Macrophage sensing of extracellular ATP during inflammation

Inflammation is the response of the body to threats such as infection and injury. During inflammation, the body releases danger signals that alert immune cells that something is wrong. The first immune cells to encounter these signals are called macrophages and their main job is to destroy the threat and call for back up to completely fight the danger to restore health. However sometimes the immune system fails and inflammation continues even when the threat is gone. In these cases what was once your best friend can quickly become your worst enemy. With nothing to destroy macrophages will now attack your own body and cause damage. This is the cause of many inflammatory conditions including arthritis, cardiovascular disease or lung diseases such as COPD (Chronic Obstructive Pulmonary Disorders).

Upon sensing danger macrophages behave like factory assembly plants, putting a lot of pieces together in order to manufacture the right artillery to fight and remove the threat. These different pieces are called proteins and they need to be assembled in the right place and in a specific order to function properly. If the assembly of these proteins occurs in the wrong moment or in the wrong order it can misfire causing chronic inflammation, and consequently disease.

One of the danger signals that macrophages can sense is ATP. ATP is only found within healthy cells, but when cells become stressed they release it into their surrounding environment. Macrophages sense ATP through a protein called P2X7R initiating a series of events (or assembly lines) that lead to inflammation. However we do not understand what these events are and how they are regulated.

Here we will investigate how the different assembly lines initiated when ATP is sensed by macrophages work. We will investigate which proteins are required, in which order and if these are faulty in inflammatory conditions such as COPD. Understanding this would have a beneficial effect in people with inflammatory disease since this will help to develop new drugs that could reverse or stop inflammation to achieve health.

Innate immune recognition of danger signals is an important mechanism that protects against infection, and injury. ATP is released from infected or damaged cells and its extracellular presence alerts macrophages of impending danger. At high levels, extracellular ATP (eATP) binds to the P2X7 receptor, expressed on macrophages, triggering a potent pro-inflammatory immune response. This mechanism has been shown to be crucial in our defence against pathogens, but also plays a role in inflammatory diseases. Little is known about how P2X7R relays information from ATP binding, yet there is increasing evidence that kinase signalling plays an important downstream role, suggesting that the posttranslational modification phosphorylation might be key in this process.

In this project, we will use quantitative proteomics to characterise the phosphorylation signals regulated by P2X7R upon eATP activation in macrophages. We will use this data to build computational network models driving hypotheses as to how these signals can be therapeutically targeted. We will also integrate how these networks control the biological outputs induced by P2X7R, for example release of inflammatory cytokines. Together, this will provide, for the first time, a comprehensive overview of the signalling triggered by the danger signal eATP in macrophages, providing avenues of potential new therapeutics in a wide-range of inflammatory diseases.

This research will be beneficial to several sectors in addition to academics. It will be relevant to industry. There is a great interest from the Pharma sector in developing novel therapeutics to target chronic inflammatory conditions, including arthritis, cardiovascular disease or COPD. Our work will inform the sector on novel findings on how P2X7R works. This will not only provide a deep understanding on the benefits or disadvantages of using P2X7R inhibitors as therapeutics in these pathologies, but will also identify new therapeutic targets that could therefore influence Pharma drug development programs.

This research will also be beneficial to clinicians and patients. Although in the short term the results obtained here will not be applied to the clinic, they will be relevant to influence future translational research, that could change how we treat inflammation. It will therefore be of interest to clinicians and patient groups where inflammation is a component of their poor health. During this project we will establish conversations with these two groups to identify new translational needs for future research projects.

The staff working in the project (the RA and PDRA) will also benefit. They will be part of a multidisciplinary team. They will need to understand different areas of research, be able to discuss their work effectively with all members of the team as well as present their work in an accessible manner to scientists working in different research areas. To achieve this they will need to develop excellent communication and organizational skills, which would be key to succeed in most jobs, no matter in which employment sector.

Finally this research will also benefit the general public. Understanding that production of danger signals that sustain inflammation, is triggered by factors such as smoking and obesity, among others, and that this can lead to disease, will raise awareness that might influence people lifestyle having a positive impact on their wellbeing. We will communicate our research at different public events museums, and schools as well as in other venues if the opportunity arises.