A novel role for the glucocorticoid receptor in the regulation of monocyte chemoattractant protein-1 mRNA stability

Transcriptome-wide analysis for glucocorticoid receptor-mediated mRNA decay reveals various classes of target transcripts

The glucocorticoid receptor (GR) can bind to DNA or RNA, eliciting transcriptional activation/repression or rapid messenger RNA (mRNA) degradation, respectively. Although GR-mediated transcriptional regulation has been well-characterized, the molecular details of rapid mRNA degradation induced by glucocorticoids are not yet fully understood. Here, we demonstrate that glucocorticoid-induced GR-mediated mRNA decay (GMD) takes place in the nucleus and the cytoplasm, acting on pre-mRNAs and mRNAs. We also performed cross-linking and immunoprecipitation coupled with high-throughput sequencing analysis for GMD factors (GR, YBX1, and HRSP12) and mRNA sequencing analysis to identify endogenous GMD substrates. Our comprehensive coupled with high-throughput sequencing and mRNA sequencing analyses reveal that a range of cellular transcripts containing a common binding site for GR, YBX1, and HRSP12 are preferential targets for GMD, suggesting possible new functions of GMD in various biological events.

Changes in the Proteome of Platelets from Patients with Critical Progression of COVID-19

Platelets, the smallest cells in human blood, known for their role in primary hemostasis, are also able to interact with pathogens and play a crucial role in the immune response. In severe coronavirus disease 2019 (COVID-19) cases, platelets become overactivated, resulting in the release of granules, exacerbating inflammation and contributing to the cytokine storm. This study aims to further elucidate the role of platelets in COVID-19 progression and to identify predictive biomarkers for disease outcomes. A comparative proteome analysis of highly purified platelets from critically diseased COVID-19 patients with different outcomes (survivors and non-survivors) and age- and sex-matched controls was performed. Platelets from critically diseased COVID-19 patients exhibited significant changes in the levels of proteins associated with protein folding. In addition, a number of proteins with isomerase activity were found to be more highly abundant in patient samples, apparently exerting an influence on platelet activity via the non-genomic properties of the glucocorticoid receptor (GR) and the nuclear factor κ-light-chain-enhancer of activated B cells (NFκB). Moreover, carbonic anhydrase 1 (CA-1) was found to be a candidate biomarker in platelets, showing a significant increase in COVID-19 patients.

Noncanonical contribution of microglial transcription factor NR4A1 to post-stroke recovery through TNF mRNA destabilization

Microglia-mediated neuroinflammation is involved in various neurological diseases, including ischemic stroke, but the endogenous mechanisms preventing unstrained inflammation is still unclear. The anti-inflammatory role of transcription factor nuclear receptor subfamily 4 group A member 1 (NR4A1) in macrophages and microglia has previously been identified. However, the endogenous mechanisms that how NR4A1 restricts unstrained inflammation remain elusive. Here, we observed that NR4A1 is up-regulated in the cytoplasm of activated microglia and localizes to processing bodies (P-bodies). In addition, we found that cytoplasmic NR4A1 functions as an RNA-binding protein (RBP) that directly binds and destabilizes Tnf mRNA in an N6-methyladenosine (m6A)-dependent manner. Remarkably, conditional microglial deletion of Nr4a1 elevates Tnf expression and worsens outcomes in a mouse model of ischemic stroke, in which case NR4A1 expression is significantly induced in the cytoplasm of microglia. Thus, our study illustrates a novel mechanism that NR4A1 posttranscriptionally regulates Tnf expression in microglia and determines stroke outcomes.

Dexamethasone for Severe COVID-19: How Does It Work at Cellular and Molecular Levels?

The coronavirus disease 2019 (COVID-19) caused by infection of the severe respiratory syndrome coronavirus-2 (SARS-CoV-2) significantly impacted human society. Recently, the synthetic pure glucocorticoid dexamethasone was identified as an effective compound for treatment of severe COVID-19. However, glucocorticoids are generally harmful for infectious diseases, such as bacterial sepsis and severe influenza pneumonia, which can develop respiratory failure and systemic inflammation similar to COVID-19. This apparent inconsistency suggests the presence of pathologic mechanism(s) unique to COVID-19 that renders this steroid effective. We review plausible mechanisms and advance the hypothesis that SARS-CoV-2 infection is accompanied by infected cell-specific glucocorticoid insensitivity as reported for some other viruses. This alteration in local glucocorticoid actions interferes with undesired glucocorticoid to facilitate viral replication but does not affect desired anti-inflammatory properties in non-infected organs/tissues. We postulate that the virus coincidentally causes glucocorticoid insensitivity in the process of modulating host cell activities for promoting its replication in infected cells. We explore this tenet focusing on SARS-CoV-2-encoding proteins and potential molecular mechanisms supporting this hypothetical glucocorticoid insensitivity unique to COVID-19 but not characteristic of other life-threatening viral diseases, probably due to a difference in specific virally-encoded molecules and host cell activities modulated by them.

A primate-specific RNA-binding protein (RBMXL3) is involved in glucocorticoid regulation of human pulmonary surfactant protein B (SP-B) mRNA stability

The ability of pulmonary surfactant to reduce alveolar surface tension requires adequate levels of surfactant protein B (SP-B). Dexamethasone (DEX) increases human SP-B expression, in part, through increased SP-B mRNA stability. A 30-nt-long hairpin element (RBE) in the 3'-untranslated region of human SP-B mRNA mediates both DEX-induced and intrinsic mRNA stabilities, but the mechanism is unknown. Proteomic analysis of RBE-interacting proteins identified a primate-specific protein, RNA-binding motif X-linked-like-3 (RBMXL3). siRNA directed against RBMXL3 reduces DEX-induced SP-B mRNA expression in human bronchoalveolar cells. Human SP-B mRNA stability, measured by our dual cistronic plasmid assay, is unaffected by DEX in mouse lung epithelial cells lacking RBMXL3, but DEX increases human SP-B mRNA stability when RBMXL3 is expressed and requires the RBE. In the absence of DEX, RBE interacts with cellular proteins, reducing intrinsic SP-B mRNA stability in human and mouse lung epithelial cells. RBMXL3 specifically binds the RBE in vitro, whereas RNA immunoprecipitation and affinity chromatography analyses indicate that binding is enhanced in the presence of DEX. These results describe a model where intrinsic stability of human SP-B mRNA is reduced through binding of cellular mRNA decay factors to RBE, which is then relieved through DEX-enhanced binding of primate-specific RBMXL3.

Glucocorticoid counteracts cellular mechanoresponses by LINC01569-dependent glucocorticoid receptor-mediated mRNA decay

Mechanical stimuli on cells and mechanotransduction are essential in many biological and pathological processes. Glucocorticoid is an important hormone, roles, and mechanisms of which in cellular mechanotransduction remain unknown. Here, we report that glucocorticoid counteracted cellular mechanoresponses dependently on a novel long noncoding RNA (lncRNA), LINC01569 Further, LINC01569 mediated glucocorticoid effects on mechanotransduction by destabilizing messenger RNA (mRNA) of mechanosensors including early growth response protein 1 (EGR1), Cbp/P300-interacting transactivator 2 (CITED2), and bone morphogenic protein 7 (BMP7) in glucocorticoid receptor-mediated mRNA decay (GMD) manner. Mechanistically, LINC01569 directly bound to the GMD factor Y-box-binding protein 1 (YBX1). Then, the LINC01569-YBX1 complex was guided to the mRNAs of EGR1, CITED2, and BMP7 through specific LINC01569-mRNA interaction, thereby contributing to the successful assembly of GMD complex and triggering GMD. Our results uncovered roles of glucocorticoid in cellular mechanotransduction and novel lncRNA-dependent GMD machinery and provided potential strategy for early intervention in mechanical disorder-associated diseases.

Post-transcriptional regulation of C-C motif chemokine ligand 2 expression by ribosomal protein L22 during LPS-mediated inflammation

Monocyte infiltration to the site of pathogenic invasion is critical for inflammatory response and host defence. However, this process demands precise regulation as uncontrolled migration of monocytes to the site delays resolution of inflammation and ultimately promotes chronic inflammation. C-C motif chemokine ligand 2 (CCL2) plays a key role in monocyte migration, and hence, its expression should be tightly regulated. Here, we report a post-transcriptional regulation of CCL2 involving the large ribosomal subunit protein L22 (RPL22) in LPS-activated, differentiated THP-1 cells. Early events following LPS treatment include transcriptional upregulation of RPL22 and its nuclear accumulation. The protein binds to the first 20 nt sequence of the 5'UTR of ccl2 mRNA. Simultaneous nuclear translocation of up-frameshift-1 protein and its interaction with RPL22 results in cytoplasmic degradation of the ccl2 mRNA at a later stage. Removal of RPL22 from cells results in increased expression of CCL2 in response to LPS causing disproportionate migration of monocytes. We propose that post-transcriptional regulation of CCL2 by RPL22 fine-tunes monocyte infiltration during a pathogenic insult and maintains homeostasis of the immune response critical to resolution of inflammation. DATABASES: Microarray data are available in NCBI GEO database (Accession No GSE126525).

ENPD - A Database of Eukaryotic Nucleic Acid Binding Proteins: Linking Gene Regulations to Proteins

Eukaryotic nucleic acid binding protein database (ENPD, http://qinlab.sls.cuhk.edu.hk/ENPD/) is a library of nucleic acid binding proteins (NBPs) and their functional information. NBPs such as DNA binding proteins (DBPs), RNA binding proteins (RBPs), and DNA and RNA binding proteins (DRBPs) are involved in every stage of gene regulation through their interactions with DNA and RNA. Due to the importance of NBPs, the database was constructed based on manual curation and a newly developed pipeline utilizing both sequenced transcriptomes and genomes. In total the database has recorded 2.8 million of NBPs and their binding motifs from 662 NBP families and 2423 species, constituting the largest NBP database. ENPD covers evolutionarily important lineages which have never been included in the previous NBP databases, while lineage-specific NBP family expansions were also found. ENPD also focuses on the involvements of DBPs, RBPs and DRBPs in non-coding RNA (ncRNA) mediated gene regulation. The predicted and experimentally validated targets of NBPs have both been recorded and manually curated in ENPD, linking the interactions between ncRNAs, DNA regulatory elements and NBPs in gene regulation. This database provides key resources for the scientific community, laying a solid foundation for future gene regulatory studies from both functional and evolutionary perspectives.

Intrathyroid injection of dexamethasone inhibits Th2 cells in Graves' disease

OBJECTIVE

Intrathyroid injection of dexamethasone (IID) was used for decrease the relapse rate of hyperthyroidism in the treatment of Graves' disease (GD), but the mechanism is still unclear. We aimed to explore the effect of IID on T help (Th)1/Th2 cells and their chemokine in patients with GD.

SUBJECTS AND METHODS

A total of 42 patients with GD who were euthyroidism by methimazole were randomly divided into IID group (n = 20) and control group (n = 22). Thyroid function and associated antibody, Th1/Th2 cells proportion, serum CXCL10 and CCL2 levels, and CXCR3/CCR2 mRNA expression in peripheral blood mononuclear cells before and after 3-month IID treatment were tested by chemiluminescence assay, Flow cytometry, ELISA, and real-time PCR, respectively. Thyroid follicular cells were stimulated by IFN-γ and TNF-α and treated with dexamethasone in vitro. CXCL10 and CCL2 levels in supernatant were determined.

RESULTS

After 3-month therapy, the proportion of Th2 cells and serum CCL2 levels, as well as TPOAb, TRAb levels and thyroid volume decreased in IID group (p < 0.05). However, the proportion of Th1 and CXCL10 levels had no change in IID group and control (p > 0.05). The CXCR3/CCR2 ratio had no change in both groups (p > 0.05).

CONCLUSION

IID therapy could inhibit peripheral Th2 cells via decreasing CCL2 level in peripheral blood, and this result partly explain the effects of IID therapy on prevention of relapse of GD. Arch Endocrinol Metab. 2020;64(3):243-50.

The olfactory mucosa, first actor of olfactory detection, is sensitive to glucocorticoid hormone

The olfactory mucosa (OM) is the primary site of odorant detection, and its axonal projections relay information to brain structures for signal processing. We have previously observed that olfactory function can be affected during a prolonged stress challenge in Wistar rats. The stress response is a neuroendocrine retro-controlled loop allowing pleiotropic adaptive tissue alterations, which are partly mediated through the release of glucocorticoid hormones. We hypothesised that, as part of their wide-ranging pleiotropic effects, glucocorticoids might affect the first step of olfactory detection. To study this, we used a number of approaches ranging from the molecular detection and functional characterisation of glucocorticoid receptors (GRs) in OM cells, to the study of GR acute activation in vivo at the molecular, electrophysiological and behavioural levels. In contrast to previous reports, where GR was reported to be exclusive in olfactory sensory neurones, we located functional GR expression mostly in olfactory ensheathing cells. Dexamethasone (2 mg/kg) was injected intraperitoneally to activate GR in vivo, and this led to functional odorant electrophysiological response (electro-olfactogram) and OM gene expression changes. In a habituation/cross-habituation test of olfactory sensitivity, we observed that DEX-treated rats exhibited higher responsiveness to a complex odorant mixture. These findings support the idea that olfactory perception is altered in stressed animals, as glucocorticoids might enhance odour detection, starting at the first step of detection.

Role of NF-κB in Platelet Function

Platelets are megakaryocyte-derived fragments lacking nuclei and prepped to maintain primary hemostasis by initiating blood clots on injured vascular endothelia. Pathologically, platelets undergo the same physiological processes of activation, secretion, and aggregation yet with such pronouncedness that they orchestrate and make headway the progression of atherothrombotic diseases not only through clot formation but also via forcing a pro-inflammatory state. Indeed, nuclear factor-κB (NF-κB) is largely implicated in atherosclerosis and its pathological complication in atherothrombotic diseases due to its transcriptional role in maintaining pro-survival and pro-inflammatory states in vascular and blood cells. On the other hand, we know little on the functions of platelet NF-κB, which seems to function in other non-genomic ways to modulate atherothrombosis. Therein, this review will resemble a rich portfolio for NF-κB in platelets, specifically showing its implications at the levels of platelet survival and function. We will also share the knowledge thus far on the effects of active ingredients on NF-κB in general, as an extrapolative method to highlight the potential therapeutic targeting of NF-κB in coronary diseases. Finally, we will unzip a new horizon on a possible extra-platelet role of platelet NF-κB, which will better expand our knowledge on the etiology and pathophysiology of atherothrombosis.

UPFront and center in RNA decay: UPF1 in nonsense-mediated mRNA decay and beyond

Nonsense-mediated mRNA decay (NMD), which is arguably the best-characterized translation-dependent regulatory pathway in mammals, selectively degrades mRNAs as a means of post-transcriptional gene control. Control can be for the purpose of ensuring the quality of gene expression. Alternatively, control can facilitate the adaptation of cells to changes in their environment. The key to NMD, no matter what its purpose, is the ATP-dependent RNA helicase upstream frameshift 1 (UPF1), without which NMD fails to occur. However, UPF1 does much more than regulate NMD. As examples, UPF1 is engaged in functionally diverse mRNA decay pathways mediated by a variety of RNA-binding proteins that include staufen, stem-loop-binding protein, glucocorticoid receptor, and regnase 1. Moreover, UPF1 promotes tudor-staphylococcal/micrococcal-like nuclease-mediated microRNA decay. In this review, we first focus on how the NMD machinery recognizes an NMD target and triggers mRNA degradation. Next, we compare and contrast the mechanisms by which UPF1 functions in the decay of other mRNAs and also in microRNA decay. UPF1, as a protein polymath, engenders cells with the ability to shape their transcriptome in response to diverse biological and physiological needs.

Extensive epigenomic integration of the glucocorticoid response in primary human monocytes and in vitro derived macrophages

Glucocorticoid receptor is a transcription factor that is ubiquitously expressed. Glucocorticoids are circadian steroids that regulate a wide range of bodily functions, including immunity. Here we report that synthetic glucocorticoids affect 1035 mRNAs in isolated healthy human blood monocytes but only 165 in the respective six day-old monocyte-derived macrophages. The majority of the glucocorticoid response in monocytes concerns genes that are dynamic upon monocyte to macrophage differentiation, whereby macrophage-like mRNA levels are often reached in monocytes within four hours of treatment. Concomitantly, over 5000 chromosomal H3K27ac regions undergo remodelling, of which 60% involve increased H3K27ac signal. We find that chromosomal glucocorticoid receptor binding sites correlate with positive but not with negative local epigenomic effects. To investigate further we assigned our data to topologically associating domains (TADs). This shows that about 10% of macrophage TADs harbour at least one GR binding site and that half of all the glucocorticoid-induced H3K27ac regions are confined to these TADs. Our analyses are therefore consistent with the notion that TADs naturally accommodate information from sets of distal glucocorticoid response elements.

Endogenous glucocorticoids prevent gastric metaplasia by suppressing spontaneous inflammation

In the stomach, chronic inflammation causes metaplasia and creates a favorable environment for the evolution of gastric cancer. Glucocorticoids are steroid hormones that repress proinflammatory stimuli, but their role in the stomach is unknown. In this study, we show that endogenous glucocorticoids are required to maintain gastric homeostasis. Removal of circulating glucocorticoids in mice by adrenalectomy resulted in the rapid onset of spontaneous gastric inflammation, oxyntic atrophy, and spasmolytic polypeptide-expressing metaplasia (SPEM), a putative precursor of gastric cancer. SPEM and oxyntic atrophy occurred independently of lymphocytes. However, depletion of monocytes and macrophages by clodronate treatment or inhibition of gastric monocyte infiltration using the Cx3cr1 knockout mouse model prevented SPEM development. Our results highlight the requirement for endogenous glucocorticoid signaling within the stomach to prevent spontaneous gastric inflammation and metaplasia, and suggest that glucocorticoid deficiency may lead to gastric cancer development.

Dexamethasone Inhibits Synergistic Induction of PDE4B Expression by Roflumilast and Bacterium NTHi

Phosphodiesterase 4B (PDE4B) plays an important role in inflammation. Recently we have reported that roflumilast as a PDE4-selective inhibitor, synergizes with nontypeable Haemophilus influenzae (NTHi) to up-regulate PDE4B expression in vitro and in vivo. Clinical evidence and our previous results suggest that synergistic induction of PDE4B could be counterproductive for suppressing inflammation or may contribute to tolerance to roflumilast. We thus investigated if dexamethasone inhibits the synergistic induction of PDE4B by roflumilast and NTHi as well as inflammation. Here, dexamethasone markedly suppressed the synergistic induction of PDE4B in human lung epithelial cells and in vivo. We also found that dexamethasone further suppressed NTHi-induced inflammatory response in vitro and in vivo. Moreover, Compound A, as a dissociating non-steroidal glucocorticoid receptor (GR) ligand, inhibited the synergistic induction of PDE4B, thereby suggesting the requirement of dexamethasone-mediated GR activation in the suppression of PDE4B expression. Taken together, our data suggest that dexamethasone may help attenuate inflammation and tolerance through suppressing the PDE4B expression in chronic obstructive pulmonary disease (COPD) patients using roflumilast.

Glucocorticoid deficiency causes transcriptional and post-transcriptional reprogramming of glutamine metabolism

Background

Deficient glucocorticoid biosynthesis leading to adrenal insufficiency is life-threatening and is associated with significant co-morbidities. The affected pathways underlying the pathophysiology of co-morbidities due to glucocorticoid deficiency remain poorly understood and require further investigation.

Methods

To explore the pathophysiological processes related to glucocorticoid deficiency, we have performed global transcriptional, post-transcriptional and metabolic profiling of a cortisol-deficient zebrafish mutant with a disrupted ferredoxin (fdx1b) system.

Findings

fdx1b^−/− mutants show pervasive reprogramming of metabolism, in particular of glutamine-dependent pathways such as glutathione metabolism, and exhibit changes of oxidative stress markers. The glucocorticoid-dependent post-transcriptional regulation of key enzymes involved in de novo purine synthesis was also affected in this mutant. Moreover, fdx1b^−/− mutants exhibit crucial features of primary adrenal insufficiency, and mirror metabolic changes detected in primary adrenal insufficiency patients.

Interpretation

Our study provides a detailed map of metabolic changes induced by glucocorticoid deficiency as a consequence of a disrupted ferredoxin system in an animal model of adrenal insufficiency. This improved pathophysiological understanding of global glucocorticoid deficiency informs on more targeted translational studies in humans suffering from conditions associated with glucocorticoid deficiency.

Fund

Marie Curie Intra-European Fellowships for Career Development, HGF-programme BIFTM, Deutsche Forschungsgemeinschaft, BBSRC.

Defining the role of glucocorticoids in inflammation

An established body of knowledge and clinical practice has argued in favor of the use of glucocorticoids in various chronic inflammatory and autoimmune diseases. However, the very well-known adverse effects associated with their treatment hampers continuation of therapy with glucocorticoids. Analyses of the molecular mechanisms underlying the actions of glucocorticoids have led to the discovery of several mediators that add complexity and diversity to the puzzling world of these hormones and anti-inflammatory drugs. Such mediators hold great promise as alternative pharmacologic tools to be used as anti-inflammatory drugs with the same properties as glucocorticoids, but avoiding their metabolic side effects. This review summarizes findings about the molecular targets and mediators of glucocorticoid function.

The regulation and importance of monocyte chemoattractant protein-1

PURPOSE OF REVIEW

Monocyte chemoattractant protein (MCP)-1, a chemokine regulating monocyte chemotaxis and T-lymphocyte differentiation by binding to the CC chemokine receptor 2 (CCR2), plays a crucial role in the pathogenesis of inflammatory diseases, atherosclerosis and cancer. This review summarizes the current knowledge on the regulation and importance of the MCP-1/CCR2 axis, focusing on the therapeutic potential of its inhibition.

RECENT FINDINGS

Differential modulation of MCP-1 and CCR2 lead to downstream activation pathways, pathogenetic to differing disease conditions characterized by dysregulated monocyte/macrophage tissue recruitment. Pharmacological targeting of the MCP-1/CCR2 axis has led to selective MCP-1/CCR2 antagonists that have now entered phase I/II clinical trials for the treatment of inflammatory diseases, atherosclerosis and cancer. The pleiotropic nonselective MCP-1/CCR2 inhibition by current pharmacological agents is thought to contribute to their anti-inflammatory and antiatherosclerotic effects that is also seen for nutraceutical compounds such as curcumin.

SUMMARY

MCP-1 has a critical role in regulating chemotaxis both in health and disease, with increasing interest in its pharmacological inhibition. However, the therapeutic efficacy and safety of targeting the MCP-1/CCR2 axis is still in evolution.

Vitamin D effects on monocytes' CCL-2, IL6 and CD14 transcription in Addison's disease and HLA susceptibility

Addison's disease is a rare autoimmune disorder leading to adrenal insufficiency and life-long glucocorticoid dependency. Vitamin D receptor (VDR) polymorphisms and vitamin D deficiency predispose to Addison's disease. Aim of the current study was, to investigate potential anti-inflammatory vitamin D effects on monocytes in Addison's disease, focusing on inflammatory CCL-2 and IL6, as well on monocyte CD14 markers. Addison's disease is genetically linked to distinct HLA susceptibility alleles. Therefore we analyzed, whether HLA genotypes differed for vitamin D effects on monocyte markers. CD14⁺ monocytes were isolated from Addison's disease patients (AD, n=13) and healthy controls (HC, n=15) and stimulated with 1,25-dihydroxyvitamin D₃ and IL1β as an inflammatory stimulant. Cells were processed for mRNA expression of CCL-2, IL6 and CD14 and DNA samples were genotyped for major histocompatibility class (MHC) class II-encoded HLA- DQA1-DQB1 haplotypes. We found a downregulation of CCL-2 after vitamin D treatment in IL1β-stimulated monocytes both from AD patients and HC (AD p<0.001; HC p<0.0001). CD14 expression however, was upregulated in both HC and AD patients after vitamin D treatment (p<0.001, respectively). HC showed higher CD14 transcription level than AD patients after vitamin D treatment (p=0.04). Compared to IL1β-induced inflammation, HC have increased CD14 levels after vitamin D treatment (p<0.001), whereas the IL1β-induced CD14 expression of AD patients' monocytes did not change after vitamin D treatment (p=0.8). AD patients carrying HLA high-risk haplotypes showed an increased CCL-2 expression after IL1β-induced inflammation compared to intermediate-risk HLA carriers (p=0.05). Also HC monocytes' CD14 transcription after IL1β and vitamin D co-stimulation differed according to HLA risk profile. We show that vitamin D can exert anti-inflammatory effects on AD patients' monocytes which may be modulated by HLA risk genotypes.

Beyond Transcription: Roles of Transcription Factors in Pre-mRNA Splicing

Whereas individual steps of protein-coding gene expression in eukaryotes can be studied in isolation in vitro, it has become clear that these steps are intimately connected within cells. Connections not only ensure quality control but also fine-tune the gene expression process, which must adapt to environmental changes while remaining robust. In this review, we systematically present proven and potential mechanisms by which sequence-specific DNA-binding transcription factors can alter gene expression beyond transcription initiation and regulate pre-mRNA splicing, and thereby mRNA isoform production, by (i) influencing transcription elongation rates, (ii) binding to pre-mRNA to recruit splicing factors, and/or (iii) blocking the association of splicing factors with pre-mRNA. We propose various mechanistic models throughout the review, in some cases without explicit supportive evidence, in hopes of providing fertile ground for future studies.

Altered Neuroendocrine Immune Responses, a Two-Sword Weapon against Traumatic Inflammation

During the occurrence and development of injury (trauma, hemorrhagic shock, ischemia and hypoxia), the neuroendocrine and immune system act as a prominent navigation leader and possess an inter-system crosstalk between the reciprocal information dissemination. The fundamental reason that neuroendocrinology and immunology could mix each other and permeate toward the field of traumatology is owing to their same biological languages or chemical information molecules (hormones, neurotransmitters, neuropeptides, cytokines and their corresponding receptors) shared by the neuroendocrine and immune systems. The immune system is not only modulated by the neuroendocrine system, but also can modulate the biological functions of the neuroendocrine system. The interactive linkage of these three systems precipitates the complicated space-time patterns for the courses of traumatic inflammation. Recently, compelling evidence indicates that the network linkage pattern that initiating agents of neuroendocrine responses, regulatory elements of immune cells and effecter targets for immune regulatory molecules arouse the resistance mechanism disorders, which supplies the beneficial enlightenment for the diagnosis and therapy of traumatic complications from the view of translational medicine. Here we review the alternative protective and detrimental roles as well as possible mechanisms of the neuroendocrine immune responses in traumatic inflammation.

Identification and molecular characterization of cellular factors required for glucocorticoid receptor-mediated mRNA decay

In this study, Park et al. investigated the molecular mechanisms regulating glucocorticoid receptor-mediated mRNA decay (GMD). The authors characterize the molecular details of GMD, identify specific factors required for efficient GMD, and perform RNA sequencing, identifying many endogenous GMD substrates.

Glucocorticoid (GC) receptor (GR) has been shown recently to bind a subset of mRNAs and elicit rapid mRNA degradation. However, the molecular details of GR-mediated mRNA decay (GMD) remain unclear. Here, we demonstrate that GMD triggers rapid degradation of target mRNAs in a translation-independent and exon junction complex-independent manner, confirming that GMD is mechanistically distinct from nonsense-mediated mRNA decay (NMD). Efficient GMD requires PNRC2 (proline-rich nuclear receptor coregulatory protein 2) binding, helicase ability, and ATM-mediated phosphorylation of UPF1 (upstream frameshift 1). We also identify two GMD-specific factors: an RNA-binding protein, YBX1 (Y-box-binding protein 1), and an endoribonuclease, HRSP12 (heat-responsive protein 12). In particular, using HRSP12 variants, which are known to disrupt trimerization of HRSP12, we show that HRSP12 plays an essential role in the formation of a functionally active GMD complex. Moreover, we determine the hierarchical recruitment of GMD factors to target mRNAs. Finally, our genome-wide analysis shows that GMD targets a variety of transcripts, implicating roles in a wide range of cellular processes, including immune responses.

Involvement of the Glucocorticoid Receptor in Pro-inflammatory Transcription Factor Inhibition by Daucane Esters from Laserpitium zernyi

Species of the genus Laserpitium have been used traditionally to treat inflammation and infection. From the herb of Laserpitium zernyi, six new compounds were isolated and their structures elucidated (using IR, NMR, HRMS data) as derivatives of 8-daucene-2,4,10-triol (1, 2, and 4), 7-daucene-2,4,10-triol (3), a lapiferin derivative featuring a C-2 ester moiety (5), and a daucane featuring an exomethylene group at C-8 (6). Also isolated were the rare daucanes vaginatin (7) and laserpitin (8). In a search for selective glucocorticoid receptor (GR) modulators, the compounds were tested for their capacity to inhibit NF-κB and AP-1 pro-inflammatory factors and for a potential competitive effect on a dexamethasone (Dex)-induced GR-driven glucocorticoid response element (GRE) reporter gene. The new 2β-angeloyloxy-10α-acetoxy-8-daucene-2,4,10-triol (2) significantly inhibited transactivation of both NF-κB and AP-1, while vaginatin (7) was the most active of the compounds tested in blocking AP-1. Both compounds competitively repressed Dex-induced GRE-driven promoter activities, indicative of a potential role for GR. In addition, a decreased potential to inhibit NF-κB was apparent in GR knockout A549 cells. In line with the transcriptional assays, compounds 2 and 7 also significantly lowered CCL-2 chemokine production, albeit to a lesser extent than Dex. The results suggest that daucanes may be interesting candidates in the search for compounds with GR-modulating activities.

Endothelial Response to Glucocorticoids in Inflammatory Diseases

The endothelium plays a crucial role in inflammation. A balanced control of inflammation requires the action of glucocorticoids (GCs), steroidal hormones with potent cell-specific anti-inflammatory properties. Besides the classic anti-inflammatory effects of GCs on leukocytes, recent studies confirm that endothelial cells also represent an important target for GCs. GCs regulate different aspects of endothelial physiology including expression of adhesion molecules, production of pro-inflammatory cytokines and chemokines, and maintenance of endothelial barrier integrity. However, the regulation of endothelial GC sensitivity remains incompletely understood. In this review, we specifically examine the endothelial response to GCs in various inflammatory diseases ranging from multiple sclerosis, stroke, sepsis, and vasculitis to atherosclerosis. Shedding more light on the cross talk between GCs and endothelium will help to improve existing therapeutic strategies and develop new therapies better tailored to the needs of patients.

Effects of delayed delivery of dexamethasone-21-phosphate via subcutaneous microdialysis implants on macrophage activation in rats

Macrophage activation is of interest in the biomaterials field since macrophages with an M(Dex) characteristic phenotype, i.e., CD68(+)CD163(+), are believed to result in improved integration of the biomaterial as well as improved tissue remodeling and increased biomaterial longevity. To facilitate delivery of a macrophage modulator, dexamethasone-21-phosphate (Dex), microdialysis probes were subcutaneously implanted in male Sprague-Dawley rats. Dex localized delivery was delayed to the third day post implantation as a means to alter macrophage activation state at an implant site. To better elucidate the molecular mechanisms associated with M(Dex) macrophage activation, CCL2 was quantified in dialysates, gene expression ratios were determined from excised tissue surrounding the implant, histological analyses, and immunohistochemical analyses (CD68, CD163) were performed. Delayed Dex infusion resulted in the up-regulation of IL-6 at the transcript level in the tissue in contact with the microdialysis probe and decreased CCL2 concentrations collected in dialysates. Histological analyses showed increased cellular density as compared to controls in response to delayed Dex infusion. Dex delayed infusion resulted in an increased percentage of CD68(+)CD163(+), M(Dex), macrophages in the tissue surrounding the microdialysis probe as compared to probes that served as controls.

Coordinated post-transcriptional regulation of the chemokine system: messages from CCL2

The molecular cross-talk between epithelium and immune cells in the airway mucosa is a key regulator of homeostatic immune surveillance and is crucially involved in the development of chronic lung inflammatory diseases. The patterns of gene expression that follow the sensitization process occurring in allergic asthma and chronic rhinosinusitis and those present in the neutrophilic response of other chronic inflammatory lung diseases such as chronic obstructive pulmonary disease (COPD) are tightly regulated in their specificity. Studies exploring the global transcript profiles associated with determinants of post-transcriptional gene regulation (PTR) such as RNA-binding proteins (RBP) and microRNAs identified several of these factors as being crucially involved in controlling the expression of chemokines upon airway epithelial cell stimulation with cytokines prototypic of Th1- or Th2-driven responses. These studies also uncovered the participation of these pathways to glucocorticoids' inhibitory effect on the epithelial chemokine network. Unmasking the molecular mechanisms of chemokine PTR may likely uncover novel therapeutic strategies for the blockade of proinflammatory pathways that are pathogenetic for asthma, COPD, and other lung inflammatory diseases.

Glucocorticoid receptor interacts with PNRC2 in a ligand-dependent manner to recruit UPF1 for rapid mRNA degradation

Glucocorticoid receptor (GR), which was originally known to function as a nuclear receptor, plays a role in rapid mRNA degradation by acting as an RNA-binding protein. The mechanism by which this process occurs remains unknown. Here, we demonstrate that GR, preloaded onto the 5'UTR of a target mRNA, recruits UPF1 through proline-rich nuclear receptor coregulatory protein 2 (PNRC2) in a ligand-dependent manner, so as to elicit rapid mRNA degradation. We call this process GR-mediated mRNA decay (GMD). Although GMD, nonsense-mediated mRNA decay (NMD), and staufen-mediated mRNA decay (SMD) share upstream frameshift 1 (UPF1) and PNRC2, we find that GMD is mechanistically distinct from NMD and SMD. We also identify de novo cellular GMD substrates using microarray analysis. Intriguingly, GMD functions in the chemotaxis of human monocytes by targeting chemokine (C-C motif) ligand 2 (CCL2) mRNA. Thus, our data provide molecular evidence of a posttranscriptional role of the well-studied nuclear hormone receptor, GR, which is traditionally considered a transcription factor.

Identification of genes and transcription factors associated with glucocorticoid response in lens epithelial cells

Prolonged glucocorticoids (GCs) treatment may lead to the formation of posterior subcapsular cataracts. The present study aimed to investigate differential gene expression in lens epithelial cells (LECs) in response to GCs using DNA microarray profiling. The gene expression profile of GSE13040 was downloaded from the Gene Expression Omnibus database, which includes 12 human LECs treated with vehicle or dexamethasone (Dex) for 4 or 16 h with six samples at each time period, of which three samples were treated with vehicle (control group) and three samples were treated with Dex (Dex group) at each time point. The differentially expressed genes (DEGs) were identified between the control group and the Dex group at each time period with the thresholds of P<0.05 and |logFC|>1. The DEGs were further analyzed using bioinformatics methods. Firstly, DEGs were subject to a hierarchical cluster analysis. Subsequently, the functional enrichment analysis was performed for the common DEGs between the two time periods. Finally, the transcription factors and binding sites of DEGs associated with response to GC stimulus were analyzed. A total of 696 and 949 DEGs were identified at 4 h and 16 h, respectively. Hierarchical cluster analysis revealed that DEG expression was higher in the Dex group than in the control group (P<0.05). A total of 13 significant functions were enriched for the 72 common DEGs at the two time periods. Chemokine (C-C motif) ligand 2 (CCL2), dual-specificity phosphatase-1 (DUSP1) and FAS were associated with the response to GC stimulus and the transcription factor c-Jun bound to promoter regulation regions of CCL2, DUSP1 and FAS. In conclusion, the transcription factors and binding sites of DEGs associated with the response of LECs to GCs may provide potential gene targets for designing and developing drugs to protect against GC-induced cataract formation.

Glucocorticoids suppress inflammation via the upregulation of negative regulator IRAK-M

Glucocorticoids are among the most commonly used anti-inflammatory agents. Despite the enormous efforts in elucidating the glucocorticoid-mediated anti-inflammatory actions, how glucocorticoids tightly control overactive inflammatory response is not fully understood. Here we show that glucocorticoids suppress bacteria-induced inflammation by enhancing IRAK-M, a central negative regulator of Toll-like receptor signalling. The ability of glucocorticoids to suppress pulmonary inflammation induced by non-typeable Haemophilus influenzae is significantly attenuated in IRAK-M-deficient mice. Glucocorticoids improve the survival rate after a lethal non-typeable Haemophilus influenzae infection in wild-type mice, but not in IRAK-M-deficient mice. Moreover, we show that glucocorticoids and non-typeable Haemophilus influenzae synergistically upregulate IRAK-M expression via mutually and synergistically enhancing p65 and glucocorticoid receptor binding to the IRAK-M promoter. Together, our studies unveil a mechanism by which glucocorticoids tightly control the inflammatory response and host defense via the induction of IRAK-M and may lead to further development of anti-inflammatory therapeutic strategies.

The structure, function and evolution of proteins that bind DNA and RNA

Proteins that bind both DNA and RNA typify the ability of a single gene product to perform multiple functions. Such DNA- and RNA-binding proteins (DRBPs) have unique functional characteristics that stem from their specific structural features; these developed early in evolution and are widely conserved. Proteins that bind RNA have typically been considered as functionally distinct from proteins that bind DNA and studied independently. This practice is becoming outdated, in partly owing to the discovery of long non-coding RNAs (lncRNAs) that target DNA-binding proteins. Consequently, DRBPs were found to regulate many cellular processes, including transcription, translation, gene silencing, microRNA biogenesis and telomere maintenance.

Novel aspects of glucocorticoid actions

Normal hypothalamic-pituitary-adrenal (HPA) axis activity leading to the rhythmic and episodic release of adrenal glucocorticoids (GCs) is essential for body homeostasis and survival during stress. Acting through specific intracellular receptors in the brain and periphery, GCs regulate behaviour, as well as metabolic, cardiovascular, immune and neuroendocrine activities. By contrast to chronic elevated levels, circadian and acute stress-induced increases in GCs are necessary for hippocampal neuronal survival and memory acquisition and consolidation, as a result of the inhibition of apoptosis, the facilitation of glutamatergic neurotransmission and the formation of excitatory synapses, and the induction of immediate early genes and dendritic spine formation. In addition to metabolic actions leading to increased energy availability, GCs have profound effects on feeding behaviour, mainly via the modulation of orexigenic and anorixegenic neuropeptides. Evidence is also emerging that, in addition to the recognised immune suppressive actions of GCs by counteracting adrenergic pro-inflammatory actions, circadian elevations have priming effects in the immune system, potentiating acute defensive responses. In addition, negative-feedback by GCs involves multiple mechanisms leading to limited HPA axis activation and prevention of the deleterious effects of excessive GC production. Adequate GC secretion to meet body demands is tightly regulated by a complex neural circuitry controlling hypothalamic corticotrophin-releasing hormone (CRH) and vasopressin secretion, which are the main regulators of pituitary adrenocorticotrophic hormone (ACTH). Rapid feedback mechanisms, likely involving nongenomic actions of GCs, mediate the immediate inhibition of hypothalamic CRH and ACTH secretion, whereas intermediate and delayed mechanisms mediated by genomic actions involve the modulation of limbic circuitry and peripheral metabolic messengers. Consistent with their key adaptive roles, HPA axis components are evolutionarily conserved, being present in the earliest vertebrates. An understanding of these basic mechanisms may lead to novel approaches for the development of diagnostic and therapeutic tools for disorders related to stress and alterations of GC secretion.

Cardiac overexpression of Mammalian enabled (Mena) exacerbates heart failure in mice

Mammalian enabled (Mena) is a key regulator of cytoskeletal actin dynamics, which has been implicated in heart failure (HF). We have previously demonstrated that cardiac Mena deletion produced cardiac dysfunction with conduction abnormalities and hypertrophy. Moreover, elevated Mena expression correlates with HF in human and animal models, yet the precise role of Mena in cardiac pathophysiology is unclear. In these studies, we evaluated mice with cardiac myocyte-specific Mena overexpression (TTA/TgTetMena) comparable to that observed in cardiac pathology. We found that the hearts of TTA/TgTetMena mice were functionally and morphologically comparable to wild-type littermates, except for mildly increased heart mass in the transgenic mice. Interestingly, TTA/TgTetMena mice were particularly susceptible to cardiac injury, as these animals experienced pronounced decreases in ejection fraction and fractional shortening as well as heart dilatation and hypertrophy after transverse aortic constriction (TAC). By "turning off" Mena overexpression in TTA/TgTetMena mice either immediately prior to or immediately after TAC surgery, we discovered that normalizing Mena levels eliminated cardiac hypertrophy in TTA/TgTetMena animals but did not preclude post-TAC cardiac functional deterioration. These findings indicate that hearts with increased levels of Mena fare worse when subjected to cardiac injury and suggest that Mena contributes to HF pathophysiology.

Cardiac intercellular communication: are myocytes and fibroblasts fair-weather friends?

The cardiac fibroblast (CF) has historically been thought of as a quiescent cell of the heart, passively maintaining the extracellular environment for the cardiomyocytes (CM), the functional cardiac cell type. The increasingly appreciated role of the CF, however, extends well beyond matrix production, governing many aspects of cardiac function including cardiac electrophysiology and contractility. Importantly, its contributions to cardiac pathophysiology and pathologic remodeling have created a shift in the field's focus from the CM to the CF as a therapeutic target in the treatment of cardiac diseases. In response to cardiac injury, the CF undergoes a pathologic phenotypic transition into a myofibroblast, characterized by contractile smooth muscle proteins and upregulation of collagens, matrix proteins, and adhesion molecules. Further, the myofibroblast upregulates expression and secretion of a variety of pro-inflammatory, profibrotic mediators, including cytokines, chemokines, and growth factors. These mediators act in both an autocrine fashion to further activate CFs, as well as in a paracrine manner on both CMs and circulating inflammatory cells to induce myocyte dysfunction and chronic inflammation, respectively. Together, cell-specific cytokine-induced effects exacerbate pathologic remodeling and progression to HF. A better understanding of this dynamic intercellular communication will lead to novel targets for the attenuation of cardiac remodeling. Current strategies aimed at targeting cytokines have been largely unsuccessful in clinical trials, lending insights into ways that such intercellular cross talk can be more effectively attenuated. This review will summarize the current knowledge regarding CF functions in the heart and will discuss the regulation and signaling behind CF-mediated cytokine production and function. We will then highlight clinical trials that have exploited cytokine cross talk in the treatment of heart failure and provide novel strategies currently under investigation that may more effectively target pathologic CF-CM communication for the treatment of cardiac disease. This review explores novel mechanisms to directly attenuate heart failure progression through inhibition of signaling downstream of pro-inflammatory cytokines that are elevated after cardiac injury.

Y-box binding protein 1 and RNase UK114 mediate monocyte chemoattractant protein 1 mRNA stability in vascular smooth muscle cells

Monocyte chemoattractant protein 1 (MCP-1) plays a pivotal role in many inflammatory processes, including the progression of atherosclerosis and the response of the arterial wall to injury. We previously demonstrated that dexamethasone (Dex) inhibits MCP-1 mRNA accumulation in smooth muscle cells by decreasing its half-life. The effect of Dex was dependent upon the glucocorticoid receptor (GR) and independent of new transcription. Using RNA affinity and column chromatography, we have identified two proteins involved in regulating MCP-1 mRNA stability: Y-box binding protein 1 (YB-1), a multifunctional DNA/RNA-binding protein, and endoribonuclease UK114 (UK). By immunoprecipitation, YB and GR formed a complex present in equal amounts in extracts from untreated and Dex-treated cells. YB-1, UK, and GR small interfering RNA (siRNA) substantially inhibited the effect of Dex on MCP-1 mRNA accumulation. In addition, YB-1 antibody blocked the degradation of MCP-1 mRNA by cytoplasmic extracts from the Dex-treated cells. The degradative activity of extracts immunoprecipitated with antibodies to either YB-1 or GR was blocked with UK antibody. UK did not degrade MCP-1 mRNA; however, upon addition to nondegrading control extracts, it rapidly degraded MCP-1 mRNA. These studies define new roles for GR, YB-1, and UK in the formation of a molecular complex that degrades MCP-1 mRNA.

Monocyte Chemoattractant Protein 1 (MCP-1) in obesity and diabetes

Monocyte Chemoattractant Protein-1 (MCP-1) is the first discovered and most extensively studied CC chemokine, and the amount of studies on its role in the etiologies of obesity- and diabetes-related diseases have increased exponentially during the past two decades. This review attempted to provide a panoramic perspective of the history, regulatory mechanisms, functions, and therapeutic strategies of this chemokine. The highlights of this review include the roles of MCP-1 in the development of obesity, diabetes, cardiovascular diseases, insulitis, diabetic nephropathy, and diabetic retinopathy. Therapies that specifically or non-specifically inhibit MCP-1 overproduction have been summarized.

Regulation of cytoplasmic mRNA decay

Discoveries made over the past 20 years highlight the importance of mRNA decay as a means of modulating gene expression and thereby protein production. Up until recently, studies largely focused on identifying cis-acting sequences that serve as mRNA stability or instability elements, the proteins that bind these elements, how the process of translation influences mRNA decay and the ribonucleases that catalyse decay. Now, current studies have begun to elucidate how the decay process is regulated. This Review examines our current understanding of how mammalian cell mRNA decay is controlled by different signalling pathways and lays out a framework for future research.

Ciclesonide inhibits TNFα- and IL-1β-induced monocyte chemotactic protein-1 (MCP-1/CCL2) secretion from human airway smooth muscle cells

Monocyte chemotactic protein-1 (MCP-1) is a member of the CC family of cytokines. It has monocyte and lymphocyte chemotactic activity and stimulates histamine release from basophils. MCP-1 is implicated in the pathogenesis of inflammatory diseases, including asthma. The airway smooth muscle (ASM) layer is thickened in asthma, and the growth factors and cytokines secreted by ASM cells play a role in the inflammatory response of the bronchial wall. Glucocorticoids and β₂-agonists are first-line drug treatments for asthma. Little is known about the effect of asthma treatments on MCP-1 production from human ASM cells. Here, we determined the effect of ciclesonide (a glucocorticoid) and formoterol (a β₂-agonist) on MCP-1 production from human ASM cells. TNFα and IL-1β induced MCP-1 secretion from human ASM cells. Formoterol had no effect on MCP-1 expression, while ciclesonide significantly inhibited IL-1β- and TNFα-induced MCP-1. Furthermore, ciclesonide inhibited IL-1β- and TNFα-induced MCP-1 mRNA and IL-1β- and TNFα-induced MCP-1 promoter and enhancer luciferase reporters. Western blots showed that ciclesonide had no effect on IκB degradation. Finally, ciclesonide inhibited an NF-κB luciferase reporter. Our data show that ciclesonide inhibits IL-1β- and TNFα-induced MCP-1 production from human ASM cells via a transcriptional mechanism involving inhibition of NF-κB binding.

Maps and legends: the quest for dissociated ligands of the glucocorticoid receptor

Glucocorticoids are steroid hormones that have pleiotropic effects on development, metabolism, cognitive function and other aspects of physiology. Since the demonstration more than sixty years ago of their capacity to suppress inflammation, synthetic glucocorticoids have been extremely widely used in the treatment of inflammatory diseases. However, their clinical use is limited by numerous, unpredictable and potentially serious side effects. Glucocorticoids regulate gene expression both positively and negatively. Both of these effects are mediated by the glucocorticoid receptor, a ligand-dependent transcription factor. It has become widely accepted that anti-inflammatory effects of glucocorticoids are mostly due to inhibition of transcription, whereas the activation of transcription by the glucocorticoid receptor accounts for the majority of side effects. This dogma (which we refer to as the "transrepression hypothesis") predicts the possibility of uncoupling therapeutic, anti-inflammatory effects from side effects by identifying novel, selective ligands of the glucocorticoid receptor, which preferentially mediate inhibition rather than activation of transcription. It is argued that such "dissociated" glucocorticoid receptor ligands should retain anti-inflammatory potency but cause fewer side effects. Here we critically re-examine the history and foundations of the transrepression hypothesis. We argue that it is incompatible with the complexity of gene regulation by glucocorticoids and poorly supported by experimental evidence; that it no longer aids clear thinking about the actions of the glucocorticoid receptor; and that it will not prove a fruitful basis for continued refinement and improvement of anti-inflammatory drugs that target the glucocorticoid receptor.

The human glucocorticoid receptor as an RNA-binding protein: global analysis of glucocorticoid receptor-associated transcripts and identification of a target RNA motif

Posttranscriptional regulation is emerging as a key factor in glucocorticoid (GC)-mediated gene regulation. We investigated the role of the human GC receptor (GR) as an RNA-binding protein and its effect on mRNA turnover in human airway epithelial cells. Cell treatment with the potent GC budesonide accelerated the decay of CCL2 mRNA (t(1/2) = 8 ± 1 min versus 62 ± 17 min in DMSO-treated cells) and CCL7 mRNA (t(1/2) = 15 ± 4 min versus 114 ± 37 min), but not that of CCL5 mRNA (t(1/2)=231 ± 8 min versus 266 ± 5 min) in the BEAS-2B cell line. This effect was inhibited by preincubation with an anti-GR Ab, indicating that GR itself plays a role in the turnover of these transcripts. Coimmunoprecipitation and biotin pulldown experiments showed that GR associates with CCL2 and CCL7 mRNAs, but not CCL5 mRNA. These methods confirmed CCL2 mRNA targeting by GR in human primary airway epithelial cells. Association of the GR was localized to the 5' untranslated region of CCL2 mRNA and further mapped to nt 44-60. The collection of transcripts associated with GR, identified by immunoprecipitation of GR-mRNA complexes followed by microarray analysis, revealed 479 transcripts that associated with GR. Computational analysis of the primary sequence and secondary structures of these transcripts yielded a GC-rich motif, which was shown to bind to GR in vitro. This motif was used to predict binding of GR to an additional 7889 transcripts. These results indicate that cytoplasmic GR interacts with a subset of mRNA through specific sequences and can regulate turnover rates, suggesting a novel posttranscriptional role for GR as an RNA-binding protein.

Role of glucocorticoids in tuning hindbrain stress integration

The nucleus of the solitary tract (NTS) is a critical integrative site for coordination of autonomic and endocrine stress responses. Stress-excitatory signals from the NTS are communicated by both catecholaminergic [norepinephrine (NE), epinephrine (E)] and noncatecholaminergic [e.g., glucagon-like peptide-1 (GLP-1)] neurons. Recent studies suggest that outputs of the NE/E and GLP-1 neurons of the NTS are selectively engaged during acute stress. This study was designed to test mechanisms of chronic stress integration in the paraventricular nucleus, focusing on the role of glucocorticoids. Our data indicate that chronic variable stress (CVS) causes downregulation of preproglucagon (GLP-1 precursor) mRNA in the NTS and reduction of GLP-1 innervation to the paraventricular nucleus of the hypothalamus. Glucocorticoids were necessary for preproglucagon (PPG) reduction in CVS animals and were sufficient to lower PPG mRNA in otherwise unstressed animals. The data are consistent with a glucocorticoid-mediated withdrawal of GLP-1 in key stress circuits. In contrast, expression of tyrosine hydroxylase mRNA, the rate-limiting enzyme in catecholamine synthesis, was increased by stress in a glucocorticoid-independent manner. These suggest differential roles of ascending catecholamine and GLP-1 systems in chronic stress, with withdrawal of GLP-1 involved in stress adaptation and enhanced NE/E capacity responsible for facilitation of responses to novel stress experiences.

Nuclear emancipation: a platelet tour de force

Mammalian platelets are anucleate cells produced by the polyploid megakaryocyte. Platelets are more than just key players in hemostasis (blood clotting in response to injury); they also have important roles in inflammation, immunity, tumor progression, and thrombosis. Complex systems of homeostasis have been described for platelets, including posttranscriptional and translational mechanisms to regulate platelet function. Platelets contain transcription factors, and these proteins have essential roles in regulating nongenomic processes. A study provides evidence for a previously unknown negative feedback pathway for limiting platelet activation that occurs through the nuclear factor κB transcription factor family. This pathway is mediated by an adenosine 3',5'-monophosphate-independent protein kinase A activity in response to platelet stimulation. Our appreciation of the role of transcription factors in mammalian platelet biology is nascent but holds great promise for both understanding platelet function and translation into clinical uses.

Minireview: global regulation and dynamics of ribonucleic Acid

Gene expression starts with transcription and is followed by multiple posttranscriptional processes that carry out the splicing, capping, polyadenylation, and export of each mRNA. Interest in posttranscriptional regulation has increased recently with explosive discoveries of large numbers of noncoding RNAs such as microRNAs, yet posttranscriptional processes depend largely on the functions of RNA-binding proteins as well. Glucocorticoid nuclear receptors are classical examples of environmentally reactive activators and repressors of transcription, but there has also been a significant increase in studies of the role of posttranscriptional regulation in endocrine responses, including insulin and insulin receptors, and parathyroid hormone as well as other hormonal responses, at the levels of RNA stability and translation. On the global level, the transcriptome is defined as the total RNA complement of the genome, and thereby, represents the accumulated levels of all expressed RNAs, because they are each being produced and eventually degraded in either the nucleus or the cytoplasm. In addition to RNA turnover, the many underlying posttranscriptional layers noted above that follow from the transcriptome function within a dynamic ribonucleoprotein (RNP) environment of global RNA-protein and RNA-RNA interactions. With the exception of the spliceosome and the ribosome, thousands of heterodispersed RNP complexes wherein RNAs are dynamically processed, trafficked, and exchanged are heterogeneous in size and composition, thus providing significant challenges to their investigation. Among the diverse RNPs that show dynamic features in the cytoplasm are processing bodies and stress granules as well as a large number of smaller heterogeneous RNPs distributed throughout the cell. Although the localization of functionally related RNAs within these RNPs are responsive to developmental and environmental signals, recent studies have begun to elucidate the global RNA components of RNPs that are dynamically coordinated in response to these signals. Among the factors that have been found to affect coordinated RNA regulation are developmental signals and treatments with small molecule drugs, hormones, and toxins, but this field is just beginning to understand the role of RNA dynamics in these responses.

Platelets and megakaryocytes contain functional nuclear factor-kappaB

OBJECTIVE

To investigate the presence and role of NF-kappaB proteins in megakaryocytes and platelets. The nuclear factor-kappaB (NF-kappaB) transcription factor family is well known for its role in eliciting inflammation and promoting cell survival. We discovered that human megakaryocytes and platelets express the majority of NF-kappaB family members, including the regulatory inhibitor-kappaB (I-kappaB) and I-kappa kinase (IKK) molecules.

METHODS AND RESULTS

Anucleate platelets exposed to NF-kappaB inhibitors demonstrated impaired fundamental functions involved in repairing vascular injury and thrombus formation. Specifically, NF-kappaB inhibition diminished lamellapodia formation, decreased clot retraction times, and reduced thrombus stability. Moreover, inhibition of I-kappaB-alpha phosphorylation (BAY-11-7082) reverted fully spread platelets back to a spheroid morphology. Addition of recombinant IKK-beta or I-kappaB-alpha protein to BAY inhibitor-treated platelets partially restored platelet spreading in I-kappaB-alpha inhibited platelets, and addition of active IKK-beta increased endogenous I-kappaB-alpha phosphorylation levels.

CONCLUSIONS

These novel findings support a crucial and nonclassical role for the NF-kappaB family in modulating platelet function and reveal that platelets are sensitive to NF-kappaB inhibitors. As NF-kappaB inhibitors are being developed as antiinflammatory and anticancer agents, they may have unintended effects on platelets. On the basis of these data, NF-kappaB is also identified as a new target to dampen unwanted platelet activation.

Chemokine CCL2/MCP-1 negatively regulates metastasis in a highly bone marrow-metastatic mouse breast cancer model

Bone is the most frequent site of breast cancer metastasis, and once such metastasis occurs, complete remission is extremely difficult to achieve. In an effort to define the mechanisms underlying metastatic spread of breast cancer to bone, we previously developed and characterized the highly bone metastatic 4T1E/M3 mouse breast cancer cells. We found that following injection into mice, 4T1E/M3 cells exhibited greater bone metastasis and greater in vitro anchorage-independent growth and cell migration than their parental cells (4T1E). We also found that expression of intracellular adhesion molecule-1 (ICAM-1) is crucially involved in these metastatic activities of 4T1E/M3 cells. In the present study, our analysis of gene and protein expression revealed that production of chemokine CCL2 (MCP-1) is dramatically reduced in 4T1E/M3 cells, and that restoration of CCL2 expression in 4T1E/M3 cells diminishes their metastasis to bone and lung. Overexpression of CCL2 in 4T1E/M3 cells significantly reduced not only in vitro anchorage-independent cell growth and cell migration, but also mRNA and cell surface expression of ICAM-1. Conversely, knocking down CCL2 in 4T1E parental cells augmented their metastatic spread to spine and lung. The expression of ICAM-1 was also upregulated in 4T1E-derived CCL2 knockdown cells. Taken together, these results suggest that CCL2 expression may negatively regulate breast cancer metastasis to bone marrow and lung in our model and that expression of ICAM-1 plays a crucial role in that process.

Glucocorticoids increase CD4CD25 cell percentage and Foxp3 expression in patients with multiple sclerosis

OBJECTIVES

To determine whether percentages of CD4(+)CD25(high) T cells (a group of regulatory T cells, Treg) differ in patients with multiple sclerosis (MS) in relapse vs remission after glucocorticoid treatment and whether treatment for relapses changes Treg population and the expression of Foxp3, a key Treg-associated molecule.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMC) were obtained from 20 patients with MS during relapse, just before and 2 days after starting steroid treatment (i.v. methylprednisolone 1 g/day for 3 days) and then 6 weeks after treatment. CD4(+)CD25(hi) cells were analysed by using flow cytometry. Cytokines were measured by using an ELISA and Foxp3, CD3 and CD25 expression by using quantitative real-time PCR.

RESULTS

The percentage of CD4(+)CD25(hi) cells, plasma IL-10 and Foxp3/CD3 ratio increased 48 h after methylprednisolone initiation and returned to baseline values by 6 weeks post-treatment.

CONCLUSIONS

Results suggest that glucocorticoids increase Treg cell functional molecules and percentages. This may be a mechanism whereby steroids expedite recovery from MS relapses.

Glucocorticoid regulation of preproglucagon transcription and RNA stability during stress

Stress elicits a synchronized response of the endocrine, sympathetic, and central nervous systems to preserve homeostasis and well-being. Glucagon-like peptide-1 (GLP-1), a primary posttranslational product of the preproglucagon (PPG) gene, activates both physical and psychological stress responses. The current study examined mechanisms regulating expression of PPG gene products in the hindbrain. Our results indicate that PPG mRNA decreases rapidly after exposure to acute stressors of multiple modalities. Reduced mRNA levels are accompanied by reduced GLP-1 immunoreactivity in the paraventricular nucleus of hypothalamus, suggesting release at PPG terminals. Stress-induced decrements in PPG mRNA were attenuated in adrenalectomized-corticosterone-replaced rats, suggesting that mRNA down-regulation is due at least in part to glucocorticoid secretion. In contrast, acute stress increased levels of PPG heteronuclear RNA (hnRNA) in a glucocorticoid-dependent manner, suggesting that decreases in PPG mRNA are due to increased degradation rather than reduced transcription. Glucocorticoid administration to unstressed rats is sufficient to cause decrements in PPG mRNA and increments in PPG hnRNA. These findings suggest that glucocorticoids deplete the pool of transcribed PPG mRNA and concurrently stimulate PPG gene transcription, with the latter allowing a mechanism for replenishment of PPG mRNA after stress cessation. The combination of rapid PPG mRNA depletion and initiation of PPG transcription within 30 min is consistent with a rapid action of glucocorticoids on GLP-1 bioavailability, resulting in a transient reduction in the capacity for neuropeptidergic excitation of stress responses.

Therapeutic manipulation of glucocorticoid metabolism in cardiovascular disease

The therapeutic potential for manipulation of glucocorticoid metabolism in cardiovascular disease was revolutionized by the recognition that access of glucocorticoids to their receptors is regulated in a tissue-specific manner by the isozymes of 11beta-hydroxysteroid dehydrogenase. Selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 have been shown recently to ameliorate cardiovascular risk factors and inhibit the development of atherosclerosis. This article addresses the possibility that inhibition of 11beta-hydroxsteroid dehydrogenase type 1 activity in cells of the cardiovascular system contributes to this beneficial action. The link between glucocorticoids and cardiovascular disease is complex as glucocorticoid excess is linked with increased cardiovascular events but glucocorticoid administration can reduce atherogenesis and restenosis in animal models. There is considerable evidence that glucocorticoids can interact directly with cells of the cardiovascular system to alter their function and structure and the inflammatory response to injury. These actions may be regulated by glucocorticoid and/or mineralocorticoid receptors but are also dependent on the 11beta-hydroxysteroid dehydrogenases which may be expressed in cardiac, vascular (endothelial, smooth muscle) and inflammatory (macrophages, neutrophils) cells. The activity of 11beta-hydroxysteroid dehydrogenases in these cells is dependent upon differentiation state, the action of pro-inflammaotory cytokines and the influence of endogenous inhibitors (oxysterols, bile acids). Further investigations are required to clarify the link between glucocorticoid excess and cardiovascular events and to determine the mechanism through which glucocorticoid treatment inhibits atherosclerosis/restenosis. This will provide greater insights into the potential benefit of selective 11beta-hydroxysteroid dehydrogenase inhibitors in treatment of cardiovascular disease.

Monocyte-mediated defense against microbial pathogens

Circulating blood monocytes supply peripheral tissues with macrophage and dendritic cell (DC) precursors and, in the setting of infection, also contribute directly to immune defense against microbial pathogens. In humans and mice, monocytes are divided into two major subsets that either specifically traffic into inflamed tissues or, in the absence of overt inflammation, constitutively maintain tissue macrophage/DC populations. Inflammatory monocytes respond rapidly to microbial stimuli by secreting cytokines and antimicrobial factors, express the CCR2 chemokine receptor, and traffic to sites of microbial infection in response to monocyte chemoattractant protein (MCP)-1 (CCL2) secretion. In murine models, CCR2-mediated monocyte recruitment is essential for defense against Listeria monocytogenes, Mycobacterium tuberculosis, Toxoplasma gondii, and Cryptococcus neoformans infection, implicating inflammatory monocytes in defense against bacterial, protozoal, and fungal pathogens. Recent studies indicate that inflammatory monocyte recruitment to sites of infection is complex, involving CCR2-mediated emigration of monocytes from the bone marrow into the bloodstream, followed by trafficking into infected tissues. The in vivo mechanisms that promote chemokine secretion, monocyte differentiation and trafficking, and finally monocyte-mediated microbial killing remain active and important areas of investigation.