NF-kappa B regulates VCAM-1 expression on fibroblast-like synoviocytes

Induced regulatory T cells remain suppressive capability on effector T cells and synovial fibroblasts in collagen-induced arthritis

Rheumatoid arthritis (RA) is a common autoimmune disorder initiated by inflammatory synovitis. Hyperproliferation of destructive synovial fibroblasts (SFs) is one of the pathogenic mechanisms of RA. Abnormalities in regulatory T cells (Tregs) may also play a critical role in this progression. To date, it is unclear whether both natural Tregs (nTregs) and induced Tregs (iTregs) share similar characteristics in RA progression and whether Tregs directly suppress the autoaggressive activities of SFs. In this study, we compared suppressive effects on effector T cells (Teffs) and inflamed SFs between nTregs and iTregs in a collagen-induced arthritis (CIA) model. Our results demonstrated that iTregs but not nTregs maintained a suppressive effect on Teffs after adoptive transfer into CIA mice. Additionally, we discovered that iTregs directly inhibited the destructive activities of CIA-SFs. Thus, this study suggests that administration of the iTreg subset has great potential for treatment of RA in the clinic in the future.

Altered Expression of Vascular Cell Adhesion Molecule-1 in Oral Lichen Planus

Oral lichen planus (OLP) is a T cell-mediated chronic inflammatory mucocutaneous disease affected by the interaction between keratinocytes and T cells. Recent evidence indicates that vascular cell adhesion molecule-1 (VCAM1) plays a vital role in mediating immune and inflammatory responses. In this study, the expression of VCAM1 in OLP was detected by immunohistochemical staining and its correlations with clinical features were analyzed. The disease severity of OLP was assessed by the reticular, atrophic, and erosive scoring system. We found that VCAM1 was generally localized in the cytoplasm of epithelial cells, and in nucleus, cytoplasm, and extracellular matrix of subepithelial infiltrated cells in superficial layer of lamina propria. Moreover, VCAM1 levels in epithelium and lamina propria of OLP were significantly higher than that in controls, respectively. In addition, VCAM1 level in epithelium was increased compared with that of lamina propria. There were no significant differences for VCAM1 expression between nonerosive and erosive forms of OLP. The expression of VCAM1 in OLP was not associated with the severity of disease, gender, and age. Thus, we speculated that spatial expression differences of VCAM1 in local lesions of OLP may involve the pathogenesis of OLP.

Ectopic Tumor VCAM-1 Expression in Cancer Metastasis and Therapy Resistance

Vascular Cell Adhesion Molecule-1 (VCAM-1; CD106) is a membrane protein that contributes critical physiologic functional roles in cellular immune response, including leukocyte extravasation in inflamed and infected tissues. Expressed as a cell membrane protein, VCAM-1 can also be cleaved from the cell surface into a soluble form (sVCAM-1). The integrin α4β1 (VLA-4) was identified as the first major ligand for VCAM-1. Ongoing studies suggest that, in addition to mediating physiologic immune functions, VCAM-1/VLA-4 signaling plays an increasingly vital role in the metastatic progression of various tumors. Additionally, elevated concentrations of sVCAM-1 have been found in the peripheral blood of patients with cancer, suggesting the tumor microenvironment (TME) as the source of sVCAM-1. Furthermore, over-expression of VLA-4 was linked to tumor progression in various malignancies when VCAM-1 was also up-regulated. This review explores the functional role of VCAM-1 expression in cancer metastasis and therapy resistance, and the potential for the disruption of VCAM-1/VLA-4 signaling as a novel immunotherapeutic approach in cancer, including osteosarcoma, which disproportionately affects the pediatric, adolescent and young adult population, as an unmet medical need.

Impact of isolation method on cellular activation and presence of specific tendon cell subpopulations during in vitro culture

Tendon injuries are common and heal poorly, due in part to a lack of understanding of fundamental tendon cell biology. A major impediment to the study of tendon cells is the absence of robust, well-characterized in vitro models. Unlike other tissue systems, current tendon cell models do not account for how differences in isolation methodology may affect the activation state of tendon cells or the presence of various tendon cell subpopulations. The objective of this study was to characterize how common isolation methods affect the behavior, fate, and lineage composition of tendon cell cultures. Tendon cells isolated by explant exhibited reduced proliferative capacity, decreased expression of tendon marker genes, and increased expression of genes associated with fibroblast activation compared to digested cells. Consistently, explanted cells also displayed an increased propensity to differentiate to myofibroblasts compared to digested cells. Explanted cultures from multiple different tendons were substantially enriched for the presence of scleraxis-lineage (Scx-lin+) cells compared to digested cultures, while the overall percentage of S100a4-lineage (S100a4-lin+) cells was dependent on both isolation method and tendon of origin. Neither isolation methods preserved the ratios of Scx-lin+ or S100a4-lin+ to non-lineage cells seen in tendons in vivo. Combined, these data indicate that further refinement of in vitro cultures models is required in order to more accurately understand the effects of various stimuli on tendon cell behavior. Statement of clinical significance: The development of informed in vitro tendon cell models will facilitate enhanced screening of potential therapeutic candidates to improve tendon healing.

Induced, but not natural, regulatory T cells retain phenotype and function following exposure to inflamed synovial fibroblasts

Aberrant number and/or dysfunction of CD4⁺Foxp3⁺ Regulatory T cells (T_regs) are associated with the pathogenesis of rheumatoid arthritis (RA). A previous study has demonstrated that thymus-derived, natural T_regs (nT_regs) prefer to accumulate in inflamed joints and transdifferentiate to T_H17 cells under the stimulation of inflamed synovial fibroblasts (SFs). In this study, we made a head-to-head comparison of both T_reg subsets and demonstrated that induced T_regs (iT_regs), but not nT_regs, retained Foxp3 expression and regulatory function on T effector cells (T_effs) after being primed with inflamed SFs. In addition, iT_regs inhibited proliferation, inflammatory cytokine production, migration, and invasion ability of collagen-induced arthritis (CIA)-SFs in vitro and in vivo. Moreover, we noted that iT_regs directly targeted inflamed SFs to treat autoimmune arthritis, while nT_regs failed to do this. Thus, manipulation of the iT_reg subset may have a greater potential for prevention or treatment of patients with RA.

HMGB1 Inhibits HNF1A to Modulate Liver Fibrogenesis via p65/miR-146b Signaling

High mobility group box 1 (HMGB1) is essential for the pathogenesis of liver injury and liver fibrosis. We previously revealed that miR-146b promotes hepatic stellate cells (HSCs) activation and proliferation. Nevertheless, the potential mechanisms are still unknown. Herein, HMGB1 increased HSCs proliferation and COL1A1 and α-SMA protein levels. However, the knockdown of miR-146b inhibited HSCs proliferation and COL1A1 and α-SMA protein levels induced via HMGB1 treatment. miR-146b was upregulated by HMGB1 and miR-146b targeted hepatocyte nuclear factor 1A (HNF1A) 3'-untranslated region (3'UTR) to modulate its expression negatively. Further, we confirmed that HMGB1 might elicit miR-146b expression via p65 within HSCs. Knockdown or block of HMGB1 relieved the CCl₄-induced liver fibrosis. In fibrotic liver tissues, miR-146b expression was positively correlated with p65 mRNA, but HNF1A mRNA was inversely correlated with p65, and miR-146b expression. In summary, our findings suggest that HMGB1/p65/miR-146b/HNF1A signaling exerts a crucial effect on liver fibrogenesis via the regulation of HSC function.

Engineered DNA nanodrugs alleviate inflammation in inflammatory arthritis

Rheumatoid arthritis (RA) is an autoimmune disease featured with chronic joint inflammation. Suppression of inflammation is critical to RA treatment and joint protection. In this study, DNA nanodrugs are prepared via the conjugation of NF-κB decoy oligodeoxynucleotides (dODNs) and VCAM-1 targeted peptides (P) onto self-assembled DNA tetrahedrons (TDs). Physicochemical properties of DNA nanodrugs are characterized using atomic force microscopy (AFM), gel electrophoresis and Fourier Transform Infrared Spectrometer (FTIR). Cytotoxicity, cellular uptake and anti-inflammatory efficacy of DNA nanodrugs are evaluated in vitro. Clinical arthritis index, inflammatory proteins in serum and joint pathophysiology are also investigated in vivo. TD-P-dODN possesses one dODN and one P and exhibits faster and higher cellular uptake by inflammatory cells compared with free dODNs. TD-P-dODN also significantly reduce inflammatory proteins in cells and adjuvant induced arthritis (AIA) mice. Reduced clinical arthritis index and improved joint rehabilitation are also achieved by TD-P-dODN treatment. This study demonstrates that an engineered DNA nanodrug (TD-P-dODN) enhances the efficacy of nucleic acid drugs and represents a promising strategy for RA treatment.

Vasculature submucosal changes at early stages of osteonecrosis of the jaw (ONJ)

Osteonecrosis of the jaw (ONJ), a rare, but potentially severe side effect of anti-resorptive medications, presents as exposed bone in the maxillofacial region lasting for at least 8 weeks. While clinical experience and animal models concur in finding that systemic antiresorptive treatment in conjunction with local risk factors, such as tooth extraction or dental disease may lead to ONJ development, the subclinical molecular changes that precede bone exposure remain poorly understood. The identification of these changes is not only important in understanding disease pathophysiology, but could provide potential for treatment development. Here, we evaluated the early stages of ONJ utilizing a model of experimental periodontitis (EP) in mice treated with two different types of antiresorptives, targeting potential changes in vasculature, hypoxia, oxidative stress, and apoptosis. Antiresorptive treatment in animals with EP increased levels of empty osteocytic lacunae and increased ONJ prevalence compared to Veh animals. The arteriole and venule network seen around EP areas was diminished in animals treated with antiresorptives. Higher levels of vascular endothelial growth factor A (VEGF-A) and vascular cell adhesion protein-1 (VCAM-1) were observed 1-week following EP in treated animals. Finally, levels of hypoxia, oxidative stress, and apoptosis remained high in antiresorptive treated animals with EP through the duration of the experiment. Together, our data point to subclinical vasculature organizational disturbances that subsequently affect levels of hypoxia, oxidative stress, and apoptosis in the area of developing ONJ.

A novel diindolylmethane analog, 1,1-bis(3'-indolyl)-1-(p-chlorophenyl) methane, inhibits the tumor necrosis factor-induced inflammatory response in primary murine synovial fibroblasts through a Nurr1-dependent mechanism

The progression of rheumatoid arthritis involves the thickening of the synovial lining due to the proliferation of fibroblast-like synoviocytes (FLS) and infiltration by inflammatory cells. Tumor necrosis factor alpha (TNFα) is a pro-inflammatory cytokine involved in progression of the disease. Under rheumatoid conditions, FLS express the tumor necrosis factor (TNF)-recognition complex (TNFR1, TNFR2, VCAM-1 and ICAM-1), which induces local macrophage activation and leads to downstream nuclear factor κB (NF-κB) signaling. The NF-κB-regulated inflammatory gene, cyclooxygenase (COX), increases synthesis of prostaglandins that contribute to the propagation of inflammatory damage within the joint. Because the nuclear orphan receptor, NR4A2 (Nurr1), can negatively regulate NF-κB-dependent inflammatory gene expression in macrophages, we postulated that activation of this receptor by the Nurr1 ligand 1,1-bis(3'-indolyl)-1-(p-chlorophenyl) methane (C-DIM12) would modulate inflammatory gene expression in synovial fibroblasts by inhibiting NF-κB. Treatment with C-DIM12 suppressed TNFα-induced expression of adhesion molecules and NF-κB regulated genes in primary synovial fibroblasts including vascular adhesion molecule 1 (VCAM-1), PGE2 and COX-2. Immunofluorescence studies indicated that C-DIM12 did not prevent translocation of p65 and stabilized nuclear localization of Nurr1 in synovial fibroblasts. Knockdown of Nurr1 expression by RNA interference prevented the inhibitory effects of C-DIM12 on inflammatory gene expression, indicating that the anti-inflammatory effects of this compound are Nurr1-dependent. Collectively, these data suggest that this receptor may be a viable therapeutic target in RA.

Discovery of anti-inflammatory components from Guge Fengtong tablet based on inflammatory markers and exploration of its molecular mechanism

In this work, we discovered GGFTT and its bioactive combinatorial components (10C) could significantly decrease the production of TNF-α, IL-1β, IL-6. 10C exert comparable anti-inflammatory effect through NF-κB and MAPKs signaling pathways as GGFTT.

Detecting changes in arthritic fibroblast-like synoviocytes using atomic force microscopy

The morphological and quantitative differences between arthritic fibroblast-like synoviocytes (FLS) and normal FLS were determined as an effective diagnostic tool for rheumatoid arthritis (RA), and confirmed using atomic force microscopy (AFM). Collagen-induced arthritic (CIA) mice and normal mice were prepared and FLS were isolated by enzymatic digestion from the synovial tissue of sacrificed mice at 5-week and 8-week pathogenesis periods. Analysis of cell morphology using AFM revealed that the surface roughness around the nucleus and around the branched cytoplasm was significantly higher in CIA FLS (P < 0.05) than that in normal FLS. In addition, the roughness of two different sites on the arthritic FLS increased with an increase in the duration of pathogenesis. These results strongly suggest that AFM can be widely used as a diagnostic tool in cytopathology to detect the early signs of RA and various others diseases at the intercellular level.

An ethanol root extract of Cynanchum wilfordii containing acetophenones suppresses the expression of VCAM-1 and ICAM-1 in TNF-α-stimulated human aortic smooth muscle cells through the NF-κB pathway

The root of Cynanchum wilfordii (C. wilfordii) contains several biologically active compounds which have been used as traditional medicines in Asia. In the present study, we evaluated the anti-inflammatory effects of an ethanol root extract of C. wilfordii (CWE) on tumor necrosis factor (TNF)-α-stimulated human aortic smooth muscle cells (HASMCs). The inhibitory effects of CWE on vascular cell adhesion molecule (VCAM)-1 expression under an optimum extraction condition were examined. CWE suppressed the expression of VCAM-1 and ICAM-1 and the adhesion of THP-1 monocytes to the TNF-α-stimulated HASMCs. Consistent with the in vitro observations, CWE inhibited the aortic expression of ICAM-1 and VCAM-1 in atherogenic diet-fed mice. CWE also downregulated the expression of nuclear factor-κB (NF-κB p65) and its uclear translocation in the stimulated HASMCs. In order to identify the active components in CWE, we re-extracted CWE using several solvents, and found that the ethyl acetate fraction was the most effective in suppressing the expression of VCAM-1 and ICAM-1. Four major acetophenones were purified from the ethyl acetate fraction, and two components, p-hydroxyacetophenone and cynandione A, potently inhibited the expression of ICAM-1 and VCAM-1 in the stimulated HASMCs. We assessed and determined the amounts of these two active components from CWE, and our results suggested that the root of C. wilfordii and its two bioactive acetophenones may be used for the prevention and treatment of atherosclerosis and vascular inflammatory diseases.

Characterisation of fibroblast-like synoviocytes from a murine model of joint inflammation

Introduction

Fibroblast-like synoviocytes (FLS) play a central role in defining the stromal environment in inflammatory joint diseases. Despite a growing use of FLS isolated from murine inflammatory models, a detailed characterisation of these cells has not been performed.

Methods

In this study, FLS were isolated from inflamed joints of mice expressing both the T cell receptor transgene KRN and the MHC class II molecule Ag7 (K/BxN mice) and their purity in culture determined by immunofluorescence and real-time reverse transcription polymerase chain reaction (real-time RT-PCR). Basal expression of proinflammatory genes was determined by real-time RT-PCR. Secreted interleukin 6 (IL-6) was measured by enzyme-linked immunosorbent assay (ELISA), and its regulation by tumor necrosis factor-alpha (TNF-α and corticosterone (the major glucocorticoid in rodents) measured relative to other mesenchymal cell populations.

Results

Purity of FLS culture was identified by positive expression of fibronectin, prolyl 4-hydroxylase, cluster of differentiation 90.2 (CD90.2) and 248 (CD248) in greater than 98% of the population. Cultured FLS were able to migrate and invade through matrigel, a process enhanced in the presence of TNF-α. FLS isolated from K/BxN mice possessed significantly greater basal expression of the inflammatory markers IL-6, chemokine ligand 2 (CCL-2) and vascular cell adhesion molecule 1 (VCAM-1) when compared to FLS isolated from non-inflamed tissue (IL-6, 3.6 fold; CCL-2, 11.2 fold; VCAM-1, 9 fold; P < 0.05). This elevated expression was abrogated in the presence of corticosterone at 100 nmol/l. TNF-α significantly increased expression of all inflammatory markers to a much greater degree in K/BxN FLS relative to other mesenchymal cell lines (K/BxN; IL-6, 40.8 fold; CCL-2, 1343.2 fold; VCAM-1, 17.8 fold; ICAM-1, 13.8 fold; P < 0.05), with secreted IL-6 mirroring these results (K/BxN; con, 169 ± 29.7 versus TNF-α, 923 ± 378.8 pg/ml/1 × 10⁵ cells; P < 0.05). Dose response experiments confirmed effective concentrations between 10 and 100 nmol/l for corticosterone and 1 and 10 ng/ml for TNF-α, whilst inflammatory gene expression in FLS was shown to be stable between passages four and seven.

Conclusions

This study has established a well characterised set of key inflammatory genes for in vitro FLS culture, isolated from K/BxN mice and non-inflamed wild-type controls. Their response to both pro- and anti-inflammatory signalling has been assessed and shown to strongly resemble that which is seen in human FLS culture. Additionally, this study provides guidelines for the effective characterisation, duration and treatment of murine FLS culture.

Isolation and characterization of multipotential mesenchymal cells from the mouse synovium

The human synovium contains mesenchymal stem cells (MSCs), which are multipotential non-hematopoietic progenitor cells that can differentiate into a variety of mesenchymal lineages and they may therefore be a candidate cell source for tissue repair. However, the molecular mechanisms by which this can occur are still largely unknown. Mouse primary cell culture enables us to investigate the molecular mechanisms underlying various phenomena because it allows for relatively easy gene manipulation, which is indispensable for the molecular analysis. However, mouse synovial mesenchymal cells (SMCs) have not been established, although rabbit, cow, and rat SMCs are available, in addition to human MSCs. The aim of this study was to establish methods to harvest the synovium and to isolate and culture primary SMCs from mice. As the mouse SMCs were not able to be harvested and isolated using the same protocol for human, rat and rabbit SMCs, the protocol for humans was modified for SMCs from the Balb/c mouse knee joint. The mouse SMCs obtained showed superior proliferative potential, growth kinetics and colony formation compared to cells derived from muscle and bone marrow. They expressed PDGFRá and Sca-1 detected by flow cytometry, and showed an osteogenic, adipogenic and chondrogenic potential similar or superior to the cells derived from muscle and bone marrow by demonstrating in vitro osteogenesis, adipogenesis and chondrogenesis. In conclusion, we established a primary mouse synovial cell culture method. The cells derived from the mouse synovium demonstrated both the ability to proliferate and multipotentiality similar or superior to the cells derived from muscle and bone marrow.

Anti-inflammatory activities of Chinese herbal medicine sinomenine and Liang Miao San on tumor necrosis factor-α-activated human fibroblast-like synoviocytes in rheumatoid arthritis

AIM OF THE STUDY

Sinomenine, an alkaloid isolated from the root of Sinomenium acutum, has been used to alleviate the symptoms of rheumatic diseases. Liang Miao San (LMS), composed of the herbs Rhizoma Atractylodis (Cangzhu) and Cotex Phellodendri (Huangbai), is another traditional Chinese medicine formula for rheumatoid arthritis (RA) treatment. Although numerous studies have demonstrated the potential anti-inflammatory activities of sinomenine and LMS, the underlying intracellular mechanisms regulating the anti-inflammatory activities of sinomenine and LMS on human primary fibroblast-like synoviocytes (FLS) from RA patients and normal control subjects have not been elucidated.

MATERIALS AND METHODS

We investigated the in vitro anti-inflammatory activity of sinomenine and LMS on inflammatory cytokine tumor necrosis factor (TNF)-α-mediated activation of human normal and RA-FLS. The underlying intracellular signaling molecules were analyzed quantitatively using flow cytometry.

RESULTS

Sinomenine was found to significantly inhibit TNF-α induced cell surface expression of vascular cell adhesion molecule (VCAM)-1 and release of inflammatory cytokine and chemokine IL-6, CCL2 and CXCL8 from both normal and RA-FLS (all p<0.05). Moreover, the suppression of sinomenine on TNF-α induced VCAM-1 expression and IL-6 release of RA-FLS was significantly higher than that of normal FLS (p<0.05). LMS significantly inhibited TNF-α-induced inflammatory chemokines CXCL10 and CCL5 release from both normal and RA-FLS, with significantly higher suppression on CXCL10 secretion in RA-FLS than that of normal FLS (all p<0.05). Further investigations showed that sinomenine and LMS could significantly suppress TNF-α-induced phosphorylation of inhibitor κBα and extracellular signal-regulated protein kinase, the central signaling molecules mediating TNF-α-induced VCAM-1 expression and chemokine production.

CONCLUSION

Our results therefore provide a new insight into the differential anti-inflammatory activities of sinomenine and LMS through the suppression of TNF-α-activated FLS by modulating distinct intracellular signaling pathways in RA.

Effects of inflammatory cytokine IL-27 on the activation of fibroblast-like synoviocytes in rheumatoid arthritis

Introduction

Interleukin (IL)-27 is a novel member of the IL-6/IL-12 family cytokines that are produced early by antigen-presenting cells in T helper (Th)1-mediated inflammation. Elevated expression of IL-27 has been detected in the synovial membranes and fluid of rheumatoid arthritis (RA).

Methods

We investigated the in vitro effects of IL-27, alone or in combination with inflammatory cytokine tumor necrosis factor (TNF)-α or IL-1 β on the pro-inflammatory activation of human primary fibroblast-like synoviocytes (FLS) from RA patients and normal control subjects, and the underlying intracellular signaling molecules were determined by intracellular staining using flow cytometry.

Results

Significantly higher plasma concentration of IL-27 was found in RA patients (n = 112) than control subjects (n = 46). Both control and RA-FLS constitutively express functional IL-27 receptor heterodimer, gp130 and WSX-1, with more potent IL-27-mediated activation of signal transducers and activators of transcription (STAT)1 in RA-FLS. IL-27 was found to induce significantly higher cell surface expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 and release of inflammatory chemokine IL-6, CCL2, CXCL9, CXCL10 and matrix metalloproteinase-1 of RA-FLS than that of control FLS (all P < 0.05). Moreover, an additive or synergistic effect was observed in the combined treatment of IL-27 and TNF-α or IL-1 β on the surface expression of ICAM-1 and VCAM-1 and the release of CXCL9 and CXCL10 of RA-FLS. Further investigations showed that the expression of ICAM-1, VCAM-1 and chemokines stimulated by IL-27 was differentially regulated by intracellular activation of phosphatidylinositol 3-OH kinase-AKT, c-Jun amino-terminal kinase and Janus kinase pathways.

Conclusions

Our results therefore provide a new insight into the IL-27-activated immunopathological mechanisms mediated by distinct intracellular signal transductions in joint inflammation of RA.

Interleukin-1beta induces ICAM-1 expression enhancing leukocyte adhesion in human rheumatoid arthritis synovial fibroblasts: involvement of ERK, JNK, AP-1, and NF-kappaB

Interleukin-1beta (IL-1beta) has been shown to induce the expression of adhesion molecules on various cell types and contributes to inflammatory responses. However, the molecular mechanisms by which IL-1beta induced intercellular adhesion molecule (ICAM)-1 expression remain unclear in human rheumatoid arthritis synovial fibroblasts (RASFs). Here, we demonstrated that IL-1beta induces ICAM-1 gene expression via the de novo protein synthesis through transcription and translation, which is attenuated by pretreatment with actinomycin D and cycloheximide, respectively. IL-1beta-induced ICAM-1 expression, extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK) phosphorylation, AP-1 activation, and nuclear factor-kappaB (NF-kappaB) p65 translocation were attenuated by the inhibitors of MEK1/2 (U0126), JNK (SP600125), AP-1 (tanshinone IIA), and NF-kappaB (helenalin) or transfection with respective short hairpin RNA plasmids. Moreover, IL-1beta-stimulated NF-kappaB p65 translocation was blocked by helenalin, but not by U0126 or SP600125, revealing that MAPKs and NF-kappaB pathways were independent on these responses. IL-1beta-stimulated AP-1 activation was blocked by U0126 or SP600125, revealing that ERK and JNK linked to AP-1 on these responses. IL-1beta-stimulated ICAM-1 gene expression was attenuated by pretreatment with U0126, SP600125, tanshinone IIA, or helenalin, revealed by ICAM-1 promoter assay and real-time RT-PCR analysis. Finally, up-regulation of ICAM-1 enhanced the adhesion of leukocytes to RASFs exposed to IL-1beta. These results suggest that in human RASFs, activation of ERK, JNK, AP-1, and NF-kappaB are essential for IL-1beta-induced ICAM-1 expression and leukocyte adhesion.

Cell-based osteoprotegerin therapy for debris-induced aseptic prosthetic loosening on a murine model

Exogenous OPG gene modification appears a therapeutic strategy for osteolytic aseptic loosening. The feasibility and efficacy of a cell-based OPG gene delivery approach were investigated using a murine model of knee prosthesis failure. A titanium pin was implanted into mouse proximal tibia to mimic a weight-bearing knee arthroplasty, followed by titanium-particles challenge to induce periprosthetic osteolysis. Mouse fibroblast-like synoviocytes were transduced in vitro with either AAV-OPG or AAV-LacZ before transfused into the osteolytic prosthetic joint 3 weeks post surgery. Successful transgene expression at the local site was confirmed 4 weeks later after sacrifice. Biomechanical pull-out test indicated a significant restoration of implant stability following the cell-based OPG gene therapy. Histology revealed that inflammatory pseudo-membranes existed ubiquitously at bone-implant interface in control groups, while only observed sporadically in OPG gene-modified groups. TRAP+ osteoclasts and TNFα, IL-1β, CD68+ expressing cells were significantly reduced in periprosthetic tissues of OPG gene-modified mice. No transgene dissemination or tumorigenesis was detected in remote organs and tissues. Data suggest that cell based ex vivo OPG gene therapy was comparable in efficacy with in vivo local gene transfer technique to deliver functional therapeutic OPG activities, effectively halted the debris-induced osteolysis and regained the implant stability in this model.

Involvement of MAPKs and NF-kappaB in tumor necrosis factor alpha-induced vascular cell adhesion molecule 1 expression in human rheumatoid arthritis synovial fibroblasts

OBJECTIVE

To investigate the roles of MAPKs and NF-kappaB in tumor necrosis factor alpha (TNFalpha)-induced expression of vascular cell adhesion molecule 1 (VCAM-1) in human rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS

Human RASFs were isolated from synovial tissue obtained from patients with RA who underwent knee or hip surgery. The involvement of MAPKs and NF-kappaB in TNFalpha-induced VCAM-1 expression was investigated using pharmacologic inhibitors and transfection with short hairpin RNA (shRNA) and measured using Western blot, reverse transcriptase-polymerase chain reaction, and gene promoter assay. NF-kappaB translocation was determined by Western blot and immunofluorescence staining. The functional activity of VCAM-1 was evaluated by lymphocyte adhesion assay.

RESULTS

TNFalpha-induced VCAM-1 expression, phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK, and translocation of NF-kappaB were attenuated by the inhibitors of MEK-1/2 (U0126), p38 (SB202190), JNK (SP600125), and NF-kappaB (helenalin) or by transfection with their respective shRNA. TNFalpha-stimulated translocation of NF-kappaB into the nucleus and NF-kappaB promoter activity were blocked by Bay11-7082, but not by U0126, SB202190, or SP600125. VCAM-1 promoter activity was enhanced by TNFalpha in RASFs transfected with VCAM-1-Luc, and this promoter activity was inhibited by Bay11-7082, U0126, SB202190, and SP600125. Moreover, up-regulation of VCAM-1 increased the adhesion of lymphocytes to the RASF monolayer, and this adhesion was attenuated by pretreatment with helenalin, U0126, SP600125, or SB202190 prior to exposure to TNFalpha or by anti-VCAM-1 antibody before the addition of lymphocytes.

CONCLUSION

In RASFs, TNFalpha-induced VCAM-1 expression is mediated through activation of the p42/p44 MAPK, p38 MAPK, JNK, and NF-kappaB pathways. These results provide new insights into the mechanisms underlying cytokine-initiated joint inflammation in RA and may inspire new targeted therapeutic approaches.

Reduction of particle-induced osteolysis by interleukin-6 involves anti-inflammatory effect and inhibition of early osteoclast precursor differentiation

The goal of this study was to define the anti-osteoclastogenic and/or anti-inflammatory role of IL-6 in inflammatory bone resorption using in vivo and in vitro methods. To this end, titanium particles were placed on murine calvaria, and bone resorption and osteoclast formation quantified in wild-type and IL-6(-/-) mice. In this model, calvarial bone loss and osteoclast formation were increased in titanium-treated IL-6(-/-) mice. Although basal numbers of splenic osteoclast precursors (OCP) were similar, IL-6(-/-) mice treated with particles in vivo had increased splenic OCP suggesting an enhanced systemic inflammatory response. In vitro osteoclastogenesis was measured using splenic (OCP) at various stages of maturation, including splenocytes from WT, IL-6(-/-) and TNFalpha transgenic mice. ELISA was used to measure TNFalpha production. IL-6 inhibited osteoclastogenesis in early OCP obtained from wild-type and IL-6(-/-) spleens. Pre-treatment of OCP with M-CSF for three days increased the CD11b(high)/c-Fms+ cell population, resulting in an intermediate staged OCP. Osteoclastogenesis was unaffected by IL-6 in M-CSF pre-treated and TNFalpha transgenic derived OCP. IL-6(-/-) splenocytes secreted greater concentrations of TNFalpha in response to titanium particles than WT; addition of exogenous IL-6 to these cultures decreased TNFalpha expression while anti-IL-6 antibody increased TNFalpha. While IL-6 lacks effects on intermediate staged precursors, the dominant in vivo effects of IL-6 appear to be related to strong suppression of early OCP differentiation and an anti-inflammatory effect targeting TNFalpha. Thus, the absence of IL-6 results in increased inflammatory bone loss.

Titanium particles stimulate COX-2 expression in synovial fibroblasts through an oxidative stress-induced, calpain-dependent, NF-kappaB pathway

In prosthetic loosening, bone resorption is induced by wear debris particles generated from the artificial joint articulation. Our prior work showed that synovial-like fibroblasts respond to titanium particles by producing receptor activator of NF-kappaB ligand (RANKL), a critical activator of osteoclastogenesis. While this effect occurs through a cyclooxygenase-2 (COX-2)-dependent pathway, the mechanism of COX-2 stimulation by titanium particles is not clear. Here we show that titanium particles induce COX-2 gene expression by activating NF-kappaB signaling. Inhibitor of NF-kappaB (IkappaBalpha) is degraded following particle treatment, permitting active NF-kappaB to translocate to the nucleus where it interacts with the COX-2 promoter and drives transcription. NF-kappaB activation is dependent on reactive oxygen species since antioxidants block the NF-kappaB signaling induced by particles. Surprisingly, IkappaBalpha degradation is independent of IKK (IkappaB kinase) and the 26S proteasome. Instead, calpain inhibitor can block the IkappaBalpha degradation induced by particles. Furthermore, the calpain-targeted COOH-terminal PEST sequence of IkappaBalpha is necessary for phosphorylation and degradation, consistent with a proteasome-independent mechanism of catabolism. Altogether, the data demonstrate a signaling pathway by which titanium particles induce oxidative stress, stimulate calpain-mediated NF-kappaB activation, and activate target gene expression, including COX-2. These findings define important targets for osteolysis but may also have importance in other diseases where fibroblasts respond to environmental particles, including pulmonary diseases.

Role of adhesion molecules in synovial inflammation

PURPOSE OF REVIEW

The ability of cells to adhere to other cells and extracellular matrix (ECM) through cellular adhesion molecules (CAMs) is central to tissue remodeling and inflammation. This review discusses the potential role of CAMs in development of synovial inflammation through regulating the recruitment of inflammatory cells via endothelial-leukocyte interactions, the organization and activation of leukocytes in the synovial sublining, and the formation and behavior of the hyperplastic synovial lining.

RECENT FINDINGS

Over the past several years valuable insight has been gained into the role of cell-cell and cell-ECM adhesive interactions in synovial organization and inflammation. Recently, cadherin-11 was identified on fibroblast-like synoviocytes and has been demonstrated to play a central role in synovial lining organization. Furthermore, studies using animal models of inflammatory arthritis have demonstrated critical roles for E- and P-selectins, CD11a/CD18 [lymphocyte function-associated antigen (LFA)-1], alpha4beta1 integrin, and cadherin-11 in the development of synovial inflammation.

SUMMARY

Cell-cell and cell-ECM interactions through CAMs play an important role in synovial inflammation. Future studies of CAMs are needed to define more thoroughly their role in synovial inflammation and their potential as therapeutic targets in the treatment of rheumatoid arthritis and related inflammatory arthritic conditions.

TNF-alpha upregulates VCAM-1 and NF-kappaB in fibroblasts from nasal polyps

OBJECTIVE

Lung and synovial fibroblasts produce VCAM-1 in response to TNF-alpha. However, the massive infiltration of eosinophils, the effects of the increased amount of TNF-alpha and the production of VCAM-1 in human nasal polyp fibroblasts are not yet fully understood. The present study examines the role of VCAM-1 and the molecular mechanism of its expression in nasal fibroblasts.

METHODS

Nasal fibroblasts were isolated from human nasal polyps and after four passages, the cells were stimulated with TNF-alpha and VCAM-1 expression was examined by ELISA, flow cytometry, and RT-PCR. The activation of NF-kappaB induced by TNF-alpha was determined by electrophoretic mobility shift assays and the influence on the expression of VCAM-1 was investigated.

RESULTS

VCAM-1 protein and mRNA were expressed in unstimulated controls and remarkably increased by TNF-alpha stimulation. NF-kappaB activity was enhanced by TNF-alpha stimulation and remarkably suppressed by NF-kappaB proteasome inhibitor.

CONCLUSIONS

The present study discovered that nasal fibroblasts produce VCAM-1 protein and mRNA and that production is increased by TNF-alpha stimulation. Furthermore, VCAM-1 expression in nasal fibroblasts is induced through an NF-kappaB-dependent pathway. These findings might provide a rationale for using NF-kappaB inhibitors as a treatment for nasal inflammatory diseases such as polyps.

Periosteal progenitor cell fate in segmental cortical bone graft transplantations: implications for functional tissue engineering

A murine segmental femoral bone graft model was used to show the essential role of donor periosteal progenitor cells in bone graft healing. Transplantation of live bone graft harvested from Rosa 26A mice showed that approximately 70% of osteogenesis on the graft was attributed to the expansion and differentiation of donor periosteal progenitor cells. Furthermore, engraftment of BMP-2-producing bone marrow stromal cells on nonvital allografts showed marked increases in cortical graft incorporation and neovascularization, suggesting that gene-enhanced, tissue engineered functional periosteum may improve allograft incorporation and repair.

INTRODUCTION

The loss of cellular activity in a structural bone allograft markedly reduces its healing potential compared with a live autograft. To further understand the cellular mechanisms for structural bone graft healing and repair and to devise a therapeutic strategy aimed at enhancing the performance of allograft, we established a segmental femoral structural bone graft model in mice that permits qualitative and quantitative analyses of graft healing and neovascularization.

MATERIALS AND METHODS

Using this segmental femoral bone graft model, we transplanted live isografts harvested from Rosa 26A mice that constitutively express beta-galactosidase into their wildtype control mice. In an attempt to emulate the osteogenic and angiogenic properties of periosteum, we applied a cell-based, adenovirus-mediated gene therapy approach to engraft BMP-2-producing bone marrow stromal cells onto devitalized allografts.

RESULTS

X-gal staining for donor cells allowed monitoring the progression of periosteal progenitor cell fate and showed that 70% of osteogenesis was attributed to cellular proliferation and differentiation of donor progenitor cells on the surface of the live bone graft. Quantitative muCT analyses showed a 3-fold increase in new bone callus formation and a 6.8-fold increase in neovascularization for BMP-2/stromal cell-treated allograft compared with control acellular allografts. Histologic analyses showed the key features of autograft healing in the BMP-2/stromal cell-treated allografts, including the formation of a mineralized bone callus completely bridging the segmental defects, abundant neovascularization, and extensive resorption of bone graft.

CONCLUSIONS

The marked improvement of healing in these cellularized allografts suggests a clinical strategy for engineering a functional periosteum to improve the osteogenic and angiogenic properties of processed allografts.

Effect of a small molecule inhibitor of nuclear factor-kappaB nuclear translocation in a murine model of arthritis and cultured human synovial cells

A small cell-permeable compound, dehydroxymethylepoxyquinomicin (DHMEQ), does not inhibit phosphorylation and degradation of IκB (inhibitor of nuclear factor-κB [NF-κB]) but selectively inhibits nuclear translocation of activated NF-κB. This study aimed to demonstrate the antiarthritic effect of this novel inhibitor of the NF-κB pathway in vivo in a murine arthritis model and in vitro in human synovial cells. Collagen-induced arthritis was induced in mice, and after onset of arthritis the mice were treated with DHMEQ (5 mg/kg body weight per day). Using fibroblast-like synoviocyte (FLS) cell lines established from patients with rheumatoid arthritis (RA), NF-κB activity was examined by electrophoretic mobility shift assays. The expression of molecules involved in RA pathogenesis was determined by RT-PCR, ELISA, and flow cytometry. The proliferative activity of the cells was estimated with tritiated thymidine incorporation. After 14 days of treatment with DHMEQ, mice with collagen-induced arthritis exhibited decreased severity of arthritis, based on the degree of paw swelling, the number of swollen joints, and radiographic and histopathologic scores, compared with the control mice treated with vehicle alone. In RA FLS stimulated with tumor necrosis factor-α, activities of NF-κB components p65 and p50 were inhibited by DHMEQ, leading to suppressed expression of the key inflammatory cytokine IL-6, CC chemokine ligand-2 and -5, matrix metalloproteinase-3, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1. The proliferative activity of the cells was also suppressed. This is the first demonstration of an inhibitor of NF-κB nuclear translocation exhibiting a therapeutic effect on established murine arthritis, and suppression of inflammatory mediators in FLS was thought to be among the mechanisms underlying such an effect.

Fibroblasts express RANKL and support osteoclastogenesis in a COX-2-dependent manner after stimulation with titanium particles

Synovial fibroblasts are possible mediators of osteolysis. Fibroblasts respond directly to titanium particles and increase RANKL expression through a COX-2/PGE2/EP4/PKA signaling pathway. Fibroblasts pretreated with titanium or PGE2 stimulated osteoclast formation, showing the functional importance of RANKL induction. Synovial fibroblasts and their activation pathways are potential targets to prevent osteolysis.

INTRODUCTION

Bone loss adjacent to the implant is a major cause of joint arthroplasty failure. Although the cellular and molecular response to microscopic wear debris particles is recognized as causative, little is known concerning role of synovial fibroblasts in these events.

MATERIALS AND METHODS

Murine embryonic fibroblasts and knee synovial fibroblasts in culture stimulated with titanium particles were examined by FACS, real time RT-PCR, Northern blot, and Western blot for expressions of vascular cell adhesion molecule (VCAM)1, RANKL, cyclooxygenase (COX)-1, and COX-2, and the four prostaglandin E2 (PGE2) receptor isoforms. Experiments were performed in the presence and absence of COX inhibitors, protein kinase A (PKA) and protein kinase C (PKC) inhibitors, and various EP receptor agonists. Osteoclast formation was examined in co-cultures of pretreated glutaraldehyde-fixed fibroblasts and primary murine spleen cells treated with macrophage-colony stimulating factor (M-CSF) for 7-days.

RESULTS

TNF-alpha stimulated VCAM1 expression, consistent with a synovial fibroblast phenotype. Titanium particles stimulated RANKL gene and protein expressions in fibroblasts in a dose-dependent manner. Gene expression was increased 5-fold by 4 h, and protein levels reached a maximum after 48 h. Within 1 h, titanium particles also induced COX-2 mRNA and protein levels, whereas both indomethacin and celecoxib blocked the stimulation of RANKL, suggesting a COX-2-mediated event. Furthermore, PGE2 induced RANKL gene and protein expression and rescued RANKL expression in titanium-treated cultures containing COX-2 inhibitors. Fibroblast cultures pretreated with either PGE2 or titanium particles enhanced osteoclast formation, indicating the functional importance of RANKL induction. EP4 was the most abundant PGE2 receptor isoform, EP1 and EP2 were expressed at low levels, and EP3 was absent. The EP1 selective agonist iloprost and the EP2 selective agonist butaprost minimally stimulated RANKL. In contrast, the EP2 and EP4 agonist misoprostol induced RANKL to a magnitude similar to PGE2. Finally, PKA antagonism strongly repressed RANKL stimulation by PGE2.

CONCLUSION

Fibroblasts respond directly to titanium particles and increase RANKL expression through a COX-2/PGE2/EP4/PKA signaling pathway. Thus, the synovial fibroblast is important mediator of osteolysis and target for therapeutic strategies.

Cytokine-stimulated GTP cyclohydrolase I expression in endothelial cells requires coordinated activation of nuclear factor-kappaB and Stat1/Stat3

Endothelial production of nitric oxide (NO) is dependent on adequate cellular levels of tetrahydrobiopterin (BH4), an important cofactor for the nitric oxide synthases. Vascular diseases are often characterized by vessel wall inflammation and cytokine treatment of endothelial cells increases BH4 levels, in part through the induction of GTP cyclohydrolase I (GTPCH I), the rate-limiting enzyme for BH4 biosynthesis. However, the molecular mechanisms of cytokine-mediated GTPCH I induction in the endothelium are not entirely clear. We sought to investigate the signaling pathways whereby cytokines induce GTPCH I expression in human umbilical vein endothelial cells (HUVECs). Interferon-gamma (IFN-gamma) induced endothelial cell GTPCH I protein and BH4 modestly, whereas high-level induction required combinations of IFN-gamma and tumor necrosis factor-alpha (TNF-alpha). In the presence of IFN-gamma, TNF-alpha increased GTPCH I mRNA in a manner dependent on nuclear factor-kappaB (NF-kappaB), as this effect was abrogated by overexpression of a dominant-negative IkappaB construct. HUVEC IFN-gamma treatment resulted in signal transducer and activator of transcription 1 (Stat1) activation and DNA binding in a Jak2-dependent manner, as this was inhibited by AG490. Conversely, overexpression of Jak2 effectively substituted for IFN-gamma in supporting TNF-alpha-mediated GTPCH I induction. The role of IFN-gamma was also Stat1-dependent as Stat1-null cells exhibited no GTPCH I induction in response to cytokines. However, Stat1 activation with oncostatin M failed to support TNF-alpha-mediated GTPCH I induction because of concomitant Stat3 activation. Consistent with this notion, siRNA-mediated Stat3 gene silencing allowed oncostatin M to substitute for IFN-gamma in this system. These data implicate both NF-kappaB and Stat1 in endothelial cell cytokine-stimulated GTPCH I induction and highlight the role of Stat3 in modulating Stat1-supported gene transcription. Thus, IFN-gamma and TNF-alpha exert distinct but cooperative roles for BH4 biosynthesis in endothelium that may have important implications for vascular function during vascular inflammation.

The advanced glycation end product pentosidine correlates to IL-6 and other relevant inflammatory markers in rheumatoid arthritis

OBJECTIVE

Oxidative stress and inflammatory processes accelerate the formation of advanced glycation end products (AGE), e.g. of pentosidine. The aim of this study was to investigate the relationships between levels of pentosidine in serum and synovial fluid, proinflammatory cytokines, other markers of inflammatory activity, and the state of radiologically visible bone destruction in patients with rheumatoid arthritis (RA).

OBJECTIVES

One hundred thirty-three nondiabetic RA patients and 56 age-matched, healthy subjects were included. Serum and synovial fluid pentosidine, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and rheumatoid factor levels were determined. In 30 patients, the proinflammatory cytokines interleukin (IL)-1beta, IL-6, and TNF-alpha and the soluble receptors sIL-2R, sIL-6R, sTNF-alpha, and RI/RII were also measured.

RESULTS

Serum levels of pentosidine were on average significantly higher in RA patients than in healthy subjects and correlated significantly to ESR, CRP, and serum levels of IL-6. Serum and synovial fluid pentosidine did not show any differences. Rheumatoid factor-positive RA patients had higher pentosidine levels in the synovial fluid than rheumatoid factor-negative patients. Correlations could not be found between pentosidine and the other cytokines or cytokine receptors measured.

CONCLUSION

The binding of AGE on cell receptors induces activation of nuclear factor kappa B, resulting in enhanced synthesis of proinflammatory cytokines. Moreover, AGE generation may also lead to the formation of new, immunologically relevant epitopes at synovial proteins. Both mechanisms could contribute to initiation and perpetuation of the inflammatory and destructive processes in RA.

NF-kappaB p65 involves in reperfusion injury and iNOS gene regulation in skeletal muscle

This study investigated the effects of inhibition of NF-kappaB activation on microcirculation and inducible NOS expression in reperfused rat cremaster muscle. The muscle from 16 rats underwent 5-h ischemia and 90-min reperfusion. Each rat received NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC, 150 mg/kg) or phosphate-buffered saline 15 min before reperfusion. Results showed that PDTC treatment had a significant overall increase in muscle blood flow during reperfusion. Blood flow more rapidly recovered to and over baseline in the PDTC-treated group than in controls, with a significant difference at 10-30 min and 70-90 min. Expression of iNOS mRNA had a 167-fold increase from normal in controls, but was significantly (P < 0.05) reduced to a 63-fold increase in PDTC-treated muscles. In addition, PDTC treatment significantly (P < 0.05) decreased a reperfusion-induced increase in activated NF-kappaB p65 and nuclear p65 protein. Our results suggest that NF-kappaB is involved in I/R injury and that inhibition of NF-kappaB p65 activation affords protection against I/R injury, perhaps via downregulating expression of iNOS transcription.

Systemic tumor necrosis factor alpha mediates an increase in peripheral CD11bhigh osteoclast precursors in tumor necrosis factor alpha-transgenic mice

OBJECTIVE

To investigate the mechanisms whereby tumor necrosis factor alpha (TNFalpha) increases osteoclastogenesis in vivo.

METHODS

TNFalpha-transgenic (TNF-Tg) and wild-type mice injected with TNFalpha were studied. In vitro osteoclastogenesis assays, monocyte colony-forming assays, and fluorescence-activated cell sorting were performed using splenocytes, peripheral blood mononuclear cells (PBMCs), and bone marrow cells to quantify and characterize osteoclast precursors (OCPs). Etanercept, a TNFalpha antagonist, was used to block TNFalpha activity in vivo. The effects of TNFalpha on proliferation, apoptosis, and differentiation of OCPs were assessed using 5-bromo-2'-deoxyuridine labeling, annexin V staining, and reverse transcriptase-polymerase chain reaction.

RESULTS

OCP numbers were increased 4-7-fold in PBMCs and spleen, but not in bone marrow of TNF-Tg mice. The OCPs in spleen were in the CD11b(high) population and contained both c-Fms- and c-Fms+ cells. The increased number of OCPs correlated with the initiation of detectable TNFalpha in serum and the onset of inflammatory arthritis in TNF-Tg mice. Etanercept eliminated the increase in peripheral OCPs. TNFalpha did not affect proliferation, survival, or differentiation of CD11b(high) splenocytes in vivo or in vitro, but caused a rapid increase in CD11b+ cells in blood within 4 hours of a single injection and an accumulation of CD11b(high) OCPs in spleen after 3 days of multiple injections.

CONCLUSION

Systemic TNFalpha induces a marked increase in circulating OCPs that is reversible by anti-TNF therapy and may result from their mobilization from bone marrow. Our findings provide a new mechanism whereby TNFalpha stimulates osteoclastogenesis in patients with inflammatory arthritis, suggesting that CD11b+ PBMCs could be used to evaluate a patient's potential for erosive disease and the efficacy of anti-TNF therapy.

RANK signaling is not required for TNFalpha-mediated increase in CD11(hi) osteoclast precursors but is essential for mature osteoclast formation in TNFalpha-mediated inflammatory arthritis

To address the controversy of whether TNFalpha can compensate for RANKL in osteoclastogenesis in vivo, we used a TNFalpha-induced animal model of inflammatory arthritis and blocked RANKL/RANK signaling. TNFalpha increased osteoclast precursors available for RANK-dependent osteoclastogenesis. RANK signaling is not required for the TNFalpha-stimulated increase in CD11b(hi) osteoclast precursors but is essential for mature osteoclast formation.

INTRODUCTION

Although critical roles of TNFalpha in inflammatory arthritis and RANKL in bone resorption have been firmly established, a central controversy remains about the extent to which TNFalpha can compensate for RANKL during osteoclastogenesis and the stage at which RANK signaling is required for osteoclastogenesis. Here, we used the human TNFalpha transgenic mouse model (TNF-Tg) of erosive arthritis to determine if there are both RANK-dependent and -independent stages of osteoclastogenesis in TNFalpha-induced erosive arthritis.

MATERIALS AND METHODS

Osteoclastogenesis and osteoclast precursor (OCP) frequency were analyzed using histology, fluorescence-activated cell sorting (FACS), and cell culture from (1) TNF-Tg mice treated with the RANKL antagonist, RANK:Fc, or (2) TNF-Tg X RANK -/- mice generated by crossing TNF-Tg mice with RANK-/- mice.

RESULTS

Treatment of TNF-Tg mice, which have increased OCPs in their spleens, with RANK:Fc dramatically reduced osteoclast numbers on the surface of their arthritic joints and within their bones, but did not decrease CD11b(hi) OCP numbers in their spleens. Long-term RANK:Fc administration alleviated joint erosion. Furthermore, TNF-Tg x RANK -/- mice had severe osteopetrosis, no osteoclasts, and no joint erosion, but increased CD11b(hi) precursor numbers that failed to form mature osteoclasts in vitro.

CONCLUSION

RANK signaling is essential for mature osteoclast formation in TNFalpha-mediated inflammatory arthritis but not for the TNFalpha-induced increase in CD11b(hi) OCP that subsequently can differentiate into osteoclasts in inflamed joints.

Apoptosis in rheumatoid arthritis

Apoptosis is a key mechanism that regulates tissue composition and homeostasis. Alterations in the apoptosis of synovial cells have been described in residential synoviocytes as well as inflammatory cells and associated with the pathogenesis of rheumatoid arthritis. These changes constitute hallmarks of synovial cell activation and contribute to both chronic inflammation and hyperplasia. Rheumatoid arthritis synovial fibroblasts are affected most prominently, and their resistance to apoptosis has been linked closely to the progressive destruction of articular cartilage. Although a detailed understanding of mechanisms that prevent synovial fibroblasts from programmed cell death is lacking, several antiapoptotic molecules have been identified. Among them, downstream modulators of Fas-signaling, such as sentrin-1/small ubiquitin-like modifier (SUMO)-1 and Fas-associated death domain-like interleukin (IL)-1beta-converting enzyme-inhibitory protein (FLIP), as well as transcriptional regulators such as NFkappaB, Stat3, and p53, have been suggested to regulate apoptosis most prominently. Current efforts are aimed at elucidating the specific role of these molecules in regulating the apoptosis of rheumatoid fibroblasts and at identifying molecular targets to interfere with altered apoptosis.

HMGB1 interacts differentially with members of the Rel family of transcription factors

HMGB1 is an architectural factor that enhances the DNA binding affinity of several proteins. We have investigated the influence of HMGB1 on DNA binding by members of the Rel family. HMGB1 enhances DNA binding by p65/p50 and p50/p50, but reduces binding by p65/p65, c-Rel/c-Rel, p65/c-Rel, and p50/c-Rel. In pull-down assays, HMGB1 interacts directly with the p50 subunit via its HMG boxes and this interaction is weakened by the presence of the acidic tail. Functionally, HMGB1 is required for the NF-kappaB-dependent expression of the adhesion molecule VCAM-1.

Molecular aspects of glucocorticoid hormone action in rheumatoid arthritis

Glucocorticoids (GC) are the most powerful anti-inflammatory drugs used in the treatment of autoimmune diseases such as rheumatoid arthritis. In addition, endogenous GC are involved in numerous physiological processes. Most of their effects are mediated by the glucocorticoid receptor (GR) via activation or repression of gene expression. Whereas activation requires DNA binding of the receptor, repression is mediated by protein-protein interactions with other transcription factors. In particular, most immunosuppressive and anti-inflammatory effects are exerted by an interaction of GR with the activating protein 1 (AP-1) and nuclear factor kappaB (NF-kappaB) families of transcription factors without DNA binding. Cytokines such as tumor necrosis factor alpha (TNF-alpha) and interleukin 1 (IL-1) activate the hypothalamus pituitary adrenal (HPA) axis, whereas GC inhibit IL-1 and TNF-alpha forming a cytokine-HPA axis feedback circuit. The high effectiveness of cytokine-antagonists blocking TNF-alpha or IL-1 in RA and the understanding of the precise molecular mechanisms of GC function will enhance our understanding of autoimmune diseases, such as RA, and could suggest new beneficial therapeutic approaches with fewer side-effects.

Novel biologically based therapeutic strategies in myeloma

Multiple myeloma remains incurable despite advances in conventional chemotherapy and wider applicability of high dose chemotherapy with single and/or tandem autologous peripheral blood stem cell transplantation. Although a complete remission rate of 41% and an event-free survival of 43 months have been reported after tandem transplantation, it is highly unlikely that further improvements in the outcome of multiple myeloma will be achieved by escalating cytotoxic chemotherapy alone. Novel biologically based therapies are therefore urgently required. Targeted therapeutic approaches based on: identification of genetic abnormalities in malignant plasma cells; interrupting growth of myeloma cells; triggering apoptotic signaling cascades in tumor cells; modulating growth and survival of multiple myeloma cells in the bone marrow microenvironment, i.e. angiogenesis and cytokine networks; enhancing allogeneic and autologous antimyeloma immunity; and characterizing newer myeloma antigens for serotherapy are under development. These therapies offer great promise, used alone/or in combination with conventional treatment approaches, to improve the outcome in this disease in newly diagnosed/refractory or relapsed patients with multiple myeloma.

Structural changes in the forefoot of individuals with diabetes and a prior plantar ulcer

BACKGROUND

Plantar ulcers produced by diabetic foot disease are devastating and costly. Better understanding of the ulcer-producing process is important to improve detection of feet that are at risk and to improve intervention. We identified and quantified soft-tissue and osseous structural changes in the forefoot of diabetic patients with a prior plantar ulcer.

METHODS

Thirty-two individuals with a mean age (and standard deviation) of 57 +/- 11 years were studied; sixteen had diabetes (of a mean of 20 +/- 11 years' duration), peripheral neuropathy, and a prior plantar ulcer, and sixteen were matched controls. Computed tomography was used to evaluate forefoot structure, including the plantar soft-tissue (muscle) density, soft-tissue thickness beneath the metatarsal heads, metatarsophalangeal joint angle, metatarsal bone density, and metatarsophalangeal joint arthropathy.

RESULTS

Plantar soft-tissue (muscle) density was lower in the individuals with diabetes (mean, 1 HU [Hounsfield unit]) than it was in the controls (mean, 18 HU). There was no difference in the soft-tissue thickness beneath the metatarsal heads (mean, 10 mm) between the individuals with diabetes and the controls, but the soft-tissue thickness decreased with age. The individuals with diabetes had greater extension deformity of the first, second, and third metatarsophalangeal joints and greater arthropathy of the second, third, and fourth metatarsophalangeal joints. There were no significant differences in metatarsal bone density between the groups.

CONCLUSIONS

There were significant differences between the forefeet of individuals with diabetes and a previous plantar ulcer and those of controls: plantar muscle density was decreased, and metatarsophalangeal joint extension and arthropathy were increased. Interestingly, the soft-tissue thickness under the metatarsal heads in the controls was not greater than that in the diabetic patients.

CLINICAL RELEVANCE

This study demonstrated structural differences between the forefeet of patients with diabetes and a previous ulcer and those of normal age-matched controls. The information can serve to guide new interventions to prevent or treat foot ulcerations in this patient population.

Role of nuclear factor kappaB in synovial inflammation

The evaluation of molecular pathways has revealed novel insights into the pathophysiology of rheumatoid arthritis in the last several years. Gene transcription factors such as nuclear factor kB (NFkB) are activated by extracellular signals or cell-to-cell interactions that are converted into intracellular activation signals through receptor molecules located in the cell membrane. The number of known genes being translated after NFkB activation is increasing steadily. These genes includes cytokines, chemokines, growth factors, cellular ligands, and adhesion molecules. Because many of these genes are part of the pathogenesis of RA, there is considerable interest in the evaluation of the synovium-specific effects of NFkB to unveil its potential for future therapeutic strategies. The goal is to evolve these strategies from the therapies that have a wide spectrum of effects and side effects into rheumatoid arthritis-specific therapies designed to inhibit distinct molecular pathways within the synovium.

NF-kappa B as a therapeutic target in multiple myeloma

We have shown that thalidomide (Thal) and its immunomodulatory derivatives (IMiDs), proteasome inhibitor PS-341, and As(2)O(3) act directly on multiple myeloma (MM) cells and in the bone marrow (BM) milieu to overcome drug resistance. Although Thal/IMiDs, PS-341, and As(2)O(3) inhibit nuclear factor (NF)-kappaB activation, they also have multiple and varied other actions. In this study, we therefore specifically address the role of NF-kappaB blockade in mediating anti-MM activity. To characterize the effect of specific NF-kappaB blockade on MM cell growth and survival in vitro, we used an IkappaB kinase (IKK) inhibitor (PS-1145). Our studies demonstrate that PS-1145 and PS-341 block TNFalpha-induced NF-kappaB activation in a dose- and time-dependent fashion in MM cells through inhibition of IkappaBalpha phosphorylation and degradation of IkappaBalpha, respectively. Dexamethasone (Dex), which up-regulates IkappaBalpha protein, enhances blockade of NF-kappaB activation by PS-1145. Moreover, PS-1145 blocks the protective effect of IL-6 against Dex-induced apotosis. TNFalpha-induced intracellular adhesion molecule (ICAM)-1 expression on both RPMI8226 and MM.1S cells is also inhibited by PS-1145. Moreover, PS-1145 inhibits both IL-6 secretion from BMSCs triggered by MM cell adhesion and proliferation of MM cells adherent to BMSCs. However, in contrast to PS-341, PS-1145 only partially (20-50%) inhibits MM cell proliferation, suggesting that NF-kappaB blockade cannot account for all of the anti-MM activity of PS-341. Importantly, however, TNFalpha induces MM cell toxicity in the presence of PS-1145. These studies demonstrate that specific targeting of NF-kappaB can overcome the growth and survival advantage conferred both by tumor cell binding to BMSCs and cytokine secretion in the BM milieu. Furthermore, they provide the framework for clinical evaluation of novel MM therapies based upon targeting NF-kappaB.

Viral interleukin-10 gene inhibition of inflammation, osteoclastogenesis, and bone resorption in response to titanium particles

OBJECTIVE

To evaluate the potential of viral interleukin-10 (vIL-10) gene therapy as an approach to prevent wear debris-induced inflammation, osteoclastogenesis, and bone resorption as it relates to periprosthetic osteolysis in patients with total joint replacements.

METHODS

Replication-defective adenovirus vectors expressing vIL-10 (AdvIL-10) or LacZ (AdLacZ) target genes were used to transduce fibroblast-like synoviocytes (FLS) in vitro, and the effects of these cells on wear debris-induced proinflammatory cytokine production and receptor activator of nuclear factor kappaB ligand + macrophage colony-stimulating factor splenocyte osteoclastogenesis were assessed by enzyme-linked immunosorbent assay and tartrate-resistant acid phosphatase assay. The effects of AdvIL-10 administration on wear debris-induced osteolysis in vivo were analyzed using the mouse calvaria model, in which AdLacZ was used as the control.

RESULTS

In the presence of AdLacZ-infected FLS, titanium particle-stimulated macrophages exhibited a marked increase in secretion of tumor necrosis factor alpha (TNFalpha) (6.5-fold), IL-6 (13-fold), and IL-1 (5-fold). Coculture with AdvIL-10-transduced FLS suppressed cytokine secretion to basal levels, while addition of an anti-IL-10 neutralizing antibody completely blocked this effect. The vIL-10-transduced FLS also inhibited osteoclastogenesis 10-fold in an anti-IL-10-sensitive manner. In vivo, titanium implantation resulted in a 2-fold increase in osteoclasts (P < 0.05) and in a 2-fold increase in sagittal suture area (P < 0.05). This increase over control levels was completely blocked in mice receiving intraperitoneal injections of AdvIL-10, all of whom had measurable serum vIL-10 levels for the duration of the experiment. Immunohistochemistry demonstrated reduced cyclooxygenase 2 and TNFalpha expression in AdvIL-10-infected animals.

CONCLUSION

This study demonstrates that gene delivery of vIL-10 inhibits 3 processes critically involved in periprosthetic osteolysis: 1) wear debris-induced proinflammatory cytokine production, 2) osteoclastogenesis, and 3) osteolysis.

Efficacy of ex vivo OPG gene therapy in preventing wear debris induced osteolysis

Aseptic loosening of prosthetic implants remains a serious orthopaedic problem and the greatest limitation to total joint arthroplasty. Central to the etiology of aseptic loosening is periprosthetic osteolysis at the bone-implant interface, which is caused by wear debris-induced inflammation. This inflammation produces the critical osteoclast differentiation factor RANKL, which directly stimulates osteoclastogenesis and osteoclastic bone resorption. A dominant factor known to counteract this process is the natural RANKL receptor antagonist protein OPG. Here we explore the potential of ex vivo OPG gene therapy for aseptic loosening by evaluating the eflicacy of stably transfected fibroblast-like synoviocytes (FLS) expressing OPG in preventing wear debris-induced osteoclastogenesis, in a mouse calvaria model. Although the stably transfected fibroblasts produced small amounts of OPG (0.3 ng/ml/72 h/10(6) cells), this protein was very effective in preventing osteoclastic resorption as determined in a bone wafer assay. More importantly. implantation of 10(7) FLS-OPG, together with 30 mg of Ti wear debris, onto the calvaria of mice, completely inhibited osteoclastogenesis 3 days after surgery. Animals given FLS-LacZ control cells, which persisted for 3 days as determined by X-gal staining, together with the Ti particles, had a 6-fold increase in osteoclastogenesis compared to controls without Ti. This increased osteoclastogenesis was completely inhibited by the FLS-OPG, as osteoclast numbers in the calvaria of these animals were similar to that seen in the SHAM controls.

A novel role for interleukin-18 in adhesion molecule induction through NF kappa B and phosphatidylinositol (PI) 3-kinase-dependent signal transduction pathways

Interleukin-18 (IL-18) is a novel proinflammatory cytokine found in serum and joints of patients with rheumatoid arthritis (RA). We studied a novel role for IL-18 in mediating cell adhesion, a vital component of the inflammation found in RA and other inflammatory diseases. We examined the expression of cellular cell adhesion molecules E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) on endothelial cells and RA synovial fibroblasts using flow cytometry. Adhesion of the monocyte-like cell line HL-60 to endothelial cells was determined by immunofluorescence. IL-18 significantly enhanced ICAM-1 and VCAM-1 expression on endothelial cells and RA synovial fibroblasts. In addition, IL-18 induced E-selectin expression on endothelial cells and promoted the adhesion of HL-60 cells to IL-18-stimulated endothelial cells. Neutralizing anti-VCAM-1 and anti-E-selectin could completely inhibit HL-60 adherence to endothelial cells. IL-18-induced adhesion molecule expression appears to be mediated through nuclear factor kappa B (NF kappa B) and phosphatidyl-inositol 3 kinase (PI 3-kinase) since addition of inhibitors to either NF kappa B (pyrrolidine dithiocarbamate and N-acetyl-l-cysteine) or PI 3-kinase (LY294002) inhibited RA synovial fibroblast VCAM-1 expression by 50 to 60%. Addition of both inhibitors resulted in inhibition of VCAM-1 expression by 85%. In conclusion, the ability of IL-18 to induce adhesion molecule expression on endothelial cells and RA synovial fibroblasts indicates that IL-18 may contribute to RA joint inflammation by enhancing the recruitment of leukocytes into the joint. IL-18 requires NF kappa B as well as PI 3-kinase to induce VCAM-1 on RA synovial fibroblasts, suggesting that there may be two distinct pathways in IL-18-induced adhesion molecule expression.

The role of tumor necrosis factor alpha in the pathophysiology of human multiple myeloma: therapeutic applications

In this study we demonstrate that tumor necrosis factor alpha (TNFalpha) triggers only modest proliferation, as well as p44/p42 mitogen-activated protein kinase (MAPK) and NF-kappaB activation, in MM.1S multiple myeloma (MM) cells. TNFalpha also activates NF-kappaB and markedly upregulates (fivefold) secretion of interleukin-6 (IL-6), a myeloma growth and survival factor, in bone marrow stromal cells (BMSCs). TNFalpha in both a dose and time dependent fashion induced expression of CD11a (LFA-1), CD54 (intercellular adhesion molecule-1, ICAM-1), CD106 (vascular cell adhesion molecule-1, VCAM-1), CD49d (very late activating antigen-4, VLA-4), and/or MUC-1 on MM cell lines; as well as CD106 (VCAM-1) and CD54 (ICAM-1) expression on BMSCs. This resulted in increased (2-4-fold) per cent specific binding of MM cells to BMSCs, with related IL-6 secretion. Importantly, the proteasome inhibitor PS-341 abrogated TNFalpha-induced NF-kappaB activation, induction of ICAM-1 or VCAM-1, and increased adhesion of MM cells to BMSCs. Agents which act to inhibit TNFalpha may therefore abrogate the paracrine growth and survival advantage conferred by MM cell adhesion in the BM microenvironment.

Targeted therapy for multiple myeloma

Multiple myeloma (MM) remains incurable with conventional treatment approaches, and novel biologically based therapies are therefore urgently needed. Targeted therapies are either under development or already undergoing clinical evaluation predicated upon: identifying genetic abnormalities in myeloma cells to enhance chemoradiosensitivity; interrupting growth or triggering apoptotic signaling cascades in tumor cells; treating both the tumor cell and its microenvironment; enhancing allogeneic and autologous antimyeloma immunity; and characterizing new myeloma antigens for serotherapy. These therapies, alone or in combination with conventional treatments, offer great promise to improve the outcome for patients with MM.

Isolation and characterization of rheumatoid arthritis synovial fibroblasts from primary culture--primary culture cells markedly differ from fourth-passage cells

To reduce culture artifacts by conventional repeated passaging and long-term culture in vitro, the isolation of synovial fibroblasts (SFB) was attempted from rheumatoid arthritis (RA) synovial membranes by trypsin/collagenase digest, short-term in vitro adherence (7 days), and negative isolation using magnetobead-coupled anti-CD14 monoclonal antibodies. This method yielded highly enriched SFB (85% prolyl-4-hydroxylase+/74% Thy-1/CD90+ cells; <2% contaminating macrophages; <1% leukocytes/endothelial cells) that, in comparison with conventional fourth-passage RA-SFB, showed a markedly different phenotype and significantly lower proliferation rates upon stimulation with platelet-derived growth factor and IL-1beta. This isolation method is simple and reliable, and may yield cells with features closer to the in vivo configuration of RA-SFB by avoiding extended in vitro culture.