Dissecting out the abnormal signalling pathways that lead to the exaggerated inflammatory response characteristic of Ulc
Lead Research Organisation:
University College London
Department Name: Medicine
Abstract
Ulcerative colitis (UC) a chronic inflammatory disease, resulting in ulceration of the bowel, affecting 1 in 1000 of the population, the majority present at age 15-30 years. It is associated with considerable morbidity and increased risk of colorectal Cancer. One fifth of patients with severe disease require a colectomy which has significant social and psychological implications, especially in this young population.
The underlying cause of UC remains unknown. It is thought to results from an abnormal, exaggerated, inflammatory response to bowel flora that are usually innocuous, but which induce inflammation in genetically susceptible individuals.
Professor Segal‘s laboratory has shown that an elevated and prolonged inflammatory response is seen when UC patients, or their isolated cells, are exposed to intact or individual components of gut bacteria.
Part of the pathway by which this occurs has been identified and it is my aspiration to expand these findings and identify specific defects in individual UC patients. This will be done by using molecular, biochemical and genetic analysis of tissue from normal volunteers and patients with UC.
Defective pathways and genes could be potential drug targets and ultimately aid in the development of new therapeutics to treat this debilitating human disease.
The underlying cause of UC remains unknown. It is thought to results from an abnormal, exaggerated, inflammatory response to bowel flora that are usually innocuous, but which induce inflammation in genetically susceptible individuals.
Professor Segal‘s laboratory has shown that an elevated and prolonged inflammatory response is seen when UC patients, or their isolated cells, are exposed to intact or individual components of gut bacteria.
Part of the pathway by which this occurs has been identified and it is my aspiration to expand these findings and identify specific defects in individual UC patients. This will be done by using molecular, biochemical and genetic analysis of tissue from normal volunteers and patients with UC.
Defective pathways and genes could be potential drug targets and ultimately aid in the development of new therapeutics to treat this debilitating human disease.
Technical Summary
Background:
Ulcerative colitis (UC), a chronic inflammatory disease affecting 1 in 1000 of the population, is associated with morbidity and an increased risk of colorectal cancer. It is widely viewed as a primary T-cell mediated autoimmune disorder with loss of immune tolerance to commensal bowel flora in genetically susceptible individuals. Although strong evidence supports an exuberant response to microbial components in the pathogenesis, to date no intrinsic T-cell defect or underlying mechanism has been identified.
Macrophages coordinate the immune response to microbes via pathogen recognition receptors such as Toll- like receptors (TLR). Professor Segal‘s laboratory has recently highlighted the importance of macrophage-mediated innate immune dysfunction in the pathogenesis of Crohn‘s disease. Patients with UC were used as disease controls in these experiments during which abnormalities were discovered in the inflammatory response in UC. Patients with UC demonstrated an elevated and prolonged acute inflammatory reaction to E.coli in vivo, with raised CXCL10 levels in the circulation. In vitro studies with E. coli stimulated peripheral blood monocyte-derived macrophages also resulted in elevated CXCL10 secretion and identified a specific TLR4-mediated TRIF-dependent response, resulting in over-expression of molecules strongly associated with T-cell recruitment and activation. These findings implicate an abnormal TLR4-mediated innate response to bacterial flora as a primary abnormality in the pathogenesis of UC, which eventuates in classic T-cell mediated inflammation in the gut.
Aim and objectives:
My aim is to characterise the mechanisms involved in the abnormal bacterial response that has been identified in UC patients. Hopefully these investigations will identify pathways and genes which are abnormal in UC, and eventually lead to the development of new diagnostics and therapeutics.
Methodology:
Ethical approval has been granted to study patients with inflammatory bowel disease (~4,000) available through the gastroenterology departments at University College and Royal Free Hospitals.
A detailed investigation into the macrophage response to stimulation with bacteria and individual ligands will be conducted. Previously acquired microarray data is currently being evaluated and abnormal molecules identified will be confirmed by qPCR and western blotting. The relative importance of these molecules in respect to immune modulation, cytokine secretion and macrophage biology will be investigated. Links between individual genes and the abnormal macrophage response previously described will identify potential pathway defects which will be further investigated in our UC cohort.
Abnormalities identified will potentially be drug targets and aid in the development of new therapeutics to treat this chronic disease.
Ulcerative colitis (UC), a chronic inflammatory disease affecting 1 in 1000 of the population, is associated with morbidity and an increased risk of colorectal cancer. It is widely viewed as a primary T-cell mediated autoimmune disorder with loss of immune tolerance to commensal bowel flora in genetically susceptible individuals. Although strong evidence supports an exuberant response to microbial components in the pathogenesis, to date no intrinsic T-cell defect or underlying mechanism has been identified.
Macrophages coordinate the immune response to microbes via pathogen recognition receptors such as Toll- like receptors (TLR). Professor Segal‘s laboratory has recently highlighted the importance of macrophage-mediated innate immune dysfunction in the pathogenesis of Crohn‘s disease. Patients with UC were used as disease controls in these experiments during which abnormalities were discovered in the inflammatory response in UC. Patients with UC demonstrated an elevated and prolonged acute inflammatory reaction to E.coli in vivo, with raised CXCL10 levels in the circulation. In vitro studies with E. coli stimulated peripheral blood monocyte-derived macrophages also resulted in elevated CXCL10 secretion and identified a specific TLR4-mediated TRIF-dependent response, resulting in over-expression of molecules strongly associated with T-cell recruitment and activation. These findings implicate an abnormal TLR4-mediated innate response to bacterial flora as a primary abnormality in the pathogenesis of UC, which eventuates in classic T-cell mediated inflammation in the gut.
Aim and objectives:
My aim is to characterise the mechanisms involved in the abnormal bacterial response that has been identified in UC patients. Hopefully these investigations will identify pathways and genes which are abnormal in UC, and eventually lead to the development of new diagnostics and therapeutics.
Methodology:
Ethical approval has been granted to study patients with inflammatory bowel disease (~4,000) available through the gastroenterology departments at University College and Royal Free Hospitals.
A detailed investigation into the macrophage response to stimulation with bacteria and individual ligands will be conducted. Previously acquired microarray data is currently being evaluated and abnormal molecules identified will be confirmed by qPCR and western blotting. The relative importance of these molecules in respect to immune modulation, cytokine secretion and macrophage biology will be investigated. Links between individual genes and the abnormal macrophage response previously described will identify potential pathway defects which will be further investigated in our UC cohort.
Abnormalities identified will potentially be drug targets and aid in the development of new therapeutics to treat this chronic disease.
