controls. The mean Bristol scale score was significantly lower in the CSDS group, but the fecal sodium concentration did not differ between CSDS mice and controls. The level of plasma corticosterone was significantly higher in the CSDS group than in the controls immediately after the 10th day of CSDS. The expression of both GN and UGN was significantly decreased in the CSDS mice. GN was expressed in all colonic epithelial cells, and UGN was expressed in ovoid or pyramidal epithelial cells in the colonic mucosa. The expression of both GN and UGN was significantly decreased in the CSDS mice relative to controls. The expression of both GN and UGN was significantly suppressed in Lovo cells upon stimulation with dexamethasone. Psychological stress-induced glucocorticoid may suppress colonic GN/UGN expression, resulting in a change in stool properties leading to constipation.

miR-331-3p is involved in glucocorticoid resistance reversion by rapamycin through suppression of the MAPK signaling pathway

Glucocorticoids (GCs) are commonly used as therapeutic agents for immune-mediated diseases and leukemia. However, considerable inter-individual differences in efficacy have been reported. Several reports indicate that the inhibitor of mTOR rapamycin can reverse GC resistance, but the molecular mechanism involved in this synergistic effect has not been fully defined. In this context, we explored the differential miRNA expression in a GC-resistant CCRF-CEM cell line after treatment with rapamycin alone or in co-treatment with methylprednisolone (MP). The expression analysis identified 70, 99 and 96 miRNAs that were differentially expressed after treatment with MP, rapamycin and their combination compared to non-treated controls, respectively. Two pathways were exclusively altered as a result of the co-treatment: the MAPK and ErbB pathways. We validated the only miRNA upregulated specifically by the co-treatment associated with the MAPK signaling, miR-331-3p. Looking for miR-331-3p targets, MAP2K7, an essential component of the JNK/MAPK pathway, was identified. Interestingly, MAP2K7 expression was downregulated during the co-treatment, causing a decrease in terms of JNK activity. miR-331-3p in mimic-transfected cells led to a significant decrease in MAP2K7 levels and promoted the reversion of GC resistance in vitro. Interestingly, miR-331-3p expression was also associated with GC-resistance in patient leukemia cells taken at diagnosis. The combination of rapamycin with MP restores GC effectiveness through the regulation of different miRNAs, suggesting the important role of these pharmacoepigenetic factors in GC response.

Effects of dietary energy level on appetite and central adenosine monophosphate-activated protein kinase (AMPK) in broilers

Adenosine monophosphate-activated protein kinase (AMPK) acts as a sensor of cellular energy changes and is involved in the control of food intake. A total of 216 1-d-old broilers were randomly allotted into 3 treatments with 6 replicates per treatment and 12 broilers in each cage. The dietary treatments included 1) high-energy (HE) diet (3,500 kcal/kg), 2) normal-energy (NE) diet (3,200 kcal/kg), and 3) low-energy (LE) diet (2,900 kcal/kg). The present study was conducted to investigate the effects of dietary energy level on appetite and the central AMPK signal pathway. The results showed that a HE diet increased average daily gain (ADG), whereas a LE diet had the opposite effect (P < 0.05, N = 6). The average daily feed intake (ADFI) of the chickens fed the LE diet was significantly higher than that of the control (P < 0.05, N = 6). Overall, the feed conversion rate gradually decreased with increasing dietary energy level (P < 0.05, N = 6). Moreover, the chickens fed the LE and HE diets demonstrated markedly improved urea content compared with the control group (P < 0.0001, N = 8). The triglyceride (TG) content in the LE group was obviously higher than that in the HE group but showed no change compared with the control (P = 0.0678, N = 8). The abdominal fat rate gradually increased with increased dietary energy level (P = 0.0927, N = 8). The HE group showed downregulated gene expression levels of liver kinase B1 (LKB1), neuropeptide Y (NPY), cholecystokinin (CCK), and glucocorticoid receptor (GR) in the hypothalamus compared with the control group (P < 0.05, N = 8). However, LE treatment significantly increased the mRNA level of AMP-activated protein kinase α2 (AMPKα2) compared with other groups (P = 0.0110, N = 8). In conclusion, a HE diet inhibited appetite and central AMPK signaling. In contrast, a LE diet activated central AMPK and appetite. Overall, the central AMPK signal pathway and appetite were modulated in accordance with the energy level in the diet to regulate nutritional status and maintain energy homeostasis in birds.

Vamorolone, a dissociative steroidal compound, reduces collagen antibody-induced joint damage and inflammation when administered after disease onset

OBJECTIVE AND DESIGN

The objective of this study was to assess the effect of vamorolone, a first-in-class dissociative steroidal compound, to inhibit inflammation when administered after disease onset in the murine collagen antibody-induced arthritis model of arthritis.

ANIMALS

84 DBA1/J mice were used in this study (n = 12 per treatment group).

TREATMENT

Vamorolone or prednisolone was administered orally after disease onset for a duration of 7 days.

METHODS

Disease score and bone erosion were assessed using previously described scoring systems. Cytokines were measured in joints via immunoassay, and joint cathepsin B activity (marker of inflammation) was assessed using optical imaging of joints on live mice.

RESULTS

We found that vamorolone treatment led to a reduction of several disease parameters including disease score, joint inflammation, and the presence of pro-inflammatory mediators to a degree similar of that observed with prednisolone treatment. More importantly, histopathological analysis of affected joints showed that vamorolone treatment significantly reduced the degree of bone erosion while this bone-sparing property was not observed with prednisolone treatment at any of the tested doses.

CONCLUSIONS

While many intervention regimens in other studies are administered prior to disease onset in animal models, the current study involves delivery of the potential therapeutic after disease onset. Based on the findings, vamorolone may offer an efficacious, yet safer alternative to conventional steroidal compounds in the treatment of rheumatoid arthritis and other inflammatory diseases.

Hypoplastic acute myeloid leukemia in an elderly patient. A long-term partial remission with low-dose prednisone and G-CSF

Hypoplastic acute myeloid leukemia (AML) is a rare variant of AML that mainly affects the elderly and accounts for 5%-7% of de novo AML. Prognosis for this disease is poor, and there is no standard therapy. We have treated an elderly patient with hypoplastic AML with low-dose prednisone and G-CSF with good results. We propose that this treatment may be a viable alternative to supportive therapy alone, or the tenuous chemotherapeutic challenge to elderly patients with hypoplastic AML.

Inhibition of Heat Shock Factor 1 Enhances Repressive Molecular Mechanisms on the POMC Promoter

BACKGROUND

Cushing's disease (CD) is caused by adrenocorticotropic hormone (ACTH)-secreting pituitary tumours. They express high levels of heat shock protein 90 and heat shock factor 1 (HSF1) in comparison to the normal tissue counterpart, indicating activated cellular stress.

AIMS

Our objectives were: (1) to correlate HSF1 expression with clinical features and hormonal/radiological findings of CD, and (2) to investigate the effects of HSF1 inhibition as a target for CD treatment.

PATIENTS/METHODS

We examined the expression of total and pSer326HSF1 (marker for its transcriptional activation) by Western blot on eight human CD tumours and compared to the HSF1 status of normal pituitary. We screened a cohort of 45 patients with CD for HSF1 by immunohistochemistry and correlated the HSF1 immunoreactivity score with the available clinical data. We evaluated the effects of HSF1 silencing with RNA interference and the HSF1 inhibitor KRIBB11 in AtT-20 cells and four primary cultures of human corticotroph tumours.

RESULTS

We show that HSF1 protein is highly expressed and transcriptionally active in CD tumours in comparison to normal pituitary. The immunoreactivity score for HSF1 did not correlate with the typical clinical features of the disease. HSF1 inhibition reduced proopiomelanocortin (Pomc) transcription in AtT-20 cells. The HSF1 inhibitor KRIBB11 suppressed ACTH synthesis from 75% of human CD tumours in primary cell culture. This inhibitory action on Pomc transcription was mediated by increased glucocorticoid receptor and suppressed Nurr77/Nurr1 and AP-1 transcriptional activities.

CONCLUSIONS

These data show that HSF1 regulates POMC transcription. Pharmacological targeting of HSF1 may be a promising treatment option for the control of excess ACTH secretion in CD.

Anti-inflammatory effect of external use of escin on cutaneous inflammation: possible involvement of glucocorticoids receptor

Escin, as an internally applied anti-inflammatory agent, has been widely used in the treatment of inflammation and edema resulting from trauma or operation in the clinic. However, the effect of its external use on cutaneous inflammation and edema remains unexplored. In the present study, the anti-inflammatory and anti-edematous effects of external use of escin were studied in carrageenan-induced paw edema and histamine-induced capillary permeability in rats, paraxylene-induced ear swelling in mice, and cotton pellet-induced granuloma in rats. Effects of external use of escin gel on prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) were determined by ELISA. The anti-inflammatory mechanism was explored by detecting the expression of glucocorticoid receptor (GR) with Western blotting and Real-time PCR analyses, with further exploration of nuclear factor-κB (NF-κB), p38 mitogen-activated protein kinase (P38MAPK) and activator protein-1 (AP-1) expressions. We demonstrated that external use of escin showed significant anti-inflammatory effects on acute and chronic inflammation in different animal models and its anti-inflammatory effects might be related to down-regulation of PGE2, TNF-α, and IL-1β. The results also showed that escin exerted its anti-inflammatory effects by promoting the expression of GR, with the possible mechanism being inhibition of the expressions of GR-related signaling molecules such as NF-κB and AP-1.

Analysis of NFATc1 amplification in T cells for pharmacodynamic monitoring of tacrolimus in kidney transplant recipients

Background

Therapeutic drug monitoring (TDM) of tacrolimus, based on blood concentrations, shows an imperfect correlation with the occurrence of rejection. Here, we tested whether measuring NFATc1 amplification, a member of the calcineurin pathway, is suitable for TDM of tacrolimus.

Materials and methods

NFATc1 amplification was monitored in T cells of kidney transplant recipients who received either tacrolimus- (n = 11) or belatacept-based (n = 10) therapy. Individual drug effects on NFATc1 amplification were studied in vitro, after spiking blood samples of healthy volunteers with either tacrolimus, belatacept or mycophenolate mofetil.

Results

At day 30 after transplantation, in tacrolimus-treated patients, NFATc1 amplification was inhibited in CD4⁺ T cells expressing the co-stimulation receptor CD28 (mean inhibition 37%; p = 0.01) and in CD8⁺CD28⁺ T cells (29% inhibition; p = 0.02), while this was not observed in CD8⁺CD28^- T cells or belatacept-treated patients. Tacrolimus pre-dose concentrations of these patients correlated inversely with NFATc1 amplification in CD28⁺ T cells (r_s = -0.46; p < 0.01). In vitro experiments revealed that 50 ng/ml tacrolimus affected NFATc1 amplification by 58% (mean; p = 0.02).

Conclusion

In conclusion, measuring NFATc1 amplification is a direct tool for monitoring biological effects of tacrolimus on T cells in whole blood samples of kidney transplant recipients. This technique has potential that requires further development before it can be applied in daily practice.

Different chromatin and DNA sequence characteristics define glucocorticoid receptor binding sites that are blocked or not blocked by coregulator Hic-5

The glucocorticoid receptor (GR) regulates genes in many physiological pathways by binding to enhancer and silencer elements of target genes, where it recruits coregulator proteins that remodel chromatin and regulate the assembly of transcription complexes. The coregulator Hydrogen peroxide-inducible clone 5 (Hic-5) is necessary for glucocorticoid (GC) regulation of one group of GR target genes, is irrelevant for a second group, and inhibits GR binding to a third gene set, thereby blocking their regulation by GC. Gene-specific characteristics that distinguish GR binding regions (GBR) at Hic-5 blocked genes from GBR at other GC-regulated genes are unknown. Here we show genome-wide that blocked GBR generally require CHD9 and BRM for GR occupancy in contrast to GBR that are not blocked by Hic-5. Hic-5 blocked GBR are enriched near Hic-5 blocked GR target genes but not near GR target genes that are not blocked by Hic-5. Furthermore blocked GBR are in a closed conformation prior to Hic-5 depletion, and require Hic-5 depletion and glucocorticoid treatment to create an open conformation necessary for GR occupancy. A transcription factor binding motif characteristic of the ETS family was enriched near blocked GBR and blocked genes but not near non-blocked GBR or non-blocked GR target genes. Thus, we identify specific differences in chromatin conformation, chromatin remodeler requirements, and local DNA sequence motifs that contribute to gene-specific actions of transcription factors and coregulators. These findings shed light on mechanisms that contribute to binding site selection by transcription factors, which vary in a cell type-specific manner.

MiRNA-Mediated Macrophage Polarization and its Potential Role in the Regulation of Inflammatory Response

Monocytes and macrophages are important components of the immune system, specialized in either removing pathogens as part of innate immunity or contributing to adaptive immunity through antigen presentation. Essential to such functions is classical activation (M1) and alternative activation (M2) of macrophages. M1 polarization of macrophages is characterized by production of pro-inflammatory cytokines, antimicrobial and tumoricidal activity, whereas M2 polarization of macrophages is linked to immunosuppression, tumorigenesis, wound repair, and elimination of parasites. MiRNAs are small non-coding RNAs with the ability to regulate gene expression and network of cellular processes. A number of studies have determined miRNA expression profiles in M1 and M2 polarized human and murine macrophages using microarray and RT-qPCR arrays techniques. More specifically, miR-9, miR-127, miR-155, and miR-125b have been shown to promote M1 polarization while miR-124, miR-223, miR-34a, let-7c, miR-132, miR-146a, and miR-125a-5p induce M2 polarization in macrophages by targeting various transcription factors and adaptor proteins. Further, M1 and M2 phenotypes play distinctive roles in cell growth and progression of inflammation-related diseases such as sepsis, obesity, cancer, and multiple sclerosis. Hence, miRNAs that modulate macrophage polarization may have therapeutic potential in the treatment of inflammation-related diseases. This review highlights recent findings in miRNA expression profiles in polarized macrophages from murine and human sources, and summarizes how these miRNAs regulate macrophage polarization. Last, therapeutic potential of miRNAs in inflammation-related diseases through modulation of macrophage polarization is also discussed.

Tethering not required: the glucocorticoid receptor binds directly to activator protein-1 recognition motifs to repress inflammatory genes

The glucocorticoid receptor (GR) is a ligand-regulated transcription factor that controls the expression of extensive gene networks, driving both up- and down-regulation. GR utilizes multiple DNA-binding-dependent and -independent mechanisms to achieve context-specific transcriptional outcomes. The DNA-binding-independent mechanism involves tethering of GR to the pro-inflammatory transcription factor activator protein-1 (AP-1) through protein-protein interactions. This mechanism has served as the predominant model of GR-mediated transrepression of inflammatory genes. However, ChIP-seq data have consistently shown GR to occupy AP-1 response elements (TREs), even in the absence of AP-1. Therefore, the current model is insufficient to explain GR action at these sites. Here, we show that GR regulates a subset of inflammatory genes in a DNA-binding-dependent manner. Using structural biology and biochemical approaches, we show that GR binds directly to TREs via sequence-specific contacts to a GR-binding sequence (GBS) half-site found embedded within the TRE motif. Furthermore, we show that GR-mediated transrepression observed at TRE sites to be DNA-binding-dependent. This represents a paradigm shift in the field, showing that GR uses multiple mechanisms to suppress inflammatory gene expression. This work further expands our understanding of this complex multifaceted transcription factor.

The Mechanism of Negative Transcriptional Regulation by Thyroid Hormone: Lessons From the Thyrotropin β Subunit Gene

Thyroid hormone (T3) activates (positive regulation) or represses (negative regulation) target genes at the transcriptional level. The molecular mechanism of the former has been elucidated in detail; however, the mechanism for negative regulation has not been established. The best example of the gene that is negatively regulated by T3 is the thyrotropin (thyroid-stimulating hormone) β subunit (TSHβ) gene. Analogous to the T3-responsive element (TRE) in positive regulation, a negative TRE (nTRE) has been postulated in the TSHβ gene. However, TSHβ promoter analysis, performed in the presence of transcription factors Pit1 and GATA2, which are determinants of thyrotroph differentiation in the pituitary, revealed that the nTRE is dispensable for inhibition by T3. We propose a tethering model in which the T3 receptor is tethered to GATA2 via protein-protein interaction and inhibits GATA2-dependent transactivation of the TSHβ gene in a T3-dependent manner.

Genomic effects of glucocorticoids

Glucocorticoids and their receptor (GR) have been an important area of research because of their pleiotropic physiological functions and extensive use in the clinic. In addition, the association between GR and glucocorticoids, which is highly specific, leads to rapid nuclear translocation where GR associates with chromatin to regulate gene transcription. This simplified model system has been instrumental for studying the complexity of transcription regulation processes occurring at chromatin. In this review we discuss our current understanding of GR action that has been enhanced by recent developments in genome wide measurements of chromatin accessibility, histone marks, chromatin remodeling and 3D chromatin structure in various cell types responding to glucocorticoids.

Systematic dissection of genomic features determining transcription factor binding and enhancer function

Enhancers regulate gene expression through the binding of sequence-specific transcription factors (TFs) to cognate motifs. Various features influence TF binding and enhancer function-including the chromatin state of the genomic locus, the affinities of the binding site, the activity of the bound TFs, and interactions among TFs. However, the precise nature and relative contributions of these features remain unclear. Here, we used massively parallel reporter assays (MPRAs) involving 32,115 natural and synthetic enhancers, together with high-throughput in vivo binding assays, to systematically dissect the contribution of each of these features to the binding and activity of genomic regulatory elements that contain motifs for PPARγ, a TF that serves as a key regulator of adipogenesis. We show that distinct sets of features govern PPARγ binding vs. enhancer activity. PPARγ binding is largely governed by the affinity of the specific motif site and higher-order features of the larger genomic locus, such as chromatin accessibility. In contrast, the enhancer activity of PPARγ binding sites depends on varying contributions from dozens of TFs in the immediate vicinity, including interactions between combinations of these TFs. Different pairs of motifs follow different interaction rules, including subadditive, additive, and superadditive interactions among specific classes of TFs, with both spatially constrained and flexible grammars. Our results provide a paradigm for the systematic characterization of the genomic features underlying regulatory elements, applicable to the design of synthetic regulatory elements or the interpretation of human genetic variation.

Direct GR Binding Sites Potentiate Clusters of TF Binding across the Human Genome

The glucocorticoid receptor (GR) binds the human genome at >10,000 sites but only regulates the expression of hundreds of genes. To determine the functional effect of each site, we measured the glucocorticoid (GC) responsive activity of nearly all GR binding sites (GBSs) captured using chromatin immunoprecipitation (ChIP) in A549 cells. 13% of GBSs assayed had GC-induced activity. The responsive sites were defined by direct GR binding via a GC response element (GRE) and exclusively increased reporter-gene expression. Meanwhile, most GBSs lacked GC-induced reporter activity. The non-responsive sites had epigenetic features of steady-state enhancers and clustered around direct GBSs. Together, our data support a model in which clusters of GBSs observed with ChIP-seq reflect interactions between direct and tethered GBSs over tens of kilobases. We further show that those interactions can synergistically modulate the activity of direct GBSs and may therefore play a major role in driving gene activation in response to GCs.

Regulation of Hspb7 by MEF2 and AP-1: implications for Hspb7 in muscle atrophy

Mycocyte enhancer factor 2 (MEF2) and activator protein 1 (AP-1) transcription complexes have been individually implicated in myogenesis, but their genetic interaction has not previously been addressed. Using MEF2A, c-Jun and Fra-1 chromatin immunoprecipitation sequencing (ChIP-seq) data and predicted AP-1 consensus motifs, we identified putative common MEF2 and AP-1 target genes, several of which are implicated in regulating the actin cytoskeleton. Because muscle atrophy results in remodelling or degradation of the actin cytoskeleton, we characterized the expression of putative MEF2 and AP-1 target genes (Dstn, Flnc, Hspb7, Lmod3 and Plekhh2) under atrophic conditions using dexamethasone (Dex) treatment in skeletal myoblasts. Heat shock protein b7 (Hspb7) was induced by Dex treatment and further analyses revealed that loss of MEF2A using siRNA prevented Dex-regulated induction of Hspb7. Conversely, ectopic Fra-2 or c-Jun expression reduced Dex-mediated upregulation of Hspb7 whereas AP-1 depletion enhanced Hspb7 expression. In vivo, expression of Hspb7 and other autophagy-related genes was upregulated in response to atrophic conditions in mice. Manipulation of Hspb7 levels in mice also impacted gross muscle mass. Collectively, these data indicate that MEF2 and AP-1 confer antagonistic regulation of Hspb7 gene expression in skeletal muscle, with implications for autophagy and muscle atrophy.

JNK Signaling: Regulation and Functions Based on Complex Protein-Protein Partnerships

The c-Jun N-terminal kinases (JNKs), as members of the mitogen-activated protein kinase (MAPK) family, mediate eukaryotic cell responses to a wide range of abiotic and biotic stress insults. JNKs also regulate important physiological processes, including neuronal functions, immunological actions, and embryonic development, via their impact on gene expression, cytoskeletal protein dynamics, and cell death/survival pathways. Although the JNK pathway has been under study for >20 years, its complexity is still perplexing, with multiple protein partners of JNKs underlying the diversity of actions. Here we review the current knowledge of JNK structure and isoforms as well as the partnerships of JNKs with a range of intracellular proteins. Many of these proteins are direct substrates of the JNKs. We analyzed almost 100 of these target proteins in detail within a framework of their classification based on their regulation by JNKs. Examples of these JNK substrates include a diverse assortment of nuclear transcription factors (Jun, ATF2, Myc, Elk1), cytoplasmic proteins involved in cytoskeleton regulation (DCX, Tau, WDR62) or vesicular transport (JIP1, JIP3), cell membrane receptors (BMPR2), and mitochondrial proteins (Mcl1, Bim). In addition, because upstream signaling components impact JNK activity, we critically assessed the involvement of signaling scaffolds and the roles of feedback mechanisms in the JNK pathway. Despite a clarification of many regulatory events in JNK-dependent signaling during the past decade, many other structural and mechanistic insights are just beginning to be revealed. These advances open new opportunities to understand the role of JNK signaling in diverse physiological and pathophysiological states.

Leucine alleviates dexamethasone-induced suppression of muscle protein synthesis via synergy involvement of mTOR and AMPK pathways

Both mTOR and AMPK pathways are involved in the DEX-induced suppression of protein synthesis in muscle cells. Leucine supplementation relieves DEX-induced inhibition on protein synthesis by evoking mTOR and suppressing AMPK pathway.

Glucocorticoids (GCs) are negative muscle protein regulators that contribute to the whole-body catabolic state during stress. Mammalian target of rapamycin (mTOR)-signalling pathway, which acts as a central regulator of protein metabolism, can be activated by branched-chain amino acids (BCAA). In the present study, the effect of leucine on the suppression of protein synthesis induced by GCs and the pathway involved were investigated. In vitro experiments were conducted using cultured C2C12 myoblasts to study the effect of GCs on protein synthesis, and the involvement of mTOR pathway was investigated as well. After exposure to dexamethasone (DEX, 100 μmol/l) for 24 h, protein synthesis in muscle cells was significantly suppressed (P<0.05), the phosphorylations of mTOR, ribosomal protein S6 protein kinase 1 (p70s6k1) and eukaryotic initiation factor 4E binding protein 1 (4EBP1) were significantly reduced (P<0.05). Leucine supplementation (5 mmol/l, 10 mmol/l and 15 mmol/l) for 1 h alleviated the suppression of protein synthesis induced by DEX (P<0.05) and was accompanied with the increased phosphorylation of mTOR and decreased phosphorylation of AMPK (P<0.05). Branched-chain amino transferase 2 (BCAT2) mRNA level was not influenced by DEX (P>0.05) but was increased by leucine supplementation at a dose of 5 mmol/l (P<0.05).

Epigenetic modulation of chronic anxiety and pain by histone deacetylation

Prolonged exposure of the central amygdala (CeA) to elevated corticosteroids (CORT) facilitates long-term anxiety and pain through activation of glucocorticoid receptors (GRs) and corticotropin-releasing factor (CRF). However, the mechanisms maintaining these responses are unknown. Since chronic phenotypes can be sustained by epigenetic mechanisms, including histone modifications such as deacetylation, we tested the hypothesis that histone deacetylation contributes to the maintenance of chronic anxiety and pain induced by prolonged exposure of the CeA to CORT. We found that bilateral infusions of a histone deacetylase inhibitor into the CeA attenuated anxiety-like behavior as well as somatic and visceral hypersensitivity resulting from elevated CORT exposure. Moreover, we delineated a novel pathway through which histone deacetylation could contribute to CORT regulation of GR and subsequent CRF expression in the CeA. Specifically, deacetylation of histone 3 at lysine 9 (H3K9), through the coordinated action of the NAD+-dependent protein deacetylase sirtuin-6 (SIRT6) and nuclear factor kappa B (NFκB), sequesters GR expression leading to disinhibition of CRF. Our results indicate that epigenetic programming in the amygdala, specifically histone modifications, is important in the maintenance of chronic anxiety and pain.

Formoterol synergy with des-ciclesonide inhibits IL-4 expression in IgE/antigen-induced mast cells by inhibiting JNK activation

Inhaled corticosteroid (ICS) therapy in combination with long-acting β-adrenergic agonists (LABA) is the most important treatment for allergic asthma, although the mechanism still remains unclear. However, mast cells play a central role in the pathogenesis of asthma. In this study, we explored the sole or synergetic effects of des-ciclesonide (ICS) and formoterol (LABA) on the cytokines IL-4 and IL-13 and on histamine release from mast cells (RBL-2H3 cells). We found that des-ciclesonide (0.1, 1 and 10nM) and formoterol (0.1, 1 and 10μM) alone attenuated DNP-BSA-induced IL-4 and IL-13 production, respectively, in a concentration-dependent manner in DNP-IgE-sensitized mast cells. Des-ciclesonide (0.2nM) and formoterol (1μM) alone also reduced histamine production. However, the combination of des-ciclesonide (0.2nM) and formoterol (1μM) had a synergistic inhibition effect on IL-4 mRNA expression and protein production but not IL-13 and histamine release. The JNK inhibitor SP600125 (10μM) inhibited antigen-induced mRNA expression and protein production of IL-4. Des-ciclesonide and formoterol alone inhibited the activation of JNK in a concentration-dependent manner, and the combination of des-ciclesonide (0.2nM) and formoterol (1μM) exhibited greater inhibition effect compared with des-ciclesonide (0.2nM) or formoterol (1μM) alone. Taken together, these synergistic effects on mast cells might provide the rationale for the development of the most recent ICS/LABA combination approved for asthma therapy.

VBP15, a novel anti-inflammatory, is effective at reducing the severity of murine experimental autoimmune encephalomyelitis

Multiple sclerosis is a chronic disease of the central nervous system characterized by an autoimmune inflammatory reaction that leads to axonal demyelination and tissue damage. Glucocorticoids, such as prednisolone, are effective in the treatment of multiple sclerosis in large part due to their ability to inhibit pro-inflammatory pathways (e.g., NFκB). However, despite their effectiveness, long-term treatment is limited by adverse side effects. VBP15 is a recently described compound synthesized based on the lazeroid steroidal backbone that shows activity in acute and chronic inflammatory conditions, yet displays a much-reduced side effect profile compared to traditional glucocorticoids. The purpose of this study was to determine the effectiveness of VBP15 in inhibiting inflammation and disease progression in experimental autoimmune encephalomyelitis (EAE), a widely used mouse model of multiple sclerosis. Our data show that VBP15 is effective at reducing both disease onset and severity. In parallel studies, we observed that VBP15 was able to inhibit the production of NFκB-regulated pro-inflammatory transcripts in human macrophages. Furthermore, treatment with prednisolone-but not VBP15-increased expression of genes associated with bone loss and muscle atrophy, suggesting lack of side effects of VBP15. These findings suggest that VBP15 may represent a potentially safer alternative to traditional glucocorticoids in the treatment of multiple sclerosis and other inflammatory diseases.

Opposing regulation of BIM and BCL2 controls glucocorticoid-induced apoptosis of pediatric acute lymphoblastic leukemia cells

Glucocorticoids are critical components of combination chemotherapy regimens in pediatric acute lymphoblastic leukemia (ALL). The proapoptotic BIM protein is an important mediator of glucocorticoid-induced apoptosis in normal and malignant lymphocytes, whereas the antiapoptotic BCL2 confers resistance. The signaling pathways regulating BIM and BCL2 expression in glucocorticoid-treated lymphoid cells remain unclear. In this study, pediatric ALL patient-derived xenografts (PDXs) inherently sensitive or resistant to glucocorticoids were exposed to dexamethasone in vivo. Microarray analysis showed that KLF13 and MYB gene expression changes were significantly greater in dexamethasone-sensitive than -resistant PDXs. Chromatin immunoprecipitation (ChIP) analysis detected glucocorticoid receptor (GR) binding at the KLF13 promoter to trigger KLF13 expression only in sensitive PDXs. Next, KLF13 bound to the MYB promoter, deactivating MYB expression only in sensitive PDXs. Sustained MYB expression in resistant PDXs resulted in maintenance of BCL2 expression and inhibition of apoptosis. ChIP sequencing analysis revealed a novel GR binding site in a BIM intronic region (IGR) that was engaged only in dexamethasone-sensitive PDXs. The absence of GR binding at the BIM IGR was associated with BIM silencing and dexamethasone resistance. This study has identified novel mechanisms of opposing BCL2 and BIM gene regulation that control glucocorticoid-induced apoptosis in pediatric ALL cells in vivo.

Discovery of GW870086: a potent anti-inflammatory steroid with a unique pharmacological profile

BACKGROUND AND PURPOSE

Glucocorticoids are highly effective therapies for a range of inflammatory diseases. Advances in the understanding of the diverse molecular mechanisms underpinning glucocorticoid action suggest that anti-inflammatory molecules with reduced side effect liabilities can be discovered. Here we set out to explore whether modification of the 17α position of the steroid nucleus could generate molecules with a unique pharmacological profile and to determine whether such molecules would retain anti-inflammatory activity.

EXPERIMENTAL APPROACH

The pharmacological properties of GW870086 were compared with fluticasone propionate (FP) using a range of cellular and in vivo model systems, including extensive gene expression profiling.

KEY RESULTS

GW870086 repressed inflammatory cytokine release from lung epithelial cells in a similar manner to FP but antagonized the effect of dexamethasone on MMTV-driven reporter gene transactivation. GW870086 had a strong effect on the expression of some glucocorticoid-regulated genes (such as PTGS2), while having minimal impact on the expression of other known target genes (such as SGK). GW870086 retained the ability to strengthen tight junctions in epithelial cell culture but, unlike FP, was unable to protect the culture from elastase-mediated damage. In murine models of irritant-induced contact dermatitis and ovalbumin-induced allergic inflammation, GW870086 showed comparable anti-inflammatory efficacy to FP.

CONCLUSION AND IMPLICATIONS

GW870086 is a potent anti-inflammatory compound with a unique ability to regulate only a subset of those genes that are normally affected by classical glucocorticoids. It has the potential to become a new topical steroid with a different safety profile to existing therapies.

The neuropeptide Y Y1 receptor knockdown modulates activator protein 1-involved feeding behavior in amphetamine-treated rats

BACKGROUND

Hypothalamic neuropeptide Y (NPY) and two immediate early genes, c-fos and c-jun, have been found to be involved in regulating the appetite-suppressing effect of amphetamine (AMPH). The present study investigated whether cerebral catecholamine (CA) might regulate NPY and POMC expression and whether NPY Y1 receptor (Y1R) participated in activator protein-1 (AP-1)-mediated feeding.

METHODS

Rats were given AMPH daily for 4 days. Changes in the expression of NPY, Y1R, c-Fos, c-Jun, and AP-1 were assessed and compared.

RESULTS

Decreased CA could modulate NPY and melanocortin receptor 4 (MC4R) expressions. NPY and food intake decreased the most on Day 2, but Y1R, c-Fos, and c-Jun increased by approximately 350%, 280%, and 300%, respectively, on Day 2. Similarly, AP-1/DNA binding activity was increased by about 180% on Day 2. The expression patterns in Y1R, c-Fos, c-Jun, and AP-1/DNA binding were opposite to those in NPY during AMPH treatment. Y1R knockdown was found to modulate the opposite regulation between NPY and AP-1, revealing an involvement of Y1R in regulating NPY/AP-1-mediated feeding.

CONCLUSIONS

These results point to a molecular mechanism of CA/NPY/Y1R/AP-1 signaling in the control of AMPH-mediated anorexia and may advance the medical research of anorectic and anti-obesity drugs.

Transcriptional activity of c-Jun is critical for the suppression of AR function

Androgen receptor (AR) signaling plays a pivotal role in growth and survival of prostate cancer cells. c-Jun is an important member of the activator protein 1 (AP-1) family and was shown to interact with AR. However, the role of c-Jun in AR signaling remains controversial, with being a coactivator or a corepressor reported. Here, utilizing multiple approaches, we show that c-Jun efficiently inhibits AR activity and the growth of prostate cancer cells. Overexpression of c-Jun inhibits not only the activities of various androgen-responsive promoters but also the transcripts of multiple AR target genes. Interestingly, long-term c-Jun overexpression also down-regulates AR expression at both the protein and mRNA levels. Molecular analysis suggests that c-Jun inhibits AR transactivation potential via an unknown target gene. The inhibition of AR by c-Jun occurs in both hormone naïve and castration-resistant prostate cancer cells. Our results unravel a novel mechanism by which c-Jun antagonizes the AR signaling.

VBP15, a glucocorticoid analogue, is effective at reducing allergic lung inflammation in mice

Asthma is a chronic inflammatory condition of the lower respiratory tract associated with airway hyperreactivity and mucus obstruction in which a majority of cases are due to an allergic response to environmental allergens. Glucocorticoids such as prednisone have been standard treatment for many inflammatory diseases for the past 60 years. However, despite their effectiveness, long-term treatment is often limited by adverse side effects believed to be caused by glucocorticoid receptor-mediated gene transcription. This has led to the pursuit of compounds that retain the anti-inflammatory properties yet lack the adverse side effects associated with traditional glucocorticoids. We have developed a novel series of steroidal analogues (VBP compounds) that have been previously shown to maintain anti-inflammatory properties such as NFκB-inhibition without inducing glucocorticoid receptor-mediated gene transcription. This study was undertaken to determine the effectiveness of the lead compound, VBP15, in a mouse model of allergic lung inflammation. We show that VBP15 is as effective as the traditional glucocorticoid, prednisolone, at reducing three major hallmarks of lung inflammation—NFκB activity, leukocyte degranulation, and pro-inflammatory cytokine release from human bronchial epithelial cells obtained from patients with asthma. Moreover, we found that VBP15 is capable of reducing inflammation of the lung in vivo to an extent similar to that of prednisone. We found that prednisolone–but not VBP15 shortens the tibia in mice upon a 5 week treatment regimen suggesting effective dissociation of side effects from efficacy. These findings suggest that VBP15 may represent a potent and safer alternative to traditional glucocorticoids in the treatment of asthma and other inflammatory diseases.

Identification of transcriptional macromolecular associations in human bone using browser based in silico analysis in a giant correlation matrix

Intracellular signaling is critically dependent on gene regulatory networks comprising physical molecular interactions. Presently, there is a lack of comprehensive databases for most human tissue types to verify such macromolecular interactions. We present a user friendly browser which helps to identify functional macromolecular interactions in human bone as significant correlations at the transcriptional level. The molecular skeletal phenotype has been characterized by transcriptome analysis of iliac crest bone biopsies from 84 postmenopausal women through quantifications of ~23,000 mRNA species. When the signal levels were inter-correlated, an array containing >260 million correlations was generated, thus recognizing the human bone interactome at the RNA level. The matrix correlation and p values were made easily accessible by a freely available online browser. We show that significant correlations within the giant matrix are reproduced in a replica set of 13 male vertebral biopsies. The identified correlations differ somewhat from transcriptional interactions identified in cell culture experiments and transgenic mice, thus demonstrating that care should be taken in extrapolating such results to the in vivo situation in human bone. The current giant matrix and web browser are a valuable tool for easy access to the human bone transcriptome and molecular interactions represented as significant correlations at the RNA-level. The browser and matrix should be a valuable hypothesis generating tool for identification of regulatory mechanisms and serve as a library of transcript relationships in human bone, a relatively inaccessible tissue.

Estradiol antagonism of glucocorticoid-induced GILZ expression in human uterine epithelial cells and murine uterus

Sex hormone signaling regulates a variety of functions in the uterine endometrium essential for embryo implantation and immunity. Epithelial cells of the uterine endometrium are the target of the coordinated actions of estradiol (E(2)) and progesterone. However, little information exists regarding the interplay of estrogens with glucocorticoids in this tissue. Using the human uterine epithelial cell line ECC1, E(2) was found to antagonize induction of the glucocorticoid-induced leucine zipper (GILZ) gene expression, which is associated with several of the immune-related functions of glucocorticoids. Interestingly, E(2) antagonizes glucocorticoid regulated nascent RNA GILZ expression within 1 h of hormone treatment. Repression of glucocorticoid-induced GILZ expression requires the estrogen receptor (ER), because both treatment with the ER-antagonist ICI 182,780 and small interfering RNA knockdown of ERα block E(2)'s ability to repress GILZ gene expression. Antagonism of glucocorticoid-induced GILZ expression may not be unique to ERα, as the ERβ agonist Liquiritigenin is also able to antagonize glucocorticoid signaling. Transcriptional regulation appears to be at the level of promoter binding. Both the glucocorticoid receptor and ERα are recruited to regions of the GILZ promoter containing glucocorticoid response elements and the transcriptional start site. Glucocorticoid receptor binding to these regions in the presence of dexamethasone decreases with E(2) treatment. GILZ gene expression was also found to be repressed in the whole mouse uterus treated with a combination of dexamethasone and E(2). Regulation of the antiinflammatory gene GILZ by glucocorticoids and E(2) suggests cross talk between the immune modulating functions of glucocorticoids and the reproductive actions of estradiol signaling.

Skeletal muscle fatty acids shift from oxidation to storage upon dexamethasone treatment in chickens

The effect of an exogenous glucocorticoid on the lipid metabolism and fatty acid pattern of skeletal muscle in broiler chickens (Gallus gallus domesticus) was investigated in vivo and in vitro. Male Arbor Acres chickens were subjected to dexamethasone (DEX) treatment for 3days. We found that DEX retarded body growth, facilitated lipid accumulation in adipose and skeletal muscle tissues, and elevated the thigh monounsaturated fatty acids (MUFA) to saturated fatty acids (SFA) ratio at fasted state. DEX-treated chickens exhibited increased stearoyl-CoA desaturase-1 (SCD1) activity and decreased carnitine palmitoyltransferase-1 (CPT1) activity in the thigh muscle under fasting conditions and in primary cultured myoblasts. Phosphorylation of AMP-activated protein kinase alpha at Thr172 did not occur in vivo but was increased in vitro by DEX. In cells exposed to DEX, fatty acid transport protein-1 mRNA expression and fatty acid storage were enhanced while fatty acid oxidation was repressed. In conclusion, in oxidative muscle of fasted chickens, DEX stimulated uptake of myocellular fatty acids which was stored with the modified MUFA to SFA ratio in a process that maybe involved SCD1 activation. The altered fatty acid composition together with the inactivation of CPT1 showed an increased tendency towards fatty acid accumulation as opposed to oxidation. These findings provide important insight concerning the influence of glucocorticoids on lipid metabolism.

Dexamethasone facilitates lipid accumulation in chicken skeletal muscle

The effects of glucocorticoid on lipid metabolism of broiler chicken (Gallus gallus domesticus) skeletal muscle were investigated. Male Arbor Acres chickens (35 days old) were subjected to dexamethasone treatment for 3 days. We found that dexamethasone retards body growth while facilitating lipid accumulation. In M. pectoralis major (PM), dexamethasone increased the expression of glucocorticoid receptor (GR), fatty acid transport protein 1 (FATP1), heart fatty acid-binding protein (H-FABP) and long-chain acyl-CoA dehydrogenase (LCAD) mRNA and decreased the expression of liver carnitine palmitoyltransferase 1 (L-CPT1), adenosine-monophosphate-activated protein kinase (AMPK) α2 and lipoprotein lipase (LPL) mRNA. LPL activity was also decreased. In M. biceps femoris (BF), the levels of GR, FATP1 and L-CPT1 mRNA were increased. AMPKα (Thr172) phosphorylation and CTP1 activity of skeletal muscle were decreased by dexamethasone. In fed chickens, dexamethasone enhanced very low-density lipoprotein receptor (VLDLR) expression and AMPK activity in muscle, but it impaired the expression of LPL and L-CPT1 mRNA and LPL activity in PM and augmented the expression of GR, LPL, H-FABP, L-CPT1, LCAD and AMPKα2 mRNA in BF. Adipose triglyceride lipase (ATGL) protein expression was not affected by dexamethasone. In conclusion, in the fasting state, dexamethasone-induced-retarded fatty acid utilisation may be involved in the augmented intramyocellular lipid accumulation in both glycolytic (PM) and oxidative (BF) muscle tissues. In the fed state, dexamethasone promoted the transcriptional activity of genes related to lipid uptake and oxidation in muscles. Unmatched lipid uptake and utilisation are suggested to be involved in the augmented intramyocellular lipid accumulation.

Liganded thyroid hormone receptor inhibits phorbol 12-O-tetradecanoate-13-acetate-induced enhancer activity via firefly luciferase cDNA

Thyroid hormone receptor (TR) belongs to the nuclear hormone receptor (NHR) superfamily and regulates the transcription of its target genes in a thyroid hormone (T3)-dependent manner. While the detail of transcriptional activation by T3 (positive regulation) has been clarified, the mechanism of T3-dependent repression (negative regulation) remains to be determined. In addition to naturally occurring negative regulations typically found for the thyrotropin β gene, T3-bound TR (T3/TR) is known to cause artificial negative regulation in reporter assays with cultured cells. For example, T3/TR inhibits the transcriptional activity of the reporter plasmids harboring AP-1 site derived from pUC/pBR322-related plasmid (pUC/AP-1). Artificial negative regulation has also been suggested in the reporter assay with firefly luciferase (FFL) gene. However, identification of the DNA sequence of the FFL gene using deletion analysis was not performed because negative regulation was evaluated by measuring the enzymatic activity of FFL protein. Thus, there remains the possibility that the inhibition by T3 is mediated via a DNA sequence other than FFL cDNA, for instance, pUC/AP-1 site in plasmid backbone. To investigate the function of FFL cDNA as a transcriptional regulatory sequence, we generated pBL-FFL-CAT5 by ligating FFL cDNA in the 5' upstream region to heterologous thymidine kinase promoter in pBL-CAT5, a chloramphenicol acetyl transferase (CAT)-based reporter gene, which lacks pUC/AP-1 site. In kidney-derived CV1 and choriocarcinoma-derived JEG3 cells, pBL-FFL-CAT5, but not pBL-CAT5, was strongly activated by a protein kinase C activator, phorbol 12-O-tetradecanoate-13-acetate (TPA). TPA-induced activity of pBL-FFL-CAT5 was negatively regulated by T3/TR. Mutation of nt. 626/640 in FFL cDNA attenuated the TPA-induced activation and concomitantly abolished the T3-dependent repression. Our data demonstrate that FFL cDNA sequence mediates the TPA-induced transcriptional activity, which is inhibited by T3/TR.

Glucocorticoid therapy of antigen-induced arthritis depends on the dimerized glucocorticoid receptor in T cells

Despite several side effects, glucocorticoids (GCs) have been widely used for 60 y to treat rheumatoid arthritis on the basis of their antiinflammatory effects. However, the cells targeted by GCs and the transcriptional mechanisms underlying their actions through the glucocorticoid receptor (GR) in steroid therapy remain poorly defined. Using cell type-specific GR-deficient mice subjected to antigen-induced arthritis (AIA) as a model of human rheumatoid arthritis, we show that GC action on T cells but not myeloid cells is critical for therapeutic intervention in AIA. Furthermore, the resistance of mice expressing a DNA binding-defective GR (GR(dim)) to GC treatment reveals that dimerization of the GR is indispensable for the antiinflammatory effects. In these mice, the GC-induced suppression of T(H)1 and T(H)17 cell-derived proinflammatory cytokines is impaired. Our finding that IL-17A(-/-) mice are resistant to GC therapy, whereas IFN-γ(-/-) mice respond as efficiently as WT mice implies that IL-17-producing T cells and not IFN-γ-producing T cells are the most important targets for an efficient GC therapy. The present study's identification of the critical cell type and the mode of GR action in steroid therapy of AIA significantly advances our understanding of steroid therapy and should lead to therapies with greater efficiency and fewer side effects.

Research resource: transcriptional response to glucocorticoids in childhood acute lymphoblastic leukemia

Glucocorticoids (GC) induce apoptosis in lymphoblasts and are thus essential in the treatment of acute lymphoblastic leukemia (ALL). Their effects result from gene regulations via the GC receptor (NR3C1/GR), but it is unknown how these changes evolve, what the primary GR targets are, and to what extent responses differ between ALL subtypes and nonlymphoid malignancies. We delineated the transcriptional response to GC on the exon level in a time-resolved manner in a precursor B- and a T childhood ALL model employing Exon microarrays and combined this with genome-wide NR3C1-binding site detection using chromatin immunoprecipitation-on-chip technology. This integrative approach showed that the response was strongly influenced by kinetics and extent of GR autoinduction in both models. Although remarkable differences between the ALL systems were apparent, we defined a set of common response genes enriched in apoptosis-related processes. Globally, GR binding was higher for GC-induced vs. -repressed genes, suggesting that GR mediates gene repression by interaction with distant enhancers or by cross talk with other transcription factors. Exon level analysis defined several new GC-regulated transcript variants of genes, including ATP4B, GPR98, TBCD, and ZBTB16. Our study provides unprecedented insight into the transcriptional response to GC in ALL cells, essential to understand this biologically and clinically important phenomenon. We found evidence of cell type-specific as well as common responses, possibly related to apoptosis induction, and detected induction of novel transcript variants by GC in the investigated systems. Finally, we implemented a bioinformatic framework that might be useful for high-density microarray analyses to identify alternative transcript variant expression.

Regulation of drug-metabolizing cytochrome P450 enzymes by glucocorticoids

The regulation of drug-metabolizing cytochrome P450 enzymes (CYP) is a complex process involving multiple mechanisms. Among them, transcriptional regulation through ligand-activated nuclear receptors is the crucial mechanism involved in hormone-controlled and xenobiotic-induced expression of drug-metabolizing CYPs. In this article, we focus, in detail, on the role of the glucocorticoid receptor (GR) in the transcriptional regulation of human drug-metabolizing CYP enzymes and the mechanisms of the regulation. There are at least three distinct transcriptional mechanisms by which GR controls the expression of CYPs: 1) direct binding of GR to a specific gene-promoter sequence called the glucocorticoid responsive element (GRE); 2) indirect binding of GR in the form of a multiprotein complex to gene promoters without a direct contact between GR and promoter DNA; and 3) up- or downregulation of other CYP transcriptional regulators or nuclear receptors (i.e., transcriptional regulatory cross-talk). However, due to the general effect of glucocorticoids on numerous cellular pathways and functions, the net transcriptional effect of glucocorticoids on drug-metabolizing enzymes is usually a combination of several mechanisms. Since synthetic glucocorticoids are widely prescribed in human pharmacotherapy for the treatment of many diseases, comprehensive understanding of the transcriptional regulation of drug-metabolizing CYPs via GR with respect to glucocorticoid therapy or glucocorticoid hormonal status will aid in the development of efficient individualized pharmacotherapy without drug-drug interactions.