Anti-integrin immunotherapy in rheumatoid arthritis: protective effect of anti-alpha 4 antibody in adjuvant arthritis

The association between the lymphocyte-monocyte ratio and disease activity in rheumatoid arthritis

The lymphocyte-monocyte ratio (LMR) is a systemic inflammatory marker for prediction of disease development, progress, and survival. Recently, a genome-wide association study identified genetic variations in ITGA4 and HLA-DRB1 that affect the LMR levels and were widely believed to be susceptibility genes for autoimmune diseases, including rheumatoid arthritis (RA). However, the role of LMR in RA patients remains unclear. The LMR level and other laboratory data of 66 RA patients, 163 osteoarthritis (OA) patients, and 131 healthy controls (HC) were compared using binary logistic regression. The correlations between LMR and disease activity and other inflammatory markers were measured using the Spearman rank test. ROC curve analyses assessed the diagnostic accuracy of LMR in RA. The LMR and lymphocyte count were significantly lower in RA patients, whereas the monocyte count was significantly higher relative to the HC group/OA patients (p < 0.01). A decreased LMR has been associated with increased disease activity (p = 0.012). In addition, the DAS28 and traditional inflammatory markers, including ESR, CRP, RDW, PLR, and NLR, and immune-related factors, such as C4, IgA, and IgM, were inversely correlated with LMR, while hemoglobin and albumin were positively correlated with LMR. The ROC curve showed that the area under the curve of LMR was 0.705 (95%CI = 0.630-0.781). The corresponding specificity and sensitivity were 82.82 and 45.45%, respectively. The present study shows that the LMR is an important inflammatory marker which could be used to identify disease activity in RA patients and to distinguish RA from OA patients.

Hypoxia and hypoxia mimetics inhibit TNF-dependent VCAM1 induction in the 5A32 endothelial cell line via a hypoxia inducible factor dependent mechanism

BACKGROUND

We previously reported that iron chelators inhibit TNFα-mediated induction of VCAM-1 in human dermal microvascular endothelial cells. We hypothesized that iron chelators mediate inhibition of VCAM-1 via inhibition of iron-dependent enzymes such as those involved with oxygen sensing and that similar inhibition may be observed with agents which simulate hypoxia.

OBJECTIVE

We proposed to examine whether non-metal binding hypoxia mimetics inhibit TNFα-mediated VCAM-1 induction and define the mechanisms by which they mediate their effects on VCAM-1 expression.

METHODS

These studies were undertaken in vitro using immortalized dermal endothelial cells, Western blot analysis, ELISA, immunofluorescence microscopy, quantitative real-time PCR, and chromatin immunoprecipitation.

RESULTS

Hypoxia and the non-iron binding hypoxia mimetic dimethyl oxallyl glycine (DMOG) inhibited TNFα-mediated induction of VCAM-1. DMOG inhibition of VCAM-1 was dose-dependent, targeted VCAM-1 gene transcription independent of NF-κB nuclear translocation, and blocked TNFα-mediated chromatin modifications of relevant elements of the VCAM-1 promoter. Combined gene silencing of both HIF-1α and HIF-2α using siRNA led to a partial rescue of VCAM expression in hypoxia mimetic-treated cells.

CONCLUSION

Iron chelators, non-metal binding hypoxia mimetics, and hypoxia all inhibit TNFα-mediated VCAM-1 expression. Inhibition is mediated independent of nuclear translocation of NF-κB, appears to target TNFα-mediated chromatin modifications, and is at least partially dependent upon HIF expression. The absence of complete VCAM-1 expression rescue with HIF silencing implies an important regulatory role for an Fe(II)/α-ketoglutarate dioxygenase distinct from the prolyl and asparagyl hydroxylases that control HIF function. Identification of this dioxygenase may provide a valuable target for modulating inflammation in human tissues.

Vascular endothelium and immune responses: implications for inflammation and angiogenesis

ECs are involved in several mechanisms during the immune response, particularly in inflammation. These cells are able to produce vasodilatory mediators and several factors lead to increased vascular permeability. ECs play a central role in leukocyte extravasation, a key feature of inflammation. Several adhesion molecules, termed integrins, selectins, immunoglobulins, and others, act in concert and regulate the sequence of distinct steps. Leukocyte-EC adhesion is regulated by the interactions of receptor-ligand CAM pairs, as well as by soluble mediators, such as proinflammatory cytokines. ECs are active participants in angiogenesis. The outcome of neovascularization is highly dependent on the balance or imbalance between angiogenic mediators and inhibitors. Angiogenic mediators form a complex interactive network that regulates the perpetuation of angiogenesis. Naturally-produced or administered angiostatic agents downregulate the effects of angiogenic factors. There have been several attempts to therapeutically interfere with the cellular and molecular mechanisms described above. Most studies were performed using animal models of various types of inflammation. A limited number of human clinical trials, such as the one using anti-ICAM-1 antibody in RA, had promising results. Specific targeting of pathologic endothelial function may be useful for the future management of various inflammatory diseases.

Combinatorial approaches to inhibitors of VLA-4: piperazine-peptoid-bisarylureas

A combinatorial approach towards identifying inhibitors of VALA-4 was investigated. A library of piperazine-peptoid-bisarylureas was assembled in solid phase and screening in the novel v-well assay enabled the identification of active compounds.

Design and synthesis of potent and selective inhibitors of integrin VLA-4

The synthesis and identification of a novel series of inhibitors of integrin VLA-4 are described. Their in vitro activity and selectivity against closely related integrins are also presented.

Integrin expression at the bone/biomaterial interface

The aim of this study was to visualize integrin expression by cells in interface tissue in relation to their ligands. Tissue samples were obtained from 25 patients undergoing revision of aseptically loose total joint replacements. Serial sections were immunolabeled for the integrins alpha(2)beta(1), alpha(v)beta(3), alpha(4)beta(1), alpha(L)beta(2) (CD11a), alpha(M)beta(2) (CD11b), and alpha(X)beta(2) (CD11c), and the ligands fibronectin, laminin, vitronectin, intercellular adhesion molecule-1, and vascular adhesion molecule-1. Most cells were found to express alpha(2)beta(1), most macrophages and giant cells expressed CD11b, and the majority of CD11a was found on perivascular T lymphocytes. From the small amount of alpha(4)beta(1) and vascular adhesion molecule-1 expression in the interface tissue and the combination of CD11a, CD11b, and intercellular adhesion molecule-1 expression, it would seem that macrophages use beta(2) integrins to transmigrate.

E-selectin, but not P-selectin, is required for development of adjuvant-induced arthritis in the rat

OBJECTIVE

To determine the role of the endothelial cell adhesion molecules E- and P-selectin in the development and severity of adjuvant-induced arthritis (AIA) in the rat.

METHODS

Lewis rats were immunized subcutaneously with Mycobacterium butyricum (Mb), and blocking monoclonal antibodies (mAb) to rat E- and P-selectin were administered. Clinical score, radiolabeled (51Cr and 111In) blood polymorphonuclear leukocyte (PMN) and monocyte migration to joints, and histologic features were monitored.

RESULTS

When mAb treatment was started on day 5 postimmunization with Mb (preclinical stage), development of AIA was significantly (P < 0.01) inhibited by mAb to E- but not to P-selectin (mean score on day 14 control 10.2, anti-E 2.8, anti-P 9.1). This was associated with markedly decreased migration (by 66-94%) of PMN and monocytes to arthritic joints and diminished cartilage degradation. When treatment was delayed until animals showed signs of arthritis (day 10 postimmunization), only a marginal and variable effect was observed as compared with blockade during the preclinical (day 5) stage. E-selectin blockade on day 5 and day 7 postimmunization resulted in inhibition of antigen-dependent T cell-mediated inflammation, since it decreased T cell migration to sites of dermal-delayed hypersensitivity induced by Mb without affecting migration to concanavalin A or cytokines. The proliferative response of T cells to Mb in vitro was not altered.

CONCLUSION

E-selectin plays an important role early in the development of AIA. This adhesion molecule may contribute to the migration of antigen-reactive T cells to peripheral tissues, including the joints where T cells initiate the arthritis.

Cytokine mRNA in the joints and draining lymph nodes of rats with adjuvant arthritis and effects of cyclosporin A

TNF-alpha and IL-1beta promote leukocyte recruitment to arthritic joints and may contribute to cartilage degradation while regulatory cytokines such as IL-4 and IL-1RA may in part determine the course of arthritis. Here we report the pattern of TNF-alpha, IL-1beta, IL-6, IFN-gamma, IL-1RA, and IL-4 mRNA expression, detected by RT/PCR, in the talar joint and draining popliteal lymph node (PLN) of rats with adjuvant arthritis (AA). Levels of TNF-alpha and IFN-gamma mRNA were increased in the PLN before clinical signs of arthritis. This was followed by increases in IL-1beta and IL-1RA mRNA at d9 and IL-6 mRNA at d12. PLN IL-1RA mRNA levels were positively correlated with those of IL-1beta and TNF-alpha throughout d5-d20. IL-4 mRNA levels were highest on days 7 and 20. In the synovium, a small increase in TNF-alpha, IL-1beta, and IL-6 mRNA was detected on d5 then again on d12. Maximal synovial TNF-alpha levels were reached on d20, while IL-1beta peak expression was on d16 and IL-6 on d14. IL-4, IL-1RA, and IFN-gamma mRNA was undetectable in the synovium. Cyclosporin treatment for 4 days, initiated at the height of arthritis, rapidly decreased clinical disease, and decreased migration of neutrophils and T lymphocytes into the joints. Yet no significant effect of CyA was observed on inflammatory cytokine expression, although the correlation between PLN IL-1RA and IL-1beta or TNF-alpha was lost in treated animals. Thus there is a variable pattern of cytokine gene expression in rat AA, the undetectable IL-4 and IFN-gamma mRNA in synovium being analogous to human rheumatoid arthritis.

Use of biologics in the treatment of childhood rheumatic diseases

Over the last two decades, progression in the knowledge of molecular biologic techniques has led to a better understanding of immunopathogenesis and identification of several cytokines, which propagate chronic arthritis in both adult and pediatric patients. A number of biologic agents have been developed in targeting different immune markers or mediators with the hope that they may help in controlling the inflammation in the group of patients who are resistant to disease-modifying antirheumatic drugs (DMARDs) and may alter the natural history of the diseases. Tumor necrosis factor (TNF)-alpha is the first to be targeted and its antagonists have been approved. Other biologic agents targeting different markers/mediators have followed and have been tested in clinical trials especially in adult rheumatoid arthritis (RA). Experiences in pediatric use are limited and agents proved to be effective in adult RA are not always transferred the same efficacy in different subtypes of juvenile idiopathic arthritis (JIA). It is reasonable to see the efficacy, and more importantly the safety profiles of each agent before the decision is made to use them in children. This article reviews the published and anecdotal reports of biologic agents that have been used in children with JIA and also focuses on the potential use of other biologic agents in JIA that have been used in trials to combat adult RA.

Potent cyclic monomeric and dimeric peptide inhibitors of VLA-4 (alpha4beta1 integrin)-mediated cell adhesion based on the Ile-Leu-Asp-Val tetrapeptide

Potent monomeric and dimeric cyclic peptide very late antigen-4 (VLA-4) inhibitors have been designed based on a tetrapeptide (Ile-Leu-Asp-Val) sequence present in a 25-amino acid peptide (CS-1) reported in the literature. The peptides, synthesized by the SPPS techniques, were evaluated in the in vitro cell adhesion assays and in the in vivo inflammation models. The N- to C-terminal cyclic peptides such as cyclo(Ile-Leu-Asp-Val-NH-(CH2)2-S-(CH2)2-CO) (28) and cyclo(MeIle-Leu-Asp-Val-D-Ala-D-Ala) (31), monomeric and dimeric peptides containing piperazine (Pip) or homopiperazine (hPip) residues as linking groups, e.g. cyclo(MeIle-Leu-Asp-Val-Pip-CH2CO-NH-(CH2)2-S-CH2-CO) (49) and cyclo(MeIle-Leu-Asp-Val hPip-CH2CO-MeIle-Leu-Asp-Val-hPip-CH2CO) (58) and cyclic peptides containing an amide bond between the side chain amino group of an amino acid such as Lys and the C-terminal Val carboxyl group, e.g. Ac-cyclo(D-Lys-D-Ile-Leu-Asp-Val) (62) and beta-Ala-cyclo(D-Lys-D-Leu-Leu-Asp-Val) (68) were more potent than CS-1 in inhibiting the adhesion of the VLA-4-expressing MOLT-4 cells to fibronectin. The more potent compounds were highly selective and did not affect U937 cell adhesion to fibronectin (VLA-5), PMA-differentiated U937 cell adhesion to intercellular cell adhesion molecule- 1-expressing Chinese hamster ovary cells (LFA-1) and ADP-induced platelet aggregation (GPIIb/IIIa). A number of the more potent compounds inhibited ovalbumin-induced delayed type hypersensitivity in mice and some were 100-300 times more potent (ED50 = 0.003-0.009 mg/kg/day, s.c.) than CS-1. Two peptides, Ac-cyclo(D-Lys D-Ile-Leu-Asp-Val) (62) and cyclo(CH2CO-Ile-Leu-Asp-Val-Pip-CH2CO-Ile-Leu-Asp-Val-Pip) (55), were formulated in poly(DL-lactide-co-glycolide) depots and the release profile was investigated in vitro over a 30-day period.

The role of alpha(4) and LFA-1 integrins in selectin-independent monocyte and neutrophil migration to joints of rats with adjuvant arthritis

Monocytes and neutrophils are chronically recruited to joints in rheumatoid arthritis. In the joints of rats with adjuvant arthritis, this is mediated, in part, by selectin-dependent and selectin-independent mechanisms. To define the selectin-independent mechanisms, (51)Cr-labeled blood monocytes, (111)In-labeled neutrophils and function blocking mAb to the selectins and integrins were utilized. Integrins contributed to the selectin-independent monocyte migration to arthritic joints with 58-70% inhibition of this recruitment by anti-alpha(4) or anti-LFA-1 mAb, relative to selectin blockade alone. alpha(4) plus P-selectin blockade was as effective as combined blockade of alpha(4), P-, E- and L-selectin, mediating approximately 83% of the overall monocyte migration to the joints. In contrast, LFA-1 was the predominant selectin-independent mechanism for neutrophil recruitment to the joints. LFA-1 together with P-selectin had essential roles in the talar joint. In dermal inflammation in the arthritic rats, LFA-1 accounted for most (69%) of the selectin-independent monocyte migration to the chemoattractant C5a(desArg) (zymosan-activated serum), whereas LFA-1 and Mac-1 both contributed to selectin-independent neutrophil recruitment to C5a(desArg). alpha(4) integrin and P-selectin in concert mediated monocyte recruitment to lipopolysaccharide and IFN-gamma lesions (81%). Thus: (1) either alpha(4) or LFA-1 can mediate monocyte migration to arthritic joints in the absence of selectin function and alpha(4) together with P-selectin is particularly important; (2) LFA-1 is the predominant mechanism of selectin-independent migration of neutrophils to inflamed joints; and (3) in arthritic rats, selectin-independent migration of monocytes and neutrophils to dermal inflammation is mediated by alpha(4) or LFA-1 or both LFA-1 and Mac-1, depending on the leukocyte type, and inflammatory stimulus.

Cell-cell interactions in synovitis. Endothelial cells and immune cell migration

Leukocyte ingress into the synovium is a key process in the pathogenesis of rheumatoid arthritis and other inflammatory conditions. In this review, the role of endothelial cells in leukocyte extravasation will be discussed, including the role of the most relevant cellular adhesion molecules. These molecules play an important role in mediating leukocyte--endothelial interactions. It is likely that different adhesive pathways are involved in different steps of leukocyte adhesion to and migration through endothelia. Targeting of pathological endothelial function, including leukocyte--endothelial adhesion, may be useful for the future management of inflammatory arthritis.

Adhesion molecules in inflammatory diseases

Cell adhesion molecules (CAM) have a key role in the inflammatory response. Selectins, integrins and immunoglobulin (Ig) gene superfamily adhesion receptors mediate the different steps of the migration of leucocytes from the blood-stream towards inflammatory foci. The activation of endothelial cells (EC) upregulates the expression of several CAM and triggers the interaction of these cells with leucocytes. Selectins are involved in the initial interactions (tethering/rolling) of leucocytes with activated endothelium, whereas integrins and Ig superfamily CAM mediate the firm adhesion of these cells and their subsequent extravasation. During rolling, leucocytes are activated through the intracellular signals generated by CAM and chemokine receptors. Blockade of the function or expression of CAM has emerged as a new therapeutic target in inflammatory diseases. Different drugs are able to interfere with cell adhesion phenomena. In addition, new antiadhesion therapeutic approaches (blocking monoclonal antibodies, soluble receptors, synthetic peptides, peptidomimetics, etc.) are currently in development.

Effects of thrombospondin-1 on disease course and angiogenesis in rat adjuvant-induced arthritis

Leukocyte extravasation into the synovium is important in rheumatoid arthritis (RA). Thrombospondin (TSP)-1 mediates cell adhesion and migration and inhibits angiogenesis, and it has been implicated in RA. However, little information is available on the role of TSP-1 in arthritis-associated inflammation and neovascularization. Therefore, we analyzed the effects of TSP-1 in adjuvant-induced arthritis (AIA), a rat model for RA. Hydron pellets containing TSP-1 were implanted in one ankle of AIA rats post-adjuvant injection, while the contralateral ankle received sham implants. Body weight loss and joint swelling were determined in comparison to nonimplanted AIA controls. In addition, synovial vessel counts were obtained in TSP-1-versus sham-implanted ankles of the same rat. The implantation of TSP-1 pellets into one ankle resulted in an enhancement of swelling in both ankles. Furthermore, TSP-1 exhibited a biphasic modulatory effect on synovial vessel counts (P < 0.05). In conclusion, TSP-1 implanted into one ankle of AIA rats may augment the severity of the disease. One possible explanation, among others, for the modulating effect of TSP-1 on inflammation may be its effect on arthritis-related angiogenesis.

Potent alpha 4 beta 1 peptide antagonists as potential anti-inflammatory agents

The migration, adhesion, and subsequent extravasation of leukocytes into inflamed tissues contribute to the pathogenesis of a variety of inflammatory diseases including asthma, rheumatoid arthritis, inflammatory bowel disease, and multiple sclerosis. The integrin adhesion receptor alpha 4 beta 1 expressed on leukocytes binds to the extracellular matrix protein fibronectin and to the cytokine inducible vascular cell adhesion molecule-1 (VCAM-1) at inflamed sites. Binding of alpha 4 beta 1 to VCAM-1 initiates firm adhesion of the leukocyte to the vascular endothelium followed by extravasation into the tissue. Monoclonal antibodies generated against either alpha 4 beta 1 or VCAM-1 can moderate this inflammatory response in a variety of animal models. Recently peptides containing a consensus LDV sequence based on the connecting segment-1 (CS-1) of fibronectin and cyclic peptides containing an RCD motif have shown promise in modulating leukocyte migration and inflammation presumably by blocking the interaction of alpha 4 beta 1 with VCAM-1. Here we describe novel, highly potent, cyclic peptides that competitively inhibit alpha 4 beta 1 binding to VCAM-1 and fibronectin at sub nanomolar concentrations. The structure of a representative analog was determined via NMR spectroscopy and used to facilitate optimization of peptide leads. The peptides discussed here utilize similar functional groups as the binding epitope of VCAM-1, inhibit lymphocyte migration in vivo, and are highly selective for alpha 4 beta 1. Furthermore the structure--activity relationships described here have provided a template for the structure-based design of small molecule antagonists of alpha 4 beta 1-mediated cell adhesion processes.

Treatment of established adjuvant arthritis in rats with monoclonal antibody to CD18 and very late activation antigen-4 integrins suppresses neutrophil and T-lymphocyte migration to the joints and improves clinical disease

The migration of leucocytes from blood into the joint is a key feature of human and experimental arthritis. Adhesion molecules on leucocytes and vascular endothelium are important in this process and may be therapeutic targets for intervention in arthritis. We investigated whether monoclonal antibody treatment to block the alpha 4 integrin, very late activation antigen-4 (VLA-4), and beta 2 integrins (CD11/CD18) administered to rats during the preclinical (day 5) or clinical phase (day 10+) would modify disease. When treatment was initiated 5 days after induction of disease, development of arthritis was significantly reduced by either anti-alpha 4 (TA-2) or anti-beta 2 (WT.3) monoclonal antibodies (mAb) and the combination of both mAb was even more effective (clinical scores: control 11.4; anti-alpha 4 6.6; anti-beta 2 6.8; anti-alpha 4 + anti-beta 2 3.9). When treatment was delayed until arthritis was apparent (day 10), the anti-alpha 4 + anti-beta 2 mAb combination still significantly diminished the arthritis score on day 14 (control 13; anti-alpha 4 + anti-beta 2 7.9). Treatment with anti-alpha 4 + anti-beta 2 mAb decreased the migration to the joints of blood polymorphonuclear leucocytes (PMNL) by 66-79% and of spleen T lymphocytes by 56-75%, depending on the joint. In contrast, PMNL migration was abolished (> 98%) and T-cell migration markedly (87%) inhibited to dermal inflammatory reactions in the same animals. These findings demonstrate: that blocking mAb to alpha 4 and beta 2 integrins can reduce the severity of adjuvant arthritis, even after joint inflammation has developed; that this treatment can markedly inhibit PMNL and T-lymphocyte migration to the joints; and that yet to be defined mechanisms distinct from alpha 4 (CD49d) and beta 2 (CD11/CD18) integrins, also contribute to leucocyte migration to inflamed joints. Identifying these additional adhesion mechanisms may be required to control joint inflammation further.