Nociceptor-expressed ephrin-B2 regulates inflammatory and neuropathic pain

Background: EphB receptors and their ephrin-B ligands play an important role in nervous system development, as well as synapse formation and plasticity in the adult brain. Recent studies show that intrathecal treatment with EphB-receptor activator ephrinB2-Fc induced thermal hyperalgesia and mechanical allodynia in rat, indicating that ephrin-B2 in small dorsal root ganglia (DRG) neurons and EphB receptors in the spinal cord modulate pain processing. To examine the role of ephrin-B2 in peripheral pain pathways, we deleted ephrin-B2 in Nav1.8+ nociceptive sensory neurons with the Cre-loxP system. Sensory neuron numbers and terminals were examined using neuronal makers. Pain behavior in acute, inflammatory and neuropathic pain models was assessed in the ephrin-B2 conditional knockout (CKO) mice. We also investigated the c-Fos expression and NMDA receptor NR2B phosphorylation in ephrin-B2 CKO mice and littermate controls.Results: The ephrin-B2 CKO mice were healthy with no sensory neuron loss. However, pain-related behavior was substantially altered. Although acute pain behavior and motor co-ordination were normal, inflammatory pain was attenuated in ephrin-B2 mutant mice. Complete Freund's adjuvant (CFA)-induced mechanical hyperalgesia was halved. Formalin-induced pain behavior was attenuated in the second phase, and this correlated with diminished tyrosine phosphorylation of N-methyl-D-aspartic acid (NMDA) receptor subunit NR2B in the dorsal horn. Thermal hyperalgesia and mechanical allodynia were significantly reduced in the Seltzer model of neuropathic pain.Conclusions: Presynaptic ephrin-B2 expression thus plays an important role in regulating inflammatory pain through the regulation of synaptic plasticity in the dorsal horn and is also involved in the pathogenesis of some types of neuropathic pain

Sick leave among home-care personnel: a longitudinal study of risk factors

BACKGROUND: Sick leave due to neck, shoulder and back disorders (NSBD) is higher among health-care workers, especially nursing aides/assistant nurses, compared with employees in other occupations. More information is needed about predictors of sick leave among health care workers. The aim of the study was to assess whether self-reported factors related to health, work and leisure time could predict: 1) future certified sick leave due to any cause, in nursing aides/assistant nurses (Study group I) and 2) future self-reported sick leave due to NSBD in nursing aides/assistant nurses (Study group II). METHODS: Study group I, comprised 443 female nursing aides/assistant nurses, not on sick leave at baseline when a questionnaire was completed. Data on certified sick leave were collected after 18 months. Study group II comprised 274 of the women, who at baseline reported no sick leave during the preceding year due to NSBD and who participated at the 18 month follow-up. Data on sick leave due to NSBD were collected from the questionnaire at 18 months. The associations between future sick leave and factors related to health, work and leisure time were tested by logistic regression analyses. RESULTS: Health-related factors such as previous low back disorders (OR: 1.89; 95% CI 1.20–2.97) and previous sick leave (OR 6.40; 95%CI 3.97–10.31), were associated with a higher risk of future sick leave due to any cause. Factors related to health, work and leisure time, i.e. previous low back disorders (OR: 4.45; 95% CI 1.27–15.77) previous sick leave, not due to NSBD (OR 3.30; 95%CI 1.33–8.17), high strain work (OR 2.34; 95%CI 1.05–5.23) and high perceived physical exertion in domestic work (OR 2.56; 95%CI 1.12–5.86) were associated with a higher risk of future sick leave due to NSBD. In the final analyses, previous low back disorders and previous sick leave remained significant in both study groups. CONCLUSION: The results suggest a focus on previous low back disorders and previous sick leave for the design of early prevention programmes aiming at reducing future sick leave due to any cause, as well as due to NSBD, among nursing aides/assistant nurses. A multifactorial approach may be of importance in the early prevention of sick leave due to NSBD

Comparison of two self-reported measures of physical work demands in hospital personnel: A cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Low back pain (LBP) is a frequent health complaint among health care personnel. Several work tasks and working postures are associated with an increased risk of LBP. The aim of this study was to compare two self-reported measures of physical demands and their association with LBP (the daily number of patient handling tasks and Hollmann's physical load index).</p> <p>Methods</p> <p>A questionnaire was distributed to 535 hospital employees in a psychiatric and an orthopedic ward in a Danish hospital. Of these 411 (77%) filled in and returned the questionnaire. Only the 373 respondents who had non-missing values on both measures of physical demands were included in the analyses. The distribution of physical demands in different job groups and wards are presented, variance analysis models are employed, and logistic regression analysis is used to analyze the association between measures of physical demands and LBP.</p> <p>Results</p> <p>In combination, hospital ward and job category explained 56.6% and 23.3% of the variance in the self-reported physical demands measured as the daily number of patient handling tasks and as the score on the physical load index, respectively. When comparing the 6% with the highest exposure the prevalence odds ratio (POR) for LBP was 5.38 (95% CI 2.03–14.29) in the group performing more than 10 patient handling tasks per day and 2.29 (95% CI 0.93–5.66) in the group with the highest score on the physical load index.</p> <p>Conclusion</p> <p>In specialized hospital wards the daily number of patient handling tasks seems to be a more feasible measure of exposure when assessing the risk of LBP compared to more advanced measures of physical load on the lower lumbar spine.</p

Prevalence of and risk factors for different measures of low back pain among female nursing aides in Taiwanese nursing homes

<p>Abstract</p> <p>Background</p> <p>Although low back pain (LBP) among nursing staff, especially in nursing aides (NAs), has been a major health problem around the world, there is limited information on its prevalence in Taiwan. In addition, various measurements have been used to determine LBP; understanding the risk factors for each measurement of LBP is essential for prevention. This study aimed to assess the prevalence of and risk factors for different measures of LBP among NAs in Taiwan.</p> <p>Methods</p> <p>A cross-sectional study was conducted among 244 female NAs from 31 nursing homes in central Taiwan. A self-administered questionnaire, including the Nordic questionnaire and the Karasek's job content questionnaire, was used to collect data regarding five different measures of LBP and about demographic, physical and psychosocial factors. Also, on-site observation at the workplace was conducted to measure the frequency of five high risk patient-handling tasks.</p> <p>Results</p> <p>Based on the subjects' reports on the previous twelve months, the prevalence rates for pain lasting for at least one day, seeking of medical care, intense pain, sick leave, and chronic pain were 66.0%, 43.9%, 38.1%, 10.7%, and 8.6%, respectively. While multiple logistic regression analyses indicated that the risk factors varied with different measures of LBP, at least one high risk patient-handling task and one psychosocial factor were observed to be associated each LBP related measure. Three risk factors, including manual transfer of patients between bed/wheelchair and bath cart, perceived physical exertion, and psychological demands, were consistently associated with different measures of LBP. Besides, age was found to be associated with an increased risk of only chronic pain.</p> <p>Conclusion</p> <p>The prevalence of LBP among NAs in Taiwan is high and should be actively addressed. Certain manual patient-transfer tasks and psychological demands seemed to play more important roles in severe LBP (such as care seeking, intense pain, and sick leave) than in minor LBP (pain lasting for at least one day). Because different LBP related measures might be involved with different etiological risk factors, any LBP reduction interventions that aim to improve ergonomic and psychosocial work environments for NAs should take this information into consideration.</p

Genome-wide profiling of G protein-coupled receptors in cerebellar granule neurons using high-throughput, real-time PCR

<p>Abstract</p> <p>Background</p> <p>G protein-coupled receptors (GPCRs) are major players in cell communication, regulate a whole range of physiological functions during development and throughout adult life, are affected in numerous pathological situations, and constitute so far the largest class of drugable targets for human diseases. The corresponding genes are usually expressed at low levels, making accurate, genome-wide quantification of their expression levels a challenging task using microarrays.</p> <p>Results</p> <p>We first draw an inventory of all endo-GPCRs encoded in the murine genome. To profile GPCRs genome-wide accurately, sensitively, comprehensively, and cost-effectively, we designed and validated a collection of primers that we used in quantitative RT-PCR experiments. We experimentally validated a statistical approach to analyze genome-wide, real-time PCR data. To illustrate the usefulness of this approach, we determined the repertoire of GPCRs expressed in cerebellar granule neurons and neuroblasts during postnatal development.</p> <p>Conclusions</p> <p>We identified tens of GPCRs that were not detected previously in this cell type; these GPCRs represent novel candidate players in the development and survival of cerebellar granule neurons. The sequences of primers used in this study are freely available to those interested in quantifying GPCR expression comprehensively.</p

Genetically encoded photocross-linkers determine the biological binding site of exendin-4 peptide in the N-terminal domain of the intact human glucagon-like peptide-1 receptor (GLP-1R)

The glucagon-like peptide-1 receptor (GLP-1R) is a key therapeutic target in the management of type II diabetes mellitus, with actions including regulation of insulin biosynthesis and secretion, promotion of satiety, and preservation of β-cell mass. Like most class B G protein-coupled receptors (GPCRs), there is limited knowledge linking biological activity of the GLP-1R with the molecular structure of an intact, full-length, and functional receptor·ligand complex. In this study, we have utilized genetic code expansion to site-specifically incorporate the photoactive amino acid p-azido-l-phenylalanine (azF) into N-terminal residues of a full-length functional human GLP-1R in mammalian cells. UV-mediated photolysis of azF was then carried out to induce targeted photocross-linking to determine the proximity of the azido group in the mutant receptor with the peptide exendin-4. Cross-linking data were compared directly with the crystal structure of the isolated N-terminal extracellular domain of the GLP-1R in complex with exendin(9–39), revealing both similarities as well as distinct differences in the mode of interaction. Generation of a molecular model to accommodate the photocross-linking constraints highlights the potential influence of environmental conditions on the conformation of the receptor·peptide complex, including folding dynamics of the peptide and formation of dimeric and higher order oligomeric receptor multimers. These data demonstrate that crystal structures of isolated receptor regions may not give a complete reflection of peptide/receptor interactions and should be combined with additional experimental constraints to reveal peptide/receptor interactions occurring in the dynamic, native, and full-length receptor state

The Adhesion GPCR GPR125 is specifically expressed in the choroid plexus and is upregulated following brain injury

<p>Abstract</p> <p>Background</p> <p>GPR125 belongs to the family of <it>Adhesion </it>G protein-coupled receptors (GPCRs). A single copy of GPR125 was found in many vertebrate genomes. We also identified a <it>Drosophila </it>sequence, DmCG15744, which shares a common ancestor with the entire Group III of <it>Adhesio</it>n GPCRs, and also contains Ig, LRR and HBD domains which were observed in mammalian GPR125.</p> <p>Results</p> <p>We found specific expression of GPR125 in cells of the choroid plexus using <it>in situ </it>hybridization and protein-specific antibodies and combined <it>in situ</it>/immunohistochemistry co-localization using cytokeratin, a marker specific for epithelial cells. Induction of inflammation by LPS did not change GPR125 expression. However, GPR125 expression was transiently increased (almost 2-fold) at 4 h after traumatic brain injury (TBI) followed by a decrease (approximately 4-fold) from 2 days onwards in the choroid plexus as well as increased expression (2-fold) in the hippocampus that was delayed until 1 day after injury.</p> <p>Conclusion</p> <p>These findings suggest that GPR125 plays a functional role in choroidal and hippocampal response to injury.</p