Project description:Histone deacetylase inhibitors (HDACIs) interfere with the epigenetic process of histone acetylation and are known to have analgesic properties in models of chronic inflammatory pain. The aim of this study was to determine whether these compounds could also affect neuropathic pain. Different class I HDACIs were delivered intrathecally into rat spinal cord in models of traumatic nerve injury and antiretroviral drug-induced peripheral neuropathy (stavudine, d4T). Mechanical and thermal hypersensitivity was attenuated by 40% to 50% as a result of HDACI treatment, but only if started before any insult. The drugs globally increased histone acetylation in the spinal cord, but appeared to have no measurable effects in relevant dorsal root ganglia in this treatment paradigm, suggesting that any potential mechanism should be sought in the central nervous system. Microarray analysis of dorsal cord RNA revealed the signature of the specific compound used (MS-275) and suggested that its main effect was mediated through HDAC1. Taken together, these data support a role for histone acetylation in the emergence of neuropathic pain. n = 4, HDACi treated vs. vehicle treated. Injured ipsilateral DRG after L5 spinal nerve transection. Spinal cord tissue was run in a separate Affymetrix experiment.
Project description:Histone deacetylase inhibitors (HDACIs) interfere with the epigenetic process of histone acetylation and are known to have analgesic properties in models of chronic inflammatory pain. The aim of this study was to determine whether these compounds could also affect neuropathic pain. Different class I HDACIs were delivered intrathecally into rat spinal cord in models of traumatic nerve injury and antiretroviral drug-induced peripheral neuropathy (stavudine, d4T). Mechanical and thermal hypersensitivity was attenuated by 40% to 50% as a result of HDACI treatment, but only if started before any insult. The drugs globally increased histone acetylation in the spinal cord, but appeared to have no measurable effects in relevant dorsal root ganglia in this treatment paradigm, suggesting that any potential mechanism should be sought in the central nervous system. Microarray analysis of dorsal cord RNA revealed the signature of the specific compound used (MS-275) and suggested that its main effect was mediated through HDAC1. Taken together, these data support a role for histone acetylation in the emergence of neuropathic pain. n = 4, HDACi treated vs. vehicle treated. Ipsilateral dorsal spinal cord tissue after L5 spinal nerve transection, DRG tissue was run in a separate Affymetrix experiment.
Project description:Chronic neuropathic pain is a major morbidity of neural injury, yet its mechanisms are incompletely understood. Hypersensitivity to previously non-noxious stimuli (allodynia) is a common symptom. Here, we demonstrate that the onset of cold hypersensitivity precedes tactile allodynia and this temporal divergence was associated with major differences in global gene expression in dorsal root ganglia. Transcripts whose expression correlate with the onset of cold allodynia were nociceptor-related whereas those correlating with tactile hypersensitivity were enriched for immune cell activity. Selective ablation of TrpV1 lineage nociceptors resulted in mice that did not acquire cold allodynia but developed normal tactile hypersensitivity. Whereas depletion of macrophages or T cells reduced neuropathic tactile allodynia but not cold hypersensitivity. We conclude that neuropathic pain is contributed to by reactive processes of sensory neurons and immune cells, each leading to distinct forms of pain hypersensitivity, potentially allowing effective drug development targeted to each pain modality.
Project description:Chronic neuropathic pain is a major morbidity of neural injury, yet its mechanisms are incompletely understood. Hypersensitivity to previously non-noxious stimuli (allodynia) is a common symptom. Here, we demonstrate that the onset of cold hypersensitivity precedes tactile allodynia and this temporal divergence was associated with major differences in global gene expression in dorsal root ganglia (DRG). Transcripts whose expression correlate with the onset of cold allodynia were nociceptor-related, whereas those correlating with tactile hypersensitivity were enriched for immune cell activity. Selective ablation of TrpV1 lineage nociceptors resulted in mice that did not acquire cold allodynia but developed normal tactile hypersensitivity. Whereas, depletion of macrophages or T cells reduced neuropathic tactile allodynia but not cold hypersensitivity. We conclude that neuropathic pain is contributed to by reactive processes of sensory neurons and immune cells, each leading to distinct forms of pain hypersensitivity, potentially allowing effective drug development targeted to each pain modality.
Project description:Chronic neuropathic pain’s impact, persistence, and limited treatments render it relevant for gene therapy. Here, we describe the development and application of self-assembling dimeric peptide inhibitors of the pain-associated scaffolding protein PICK1 (protein interacting with C-kinase 1) delivered by adeno-associated viral (AAV) vectors. In mice, these peptides prevented mechanical allodynia in inflammatory and neuropathic pain models and reversed neuropathic pain for up to one year. Targeting of somatosensory pain pathways relieved pain without overt side effects, while selective transduction of dorsal root ganglion (DRG) neurons was sufficient for providing pain relief. Using proteomic and phosphoproteomic analysis of DRG tissue, we identified protein kinase C alpha (PRKCA) substrate candidate, that potentially shape this pain-relieving phenotype. We also confirmed PICK1 expression and peptide target engagement in mice and human donor tissue, supporting the potential of AAV-based PICK1 inhibitors as a clinically meaningful strategy for neuropathic pain conditions.
Project description:Chronic neuropathic pain’s impact, persistence, and limited treatments render it relevant for gene therapy. Here, we describe the development and application of self-assembling dimeric peptide inhibitors of the pain-associated scaffolding protein PICK1 (protein interacting with C-kinase 1) delivered by adeno-associated viral (AAV) vectors. In mice, these peptides prevented mechanical allodynia in inflammatory and neuropathic pain models and reversed neuropathic pain for up to one year. Targeting of somatosensory pain pathways relieved pain without overt side effects, while selective transduction of dorsal root ganglion (DRG) neurons was sufficient for providing pain relief. Using proteomic and phosphoproteomic analysis of DRG tissue, we identified protein kinase C alpha (PRKCA) substrate candidate, that potentially shape this pain-relieving phenotype. We also confirmed PICK1 expression and peptide target engagement in mice and human donor tissue, supporting the potential of AAV-based PICK1 inhibitors as a clinically meaningful strategy for neuropathic pain conditions.
Project description:Comparison of L5 DRG gene expression profiles at day 14 from SNT treated animals vs. sham controls. This experiment is part of larger study, where the expression profiles of three disparate models of neuropathic pain (SNT, VZV infection and gp120+ddC) are compared in order to find genes that are responsible for mechanical hypersensitivity
Project description:Spinal microglia play a pivotal role in the development of neuropathic pain. Peripheral nerve injury induces changes in the transcriptional profile of microglia, including increased expression of components of translational machinery. Whether microglial protein synthesis is stimulated following nerve injury and has a functional role in mediating pain hypersensitivity is unknown. Here, we show that nascent protein synthesis is upregulated in spinal microglia following peripheral nerve injury. Stimulating mRNA translation in microglia, via selective ablation of the translational repressor, eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), promoted the transition of microglia to a reactive state and induced mechanical hypersensitivity. Conversely, inhibiting microglial translation by expressing mutant 4E-BP1 in microglia attenuated their peripheral nerve injury-induced activation and alleviated neuropathic pain. Thus, the stimulation of 4E-BP1-dependent translation promotes microglia reactivity and mechanical hypersensitivity, whereas its inhibition alleviates neuropathic pain.