Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces rheumatoid arthritis synovial fibroblast proliferation through mitogen-activated protein kinases and phosphatidylinositol 3-kinase/Akt

Multiple effects of TRAIL in human carcinoma cells: induction of apoptosis, senescence, proliferation, and cytokine production

TRAIL is a death ligand that induces apoptosis in malignant but not normal cells. Recently the ability of TRAIL to induce proliferation in apoptosis-resistant normal and malignant cells was reported. In this study, we analyzed TRAIL effects in apoptosis sensitive MCF7, OVCAR3 and H460 human tumor cell lines. TRAIL at low concentrations preferentially induced cell proliferation. At 100 ng/ml, apoptotic death was readily observed, however surviving cells acquired higher proliferative capacity. TRAIL-stimulated production of several cytokines, IL-8, RANTES, MCP-1 and bFGF, and activation of caspases 1 and 8 was essential for this effect. Antibodies to IL-8, RANTES, and bFGF blocked TRAIL-induced cell proliferation and further stimulated apoptosis. For the first time, we report that high TRAIL concentrations induced cell senescence as determined by the altered morphology and expression of several senescence markers: SA-beta-gal, p21Waf1/Cip1, p16INK4a, and HMGA. Caspase 9 inhibition protected TRAIL-treated cells from senescence, whereas inhibition of caspases 1 and 8 increased the yield of SLP cells. In conclusion, in cultured human carcinoma cells, TRAIL therapy results in three functional outcomes, apoptosis, proliferation and senescence. TRAIL-induced proapoptotic and prosurvival responses correlate with the strength of signaling. TRAIL-induced cytokine production is responsible for its proliferative and prosurvival effects.

TRAIL stimulates proliferation of vascular smooth muscle cells via activation of NF-kappaB and induction of insulin-like growth factor-1 receptor

TRAIL/Apo2L (tumor necrosis factor-related apoptosis-inducing ligand) is a multifunctional protein regulating homeostasis of the immune system, infection, autoimmune diseases, and apoptosis. However, its function in normal, nontransformed tissues is not clear. Here we show that TRAIL increases vascular smooth muscle cell (VSMC) proliferation in vitro, effects that can be blocked with neutralizing antibodies to TRAIL receptors DR4 and DcR1. In aortocoronary saphenous vein bypass grafts in vivo, TRAIL co-localizes with VSMC, proliferating cell nuclear antigen, and insulin-like growth factor type 1 receptor (IGF1R) expression but not active caspase-3. TRAIL is required for serum-inducible IGF1R expression, and antisense IGF1R inhibits TRAIL-induced VSMC proliferation. At 1 ng/ml, TRAIL stimulates IGF1R mRNA expression greater than insulin-like growth factor-1 and also activates the IGF1R promoter 7-fold. TRAIL-inducible IGF1R expression requires NF-kappaB activation. Consistent with this, ammonium pyrrolidine dithiocarbamate, a pharmacological inhibitor of NF-kappaB, blocks TRAIL-induced IGF1R expression, and p65 overexpression increases IGF1R protein levels. In addition, NF-kappaB binds a novel TRAIL-responsive element on the IGF1R promoter. Our findings suggest that the biological functions of TRAIL in VSMC extend beyond its role in promoting apoptosis. Thus, TRAIL may play an important role in atherosclerosis by regulating IGF1R expression in VSMC in an NF-kappaB-dependent manner.

PI3-K/Akt-dependent activation of cAMP-response element-binding (CREB) protein in Jurkat T leukemia cells treated with TRAIL

We recently demonstrated the activation of phosphatidylinositol 3-kinase (PI3-K/Akt) survival pathway in Jurkat T leukemia cells known for their sensitivity to the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)/Apo2L cytotoxic action. The present investigation was done to elucidate the role of cAMP-response element-binding (CREB) protein in this system. Jurkat T cells were treated with 100-1,000 ng/ml TRAIL for time intervals up to 24 h in the presence or absence of selective pharmacologic inhibitors of PI3-K/Akt (LY294002) or p38 MAPK (SB253580) pathways. Upon TRAIL treatment, a dose-dependent increase in the percentage of apoptotic cells as well as in caspase-3 activity was observed. A further enhancement of apoptotic cell death was obtained with the use of CREB1 siRNA technology, as demonstrated by flow cytometry. Western blot analysis showed a high constitutive level of CREB phosphorylation at Ser(133) in Jurkat T cells under normal serum culture conditions. Under low serum culture conditions, an early (within 1 h) and transient increase in CREB phosphorylation was detected in response to both TRAIL doses and reduced upon pre-treatment with LY294002 or SB253580, demonstrating the PI3-K/Akt- and p38 MAPK-dependency of this effect. The parallel analysis in immune fluorescence demonstrated the nuclear translocation of the phosphorylated form upon treatment with 100 ng/ml TRAIL, whereas the immune labeling was mainly detectable in the cytoplasm compartment upon the higher more cytotoxic dose. These results let us hypothesize that CREB activation can be an important player in the complex cross-talk among pro- and anti-apoptotic pathways in this peculiar cell model.

TRAIL in cancer therapy: present and future challenges

Since its identification in 1995, TNF-related apoptosis-inducing ligand (TRAIL) has sparked growing interest in oncology due to its reported ability to selectively trigger cancer cell death. In contrast to other members of the TNF superfamily, TRAIL administration in vivo is safe. The relative absence of toxic side effects of this naturally occurring cytokine, in addition to its antitumoural properties, has led to its preclinical evaluation. However, despite intensive investigations, little is known in regards to the mechanisms underlying TRAIL selectivity or efficiency. An appropriate understanding of its physiological relevance, and of the mechanisms controlling cancer cells escape from TRAIL-induced cell death, will be required to optimally use the cytokine in clinics. The present review focuses on recent advances in the understanding of TRAIL signal transduction and discusses the existing and future challenges of TRAIL-based cancer therapy development.

Expression, regulation and function of trail in atherosclerosis

Atherosclerosis is a condition where vascular smooth muscle cells (VSMCs), inflammatory cells, lipids, cholesterol and cellular waste accumulate in the inner lining of an artery, producing a fibro-fatty plaque and resulting in the thickening of the arterial wall. The tumor necrosis factor (TNF) family of cytokines plays a major role in the progression of atherosclerosis. Recently, TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, has been implicated in the development of atherosclerosis since it has been detected in normal and diseased atherosclerotic tissue. Not only is TRAIL involved in apoptosis and immune regulation, recent studies have provided a new function of TRAIL on vascular cells, such that TRAIL can promote endothelial cell (EC) and VSMCs migration and proliferation. In addition, TRAIL is implicated in regulating vascular tone. This review discusses our current understanding of TRAIL expression, regulation and function, and summarises the recent data implicating a role for TRAIL in atherosclerosis.

Titin expression in human articular cartilage and cultured chondrocytes: a novel component in articular cartilage biomechanical sensing?

In striated muscle tissues, the giant protein titin acts as a biomechanically active filament system, coupling stress/strain to gene expression. The objective of the study is to show the existence of titin fragments in human articular cartilage, as in diarthodial joints, chondrocytes are also known to sense and respond to stretching. We have surveyed human cultured cartilage collected from adults with osteoarthritis (OA), without OA and from infants with a set of titin antibodies and primer pairs. Three different antibodies were used for immunolabelling, reacting with titin's N-terminal Z1-Z2 domains, its Novex III exon, and with its PEVK region. An antibody directed to a titin ligand was included, since in cardiac muscle, this has been shown to participate in the transmission of stretch dependent titin-based signals. Our results indicate that although at low levels, titin is expressed in cartilage. Primer pairs detected titin transcripts in cartilage, and consistent with this, antibodies directed to titin's Z-disc region and to its elastic region stained cartilage. Moreover, we also could detect transcription of the titin ligand CARP. Components of the stretch dependent signal machinery in muscle are also expressed in cartilage. Further studies are warranted to address if common stress/strain dependent signalling are conserved in muscle and cartilage tissues.

Inhibition of trail gene expression by cyclopentenonic prostaglandin 15-deoxy-delta12,14-prostaglandin J2 in T lymphocytes

15-Deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) is a cyclopentenonic prostaglandin endowed with powerful anti-inflammatory activities, as shown in animal models of inflammatory/autoimmune diseases, where pharmacological administration of this prostanoid can ameliorate inflammation and local tissue damage via activation of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) and/or covalent modifications of cellular proteins. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily expressed in most of the cells, including those of immune system such as T lymphocytes, in which it is up-regulated upon antigen-specific stimulation. This cytokine plays an important role in regulating various physiological and immunopathological processes, such as immunosurveillance of tumors and tissue destruction associated with different inflammatory and autoimmune diseases. Here, we demonstrate that 15d-PGJ(2) inhibits trail mRNA and protein expression by down-regulating the activity of its promoter in human T lymphocytes. Our data indicate that both the chemically reactive cyclopentenone moiety of 15d-PGJ(2) and the activation of PPARgamma may be involved in this repressive mechanism. We identified nuclear factor kappaB (NF-kappaB) as a direct target of the prostanoid. 15d-PGJ(2) significantly decreases the expression and/or DNA binding of c-rel, RelA, and p50 transcription factors to the NF-kappaB1 site of trail promoter. Moreover, 15d-PGJ(2)-mediated activation of the transcription factor heat shock factor-1 may contribute to inhibit trail promoter activity in transfected Jurkat T cells. These results suggest that modulation of TRAIL gene expression by 15d-PGJ(2) in T cells may provide a novel pharmacological tool to modify the onset and the progression of specific autoimmune and inflammatory disorders.

Reduction of TRAIL-induced Mcl-1 and cIAP2 by c-Myc or sorafenib sensitizes resistant human cancer cells to TRAIL-induced death

Cells expressing oncogenic c-Myc are sensitized to TNF superfamily proteins. c-Myc also is an important factor in determining whether a cell is sensitive to TRAIL-induced apoptosis, and it is well established that the mitochondrial pathway is essential for apoptosis induced by c-Myc. We investigated whether c-Myc action on the mitochondria is required for TRAIL sensitivity and found that Myc sensitized cells with defective intrinsic signaling to TRAIL. TRAIL induced expression of antiapoptotic Mcl-1 and cIAP2 through activation of NF-kappaB. Both Myc and the multikinase inhibitor sorafenib block NF-kappaB. Combining sorafenib with TRAIL in vivo showed dramatic efficacy in TRAIL-resistant tumor xenografts. We propose the combination of TRAIL with sorafenib holds promise for further development.

cFLIPL prevents TRAIL-induced apoptosis of hepatocellular carcinoma cells by inhibiting the lysosomal pathway of apoptosis

Sensitivity to TNF-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis and the lysosomal pathway of cell death are features of cancer cells. However, it is unknown if TRAIL cytotoxic signaling engages the lysosomal pathway of cell death. Our aim, therefore, was to ascertain if TRAIL killing involves lysosomal permeabilization. TRAIL-induced apoptosis of hepatocellular carcinoma cells (HuH-7, Hep3B) was associated with lysosomal permeabilization, as demonstrated by redistribution of the lysosomal protease cathepsin B into the cytosol. Pharmacological and short hairpin RNA-targeted inhibition of cathepsin B reduced apoptosis. Because cellular FLICE-inhibitory protein (cFLIP) inhibits TRAIL-induced cell death and is frequently overexpressed by human cancers, the ability of cFLIP to prevent lysosomal permeabilization during TRAIL treatment was examined. Enforced long-form cFLIP (cFLIP(L)) expression reduced release of cathepsin B from lysosomes and attenuated apoptosis. cFLIP(L) overexpression was also associated with robust p42/44 MAPK activation following exposure to TRAIL. In contrast, cFLIP(L) overexpression attenuated p38 MAPK activation and had no significant effect on JNK and NF-kappaB activation. Inhibition of p42/44 MAPK by PD98059 restored TRAIL-mediated lysosomal permeabilization and apoptosis in cFLIP-overexpressing cells. In conclusion, these results demonstrate that lysosomal permeabilization contributes to TRAIL-induced apoptosis of hepatocellular carcinoma cells and suggest that cFLIP(L) cytoprotection is, in part, due to p42/44 MAPK-dependent inhibition of lysosomal breakdown.

T Cell TRAIL Promotes Murine Lupus by Sustaining Effector CD4 Th Cell Numbers and by Inhibiting CD8 CTL Activity

T cells play an essential role in driving humoral autoimmunity in lupus. Molecules such as TRAIL exhibit strong T cell modulatory effects and are up-regulated in lupus, raising the possibility that they may influence disease severity. To address this possibility, we examined the role of TRAIL expression on pathogenic T cells in an induced model of murine lupus, the parent-into-F(1) (P-->F(1)) model of chronic graft-vs-host disease (GVHD), using wild-type or TRAIL-deficient donor T cells. Results were compared with mice undergoing suppressive acute GVHD. Although chronic GVHD mice exhibited less donor T cell TRAIL up-regulation and IFN-alpha-inducible gene expression than acute GVHD mice, donor CD4(+) T cell TRAIL expression in chronic GVHD was essential for sustaining effector CD4(+) Th cell numbers, for sustaining help to B cells, and for more severe lupus-like renal disease development. Conversely, TRAIL expression on donor CD8(+) T cells had a milder, but significant down-regulatory effect on CTL effector function, affecting the perforin/granzyme pathway and not the Fas ligand pathway. These results indicate that, in this model, T cell-expressed TRAIL exacerbates lupus by the following: 1) positively regulating CD4(+) Th cell numbers, thereby sustaining T cell help for B cells, and 2) to a lesser degree by negatively regulating perforin-mediated CD8(+) CTL killing that could potentially eliminate activated autoreactive B cells.

Proinflammatory effects of tumour necrosis factor-like weak inducer of apoptosis (TWEAK) on human gingival fibroblasts

Tumour necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK), a member of the TNF family, is a multi-functional cytokine that regulates cellular proliferation, angiogenesis, inflammation and apoptosis. In this study, we investigated TWEAK expression in periodontally diseased tissues and the effect of TWEAK on human gingival fibroblasts (HGF). Reverse transcription-polymerase chain reaction (RT-PCR) analysis and immunohistochemistry revealed that TWEAK and the TWEAK receptor, fibroblast growth factor-inducible 14 (Fn14), mRNA and protein were expressed in periodontally diseased tissues. HGF expressed Fn14 and produced interleukin (IL)-8 and vascular endothelial growth factor (VEGF) production upon TWEAK stimulation in a dose-dependent manner. The IL-8 and VEGF production induced by TWEAK was augmented synergistically by simultaneous stimulation with transforming growth factor (TGF)-beta1 or IL-1beta. IL-1beta and TGF-beta1 enhanced Fn14 expression in a dose-dependent manner. Moreover, TWEAK induced intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression on HGF in a dose-dependent manner. The ICAM-1 expression induced by TWEAK was augmented by TGF-beta1. On the other hand, the TWEAK-induced VCAM-1 expression was inhibited by TGF-beta1. Phosphatidylinositol 3-kinase (PI3K) and nuclear factor-kappaB (NF-kappaB) inhibitor inhibit both ICAM-1 and VCAM-1 expression induced by TWEAK. However, mitogen-activated protein kinase (MEK) and c-Jun NH2-terminal kinase (JNK) inhibitor enhanced only VCAM-1 expression on HGF. These results suggest that TWEAK may be involved in the pathophysiology of periodontal disease. Moreover, in combination with IL-1beta or TGF-beta1, TWEAK may be related to the exacerbation of periodontal disease to induce proinflammatory cytokines and adherent molecules by HGF.

TRAIL signalling: decisions between life and death

The TNF-related apoptosis-inducing ligand, TRAIL, has been shown to selectively kill tumour cells. This property has made TRAIL and agonistic antibodies against its death inducing receptors (TRAIL-R1 and TRAIL-R2) to some of the most promising novel biotherapeutic agents for cancer therapy. Here we review the signalling pathways initiated by the apoptosis- as well as the non-apoptosis-inducing receptors, TRAIL-R3 and TRAIL-R4. The TRAIL "death-inducing signalling complex" (DISC) transmits the apoptotic signal. DISC formation leads to activation of a protease cascade, finally resulting in cell death. The TRAIL death receptor-mediated "extrinsic" pathway and the "intrinsic" pathway, which is controlled by the interaction of members of the Bcl-2 family, interact with each other in the decision about life or death of a cell. Apoptotic and non-apoptotic signalling is influenced by the NF-kappaB, PKB/Akt and the MAPK signalling pathways. In this review we intend to summarise the most important findings on the TRAIL signalling network and the interplay in the decisions between life and death of a tumor cell.

Interaction of vascular endothelial growth factor 165 with neuropilin-1 protects rheumatoid synoviocytes from apoptotic death by regulating Bcl-2 expression and Bax translocation

Rheumatoid arthritis (RA) synoviocytes are resistant to apoptosis and exhibit a transformed phenotype, which might be caused by chronic exposure to genotoxic stimuli including reactive oxygen species and growth factors. In this study, we investigated the role of vascular endothelial growth factor165 (VEGF165), a potent angiogenic factor, and its receptor in the apoptosis of synoviocytes. We demonstrated here that neuropilin-1, rather than fms-like tyrosine kinase-1 and kinase insert domain-containing receptor, is the major VEGF165 receptor in the fibroblast-like synoviocytes. Neuropilin-1 was highly expressed in the lining layer, infiltrating leukocytes, and endothelial cells of rheumatoid synovium. The production of VEGF165, a ligand for neuropilin, was significantly higher in the RA synoviocytes than in the osteoarthritis synoviocytes. The ligation of recombinant VEGF165 to its receptor prevented the apoptosis of synoviocytes induced by serum starvation or sodium nitroprusside (SNP). VEGF165 rapidly triggered phospho-Akt and phospho-ERK activity and then induced Bcl-2 expression in the rheumatoid synoviocytes. The Akt or ERK inhibitor cancelled the protective effect of VEGF165 on SNP-induced synoviocyte apoptosis. Moreover, VEGF165 blocks SNP-induced Bcl-2 down-regulation as well as SNP-induced Bax translocation from the cytosol to the mitochondria. The down-regulation of the neuropilin-1 transcripts by short interfering RNA caused spontaneous synoviocyte apoptosis, which was associated with both the decrease in Bcl-2 expression and the increase in Bax translocation to mitochondria. Collectively, our data suggest that the interaction of VEGF165 with neuropilin-1 is crucial to the survival of rheumatoid synoviocytes and provide important implications for the abnormal growth of synoviocytes and therapeutic intervention in RA.

Phosphoinositide 3-kinase signalling and FoxO transcription factors in rheumatoid arthritis

Although the mechanisms leading to the induction of RA (rheumatoid arthritis) are poorly understood, improper activation, proliferation, survival and retention of neutrophils, macrophages, lymphocytes and other leucocytes contribute to perpetuation of inflammation and eventual joint destruction through activation of stromal fibroblast-like synoviocytes. Fundamental studies in developmental biology, cellular biology and immunology have established critical roles for PI3K (phosphoinositide 3-kinase) signal transduction pathways in cellular chemotactic responses, proliferation, apoptosis and survival. Despite profound alteration of these cellular processes in RA, involvement of PI3K signalling pathways in this chronic inflammatory disease, and their assessment as potential therapeutic targets, has until recently received scant attention. This review highlights recent advances in our understanding of PI3K signalling pathways, in particular regulation of FoxO (forkhead box O) transcription factors, and their relevance to RA.

Evidence for two modes of development of acquired tumor necrosis factor-related apoptosis-inducing ligand resistance. Involvement of Bcl-xL

Previous studies have shown that repeated application of TRAIL induces acquired resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Using human prostate adenocarcinoma DU-145 and human pancreatic carcinoma MiaPaCa-2 cells as a model, we now demonstrate for the first time that two states of acquired TRAIL resistance can be developed after TRAIL treatment. Data from survival assay and Western blot analysis show that acquired TRAIL resistance was developed within 1 day and gradually decayed within 6 days after TRAIL treatment in both cell lines. After TRAIL treatment, the level of Bcl-xL increased and reached a maximum within 2 days and gradually decreased in both cell lines. Bcl-xL-mediated development of acquired TRAIL resistance was suppressed by knockdown of Bcl-xL expression. Protein interaction assay revealed that during the development of TRAIL resistance, Bcl-xL dissociated from Bad and then associated with Bax. Overexpression of mutant-type Bad (S136A), which prevents this dissociation, partially suppressed the development of acquired TRAIL resistance. Thus, our results suggest that (a) dissociation of Bad from Bcl-xL and (b) an increase in the intracellular level of Bcl-xL are responsible for development of acquired TRAIL resistance.

Trail interacts redundantly with nitric oxide in rat astrocytes: potential contribution to neurodegenerative processes

The proapoptotic cytokine TRAIL has been shown to enhance amyloid-beta-dependent neurotoxicity. Here are reported interactions between TRAIL and nitric oxide (NO) in cultured rat astrocytes in vitro. Rat astrocytes expressed all TRAIL receptor mRNAs and proteins. However, TRAIL failed in inducing apoptosis of astrocytes, whereas these cells released substantial amounts of nitrites. A TRAIL-neutralizing antibody was able to prevent LPS-induced iNOS expression in astrocytes. Interestingly, TRAIL induced its own expression in astrocytes. These data suggest that redundancy between TRAIL and NO in astrocytes could be fueling neuronal damage/death processes, potentially uncovering novel molecular targets for the treatment of neurodegenerative disorders.

JAB1 determines the response of rheumatoid arthritis synovial fibroblasts to tumor necrosis factor-alpha

Fibroblast-like synoviocytes (FLSs) of patients with rheumatoid arthritis (RA FLSs) exhibit prosurvival, rather than apoptotic, response to tumor necrosis factor (TNF)-alpha stimulation. Here, we show that JAB1 is a critical regulator of the TNF-alpha-mediated anti-apo-ptosis pathways in RA FLSs. We found that knockdown of JAB1 using small interfering (si)RNA led to restoration of the TNF-alpha-induced apoptosis response, reduction of nuclear factor-kappaB activity, delayed degradation of IkappaB-alpha, and inhibited phosphorylation of JNK. Analysis of the interactions of JAB1 by reciprocal co-immunoprecipitations and confocal microscopy revealed that JAB1 interacts with TNF receptor-associated-factor 2 (TRAF2). The generation of the anti-apoptotic signal on binding of TNF-alpha to the TNF receptor (TNFR)1 has been shown to be associated with the recruitment of TRAF2 to the TNFR1 in a process that requires ubiquitination of TRAF2 with lysine-63-linked polyubiquitin chains. We found that TNF-alpha stimulation of JAB1 siRNA-transfected RA FLSs failed to stimulate ubiquitination of TRAF2. Thus, we conclude that JAB1-regulated ubiquitination of TRAF2 is a novel mechanism whereby TNF-alpha can induce anti-apoptosis signaling and production of matrix metalloproteinases through activation of nuclear factor-kappaB and JNK in RA FLSs.

TNF-related apoptosis-inducing ligand as a therapeutic agent in autoimmunity and cancer

Recombinant, soluble TNF-related apoptosis-inducing ligand (TRAIL) is currently being developed as a promising natural immune molecule for trial in cancer patients because it selectively induces apoptosis in transformed or stressed cells but not in most normal cells. In cancer patients, phase 1 and 2 clinical trials using agonistic mAbs that engage the human TRAIL receptors DR4 and DR5 have also provided encouraging results. It is now evident that TRAIL suppresses autoimmune disease in various experimental animal models, suggesting that the therapeutic value of recombinant TRAIL and agonistic DR4 and DR5 mAbs might also extend to the suppression of autoimmune disease. This review provides an insight into our current understanding of the role(s) of TRAIL in disease, with a specific focus on cancer and autoimmunity. We also emphasize biological agents and drugs that sensitize tumour cells to TRAIL-mediated apoptosis and discuss the potential molecular basis for their sensitization.

The role of PI3K/AKT, MAPK/ERK and NFkappabeta signalling in the maintenance of human embryonic stem cell pluripotency and viability highlighted by transcriptional profiling and functional analysis

Understanding the molecular mechanism by which pluripotency is maintained in human embryonic stem cells (hESC) is important for the development of improved methods to derive, culture and differentiate these into cells of potential therapeutic use. Large-scale transcriptional comparison of the hES-NCL1 line derived from a day 8 embryo with H1 line derived from a day 5 embryo (WiCell Inc.) showed that only 0.52% of the transcripts analysed varied significantly between the two cell lines. This is within the variability range that has been reported when hESC derived from days 5-6 embryos have been compared with each other. This implies that transcriptional differences between the cell lines are likely to reflect their genetic profile rather than the embryonic stage from which they were derived. Bioinformatic analysis of expression changes observed when these cells were induced to differentiate as embryoid bodies suggested that quite a few of the downregulated genes were components of signal transduction networks. Subsequent analysis using western blotting, flow cytometry and antibody arrays implicated components of the PI3K/AKT kinase, MAPK/ERK and NFkappabeta pathways and confirmed that these components are decreased upon differentiation. Disruption of these pathways in isolation using specific inhibitors resulted in loss of pluripotency and/or loss of viability suggesting the importance of such signalling pathways in embryonic stem cell maintenance.

Remitting seronegative symmetrical synovitis pitting oedema after BCG instillation

Remitting seronegative symmetrical synovitis pitting oedema (RS3PE) is a distinct form of seronegative rheumatoid arthritis like polyarthritis. It is characterized by late onset symmetrical joint involvement and pitting oedema of hands and feet (JAMA 254(19):2763-2767, [1]). Polyarthritis secondary to intravesical Bacillus Calmette Guerin (BCG) therapy has been reported (Clin Rheumatol 21:536-537, [2]). To our knowledge, about 0.5% of patients receiving BCG instillation presented polyarthritis, but only one case of RS3PE has been reported (J Rheumatol 28:1699-1701, [3]). We described the second case of RS3PE following intravesical BCG instillation of bladder carcinoma.

Trichostatin A sensitises rheumatoid arthritis synovial fibroblasts for TRAIL-induced apoptosis

BACKGROUND

Histone acetylation/deacetylation has a critical role in the regulation of transcription by altering the chromatin structure.

OBJECTIVE

To analyse the effect of trichostatin A (TSA), a streptomyces metabolite which specifically inhibits mammalian histone deacetylases, on TRAIL-induced apoptosis of rheumatoid arthritis synovial fibroblasts (RASF).

METHODS

Apoptotic cells were detected after co-treatment of RASF with TRAIL (200 ng/ml) and TSA (0.5, 1, and 2 micromol/l) by flow cytometry using propidium iodide/annexin-V-FITC staining. Cell proliferation was assessed using the MTS proliferation test. Induction of the cell cycle inhibitor p21Waf/Cip1 by TSA was analysed by western blot. Expression of the TRAIL receptor-2 (DR5) on the cell surface of RASF was analysed by flow cytometry. Levels of soluble TRAIL were measured in synovial fluid of patients with RA and osteoarthritis (OA) by ELISA.

RESULTS

Co-treatment of the cells with TSA and TRAIL induced cell death in a synergistic and dose dependent manner, whereas TRAIL and TSA alone had no effect or only a modest effect. RASF express DR5 (TRAIL receptor 2), but treatment of the cells with TSA for 24 hours did not change the expression level of DR5, as it is shown for cancer cells. TSA induced cell cycle arrest in RASF through up regulation of p21Waf1/Cip1. Levels of soluble TRAIL were significantly higher in RA than in OA synovial fluids.

CONCLUSION

Because TSA sensitises RASF for TRAIL-induced apoptosis, it is concluded that TSA discloses sensitive sites in the cascade of TRAIL signalling and may represent a new principle for the treatment of RA.

Nonapoptotic functions of FADD-binding death receptors and their signaling molecules

Death receptors (DRs) are surface receptors that when triggered have the capacity to induce apoptosis in cells by forming the death-inducing signaling complex (DISC). The first protein recruited to form the DISC is the adaptor protein FADD/Mort1. Some members of the DR family, CD95 and the TRAIL receptors DR4 and DR5, directly bind FADD, whereas others, such as TNF receptor I and DR3, initially bind another adaptor protein, TRADD, which then recruits FADD. While all DRs can activate both apoptotic and non-apoptotic pathways, it has been widely assumed that the main physiological role of FADD-binding death receptors is to trigger apoptosis. However, recent work has ascribed multiple non-apoptotic activities to these receptors and/or the signaling components of the DISC.