Peripheral Neuronal and Non-neuronal Mechanisms of Fabry Disease Pain

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PROJECT SUMMARY Fabry Disease (FD) is one of the most common lysosomal storage diseases and causes devastating pain in patients starting at a young age. While clinical literature has shown that patients with FD have mechanically- evoked pain, ongoing pain, and peripheral nerve damage, it is unclear how FD pain is mediated in the peripheral nervous system (PNS). My proposal will investigate how PNS cellular mechanisms mediate FD pain using the FD rat model, which recapitulates the pain phenotypes seen in patients. Abnormal ion channel activity on neurons is linked to peripherally mediated pain in many diseases. However, recent evidence has shown that pain-associated ion channels in neurons are also expressed in non-neuronal cells. Decreasing Schwann cell (SC) ion channel activity can ameliorate mechanically-evoked pain behaviorally in other pain conditions. It has been hypothesized that algogens released from SCs are influencing mechanically-evoked pain. We have shown that mechanically-evoked pain in FD depends on the activity of the ion channel Transient Receptor Potential Ankyrin 1 (TRPA1) in the PNS. In my proposal, I will determine if TRPA1 also mediates ongoing pain through PNS activity of FD rats. I will also determine if algogens released from FD SCs activate or sensitize neurons to mechanical force, and if SC TRPA1 drives mechanically-evoked pain in FD. I hypothesize that increased activity of TRPA1 in both Schwann cells and neurons is critical for maintaining chronic pain phenotypes in the FD rat. In Aim 1, I will determine if the FD rat has behavioral ongoing pain and aberrant peripheral nerve activity that is dependent on TRPA1. I will use a battery of ongoing pain behavior techniques and determine if TRPA1 inhibition alleviates this pain (Aim 1A). I will then determine whether peripheral TRPA1 is required for spontaneous axonal activity in the FD rat by using ex vivo teased fiber recordings (Aim 1B). In Aim 2, I will investigate the role that SCs play in TRPA1-dependent mechanical hypersensitivity in FD. First, I will determine if sensory neurons are activated or sensitized by algogens released from FD SCs, and if neuronal TRPA1 is required for this activation (Aim 2A). Next, I will determine if algogens from FD SCs sensitize neurons to mechanical stimulation using patch-clamp recordings, and if this depends on neuronal TRPA1 activity (Aim 2B). Finally, I will determine if viral inhibition of SC TRPA1 can alleviate FD mechanical hypersensitivity through a battery of pain behavior assays (Aim 2C). My proposal will provide a basis for how Schwann cells mediate chronic pain and will advance our understanding of Fabry Disease pain.