Selective inhibition of vascular endothelial growth factor-mediated angiogenesis by cyclosporin A: roles of the nuclear factor of activated T cells and cyclooxygenase 2

Transgenic delivery of VEGF to mouse skin leads to an inflammatory condition resembling human psoriasis

Gene therapy approaches involving vascular endothelial growth factor (VEGF) to promote therapeutic angiogenesis are under consideration for conditions ranging from ischemic heart disease to nonhealing skin ulcers. Here we make the surprising observation that the transgenic delivery of VEGF to the skin results in a profound inflammatory skin condition with many of the cellular and molecular features of psoriasis, including the characteristic vascular changes, epidermal alterations, and inflammatory infiltrates. Even longstanding psoriatic disease remains dependent on the transgenic VEGF in this model because it can be effectively reversed by the addition of VEGF Trap, a potent VEGF antagonist. Previous attempts to faithfully replicate the psoriatic phenotype through the transgenic delivery of epidermal keratinocyte growth factors or inflammatory mediators generated phenotypes with only partial resemblance to human psoriasis, leaving unanswered questions about the etiology of this disease. The ability of transgenic VEGF to induce a psoriasiform phenotype suggests a new etiology and treatment approach for this disease and further substantiates emerging concerns about possible proinflammatory adverse effects that might be associated with therapeutic attempts to deliver VEGF.

The role of COX-2 in angiogenesis and rheumatoid arthritis

Recent evidence suggests that cyclooxygenase (COX)-2 is a mediator of angiogenesis, and COX-2 activity is known to be upregulated in the rheumatoid arthritis (RA) synovium. We examined whether mediation of angiogenesis by COX-2 was occuring in cells of the RA synovium and in microvascular endothelial cells (ECs) that are similar to those found in the RA synovium. We demonstrate that rofecoxib, a selective COX-2 inhibitor, acts directly on human dermal microvascular ECs (HMVECs) to inhibit their chemotactic and tube forming ability. Likewise, pretreatment of HMVECs with rofecoxib significantly inhibited their ability to form tubes induced by conditioned media (CM) of activated RA synovial fibroblasts. When RA synovial fibroblasts were pretreated with rofecoxib for 16 h and then stimulated with interleukin (IL)-1beta, their CM induced significantly less HMVEC tube formation when compared with CM from vehicle-treated RA synovial fibroblasts. ELISAs performed on activated RA fibroblast CM for known proangiogenic factors demonstrated a significant reduction in bFGF, in addition to the expected decrease in PGE(2). Our studies suggest that COX-2-induced angiogenic activity is an active mechanism within diseased synovium and may provide an additional rationale for the use of COX-2 inhibitors in RA.

A constitutively active NFATc1 mutant induces a transformed phenotype in 3T3-L1 fibroblasts

The calcineurin/nuclear factor of activated T cells (NFAT) signaling pathway is best known for its role in T lymphocyte activation. However, it has become increasingly apparent that this signaling pathway is also involved in the regulation of cell growth and development in a wide variety of different tissues and cell types. Here we have investigated the effects of sustained NFATc1 signaling on the growth and differentiation of the murine 3T3-L1 preadipocyte cell line. Remarkably, we find that expression of a constitutively active NFATc1 mutant (caNFATc1) in these immortalized cells inhibits their differentiation into mature adipocytes and causes them to adopt a transformed cell phenotype, including loss of contact-mediated growth inhibition, reduced serum growth requirements, protection from growth factor withdrawal-induced apoptosis, and formation of colonies in semisolid media. Furthermore, we find that caNFATc1-expressing cells acquire growth factor autonomy and are able to proliferate even in the complete absence of serum. We provide evidence that this growth factor independence is caused by the NFATc1-dependent production of a soluble heat-labile autocrine factor that is capable of promoting the growth and survival of wild type 3T3-L1 cells as well as potently inhibiting their differentiation into mature adipocytes. Finally, we demonstrate that cells expressing caNFATc1 form tumors in nude mice. Taken together, these results indicate that deregulated NFATc1 activity is able to induce the immortalized 3T3-L1 preadipocyte cell line to acquire the well established hallmarks of cellular transformation and thereby provide direct evidence for the oncogenic potential of the NFATc1 transcription factor.

Plasminogen activator inhibitor type-1 inhibits insulin signaling by competing with alphavbeta3 integrin for vitronectin binding

Functional cooperation between integrins and growth factor receptors has been reported for several systems, one of which is the modulation of insulin signaling by alphavbeta3 integrin. Plasminogen activator inhibitor type-1 (PAI-1), competes with alphavbeta3 integrin for vitronectin (VN) binding. Here we report that PAI-1, in a VN-dependent manner, prevents the cooperation of alphavbeta3 integrin with insulin signaling in NIH3T3 fibroblasts, resulting in a decrease in insulin-induced protein kinase B (PKB) phosphorylation, vascular endothelial growth factor (VEGF) expression and cell migration. Insulin-induced HUVEC migration and angiotube formation was also enhanced in the presence of VN and this enhancement is inhibited by PAI-1. By using specific PAI-1 mutants with either VN binding or plasminogen activator (PA) inhibiting activities ablated, we have shown that the PAI-1-mediated interference with insulin signaling occurs through its direct interaction with VN, and not through its PA neutralizing activity. Moreover, using cells deficient for uPA receptor (uPAR) we have demonstrated that the inhibition of PAI-1 on insulin signaling is independent of uPAR-VN binding. These results constitute the first demonstration of the interaction of PAI-1 with the insulin response.

Cyclooxygenase-2: a therapeutic target in angiogenesis

Angiogenesis has a role in the pathogenesis of several disorders, including cancer, chronic inflammatory diseases and retinopathies. Recent evidence demonstrates that the production of prostanoids by cyclooxygenase-2 (COX-2) promotes the expression of pro-angiogenic factors. Furthermore, inhibition of COX-2 by non-steroidal anti-inflammatory drugs leads to restricted angiogenesis and downregulated production of pro-angiogenic factors, such as vascular endothelial growth factor and basic fibroblast growth factor. These findings suggest that COX enzymes could be important therapeutic targets in the treatment of pathological angiogenesis.

NFATc1 mediates vascular endothelial growth factor-induced proliferation of human pulmonary valve endothelial cells

Mice deficient for the transcription factor NFATc1 fail to form pulmonary and aortic valves, a defect reminiscent of some types of congenital human heart disease. We examined the mechanisms by which NFATc1 is activated and translocated to the nucleus in human pulmonary valve endothelial cells to gain a better understanding of its potential role(s) in post-natal valvular repair as well as valve development. Herein we demonstrate that activation of NFATc1 in human pulmonary valve endothelial cells is specific to vascular endothelial growth factor (VEGF) signaling through VEGF receptor 2. VEGF-induced NFATc1 nuclear translocation was inhibited by either cyclosporin A or a calcineurin-specific peptide inhibitor; these findings suggest that VEGF stimulates NFATc1 nuclear import in human pulmonary valve endothelial cells by a calcineurin-dependent mechanism. Importantly, both cyclosporin A and the calcineurin-specific peptide inhibitor reduced VEGF-induced human pulmonary valve endothelial cell proliferation, indicating a functional role for NFATc1 in endothelial growth. In contrast, VEGF-induced proliferation of human dermal microvascular and human umbilical vein endothelial cells was not sensitive to cyclosporin A. Finally, NFATc1 was detected in the endothelium of human pulmonary valve leaflets by immunohistochemistry. These results suggest VEGF-induced NFATc1 activation may be an important mechanism in cardiac valve maintenance and function by enhancing endothelial proliferation.

Cyclosporine A suppresses cyclooxygenase-2 expression in the rat kidney

On the basis of recent evidence that the cyclooxygenase-2 (COX-2) gene promoter contains functional binding sites for the nuclear factor of activated T cells (NFAT) and that COX-2 is expressed in a regulated fashion in the kidney, this study aimed to assess the effect of immunosuppressants on COX-2 expression in the kidney. Therefore, Wistar-Kyoto rats were treated with cyclosporine A (CsA; 15 mg/kg per day) or tacrolimus (5 mg/kg per day) for 7 d each. Both drugs markedly lowered COX-2 expression while COX-1 expression remained unaltered. Furthermore, CsA blunted the increase of renocortical COX-2 expression in response to low salt intake or a combination of low-salt diet with the ACE inhibitor ramipril (10 mg/kg per day), which strongly stimulates renocortical COX-2 expression. At the same time, calcineurin inhibitors moderately enhanced basal as well as stimulated renin secretion and renin gene expression. These findings suggest that inhibition of calcineurin could be a crucial determinant for the regulated expression of COX-2 in the kidney. Inhibition of COX-2 expression may therefore at least in part account for the well-known adverse effects of immunosuppressants in the kidney. Moreover, our data suggest that the stimulation of the renin system by low salt and by ACE inhibitors is not essentially mediated by COX-2 activity.

Recent advances in cutaneous angiogenesis

An understanding of the molecular basis of angiogenesis is key to the appreciation of many of the advances made in the field of neovascularization over the past two decades. The sequence of events involved in angiogenesis includes: (i) increased vascular permeability and leakage; (ii) degradation of basement membrane; (iii) endothelial cell proliferation and migration through the surrounding extracellular matrix; and (iv) maturation and stabilization of the newly formed vessel bed. This review provides an update on the molecular basis of such pathways in the skin, with particular emphasis on the endothelial cell-specific vascular endothelial growth factor and angiopoietins as modulators of angiogenesis that can be targeted in therapy of cutaneous disease.

Activation of monocyte cyclooxygenase-2 gene expression by human herpesvirus 6. Role for cyclic AMP-responsive element-binding protein and activator protein-1

Prostaglandin E(2) (PGE(2)) is an arachidonic acid metabolite mainly produced by activated monocytes/macrophages (Mo/Mphi) that display broad immunomodulatory activities. Several viruses capable of infecting Mo/Mphi modulate PGE(2) synthesis in a way that favors the infection processes and the spread of virions. In the present work, we studied the effect of human herpesvirus 6 (HHV-6) infection of Mo/Mphi on PGE(2) synthesis. Our results indicate that HHV-6 induces COX-2 gene expression and PGE(2) synthesis within a few hours of infection. We mapped the different promoter elements associated with COX-2 gene activation by HHV-6 to two cis-acting elements: a cyclic AMP-responsive element and an activator protein-1 element. HHV-6 immediate-early protein 2 was identified as a modulator of COX-2 gene expression in Mo/Mphi. Finally, addition of PGE(2) to HHV-6-infected peripheral blood mononuclear cells cultures was found to increase significantly viral replication. Overall, these results further contribute to the immunomodulatory properties of HHV-6 and highlight a potential role for eicosanoids in the replication process of this virus.

Cyclophilin-mediated pathways in the effect of cyclosporin A on endothelial cells: role of vascular endothelial growth factor

The relative importance of cyclophilin (CyP) versus calcineurin (Cn)-mediated mechanisms in the effect of cyclosporin A (CsA) on endothelial cells (ECs) is largely unknown. In cultured ECs, CsA was cytotoxic/proapoptotic or cytoprotective/antiapoptotic at high or low concentrations, respectively. CsA analogs (MeVal-4-CsA and MeIle-4-CsA), which bind to CyP but do not inhibit Cn, closely reproduced the CsA effects. Based on our previous data, the role of vascular endothelial growth factor (VEGF) as a mediator of CsA-induced cytoprotection was further analyzed. The actions of CsA and CsA analogs were shifted from a protective to a cell-damaging pattern in the presence of a specific anti-VEGF monoclonal antibody (mAb). This positive interaction was further supported by a transient increase in cytosolic free calcium concentration ([Ca(2+)](i)) by VEGF after pretreatment with either CsA or MeVal-4-CsA and an increase in the expression and synthesis of VEGF receptor 2 (VEGFR2). Of functional importance, blockade of the interaction between VEGF and VEGFR2 by a VEGFR2 mAb abolished the cytoprotective effect of CsA. In addition, preconditioning with low concentrations of CsA or CsA analogs increased both cytoprotection and VEGFR2 mRNA expression when EC were exposed to higher concentrations of CsA. In summary, our results reveal that (1) the biphasic responses to CsA in EC are related to the interaction of CsA with CyP rather than with Cn and (2) VEGF is a critical factor in the cytoprotective effect of CsA, by a mechanism that involves VEGFR2.

Purification and characterization of a cyclooxygenase-2 and angiogenesis suppressing factor produced by human fibroblasts

Cyclooxygenase-2 (COX-2) is an inducible enzyme that plays an important role in several pathophysiological processes, including inflammation, angiogenesis, and tumorigenesis. We have recently observed that COX-2 induction is restrained in proliferating fibroblasts. The mechanism by which this occurs is unclear. Here, we report the detection and isolation from the conditioned medium of proliferating fibroblasts a factor that suppressed COX-2 expression. This factor, which was named cytoguardin, suppressed COX-2 protein levels induced by phorbol 12-myristate 13-acetate, interleukin-1beta, tumor necrosis factor alpha, and lipopolysaccharide (LPS) in fibroblasts and LPS-induced COX-2 protein levels and promoter activities in human endothelial cells and murine RAW 264.7 cells in a comparable concentration-dependent manner. It inhibited COX-2 expression induced by angiogenic factors and endothelial tube formation induced by angiogenic factors and colon cancer cell medium. These findings provide evidence for the control of COX-2 transcription by an endogenous cellular factor.

Angiogenesis and chemokines in rheumatoid arthritis and other systemic inflammatory rheumatic diseases

Angiogenesis, the formation of new vessels, is important in the pathogenesis of rheumatoid arthritis (RA) and other inflammatory diseases. Chemotactic cytokines termed chemokines mediate the ingress of leukocytes, including neutrophils and monocytes into the inflamed synovium. In this review, authors discuss the role of the most important angiogenic factors and angiogenesis inhibitors, as well as relevant chemokines and chemokine receptors involved in chronic inflammatory rheumatic diseases. RA was chosen as a prototype to discuss these issues, as the majority of studies on the role of angiogenesis and chemokines in inflammatory diseases were carried out in arthritis. However, other systemic inflammatory (autoimmune) diseases including systemic lupus erythematosus (SLE), systemic sclerosis (SSc), Sjögren's syndrome (SS), mixed connective tissue disease (MCTD), polymyositis/dermatomyositis (PM/DM) and systemic vasculites are also discussed in this context. As a number of chemokines may also play a role in neovascularization, this issue is also described here. Apart from discussing the pathogenic role of angiogenesis and chemokines, authors also review the regulation of angiogenesis and chemokine production by other inflammatory mediators, as well as the important relevance of neovascularization and chemokines for antirheumatic intervention.

A new in vitro model to study endothelial injury

BACKGROUND

Endothelial dysfunction or "endothelialitis" is a prominent feature in several disease states ranging from atherosclerosis to transplant rejection. This dysfunction is also caused by drugs such as cyclosporin A (CyA) and leads to allograft vasculopathy and eventual graft loss. Despite the frequency and importance of this injury, there is no model to study the morphological effects of endothelial injury and dysfunction in vitro.

METHODS

We utilized a model in which mouse endothelial cells (SVEC 4-10) can be induced to form capillary tubes by culturing on a laminin-rich matrix (Matrigel). In this morphological model of endothelial cell function, we studied the effect of varying doses of CyA on two parameters of tube formation: initiation of tube formation and disruption of mature capillary tubes. As a positive control we used IFN-gamma, which inhibited capillary tube formation. We developed this assay in 96-well culture plates to test several samples simultaneously.

RESULTS

The assay could be adapted to a 96-well format by optimizing the cell density. Endothelial dysfunction was seen when the endothelial cells were incubated with cyclosporin A, which affected both morphological parameters of tube formation. At higher doses (2-20 microg/ml) CyA both inhibited capillary tube formation and disrupted mature capillary tubes. At lower doses CyA only inhibited the initiation of tube formation; it did not disrupt mature capillary tubes. IL-2 (400-1000 pg/ml) and IFN-gamma (10-400 pg/ml) inhibited initiation of tube formation but did not disrupt mature capillary tubes. None of these agents, including high doses of CyA, impaired endothelial cell viability.

CONCLUSION

CyA-induced endothelial dysfunction can be modeled in vitro by this novel morphological assay of capillary tube formation. This assay can discern mild and severe degrees of endothelial dysfunction. The different effects of low and high levels of CyA on capillary tube formation imply that similar dysfunction in vivo may be responsible for allograft vasculopathy caused by CyA. This novel model can also be utilized to study other forms of vasculitis.

VEGF and imaging of vessels in rheumatoid arthritis

Angiogenesis is a prominent feature of rheumatoid synovitis. Formation of new blood vessels permits a supply of nutrients and oxygen to the augmented inflammatory cell mass and so contributes to perpetuation of joint disease. Vascular endothelial growth factor (VEGF) is a potent endothelial cell-specific growth factor that is upregulated by proinflammatory cytokines and by hypoxia. Serum VEGF concentrations are elevated in rheumatoid arthritis (RA) and correlate with disease activity. Furthermore, serum VEGF measured at first presentation in RA is highly significantly correlated with radiographic progression of disease over the subsequent year. Power Doppler ultrasonography is a sensitive method for demonstrating the presence of blood flow in small vessels and there is a very close relation between the presence or absence of vascular flow signal on power Doppler imaging and the rate of early synovial enhancement on dynamic gadolinium-enhanced magnetic resonance imaging (MRI) of joints with RA. Images obtained by both dynamic enhanced MRI and power Doppler ultrasonography correlate with vascularity of synovial tissue as assessed histologically. In early RA, there is a striking association between joint erosions assessed on high-resolution ultrasonography and vascular signal in power Doppler mode. Collectively, these findings implicate vascular pannus in the erosive phase of disease and strongly suggest that proangiogenic molecules such as VEGF are targets for novel therapies in RA. Animal model data supports this concept. It seems likely that serological and imaging measures of vascularity in RA will become useful tools in the assessment of disease activity and response to therapy.

Cyclosporine inhibition of vascular endothelial growth factor production in rheumatoid synovial fibroblasts

OBJECTIVE

To determine the antiangiogenic effect of cyclosporin A (CSA) in rheumatoid arthritis (RA).

METHODS

We investigated the effect of CSA on the production of vascular endothelial growth factor (VEGF) by rheumatoid synovial fibroblasts. Fibroblast-like synoviocytes (FLS) were prepared from the synovial tissues of RA patients, and cultured in the presence of CSA. The production of VEGF by FLS was measured in culture supernatants by enzyme-linked immunosorbent assay. The VEGF messenger RNA (mRNA) expression and activator protein 1 (AP-1) binding activity for VEGF transcription were determined by polymerase chain reaction and electrophoretic mobility shift assay, respectively.

RESULTS

CSA dose-dependently inhibited both constitutive and transforming growth factor beta-induced VEGF production at the protein and mRNA levels. The suppressive action of CSA on VEGF synthesis was calcineurin dependent, as evidenced by a comparable inhibition by FK-506. Agonists of cAMP, 3-isobutyl-1-methylxanthine and N-2-O-dibutyryl-cAMP, mimicked the effect of CSA on VEGF production, while a cAMP antagonist, 2',3'-dideoxyadenosine, abrogated the effect of CSA. A gel mobility shift assay showed that the inhibitory effect of CSA was associated with decreased AP-1 binding activity to the VEGF promoter, in a cAMP-dependent manner.

CONCLUSION

CSA may exert an antiangiogenic effect by inhibiting AP-1-mediated VEGF expression in rheumatoid synovial fibroblasts.

NFAT signaling: choreographing the social lives of cells

Calcium signaling activates the phosphatase calcineurin and induces movement of NFATc proteins into the nucleus, where they cooperate with other proteins to form complexes on DNA. Nuclear import is opposed by kinases such as GSK3, thereby rendering transcription continuously responsive to receptor occupancy. Disruptions of the genes involved in NFAT signaling are implicating this pathway as a regulator of developmental cell-cell interactions.

Doxorubicin induces apoptosis and CD95 gene expression in human primary endothelial cells through a p53-dependent mechanism

Regulation of the homeostasis of vascular endothelium is critical for the processes of vascular remodeling and angiogenesis under physiological and pathological conditions. Here we show that doxorubicin (Dox), a drug used in antitumor therapy, triggered a marked accumulation of p53 and induced CD95 gene expression and apoptosis in proliferating human umbilical vein endothelial cells (HUVECs). Transfection and site-directed mutagenesis experiments using the CD95 promoter fused to an intronic enhancer indicated the requirement for a p53 site for Dox-induced promoter activation. Furthermore, the p53 inhibitor pifithrin-alpha (PFT-alpha) blocked both promoter inducibility and protein up-regulation of CD95 in response to Dox. Up-regulated CD95 in Dox-treated cells was functional in eliciting apoptosis upon incubation of the cells with an agonistic CD95 antibody. However, Dox-mediated apoptosis was independent of CD95/CD95L interaction. The analysis of apoptosis in the presence of PFT-alpha and benzyloxycarbonyl-Val-Ala-dl-Asp-fluoromethylketone revealed that both p53 and caspase activation are required for Dox-mediated apoptosis of HUVECs. Finally, Dox triggered Bcl-2 down-regulation, cytochrome c release from mitochondria, and the activation of caspases 9 and 3, suggesting the involvement of a mitochondrially operated pathway of apoptosis. These results highlight the role of p53 in the response of primary endothelial cells to genotoxic drugs and may reveal a novel mechanism underlying the antitumoral properties of Dox, related to its ability to induce apoptosis in proliferating endothelial cells.

NFAT: ubiquitous regulator of cell differentiation and adaptation

The nuclear factor of activated T cells (NFAT) proteins are a family of transcription factors whose activation is controlled by calcineurin, a Ca(2+)-dependent phosphatase. Originally identified in T cells as inducers of cytokine gene expression, NFAT proteins play varied roles in cells outside of the immune system. This review addresses the recent data implicating NFAT in the control of gene expression influencing the development and adaptation of numerous mammalian cell types.

CD40 signaling and plaque instability

Today, multiple lines of evidence support the view of atherosclerosis as a chronic inflammatory disease and implicate components of the immune system in atherogenesis. Recent work has documented overexpression of the potent immune mediator CD40 and its counterpart CD40 ligand (CD40L) in experimental and human atherosclerotic lesions. Notably, interruption of CD40/CD40L interactions not only diminished the formation and progression of mouse atheroma, but also fostered changes in lesion biology and structure, which are associated in humans with "plaque stabilization." In accordance with the hypothesis that CD40 signaling promotes plaque instability, in vitro studies demonstrated that ligation of CD40 on atheroma-associated cell types, namely endothelial cells, smooth muscle cells, and macrophages, mediates functions considered crucial to the process of atherogenesis, such as the expression of cytokines, chemokines, growth factors, matrix metalloproteinases, and procoagulants. The combination of the broad gamut of proatherogenic biological responses triggered by ligation of CD40 on endothelial cells, smooth muscle cells, and macrophages in vitro and the results of in vivo studies of interruption of CD40 signaling suggests a central role for this receptor/ligand dyad during atherogenesis, proposing CD40/CD40L interactions as a novel potential therapeutic target for this prevalent human disease.

Transcription factors

The regulation of gene expression by transcription factors is fundamental to the phenotype of all cells. The activated phenotype of cells engaged in inflammatory processes is characterized by induced expression of a diverse set of genes, including cytokines, enzymes and cell adhesion molecules. A relatively small number of inducible transcription factors, particularly NF-kappaB, AP-1, NFATs and STATs, are responsible for the expression of a wide variety of inflammatory phenotypic characteristics and therefore play a central role in the pathogenesis of rheumatic diseases. Each of these transcription factors can be modified by existing anti-rheumatic and anti-inflammatory drugs, although adverse effects and limited efficacy remain problems. The future development of therapeutic agents with specificity for transcription factors, especially NF-kappaB, might lead to safer and more effective treatment.

Inhibition of angiogenesis by humulone, a bitter acid from beer hop

On the basis of our previous finding that humulone, a bitter acid from beer hop extract, was a potent inhibitor of bone resorption and inhibited the catalytic activity of cyclooxygenase-2 (COX-2) and more potently the transcription of the COX-2 gene, we examined the effect of humulone on angiogenesis, using chick embryo chorioallantoic membranes (CAMs) and vascular endothelial and tumor cells. Humulone significantly prevented in vivo angiogenesis in CAM in a dose-dependent manner with an ED(50) of 1.5 microg/CAM. Humulone also inhibited in vitro tube formation of vascular endothelial cells. Moreover, it suppressed the proliferation of endothelial cells and the production of vascular endothelial growth factor (VEGF), an angiogenic growth factor, in endothelial and tumor cells. Thus, humulone is a potent angiogenic inhibitor, and may be a novel powerful tool for the therapy of various angiogenic diseases involving solid tumor growth and metastasis.

NFAT signaling in vertebrate development

NFATc proteins transduce Ca(2+) signals to the nucleus and then pair with other proteins on DNA to generate NFAT complexes that activate transcription in response to both electrical and tyrosine kinase signaling. The four NFATc genes arose at the origin of vertebrates, implying that they have evolved for the development of vertebrate-specific functions, such as a complex nervous system, a recombinational immune system, and a vascular system with a complex heart. These speculations are borne out by studies of mice with null mutations in the different family members.

Cot kinase induces cyclooxygenase-2 expression in T cells through activation of the nuclear factor of activated T cells

Cyclooxygenase-2 (COX-2) is induced in human T lymphocytes upon T cell receptor triggering. Here we report that Cot kinase, a mitogen-activated protein kinase kinase kinase involved in T cell activation, up-regulates COX-2 gene expression in Jurkat T cells. Induction of COX-2 promoter activity by Cot kinase occurred mainly through activation of the nuclear factor of activated T cells (NFAT). Mutation of the distal (-105/-97) and proximal (-76/-61) NFAT response elements in the COX-2 promoter abolished the activation induced by Cot kinase. Even more, coexpression of a dominant negative version of NFAT inhibited Cot kinase-mediated COX-2 promoter activation, whereas cotransfection of a constitutively active version of the calcium-dependent phosphatase calcineurin synergizes with Cot kinase in the up-regulation of COX-2 promoter-driven transcription. Strikingly, Cot kinase increased transactivation mediated by a GAL4-NFAT fusion protein containing the N-terminal transactivation domain of NFATp. In contrast to phorbol ester plus calcium ionophore A23187, Cot kinase increases both COX-2 promoter activity and NFAT-mediated transactivation in a cyclosporin A-independent manner. These data indicate that Cot kinase up-regulates COX-2 promoter-driven transcription through the NFAT response elements, being the Cot kinase-induced NFAT-dependent transactivation presumably implicated in this up-regulation.