Inflammatory Cell Biology Lab

Our research is geared toward understanding of the biochemical mechanisms that facilitate the process of inflammation. This is a beneficial host response to foreign challenge or tissue injury that leads ultimately to the restoration of tissue structure and function. Some diseases, such as rheumatoid arthritis, are driven by the inflammatory process. Others, such as sepsis syndrome, are due to inflammation contributing as much to the disease process as the provoking infectious agents, whilst yet others, such as hepatic cirrhosis, are due largely to a post-inflammatory fibrosis. The inflammatory response requires innate immunity and in some cases adaptive responses which are the two main integral components of the hosts’ defence system against invading pathogens. Innate immunity acts as a first line of defence against noxious material and can provide the necessary signals to instruct the adaptive immune system to mount a response. In turn, the adaptive immune response relies on the innate immune system to provide necessary effectors in the form of phagocytes and granulocytes to deal with the initiating stimulus.

My research focuses on PI3K and its role in the inflammatory process. Since the discovery of the prototypical PI3K in the late 1980’s, the family of PI3Ks and their lipid products (PI(3)P, PI(3,4)P2 and PI(3,4,5)P3 [PIP3]) have been the focus of intense investigation. Since the mid-1990’s I have used pharmacological and molecular approaches to identify the biochemical and physiological importance of PI3K-dependent-signalling pathways in the immune system. PI3Ks regulate important signalling cascade(s) involved in a plethora of cellular functional events such as survival, gene regulation, cell migration, growth and proliferation. My group is currently studying the activation of this signalling cascade during activation of the immune system. Specifically we are interested in the role that this molecule and its downstream biochemical and functional effectors play in key immune cells such as lymphocytes, macrophages, mast cells and eosinophils following activation by antigen, inflammatory mediators (e.g. chemokines and cytokines) and novel phospholipids immune regulators.

The Therapeutic Potential of our Work

Pharmacology has contributed greatly to the therapeutic tools currently used to treat a plethora of inflammatory diseases. It is sobering to realize that in spite of the diversity of these diseases, the number of drugs available to the clinician to treat inflammatory diseases is actually very limited. Drugs such as COX-2 inhibitors and synthetic glucocorticoids remain a mainstay in the treatment of many of these inflammatory diseases. Intense research activity over the past 20 years has revealed a whole host of potential targets, a most recent success being TNF, which can be inhibited with engineered soluble receptors or blocking humanized monoclonal antibodies. More successes are likely to follow and the important role of PI3K isoforms and chemokines in both innate and adaptive immunity suggests that selective inhibitors may be therapeutically useful in inflammatory and autoimmune disorders. In addition, there is also potential for the wider application of these inhibitors in other diseases such as thrombosis, cardiac disease and hypertension, so it is imperative that we understand the complexities and subtleties of this signalling pathway.

Use of bioprobes to analyse the spatio-temporal regulation of phospholipids during T cell migration and activation

Phosphoinositide 3-kinases (PI3Ks) phosphorylate phosphoinositide (PI) lipids at the 3'OH position of the inositol ring which in turn have been implicated in a plethora of biological events including migration and activation of lymphocytes. The main 3'-phosphorylated PI species found in mammalian cells after receptor stimulation are PI(3,4)P2 and PI(3,4,5)P3. The principle aim of my work is to visualise the spatio-temporal organisation of the major PI3K lipid products PI(3)P, PI(3,4)P2 and PI(3,4,5)P3 in T lymphocytes undergoing two distinct types of polarised response: (i) directional migration towards chemokines and (ii) stimulation of the T cell antigen receptor. This is acheived by using fluorescently-tagged (e.g. green fluorescent protein) lipid binding domains with specificity for PI(3)P, PI(3,4)P2 and PI(3,4,5)P3 (e..g. GFP-PKB PH domain) which have been stably transfected into T cell lines/human peripheral blood-derived T cells or which are transgenically expressed in murine T cells . To assess the role of individual PI3K isoforms in the accumulation of distinct PI lipids, isoforms are targeted by a combination of isoform-selective inhibitors, expression of gain-of/loss-of function mutants, as well as siRNA and use of isoform-selective gene knockout mice.

Chemokine receptor internalisation and trafficking

Another area of interest in my lab is the analysis of signaling pathways involved in the internalisation and recycling of chemokine receptors on the surface of leukocytes. Once again, we are using fluorescently-tagged proteins (e.g. receptors and signaling proteins such as PI3K and RabGTPAses) to monitor these events.

Toward understanding molecular and cellular basis of inflammatory bowel disease

The Inflammatory Bowel Diseases (IBD) are chronic relapsing and remitting disorders characterised by dysregulated intestinal inflammation. Tri-directional cytokine/chemokine signals between myofibroblasts, epithelial and T cells are involved in regulating immune activation in the gut.

My group is engaged in identifying cross-talk between these cells during the activation versus restitution stages of the inflammatory response. Specifically, we are addressing the role of a range of inflammatory mediators (including cytokines, chemokines and lipid chemoattractants) and their receptors in the regulation of recruitment, activation and function of these and other cells during intestinal immune response. Our studies are currently focused on characterising expression and function of inflammatory mediators and their receptors primarily in the large intestine (but also in the small intestine and elsewhere in the GI tract). Current interests include exploring the homing and role of circulating fibrocytes as well as resident myofibroblasts in wound healing and restitution of inflammation and investigating the role of mast cells as well as the Treg and ThIL-17 T cell subsets in the mucosal immune response. Our research is therefore very much orientated toward translation into a clinical setting and is therefore performed in close collaboration with clinicians at the Royal United Hospital, Bath.  

Drug targets in lung transdifferentiation and airway disease

Transdifferentiation is defined as the conversion of one cell type to another. One example is the transformation of epithelial cells to fibroblasts (or myofibroblasts) (more commonly referred to as epithelial mesenchymal transition EMT). EMT is a key feature of several fibrotic interstitial lung diseases and is characterised by tissue remodelling, fibroproliferation and deposition of extracellular matrix in the lung parenchyma. The prototypical fibrotic lung disease is idiopathic pulmonary fibrosis (IPF), a progressive disorder that culminates in premature death from respiratory failure and in which no treatment intervention has been effective to date. The mechanisms underlying EMT in the lung are poorly understood but are believed to involve production of inflammatory cytokines and/or chemokines. We are presently engaged in identifying the molecular and cellular events in EMT and/or transdifferentiation in order to help identify new drug targets for future therapies.