Plasma Levels Of Soluble L-selectin Research Articles

L-selectin and Skin Damage in Systemic Sclerosis

BackgroundL-selectin ligands are induced on the endothelium of inflammatory sites. L-selectin expression on neutrophils and monocytes may mediate the primary adhesion of these cells at sites of inflammation by mediating the leukocyte-leukocyte interactions that facilitate their recruitment. L-selectin retains functional activity in its soluble form. Levels of soluble L-selectin have been reported as both elevated and lowered in patients with systemic sclerosis (SSc). This preliminary study seeks to discern amongst these disparate results and to discover whether there is an association between L-selectin concentrations in plasma and skin damage in SSc patients.Methodology and Principal FindingsNineteen cases with limited systemic sclerosis (lSSc) and 11 cases with diffuse systemic sclerosis (dSSc) were compared on a pairwise basis to age- and sex-matched controls. Criteria of the American College of Rheumatology were used to diagnose SSc. Skin involvement was assessed using the modified Rodnan skin score (mRSS). We find no association between mRSS and plasma L-selectin concentration in lSSc cases (p = 0.9944) but a statistically significant negative correlation in dSSc cases (R2 = 73.11 per cent, p = 0.0008). The interpretation of the slope for dSSc cases is that for each increase of 100 ng/ml in soluble L-selectin concentration, the mRSS drops 4.22 (95 per cent CI: 2.29, 6.16). There was also a highly statistically significant negative correlation between sL-selectin and disease activity (p = 0.0007) and severity (p = 0.0007) in dSSc cases but not in lSSc cases (p = 0.2596, p = 0.7575, respectively).Conclusions and SignificanceNo effective treatments exist for skin damage in SSc patients. Nor is there a laboratory alternative to the modified Rodnan skin score as is the case for other organs within the body. Modulation of circulating L-selectin is a promising target for reducing skin damage in dSSc patients. Plasma levels of soluble L-selectin could serve as an outcome measure for dSSc patients in clinical trials.

ADAM17 deficiency by mature neutrophils has differential effects on L-selectin shedding (97.14)

Abstract L-selectin directs neutrophils to sites of inflammation, and upon their activation, surface expression of the receptor is rapidly downregulated by ectodomain shedding. ADAM17 (also known as Tumor necrosis factor-alpha-converting enzyme or TACE) is a sheddase of L-selectin; however, Adam17 gene-targeting (ADAM17−/−) in mice is perinatal lethal and its role in L-selectin shedding by mature leukocytes has not been determined. This issue was addressed here by generating radiation-chimeric mice reconstituted with ADAM17−/−fetal liver progenitor cells. ADAM17-deficient neutrophils, monocytes and lymphocytes failed to shed L-selectin in response to PMA, as did neutrophils infiltrating the inflamed peritoneum. In addition, the lack of functional ADAM17 resulted in significantly increased levels of L-selectin surface expression by leukocytes in peripheral blood, suggesting the sheddase is also involved in the constitutive cleavage of L-selectin. Interestingly, it seems that ADAM17 is not required in all manners of L-selectin turnover. Plasma levels of soluble L-selectin were similar between ADAM17−/−chimeric and control mice, as was the shedding of L-selectin by neutrophils undergoing apoptosis. The latter process, however, was diminished by a metalloprotease inhibitor (TAPI-0), indicating the involvement of a metalloprotease sheddase other than ADAM17. Our data is the first to demonstrate that L-selectin’s surface density on neutrophils is regulated by ADAM17, but homeostatic cleavage of L-selectin is not. This work is supported by grant HL61613 (B.W.) from the National Institutes of Health.

LeuCAM and Reactive Oxygen Species during Long-Term Exercise Combined with Sleep and Energy Deficiency

During the Norwegian military ranger-training course, cadets are exposed to prolonged physical exercise combined with sleep-, energy-, and food deficiency. The open-window postexercise hypothesis indicates that after hard physical activity, there is an increased risk of contracting infectious diseases. The purpose of the present study was to determine leukocyte reactive oxygen species (ROS) levels, total antioxidant status (TAS), leukocyte expression of the cell adhesion molecules CD62L and CD11b, and plasma levels of soluble adhesion molecule L-selectin before, during, and in the recovery phase of a military ranger-training course. Ten cadets from the Norwegian Military Academy were recruited to the study. Flow cytometry was used to study the intracellular levels of ROS in leukocytes (basally, as well as after in vitro stimulation with phorbol myristate acetate (PMA)), applying the probes dihydroethidium (DHE) and dihydrorhodamine 123 (DHR) and the leukocyte expression of adhesion molecules CD62L and CD11b. ELISA was used to assess the plasma levels of soluble L-selectin, and TAS in plasma was measured using the ABTS+ reduction assay kit. The basal levels of ROS as well as PMA-stimulated ROS in leukocytes declined gradually during the ranger-training course, being lowest on the last day (P < 0.05). The level of TAS increased (P < 0.01) during the course. A striking decrease (P < 0.001) was observed in leukocyte CD62L expression and was sustained even after 3 d of recovery. The leukocyte expression of CD11b remained unchanged. The ranger-training course leads to a partial exhaustion of the leukocyte ROS-generating machinery and to a nearly total extinguishing of leukocyte CD62L expression. These changes may support the open-window hypothesis indicating reduced ability to combat microbial invasions before total restitution.

L-selectin shedding does not regulate constitutive T cell trafficking but controls the migration pathways of antigen-activated T lymphocytes.

L-Selectin mediates rolling of lymphocytes in high endothelial venules (HEVs) of peripheral lymph nodes (PLNs). Cross-linking of L-selectin causes proteolytic shedding of its ectodomain, the physiological significance of which is unknown. To determine whether L-selectin shedding regulates lymphocyte migration, a mutant form that resists shedding (LΔP-selectin) was engineered. Transgenic mice expressing either LΔP or wild-type (WT) L-selectin on T cells were crossed with L-selectin knockout (KO) mice. The cellularity and subset composition of secondary lymphoid organs did not differ between LΔP and WT mice, however, they were different from C57BL/6. Plasma levels of soluble L-selectin in LΔP mice were reduced to <5% of WT and C57BL/6 mice. The rolling properties of T lymphocytes from LΔP and WT mice on immobilized L-selectin ligands were similar. Furthermore, similar numbers of LΔP and WT T lymphocytes were recruited from the bloodstream into PLNs in mice, although LΔP T cells transmigrated HEVs more slowly. WT, but not LΔP-selectin, underwent rapid, metalloproteinase-dependent shedding after TCR engagement, and LΔP T cells retained the capacity to enter PLNs from the bloodstream. These results suggest that the ability to shed L-selectin is not required for T cell recirculation and homing to PLNs. However, L-selectin shedding from antigen-activated T cells prevents reentry into PLNs.

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.

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

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

Phenotypic changes in neutrophils related to anti-inflammatory therapy

Previous work from the group has shown that non-steroidal anti-inflammatory agents given to volunteers and patients inhibit PMN function possibly by affecting the developing neutrophil during the differentiation process. In this study indomethacin treatment in vivo reduced neutrophil chemotaxis and proteolytic degradation of fibronectin, with a maximal effect after 14 days. Stimulated neutrophil adherence to fibronectin was also reduced but this was not due to quantitative changes in β 2 integrin expression or function. L-Selectin expression on resting and stimulated neutrophils was increased after 14 days and there was a small decrease in plasma levels of soluble L-selectin. These effects, however, could not be reproduced by treatment of neutrophils with indomethacin in vitro, suggesting they are due to effects on differentiating/maturing PMNs. In an attempt to interpret these changes, studies were performed with dexamethasone, which is known to alter neutrophil function and kinetics. Dexamethasone treatment reduced chemotaxis and increased superoxide generation after 1 day and was associated with increased expression of activated β 2 integrins and reduced L-selectin expression on resting neutrophils. This suggests the appearance of mainly ‘activated’ cells as a result of demargination and indicates that the effects of indomethacin are distinctive and not related to changes in compartmentalisation.

Increased release of the soluble form of the adhesion molecules L-selectin and ICAM-1 but not E-selectin during attacks of angina pectoris.

Myocardial ischemia leads to the activation of neutrophils as well as endothelial cells. The interaction between these cells is dependent on certain adhesion glycoproteins which are expressed on their surface. Adhesion of neutrophils to endothelium, mediated by adhesion molecules, has been shown to result in coronary capillary plugging and impairment of coronary blood flow. In certain conditions, upon cell activation, adhesion proteins may be released in soluble form into the circulating blood. The purpose of our study was to verify whether myocardial ischemia occurring during angina episodes results in the release of the soluble adhesion molecules, L-selectin, E-selectin, and intracellular adhesion molecule-1 (ICAM-1), into the circulation. Plasma samples were collected by venepuncture from 15 patients admitted to the emergency room with chest pain caused by attacks of angina pectoris and 15 patients with noncardiac chest pain. To confirm the diagnosis, all patients underwent an exercise stress test and, if not conclusive, 99mTc MIBI SPECT or coronary arteriography. Another set of plasma samples were taken from each patient in the absence of chest pain. In addition, blood for analysis was obtained from 15 sex-and age-matched healthy subjects. Soluble adhesion molecules plasma levels were measured by standard enzyme-linked immunosorbent assay. In patients with angina pectoris, plasma levels of soluble L-selectin estimated during chest pain were significantly higher than in the control group and decreased in the absence of chest pain. Similarly, the mean concentration of soluble ICAM-1 at the time of angina onset was significantly elevated in the patients in comparison with the control group and remained higher, although not significantly, in the absence of chest pain. In patients with noncardiac chest pain, plasma levels of soluble L-selectin did not differ significantly from those observed in control subjects. In this group of patients, the plasma levels of soluble ICAM-1 estimated during pain onset and in the absence of this symptom were not significantly elevated. On the contrary, the mean values of soluble E-selectin in the patients with ischemic cardiac pain during chest pain and in the absence of this symptom, as well as those in the patients with noncardiac chest pain during or without symptoms, remained unchanged in comparison with the control group. During attacks of angina pectoris an increase in the plasma levels of the soluble adhesion molecules, ICAM-1 and L-selectin, was noted, possibly reflecting activation of neutrophils and endothelial cells during myocardial ischemia. However, E-selectin plasma levels remained unchanged in response to myocardial ischemia.

Leukocyte L-selectin is up-regulated after mechanical trauma in adults.

Infection and multiple organ failure remain the principal causes of late mortality after trauma despite advances in the resuscitation of injured patients. Because a better understanding of postinjury leukocyte trafficking is essential to the development of possible therapeutic measures aimed at preventing these complications, we have performed a study of one factor in the early posttrauma endothelial adhesion behavior of monocytes, lymphocytes, and neutrophils: their cell surface expression of L-selectin (CD62L). We have also studied the plasma levels of soluble L-selectin in these patients. Two venous blood samples were taken from each of 41 trauma patients at median times of 1 and 20 hours after injury. The study group included 16 patients with major (Injury Severity Score (ISS) > or = 16), 17 with moderate (ISS = 9-15), and 8 with minor (ISS < 9) trauma. Cell surface L-selectin was measured on leukocyte subsets by staining with specific fluorescent-labeled monoclonal antibodies to CD62L and using flow cytometry. Both the percentage of cells expressing the molecule and the mean channel fluorescence were measured. Levels of soluble L-selectin were measured in the plasma, sampled concurrently, by enzyme-linked immunosorbent assay. Monocytes, lymphocytes, and neutrophils all showed an early increase in cell surface L-selectin expression as measured by mean channel fluorescence (p < 0.0001, p < 0.001, and p < 0.0001, respectively), and this persisted in later samples taken at a median 20 hours after injury (p < 0.0001,p < 0.0001, and p < 0.01). Only monocytes showed an increased percentage of cells expressing the molecule in the early phase (p < 0.02), and this remained in the later phase (p < 0.001). Monocytes also showed a further significant increase in mean channel fluorescence (p < 0.02) between the two periods. No significant changes in levels of plasma soluble L-selectin were found at either stage. An increase in the expression of L-selectin on each of three leukocyte populations has been demonstrated in the early phase after trauma. This would tend to promote rolling behavior of leukocytes and increase their contact with the vascular endothelium. There were marked differences in the later responses of the three populations, which may represent differential control of their behavior.

Effects of trauma and sepsis on soluble L-selectin and cell surface expression of L-selectin and CD11b.

To examine (1) the effects of trauma on changes in neutrophil L-selectin and CD11b expression and on the levels of soluble L-selectin and (2) whether these alterations are different on leukocyte subpopulations in those patients who develop multiple organ dysfunction syndrome. Twenty patients with Injury Severity Score (ISS) > or = 16 and 15 patients with ISS score < 16 were studied. Arterial blood were collected serially after injury. The staining of leukocyte surface adhesion molecules was performed with antibodies against L-selectin and CD11b. Positive cell count and mean fluorescence intensity were determined by flow cytometry. Soluble L-selectin was measured using enzyme-linked immunosorbent assay. In patients with ISS > or = 16, neutrophil L-selectin expression showed an immediate increase, reaching peak levels between 3 to 4 hours after injury (p < 0.05 vs. patients with ISS < 16), followed by a gradual decrease. Plasma levels of soluble L-selectin reached peak levels at 6 hours after injury. However, in patients with ISS < 16, minimal changes in L-selectin expression and soluble L-selectin were observed. Neutrophil CD11b expression showed an immediate increase for the first 3 hours followed by a gradual increase up to 24 hours after injury. In patients who developed multiple organ dysfunction syndrome, CD11b both on neutrophils and lymphocytes remained elevated for 120 hours. These findings suggest that acute neutrophil activation is an early event after trauma and may be implicated as "a vulnerable window" for leukocyte-mediated end organ injury.