A new aspect of chronic pain as a lifestyle-related disease

Investigating neuroepigenetic alterations in chronic low back pain with positron emission tomography

ABSTRACT

Epigenetics has gained considerable interest as potential mediators of molecular alterations that could underlie the prolonged sensitization of nociceptors, neurons, and glia in response to various environmental stimuli. Histone acetylation and deacetylation, key processes in modulating chromatin, influence gene expression; elevated histone acetylation enhances transcriptional activity, whereas decreased acetylation leads to DNA condensation and gene repression. Altered levels of histone deacetylase (HDAC) have been detected in various animal pain models, and HDAC inhibitors have demonstrated analgesic effects in these models, indicating HDACs' involvement in chronic pain pathways. However, animal studies have predominantly examined epigenetic modulation within the spinal cord after pain induction, which may not fully reflect the complexity of chronic pain in humans. Moreover, methodological limitations have previously impeded an in-depth study of epigenetic changes in the human brain. In this study, we employed [11C]Martinostat, an HDAC-selective radiotracer, positron emission tomography to assess HDAC availability in the brains of 23 patients with chronic low back pain (cLBP) and 11 age-matched and sex-matched controls. Our data revealed a significant reduction of [11C]Martinostat binding in several brain regions associated with pain processing in patients with cLBP relative to controls, highlighting the promising potential of targeting HDAC modulation as a therapeutic strategy for cLBP.

Estimation of cognitive impairment in chronic pain patients and characteristics of estimated mild cognitive impairment

Background

Patients with chronic pain suffer from psychological effects such as anxiety due to the pain itself. Pain can not only impair activities of daily living (ADL) and quality of life (QOL), but also impair cognitive function. Therefore, in this study, we aimed to estimate the cognitive function of chronic pain patients using a deep neural network (DNN) model that has already been implemented in society. We investigated the characteristics of patients presumed to have mild cognitive impairment (MCI) and, at the same time, verified the relationship with the questionnaire commonly used in chronic pain research, which is administered by 43 university affiliated hospitals and medical institutions participating in the chronic pain research group of the Ministry of Health, Labor and Welfare in Japan (assessment batteries).

Method

The study included 114 outpatients from a multidisciplinary pain clinic, and we estimated their Mini-Mental State Examination (MMSE) scores based on age and basic blood test data (23 items). Furthermore, we classified the estimated MMSE scores of chronic pain patients into two groups based on a cutoff score of 27, which indicates MCI, and compared the blood data and assessment batteries. Additionally, we used a control group of 252 healthy adults aged 45 years or older who visited a dementia prevention outpatient clinic for comparison with the MMSE scores of chronic pain patients.

Result

The MMSE scores in chronic pain patients were below the cutoff for MCI. When classified into two groups based on the estimated MMSE score of 27 points, WBC, RBC, Hb, Hct, PLT, UA, BUN, creatinine, Triglyceride, and γ-GT were significantly higher in the blood data. In the MCI group, PDAS values were significantly lower. Furthermore, only in the non-MCI group, a significant correlation was found between the estimated MMSE value and BPI, PDAS, and Locomo. The estimated MMSE scores were significantly lower in chronic pain patients than in healthy adults (p = 0.04).

Conclusion

Patients with chronic pain may exhibit cognitive impairment due to systemic metabolic disturbances. This suggests that chronic pain affects activities of daily living, resulting in systemic metabolic disorders.

Eating habits and the desire to eat healthier among patients with chronic pain: a registry-based study

Healthcare professionals often meet pain patients with a poor nutritional status such as obesity, unhealthy dietary behaviors, and a suboptimal dietary intake. A poor nutritional status may play a significant role in the occurrence, development, and prognosis of chronic pain. This study investigated eating habits in a specialized pain rehabilitation center using data (N = 2152) from the Swedish quality registry for pain rehabilitation during the period 2016-2021. Patients answered a lifestyle questionnaire regarding their eating habits and desire to modify their lifestyle. The mean (SD) patient age was 46.1 (14.6) years, with 24.8% classified as obese. Suboptimal eating habits included irregular mealtimes (27.2%), weekly consumption of fast-food (20.3%) and nearly daily consumption of confectionery (33.3%). Approximately 20% (n = 426) reported a desire to eat healthier. Frequent confectionery intake (Odds ratio [OR] 1.23, 95% Confidence Interval (CI) 1.04-1.47) and fast-food consumption (OR 1.58, 95% CI 1.24-2.02) increased the likelihood to desire healthier eating. Younger patients (18-29 years), those classified as obese, and those with more extended spatial pain were more likely to express a desire to eat healthier. Eating habits should be addressed in pain management and interdisciplinary pain rehabilitation teams are encouraged to provide nutritional care tailored to the patient's needs.

Digital Therapeutics for Improving Effectiveness of Pharmaceutical Drugs and Biological Products: Preclinical and Clinical Studies Supporting Development of Drug + Digital Combination Therapies for Chronic Diseases

Limitations of pharmaceutical drugs and biologics for chronic diseases (e.g., medication non-adherence, adverse effects, toxicity, or inadequate efficacy) can be mitigated by mobile medical apps, known as digital therapeutics (DTx). Authorization of adjunct DTx by the US Food and Drug Administration and draft guidelines on "prescription drug use-related software" illustrate opportunities to create drug + digital combination therapies, ultimately leading towards drug-device combination products (DTx has a status of medical devices). Digital interventions (mobile, web-based, virtual reality, and video game applications) demonstrate clinically meaningful benefits for people living with Alzheimer's disease, dementia, rheumatoid arthritis, cancer, chronic pain, epilepsy, depression, and anxiety. In the respective animal disease models, preclinical studies on environmental enrichment and other non-pharmacological modalities (physical activity, social interactions, learning, and music) as surrogates for DTx "active ingredients" also show improved outcomes. In this narrative review, we discuss how drug + digital combination therapies can impact translational research, drug discovery and development, generic drug repurposing, and gene therapies. Market-driven incentives to create drug-device combination products are illustrated by Humira® (adalimumab) facing a "patent-cliff" competition with cheaper and more effective biosimilars seamlessly integrated with DTx. In conclusion, pharma and biotech companies, patients, and healthcare professionals will benefit from accelerating integration of digital interventions with pharmacotherapies.

The Role of the Brain-Derived Neurotrophic Factor in Chronic Pain: Links to Central Sensitization and Neuroinflammation

Chronic pain is sustained, in part, through the intricate process of central sensitization (CS), marked by maladaptive neuroplasticity and neuronal hyperexcitability within central pain pathways. Accumulating evidence suggests that CS is also driven by neuroinflammation in the peripheral and central nervous system. In any chronic disease, the search for perpetuating factors is crucial in identifying therapeutic targets and developing primary preventive strategies. The brain-derived neurotrophic factor (BDNF) emerges as a critical regulator of synaptic plasticity, serving as both a neurotransmitter and neuromodulator. Mounting evidence supports BDNF's pro-nociceptive role, spanning from its pain-sensitizing capacity across multiple levels of nociceptive pathways to its intricate involvement in CS and neuroinflammation. Moreover, consistently elevated BDNF levels are observed in various chronic pain disorders. To comprehensively understand the profound impact of BDNF in chronic pain, we delve into its key characteristics, focusing on its role in underlying molecular mechanisms contributing to chronic pain. Additionally, we also explore the potential utility of BDNF as an objective biomarker for chronic pain. This discussion encompasses emerging therapeutic approaches aimed at modulating BDNF expression, offering insights into addressing the intricate complexities of chronic pain.

Changes in pain, daily occupations, lifestyle, and health following an occupational therapy lifestyle intervention: a secondary analysis from a feasibility study in patients with chronic high-impact pain

OBJECTIVES

This study explored changes in pain-related parameters, occupational function, occupational balance, lifestyle factors, and self-perceived health status in adults with chronic high-impact pain participating in an occupational therapy lifestyle intervention.

METHODS

This one-group longitudinal feasibility study was performed in three continuous feasibility rounds. The occupational therapists-led intervention targeted meaningful occupations, regular physical activity, and a healthy diet. The intervention contained individual and group sessions and was added to the standard multidisciplinary chronic pain treatment. Outpatients (n=40, 85 % females, 46.6 ± 10.9 years old) participated in the study between April 2019 and December 2021. The analysis includes data for 31 participants. Analysis of pre-post changes assessed after each feasibility round were performed for the outcomes: pain intensity, pain sensitivity and pain modulation (pressure pain threshold and tolerance, temporal summation of pain and conditioned pain modulation), pain self-efficacy, pain catastrophizing, motor and process skills, occupational balance, daily wake-time movement, daily walking steps, body mass index, waist circumference, blood pressure, and self-perceived health status.

RESULTS

Improvements in motor skills (assessment of motor and process skills score=0.20 (1.37; 1.57), 95 % CI 0.01; 0.38) and temporal summation of pain (-1.19 (2.86; -1.67), 95 % CI -2.16; -0.22), but a decrease in pain tolerance (-7.110 (54.42; 47.32), 95 % CI -13.99; -0.22) were observed. Correlation analysis suggested moderate-to-very strong statistically significant relationships in several outcomes related to pain, health, pain coping, occupational balance, occupational functioning, body anthropometrics, and pain sensitivity.

CONCLUSIONS

This study suggested that the lifestyle intervention would benefit motor skills while effects on other outcomes were unclear in adults with chronic pain. To confirm the findings, a randomized trial evaluating effectiveness is needed. Ethical committee number: SJ-307 Reg. Clinicaltrials.gov: NCT03903900.

Antinociceptive effect of intermittent fasting via the orexin pathway on formalin-induced acute pain in mice

It has been suggested that stress responses induced by fasting have analgesic effects on nociception by elevating the levels of stress-related hormones, while there is limited understanding of pain control mechanisms. Here, we investigated whether acute or intermittent fasting alleviates formalin-induced pain in mice and whether spinal orexin A (OXA) plays a role in this process. 6, 12, or 24 h acute fasting (AF) and 12 or 24 h intermittent fasting (IF) decreased the second phase of pain after intraplantar formalin administration. There was no difference in walking time in the rota-rod test and distance traveld in the open field test in all groups. Plasma corticosterone level and immobility time in the forced swim test were increased after 12 h AF, but not after 12 h IF. 12 h AF and IF increased not only the activation of OXA neurons in the lateral hypothalamus but also the expression of OXA in the lateral hypothalamus and spinal cord. Blockade of spinal orexin 1 receptor with SB334867 restored formalin-induced pain and spinal c-Fos immunoreactivity that were decreased after 12 h IF. These results suggest that 12 h IF produces antinociceptive effects on formalin-induced pain not by corticosterone elevation but by OXA-mediated pathway.

Exercise therapy for chronic pain: How does exercise change the limbic brain function?

We are exposed to various external and internal threats which might hurt us. The role of taking flexible and appropriate actions against threats is played by "the limbic system" and at the heart of it there is the ventral tegmental area and nucleus accumbens (brain reward system). Pain-related fear causes excessive excitation of amygdala, which in turn causes the suppression of medial prefrontal cortex, leading to chronification of pain. Since the limbic system of chronic pain patients is functionally impaired, they are maladaptive to their situations, unable to take goal-directed behavior and are easily caught by fear-avoidance thinking. We describe the neural mechanisms how exercise activates the brain reward system and enables chronic pain patients to take goal-directed behavior and overcome fear-avoidance thinking. A key to getting out from chronic pain state is to take advantage of the behavioral switching function of the basal nucleus of amygdala. We show that exercise activates positive neurons in this nucleus which project to the nucleus accumbens and promote reward behavior. We also describe fear conditioning and extinction are affected by exercise. In chronic pain patients, the fear response to pain is enhanced and the extinction of fear memories is impaired, so it is difficult to get out of "fear-avoidance thinking". Prolonged avoidance of movement and physical inactivity exacerbate pain and have detrimental effects on the musculoskeletal and cardiovascular systems. Based on the recent findings on multiple bran networks, we propose a well-balanced exercise prescription considering the adherence and pacing of exercise practice. We conclude that therapies targeting the mesocortico-limbic system, such as exercise therapy and cognitive behavioral therapy, may become promising tools in the fight against chronic pain.

EEG-based sensory testing reveals altered nociceptive processing in elite endurance athletes

Increased exercise loads, as observed in elite athletes, seem to modulate the subjective pain perception in healthy subjects. The combination of electroencephalography (EEG) and standardized noxious stimulation can contribute to an objective assessment of the somatosensory stimulus processing. We assessed the subjective pain ratings and the electroencephalogram (EEG)-based response after standardized noxious mechanical and thermal stimuli as well as during conditioned pain modulation (CPM) in 26 elite endurance athletes and compared them to 26 recreationally active controls. Elite endurance athletes had consistently stronger somatosensory responses in the EEG to both mechanical and thermal noxious stimuli than the control group. We observed no significant group differences in the subjective pain ratings, which may have been influenced by our statistics and choice of stimuli. The CPM testing revealed that our conditioning stimulus modulated the subjective pain perception only in the control group, whereas the EEG indicated a modulatory effect of the conditioning stimulus on the spectral response only in the athletes group. We conclude that a higher activation in the cortical regions that process nociceptive information may either be an indicator for central sensitization or an altered stimulus salience in the elite endurance athletes' group. Our findings from our CPM testing were limited by our methodology. Further longitudinal studies are needed to examine if exercise-induced changes in the somatosensory system might have a critical impact on the long-term health of athletes.

Combined influence of sedentary behaviours and chronic pain on depressive symptoms in older Korean adults with hypertension

AIMS

Depressive symptoms in hypertensive patients are linked to poor adherence to treatment. Sedentary behaviours and chronic pain can increase blood pressure and depressive symptoms, respectively. However, the impact of their coexistence on depressive symptoms in older adults with hypertension has not yet been investigated. This study aimed to identify the combined influence of sedentary behaviours and chronic pain on depressive symptoms in older adults with hypertension in Korea.

METHODS AND RESULTS

This cross-sectional study used data from the sixth Korea National Health and Nutrition Examination Survey from January to December 2014. The survey adopted multistage stratified sampling by geographical region, gender, and age. For the data analysis, a total of 573 patients with hypertension aged 65 years or older were included. Approximately, 61.0% of depressed older patients had both sedentary behaviours and chronic pain compared with patients without depressive symptoms. In multivariate logistic regression analysis, compared with patients without either sedentary behaviours or chronic pain, older adults with hypertension who presented both sedentary behaviours, and chronic pain had the highest risk of depressive symptoms (odds ratio = 13.86, 95% confidence interval = 5.87-32.71; P < 0.001).

CONCLUSION

Coexistence of sedentary behaviours and chronic pain in older hypertensive patients may lead to depressive symptoms. Evaluating both sedentary behaviours and chronic pain when assessing depressive symptoms in patients with hypertension would be beneficial in planning a patient-centred approach for controlling blood pressure. More prospective cohort studies with larger samples are required to identify the causal relationships.

Occupational therapy lifestyle intervention added to multidisciplinary treatment for adults living with chronic pain: a feasibility study

OBJECTIVES

To evaluate the feasibility and outcomes of an occupational therapy lifestyle intervention for adults living with chronic pain.

DESIGN

This one-group pre-post interventional study investigated the feasibility and outcomes of the Redesign Your Everyday Activities and Lifestyle with Occupational Therapy (REVEAL(OT)) intervention targeting meaningful activities and lifestyle.

SETTINGS

The occupational therapist-led intervention was added to standard multidisciplinary chronic pain treatment at a Danish pain centre.

PARTICIPANTS

Of the 40 adult participants aged 18-64 (mean 46.6±10.9 years old, 85% females, chronic pain duration ≥3 months), there were 31 completers.

INTERVENTION

Three feasibility rounds were carried out in 2019-2021. The intervention focused on meaningful activities, healthy eating habits and daily physical activity. Methods of didactical presentations, group discussions, personal reflection and experiential learning were used in the intervention composed both of individual and group sessions.

OUTCOMES

Primary outcomes were predefined research progression criteria evaluated by the red-amber-green method. Secondary outcomes measured pre-post changes in health-related quality of life and occupational performance and satisfaction.

RESULTS

The study demonstrated satisfactory programme adherence (77.5%), patients' self-perceived relevance (97%), timing and mode of delivery (97%) and assessment procedure acceptance (95%). No adverse events causing discontinuation occurred. Recruitment rate (n=5.7 monthly), retention (77.5%) and the fidelity of delivery (83.3%) needed improvement. We observed no improvement in health-related quality of life (mean=0.04, 95% CI -0.03 to 0.12) but positive change in occupational performance (mean=1.80, 95% CI 1.25 to 2.35) and satisfaction (mean=1.95, 95% CI 1.06 to 2.84). The participants reached the minimal clinically important difference for occupational performance (≥3.0 points in 13.8%) and satisfaction (≥3.2 points in 24.0%).

CONCLUSIONS

The REVEAL(OT) intervention was feasible to deliver and beneficial for the participants' occupational performance and satisfaction. The interventions' recruitment, retention and delivery strategies need optimisation in a future definitive trial.

TRIAL REGISTRATION NUMBER

NCT03903900.

Machine Learning Identifies Chronic Low Back Pain Patients from an Instrumented Trunk Bending and Return Test

Nowadays, the better assessment of low back pain (LBP) is an important challenge, as it is the leading musculoskeletal condition worldwide in terms of years of disability. The objective of this study was to evaluate the relevance of various machine learning (ML) algorithms and Sample Entropy (SampEn), which assesses the complexity of motion variability in identifying the condition of low back pain. Twenty chronic low-back pain (CLBP) patients and 20 healthy non-LBP participants performed 1-min repetitive bending (flexion) and return (extension) trunk movements. Analysis was performed using the time series recorded by three inertial sensors attached to the participants. It was found that SampEn was significantly lower in CLBP patients, indicating a loss of movement complexity due to LBP. Gaussian Naive Bayes ML proved to be the best of the various tested algorithms, achieving 79% accuracy in identifying CLBP patients. Angular velocity of flexion movement was the most discriminative feature in the ML analysis. This study demonstrated that: supervised ML and a complexity assessment of trunk movement variability are useful in the identification of CLBP condition, and that simple kinematic indicators are sensitive to this condition. Therefore, ML could be progressively adopted by clinicians in the assessment of CLBP patients.

Brain Mechanisms of Exercise-Induced Hypoalgesia: To Find a Way Out from "Fear-Avoidance Belief"

It is well known that exercise produces analgesic effects (exercise-induced hypoalgesia (EIH)) in animal models and chronic pain patients, but the brain mechanisms underlying these EIH effects, especially concerning the emotional aspects of pain, are not yet fully understood. In this review, we describe drastic changes in the mesocorticolimbic system of the brain which permit the induction of EIH effects. The amygdala (Amyg) is a critical node for the regulation of emotions, such as fear and anxiety, which are closely associated with chronic pain. In our recent studies using neuropathic pain (NPP) model mice, we extensively examined the association between the Amyg and EIH effects. We found that voluntary exercise (VE) activated glutamate (Glu) neurons in the medial basal Amyg projecting to the nucleus accumbens (NAc) lateral shell, while it almost completely suppressed NPP-induced activation of GABA neurons in the central nucleus of the Amyg (CeA). Furthermore, VE significantly inhibited activation of pyramidal neurons in the ventral hippocampus-CA1 region, which play important roles in contextual fear conditioning and the retrieval of fear memory. This review describes novel information concerning the brain mechanisms underlying EIH effects as a result of overcoming the fear-avoidance belief of chronic pain.

Tumor suppression and improvement in immune systems by specific activation of dopamine D1-receptor-expressing neurons in the nucleus accumbens

Recent research has suggested that the mesolimbic dopamine network that mainly terminates in the nucleus accumbens may positively control the peripheral immune system. The activation of dopamine receptors in neurons in the nucleus accumbens by the release of endogenous dopamine is thus expected to contribute to efferent immune regulation. As in the stimulation of Gs-coupled dopamine D1-receptors or Gi-coupled D2-receptors by endogenous dopamine, we investigated whether specific stimulation of dopamine D1-receptor-expressing neurons or inhibition of dopamine D2-receptor-expressing neurons in the nucleus accumbens could produce anti-tumor effects and improve the immune system in transgenic mice using pharmacogenetic techniques. Repeated stimulation of D1-receptor-expressing neurons in either the medial shell, lateral shell or core regions of the nucleus accumbens significantly decreased tumor volume under a state of tumor transplantation, whereas repeated suppression of D2-receptor-expressing neurons in these areas had no effect on this event. The number of splenic CD8⁺ T cells was significantly increased following repeated stimulation of D1-receptor-expressing neurons in the nucleus accumbens of mice with tumor transplantation. Furthermore, this stimulation produced a significant reduction in the population of splenic CD8⁺ T cells that expressed immune checkpoint-related inhibitory receptors, PD-1, TIM-3 and LAG-3. These findings suggest that repeated stimulation of D1-receptor-expressing neurons (probably D1-receptor-expressing medium spiny neurons) in the nucleus accumbens suppressed tumor progression and improved the immune system by suppressing the exhaustion of splenic CD8⁺ T cells.

Depression Among Patients with Chronic Pain, in Jimma Town Public Hospitals, Ethiopia

Introduction

The co-occurrence of depression and chronic pain causes additive adverse effects on patients” outcomes, response to treatment, and poorer functioning. Despite this, there is a dearth of studies in developing countries. Therefore, this study aimed to provide a new insight into the understanding of the prevalence and associated factors between chronic pain and depression among patients with chronic pain in Jimma town public hospitals.

Methods

Institution-based cross-sectional study was conducted in Jimma town public hospitals. A total of 422 sampled patients with chronic pain participated in the study. Depression was assessed using the PHQ-9 scale. The coded data were entered to Epi Data version 3.1 and exported into SPSS version 23.0 for analysis. Logistic regression analysis model was used to identify factors independently associated with depression.

Result

The prevalence of depression among chronic pain patients was found to be 43.3%. The number of presenting compliant (AOR = 3.092, 95% CI: 1.684-5.678), history of depression (AOR = 0.319, CI: 0.133-0.766), pain intensity (AOR = 5.296, 95% CI: 2.018-13.901), pain location (AOR = 0.318, 95% CI: 0.158-0.638), pain persistence (AOR = 5.163, 95% CI: 2.784-9.576), the extent the pain compromised the respondent quality of life (AOR = 3.816, 95% CI: 1.685-8.643), and episodes of the pain associated with activities (AOR = 0.247, 95% CI: 0.138-0.442) were significantly associated with depression among patients with chronic pain.

Conclusion

This study has shown a high prevalence of depression among patients with chronic pain. Furthermore, depression was associated with various pain-related factors. Hence, effective screening and management of depression among chronic pain patients’ needs noteworthy attention.

Ten years of interfaculty pain curriculum at the University of Toronto: impact on student learning

Supplemental Digital Content is Available in the Text.

The University of Toronto Interfaculty Pain Curriculum has significantly improved students' pain knowledge and ability to develop interprofessional care plans over the period 2009 to 2019.

Introduction:

Delivery of interprofessional pain education for prelicensure healthcare professionals is strongly recommended to advance a workforce ready for collaborative practice and to improve the quality and outcomes of pain care.

Objectives:

We report a 10-year (2009–2019) longitudinal evaluation of a 20-hour undergraduate Interfaculty Pain Curriculum (IPC) delivered to students in the Faculties of Dentistry, Nursing, Pharmacy, and Medicine (also including the Departments of Physical Therapy, Occupational Therapy and Physician Assistant) at the University of Toronto, Canada. The IPC follows a constructivist approach to facilitate interactive and multifaceted learning.

Methods:

Evaluation methods based on the Kirkpatrick model were used to appraise changes in participating students' pain knowledge and beliefs and their ability to collaboratively develop an interprofessional pain management plan.

Results:

A total of 10,693 students participated over the 10-year study period. The mean annual attendance was 972 students and participation to the program increased significantly over the years. Overall, the IPC was effective in improving students' mean pain knowledge and beliefs scores; however, the mean knowledge score gains were negatively correlated with time, likely related to increased uniprofessional pain education. Although an increasing trend in mean interprofessional pain management plan scores was observed, the scores were not significantly correlated with time.

Conclusions:

The interactive and multifaceted IPC is consistently effective in improving knowledge and beliefs and interprofessional pain management care plan development among participating student cohorts. Future inquiry is required to better understand the mechanisms behind student learning in interprofessional pain education to enhance pain curriculum development and delivery.

Environmental exposure to 17β-trenbolone during adolescence inhibits social interaction in male mice

Puberty is a critical period for growth and development. This period is sensitive to external stimuli, which ultimately affects the development of nerves and the formation of social behaviour. 17β-Trenbolone (17β-TBOH) is an endocrine disrupting chemicals (EDCs), which had been widely reported in aquatic vertebrates. But there is little known about the effects of 17β-TBOH on mammals, especially on adolescent neurodevelopment. In this study, we found that 17β-TBOH acute 1 h exposure can cause the activation of the dopamine circuit in pubertal male balb/c mice. At present, there is little known about the effects of puberty exposure of endocrine disruptors on these neurons/nerve pathways. Through a series of behavioural tests, exposure to 80 μgkg^-1 d^-1 of 17β-TBOH during adolescence increased the anxiety-like behaviour of mice and reduced the control of wheel-running behaviour and the response of social interaction behaviour. The results of TH immunofluorescence staining showed that exposure to 17β-TBOH reduced dopamine axon growth in the medial prefrontal cortex (mPFC). In addition, the results of real-time PCR showed that exposure to 17β-TBOH not only down-regulated the expression of dopamine axon development genes, but also affected the balance of excitatory/inhibitory signals in mPFC. In this research, we reveal the effects of 17β-TBOH exposure during adolescence on mammalian behaviour and neurodevelopment, and provide a reference for studying the origin of adolescent diseases.

Cognitive Reserve as a Protective Factor of Mental Health in Middle-Aged Adults Affected by Chronic Pain

Chronic pain is associated with worse mental health and cognitive impairment, which can be a cause or a consequence of brain structure and function alterations, e.g., maladaptive plasticity, antinociceptive system dysregulation. Cognitive reserve reflects the effectiveness of the internal connections of the brain and it has been shown to be a protective factor in brain damage, slowing cognitive aging or reducing the risk of mental health disorders. The current study explored the impact of chronic pain on psychosocial factors, mental health, and cognition. Furthermore, we aimed to examine the role of cognitive reserve in the relationship between mental health and chronic pain clinical characteristics in middle-aged adults. The study group consisted of 477 volunteers from the Barcelona Brain Health Initiative who completed online surveys on pain, mental health, cognitive reserve, and psychosocial factors (sleep and quality of life). We described the differences in sociodemographic data, psychosocial factors, mental health, and self-perceived cognitive impairment, and neuropsychological assessment, between participants reporting pain compared with those without pain, as well as the main characteristics of the chronic pain group. Finally, to study the role of cognitive reserve in the modulation of the relationship between chronic pain and mental health, we compared variables between subgroups of participants with high/low pain intensity and cognitive reserve. The results showed that chronic pain was reported by 45.5% of middle-aged adults. Our results revealed that participants with chronic pain were older and had worse health status than people without pain. The presence of chronic pain affected working memory, mental health, and daily life activities. Moreover, cognitive reserve moderated the influence of pain intensity on mental health, resulting in less mental health affection in people suffering from high pain intensity with high cognitive reserve. In conclusion, the construct of the cognitive reserve could explain differential susceptibility between chronic pain and its mental health association and be a powerful tool in chronic pain assessment and treatment, principally due to its modifiable nature.

Patterns of brain c-Fos expression in response to feeding behavior in acute and chronic inflammatory pain condition

OBJECTIVES

Feeding behavior is known to have potential to alleviate pain. We recently demonstrated that both 24 h fasting and 2 h refeeding (food intake after 24 h fasting) induce analgesia in inflammatory pain conditions via different brain mechanisms. However, brain structures that distinctly involved fasting- and refeeding-induced analgesia is still unknown. Hence, this study is aimed to reveal brain structures mediating fasting- and refeeding-induced analgesia.

METHODS

Mice were given intraplantar (i.pl.) injection of formalin and complete Freund's adjuvant into the left hind paw to induce acute and chronic inflammatory pain, respectively. We examined changes in c-Fos expression with 24 h fasting and 2 h refeeding under acute and chronic inflammatory pain conditions in the contralateral brain.

RESULTS

Under acute pain condition, c-Fos expression changed with fasting in the anterior cingulate cortex (ACC), central amygdala (CeA), lateral hypothalamus (LH) and nucleus accumbens core (NAcC). Refeeding changed c-Fos expression in the CeA, LH and lateral parabrachial nucleus (lPBN). On the other hand, under chronic inflammatory pain condition, c-Fos expression changed with fasting in the lPBN, medial prefrontal cortex (mPFC) and nucleus accumbens shell (NAcS) while refeeding changed c-Fos expression in the anterior insular cortex, lPBN, mPFC and NAcS.

CONCLUSION

The present results show that brain regions that participated in the fasting- and refeeding-induced analgesia were completely different in acute and chronic inflammatory pain conditions. Also, refeeding recruits more brain regions under chronic inflammatory pain conditions compared to the acute inflammatory pain condition. Collectively, our findings provide novel insights into brain regions involved in fasting- and refeeding-induced analgesia, which can be potential neural circuit-based targets for the development of novel therapeutics.

Voluntary Forelimbs Exercise Reduces Immobilization-Induced Mechanical Hyperalgesia in the Rat Hind Paw

Voluntary exercise is sufficient to protect against neuropathic pain. However, it is unclear whether voluntary exercise reduces immobilization-induced hyperalgesia. We examined the effect of voluntary forelimb exercise on immobilized-induced hyperalgesia in hind paws of rats. Wistar rats were randomly divided into the (1) both hind limbs immobilized group (IM group), (2) immobilization and exercise with nonimmobilized fore limbs group (EX group), and (3) control group. In the IM and EX groups, the bilateral ankle joints of each rat were immobilized in full plantar flexion with a plaster cast for eight weeks. In the EX group, voluntary exercise using nonimmobilized forelimbs in the running wheel was administered during the immobilization period, while hind limbs were kept immobilized (60 min/day, 5 days/week). Mechanical hyperalgesia in the hind paw was measured using a digital von Frey device every week. To investigate the abnormality of primary sensory neurons and central sensitization, the number of calcitonin gene-related peptide-positive cells in the dorsal root ganglion and the expression level of calcitonin gene-related peptide in the spinal dorsal horn were analyzed by immunohistochemical staining. Immobilization-induced mechanical hyperalgesia was inhibited in the EX group compared to the IM group at three weeks after immobilization. In the EX group, the number of calcitonin gene-related peptide-positive cells in the dorsal root ganglion and the expression level of calcitonin gene-related peptide were significantly decreased compared to those in the IM group. Our results therefore suggest that voluntary forelimb exercise during hind limb immobilization partially reduces immobilization-induced hyperalgesia by suppressing that the plastic changes of the primary sensory nerves that excessively transmit pain and increased responsiveness of nociceptive neurons in the spinal dorsal horn.

Plastic changes in amygdala subregions by voluntary running contribute to exercise-induced hypoalgesia in neuropathic pain model mice

Physical exercise has been established as a low-cost, safe, and effective way to manage chronic pain, but exact mechanisms underlying such exercise-induced hypoalgesia (EIH) are not fully understood. Since a growing body of evidence implicated the amygdala (Amyg) as a critical node in emotional affective aspects of chronic pain, we hypothesized that the Amyg may play important roles to produce EIH effects. Here, using partial sciatic nerve ligation (PSL) model mice, we investigated the effects of voluntary running (VR) on the basal amygdala (BA) and the central nuclei of amygdala (CeA). The present study indicated that VR significantly improved heat hyperalgesia which was exacerbated in PSL-Sedentary mice, and that a significant positive correlation was detected between total running distances after PSL-surgery and thermal withdrawal latency. The number of activated glutamate (Glu) neurons in the medal BA (medBA) was significantly increased in PSL-Runner mice, while those were increased in the lateral BA in sedentary mice. Furthermore, in all subdivisions of the CeA, the number of activated gamma-aminobutyric acid (GABA) neurons was dramatically increased in PSL-Sedentary mice, but these numbers were significantly decreased in PSL-Runner mice. In addition, a tracer experiment demonstrated a marked increase in activated Glu neurons in the medBA projecting into the nucleus accumbens lateral shell in runner mice. Thus, our results suggest that VR may not only produce suppression of the negative emotion such as fear and anxiety closely related with pain chronification, but also promote pleasant emotion and hypoalgesia. Therefore, we conclude that EIH effects may be produced, at least in part, via such plastic changes in the Amyg.

The genetic influence of the brain-derived neurotrophic factor Val66Met polymorphism in chronic low back pain

BACKGROUND

The Val66Met polymorphism of the brain-derived neurotrophic factor (BDNF) gene is a potential biomarker of vulnerability to pain. Thus, the present study aimed to investigate the association of this polymorphism with clinical and biopsychosocial factors in patients with chronic low back pain (CLBP).

METHODS

A total of 107 individuals with CLBP answered questionnaires that were validated and adapted for the Brazilian population, including the Brief Inventory of Pain, the Central Sensitization Inventory, the Roland Morris Disability Questionnaire, the Tampa Scale for Kinesiophobia, the Pain Catastrophizing Scale, the Survey of Pain Attitude-Brief, and the Hospital Anxiety and Depression Scale. All of the subjects were genotyped for the BDNF Val66Met polymorphism.

RESULTS

The sample showed moderate scores of disability, central sensitization, and kinesiophobia, in addition to mild anxiety, hopelessness, and ruminant thoughts. No significant association was observed between the Val66Met polymorphism and the variables analyzed. Besides, there was no relationship between the BDNF Val66Met polymorphism with CSI, catastrophization, or disabilities that were generated by CLBP.

CONCLUSION

The results showed that the Val66Met polymorphism of the BDNF gene was not associated with clinical and biopsychosocial characteristics of CLBP in the sample studied.

Serotonergic Neurotransmission System Modulator, Vortioxetine, and Dopaminergic D2/D3 Receptor Agonist, Ropinirole, Attenuate Fibromyalgia-Like Symptoms in Mice

Fibromyalgia is a disease characterized by lowered pain threshold, mood disorders, and decreased muscular strength. It results from a complex dysfunction of the nervous system and due to unknown etiology, its diagnosis, treatment, and prevention are a serious challenge for contemporary medicine. Impaired serotonergic and dopaminergic neurotransmission are regarded as key factors contributing to fibromyalgia. The present research assessed the effect of serotonergic and dopaminergic system modulators (vortioxetine and ropinirole, respectively) on the pain threshold, depressive-like behavior, anxiety, and motor functions of mice with fibromyalgia-like symptoms induced by subcutaneous reserpine (0.25 mg/kg). By depleting serotonin and dopamine in the mouse brain, reserpine induced symptoms of human fibromyalgia. Intraperitoneal administration of vortioxetine and ropinirole at the dose of 10 mg/kg alleviated tactile allodynia. At 5 and 10 mg/kg ropinirole showed antidepressant-like properties, while vortioxetine had anxiolytic-like properties. None of these drugs influenced muscle strength but reserpine reduced locomotor activity of mice. Concluding, in the mouse model of fibromyalgia vortioxetine and ropinirole markedly reduced pain. These drugs affected emotional processes of mice in a distinct manner. Hence, these two repurposed drugs should be considered as potential drug candidates for fibromyalgia. The selection of a specific drug should depend on patient’s key symptoms.

Association of Temporomandibular Disorder Symptoms with Physical Fitness among Finnish Conscripts

Studies on the role of physical fitness, physical activity and obesity as risk factors for temporomandibular disorders (TMD) are scarce. The aim of the present study was to evaluate the association of TMD symptoms with physical fitness, physical activity and body mass index (BMI) among Finnish conscripts. The study sample consisted of 8685 Finnish conscripts. Data on self-reported TMD symptoms were used as outcome variables. Physical activity (questionnaire), physical fitness (measured with physical tests: Cooper test, push-ups, sit-ups and standing long jump) and body mass index (BMI) were used as explanatory variables. The associations between TMD symptoms and explanatory variables were evaluated using Chi-squared test and logistic regression analysis. The prevalence of all TMD symptoms was significantly higher among those who exercised more rarely than weekly. Pain-related TMD symptoms were also significantly more frequent among those who were overweight (BMI ≥ 25). Poor push-up results and overweight (BMI ≥ 25) were significantly associated with jaw pain and TMJ pain at jaw rest. The present study showed that good physical fitness may be a protective factor against TMD pain. Dentists should also be prepared to motivate TMD patients to physical activity and regular exercise as part of the treatment.

The Aftermath of COVID-19 Lockdown on Daily Life Activities in Orthopaedic Patients

PURPOSE

Following the 2019 coronavirus (COVID-19) pandemic, many reports have investigated the psychosocial effects of the lockdown. The aim of our study was to investigate the effects of the lockdown on the daily life habits of orthopaedic patients.

PATIENTS AND METHODS

Around 30 days after the start of the Italian lockdown, from April 17th to the end of the containment measures on May 18th, the Sapienza University of Rome carried out a 19-item survey on the effects the lockdown caused in patients suffering from an orthopaedic pathology (with regard to changes in lifestyle, pain, treatment) by stratifying the sample by age, sex, profession, pain location, pathogenesis and prior surgeries.

RESULTS

A total of 292 subjects with orthopaedic pathologies took part in the survey. Taking into consideration the totality of the sample, physical activity was significantly reduced (p <0.001). The increase of a sedentary lifestyle was statistically significant (p <0.001), as well as an increase in pain (p <0.001) and the need to adjust the pharmacological treatment (p <0.001). The increase in pain was particularly significant in the 50-70 age group, among workers, and in polyarthralgic patients. About 55.48% stated that the lockdown period worsened their underlying pathological condition and 53.77% expressed the need to undergo a new clinical evaluation at the end of the lockdown.

CONCLUSION

The impact of the COVID-19 pandemic lockdown and resulting sudden changes in lifestyle led to a change in patient perception of orthopedic pathology including a worsening of musculoskeletal pain requiring an adjustment or change in pharmacological and physical therapy.

Comprehensive Analysis of Aerobic Exercise-Related Genes Identifies CDCA4 That Promotes the Progression of Osteosarcoma

Background

Exercise has a positive impact on patients with osteosarcoma, improving function, reducing disability, maintaining independence and quality of life. Exercise may also directly affect the effectiveness of cancer treatment. Cell division cycle-associated protein 4 (CDCA4) is reported to function importantly during numerous human cancers development. Nevertheless, the details toward CDCA4 function are still to be investigated.

Methods

This study comprehensively analyzed the GSE74194 database and obtained aerobic exercise-related genes. Protein-protein interaction network (PPI) and Gene Ontology (GO) analysis were performed on the differentially expressed genes (DEGs). Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and tumor genome atlas (TCGA) data mining were applied to measure aerobic exercise-related gene CDCA4 level in osteosarcoma tissue. We conducted lots of functional experiments to uncover CDCA4 function and its corresponding mechanism in osteosarcoma.

Results

We screened a total of 547 DEGs related to aerobic exercise, of which 373 were up-regulated and 174 were down-regulated. PPI analysis revealed 90 genes that might play key roles. GO analysis showed that aerobic exercise-related DEGs were significantly enriched during the mitotic cell cycle, cell division, mitotic nuclear division and sister chromatid segregation, nuclear division, microtubule cytoskeleton organization involved protein, microtubule-based process, spindle organization, G2/M transition of mitotic cell cycle. Our results indicated that CDCA4 was increased in osteosarcoma tissues and cell lines, and its level had association with high mortality of osteosarcoma patients. Further studies revealed that absence of CDCA4 largely hindered osteosarcoma cancer cell proliferation, invasion, and migration.

Conclusion

Comprehensive bioinformatics analysis improves our understanding of the underlying molecular mechanisms of aerobic exercise on osteosarcoma. This provides evidence for the effect of aerobic exercise on CDCA4 expression. Our data suggested that CDCA4 could facilitate osteosarcoma development, and gave a hint that CDCA4 was a candidate target in the treatment of osteosarcoma, aerobic exercise might help the treatment and prognosis of patients with osteosarcoma.

Adaptive and maladaptive coping strategies in older adults with chronic pain after lumbar surgery

This study investigated whether adaptive and maladaptive coping strategies mediate the association between chronic pain and health-related quality of life among older adults experiencing chronic pain after lumbar surgery. Participants were 103 older adults with either or both of chronic lower back pain and leg pain after lumbar surgery (median age = 75 years, men = 44, women = 59). Intensity of chronic lower back and leg pain (11-point numerical rating scale), physical activities (Physical Activity Scale for the Elderly) as an adaptive coping strategy, maladaptive coping strategies (e.g. guarding, resting; Chronic Pain Coping Inventory), and health-related quality of life (12-item Short-Form Health Survey) were measured. Hypothetical models with adaptive and maladaptive coping strategies as mediators of pain intensity and health-related quality of life were tested using structural equation modeling. Model fitness was acceptable (adjusted goodness of fit index: 0.94-0.98, comparative fit index: 1.00, root mean square error of approximation: 0.00). The results showed that (1) the adaptive coping strategy of physical activity positively mediated the association between lower back and leg pain, and physical health but not mental and social health; (2) maladaptive coping strategies negatively mediated the association between pain and physical, mental, and social health; (3) physical activities were negatively associated with maladaptive coping strategies. This study demonstrated that adaptive and maladaptive coping strategies serve as mediators of the relationship between chronic pain and health-related quality of life in older adults after lumbar surgery.

Lifestyle and Chronic Pain across the Lifespan: An Inconvenient Truth?

Chronic pain has a tremendous personal and socioeconomic impact and remains difficult to treat. Therefore, it is important to provide an update on the current understanding regarding lifestyle factors in people with chronic pain across the lifespan. Lifestyle factors such as physical (in)activity, sedentary behavior, stress, poor sleep, unhealthy diet, and smoking are associated with chronic pain severity and sustainment. This applies to all age categories, that is, chronic pain across the lifespan. Yet current treatment options often do not or only partly address the many lifestyle factors associated with chronic pain or attempt to address them in a standard format rather than providing an individually tailored multimodal lifestyle intervention. The evidence regarding lifestyle factors is available in adults, but limited in children and older adults having chronic pain, providing important avenues for future research. In conclusion, it is proposed that treatment approaches for people with chronic pain should address all relevant lifestyle factors concomitantly in an individually-tailored multimodal intervention. Ultimately, this should lead to improved outcomes and decrease the psychological and socioeconomic burden of chronic pain. Level of Evidence: IV.

Music-Enhanced Analgesia and Antiseizure Activities in Animal Models of Pain and Epilepsy: Toward Preclinical Studies Supporting Development of Digital Therapeutics and Their Combinations With Pharmaceutical Drugs

Digital therapeutics (software as a medical device) and mobile health (mHealth) technologies offer a means to deliver behavioral, psychosocial, disease self-management and music-based interventions to improve therapy outcomes for chronic diseases, including pain and epilepsy. To explore new translational opportunities in developing digital therapeutics for neurological disorders, and their integration with pharmacotherapies, we examined analgesic and antiseizure effects of specific musical compositions in mouse models of pain and epilepsy. The music playlist was created based on the modular progression of Mozart compositions for which reduction of seizures and epileptiform discharges were previously reported in people with epilepsy. Our results indicated that music-treated mice exhibited significant analgesia and reduction of paw edema in the carrageenan model of inflammatory pain. Among analgesic drugs tested (ibuprofen, cannabidiol (CBD), levetiracetam, and the galanin analog NAX 5055), music intervention significantly decreased paw withdrawal latency difference in ibuprofen-treated mice and reduced paw edema in combination with CBD or NAX 5055. To the best of our knowledge, this is the first animal study on music-enhanced antinociceptive activity of analgesic drugs. In the plantar incision model of surgical pain, music-pretreated mice had significant reduction of mechanical allodynia. In the corneal kindling model of epilepsy, the cumulative seizure burden following kindling acquisition was lower in animals exposed to music. The music-treated group also exhibited significantly improved survival, warranting further research on music interventions for preventing Sudden Unexpected Death in Epilepsy (SUDEP). We propose a working model of how musical elements such as rhythm, sequences, phrases and punctuation found in K.448 and K.545 may exert responses via parasympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. Based on our findings, we discuss: (1) how enriched environment (EE) can serve as a preclinical surrogate for testing combinations of non-pharmacological modalities and drugs for the treatment of pain and other chronic diseases, and (2) a new paradigm for preclinical and clinical development of therapies leading to drug-device combination products for neurological disorders, depression and cancer. In summary, our present results encourage translational research on integrating non-pharmacological and pharmacological interventions for pain and epilepsy using digital therapeutics.

Activation of mesolimbic reward system via laterodorsal tegmental nucleus and hypothalamus in exercise-induced hypoalgesia

Ventral tegmental area (VTA) dopamine (DA) neurons are the primary source of dopamine in target structures that constitute the mesolimbic reward system. Previous studies demonstrated that voluntary wheel running (VWR) by neuropathic pain (NPP) model mice produces exercise-induced hypoalgesia (EIH), and that activation of mesolimbic reward system may lead to EIH. However, the neuronal mechanism by which the mesolimbic reward system is activated by VWR is unknown. Here, we found that VWR produces EIH effects and reverses the marked reduction in activated lateral VTA (lVTA)-DA neurons induced by NPP. The proportions of activated laterodorsal tegmental nucleus (LDT)-cholinergic and lateral hypothalamus-orexin neurons were significantly enhanced by VWR. Retrograde tracing and dual immunostaining revealed that VWR activates lVTA-projecting LDT-cholinergic/non-cholinergic and lateral hypothalamic area (LHA)-orexin/non-orexin neurons. Therefore, EIH effects may be produced, at least in part, by activation of the mesolimbic reward system via activation of LDT and LHA neurons.

Enriched Environment and Effects on Neuropathic Pain: Experimental Findings and Mechanisms

Neuropathic pain inflicts tremendous biopsychosocial suffering for patients worldwide. However, safe and effective treatment of neuropathic pain is a prominent unmet clinical need. Environmental enrichment (EE) is an emerging cost-effective nonpharmacological approach to alleviate neuropathic pain and complement rehabilitation care. We present here a review of preclinical studies in ascertaining the efficacy of EE for neuropathic pain. Their proposed mechanisms, including the suppression of ascending nociceptive signaling to the brain, enhancement of the descending inhibitory system, and neuroprotection of the peripheral and central nervous systems, may collectively reduce pain perception and improve somatic and emotional functioning in neuropathic pain. The current evidence offers critical insights for future preclinical research and the translational application of EE in clinical pain management.