Co-operative interactions between NFAT (nuclear factor of activated T cells) c1 and the zinc finger transcription factors Sp1/Sp3 and Egr-1 regulate MT1-MMP (membrane type 1 matrix metalloproteinase) transcription by glomerular mesangial cells

Harmine suppresses collagen production in hepatic stellate cells by inhibiting DYRK1B

Liver fibrosis is a major consequence of chronic liver disease, where excess extracellular matrix is deposited, due caused by the activation of hepatic stellate cells (HSCs). The suppression of collagen production in HSCs is therefore regarded as a therapeutic target of liver fibrosis. The present study investigated effects of harmine, which is a β-carboline alkaloid and known as an inhibitor of dual-specificity tyrosine-regulated kinases (DYRKs), on the production of collagen in HSCs. LX-2 cells, a human HSC cell line, were treated with harmine (0-10 μM) for 48 h in the presence or absence of TGF-β1 (5 ng/ml). The expression of collagen type I α1 (COL1A1) and DYRK isoforms was investigated by Western blotting, quantitative RT-PCR, or immunofluorescence. The influence of knockdown of each DYRK isoform on the COL1A1 expression was further investigated. The expression of COL1A1 was markedly increased by treating with TGF-β1 for 48 h in LX-2 cells. Harmine (10 μM) significantly inhibited the increased expression of COL1A1. LX-2 cells expressed mRNAs of DYRK1A, DYRK1B, DYRK2, and DYRK4, although the expression of DYRK4 was much lower than the others. Knockdown of DYRK1B, but not DYRK1A or DYRK2, with siRNA significantly suppressed TGF-β1-induced increase in COL1A1 expression. These results suggest that harmine suppresses COL1A1 expression via inhibiting DYRK1B in HSCs and therefore might be effective for the treatment of liver fibrosis.

An autonomous TCR signal-sensing switch influences CD4/CD8 lineage choice in mice

How multipotential cells initiate distinct gene expression programs in response to external cues to instruct cell fate choice remains a fundamental question in biology. Establishment of CD4 and CD8 T cell fates during thymocyte development is critically regulated by T cell receptor (TCR) signals, which in turn control expression of the CD4-determining transcription factor ThPOK. However, the mechanism whereby differential TCR signals are molecularly interpreted to promote or antagonize ThPOK expression, and thereby CD4 versus CD8 lineage fates remains unknown. Here we show, using reverse genetic and molecular approaches that an autonomous, position-independent TCR-sensing switch is embedded within the ThPOK locus. Further, using an in vivo mutagenesis approach, we demonstrate that differential TCR signals are interpreted during lineage commitment by relative binding of EGR, NFAT and Ebox factors to this bistable switch. Collectively our study reveals the central molecular mechanism whereby TCR signaling influences differential lineage choice. Ultimately, these findings may provide an important new tool for skewing T cell fate to treat cancer and autoimmune diseases.

Anemopsis californica Attenuates Photoaging by Regulating MAPK, NRF2, and NFATc1 Signaling Pathways

Long-term exposure of the skin to solar radiation causes chronic inflammation and oxidative stress, which accelerates collagen degradation. This contributes to the formation of wrinkles and dark spots, skin fragility, and even skin cancer. In this study, Anemopsis californica (AC), a herb from North America that is well known for treating microorganism infection and promoting wound healing, was investigated for its photoprotective effects. The biological effects of AC were studied on two in vitro models, namely, lipopolysaccharide (LPS)-induced macrophages and ultraviolet B (UVB)-irradiated dermal fibroblasts, to characterize its underlying molecular mechanisms. The results showed that AC decreased the mRNA levels of inflammatory mediators in sensitized macrophages, including cytokines, inducible nitric oxide synthase (iNOS), and cyclooxygenase (COX-2). Moreover, AC alleviated UVB-induced photoaging in dermal fibroblasts by restoring procollagen synthesis. This resulted from the regulation of excessive reactive oxygen species (ROS) by AC, which was mediated by the activation of the antioxidative system nuclear factor erythroid 2-related factor 2 (NRF2). AC also alleviated oxidative stress and inflammatory responses by inhibiting the phosphorylation of mitogen-activated protein kinase (MAPK) and interfering with the nuclear translocation of the immune regulator nuclear factor of activated T-cells 1 (NFATc1). In conclusion, the protective effects of AC on skin cellular components suggested that it has the potential for use in the development of drugs and cosmetics that protect the skin from UVB-induced chronic inflammation and aging.

Membrane-type I matrix metalloproteinase (MT1-MMP), lipid metabolism and therapeutic implications

Lipids exert many essential physiological functions, such as serving as a structural component of biological membranes, storing energy, and regulating cell signal transduction. Dysregulation of lipid metabolism can lead to dyslipidemia related to various human diseases, such as obesity, diabetes, and cardiovascular disease. Therefore, lipid metabolism is strictly regulated through multiple mechanisms at different levels, including the extracellular matrix. Membrane-type I matrix metalloproteinase (MT1-MMP), a zinc-dependent endopeptidase, proteolytically cleaves extracellular matrix components, and non-matrix proteins, thereby regulating many physiological and pathophysiological processes. Emerging evidence supports the vital role of MT1-MMP in lipid metabolism. For example, MT1-MMP mediates ectodomain shedding of low-density lipoprotein receptor and increases plasma low-density lipoprotein cholesterol levels and the development of atherosclerosis. It also increases the vulnerability of atherosclerotic plaque by promoting collagen cleavage. Furthermore, it can cleave the extracellular matrix of adipocytes, affecting adipogenesis and the development of obesity. Therefore, the activity of MT1-MMP is strictly regulated by multiple mechanisms, such as autocatalytic cleavage, endocytosis and exocytosis, and post-translational modifications. Here, we summarize the latest advances in MT1-MMP, mainly focusing on its role in lipid metabolism, the molecular mechanisms regulating the function and expression of MT1-MMP, and their pharmacotherapeutic implications.

BRLF1-dependent viral and cellular transcriptomes and transcriptional regulation during EBV primary infection in B lymphoma cells

The immediate-early protein BRLF1 plays important roles in lytic infection of Epstein-Barr virus (EBV), in which it activates lytic viral transcription and replication. However, knowledge of the influence of BRLF1 on cellular gene expression and transcriptional reprogramming during the early lytic cycle remains limited. In the present study, deep RNA-sequencing analysis identified all differentially expressed genes (DEGs) and alternative splicing in B lymphoma cells subjected to wild-type and BRLF1-deficient EBV primary infection. The BRLF1-dependent cellular DEGs were annotated, and major differentially enriched pathways were related to DNA replication and transcription, immune and inflammatory responses, cytokine-receptor interactions and chemokine signaling and metabolic processes. Furthermore, analysis of BRLF1-binding proteins by mass spectrometry shows that BRLF1 binds to and cooperates with several transcription factors and components of the spliceosome and then influences both RNA polymerase II-dependent transcription and pre-mRNA splicing. The RTA-binding RRE motifs or specific motifs of unique cooperative transcription factors in viral and cellular DEG promoter regions indicate that BRLF1 employs different strategies for regulating viral and cellular transcription. Thus, our study characterized BRLF1-dependent cellular and viral transcriptional profile during primary infection and then revealed the comprehensive virus-cell interaction and alterations of transcription during EBV primary infection and lytic replication.

Myofibroblasts and Fibrosis: Mitochondrial and Metabolic Control of Cellular Differentiation

Cardiac fibrosis is mediated by the activation of resident cardiac fibroblasts, which differentiate into myofibroblasts in response to injury or stress. Although myofibroblast formation is a physiological response to acute injury, such as myocardial infarction, myofibroblast persistence, as occurs in heart failure, contributes to maladaptive remodeling and progressive functional decline. Although traditional pathways of activation, such as TGFβ (transforming growth factor β) and AngII (angiotensin II), have been well characterized, less understood are the alterations in mitochondrial function and cellular metabolism that are necessary to initiate and sustain myofibroblast formation and function. In this review, we highlight recent reports detailing the mitochondrial and metabolic mechanisms that contribute to myofibroblast differentiation, persistence, and function with the hope of identifying novel therapeutic targets to treat, and potentially reverse, tissue organ fibrosis.

EGR-mediated control of STIM expression and function

Ca²⁺ is a ubiquitous, dynamic and pluripotent second messenger with highly context-dependent roles in complex cellular processes such as differentiation, proliferation, and cell death. These Ca²⁺ signals are generated by Ca²⁺-permeable channels located on the plasma membrane (PM) and endoplasmic reticulum (ER) and shaped by PM- and ER-localized pumps and transporters. Differences in the expression of these Ca²⁺ homeostasis proteins contribute to cell and context-dependent differences in the spatiotemporal organization of Ca²⁺ signals and, ultimately, cell fate. This review focuses on the Early Growth Response (EGR) family of zinc finger transcription factors and their role in the transcriptional regulation of Stromal Interaction Molecule (STIM1), a critical regulator of Ca²⁺ entry in both excitable and non-excitable cells.

Interleukin-6 increases matrix metalloproteinase-14 (MMP-14) levels via down-regulation of p53 to drive cancer progression

Matrix metalloproteinases (MMPs) play critical roles in cancer invasion and metastasis by digesting basement membrane and extracellular matrix (ECM). Much attention has focused on the enzymatic activities of MMPs; however, the regulatory mechanism of MMP expression remains elusive. By employing bioinformatics analysis, we identified a potential p53 response element within the MMP-14 promoter. Experimentally, we found that p53 can repress MMP-14 promoter activity, whereas deletion of this p53 response element abrogated this effect. Furthermore, we found that p53 expression decreases MMP-14 mRNA and protein levels and attenuates MMP-14-mediated cellular functions. Additional promoter analysis and chromatin immunoprecipitation studies identified a mechanism of regulation of MMP-14 expression by which p53 and transcription factor Sp1 competitively bind to the promoter. As the correlation between inflammation and cancer aggressiveness is well described, we next sought to evaluate if inflammatory cytokines could differentially affect p53 and MMP-14 levels. We demonstrate that interleukin-6 (IL-6) down-regulates p53 protein levels and thus results in a concomitant increase in MMP-14 expression, leading to enhanced cancer cell invasion and metastasis. Our data collectively indicate a novel mechanism of regulation of MMP-14 by a cascade of IL-6 and p53, demonstrating that the tumor microenvironment directly stimulates molecular changes in cancer cells to drive an invasive phenotype.

Immunosuppression With FTY720 Reverses Cardiac Dysfunction in Hypomorphic ApoE Mice Deficient in SR-BI Expression That Survive Myocardial Infarction Caused by Coronary Atherosclerosis

AIMS

We recently reported that immunosuppression with FTY720 improves cardiac function and extends longevity in Hypomorphic ApoE mice deficient in scavenger receptor Type-BI expression, also known as the HypoE/SR-BI(–/–) mouse model of diet-induced coronary atherosclerosis and myocardial infarction (MI). In this study, we tested the impact of FTY720 on cardiac dysfunction in HypoE/SR-BI(–/–) mice that survive MI and subsequently develop chronic heart failure.

METHODS/RESULTS

HypoE/SR-BI(–/–) mice were bred to Mx1-Cre transgenic mice, and offspring were fed a high-fat diet (HFD) for 3.5 weeks to provoke hyperlipidemia, coronary atherosclerosis, and recurrent MIs. In contrast to our previous study, hyperlipidemia was rapidly reversed by inducible Cre-mediated gene repair of the HypoE allele and switching mice to a normal chow diet. Mice that survived the period of HFD were subsequently given oral FTY720 in drinking water or not, and left ventricular (LV) function was monitored using serial echocardiography for up to 15 weeks. In untreated mice, LV performance progressively deteriorated. Although FTY720 treatment did not initially prevent a decline of heart function among mice 6 weeks after Cre-mediated gene repair, it almost completely restored normal LV function in these mice by 15 weeks. Reversal of heart failure did not result from reduced atherosclerosis as the burden of aortic and coronary atherosclerosis actually increased to similar levels in both groups of mice. Rather, FTY720 caused systemic immunosuppression as assessed by reduced numbers of circulating T and B lymphocytes. In contrast, FTY720 did not enhance the loss of T cells or macrophages that accumulated in the heart during the HFD feeding period, but it did enhance the loss of B cells soon after plasma lipid lowering. Moreover, FTY720 potently reduced the expression of matrix metalloproteinase-2 and genes involved in innate immunity-associated inflammation in the heart.

CONCLUSIONS

Our data demonstrate that immunosuppression with FTY720 prevents postinfarction myocardial remodeling and chronic heart failure.

The effect of non-coding DNA variations on P53 and cMYC competitive inhibition at cis-overlapping motifs

Non-coding DNA variations play a critical role in increasing the risk for development of common complex diseases, and account for the majority of SNPs highly associated with cancer. However, it remains a challenge to identify etiologic variants and to predict their pathological effects on target gene expression for clinical purposes. Cis-overlapping motifs (COMs) are elements of enhancer regions that impact gene expression by enabling competitive binding and switching between transcription factors. Mutations within COMs are especially important when the involved transcription factors have opposing effects on gene regulation, like P53 tumor suppressor and cMYC proto-oncogene. In this study, genome-wide analysis of ChIP-seq data from human cancer and mouse embryonic cells identified a significant number of putative regulatory elements with signals for both P53 and cMYC. Each co-occupied element contains, on average, two COMs, and one common SNP every two COMs. Gene ontology of predicted target genes for COMs showed that the majority are involved in DNA damage, apoptosis, cell cycle regulation, and RNA processing. EMSA results showed that both cMYC and P53 bind to cis-overlapping motifs within a ChIP-seq co-occupied region in Chr12. In vitro functional analysis of selected co-occupied elements verified enhancer activity, and also showed that the occurrence of SNPs within three COMs significantly altered enhancer activity. We identified a list of COM-associated functional SNPs that are in close proximity to SNPs associated with common diseases in large population studies. These results suggest a potential molecular mechanism to identify etiologic regulatory mutations associated with common diseases.

NFAT-1, Sp-1, Sp-3, and miR-21: New regulators of chemokine C receptor 7 expression in mature human dendritic cells

The chemokine C receptor 7 (CCR7) is a G-protein-coupled heptahelical receptor (GPCR) that is expressed on a wide variety of cells including memory T cells, B cells, mature dendritic cells, and cancer cells. Activated by its ligands CCL19 or CCL21, CCR7 plays a major role in metastasis of cancer cells. Recent studies demonstrated the role of NF-κB and AP-1 transcription factors in addition to let-7 microRNA in CCR7 expression. Our ChIP assays further show the binding of Sp-1, Sp-3 and NFAT-1 transcription factors to their potential binding sites in the 1Kb promoter region with the later found to inhibit whilst Sp-1, and Sp-3 were found to stimulate CCR7 expression as demonstrated by transfection assays. On the other hand, in addition to the known let-7 regulation of CCR7, we found miR-21 to have a highly conserved target region in CCR7 3'UTR and to be significantly down-regulated during the course of dendritic cell maturation, allowing for high expression of CCR7.

Nuclear factor of activated T cells in cancer development and treatment

Since nuclear factor of activated T cells (NFAT) was first identified as a transcription factor in T cells, various NFAT isoforms have been discovered and investigated. Accumulating studies have suggested that NFATs are involved in many aspects of cancer, including carcinogenesis, cancer cell proliferation, metastasis, drug resistance and tumor microenvironment. Different NFAT isoforms have distinct functions in different cancers. The exact function of NFAT in cancer or the tumor microenvironment is context dependent. In this review, we summarize our current knowledge of NFAT regulation and function in cancer development and treatment. NFATs have emerged as a potential target for cancer prevention and therapy.

Early growth response-1 (EGR-1) and nuclear factor of activated T cells (NFAT) cooperate to mediate CD40L expression in megakaryocytes and platelets

Increasing evidence implicates circulating platelets as mediators of chronic inflammatory and autoimmune diseases via the expression and release of CD40L, an important modulator of inflammation and adaptive immune responses traditionally associated with activated T cells. Emerging evidence suggests that platelet CD40L is dynamically regulated in several chronic inflammatory and autoimmune diseases and may mediate progression and secondary pathology associated with those disease states. The present study identifies NFATc2 as a key transcriptional modulator of CD40L expression in megakaryocytes and inflammatory activity of platelets. Furthermore, the current data show that EGR-1, a member of the early growth response family of zinc finger transcription factors, modulates NFATc2-dependent regulation of CD40L expression in megakaryocytes. Our novel demonstration that in vivo biochemical or genetic inhibition of NFATc2 activity in megakaryocyte diminishes platelet CD40L implicates the NFATc2/EGR-1 axis as a key regulatory pathway of inflammatory and immunomodulatory activity in platelets and represents a target for the development of therapeutics for the potential treatment of chronic inflammatory and autoimmune diseases.

Methyl jasmonate abolishes the migration, invasion and angiogenesis of gastric cancer cells through down-regulation of matrix metalloproteinase 14

BACKGROUND

Recent evidence indicates that methyl jasmonate (MJ), a plant stress hormone, exhibits anti-cancer activity on human cancer cells. The aim of this study is to determine whether sub-cytotoxic MJ can abolish the migration, invasion and angiogenesis gastric cancer cells.

METHODS

Human gastric cancer cell lines SGC-7901 and MKN-45 were treated with diverse concentrations of MJ. Cell viability, proliferation, migration, invasion and angiogenesis capabilities of cancer cells were measured by MTT colorimetry, EdU incorporation, scratch assay, matrigel invasion assay, and tube formation assay. Gene expression was detected by western blot and real-time quantitative RT-PCR. Binding of transcription factor on gene promoter was detected by chromatin immunoprecipitation.

RESULTS

Sub-cytotoxic (0.05 to 0.2 mM) MJ attenuated the migration, invasion and angiogenesis, but not the cell viability or proliferation, of gastric cancer cells in a time- and dose-dependent manner, with down-regulation of matrix metalloproteinase 14 (MMP-14) and its downstream gene vascular endothelial growth factor. Restoration of MMP-14 expression rescued the SGC-7901 and MKN-45 cells from sub-cytotoxic MJ-inhibited migration, invasion and angiogenesis. In addition, sub-cytotoxic MJ decreased the specificity protein 1 (Sp1) expression and binding on MMP-14 promoter, while restoration of Sp1 expression rescued the cancer cells from sub-cytotoxic MJ-mediated defects in MMP-14 expression, migration, invasion and angiogenesis.

CONCLUSIONS

Sub-cytotoxic MJ attenuates the MMP-14 expression via decreasing the Sp1 expression and binding on MMP-14 promoter, thus inhibiting the migration, invasion and angiogenesis of gastric cancer cells.

EGR1 and EGR2 involvement in vertebrate tendon differentiation

The molecules involved in vertebrate tendon formation during development remain largely unknown. To date, only two DNA-binding proteins have been identified as being involved in vertebrate tendon formation, the basic helix-loop-helix transcription factor Scleraxis and, recently, the Mohawk homeobox gene. We investigated the involvement of the early growth response transcription factors Egr1 and Egr2 in vertebrate tendon formation. We established that Egr1 and Egr2 expression in tendon cells was correlated with the increase of collagen expression during tendon cell differentiation in embryonic limbs. Vertebrate tendon differentiation relies on a muscle-derived FGF (fibroblast growth factor) signal. FGF4 was able to activate the expression of Egr genes and that of the tendon-associated collagens in chick limbs. Egr gene misexpression experiments using the chick model allowed us to establish that either Egr gene has the ability to induce de novo expression of the reference tendon marker scleraxis, the main tendon collagen Col1a1, and other tendon-associated collagens Col3a1, Col5a1, Col12a1, and Col14a1. Mouse mutants for Egr1 or Egr2 displayed reduced amounts of Col1a1 transcripts and a decrease in the number of collagen fibrils in embryonic tendons. Moreover, EGR1 and EGR2 trans-activated the mouse Col1a1 proximal promoter and were recruited to the tendon regulatory regions of this promoter. These results identify EGRs as novel DNA-binding proteins involved in vertebrate tendon differentiation by regulating type I collagen production.

Regulation of embryonic kidney branching morphogenesis and glomerular development by KISS1 receptor (Gpr54) through NFAT2- and Sp1-mediated Bmp7 expression

G-protein-coupled receptor 54 (Gpr54, KISS1 receptor) plays critical roles in puberty regulation, tumor metastasis suppression, and vasoconstriction. Bone morphogenetic protein-7 (Bmp7) is required for kidney organogenesis. However, whether Gpr54 is involved in embryonic kidney development and how Bmp7 expression is regulated in the kidney are largely unknown. Here we report that Gpr54 deletion leads to kidney branching morphogenesis and glomerular development retardation in embryonic kidneys in vivo and in explanted kidneys in vitro. Gpr54 inactivation results in a high risk of low glomerular number in adult kidneys. Gpr54 is expressed in condensed mesenchyme at E12.5 and epithelial cells of proximal and distal tubules and collecting ducts at E17.5 and P0 mouse kidney. Deletion of Gpr54 decreases Bmp7 expression and Smad1 phosphorylation in the developing kidney. Using chromatin immunoprecipitation and luciferase assays, we demonstrate that Gpr54 regulates NFAT2- and Sp1-mediated Bmp7 transcription. Furthermore, we show that NFAT2 cooperates with Sp1 to promote Bmp7 transcription activation. Together, these data suggest that Gpr54 regulates Bmp7 expression through NFAT2 and Sp1 and plays an important role in embryonic kidney branching morphogenesis and glomerular development.

Polyoma virus-induced osteosarcomas in inbred strains of mice: host determinants of metastasis

The mouse polyoma virus induces a broad array of solid tumors in mice of many inbred strains. In most strains tumors grow rapidly but fail to metastasize. An exception has been found in the Czech-II/Ei mouse in which bone tumors metastasize regularly to the lung. These tumors resemble human osteosarcoma in their propensity for pulmonary metastasis. Cell lines established from these metastatic tumors have been compared with ones from non-metastatic osteosarcomas arising in C3H/BiDa mice. Osteopontin, a chemokine implicated in migration and metastasis, is known to be transcriptionally induced by the viral middle T antigen. Czech-II/Ei and C3H/BiDa tumor cells expressed middle T and secreted osteopontin at comparable levels as the major chemoattractant. The tumor cell lines migrated equally well in response to recombinant osteopontin as the sole attractant. An important difference emerged in assays for invasion in which tumor cells from Czech-II/Ei mice were able to invade across an extracellular matrix barrier while those from C3H/BiDa mice were unable to invade. Invasive behavior was linked to elevated levels of the metalloproteinase MMP-2 and of the transcription factor NFAT. Inhibition of either MMP-2 or NFAT inhibited invasion by Czech-II/Ei osteosarcoma cells. The metastatic phenotype is dominant in F1 mice. Osteosarcoma cell lines from F1 mice expressed intermediate levels of MMP-2 and NFAT and were invasive. Osteosarcomas in Czech-II/Ei mice retain functional p53. This virus-host model of metastasis differs from engineered models targeting p53 or pRb and provides a system for investigating the genetic and molecular basis of bone tumor metastasis in the absence of p53 loss.

The oncogenic mouse polyoma virus and its mutants have previously been used to investigate viral determinants of tumor induction using a standard inbred mouse strain as a common host. Here we use wild type virus to investigate the role of the host genetic background, focusing on two host strains that differ with respect to bone tumor metastasis. Comparing osteosarcoma cell lines from these mice, we have identified a molecular pathway that underlies invasive behavior in vitro and correlates with metastasis in vivo. The pathway involves secretion of the metalloproteinase MMP-2 under partial control of NFAT as a transcriptional regulator. This virus-host system reflects an important feature of human osteosarcoma with respect to pulmonary metastasis. Based on naturally occurring differences among inbred mice, the model differs from genetically engineered models targeting p53 or pRb as known risk factors in the human disease. Here, metastatic osteosarcomas retain functional p53. As noted by others, the frequency of p53 loss in patients with localized versus metastatic disease is the same, suggesting that events beyond p53 loss are important in metastasis. While the downstream effectors of metastasis in the genetically engineered models remain unknown, evidence presented here implicates upregulation of an NFAT → MMP-2 pathway in the development of metastatic osteosarcoma.

Navigating ECM barriers at the invasive front: the cancer cell-stroma interface

A seminal event in cancer progression is the ability of the neoplastic cell to mobilize the necessary machinery to breach surrounding extracellular matrix barriers while orchestrating a host stromal response that ultimately supports tissue-invasive and metastatic processes. With over 500 proteolytic enzymes identified in the human genome, interconnecting webs of protease-dependent and protease-independent processes have been postulated to drive the cancer cell invasion program via schemes of daunting complexity. Increasingly, however, a body of evidence has begun to emerge that supports a unifying model wherein a small group of membrane-tethered enzymes, termed the membrane-type matrix metalloproteinases (MT-MMPs), plays a dominant role in regulating cancer cell, as well as stromal cell, traffic through the extracellular matrix barriers assembled by host tissues in vivo. Understanding the mechanisms that underlie the regulation and function of these metalloenzymes as host cell populations traverse the dynamic extracellular matrix assembled during neoplastic states should provide new and testable theories regarding cancer invasion and metastasis.

Cyclosporine A inhibits the expression of membrane type-I matrix metalloproteinase in gingiva

BACKGROUND AND OBJECTIVE

Membrane type-I matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase-2 (TIMP-2) regulate the activation of MMP-2; however, their roles in the activation of MMP-2 in gingiva during treatment with cyclosporine A are still unknown. Therefore, the expressions of membrane type-I MMP and TIMP-2, as well as MMP-2, in gingivae upon treatment with cyclosporine A were examined in vivo and in vitro.

MATERIAL AND METHODS

Thirty-four rats were divided into two groups after edentulous ridges were established. The experimental group received 30 mg/kg/d of cyclosporine A and the control group received vehicle. At the end of the experimental period, the rats were killed, the gingivae were obtained and the expression of mRNA and protein of membrane type-I MMP, TIMP-2 and MMP-2 in gingiva were examined using real-time polymerase chain reaction and immunohistochemistry. In human gingival fibroblasts, the activity of MMP-2 and the expression of MMP-2, membrane type-I MMP and TIMP-2 mRNAs were examined (using zymography and reverse transcription-polymerase chain reaction, respectively) after treatment with cyclosporine A.

RESULTS

In gingivae of rats, cyclosporine A significantly decreased the expression of mRNA and protein of membrane type-I MMP, but not of TIMP-2. The expression of MMP-2 mRNA was unaffected but the expression of MMP-2 protein showed a significant decrease upon treatment with cyclosporine A. In fibroblast culture medium, the presence of cyclosporine A induced a decrease in MMP-2 activity in a dose-dependent manner. The expression of MMP-2, membrane type-I MMP and TIMP-2 mRNAs in fibroblasts was not significantly affected by cyclosporine A; however, in fibroblasts the ratio of mRNA expression of membrane type-I MMP to that of TIMP-2 decreased as the cyclosporine A dose was increased.

CONCLUSION

Cyclosporine A inhibits the expression of membrane type-I MMP in gingiva and it may further reduce the activation of MMP-2.

Characterization of the transcriptional regulation of the human MT1-MMP gene and association of risk reduction for focal-segmental glomerulosclerosis with two functional promoter SNPs

BACKGROUND

The matrix metalloproteinase MT1-MMP (MMP-14) is an important player in wound healing, bone development, angiogenesis, inflammation and tumour invasion. MT1-MMP also plays an important role in the development and resolution of experimental kidney diseases. The role of MT1-MMP was investigated for distinction between minimal-change glomerulonephritis (MCGN) and focal-segmental glomerulosclerosis (FSGS) that can sometimes be difficult due to sampling error in renal biopsy.

METHODS

We defined the transcriptional regulation of the human MT1-MMP and the influence of single nucleotide polymorphisms (SNPs) within its promoter region in renal mesangial cells with reporter gene constructs and gel sift analysis. Genomic DNA from healthy blood donors (n = 500) and from kidney biopsies with defined renal diseases (MCGN: n = 189, FSGS: n = 311) was screened for MT1-MMP promoter SNPs.

RESULTS

Transcription of MT1-MMP is regulated by two enhancers, an Sp1 binding site and a regulatory region 1 (RR1). RR1 contains an Ets site binding the transcription factors Elf-1 and E1AF but not NFAT. The MT1-MMP promoter contains two SNPs (-378 T/C and -364 G/T) in close vicinity to the RR1. Occurrence of the SNP variant -378 C leads to strong inhibition of nuclear protein binding to the RR1 reducing its enhancer function. Appearance of either variant -378 C or variant -364 T in at least one copy of the MT1-MMP promoter was associated with a significant risk reduction for the development of FSGS (P < 0.048).

CONCLUSION

Genetic testing for MT1-MMP promoter SNPs could put renal biopsy results into new perspective. An independent study will be required to verify these findings and their possible diagnostic value for differentiation between certain renal diseases.

Egr-1 mediates Si0(2)-driven transcription of membrane type I matrix metalloproteinase in macrophages

The up-regulation mechanism of membrane type I matrix metalloproteinase (MT1-MMP) in macrophages stimulated by silica in vitro and the contribution of early growth response 1 (Egr-1) transcription factor in the gene expression pathway were investigated. Macrophages stimulated by silica were treated with Egr-1 antibody or Egr-1 decoy oligodeoxynucleotides (ODN). The levels of MT1-MMP proteins were determined by Western blot and the expression of MT1-MMP mRNAs was detected by RT-PCR. The results showed as compared with control macrophages, silica-stimulated group showed up-regulated gene expression of MT1-MMP via Egr-1 (P<0.01). Compared with silica-stimulated macrophages untreated with antibody, the cells treated with 5 microg/mL Egr-1 antibody were associated with reduced expression of MT1-MMP protein (P<0.01) and mRNA (P<0.01). Compared with silica-stimulated untransfected group, the Egr-1 "decoy" ODN group was associated with reduction in the expression of MT1-MMP protein and mRNA (P<0.01). It was concluded gene expression of MT1-MMP which may play a critical role in silicosis was up-regulated by silica in macrophages. Egr-1 participated in the expression of MT1-MMP and positively regulated the expression. Both Egr-1 antibody and Egr-1 decoy ODN suppressed the expression of MT1-MMP through the Egr-1 pathway and may become a potential therapeutic tool in the management of silicosis in the future.

Glycogen synthase kinase 3beta regulation of nuclear factor of activated T-cells isoform c1 in the vascular smooth muscle cell response to injury

The migration and proliferation of vascular smooth muscle cells (vSMCs) are critical events in neointima formation during atherosclerosis and restenosis. The transcription factor nuclear factor of activated T-cells-isoform c1 (NFATc1) is regulated by atherogenic cytokines, and has been implicated in the migratory and proliferative responses of vSMCs through the regulation of gene expression. In T-cells, calcineurin de-phosphorylates NFATc1, leading to its nuclear import, while glycogen synthase kinase 3 beta (GSK3beta) phosphorylates NFATc1 and promotes its nuclear export. However, the relationship between NFATc1 and GSK3beta has not been studied during SMC migration and proliferation. We investigated this by scrape wounding vSMCs in vitro, and studying wound repair. NFATc1 protein was transiently increased, reaching a peak at 8 h after wounding. Cell fractionation and immunocytochemistry revealed that NFATc1 accumulation in the nucleus was maximal at 4 h after injury, and this was coincident with a significant 9 fold increase in transcriptional activity. Silencing NFATc1 expression with siRNA or inhibition of NFAT with cyclosporin A (CsA) attenuated wound closure by vSMCs. Phospho-GSK3beta (inactive) increased to a peak at 30 min after injury, preceding the nuclear accumulation of NFATc1. Overexpression of a constitutively active mutant of GSK3beta delayed the nuclear accumulation of NFATc1, caused a 50% decrease in NFAT transcriptional activity, and attenuated vSMC wound repair. We conclude that NFATc1 promotes the vSMC response to injury, and that inhibition of GSK3beta is required for the activation of NFAT during wound repair.

TNF-alpha induces MMP2 gelatinase activity and MT1-MMP expression in an in vitro model of nucleus pulposus tissue degeneration

STUDY DESIGN

In vitro-formed bovine nucleus pulposus (NP) tissues were used as a model for tumor necrosis factor-alpha (TNF-alpha) induced NP degeneration.

OBJECTIVE

To elucidate the signal transduction mechanisms regulating TNF-alpha induced matrix metalloproteinase (MMP) activity.

SUMMARY OF BACKGROUND DATA

TNF-alpha is thought to contribute to the pathophysiology of intervertebral disc (IVD) degeneration by up-regulating MMPs, such as MMP-2. MMP-2 has been implicated in influencing disease progression and in the induction of neovascularization.

METHODS

In vitro-formed bovine NP tissues were treated with TNF-alpha to examine its effect on MMP-2 gene and protein levels and activity. The effect of TNF-alpha on membrane type (MT)1-MMP, an activator of MMP-2, was also assessed. MT1-MMP functional activation by TNF-alpha was confirmed using promoter-reporter luciferase constructs. Immunoblots and electrophoretic mobility shift assays were used to examine the expression and DNA binding activity of transcription factors known to regulate transcriptional activation of MT1-MMP.

RESULTS

TNF-alpha treatment induced MMP-2 gelatinase activity, which occurred in the absence of any change in MMP-2 gene or protein expression, but did correlate with increased MT1-MMP mRNA and protein levels. Up-regulation of MMP-2 activity was dependent on the ERK-MAPK pathway. ERK-1/2 activation up-regulated early growth factor (Egr-1) expression and its DNA binding activity to the MT1-MMP promoter. There was no effect on Sp-1 binding activity. Reporter constructs demonstrated that TNF-alpha induced MT1-MMP transcriptional activation and that this response was dependant on ERK MAPK and Egr-1.

CONCLUSION

TNF-alpha induced MMP-2 gelatinase activity correlated with induction of MT1-MMP and not MMP-2 expression. MMP-2 activation was dependent on the ERK-MAPK pathway. As ERK also appeared to regulate MT1-MMP production, this suggests that TNF-alpha induction of MMP-2 gelatinase activity may be regulated by MT1-MMP. These findings elucidate the regulation of gelatinase activity and identify a mechanism whereby TNF-alpha may contribute to matrix degradation in NP tissue.

Subtype specific estrogen receptor action protects against changes in MMP-2 activation in mouse retinal pigmented epithelial cells

Eyes with age-related macular degeneration (AMD) demonstrate accumulation of specific deposits and extracellular matrix (ECM) molecules under the retinal pigment epithelium (RPE). AMD is about two times more prevalent in aging postmenopausal women. Therefore we studied whether 17beta-estradiol (E(2)) modulates the expression and activity of the trimolecular complex (MMP-2, TIMP-2 and MMP-14), molecules which are of major importance for ECM turnover in RPE. We used cell lines isolated from estrogen receptor knockout mice (ERKO) to determine which ER (estrogen receptor) subtype was important for ECM regulation in RPE cells. We found that mouse RPE sheets had higher baseline MMP-2 activity in the presence of ERbeta. This correlated with higher MMP-2 activity in RPE cell lines isolated from ERKOalpha mice. Exposure to E(2) increased MMP-2 activity in mouse RPE cell lines. In addition E(2) increased transcriptional activation of the MMP-2 promoter through a functional Sp1 site which required the presence of ERbeta, but not ERalpha. E(2) also maintained levels of pro MMP-2, and MMP-14 and TIMP-2 activity after oxidant injury. Since the direct effects of E(2) on MMP-2 transcriptional activation and the regulation of the trimolecular complex after oxidant-induced injury requires ERbeta, this receptor subtype may have a role as a potential therapeutic target to prevent changes in activation of MMP-2.

Transcription factors NFAT2 and Egr1 cooperatively regulate the maturation of T-lymphoma in vitro

We have demonstrated that transcription factors Egr1 and NFAT2 cooperate in regulation of the early stages of T-lymphocyte development, whereas the related factors Egr2 and Egr3 do not cooperate with NFAT2. Egr1 and NFAT2 are shown to cooperatively control gene expression of the regulatory factor Id3 and recombinase Rag2, whose functions are critical for T-lymphocyte differentiation. Thus, the concerted action of the transcription factors Egr1 and NFAT2 can play a crucial role in regulation of the T cell differentiation in vitro due to the cooperative regulation of Id3 and Rag2 gene expression.

Early growth response-1 contributes to galactosamine/lipopolysaccharide-induced acute liver injury in mice

Early growth response (Egr)-1 is a transcription factor that regulates genes involved in inflammation, innate and adaptive immunity, coagulation, and wound healing; however, little is known about the role of Egr-1 in acute liver injury. We tested the hypothesis that Egr-1 is involved in acute liver injury induced by galactosamine/lipopolysaccharide (GalN/LPS). GalN/LPS exposure biphasically increased hepatic egr-1 mRNA accumulation at 1 h and again at 4-5.5 h after treatment in wild-type mice. Within 4-5.5 h after GalN/LPS exposure, wild-type mice exhibited histological evidence of hepatocyte injury, cell death, and extensive areas of hemorrhage, as well as increased plasma alanine aminotransferase activities. In contrast, these parameters were largely attenuated in egr-1(-/-) mice. The initial expression of tumor necrosis factor-alpha, macrophage inflammatory protein-2, monocyte chemoattractant protein-1, and intercellular adhesion molecule-1 mRNA or protein was equivalent between genotypes at 1 h after GalN/LPS administration. However, at subsequent time points, hepatic expression of these genes was decreased in egr-1(-/-) compared with wild-type mice. In addition, neutrophil extravasation from hepatic sinusoids into the liver parenchyma was decreased in egr-1(-/-) compared with wild-type mice 4 h after GalN/LPS. Whereas caspase-3 activation and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive nuclei were detected in wild-type mice at 4 and 5.5 h after GalN/LPS administration, respectively, these markers of apoptosis were delayed in egr-1(-/-) mice. Delayed development of apoptosis was associated with an extension of survival by 1 h in egr-1(-/-) compared with wild-type mice. These data demonstrate that Egr-1 plays an important role in acceleration of hepatic inflammation, apoptosis, and subsequent mortality in GalN/LPS-induced acute liver injury.

Early growth response 1 and NF-ATc1 act in concert to promote thymocyte development beyond the beta-selection checkpoint

Development of immature T cell precursors beyond the beta-selection checkpoint is regulated by signals transduced by the pre-TCR complex. The pre-TCR-induced differentiation program is orchestrated by a network of transcription factors that serve to integrate this signaling information. Among these transcription factors are those of the early growth response (Egr) and NF-AT families. In this study, we demonstrate that Egr1 and NF-ATc1 act together to promote development of T cell precursors beyond the beta-selection checkpoint to the CD8 immature single-positive and CD4+ CD8+ double-positive stages. Moreover, we find that Egr1 and NF-AT cooperatively induce the expression of inhibitor of DNA binding 3 (Id3), a regulatory factor known to play an important role in positive selection of thymocytes, but not previously demonstrated to be required for beta-selection. Importantly, we show in this study that Id3 deficiency abrogates the ability of ectopically expressed Egr1 to promote traversal of the beta-selection checkpoint. Id3 is presumably essential for traversal of the beta-selection checkpoint in this context because of the inability of other inhibitor of DNA binding family members to compensate, since transgenic Egr1 does not induce expression of inhibitor of DNA binding 1 (Id1) or 2 (Id2). Taken together, these data demonstrate that Id3 is a cooperatively induced target that is important for Egr-mediated promotion of development beyond the beta-selection checkpoint. Moreover, these data indicate that the ERK and calcium signaling pathways may converge during beta-selection through the concerted action of Egr1 and NF-ATc1, respectively.

Membrane type-1 matrix metalloproteinase is induced following cyclic compression of in vitro grown bovine chondrocytes

OBJECTIVE

To determine if membrane type-1 matrix metalloproteinase (MT1-MMP) will respond to cyclic compression of chondrocytes grown in vitro and the regulatory mechanisms underlying this response.

METHODS

Cyclic compression (30min, 1kPa, 1Hz) was applied to bovine chondrocytes (6-9-month-old animals) grown on top of a biodegradable substrate within 3 days of initiating culture. Luciferase assays using bovine articular chondrocytes were undertaken to demonstrate the mechanosensitivity of MT1-MMP. Semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) and western blot analysis were used to establish the time course of gene and protein upregulation in response to cyclic compression. The regulation of MT1-MMP was assessed by electrophoretic mobility shift assays, RT-PCR and western blot analysis. As well, an MT1-MMP decoy oligonucleotide and an extracellular signal-regulated kinase 1/2 (ERK1/2) pharmacological inhibitor were utilized to further characterize MT1-MMP regulation.

RESULTS

After cyclic compression, MT1-MMP showed a rapid and transient increase in gene expression. Elevated protein levels were detected within 2h of stimulation which returned to baseline by 6h. During cyclic compression, phosphorylation of the mitogen activated protein kinase ERK1/2 increased significantly. This was followed by increased gene and protein expression of the transcription factor; early growth factor-1 (Egr-1) and Egr-1 binding to the MT1-MMP promoter. Blocking Egr-1 DNA binding with a decoy MT1-MMP oligonucleotide, downregulated MT1-MMP gene expression. The ERK1/2 inhibitor U0126 also reduced Egr-1 DNA binding activity to MT1-MMP promoter sequences and subsequent transcription of MT1-MMP.

CONCLUSIONS

These data suggest that cyclic compression of chondrocytes in vitro upregulates MT1-MMP via ERK1/2 dependent activation of Egr-1 binding. Delineation of the regulatory pathways activated by mechanical stimulation will further our understating of the mechanisms influencing tissue remodeling.

Membrane-type-1 matrix metalloproteinase transcription and translation in myocardial fibroblasts from patients with normal left ventricular function and from patients with cardiomyopathy

Past studies have identified that a unique type of matrix metalloproteinase, the membrane-type-1 MMP (MT1-MMP), is increased within the left ventricle (LV) of patients with dilated cardiomyopathy (DCM). However, the cellular and molecular basis for this induction of MT1-MMP with DCM is unknown. LV myocardial biopsies from nonfailing, reference normal patients (defined as LV ejection fraction >50%, elective coronary bypass surgery, no perfusion defect at biopsy site, n = 6) and DCM patients (LV ejection fraction <20%, at transplant, n = 5) were used to establish fibroblast cultures (FIBROS). Confluent LV FIBROS from culture passages 2-5 were measured with respect to MT1-MMP mRNA and protein levels and the distribution of the MT1-MMP mRNA pool in ribosomal fractions. Total MT1-MMP mRNA within DCM FIBROS increased by over 140%, and MT1-MMP protein increased by over 190% from reference normal FIBROS (both P < 0.05). MT1-MMP mRNA in monosome fractions decreased by over twofold in DCM FIBROS compared with reference normal (P < 0.05) and remained lower in polyribosomal fractions (i.e., 15.7 +/- 5.2 vs. 1.4 +/- 0.6% in polysomal fraction 6, P < 0.05). These differences in DCM MT1-MMP FIBROS transcription and translation persisted throughout passages 2-5. The unique findings from this study demonstrated that elevated steady-state MT1-MMP mRNA and protein levels occurred in DCM FIBROS despite a decline in translational deficiency. These phenotypic changes in DCM fibroblasts may provide the basis for developing cell specific pharmacological targets for control of MT1-MMP expression.

Membrane-type 1 matrix metalloproteinase is regulated by sp1 through the differential activation of AKT, JNK, and ERK pathways in human prostate tumor cells

We and other investigators have previously shown that membrane-type 1 matrix metalloproteinase (MT1-MMP) is overexpressed in invasive prostate cancer cells. However, the mechanism for this expression is not known. Here, we show that MT1-MMP is minimally expressed in nonmalignant primary prostate cells, moderately expressed in DU-145 cells, and highly expressed in invasive PC-3 and PC-3N cells. Using human MT1-MMP promoter reporter plasmids and mobility shift assays, we show that Sp1 regulates MT1-MMP expression in DU-145, PC-3, and PC-3N cells and in PC3-N cells using chromatin immunoprecipitation analysis and silencing RNA. Investigation of signaling pathway showed that DU-145 cells express constitutively phosphorylated extracellular stress-regulated kinase (ERK), whereas PC-3 and PC-3N cells express constitutively phosphorylated AKT/PKB and c-Jun NH2 terminal kinase (JNK). We show that MT1-MMP and Sp1 levels are decreased in PC-3 and PC-3N cells when phosphatidylinositol-3 kinase and JNK are inhibited, and that MT1-MMP levels are decreased in DU-145 cells when MEK is inhibited. Transient transfection of PC-3 and PC-3N cells with a dominant-negative JNK or p85, and of DU-145 cells with a dominant negative ERK, reduces MT1-MMP promoter activity. These results indicate differential signaling control of Sp1-mediated transcriptional regulation of MT1-MMP in prostate cancer cell lines.

Cardiac matrix metalloproteinase-2 expression independently induces marked ventricular remodeling and systolic dysfunction

Although enhanced cardiac matrix metalloproteinase (MMP)-2 synthesis has been associated with ventricular remodeling and failure, whether MMP-2 expression is a direct mediator of this process is unknown. We generated transgenic mice expressing active MMP-2 driven by the α-myosin heavy chain promoter. At 4 mo MMP-2 transgenic hearts demonstrated expression of the MMP-2 transgene, myocyte hypertrophy, breakdown of Z-band registration, lysis of myofilaments, disruption of sarcomere and mitochondrial architecture, and cardiac fibroblast proliferation. Hearts from 8-mo-old transgenic mice displayed extensive myocyte disorganization and dropout with replacement fibrosis and perivascular fibrosis. Older transgenic mice also exhibited a massive increase in cardiac MMP-2 expression, representing recruitment of endogenous MMP-2 synthesis, with associated expression of MMP-9 and membrane type 1 MMP. Increases in diastolic [control (C) 33 ± 3 vs. MMP 51 ± 12 μl; P = 0.003] and systolic (C 7 ± 2 vs. MMP 28 ± 14 μl; P = 0.003) left ventricular (LV) volumes and relatively preserved stroke volume (C 26 ± 4 vs. MMP 23 ± 3 μl; P = 0.16) resulted in markedly decreased LV ejection fraction (C 78 ± 7% vs. MMP 48 ± 16%; P = 0.0006). Markedly impaired systolic function in the MMP transgenic mice was demonstrated in the reduced preload-adjusted maximal power (C 240 ± 84 vs. MMP 78 ± 49 mW/μl2; P = 0.0003) and decreased end-systolic pressure-volume relation (C 7.5 ± 1.5 vs. MMP 4.7 ± 2.0; P = 0.016). Expression of active MMP-2 is sufficient to induce severe ventricular remodeling and systolic dysfunction in the absence of superimposed injury.

Molecular mechanisms of cyclosporin A inhibition of the cytokine-induced matrix metalloproteinase-9 in glomerular mesangial cells

The effects of the immunosuppressants cyclosporin A (CsA) and tacrolimus (FK506) on the IL-1beta-induced matrix metalloproteinase-9 (MMP-9) were investigated. Impairment of the protease-antiprotease balance contributes to renal fibrosis, which is observed collectively under long-term treatment with either immunosuppressant. It is demonstrated that CsA, in contrast to FK506, reduced the IL-1beta-induced MMP-9 content in conditioned media of mesangial cells, which coincides with a reduction in the cytokine-induced MMP-9 mRNA level. Similar to FK506, the VIVIT peptide, a specific inhibitor of the nuclear factor of activated T cells, did not affect the cytokine-induced MMP-9 level. Moreover, CsA caused a dose-dependent inhibition on the IL-1beta-induced luciferase activity of a 1.3-kb MMP-9 promoter fragment. Concomitant, electrophoretic mobility shift assay revealed that CsA selectively inhibits the cytokine-induced DNA binding of activator protein-1 and NF-kappaB. The effects on NF-kappaB binding were accompanied by a marked reduction in the nuclear content of the p65 subunit of NF-kappaB. Accordingly, CsA specifically impaired the IL-1beta-triggered degradation of inhibitory NF-kappaB. The suppressive effects by CsA on MMP-9 expression were accompanied by a reduction in the cytokine-induced phosphorylation of p42/p44 and c-Jun N-terminal Kinase (JNK). It is interesting that only the JNK inhibitor SP600125 impaired the cytokine-triggered MMP-9 level, suggesting that CsA, via inhibition of the JNK pathway, negatively interferes with the NF-kappaB-dependent transcriptional control of MMP-9. Interference with MMP-9 transcription may account for the accumulation of extracellular matrix underlying the high fibrotic potential of CsA during anti-inflammatory therapies with calcineurin inhibitors.

Cardiac ischemia-reperfusion injury induces matrix metalloproteinase-2 expression through the AP-1 components FosB and JunB

Matrix metalloproteinase-2 (MMP-2) is a central component of the response to injury in the heart. During ischemia, MMP-2 influences ventricular performance and is a determinant of postinfarction remodeling. Elevation of MMP-2 during reperfusion after ischemia suggests that new protein is synthesized, but the molecular regulation of MMP-2 generation during ischemia-reperfusion (I/R) injury has not been studied. Using the MMP-2 promoter linked to a β-galactosidase reporter in transgenic mice, we investigated the transcriptional regulation and cellular sources of MMP-2 in isolated, perfused mouse hearts subjected to acute global I/R injury. I/R injury induced a rapid activation of MMP-2 promoter activity with the appearance of β-galactosidase antigen in cardiomyocytes, fibroblasts, and endothelial cells. Activation of intrinsic MMP-2 transcription and translation was confirmed by real-time PCR and quantitative Western blot analyses. MMP-2 transcription and translation were inhibited by perfusion with 1.0 mM hydroxyl radical scavenger N-(-2-mercaptopropionyl)-glycine. Nuclear extracts demonstrated increased abundance of two activator proteins-1 (AP-1) components JunB and FosB following I/R injury. Immunohistochemical staining localized JunB and FosB proteins to the nuclei of all three cardiac cell types following I/R injury, consistent with enhanced nuclear transport of these transcription factors. Chromatin immunoprecipitation (ChIP) of the AP-1 binding site in the intrinsic murine MMP-2 promoter yielded only JunB under control conditions, whereas ChIP following I/R injury recovered both JunB and FosB, consistent with a change in occupancy from JunB homodimers in controls to JunB/FosB heterodimers following I/R injury. We conclude that enhanced MMP-2 transcription and translation following I/R injury are mediated by induction, via oxidant stress, of discrete AP-1 transcription factor components.

MT1-MMP: universal or particular player in angiogenesis?

Tumorigenesis involves not only tumor cells that become transformed but also the peritumoral stroma which reacts inducing inflammatory and angiogenic responses. Angiogenesis, the formation of new capillaries from preexisting vessels, is an absolute requirement for tumor growth and metastasis, and it can be induced and modulated by a wide variety of soluble factors. During angiogenesis, quiescent endothelial cells are activated and they initiate migration by degrading the basement membranes through the action of specific proteases, in particular of matrix metalloproteinases (MMPs). Among these, the membrane type 1-matrix metalloproteinase (MT1-MMP) has been identified as a key player during the angiogenic response. In this review, we will summarize the role of MT1-MMP in angiogenesis and the regulatory mechanisms of this protease in endothelial cells. Since our recent findings have suggested that MT1-MMP is not universally required for angiogenesis, we hypothesize that the regulation and participation of MT1-MMP in angiogenesis may depend on the nature of the angiogenic stimulus. Experiments aimed at testing this hypothesis have shown that similarly to the chemokine stromal cell-derived factor-1 (SDF-1)/CXCL12, lipopolysaccharide (LPS) seems to induce the formation of capillary tubes by human or mouse endothelial cells (ECs) in an MT1-MMP-independent manner. The implications of these findings in the potential use of MT1-MMP inhibitors in cancer therapy are discussed.

Transcription of the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase type 3 gene, ATP2A3, is regulated by the calcineurin/NFAT pathway in endothelial cells

Histamine, known to induce Ca2+ oscillations in endothelial cells, was used to alter Ca2+ cycling. Treatment of HUVEC (human umbilical-vein endothelial cell)-derived EA.hy926 cells with histamine for 1-3 days increased the levels of SERCA (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase) 3, but not of SERCA 2b, transcripts and proteins. Promoter-reporter gene assays demonstrated that this increase in expression was due to activation of SERCA 3 gene transcription. The effect of histamine was abolished by mepyramine, but not by cimetidine, indicating that the H1 receptor, but not the H2 receptor, was involved. The histamine-induced up-regulation of SERCA 3 was abolished by cyclosporin A and by VIVIT, a peptide that prevents calcineurin and NFAT (nuclear factor of activated T-cells) from interacting, indicating involvement of the calcineurin/NFAT pathway. Histamine also induced the nuclear translocation of NFAT. NFAT did not directly bind to the SERCA 3 promoter, but activated Ets-1 (E twenty-six-1), which drives the expression of the SERCA 3 gene. Finally, cells treated with histamine and loaded with fura 2 exhibited an improved capacity in eliminating high cytosolic Ca2+ concentrations, in accordance with an increase in activity of a low-affinity Ca2+-ATPase, like SERCA 3. Thus chronic treatment of endothelial cells with histamine up-regulates SERCA 3 transcription. The effect of histamine is mediated by the H1R (histamine 1 receptor) and involves activation of the calcineurin/NFAT pathway. By increasing the rate of Ca2+ sequestration, up-regulation of SERCA 3 counteracts the cytosolic increase in Ca2+ concentration.

Activation of Vav/Rho GTPase signaling by CXCL12 controls membrane-type matrix metalloproteinase-dependent melanoma cell invasion

Melanoma cells express the chemokine receptor CXCR4, which confers invasive signals on binding to its ligand CXCL12. We show here that knocking down membrane-type matrix metalloproteinase (MT1-MMP) expression translates into a blockade of invasion across reconstituted basement membranes and type I collagen gels in response to CXCL12, which is the result of lack of MMP-2 activation. Interference with MMP-2 expression further confirms its important role during this invasion. Vav proteins are guanine-nucleotide exchange factors for Rho GTPases that regulate actin dynamics and gene expression. We show that melanoma cells express Vav1 and Vav2, which are activated by CXCL12 involving Jak activity. Blocking Vav expression by RNA interference results in impaired activation of Rac and Rho by CXCL12 and in a remarkable inhibition of CXCL12-promoted invasion. Importantly, up-regulation of MT1-MMP expression by CXCL12, a mechanism contributing to melanoma cell invasion, is blocked by knocking down Vav expression or by inhibiting Jak. Together, these data indicate that activation of Jak/Vav/Rho GTPase pathway by CXCL12 is a key signaling event for MT1-MMP/MMP-2-dependent melanoma cell invasion.

Decrease in LDL receptor-related protein expression and function correlates with advanced stages of Wilms tumors

BACKGROUND

The molecular processes responsible for the invasive phenotype of pediatric Wilms tumors (WT) are poorly understood. A candidate WT suppressor gene (WT1) has been found mutated in a number of these pediatric kidney tumors. However, the disruption of normal WT1 protein function cannot solely explain WT growth. The aim of the present study is to identify new molecular players that regulate the invasive character of WT.

PROCEDURE

Fresh frozen samples from 45 renal tumors of Wilms were obtained from the National Wilms Tumor Study Group's Biological Samples Bank. Gelatin zymography, Western blotting, and immunodetection were used to compare tissue biopsies originating from the infiltrating (stage III), metastatic (stage IV), and anaplastic phenotype of Wilms tumors (WT).

RESULTS

The expression of the low-density lipoprotein receptor-related protein (LRP) diminished in stage IV and anaplastic WT. Moreover, the expression of RAP, an LRP intracellular chaperone, was also decreased. The diminished expression of LRP and RAP correlated with increased levels of several known extracellular ligands that LRP usually recycles from the extracellular matrix (ECM) environment, including PAI-1, MMP-9, and TIMP-1. The proteolytic processing of MT1-MMP, a functional regulator of LRP, also correlated with the WT invasive phenotype.

CONCLUSIONS

The low expression of LRP, whose function is regulated by MT1-MMP and whose activity in recycling ECM-associated proteolytic enzymes becomes drastically diminished in advanced stages of WT, may in part explain the acquired invasive potential of the developing WT pediatric cancer.

Intronic regulation of matrix metalloproteinase-2 revealed by in vivo transcriptional analysis in ischemia

Matrix metalloproteinase-2 (MMP-2) plays an essential role in angiogenesis and arteriogenesis, two processes critical to restoration of tissue perfusion after ischemia. MMP-2 expression is increased in tissue ischemia, but the responsible mechanisms remain unknown. We studied the transcriptional activation of the MMP-2 gene in a model of hindlimb ischemia by using various MMP-2-lacZ reporter mice and chromatin immunoprecipitation. MMP-2 activity and mRNA were increased after hindlimb ischemia. Mice with targeted deletion of MMP-2 had impaired restoration of perfusion and a high incidence of limb gangrene, indicating that MMP-2 plays a critical role in ischemia-induced revascularization. Ischemia induced the expression and binding of c-Fos, c-Jun, JunB, FosB, and Fra2 to a noncanonical activating protein-1 (AP-1) site present in the MMP-2 promoter and decreased binding of the transcriptional repressor JunD. Ischemia also activated the expression and binding of p53 to an adjacent enhancer site (RE-1) and increased expression and binding of nuclear factor of activated T-cells-c2 to consensus sequences within the first intron. Deletion of either the 5' AP-1/RE-1 region of the promoter or substitution of the first intron abolished ischemia-induced MMP-2 transcription in vivo. Thus, AP-1 transcription factors and intronic activation by nuclear factor of activated T-cells-c2 act in concert to drive ischemia-induced MMP-2 transcription. These findings define a critical role for MMP-2 in ischemia-induced revascularization and identify both previously uncharacterized regulatory elements within the MMP-2 gene and the cognate transcription factors required for MMP-2 activation in vivo after tissue ischemia.

Transcriptional Regulation of the HumanCD3γ Gene: The TATA-LessCD3γ Promoter Functions via an Initiator and Contiguous Sp-Binding Elements

Growing evidence that the CD3gamma gene is specifically targeted in some T cell diseases focused our attention on the need to identify and characterize the elusive elements involved in CD3gamma transcriptional control. In this study, we show that while the human CD3gamma and CD3delta genes are oriented head-to-head and separated by only 1.6 kb, the CD3gamma gene is transcribed from an independent but weak, lymphoid-specific TATA-less proximal promoter. Using RNA ligase-mediated rapid amplification of cDNA ends, we demonstrate that a cluster of transcription initiation sites is present in the vicinity of the primary core promoter, and the major start site is situated in a classical initiator sequence. A GT box immediately upstream of the initiator binds Sp family proteins and the general transcription machinery, with the activity of these adjacent elements enhanced by the presence of a second GC box 10 nt further upstream. The primary core promoter is limited to a sequence that extends upstream to -15 and contains the initiator and GT box. An identical GT box located approximately 50 nt from the initiator functions as a weak secondary core promoter and likely generates transcripts originating upstream from the +1. Finally, we show that two previously identified NFAT motifs in the proximal promoter positively (NFATgamma(1)) or negatively (NFATgamma(1) and NFATgamma(2)) regulate expression of the human CD3gamma gene by their differential binding of NFATc1 plus NF-kappaB p50 or NFATc2 containing complexes, respectively. These data elucidate some of the mechanisms controlling expression of the CD3gamma gene as a step toward furthering our understanding of how its transcription is targeted in human disease.

Identification and characterization of PDE4A11, a novel, widely expressed long isoform encoded by the human PDE4A cAMP phosphodiesterase gene

PDE4A11 is a novel cAMP-specific phosphodiesterase that is conserved in humans, mouse, rat, pig, and bat. Exon-1(4A11) encodes its unique, 81 amino acid N-terminal region. Reverse-transcriptase polymerase chain reaction performed across the splice junction, plus identification of expressed sequence tags, identifies PDE4A11 as a long isoform possessing UCR1 and UCR2 regulatory domains. Transcript analysis shows that PDE4A11 is widely expressed compared with PDE4A10 and PDE4A4B long isoforms. Truncation analysis identifies a putative promoter in a 250-base pair region located immediately upstream of the start site in Exon-1(4A11). Recombinant PDE4A11, expressed in COS-7 cells, is a 126-kDa protein localized predominantly around the nucleus and in membrane ruffles. PDE4A11 exhibits a K(m) for cAMP hydrolysis of 4 microM, with relative V(max) similar to that of PDE4A10 and PDE4A4B. PDE4A11 is dose-dependently inhibited by rolipram, 4-[(3-butoxy-4-methoxyphenyl)-methyl]-2-imidazolidinone (Ro 20-1724), cilomilast, roflumilast, and denbufylline, with IC(50) values of 0.7, 0.9, 0.03, 0.004, and 0.3 microM, respectively. Soluble and particulate PDE4A11 exhibit distinct rates of thermal inactivation (55 degrees C; T((0.5)) = 2.5 and 4.4 min, respectively). Elevating cAMP levels in COS-7 cells activates PDE4A11 concomitant with its phosphorylation at Ser119 by protein kinase A (PKA). PDE4A11 differs from PDE4A4 in sensitivity to cleavage by caspase-3, interaction with LYN SH3 domain, redistribution upon long-term rolipram challenge, and sensitivity to certain PDE4 inhibitors. PDE4A11, PDE4A10, and PDE4A4 all can interact with betaarrestin. PDE4A11 is a novel, widely expressed long isoform that is activated by PKA phosphorylation and shows a distinct intracellular localization, indicating that it may contribute to compartmentalized cAMP signaling in cells in which it is expressed.

RETRACTED: Transcriptional regulation of the AT1 receptor gene in immortalized human trophoblast cells

Studies investigating the mechanisms that govern the expression of the human angiotensin II (Ang II) type 1 receptor (hAT1R) gene have progressed slowly due to the lack of human cell lines that express the AT1R. Recently, however, an immortalized human trophoblast cell line (HTR-8/SVNeo) was demonstrated to respond to Ang II. Therefore, we utilized this cell line to characterize the AT1R expressed on the cell surface and to investigate the mechanisms by which the hAT1R gene is regulated in these cells. HTR-8/SVNeo cells were shown to express functional high affinity AT1Rs having a Bmax value of 114+/-11 fmol/mg protein and a Kd value of 0.14+/-0.1 nM. Additionally, Ang II-induced IP3 production was mediated via the AT1R. Deletional analysis of the hAT1R promoter localized a major basal regulatory sequence within the -105 to -79 bp region, relative to the transcription start site, in HTR-8/SVNeo cells. Electrophoretic mobility shift assay (EMSA) and Chromatin Immunoprecipitation (ChIP) assay demonstrated that the transcription factors, Sp1 and Sp3, interact with this region of the hAT1R promoter in vitro and in vivo. Taken together, our data demonstrate that HTR-8/SVNeo cells express functional AT1Rs and that basal level expression of this gene is regulated, in part, by Sp1 and Sp3 in this cell line.