Mechanisms and therapeutic implications of impaired sensory neuron opioid receptor expression, coupling and function in streptozotocin-induced diabetes

以前，我们已经研究了人类疾病状态下阿片类药物反应性的差异分子和细胞调节，例如炎症性疼痛。由于疼痛性糖尿病神经病变是一种外周感觉神经元疾病，难以治疗，并且已知对阿片类镇痛药不太敏感，因此我们将在本项目中使用体外和体内实验研究阿片类药物反应性降低的时间过程，并专注于识别一些假定的机制。在第一种方法（目标A）中，我们测试了患有链脲佐菌素（STZ）诱导的糖尿病的大鼠发展外周感觉神经元μ-阿片受体偶联、信号传导和功效的显著损害的假设。在我们的第二种方法（目标B）中，我们测试了以下假设：在早期阶段，感觉神经元μ-阿片样物质受体通过PKC/PKC依赖性机制磷酸化，在晚期阶段，由于增强的溶酶体靶向和随后的降解，感觉神经元μ-阿片样物质受体的数量和密度大大降低。将评估可能的治疗策略，如β-内酰胺酶/PKC抑制、生长因子（例如NGF）治疗和/或溶酶体/蛋白酶体抑制，以拯救μ-阿片受体表达、信号传导和功能。新的见解可能使我们能够更好地理解为什么疼痛性糖尿病神经病变患者对阿片类药物治疗的反应或多或少有效，并在病理条件下开发改善阿片类药物反应性的新治疗策略。

Previously we have examined the differential molecular and cellular regulations of opioid responsiveness during states of human disease, e.g. inflammatory pain. Since painful diabetic neuropathy is a peripheral sensory neuron disease, is difficult to treat and is known to be less susceptible to opioid analgesics, we will investigate in this project the time course of reduced opioid responsiveness using in vitro and in vivo experiments and focus on the identification of some of the putative mechanisms. In a first approach (goal A) we test the hypothesis that rats with streptozotocin (STZ)-induced diabetes develop significant impairment of peripheral sensory neuron mu-opioid receptor coupling, signaling and efficacy. In our second approach (goal B) we test the hypotheses that during early stages sensory neuron mu-opioid receptors get phosphorylated by RAGE/PKC dependent mechanisms and during late stages the number and density of sensory neuron mu-opioid receptors is greatly reduced due to enhanced lysosomal targeting and subsequent degradation. Possible therapeutic strategies such as RAGE/PKC inhibition, growth factor (e.g. NGF) treatment and/or lysosomal/proteasomal inhibition will be assessed to rescue mu-opioid receptor expression, signaling and function. New insights may enable us to better understand why patients with painful diabetic neuropathy do more or less effectively respond to opioid treatment and to develop novel therapeutic strategies of improving opioid responsiveness under pathologic conditions.