Attenuation of colitis in the cotton-top tamarin by anti-alpha 4 integrin monoclonal antibody

N-(arylacetyl)-biphenylalanines as potent VLA-4 antagonists

A series of potent N-(aralkyl-, arylcycloalkyl-, and heteroaryl-acyl)-4-biphenylalanine VLA-4 antagonists was prepared by rapid analogue methods using solid-phase chemistry. Further optimization led to several highly potent compounds (IC(50) <1 nM). Evaluation of rat pharmacokinetic revealed generally high clearance.

A cell-free electrochemiluminescence assay for measuring beta1-integrin-ligand interactions

We have developed a cell-free assay for binding of solubilized beta1 integrins to their physiologically relevant ligands using an electrochemiluminescent detection method. The method utilizes ruthenium-conjugated monoclonal antibodies for detection of either purified integrins or, more conveniently, integrin-expressing cell lysates, which are captured on beads coated with extracellular matrix or vascular ligand proteins. For the interaction of alpha1beta1 integrin with collagen IV, a signal of 10-fold over background was generated with samples containing only 10 ng (0.05 pmol) of integrin. This interaction is cation-dependent and can be inhibited by blocking antibodies to the alpha1 subunit. The method was extended to studies of ligand binding by integrins alpha2beta1, alpha4beta1, alpha5beta1, and alpha6beta1. For each integrin-ligand pair, the specificity of the interaction was verified with neutralizing antibodies against the specific integrin. The specific binding signal correlated with the activating ability of the labeled antibody used for detection, although the ability of divalent cations (Mn2+, Mg2+, Ca2+) to support integrin-ligand binding varied dramatically among the various integrin-ligand pairs. The assay provides a simple method for investigating integrin-ligand interactions without avidity and/or signaling effects which can complicate conventional cell-based assay methods.

Advances in the medical therapy of inflammatory bowel disease

The medical therapy of inflammatory bowel disease (IBD) has advanced significantly over the past year. Serologic markers of IBD have been further investigated and better defined, showing some discriminatory power with potential therapeutic implications. Studies of azathioprine and 6-mercaptopurine metabolites will make it easier and safer to use these effective drugs. Clinical data using other immunomodulators, including 6-thioguanine, mycophenolate mofetil, cyclosporine, and tacrolimus, continue to accrue with positive results. Infliximab has become even more firmly established as a reliable and effective therapy for active and fistulizing Crohn disease and may even be helpful in some patients with resistant ulcerative colitis. However, the recognition of potential complications of infliximab therapy has increased with the accumulated clinical experience. Results from trials of other biologic therapies directed at tumor necrosis factor alpha have been disappointing so far, although preliminary studies with biologics directed at adhesion molecules are encouraging. Growing appreciation of the importance of the enteric microflora in IBD has led to a considerable interest in manipulating intestinal bacteria for therapeutic benefit, and trials of both probiotics and prebiotics show promise.

beta7 Integrin expression is not required for the localization of T cells to the intestine and colitis pathogenesis

beta7 Integrins have been shown to have an important role in the localization of T cells to the intestine. Utilizing two different experimental mouse models of inflammatory bowel disease (IBD), this study was undertaken to determine if beta7 integrin expression is critical for T cell localization to the intestine and colitis pathogenesis. Transfer of CD4+ CD45RBhigh cells into immunodeficient mice results in colitis. To examine the role of beta7 integrins, donor cells were obtained from beta7 integrin gene-deficient animals and disease induction was examined following transfer into severe combined immunodeficiency (SCID) mice. Additionally, beta7 integrin gene-deficient animals were crossed to IL-2-deficient mice and the onset of spontaneous colitis that normally occurs in IL-2-deficient animals was examined. No differences in the onset or severity of spontaneous colitis was noted in animals that were deficient in both beta7 integrin and IL-2. In contrast, the onset of colitis in recipients of T cells from beta7 integrin-deficient donors was delayed significantly. In mice receiving beta7 integrin negative cells, the initial lack of colitis appeared to correlate with fewer numbers of CD3+beta7 integrin -/- donor lymphocytes present in the host colon. The eventual development of disease, however, was associated with increased numbers of donor beta7 integrin -/- lymphocytes. These results show that beta7 integrin expression is not absolutely required for T cell localization to the intestine and colitis pathogenesis.

Antiadhesion molecule therapy in inflammatory bowel disease

Adhesion molecules regulate the influx of leukocytes in normal and inflamed gut. Some of these molecules such as MadCAM-1 are specific for the gastrointestinal endothelium, but in inflammatory bowel diseases most of the adhesion factors are up-regulated. Adhesion molecules also are involved in local lymphocyte stimulation and antigen presentation within the intestinal mucosa. Recently, therapeutic compounds directed against trafficking of lymphocytes toward the gut mucosa have been designed, and are being developed as a novel class of drugs in the treatment of Crohn's disease (CD) and ulcerative colitis. This review deals with the immunological aspects of leukocyte trafficking focused on gut homing of T cells. Secondly, the changes in adhesion molecules and T-cell trafficking during intestinal inflammation are discussed. Finally, we review the clinical data that have been gathered in trials of biological therapies directed against adhesion molecules. Both antiintercellular adhesion molecule-1 (ICAM-1) and anti-alpha4 integrin strategies are being developed. Trials with the anti-ICAM-1 antisense oligonucleotide, ISIS-2302, in steroid-refractory CD have provided conflicting efficacy data. The anti-alpha4 integrin antibodies natalizumab (Antegren) and LDP-02 are in phase III and phase II trials, respectively. In the near future, these novel biological agents may prove valuable therapeutic tools in the management of refractory IBD.

N-Tetrahydrofuroyl-(L)-phenylalanine derivatives as potent VLA-4 antagonists

Given the proposed involvement of VLA-4 in inflammatory processes, a program to identify orally active VLA-4 antagonists was initiated. Herein, we report the discovery of a N-tetrahydrofuroyl-(L)-phenylalanine derivative (17) and related analogues as potent VLA-4 antagonists with good oral bioavailability.

Substituted tetrahydrofuroyl-1-phenylalanine derivatives as potent and specific VLA-4 antagonists

A series of substituted tetrahydrofuroyl-1-phenylalanine derivatives was prepared and evaluated as VLA-4 antagonists. Substitution of the alpha carbon of the tetrahydrofuran with aryl groups increased the specificity for VLA-4 versus alpha(4)beta(7) while amide substitution increased the potency of the series without increasing the specificity. Substitution of the beta carbon of the tetrahydrofuran with keto or amino groups slightly improved the specificity for VLA-4 versus alpha(4)beta(7) but with a significant loss in binding affinity for VLA-4.

Biologic therapy of inflammatory bowel disease

Advancing knowledge regarding the biology of chronic inflammation has led to the development of specific biologic therapies that mechanistically target individual inflammatory pathways. Many biologic therapies are being evaluated for the treatment of the chronic inflammatory bowel diseases, Crohn's disease and ulcerative colitis. Biologic compounds proven to be effective for Crohn's disease include monoclonal antibodies to tumor necrosis factor (infliximab and CDP571) and to the leukocyte adhesion molecule alpha4 integrin (natalizumab). Other biologic compounds for which there is insufficient evidence to judge efficacy for inflammatory bowel disease include: p55 tumor necrosis factor binding protein (onercept); interferon alpha; interferon beta-1a; anti-interferon gamma antibody; anti-interleukin 12 antibody; p65 anti-sense oligonucleotide (blocks NF-kappaB); granulocyte colony stimulating factor, and granulocyte macrophage colony stimulating factor; anti-interleukin 2 receptor antibody; epidermal growth factor; keratinocyte growth factor 2 (repifermin); human growth hormone; anti-CD4 antibody; and anti-alpha4beta7 antibody. Biologic therapies that have been proven ineffective for inflammatory bowel disease include: interleukin 10; interleukin 11; anti-sense intercellular adhesion molecule-1; and the tumor necrosis factor receptor fusion protein etanercept. Based on the early successes of infliximab, CDP571 and natalizumab, it seems certain that biologic therapy will play an important role in the future treatment of inflammatory bowel disease.

Differential expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in ulcerative colitis and Crohn's disease

Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is selectively expressed in the endothelial cells of intestinal mucosa and gut-associated lymphoid tissue (GALT). Engagement of MAdCAM-1 to its ligand, integrin alpha4beta7, on lymphocytes is associated with the homing of gut-associated lymphocytes to normal gastrointestinal tract and inflammation sites. The present study was designed to elucidate differences between Crohn's disease (CrD) and ulcerative colitis (UC) from the expression patterns of MAdCAM-1. Samples were taken from 40 patients with CrD and 24 patients with UC at surgical resection. Using frozen sections, immunohistochemistry was performed for MAdCAM-1, E-selectin and CD34. MAdCAM-1+ venules were abundant in inflamed mucosa in both UC and CrD. In contrast, clear differences were noted between UC and CrD in the inflammatory area in the ulcer base, that is, MAdCAM-1+ venules were more abundant in CrD than in UC (P < 0.001), while E-selectin was expressed equally in these venules in both diseases. Furthermore, CrD was characterized by the occurrence of MAdCAM-1+ venules in deeper layers of the intestinal tissue, mainly in lymphoid aggregates. Our data indicated more extensive expression of MAdCAM-1 in CrD, which could contribute not only to mucosal inflammation, but also to transmural inflammation in CrD.

A pilot study of treatment of active ulcerative colitis with natalizumab, a humanized monoclonal antibody to alpha-4 integrin

BACKGROUND

Alpha-4 integrins facilitate leucocyte migration across vascular endothelium.

AIM

To assess the safety and efficacy of natalizumab (Antegren), a humanized antibody to alpha-4 integrin, in patients with active ulcerative colitis.

METHODS

Ten patients with active ulcerative colitis, defined by a Powell-Tuck activity score > 4, received a single 3 mg/kg natalizumab infusion. The primary end-point was the change in Powell-Tuck score at 2 weeks post-infusion.

RESULTS

Significant decreases in the median Powell-Tuck score were observed at 2 and 4 weeks post-infusion (7.5 and 6, respectively) compared to the median baseline score (10). Five of 10 patients achieved a good clinical response at 2 weeks and one more patient by 4 weeks, defined by a Powell-Tuck score of < or = 5. Significant improvements in quality of life scores were found at week 4. Rescue medication was required by two (20%), three (30%) and eight (80%) patients by weeks 2, 4 and 8, respectively (median, 34 days; range, 8-43 days). One patient remained in remission at 12 weeks. The median C-reactive protein at 2 weeks (6 mg/L) was lower than that pre-treatment (16 mg/L).

CONCLUSIONS

A single 3 mg/kg infusion of natalizumab was well tolerated by ulcerative colitis patients. The positive efficacy demonstrated in this study merits further investigation by randomized, placebo-controlled trials.

N-aryl 2,6-dimethoxybiphenylalanine analogues as VLA-4 antagonists

A series of N-arylated phenylalanine derivatives has been synthesized and has been shown to be potent inhibitors of the integrin VLA-4. N-phenyl and N-heteroaryl derivatives with hydrogen bond acceptors in the meta position demonstrated low nanomolar activity against VLA-4.

3D QSAR (COMFA) of a series of potent and highly selective VLA-4 antagonists

The integrin VLA-4 (alpha4,beta1) is involved in the migration of white blood cells to sites of inflammation, and is implicated in the pathology of a variety of diseases including asthma and multiple sclerosis. We report the structure-activity relationships of a series of VLA-4 antagonists that were based upon the integrin-binding sequence of the connecting segment peptide of fibronectin (Leu-Asp-Val), and of VCAM-1 (Ile-Asp-Ser), both natural ligands of VLA-4. We explore variation in the ligand derived peptide portion of these antagonists and also in the novel N-terminal cap, which have discovered through chemical optimization, and which confers high affinity and selectivity. Using the X-ray derived conformation of the Ile-Asp-Ser region of VCAM-1, we rationalize the structure-activity relationships of these antagonists using 3D QSAR (COMFA). The COMFA model was found to be highly predictive with a cross-validated R2CV of 0.7 and a PRESS of 0.49. The robustness of the model was confirmed by testing the influence of various parameters, including grid size, column filtering, as well as the role of orientation of the aligned molecules. Our results suggest that the VCAM-1 structure is useful in generating highly predictive models of our VLA-4 antagonists. The COMFA model coupled with the knowledge that the peptide amides are tolerant to methylation should prove useful in future peptidomimetic design studies.

New developments in the treatment of inflammatory bowel disease

Therapy of inflammatory bowel disease (IBD) is rapidly changing with the advent of new discoveries in disease pathogenesis. The need for targeted therapies against the uncontrolled immuno-inflammatory reaction in IBD together with a prerequisite for minimal side effects is driving improvement in old medicines and is leading to the development of new drugs. This review introduces emerging changes in IBD treatment, such as improvements in conventional IBD medications or their use. Balsalazide, budesonide and changes in the use of 5-aminosalicylate (5-ASA) products and purine analogues, such as azathioprine, are discussed. Additionally, studies examining the role of drugs newly introduced into IBD therapy, such as mycophenolate mofetil (MMF), thalidomide and heparin, are stated. Emerging biological therapies, such as therapies against TNF, therapies to enhance anti-inflammatory cytokines, therapeutic manoeuvres to disrupt immune cell trafficking, anti-oxidant therapies, as well as non-conventional treatments, such as diet therapies, prebiotics and probiotics, and helminth therapies are discussed.

Immunological basis of inflammatory bowel disease: role of the microcirculation

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the intestine and/or colon of unknown etiology in which patients suffer from severe diarrhea, rectal bleeding, abdominal pain, fever, and weight loss. Active episodes of IBD are characterized by vasodilation, venocongestion, edema, infiltration of large numbers of inflammatory cells, and erosions and ulcerations of the bowel. It is becoming increasingly apparent that chronic gut inflammation may result from a dysregulated immune response toward components of the normal intestinal flora, resulting in a sustained overproduction of proinflammatory cytokines and mediators. Many of these Th1 and macrophage-derived cytokines and lipid metabolites are known to activate microvascular endothelial cells, thereby promoting leukocyte recruitment into the intestinal interstitium. This review discusses the basic immune mechanisms involved in the regulation of inflammatory responses in the gut and describes how a breakdown in this protective response initiates chronic gut inflammation.

Biological and novel therapies for inflammatory bowel disease in children

During the past decade, a tremendous wealth of information regarding the pathogenesis, genetics, and therapy of IBD has been discovered. Judging by the number of new publications published every month in scientific journals and the great enthusiasm at scientific meetings, this outstanding pace surely will continue. In the near future, clinicians may be able to classify IBD into several subtypes depending on patients' cytokine and gene profiles. For example, two groups of researchers recently have identified mutation in the NOD2 gene, which is associated with susceptibility to CD. This identification may allow the clinician to better predict outcome and response to medical therapy. At the same time, several promising new therapies are being investigated. Technologic advances will continue to result in the development of potent and specific agents that will control and possibly correct the abnormal inflammatory processes responsible for pediatric IBD.

Selective intracellular delivery of dexamethasone into activated endothelial cells using an E-selectin-directed immunoconjugate

In chronic inflammatory diseases, the endothelium is an attractive target for pharmacological intervention because it plays an important role in leukocyte recruitment. Hence, inhibition of endothelial cell activation and consequent leukocyte infiltration may improve therapeutic outcome in these diseases. We report on a drug targeting strategy for the selective delivery of the anti-inflammatory drug dexamethasone to activated endothelial cells, using an E-selectin-directed drug-Ab conjugate. Dexamethasone was covalently attached to an anti-E-selectin Ab, resulting in the so-called dexamethasone-anti-E-selectin conjugate. Binding of the conjugate to E-selectin was studied using surface plasmon resonance and immunohistochemistry. Furthermore, internalization of the conjugate was studied using confocal laser scanning microscopy and immuno-transmission electron microscopy. It was demonstrated that the dexamethasone-anti-E-selectin conjugate, like the unmodified anti-E-selectin Ab, selectively bound to TNF-alpha-stimulated endothelial cells and not to resting endothelial cells. After binding, the conjugate was internalized and routed to multivesicular bodies, which is a lysosome-related cellular compartment. After intracellular degradation, pharmacologically active dexamethasone was released, as shown in endothelial cells that were transfected with a glucocorticoid-responsive reporter gene. Furthermore, intracellularly delivered dexamethasone was able to down-regulate the proinflammatory gene IL-8. In conclusion, this study demonstrates the possibility to selectively deliver the anti-inflammatory drug dexamethasone into activated endothelial cells, using an anti-E-selectin Ab as a carrier molecule.

Effects of VLA-4 antagonists in rat whole embryo culture

BACKGROUND

Pharmacological antagonism of VLA-4 (Very Late Antigen 4, alpha(4)beta(1) integrin) has become an attractive target for the treatment of predominantly eosinophil mediated disease states such as asthma, allergic rhinitis, multiple sclerosis, rheumatoid arthritis, diabetes, and inflammatory bowel disease. Gene knockouts of the alpha(4)-integrin subunit of VLA-4 or its cell surface ligand, VCAM-1, however, have been shown to result in embryo-lethality in homozygous null mice due to defects in chorio-allantoic or epi-myocardial fusion. Although gene knockout phenotypes are not always manifested by pharmacological antagonism, those studies suggested that VLA-4 antagonists might cause embryo-lethality or drug-induced malformations.

METHODS

To test these concepts, early neurulating rat embryos were cultured by the methods of New ('78) after intra-coelomic microinjection of a VLA-4 blocking antibody or in the presence of small molecule VLA-4 antagonists.

RESULTS

Defects in chorio-allantoic fusion were induced after microinjection of VLA4 blocking antibody and after continuous exposure to small molecule antagonists. In a minority of affected embryos chorio-allantoic fusion was completely blocked whereas the majority of affected embryos had only superficial chorio-allantoic fusion and the allantois was enlarged and edematous. Although the allantoic mesoderm covered the trophoblasts of the chorionic plate and contained blood vessels there was only minimal invasion of the trophoblasts by the allantoic mesoderm. The lowest observed effect level generally correlated with the IC(approximately 95), as determined in 90% plasma.

DISCUSSION

Based on these data, VLA-4 antagonism might represent a significant risk to the developing embryo/fetus. In vitro exposure, however, is "constant" and does not take into account the elimination phase of these xenobiotics in vivo. Given the high concentrations required to elicit an effect, therapeutic blood levels in vivo may be several fold lower than those that affect the conceptus, depending on the tissue penetration of the compound and the route of administration. VLA-4 also exists in a range of conformations and activation states in vivo and the gene KOs and present studies do not define whether these developmental processes are dependent upon a particular activation state of VLA-4. Therefore, state-selective antagonists may have an improved embryonic safety profile. Additional studies will be required to determine potential effects of VLA-4 antagonists on embryo/fetal development in vivo.

Microbiological and immunological strategies for treatment of inflammatory bowel disease

Chronic inflammatory bowel diseases such as Crohn's disease or ulcerative colitis, affect around 1 in every 1000 individuals in western countries. They probably result from an inappropriate reaction towards the commensal microflora and are currently treated with anti-inflammatory drugs or surgery. Novel strategies aim at blocking lymphocyte recruitment and activation, improved targeting of therapeutics and modification of gut microflora.

Isoxazolyl, oxazolyl, and thiazolylpropionic acid derivatives as potent alpha(4)beta(1) integrin antagonists

A series of isoxazolyl, oxazolyl, and thiazolylpropionic acid derivatives derived from LDV was found to be a potent antagonist of the alpha(4)beta(1) integrin. The synthesis and SAR leading up to 3-[3-(1-[-[3-methoxy-4-(3-o-tolyl-ureido)-phenyl]-acetylamino]-3-methyl-butyl)-isoxazol-5-yl]-propionic acid (22) are reported. In an allergic mouse model, compound 22 was efficacious delivered systemically (58% inhib @ 10 mg/kg, sc) as well as by intra-tracheal instillation (ED(50)=2 microg/kg).

A randomized placebo-controlled trial of a humanized monoclonal antibody to alpha4 integrin in active Crohn's disease

BACKGROUND & AIMS

alpha4 integrins are important mediators of leukocyte migration across vascular endothelium. This pilot placebo-controlled study aimed to assess the safety and efficacy of natalizumab, a recombinant humanized monoclonal antibody to alpha4 integrin, in patients with mild to moderately active Crohn's disease.

METHODS

Thirty patients with active Crohn's disease (Crohn's Disease Activity Index [CDAI] > or =151 and < or =450) received a 3-mg/kg infusion of natalizumab (n = 18) or placebo (n = 12) by double-blind randomization. The study's primary endpoint was change in CDAI at week 2.

RESULTS

At week 2, the CDAI decreased significantly from baseline after infusion of natalizumab (mean 45 points) but not placebo (mean 11 points). Seven (39%) natalizumab-treated patients achieved remission at week 2, compared with 1 (8%) treated with placebo. In contrast, 4 (33%) of the placebo-treated patients required rescue medication by week 2, compared with 2 (11%) natalizumab-treated patients. Significant increases in circulating B and T lymphocytes were detected only after natalizumab administration. The frequency of commonly reported adverse events did not differ significantly between groups.

CONCLUSIONS

A single 3-mg/kg natalizumab infusion was well tolerated by Crohn's disease patients, although the dose used may have been suboptimal. Elevated circulating lymphocyte levels after natalizumab suggest interrupted lymphocyte trafficking. Natalizumab therapy in active Crohn's disease merits further investigation.

Novel therapies in the treatment of ulcerative colitis

Ulcerative colitis is a chronic inflammatory disease of unknown cause. Its course is one of relapse and remission and requires therapy for both the induction and maintenance of remission. The progress in the fields of genetics and immunology has afforded important advances in our understanding of the inflammatory process. Traditional therapy with non-specific anti-inflammatories for ulcerative colitis remains our gold standard as newer targeted therapies have failed to provide any improved efficacy. This review examines the most recent compounds in development for the treatment of ulcerative colitis, including data from early clinical trials and the potential clinical impact of future entities.

Human leukocyte subpopulations from inflamed gut bind to joint vasculature using distinct sets of adhesion molecules

Reactive arthritis can be triggered by inflammatory bowel diseases. We hypothesized that migration of mucosal immune cells from inflamed gut to joints could contribute to the development of reactive arthritis. Here we isolated gut-derived leukocytes from patients with Crohn's disease and ulcerative colitis. Using function-blocking mAbs and in vitro frozen section adhesion assays we studied whether these cells bind to synovial vessels and which molecules mediate the interaction. The results showed that mucosal leukocytes from inflammatory bowel diseased gut bind well to venules in synovial membrane. Small intestinal lymphocytes adhered to synovial vessels using multiple homing receptors and their corresponding endothelial ligands (CD18-ICAM-1, alpha(4)beta(7)/alpha(4)beta(1)-integrin-VCAM-1, L-selectin-peripheral lymph node addressins, and CD44). Of these, only ICAM-1 significantly supported binding of immunoblasts. In contrast, P-selectin glycoprotein ligand-1-P-selectin interaction accounted for practically all synovial adherence of mucosal macrophages. In addition, blocking of vascular adhesion protein-1 significantly inhibited binding of all these leukocyte subsets to joint vessels. We conclude that different leukocyte populations derived from inflamed gut bind avidly to synovial vessels using distinct repertoire of adhesion molecules, suggesting that their recirculation may contribute to the development of reactive arthritis in inflammatory bowel diseases.

Differential role of selectins in experimental colitis

BACKGROUND AND AIMS

The role of selectins in experimental colitis remains unknown. The aims of this study were to characterize the time-course expression of selectins in trinitrobenzene sulfonic acid (TNBS)-induced colitis, the functional role of selectins in colonic leukocyte-endothelial cell interactions, and the therapeutic usefulness of selectin blockade in this model.

METHODS

Control and TNBS-induced colitic rats were studied. Expression of P- and E-selectin was assessed by the radiolabeled antibody technique, and L-selectin by flow cytometry. Leukocyte-endothelial cell interactions were studied in colonic venules by using intravital microscopy under basal conditions and after P-, E-, or L-selectin immunoblockade. Additional groups of animals were treated with anti-P-selectin antibody, a nonbinding antibody, or dexamethasone, for 7 days.

RESULTS

P-selectin and E-selectin expression were markedly up-regulated in colitic rats. Increased leukocyte rolling was abrogated by anti-P-selectin, but only attenuated by anti-E- or anti-L-selectin antibodies. Only pretreatment with anti-P- selectin decreased leukocyte adhesion. Animals chronically treated with dexamethasone, but not with anti- P-selectin, had significantly lower macroscopic and histologic damage scores, colon weight, and myeloperoxidase (MPO) activity than those treated with nonbinding antibody.

CONCLUSIONS

P-selectin plays a key role on leukocyte rolling and its blockade attenuates leukocyte adhesion in TNBS-induced colitis. However, treatment with an anti-P-selectin antibody does not significantly improve colitis.

Role of intercellular adhesion molecule 1 in indomethacin-induced ileitis

Adhesion molecules have been implicated in the pathogenesis of inflammatory bowel diseases. We investigated their expression and contribution to leukocyte recruitment in experimental intestinal inflammation. Ileitis was induced in Sprague-Dawley rats by two injections of indomethacin (7.5 mg/kg), given 24 h apart. Endothelial intercellular adhesion molecule-1 (ICAM-1) expression was quantified using the dual radiolabeled monoclonal antibody technique and Mac-1 (CD11b/CD18) expression on leukocytes by flow cytometry. Leukocyte infiltration was monitored by tissue myeloperoxidase (MPO) activity. The first indomethacin injection induced a time- and site-dependent increase of ICAM-1 expression in ileal mucosa and muscularis. The second injection resulted in a reduction of ICAM-1 expression below constitutive levels whereas Mac-1 was upregulated. MPO changes paralleled lesion development over 48 h. ICAM-1 and MPO values were correlated for the first 24 h. Immunoneutralization of either ICAM-1 or Mac-1 attenuated mucosal injury. We conclude that (i) indomethacin-induced ileitis is associated with a temporally disassociated upregulation of ICAM-1 and (ii) despite a reduction in ICAM-1 after 24 h, ICAM-1, in concert with Mac-1, contributes to mucosal injury and leukocyte infiltration elicited by indomethacin.

Current use of biologicals for the treatment of spondyloarthropathies

Spondyloarthropathies (SpA) are a group of related disorders. The hallmark symptoms include spondylitis, pauci-articular synovitis and enthesiopathy. In an important number of cases, subclinical gut inflammation with pathological findings resembling Crohn's disease can be found. Some of these patients may eventually develop overt Crohn's disease. Conventional medical therapy in patients with SpA consists of non-steroidal anti-inflammatory drugs (NSAIDs). Sulphasalazin can be co-administered, especially in cases of chronic synovitis or enthesiopathy. Recently, experience with anti-TNF-alpha monoclonal antibodies (infliximab), a new class of biological compounds, has opened new avenues for treating patients with SpA. In particular, infliximab used in two open studies gave significant benefit on the locomotor manifestations in patients with Crohn's disease, in patients with ankylosing spondylitis, undifferentiated SpA and psoriatic arthritis. Etanercept, another TNF-alpha antagonist (soluble receptor), was shown to induce benefit in a placebo-controlled study in patients with psoriatic arthritis. The relationship between SpA and inflammatory bowel disease lead to the hypothesis that interfering with gut inflammation in patients with SpA would yield a potential target for modulating the synovitis in these patients. Thus, besides TNF-alpha blockade, other strategies with potential efficacy can be envisioned, such as IL-10, ICAM-1 antisense or anti-(4)beta(7) antibodies.

CD4(+)CD45RO(+)CD49d(high) cells are involved in the pathogenesis of relapsing-remitting multiple sclerosis

In the animal model of multiple sclerosis, experimental autoimmune encephalomyelitis, encephalitogenic T cells differ from the non-encephalitogenic ones in their expression of CD49d. The disease-inducing CD49d(high) and not the CD49d(low) cells enter the brain parenchyma. In this context, we characterized CD4(+)(CD45RO(+))CD49d(high) cells in relapsing-remitting multiple sclerosis (RR-MS) patients. These cells, showing characteristics of activated cells able to produce pro-inflammatory cytokines, were found to be increased in peripheral blood during relapses and present in high numbers in cerebrospinal fluid. These results suggest that the CD4(+)CD45RO(+)CD49d(high) subpopulation in RR-MS patients includes autoreactive cells and may be target for immunotherapy.

VCAM-1, but not ICAM-1 or MAdCAM-1, immunoblockade ameliorates DSS-induced colitis in mice

Adhesion molecule immunoneutralization is envisioned as a promising therapy for inflammatory bowel disease, but the relative value of selective blockade of different adhesion molecules has not been established. The aims of this study were to measure expression and functional relevance of endothelial intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and mucosal addressin cell adhesion molecule 1 (MAdCAM-1) in leukocyte recruitment in experimental colitis and to compare the therapeutic effectiveness of their selective blockade. For this purpose, cell adhesion molecule expression was measured by the dual radiolabeled antibody technique in mice with dextran sulfate sodium-induced colitis and controls. Leukocyte-endothelial cell interactions were determined in colonic venules by fluorescence intravital microscopy. Therapeutic effects of chronic treatment with anti-ICAM-1, anti-VCAM-1, or anti-MAdCAM-1 antibodies were also assessed. Whereas colonic endothelial ICAM-1 was constitutively expressed and had a mild up-regulation in colitic animals, constitutive expression of VCAM-1 and MAdCAM-1 was low, but markedly increased after induction of colitis. Leukocyte adhesion was abrogated by immunoneutralization of VCAM-1 or MAdCAM-1 but not by treatment with an anti-ICAM-1 antibody. Chronic administration of anti-VCAM-1 antibody, but not anti-ICAM-1 or anti-MAdCAM-1, resulted in significant attenuation of colitis in terms of disease activity index, colon length, ratio of colon weight to length, and myeloperoxidase activity. In conclusion, VCAM-1 plays a central role in leukocyte recruitment in colitis and blockade of this adhesion molecule has higher therapeutic effect than immunoneutralization of ICAM-1 or MAdCAM-1 in this experimental model.

Treatment of murine colitis by Lactococcus lactis secreting interleukin-10

The cytokine interleukin-10 (IL-10) has shown promise in clinical trials for treatment of inflammatory bowel disease (IBD). Using two mouse models, we show that the therapeutic dose of IL-10 can be reduced by localized delivery of a bacterium genetically engineered to secrete the cytokine. Intragastric administration of IL-10-secreting Lactococcus lactis caused a 50% reduction in colitis in mice treated with dextran sulfate sodium and prevented the onset of colitis in IL-10(-/-) mice. This approach may lead to better methods for cost-effective and long-term management of IBD in humans.

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.

Blockade of the integrin alphaLbeta2 but not of integrins alpha4 and/or beta7 significantly prolongs intestinal allograft survival in mice

BACKGROUND

Small bowel transplantation remains a difficult therapeutic option endangered by a high rate of rejection and infectious complications. To improve these clinical results, it is mandatory to set up animal models to test alternative immunosuppressive regimens which may lead to immunotolerance.

AIMS

To determine the value of blockade of alphaLbeta2 (LFA-1) and alpha4 and beta7 integrins (alpha4beta1, alpha4beta7, and alphaEbeta7) in the prevention of rejection of fetal small bowel grafts in mice and the effect of the association of calcineurin dependent drugs in anti-LFA-1 treated mice.

METHODS

Adult recipient mice engrafted with allogeneic fetal small bowel received a short course of anti-alpha4 and/or anti-LFA-1 monoclonal antibodies (mAb) with or without FK506 or cyclosporin A. In addition, in a set of experiment, beta7-/- mice were used as recipients. Graft biopsies were performed and processed for standard histology.

RESULTS

Blockade of the pathways of the integrins alpha4 and beta7 had a modest or no effect on intestinal graft survival. In contrast, transitory, short administration of anti-LFA-1 monoclonal antibody alone, when started before engraftment (day -1), allowed long term survival of intestinal grafts, even when associated with calcineurin dependent drugs. However, early withdrawal of FK506 reversed the immunosuppressive effect of anti-LFA-1 treatment.

CONCLUSION

These results suggest that firstly, anti-LFA-1, but not anti-alpha4 mAb treatment, may be useful in improving the results of intestinal transplantation, and secondly, that this treatment is not incompatible with long term administration of tacrolimus currently used in the prevention of small bowel graft rejection in humans.

E-Selectin expression in a murine model of chronic colitis

The objective of this study was to quantify E-selectin surface expression in the colon as well as other tissues in a CD4(+) T-cell model of chronic colitis in mice using the newly developed dual radiolabel monoclonal antibody technique. Male SCID mice were reconstituted with either 5 x 10(5) CD4(+) CD45RB(low) or CD45RB(high) T-cells isolated from normal CB-17 donor mouse spleens and subsequently monitored for clinical signs of colitis. We found that animals injected with CD45RB(high) but not CD45RB(low) T-cells nor PBS developed colitis at 6-8 weeks following reconstitution as assessed by loss of body weight, development of loose stools and/or diarrhea, and histopathology. Concurrent with the onset of distal bowel inflammation was enhanced expression of E-selectin compared to SCID mice injected with PBS or reconstituted with CD45RB(low) T-cells, both of which did not develop colitis. We also observed significant increases in E-selectin expression in cecum, small intestine, mesentery, and liver of colitic mice. Our data confirm that reconstitution of SCID mice with CD45RB(high) but not CD45RB(low) T-cells induces chronic colitis and demonstrate that this chronic colitis is associated with enhanced expression of an endothelial cell-specific adhesion molecule. Furthermore, our studies demonstrate that reconstitution of SCID mice with CD45RB(high) T-cells enhances E-selectin expression in a variety of tissues distant from the site of active inflammation.

Therapy of inflammatory bowel disease

In the last decade, substantial gains have been made in the treatment of inflammatory bowel disease (IBD). Refinements in drug formulation have provided the ability to target distinct sites of delivery, enhancing the safety and efficacy of older agents. Immunosuppressive agents beyond corticosteroids have assumed a routine part in the care of patients with IBD. Moreover, as the century closes, we stand at the threshold of unprecedented advances in knowledge of the pathogenesis of ulcerative colitis and Crohn's disease. Simultaneous progress in biotechnology has fostered the development of new agents that strategically target pivotal processes in disease pathogenesis. This review covers agents currently used in the treatment of IBD and seeks to provide an overview of emerging therapies.

Tissue Specificity of E- and P-Selectin Ligands in Th1-Mediated Chronic Inflammation

The demonstrated role of E- and P-selectin ligands in the recruitment of Th1 cells raises the question of tissue specificity determination by pathogenic T cells. We took advantage of the fact that chronic Th1-mediated inflammation in the scid/scid CD4+CD45RBhigh T cell transfer model can occur at multiple tissue sites, resembling inflammatory bowel disease in the colon and psoriasis in the skin. We show that the majority of infiltrating effector T cells from psoriatic skin expresses high levels of functional P-selectin ligand (87 ± 3%), detected by P-selectin-Ig (PIg), while a significantly smaller subset of T cells from colitic lesions expresses this ligand (24 ± 2%). Similarly, E-selectin ligand is preferentially expressed on CD4+ T cells infiltrating the skin (24 ± 2%), but only on very few CD4+ T cells infiltrating the colon (CIT; 1.3 ± 0.8%). In contrast, CD4+ T cells infiltrating the skin express α4β7 at a significantly lower level than CIT (mean fluorescence intensity, 28 vs 61, respectively), although, interestingly, αEβ7 was expressed at high levels on both populations. Analysis of the disease-inducing potential of PIg+ and PIg− CD4+ CIT cells revealed that both populations not only express similar levels of the gut-homing molecule α4β7 (mean fluorescence intensity, 50 vs 56, respectively), but do not differ in their capacity to express IFN-γ. Furthermore, CIT depleted of cells expressing functional P-selectin ligand were able to induce colitis upon transfer, suggesting that induction of colitis in this model may be independent of E- and P-selectin. These results indicate that adhesion molecule expression and the homing pattern of inflammatory T cells are regulated by the local environment independently of their inflammatory capacity.

Inhibition of dextran sulphate sodium (DSS)-induced colitis in mice by intracolonically administered antibodies against adhesion molecules (endothelial leucocyte adhesion molecule-1 (ELAM-1) or intercellular adhesion molecule-1 (ICAM-1))

We examined the effect of intracolonic administration of anti-adhesion molecule antibodies on DSS-induced colitis in mice. Immunohistochemical staining in mice with colitis showed increased expression of ELAM-1 and ICAM-1 on endothelial cells of vessels in the lamina propria and submucosa at sites of inflamed lesions. Intracolonic administration of anti-ELAM-1 or anti-ICAM-1 antibody decreased bloody stools, anaemia, and histologically evident damage, as well as myeloperoxidase activity and IL-1beta content. We concluded that adhesion molecule expression is important in the development of DSS-induced colitis in mice and that intracolonic administration of anti-adhesion molecule antibodies, especially anti-ELAM-1 antibody, effectively inhibits the colonic inflammation. Intracolonic administration of anti-adhesion molecule antibodies may show therapeutic promise in ulcerative colitis.

Regulation of ICAM-1-mediated fibroblast-T cell reciprocal interaction: implications for modulation of gut inflammation

BACKGROUND & AIMS

Immune-nonimmune cell interactions modulate mucosal immunity. We investigated the expression of adhesion molecules by intestinal fibroblasts, the effect of immune cell-derived factor on fibroblast binding of T cells, and the consequences of interfering with adhesion molecule expression on fibroblast-T cell interaction.

METHODS

Expression of fibroblast intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 surface and messenger RNA (mRNA) was measured before and after exposure to immune cell-derived supernatants. Fibroblasts were treated with antibodies to ICAM-1 or VCAM-1, or ICAM-1 antisense oligonucleotide Isis 2302, before a T-cell adhesion assay.

RESULTS

Fibroblast activation by immune cell-derived cytokines enhanced ICAM-1 and VCAM-1 surface expression and mRNA as well as adhesiveness for T cells. Blockade with neutralizing antibodies showed that binding was almost exclusively dependent on ICAM-1. Isis 2302 specifically reduced fibroblast ICAM-1 mRNA and dose-dependently inhibited ICAM-1 surface expression and T-cell binding.

CONCLUSIONS

ICAM-1 is essential for intestinal fibroblast binding of T cells, a phenomenon that is efficiently and specifically disrupted by ICAM-1 antisense oligonucleotides. These observations emphasize the crucial regulatory role of fibroblasts in mucosal immunity and their potential as targets for therapeutic intervention in intestinal inflammation.

Novel therapies for inflammatory bowel disease

Looking back at successes and failures in newer approaches to treating IBD, it is tempting--although still difficult--to draw conclusions about pathogenesis. When a therapy proves effective, do clinicians truly know how it works? Even with a therapy as specific as anti-TNF antibody, it is not clear if the benefit is attributable to simple binding and clearance of TNF-alpha or to binding on the cell surface and subsequent deletion of the activated macrophage. When a drug appears to be less effective than preclinical models suggest, can failures in effectiveness from delivery or dosing be differentiated? The disappointing results of clinical trials with IL-10--so at odds with the prediction of benefit from animal models--bring into question the validity of those models as well as the soundness of design of the clinical trials on which efficacy of IL-10 is judged. The variability of response even to the most narrowly targeted agents suggests that these diseases are far more heterogeneous in humans than in their murine counterparts. Clinicians are only just beginning to recognize subclinical markers of response, and it may soon be possible to predict response on the basis of genetic composition. For the moment, however, the field of pharmacogenetics is embryonic. Challenges in developing new therapeutic strategies include not only identifying novel agents, but also improving the definitions of clinical endpoints and defining efficacy at the biologic level. Only through considered evaluation of clinical evidence may clinicians determine which therapies should remain novelties and which should become an accepted part of the armamentarium.

Investigation of the expression of IL-1beta converting enzyme and apoptosis in normal and inflammatory bowel disease (IBD) mucosal macrophages

Activated mucosal macrophages are derived from circulating monocytes and appear to play a major role in the pathogenesis of IBD. We have recently shown that IBD, but not normal, mucosal macrophages express the active form of IL-1beta converting enzyme (ICE) and are therefore capable of releasing mature IL-1beta. ICE expression by other mucosal cell types is unknown. Active ICE expression has also been implicated in apoptosis. The aim of this study was to investigate ICE expression (using an antibody that recognizes both active and precursor forms) in normal and IBD mucosa and to determine whether ICE-expressing macrophages are undergoing apoptosis. Normal and active IBD mucosal cells, in tissue sections and after isolation, were studied by immunohistochemistry and flow cytometry. In the mucosa, macrophages were the predominant ICE-expressing cell type. In contrast to normal, most IBD mucosal macrophages expressed ICE. Of IBD colonic macrophages 11.8 +/- 3.2%, and of normal colonic macrophages 6.6 +/- 0.6% expressed Apo2.7, a marker for apoptotic cells. Similar data were obtained when annexin V was used to identify cells undergoing apoptosis. DNA fluorescence flow cytometric analysis of normal and IBD lamina propria cells showed the presence of only small hypodiploid DNA peaks. We conclude that in the human intestinal mucosa, macrophages are the predominant ICE-expressing cell type. Expression of the active form of ICE and macrophage apoptosis are not interdependent. One mechanism of loss of resident macrophages from normal mucosa and of recruited macrophages from IBD mucosa is by apoptosis.

Administration of mAb Against αEβ7 Prevents and Ameliorates Immunization-Induced Colitis in IL-2−/− Mice

We previously demonstrated that 2,4,6-trinitrophenol (TNP)-OVA immunization leads to a transmural colitis in the IL-2−/− mouse that is caused by IL-12-driven CD4+ Th1 T cells and resembles human Crohn’s disease. The integrin αEβ7 is highly expressed on colonic intraepithelial lymphocytes and has been suggested to function as a homing or retention molecule for intraepithelial lymphocytes. To evaluate the role of αEβ7 in colitis, we administered a mAb against αEβ7 to IL-2−/− mice that were immunized at the same time with TNP-OVA in CFA. To our surprise, this treatment resulted in a significantly reduced colitis severity score, 0–2 vs 3–4, that was associated with a significant reduction in CD4+ lamina propria lymphocyte subpopulation (p &lt; 0.01). In contrast, the total number of splenic CD4+ T cells of treated animals was significantly elevated compared with that of untreated animals (3.2 ± 0.6 × 107 vs 1.2 ± 0.2 × 107; p &lt; 0.05). Similarly, functional studies revealed that IFN-γ production by lamina propria lymphocytes isolated from IL-2−/− TNP-OVA-immunized mice treated with anti-αEβ7 was significantly lower than in untreated IL-2−/− TNP-OVA-immunized mice. In contrast, IFN-γ production by splenic cells isolated from treated IL-2−/− TNP-OVA-immunized mice was significantly higher than in untreated mice. Finally, TNP-OVA-immunized IL-2−/− mice that were treated after the colitis had been established also showed a significant decrease in mucosal inflammation after αEβ7 mAb administration. Thus, the above findings demonstrate that the onset and maintenance of inflammatory bowel disease depends on the colonic localization of lamina propria CD4+ lymphocytes expressing αEβ7.

VCAM-1 and ICAM-1 mediate leukocyte-endothelial cell adhesion in rat experimental colitis

BACKGROUND & AIMS

The molecular mechanisms responsible for leukocyte recruitment in experimental colitis are poorly understood. The aims of this study were to measure expression of endothelial intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) and to determine their role in leukocyte recruitment in experimental colitis.

METHODS

Rats with trinitrobenzene sulfonic acid (TNBS)-induced colitis and control rats were studied 1, 7, or 21 days after treatment. ICAM-1 and VCAM-1 expressions were measured by the double radiolabeled antibody technique. Leukocyte-endothelial cell interactions were determined in colonic venules by fluorescence intravital microscopy. Therapeutic effects of treatment with anti-VCAM-1 antibodies were also assessed.

RESULTS

Colonic endothelial ICAM-1 was constitutively expressed and did not increase in colitic animals. In contrast, constitutive expression of VCAM-1 was low but markedly increased (6-fold) 1 and 7 days after induction of colitis. Increased colonic expression of VCAM-1 paralleled macroscopic damage score, myeloperoxidase activity, and increased leukocyte adhesion in colonic venules. The latter was significantly decreased by immunoneutralization of ICAM-1 and completely abrogated by immunoneutralization of VCAM-1. Long-term administration of anti-VCAM-1 antibody resulted in significant attenuation of colitis.

CONCLUSIONS

Induction of colitis in rats by TNBS is followed by up-regulation of endothelial VCAM-1. VCAM-1 and constitutive ICAM-1 are major determinants of leukocyte recruitment to the inflamed intestine.

Anti-inflammatory drugs and endothelial cell adhesion molecule expression in murine vascular beds

BACKGROUND

Inflammatory bowel diseases (IBD) are characterised by an intense infiltration of leucocytes that is mediated by adhesion molecules expressed on the surface of activated endothelial cells.

AIMS

To determine whether drugs used in the treatment of IBD, specifically dexamethasone (DEX), 5-aminosalicylic acid (5-ASA), methotrexate (MTX), and 6-mercaptopurine (6-MP), alter the expression of endothelial cell adhesion molecules (ECAMs).

METHODS

The expression of P-selectin, E-selectin, intercellular adhesion molecule 1 (ICAM-1), and vascular CAM 1 (VCAM-1) in different vascular beds of C57Bl/6J mice was measured using the dual radiolabelled monoclonal antibody technique.

RESULTS

Lipopolysaccharide (LPS) elicited a profound increase in the expression of all ECAMs in the mesentery, small intestine, caecum, and distal colon. The LPS induced increase in CAM expression was not significantly affected by prior treatment with either MTX or 6-MP. However, pretreatment with either DEX or 5-ASA significantly attenuated LPS induced increases in expression of P- and E-selectin, and VCAM-1 in the majority of tissues evaluated. DEX also blunted the LPS induced increase in ICAM-1 expression in the caecum and distal colon. DEX, but not 5-ASA, largely abolished the rise in plasma tumour necrosis factor alpha elicited by LPS.

CONCLUSIONS

These findings suggest that DEX and 5-ASA may exert their beneficial therapeutic action in IBD, at least in part, by inhibiting the expression of ECAMs which mediate leucocyte adhesion and transmigration in the microvasculature.

Acquired increase in leucocyte binding by intestinal microvascular endothelium in inflammatory bowel disease

BACKGROUND

Endothelial cells that line microvascular blood vessels have an important role in inflammation through their ability to bind and recruit circulating leucocytes. Endothelial cells from the intestines of patients with chronically inflamed Crohn's disease and ulcerative colitis--the two forms of inflammatory bowel disease--display an increased leucocyte-binding capacity in vitro. We investigated whether this enhanced leucocyte binding is a primary or an acquired defect.

METHODS

We cultured human intestinal microvascular endothelial cells (HIMEC) from the uninvolved intestine and chronically inflamed bowel of three patients with inflammatory bowel disease (two Crohn's disease, one ulcerative colitis). We assessed HIMEC binding to polymorphonuclear leucocytes and U937 cells by means of an adhesion assay.

FINDINGS

After activation with interleukin-1beta or lipopolysaccharide, HIMEC from the chronically inflamed tissue in all three patients with inflammatory bowel disease bound twice as many polymorphonuclear leucocytes and U937 cells as endothelial cells from uninvolved tissue.

INTERPRETATION

Enhanced leucocyte binding by HIMEC from chronically inflamed tissue in patients with inflammatory bowel disease is an acquired defect since it is not found in the uninvolved intestinal segments from the same individuals. Because interaction between endothelial cells and leucocytes is a key regulatory step in the inflammatory process, this enhanced binding may contribute to the pathophysiology of chronic intestinal inflammation.

Novel inhibitors of alpha 4 beta 1 integrin receptor interactions through library synthesis and screening

A library of 2302 small molecule beta-turn mimetics was screened for inhibition of the alpha 4 beta 1 integrin-CS1 splice variant binding interaction. Preliminary data revealed several active ligands, and validation with purified material culminated in the identification of some of the first small molecule ligands (1, IC50 = 5 microM, and 2, IC50 = 8 microM) to be reported for this class of integrins.

Adhesion molecules in clinical medicine

Cellular adhesion molecules (CAMs) are critical components in the processes of embryogenesis, tissue repair and organization, lymphocyte function, lymphocyte homing and tumor metastasis, as well as being central to the interactions between hemopoietic progenitors and bone marrow microenvironment, and between leukocytes and platelets with vascular endothelium. Expression of CAMs regulates normal hemopoiesis and migration and function of mature hemopoietic cells. CAMs are an important part of the inflammatory response and may regulate cytokine synthesis. In addition, CAM expression may be critical for tumorigenesis. Monoclonal antibodies to CAMs have been developed for clinical use; initial results suggest that these agents have great potential in the prevention and treatment of inflammation, thrombosis, reperfusion injury, and graft rejection.

Very late antigen 4 (VLA4) antagonists as anti-inflammatory agents

In recent years antagonists of very late antigen-4 (VLA4, also known as integrin alpha(4) beta(1)) have shown great promise in treating inflammatory disorders in a number of animal models. The most advanced in this endeavor is a humanized anti-alpha(4) antibody, Antegren, which is in phase II clinical trials for multiple sclerosis. The first reported small-molecule VLA4 antagonist to advance into clinical trials is currently in phase I as an aerosol for treating asthma. A number of peptides, cyclic peptides and peptidomimetics have been disclosed and are in preliminary stages of development.