Ligation of VLA-4 on T cells stimulates tyrosine phosphorylation of a 105-kD protein

The role of Cas-L/NEDD9 as a regulator of collagen-induced arthritis in a murine model

Cas-L/NEDD9 is a cytoplasmic docking protein downstream of β1 integrin-mediated signaling pathway and is essential for cellular migration and β1 integrin-mediated costimulation of T cells. We previously found that increased number of Cas-L positive leukocytes migrated into the inflamed joints of HTLV-I tax transgenic mice which spontaneously develop polyarthritis, suggesting a role of Cas-L in rheumatoid arthritis (RA) pathophysiology. Our current study expanded these findings on the role of Cas-L/NEDD9 in the development of RA by analyzing the pathophysiological changes in a Nedd9(-/-) mouse collagen-induced arthritis (CIA) model. Nedd9(-/-) mice exhibited a decrease in arthritis severity as compared to Nedd9(+/+) mice. In addition, as being conducted bone marrow transplantation experiments with a CIA model, Nedd9(-/-)→Nedd9(+/+) transplant showed a decrease in the incidence and severity score of arthritis, compared to those of Nedd9(+/+)→Nedd9(-/-) transplant. For analysis of serum levels of various cytokines, IL-1β, IL-6, IL-17, TNF-α, IFN-γ and anti-collagen antibody were decreased, while IL-4 and IL-10 levels were increased, in Nedd9(-/-) mice as compared to those in Nedd9(+/+) mice. Furthermore, collagen-mediated cellular responses of lymphocytes isolated from spleen or affected lymph nodes of Nedd9(-/-) mice were reduced. Our results strongly suggest that Cas-L/NEDD9 plays a pivotal role in the pathophysiology of CIA, and that Cas-L/NEDD9 may be a potential molecular target for the treatment of RA.

Phase I clinical trial of fibronectin CH296-stimulated T cell therapy in patients with advanced cancer

BACKGROUND

Previous studies have demonstrated that less-differentiated T cells are ideal for adoptive T cell transfer therapy (ACT) and that fibronectin CH296 (FN-CH296) together with anti-CD3 resulted in cultured cells that contain higher amounts of less-differentiated T cells. In this phase I clinical trial, we build on these prior results by assessing the safety and efficacy of FN-CH296 stimulated T cell therapy in patients with advanced cancer.

METHODS

Patients underwent fibronectin CH296-stimulated T cell therapy up to six times every two weeks and the safety and antitumor activity of the ACT were assessed. In order to determine immune function, whole blood cytokine levels and the number of peripheral regulatory T cells were analyzed prior to ACT and during the follow up.

RESULTS

Transferred cells contained numerous less-differentiated T cells greatly represented by CD27+CD45RA+ or CD28+CD45RA+ cell, which accounted for approximately 65% and 70% of the total, respectively. No ACT related severe or unexpected toxicities were observed. The response rate among patients was 22.2% and the disease control rate was 66.7%.

CONCLUSIONS

The results obtained in this phase I trial, indicate that FN-CH296 stimulated T cell therapy was very well tolerated with a level of efficacy that is quite promising. We also surmise that expanding T cell using CH296 is a method that can be applied to other T- cell-based therapies.

TRIAL REGISTRATION

UMIN UMIN000001835.

Activated human hepatic stellate cells induce myeloid derived suppressor cells from peripheral blood monocytes in a CD44-dependent fashion

BACKGROUND & AIMS

Myeloid derived suppressor cells (MDSCs) are a heterogeneous population of cells associated with the suppression of immunity. However, little is known about how or where MDSCs are induced and from which cells they originate. The liver is known for its immune regulatory functions. Here, we investigated the capacity of human hepatic stellate cells (HSCs) to transform peripheral blood monocytes into MDSCs.

METHODS

We cultured freshly isolated human monocytes from healthy donors on primary human HSCs or an HSC cell-line and characterized the phenotype and function of resulting CD14(+)HLA-DR(-/low) monocytes by flow cytometry, quantitative PCR, and functional assays. We analyzed the molecular mechanisms underlying the induction and function of the CD14(+)HLA-DR(-/low) cells by using blocking antibodies or knock-down technology.

RESULTS

Mature peripheral blood monocytes co-cultured with HSCs downregulated HLA-DR and developed a phenotypic and functional profile similar to MDSCs. Only activated but not freshly isolated HSCs were capable of inducing CD14(+)HLA-DR(-/low) cells. Such CD14(+)HLA-DR(-/low) monocyte-derived MDSCs suppressed T-cell proliferation in an arginase-1 dependent fashion. HSC-induced development of CD14(+)HLA-DR(-/low) monocyte-derived MDSCs was not mediated by soluble factors, but required physical interaction and was abrogated by blocking CD44.

CONCLUSIONS

Our study shows that activated human HSCs convert mature peripheral blood monocytes into MDSCs. As HSCs are activated during chronic inflammation, the subsequent local induction of MDSCs may prevent ensuing excessive liver injury. HSC-induced MDSCs functionally and phenotypically resemble those isolated from liver cancer patients. Thus, our data suggest that local generation of MDSCs by liver-resident HSCs may contribute to immune suppression during inflammation and cancer in the liver.

Effect of natalizumab on circulating CD4+ T-cells in multiple sclerosis

In multiple sclerosis (MS), treatment with the monoclonal antibody natalizumab effectively reduces the formation of acute lesions in the central nervous system (CNS). Natalizumab binds the integrin very late antigen (VLA)-4, expressed on the surface of immune cells, and inhibits VLA-4 dependent transmigration of circulating immune-cells across the vascular endothelium into the CNS. Recent studies suggested that natalizumab treated MS patients have an increased T-cell pool in the blood compartment which may be selectively enriched in activated T-cells. Proposed causes are sequestration of activated T-cells due to reduced extravasation of activated and pro-inflammatory T-cells or due to induction of VLA-4 mediated co-stimulatory signals by natalizumab. In this study we examined how natalizumab treatment altered the distribution of effector and memory T-cell subsets in the blood compartment and if T-cells in general or myelin-reactive T-cells in particular showed signs of increased immune activation. Furthermore we examined the effects of natalizumab on CD4(+) T-cell responses to myelin in vitro. Natalizumab-treated MS patients had significantly increased numbers of effector-memory T-cells in the blood. In T-cells from natalizumab-treated MS patients, the expression of TNF-α mRNA was increased whereas the expression of fourteen other effector cytokines or transcription factors was unchanged. Natalizumab-treated MS patients had significantly decreased expression of the co-stimulatory molecule CD134 on CD4(+)CD26(HIGH) T-cells, in blood, and natalizumab decreased the expression of CD134 on MBP-reactive CD26(HIGH)CD4(+) T-cells in vitro. Otherwise CD4(+) T-cells from natalizumab-treated and untreated MS patients showed similar responses to MBP. In conclusion natalizumab treatment selectively increased the effector memory T-cell pool but not the activation state of T-cells in the blood compartment. Myelin-reactive T-cells were not selectively increased in natalizumab treated MS.

Impact of the integrin signaling adaptor protein NEDD9 on prognosis and metastatic behavior of human lung cancer

PURPOSE

In a substantial population of non-small cell lung cancer (NSCLC), expression and activation of EGF receptor (EGFR) have been reported and is regarded as a novel molecular target. A growing body of evidence has shown the signaling crosstalk between EGFR and integrins in cellular migration and invasion. NEDD9 is an integrin signaling adaptor protein composed of multiple domains serving as substrate for a variety of tyrosine kinases. In the present study, we aimed at elucidating a role of NEDD9 in the signaling crosstalk between EGFR and integrins.

EXPERIMENTAL DESIGN

Using NSCLC cell lines, we conducted immunoblotting and cellular migration/invasion assay in vitro. Next, we analyzed metastasis assays in vivo by the use of xenograft transplantation model. Finally, we retrospectively evaluated clinical samples and records of patients with NSCLCs.

RESULTS

We showed that tyrosine phosphorylation of NEDD9 was reduced by the inhibition of EGFR in NSCLC cell lines. Overexpression of constitutively active EGFR caused tyrosine phosphorylation of NEDD9 in the absence of integrin stimulation. By gene transfer and gene knockdown, we showed that NEDD9 plays a pivotal role in cell migration and invasion of those cells in vitro. Furthermore, overexpression of NEDD9 promoted lung metastasis of an NSCLC cell line in NOD/Shi-scid, IL-2Rγ(null) mice (NOG) mice. Finally, univariate and multivariate Cox model analysis of NSCLC clinical specimens revealed a strong correlation between NEDD9 expression and recurrence-free survival as well as overall survival.

CONCLUSION

Our data thus suggest that NEDD9 is a promising biomarker for the prognosis of NSCLCs and its expression can promote NSCLC metastasis.

Synergistic effect of CH-296 and interferon gamma on cytokine-induced killer cells expansion for patients with advanced-stage malignant solid tumors

BACKGROUND

Cytokine-induced killer cells (CIKs) are heterogenous antitumor effectors including interferon gamma (IFN-γ)-amplified CD3(+)CD56(+) cells. CH-296 has been shown to stimulate T-cell proliferation in the presence of T cell receptor (TCR)-stimulating signals. The purpose of this study was to investigate the synergistic effect of CH-296 and IFN-γ on expansion of CIKs for treating patients with advanced-stage malignant solid tumors.

METHODS

CIKs were cultured with immobilized CH-296 in the presence (retronectin [RN]-CIKs) or absence of IFN-γ (RN-CIKs/del) for 14 days. Proliferation, apoptosis, phenotype, and cytotoxicity were detected. Twenty (20) patients (18 patients with stage IV solid tumors) received three cycles of RN-CIKs treatment. The clinical responses were evaluated using Karnofsky Performance Status scoring and computed-tomography scanning.

RESULTS

CH-296 promoted CIKs expansion in a time-dependent manner by inhibiting apoptosis and increasing proliferation. Costimulation of CH-296 and IFN-γ amplified more antitumor effectors of CIKs with activated T-cell phenotype, which displayed potent cytotoxicity and increased cytokines secretion upon antigen priming. Sixteen (16) patients receiving RN-CIKs experienced relief of clinical symptoms. The overall clinical response rate was 65% (13/20) and the mean overall survival was 16.95±6.10 months. No severe adverse events were observed in the clinical trial.

CONCLUSIONS

CH-296 and IFN-γ synergistically promote antitumor efficiency of CIKs by increasing proliferation, inhibiting apoptosis, and enhancing cytotoxicity.

Optimization of lentiviral vector transduction into peripheral blood mononuclear cells in combination with the fibronectin fragment CH-296 stimulation

Large scale T-cell expansion and efficient gene transduction are required for adoptive T-cell gene therapy. Based on our previous observations, human peripheral blood mononuclear cells (PBMCs) can be expanded efficiently while conserving a naïve phenotype by stimulating with both recombinant human fibronectin fragment (CH-296) and anti-CD3 monoclonal antibodies. In this article, we explored the possibility of using this co-stimulation method to generate engineered T cells using lentiviral vector. Human PBMCs were stimulated with anti-CD3 together with immobilized CH-296 or anti-CD28 antibody as well as anti-CD3/anti-CD28 conjugated beads and transduced with lentiviral vector simultaneously. Co-stimulation with CH-296 gave superior transduction efficiency than with anti-CD28. Next, PBMCs were stimulated and transduced with anti-CD3/CH-296 or with anti-CD3/CD28 beads. T-cell expansion, gene transfer efficiencies and immunophenotypes were analysed. Stimulation with anti-CD3/CH-296 resulted in more than 10-times higher cell expansion and higher gene transfer efficiency with conservation of the naïve phenotype compared with anti-CD3/CD28 stimulation method. Thus, lentiviral transduction with anti-CD3/CH-296 co-stimulation is an efficient way to generate large numbers of genetically modified T cells and may be suitable for many gene therapy protocols that use adoptive T-cell transfer therapy.

Semaphorin 6D regulates the late phase of CD4+ T cell primary immune responses

The semaphorin and plexin family of ligand and receptor proteins provides important axon guidance cues required for development. Recent studies have expanded the role of semaphorins and plexins in the regulation of cardiac, circulatory and immune system function. Within the immune system, semaphorins and plexins regulate cell-cell interactions through a complex network of receptor and ligand pairs. Immune cells at different stages of development often express multiple semaphorins and plexins, leading to multivariate interactions, involving more than one ligand and receptor within each functional group. Because of this complexity, the significance of semaphorin and plexin regulation on individual immune cell types has yet to be fully appreciated. In this work, we examined the regulation of T cells by semaphorin 6D. Both in vitro and in vivo T cell stimulation enhanced semaphorin 6D expression. However, semaphorin 6D was only expressed by a majority of T cells during the late phases of activation. Consequently, the targeted disruption of semaphorin 6D receptor-ligand interactions inhibited T cell proliferation at late but not early phases of activation. This proliferation defect was associated with reduced linker of activated T cells protein phosphorylation, which may reflect semaphorin 6D regulation of c-Abl kinase activity. Semaphorin 6D disruption also inhibited expression of CD127, which is required during the multiphase antigen-presenting cell and T cell interactions leading to selection of long-lived lymphocytes. This work reveals a role for semaphorin 6D as a regulator of the late phase of primary immune responses.

Regulation of epithelial cell adhesion and repulsion: role of endocytic recycling

A proper balance between cell adhesion and repulsion is essential for cellular morphogenesis during epithelial-mesenchymal transition and mesenchymal-epithelial transition. A number of ligand-receptor pairs including hepatocyte growth factor/scatter factor-Met and semaphorin-plexin are known to control this balance through the complex intracellular signaling pathways. Cell adhesion to other cells and extracellular matrix (ECM) is mediated by cell adhesion molecules (CAMs) and ECM receptors, respectively, which are associated with cytoskeleton through a variety of plaque proteins strengthening and/or weakening adhesion activities. Cell repulsion requires the downregulation of cell adhesion and the extensive changes in cytoskeletal dynamics. The endocytic recycling of CAMs and ECM receptors has recently emerged as an important mechanism to control the balance between cell adhesion and repulsion. Molecule interacting with CasL (MICAL) family proteins are originally identified as a plaque protein associated with ECM receptors integrins and implicated in semaphorin-plexin dependent repulsive axon guidance. We have recently shown that MICAL family protein JRAB/MICAL-L2 functions as an effector protein for Rab family small G protein Rab13 and regulates the endocytic recycling of tight junctional CAM occludin and controls the adhesion and repulsion of epithelial cells.

In vivo persistence of genetically modified T cells generated ex vivo using the fibronectin CH296 stimulation method

Recombinant human fibronectin fragment (FN-CH296, RetroNectin) has been widely used for retroviral gene therapy to enhance gene transfer efficiency. Based on the observation that immobilized FN-CH296 together with anti-CD3 monoclonal antibodies (anti-CD3) enhanced cell proliferation while conserving the naive phenotype of T cells, we used FN-CH296 costimulation to generate engineered T cells. For comparison, human peripheral blood mononuclear cells were stimulated under three kinds of conditions including anti-CD3 only, anti-CD3 and anti-CD28 monoclonal antibodies conjugated with beads (anti-CD3/anti-CD28) and immobilized FN-CH296 together with anti-CD3 (anti-CD3/FN-CH296); all three treatments were followed by retroviral gene transfer. Of all the stimulation methods, the one involving anti-CD3/FN-CH296 produced the most cell expansion with conservation of the naive phenotype. Engineered T cells were transplanted into NOD/SCID (non-obese diabetic/severe combined immunodeficient) mice, and all the mice were killed 14 days later. Transplanted T cells were detected in all the mice; however, mice injected with anti-CD3/FN-CH296-stimulated T cells showed higher transgene expression in organs than mice injected with anti-CD3-stimulated cells. These results demonstrate that the anti-CD3/FN-CH296 stimulation can be an efficient way to generate large numbers of genetically modified T cells that can provide higher and longer lasting levels of transgene expression in vivo and that are suitable for adoptive T-cell transfer therapy.

Pharmacological properties, toxicology and scientific rationale for the use of natalizumab (Tysabri) in inflammatory diseases

Natalizumab (Tysabri) was the first adhesion molecule antagonist to make it into clinical trial for patients with multiple sclerosis (MS) and other inflammatory disorders. Natalizumab is a humanized recombinant monoclonal antibody (MAb) that binds to the alpha (alpha)(4) chain of the alpha(4) beta (beta)(1) (very late activating antigen 4; VLA-4) and alpha(4)beta(7) integrins. The scientific rationale for natalizumab therapy is the reduction of leukocyte extravasation into peripheral tissues. Natalizumab, like other VLA-4 antagonists, may also interfere with the activation of T lymphocytes in secondary lymphoid organs and their reactivation in the central nervous system (CNS). Shortly after its approval for the treatment of relapsing-remitting MS (RR-MS), three patients who were treated with natalizumab in the setting of clinical trials developed progressive multifocal leukoencephalopathy (PML), an opportunistic infection of the brain with the polyoma virus JC. It remains to be elucidated why the use of this VLA-4 antagonist is associated with an increased incidence of PML. Natalizumab was recently reapproved for the treatment of relapsing forms of MS. In this review, we outline the scientific rationale for using natalizumab in MS and other inflammatory disorders. In addition, an overview of pharmacological properties, clinical efficacy, safety, and toxicology of natalizumab is provided.

Alpha4 and beta2 integrins have nonredundant roles for asthma development, but for optimal allergen sensitization only alpha4 is critical

OBJECTIVE

Recruitment of effector cell subsets to inflammatory lung, together with airway resident cells responsive to secreted products, play pivotal roles in developing and maintaining asthma. Differential use of adhesion molecules dictates the recruitment patterns of specific cell subsets, yet a clear understanding of the distinctive adhesive molecular pathways guiding them to lung is lacking. To provide further insight into the role of alpha4beta1/VCAM-1 pathway and to compare this to the role of beta2 integrin in the development of acute asthma phenotype, we used genetically deficient mice, in contrast to previous studies with anti-functional antibodies yielding ambiguous results.

METHODS

Allergen-dependent airway inflammation and hyperresponsiveness was induced in conditional alpha4(Delta/Delta), VCAM-1(-/-), and beta2(-/-) mice. Cytology, immunocytochemistry, cytokine and immunoglobulin measurements, and cell type accumulation in lung, BAL fluid, plasma, and hemopoietic tissues were carried out.

RESULTS

Asthma phenotype was totally abrogated in alpha4- or beta2-deficient mice. Adoptive transfer of sensitized alpha4(Delta/Delta) CD4(+) cells into challenged normal mice failed to induce asthma, whereas alpha4(+/+) CD4(+) cells were able to induce asthma in challenged alpha4(Delta/Delta) mice. Parallel studies with beta2(-/-) or VCAM-1(-/-) mice uncovered novel mechanistic insights in primary sensitization and into redundant or unique functional roles of these adhesion pathways in allergic asthma.

CONCLUSIONS

The lack of alpha4 integrin not only impedes the migration of all white cell subsets to lung and airways, but also prevents upregulation of vascular cell adhesion molecule-1 (VCAM-1) in inflamed lung vasculature and, unlike beta2, attenuates optimal sensitization and ovalbumin-specific IgE production in vivo. As VCAM-1 deficiency did not protect mice from asthma, interactions of alpha4beta1(+) or alpha4beta7(+) cells with other ligands are suggested.

Endothelial Lu/BCAM glycoproteins are novel ligands for red blood cell alpha4beta1 integrin: role in adhesion of sickle red blood cells to endothelial cells

The Lutheran (Lu) blood group and basal cell adhesion molecule (BCAM) antigens are both carried by 2 glycoprotein isoforms of the immunoglobulin superfamily representing receptors for the laminin alpha(5) chain. In addition to red blood cells, Lu/BCAM proteins are highly expressed in endothelial cells. Abnormal adhesion of red blood cells to the endothelium could potentially contribute to the vaso-occlusive episodes in sickle cell disease. Considering the presence of integrin consensus-binding sites in Lu/BCAM proteins, we investigated their potential interaction with integrin alpha(4)beta(1), the unique integrin expressed on immature circulating sickle red cells. Using cell adhesion assays under static and flow conditions, we demonstrated that integrin alpha(4)beta(1) expressed on transfected cells bound to chimeric Lu-Fc protein. We showed that epinephrine-stimulated sickle cells, but not control red cells, adhered to Lu-Fc via integrin alpha(4)beta(1) under flow conditions. Antibody-mediated activation of integrin alpha(4)beta(1) induced adhesion of sickle red cells to primary human umbilical vein endothelial cells; this adhesion was inhibited by soluble Lu-Fc and vascular cell adhesion molecule-1 (VCAM-1)-Fc proteins. This novel interaction between integrin alpha(4)beta(1) in sickle red cells and endothelial Lu/BCAM proteins could participate in sickle cell adhesion to endothelium and potentially play a role in vaso-occlusive episodes.

HTLV-I Tax induces and associates with Crk-associated substrate lymphocyte type (Cas-L)

Crk-associated substrate lymphocyte type (Cas-L) is a docking protein that is heavily tyrosine phosphorylated by the engagement of beta1 integrins in T cells. In the present study, we attempted to evaluate the role of Cas-L in the pathophysiology of adult T-cell leukemia (ATL). Examination of peripheral blood mononuclear cells from ATL patients as well as ATL-derived T cell lines showed an elevation of Cas-L in these cells. We showed that tyrosine phosphorylation as well as expression of Cas-L was markedly elevated through the induction of human T-lymphotropic virus type I (HTLV-I) Tax in JPX-9 cells, with these cells showing marked motile behavior on the ligands for integrins. We next performed yeast two-hybrid screening of cDNA library from an HTLV-I-transformed T cell line, which resulted in the identification of Tax as a putative binding partner for Cas-L. Co-precipitation experiments revealed that the serine-rich region of Cas-L might serve as the binding site with the highest affinity for Tax. Co-localization study showed that Tax and Cas-L partly merged in the cytoplasm. Finally, we showed that exogenous Cas-L inhibited Tax-mediated transactivation of nuclear factor kappaB (NF-kappaB), while Tax-independent activation of NF-kappaB remained intact, hence indicating that Cas-L might specifically regulate Tax-NF-kappaB pathway.

T Cell Integrin Overexpression as a Model of Murine Autoimmunity

Integrin adhesion molecules have important adhesion and signaling functions. They also play a central role in the pathogenesis of many autoimmune diseases. Over the past few years we have described a T cell adoptive transfer model to investigate the role of T cell integrin adhesion molecules in the development of autoimmunity. This report summarizes the methods we used in establishing this murine model. By treating murine CD4+ T cells with DNA hypomethylating agents and by transfection we were able to test the in vitro effects of integrin overexpression on T cell autoreactive proliferation, cytotoxicity, adhesion and trafficking. Furthermore, we showed that the ability to induce in vivo autoimmunity may be unique to the integrin lymphocyte function associated antigen-1 (LFA-1).

CD49d overexpression and T cell autoimmunity

D10.G4.1 (D10) cells, a murine conalbumin-reactive Th2 cell line, made to overexpress the beta(2) integrin LFA-1 by pharmacological manipulation or by transfection become autoreactive and are capable of inducing in vivo autoimmunity. However, whether this is specific to LFA-1 and whether overexpression of other T cell integrin molecules has the same effect are unknown. We examined the functional consequences of T cell CD49d (alpha(4) integrin) overexpression by transfecting murine CD49d cDNA into D10 cells. Similar to the LFA-1-transfected cells, the CD49d-overexpressing T cells are autoreactive and proliferate in response to APCs in an MHC class II-dependent manner in the absence of nominal Ag. Additionally, CD49d overexpression is associated with increased in vitro adhesion to endothelial cells and increased in vivo splenic homing. However, in contrast to LFA-1 overexpression, increased T cell CD49d expression is not associated with autoreactive cytotoxicity or the ability to induce in vivo autoimmunity. In addition to the novel observation that CD49d overexpression is sufficient to induce T cell autoreactivity, our results also support the hypothesis that the ability to induce in vivo autoimmunity is related to T cell cytotoxicity and not to T cell proliferation function in the D10 murine adoptive transfer model of autoimmunity.

Role of Crk-associated substrate lymphocyte type in the pathophysiology of rheumatoid arthritis in tax transgenic mice and in humans

OBJECTIVE

To investigate the role of Crk-associated substrate lymphocyte type (Cas-L), a downstream signaling molecule of beta1 integrins, in the pathophysiology of rheumatoid arthritis (RA).

METHODS

We analyzed human T lymphotropic virus type I (HTLV-I) tax transgenic mice as well as samples from human RA patients. Splenocytes from tax transgenic mice were cultured on mouse endothelial cell-covered Transwell inserts, and cells migrating through the endothelial monolayer were counted. Biochemical studies were performed to analyze the protein expression and tyrosine phosphorylation of Cas-L. Immunohistochemical analysis was performed to detect Cas-L-positive cells that had infiltrated into the joints.

RESULTS

Migratory activity of splenocytes from tax transgenic mice with arthritis (ATg) was much higher than that of tax transgenic mice without arthritis (NTg) and littermate control mice. The expression of Cas-L protein and its tyrosine phosphorylation were increased in ATg mice compared with NTg and control mice, and this was accompanied by enhanced autophosphorylation of Fyn and Lck. Immunohistochemical analysis demonstrated a large number of Cas-L-positive lymphocytes migrating into the affected joints. Furthermore, in human RA, Cas-L-positive lymphocytes were shown to infiltrate to the inflammatory lesions.

CONCLUSION

These results strongly suggest that Cas-L plays an important role in the pathophysiology of RA.

beta1 integrin-mediated signaling induces intercellular adhesion molecule 1 and Fas on rheumatoid synovial cells and Fas-mediated apoptosis

OBJECTIVE

Rheumatoid arthritis (RA) synovial cells interact with inflammatory cells, as well as extracellular matrices, through integrins. However, the relevance of beta1 integrin to inflammatory processes in RA remains unclear. We examined the role of beta1 integrin-mediated signaling in RA.

METHODS

Expression of cell-surface molecules was assessed by FACScan. Engagement of beta1 integrins was performed by crosslinking using a specific monoclonal antibody (mAb) and ligand matrices such as fibronectin or collagen. To determine the involvement of tyrosine kinases in beta1 integrin-mediated signaling, the cells were pretreated with various inhibitors of intracytoplasmic signaling or were transfected with a wild-type focal adhesion kinase (FAK) or a dominant negative truncation of the FAK expression plasmid via cationic liposome-mediated transfection. Apoptosis of synovial cells was detected by double staining with propidium iodide and annexin V.

RESULTS

beta1 integrin was highly expressed on RA synovial cells. Engagement of beta1 integrins by crosslinking as well as by ligand matrices markedly up-regulated expression of intercellular adhesion molecule 1 (ICAM-1) and Fas. Up-regulation of ICAM-1 and Fas induced by beta1 integrin was mediated by the tyrosine kinase signaling pathway, especially involving FAK. Fas-mediated early apoptotic change in the cells was amplified by beta1 crosslinking.

CONCLUSION

Our results suggest that interaction of beta1 integrins with extracellular matrix augments expression of ICAM-1 and Fas on RA synovial cells, as well as Fas-mediated apoptosis of synovial cells. This might lead to the spontaneous growth arrest through the Fas/Fas ligand pathway observed in RA synovitis.

MICAL, a novel CasL interacting molecule, associates with vimentin

CasL/HEF1 belongs to the p130(Cas) family. It is tyrosine-phosphorylated following beta(1) integrin and/or T cell receptor stimulation and is thus considered to be important for immunological reactions. CasL has several structural motifs such as an SH3 domain and a substrate domain and interacts with many molecules through these motifs. To obtain more insights on the CasL-mediated signal transduction, we sought proteins that interact with the CasL SH3 domain by far Western screening, and we identified a novel human molecule, MICAL (a Molecule Interacting with CasL). MICAL is a protein of 118 kDa and is expressed in the thymus, lung, spleen, kidney, testis, and hematopoietic cells. MICAL has a calponin homology domain, a LIM domain, a putative leucine zipper motif, and a proline-rich PPKPP sequence. MICAL associates with CasL through this PPKPP sequence. MICAL is a cytoplasmic protein and colocalizes with CasL at the perinuclear area. Through the COOH-terminal region, MICAL also associates with vimentin that is a major component of intermediate filaments. Immunostaining revealed that MICAL localizes along with vimentin intermediate filaments. These results suggest that MICAL may be a cytoskeletal regulator that connects CasL to intermediate filaments.

A novel ability of Smad3 to regulate proteasomal degradation of a Cas family member HEF1

Smad3 is a key signal transducer of transforming growth factor-ss (TGF-ss) and activin, and is known to be a DNA-binding transcriptional regulator. Here we report a novel property of Smad3 in regulating the proteasomal degradation of the human enhancer of filamentation 1 (HEF1), which is a member of the Cas family of cytoplasmic docking proteins. Our studies revealed that Smad3 interacts with HEF1 and triggers the proteasomal degradation of HEF1 in overexpression systems. In addition, TGF-ss stimulation induces rapid proteasomal degradation of endogenous HEF1 in different TGF-ss-responsive cell lines. Interestingly, the degradation of HEF1 protein in epithelial cells is followed closely by an increase in HEF1 mRNA, resulting in a time-dependent increase in HEF1 protein level in TGF-ss-treated cells. Furthermore, we observed that an elevated HEF1 protein level inhibits TGF-ss-induced Smad3-mediated gene responses. These data provide the first evidence for a novel cytoplasmic activity of Smad3 in regulating proteasomal degradation of HEF1 and also suggest a role for HEF1 in a negative feedback mechanism of the TGF-ss signaling pathway.

Potent costimulation of effector T lymphocytes by human collagen type I

Purified, resting peripheral blood T lymphocytes were previously reported to undergo beta(1) integrin-dependent activation when cultured with anti-CD3 mAb coimmobilized with fibronectin, but not type I collagen. However, the extravascular T cells that encounter immobilized extracellular matrix proteins and are involved in disease pathogenesis have different properties from resting peripheral blood cells. In this study, we confirm that resting CD4(+) and CD8(+) T cells from peripheral blood are costimulated by immobilized fibronectin, but not type I collagen. In contrast, Ag- or mitogen-stimulated CD4(+) and CD8(+) T cell lines, used as models of the effector cells involved in disease, are more potently costimulated by type I collagen than fibronectin. The collagen-induced effects are similar in assays with serum-free medium and in more physiological assays in which anti-CD3 mAb is replaced by a threshold concentration of Ag and irradiated autologous PBMC as APC. The responses are beta(1) integrin dependent and mediated largely by very late Ag (VLA) 1 and 2, as shown by their up-regulation on the T cell lines as compared with freshly purified resting PBL, and by the effects of blocking mAb. Reversed phase HPLC located the major costimulatory sequence(s) in the alpha1 chain of type I collagen, the structure of which was confirmed by amino acid sequencing. The results demonstrate the potential importance of type I collagen, an abundant extracellular matrix protein, in enhancing the activation of extravascular effector T cells in inflammatory disease, and point to a new immunotherapeutic target.

Differential induction of gelatinase B (MMP-9) and gelatinase A (MMP-2) in T lymphocytes upon alpha(4)beta(1)-mediated adhesion to VCAM-1 and the CS-1 peptide of fibronectin

Integrin alpha(4)beta(1) on the surface of T lymphocytes interacts with vascular cell adhesion molecule-1 (VCAM-1) and fibronectin during migration of lymphocytes from the blood to sites of inflammation. Migrating lymphocytes actively modify their environment through a number of mechanisms including proteolysis of the extracellular matrix by matrix metalloproteinases (MMP) synthesized by the cells. In this study, expression of MMP upon alpha(4)beta(1)-mediated adhesion of leukocytes to two major ligands, the IIICS-1 domain of fibronectin and VCAM-1, has been examined. Adhesion of T lymphoblastoid Jurkat cells to the CS-1 peptide induced expression of mRNA for two MMPs, gelatinase A (MMP-2) and gelatinase B (MMP-9). As evaluated by relative RT-PCR and Northern blot analyses, the level of mRNA was upregulated about 4- to 5-fold for both MMPs compared to control cells maintained in suspension. With time, both enzymes were detected in conditioned media and inside the cells, and their identities were verified by Western blotting and gelatin zymography. Adhesion of Jurkat cells to the second major alpha(4)beta(1) ligand, VCAM-1, upregulated mRNA for MMP-2 (3.5-fold) and failed to induce expression of mRNA for MMP-9. Accordingly, only MMP-2 protein was detected in conditioned media of cells adherent to VCAM-1. Occupancy of alpha(4)beta(1) on the surface of suspended cells with soluble CS-1 peptide or VCAM-1 did not upregulate synthesis and release of MMPs. A similar pattern of induction of MMPs after adhesion to CS-1 and VCAM-1 was observed in T lymphocytes isolated from human blood. These results demonstrate that adhesion of T lymphocytes through alpha(4)beta(1) to different ligands, which bind to similar or overlapping sites in the integrin, induces intracellular events leading to distinct patterns of MMPs biosynthesis.

Fibronectin-mononuclear cell interactions regulate type 1 helper T cell cytokine network in tolerant transplant recipients

Fibronectin (FN), expressed primarily by macrophages, endothelial cells, and smooth muscle cells, represents an integral feature of the rejection response in transplant recipients. Here we demonstrate a unique pattern of cellular FN expression in rat recipients of cardiac allografts rendered tolerant in an infectious manner with either nondepleting CD4 mAb or regulatory spleen cells. Unlike in rejecting controls, cellular FN in tolerant hosts was restricted to the graft vessels and no vascular cell adhesion molecule-1 or intercellular adhesion molecule-1 expression could be found, supporting the role of FN in leukocyte sequestration at the graft site. The lack of myocardial FN in tolerant rats, despite dense macrophage infiltration, correlated with profound depression of Th1 (interleukin-2 and interferon-gamma) cytokines. Treatment with CD4-depleting mAb prevented tolerance induction and restored myocardial expression of FN in parallel with marked increase in the expression of interleukin-2 and interferon-gamma mRNA/protein. Furthermore, connective segment-1 peptide-facilitated adjunctive blockade of FN-alpha4beta1 interactions in recipients conditioned with CD4 depleting mAb, significantly depressed intragraft expression of interleukin-2 and interferon-gamma mRNA/protein. Hence, the lack of FN associated with infiltrating leukocytes plays an important role in the maintenance of tolerance in transplant recipients by depressing local expression of Th1 cytokines that otherwise facilitate acute graft rejection.

A small-molecule, tight-binding inhibitor of the integrin alpha(4)beta(1) blocks antigen-induced airway responses and inflammation in experimental asthma in sheep

The leukocyte integrin very late antigen-4 (alpha(4)beta(1), CD49d/CD29) is an adhesion receptor that plays an important role in allergic inflammation and contributes to antigen-induced late responses (LAR) and airway hyperresponsiveness (AHR). In this study, we show that single doses of a new small-molecule, tight-binding inhibitor of alpha(4), BIO-1211, whether given by aerosol or intravenously, either before or 1.5 h after antigen challenge blocks allergen- induced LAR and post-antigen-induced AHR in allergic sheep. Multiple treatments with doses of BIO-1211 that were ineffective when given singly, were protective. BIO-1211 also provided dose-dependent inhibition of the early airway response (EAR) to antigen. In conjunction with the functional protection against the antigen-induced LAR and AHR, sheep treated with BIO-1211 before challenge showed significantly reduced: (1) numbers of eosinophils in bronchoalveolar lavage (BAL), (2) BAL levels of the inflammatory marker tissue kallikrein, and (3) numbers of inflammatory cells (lymphocytes, eosinophils, metachromatic staining cells, and neutrophils) in bronchial biopsies obtained after challenge when compared with corresponding biopsies after vehicle treatment. More importantly, we show for the first time that an inhibitor of alpha(4) was able to reverse post-antigen-induced AHR, thereby decreasing the time of recovery from the normal period of > 9 d to 3 d. Our results show that effective inhibition of antigen-induced airway responses can be achieved with single doses of a potent small-molecule inhibitor of alpha(4) and that such agents may be used therapeutically, as well as prophylactically, to alleviate allergen- induced inflammatory events. These data provide further support and extend the evidence for the role of alpha(4) integrins in the pathophysiologic events that follow airway antigen challenge.

The mechanism of mononuclear cell infiltration in oral lichen planus: the role of cytokines released from keratinocytes

To clarify the pathogenesis of oral lichen planus (OLP), we investigated the roles of keratinocytes (KC) in mononuclear cell infiltration. When peripheral blood mononuclear cells (PBMC) obtained from healthy donors were cultured in the presence of culture supernatants of KC separated from the noninflamed gingivae (Nor-KC) and cheek mucosae of patients with OLP (OLP-KC), the number of migrated PBMC across monolayered human umbilical vein endothelial cells (HUVEC) were increased to about 1.3-fold and 1.5-fold of the control level, respectively, with increases of the expression of CD11a, CD11b, CD18, and CD49d on PBMC and intracellular adhesion molecule-1, vascular cell adhesion molecule-1, and endothelial-leukocyte adhesion molecule-1 on HUVEC. The number of migrated PBMC was reduced to about 60% of the control level by pretreatment of PBMC with anti-CD11a or anti-CD18 MAb and reduced to about 70% by pretreatment of HUVEC with anti-CD54 MAb. The pretreatment of PBMC with genistein, H-7, wortmannin, or exoenzyme C3 decreased the migrated PBMC by about 70 to 90%. In agreement with these results, the culture supernatants of OLP-KC up-regulated tyrosine phosphorylation of 62-kDa, 70-kDa, and 102-kDa proteins, phosphatidylinositol-3 kinase, and protein kinase C activities and activated Rho protein level more so than did those of Nor-KC. Additionally, actin reorganization with the formation of membrane ruffles and lamellipodia was distinctly induced by the culture supernatants of OLP-KC. These results indicate that cytokines generated by KC transduce their signals in PBMC, up-regulating the expression of cell surface adhesion molecules and migration activity with reorganization of actin filaments.

Postanoxic T lymphocyte-endothelial cell interactions induce tumor necrosis factor-alpha production and neutrophil adhesion: role of very late antigen-4/vascular cell adhesion molecule-1

The objective of this study was to define the influence of postanoxic T-lymphocyte-endothelial cell interactions on anoxia-reoxygenation (A/R)-induced neutrophil-endothelial cell adhesion and cell adhesion molecule (CAM) expression on human umbilical vein endothelial cells (HUVECs). HUVEC monolayers were exposed to 60 minutes of anoxia, followed by 24 hours of reoxygenation, wherein freshly isolated human T lymphocytes were added at 6 hours during reoxygenation. After an additional 18 hours of incubation (ie, total of 24 hours of reoxygenation), the T-cell/endothelial cell (TC/EC) coculture media were collected and added to naive HUVEC monolayers incubated with neutrophils. Although the A/R-conditioned media per se had no effect on neutrophil adhesion, the media from TC/EC cocultures significantly increased the adhesion response. This enhanced adhesive interaction was associated with significant increases in tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8) levels in the TC/EC coculture media and was accompanied by a pronounced increase in endothelial E-selectin expression. Treatment of the TC/EC coculture media with anti-TNF-alpha or anti-IL-8 antibodies reduced the media-induced neutrophil adhesion response. The enhanced neutrophil adhesion and the elevated medium levels of TNF-alpha, but not IL-8, were markedly reduced by inserts that prevented direct TC/EC contact and by monoclonal antibodies directed against vascular cell adhesion molecule-1 (VCAM-1) or very late antigen-4 (VLA-4). Collectively, these findings show that VLA-4-/VCAM-1-mediated interactions between T lymphocytes and postanoxic endothelial cells stimulates TNF-alpha production, which in turn elicits endothelial cell adhesion molecule expression and a corresponding increase in neutrophil adhesion.

Beta 1-integrin-mediated cell signaling in T lymphocytes

beta1-integrins play crucial roles in a variety of cell processes such as adhesion, migration, proliferation, and differentiation of lymphocytes. For understanding the molecular mechanisms of these various biological effects, it may be particularly important to analyze cell signaling through the beta1-integrins. Our previous study had shown that PLC-gamma, pp125FAK (focal adhesion kinase), pp105, paxillin, p59fyn, p56lck and ERK1/2 are phosphorylated in their tyrosine residues upon engagement of beta1-integrins. We identified pp105 as Cas (Crk-associated substrate)-related protein and successfully cloned its cDNA. pp105 is a Cas homologue predominantly expressed in the cells of lymphoid lineage, which led us to designate it as Cas-L. Like p130Cas, Cas-L contains a single SH3 domain and multiple SH2 binding sites (YXXP motif), which is suggested to bind SH2 domains of Crk, Nck, and SHPTP2. Subsequent studies revealed that pp125FAK binds Cas-L on its SH3 domain and phosphorylates its tyrosine residues upon beta1-integrin stimulation. Since Cas-L is preferentially expressed in lymphocytes, it is conceivable that Cas-L plays an important role in lymphocyte-specific signals. We have shown that Cas-L is involved in the T-cell receptor (TCR)/CD3 signaling pathway as well as the beta1-integrin signaling pathway. Cas-L is transiently phosphorylated following CD3 cross-linking, and tyrosine-phosphorylated Cas-L binds to Crk and C3G. Furthermore, a Cas-L mutant (Cas-LDeltaSH3), which lacks the binding site for FAK, is still tyrosine-phosphorylated upon CD3 cross-linking, but not upon beta1-integrin cross-linking, suggesting that FAK is not involved in CD3-dependent Cas-L phosphorylation. Finally, we have identified a crucial role of Cas-L in beta1-integrin-mediated T-cell co-stimulation. beta1-integrins have known to provide a co-stimulus for TCR/CD3-driven interleukin-2 production and proliferation of peripheral T-cells. We have found that this co-stimulatory pathway is impaired in the Jurkat T-cell line, and that the expression level of Cas-L is reduced in Jurkat cells compared with peripheral T-cells. The transfection of Cas-L cDNA into Jurkat cells restored the beta1-integrin-mediated co-stimulation, while the transfection of Cas-LDeltaSH3 mutant failed to do so, showing a contrast to the case with CD3-mediated signaling. These results indicate that Cas-L plays a key role through the association and phosphorylation by FAK in the beta1-integrin-mediated T-cell co-stimulation. Taken together, Cas-L might be the bi-modal docking protein that assembles the signals through beta1-integrins and TCR/CD3, and participates in a variety of T-cell functions.

Adhesion to fibronectin promotes the activation of the p125(FAK)/Zap-70complex in human T cells

The beta1 integrins are a family of heterodimeric adhesion receptors involved in cell-to-cell contacts and cell-to-extracellular matrix interactions. Through their adhesive role, integrins participate in transduction of outside/inside signals and contribute to trigger a multitude of cellular events such as differentiation, cell activation, and motility. The fibronectin integrin receptors, alpha4beta1 and alpha5beta1, can function as costimulatory molecules in T-cell receptor (TCR)-dependent T-cell activation. In the current study the Jurkat T-cell line was used as a model system to investigate the TCR-independent role of cell adhesion to fibronectin in the activation of Zap-70, a central molecule in the signalling events in T cells. Upon adhesion to plastic immobilized fibronectin but not to bovine serum albumin (BSA) the phosphorylation of p125FAK, a protein kinase that localizes to focal adhesion sites, was induced. Moreover, clustering of fibronectin receptors led to the detection of a p125FAK/Zap-70 complex. Finally, while the complex between fak-B, another protein kinase localized to focal adhesion sites, and Zap-70 was detected in cells plated either on BSA or on fibronectin, the formation of the p125FAK/Zap-70 complex appeared specifically induced following fibronectin-mediated integrin clustering. These data suggest the existence of a high degree of specificity when the members of the beta1 integrin family mediate signalling pathways in T cells.

Activation of complement receptor 3 on human monocytes by cross-linking of very-late antigen-5 is mediated via protein tyrosine kinases

Bordetella pertussis interacts with very-late antigen-5 (VLA-5) receptors on the human monocyte resulting in cross-linking of these receptors followed by activation of complement receptor 3 (CR3) and firm adhesion of B. pertussis to these monocytes. In the present study we investigated whether protein tyrosine kinases are involved in the activation of CR3 on monocytes, which was assessed by the binding of C3bi-coated erythrocytes (EC3bi). Pre-incubation of monocytes with tyrphostin-A47, a specific protein tyrosine kinase inhibitor, before adherence of the cells to an anti-VLA-5 monoclonal antibody-coated surface, or addition of tyrphostin-A47 within 10 min of the adherence to such surface, reduced the binding of EC3bi to monocytes significantly. Pre-incubation of monocytes with tyrphostin-A47 reduced the binding of B. pertussis to such monocytes as well. Inhibitors of protein kinase A and/or C had no effect on EC3bi binding to monocytes. Cross-linking of VLA-5 on monocytes resulted in tyrosine phosphorylation of several proteins. Together, these results indicate that protein tyrosine kinases are involved in the VLA-5-induced activation of CR3 on human monocytes.

Emigrated neutrophils regulate ventricular contractility via alpha4 integrin

We have previously shown that CD18 and alpha4 integrin were important in the adherence of emigrated neutrophils to cardiac myocytes. Whether either of these molecules is important in myocyte dysfunction is unclear. In this study, we measured contractility as an index of myocyte function. Control contractility was compared with shortening response in myocytes exposed to neutrophils in the presence and absence of anti-CD18 or anti-alpha4 antibodies. Control unloaded cell shortening, expressed as a percentage of resting cell length, measured 10.06+/-1.16% (n=10) at 5 minutes. Circulating neutrophils caused a 35% reduction in cell shortening, an event prevented by anti-CD18, but not by anti-alpha4 antibody. When emigrated neutrophils were added to the myocytes, a profound reduction (50%) in unloaded cell shortening was noted. A significant increase in CD18 and alpha4 integrin was found on emigrated neutrophils. Addition of anti-CD18 antibody did not protect the myocyte from the emigrated neutrophils, whereas the addition of an anti-alpha4 antibody significantly reduced neutrophil-induced cell shortening, despite some neutrophils still adhering to the myocytes. Furthermore, emigrated neutrophils were able to cause myocytes to go into contracture within 5 minutes in the presence of neutrophils with or without anti-CD18 antibody. In addition to the impairment in unloaded cell shortening, at later times (10 minutes), neutrophils also caused a 40% reduction in the rate of contraction and relaxation. The addition of either anti-CD18 or anti-alpha4 antibody protected the myocytes from these changes. The data suggest that immunosuppression of CD18 on emigrated neutrophils was only partially effective in reducing myocyte dysfunction. In contrast, immunosuppression of the alpha4 integrin alone was sufficient to dramatically reduce all parameters of cell dysfunction measured in this study.

Fyn and Lck tyrosine kinases regulate tyrosine phosphorylation of p105CasL, a member of the p130Cas docking protein family, in T-cell receptor-mediated signalling

We have previously shown that engagement of the T-cell receptor (TCR)/CD3 complex with anti-CD3 antibody induces tyrosine phosphorylation of p105CasL (CasL), a member of the p130Cas docking protein family. In the present work, we attempted to determine which protein tyrosine kinases (PTKs) regulate TCR-mediated phosphorylation of CasL. We show here that an association between CasL and two types of Src family PTKs, Fyn and Lck, is induced by anti-CD3 cross-linking of human H9 T cells. In contrast, ZAP-70, another PTK that also plays a critical role in the TCR signalling, failed to bind CasL, even after anti-CD3 stimulation. In vitro kinase assays revealed that Fyn and Lck, but not ZAP-70, were capable of phosphorylating CasL. Moreover, we found that CasL was constitutively hyperphosphorylated in vivo in splenocytes of MRL-MP-lpr/lpr mice, in which overproduction and excessive activation of Fyn and Lck have previously been shown to occur. Constitutive in vivo binding of CasL to both kinases was also demonstrated in lpr splenocytes. These results strongly suggest that CasL is a substrate for Fyn and Lck PTKs in TCR signal transduction.

Selective Requirements for Leukocyte Adhesion Molecules in Models of Acute and Chronic Cutaneous Inflammation: Participation of E- and P- But Not L-Selectin

Adhesion molecules borne by both endothelial cells and circulating leukocytes are in large measure responsible for guiding the process of extravasation. The selectin family has been primarily associated with the early stages of adhesion involving initial contact and rolling. A significant body of evidence has accumulated indicating a fundamental role for the endothelial members of this family, E- and P-selectin, in a variety of inflammatory states and models. Although originally identified as the lymph node-specific lymphocyte homing receptor, L-selectin has also been suggested to play an important role in leukocyte recruitment to sites of inflammation. We have recently demonstrated, using L-selectin–deficient mice, that defects in contact hypersensitivity (CHS) responses are in essence due to the inability of T cells to home to and be sensitized within peripheral lymph nodes, whereas nonspecific effector cells are fully capable of entry into sites of cutaneous inflammation (Catalina et al, J Exp Med184:2341, 1996). In the present study, we perform an analysis of adhesion molecule usage in two models of skin inflammation and show in both L-selectin–deficient as well as wild-type mice that a combination of P- and E-selectin is crucial for the development of both acute (croton oil) and chronic (contact hypersensitivity) inflammation at sites of the skin, whereas L-selectin does not appear to play a significant role. Moreover, 4 integrins are shown to be integral to a CHS but not an acute irritant response, whereas CD44 does not significantly contribute to either. These results provide a systematic examination in one study of major adhesion molecules that are critical in acute and chronic skin inflammation. They reinforce the essential role of the collaboration of E- and P-selectin in both specific and nonspecific skin inflammatory responses and the importance of 4 in the specific response only. In addition, they substantiate only a limited role, if any, for L-selectin in these cutaneous effector mechanisms and demonstrate the essential equivalence in this analysis of L-selectin–deficient mice compared with normal mice treated with blocking antibodies.

Selective Requirements for Leukocyte Adhesion Molecules in Models of Acute and Chronic Cutaneous Inflammation: Participation of E- and P- But Not L-Selectin

Adhesion molecules borne by both endothelial cells and circulating leukocytes are in large measure responsible for guiding the process of extravasation. The selectin family has been primarily associated with the early stages of adhesion involving initial contact and rolling. A significant body of evidence has accumulated indicating a fundamental role for the endothelial members of this family, E- and P-selectin, in a variety of inflammatory states and models. Although originally identified as the lymph node-specific lymphocyte homing receptor, L-selectin has also been suggested to play an important role in leukocyte recruitment to sites of inflammation. We have recently demonstrated, using L-selectin–deficient mice, that defects in contact hypersensitivity (CHS) responses are in essence due to the inability of T cells to home to and be sensitized within peripheral lymph nodes, whereas nonspecific effector cells are fully capable of entry into sites of cutaneous inflammation (Catalina et al, J Exp Med184:2341, 1996). In the present study, we perform an analysis of adhesion molecule usage in two models of skin inflammation and show in both L-selectin–deficient as well as wild-type mice that a combination of P- and E-selectin is crucial for the development of both acute (croton oil) and chronic (contact hypersensitivity) inflammation at sites of the skin, whereas L-selectin does not appear to play a significant role. Moreover, 4 integrins are shown to be integral to a CHS but not an acute irritant response, whereas CD44 does not significantly contribute to either. These results provide a systematic examination in one study of major adhesion molecules that are critical in acute and chronic skin inflammation. They reinforce the essential role of the collaboration of E- and P-selectin in both specific and nonspecific skin inflammatory responses and the importance of 4 in the specific response only. In addition, they substantiate only a limited role, if any, for L-selectin in these cutaneous effector mechanisms and demonstrate the essential equivalence in this analysis of L-selectin–deficient mice compared with normal mice treated with blocking antibodies.

Integrin signalling defects in T-lymphocytes in systemic lupus erythematosus

OBJECTIVE

To establish the relationship between T cell responses to integrin coreceptor stimulation and B cell hyperreactivity as measured by pathologic autoantibody production.

METHODS

Peripheral blood mononuclear cells from 42 patients with SLE according to the American Rheumatism Association criteria were examined for their ability to adhere to plate-immobilised fibronectin. Co-stimulation assays were performed on the same cells using anti-CD3 antibody alone or co-immobilised with an anti-beta1-integrin antibody. Proliferative responses were measured by 3[H]thymidine pulsing on day 3 and activation was determined using a commercial protein kinase C assay, the protocol being established by our group in association with Promega. Beta-integrin expression was established by FACS analysis.

RESULTS

An impaired PKC response to integrin-mediated activation was found in T-lymphocytes from 6/21 (29%) SLE patients, which correlated significantly with an absence of anti-dsDNA antibody in patient sera, irrespective of prednisolone treatment. Integrin co-stimulation of TcR/CD3-induced proliferation and T cell adhesion to fibronectin were also impaired among 5/21 (24%) and 6/15 (40%) patients studied, respectively.

CONCLUSION

We hypothesise that the integrity of beta1-integrin signalling pathways may influence pathological antibody production in SLE by affecting T-lymphocyte activation and interactions between T- and B-lymphocytes.

Effect of the interaction between fibronectin and VLA-4 on the proliferation of human B cells, especially a novel human B-cell line, OPM-3

Very late antigen (VLA)-4 integrin has been suggested to play an important role in haemopoiesis. However, little is known concerning the roles of the fibronectin (FN)/VLA-4 interaction in the proliferation of human B cells. In this study we investigated the effect of immobilized FN on the proliferation of various B-cell lines, including a newly-established B-cell line, OPM-3, and human tonsillar B cells, that primarily express VLA-4 but not VLA-5. Immobilized FN significantly promoted the proliferation of OPM-3 cells and normal B cells via VLA-4. The cross-linking of beta1 integrins of OPM-3 cells resulted in the phosphorylation of the focal adhesion kinase (FAK) associated 90 kD protein, an increase in FAK-associated kinase activity, and the phosphorylation of Raf-1. Furthermore, the MEK1 inhibitor, PD98059, inhibited the FN-promoted proliferation of OPM-3 cells. These results demonstrate that the FN/VLA-4 interaction transmits the growth signal(s) which may be mediated by Ras pathway in OPM-3 cells, and suggest that OPM-3 cells may be of great value in studying the roles of the FN/VLA-4 interaction in human B-cell growth.

Involvement of alpha-4 integrins in allergic airway responses and mast cell degranulation in vivo

Antibodies against integrins have been shown to inhibit allergic airway responses. The purpose of this study was to test the hypothesis that the beta1 integrin, very late antigen-4 (VLA-4), is involved in mast cell activation triggered by allergen exposure in sensitized animals. To do this we studied Brown Norway rats that were sensitized to ovalbumin (OA; 1 mg subcutaneously) using Bordetella pertussis as an adjuvant. Two weeks later rats were challenged with OA, pulmonary resistance (RL) was determined, and the concentrations of histamine and tryptase in bronchoalveolar lavage fluid and N-acetyl-leukotriene (LT)E4 in bile were measured. Pretreatment with a monoclonal antibody against VLA-4 (TA-2) attenuated the early response after OA challenge (342.9 +/- 24.4% baseline RL versus 153.3 +/- 19.4%; p < 0.01). There were significantly lower concentrations of histamine (67.11 +/- 11.90 microgram/ml versus 26.69 +/- 1.84; p < 0.01) and tryptase (0.143 +/- 0. 035 microgram/ml versus 0.053 +/- 0.022 microgram/ml; p < 0.01) in TA-2-treated animals. The increases in the concentrations of biliary N-acetyl-LTE4 after OA challenge were also significantly lower in TA-2-treated animals. These data suggest that a selective anti-VLA-4 monoclonal antibody prevents early responses through inhibition of mast cell activation.

Modulation of K+ currents in monocytes by VCAM-1 and E-selectin on activated human endothelium

Resting membrane potential (RMP) and whole cell currents were recorded in human THP-1 monocytes adherent to polystyrene, unstimulated human umbilical vein endothelial cells (HUVECs), lipopolysaccharide (LPS)-treated HUVECs, immobilized E-selectin, or vascular cell adhesion molecule 1 (VCAM-1) using the patch-clamp technique. RMP after 5 h on polystyrene was -24.3 +/- 1.7 mV (n = 42) with delayed rectifier K+ (Idr) and Cl- currents (ICl) present in >75% of the cells. Inwardly rectifying K+ currents (Iir) were present in only 14% of THP-1 cells. Adherence to unstimulated HUVECs or E-selectin for 5 h had no effect on Iir or ICl but decreased Idr. Five hours after adherence to LPS-treated HUVECs, outward currents were unchanged, but Iir was present in 81% of THP-1 cells. A twofold increase in Iir and a hyperpolarization (-41.3 +/- 3.7 mV, n = 16) were abolished by pretreatment of THP-1 cells with cycloheximide, a protein synthesis inhibitor, or herbimycin A, a tyrosine kinase inhibitor, or by pretreatment of the LPS-treated HUVECs with anti-VCAM-1. Only a brief (15-min) interaction between THP-1 cells and LPS-treated HUVECs was required to induce Iir expression 5 h later. THP-1 cells adherent to VCAM-1 exhibited similar conductances to cells adherent to LPS-treated HUVECs. Thus engagement of specific integrins results in selective modulation of different K+ conductances.

Ligation of the beta2 integrin triggers activation and degranulation of human eosinophils

Evidence suggests that cellular adhesion is critical for eosinophil effector functions. Here, we tested the hypothesis that an adhesion molecule, specifically beta2 integrin, participates in intracellular signaling events of eosinophils. Eosinophils stimulated with interleukin (IL)-5 and adherent to protein-coated tissue culture plates via beta2 integrin (CD18) showed tyrosine phosphorylation of a number of proteins. Among these proteins, tyrosine phosphorylation of the 105 kD and 115 kD proteins and the product of the c-cbl protooncogene, Cbl, was specifically inhibited using soluble anti-CD18 monoclonal antibody (mAb) to block eosinophil cell adhesion. Furthermore, phosphoinositide turnover of IL-5-stimulated adherent eosinophils was also inhibited by anti-CD18 mAb, suggesting that cellular adhesion plays important roles in eosinophil signal transduction. alphaM beta2 (Mac-1, CD11b/18) was one of the beta2 integrins involved in eosinophil adhesion to protein-coated plates. We found that direct ligation of eosinophil alphaM beta2 with anti-CD11b mAb coupled to polystyrene microbeads induced tyrosine phosphorylation of a 115 kD protein and Cbl. Furthermore, anti-CD11b mAb microbeads induced increases in both phosphoinositide hydrolysis and the eosinophil degranulation response. Control antibodies, such as mouse myeloma IgG1 and anti-HLA class I antigen mAb, did not induce these cellular responses. These results suggest that engagement of beta2 integrin either by cell adhesion or by anti-CD11b mAb triggers activation of an intracellular signaling cascade, including protein tyrosine phosphorylation and phosphoinositide turnover, and subsequent cellular degranulation in human eosinophils. Tyrosine phosphorylation of a 115 kD protein and Cbl may play important roles in adhesion-dependent cellular functions of eosinophils.

Protein kinase C mediates the signal for interferon-gamma mRNA expression in cytotoxic T cells after their adhesion to laminin

A cytotoxic T-cell line, CTLL-2 cells, showed spreading after adhering to extracellular matrix proteins such as fibronectin (FN), laminin (LN) and hyarulonic acid (HA). The adhesion of CTLL-2 cells to LN was mediated by very late activation antigen-6 (VLA-6). Expression of interferon-gamma (IFN-gamma) mRNA was enhanced in CTLL-2 cells, also when they adhered to extracellular matrix proteins; and the enhanced IFN-gamma mRNA expression by adhering to LN was blocked by anti-alpha 6 antibody. Calphostin C, a protein kinase C (PKC) inhibitor, markedly inhibited the enhancement of IFN-gamma mRNA expression in a dose-dependent manner, which suggested that PKC acted as a second messenger in the IFN-gamma mRNA expression mediated by the interaction of VLA-6 with LN in CTLL-2 cells. Furthermore, confocal laser-microscopic analysis and Western blot analysis revealed that PKC-alpha was activated after CTLL-2 cells adhered to LN. PKC activity translocated from the cytosol fraction to the particulate fraction, after CTLL-2 cells adhered to LN. Altogether, we suggest that PKC plays an important role in the signal transduction for IFN-gamma mRNA expression after cytotoxic T cells adhere to LN.

T cell receptor-mediated tyrosine phosphorylation of Cas-L, a 105-kDa Crk-associated substrate-related protein, and its association of Crk and C3G

Cas-L (pp105), a Crk-associated substrate (p130(Cas))-related protein, was first identified as a 105-kDa protein that is tyrosine-phosphorylated following beta1 integrin cross-linking in T cells. Cas-L contains possible multiple binding sites for the Src homology (SH) 2 domains of various signaling molecules, and appears to be involved in signal transduction through phosphorylated tyrosine-mediated protein-protein interaction. Since Cas-L is preferentially expressed in lymphocytes, it is conceivable that Cas-L plays an important role in lymphocyte-specific signals. Here, we show the involvement of Cas-L in the T cell receptor (TCR)/CD3 signaling pathway. Cas-L is transiently phosphorylated following CD3 cross-linking, and tyrosine-phosphorylated Cas-L binds to Crk and C3G. Furthermore, a Cas-L mutant that lacks the SH3 domain, the binding site for focal adhesion kinase (FAK), is also tyrosine-phosphorylated upon CD3 cross-linking, but not upon beta1 integrin crosslinking, suggesting that FAK is not involved in CD3-dependent Cas-L phosphorylation. Taken together, the present study indicates a novel signaling pathway mediated by tyrosine-phosphorylated Cas-L upon the TCR/CD3 stimulation.

BCR/ABL-induced leukemogenesis causes phosphorylation of Hef1 and its association with Crkl

BCR/ABL is considered responsible for the development of Philadelphia chromosome-positive leukemia. Experimental animal models, such as transgenic mice, have demonstrated unambiguously that Bcr/Abl is capable of inducing leukemogenesis. The adaptor molecule Crkl is a major in vivo substrate of the deregulated Bcr/Abl tyrosine kinase and functions as a molecular link with other signaling proteins. While associated in vivo with Bcr/Abl through its SH3 domain, Crkl can interact simultaneously via its SH2 domain with other tyrosine-phosphorylated proteins. Here we report the identification of prominently tyrosine-phosphorylated proteins with a molecular mass of approximately 110 kDa, which bind specifically to the Crkl SH2 domain in leukemic tissues of P190BCR/ABL transgenic mice. We demonstrate that these proteins are identical to Hef1/Cas-L, which is related to p130(Cas). The proto-oncoprotein p120(Cbl) and Hef1, but not p130(Cas), were detectably phosphorylated on tyrosine in P190Bcr/Abl-expressing leukemic cells and were found in complex with Crkl, showing the existence of protein complexes in P190Bcr/Abl leukemic cells, consisting of P190Bcr/Abl, Crkl, and Hef1 or p120(Cbl). This supports a model in which Crkl acts as mediator between Bcr/Abl and downstream effectors. Since Hef1 is involved in the beta1-integrin signaling pathway, our study demonstrates that Bcr/Abl could specifically interfere with normal beta1-integrin signaling.

Altered Tyrosine Phosphorylation Via the Very Late Antigen (VLA)/β1 Integrin Stimulation Is Associated With Impaired T-Cell Signaling Through VLA-4 After Allogeneic Bone Marrow Transplantation

Our previous study showed that the cross-linking of very late antigen (VLA)/β1 with anti-CD29 monoclonal antibody (MoAb), or interactions with extracellular matrix (ECM) proteins through VLA/β1, failed to induce T-cell costimulation via the CD3/T cell receptor (TCR) pathway for over 1 year after allogeneic bone marrow transplantation (allo-BMT), although normal CD29 and CD3 expression was observed after 3 months following allo-BMT. Molecular analysis revealed altered tyrosine phosphorylation of cellular proteins by the solid-phase cross-linking of VLA/β1 molecules in T cells from patients after allo-BMT. In T cells from early allo-BMT patients (<4 months), various sizes of highly tyrosine phosphorylated proteins were observed as high background even without the stimulation through VLA/β1 integrin. The high tyrosine phosphorylation pattern gradually disappeared and it was finally returned to normal tyrosine phosphorylation patterns by 2 years after BMT. Interestingly, poor expression of focal adhesion kinase (pp125FAK ), a VLA/β1-mediated signaling molecule, was observed within 1 year after BMT. These results suggest that these molecular defects appear to be implicated in the impaired VLA/β1-mediated signaling in T cells from patients after allo-BMT, and it could explain, in part, the persistent immunoincompetent state after allo-BMT at least 1 year.

Tyrosine phosphorylation of Crk-associated substrates by focal adhesion kinase. A putative mechanism for the integrin-mediated tyrosine phosphorylation of Crk-associated substrates

Integrin-ligand binding induces the tyrosine phosphorylation of various proteins including focal adhesion kinase (pp125(FAK)) and Crk-associated substrate (Cas). FAK is activated and autophosphorylated by the ligation of integrins, although the substrate of FAK has not been revealed. We show here that p130(Cas) and Cas-L are FAK substrates. FAK directly phosphorylates Cas proteins primarily at the YDYVHL sequence that is conserved among all Cas proteins. Furthermore, the phosphorylated YDYVHL sequence is a binding site for Src family protein-tyrosine kinases, and the recruited Src family kinase phosphorylates the other tyrosine residues within Cas. The Cas-L YDYVHL sequence is phosphorylated upon integrin-ligand binding, and this integrin-mediated tyrosine phosphorylation is inhibited by the cotransfection of the FAK COOH-terminal domain that does not contain a kinase domain. These findings strongly suggest that FAK initiates integrin-mediated tyrosine phosphorylation of Cas proteins; then, Src family tyrosine kinases, which are recruited to phosphorylated Cas and FAK, further phosphorylate Cas proteins.

Mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Its binding motif for alpha 4 beta 7 and role in experimental colitis

The integrin alpha 4 beta 7 and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) are molecules involved in the normal recirculation of lymphocytes between the blood and the gastrointestinal tract. These molecules may play a complementary and significant role in animal models of colitis. We have investigated the structural interaction between alpha 4 beta 7 and MAdCAM-1. Site-directed mutagenesis studies of the MAdCAM-1 molecule has led to the identification of the amino acid residue (LDT) in the loop between beta strands C and D of the Ig-superfamily-like folds being involved in the adhesive and cell activation functions of MAdCAM-1 with alpha 4 beta 7.

Blockade of late-phase airway responses and airway hyperresponsiveness in allergic sheep with a small-molecule peptide inhibitor of VLA-4

The leukocyte integrin very late antigen-4 (VLA-4) (alpha 4 beta 1, CD49d/CD29) is an adhesion receptor predominantly expressed on lymphocytes, monocytes, and eosinophils, but not on neutrophils. Recent studies with monoclonal antibodies against VLA-4 suggest that antigen-induced late responses and airway hyperresponsiveness (AHR) may depend on the recruitment and/or activation of VLA-4-expressing leukocytes. To further test this hypothesis, we administered by aerosol either a potent small-molecule inhibitor of VLA-4, which prevents VLA-4-mediated binding to fibronectin (CS-1 ligand mimic), or an inactive control (30 mg twice daily for 3 d, and on the fourth day 0.5 h before and 4 h after antigen challenge) to six sheep with airway hypersensitivity to Ascaris suum antigen. Treatment with the small-molecule VLA-4 inhibitor resulted in a significant decrease in the early antigen-induced bronchial response (40%, p < 0.05), and almost complete blockade of the late-phase airway response (88%, p < 0.05). Moreover, at 24 h after antigen challenge, AHR to inhaled carbachol was not observed when the animals were dosed with the small-molecule VLA-4 inhibitor. In accord with protection against the functional abnormalities associated with antigen challenge, analysis of biopsy specimens taken 24 h after challenge indicated that the total numbers of VLA-4-positive cells (lymphocytes, eosinophils, and metachromatic-staining cells) in the group treated with the VLA-4 inhibitor did not increase, whereas these cells increased in the control group. The active agent, but not the inactive control, significantly blocked macrophage adherence to fibronectin (FN), indicating that the CS-1 ligand interfered with VLA-4-mediated adhesion in sheep cells. These results support our previous findings with a monoclonal antibody to VLA-4, and demonstrate that a small-molecule VLA-4 inhibitor, when given by aerosol, has a protective effect against antigen-induced late responses and AHR in allergic sheep.

Ligation of the T cell antigen receptor induces tyrosine phosphorylation of p105CasL, a member of the p130Cas-related docking protein family, and its subsequent binding to the Src homology 2 domain of c-Crk

p105CasL (CasL) is a recently identified signaling molecule closely related to the p130Cas (Crk-associated substrate) docking protein. CasL has a single Src homology (SH) 3 domain in its N-terminal portion followed by multiple consensus motifs for binding to SH2 domains. Like original p130Cas, CasL undergoes tyrosine phosphorylation upon integrin-mediated cell adhesion. In the present report, we provide direct evidence that CasL is also involved in T cell antigen receptor (TcR)-mediated signal transduction. In binding studies in vitro using glutathione-S-transferase fusion proteins, we have identified 105- and 120-kDa phosphotyrosyl proteins (pp105 and pp120, respectively) tightly bound to the SH2 domain of the Crk adapter protein in the H9 human T cell line after stimulation through the CD3/TcR complex. pp120, but not pp105, also bound to the SH3 of another adapter protein, Ash/Grb2. Immunoblotting with specific antibodies revealed that pp120 and pp105 were identical to the c-cbl proto-oncogene product (p120cbl) and CasL, respectively. Association between Crk and tyrosine-phosphorylated CasL after TcR stimulation was also confirmed in vivo. CasL phosphorylation induced by TcR ligation reached maximal levels within 2 min and rapidly declined thereafter, whereas the integrin-dependent response occurred slowly and was more prolonged. Finally, we demonstrated that Crk/CasL association occurred in peripheral blood T lymphocytes in response to TcR engagement. Our findings suggest that CasL is involved in T cell activation signals and resides at a point where two distinct receptor-mediated signaling pathways converge. This provides one mechanism by which integrins may mediate T cell co-stimulation.

CD106 (VCAM-1) in testicular immunoregulation

The expression of CD18, CD49d/CD29, CD44, CD54 and CD106 was studied in the testis of normal mice at various ages, in the cryptorchid testis, in the testis of estrogen-treated mice and in the testis of non-obese diabetic (NOD) mice, using immunocytochemistry to see which of these lymphocyte and endothelial adhesion proteins may be involved in lymphocyte regulation in the testis. CD18-, CD49d/CD29-, CD44- and CD54-expressing cells were not found in the normal > 10-week-old BALB/c mouse testis. Leydig cells expressed CD106 strongly at this age. In contrast to the > 10-week-old testis, only very few interstitial cells of the 2-week-old normal mice expressed CD106. The expression of CD106 increased gradually with age so that at 6 weeks of age the expression of CD106 was moderate in the interstitial tissue. In the experimentally abdominal testis, CD106 was expressed in the interstitial tissue as strongly as in the contralateral scrotal testis. CD44- and CD18-expressing cells were occasionally present in the interstitial tissue of the abdominal testis, but not in the contralateral scrotal testis. CD54 was present in the epithelium of the ductuli efferentes. In the testis of the estrogen-treated mice, CD106 was expressed in the interstitial tissue as strongly as in the normal mice. Occasional CD44- and CD18-expressing cells were found in the testicular capsule. In the testis of adult NOD mice, CD106 was present in the interstitial tissue, but none of the other studied proteins. Immunoblotting of CD106 from the adult testis under reducing conditions demonstrated a single broad band with a M(r) of 51-65 kDa. This is a novel isoform of CD106. In a modified Stamper-Woodruff assay, lymphocytes bound to the testicular interstitial tissue. In co-incubations of native Leydig cells and lymphocytes, anti-CD106 antibodies prevented formation of Leydig cell-lymphocyte rosettes more than isotype-matched irrelevant control antibodies, suggesting that Leydig cell lymphocyte binding occurs through CD106-CD49d interactions. In lymphocyte cultures in the presence of anti-CD3, anti-CD28, the M(r) > 5 K fraction of testis extract (containing CD106 as shown by immunoblotting) and anti-CD106 or control antibody, anti-CD106 did not consistently affect T cell 3H-TdR incorporation. The present results suggest that CD106 expressed by the Leydig cells may act as an adhesion-promoting molecule or a co-stimulatory factor for T cells migrating to the testis.