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The pharmacological management of musculoskeletal pain starts with NSAIDs, followed by weak or strong opioids until the pain is under control. However, the treatment outcome is usually unsatisfying due to inter-individual differences. To investigate the genetic component of treatment outcome differences, we performed a genome-wide association study (GWAS) in ~23,000 participants with musculoskeletal pain from the UK Biobank. NSAID vs. opioid users were compared as a reflection of the treatment outcome of NSAIDs. We identified one genome-wide significant hit in chromosome 4 (rs549224715, P = 3.88 × 10 -8 ). Suggestive significant (P < 1 × 10 -6 ) loci were functionally annotated to 18 target genes, including four genes linked to neuropathic pain processes or musculoskeletal development. Pathway and network analyses identified immunity-related processes and a (putative) central role of EGFR. However, this study should be viewed as a first step to elucidate the genetic background of musculoskeletal pain treatment., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

miRNAs are involved in the generation and progression of musculoskeletal pain, a condition that causes significant clinical, economic and social burden. In runners, the presence of musculoskeletal pain related to an inflammatory state or ongoing underlying tissue damage may result in poor training ability and performance. This study aims to evaluate the association between circulating and salivary miRNAs and pain in runners with and without musculoskeletal pain and to observe whether dysregulated miRNAs can distinguish between responders and nonresponders to a kinesiological intervention. The possible correlation between these miRNAs and inflammatory molecules, stress parameters and individual or behavioral characteristics will be evaluated. Finally, in silico analysis will be used to characterize miRNAs function. Ethics approval was obtained.

Chronic multisite musculoskeletal pain (CMP) is common and highly morbid. However, vulnerability factors for CMP are poorly understood. Previous studies have independently shown that both small hippocampal brain volume and genetic risk alleles in a key stress system gene, FKBP5, increase vulnerability for chronic pain. However, little is known regarding the relationship between these factors and CMP. Here we tested the hypothesis that both small hippocampal brain volume and FKBP5 genetic risk, assessed using the tagging risk variant, FKBP5rs3800373, increase vulnerability for CMP. We used participant data from 36,822 individuals with available genetic, neuroimaging, and chronic pain data in the UK Biobank study. Although no main effects were observed, the interaction between FKBP5 genetic risk and right hippocampal volume was associated with CMP severity (β = -0.020, p raw  = 0.002, p adj  = 0.01). In secondary analyses, severity of childhood trauma further moderated the relationship between FKBP5 genetic risk, right hippocampal brain volume, and CMP (β = -0.081, p = 0.016). This study provides novel evidence that both FKBP5 genetic risk and childhood trauma moderate the relationship between right hippocampal brain volume and CMP. The data increases our understanding of vulnerability factors for CMP and builds a foundation for further work assessing causal relationships that might drive CMP development., (© 2022. The Author(s).)

Abstract: There is a need to better understand biological factors that increase the risk of persistent musculoskeletal (MSK) pain and heightened pain sensitivity. Knowing the heritability (how genes account for differences in people's traits) can enhance the understanding of genetic vs environmental influences of pain and pain sensitivity. However, there are gaps in current knowledge, including the need for intergenerational studies to broaden our understanding of the genetic basis of pain. Data from Gen1 and Gen2 of the Raine Study were used to investigate the heritability of MSK pain and pressure and cold pain sensitivity. Participants included parents (Gen1, n = 1092) and their offspring (Gen2, n = 688) who underwent a battery of testing and questionnaires including pressure and cold pain threshold testing and assessments of physical activity, sleep, MSK pain, mental health, and adiposity. Heritability estimates were derived using the Sequential Oligogenic Linkage Analysis Routines software. Heritability estimates for MSK pain and pressure pain sensitivity were significant, accounting for between 0.190 and 0.289 of the variation in the phenotype. By contrast, heritability of cold pain sensitivity was not significant. This is the largest intergenerational study to date to comprehensively investigate the heritability of both MSK pain and pain sensitivity, using robust statistical analysis. This study provides support for the heritability of MSK pain and pain sensitivity to pressure, suggesting the need for further convergence of genetic and environmental factors in models for the development or maintenance of these pain disorders., (Copyright © 2021 International Association for the Study of Pain.)

Background and Objectives: Chronic widespread musculoskeletal pain (CWP) is a symptom of fibromyalgia and a complex trait with poorly understood pathogenesis. CWP is heritable (48%-54%), but its genetic architecture is unknown and candidate gene studies have produced inconsistent results. We conducted a genome-wide association study to get insight into the genetic background of CWP., Methods: Northern Europeans from UK Biobank comprising 6914 cases reporting pain all over the body lasting >3 months and 242 929 controls were studied. Replication of three independent genome-wide significant single nucleotide polymorphisms was attempted in six independent European cohorts (n=43 080; cases=14 177). Genetic correlations with risk factors, tissue specificity and colocalisation were examined., Results: Three genome-wide significant loci were identified ( rs1491985, rs10490825, rs165599 ) residing within the genes Ring Finger Protein 123 ( RNF123 ), ATPase secretory pathway Ca 2+ transporting 1 ( ATP2C1 ) and catechol-O-methyltransferase ( COMT ). The RNF123 locus was replicated (meta-analysis p=0.0002), the ATP2C1 locus showed suggestive association (p=0.0227) and the COMT locus was not replicated. Partial genetic correlation between CWP and depressive symptoms, body mass index, age of first birth and years of schooling were identified. Tissue specificity and colocalisation analysis highlight the relevance of skeletal muscle in CWP., Conclusions: We report a novel association of RNF123 locus and a suggestive association of ATP2C1 locus with CWP. Both loci are consistent with a role of calcium regulation in CWP. The association with COMT , one of the most studied genes in chronic pain field, was not confirmed in the replication analysis., Competing Interests: Competing interests: YSA is co-owner of Maatschap PolyOmica and PolyKnomics BV, private organisations, providing services, research and development in the field of computational and statistical, quantitative and computational (gen)omics., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.)

Background: Musculoskeletal pain (MSKP) is the most reported symptom during treatment with aromatase inhibitors (AIs) for breast cancer. The mechanisms underlying MSKP are multidimensional and not well understood. The goals of this biological pathway analysis were to (1) gain an understanding of the genetic variation and biological mechanisms underlying MSKP with AI therapy and (2) identify plausible biological pathways and candidate genes for future investigation., Method: Genes associated with MSKP during AI therapy or genes involved in drug metabolism of and response to AIs were identified from the literature. Studies published through February 2019 were queried in PubMed®. The genes identified from the literature were entered into QIAGEN's Ingenuity® Pathway Analysis (IPA) software to generate canonical pathways, upstream regulators, and networks through a core analysis., Results: The 17 genes identified were ABCB1 , ABCG1 , CYP17A1 , CYP19A1 , CYP27B1 , CYP2A6 , CYP3A4 , CYP3A5 , ESR1 , OATP1B1 , OPG , RANKL, SLCO3A1 , TCL1A , UGT2A1 , UGT2B17 , and VDR . These genes are involved in encoding bone-remodeling regulators, drug-metabolizing enzymes (cytochrome P450 family, UDP-glucuronosyltransferases family), or drug transporters (ATP-binding cassette transporters, organic anion transporters). Multiple plausible biological pathways (e.g., nicotine degradation, melatonin degradation) and candidate genes (e.g., NFKB , HSP90 , AKT , ERK1/2 , FOXA2 ) are proposed for future investigation based on the IPA results., Conclusion: Multiple genes and molecular-level etiologies may contribute to MSKP with AI therapy in women with breast cancer. Our innovative combination of gene identification from the literature plus biological pathway analysis allowed for the emergence of novel candidate genes and biological pathways for future investigations.

African Americans experience an increased burden of motor vehicle collision (MVC), post-MVC musculoskeletal pain, and vitamin D insufficiency. In this prospective multicenter study, we tested the hypothesis that African Americans (n = 133) presenting to the emergency department after MVC with low peritraumatic vitamin D levels would have worse chronic musculoskeletal pain outcomes compared to individuals with sufficient vitamin D. Vitamin D levels were assessed in the early aftermath of MVC through enzyme-linked immunosorbent assay, and pain severity was assessed using the 0 to 10 numeric rating scale at 6 weeks, 6 months, and 1 year. In repeated-measures analysis, African American MVC survivors with vitamin D insufficiency experienced more severe chronic pain (β = 1.18, P = 0.031). In secondary analyses, we assessed for evidence that the effect of vitamin D on post-MVC pain outcomes is mediated, at least in part, by the influence of vitamin D on genetic variants in genes involved in immune system regulation (IL-10 and NLRP3). Genotyping was performed using a genome-wide microarray using collected DNA samples. Secondary analyses suggest that the effect of vitamin D on post-MVC pain outcomes may be influenced by genetic variation in IL-10 and NLRP3. Further studies are needed to assess the impact of vitamin D insufficiency on pain outcomes in African Americans experiencing MVC and other common trauma exposures, to assess factors affecting this relationship, and to assess the efficacy of administering vitamin D in the immediate aftermath of MVC to prevent chronic pain. Such low-cost, nonopioid interventions are urgently needed to address chronic pain development after MVC.

Our study aimed to identify differentially methylated CpGs/regions and their enriched genomic pathways associated with underlying chronic musculoskeletal pain in older individuals. We recruited cognitively healthy older adults with ( n  = 20) and without ( n  = 9) self-reported musculoskeletal pain and collected DNA from peripheral blood that was analyzed using MethylationEPIC arrays. We identified 31,739 hypermethylated CpG and 10,811 hypomethylated CpG probes ( p s ≤ 0.05). All CpG probes were clustered into 5966 regions, among which 600 regions were differentially methylated at p ≤ 0.05 level, including 294 hypermethylated regions and 306 hypomethylated regions (differentially methylated regions). Ingenuity pathway enrichment analysis revealed that the pain-related differentially methylated regions were enriched across multiple pathways. The top 10 canonical pathways were linked to cellular signaling processes related to immune responses (i.e. antigen presentation, programed cell death 1 receptor/PD-1 ligand 1, interleukin-4, OX40 signaling, T cell exhaustion, and apoptosis) and gamma-aminobutyric acid receptor signaling. Further, Weighted Gene Correlation Network Analysis revealed a comethylation network module in the pain group that was not preserved in the control group, where the hub gene was the cyclic adenosine monophosphate-dependent transcription factor ATF-2. Our preliminary findings provide new epigenetic insights into the role of aberrant immune signaling in musculoskeletal pain in older adults while further supporting involvement of dysfunctional GABAergic signaling mechanisms in chronic pain. Our findings need to be urgently replicated in larger cohorts as they may serve as a basis for developing and targeting future interventions.

Co-morbid chronic musculoskeletal pain (CMSP) and posttraumatic stress symptoms (PTSS) are frequent sequelae of motor vehicle collision, are associated with greater disability than either outcome alone, and are more prevalent in women than men. In the current study we assessed for evidence that gene transcripts originating from the X chromosome contribute to sex differences in vulnerability to CMSP and PTSS after motor vehicle collision. Nested samples were drawn from a longitudinal study of African American individuals, and CMSP (0-10 numeric rating scale) and PTSS (impact of events scale, revised) outcomes were assessed 6 months following motor vehicle collision. Blood RNA were sequenced (n = 101) and the relationship between X chromosome mRNA expression levels and co-morbid CMSP and PTSS outcomes was evaluated using logistic regression analyses. A disproportionate number of peritraumatic X chromosome mRNA predicting CMSP and PTSS in women were genes previously found to escape X chromosome inactivation (11/40, z = -2.9, p = .004). Secondary analyses assessing gene ontology relationships between these genes identified an enrichment in genes known to influence neuronal plasticity. Further, the relationship of expression of two critical regulators of X chromosome inactivation, X-inactive specific transcript (XIST) and Yin Yang 1 (YY1), was different in women developing CMSP and PTSS. Together, these data suggest that X chromosome genes that escape inactivation may contribute to sex differences in vulnerability to CMSP and PTSS after motor vehicle collision., (© 2018 Wiley Periodicals, Inc.)

Chronic muscle pain is a prominent symptom of the hand-arm vibration syndrome (HAVS), an occupational disease induced by exposure to vibrating power tools, but the underlying mechanism remains unknown. We evaluated the hypothesis that vibration induces an interleukin 6 (IL-6)-mediated downregulation of the potassium voltage-gated channel subfamily A member 4 (KV1.4) in nociceptors leading to muscle pain. Adult male rats were submitted to a protocol of mechanical vibration of the right hind limb. Twenty-four hours after vibration, muscle hyperalgesia was observed, concomitant to increased levels of IL-6 in the gastrocnemius muscle and decreased expression of KV1.4 in the dorsal root ganglia. Local injection of neutralizing antibodies against IL-6 attenuated the muscle hyperalgesia induced by vibration, whereas antisense knockdown of this channel in the dorsal root ganglia mimicked the muscle hyperalgesia observed in the model of HAVS. Finally, knockdown of the IL-6 receptor signaling subunit glycoprotein 130 (gp130) attenuated both vibration-induced muscle hyperalgesia and downregulation of KV1.4. These results support the hypothesis that IL-6 plays a central role in the induction of muscle pain in HAVS. This likely occurs through intracellular signaling downstream to the IL-6 receptor subunit gp130, which decreases the expression of KV1.4 in nociceptors.

Objectives: Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by reduced lacrimal and salivary secretion. Sicca symptoms together with fatigue and musculoskeletal pain can significantly reduce the patients' quality of life. Furthermore, low salivary secretion may disrupt the oral microbial homeostasis. The aim of this study was to compare the salivary microbiota from pSS patients with patients with sicca symptoms not fulfilling the classification criteria for pSS (non-SS), and with healthy controls without sicca complaints., Methods: Pellets from centrifuged chewing-stimulated whole saliva from pSS patients (n = 15), non-SS sicca patients (n = 15) and healthy controls (n = 15) were prepared. DNA was extracted and analyzed by 16S rRNA gene sequencing. The acquired sequencing data were performed using the human oral microbiome database (HOMD)., Results: We detected 42, 45, and 34 bacterial genera in saliva samples from pSS patients, non-SS sicca patients, and healthy controls, respectively. The most abundant genera in all samples were Prevotella, Veillonella, Streptococcus, and Haemophilus. At species level Streptococcus intermedius, Prevotella intermedia, Fusobacterium nucleatum subsp. vincentii, Porphyromonas endodontalis, Prevotella nancensis, Tannerella spp., and Treponema spp. were detected in the samples from pSS and non-SS only, while Porphyromonas pasteri was mostly found among the healthy controls., Conclusion: Our study indicated dysbiosis in the salivary microbiota from pSS and non-SS patients compared to healthy controls. Additionally, the results showed that the salivary microbiome in the pSS group differed significantly from the non-SS group., Competing Interests: The authors have declared that no competing interests exist.

We previously performed genetic analysis in six unrelated families with infantile limb pain episodes, characterized by cold-induced deterioration and mitigation in adolescence, and reported two new mutations p.R222H/S in SCN11A responsible for these episodes. As no term described this syndrome (familial episodic pain: FEP) in Japanese, we named it as"". In the current study, we recruited an additional 42 new unrelated Japanese FEP families, between March 2016 and March 2018, and identified a total of 11 mutations in SCN11A: p.R222H in seven families, and p.R225C, p.F814C, p.F1146S, or p.V1184A, in independent families. A founder mutation, SCN11A p.R222H was confirmed to be frequently observed in patients with FEP in the Tohoku region of Japan. We also identified two novel missense variants of SCN11A, p.F814C and p.F1146S. To evaluate the effects of these latter two mutations, we generated knock-in mouse models harboring p.F802C (F802C) and p.F1125S (F1125S), orthologues of the human p.F814C and p.F1146S, respectively. We then performed electrophysiological investigations using dorsal root ganglion neurons dissected from the 6-8 week-old mice. Dissected neurons of F802C and F1125S mice showed increased resting membrane potentials and firing frequency of the action potentials (APs) by high input-current stimulus compared with WT mice. Furthermore, the firing probability of evoked APs increased in low stimulus input in F1125S mice, whereas several AP parameters and current threshold did not differ significantly between either of the mutations and WT mice. These results suggest a higher level of excitability in the F802C or F1125S mice than in WT, and indicate that these novel mutations are gain of function mutations. It can be expected that a considerable number of potential patients with FEP may be the result of gain of function SCN11A mutations., Competing Interests: The authors of this manuscript have read the journal’s policy and have the following competing interests: Prof. Akio Koizumi, Dr. Hatasu Kobayashi, Dr. Kouji H. Harada, Prof. Tsutomu Takahashi, Dr. Atsuko Noguchi and Dr. Daiki Kondo have a patent pending regarding with SCN11A (name of patent ‘pain gene and its applications’, Japanese Patent Application No. 2014-238250). This does not alter the authors’ adherence to PLOS genetics policies on sharing data and materials.

Chronic widespread musculoskeletal pain (CWP) and frailty are prevalent conditions in older people. We have shown previously that interindividual variation in frailty and CWP is genetically determined. We also reported an association of frailty and CWP caused by shared genetic and common environmental factors. The aim of this study was to use omic approaches to identify molecular genetic factors underlying the heritability of frailty and its genetic correlation with CWP. Frailty was quantified through the Rockwood Frailty Index (FI) as a proportion of deficits from 33 binary health deficit questions in 3626 female twins. Common widespread pain was assessed using a screening questionnaire. OMICS analysis included 305 metabolites and whole-genome (>2.5 × 10 SNPs) and epigenome (∼1 × 10 MeDIP-seq regions) assessments performed on fasting blood samples. Using family-based statistical analyses, including path analysis, we examined how FI scores were related to molecular genetic factors and to CWP, taking into account known risk factors such as fat mass and smoking. Frailty Index was significantly correlated with 51 metabolites after correction for multiple testing, with 20 metabolites having P-values between 2.1 × 10 and 4.0 × 10. Three metabolites (uridine, C-glycosyl tryptophan, and N-acetyl glycine) were statistically independent and thought to exert a direct effect on FI. Epiandrosterone sulphate, previously shown to be highly inversely associated with CWP, was found to exert an indirect influence on FI. Bioinformatics analysis of genome-wide association study and EWAS showed that FI and its covariation with CWP was through genomic regions involved in neurological pathways. Neurological pathway involvement accounts for the associated conditions of aging CWP and FI.

Previous studies have shown that common variants of the gene coding for FK506-binding protein 51 ( FKBP5 ), a critical regulator of glucocorticoid sensitivity, affect vulnerability to stress-related disorders. In a previous report, FKBP5 rs1360780 was identified as a functional variant because of its effect on gene methylation. Here we report evidence for a novel functional FKBP5 allele, rs3800373. This study assessed the association between rs3800373 and post-traumatic chronic pain in 1607 women and men from two ethnically diverse human cohorts. The molecular mechanism through which rs3800373 affects adverse outcomes was established via in silico , in vivo , and in vitro analyses. The rs3800373 minor allele predicted worse adverse outcomes after trauma exposure, such that individuals with the minor (risk) allele developed more severe post-traumatic chronic musculoskeletal pain. Among these individuals, peritraumatic circulating FKBP5 expression levels increased as cortisol and glucocorticoid receptor ( NR3C1 ) mRNA levels increased, consistent with increased glucocorticoid resistance. Bioinformatic, in vitro , and mutational analyses indicate that the rs3800373 minor allele reduces the binding of a stress- and pain-associated microRNA, miR-320a, to FKBP5 via altering the FKBP5 mRNA 3'UTR secondary structure (i.e., is a riboSNitch). This results in relatively greater FKBP5 translation, unchecked by miR-320a. Overall, these results identify an important gene-miRNA interaction influencing chronic pain risk in vulnerable individuals and suggest that exogenous methods to achieve targeted reduction in poststress FKBP5 mRNA expression may constitute useful therapeutic strategies. SIGNIFICANCE STATEMENT FKBP5 is a critical regulator of the stress response. Previous studies have shown that dysregulation of the expression of this gene plays a role in the pathogenesis of chronic pain development as well as a number of comorbid neuropsychiatric disorders. In the current study, we identified a functional allele (rs3800373) in the 3'UTR of FKBP5 that influences vulnerability to chronic post-traumatic pain in two ethnic cohorts. Using multiple complementary experimental approaches, we show that the FKBP5 rs3800373 minor allele alters the secondary structure of FKBP5 mRNA, decreasing the binding of a stress- and pain-associated microRNA, miR-320a. This results in relatively greater FKBP5 translation, unchecked by miR-320a, increasing glucocorticoid resistance and increasing vulnerability to post-traumatic pain., (Copyright © 2018 the authors 0270-6474/18/388408-14$15.00/0.)

This study aimed to clarify whether there are shared genetic and/or environmental factors explaining the strong link between pain catastrophizing (PC) and chronic widespread pain (CWP). Data were available for N = 1,109 female twins from TwinsUK. Information on self-reported CWP and PC was subject to variance component twin analysis. Heritabilities were 40% for PC and 77% for CWP. The genetic correlation between PC and CWP was .40%, whereas no evidence of an environmental correlation could be detected (.0). According to the best-fitting additive genetic, non-shared environmental (AE) Cholesky model, an additive genetic factor loading on PC as well as CWP, as well as an additive genetic factor loading on CWP alone was found. In terms of environmental influences, 2 individual environmental factors could be identified, loading separately on PC and CWP. Overall, the results add to the knowledge on the nature of CWP and the basis of its close relationship with PC by suggesting a shared genetic etiological structure. The findings highlight a potential avenue for future research and may provide useful insight for the clinical management of pain and pain coping., Perspective: Results suggest a shared genetic etiological structure between CWP and PC with no shared influence of environmental factors. Clinicians should be aware of this biological link within the context of clinical management of pain and pain coping., (Copyright © 2017 American Pain Society. Published by Elsevier Inc. All rights reserved.)

Chronic widespread musculoskeletal pain (CWP), has a considerable heritable component, which remains to be explained. Epigenetic factors may contribute to and account for some of the heritability estimate. We analysed epigenome-wide methylation using MeDIPseq in whole blood DNA from 1708 monozygotic and dizygotic Caucasian twins having CWP prevalence of 19.9%. Longitudinally stable methylation bins (lsBINs), were established by testing repeated measurements conducted ≥3 years apart, n = 292. DNA methylation variation at lsBINs was tested for association with CWP in a discovery set of 50 monozygotic twin pairs discordant for CWP, and in an independent dataset (n = 1608 twins), and the results from the 2 samples were combined using Fisher method. Functional interpretation of the most associated signals was based on functional genomic annotations, gene ontology, and pathway analyses. Of 723,029 signals identified as lsBINs, 26,399 lsBINs demonstrated the same direction of association in both discovery and replication datasets at nominal significance (P ≤ 0.05). In the combined analysis across 1708 individuals, whereas no lsBINs showed genome-wide significance (P < 10-8), 24 signals reached p≤9E-5, and these included association signals mapping in or near to IL17A, ADIPOR2, and TNFRSF13B. Bioinformatics analyses of the associated methylation bins showed enrichment for neurological pathways in CWP. We estimate that the variance explained by epigenetic factors in CWP is 6%. This, the largest study to date of DNA methylation in CWP, points towards epigenetic modification of neurological pathways in CWP and provides proof of principle of this method in teasing apart the complex risk factors for CWP.

α2A adrenergic receptor (α2A-AR) activation has been shown in animal models to play an important role in regulating the balance of acute pain inhibition vs facilitation after both physical and psychological stress. To our knowledge, the influence of genetic variants in the gene encoding α2A-AR, ADRA2A, on acute pain outcomes in humans experiencing traumatic stress has not been assessed. In this study, we tested whether a genetic variant in the 3'UTR of ADRA2A, rs3750625, is associated with acute musculoskeletal pain (MSP) severity following motor vehicle collision (MVC, n = 948) and sexual assault (n = 84), and whether this influence was affected by stress severity. We evaluated rs3750625 because it is located in the seed binding region of miR-34a, a microRNA (miRNA) known to regulate pain and stress responses. In both cohorts, the minor allele at rs3750625 was associated with increased musculoskeletal pain in distressed individuals (stress*rs3750625 P = 0.043 for MVC cohort and P = 0.007 for sexual assault cohort). We further found that (1) miR-34a binds the 3'UTR of ADRA2A, (2) the amount of repression is greater when the minor (risk) allele is present, (3) miR-34a in the IMR-32 adrenergic neuroblastoma cell line affects ADRA2A expression, (4) miR-34a and ADRA2A are expressed in tissues known to play a role in pain and stress, (5) following forced swim stress exposure, rat peripheral nerve tissue expression changes are consistent with miR-34a regulation of ADRA2A. Together, these results suggest that ADRA2A rs3750625 contributes to poststress musculoskeletal pain severity by modulating miR-34a regulation.

Background: Chronic widespread musculoskeletal pain (CWP) is the cardinal symptom of fibromyalgia and affects about 12% of the general population. Familial aggregation of CWP has been repeatedly demonstrated with estimated heritabilities of around 50%, indicating a genetic susceptibility. The objective of the study was to explore genome-wide disease-differentially methylated positions (DMPs) for chronic widespread pain (CWP) in a sample of unrelated individuals and a subsample of discordant monozygotic (MZ) twins., Methodology/principle Findings: A total of N = 281 twin individuals from the TwinsUK registry, including N = 33 MZ twins discordant for self-reported CWP, were part of the discovery sample. The replication sample included 729 men and 756 women from a subsample of the KORA S4 survey-an independent population-based cohort from Southern Germany. Epigenome-wide analysis of DNA methylation was conducted using the Illumina Infinium HumanMethylation 450 DNA BeadChip in both the discovery and replication sample. Of our 40 main loci that were carried forward for replication, three CPGs reached significant p-values in the replication sample, including malate dehydrogenase 2 (MDH2; p-value 0.017), tetranectin (CLEC3B; p-value 0.039), and heat shock protein beta-6 (HSPB6; p-value 0.016). The associations between the collagen type I, alpha 2 chain (COL1A2) and monoamine oxidase B (MAOB) observed in the discovery sample-both of which have been previously reported to be biological candidates for pain-could not be replicated., Conclusion/significance: Our results may serve as a starting point to encourage further investigation in large and independent population-based cohorts of DNA methylation and other epigenetic changes as possible disease mechanisms in CWP. Ultimately, understanding the key mechanisms underlying CWP may lead to new treatments and inform clinical practice., Competing Interests: The authors declare no conflict of interest.

Background: Aromatase inhibitor (AI) therapy is associated with musculoskeletal (MS) toxicity, which adversely affects quality of life and therapy adherence. Our objective was to evaluate whether genetic variants may predict endocrine therapy-related MS pain and hot flashes in a prospective observational cohort study., Patients & Methods: 254 early breast cancer patients starting AI (n = 159) or tamoxifen therapy (n = 95) were included in this genetic biomarker study. MS and vasomotor symptoms were assessed at baseline and after 3, 6 and 12 months of therapy. AI-induced MS pain was defined as an increase in arthralgia or myalgia relative to baseline. Single nucleotide polymorphisms (SNP) in candidate genes involved in oestrogen signalling or previously associated with AI-related MS pain or oestrogen levels were selected., Results: Overall, 13 SNPs in CYP19, CYP17, osteoprotegerin (OPG) and oestrogen receptor 1 exhibited an allele frequency >0.05 and were included in the analysis. Patients carrying the G allele of rs2073618 in OPG experienced significantly more AI-induced MS toxicity compared to the wildtype allele, after correction for multiple testing (P = 0.046). Furthermore, this SNP was associated with severity of pain (P = 0.018). No association was found with regard to the other SNPs, both in AI and tamoxifen-treated patients. Neither could an association with vasomotor symptoms be demonstrated., Conclusion: The SNP rs2073618 in OPG is associated with an increased risk of MS symptoms and pain with AI therapy, which has not been reported previously. Validation of this finding in larger cohorts and further functional studies are required., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Musculoskeletal pain (MSP) is a common sequela of traumatic stress exposure. While biological factors contributing to chronic MSP after motor vehicle collision (MVC) have traditionally focused on tissue injury, increasing evidence suggests that neuro/stress/immune processes mediated by stress system activation may play a more dominant role. In a previous study, we found that genetic variants in the hypothalamic-pituitary-adrenal (HPA) axis-related gene FKBP5 influence vulnerability to persistent MSP 6 weeks after MVC. In the present cohort study (n = 855), we evaluated whether genetic variants in several other important HPA axis-related genes, including the glucocorticoid receptor (NR3C1), corticotropin-releasing hormone receptor R1 (CRHR1), and corticotropin-releasing hormone-binding protein (CRHBP), influence risk of chronic MSP over time after MVC. Genetic polymorphism rs7718461 in the CRHBP gene showed significant association (P = 0.0012) with overall pain severity during the year after MVC in regression models controlling for multiple comparisons. Two additional CRHBP alleles in high linkage disequilibrium with rs7718461 also showed trend-level significance. In secondary analyses, a significant interaction between this CRHBP locus (minor allele frequency = 0.33) and time was observed (P = 0.015), with increasing effect observed over time following trauma. A significant CRHBP × FKBP5 interaction was also observed, with substantially increased MSP after MVC in those with a risk allele in both genes compared with either gene alone. The results of this study indicate that genetic variants in 2 different HPA axis genes predict chronic MSP severity following MVC and support the hypothesis that the HPA axis is involved in chronic post-MVC MSP pathogenesis.

Background: Chronic widespread muscoloskeletal pain (CWP) is prevalent in the general population and associated with high health care costs, so understanding the risk factors for chronic pain is important for both those affected and for society. In the present study we investigated the underlying etiological structure of CWP to understand better the association between the major clinical features of fatigue, depression and dihydroepiandrosterone sulphate (DHEAS) using a multivariate twin design., Methodology/principle Findings: Data were available in 463 UK female twin pairs including CWP status and information on depression, chronic fatigue and serum DHEAS levels. High to moderate heritabilities for all phenotypes were obtained (42.58% to 74.24%). The highest phenotypic correlation was observed between fatigue and CWP (r = 0.45), and the highest genetic correlation between CWP and fatigue (rg = 0.78). Structural equation modeling revealed the AE Cholesky model to provide the best model of the observed data. In this model, two additive genetic factors could be detected loading heavily on CWP-A2 explaining 40% of the variance and A3 20%. The factor loading heaviest on DHEAS showed only a small loading on the other phenotypes and none on fatigue at all. Furthermore, one distinct non-shared environmental factor loading specifically on CWP-but not on any of the other phenotypes-could be detected suggesting that the association between CWP and the other phenotypes is due only to genetic factors., Conclusions/significance: Our results suggest that CWP and its associated features share a genetic predisposition but that they are relatively distinct in their environmental determinants.

Chronic widespread musculoskeletal pain (CWP) is common, having a population prevalence of 10%. This study aimed to define the biological basis of the CWP/body mass association by using a systems biology approach. Adult female twins (n = 2444) from the TwinsUK registry who had extensive clinical, anthropometric, and "omic" data were included. Nontargeted metabolomics screening including 324 metabolites was carried out for CWP and body composition using dual-energy X-ray absorptiometry. The biological basis of these associations was explored through a genome-wide association study and replicated in an independent population sample (Cooperative Health Research in the Region of Augsburg [KORA] study, n = 2483). A causal role for the genetic variants identified was sought in CWP using a Mendelian randomisation study design. Fat mass/height2 was the body composition variable most strongly associated with CWP (TwinsUK: P = 2.4 × 10(-15) and KORA: P = 1.59 × 10(-10)). Of 324 metabolites examined, epiandrosterone sulfate (EAS) was highly associated with both CWP (P = 1.05 × 10(-09) in TwinsUK and P = 3.70 × 10(-06) in KORA) and fat mass/height2. Genome-wide association study of EAS identified imputed single nucleotide polymorphism rs1581492 at 7q22.1 to be strikingly associated with EAS levels (P ≤ 2.49 × 10(-78)), and this result was replicated in KORA (P = 2.12 × 10(-9)). Mendelian randomization by rs1581492 genotype showed that EAS is unlikely to be causally related to CWP. Using an agnostic omics approach to focus on the association of CWP with body mass index, we have confirmed a steroid hormone association and identified a genetic variant upstream of the CYP genes, which likely controls this response. This study suggests that steroid hormone abnormalities result from pain rather than causing it, and EAS may provide a biomarker that identifies subgroups at risk of CWP.

Introduction: Many patients with low back pain (LBP) are treated in a similar manner as if they were a homogenous group. However, scientific evidence is available that pain is a complex perceptual experience influenced by a wide range of genetic, psychological, and activity-related factors. The leading question for clinical practice should be what works for whom., Objectives: The main aim of the present review is to discuss the current state of evidence of subgrouping based on genetic, psychosocial, and activity-related factors in order to understand their contribution to individual differences., Results: Based on these perspectives, it is important to identify patients based on their specific characteristics. For genetics, very promising results are available from other chronic musculoskeletal pain conditions. However, more research is warranted in LBP. With regard to subgroups based on psychosocial factors, the results underpin the importance of matching patients' characteristics to treatment. Combining this psychosocial profile with the activity-related behavioral style may be of added value in tailoring the patient's treatment to his/her specific needs., Conclusions: For future research and treatment it might be challenging to develop theoretical frameworks combining different subgrouping classifications. On the basis of this framework, tailoring treatments more specifically to the patient needs may result in improvements in treatment programs for patients with LBP.

Background: Little is known about the association between parental chronic musculoskeletal pain (CMP) and occurrence of CMP in the adult offspring. The main objective of this study was to assess the parent-offspring association of CMP, and also to examine possible modifying effects of age and sex., Methods: The study includes 11 248 parent-offspring trios from the Norwegian HUNT Study with information on parental CMP obtained in 1995-97 and offspring CMP obtained in 2006-08. Logistic regression was used to calculate adjusted odds ratios (ORs) for offspring CMP associated with parental CMP., Results: Maternal and paternal CMP was associated with 20-40% increased odds of CMP in sons and daughters. Both sons and daughters had an OR of 1.6 (95% CI 1.4 to 1.9) when both parents reported CMP, compared to when none of the parents had CMP. Restricting the analyses to parental CMP that was associated with limited work ability and leisure time activity did not change the strength of the association. Further, analyses stratified by parental age ± 65 years showed no clear difference in the estimated associations, and there was no evidence of interaction for parental sex (P ≥ 0.39) or offspring age ± 40 years (P ≥ 0.26)., Conclusions: This large family-linkage study show that maternal and paternal CMP are positively associated with CMP in the adult offspring, irrespective of parental and offspring age, and that the associations are strongest when both parents have CMP. Although the high prevalence of CMP in both parents and offspring suggests that not all cases are clinically relevant, the results suggest that chronic pain has a heritable component.

Chronic pain syndromes (CPS) are highly prevalent in the general population, and increasingly the evidence points to a common etiological pathway. Using a large cohort of twins (n=8564) characterized for chronic widespread musculoskeletal pain (CWP), chronic pelvic pain (PP), migraine (MIG), dry eye disease, and irritable bowel syndrome (IBS), we explored the underlying genetic and environmental factors contributing to CPS and the correlation between them. The sample was predominantly female (87.3%), with a mean age of 54.7 (±14.7) years. Prevalence of the different CPS ranged from 7.4% (PP) to 15.7% (MIG). For all CPS the within-twin correlation in monozygotic twin pairs was higher than in dizygotic pairs, suggesting a heritable component. Estimated heritability ranged from 19% (IBS) to 46% (PP). Except for MIG, we found significant pairwise phenotypic correlations between the CPS. The phenotypic correlation was highest between CWP and IBS (0.40; 95% confidence interval: 0.27 to 0.46). Excluding MIG from further analyses, cross-twin cross-trait correlations were higher in monozygotic compared with dizygotic twin pairs, suggestive of shared genetic factors between CWP, PP, IBS, and dry eye disease. Twin modeling analysis revealed the common pathway model as the model best explaining the observed pattern of correlation between the traits, with an estimated heritability of 66% of the underlying latent variable. These results are evidence of shared genetic factors in conditions manifesting chronic pain and justify the search for underlying genetic variants., (Copyright © 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.)

Catechol-O-methyltransferase, encoded by COMT gene, is the primary enzyme that metabolizes catecholamines. COMT haplotypes have been associated with vulnerability to persistent non-traumatic pain. In this prospective observational study, we investigated the influence of COMT on persistent pain and pain interference with life functions after motor vehicle collision (MVC) in 859 European American adults for whom overall pain (0-10 numeric rating scale) and pain interference (Brief Pain Inventory) were assessed at week 6 after MVC. Ten single nucleotide polymorphisms spanning the COMT gene were successfully genotyped, and nine were present in three haploblocks: block 1 (rs2020917, rs737865, rs1544325), block 2 (rs4633, rs4818, rs4680, rs165774), and block 3 (rs174697, rs165599). After adjustment for multiple comparisons, haplotype TCG from block 1 predicted decreased pain interference (p = 0.004). The pain-protective effect of the low pain sensitivity (CGGG) haplotype from block 2 was only observed if at least one TCG haplotype was present in block 1 (haplotype × haplotype interaction p = 0.002 and <0.0001 for pain and pain interference, respectively). Haplotype AG from block 3 was associated with pain and interference in males only (sex × haplotype interaction p = 0.005 and 0.0005, respectively). These results suggest that genetic variants in the distal promoter are important contributors to the development of persistent pain after MVC, directly and via the interaction with haplotypes in the coding region of the gene.

There has been no previous side-by-side comparison of the diagnostic criteria for restless legs syndrome (RLS) (Willis-Ekbom disease) and growing pains. In our review, we explore this comparison emphasizing overlaps and disconnects, summarize recent literature exploring the relationship between the 2 entities, and make suggestions for future research. There is considerable overlap in the diagnostic criteria for childhood RLS and growing pains. The literature also indicates that RLS and growing pains more commonly occur together than one would expect based on chance alone, and the family histories of RLS and growing pains often are overlapping. Leg rubbing to obtain relief from leg discomfort is common to both disorders, though walking to obtain relief seems unique to RLS. Childhood RLS also has been reported to be painful in up to 45% of cases. The development of standard diagnostic criteria is necessary to move forward in the field of growing pains research. A quantitative and validated rating scale for growing pains severity already exists. Because of the clinical and genetic similarity between RLS and growing pains, studies that parallel those previously performed in RLS patients are recommended for growing pains patients. For example, a genome wide association study in growing pains patients of all possible genes with particular attention to those identified as related to RLS and a therapeutic trial of medications known to be effective in RLS would be welcome. Abnormalities in vitamin D metabolism also may be common to both disorders., (Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.)

Individual vulnerability factors influencing the function of the hypothalamic-pituitary-adrenal axis may contribute to the risk of the development of persistent musculoskeletal pain after traumatic stress exposure. The objective of the study was to evaluate the association between polymorphisms in the gene encoding FK506 binding protein 51, FKBP5, a glucocorticoid receptor co-chaperone, and musculoskeletal pain severity 6 weeks after 2 common trauma exposures. The study included data from 2 prospective emergency department-based cohorts: a discovery cohort (n=949) of European Americans experiencing motor vehicle collision and a replication cohort of adult European American women experiencing sexual assault (n=53). DNA was collected from trauma survivors at the time of initial assessment. Overall pain and neck pain 6 weeks after trauma exposure were assessed using a 0-10 numeric rating scale. After adjustment for multiple comparisons, 6 FKBP5 polymorphisms showed significant association (minimum P<0.0001) with both overall and neck pain in the discovery cohort. The association of rs3800373, rs9380526, rs9394314, rs2817032, and rs2817040 with neck pain and/or overall pain 6 weeks after trauma was replicated in the sexual assault cohort, showing the same direction of the effect in each case. The results of this study indicate that genetic variants in FKBP5 influence the severity of musculoskeletal pain symptoms experienced during the weeks after motor vehicle collision and sexual assault. These results suggest that glucocorticoid pathways influence the development of persistent posttraumatic pain, and that such pathways may be a target of pharmacologic interventions aimed at improving recovery after trauma., (Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.)

Musculoskeletal pain conditions, such as fibromyalgia and low back pain, tend to coexist in affected individuals and are characterized by a report of pain greater than expected based on the results of a standard physical evaluation. The pathophysiology of these conditions is largely unknown, we lack biological markers for accurate diagnosis, and conventional therapeutics have limited effectiveness. Growing evidence suggests that chronic pain conditions are associated with both physical and psychological triggers, which initiate pain amplification and psychological distress; thus, susceptibility is dictated by complex interactions between genetic and environmental factors. Herein, we review phenotypic and genetic markers of common musculoskeletal pain conditions, selected based on their association with musculoskeletal pain in previous research. The phenotypic markers of greatest interest include measures of pain amplification and 'psychological' measures (such as emotional distress, somatic awareness, psychosocial stress and catastrophizing). Genetic polymorphisms reproducibly linked with musculoskeletal pain are found in genes contributing to serotonergic and adrenergic pathways. Elucidation of the biological mechanisms by which these markers contribute to the perception of pain in these patients will enable the development of novel effective drugs and methodologies that permit better diagnoses and approaches to personalized medicine.

Background: Numerous studies focus on intramuscular (i.m.) injection of hypertonic saline-induced muscle pain and nociception. The spatio-temporal characteristics and dynamic variation of spinal neuronal activities elicited by i.m. hypertonic saline remain unknown., Methods: The spatio-temporal variations of c-Fos expression in the lumbar spinal cord exposed to i.m. injection of 5.8% saline were investigated in male rats., Results: After a unilateral i.m. 5.8% saline injection, c-Fos expression in dorsal horn of spinal L4-6 segments was significantly enhanced bilaterally (p < 0.05 and p < 0.001). These 5.8% saline-induced bilateral spinal Fos expression occurred rapidly 0.5 h following the i.m. injection, and reached the peak levels within 1 h, which declined gradually and returned to the control levels within 8 h. Compared with intact rats without i.m. insults, no significant influence of the spinalization on spinal c-Fos expression was found. However, the 5.8% saline-induced increases in Fos expression in intact and spinalized rats differed significantly. During muscle nociception, the c-Fos expression within the superficial layer (laminae I-II) and the deep layer (laminae V-VI) in spinalized rats were significantly lower and higher than that of in intact rats (p < 0.05 and p < 0.001). Fentanyl (20 μg/kg, intraperitoneal) completely attenuated the 5.8% saline intramuscularly induced increases in c-Fos expression in laminae III-VI (p < 0.001), but not laminae I-II., Conclusions: It is suggested that spinal nociceptive neuronal activities in superficial and deep layers may differently be modulated by endogenous descending facilitation and inhibition, respectively., (© 2012 European Federation of International Association for the Study of Pain Chapters.)

Aims: The aim of this study was to determine if genetic variation in the pain-modulating gene DREAM and its pathway genes influence susceptibility to reporting musculoskeletal pain in the population., Methods: Pairwise tag single nucleotide polymorphisms (SNPs) in DREAM, PDYN and OPRK1 were genotyped in a UK population-based discovery cohort in whom pain was assessed using blank body manikins at three time points. Depression and anxiety symptoms were assessed at the first time point. Zero-inflated negative binomial regression was used to test for association between SNPs and the maximum number of pain sites reported (0-29) across the three time points. Significantly associated SNPs (p < 0.05) were subsequently genotyped for validation in a cohort of European men with pain assessed at two time points., Results: Thirty-five SNPs were genotyped in 1055 subjects, of whom 83% reported pain, in the discovery cohort. SNPs in each gene were associated with the maximum number of pain sites reported, were independent of symptoms of anxiety and depression and had a significant cumulative effect (p = 7.0 × 10(-5) ). Significantly associated SNPs were successfully genotyped in 1733 men, 76% of whom reported pain, in the validation cohort, but did not show significant association with the number of pain sites., Conclusions: Genetic variation in the DREAM pathway genes was associated with the extent of pain reporting in a population-based cohort. These findings were not replicated in a single independent cohort; however, given the potential of this pathway as a therapeutic target, further investigation in additional cohorts is warranted., (© 2012 European Federation of International Association for the Study of Pain Chapters.)

Background: There is significant evidence to suggest that psychological and stress-related factors are important predictors of the onset of chronic widespread pain (CWP) and fibromyalgia (FM). The hypothalamic-pituitary-adrenal axis, together with the efferent sympathetic/adrenomedullary system, influence all body organs (including muscles) during short- and long-term threatening stimuli. The aim of this study was to investigate the relationship between genetic variants in adrenergic candidate genes and chronic musculoskeletal complaints (MSCs) in adolescents., Methods: Adolescents from the Western Australian Pregnancy (Raine) Cohort attending the 17-year cohort review completed a questionnaire containing a broad range of psychosocial factors and pain assessment (n = 1004). Blood samples were collected for DNA extraction and genotyping. Genotype data was obtained for 14 single nucleotide polymorphisms (SNPs) in two candidate genes - beta-2 adrenergic receptor (ADRB2) and catecholamine-O-methyltransferase (COMT). Haplotypes were reconstructed for all individuals with genotype data., Results and Conclusion: Both female gender and poor mental health were associated with (1) an increased risk for chronic, disabling comorbid neck and low back pain (CDCP); and (2) an increase in the number of areas of pain. Of the 14 SNPs evaluated, only SNP rs2053044 (ADRB2, recessive model) displayed an association with CDCP [odds ratio (OR) = 2.49; 95% confidence interval (CI) = 1.25, 4.98; p = 0.01] and pain in three to four pain areas in the last month (OR = 1.86; 95% CI = 1.13, 3.06; p = 0.02). These data suggest that genetic variants in ADRB2 may be involved in chronic MSCs., (© 2012 European Federation of International Association for the Study of Pain Chapters.)

Background: Growing pains (GP) is a prevalent familial childhood disorder of unknown aetiology. Familial occurrence of GP, and individual and familial association of GP with restless legs syndrome (RLS) has been reported., Methods: We applied a twin family design to search for evidence of genetic susceptibility to GP, and for a genetic relationship between GP and RLS. The parents of 1843 twin pairs aged 3-16 years were administered a questionnaire, which identified 88 pairs with at least one twin individual fulfilling criteria for GP. Standard questionnaires for history of GP and RLS were completed for these twin pairs, their siblings and parents., Results: Twenty-five of 34 monozygotic (MZ) pairs were concordant for GP, compared with 12 of the 54 dizygotic (DZ) pairs. The casewise concordance was 0.85 and 0.36 for MZ and DZ pairs, respectively (p < 0.001). The lifetime GP prevalence for relatives of twins with GP was 51% for non-twin siblings, 47% for parents. Twenty-three percent of twin individuals with GP met RLS criteria compared with 8% of twin individuals without GP (p = 0.03). Of the twins with GP concordance, 19% met RLS criteria compared with 2% of twins with GP discordance (p = 0.01). In two MZ pairs, one had GP and the other RLS. The lifetime prevalence of RLS was 40% for mothers, and 24% for fathers and 18% for non-twin siblings., Conclusion: This first twin family study of GP provides evidence for a genetic aetiology and for a genetic relationship to RLS., (© 2012 European Federation of International Association for the Study of Pain Chapters.)

In human studies, low COMT (catechol-O-methyltransferase) activity has been associated with increased sensitivity to acute clinical preoperative or postoperative pain. We explored the association between the COMT genotype and three chronic pain conditions: migrainous headache, fibromyalgia, or chronic widespread pain and chronic musculoskeletal pain. Furthermore, we evaluated whether COMT genotype affects the efficacy of opioids in chronic pain. After a systematic literature review, we carried out meta-analyses on the three chronic pain conditions. The efficacy of opioids was evaluated using a systematic review only. The meta-analyses showed that fibromyalgia or chronic widespread pain is the only type of chronic pain that could be associated with the COMT single nucleotide polymorphism rs4680 (Val158Met). Met158, which results in the low-activity variant of COMT, is the risk allele. In chronic clinical pain, the effect of the COMT polymorphism depends on the pain condition. Low COMT activity is not associated with migrainous headache or chronic musculoskeletal pain conditions, but it may increase the risk for fibromyalgia or chronic widespread pain. Low COMT activity increases opioid receptors and enhances opioid analgesia and adverse effects in some cancer pains. Findings from animal studies that have utilized COMT inhibitors elucidate the mechanism behind these findings. In rodent pain models, COMT inhibitors are pronociceptive, except for neuropathic pain models, where nitecapone was found to be antiallodynic. The complex interplay between enhanced adrenergic and dopaminergic activity in different parts of the nociceptive system probably explains the complicated actions of low COMT activity.

Introduction: Arthralgias and myalgias are major side effects associated with aromatase inhibitor (AI) therapy of breast cancer. In a recent genome-wide association study, we identified SNPs - including one that created an estrogen response element near the 3' end of the T-cell leukemia 1A (TCL1A) gene - that were associated with musculoskeletal pain in women on adjuvant AI therapy for breast cancer. We also showed estrogen-dependent, SNP-modulated variation in TCL1A expression and, in preliminary experiments, showed that TCL1A could induce IL-17RA expression. In the present study, we set out to determine whether these SNPs might influence cytokine expression and effect more widely, and, if so, to explore the mechanism of TCL1A-related AI-induced side effects., Methods: The functional genomic experiments performed included determinations of TCL1A, cytokine and cytokine receptor expression in response to estrogen treatment of U2OS cells and lymphoblastoid cell lines that had been stably transfected with estrogen receptor alpha. Changes in mRNA and protein expression after gene knockdown and overexpression were also determined, as was NF-κB transcriptional activity., Results: Estradiol (E2) increased TCL1A expression and, in a TCL1A SNP-dependent fashion, also altered the expression of IL-17, IL-17RA, IL-12, IL-12RB2 and IL-1R2. TCL1A expression was higher in E2-treated lymphoblastoid cell lines with variant SNP genotypes, and induction of the expression of cytokine and cytokine receptor genes was mediated by TCL1A. Finally, estrogen receptor alpha blockade with ICI-182,780 in the presence of E2 resulted in greatly increased NF-κB transcriptional activity, but only in cells that carried variant SNP genotypes. These results linked variant TCL1A SNP sequences that are associated with AI-dependent musculoskeletal pain with increased E2-dependent TCL1A expression and with downstream alterations in cytokine and cytokine receptor expression as well as NF-κB transcriptional activity., Conclusions: SNPs near the 3' terminus of TCL1A were associated with AI-dependent musculoskeletal pain. E2 induced SNP-dependent TCL1A expression, which in turn altered IL-17, IL-17RA, IL-12, IL-12RB2, and IL-1R2 expression as well as NF-κB transcriptional activity. These results provide a pharmacogenomic explanation for a clinically important adverse drug reaction as well as insights into a novel estrogen-dependent mechanism for the modulation of cytokine and cytokine receptor expression.

Fibromyalgia syndrome (FS) is a rheumatic syndrome affecting to 2-3% of individuals of productive age, mainly women. Neuroendocrine and genetic factors may play a significant role in development of the disease which is characterized by diffuse chronic pain and presence of tender points. Several studies have suggested an association between FS, especially pain sensitivity, and polymorphism of the catechol-O-methyltransferase (COMT) gene. The aim of the present study was to characterize the SNPs rs4680 and rs4818 of the COMT gene and assess its influence in pain sensitivity of patients with fibromyalgia screened by the Fibromyalgia Impact Questionnaire (FIQ). DNA was extracted from peripheral blood of 112 patients with fibromyalgia and 110 healthy individuals and was used as template in PCR for amplification of a 185-bp fragment of the COMT gene. The amplified fragment was sequenced for analyses of the SNPs rs4680 and rs4818. The frequency of mutant genotype AA of SNP rs6860 was 77.67% in patients with FS and 28.18% for the control group. For the SNP rs4818, the frequency of mutant genotype CC was 73.21 and 39.09% for patients with FS and controls, respectively. Moreover, the FIQ score was higher in patients with the homozygous mutant genotype for SNPs rs4680 (87.92 points) and rs4818 (86.14 points). These results suggest that SNPs rs4680 and rs4818 of the COMT gene may be associated with fibromyalgia and pain sensitivity in FS Brazilian patients.

Acid-sensing ion channels (ASICs) are activated by acidic pH and may play a significant role in the development of hyperalgesia. Earlier studies show ASIC3 is important for induction of hyperalgesia after muscle insult using ASIC3-/- mice. ASIC3-/- mice lack ASIC3 throughout the body, and the distribution and composition of ASICs could be different from wild-type mice. We therefore tested whether knockdown of ASIC3 in primary afferents innervating muscle of adult wild-type mice prevented development of hyperalgesia to muscle inflammation. We cloned and characterized artificial miRNAs (miR-ASIC3) directed against mouse ASIC3 (mASIC3) to downregulate ASIC3 expression in vitro and in vivo. In CHO-K1 cells transfected with mASIC3 cDNA in culture, the miR-ASIC3 constructs inhibited protein expression of mASIC3 and acidic pH-evoked currents and had no effect on protein expression or acidic pH-evoked currents of ASIC1a. When miR-ASIC3 was used in vivo, delivered into the muscle of mice using a herpes simplex viral vector, both muscle and paw mechanical hyperalgesia were reduced after carrageenan-induced muscle inflammation. ASIC3 mRNA in DRG and protein levels in muscle were decreased in vivo by miR-ASIC3. In CHO-K1 cells co-transfected with ASIC1a and ASIC3, miR-ASIC3 reduced the amplitude of acidic pH-evoked currents, suggesting an overall inhibition in the surface expression of heteromeric ASIC3-containing channels. Our results show, for the first time, that reducing ASIC3 in vivo in primary afferent fibers innervating muscle prevents the development of inflammatory hyperalgesia in wild-type mice, and thus, may have applications in the treatment of musculoskeletal pain in humans., (Copyright © 2011. Published by Elsevier B.V.)

Objective: The aim of the current study was to investigate whether genetic variation in genes across the serotoninergic system is associated with chronic widespread pain (CWP) and the number of pain sites reported., Methods: A discovery cohort, with pain data at 3 time points, was used to investigate genetic associations with 2 phenotypes: 1) CWP (at ≥ 2 time points; n = 164) compared with pain-free controls (at 3 time points; n = 172), and 2) the maximum number of pain sites reported at any 1 of the 3 time points (range of sites 0-29; n = 989). A cohort of 2,285 men for whom a DNA sample and pain data were available (including 203 CWP cases and 929 controls) was used for validation. Pairwise tagging (r(2) > 0.8) single-nucleotide polymorphisms (SNPs) were genotyped. Logistic and zero-inflated negative binomial regression analyses were used to test for SNP associations with CWP and the number of pain sites, respectively., Results: SNPs in HTR2A were associated with both pain phenotypes in the discovery cohort, and a number of these SNP associations were replicated in the validation cohort, some of which were attenuated after adjustment for depression. There was an increased likelihood of having CWP in subjects with 1 or 2 copies of the T allele of rs12584920 (odds ratio [OR] 1.64, 95% confidence interval [95% CI] 1.01-2.60 [P = 0.03] in the discovery cohort, and OR 1.46, 95% CI 1.07-2.00 [P = 0.018] in the validation cohort). A similar association was observed between rs17289394 and the maximum number of pain sites reported in both cohorts. Results from a meta-analysis of the data from the 2 cohorts further strengthened these findings., Conclusion: The findings of this study support the role of HTR2A in the genetic predisposition to musculoskeletal pain., (Copyright © 2011 by the American College of Rheumatology.)