Reduced hypothalamic-pituitary-adrenal axis activity in chronic multi-site musculoskeletal pain: partly masked by depressive and anxiety disorders

The Difficulties of Managing Pain in People Living with Frailty: The Potential for Digital Phenotyping

Pain and frailty are closely linked. Chronic pain is a risk factor for frailty, and frailty is a risk factor for pain. People living with frailty also commonly have cognitive impairment, which can make assessment of pain and monitoring of pain management even more difficult. Pain may be sub-optimally treated in people living with frailty, people living with cognitive impairment and those with both these factors. Reasons for sub-optimal treatment in these groups are pharmacological (increased drug side effects, drug-drug interactions, polypharmacy), non-pharmacological (erroneous beliefs about pain, ageism, bidirectional communication challenges), logistical (difficulty in accessing primary care practitioners and unaffordable cost of drugs), and, particularly in cognitive impairment, related to communication difficulties. Thorough assessment and characterisation of pain, related sensations, and their functional, emotional, and behavioural consequences ("phenotyping") may help to enhance the assessment of pain, particularly in people with frailty and cognitive impairment, as this may help to identify who is most likely to respond to certain types of treatment. This paper discusses the potential role of "digital phenotyping" in the assessment and management of pain in people with frailty. Digital phenotyping is concerned with observable characteristics in digital form, such as those obtained from sensing-capable devices, and may provide novel and more informative data than existing clinical approaches regarding how pain manifests and how treatment strategies affect it. The processing of extensive digital and usual data may require powerful algorithms, but processing these data could lead to a better understanding of who is most likely to benefit from specific and targeted treatments.

Neurophysiological and Psychosocial Mechanisms of Fibromyalgia: A Comprehensive Review and Call for An Integrative Model

Research into the neurobiological and psychosocial mechanisms involved in fibromyalgia has progressed remarkably in recent years. Despite this, current accounts of fibromyalgia fail to capture the complex, dynamic, and mutual crosstalk between neurophysiological and psychosocial domains. We conducted a comprehensive review of the existing literature in order to: a) synthesize current knowledge on fibromyalgia; b) explore and highlight multi-level links and pathways between different systems; and c) build bridges connecting disparate perspectives. An extensive panel of international experts in neurophysiological and psychosocial aspects of fibromyalgia discussed the collected evidence and progressively refined and conceptualized its interpretation. This work constitutes an essential step towards the development of a model capable of integrating the main factors implicated in fibromyalgia into a single, unified construct which appears indispensable to foster the understanding, assessment, and intervention for fibromyalgia.

The Biology of Stress Intolerance in Patients with Chronic Pain—State of the Art and Future Directions

Stress has been consistently linked to negative impacts on physical and mental health. More specifically, patients with chronic pain experience stress intolerance, which is an exacerbation or occurrence of symptoms in response to any type of stress. The pathophysiological mechanisms underlying this phenomenon remain unsolved. In this state-of-the-art paper, we summarised the role of the autonomic nervous system (ANS) and hypothalamus-pituitary-adrenal (HPA) axis, the two major stress response systems in stress intolerance. We provided insights into such mechanisms based on evidence from clinical studies in both patients with chronic pain, showing dysregulated stress systems, and healthy controls supported by preclinical studies, highlighting the link between these systems and symptoms of stress intolerance. Furthermore, we explored the possible regulating role for (epi)genetic mechanisms influencing the ANS and HPA axis. The link between stress and chronic pain has become an important area of research as it has the potential to inform the development of interventions to improve the quality of life for individuals living with chronic pain. As stress has become a prevalent concern in modern society, understanding the connection between stress, HPA axis, ANS, and chronic health conditions such as chronic pain is crucial to improve public health and well-being.

Neuromodulation as a Potential Disease-Modifying Therapy for Osteoarthritis

PURPOSE OF REVIEW

The following review discusses the therapeutic potential of targeting the autonomic nervous system (ANS) for osteoarthritis (OA) treatment and encourages the field to consider the candidacy of bioelectronic medicine as a novel OA treatment strategy.

RECENT FINDINGS

The study of OA pathogenesis has focused on changes occurring at the joint level. As such, treatments for OA have been aimed at the local joint environment, intending to resolve local inflammation and decrease pain. However, OA pathogenesis has shown to be more than joint wear and tear. Specifically, OA-related peripheral and central sensitization can prompt neuroplastic changes in the nervous system beyond the articular joint. These neuroplastic changes may alter physiologic systems, like the neuroimmune axis. In this way, OA and related comorbidities may share roots in the form of altered neuroimmune communication and autonomic dysfunction. ANS modulation may be able to modify OA pathogenesis or reduce the impact of OA comorbidities. Moreover, blocking chronic nociceptive drive from the joint may help to prevent maladaptive nervous system plasticity in OA.

Sciatic nerve injury rebalances the hypothalamic-pituitary-adrenal axis in rats with persistent changes to their social behaviours

Increased glucocorticoids characterise acute pain responses, but not the chronic pain state, suggesting specific modifications to the hypothalamic-pituitary-adrenal (HPA)-axis preventing the persistent nature of chronic pain from elevating basal glucocorticoid levels. Individuals with chronic pain mount normal HPA-axis responses to acute stressors, indicating a rebalancing of the circuits underpinning these responses. Preclinical models of chronic neuropathic pain generally recapitulate these clinical observations, but few studies have considered that the underlying neuroendocrine circuitry may be altered. Additionally, individual differences in the behavioural outcomes of these pain models, which are strikingly similar to the range of behavioural subpopulations that manifest in response to stress, threat and motivational cues, may also be reflected in divergent patterns of HPA-axis activity, which characterises these other behavioural subpopulations. We investigated the effects of sciatic nerve chronic constriction injury (CCI) on adrenocortical and hypothalamic markers of HPA-axis activity in the subpopulation of rats showing persistent changes in social interactions after CCI (Persistent Effect) and compared them with rats that do not show these changes (No Effect). Basal plasma corticosterone did not change after CCI and did not differ between groups. However, adrenocortical sensitivity to adrenocorticotropic hormone (ACTH) diverged between these groups. No Effect rats showed large increases in basal plasma ACTH with no change in adrenocortical melanocortin 2 receptor (MC₂ R) expression, whereas Persistent Effect rats showed modest decreases in plasma ACTH and large increases in MC₂ R expression. In the paraventricular nucleus of the hypothalamus of Persistent Effect rats, single labelling revealed significantly increased numbers of corticotropin releasing factor (CRF) +ve and glucocorticoid receptor (GR) +ve neurons. Double-labelling revealed fewer GR +ve CRF +ve neurons, suggesting a decreased hypothalamic sensitivity of CRF neurons to circulating corticosterone in Persistent Effect rats. We suggest that in addition to rebalancing the HPA-axis, the increased CRF expression in Persistent Effect rats contributes to changes in complex behaviours, and in particular social interactions.

Persistent inflammatory pain is linked with anxiety-like behaviors, increased blood corticosterone, and reduced global DNA methylation in the rat amygdala

Chronic pain increases the risk of developing anxiety, with limbic areas being likely neurological substrates. Despite high clinical relevance, little is known about the precise behavioral, hormonal, and brain neuroplastic correlates of anxiety in the context of persistent pain. Previous studies have shown that decreased nociceptive thresholds in chronic pain models are paralleled by anxiety-like behavior in rats, but there are conflicting ideas regarding its effects on the stress response and circulating corticosterone levels. Even less is known about the molecular mechanisms through which the brain encodes pain-related anxiety. This study examines how persistent inflammatory pain in a rat model would impact anxiety-like behaviors and corticosterone release, and whether these changes would be reflected in levels of global DNA methylation in brain areas involved in stress regulation. Complete Freund's adjuvant (CFA) or saline was administered in the right hindpaw of adult male Wistar rats. Behavioral testing included the measurement of nociceptive thresholds (digital anesthesiometer), motor function (open field test), and anxiety-like behaviors (elevated plus maze and the dark-light box test). Corticosterone was measured via radioimmunoassay. Global DNA methylation (enzyme immunoassay) as well as DNMT3a levels (western blotting) were quantified in the amygdala, prefrontal cortex, and ventral hippocampus. CFA administration resulted in persistent reduction in nociceptive threshold in the absence of locomotor abnormalities. Increased anxiety-like behaviors were observed in the elevated plus maze and were accompanied by increased blood corticosterone levels 10 days after pain induction. Global DNA methylation was decreased in the amygdala, with no changes in DNMT3a abundance in any of the regions examined. Persistent inflammatory pain promotes anxiety -like behaviors, HPA axis activation, and epigenetic regulation through DNA methylation in the amygdala. These findings describe a molecular mechanism that links pain and stress in a well-characterized rodent model.

How Well Do Current Laboratory Biomarkers Inform Clinical Decision-Making in Chronic Pain Management?

OBJECTIVE

Decision-making in chronic pain patients involves a combination of subjective and objective criteria, including patient history, physical examination, imaging, and patient response to prior treatments, clinical experience, probabilities, and recognition of patterns. However, there is a distinct lack of objective laboratory biomarkers in use in routine clinical care. The objective was to review the literature to identify and describe specific biomarkers in chronic pain management.

METHODS

This is a narrative review of the literature regarding the use of laboratory biomarkers in chronic pain. A librarian-assisted literature search of the PubMed, Science Direct, and Google Scholar databases was performed and resulted in 304 possible manuscripts. We included manuscripts assessing laboratory collected biomarkers from urine, serum, cerebrospinal fluid, and saliva. After screening and review of the initial literature search results, a total of 75 manuscripts were included in the narrative review.

CONCLUSION

The studies reviewed suggested that specific biomarkers may help identify those patients at risk of disease development and function as a prognostic indicator for disease progression and treatment response. However, additional research is necessary before specific recommendations can be made, and current clinical decision-making is modified.

Impaired Cognitive Empathy in Outpatients with Chronic Musculoskeletal Pain: A Cross-Sectional Study

Background

In recent years, a growing number of researchers showed significant interest in psychological and social interventions to manage chronic musculoskeletal (MSK) pain. Cognitive and emotional empathy is an attractive and valuable sociopsychological factor that may provide protection and resilience against chronic MSK pain. However, its effect on outpatients remains underexplored.

Objective

To compare the empathy ability between chronic MSK pain outpatients and healthy controls and explore the relationship between cognitive/emotional empathy and chronic pain.

Methods

Patients with chronic MSK pain (n = 22) and healthy controls (n = 26) completed the pain assessment and empathy ability task, utilizing a multidimensional empathy assessment tool with satisfactory reliability and validity (i.e., the Chinese version of the Multifaceted Empathy Test (MET-C)).

Results

The data indicated that the chronic MSK pain outpatients had impaired cognitive empathy (i.e., lower squared cognitive empathy accuracy: Student's t = −2.119, P = 0.040, and longer task completion time: Student's t = 3.382, P = 0.002) compared to healthy controls, and cognitive empathy was negatively correlated with pain intensity (r = −0.614, P = 0.002). Further, the impaired cognitive empathy was present in identifying positive, but not negative emotions.

Conclusion

These results indicate that chronic MSK pain is associated with impaired empathy ability. Our studies contribute to offering a potential direction for developing psychosocial interventions to treat chronic MSK pain.

Multiple Factors Affecting Health-Related Quality of Life in Women With Chronic Multisite Musculoskeletal Pain: A Cross-Sectional Study in Ankara, Turkey

Although chronic multi-site musculoskeletal pain is known to cause decreased physical function and impair work and social life, there is insufficient research about its impact on health-related quality of life (HRQoL) in women. The aim of this study was to investigate multiple factors affecting HRQoL in women with chronic multi-site musculoskeletal pain. This study included 227 women with two or more musculoskeletal areas which were painful during the last 3 months. The HRQoL and musculoskeletal system symptoms were evaluated with the Nottingham Health Profile (NHP) and the Nordic Musculoskeletal Questionnaire (NMQ), respectively. Physical activity level, social functionality and depressive symptoms were assessed with the International Physical Activity Questionnaire-Short Form (IPAQ- SF), Social Functioning Scale (SFS) and Beck Depression Inventory (BDI), respectively. Significant predictors for the total score on the NHP were found to be the number of children (p < 0.001), social engagement/withdrawal scale (p:0.094), the number of regions with musculoskeletal pain during the last year (p:0.002) and last 7 days (p:0.036), depressive symptoms (p < 0.001), current employment status (p:0.084), and the presence of chronic disease (p < 0.001). The results of this study demonstrated that both sociodemographic characteristics, and social and psychological factors may affect the HRQoL in women with chronic multi-site musculoskeletal pain.

Morning and evening salivary cortisol levels in patients with chronic widespread pain and those at high risk

BACKGROUND

Hypothalamic-Pituitary-Adrenal (HPA) axis dysregulation has been implicated in chronic widespread pain (CWP); the hallmark of fibromyalgia (FM). This is the first study to compare HPA axis changes in individuals with CWP and those at high risk of symptom development.

METHODS

We sought to determine differences in morning and evening salivary cortisol levels in FM (n = 19), those at-risk (n = 20) and pain-free controls (n = 17). Risk factors included non-CWP pain, somatic symptoms, illness behaviour and sleep disturbance. We conducted the study in the absence of centrally acting medication, to address limitations of previous research.

RESULTS

Repeated measures ANOVA revealed significant main effects of group (p = 0.003), and time of day (p = 0.002), with no significant interaction. Cortisol levels were higher in FM (p = 0.027) and at-risk (p = 0.003) groups, compared to controls, but there was no significant difference between FM and at-risk groups. The main effect of group remained significant with sleep problems (p = 0.021) and life events (p = 0.007), but was not significant with anxiety (p = 0.076) or depression (p = 0.098) scores as covariates. With sleep problems as a covariate, cortisol levels remained significantly higher only in the at-risk group (p = 0.017).

CONCLUSIONS

This study indicates elevated salivary cortisol in FM and those at high risk, and identifies anxiety, depression and sleep problems as potential contributing factors. The results shed light on the dynamic relationship between stress, mood and sleep disorders and the brain's resilience to pain.

SIGNIFICANCE

This study examines neurobiological changes in chronic widespread pain and high risk individuals. One strength of the study is the absence of centrally acting medication. We found high salivary cortisol common to Fibromyalgia and those at risk and identified contributing factors. Our results offer insight into the early mechanistic changes underlying Fibromyalgia development and open up possibilities for early diagnosis and prevention.

Associations of frequent pain symptoms with excessive daytime sleepiness in adolescents: a longitudinal study

STUDY OBJECTIVES

Pain symptoms, sleep disturbance, and daytime sleepiness are common in adolescents. This study examined the cross-sectional and prospective associations between pain symptoms and excessive daytime sleepiness (EDS) in a large sample of adolescents.

METHODS

Participants were 7,072 adolescents (mean age = 14.6 years) in a follow-up study of behavior and health in Shandong, China. A self-administered structured questionnaire was used to assess pain symptoms (headache, stomachache, and other general pain), body weight and height, sleep, anxiety/depression, substance use, and family environment in November-December in 2015 and one year later. The Chinese adolescent daytime sleepiness scale (CADSS) was used to measure daytime sleepiness.

RESULTS

Of the sample, 19.8% and 23.2% had moderate or severe EDS at baseline and at 1-year follow-up, respectively. The prevalence and 1-year incidence rates of EDS significantly increased with the frequencies of pain symptoms. Frequent pain was significantly associated with increased risk of EDS at baseline (OR=2.01, 95% CI=1.56-2.59), incident EDS (OR=1.41, 95% CI=1.03-1.93), and persistent EDS (OR=2.17, 95% CI=1.52-3.09) while adjusting for adolescent and family covariates, including anxiety/depression, nocturnal sleep duration, insomnia symptoms, frequent snoring, body mass index, and hypnotic use. Similar associations were observed across headache, stomachache, and other pain.

CONCLUSIONS

Frequent pain is significantly and independently associated with increased risk of EDS. Our findings suggest that assessing and treating pain symptoms is important to improve healthy sleep and reduce risk of EDS in adolescents. Further research is needed to understand the underlying psychological and neurobiological mechanisms between pain and daytime sleepiness in adolescents.

MRI-Based Assessment of Masticatory Muscle Changes in TMD Patients after Whiplash Injury

Objective: to investigate the change in volume and signal in the masticatory muscles and temporomandibular joint (TMJ) of patients with temporomandibular disorder (TMD) after whiplash injury, based on magnetic resonance imaging (MRI), and to correlate them with other clinical parameters. Methods: ninety patients (64 women, 26 men; mean age: 39.36 ± 15.40 years), including 45 patients with symptoms of TMD after whiplash injury (wTMD), and 45 age- and sex-matched controls with TMD due to idiopathic causes (iTMD) were included. TMD was diagnosed using the study diagnostic criteria for TMD Axis I, and MRI findings of the TMJ and masticatory muscles were investigated. To evaluate the severity of TMD pain and muscle tenderness, we used a visual analog scale (VAS), palpation index (PI), and neck PI. Results: TMD indexes, including VAS, PI, and neck PI were significantly higher in the wTMD group. In the wTMD group, muscle tenderness was highest in the masseter muscle (71.1%), and muscle tenderness in the temporalis (60.0%), lateral pterygoid muscle (LPM) (22.2%), and medial pterygoid muscle (15.6%) was significantly more frequent than that in the iTMD group (all p < 0.05). The most noticeable structural changes in the masticatory muscles occurred in the LPM with whiplash injury. Volume (57.8% vs. 17.8%) and signal changes (42.2% vs. 15.6%) of LPM were significantly more frequent in the wTMD group than in the iTMD group. The presence of signal changes in the LPM was positively correlated with the increased VAS scores only in the wTMD group (r = 0.346, p = 0.020). The prevalence of anterior disc displacement without reduction (ADDWoR) (53.3% vs. 28.9%) and disc deformity (57.8% vs. 40.0%) were significantly higher in the wTMD group (p < 0.05). The presence of headache, sleep problems, and psychological distress was significantly higher in the wTMD group than in the iTMD group. Conclusion: abnormal MRI findings and their correlations with clinical characteristics of the wTMD group were different from those of the iTMD group. The underlying pathophysiology may differ depending on the cause of TMD, raising the need for a treatment strategy accordingly.

Are psychological symptoms a risk factor for musculoskeletal pain in adolescents?

Adolescent musculoskeletal pain is common and is associated with musculoskeletal pain in adulthood. Psychological symptoms, also common in adolescence, have been shown to be associated with musculoskeletal pain, but the current evidence is mixed and may be dependent on effect modifiers. This study investigated whether adolescents with psychological symptoms (internalizing and externalizing constructs) at age 13 years were at higher odds for musculoskeletal pain at age 17 years and whether the associations were modified by pubertal status and sex. A prospective cohort design examined data on 3865 adolescents from the Avon Longitudinal Study of Parents and Children (ALSPAC). Associations between baseline (aged 13 years) internalizing and externalizing symptoms and musculoskeletal pain at follow-up (aged 17 years) were investigated using logistic regression producing odds ratios (OR) and 95% confidence intervals (95% CI). In total 43.1% of adolescents reported musculoskeletal pain at follow-up. Externalizing symptoms at baseline increased the odds of musculoskeletal pain (OR 1.68, 95% CI 1.28, 2.20), and internalizing symptoms demonstrated a non-significant increase (OR 1.26, 95% CI 0.98, 1.62). Effect modification analysis showed an increased effect dependent on pubertal status.Conclusion: Adolescents with externalizing symptoms, and to some extent internalizing symptoms, are at increased odds of later musculoskeletal pain. Future research is now required to understand the reasons for these associations. What is Known: • Current evidence regarding the association between internalizing symptoms and externalizing symptoms and future musculoskeletal pain in adolescents is mixed. What is New: • This study found that adolescents with externalizing symptoms, and to some extent internalizing symptoms, are at increased odds for musculoskeletal pain, with an increased influence dependent on pubertal status. • These results are of interest for the development of timely preventative interventions designed to reduce the risk of musculoskeletal pain.

Psychosocial Moderators and Mediators of Sensorimotor Exercise in Low Back Pain: A Randomized Multicenter Controlled Trial

The effects of exercise interventions on unspecific chronic low back pain (CLBP) have been investigated in many studies, but the results are inconclusive regarding exercise types, efficiency, and sustainability. This may be because the influence of psychosocial factors on exercise induced adaptation regarding CLBP is neglected. Therefore, this study assessed psychosocial characteristics, which moderate and mediate the effects of sensorimotor exercise on LBP. A single-blind 3-arm multicenter randomized controlled trial was conducted for 12-weeks. Three exercise groups, sensorimotor exercise (SMT), sensorimotor and behavioral training (SMT-BT), and regular routines (CG) were randomly assigned to 662 volunteers. Primary outcomes (pain intensity and disability) and psychosocial characteristics were assessed at baseline (M1) and follow-up (3/6/12/24 weeks, M2-M5). Multiple regression models were used to analyze whether psychosocial characteristics are moderators of the relationship between exercise and pain, meaning that psychosocial factors and exercise interact. Causal mediation analysis were conducted to analyze, whether psychosocial characteristics mediate the exercise effect on pain. A total of 453 participants with intermittent pain (mean age = 39.5 ± 12.2 years, f = 62%) completed the training. It was shown, that depressive symptomatology (at M4, M5), vital exhaustion (at M4), and perceived social support (at M5) are significant moderators of the relationship between exercise and the reduction of pain intensity. Further depressive mood (at M4), social-satisfaction (at M4), and anxiety (at M5 SMT) significantly moderate the exercise effect on pain disability. The amount of moderation was of clinical relevance. In contrast, there were no psychosocial variables which mediated exercise effects on pain. In conclusion it was shown, that psychosocial variables can be moderators in the relationship between sensorimotor exercise induced adaptation on CLBP which may explain conflicting results in the past regarding the merit of exercise interventions in CLBP. Results suggest further an early identification of psychosocial risk factors by diagnostic tools, which may essential support the planning of personalized exercise therapy. Level of Evidence: Level I. Clinical Trial Registration: DRKS00004977, LOE: I, MiSpEx: grant-number: 080102A/11-14. https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00004977.

Evaluating sensory profiles in nociplastic chronic low back pain: a cross-sectional validation study

BACKGROUND

Sensory profiles (SPs) may be useful in classifying patients based on sensory sensitivity and behavioral responses to stimuli to develop personalized treatments for nonspecific chronic low back pain (CLBP). The Adolescent/Adult Sensory Profile (AASP) identifies four sensitivity and behavioral response-related quadrants: Sensory Sensitive, Sensation Avoiding, Low Registration, and Sensation Seeking. It is an appropriate questionnaire for evaluating SPs; however, it has not been validated in CLBP.

OBJECTIVES

To assess the internal consistency, test-retest reliability, agreement, and construct validity of the AASP in a CLBP population with nociplastic pain in primary care physiotherapy.

DESIGN

Two evaluations were performed at a 2-week interval in this non-experimental cross-sectional study.

PARTICIPANTS

Patients with CLBP.

METHODS

Questionnaires were used to compare outcomes with the AASP. Reliability was evaluated by assessing internal consistency and test-retest reliability. Construct validity was evaluated in response to the a priori hypothesis.

RESULTS

Ninety patients with CLBP were included. Internal consistency was excellent for all SPs (Cronbach's alpha, 0.91-0.92). Test-retest reliability Intraclass Correlation Coefficient (ICC (3,2)) 0.82-0.87, for the SPs (95% CI 0.74-0.91, p< .001). Construct validity correlated positively with Low Registration, Sensory Sensitive, and Sensation Avoiding and negatively with Sensation Seeking.

CONCLUSION

The AASP is suitable for evaluating SPs in primary care CLBP patients.

The Microbiome and the Gut-Liver-Brain Axis for Central Nervous System Clinical Pharmacology: Challenges in Specifying and Integrating In Vitro and In Silico Models

The complexity of integrating microbiota into clinical pharmacology, environmental toxicology, and opioid studies arises from bidirectional and multiscale interactions between humans and their many microbiota, notably those of the gut. Hosts and each microbiota are governed by distinct central dogmas, with genetics influencing transcriptomics, proteomics, and metabolomics. Each microbiota's metabolome differentially modulates its own and the host's multi‐omics. Exogenous compounds (e.g., drugs and toxins), often affect host multi‐omics differently than microbiota multi‐omics, shifting the balance between drug efficacy and toxicity. The complexity of the host‐microbiota connection has been informed by current methods of in vitro bacterial cultures and in vivo mouse models, but they fail to elucidate mechanistic details. Together, in vitro organ‐on‐chip microphysiological models, multi‐omics, and in silico computational models have the potential to supplement the established methods to help clinical pharmacologists and environmental toxicologists unravel the myriad of connections between the gut microbiota and host health and disease.

Effects and Mechanisms of Electroacupuncture on Chronic Inflammatory Pain and Depression Comorbidity in Mice

Comorbidity of chronic pain and major depression disorder (MDD) are common diseases. However, the mechanisms of electroacupuncture (EA) and the responses of N-methyl-D-aspartate receptors in the brain remain unclear. Three injections of complete Freund's adjuvant (CFA) were administered to induce chronic inflammatory pain (CIP). EA was then performed once every other day from days 14 to 28. Behavior tests of chronic pain and depression were evaluated to make sure of the successful induction of comorbidity. We used Western blotting to analyze brain tissue from the prefrontal cortex (PFC), hippocampus, and hypothalamus for levels of phosphorylated N-methyl-D-aspartate receptor subunit 1 (pNR1), NR1, pNR2B, NR2B, and calcium/calmodulin-dependent protein kinase type II alpha isoform (pCaMKIIα). The mechanical hyperalgesia, thermal hyperalgesia, and depression were observed in the CIP group. Furthermore, decreased levels of N-methyl-D-aspartate receptors (NMDARs) were also noted. Not Sham EA but EA reversed chronic pain and depression as well as the decreased levels of NMDA in the signaling pathway. The CFA injections successfully induced a significant comorbidity model. EA treated the comorbidity by upregulating the NMDA signaling pathway in the PFC, hippocampus, and hypothalamus. Our results indicated significant mechanisms of comorbidity of chronic pain and MDD and EA-analgesia that involves the regulation of the NMDAR signaling pathway. These findings may be relevant to the evaluation and treatment of comorbidity of chronic pain and MDD.

The effect of treatment regimens on salivary cortisol levels in patients with chronic musculoskeletal disorders

BACKGROUND

Increased levels of circulating cortisol have been associated with pain severity in patients with chronic musculoskeletal disorders (CMD). Little is known about the potential association between pain management and salivary cortisol alterations in CPM patients treated with different regimens.

OBJECTIVES

This prospective feasibility study aimed to determine the effect of two treatment regimens in comparison with sham therapy on pain intensity and disability and salivary cortisol concentration (SCC) in patients with CMD.

METHODS

Thirty patients were randomly assigned to 3 groups of 10: two experimental groups (A and B) and a control group (C). The experimental groups followed physiotherapy treatment (A) or acupuncture (B), while the control group (C) followed a sham therapy for 10 sessions. Pain data were collected using the Chronic Pain Grade (CPG) questionnaire and SCC was measured by enzyme-linked immunosorbent assay at pre- and posttreatment.

RESULTS

Repeated-measures analysis of variance showed that patients treated with acupuncture experienced greater decreases in pain intensity/pain disability (P < 0.05) than the physiotherapy and sham therapy groups. No statistical differences were found between the three groups for the SCC outcome variable. Bonferroni adjustments showed that the mean values of SCC were significantly decreased at posttreatment (P < 0.05) across the three groups.

CONCLUSION

There was a significant decrease in both pain and cortisol outcomes at posttreatment in patients with CMD. Because of the limitations of this study, we cannot draw conclusions regarding whether the lower SCC could be an indication of pain reduction in patients with CMD.

MgO and ZnO nanoparticles anti-nociceptive effect modulated by glutamate level and NMDA receptor expression in the hippocampus of stressed and non-stressed rats

The anti-nociceptive mechanisms of MgO and ZnO nanoparticles have not been thoroughly investigated; in this study, we evaluated the effects of anti-nociceptive dose of MgO and ZnO NPs on glutamate level and NMDA receptor subunits expression (NR1, NR2 and NR2B) in the rat whole hippocampus with and without acute restraint stress. Adult rats were divided into control, MgO and ZnO NPs 5 mg/kg, the stress of 90 min alone and with MgO or ZnO NPs 5 mg/kg groups. All components injected intraperitoneally and the nociceptive response was measured with hot plate apparatus 90 min after injections or stress induction. Magnesium, zinc, glutamate levels and NMDA receptor subunits expression were measured in the animal hippocampus. MgO NPs, ZnO NPs and acute stress induced anti-nociceptive effect. MgO NPs observably decreased glutamate and increased magnesium levels and NR2B subunit expression. ZnO NPs decreased glutamate level. Stress elevated endogenous magnesium and zinc levels and also the NR2B expression, but did not change glutamate level. MgO and ZnO NPs in the presence of stress increased the glutamate level and ZnO NPs increased the zinc and the NR2A expression. Stress decreased endogenous magnesium in the hippocampus. MgO and ZnO NPs could affect pain perception by changing glutamate level in the whole hippocampus tissue, while ion level changes followed by injection could probably affect the gene expression in the presence and the absence of stress. It seems that stress indirectly could adverse nanoparticles effects on glutamate level and increase zinc ion releasing from ZnO NPs by activating the gene expression without affecting pain perception.

Transitioning from acute to chronic pain: a simulation study of trajectories of low back pain

Background

Identifying how pain transitions from acute to chronic is critical in designing effective prevention and management techniques for patients’ well-being, physically, psychosocially, and financially. There is an increasingly pressing need for a quantitative and predictive method to evaluate how low back pain trajectories are classified and, subsequently, how we can more effectively intervene during these progression stages.

Methods

In order to better understand pain mechanisms, we investigated, using computational modeling, how best to describe pain trajectories by developing a platform by which we studied the transition of acute chronic pain.

Results

The present study uses a computational neuroscience-based method to conduct such trajectory research, motivated by the use of hypothalamic–pituitary–adrenal (HPA) axis activity-history over a time-period as a way to mimic pain trajectories. A numerical simulation study is presented as a “proof of concept” for this modeling approach.

Conclusions

This model and its simulation results have highlighted the feasibility and the potential of developing such a broader model for patient evaluations.

Socioeconomic Deprivation, Adverse Childhood Experiences and Medical Disorders in Adulthood: Mechanisms and Associations

Severe socioeconomic deprivation (SED) and adverse childhood experiences (ACE) are significantly associated with the development in adulthood of (i) enhanced inflammatory status and/or hypothalamic-pituitary-adrenal (HPA) axis dysfunction and (ii) neurological, neuroprogressive, inflammatory and autoimmune diseases. The mechanisms by which these associations take place are detailed. The two sets of consequences are themselves strongly associated, with the first set likely contributing to the second. Mechanisms enabling bidirectional communication between the immune system and the brain are described, including complex signalling pathways facilitated by factors at the level of immune cells. Also detailed are mechanisms underpinning the association between SED, ACE and the genesis of peripheral inflammation, including epigenetic changes to immune system-related gene expression. The duration and magnitude of inflammatory responses can be influenced by genetic factors, including single nucleotide polymorphisms, and by epigenetic factors, whereby pro-inflammatory cytokines, reactive oxygen species, reactive nitrogen species and nuclear factor-κB affect gene DNA methylation and histone acetylation and also induce several microRNAs including miR-155, miR-181b-1 and miR-146a. Adult HPA axis activity is regulated by (i) genetic factors, such as glucocorticoid receptor polymorphisms; (ii) epigenetic factors affecting glucocorticoid receptor function or expression, including the methylation status of alternative promoter regions of NR3C1 and the methylation of FKBP5 and HSD11β2; (iii) chronic inflammation and chronic nitrosative and oxidative stress. Finally, it is shown how severe psychological stress adversely affects mitochondrial structure and functioning and is associated with changes in brain mitochondrial DNA copy number and transcription; mitochondria can act as couriers of childhood stress into adulthood.

Hypothalamic-pituitary-adrenal axis function in traumatic spinal cord injury-related neuropathic pain: a case-control study

PURPOSE

This study aimed to investigate the hypothalamic-pituitary-adrenal (HPA) axis in spinal cord injury (SCI)-related neuropathic pain (NP) using dynamic adrenocorticotropic hormone (ACTH) stimulation tests.

METHODS

This case-control study was conducted with 22 patients diagnosed with traumatic chronic spinal cord injury (15 with and 7 without neuropathic pain) and ten age- and sex-matched healthy control subjects. Collected data included socio-demographic variables, SCI characteristics, and level of NP using a numeric rating scale (NRS) and the Leeds Assessment of Neuropathic Symptoms and Signs pain scale (LANSS). HPA axis function was measured via low-dose (1 μg) and standard-dose (250 μg) ACTH tests (LDT and SDT, respectively).

RESULTS

No significant differences existed regarding peak cortisol responses or area under the curve (AUC) of cortisol responses between the SCI patients with NP and healthy controls using LDT and SDT. In the SCI patients without pain, cortisol responses were significantly lower than those in the healthy controls for LDT and SDT. Peak cortisol and AUC responses of the LDT and SDT were positively correlated with NRS in SCI patients with NP.

CONCLUSIONS

This study demonstrated that, in chronic SCI patients with NP, basal cortisol levels are relatively higher compared to healthy controls, and that HPA axis can be activated with low- and standard-dose ACTH stimulation tests. Although NP following SCI was not significantly associated with hypo- or hypercortisolemia, either after low- or standard-dose ACTH stimulation test, the severity of NP during chronic SCI may be positively associated with HPA axis activity.

Multiple types of somatic pain increase suicide attempts and depression: A nationwide community sample of Korean adults

OBJECTIVE

Somatic pain is an important risk factor for suicide and suicidal behaviors. However, the association between the number of somatic pain conditions and lifetime suicide attempts (LSA) has not been well established yet. Therefore, the objective of this study was to examine associations between LSA and multiple somatic pain (MSP), singe pain, and no pain in a nationwide survey.

METHODS

A total of 12,532 adults were randomly selected from the population using the one-person-per-household method. Each participant completed a face-to-face interview using the Korean Composite International Diagnostic Interview (K-CIDI) with Suicide Module, and the Barratt Impulsiveness Scale 11 (BIS-11). The MSP was defined as pain in two or more parts of one's body, including abdominal pain, back pain, arthralgia, arm or leg pain, chest pain, headache, menstrual pain, dysuria, genital pain, and other pain.

RESULTS

Among 12,532 subjects, 858 (6.85%) had MSP. Among the three groups (MSP, single pain, and no pain) of subjects, the MSP group had higher percentages of females, those with lower education, and divorced/widowed/separated individuals. However, there were no significant differences in monthly income or residence among the three groups. The MSP group showed four times higher suicide attempts and six times higher multiple attempts than did the no pain group. The BIS total score of the MSP group was the highest among the three groups. Genital pain showed the highest odds ratio for LSA. The higher the number of somatic pain, the higher the odds ratios were for LSA, major depressive disorder (MDD), and anxiety disorders. Subjects having both MSP and MDD showed a significant association with LSA (AOR = 14.78, 95% CI 10.08-21.67, p < 0.001) compared to those having neither somatic pain nor MDD.

CONCLUSIONS

MSP was significantly associated with LSA. It had greater prevalence among individuals reporting a higher number of somatic pain conditions and comorbid MDD.

The molecular neurobiology of chronic pain-induced depression

The increasing number of individuals with comorbidities poses an urgent need to improve the management of patients with multiple co-existing diseases. Among these comorbidities, chronic pain and mood disorders, two long-lasting disabling conditions that significantly reduce the quality of life, could be cited first. The recent development of animal models accelerated the studies focusing on the underlying mechanisms of the chronic pain and depression/anxiety comorbidity. This review provides an overview of clinical and pre-clinical studies performed over the past two decades addressing the molecular aspects of the comorbid relationship of chronic pain and depression. We thus focused on the studies that investigated the molecular characteristics of the comorbid relationship between chronic pain and mood disorders, especially major depressive disorders, from the genetic and epigenetic point of view to key neuromodulators which have been shown to play an important role in this comorbidity.

Central sensitization in chronic pain and medically unexplained symptom research: A systematic review of definitions, operationalizations and measurement instruments

OBJECTIVE

Central sensitization (CS), a mechanism explaining the persistence of symptoms, has been the focus of many research projects. Explanations given to patients with chronic pain are often based on this mechanism. It is hypothesized that CS also plays an important role in the persistence of medically unexplained symptoms (MUS). However, definitions and operationalizations of CS vary. We conducted a systematic review of definitions, operationalizations and measurement instruments of CS.

METHODS

We searched in PubMed, EMBASE, PsycINFO, Cinahl and The Cochrane Library till September 2017 and included papers that addressed CS in relation to chronic pain and/or MUS. Two reviewers independently selected, analysed and classified information from the selected publications. We performed a thematic analysis of definitions and operationalizations. We listed the measurement instruments.

RESULTS

We included 126 publications, 79 publications concerned chronic pain, 47 publications concerned MUS. Definitions of CS consistently encompass the theme hyperexcitability of the central nervous system (CNS). Additional themes are variably present: CNS locations, nature of sensory input, reduced inhibition and activation and modulation of the NDMA receptor. Hyperalgesia and allodynia are widely mentioned as operationalizations of CS. Quantitative sensory testing (QST) and (f)MRI are the most reported measurement instruments.

CONCLUSIONS

There is consensus that hyperexcitability is the central mechanism of CS. Operationalizations are based on this mechanism and additional components. There are many measurement instruments available, whose clinical value has still to be determined. There were no systematic differences in definitions and operationalizations between the publications addressing MUS and those addressing chronic pain.

Lowering barometric pressure induces neuronal activation in the superior vestibular nucleus in mice

Weather changes accompanied by decreases in barometric pressure are suggested to trigger meteoropathy, i.e., weather-related pain. We previously reported that neuropathic pain-related behavior in rats is aggravated by lowering barometric pressure, and that this effect is abolished by inner ear lesions. These results suggest that mechanisms that increase vestibular neuronal activity may parallel those that contribute to meteoropathy generation. However, it remains unknown whether changes in barometric pressure activate vestibular neuronal activity. To address this issue, we used expression of c-Fos protein as a marker for neural activation. Male and female mice were placed in a climatic chamber, and the barometric pressure was lowered by 40 hPa, from 1013 hPa, for 50 min (LP stimulation). The total number of c-Fos-positive cells in the vestibular nuclei was counted bilaterally after LP stimulation. We also video-recorded mouse behaviors and calculated the total activity score during the LP stimulation. LP stimulation resulted in significant c-Fos expression in the superior vestibular nucleus (SuVe) of male and female mice. There was no effect of LP stimulation on the total activity score. These data show that distinct neurons in the SuVe respond to LP stimulation. Similar mechanisms may contribute to the generation of meteoropathy in humans.

Phenotypic Characterization of Paclitaxel-Induced Peripheral Neuropathy in Cancer Survivors

CONTEXT

Although paclitaxel is one of the most commonly used drugs to treat breast, ovarian, and lung cancers, little is known about the impact of paclitaxel-induced peripheral neuropathy (PIPN) on cancer survivors.

OBJECTIVES

The purposes of this study were to evaluate for differences in demographic and clinical characteristics as well as measures of sensation, balance, upper extremity function, perceived stress, symptom burden, and quality of life (QOL) between survivors who received paclitaxel and did (n = 153) and did not (n = 58) develop PIPN.

METHODS

Pain characteristics associated with PIPN are described in detail. Both subjective and objective measures were used to evaluate the impact of PIPN.

RESULTS

Survivors with PIPN were significantly older, had a higher body mass index, and a worse comorbidity profile. The duration of PIPN was almost four years, and pain scores were in the moderate range. Compared with survivors without PIPN, survivors with PIPN had a higher number of upper and lower extremity sites that had lost light touch, cold, and pain sensations. Survivors with PIPN had worse upper extremity function, more problems with balance, a higher symptom burden, and higher levels of perceived stress. In addition, survivors with PIPN had worse QOL scores particularly in the domain of physical functioning.

CONCLUSION

The findings from this large descriptive study are the first to document the impact of PIPN on survivors' symptom burden, functional status, and QOL.

Undercover Dogs: Pet Dogs in the Sleep Environment of Patients with Chronic Pain

(1) Background: Chronic pain is a significant and prevalent condition in many industrialized nations. Pain and sleep’s reciprocal nature suggests that interventions to improve sleep may decrease pain symptoms. Little attention has been paid to the influence that owning a pet dog has on the pain/sleep relationship. Typical advice to remove pets from the bedroom negates the possible positive benefit of human-animal co-sleeping. Aim: To investigate pain patients’ perceived impact of pet dog ownership on sleep. (2) Methods: We carried out a content analysis of interview data focused on the impact of pet dog ownership on sleep. The qualitative dataset comes from a subgroup of participants in a larger study examining the pain patient/canine relationship. This subgroup of participants from the larger study was asked, “Does your dog have a positive or negative impact on your sleep?” The data were thematically coded using an iterative approach. (3) Findings: Codes included: companionship; physical presence/’cuddles’; routine/schedule; distraction from anxiety/worry at night; reassuring/protective presence; active intervention to keep participant safe; daytime activity to promote sleeping at night; and reciprocal concern for the sleep of the pet dog. (4) Conclusions: Pet dogs may play important roles in helping people with chronic pain achieve sleep onset and maintenance. Removing the dog to improved sleep could be counter-productive and lead to additional sleep-related issues.

Associations Between Perceived Stress and Chemotherapy-Induced Peripheral Neuropathy and Otoxicity in Adult Cancer Survivors

CONTEXT

The most common adverse effects from neurotoxic chemotherapy are chemotherapy-induced neuropathy (CIPN), hearing loss, and tinnitus. Although associations between perceived stress and persistent pain, hearing loss, and tinnitus are documented, no studies have examined these associations in cancer survivors who received neurotoxic chemotherapy.

OBJECTIVES

In this cross-sectional study, we evaluated for associations between perceived stress and the occurrence of CIPN, hearing loss, and tinnitus, in 623 adult cancer survivors who received platinum and/or taxane compounds.

METHODS

Survivors completed self-report measures of hearing loss, tinnitus, and perceived stress (i.e., Impact of Events Scale-Revised [IES-R]). Separate logistic regression analyses were done for each neurotoxicity to evaluate whether each of the IES-R subscale (i.e., intrusion, avoidance, hyperarousal) and total scores made a significant independent contribution to neurotoxicity group membership.

RESULTS

Of the 623 survivors in this study, 68.4% had CIPN, 34.5% reported hearing loss, and 31.0% reported tinnitus. Older age, higher body mass index, poorer functional status, being born prematurely, cancer diagnosis, and higher intrusion (P = 0.013), hyperarousal (P = 0.014), and total (P = 0.047) IES-R scores were associated with CIPN. Older age, being male, poorer functional status, a worse comorbidity profile, and a higher IES-R hyperarousal (P = 0.007) score were associated with hearing loss. Being male, having less education, a worse comorbidity profile, and a higher IES-R hyperarousal (P = 0.029) score were associated with tinnitus.

CONCLUSION

These findings suggest that increased levels of perceived stress are associated with the most common chemotherapy-induced neurotoxicities.

Stress and Alterations in the Pain Matrix: A Biopsychosocial Perspective on Back Pain and Its Prevention and Treatment

The genesis of chronic pain is explained by a biopsychosocial model. It hypothesizes an interdependency between environmental and genetic factors provoking aberrant long-term changes in biological and psychological regulatory systems. Physiological effects of psychological and physical stressors may play a crucial role in these maladaptive processes. Specifically, long-term demands on the stress response system may moderate central pain processing and influence descending serotonergic and noradrenergic signals from the brainstem, regulating nociceptive processing at the spinal level. However, the underlying mechanisms of this pathophysiological interplay still remain unclear. This paper aims to shed light on possible pathways between physical (exercise) and psychological stress and the potential neurobiological consequences in the genesis and treatment of chronic pain, highlighting evolving concepts and promising research directions in the treatment of chronic pain. Two treatment forms (exercise and mindfulness-based stress reduction as exemplary therapies), their interaction, and the dose-response will be discussed in more detail, which might pave the way to a better understanding of alterations in the pain matrix and help to develop future prevention and therapeutic concepts.

Morning cortisol and fasting glucose are elevated in women with chronic widespread pain independent of comorbid restless legs syndrome

Background and aims:

Chronic widespread pain (CWP) is associated with poor quality of sleep, but the detailed underlying mechanisms are still not fully understood. In this study we investigated the influence of CWP on morning cortisol and fasting glucose concentrations as well as sleep disordered breathing.

Methods:

In this case-control study, subjects with CWP (n=31) and a control group without CWP (n=23) were randomly selected from a population-based cohort of women. Current pain intensity, sleep quality, excessive daytime sleepiness [Epworth sleepiness scale (ESS)], psychiatric comorbidity and occurrence of restless legs syndrome (RLS) were assessed. Overnight polygraphy was applied to quantify sleep apnoea, airflow limitation and attenuations of finger pulse wave amplitude (>50%) as a surrogate marker for increased skin sympathetic activity. Morning cortisol and fasting glucose concentrations were determined. Generalised linear models were used for multivariate analyses.

Results:

CWP was associated with higher cortisol (464±141 vs. 366±111 nmol/L, p=0.011) and fasting glucose (6.0±0.8 vs. 5.4±0.7 mmol/L, p=0.007) compared with controls. The significance remained after adjustment for age, body mass index, RLS and anxiety status (β=122±47 nmol/L and 0.89±0.28 mmol/L, p=0.009 and 0.001, respectively). The duration of flow limitation in sleep was longer (35±22 vs. 21±34 min, p=0.022), and pulse wave attenuation was more frequent (11±8 vs. 6±2 events/h, p=0.048) in CWP subjects compared with controls. RLS was associated with higher ESS independent of CWP (β=3.1±1.3, p=0.018).

Conclusions:

Elevated morning cortisol, impaired fasting glucose concentration and increased skin sympathetic activity during sleep suggested an activated adrenal medullary system in subjects with CWP, which was not influenced by comorbid RLS.

Implications:

CWP is associated with activated stress markers that may deteriorate sleep.

[Adaptation to physical activity and mental stress in the context of pain : Psychobiological aspects]

The genesis of chronic pain is predominantly explained by a multidimensional pain model approach that is based on the dysfunctional influence of biological, psychological and social variables as key risk factors inducing aberrant long-term changes. Biological facets comprise adaptation processes on the neuronal, musculoskeletal and (psycho) biological level that can be influenced by physical training or psychosocial factors, such as stress. These factors can play a causative role in developing dysfunctional adaptation mechanisms, which in turn prepare the biological ground to facilitate negative long-term changes in the peripheral and central nervous systems. Hence, these processes can be assumed to be fundamentally involved in the transition from acute to chronic and persistent pain. The aim of this review article is to discuss hypotheses for the genesis of chronic pain and possible treatment strategies. Selected research results about maladaptive processes in chronic pain due to psychological stress and physical activity are presented in order to inspire discussions about the ideal dose-response relationship of physical activity and the combination of different therapeutic concepts.

Hypothalamic Dysfunction and Multiple Sclerosis: Implications for Fatigue and Weight Dysregulation

Signs and symptoms of multiple sclerosis are usually attributed to demyelinating lesions in the spinal cord or cerebral cortex. The hypothalamus is a region that is often overlooked yet controls many important homeostatic functions, including those that are perturbed in multiple sclerosis. In this review we discuss how hypothalamic dysfunction may contribute to signs and symptoms in people with multiple sclerosis. While dysfunction of the hypothalamic-pituitary-adrenal axis is common in multiple sclerosis, the effects and mechanisms of this dysfunction are not well understood. We discuss three hypothalamic mechanisms of fatigue in multiple sclerosis: (1) general hypothalamic-pituitary-adrenal axis hyperactivity, (2) disordered orexin neurotransmission, (3) abnormal cortisol secretion. We then review potential mechanisms of weight dysregulation caused by hypothalamic dysfunction. Lastly, we propose future studies and therapeutics to better understand and treat hypothalamic dysfunction in multiple sclerosis. Hypothalamic dysfunction appears to be common in multiple sclerosis, yet current studies are underpowered and contradictory. Future studies should contain larger sample sizes and standardize hormone and neuropeptide measurements.

The IL-1Ra gene variable number tandem repeat variant is associated with susceptibility to temporomandibular disorders in Turkish population

BACKGROUND

Temporomandibular joint disorders (TMD) are a group of disorders involving temporomandibular joint and related structures. Interleukine-1 receptor antagonist (IL-1Ra) is an important anti-inflammatory molecule that competes with other interleukin-1 molecules. This study was designed to investigate the possible association of the IL-1Ra VNTR variant with the risk of TMD in the Turkish population.

METHODS

Peripheral blood samples were collected from 100 patients with TMD (23 males, 77 females) and 110 healthy individuals (35 males, 75 females). Genotyping of IL-1Ra 86 bp VNTR variant was evaluated by gel electrophoresis after polymerase chain reaction (PCR).

RESULTS

Our results show that there is a statistically significant difference between TMD patients and control group with respect to IL-1Ra genotype distribution and allele frequencies. 1.2, 1.4, and 4.4 genotypes were more common in patients, while 2.2 and 3.3 genotypes were rarer (P<.000). Frequency of alleles 1 and 4 was higher in patient groups (P<.000), whereas alleles 2 and 3 had a lower frequency in patients with TMD (P<.000).

CONCLUSIONS

This is the first correlation study that evaluates the association between IL-1Ra gene VNTR variant and TMD. The VNTR variant related to IL-1Ra gene showed a strong pattern of association with TMD that may have a potential impact on disease counseling and management. Larger studies with various ethnicities are needed to establish the impact of IL-1Ra VNTR variant on risk of developing TMD.

Chronic Pain and Chronic Stress: Two Sides of the Same Coin?

Pain and stress share significant conceptual and physiological overlaps. Both phenomena challenge the body's homeostasis and necessitate decision-making to help animals adapt to their environment. In addition, chronic stress and chronic pain share a common behavioral model of failure to extinguish negative memories. Yet, they also have discrepancies such that the final brain endophenotype of posttraumatic stress disorder, depression, and chronic pain appears to be different among the three conditions, and the role of the hypothalamic-pituitary-adrenal axis remains unclear in the physiology of pain. Persistence of either stress or pain is maladaptive and could lead to compromised well-being. In this brief review, we highlight the commonalities and differences between chronic stress and chronic pain, while focusing particularly on the central role of the limbic brain. We assess the current attempts in the field to conceptualize and understand chronic pain, within the context of knowledge gained from the stress literature. The limbic brain-including hippocampus, amygdala, and ventromedial pre-frontal cortex-plays a critical role in learning. These brain areas integrate incoming nociceptive or stress signals with internal state, and generate learning signals necessary for decision-making. Therefore, the physiological and structural remodeling of this learning circuitry is observed in conditions such as chronic pain, depression, and posttraumatic stress disorder, and is also linked to the risk of onset of these conditions.

Mechanisms of Neurotoxic Symptoms as a Result of Breast Cancer and Its Treatment: Considerations on the Contribution of Stress, Inflammation, and Cellular Bioenergetics

PURPOSE OF REVIEW

Breast cancer and its treatment are associated with a range of neurotoxic symptoms, such as fatigue, cognitive impairment, and pain. Although these symptoms generally subside after treatment completion, they become chronic in a significant subset of patients. We here summarize recent findings on neuroinflammation, stress, and mitochondrial dysfunction as mechanistic pathways leading to neurotoxic symptom experience in breast cancer patients and survivors.

RECENT FINDINGS

Neuroinflammation related to stress or cancer treatment and stress resulting from diagnosis, treatment, or (cancer-related) worrying are important predictors of a neurotoxic symptom experience, both during and after treatment for breast cancer. Both inflammation and stress hormones, as well as cancer treatment, can induce mitochondrial dysfunction resulting in reduced cellular energy.

SUMMARY

We propose reduced cellular energy (mitochondrial dysfunction) induced by inflammation, oxygen radical production, and stress as a result of cancer and/or cancer treatment as a final mechanism underlying neurotoxic symptoms.

Neuroplasticity of Supraspinal Structures Associated with Pathological Pain

Peripheral nerve and spinal cord injuries, along with other painful syndromes such as fibromyalgia, diabetic neuropathy, chemotherapeutic neuropathy, trigeminal neuralgia, complex regional pain syndrome, and/or irritable bowel syndrome, cause several neuroplasticity changes in the nervous system along its entire axis affecting the different neuronal nuclei. This paper reviews these changes, focusing on the supraspinal structures that are involved in the modulation and processing of pain, including the periaqueductal gray matter, red nucleus, locus coeruleus, rostral ventromedial medulla, thalamus, hypothalamus, basal ganglia, cerebellum, habenula, primary, and secondary somatosensory cortex, motor cortex, mammillary bodies, hippocampus, septum, amygdala, cingulated, and prefrontal cortex. Hyperexcitability caused by the modification of postsynaptic receptor expression, central sensitization, and potentiation of presynaptic delivery of neurotransmitters, as well as the reduction of inhibitory inputs, changes in dendritic spine, neural circuit remodeling, alteration of gray matter, and upregulation of proinflammatory mediators (e.g., cytokines) by reactivation of astrocytes and microglial cells are the main functional, structural, and molecular neuroplasticity changes observed in the above supraspinal structures, associated with pathological pain. Studying these changes in greater depth may lead to the implementation and improvement of new therapeutic strategies against pathological pain. Anat Rec, 300:1481-1501, 2017. © 2017 Wiley Periodicals, Inc.

Anti-Müllerian Hormone Levels and Urinary Cortisol in Women With Chronic Abdominal Pain

OBJECTIVE

To explore the association of hypothalamic-pituitary-adrenal activity with ovarian functioning in women with and without chronic abdominal pain (CAP).

DESIGN AND SETTING

A secondary data analysis was performed with data from female participants in a natural history protocol at the National Institutes of Health.

PARTICIPANTS

A total of 36 women (age range = 19-39 years, mean = 27.11 years) were included in the study.

METHODS

This pilot study was conducted with a subset of participants enrolled in a natural history protocol conducted in the Hatfield Clinical Research Center at the National Institutes of Health. The parent study included participants with and without CAP who provided a 5-hour urine sample for determination of cortisol levels and serum samples for determination of circulating levels of cortisol, luteinizing hormone, and follicle-stimulating hormone. CAP was defined as presence or absence of chronic pain for at least 6 months and was determined via self-report.

RESULTS

Anti-Müllerian hormone (AMH) concentrations declined significantly with age as expected. When AMH levels were dichotomized as normal or abnormal (defined as higher or lower than age-specific normative ranges, respectively), there were significant associations between abnormal AMH levels and CAP and urine cortisol levels. Participants with CAP or low urine cortisol levels were significantly more likely to have abnormal AMH levels.

CONCLUSION

Results suggest that chronic abdominal pain and hypothalamic-pituitary-adrenal dysregulation may be associated with abnormal AMH levels.

The brain-derived neurotrophic factor pathway, life stress, and chronic multi-site musculoskeletal pain

Introduction

Brain-derived neurotrophic factor (BDNF) disturbances and life stress, both independently and in interaction, have been hypothesized to induce chronic pain. We examined whether (a) the BDNF pathway (val⁶⁶met genotype, gene expression, and serum levels), (b) early and recent life stress, and (c) their interaction are associated with the presence and severity of chronic multi-site musculoskeletal pain.

Methods

Cross-sectional data are from 1646 subjects of the Netherlands Study of Depression and Anxiety. The presence and severity of chronic multi-site musculoskeletal pain were determined using the Chronic Pain Grade (CPG) questionnaire. The BDNF val⁶⁶met polymorphism, BDNF gene expression, and BDNF serum levels were measured. Early life stress before the age of 16 was assessed by calculating a childhood trauma index using the Childhood Trauma Interview. Recent life stress was assessed as the number of recent adverse life events using the List of Threatening Events Questionnaire.

Results

Compared to val⁶⁶val, BDNF met carriers more often had chronic pain, whereas no differences were found for BDNF gene expression and serum levels. Higher levels of early and recent stress were both associated with the presence and severity of chronic pain (p < 0.001). No interaction effect was found for the BDNF pathway with life stress in the associations with chronic pain presence and severity.

Conclusions

This study suggests that the BDNF gene marks vulnerability for chronic pain. Although life stress did not alter the impact of BDNF on chronic pain, it seems an independent factor in the onset and persistence of chronic pain.

A low cortisol response to stress is associated with musculoskeletal pain combined with increased pain sensitivity in young adults: a longitudinal cohort study

Background

In this study, we investigated whether an abnormal hypothalamic-pituitary-adrenal (HPA) axis response to psychosocial stress at 18 years of age is associated with musculoskeletal (MS) pain alone and MS pain combined with increased pain sensitivity at 22 years of age.

Methods

The study sample included 805 participants from the Western Australian Pregnancy Cohort (Raine) Study who participated in the Trier Social Stress Test (TSST) at age 18 years. Number of pain sites, pain duration, pain intensity and pain frequency were assessed at age 22 to measure severity of MS pain. Cold and pressure pain thresholds were determined at age 22. Group-based trajectory modeling was applied to establish cortisol response patterns based on the TSST. Logistic regression was used to study the association of TSST patterns with MS pain alone and MS pain combined with increased cold or pressure pain sensitivity, adjusted for relevant confounding factors. All analyses were stratified by sex.

Results

The mean (standard deviation) age during the TSST was 18.3 (0.3) years, and during MS pain assessment it was 22.2 (0.6). Forty-five percent of the participants were female. Three cortisol response patterns were identified, with cluster 1 (34 % of females, 21 % of males) reflecting hyporesponse, cluster 2 (47 %, 54 %) reflecting intermediate response and cluster 3 (18 %, 24 %) reflecting hyperresponse of the HPA axis. MS pain was reported by 42 % of females and 33 % of males at age 22 years. Compared with females in cluster 2, females in cluster 1 had an increased likelihood of having any MS pain (odds ratio 2.3, 95 % confidence interval 1.0–5.0) and more severe MS pain (2.8, 1.1–6.8) if their cold pain threshold was above the median. In addition, females in cluster 1 had an increased likelihood (3.5, 1.3–9.7) of having more severe MS pain if their pressure pain threshold was below the median. No statistically significant associations were observed in males.

Conclusions

This study suggests that a hyporesponsive HPA axis at age 18 years is associated with MS pain at 22 years in young females with increased pain sensitivity.

Cardiovascular responses to an acute psychological stressor are associated with the cortisol awakening response in individuals with chronic neck pain

INTRODUCTION

Dysregulation of the hypothalamic-pituitary-adrenal axis (HPA-axis) is common in individuals who experience chronic psychological stress, as well as individuals with chronic pain. Changes in cortisol availability in the presence of a chronic stressor such as pain may influence the sympathetic-adrenal-medullary (SAM) system, which contributes to cardiovascular responses to stress and also exhibits altered responsiveness in the presence of pain. The purpose of this study was to investigate the relationship between HPA activity during the cortisol awakening response and cardiovascular reactivity during exposure to an acute psychological stressor in individuals with chronic neck pain.

METHODS

Area under the curve (AUC) of the salivary cortisol awakening response was assessed in 41 individuals with chronic neck pain aged 19-80 years (22 men, 23 women). Slopes representing the change in mean arterial pressure and heart rate during a baseline quiet sitting condition, a low stress condition with mental concentration, and a high stress condition combining mental concentration with social evaluative threat were calculated for each individual as an index of cardiovascular responsiveness to the acute stressor. Cardiovascular responses were regressed on cortisol awakening AUC and pain duration, adjusting for age and sex.

RESULTS

Greater mean arterial pressure (β = -0.33, p = 0.02) and heart rate responses (β = -0.41, p = 0.007) to the acute psychological stressor were associated with lower cortisol awakening responses after adjusting for age and sex. Individuals with a shorter duration of chronic pain also demonstrated a larger increase in mean arterial pressure during the laboratory stressor (β = -0.39, p = 0.01), but there was no relationship between pain duration and changes in heart rate (p = 0.25).

CONCLUSIONS

Individuals with a shorter duration of chronic neck pain who demonstrate heightened cardiovascular responsiveness to an acute psychological stressor also exhibit lower cortisol awakening response. These results are consistent with time-dependent adaptations across the two major stress systems in the presence of chronic pain.

Brain-derived neurotrophic factor as a driving force behind neuroplasticity in neuropathic and central sensitization pain: a new therapeutic target?

INTRODUCTION

Central sensitization is a form of maladaptive neuroplasticity underlying many chronic pain disorders, including neuropathic pain, fibromyalgia, whiplash, headache, chronic pelvic pain syndrome and some forms of osteoarthritis, low back pain, epicondylitis, shoulder pain and cancer pain. Brain-derived neurotrophic factor (BDNF) is a driving force behind neuroplasticity, and it is therefore crucial for neural maintenance and repair. However, BDNF also contributes to sensitization of pain pathways, making it an interesting novel therapeutic target.

AREAS COVERED

An overview of BDNF's sensitizing capacity at every level of the pain pathways is presented, including the peripheral nociceptors, dorsal root ganglia, spinal dorsal horn neurons, and brain descending inhibitory and facilitatory pathways. This is followed by the presentation of several potential therapeutic options, ranging from indirect influencing of BDNF levels (using exercise therapy, anti-inflammatory drugs, melatonin, repetitive transcranial magnetic stimulation) to more specific targeting of BDNF's receptors and signaling pathways (blocking the proteinase-activated receptors 2-NK-κβ signaling pathway, administration of phencyclidine for antagonizing NMDA receptors, or blockade of the adenosine A2A receptor).

EXPERT OPINION

This section focuses on combining pharmacotherapy with multimodal rehabilitation for balancing the deleterious and therapeutic effects of BNDF treatment in chronic pain patients, as well as accounting for the complex and biopsychosocial nature of chronic pain.