Inhibition Of NFAT Activation Research Articles

Rocaglamide Prolonged Allograft Survival by Inhibiting Differentiation of Th1/Th17 Cells in Cardiac Transplantation.

Background Aglaia (Meliaceae) species are used for treating autoimmune disorders and allergic diseases in Asian countries. Rocaglamide, an extract obtained from Aglaia species, exhibits suppressive effect by regulating the T cell subset balance and cytokine network in cancer. However, whether it can be used in organ transplantation is unknown. In this study, we investigated the antirejection effect and mechanism of action of rocaglamide in a mouse cardiac allograft model. Methods Survival studies were performed by administering mice with phosphate-buffered saline (PBS) (n = 6) and rocaglamide (n = 8). Heart grafts were monitored until they stopped beating. After grafting, the mice were sacrificed on day 7 for histological, mixed lymphocyte reaction (MLR), enzyme-linked immunosorbent assay (ELISA), and flow cytometric analyses. Results Rocaglamide administration significantly prolonged the median survival of the grafts from 7 to 25 days compared with PBS treatment (P < 0.001). On posttransplantation day 7, the rocaglamide-treated group showed a significant decrease in the percentage of Th1 cells (7.9 ± 0.9% vs. 1.58 ± 0.5%, P < 0.001) in the lymph nodes and spleen (8.0 ± 2.5% vs. 2.4 ± 1.3%, P < 0.05). Rocaglamide treatment also significantly inhibited the production of Th17 cells (6.4 ± 1.0% vs. 1.8 ± 0.4%, P < 0.01) in the lymph nodes and spleen (5.9 ± 0.3% vs. 2.9 ± 0.8%, P < 0.01). Furthermore, the prolonged survival of the grafts was associated with a significant decrease in IFN-γ and IL-17 levels. Our results also showed that NF-AT activation was inhibited by rocaglamide, which also induced p38 and Jun N-terminal kinase (JNK) phosphorylation in Jurkat T cells. Furthermore, by using inhibitors that suppressed p38 and JNK phosphorylation, rocaglamide-mediated reduction in NF-AT protein levels was prevented. Conclusion We identified a new immunoregulatory property of rocaglamide, wherein it was found to regulate oxidative stress response and reduce inflammatory cell infiltration and organ injury, which have been associated with the inhibition of NF-AT activation in T cells.

CC-401 Promotes β-Cell Replication via Pleiotropic Consequences of DYRK1A/B Inhibition.

Pharmacologic expansion of endogenous β cells is a promising therapeutic strategy for diabetes. To elucidate the molecular pathways that control β-cell growth we screened ∼2400 bioactive compounds for rat β-cell replication-modulating activity. Numerous hit compounds impaired or promoted rat β-cell replication, including CC-401, an advanced clinical candidate previously characterized as a c-Jun N-terminal kinase inhibitor. Surprisingly, CC-401 induced rodent (in vitro and in vivo) and human (in vitro) β-cell replication via dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) 1A and 1B inhibition. In contrast to rat β cells, which were broadly growth responsive to compound treatment, human β-cell replication was only consistently induced by DYRK1A/B inhibitors. This effect was enhanced by simultaneous glycogen synthase kinase-3β (GSK-3β) or activin A receptor type II-like kinase/transforming growth factor-β (ALK5/TGF-β) inhibition. Prior work emphasized DYRK1A/B inhibition-dependent activation of nuclear factor of activated T cells (NFAT) as the primary mechanism of human β-cell-replication induction. However, inhibition of NFAT activity had limited effect on CC-401-induced β-cell replication. Consequently, we investigated additional effects of CC-401-dependent DYRK1A/B inhibition. Indeed, CC-401 inhibited DYRK1A-dependent phosphorylation/stabilization of the β-cell-replication inhibitor p27Kip1. Additionally, CC-401 increased expression of numerous replication-promoting genes normally suppressed by the dimerization partner, RB-like, E2F and multivulval class B (DREAM) complex, which depends upon DYRK1A/B activity for integrity, including MYBL2 and FOXM1. In summary, we present a compendium of compounds as a valuable resource for manipulating the signaling pathways that control β-cell replication and leverage a DYRK1A/B inhibitor (CC-401) to expand our understanding of the molecular pathways that control β-cell growth.

NFAT transcription factors regulate survival, proliferation, migration, and differentiation of neural precursor cells.

The study of factors that regulate the survival, proliferation, and differentiation of neural precursor cells (NPCs) is essential to understand neural development as well as brain regeneration. The Nuclear Factor of Activated T Cells (NFAT) is a family of transcription factors that can affect these processes besides playing key roles during development, such as stimulating axonal growth in neurons, maturation of immune system cells, heart valve formation, and differentiation of skeletal muscle and bone. Interestingly, NFAT signaling can also promote cell differentiation in adults, participating in tissue regeneration. The goal of the present study is to evaluate the expression of NFAT isoforms in NPCs, and to investigate its possible role in NPC survival, proliferation, migration, and differentiation. Our findings indicate that NFAT proteins are active not only in neurogenic brain regions such as hippocampus and subventricular zone (SVZ), but also in cultured NPCs. The inhibition of NFAT activation with the peptide VIVIT reduced neurosphere size and cell density in NPC cultures by decreasing proliferation and increasing cell death. VIVIT also decreased NPC migration and differentiation of astrocytes and neurons from NPCs. In addition, we identified NFATc3 as a predominant NFAT isoform in NPC cultures, finding that a constitutively-active form of NFATc3 expressed by adenoviral infection reduces NPC proliferation, stimulates migration, and is a potent inducer of NPC differentiation into astrocytes and neurons. In summary, our work uncovers active roles for NFAT signaling in NPC survival, proliferation and differentiation, and highlights its therapeutic potential for tissue regeneration.

The Crosstalk between the Bone and the Immune System: Osteoimmunology

Osteoimmunology is an interdisciplinary research field focused on the molecular understanding of the interplay between the skeletal and immune systems. Recent reports suggest that a large number of molecules affect both bone and immune cells. Furthermore, it has been demonstrated that immune cells express molecules modulating bone cell development and bone is known to provide important signal to the hematopoietic and immune cells, which develop in the bone marrow and then migrate to peripheral organs. All these concepts are well represented in this special issue, starting from a large overview of bone cell differentiation, followed by the general mechanisms highlighting the interaction between bone and immune cells described by G. Mori et al. The effect of the numerous T-cell subsets on bone cells is very complex. In particular, a clear overview on Th17 and Treg and their involvement in bone diseases is presented by M. Wang et al., whereas a more detailed description of the negative regulatory feedback loop between osteoclasts and CD8+ T cells that contributes to homeostasis of both the skeletal and immune systems is provided by Z. S. Buchwald and R. Aurora. The first identified pioneer cytokine regulating both bone and immune systems is RANKL, revised by N. Lo Iacono et al. The authors also report that a genetic defect impairing RANKL function leads to a peculiar form of an invalidating rare bone disease, named autosomal recessive osteopetrosis. In addition to RANKL, TNF-alpha is another cytokine known to play a fundamental role during osteoclastogenesis in the context of inflammatory arthritis, as described by H. Kitaura et al. Comprehensive reports detailing the interaction between bone and immune cells in the periodontal diseases and postmenopausal osteoporosis are reported, respectively, by A. Di Benedetto et al. and M. F. Faienza et al. The involvement of T cells in bone metastatic solid tumors has been carefully reviewed by I. Roato. Immune cell contribution in multiple myeloma bone disease is well described by A. Oranger et al. Understanding how bone and immune cells mutually interact with each other can give rise to new therapeutical targets as described by A. Corrado et al. in the context of rheumatoid arthritis. Moreover, T. Fujimura et al. demonstrated that, in invasive extramammary Paget's disease, the administration of bisphosphonates, privileged antiresorptive drugs, has also an immunosuppressive role in addition to blocking osteoclast activity. Recent findings suggested that immune cells are critical mediators of the effect of different hormones on bone cells. In particular, G. Colaianni et al. analyzed the Pituitary/Immune/Bone Axis, highlighting the effect immune cell-mediated of hormones such as FSH and TSH on bone remodeling. Finally, further sustaining the role of bone cells on the regulation of haematopoiesis, C. L. Sesler and M. Zayzafoon demonstrated that the inhibition of NFAT activation in osteoblasts increases bone formation while decreasing B-cell development in the bone marrow microenvironment. These manuscripts represent an exciting and insightful snapshot of current research on osteoimmunology. State-of-the-art and emerging future topics are highlighted in this special issue, which may help to advance the present research on the crosstalk between bone and immune cells. Giacomina Brunetti Giorgio Mori Patrizia D'Amelio Roberta Faccio

Akt/Protein Kinase B and Glycogen Synthase Kinase-3β Signaling Pathway Regulates Cell Migration through the NFAT1 Transcription Factor

The phosphoinositide 3-kinase (PI3K) pathway regulates a multitude of cellular processes. Deregulation of PI3K signaling is often observed in human cancers. A major effector of PI3K is Akt/protein kinase B (PKB). Recent studies have pointed to distinct roles of Akt/PKB isoforms in cancer cell signaling. Studies have shown that Akt1 (PKBalpha) can attenuate breast cancer cell motility, whereas Akt2 (PKBbeta) enhances this phenotype. Here, we have evaluated the mechanism by which Akt1 blocks the migration of breast cancer cells through the transcription factor NFAT. A major effector of Akt/PKB is glycogen synthase kinase-3beta (GSK-3beta), also a NFAT kinase. Inhibition of GSK-3beta using short hairpin RNA or a selective inhibitor potently blocks breast cancer cell migration concomitant with a reduction in NFAT activity. GSK-3beta-mediated inhibition of NFAT activity is due to proteasomal degradation. Experiments using GSK-3beta mutants, which are unresponsive to Akt/PKB, reveal that inhibition of cell migration by Akt/PKB is mediated by GSK-3beta. These effects are recapitulated at the levels of NFAT degradation by the proteasome. Our studies show that activation of Akt/PKB leads to inactivation of the effector GSK-3beta and the outcome of this signaling event is degradation of NFAT by the proteasome and subsequent inhibition of cell migration.

Immune-suppressive activity of punicalagin via inhibition of NFAT activation

Since T cell activation is central to the development of autoimmune diseases, we screened a natural product library comprising 1400 samples of medicinal herbal extracts, to identify compounds that suppress T cell activity. Punicalagin (PCG) isolated from the fruit of Punica granatum was identified as a potent immune suppressant, based on its inhibitory action on the activation of the nuclear factor of activated T cells (NFAT). PCG downregulated the mRNA and soluble protein expression of interleukin-2 from anti-CD3/anti-CD28-stimulated murine splenic CD4+ T cells and suppressed mixed leukocytes reaction (MLR) without exhibiting cytotoxicity to the cells. In vivo, the PCG treatment inhibited phorbol 12-myristate 13-acetate (PMA)-induced chronic ear edema in mice and decreased CD3+ T cell infiltration of the inflamed tissue. These results suggest that PCG could be a potential candidate for the therapeutics of various immune pathologies.

Extracellular acidification enhances osteoclast survival through an NFAT-independent, protein kinase C-dependent pathway

Systemic acidosis has detrimental effects on the skeleton and local acidosis is associated with bone destruction in inflammatory and neoplastic diseases. However, the mechanisms by which acidosis enhances osteoclastic bone resorption are poorly understood. Our aim was to examine the effects of acid on osteoclast survival and the involvement of cytosolic Ca 2+ in mediating these effects. Osteoclasts were isolated from long bones of newborn rats, and multinucleated osteoclast-like cells were generated from RAW 264.7 cells. Cytosolic free Ca 2+ concentration ([Ca 2+] i) was monitored using fura-2. Survival of rat osteoclasts over a period of 18 h was significantly enhanced by acidification of the medium from 40 ± 10% at pH 7.6 to 83 ± 4% at pH 7.0. Consistent with its effects on survival, acidosis suppressed osteoclast apoptosis at 6 h. We examined the possible involvement of the proton-sensing receptor ovarian cancer G protein-coupled receptor 1 (OGR1) in mediating the effects of acid. Acid-induced rise of [Ca 2+] i was inhibited by the OGR1 antagonist Cu 2+ and was suppressed in osteoclast-like cells in which OGR1 transcripts were depleted using RNA interference. These findings support an essential role for OGR1 in acid-induced Ca 2+ signaling in osteoclasts. Addition of Cu 2+ or chelation of cytosolic Ca 2+ with BAPTA abolished the ability of acidification to enhance osteoclast survival. Inhibition of NFAT activation with the cell-permeable peptide 11R-VIVIT did not alter the ability of acid to promote survival; however, it suppressed the increase in survival induced by RANKL. In contrast, inhibition of protein kinase C (PKC) blocked the effect of acid on osteoclast survival. Thus, this study reveals that extracellular acidification enhances osteoclast survival through an NFAT-independent, PKC-dependent pathway. Increased osteoclast survival may contribute to bone loss in systemic and local acidosis.

Modulation of NFAT-dependent gene expression by the RhoA signaling pathway in T cells.

We have reported previously that p115Rho guanine nucleotide exchange factor, its upstream activator Galpha13, and its effector RhoA are able to inhibit HIV-1 replication. Here, we show that RhoA is able to inhibit HIV-1 gene expression through the NFAT-binding site in the HIV long-terminal repeat. Constitutively active NFAT counteracts the inhibitory activity of RhoA, and inhibition of NFAT activation also inhibits HIV-1 gene expression. We have shown further that RhoA inhibits NFAT-dependent transcription and IL-2 production in human T cells. RhoA does not inhibit nuclear localization of NFAT but rather, inhibits its transcriptional activity. In addition, RhoA decreases the level of acetylated histone H3, but not NFAT occupancy, at the IL-2 promoter. These data suggest that activation of RhoA can modulate IL-2 gene expression by inhibiting the transcriptional activity of NFAT and chromatin structure at the IL-2 promoter during T cell activation.

Ritonavir Inhibits NF-AT Activation Through Effects on the PI-3 Kinase/Akt Pathway

The HIV protease inhibitor ritonavir has been reported to have activities unrelated to inhibition of HIV protease, including anti-tumor activity in vivo and in vitro, induction of lipodystrophy in vivo, inhibition of the 20S proteasome, and inhibition of NFkB activation. Here we show that ritonavir also inhibits activation of NF-AT by PMA plus ionomycin and by the HHV-8 vGPCR. Inhibition of NF-AT activation occurs through the PI-3 kinase/Akt/GSK3 pathway, since ritonavir treatment leads to decreased Akt phosphorylation and a resultant decrease in GSK-3 phosphorylation. Treatment with ritonavir also inhibits the expression of NF-AT-dependent pro-inflammatory factors. Inhibition of multiple signaling pathways may help to explain the anti-tumor and other effects of ritonavir that are unrelated to its anti-retroviral activity. from 2005 International Meeting of The Institute of Human Virology Baltimore, USA, 29 August – 2 September 2005

Rocaglamide Derivatives Are Immunosuppressive Phytochemicals That Target NF-AT Activity in T Cells

Aglaia (family Meliaceae) plants are used in traditional medicine (e.g., in Vietnam) for the treatment of inflammatory skin diseases and allergic inflammatory disorders such as asthma. Inflammatory diseases arise from inappropriate activation of the immune system, leading to abnormal expression of genes encoding inflammatory cytokines and tissue-destructive enzymes. The active compounds isolated from these plants are derivatives of rocaglamide. In this study we show that rocaglamides are potent immunosuppressive phytochemicals that suppress IFN-gamma, TNF-alpha, IL-2, and IL-4 production in peripheral blood T cells at nanomolar concentrations. We demonstrate that rocaglamides inhibit cytokine gene expression at the transcriptional level. At the doses that inhibit cytokine production, they selectively block NF-AT activity without impairing NF-kappaB and AP-1. We also show that inhibition of NF-AT activation by rocaglamide is mediated by strong activation of JNK and p38 kinases. Our study suggests that rocaglamide derivatives may serve as a new source of NF-AT-specific inhibitors for the treatment of certain inflammatory diseases.

Vav exchange factor counteracts the HIV-1 Nef-mediated decrease of plasma membrane GM1 and NF-AT activity in T cells.

Several findings support the importance of GM1-enriched lipid microdomains of plasma membrane and of Vav, an essential regulator of actin cytoskeletal rearrangement, in the regulation of T cell activation. Moreover, a functional link among lipid microdomains, Vav and the HIV product Nef has been described. These observations suggest that Nef can modify plasma membrane GM1, affecting the behavior of HIV-infected cells towards antigen recognition and Vav towards counteracting such an effect. We observed that Nef expression, either following viral infection or ectopic expression, significantly decreased the level of plasma membrane GM1 in unstimulated T cells. This down-regulation was associated with the inhibition of NF-AT activation, but not with NF-kappaB activation induced by TCR engagement. Dissecting the signaling pathway that regulates NF-AT activation, we found that Nef inhibited exclusively the Ca(2+)/calcineurin cascade, whereas the JNK cascade and AP-1 transcriptional activity were not affected. Our evidence that Vav overexpression counteracted both the Nef-induced decrease of GM1 expression and the inhibition of NF-AT activity, suggests a novel mechanism by which Nef may interfere with TCR-mediated activation through the modulation of intracellular trafficking and clustering of GM1-enriched microdomains at the cell surface.

Requirement of transcription factor NFAT in developing atrial myocardium

Nuclear factor of activated T cell (NFAT) is a ubiquitous regulator involved in multiple biological processes. Here, we demonstrate that NFAT is temporally required in the developing atrial myocardium between embryonic day 14 and P0 (birth). Inhibition of NFAT activity by conditional expression of dominant-negative NFAT causes thinning of the atrial myocardium. The thin myocardium exhibits severe sarcomere disorganization and reduced expression of cardiac troponin-I (cTnI) and cardiac troponin-T (cTnT). Promoter analysis indicates that NFAT binds to and regulates transcription of the cTnI and the cTnT genes. Thus, regulation of cytoskeletal protein gene expression by NFAT may be important for the structural architecture of the developing atrial myocardium.

NFAT Mediates Invasion

Carcinoma cells can invade surrounding normal tissue, and integrins have been linked to promoting such progression because of their role in regulating cell adhesion and migration. Jauliac et al. report a correlation in breast and colon cancer cells between the expression of integrins containing the β 4 subunit and the expression and activity of a transcription factor called NFAT. Inhibition of NFAT activity inhibited cancer cell migration in an invasion assay. NFAT activity and cell migration were also stimulated upon integrin clustering and exposure of cells to chemoattractants. Moreover, tissue from breast cancer patients revealed increased expression of both β 4 and NFAT. NFATs appear to be targets of integrin activation and may be important drug targets to control cancer progression. S. Jauliac, C. Lopez-Rodriguez, L. M. Shaw, L. F. Brown, A. Rao, A. Toker, The role of NFAT transcription factors in integrin-mediated carcinoma invasion. Nature Cell Biol. 4 , 540-544 (2002). [Online Journal]

Nonsteroidal Anti-inflammatory Drugs Suppress T-cell Activation by Inhibiting p38 MAPK Induction

In addition to antagonizing inflammation by inhibiting the activity of cyclooxygenases (COX), nonsteroidal anti-inflammatory drugs (NSAID) block T-cell activation. The immunosuppressant activity of NSAID correlates with their ability to block transcription factors required for the expression of inducible response genes triggered by T-cell antigen receptor (TCR) engagement. Whereas the inhibition of nuclear factor-kappaB by aspirin and sodium salicylate can be partly accounted for by their binding to IkappaB kinase-beta, the broad range of transcriptional targets of NSAID suggests that the products of COX activity might affect one or more among the early steps in the TCR-signaling cascade. Here we show that the inhibition of NF-AT activation by NSAID correlates with a selective inhibition of p38 MAP kinase induction. The suppression of TCR-dependent p38 activation by NSAID can be fully overcome by prostaglandin E(2), underlining the requirement for COX activity in p38 activation. Furthermore, the inhibition of COX-1 results in defective induction of the COX-2 gene, which behaves as an early TCR responsive gene. The data identify COX-1 and COX-2 as integral and sequential components of TCR signaling to p38 and contribute to elucidate the molecular basis of immunosuppression by NSAID.

Docking Protein Gab2 Is Phosphorylated by ZAP-70 and Negatively Regulates T Cell Receptor Signaling by Recruitment of Inhibitory Molecules

To maintain various T cell responses and immune equilibrium, activation signals triggered by T cell antigen receptor (TCR) must be regulated by inhibitory signals. Gab2, an adaptor protein of the insulin receptor substrate-1 family, has been shown to be involved in the downstream signaling from cytokine receptors. We investigated the functional role of Gab2 in TCR-mediated signal transduction. Gab2 was phosphorylated by ZAP-70 and co-precipitated with phosphoproteins, such as ZAP-70, LAT, and CD3zeta, upon TCR stimulation. Overexpression of Gab2 in Jurkat cells or antigen-specific T cell hybridomas resulted in the inhibition of NF-AT activation, interleukin-2 production, and tyrosine phosphorylation. The structure-function relationship of Gab2 was analyzed by mutants of Gab2. The Gab2 mutants lacking SHP-2-binding sites mostly abrogated the inhibitory activity of Gab2, but its inhibitory function was restored by fusing to active SHP-2 as a chimeric protein. A mutant with defective phosphatidylinositol 3-kinase binding capacity also impaired the inhibitory activity, and the pleckstrin homology domain-deletion mutant revealed a crucial function of the pleckstrin homology domain for localization to the plasma membrane. These results suggest that Gab2 is a substrate of ZAP-70 and functions as a switch molecule toward inhibition of TCR signal transduction by mediating the recruitment of inhibitory molecules to the TCR signaling complex.

Vanadium-induced Nuclear Factor of Activated T Cells Activation through Hydrogen Peroxide

The present study investigated the role of reactive oxygen species (ROS) in activation of nuclear factor of activated T cells (NFAT), a pivotal transcription factor responsible for regulation of cytokines, by vanadium in mouse embryo fibroblast PW cells or mouse epidermal Cl 41 cells. Exposure of cells to vanadium led to the transactivation of NFAT in a time- and dose-dependent manner. Scavenging of vanadium-induced H(2)O(2) with N-acety-L-cyteine (a general antioxidant) or catalase (a specific H(2)O(2) inhibitor) or the chelation of vanadate with deferoxamine, resulted in inhibition of NFAT activation. In contrast, an increase in H(2)O(2) generation by the addition of superoxide dismutase or NADPH enhanced vanadium-induced NFAT activation. This vanadate-mediated H(2)O(2) generation was verified by both electron spin resonance and fluorescence staining assay. These results demonstrate that H(2)O(2) plays an important role in vanadium-induced NFAT transactivation in two different cell types. Furthermore, pretreatment of cells with nifedipine, a calcium channel blocker, inhibited vanadium-induced NFAT activation, whereas and ionomycin, two calcium ionophores, had synergistic effects with vanadium for NFAT induction. Incubation of cells with cyclosporin A (CsA), a pharmacological inhibitor of the phosphatase calcineurin, blocked vanadium-induced NFAT activation. All data show that vanadium induces NFAT activation not only through a calcium-dependent and CsA-sensitive pathway but also involved H(2)O(2) generation, suggesting that H(2)O(2) may be involved in activation of calcium-calcineurin pathways for NFAT activation caused by vanadium exposure.