Contribution of Neuro-inflammation to Cerebral Ischaemia

Inflammation is our bodies' response to infection and injury. It is characterised by redness, swelling, and heat and requires recruitment of cells from the blood to an infected or injured area. Typically inflammation is a beneficial response. However, a failure to switch off an inflammatory response, or for it to resolve, can lead to chronic or inappropriate inflammation. This can result in the death of healthy cells and tissue. As we age the bodies control of how it regulates inflammation begins to diminish. Therefore when our bodies are challenged by an injury or an infection they fail to cope efficiently. Much research on mechanisms of inflammation has been carried out with respect to many types of infection and injury in many organs and great progress has been made. However, how inflammation is regulated in the brain is far less studied and we do not currently understand how the responses are coordinated. The main aim of this proposal is to understand the regulation of inflammation in the brain. We have access to mice in which specific parts of the inflammatory response have been removed, or knocked out. Using these mice we can examine the inflammatory response in the brain after an injury such as caused by stroke. This will give us information on the specific reactions that occur and their consequence. Brain inflammation has a significant impact on the health and wellbeing of the population, and particularly so for people of old age. Thus understanding how the brain regulates inflammation could lead to new strategies to treat brain injury and disease.

Inflammation that occurs in response to tissue injury in the absence of pathogen is considered sterile, and can contribute to damage. The primary inflammatory cytokines associated with sterile inflammatory responses are members of the interleukin-1 (IL-1) family, IL-1a and IL-1b. IL-1 release from activated immune cells is regulated by a protein complex called the inflammasome. IL-1 is expressed in response to damage associated molecular patterns (DAMPs) that stimulate pattern recognition receptors (PRRs) on cells of the innate immune system. Once expressed, pro-IL-1 remains intracellular until an additional DAMP stimulation activates inflammasomes. Inflammasomes activate caspase-1 which in turn processes pro-IL-1 allowing release of the mature cytokine. We have discovered that brain inflammation after cerebral ischaemia is dependent upon the AIM2 and NLRC4 inflammasomes and also requires the inflammasome component ASC. However, we do not understand whether these inflammasomes are activated in the brain, whether they drive systemic inflammation, or indeed whether they contribute directly to cell death. We aim to identify the cell type and location driving the respective inflammasome-dependent responses, and to dissect the inflammasome-dependent neurotoxic and inflammatory responses activated by CI.

We will use a number of complimentary approaches to achieve the aims of this proposal. The middle cerebral artery occlusion (MCAo) model of stroke is a robust and clinically relevant model which we will use in mice in which components of different inflammasomes (e.g. AIM2, NLRP3, NLRC4, ASC) have been knocked out. Inflammatory, injury, and behavioural endpoints will provide a comprehensive view of the role of these proteins in the inflammatory response. We will also use functionalised carbon nanotubes (f-CNTs) to deliver RNAi to specific brain areas to uncouple the inflammatory response from cell death, and so fully interrogate mechanisms of inflammasome function.

- Who will benefit from this research?
The immediate beneficiaries of this research will be the Faculty here at the University of Manchester. The development of methodologies, the training of students and of postdoctoral researchers will bring many benefits that will ultimately enrich the research environment. The potential identification of drug targets will benefit our local commercialisation team (UMIP) and may, in the longer term, provide economic benefits. Beyond this the presentation/publication of papers at conferences and in international high impact peer reviewed journals will benefit the wider scientific community and the University in general. The data generated through the course of this proposal may inform strategy boards of funding bodies (UK and overseas) on the growing recognition of the importance of inflammation to brain disorders and to disease in general. Clinicians may be informed of new strategies or treatments for the management of inflammatory brain disease that will ultimately lead to benefits for patients. The wider public will also benefit from increased understanding of and exposure to science through activities run by our labs. We also participate in careers fairs with local schools benefiting local school children to learn about future careers in science.

- How will they benefit from this research?
Most immediately research from this proposal will help inform researchers in the field and in the scientific community in general about key, up to now, unknown mechanisms of inflammation. The creative experiments we have designed, and the discoveries we make, will inspire other researchers to investigate similar mechanisms and thus our levels of knowledge on these process in general will increase substantially. The new areas of research that our discoveries will open will lead to the recruitment and training of students in this area which will spawn further developments. Many of these future developments will likely involve the identification of targets that may eventually lead to interventions that inhibit inflammation in animal models of brain disease. These will inform clinical studies and may lead to new treatments for disease. Due to the nature of this research there is scope for the commercialisation of the discoveries and potential economic benefits to the University and to the economy in general. Inflammatory disease has a massive impact on human suffering and thus research into the mechanisms of inflammation has potentially a direct impact on the health and wellbeing of people in the UK and worldwide.