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

6-Shogaol reduced chronic inflammatory response in the knees of rats treated with complete Freund's adjuvant

BACKGROUND

6-Shogaol is one of the major compounds in the ginger rhizome that may contribute to its anti-inflammatory properties. Confirmation of this contribution was sought in this study in Sprague- Dawley rats (200-250 g) treated with a single injection (0.5 ml of 1 mg/ml) of a commercial preparation of complete Freund's Adjuvant (CFA) to induce monoarthritis in the right knee over a period of 28 days. During this development of arthritis, each rat received a daily oral dose of either peanut oil (0.2 ml-control) or 6-shogaol (6.2 mg/Kg in 0.2 ml peanut oil).

RESULTS

Within 2 days of CFA injection, the control group produced maximum edematous swelling of the knee that was sustained up to the end of the investigation period. But, in the 6-shogaol treated group, significantly lower magnitudes of unsustained swelling of the knees (from 5.1 +/- 0.2 mm to 1.0 +/- 0.2 mm, p < 0.002, n = 6) were produced during the investigation period. Unsustained swelling of the knees (from 3.2 +/- 0.6 mm to 0.8 +/- 1.1 mm, p < 0.00008, n = 6) was also produced after 3 days of treatment with indomethacin (2 mg/Kg/day) as a standard anti-inflammatory drug, but during the first 2 days of drug treatment swelling of the knees was significantly larger (11.6 +/- 2.0 mm, p < 0.0002, n = 6) than either the controls or the 6-shogaol treated group of rats. This exaggerated effect in the early stage of indomethacin treatment was inhibited by montelukast, a cysteinyl leukotriene receptor antagonist. Also, 6-shogaol and indomethacin were most effective in reducing swelling of the knees on day 28 when the controls still had maximum swelling. The effect of 6-shogaol compared to the controls was associated with significantly lower concentration of soluble vascular cell adhesion molecule-1 (VCAM-1) in the blood and infiltration of leukocytes, including lymphocytes and monocytes/macrophages, into the synovial cavity of the knee. There was also preservation of the morphological integrity of the cartilage lining the femur compared to damage to this tissue in the peanut oil treated control group of rats.

CONCLUSION

From these results, it is concluded that 6-shogaol reduced the inflammatory response and protected the femoral cartilage from damage produced in a CFA monoarthritic model of the knee joint of rats.

Inhibition of angiogenesis by interleukin-4 gene therapy in rat adjuvant-induced arthritis

OBJECTIVE

Interleukin-4 (IL-4) can modulate neovascularization. In this study, we used a gene therapy approach to investigate the role of IL-4 in angiogenesis in rat adjuvant-induced arthritis (AIA), a model for rheumatoid arthritis.

METHODS

Rats received an adenovirus producing IL-4 (AxCAIL-4), a control virus without insert, or control vehicle (phosphate buffered saline) intraarticularly before arthritis onset. At peak onset of arthritis, rats were killed. Vascularization was determined in the synovial tissue, and correlations with inflammation were assessed. Ankle homogenates were used in angiogenesis assays in vitro and in vivo, and protein levels of cytokines and growth factors were assessed by enzyme-linked immunosorbent assay. Synovial tissue expression of alphav integrins was determined by immunohistochemistry.

RESULTS

IL-4 induced a reduction in synovial tissue vessel density, which was paralleled by a decrease in inflammation. AxCAIL-4 joint homogenates significantly (P < 0.05) inhibited both endothelial cell (EC) migration and tube formation in vitro. Similarly, AxCAIL-4 inhibited capillary sprouting in the rat aortic ring assay, and vessel growth in the in vivo Matrigel plug assay. The angiostatic effect occurred despite high levels of vascular endothelial growth factor (VEGF), and was associated with down-regulation of the proangiogenic cytokines IL-18, CXCL16, and CXCL5 and up-regulation of the angiogenesis inhibitor endostatin. Of interest, AxCAIL-4 also resulted in decreased EC expression of the alphav and beta3 integrin chains.

CONCLUSION

In rat AIA, IL-4 reduces synovial tissue vascularization via angiostatic effects, mediates inhibition of angiogenesis via an association with altered pro- and antiangiogenic cytokines, and may inhibit VEGF-mediated angiogenesis and exert its angiostatic role in part via alphavbeta3 integrin. This knowledge of the specific angiostatic effects of IL-4 may help optimize target-oriented treatment of inflammatory arthritis.

CXCL16-mediated cell recruitment to rheumatoid arthritis synovial tissue and murine lymph nodes is dependent upon the MAPK pathway

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by profound mononuclear cell (MNC) recruitment into synovial tissue (ST), thought to be due in part to tumor necrosis factor alpha (TNFalpha), a therapeutic target for RA. Although chemokines may also be involved, the mechanisms remain unclear. We undertook this study to examine the participation of CXCL16, a novel chemokine, in recruitment of MNCs to RA ST in vivo and to determine the signal transduction pathways mediating this process.

METHODS

Using a human RA ST-SCID mouse chimera, immunohistochemistry, enzyme-linked immunosorbent assay, real-time reverse transcription-polymerase chain reaction, flow cytometry, and in vitro chemotaxis assays, we defined the expression and function of CXCL16 and its receptor, CXCR6, as well as the signal transduction pathways utilized by them for MNC homing in vitro and in vivo.

RESULTS

CXCL16 was markedly elevated in RA synovial fluid (SF) samples, being as high as 145 ng/ml. Intense macrophage and lining cell staining for CXCL16 in RA ST correlated with increased CXCL16 messenger RNA levels in RA ST compared with those in osteoarthritis and normal ST. By fluorescence-activated cell sorting analysis, one-half of RA SF monocytes and one-third of memory lymphocytes expressed CXCR6. In vivo recruitment of human MNCs to RA ST implanted in SCID mice occurred in response to intragraft injection of human CXCL16, a response similar to that induced by TNFalpha. Lipofection of MNCs with antisense oligodeoxynucleotides for ERK-1/2 resulted in a 50% decline in recruitment to engrafted RA ST and a 5-fold decline in recruitment to regional lymph nodes. Interestingly, RA ST fibroblasts did not produce CXCL16 in response to TNFalpha in vitro, suggesting that CXCL16 protein may function in large part independently of TNFalpha.

CONCLUSION

Taken together, these results point to a unique role for CXCL16 as a premier MNC recruiter in RA and suggest additional therapeutic possibilities, targeting CXCL16, its receptor, or its signaling pathways.

The Inhibitory Co-Receptor, PECAM-1 Provides a Protective Effect in Suppression of Collagen-Induced Arthritis

Studies of PECAM-1(-/-) mice have identified that PECAM-1 functions as an inhibitory co-receptor to modulate immunological responsiveness. In this study, we describe the in vivo consequences of PECAM-1 deficiency in mouse models of collagen-induced arthritis (CIA) and K/BxN passive transfer model that resembles many of the features of human rheumatoid arthritis. Immunization of PECAM-1(-/-) C57BL/6 (H-2b) mice with chicken collagen type II induced CIA with an incidence of 82% by day 49, while 33%; of wild-type and 100% of DBA/1 mice developed arthritis in a similar time frame. The mean onset of disease for PECAM-1(-/-) C57BL/6 mice was day 32 compared to day 51 for wild-type C57BL/6 mice and day 18 for DBA/1 mice (H-2q susceptible). In terms of disease severity, the mean maximal arthritic index for PECAM-1(-/-) C57BL/6 mice was comparable to DBA/1 mice (8.91 +/- 0.91 vs 11.67 +/- 0.82). This mean maximal index in PECAM-1(-/-) C57BL/6 mice was significantly higher than wild-type C57BL/6 mice (5.00 +/- 0.73). IgG1 and IgG2b antibody responses against CII were elevated in arthritic PECAM-1(-/-) C57BL/6 mice compared to wild-type C57BL/6 mice. Histological examination of arthritic paws of PECAM-1(-/-) C57BL/6 mice revealed inflammatory infiltrates of lymphocytic/monocytic cells and cartilage/bone destruction similar to CIA-induced DBA/1 arthritic paws. In the K/BxN model, the arthritis was not augmented in PECAM-1(-/-) mice compared to wild-type mice. In contrast, in active CIA, PECAM-1(-/-) mice developed severe disease comparable to susceptible DBA/1 mice and profoundly more severe than C57BL/6 mice, where only one third developed a mild/moderate disease. Together these observations suggest that PECAM-1 plays a crucial role in the suppression of development of autoimmune arthritis.

Chemokine receptor expression in rat adjuvant-induced arthritis

OBJECTIVE

Chemokine receptors mediate leukocyte migration into inflamed rheumatoid arthritis (RA) synovial tissue (ST). Knowledge of their distribution is crucial for understanding the evolution of the inflammatory process. In this study, we used rat adjuvant-induced arthritis (AIA), a model for RA, to define the temporospatial expression of chemokine receptors.

METHODS

ST from rats with AIA was immunostained, the percentage of cells expressing each receptor was determined, and findings were correlated with levels of inflammation. Chemokine receptor expression was evaluated on rat macrophages in vitro.

RESULTS

CCR1, a receptor for macrophage inflammatory protein 1alpha (MIP-1alpha)/CCL3 and RANTES/CCL5, exhibited high constitutive expression on macrophages in AIA. CCR5, binding MIP-1alpha/CCL3 and RANTES/CCL5, was up-regulated on ST macrophages during the course of AIA, correlating with macrophage expression of CCR2, a receptor for monocyte chemoattractant protein 1/CCL2. Endothelial cell (EC) CCR2 was down-regulated as arthritis progressed, inversely correlating with inflammation. CCR3, another RANTES/CCL5 receptor, was constitutively high on macrophages in vivo and in vitro, with down-regulation during AIA. CXCR4, a receptor for stromal cell-derived factor 1/CXCL12), was prominently up-regulated on ECs, preceding the peak of inflammation.

CONCLUSION

These findings show that 1) constitutive expression of CCR1 on macrophages remains high during AIA; 2) CCR2 and CCR3 may play a role in initial recruitment of leukocytes to ST in AIA; 3) macrophage expression of CCR2 and CCR5 may be important for sustaining inflammatory changes; and 4) EC CXCR4 may be a harbinger of inflammatory changes. Our results may help guide chemokine receptor blockade-targeting treatment strategies in inflammatory arthritis.

A pattern of protein expression in peripheral blood mononuclear cells distinguishes rheumatoid arthritis patients from healthy individuals

We compared the expression levels of proteins in peripheral blood mononuclear cells (PBMCs) of healthy control individuals to those of patients diagnosed with rheumatoid arthritis (RA) using a proteomics approach. Using two-dimensional electrophoresis we identified 18 proteins that were 2-fold or more highly expressed in patients than in controls, and 11 proteins that were 2-fold or more highly expressed in controls than in patients. Some of these differentially expressed proteins, identified by MALDI-TOF spectrometry, have previously been shown to play a potential role in the pathogenesis of RA. Hierarchical cluster analyses of the data segregated the samples into two groups, one which contained only controls and the other which contained only patients, and was used to compare the expression pattern of these 29 proteins in individual samples with the median expression pattern determined in the healthy control and in the RA patient groups. This analyses was able to predict whether a sample was derived from a rheumatoid arthritis patient or from a healthy individual, suggesting that a comparison of such protein expression patterns may be of diagnostic value.

Use of anti-platelet-endothelial cell adhesion molecule-1 antibody in the control of disease progression in established collagen-induced arthritis in DBA/1J mice

Platelet-endothelial cell adhesion molecule-1 (PECAM-1) is expressed on the membrane of leukocytes and vascular endothelial cells. PECAM-1 has been shown to play an important role in the process of leukocyte transmigration in various animal models of acute inflammation. We investigated the role of PECAM-1 in the progression of arthritis by systemically administering anti-murine PECAM-1 monoclonal antibody, 2H8, to DBA/1J mice with collagen-induced arthritis (CIA). Subcutaneous administration of dexamethasone (0.5 mg/kg per 2 days) significantly reduced hindpaw swelling and the clinical score of established CIA. Intraperitoneal administration of 2H8 (0.25 mg/mouse per 2 days) significantly inhibited hindpaw swelling in a time-dependent manner. 2H8 also significantly prevented further deterioration in the clinical score, but failed to reverse joint destruction discernible at the histological level. Both dexamethasone and 2H8 inhibited body weight decrease by preventing the further development of arthritis. Histopathological assessment revealed that 2H8, as well as dexamethasone, inhibited inflammatory cell transmigration into the synovium of the hind paw joint and ameliorated synovitis and cartilage erosion. These results suggest that PECAM-1 plays an important role in the progression of CIA and that an inhibitor of PECAM-1 might have therapeutic value for clinical treatment of rheumatoid arthritis.