Fas (CD95)-related apoptosis and rheumatoid arthritis

The development of anti-PD-1 antibody-induced spinal cord injury in bone marrow transplant C57BL/6 Rag1-/- mouse model

Aims: This paper was to scrutinize the toxicity mechanism of anti-programmed death 1 (anti-PD-1) therapy-caused spinal cord injury (SCI). Methods: Bone marrow transplant Rag1-/- mice were used to establish SCI model. Results: Anti-PD-1 results in SCI via CD8+ T-cells activation, while excessive activation of CD8+ T-cells further aggravated SCI. Both anti-PD-1 and the activation of CD8+ T-cells induced the expression of apoptosis-related perforin, GrB and FasL, but suppressed PI-9 level. The opposite results were observed in the effects of neuroserpin on these factors. CD8+ T-cells activation induced neurotoxicity via upregulation perforin, GrB and FasL and inhibiting PI-9. Additionally, neuroserpin suppressed CD8+ T-cells activation via perforin/GrB/PI-9/FasL pathways. Conclusion: These results may provide theoretical foundation for the clinical treatment of SCI caused by anti-PD-1.

Leukocyte Ig-like receptor A3 facilitates inflammation, migration and invasion of synovial tissue-derived fibroblasts via ERK/JNK activation

OBJECTIVE

Leukocyte Ig-like receptor A3 (LILRA3) is a soluble receptor belongs to the immunoglobulin superfamily. Our previous studies demonstrated that LILRA3 is a common genetic risk for multiple autoimmune diseases, including RA. Functional LILRA3 conferred increased risk of joint destruction in patients with early RA. We undertook this study to further investigate the pathological role of LILRA3 in joint inflammation of RA.

METHODS

Soluble LILRA3 was measured by ELISA. LILRA3 plasmids were transfected into human fibroblast-like synoviocytes (FLSs) using electroporation. Activation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) was determined by western blots. Cytokine transcripts were quantified by real-time PCR. Migratory and invasive capacities of FLSs were evaluated using transwell migration and Matrigel invasion assays. FLS apoptosis was analysed using flow cytometry. Colocalization of LILRA3, LILRB1 and HLA-G in RA-FLSs was visualized by immunofluorescence staining.

RESULTS

Soluble LILRA3 was specifically expressed in synovial fluid and serum LILRA3 was significantly increased and positively correlated with disease activity/severity in RA patients. LILRA3 induced an increased expression of IL-6, IL-8 and MMP3 in RA-FLSs. In vitro LILRA3 stimulation or overexpression promoted RA-FLS migration and invasion, and enhanced phosphorylation of ERK/JNK. Inhibition of ERK/JNK resulted in suppression of IL-6/IL-8 expression in LILRA3-stimulated RA-FLSs. LILRA3 was co-localized with its homologue LILRB1 and shared ligand HLA-G in RA-FLSs.

CONCLUSION

The present study provides the first evidence that soluble LILRA3 is a novel proinflammatory mediator involved in synovial inflammation by promoting RA-FLS activation, migration and invasion, probably through the ERK/JNK signalling pathways.

Identification and Development of Synovial B-Cell-Related Genes Diagnostic Signature for Rheumatoid Arthritis

Background

The aim of the study was to investigate the landscape of B-cell-related gene expression profiling in rheumatoid arthritis (RA) synovium and explore the biological and clinical significance of these genes in RA.

Methods

Expression profiling of synovial biopsies from subjects with 152 RA patients, 22 osteoarthritis (OA) patients, and 28 healthy controls was downloaded from the Gene Expression Omnibus database. Single-sample gene set enrichment analysis (ssGSEA) was performed to evaluate the abundance of infiltrated immune cells, and the results were validated using immunohistochemical staining. GSEA was employed to decipher differences in B-cell-related biological pathways. B-cell-related differential expression genes (BRDEGs) were screened, and BRDEGs-based model was developed by machine learning algorithms and evaluated by an external validation set and clinical RA cohort, then biological functions were further analyzed.

Results

High levels of immune cell infiltration and B-cell-related pathway activation were revealed in RA synovium. BRDEGs were screened, and three key molecular markers consisting of FAS, GPR183, and TFRC were identified. The diagnosis model was established, and these gene markers have good discriminative ability for RA. Molecular pathological evaluation confirmed RA patients with high-risk scores presented higher levels of B-cell activation and RA characteristics. In addition, a competitive endogenous RNA network was established to elucidate the molecular mechanisms of the posttranscriptional network.

Conclusions

We described the B-cell-related molecular landscape of RA synovium and constructed a molecular diagnostic model in RA. The three genes FAS, GPR183, and TFRC may be potential targets for clinical diagnosis and immunoregulatory therapy of RA.

Expression profiling of genes in rheumatoid fibroblast-like synoviocytes regulated by Fas ligand via cDNA microarray analysis

Rheumatoid arthritis (RA) is an autoimmune disease that causes chronic inflammation in synovial tissues. Hyperplasia of synovial tissues leads to the formation of pannus that invades the joint cartilage and bone, resulting in joint destruction. Fas ligand (FasL), which is a member of the tumor necrosis factor superfamily, contributes to the pathogenesis of autoimmune diseases, including RA. The current study attempted to identify genes whose expressions in rheumatoid fibroblast-like synoviocytes (RA-FLS) were regulated by FasL, using cDNA microarray. A total of four individual lines of primary cultured RA-FLS were incubated either with recombinant human FasL protein or PBS as an unstimulated control for 12 h. Gene expression was detected using a microarray assay. The results revealed the expression profiles of genes in RA-FLS regulated by Fas and investigated the functions of the genes that were regulated. Among the genes in this profile, the mRNA expression changes of the following genes were indicated to be of note using RT-qPCR: Dual specificity phosphatase 6, epiregulin, interleukin 11, angiopoietin-like 7, protein inhibitor of activated STAT 2 and growth differentiation factor 5. These genes may affect the pathogenesis of RA by affecting apoptosis, proliferation, cytokine production, cytokine-induced inflammation, intracellular signaling, angiogenesis, bone destruction and chondrogenesis. To the best of our knowledge, the current study is the first study to reveal the expression profile of genes in RA-FLS regulated by FasL. The data demonstrated that FasL may regulate the expression of a number of key molecules in RA-FLS, thus affecting RA pathogenesis. Further studies of the genes detected may improve the understanding of RA pathogenesis and provide novel treatment targets for RA.

Changes in genotoxicity, inflammatory and oxidative stress parameters of workers in marble processing plants

Workers in marble processing plants are at high risk of exposure to high levels of marble dust containing silica, but there are limited studies evaluating the genotoxicity and oxidative stress parameters of workers occupationally exposed to marble dust. In this study, we aimed to clarify how marble dust affects genotoxicity and immunotoxicity mechanisms alongside oxidative stress in the workers in the marble processing plants of Iscehisar, Turkey. The oxidative stress and immune system parameters were determined spectrophotometrically using commercial kits. Genotoxicity was evaluated by Comet and micronucleus (MN) assays in the lymphocytes and buccal cells, respectively. The enzyme activities of superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, and the levels of glutathione, and Clara cell secretory protein CC16 in workers (n = 48) were significantly lower than in controls (n = 41), whereas the levels of malondialdehyde, 8-oxo-7,8-dihydro-2'-deoxyguanosine, tumor necrosis factor-alpha, interleukin-1beta were significantly higher in workers. DNA damage in workers were significantly higher than in controls and there was a clear correlation between the increase in DNA damage and the duration of exposure. Marble workers had significantly higher MN frequencies when compared to controls. The results indicate the possibility of immunotoxic and genotoxic risks to workers in marble industry.

Genetic and molecular biology of systemic lupus erythematosus among Iranian patients: an overview

BACKGROUND

Systemic lupus erythematosus (SLE) is a clinicopathologically heterogeneous chronic autoimmune disorder affecting different organs and tissues. It has been reported that there is an increasing rate of SLE incidence among Iranian population. Moreover, the Iranian SLE patients have more severe clinical manifestations compared with other countries. Therefore, it is required to introduce novel methods for the early detection of SLE in this population. Various environmental and genetic factors are involved in SLE progression.

MAIN BODY

In present review we have summarized all of the reported genes which have been associated with clinicopathological features of SLE among Iranian patients.

CONCLUSIONS

Apart from the reported cytokines and chemokines, it was interestingly observed that the apoptosis related genes and non-coding RNAs were the most reported genetic abnormalities associated with SLE progression among Iranians. This review clarifies the genetics and molecular biology of SLE progression among Iranian cases. Moreover, this review paves the way of introducing an efficient panel of genetic markers for the early detection and better management of SLE in this population.

Effects of sorafenib on fibroblast-like synoviocyte apoptosis in rats with adjuvant arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that is characterized by synovial inflammation and hyperplasia resulting from an imbalance between the proliferation and apoptosis of fibroblast-like synoviocytes (FLSs). Our previous study found that sorafenib had inhibitory effects in rats with adjuvant arthritis (AA). The present study investigated the role of sorafenib in the induction of AA FLS apoptosis in vitro. FLSs obtained from AA rats were cultured in vitro and identified. Cell apoptosis was detected using terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and annexin V-fluorescein isothiocyanate (FITC) and propidium iodide (PI) labeling methods. Real-time PCR and Western blotting assays were used to quantify the expression levels of Fas, Caspase-3, Mcl-1, NF-κB and C-jun gene products in AA FLSs. Our data revealed that sorafenib (4 μmol/L) induced apoptosis in AA FLSs, and flow cytometry analysis showed that AA FLSs treated with sorafenib (4 μmol/L) in vitro accumulated in early and late apoptosis. There were significant increases in the expression levels of Fas, Caspase-3 and Mcl-1, and significant decreases in NF-κB and C-jun expression in AA FLSs treated with sorafenib. In summary, these results demonstrate that sorafenib promotes AA FLS apoptosis, which may be related to the upregulation of Fas and Caspase-3 and downregulation of NF-κB and C-jun. All of these findings suggest that sorafenib exerts an inhibitory effect on AA rats in vivo via AA FLS apoptotic induction, which has potential therapeutic implications for RA.

Investigation of the Association Between Carotid Artery Intima-Media Thickness (IMT) and Cardiac Risk Factors in Patients with Systemic Lupus Erythematosus

BACKGROUND

The relationship between SLE and traditional risk factors for cardiovascular events was evaluated.

METHODS

The data regarding sixty patients with SLE and 30 healthy controls (age and sex matched) were gathered using SLEDAI forms. Venous blood (10mL) from all the participants was examined for hs-CRP, homocysteine, VCAM1, CBC, anti-DNA antibody, C3, C4, low-density lipoprotein (LDL), cholesterol, FBS and triglyceride. The IMT of carotid arteries was determined bilaterally by ultrasound. Other measurements included insulin levels via Elisa (Linco/Millipore Corp) and the HOMA-IR index for insulin resistance.

RESULTS

The mean age (in years) in the test and control groups was 28.8±10.3 (18-52) and 33.8±9.13 (18-48), respectively. The average IMT in the test group was directly related to serum levels of VCAM1 (p<0.001), homocysteine (p<0.001), cholesterol (p<0.009), LDL (p<0.001), TG (p<0.001), and FPG (p=0.004). The association between other risk factors, insulin resistance, carotid IMT and SLEDAI, was nonexistent. Mean insulin and insulin resistance levels in all the participants were 0.43±2.06 µU/mL and 0.09±0.44, respectively. There was no significant difference between the test and control groups regarding serum insulin and insulin resistance levels (p=0.42 and p=0.9, respectively). None of the risk factors, such as hsCRP, VCAM1, or homocysteine, were shown to be related to insulin resistance (p=0.6, p=0.6, p=0.09, respectively).

CONCLUSION

Our findings did not show an increase in the prevalence of atherosclerosis in patients with SLE. There was no association between IMT and insulin resistance. However, the former was associated with FPG, total cholesterol, LDL, TG, homocystein and VCAM1.

Low intensity pulsed ultrasound increases mandibular height and Col-II and VEGF expression in arthritic mice

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic inflammatory disease involving persistent inflammation resulting in cartilage and bone damage. RA can affect the temporomandibular joint (TMJ), and damage to the TMJ condyle can lead to craniofacial developmental disturbances, causing micrognathia, malocclusion, retrognathia, and increased overjet. Current treatments of TMJ arthritis are unsatisfactory. This pilot study aimed to investigate the effect of low intensity pulsed ultrasound (LIPUS) on the mandible and TMJ condyles in an RA mouse model using micro-computed tomography (Micro-CT), histologic, and immunohistochemical analyses.

METHODS

MRL-lpr/lpr mice received LIPUS application to their TMJs for 20 min/day for 2 and 4 weeks. Micro-CT analysis measured condylar length and width, posterior mandibular height (P.M.H), mandibular ramus length (M.R.L), effective mandibular length (Ef.M.L), angular process length (A.P.L), mandibular plane (M.P), mandibular axis (M.Ax), and lower incisor height (L.I.H). Condylar cartilage thickness was histologically measured, and type II collagen (Col-II), vascular endothelial growth factor (VEGF), nuclear factor kappa-B ligand (RANKL), and osteoprotegerin (OPG) expression was analyzed using immunohistochemistry.

RESULTS

Comparing the LIPUS-treated group with the control, P.M.H, M.R.L, and M.P were significantly greater in the LIPUS-treated group. Immunostaining for Col-II and VEGF was stronger in the LIPUS-treated group after 4 weeks. OPG showed slightly more expression in the LIPUS group.

CONCLUSIONS

LIPUS may enhance mandibular and TMJ condylar bone formation in this RA mouse model by preventing any growth disturbances involved in inflammation. Further studies are recommended to analyze the effect of LIPUS on TMJ of RA in other animal models.

ADAM15 in Apoptosis Resistance of Synovial Fibroblasts: Converting Fas/CD95 Death Signals Into the Activation of Prosurvival Pathways by Calmodulin Recruitment

OBJECTIVE

To investigate mechanisms underlying the capability of ADAM15 to transform FasL-mediated death-inducing signals into prosurvival activation of Src and focal adhesion kinase (FAK) in rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS

Caspase 3/7 activity and apoptosis rate were determined in RASFs and ADAM15-transfected T/C28a4 cells upon Fas/CD95 triggering using enzyme assays and annexin V staining. Phosphorylated Src and FAK were analyzed by immunoblotting. Interactions of ADAM15 and CD95 with calmodulin (CaM), Src, or FAK were analyzed by pull-downs using CaM-Sepharose and coimmunoprecipitations with specific antibodies. Protein binding assays were performed using recombinant CaM and ADAM15. Immunofluorescence was performed to investigate subcellular colocalization of ADAM15, Fas/CD95, and CaM.

RESULTS

The antiapoptotic effect of ADAM15 in FasL-stimulated cells was demonstrated either by increased apoptosis of cells transfected with an ADAM15 construct lacking the cytoplasmic domain compared to cells transfected with full-length ADAM15 or by reduced apoptosis resistance of RASFs upon RNA interference silencing of ADAM15. Fas ligation triggered a Ca²⁺  release-activated Ca²⁺ /calcium release-activated calcium channel protein 1 (CRAC/Orai1) channel-dependent CaM recruitment to Fas/CD95 and ADAM15 in the cell membrane. Simultaneously, Src associated with CaM was shown to become engaged in the ADAM15 complex also containing cytoplasmic-bound FAK. Accordingly, Fas ligation in RASFs led to ADAM15-dependent phosphorylation of Src and FAK, which was associated with increased survival. Pharmacologic interference with either the CaM inhibitor trifluoperazine or the CRAC/Orai inhibitor BTP-2 simultaneously applied with FasL synergistically enhanced Fas-mediated apoptosis in RASFs.

CONCLUSION

ADAM15 provides a scaffold for formation of CaM-dependent prosurvival signaling complexes upon CRAC/Orai coactivation by FasL-induced death signals and a potential therapeutic target to break apoptosis resistance in RASFs.

Fas receptor induces apoptosis of synovial bone and cartilage progenitor populations and promotes bone loss in antigen-induced arthritis

Rheumatoid arthritis (RA) is an inflammatory joint disease that eventually leads to permanent bone and cartilage destruction. Fas has already been established as the regulator of inflammation in RA, but its role in bone formation under arthritic conditions is not completely defined. The aim of this study was to assess the effect of Fas inactivation on the bone damage during murine antigen-induced arthritis. Subchondral bone of wild-type (WT) and Fas-knockout (Fas^-/-) mice was evaluated by histomorphometry and microcomputerized tomography. Proportions of synovial bone and cartilage progenitors were assessed by flow cytometry. Synovial bone and cartilage progenitors were purified by fluorescence-activated cell sorting and expression of Fas and Fas-induced apoptosis were analyzed in vitro. Results showed that Fas^-/- mice developed attenuated arthritis characterized by preserved epiphyseal bone and cartilage. A proportion of the earliest CD200⁺ bone and cartilage progenitors was reduced in WT mice with arthritis and was unaltered in Fas^-/- mice. During osteoblastic differentiation in vitro, CD200⁺ cells express the highest levels of Fas and are removed by Fas ligation. These results suggest that Fas-induced apoptosis of early CD200⁺ osteoprogenitor population represents potential mechanism underlying the impaired bone formation in arthritis, so their preservation may represent the bone-protective mechanism during arthritis.-Lazić Mosler, E., Lukač, N., Flegar, D., Fadljević, M., Radanović, I., Cvija, H., Kelava, T., Ivčević, S., Šućur, A., Markotić, A., Katavić, V., Marušić, A., Grčević, D., Kovačić, N. Fas receptor induces apoptosis of synovial bone and cartilage progenitor populations and promotes bone loss in antigen-induced arthritis.

Uncovering Cellular retinoic acid-binding protein 2 as a potential target for rheumatoid arthritis synovial hyperplasia

Rheumatoid arthritis (RA) is a systemic autoimmune disease including synovitis and synovial hyperplasia that contribute to joint destruction. Pivotal pathogenic mechanisms in this process are the dysregulated proliferation and apoptosis of fibroblast-like synoviocytes (FLS). Unfortunately, the mechanisms of FLS dysregulation are not completely elucidated. Here, we explored a new hypothesis based in the potent anti-proliferative and pro-apoptotic activity of retinoids in some types of cancer. Specifically, we investigated the role of retinoids and of the retinoic acid binding proteins, CRABP2 and FABP5, on the proliferation and apoptosis of FLS from RA by adding all-trans retinoic acid (ATRA) or silencing CRABP2 and FABP5. We showed an unconventional behaviour of RA FLS, which were relatively insensitive to ATRA. In effect, ATRA increased the resistance to apoptosis despite the high CRABP2/FABP5 ratio of RA FLS; and CRABP2 suppression sensitized RA FLS to Fas-induced apoptosis. This latter effect was associated with changes in expression of kinases, ASK1 up-regulation and ERK down-regulation, and increased phosphorylation of JNK. In addition, the potentiation of FLS apoptosis by CRABP2 silencing persisted in the presence of pro-inflammatory mediators, TNF e IL1β. Therefore, the results point to CRABP2 as a potential target to decrease synovial hyperplasia in RA.

Use of Lentiviral Particles As a Cell Membrane-Based mFasL Delivery System for In Vivo Treatment of Inflammatory Arthritis

During budding, lentiviral particles (LVP) incorporate cell membrane proteins in the viral envelope. We explored the possibility of harnessing this process to generate LVP-expressing membrane proteins of therapeutic interest and studied the potential of these tools to treat different pathologies. Fas-mediated apoptosis is central to the maintenance of T cell homeostasis and prevention of autoimmune processes. We prepared LVP that express murine FasL on their surface. Our data indicate that mFasL-bearing LVP induce caspase 3 and 9 processing, cytochrome C release, and significantly more cell death than control LVP in vitro. This cytotoxicity is blocked by the caspase inhibitor Z-VAD. Analysis of the application of these reagents for the treatment of inflammatory arthritis in vivo suggests that FasL-expressing LVP could be useful for therapy in autoimmune diseases such as rheumatoid arthritis, where there is an excess of Fas-expressing activated T cells in the joint. LVP could be a vehicle not only for mFasL but also for other membrane-bound proteins that maintain their native conformation and might mediate biological activities.

Negative Regulators of JAK/STAT Signaling in Rheumatoid Arthritis and Osteoarthritis

Elevated levels of pro-inflammatory cytokines are generally thought to be responsible for driving the progression of synovial joint inflammation in rheumatoid arthritis (RA) and osteoarthritis (OA). These cytokines activate several signal transduction pathways, including the Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT), Stress-Activated/Mitogen-Activated Protein Kinase (SAPK/MAPK) and phosphatidylinositol-3-kinase/Akt/mechanistic target of rapamycin (PI3K/Akt/mTOR) pathways which regulate numerous cellular responses. However, cytokine gene expression, matrix metalloproteinase gene expression and aberrant immune cell and synoviocyte survival via reduced apoptosis are most critical in the context of inflammation characteristic of RA and OA. Negative regulation of JAK/STAT signaling is controlled by Suppressor of Cytokine Signaling (SOCS) proteins. SOCS is produced at lower levels in RA and OA. In addition, gaining further insight into the role played in RA and OA pathology by the inhibitors of the apoptosis protein family, cellular inhibitor of apoptosis protein-1, -2 (c-IAP1, c-IAP2), X (cross)-linked inhibitor of apoptosis protein (XIAP), protein inhibitor of activated STAT (PIAS), and survivin (human) as well as SOCS appears to be a worthy endeavor going forward.

Increased autophagy in CD4+ T cells of rheumatoid arthritis patients results in T-cell hyperactivation and apoptosis resistance

Rheumatoid arthritis (RA) is an autoimmune disease hallmarked by aberrant cellular homeostasis, resulting in hyperactive CD4⁺ T cells that are more resistant to apoptosis. Both hyperactivation and resistance to apoptosis may contribute to the pathogenicity of CD4⁺ T cells in the autoimmune process. A better knowledge of the mechanisms determining such impaired homeostasis could contribute significantly to both the understanding and the treatment of the disease. Here we investigated whether autophagy, is dysregulated in CD4⁺ T cells of RA patients, resulting in disturbed T-cell homeostasis. We demonstrate that the rate of autophagy is significantly increased in CD4⁺ T cells from RA patients, and that increased autophagy is also a feature of in vitro activated CD4⁺ T cells. The increased apoptosis resistance observed in CD4⁺ T cells from RA patients was significantly reversed upon autophagy inhibition. These mechanisms may contribute to RA pathogenesis, as autophagy inhibition reduced both arthritis incidence and disease severity in a mouse collagen induced arthritis mouse model. Conversely, in Atg5^flox/flox -CD4-Cre⁺ mice, in which all T cells are autophagy deficient, T cells showed impaired activation and proliferation. These data provide novel insight into the pathogenesis of RA and underscore the relevance of autophagy as a promising therapeutic target.

Prognostic Investigations of Expression Level of Two Genes FasL and Ki-67 as Independent Prognostic Markers of Human Retinoblastoma

In this study, expression of FasL and Ki-67 messenger RNA (FasL and Ki-67 mRNA) in human retinoblastoma (HRB) was examined by the immunohistochemistry method and quantitative real-time PCR. Positive expression of Ki-67 in tumor cells was detected in 16 of 30 patients (53.33%), and only 9 (30%) of the tissues from patients with retinoblastoma showed positive staining for FasL. Our results revealed that FasL expression was significantly higher in tumor tissue with invasion compared with the noninvasion form (p = 0.033). Ki-67 expression was markedly increased in tumor tissues with invasion compared with the noninvasion group (p = 0.04), but no significant correlation was found between FasL expression and differentiation (p > 0.05). In addition, Ki-67 expression was strongly linked to differentiation (p < 0.002). Expression of these FasL was correlated with shorter overall survival of patients, but its expression was not significantly associated with overall survival (p = 0.15). The impact of Ki-67 expression on survival in patients was also evaluated. Ki-67 expression level was not found to be significantly associated with shorter survival (Kaplan–Meier; p = 0.09). Univariate analysis revealed that massive choroidal invasion was correlated with poor prognosis. Taken together, the data suggest that massive choroidal invasion is also an important indicator of poor prognosis for HRB.

Upregulation of the sFas/sFasL system in psoriatic patients

PURPOSE

Psoriasis is a chronic, recurrent, inflammatory disease. Recent investigations indicate its autoimmune pathogenesis. Apoptosis plays an important role in the development of many autoimmune diseases. The aim of this study was to evaluate the influence of topical treatment of psoriasis on soluble Fas (sFas) and soluble Fas-ligand (sFasL).

MATERIAL/METHODS

Serum concentrations of sFas and sFasL were measured using ELISA in 40 psoriatic patients before and after topical treatment with dithranol and compared to the values obtained from 16 healthy subjects. Data were analyzed with respect to severity of psoriasis, duration of the disease and coexisting obesity, diabetes and hypertension.

RESULTS

We found that serum levels of sFas before (11.9±2.4ng/mL) and after treatment (12.2±2.5ng/mL) were significantly higher in patients with psoriasis as compared to the control group (6.4±1.8ng/mL). Concentrations of sFasL did not differ significantly from healthy subjects, but increased after treatment. The sFas/sFasL ratio was significantly higher in psoriasis (128±47) than in the control group and, even though it tended to decrease after treatment, it still remained higher than in the control group (65±22). Additionally we observed a positive correlation of sFas/sFasL ratio with the age of patients and duration of the disease. Psoriatic patients suffering from hypertension and overweight had significantly higher sFas/sFasL ratio than other psoriatic patients.

CONCLUSIONS

Our data indicate upregulation of the sFas/sFasL system in psoriatic patients. We demonstrate association of sFas/sFasL with commorbidities - components of metabolic syndrome.

Distinct effects of soluble and membrane-bound fas ligand on fibroblast-like synoviocytes from rheumatoid arthritis patients

OBJECTIVE

Injection of agonistic anti-Fas antibody has been shown to decrease disease symptoms in mouse models of arthritis. Additionally, membrane-bound FasL (mFasL) has been shown to induce cell death in fibroblast-like synoviocytes (FLS) from rheumatoid arthritis (RA) patients. However, levels of soluble FasL (sFasL) are increased in the joints of RA patients and have been associated with disease severity, indicating that mFasL and sFasL play opposing roles in RA. The purpose of this study was to analyze the effects of FasL on RA FLS responses.

METHODS

The responses of FLS from RA and osteoarthritis (OA) patients to soluble and oligomeric FasL, the latter mimicking mFasL, were analyzed by fluorescence-activated cell sorting and proliferation assays, using 3 different FasL variants. The signaling pathways that trigger FasL responses were characterized by Western blotting.

RESULTS

We found that mFasL and sFasL have distinct roles in RA FLS. Crosslinked FasL preferentially induced apoptosis, whereas sFasL stimulated proliferation. Moreover, sFasL activated several signaling pathways in RA FLS, such as ERK-1/2, phosphatidylinositol 3-kinase, caspase 8, and JNK, with a prominent role of JNK, since only the blockade of this pathway rendered FLS more susceptible to FasL-induced apoptosis. Crosslinked FasL induced apoptosis in FLS from OA patients, but sFasL failed to stimulate their proliferation.

CONCLUSION

Our findings suggest that sFasL is a disease promoter in RA, a finding consistent with previous reports describing a tumor-promoting role of FasL. Therefore, blocking of sFasL could be a therapeutic strategy for RA.

Targeting the Fas/FasL system in Rheumatoid Arthritis therapy: Promising or risky?

Rheumatoid Arthritis (RA) is a chronic inflammatory disease affecting synovial joints. Tumor necrosis factor (TNF) α is a key component of RA pathogenesis and blocking this cytokine is the most common strategy to treat the disease. Though TNFα blockers are very efficient, one third of the RA patients are unresponsive or present side effects. Therefore, the development of novel therapeutic approaches is required. RA pathogenesis is characterized by the hyperplasia of the synovium, closely associated to the pseudo-tumoral expansion of fibroblast-like synoviocytes (FLS), which invade and destroy the joint structure. Hence, depletion of RA FLS has been proposed as an alternative therapeutic strategy. The TNF family member Fas ligand (FasL) was reported to trigger apoptosis in FLS of arthritic joints by binding to its receptor Fas and therefore suggested as a promising candidate for targeting the hyperplastic synovial tissue. However, this cytokine is pleiotropic and recent data from the literature indicate that Fas activation might have a disease-promoting role in RA by promoting cell proliferation. Therefore, a FasL-based therapy for RA requires careful evaluation before being applied. In this review we aim to overview what is known about the apoptotic and non-apoptotic effects of Fas/FasL system and discuss its relevance in RA.

Smoking and rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease caused by both genetic and environmental factors. Smoking has been implicated as one of the most important extrinsic risk factors for its development and severity. Recent developments have shed light on the pathophysiology of RA in smokers, including oxidative stress, inflammation, autoantibody formation and epigenetic changes. The association of smoking and the development of RA have been demonstrated through epidemiologic studies, as well as through in vivo and animal models of RA. With increased use of biological agents in addition to standard disease-modifying antirheumatic drugs (DMARDs), there has been interest in how smoking affects drug response in RA treatment. Recent evidence suggests the response and drug survival in people treated with anti-tumour necrosis factor (anti-TNF) therapy is poorer in heavy smokers, and possible immunological mechanisms for this effect are presented in the current paper.

Tocilizumab treatment increases left ventricular ejection fraction and decreases left ventricular mass index in patients with rheumatoid arthritis without cardiac symptoms: assessed using 3.0 tesla cardiac magnetic resonance imaging

OBJECTIVE

The aim of our pilot study was to prospectively evaluate the effect of inhibiting interleukin 6 on the left ventricular (LV) structure and function in patients with rheumatoid arthritis (RA) without cardiac symptoms, using cardiac magnetic resonance (CMR).

METHODS

Female patients with RA with active disease and healthy controls were enrolled. Cardiac symptoms were absent in all subjects. Tocilizumab (TCZ; 8 mg/kg IV every 4 weeks) was prescribed for patients with RA with an inadequate clinical response to methotrexate. All subjects underwent baseline evaluation of LV function and structure measured by CMR. We compared measures of LV geometry and function between patients with RA and patients without RA controls at baseline, and changes in the same variables between baseline and after 52 weeks of treatment among the group with RA.

RESULTS

Twenty women with RA were compared with 20 women without RA of similar mean age. In patients with RA at baseline, ejection fraction (EF) was significantly lower (-3.7%) and LV mass index (LVMI) significantly higher (+9.2%) compared with controls. TCZ treatment resulted in a significant decrease in the Simplified Disease Activity Index (SDAI) after 52 weeks of treatment, paralleling a significant increase in EF (+8.2%) and a significant decrease in LVMI (-24.4%) over the same period. The percentage change in LVMI correlated strongly with the percentage change in SDAI (r = -0.63, p = 0.0028). LV geometry in the group with RA at baseline showed eccentric hyper-trophy compared with the group without RA, a condition that normalized after TCZ treatment.

CONCLUSION

TCZ treatment significantly increased EF and decreased LVMI associated with disease activity.

Disease activity improvement in rheumatoid arthritis treated with tumor necrosis factor-α inhibitors correlates with increased soluble Fas levels

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by chronic synovial inflammation and hyperplasia. Tumor necrosis factor-α (TNF-α) plays a pivotal role in RA by interfering with the Fas-Fas ligand (FasL) proapoptotic pathway. We investigated the circulating levels of soluble Fas (sFas) and soluble FasL (sFasL), and their possible correlation with disease activity and improvement after anti-TNF-α treatment in RA.

METHODS

Serum levels of sFas and sFasL were measured by quantitative ELISA in 52 patients with RA before and after 3 months of anti-TNF-α treatment (adalimumab, n = 32; infliximab, n = 20). Disease activity measures [Disease Activity Score at 28 joints-erythrocyte sedimentation rate (DAS28-ESR), C-reactive protein (CRP)] were recorded before and after treatment. Forty age-matched and sex-matched healthy subjects served as controls.

RESULTS

No significant differences in serum sFas levels were detected between anti-TNF-α-naive patients with RA and controls. After anti-TNF-α treatment, serum sFas levels significantly increased in patients with RA compared to both anti-TNF-α-naive patients and controls. Increased sFas levels inversely correlated with disease activity variables (DAS28-ESR: r = -0.739, CRP: r = -0.636, both p < 0.001). No significant differences in sFasL levels were detected in patients with RA before and after anti-TNF-α treatment.

CONCLUSION

In RA, an increase in sFas levels closely correlates with improvement in disease activity induced by TNF-α inhibitors, suggesting their ability to modulate Fas-mediated synoviocyte apoptosis.

Role of cytolytic impairment of natural killer and natural killer T-cell populations in rheumatoid arthritis

Innate immunity has been widely accepted as one of the major cause for the alteration of immune system and progression of autoimmune diseases. Natural killer (NK) cells and natural killer T (NKT) cells have not been explored in clinical studies for their cytolytic components in association with rheumatoid arthritis (RA). The literature available for these potential candidates is controversial in terms of their protective or pathogenic role in disease severity of RA. Present study explained the role of NK and NKT cell populations and intracellular expression of caspases, perforin, granzymes A and B in the pathogenesis of RA in patients. DAS28 score was measured as the disease severity. Immunochemical parameters were studied by using monoclonal antibodies (mAbs) against different cell types in flow cytometry. Results indicated that that whatsoever is the change in percentage cell populations, ratio of NK and NKT cell populations always remained poised even in the disease state. Reactive oxygen species (ROS) levels were elevated with increased intracellular active caspase-3, perforin and granzyme expression in RA patients. Their elevated expressions were positively correlated with DAS28 suggesting the pathogenic role in RA. The expressions of pro-inflammatory cytokines were enhanced while the anti-inflammatory cytokine expressions were diminished in the patients. Present study may point towards futuristic therapeutic targets which can fascinate the pharmaceutical industries to selectively target these molecules in designing the therapeutic strategy of RA patients.

Bi(o)communications among peripheral blood fractions: a focus on NK and NKT cell biology in rheumatoid arthritis

Rheumatoid Arthritis (RA) is an autoimmune disease with unknown pathophysiology involving many interwoven signalling cascades. ROS, NK and NKT cells might be crucial in the disease severity of RA of which the role of NK and NKT cells are controversial in literature. However, the role of oxidative stress, its impact on NK and NKT cell immunobiology and disease activity (DAS28) is largely unknown. Therefore, we studied the role of oxidative stress and NK cell subsets in the pathogenesis of RA. The state of oxidative stress in various peripheral blood fractions, percentage NK and NKT cell expression, their altered apoptotic signaling pathways involving mitochondrial membrane potential, FAS associated death domain (FADD) mediated pathways and DNA damage were analyzed. Results indicated a state of profound oxidative stress in the peripheral blood of RA patients where percentage of NK and NKT cell subsets diminished while ROS levels increased. The depolarized mitochondrial membrane potential, FAS, FASL and active caspase-3 positive NK and NKT cell subsets were considerably elevated in patients. The DNA damage, assessed as percentage of DNA in comet tail, was significantly elevated. Findings of the present work indicate increased apoptosis of peripheral NK and NKT cells in the diseased condition. PBMC and RBC are the major sites of enhanced oxidative stress. The state of oxidative stress and altered immunobiology of NK and NKT cells strongly correlated with Disease activity score. The present study strongly supports the protective role of NK cell subsets in the pathogenesis of RA.

B cell resistance to Fas-mediated apoptosis contributes to their ineffective control by regulatory T cells in rheumatoid arthritis

OBJECTIVE

To investigate whether regulatory T cells (Treg) can control B cell function in rheumatoid arthritis (RA) and if not to explore the basis for this defect.

METHODS

Suppression of B cell responses by Treg was analysed in vitro by flow cytometry and ELISA using peripheral blood mononuclear cells from 65 patients with RA and 41 sex-matched and aged-matched healthy volunteers. Blocking and agonistic antibodies were used to define the role of Fas-mediated apoptosis in B cell regulation.

RESULTS

Treg failed to restrain B cell activation, proinflammatory cytokine and antibody production in the presence of responder T cells in RA patients. This lack of suppression was not only caused by impaired Treg function but was also due to B cell resistance to regulation. In healthy donors, control by Treg was associated with increased B cell death and relied upon Fas-mediated apoptosis. In contrast, RA B cells had reduced Fas expression compared with their healthy counterparts and were resistant to Fas-mediated apoptosis.

CONCLUSIONS

These studies demonstrate that Treg are unable to limit B cell responses in RA. This appears to be primarily due to B cell resistance to suppression, but Treg defects also contribute to this failure of regulation. Our data identify the Fas pathway as a novel target for Treg-mediated suppression of B cells and highlight a potential therapeutic approach to restore control of B cells by Treg in RA patients.

Association of systemic and intra-articular osteoclastogenic potential, pro-inflammatory mediators and disease activity with the form of inflammatory arthritis

PURPOSE

We aimed to assess osteoclastogenic potential of peripheral blood mononuclear cells (PBMC) and synovial fluid-derived mononuclear cells (SFMC) in different forms of arthritis and to correlate it with inflammatory mediators within intra-articular and circulatory compartments.

METHODS

Paired PBMC and SFMC samples of patients with rheumatoid arthritis (RA; n = 10) and psoriatic arthritis (PsA; n = 10), and PBMC of healthy controls were cultured to assess osteoclastogenic potential by the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts (OCs) and expression of OC-related genes (receptor activator of nuclear factor-κΒ (RANK), cFMS, and TRAP). Osteoclastogenesis was correlated with the arthritis-related inflammatory indicators in serum and synovial fluid (SF).

RESULTS

Number of OCs differentiated from PBMC was significantly higher in RA and PsA compared with control, with RA having more OCs compared with PsA. There was no difference in SFMC OC number between arthritic patients, but RANK expression in OCs differentiated from SFMC was higher in PsA compared with RA. SF of PsA patients more potently induced OC differentiation from control CD3(-)CD19(-)CD56(-)CD11b(+)CD115(+) PBMC compared with RA, paralleled with higher RANK-ligand expression in PsA SFMC. Positive correlations of OC number with erythrocyte sedimentation rate, serum level of CCL2, and PBMC gene expression of interleukin-18 and Fas-ligand were observed.

CONCLUSION

Osteoclastogenic potential is systemically enhanced in patients with RA, paralleled by disordered systemic and local expression of proinflammatory mediators, whereas PsA involves specific deregulation in RANKL/RANK axis. Our study reveals arthritis-specific mediators associated with the form of arthritis, indicating clinical relevance for diagnosis and treatment.

IL-17-mediated Bcl-2 expression regulates survival of fibroblast-like synoviocytes in rheumatoid arthritis through STAT3 activation

Introduction

Fibroblast-like synoviocytes (FLSs) are a major cell population of the pannus that invades adjacent cartilage and bone in rheumatoid arthritis (RA). The study was undertaken to determine the effect of interleukin-17 (IL-17) on the survival and/or proliferation of FLSs from RA patients and to investigate whether signal tranducer and activator of transcription 3 (STAT3) is implicated in this process.

Methods

Bcl-2 and Bax expression in FLSs was determined using the real-time PCR and western blot analysis. The expression of Bcl-2 and phosphoSTAT3 in synovial tissues was investigated by confocal microscope. Apoptosis of FLSs was detected by Annexin V/propidium iodide staining and/or phase contrast microscopy. The proliferation of FLSs was determined by CCK-8 ELISA assay.

Results

The pro-apoptotic Bax is decreased and anti-apoptotic Bcl-2 is increased in FLSs from RA patients compared with those from patients with osteoarthritis (OA). IL-17 upregulated the expression of Bcl-2 in FLSs from RA patients, but not in FLSs from OA patients. STAT3 was found to mediate IL-17-induced Bcl-2 upregulation in FLSs from RA patients. Additionally, IL-17 promoted the survival and proliferation of FLSs from RA patients. Most importantly, treatment with STAT3 inhibitor reversed the protective effect of IL-17 on FLSs apoptosis induced by sodium nitroprusside (SNP).

Conclusions

Our data demonstrate that STAT3 is critical in IL-17-induced survival of FLS from RA patients. Therefore, therapeutic strategies that target the IL-17/STAT3 pathway might be strong candidates for RA treatment modalities.

The microbial capsular polysaccharide galactoxylomannan inhibits IL-17A production in circulating T cells from rheumatoid arthritis patients

The persistence of activated T cells in rheumatoid arthritis (RA) synovium may be attributable to increased homing, increased retention or a possible imbalance between cell proliferation and programmed cell death. Induction of apoptosis may represent a potential therapeutic approach. Galactoxylomannan (GalXM) from the opportunistic fungus Cryptococcus neoformans can interact with T cells and induce T-cell apoptosis through the inhibition of CD45 phosphatase activity. The aim of this study was to determine the effect of GalXM on circulating T cells from patients with RA and the underlying mechanisms. GalXM immunomodulating effect on apoptosis and signal transduction pathway involved in IL-17A production was evaluated on T cells. RA T-cell apoptosis, higher than that of control T cells, was further increased by GalXM through induction of caspase-3 activation. Activated T cells expressing the CD45RO molecule and producing IL-17A were the main target of GalXM-induced apoptosis. GalXM induced consistent impairment of IL-17A production and inhibition of STAT3, which was hyperactivated in RA. In conclusion, GalXM triggered apoptosis of activated memory T cells and interfered with IL-17A production in RA. These data suggest therapeutic targeting of deleterious Th17 cells in RA and other autoimmune diseases.

Keynote lecture in the 13th Japanese Society of Immunotoxicology (JSIT 2006) : -Pathophysiological Development and Immunotoxicology: what we have found from research related to silica and silicate such as asbestos-

Silica and silicates may disturb immune functions such as autoimmunity and tumor immunity, because people who are exposed to the materials sometimes develop autoimmune and malignant diseases, respectively. Although silica-induced disorders of autoimmunity have been explained as adjuvant-type effects of silica, more precise analyses are needed and should reflect the recent progress in immunomolecular findings. A brief summary of our investigations related to the immunological effects of silica/asbestos is presented. Recent advances in immunomolecular studies led to detailed analyses of the immunological effects of asbestos and silica. Both affect immuno-competent cells and these effects may be associated with the pathophysiological development of complications in silicosis and asbestos-exposed patients such as the occurrence of autoimmune disorders and malignant tumors, respectively. In addition, immunological analyses may lead to the development of new clinical tools for the modification of the pathophysiological aspects of diseases such as the regulation of autoimmunity or tumor immunity using cell-mediated therapies, various cytokines, and molecule-targeting therapies. In particular, as the incidence of asbestos-related malignancies is increasing and such malignancies have been a medical and social problem since the summer in 2005 in Japan, efforts should be focused on developing a cure for these diseases to eliminate the nation wide anxiety about these malignancies.

B lymphocyte-typing for prediction of clinical response to rituximab

INTRODUCTION

The prediction of therapeutic response to rituximab in rheumatoid arthritis is desirable. We evaluated whether analysis of B lymphocyte subsets by flow cytometry would be useful to identify non-responders to rituximab ahead of time.

METHODS

Fifty-two patients with active rheumatoid arthritis despite therapy with TNF-inhibitors were included in the national rituximab registry. DAS28 was determined before and 24 weeks after rituximab application. B cell subsets were analyzed by high-sensitive flow cytometry before and 2 weeks after rituximab administration. Complete depletion of B cells was defined as CD19-values below 0.0001 x10⁹ cells/liter.

RESULTS

At 6 months 19 patients had a good (37%), 23 a moderate (44%) and 10 (19%) had no EULAR-response. The extent of B lymphocyte depletion in peripheral blood did not predict the success of rituximab therapy. Incomplete depletion was found at almost the same frequency in EULAR responders and non-responders. In comparison to healthy controls, non-responders had elevated baseline CD95⁺ pre-switch B cells, whereas responders had a lower frequency of plasmablasts.

CONCLUSIONS

The baseline enumeration of B lymphocyte subsets is still of limited clinical value for the prediction of response to anti-CD20 therapy. However, differences at the level of CD95⁺ pre switch B cells or plasmablasts were noticed with regard to treatment response. The criterion of complete depletion of peripheral B cells after rituximab administration did not predict the success of this therapy in rheumatoid arthritis.

Anti-arthritic effects of FasL gene transferred intra-articularly by an inducible lentiviral vector containing improved tet-on system

The objective of this study is to construct and identify an inducible lentiviral vector containing improved tet-on system and FasL gene and observe its effects on pristane-induced arthritis (PIA). FasL gene was amplified from the spleen of Lewis rats by RT-PCR. The tet-on system was improved with insertion of a chicken chromatin insulator (cHS4) element and an rtTA-dependent, tet-responsive element containing modifications of the tetO sequence (TRE-tight1). Pro-apoptosis effect of the vector pTREFasLcHS4V16 on synovial cells was evaluated by flow cytometer in vitro. Anti-arthritis effects of the vector on PIA after intra-articular injection were observed by clinical evaluation and joint histology. Cytokines in synovial tissue were measured by ELISA. The recombinant inducible lentiviral vector pTREFasLcHS4V16 was successfully constructed. The expression response and the pro-apoptosis effects of the vector were doxycycline dose-dependent. The vector injected intra-articularly attenuated the severity of PIA and decreased the level of cytokines in inflamed joints. pTREFasLcHS4V16 with an improved tet-on system can precisely regulate the expression of FasL gene and apoptosis. Anti-arthritis effects were observed after intra-articular injection of the inducible vector.

Melittin enhances apoptosis through suppression of IL-6/sIL-6R complex-induced NF-κB and STAT3 activation and Bcl-2 expression for human fibroblast-like synoviocytes in rheumatoid arthritis

OBJECTIVE

Resistance to apoptosis of fibroblast-like synoviocytes (FLS) is considered as a major characteristic in RA. This study was designed to identify whether melittin has a pro-apoptotic effect in IL-6/sIL6R-stimulated human FLS by investigating the expression of mitochondrial apoptosis-related genes, nuclear factor-κB (NF-κB), and signal transducer and activators of transcription (STAT) activation.

METHODS

Cell viability was determined using a MTT assay after melittin treatment. Expressions of STAT3 and mitochondrial apoptosis-related genes induced by the IL-6/sIL-6R complex were determined by real time-polymerase chain reaction and western blotting. The expression of NF-κB p65 following IL-6 stimulation was determined by western blot analysis. The effects of melittin on the expression of apoptosis-related genes and the transcription factors NF-κB p65 and STAT3 were assessed in FLS. Apoptosis of FLS was determined by TUNEL-labeling to detect DNA strand breaks and DNA fragmentation assays. Caspase-3 activity was determined by a colorimetric assay.

RESULTS

IL-6/sIL-6R induced the activation of the transcription factors, STAT3, NF-κB p65 (nucleus), and Bcl-2. Melittin increased the expression of pro-apoptosis-related molecules, namely caspase-3, caspase-9, Apaf-1, and cytosolic cytochrome c, in a dose-dependent manner after treatment with IL-6/sIL-6R. Melittin inhibited STAT3 activation, translocation of NF-κB p65 into the nucleus, and expression of anti-apoptotic genes such as Bcl-2 and mitochondrial cytochrome c.

CONCLUSIONS

The pro-apoptotic effects of melittin likely result from inhibition of the activation of the transcription factors, STAT3 and NF-κB p65, and regulation of mitochondrial apoptosis-related genes. Melittin is thus a promising therapeutic option for RA as it induces apoptosis in apoptosis-resistant synoviocytes.

Extracellular calreticulin is present in the joints of patients with rheumatoid arthritis and inhibits FasL (CD95L)-mediated apoptosis of T cells

OBJECTIVE

The binding of FasL (CD95L) to its receptor, Fas (CD95), induces apoptosis. Studies have shown that in patients with rheumatoid arthritis (RA), T lymphocytes are resistant to FasL-induced apoptosis in vivo but are susceptible to FasL-induced apoptosis in vitro. Dysfunction in this mechanism may be an important contributor to the pathophysiology of RA. Thus, the present study was undertaken to determine which factors might inhibit FasL-Fas binding in vivo and those that would inhibit apoptosis of T lymphocytes in an in vitro model system.

METHODS

Human Jurkat T cells rendered apoptotic by FasL exposure were analyzed by flow cytometry. Necrosis was determined according to measurement of lactate dehydrogenase release. Quantification of calreticulin in plasma and synovial fluid and of calreticulin-FasL binding was performed by enzyme-linked immunosorbent assay. Measurement of nitrite/nitrate in the plasma and synovial fluid was carried out by chemiluminescence assay.

RESULTS

Extracellular calreticulin was present at a significantly higher concentration in the plasma (median 10.3 ng/ml, interquartile range [IQR] 14.8 ng/ml) and synovial fluid (median 10.3 ng/ml, IQR 12.0 ng/ml) of RA patients (each P < 0.05) compared with the plasma (median 3.1 ng/ml, IQR 1.3 ng/ml) and synovial fluid (median 2.9 ng/ml, IQR 0.9 ng/ml) of patients with psoriatic arthritis and the plasma of healthy control subjects (median 2.9 ng/ml, IQR 0.9 ng/ml). Calreticulin concentrations in the synovial fluid correlated with the tender and swollen joint counts and the activity scores on the 28-joint Disease Activity Score assessment. Calreticulin also bound directly to FasL. In vitro, calreticulin (2-16 ng/ml) inhibited FasL-induced apoptosis of Jurkat T cells.

CONCLUSION

Calreticulin was present at higher concentrations in the plasma and synovial fluid of RA patients. Calreticulin had the capacity to bind directly to FasL and to inhibit FasL-mediated apoptosis of Jurkat T cells, and thus might play a role in inhibiting apoptosis of inflammatory T cells in RA.

Targeting Fas in osteoresorptive disorders

IMPORTANCE OF THE FIELD

Fas receptor is a mediator of the external apoptotic pathway in many cells and tissues. It is proposed that Fas receptor mediates osteoresorptive effects of estrogen deficiency and local/systemic inflammation.

AREAS COVERED IN THIS REVIEW

This review covers the past two decades of research on the expression and function of the Fas-Fas ligand system on bone cells, involvement in the pathogenesis of osteoresorption and potential therapeutic modulation.

WHAT THE READER WILL GAIN

We review the structure, biological function and intracellular signaling pathways of the Fas-Fas ligand system emphasizing the role of the non-apoptotic signaling pathways in bone cells, particularly osteoblast differentiation. We also present data on the in vitro expression and function of the Fas-Fas ligand system on osteoblast/osteoclast lineage cells, animal and human studies confirming its involvement in osteoresorptive disorders and potential therapeutic approaches to modulate its function.

TAKE HOME MESSAGE

Tissue specific therapeutic approaches need to be established to modify the Fas-Fas ligand system in osteoresorptive disorders as systemic targeting has many side effects. The most promising approach would be to target Fas signaling molecules coupled with osteoblast/osteoclast differentiation pathways, but a precise definition of these targets is still needed.

Akt activity protects rheumatoid synovial fibroblasts from Fas-induced apoptosis by inhibition of Bid cleavage

Introduction

Synovial hyperplasia is a main feature of rheumatoid arthritis pathology that leads to cartilage and bone damage in the inflamed joints. Impaired apoptosis of resident synoviocytes is pivotal in this process. Apoptosis resistance seems to involve defects in the extrinsic and intrinsic apoptotic pathways. The aim of this study was to investigate the association of PI3Kinase/Akt and the mitochondrial apoptotic pathway in the resistance of rheumatoid arthritis (RA) fibroblast like synovial cells (FLS) to Fas-mediated apoptosis.

Methods

Apoptosis was assessed by ELISA quantification of nucleosomal release, Hoechst staining and activated caspase-3/7 measure in cultured RA FLS stimulated with anti-Fas antibody. Two Phosphoinositol-3-kinase/protein Kinase B (PI3 Kinase) inhibitors, Wortmannine and LY294002, were used before anti-Fas stimulation. Proapoptotic BH3 interacting domain death agonist (Bid) was suppressed in RA FLS by small interfering RNA (siRNA) transfection. Bid was overexpressed by transfection with the pDsRed2-Bid vector. Phosphorylated Akt, caspase-9, and Bid expression were analysed by western blot.

Results

PI3 kinase inhibition sensitizes RA FLS to Fas-induced apoptosis by increasing cleavage of Bid protein. Bid suppression completely abrogated Fas-induced apoptosis and Bid overexpression highly increased apoptotic rate of RA FLS in association with cleavage of caspase-9.

Conclusions

In RA FLS, phosphorylation of Akt protects against Fas-induced apoptosis through inhibition of Bid cleavage. The connection between the extrinsic and the intrinsic apoptotic pathways are critical in this Fas- mediated apoptosis and points to PI3Kinase as potential therapeutic target for RA.

Peripheral blood expression profiles of bone morphogenetic proteins, tumor necrosis factor-superfamily molecules, and transcription factor Runx2 could be used as markers of the form of arthritis, disease activity, and therapeutic responsiveness

OBJECTIVE

To assess whether different forms of arthritis and disease activity could be distinguished by peripheral blood expression profiles of bone-regulatory factors including tumor necrosis factor (TNF)-superfamily [TNF-related apoptosis-inducing ligand (TRAIL), the Fas ligand (FasL), and the ligand for herpesvirus entry mediator (LIGHT)] and bone morphogenetic protein (BMP)-family members (BMP-2, BMP-4, BMP-6) as well as osteoblast differentiation gene Runx2.

METHODS

Blood cells from healthy controls (n = 25) and patients at different disease stages with rheumatoid arthritis (RA; n = 49), osteoarthritis (OA; n = 17), or spondyloarthritis, including ankylosing spondylitis (AS; n = 27) or psoriatic arthritis (PsA; n = 23), were processed for quantitative polymerase chain reaction. Gene expression was assessed in comparison with control samples, correlated with clinical data of different forms of arthritis, and analyzed for discriminative efficacy between groups by receiver-operation characteristic (ROC) curves. Results were confirmed on diagnostic RA (n = 5) and AS (n = 8) samples.

RESULTS

BMP-4, BMP-6, and Runx2 expressions were significantly decreased in patients with RA and OA versus controls. Patients with RA also had decreased FasL and LIGHT expression, while patients with AS had increased Runx2 expression. Negative correlation with disease activity was found for BMP-4, FasL, and Runx2 in RA and for Runx2 in PsA, while positive correlation was found for BMP-4 in PsA. Gene expression was higher in the therapy-resistant form of AS (for BMP-4, LIGHT, and Runx2) and in methotrexate-treated patients in RA (for BMP-2 and LIGHT). ROC curve analysis confirmed discrimination between groups, particularly decreased LIGHT and Runx2 for RA and increased Runx2 for AS.

CONCLUSION

Our study identified BMP and Runx2 as possible biomarkers of bone metabolism in several forms of arthritis, while lower FasL and LIGHT were associated with RA. Correlation between gene expression and disease activity may be clinically useful in assessing therapeutic effectiveness and disease monitoring.

Resistance to activation-induced cell death and elevated FLIPL expression of CD4+ T cells in a polyI:C-induced primary biliary cirrhosis mouse model

Primary biliary cirrhosis (PBC) is a type of organ-specific autoimmune disease in which immune tolerance is impaired by an unknown mechanism. We established a PBC animal model by injecting C57BL/6 mice with polyI:C to study activation-induced cell death (AICD) in CD4+ T lymphocytes and changes of apoptosis-associated molecules as a first step to understand the immune tolerance of PBC mice. Obvious inflammatory cell infiltration was observed in the portal area of the liver tissues in model mice and antimitochondrial antibodies (AMA) positive rate was 80%. The AICD level in both splenic and hepatic CD4+ T cells in the model group were all lower than those in controls, and in the model group the level for hepatic CD4+ T cells were significantly lower than that for splenic CD4+ T cells. Quantitative PCR revealed that FasL mRNA and TRAIL expression in CD4+ T cells in the model group decreased significantly compared with that in the control group. Western blots revealed that the expression of the anti-apoptotic protein FLIP(L) in the model group increased significantly with the FLIP(L) expression in hepatic CD4+ T cells significantly higher than that in splenic CD4+ T cells. There was a positive linear correlation between the number of infiltrated portal areas and relative expression of FLIP(L) in splenic CD4+ T cells in model group. There were no obvious changes for caspase-8 in either group. These results show that the anti-apoptotic ability of CD4+ T lymphocytes play an important role in immune tolerance in the PBC mouse model, and elevated FLIP(L) expression may enhance this ability. The inhibition of FasL and TRAIL expression may also help enhance this anti-apoptotic ability in CD4+ T lymphocytes and contribute to the aggravation of portal area inflammation.

Poly(ADP-ribose) polymerase suppression protects rheumatoid synovial fibroblasts from Fas-induced apoptosis

OBJECTIVES

To investigate the effect of poly(ADP-ribose) polymerase 1 (PARP-1) suppression on CD95/Apo-1 (Fas)-induced apoptosis in fibroblast-like synoviocytes (FLS) from RA patients.

METHODS

Apoptosis, determined by Hoechst staining and quantification of nucleosomal release by ELISA, was induced by stimulation with anti-Fas antibody with or without pre-treatment with cycloheximide (CHX). PARP-1 and poly(ADP-ribose) glycohydrolase (PARG) were suppressed in RA FLS by small interfering RNA (siRNA) transfection. Fas-associated via death domain (FADD), pro-caspase-8, Fas, c-Fas-associated death domain-like IL-1b-converting enzyme-inhibitory protein (FLIP) expression, and AKT and GSK phosphorylation were analysed by western blot.

RESULTS

PARP-1-deficient FLS showed significantly lower apoptosis than non-transfected and control siRNA-transfected FLS. The expression of death-inducing signaling complex (DISC) components such as Fas, FADD and pro-caspase-8 was not modified by PARP-1 suppression; however, FLS lacking PARP-1 showed high activation of the Akt-GSK survival pathway and up-regulation of the c-FLIP-S isoform after Fas triggering. Inhibition of PI3K/Akt pathway did not modify the difference between PARP-1-competent or -deficient FLS in Fas-mediated apoptosis or c-FLIP-S expression. Poly(ADP-ribose) accumulation induced by PARG supression did not modify the apoptotic response.

CONCLUSION

PARP-1 deficiency increases the resistance of RA FLS to Fas-induced apoptosis through activation of the Akt-GSK survival pathway and up-regulation of c-FLIP-S isoform.

Calycopterin, an immunoinhibitory compound from the extract of Dracocephalum kotschyi

Medicinal plants have been widely investigated for their various effects. Dracocephalum kotschyi Boiss (Labiatae) is used in Iranian traditional medicine for the treatment of rheumatoid diseases. The inhibitory effect of D. kotschyi on the lectin-induced cellular immune response has been demonstrated previously. In this study, mitogen-treated lymphocytes were exposed to the extract of D. kotschyi and analysed for the induction of apoptosis using flow cytometry and gel electrophoresis. The data obtained indicated a dose-dependent increase of cells in the sub-G1 phase of cell cycle. Study of internucleosomal DNA fragmentation showed a typical DNA laddering in agarose gels. A bioactivity-guided fractionation assay to find the active components responsible for the inhibitory effect of D. kotschyi on mitogen-induced lymphocyte proliferation led to the isolation of calycopterin from the ethyl acetate extract of D. kotschyi. Its structure was identified by spectroscopic methods including( 1)H-NMR, (13)C-NMR, MS and UV spectra. Calycopterin inhibited lymphocyte proliferation in a dose-dependent manner with an IC(50) value of 1.7 microg/mL. In conclusion, the results of this study suggest that D. kotschyi extract has the capacity to induce apoptosis in the lymphocytes and that isolated calycopterin is responsible for the inhibitory effect of D. kotschyi on lymphocyte proliferation.

Circulating levels of TNF-like cytokine 1A (TL1A) and its decoy receptor 3 (DcR3) in rheumatoid arthritis

TL1A is a novel TNF-like cytokine, which provides co-stimulatory and Th1-polarizing signals to activated lymphocytes, via binding to death-domain receptor 3 (DR3). These functions are inhibited when TL1A associates to decoy receptor 3 (DcR3). We investigated the serum expression of TL1A and DcR3 in 81 patients with RA and 51 healthy controls. TL1A concentrations were elevated in patients by 5-fold (P<0.00001). This increase was more prominent in RFactor-positive patients and correlated with clinical activity in this subgroup. DcR3 was detected more frequently and in significantly higher values in RA-derived sera, correlated strongly with TL1A, and was present in inflammatory synovial fluid. Severe RA stage was associated with highly elevated TL1A and DcR3 serum levels. Treatment with an anti-TNF agent significantly decreased TL1A serum levels. We conclude that TL1A may serve as an inflammatory marker in RA. Interactions between TL1A and its receptors may be important in the pathogenesis of RA.

Expression levels of FAS are regulated through an evolutionary conserved element in intron 2, which modulates cystic fibrosis disease severity

We have analyzed frequent naturally occurring variants in the autogene FAS in two independent cystic fibrosis (CF) patient populations. Analysis of FAS expression levels from intestinal epithelial biopsies from 16 unrelated F508del-CFTR homozygotes showed a correlation between FAS intron 2 SNP rs7901656 and signals for Affymetrix GeneChip U133 Plus 2.0 probeset 204781_s_at consistent with a dominant model (P=0.0009). Genotype and haplotype analysis at six informative SNPs spanning the FAS gene locus was carried out on 37 nuclear families representing extreme clinical phenotypes that were selected from the European CF Twin and Sibling Study population of more than 300 affected sibling pairs. Case-control comparison of the haplotype composed of rs2296603-rs7901656-rs1571019 encompassing intron 2 of FAS reached significance (P=0.0246). Comparative phylogenetic analysis and functional annotation of the FAS intron 2 sequence revealed a conserved non-coding sequence surrounding rs7901656 and predicted binding sites for four transcription factors whereby the binding site of c-Rel is altered by rs7901656. Taken together, these findings from two independent CF patient cohorts indicate that allelic variants within FAS intron 2 alter FAS gene expression and that these functional variants modulate the manifestation of CF disease.