MICA: Towards targeted treatment for complex regional pain syndrome through determination of the underlying molecular mechanisms

复杂性区域疼痛综合征（CRPS）是一种慢性疼痛状况，可能发生在受伤后，如骨折，并导致局部疼痛和肿胀。CRPS在20-30%的病例中在一年内自发消退，但在此之后它变成慢性并且很少改善。与许多其他形式的慢性疼痛一样，CRPS患者的治疗选择非常有限，无针对性，并且通常具有显著的副作用。因此，了解CRPS的发病原因及其潜在机制，对于开发更有效的疼痛和炎症药物，改善CRPS患者的生活至关重要。我们通常可以通过观察基因的变化（突变）来了解疾病的发病原因，这反过来有助于设计新药，如止痛药（镇痛药）。例如，在一个感觉不到疼痛的家庭中发现了一种称为神经生长因子的基因的变化（作为一种非常罕见的疾病遗传），这导致了一类新的止痛药的发现，特别有助于对抗关节炎疼痛。我们想看看与非患者相比，CRPS患者的基因是否发生突变，这可能会改变他们对这种疾病的易感性。我们发现，与没有CRPS的人相比，CRPS患者更有可能在四个基因中发生突变。假设这些突变中的每一个都引起蛋白质功能的改变。我们和其他人已经证明这四种基因在单核细胞和/或巨噬细胞（吞噬外来颗粒并引起炎症的细胞）中表达。重要的是，所有四个基因都与含NOD、LRR和pyrin结构域的蛋白3（NLRP 3）炎症通路相关，该通路可以感知外来颗粒并通过释放炎症分子和细胞死亡来清除它们。这些数据表明，NLRP 3炎性体途径可能在CRPS的病理学中是重要的。在这个提议中，我们将研究CRPS突变基因如何影响NLRP 3炎性小体的活性。为了做到这一点，我们将基因突变引入人单核细胞系（THP-1细胞）。接下来，我们将通过测量THP-1细胞中炎症分子的产生和细胞死亡来确定这些突变是否改变了NLRP 3炎性体的活性。我们将通过测量来自具有CRPS相关突变的健康个体的细胞中的炎性小体活性来验证THP-1模型。我们的下一步将是确定NLRP 3炎性体活性的这些变化如何影响疼痛神经元激活，作为模拟CRPS中过度疼痛的方法。最后，我们将测试NLRP 3调节剂如何影响疼痛和炎症，以便将我们的发现转化为CRPS新药的开发。我们预计我们的研究将导致一类新的非成瘾性止痛药的鉴定，这将减少炎症和疼痛，以阻止慢性阶段的CRPS的发展。这将对疼痛管理、炎症和抑郁、发病率和死亡率产生非常显著的影响，这些都是长期严重疼痛的后果。

Complex regional pain syndrome (CRPS) is a chronic pain condition that can occur after an injury, such as a fracture and results in localised pain and swelling. CRPS spontaneously resolves within a year in 20-30% of cases, but after this time it becomes chronic and rarely improves. Treatment options for CRPS patients, as with many other forms of chronic pain, are very limited, untargeted, and often have significant side effects. It is, therefore, important to understand why CRPS develops and the underlying mechanisms involved in order to try and develop more effective drugs targeting pain and inflammation and improve lives of those living with CRPS.We can often gain insight into why a disease develops by looking at changes found in genes (mutations), which in turn helps design new drugs, such as pain killers (analgesics). For example, changes in a gene called nerve growth factor, were found in a family unable to feel pain (inherited as a very rare disease), and this led to the discovery of a new class of analgesics that is particularly helpful against arthritic pain. We wanted to see if patients with CRPS had mutations in their genes, compared to non-sufferers, which could alter their susceptibility to the condition. We found that CRPS patients were more likely to have mutations in four genes compared to people without CRPS. Each of these mutations was hypothesised to cause alterations of protein function. We, and others, have shown these four genes are expressed in monocytes and/or macrophages (cells that engulf foreign particles and cause inflammation). Importantly, all four genes are linked to the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammatory pathway that senses foreign particles and removes them by causing release of inflammatory molecules and cell death. These data suggest that the NLRP3 inflammasome pathway is likely to be important in the pathology of CRPS. In this proposal we will investigate how the CRPS-mutated genes affect the activity of the NLRP3 inflammasome. In order to do this, we will introduce the gene mutations into a human monocyte cell line (THP-1 cells). Next, we will determine if these mutations alter the activity of the NLRP3 inflammasome by measuring the production of inflammatory molecules and cell death in THP-1 cells. We will validate the THP-1 model by measuring inflammasome activity in cells from healthy individuals with the CRPS-associated mutations. Our next step will be to determine how these changes in NLRP3 inflammasome activity influence pain neuron activation as a method to model the excessive pain seen in CRPS. Lastly, we will test how NLRP3 modulators affect pain and inflammation in order to translate our findings towards the development of new drugs for CRPS. We anticipate our research will lead to the identification of a new class of non-addictive pain-killers that will reduce inflammation and pain to stop the chronic stage of CRPS from developing. This would have very significant effects on pain management, inflammation and the depression, morbidity and mortality that are a consequence of prolonged severe pain.