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Results for “Integrin alpha4beta1”

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At least 1,117 records · Page 62Linked to original sources
PubMed2004

Anti-vascular cell adhesion molecule-1 and anti-very late antigen-4 monoclonal antibodies inhibit neointimal hyperplasia in the murine model of arterial injury.

OBJECTIVE: Arterial restenosis after angioplasty limits long-term survival of patients. Murine arterial injury models develop neointimal hyperplasia similar to that observed in clinical coronary arterial restenosis after angioplasty. Adhesion of vascular cell adhesion molecule (VCAM)-1 and its ligand very late antigen (VLA)-4 plays an important role in neointimal formation after vascular injury. METHODS AND RESULTS: To evaluate the effectiveness of blocking VCAM-1 and VLA-4 adhesion to prevent neointimal formation, mice with induced abdominal aortic injury were treated with the combined anti-VCAM-1 and anti-VLA-4 mAbs (n = 8) or not treated (n = 6). Injured arteries were harvested at day 14. Immunohistochemistry and in situ reverse transcriptase polymerase chain reaction were performed for detection of VCAM-1, intercellular adhesion molecule (ICAM)-1 and platelet-derived growth factor (PDGF)-B mRNA expression in the arteries. Arteries without treatment showed significant neointimal formation with enhancement of ICAM-1, VCAM-1 and PDGF-B mRNA, while expression of these and intimal thickening were almost nonexistent in the recipients of mAbs to VCAM-1 and VLA-4. CONCLUSION: Anti-VCAM-1 and anti-VLA-4 mAbs prevent arterial neointimal formation after arterial injury.

Animals↗
PubMed2004

The discovery of VLA-4 antagonists.

Starting with a cyclic peptide of moderate potency as a VLA-4 antagonist, highly potent and conformationally defined cyclic peptides were developed incorporating a constrained tyrosine and an achiral Asp-Pro spacer. N-Acyl phenylalanine derivatives were also discovered to have VLA-4 antagonist activity. During the course of development of this series, we found that the active acylphenylalanines mimic the pharmacophores present in the cyclic peptides and hypothesized that they bind to the same site on VLA-4. This insight guided our optimization strategy. Based on the emerging SAR, as well as insights from the recent X-ray crystal structure of the integrin alphavbeta3 bound to a RGD containing cyclic peptide, we propose a binding model for these compounds.

Humans↗
PubMed2004

The discovery and potential of N-sulfonylated dipeptide VLA-4 antagonists.

Through a directed screening of a combinatorial library containing carboxylic acids, N-sulfonylated dipeptides were identified as leads in the Merck Research Laboratories VLA-4 antagonist program. Further optimization quickly identified subnanomolar compounds with varying degrees of specificity over the related integrin alpha4beta7. Various metabolic liabilities were identified and addressed. However, the pharmacokinetic properties of nearly all compounds in this class were unacceptable. Other leads were identified with apparent good oral bioavailability, but these were generally associated with very high plasma protein binding and a loss of potency. The mechanism of high plasma clearance was identified in the rat as the organic acid transporter, mrp-2. Compounds were identified that were not substrates of mrp-2, but they still suffered from poor oral bioavailability. Finally, a shift in strategy to identifying VLA-4 antagonists that would be suitable as candidates for inhalation therapy resulted in the preparation of compounds with exception tight binding properties. These compounds were superior to BIO-1211 in the ovalbumin-sensitized mouse model of eosinophil trafficking to the lung. One particular compound had an exceptionally long off-rate with a KD < or = 2 pM. The evolution of the structure activity relationships in our laboratories and strategies for improving potencies and pharmacokinetic profiles are the subject of this review.

Animals↗
PubMed2003

[Effects of BIO-1211 on eosinophil chemotaxis, recruitment and mediator release].

OBJECTIVE: To study the effects of very late antigen(VLA) antagonist BIO-1211 on eosinophil chemotaxis, recruitment and mediator release. METHODS: Eosinophil chemotaxis was induced by platelet activating factor(PAF) in vitro and eosinophil recruitment and release were determined in vivo. RESULT: VLA antagonist BIO-1211 inhibited eosinophil chemotaxis induced by PAF. The inhibitory rates at 4x10(-11), 4x10(-10), 4x10(-9) mol x L(-1) were 24.9%, 29.9%, and 31.3%, respectively. Pretreatment by BIO-1211 1, 3 and 10 mg x kg(-1) intraperitoneally inhibited the recruitment of eosinophils in PAF in the rat induced by Sephadex in a dose dependent manner. Inhibitory rates were 60.3%, 68.9%, and 72.9%(P<0.05), respectively. BIO-1211 did not inhibit eosinophil peroxidase(EPO) release from eosinophils. CONCLUSION: BIO-1211 inhibits eosinophil chemotaxis and recruitment, alleviates local inflammation, and may represent a new type of drug for allergic diseases.

Animals↗
PubMed2002

The role of bone marrow-derived stromal cells in the maintenance of plasma cell longevity.

Protective circulating Abs originate primarily from long-lived plasma cells in the bone marrow. However, the molecular and cellular basis of plasma cell longevity is unknown. We investigated the capacity of primary bone marrow-derived stromal cells to maintain plasma cell viability in vitro. Plasma cells purified from the bone marrow or lymph nodes died rapidly when plated in media, but a subpopulation of plasma cells survived and secreted high levels of Ab for up to 4 wk when cocultured with stromal cells. Ab secretion was inhibited by the addition of anti-very late Ag-4 to plasma cell/stromal cell cocultures indicating that direct interactions occur and are necessary between stromal cells and plasma cells. The addition of rIL-6 to plasma cells cultured in media alone partially relieved the sharp decline in Ab secretion observed in the absence of stromal cells. Moreover, when stromal cells from IL-6(-/-) mice were used in plasma cell/stromal cell cocultures, Ab levels decreased 80% after 7 days as compared with wild-type stromal cells. Further, IL-6 mRNA message was induced in stromal cells by coculture with plasma cells. These data indicate that bone marrow plasma cells are not intrinsically long-lived, but rather that plasma cells contact and modify bone marrow stromal cells to provide survival factors.

Animals↗
PubMed2003

Paxillin binding to the alpha 4 integrin subunit stimulates LFA-1 (integrin alpha L beta 2)-dependent T cell migration by augmenting the activation of focal adhesion kinase/proline-rich tyrosine kinase-2.

Engagement of very late Ag-4 (integrin alpha(4)beta(1)) by ligands such as VCAM-1 markedly stimulates leukocyte migration mediated by LFA-1 (integrin alpha(L)beta(2)). This form of integrin trans-regulation in T cells requires the binding of paxillin to the alpha(4) integrin cytoplasmic domain. This conclusion is based on the abolition of trans-regulation in Jurkat T cells by an alpha(4) mutation (alpha(4)(Y991A)) that disrupts paxillin binding. Furthermore, cellular expression of an alpha(4)-binding fragment of paxillin that blocks the alpha(4)-paxillin interaction, selectively blocked VCAM-1 stimulation of alpha(L)beta(2)-dependent cell migration. The alpha(4)-paxillin association mediates trans-regulation by enhancing the activation of tyrosine kinases, focal adhesion kinase (FAK) and/or proline-rich tyrosine kinase-2 (Pyk2), based on two lines of evidence. First, disruption of the paxillin-binding site in the alpha(4) tail resulted in much less alpha(4)beta(1)-mediated phosphorylation of Pyk2 and FAK. Second, transfection with cDNAs encoding C-terminal fragments of Pyk2 and FAK, which block the function of the intact kinases, blocked alpha(4)beta(1) stimulation of alpha(L)beta(2)-dependent migration. These results define a proximal protein-protein interaction of an integrin cytoplasmic domain required for trans-regulation between integrins, and establish that augmented activation of Pyk2 and/or FAK is an immediate signaling event required for the trans-regulation of integrin alpha(L)beta(2) by alpha(4)beta(1).

Amino Acid Substitution↗
PubMed2003

Determinants of human B cell migration across brain endothelial cells.

Circulating B cells enter the CNS as part of normal immune surveillance and in pathologic states, including the common and disabling illness multiple sclerosis. However, little is known about the molecular mechanisms that mediate human B cell interaction with the specialized brain endothelial cells comprising the blood-brain barrier (BBB). We studied the molecular mechanisms that regulate the migration of normal human B cells purified ex vivo, across human adult brain-derived endothelial cells (HBECs). We found that B cells migrated across HBECs more efficiently than T cells from the same individuals. B cell migration was significantly inhibited by blocking Abs to the adhesion molecules ICAM-1 and VLA-4, but not VCAM-1, similar to the results previously reported for T cells. Blockade of the chemokines monocyte chemoattractant protein-1 and IL-8, but not RANTES or IFN-gamma-inducible protein-10, significantly inhibited B cell migration, and these results were correlated with the chemokine receptor expression of B cells measured by flow cytometry and by RNase protection assay. Tissue inhibitor of metalloproteinase-1, a natural inhibitor of matrix metalloproteinases, significantly decreased B cell migration across the HBECs. A comprehensive RT-PCR comparative analysis of all known matrix metalloproteinases and tissue inhibitors of metalloproteinases in human B and T cells revealed distinct profiles of expression of these molecules in the different cell subsets. Our results provide insights into the molecular mechanisms that underlie human B cell migration across the BBB. Furthermore, they identify potential common, and unique, therapeutic targets for limiting CNS B cell infiltration and predict how therapies currently developed to target T cell migration, such as anti-VLA-4 Abs, may impact on B cell trafficking.

Adult↗
PubMed2004

Dysregulated FcepsilonRI signaling and altered Fyn and SHIP activities in Lyn-deficient mast cells.

Studies in B cells from Lyn-deficient mice have identified Lyn as both a kinetic accelerator and negative regulator of signaling through the BCR. The signaling properties of bone marrow-derived mast cells from Lyn(-/-) mice (Lyn(-/-) BMMCs) have also been explored, but their signaling phenotype remains controversial. We confirm that Lyn(-/-) BMMCs release more beta-hexosaminidase than wild-type BMMCs following FcepsilonRI cross-linking and show that multiple mast cell responses to FcepsilonRI cross-linking (the phosphorylation of receptor subunits and other proteins, the activation of phospholipase Cgamma isoforms, the mobilization of Ca(2+), the synthesis of phosphatidylinositol 3,4,5-trisphosphate, the activation of the alpha(4)beta(1) integrin, VLA-4) are slow to initiate in Lyn(-/-) BMMCs, but persist far longer than in wild-type cells. Mechanistic studies revealed increased basal as well as stimulated phosphorylation of the Src kinase, Fyn, in Lyn(-/-) BMMCs. Conversely, there was very little basal or stimulated tyrosine phosphorylation or activity of the inositol phosphatase, SHIP, in Lyn(-/-) BMMCs. We speculate that Fyn may substitute (inefficiently) for Lyn in signal initiation in Lyn(-/-) BMMCs. The loss of SHIP phosphorylation and activity very likely contributes to the increased levels of phosphatidylinositol 3,4,5-trisphosphate and the excess FcepsilonRI signaling in Lyn(-/-) BMMCs. The unexpected absence of the transient receptor potential channel, Trpc4, from Lyn(-/-) BMMCs may additionally contribute to their altered signaling properties.

Adaptor Proteins, Signal Transducing↗
PubMed2004

IFN-alpha subtypes differentially affect human T cell motility.

The type I IFN family includes 14 closely related antiviral cytokines that are produced in response to viral infections. They bind to a common receptor, and have qualitatively similar biological activities. The physiological relevance of this redundancy is still unclear. In this study, we analyzed and compared the effects of two potent antiviral type I IFNs, IFN-alpha 2 and IFN-alpha 8, on the motility of various populations of human T lymphocytes in vitro. In this study, we show that IFN-alpha 2 induces chemokinesis of both CD4(+) and CD8(+) T cells at various stages of differentiation, and induces functional changes that result in enhanced T cell motility, including up-regulation of the integrins LFA-1 and VLA-4, and subsequently, increased ICAM-1- and fibronectin-dependent migration. In contrast, IFN-alpha 8 did not affect T cell motility, despite having similar antiviral properties and similar effects on the induction of the antiviral protein MxA. However, transcription of other IFN-stimulated genes showed that transcription of these genes is selectively activated by IFN-alpha 2, but not IFN-alpha 8, in T cells. Finally, while the antiviral activity of the two subtypes is inhibited by Abs against the two subunits of the IFN-alpha receptor, the chemokinetic effect of IFN-alpha 2 is selectively blocked by Abs against the A1 receptor subunit. These observations are consistent with the possibility that subtype-specific intracellular signaling pathways are activated by type I IFNs in T lymphocytes.

Antibodies, Monoclonal↗
PubMed2004

Rapid response of marginal zone B cells to viral particles.

Marginal zone (MZ) B cells are thought to be responsible for the first wave of Abs against bacterial Ags. In this study, we assessed the in vivo response of MZ B cells in mice immunized with viral particles derived from the RNA phage Qbeta. We found that both follicular (FO) and MZ B cells responded to immunization with viral particles. MZ B cells responded with slightly faster kinetics, but numerically, FO B cells dominated the response. B1 B cells responded similarly to MZ B cells. Both MZ and FO B cells underwent isotype switching, with MZ B cells again exhibiting faster kinetics. In fact, almost all Qbeta-specific MZ B cells expressed surface IgG by day 5. Histological analysis demonstrated that a population of activated B cells remain associated with the MZ, probably due to the elevated integrin levels expressed by these cells. Thus, both MZ and FO B cells respond with rapid proliferation to viral infection and both populations undergo isotype switching, but MZ B cells remain in the MZ and may be responsible for local Ab production, opsonizing pathogens entering the spleen.

Allolevivirus↗
PubMed2005

Resistance to myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis by death receptor 6-deficient mice.

Genetic disruption of death receptor 6 (DR6) results in enhanced CD4+ T cell expansion, Th2 differentiation, and humoral responses after stimulation. However, the in vivo consequences of DR6 targeting (DR6-/-) during the initiation and progression of inflammatory autoimmune disease are unclear. Using a myelin oligodendrocyte glycoprotein (MOG(35-55))-induced model of experimental autoimmune encephalomyelitis, DR6-/- mice were found to be highly resistant to both the onset and the progression of CNS disease compared with wild-type (WT) littermates. DR6-/- mice exhibited fewer inflammatory foci along with minimal demyelination and perivascular cuffing of inflammatory cells. Consistent with these observations, mononuclear cell infiltration, including CD4+ T cells and macrophages, in the spinal cord of DR6-/- mice was dramatically reduced. Furthermore, CD4+ T cells from DR6-/- mice exhibited profoundly reduced cell surface expression of VLA-4 before and after stimulation. Compared with WT mice, DR6-/- mice exhibited significantly increased autoantigen-induced T cell proliferative responses along with greater numbers of IL-4-producing and similar or slightly higher numbers of IFN-gamma-producing CD4+ T cells. DR6-/- CD4+ T cells secreted higher levels of the Th2 cytokine, IL-4, and similar levels of the Th1 cytokine, IFN-gamma, compared with WT cells. Taken together, our data demonstrate that DR6 plays an important role in regulating leukocyte infiltration and function in the induction and progression of experimental autoimmune encephalomyelitis.

Amino Acid Sequence↗
PubMed2002

[Expression of EIIIA-fibronectin in injured rat skin used in estimation of wound interval].

OBJECTIVE: To observe the means of fibronectin(FN) alternative splicing and the expression of EIIIA-FN variant in rat skin after bruise, for the sake of providing some help for forensic estimation of wound interval. METHODS: Total RNA was isolated from wounded skin, and reverse transcription polymerase chain reaction was conducted to amplify target segments. RESULTS: Detectable EIIIA+(526 bp) segments, lacked in normal organize, was amplified at 1 h after experimental wound, and the levels were increased within 24 h. CONCLUSION: The alternative splicing EIIIA-fibronectin variant would be a satisfied criterion for research of skin injury.

Alternative Splicing↗
PubMedDate not supplied

Activation of vascular endothelial cell adhesion molecule expression by sickle blood cells.

Microvascular complications in sickle cell disease occur as a result of obstruction of small vessels by deoxygenated sickle cells. Cerebrovascular complications are also common and result from obstruction of large blood vessels by thrombosis with changes in vessels that have some similarity to those found in arteriosclerotic vascular disease. Endothelial damage and activation from sickle cell-endothelial interactions may contribute to both. We find that endothelial cells have increased expression of VCAM-1, E-selectin, and ICAM-1 when exposed to sickle blood cells. The concentration-dependent, sickle-induced, adhesion molecule expression is significantly greater than that promoted by normal cells. The time course of Cell Adhesion Molecule (CAM) expression is similar to that induced by TNF-alpha and IL1. Studies after white cell enrichment and reduction suggest leukocytes are the primary mediators. CAM expression by endothelial cells appears stimulated by soluble factors. Antibody inhibition studies support TNF-alpha and IL-1, produced by sickle leukocytes, as the primary soluble factors responsible for the observed CAM expression. Both the induction of endothelial CAM expression and subsequent endothelial adherence of sickle erythrocytes may play significant roles in the pathophysiology of sickle-related complications, and reduction in CAM expression may provide a new approach to treatment.

Anemia, Sickle Cell↗
PubMed2003

Lymphocyte-facilitated tumour cell adhesion to endothelial cells: the role of high affinity leucocyte integrins.

AIM: Lymphocytes transiently express an active form of the beta_2 integrin LFA-1 (LFA-1Af) which has conformational changes in extracellular domains enabling higher affinity binding to the ligand ICAM-1. In this study, we investigated the role of lymphocytes bearing LFA-1Af as potential mediators of binding of ICAM-1-positive tumour cells to endothelium. METHODS: LFA-1 expression on 51Cr-PBLs was modulated in order to express high affinity LFA-1Af and conjugates were formed with 35S-labelled COLO526. The binding of the conjugates to resting or IL-1beta-stimulated human umbilical vein endothelial cells (HUVECs) was then assessed via a modified radioactive HUVEC binding assay. In addition, the binding of PBL-COLO526 conjugates to HUVECs was demonstrated by confocal microscopy. RESULTS: The binding of COLO526 to endothelial cells did not change significantly between unstimulated and stimulated HUVECs. In addition, pre-incubating the COLO526 with fresh PBLs did not significantly alter the binding of COLO526 to resting or activated HUVECs; whereas, in the presence of PBLs with LFA-1Af, the COLO526 conjugate binding dramatically increased from basal levels to 41% on resting HUVECs and 81% on stimulated HUVECs. COLO526-PBL(LFA-1Af) conjugate adhesion to stimulated HUVECs was inhibited by blocking antibody to LFA-1 (50%), VLA-4 (32%) or L-selectin (40%). Antibodies to the HUVEC adhesion molecules ICAM-1, VCAM-1 and E-selectin also inhibited COLO526-PBL(LFA-1Af) conjugate binding to activated HUVECs by 79, 60 and 73%, respectively. CONCLUSIONS: PBLs bearing LFA-1Af can enhance COLO526 adhesion to both resting and activated HUVECs. Furthermore, blocking studies demonstrate that a range of pathways are involved in this phenomenon (LFA-1/ICAM-1, VLA4/VCAM-1, L-selectin/E-selectin). These studies have identified a novel alternative pathway for lymphocyte-facilitated tumour cell adhesion to endothelial cells.

Antibodies, Blocking↗
PubMed2003

Correlation between VLA-4 integrin and hematopoietic cell migration.

To clarify the relationship between VLA-4 (CD49d) expression and hematopoietic cell migrating direction, mice were injected subcutaneously with diluted rhG-CSF for different times. The expressions of CD49d on Sca-1(+) cells were examined by flow cytometry. The relations between CD49d expression and Sca-1(+) cell enumerations were performed by statistical analysis. The results showed that with the administration of G-CSF, the expressions of CD49d in bone marrow (BM) and peripheral blood (PB) declined, meanwhile the number of Sca-1(+) cells in peripheral blood reached the peak in sharp contrast to BM nucleated cell number dropping on the seventh to ninth day. When CD49d expression rose again, the PB Sca-1(+) cells descended with the rising of BM nucleated cell number. In conclusion, VLA-4 mediates the hematopoietic cell adhesion to BM microenvironment. The regulation of CD49d expression may result in different migrating direction of hematopoietic cell between bone marrow and peripheral blood.

Animals↗