Oncostatin M stimulates c-Fos to bind a transcriptionally responsive AP-1 element within the tissue inhibitor of metalloproteinase-1 promoter

Cut loose TIMP-1: an emerging cytokine in inflammation

Appreciation of the entire biological impact of an individual protein can be hampered by its original naming based on one function only. Tissue inhibitor of metalloproteinases-1 (TIMP-1), mostly known for its eponymous function to inhibit metalloproteinases, exhibits only a fraction of its cellular effects via this feature. Recently, TIMP-1 emerged as a potent cytokine acting via various cell-surface receptors, explaining a so-far under-appreciated role of TIMP-1-mediated signaling on immune cells. This, at least partly, resolved why elevated blood levels of TIMP-1 correlate with progression of numerous inflammatory diseases. Here, we emphasize the necessity of unbiased name-independent recognition of structure-function relationships to properly appreciate the biological potential of TIMP-1 and other cytokines in complex physiological processes such as inflammation.

TIMP-1 is Overexpressed and Secreted by Platinum Resistant Epithelial Ovarian Cancer Cells

Epithelial Ovarian Cancer (EOC) is the most lethal gynecological cancer in developed countries, and the development of new strategies to overcome chemoresistance is an awaited clinical need. Angiogenesis, the development of new blood vessels from pre-existing vasculature, has been validated as a therapeutic target in this tumor type. The aim of this study is to verify if EOC cells with acquired resistance to platinum (PT) treatment display an altered angiogenic potential. Using a proteomic approach, we identified the tissue inhibitor of metalloproteinases 1 (TIMP-1) as the only secreted factor whose expression was up-regulated in PT-resistant TOV-112D and OVSAHO EOC cells used as study models. We report that TIMP-1 acts as a double-edged sword in the EOC microenvironment, directly affecting the response to PT treatment on tumor cells and indirectly altering migration and proliferation of endothelial cells. Interestingly, we found that high TIMP-1 levels in stage III–IV EOC patients associate with decreased overall survival, especially if they were treated with PT or bevacizumab. Taken together, these results pinpoint TIMP-1 as a key molecule involved in the regulation of EOC PT-resistance and progression disclosing the possibility that it could be used as a new biomarker of PT-resistance and/or therapeutic target.

Macrophage Polarization and Bone Formation: A review

The contribution of inflammation to bone loss is well documented in arthritis and other diseases with an emphasis on how inflammatory cytokines promote osteoclastogenesis. Macrophages are the major producers of cytokines in inflammation, and the factors they produce depend upon their activation state or polarization. In recent years, it has become apparent that macrophages are also capable of interacting with osteoblasts and their mesenchymal precursors. This interaction provides growth and differentiation factors from one cell that act on the other and visa versa-a concept akin to the requirement for a feeder layer to grow hemopoietic cells or the coupling that occurs between osteoblasts and osteoclasts to maintain bone homeostasis. Alternatively, activated macrophages are the most likely candidates to promote bone formation and have also been implicated in the tissue repair process in other tissues. In bone, a number of factors, including oncostatin M, have been shown to promote osteoblast formation both in vitro and in vivo. This review discusses the different cell types involved, cellular mediators, and how this can be used to direct new bone anabolic approaches.

Novel targets for Spinal Cord Injury related neuropathic pain

Millions of people suffer from spinal cord injury (SCI) with little known effective clinical therapy. Neuropathic pain (NP) is often accompanied with SCI, making clinical treatment challenging. Even though the key mediators in the development of NP have been discovered, the pathogenesis is still unclear. Some of the key mediators in the sustenance of NP include the inflammatory processes, cannabinoid receptors, matrix metalloproteases, and their tissue inhibitors. Animal models have shown promising results with modulation of these mediators, yet the clinical models have been unsuccessful. One such study with matrix metalloproteases (MMPs) has yielded encouraging results. The relationship between MMPs and their tissue inhibitors (TIMPs) plays a significant role in the pathogenesis and recovery of SCI and the CNS. Key factors that lead to the functional consequences of MMP activity are cellular localization, tissue distribution, and temporal pattern of MMP expression. Studies concluding that MMPs can be seen as contributors of tissue damage and as contributors in the repair mechanisms have provided a need to reexamine their roles after acute and chronic neuropathic pain

The regulation of hepcidin expression by serum treatment: requirements of the BMP response element and STAT- and AP-1-binding sites

Expression of hepcidin, a central regulator of systemic iron metabolism, is transcriptionally regulated by the bone morphogenetic protein (BMP) pathway. However, the factors other than the BMP pathway also participate in the regulation of hepcidin expression. In the present study, we show that serum treatment increased hepcidin expression and transcription without inducing the phosphorylation of Smad1/5/8 in primary hepatocytes, HepG2 cells or Hepa1-6 cells. Co-treatment with LDN-193189, an inhibitor of the BMP type I receptor, abrogated this hepcidin induction. Reporter assays using mutated reporters revealed the involvement of the BMP response element-1 (BMP-RE1) and signal transducers and activator of transcription (STAT)- and activator protein (AP)-1-binding sites in serum-induced hepcidin transcription in HepG2 cells. Serum treatment induced the expression of the AP-1 components c-fos and junB in primary hepatocytes and HepG2 cells. Forced expression of c-fos or junB enhanced the response of hepcidin transcription to serum treatment. By contrast, the expression of dominant negative (dn)-c-fos and dn-junB decreased hepcidin transcription. The present study reveals that serum contains factors stimulating hepcidin transcription. Basal BMP activity is essential for the serum-induced hepcidin transcription, although serum treatment does not stimulate the BMP pathway. The induction of c-fos and junB by serum treatment stimulates hepcidin transcription, through possibly cooperation with BMP-mediated signaling. Considering that AP-1 is induced by various stimuli, the present results suggest that hepcidin expression is regulated by more diverse factors than had been previously considered.

Cells of the immune system orchestrate changes in bone cell function

There is a complex interplay between the cells of the immune system and bone. Immune cells, such as T and NK cells, are able to enhance osteoclast formation via the production of RANKL. Yet there is increasing evidence to show that during the resolution of inflammation or as a consequence of increased osteoclastogenesis there is an anabolic response via the formation of more osteoblasts. Furthermore, osteoblasts themselves are involved in the control of immune cell function, thus promoting the resolution of inflammation. Hence, the concept of "coupling"-how bone formation is linked to resorption-needs to be more inclusive rather than restricting our focus to osteoblast-osteoclast interactions as in a whole organism these cells are never in isolation. This review will investigate the role of immune cells in normal bone homeostasis and in inflammatory diseases where the balance between resorption and formation is lost.

Protein kinase C isoforms zeta and iota mediate collagenase expression and cartilage destruction via STAT3- and ERK-dependent c-fos induction

The protein kinase C (PKC) signaling pathway is a major regulator of cellular functions and is implicated in pathologies involving extracellular matrix remodeling. Inflammatory joint disease is characterized by excessive extracellular matrix catabolism, and here we assess the role of PKC in the induction of the collagenases, matrix metalloproteinase (MMP)-1 and MMP-13, in human chondrocytes by the potent cytokine stimulus interleukin-1 (IL-1) in combination with oncostatin M (OSM). IL-1 + OSM-stimulated collagenolysis and gelatinase activity were ameliorated by pharmacological PKC inhibition in bovine cartilage, as was collagenase gene induction in human chondrocytes. Small interfering RNA-mediated silencing of PKC gene expression showed that both novel (nPKC delta, nPKC eta) and atypical (aPKC zeta, aPKC iota) isoforms were involved in collagenase induction by IL-1. However, MMP1 and MMP13 induction by IL-1 + OSM was inhibited only by aPKC silencing, suggesting that only atypical isoforms play a significant role in complex inflammatory milieus. Silencing of either aPKC led to diminished IL-1 + OSM-dependent extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription (STAT) 3 phosphorylation, and c-fos expression. STAT3 gene silencing or ERK pathway inhibition also resulted in loss of IL-1 + OSM-stimulated c-fos and collagenase expression. Silencing of c-fos and c-jun expression was sufficient to abrogate IL-1 + OSM-stimulated collagenase gene induction, and overexpression of both c-fos and c-jun was sufficient to drive transcription from the MMP1 promoter in the absence of a stimulus. Our data identify atypical PKC isozymes as STAT and ERK activators that mediate c-fos and collagenase expression during IL-1 + OSM synergy in human chondrocytes. aPKCs may constitute potential therapeutic targets for inflammatory joint diseases involving increased collagenase expression.

Molecular Mechanism of Liver Development and Regeneration

The liver is the central organ for metabolism and has strong regenerative capability. Although the liver has been studied mostly biochemically and histopathologically, genetic studies using gene-targeting technology have identified a number of cytokines, intracellular signaling molecules, and transcription factors involved in liver development and regeneration. In addition, various in vitro systems such as fetal liver explant culture and primary culture of fetal liver cells have been established, and the combination of genetic and in vitro studies has accelerated investigation of liver development. Identification of the cell-surface molecules of liver progenitors has made it possible to identify and isolate liver progenitors, making the liver a unique model for stem cell biology. In this review, we summarize progresses in understanding liver development and regeneration.

TIMP-1 is a key factor of fibrogenic response to bleomycin in mouse lung

Pulmonary fibrosis is characterized by the excessive deposition of extracellular matrix in the interstitium, resulting in respiratory failure. The role of remodeling mediators such as metalloproteinases (MMPs) and their inhibitors (TIMPs) in the fibrogenic process remains misunderstood. We investigated MMP-9, MMP-2, TIMP-1, TIMP-2 and TIMP-3 in the fibrotic response to bleomycin of fibrosis prone C57BL/6J and fibrosis resistant BALB/c mice. Mice were administered with 0.1 mg bleomycin by intranasal administration. Either 24 h or 14 days after, the mice were anesthetized and underwent either bronchoalveolear lavage (BAL) or lung removal. Collagen deposition in lung tissue was determined by hydroxyproline measurement, MMP activity was analyzed by zymography, and other mediators were analyzed by ELISA. TIMP-1 was localized in lung sections by immunohistochemistry and real time PCR was performed to gene expression in lung. Non parametric Mann-Whitney and Spearman tests were used for statistical analysis. Fourteen days after bleomycin administration, hydroxyproline assay and histological study revealed that BALB/c mice developed significantly less fibrosis compared to C57BL/6J mice. At day 1, bleomycin enhanced TIMP-1, MMP-2 and MMP-9 protein levels in BALF, and induced corresponding genes in lung tissue of both strains. The rise of Timp-1, Mmp-9 and Mmp-2 gene levels were significantly stronger in lungs of C57BL/6J, whereas gelatinase activities of MMP-2 and MMP-9 were similar. Immunohistochemistry revealed that TIMP-1 macrophages and epithelial cells were prominent TIMP-1 producers in both strains. At day 14, neither MMP-2 nor MMP-9 levels exhibited strain-dependent protein level or gene expression, although TIMP-1 was strongly associated with fibrosis. Interestingly, bleomycin induced neither Timp-2 nor Timp-3 in lung tissue at any time of the study. The present study shows that early altered regulation of TIMP-1 following bleomycin administration may be involved in bleomycin-induced pulmonary fibrosis.

A novel mechanism of tissue inhibitor of metalloproteinases-1 activation by interleukin-1 in primary human astrocytes

Reactive astrogliosis is the gliotic response to brain injury with activated astrocytes and microglia being the major effector cells. These cells secrete inflammatory cytokines, proteinases, and proteinase inhibitors that influence extracellular matrix (ECM) remodeling. In astrocytes, the expression of tissue inhibitor of metalloproteinases-1 (TIMP-1) is up-regulated by interleukin-1 (IL-1), which is a major neuroinflammatory cytokine. We report that IL-1 activates TIMP-1 expression via both the IKK/NF-kappaB and MEK3/6/p38/ATF-2 pathways in astrocytes. The activation of the TIMP-1 gene can be blocked by using pharmacological inhibitors, including BAY11-7082 and SB202190, overexpression of the dominant-negative inhibitor of NF-kappaB (IkappaBalphaSR), or by the knock-down of p65 subunit of NF-kappaB. Binding of activated NF-kappaB (p50/p65 heterodimer) and ATF-2 (homodimer) to two novel regulatory elements located -2.7 and -2.2 kb upstream of the TIMP-1 transcription start site, respectively, is required for full IL-1-responsiveness. Mutational analysis of these regulatory elements and their weak activity when linked to the minimal tk promoter suggest that cooperative binding is required to activate transcription. In contrast to astrocytes, we observed that TIMP-1 is expressed at lower levels in gliomas and is not regulated by IL-1. We provide evidence that the lack of TIMP-1 activation in gliomas results from either dysfunctional IKK/NF-kappaB or MEK3/6/p38/ATF-2 activation by IL-1. In summary, we propose a novel mechanism of TIMP-1 regulation, which ensures an increased supply of the inhibitor after brain injury, and limits ECM degradation. This mechanism does not function in gliomas, and may in part explain the increased invasiveness of glioma cells.

Rac upregulates tissue inhibitor of metalloproteinase-1 expression by redox-dependent activation of extracellular signal-regulated kinase signaling

The Rho-like GTPase Rac regulates distinct actin cytoskeleton changes required for adhesion, migration and invasion of cells. Tiam1 specifically activates Rac, and Rac has been shown to affect several signaling pathways in a partly cell-type-specific manner. Recently, we demonstrated that Rac activation inhibits Matrigel invasion of human carcinoma cells by transcriptional upregulation of tissue inhibitor of metalloproteinase-1. The purpose of the present study was to identify key mediators of Tiam1/Rac-induced tissue inhibitor of metalloproteinase-1 expression. Mutational analysis of the human tissue inhibitor of metalloproteinase-1 promoter revealed a major role for a distinct activating protein-1 site at -92/-86 and a minor role for an adjacent polyoma enhancer A3 site. Moreover, Rac activation induced the generation of reactive oxygen species and subsequent reactive oxygen species-dependent activation of extracellular signal-regulated kinase 1,2. In contrast, c-Jun N-terminal kinase and p38 mitogen-activated protein kinase activities were not affected. In line with this, Tiam1/Rac-induced tissue inhibitor of metalloproteinase-1 expression as well as Tiam1/Rac-induced binding of nuclear extracts to the activating protein-1 site at -92/-86 were inhibited by catalase and by specific inhibitors of the extracellular signal-related kinase-1,2 activators, mitogen-activated protein kinase kinase-1 and mitogen-activated protein kinase kinase-2 (PD098059, U0126). In conclusion, Rac-induced transcriptional upregulation of tissue inhibitor of metalloproteinase-1 is mediated by reactive oxygen species-dependent activation of extracellular signal-related kinase-1,2 and by transcription factors of the activating protein-1 family.

Leptin increases tissue inhibitor of metalloproteinase I (TIMP-1) gene expression by a specificity protein 1/signal transducer and activator of transcription 3 mechanism

Leptin has properties of a profibrogenic cytokine. In liver, the activated hepatic stellate cell (HSC) is responsible for a net production of extracellular matrix. A key molecule synthesized is the tissue inhibitor of metalloproteinase I (TIMP-1), which acts to inhibit the activity of matrix metalloproteinases. The purpose of the present study was to determine how leptin, a gp130 cytokine, orchestrates the regulation of TIMP-1 gene activation and expression. Transient transfection of primary HSCs revealed that leptin significantly increased luciferase activity of a 229-bp TIMP-1 promoter construct (TIMP-1-229). An EMSA revealed that leptin enhanced specificity protein 1 (Sp1) binding. Site-directed mutagenesis for Sp1 reduced the enhancing effect of leptin on TIMP-1 transcriptional activation, and this effect was dose dependent on the number of Sp1 sites mutated. Chromatin immunoprecipitation revealed that leptin enhanced binding of Sp1; however, inhibition of signal transducer and activator of transcription (STAT) 3 phosphorylation by AG490 also blocked Sp1 phosphorylation and significantly reduced leptin-associated TIMP-1-229 promoter activity, indicating that one mechanism for leptin-increased transcriptional activity is via phosphorylation of Sp1 and subsequent promoter binding. Finally, we demonstrate that leptin also results in intranuclear pSTAT3 binding to Sp1. We propose a novel mechanism whereby leptin-mediated TIMP-1 transcription employs a Sp1/pSTAT3-dependent mechanism, one of which is a noncanonical association between Sp1 and pSTAT3. These data provide a new molecular mechanism whereby the adipocytokine leptin plays a role in complications of the metabolic syndrome.

Novel functions of TIMPs in cell signaling

Tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of matrix metalloproteinases (MMPs) and the balance between MMPs/TIMPs regulates the extracellular matrix (ECM) turnover and remodeling during normal development and pathogenesis. Increasing evidence indicates a much more complex role for TIMPs during tumor progression and angiogenesis, in addition to their regulation of MMP-mediated ECM degradation. In this article, we review both the MMP-dependent and -independent actions of TIMPs for the regulation of cell death, cell proliferation, and angiogenesis, with a particular emphasis on TIMP-1 in the regulation of tetraspanin/integrin-mediated cell survival signal transduction pathways.

Induced secretion of tissue inhibitor of metalloproteinases-1 (TIMP-1) in vivo and in vitro by hepatotoxin rubratoxin B

To elucidate the mechanism of rubratoxin B toxicity, we investigated rubratoxin B-induced secretion of tissue inhibitor of metalloproteinases-1 (TIMP-1) in mice and cultured cells; we also documented the involvement of stress-activated MAP kinases (c-Jun-N-terminal kinases [JNKs] and p38s) in this process. Rubratoxin B significantly (P<0.05) induced serum TIMP-1 levels in mice. Because TIMP-1 is thought to play a crucial role in the process of liver fibrosis, rubratoxin B may cause liver fibrosis. Rubratoxin B enhanced TIMP-1 secretion in HepG2 cells to a peak level of approximately 40 microg/ml. The amount of TIMP-1 mRNA increased with the duration of rubratoxin B treatment; and this hepatotoxin appears to induce TIMP-1 secretion through a transcriptional control mechanism. Unlike similar treatment with rubratoxin B and JNK inhibitor, concomitant treatment with rubratoxin B and p38 inhibitor increased rubratoxin B-induced TIMP-1 secretion, suggesting that p38s (but not JNKs) antagonize this process. In addition, treatment with p38 inhibitor slightly increased the amount of rubratoxin B-induced TIMP-1 mRNA, suggesting that p38s control rubratoxin B-induced TIMP-1 secretion chiefly post-transcriptionally. In this study, we showed that rubratoxin B induces TIMP-1 production in vivo and in vitro and that p38s antagonize rubratoxin B-induced TIMP-1 secretion.

Oncostatin-M Up-Regulates VCAM-1 and Synergizes with IL-4 in Eotaxin Expression: Involvement of STAT6

Oncostatin-M (OSM) is an IL-6/gp130 family member that can stimulate the eosinophil-selective CC chemokine eotaxin-1 in vitro and eosinophil accumulation in mouse lung in vivo. The adhesion molecule VCAM-1 and eotaxin have been implicated in extravasation and accumulation of eosinophils into tissue in animal models of asthma. In this study, we investigated the role of OSM in regulation of VCAM-1 expression, and STAT6 tyrosine 641 phosphorylation in murine fibroblasts. OSM induced VCAM-1 expression in C57BL/6 mouse lung fibroblasts (MLF) and NIH 3T3 fibroblasts at the protein and mRNA level in vitro. OSM also induced STAT6 Y641 phosphorylation in MLF and NIH 3T3 fibroblasts, an activity not observed with other IL-6/gp130 cytokine family members (IL-6, leukemia inhibitory factor, cardiotropin-1, and IL-11) nor in cells derived from STAT6(-/-) mice (STAT6(-/-) MLF). STAT6 was not essential for OSM-induced VCAM-1 or eotaxin-1 as assessed in STAT6(-/-) MLF. Combination of IL-4 and OSM synergistically enhanced eotaxin-1 expression in MLF. IL-4 induction and the IL-4/OSM synergistic induction of eotaxin-1 was abrogated in STAT6(-/-) MLF, however, regulation of IL-6 was similar in -/- or wild-type MLF. Induction of VCAM-1 by OSM was diminished by pharmacological inhibitors of PI3K (LY294002) but not inhibitors of ERK1/2 (PD98059) or p38 MAPK (SB203580). These data support the role of OSM in eosinophil accumulation into lung tissue through eotaxin-1 and VCAM-1 expression and the notion that OSM is able to induce unique signal transduction events through its receptor complex of OSMR beta-chain and gp130.

Transforming Growth Factor-β1 Induces Tissue Inhibitor of Metalloproteinase-1 Expression via Activation of Extracellular Signal-Regulated Kinase and Sp1 in Human Fibrosarcoma Cells

The net balance of matrix metalloproteinases (MMP) and tissue inhibitor of metalloproteinases (TIMP) system has been known to be a key factor in tumor cell invasion. In the present study, we investigated the molecular mechanisms of anti-invasive and antimigrative activity of transforming growth factor (TGF)-beta1 on HT1080 human fibrosarcoma cells. In in vitro Matrigel invasion and Transwell migration assays, TGF-beta1 dose-dependently inhibited the invasion and migration of HT1080 cells, respectively. Gelatin zymography, Western blot, and real-time PCR analysis showed that TGF-beta1 enhanced the expression and secretion of MMP-2, TIMP-1, and, to a lesser degree, MMP-9 but not membrane type 1-MMP and TIMP-2. The addition of recombinant TIMP-1 protein reduced the Matrigel invasion and Transwell migration of HT1080 cells, similar to TGF-beta1. Because augmentation of TIMP-1 might be the major factor for the anti-invasive and antimigrative activity of TGF-beta1, we investigated possible molecular mechanisms responsible for the expression of TIMP-1 induced by TGF-beta1. Treatment of HT1080 cells with TGF-beta1 rapidly phosphorylated three mitogen-activated protein kinases [MAPK; extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and c-Jun NH2-terminal kinase] and Akt. Among these kinases, the inhibition of only ERK1/2 pathway by PD98059, a specific inhibitor of MAPK/ERK kinase(MEK)-1, and transfection of dominant-negative MEK 1 effectively blocked the TIMP-1 induction by TGF-beta1. Mithramycin, a specific inhibitor of Sp1 transcription factor, but not curcumin, an inhibitor of activator protein-1, and transfection of Sp1 small interfering RNA significantly inhibited the TGF-beta1-induced expression of TIMP-1. In addition, electrophoretic mobility shift assay showed that TGF-beta1 up-regulated Sp1 DNA-binding activity, and PD98059 and mithramycin effectively inhibited these events. Finally, pretreatment of HT1080 cells with PD98059 and mithramycin, but not curcumin, restored the invasive activity of these cells. Taken together, these data suggest that TGF-beta1 modulates the net balance of the MMPs/TIMPs the systems in HT1080 cells for anti-invasion and antimigration by augmenting TIMP-1 through ERK1/2 pathway and Sp1 transcription factor.

Immune cell activation and subsequent epithelial dysfunction by Staphylococcus enterotoxin B is attenuated by the green tea polyphenol (-)-epigallocatechin gallate

Bacterial superantigens (SAg) are potent T cell activators and when delivered systemically elicit a self-limiting enteropathy in mice. Also, SAg-stimulated human peripheral blood mononuclear cells (PBMC) increase enteric epithelial cell monolayer permeability in vitro. Epigallocatechin gallate (EGCG), the major polyphenol component of green tea (Camilla sinesis) leaf, has been presented as an anti-inflammatory agent. We tested the hypothesis that EGCG (10-100 microM) would block PBMC activation by the SAg, Staphylococcus aureus enterotoxin B (SEB, 1 microg/ml), thus preventing disruption of the epithelial barrier. Pretreatment or co-treatment of human PBMC or murine lymphnode cells with EGCG significantly reduced SEB-induced proliferation and IL-2, IFNgamma, and TNFalpha production. ConA-induced proliferation was also inhibited by EGCG (50 microM) co-treatment. These effects of EGCG were not due to induction of immune cell apoptosis, and were independent of EGCGs anti-oxidant activity, and inhibition of NF-kappaB or AP-1 activation. Moreover, addition of exogenous IL-2 (20 ng/ml) to the cultures could not overcome the immunosuppressive effect of EGCG. Culture supernatant from PBMC stimulated in the presence of EGCG failed to increase the permeability of T84 epithelial cell monolayers: a finding consistent with the reduced IFNgamma and TNFalpha production by SAg+EGCG treated PBMC. These data promote EGCG as a suppressor of T cell activation, and given the prominent role that bacteria and T cells play in inflammatory disease we suggest that EGCG could be a useful addition to current treatments for enteric immune disorders and T cell driven immunopathologies.

Induction by IL-1β of Tissue Inhibitor of Metalloproteinase-1 in Human Orbital Fibroblasts: Modulation of Gene Promoter Activity by IL-4 and IFN-γ

Thyroid-associated ophthalmopathy (TAO), an autoimmune component of Graves' disease, is associated with profound connective tissue remodeling and fibrosis that appear to involve the selective activation of orbital fibroblasts. Accumulation of extracellular matrix molecules is a hallmark of this process. Here we report that orbital fibroblasts treated with IL-1beta express high levels of tissue inhibitor of metalloproteinase-1 (TIMP-1), an important modulator of matrix metalloproteinase activity. These high levels are associated with increased TIMP-1 activity. The induction is mediated at the pretranslational level and involves activating the TIMP-1 gene promoter. IL-1beta activates the ERK 1/2 pathway in these fibroblasts and interrupting this signaling either with PD98059, a chemical inhibitor of MEK, or by transfecting cells with a dominant negative ERK 1 plasmid results in the attenuation of TIMP-1 induction. Surprisingly, treatment with IL-4 or IFN-gamma could also block the IL-1beta induction by attenuating TIMP-1 gene promoter activity. These findings suggest that TIMP-1 expression in orbital fibroblasts following activation with IL-1beta could represent an important therapeutic target for modifying the proteolytic environment. This might alter the natural course of tissue remodeling in TAO.

Autoimmunity gene expression portrait: specific signature that intersects or differentiates between multiple sclerosis and systemic lupus erythematosus

Autoimmune diseases are either tissue-specific like multiple sclerosis (MS) or multisystemic like systemic lupus erythematosus (SLE), although clinically both exhibit common features. To gain insight into the properties of the genes involved in each disease we have investigated the gene expression signature of peripheral blood mononuclear cells (PBMC) in MS and SLE in comparison to healthy subjects. Total RNA was purified, hybridized to Genechip array and analysed in 36 subjects (13 relapsing-remitting MS patients, five SLE patients and 18 age-matched healthy subjects that served as controls). Additional blood samples from 15 relapsing-remitting MS patients, 8 SLE patients and 10 healthy subjects were used for confirmation of microarray gene expression findings by ELISA and RT-PCR. MS and SLE patients demonstrated a common gene expression autoimmune signature of 541 genes which differentiated them from healthy subjects. The autoimmune signature included genes that encode proteins involved in apoptosis, cell cycle, inflammation and regulation of matrix metalloproteinase pathways. Specifically, decreased TIMP1 gene expression in the autoimmunity signature suggests increased MMP activity in target tissues as a result of the lack of feedback mechanism. An additional different disease specific signature identified the gene expression pattern for MS (1031 genes), mainly associated with over-expression of adhesion molecules and down-expression of heat shock proteins; the SLE specific signature (1146 genes) mainly involved DNA damage/repair pathways that result in production of nuclear autoantibodies. These results provide insights into the genetic pathways underlying autoimmune diseases, and identify specific disease-associated signatures that may enable targetted disease-related specific therapies to be developed.

Green tea polyphenol (-)-epigallocatechin gallate blocks epithelial barrier dysfunction provoked by IFN-gamma but not by IL-4

A characteristic of many enteropathies is increased epithelial permeability, a potentially pathophysiological event that can be evoked by T helper (Th)-1 (i.e., IFN-gamma) and Th2 (i.e., IL-4) cytokines and bacterial infection [e.g., enteropathogenic Escherichia coli (EPEC)]. The green tea polyphenol (-)-epigallocatechin gallate (EGCG) has immunosuppressive properties, and we hypothesized that it would ameliorate the increased epithelial permeability induced by IFN-gamma, IL-4, and/or EPEC. EGCG, but not the related epigallocatechin, completely prevented the increase in epithelial (i.e., T84 cell monolayer) permeability caused by IFN-gamma exposure as gauged by transepithelial resistance and horseradish peroxidase flux; EGCG did not alleviate the barrier disruption induced by IL-4 or EPEC. IFN-gamma-treated T84 and THP-1 (monocytic cell line) cells displayed STAT1 activation (tyrosine phosphorylation on Western blot analysis, DNA binding on EMSA) and upregulation of interferon response factor-1 mRNA, a STAT1-dependent gene. All three events were inhibited by EGCG pretreatment. Aurintricarboxylic acid also blocked IFN-gamma-induced STAT1 activation, but it did not prevent the increase in epithelial permeability. Additionally, pharmacological blockade of MAPK signaling did not affect IFN-gamma-induced epithelial barrier dysfunction. Thus, as a potential adjunct anti-inflammatory agent, EGCG can block STAT1-dependent events in gut epithelia and monocytes and prevent IFN-gamma-induced increased epithelial permeability. The latter event is both a STAT1- and MAPK-independent event.

Mitogen-activated protein kinases Erk1/2 and p38 are required for maximal regulation of TIMP-1 by oncostatin M in murine fibroblasts

Oncostatin M (OSM) regulates expression of various genes in connective tissue (CT) cells, including tissue inhibitor of metalloproteinases-1 (TIMP-1). In mouse fibroblast cell lines MLg, NIH 3T3 and primary mouse lung fibroblasts (MLF), murine OSM (muOSM) stimulated high TIMP-1 mRNA expression in comparison to leukemia inhibitory factor (LIF), epidermal growth factor (EGF), interleukin (IL)-1beta and transforming growth factor (TGF)beta. In cell signaling, muOSM induced strong phosphorylation of extracellular-signal regulated protein kinase (Erk) 1/2, p38 and Akt in addition to phosphorylation of signal transducer and activator of transcription (STAT) 1, STAT3 and STAT5 within 15 min. LIF and TGFbeta had no such effects. EGF stimulated comparable or lower Erk1/2, p38 and Akt phosphorylation while IL-1beta induced p38 phosphorylation in the fibroblast cell lines. The Erk1/2 inhibitor PD98059 and the p38 inhibitor SB203580 inhibited TIMP-1 mRNA response to muOSM, whereas the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 enhanced the TIMP-1 mRNA response in NIH 3T3 and MLg cells. PD98059 and SB203580, but not LY294002, also inhibited fold induction of a chloramphenicol acetyltransferase (CAT) reporter gene driven by a minimal TIMP-1 promoter that contained a proximal activator protein-1 (AP-1) site. Co-transfection with JunB or c-Jun expression vector in NIH 3T3 cells caused marked transactivation of the TIMP-1 promoter/CAT reporter gene. muOSM caused a rapid increase of JunB and c-Jun protein in NIH 3T3 cells. PD98059 partially inhibited the increase of JunB, but not c-Jun, whereas SB203580 did not induce detectable changes in expression of either AP-1 factor in response to muOSM. These results demonstrate that Erk1/2 and p38 contribute to the elevation of muOSM induced TIMP-1 expression, but PI3K does not, and suggest that Erk1/2 does so by enhancing JunB expression.

The brain angiotensin system and extracellular matrix molecules in neural plasticity, learning, and memory

The brain renin-angiotensin system (RAS) has long been known to regulate several classic physiologies including blood pressure, sodium and water balance, cyclicity of reproductive hormones and sexual behaviors, and pituitary gland hormones. These physiologies are thought to be under the control of the angiotensin II (AngII)/AT1 receptor subtype system. The AT2 receptor subtype is expressed during fetal development and is less abundant in the adult. This receptor appears to oppose growth responses facilitated by the AT1 receptor, as well as growth factor receptors. Recent evidence points to an important contribution by the brain RAS to non-classic physiologies mediated by the newly discovered angiotensin IV (AngIV)/AT4 receptor subtype system. These physiologies include the regulation of blood flow, modulation of exploratory behavior, and a facilitory role in learning and memory acquisition. This system appears to interact with brain matrix metalloproteinases in order to modify extracellular matrix molecules thus permitting the synaptic remodeling critical to the neural plasticity presumed to underlie memory consolidation, reconsolidation, and retrieval. There is support for an inhibitory influence by AngII activation of the AT1 subtype, and a facilitory role by AngIV activation of the AT4 subtype, on neuronal firing rate, long-term potentiation, associative and spatial learning. The discovery of the AT4 receptor subtype, and its facilitory influence upon learning and memory, suggest an important role for the brain RAS in normal cognitive processing and perhaps in the treatment of dysfunctional memory disease states.

Hepatocyte proliferation and tissue remodeling is impaired after liver injury in oncostatin M receptor knockout mice

Oncostatin M (OSM) is a member of the IL-6 family of cytokines. Mice deficient in the OSM receptor (OSMR(-/-)) showed impaired liver regeneration with persistent parenchymal necrosis after carbon tetrachloride (CCl(4)) exposure. The recovery of liver mass from partial hepatectomy was also significantly delayed in OSMR(-/-) mice. In contrast to wildtype mice, CCl(4) administration only marginally induced expression of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 genes in OSMR(-/-) mice, correlating with the increased gelatinase activity of matrix metalloproteinase (MMP)-9 and matrix degradation in injured livers. The activation of STAT3 and expression of immediate early genes and cyclins were decreased in OSMR(-/-) liver, indicating that OSM signaling is required for hepatocyte proliferation and tissue remodeling during liver regeneration. We also found that CCl(4) administration in IL-6(-/-) mice failed to induce OSM expression and that OSM administration in IL-6(-/-) mice after CCl(4) injection induced the expression of cyclin D1 and proliferating cell nuclear antigen, suggesting that OSM is a key mediator of IL-6 in liver regeneration. Consistent with these results, administration of OSM ameliorated liver injury in wildtype mice by preventing hepatocyte apoptosis as well as tissue destruction. In conclusion, OSM and its signaling pathway may provide a useful therapeutic target for liver regeneration.

The TIMPs tango with MMPs and more in the central nervous system

The matrix metalloproteinases (MMPs) are a family of zinc-dependent extracellular proteases that have been implicated in CNS development and disease. Crucial homeostatic regulation of MMPs is mediated through the expression and actions of the tissue inhibitors of metalloproteinases (TIMPs). Although the TIMPs are recognized inhibitors of the MMPs, recent studies have revealed that these proteins also can exhibit biological activities that are distinct from their interactions with or inhibition of the MMPs. With our understanding of the roles of the TIMPs in the CNS continuously emerging, this review examines the current state of knowledge regarding the multifarious and novel functions of this family of proteins, with particular attention to their increasing potential in the development, plasticity, and pathology of the CNS.

Bile acids up-regulate death receptor 5/TRAIL-receptor 2 expression via a c-Jun N-terminal kinase-dependent pathway involving Sp1

Bile acids up-regulate death receptor 5 (DR5)/TRAIL-receptor 2 (TRAIL-R2) expression thereby sensitizing hepatocytes to TRAIL-mediated apoptosis. However, the precise mechanism by which bile acids enhance DR5/TRAIL-R2 expression is unknown. Although several bile acids enhanced DR5/TRAIL-R2 expression, deoxycholic acid (DCA) was the most potent. DCA stimulated JNK activation and the JNK inhibitor SP600125 blocked DCA-induced DR5/TRAIL-R2 mRNA and protein expression. Reporter gene analysis identified a 5'-flanking region containing two Sp1 binding sites within the DR5/TRAIL-R2 promoter as bile acid responsive. Sp1 binding to one of the two sites was enhanced by DCA treatment as evaluated by electrophoretic mobility shift assays and chromatin immunoprecipitation studies. JNK inhibition with SP600125 also blocked binding of Sp1 to the DR5/TRAIL-R2 promoter. Finally, point mutations of the Sp1 binding site attenuated promoter activity. In conclusion, Sp1 is a bile acid-responsive transcription factor that mediates DR5/TRAIL-R2 gene expression downstream of JNK.

STAT proteins mediate angiotensin II-induced production of TIMP-1 in human proximal tubular epithelial cells

BACKGROUND

Angiotensin II and tissue type inhibitor metalloproteinase-1 (TIMP-1) have been implicated in renal tubulointerstitial fibrosis, but the exact mediating signaling pathway is still unknown. Angiotensin II has been reported to activate signal transducers and activators of transcription (STAT) and induce proliferation of myocyte and vascular smooth muscle cells (VSMC). We hypothesized that the STAT signal pathway is involved in the process of renal tubulointerstitial fibrosis. Therefore, we designed the present study to explore whether angiotensin II could induce TIMP-1 expression in human proximal tubular epithelial cells, and whether it was mediated through the STAT signaling pathway.

METHODS

Electrophoretic mobility shift assay (EMSA) was employed to determine the DNA-STAT binding activity. Supershift assay was used to test the components of activated STAT proteins. Nuclear translocation of activated STATs was observed with laser scanning confocal microscopy. TIMP-1 expression was analyzed with Northern and Western blots. Valsartan and PD123319 were used to block the effects of angiotensin II type 1 (AT1) and angiotensin II type 2 (AT2) receptors of angiotensin II, respectively.

RESULTS

Cultured human proximal tubular epithelial cells constitutively expressed TIMP-1. Angiotensin II induced TIMP-1, mRNA, and protein expressions in time- and dose-dependent manners, which could be inhibited by the AT1 receptor antagonist valsartan, but not by the AT2 antagonist PD123319. Angiotensin II also activated STAT-DNA binding activity in both dose-dependent and biphasic time-dependent manners, and increased the phosphorylation and nuclear translocation of STAT proteins. To examine the role of STAT in angiotensin II-induced TIMP-1 expression, STAT1 and STAT3 antisense oligonucleotides were used. Northern and Western blots showed that STAT1 and STAT3 antisense oligonucleotides could inhibit angiotensin II-induced TIMP-1 expressions, and STAT1 and STAT3 proteins, respectively, could be supershifted by their polyclonal antibodies.

CONCLUSION

STAT1 and STAT3 may, at least in part, mediate angiotensin II-induced TIMP-1 mRNA expression in human renal proximal tubular epithelial cells, implicating a role of the STAT signaling pathway in pathogenesis of renal tubulointerstitial fibrosis.

Increased expression of extracellular matrix regulators TIMP1 and MMP1 in deteriorating heart failure

BACKGROUND

The authors previously identified and compared alterations in gene expression in the myocardia of patients with deteriorating heart failure who underwent left ventricular assist device (LVAD) implantation with those of patients with stable end-stage failure (ESF). We hypothesized that matrix metalloproteinases (MMPs) and their endogenous inhibitors, the tissue inhibitors of MMPs (TIMPs), would be implicated in the mechanisms that underlie deteriorating heart failure.

METHODS

Gridded macro-array filters were used to provide a broad overview of MMP and TIMP mRNA expression in heart failure. Precise mRNA levels of TIMP1, MMP1, and beta-spectrin were determined using quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR) of myocardial samples from 27 patients with deteriorating heart failure who underwent LVAD implantation, from 17 patients with stable ESF who underwent elective heart transplantation, and from 28 donor organs with good hemodynamic function.

RESULTS

Gridded macro-arrays analysis of pooled failing heart samples determined that TIMP1 mRNA was the most readily detectable TIMP in failing myocardium. Quantitative RT-PCR showed that expression levels in individual patients were similar in patients with stable ESF (1.00 +/- 0.24, n = 17) and in donor organ samples (1.49 +/- 0.22, n = 28) but were significantly increased in the deteriorating heart failure group (5.38 +/- 0.32, n = 26, p < 0.0001 compared with patients with ESF). Similarly, MMP1 levels did not differ between donor and ESF groups but increased in the deteriorating failure group (6.04 +/- 0.50, n = 27, p < 0.001 compared with the ESF group). Levels of beta-II spectrin were the same in all 3 groups. Both TIMP1 and MMP1 showed positive correlation with each other and with previously determined levels of mRNA for both interleukin-1beta (IL-1beta) and IL-6 in this patient series when considering all patients individually, but neither correlated with tumor necrosis factor alpha.

CONCLUSIONS

Patients with deteriorating heart failure have increased expression of TIMP1 and MMP1 mRNA. Correlation with pro-inflammatory cytokines suggests common pathways of regulation and potential activation by IL-6 and IL1-beta.

Extracellular matrix metabolism in diabetic nephropathy

Diabetic nephropathy is characterized by excessive deposition of extracellular matrix proteins in the mesangium and basement membrane of the glomerulus and in the renal tubulointerstitium. This review summarizes the main changes in protein composition of the glomerular mesangium and basement membrane and the evidence that, in the mesangium, these are initiated by changes in glucose metabolism and the formation of advanced glycation end products. Both processes generate reactive oxygen species (ROS). The review includes discussion of how ROS may activate intracellular signaling pathways leading to the activation of redox-sensitive transcription factors. This in turn leads to change in the expression of genes encoding extracellular matrix proteins and the protease systems responsible for their turnover.

The comparative role of activator protein 1 and Smad factors in the regulation of Timp-1 and MMP-1 gene expression by transforming growth factor-beta 1

The balance between matrix metalloproteinases (MMPs) and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), is pivotal in the remodeling of extracellular matrix. TGF-beta has profound effects on extracellular matrix homeostasis, in part via its ability to alter this balance at the level of gene expression. The intracellular signaling pathways by which TGF-beta mediates its actions include the Smad pathway, specific to the TGF-beta superfamily, but also, for example, mitogen-activated protein kinase pathways; furthermore, cross-talk between the Smads and other signaling pathways modifies the TGF-beta response. The reciprocal effect of TGF-beta on the expression of Timp-1 and MMP-1 supports its role in matrix anabolism, yet the mechanisms by which TGF-beta induces Timp-1 and represses induced MMP-1 have remained opaque. Here, we (i) investigate the mechanism(s) by which TGF-beta1 induces expression of the Timp-1 gene and (ii) compare this with TGF-beta1 repression of phorbol ester-induced MMP-1 expression. We report that the promoter-proximal activator protein 1 (AP1) site is essential for the response of both Timp-1 and MMP-1 to TGF-beta (induction and repression, respectively). c-Fos, JunD, and c-Jun are essential for the induction of Timp-1 gene expression by TGF-beta1, but these AP1 factors transactivate equally well from both Timp-1 and MMP-1 AP1 sites. Smad-containing complexes do not interact with the Timp-1 AP1 site, and overexpression of Smads does not substitute or potentiate the induction of the gene by TGF-beta1; furthermore, Timp-1 is still induced by TGF-beta1 in Smad knockout cell lines, although to varying extents. In contrast, Smads do interact with the MMP-1 AP1 site and mediate repression of induced MMP-1 gene expression by TGF-beta1.

Oncostatin M regulates eotaxin expression in fibroblasts and eosinophilic inflammation in C57BL/6 mice

Oncostatin M (OSM) is a member of the IL-6/LIF (or gp130) cytokine family, and its potential role in inflammation is supported by a number of activities identified in vitro. In this study, we investigate the action of murine OSM on expression of the CC chemokine eotaxin by fibroblasts in vitro and on mouse lung tissue in vivo. Recombinant murine OSM stimulated eotaxin protein production and mRNA levels in the NIH 3T3 fibroblast cell line. IL-6 could regulate a small induction of eotaxin in NIH 3T3 cells, but other IL-6/LIF cytokines (LIF, cardiotrophin-1 (CT-1)) had no effect. Cell signaling studies showed that murine OSM, LIF, IL-6, and CT-1 stimulated the tyrosine phosphorylation of STAT-3, suggesting STAT-3 activation is not sufficient for eotaxin induction in NIH 3T3 cells. OSM induced ERK-1,2 and p38 mitogen-activated protein kinase phosphorylation in NIH 3T3 cells, and inhibitors of ERK (PD98059) or p38 (SB203580) could partially reduce OSM-induced eotaxin production, suggesting partial dependence on mitogen-activated protein kinase signaling. OSM (but not LIF, IL-6, or CT-1) also induced eotaxin release by mouse lung fibroblast cultures derived from C57BL/6 mice. Overexpression of murine OSM in lungs of C57BL/6 mice using an adenovirus vector encoding murine OSM resulted in a vigorous inflammatory response by day 7 after intranasal administration, including marked extracellular matrix accumulation and eosinophil infiltration. Elevated levels of eotaxin mRNA in whole lung were detected at days 4 and 5. These data strongly support a role of OSM in lung inflammatory responses that involve eosinophil infiltration.

Matrix metalloproteinases in the adult brain physiology: a link between c-Fos, AP-1 and remodeling of neuronal connections?

Matrix metalloproteinases (MMPs), together with their endogenous inhibitors (TIMPs) form an enzymatic system that plays an important role in a variety of physiological and pathological conditions. These proteins are also expressed in the brain, especially under pathological conditions, in which glia as well as invading inflammatory cells provide the major source of the MMP activity. Surprisingly little is known about the MMP function(s) in adult neuronal physiology. This review describes available data on this topic, which is presented in a context of knowledge about the MMP/TIMP system in other organs as well as in brain disorders. An analysis of the MMP and TIMP expression patterns in the brain, along with a consideration of their regulatory mechanisms and substrates, leads to the proposal of possible roles of the MMP system in the brain. This analysis suggests that MMPs may play an important role in the neuronal physiology, especially in neuronal plasticity, including their direct participation in the remodeling of synaptic connections-a mechanism pivotal for learning and memory.

TGF-beta1 and HGF coordinately facilitate collagen turnover in subepithelial mesenchyme

We have employed co-culture of proximal tubular epithelial cells (PTEC) and renal tubulo-interstitial fibroblasts (TFB) to study the role of transforming growth factor-beta1 (TGF-beta1) and hepatocyte growth factor (HGF) in epithelial-mesenchymal interactions. In co-culture, TGF-beta1 stimulated TFB to produce type I collagen (COLI). This effect was both direct and indirect, via connective tissue growth factor (CTGF) produced by the co-cultured PTEC. Co-administration of TGF-beta1 and HGF significantly increased overall COLI production by TFB by 24h. However, in detail, this co-administration enhanced CTGF induction in PTEC during the first 8h, and then decreased its expression, resulting in a rapid decrease in expression of the alpha1(I) procollagen gene in TFB by 24h. Additionally, tissue inhibitor of metalloproteinase-1 was induced in PTEC by TGF-beta1 with or without co-administration of HGF, which contributed to the COLI accumulation. In contrast, HGF alone or co-administered with TGF-beta1 significantly increased collagenolytic activity derived from PTEC. Therefore, TGF-beta1 and HGF seem to coordinately modulate epithelial-mesenchymal interactions to facilitate COLI turnover in subepithelial mesenchyme.

Oncostatin M induced alpha1-antitrypsin (AAT) gene expression in Hep G2 cells is mediated by a 3' enhancer

alpha(1)-Antitrypsin (AAT) is the major serine proteinase inhibitor (SERPIN A1) in human plasma. Its target proteinase is neutrophil elastase and its main physiological function is protection of the lower respiratory tract from the destructive effects of neutrophil elastase during an inflammatory response. Circulating levels of AAT rise 2-3-fold during inflammation and the liver produces most of this increase. The cytokines oncostatin M (OSM) and interleukin-6 have been shown to be mainly responsible for this effect, which is mediated via the interaction of cytokine-inducible transcription factors with regulatory elements within the gene. In the present study, we report for the first time that OSM stimulation of hepatocyte AAT occurs via an interaction between the hepatocyte promoter and an OSM-responsive element at the 3'-end of the AAT gene. This effect is mediated by the transcription factor signal transducer and activator of transcription 3 ('STAT 3') binding to an OSM-responsive element (sequence TTCTCTTAA), and this site is distinct from, but close to, a previously reported interleukin-6-responsive element.

Staurosporine enhances the expression of tissue inhibitor of metalloproteinase-1 in human prostate cancer cells

We reported previously that human prostate cancer cell line TSU-Pr1 can differentiate into neuronal cells by staurosporine treatment. In this process, reduction of invasive abilities was observed in staurosporine treated TSU-Pr1 cells. In the present study, we investigated the effect of staurosporine on tissue inhibitor of metalloproteinases (TIMPs) in prostate cancer cells. We show that treatment of TSU-Pr1 cells with staurosporine results in induction of TIMP-1 mRNA and protein secretion. The induction of TIMP-1 mRNA expression by staurosporine is likely to be caused by increased transcriptional activity and this mechanism is indirect. Furthermore, recombinant human TIMP-1 reduces the invasive activity of TSU-Pr1 cells. We are the first to report that mRNA expression and protein secretion of TIMP-1 are enhanced by staurosporine treatment in prostate cancer cells. These findings suggest that enhancement of TIMP-1 is associated with suppression of invasive activity caused by staurosporine treatment.

Adenoviral transfer of murine oncostatin M elicits periosteal bone apposition in knee joints of mice, despite synovial inflammation and up-regulated expression of interleukin-6 and receptor activator of nuclear factor-kappa B ligand

Oncostatin M (OSM) has been described as a bone-remodeling factor either stimulating osteoblast activity or osteoclast formation in vitro. To elucidate the in vivo effect of OSM on bone remodeling, we injected an adenoviral vector encoding murine OSM in knee joints of mice. OSM strongly induced interleukin (IL)-6 gene expression, a known mediator of osteoclast development. We investigated the OSM effect in wild-type and IL-6-deficient mice and found a similar degree of OSM-induced joint inflammation. Within the first week of inflammation, the periosteum along the femur and tibia increased in cell number and stained positive for the osteoblast marker alkaline phosphatase. At these sites bone apposition occurred in both strains as demonstrated by Goldner and Von Kossa staining. In vitro OSM enhanced the effect of bone morphogenetic protein-2 on osteoblast differentiation. Immunohistochemistry demonstrated expression of receptor activator of nuclear factor-kappa B ligand (RANKL) and its receptor, receptor activator of nuclear factor-kappa B (RANK), in the periosteum but osteoclasts were not detected at sites of bone apposition. Induced mRNA expression for the receptor activator of nuclear factor-kappa B ligand inhibitor osteoprotegerin probably controlled osteoclast development during OSM overexpression. Our results show that OSM favors bone apposition at periosteal sites instead of resorption in vivo. This effect was not dependent on or inhibited by IL-6.

STAT1 and STAT3 mediate thrombin-induced expression of TIMP-1 in human glomerular mesangial cells

BACKGROUND

Thrombin exhibits numerous biological effects on glomerular resident cells, such as cell proliferation, release and synthesis of cytokines and collagen, expressions of metalloproteinases and their inhibitors, especially tissue inhibitor of metalloproteinase-1 (TIMP-1). However, the signaling mechanisms underlying these cellular events have not been fully elucidated. The present study was designed to examine the role of signal transducers and activators of transcription (STAT) in thrombin-induced TIMP-1 expression in human mesangial cells.

METHODS

Cultured human glomerular mesangial cells were incubated with thrombin up to 12 hours. The effects of the antisense of STAT1 and antisense of STAT3 on stimulated TIMP-1 mRNA levels and DNA-binding activities of both STAT1 and STAT3 were determined using Northern blot, electrophoretic mobility shift assay (EMSA), and supershift assay.

RESULTS

Cultured human mesangial cells constitutively expressed TIMP-1, and thrombin induced TIMP-1 gene transcription in a time- and dose-dependent manner. Hirudin, a specific inhibitor of thrombin, could block thrombin-induced TIMP-1 expression. Thrombin also induced STAT-DNA binding activity in a similar time- and dose-dependent manner. In order to examine the role of STAT in thrombin-induced TIMP-1 expression, STAT1 and STAT3 antisense oligonucleotides were used. EMSA showed that STAT1 and STAT3 antisense oligonucleotides could inhibit both thrombin-induced STAT-DNA binding activities and TIMP-1 mRNA expression; the supershift assay showed that the SIF band consisted of STAT1 and STAT3 proteins.

CONCLUSIONS

Both STAT1 and STAT3 may be involved, at least in part, in thrombin-induced expression of the TIMP-1 gene in cultured human mesangial cells.

Oncostatin M stimulates tissue inhibitor of metalloproteinase-1 via a MEK-sensitive mechanism in human myofibroblasts

BACKGROUND/AIMS

We previously showed that in cultured human myofibroblasts (hMFBs), Oncostatin M (OSM)-stimulated collagen accumulation is associated with increased tissue inhibitor of metalloproteinase (TIMP)1 message. However, the mechanism is unknown.

METHODS

hMFBs were isolated by outgrowth from cirrhotic liver explants and cultured. Using OSM (10 ng/ml) stimulation, with and without PD98059 (PD, a specific mitogen-activated protein kinase/extracellular signal-related kinase (MEK) inhibitor), we measured: TIMP-1 protein in culture medium by Western blot, TIMP-1 mRNA levels and stability by Northern analysis, TIMP-1 promoter activity (including transcription site mutation analysis), DNA binding activity to nuclear proteins by electrophoretic mobility shift assay (EMSA), and total and phosphorylated MAP kinase in hMFB extracts by Western blot.

RESULTS

OSM stimulation of hMFBs increased TIMP-1 protein production 1.69-fold, TIMP-1 mRNA levels 2.36-fold, promoter activity 2.22-fold, TIMP-1 message stability, and phosphorylation of mitogen-activated protein kinase (MAPK). PD inhibited OSM-mediated stimulation of TIMP-1 protein, mRNA, promoter activity, phosphorylation of MAPK, and TIMP-1 message stability. An SP-1 transcription site of the TIMP-1 promoter is essential for OSM induction of TIMP-1 promoter activity. EMSA demonstrates that this site binds to transcriptional factors SP-1 and SP-3.

CONCLUSIONS

OSM stimulates the TIMP-1 axis in hMFBs in vitro via a MEK-MAP kinase cascade.

NF-Y regulates LIF-induced transcription of the signaling adaptor SKAP55R in myeloid cells

Previously, we have shown that interleukin-6 (IL-6) or leukemia inhibitory factor (LIF)-induced differentiation of the myeloid cell line M1 was associated with a rapid increase in the level of mRNA encoding the signaling adaptor protein, SKAP55R. Furthermore, enforced over-expression of SKAP55R in primary bone marrow cells inhibited colony growth. In this study, we have identified the cis-acting elements that control SKAP55R transcription in myeloid cells. The 980 bp genomic sequence upstream of the transcriptional start site was cloned into a GFP reporter vector for transient (293 cells) or stable (M1 cells) transfection assays. This region contained cis-acting elements necessary for transcriptional activity in unstimulated 293 cells (10-fold higher levels than the control vector) or unstimulated M1 cells (two-fold higher levels). Significant LIF-induced transcription was observed in M1 (3.4-fold induction, P < 0.001), but not 293 cells. Deletion reporter constructs defined a promoter region (-317/-137) essential for the transcriptional activity in M1 cells. This region contained a CCAAT element recently implicated in IL-6/LIF-induced transcriptional regulation of junB in M1 cells. Mutation of the CCAAT element (-250/-246) significantly reduced both basal and LIF-induced transcription (P < 0.01). Electrophoretic mobility shift assays demonstrated that NF-Y bound to the CCAAT element of both SKAP55R and junB. These results suggest NF-Y binding may be a common mechanism of IL-6/LIF-regulated transcription in myeloid cells.

Synergistic induction of matrix metalloproteinase 1 by interleukin-1alpha and oncostatin M in human chondrocytes involves signal transducer and activator of transcription and activator protein 1 transcription factors via a novel mechanism

OBJECTIVE

To investigate the mechanism of interleukin-1alpha (IL-1alpha) and oncostatin M (OSM) synergistic regulation of matrix metalloproteinase 1 (MMP-1) in human chondrocytes.

METHODS

Using an immortalized human chondrocyte cell line (T/C28a4), we investigated regulation of the MMP-1 gene. Northern blotting and flow cytometric analysis were used to assess changes in receptor, MMP-1, and c-fos expression. Transient transfections using MMP-1 promoter/luciferase constructs, electrophoretic mobility shift assay, and site-directed mutagenesis were used to investigate MMP-1 promoter activation.

RESULTS

We found no alteration in the expression of receptors used by these cytokines after stimulation with IL-1alpha/OSM. Using MMP-1 promoter/luciferase reporter constructs, we found that the proximal (-517/+63) region of the MMP-1 promoter was sufficient to support a synergistic activation. A role for activated signal transducers and activators of transcription (STAT-3) was demonstrated, although no binding of STAT-3 to the MMP-1 promoter was found. However, constitutive binding of activator protein 1 (AP-1) was detected, and changes in c-fos expression could modulate promoter activity.

CONCLUSION

Since no changes in receptor expression were observed, receptor modulation cannot account for the IL-1alpha/OSM synergy observed. Instead, the interplay of various intracellular signaling pathways is a more likely explanation. STAT activation is required, but STAT proteins do not interact directly with the MMP-1 promoter. We propose that activated STATs stimulate c-fos expression, and changes in expression of the AP-1 components regulate MMP-1 expression. We highlight a new mechanism for MMP-1 regulation in human chondrocytes that could provide potential new therapeutic targets.

CD40L induces matrix-metalloproteinase-9 but not tissue inhibitor of metalloproteinases-1 in cervical carcinoma cells: imbalance between NF-kappaB and STAT3 activation

Matrix-metalloproteinases (MMPs) are essentially required for tumor cell invasion and metastasis. Production of precursor enzymes is regulated on transcriptional level, while activation of the pro-enzymes is tightly controlled by posttranscriptional mechanisms. The enzyme activity can be blocked by specific tissue inhibitors of MMPs (TIMPs). In cervical carcinomas strong up-regulation of the type IV collagenase MMP-9 had been demonstrated. We show that activation of CD40, a receptor highly expressed on cervical carcinomas, induces MMP-9 in cervical carcinoma cells, whereas TIMP-1 production inhibiting MMP-9 activity was not affected. This gene induction pattern corresponded to the differential activation of the transcription factor nuclear factor kappaB (NF-kappaB) regulating MMP-9, but not signal transducer and activator of transcription 3 (STAT3), which is involved in TIMP-1 gene regulation. Transient expression of the CD40-inducible NF-kappaB subunit p65 was sufficient for MMP-9 induction. Agents that suppressed CD40-mediated NF-kappaB activation also reduced MMP-9 induction, further supporting an important role of NF-kappaB in CD40-mediated MMP-9 induction. Our data suggest that CD40 expression in carcinoma cells might convert a CD40L-dependent immunological defense signal into a tumor-promoting signal. Selective CD40-mediated signaling through NF-kappaB but not STAT3 correlates to a shift of the balance between MMP-9 and TIMP-1 toward the protease.

Synergistic effects of glycoprotein 130 binding cytokines in combination with interleukin-1 on cartilage collagen breakdown

OBJECTIVE

To determine whether other glycoprotein 130 (gp130) binding cytokines can mimic the effects of oncostatin M (OSM) in acting synergistically with interleukin-1alpha (IL-1alpha) to induce cartilage collagen breakdown and collagenase expression, and to determine which receptors mediate these effects.

METHODS

The release of collagen and proteoglycan was assessed in bovine and human cartilage explant cultures. Messenger RNA (mRNA) and protein production from immortalized human chondrocytes (T/C28a4) was analyzed by Northern blotting and specific enzyme-linked immunosorbent assays. Collagenase activity was measured by bioassay. Cell surface receptors were detected by flow cytometry.

RESULTS

OSM in combination with IL-1alpha caused a rapid synergistic induction of matrix metalloproteinase 1 mRNA, which was sustained over a 72-hour period. Flow cytometric analyses detected both the OSM-specific receptor and the gp130 receptor at the chondrocyte cell surface, but failed to detect the leukemia inhibitory factor receptor (LIFR). Cartilage degradation assays revealed that, of the gp130 binding cytokines, only OSM and IL-6, in the presence of its soluble receptor (sIL-6R), were able to act synergistically with IL-1alpha to promote collagen release.

CONCLUSION

This study demonstrates that IL-6 can mimic OSM in synergizing with IL-1alpha to induce chondrocyte-mediated cartilage collagen breakdown and collagenase production. In order to have this effect, IL-6 requires the presence of its soluble receptor. The apparent absence of LIFR explains why other gp130 binding cytokines do not act in synergy with IL-1alpha. Since OSM, IL-6, and sIL-6R levels have all been shown to be elevated in the rheumatoid joint, our findings suggest that these cytokines may be key mediators of cartilage collagen catabolism in the inflammatory arthritides.

Oncostatin M-induced matrix metalloproteinase and tissue inhibitor of metalloproteinase-3 genes expression in chondrocytes requires Janus kinase/STAT signaling pathway

Oncostatin M (OSM), a member of the IL-6 superfamily of cytokines, is elevated in patients with rheumatoid arthritis and, in synergy with IL-1, promotes cartilage degeneration by matrix metalloproteinases (MMPs). We have previously shown that OSM induces MMP and tissue inhibitor of metalloproteinase-3 (TIMP-3) gene expression in chondrocytes by protein tyrosine kinase-dependent mechanisms. In the present study, we investigated signaling pathways regulating the induction of MMP and TIMP-3 genes by OSM. We demonstrate that OSM rapidly stimulated phosphorylation of Janus kinase (JAK) 1, JAK2, JAK3, and STAT1 as well as extracellular signal-regulated kinase (ERK) 1/2, p38, and c-Jun N-terminal kinase 1/2 mitogen-activated protein kinases in primary bovine and human chondrocytes. A JAK3-specific inhibitor blocked OSM-stimulated STAT1 tyrosine phosphorylation, DNA-binding activity of STAT1 as well as collagenase-1 (MMP-1), stromelysin-1 (MMP-3), collagenase-3 (MMP-13), and TIMP-3 RNA expression. In contrast, a JAK2-specific inhibitor, AG490, had no impact on these events. OSM-induced ERK1/2 activation was also not affected by these inhibitors. Similarly, curcumin (diferuloylmethane), an anti-inflammatory agent, suppressed OSM-stimulated STAT1 phosphorylation, DNA-binding activity of STAT1, and c-Jun N-terminal kinase activation without affecting JAK1, JAK2, JAK3, ERK1/2, and p38 phosphorylation. Curcumin also inhibited OSM-induced MMP-1, MMP-3, MMP-13, and TIMP-3 gene expression. Thus, OSM induces MMP and TIMP-3 genes in chondrocytes by activating JAK/STAT and mitogen-activated protein kinase signaling cascades, and interference with these pathways may be a useful approach to block the catabolic actions of OSM.

Cytokine-induced changes in chromatin structure and in vivo footprints in the inducible NOS promoter

Transcription of the human inducible nitric oxide synthase (iNOS) gene is regulated by inflammatory cytokines in a tissue-specific manner. To determine whether differences in cytokine-induced mRNA levels between pulmonary epithelial cells (A549) and hepatic biliary epithelial cells (AKN-1) result from different protein or DNA regulatory mechanisms, we identified cytokine-induced changes in DNase I-hypersensitive (HS) sites in 13 kb of the iNOS 5'-flanking region. Data showed both constitutive and inducible HS sites in an overlapping yet cell type-specific pattern. Using in vivo footprinting and ligation-mediated PCR to detect potential DNA or protein interactions, we examined one promoter region near -5 kb containing both constitutive and cytokine-induced HS sites. In both cell types, three in vivo footprints were present in both control and cytokine-treated cells, and each mapped within a constitutive HS site. The remaining footprint appeared only in response to cytokine treatment and mapped to an inducible HS site. These studies, performed on chromatin in situ, identify a portion of the molecular mechanisms regulating transcription of the human iNOS gene in both lung- and liver-derived epithelial cells.

Ets target genes: past, present and future

Ets is a family of transcription factors present in species ranging from sponges to human. All family members contain an approximately 85 amino acid DNA binding domain, designated the Ets domain. Ets proteins bind to specific purine-rich DNA sequences with a core motif of GGAA/T, and transcriptionally regulate a number of viral and cellular genes. Thus, Ets proteins are an important family of transcription factors that control the expression of genes that are critical for several biological processes, including cellular proliferation, differentiation, development, transformation, and apoptosis. Here, we tabulate genes that are regulated by Ets factors and describe past, present and future strategies for the identification and validation of Ets target genes. Through definition of authentic target genes, we will begin to understand the mechanisms by which Ets factors control normal and abnormal cellular processes.

Direct regulation of pituitary proopiomelanocortin by STAT3 provides a novel mechanism for immuno-neuroendocrine interfacing

Neuroendocrine ACTH secretion responds to peripheral inflammatory and stress signals. We previously demonstrated that the proinflammatory cytokine, leukemia inhibitory factor (LIF), affects the hypothalamo-pituitary-adrenal axis (HPA) by stimulating in vitro and in vivo pituitary proopiomelanocortin (POMC) gene expression and ACTH secretion and by potentiating the action of hypothalamic corticotropin releasing hormone (CRH). Whereas pathways shown thus far to regulate POMC expression exclusively involve cAMP or calcium, we here describe a direct and indirect STAT3-dependent regulation of POMC transcription by LIF. Using progressive 5'-deletions of POMC promoter, we identified a LIF-responsive -407/-301 region that contains two juxtaposed sequences within -399/-379 related to a STAT3 DNA-binding motif. Each sequence within -399/-379 separately corresponds to a low-affinity and direct binding site for STAT3, but, in combination, these sequences bind STAT3 cooperatively and with high affinity. Moreover, LIF-activated STAT3 indirectly mediates LIF corticotroph action by inducing and potentiating CRH-induced c-fos and JunB expression and binding to the POMC AP-1 element. We therefore conclude that both a direct and indirect route mediate LIF-induced STAT3 activation of POMC transcription. Demonstration of STAT3-dependent regulation of the POMC gene represents a powerful mechanism for immuno-neuroendocrine interfacing and implies a direct stimulation of ACTH secretion by inflammatory and stress-derived STAT3-inducing cytokines.

Regulation of AP1 (Jun/Fos) factor expression and activation in ovarian granulosa cells. Relation of JunD and Fra2 to terminal differentiation

AP1 transcription factors control rapid responses of mammalian cells to stimuli that impact proliferation, differentiation, and transformation. To determine which AP1 factors are present in and regulated by hormones in ovarian cells during specific stages of proliferation and differentiation, we used both in vitro and in vivo models, Western blotting, immunohistochemistry, DNA binding assays, and transfections of AP1 promoter-reporter constructs. The expression patterns of Jun and Fos family members in response to hormones (follicle-stimulating hormone (FSH), luteinizing hormone (LH), and cAMP) were distinct. JunB, c-Jun, c-Fos, and Fra2 were rapidly but transiently induced by FSH in immature granulosa cells. JunD and Fra2 were induced by LH and maintained as granulosa cells terminally differentiated into luteal cells. Forskolin and phorbol myristate acetate acted synergistically to enhance transcription of an AP1(-73COL)-luciferase construct. JunD appears to be one mediator of this effect, since JunD was a major component of the AP1-DNA binding complex in granulosa cells, and menin, a selective inhibitor of JunD, blocked transcription of -73COL-luciferase. Thus, FSH and LH via cAMP induce specific AP1 factors, the AP1 expression patterns are distinct, and that of JunD and Fra2 correlates with the transition of proliferating granulosa cells to terminally differentiated, non-dividing luteal cells.