Biomedical subjects

M A Gimbrone

Publications and source records attributed to M A Gimbrone.

At least 73 records · Page 4Linked to original sources

PubMed1994

The omega-3 fatty acid docosahexaenoate reduces cytokine-induced expression of proatherogenic and proinflammatory proteins in human endothelial cells.

The mechanisms by which dietary fatty acids can modulate atherogenesis and inflammation are poorly understood. Induction in endothelial cells of adhesion molecules for circulating leukocytes and of inflammatory mediators by cytokines probably contributes to the early phases of atherogenesis and inflammation. We report here that incorporation into cellular lipids of docosahexaenoic acid (DHA), a specific fatty acid of the omega 3 family, decreases cytokine-induced expression of endothelial leukocyte adhesion molecules, secretion of inflammatory mediators, and leukocyte adhesion to cultured endothelial cells. DHA, but not eicosapentaenoic acid, decreased in a dose- and time-dependent fashion the expression of vascular cell adhesion molecule 1 (VCAM-1) induced by interleukin (IL)-1, tumor necrosis factor (TNF), IL-4, or bacterial lipopolysaccharide, with half-maximum inhibition at < 10 mumol/L. This reduction required prolonged (24- to 96-hour) exposure of endothelial cells to DHA and correlated with the degree of DHA incorporation into cellular lipids. DHA also limited cytokine-stimulated endothelial cell expression of E-selectin and intercellular adhesion molecule 1 and the secretion of IL-6 and IL-8 into the medium but not the surface expression of constitutive surface molecules. Cyclooxygenase inhibition did not block the effect of DHA on VCAM-1. In parallel with reduced surface VCAM-1 protein expression, DHA reduced VCAM-1 mRNA induction by IL-1 or TNF. DHA treatment also reduced the adhesion of human monocytes and of monocytic U937 cells to cytokine-stimulated endothelial cells. These properties of DHA may contribute to antiatherogenic and anti-inflammatory effects of omega 3 fatty acids.

Arteriosclerosis↗

PubMed1994

Lysophosphatidylcholine transcriptionally induces growth factor gene expression in cultured human endothelial cells.

Lysophosphatidylcholine (lyso-PC) is a major phospholipid component of atherogenic lipoproteins (e.g., oxidized LDL and beta-VLDL) and also can be generated through the action of leukocyte-secreted phospholipase A2 at sites of inflammation. We have previously reported that lyso-PC can activate cultured endothelia, resulting in the selective upregulation of adhesion molecules, such as vascular cell adhesion molecule-1 and intercellular adhesion molecule-1. In this study, we have found that lyso-PC increased steady state mRNA levels for two smooth muscle/fibroblast-directed growth factors, the A and B chains of PDGF and heparin-binding EGF-like protein (HB-EGF), in cultured human endothelial cells. Lyso-PC did not upregulate the expression of certain other inducible endothelial genes, including E-selectin, IL-8, or monocyte chemoattractant protein-1 in the same cells, in contrast to the coordinate pattern of activation typically observed with other stimuli, such as TNF alpha, bacterial endotoxin, or PMA. Nuclear runoff assays documented an increased transcriptional rate for the HB-EGF gene in lyso-PC-treated cells. Northern blot analyses, after actinomycin D treatment, further indicated that the increased amounts of mRNA for HB-EGF, PDGF A and B chains, and intercellular adhesion molecule-1 were not dependent upon message stabilization. We conclude that lyso-PC can induce growth factor gene expression in cultured endothelial cells and thus may contribute to the migration and proliferation of smooth muscle cells and fibroblasts in various response-to-injury settings in vivo.

Bacterial Toxins↗

PubMed1994

Shear stress selectively upregulates intercellular adhesion molecule-1 expression in cultured human vascular endothelial cells.

Hemodynamic forces induce various functional changes in vascular endothelium, many of which reflect alterations in gene expression. We have recently identified a cis-acting transcriptional regulatory element, the shear stress response element (SSRE), present in the promoters of several genes, that may represent a common pathway by which biomechanical forces influence gene expression. In this study, we have examined the effect of shear stress on endothelial expression of three adhesion molecules: intercellular adhesion molecule-1 (ICAM-1), which contains the SSRE in its promoter, and E-selectin (ELAM-1) and vascular cell adhesion molecule-1 (VCAM-1), both of which lack the SSRE. Cultured human umbilical vein endothelial cells, subjected to a physiologically relevant range of laminar shear stresses (2.5-46 dyn/cm2) in a cone and plate apparatus for up to 48 h, showed time-dependent but force-independent increases in surface immunoreactive ICAM-1. Upregulated ICAM-1 expression was correlated with increased adhesion of the JY lymphocytic cell line. Northern blot analysis revealed increased ICAM-1 transcript as early as 2 h after the onset of shear stress. In contrast, E-selectin and vascular cell adhesion molecule-1 transcript and cell-surface protein were not upregulated at any time point examined. This selective regulation of adhesion molecule expression in vascular endothelium suggests that biomechanical forces, in addition to humoral stimuli, may contribute to differential endothelial gene expression and thus represent pathophysiologically relevant stimuli in inflammation and atherosclerosis.

Cell Adhesion↗

PubMed1994

Fluid flow modulates vascular endothelial cytosolic calcium responses to adenine nucleotides.

OBJECTIVE: To determine whether fluid flow influences the action of soluble vasoactive agonists on vascular endothelium. METHODS: Confluent monolayers of bovine aortic endothelial cells (BAEC) were cultured on glass coverslips, prelabeled with the Ca(2+)-sensitive dye fura-2, and placed in a parallel-plate flow chamber designed to generate defined laminar fluid flow. Cytosolic free Ca2+ concentration ([Ca2+]i) in individual BAEC was monitored during perfusion with medium containing adenine nucleotide under defined flow conditions. RESULTS: Continuous perfusion with ATP (0.3-3.0 microM) or ADP (0.1-1.0 microM) evoked repetitive oscillations in [Ca2+]i in individual BAEC. The frequency of the [Ca2+]i oscillations was dependent on both nucleotide concentration and levels of applied shear stress; at constant bulk concentration of nucleotide, the frequency increased with shear stress. Stopping flow in the continuous presence of agonists immediately extinguished the oscillatory response. Elimination of extracellular Ca2+ did not inhibit the [Ca2+]i oscillations. In the presence of nonhydrolyzable nucleotide analog, ATP gamma S or ADP beta S, application of flow resulted in similar shear-dependent [Ca2+]i oscillations, suggesting that flow modulation of the [Ca2+]i response was not simply due to depletion of ATP or ADP in the vicinity of BAEC monolayers as a result of hydrolysis of nucleotides by ectonucleotidases. CONCLUSIONS: These findings suggest that local hemodynamic conditions may modulate the action of vasoactive agents on the vascular endothelium in vivo.

Adenine Nucleotides↗

PubMed1993

Intravenous interleukin-8 inhibits granulocyte emigration from rabbit mesenteric venules without altering L-selectin expression or leukocyte rolling.

Injection (i.v.) of the granulocyte chemoattractant/activator IL-8 has been shown to reduce neutrophil recruitment into dermal inflammatory sites in vivo. To further investigate the mechanism of this phenomenon, we examined the effect of i.v. [Ser-IL-8]72 (12-20 micrograms/kg) on leukocyte rolling and chemoattractant-induced emigration in mesenteric venules of New Zealand White rabbits and on expression of L-selectin (mAb LAM1-3) and CD18 (mAb 60.3) on circulating rabbit granulocytes. Within 1 min of IL-8 i.v., granulocytes virtually disappeared from carotid blood samples for approximately 5 min. Concomitantly, the flux of rolling leukocytes in mesenteric venules fell from 83 +/- 21 to 2 +/- 1 leukocytes/min. Both rolling leukocyte flux and systemic granulocyte count returned to or exceeded control values within less than 30 min. The chemoattractant/activator FMLP (0.15 microgram/kg i.v.) produced similar results. A second i.v. injection of IL-8 or FMLP, 90 min after the first challenge, had equipotent effects. Local extravascular application of IL-8 via micropipette close to a venule induced adhesion and emigration of 63 +/- 21 leukocytes per site before, but only 26 +/- 9 leukocytes per site 50 to 75 min after i.v. IL-8, when systemic granulocyte count and rolling leukocyte flux had reached or exceeded control values. This was not due to agonist-specific desensitization, because a similar reduction of leukocyte emigration was seen after FMLP i.v. Rabbit granulocytes circulating in vivo uniformly expressed near-control levels of L-selectin at all times between 3 and 360 min after IL-8 i.v. CD18 expression transiently increased after IL-8 i.v. and returned to base line by 90 min. These findings show that IL-8 i.v. reduces granulocyte recruitment to inflammatory sites by inhibiting function(s) necessary for transmigration that are independent of L-selectin and subsequent to rolling.

Animals↗

PubMed1993

Platelet-derived growth factor B chain promoter contains a cis-acting fluid shear-stress-responsive element.

The endothelial lining of blood vessels is constantly exposed to fluid mechanical forces generated by flowing blood. In vitro application of fluid shear stresses to cultured endothelial cells influences the expression of multiple genes, as reflected by changes in their steady-state mRNA levels. We have utilized the B chain of platelet-derived growth factor (PDGF-B) as a model to investigate the mechanisms of shear-stress-induced gene regulation in cultured bovine aortic endothelial cells (BAECs). Northern blot analysis revealed elevated endogenous PDGF-B transcript levels in BAECs, after exposure to a physiological level of laminar shear stress (10 dynes/cm2; 1 dyne = 100 mN) for 4 h. A transfected reporter gene, consisting of a 1.3-kb fragment of the human PDGF-B promoter coupled to chloramphenicol acetyltransferase (CAT), indicated a direct effect on transcriptional activity. Transfection of a series of PDGF-B-CAT deletion mutants led to the characterization of a cis-acting component within the PDGF-B promoter that was necessary for shear-stress responsiveness. In gel-shift assays, overlapping oligonucleotide probes of this region formed several protein-DNA complexes with nuclear extracts prepared from both static and shear-stressed BAECs. A 12-bp component (CTCTCAGAGACC) was identified that formed a distinct pattern of complexes with nuclear proteins extracted from shear-stressed BAECs. This shear-stress-responsive element does not encode binding sites for any known transcription factor but does contain a core binding sequence (GAGACC), as defined by deletion mutation in gel-shift assays. Interestingly, this putative transcription factor binding site is also present in the promoters of certain other endothelial genes, including tissue plasminogen activator, intercellular adhesion molecule 1, and transforming growth factor beta 1, that also are induced by shear stress. Thus, the expression of PDGF-B and other pathophysiologically relevant genes in vascular endothelium appears to be regulated, in part, by shear-stress-induced transcription factors interacting with a common promoter element.

Animals↗

PubMed1993

Regulation of adenine nucleotide concentration at endothelium-fluid interface by viscous shear flow.

The action of adenine nucleotides on vascular endothelial cells is apparently mediated by the local flow conditions. Because nucleotides are sequentially degraded from ATP-->ADP-->AMP-->adenosine by ecto-enzymes at the endothelial surface, it has been hypothesized that the observed flow effect is caused by the flow-dependent change of nucleotide concentration at the cell surface. In this study, we have calculated the concentration profiles of adenine nucleotides at the cell surface under flow conditions encountered in an in vitro parallel-plate flow system, as has been used in several related experimental studies. When medium containing uniformly distributed ATP is perfused over endothelial monolayers, our results show that ATP concentration in the cell vicinity gradually decreases in the streamwise direction as a result of enzymatic degradation. This hydrolysis of ATP results in the generation of ADP, and ADP concentration in turn gradually increases at the cell surface. The concentration profiles of nucleotides are dependent on the levels of applied wall shear rate. As the corresponding shear stress increases from 0.1 to 30 dynes/cm2, ATP concentration at the cell surface at the center of coverslip increases from 0.66 to 0.93. Under no-flow conditions, our model predicts a steady decline of ATP concentration and a transient increase of ATP-derived ADP, comparable to the published results of previous experiments. These numerical results, combined with our recent experimental data, provide insights into the cellular mechanisms by which hemodynamic flow modulates the effects of vasoactive agents on endothelium.

Adenine Nucleotides↗

PubMed1993

An atherogenic diet rapidly induces VCAM-1, a cytokine-regulatable mononuclear leukocyte adhesion molecule, in rabbit aortic endothelium.

Accumulation of monocyte-derived foam cells in focal areas of the arterial intima is a key step in early atherogenesis. We investigated the expression of vascular cell adhesion molecule-1 (VCAM-1), a mononuclear leukocyte adhesion molecule, in the arterial endothelium during the early phases of diet-induced atherogenesis in rabbits in vivo and the regulation of VCAM-1 expression by cytokines in rabbit aortic organoid cultures in vitro. Rabbits were fed either an atherogenic diet (containing 0.3% cholesterol, 9% coconut oil, and 1% corn oil) or an isocaloric control diet (10% corn oil) for 4 days or 1, 3, 6, or 13 weeks. The endothelium in the ascending aorta focally expressed VCAM-1 after only 1 week on the atherogenic diet but before the first appearance of intimal macrophages, as judged by immunohistochemical staining of serial sections. The rabbits that consumed the atherogenic diet for 3 weeks or longer developed lesions in the intima composed of macrophages bearing class II major histocompatibility antigen (MHC-II). Endothelial cells continued to focally express VCAM-1 at sites of MHC-II-positive intimal macrophages for up to 13 weeks. The ascending aortas of control rabbits lacked VCAM-1 or MHC-II-positive endothelium or macrophages at all times studied. These observations demonstrate the focal activation of arterial endothelium as early as 7 days after initiation of an atherogenic diet (at serum cholesterol levels of 308 +/- 57 mg/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Inducible expression of vascular cell adhesion molecule-1 by vascular smooth muscle cells in vitro and within rabbit atheroma.

Vascular cell adhesion molecule-1 (VCAM-1), a mononuclear leukocyte adhesion molecule, is expressed in cultured vascular endothelial cells activated by cytokines and is induced in rabbit aortic endothelium in vivo within 1 week after initiation of an atherogenic diet. We now demonstrate that vascular smooth muscle cells can also express VCAM-1 in rabbit atherosclerotic lesions in vivo and in response to cytokines in vitro. Immunohistochemical staining of aortas from rabbits fed a 0.3% cholesterol-containing diet revealed that a portion of smooth muscle cells within intimal foam cell-rich lesions expressed VCAM-1. The intimal VCAM-1-expressing cells localized predominantly in regions above the internal elastic lamina. These VCAM-1-positive cells had the typical spindle shape of smooth muscle cells but had reduced alpha-actin expression in comparison to normal medial smooth muscle cells, and did not bear markers for endothelium, macrophages, and T cells. In culture, rabbit aortic smooth muscle cells expressed VCAM-1 mRNA and protein in a time- and concentration-dependent fashion when exposed to interferon-gamma or Gram-negative bacterial lipopolysaccharide. Cultured human vascular smooth muscle cells also expressed VCAM-1 mRNA and protein in response to lipopolysaccharide, interferon-gamma, and interleukin-4. The monokines interleukin-1 alpha and tumor necrosis factor-alpha did not induce VCAM-1 expression in either rabbit or human vascular smooth muscle cells. Inducible VCAM-1 expression by vascular smooth muscle cells in vivo during hypercholesterolemia and in vitro in response to certain cytokines suggests a broader range of VCAM-1 functions in vascular biology than heretofore appreciated.

Actins↗

PubMed1993

Neutrophil-mediated damage to human vascular endothelium. Role of cytokine activation.

Cytokine activation of cultured human vascular endothelial cells renders them hyperadhesive for blood leukocytes. Co-incubation of freshly isolated, unstimulated human blood neutrophils with confluent cytokine-activated human endothelial monolayers for 90 minutes results in extensive endothelial detachment and destruction of monolayer integrity. In contrast, unactivated endothelial monolayers remain intact. Using this in vitro model, we have explored the neutrophil-effector mechanisms involved in this injury. Coincubation in the presence of a serine protease inhibitor (phenylmethylsulfonyl fluoride) or specific elastase inhibitors (Ala-Ala-Pro-Val-chloromethyl ketone or alpha-1-protease inhibitor) markedly diminished injury. In contrast, scavengers or inhibitors of oxygen-derived free radicals (superoxide dismutase, catalase, mannitol, or sodium azide) were not protective. Purified human neutrophil elastase mimicked the effect of the neutrophils suggesting a key role for elastase in the neutrophil-mediated injury in this model. Interfering with direct neutrophil-endothelial cell contact by interposing a microporous barrier insert prevented endothelial cell detachment. Furthermore, this neutrophil-mediated detachment could be inhibited with interleukin-8, an action correlated with a decrease in neutrophil adhesion to activated endothelial monolayers. By defining the role of endothelial activation in neutrophil-mediated injury, this in vitro model may provide useful insights into potential therapeutic interventions designed to prevent disruption of the endothelial barrier function.

Cell Adhesion↗

PubMed1992

In vitro inhibitory effect of IL-8 and other chemoattractants on neutrophil-endothelial adhesive interactions.

We have previously reported that cytokine- or LPS-activated human umbilical vein endothelial cell (HUVEC) monolayers secrete IL-8 that can act as a neutrophil-selective adhesion inhibitor. In our study we investigated the mechanisms involved in the leukocyte adhesion inhibitory action of IL-8. The leukocyte adhesion inhibitory effect appears to be mediated by the action of IL-8 on the neutrophil, does not involve down-regulation of relevant endothelial adhesion molecules such as endothelial-leukocyte adhesion molecule-1 or intercellular adhesion molecule-1, and is quantitatively similar in different endothelial activation states that are predominantly endothelial-leukocyte adhesion molecule-1 dependent or intercellular adhesion molecule-1 dependent. In addition to inhibiting the attachment of freshly isolated peripheral blood neutrophils to cytokine-activated HUVEC monolayers, IL-8 also promoted a rapid detachment of tightly adherent neutrophils from activated HUVEC, and abolished neutrophil transendothelial migration. Certain other chemoattractants, including FMLP and C5a, had similar inhibitory actions, indicating IL-8 was not unique in its ability to inhibit various neutrophil-endothelial interactions. In contrast, two other neutrophil agonists 1-0-alkyl-2-acetyl sn-glycero-3-phosphocholine and granulocyte-macrophage-CSF, which, like IL-8, are produced by activated HUVEC, as well as the leukocyte-derived chemoattractant leukotriene B4, exerted minimal inhibitory effects on adhesion. Regardless of their ability to modulate neutrophil-endothelial cell adhesion, all these agents induced altered leukocyte surface expression of functionally important adhesion molecules, including loss of L-selectin (leukocyte adhesion molecule-1, LECAM-1) and increase in CD11b/CD18. Thus, although the above agonists have been characterized primarily as chemoattractants, our findings demonstrate that these agents can exert a wide range of modulatory effects on neutrophil-endothelial adhesive interactions.

Antigens, CD↗

PubMed1992

Human endothelial cells express integrin receptors on the luminal aspect of their membrane.

Endothelial cells (EC) form a dynamic interface between blood and the rest of the body. EC surface properties promoting adhesion of reactive plasma proteins and/or circulating cells might be of pivotal importance for the homeostasis of blood and tissues. EC express multiple integrin receptors that promote their attachment to the subendothelial matrix proteins. Among these receptors, alpha v beta 3 is of particular relevance on EC, since it is abundantly expressed and can bind many different matrix and plasma proteins. It is still unknown whether integrin receptors are selectively located to the basal side of EC membrane or may also be exposed on the cell surface in contact with blood. This issue was addressed using different experimental approaches. First, selective surface radioiodination using lactoperoxidase (LPO)-latex beads and immunoprecipitation analysis were performed. We found that cultured EC, similarly to human skin fibroblasts (HSF), expose alpha v beta 3 on both their apical (free) and basal (substratum-attached) surfaces. This held also for other integrins such as alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, and alpha 6 beta 1. Immunoprecipitation data were verified by morphological techniques. Immunofluorescence and immunogold-staining of EC with alpha v beta 3, as well as with beta 1 subfamily antibodies, showed a diffuse and granular distribution of these integrins on EC surface. alpha v beta 3 and beta 1 integrins were also detected on the apical membrane of EC at higher magnification by scanning electron microscopy (SEM). Finally, data obtained on cultured EC were confirmed in vivo on immunogold-labeled ultrathin cryosections of human vessels by transmission electron microscopy (TEM). Data indicate, that in addition to their role in promoting EC attachment to extracellular matrix proteins, integrin receptors of EC can be exposed to blood-stream and eventually be available for binding of plasma proteins and circulating cells.

Cell Membrane↗

PubMed1992

Nucleotide sequence of rat vascular cell adhesion molecule-1 cDNA.

Vascular cell adhesion molecule 1 (VCAM-1) is an inducible transmembrane protein which is expressed by vascular endothelium following cytokine activation. VCAM-1 mediated the adhesion of certain blood leukocytes and tumor cells via the interaction with its counter-receptor, the integrin VLA4. When initially cloned from interleukin-1 (IL-1) stimulated human umbilical vein endothelial cells, VCAM-1 was reported to contain six immunoglobulin-like domains. However, subsequent cDNA clones and structural analysis of the human gene evealed an alternatively spliced seventh immunoglobulin domain. This seven domain form appears to be the predominant transcript in IL-1 activated endothelium. In this report, the cloning and nucleotide sequence of rat VCAM-1 is described.

Amino Acid Sequence↗

PubMed1992

Monocyte attachment to activated human vascular endothelium in vitro is mediated by leukocyte adhesion molecule-1 (L-selectin) under nonstatic conditions.

The receptors that mediate monocyte adhesion to cytokine-stimulated endothelial monolayers were assessed using a nonstatic (rotating) cell-attachment assay. In this system, leukocyte adhesion molecule-1 (LAM-1) (L-selectin) mediated a major portion (87 +/- 15% at 37 degrees C) of monocyte attachment to activated endothelium. mAb blocking of endothelial leukocyte adhesion molecule-1 (41% inhibition), CD18 (36%), and vascular cell adhesion molecule-1 (25%) function had lesser effects on attachment. These results suggest that LAM-1 may serve an important role in monocyte attachment to endothelium at sites of inflammation.

Antibodies, Monoclonal↗

PubMed1992

IL-4 induces adherence of human eosinophils and basophils but not neutrophils to endothelium. Association with expression of VCAM-1.

The present studies were performed to explore potentially selective mechanisms of leukocyte adhesion in an attempt to understand how preferential recruitment of eosinophils and basophils might occur during allergic and other inflammatory reactions. Stimulation of human vascular endothelial cells for 24 h with IL-4 (30 to 1,000 U/ml) induced adhesion for eosinophils (up to approximately four-fold of control) and basophils (up to approximately twofold of control) but not neutrophils (less than 125% of control). Analysis of endothelial expression of adhesion molecules by flow cytometry revealed that IL-4 treatment induced vascular cell adhesion molecule-1 (VCAM-1) expression without significantly affecting the expression of other adhesion molecules, namely endothelial-leukocyte adhesion molecule-1 (ELAM-1) or intercellular adhesion molecule-1 (ICAM-1). The concentration-response curve for IL-4-induced VCAM-1 expression paralleled that for adhesion. Endothelial cells stimulated with IL-4 expressed adhesive properties for eosinophils by 3 h; the response increased steadily during a 24-h time course study. Eosinophils and basophils adhered to plates coated with a recombinant form of VCAM-1. This adhesion was blocked with antibodies to VCAM-1 but not ELAM-1. mAb directed against either VCAM-1 or VLA-4 inhibited (by approximately 75%) the binding of eosinophils and basophils to IL-4-stimulated endothelial cells. Because VLA-4 and VCAM-1 have been demonstrated to bind to each other in other adhesion systems, these results suggest that IL-4 stimulates eosinophil and basophil adhesion by inducing endothelial cell expression of VCAM-1 which binds to eosinophil and basophil VLA-4. The lack of expression of VLA-4 on neutrophils and the failure of IL-4 to stimulate neutrophil adherence support this conclusion. It is proposed that local release of IL-4 in vivo in allergic diseases or after experimental allergen challenge may partly explain the enrichment of eosinophils and basophils (vs neutrophils) observed in these situations.

Antibodies, Monoclonal↗

PubMed1992

Nucleotide sequence of endothelin-1 cDNA from rabbit endothelial cells.

A cDNA encoding rabbit endothelin-1 (ET-1) was isolated by plaque hybridization from a rabbit inferior vena caval endothelial cell lambda gt11 cDNA library using human ET-1 cDNA as the hybridization probe. DNA sequence analysis indicates that mature 21 amino acid rabbit ET-1 is derived from a 202 amino acid precursor, via a 39 amino acid intermediate 'big' ET-1.

Amino Acid Sequence↗

PubMed1992

Interleukin-8 induces changes in human neutrophil actin conformation and distribution: relationship to inhibition of adhesion to cytokine-activated endothelium.

Interleukin-8 (IL-8) induces diverse biological responses in neutrophils, including inhibition of adhesion to cytokine-activated endothelium, which we have termed the leukocyte adhesion inhibition (LAI) effect. Pretreatment of neutrophils with cytochalasin B abolished the LAI effect of IL-8, suggesting a microfilament-dependent mechanism. Interleukin-8 induced a rapid increase (less than or equal to 15 s) in the polymerization of actin filaments in human neutrophils that was blocked by pretreatment with cytochalasin B. F-actin depolymerization occurred gradually at a rate inversely proportional to IL-8 concentration. This temporal pattern of actin polymerization-depolymerization was similar to that induced by other chemotactic factors such as C5a and N-formylmethionyl-leucyl-phenylalanine, which also exhibit a marked LAI effect, but the lipid mediators, leukotriene B4 and platelet-activating factor, lack any significant LAI effect. Scanning confocal microscopy demonstrated that neutrophil actin microfilaments undergo a dramatic rearrangement prior to detachment of the neutrophil from a surface. We suggest that the ability of IL-8 and certain other leukocyte agonists to regulate the actin polymer network of neutrophils may play an important role in adhesive interactions with the vascular endothelium.

Actins↗

PubMed1992

The distribution of fluid forces on model arterial endothelium using computational fluid dynamics.

Numerical calculations are used in conjunction with linear perturbation theory to analyze the problem of laminar flow of an incompressible fluid over a wavy surface which approximates a monolayer of vascular endothelial cells. These calculations model flow conditions in an artery very near the vessel wall at any instant in time, providing a description of the velocity field with detail that would be difficult to identify experimentally. The surface pressure and shear stress distributions are qualitatively similar for linear theory and numerical computations. However, the results diverge as the amplitude of surface undulation is increased. The shear stress gradient along the cell model surface is reduced for geometries which correspond to aligned endothelial cells (versus nonaligned geometries).

Arteries↗