Superinduction of COX-2 mRNA by cycloheximide and interleukin-1beta involves increased transcription and correlates with increased NF-kappaB and JNK activation

Epigenetic modifications control CYP1A1 Inducibility in human and rat keratinocytes

Serially passaged rat keratinocytes exhibit dramatically attenuated induction of Cyp1a1 by aryl hydrocarbon receptor ligands such as TCDD. However, the sensitivity to induction can be restored by protein synthesis inhibition. Previous work revealed that the functionality of the receptor was not affected by passaging. The present work explored the possibility of epigenetic silencing on CYP1A1 inducibility in both rat and human cells. Use of an array of small molecule epigenetic modulators demonstrated that inhibition of histone deacetylases mimicked the effect of protein synthesis inhibition. Consistent with this finding, cycloheximide treatment also reduced histone deacetylase activity. More importantly, when compared to human CYP1A1, rat Cyp1a1 exhibited much greater sensitivity toward epigenetic modulators, particularly inhibitors of histone deacetylases. Other genes in the aryl hydrocarbon receptor domain showed variable and less dramatic responses to histone deacetylase inhibitors. These findings highlight a potential species difference in epigenetics that must be considered when extrapolating results from rodent models to humans and has implications for xenobiotic- or drug-drug interactions where CYP1A1 activity plays an important role.

Differential regulation of BIRC2 and BIRC3 expression by inflammatory cytokines and glucocorticoids in pulmonary epithelial cells

Roles for the baculoviral inhibitor of apoptosis repeat-containing (BIRC) genes, BIRC2 and BIRC3, may include signaling to the inflammatory transcription factor, nuclear factor-κB (NF-κB) and protection from cell death. However, distinct functions for each BIRC are not well-delineated. Given roles for the epithelium in barrier function and host defence, BIRC2 and BIRC3 expression was characterized in pulmonary epithelial cell lines and primary human bronchial epithelial cells (pHBECs) grown as undifferentiated cells in submersion culture (SC) or as highly differentiated cells at air-liquid interface (ALI). In A549 cells, interleukin-1β (IL1B) and tumor necrosis factor α (TNF) induced BIRC3 mRNA (~20-50-fold), with maximal protein expression from 6-24 h. Similar effects occurred in BEAS-2B and Calu-3 cells, as well as SC and ALI pHBECs. BIRC2 protein was readily detected in unstimulated cells, but was not markedly modulated by IL1B or TNF. Glucocorticoids (dexamethasone, budesonide) modestly increased BIRC3 mRNA and protein, but showed little effect on BIRC2 expression. In A549 cells, BIRC3 mRNA induced by IL1B was unchanged by glucocorticoids and showed supra-additivity with TNF-plus-glucocorticoid. Supra-additivity was also evident for IL1B-plus-budesonide induced-BIRC3 in SC and ALI pHBECs. Using A549 cells, IL1B- and TNF-induced BIRC3 expression, and to a lesser extent, BIRC2, was prevented by NF-κB inhibition. Glucocorticoid-induced BIRC3 expression was prevented by silencing and antagonism of the glucocorticoid receptor. Whereas TNF, but not IL1B, induced degradation of basal BIRC2 and BIRC3 protein, IL1B- and TNF-induced BIRC3 protein remained stable. Differential regulation by cytokines and glucocorticoids shows BIRC2 protein expression to be consistent with roles in rapid signaling events, whereas cytokine-induced BIRC3 may be more important in later effects. While TNF-induced degradation of both BIRCs may restrict their activity, cytokine-enhanced BIRC3 expression could prime for its function. Finally, shielding from glucocorticoid repression, or further enhancement by glucocorticoid, may indicate a key protective role for BIRC3.

Articular Chondrocyte Phenotype Regulation through the Cytoskeleton and the Signaling Processes That Originate from or Converge on the Cytoskeleton: Towards a Novel Understanding of the Intersection between Actin Dynamics and Chondrogenic Function

Numerous studies have assembled a complex picture, in which extracellular stimuli and intracellular signaling pathways modulate the chondrocyte phenotype. Because many diseases are mechanobiology-related, this review asked to what extent phenotype regulators control chondrocyte function through the cytoskeleton and cytoskeleton-regulating signaling processes. Such information would generate leverage for advanced articular cartilage repair. Serial passaging, pro-inflammatory cytokine signaling (TNF-α, IL-1α, IL-1β, IL-6, and IL-8), growth factors (TGF-α), and osteoarthritis not only induce dedifferentiation but also converge on RhoA/ROCK/Rac1/mDia1/mDia2/Cdc42 to promote actin polymerization/crosslinking for stress fiber (SF) formation. SF formation takes center stage in phenotype control, as both SF formation and SOX9 phosphorylation for COL2 expression are ROCK activity-dependent. Explaining how it is molecularly possible that dedifferentiation induces low COL2 expression but high SF formation, this review theorized that, in chondrocyte SOX9, phosphorylation by ROCK might effectively be sidelined in favor of other SF-promoting ROCK substrates, based on a differential ROCK affinity. In turn, actin depolymerization for redifferentiation would “free-up” ROCK to increase COL2 expression. Moreover, the actin cytoskeleton regulates COL1 expression, modulates COL2/aggrecan fragment generation, and mediates a fibrogenic/catabolic expression profile, highlighting that actin dynamics-regulating processes decisively control the chondrocyte phenotype. This suggests modulating the balance between actin polymerization/depolymerization for therapeutically controlling the chondrocyte phenotype.

Efficacy of methylprednisolone on T-2 toxin-induced cardiotoxicity in vivo: A pathohistological study

Our aim was to compare the protective efficacy of two different formulations of methylprednisolone in T-2 toxin-induced cardiomyopathy. Methylprednisolone (soluble form, Lemod-solu^® and/or depot form, Lemod-depo^®, a total single dose of 40 mg/kg im) was given immediately after T-2 toxin (1 LD₅₀ 0.23 mg/kg sc). The myocardial tissue samples were examinated by using histopathology, semiquantitative and imaging analyses on day 1, 7, 14, 21, 28 and 60 of the study. Therapeutic application of Lemod-solu^® significantly decreased the intensity of myocardial degeneration and haemorrhages, distribution of glycogen granules in the endo- and perimysium, a total number of mast cells and the degree of their degranulation was in correlation with the reversible heart structural lesions (p <  0.01 vs. T-2 toxin). These changes were completely abolished by the therapeutic use of Lemod-solu^® plus Lemod-depo^® (p <  0.001 vs. T-2 toxin). Our results show that a significant cardioprotective efficacy of methylprednisolone is mediated by its anti-inflammatory activity.

Hypoxia-inducible factor (HIF)-prolyl hydroxylase 3 (PHD3) maintains high HIF2A mRNA levels in clear cell renal cell carcinoma

Most clear cell renal cell carcinomas (ccRCCs) have inactivation of the von Hippel-Lindau tumor suppressor protein (pVHL), resulting in the accumulation of hypoxia-inducible factor α-subunits (HIF-α) and their downstream targets. HIF-2α expression is particularly high in ccRCC and is associated with increased ccRCC growth and aggressiveness. In the canonical HIF signaling pathway, HIF-prolyl hydroxylase 3 (PHD3) suppresses HIF-2α protein by post-translational hydroxylation under sufficient oxygen availability. Here, using immunoblotting and immunofluorescence staining, qRT-PCR, and siRNA-mediated gene silencing, we show that unlike in the canonical pathway, PHD3 silencing in ccRCC cells leads to down-regulation of HIF-2α protein and mRNA. Depletion of other PHD family members had no effect on HIF-2α expression, and PHD3 knockdown in non-RCC cells resulted in the expected increase in HIF-2α protein expression. Accordingly, PHD3 knockdown decreased HIF-2α target gene expression in ccRCC cells and expression was restored upon forced HIF-2α expression. The effect of PHD3 depletion was pinpointed to HIF2A mRNA stability. In line with these in vitro results, a strong positive correlation of PHD3 and HIF2A mRNA expression in ccRCC tumors was detected. Our results suggest that in contrast to the known negative regulation of HIF-2α in most cell types, high PHD3 expression in ccRCC cells maintains elevated HIF-2α expression and that of its target genes, which may enhance kidney cancer aggressiveness.

Long-Acting β2-Adrenoceptor Agonists Enhance Glucocorticoid Receptor (GR)-Mediated Transcription by Gene-Specific Mechanisms Rather Than Generic Effects via GR

In asthma, the clinical efficacy of inhaled corticosteroids (ICSs) is enhanced by long-acting β2-adrenoceptor agonists (LABAs). ICSs, or more accurately, glucocorticoids, promote therapeutically relevant changes in gene expression, and, in primary human bronchial epithelial cells (pHBECs) and airway smooth muscle cells, this genomic effect can be enhanced by a LABA. Modeling this interaction in human bronchial airway epithelial BEAS-2B cells transfected with a 2× glucocorticoid response element (2×GRE)-driven luciferase reporter showed glucocorticoid-induced transcription to be enhanced 2- to 3-fold by LABA. This glucocorticoid receptor (GR; NR3C1)-dependent effect occurred rapidly, was insensitive to protein synthesis inhibition, and was maximal when glucocorticoid and LABA were added concurrently. The ability of LABA to enhance GR-mediated transcription was not associated with changes in GR expression, serine (Ser203, Ser211, Ser226) phosphorylation, ligand affinity, or nuclear translocation. Chromatin immunoprecipitation demonstrated that glucocorticoid-induced recruitment of GR to the integrated 2×GRE reporter and multiple gene loci, whose mRNAs were unaffected or enhanced by LABA, was also unchanged by LABA. Transcriptomic analysis revealed glucocorticoid-induced mRNAs were variably enhanced, unaffected, or repressed by LABA. Thus, events leading to GR binding at target genes are not the primary explanation for how LABAs modulate GR-mediated transcription. As many glucocorticoid-induced genes are independently induced by LABA, gene-specific control by GR- and LABA-activated transcription factors may explain these observations. Because LABAs promote similar effects in pHBECs, therapeutic relevance is likely. These data illustrate the need to understand gene function(s), and the mechanisms leading to gene-specific induction, if existing ICS/LABA combination therapies are to be improved.

Cyclooxygenase 2: its regulation, role and impact in airway inflammation

Cyclooxygenase 2 (COX-2: official gene symbol - PTGS2) has long been regarded as playing a pivotal role in the pathogenesis of airway inflammation in respiratory diseases including asthma. COX-2 can be rapidly and robustly expressed in response to a diverse range of pro-inflammatory cytokines and mediators. Thus, increased levels of COX-2 protein and prostanoid metabolites serve as key contributors to pathobiology in respiratory diseases typified by dysregulated inflammation. But COX-2 products may not be all bad: prostanoids can exert anti-inflammatory/bronchoprotective functions in airways in addition to their pro-inflammatory actions. Herein, we outline COX-2 regulation and review the diverse stimuli known to induce COX-2 in the context of airway inflammation. We discuss some of the positive and negative effects that COX-2/prostanoids can exert in in vitro and in vivo models of airway inflammation, and suggest that inhibiting COX-2 expression to repress airway inflammation may be too blunt an approach; because although it might reduce the unwanted effects of COX-2 activation, it may also negate the positive effects. Evidence suggests that prostanoids produced via COX-2 upregulation show diverse actions (and herein we focus on prostaglandin E2 as a key example); these can be either beneficial or deleterious and their impact on respiratory disease can be dictated by local concentration and specific interaction with individual receptors. We propose that understanding the regulation of COX-2 expression and associated receptor-mediated functional outcomes may reveal number of critical steps amenable to pharmacological intervention. These may prove invaluable in our quest towards future development of novel anti-inflammatory pharmacotherapeutic strategies for the treatment of airway diseases.

Regulation of the Expression of Heparan Sulfate 3-O-Sulfotransferase 3B (HS3ST3B) by Inflammatory Stimuli in Human Monocytes

Heparan sulfate (HS) is recognized as an important player in a wide range of dynamic steps of inflammatory reactions. Thereby, structural HS remodeling is likely to play an important role in the regulation of inflammatory and immune responses; however, little is known about underlying mechanism. In this study, we analyzed the regulation of expression of HS 3-O-sulfotransferases (HS3STs) in response to inflammatory stimuli. We found that among the seven HS3ST isoenzymes, only the expression of HS3ST3B was markedly up-regulated in human primary monocytes and the related cell line THP1 after exposure to TLR agonists. TNF-α was also efficient, to a lesser extent, to increase HS3ST3B expression, while IL-6, IL-4, and IFN-γ were poor inducers. We then analyzed the molecular mechanisms that regulate the high expression of HS3ST3B in response to LPS. Based on the expression of HS3ST3B transcripts and on the response of a reporter gene containing the HS3ST3B1 promoter, we provide evidence that LPS induces a rapid and strong transcription of HS3ST3B1 gene, which was mainly dependent on the activation of NF-κB and JNK signaling pathways. Additionally, active p38 MAPK and de novo synthesized proteins are involved in post-transcriptional mechanisms to maintain a high level of HS3ST3B mRNA to a steady state. Altogether, our findings indicate that HS3ST3B1 gene behaves as a primary response gene, suggesting that it may play an important role in making 3-O-sulfated HS with specific functions in the regulation of inflammatory and immune responses. J. Cell. Biochem. 117: 1529-1542, 2016. © 2015 Wiley Periodicals, Inc.

Regulation of peroxisome proliferator-activated receptors (PPAR) α and -γ of rat brain astrocytes in the course of activation by toll-like receptor agonists

Peroxisome proliferator-activated receptors (PPAR)-α and -γ in astrocytes play important roles in inflammatory brain pathologies. Understanding the regulation of both activity and expression levels of PPARs is an important neuroscience issue. Toll-like receptor (TLR) agonists are inflammatory stimuli that could modulate PPAR, but the mechanisms of their control in astrocytes are poorly understood. In the present study, we report that lipopolysaccharide, peptidoglycan, and flagellin, which are agonists of TLR4, TLR1/2, and TLR5, respectively, exert time- and nuclear factor kappa-light-chain-enhancer of activated B cells-dependent suppression of mRNA, protein and activity of PPARα and PPARγ. In naïve astrocytes, PPARα and PPARγ mRNA have short turnover time (half-life about 30 min for PPARα, 75 min for PPARγ) with a nearly two-fold stabilization after TLR-activation. p38 inhibition abolished TLR-induced stabilization. The levels of PPARα and PPARγ mRNA, and protein and DNA-binding activity could be modified using c-Jun N-terminal Kinase and p38 inhibitors. In addition, the expression levels of both PPARα and PPARγ isotypes were induced after inhibition of protein synthesis. This induction signifies participation of additional regulatory proteins with short life-time. They are p38-sensitive for PPARα and c-Jun N-terminal Kinase-sensitive for PPARγ. Thus, PPARα and PPARγ are regulated in astrocytes on mRNA and protein levels, mRNA stability, and DNA-binding activity during TLR-mediated responses. Astrocytes have the triad of PPARα, PPARβ/δ, and PPARγ in regulation of proinflammatory responses. Activation of Toll-like receptors (TLR) leads to PPARβ/δ overexpression, PPARα and PPARγ suppression via TLR/NF-κB pathway on mRNA, protein and activity levels. Mitogen-activated protein kinases (MAPK) p38 and JNK are involved in regulation of PPAR expression. p38 MAPK plays a special role in stabilization of PPAR mRNA.

c-Jun N-terminal kinase - c-Jun pathway transactivates Bim to promote osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disorder. Previous studies have shown abnormally increased apoptosis of chondrocytes in patients and animal models of OA. TNF-α and nitric oxide have been reported to induce chondrocyte ageing; however, the mechanism of chondrocyte apoptosis induced by IL-1β has remained unclear. The aim of this study is to identify the role of the c-Jun N-terminal kinase (JNK) - c-Jun pathway in regulating induction of Bim, and its implication in chondrocyte apoptosis. This study showed that Bim is upregulated in chondrocytes obtained from the articular cartilage of OA patients and in cultured mouse chondrocytes treated with IL-1β. Upregulation of Bim was found to be critical for chondrocyte apoptosis induced by IL-1β, as revealed by the genetic knockdown of Bim, wherein apoptosis was greatly reduced in the chondrocytes. Moreover, activation of the JNK-c-Jun pathway was observed under IL-1β treatment, as indicated by the increased expression levels of c-Jun protein. Suppression of the JNK-c-Jun pathway, using chemical inhibitors and RNA interference, inhibited the Bim upregulation induced by IL-1β. These findings suggest that the JNK-c-Jun pathway is involved in the upregulation of Bim during OA and that the JNK-c-Jun-Bim pathway is vital for chondrocyte apoptosis.

Calcium-mediated increased expression of fibroblast growth factor-2 acts through NF-κB and PGE2/EP4 receptor signaling pathways in cementoblasts

We reported previously that cementoblasts are provided with sensing mechanisms for extracellular Ca2+ and that elevated extracellular Ca2+ increases fibroblast growth factor-2 (FGF-2) gene and protein expression levels via a cyclic AMP/protein kinase A (PKA) dependent pathway. In the present study, we found that stimulation of murine cementoblasts with 10 mM CaCl2 induced cyclooxygenase-2 (COX-2) gene expression and prostaglandin E2 (PGE2) biosynthesis. NS-398, a COX-2 inhibitor, significantly reduced CaCl2-induced increase in Fgf-2 gene expression, indicating that PGE2 synthesized by COX-2 may be involved in FGF-2 induction. The inhibitory effect of NS-398 was restored completely by the addition of PGE2 receptor 4 (E-prostanoid receptor 4, called EP4) agonist, but not agonists for EP1, EP2, and EP3. Furthermore, EP4 antagonist significantly reduced CaCl2-induced Fgf-2 induction, suggesting that it is mediated by EP4 activation. However, stimulation with EP4 agonist alone in the absence of CaCl2 had no effect on the Fgf-2 induction, indicating that EP4 signaling alone is not sufficient. CaCl2 also upregulated gene expression levels of Ep4 and Cox-2, as well as Fgf-2 and induction of these genes was abolished by pretreatment with BMS-345541, a nuclear factor-κB (NF-κB) inhibitor, indicating that NF-κB signaling triggered by CaCl2 is indispensable for FGF-2 induction. Furthermore, CaCl2-induced Fgf-2 induction was synergistically enhanced by the addition of EP4 agonist. This indicates that the signaling triggered via CaCl2 and its combination with EP4 agonist may be useful as a novel strategy for periodontal regeneration.

CD69 is a TGF-β/1α,25-dihydroxyvitamin D3 target gene in monocytes

CD69 is a transmembrane lectin that can be expressed on most hematopoietic cells. In monocytes, it has been functionally linked to the 5-lipoxygenase pathway in which the leukotrienes, a class of highly potent inflammatory mediators, are produced. However, regarding CD69 gene expression and its regulatory mechanisms in monocytes, only scarce data are available. Here, we report that CD69 mRNA expression, analogous to that of 5-lipoxygenase, is induced by the physiologic stimuli transforming growth factor-β (TGF-β) and 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) in monocytic cells. Comparison with T- and B-cell lines showed that the effect was specific for monocytes. CD69 expression levels were increased in a concentration-dependent manner, and kinetic analysis revealed a rapid onset of mRNA expression, indicating that CD69 is a primary TGF-β/1α,25(OH)2D3 target gene. PCR analysis of different regions of the CD69 mRNA revealed that de novo transcription was initiated and proximal and distal parts were induced concomitantly. In common with 5-lipoxygenase, no activation of 0.7 kb or ∼2.3 kb promoter fragments by TGF-β and 1α,25(OH)2D3 could be observed in transient reporter assays for CD69. Analysis of mRNA stability using a transcription inhibitor and a 3'UTR reporter construct showed that TGF-β and 1α,25(OH)2D3 do not influence CD69 mRNA stability. Functional knockdown of Smad3 clearly demonstrated that upregulation of CD69 mRNA, in contrast to 5-LO, depends on Smad3. Comparative studies with different inhibitors for mitogen activated protein kinases (MAPKs) revealed that MAPK signalling is involved in CD69 gene regulation, whereas 5-lipoxygenase gene expression was only partly affected. Mechanistically, we found evidence that CD69 gene upregulation depends on TAK1-mediated p38 activation. In summary, our data indicate that CD69 gene expression, conforming with 5-lipoxygenase, is regulated monocyte-specifically by the physiologic stimuli TGF-β and 1α,25(OH)2D3 on mRNA level, although different mechanisms account for the upregulation of each gene.

T(H)2-like chemokine patterns correlate with disease severity in patients with recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP), characterized by the recurrent growth of benign tumors of the respiratory tract, is caused by infection with human papillomavirus (HPV), predominantly types 6 and 11. Surgical removal of these lesions can be required as frequently as every 3 to 4 wks to maintain a patent airway. There is no approved medical treatment for this disease. In this study, we have characterized the T(H)2-like chemokine profile (CCL17, CCL18, CCL20, CCL22) in patients with RRP and asked whether it was modulated in patients who had achieved significant clinical improvement. CCL17, CCL18 and CCL22 messenger RNAs (mRNAs) were increased in papillomas compared with clinically normal laryngeal epithelium of the RRP patients. Overall, CCL20 mRNA expression was not increased, but there was intense, selective CCL20 protein expression in the basal layer of the papillomas. Patients with RRP expressed more CCL17 (p = 0.003), CCL18 (p = 0.0003), and CCL22 (p = 0.007) in their plasma than controls. Plasma CCL18 decreased over time in three patients enrolled in a pilot clinical trial of celecoxib, and the decrease occurred in conjunction with clinical improvement. There was a significant correlation between sustained clinical remission in additional patients with RRP and reduced levels of CCL17 (p = 0.01), CCL22 (p = 0.002) and CCL18 (p = 0.05). Thus, the change in expression of these three plasma T(H)2-like chemokines may, with future studies, prove to serve as a useful biomarker for predicting disease prognosis.

Clara cell 10-kDa protein gene transfection inhibits NF-κB activity in airway epithelial cells

BACKGROUND

Clara cell 10-kDa protein (CC10) is a multifunctional protein with anti-inflammatory and immunomodulatory effects. Induction of CC10 expression by gene transfection may possess potential therapeutic effect. Nuclear factor κB (NF-κB) plays a key role in the inflammatory processes of airway diseases.

METHOD/RESULTS

To investigate potential therapeutic effect of CC10 gene transfection in controlling airway inflammation and the underlying intracellular mechanisms, in this study, we constructed CC10 plasmid and transfected it into bronchial epithelial cell line BEAS-2B cells and CC10 knockout mice. In BEAS-2B cells, CC10's effect on interleukin (IL)-1β induced IL-8 expression was explored by means of RT-PCR and ELISA and its effect on NF-κB classical signaling pathway was studied by luciferase reporter, western blot, and immunoprecipitation assay. The effect of endogenous CC10 on IL-1β evoked IL-8 expression was studied by means of nasal explant culture. In mice, CC10's effect on IL-1β induced IL-8 and nuclear p65 expression was examined by immunohistochemistry. First, we found that the CC10 gene transfer could inhibit IL-1β induced IL-8 expression in BEAS-2B cells. Furthermore, we found that CC10 repressed IL-1β induced NF-κB activation by inhibiting the phosphorylation of IκB-α but not IκB kinase-α/β in BEAS-2B cells. Nevertheless, we did not observe a direct interaction between CC10 and p65 subunit in BEAS-2B cells. In nasal explant culture, we found that IL-1β induced IL-8 expression was inversely correlated with CC10 levels in human sinonasal mucosa. In vivo study revealed that CC10 gene transfer could attenuate the increase of IL-8 and nuclear p65 staining in nasal epithelial cells in CC10 knockout mice evoked by IL-1β administration.

CONCLUSION

These results indicate that CC10 gene transfer may inhibit airway inflammation through suppressing the activation of NF-κB, which may provide us a new consideration in the therapy of airway inflammation.

Antigen-independent IFN-γ production by human naïve CD4 T cells activated by IL-12 plus IL-18

The role of T cells in innate immunity is not well defined. In this report, we show that a subset of human peripheral blood CD4⁺ T cells responds to IL-12 plus IL-18, but not to IL-12 or IL-18 alone, by producing IFN-γ in the absence of any antigenic stimulation or cell proliferation. Intracellular staining reveals a small percentage of resting CD4⁺ T cells (0.5 to 1.5%) capable of producing IFN-γ in response to IL-12 plus IL-18. Interestingly, both naïve (CD45RA⁺) and memory (CD45RO⁺) CD4⁺ populations were responsive to IL-12 plus IL-18 stimulation in producing IFN-γ. The expression of IFN-γinduced by IL-12 and IL-18 is sensitive to rapamycin and SB203580, indicating the possible involvement of mTOR and p38 MAP kinase, respectively, in this synergistic pathway. While p38MAP kinase is involved in transcription, mTOR is involved in message stabilization. We have also shown that NFκB family member, cRel, but not GADD45β and GADD45γ, plays an important role in IL-12 plus IL-18-induced IFN-γ transcription. Thus, the present study suggests that naïve CD4⁺ T cells may participate in innate immunity or amplify adaptive immune responses through cytokine-induced antigen-independent cytokine production.

Anti-inflammatory effects of Cynanchum taiwanianum rhizome aqueous extract in IL-1β-induced NRK-52E cells

CONTEXT

Cynanchum taiwanianum T. Yamaza (Asclepiadaceae) is a medicinal herb used in folk medicine for the treatment of several inflammation-related diseases such as hepatitis and dermatitis in Taiwan.

OBJECTIVE

In the present study, we investigated the anti-inflammatory effect of C. taiwanianum T. Yamaza rhizome aqueous extract (CTAE).

MATERIALS AND METHODS

The present study investigated the anti-inflammatory effect of CTAE using IL-1β-induced NRK-52E cells. Production of NO and PGE(2) by ELISA, the mRNA and protein expression of iNOS and COX-2, phosphorylation of IκBα, and activation of NF-κB by RT-PCR and western blotting were determined.

RESULTS

The CTAE significantly (P < 0.05) inhibited NO and PGE(2) production (decreased by 46.1% and 51%, respectively), and also significantly (P < 0.05) attenuated protein and mRNA expression of iNOS and COX-2 (decreased by 90% and 55% for iNOS and by 72% and 74%% for COX-2, respectively) in IL-1β-induced NRK-52E cells, in a dose-dependent manner, without obvious cytotoxic effects. Furthermore, the CTAE suppressed the NF-κB nuclear translocation, in terms of inhibition of IκBα phosphorylation.

DISCUSSION AND CONCLUSION

Our results provided evidence for its folkloric uses and suggest that the anti-inflammatory activities of CTAE may result from the inhibition of inflammatory mediators, such as NO and PGE(2), and an upstream suppression of a NF-κB-dependent mechanism, might be involved.

Roles of oxidative stress in signaling and inflammation induced by particulate matter

This review reports the role of oxidative stress in impairing the function of lung exposed to particulate matter (PM). PM constitutes a heterogeneous mixture of various types of particles, many of which are likely to be involved in oxidative stress induction and respiratory diseases. Probably, the ability of PM to cause oxidative stress underlies the association between increased exposure to PM and exacerbations of lung disease. Mostly because of their large surface area, ultrafine particles have been shown to cause oxidative stress and proinflammatory effects in different in vivo and in vitro studies. Particle components and surface area may act synergistically inducing lung inflammation. In this vein, reactive oxygen species elicited upon PM exposure have been shown to activate a number of redox-responsive signaling pathways and Ca(2+) influx in lung target cells that are involved in the expression of genes that modulate relevant responses to lung inflammation and disease.

TLR4-mediated podosome loss discriminates gram-negative from gram-positive bacteria in their capacity to induce dendritic cell migration and maturation

Chronic infections are caused by microorganisms that display effective immune evasion mechanisms. Dendritic cell (DC)-dependent T cell-mediated adaptive immunity is one of the mechanisms that have evolved to prevent the occurrence of chronic bacterial infections. In turn, bacterial pathogens have developed strategies to evade immune recognition. In this study, we show that gram-negative and gram-positive bacteria differ in their ability to activate DCs and that gram-negative bacteria are far more effective inducers of DC maturation. Moreover, we observed that only gram-negative bacteria can induce loss of adhesive podosome structures in DCs, a response necessary for the induction of effective DC migration. We demonstrate that the ability of gram-negative bacteria to trigger podosome turnover and induce DC migration reflects their capacity to selectively activate TLR4. Examining mice defective in TLR4 signaling, we show that this DC maturation and migration are mainly Toll/IL-1 receptor domain-containing adaptor-inducing IFNbeta-dependent. Furthermore, we show that these processes depend on the production of PGs by these DCs, suggesting a direct link between TLR4-mediated signaling and arachidonic metabolism. These findings demonstrate that gram-positive and gram-negative bacteria profoundly differ in their capacity to activate DCs. We propose that this inability of gram-positive bacteria to induce DC maturation and migration is part of the armamentarium necessary for avoiding the induction of an effective cellular immune response and may explain the frequent involvement of these pathogens in chronic infections.

Inhibition of NF-kappaB-dependent transcription by MKP-1: transcriptional repression by glucocorticoids occurring via p38 MAPK

Acting via the glucocorticoid receptor (GR), glucocorticoids exert potent anti-inflammatory effects partly by repressing inflammatory gene transcription occurring via factors such as NF-kappaB. In the present study, the synthetic glucocorticoid, dexamethasone, induces expression of MKP-1 (mitogen-activated protein kinase (MAPK) phosphatase-1) in human bronchial epithelial (BEAS-2B) and pulmonary (A549) cells. This correlates with reduced TNFalpha-stimulated p38 MAPK phosphorylation. Since NF-kappaB-dependent transcription and IL-8 protein, mRNA, and unspliced RNA (a surrogate of transcription rate) are sensitive to p38 MAPK inhibitors (SB203580 and SB239063), we explored the role of MKP-1 in repression of these outputs. Repression of TNFalpha-induced p38 MAPK phosphorylation, NF-kappaB-dependent transcription, and IL-8 expression by dexamethasone are sensitive to transcriptional or translational inhibitors. This indicates a role for de novo gene synthesis. Adenoviral expression of MKP-1 profoundly reduces p38 MAPK phosphorylation and IL-8 expression. Similarly, NF-kappaB-dependent transcription is significantly reduced to levels consistent with maximal p38 MAPK inhibition. Thus, MKP-1 attenuates TNFalpha-dependent activation of p38 MAPK, induction of IL-8 expression, and NF-kappaB-dependent transcription. Small interfering RNA knockdown of dexamethasone-induced MKP-1 expression partially reverses the repression of TNFalpha-activated p38 MAPK, demonstrating that MKP-1 participates in the dexamethasone-dependent repression of this pathway. In the presence of MKK6 (MAPK kinase 6), a p38 MAPK activator, dexamethasone dramatically represses TNFalpha-induced NF-kappaB-dependent transcription, and this is significantly reversed by MKP-1-targeting small interfering RNA. This reveals an important and novel role for transcriptional activation (transactivation) of MKP-1 in the repression of NF-kappaB-dependent transcription by glucocorticoids. We conclude that GR transactivation is essential to the anti-inflammatory properties of GR ligands.

Dynamic compression alters NFkappaB activation and IkappaB-alpha expression in IL-1beta-stimulated chondrocyte/agarose constructs

OBJECTIVE AND DESIGN

Determine the effect of IL-1beta and dynamic compression on NFkappaB activation and IkappaB-alpha gene expression in chondrocyte/agarose constructs.

METHODS

Constructs were cultured under free-swelling conditions or subjected to dynamic compression for up to 360 min with IL-1beta and/or PDTC (inhibits NFkappaB activation). Nuclear translocation of NFkappaB-p65 was analysed by immunofluoresence microscopy. Gene expression of IkappaB-alpha, iNOS, IL-1beta and IL-4 was assessed by real-time qPCR.

RESULTS

Nuclear translocation of NFkappaB-p65 was concomitant with an increase in nuclear fluorescence intensity which reached maximum values at 60 min with IL-1beta (p < 0.001). Dynamic compression or PDTC reduced nuclear fluorescence and NFkappaB nuclear translocation in cytokine-treated constructs (p < 0.001 and p < 0.01 respectively). IL-1beta increased IkappaB-alpha expression (p < 0.001) at 60 min and either induced iNOS (p < 0.001) and IL-1beta (p < 0.01) or inhibited IL-4 (p < 0.05) expression at 360 min. These time-dependent events were partially reversed by dynamic compression or PDTC (p < 0.01) with IL-1beta. Co-stimulation by dynamic compression and PDTC favoured suppression (IkappaB-alpha, iNOS, IL-1beta) or induction (IL-4) of gene expression.

CONCLUSIONS

NFkappaB is one of the key players in the mechanical and inflammatory pathways, and its inhibition by a biophysical/therapeutic approach could be a strategy for attenuating the catabolic response in osteoarthritis.

PIM2 Induced COX-2 and MMP-9 expression in macrophages requires PI3K and Notch1 signaling

Activation of inflammatory immune responses during granuloma formation by the host upon infection of mycobacteria is one of the crucial steps that is often associated with tissue remodeling and breakdown of the extracellular matrix. In these complex processes, cyclooxygenase-2 (COX-2) plays a major role in chronic inflammation and matrix metalloproteinase-9 (MMP-9) significantly in tissue remodeling. In this study, we investigated the molecular mechanisms underlying Phosphatidyl-myo-inositol dimannosides (PIM2), an integral component of the mycobacterial envelope, triggered COX-2 and MMP-9 expression in macrophages. PIM2 triggers the activation of Phosphoinositide-3 Kinase (PI3K) and Notch1 signaling leading to COX-2 and MMP-9 expression in a Toll-like receptor 2 (TLR2)-MyD88 dependent manner. Notch1 signaling perturbations data demonstrate the involvement of the cross-talk with members of PI3K and Mitogen activated protein kinase pathway. Enforced expression of the cleaved Notch1 in macrophages induces the expression of COX-2 and MMP-9. PIM2 triggered significant p65 nuclear factor -κB (NF-κB) nuclear translocation that was dependent on activation of PI3K or Notch1 signaling. Furthermore, COX-2 and MMP-9 expression requires Notch1 mediated recruitment of Suppressor of Hairless (CSL) and NF-κB to respective promoters. Inhibition of PIM2 induced COX-2 resulted in marked reduction in MMP-9 expression clearly implicating the role of COX-2 dependent signaling events in driving the MMP-9 expression. Taken together, these data implicate PI3K and Notch1 signaling as obligatory early proximal signaling events during PIM2 induced COX-2 and MMP-9 expression in macrophages.

HIV-1 envelope glycoprotein 120 induces cyclooxygenase-2 expression in astrocytoma cells through a nuclear factor-kappaB-dependent mechanism

Human immunodeficiency virus-1 gp120 alters astroglial function, which compromises the function of the nearby of neuronal cells contributing to the cognitive impairment in human immunodeficiency virus-1 infection. Cyclooxygenase (COX)-2 has been involved in this process, although the intracellular pathways and second messengers involved are yet unknown. We have investigated the role of gp120-induced COX-2 in the astrocytoma human cell line U-87, and the different pathways involved in this activation. COX-2 mRNA and protein expression were detected in gp120-stimulated cells. Moreover, gp120 induces COX-2 promoter transcription. The effect of gp120 was abrogated by a neutralizing antibody against the chemokine receptor CXCR4 neutralizing antibody. Analysis of the promoter show that deletion or mutation of a proximal nuclear factor (NF)-kappaB site completely abrogated gp120-dependent transcription. NF-kappaB but neither Activating protein-1 nor nuclear factor of activated T-cells-dependent transcription was induced by gp120, as shown by reporter and electrophoretic mobility shift assays. In addition, transfection assays with the NF-kappaB inhibitor, IkappaBalpha, prevented gp120-mediated COX-2 induction. In contrast, there was no inhibition of COX-2 promoter transcription by expressing a dominant negative c-Jun, or nuclear factor of activated T-cells constructs. The antioxidant pyrrolidine dithiocarbamate inhibited COX-2 protein expression and COX-2 transcriptional activity induced by gp120. Thus, our results indicate that gp120 induced COX-2 transcription through NF-kappaB activation in astrocytoma cells.

Protein synthesis inhibitors, gene superinduction and memory: too little or too much protein?

To date, the effects of protein synthesis inhibitors (PSI) in learning and memory processes have been attributed to translational arrest and consequent inhibition of de novo protein synthesis. Here we argue that amnesia produced by PSI can be the direct result of their abnormal induction of mRNA-a process termed gene superinduction. This action exerted by PSI involves an abundant and prolonged accumulation of mRNA transcripts of genes that are normally transiently induced. We summarize experimental evidence for the multiple mechanisms and signaling pathways mediating gene superinduction and consider its relevance for PSI-induced amnesia. This mechanistic alternative to protein synthesis inhibition is compared to models of electroconvulsive seizures and fragilexsyndrome associated with enhanced mRNA/protein levels and cognitive deficits.

Cyclooxygenase activity is important for efficient replication of mouse hepatitis virus at an early stage of infection

Cyclooxygenases (COXs) play a significant role in many different viral infections with respect to replication and pathogenesis. Here we investigated the role of COXs in the mouse hepatitis coronavirus (MHV) infection cycle. Blocking COX activity by different inhibitors or by RNA interference affected MHV infection in different cells. The COX inhibitors reduced MHV infection at a post-binding step, but early in the replication cycle. Both viral RNA and viral protein synthesis were affected with subsequent loss of progeny virus production. Thus, COX activity appears to be required for efficient MHV replication, providing a potential target for anti-coronaviral therapy.

Interleukin-4 induction of the CC chemokine TARC (CCL17) in murine macrophages is mediated by multiple STAT6 sites in the TARC gene promoter

Background

Macrophages (Mθ) play a central role in the innate immune response and in the pathology of chronic inflammatory diseases. Macrophages treated with Th2-type cytokines such as Interleukin-4 (IL-4) and Interleukin-13 (IL-13) exhibit an altered phenotype and such alternatively activated macrophages are important in the pathology of diseases characterised by allergic inflammation including asthma and atopic dermatitis. The CC chemokine Thymus and Activation-Regulated Chemokine (TARC/CCL17) and its murine homologue (mTARC/ABCD-2) bind to the chemokine receptor CCR4, and direct T-cell and macrophage recruitment into areas of allergic inflammation. Delineating the molecular mechanisms responsible for the IL-4 induction of TARC expression will be important for a better understanding of the role of Th2 cytokines in allergic disease.

Results

We demonstrate that mTARC mRNA and protein are potently induced by the Th2 cytokine, Interleukin-4 (IL-4), and inhibited by Interferon-γ (IFN-γ) in primary macrophages (Mθ). IL-4 induction of mTARC occurs in the presence of PI3 kinase pathway and translation inhibitors, but not in the absence of STAT6 transcription factor, suggesting a direct-acting STAT6-mediated pathway of mTARC transcriptional activation. We have functionally characterised eleven putative STAT6 sites identified in the mTARC proximal promoter and determined that five of these contribute to the IL-4 induction of mTARC. By in vitro binding assays and transient transfection of isolated sites into the RAW 264.7 Mθ cell-line, we demonstrate that these sites have widely different capacities for binding and activation by STAT6. Site-directed mutagenesis of these sites within the context of the mTARC proximal promoter revealed that the two most proximal sites, conserved between the human and mouse genes, are important mediators of the IL-4 response.

Conclusion

The induction of mTARC by IL-4 results from cooperative interactions between STAT6 sites within the mTARC gene promoter. Significantly, we have shown that transfer of the nine most proximal mTARC STAT6 sites in their endogenous conformation confers potent (up to 130-fold) IL-4 inducibility on heterologous promoters. These promoter elements constitute important and sensitive IL-4-responsive transcriptional units that could be used to drive transgene expression in sites of Th2 inflammation in vivo.

Regulation of SOX9 mRNA in human articular chondrocytes involving p38 MAPK activation and mRNA stabilization

Human articular chondrocytes rapidly lose their phenotype in monolayer culture. Recently we have shown that overexpression of the transcription factor SOX9 greatly enhanced re-expression of the phenotype in three-dimensional aggregate cultures. Here we show that endogenous SOX9 mRNA can be rapidly up-regulated in subcultured human articular chondrocytes if grown in alginate, in monolayer with cytochalasin D, or with specific inhibition of the RhoA effector kinases ROCK1 and -2, which all prevent actin stress fiber formation. Disruption of actin stress fibers using any of these redifferentiation stimuli also supported the superinduction of SOX9 by cycloheximide. The superinduction was blocked by inhibitors of the p38 MAPK signaling pathway and involved the stabilization of SOX9 mRNA. Furthermore stimulation of chondrocyte p38 MAPK activity with interleukin-1beta resulted in increased levels of SOX9 mRNA, and this was again dependent on the absence of actin stress fibers in the cells. In this study of chondrocyte redifferentiation we have provided further evidence of the early involvement of SOX9 and have discovered a novel post-transcriptional regulatory mechanism activated by p38 MAPK, which stabilized SOX9 mRNA.

Interleukin-13 enhances cyclooxygenase-2 expression in activated rat brain microglia: implications for death of activated microglia

Brain inflammation has recently attracted widespread interest because it is a risk factor for the onset and progression of brain diseases. In this study, we report that cyclooxygenase-2 (COX-2) plays a key role in the resolution of brain inflammation by inducing the death of microglia. We previously reported that IL-13, an anti-inflammatory cytokine, induced the death of activated microglia. These results revealed that IL-13 significantly enhanced COX-2 expression and production of PGE(2) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) in LPS-treated microglia. Two other anti-inflammatory cytokines, IL-10 and TGF-beta, neither induced microglial death nor enhanced COX-2 expression or PGE(2) or 15d-PGJ(2) production. Therefore, we hypothesized that the effect of IL-13 on COX-2 expression may be linked to death of activated microglia. We found that COX-2 inhibitors (celecoxib and NS398) suppressed the death of microglia induced by a combination of LPS and IL-13 and that exogenous addition of PGE(2) and 15d-PGJ(2) induced microglial death. Agonists of EP2 (butaprost) and peroxisome proliferator-activated receptor gamma (ciglitazone) mimicked the effect of PGE(2) and 15d-PGJ(2), and an EP2 antagonist (AH6809) and a peroxisome proliferator-activated receptor gamma antagonist (GW9662) suppressed microglial death induced by LPS in combination with IL-13. In addition, IL-13 potentiated LPS-induced activation of JNK, and the JNK inhibitor SP600125 suppressed the enhancement of COX-2 expression and attenuated microglial death. Taken together, these results suggest that IL-13 enhanced COX-2 expression in LPS-treated microglia through the enhancement of JNK activation. Furthermore, COX-2 products, PGE(2) and 15d-PGJ(2), caused microglial death, which terminates brain inflammation.

Validation of the anti-inflammatory properties of small-molecule IkappaB Kinase (IKK)-2 inhibitors by comparison with adenoviral-mediated delivery of dominant-negative IKK1 and IKK2 in human airways smooth muscle

Asthma and chronic obstructive pulmonary disease (COPD) are characterized by chronic airway inflammation. However, because patients with COPD and certain patients with asthma show little or no therapeutic benefit from existing corticosteroid therapies, there is an urgent need for novel anti-inflammatory strategies. The transcription factor nuclear factor-kappaB (NF-kappaB) is central to inflammation and is necessary for the expression of numerous inflammatory genes. Proinflammatory cytokines, including interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha, activate the IkappaB kinase complex (IKK) to promote the degradation of inhibitory IkappaB proteins and activate NF-kappaB. This pathway and, in particular, the main IkappaB kinase, IKK2, are now considered prime targets for novel anti-inflammatory drugs. Therefore, we have used adenoviral overexpression to demonstrate NF-kappaB and IKK2 dependence of key inflammatory genes, including intercellular adhesion molecule (ICAM)-1, cyclooxygenase-2, IL-6, IL-8, granulocyte macrophage-colony-stimulating factor (GM-CSF), regulated on activation normal T cell expressed and secreted (RANTES), monocyte chemotactic protein-1 (MCP-1), growth-regulated oncogene-alpha (GROalpha), neutrophil-activating protein-2 (NAP-2), and epithelial neutrophil activating peptide 78 (ENA-78) in primary human airways smooth muscle cells. Because this cell type is central to the pathogenesis of airway inflammatory diseases, these data predict a beneficial effect of IKK2 inhibition. These validated outputs were therefore used to evaluate the novel IKK inhibitors N-(6-chloro-9H-beta-carbolin-8-yl) nicotinamide (PS-1145) and N-(6-chloro-7-methoxy-9H-beta-carbolin-8-yl)-2-methyl-nicotinamide (ML120B) on IL-1beta and TNFalpha-induced expression, and this was compared with the corticosteroid dexamethasone. As observed above, ICAM-1, IL-6, IL-8, GM-CSF, RANTES, MCP-1, GROalpha, NAP-2, and ENA-78 expression was reduced by the IKK inhibitors. Furthermore, this inhibition was either as effective, or for ICAM-1, MCP-1, GROalpha, and NAP-2, more effective, than a maximally effective concentration of dexamethasone. We therefore suggest that IKK inhibitors may be of considerable benefit in inflammatory airways diseases, particularly in COPD or severe asthma, in which corticosteroids are ineffective.

JNK inhibitor SP600125 reduces COX-2 expression by attenuating mRNA in activated murine J774 macrophages

Inducible prostaglandin synthase (cyclooxygenase-2, COX-2) is highly expressed in inflammation. The signaling mechanisms involved in the up-regulation of COX-2 are not known in detail. In the present study we investigated the role of c-Jun NH2-terminal kinase (JNK), a member of the mitogen-activated protein kinase (MAPK) family in COX-2 expression and prostaglandin (PG) E2 production in murine J774 macrophages activated by bacterial lipopolysaccharide (LPS). LPS caused a transient activation of JNK which was followed by increased COX-2 expression. Anthra(1,9-cd)pyrazol-6(2H)-one (SP600125), an inhibitor of JNK, inhibited phosphorylation of c-Jun with an IC50 of 5-10 microM. At the same concentrations SP600125 suppressed also LPS-induced COX-2 protein levels and PGE2 production. SP600125 did not alter LPS-induced COX-2 mRNA levels when measured 3 h after addition of LPS, whereas mRNA levels were significantly reduced in SP600125-treated cells when measured 24 h after addition of LPS. LPS-induced COX-2 mRNA levels reduced faster in cells treated with SP600125 than in control cells. Cycloheximide (that is known to activate JNK) enhanced COX-2 expression and its effect was inhibited by SP600125. The present results suggest that JNK pathway is involved in the up-regulation of COX-2 expression possibly by a mechanism related to the stability of COX-2 mRNA.

GRO-alpha regulation in airway smooth muscle by IL-1beta and TNF-alpha: role of NF-kappaB and MAP kinases

Airway smooth muscle cells (ASMC) are a source of inflammatory chemokines that may propagate airway inflammatory responses. We investigated the production of the CXC chemokine growth-related oncogene protein-alpha (GRO-alpha) from ASMC induced by cytokines and the role of MAPK and NF-kappaB pathways. ASMC were cultured from human airways, grown to confluence, and exposed to cytokines IL-1beta and TNF-alpha after growth arrest. GRO-alpha release, measured by ELISA, was increased by >50-fold after IL-1beta (0.1 ng/ml) or 5-fold after TNF-alpha (1 ng/ml) in a dose- and time-dependent manner. GRO-alpha release was not affected by the T helper type 2 cytokines IL-4, IL-10, and IL-13. IL-1beta and TNF-alpha also induced GRO-alpha mRNA expression. Supernatants from IL-1beta-stimulated ASMC were chemotactic for neutrophils; this effect was inhibited by anti-GRO-alpha blocking antibody. AS-602868, an inhibitor of IKK-2, and PD-98059, an inhibitor of ERK, inhibited GRO-alpha release and mRNA expression, whereas SP-600125, an inhibitor of JNK, reduced GRO-alpha release without effect on mRNA expression. SB-203580, an inhibitor of p38 MAPK, had no effect. AS-602868 but not PD-98059 or SP-600125 inhibited p65 DNA-binding induced by IL-1beta and TNF-alpha. By chromatin immunoprecipitation assay, IL-1beta and TNF-alpha enhanced p65 binding to the GRO-alpha promoter, which was inhibited by AS-602868. IL-1beta- and TNF-alpha-stimulated expression of GRO-alpha from ASMC is regulated by independent pathways involving NF-kappaB activation and ERK and JNK pathways. GRO-alpha released from ASMC participates in neutrophil chemotaxis.

Leishmania major: low infection dose causes short-lived hyperalgesia and cytokines upregulation in mice

Neural involvement was traditionally associated with leprosy. However, more recent studies have shown the presence of a persistent hyperalgesia in cutaneous leishmaniasis caused by the infection of BALB/c mice with a high dose of Leishmania major. In this study, we report the presence of hyperalgesia within the first two weeks of infection caused by a low dose of the parasite. Using BALB/c mice, we demonstrate the presence of hyperalgesia during the first 10 days of infection as assessed by thermal pain tests. After 10 days these decreased pain thresholds start to recover resulting in similar levels to those in uninfected controls during the third week of infection. This hyperalgesia is accompanied by a sustained upregulation of interleukin-1beta (IL-1beta) and an early upregulation of interleukin-6 (IL-6) which is restored to normal levels after five days of infection. In conclusion, this study shows that, during early infection, the low dose of L. major causes hyperalgesia accompanied by an upregulation of IL-1beta and IL-6 and that these effects are reversed within the first two weeks of infection.

Inhibition of p38 mitogen-activated protein kinase enhances c-Jun N-terminal kinase activity: implication in inducible nitric oxide synthase expression

Background

Nitric oxide (NO) is an inflammatory mediator, which acts as a cytotoxic agent and modulates immune responses and inflammation. p38 mitogen-activated protein kinase (MAPK) signal transduction pathway is activated by chemical and physical stress and regulates immune responses. Previous studies have shown that p38 MAPK pathway regulates NO production induced by inflammatory stimuli. The aim of the present study was to investigate the mechanisms involved in the regulation of inducible NO synthesis by p38 MAPK pathway.

Results

p38 MAPK inhibitors SB203580 and SB220025 stimulated lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) expression and NO production in J774.2 murine macrophages. Increased iNOS mRNA expression was associated with reduced degradation of iNOS mRNA. Treatment with SB220025 increased also LPS-induced c-Jun N-terminal kinase (JNK) activity. Interestingly, JNK inhibitor SP600125 reversed the effect of SB220025 on LPS-induced iNOS mRNA expression and NO production.

Conclusion

The results suggest that inhibition of p38 MAPK by SB220025 results in increased JNK activity, which leads to stabilisation of iNOS mRNA, to enhanced iNOS expression and to increased NO production.

IL-1beta induces IL-8 in bronchial cells via NF-kappaB and NF-IL6 transcription factors and can be suppressed by glucocorticoids

IL-1beta may contribute to airway inflammation by inducing pro-inflammatory cytokines and chemokines from bronchial epithelial cells. In the current study, we investigated the cis-acting sites within the IL-8 promoter, and signalling pathways important in IL-8 production from BEAS2B cells following IL-1beta stimulation. IL-1beta treatment (0.1-10 ng/mL) upregulated IL-8 protein production in a dose dependent manner and IL-8 mRNA in a time dependent manner. IL-1beta induced upregulation of IL-8 promoter-reporter constructs, indicating that the mechanism of upregulation was pre-transcriptional. Using IL-8 promoter constructs with mutated cis-acting sites, it was found that both the NF-kappaB and NF-IL6 sites together were required for IL-8 promoter induction following IL-1beta treatment. Using chemical inhibitors or dominant negative mutants, we found that IL-8 promoter activity required IkappaB kinase beta, IkappaB, but not the MAP kinases p38 or c-Jun N-terminal kinase 2. Fluticasone propionate was able to suppress IL-1beta induced IL-8 protein and promoter activation, using both a -1481 bp fragment and a -133 bp fragment, indicating that the glucocorticoid response element found at -330 bp was not required for fluticasone mediated suppression of IL-8 promoter activation.

Superinduction of IL-6 by cycloheximide is associated with mRNA stabilization and sustained activation of p38 map kinase and NF-kappaB in cultured caco-2 cells

Protein synthesis inhibitors paradoxically increase the expression of early-gene products, including various cytokines, through a process known as superinduction. Superinduction is cell-specific and the mechanisms involved are not fully understood but are usually attributed to decreased mRNA degradation. There is, however, increasing evidence that activation of signaling cascades and increased transcriptional activation may be involved as well. Recent studies suggest that IL-6 production in the intestinal mucosa is particularly important due to its anti-inflammatory and protective effects. The effect of protein synthesis inhibitors on IL-6 production in enterocytes, however, is unknown. Treatment of Caco-2 cells with cycloheximide (10 microg/ml) increased IL-6 mRNA and protein levels in IL-1beta-treated cells and this was associated with increased mRNA stabilization. In addition, cycloheximide suppressed IkappaBalpha resynthesis and prolonged p38MAP kinase activation and these changes were associated with sustained activation of the transcription factor NF-kappaB. NF-kappaB activation, in turn, was prevented by the specific p38MAP kinase inhibitor SB208350. Our results suggest that superinduction of IL-6 by cycloheximide in enterocytes results from both increased mRNA stabilization and upregulated transcriptional activity mediated by prolonged activation of the p38 MAP kinase and NF-kappaB.

The p50-p50 NF-kappaB complex as a stimulus-specific repressor of gene activation

The transcription factor NF-kappaB can be activated in different forms, including transcriptional activating and repressing forms. Intestinal epithelial cells have been found to modulate the relative levels of the p65-p50 and p50-p50 NF-kappaB complexes in a number of instances, and here we show that this ratio was altered in response to dietary fiber (wheat bran) and carcinogen exposure (azoxymethane). The influence of these complexes on gene regulation was examined in more detail in cell culture models. The colon-derived HT-29 cell line likewise activated both p65-p50 and p50-p50 NF-kappaB complexes: TNF-alpha triggered a strong, sustained p65-p50 activation with lower relative levels of p50-p50, whereas IL-1beta transiently activated p65-p50 with higher relative levels of p50-p50. Transfection experiments with an NF-kappaB reporter plasmid indicated that p50 was a repressor in HT-29 cells. Increased expression of the p50-p50 dimer by an adenovirus showed that the p50-p50 dimer suppressed IL-1beta activation of endogenous genes more than 5-fold (TNF-alpha, Cox-2 and IL-8), whereas gene activation by TNF-alpha was not significantly affected. DNA binding analyses showed a number of strong p50-p50 binding sites on these promoters. The selective p50-p50 suppression of IL-1beta gene activation corresponded to the transient nature of p65-p50 activation induced by IL-1beta (in both HT-29 and Caco-2 cells). Our findings demonstrate a novel gene regulatory mechanism for the NF-kappaB p50-p50 complex: a signal-specific transcriptional repression that appears to selectively inhibit stimuli that transiently activate p65-p50 complexes.

Inhibition of tristetraprolin expression by dexamethasone in activated macrophages

Tristetraprolin (TTP) is a factor that regulates mRNA stability and the expression of certain inflammatory genes. In the present study, we found that TTP expression was increased in macrophages exposed to bacterial lipopolysaccharide (LPS). Dexamethasone and dissociated steroid RU24858 inhibited LPS-induced TTP protein and mRNA expression and the inhibitory effect was reversed by a glucocorticoid receptor antagonist mifepristone. Histone deacetylase inhibitors trichostatin A (TSA) and apicidin reduced the inhibitory effect of dexamethasone and RU24858 on TTP expression, but the glucocorticoids did not alter TTP mRNA half-life. These results suggest that anti-inflammatory steroids reduce TTP expression in activated macrophages by a glucocorticoid response element (GRE)-independent mechanism, possibly through histone deacetylation and transcriptional silencing.

Cellular and molecular mechanisms for immune modulation by deoxynivalenol and other trichothecenes: unraveling a paradox

Macrophages, T cells, and B cells of the immune system are central targets of deoxynivalenol (DON) and other trichothecenes-mycotoxins that can be immunostimulatory or immunosuppressive depending on dose, exposure frequency and timing of functional immune assay. Notably, low dose trichothecene exposure transcriptionally and post-transcriptionally upregulates expression of cytokines, chemokines and inflammatory genes with concurrent immune stimulation, whereas high dose exposure promotes leukocyte apoptosis with concomitant immune suppression. DON and other trichothecenes, via a mechanism known as the ribotoxic stress response, bind to ribosomes and rapidly activate mitogen-activated protein kinases (MAPKs). The latter are important transducers of downstream signaling events related to immune response and apoptosis. Using cloned macrophages, our laboratory has identified two critical upstream transducers of DON-induced MAPK activation. One transducer is double-stranded RNA-(dsRNA)-activated protein kinase (PKR), a widely-expressed serine/theonine protein kinase that can be activated by dsRNA, interferon, and other agents. The second transducer is hematopoetic cell kinase (Hck), a non-receptor associated Src family kinase. Inhibitors and gene silencing studies have revealed that Hck and PKR play roles in DON induced gene expression and apoptosis. Future studies should focus on the molecular linkages between these kinases and trichothecene toxicity.

IGF-II-mediated COX-2 gene expression in human keratinocytes through extracellular signal-regulated kinase pathway

We monitored cyclooxygenase-2 (COX-2) expression in the insulin-like growth factor-II (IGF-II) treated human keratinocytes and explored the IGF-II signaling pathways with respect to the expression of COX-2. IGF-II induced COX-2 mRNA and protein levels, and the up-regulation of COX-2 expression by IGF-II was reduced by pretreatment with inhibitors of tyrosine kinase, Src and PI3-kinase. The inhibition of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) 1 also reduced the increased expression of COX-2 by IGF-II, but the inhibition of p38 did not. To further examine the roles of these mitogen-activated protein kinases (MAPKs) in IGF-II-induced COX-2 expression, we performed COX-2 promoter analysis using dominant negative plasmids of MEK1 (DN-MEK1), p38 (DN-p38) and JNK1 (DN-JNK1). Although IGF-II increased COX-2 promoter activity approximately 2.5-fold, this increase was blocked by cotransfection with DN-MEK1 or DN-JNK1. However, DN-p38 did not block the IGF-II-induced COX-2 promoter activity. In addition, inhibition of ERK or JNK1 reduced the increase of IGF-II-induced prostaglandin E(2) synthesis or cell proliferation. These results suggest that IGF-II induces COX-2 expression through the tyrosine kinase-Src-ERK and tyrosine kinase-PI3-kinase pathways, but not via p38 MAPK pathway, and that the basal JNK activity is required for the upregulation of COX-2 by IGF-II, as well.

Essential role of c-Jun induction and coactivator p300 in epidermal growth factor-induced gene expression of cyclooxygenase-2 in human epidermoid carcinoma A431 cells

Cyclooxygenase-2 (COX-2) is an inducible enzyme responsible for high-level prostaglandin production during inflammation and carcinogenesis. In this study, the transcriptional regulation of COX-2 expression induced by epidermal growth factor (EGF) in human epidermoid carcinoma A431 cells was studied. EGF treatment induced the expression of COX-2 mRNA, protein, promoter and enzyme activity in a time-dependent manner. EGF-induced COX-2 promoter activity was inhibited by overexpression of the dominant-negative forms of Ras and ERK2. Induction of COX-2 and c-Jun by EGF was completely suppressed by MEK inhibitor combined with JNK inhibitor. Analysis of the COX-2 promoter binding proteins by gel mobility shift assay and DNA affinity precipitation assay revealed that c-Jun and p300 binding to CRE/E-box site were responsible for the EGF-induced COX-2 gene transcription. Overexpression of p300 significantly enhanced COX-2 promoter activity in cells overexpressed of c-Jun or treated with EGF. EGF- and c-Jun-induced transcription of COX-2 promoter was repressed by cotransfection of E1A in a dose-dependent manner. All together, these results indicated that the EGF-induced expression of COX-2 in A431 cells was mediated through the Ras-ERK/JNK signaling pathway, and subsequent induction of c-Jun following MAPK activation, in cooperation with coactivator p300, was required for the EGF response.

Transcriptional and posttranscriptional roles for p38 mitogen-activated protein kinase in upregulation of TNF-alpha expression by deoxynivalenol (vomitoxin)

Deoxynivalenol (DON, vomitoxin) is a trichothecene mycotoxin that potentially mediates toxicity by upregulating proinflammatory cytokine gene expression in vitro and in vivo. The purpose of this study was to test the hypothesis that DON-induced activation of mitogen-activated protein kinases (MAPKs) mediates transcriptional and posttranscriptional upregulation of TNF-alpha gene expression. RNAse protection assay revealed that DON at 100 to 500 ng/ml induced mRNA expression of TNF-alpha as well as IL-6, IFN-gamma, TGFbeta-1, and TGFbeta-3 and that these effects were potentiated by 100 ng/ml lipopolysaccharide (LPS). DON was found to induce phosphorylation of p38 kinase, extracellular signal-regulated kinases (ERKs), and c-Jun amino terminal kinases (JNKs) in a dose-dependent manner in the RAW 264.7 murine macrophage model. A luciferase reporter gene driven by the murine TNF-alpha promoter was used to assess the role of various MAPKs on DON upregulation of TNF-alpha gene transcription. The p38 inhibitor SB203580 reduced induction of luciferase activity by DON, LPS, and DON + LPS. In addition, the ERK inhibitor PD 98059 blocked DON- and DON + LPS-induced luciferase activity whereas the JNK inhibitor impaired LPS- and DON + LPS-induced luciferase activity. To study the effects of MAPKs on DON-induced TNF-alpha mRNA stability, an asynchronous model was used whereby cells were pretreated with LPS for 4 h and the medium was removed. Following incubation with medium containing a transcription inhibitor, 5,6-dichloro-beta-D-ribofuranosyl-benzimidazole, MAPK inhibitors and/or DON (250 ng/ml) cultures were monitored for TNF-alpha mRNA expression. DON-induced TNF-alpha mRNA stabilization was abrogated in the presence of SB 203580, whereas the stabilization by DON was not affected by PD 98059 or SP 600125. To verify the role of MAPKs in DON + LPS-induced TNF-alpha production, cells were incubated with LPS, DON, or LPS + DON for 18 h in the presence of inhibitors. ELISA of supernatant indicated that induction of TNF-alpha production by DON alone was significantly reduced by SB 203580 and PD 98059, whereas all three inhibitors blocked LPS- and DON + LPS-induced TNF-alpha production. Taken together, these results suggest that relative to DON-induced TNF-alpha mRNA expression, p38 and ERK activation contribute to DON-induced transcriptional upregulation whereas p38 plays a role in increasing mRNA stability.

Altered expression and in vivo lung function of protease-activated receptors during influenza A virus infection in mice

Protease-activated receptors (PARs) are widely distributed in human airways, and recent evidence indicates a role for PARs in the pathophysiology of inflammatory airway disease. To further investigate the role of PARs in airway disease, we determined the expression and function of PARs in a murine model of respiratory tract viral infection. PAR-1, PAR-2, PAR-3, and PAR-4 mRNA and protein were expressed in murine airways, and confocal microscopy revealed colocalization of PAR-2 and cyclooxygenase (COX)-2 immunostaining in basal tracheal epithelial cells. Elevated levels of PAR immunostaining, which was particularly striking for PAR-1 and PAR-2, were observed in the airways of influenza A/PR-8/34 virus-infected mice compared with sham-infected mice. Furthermore, increased PAR-1 and PAR-2 expression was associated with significant changes in in vivo lung function responses. PAR-1 agonist peptide potentiated methacholine-induced increases in airway resistance in anesthetized sham-infected mice (and in indomethacin-treated, virus-infected mice), but no such potentiation was observed in virus-infected mice. PAR-2 agonist peptide transiently inhibited methacholine-induced bronchoconstriction in sham-infected mice, and this effect was prolonged in virus-infected mice. These findings suggest that during viral infection, the upregulation of PARs in the airways is coupled to increased activation of COX and enhanced generation of bronchodilatory prostanoids.

Relationship of trichothecene structure to COX-2 induction in the macrophage: selective action of type B (8-keto) trichothecenes

The trichothecene mycotoxin deoxynivalenol (DON, vomitoxin), when at partially cytotoxic concentrations, induces cyclooxygenase-2 (COX-2) expression by promoting transcriptional activity and mRNA stability via mitogen-activated protein kinase (MAPK) signaling pathways. The purpose of this study was to test the hypothesis that trichothecenes differentially affect COX-2 gene expression and that these effects were related to MAPK activation. Representative members of the three major trichothecene families (A, B, and D) were compared for their capacity to induce COX-2 in the RAW 264.7 murine macrophage cell line. When cells were treated with concentrations that inhibited the 3-(4,5-di-methylthizol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) viability response by 20% (IC20), Type B trichothecenes including DON, 15-acetyl-DON, 3-acetyl-DON, and fusarenon-X were found to be effective inducers of COX-2 mRNA expression, whereas equitoxic Type A and Type D trichothecenes had markedly less effects. To compare effects of COX-2 gene transactivation and mRNA stabilization, luciferase reporter vectors containing 5'-promoter or 3'-untranslated regions of the gene, respectively, were transfected into RAW 264.7 cells and the effects of various trichothecenes on luciferase activities were measured. Type B but not Type A or D toxins at concentrations up to the MTT IC50 enhanced luciferase activities, indicating preferential COX-2 transcriptional activation and mRNA stabilization by this trichothecene subset. At their respective IC20s, Type B trichothecenes also significantly activated the three major MAPK families, whereas Type A and D did not. Blocking ERK and p38 with chemical inhibitors significantly suppressed Type B-induced COX-2 expression. Although JNK reportedly contributes to COX-2 expression in the other signaling models, transfection with the dominant negative JNK vector did not diminish the COX-2 expression. Taken together, Type B trichothecenes selectively enhanced transcription and stabilization of the COX-2 gene, and this was mediated by the ERK 1/2 and p38 signaling pathways. Selective action on COX-2 might contribute to unique pathologic manifestations associated with Type B trichothecene-mediated immunotoxicity.

c-Jun NH2-terminal kinase inhibitor anthra(1,9-cd)pyrazol-6(2H)-one reduces inducible nitric-oxide synthase expression by destabilizing mRNA in activated macrophages

In this study, we investigated the role of c-Jun NH2-terminal kinase (JNK), a member of the mitogen-activated protein kinase (MAPK) family, in lipopolysaccharide (LPS)-stimulated inducible nitric-oxide synthase (iNOS) expression and nitric oxide (NO) production in J774 murine macrophages. Anthra(1,9-cd)pyrazol-6(2H)-one (SP600125), a pharmacological inhibitor of JNK, inhibited phosphorylation of c-Jun with an IC50 of 5 to 10 microM. At the same concentrations, SP600125 inhibited LPS-induced iNOS protein expression and NO production. SP600125 had no effect on the activation of nuclear factor kappaB, which is an important transcription factor for iNOS expression. SP600125 had no significant effect on iNOS mRNA levels if measured 4 h after LPS. In contrast, SP600125 reduced iNOS mRNA levels >90% when measured 8 h after LPS. These data suggest that SP600125 reduced iNOS mRNA stability, and this was confirmed in the mRNA degradation assay using actinomycin D, in which SP600125 reduced the iNOS mRNA half-life from 5 to 2 h. These results show that the JNK pathway is involved in the up-regulation of LPS-induced iNOS expression and NO production by a mechanism related to the stabilization of iNOS mRNA.

Responses to the proinflammatory cytokines interleukin-1 and tumor necrosis factor alpha in cells derived from rheumatoid synovium and other joint tissues involve nuclear factor kappaB-mediated induction of the Ets transcription factor ESE-1

OBJECTIVE

To investigate the expression of the novel Ets transcription factor ESE-1 in rheumatoid synovium and in cells derived from joint tissues, and to analyze the role of nuclear factor kappaB (NF-kappaB) as one of the central downstream targets in mediating the induction of ESE-1 by proinflammatory cytokines.

METHODS

ESE-1 protein expression was analyzed by immunohistochemistry using antibodies in synovial tissues from patients with rheumatoid arthritis (RA) and osteoarthritis (OA). ESE-1 messenger RNA (mRNA) levels were analyzed by reverse transcriptase-polymerase chain reaction or Northern blotting in human chondrocytes, synovial fibroblasts, osteoblasts, and macrophages, before and after exposure to interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNFalpha), or lipopolysaccharide (LPS) with or without prior infection with an adenovirus encoding the inhibitor of nuclear factor kappaB (IkappaB). The wild-type ESE-1 promoter and the ESE-1 promoter mutated in the NF-kappaB site were cloned into a luciferase reporter vector and analyzed in transient transfections. Electrophoretic mobility shift assays (EMSAs) and supershift assays with antibodies against members of the NF-kappaB family were conducted using the NF-kappaB site from the ESE-1 promoter as a probe.

RESULTS

Immunohistochemical analysis showed specific expression of ESE-1 in cells of the synovial lining layer and in some mononuclear and endothelial cells in RA and OA synovial tissues. ESE-1 mRNA expression could be induced by IL-1beta and TNFalpha in cells such as synovial fibroblasts, chondrocytes, osteoblasts, and monocytes. Transient transfection experiments and EMSAs showed that induction of ESE-1 gene expression by IL-1beta requires activation of NF-kappaB and binding of p50 and p65 family members to the NF-kappaB site in the ESE-1 promoter. Overexpression of IkappaB using an adenoviral vector blocked IL-1beta-induced ESE-1 mRNA expression. Chromatin immunoprecipitation further confirmed that NF-kappaB binds to the ESE-1 promoter in vivo.

CONCLUSION

ESE-1 is expressed in synovial tissues in RA and, to a variable extent, in OA, and is specifically induced in synovial fibroblasts, chondrocytes, osteoblasts, and monocyte/macrophages by IL-1beta, TNFalpha, or LPS. This induction relies on the translocation of the NF-kappaB family members p50 and p65 to the nucleus and transactivation of the ESE-1 promoter via a high-affinity NF-kappaB binding site. ESE-1 may play a role in mediating some effects of proinflammatory stimuli in cells at sites of inflammation.