PubMed Health⌕ Search

Biomedical subjects

S M Albelda

Publications and source records attributed to S M Albelda.

At least 91 records · Page 5Linked to original sources
PubMed1994

T lymphocytes adhere to airway smooth muscle cells via integrins and CD44 and induce smooth muscle cell DNA synthesis.

Asthma is a disease of airway inflammation and hyperreactivity that is associated with a lymphocytic infiltrate in the bronchial submucosa. The interactions between infiltrating T lymphocytes with cellular and extracellular matrix components of the airway and the consequences of these interactions have not been defined. We demonstrate the constitutive expression of CD44 on human airway smooth muscle (ASM) cells in culture as well as in human bronchial tissue transplanted into severe combined immunodeficient mice. In contrast, basal levels of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) expression are minimal but are induced on ASM by inflammatory mediators such as tumor necrosis factor alpha (TNF-alpha). Activated, but not resting T cells, adhere to cultured ASM; stimulation of the ASM with TNF-alpha enhanced this adhesion. Adhesion was partially blocked by monoclonal antibodies (mAb) specific for lymphocyte function-associated antigen 1 (LFA-1) and very late antigen 4 (VLA-4) on T cells and ICAM-1 and VCAM-1 on ASM cells. The observed integrin-independent adhesion was mediated by CD44/hyaluronate interactions as it was inhibited by anti-CD44 mAb 5F12 and by hyaluronidase. Furthermore, the adhesion of activated T lymphocytes induced DNA synthesis in growth-arrested ASM cells. Thus, the interaction between T cells and ASM may provide insight into the mechanisms that induce bronchial inflammation and possibly ASM cell hyperplasia seen in asthma.

Animals↗
PubMed1994

Biosynthesis and processing of the cell adhesion molecule PECAM-1 includes production of a soluble form.

PECAM-1 (CD31) is a 130-kDa glycoprotein found on platelets, endothelial cells, granulocytes, and monocytes, as well as on certain myelomonocytic cell lines. Recent studies have shown that PECAM-1 may be involved in activation of leukocyte integrins and may also be involved in adhesive interactions of circulating leukocytes and the vessel wall. In spite of the important functional role that PECAM-1 plays in these processes, little is known about the biosynthesis, processing, and turnover of PECAM-1 on the cell surface. We have studied the biosynthesis of PECAM-1 in the promonocytic cell line U937, and in endothelial cells, by pulse-chase labeling and immunoprecipitation. PECAM-1 was synthesized as a 110-kDa precursor form, which was processed into the 130-kDa mature form within 1-3 h, during which time it began to move to the cell surface. The protein disappeared from the cell surface in both cell types about 48 h after labeling. A soluble form of PECAM-1, which is 5-10 kDa smaller than cell-associated PECAM-1 and contains the cytoplasmic tail, was observed in the culture media of HUVECs and phorbol ester-treated U937 cells. This form of soluble PECAM-1 is encoded by an alternatively spliced mRNA from which the exon containing the transmembrane domain has been removed. Soluble PECAM-1 was also detected in normal human plasma at levels of 10-25 ng/ml. Two isoforms of plasma PECAM-1, which differed in the presence of the cytoplasmic tail, were observed by Western blot analysis. In parallel with soluble forms of other cell adhesion molecules, soluble PECAM-1 may play a role in modulating the inflammatory response.

Alternative Splicing↗
PubMed1994

Use of recombinant adenovirus to transfer the herpes simplex virus thymidine kinase (HSVtk) gene to thoracic neoplasms: an effective in vitro drug sensitization system.

Transfer of the herpes simplex virus thymidine kinase (HSVtk) gene into tumor cells using retroviral vectors followed by administration of ganciclovir provides a potential strategy for the treatment of malignancy. Because of the limitations of using retroviral vectors for clinical application, the feasibility of using a recombinant adenovirus containing HSVtk was examined. Cell lines derived from human malignant mesotheliomas and non-small cell lung cancers infected with a recombinant adenovirus containing HSVtk showed strong expression of HSVtk protein as determined by immunohistochemical staining. Infection with a recombinant adenovirus containing HSVtk rendered cells sensitive to doses of ganciclovir that were 2-3 logs lower than uninfected cells or those infected with a control virus. A strong "bystander effect" was noted in mesothelioma lines; there was no diminution in the efficacy of ganciclovir treatment until the ratio of infected:uninfected cells fell below 1:10. This study thus demonstrates in vitro efficacy of an adenovirus-transduced HSVtk drug sensitization gene therapy system in thoracic malignancies. Recombinant adenovirus transfer of the HSVtk gene followed by ganciclovir may have promise as an in situ treatment for tumors.

Adenoviridae↗
PubMed1994

Leukocyte recruitment into human skin transplanted onto severe combined immunodeficient mice induced by TNF-alpha is dependent on E-selectin.

In order to study the in vivo role of E-selectin in human inflammation, we have developed a model in which human skin is transplanted onto severe combined immunodeficient (SCID) mice. The grafted skin closely resembles normal skin and retains its human vasculature. After intradermal injection of rTNF-alpha, human E-selectin was rapidly up-regulated on dermal microvessels, with significant expression (determined immunohistochemically) at 1 h postinjection and maximum expression at 2 h postinjection. To study the functional role of E-selectin, a murine Ab against human E-selectin (mAb HEL 3/2) was developed that inhibited the in vitro adhesion of both human U937 cells and murine 32D cells to TNF-alpha-stimulated human endothelial cells. After intradermal injection of TNF-alpha, large numbers of murine leukocytes migrated into the grafts within 2 h. Intravenous injection of the antihuman E-selectin mAb 3/2 completely inhibited murine white blood cell (WBC) transmigration into the skin grafts, but an isotype-matched control Ab that also bound to human endothelium had no effect. Antihuman E-selectin mAb 3/2 was also able to inhibit the migration of i.v. 51Cr-labeled human neutrophils. These findings demonstrate that E-selectin is important in early white blood cell adhesion events and is required for TNF-alpha-induced white blood cell transmigration in the human/SCID mouse chimeric model.

Animals↗
PubMed1994

Identification of integrin receptors on cultured human bone cells.

The interactions of bone cells with their surrounding extracellular microenvironment may be mediated by integrins, a family of heterodimeric glycoproteins consisting of alpha and beta subunits that noncovalently interact to form cell-substratum adhesion receptors. We previously described the integrins on calvarial bone cells in rats with use of polyclonal antibodies against some integrin subunits. In the present study, we expanded this initial characterization by employing a more complete panel of monoclonal antibodies to identify integrins on human bone cells. Minced fragments of trabecular bone obtained during total knee arthroplasty were grown in culture until bone cells became confluent. The cells then were dissociated, plated again, grown to confluence, and assayed for alkaline phosphatase activity, response of cyclic adenosine monophosphate to stimulation with parathyroid hormone, and osteocalcin content. The percentage of the cells that adhered to various substrates was measured; 60-70% adhered to type-I collagen, fibronectin, vitronectin, and poly-D-lysine; 40-50% adhered to type-IV collagen, laminin, and gelatin; and only 10% adhered to fibrinogen. Flow cytometric analysis with anti-integrin monoclonal antibodies and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of immunoprecipitates of the human bone cells revealed high levels of alpha 1 beta 1, alpha 3 beta 1, alpha 5, beta 1 and alpha v beta 5 integrins and much lower levels of alpha 2 beta 1, alpha 4 beta 1, alpha v beta 1, and alpha v beta 3 integrins. This description of the integrin repertoire of cultured human bone cells represents the first step toward an understanding of the role played by integrins in the growth, maintenance, and repair of bone.

Aged↗
PubMed1994

Successful adenovirus-mediated gene transfer in an in vivo model of human malignant mesothelioma.

Malignant mesothelioma remains a frustrating clinical problem with uniformly poor responses to current therapeutic regimens. However, the localized nature of the disease, the potential accessibility of the tumor, and the relative lack of distant metastases make it a particularly attractive candidate for somatic gene therapy. The purpose of this study was to evaluate the ability of an adenoviral vector system to transfer genetic material to human mesothelioma cells in vitro and in vivo. Using a replication-deficient recombinant adenovirus carrying the Escherichia coli lacZ marker gene, we found that human mesothelioma cell lines were susceptible to adenovirus infection. Furthermore, surprisingly effective gene transfer was accomplished within tumor implants of human mesothelioma growing within the peritoneal cavity of immunodeficient mice after intraperitoneal administration of virus. These studies demonstrate that adenoviral vectors hold promise as vehicles to deliver gene therapy in human malignant mesothelioma.

Abdomen↗
PubMed1994

Molecular and functional aspects of PECAM-1/CD31.

Among vascular cell adhesion molecules, platelet-endothelial cell adhesion molecule (PECAM-1/CD31) has the distinctive feature of being expressed on several of the major cell types associated with the vascular compartment. This makes it uniquely positioned to mediate multiple and important cell-cell interactions involving platelets, leukocytes and endothelial cells. Thus, PECAM-1 may represent a potential target for new therapeutic agents directed at a variety of pathological states.

Alternative Splicing↗
PubMed1994

Deletions in the cytoplasmic domain of platelet-endothelial cell adhesion molecule-1 (PECAM-1, CD31) result in changes in ligand binding properties.

Platelet/endothelial cell adhesion molecule-1 (PECAM-1, CD31) is a member of the immunoglobulin superfamily present on platelets, endothelial cells, and leukocytes that may function as a vascular cell adhesion molecule. The purpose of this study was to examine the role of the cytoplasmic domain in PECAM-1 function. To accomplish this, wild-type and mutated forms of PECAM-1 cDNA were transfected into murine fibroblasts and the functional characteristics of the cells analyzed. Wild-type PECAM-1 localized to the cell-cell borders of adjacently transfected cells and mediated heterophilic, calcium-dependent L-cell aggregation that was inhibitable by a polyclonal and two monoclonal anti-PECAM-1 antibodies. A mutant protein lacking the entire cytoplasmic domain did not support aggregation or move to cell-cell borders. In contrast, both forms of PECAM-1 with partially truncated cytoplasmic domains (missing either the COOH-terminal third or two thirds of the cytoplasmic domain) localized to cell-cell borders in 3T3 cells in a manner analogous to the distribution seen in cultured endothelial cells. L-cells expressing these mutants demonstrated homophilic, calcium-independent aggregation that was blocked by the polyclonal anti-PECAM-1 antibody, but not by the two bioactive monoclonal antibodies. Although changes in the cytoplasmic domain of other receptors have been shown to alter ligand-binding affinity, to our knowledge, PECAM-1 is the first example of a cell adhesion molecule where changes in the cytoplasmic domain result in a switch in the basic mechanism of adhesion leading to different ligand-binding specificity. Variations in the cytoplasmic domain could thus be a potential mechanism for regulating PECAM-1 activity in vivo.

3T3 Cells↗
PubMed1994

Differential expression of the cell adhesion molecules ICAM-1, VCAM-1, and E-selectin in normal and posttransplantation myocardium. Cell adhesion molecule expression in human cardiac allografts.

BACKGROUND: Cell adhesion molecules (CAMs) have been implicated in cardiac allograft rejection. However, previous studies have used qualitative analysis of immunohistochemical data and did not exclude patients with infection or malignancy. METHODS AND RESULTS: We analyzed 40 endomyocardial biopsy specimens from 25 cardiac transplant patients and 8 specimens from patients undergoing cardiac surgery. Patients with evidence of infection or malignancy were excluded. Specimens were stained with monoclonal antibodies against ICAM-1, E-selectin, VCAM-1, and PECAM-1 (which labels all vessels). ICAM-1 expression was assessed by counting ICAM-1-positive vessels and dividing by the total number of vessels (measured by PECAM staining). Specimens were scored as positive or negative for VCAM-1 and E-selectin. We also determined whether serum-soluble ICAM-1 levels (sICAM) correlated with rejection by evaluating 145 serum specimens from 48 cardiac transplant patients and 8 specimens from patients undergoing diagnostic cardiac catheterization. ICAM-1 was present on 50% to 60% of vessels in normal and nonrejecting specimens. Specimens with histologically significant rejection (focal moderate, moderate, or severe) had an increased percentage of ICAM-1-positive vessels: focal moderate, 77%; moderate/severe, 92% (P < .01). E-selectin expression did not differ between groups. VCAM-1 frequently was not present on rejecting specimens. No correlation was noted between sICAM levels and the presence or absence of rejection. CONCLUSIONS: (1) ICAM-1 expression is strongly correlated with histologically significant cardiac allograft rejection. (2) The use of PECAM-1 staining as a vascular marker permits quantitative analysis of ICAM-1 expression. (3) VCAM-1 and E-selectin are not consistently increased during cardiac allograft rejection. (4) sICAM levels do not accurately reflect endomyocardial biopsy results.

Antigens, CD↗
PubMed1994

Expression of endothelial cell adhesion molecules in human bronchial xenografts.

The role of endothelial cell adhesion molecules (CAMs) in the selective recruitment of leukocyte subsets to the airway remains unclear. The goal of the present study was to examine the expression of human endothelial CAM in a cytokine-induced airway inflammatory response. To accomplish this, an in vivo model of human bronchus was developed by heterotopically transplanting intact sections of human airway into severe combined immunodeficient (SCID) mice. Three weeks after transplantation, the xenografts closely resembled normal bronchus with little evidence of rejection. Less than 15% of the submucosal vessels expressed E-selectin and vascular cell adhesion molecule-1 (VCAM-1), whereas intercellular adhesion molecule-1 (ICAM-1) was present constitutively on approximately 35% of bronchial microvessels. Intrabronchial instillation of tumor necrosis factor-alpha (TNF-alpha) significantly increased expression of microvascular E-selectin to 40%, ICAM-1 to 65%, and VCAM-1 to 41%, and was accompanied by an influx of murine leukocytes into the bronchial submucosa. These results demonstrate that the human bronchial microvasculature expresses cytokine-inducible adhesion molecules. Mast cells and other resident or migratory cells that secrete TNF-alpha may thus activate the bronchial microvasculature and thereby recruit leukocytes to the airway.

Animals↗
PubMed1994

Platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31): alternatively spliced, functionally distinct isoforms expressed during mammalian cardiovascular development.

The establishment of the cardiovascular system represents an early, critical event essential for normal embryonic development. An important component of vascular ontogeny is the differentiation and development of the endothelial and endocardial cell populations. This involves, at least in part, the expression and function of specific cell surface receptors required to mediate cell-cell and cell-matrix adhesion. Platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) may well serve such a function. It is a member of the immunoglobulin superfamily expressed by the entire vascular endothelium in the adult. It is capable of mediating adhesion by a heterophilic mechanism requiring glycosaminoglycans, as well as by a homophilic, glycosaminoglycan independent, mechanism. It has been shown to regulate the expression of other adhesion molecules on naive T cells. This report documents by RT-PCR and immunohistochemical analysis the expression of PECAM-1 during early post implantation mouse embryo development. PECAM-1 was expressed by early endothelial precursors first within the yolk sac and subsequently within the embryo itself. Interestingly, embryonic PECAM-1 was expressed as multiple isoforms in which one or more clusters of polypeptides were missing from the cytoplasmic domain. The sequence and location of the deleted polypeptides corresponded to exons found in the human PECAM-1 gene. The alternatively spliced isoforms were capable of mediating cell-cell adhesion when transfected into L-cells. The isoforms differed, however, in their sensitivity to a panel of anti-PECAM-1 monoclonal antibodies. These data suggest that changes in the cytoplasmic domain of PECAM-1 may affect its function during cardiovascular development, and are consistent with our earlier report that systematic truncation of the cytoplasmic domain of human PECAM-1 resulted in changes in its ligand specificity, divalent cation and glycosaminoglycan dependence, as well as its susceptibility to adhesion blocking monoclonal antibodies. This is the first report of naturally occurring alternatively spliced forms of PECAM-1 having possible functional implications.

Amino Acid Sequence↗
PubMed1994

Adhesion molecules and inflammatory injury.

Neutrophil-endothelial cell interactions are mediated by interacting sets of cell adhesion molecules (CAMs) and chemoattractant/activator molecules to form an "adhesion cascade." The initial phase of inflammation, a transient slowing of neutrophils in postcapillary venules, is mediated by selectins. Subsequently, firm adhesion of neutrophils to the vessel wall occurs via interaction of the CD11/CD18 (beta 2) integrins to endothelial ligands such as intercellular adhesion molecule-1 (ICAM-1). This binding requires activation of CD11/CD18 by exposure of the neutrophil to a variety of activating/chemoattractant molecules, such as platelet-activating factor or interleukin-8. Finally, transmigration into tissues occurs, a process that requires both a chemotactic stimulus and engagement of platelet-endothelial cell adhesion molecule-1 (PECAM-1). Several approaches have been used to probe the role of CAMs in vivo. These include the use of blocking antibodies, chimeric selectin-immunoglobulin proteins, sialyl Lewisx oligosaccharides and peptides, along with the study of humans and animals with genetically determined adhesion deficiencies. These studies demonstrate that CAM blockade can effectively inhibit inflammation; however, there appear to be clear differences in the adhesion requirements for particular types of inflammation. By understanding the CAM/chemoattractant profiles involved in specific disease states, it may be possible to precisely and effectively target therapy to a wide variety of inflammatory diseases.

Cell Adhesion↗
PubMed1993

Involvement of platelet-endothelial cell adhesion molecule-1 in neutrophil recruitment in vivo.

During inflammation, neutrophils migrate from the vascular lumen into extravascular sites. In vitro assays have suggested that platelet-endothelial cell adhesion molecule-1 [PECAM-1 (CD31)], a member of the immunoglobulin superfamily, is required for the transmigration of neutrophils across endothelial monolayers. Antibody to human PECAM-1, which cross-reacts with rat PECAM-1, was found to block not only in vivo accumulation of rat neutrophils into the peritoneal cavity and the alveolar compartment of the lung but also neutrophil accumulation in human skin grafts transplanted onto immunodeficient mice. On the basis of these findings in three different models of inflammation, it appears that PECAM-1 is required for neutrophil transmigration in vivo and may thus be a potential therapeutic target.

Animals↗
PubMed1993

Platelet/endothelial cell adhesion molecule-1 (CD31)-mediated cellular aggregation involves cell surface glycosaminoglycans.

Platelet/endothelial cell adhesion molecule-1 (PECAM-1, CD31) is a 130-kDa integral membrane glycoprotein expressed on endothelial cells, platelets, and leukocytes. Experiments analyzing the aggregation of mouse L-cells stably transfected with full-length PECAM-1 cDNA have demonstrated that PECAM-1 is capable of mediating calcium-dependent heterophilic aggregation. In this report the ligand interactions involved in the aggregation process were studied. This aggregation was inhibited by heparin and chondroitin sulfate, but not by other glycosaminoglycans. Enzymatic removal of cell surface glycosaminoglycans confirmed a PECAM-1-glycosaminoglycan interaction and suggested that this interaction involved glycosaminoglycans on adjacent cells. PECAM-1 contains a glycosaminoglycan consensus binding sequence in the second immunoglobulin-like domain of the molecule's extracellular domain. A comparable region in the related adhesion protein N-CAM has been shown to mediate the adhesive properties of N-CAM. Cells expressing mutant PECAM-1 protein missing the second domain failed to aggregate. Synthetic peptides mimicking the consensus glycosaminoglycan binding sequence, L-K-R-E-K-N, inhibited aggregation. These results demonstrate that PECAM-1-mediated aggregation is dependent on the binding of PECAM-1 to specific glycosaminoglycans on adjacent cells via a glycosaminoglycan consensus binding sequence in the second immunoglobulin-like homology domain.

3T3 Cells↗
PubMed1993

Murine platelet endothelial cell adhesion molecule (PECAM-1)/CD31 modulates beta 2 integrins on lymphokine-activated killer cells.

Lymphokine-activated killer (LAK) cells are able to colonize sites of tumor lesions in mouse and man. The molecular mechanisms of homing in on tumors are largely unknown. However, before LAK cells can reach the tumor, they must adhere to the vascular endothelial within the lesion and then extravasate. We developed a novel mAb, EA-3, which recognizes the murine homologue of the human adhesion molecule CD31. It is present on a subpopulation of murine LAK cells and all endothelial cells. CD31 was also involved in the adhesion of LAK cells to endothelium. Since CD31 can initiate integrin activation by inside-out signaling after binding to its ligand, EA-3 was used to minimic this in adhesion assays. It induces modifications in the beta 2 integrin LFA-1, leading to increased binding capacities of the cells to endothelium. In contrast, beta 1 integrins and RGD-binding integrins were not affected. These results suggest that expression of CD31 might confer adhesive advantages for LAK cells prone to tumor infiltration.

Amino Acid Sequence↗
PubMed1993

Platelet endothelial cell adhesion molecule (CD31).

PECAM-1/CD31 represents a new addition to the cell adhesion molecules of the Ig superfamily. Recent work has revealed that it is capable of complex ligand interactions, although the specific ligands involved are still unknown. The wide distribution of PECAM-1 among vascular associated cells suggests that it may have number of important physiological functions. The ability of anti-PECAM-1 antibodies to block normal endothelial cell-cell contacts and influence cell migration point to a role in angiogenesis and wound healing. PECAM-1 may also contribute to early cardiovascular development. Augmentation of integrin-mediated white blood cell adhesion by engagement of PECAM-1 suggests that it may be involved in the adhesion of leukocytes to the endothelium and thus participate in the inflammatory response. Its function on platelets, however, still remains to be determined. Activational events are probably required in vivo for the molecule to function, given the high levels of constitutive expression. Phosphorylation of the cytoplasmic domain may be one of these events. It is anticipated that, as our understanding of the molecular and functional properties of PECAM-1 grows, we will gain new insights into the processes of inflammation, wound healing and angiogenesis.

Animals↗
PubMed1993

Maximal migration of human smooth muscle cells on fibronectin and type IV collagen occurs at an intermediate attachment strength.

Although a biphasic dependence of cell migration speed on cell-substratum adhesiveness has been predicted theoretically, experimental data directly demonstrating a relationship between these two phenomena have been lacking. To determine whether an optimal strength of cell-substratum adhesive interactions exists for cell migration, we measured quantitatively both the initial attachment strength and migration speed of human smooth muscle cells (HSMCs) on a range of surface concentrations of fibronectin (Fn) and type IV collagen (CnIV). Initial attachment strength was measured in order to characterize short time-scale cell-substratum interactions, which may be representative of dynamic interactions involved in cell migration. The critical fluid shear stress for cell detachment, determined in a radial-flow detachment assay, increased linearly with the surface concentrations of adsorbed Fn and CnIV. The detachment stress required for cells on Fn, 3.6 +/- 0.2 x 10(-3) mu dynes/absorbed molecule, was much greater than that on CnIV, 5.0 +/- 1.4 x 10(-5) mu dynes/absorbed molecule. Time-lapse videomicroscopy of individual cell movement paths showed that the migration behavior of HSMCs on these substrates varied with the absorbed concentration of each matrix protein, exhibiting biphasic dependence. Cell speed reached a maximum at intermediate concentrations of both proteins, with optimal concentrations for migration at 1 x 10(3) molecules/micron2 and 1 x 10(4) molecules/micron2 on Fn and CnIV, respectively. These optimal protein concentrations represent optimal initial attachment strengths corresponding to detachment shear stresses of 3.8 mu dyne/micron2 on Fn and 1.5 mu dyne/micron2 on CnIV. Thus, while the optimal absorbed protein concentrations for migration on Fn and CnIV differed by an order of magnitude, the optimal initial attachment strengths for migration on these two proteins were very similar. Further, the same minimum strength of initial attachment, corresponding to a detachment shear stress of approximately 1 mu dyne/micron2, was required for movement on either protein. These results suggest that initial cell-substratum attachment strength is a central variable governing cell migration speed, able to correlate observations of motility on substrata differing in adhesiveness. They also demonstrate that migration speed depends in biphasic manner on attachment strength, with maximal migration at an intermediate level of cell-substratum adhesiveness.

Cell Adhesion↗