David R Thickett

Vascular endothelial growth factor (VEGF) in inflammatory and malignant pleural effusions.

BACKGROUND Investigation and management of pleural effusions is an important clinical problem yet the pathogenesis of pleural fluid accumulation is poorly understood. Vascular endothelial growth factor (VEGF) is a potent inducer of capillary permeability that is produced by both malignant and inflammatory cells. A study was undertaken to determine whether VEGF has a potential pathogenic role in the development of pleural effusions and whether VEGF receptors are present on human pleural mesothelial cells. METHODS Normal and inflamed pleura were examined immunohistochemically for the presence of FLT-1 (the fms-like tyrosine kinase receptor of VEGF). VEGF levels were measured by ELISA in 78 consecutive patients presenting with undiagnosed unilateral pleural effusions and the levels were correlated with the aetiology of the effusions. RESULTS Immunohistochemical staining of normal and diseased pleura demonstrated the presence of the FLT-1 VEGF receptor on human mesothelial cells. Median VEGF levels were 2500u2009pg/ml in the malignant group and 305u2009pg/ml in the non-malignant group (median difference 1397.5u2009pg/ml (95% CI 851 to 2693), p<0.005). Median VEGF levels varied according to tumour histology. VEGF levels were also significantly raised compared with transudates (median 36.5u2009pg/ml) in empyema (4651u2009pg/ml (95% CI 833 to 10u2009000), p<0.001) and parainfectious effusions (360u2009pg/ml (95% CI 46 to 597), p<0.005). CONCLUSIONS This first report of VEGF receptors on pleural mesothelial cells has indicated a potential mechanism for the biological activity of VEGF on pleural tissue. VEGF levels are raised in the majority of exudative effusions, implying a pathogenic role for this molecule in the development of pleural effusions.

MMP expression and abnormal lung permeability are important determinants of outcome in IPF

Matrix metalloproteinases (MMPs) degrade all of the extracellular matrix components of the intersititium and may play a role in abnormal alveolar permeability, which is a feature of idiopathic pulmonary fibrosis (IPF). The aims of the present study were to evaluate MMP protein levels in patients with IPF and determine any relationship to treatment and markers of permeability. In total, 20 patients with IPF and eight normal controls underwent bronchoalveolar lavage. MMP, tissue inhibitor of metalloproteinase, and vascular endothelial growth factor (VEGF) levels were related to clinical outcome and protein permeability index. MMP-3, -7, -8 and -9 were elevated in IPF lavage fluid and levels remained high despite treatment. Levels of MMP-3, -7, -8 and -9, VEGF and protein permeability index were higher in those who died early during follow-up. VEGF, and MMP-8 and -9 levels were higher in those with a rapidly declining lung function over 1u2005yr. Levels of MMP-3, -7, -8 and -9 correlated with an increased permeability index. Matrix metalloproteinase levels were elevated in idiopathic pulmonary fibrosis patients and were not modulated by current standard treatment. Matrix metalloproteinase production through an interaction with the known vascular permogen, vascular endothelial growth factor, was potentially associated with abnormal capillary permeability and may have potentiated the neo-angiogenesis seen in idiopathic pulmonary fibrosis. The changes were greatest in those who died or progressed during follow-up, suggesting that drugs targeting vascular endothelial growth factor or matrix metalloproteinase activity warrant assessment as novel therapy for idiopathic pulmonary fibrosis.

Regulation of vascular endothelial growth factor bioactivity in patients with acute lung injury

Background: Reduced bioactive vascular endothelial growth factor (VEGF) has been demonstrated in several inflammatory lung conditions including the acute respiratory distress syndrome (ARDS). sVEGFR-1, a soluble form of VEGF-1 receptor, is a potent natural inhibitor of VEGF. We hypothesised that sVEGFR-1 plays an important role in the regulation of the bioactivity of VEGF within the lung in patients with ARDS. Methods: Forty one patients with ARDS, 12 at risk of developing ARDS, and 16 normal controls were studied. Bioactive VEGF, total VEGF, and sVEGFR-1 were measured by ELISA in plasma and bronchoalveolar lavage (BAL) fluid. Reverse transcriptase polymerase chain reaction for sVEGFR-1 was performed on BAL cells. Results: sVEGFR-1 was detectable in the BAL fluid of 48% (20/41) of patients with early ARDS (1.4–54.8 ng/ml epithelial lining fluid (ELF)) compared with 8% (1/12) at risk patients (pu200a=u200a0.017) and none of the normal controls (pu200a=u200a0.002). By day 4 sVEGFR-1 was detectable in only 2/18 ARDS patients (pu200a=u200a0.008). Patients with detectable sVEGFR-1 had lower ELF median (IQR) levels of bioactive VEGF than those without detectable sVEGFR-1 (1415.2 (474.9–3192) pg/ml v 4761 (1349–7596.6) pg/ml, median difference 3346 pg/ml (95% CI 305.1 to 14711.9), pu200a=u200a0.016), but there was no difference in total VEGF levels. BAL cells expressed mRNA for sVEGFR-1 and produced sVEGFR-1 protein which increased following incubation with tumour necrosis factor α. Conclusion: This study shows for the first time the presence of sVEGFR-1 in the BAL fluid of patients with ARDS. This may explain the presence of reduced bioactive VEGF in patients early in the course of ARDS.

Long-term impact of developing a postoperative pulmonary complication after lung surgery

Introduction Postoperative pulmonary complications (PPC) such as atelectasis and pneumonia are common following lung resection. PPCs have a significant clinical impact on postoperative morbidity and mortality. We studied the long-term effects of PPCs and sought to identify independent risk factors. Methods A prospective observational study involved all patients following lung resection in a regional thoracic centre over 4u2005years. PPCs were assessed daily in hospital using the Melbourne group scale based on chest X-ray, white cell count, fever, purulent sputum, microbiology, oxygen saturations, physician diagnosis and intensive therapy unit (ITU)/high-dependency unit readmission. Follow-up included hospital length of stay (LOS), 30-day readmissions, and mortality. Results 86 of 670 patients (13%) who had undergone a lung resection developed a PPC. Those patients had a significantly longer hospital LOS in days (13, 95% CI 10.5–14.9 vs 6.3, 95% CI 5.9 to 6.7; p<0.001) and higher rates of ITU admissions (28% vs 1.9%; p<0.001) and 30-day hospital readmissions (20.7% vs 11.9%; p<0.05). Significant independent risk factors for development of PPCs were COPD and smoking (p<0.05), not age. Excluding early postoperative deaths, developing a PPC resulted in a significantly reduced overall survival in months (40, 95% CI 34 to 44 vs 46, 95% CI 44 to 47; p=0.006). Those who developed a PPC had a higher rate of non-cancer-related deaths (11% vs 5%; p=0.020). PPC is a significant independent risk factor for late deaths in non-small cell lung cancer patients (HR 2.0, 95% CI 1.9 to 3.2; p=0.006). Conclusions Developing a PPC after thoracic surgery is common and is associated with a poorer long-term outcome.

The rise and fall of β-agonists in the treatment of ARDS

The acute respiratory distress syndrome (ARDS) is a severe inflammatory condition of the lung, which can be triggered by a number of different pulmonary and extra-pulmonary insults [1]. The characteristic pathological changes of ARDS include an exudative phase, with the accumulation of fluid within the lung, the release of pro-inflammatory cytokines and infiltration of inflammatory cells, especially neutrophils, into the lung parenchyma. Damage to the alveolar epithelium and pulmonary capillary endothelium occur and patients develop the characteristic histological appearance of diffuse alveolar damage [1]. This manifests clinically as non-cardiogenic pulmonary edema, which reduces lung compliance and impairs gas exchange.

Neutrophil chemotaxis in granulomatosis with polyangiitis (Wegener’s) and idiopathic pulmonary fibrosis

The presence of antineutrophil cytoplasmic antibodies in granulomatosis with polyangiitis (Wegener’s) (GPA) implicates the neutrophil as a key effector cell. Previous studies have reported elevated neutrophil counts in the lung, although the determinants of neutrophil chemotaxis in the GPA lung are unknown. Bronchoalveolar lavage fluid (BALF) cell counts, myeloperoxidase (MPO) and chemokines were measured in 27 patients with GPA, 20 disease controls with idiopathic pulmonary fibrosis (IPF) and six healthy controls. CXC chemokine ligand (CXCL)8, interleukin (IL)-1&bgr;, epithelial neutrophil-activating protein 78, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor were measured by ELISA. The neutrophil chemotactic potential of BALF was investigated using the under-agarose method, and specific antibodies were used to examine the role of CXCL8 and IL-1&bgr;. GPA BALF had an increased neutrophil percentage, and elevated MPO, CXCL8 and G-CSF concentrations compared with healthy controls. Chemotaxis of control neutrophils towards BALF from patients with active (p=0.006) and remission (p=0.077) GPA, and IPF (p=0.001) patients was increased compared with normal controls. BALF-induced chemotaxis correlated with BALF IL-1&bgr; (r=0.761, p=0.001) and CXCL8 (r=0.640, p=0.012) in GPA, and was inhibited by anti-CXCL8 (85%; p<0.001) and anti-IL-1&bgr; (69%; p<0.001). Our study confirms a neutrophilia and pro-inflammatory alveolar milieu that persists in clinical remission. CXCL8 and IL-1&bgr; appear to play important roles in the neutrophil chemotactic response to BALF.

Using a non-invasive assessment of lung injury in a murine model of acute lung injury

Arterial oxygen saturation has not been assessed sequentially in conscious mice as a direct consequence of an in vivo murine model of acute lung injury. Here, we report daily changes in arterial oxygen saturation and other cardiopulmonary parameters by using infrared pulse oximetry following intratracheal lipopolysaccharide (IT-LPS) for up to 9u2005days, and following IT-phosphate buffered saline up to 72u2005h as a control. We show that arterial oxygen saturation decreases, with maximal decline at 96u2005h post IT-LPS. Blood oxygen levels negatively correlate with 7 of 10 quantitative markers of murine lung injury, including neutrophilia and interleukin-6 expression. This identifies infrared pulse oximetry as a method to non-invasively monitor arterial oxygen saturation following direct LPS instillations.

Exchange protein directly activated by cyclic AMP (EPAC) activation reverses neutrophil dysfunction induced by β2-agonists, corticosteroids, and critical illness

BACKGROUNDnNeutrophils play a role in the pathogenesis of asthma, chronic obstructive pulmonary disease, and pulmonary infection. Impaired neutrophil phagocytosis predicts hospital-acquired infection. Despite this, remarkably few neutrophil-specific treatments exist.nnnOBJECTIVESnWe sought to identify novel pathways for the restoration of effective neutrophil phagocytosis and to activate such pathways effectively in neutrophils from patients with impaired neutrophil phagocytosis.nnnMETHODSnBlood neutrophils were isolated from healthy volunteers and patients with impaired neutrophil function. In healthy neutrophils phagocytic impairment was induced experimentally by using β2-agonists. Inhibitors and activators of cyclic AMP (cAMP)-dependent pathways were used to assess the influence on neutrophil phagocytosis inxa0vitro.nnnRESULTSnβ2-Agonists and corticosteroids inhibited neutrophil phagocytosis. Impairment of neutrophil phagocytosis by β2-agonists was associated with significantly reduced RhoA activity. Inhibition of protein kinase Axa0(PKA) restored phagocytosis and RhoA activity, suggesting that cAMP signals through PKA to drive phagocytic impairment. However, cAMP can signal through effectors other than PKA, such as exchange protein directly activated by cyclic AMP (EPAC). An EPAC-activating analog of cAMP (8CPT-2Me-cAMP) reversed neutrophil dysfunction induced by β2-agonists or corticosteroids but did not increase RhoA activity. 8CPT-2Me-cAMP reversed phagocytic impairment induced by Rho kinase inhibition but was ineffective in the presence of Rap-1 GTPase inhibitors. 8CPT-2Me-cAMP restored function to neutrophils from patients with known acquired impairment of neutrophil phagocytosis.nnnCONCLUSIONSnEPAC activation consistently reverses clinical and experimental impairment of neutrophil phagocytosis. EPAC signals through Rap-1 and bypasses RhoA. EPAC activation represents a novel potential means by which to reverse impaired neutrophil phagocytosis.

VEGF levels in pulmonary fibrosis

We read with interest the paper by Simler et al investigating angiogenic cytokines in patients with idiopathic interstitial pneumonia.1 We were surprised by their reported high levels of vascular endothelial growth factor (VEGF) inxa0the plasma in the normal control group. Several other groups—including the manufacturers of the ELISA (R&D Systems)—have previously quoted normal plasma VEGF levels in the range 36–76 pg/ml.2,3 Indeed, one of the authors of the paper previously quoted normal VEGF levels as 76 pg/ml using a matched pair ELISA.4 It is clear therefore that the levels of 648 pg/ml quoted for normal controls are nearly 10 times higher than …

Interferon gamma release assays and the NICE 2011 guidelines on the diagnosis of latent tuberculosis

In this clinical audit, we assessed retrospectively the current practice of respiratory physicians with respect to interferon gamma (IFNγ) release assay (IGRA) testing for tuberculosis (TB), as recommended by the 2011 National Institute of Health and Care Excellence (NICE) guidelines for the diagnosis and management of TB. All IGRAs requested by respiratory physicians over a 3-year period were identified retrospectively, and both results and clinical indications analysed. Of the total number of IGRAs carried out, 90% formed part of investigations of suspected active TB. However, 89% of the patients had not had a documented Mantoux test and human immunodeficiency virus (HIV) status was unclear in the 35.2% of patients treated for active TB. Of patients with chest X-rays suggestive of TB, 92.3% were treated for active TB. Of the patients under the age of 35 with reactive IGRAs, 84.6% were treated for active or latent TB and 15.4% had justifiable reasons for not receiving chemoprophylaxis. Based on the results of our audit, IGRAs are commonly being utilised for the investigation of active TB, which is contrary to current guidance.