Mechanisms of Epigenetic Plasticity in Neuropathic Pain

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Mechanisms of Epigenetic Plasticity in Neuropathic Pain The major objective of our project is to determine how traumatic nerve injury impacts epigenetic regulatory networks involved in chronic pain. Neuropathic pain remains a major clinical problem and therapeutic challenge. Both sustained changes in gene expression in primary afferent neurons and synaptic plasticity at the spinal cord level are essential for to the development of chronic pain. α2δ-1 (encoded by the Cacna2d1 gene) is a clinically validated neuropathic pain target and mediates the therapeutic actions of gabapentinoids. Traumatic nerve injury and certain cancer chemotherapeutic drugs cause α2δ-1 upregulation in the dorsal root ganglion and spinal cord, which augments nociceptive input to spinal dorsal horn neurons by directly interacting with NMDA receptors. Yet we know almost nothing about how nerve injury initiates and sustains the high expression level of α2δ-1. Acetylation of lysine residues in histone tails is dynamically regulated by various histone deacetylases (HDACs). However, the specific HDAC subtypes responsible for the upregulation of α2δ- 1 and other neuroplasticity-related genes in neuropathic pain have not been rigorously studied or identified. To address this key knowledge gap, we will specifically determine the role of class I HDAC subtypes in the control of histone acetylation and expression of α2δ-1 and other gene targets implicated in synaptic plasticity in two neuropathic pain models. On the basis of our preliminary data, we propose to test the overall hypothesis that nerve injury and chemotherapy diminish HDAC2 occupancy to induce histone hyperacetylation, via CK2- mediated phosphorylation, at the promoters of Cacna2d1 and other neuroplasticity-related genes in the DRG and that HDAC2 constitutively restrains chronic pain by repressing Cacna2d1 transcription and α2δ-1– dependent NMDA receptor activation at the spinal cord level. We will apply several innovative and vigorous approaches, including unbiased genome-wide epigenetic analyses, transgenic mice, and synaptic recordings to study neuroplasticity at molecular, cellular, and behavioral levels. Our project will generate fundamental new information about the epigenetic basis of neuropathic pain. Findings from our project are expected to advance our knowledge of molecular mechanisms of epigenetic plasticity and to guide the development of new strategies for treating neuropathic pain.