Biology subjects

Dussor, G.

Publications and source records attributed to Dussor, G..

32 records · Page 2Linked to original sources

bioRxiv2021

A female-specific role for Calcitonin Gene-Related Peptide (CGRP) in rodent pain models

We aimed to investigate a potentially sexually dimorphic role of Calcitonin Gene-Related Peptide (CGRP) in mouse and rat models of pain. Based on findings in migraine where CGRP has a preferential pain-promoting effect in female rodents, we hypothesized that CGRP antagonists and antibodies would attenuate pain sensitization more efficaciously in female than male mice and rats. In hyperalgesic priming induced by activation of interleukin 6 (IL-6) signaling, CGRP receptor antagonists, olcegepant and CGRP8-37, both given intrathecally, blocked and reversed hyperalgesic priming only in females. A monoclonal antibody against CGRP, given systemically, blocked priming specifically in female rodents but failed to reverse it. In the spared nerve injury (SNI) model, there was a transient effect of both CGRP antagonists, given intrathecally, on mechanical hypersensitivity in female mice only. Consistent with these findings, intrathecally applied CGRP caused a long-lasting, dose-dependent mechanical hypersensitivity in female mice but more transient effects in males. This CGRP-induced mechanical hypersensitivity was reversed by the KCC2 activator, CLP257 suggesting a role for anionic plasticity in the dorsal horn in the pain-promoting effects of CGRP in females. In spinal dorsal horn slices, CGRP shifted GABAA reversal potentials to significantly more positive values but, again, only in female mice. Therefore, CGRP may regulate KCC2 expression and/or activity specifically in females. However, KCC2 hypofunction promotes mechanical pain hypersensitivity in both sexes because CLP257 alleviated hyperalgesic priming in male and female mice. We conclude that CGRP promotes pain plasticity in female mice, but has a limited impact in male mice. Significance StatementThe majority of patients impacted by chronic pain are women. Mechanistic studies in rodents are creating a clear picture that molecular events promoting chronic pain are different in male and female animals. Far more is known about chronic pain mechanisms in male animals. We sought to build on recent evidence showing that CGRP is a more potent and efficacious promoter of headache pain in female than in male rodents. To test this, we used hyperalgesic priming and the spared nerve injury (SNI) neuropathic pain models in mice. Our findings show a clear sex dimorphism wherein CGRP promotes pain in female but not male mice. Our work suggests that CGRP antagonists could be tested for efficacy in women for a broader variety of pain conditions.

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bioRxiv2021

Spatial transcriptomics reveals unique molecular fingerprints of human nociceptors

Nociceptors are specialized sensory neurons that detect damaging or potentially damaging stimuli and are found in the dorsal root (DRG) and trigeminal ganglia. These neurons are critical for the generation of neuronal signals that ultimately create the perception of pain. These neurons are also primary targets for acute and chronic pain therapeutics. Single-cell transcriptomics on mouse nociceptors has transformed our understanding of pain mechanisms. We sought to generate equivalent information for human nociceptors with the goal of identifying transcriptomic signatures of nociceptors, identifying species differences and elucidating new drug targets. We used spatial transcriptomics to molecularly characterize transcriptomes of single dorsal root ganglion (DRG) neurons from 8 organ donors. We identified 12 clusters of human sensory neurons, 5 of which are C nociceptors; as well as 1 A{beta} nociceptor, 2 A{delta}, 2 A{beta} and 1 proprioceptor subtypes. By focusing on expression profiles for ion channels, G-protein coupled receptors (GPCRs) and other pharmacological targets, we provide a rich map of drug targets in the human DRG with direct comparison to mouse sensory neuron transcriptomes. We also compare human DRG neuronal subtypes to non-human primates showing conserved patterns of gene expression among many cell types, but divergence among specific nociceptor subsets. Finally, we identify sex differences in human DRG subpopulation transcriptomes, including a marked increase in CALCA expression in female pruritogen receptor enriched nociceptors. Our data open the door to development of drug discovery programs for new pain targets and unparalleled molecular characterization of clinical sensory disorders. One Sentence SummaryWe used spatial transcriptomics to molecularly characterize human sensory neurons, comparing them to mouse and non-human primate finding similarities but also divergence, in particular among drug targets.

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bioRxiv2021

Diversity of receptor expression in central and peripheral mouse neurons estimated from single cell RNA sequencing

Because somatosensory PNS neurons, in particular nociceptors, are specially tuned to be able to detect a wide variety of both exogenous and endogenous signals, it is widely assumed that these neurons express a greater variety of receptor genes. Because cells detect such signals via cell surface receptors, we sought to formally test the hypothesis that PNS neurons might express a broader array of cell surface receptors than CNS neurons using existing single cell RNA sequencing resources from mouse. We focused our analysis on ion channels, G-protein coupled receptors (GPCRS), receptor tyrosine kinase and cytokine family receptors. In partial support of our hypothesis, we found that mouse PNS somatosensory, sympathetic and enteric neurons and CNS neurons have similar receptor expression diversity in families of receptors examined, with the exception of GPCRs and cytokine receptors which showed greater diversity in the PNS. Surprisingly, these differences were mostly driven by enteric and sympathetic neurons, not by somatosensory neurons or nociceptors. Secondary analysis revealed many receptors that are very specifically expressed in subsets of PNS neurons, including some that are unique among neurons for nociceptors. Finally, we sought to examine specific ligand-receptor interactions between T cells and PNS and CNS neurons. Again, we noted that most interactions between these cells are shared by CNS and PNS neurons despite the fact that T cells only enter the CNS under rare circumstances. Our findings demonstrate that both PNS and CNS neurons express an astonishing array of cell surface receptors and suggest that most neurons are tuned to receive signals from other cells types, in particular immune cells.

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bioRxiv2020

Sex differences in nociceptor translatomes contribute to divergent prostaglandin signaling in male and female mice

BackgroundThere are clinically relevant sex differences in acute and chronic pain mechanisms, but we are only beginning to understand their mechanistic basis. Transcriptome analyses of rodent whole dorsal root ganglion (DRG) have revealed sex differences, mostly in immune cells. We examined the transcriptome and translatome of the mouse DRG with the goal of identifying sex differences. MethodsWe used Translating Ribosome Affinity Purification (TRAP) sequencing and behavioral pharmacology to test the hypothesis that nociceptor (Nav1.8 expressing neurons) translatomes would differ by sex. ResultsWe found 66 genes whose mRNA were sex-differentially bound to nociceptor ribosomes. Many of these genes have known neuronal functions but have not been explored in sex differences in pain. We focused on Ptgds, which was increased in female mice. The mRNA encodes the prostaglandin D2 (PGD2) synthesizing enzyme. We observed increased Ptgds protein and PGD2 in female mouse DRG. The Ptgds inhibitor AT-56 caused intense pain behaviors in male mice but was only effective at high doses in females. Conversely, female mice responded more robustly to another major prostaglandin, PGE2, than did male mice. Ptgds protein expression was also higher in female cortical neurons, suggesting DRG findings may be generalizable to other nervous system structures. ConclusionsNociceptor TRAP sequencing (TRAP-seq) reveals unexpected sex differences in one of the oldest known nociceptive signaling molecule families, the prostaglandins. Our results demonstrate that translatome analysis reveals physiologically relevant sex differences important for fundamental protective behaviors driven by nociceptors.

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bioRxiv2020

Transient receptor potential canonical 5 (TRPC5) mediates inflammatory mechanical pain

Persistent tactile pain is a poorly managed symptom of inflammatory and neuropathic injury. To develop therapies for this maladaptive sensation, the underlying molecular mediators must be identified. Using knockout mice and pharmacological inhibitors, we identified transient receptor canonical 5 (TRPC5) as a key contributor to the persistent tactile pain that occurs in many inflammatory and neuropathic preclinical rodent models. TRPC5 inhibition was effective in injuries associated with elevated levels of the bioactive phospholipid lysophosphatidylcholine (LPC). Exogenous application of LPC induced TRPC5-dependent behavioral mechanical allodynia, neuronal mechanical hypersensitivity, and spontaneous pain. In vitro, LPC activated both homomeric mouse and human TRPC5 channels, which upon examination of human dorsal root ganglia tissue, were expressed in 75% of human sensory neurons. Based on these results, TRPC5 inhibitors should be pursued as personalized therapy for spontaneous and tactile pain in conditions where elevated LPC is a biomarker.

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bioRxiv2020

Neuroendocrine mechanisms governing sex-differences in chronic pain involve prolactin receptor sensory neuron signaling

Many clinical and preclinical studies report higher prevalence and severity of chronic pain in females. We used hyperalgesic priming with interleukin 6 (IL-6) priming and PGE2 as a second stimulus as a model for pain chronicity. Intraplantar IL-6 induced hypersensitivity was similar in magnitude and duration in both males and females, while both paw and intrathecal PGE2 hypersensitivity was more persistent in females. This difference in PGE2 response was dependent on both circulating estrogen and translation regulation signaling in the spinal cord. In males, the duration of hypersensitivity was regulated by testosterone. Since the prolactin receptor (Prlr) is regulated by reproductive hormones and is female-selectively activated in sensory neurons, we evaluated whether Prlr signaling contributes to hyperalgesic priming. Using {Delta}PRL, a competitive Prlr antagonist, and a mouse line with ablated Prlr in the Nav1.8 sensory neuronal population, we show that Prlr in sensory neurons is necessary for the development of hyperalgesic priming in female but not male mice. Overall, sex-specific mechanisms in the initiation and maintenance of chronic pain are regulated by the neuroendocrine system and, specifically, sensory neuronal Prlr signaling. Significance StatementFemales are more likely to experience chronic pain than males, but the mechanisms that underlie this sex difference are not completely understood. Here, we demonstrate that the duration of mechanical hypersensitivity is dependent on circulating sex hormones in mice - where estrogen caused an extension of sensitivity and testosterone was responsible for a decrease in the duration of the hyperalgesic priming model of chronic pain. Additionally, we demonstrated that Prolactin receptor expression in Nav1.8+ neurons was necessary for hyperalgesic priming in female, but not male mice. Our work demonstrates a female-specific mechanism for the promotion of chronic pain involving the neuroendrocrine system and mediated by sensory neuronal prolactin receptor.

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bioRxiv2020

A pharmacological interactome platform for discovery of pain mechanisms and targets

Cells communicate with each other through ligand and receptor interactions. In the case of the peripheral nervous system, these ligand-receptor interactions shape sensory experience. In disease states, such as chronic pain, these ligand-receptor interactions can change the excitability of target neurons augmenting nociceptive input to the CNS. While the importance of these cell to neuron interactions are widely acknowledged, they have not been thoroughly characterized. We sought to address this by cataloging how peripheral cell types interact with sensory neurons in the dorsal root ganglion (DRG) using RNA sequencing datasets. Using single cell sequencing datasets from mouse we created a comprehensive interactome map for how mammalian sensory neurons interact with 42 peripheral cell types. We used this knowledge base to understand how specific cell types and sensory neurons interact in disease states. In mouse datasets, we created an interactome of colonic enteric glial cells in the naive and inflamed state with sensory neurons that specifically innervate this tissue. In human datasets, we created interactomes of knee joint macrophages from rheumatoid arthritis patients and pancreatic cancer samples with human DRG. Collectively, these interactomes highlight ligand-receptor interactions in mouse models and human disease states that reflect the complexity of cell to neuron signaling in chronic pain states. These interactomes also highlight therapeutic targets, such as the epidermal growth factor receptor (EGFR), which was a common interaction point emerging from our studies.

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bioRxiv2020

The cellular basis of protease activated receptor type 2 (PAR2) evoked mechanical and affective pain

Protease-activated receptor type-2 (PAR2) has long been implicated in inflammatory and visceral pain, but the cellular basis of PAR2-evoked pain has not been delineated. While many studies have attributed PAR2-evoked pain to sensory neuron expression, RNA-sequencing experiments are ambiguous on detection of F2rl1 mRNA. Moreover, many pharmacological tools for PAR2 have been shown to be non-specific as they also act on the Mas-related (Mrg) family of g-protein coupled receptors (GPCRs) that are highly enriched in sensory neurons. We sought to bring clarity to the cellular basis of PAR2 pain. We developed a PAR2 conditional mutant mouse by loxp targeting of exon 2 of the F2rl1 gene and specifically deleted PAR2 in all sensory neurons using the PirtCre mouse line. Our behavioral findings show that PAR2 agonist-evoked mechanical hyperalgesia and facial grimacing, but not thermal hyperalgesia, is completely dependent on PAR2 expression in sensory neurons that project to the hindpaw in male and female mice. F2rl1 mRNA is expressed in a discrete population (~4%) of sensory neurons that also express the Nppb and IL31ra genes. This cell population has previously been implicated in itch, but our work shows that PAR2 activation in these cells causes clear pain-related behaviors from the skin. Our findings clarify the mechanism through which proteases, like tryptase and elastase, cause pain via PAR2 activation in a small subset of nociceptors.

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bioRxiv2019

Type I interferons act directly on nociceptors to produce pain sensitization: Implications for viral infection-induced pain

One of the first signs of viral infection is body-wide aches and pain. While this type of pain usually subsides, at the extreme, viral infections can induce painful neuropathies that can last for decades. Neither of these types of pain sensitization are well understood. A key part of the response to viral infection is production of interferons (IFNs), which then activate their specific receptors (IFNRs) resulting in downstream activation of cellular signaling and a variety of physiological responses. We sought to understand how type I IFNs (IFN- and IFN-{beta}) might act directly on nociceptors in the dorsal root ganglion (DRG) to cause pain sensitization. We demonstrate that type I IFNRs are expressed in small/medium DRG neurons and that their activation produces neuronal hyper-excitability and mechanical pain in mice. Type I IFNs stimulate JAK/STAT signaling in DRG neurons but this does not apparently result in PKR-eIF2 activation that normally induces an anti-viral response by limiting mRNA translation. Rather, type I interferons stimulate MNK-mediated eIF4E phosphorylation in DRG neurons to promote pain hypersensitivity. Endogenous release of type I IFNs with the double stranded RNA mimetic poly(I:C) likewise produces pain hypersensitivity that is blunted in mice lacking MNK-eIF4E signaling. Our findings reveal mechanisms through which type I IFNs cause nociceptor sensitization with implications for understanding how viral infections promote pain and can lead to neuropathies. SIGNIFICANCE STATEMENTIt is increasingly understood that pathogens interact with nociceptors to alert organisms to infection as well as to mount early host defenses. While specific mechanisms have been discovered for diverse bacteria and fungal pathogens, mechanisms engaged by viruses have remained elusive. Here we show that type 1 interferons, one of the first mediators produced by viral infection, act directly on nociceptors to produce pain sensitization. Type I interferons act via a specific signaling pathway (MNK-eIF4E signaling) that is known to produce nociceptor sensitization in inflammatory and neuropathic pain conditions. Our work reveals a mechanism through which viral infections cause heightened pain sensitivity

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bioRxiv2019

Transcriptomic analysis of native versus cultured human and mouse dorsal root ganglia focused on pharmacological targets

Dorsal root ganglion (DRG) neurons detect sensory inputs and are crucial for pain processing. They are often studied in vitro as dissociated cell cultures with the assumption that this reasonably represents in vivo conditions. However, to our knowledge, no study has ever directly compared genome-wide transcriptomes of DRG tissue in vivo versus in vitro, or between different labs and culturing protocols. We extracted bilateral lumbar DRG from C57BL6/J mice and human organ donors, and acutely froze one side and processed the other side as a dissociated cell culture, which was then maintained in vitro for 4 days. RNA was extracted and sequenced using the NextSeq Illumina platform. Comparing native to cultured human or mouse DRG, we found that the overall expression level of many ion channels and GPCRs specifically expressed in neurons is markedly lower in culture, but still expressed. This suggests that most pharmacological targets expressed in vivo are present in culture conditions. However, there are changes in expression levels for these genes. The reduced relative expression for neuronal genes in human DRG cultures is likely accounted for by increased expression of genes in fibroblast-like and other proliferating cells, consistent with the mitotic status of many cells in these cultures. We did find a subset of genes that are typically neuronally expressed, increased in human and mouse DRG cultures, including genes associated with nerve injury and/or inflammation in preclinical models such as BDNF, MMP9, GAL, and ATF3. We also found a striking upregulation of a number of inflammation-associated genes in DRG cultures, although many were different between mouse and human. Our findings suggest an injury-like phenotype in DRG cultures that has important implications for the use of this model system for pain drug discovery.

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bioRxiv2018

Transcriptome analysis of the human tibial nerve identifies sexually dimorphic expression of genes involved in pain, inflammation and neuro-immunity

Sex differences in gene expression are important contributors to normal physiology and mechanisms of disease. This is increasingly apparent in understanding and potentially treating chronic pain where molecular mechanisms driving sex differences in neuronal plasticity are giving new insight into why certain chronic pain disorders preferentially affect women versus men. Large transcriptomic resources are increasingly available and can be used to mine for sex differences and molecular insight using donor cohorts. We analyzed more than 250 human tibial nerve (hTN) transcriptomes from the GTex Consortium project to gain insight into sex-dependent gene expression in the peripheral nervous system (PNS). We discover 149 genes with sex differential expression. Many of the genes upregulated in men are associated with inflammation, and appear to be primarily expressed by glia or immune cells. In women, we find the differentially upregulated transcription factor SP4 that drives a regulatory program, and may impact sex differences in PNS physiology. Many of these 149 DE genes have some previous association with chronic pain but few of them have been explored thoroughly. Additionally, using clinical data in the GTex database, we identify a subset of differentially expressed (DE) genes in diseases associated with chronic pain, arthritis and type II diabetes. Our work identifies sexually dimorphic gene expression in the human PNS with implications for discovery of sex-specific pain mechanisms.

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bioRxiv2018

Nociceptor translational profiling reveals the RagA-mTORC1 network as a critical generator of neuropathic pain

Pain sensing neurons, nociceptors, are key drivers of neuropathic pain. We used translating ribosome affinity purification (TRAP) to comprehensively characterize up-and down-regulated mRNA translation in Scn10a-positive nociceptors in chemotherapy-induced neuropathic pain. We provide evidence that an underlying mechanism driving these changes in gene expression is a sustained mTORC1 activation driven by MNK1-eIF4E signaling. RagA, a GTPase controlling mTORC1 activity, is identified as a novel target of MNK1-eIF4E signaling, demonstrating a new link between these distinct signaling pathways. Neuropathic pain and RagA translation are strongly attenuated by genetic ablation of eIF4E phosphorylation, MNK1 elimination or treatment with the MNK inhibitor eFT508. We reveal a novel translational circuit for the genesis of neuropathic pain with important implications for next generation neuropathic pain therapeutics.\n\nOne Sentence SummaryCell-specific sequencing of translating mRNAs elucidates signaling pathology that can be targeted to reverse neuropathic pain

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bioRxiv2017

Comparative transcriptome profiling of the human and mouse dorsal root ganglia: An RNA-seq-based resource for pain and sensory neuroscience research

Molecular neurobiological insight into human nervous tissues is needed to generate next generation therapeutics for neurological disorders like chronic pain. We obtained human Dorsal Root Ganglia (DRG) samples from organ donors and performed RNA-sequencing (RNA-seq) to study the human DRG (hDRG) transcriptional landscape, systematically comparing it with publicly available data from a variety of human and orthologous mouse tissues, including mouse DRG (mDRG). We characterized the hDRG transcriptional profile in terms of tissue-restricted gene co-expression patterns and putative transcriptional regulators, and formulated an information-theoretic framework to quantify DRG enrichment. Our analyses reveal an hDRG-enriched protein-coding gene set (~140), some of which have not been described in the context of DRG or pain signaling. A majority of these show conserved enrichment in mDRG, and were mined for known drug - gene product interactions. Comparison of hDRG and tibial nerve transcriptomes suggest pervasive mRNA transport of sensory neuronal genes to axons in adult hDRG, with potential implications for mechanistic insight into chronic pain in patients. Relevant gene families and pathways were also analyzed, including transcription factors (TFs), g-protein coupled receptors (GCPRs) and ion channels. We present our work as an online, searchable repository (http://www.utdallas.edu/bbs/painneurosciencelab/DRGtranscriptome), creating a valuable resource for the community. Our analyses provide insight into DRG biology for guiding development of novel therapeutics, and a blueprint for cross-species transcriptomic analyses.\n\nSummaryWe generated RNA sequencing data from human DRG samples and comprehensively compared this transcriptome to other human tissues and a matching panel of mouse tissues. Our analysis uncovered functionally enriched genes in the human and mouse DRG with important implications for understanding sensory biology and pain drug discovery.

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bioRxiv2017

Macrophage-to-sensory neuron crosstalk mediated by Angiotensin II type-2 receptor elicits neuropathic pain

Peripheral nerve damage initiates a complex series of cellular and structural processes that culminate in chronic neuropathic pain. Our study defines local angiotensin signaling via activation of the Angiotensin II (Ang II) type-2 receptor (AT2R) on macrophages as the critical trigger of neuropathic pain. An AT2R-selective antagonist attenuates neuropathic, but not inflammatory pain hypersensitivity in mice, and requires the cell damage-sensing ion channel transient receptor potential family-A member-1 (TRPA1). Mechanical and cold pain hypersensitivity that are characteristic of neuropathic conditions can be attenuated by chemogenetic depletion of peripheral macrophages and AT2R-null hematopoietic cell transplantation. Our findings show no AT2R expression in mouse or human sensory neurons, rather AT2R expression and activation in macrophages triggers production of reactive oxygen/nitrogen species, which trans-activate TRPA1 on sensory neurons. Our study defines the precise neuro-immune crosstalk underlying nociceptor sensitization at the site of nerve injury. This form of cell-to-cell signaling represents a critical peripheral mechanism for chronic neuropathic pain, and therefore identifies multiple analgesic targets.

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