Mitogen-activated protein kinase kinase 1/extracellular signal-regulated kinase (MEK-1/ERK) inhibitors sensitize reduced glucocorticoid response mediated by TNFalpha in human epidermal keratinocytes (HaCaT)

ERK/MEK Pathway Regulates Th17 Cell Differentiation in Patients with Pemphigus Vulgaris

Background

T helper (Th) cells are involved in the pathogenesis of pemphigus vulgaris (PV). However, the mechanism still needs more exploration.

Aims

This study aimed to evaluate the molecular mechanism of the dysregulation of Th17 cells in the peripheral blood of patients with PV.

Materials and Methods

Serum levels of IL-17 and anti-Dsg3 titres in patients with PV were analysed using ELISA. The mRNA expression of retinoic acid orphan receptor γt (RORγt) in CD4+ T cells was detected using reverse transcription-quantitative PCR (qPCR). The number of Th17 cells was examined using flow cytometry. Western blot analysis and immunofluorescent staining were also performed to investigate the expression levels of ERK/MAPK signalling proteins and Th17 lineage-associated proteins.

Results

The proportion of Th17 cells and Th17 spectrum-associated proteins (p-STAT3, RORγt and IL-17) were upregulated in CD4+ cells in PV patients. The increased transcriptional levels of RORγt and IL-17 correlated positively with the severity of PV. Elevated phosphorylation of the ERK signalling factors was found in the collected CD4+ T cells in PV patients. The inhibition of the ERK signalling pathway significantly reduced the differentiation of Th17 cells in PV patients in vitro.

Conclusion

Th17 cells are essential in the dysregulation of PV, and ERK signalling is involved in Th17-type immunity and promotes the development of PV. The study here provides us with a potential therapeutic target for PV.

Glucocorticoids and Glucocorticoid-Induced-Leucine-Zipper (GILZ) in Psoriasis

Psoriasis is a prevalent chronic inflammatory human disease initiated by impaired function of immune cells and epidermal keratinocytes, resulting in increased cytokine production and hyperproliferation, leading to skin lesions. Overproduction of Th1- and Th17-cytokines including interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-23, IL-17, and IL-22, is a major driver of the disease. Glucocorticoids (GCs) represent the mainstay protocol for treating psoriasis as they modulate epidermal differentiation and are potent anti-inflammatory compounds. The development of safer GC-based therapies is a high priority due to potentially severe adverse effects associated with prolonged GC use. Specific efforts have focused on downstream anti-inflammatory effectors of GC-signaling such as GC-Induced-Leucine-Zipper (GILZ), which suppresses Th17 responses and antagonizes multiple pro-inflammatory signaling pathways involved in psoriasis, including AP-1, NF-κB, STAT3, and ROR-γt. Here we review evidence regarding defective GC signaling, GC receptor (GR) function, and GILZ in psoriasis. We discuss seemingly contradicting data on the loss- and gain-of-function of GILZ in the imiquimod-induced mouse model of psoriasis. We also present potential therapeutic strategies aimed to restore GC-related pathways.

Glucocorticoid insensitivity by staphylococcal enterotoxin B in keratinocytes of allergic dermatitis is associated with impaired nuclear translocation of the Glucocorticoid Receptor α

BACKGROUND

staphylococcal enterotoxin plays an important role in patients with glucocorticoid (GC)-resistant atopic dermatitis (AD), but the exact mechanism is not fully understood.

OBJECTIVE

The aim of this study was to investigate the mechanisms underlying the ability of staphylococcal enterotoxin B (SEB) to induce steroid insensitivity through impaired nuclear translocation of GRα in keratinocytes.

METHODS

The steroid-resistant AD induced by SEB was assessed by analyzing dermatitis score, dermal thickness, scratching behavior, infiltrating cells/HPF, levels of SEB-specific IgE and IgG2a antibody. In addition, dexamethasone (DEX)-induced GRα nuclear translocation and keratinocyte-derived cytokines and chemokines were analyzed in the lesional keratinocytes of AD and in HaCaT cells. Furthermore, the expressions of immunophilins FKBP51, FKBP52 and HSP90 responsive to GC in HaCaT cells were determined in the presence of SEB.

RESULTS

SEB dose-dependently diminished the inhibitory effect of DEX on dermatitis score, dermal thickness, scratching behavior, infiltrating cells/HPF, keratinocyte-derived cytokines and chemokines such as RANTES, MCP-1, TSLP and GM-CSF. In vivo and in vitro data showed that in the presence of DEX, SEB dose-dependently caused a marked decrease of GRα nuclear translocation in lesional keratinocytes of AD and in HaCaT cells. Importantly, in the presence of DEX, SEB increased the expression of FKBP51 and the product of keratinocyte-derived cytokines and chemokines in HaCaT cells.

CONCLUSION

These results demonstrate that GC insensitivity by SEB in keratinocytes of AD is associated with impaired nuclear translocation of the GRα. Increased DEX-induced FKBP51 by SEB may contribute to accumulation of the GRα in cytoplasm of keratinocytes.

Inflammatory Signaling in Hypertension: Regulation of Adrenal Catecholamine Biosynthesis

The immune system is increasingly recognized for its role in the genesis and progression of hypertension. The adrenal gland is a major site that coordinates the stress response via the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal system. Catecholamines released from the adrenal medulla function in the neuro-hormonal regulation of blood pressure and have a well-established link to hypertension. The immune system has an active role in the progression of hypertension and cytokines are powerful modulators of adrenal cell function. Adrenal medullary cells integrate neural, hormonal, and immune signals. Changes in adrenal cytokines during the progression of hypertension may promote blood pressure elevation by influencing catecholamine biosynthesis. This review highlights the potential interactions of cytokine signaling networks with those of catecholamine biosynthesis within the adrenal, and discusses the role of cytokines in the coordination of blood pressure regulation and the stress response.

Long-acting β2-agonists promote glucocorticoid-mediated repression of NF-κB by enhancing expression of the feedback regulator TNFAIP3

Glucocorticoids, or corticosteroids, are effective treatments for many chronic inflammatory diseases, and in mild/moderate asthma, long-acting β₂-adrenoceptor agonists (LABAs) enhance the efficacy of inhaled corticosteroids (ICSs) more than increasing the ICS dose. In human bronchial epithelial, BEAS-2B, cells, expression of TNFα-induced protein-3 (TNFAIP3), or A20, a dual-ubiquitin ligase that provides feedback inhibition of NF-κB, was induced by budesonide, an ICS, and formoterol, a LABA, and was further enhanced by budesonide-formoterol combination. The proinflammatory cytokine TNF induced TNFAIP3 and TNF expression. Whereas subsequent budesonide treatment enhanced TNF-induced TNFAIP3 and reduced TNF expression, formoterol amplified these differential effects. In primary human airway smooth muscle cells, TNFAIP3 expression was induced by TNF. This was largely unaffected by budesonide but was acutely enhanced by budesonide-formoterol combination. In BEAS-2B cells, TNF recruited RELA, the main NF-κB transactivating subunit, to a 3' region of the TNF gene. RELA binding was reduced by budesonide, was further reduced by formoterol cotreatment, and was associated with reduced RNA polymerase II recruitment to the TNF gene. This is consistent with reduced TNF expression. TNFAIP3 knockdown enhanced TNF expression in the presence of TNF, TNF plus budesonide, and TNF plus budesonide-formoterol combination and confirms feedback inhibition. A luciferase reporter containing the TNF 3' RELA binding region recapitulated TNF inducibility and was inhibited by an IκB kinase inhibitor and TNFAIP3 overexpression. Repression of reporter activity by budesonide was increased by formoterol and involved TNFAIP3. Thus LABAs may improve the anti-inflammatory properties of ICSs by augmenting TNFAIP3 expression to negatively regulate NF-κB.

Blockade of interleukin-6 receptor enhances the anti-arthritic effect of glucocorticoids without decreasing bone mineral density in mice with collagen-induced arthritis

In a mouse arthritis model, we investigated whether interleukin-6 receptor (IL-6R) blockade would enhance the anti-arthritic effect of glucocorticoids (GCs). DBA/1J mice were immunized with type II collagen (CII), and were treated with prednisolone (PSL) and/or anti-mouse IL-6R antibody (MR16-1). Also, the effects of IL-6 on gene expression and the nuclear translocation of glucocorticoid receptors (GRs) were examined in cultured cells treated with dexamethasone (DEX). PSL reduced the arthritis score dose-dependently in the collagen-induced arthritis (CIA) mouse model. The arthritis score in the PSL (3 mg/kg) + MR16-1 group was lower than in the PSL (3 mg/kg) group, and at the same level as in the PSL (6 mg/kg) group. Lumbar vertebra bone mineral density (BMD) was decreased significantly in CIA mice and was higher in the PSL (3 mg/kg) + MR16-1 group than in the PSL (6 mg/kg) group. In the in-vitro synovial cells, IL-6 pretreatment attenuated the inhibitory effect of DEX on cyclooxygenase (COX)-2 expression and inhibited the nuclear translocation of GR induced by DEX. In contrast, in MC3T3-E1 osteoblastic cells, IL-6 pretreatment exacerbated the decrease in expression of osteocalcin and the increase in expression of receptor activator of nuclear factor kappa-B ligand (RANKL) by DEX. We demonstrated that IL-6 signalling blockade by an anti-IL-6R antibody can augment the anti-arthritic effect of GCs and inhibit the bone loss they cause.

Cytokine-induced loss of glucocorticoid function: effect of kinase inhibitors, long-acting β(2)-adrenoceptor [corrected] agonist and glucocorticoid receptor ligands

Acting on the glucocorticoid receptor (NR3C1), glucocorticoids are widely used to treat inflammatory diseases. However, glucocorticoid resistance often leads to suboptimal asthma control. Since glucocorticoid-induced gene expression contributes to glucocorticoid activity, the aim of this study was to use a 2 × glucocorticoid response element (GRE) reporter and glucocorticoid-induced gene expression to investigate approaches to combat cytokine-induced glucocorticoid resistance. Pre-treatment with tumor necrosis factor-α (TNF) or interleukin-1β inhibited dexamethasone-induced mRNA expression of the putative anti-inflammatory genes RGS2 and TSC22D3, or just TSC22D3, in primary human airway epithelial and smooth muscle cells, respectively. Dexamethasone-induced DUSP1 mRNA was unaffected. In human bronchial epithelial BEAS-2B cells, dexamethasone-induced TSC22D3 and CDKN1C expression (at 6 h) was reduced by TNF pre-treatment, whereas DUSP1 and RGS2 mRNAs were unaffected. TNF pre-treatment also reduced dexamethasone-dependent 2×GRE reporter activation. This was partially reversed by PS-1145 and c-jun N-terminal kinase (JNK) inhibitor VIII, inhibitors of IKK2 and JNK, respectively. However, neither inhibitor affected TNF-dependent loss of dexamethasone-induced CDKN1C or TSC22D3 mRNA. Similarly, inhibitors of the extracellular signal-regulated kinase, p38, phosphoinositide 3-kinase or protein kinase C pathways failed to attenuate TNF-dependent repression of the 2×GRE reporter. Fluticasone furoate, fluticasone propionate and budesonide were full agonists relative to dexamethasone, while GSK9027, RU24858, des-ciclesonide and GW870086X were partial agonists on the 2×GRE reporter. TNF reduced reporter activity in proportion with agonist efficacy. Full and partial agonists showed various degrees of agonism on RGS2 and TSC22D3 expression, but were equally effective at inducing CDKN1C and DUSP1, and did not affect the repression of CDKN1C or TSC22D3 expression by TNF. Finally, formoterol-enhanced 2×GRE reporter activity was also proportional to agonist efficacy and functionally reversed repression by TNF. As similar effects were apparent on glucocorticoid-induced gene expression, the most effective strategy to overcome glucocorticoid resistance in this model was addition of formoterol to high efficacy NR3C1 agonists.

Impact of ozone exposure on the response to glucocorticoid in a mouse model of asthma: involvements of p38 MAPK and MKP-1

Background

Molecular mechanisms involved in the oxidative stress induced glucocorticoids insensitivity remain elusive. The mitogen-activated protein kinase phosphatase (MKP) 1 mediates a part of glucocorticoids action and can be modified by exogenous oxidants. Whether oxidant ozone (O₃) can affect the function of MKP-1 and hence blunt the response to corticotherapy is not clear.

Methods

Here we employed a murine model of asthma established with ovalbumin (OVA) sensitization and challenge to evaluate the influence of O₃ on the inhibitory effect of dexamethasone on AHR and airway inflammation, and by administration of SB239063, a selective p38 MAPK inhibitor, to explore the underlying involvements of the activation of p38 MAPK and the expression of MKP-1.

Results

Ozone exposure not only aggravated the pulmonary inflammation and AHR, but also decreased the inhibitory effects of dexamethasone, accompanied by the elevated oxidative stress, airway neutrophilia, enhanced phosphorylation of p38 MAPK, and upregulated expression of IL-17. Administration of SB239063 caused significant inhibition of the p38 MAPK phosphorylation, alleviation of the airway neutrophilia, and decrement of the ozone-induced IL-17 expression, and partly restored the ozone-impaired effects of dexamethasone. Ozone exposure not only decreased the protein expression of MKP-1, but also diminished the dexamethasone-mediated induction process of MKP-1 mRNA and protein expression.

Conclusions

The glucocorticoids insensitivity elicited by ozone exposure on current asthma model may involve the enhanced phosphorylation of p38 MAPK and disturbed expression of MKP-1.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0126-x) contains supplementary material, which is available to authorized users.

Dominance of the strongest: inflammatory cytokines versus glucocorticoids

Pro-inflammatory cytokines are involved in the pathogenesis of many inflammatory diseases, and the excessive expression of many of them is normally counteracted by glucocorticoids (GCs), which are steroids that bind to the glucocorticoid receptor (GR). Hence, GCs are potent inhibitors of inflammation, and they are widely used to treat inflammatory diseases, such as asthma, rheumatoid arthritis and inflammatory bowel disease. However, despite the success of GC therapy, many patients show some degree of GC unresponsiveness, called GC resistance (GCR). This is a serious problem because it limits the full therapeutic exploitation of the anti-inflammatory power of GCs. Patients with reduced GC responses often have higher cytokine levels, and there is a complex interplay between GCs and cytokines: GCs downregulate pro-inflammatory cytokines while cytokines limit GC action. Treatment of inflammatory diseases with GCs is successful when GCs dominate. But when cytokines overrule the anti-inflammatory actions of GCs, patients become GC insensitive. New insights into the molecular mechanisms of GR-mediated actions and GCR are needed for the design of more effective GC-based therapies.

The expression of the glucocorticoid receptor in human erythroblasts is uniquely regulated by KIT ligand: implications for stress erythropoiesis

Studies in mice indicated that activation of the erythroid stress pathway requires the presence of both soluble KIT ligand (KITL) and the glucocorticoid receptor (GR). To clarify the relative role of KITL and GR in stress erythropoiesis in humans, the biological activities of soluble full length- (fl-, 26-190 aa), carboxy-terminus truncated (tr-, 26-162 aa) human (hKITL) and murine (mKITL) KITL in cultures of cord blood (CB) mononuclear cells (MNCs) and CD34(pos) cells that mimic either steady state (growth factors alone) or stress (growth factors plus dexamethasone [DXM]) erythropoeisis were investigated. In steady state cultures, the KITLs investigated were equally potent in sustaining growth of hematopoietic colonies and expansion of megakaryocytes (MK) and erythroid precursors (EBs). By contrast, under stress erythropoiesis conditions, fl-hKITL generated greater numbers of EBs (fold increase [FI]=140) than tr-hKITL or mKITL (FI=20-40). Flow cytometric analyses indicated that only EBs generated with fl-hKITL remained immature (>70% CD36(pos)/CD235a(neg/low)), and therefore capable to proliferate, until day 8-12 in response to DXM. Signaling studies indicated that all KITLs investigated induced EBs to phosphorylate signal transducer and activator of transcription 5 (STAT5) but that extracellular-signaling-regulated-kinases (ERK) activation was observed mainly in the presence of fl-hKITL. EBs exposed to fl-hKITL also expressed higher levels of GRα than those exposed to mKITL (and tr-hKITL) which were reduced upon exposure to the ERK inhibitor U0126. These data reveal a unique requirement for fl-hKITL in the upregulation of GRα and optimal EB expansion in cultures that mimic stress erythropoiesis.

Glucocorticoid receptor dimerization induces MKP1 to protect against TNF-induced inflammation

Glucocorticoids acting through the glucocorticoid receptor (GR) inhibit TNF-induced lethal inflammation. Here, we demonstrate that GR dimerization plays a role in reducing TNF sensitivity. In mutant mice unable to dimerize GR, we found that TNF failed to induce MAPK phosphatase 1 (MKP1). We assessed TNF sensitivity in Mkp1(-/-) mice and found increased inflammatory gene induction in livers, increased circulating cytokines, cell death in intestinal epithelium, severe intestinal inflammation, hypothermia, and death. Mkp1(-/-) mice had increased levels of phosphorylated JNK, which promotes apoptosis, in liver tissue. We further examined JNK-deficient mice for their response to TNF. Although Jnk1(-/-) mice showed no change in sensitivity to TNF, Jnk2(-/-) mice were significantly protected against TNF, identifying JNK2 as an essential player in inflammation induced by TNF. Furthermore, we found that loss of Jnk2 partially rescued the increased sensitivity of Mkp1(-/-) and mutant GR mice to TNF. Our data show that GR dimerization inhibits JNK2 through MKP1 and protects from TNF-induced apoptosis and lethal inflammation.

Glucocorticoids inhibit lipopolysaccharide-mediated inflammatory response by downregulating microRNA-155: a novel anti-inflammation mechanism

Glucocorticoids (GCs) are among the most widely used and effective therapies for many chronic inflammatory diseases. Although attempts have been made to identify important protein-coding genes and pathways involved in the anti-inflammatory effect of GCs, knowledge of genomic aberrations associated with noncoding genes, such as micro-RNAs (miRNAs), and their contributions is relatively limited. In this study, a systematic screening of the miRNA expression profile by microarray showed that GCs inhibited the expression of miR-155 in lipopolysaccharide (LPS)-induced macrophage inflammatory responses. Overexpression of miR-155 markedly reversed the suppressive action of GCs, whereas inhibition of miR-155 exhibited an effect similar to that of GCs on LPS-treated RAW264.7 cells, indicating miR-155 to be a functional regulator in the anti-inflammatory effect of GCs. Furthermore, GCs inhibited miR-155 expression in a GC receptor- and NF-κB-dependent manner. Bioinformatics analysis and luciferase assay revealed that the NF-κB binding site located in the promoter region of the B-cell integration cluster was important in mediating the GC-driven suppression of miR-155 in response to LPS stimulation. In addition, the combination of treatment with GCs and inhibition of miR-155 enhanced the anti-inflammatory effect of GCs on LPS-stimulated RAW264.7 cells. Therefore, we identify miR-155 to be a novel target through which GCs exert their anti-inflammatory effect on the LPS-induced macrophage inflammatory response. These findings may provide a basic rationale for new approaches in the effort to develop anti-inflammatory therapeutics.

Glucocorticoid receptor-mediated transcriptional activation of S100P gene coding for cancer-related calcium-binding protein

S100P is a member of the S100 family of calcium-binding proteins involved in calcium sensing and signal transduction. Its abnormal expression and biological activities are linked to tumor phenotype, namely to increased survival, proliferation, invasion and metastatic propensity of tumor cells. Association of S100P with outcome of tumor treatment and preliminary data from S100P promoter analysis prompted us to study regulation of S100P expression by glucocorticoids, which are implicated in tumor response to chemotherapy. We showed that dexamethasone (DX), a representative glucocorticoid, was capable to induce activity of S100P promoter by means of increased expression, nuclear translocation, and transactivation properties of the glucocorticoid receptor (GR). Moreover, DX treatment led to decreased phosphorylation of ERK1/2, reduced transcriptional activity of AP1, and modulated activity of some additional transcription factors. We identified a promoter region responsible for DX-mediated transactivation and proved GR binding to S100P promoter. We found that the effect of DX was enhanced by partial but not complete inhibition of the MAPK/ERK pathway, supporting an active crosstalk between GR and MAPK/ERK signal transduction in control of S100P expression. On the other hand, suppression of GR mRNA level by transient siRNA expression resulted in reduced S100P transcription. The role of GR activation in S100P regulation was supported by co-expression of GR with S100P in cells treated with DX. These data suggest that S100P is a direct transcriptional target of glucocorticoid-mediated signaling in tumor cells that is activated through the interplay of GR and MAPK pathways.

Crosstalk between TNF and glucocorticoid receptor signaling pathways

TNF is a Janus-faced protein. It possesses impressive anti-tumor activities, but it is also one of the strongest known pro-inflammatory cytokines, which hampers its use as a systemic anti-cancer agent. TNF has been shown to play a detrimental role in inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease. Glucocorticoids are strongly anti-inflammatory and exert their therapeutic effects through binding to their receptor, the glucocorticoid receptor. Therefore, glucocorticoids have been used for over half a century for the treatment of inflammatory diseases. However, many patients are or become resistant to the therapeutic effects of glucocorticoids. Inflammatory cytokines have been suggested to play an important role in this steroid insensitivity or glucocorticoid resistance. This review aims to highlight the mechanisms of mutual inhibition between TNF and GR signaling pathways.

Cytokines and glucocorticoid receptor signaling. Relevance to major depression

Data suggest that the activation of immune responses and the release of inflammatory cytokines may play a role in the pathophysiology of major depression. One mechanism by which cytokines may contribute to depression is through their effects on the glucocorticoid receptor (GR). Altered GR function in depression has been demonstrated by neuroendocrine challenge tests that reliably reveal reduced GR sensitivity as manifested by nonsuppression of cortisol following dexamethasone administration in vivo and lack of immune suppression following administration of glucocorticoids in vitro. Relevant to the GR, cytokines have been shown to decrease GR expression, block translocation of the GR from cytoplasm to nucleus, and disrupt GR-DNA binding through nuclear protein-protein interactions. In addition, cytokines have been shown to increase the expression of the relatively inert GR beta isoform. Specific cytokine signaling molecules that have been shown to be involved in the disruption of GR activity include p38 mitogen-activated protein kinase, which is associated with reduced GR translocation, and signal transducer and activator of transcription (STAT)5, which binds to GR in the nucleus. Nuclear factor-kappaB (NF-kappaB) also has been shown to lead to GR suppression through mutually inhibitory GR-NF-kappaB nuclear interactions. Interestingly, several antidepressants have been shown to enhance GR function, as has activation of protein kinase A (PKA). Antidepressants and PKA activation have also been found to inhibit inflammatory cytokines and their signaling pathways, suggesting that drugs that target both inflammatory responses and the GR may have special efficacy in the treatment of depression.

Regulation of human tissue kallikrein-related peptidase expression by steroid hormones in 32 cell lines

Human tissue kallikrein-related peptidases(KLK), which are secreted serine proteases, are encoded by 15 genes located on chromosome 19q 13.4. Previous studies have shown that KLK expression is regulated by steroid hormones and many KLKs are dysregulated in hormone dependent malignancies. Some KLKs are proposed biomarkers for these cancers. We have characterized KLK hormonal regulation patterns using a large number of human cell lines. KLK levels were quantified in supernatants from 32 cell lines, each subjected to four hormonal stimulations (dexamethasone, norgestrel, dihydrotestosterone or estradiol), using ELISAs. Cell lines included breast, prostate, ovarian, lung, pancreatic, colon, and cervical cancer cells, T-lymphocytes, keratinocytes and non-cancerous epithelial breast cell line. KLKs were regulated in several cell lines not previously studied, such as keratinocytes (KLK 5, 6, and 7), ovarian cancer (KLK 5 and 9) and cervical cancer (KLK 3, 5, 6, 7,8, 10, 11, and 13) cells. Many KLKs were regulated by the synthetic glucocorticoid dexamethasone; specifically, KLK 5, 6, 8, 10, and 11 were upregulated in several breast cancer lines and downregulated in several cervical cancer lines. Knowledge of KLK hormonal regulation patterns will help to shed further light on their potential use as biomarkers and therapeutic targets for hormone-related malignancies.

Anti-inflammatory functions of glucocorticoid-induced genes

There is a broad consensus that glucocorticoids (GCs) exert anti-inflammatory effects largely by inhibiting the function of nuclear factor kappaB (NFkappaB) and consequently the transcription of pro-inflammatory genes. In contrast, side effects are thought to be largely dependent on GC-induced gene expression. Biochemical and genetic evidence suggests that the positive and negative effects of GCs on transcription can be uncoupled from one another. Hence, novel GC-related drugs that mediate inhibition of NFkappaB but do not activate gene expression are predicted to retain therapeutic effects but cause fewer or less severe side effects. Here, we critically re-examine the evidence in favor of the consensus, binary model of GC action and discuss conflicting evidence, which suggests that anti-inflammatory actions of GCs depend on the induction of anti-inflammatory mediators. We propose an alternative model, in which GCs exert anti-inflammatory effects at both transcriptional and post-transcriptional levels, both by activating and inhibiting expression of target genes. The implications of such a model in the search for safer anti-inflammatory drugs are discussed.

The stimulus-dependent co-localization of serum- and glucocorticoid-regulated protein kinase (Sgk) and Erk/MAPK in mammary tumor cells involves the mutual interaction with the importin-alpha nuclear import protein

In Con8 rat mammary epithelial tumor cells, indirect immunofluorescence revealed that Sgk (serum- and glucocorticoid-regulated kinase) and Erk/MAPK (extracellular signal-regulated protein kinase/mitogen activated protein kinase) co-localized to the nucleus in serum-treated cells and to the cytoplasmic compartment in cells treated with the synthetic glucocorticoid dexamethasone. Moreover, the subcellular distribution of the importin-alpha nuclear transport protein was similarly regulated in a signal-dependent manner. In vitro GST-pull down assays revealed the direct interaction of importin-alpha with either Sgk or Erk/MAPK, while RNA interference knockdown of importin-alpha expression disrupted the localization of both Sgk and Erk into the nucleus of serum-treated cells. Wild type or kinase dead forms of Sgk co-immunoprecipitated with Erk/MAPK from either serum- or dexamethasone-treated mammary tumor cells, suggesting the existence of a protein complex containing both kinases. In serum-treated cells, nucleus residing Sgk and Erk/MAPK were both hyperphosphorylated, indicative of their active states, whereas, in dexamethasone-treated cells Erk/MAPK, but not Sgk, was in its inactive hypophosphorylated state. Treatment with a MEK inhibitor, which inactivates Erk/MAPK, caused the relocalization of both Sgk and ERK to the cytoplasm. We therefore propose that the signal-dependent co-localization of Sgk and Erk/MAPK mediated by importin-alpha represents a new pathway of signal integration between steroid and serum/growth factor-regulated pathways.

De-phosphorylation of TRalpha-1 by p44/42 MAPK inhibition enhances T(3)-mediated GLUT5 gene expression in the intestinal cell line Caco-2 cells

Thyroid hormone and p44/42 MAPK inactivation are important in intestinal differentiation. We demonstrated not only that treatment with p44/42 MAPK inhibitor U0126 in intestinal cell line Caco-2 cells reduced the phosphorylation of serine and threonine residues of TRalpha-1, but also that T(3) and U0126 synergistically induced GLUT5 gene expression. EMSA demonstrated that the binding activity of TRalpha-1-RXR heterodimer on GLUT5-TRE in nuclear proteins of Caco-2 cells was synergistically enhanced by co-incubation in vitro with T(3) and CIAP, which strongly de-phosphorylates proteins. ChIP and transfection assays revealed that co-treatment of T(3) and U0126 induces TRalpha-1-RXR binding to GLUT5-TRE on the human GLUT5 enhancer region, and recruitment of the transcriptional complex in cells. These results suggest that inactivation of p44/42 MAPK enhances T(3)-induced GLUT5 gene expression in Caco-2 cells through increasing TRalpha-1 transactivity and binding activity to the GLUT5-TRE, probably due to de-phosphorylation of TRalpha-1.