Soluble L-selectin is present in human plasma at high levels and retains functional activity

Elevated serum L-selectin levels and decreased L-selectin expression on CD8(+) lymphocytes in systemic sclerosis

L-selectin is expressed on most circulating leucocytes and mediates leucocyte rolling on endothelium at sites of inflammation. Following rolling or activation of leucocytes, cell surface L-selectin is released as soluble L-selectin (sL-selectin). In the present study, we assessed serum levels of sL-selectin by ELISA and blood leucocyte L-selectin expression by flow cytometry in patients with systemic sclerosis (SSc). Serum levels of sL-selectin in patients with SSc (n = 51) were significantly higher than in normal controls (n = 30) while sL-selectin levels were similar for systemic lupus erythematosus patients (n = 20) and normal controls. Furthermore, SSc patients with elevated sL-selectin levels had inflammatory joint involvement, pitting scar/ulcers, and diffuse pigmentation more frequently than those with normal sL-selectin levels. The frequency of L-selectin(+) population among CD8(+) T cells was significantly decreased in SSc patients (n = 30) compared with normal controls (n = 20), while that among CD4(+) T cells, B cells, monocytes, and neutrophils was similar for SSc patients and normal controls. These suggest that elevated sL-selectin levels and decreased frequency of L-selectin+ CD8(+) T cells in SSc patients may be involved in inflammation associated with SSc.

Local inflammatory responses following bronchial endotoxin instillation in humans

To study local lung inflammation, 34 subjects had endotoxin (1-4 ng/kg) instilled into a lung segment and saline instilled into a contralateral segment followed by bronchoalveolar lavage (BAL) at 2 h, 6 h, 24 h, or 48 h. Endotoxin instillation resulted in a focal inflammatory response with a distinct time course. An early phase (2 h to 6 h) revealed an increase in neutrophils (p = 0.0001) with elevated cytokines (tumor necrosis factor [TNF]-alpha, TNF receptors [TNFR], interleukin [IL]-1beta, IL-1 receptor antagonist, IL-6, granulocyte-colony-stimulating factor [G-CSF], all p < or = 0.002, but no change in IL-10) and chemokines (IL-8, epithelial neutrophil activating protein-78, monocyte chemotactic protein-1, macrophage inflammatory protein [MIP]-1alpha, MIP-1beta, all p < or = 0.001, but no change in growth-regulated peptide-alpha). A later phase (24 h to 48 h) showed increased neutrophils, macrophages, monocytes, and lymphocytes (all p < or = 0.02), and a return to basal levels of most mediators. Elevated levels of inflammatory markers (TNFR(1), TNFR(2), L-selectin, lactoferrin, and myeloperoxidase) persisted in the BAL at 48 h (p < or = 0.001). Increased permeability to albumin occurred throughout both phases (p = 0.001). Blood C-reactive protein, serum amyloid A, IL-6, IL-1ra, G-CSF, but not TNF-alpha increased by 8 h (all p < or = 0.008). The local pulmonary inflammatory response to endotoxin has a unique qualitative and temporal profile of inflammation compared with previous reports of intravenous endotoxin challenges. This model provides a means to investigate factors that initiate, amplify, and resolve local lung inflammation.

Functions of selectins

The selectins are cell surface lectins that have evolved to mediate the adhesion of white blood cells to endothelial cells and platelets under flow. They recognize fucosylated, sialylated and in some cases sulfated ligands expressed on scaffold glycoproteins serving as functional counter-receptors. Selectins are regulated at the transcriptional level, through proteolytic processing, through cellular sorting, and through regulated expression of glycosyl-transferases responsible for the formation of functional ligands. The selectins are physiologically important in inflammation, lymphocyte homing, immunological responses, and homing of bone marrow stem cells. They play a role in atherosclerosis, ischemia-reperfusion injury, inflammatory diseases, and metastatic spreading of some cancers.

Antibody binding to a conformation-dependent epitope induces L-selectin association with the detergent-resistant cytoskeleton

L-Selectin mediates leukocyte rolling on endothelium and immobilized leukocytes. Its regulation has been the subject of much study, and the conformation of the molecule may play an important role in its function. Here we report that a conformational change in L-selectin, induced by an anti-lectin domain mAb (LAM1-116) and recognized by another mAb directed to a conserved epitope on L-selectin (EL-246), predisposed L-selectin to cytoskeletal association. This effect was due to direct binding of the mAb, not to overt signaling events, and was specific to LAM1-116. Nineteen other anti-L-selectin mAbs directed against the lectin, epidermal growth factor, or short consensus repeat domains lacked this activity. The induced conformational change occurred at 37 degrees C, at 4 degrees C, in the presence of sodium azide and tyrosine kinase inhibitors herbimycin A and genistein, and with soluble detergent-extracted L-selectin. In the presence of LAM1-116, EL-246 induced cytoskeletal association of L-selectin in the absence of Ab cross-linking as visualized by L-selectin staining after low dose detergent treatment of the cells. We propose that the conformational change described herein regulates L-selectin-mediated events by exposing a high avidity binding site that, when engaged, triggers association of L-selectin with the cytoskeleton, which may lead to stronger tethers with physiological ligands.

Adhesion molecules in different treatments of acute myocardial infarction

BACKGROUND

Tissue damage after ischemia and reperfusion involves leukocyte endothelial interactions mediated by cell adhesion molecules. This study was designed to determine the time course of soluble adhesion molecules in patients with acute myocardial infarction after attempted reperfusion by thrombolysis with tissue plasminogen activator (tPA) or streptokinase (SK), or percutaneous transluminal coronary angioplasty (PTCA).

METHODS

In 3 x 10 randomly selected patients with acute myocardial infarction undergoing thrombolysis with tPA or SK, or treated with PTCA, plasma concentrations of soluble L-selectin, P-selectin, E-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and platelet endothelial cell adhesion molecule-1 (PECAM-1) were measured by enzyme-linked immunosorbent assay, 30 min and 1, 2, 4, 8, 12 and 24 hours after intervention.

RESULTS

After thrombolysis with tPA, soluble L-selectin concentrations were persistently depressed and soluble PECAM-1 concentrations were elevated, compared with controls, SK and PTCA. While soluble VCAM-1 concentrations did not differ within the first hours after interventions between the three groups, soluble VCAM-1 rose by 24 hours after tPA thrombolysis but did not increase after SK and PTCA treatment. Soluble ICAM-1 concentrations were consistently elevated after PTCA compared with controls and thrombolysed patients. Soluble E-selectin was depressed after tPA thrombolysis and PTCA in comparison with controls, while the SK group showed an increase throughout the observation period. Soluble P-selectin was increased after PTCA and SK lysis up to 8 hours after treatment compared with controls, but no significant differences could be found between treatment groups.

CONCLUSION

Adhesion molecules mediating leukocyte endothelial interactions are altered subsequent to postischemic reperfusion and by treatment with thrombolytic agents and angioplasty. The clinical relevance of these biological changes remains to be determined.

Platelet and leukocyte deactivation after intracoronary stent placement in patients receiving combined antiplatelet therapy

Activated platelets and leukocytes have been demonstrated to play a role in the development of stent thrombosis, and coronary angioplasty has been shown to result in activation of platelets, leukocytes, and endothelial cells. We aimed to evaluate the effects of intracoronary stent placement and aspirin plus ticlopidine treatment on platelets, leukocytes, and endothelial cells via observing the serial changes in the circulating soluble forms of adhesion molecules in 54 patients with coronary artery disease, who had elective coronary angioplasty and stent implantation for a single lesion of the left anterior descending artery. After stent placement, intravenous heparin infusion was administered only for 24 hours, and aspirin plus ticlopidine treatment was applied for 1 month. Venous blood samples were drawn before stent placement, and repeated 24 and 48 hours after the procedure. Patients were excluded if they had had recent cardiovascular events or any illness that might influence platelet, leukocyte, and endothelial cell function. The plasma level of sL-selectin was significantly decreased 48 hours after coronary stenting (636+/-110 ng/mL vs 567+/-93 ng/mL; P = 0.001, respectively). Likewise, the plasma level of sP-selectin was also decreased significantly 48 hours after the procedure (260+/-61 ng/mL vs 233+/-83 ng/mL, P = 0.01). The sE-selectin level was found to be significantly increased 24 hours (31+/-9 ng/mL vs 39+/-12 ng/mL, P = 0.0001) and 48hours(31+/-9 ng/mL vs 42+/-15 ng/mL, P = 0.001) after coronary stenting. The results of our study suggest that significant platelet and leukocyte deactivation take place in patients treated with combined antiplatelet therapy after stenting; endothelial cell activation also occurs during this treatment.

Effects of endotoxin on neutrophil-mediated I/R injury in isolated perfused rat hearts

With the use of a syngeneic model, we demonstrate that rat polymorphonuclear neutrophils (PMNs) exacerbate ischemia-reperfusion injury in the isolated rat heart. However, PMNs (19 x 10(6) cells) from lipopolysaccharide (LPS)-treated rats (LPS-PMNs; 100 mg/kg administered 7 h before exsanguination) induce less reperfusion injury in the isolated heart. Average recovery of left ventricular developed pressure after 20 min of ischemia and 60 min of reperfusion was 51 +/- 4% in hearts receiving PMNs from saline-treated control rats (saline-PMNs) versus 78 +/- 2% in hearts receiving LPS-PMNs. Ischemic hearts reperfused with LPS-PMNs recovered to the same extent as did hearts reperfused with Krebs buffer only. LPS-PMNs and saline-PMNs showed no difference in basal or phorbol ester-induced superoxide production. Whereas twice the number of LPS-PMNs was positive for nitroblue tetrazolium, the percent positive for L-selectin, a receptor integral in PMN-adhesion to endothelium, was 50% less in LPS-PMNs than in controls. After reperfusion, three-fourths of the saline-PMNs remained within the hearts, whereas only one-fourth of LPS-PMNs were trapped. These data suggest that PMNs from LPS-treated rats do not exacerbate ischemia-reperfusion injury as do control PMNs, possibly, due to impaired PMN adhesion to endothelium as a result of decreased L-selectin receptors.

IgE-mediated downregulation of L-selectin (CD62L) on lymphocytes from asthmatic patients

BACKGROUND

L-selectin (CD62L) mediates the binding of lymphocytes to high endothelial venules of peripheral lymph nodes and is also involved in leukocyte attachment to the endothelium at sites of inflammation. Although it has been demonstrated that L-selectin is shed after lymphocyte activation, it is unknown whether the expression of L-selectin on the surface of lymphocytes can be modulated by an IgE-dependent mechanism or whether immunotherapy (IT) might affect this mechanism.

METHODS

One group of adult allergic asthmatic patients had received IT for the previous 3 years. Another similar group was not treated with IT. We challenged peripheral blood lymphocytes from both groups of asthmatic patients in vitro with an anti-IgE antibody (Ab). Expression of L-selectin on the lymphocyte surface was analyzed by flow cytometry, and the levels of soluble L-selectin (sL-selectin) on culture supernatant by ELISA.

RESULTS

L-selectin was downregulated from the surface of lymphocytes in a time- and anti-IgE antibody dose-dependent manner (with a concomitant upregulation of shed L-selectin in the supernatant). When lymphocytes from non-IT asthmatic patients were cultivated with anti-IgE Ab, a statistically significantly greater CD62L downmodulation on the lymphocyte surface was observed compared with lymphocytes from the healthy group (P<0.002) and from the IT-asthmatic group (P<0.001). When lymphocytes from non-IT asthmatic patients were cultivated with anti-IgE Ab, a significantly greater sL-selectin level in the culture supernatant was observed compared with lymphocytes from the healthy group (P<0.001) and with lymphocytes from IT-asthmatic group (P<0.001).

CONCLUSIONS

We present evidence that the expression of L-selectin on the surface of lymphocytes can be modulated by an IgE-dependent mechanism. This mechanism can be affected by IT.

Circulating soluble adhesion molecules in ANCA-associated vasculitis

BACKGROUND

To evaluate whether changes in concentrations of soluble (s) E-selectin, sP-selectin, sL-selectin, intercellular adhesion molecule 1 (sICAM-1), and vascular cell adhesion molecule 1 (sVCAM-1) reflect disease activity in patients with ANCA-associated vasculitis and whether serum levels of these adhesion molecules are related to the degree of renal failure in patients with chronic renal failure (CRF).

SUBJECTS AND METHODS

A sandwich ELISA was used to measure these soluble adhesion molecules in (i) sera from 20 patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (10 patients with Wegener's granulomatosis (WG) and 10 patients with microscopic polyangiitis (MPA)), obtained at the time of diagnosis and during the remission period; (ii) sera from 40 patients with CRF not undergoing haemodialysis.

RESULTS

At the time of diagnosis, serum levels of sE-selectin, sICAM-1 and sVCAM-1 (88+/-42 ng/ml, 437+/-184 ng/ml, 1720+/-1174 ng/ml respectively) were significantly higher in patients with ANCA-associated vasculitis than in healthy controls (P<0.0001, P=0.002 and P=0.001 respectively). Serum sP-selectin values did not differ from those obtained in normal donors. In contrast, sL-selectin levels (940+/-349 ng/ml) were significantly lower in patients than those recorded in healthy controls (P<0.0001). A significant decrease in concentrations of sE-selectin, sP-selectin, sICAM-1, and sVCAM-1 was observed between active and remission phases (P<0.0001, P=0.002, P=0.001 and P=0.001 respectively). No significant differences were observed in sL-selectin levels between active and remission phases. sL-selectin concentrations (802+/-306 ng/ml) during the remission phase remained lower than those observed in healthy controls (P<0.0001). No correlation was observed between serum creatinine and sE-selectin, sP-selectin, sICAM-1 and sVCAM-1 in patients of the CRF group. A slight negative correlation was established between creatinine and sL-selectin concentration.

CONCLUSIONS

Increased serum levels of sE-selectin, sICAM-1, and sVCAM-1 and decreased levels of sL-selectin in active ANCA-associated vasculitis, and the normalization of sE-selectin, sICAM-1, and sVCAM-1 during the remission phase suggest that the concentration of soluble levels of these adhesion molecules reflects disease activity. The decrease in sP-selectin levels between active and inactive phases also suggest that this receptor may reflect clinical activity. The lack of correlation between serum levels of sE-selectin, sP-selectin, sICAM-1, and sVCAM-1 and the degree of renal failure in patients with CRF suggests that the mechanism of clearance of these molecules is not renal.

Soluble L-selectin at levels present in septic patients diminishes leukocyte-endothelial cell interactions in mice in vivo: a mechanism for decreased leukocyte delivery to remote sites in sepsis

OBJECTIVE

Recent in vivo studies of both septic humans and animals demonstrate that leukocyte delivery is attenuated to sites remote from the primary infection. The mechanisms for this are not entirely clear. L-selectin is integral to rolling, the first step in leukocyte recruitment to an inflammatory site. L-selectin is shed from leukocytes in sepsis, resulting in increased levels of soluble L-selectin in plasma (2.33 microg/mL). This study investigates the effects of soluble L-selectin at levels found in sepsis on leukocyte trafficking in vivo.

DESIGN

Prospective, controlled trial.

SETTING

Surgical research laboratory in a university hospital.

SUBJECTS

Swiss white male mice of 25-35 g.

INTERVENTIONS

Mice were randomized to one of three study groups: soluble L-selectin 2.33, soluble L-selectin 8.0, or albumin. Intravital microscopy was performed on postcapillary venules of 20-40 microm in diameter in the cremaster muscle of mice. Leukocyte-endothelial cell interactions (rolling, adherence, and rolling velocity) were measured pre- and post- (1, 15, 30, and 45 mins) intravenous infusion of human recombinant soluble L-selectin (2.33 and 8.0 microg/mL) or human albumin (8.0 microg/mL).

MEASUREMENTS AND MAIN RESULTS

The intravenous administration of soluble L-selectin to a systemic concentration of 2.33 microg/mL diminished rolling significantly. Soluble L-selectin at 8.0 microg/mL decreased rolling and increased rolling velocity to a greater degree. Injection of albumin did not alter leukocyte-endothelial cell interactions at any time point. No difference between groups in blood pressure, shear rate, or leukocyte counts was detected.

CONCLUSIONS

Soluble L-selectin diminishes leukocyte rolling at levels present in sepsis (2.33 microg/mL). This effect is dose dependent, and could not be explained by differences in blood pressure, shear rate, or leukocyte counts. These findings identify increased soluble L-selectin levels as one of the mechanisms for decreased leukocyte delivery and exudation to remote sites in septic patients.

Elevated serum levels of soluble L-selectin in patients with systemic sclerosis declined after intravenous injection of lipo-prostaglandin E1

To determine whether serum soluble L-selectin (sL-selectin) levels are elevated in patients with systemic sclerosis (SSc) and whether serum sL-selectin levels change after treatment with lipo-prostaglandin E1 (lipo-PGE1), serum sL-selectin levels were examined by ELISA in patients with SSc (n=24), psoriasis vulgaris (n=22), and contact dermatitis (n=9), as well as normal control subjects (n=26). In five patients with SSc, serum sL-selectin levels were examined before and after intravenous injections of lipo-PGE1. Serum sL-selectin levels were significantly increased in patients with SSc (P<0.01) than those in normal control subjects. The elevated serum sL-selectin levels in patients with SSc significantly decreased 1 day (P<0.05), 7 days (P<0.05) and 14 days (P<0.05) after starting the treatment with lipo-PGE1. These results suggest that L-selectin may be involved in the disease process in SSc, and lipo-PGE1 may alter some inflammatory events in SSc.

Drugs, inflammation and cell adhesion receptors

The cell adhesion receptors that participate in the extravasation and migration of leucocytes towards inflammatory foci mainly include the selectins and different members of the integrin and immunoglobulin superfamilies. These adhesion receptors mediate the sequential steps of leucocyte-endothelial cell interaction and, together with chemoattractant molecules (e.g., chemokines), direct the influx of inflammatory cells and define the characteristics of the cell infiltrate. Many different drugs, including non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, rheumatoid arthritis disease-modifying agents and phosphodiesterase inhibitors, interfere with the expression and/or function of cell adhesion receptors and this effect accounts for, at least in part, their anti-inflammatory activity. In recent years, novel approaches for the modulation of the cell membrane receptors involved in inflammation have been active areas in pharmaceutical research. Upgraded synthetic blocking compounds, chimeric monoclonal antibodies or improved antisense oligonucleotides represent important advances in this field. The proper development of these novel approaches, as well as other alternative strategies, will allow a better and more specific pharmacological modulation of the inflammatory phenomenon.

Serial analysis of serum and ascitic fluid levels of soluble adhesion molecules and chemokines in patients with spontaneous bacterial peritonitis

The aim of this work was the evaluation of serum and ascitic fluid levels of chemokines (IL-8, growth-regulated oncogene (Gro-alpha), and monocyte chemotactic protein-1 (MCP-1)), and of soluble adhesion molecules (P-selectin, E-selectin, L-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1)) in patients with spontaneous bacterial peritonitis (SBP). These compounds were serially analysed in serum and ascitic fluid by ELISA in patients with SBP (n = 20), non-infected cirrhotic controls (n = 12), and healthy controls (n = 15). Infected and non-infected cirrhotic patients showed significantly higher serum levels of adhesion molecules. SBP was associated with significantly higher serum and ascitic fluid levels of IL-8, Gro-alpha and ICAM-1 and with ascitic fluid concentrations of MCP-1. Significantly elevated serum levels of both ICAM-1 and VCAM-1 were detected in patient non-survivors after SBP. Thus, higher ascitic fluid levels of chemokines could be implicated in the peritoneal infiltrate in patients with SBP. Prognostic significance can be attributed to serum levels of ICAM-1 and VCAM-1 in these patients.

COX-2 inhibitors vs. NSAIDs in gastrointestinal damage and prevention

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit production of protective gastric mucosal prostaglandins and also have a direct topical irritant effect. In some patients this results in dyspepsia and development of gastroduodenal erosions and ulceration. The risk of ulcer complications, such as bleeding, perforation and death is increased approximately 4-fold in NSAID users. Patients at high risk of ulcer complications include the elderly, those taking anticoagulants, steroids and aspirin, those with a previous history of peptic ulceration and patients with concomitant serious medical problems. The interaction of NSAIDs with Helicobacter pylori (the major cause of peptic ulceration in non-NSAID users) is controversial and some studies suggest that H. pylori infection may even protect against NSAID-induced ulceration. Selective inhibitors of the inducible cyclooxygenase-2 (COX-2) enzyme spare COX-1 in the gastric mucosa and, hence, do not inhibit production of mucosal prostaglandins. COX-2-selective inhibitors are associated with a significant reduction in gastroduodenal damage compared with traditional NSAIDs. Proton pump inhibitors (PPI) are probably the best agents for healing and prevention of NSAID-induced ulcers. Preliminary studies suggest that COX-2 selective inhibitors, like traditional NSAIDs, may prevent lower gastrointestinal cancer. Further studies are needed but they may be useful in individuals at high risk of certain types of lower gastrointestinal malignancy with increased gastrointestinal tolerability and safety.

Serum soluble E- and L-selectin in the very early neonatal period

Both E- and L-selectin are cell adhesion molecules. E-selectin is expressed by activated endothelial cells, whereas L-selectin by quiescent leukocytes and is rapidly cleaved off after activation. Both selectins take part in the first step of the 'adhesion cascade', the 'rolling of leukocytes', leading to the extravasation of the white cells to the sites of inflammation, infection or damage. For this reason their soluble forms (sE- and sL-selectin, respectively), are considered early and reliable markers of the immune activation and response. Moreover, sE-selectin has been reported to be a potent angiogenic factor and a reliable marker of infection and sepsis in neonates, as well as endothelial activation, while sL-selectin of the leukocyte function and maturity. Following informed maternal consent, we evaluated prospectively by ELISA, sE- and sL-selectin in the serum of 40 (19 females, 21 males), healthy, term, infection-free neonates, on the second and fifth day of life, and compared them with the respective values in 20 healthy adults (10 females, 10 males), with the purpose of examining the pattern of their values in the early postpartum days, and to establish reference values for both selectins. Values (mean+/-S.D.) of sE-selectin both on the second (139+/-48 ng/ml) and fifth day of life (111+/-35 ng/ml) were found to be highly increased, as compared with those in controls (48+/-13 ng/ml; P<4 x 10(-11) and P<4 x 10(-10), respectively), while sL-selectin values on both the second (674+/-223 ng/ml) and the fifth day of life (684+/-221 ng/ml), were significantly lower than those in controls (938+/-181 ng/ml); P<0.0001 and P<0.0003, respectively). A significant decrease was noted in sE-selectin values, from the second to the fifth day of life (P<10(-7)), while sL-selectin values showed no significant change in the same time interval. A strong correlation was found between values on the second and the fifth day of life of both sE- and sL-selectin (r(P)=0.885 and r(P)=0.813, respectively; P<0.00001). Neonatal values of both sE- and sL-selectin on the second or on the fifth day of life, did not depend on the perinatal factors, neonatal sex, or birth weight, mode of delivery, and maternal age or parity. In conclusion, in the very early neonatal period, our findings of highly increased sE-selectin, while low sL-selectin, suggest an immune and more specifically endothelial activation and an immature and decreased leukocyte function.

Neutrophil activation in preeclampsia and isolated intrauterine growth restriction

OBJECTIVE

Neutrophils have been implicated in the pathogenesis of preeclampsia. Because preeclampsia and intrauterine growth restriction result from similar placental lesions, the aim of this study was to investigate neutrophil activation in isolated intrauterine growth restriction relative to preeclampsia and uncomplicated pregnancy. Polymorphonuclear neutrophil activation was analyzed by measuring cell surface and soluble cell adhesion molecule expressions.

STUDY DESIGN

L -Selectin (CD62L ) and CD11b surface expressions on polymorphonuclear neutrophils were analyzed in 13 women with preeclampsia, 11 women with isolated intrauterine growth restriction, and 17 age- and gestation-matched control women by means of a standardized quantitative flow cytometry assay. Serum levels of soluble L -selectin were measured by enzyme-linked immunosorbent assay.

RESULTS

Neutrophils from women with isolated intrauterine growth restriction and women with preeclampsia displayed higher levels of CD11b and lower levels of CD62L than did neutrophils from healthy pregnant women. Soluble L -selectin serum levels were significantly increased in the preeclampsia and intrauterine growth restriction groups relative to normal values. No significant difference in the levels of CD11b, CD62L, and soluble L -selectin were observed between women with isolated intrauterine growth restriction and those with preeclampsia. Leukocyte activation was not correlated with disease severity.

CONCLUSION

The observed alteration in polymorphonuclear neutrophil adhesion molecule expressions and increased serum soluble L -selectin levels are consistent with activation of peripheral blood neutrophils occurring in isolated intrauterine growth restriction in a manner similar to that seen in preeclampsia. This evidence of neutrophil activation may help to advance our understanding of the disease process in isolated intrauterine growth restriction.

Decreased expression levels of L-selectin on subsets of leucocytes and increased serum L-selectin in severe psoriasis

L-selectin is a leucocyte adhesion molecule involved in leucocyte interactions with vascular endothelial cells. Following leucocyte activation L-selectin is endoproteolytically released from the cell surface. To assess whether psoriasis vulgaris results in systemic leucocyte activation, we examined expression levels of L-selectin on subsets of peripheral blood leucocytes from patients with psoriasis (n = 25) and normal control subjects. Serum levels of soluble L-selectin were quantified by ELISA in patients with psoriasis (n = 75), pustulosis palmaris et plantaris, and contact dermatitis, as well as normal control subjects. Psoriasis severity was evaluated by psoriasis area and severity index (PASI). L-selectin expression levels on CD4+ T cells, B cells, monocytes, and neutrophils from patients with severe-type psoriasis (PASI > or = 15) was significantly decreased compared with leucocytes from normal control subjects. Furthermore, L-selectin expression on CD4+ T cells showed good inverse correlation with PASI scores. Monocyte L-selectin expression was restored when the skin lesions of psoriasis were remitted. The frequencies of L-selectin+ CD4+ T cells or L-selectin+ CD8+ T cells from patients with psoriasis were almost normal. Serum L-selectin levels in patients with severe-type psoriasis were significantly higher than those in normal control subjects. These results suggest that subsets of leucocytes may be activated in psoriasis, and that L-selectin expression levels on some leucocyte subsets, especially CD4+ T cells, tend to correlate with disease severity of psoriasis.

Down-regulation of L-selectin expression in neutrophils by nonsteroidal anti-inflammatory drugs: role of intracellular ATP concentration

L-selectin is an adhesion molecule that plays an essential role in the early events of the inflammatory response. Our group has recently described that several nonsteroidal anti-inflammatory drugs (NSAIDs) are able to induce both in vivo and in vitro the shedding of L-selectin in neutrophils through an unknown mechanism. In this work, we have studied potential mechanisms involved in the shedding of L-selectin induced by NSAIDs. This effect of NSAIDs did not involve any detectable intracellular calcium flux. Pretreatment of neutrophils either with Ro 31-8220 and H7, 2 specific inhibitors of protein kinase C (PKC), or with inhibitors of protein tyrosine kinases such as tyrphostin A25 or herbimycin A did not prevent the NSAID-mediated L-selectin shedding. However, the KD-IX-73-4, an inhibitor of L-selectin proteolysis was able to block the effect of NSAIDs on L-selectin expression. Remarkably, NSAIDs caused a variable reduction in the neutrophil intracellular ATP concentration that highly correlated with the differential ability of NSAIDs to trigger L-selectin shedding (r = 0.8, P &lt; .01). In agreement with this finding, azide plus 2-deoxy-D-glucose, 2 metabolic blockers, also induced a rapid L-selectin shedding (65% ± 8%) without affecting the neutrophil viability, activation, or expression level of other surface molecules with soluble isoforms such as CD16 and CD59. These data indicate that the maintenance of L-selectin on the neutrophil surface requires energy consumption, which suggests that L-selectin is shed in neutrophils by default. Interestingly, NSAIDs seem to cause the shedding of L-selectin, at least in part, through the reduction of the intracellular ATP concentration.

Down-regulation of L-selectin expression in neutrophils by nonsteroidal anti-inflammatory drugs: role of intracellular ATP concentration

L-selectin is an adhesion molecule that plays an essential role in the early events of the inflammatory response. Our group has recently described that several nonsteroidal anti-inflammatory drugs (NSAIDs) are able to induce both in vivo and in vitro the shedding of L-selectin in neutrophils through an unknown mechanism. In this work, we have studied potential mechanisms involved in the shedding of L-selectin induced by NSAIDs. This effect of NSAIDs did not involve any detectable intracellular calcium flux. Pretreatment of neutrophils either with Ro 31-8220 and H7, 2 specific inhibitors of protein kinase C (PKC), or with inhibitors of protein tyrosine kinases such as tyrphostin A25 or herbimycin A did not prevent the NSAID-mediated L-selectin shedding. However, the KD-IX-73-4, an inhibitor of L-selectin proteolysis was able to block the effect of NSAIDs on L-selectin expression. Remarkably, NSAIDs caused a variable reduction in the neutrophil intracellular ATP concentration that highly correlated with the differential ability of NSAIDs to trigger L-selectin shedding (r = 0.8, P < .01). In agreement with this finding, azide plus 2-deoxy-D-glucose, 2 metabolic blockers, also induced a rapid L-selectin shedding (65% ± 8%) without affecting the neutrophil viability, activation, or expression level of other surface molecules with soluble isoforms such as CD16 and CD59. These data indicate that the maintenance of L-selectin on the neutrophil surface requires energy consumption, which suggests that L-selectin is shed in neutrophils by default. Interestingly, NSAIDs seem to cause the shedding of L-selectin, at least in part, through the reduction of the intracellular ATP concentration.

Correlation of virus load and soluble L-selectin, a marker of immune activation, in pediatric HIV-1 infection

OBJECTIVE

HIV infections in children are characterized by high viral load and, in some perinatally infected newborns, delayed appearance of viral markers. Both phenomena may be related to different levels of immune activation affecting viral replication. This study was designed to investigate the relationship between immune activation and viral replication in pediatric HIV infection, and the role of pre-existent immune activation in facilitating HIV transmission to the fetus/newborn.

DESIGN

Plasma levels of soluble L-selectin (s-LS), an immune activation marker, were determined in 100 infants with perinatally transmitted HIV infection, compared with 106 age-matched HIV-exposed uninfected controls. Included in the analysis were samples from 31 HIV-infected (10 PCR+ and 21 PCR-) and 35 uninfected newborns aged < 2 days.

METHODS

To determine s-LS levels, a solid phase ELISA was performed on plasma samples of patients and controls.

RESULTS

s-LS levels in uninfected children were higher than those in normal adults. HIV-infected patients had more rapidly increasing values in the first 6 months of life compared with uninfected infants. Plasma s-LS levels correlated with HIV viral loads (r, 0.50). Among newborns in the first 2 days of life, s-LS levels were lowest in those with negative PCR tests, compared with PCR-positive or uninfected infants.

CONCLUSIONS

These results suggest that higher immune activation in children contributes to higher viral loads, and that the level of pre-existent immune activation may have a role in determining which infants have detectable virus in peripheral blood at birth.

Leukocyte and endothelial activation in a laboratory model of extracorporeal membrane oxygenation (ECMO)

An inflammatory response and a capillary leak syndrome frequently develop during the treatment of neonatal respiratory failure by extracorporeal membrane oxygenation (ECMO). The present study was performed to investigate leukocyte activation and endothelial cell dysfunction that are associated with prolonged contact of blood components with synthetic surfaces. Laboratory ECMO was performed with fresh human blood at 37 degrees C for 8 h (n = 6). Leukocyte activation was measured by L-selectin (CD62L) and CD18 integrin surface expression and by neutrophil-derived elastase release. To monitor endothelial activation, endothelial cell ICAM-1 (CD54) expression was measured in cultured endothelial cells from human umbilical veins (HUVEC) after incubation with plasma from the ECMO experiments. CD18 integrin expression was found significantly up-regulated on polymorphonuclear neutrophils and monocytes after 2-4 h of laboratory ECMO. L-selectin was reduced on both cell types during the total duration of the experiments. Soluble L-selectin (sCD62L) and total and differential leukocyte counts remained unchanged during the experiment. Neutrophil-derived elastase content was maximal after 8 h of ECMO. Plasma from the ECMO experiments did not induce ICAM-1 expression of cultured HUVEC. We conclude that prolonged contact with synthetic surfaces during ECMO activates phagocytes, which may contribute to the inflammatory response seen in ECMO-treated patients. Activated phagocytes do not accumulate in the extracorporeal system nor release humoral factors inducing ICAM-1 expression on endothelial cells.

Production of soluble CD34 by human myeloid cells

CD34, a glycophosphoprotein present in lymphohaematopoietic stem and progenitor cells, as well as in other cell types, exists in both transmembrane and intracytoplasmic forms. Transmembrane CD34 expression, which is high in the earliest haematopoietic precursors, decreases as cells mature. However, to our knowledge, there is no information on whether a decrease in transmembrane CD34 can also predict a release of the molecule from the cell membrane into the extracellular fluid. To investigate the above possibility, we studied conditions (incubation time, cell density and proliferative status) in human myeloid cells (lines KG-1a, KG-1 and cord blood-derived cells) that may cause a decrease in surface CD34 and the generation of a soluble form of the molecule. The latter, as demonstrated by Western blot analysis, adds more complexity to the proposed structural features and functional properties of CD34 in myeloid cells.

Cardiovascular disease in diabetes mellitus type 2: a potential role for novel cardiovascular risk factors

A major consequence of diabetes mellitus type 2 is the accelerated development of atherosclerosis. Assessment of conventional risk factors such as plasma lipids, lipoproteins and hypertension only partly account for the excessive risk of developing cardiovascular disease in this population. Increasing evidence has emerged suggesting that conditions associated with diabetes mellitus type 2, such as insulin resistance, hyperinsulinemia and hyperglycemia, may also play a significant role in regulating 'novel' cardiovascular risk factors. These factors and their potential roles in the development of atherosclerosis and cardiovascular events are discussed in this review.

Sialyl LewisX oligosaccharide preserves myocardial and endothelial function during cardioplegic ischemia

BACKGROUND

Neutrophil adhesion to endothelium contributes to myocardial reperfusion injury after cardiac operation. Initial neutrophil-endothelial interactions involve selectins, which bind Sialyl-LewisX on neutrophils. Blockade of selectin-mediated neutrophil-endothelial interactions with CY-1503, a synthetic analogue of Sialyl-LewisX, might reduce reperfusion injury after myocardial ischemia.

METHODS

The efficacy of CY-1503 to attenuate global myocardial reperfusion injury was assessed in isolated blood-perfused neonatal lamb hearts that had 2 hours of cold cardioplegic ischemia. CY-1503 (40 mg/L) or saline vehicle was added to blood perfusate before ischemia. Contractile function (developed pressure, dP/dt) and coronary vascular endothelial function (acetylcholine response) were assessed at base line and during reperfusion. Myocardial neutrophil accumulation was assessed by myeloperoxidase quantification.

RESULTS

Compared to controls, treatment with CY-1503 improved recovery of all indices of contractile function, preserved coronary vascular endothelial function, and reduced myocardial neutrophil accumulation.

CONCLUSIONS

In isolated neonatal lamb hearts that underwent hypothermic cardioplegic ischemia, CY-1503 administration reduced myocardial neutrophil accumulation and preserved endothelial and contractile function. Selectin blockade of leukocyte-endothelial interactions might attenuate reperfusion injury and enhance myocardial protection during cardiac surgical procedures.

Early role of neutrophil L-selectin in posttraumatic acute lung injury

OBJECTIVE

To investigate whether early numerical and functional changes in circulating neutrophils and expression of neutrophil L-selectin and soluble L-selectin are related to the subsequent development of posttraumatic acute lung injury (ALI), the systemic inflammatory response syndrome, sepsis, and organ failure.

DESIGN

Prospective study of whole blood and plasma samples to assess numerical and functional changes in circulating neutrophils and in soluble L-selectin.

SETTING

The emergency department of a university hospital.

PATIENTS

A total of 147 patients admitted to the resuscitation room after trauma were compared with 69 control subjects. Ten patients developed ALI.

LABORATORY ANALYSIS

Flow cytometry of whole blood and ELISA of plasma.

RESULTS

Total leukocyte and neutrophil counts, expression of L-selectin, and the ratio of neutrophil to plasma L-selectin increased with injury and were highest in those who developed ALI. Soluble L-selectin decreased with injury severity and was lowest in those who developed ALI.

CONCLUSIONS

Early changes in the average expression of L-selectin per cell do not correlate with the development of subsequent posttraumatic ALI. However, the development of ALI is related to the total expression of L-selectin in the neutrophil mass, and the most striking association is in those with lower concentrations of plasma L-selectin.

Soluble L-selectin and interleukin-8 in otitis media with effusion

OBJECTIVE

adhesion of leukocytes to vascular endothelium and their invasion into local tissues are important steps in inflammation. L-selectin plays a crucial role in leukocyte rolling and adhesion on endothelial cell surface. Interleukin-8 (IL-8) is a potent chemotactic substance toward neutrophils and lymphocytes-T and mediate their migration to local inflammation. The levels of soluble L-selectin (sL-selectin) and IL-8 were measured in middle ear effusions (MEE) from children with otitis media (OM) to estimate their role in pathogenesis of inflammation in middle ear.

METHODS

MEE were collected from 113 ears of 62 children during routine myringotomy. The entire specimen was diluted with phosphate-buffered saline (PBS) to 2 ml and centrifugated at 1500 rpm for 15 min to separate cellular components. Supernatants of MEE were stored frozen at -20 degrees C for sL-selectin and at -80 degrees C for IL-8 assessment. The concentration of sL-selectin and IL-8 were estimated with ELISA and compared with total protein concentration measured by Bradford assay.

RESULTS

MEEs from children with chronic mucous otitis media contained significantly higher mean concentrations of IL-8 559.4 pg/mg total protein (TP) (+/-535.6) in comparison with normal serum 17.79 pg/mg TP (+/-10.9), serous OM 40.3 pg/mg TP (+/-28.1) and purulent OM 104.4 pg/mg TP (+/-128.6). High concentration of IL-8 was found in MEE from the children with early recurrence of OMS. The levels of sL-selectin were higher in purulent effusions 77.2 ng/mg TP (+/-67.4) than those of chronic mucoid 27.6 ng/mg TP (+/-36.7) and serous OM 26.3 ng/mg TP (+/-27.1).

CONCLUSION

the results support a hypothesis that IL-8 can be responsible for prolongation of inflammatory process in middle ear, therefore long-term treatment and observation of children with the high levels of IL-8 in MEE may be necessary. Elevated level of sL-selectin in acute OM suggests the involvement of L-selectin in the acute phase of OM.

Identification of soluble forms of lectin-like oxidized LDL receptor-1

Lectin-like oxidized LDL receptor-1 (LOX-1) is a type II membrane protein belonging to the C-type lectin family molecules, which can act as a cell-surface endocytosis receptor for atherogenic oxidized LDL. In this study, we show that soluble forms of LOX-1 are present in conditioned media of cultured bovine aortic endothelial cells (BAECs) and CHO-K1 cells stably transfected with LOX-1 cDNA. Immunoblot analysis of conditioned media from TNF-alpha-activated BAECs and CHO-K1 cells stably expressing LOX-1 revealed that soluble LOX-1 has an approximate molecular mass of 35 kDa. In TNF-alpha-activated BAECs, cell-surface expression of LOX-1 precedes soluble LOX-1 production. Cell-surface biotinylation followed by immunoprecipitation and immunoblotting showed that soluble LOX-1 in cell-conditioned media is derived from LOX-1 expressed on the cell surface. Production of soluble LOX-1 was inhibited by PMSF, suggesting that PMSF-sensitive proteases may be involved in this process. Purification of soluble LOX-1 by high-performance liquid chromatography and N-terminal amino acid sequencing of soluble LOX-1 identified the 2 cleavage sites between Arg(86)-Ser(87) and Lys(89)-Ser(90), which were located in the membrane proximal extracellular domain of LOX-1. The data demonstrate that cell-surface LOX-1 can be cleaved at 2 different sites and transformed into soluble forms. Further studies may explore therapeutic and diagnostic applications of soluble LOX-1 in atherosclerotic diseases.

Soluble L-selectin and neutrophil derived oxidative stress after pacing induced myocardial ischemia in chronic stable coronary artery disease

We studied the effect of atrial pacing induced myocardial ischemia on levels of soluble L-selectin (sL-selectin) and generation of neutrophil derived reactive oxygen species (ROS) in 10 patients with coronary artery disease (CAD) and stable angina and in six individuals without CAD. Myocardial ischemia was measured metabolically by lactate sampling from the coronary sinus (CS) and arterial blood at each pacing step. Before each pacing step, at peak pacing and shortly after cessation, plasma concentrations of sL-selectin and generation of ROS using the chemiluminescence method were measured in CS and femoral artery blood. Baseline sL-selectin levels in CS samples were significantly lower in the CAD compared to the control group (547 +/- 80 vs 836 +/- 82 ng/mL, P = 0.03). At peak pacing, nine of ten patients with CAD developed myocardial ischemia (lactate extraction ratio at rest 28% +/- 7%, at peak pacing -16% +/- 6%). In these patients, luminol-enhanced chemiluminescence (CL, 0.88 +/- 0.45 vs 1.9 +/- 0.9 cpm x 10(5), P = 0.09) and levels of sL-selectin (547 +/- 80 vs 764 +/- 86 ng/mL, P = 0.03) from naive neutrophils increased significantly in CS blood suggesting a potent in vivo activation of neutrophils. In control patients, incremental pacing caused neither myocardial ischemia nor a significant change of chemiluminescence or of sL-selectin levels. In conclusion, myocardial ischemia induced by pacing tachycardia is able to activate neutrophils in patients with chronic stable coronary artery disease leading to increased generation of ROS and shedding of L-selectin into the coronary circulation.

Effects of oral L-arginine on endothelium-dependent vasodilation and markers of inflammation in healthy postmenopausal women

OBJECTIVES

We examined whether oral administration of L-arginine, the substrate for nitric oxide (NO) synthesis, increases NO bioactivity in healthy postmenopausal women.

BACKGROUND

Nitric oxide may protect arteries against atherosclerosis, as suggested by experimental studies in animals. Estrogen therapy, which has been shown to increase NO bioactivity in the vasculature of healthy postmenopausal women, is not acceptable for long-term use by many women.

METHODS

In a randomized, double-blind, crossover study, 10 postmenopausal women without additional risk factors for atherosclerosis received L-arginine 9 g or placebo daily for one month, with treatment periods separated by one month. Nitric oxide levels in serum (as an index of endothelial NO release), brachial artery endothelium-dependent dilator responses to hyperemia by ultrasonography (as an index of vascular NO bioactivity) and markers of inflammation in blood that are inhibited by NO in cell culture experiments were measured at the end of each treatment period.

RESULTS

L-arginine levels in plasma were increased in all women during L-arginine treatment compared with placebo (136.8 +/- 63.1 vs. 75.2 +/- 16.2 micromol/liter, p = 0.009). However, there was no change in serum nitrogen oxide levels (42.1 +/- 24.5 vs. 39.1 +/- 16.6 micromol/liter, p = 0.61), nor was there an effect of L-arginine on flow-mediated dilation during hyperemia (3.8 +/- 3.0% vs. 4.9 +/- 4.8%, p = 0.53) compared with placebo. Our study had sufficient power (beta = 0.80) to detect a true absolute treatment difference in flow-mediated brachial artery dilation of 1.7% or larger as statistically significant at alpha = 0.05. There was no effect of L-arginine on serum levels of soluble cell adhesion molecules compared with placebo: E-selectin (50.6 +/- 14.8 vs. 52.1 +/- 17.0 ng/ml, p = 0.45), intercellular adhesion molecule-1 (230 +/- 51 vs. 230 +/- 52 ng/ml, p = 0.97) and vascular cell adhesion molecule-1 (456 +/- 62 vs. 469 +/- 91 ng/ml, p = 0.53).

CONCLUSIONS

Oral administration of L-arginine may not augment endothelial NO synthesis and release in postmenopausal women and is thus unlikely to be of general benefit to healthy postmenopausal women in protection from the development of atherosclerosis.

Circulating L-selectin concentrations in children with recent-onset IDDM

To clarify conflicting claims of altered serum concentrations of soluble L-selectin (sCD62L) in recent-onset IDDM, sCD62L was measured in 89 children and adolescents with IDDM (35 recent-onset, 12 during the first year of insulin treatment, and 42 with long-standing (> 1 yr) treatment) alongside 124 controls. Children < 14 yr of age both with and without IDDM (n = 160) had grossly elevated sCD62L concentrations (20.2 +/- 4.9 nmol/l), as compared with adolescents (14-18 yr, n = 23; 15.9 +/- 3.9 nmol/l) and adults (> 18 yr, n = 30; 11.2 +/- 2.3 nmol/l) (p < 0.0001). Multivariate analysis confirmed the strong inverse association between age and sCD62L (p < 0.001) while revealing that sCD62L concentrations were slightly elevated in recent-onset IDDM, as compared with insulin-treated IDDM patients or nondiabetic controls (p = 0.028). Actual sCD62L concentrations in the 35 recent-onset IDDM patients were 22.2 +/- 4.9 nmol/L vs 19.6 +/- 3.6 nmol/l in 35 non-diabetic controls matched for age (p = 0.022). While this significant but small rise of systemic sCD62L reflects leukocyte activation, it is obscured by the inverse association between sCD62L and chronological age in children and adolescents. Therefore, determining sCD62L serum concentrations appears to be of limited value for clinical investigators caring for children and adolescents with IDDM.

L-selectin in trauma patients: a marker for organ dysfunction and outcome?

BACKGROUND

Systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS) are important factors affecting morbidity and mortality after trauma. Adhesion molecules, e.g. L-selectin (CD62 L), play crucial roles in both conditions.

PATIENTS AND METHODS

In 51 multiple trauma patients, CD62 L surface expression on granulocytes, monocytes, lymphocytes, as well as sCD62 L plasma concentrations were determined during the first 6 days after trauma, starting at the site of accident. Clinical parameters were severity of injury scores (ISS, APACHE II), requirement of red blood cell transfusion, acute lung or liver failure, development of MODS or SIRS, early (< or = 6 d) or late (> 6 d), and outcome.

RESULTS

CD62 L expression was reversibly elevated on granulocytes, T cells and monocytes in comparison with initial values. sCD62 L plasma concentrations did not show temporal variations but were depressed throughout observation period, in comparison with healthy controls. Lung failure within the first 6 days was associated with increased CD62 L expression on monocytes and B cells on admission and increased sCD62 L concentrations after 12 and 24 h. Patients with more severe injuries (APACHE II > 20 points) had higher sCD62 L concentrations after 24 h. Non-survivors had decreased sCD62 L (on admission) and T-cell CD62 L expression (after 4 h). Patients with early MODS or SIRS showed increased monocyte CD62 L expression after 6 days.

CONCLUSIONS

In multiple trauma patients, severe organ dysfunction is associated with altered CD62 L expression on leukocytes and circulating sCD62 L plasma concentrations. However, the obvious complexity of the pattern currently restricts use of CD62 L quantitation for clinical purposes.

Neutrophil Dysfunctions, IL-8, and Soluble L-Selectin Plasma Levels in Rapidly Progressive Versus Adult and Localized Juvenile Periodontitis: Variations According to Disease Severity and Microbial Flora

We used flow cytometry to analyze the expression of adhesion molecules and the oxidative burst of whole-blood polymorphonuclear neutrophils (PMN) from 26 patients with periodontitis. Three different clinical entities were studied: adult periodontitis (AP), localized juvenile periodontitis (LJP), and rapidly progressive periodontitis (RPP). Unstimulated PMN from the patients showed reduced Lewis x, sialyl-Lewis x, and L-selectin expression relative to those from healthy control subjects. These alterations were present whatever the severity of periodontal disease. However, PMN from RPP patients showed increased basal H2O2 production and decreased L-selectin shedding. These latter impairments, which correlated with increased IL-8 plasma levels, could contribute to initial vascular damage. In addition, decreased IL-8 priming of H2O2 production by PMN from RPP patients could account for a lower bactericidal capacity of PMN, leading to the large number of bacteria in the subgingival region of RPP patients. Soluble L-selectin plasma levels were also decreased in the RPP group, indicating more severe or diffuse endothelial damage. These abnormalities were not found in the patients with less destructive forms of periodontitis (AP and LJP). Porphyromonas gingivalis, a bacterial pathogen known to increase IL-8 production by PMN, was found in the periodontal pockets of RPP patients only. These results show links among PMN abnormalities, the clinical form of periodontitis, and the gingival bacterial flora.

Painful stimulation suppresses joint inflammation by inducing shedding of L-selectin from neutrophils

Although the inflammatory response is essential for protecting tissues from injury and infection, unrestrained inflammation can cause chronic inflammatory diseases such as arthritis, colitis and asthma. Physiological mechanisms that downregulate inflammation are poorly understood. Potent control might be achieved by regulating early stages in the inflammatory response, such as accumulation of neutrophils at the site of injury, where these cells release chemical mediators that promote inflammatory processes including plasma extravasation, bacteriocide and proteolysis. To access an inflammatory site, neutrophils must first adhere to the vascular endothelium in a process mediated in part by the leukocyte adhesion molecule L-selectin. This adhesion is prevented when L-selectin is shed from the neutrophil membrane. Although shedding of L-selectin is recognized as a potentially important mechanism for regulating neutrophils, its physiological function has not been demonstrated. Shedding of L-selectin may mediate endogenous downregulation of inflammation by limiting neutrophil accumulation at inflammatory sites. Here we show that activation of nociceptive neurons induces shedding of L-selectin from circulating neutrophils in vivo and that this shedding suppresses an ongoing inflammatory response by inhibiting neutrophil accumulation. These findings indicate a previously unknown mechanism for endogenous feedback control of inflammation. Failure of this mechanism could contribute to the etiology of chronic inflammatory disease.

Ligation of the CD4 receptor induces activation-independent down-regulation of L-selectin

Lymphocyte circulation plays an important role in the generation of a specific immune response. Mature lymphocytes continuously circulate between blood and lymph, entering the lymphoid tissue via high endothelial venules. Trafficking across high endothelial venules of peripheral lymph nodes (PLN) depends on the expression of L-selectin. It has been shown that L-selectin is rapidly cleaved from the surface by a metalloproteinase after in vitro activation. Here, we show that ligation of CD4, without ligation of the T cell receptor for antigen, causes down-regulation of L-selectin on T helper cells. This down-regulation is caused by proteolytic cleavage by a metalloproteinase and is reversible by the addition of hydroxamic acid-based metalloproteinase inhibitors. We show that in vivo down-regulation of L-selectin in huCD4tg mice by mAb reduces the homing of lymphocytes to PLN in adoptive transfer experiments. Because CD4 is a coreceptor for HIV-1, the down-regulation of L-selectin induced by CD4 ligation could play a role in the pathogenesis of AIDS. We provide evidence that CD4 ligation by HIV-1 induces metalloproteinase-dependent L-selectin down-regulation. Reduced levels of L-selectin expression might contribute to immune deficiency in individuals infected with HIV by inhibiting T cell redistribution and decreasing the probability of an encounter between specific lymphocytes and viral antigens in PLN.

Differential up-regulation of circulating soluble selectins and endothelial adhesion molecules in Sicilian patients with Boutonneuse fever

In 150 patients with Boutonneuse fever (BF), caused by Rickettsia conorii, we studied the plasma levels of soluble L-selectin (sL-selectin), vascular cell adhesion molecule-1 (sVCAM-1), intercellular adhesion molecule-1 (sICAM-1) and E-selectin (sE-selectin) in various phases of disease to clarify their role in disease evolution. Results indicate that during the acute phase of BF there is a significant increase in the serum levels of sL-selectin, sE-selectin, sVCAM-1 and sICAM-1. sL-selectin and sVCAM-1 returned to normal levels in the third week of disease, whereas sE-selectin and sICAM-1 persisted at significantly high levels even after the third week. The secretion of these soluble CAMs in BF is mainly the result of leucocyte expression and endothelial cell activation, but secretion also appears to mediate anti-inflammatory activities, moderating leucocyte adhesion and reducing in particular lymphocyte and monocyte infiltration. Only sL-selectin serum levels were found to correlate with the acute phase of infection characterized by fever.

Identification of a natural soluble form of human CD5

CD5 is a 67 kDa type I glycoprotein which belongs to the Scavenger Receptor Cysteine-Rich (SRCR) family of receptors. This family includes either cell-surface (e.g. CD6) or secreted (e.g. Spalpha) proteins implicated in the development of the immune system and the regulation of immune responses. In this study, we purified and characterised a circulating natural soluble CD5 form (nsCD5) which is indistinguishable (in apparent molecular mass, glycosylation pattern, and antibody reactivity) from a recombinant soluble CD5 form (rsCD5) composed of the three extracellular SCRC domains. The nsCD5 is a N-glycosylated 52 kDa molecule present in normal human serum and in supernatants of in vitro phorbol ester- and CD3-stimulated peripheral blood mononuclear cells. The nsCD5 concentration in sera from healthy donors is relatively low (median 1.75 ng/ml, rn=166) and is similar to that found in sera from patients suffering of various autoimmune (systemic lupus erythematosus, primary Sjogren syndrome, rheumatoid arthritis) and non-autoimmune (chronic renal failure, B-cell chronic lymphocytic leukemia) disorders. In vitro experiments indicate that nsCD5 is released by proteolytic cleavage of the membrane form. These results represent the first evidence of proteolytic release of a transmembrane SRCR family member following cell activation.

Increased levels of circulating ICAM-1, VCAM-1, and L-selectin in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) may be one of the most important risk factors of cardiovascular disorders, although the exact mechanism remains to be elucidated. In the present study, we hypothesized that OSAS-induced hypoxic stress might be involved in the etiology of cardiovascular disorders by activating adhesion molecules, including intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and L-selectin. To examine this hypothesis, we measured circulating ICAM-1, VCAM-1, and L-selectin levels before and after sleep in OSAS patients and age-matched controls. The circulating ICAM-1, VCAM-1, and L-selectin levels increased in the OSAS patients before sleep compared with the normal subjects (ICAM-1: 392.9 +/- 48.5 vs. 201.2 +/- 55.0 ng/ml, P < 0.05; VCAM-1: 811.0 +/- 87.8 vs. 574.2 +/- 42.7 ng/ml, P < 0.05; L-selectin: 1,386.6 +/- 77.9 vs. 1,038.8 +/- 78.6 ng/ml, P < 0.01, respectively). After sleep, significantly greater levels of ICAM-1 and L-selectin, but not VCAM-1, were observed in the OSAS group. These observations suggest that OSAS-induced hypoxia activates adhesion molecules, resulting in the important risk factor of cardiovascular disorders. Treatment of OSAS can be, therefore, a potential approach to prevention of cardiovascular events.

Adhesion molecules and lymphocyte subsets in milk and blood of periparturient Holstein cows

Migration of leukocytes into the mammary gland is an essential element of resistance to infection which is likely influenced by expression of adhesion molecules. The contribution of subsets to mammary gland resistance remains unclear. Mononuclear cells from milk and blood of dairy cows were examined for variation in CD4+, CD8+, and WC1+ (Workshop Cluster 1; marker for gammadelta T cells) lymphocyte phenotypes and expression of LFA-1 and L-selectin at several time points during the periparturient period and at Week 16 of lactation. Proportions of CD4+ T cells were higher (p < or = 10.05) in blood than milk at all times between Week 0 and Week 16 relative to calving; the inverse was true of CD8+ cells. Expression of L-selectin was lower (p < or = 0.05) on CD4+ cells and higher on CD8+ cells from milk. The WC1+ subset was more frequent in blood than in milk except at calving when the opposite was true. After calving, proportions of L-selectin+ WC1+ cells decreased steadily to Week 16. Expression of LFA-1 was examined on mononuclear cell populations and found to be lower on milk cells and did not vary over time. We conclude that proportions of T cells subsets differ significantly between blood and milk, particularly around calving. Corresponding variations in L-selectin expression may indicate a role for this molecule in regulating the movement of CD8+ and WC1+ T cells into the bovine mammary gland.

Serum soluble L-selectin in childhood acute lymphoblastic leukemia

BACKGROUND

Determination of the serum level of soluble (s)L-selectin has been advocated for monitoring patient response to treatment in leukemia. The aim of the present study was to find out whether serum levels of sL-selectin correlated with treatment for acute lymphoblastic leukemia (ALL) in children.

METHODS AND RESULTS

Serum samples were obtained from 30 children with ALL, either newly diagnosed during induction therapy, in remission, in maintenance therapy, at the end of treatment or after relapse. Levels of sL-selectin were assayed in the serum of children during the clinical course of ALL using the sandwich enzyme-linked immunoabsorbent assay. Serum sL-selectin concentrations decreased significantly from diagnosis to the end of intensive chemotherapy in children with ALL and increased in the time of relapse.

CONCLUSION

These results suggest that monitoring of sL-selectin may be useful for evaluating leukemia activity.

Cellular and molecular mechanisms of inflammation and thrombosis

In the last 20 years, the cellular and molecular mechanisms of inflammation and thrombosis have been characterised. These are essentially cell adhesion processes which are regulated by vascular endothelium. Many of the cell adhesion molecules and leucocyte chemoattractants expressed and generated at sites of inflammation have been sequenced and cloned. These inflammatory molecules work together in concert to mediate the adhesion between leucocytes, platelets and vascular endothelium which occurs during the occlusive, thromboembolic, reperfusion and septic complications of atherosclerotic and diabetic vascular diseases. This review aims to summarise our current understanding of the molecular basis of these disorders and the therapeutic implications.

H (0) blood group determinant is present on soluble human L-selectin expressed in BHK-cells

In the present study we show that the H (0) blood group determinant Fuc alpha1-2Gal beta1-4GlcNAc beta1-R is present on N-linked glycans of soluble human L-selectin recombinantly expressed in baby hamster kidney (BHK) cells. The glycans were isolated using complementary HPLC techniques and characterized by a combination of exoglycosidase digestion and mass spectrometry. The linkage of the fucose residues was determined by incubation of the glycans with specific fucosidases. The H blood determinant Fuc alpha1-2Gal beta1-4GlcNAc beta1 was detected for bi-, 2,4 branched tri- and tetraantennary structures. To our knowledge, the proposed oligosaccharide structures represent a new glycosylation motif for recombinant glycoproteins expressed on BHK cells.

Adult respiratory distress syndrome - an update

In adults, acute lung injury or adult respiratory distress syndrome (ARDS) may complicate a wide range of serious medical and surgical conditions, only some of which involve direct pulmonary insult. The characteristic histological feature of ARDS is an intense inflammatory process in the lungs, which may progress to fibrosis. The earliest physiological characteristic is an increase in the protein permeability across the endothelial and epithelial barriers of the lungs. This clinical syndrome is characterized by arterial hypoxaemia and bilateral radiographic infiltrates, which represent protein-rich oedema fluid. In addition there is a neutrophilic and macrophage infiltrate. Pulmonary endothelium is actively involved in the development of ARDS. It alters cell-cell adhesion as the initial step in leucocyte migration which, in turn, changes the permeability that allows protein-rich fluid to move into the interstitium. The quantity of this interstitial oedema may be sufficient to cause bulk flow through the epithelial barrier. There is probably independent epithelial injury. Finally, the endothelium can release and metabolize vasoactive and inflammatory substances, such as endothelins, nitric oxide and cytokines, etc. No single substance is responsible for acute lung injury, but rather a complex interplay exists between diverse pro- and anti-inflammatory mediators.

Relevance of L-selectin shedding for leukocyte rolling in vivo

The velocity of rolling leukocytes is thought to be determined by the expression of adhesion molecules and the prevailing wall shear stress. Here, we investigate whether rapid cleavage of L-selectin may be an additional physiologic regulatory parameter of leukocyte rolling. A unique protease in the membrane of leukocytes cleaves L-selectin after activation, resulting in L-selectin shedding. The hydroxamic acid-based metalloprotease inhibitor KD-IX-73-4 completely prevented L-selectin shedding in vitro and significantly decreased the rolling velocity of leukocytes in untreated wild-type C57BL/6 mice from 55 to 35 micrometer/seconds in vivo. When E-selectin was expressed on the endothelium (tumor necrosis factor [TNF]-alpha treatment 2.5-3 h before the experiment), rolling velocity was 4 micrometer/seconds and did not change after the application of KD-IX-73-4. However, KD-IX-73-4 decreased mean rolling velocity by 29% from 23 to 16 micrometer/seconds in E-selectin-deficient mice treated with TNF-alpha. The reduction of velocity caused by KD-IX-73-4 was immediate (<5 s) after injection of KD-IX-73-4 as shown by a novel method using a local catheter. These results establish a role for L-selectin shedding in regulating leukocyte rolling velocity in vivo.

Expression and release of adhesion molecules by human acute myelogenous leukemia blasts

The expression and release of adhesion molecules by acute myelogenous leukemia (AML) blasts was investigated in vitro. For most patients AML blasts expressed relatively low levels of membrane-bound L-selectin and Intercellular adhesion molecule 1 (ICAM-1), but their soluble forms were detected in the supernatants for the majority of patients when AML blasts were cultured in vitro. These in vitro levels of SL-selectin and sICAM-1 were considerably lower than the normal serum levels. Divergent and relatively small alterations in SL-selectin and sICAM-1 levels were usually observed when exogenous growth factors were present during AML blast culture, whereas increased SL-selectin levels were observed after coculture of AML blasts and normal leucocytes. E- and P-selectin were neither expressed nor released by AML blasts. We conclude that AML blasts are a source of soluble adhesion molecules.

Mechanisms for induction of L-selectin loss from T lymphocytes by a cryptococcal polysaccharide, glucuronoxylomannan

Disseminated cryptococcosis is accompanied by cryptococcal polysaccharides in the serum and the lack of cellular infiltrates in infected tissues. Cryptococcal polysaccharides given intravenously to mice inhibit the influx of T lymphocytes into the sites of cell-mediated immune response. The focus here was to determine whether cryptococcal polysaccharides modulate the expression of molecules, such as L-selectin, that are important in extravasation of T cells. Cryptococcal glucuronoxylomannan (GXM), but not galactoxylomannan or mannoprotein, was found to cause loss of L-selectin from freshly isolated human T cells of both CD4 and CD8 subsets and from Jurkat cells. With the signaling-pathway inhibitors staurosporine (which inhibits protein kinase C) and herbimycin A (which inhibits protein tyrosine kinases), we showed that GXM or the cryptococcal culture filtrate antigen CneF directly induces L-selectin loss from CD4(+) and CD8(+) T cells via a herbimycin A-sensitive pathway(s) presumably involving one or more protein tyrosine kinases but not via a pathway involving protein kinase C. Loss of L-selectin from the T cells before the T cells have a chance to bind to L-selectin ligands on endothelial cells would be expected to prevent T-cell migration into inflamed tissues and/or lymph organs.