Early life stress modulates neonatal somatosensation and the transcriptional profile of immature sensory neurons
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ABSTRACT: Early life stress (ELS) is associated with an increased risk of experiencing chronic pain during adulthood, but surprisingly little is known about the short-term influence of ELS on nociceptive processing in the immature nervous system and the concomitant effects on somatosensation in the neonate. Here we investigate how ELS modulates pain in neonatal mice as well as the transcriptional and electrophysiological signatures of immature dorsal root ganglia (DRG). Shortly after the administration of a neonatal limiting bedding (NLB) paradigm from postnatal days (P)2 to P9, both male and female pups exhibited robust hyperalgesia in response to mechanical, pressure and noxious cold stimuli compared to a control group housed under standard conditions, with no change in their sensitivity to noxious heat. Bulk RNA-seq analysis of L3-L5 DRGs at P9 revealed significant alterations in the transcription of pain- and itch-related genes following ELS, highlighted by a marked downregulation in Sst, Nppb, Chrna6, Trpa1 and Il31ra. Nonetheless, ex vivo whole cell patch-clamp recordings from putative A- and C-fiber sensory neurons in the neonatal DRG found no significant changes in their intrinsic membrane excitability following NLB. Overall, these findings suggest that ELS triggers hyperalgesia in neonates across multiple pain modalities that is accompanied by transcriptional plasticity within developing sensory neurons. A better understanding of the mechanisms governing the interactions between chronic stress and pain during the neonatal period could inform the future development of novel interventional strategies to relieve pain in infants and children who have experienced trauma.
Project description:Sensory neuron mechanically-activated slowly adapting currents have been linked to noxious mechanosensation. We identified a Conotoxin, Noxious Mechanosensation Blocker -1, that blocks such currents selectively. Using an active biotinylated form of the toxin we identified 67 binding proteins in sensory neurons and sensory neuron-derived cell lines using mass spectrometry. Annexin A6 was the most frequently identified binding protein. Annexin A6 knockout mice showed an enhanced sensitivity to mechanical stimuli. Rapidly adapting currents were enhanced and slowly adapting channels diminished. The percentage of neurons expressing slowly adapting currents fell and non-responsive neurons increased. Conversely, overexpression of annexin A6 in DRG neurons inhibited rapidly adapting currents without effects on slowly adapting currents. Co-expression of annexin A6 with Piezo 2 led to an inhibition of Piezo-mediated rapidly adapting currents. AAV-mediated gene delivery of annexin A6 to sensory neurons in a mouse model of osteoarthritis attenuated mechanical pain. These data demonstrate a role for annexin A6 in somatosensory mechanotransduction.
Project description:The dorsal root ganglion (DRG) neurons take in charge of primary detection and transmission of peripheral pain and itch stimuli, however, as two distinct noxious sensation, it is still attractive for this field that how the DRG neurons differentially response and code pain and itch. Here, we investigate the response and activation spectrum of DRG neurons under peripheral pain and itch stimuli using in vivo two-photon calcium imaging, and find differences in the responsive intensity to pain and itch between multisensory neurons (both pain and itch) and single-sensory neurons (either pain or itch). Besides, single-cell RNA sequencing (scRNA-seq) is used to reveal the heterogeneity of distinct subpopulations based on their expression of pain- or itch-related marker genes and indicates the similarity and difference of their transcriptomic changes under chronic pain and itch. Our results will provide fundamental insights to the peripheral pain and itch differential coding mechanism, moreover, benefit the development of pain and itch therapies.
Project description:Inflammation plays a role in neuropathic pain conditions as well as in pain induced solely by an inflammatory stimulus. Robust mechanical hyperalgesia and allodynia can be induced by locally inflaming the L5 dorsal root ganglion (DRG) in rat. This model allows investigation of the contribution of inflammation per se to chronic pain conditions. Most previous microarray studies of DRG gene expression have investigated neuropathic pain models involving axon transection. To examine the role of inflammation, we used microarray methods to examine gene expression 3 days after local inflammation of the L5 DRG in rat. We observed significant regulation in a large number of genes (23% of observed transcripts), and examined 221 (3%) with a fold-change of 1.5-fold or more in more detail. Immune-related genes were the largest category in this group and included members of the complement system as well as several pro-inflammatory cytokines. However, these upregulated cytokines had no prior links to peripheral pain in the literature other than through microarray studies, though most had previously described roles in CNS (especially neuroinflammatory conditions) as well as in immune responses. The L5 dorsal root ganglion (DRG) was locally inflamed with zymosan/Incomplete Freund's Adjuvant. DRG were isolated 3 days later. Each sample was RNA extracted from a single DRG. 6 samples from rats with local DRG inflammation were compared with 6 samples from sham-operated rats.
Project description:Diabetic peripheral neuropathy (DPN) is characterized by spontaneous pain in the extremities. Incidence of DPN continues to rise with the global diabetes epidemic. However, there remains a lack of safe, effective analgesics to control this chronic painful condition. Dorsal root ganglia (DRG) contain soma of sensory neurons and modulate sensory signal transduction into the central nervous system. In this study, we aimed to gain a deeper understanding of changes in molecular pathways in the DRG of DPN patients with chronic pain. We recently reported transcriptomic changes in the DRG with DPN. Here, we expand upon those results with integrated metabolomic, proteomic, and phosphoproteomic analyses to compare the molecular profiles of DRG from DPN
donors and DRG from control donors without diabetes or chronic pain. Our analyses identified decreases of select amino acids and phospholipid metabolites in the DRG from DPN donors, which are important for cellular maintenance. Additionally, our analyses revealed changes suggestive of extracellular matrix (ECM) remodeling and altered mRNA processing. These results reveal new insights into changes in the molecular profiles associated with DPN.
Project description:Early-life stress (ELS) leads to increased vulnerability to psychiatric illness including cognitive impairment later in life. Neuroinflammatory processes have been implicated in ELS-induced negative health outcomes, but, how ELS impacts microglia, the macrophages of the central nervous system, is unknown. Here, we determined the effects of ELS induced by limited bedding and nesting material during the first week of life (P2 – P9) on the morphology and gene expression of microglia from young (postnatal day (P)9) and adult (P200) mice. ELS led to a change in the proportion of morphological microglia subtypes in adulthood, associated with immune reactivity. At the transcriptional level, whereas at P9 no ELS mediated changes were detected, at P200 ELS induced transcriptional changes in microglia genes involved in the immune response and protein ubiquitination. Additionally, ELS altered microglia gene expression changes during development from P9 to P200 and in response to LPS at P200, in both cases marked by GO-terms associated with the immune response. Concluding, these data show that ELS has persistent effects on the morphology and gene expression program of microglia and results in an altered transcriptional response to a systemic LPS challenge.
Project description:Somatosensory neurons with cell bodies in the dorsal root ganglia (DRG) project to the skin, muscles, bones, and viscera to detect touch and temperature as well as to mediate proprioception and many types of interoception. In addition, the somatosensory system conveys the clinically relevant noxious sensations of pain and itch. Here we used single nuclear transcriptomics to characterize the classes of human DRG neurons that detect these diverse types of stimuli. Notably, multiple types of human DRG neurons have transcriptomic features that resemble their mouse counterparts although expression of genes considered important for sensory function often differed between species. More unexpectedly, we demonstrated that several classes of mouse neurons have no direct equivalents in humans and human specific cell-types were also identified. This dataset should serve as a valuable resource for the community, for example as means of focusing translational efforts on molecules with conserved expression across species.
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:Nociceptors are a type of sensory neurons that is integral to most forms of pain. Targeted disruption of nociceptor sensitization affords unique opportunities to prevent pain. An emerging model for nociceptors are sensory neurons derived from human stem cells. Here, we subjected five groups to high-throughput sequencing: human induced pluripotent stem cells (hiPSCs) prior to differentiation, mature hiPSC-derived sensory neurons, mature co-cultures containing hiPSC-derived astrocytes and sensory neurons, mouse DRG tissues, and mouse DRG cultures. Co-culture of nociceptors and astrocytes promotes expression of transcripts enriched in DRG tissues. Comparisons of the hiPSC models to tissue samples reveals that many key genes linked to pain are present. Marker genes indicative of a range of neuronal subtypes present in the DRG were detected in mature hiPSCs. Intriguingly, translation factors were maintained at consistently high expression levels across species and culture systems. As a proof of concept for the utility of this resource, we validated expression of eukaryotic initiation factor 5A (eIF5A) in DRG tissues and hiPSC samples. eIF5A is subject to a unique post-translational hypusine modification required for its activity. Inhibition of hypusine biosynthesis prevented hyperalgesic priming by inflammatory mediators in vivo. One of two hypusine inhibitors diminished hiPSC activity in vitro. Collectively, our results illuminate the transcriptomes of hiPSC sensory neuron models. We provide a proof of concept for this resource through our investigation of eIF5A. Our findings reveal hypusine as a potential target for inflammation associated pain in males.
Project description:A novel missense mutation has been identified in a human pain-insensitive family in the gene ZFHX2. We modelled this mutation in mice by changing the orthologous amino acid and carried out pain behaviour tests in mutant BAC transgenic mice. These showed a phenotype of hyposensitivity to noxious thermal stimuli. ZFHX2 has enriched expression in dorsal root ganglia neurons, and so we carried out microarray analyses in mutant vs wild type controls from lumbar DRG to see which genes were deregulated by the mutant ZFHX2 protein. To understand which genes are differentially expressed in lumbar DRG (L1-6) between Zfhx2 p.R1907K BAC transgenic mice (n=5, genomic BAC copy number of 4) and wild-type controls (n=7). Complementary ChIP-seq data for this study have also been deposited at ArrayExpress under accession number E-MTAB-5651 ( https://www.ebi.ac.uk/arrayexpress/experiments/E-MTAB-5651 ).
Project description:Purpose: Nerve injury-induced hyperactivity of primary sensory neurons in the dorsal root ganglion (DRG) contributes critically to chronic pain development, but its underlying mechanisms remain incompletely understood. Chronic neuropathic pain has a clear epigenetic component, however, most studies so far have focused on histone modifications. We determined changes of DNA methylation in the rat DRG, spinal cord, and prefrontal cortex after spinal nerve ligation (SNL).