Glucocorticoids limit acute lung inflammation in concert with inflammatory stimuli by induction of SphK1.

Acute lung injury (ALI) is a severe inflammatory disease for which no specific treatment exists. As glucocorticoids have potent immunosuppressive effects, their application in ALI is currently being tested in clinical trials. However, the benefits of this type of regimen remain unclear. Here we identify a mechanism of glucocorticoid action that challenges the long-standing dogma of cytokine repression by the glucocorticoid receptor. Contrarily, synergistic gene induction of sphingosine kinase 1 (SphK1) by glucocorticoids and pro-inflammatory stimuli via the glucocorticoid receptor in macrophages increases circulating sphingosine 1-phosphate levels, which proves essential for the inhibition of inflammation. Chemical or genetic inhibition of SphK1 abrogates the therapeutic effects of glucocorticoids. Inflammatory p38 MAPK- and mitogen- and stress-activated protein kinase 1 (MSK1)-dependent pathways cooperate with glucocorticoids to upregulate SphK1 expression. Our findings support a critical role for SphK1 induction in the suppression of lung inflammation by glucocorticoids, and therefore provide rationales for effective anti-inflammatory therapies.

Glucocorticoid receptor dimerization is required for survival in septic shock via suppression of interleukin-1 in macrophages.

Sepsis is controlled by endogenous glucocorticoids (GCs). Previous studies provided evidence that crosstalk of the monomeric GC receptor (GR) with proinflammatory transcription factors is the crucial mechanism underlying the suppressive GC effect. Here we demonstrate that mice with a dimerization-deficient GR (GR(dim)) are highly susceptible to sepsis in 2 different models, namely cecal ligation and puncture and lipopolysaccharide (LPS)-induced septic shock. TNF-α is normally regulated in these mice, but down-regulation of IL-6 and IL-1ß is diminished. LPS-treated macrophages derived from GR(dim) mice are largely resistant to GC actions in vitro in terms of morphology, surface marker expression, and gene expression. Treatment with recombinant IL-1 receptor antagonist improved survival of GR(dim) mice and mice lacking the GR in macrophages (GR(LysMCre)) mice. This suggests that regulation of IL-1ß in macrophages by GCs is pivotal to control sepsis.

In vivo phosphoenolpyruvate carboxykinase promoter mapping identifies disrupted hormonal synergism as a target of inflammation during sepsis in mice.

UNLABELLED: In mammals, proper maintenance of blood glucose levels within narrow limits is one of the most critical prerequisites for healthy energy homeostasis and body function. Consequently, hyper- and hypoglycemia represent hallmarks of severe metabolic pathologies, including type II diabetes and acute sepsis, respectively. Although the liver plays a crucial role in the control of systemic glucose homeostasis, the molecular mechanisms of aberrant hepatic glucose regulation under metabolic stress conditions remain largely unknown. Here we report the development of a liver-specific adenoviral in vivo system for monitoring promoter activity of the key gluconeogenic enzyme gene phosphoenolpyruvate carboxykinase (PEPCK) in mice. By employing in vivo promoter deletion technology, the glucocorticoid response unit (GRU) and the cyclic adenosine monophosphate (cAMP)-responsive element (CRE) were identified as critical cis-regulatory targets of proinflammatory signaling under septic conditions. In particular, both elements were found to be required for inhibition of PEPCK transcription during sepsis, thereby mediating endotoxic hypoglycemia. Indeed, expression of nuclear receptor cofactor peroxisome proliferator-activator receptor coactivator 1alpha (PGC-1alpha), the molecular mediator of GRU/CRE synergism on the PEPCK promoter, was found to be specifically repressed in septic liver, and restoration of PGC-1alpha in cytokine-exposed hepatocytes blunted the inhibitory effect of proinflammatory signaling on PEPCK gene expression. CONCLUSION: The dysregulation of hormonal synergism through the repression of PGC-1alpha as identified by in vivo promoter monitoring may provide a molecular rationale for hypoglycemia during sepsis, thereby highlighting the importance of hepatic glucose homeostasis for metabolic dysfunction in these patients.

Cell-specific regulation of PTX3 by glucocorticoid hormones in hematopoietic and nonhematopoietic cells.

PTX3 (prototypic long pentraxin 3) is a fluid phase pattern recognition receptor, which plays nonredundant roles in the resistance against diverse pathogens, in the assembly of a hyaluronic acid-rich extracellular matrix, and in female fertility. Inflammatory signals induce production of PTX3 in diverse cell types, including myeloid dendritic cells (DC), fibroblasts, and endothelial cells (EC). The present study was designed to explore the effect of glucocorticoid hormones (GC) on PTX3 production in different cellular contexts. In myeloid DC, GC inhibited the PTX3 production. In contrast, in fibroblasts and EC, GC alone induced and, under inflammatory conditions, enhanced and extended PTX3 production. In vivo administration of GC augmented the blood levels of PTX3 in mice and humans. Moreover, patients with Cushing syndrome had increased levels of circulating PTX3, whereas PTX3 levels were decreased in subjects affected by iatrogenic hypocortisolism. In nonhematopoietic cells, GC receptor (GR) functioned as a ligand-dependent transcription factor (dimerization-dependent) to induce PTX3 gene expression. In contrast, in hematopoietic cells, GR repressed PTX3 gene transcription by interfering (dimerization-independent) with the action of other signaling pathways, probably NFkappaB and AP-1. Thus, divergent effects of GC were found to be due to different GR mechanisms. The results presented here indicate that GC have divergent effects on PTX3 production in hematopoietic (DC and macrophages) and nonhematopoietic (fibroblasts and EC) cells. The divergent effects of GC on PTX3 production probably reflect the different functions of this multifunctional molecule in innate immunity and in the construction of the extracellular matrix.

Peripheral T cells are the therapeutic targets of glucocorticoids in experimental autoimmune encephalomyelitis.

High-dose glucocorticoid (GC) therapy is widely used to treat multiple sclerosis (MS), but the underlying mechanisms remain debatable. In this study, we investigated the impact of GC administration on experimental autoimmune encephalomyelitis using different GC receptor (GR)-deficient mutants. Heterozygous GR knockout mice were less sensitive to dexamethasone therapy, indicating that the expression level of the receptor determines therapeutic efficacy. Mice reconstituted with homozygous GR knockout fetal liver cells showed an earlier onset of the disease and were largely refractory to GC treatment, indicating that the GR in hematopoietic cells is essential for the beneficial effects of endogenous GCs and dexamethasone. Using cell-type specific GR-deficient mice, we could demonstrate that GCs mainly act on T cells, while modulation of macrophage function was largely dispensable in this context. The therapeutic effects were achieved through induction of apoptosis and down-regulation of cell adhesion molecules in peripheral T(H)17 and bystander T cells, while similar effects were not observed within the spinal cord. In addition, dexamethasone inhibited T cell migration into the CNS, confirming that peripheral but not CNS-residing T lymphocytes are the essential targets of GCs. Collectively, our findings reveal a highly selective mechanism of GC action in experimental autoimmune encephalomyelitis and presumably multiple sclerosis.

Glucocorticoid receptor action in beneficial and side effects of steroid therapy: lessons from conditional knockout mice.

Glucocorticoids (GCs) are potent immune suppressive drugs with unfortunately severe side effects. Different molecular modes of actions of the GC receptor (GR) have been identified. Transcriptional transactivation by binding of a dimerized GR protein complex to the promoter of GC regulated genes or interference with activity of pro-inflammatory transcription factors by GR monomers are considered as the two major mechanisms. It has been hypothesized that selective GR agonists (SEGRAs) addressing dimer-independent function would reveal potent steroid therapeutic activity with reduced side effects. Recent studies of a mouse knock-in strain with a dimerization-deficient GR demonstrate that some inflammatory processes can be suppressed by GCs, while others cannot. Also side effects of GCs occur in these mice. Thus, depending on the process that is treated, SEGRA could be therapeutically more or less effective and not all side effects of steroid therapy may be reduced.

Macrophages and neutrophils are the targets for immune suppression by glucocorticoids in contact allergy.

Glucocorticoids (GCs) are widely used in the treatment of allergic skin conditions despite having numerous side effects. Here we use Cre/loxP-engineered tissue- and cell-specific and function-selective GC receptor (GR) mutant mice to identify responsive cell types and molecular mechanisms underlying the antiinflammatory activity of GCs in contact hypersensitivity (CHS). CHS was repressed by GCs only at the challenge phase, i.e., during reexposure to the hapten. Inactivation of the GR gene in keratinocytes or T cells of mutant mice did not attenuate the effects of GCs, but its ablation in macrophages and neutrophils abolished downregulation of the inflammatory response. Moreover, mice expressing a DNA binding-defective GR were also resistant to GC treatment. The persistent infiltration of macrophages and neutrophils in these mice is explained by an impaired repression of inflammatory cytokines and chemokines such as IL-1beta, monocyte chemoattractant protein-1, macrophage inflammatory protein-2, and IFN-gamma-inducible protein 10. In contrast TNF-alpha repression remained intact. Consequently, injection of recombinant proteins of these cytokines and chemokines partially reversed suppression of CHS by GCs. These studies provide evidence that in contact allergy, therapeutic action of corticosteroids is in macrophages and neutrophils and that dimerization GR is required.

Antiinflammatory effects of dexamethasone are partly dependent on induction of dual specificity phosphatase 1.

Glucocorticoids (GCs), which are used in the treatment of immune-mediated inflammatory diseases, inhibit the expression of many inflammatory mediators. They can also induce the expression of dual specificity phosphatase 1 (DUSP1; otherwise known as mitogen-activated protein kinase [MAPK] phosphatase 1), which dephosphorylates and inactivates MAPKs. We investigated the role of DUSP1 in the antiinflammatory action of the GC dexamethasone (Dex). Dex-mediated inhibition of c-Jun N-terminal kinase and p38 MAPK was abrogated in DUSP1-/- mouse macrophages. Dex-mediated suppression of several proinflammatory genes (including tumor necrosis factor, cyclooxygenase 2, and interleukin 1alpha and 1beta) was impaired in DUSP1-/- mouse macrophages, whereas other proinflammatory genes were inhibited by Dex in a DUSP1-independent manner. In vivo antiinflammatory effects of Dex on zymosan-induced inflammation were impaired in DUSP1-/- mice. Therefore, the expression of DUSP1 is required for the inhibition of proinflammatory signaling pathways by Dex in mouse macrophages. Furthermore, DUSP1 contributes to the antiinflammatory effects of Dex in vitro and in vivo.

Molecular mechanisms of glucocorticoids in the control of inflammation and lymphocyte apoptosis.

The immune system must be tightly controlled not only to guarantee efficient protection from invading pathogens and oncogenic cells but also to avoid exaggerated immune responses and autoimmunity. This is achieved through interactions amongst leukocytes themselves, by signals from stromal cells and also by various hormones, including glucocorticoids. The glucocorticoids are a class of steroid hormones that exert a wide range of anti-inflammatory and immunosuppressive activities after binding to the glucocorticoid receptor. The power of these hormones was acknowledged many decades ago, and today synthetic derivatives are widely used in the treatment of inflammatory disorders, autoimmunity and cancer. In this review, we summarize our present knowledge of the molecular mechanisms of glucocorticoid action, their influence on specific leukocytes and the induction of thymocyte apoptosis, with an emphasis on how molecular genetics has contributed to our growing, although still incomplete, understanding of these processes.

HERV-K(HML-2) GAG/ENV antibodies as indicator for therapy effect in patients with germ cell tumors.

Germ cell tumors (GCT) are strictly associated with the expression of HERV-K(HML-2) proviruses, and the majority of GCT patients produce antibodies to structural proteins of these proviruses. The objective of our study was to determine the significance of the serological response to HERV-K(HML-2) Gag and Env proteins for diagnosis, management of GCT patients and estimation of the therapy success. The data document a strong association of HERV-K(HML-2) antibodies and the clinical manifestation of the disease and therapy success. HERV-K(HML-2) antibodies seem to have an important diagnostic value as well as indicator of chemotherapy success.