Cyclosporin A selectively inhibits mitogen-induced cyclooxygenase-2 gene transcription in vascular smooth muscle cells

Cinnamomum verum-derived O-methoxycinnamaldehyde prevents lipopolysaccharide-induced depressive-like behavior in mice via NFAT mRNA stability in T lymphocytes

BACKGROUND

Depressive-like behaviors are related to inflammatory immune activation. Cinnamomum verum (CV) has anti-inflammatory effects, but the molecular mechanisms underlying the antidepressant effects after immunological activation still remain elusive.

PURPOSE

The aim of the present study was to investigate the effect of CV in improving depressive-like behavior and explore its underlying mechanism in T lymphocytes.

METHODS

Mice were randomly divided into Control, LPS, LPS plus fluoxetine, LPS plus CV, and LPS plus MCA groups. Behavior was evaluated using forced swimming test (FST) and tail suspension test (TST). The experimental group mice were exposed to LPS to induce depressive-like behavior. Cell viability was measured upon treating splenic T lymphocytes and Jurkat T cells with CV. Cytokine activity was measured using ELISA and RT-qPCR. The components of CV were analyzed by HPLC. NFAT expression was evaluated by western blotting, immunofluorescence, and luciferase assay. To verify the half-life of NFAT mRNA, Jurkat cells were treated with actinomycin D for 1.5, 3, and 4.5 h.

RESULTS

CV effectively prevents inflammation-induced depressive-like behaviors. CV dose-dependently decreased protein and mRNA levels of TNFα and IL-2. Inhibition of TNFα and IL-2 production involves an MCA-mediated decrease in NFAT mRNA level, rather than inhibition of nuclear translocation. This mechanism was independent of NFAT transcription inducer p38 MAPK; it can be attributed to the promotion of NFAT mRNA decay.

CONCLUSION

Overall, MCA might be an alternative or adjuvant to existing NFAT-targeting immunosuppressants for clinical prophylaxis or therapy in the context of inflammation-induced depressive disorder or other T-cell-associated inflammatory disorders.

Slug, a Cancer-Related Transcription Factor, is Involved in Vascular Smooth Muscle Cell Transdifferentiation Induced by Platelet-Derived Growth Factor-BB During Atherosclerosis

Background Heart attacks and stroke often result from occlusive thrombi following the rupture of vulnerable atherosclerotic plaques. Vascular smooth muscle cells (VSMCs) play a pivotal role in plaque vulnerability because of their switch towards a proinflammatory/macrophage-like phenotype when in the context of atherosclerosis. The prometastatic transcription factor Slug/Snail2 is a critical regulator of cell phenotypic transition. Here, we aimed to investigate the role of Slug in the transdifferentiation process of VSMCs occurring during atherogenesis. Methods and Results In rat and human primary aortic smooth muscle cells, Slug protein expression is strongly and rapidly increased by platelet-derived growth factor-BB (PDGF-BB). PDGF-BB increases Slug protein without affecting mRNA levels indicating that this growth factor stabilizes Slug protein. Immunocytochemistry and subcellular fractionation experiments reveal that PDGF-BB triggers a rapid accumulation of Slug in VSMC nuclei. Using pharmacological tools, we show that the PDGF-BB-dependent mechanism of Slug stabilization in VSMCs involves the extracellular signal-regulated kinase 1/2 pathway. Immunohistochemistry experiments on type V and type VI atherosclerotic lesions of human carotids show smooth muscle-specific myosin heavy chain-/Slug-positive cells surrounding the prothrombotic lipid core. In VSMCs, Slug siRNAs inhibit prostaglandin E2 secretion and prevent the inhibition of cholesterol efflux gene expression mediated by PDGF-BB, known to be involved in plaque vulnerability and/or thrombogenicity. Conclusions Our results highlight, for the first time, a role of Slug in aortic smooth muscle cell transdifferentiation and enable us to consider Slug as an actor playing a role in the atherosclerotic plaque progression towards a life-threatening phenotype. This also argues for common features between acute cardiovascular events and cancer.

Regulator of calcineurin 1 modulates vascular contractility and stiffness through the upregulation of COX-2-derived prostanoids

Cyclooxygenase-2 (COX-2) derived-prostanoids participate in the altered vascular function and mechanical properties in cardiovascular diseases. We investigated whether regulator of calcineurin 1 (Rcan1) participates in vascular contractility and stiffness through the regulation of COX-2. For this, wild type (Rcan1^+/+) and Rcan1-deficient (Rcan1^-/-) mice untreated or treated with the COX-2 inhibitor rofecoxib were used. Vascular function and structure were analysed by myography. COX-2 and phospo-p65 expression were studied by western blotting and immunohistochemistry and TXA₂ production by ELISA. We found that Rcan1 deficiency increases COX-2 and IL-6 expression and NF-κB activation in arteries and vascular smooth muscle cells (VSMC). Adenoviral-mediated re-expression of Rcan1.4 in Rcan1^-/- VSMC normalized COX-2 expression. Phenylephrine-induced vasoconstrictor responses were greater in aorta from Rcan1^-/- compared to Rcan1^+/+ mice. This increased response were diminished by etoricoxib, furegrelate, SQ 29548, cyclosporine A and parthenolide, inhibitors of COX-2, TXA₂ synthase, TP receptors, calcineurin and NF-κB, respectively. Endothelial removal and NOS inhibition increased phenylephrine responses only in Rcan1^+/+ mice. TXA₂ levels were greater in Rcan1^-/- mice. In small mesenteric arteries, vascular function and structure were similar in both groups of mice; however, vessels from Rcan1^-/- mice displayed an increase in vascular stiffness that was diminished by rofecoxib. In conclusion, our results suggest that Rcan1 might act as endogenous negative modulator of COX-2 expression and activity by inhibiting calcineurin and NF-kB pathways to maintain normal contractility and vascular stiffness in aorta and small mesenteric arteries, respectively. Our results uncover a new role for Rcan1 in vascular contractility and mechanical properties.

Reversing multidrug resistance in hepatocellular carcinoma cells by inhibiting extracellular signal-regulated kinase/mitogen-activated protein kinase signaling pathway activity

The aim of the present study was to evaluate whether downregulation of extracellular signal-regulated kinase 1/2 (ERK1/2) is involved in conventional reversal methods and whether the inhibitors of the ERK signaling pathway reverse multidrug resistance (MDR) in hepatocellular carcinoma (HCC) cells. The sensitivities of SMMC7721 and BEL7402, and the MDR SMMC7721/Adriamycin (ADM) and BEL7402/ADM HCC cell lines to ADM were evaluated by CellTiter-Glo^® luminescent cell viability assay through calculating the half maximal inhibitory concentration (IC₅₀) of ADM. In addition, the expression levels of ERK1/2 and phosphorylated (p)ERK1/2 were determined by western blot analysis subsequent to treatment of the cells with PD98059, an MEK inhibitor, or sorafenib, a multikinase inhibitor. The results revealed that the ADM IC₅₀ for the SMMC7721/ADM cells was 16.44 times higher than that of the SMMC7721 cells (P<0.05), and the ADM IC₅₀ for the BEL7402/ADM cells was 20.34 times higher than that of the BEL7402 cells (P<0.05). Following treatment with PD98059 or sorafenib, the expression levels of pERK1/2 in the MDR cells decreased in a dose-dependent manner. Subsequent to treatment with 5 μM PD98059, the ADM IC₅₀ values for the SMMC7721/ADM and BEL7402/ADM cells were reduced to 0.8±0.056 and 1.583±0.284 μg/ml, respectively. Following treatment with 2.5 μM sorafenib, the ADM IC₅₀ values for the SMMC7721/ADM and BEL7402/ADM cells were reduced to 0.264±0.049 and 1.099±0.135 μg/ml, respectively. Subsequent to incubation with 4 μg/ml cyclosporine A (CsA), a classic MDR reversal agent, the ADM IC₅₀ values in the SMMC7721/ADM and BEL7402/ADM cells were reduced to 0.349±0.023 and 0.427±0.039 μg/ml, respectively. CsA treatment also increased the expression levels of pERK1/2 without affecting the total ERK1/2 levels. Therefore, the inhibition of ERK signaling pathway activity may be an important method to reverse the MDR of HCC cells, but is not unique.

Inhibition of breast cancer cell proliferation through disturbance of the calcineurin/NFAT pathway by human herpesvirus 6B U54 tegument protein

Nuclear factor of activated T cell (NFAT) proteins are key regulators involved in multiple physiological mechanisms, such as immune response and cell growth. The capacity of selective calcineurin/NFAT inhibitors to decrease NFAT-dependent cancer cell progression, particularly in breast cancer, has already been demonstrated. In this study, we report a role for the human herpesvirus 6B (HHV-6B) U54 tegument protein in inhibiting MCF-7 breast cancer cell proliferation by inhibiting NFAT activation.

Genome-wide microarray analyses identify the protein C receptor as a novel calcineurin/nuclear factor of activated T cells-dependent gene in vascular smooth muscle cell phenotypic modulation

OBJECTIVE

Calcineurin (Cn) and the nuclear factor of activated T cells (NFAT) family of transcription factors are critical in vascular smooth muscle cell (SMC) development and pathology. Here, we used a genomics approach to identify and validate NFAT gene targets activated during platelet-derived growth factor-BB (PDGF-BB)-induced SMC phenotypic modulation.

METHODS AND RESULTS

Genome-wide expression arrays were used to identify genes both (1) differentially activated in response to PDGF-BB and (2) whose differential expression was reduced by both the Cn inhibitor cyclosporin A and the NFAT inhibitor A-285222. The 20 most pharmacologically sensitive genes were validated by quantitative reverse transcription-polymerase chain reaction analysis of PDGF-BB-stimulated SMCs in the presence of Cn/NFAT inhibitors, including the VIVIT peptide. In all experiments, protein C receptor (PROCR) gene activation was reduced. We showed that PROCR expression was virtually absent in untreated, quiescent SMCs. PDGF-BB stimulation, however, induced significant PROCR promoter activation and downstream protein expression in a Cn/NFAT-dependent manner. Mutation of a species-conserved, NFAT binding motif significantly attenuated PDGF-BB-induced PROCR promoter activity, thereby distinguishing NFAT as the first PROCR transcriptional activator to date. Moreover, SMC PROCR expression was upregulated in the neointima as early as 7 days following acute vascular injury in rat carotid arteries.

CONCLUSION

We hereby report PROCR as a novel, NFAT-dependent gene that may be implicated in vascular restenosis and consequent inward remodeling.

E-cadherin, as a negative regulator of invasive behavior of human trophoblast cells, is down-regulated by cyclosporin A via epidermal growth factor/extracellular signal-regulated protein kinase signaling pathway

Our previous study has demonstrated cyclosporin A (CsA) promotes the invasiveness of human first-trimester trophoblast cells. In the present study, we further investigated the intracellular signaling pathway responsible for the improvements in CsA-induced invasiveness of human trophoblast cells. We showed that CsA down-regulated E-cadherin transcription and translation in human primary cultured trophoblast cells and choriocarcinoma cell line JEG-3. U0126, an inhibitor of extracellular signal-regulated protein kinase (ERK), attenuated the CsA-induced transcriptional repressor SNAI2 (also called Slug) expression and restored E-cadherin expression inhibited by CsA in JEG-3 cells. We further demonstrated that CsA amplified epidermal growth factor (EGF)-stimulated EGF receptor (EGFR) tyrosine phosphorylation in JEG-3 cells, and inhibition of EGFR tyrosine phosphorylation by AG1478, an EGFR tyrosine kinase inhibitor, abolished the down-regulation of E-cadherin by CsA through ERK signaling pathway. Moreover, our data showed that E-cadherin expression was negatively correlated to the invasiveness of JEG-3 cells, and CsA could reverse the decreased invasiveness of JEG-3 cells that resulted from E-cadherin overexpression. In conclusion, these observations indicate that CsA may decrease E-cadherin expression via EGFR/ERK signaling pathway and, ultimately, contribute to the invasiveness improvement of human trophoblast cells.

Differential effects of immunosuppressive drugs on COX-2 activity in vitro and in kidney transplant patients in vivo

BACKGROUND

It was hypothesized that calcineurin inhibitors suppress vascular cyclooxygenase (COX)-2 and exert a reciprocal influence on in vivo prostacyclin and thromboxane. This could contribute to cardiovascular morbidity in transplanted patients.

METHODS

The ability of immunosuppressives to suppress vascular COX-2 expression in vitro was studied in cultured human vascular smooth muscle cells. Blood and urine samples were collected from 28 renal transplant patients before and 2, 4 and 6 h after intake of immunosuppressives and from 11 controls. ELISA was used to measure (1) plasma 6-keto-PGF1alpha and TxB2; (2) urine excretion of PGI-M and TxB(2); (3) 6-keto-PGF1alpha in the whole-blood COX-2 assay; and (4) TxB2 in the whole-blood COX-1 assay. Platelet aggregation was measured optically.

RESULTS

COX-2 in cultured vascular smooth muscle cells was suppressed by cyclosporine A (CsA); tacrolimus and rapamycin had no effect. Human renal arteries and vascular smooth muscle expressed calcineurin Abeta and Agamma isoforms. CsA had no effect on plasma 6-keto-PGF1alpha, whole-blood COX-2 activity or PGI-M urine excretion; after rapamycin intake, the former two increased. Plasma TxB2 did not change after drug intake. TxB2 in the COX-1 assay and urine excretion of TxB2 was significantly lower in tacrolimus- and rapamycin-treated patients compared to the CsA group. Platelet aggregation was increased significantly in the CsA group.

CONCLUSIONS

Although CsA suppressed COX-2 in cultured vascular smooth muscle cells, systemic prostacyclin was not suppressed by either CsA or tacrolimus in vivo. Rapamycin and tacrolimus may actively suppress platelet and renal thromboxane formation. Differential changes in prostanoids may have implications for long-term cardiovascular hazard in patients treated with immunosuppressives.

Platelet-derived growth factor-induced stabilization of cyclooxygenase 2 mRNA in rat smooth muscle cells requires the c-Src family of protein-tyrosine kinases

Cyclooxygenases (COXs) are crucial rate-limiting enzymes required for the biosynthesis of prostaglandins. COX-2 is an inducible isoform of this enzyme, which is believed to play important roles in the development of atherosclerotic vascular disease. We found that COX-2 expression rapidly increases in response to various signaling events, including activation of the platelet-derived growth factor (PDGF) pathway. Activation of PDGF receptor (PDGFR) in rat aortic vascular smooth muscle cells leads to c-Src-dependent stabilization of COX-2 mRNA requiring an AU-rich region within the 3'-untranslated region of this transcript. This regulation correlates with tyrosine phosphorylation of the RNA-associated protein, CUG-binding protein 2 (CUGBP2), which appears to enhance its interaction with COX-2 mRNA. Site-directed mutagenesis of putative tyrosine phosphorylation sites in CUGBP2 identified tyrosine 39 as a c-Src target, and a CUGBP2 with a mutated tyrosine 39 displayed an attenuated ability to bind COX-2 mRNA. We further show that silencing of CUGBP2 with specific small interference RNAs significantly reduces PDGF-dependent induction of COX-2 at both mRNA and protein levels. Furthermore, forced expression of CUGBP2 or constitutively active c-Src leads to stabilization of co-expressed COX-2 mRNA. Finally, in vitro RNA decay assay demonstrates that CUGBP2 is functionally required for the stabilization of COX-2 mRNA. Therefore, our data suggest that tyrosine phosphorylation of CUGBP2 is an important underlying mechanism for the ability of PDGFR/c-Src signaling to control the stability of COX-2 mRNA.

Therapeutic potential of VIVIT, a selective peptide inhibitor of nuclear factor of activated T cells, in cardiovascular disorders

Cardiovascular disease is the major cause of death in industrialized nations. Targeted intervention in calcineurin, a calmodulin-dependent, calcium-activated phosphatase and its substrate, nuclear factor of activated T cells (NFAT), was demonstrated to be effective in the treatment of cardiovascular diseases. Although effective in the disruption of calcineurin phosphatase activity, cyclosporin A (CsA) and FK506 also resulted in undesired side effects and toxicity, prompting the discovery of VIVIT, a novel peptide inhibitor. VIVIT selectively and potently inhibits calcineurin/NFAT interaction, but does not compromise calcineurin phosphatase activity and non-NFAT-mediated signaling. VIVIT displays a favorable therapeutic profile as a potential drug candidate and constitutes a useful tool in exploring calcineurin-NFAT functionality. This review describes the development of VIVIT peptide as a selective NFAT inhibitor and its application as a therapeutic agent in cardiovascular disorders including cardiac hypertrophy, restenosis, atherosclerosis, and angiogenesis.

Bradykinin-induced nuclear factor of activated T-cells-dependent transcription in rat dorsal root ganglion neurons

Bradykinin produced at sites of tissue injury and inflammation elicits acute pain and alters the sensitivity of nociceptive neurons to subsequent stimuli. We tested the hypothesis that bradykinin could elicit long-lasting changes in nociceptor function by activating members of the nuclear factor of activated T-cells (NFAT) family of transcription factors. Bradykinin activation of B2 receptors evoked concentration-dependent (EC50 = 6.0 +/- 0.3 nM) increases in intracellular Ca2+ concentration ([Ca2+]i) in a proportion of dorsal root ganglion neurons in primary culture. These [Ca2+] increases were sensitive to inhibition of phospholipase C (PLC) and depletion of Ca2+ stores. In neurons expressing a green fluorescent protein (GFP)-NFAT4 fusion protein, a 2-min exposure to bradykinin induced the translocation of GFP-NFAT4 from the cytoplasm to the nucleus. Translocation was partially inhibited by the removal of extracellular Ca2+ and was blocked by inhibition of calcineurin. Furthermore, bradykinin triggered a concentration-dependent increase in NFAT-mediated transcription of a luciferase gene reporter (EC50 = 24.2 +/- 0.1 nM). This depended on the B2 receptor, PLC activation, and inositol triphosphate-mediated Ca2+ release. Transcription was not inhibited by capsazepine. Finally, as indicated by quantitative reverse transcription-polymerase chain reaction, bradykinin elicited an increase in cyclooxygenase mRNA. This increase was sensitive to calcineurin and B2 receptor inhibition. These findings suggest a mechanism by which short-lived bradykinin-mediated stimuli can enact lasting changes in nociceptor function and sensitivity.

Macrophage transcriptional responses following in vitro infection with a highly virulent African swine fever virus isolate

We used a porcine microarray containing 2,880 cDNAs to investigate the response of macrophages to infection by a virulent African swine fever virus (ASFV) isolate, Malawi LIL20/1. One hundred twenty-five targets were found to be significantly altered at either or both 4 h and 16 h postinfection compared with targets after mock infection. These targets were assigned into three groups according to their temporal expression profiles. Eighty-six targets showed increased expression levels at 4 h postinfection but returned to expression levels similar to those in mock-infected cells at 16 h postinfection. These encoded several proinflammatory cytokines and chemokines, surface proteins, and proteins involved in cell signaling and trafficking pathways. Thirty-four targets showed increased expression levels at 16 h postinfection compared to levels at 4 h postinfection and in mock-infected cells. One host gene showed increased expression levels at both 4 and 16 h postinfection compared to levels in mock-infected cells. The microarray results were validated for 12 selected genes by quantitative real-time PCR. Levels of protein expression and secretion were measured for two proinflammatory cytokines, interleukin 1beta and tumor necrosis factor alpha, during a time course of infection with either the virulent Malawi LIL20/1 isolate or the OUR T88/3 nonpathogenic isolate. The results revealed differences between these two ASFV isolates in the amounts of these cytokines secreted from infected cells.

Bombesin induces cyclooxygenase-2 expression through the activation of the nuclear factor of activated T cells and enhances cell migration in Caco-2 colon carcinoma cells

Cyclooxygenase-2 (Cox-2), the gastrin-release peptide (GRP) and its cognate receptor (GRP-R) are overexpressed in a significant percentage of colorectal carcinomas and are associated with cell growth, invasiveness and tumor progression. However, a molecular link between all of them in adenocarcinomas has not been established. Here, we show that bombesin (BBS), a GRP homolog, stimulates the expression of Cox-2 mRNA and protein in human colon adenocarcinoma Caco-2 cells, resulting in enhanced release of prostaglandin E(2). These effects were markedly inhibited by the specific BBS antagonist RC-3940-II. BBS promotes the activation of the nuclear factor of activated T cells (NFAT) through a Ca(2+)/calcineurin (Cn)-linked pathway. Upon BBS stimulation, the NFATc1 isoform translocates into the nucleus with a concomitant increase in NFATc1 binding to two specific recognition sites in the promoter region of the Cox-2 gene. Furthermore, inhibition of Cn activity by the immunosuppressive drug cyclosporin A impaired NFAT activation and diminished Cox-2 expression in BBS-stimulated cells. Interestingly, BBS pretreatment strongly enhances the invasive capacity of carcinoma cells, effect which was inhibited by a Cox-2-specific inhibitor. These findings provide the first evidence for the involvement of the Ca(2+)/Cn/NFAT pathway in BBS-mediated induction of genes involved in colon carcinoma invasiveness such as Cox-2.

Cell signalling diversity of the Gqalpha family of heterotrimeric G proteins

Many receptors for neurotransmitters and hormones rely upon members of the Gqalpha family of heterotrimeric G proteins to exert their actions on target cells. Galpha subunits of the Gq class of G proteins (Gqalpha, G11alpha, G14alpha and G15/16alpha) directly link receptors to activation of PLC-beta isoforms which, in turn, stimulate inositol lipid (i.e. calcium/PKC) signalling. Although Gqalpha family members share a capacity to activate PLC-beta, they also differ markedly in their biochemical properties and tissue distribution which predicts functional diversity. Nevertheless, established models suggest that Gqalpha family members are functionally redundant and that their cellular responses are a result of PLC-beta activation and downstream calcium/PKC signalling. Growing evidence, however, indicates that Gqalpha, G11alpha, G14alpha and G15/16alpha are functionally diverse and that many of their cellular actions are independent of inositol lipid signalling. Recent findings show that Gqalpha family members differ with regard to their linked receptors and downstream binding partners. Reported binding partners distinct from PLC-beta include novel candidate effector proteins, various regulatory proteins, and a growing list of scaffolding/adaptor proteins. Downstream of these signalling proteins, Gqalpha family members exhibit unexpected differences in the signalling pathways and the gene expression profiles they regulate. Finally, genetic studies using whole animal models demonstrate the importance of certain Gqalpha family members in cardiac, lung, brain and platelet functions among other physiological processes. Taken together, these findings demonstrate that Gqalpha, G11alpha, G14alpha and G15/16alpha regulate both overlapping and distinct signalling pathways, indicating that they are more functionally diverse than previously thought.

Induction of cyclooxygenase-2 expression by allergens in lymphocytes from allergic patients

Cyclooxygenase (COX) is a key enzyme in prostaglandin (PG) synthesis. Up-regulation of COX-2 expression is responsible for increased PG release during inflammatory conditions and is thought to be also involved in allergic states. In this study, we demonstrate that in human T, B and natural killer lymphocytes from allergic patients, COX-2 expression became induced upon cell challenge with specific allergens and that this process is presumably IgE dependent and occurs after CD23 receptor ligation. This induction took place at both mRNA and protein levels and was accompanied by PGD2 release. IgE-dependent lymphocyte treatment elicited, in parallel, an activation of the MAPK p38 and extracellular signal-regulated kinase 1/2, an enhancement of calcineurin (CaN) activity, and an increase of the DNA-binding activity of the nuclear factor of activated T cells and of NF-kappaB, with a concomitant decrease in the levels of the cytosolic inhibitor of kappaB, IkappaB. In addition, specific chemical inhibitors of MAPK, such as PD098059 and SB203580, as well as MG-132, an inhibitor of proteasomal activity, abolished allergen-induced COX-2 up-regulation, suggesting that this process is mediated by MAPK and NF-kappaB. However, induction of COX-2 expression was not hampered by the CaN inhibitor cyclosporin A. We also examined the effect of a selective COX-2 inhibitor, NS-398, on cytokine production by human lymphocytes. Treatment with NS-398 severely diminished the IgE-dependently induced production of IL-8 and TNF-alpha. These results underscore the relevant role of lymphocyte COX-2 in allergy and suggest that COX-2 inhibitors may contribute to the improvement of allergic inflammation through the reduction of inflammatory mediator production by human lymphocytes.

Differential effects of Gq alpha, G14 alpha, and G15 alpha on vascular smooth muscle cell survival and gene expression profiles

Gqalpha family members (Gqalpha, G11alpha, G14alpha, and G15/16alpha) stimulate phospholipase Cbeta (PLCbeta) and inositol lipid signaling but differ markedly in amino acid sequence and tissue distribution predicting unappreciated functional diversity. To examine functional differences, we compared the signaling properties of Gqalpha, G14alpha, and G15alpha and their cellular responses in vascular smooth muscle cells (VSMC). Constitutively active forms of Gqalpha, G14alpha, or G15alpha elicit markedly different responses when introduced to VSMC. Whereas each Galpha stimulated PLCbeta to similar extents when expressed at equal protein levels, Gqalpha and G14alpha but not G15alpha initiated profound cell death within 48 h. This response was the result of activation of apoptotic pathways, because Gqalpha and G14alpha, but not G15alpha, stimulated caspase-3 activation and did not alter phospho-Akt, a regulator of cell survival pathways. Gqalpha and G14alpha stimulate nuclear factor of activated T cell (NFAT) activation in VSMC, but Galpha-induced cell death seems independent of PKC, InsP(3)/Ca(2+), and NFAT, in that pharmacological inhibitors of these pathways did not block cell death. Gene expression analysis indicates that Gqalpha, G14alpha, and G15alpha each elicit markedly different profiles of altered gene sets in VSMC after 24 h. Whereas all three Galpha stimulated changes (> or =2-fold) in 50 shared mRNA, Gqalpha and G14alpha (but not G15alpha) stimulated changes in 221 shared mRNA, many of which are reported to be pro-apoptotic and/or involved with TNF-alpha signaling. We were surprised to find that each Galpha also stimulated changes in nonoverlapping Galpha-specific gene sets. These findings demonstrate that Gqalpha family members activate both overlapping and distinct signaling pathways and are more functionally diverse than previously thought.

Sphingosine 1-phosphate receptors mediate the lipid-induced cAMP accumulation through cyclooxygenase-2/prostaglandin I2 pathway in human coronary artery smooth muscle cells

Sphingosine 1-phosphate (S1P) has been shown to exert a variety of biological responses through extracellular specific receptors or intracellular mechanisms. In the present study, we characterized a signaling pathway of S1P-induced cAMP accumulation in human coronary artery smooth muscle cells (CASMCs). S1P induced biphasic cAMP accumulation composed of a short-term and transient response (a peak at 2.5 min) and a late and sustained response ( approximately 4-6 h). The late phase of cAMP accumulation was parallel to the increment of cyclooxygenase-2 protein expression and was inhibited by N-[2-(cyclohexyloxyl)-4-nitrophenyl]-methane sulfonamide (NS398), a cyclooxygenase-2-specific inhibitor. We were surprised to find that the cyclooxygenase-2 inhibitor also inhibited short-term cAMP accumulation even when cyclooxygenase-2 protein expression was not yet increased. More interestingly, the short-term cAMP accumulation was also completely inhibited by pertussis toxin, an inhibitor of G(i/o) proteins. JTE-013, a specific antagonist for S1P(2) receptors, inhibited the S1P-induced cAMP accumulation. Furthermore, small interfering RNAs targeted for S1P(2) receptors significantly inhibited the S1P-induced cAMP accumulation. The cAMP response was also inhibited by specific inhibitors for phospholipase C, extracellular signal-regulated kinase pathways, and cytosolic phospholipase A(2). S1P actually activated these enzyme activities and stimulated prostaglandin I(2) (PGI(2)) synthesis. Finally, exogenously applied arachidonic acid and PGI(2) induced cAMP accumulation to a similar extent as S1P. In conclusion, S1P induced cAMP accumulation through S1P receptors, including S1P(2) receptor and G(i/o) protein-mediated stimulation of intracellular signaling pathways involving cyclooxygenase-2-dependent PGI(2) synthesis.

Expression and Function of the Nuclear Factor of Activated T Cells in Colon Carcinoma Cells

Increasing evidence shows a crucial role of the Ca2+/ calcineurin-mediated activation of the nuclear factor of activated T cells (NFAT) in the regulation of a variety of processes in nonimmune cells. Here we provide evidence that NFATc1 and NFATc2 are expressed in human colon carcinoma cell lines. These proteins are translocated from the cytoplasm to the nucleus upon treatment with a combination of phorbol 12-myristate 13-acetate plus the calcium ionophore A23187. Subsequent to translocation to the nucleus, NFATc1 and NFATc2 were able to bind to a NFAT response element in the DNA, regulating transcriptional activation of genes containing a NFAT-responsive element such as cyclooxygenase-2 (COX-2). COX-2 expression and prostaglandin E2 (PGE2) production were induced upon pharmacological stimuli leading to NFAT activation and blunted by inhibition of calcineurin phosphatase with cyclosporin A or tacrolimus (FK506). Expression of NFAT wild type protein or the active catalytic subunit of calcineurin transactivates COX-2 promoter activity, whereas a dominant negative mutant of NFAT inhibited COX-2 induction in colon carcinoma cell lines. Furthermore, mutation or deletion of NFAT binding sites in the human COX-2 promoter greatly diminished its induction by phorbol 12-myristate 13-acetate/calcium ionophore A23187. These findings demonstrate the presence and activation of NFAT in human colon carcinoma cells, with important implications in the regulation of genes involved in the transformed phenotype as COX-2.

Involvement of TNF and NF-κB in the Transcriptional Control of Cyclooxygenase-2 Expression by IFN-γ in Macrophages

IFN-gamma induces cyclooxygenase (COX)-2 expression and PG production in mouse macrophage cells. IFN-gamma activates COX-2 promoter-driven transcription. Deletion of the IFN sequence regulatory element (ISRE) I -1541/-1522 and ISRE II -1215/-1206 sites of the mouse COX-2 promoter minimally decrease this IFN-gamma induction. In contrast, deletion of the -965/-150 region from the COX-2 promoter abrogated IFN-gamma induction. In this region a NF-kappaB site has been described and mutation of this site impairs the induction of the full COX-2 promoter by IFN-gamma. Moreover, IFN-gamma induction of the COX-2 promoter was also strongly reduced by transfection of plasmid encoding the NF-kappaB inhibitor, IkappaBalpha. Interestingly, IFN-gamma induction of the COX-2 and PGE(2) synthesis was absent in macrophages from TNF(-/-) mice, and neutralizing anti-TNF Abs inhibited COX-2 promoter induction by IFN-gamma in RAW 264.7 macrophages. Moreover, NF-kappaB activity was induced late after stimulation with IFN-gamma correlating with the effect of autocrine TNF, and this NF-kappaB activation was absent in macrophages from TNF(-/-) mice. Taken together our results suggest a model in which IFN-gamma-induced TNF activates NF-kappaB, which is required for full COX-2 expression.

Calcineurin signaling in avian cardiovascular development

Experiments were initiated in avian embryos to determine the embryonic expression of calcineurin protein phosphatase isoforms as well as to identify developmental processes affected by inhibition of calcineurin signal transduction. Chicken calcineurin A alpha (CnAalpha) and calcineurin A beta (CnAbeta) are differentially expressed in the developing cardiovascular system, including primitive heart tube and valve primordia. Inhibition of calcineurin signaling by cyclosporin A (CsA) treatment in ovo resulted in distinct cardiovascular malformations, depending on the timing and localization of treatment. Initial formation of the heart tube was apparently normal in embryos treated with CsA from embryonic day (E)1 to E2, but hallmarks of heart failure were apparent with treatment from E2 to E3. Vascular defects were apparent in whole embryos treated on either day, but local administration of CsA directly to the forming vessels on E2 did not inhibit blood vessel formation. This observation supports an indirect effect of calcineurin inhibition on angiogenic remodeling as a result of compromised heart development. Together these studies are consistent with multiple roles for calcineurin signaling in the developing cardiovascular system.

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.

Evidence that Galpha(q)-coupled receptor-induced interleukin-6 mRNA in vascular smooth muscle cells involves the nuclear factor of activated T cells

The immunosuppressant cyclosporin A inhibits transcription mediated by the nuclear factor of activated T-cells (NFAT), a key regulator of cytokine gene expression in lymphocytes that integrates phospholipase C signaling. NFAT is also expressed in vascular smooth muscle cells, but the genes it regulates there are unknown. Here we show that Galpha(q)-coupled P2Y nucleotide receptor signaling in rat vascular smooth muscle cells increases NFAT-mediated luciferase reporter expression. It also induces interleukin (IL)-6 gene expression but not other cytokine mRNAs including IL-1, IL-2, IL-3, IL-4, IL-10, gamma-interferon, tumor necrosis factor-alpha, or tumor necrosis factor-beta. IL-6 mRNA induction by UTP is more rapid and transient then that caused by IL-1beta stimulation and is partially blocked by cyclosporin A or by expression of a trans-dominant NFAT inhibitor. Expression of recombinant NFATc1 markedly augments IL-6 mRNA induction by these and other agonists, which is partially attributable to NFAT-regulated paracrine mediators. However, trans-dominant NFkappaB inhibitors strongly interfere with IL-6 mRNA induction both by IL-1beta and by UTP, which synergistically evoke IL-6 mRNA expression. These findings suggest that NFAT is among the cofactors involved in NFkappaB-dependent IL-6 gene induction by Ca(2+)-mobilizing receptors in vascular smooth muscle cells.