Role of selectins in development of adult respiratory distress syndrome

ADAM17 activity during human neutrophil activation and apoptosis

Substrates of the metalloprotease ADAM17 (also known as TNF-alpha converting enzyme or TACE) undergo ectodomain shedding and include various inflammatory modulators. Though polymorphonuclear leukocytes contribute significantly to inflammation, direct analyses of ADAM17 on human neutrophils are very limited. In addition, the current understanding of the processes regulating ADAM17 activity primarily relate to its rapid activation. Therefore, to extend insights into the mechanisms of ADAM17 activity, we examined its surface expression and the shedding of its substrates during extended periods of neutrophil activation and apoptosis. Contrary to studies with immortalized hematopoietic cell lines, we report that surface expression of ADAM17 is maintained by human neutrophils activated with formyl peptides or by FcR/complement receptor-mediated phagocytosis. Interestingly, bacterial phagocytosis resulted in a significant increase in ADAM17 expression several hours after pathogen engulfment. We provide novel evidence that ADAM17 surface expression is also maintained during spontaneous and anti-Fas-induced neutrophil apoptosis. The well-validated ADAM17 substrates L-selectin and proTNF-alpha were shed efficiently by neutrophils under each of the conditions tested. Our data thus indicate prolonged ADAM17 expression during neutrophil effector functions. The implications of this may be a role by ADAM17 in both the induction and down-regulation of neutrophil activity.

Neutrophil Priming for Elastase Release in Adult Blunt Trauma Patients

BACKGROUND

Elevated plasma elastase levels have been reported following major trauma and isolated femoral fracture. Reamed femoral nailing has been shown to further increase plasma elastase levels. The aim of this study was to investigate polymorphonuclear neutrophil (PMN) priming for degranulation following major trauma and isolated long-bone/pelvis fracture by assessing the ability of PMN to release elastase in vitro in response to a stimulus.

METHODS

We further analyzed PMN surface expression of the integrins CD11b and CD18 as markers of PMN activation. Ten major trauma (Injury Severity Score>or=18) patients and 12 patients with isolated long-bone/pelvis fracture were included in the study. Patients in the isolated fracture group were further stratified into reamed nail and external-fixation groups following surgery.

RESULTS

A significant increase in the capacity of PMN to release elastase was seen following major trauma, but not in isolated fracture patients. Surgery did not further alter PMN elastase release. CD11b and CD18 expression was essentially unaltered in all groups.

CONCLUSIONS

PMN is primed for increased degranulation following major trauma but not following isolated long-bone/pelvis fracture. Accumulation of primed, hyperactive PMN into tissues can lead to severe tissue damage and thus multiple organ failure.

L-selectin: adhesion, signalling and its importance in pathologic posttraumatic endotoxemia and non-septic inflammation

The leucocyte expressed surface-bound L-selectin belongs to the selectin family of adhesion molecules. It exhibits adhesive as well as signalling functions. Mainly, it is of importance in lymphocyte homing and in the extravasation of leucocytes into the surrounding tissue during inflammation. Acting in the initial step of the cell adhesion cascade, L-selectin is responsible for the rolling of leucocytes on endothelial layers. Therefore, L-selectin is thought to be an adequate target for pharmacological interventions. Beneath the discussion of the molecules' general features like molecule structure and its regulation, the review focuses firstly on L-selectin in the context of posttraumatic inflammatory disorders, and secondly on the importance of L-selectin specific signalling events.

No association between E- and L-selectin genes and SLE: soluble L-selectin levels do correlate with genotype and a subset in SLE

Altered function of selectin glycoprotein adhesion molecules may modulate severity and organ-specific manifestations of autoimmune and inflammatory disease via changes in leukocyte trafficking. Serum concentrations of selectin molecules have been suggested as useful biomarkers in systemic lupus erythematosus (SLE). We identified increased levels of soluble L-selectin (sL-selectin), but not soluble E-selectin (sE-selectin) in 278 European-Caucasian lupus patients compared to 230 healthy siblings (P=0.002). sL-selectin levels were markedly elevated in patients with IgG antiphospholipid autoantibodies (P=0.002), suggesting that perhaps sL-selectin defines a subgroup of lupus with vasculopathy. sL-selectin level was also influenced by two L-selectin polymorphisms: 665C>T, F206L in the epidermal growth factor-like domain (P=0.015) and rs12938 in the 3'-untranslated region (P=0.06). Having shown increased sL-selectin levels in lupus patients, we used genetics to investigate whether this was a secondary phenomena or the result of an underlying genetic mechanism. The inheritance of nine single-nucleotide polymorphisms (SNP) spanning the selectin locus was tested in 523 UK simplex SLE families. No association with SLE, or related phenotypes, was evident with any single SNP, or haplotype in family-based tests of association. Selectin polymorphisms are, therefore, unlikely to be independent factors in SLE susceptibility.

Reversibility of lung inflammation caused by SP-B deficiency

Whereas decreased concentrations of surfactant protein (SP)-B are associated with lung injury and respiratory distress, potential causal relationships between SP-B deficiency and lung inflammation remain unclear. A transgenic mouse in which human SP-B expression was placed under conditional control of doxycycline via the CCSP promoter was utilized to determine the role of SP-B in the initiation of pulmonary inflammation. Adult mice, made SP-B deficient by removal of doxycycline, developed severe respiratory failure within 4 days. Deficiency of SP-B was associated with increased minimal surface tension of the surfactant and perturbed lung mechanics. Four days of SP-B deficiency did not alter SP-C content or surfactant phospholipid content or composition. SP-B deficiency was associated with lung inflammation and increased soluble L-selectin, STAT-3, and phosphorylated STAT-3 in alveolar macrophages and alveolar epithelial cells. Alveolar IL-6, IL-1beta, and macrophage inflammatory protein-2 concentrations were increased after removal of doxycycline, indicating pulmonary inflammation. Restoration of SP-B expression following administration of doxycycline rapidly reversed SP-B-dependent abnormalities in lung mechanics and inflammation. SP-B deficiency is sufficient to cause lung dysfunction and inflammation in adult mice. SP-B reversed inflammation and maintained lung function in vivo, indicating its potential utility for the prevention and treatment of pulmonary injury and surfactant deficiency.

Regulation of peritoneal and systemic neutrophil-derived tumor necrosis factor-alpha release in patients with severe peritonitis: role of tumor necrosis factor-alpha converting enzyme cleavage

OBJECTIVE

Polymorphonuclear neutrophil (PMN) influx and peritoneal tumor necrosis factor (TNF)-alpha production are key host defense mechanisms during peritonitis. The aim of this study was to explore the potential interactions between TNF-alpha production and TNF-alpha converting enzyme (TACE) expression by PMN in the blood and peritoneum of patients with severe peritonitis.

DESIGN

A prospective study.

SETTING

A surgical adult intensive care unit in a university hospital.

PATIENTS

A total of 29 consecutive immunocompetent patients with severe sepsis within 48 hrs of onset were enrolled and underwent laparotomy for a diffuse secondary peritonitis. Thirteen volunteers served as controls.

MEASUREMENTS

Blood and peritoneal fluid recovered during laparotomy were analyzed and compared for 1) soluble TNF-alpha, soluble L-selectin, and type I and II TNF-alpha receptor levels; 2) PMN membrane TNF-alpha, membrane L-selectin, and TACE expression (flow cytometry); and 3) TNF-alpha production by cultured PMN. Correlations between these forms of PMN-derived TNF-alpha and the severity of the peritonitis and patient's outcome were investigated.

MAIN RESULTS

Elevated soluble TNF-alpha levels in both plasma and peritoneal fluid from the patients were found, together with decreased expression of membrane TNF-alpha and TACE up-regulation at the PMN surface. Soluble L-selectin and type I and II TNF receptors were highly released, suggesting also the role of TACE. In contrast, the capacity of both blood and peritoneal PMN to synthesize TNF-alpha in vitro, in optimal conditions of stimulation (lipopolysaccharide + interferon-gamma), was impaired as compared with controls' blood PMN. Regulation of PMN-derived TNF-alpha was similar in the two compartments, but responses were more pronounced in the peritoneum. TACE up-regulation at the surface of blood-derived PMN correlated with the Sequential Organ Failure Assessment score and vital outcome.

CONCLUSION

These human data demonstrate that mTACE is up-regulated at the PMN surface during severe peritonitis. This finding could be related to a paracrine regulatory loop involving some TACE substrates such as TNF-alpha, L-selectin, and TNF receptors.

Serum biomarkers in acute respiratory distress syndrome an ailing prognosticator

The use of biomarkers in medicine lies in their ability to detect disease and support diagnostic and therapeutic decisions. New research and novel understanding of the molecular basis of the disease reveals an abundance of exciting new biomarkers who present a promise for use in the everyday clinical practice. The past fifteen years have seen the emergence of numerous clinical applications of several new molecules as biologic markers in the research field relevant to acute respiratory distress syndrome (translational research). The scope of this review is to summarize the current state of knowledge about serum biomarkers in acute lung injury and acute respiratory distress syndrome and their potential value as prognostic tools and present some of the future perspectives and challenges.

Systemic inflammation and disseminated intravascular coagulation in early stage of ALI and ARDS: role of neutrophil and endothelial activation

To determine the existence of a close link between inflammation and coagulation in patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) and to examine their prognostic value in the development of ARDS and clinical outcome, we made a prospective cohort study. The study subjects consisted of 57 patients: 19 patients with ARDS and 38 patients with ALI as defined by a Lung Injury Score of > or =2.5 and 1.0 to less than 2.5, respectively. According to the outcome, the patients were subdivided into the survivors and the nonsurvivors. Ten normal healthy volunteers served as control subjects. Plasma levels of soluble L-, P-, and E-selectins, intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), thrombomodulin (sTM), and neutrophil elastase were measured within 24 h after the diagnosis of ALI or ARDS. The number of systemic inflammatory response syndrome (SIRS) criteria being met by the patients and the disseminated intravascular coagulation (DIC) scores were determined simultaneously. The number of SIRS criteria and the DIC scores of the patients with ALI or ARDS showed high values, and more than half of the patients were complicated by DIC. The levels of sL-selectin in both groups of the patients were significantly lower than those of the control subjects. All other soluble adhesion molecules, neutrophil elastase, and sTM in the patients with ALI and ARDS were markedly elevated than those in the control subjects. The levels sICAM-1, sVCAM-1, and sTM in the ARDS patients significantly increased compared with the ALI patients. The number of SIRS criteria and the DIC scores in the nonsurvivors showed higher values than those in the survivors. In addition, we found significant differences in the levels of soluble adhesion molecules, neutrophil elastase, and sTM between the survivors and the nonsurvivors. In conclusion, we found a concurrent activation of both inflammation and coagulation in the patients with ALI or ARDS. The results also suggest that systemic activation of inflammation and coagulation associated with endothelial injury has prognostic value for the development of ARDS and poor outcome.

Comparison of the effect of aminophylline and low PEEP vs. high PEEP on EGF concentration in critically ill patients with ALI/ARDS

BACKGROUND

Acute respiratory distress syndrome (ARDS) remains a serious, often fatal, condition, despite progress in modern critical care treatment. Cytokines play important roles in the pathogenesis of the syndrome, although their roles in the evaluation and outcome have not been clearly elucidated yet.

OBJECTIVES

We tested whether serum concentration of epidermal growth factor (EGF), as one of the important inflammatory mediators, changes with time and administration of mechanical ventilation and aminophylline.

PATIENTS AND METHODS

Thirty patients [mean (SD): age = 56.6 (17.4) years] with ARDS were enrolled. After diagnosis based on inclusion and exclusion criteria, the patients were intubated and mechanically ventilated. Two hours after ventilation with definite positive end-expiratory pressure (PEEP), aminophylline with a specific dose was started. Serum samples were obtained at five time points of 0, 2, 2.5, 4 and 8 h post-starting PEEP.

RESULTS

Serum EGF concentration decreased after mechanical ventilation with PEEP (P < 0.05). The serum EGF concentrations 8 h after intervention was statistically lower in the low PEEP group than in the high PEEP group. The Acute Physiology and Chronic Health Evaluation (APACHE) Pi score and PaO2/FiO2 improved significantly after 8 h (P < 0.05).

CONCLUSION

Beneficial effects of mechanical ventilation and aminophylline on APACHE Pi score and PaO2/FiO2 influence serum EGF levels. These findings may have relevance to the development of multisystem organ failure.

The effects of surgical fracture fixation on the systemic inflammatory response to major trauma

Early stabilization of major long bone fractures is beneficial in reducing the incidence of acute respiratory distress syndrome and multiple organ failure, both of which are caused by activation of the systemic inflammatory response. This activation results in tissue recruitment of and injury by circulating polymorphonuclear leukocytes. The reasons for clinical benefits of early fracture stabilization in major trauma are unknown. Published studies indicate that fracture surgery increases the posttraumatic inflammatory response. Major surgery to stabilize fractures carries a higher complication rate when performed on patients whose hypovolemic shock is not fully corrected. Thus, fracture care should be tailored to the patient, not dictated by the injured bone. Understanding the impact of fracture surgery on the systemic inflammatory response to major trauma is necessary to refine treatment and to apply it optimally to all patients.

Prognostic Value of an Early Soluble L-Selectin (sCD62L) Assay for Risk Assessment in Blunt Multiple Trauma: A Metaanalysis

Background: After severe trauma, decreased plasma concentrations of the soluble adhesion molecule L-selectin (sCD62L) have been linked to an increased incidence of lung failure and multiorgan dysfunction syndrome (MODS). Individual studies have had conflicting results, however. We examined multiple studies in an attempt to determine whether early sCD62L concentrations are predictive of major complications after severe trauma.

Methods: We performed a systematic review of six electronic databases and a manual search for clinical studies comparing outcomes of multiply injured patients (Injury Severity Score ≥16) depending on their early sCD62L blood concentrations. Because of various outcome definitions, acute lung injury (ALI) and adult respiratory distress syndrome (ARDS) were studied as a composite endpoint. Weighted mean differences (WMDs) in sCD62L concentrations were calculated between individuals with and without complications by fixed- and random-effects models.

Results: Altogether, 3370 citations were identified. Seven prospective studies including 350 patients were eligible for data synthesis. Published data showed the discriminatory features of sCD62L but did not allow for calculation of measures of test accuracy. Three of four studies showed lower early sCD62L concentrations among individuals progressing to ALI and ARDS (WMD = −229 μg/L; 95% confidence interval, −476 to 18 μg/L). No differences in sCD62L concentrations were noted among patients with or without later MODS. Nonsurvivors had significantly lower early sCD62L plasma concentrations (WMD = 121 μg/L; 95% confidence interval, 63–179 μg/L), but little information was available on potential confounders in this group.

Conclusions: Early decreased soluble L-selectin concentrations after multiple trauma may signal an increased likelihood of lung injury and ARDS. The findings of this metaanalysis warrant a large cohort study to develop selectin-based models targeting the risk of inflammatory complications.

The effect of anti-L-selectin (aselizumab) in multiple traumatized patients--results of a phase II clinical trial

OBJECTIVE

The objectives of this study were to evaluate safety (primary) and clinical efficacy (secondary) of the humanized monoclonal anti-L-selectin antibody aselizumab in severely injured patients.

DESIGN

Prospective phase II, parallel group, double-blind, randomized, placebo-controlled clinical trial.

SETTING

Fourteen medical intensive care units or trauma units in level I trauma centers in Belgium, Germany, and Poland.

PATIENTS

Eighty-four patients with a sustained trauma due to a blunt or penetrating injury and a total Injury Severity Scale score of > or =25.

INTERVENTIONS

Patients received either aselizumab at dosages of 0.5, 1, or 2 mg/kg or placebo within 6 hrs of the traumatic event and were followed for 6 wks.

MEASUREMENTS AND MAIN RESULTS

The number of expeditable adverse events increased dose dependently over the aselizumab groups compared with placebo. There were no statistically significant differences between all groups regarding leukopenia and risk of infection. No immunologic response following infusion of aselizumab was noted. The number of patients with multiple organ failure, defined as a median value of the total Goris Multiple Organ Failure score of > or =5 on > or =2 consecutive days within 14 days, was not significantly different for the 0.5 mg/kg, 1 mg/kg, 2 mg/kg, and placebo groups. There were no statistically significant differences in time of mechanical ventilation, length of stay in an intensive care unit, and total duration of hospitalization between treatment groups.

CONCLUSIONS

Aselizumab was associated with a higher rate of infections and leucopenia; however, this difference was not significantly different compared with placebo. For all efficacy variables, aselizumab presented no significant trends but only a few scattered statistically significant differences between groups.

High frequency oscillatory ventilation in burn patients with the acute respiratory distress syndrome

BACKGROUND

High frequency oscillatory ventilation (HFOV) improves gas exchange while providing lung protective effects during the ventilation of patients with the acute respiratory distress syndrome (ARDS). The purpose of this study was to review our experience with HFOV in adult burn patients with oxygenation failure secondary to ARDS.

METHODS

Retrospective cohort review of all burn patients treated with HFOV at a regional adult burn center.

RESULTS

All values are reported as the mean +/- standard deviation (S.D.). HFOV was used on 28 occasions in 25 patients (age 44 +/- 16 years, %TBSA burns 40 +/- 15, and a 28% incidence of inhalation injury) who had severe oxygenation failure from ARDS (PaO2/FiO2 ratio 98 +/- 26, and oxygenation index (OI) (FiO2 x 100 x mean airway pressure/PaO2) 27 +/- 10) following 4.8 +/- 4.4 days of conventional mechanical ventilation (CMV). After switching from CMV to HFOV, there were significant improvements in the PaO(2)/FiO2 ratio within 1h and in the oxygenation index within 24 h. The duration of HFOV was 6.1 +/- 5.8 days. HFOV was continued during 26 surgeries for 14 patients where a mean of 18 +/- 9% TBSA burns were excised and closed. The only complications related to HFOV were three episodes of severe hypercapnia. In-hospital mortality was 32%.

CONCLUSIONS

HFOV was safe, and was highly effective in correcting oxygenation failure associated with ARDS in burn patients, and can be successfully used as an intra-operative ventilation modality for burn patients.

Altered L-selectin expression in lymphocytes and increased adhesion to endothelium in patients with diabetic retinopathy

AIM

To investigate L-selectin expression and shedding in patients with and without retinopathy and to determine if any observed changes are reflected by a functional change in the adhesion of leucocytes to an endothelial monolayer.

METHODS

Age matched diabetic patients (26 with retinopathy, 19 without retinopathy) were compared to 24 non-diabetic controls to determine L-selectin surface protein expression, L-selectin mRNA production, and serum L-selectin levels by flow cytometry, RT-PCR, and ELISA, respectively. An adhesion assay was used to determine the binding of lymphocytes from the respective test groups to a monolayer of human endothelial cells.

RESULTS

Significantly reduced (p = 0.004) L-selectin expression was demonstrated on lymphocytes (CD3+) from patients with diabetes compared to controls, the lowest levels being found in those with diabetic retinopathy (p = 0.004). L-selectin mRNA levels (p = 0.007) were significantly higher in the retinopathy group than in the no retinopathy group. Serum L-selectin levels were significantly higher (p = 0.04) in those with retinopathy compared to controls. Lymphocyte adhesion relative to control (100%) was essentially unchanged (84.0% (SD 27.7%), p = 0.15) for diabetic patients with no retinopathy and was markedly increased (192% (37.6%)) for those with retinopathy (p = 0.0001).

CONCLUSION

Lymphocyte activation, reduced surface L-selectin, increased circulating L-selectin, and a corresponding increase in adhesion of patients' cells using an in vitro assay, is evident in people with diabetic retinopathy. This suggests a role for lymphocyte activation in the pathogenesis of diabetic retinopathy.

Pulmonary endothelium in acute lung injury: from basic science to the critically ill

BACKGROUND

Pulmonary endothelium is an active organ possessing numerous physiological, immunological, and metabolic functions. These functions may be altered early in acute lung injury (ALI) and further contribute to the development of acute respiratory distress syndrome (ARDS). Pulmonary endothelium is strategically located to filter the entire blood before it enters the systemic circulation; consequently its integrity is essential for the maintenance of adequate homeostasis in both the pulmonary and systemic circulations. Noxious agents that affect pulmonary endothelium induce alterations in hemodynamics and hemofluidity, promote interactions with circulating blood cells, and lead to increased vascular permeability and pulmonary edema formation.

OBJECTIVE

We highlight pathogenic mechanisms of pulmonary endothelial injury and their clinical implications in ALI/ARDS patients.

Acute lung injury and acute respiratory distress syndrome

Acute lung injury and acute respiratory distress syndrome are an important challenge for pediatric intensive care units. These disorders are characterized by a significant inflammatory response to a local (pulmonary) or remote (systemic) insult resulting in injury to alveolar epithelial and endothelial barriers of the lung, acute inflammation and protein rich pulmonary edema. The reported rates in children vary from 8.5 to 16 cases / 1000 pediatric intensive care unit (PICU) admissions. The pathological features of ARDS are described as passing through three overlapping phases - an inflammatory or exudative phase (0-7 days), a proliferative phase (7-21 days) and lastly a fibrotic phase (from day 10). The treatment of ARDS rests on good supportive care and control of initiating cause. The goal of ventilating patients with ALI/ARDS should be to maintain adequate gas exchange with minimal ventilator induced lung injury. This can be achieved by use of optimum PEEP, low tidal volume and appropriate FiO2. High frequency ventilation can improve oxygenation but does affect the outcomes. Prone positioning is a useful strategy to improve oxygenation. Pharmacological strategies have not made any significant impact on the outcomes. Preliminary data suggests some role for use of corticosteroids in non-resolving ARDS. The mortality rates have declined over the last decade chiefly due to the advances in supporting critically ill patients.

Elevated plasma and lung endothelial selectin levels in patients with acute respiratory distress syndrome and a history of chronic alcohol abuse

OBJECTIVE

Activation of endothelial cells is a critical step in the pathogenesis of acute respiratory distress syndrome (ARDS). Soluble endothelial selectin (sE-selectin), an endothelial cell-specific molecule that mediates leukocyte-endothelial cell adhesion has never been measured in the bronchoalveolar lavage fluid of critically ill patients. Based on the effects of alcohol on endothelial cell and alveolar-capillary barrier function, we hypothesized that chronic alcohol exposure may be associated with increased sE-selectin in ARDS patients.

DESIGN

Prospective observational cohort study.

SETTING

Medical and surgical intensive care units; an inpatient alcohol detoxification unit within university-affiliated hospitals.

PATIENTS

A total of 20 ARDS patients (50% with chronic alcohol abuse); seven individuals with a history of chronic alcohol abuse.

INTERVENTION

Patients underwent bronchoalveolar lavage within 72 hrs of ARDS diagnosis. Individuals with a history of chronic alcohol abuse underwent bronchoalveolar lavage within 7 days of their last alcoholic beverage. A history of chronic alcohol abuse was determined by a Short Michigan Alcohol Screening Test score of > or =3 or a history of an alcohol-related diagnosis. sE-selectin was measured in plasma and bronchoalveolar lavage.

MEASUREMENTS AND MAIN RESULTS

Neither severity of illness nor at-risk diagnosis differed by alcohol history. sE-selectin levels in the plasma of ARDS patients who abused alcohol chronically were significantly elevated compared with nonalcoholic ARDS patients (181 ng/mL [56-328] vs. 32 ng/mL [14-55], p <.01). The bronchoalveolar lavage sE-selectin levels from the patients with ARDS and alcohol abuse were also significantly elevated compared with nonalcoholic ARDS patients (1.51 ng/mL [1.09-3.11] vs. 0.69 ng/mL [0.33-0.94], p <.002) and were higher than those measured in individuals with a history of chronic alcohol abuse but without ARDS (0.46 ng/mL [0.12-2.75], p =.15).

CONCLUSIONS

ARDS patients who chronically abuse alcohol have elevated concentrations of sE-selectin in both the plasma and epithelial lining fluid consistent with altered endothelial cell and alveolar-capillary barrier function.

Neutrophil adhesion molecule expression in the developing neonatal rat exposed to hyperoxia

Neonatal rats have an increased tolerance to hyperoxia, which is associated with a diminished pulmonary inflammatory response compared with adults. To investigate this differing response, expression of the neutrophil adhesion molecules, L-selectin and CD18, and levels of soluble L-selectin, were examined using flow cytometry and sandwich enzyme-linked immunosorbent assay on air-exposed neonatal rat neutrophils at 0-24 and 72 h and 7, 10, 14, and 21 d of age compared with the adult and after exposure to hyperoxia (>/= 98% O2) for 56 h in adults and for 72 h and 7 d in neonates. Expression of L-selectin in 0-24-h neonates was similar to adults, but was significantly lower than adults at 72 h and 7 d (P = 0.011). Soluble L-selectin levels were significantly higher than those in adults in the 0-24- and 72-h neonates (P < 0.001). CD18 expression in unstimulated and activated neutrophils of neonatal rats was higher at 0-24 h than in the adult (P < 0.001), but thereafter did not differ from adults. After hyperoxic exposure, L-selectin did not differ between the exposure groups but soluble L-selectin tended to increase in neonates after 7 d of O2 exposure Finally, CD18 was significantly higher after hyperoxic exposure of the adult (P = 0.008), but did not change with oxygen exposure in the neonate. Based on these findings, we speculate that differences between neonatal and adult rats in expression of L-selectin may contribute to delayed oxygen toxicity in neonatal rats.

Elevated levels of circulating adhesion molecules in patients with active pulmonary tuberculosis

OBJECTIVE

Recent studies have indicated the importance of cell adhesion molecules in the pathogenesis of various inflammatory lung diseases. Our study was designed to determine whether five soluble adhesion molecules including soluble L-, E- and P-selectin (sL-, sE- and sP-selectin), intercellular adhesion molecule-1 (sICAM-1), and vascular cell adhesion molecule-1 (sVCAM-1) in serum reflect the severity of active pulmonary tuberculosis (TB), and whether there is a distinct profile of these soluble molecules in this disease.

METHODOLOGY

Using enzyme-linked immunosorbent assays, we measured the serum levels of these five soluble adhesion molecules in 31 patients with active TB and 11 healthy volunteers.

RESULTS

Serum levels of sE-selectin, sP-selectin and sICAM-1, but not sL-selectin or sVCAM-1, were significantly higher in patients with active TB than in the control subjects (P < 0.001, each). Significant correlations were detected only between serum levels of sE-selectin and sP-selectin, sE-selectin and sICAM-1, and sP-selectin and sICAM-1. There was a significant correlation between the Gaffky scale result (a scale assessing the number of mycobacteria bacilli present) and all of the above adhesion molecules, except for sL-selectin. Serum levels of sE-selectin, sL-selectin and sICAM-1 also correlated with the CXR radiological score. Higher levels of sL-selectin and sICAM-1 were detected in the serum of patients with radiological cavity formation compared to those without. The ESR, C-reactive protein and circulating neutrophil counts all correlated significantly with sE-selectin, sP-selectin, sICAM-1 and sVCAM-1.

CONCLUSION

The results suggest that there is a distinct profile of soluble adhesion molecules in active pulmonary TB and that sE-selectin, sP-selectin, and especially sICAM-1 appear to be the most sensitive clinical measures of disease severity.

ADAM-17-independent shedding of L-selectin

L-selectin is expressed by leukocytes and facilitates their adhesion under flow along the walls of blood vessels. As do a variety of membrane proteins, L-selectin undergoes ectodomain shedding. Using approaches that monitor full-length L-selectin in short-term assays, it has been determined that L-selectin shedding is defective in tumor necrosis factor alpha-converting enzyme (ADAM-17)-deficient cells. In this study, we examined the steady-state levels of L-selectin on ADAM-17-deficient cells using a monoclonal antibody to the cytoplasmic region of L-selectin, which allows for the detection of total L-selectin (full-length and the membrane-associated cleavage fragment). We demonstrate that ADAM-17-deficient cells generate a 6-kDa transmembrane fragment of L-selectin. Although inducible L-selectin shedding by phorbol 12-myristate 13-acetate stimulation was not observed by these cells in short-term assays, basal turnover did occur, resulting in the production of soluble L-selectin, as determined by enzyme-linked immunosorbent assay. L-selectin turnover was greatly increased upon ADAM-17 reconstitution. Truncating the juxtamembrane region of L-selectin blocked ADAM-17-independent shedding as did a hydroxymate metalloprotease inhibitor. Together, these findings demonstrate that a metalloprotease activity separate from ADAM-17 can use the cleavage domain of L-selectin. We speculate that separate proteolytic mechanisms of L-selectin shedding may regulate distinct antiadhesive mechanisms, such as inducible shedding for the rapid dissociation of cell-cell interactions and constitutive shedding for the homeostatic maintenance of high serum levels of soluble L-selectin, a potential adhesion buffer.

Soluble E-selectin, soluble L-selectin and soluble ICAM-1 in bronchopulmonary dysplasia, and changes with dexamethasone

OBJECTIVE

To evaluate longitudinal change in arterial blood plasma levels of soluble adhesion molecules in infants of <30 weeks' gestation with respiratory distress syndrome (RDS) and to look for differences in these levels in neonates who subsequently developed bronchopulmonary dysplasia (BPD) compared with those neonates who did not, and also to investigate the effect of dexamethasone treatment on levels of soluble adhesion molecules in plasma.

METHODS

We measured plasma concentrations of soluble L-selectin (sL-selectin), soluble E-selectin (sE-selectin), and soluble intercellular adhesion molecule-1 on days 1, 3, 7, 14, 21, and 28 of life and before and 2 to 3 days after initiating a 6-day course of dexamethasone treatment. Infants with RDS were followed until discharge and were classified as non-BPD and either 1) BPD day 28 reflecting oxygen requirement on day 28 but not at 36 corrected weeks or 2) BPD 36 weeks reflecting oxygen requirement at 36 (corrected) weeks' gestation. The classification of presence or absence of BPD by oxygen requirement was supported by and was consistent with radiologic findings of BPD for all infants. The difference between BPD day 28 and BPD 36 weeks was supported by more extensive radiologic effects in the latter.

RESULTS

The arterial plasma level of sL-selectin in infants who had RDS and did not develop BPD was significantly decreased compared with term healthy infants, as was the level of sE-selectin. Compared with infants who had RDS and did not develop BPD, sL-selectin levels were even further decreased in infants who had RDS and did develop BPD both at birth and throughout the first 4 weeks of life (day 1 through day 28). Infants with BPD also showed increasing levels of sE-selectin during this period of time, whereas infants without BPD did not. Levels of soluble intercellular adhesion molecule-1 in infants without BPD were not different from infants with BPD initially but increased in infants with BPD compared with infants without BPD, significant on day 28 in both groups. Dexamethasone treatment increased concentration of sL-selectin and decreased concentration of sE-selectin.

CONCLUSIONS

Low sL-selectin may be an early indicator of enhanced risk for BPD. Low levels of sL-selectin and increasing levels of sE-selectin may be risk factors for BPD. The effects of dexamethasone treatment include significant modulation of adhesion molecules.

Recombinant human growth hormone modulates the hepatic acute-phase response and P-selectin in burned rats

The purpose of this study was to determine the effect of recombinant human growth hormone (rhGH) on serum constitutive proteins, cytokines, P-selectin, and insulin-like growth factor (IGF-1) in the thermally injured rats.Sprague-Dawley rats (64 males) were given 30% total body surface area full thickness scald burn. They were randomly divided to receive either 2.5mg/kg per day im rhGH or saline (control). Rats were sacrified on postburn days 1, 2, 5, and 7, and serum constitutive proteins, cytokines, P-selectin, and IGF-1 levels were measured.Serum IGF-1 levels were increased on days 2, 5, or 7 after burn in rhGH-treated rats compared with controls (P<0.001, <0.01 and <0.001, respectively). Serum transferrin and albumin levels were increased on days 7 after burn in rhGH-treated rats compared with controls (P<0.05). The cytokines increased after thermal injury. The rhGH decreased serum levels of tumor necrosis factor-alpha on postburn days 1 compared with controls (P<0.001). Serum levels of interleukin-1 were decreased on days 1 and 2 after burn in rhGH treated rats compared with controls (P<0.001, <0.01, respectively). Rats receiving rhGH showed significantly increased P-selectin levels at 5 and 7 postburn days compared with controls (P<0.001). Our data indicate that rhGH, given after thermal injury, increased albumin, transferrin, IGF-1, and P-selectin levels and decreased serum tumor necrosis factor-alpha and interleukin-1 levels.

Association between increased levels of IL-2 and IL-15 and outcome in patients with early acute respiratory distress syndrome

BACKGROUND

Acute respiratory distress syndrome remains a serious, often fatal, condition, despite progress in modern critical care treatment. Cytokines play an important role in the pathogenesis of the syndrome, although their role in the evolution and outcome has not been clearly elucidated. We explored whether the measurement of serum and bronchoalveolar lavage IL-2 and IL-15 at the time of hospital admission can predict the outcome of this syndrome.

METHODS

Serum and bronchoalveolar lavage levels of IL-2 and IL-15 were measured in eight patients with ARDS (group A) and 26 patients on high risk for ARDS development who never developed ARDS (group B) from samples obtained at the time of admission.

RESULTS

Serum IL-2 (P > 0.05) and IL-15 (P < 0.05) levels were higher in group A than in group B. Serum levels of both cytokines were higher in patients who did not survive in both of the groups A and B compared to those who survived (P < 0.05, and P < 0.0001, respectively). The only significant change in BALF was the higher level of IL-15 in surviving group A patients (P < 0.05) when compared with the non survivors of the same group. For a serum cut-off level of 173 pg mL(-1) for IL-2 and 250 pg mL(-1) for IL-15, they exhibited a very high positive predictive value (PPV), negative predictive value (NPV), sensitivity and specificity for survival (100% in all). A positive correlation was found between serum levels of both cytokines and APACHE II score (IL-2, r = 0.61, and IL-15, r = 0.62, respectively, and P < 0.0001 for both).

CONCLUSION

Determination of serum IL-2 and IL-15 levels may be a valuable and simple aid to improve identification of patients with ARDS or at risk for ARDS who are at high risk of subsequent mortality.

A functional role for circulating mouse L-selectin in regulating leukocyte/endothelial cell interactions in vivo

L-selectin mediates the initial capture and subsequent rolling of leukocytes along inflamed vascular endothelium and mediates lymphocyte migration to peripheral lymphoid tissues. Leukocyte activation induces rapid endoproteolytic cleavage of L-selectin from the cell surface, generating soluble L-selectin (sL-selectin). Because human sL-selectin retains ligand-binding activity in vitro, mouse sL-selectin and its in vivo relevance were characterized. Comparable with humans, sL-selectin was present in adult C57BL/6 mouse sera at approximately 1.7 micro g/ml. Similar levels of sL-selectin were present in sera from multiple mouse strains, despite their pronounced differences in cell surface L-selectin expression levels. Adhesion molecule-deficient mice prone to spontaneous chronic inflammation and mice suffering from leukemia/lymphoma had 2.5- and 20-fold increased serum sL-selectin levels, respectively. By contrast, serum sL-selectin levels were reduced by 70% in Rag-deficient mice lacking mature lymphocytes. The majority of serum sL-selectin had a molecular mass of 65-75 kDa, consistent with its lymphocyte origin. Slow turnover may explain the relatively high levels of sL-selectin in vivo. The t(1/2) of sL-selectin, assessed by transferring sera from wild-type mice into L-selectin-deficient mice and monitoring serum sL-selectin levels by ELISA, was >20 h, and it remained detectable for longer than 1 wk. Short-term in vivo lymphocyte migration assays demonstrated that near physiologic levels ( approximately 0.9 micro g/ml) of sL-selectin decreased lymphocyte migration to peripheral lymph nodes by >30%, with dose-dependent inhibition occurring with increasing sL-selectin concentrations. These results suggest that sL-selectin influences lymphocyte migration in vivo and that the increased sL-selectin levels present in certain pathologic conditions may adversely affect leukocyte migration.

Inflammatory changes in the lungs of premature infants with symptomaticpatent ductus arteriosus

BACKGROUND

The aim of the study was to observe the inflammatory changes during the therapy for symptomatic patent ductus arteriosus (sPDA).

METHODS

We investigated biochemically the sample of the tracheobroncheal aspirates (TA) from 11 intubated premature infants. Three i.v. doses of indomethacin (0.2 mg/kg)were administered with 24-h intervals. The samples were divided into two groups, the effective occasions (n = 10)and non-effective occasions (n = 6). The amounts of myeloperoxidase (MPO), soluble L-selectin (sL-selectin)in TA, and the polymorphonuclear leukocytes (PMN) of peripheral blood stream and TA were analyzed before and after treatment ofsPDA with indomethacin.

RESULTS

In effective occasions, there were significant decreases of peripheral PMN and MPO and PMN in TA. However, this group had a significant increase of sL-selectin. In non-effective occasions, five out of six samples had decreases of MPO and PMNin TA, but not significantly. In contrast, there was a significant decrease of sL-selectin.

CONCLUSION

These data suggested that anti-inflammatory change after closure of sPDA may be caused by not only indomethacin itself, but also ductal closure itself. However, further study is necessary to clarify the relationship between the closure of the ductus itself and anti-inflammatory action in the lung.

Soluble L-selectin attenuates tumor necrosis factor-alpha-mediated leukocyte adherence and vascular permeability: a protective role for elevated soluble L-selectin in sepsis

OBJECTIVE

We have previously demonstrated that leukocyte delivery to remote sites is decreased in sepsis and that increased concentrations of soluble L-selectin are, in part, responsible for this finding. Given that leukocytes have been implicated in the pathogenesis of vascular leakage, we hypothesized that the elevated soluble L-selectin concentrations in sepsis may translate into decreased inflammation-mediated leukocyte-endothelial cell interactions and vascular leakage at these sites.

DESIGN

Prospective, controlled animal study.

SETTING

Surgical research laboratory in a university hospital.

SUBJECTS

Swiss white male mice weighing 25-35 g.

INTERVENTIONS

Mice were randomized to one of three study groups: intracremaster tumor necrosis factor-alpha with subsequent intravenous bicarbonate buffered solution; intracremaster tumor necrosis factor-alpha with intravenous soluble L-selectin (10 microg/mL); and intracremaster bicarbonate buffered solution with intravenous bicarbonate buffered solution. The cremaster muscle was prepared for both light and fluorescence intravital microscopy 2 hrs after intracremaster injection, and fluorescein isothiocyanate-labeled albumin was injected intravenously. Leukocyte-endothelial interactions (rolling flux, rolling velocity, and adherence) were counted off-line. Postcapillary venule leakage was determined by the permeability index (perivenular/intravenular fluorescence) after intravenous injection of fluorescent albumin.

MEASUREMENTS AND MAIN RESULTS

Soluble L-selectin significantly attenuated tumor necrosis factor-alpha-mediated increases in leukocyte adherence and vascular leakage. Leukocyte rolling velocity was restored to baseline with soluble L-selectin; however, rolling flux was not altered. Blood pressure, shear rate, and leukocyte counts did not differ between groups.

CONCLUSIONS

Soluble L-selectin decreases local inflammation-mediated leukocyte adherence and vascular leakage in vivo. The increased concentrations of soluble L-selectin in sepsis may represent a protective mechanism by which the host attempts to diminish the deleterious systemic effects of activated leukocytes during sepsis.

Role of L-selectin in the development of ventilator-associated pneumonia in patients after major surgery

BACKGROUND

The circulating level of soluble L-selectin (sL-selectin) has been reported to be low in adult respiratory distress syndrome and acute lung injury. This study explores the role of L-selectin in the development of ventilator-associated pneumonia (VAP) in patients undergoing major surgery.

PATIENTS AND METHODS

Thirty-four patients who underwent esophagectomy were maintained by mechanical ventilation in a surgical intensive care unit. Fourteen patients developed VAP by postoperative day (POD) 7, while 20 patients did not. The plasma levels of soluble adhesion molecules and elastase were measured serially by ELISA or EIA. The expression of L-selectin on polymorphonuclear neutrophils (PMNs) was analyzed by flow cytometry.

RESULTS

In multiple logistic regression analysis, only the preoperative plasma level of sL-selectin was significantly associated with VAP. The plasma sL-selectin level before surgery was significantly lower in the patients who developed VAP compared with the patients who did not develop VAP. After surgery, the level of sL-selectin did not change. The plasma level of soluble intercellular adhesion molecule-1 increased in the patients with and without VAP. The plasma level of soluble vascular cell adhesion molecule-1 was significantly higher in the patients with VAP. L-selectin expression on PMNs showed a peak on POD 2 in the patients without VAP, whereas it was impaired in the patients with VAP.

CONCLUSIONS

Determination of the preoperative plasma level of sL-selectin may help to identify patients at high risk for VAP after esophagectomy.

The pulmonary physician in critical care * 6: The pathogenesis of ALI/ARDS

An understanding of the pathogenesis of ARDS is essential for choosing management strategies and developing new treatments. The key mediators involved in the inflammatory and fibroproliferative responses are reviewed and the mechanisms which regulate these responses are highlighted.

Malaria and the lung

Pulmonary edema that results from increased pulmonary capillary permeability is the most important pulmonary manifestation of malaria. It is a common feature of severe malaria but also occurs rarely in milder disease. Mortality rate is high. The pathophysiologic basis is unclear. In the field, there is much clinical overlap between malaria and pneumonia in children. For physicians in nonmalarial areas, malaria always should be considered in the differential diagnosis of a sick patient who has traveled to a malaria-endemic area. More research is needed to better define and tailor treatments for malarial and nonmalarial ALI and ARDS.

Hydroxyurea corrects the dysregulated L-selectin expression and increased H(2)O(2) production of polymorphonuclear neutrophils from patients with sickle cell anemia

Impaired polymorphonuclear neutrophil (PMN) functions during sickle cell anemia (SCA) may have a pathogenic role in the onset of vasoocclusive events. We used flow cytometry to study, in whole blood, the adhesion molecule expression and respiratory burst of PMNs from children with SCA. Three different clinical groups were studied: (1) patients with no history of vasoocclusive events (n = 15); (2) patients with a history of vasoocclusive events (n = 17); and (3) patients receiving hydroxyurea therapy for severe vasoocclusive events (n = 9). Unstimulated PMNs showed decreased L selectin expression and increased H(2)O(2) production whatever the severity of the disease, reflecting PMN activation. This could contribute to endothelial activation reflected by abnormal plasma levels of soluble adhesion molecules (soluble intercellular adhesion molecule-1, sE selectin, and sL selectin). After stimulation with bacterial N-formyl peptides (N-formyl-methionyl-leucyl-phenylalanine [fMLP]), PMNs from untreated patients with a history of vasoocclusive events showed dysregulated L selectin shedding and increased H(2)O(2) production. Furthermore, in these patients, tumor necrosis factor priming followed by fMLP stimulation induced an H(2)O(2) production significantly higher than in the other patient groups and controls. These impairments could immobilize PMNs on the endothelium, thereby inducing reduced blood flow and fostering microvascular occlusion and vascular damage. In contrast, children treated with hydroxyurea showed near-normal basal and poststimulation H(2)O(2) production as well as normal L selectin shedding after stimulation but no change in plasma levels of soluble adhesion molecules. To our knowledge, this is the first report showing major qualitative changes of PMN abnormalities upon hydroxyurea treatment in SCA patients. This strongly suggests that PMNs are a primary target of this drug.

L-selectin in health and disease

This article reviews recent advances in the knowledge of the role of L-selectin, an adhesion molecule that is expressed on the surface of circulating leucocytes, in animal and human physiology and pathophysiology. After a brief discussion on nomenclature and structure, it progresses through the evidence for expression and regulation of L-selectin, cell collection and purification, physiological function and roles. The special role of knock out mice and monoclonal antibodies in determining a role for L-selectin in inflammatory states is described before proceeding to discuss the importance of L-selectin ligands and shed L-selectin. A second section describes a role for L-selectin in pathophysiological states in animals and man, with special reference to trauma, systemic inflammatory syndromes and sepsis. The review concludes with a summary of the potential role of anti-inflammatory medication and L-selectin blockers in the management of inflammation.

Soluble intercellular cell adhesion molecule-1 and L-selectin plasma concentrations and response to surfactant in preterm infants

OBJECTIVE

To investigate whether plasma concentrations of soluble intercellular cell adhesion molecule (ICAM)-1 and L-selectin at 24 hrs of life are related to good or poor response to exogenous surfactant in preterm infants.

DESIGN

Prospective study of markers of inflammation in circulating blood at 24 hrs of life.

SETTING

Level III neonatal intensive care unit.

PATIENTS

Twenty-nine preterm newborns suffering from severe respiratory distress syndrome (Fio(2) > 0.4) without signs of infection or fetal acidosis, and 17 healthy preterm newborns of similar gestational age serving as controls.

INTERVENTIONS

Infants with respiratory distress were treated with natural surfactant at 0.3-5 hrs of life. A response to surfactant, defined as a decrease of Fio(2) >50% within 6 hrs after surfactant, was seen in 21 infants.

MEASUREMENTS AND MAIN RESULTS

Soluble ICAM-1 and L-selectin concentrations were determined in plasma samples taken at 24 hrs of age. ICAM-1 was elevated (p <.001) in infants who responded poorly to surfactant (median, 392 ng/mL; range, 58.26-4884.24 ng/mL) compared with good responders (20.52 ng/mL, 2.32-138.58 ng/mL) or controls (21.91 ng/mL, 2.61-65.73 ng/mL), without differences between controls and good responders. L-selectin was lower (p =.004) in surfactant-treated infants (4.45 nmol/L, 2.0-10.4 ng/mL) than in controls (6.0/2.35-10.25 nmol/L) without differences between surfactant good and poor responders. However, infants requiring supplemental oxygen at 36 wks of gestational age had reduced L-selectin at 24 hrs of age (3.2/2.0-3.45 vs. 5.0/2.35-10.4 nmol/L, p =.004), whereas there was no difference in ICAM-1.

CONCLUSIONS

In preterm infants with respiratory distress, a poor response to surfactant within 6 hrs of administration is associated with elevated circulating ICAM-1 concentrations at 24 hrs of age. Low plasma L-selectin at 24 hrs of age predicts prolonged requirement for supplemental oxygen.

Early clinical experience with high-frequency oscillatory ventilation for ARDS in adult burn patients

Lung protective ventilation strategies are recommended in acute respiratory distress syndrome to avoid ventilator associated lung injury, a recently characterized complication of mechanical ventilation. High-frequency oscillatory ventilation (HFOV) is an unconventional ventilation strategy which may achieve this goal. We reviewed our experience with HFOV in six severely burned patients with acute respiratory distress syndrome. The mean age (+/- SD) of the patients was 34 +/- 13 years, and the mean TBSA burn was 52 +/- 10%, with a mean full-thickness injury of 49 +/- 12%. HFOV was initiated as "rescue therapy" in three patients with oxygenation failure (mean PaO2/FIO2 ratio of 71 +/- 8 and mean oxygenation index [OI] of 42 +/- 3) that was unresponsive to conventional ventilation (mean FIO2, 1.0 +/- 0; mean positive end expiratory pressure, 14.8 +/- 2.8 cm H2O; and mean inhaled nitric oxide, 20 +/- 0 ppm). In the other three cases, HFOV was initiated "prophylactically" as a lung protective ventilation strategy in an attempt to prevent further respiratory deterioration. All six patients showed a rapid and substantial improvement in oxygenation after initiation of HFOV, with significant improvements in the PaO2/FIO2 and OI by 12 hours (P = 0.02). In four patients HFOV was also used during anesthesia and surgery, where a total of 10 procedures involving a mean excision and closure of 15 +/- 7% TBSA burns was performed. Five of the six patients died, but none died because of oxygenation failure. In three patients death resulted from sepsis and multiple organ dysfunction syndrome; their mean PaO2/FIO2 was 107 +/- 31 and their mean OI was 30 +/- 11 immediately before death. Two patients with multiple organ dysfunction syndrome died after withdrawal of life support; their mean PaO2/FIO2 and OI were 178 +/- 31 and 18 +/- 2 respectively, at the time of this decision. Although HFOV had no impact on mortality, it played a useful role in the supportive management of burn patients with severe oxygenation failure unresponsive to conventional ventilation. Importantly, HFOV allowed surgery to proceed in patients who may have otherwise been too unstable to go to the operating room. As far as we are aware, this is the first report of the use of intraoperative HFOV in burn patients.

Changes in endothelial, leucocyte and platelet markers following contrast medium injection during angiography in patients with peripheral artery disease

Peripheral artery angiography, a common diagnostic procedure, may cause early and late adverse reactions, such as anaphylaxis, thrombosis and possible progression of the underlying arterial disease. To test the hypothesis that radiographic contrast medium may contribute to these events by adversely affecting the endothelium, leucocytes and/or platelets, 19 subjects undergoing angiography for the investigation and/or treatment of lower limb atherosclerosis were recruited. Blood was obtained from the external iliac vein before, and at serial intervals after, the injection of radiographic contrast medium into the ipsilateral femoral artery for diagnostic use. Markers of endothelial cell injury (von Willebrand factor (vWf)), platelet activation (soluble P-selectin) and leucocyte activation (neutrophil elastase and soluble L-selectin) were measured in citrated plasma. Soluble intercellular adhesion molecule-1 (sICAM-1) and thromboxane B(2), which are non-specific markers of inflammation, were also measured. Compared with the sample prior to angiography, levels of soluble L-selectin and sICAM-1 were reduced (p<0.02) immediately after passage of the last bolus of contrast medium. 15 min later, levels returned to normal but the level of vWf had increased (p<0.02). After 30 min, only levels of thromboxane B(2) were increased (p<0.05). The following day both vWf (p<0.01) and soluble P-selectin (p<0.05) were increased. These data point to both early and late effects of contrast medium on markers of endothelial, platelet and leucocyte function.

Elevated plasma surfactant protein-B predicts development of acute respiratory distress syndrome in patients with acute respiratory failure

Surfactant protein-B is a lung specific protein secreted into the air spaces by pulmonary epithelial type II cells that leaks into the bloodstream in increased amounts in patients with ARDS. To test whether elevated plasma levels of surfactant protein-B would predict the development of ARDS in patients with acute hypoxemic respiratory failure, plasma and lung injury scores were collected at study entry and daily thereafter for 3 d from 54 patients admitted to our intensive care unit. ARDS was defined as a new bilateral infiltrate on chest radiograph and a lung injury score > or = 2.5. Twenty patients developed ARDS, of whom seven died. Although the initial lung injury score was not predictive of ARDS, the initial plasma surfactant protein-B was predictive (area under the curve = 0.77 [0.63 to 0.90], nonparametric receiver-operating characteristic analysis). In this cohort, plasma surfactant protein-B was particularly predictive of ARDS when applied to patients suffering a direct lung insult (area under the curve = 0.87 [0.72 to 1.02]), with a sensitivity of 85% (95% CI: 55 to 98%) and specificity of 78% (40 to 97%) at a cutoff of 4,994 ng/ml.

Shed L-selectin (sCD62L) load in trauma patients

BACKGROUND

Low circulating plasma concentrations of the leukocyte adhesion molecule L-selectin (sCD62L) were found to be associated with an increased risk for subsequent lung failure and case fatality after severe trauma. The objective of this study was to determine the robustness of soluble L-selectin, correcting for a broad spectrum of physiological variables.

METHODS

Patients with suspected multiple and/or trunk injuries were enrolled into this study over a 1-year period. Plasma samples were obtained on hospital presentation, and circulating soluble L-selectin was measured with a commercially available ELISA kit. Study records comprised all relevant clinical and laboratory data. Thirty-day survival rate, subsequent acute lung failure, and nosocomial pneumonia were defined as study endpoints. Statistical analysis was performed using multivariate logistic regression models.

RESULTS

Seventy patients with a mean age of 35.51 years (range, 10-87 years) and a mean ISS score of 36.61 (95% CI, 31.08-42.14) entered the study. Eleven patients died, leading to an attributable mortality of 15.70%. L-Selectin levels did not differ between survivors and nonsurvivors. Five patients progressed to acute lung injury, whereas 11 patients developed hospital-acquired pneumonia. Lower L-selectin levels indicated patients at risk for lung injury with a relative odds estimated at 4.43 (P = 0.017). Statistical significance diminished in the multivariate model. In contrast, plasma concentrations of circulating sCD62L were significantly decreased in patients developing nosocomial pneumonia (P = 0.023), with a twofold increased relative odds (OR, 1.96; 95% CI, 0.51-7.50). No effect modification was observed by the included covariables.

CONCLUSIONS

The results of this study highlight the independent predictive value of initially decreased soluble L-selectin levels for the identification of patients susceptible to subsequent respiratory complications after severe trauma.

Neutrophil adhesion is impaired in the mesentery but not in the liver sinusoids of portal hypertensive rats

Altered leukocyte/cytokine response to inflammation has been observed in human and experimental portal hypertension. The aim of this study was to characterize leukocyte adhesion in portal hypertensive (PPVL) rats stimulated with endotoxin. Leukocyte rolling, adhesion, and migration assessed by intravital microscopy were impaired in mesenteric venules after lipopolysaccharide administration (150 microg/kg) in PPVL vs. sham-operated rats. Analysis of leukocyte L-selectin expression and soluble L-selectin showed that this defective adhesion was related to increased L-selectin shedding. In vitro experiments using isolated leukocytes treated with phorbol 12-myristate 13-acetate showed that monocytes and neutrophils but not lymphocytes were hyperreactive to cell activation, as measured by CD11b overexpression and increased L-selectin shedding in PPVL rats. However, neutrophil emigration in liver sinusoids and in the lung 3 h after endotoxin injection were similar in both groups of animals. Thus the alterations in leukocyte activation and adhesion molecule expression observed in this study may contribute to a better understanding of the higher susceptibility and severity of bacterial infections in cirrhotic patients with portal hypertension.

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.

Impaired transendothelial migration of B-CLL lymphocytes: a defect linked to low L-selectin expression

The emigration of lymphocytes from blood into lymph nodes is regulated by the expression of the adhesion molecule, L-selectin on the lymphocyte surface which arrests the rolling of the cell on the vessel wall and allows firmer adhesive interactions to develop. The expression of L-selectin on B-CLL lymphocytes is less than half that on normal lymphocytes and this difference correlates with an impaired capacity of B-CLL lymphocytes to migrate beneath a monolayer of human umbilical vein endothelial cells. Both the B-cell and T-cell lymphocytes from normal subjects and B-CLL patients show down-regulation of L-selectin and CD23 after transendothelial migration. The reduced expression of L-selectin on B-CLL lymphocytes leads to a relative "trapping" of these cells in the vascular space and is one factor contributing to the elevation of peripheral lymphocyte count.

Soluble P-selectin and the postoperative course following cardiopulmonary bypass in children

BACKGROUND

Cytokine-inducible leucocyte-endothelial adhesion molecules were shown to affect the postoperative inflammatory response following cardiopulmonary bypass (CPB). Soluble P-selectin (sP-selectin) is one of these molecules. We investigated the correlation between plasma sP-selectin levels and the intra- and postoperative course in children undergoing CPB.

METHODS

Serial blood samples of 13 patients were collected preoperatively upon initiation of CPB and seven times postoperatively. Plasma was recovered immediately and frozen at - 70 degrees C until use. Circulating soluble selectin molecules were measured with a sandwich enzyme-linked immunoabsorbent assay technique.

RESULTS

The significant post-CPB changes in sP-selectins plasma levels were associated with patient characteristics, operative variables and postoperative course. sP-selectin levels correlated significantly with surgery time, aortic cross-clamping time and inotropic support, as well as with the postoperative Pediatric Risk of Mortality score, hypotension and tachycardia.

CONCLUSIONS

A relation between CPB-induced mediators and both early and late clinical effects is suggested. The up-regulation and expression of sP-selectin indicate neutrophil activation as a possible mechanism for the increase, and inhibiting it may reduce the inflammatory response associated with CPB.

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.

Acute lung injury: cellular mechanisms and derangements

The clinical course of acute lung injury (ALI) is a complex and variable process accompanied by severe lung dysfunction, which persists for a long period of time with variable recovery of pulmonary function. The extent and severity of the lung disease associated with ALI varies with those patients having the most severe manifestations of lung disease being grouped as acute respiratory distress syndrome (ARDS). The pathological injury associated with this disease process, termed diffuse alveolar damage (DAD), has three overlapping phases (exudative, proliferative and fibrotic) which are the consequences of severe injury to the alveolar-capillary unit. There is no uniformity to the progression and length of each stage. This review explores those cellular mechanisms and derangements involved in the progression of ARDS. Those areas that demonstrate the major advances within the field are highlighted because of the diverse and vast nature of the cellular components involved in the process of ALI. We are beginning to identify those processes that contribute to the cellular derangements which are the hallmark of ALI. By expanding our understanding of those factors, we should in the future be able to construct therapeutic interventions that address the aetiology of ALI.