Pronociceptive and antinociceptive effects of estradiol through endogenous opioid neurotransmission in women

Deciphering nociplastic pain: clinical features, risk factors and potential mechanisms

Nociplastic pain is a mechanistic term used to describe pain that arises or is sustained by altered nociception, despite the absence of tissue damage. Although nociplastic pain has distinct pathophysiology from nociceptive and neuropathic pain, these pain mechanisms often coincide within individuals, which contributes to the intractability of chronic pain. Key symptoms of nociplastic pain include pain in multiple body regions, fatigue, sleep disturbances, cognitive dysfunction, depression and anxiety. Individuals with nociplastic pain are often diffusely tender - indicative of hyperalgesia and/or allodynia - and are often more sensitive than others to non-painful sensory stimuli such as lights, odours and noises. This Review summarizes the risk factors, clinical presentation and treatment of nociplastic pain, and describes how alterations in brain function and structure, immune processing and peripheral factors might contribute to the nociplastic pain phenotype. This article concludes with a discussion of two proposed subtypes of nociplastic pain that reflect distinct neurobiological features and treatment responsivity.

Musculoskeletal pain among Chinese women during the menopausal transition: findings from a longitudinal cohort study

ABSTRACT

The profiles of muscle and joint pain throughout the menopausal transition and the factors associated with these symptoms have not been determined. A total of 609 participants from a longitudinal cohort study conducted in an urban Chinese community were enrolled in this study. We assessed the prevalence of musculoskeletal symptoms at different menopausal stages and explored the factors associated with these symptoms. The prevalence and severity of muscle and joint pain increase as menopausal stages progress, and late menopausal transition may be a crucial timepoint that triggers the onset of musculoskeletal pain. The results of the multivariate analysis revealed that poor health status (OR = 2.245, 95% CI = 1.714-2.94, P < 0.001), body mass index (BMI) (OR = 1.046, 95% CI = 1.01-1.084, P = 0.011), the presence of anxiety (OR = 1.601, 95% CI = 1.211-2.117, P < 0.001), and depression (OR = 1.368, 95% CI = 1.143-1.639, P < 0.001) were independently associated with muscle and joint pain. In addition, the severity of musculoskeletal pain was related to poor health status (OR = 2.738, 95% CI = 1.91-3.924, P < 0.001) and depression (OR = 1.371, 95% CI = 1.095-1.718, P = 0.006). Musculoskeletal symptoms are frequent somatic symptoms experienced by Chinese middle-aged women. Women with poor health status, high BMI, anxiety, and depression were at heightened risk of experiencing musculoskeletal pain. The severity of pain increased over time.

Sex Differences in Visceral Pain and Comorbidities: Clinical Outcomes, Preclinical Models, and Cellular and Molecular Mechanisms

Sexual dimorphism of visceral pain has been documented in clinics and experimental animal models. Aside from hormones, emerging evidence suggests the sex-differential intrinsic neural regulation of pain generation and maintenance. According to the International Association for the Study of Pain (IASP) and the American College of Gastroenterology (ACG), up to 25% of the population have visceral pain at any one time, and in the United States 10-15 percent of adults suffer from irritable bowel syndrome (IBS). Here we examine the preclinical and clinical evidence of sex differences in visceral pain focusing on IBS, other forms of bowel dysfunction and IBS-associated comorbidities. We summarize preclinical animal models that provide a means to investigate the underlying molecular mechanisms in the sexual dimorphism of visceral pain. Neurons and nonneuronal cells (glia and immune cells) in the peripheral and central nervous systems, and the communication of gut microbiota and neural systems all contribute to sex-dependent nociception and nociplasticity in visceral painful signal processing. Emotion is another factor in pain perception and appears to have sexual dimorphism.

Interactions Between Endocannabinoid and Endogenous Opioid Systems Prospectively Influence Postoperative Opioid Use in Pregnant Patients Undergoing Cesarean Delivery

Both endocannabinoid (EC) and endogenous opioid systems are involved in nociceptive processing and may work together synergistically based on preclinical models. This study evaluated the interactive effects of preoperative beta-endorphin concentrations (a key analgesic endogenous opioid) in cerebrospinal fluid (CSF) and ECs (CSF and plasma 2-arachidonoylglycerol [2-AG] and plasma anandamide [AEA]) on postoperative opioid use and pain intensity in a prospective cohort of n = 112 pregnant patients undergoing scheduled cesarean delivery. Maternal blood and CSF samples were collected preoperatively for beta-endorphin and EC assays. Patients completed measures of outpatient opioid use (number of tablets used and days of use) and average pain intensity at 2 weeks postoperatively. Results of general linear model analyses controlling for maternal age, BMI at time of delivery, and race revealed significant multiplicative interactions between EC and beta-endorphin concentrations on number of opioid tablets used (based on pill count), days of opioid use, and total milligram morphine equivalents used in the 2 week follow-up period. Elevated preoperative plasma and CSF 2-AG predicted reduced outpatient opioid analgesic use particularly for patients low in CSF beta-endorphin. Similar analyses for pain intensity at 2-week follow-up indicated a significant interaction (p<.02) characterized by higher preoperative beta-endorphin concentrations being associated with lower subsequent pain only for individuals with low preoperative plasma AEA concentrations. Further exploration of interactions between EC and endogenous opioid inhibitory systems as they influence responses to opioid analgesics in other clinical pain populations may help guide development of precision pain management approaches. PERSPECTIVE: In the postoperative setting of patients undergoing cesarean delivery, elevated endocannabinoids were linked to reduced outpatient opioid analgesic use in individuals who had low endogenous opioid concentrations in cerebrospinal fluid. Further exploration of interactions between these two inhibitory systems as they impact on responses to pain management interventions appears warranted.

Associations between the severity of menopausal symptoms and musculoskeletal pain in postmenopausal Portuguese women

OBJECTIVE

To analyze the association of the severity of the menopausal symptoms with musculoskeletal pain in Portuguese postmenopausal women.

METHODS

A cross-sectional, observational study was conducted on 167 women (63.85 ± 9.36 years). The Menopause Rating Scale was used to evaluate the menopausal symptoms severity, while the Nordic Musculoskeletal Questionnaire was employed to assess the localization of the musculoskeletal pain, and multi-located pain was determined if two or more body regions were affected. Depression (Hospital Anxiety and Depression Scale), age, body mass index (BMI) and physical activity level were considered as potential confounders.

RESULTS

A greater severity of the somato-vegetative menopausal symptoms was related to the prevention from usual activities because of pain in the neck, shoulders, elbows, wrists/hands and knees (R2 of Nagelkerke = 0.064, 0.043, 0.074, 0.045 and 0.045, respectively). Associations were also observed between greater age and pain in the knees, ankles and feet (R2 of Nagelkerke = 0.036 and 0.034, respectively), and being physically inactive with upper back pain (R2 of Nagelkerke = 0.060). Higher depressive symptoms were linked to pain in the hip/thighs and knees (R2 of Nagelkerke = 0.067 and 0.085, respectively), as well as being physically inactive was related ton in the neck (R2 of Nagelkerke = 0.053). Only a greater BMI was related to multi-located pain in the last 7 days (R2 of Nagelkerke = 0.041).

CONCLUSIONS

The findings of our study showed that, taking into account possible confounders, greater severity of the menopausal symptoms at a somatic-vegetative level was associated with more anatomical regions with musculoskeletal pain.

Sex- and gender-specific differences in symptoms and health-related quality of life among patients with gastroesophageal reflux disease

Gastroesophageal Reflux Disease (GERD) is a common chronic gastrointestinal disorder affecting both men and women. Nonerosive reflux disease generally affects more women, whereas GERD complications such as Barrett's esophagus (BE) or esophageal cancer affect more men. The aim of this study was to evaluate sex- and gender-specific symptoms and health-related quality of life (HRQoL) among men and women with GERD. Patients with clinical signs of reflux and completion of 24-hour pH-Impedance testing at the University Hospital Cologne were included into the study. Evaluation of symptoms and HRQoL included the following validated questionnaires: GERD-Health-Related Quality of Life (GERD HRQL), Gastrointestinal Quality of Life Index (GIQLI), and Hospital Anxiety and Depression Scale (HADS). In all, 509 women and 355 men with GERD were included. Men had a significantly higher DeMeester score (60.2 ± 62.6 vs. 43 ± 49.3, P < 0.001) and a higher incidence of BE (18.6 vs. 11.2%, P = 0.006). Women demonstrated significantly higher levels of anxiety (30.9 vs. 14.5%, P = 0.001), more severely impacting symptoms (45.3 ± 11.3 vs. 49.9 ± 12.3, P < 0.001), as well as physical (14.2 ± 5.7 vs. 16.7 ± 5.6, P < 0.001) and social dysfunction (13.3 ± 4.8 vs. 14.8 ± 4.3, P = 0.002). Women further reported a lower HRQoL (85.3 ± 22.7 vs. 92.9 ± 20.8, P < 0.001). Men and women differ on biological, psychological, and sociocultural levels.

Estradiol and Mu opioid-mediated reward: The role of estrogen receptors in opioid use

Opioid use and opioid use disorder are characterized by sex and gender differences, and some of these differences may be mediated by differences in the hormonal milieu within and across individuals. This review focuses on the role of ovarian hormones, and particularly estradiol, on the endogenous mu opioid receptor system. There is an abundance of data indicating that estradiol influences the activity of endogenous mu opioid peptides, the activation of mu opioid receptors, and the internalization and desensitization of mu opioid receptors. These effects have functional consequences on behaviors mediated by endogenous mu opioid receptor activity and on sensitivity to mu opioid agonists and antagonists. Recent behavioral data suggest these consequences extend to mu opioid reward, and preclinical studies report that estradiol decreases self-administration of mu opioid receptor agonists across a range of experimental conditions. Data collected in human laboratory studies suggest that estradiol may have functionally similar effects in clinical populations, and thus estrogen receptors may be a potential target in the development of novel therapeutics. This review summarizes data from cellular assays to clinical trials to explore how estradiol influences mu opioid receptor activity, as well as potential ways in which estrogen receptors may be targeted to address the problems of opioid use.

Daily treatment with the dual orexin receptor antagonist DORA-12 during oxycodone abstinence decreases oxycodone conditioned reinstatement

Chronic opioid use disturbs circadian rhythm and sleep, encouraging opioid use and relapse. The orexin (OX) system is recruited by opioids and regulates physiological processes including sleep. Dual OX receptor antagonists (DORAs), developed for insomnia treatment, may relieve withdrawal-associated sleep disturbances. This study investigated whether DORA-12, a recently developed DORA, reduces physiological activity disturbances during oxycodone abstinence and consequently prevents oxycodone-seeking behavior. Male and female Wistar rats were trained to intravenously self-administer oxycodone (0.15 mg/kg, 21 sessions; 8 h/session) in the presence of a contextual/discriminative stimulus (SD). The rats were subsequently housed individually (22 h/day) to monitor activity, food and water intake. They received DORA-12 (0-30 mg/kg, p.o.) after undergoing daily 1-h extinction training (14 days). After extinction, the rats were tested for oxycodone-seeking behavior elicited by the SD. Hypothalamus sections were processed to assess oxycodone- or DORA-12-associated changes to the OX cell number. In males, oxycodone-associated increases in activity during the light-phase, reinstatement, and decreases in the number of OX cells observed in the vehicle-treated group were not observed with DORA-12-treatment. Oxycodone-associated increases in light-phase food and water intake were not observed by day 14 of 3 mg/kg DORA-12-treatment and dark-phase water intake was increased across treatment days. In females, OX cell number was unaffected by oxycodone or DORA-12. Three and 30 mg/kg DORA-12 increased females' day 7 dark-phase activity and decreased reinstatement. Thirty mg/kg DORA-12 reduced oxycodone-associated increases in light-phase food and water intake. The results suggest that DORA-12 improves oxycodone-induced disruptions to physiological activities and reduces relapse.

Advances of autoimmune rheumatic diseases related to malignant tumors

BACKGROUND

Malignant neoplasms are a well-recognized global public health concern, with significant impacts on human health and quality of life. The interplay between tumors and autoimmune rheumatic diseases is complex, and the resulting tumor-associated rheumatic diseases represent a rare and intricate group of conditions that occur in the context of malignant tumors. In addition, various rheumatic diseases can arise as a consequence of oncology treatment. These diseases present with intricate clinical manifestations and pathological features, often rendering them challenging to diagnose and impacting patients' quality of life. Despite this, they have yet to be fully recognized.

METHODS

This article presents a literature review of published original articles and review articles concerning paraneoplastic rheumatic syndromes and rheumatic diseases associated with cancer treatment. We conducted a comprehensive literature search in PubMed, Web of Science and Google Scholar databases, excluding duplicated and irrelevant studies. In cases of duplicated research, we selected articles with higher impact factors for the review.

RESULTS

This review focuses on the clinical features, diagnosis, and treatment of paraneoplastic rheumatic diseases, as well as the pathogenesis of these diseases. Additionally, we summarize the autoimmune rheumatic diseases associated with cancer treatment. Ultimately, the goal of this review is to enhance recognition and improve the management of autoimmune rheumatic diseases related to tumors.

Migraine in older adults

Migraine is an evolving, and sometimes lifelong disorder. The prevalence of episodic migraine peaks among individuals aged in their late 30s, implying a tendency for the disorder to remit with increasing age thereafter, whereas chronic migraine is more likely to persist into later life. Diagnosis and treatment of migraine in older adults, defined as individuals aged 60 years or older, is rendered more complex by increasing probabilities of atypical clinical features and comorbidities, with patients' comorbidities sometimes limiting their therapeutic options. However, the changing clinical presentation of migraine over an individual's lifespan is not well characterised. The neurobiological basis of remission in older adults remains unclear, although vascular, neuronal, and hormonal changes are likely to be involved. Long-term longitudinal studies of individuals with migraine would be particularly informative, with the potential not only to suggest new research directions, but also to lead to the identification of novel therapeutic agents. Although several novel migraine medications are becoming available, their effectiveness, tolerability, and safety often remain uncertain in older adults, who have commonly been excluded from the evaluation of these agents in randomised controlled trials, or who constitute only a small proportion of study populations. There is a need to recognise these limitations in the available evidence, and the specific, and often unmet, clinical needs of older adults with migraine, not least because older adults constitute an increasing proportion of populations worldwide.

Sexual Dimorphism in the Mechanism of Pain Central Sensitization

It has long been recognized that men and women have different degrees of susceptibility to chronic pain. Greater recognition of the sexual dimorphism in chronic pain has resulted in increasing numbers of both clinical and preclinical studies that have identified factors and mechanisms underlying sex differences in pain sensitization. Here, we review sexually dimorphic pain phenotypes in various research animal models and factors involved in the sex difference in pain phenotypes. We further discuss putative mechanisms for the sexual dimorphism in pain sensitization, which involves sex hormones, spinal cord microglia, and peripheral immune cells. Elucidating the sexually dimorphic mechanism of pain sensitization may provide important clinical implications and aid the development of sex-specific therapeutic strategies to treat chronic pain.

Low back pain and osteoarthritis pain: a perspective of estrogen

Low back pain (LBP) is the world's leading cause of disability and is increasing in prevalence more rapidly than any other pain condition. Intervertebral disc (IVD) degeneration and facet joint osteoarthritis (FJOA) are two common causes of LBP, and both occur more frequently in elderly women than in other populations. Moreover, osteoarthritis (OA) and OA pain, regardless of the joint, are experienced by up to twice as many women as men, and this difference is amplified during menopause. Changes in estrogen may be an important contributor to these pain states. Receptors for estrogen have been found within IVD tissue and nearby joints, highlighting the potential roles of estrogen within and surrounding the IVDs and joints. In addition, estrogen supplementation has been shown to be effective at ameliorating IVD degeneration and OA progression, indicating its potential use as a therapeutic agent for people with LBP and OA pain. This review comprehensively examines the relationship between estrogen and these pain conditions by summarizing recent preclinical and clinical findings. The potential molecular mechanisms by which estrogen may relieve LBP associated with IVD degeneration and FJOA and OA pain are discussed.

The historical progression of positron emission tomography research in neuroendocrinology

The rapid and continual development of a number of radiopharmaceuticals targeting different receptor, enzyme and small molecule systems has fostered Positron Emission Tomography (PET) imaging of endocrine system actions in vivo in the human brain for several decades. PET radioligands have been developed to measure changes that are regulated by hormone action (e.g., glucose metabolism, cerebral blood flow, dopamine receptors) and actions within endocrine organs or glands such as steroids (e.g., glucocorticoids receptors), hormones (e.g., estrogen, insulin), and enzymes (e.g., aromatase). This systematic review is targeted to the neuroendocrinology community that may be interested in learning about positron emission tomography (PET) imaging for use in their research. Covering neuroendocrine PET research over the past half century, researchers and clinicians will be able to answer the question of where future research may benefit from the strengths of PET imaging.

Ovarian vein surgical ablation versus endovascular technique for treatment of pelvic vein incompetence

OBJECTIVE

Chronic pelvic pain in women is a disorder brought on by pelvic vein incompetence (PVI). In this prospective, randomized study, the effects of percutaneous coil embolization and surgical ovarian vein ligation and division combined with retrograde sclerotherapy were compared with regard to ovarian vein occlusion, improvement of pelvic congestion symptoms, and their influence on estradiol level after intervention.

METHODS

A total of 50 patients with PVI were enrolled, with a mean age of 31.9 ± 4.7 years and a pain score of 9 (range, 0-10; from 0 [no pain] to 10 [the highest level of pain]). Both percutaneous coil embolization of ovarian veins (endovascular group) and surgical ovarian vein ablation with retrograde sclerotherapy were offered to the patients at random.

RESULTS

In the open group, the pain level decreased to 2, whereas in the endovascular group, it decreased to 1 (range, 0-10). Estradiol levels were 224 (range, 9-612) in the open group and 478 (range, 18-613) in the endovascular group before the intervention, with no significant change (P = .1120). After 1 week of intervention, estradiol levels in the open group were 89 (range, 18-243) and 124 (range, 22-298) in the endovascular group, respectively, with statistical insignificance (P = .225). After 1 month of intervention, the endovascular group's estradiol level was 101 (range, 20-196) and the open group's was 89 (range, 15-190) (P = .382). After 3 months of intervention, the open group's estradiol level was 78 (range, 12-132) and the endovascular group's was 65 (range, 18-110) (P = .045).

CONCLUSIONS

In addressing PVI, both methods seemed to have promising results. Nevertheless, endovascular management was more effective at decreasing estrogen levels and relieving discomfort. Three months should be the time at which estradiol levels are measured, because this is when they are at their lowest. In both the open and endovascular groups as well as in the pooled data, there was a significant association between estradiol level from before the intervention and improvement in pain scores (P = .005). Because it was linked to a lower pain score, the high preoperative estradiol level can be used to predict postintervention improvement.

The effects of estradiol levels on crossmodal perception: a study on the sound induced flash illusion in healthy and menstrually related migraine individuals

OBJECTIVE

The sound-induced flash illusion (SIFI) is a valid paradigm to study multisensorial perception. In the "fission" SIFI, multiple flashes are perceived when observing a single flash paired with two or more beeps. SIFI is largely dependent on visual and acoustic cortex excitability; in migraine, dysfunctional cortical excitability affects SIFI perception. Since estrogen peak occurring during ovulation can increase neuronal excitability, the present study aims to verify whether cortical excitability shifts linked to the menstrual cycle could influence SIFI.

METHODS

In a comparative prospective study, we tested the effect of estrogens on crossmodal perception using the SIFI. We recruited 27 females in reproductive age, including 16 healthy and 11 menstrually related migraine females, testing their proneness to SIFI on day 14 (high estradiol) and day 27 (low estradiol) of menstrual cycle.

RESULTS

Women on day 14 reported less flashes than on day 27 (p = 0.02) in the fission illusion, suggesting a pro-excitatory effect of estradiol on visual cortex excitability during ovulation. Moreover, we confirmed that migraine women perceived less flashes (p = 0.001) than controls, independently from cycle phase. Non-migraineurs women significantly reported more flashes on day 27 than on day 14 (p = 0.04).

CONCLUSIONS

This study suggests that estradiol may influence the multisensory perception due to changes of visual cortex excitability, with high estradiol peak leading to increased visual cortical sensitivity during ovulation in non-migraineurs. Visual cortex hyperresponsiveness, here reflected by reduced SIFI, is not influenced by estradiol fluctuations in migraine women, as shown by reduced fission effects on day 14 and 27.

Sex-specific differences in alcohol-induced pain sensitization

Pain sensitization is a phenomenon that occurs to protect tissues from damage and recent studies have shown how a variety of non-noxious stimuli included in our everyday lives can lead to pain sensitization. Consumption of large amounts of alcohol over a long period of time invokes alcohol use disorder (AUD), a complex pathological state that has many manifestations, including alcohol peripheral neuropathy (neuropathic pain). We asked if 'non-pathological' alcohol consumption can cause pain sensitization in the absence of other pathology? Studies have pointed to glia and other immune cells and their role in pain sensitization that results in cell and sex-specific responses. Using a low-dose and short-term ethanol exposure model, we investigated whether this exposure would sensitize mice to a subthreshold dose of an inflammatory mediator that normally does not induce pain. We observed female mice exhibited specific mechanical and higher thermal sensitivity than males. We also observed an increase in CD68⁺ macrophages in the ipsilateral dorsal root ganglia (DRG) and Iba1⁺ microglia in the ipsilateral spinal dorsal horn of animals that were exposed to ethanol and injected with subthreshold inflammatory prostaglandin E2. Our findings suggest that short-term ethanol exposure stimulates peripheral and central, immune and glial activation, respectively to induce pain sensitization. This work begins to reveal a possible mechanism behind the development of alcoholic peripheral neuropathy.

The genetic basis of endometriosis and comorbidity with other pain and inflammatory conditions

Endometriosis is a common condition associated with debilitating pelvic pain and infertility. A genome-wide association study meta-analysis, including 60,674 cases and 701,926 controls of European and East Asian descent, identified 42 genome-wide significant loci comprising 49 distinct association signals. Effect sizes were largest for stage 3/4 disease, driven by ovarian endometriosis. Identified signals explained up to 5.01% of disease variance and regulated expression or methylation of genes in endometrium and blood, many of which were associated with pain perception/maintenance (SRP14/BMF, GDAP1, MLLT10, BSN and NGF). We observed significant genetic correlations between endometriosis and 11 pain conditions, including migraine, back and multisite chronic pain (MCP), as well as inflammatory conditions, including asthma and osteoarthritis. Multitrait genetic analyses identified substantial sharing of variants associated with endometriosis and MCP/migraine. Targeted investigations of genetically regulated mechanisms shared between endometriosis and other pain conditions are needed to aid the development of new treatments and facilitate early symptomatic intervention.

Suvorexant, an FDA-approved dual orexin receptor antagonist, reduces oxycodone self-administration and conditioned reinstatement in male and female rats

Background: The Department of Health and Human Services reports that prescription pain reliever (e.g., oxycodone) misuse was initiated by 4,400 Americans each day in 2019. Amid the opioid crisis, effective strategies to prevent and treat prescription opioid use disorder (OUD) are pressing. In preclinical models, the orexin system is recruited by drugs of abuse, and blockade of orexin receptors (OX receptors) prevents drug-seeking behavior. The present study sought to determine whether repurposing suvorexant (SUV), a dual OX receptor antagonist marketed for the treatment of insomnia, can treat two features of prescription OUD: exaggerated consumption and relapse. Methods: Male and female Wistar rats were trained to self-administer oxycodone (0.15 mg/kg, i. v., 8 h/day) in the presence of a contextual/discriminative stimulus (S^D) and the ability of SUV (0-20 mg/kg, p. o.) to decrease oxycodone self-administration was tested. After self-administration testing, the rats underwent extinction training, after which we tested the ability of SUV (0 and 20 mg/kg, p. o.) to prevent reinstatement of oxycodone seeking elicited by the S^D. Results: The rats acquired oxycodone self-administration and intake was correlated with the signs of physical opioid withdrawal. Additionally, females self-administered approximately twice as much oxycodone as males. Although SUV had no overall effect on oxycodone self-administration, scrutiny of the 8-h time-course revealed that 20 mg/kg SUV decreased oxycodone self-administration during the first hour in males and females. The oxycodone S^D elicited strong reinstatement of oxycodone-seeking behavior that was significantly more robust in females. Suvorexant blocked oxycodone seeking in males and reduced it in females. Conclusions: These results support the targeting of OX receptors for the treatment for prescription OUD and repurposing SUV as pharmacotherapy for OUD.

Association between nociplastic pain and premature endocrine therapy discontinuation in breast cancer patients

PURPOSE

At least 5 years of adjuvant endocrine therapy (ET) is recommended for patients with hormone receptor-positive invasive breast cancer to reduce cancer recurrence risk. Up to half of patients prematurely discontinue ET, often due to musculoskeletal pain. Nociplastic pain is abnormal central nervous system pain processing without evidence of tissue or neuronal damage. This study aimed to evaluate the relationship between baseline nociplastic pain and ET discontinuation.

METHODS

This was a retrospective, single center, cohort study. Included patients were female, had stage 0-III invasive breast cancer, did not receive neoadjuvant therapy, and completed quality of life questionnaires prior to breast surgery, including Fibromyalgia Survey for nociplastic pain. Clinical data including duration of ET were abstracted from the medical record. Patient characteristics were analyzed with t-tests and Chi-squared tests, as appropriate. Univariate and multivariable regressions were performed with Cox proportional hazard models.

RESULTS

Six hundred eighty-one patients diagnosed between 2012 and 2019 met inclusion criteria; 480 initiated ET and were included in the analysis. Of these 480 patients, 203 (42.3%) prematurely discontinued initial ET therapy. On univariate analysis, tamoxifen use (hazard ratio [HR] 0.70, p = 0.021) and premenopausal status (HR 0.73, p = 0.04) were inversely associated with ET discontinuation, while Fibromyalgia Score was positively associated (HR 1.04, p = 0.043). On multivariable analysis, baseline Fibromyalgia Score remained associated with ET discontinuation.

CONCLUSION

Nociplastic pain present prior to surgery was associated with premature ET discontinuation. Fibromyalgia Score screening may be useful for evaluating ET discontinuation risk. Treatments targeting nociplastic pain may be more effective for treating ET-emergent pain.

Sex Differences in Pain and Its Treatment

Pain is a highly personal experience. Pain is often considered to be a purely neurologic phenomenon, but in actuality, it is a combination of both sensory and emotional experiences. This has sometimes been translated clinically toward a more mechanistic approach to the assessment and treatment of pain instead of one that does not discount pain mechanisms, but also is more inclusive of the need for humanism - considering the individual. In today's medical environment, more than ever before there is a significant amount of attention being paid to educating clinicians to better understand that several physiological, neurophysiological, and psychosocial factors can significantly impact responses to pain. The composition of these factors will be unique to that individual's life narrative, context, sex, and prior life experiences. Thus, the concept that a templated approach to pain assessment and pharmacotherapeutic treatment planning should not be expected to provide optimal patient satisfaction and treatment outcomes in the majority. The hypotheses that there may be sex-based differences in the pain experience in a variety of ways including pain sensitivity, tolerance to pain, threshold at which something becomes painful, and the effectiveness of endogenous pain modulation systems are not new and have been well represented in the literature. This chapter reviews important key findings in the scientific literature with respect to sex-based differences in pain and pain responses to experimentally induced painful stimuli, pain experienced in commonly occurring painful medical conditions, and variations in responses to pain treatments. Possible explanations to account for observed differences or similarities will also be discussed.

Cardiovascular Disease in Women: What the Radiologist Needs to Know

BACKGROUND

 Sex-specific disparities are well documented for cardiovascular disease (CVD). There are differences in physiology and pathophysiology, pain perception, spectrum of disease, risk, therapeutic aspects, prognosis, and outcome. CVD represents a broad spectrum of disorders. This review focuses on cardiovascular and cardiac pathology.

METHOD

 This review summarizes the current state of the literature on cardiovascular disease in women from a radiological viewpoint. It aims to provide a deeper understanding of these differences and thereby alerts the reader to the potential of CT and MRI for diagnosing CVD in women. Special attention is paid to disparities in the underlying physiological and pathophysiological processes, clinical presentation, and the quality of care to provide a deep understanding of the topic. Cardiovascular and cardiac pathologies with a sex-specific pattern of disease are presented and typical CT and MRI findings are arranged and illustrated with imaging findings.

RESULTS AND CONCLUSION

 Sex-specific differences are not only sex hormonal in nature but are rooted in the epigenome and encompass a multitude of physiological systems. In fact, cardiovascular disease shows sex-specific characteristics spanning from incidence to clinical presentation, course of disease, and prognosis. This is of significance regarding pretest probabilities, the power of tests, imaging strategies, and interpretation of imaging results. Key sex-specific issues encompass obstructive and non-obstructive coronary artery disease (CAD), microvascular angina, myocardial infarction with non-obstructive CAD, and coronary artery dissection. Sex-specific patterns are also noted in myocardial disease and heart failure such as pregnancy-related heart disease, Takotsubo syndrome, and anthracycline-induced cardiotoxicity.

KEY POINTS

  · Cardiovascular diseases have sex-specific characteristics.. · Imaging strategies and interpretation of imaging results should be adjusted for women.. · Imaging helps in the improvement of the sex-specific management of cardiovascular disease..

Effects of sarcopenia and sarcopenic obesity on joint pain and degenerative osteoarthritis in postmenopausal women

This study aimed to identify the prevalence of sarcopenia, obesity, and sarcopenic obesity and examine their association with radiographic knee osteoarthritis (OA) and knee pain in Korean postmenopausal women. This cross-sectional study utilized the data from Korean National Health and Nutrition Examination Surveys 2009–2011. The participants were categorized into 4 groups based on body composition: either sarcopenic (appendicular skeletal muscle < 23%) or not, either obese (body mass index ≥ 25.0 kg/m²) or not. The prevalence of radiographic knee OA and knee pain was calculated. The effect of hormone replacement therapy (HRT) was also evaluated. The prevalence of radiographic knee OA, knee pain, and both were all highest in the sarcopenic obese group and lowest in the control group (61.49% vs. 41.54%, 39.11% vs. 27.55%, 32.04% vs. 17.82%, all p < 0.001). Without sarcopenia, obese women showed significantly higher ratio of radiographic knee OA only (57.64% vs. 41.54%, p < 0.001). With sarcopenia, the coexistence of obesity presented higher ratio of radiographic knee OA, knee pain, and both compared to sarcopenia without obesity (61.49% vs. 41.82%, 39.11% vs. 27.61%, 32.04% vs. 17.60%, all p < 0.001). The use of HRT for more than 1 year was not associated with radiographic knee OA, knee pain, or both (p = 0.147, 0.689 and 0.649, respectively). Obesity with sarcopenia had greater effect on knee OA compared to obesity without sarcopenia. Moreover, HRT use for more than 1 year was not associated with the prevalence of knee OA. Therefore, more efforts should focus on reducing body fat and increasing muscle in postmenopausal women with knee OA.

Modulation of morphine physical dependence and discriminative stimulus effects by ovarian hormones: Role of estradiol

Ovarian hormones influence the activity of endogenous opioids, and exogenous administration of estradiol reduces opioid intake and opioid seeking in animal models of opioid reward and reinforcement. The purpose of this study was to examine the effects of ovarian hormones on the discriminative stimulus effects of morphine and naloxone-precipitated opioid withdrawal. To this end, separate groups of ovariectomized female rats were trained to discriminate the stimulus effects of either 3.0 or 10 mg/kg morphine, and substitution tests were conducted with estradiol or progesterone alone and in combination with morphine. At the conclusion of discrimination testing, rats were treated chronically with estradiol, progesterone, or their combination, and challenged with naloxone to measure opioid-like withdrawal symptoms. Finally, the effects of estradiol, progesterone, and their combination were examined on naloxone-precipitated withdrawal in morphine-dependent rats. Neither estradiol nor progesterone substituted for the morphine discriminative stimulus, but estradiol significantly increased the potency of morphine in rats trained to discriminate 10 mg/kg but not 3 mg/kg morphine. When administered chronically, neither hormone nor their combination produced an opioid-like withdrawal syndrome following a naloxone challenge. Acute administration of estradiol, but not progesterone or a combination of estradiol and progesterone, significantly reduced naloxone-precipitated weight loss in morphine-dependent rats. These data indicate that estradiol influences the behavioral effects of morphine, possibly by increasing endogenous tone at mu opioid receptors.

Resistance training reduced luteinising hormone levels in postmenopausal women in a substudy of a randomised controlled clinical trial: A clue to how resistance training reduced vasomotor symptoms

Background

Vasomotor symptoms (VMS) are common around menopause. Menopausal hormone therapy is the most effective treatment for VMS. Physical exercise has been proposed as an alternative treatment since physically active women have previously been found to experience fewer VMS than inactive women. In our randomised controlled trial on resistance training to treat VMS, sympoms were reduced by 50% in the intervention group compared with the control group.

Objectives

To propose a mechanism to explain how resistance training reduced VMS and to assess if luteinizing hormone (LH) and follicle stimulating hormone (FSH) were affected in accordance with the proposed mechanism.

Trial design and methods

A substudy of a randomized controlled trial on 65 postmenopausal women with VMS and low physical activity who were randomised to 15 weeks of resistance training three times per week (n = 33) or to a control group (n = 32). To be regarded compliant to the intervention we predecided a mean of two training sessions per week. The daily number of VMS were registered before and during the 15 weeks. Blood samples were drawn for analysis of LH and FSH at baseline and after 15 weeks.

Results

LH decreased significantly in the compliant intervention group compared with the control group (-4.0±10.6 versus 2.9±9.0, p = 0.028 with Mann-Whitney U test). FSH also decreased in the compliant intervention group compared with the control group, however not enough to reach statistical significance (-3.5±16.3 versus 3.2±18.2, p = 0.063 with Mann-Whitney U test). As previously published the number of hot flushes decreased significantly more in the intervention group than in the control group but there was no association between change in LH or FSH and in number of VMS.

Conclusions

We propose that endogenous opiods such as β-endorphin or dynorphin produced during resistance training decreased VMS by stimulating KNDγ-neurons to release neurokinin B to the hypothalamic thermoregulatory centre. Through effects on KNDγ-neurons, β-endorphin could also inhibit GnRH and thereby decrease the production of LH and FSH. The significanty decreased LH in the compliant intervention group compared with the control group was in accordance with the proposed mechanism.

Reliability of conditioned pain modulation in healthy individuals and chronic pain patients: a systematic review and meta-analysis

OBJECTIVES

Conditioned pain modulation (CPM) is a psychophysical parameter that is used to reflect the efficacy of endogenous pain inhibition. CPM reliability is important for research and potential clinical applications. The aim of this systematic review and meta-analysis was to evaluate the reliability of CPM tests in healthy individuals and chronic pain patients.

METHODS

We searched three databases for peer-reviewed studies published from inception to October 2020: EMBASE, Web of Science and NCBI. Risk of bias and the quality of the included studies were assessed. A meta-analysis with a random effects model was conducted to estimate intraclass correlation coefficients (ICCs).

RESULTS

Meta-analysis was performed on 25 papers that examined healthy participants (k=21) or chronic pain patients (k=4). The highest CPM intra-session reliability was with pressure as test stimulus (TS) and ischemic pressure (IP) or cold pressor test (CPT) as conditioning stimulus (CS) in healthy individuals (ICC 0.64, 95% CI 0.45-0.77), and pressure as TS with CPT as CS in patients (ICC 0.77, 95% CI 0.70-0.82). The highest inter-session ICC was with IP as TS and IP or CPT as CS (ICC 0.51, 95% CI 0.42-0.59) in healthy subjects. The only data available in patients for inter-session reliability were with pressure as TS and CPT as CS (ICC 0.44, 95% CI 0.11-0.69). Quality ranged from very good to excellent using the QACMRR checklist. The majority of the studies (24 out of 25) scored inadequate in Kappa coefficient reporting item of the COSMIN-ROB checklist.

CONCLUSIONS

Pressure and CPT were the TS and CS most consistently associated with good to excellent intra-session reliability in healthy volunteers and chronic pain patients. The inter-session reliability was fair or less for all modalities, both in healthy volunteers and chronic pain patients.

Role of Estrogens in Menstrual Migraine

Migraine is a major neurological disorder affecting one in nine adults worldwide with a significant impact on health care and socioeconomic systems. Migraine is more prevalent in women than in men, with 17% of all women meeting the diagnostic criteria for migraine. In women, the frequency of migraine attacks shows variations over the menstrual cycle and pregnancy, and the use of combined hormonal contraception (CHC) or hormone replacement therapy (HRT) can unveil or modify migraine disease. In the general population, 18–25% of female migraineurs display a menstrual association of their headache. Here we present an overview on the evidence supporting the role of reproductive hormones, in particular estrogens, in the pathophysiology of migraine. We also analyze the efficacy and safety of prescribing exogenous estrogens as a potential treatment for menstrual-related migraine. Finally, we point to controversial issues and future research areas in the field of reproductive hormones and migraine.

Stress-induced analgesia: an evaluation of effects on temporal summation of pain and the role of endogenous opioid mechanisms

Acute stress reduced the initial pain rating in a temporal summation protocol via nonopioid mechanisms but did not affect temporal summation slope, an indicator of central sensitization.

Introduction:

Objectives:

Methods:

Results:

Conclusions:

Effects of placebo administration on immune mechanisms and relationships with central endogenous opioid neurotransmission

Behavioral conditioning and expectation can have profound impact on animal and human physiology. Placebo, administered under positive expectation in clinical trials, can have potent effects on disease pathology, obscuring active medications. Emerging evidence suggests placebo-responsive neurotransmitter systems (e.g., endogenous opioid) regulate immune function by manipulating inflammatory proteins including IL-18, a potent pro-inflammatory, nociceptive cytokine implicated in pathophysiology of various diseases. Validation that neuroimmune interactions involving brain μ-opioid receptor (MOR) activity and plasma IL-18 underlie placebo analgesic expectation could have widespread clinical applications. Unfortunately, current lack of mechanistic clarity obfuscates clinical translation. To elucidate neuroimmune interactions underlying placebo analgesia, we exposed 37 healthy human volunteers to a standardized pain challenge on each of 2 days within a Positron Emission Tomography (PET) neuroimaging paradigm using the MOR selective radiotracer, ¹¹C-Carfentanil (CFN). Each day volunteers received an intervention (placebo under analgesic expectation or no treatment), completed PET scanning, and rated their pain experience. MOR BP_ND parametric maps were generated from PET scans using standard methods. Results showed placebo reduced plasma IL-18 during pain (W₇₄ = -3.7, p < 0.001), the extent correlating with reduction in pain scores. Placebo reduction in IL-18 covaried with placebo-induced endogenous opioid release in the left nucleus accumbens (T₁₄₈ = 3.33; p_uncorr < 0.001) and left amygdala (T₁₄₈ = 3.30; p_uncorr < 0.001). These findings are consistent with a modulating effect of placebo (under analgesic expectation in humans) on a potent nociceptive, pro-inflammatory cytokine (IL-18) and underlying relationships with endogenous opioid activity, a neurotransmitter system critically involved in pain, stress, and mood regulation.

Genetics of menstrual migraine and their association with female hormonal factors

Perimenopause is linked to increased migraine (Mg), especially menstrual Mg (MMg), influenced by hormonal changes. Compared to nonmenstrual attacks, menstrual attacks are more disabling and less responsive to treatment. Women with perimenstrual estrogen withdrawal have been linked to Mg during menstruation, whereas Mg during perimenopause has been linked to unpredictable fluctuations in estrogen levels. It has been widely established that female sex hormones play a role in Mg, but how it occurs remains unclear. This narrative review was identified using Medline and PubMed searches between 1946 and 2021. Search terms included “headache,” “migraine,” “menstrual migraine,” “menstruation,” “menopause,” “perimenopause,” “estrogen,” and “progesterone.” This article focuses on the candidate genes and female hormones that play a role in MMg. More study is necessary to understand better the environmental components that play a critical role in disease development. Currently, there is insufficient clinical evidence to support the function of menstrual Mg. The specific research facts examined MMg unique candidate genes and female hormonal factors that support their association and found MMg etiologic processes for generating an early diagnostic marker.

Impact of biological sex on the outcomes of spinal cord stimulation in patients with chronic pain

BACKGROUND

Spinal cord stimulation (SCS) continues to gain increasing popularity in the pain management field for the treatment of different painful conditions; however, to-date, the correlation between the SCS effectiveness and biological sex has not been fully established. We aimed to investigate the correlation between the biological sex and SCS outcomes.

METHODS

Following Institutional Review Board approval, a retrospective cohort study was performed by collecting data for patients treated with SCS at a tertiary academic center between the years 2002 and 2019. Data was assessed with multivariable linear regression to investigate the association between biological sex and pain scores at baseline, 6-, and 12- months following SCS implantation. Propensity score matching (PSM) was performed based on a set of covariates including age, duration of pain, time since implant, BMI, opioid medications use, smoking, depression and history of alcohol, or substance abuse.

RESULTS

Of the patients treated with SCS implants, 418 patients fit the inclusion and exclusion criteria, out of which the majority were females (272, 65%). The pre-matching data reported a significant difference in history of diabetes and depression and was also significant for greater opioid use in male patients at baseline, 6-, and 12-months post-SCS implant. Propensity score matching (PSM) was performed based on the above mentioned covariant. After matching, no statistical difference was found among the variables, in both groups. Furthermore, after matching no significant differences in the pain scores at baseline, 6-, and 12-months post-SCS implant were observed.

CONCLUSION

No biological sex-based differences in the analgesic response to SCS therapy was detected at 6- and 12-months post-SCS implant between groups with similar demographics, biomedical, and psychological values.

Stress and pain: modality-specific opioid mediation of stress-induced analgesia

Preclinical research has demonstrated that exposure to acute stress is associated with attenuated pain perception, so called stress-induced analgesia (SIA). Mechanisms of SIA in humans have not been reliably demonstrated. This study examined the role of the endogenous opioid system in the impact of combined interpersonal and mental stressors on evoked pain responses in 84 participants (34 women). Using a within-subject, double-blinded, counterbalanced design, participants were administered either oral placebo or the opioid antagonist naltrexone (50 mg) across two testing sessions. In each session, they experienced two evoked pain stimuli (cold pressor test [CPT], heat pain) after an extended rest period (rest condition) and after exposure to an acute stressor (a combination of public speaking and mental arithmetic challenge; stress condition). Results showed that both stress and opioid blockade produced significant changes in hormonal and cardiovascular measures, consistent with successful induction of acute stress. Stress was associated with attenuated pain perception (SIA) as indicated by significantly increased CPT tolerance. These effects were particularly pronounced in individuals experiencing the stress condition first. More importantly, SIA effects on CPT tolerance were abolished by opioid blockade. There were no significant SIA effects on heat pain responses. This study demonstrates that the endogenous opioid system may mediate effects of acute stress on pain perception, although this effect seems to be qualified by the type of evoked pain stimuli experienced.

Variation in the μ-opioid receptor gene (OPRM1) and experiences of felt security in response to a romantic partner's quarrelsome behavior

Research suggests that endogenous opioids play a key role in the creation and maintenance of attachment bonds. Opioids acting at the μ-opioid receptor mediate reward and analgesia and are thus thought to underlie feelings of comfort and warmth experienced in the presence of close others. Disruption of μ-opioidergic activity increases separation distress in animals, suggesting that low opioid states may contribute to social pain. Accordingly, a functional μ-opioid receptor (OPRM1) polymorphism (C77G in primates, A118G in humans) affecting opioidergic signaling has been associated with separation distress and attachment behavior in nonhuman primates, and social pain sensitivity in humans. However, no research has examined the effects of this polymorphism on socioemotional experience, and specifically felt security, in daily interactions between romantic partners. Using an event-contingent recording method, members of 92 cohabiting romantic couples reported their felt security and quarrelsome behavior in daily interactions with each other for 20 days. Consistent with prior work, findings suggested that, relative to AA homozygotes, G allele carriers were more sensitive to their partners' self-reported quarrelsome behaviors (e.g., criticism), showing a greater decline in felt security when their partners reported higher quarrelsome behavior than usual. This is the first study to link variation in OPRM1 with felt security toward romantic partners in everyday social interactions. More generally, this research supports the theory that the attachment system incorporated evolutionarily primitive pain-regulating opioidergic pathways. We also discuss implications of this work for understanding of differential vulnerability to health risks posed by social stress.

Isoflavones derived from plant raw materials: bioavailability, anti-cancer, anti-aging potentials, and microbiome modulation

Isoflavones are secondary metabolites that represent the most abundant category of plant polyphenols. Dietary soy, kudzu, and red clover contain primarily genistein, daidzein, glycitein, puerarin, formononetin, and biochanin A. The structural similarity of these compounds to β-estradiol has demonstrated protection against age-related and hormone-dependent diseases in both genders. Demonstrative shreds of evidence confirmed the fundamental health benefits of the consumption of these isoflavones. These relevant activities are complex and largely driven by the source, active ingredients, dose, and administration period of the bioactive compounds. However, the preclinical and clinical studies of these compounds are greatly variable, controversial, and still with no consensus due to the non-standardized research protocols. In addition, absorption, distribution, metabolism, and excretion studies, and the safety profile of isoflavones have been far limited. This highlights a major gap in understanding the potentially critical role of these isoflavones as prospective replacement therapy. Our general review exclusively focuses attention on the crucial role of isoflavones derived from these plant materials and critically highlights their bioavailability, possible anticancer, antiaging potentials, and microbiome modulation. Despite their fundamental health benefits, plant isoflavones reveal prospective therapeutic effects that worth further standardized analysis.

TMD in Females with Menstrual Disorders

Background: Temporomandibular disorders (TMD) are a common reason for patients to present at dental offices. The majority of people with TMD are women between the age of 20 and 40 years. The purpose of this study was to assess the types and prevalence of temporomandibular disorders in female patients of reproductive age with menstrual disorders. Materials and methods: The study involved 65 females of reproductive age (18–40 years, an average of 28.00 ± 6.27 years). The women who qualified for the study were patients of the University Center for Maternal and Newborn’s Health hospitalized because of infertility or menstrual cycle disorders. Women with confirmed estrogen metabolism disorders participated in a clinical study with the use of Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Results: In the studied female patients with menstrual disorders, temporomandibular disorders (92.3%) were frequent occurrences. The most common type was intra-articular joint disorders (68%). Other reported complaints included masticatory muscle pain (44.62%), and degenerative joint diseases (12.3%). Conclusions: 1. In women with menstrual disorders, TMD may exist. 2. In women with TMD symptoms, their medical history should be extended to include the diagnosis of female hormone disorders.

Hand Osteoarthritis: investigating Pain Effects of estrogen-containing therapy (HOPE-e): a protocol for a feasibility randomised placebo-controlled trial

BACKGROUND

Hand osteoarthritis (OA) is a common condition, causing pain, stiffness and reduced quality of life. Incidence is higher amongst women, particularly around the age of the menopause. Whilst the relationship between sex hormones and OA has been studied in vitro, in epidemiological studies and in clinical trials of hormone replacement therapy (HRT), this study is the first to investigate the effect of estrogen-containing therapy on hand pain in post-menopausal women with symptomatic hand OA in a randomised study design.

METHODS

This is a feasibility study of a double-blinded placebo-controlled intervention with 1:1 randomisation to either a combination of conjugated estrogens 0.45 mg and bazedoxifene acetate 20 mg (Duavive) or placebo. The target population is post-menopausal women with symptomatic hand OA, aiming to recruit 60-90 study participants. The primary objective is to assess the feasibility of a future fully powered randomised controlled trial (RCT). Participants will take the study medication for 24 weeks and be followed up for 28 weeks after randomisation. The primary outcomes used to determine feasibility are eligible participant identification rates and routes; recruitment, randomisation and retention rates of eligible participants; study medication compliance; and the likelihood of unintentional unblinding. Secondary outcomes include measures of hand pain, function, appearance and menopausal symptoms. An end of study questionnaire and focus groups will help to refine the final protocol for a full study.

DISCUSSION

Identifying new treatments for symptomatic hand OA is a recognised research priority. The study will help us to understand whether there are sufficient interested and eligible individuals in this target population who would consider HRT for their hand symptoms. It will provide proof-of-concept RCT data on the effects of HRT on hand pain and other clinically relevant outcomes in this population. The study will gain valuable information on the feasibility of a full RCT and how best to run this. The findings will be published in a peer-reviewed journal and presented at a relevant conference.

TRIAL REGISTRATION

ISRCTN12196200 registered on 15 January 2019.

Sex-Dependent Reduction in Mechanical Allodynia in the Sural-Sparing Nerve Injury Model in Mice Lacking Merkel Cells

Innocuous touch sensation is mediated by cutaneous low-threshold mechanoreceptors (LTMRs). Aβ slowly adapting type I (SAI) neurons constitute one LTMR subtype that forms synapse-like complexes with associated Merkel cells in the basal skin epidermis. Under healthy conditions, these complexes transduce indentation and pressure stimuli into Aβ SAI LTMR action potentials that are transmitted to the CNS, thereby contributing to tactile sensation. However, it remains unknown whether this complex plays a role in the mechanical hypersensitivity caused by peripheral nerve injury. In this study, we characterized the distribution of Merkel cells and associated afferent neurons across four diverse domains of mouse hind paw skin, including a recently described patch of plantar hairy skin. We also showed that in the spared nerve injury (SNI) model of neuropathic pain, Merkel cells are lost from the denervated tibial nerve territory but are relatively preserved in nearby hairy skin innervated by the spared sural nerve. Using a genetic Merkel cell KO mouse model, we subsequently examined the importance of intact Merkel cell-Aβ complexes to SNI-associated mechanical hypersensitivity in skin innervated by the spared neurons. We found that, in the absence of Merkel cells, mechanical allodynia was partially reduced in male mice, but not female mice, under sural-sparing SNI conditions. Our results suggest that Merkel cell-Aβ afferent complexes partially contribute to mechanical allodynia produced by peripheral nerve injury, and that they do so in a sex-dependent manner.SIGNIFICANCE STATEMENT Merkel discs or Merkel cell-Aβ afferent complexes are mechanosensory end organs in mammalian skin. Yet, it remains unknown whether Merkel cells or their associated sensory neurons play a role in the mechanical hypersensitivity caused by peripheral nerve injury. We found that male mice genetically lacking Merkel cell-Aβ afferent complexes exhibited a reduction in mechanical allodynia after nerve injury. Interestingly, this behavioral phenotype was not observed in mutant female mice. Our study will facilitate understanding of mechanisms underlying neuropathic pain.

Are endogenous opioid mechanisms involved in the effects of aerobic exercise training on chronic low back pain? A randomized controlled trial

Aerobic exercise is believed to be an effective chronic low back pain (CLBP) intervention, although its mechanisms remain largely untested. This study evaluated whether endogenous opioid (EO) mechanisms contributed to the analgesic effects of an aerobic exercise intervention for CLBP. Individuals with CLBP were randomized to a 6-week, 18-session aerobic exercise intervention (n = 38) or usual activity control (n = 44). Before and after the intervention, participants underwent separate laboratory sessions to assess responses to evoked heat pain after receiving saline placebo or intravenous naloxone (opioid antagonist) in a double-blinded, crossover fashion. Chronic pain intensity and interference were assessed before and after the intervention. Endogenous opioid analgesia was indexed by naloxone-placebo condition differences in evoked pain responses (blockade effects). Relative to controls, exercise participants reported significantly greater pre-post intervention decreases in chronic pain intensity and interference (Ps < 0.04) and larger reductions in placebo condition evoked pain responsiveness (McGill Pain Questionnaire-Short Form [MPQ]-Total). At the group level, EO analgesia (MPQ-Total blockade effects) increased significantly pre-post intervention only among female exercisers (P = 0.03). Dose-response effects were suggested by a significant positive association in the exercise group between exercise intensity (based on meeting heart rate targets) and EO increases (MPQ-Present Pain Intensity; P = 0.04). Enhanced EO analgesia (MPQ-Total) was associated with a significantly greater improvement in average chronic pain intensity (P = 0.009). Aerobic exercise training in the absence of other interventions appears effective for CLBP management. Aerobic exercise-related enhancements in endogenous pain inhibition, in part EO-related, likely contribute to these benefits.

Modulation of heroin intake by ovarian hormones in gonadectomized and intact female rats

RATIONALE

Heroin intake decreases during the proestrus phase of the estrous cycle in female rats. Circulating concentrations of both estradiol and progesterone peak during proestrus, and it is not known which of these hormones, or their combination, are responsible for these effects.

OBJECTIVES

The purpose of this study was to determine the effects of estradiol, progesterone, and their combination on heroin self-administration in female rats.

METHODS

In Experiment 1, the estrous cycle of intact female rats was tracked daily. If a rat was in proestrus, either the estrogen receptor antagonist, raloxifene, the progesterone receptor antagonist, mifepristone, or their combination was administered 30 min prior to a heroin self-administration session. In Experiment 2, separate groups of ovariectomized female rats were treated chronically with exogenous estradiol, progesterone, estradiol + progesterone, or vehicle, and heroin intake was examined over a 100-fold dose range.

RESULTS

In Experiment 1, raloxifene, but not mifepristone, significantly blocked proestrus-associated decreases in heroin intake. In Experiment 2, estrogentreated rats self-administered less heroin than any other group and significantly less heroin than rats treated with progesterone.

CONCLUSIONS

These data suggest that (1) estradiol but not progesterone is responsible for proestrus-associated decreases in heroin intake and (2) estradiol decreases heroin intake relative to progesterone. These data differ from those reported previously with stimulants and suggest that estrogen-based pharmacotherapies may be of value to women with opioid use disorder.

Association between psychological factors and temporomandibular disorders in adolescents of rural and urban zones

Background

Temporomandibular disorders (TMD) are related to psychological factors. Adolescence is one of the stages in life with more psychosocial vulnerability, which is dissimilar in rural and urban zones. Thus, the aim of this investigation was to evaluate the association between psychological factors (symptoms of anxiety, depression and somatization) and TMD in adolescents between 12 and 15 years, belonging to urban and rural zones of Colombia.

Methods

180 subjects aged 12–15 years (mean 13.8, SD 1.2), enrolled in public schools in the rural (n = 90) and urban (n = 90) zones were included. All subjects were evaluated using the DC/TMD instrument; the Axis I was applied for the clinical examination and the Axis II for the psychological evaluation. Data were analyzed by means of T-student, Mann–Whitney, Kruskall–Wallis tests, Pearson Chi square and multiple-variable analysis with logistic regression.

Results

Forty percent of the included subjects presented some type of TMD. TMD related to pain were the most common (25.5% of the studied adolescents), being myalgia the most common (20% of the adolescents in urban zone and 31.1% of the adolescents in the rural zone). There was no difference between the TMD present in males and females, but there were differences in the symptoms of Anxiety, and Somatization (p < 0.05). TMD and psychological factors were more prevalent in children with 13 years of age. A statistically significant association between TMD and symptoms of Anxiety (Pearson Chi squared 25.57, p = 0.04), depression (Pearson Chi squared 33.28, p = 0.03) and somatization (Pearson Chi squared 25.79, p = 0.04) was found in subjects from rural zones. No associations between psychological aspects and TMD were found in subjects from urban zones, but overall all psychological factors significantly influenced TMD.

Conclusion

This study indicates Myalgia to be the most prevalent TMD in studied Colombian adolescents. Pain-related TMDs are associated with psychological factors in the adolescent population of rural Colombia. Symptoms of anxiety, depression and somatization were found to be associated to TMD, even when the frequency was not necessarily severe.

Characterization of rosacea in Chinese: An analysis of 254 cases

BACKGROUND

Rosacea is a common chronic inflammatory dermatosis with uncertainty of etiology. Although clinical features and risk factors of the disease in Caucasians have been reported, this information in Chinese is largely unavailable.

AIMS

To analyze the clinical features and associated risk factors of rosacea in Chinese.

METHODS

A questionnaire was given to outpatients with rosacea who visited the dermatology department of the first affiliated hospital of Kunming Medical University from June 2018 to March 2019. Analyses included demographic characteristics of subjects, clinical characteristics, and risk factors of rosacea.

RESULTS

A total of 254 outpatients completed the questionnaire. The ratio of female to male was 5.68:1.00. The mean age at onset was 31.18 ± 10.23 years. Erythematotelangiectatic subtype accounted for 51.60%, while 39% of the subjects were of papulopustular subtype. The rest were phymatous type (9.40%). Subjects with flushing, persistent facial erythema, and telangiectasia accounted for 91.73%, 90.55%, and 83.07%, respectively. One hundred and thirteen subjects (44.49%) had papules or pustules, and 24 subjects (9.40%) were with phymatous changes. The most commonly involved sites were the cheeks (93.31%), followed by the nose (82.68%), the perioral area (61.42%), and the forehead (51.97%). The clinical symptoms included burning (93.70%), dryness (90.55%), and itching (75.59%). The main risk factors were sun exposure (90.94%), temperature change (87.40%), etc. Fifty-one (20.08%) patients had comorbidities.

CONCLUSIONS

Rosacea mainly affects young females. The common signs and symptoms include flushing, persistent facial erythema, and burning. Sun exposure and temperature changes are the common risk factors. Patients can have comorbidities of systemic disorders.

Blood Dehydroepiandrosterone and Dehydroepiandrosterone Sulfate as Pathophysiological Correlates of Chronic Pain: Analyses Using a National Sample of Midlife Adults in the United States

OBJECTIVE

Identifying biomarkers is a priority in translational chronic pain research. Dehydroepiandrosterone (DHEA) and its sulfated form, DHEA-S, are adrenocortical steroids in the blood with neuroprotective properties that also produce sex hormones. They may capture key sex-specific neuroendocrine mechanisms of chronic pain.

DESIGN

Cross-sectional study.

METHODS

Using data from 1,216 community-dwelling adults aged 34-84 from the Midlife in the United States (MIDUS) cohort, we examined blood DHEA and DHEA-S levels in association with chronic pain in men and women, adjusting for demographics, chronic diseases, medications including opioids, and psychosocial factors. If an association was found, we further explored dose-response relationships by the number of pain locations and the degree of pain interference.

RESULTS

In women, chronic pain was associated with 0.072 lower (95% confidence interval [CI], -0.127 to -0.017) log10 DHEA-S µg/dL, with pain in one to two locations associated with 0.068 lower (95% CI, -0.131 to -0.006) and in three or more locations 0.071 lower (95% CI, -0.148 to 0.007) log10 DHEA-S (P for trend = 0.074). Furthermore for women, low-interference pain was associated with 0.062 lower (95% CI, -0.125 to -0.000), whereas high-interference pain was associated with 0.138 lower (95% CI, -0.233 to -0.043) log10 DHEA-S (P for trend = 0.004). Chronic pain was not associated with DHEA or DHEA-S levels in men or DHEA levels in women.

CONCLUSIONS

Chronic pain and its functional interference correspond to lower blood DHEA-S levels in women.

Epidemiology of injuries in elite Korean handball athletes: a prospective cohort study

BACKGROUND

To report injury patterns associated with training activities of South Korean elite handball athletes.

METHODS

We prospectively collected data (stratified by sex, handball position, and injury location) on site from elite handball athletes between January and December 2019 at the Korea Training Center, South Korea. We used χ2 tests and one-way analysis of variance to compare groups. Simple linear regression was conducted to determine associations between pain score and recovery time.

RESULTS

We included 188 (96 male and 92 female) athletes who sustained 767 injuries (annual average, 4.08 injuries/athlete) during the study. Female athletes had a higher (p<0.001) injury incidence rate (6.21/1000 h) than male athletes (4.39/1000 h). Most injuries occurred in the lower extremities (50.2%). The injured body areas differed by handball position (p<0.001), and injury severity differed according to sex (p<0.001), with injuries in men typically resulting in a longer recovery time. Pain score and recovery time differed (both p<0.001) depending on the injured tissue type. Pain score was the highest and recovery time longest for ligament injuries; muscle injuries resulted in a high pain score but a relatively short recovery time. An increase in pain score of 1 was associated with an increase in recovery time of approximately 1.59 days.

CONCLUSIONS

We believe that our data increase the understanding of the types and severity of injuries sustained by elite Korean handball athletes. These data should be incorporated into programs that aim to reduce the incidence of sports injuries and enhance athletic performance.

Glial and neuroimmune cell choreography in sexually dimorphic pain signaling

Chronic pain is a major global health issue that affects all populations regardless of sex, age, ethnicity/race, or country of origin, leading to persistent physical and emotional distress and to the loss of patients' autonomy and quality of life. Despite tremendous efforts in the elucidation of the mechanisms contributing to the pathogenesis of chronic pain, the identification of new potential pain targets, and the development of novel analgesics, the pharmacological treatment options available for pain management remain limited, and most novel pain medications have failed to achieve advanced clinical development, leaving many patients with unbearable and undermanaged pain. Sex-specific susceptibility to chronic pain conditions as well as sex differences in pain sensitivity, pain tolerance and analgesic efficacy are increasingly recognized in the literature and have thus prompted scientists to seek mechanistic explanations. Hence, recent findings have highlighted that the signaling mechanisms underlying pain hypersensitivity are sexually dimorphic, which sheds light on the importance of conducting preclinical and clinical pain research on both sexes and of developing sex-specific pain medications. This review thus focuses on the clinical and preclinical evidence supporting the existence of sex differences in pain neurobiology. Attention is drawn to the sexually dimorphic role of glial and immune cells, which are both recognized as key players in neuroglial maladaptive plasticity at the origin of the transition from acute pain to chronic pathological pain. Growing evidence notably attributes to microglial cells a pivotal role in the sexually dimorphic pain phenotype and in the sexually dimorphic analgesic efficacy of opioids. This review also summarizes the recent advances in understanding the pathobiology underpinning the development of pain hypersensitivity in both males and females in different types of pain conditions, with particular emphasis on the mechanistic signaling pathways driving sexually dimorphic pain responses.

Effects of sex on placebo effects in chronic pain participants: a cross-sectional study

ABSTRACT

Sex-related differences can influence outcomes of randomized clinical trials and may jeopardize the effectiveness of pain management and other therapeutics. Thus, it is essential to understand the mechanistic and translational aspects of sex differences in placebo outcomes. Recently, studies in healthy participants have shed light on how sex-related placebo effects might influence outcomes, yet no research has been conducted in a patient population. Herein, we used a tripartite approach to evaluate the interaction of prior therapeutic experience (eg, conditioning), expectations, and placebo effects in 280 chronic (orofacial) pain patients (215 women). In this cross-sectional study, we assessed sex differences in placebo effects, conditioning as a proxy of prior therapeutic effects, and expectations evaluated before and after the exposure to positive outcomes, taking into account participant-experimenter sex concordance and hormonal levels (estradiol and progesterone assessed in premenopausal women). We used mediation analysis to determine how conditioning strength and expectations impacted sex differences in placebo outcomes. Independent of gonadal hormone levels, women showed stronger placebo effects than men. We also found significant statistical sex differences in the conditioning strength and reinforced expectations whereby reinforced expectations mediated the sex-related placebo effects. In addition, the participant-experimenter sex concordance influenced conditioning strength, reinforced expectations, and placebo effects in women but not in men. Our findings suggest that women experience larger conditioning effects, expectations, and placebo effects emphasizing the need to consider sex as a biological variable when placebo components of any outcomes are part of drug development trials and in pain management.

Therapeutic Agents for the Treatment of Temporomandibular Joint Disorders: Progress and Perspective

Temporomandibular joint disorders (TMD) are a common health condition caused by the structural or functional disorders of masticatory muscles and the temporomandibular joint (TMJ). Abnormal mandibular movement in TMD patients may cause pain, chronic inflammation, and other discomfort, which could be relieved by a variety of drugs through various delivery systems. In this study, we summarized commonly used therapeutic agents in the management of TMD as well as novel bioactive molecules in preclinical stage and clinical trials. The emerging therapy strategies such as novel intra-TMJ delivery systems and implants based on tissue engineering are also discussed. This comprehensive review will strengthen our understanding of pharmacological approaches for TMD therapy.

Sex-Bias in Irritable Bowel Syndrome: Linking Steroids to the Gut-Brain Axis

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that is more common in females. Despite its high global incidence, the disease mechanism is still unclear and therapeutic options remain limited. The sexual dimorphism in IBS incidence suggests that sex steroids play a role in disease onset and symptoms severity. This review considers sex steroids and their involvement in IBS symptoms and the underlying disease mechanisms. Estrogens and androgens play important regulatory roles in IBS symptomology, including visceral sensitivity, gut motility and psychological conditions, possibly through modulating the gut-brain axis. Steroids are regulators of hypothalamic-pituitary-adrenal activity and autonomic nervous system function. They also modulate gut microbiota and enteric nervous systems, impacting serotonin and mast cell signaling. Sex steroids also facilitate bidirectional cross-talk between the microbiota and host following bacterial transformation and recycling of steroids by the intestine. The sex-specific interplay between sex steroids and the host provides neuroendocrinology insight into the pathophysiology, epigenetics and treatment of IBS patients.