Biology subjects

Burton, M. D.

Publications and source records attributed to Burton, M. D..

13 recordsLinked to original sources

bioRxiv2026

Nociceptor-restricted cannabinoid receptor 1 contributes to chronic but not acute analgesia

Understanding the complex network that regulates pain is fundamental to develop strategies to combat its growing prevalence and increase useful therapeutics. Although extensive literature identifies the importance of cannabinoid receptors and endocannabinoids in controlling pain, their efficacy and loci of action remain debated. To directly test the actions of peripherally restricted cannabinoids and elucidate the minimal circuitry capable of producing cannabinoid-mediated analgesia, we utilized a novel genetic approach that allows for cell-specific reactivation of cannabinoid receptor 1 (CB1R) selectively in peripheral sensory neurons using newly developed CB1R floxed-stop-floxed mice (CB1RLOXTB) crossed with Nav1.8-cre mice (Nav1.8+/-:CB1RLOXTB). Ex vivo and in vivo experiments confirmed successful knockout and reactivation of CB1R. Wildtype littermate controls, but neither Nav1.8+/-:CB1RLOXTB nor CB1RLOXTB animals, exhibited robust analgesia after systemic WIN55,212-2 (WIN) treatment in the tail flick assay. Furthermore, the presence of CB1R on Nav1.8 neurons was not associated with either a difference in the development of inflammatory pain or the response to WIN. However, after neuropathic injury, CB1RLOXTB animals displayed an earlier onset of both mechanical and thermal hypersensitivity than their Nav1.8+/-:CB1RLOXTB or wildtype counterparts, suggesting a dual role for CB1R in inflammatory and neuropathic pain. These studies represent an important approach to further improve our mechanistic understanding of cannabinoid modulation of pain in the nervous system and begins to settle long-standing controversies in cannabinoid literature. Table of ContentsPeripherally restricted cannabinoids show strong preclinical analgesic efficacy but have not translated clinically. Using a genetic model restricting CB1R to Nav1.8-expressing sensory neurons, we show peripheral neuronal endocannabinoid signaling is required for chronic, but not acute pain modulation. This dissociation suggests clinical failures may reflect testing peripheral cannabinoids in acute rather than chronic pain paradigms, informing future translational strategies.

neuroscience↗

bioRxiv2026

Impact of Neurons on Group B Streptococcus Interactions at the Blood Brain Barrier

Streptococcus agalactiae (Group B Streptococcus, GBS) is a Gram-positive opportunistic pathogen and the leading cause of neonatal bacterial meningitis, a life-threatening infection of the central nervous system (CNS) that occurs when bacteria cross the blood-brain barrier (BBB). GBS commonly colonizes the maternal genital tract and is a major cause of invasive neonatal disease, including bacteremia and meningitis. Despite treatment advances, GBS meningitis remains associated with substantial mortality and long-term neurological sequelae. The BBB is a highly specialized barrier formed by brain endothelial cells (BECs) that restrict microbial entry into the CNS through tightly regulated intercellular junctions. The BBB exists within the neurovascular unit, where neurons and other CNS cell types actively regulate endothelial barrier properties through intercellular signaling. However, the contribution of neuronal-endothelial interactions to BBB function during neonatal meningitis remains poorly understood. To investigate the mechanisms by which GBS disrupts and penetrates the BBB, we utilized induced pluripotent stem cell (iPSC)-derived brain-like endothelial cells. EZ-Sphere-derived neurons generated from the same iPSC source were incorporated into an isogenic BBB model to determine whether neuronal-endothelial communication influences GBS interaction with BECs. Neuronal co-culture significantly reduced GBS adherence to and invasion of BECs while preserving tight junction integrity during infection. Application of neuron-conditioned medium similarly decreased bacterial adherence and invasion, suggesting that neuron-derived soluble factors enhance barrier integrity during GBS infection. Together, these findings demonstrate that neuronal signaling enhances BBB resistance to GBS and highlight a previously underappreciated role for neurovascular crosstalk in limiting bacterial pathogenesis. ImportanceGroup B Streptococcus (GBS) is the leading cause of bacterial meningitis in newborns. GBS interacts with and crosses the blood-brain barrier (BBB) contributing to a potentially fatal infection without treatment. Understanding how the BBB interacts with bacterial pathogens is critical for developing new strategies to protect vulnerable infants. In this study, we used human stem cell-derived models to recapitulate the BBB and examine how communication between brain endothelial cells and neurons influence host response to bacterial infection. These findings identify neuronal-endothelial communication as a potential contributor to BBB protection and provide a foundation for future studies aimed at preventing GBS invasion of the central nervous system.

microbiology↗

bioRxiv2025

Life-long hydroxyurea treatment decreases chronic sickle cell disease pain

Chronic sickle cell disease (SCD) pain mechanisms remain critically understudied, even though more than 50% of patients develop this symptom as their disease progresses. Despite high face validity, there are critical gaps in transgenic SCD mouse model characterization and implementation that must be addressed in order to increase the translational relevance of these animals. First, it is unclear when the chronic pain phenotype first develops in these mice. Second, there are no studies that have measured chronic pain in animals following standard-of-care drug regimens. Herein, we address both of these gaps by performing reflexive pain behavior tests in hydroxyurea-treated Townes HbSS and HbAA mice from postnatal day 10 to 6 months of age. Hydroxyurea (HU), a compound that increases circulating levels of fetal hemoglobin (HbF), is a life-long therapy prescribed to individuals with SCD beginning as early as age 9 months. Here, we demonstrate that chronic mechanical hypersensitivity develops in Townes HbSS mice between P21-P28, a time frame that follows the HbF-to-HbS switch. When initiated at birth, HU treatment limits the extent of chronic mechanical pain development in HbSS mice. HU analgesic effects can be attributed to decreased innate immune tone in the periphery; life-long HU treatment decreases circulating monocyte counts in HbSS mice and reverses sensitization of TRPA1, a lipopolysaccharide receptor, in HbSS nociceptors. In conclusion, these studies provide additional support for early implementation of HU in SCD disease management, and furthermore, identify the LPS-TRPA1 signaling axis as a novel analgesic target for chronic SCD pain.

physiology↗

bioRxiv2025

TLR4+ Dermal fibroblasts induce acute and transitional pain states

The prominence of non-neuronal cells driving pain states has gained attention in recent years. Fibroblasts, a major stromal cell, perform essential functions during inflammation, tissue remodeling, and wound healing; however, recent studies suggest that fibroblasts may play a role in pain. Toll-like receptor 4 (TLR4) is an essential component of the innate immune system and activation of the receptor promotes pain. This study utilized a novel mouse model with dermal fibroblast specific expression of TLR4 on a TLR4-null background, which allows us to understand the sufficiency of skin fibroblast activation in pain development. Here we demonstrate that dermal fibroblast activation induces both acute inflammatory pain and hyperalgesic priming in both male and female mice. In vivo, activated dermal fibroblasts change cellular morphology in mice and humans. In vitro we observed pro-inflammatory cytokine production and activation of calcium signaling pathways. These data demonstrate that dermal fibroblast activation can cause acute pain and drive mechanisms involved in the transition to chronic pain.

neuroscience↗

bioRxiv2024

12/15-Lipoxygenases mediate neuropathic-like pain hypersensitivity in female mice

It is estimated that chronic neuropathic pain conditions exhibit up to 10% prevalence in the general population, with increased incidence in females. However, nonsteroidal inflammatory drugs (NSAIDs) are ineffective, and currently indicated prescription treatments such as opioids, anticonvulsants, and antidepressants provide only limited therapeutic benefit. In the current work, we extended previous studies in male rats utilizing a paradigm of central Toll-like receptor 4 (TLR4)-dependent, NSAID-unresponsive neuropathic-like pain hypersensitivity to male and female C57BL/6N mice, uncovering an unexpected hyperalgesic phenotype in female mice following intrathecal (IT) LPS. In contrast to previous reports in female C57BL/6J mice, female C57BL/6N mice displayed tactile and cold allodynia, grip force deficits, and locomotor hyperactivity in response to IT LPS. Congruent with our previous observations in male rats, systemic inhibition of 12/15-Lipoxygenases (12/15-LOX) in female B6N mice with selective inhibitors - ML355 (targeting 12-LOX-p) and ML351 (targeting 15-LOX-1) - completely reversed allodynia and grip force deficits. We demonstrate here that 12/15-LOX enzymes also are expressed in mouse spinal cord and that 12/15-LOX metabolites produce tactile allodynia when administered spinally (IT) or peripherally (intraplantar in the paw, IPLT) in a hyperalgesic priming model, similar to others observations with the cyclooxygenase (COX) metabolite Prostaglandin E2 (PGE2). Surprisingly, we did not detect hyperalgesic priming following IT administration of LPS, indicating that this phenomenon likely requires peripheral activation of nociceptors. Collectively, these data suggest that 12/15-LOX enzymes contribute to neuropathic-like pain hypersensitivity in rodents, with potential translatability as druggable targets across sexes and species using multiple reflexive and non-reflexive outcome measures.

pharmacology and toxicology↗

bioRxiv2023

Sensory neuron LKB1 mediates ovarian and reproductive function.

Treatments for reproductive disorders in women primarily consist of hormone replacement therapy, which can have negative health impacts. Bidirectional communication between sensory neurons and innervated organs is an emerging area of interest in tissue physiology with potential relevance for reproductive disorders. Indeed, the metabolic activity of sensory neurons can have profound effects on reproductive phenotypes. To investigate this phenomenon, we utilized a murine model with conditional deletion in sensory neurons of liver kinase B1 (LKB1), a serine/threonine kinase that regulates cellular metabolism. Female mice with this LKB1 deletion (Nav1.8cre;LKB1fl/fl) had significantly more pups per litter compared to wild-type females. Interestingly, the LKB1 genotype of male breeders had no effect on fertility outcomes, thus indicating a female-specific role of sensory neuron metabolism in fertility. LKB1 deletion in sensory neurons resulted in reduced ovarian innervation from dorsal root ganglia neurons and increased follicular turnover compared to littermate controls. In summary, LKB1 expression in peripheral sensory neurons plays an important role in modulating fertility of female mice via ovarian sensory innervation.

neuroscience↗

bioRxiv2022

Inducible co-stimulatory molecule (ICOS) alleviates Paclitaxel induced peripheral neuropathy via an IL-10-mediated mechanism in female mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a primary dose-limiting side effect caused by antineoplastic agents, such as paclitaxel. This causes damage to peripheral nerves and the dorsal root ganglia (DRG). Currently, there are no effective treatments for CIPN, which can lead to long-term morbidity in cancer patients and survivors. Neuro-immune interactions occur in CIPN and have been implicated both in the development and progression of the disease and disease resolution. We investigated the potential role of Inducible co-stimulatory molecule (ICOS) in the resolution of CIPN pain-like behaviors in mice. ICOS is an immune checkpoint molecule that is expressed on the surface of activated T cells and promotes proliferation and differentiation of T cells. We found that intrathecal administration of ICOS agonist antibody (ICOSaa) alleviates mechanical hypersensitivity caused by paclitaxel and facilitates the resolution of mechanical sensitivity in female mice. Administration of ICOSaa reduced astrocyte-gliosis in the spinal cord and satellite cell gliosis in the DRG of mice previously treated with paclitaxel. Mechanistically, ICOSaa intrathecal treatment promoted pain resolution by increasing interleukin 10 (IL-10) expression in the dorsal root ganglion. In line with these observations, blocking IL-10 receptor (IL-10R) activity occluded the effects of ICOSaa treatment on CIPN behavior in female mice. Suggesting a broader activity in neuropathic pain, ICOSaa also partially resolved mechanical hypersensitivity in the spared nerve injury (SNI) model. Our findings support a model wherein ICOSaa administration induces IL-10 expression to facilitate neuropathic pain relief in female mice. ICOSaa treatment is in clinical development for solid tumors and given our observation of T cells in the human DRG, ICOSaa therapy could be developed for combination chemotherapy - CIPN clinical trials. HighlightsO_LIICOS agonist antibody (ICOSaa) promotes pain resolution in female mice C_LIO_LIDRG T cells appear to enter an anti-inflammatory phenotype by ICOSaa treatment C_LIO_LIICOSaa treatment increases DRG levels of IL-10 cytokine C_LIO_LIICOSaa effects in female mice are blocked by IL-10 sequestering treatment C_LI

neuroscience↗

bioRxiv2021

RNA Profiling of Neuropathic Pain-Associated Human DRGs Reveal Sex-differences in Neuro-immune Interactions Promoting Pain

Neuropathic pain is a leading cause of high impact pain, is often disabling and is poorly managed by current therapeutics. Here we focused on a unique group of neuropathic pain patients undergoing thoracic vertebrectomy where the DRG is removed as part of the surgery allowing for molecular characterization and identification of mechanistic drivers of neuropathic pain independently of preclinical models. Our goal was to quantify whole transcriptome RNA abundances using RNA-seq in pain-associated human DRGs from these patients, allowing comprehensive identification of molecular changes in these samples by contrasting them with non-pain associated DRGs. We sequenced 70 human DRGs, including over 50 having mRNA libraries with neuronal mRNA. Our expression analysis revealed profound sex differences in differentially expressed genes including increase of IL1B, TNF, CXCL14, and OSM in male and including CCL1, CCL21, PENK and TLR3 in female DRGs associated with neuropathic pain. Co-expression modules revealed enrichment in members of JUN-FOS signaling in males, and centromere protein coding genes in females. Neuro-immune signaling pathways revealed distinct cytokine signaling pathways associated with neuropathic pain in males (OSM, LIF, SOCS1) and females (CCL1, CCL19, CCL21). We validated cellular expression profiles of a subset of these findings using RNAscope in situ hybridization. Our findings give direct support for sex differences in underlying mechanisms of neuropathic pain in patient populations.

neuroscience↗

bioRxiv2021

Translating outcomes from the clinical setting to preclinical models: chronic pain and functionality in chronic musculoskeletal pain

Fibromyalgia (FM) is a chronic pain disorder characterized by chronic widespread musculoskeletal pain (CWP), tenderness, and fatigue, which interferes with daily functioning and quality of life. In clinical studies, this symptomology is assessed, while preclinical models of CWP are limited to nociceptive assays. The aim of the study was to investigate the human-to-model translatability of clinical behavioral assessments for pain and muscle function in a preclinical model of CWP. We assessed correlations between pain behaviors and muscle function in a preclinical model of CWP and in women with fibromyalgia to examine whether similar relationships between outcomes existed in both settings, for usability of clinical assays in model systems. For preclinical measures, the acidic saline model of FM which induces widespread muscle pain, was used in adult female mice. Two gastrocnemius injections of acidic or physiological pH saline were given following baseline measures, five days apart. An array of adapted pain measures and functional assays were assessed for three weeks. For clinical measures, pain and functional assays were assessed in adult women with FM. For both preclinical and clinical outcomes, movement-evoked pain (MEP) was associated with mechanical pain sensitivity. Mechanical sensitivity was correlated to shifts in weight-bearing preclinically and was predictive of functionality in patients. Preclinically, it is imperative to expand how the field assesses pain behaviors when studying multi- symptom disorders like FM. Targeted pain assessments to match those performed clinically is an important aspect of improving preclinical to clinical translatability of animal models. SummaryPreclinical assessments of chronic musculoskeletal pain recapitulate several outcome measures for clinical assessment of patients with FM, particularly prolonged resting pain, and MEP.

neuroscience↗

bioRxiv2021

Transcriptomic Analysis of Human Sensory Neurons in Painful Diabetic Neuropathy Reveals Inflammation and Neuronal Loss

Pathological sensations caused by peripheral painful neuropathy occurring in Type 2 diabetes mellitus (T2DM) are often described as sharp and burning and are commonly spontaneous in origin. Proposed etiologies implicate dysfunction of nociceptive sensory neurons in dorsal root ganglia (DRG) induced by generation of reactive oxygen species, microvascular defects, and ongoing axonal degeneration and regeneration. To investigate the molecular mechanisms contributing to diabetic pain, DRGs were acquired postmortem from patients who had been experiencing painful diabetic peripheral neuropathy (DPN) and subjected to transcriptome analyses to identify genes contributing to pathological processes and neuropathic pain. DPN occurs in distal extremities resulting in the characteristic "glove and stocking" pattern. Accordingly, the L4 and L5 DRGs, which contain the perikarya of primary afferent neurons innervating the foot, were analyzed from five DPN patients and compared with seven controls. Transcriptom e analyses identified 844 differentially expressed genes. We observed increases in levels of inflammation-associated genes from macrophages in DPN patients that may contribute to increased pain hypersensitivity and, conversely, there were frequent decreases in neuronally-related genes. The elevated inflammatory gene profile and the accompanying downregulation of multiple neuronal genes provide new insights into intraganglionic pathology and mechanisms causing neuropathic pain in DPN patients with T2DM.

neuroscience↗

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.

neuroscience↗

bioRxiv2020

A Whole Cell Metal-Organic Framework Encapsulated Vaccine Against Septicemic UPEC Infection

The increasing rate of resistance of bacterial infection against antibiotics requires next generation approaches to fight potential pandemic spread. The development of vaccines against pathogenic bacteria has been difficult owing, in part, to the genetic diversity of bacteria. Hence, there are many potential target antigens and little a priori knowledge of which antigen/s will elicit protective immunity. The painstaking process of selecting appropriate antigens could be avoided with whole-cell bacteria; however, whole-cell formulations typically fail to produce long-term and durable immune responses. These complications are one reason why no vaccine against any type of pathogenic E. coli has been successfully clinically translated. As a proof of principle, we demonstrate a method to enhance the immunogenicity of a model pathogenic E. coli strain by forming a slow releasing depot. The E. coli strain CFT073 was biomimetically mineralized within a metal-organic framework (MOF). This process encapsulates the bacteria within 30 minutes in water and at ambient temperatures. Vaccination with this new formulation substantially enhances antibody production and results in significantly enhanced survival in a mouse model of bacteremia compared to standard inactivated formulations.

immunology↗

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.

neuroscience↗