B cells drive neuropathic pain-related behaviors in mice through IgG-Fc gamma receptor signaling.

Neuroimmune interactions are essential for the development of neuropathic pain, yet the contributions of distinct immune cell populations have not been fully unraveled. Here, we demonstrate the critical role of B cells in promoting mechanical hypersensitivity (allodynia) after peripheral nerve injury in male and female mice. Depletion of B cells with a single injection of anti-CD20 monoclonal antibody at the time of injury prevented the development of allodynia. B cell-deficient (muMT) mice were similarly spared from allodynia. Nerve injury was associated with increased immunoglobulin G (IgG) accumulation in ipsilateral lumbar dorsal root ganglia (DRGs) and dorsal spinal cords. IgG was colocalized with sensory neurons and macrophages in DRGs and microglia in spinal cords. IgG also accumulated in DRG samples from human donors with chronic pain, colocalizing with a marker for macrophages and satellite glia. RNA sequencing revealed a B cell population in naive mouse and human DRGs. A B cell transcriptional signature was enriched in DRGs from human donors with neuropathic pain. Passive transfer of IgG from injured mice induced allodynia in injured muMT recipient mice. The pronociceptive effects of IgG are likely mediated through immune complexes interacting with Fc gamma receptors (FcγRs) expressed by sensory neurons, microglia, and macrophages, given that both mechanical allodynia and hyperexcitability of dissociated DRG neurons were abolished in nerve-injured FcγR-deficient mice. Consistently, the pronociceptive effects of IgG passive transfer were lost in FcγR-deficient mice. These data reveal that a B cell-IgG-FcγR axis is required for the development of neuropathic pain in mice.

A role for leucine-rich, glioma inactivated 1 in regulating pain sensitivity.

Neuronal hyperexcitability is a key driver of persistent pain states including neuropathic pain. Leucine-rich, glioma inactivated 1 (LGI1), is a secreted protein known to regulate excitability within the nervous system and is the target of autoantibodies from neuropathic pain patients. Therapies that block or reduce antibody levels are effective at relieving pain in these patients, suggesting that LGI1 has an important role in clinical pain. Here we have investigated the role of LGI1 in regulating neuronal excitability and pain-related sensitivity by studying the consequences of genetic ablation in specific neuron populations using transgenic mouse models. LGI1 has been well studied at the level of the brain, but its actions in the spinal cord and peripheral nervous system (PNS) are poorly understood. We show that LGI1 is highly expressed in DRG and spinal cord dorsal horn neurons in both mouse and human. Using transgenic muse models, we genetically ablated LGI1, either specifically in nociceptors (LGI1fl/Nav1.8+), or in both DRG and spinal neurons (LGI1fl/Hoxb8+). On acute pain assays, we find that loss of LGI1 resulted in mild thermal and mechanical pain-related hypersensitivity when compared to littermate controls. In from LGI1fl/Hoxb8+ mice, we find loss of Kv1 currents and hyperexcitability of DRG neurons. LGI1fl/Hoxb8+ mice displayed a significant increase in nocifensive behaviours in the second phase of the formalin test (not observed in LGI1fl/Nav1.8+ mice) and extracellular recordings in LGI1fl/Hoxb8+ mice revealed hyperexcitability in spinal dorsal horn neurons, including enhanced wind-up. Using the spared nerve injury model, we find that LGI1 expression is dysregulated in the spinal cord. LGI1fl/Nav1.8+ mice showed no differences in nerve injury induced mechanical hypersensitivity, brush-evoked allodynia or spontaneous pain behaviour compared to controls. However, LGI1fl/Hoxb8+ mice showed a significant exacerbation of mechanical hypersensitivity and allodynia. Our findings point to effects of LGI1 at both the level of the DRG and spinal cord, including an important impact of spinal LGI1 on pathological pain. Overall, we find a novel role for LGI1 with relevance to clinical pain.

Peripheral nerve injury results in a biased loss of sensory neuron subpopulations.

ABSTRACT: There is a rich literature describing the loss of dorsal root ganglion (DRG) neurons following peripheral axotomy, but the vulnerability of discrete subpopulations has not yet been characterised. Furthermore, the extent or even presence of neuron loss following injury has recently been challenged. In this study, we have used a range of transgenic recombinase driver mouse lines to genetically label molecularly defined subpopulations of DRG neurons and track their survival following traumatic nerve injury. We find that spared nerve injury leads to a marked loss of cells containing DRG volume and a concomitant loss of small-diameter DRG neurons. Neuron loss occurs unequally across subpopulations and is particularly prevalent in nonpeptidergic nociceptors, marked by expression of Mrgprd. We show that this subpopulation is almost entirely lost following spared nerve injury and severely depleted (by roughly 50%) following sciatic nerve crush. Finally, we used an in vitro model of DRG neuron survival to demonstrate that nonpeptidergic nociceptor loss is likely dependent on the absence of neurotrophic support. Together, these results profile the extent to which DRG neuron subpopulations can survive axotomy, with implications for our understanding of nerve injury-induced plasticity and pain.

Evaluation of Nutrition and Performance Parameters in Division 1 Collegiate Athletes.

BACKGROUND: Testing and evaluating athletes is necessary and should include performance, body composition, and nutrition. The purpose of this study was to report assessments of dietary intake, V˙O2max, and body composition in D1 collegiate athletes and examine relationships between these assessments. METHODS: Dietary intake was assessed with 3-day recalls and compared to recommendations, and body composition was assessed via bioelectrical impedance analysis (BIA) (n = 48). V˙O2max was evaluated using a graded exercise test (GXT) with a verification bout (n = 35). Reliability between "true" V˙O2max and verification was determined. Correlations and regressions were performed. RESULTS: Energy, carbohydrate, and micronutrient intake was lower than recommendations. Mean V˙O2max was 47.3 and 47.4 mL·kg-1·min-1 for GXT and verification, respectively. While correlations were apparent among dietary intake, V˙O2max, and body composition, percent fat-free mass (%FFM) predicted 36% of V˙O2max. CONCLUSIONS: Collegiate athletes are not meeting energy and carbohydrate recommendations and exceed fat recommendations. Vitamin D and magnesium were low in all sports, and iron and calcium were low in females. V˙O2max ranged from 35.6 to 63.0 mL·kg-1·min-1, with females below average and males meeting typical values for their designated sport. Assessing D1 athletes can provide guidance for sports dietitians, coaches, and strength and conditioning specialists to track and monitor nutrition in athletes.

Nutrient Intake, Performance, and Body Composition of Preseason Wrestlers.

College athletes, especially in weight class sports, often experience energy deficits. Athletes competing in weight class sports such as wrestling are at greatest risk for deficiencies and little is known about the relationships between body composition, nutrient intake, and performance in these athletes. The purposes of this study were to (1) quantify macronutrient and micronutrient intake of pre-season male collegiate wrestlers and compare to estimated needs, and (2) examine relationships among nutritional intakes, body composition, and performance measurements of strength and anaerobic capacity. Male Division I wrestlers (n = 11, age: 21.3 ± 1.7 years, wrestling experience: 14.9 ± 2.5 years) were recruited during pre-season. Nutrient intake was collected from a 3-day food diary. A 7-site skinfold assessment determined fat-free mass (FFM) to estimate total daily energy expenditure (eTEE). Isokinetic and isometric strength were evaluated by a Biodex dynamometer. Anaerobic capacity was tested on a stationary cycle ergometer. Eight of eleven wrestlers were energy deficient based on estimated needs. Mean intake of four micronutrients fell below the Recommended Dietary Allowances (RDA). Significant correlations were found between dietary intake, strength and anaerobic performance variables (r = 0.603 - 0.902, p = 0.0001 - 0.05). However, after accounting for FFM, these relationships were no longer significant. Nutrient intake in tandem with body composition affects performance for weight class athletes. Achieving high FFM during the preseason may be advantageous for wrestling performance. Nutrient intake and body composition should be monitored so coaches and health professionals can create individualized recommendations to help athletes optimize performance.

Contributions from incumbent police officer's physical activity and body composition to occupational assessment performance.

Introduction: Police officers must perform various tasks in unpredictable work environments and potentially volatile situations. This study aimed to determine if cardiovascular fitness, body composition, and physical activity levels could predict performance in a Midwest Police Department's Physical Readiness Assessment (PRA). Methods: Researchers collected data from thirty incumbent police officers (33.9 ± 8.3 years, female = 5). Anthropometric data included height, body mass, body fat percentage (BF%), fat-free mass (FFM), and maximal hand grip strength. The police officers also completed a physical activity rating (PA-R) scale to estimate maximal oxygen consumption (V˙O2max) and the International Physical Activity Questionnaire (IPAQ). Police officers then conducted their department's PRA. Stepwise linear regression analyses were used to determine the relationship between predictor variables and PRA performance. Pearson's product-moment correlations investigated relationships between anthropometric, physical fitness, and physical activity variables and PRA performance using SPSS (v.28). The significance level was set at p < 0.05. Results: Descriptive data for the sample includes BF%: 27.85 ± 7.57%, FFM: 65.73 ± 10.72 kg, hand grip strength: 55.51 ± 11.07 kg, weekday sedentary time (WST): 328 ± 28.26 min, weekend day sedentary time (WDST): 310 ± 28.92 min, daily moderate-to-vigorous physical activity (MVPA): 29.02 ± 39.41 min, PRA: 273.6 ± 51.4 s and estimated V˙O2max: 43.26 ± 6.35 mL kg-1 min-1. The stepwise regression analyses indicated that BF% was predictive of PRA time (R2 = 0.32, p < 0.01); estimated V˙O2max predictive of PRA time (R2 = 0.45, p < 0.001). There were significant correlations between BF % and PRA time (r = 0.57, p < 0.001), PA-R and MVPA (r = 0.71, p < 0.001), %BF % and WDST (r = -0.606, p < 0.001), hand grip and FFM (r = 0.602, p < 0.001) and PA-R and PRA time (r = -0.36, p < 0.05). Discussion: The results of this exploratory study highlight that higher estimated V˙O2max and lower BF% were the best predictors for faster PRA completion times, accounting for 45% and 32% of the variance, respectively. The findings of this study support the need for wellness and fitness initiatives in law enforcement agencies focused on increasing cardiovascular fitness and physical activity while decreasing BF% to ensure optimal performance in policing and overall health.

Deep RNA-seq of male and female murine sensory neuron subtypes after nerve injury.

ABSTRACT: Dorsal root ganglia (DRG) neurons have been well described for their role in driving both acute and chronic pain. Although nerve injury is known to cause transcriptional dysregulation, how this differs across neuronal subtypes and the impact of sex is unclear. Here, we study the deep transcriptional profiles of multiple murine DRG populations in early and late pain states while considering sex. We have exploited currently available transgenics to label numerous subpopulations for fluorescent-activated cell sorting and subsequent transcriptomic analysis. Using bulk tissue samples, we are able to circumvent the issues of low transcript coverage and drop-outs seen with single-cell data sets. This increases our power to detect novel and even subtle changes in gene expression within neuronal subtypes and discuss sexual dimorphism at the neuronal subtype level. We have curated this resource into an accessible database for other researchers ( https://livedataoxford.shinyapps.io/drg-directory/ ). We see both stereotyped and unique subtype signatures in injured states after nerve injury at both an early and late timepoint. Although all populations contribute to a general injury signature, subtype enrichment changes can also be seen. Within populations, there is not a strong intersection of sex and injury, but previously unknown sex differences in naïve states-particularly in Aß-RA + Aδ-low threshold mechanoreceptors-still contribute to differences in injured neurons.

Comparable Acute Metabolic Responses when Walking with Blood Flow Restriction and Walking with Load Carriage: Implication for Tactical Professionals.

The current study aimed to investigate exercise with blood flow restriction (BFR) as a low-intensity conditioning strategy in tactical professionals with load carriage. During the low-intensity exercise, researchers examined the acute metabolic responses from low-intensity BFR walking, walking with load carriage, and walking with BFR and load carriage. Twelve healthy adult males (age = 21.8 ± 1.5 yrs, height = 181.3 ± 7.2 cm, body mass = 84.4 ± 11.1 kg and BMI = 25.6 ± 2.6 kg·m2) completed five bouts of 3-min treadmill walking at 4.8 km·h-1 with 1-min rest interval under three different conditions: 1) blood flow restriction (BFR), 2) loaded with 15% of body mass (LOAD) and 3) loaded with 15% of body mass with blood flow restriction (BFR-LOAD). Oxygen consumption (V̇O2), heart rate, and local muscle oxygen saturation was measured during the exercise bouts. V̇O2 increased by 7% during the BFR- LOAD (p = 0.001) compared with BFR or LOAD alone. There were no differences in V̇O2 between BFR and LOAD (p = 0.202). BFR-LOAD showed significantly lower (-9%) muscle oxygen saturation (p = 0.044) and deoxygenated hemoglobin (p = 0.047) compared to LOAD. Low-intensity walking with the addition of BFR shares acute metabolic characteristics similar to walking with a load. These characteristics suggest there is potential for the use of BFR to increase exercise intensity for individuals training with load carriage.

Comparable Levels of Objectively Measured Physical Activity and Cardiorespiratory Fitness in Firefighters From Two Midwest Fire Departments.

OBJECTIVE: The aim of the study is to objectively assess if firefighters are meeting the National Fire Protection Association (NFPA) cardiorespiratory fitness (CRF) and American College of Sports Medicine/American Heart Association physical activity (PA) guidelines. METHODS: Two independent fire departments from the Midwest participated in the study. Firefighters wore an accelerometer to track PA and associated intensities. In addition, firefighters completed a stage-graded exercise test TO determine their maximal oxygen uptake (V˙O 2max ). RESULTS: A total of 43 career firefighters completed the study (fire department 1 [FD1]: n = 29, FD2: n = 14). Almost half (44.8% FD1 and 42.9% FD2) met the NFPA CRF guidelines. Compared with the American College of Sports Medicine PA Guidelines of 30 min/d of moderate-to-vigorous PA, more than half of FD2 (57.1%) met the recommended amount of PA, whereas FD1 had less than half (48.3%). CONCLUSIONS: These data demonstrate the need to improve firefighters' PA levels, CRF, and overall health.

Customized Occupational-Specific Graded Exercise Test for Structural Firefighters: An Update.

OBJECTIVE: The aim of the study is to validate a customized V˙O 2max Graded Exercise Test (GXT) protocol specifically to accommodate firefighters with different cardiovascular fitness levels. METHODS: Career male firefighters (N = 15) completed 3 customized GXTs on a treadmill: 1 in athletic clothes and 2 in their bunker gear to determine maximal oxygen uptake (V˙O 2max ). RESULTS: The on-duty task protocol was reliable, V˙O 2max values of 40.2 ± 4.6 mL·kg·min -1 and 40.3 ± 5.3 mL·kg·min -1 between trials yielded an interclass correlation of 0.911 with a typical error of 1.48 mL·kg·min -1 and a coefficient of variation of 4.0%. The validity analysis indicated consistent maximal V˙O 2 values for the GXTs yielding mean interclass correlation of 0.94 with typical error of 1.16 mL·kg·min -1 and a coefficient of variation of 2.9%. CONCLUSIONS: The customized GXT for structural firefighters has shown to be a reliable, valid, and applicable method of testing cardiovascular fitness in firefighters.

Moderate to vigorous physical activity, leucine, and protein intake contributions to muscle health in middle age.

Objective: Identify contributors to differences in the muscle size and strength of sedentary and active young and middle-aged adults. Methods: This cross-sectional study included 98 participants aged 20-65 years. Participants were categorized based on age and self-reported physical activity (PA) habits. Participants completed a strength assessment of knee extensors (KEPT), knee flexors (KFPT), plantar flexors (PFPT), and dorsiflexors (DFPT), a 3-day dietary intake log, 7-day accelerometry, and a magnetic resonance imaging (MRI) scan for muscle cross-sectional area analysis of the right quadriceps (CSAq). Results: There were significant age and activity-related group effects for relative protein intake (p<0.001), relative energy intake (p=0.04), KEPT (p=0.01), CSAq (p=0.002), PFPT (p=0.004) and DFPT (p=0.003). Moderate, moderate-to-vigorous, and vigorous PA were positively associated with CSAq (R2=0.69- 0.71; p<0.05), KEPT (R2=0.61-0.63; p<0.05), and PFPT (R2=0.31-0.36; p<0.05). Relative protein intake and daily leucine intake were significantly and positively associated with CSAq (R2=0.70 and 0.67 respectively; p<0.05), KEPT (R2=0.62 and 0.65 respectively; p<0.05), and PFPT (R2=0.29 and 0.28 respectively; p<0.05). Conclusion: Muscle size and strength were lower in middle age relative to younger age, but increased PA, protein intake, and leucine intake was associated with the preservation of muscle size and strength in larger muscle groups of the lower body.

Nav1.7 is required for normal C-low threshold mechanoreceptor function in humans and mice.

Patients with bi-allelic loss of function mutations in the voltage-gated sodium channel Nav1.7 present with congenital insensitivity to pain (CIP), whilst low threshold mechanosensation is reportedly normal. Using psychophysics (n = 6 CIP participants and n = 86 healthy controls) and facial electromyography (n = 3 CIP participants and n = 8 healthy controls), we found that these patients also have abnormalities in the encoding of affective touch, which is mediated by the specialized afferents C-low threshold mechanoreceptors (C-LTMRs). In the mouse, we found that C-LTMRs express high levels of Nav1.7. Genetic loss or selective pharmacological inhibition of Nav1.7 in C-LTMRs resulted in a significant reduction in the total sodium current density, an increased mechanical threshold and reduced sensitivity to non-noxious cooling. The behavioural consequence of loss of Nav1.7 in C-LTMRs in mice was an elevation in the von Frey mechanical threshold and less sensitivity to cooling on a thermal gradient. Nav1.7 is therefore not only essential for normal pain perception but also for normal C-LTMR function, cool sensitivity and affective touch.

Studying human nociceptors: from fundamentals to clinic.

Chronic pain affects one in five of the general population and is the third most important cause of disability-adjusted life-years globally. Unfortunately, treatment remains inadequate due to poor efficacy and tolerability. There has been a failure in translating promising preclinical drug targets into clinic use. This reflects challenges across the whole drug development pathway, from preclinical models to trial design. Nociceptors remain an attractive therapeutic target: their sensitization makes an important contribution to many chronic pain states, they are located outside the blood-brain barrier, and they are relatively specific. The past decade has seen significant advances in the techniques available to study human nociceptors, including: the use of corneal confocal microscopy and biopsy samples to observe nociceptor morphology, the culture of human nociceptors (either from surgical or post-mortem tissue or using human induced pluripotent stem cell derived nociceptors), the application of high throughput technologies such as transcriptomics, the in vitro and in vivo electrophysiological characterization through microneurography, and the correlation with pain percepts provided by quantitative sensory testing. Genome editing in human induced pluripotent stem cell-derived nociceptors enables the interrogation of the causal role of genes in the regulation of nociceptor function. Both human and rodent nociceptors are more heterogeneous at a molecular level than previously appreciated, and while we find that there are broad similarities between human and rodent nociceptors there are also important differences involving ion channel function, expression, and cellular excitability. These technological advances have emphasized the maladaptive plastic changes occurring in human nociceptors following injury that contribute to chronic pain. Studying human nociceptors has revealed new therapeutic targets for the suppression of chronic pain and enhanced repair. Cellular models of human nociceptors have enabled the screening of small molecule and gene therapy approaches on nociceptor function, and in some cases have enabled correlation with clinical outcomes. Undoubtedly, challenges remain. Many of these techniques are difficult to implement at scale, current induced pluripotent stem cell differentiation protocols do not generate the full diversity of nociceptor populations, and we still have a relatively poor understanding of inter-individual variation in nociceptors due to factors such as age, sex, or ethnicity. We hope our ability to directly investigate human nociceptors will not only aid our understanding of the fundamental neurobiology underlying acute and chronic pain but also help bridge the translational gap.

Firefighters Are More Physically Active On-Duty Compared to Off-Duty.

Physical inactivity, coupled with increasing obesity levels, in firefighters plays a key role in aggregated cardiovascular events. The purpose of this study was to investigate device-measured physical activity (PA) for firefighters while on- and off-duty to have a clearer understanding of their overall PA level. METHODS: Twenty-nine career firefighters participated in this non-experimental, within-subjects study by wearing an accelerometer to assess PA intensities and step-count. Obesity was classified using body mass index (BMI). Dependent t-tests were used to examine mean differences in PA intensities when on- and off-duty. Pearson product-moment correlations were used to assess the association between PA intensities when on and off-duty. RESULTS: According to the World Health Organization BMI categorizations, 20 firefighters were overweight, 9 were obese, and, thus, none were normal weight. Only light PA (LPA) was statistically significant (p = 0.026) for on- and off-duty days with a small-to-medium effect size (d = 0.47), meaning that on average, firefighters performed more minutes of LPA when on-duty compared to off. There was a significant difference between on- (9060.2 ± 2636.4) and off-duty (7495.3 ± 2835.8) daily step counts (p = 0.011). CONCLUSION: As the results demonstrate, there is a dire need for increased PA levels in firefighters while on- and off-duty.

Firefighters' Physical Activity and Waist Circumference as Predictors of VO2max.

OBJECTIVE: To examine associations among objectively measured physical activity (PA), body mass index (BMI), waist circumference (WC), and cardiorespiratory fitness (CRF) in firefighters. METHODS: Career firefighters (n = 29; male = 100%) wore accelerometers to assess PA. BMI and WC classified obesity. Each participant completed a stage-graded exercise test to determine maximal oxygen uptake ((Equation is included in full-text article.)). RESULTS: Two linear regression models were used to investigate whether PA intensities, step count, BMI, or WC were predictive of "true" (Equation is included in full-text article.). Vigorous physical activity (VPA) was predictive of "true" (Equation is included in full-text article.)(F[1,27] = 7.89, R = 0.23, P < 0.01). Additionally, when BMI and WC were added, only WC was predictive of "true" (Equation is included in full-text article.)(F[1,27] = 11.76, R = 0.30, P < 0.01). CONCLUSION: Fire departments should be cognizent of ways to increase PA levels, decrease excess weight gain, and maintain CRF to adequately perform job-specific tasks.

An Occupational-Specific O2max Protocol for Structural Firefighters.

OBJECTIVE: The aim of this study was to validate a (Equation is included in full-text article.)O2max protocol designed specifically for the occupational demands of firefighters by incorporating the use of personal protective equipment (PPE). METHODS: Career firefighters completed a stage-graded exercise test (GXT) with submaximal square-wave verification bout while wearing PPE (pants and boots) to determine (Equation is included in full-text article.)O2max. Using the self-reported Physical Activity-Rating (PA-R) scale and an estimated nonexercise regression equation of (Equation is included in full-text article.)O2max for comparison to measured. RESULTS: Twenty-eight male, career firefighters performed the GXT and square-wave bout. (Equation is included in full-text article.)O2 values (mean ±â€ŠSD) from the GXT and the square-wave verification bout were 41.04 ±â€Š6.98 and 39.74 ±â€Š6.42 mL/kg/min, respectively (ICC = 0.98, typical error = 0.96 mL/kg/min, CV = 2.4%). CONCLUSION: Our data suggest an incremental treadmill protocol that incorporates PPE and square-wave verification as an occupational-specific tool to measure cardiovascular fitness in firefighters.

Proteome-based systems biology in chronic pain.

Chronic pain represents a major medical challenge in the 21st century. Enormous efforts have been invested towards deciphering the complexity of chronic pain from different angles (molecular, physiological, psychosocial, and behavioral) in both preclinical and clinical settings. While progress has been made, our understanding of the underlying mechanisms of chronic pain remains insufficient. Consequently, chronic pain treatment is often inadequate. It lacks efficacy in most patients and is associated with detrimental side effects - a situation which calls for urgent changes in pain research and management. In this review we propose that protein-centric systems biology can significantly contribute to pain research. This approach may introduce the long-awaited paradigm shift in pain research from single targets to multidimensional cellular networks. We critically discuss how recent advances in reproducible and comprehensive proteome profiling can be exploited by pain researchers in the following ways: to gain mechanistic insights into chronic pain and its diverse forms, to facilitate clinical trials and the search for new drug targets, and to objectively assess chronic pain and its stages in individual patients by defining so-called protein disease signatures (PDS). We feel that the integration of proteomics into the toolbox of pain researchers and physicians alike will open new avenues towards a better understanding and management of chronic pain. SIGNIFICANCE STATEMENT: The immense challenges associated with chronic pain call for urgent changes in pain research and management. Here, we highlight the enormous potential of a proteome-based systems biology approach for advancing our understanding of chronic pain from a mechanistic, translational and clinical angle.

Vti1b promotes TRPV1 sensitization during inflammatory pain.

Sensitization of the transient receptor potential ion channel vanilloid 1 (TRPV1) is critically involved in inflammatory pain. To date, manifold signaling cascades have been shown to converge onto TRPV1 and enhance its sensitization. However, many of them also play a role for nociceptive pain, which limits their utility as targets for therapeutic intervention. Here, we show that the vesicle transport through interaction with t-SNAREs homolog 1B (Vti1b) protein promotes TRPV1 sensitization upon inflammation in cell culture but leaves normal functioning of TRPV1 intact. Importantly, the effect of Vti1b can be recapitulated in vivo: Virus-mediated knockdown of Vti1b in sensory neurons attenuated thermal hypersensitivity during inflammatory pain without affecting mechanical hypersensitivity or capsaicin-induced nociceptive pain. Interestingly, TRPV1 and Vti1b are localized in close vicinity as indicated by proximity ligation assays and are likely to bind to each other, either directly or indirectly, as suggested by coimmunoprecipitations. Moreover, using a mass spectrometry-based quantitative interactomics approach, we show that Vti1b is less abundant in TRPV1 protein complexes during inflammatory conditions compared with controls. Alongside, we identify numerous novel and pain state-dependent binding partners of native TRPV1 in dorsal root ganglia. These data represent a unique resource on the dynamics of the TRPV1 interactome and facilitate mechanistic insights into TRPV1 regulation. We propose that inflammation-related differences in the TRPV1 interactome identified here could be exploited to specifically target inflammatory pain in the future.

Region-Resolved Quantitative Proteome Profiling Reveals Molecular Dynamics Associated With Chronic Pain in the PNS and Spinal Cord.

To obtain a thorough understanding of chronic pain, large-scale molecular mapping of the pain axis at the protein level is necessary, but has not yet been achieved. We applied quantitative proteome profiling to build a comprehensive protein compendium of three regions of the pain neuraxis in mice: the sciatic nerve (SN), the dorsal root ganglia (DRG), and the spinal cord (SC). Furthermore, extensive bioinformatics analysis enabled us to reveal unique protein subsets which are specifically enriched in the peripheral nervous system (PNS) and SC. The immense value of these datasets for the scientific community is highlighted by validation experiments, where we monitored protein network dynamics during neuropathic pain. Here, we resolved profound region-specific differences and distinct changes of PNS-enriched proteins under pathological conditions. Overall, we provide a unique and validated systems biology proteome resource (summarized in our online database painproteome.em.mpg.de), which facilitates mechanistic insights into somatosensory biology and chronic pain-a prerequisite for the identification of novel therapeutic targets.