Effects of varying shear stress profiles on the regulation of pulmonary artery endothelial cell gene expression: a focus on selected mediators of vascular tone, inflammation and angiogenesis

Background

Pulmonary arterial hypertension (PAH) is a complex pathology characterized by obliterative vascular remodeling that leads to right heart failure and death. Predisposition to PAH is associated with mutations in the BMPR2 gene in approximately 70–80% of familial cases and around 30% for that of sporadic PAH. The study of the pathogenetic basis of PAH is often performed in static endothelial cultures. Such two-dimensional, isolated cell microenvironments fail to consider the heterogeneity in mechanical stress acting on endothelial cells in various regions of the pulmonary vascular tree. In the remodeled pulmonary vasculature, low and oscillatory shear stress is observed in the proximal pulmonary artery with high shear stress in distal pre-capillary pulmonary arterioles. Therefore, the impact of varied shear profiles (including both laminar and oscillatory flow) on pulmonary artery endothelial cell (and that of BMPR2-deplete) gene expression of common vasoactive (EDN1, ENOS), proinflammatory (IL6, IL8) and angiogenic mediators (ANG2, VEGFA), are poorly described.

Purpose

To evaluate the effects of shear stress magnitude, including unidirectional and oscillatory flow on BMPR2-knockdown human pulmonary artery endothelial cell (HPAEC) gene expression of EDN1, ENOS, IL6, IL8, ANG2 and VEGFA.

Methods

HPAECs were transfected with siRNA directed against BMPR2 (siB2) or with a non-targeting control (siCon). Cells were exposed to 10 hours of laminar or oscillatory flow (1Hz; 1.5 dyn/cm2, 15 dyn/cm2 or 90 dyn/cm2) using a parallel-plate fluid flow chamber system. Measurement of mRNA expression was performed using qPCR.

Results

Shear stress intensity and flow type (unidirectional and oscillatory) mediated diverse effects on HPAEC gene expression across the markers studied. Changes in gene expression were calculated relative to that of static siCon-transfected HPAECs and in such a manner are summarized as fold changes in the table below. Asterisks are shown where significant fold differences are reported. *P≤0.05, **P≤0.01, ***P≤0.001, ****P≤0.0001. aP≤0.05, bP≤0.05, cP≤0.05, denote comparisons between groups. Of note, no significant differences in gene expression were observed between static siCon and static siB2.

Conclusions

For the markers studied, different magnitudes of shear stress and flow profiles (together with BMPR2 loss) exhibit varied patterns of gene expression in the pulmonary vascular endothelium. As such, this illustrates the need for wider study of in vitro endothelial-shear stress interactions in understanding mechanisms of remodeling in PAH.

Funding Acknowledgement

Type of funding sources: None. Table 1

Plasma S100A8/A9 heterodimer is an early prognostic marker of acute kidney injury associated with cardiac surgery

AIM

We investigated whether plasma levels of the inflammation marker S100A8/A9, could predict acute kidney injury (AKI) onset in patients undergoing cardiac surgery necessitating cardiopulmonary bypass (CPB).

PATIENTS & METHODS

Plasma levels of S100A8/A9 and other neutrophil cytosolic proteins were measured in 39 patients pre- and immediately post-CPB.

RESULTS

All markers increased significantly post-CPB with S100A8/A9, S100A12 and myeloperoxidase levels significantly higher in patients who developed AKI within 7 days. S100A8/A9 had good prognostic utility for AKI, with an area under the receiver operating characteristic curve of 0.81 (95% CI: 0.676-0.949) and a cut-off value of 10.6 μg/ml (85.7% sensitivity and 75% specificity) irrespective of age.

CONCLUSION

Plasma S100A8/A9 levels immediately after cardiac surgery, can predict onset of AKI, irrespective of age.

Drug-Coated Balloon-Only Percutaneous Coronary Intervention for the Treatment of De Novo Coronary Artery Disease: A Systematic Review

Percutaneous coronary intervention (PCI) with a drug coated balloon (DCB) is a novel treatment which seeks to acutely dilate a coronary stenosis and deliver an anti-proliferative drug to the vessel wall (reducing the risk of re-stenosis), without implanting a drug eluting stent (DES). In this study, we performed a systematic review of stentless DCB-only angioplasty in de novo coronary artery disease. We identified 41 studies examining the effects of DCB-only PCI in a variety of clinical scenarios including small vessels, bifurcations, calcified lesions, and primary PCI. DCB-only PCI appears to be associated with comparable clinical outcomes to DESs and superior angiographic outcomes to plain-old balloon angioplasty. Although current data are promising, there is still a need for further long-term randomized control trial data comparing a DCB-only approach specifically against a second- or third-generation DES. A 4-week period of dual antiplatelet therapy provides a real advantage for the DCB-only PCI approach, which is not possible with most DESs. Since rates of adverse clinical outcomes are very low for all PCI procedures attention should be turned to the development of robust endpoints with which to compare DCB-only PCI approaches to the standard treatment with a DES.

The value of mobile tablet computers (iPads) in the undergraduate medical curriculum

The deployment of mobile tablet computers in medical teaching and learning is viewed with mounting interest. Medical educators are embracing insights from technological advancements to ensure that students are equipped with the necessary tools to flourish as physicians. Here, we reflect on the benefits and challenges of the tablet learning experience within undergraduate medicine and how students may make the best use of it.

Drug-eluting balloons with provisional bail-out or adjunctive stenting in de novo coronary artery lesions-a systematic review and meta-analysis

Background

Efficacy of drug-eluting balloons (DEB) for treatment of de novo coronary lesions remains controversial. The present systematic review and meta-analysis of randomised controlled trials assessed DEB with bare-metal stents (BMS) and also DEB with provisional bail-out stents ('DEB-only' strategy), to other conventional options: plain-old balloon angioplasty (POBA), BMS and drug-eluting stents (DES).

Methods

A systematic literature search from January 2000 until May 2017 was conducted. Primary outcome measure, late lumen loss (LLL); and secondary outcomes; binary restenosis, major adverse cardiac events (MACE), target lesion revascularization (TLR), myocardial infarction (MI), cardiovascular death and stent thrombosis were analysed.

Results

Seventeen RCTs were included with 2,616 patients. Several comparative groups showed significant differences. DEB with BMS were inferior to DES for LLL [mean difference (MD) =0.12 mm; 95% confidence interval (CI), 0.03 to 0.22; P=0.01]; and binary restenosis [risk ratio (RR) =1.89; (CI, 1.13 to 3.18); P=0.02]. DEB with BMS was superior to BMS for LLL [MD =-0.27 mm; (-0.45 to -0.10); P=0.002]; and MACE [RR =0.64; (0.46 to 0.90); P=0.010]. Finally, DEB alone was superior to POBA for LLL [MD =-0.39 mm; (-0.67 to -0.11); P=0.006] and binary restenosis [RR =0.20; (0.05 to 0.85); P=0.03] in bifurcation lesions.

Conclusions

The results of this meta-analysis showed that whilst DEB with BMS is superior to BMS alone, the combination is inferior to DES for treatment of de novo coronary lesions. Thus, DEB + BMS should not be applied in de novo lesions unless in patients who have absolute contraindications to DES. DEB alone, however, should be considered for relative contraindications to DES such as small vessel disease and bifurcation lesions.

Raised plasma Robo4 and cardiac surgery-associated acute kidney injury

OBJECTIVE

Endothelial dysfunction associated with systemic inflammation can contribute to organ injury/failure following cardiac surgery requiring cardiopulmonary bypass (CPB). Roundabout protein 4 (Robo4), an endothelial-expressed transmembrane receptor and regulator of cell activation, is an important inhibitor of endothelial hyper-permeability. We investigated the hypothesis that plasma levels of Robo4 are indicative of organ injury, in particular acute kidney injury (AKI), after cardiac surgery.

METHODS

Patients (n = 32) undergoing elective cardiac surgery with CPB were enrolled, prospectively. Plasma Robo4 concentrations were measured pre-, 2 and 24 h post-operatively, using a commercially available ELISA. Plasma and endothelial markers of inflammation [interleukin (IL) -6, -8, -10: von Willibrand factor (vWF) and angiopoeitin-2 (Ang-2)] and the AKI marker, neutrophil gelatinase-associated lipocalin (NGAL), were also measured by ELISA.

RESULTS

Plasma Robo4 increased significantly (p<0.001) from pre-operative levels of 2515 ± 904 pg/ml to 4473 ± 1915 pg/ml, 2 h after surgery; and returned to basal levels (2682 ± 979 pg/ml) by 24 h. Plasma cytokines, vWF and NGAL also increased 2 h post-operatively and remained elevated at 24 h. Ang-2 increased 24 h post-operatively, only. There was a positive, significant correlation (r = 0.385, p = 0.0298) between Robo-4 and IL-10, but not other cytokines, 2 h post-operatively. Whilst raised Robo4 did not correlate with indices of lung dysfunction or other biomarkers of endothelial activation; there was a positive, significant correlation between raised (2 h) plasma NGAL and Robo4 (r = 0.4322, p = 0.0135). When patients were classed as AKI or non-AKI either using NGAL cut-off of 150 ng/ml, or the AKI Network (AKIN) clinical classification; plasma Robo4 was significantly higher (p = 0.0073 and 0.003, respectively) in AKI vs. non-AKI patients (NGAL cut-off: 5350 ± 2191 ng/ml, n = 16 vs. 3595 ± 1068 pg/ml, n = 16; AKIN: 6546 pg/ml, IQR 5025-8079, n = 6; vs. 3727 pg/ml, IQR 1962-3727, n = 26) subjects.

CONCLUSION

Plasma Robo4 levels are increased, transiently, following cardiac surgery requiring CPB; and higher levels in patients with AKI suggest a link between endothelial dysregulation and onset of AKI.

Decreased expression of receptor for advanced glycation end-products (RAGE) on neutrophils following surgery necessitating cardiopulmonary bypass (snCPB) (P5058)

Surgery necessitating cardiopulmonary bypass (snCPB) is associated with systemic inflammation which can be severe. Systemic inflammation is common in the critically ill, is linked to adverse outcome and currently has no specific therapy. Insight into the pathogenesis of systemic inflammation may lead to therapies. The receptor for advanced glycation end-products (RAGE) is an ubiquitous receptor that is up-regulated in the presence of its ligands which are glycated proteins, S100 proteins and high mobility group box 1 (HMGB1). It causes a pro-inflammatory response via NF-κB and the MAP kinases. RAGE inhibition has been associated with improved outcomes in animal models of inflammation and may represent a novel target for intervention. In this study, blood was obtained pre- and post-operation from patients having cardiac surgery involving CPB. The surface and intracellular expression levels of RAGE in neutrophils and monocytes were assessed by flow cytometry and mRNA was obtained for RT-PCR. Preliminary results showed that although snCPB made little difference to intracellular RAGE, cellular RAGE decreased significantly, suggesting that the operative procedure could have initiated shedding of the receptor. There was no significant difference in the RAGE mRNA levels pre- and post-operation. This study provides a better understanding of the involvement of RAGE in systemic inflammation suggesting that shedding of the surface RAGE might contribute to the inflammation process.

Plasma thioredoxin levels during post-cardiac arrest syndrome: relationship with severity and outcome

Introduction

Despite experimental evidence, clinical demonstration of acute state of oxidative stress and inflammation during post-cardiac arrest syndrome is lacking. Plasma level of thioredoxin (TRX), a redox-active protein induced under conditions of oxidative stress and inflammation, is increased in various critical care conditions. We determined plasma TRX concentrations after cardiac arrest and assessed relationships with severity and outcome.

Methods

Retrospective study of consecutive patients admitted to a single academic intensive care unit (ICU) for out-of-hospital cardiac arrest (between July 2006 and March 2008). Plasma levels of TRX were measured at admission, day (D) 1, 2 and 3.

Results

Of 176 patients included, median TRX values measured in ICU survivors and non-survivors were, respectively: 22 ng/mL (7.8 to 77) vs. 72.4 (21.9 to 117.9) at admission (P < 0.001); 5.9 (3.5 to 25.5) vs. 23.2 (5.8 to 81.4) at D1 (P = 0.003); 10.8 (3.6 to 50.8) vs. 11.7 (4.5 to 66.4) at D2 (P = 0.22); and 16.7 (5.3 to 68.3) vs. 17 (4.3 to 62.9) at D3 (P = 0.96). Patients dying within 24 hours had significantly (P < 0.001) higher TRX levels (118.6 ng/mL (94.8 to 280)) than those who died after 24 hours or survived (50.8 (13.9 to 95.7) and 22 (7.8 to 77)). The area under the ROC curve to predict early death was 0.84 (0.76 to 0.91).

TRX levels on admission were significantly correlated with 'low-flow' duration (P = 0.003), sequential organ failure assessment (SOFA) score (P < 0.001), and blood lactate concentration (P < 0.001), but not with 'no-flow' duration or simplified acute physiology score (SAPS) II score. TRX levels and admission arterial pO² correlated negatively (r = -0.17, P = 0.03). Finally, cardiac arrest with cardiac etiology exhibited lower levels of TRX than in cases of extra-cardiac cause (46 ng/mL (11 to 104) vs. 68 (42 to 137), P = 0.01).

Conclusions

Our data show for the first time that TRX levels were elevated early following cardiac arrest, suggestive of oxidative stress and inflammation occurring with this condition. Highest values were found in the most severe patients. TRX could be a useful tool for further exploration and comprehension of post-cardiac arrest syndrome.

Lest we forget the endothelial glycocalyx in sepsis

Sepsis is the third largest cause of death in industrialised countries, but treatment remains largely supportive and effective therapeutic interventions are urgently needed. Disruption and dysfunction of the microvascular endothelium leading directly or indirectly to multiple organ failure are now recognised to underpin the pathophysiology of sepsis. Biomarkers of endothelial activation may therefore assume an important role in guiding future research efforts. We suggest that integral to this approach is the investigation and evaluation of endothelial glycocalyx biomarkers, not only as indicators of the pathogenic process but also to inform the development of pharmacological and other therapies.

Differences in lipopolysaccharide- and lipoteichoic acid-induced cytokine/chemokine expression

Purpose

To investigate differences in cytokine/chemokine release in response to lipoteichoic acid (LTA) or lipopolysaccharide (LPS) and contributing cellular mechanisms, in order to improve understanding of the pathogenesis of sepsis.

Methods

Levels of cytokines/chemokines were measured in plasma and peritoneal lavage fluid of 10-week-old male mice (C57/B16) following intraperitoneal injection of LTA or LPS (250 µg), and in supernatants of murine J774.2 cells, immortalised blood monocytes, or isolated human monocytes treated with LTA or LPS (0–10 µg/ml). The role of cytokine/chemokine messenger RNA (mRNA) stability versus nuclear factor-kappaB (NF-κB) and activator protein-1 (AP-1) in mediating cytokine/chemokine release in J774 cells was also assessed.

Results

In mice, plasma levels of keratinocyte-derived chemokine (KC), macrophage inflammatory protein (MIP)-2, interleukin (IL)-10, interferon (IFN)-γ and tumour necrosis factor-alpha (TNF-α) and peritoneal lavage fluid levels of KC, MIP-2 and TNF-α increased significantly 1 h after LPS. Only KC and MIP-2 levels increased 1 h after LTA. LPS-treated (10 μg/ml) J774 cells released MIP-2, IL-10, IFN-γ and TNF-α but not KC (24 h), whereas cells treated with 10 μg/ml LTA released only MIP-2. LPS-stimulated human monocytes released IL-10 and IL-8 (24 h); by contrast, LTA-treated cells released only IL-8. LPS and LTA activated NF-κB and AP-1 in J774 cells. The protein synthesis inhibitor cycloheximide abolished LPS-induced IL-10 mRNA expression and increased LTA- and LPS-induced mRNA for MIP-2 in J774 cells.

Conclusion

LTA and LPS, at clinically relevant concentrations, induced differential cytokine/chemokine release in vitro and in vivo, via effects distal to activation of NF-κB/AP-1 that might include chromatin remodelling or mRNA stability.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-011-2444-5) contains supplementary material, which is available to authorized users.

The RAGE axis in systemic inflammation, acute lung injury and myocardial dysfunction: an important therapeutic target?

BACKGROUND

The sepsis syndromes, frequently complicated by pulmonary and cardiac dysfunction, remain a major cause of death amongst the critically ill. Targeted therapies aimed at ameliorating the systemic inflammation that characterises the sepsis syndromes have largely yielded disappointing results in clinical trials. Whilst there are many potential reasons for lack of success of clinical trials, one possibility is that the pathways targeted, to date, are only modifiable very early in the course of the illness. More recent approaches have therefore attempted to identify pathways that could offer a wider therapeutic window, such as the receptor for advanced glycation end-products (RAGE) and its ligands.

PURPOSE

The objectives of this study were to review the evidence supporting the role of the RAGE axis in systemic inflammation and associated acute lung injury and myocardial dysfunction, to explore some of the problems and conflicts that these RAGE studies have raised and to consider strategies by which they might be resolved.

METHODS

MEDLINE was searched (1990-2010) and relevant literature collected and reviewed.

RESULTS AND CONCLUSION

RAGE is an inflammation-perpetuating receptor with a diverse range of ligands. Evidence supporting a role of the RAGE axis in the pathogenesis of systemic inflammation, ALI and myocardial dysfunction is compelling with numerous animal experiments showing the beneficial effects of inhibiting the RAGE axis. Despite a number of unanswered questions that need to be further addressed, the potential for inhibiting RAGE-mediated inflammation in humans undoubtedly exists.

Increased plasma thioredoxin levels in patients with sepsis: positive association with macrophage migration inhibitory factor

Purpose

To establish the relationship between plasma levels of thioredoxin (Trx) and macrophage migration inhibitory factor (MIF) in systemic inflammatory stress syndrome (SIRS)/sepsis.

Methods

Enzyme-linked immunosorbent assay measurements of Trx, MIF, IL-6, -8, and -10 and enzyme-linked fluorescent assay determination of procalcitonin (PCT) in plasma from patients with SIRS/sepsis, neutropenic sepsis, healthy volunteers and pre-oesophagectomy patients.

Results

Thioredoxin was significantly higher in SIRS/sepsis patients [101.3 ng ml⁻¹, interquartile range (IQR) 68.7–155.6, n = 32] compared with that in healthy controls (49.5 ng ml⁻¹, IQR 31.4–71.1, P < 0.001, n = 17) or pre-oesophagectomy patients (40.5 ng ml⁻¹, IQR 36.9–63.2, P < 0.01, n = 7), but was not raised in neutropenics (n = 5). MIF levels were also significantly higher in SIRS/sepsis patients (12.1 ng ml⁻¹, IQR 9.5–15.5, n = 35), but not in the neutropenic group, when compared with healthy controls (9.3 ng ml⁻¹, IQR 7.3–10.7, P < 0.01, n = 20). Trx levels correlated, positively, with MIF levels and APACHE II scores. Plasma levels of IL-6, -8 and -10 and PCT increased significantly in patients with SIRS/sepsis (P < 0.001) and with neutropenic sepsis, but did not correlate with Trx or MIF levels.

Conclusion

Plasma levels of Trx, MIF, IL-6, -8, -10 and PCT were raised in patients with SIRS/sepsis. Comparisons between mediators suggest a unique correlation of Trx with MIF. Moreover, Trx and MIF differed from cytokines and PCT in that levels were significantly lower in patients with neutropenia compared with the main SIRS/sepsis group. By contrast, IL-8 and PCT levels were significantly greater in the neutropenic patient group. The link between MIF and Trx highlighted in this study has implications for future investigations into the pathogenesis of SIRS/sepsis.

PMX464, a thiol-reactive quinol and putative thioredoxin inhibitor, inhibits NF-kappaB-dependent proinflammatory activation of alveolar epithelial cells

BACKGROUND AND PURPOSE

Subtle changes in the intracellular reduction-oxidation (redox) state can modulate nuclear factor-kappaB (NF-kappaB) activity. Thioredoxin-1 (Trx) is a small, ubiquitous, redox-active thiol (-SH) protein that, with thioredoxin reductase-1 (TrxR), modifies the redox status of NF-kappaB pathway components. PMX464 is a novel thiol-reactive quinol thought to inhibit the Trx/TrxR system. The aim of this work was to investigate whether PMX464 inhibited NF-kappaB-mediated proinflammatory activation of human type II alveolar epithelial cells (A549).

EXPERIMENTAL APPROACH

Intercellular adhesion molecule-1 (ICAM-1), granulocyte-macrophage colony-stimulating factor (GM-CSF) and CXCL8, NF-kappaB DNA binding, nuclear translocation of NF-kappaB p65 subunit, IkappaBalpha degradation, IkappaB phosphorylation and IkappaB kinase (IKK) activity were assessed in A549 cells stimulated with IL-1beta with or without PMX464 pretreatment. Effects of PMX464 on ICAM-1 expression in human lung microvascular endothelial cells (HLMVEC) were also investigated. For comparison, selected measurements (ICAM-1 and IkappaB-alpha phospho-IkappaB-alpha) were made on A549 cells after RNA interference-mediated silencing (siRNA) of Trx.

KEY RESULTS

PMX464 reduced ICAM-1, GM-CSF and CXCL8 expression in IL-1beta-stimulated A549 cells and ICAM-1 in HLMVEC. PMX464 inhibited IL-1beta-induced NF-kappaB DNA binding, nuclear translocation of NF-kappaB p65 subunit and factors involved in NF-kappaB activation; specifically, IkappaBalpha degradation, IkappaB phosphorylation and IkappaB kinase (IKK) activity in A549. By contrast, Trx siRNA did not alter ICAM-1 expression or IkappaBalpha degradation/phosphorylation in IL-1beta-stimulated A549 cells.

CONCLUSION AND IMPLICATIONS

PMX464 inhibits a proinflammatory response in A549 cells targeting the NFkappaB pathway above IKK. The lack of effect with Trx siRNA suggests that PMX464 acts on thiol proteins, in addition to Trx, to elicit anti-inflammatory responses in lung epithelial cells.

Severe sepsis and Toll-like receptors

Severe sepsis dominates the mortality of non-cardiac intensive care units. The ingenious Toll-like receptor (TLR) system can recognise many infectious organisms through relatively few receptors to trigger pro-inflammatory and anti-inflammatory cytokine release. Further complexity arises from positive and negative signalling feedback loops. Severe sepsis may be a consequence of an inappropriately excessive response or inadequate endogenous negative feedback. Therapies targeting these pathways are currently being evaluated. Alternatively, in clinical scenarios such as compensatory anti-inflammatory response syndrome, chronic viral sepsis or inadequate vaccine function, TLR signalling may be inadequate. TLR agonists may augment the innate response and are being investigated.

Butanol-extracted lipoteichoic acid induces in vivo leukocyte adhesion

Lipoteichoic acid (LTA), an immunostimulatory component of the cell walls of gram positive bacteria, has pro-inflammatory effects in vitro and in vivo. However, one in vivo study concluded that LTA had no noticeable effects on leukocyte recruitment. In this study we investigated the effects of highly purified LTA, prepared by butanol extraction (Bu-LTA) at room temperature, on in vivo leukocyte adhesion. Using intravital microscopy we measured adhesion of leukocytes in mesenteric post-capillary venules of rats and mice. Topical superfusion of Bu-LTA (1 microg/ml) in rats significantly (p<0.05) increased adhesion within 30 min. By contrast, hot phenol-extracted LTA did not increase adhesion. Alkaline hydrolysis of Bu-LTA removed alanine residues and prevented adhesion. Also, pre-administration of anti-rat beta2-integrin antibody abolished Bu-LTA-induced adhesion. Finally, intraperitoneal injection of Bu-LTA (100 microg/ml) into mice also significantly (p<0.01) increased leukocyte adhesion measured at 60 min. In conclusion, Bu-LTA with intact alanine residues promotes beta2-integrin-dependent leukocyte adhesion in vivo.

Sepsis since the discovery of Toll-like receptors: disease concepts and therapeutic opportunities

OBJECTIVE

Sepsis and its sequelae are the leading cause of death in critically ill patients. Discovery in the late 1990s of Toll-like receptors as primary sensors of microbial infection led to significant advances in understanding the pathogenesis of sepsis, including emerging differences between Gram-positive and Gram-negative infection and the potential for the manipulation of Toll-like receptors for the treatment of sepsis. This review describes these advances.

METHODS

Bibliographic search of the literature since 1999, with particular emphasis on the conceptual and therapeutic implications of Toll-like receptors for patients with systemic sepsis.

RESULTS AND CONCLUSIONS

Toll-like receptors initiate the inflammatory processes that underlie the clinical response to infection and therefore represent an important putative target for therapeutic intervention.

Persistently low plasma thioredoxin is associated with meningococcal septic shock in children

OBJECTIVE

To compare plasma levels of thioredoxin (Trx), TNF-alpha and IL-1 beta in children during the acute phase of meningococcal septic shock (MSS) and in convalescence.

DESIGN AND SETTING

Retrospective, observational study in the paediatric intensive care unit of a postgraduate teaching hospital.

PATIENTS

Thirty-five children requiring intensive care for meningococcal sepsis; paired convalescent samples from 30 survivors (median interval between samples 62 days); 25 healthy control children.

MEASUREMENTS AND RESULTS

Plasma Trx levels were significantly lower in the children with MSS, both during the acute illness (5.5 ng/ml, IQR 1.4-11.4) and in convalescence (2.5 ng/ml, IQR 0.4-6.9) than controls (18.8 ng/ml, IQR 7.9-25.0). Levels of IL-1 beta and TNF-alpha were higher in patients with acute MSS (30.3 pg/ml, IQR 3.6-63.6, and 145.9 pg/ml, IQR 31.8-278.1 respectively) than controls (3.7 pg/ml, IQR 0-36.9, and 23.8 pg/ml, IQR 0-124.3, respectively). Levels fell in convalescence (3.7 pg/ml, IQR 0-25.5, 3.7 pg/ml, IQR 0-304.8, respectively). Plasma Trx was higher in non-survivors, albeit a small group (n=5), than in survivors (n=30). Trx, IL-1 beta, and TNF-alpha levels were not correlated with predicted mortality as assessed by the paediatric risk of mortality (PRISM) score.

CONCLUSIONS

Children with MSS exhibit persistently low plasma levels of Trx during acute illness and in convalescence.

Thioredoxin: friend or foe in human disease?

Thioredoxin (Trx), a small, ubiquitous thiol [sulfydryl (-SH)] protein, is one of the most important regulators of reduction-oxidation (redox) balance and, thus, redox-controlled cell functions. Although Trx was discovered 40 years ago in bacteria, the number and diversity of processes that Trx influences in human cells have only been appreciated recently. Processes influenced by Trx include the control of cellular redox balance, the promotion of cell growth, the inhibition of apoptosis and the modulation of inflammation. Not surprisingly, the role of Trx in a wide range of human diseases and conditions, including cancer, viral disease, ischaemia-reperfusion injury, cardiac conditions, aging, premature birth and newborn physiology, is subject to intense investigation. However, whether Trx contributes to or prevents the pathology of a particular condition is not always clear. In this article, we review the role of Trx in human disease and relate this to its redox activity and biological properties, and discuss the development and use of therapies that either inhibit or augment Trx activity.

Extracellular thioredoxin levels are increased in patients with acute lung injury

BACKGROUND

Acute lung injury (ALI) and its extreme manifestation the acute respiratory distress syndrome (ARDS) complicate a wide variety of serious medical and surgical conditions. Thioredoxin is a small ubiquitous thiol protein with redox/inflammation modulatory properties relevant to the pathogenesis of ALI. We therefore investigated whether thioredoxin is raised extracellulary in patients with ALI and whether the extent of any increase is dependent upon the nature of the precipitating insult.

METHODS

Bronchoalveolar lavage (BAL) fluid and plasma samples were collected from patients with ALI (n=30) and healthy controls (n=18, plasma; n=14, BAL fluid). Lung tissue was harvested from a separate group of patients and controls (n=10). Thioredoxin was measured by ELISA in fluids and by immunohistochemistry in tissue. Interleukin (IL)-8 levels were determined by ELISA. Disease severity was assessed as APACHE II and SOFA scores.

RESULTS

BAL fluid levels of thioredoxin were higher in patients with ALI than in controls (median 61.6 ng/ml (IQR 34.9-132.9) v 16.0 ng/ml (IQR 8.9-25.1), p<0.0001); plasma levels were also significantly higher. When compared with controls, sections of wax embedded lung tissue from patients with ALI showed greater positive staining for thioredoxin in alveolar macrophages and type II epithelial cells. BAL fluid levels of thioredoxin correlated with IL-8 levels in BAL fluid but not with severity of illness scores or mortality. BAL fluid levels of thioredoxin, IL-8, and neutrophils were significantly greater in patients with ALI of pulmonary origin.

CONCLUSIONS

Extracellular thioredoxin levels are raised in patients with ALI, particularly of pulmonary origin, and have a significant positive association with IL-8. Extracellular thioredoxin levels could provide a useful indication of inflammation in ALI.

Regulation of chemokine expression in atherosclerosis

(1) Chemokines play a central role in the pathogenesis of atherosclerosis, contributing to leukocyte recruitment, angiogenesis and also proliferation and migration of smooth muscle cells into atherosclerotic plaques. (2) Leukocytes and endothelial cells are an important source of chemokines, and many of the risk factors associated with atherosclerosis increase chemokine expression. There is now a body of evidence to suggest that interactions between cells such as leukocytes and endothelial cells amplify chemokine release, and this may contribute to sustained chemokine generation in inflammatory conditions. (3) This article summarises, briefly, what is currently known about chemokines release. A number of important pharmacological strategies used in the treatment of atherosclerosis inhibit chemokine release and the extent to which this may contribute to their therapeutic effect will be discussed. Understanding the mechanisms controlling chemokine expression is essential for the design of specific therapeutic interventions in atherosclerosis.

TNF-alpha potentiates C5a-stimulated eosinophil adhesion to human bronchial epithelial cells: a role for alpha 5 beta 1 integrin

Cooperative action of inflammatory mediators and adhesion molecules orchestrates eosinophil recruitment during allergic inflammation in the airways. This study investigated the mechanisms involved in increasing eosinophil adhesion to human bronchial epithelial cells (HBEC) following priming and activation of eosinophils with TNF-alpha and complement protein C5a, respectively. Under primed conditions, eosinophil adhesion increased 3-fold from basal (16%), and the effect was significantly greater (p < 0.05) than the increase following stimulation with C5a alone (2-fold). Eosinophil contact with HBEC was essential for priming. In contrast to C5a, adhesion of eotaxin-stimulated eosinophils to HBEC was not primed with TNF-alpha nor IL-5, a known eosinophil-priming agent. Priming caused activation of alpha(M)beta(2) integrin; mAb against either the common beta(2) integrin subunit or its ICAM-1 ligand reduced the primed component of adhesion. Using mAbs against beta(1) or alpha(5), but not alpha(4) integrin subunit, together with anti-beta(2) integrin mAb, reduced stimulated adhesion to basal levels. Cross-linking alpha(5)beta(1) integrin increased alpha(M)beta(2) integrin-dependent adhesion of eosinophils. There are no known adhesion molecule ligands of alpha(5)beta(1) integrin expressed on HBEC; however, fibronectin, the major matrix protein ligand for alpha(5)beta(1) integrin, was detected in association with HBEC monolayers. A mAb against fibronectin, in combination with anti-beta(2) integrin mAb, reduced adhesion to basal levels. In conclusion, alpha(5)beta(1) integrin may provide a contact-dependent costimulus for eosinophil priming that, together with TNF-alpha, potentiated C5a activation of alpha(M)beta(2) integrin and increased eosinophil adhesion to ICAM-1. Fibronectin, associated with HBEC, may act as a ligand for alpha(5)beta(1) integrin. Dual regulation of eosinophil priming may prevent inappropriate activation of eosinophils in the circulation.

Lipoteichoic Acid inhibits Lipopolysaccharide-Induced Adhesion Molecule Expression and IL-8 Release in Human Lung Microvascular Endothelial Cells

Cell adhesion molecule expression (CAM) and IL-8 release in lung microvascular endothelium facilitate neutrophil accumulation in the lung. This study investigated the effects of lipoteichoic acid (LTA), a cell wall component of Gram-positive bacteria, alone and with LPS or TNF-α, on CAM expression and IL-8 release in human lung microvascular endothelial cells (HLMVEC). The concentration-dependent effects of Staphylococcus aureus (S. aureus) LTA (0.3–30 μg/ml) on ICAM-1 and E-selectin expression and IL-8 release were bell shaped. Streptococcus pyogenes (S. pyogenes) LTA had no effect on CAM expression, but caused a concentration-dependent increase in IL-8 release. S. aureus and S. pyogenes LTA (30 μg/ml) abolished LPS-induced CAM expression, and S. aureus LTA reduced LPS-induced IL-8 release. In contrast, the effects of S. aureus LTA with TNF-α on CAM expression and IL-8 release were additive. Inhibitory effects of LTA were not due to decreased HLMVEC viability, as assessed by ethidium homodimer-1 uptake. Changes in neutrophil adhesion to HLMVEC paralleled changes in CAM expression. Using RT-PCR to assess mRNA levels, S. aureus LTA (3 μg/ml) caused a protein synthesis-dependent reduction (75%) in LPS-induced IL-8 mRNA and decreased the IL-8 mRNA half-life from &gt;6 h with LPS to ∼2 h. These results suggest that mechanisms exist to prevent excessive endothelial cell activation in the presence of high concentrations of bacterial products. However, inhibition of HLMVEC CAM expression and IL-8 release ultimately may contribute to decreased neutrophil accumulation, persistence of bacteria in the lung, and increased severity of infection.

Lipoteichoic acid inhibits lipopolysaccharide-induced adhesion molecule expression and IL-8 release in human lung microvascular endothelial cells

Cell adhesion molecule expression (CAM) and IL-8 release in lung microvascular endothelium facilitate neutrophil accumulation in the lung. This study investigated the effects of lipoteichoic acid (LTA), a cell wall component of Gram-positive bacteria, alone and with LPS or TNF-alpha, on CAM expression and IL-8 release in human lung microvascular endothelial cells (HLMVEC). The concentration-dependent effects of Staphylococcus aureus (S. aureus) LTA (0.3-30 microg/ml) on ICAM-1 and E-selectin expression and IL-8 release were bell shaped. Streptococcus pyogenes (S. pyogenes) LTA had no effect on CAM expression, but caused a concentration-dependent increase in IL-8 release. S. aureus and S. pyogenes LTA (30 microg/ml) abolished LPS-induced CAM expression, and S. aureus LTA reduced LPS-induced IL-8 release. In contrast, the effects of S. aureus LTA with TNF-alpha on CAM expression and IL-8 release were additive. Inhibitory effects of LTA were not due to decreased HLMVEC viability, as assessed by ethidium homodimer-1 uptake. Changes in neutrophil adhesion to HLMVEC paralleled changes in CAM expression. Using RT-PCR to assess mRNA levels, S. aureus LTA (3 microg/ml) caused a protein synthesis-dependent reduction (75%) in LPS-induced IL-8 mRNA and decreased the IL-8 mRNA half-life from >6 h with LPS to approximately 2 h. These results suggest that mechanisms exist to prevent excessive endothelial cell activation in the presence of high concentrations of bacterial products. However, inhibition of HLMVEC CAM expression and IL-8 release ultimately may contribute to decreased neutrophil accumulation, persistence of bacteria in the lung, and increased severity of infection.

Cytokine-induced airway epithelial ICAM-1 upregulation: quantification by high-resolution scanning and transmission electron microscopy

The aim of this study was to investigate the variation of intercellular adhesion molecule (ICAM)-1 which occurs between individual airway epithelial cells of distinct phenotype. 16HBE14o- (16HBE) and BEAS-2B cell lines and human airway explants were cultured with medium alone or a mixture of tumour necrosis factor (TNF)-alpha (10 ng x mL(-1)) and interferon (IFN)-gamma (40 ng x mL(-1)) before being immunogold-labelled and examined quantitatively using sensitive high-resolution electron microscopic techniques. By enzyme-linked immunosorbent assay there was a 1.6-fold increase of ICAM-1 in the BEAS-2B cells following the cytokine mix which was not apparent in the 16HBE cells. However, high-resolution scanning electron microscopy demonstrated that an upregulation had occurred; median and ranges for gold particle number per 10 microm2 cell surface were: 7.9 (0-40) for nonstimulated and 19.1 (0-60 for stimulated) (p<0.01, Mann-Whitney U-test). The value for the nonstimulated BEAS-2B cells was 24.2 (0-60), 3-times higher that the constitutive expression in the 16HBE cells (p<0.01), whereas following stimulation, it was 68.5 (20-130) (p<0.01). Values for explant epithelial outgrowths were similar to the 16HBE cells. Immunohistochemistry of the explanted mucosa showed both constitutive and upregulated expression of epithelial ICAM-1 associated with basal and indeterminate cells rather than with ciliated or goblet cells. These results using high-resolution techniques indicate that there is marked cell-to-cell variation in cellular adhesion molecule expression and that it is the basal cells and less well differentiated (indeterminate) epithelial cells which are likely to play key roles in leukocyte retention via intercellular adhesion molecule-1.

A CD18/ICAM-1-dependent pathway mediates eosinophil adhesion to human bronchial epithelial cells

Eosinophil adhesion to airway epithelium is believed to facilitate eosinophil accumulation and retention in asthmatic airways. Monoclonal antibodies (mAb) against intercellular adhesion molecule-1 (ICAM-1) and its CD18 leukocyte integrin ligands have been shown to inhibit airway eosinophilia in animal models of asthma, although the role of this pathway in eosinophil-epithelial adhesion is not fully understood. To investigate the role in vitro of CD18 and ICAM-1, we measured adhesion of fluorescently labeled human eosinophils to normal human bronchial epithelial cell (NHBEC) monolayers pretreated for 24 h with culture medium (low constitutive ICAM-1) or tumor necrosis factor-alpha (TNF-alpha; 1 ng/ml) and interferon-gamma (IFN-gamma) (10 ng/ml; increased ICAM-1). Stimulation of eosinophils with C5a (10(-7) M) increased adhesion measured at 30 min to unactivated NHBEC from 11.4 +/- 0.7 to 15.5 +/- 0.4% (n = 4), and this increase was CD18/ICAM-1-independent, whereas phorbolmyristate acetate (PMA) (10(-8) M)-induced adhesion (20.7 +/- 1.7%) was abolished by anti-CD18 and reduced by anti-ICAM-1. In contrast, C5a- and PMA-induced adhesion to TNF-alpha/IFN-gamma-activated NHBEC (increased from 11.1 +/- 1.3% to 21.9 +/- 1.0% and 27.6 +/- 1.9%, respectively) was CD18- and ICAM-1-dependent. Eotaxin, but not regulated on activation normal T cells expressed and secreted, macrophage inflammatory protein-1, formyl methionyl leucyl phenylalanine, leukotriene B4 or platelet-activating factor, also induced CD18/ICAM-1-dependent adhesion to activated NHBEC. In the absence of added chemoattractants, eosinophil adhesion to NHBEC increased with time and, at 120 min, was significantly greater (P < 0.01) to activated NHBEC (37.3 +/- 2.4%, n = 5) than to unactivated monolayers (24.3 +/- 1.9%); mAb against CD18 or ICAM-1 abolished increased, but not basal, adhesion. These results suggest that CD18/ICAM-1 mediated eosinophil adhesion to activated NHBEC but that adhesion to resting NHBEC was largely independent of this pathway.

Cyclo-oxygenase-2 regulates inducible ICAM-1 and VCAM-1 expression in human vascular smooth muscle cells

Prostaglandins are well characterised inflammatory mediators, whose formation is regulated by constitutive (COX-1) or inducible (COX-2) isoforms of cyclo-oxygenase. We have previously demonstrated that IL-1 beta causes an induction of COX-2 in human vascular smooth muscle (1). This present study investigates the ability of different cytokines to induce ICAM-1 and VCAM-1 on human vascular smooth muscle, and tests whether co-induced COX-2 would regulate their expression. IL-1 beta induced ICAM-1, and COX activity, while it had no affect on VCAM-1. Conversely, IL-4 induced VCAM-1, while it had no effect on PGE2 release or ICAM-1 expression. Inhibition of IL-1 beta induced COX-2 and elevated ICAM-1 expression, an effect reversed by exogenous PGE2. Furthermore, IL-1 beta inhibited IL-4 induced VCAM-1 expression, which was also reversed by COX-2 inhibition. These results demonstrate that COX-2 limits adhesion molecule expression on human vascular smooth muscle cells and suggest that COX-2 can play a protective role in cardiovascular and inflammatory diseases.

Modulation of cell adhesion molecule expression and function on human lung microvascular endothelial cells by inhibition of phosphodiesterases 3 and 4

1. Expression of cell adhesion molecules (CAM) on the lung microvascular endothelium is believed to play a key role in the recruitment of leukocytes in pulmonary inflammation. Moreover, regulation of CAM expression may be an important mechanism through which this inflammation may be controlled. Experimental evidence has suggested that combined phosphodiesterase (PDE) 3 and 4 inhibitors increase cyclic AMP levels within cells greater than inhibition of either isoenzyme alone. In the present study we assessed the effect of combinations of rolipram (PDE4 inhibitor), ORG 9935 (PDE3 inhibitor) and salbutamol (beta-agonist) on CAM expression and neutrophil or eosinophil adhesion to human lung microvascular endothelial cells (HLMVEC). 2. Tumour necrosis factor-alpha (TNF-alpha)-induced intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1 and E-selectin expression were measured on HLMVEC monolayers at 6 h by a specific ELISA technique in the presence of different combinations of medium, rolipram, ORG 9935 and salbutamol. 3. Rolipram in combination with salbutamol, but neither agent alone, inhibited TNF-alpha-induced E-selectin expression, whilst ICAM-1 and VCAM-1 expression were not affected. ORG 9935 had no significant effect on CAM expression alone. However, in combination with rolipram a syngergistic inhibition of VCAM-1 and E-selectin, but not ICAM-1, expression was observed. No further inhibition was seen in the additional presence of salbutamol. 4. Neutrophil adhesion to TNF-alpha-stimulated (6 h) HLMVEC was mainly E-selectin dependent in this model, as ENA2 an anti-E-selectin monoclonal antibody (mAb) abrogated neutrophil adhesion. Eosinophil adhesion was E-selectin-, ICAM-1- and VCAM-1-dependent, as assessed by the inhibitory activity of ENA2 and the ability of a mAb to the ICAM-1 ligand, CD18, and a mAb to the VCAM-1 ligand, VLA4, to attenuate adhesion. 5. Rolipram in the presence of salbutamol or ORG 9935 significantly inhibited neutrophil adherence to TNF-alpha-stimulated HLMVEC. Eosinophil adherence to monolayers was inhibited only when HLMVEC were activated in the presence of rolipram and ORG 9935. 6. Collectively, the findings presented in this manuscript suggest that inhibition of PDE4 with appropriate activation of adenylate cyclase is sufficient to inhibit induction of E-selectin expression on HLMVEC to a level that has functional consequences for neutrophil adhesion. In contrast, combined inhibition of PDE3 and 4 isoenzymes is necessary to inhibit VCAM-1 and to have inhibitory effects on eosinophil adhesion to activated HLMVEC. Upregulation of ICAM-1 expression on HLMVEC does not appear to be modulated by PDE3 and 4 inhibition. These data may have implications for the use of selective PDE4 inhibitors in lung inflammation.

Interleukin-4 and lipopolysaccharide synergize to induce vascular cell adhesion molecule-1 expression in human lung microvascular endothelial cells

Recent studies suggest that increased vascular cell adhesion molecule-1 (VCAM-1) expression on vascular endothelium in bronchial mucosa biopsies correlates with interleukin-4 (IL-4) levels in bronchiolar lavage fluid of allergic asthmatics. The severity of asthma in patients allergic to house dust mite has also been shown to correlate with lipopolysaccharide (LPS), rather than allergen, concentration in dust. We hypothesized that to induce effective VCAM-1 expression in human lung microvascular endothelial cells (HLMVEC), IL-4 may require the presence of a co-stimulus such as LPS. To test this hypothesis we measured, by enzyme-linked immunosorbent assay, induction of cell adhesion molecule expression on, and human eosinophil adhesion to, cultured HLMVEC monolayers pretreated with IL-4 alone or combined with LPS. IL-4 synergized with LPS to induce VCAM-1 expression at 24, 48, or 72 h, whereas IL-4 alone induced expression at 72 h only. IL-4 did not induce expression of intercellular adhesion molecule-1 or E-selectin or alter LPS-induced expression of either. Pre-exposure of HLMVEC to LPS or IL-4 (1 h), followed by IL-4 or LPS, respectively (23 h), also induced VCAM-1 expression. Eosinophil adhesion to HLMVEC monolayers treated with IL-4 and LPS together, but not alone, significantly (P < 0.001) increased from 9.6 +/- 1.5% (control) to 26.9 +/- 3.3% and was inhibited by a monoclonal antibody against the VCAM-1 ligand, very late antigen-4. Analysis of VCAM-1 mRNA revealed synergism between IL-4 and LPS which may, in part, contribute to enhanced VCAM-1 expression. These results suggest that the presence of a co-stimulus such as LPS may be necessary for IL-4 to effectively induce VCAM-1 expression in lung microvasculature.

Endogenous nitric oxide limits cytokine-induced damage of murine lung epithelial cells

This study investigated whether endogenous nitric oxide (NO) limits cytokine-induced damage to the murine lung epithelial cell line LA-4. NO production was assessed as nitrite using the Griess reaction, and cell damage was assessed using ethidium homodimer-1. Cytotoxicity was first detected after a 24-h incubation with a combination of tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma (cytomix). Nitrite production increased to 78.0 +/- 0.5 nmol/10(6) cells at 24 h. Coincubation of LA-4 with cytomix and NO synthase inhibitors, aminoguanidine (3-1,000 microM) and N(G)-monomethyl-L-arginine (10-1,000 microM), but not N(G)-monomethyl-D-arginine, or a soluble guanylate cyclase inhibitor, 1H-[1,2,4] oxadiazole [4,3-a] quinoxalin-1-one, reduced cytomix-induced nitrite production and increased cytotoxicity up to twofold (24 h). Removal of L-arginine from the medium increased damage; reintroduction of 1,000 microM L-arginine, but not D-arginine, reversed this. In aminoguanidine-treated cells, replacement of NO with an NO donor, S-nitrosoglutathione (30 microM), reversed, in part, the cell damage observed in aminoguanidine/cytomix-treated cells. These results suggest that endogenous NO limits cytokine-induced lung epithelial damage.

Tumour necrosis factor-alpha-induced ICAM-1 expression in human vascular endothelial and lung epithelial cells: modulation by tyrosine kinase inhibitors

1. Tumour necrosis factor-alpha (TNF alpha) increases the expression of the adhesion molecule intercellular adhesion molecule-1 (ICAM-1) on cultured endothelial and epithelial cells and modulation of this may be important in controlling inflammation. Activation of tyrosine kinase(s) is known to be involved in the signal transduction pathways of many cytokines. In this study we have investigated the effects of the tyrosine kinase inhibitors, ST638, tyrphostin AG 1288 and genistein, on TNF alpha-induced ICAM-1 expression in human alveolar epithelial (A549) and vascular endothelial (EAhy926) cell lines and also normal human lung microvascular endothelial cells (HLMVEC). 2. ICAM-1 expression on cultured cells was determined by a sensitive enzyme-linked immunosorbant assay (ELISA). Endothelial or epithelial monolayers were exposed to increasing doses of TNF-alpha (0.01-10 ng ml-1), in the presence or absence of either ST638 (3-100 microM), AG 1288 (3-100 microM) or genistein (100 microM) and ICAM-1 expression was measured at 4 and 24 h. Control experiments examined the effect of ST638 on phorbol 12-myristate 13-acetate (PMA, 20 ng ml-1, 4 h)-stimulated ICAM-1 and compared it to that of a specific protein kinase C inhibitor, R031-8220 (10 microM). Also, functional consequences of changes in ICAM-1 expression were assessed by measuring adhesion of 111 In-labelled human neutrophils to EAhy926 endothelial and A549 epithelial monolayers treated with TNF alpha, in the presence or absence of ST638. 3. ST638 caused a concentration-dependent reduction in TNF alpha- (0.1-10 ng ml-1)-induced ICAM-1 on EAhy926 endothelial (at 4 h) and A549 epithelial monolayers (at 4 and 24 h). In contrast, ST638 caused a concentration-dependent increase in TNF alpha- (0.1-10 ng ml-1)-induced ICAM-1 on EAhy926 endothelial cells at 24 h. Similar effects were seen with AG 1288 or genistein. ST638 (100 microM) significantly (P < 0.01) inhibited ICAM-1 expression on HLMVEC endothelial cells induced by 0.01 ng ml-1 TNF alpha at 4 or 24 h or 0.1 ng ml-1 at 4 h, but increased ICAM-1 expression induced by 0.1 ng ml-1 TNF alpha at 24 h. ST638 did not significantly change the expression of PMA-stimulated ICAM-1 on either A549 epithelial, EAhy926 or HLMVEC endothelial cells. However, PMA-induced ICAM-1 expression was inhibited by Ro31-8220. Also, treatment of epithelial or endothelial monolayers with TNF alpha and ST638 altered adhesion of human neutrophils to A549 epithelial or EAhy926 endothelial cells in a manner that corresponded to the alteration in ICAM-1 expression. 4. These results show that tyrosine kinase inhibitors alter TNF alpha-induced ICAM-1 expression, but that the cell type, concentration of TNF alpha and time of exposure to this cytokine determine whether expression is decreased or increased by the inhibitor. An increased understanding of the signal transduction pathway(s) involved in TNF alpha-induced ICAM-1 expression on lung epithelial and vascular endothelial cells may be of potential therapeutic value in the treatment of inflammatory disease.

Eotaxin stimulates eosinophil adhesion to human lung microvascular endothelial cells

Effects of the human C-C chemokines eotaxin, MIP-1 alpha, and RANTES on human eosinophil or neutrophil adhesion to human lung microvascular endothelial cells (LMVEC) were investigated. Basal adhesion of unstimulated eosinophils to LMVEC was increased following pretreatment of LMVEC with TNF alpha (10ng/ml) for 6h. Stimulation of eosinophils with eotaxin (30 and 100ng/ml) resulted in increased adhesion to LMVEC pretreated with TNF alpha but not culture medium. Neutrophil adhesion was not increased by eotaxin under similar conditions. Neither MIP-1 alpha (3-100 ng/ml) nor RANTES (3-100 ng/ml) increased eosinophil or neutrophil adhesion to LMVEC pretreated for 6 h with either TNF alpha (10 ng/ml) or culture medium. Monoclonal antibodies (mAb) against eosinophil adhesion molecule VLA-4 (2B4; 30 micrograms/ml) but not CD18 (6.5E; 10 micrograms/ml) inhibited eotaxin-induced eosinophil adhesion to TNF alpha-activated LMVEC. 2B4 in combination with 6.5E reduced adhesion to basal levels. These data show that eotaxin, but not MIP-1 alpha or RANTES, stimulates eosinophil adhesion to LMVEC and that this effect can be abolished by anti-VLA-4 and CD18 mAb in combination. These results suggest that eotaxin may facilitate eosinophil migration from blood vessels in the lung by increasing eosinophil adhesion to endothelial cells.

Regulation of ICAM-1 by dexamethasone in a human vascular endothelial cell line EAhy926

Regulation by dexamethasone of intercellular adhesion molecule-1 (ICAM-1) in cultured monolayers of the human umbilical vein endothelial cell line EAhy926 was investigated. Tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in combination or lipopolysaccharide (LPS) alone gave time- and dose-dependent increases in ICAM-1. Sustained expression of ICAM-1 was observed after short exposure (30 min) to TNF-alpha + IFN-gamma, but not to LPS. LPS-induced ICAM-1 expression was not inhibited by interleukin-1 (IL-1) receptor antagonist (0.01-100 micrograms/ml). Dexamethasone (1,000 nM) did not inhibit TNF-alpha + IFN-gamma-induced ICAM-1 expression or mRNA induction. In contrast, dexamethasone dose dependently (0.1-1,000 nM) inhibited LPS-induced ICAM-1 expression; however, its effect on mRNA was not established, because ICAM-1 mRNA induced by LPS was not detected at the time points investigated in this study (3 and 20 h). Adhesion of unstimulated human neutrophils to EAhy926 monolayers activated with TNF-alpha + IFN-gamma or LPS was increased in the presence of dexamethasone at low doses, whereas neutrophil adhesion to LPS- but not cytokine-stimulated endothelial cells was significantly reduced (P < 0.05) in the presence of a high dose of dexamethasone (1,000 nM). In conclusion, dexamethasone was demonstrated to regulate the expression and function of ICAM-1 in a stimulus-dependent manner.

Does TNF-alpha directly increase endothelial cell monolayer permeability?

The effects of dexamethasone (DEX) and N omega-nitro-L-arginine methyl ester (L-NAME) on the tumour necrosis factor-alpha (TNF-alpha)-induced increase in permeability of human umbilical vein endothelial cell (HUVEC) monolayer to [125I] labelled bovine serum albumin (BSA) were examined. Preincubation of HUVEC monolayers with DEX (1 microM, 2h) completely abolished the effect of TNF-alpha (5 ng/ml, 18 h). Administration of DEX 2 h after TNF-alpha also reduced the effect of TNF-alpha while L-NAME (5 ng/ml, 1 mM, 18 h) had no significant effect. The observed inhibition of the TNF-alpha-induced permeability increase on preincubation with DEX would suggest a role for nitric oxide (NO) in mediating the permeability response. However, this is not confirmed by the experiments with L-NAME. The inhibition caused by DEX administered after TNF-alpha would suggest alternative mechanisms by which DEX may be acting in addition to inhibition of NO synthase induction.

Modulation of human endothelial cell permeability by combinations of the cytokines interleukin-1 alpha/beta, tumor necrosis factor-alpha and interferon-gamma

The permeability of human umbilical vein endothelial cell (HUVEC) monolayers to [125I]-labelled bovine serum albumin (BSA) was examined following pretreatment of the cells with various cytokines. The electrical resistance measured across untreated, confluent, intact HUVEC monolayers was 18.2 +/- 3.8 omega.cm2 (mean +/- S.D. of 4 observations). Human recombinant (hr) interleukin-1 alpha/beta (IL-1 alpha/beta), hr tumor necrosis factor-alpha (TNF-alpha), and hr interferon-gamma (IFN-gamma) each increased HUVEC monolayer permeability in a time- and dose-dependent manner. These effects were inhibitable by neutralizing antibodies (nAb) to the corresponding cytokines, and were not due to contamination by endotoxin (abolition of cytokine effect by heat treatment, and no effect on cytokine action of the endotoxin inhibitor polymyxin B). The effects of these cytokines were not due to endothelial cell (EC) interleukin-6 (IL-6) induction (IL-6 shown not to increase permeability) and the effect of hrTNF-alpha could not be accounted for by induction of IL-1 (effect not inhibited by hrIL-1 alpha/beta nAb). The effects of three different combinations of the cytokines (each combination at two different concentrations) on HUVEC monolayer permeability were also examined. hrIFN-gamma with hrTNF-alpha or hrIL-1 alpha/beta gave an increase in permeability (at both concentration combinations) greater than that seen with either cytokine alone. hrTNF-alpha and hrIL-1 alpha/beta in combination however produced an enhanced effect only at low concentrations, high concentrations in combination producing an effect no greater than either agent alone. These results highlight the importance of investigating actions of cytokine combinations on in vitro models of endothelial cell activation.