Chronic pain is debilitating medical problem that affects millions of people. However, current clinical therapy relying on opioids and non-steroidal anti-inflammatory drugs has limited efficacy because of severe adverse effects and abuse potential. To overcome these limitations, more in-depth illustration of the mechanism that underlies the development and maintenance of chronic pain will be extremely helpful. Pain perception consists of both peripheral and central components. While the peripheral mechanisms of pain have been well studied, our current understanding of the central mechanism of pain perception, especially with respect to chronic pain, remains rather limited. The current project focuses on the mechanism by which anterior cingulate cortex (ACC) of the brain participates in pain perception. It has been well-established that synaptic plasticity in ACC represents one of the most critical mechanisms underlying the transition of pain from acute to chronic. Using mouse models of chronic pain induced by peripheral inflammatory and spared nerve injury, the research team has obtained strong evidence that acid-sensing ion channel isoform 1a (ASIC1a) plays a pivotal role in both the development and maintenance of chronic pain. Not only did ACC neuron specific ablation of ASIC1a gene mitigated inflammatory hyperalgesia and mechanical allodynia, but in situ pharmacological inhibition of ASIC1a at ACC also quickly reversed the pre-established pain hypersensitivity. More intriguingly, in situ focal application of an ASIC1a activator at ACC enhanced sensitivity to peripheral thermal and mechanical stimulation within 10 minutes in the absence of peripheral inflammation or injury, indicating a crucial role of ACC ASIC1a activity in pain processing. The current project aims to elucidate the mechanism by which ACC ASIC1a regulates central pain processing at molecular, cellular and functional levels. The central hypothesis is that in ACC excitatory neurons that receive persistent nociceptive inputs, ASIC1a, in an ion conduction-independent manner, facilitates cingulate long-term potentiation through promoting forward trafficking of AMPA receptors. The enhanced synaptic efficacy in turn leads to altered sensitivity and reactivity of the pain pathways. The two specific aims are to define molecular underpinnings of ASIC1a regulation of AMPAR trafficking during the course of LTP induction and expression in ACC excitatory neurons (AIM 1) and illustrate functional relevance of molecular interactions that control AMPAR trafficking in cingulate LTP and chronic pain (AIM 2). The collaborative project will combine the unique strengths of the two laboratories in biochemical and cell biological analysis (US lab) and electrophysiological and behavioral study of plasticity and pain (China lab) to accomplish the goals. The project will greatly enhance our understanding on mechanism of ASIC1a regulation of synaptic plasticity, especially as it relates to pain hypersensitivity through enhancing synaptic efficacy at supraspinal levels, and shed new lights on more effective ways to treat chronic pain with minimal side effects.
Through examination of the molecular mechanisms of chronic pain at anterior cingulate cortex, a major area involved in processing pain sensation in the brain, the research team aims to elucidate how our brain perceives pain and how this can be altered through changes in the function of an ion channel named acid-sensing ion channel 1a, or ASIC1a. The proposed research combines the complementary strengths of two laboratories using innovative and the state-of-the-art techniques. Chronic pain is a debilitating medical problem, affecting millions of people, to which current clinical therapy has only limited efficacy; the proposed project is expected to shed lights on new ways to treat chronic pain.
