Respiratory Immunopharmacology Group
Respiratory Immunopharmacology group
The respiratory immunopharmacology research group is focused on studies investigating mechanisms of inflammation, tissue damage and repair in respiratory diseases, including cystic fibrosis, asthma and chronic obstructive pulmonary disease (COPD).
Asthma research focuses on mechanisms of bronchial epithelial repair and, in particular, the role of coagulation factors and fibrin formation in models of epithelial wounding. In addition, the group are developing disease biomarker assays to monitor disease progression and response to therapy in clinical samples obtained non-invasively.
With Dr Mitch Lomax, in the School of Sport and Exercise Science, the effect of inspiratory muscle training on lung function and the immune system in asthma is being investigated.
The destruction of collagen and elastin by neutrophil elastase plays a central role in the pathophysiology of both cystic fibrosis and COPD. The group are investigating pharmacological regulation of elastin and collagen synthesis, and its degradation, by lung fibroblasts in culture.
In addition, the group is investigating novel mucolytic, anti-oxidant, anti-bacterial and anti-inflammatory properties of heparin for novel therapeutic applications in the treatment of obstructive airways disease. A trial of inhaled heparin in patients with COPD is currently being sponsored by the San Raffaele Hospital in Rome.
Clinical research is carried out in collaboration with Professor Anoop Chauhan, Respiratory Consultant at the Queen Alexandra Hospital in Portsmouth, and Dr Gary Connett, Pediatric Consultant and CF specialist, at Southampton General Hospital.
Our current laboratory research
The role played by coagulation cascade proteins in tissue damage and repair
Our research has revealed a previously unrecognised role for fibrin formation in normal bronchial epithelial repair. Using cell culture techniques we have shown that normal human bronchial epithelial cells (HBECs) are a local source of coagulation factors that are essential for the epithelial repair in response to mechanical wounding. Using video microscopy we have found that neutralisation of coagulation factors inhibits normal epithelial repair (see video), and that protease activated receptors play a role in the response. We are currently investigating the effect on fibrin formation of exposure of HBECs to models of virus and bacterial infection. In clinical studies we have profiled the expression of coagulation factors of the extrinsic cascade and found derangements in mild-moderate asthma that suggest excessive fibrinolysis and defective epithelial repair. In severe asthma and especially in acute exacerbations of severe asthma, fibrin formation is enhanced, and we are currently investigating its contribution to inactivation of pulmonary surfactant.
Cystic fibrosis research
Cystic fibrosis is the most common lethal genetically inherited disease affecting the Western world. Life expectancy is currently 35 years of age and most deaths are due to infection and inflammation in the lung. Airways become obstructed with dehydrated viscous mucus which patients find difficult to expectorate. Contamination with the debris of the airway inflammatory response contributes to the excessive viscoelasticity of sputum. Patients require chest physiotherapy on a daily basis. Sputum expectoration is enhanced by the use of drugs that thin mucus (mucolytics) and our research has focused on this aspect of the disease.
The role of platelets in inflammatory airway disease
Platelets are activated in the circulation in asthma, cystic fibrosis and COPD. Previous studies have indicated the accumulation of platelets in the airway in asthma, and we find increased numbers in lung tissue from cases of fatal asthma (Fig 2), but their role in the airway is unknown. Using lung microvascular endothelial cells in models of inflammatory cell migration, we have shown that platelet-derived chemokines attract T-cells and neutrophils across the endothelium. This pro-inflammatory role for platelets may be countered by a protective role in fibrin formation and epithelial repair. We are currently assessing the role of platelets in co-culture models with wounded bronchial epithelial cell layers, and the effect of anti-coagulants on the repair response. Using biopsy material we are investigating the presence of platelets and the provenance of coagulation factors in fatal and non-fatal asthma, and non-asthma deaths.
Novel applications of unfractionated inhaled heparin
Unfractionated heparin is a unique molecule in biology with interesting pharmacological properties beyond anti-coagulation. In addition to its well-known anti-inflammatory properties, we have shown that heparin has mucolytic activity when applied to sputum from patients with CF, and clinical trials have supported a role for inhaled heparin in sputum clearance strategies. We identified a previously unrecognised role for heparin in the activation of endogenous and exogenous, pharmaceutical, DNase activity and demonstrated, using atomic force microscopy and confocal microscopy (Fig 4), that extracellular DNA is the target for the mucolytic activity of heparin. Rheological analysis of sputum samples confirmed an effect of heparin on the elastic properties of sputum, suggesting the mechanism for enhanced sputum clearance in patients with cystic fibrosis, and improved drug delivery through sputum. In collaboration with Dr Marisa van der Merwe we are investigating the physical characteristics and particle size properties of nebulised unfractionated and low molecular weight heparins from a variety of different devices.
Fibroblast function in tissue repair
The degradation of the key matrix proteins, collagen and elastin, is a cardinal feature of lung tissue damage in patients with cystic fibrosis and COPD. Neutrophils are believed to play an important part in this matrix destruction. However, we are now investigating the pharmacological regulation of elastin and collagen synthesis, and its degradation, by lung fibroblasts in culture. Using quantitative specific assays for collagen and elastin synthesis at the protein level, and evidence of their degradation by Western blotting and analysis of desmosine breakdown products of elastin we are examining the effects of antibiotics and collagen peptides on elastin and collagen synthesis in fibroblasts from the lung and skin.
Regulation of expression and function of CFTR in epithelial and endothelial cells
CFTR is a chloride ion channel expressed by all epithelial cells and appears to be expressed by other cells at low levels. In a project funded by the Dunhill Medical Trust, we are investigating the expression and function of CFTR in human lung microvascular endothelial cells. The project involves the functional characterisation of CFTR using electrophysiology, molecular biology, pharmacology, immunohistochemistry and microscopy. A role for normal CFTR in negative regulation of the inflammatory response is proposed. In this study we are investigating the effect of CFTR knockdown, using pharmacological inhibitors and siRNA approaches, to test the hypothesis that defective CFTR contributes to an enhanced inflammatory response at the endothelial level in patients with cystic fibrosis. The role of CFTR in chemokine and adhesion molecule expression at the protein and mRNA level is being investigated, as well as effects on neutrophil and platelet adhesion and transendothelial migration.