BJA/RCoA Project Grants

Chronic pain is a serious health issue which affects about one in three people at any point in life. In the last decade, neuroscientists have come to understand chronic pain as a conscious experience which does not directly reflect its apparent cause (e.g., tissue damage). These findings imply that solely treating the tissue damage which likely causes the pain it is not sufficient to achieve relief. There is abundant evidence from experiments and clinical practice that thoughts and expectations about pain powerfully influence the extent to which a patient feels pain. We are planning to study how expectations and thoughts influence pain levels and the way pain-related brain areas communicate with each other.

To this end, we are planning to recruit a cohort of patients with Complex Regional Pain Syndrome (CRPS). CRPS is a debilitating chronic pain condition causing patients to feel disproportionate pain when the painful body part is softly touched. Patients typically report to be unable to wear clothing covering the affected limb or carry out even simple tasks with the painful body part. Navigating an environment in which innocuous touch is associated with pain might change the way pain-related information is propagated through brain networks and influenced by psychological processes. We are planning to test this hypothesis in a series of three neurocognitive experiments. Across two visits, we will record brain activity from 30 patient participants and 30 healthy participants using Electroencephalography.

Our project aims (1) to characterise dynamic interactions in brain networks which account for touch-evoked pain; (2) to elucidate how touch-evoked pain and its brain signatures are influenced by psychological demand and expectations of pain. In the first experiment, we aim to show that patients' brains predict identical tactile stimulus patterns differently depending on whether the painful or the non-painful hands are stimulated. We are planning to model these differences in brain activity generated by touch to the painful hand vs the non-painful hand in the group and also for each patient to characterise interindividual differences.

In the second experiment, we will occasionally intrude upon patients' expectations of painful touch by omitting the stimuli. This will enable us to dissociate the brain signature of expectations of painful touch from brain processes which reflect a neural adaptation to repetitive painful stimuli. We expect that unmet expectations of pain will generate activity in brain areas linked to pain, but there will be differences in how these brain areas communicate with each other when pain is experienced as opposed to only expected.

In the third experiment, we will investigate whether pain perception and activity in pain-related networks are modulated by cognitive demand. To this end, we will present participants with a paradigm similar to experiment 2 while additionally asking them to solve tasks with varying difficulty. We expect to find that higher cognitive demand is linked to increased pain perception and altered connectivity between frontal cortical areas related to higher cognition and pain-related brain areas. We envision that our study will help inform the development of non-invasive and drug-free treatment tailored towards each patient.

Background
Malignant hyperthermia (MH) is a genetic condition that affects the control of calcium within skeletal muscle tissue. The body normally compensates for this, but when a patient with the genetic risk for MH is given one of the commonly used anaesthetic gases, the muscle cells lose control of calcium regulation in a dramatic and potentially fatal way. MH reactions are rare (1 in 120,000 anaesthetics) but more than 1 in 2,000 people carry a genetic risk factor. We do not understand why people with the genetic risk do not always have a reaction when they have an anaesthetic. When they do, there is a lot of variation in the clinical features of the reaction. This makes diagnosis difficult, which in turn delays treatment and increases harm to the patient. We also do not understand why patients with MH gene changes experience muscle aches, muscle pains and muscle cramps that impact on their quality of life. In addition, the MH gene changes have been linked to exercise related rhabdomyolysis (breakdown of muscle tissue leading to kidney damage) and heatstroke.

Aims
We aim to determine if changes in the function of mitochondria (components of cells that generate energy) are present in MH muscle cells. Research using animal models of MH suggests this is the case and we have preliminary data to suggest this may also be the case in human MH but the proposed work is needed to rule out other explanations for these findings. Faulty mitochondria could explain at least some of the variability of MH reactions and symptoms that MH patients experience in everyday life.

Methodology
This is a laboratory project using muscle cells previously donated by MH patients attending for muscle biopsy (the procedure used for MH testing) and cultured in the laboratory. We will also use cells from MH mouse models. We will be able to compare directly the mitochondrial
function between human MH and normal cells and mouse MH and normal cells where the mice and human MH cells carry the equivalent gene change. We also plan to obtain more information about the activity of genes that regulate mitochondrial function.

Expected outcomes
We expect to find faults in the function mitochondria of MH patients and corresponding changes in the activity of relevant genes that may or may not mirror those in MH mice.

Implications
The results of this study will support an application to the Medical Research Council for a programme of research intended to find medicines that could treat the faulty mitochondria in MH patients.

Opioid drugs are used to treat pain and to do that they interact with specific targets on cells; these are called opioid receptors. Typically these drugs include morphine that is used in operations and sometimes long term in end of life pain control. The problem with opioid drugs is that they produce serious side effects such as reduced breathing, nausea and vomiting and tolerance. Tolerance is the process underlying the need to constantly increase dose to produce the same effect. It is clear that if the dose is increased then the side effects also increase and a vicious cycle sets up. Reducing tolerance (and other side effects) is a goal in the design of new pain killers. We know that opioid receptors are members of a family; there are four members. We also know that the receptors interact with each other and that when they do side effects, in particular tolerance, can reduce. Morphine interacts with a receptor called MOP and one of the other members called NOP is particularly important as it interacts with MOP and can modulate morphine actions including tolerance in the test tube.

There is a drug in advanced clinical trials called cebranopadol that activates both MOP and NOP and produces pain relief with reduced side effects including tolerance. Moreover, there is a very new experimental molecule called AT-121 that also activates MOP and NOP but it has not been tested in the clinic. We have access to cebranopadol and AT-121 and we have a model cell culture system that has both MOP and NOP receptors that we can easily study. Our hypothesis is that MOP and NOP receptors interact in our system and in both a physical and functional way. We will use a series of novel probes for these receptors that give off light when excited. This light can be seen and measured in a specialised microscope. Using a number of novel techniques we will be able to harness these probes to determine physical interaction of the receptors to form structures called dimers. We will measure activity by treating with several drugs including cebranopadol and AT-121 then looking to see what happens to receptors. The activity we will look at it how receptors move away from the surface of the cell in our model system; there is evidence that this is linked to tolerance. This will also be measured using radiation based (and more standard) methods. We predict that the responses will differ with the new mixed molecules.