Biomedical subjects

R Renkonen

Publications and source records attributed to R Renkonen.

At least 55 records · Page 3Linked to original sources

PubMed1994

Enhanced ICAM-1-dependent adhesion of myelomonocytic cells expressing increased levels of beta 2-integrins and CD43.

Interaction of ICAM-1 and its ligands plays an important role in the leukocyte binding to endothelium. The best characterized ICAM-ligands belong to the family of beta 2-integrins (CD11/CD18), but recently it has been suggested that CD43, a molecule with no structural resemblance to integrins binds ICAM-1 also. On the leukocytes the main regulatory pathway for ICAM-mediated binding is believed to be a short-term regulation of the avidity of CD11/CD18. In this study the authors investigated whether a quantitative increase in the surface expression of ICAM-ligands also can lead to enhanced binding to purified ICAM-1. PMA-treatment differentiates myelomonocytic cell lines into macrophages with a concomitant increase in the surface expression and mRNA-levels of the beta 2-integrin alpha- and beta-chains as well as that of CD43, another ICAM-ligand. The binding of the PMA-treated THP-1 cells to ICAM-1 was increased simultaneously compared to non-treated cells. The binding was blocked completely with antibodies to CD18 and ICAM-1. It is concluded that in addition to the transient qualitative regulation, a long-term quantitative regulation of ICAM-1 ligands also plays a role in increasing the adhesiveness of myelomonocytic cells. This may be relevant in chronic inflammation episodes.

Antigens, CD↗

PubMed1994

Carcinoembryonic antigen is expressed on endothelial cells. A putative mediator of tumor cell extravasation and metastasis.

Carcinoembryonic antigen (CEA) is a highly glycosylated cell surface protein. It is produced in large amounts in essentially all colon and several other adenocarcinomas. It has therefore been widely used as a clinical tumor marker. CEA is also a member of the immunoglobulin superfamily. Members of this family, such as ICAM-1, ICAM-2, VCAM-1 and NCAM, are known to participate in cell-cell adhesion. Similarly, the intercellular adhesion properties of CEA have been documented: it has been shown to mediate homotypic adhesion of cultured human colon adenocarcinoma cell lines. In this study we show for the first time that CEA is expressed on cultured human umbilical vein endothelial cells and on the endothelial cell line Ea.hy926. The expression of CEA on cultured endothelial cells can be enhanced by TNF-alpha or IFN-gamma, and decreased by IL-4. We demonstrate using immunohistochemistry that anti-CEA monoclonal antibody reacted with FVIII-positive endothelium in tissue sections prepared from lymph nodes. Finally, we were able to show that CEA-positive breast carcinoma cells bind to purified CEA protein, whereas CEA-negative breast carcinoma cells do not. These results reveal for the first time that endothelial cells express CEA on the cell surface and suggest that CEA-expressing adenocarcinomas could adhere to endothelial cells via CEA-CEA interaction, thus facilitating tumor cell extravasation and hematogenic metastasis.

Adenocarcinoma↗

PubMed1993

Down-regulation of monocytic VLA-4 leads to a decreased adhesion to VCAM-1.

The alpha 4 beta 1 integrin VLA-4 is expressed on practically all leukocytes, except on mature granulocytes. Here we show that in vitro treatment of monocytic cells with phorbol-12-myristate-13-acetate (PMA) leads to a selective decrease in the VLA-4 alpha-chain expression, both at the RNA and protein level. Meanwhile the expression of beta 1 and that of alpha 5, another alpha-chain associating with beta 1, was seen to increase. The decrease of alpha 4 expression was restricted to monocytic cells, and was not observed on other VLA-4-positive cells tested (MOLT-4 T cells and HOS sarcoma cells). The down-regulation of the VLA-4 alpha-chain was followed by a decreased binding capacity of the cells to recombinant VCAM-1. This data indicates that while previous findings show that the integrin-dependent adhesion may rapidly be regulated by altering the avidity of the interacting molecules, their quantitative modulation also has a clear impact on adhesion.

Cell Adhesion↗

PubMed1993

Regulation of CD59 expression on the human endothelial cell line EA.hy 926.

CD59 (protectin) is an 18-20-kDa inhibitor of the membrane attack complex of complement. It protects homologous cells from complement-mediated damage and has been shown to be present on the endothelial cell membranes both in vitro and in vivo. In this study we observed that the surface expression of CD59 on the cultured EA.hy 926 endothelial cell line can be up-regulated to an approximately threefold higher level after a 72-h stimulation by the protein kinase C inducers phorbol-12-myristate-13 acetate (PMA; 10 nM) and calcium ionophore, A23187 (100 nM). Similarly, an increase in the level of CD59 expression was seen by the protein kinase A inducer dibutyryl-cyclic adenosine monophosphate. In Northern blot analysis increases were observed in CD59 mRNA expression, particularly in the level of the longest 1.9-kb, 2.1-kb and 5.8-kb transcripts. A functional significance for the increased CD59 expression was implied by an observed increased resistance of the PMA-stimulated EA.hy 926 cells to complement-mediated cell lysis.

Antigens, CD↗

PubMed1993

The vascular E-selectin binds to the leukocyte integrins CD11/CD18.

Leukocyte adhesion involves at least three molecular families of adhesion proteins: the leukocyte integrins CD11/CD18, the intercellular adhesion molecules (ICAMs) and the carbohydrate-binding L-, E- and P-selectins. The intercellular adhesion molecules are well-known ligands for the CD11/CD18 integrins. We now show that E-selectin specifically binds to the sialyl Lex carbohydrate epitopes of leukocyte integrins. Thus, the different families of leukocyte adhesion molecules form an integrated adhesion network.

Antigens, CD↗

PubMed1993

Regulation of endothelial adhesion molecules by ligands binding to the scavenger receptor.

Monocyte adherence to the endothelium, their penetration to the subendothelial space and excessive lipid accumulation (foam cell formation) are the initial events in atherogenesis. Scavenger receptors have been reported to play an important role in foam cell formation, since modified low density lipoproteins can be taken up via scavenger receptors in a non-down-regulated fashion. In this study we demonstrate that stimulation of scavenger receptors in endothelial cells induces the expression of endothelial adhesion molecules. Polyinosinic acid (poly I), a known scavenger receptor ligand, significantly induced the expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin on human umbilical vein endothelial cells when compared with polycytidylic acid (poly C), a structurally related compound to poly I, which does not bind to the scavenger receptor. The effect of scavenger receptor ligands on the endothelial cell line EA hy. 926 was also tested. Poly I up-regulated ICAM-1 expression also on EA hy. 926 cells, while it had no effect on IL-1 beta or tumour necrosis factor-alpha (TNF-alpha) production on the same cell line. Poly I-induced ICAM-1 expression on EA hy. 926 cells could be inhibited by H7, a protein kinase C inhibitor, while HA 1004, a preferential protein kinase A inhibitor, had no effect on ICAM-1 expression. The role of protein kinase C in scavenger receptor-mediated adhesion molecule upregulation was confirmed by the ability of poly I to directly activate protein kinase C, when measured with 3H-phorbol dibutyrate binding to EA hy. 926 cells, while poly C again was ineffective.

Cell Adhesion Molecules↗

PubMed1993

Interferon-gamma induces a phospholipase D-dependent release of arachidonic acid from endothelial cell membranes: a mechanism for protein kinase C activation.

Interferon-gamma (IFN-gamma) induces MHC class II expression on endothelial cells in a protein kinase C (PKC)-dependent manner. Here we show that IFN-gamma induces a sixfold arachidonic acid (AA) release from cultured rat microvascular endothelial cell membranes compared with non-treated cells. Since this result suggests that AA could act as a second messenger for IFN-gamma, we analysed its capacity to directly activate PKC. We have previously shown that IFN-gamma induces a transient, multiphasic activation of PKC via the action of the phospholipase D (PLD) pathway. Here we show that AA is able to activate PKC. In an attempt to characterize the source of the liberated AA after IFN-gamma induction in endothelial cells we used a panel of enzyme inhibitors. The IFN-gamma-induced release of AA could not be modified by interfering either with the phospholipase A2 (PLA2) pathway using bromophenacyl bromide (BPB), or with the phospholipase C (PLC) pathway using neomycin. The phosphatidic acid phosphatase (PAPase) inhibitor propranolol, inhibiting the generation of diacylglycerol (DAG) and further AA from phosphatidic acid (PA), could totally down-regulate the IFN-gamma-induced release of AA. Since PA is produced solely by the action of PLD from phosphatidylcholine (PC) we conclude that the AA originated from the cell membrane-associated PC. In summary, we show here that IFN-gamma causes the liberation of cell membrane-associated, PC-linked AA. This AA could directly activate PKC in a similar multiphasic manner to IFN-gamma, suggesting that it is a true second messenger for IFN-gamma in cultured endothelial cells.

Animals↗

PubMed1993

Adhesion molecules involved in protein kinase A- and C-dependent lymphocyte adherence to microvascular endothelial cells.

A twofold increase in lymphocyte adherence to rat microvascular endothelial cells (EC) was achieved by incubating EC for 4 h with IL-1 alpha or dibutyryl-cAMP (stimulators of protein kinase A, PKA) and PMA (stimulator of protein kinase C, PKC). Monoclonal antibodies anti-CD11a, anti-CD18 (LFA-1) and anti-CD49d (VLA-4 alpha) significantly inhibited the increased lymphocyte binding to IL-1 alpha-induced EC, anti-CD18 and to a lesser extent anti-CD11a and anti-CD49d to dibutyryl-cAMP-induced EC, whereas only anti-CD11a and anti-CD18 monoclonal antibodies inhibited PMA-induced lymphocyte binding. These findings suggest that stimulation of PKA and PKC induces lymphocyte binding to EC via different adhesion molecules.

Animals↗

PubMed1992

IFN-gamma induces a phospholipase D dependent triphasic activation of protein kinase C in endothelial cells.

The IFN-gamma linked PKC activation in endothelial cells was analysed. It was shown that IFN-gamma activates PKC in three transient and separate cycles within the first 60 minutes after IFN-gamma stimulation. Before each PKC activation there was an increase in DAG level. IP3, phosphocholine and choline productions were measured to determine the origin of DAG. Neither of the PLC products, IP3 or phosphocholine, were released after IFN-gamma stimulation. On the other hand the PLD products choline and PA were released before all the three activation cycles of PKC.

Animals↗

PubMed1992

VLA-4 integrin on sarcoma cell lines recognizes endothelial VCAM-1. Differential regulation of the VLA-4 avidity on various sarcoma cell lines.

Osteosarcomas and rhabdomyosarcomas are vigorously invading tumors. Before they can extravasate to the parenchymal organs and form metastases, they have to adhere to the endothelial cells lining the blood vessels and then penetrate through the endothelium. We show that several human sarcoma cell lines, osteosarcomas HOS, MG-63, U2-OS, and a rhabdomyosarcoma RD, express VLA-4 molecule on their surface and bind to the VCAM-I-expressing activated endothelial cell line Ea.hy 926. The increased sarcoma-cell adhesion could be abolished by treating the sarcoma cells with monoclonal antibodies (MAbs) VLA4 (both alpha- and beta-chain, HP2/1 and 4B4 respectively) or treating endothelial cells with VCAM-I antibody (4B9). Furthermore, we show that sarcoma cells adhere to recombinant soluble VCAM-I protein. On the other hand, these sarcoma cell lines do not express marked amounts of other ligands (such as CDII/18 or sialyl-Lex) for other endothelial adhesion molecules (ICAM-I, ICAM-2, E- and P-selectin) indicating that the VLA-4-VCAM-I dependent pathway might be of major importance in sarcoma extravasation. VLA-4 is not always in an avid form and therefore the expression of VLA-4 does not directly predict adherence to VCAM-I. The avidity of VLA-4 (measured by adherence to soluble VCAM-I) of MG-63 and U2-OS cells could be increased by a 30-min PMA treatment, whereas the avidity of VLA-4 on HOS cells increased only after 48 hr of PMA induction. Our results show that sarcoma cell lines (HOS, MG-63, U2-OS and RD) adhere to stimulated endothelium via VLA-4-VCAM-I adhesion molecules and that VLA-4 avidity on sarcoma cells can be differentially modulated by PMA.

Base Sequence↗

PubMed1992

Recombinant E-selectin-protein mediates tumor cell adhesion via sialyl-Le(a) and sialyl-Le(x).

E-selectin (previously known as ELAM-1) is one of the adhesion molecules expressed on activated endothelium. Here we show that HL-60 cells express sialyl-Le(x), but not Sialyl-Le(a) on their surface, a colon carcinoma cell line COLO 205 express both these epitopes and another colon carcinoma COLO 320 does not express either one of them. HL-60 and COLO 205 cell adhere strongly to E-selectin coated microwells, whereas COLO 320 does not adhere at all to E-selectin. Finally we provide evidence that monoclonal anti-sialyl-Le(x) can abolish part of the adherence of HL-60 cells to recombinant E-selectin. The adherence of COLO 205 cells can be decreased by either monoclonal anti-sialyl-Le(a) or anti-sialyl-Le(x) antibodies. These results indicate that cell-associated sialylated carbohydrate moieties can act as ligands for recombinant E-selectin.

Antibodies, Monoclonal↗

PubMed1992

Evidence that lymphocyte traffic into rejecting cardiac allografts is CD11a- and CD49d-dependent.

Acute cardiac allograft rejection is characterized by infiltration of leukocytes into tissue parenchyma, but the site of entry and endothelial adhesion molecules involved are not yet defined. Lymphocyte binding to frozen sections prepared from day-3 rejecting cardiac allografts was significantly increased compared with sections made from normal hearts (number of bound lymphocytes, 983 +/- 216 per mm2 vs. 309 +/- 121, respectively, P < 0.001) or syngeneic grafts. The bound lymphocytes were located exclusively only on the top of the capillary structures and not on any other sites on the heart vasculature. We further wanted to analyze which of the cloned endothelial adhesion molecules and their counterreceptors would be involved in the increased lymphocyte binding. Lymphocyte pretreatment with mAb anti-CD11a or anti-CD49d inhibited this binding more than 50%. This inhibition on lymphocyte binding could not be increased by combining these two antibodies. Lymphocyte binding to endothelium has been shown to be at least partly organ specific; therefore, we asked whether increased lymphocytes adhere to cardiac allografts could be organ specific. Lymphocyte binding to lymph node high endothelial venules (HEV) has been shown to be inhibited by mannose-6-phosphate (M6P) and to kidney peritubular capillaries by mannose-1-phosphate (M1P). In the present study neither of these carbohydrates had any effect on lymphocyte binding to cardiac allograft endothelium. Monosaccharide inhibition studies demonstrate that the mechanism of lymphocyte adhesion to cardiac capillary endothelium differs from adhesion to kidney allografts or peripheral lymph node high endothelium.

Animals↗

PubMed1992

TNF alpha-induced expression of endothelial adhesion molecules, ICAM-1 and VCAM-1, is linked to protein kinase C activation.

The role of protein kinase C (PKC) in TNF alpha-induced activation of endothelial adhesion molecules ICAM-1 and VCAM-1 was analysed. Phorbol myristate acetate, which is known to activate PKC, was able to mimic TNF alpha-induced up-regulation of ICAM-1 and partly also VCAM-1 expression. Similarly a PKC inhibitor, H7, but not another kinase inhibitor, HA1004, inhibited TNF alpha-induced enhancement of ICAM-1 expression at both the mRNA and the protein level. Moreover we were able to measure a transient PKC activation peak at 16 min after TNF alpha induction in endothelial cells analysed by phorbol-dibutyrate binding. These results indicate that the TNF alpha-induced effect on the regulation of endothelial adhesion molecule expression is at least partly mediated by PKC activation.

Base Sequence↗

PubMed1992

IL-4 decreases IFN-gamma-induced endothelial ICAM-1 expression by a transcriptional mechanism.

Intercellular adhesion molecule-1 (ICAM-1, CD54) is a cell surface ligand for LFA-1 (CD11a/18). Several cytokines, such as IL-1, TNF-alpha or IFN-gamma, have been shown to increase the ICAM-1 expression on cultured endothelial cells. Here we show that IL-4 decreases the IFN-gamma-induced ICAM-1 expression on an endothelial cell line (EA.hy 926), whereas IL-4 alone has practically no effects on ICAM-1 expression. The down-regulative effect was also seen at the mRNA level suggesting that this regulation process is transcriptional. At the same time IL-4 was unable to alter the TNF-alpha-induced ICAM-1 up-regulation. Both IFN-gamma and TNF-alpha are able to decrease the proliferation of the endothelial cell line, but IL-4 could not modify this response when added together with the other cytokines. Taken together we show in this paper that IL-4 decreases IFN-gamma but not TNF-alpha-induced up-regulation of ICAM-1 expression on EA.hy 926 cells.

Blotting, Northern↗

PubMed1992

A novel endothelial cell surface receptor tyrosine kinase with extracellular epidermal growth factor homology domains.

Endothelial cell surfaces play key roles in several important physiological and pathological processes such as blood clotting, angiogenic responses, and inflammation. Here we describe the cloning and characterization of tie, a novel type of human endothelial cell surface receptor tyrosine kinase. The extracellular domain of the predicted tie protein product has an exceptional multidomain structure consisting of a cluster of three epidermal growth factor homology motifs embedded between two immunoglobulinlike loops, which are followed by three fibronectin type III repeats next to the transmembrane region. Additionally, a cDNA form lacking the first of the three epidermal growth factor homology domains was isolated, suggesting that alternative splicing creates different tie-type receptors. Cells transfected with tie cDNA expression vector produce glycosylated polypeptides of 117 kDa which are reactive to antisera raised against the tie carboxy terminus. The tie gene was located in chromosomal region 1p33 to 1p34. Expression of the tie gene appeared to be restricted in some cell lines; large amounts of tie mRNA were detected in endothelial cell lines and in some myeloid leukemia cell lines with erythroid and megakaryoblastoid characteristics. In addition, mRNA in situ studies further indicated the endothelial expression of the tie gene. The tie receptor tyrosine kinase may have evolved for multiple protein-protein interactions, possibly including cell adhesion to the vascular endothelium.

Amino Acid Sequence↗

PubMed1992

Selective expression of sialyl-Lewis x and Lewis a epitopes, putative ligands for L-selectin, on peripheral lymph-node high endothelial venules.

High endothelial venules (HEV) lined by the high endothelium are the sites where leukocytes enter into the lymph nodes from the blood. Lymphocyte homing into lymph nodes is organ-selective, i.e., different molecules are involved in the lymphocyte homing to peripheral nodes compared with mucosa associated lymphoid tissue. The traffic into peripheral nodes is regulated by the expression of L-selectin on leukocytes and its ligand on HEVs. The ligand for L-selectin is suggested to be a 50, 90, or 105 kd glycoprotein, which is sulfated, fucosylated, and sialylated. The two other members of the selectin family (E- and P-selectin) recognize sialyl-Lewis x and -Lewis a (sLex and sLea, respectively) carbohydrate motifs, and there is preliminary data suggesting that this would also be the case for L-selectin. We have initiated a study to identify the expression of these sialylated structures on endothelial surfaces. We present data that show that HEVs in peripheral nodes, but not in the mucosa-associated lymphoid tissue, express large quantities of sLex and sLea identified by MAbs in immunohistology. Endothelium in capillaries or larger vessels in non-lymphoid tissues do not react with anti-sLex or -Lea mAbs. Only 1-2% of the lymphocytes in the peripheral blood express sLex and so far only the skin-homing lymphocytes are known to be sLex positive in larger quantities. We show that in many occasions the B cells in the peripheral lymph-node germinal centers are also sLex-, but not sLea-positive, and provide evidence of the restricted pattern of sLex and sLea expression on peripheral lymph-node HEVs. We propose that they are at least parts of the ligand for L-selectin.

Antibodies, Monoclonal↗

PubMed1992

Expression of endothelial adhesion molecules in vivo. Increased endothelial ICAM-2 expression in lymphoid malignancies.

The authors have compared the reactivity of monoclonal antibodies (MAb) directed against endothelial adhesion molecules (ICAM-1, ICAM-2, VCAM-1, ELAM-1) in hyperplastic, nonmalignant, and malignant lymph nodes. The authors demonstrate that the reactivity with ICAM-1 MAb is stronger in the high endothelial venules (HEV) and other smaller vessels (SV) in lymphomas compared with hyperplastic lymph nodes. Similarly, the reactivity of an ICAM-2 MAb (6D5) was shown to be higher in malignant lymph nodes compared with nonmalignant ones. ICAM-2 MAb stained both the HEV and SV. VCAM-1 MAb reacted strongly with germinal centers and its endothelial reactivity was higher in the lymphoma nodes. ELAM-1 MAb stained only faintly some endothelial cells in malignant tissue. These data suggest that besides the known regulatable endothelial adhesion molecules ICAM-1 and VCAM-1, the expression of ICAM-2 can be modified.

Antibodies, Monoclonal↗

PubMed1991

Carbohydrate synthesis inhibitors decrease interleukin 1-stimulated lymphocyte binding to endothelial cells.

Lymphocyte extravasation (homing) is initiated when lymphocyte adheres to endothelial cells. All know protein structures involved in the lymphocyte binding located on the endothelial surface are heavily glycosylated. We asked therefore whether these carbohydrate motifs had a role in the lymphocyte homing. The relative importance of the N-linked chains on biological effects mediated by glycoproteins can be studied with specific inhibitors of carbohydrate processing, i.e. 1-deoxynojirimycin (DN), castonospermine (CAST), 1-deoxymannojirimycin (DMN) and swainsonine (SW), which produces different kinds of blocked carbohydrate chains. N-linked carbohydrate chains are modified in the Golgi apparatus and in the final glycoprotein they can be either of high-mannose-, hybrid- or complex-type motifs, having the same core structure but different terminal structures. We show here that when all N-linked carbohydrates were cleaved off from the cell surface glycoproteins by treating endothelial cells with N-glycosidase F interleukin 1-induced lymphocyte binding was reduced almost to non-stimulated control values. Treatment of endothelial cells with CAST led to generation of glycoproteins carrying high-mannose-type oligosaccharides, which are glucose capped with three glucose molecules on the chain. CAST treatment resulted in an 85% decrease in lymphocyte binding compared to interleukin 1-induced levels. DMN treatment, resulting in accumulation of high-mannose type oligosaccharides without any terminal glucoses on the cell surface, caused a similar inhibition of lymphocyte binding to that induced by CAST treatment. SW treatment, leading to accumulation of hybrid-type glycoproteins, decreased only slightly the lymphocyte binding. These results suggest that carbohydrates indeed have a role in lymphocyte binding to endothelial cells.

1-Deoxynojirimycin↗