A comparative phenotypical analysis of rheumatoid nodules and rheumatoid synovium with special reference to adhesion molecules and activation markers

Sceptridium ternatum extract exerts antiasthmatic effects by regulating Th1/Th2 balance and the expression levels of leukotriene receptors in a mouse asthma model

AIM OF THE STUDY

Sceptridium ternatum Lyon (ST), a common Chinese herb, has been used in treatment of allergic asthma and whooping cough. In the present study, we investigated the Th1/Th2 ratio of peripheral blood and mRNA levels of leukotriene receptors after the treatment of ST in allergic asthma mouse model.

MATERIALS AND METHODS

Mouse asthma model was developed by ovalbumin (OVA) sensitization followed by the inhalation of aerosol allergen. Montelukast (10mg/kg), as a positive control drug, and ST were administrated six days before the OVA sensitization for ten days. Airway responsiveness was evaluated by the Medlab 12.0 biological signal processing system. The ratio of Th1/Th2 cells was determined by flow cytometry. The expression level of Cyslt1 was measured by PCR. Pathological changes of lung tissues were examined by H&E staining.

RESULTS

ST significantly reduced the airway responsiveness, elevated the ratio of Th1/Th2, and decreased Cyslt1 mRNA level in a dose-dependent manner. High-dose ST distinctly prevented the pathological changes of lung tissues.

CONCLUSION

High-dose ST had the same efficacy as Montelukast in a mouse asthma model, and ST could be a potential anti-asthmatic agent.

Current imaging strategies in rheumatoid arthritis

As remission has now become a realistic therapeutic goal in the clinical management of RA due to the introduction and widespread adoption of biologic agents, there is a greater need for earlier diagnoses and objective methods for evaluating disease activity and response to treatment. In this capacity, advanced imaging strategies are assuming an expansive clinical role, particularly as they take advantage of newer imaging technologies and the shift toward imaging at the molecular level. Molecular imaging utilizes target-specific probes to non-invasively visualize molecular, cellular, and physiological perturbations in response to the underlying pathology. Probes for nuclear and MR imaging have been and are being developed that react with discrete aspects of inflammatory and destructive pathways specific to RA. These probes in addition to new MR sequences and contrast agents have the potential to provide an earlier and more reliable assessment of clinical outcome, disease activity, severity, and location, and therapeutic response. Furthermore, these imaging strategies may enable a more fundamental understanding of critical pathophysiological processes and the advent of new molecular therapies. This review will discuss these advances in both nuclear medicine and MRI strategies for imaging RA with a particular emphasis on molecular imaging.

Synovial mast cells: role in acute and chronic arthritis

Mast cells reside in the normal synovium and increase strikingly in number in rheumatoid arthritis and other joint diseases. Given the broad spectrum of activity of this lineage, it has for decades been considered probable that mast cells are involved in the pathophysiology of synovitis. Recent work in murine arthritis has substantiated this suspicion, showing that mast cells can contribute importantly to the initiation of inflammatory arthritis. However, the role of the greatly expanded population of synovial mast cells in established arthritis remains unknown. Here we review the current understanding of mast cell function in acute arthritis and consider the potentially important influence of this cell on key processes within the chronically inflamed synovium, including leukocyte recruitment and activation, fibroblast proliferation, angiogenesis, matrix remodeling, and injury to collagen and bone. We also consider recent evidence supporting an immunomodulatory or anti-inflammatory role for mast cells as well as pharmacologic approaches to the mast cell as a therapeutic target in inflammatory arthritis.

A role for type 1alpha corticotropin-releasing hormone receptors in mediating local changes in chronically inflamed tissue

Peripheral corticotropin-releasing hormone (CRH) is an important regulator of localized inflammatory responses. The aim of this study is to define the pathological signaling pathways in which peripheral CRH receptor-mediated responses reside. We report that PECAM-1-expressing synovial membrane endothelial cells are the principal source of CRH receptor subtype 1alpha in chronically inflamed synovial tissue (ST). Analysis of ST from an early arthritis patient cohort (n = 9) established that expression of CRH-R1alpha significantly (P < 0.03) colocalized with PECAM-1 and E-selectin expression in vivo. Freshly excised ST explants released a mediator(s) that acts to promote CRH-R1alpha mRNA to levels present in inflamed human synovium (n = 8). We tested the ability of conditioned medium and individual inflammatory mediators to modulate CRH-R1alpha expression. Histamine selectively induced the expression of CRH-R1alpha, and these effects were mediated through the histamine receptor type 1. Ectopic expression of CRH-R1alpha in normal human endothelial and synoviocyte cells resulted in the induction of the orphan receptor NR4A2 through the reconstitution of cAMP/protein kinase A/cAMP response element-binding protein signaling and identified a role for CRH in modulating nuclear factor kappaB transcriptional activity. CRH enhanced the expression of nitric-oxide synthase (NOS III) to promote NO production from CRH-R1alpha-expressing cells. These data establish a role for CRH receptor-mediated responses in regulating vascular changes associated with chronic synovitis.

Rheumatoid arthritis synovium contains plasmacytoid dendritic cells

We have previously described enrichment of antigen-presenting HLA-DR⁺ nuclear RelB⁺ dendritic cells (DCs) in rheumatoid arthritis (RA) synovium. CD123⁺HLA-DR⁺ plasmacytoid DCs (pDCs) and their precursors have been identified in human peripheral blood (PB), lymphoid tissue, and some inflamed tissues. We hypothesized recruitment of pDCs into the inflamed RA synovial environment and their contribution as antigen-presenting cells (APCs) and inflammatory cells in RA. CD11c⁺ myeloid DCs and CD123⁺ pDCs were compared in normal and RA PB, synovial fluid (SF), and synovial tissue by flow cytometry, immunohistochemistry, and electron microscopy and were sorted for functional studies. Nuclear RelB^-CD123⁺ DCs were located in perivascular regions of RA, in a similar frequency to nuclear RelB⁺CD123^- DCs, but not normal synovial tissue sublining. Apart from higher expression of HLA-DR, the numbers and phenotypes of SF pDCs were similar to those of normal PB pDCs. While the APC function of PB pDCs was less efficient than that of PB myeloid DCs, RA SF pDCs efficiently activated resting allogeneic PB T cells, and high levels of IFN-γ, IL-10, and tumor necrosis factor α were produced in response to incubation of allogeneic T cells with either type of SF DCs. Thus, pDCs are recruited to RA synovial tissue and comprise an APC population distinct from the previously described nuclear RelB⁺ synovial DCs. pDCs may contribute significantly to the local inflammatory environment.

Tumour necrosis factor alpha independent disease mechanisms in rheumatoid arthritis: a histopathological study on the effect of infliximab on rheumatoid nodules

BACKGROUND

It has been suggested that the immunopathology of rheumatoid nodules parallels that of inflamed synovium in rheumatoid arthritis (RA).

OBJECTIVE

To analyse the effect of infliximab on the immunopathology of rheumatoid nodules in order to provide new insights into the relationship between synovial inflammation and rheumatoid nodules.

MATERIALS AND METHODS

Nodules were present at baseline in six patients with RA and after infliximab treatment in five patients, including paired nodules before and after treatment in three patients. In one patient, the nodule appeared during treatment. Paraffin sections were used for histological analysis. Frozen sections were stained by immunohistochemistry for cellular markers (CD3, CD4, CD8, CD16, CD20, CD68), blood vessels (CD146, vWF, alphavbeta3), and adhesion molecules (E-selectin, VCAM-1, ICAM-1).

RESULTS

No manifest immunopathological differences were found between the nodules before and after infliximab treatment. All nodules depicted the classical structure with a central necrotic zone, surrounding the palisade layer, and an outer connective tissue zone. Immunohistochemistry showed the presence of CD68+ and CD16+ macrophages in the palisade and the connective tissue zone, as well as a small number of CD3+, CD4+ T lymphocytes in the perivascular areas. Small vessels were seen in the connective tissue and were sometimes positive for the neovascularisation marker alphavbeta3. They expressed no VCAM-1, E-selectin weakly, but ICAM-1 strongly. ICAM-1 was also strongly expressed on palisade cells.

CONCLUSIONS

Despite an improvement of articular symptoms, infliximab treatment had no distinct effect on the histopathology of rheumatoid nodules, suggesting that different pathogenetic mechanisms mediate the two disease manifestations in RA.

Circulating soluble E-selectin in early rheumatoid arthritis: a prospective five year study

BACKGROUND

Soluble E-selectin (sE-selectin) is a marker of activation of vascular endothelium.

OBJECTIVE

To examine serum levels of sE-selectin in a cohort of 85 patients with early rheumatoid arthritis (RA) followed up for five years.

METHODS

sE-selectin levels were assessed annually using an enzyme linked immunosorbent assay (ELISA) and related to simultaneously obtained clinical and laboratory measures. Joint inflammation was evaluated by active joint count, functional status by Health Assessment Questionnaire (HAQ), and radiographic findings in hands and feet by the Larsen method. Laboratory tests included serum C reactive protein (CRP) level, erythrocyte sedimentation rate, blood haemoglobin level, white blood cell count (WBC), and platelet count. Area under the curve (AUC) was calculated for each variable, and Jonckheere's test for ordered alternatives was applied to assess significance of association between sE-selectin AUC tertiles and other variables. Baseline sE-selectin tertiles were related to change in Larsen score and HAQ score at five years. Odds ratios (OR) with 95% confidence interval (CI) were calculated using univariate and multivariate logistic regression.

RESULTS

sE-selectin levels were associated with CRP level (p=0.012), WBC (p=0.037), active joint count (p=0.019), progression of joint destruction (p=0.038), and HAQ score at five years (p=0.021), but not with extra-articular symptoms or comorbidity. Baseline sE-selectin levels in the third tertile predicted the HAQ score at five years (OR 4.18, 95% CI 1.15 to 15.22). sE-selectin levels of patients did not differ significantly from those of healthy control subjects.

CONCLUSION

The degree of activation of vascular endothelium is associated with activity and outcome of early RA.

The autoimmune pathogenesis of rheumatoid arthritis: role of autoreactive T cells and new immunotherapies

OBJECTIVES

To review the role of T lymphocytes in the pathogenesis of rheumatoid arthritis (RA) and discuss the relevance of the components of the trimolecular complex (synovial T cells, autoantigens, and antigen presenting cells) in the pathogenic autoimmune response in RA.

METHODS

Currently available experimental data are combined into a hypothetical pathway that may explain some of the events in the RA process. The literature regarding the potential therapeutic strategies that interfere with specific components of the trimolecular complex and other mediators are discussed briefly.

RESULTS

T cells are activated in the peripheral blood, cross the endothelial cell wall, and migrate into the joints. Once in the synovial joints, T cells are reactivated by cross-reactive antigens and clonally expand. Clonally expanded T cells accumulate in the diseased joint and secrete proinflammatory cytokines that attract and activate other cells, such as monocytes and macrophages. Treatment with anti-CD4 monoclonal antibodies or anticytokine agents that prevents antigen presentation and/or T-cell activation were effective in RA. Other therapies, such as T-cell vaccination and T-cell receptor peptide vaccination targeting autoreactive T cells, showed clinical improvement, suggesting a pathogenic role of these lymphocytes in disease progression.

CONCLUSION

T cells appear to be actively involved in the pathogenesis of RA, but several parts of the pathway are hypothetical and further research is needed.

Correlation between nicotine-induced inhibition of hematopoiesis and decreased CD44 expression on bone marrow stromal cells

This study demonstrates that in vivo exposure to cigarette smoke (CS) and in vitro treatment of long-term bone marrow cultures (LTBMCs) with nicotine, a major constituent of CS, result in inhibition of hematopoiesis. Nicotine treatment significantly delayed the onset of hematopoietic foci and reduced their size. Furthermore, the number of long-term culture-initiating cells (LTC-ICs) within an adherent layer of LTBMCs was significantly reduced in cultures treated with nicotine. Although the production of nonadherent mature cells and their progenitors in nicotine-treated LTBMCs was inhibited, this treatment failed to influence the proliferation of committed hematopoietic progenitors when added into methylcellulose cultures. Bone marrow stromal cells are an integral component of the hematopoietic microenvironment and play a critical role in the regulation of hematopoietic stem cell proliferation and self-renewal. Exposure to nicotine decreased CD44 surface expression on primary bone marrow-derived fibroblastlike stromal cells and MS-5 stromal cell line, but not on hematopoietic cells. In addition, mainstream CS altered the trafficking of hematopoietic stem/progenitor cells (HSPC) in vivo. Exposure of mice to CS resulted in the inhibition of HSPC homing into bone marrow. Nicotine and cotinine treatment resulted in reduction of CD44 surface expression on lung microvascular endothelial cell line (LEISVO) and bone marrow-derived (STR-12) endothelial cell line. Nicotine treatment increased E-selectin expression on LEISVO cells, but not on STR-12 cells. These findings demonstrate that nicotine can modulate hematopoiesis by affecting the functions of the hematopoiesis-supportive stromal microenvironment, resulting in the inhibition of bone marrow seeding by LTC-ICs and interfering with stem cell homing by targeting microvascular endothelial cells.

Role of CD30+ T cells in rheumatoid arthritis: a counter-regulatory paradigm for Th1-driven diseases

CD30 has been proposed to identify Th0/2-type clones. However, the in vivo relevance of this finding is still a matter of debate, as high serum levels of soluble CD30 have been found in both Th1- and Th2- dominated disorders. Among these, rheumatoid arthritis represents a condition where the Th1 predominance is combined with the presence of CD30(+) T-cell activity, particularly in specific stages of the disease. This article discusses the hypothesis that CD30(+) T cells might play a counter-regulatory role at sites of inflammation in Th1-mediated conditions, such as rheumatoid arthritis.

PECAM-1 and leukosialin (CD43) expression correlate with heightened inflammation in rat adjuvant-induced arthritis

A hallmark of both adjuvant-induced arthritis (AIA) and rheumatoid arthritis is chronic joint inflammation characterized by ingress of leukocytes into the inflamed synovial tissue. The timing of expression of adhesion molecules, which govern the ingress of leukocytes, is important in the orchestration of an inflammatory response. We examined the expression of vascular cell adhesion molecule-1 (VCAM-1), sialo adhesin, platelet and endothelial cell adhesion molecule-1 (PECAM-1), and leukosialin (CD43) in AIA, starting at adjuvant injection (day 0), through the peak of inflammation (day 18 postadjuvant injection), until day 54. VCAM-1 is constitutively expressed on the lining layer and ECs and its expression levels do not change throughout the progression of AIA. Sialoadhesin synovial tissue lining cell expression is decreased after adjuvant injection. In contrast, PECAM-1 expression is increased on synovial tissue lining cells on day 7 and is elevated through day 54 (peaking on day 54 with six-fold more cells expressing PECAM-1). PECAM-1 expression on endothelial cells peaks on day 7 with three-fold more cells expressing it, while on macrophages expression maximizes on day 25 with six-fold more cells expressing PECAM-1. CD43 expression is increased on synovial tissue lining cells, macrophages, neutrophils, and lymphocytes on days 18 and 25, before going back to basal levels. The increased expression of PECAM-1 and CD43 on leukocytes at the height of inflammation in AIA suggests important roles for these adhesion molecules in potentially binding their EC ligands resulting in leukocyte ingress into the synovial tissue.