Intercellular adhesion molecule-1 (ICAM-1) expression and soluble ICAM-1 (sICAM-1) production by cytokine-activated human aortic endothelial cells: a possible role for ICAM-1 and sICAM-1 in atherosclerotic aortic aneurysms.

The interactions of inflammatory cells, cytokines, and cell adhesion molecules (CAM) may be important in the pathogenesis of vascular diseases such as abdominal aortic aneurysms (AAA), in which inflammation plays a role. The aim of this study was to investigate the pathogenic role of ICAM-1, a molecule involved in leucocyte-endothelial interactions, in vascular inflammation. ELISA of human explant culture supernatants revealed a four-fold increase in sICAM-1 production by AAA (n = 9) versus normal (n = 8) aortic explants. Human aortic endothelial cell (hAEC) culture was used for further studies as an in vitro model for aortic inflammatory conditions. Tumour necrosis factor-alpha (TNF-alpha) or IL-1 beta treatment of hAEC resulted in an up to 1.8-fold significant increase in sICAM-1 production compared with resting cells. In addition, the expression of ICAM-1 on cytokine-stimulated versus resting hAEC was measured by radioimmunoassay. TNF-alpha significantly induced ICAM-1 expression on these cells. These results suggest that different forms of ICAM-1, present on or released by the activated aortic endothelium, may be involved in leucocyte adhesion to and migration into the vessel wall.     

Disturbed homeostasis of lung intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 during sepsis

Cecal ligation and puncture (CLP)-induced sepsis in mice was associated with perturbations in vascular adhesion molecules. In CLP mice, lung vascular binding of (125)I-monoclonal antibodies to intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 revealed sharp increases in binding of anti-ICAM-1 and significantly reduced binding of anti-VCAM-1. In whole lung homogenates, intense ICAM-1 up-regulation was found (both in mRNA and in protein levels) during sepsis, whereas very little increase in VCAM-1 could be measured although some increased mRNA was found. During CLP soluble VCAM-1 (sVCAM-1) and soluble ICAM-1 (sICAM-1) appeared in the serum. When mouse dermal microvascular endothelial cells (MDMECs) were incubated with serum from CLP mice, constitutive endothelial VCAM-1 fell in association with the appearance of sVCAM-1 in the supernatant fluids. Under the same conditions, ICAM-1 cell content increased in MDMECs. When MDMECs were evaluated for leukocyte adhesion, exposure to CLP serum caused increased adhesion of neutrophils and decreased adhesion of macrophages and T cells. The progressive build-up in lung myeloperoxidase after CLP was ICAM-1-dependent and independent of VLA-4 and VCAM-1. These data suggest that sepsis disturbs endothelial homeostasis, greatly favoring neutrophil adhesion in the lung microvasculature, thereby putting the lung at increased risk of injury.     

Resistance to cerebral malaria in tumor necrosis factor-alpha/beta-deficient mice is associated with a reduction of intercellular adhesion molecule-1 up-regulation and T helper type 1 response.

Tumor necrosis factor (TNF) induced by Plasmodium berghei ANKA (PbA) infection was suggested to play an important role in the development of cerebral malaria (CM). We asked whether TNF-alpha/beta double-deficient mice, which have a complete disruption of the TNF-signaling pathways, are protected from CM and what might be the possible mechanisms of protection. PbA infection induces fatal CM in wild-type mice, which die within 5 to 8 days with severe neurological signs. In contrast, TNF-alpha/beta-deficient mice are completely resistant to PbA-induced CM. As PbA-induced up-regulation of endothelial intercellular adhesion molecule (ICAM)-1 expression as well as the systemic release of nitric oxide is found only in wild-type mice, TNF is apparently central for the recruitment of mononuclear cells and microvascular damage. Mononuclear cell adhesion to the endothelium, vascular leak and, perivascular hemorrhage are found only in the brain of wild-type mice. By contrast, the development of parasitemia and anemia is independent of TNF. Resistance to CM in TNF-alpha/beta-deficient mice is associated with reduced interferon-gamma and interleukin-12 expression in the brain, in the absence of increased T helper type 2 cytokines. In conclusion, TNF apparently is required for PbA-induced endothelial ICAM-1 up-regulation and subsequent microvascular pathology resulting in fatal CM. In the absence of TNF, ICAM-1 and nitric oxide up-regulation are reduced, and PbA infection fails to cause fatal CM.     

Intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 cooperatively contribute to the cutaneous Arthus reaction

Immune complex (IC)-induced inflammation is mediated by inflammatory cell infiltration, a process that is highly regulated by expression of multiple adhesion molecules. The roles and interactions of ICAM-1 and VCAM-1, the major regulators of leukocyte firm adhesion, were examined in the cutaneous reverse-passive Arthus reaction using ICAM-1-deficient (ICAM-1-/-) mice and blocking mAb against VCAM-1. Within 8 h, IC challenge of wild-type mice induced edema, hemorrhage, interstitial accumulation of neutrophils and mast cells, as well as production of TNF-alpha and IL-6. All of these inflammatory parameters were reduced significantly in ICAM-1-/- mice. The blockade of VCAM-1 in wild-type mice did not affect any inflammatory parameters. In contrast, ICAM-1-/- mice treated with anti-VCAM-1 mAb had significantly reduced edema, hemorrhage, and neutrophil infiltration. Furthermore, VCAM-1 blockade in ICAM-1-/- mice suppressed cutaneous TNF-alpha and IL-6 production. Thus, VCAM-1 plays a complementary role to ICAM-1 in the cutaneous Arthus reaction by regulating leukocyte accumulation and proinflammatory cytokine production.     

Elevation of serum soluble intercellular adhesion molecule-1 (sICAM-1) and sE-selectin levels in bronchial asthma.

Adhesion molecules such as ICAM-1 and E-selectin have been shown to play important roles in the production of allergic inflammation. In the present study, we measured serum soluble ICAM-1 (sICAM-1) and soluble E-selectin (sE-selectin) levels by ELISA in 42 patients with bronchial asthma (22 atopic and 20 non-atopic) during asthma attacks and in stable conditions in order to assess the state of ICAM-1 and E-selectin in allergic inflammation. Both serum sICAM-1 levels and serum sE-selectin levels in sera obtained during bronchial asthma attacks were higher than those in sera obtained in stable conditions. These findings were observed regardless of atopic status. To examine the regulatory mechanism in the elevation of serum sICAM-1 and sE-selectin levels, serum tumour necrosis factor-alpha (TNF-alpha) levels were measured by ELISA. TNF-alpha levels in sera obtained during bronchial asthma attacks were higher than those in sera obtained in stable conditions. There was a correlation between the nature of change in serum TNF-alpha levels and the nature of change in serum sICAM-1 levels or serum sE-selectin levels, though serum TNF-alpha levels did not correlate with serum sICAM-1 levels or serum sE-selectin levels. These results suggest that higher levels of sICAM-1 and sE-selectin during asthma attacks may reflect the up-regulation of ICAM-1 and E-selectin expression in allergic inflammation, and that the soluble form of these adhesion molecules may be useful markers for the presence of allergic inflammation. TNF-alpha is shown to enhance the expression and release of ICAM-1 and E-selectin in vitro, however; the regulatory mechanism in the elevation of serum sICAM-1 and sE-selectin levels remains to be clarified.     

Expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in acute and chronic inflammation

The objective of this study was to quantify, in vivo, constitutive and tumor necrosis factor alpha (TNF-alpha)-enhanced expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in different tissues from healthy wild-type mice (C57BL/6) as well as interleukin-10 (IL-10)-deficient mice with and without active colitis. Using the dual radiolabel monoclonal antibody technique, we found substantial constitutive expression of MAdCAM-1 in the intestine, colon, and mesenteric lymph nodes. MAdCAM-1 expression in these tissues was significantly enhanced, in a time-dependent manner, by systemic administration of TNF-alpha. Maximum surface expression was observed at 18 h after TNF-alpha administration and remained significantly elevated at 48 h post-TNF-alpha injection. No significant constitutive nor TNF-alpha-induced expression of MAdCAM-1 was detected in skeletal muscle, brain, or heart. In IL-10-deficient (IL-10 k/o) mice with no clinical or histological evidence of colitis, constitutive and TNF-alpha-induced expression of MAdCAM-1 in the intestine, cecum, and colon was not different from those values obtained with healthy wild-type controls. IL-10-deficient mice with active colitis exhibited a four- to fivefold greater expression of MAdCAM-1 in the cecum and colon compared with their healthy controls or to IL-10 k/o mice with no evidence of colitis. Taken together, these data demonstrate that TNF-alpha enhances surface expression of MAdCAM-1 in intestinal and colonic tissues to the same extent in both wild-type and IL-10 k/o mice with no colonic inflammation, whereas IL-10 k/o mice with active colitis exhibited a profound up-regulation of MAdCAM-1 in the colon.     

Soluble ICAM-1 and VCAM-1 as markers of endothelial activation

Activated endothelium releases the soluble adhesion molecules vascular cell adhesion molecule-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1). Measurement of fluid-phase adhesion molecules is therefore used to quantify endothelial activation, but it is unclear which is the better marker. The aims of the study were to compare the relationships between mRNA, surface and total expression and released VCAM-1 and ICAM-1 in endothelial cell cultures during activation, and to compare human umbilical vein endothelial cells (HUVEC) with the microvascular cell line HMEC-1. sVCAM-1 better represented mRNA and surface expression changes in HUVEC undergoing endotoxin stimulation than did sICAM-1. Very little VCAM-1 was released from endotoxin-stimulated HMEC-1, and sICAM-1 seemed a better activation marker for these cells. During incubation of HUVEC in media with glucose concentrations of 5.6, 10.6 or 20.6 m m , VCAM-1 was released to the media in a dose-dependent way without changes in surface expression. ICAM-1 was not influenced by the glucose concentration. There are situations when VCAM-1 concentrations in the media do not mirror the surface expression on HUVEC in culture, indicating that measurements of soluble adhesion molecules may not necessarily be representative of the conditions on the cell surface. Endothelium from different locations showed varying responses with respect to VCAM-1 and ICAM-1 liberation upon endotoxin stimulation. Thus, both sVCAM-1 and sICAM-1 should be quantified in clinical studies of endothelial activation until their characteristics are better clarified.     

Intercellular adhesion molecule 1 and tumor necrosis factor alpha in asthma and persistent allergic rhinitis: relationship with disease severity.

BACKGROUND: Tumor necrosis factor alpha (TNF-alpha) is involved in the up-regulation of intercellular adhesion molecule 1 (ICAM-1). Allergic rhinitis is often associated with bronchial hyperresponsiveness. OBJECTIVE: We investigated the relationship between allergic airway disease severity and serum concentrations of soluble ICAM-1 (sICAM-1) and TNF-alpha and nasal expression of ICAM-1. METHODS: Serum concentrations of TNF-alpha and sICAM-1 were investigated in 85 adults with persistent rhinitis and 90 patients with asthma. Seventy patients with rhinitis were challenged with methacholine. Nasal biopsy for ICAM-1 expression was performed in 6 patients with moderate-severe rhinitis and in 6 patients with mild rhinitis. RESULTS: In patients with rhinitis, serum sICAM-1 concentrations were as follows: group without bronchial hyperresponsiveness (n = 29), 206.85 ng/mL; group with bronchial hyperresponsiveness but without asthma symptoms (n = 20), 233.39 ng/mL; and group with newly recognized asthma (n = 21), 260.06 ng/mL. The sICAM-1 level was significantly lower in patients with mild rhinitis (216.21 ng/mL) than in patients with moderate-severe rhinitis (244.08 ng/mL). Nasal ICAM-1 expression was significantly higher in the moderate-severe rhinitis group than in the mild rhinitis group. In patients with asthma, serum concentrations of sICAM-1 were as follows: patients with mild asthma, 272.8 ng/mL; patients with moderate asthma, 340.16 ng/mL; patients with severe asthma without oral corticosteroids therapy, 426.74 ng/mL; and patients with severe asthma with oral corticosteroids therapy, 314 ng/mL. The serum TNF-alphaa concentration differed between patients with rhinitis (n = 15) (1.065 pg/mL) and patients with asthma (n = 12) (3.46 pg/mL). Among patients with asthma, TNF-alpha concentrations were similar in all groups classified according to the disease severity. CONCLUSIONS: sICAM and ICAM-1 expression correlates with airways diseases severity.     

E/P-selectin-deficient mice: an optimal mutation for abrogating antigen but not tumor necrosis factor-alpha-induced immune responses

Leukocyte recruitment in cremaster microcirculation was visualized by intravital microscopy, either in ovalbumin sensitized and challenged animals, or in response to TNF-alpha. In antigen-challenged mice a significant increase in leukocyte rolling (approximately 50 to 200-300 cells/min) and adhesion (2 to 15-20 cells/100 microm), and a very dramatic increase in emigration ( approximately 1 to >40 cells/field) was observed over 24 h. Although rolling and adhesion was dramatically blunted in P-selectin- or P selectin/ICAM-1-deficient mice, emigrated cell number was similar to that observed in wild-type mice. Leukocyte rolling, adhesion and emigration was almost entirely abrogated over 24 h in E/P-selectin-deficient mice, demonstrating that antigen-induced leukocyte recruitment can be entirely disrupted in the absence of both endothelial selectins. However, E/P-selectin-deficient mice were able to recruit leukocytes at 24 h after TNF-alpha challenge. Rolling 24 h post-TNF-alpha in E/P-selectin-deficient mice was not inhibitable with anti-L-selectin antibody, suggesting an entirely selectin-independent pathway of rolling. We identified this pathway to be alpha (4)-integrin dependent and demonstrated that VCAM-1 expression was increased only in mice challenged with TNF-alpha. These data demonstrate that, in vivo, sufficient amounts of TNF-alpha can recruit leukocytes independently of selectins, whereas inhibition of endothelial selectins is the optimal intervention in reducing the immune response to antigen.     

Effect of cytokine-induced soluble ICAM-1 from human synovial cells on synovial cell-lymphocyte adhesion.

The present study was designed to establish (i) the effects of cytokines on soluble ICAM-1 (sICAM-1) production by human synovial cells (SC) and ICAM-1 expression on these cells, and (ii) the effects of sICAM-1 on lymphocyte-SC adhesion. sICAM-1 production was enhanced in parallel with ICAM-1 expression by IL-1 beta, TNF-alpha and IFN-gamma. IL-4 showed no effects on ICAM-1 expression. In contrast with the transient elevation of cell-associated ICAM-1 by IL-1 beta, which peaked 36 h after stimulation and declined thereafter, sICAM-1 continued to accumulate in culture supernatants even after 48 h. Purified sICAM-1 was obtained from a 48 h culture synovial cell supernatant by affinity chromatography using ICAM-1 monoclonal antibody. The purified sICAM-1 significantly inhibited adhesion of lymphocytes and monocytes to cytokine-stimulated synovial cells. These results suggest that sICAM-1 may modulate chronic synovitis by inhibiting ICAM-1-mediated cell-to-cell adhesion.     

Expression of leucocyte–endothelial adhesion molecules is limited to intercellular adhesion molecule-1 (ICAM-1) in the lung of pneumoconiotic patients: role of tumour necrosis factor-alpha (TNF-α)

Coal workers' pneumoconiosis (CWP) is characterized by a chronic inflammatory lung reaction associated with macrophage accumulation in alveolar spaces. In this study, we investigated in CWP the implication of adhesion molecules such as E-selectin, ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1) and the role of TNF-α which is one of the cytokines inducing their expression. Adhesion molecule expression was analysed by immunohistochemistry on lung biopsies from patients with CWP and from healthy subjects. In parallel, soluble adhesion molecules were detected in bronchoalveolar lavage fluids (BALF) from patients by specific ELISA. The involvement of TNF in the induction of these adhesion molecules was measured (i) by immunohistochemistry on sections from lung fragments, and (ii) by evaluating in vitro the expression of adhesion molecules on endothelial cells and on alveolar epithelial cells in the presence of alveolar macrophage supernatants. In control subjects, a weak staining of ICAM-1 was detected only in alveolar walls, while E-selectin and VCAM-1 were undetectable. In pneumoconiotic patients, ICAM-1 was expressed at a high level by endothelium, by alveolar and bronchial epithelial cells and by alveolar macrophages. E-selectin and VCAM-1 expression remained undetectable. Measurement of soluble adhesion molecule showed that only the concentration of sICAM-1 was significantly increased in BALF from patients with CWP compared with controls. The involvement of TNF in this ICAM-1 expression was shown by the in vitro effect of alveolar macrophage supernatants on adhesion molecule expresssion by endothelial cells and epithelial cells (this effect was neutralized by anti-TNF antibodies) and by the increased production of TNF in the lung of pneumoconiotic patients. These data provide evidence for the involvement of ICAM-1, induced at least in part by alveolar macrophage-derived TNF, in the development of the inflammatory reaction in CWP.     

Endothelial NOS is required for SDF-1alpha/CXCR4-mediated peripheral endothelial adhesion of c-kit+ bone marrow stem cells

In the era of intravascular approaches for regenerative cell therapy, the underlying mechanisms of stem cell migration to non-marrow tissue have not been clarified. We hypothesized that next to a local inflammatory response implying adhesion molecule expression, endothelial nitric oxide synthase (eNOS)-dependent signaling is required for stromal- cell-derived factor-1 alpha (SDF-1alpha)-induced adhesion of c-kit+ cells to the vascular endothelium. SDF-1alpha/tumor necrosis factor-alpha (TNF-alpha)-induced c-kit+-cell shape change and migration capacity was studied in vitro using immunohistochemistry and Boyden chamber assays. In vivo interaction of c-kit+ cells from bone marrow with the endothelium in response to SDF-1alpha/TNF-alpha stimulation was visualized in the cremaster muscle microcirculation of wild-type (WT) and eNOS (-/-) mice using intravital fluorescence microscopy. In addition, NOS activity was inhibited with N-nitro-L-arginine-methylester-hydrochloride in WT mice. To reveal c-kit+-specific adhesion behavior, endogenous leukocytes (EL) and c-kit+ cells from peripheral blood served as control. Moreover, intercellular adhesion molecule-1 (ICAM-1) and CXCR4 were blocked systemically to determine their role in inflammation-related c-kit+-cell adhesion. In vitro, SDF-1alpha enhanced c-kit+-cell migration. In vivo, SDF-1alpha alone triggered endothelial rolling-not firm adherence-of c-kit+ cells in WT mice. While TNF-alpha alone had little effect on adhesion of c-kit+ cells, it induced maximum endothelial EL adherence. However, after combined treatment with SDF-1alpha+TNF-alpha, endothelial adhesion of c-kit+ cells increased independent of their origin, while EL adhesion was not further incremented. Systemic treatment with anti-ICAM-1 and anti-CXCR4-monoclonal antibody completely abolished endothelial c-kit+-cell adhesion. In N-nitro-L-arginine-methylester-hydrochloride-treated WT mice as well as in eNOS (-/-) mice, firm endothelial adhesion of c-kit+ cells was entirely abrogated, while EL adhesion was significantly increased. The chemokine SDF-1alpha mediates firm adhesion c-kit+ cells only in the presence of TNF-alpha stimulation via an ICAM-1- and CXCR4-dependent mechanism. The presence of eNOS appears to be a crucial and specific factor for firm c-kit+-cell adhesion to the vascular endothelium.     

Modulation of adhesion molecule expression on endothelial cells after induction by lipopolysaccharide-stimulated whole blood

The relative contribution of the pro-inflammatory cytokines tumour necrosis factor (TNF)-alpha and interleukin (IL)-1 beta and the lipopolysaccharide (LPS)-induced pathways that result in endothelial activation during sepsis are not fully understood. We have examined the effects of plasma obtained from LPS-treated human whole blood on the expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1) on human endothelial cells. Stimulation of blood with 10 pg/ml of LPS is sufficient to produce plasma that induces E-selectin and ICAM-1 expression, while direct induction by LPS alone requires a 100-fold higher concentration. Characteristics for the plasma-induced adhesion molecule expression were similar to the LPS-induced production of TNF-alpha and IL-1 beta in blood. A complete inhibition of E-selectin and ICAM-1 expression was observed when antibodies against TNF-alpha and IL-1 beta were added to plasma prior to the incubation to endothelial cultures. Significant inhibition was even observed if antibodies were added to the cultures up until 3 h after LPS-conditioned plasma. The plasma-induced adhesion molecule response could also be prevented with inhibitors of nuclear factor (NF)-kappaB, such as pyrollidine dithiocarbamate. These findings emphasize the central role of TNF-alpha and IL-1 beta in LPS-induced endothelial activation and suggest that simultaneous neutralization of these cytokines or their common pathways may, even after the initial stimulus, prevent endothelial response during sepsis.     

Evidence of vascular damage in dengue disease: demonstration of high levels of soluble cell adhesion molecules and circulating endothelial cells.

Clinical evidence suggests that vascular damage plays a key role in the pathophysiology of dengue hemorrhagic fever (DHF). In this study, the authors tested this hypothesis by examining the levels of soluble intercellular adhesion molecule and vascular cell adhesion molecule (sICAM-1 and sVCAM-1), and the presence of circulating endothelial cells (CECs), as evidence of vascular damage, in peripheral blood from DHF patients (n=13). A significant increase in plasma levels of sICAM-1 (n=12) and sVCAM-1 (n=13) was detected by enzyme-linked immunosorbent assay (ELISA) in DHF patients, compared with healthy individuals. Increased numbers of CECs, as detected by the expression of endothelial cell markers (ICAM-1, platelet cell adhesion molecule [PCAM]-1, and CD36) with flow cytometry, were observed in DHF patients (n=4), compared to healthy subjects. The high levels of sICAM-1 and sVCAM-1, together with the presence of CECs in DHF patients, provide further evidence of endothelium damage and activation in DHF patients.     

The role of ICAM-1 molecule in the migration of Langerhans cells in the skin and regional lymph node

ICAM-1 (CD54) plays an important role in the cell-cell interaction and migration of leukocytes. Previous studies have shown that ICAM-1 is involved in inflammatory reactions and that a defect in ICAM-1 gene inhibits allergic contact hypersensitivity. This study indicates that the migration of hapten presenting Langerhans cells into the regional lymph nodes was significantly reduced in ICAM-1-deficient mice compared to wild-type C57BL/6 mice. The reduced number of dendritic cells in regional lymph nodes did not result from abnormal migration of Langerhans cells into the skin of ICAM-1-deficient mice. The concentration and distribution of Langerhans cells in the na?ve skin of ICAM-1-deficient mice was equal to that of wild-type mice. Following hapten sensitization, Langerhans cell migration out of the skin and recruitment of fresh Langerhans cells back to the epidermis was not affected in ICAM-1-deficient mice. Further experiments demonstrated that ICAM-1 deficiency on lymphatic endothelium rather than on dendritic cells was responsible for the reduced migration of Langerhans cells into draining lymph nodes. This study indicates that ICAM-1 regulates the migration of dendritic cells into regional lymph nodes but not into or out of the skin.     

Expression of ICAM-1, VCAM-1, E-selectin and TNF-alpha on the endothelium of femoral and iliac arteries in thromboangiitis obliterans

Immunohistochemical light and electron microscopical analysis of surgical biopsies obtained from femoral and iliac arteries of patients with thromboangiitis obliterans (TAO) were performed to investigate the presence of tumour necrosis factor-alpha (TNF-alpha) and expression of the endothelial cell adhesion molecules intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin. Expression of ICAM-1, VCAM-1 and E-selectin was increased on endothelium and some inflammatory cells in the thickened intima in all TAO patients. Ultrastructural immunohistochemistry revealed contacts between mononuclear blood cells and ICAM-1-, and E-selectin-positive endothelial cells. These endothelial cells showed morphological signs of activation. The present data indicate that endothelial cells are activated in TAO and that vascular lesions are associated with TNF-alpha secretion by tissue-infiltrating inflammatory cells, ICAM-1-, VCAM-1- and E-selectin expression on endothelial cells and leukocyte adhesion via their ligands. The preferential expression of inducible adhesion molecules in microvessels and mononuclear inflammatory cells suggests that angiogenesis contributes to the persistence of the inflammatory process in TAO.     

Systemic endothelial activation occurs in both mild and severe malaria. Correlating dermal microvascular endothelial cell phenotype and soluble cell adhesion molecules with disease severity.

Fatal Plasmodium falciparum malaria is accompanied by systemic endothelial activation. To study endothelial activation directly during malaria and sepsis in vivo, the expression of cell adhesion molecules on dermal microvascular endothelium was examined in skin biopsies and correlated with plasma levels of soluble (circulating) ICAM-1, E-selectin, and VCAM-1 and the cytokine tumor necrosis factor (TNF)-alpha. Skin biopsies were obtained from 61 cases of severe malaria, 42 cases of uncomplicated malaria, 10 cases of severe systemic sepsis, and 17 uninfected controls. Systemic endothelial activation, represented by the up-regulation of inducible cell adhesion molecules (CAMs) on endothelium and increased levels of soluble CAMs (sCAMs), were seen in both severe and uncomplicated malaria and sepsis when compared with uninfected controls. Plasma levels of sICAM-1, sVCAM-1, and sE-selectin correlated positively with the severity of malaria whereas TNF-alpha was raised nonspecifically in malaria and sepsis. Immunohistochemical evidence of endothelial activation in skin biopsies did not correlate with sCAM levels or disease severity. This indicates a background of systemic endothelial activation, which occurs in both mild and severe malaria and sepsis. The levels of sCAMs in malaria are thus not an accurate reflection of endothelial cell expression of CAMs in a particular vascular bed, and other factors must influence their levels during disease.     

Tissue inhibitor of metalloproteinase-1 deficiency amplifies acute lung injury in bleomycin-exposed mice

Bleomycin-induced lung injury triggers a profound and durable increase in tissue inhibitor of metalloproteinase (TIMP)-1 expression, suggesting a potential role for this antiproteinase in the regulation of lung inflammation and fibrosis. TIMP-1 protein induction is spatially restricted to areas of lung injury as determined by immunohistochemistry. Using TIMP-1 null mutation mice, we demonstrate that TIMP-1 deficiency amplifies acute lung injury as determined by exaggerated pulmonary neutrophilia, hemorrhage, and vascular permeability compared with wild-type littermates after bleomycin exposure. The augmented pulmonary neutrophilia observed in TIMP-1-deficient animals was not found in similarly treated TIMP-2-deficient mice. Using TIMP-1 bone marrow (BM) chimeric mice, we observed that the TIMP-1-deficient phenotype was abolished in wild-type recipients of TIMP-1-deficient BM but not in TIMP-1-deficient recipients of wild-type BM. Acute lung injury in TIMP-1-deficient mice was accompanied by exaggerated gelatinase-B activity in the alveolar compartment. TIMP-1 deficiency did not alter neutrophil chemotactic factor accumulation in the injured lung nor neutrophil migration in response to chemotactic stimuli in vivo or in vitro. Moreover, TIMP-1 deficiency did not modify collagen accumulation after bleomycin injury. Our results provide direct evidence that TIMP-1 contributes significantly to the regulation of acute lung injury, functioning to limit inflammation and lung permeability.     

Production of soluble ICAM-1 from human endothelial cells induced by IL-1β and TNF-α

The present study was designed to establish the effects of cytokines on soluble ICAM-1 (sICAM-1) production by human endothelial cells (EC) and ICAM-1 expression on these cells and the effects of purified sICAM-1 on lympho-cyte-EC adhesion. Expression of ICAM-1 and production of sICAM-1 were measured by a specific ELISA method. ICAM-1 expression was enhanced by IL-1β, TNF-α, and most effectively by IFN-γ. IL-4, IL-6, M-CSF, or GM-CSF showed no effects on ICAM-1 expression. IL-4 (100 units/ml) or IL-6(100 units/ml) abolished the enhancing effect of IL-1β, while TNF-α (1, 10, 100 units/ml) synergized with IL-1β to promote ICAM-1 expression in EC. In contrast with the transient increase of cell-associated ICAM-1 expression after activiation by IL-1β, which peaked 40 h poststimulation and declined thereafter, sICAM-1 continued to accumulate in culture supernatants even after 48 h poststimulation in IL-1β-stimulated EC. IL-1β treatment resulted in an increase in adhesion. sICAM-1, purified from cell-free supernatants obtained after a 48-h culture of EC in IL-1β by affinity chromatography using monoclonal ICAM-1 antibody coupled to Sepharose beads, significantly inhibited lymphocyte EC adhesion. Preincubation of lymphocytes with conditioned medium of EC cultured with 100 units/ml IL-1β for 48 h, which contained a considerable amount of sICAM-1, resulted in a significant inhibition of lymphocyte adhesion to IL-1β-stimulated EC. These results suggest that there is a cumulative increase in sICAM-1 concentration in the vicinity of cytokine-stimulated EC and that this sICAM-1 modulates ICAM-1-mediated cell to cell interaction.