Estrogen receptors localization in the spinal trigeminal nucleus: an immunohistochemical study in humans

CGRP as a potential mediator for the sexually dimorphic responses to traumatic brain injury

BACKGROUND

The outcomes of traumatic brain injury (TBI) exhibit variance contingent upon biological sex. Although female sex hormones exert neuroprotective effects, the administration of estrogen and progesterone has not yielded conclusive results. Hence, it is conceivable that additional mediators, distinct from female sex hormones, merit consideration due to their potential differential impact on TBI outcomes. Calcitonin gene-related peptide (CGRP) exhibits sexually dimorphic expression and demonstrates neuroprotective effects in acute brain injuries. In this study, we aimed to examine sex-based variations in TBI structural and functional outcomes with respect to CGRP expression.

METHODS

Male and female Sprague Dawley rats were exposed to controlled cortical impact to induce severe TBI, followed by interventions with and without CGRP inhibition. In the acute phase of TBI, the study centered on elucidating the influence of CGRP on oxidative stress, nuclear factor erythroid 2-related factor 2 (Nrf2) and endothelial nitric oxide synthase (eNOS) signaling in the peri-impact tissue. Subsequently, during the chronic phase of TBI, the investigation expanded to evaluate CGRP expression in relation to lesion volume, microvascular dysfunction, and white matter injury, as well as working and spatial memory, anxiety-like, and depression-like behaviors in subjects of both sexes.

RESULTS

Female rats exhibited elevated levels of CGRP in the peri-impact brain tissue during both baseline conditions and in the acute and chronic phases of TBI, in comparison to age-matched male counterparts. Enhanced CGRP levels in specific brain sub-regions among female rats correlated with superior structural and functional outcomes following TBI compared to their male counterparts. CGRP inhibition induced heightened oxidative stress and a reduction in the expression of Nrf2 and eNOS in both male and female rats, with the observed alteration being more pronounced in females than in males.

CONCLUSIONS

This study marks the inaugural identification of CGRP as a downstream mediator contributing to the sexually dimorphic response observed in TBI outcomes.

Impact of Puberty in Girls on Prevalence of Primary Headache Disorder Among Female Schoolchildren in Kuwait

Background: The prevalence of primary headaches in the pediatric population is shaped by many factors, of which pubertal status may possibly play a substantial role. Epidemiological studies in the pediatric population in the gulf region remain scarce.

Aims and objectives: To examine the impact of puberty on the prevalence of primary headache disorders among female schoolchildren in Kuwait.

Methods: We conducted a cross-sectional study that included Kuwaiti primary and middle schoolgirls in randomly selected schools located in two governorates in Kuwait during the academic year 2018/2019. Prevalence of headache was assessed using the Headache-Attributed Restriction, Disability, Social Handicap and Impaired Participation (HARDSHIP) questionnaire for children and adolescents. Female students were asked about their menarchal status and whether they attained menarche before or after experiencing headaches.

Results: The questionnaire was completed by 669 girls with a mean age of 11.44 ± 2.14 years. The 1-year prevalence of migraine headache disorder among girls was 23.62%, and the lifetime prevalence of any headache was 84.9%, whereas the 1-year prevalence of primary headache disorders was 47.98%. The mean age of girls with headaches was 11.44 ± 2.14 years. With respect to diagnostic criteria, migraine headache was the most frequently reported (23.62%), followed by tension-type headaches (20.93%), chronic headaches (2.99%), and probable medication-overuse headaches (0.45%). Postpubertal females were at significantly higher risk of having primary headaches compared to their prepubertal counterparts (64.26 vs. 34%; p < 0.0001). All types of primary headaches were more significantly prevalent among postpubertal girls compared to those who are prepubertal.

Conclusion: Migraine headache is commonly reported among Kuwaiti schoolgirls. Postpubertal females are at higher risk of developing primary headaches compared to prepubertal females. Pubertal transition and female sex hormones may play a significant role in the pathophysiology of headaches, migraines in particular, and further research is therefore needed to investigate the underlying mechanisms.

Chronic 17β-estradiol pretreatment has pronociceptive effect on behavioral and morphological changes induced by orofacial formalin in ovariectomized rats

Background

The prevalence of craniofacial pain disorders show sexual dimorphism with generally more common appearance in women suggesting the influence of estradiol, but the exact cause remains unknown. The common point in the pathogenesis of these disorders is the activation of trigeminal system. One of the animal experimental models of trigeminal activation is the orofacial formalin test, in which we investigated the effect of chronic 17β-estradiol pretreatment on the trigeminal pain-related behavior and activation of trigeminal second-order neurons at the level of spinal trigeminal nucleus pars caudalis (TNC).

Methods

Female Sprague Dawley rats were ovariectomized and silicone capsules were implanted subcutaneously containing cholesterol in the OVX group and 17β-estradiol and cholesterol in 1:1 ratio in the OVX+E₂ group. We determined 17β-estradiol levels in serum after the implantation of capsules. Three weeks after operation, 50 µL of physiological saline or 1.5% of formalin solution was injected subcutaneously into the right whisker pad of rats. The time spent on rubbing directed to the injected area and c-Fos immunoreactivity in TNC was measured as the formalin-induced pain-related behavior, and as the marker of pain-related neuronal activation, respectively.

Results

The chronic 17β-estradiol pretreatment mimics the plasma levels of estrogen occurring in the proestrus phase and significantly increased the formalin-induced pain-related behavior and neuronal activation in TNC.

Conclusion

Our results demonstrate that the chronic 17β-estradiol treatment has strong pronociceptive effect on orofacial formalin-induced inflammatory pain suggesting modulatory action of estradiol on head pain through estrogen receptors, which are present in the trigeminal system.

Cephalic cutaneous allodynia in children and adolescents with migraine of short duration: A retrospective cohort study

BACKGROUND

Allodynia is prevalent in adults with migraine and has been associated with long disease duration and severe course. Studies of the pediatric population are sparse. The aim of this study was to evaluate the rate of cephalic cutaneous allodynia in children and adolescents within the first 6 months of migraine onset and to identify associated clinical and migraine-related parameters.

METHODS

The electronic database of a tertiary pediatric headache clinic from 2014 to 2017 was retrospectively searched for all children and adolescents diagnosed with migraine headache within 6 months or less of symptom onset. Cephalic cutaneous allodynia was identified by validated questionnaire. Demographics, symptoms, and headache-related parameters were compared between patients with and without allodynia.

RESULTS

The cohort included 119 patients, 69 girls (58.0%) and 50 (42.0%) boys, of mean age 11.6 ± 3.6 years. Mean time since onset of migraine disease was 3.6 ± 1.8 months. Cephalic cutaneous allodynia was reported by 31.1% of patients. It was significantly associated with female gender ( p = 0.03), older age at admission ( p = 0.037), older age at onset ( p = 0.042) migraine with aura ( p = 0.002), and higher rate of awakening pain ( p = 0.017).

CONCLUSIONS

Cephalic cutaneous allodynia may occur in children and adolescents already in the first 6 months of migraine onset. Contrary to adult studies, we found no association of allodynia with migraine frequency or long disease duration. Allodynia was significantly associated with migraine with aura, female gender, and awakening pain. A genetic tendency may contribute to the appearance of allodynia in the pediatric age group.

17-β-Estradiol induces spreading depression and pain behavior in alert female rats

AIMS

Test the putative contribution of 17-β-estradiol in the development of spreading depression (SD) events and head pain in awake, non-restrained rats.

MAIN METHODS

Female, Sprague-Dawley rats were intact or underwent ovariectomy followed one week later by surgery to place electrodes onto the dura to detect epidural electroencephalographic activity (dEEG). dEEG activity was recorded two days later for 12 hours after systemic administration of 17-β-estradiol (180 μg/kg, i.p.). A separate set of rats were observed for changes in exploratory, ambulatory, fine, and rearing behaviors; periorbital allodynia was also assessed.

KEY FINDINGS

A bolus of 17-β-estradiol significantly elevated serum estrogen levels, increased SD episodes over a 12-hour recording period and decreased rearing behaviors in ovariectomized rats. Pre-administration of ICI 182,780, an estrogen receptor antagonist, blocked 17-β-estradiol-evoked SD events and pain behaviors; similar results were observed when the antimigraine therapeutic sumatriptan was used.

SIGNIFICANCE

These data indicate that an estrogen receptor-mediated mechanism contributes to SD events in ovariectomized rats and pain behaviors in both ovariectomized -and intact- rats. This suggests that estrogen plays a different role in each phenomenon of migraine where intense fluctuations in concentration may influence SD susceptibility. This is the first study to relate estrogen peaks to SD development and pain behaviors in awake, freely moving female rats, establishing a framework for future preclinical migraine studies.

Gender aspects of CGRP in migraine

Background

Migraine is two to three times more prevalent in women than in men, but the mechanisms involved in this gender disparity are still poorly understood. In this respect, calcitonin gene-related peptide (CGRP) plays a key role in migraine pathophysiology and, more recently, the functional interactions between ovarian steroid hormones, CGRP and the trigeminovascular system have been recognized and studied in more detail.

Aims

To provide an overview of CGRP studies that have addressed gender differences utilizing animal and human migraine preclinical research models to highlight how the female trigeminovascular system responds differently in the presence of varying ovarian steroid hormones.

Conclusions

Gender differences are evident in migraine. Several studies indicate that fluctuations of ovarian steroid hormone (mainly estrogen) levels modulate CGRP in the trigeminovascular system during different reproductive milestones. Such interactions need to be considered when conducting future animal and human experiments, since these differences may contribute to the development of gender-specific therapies.

Signs and symptoms of temporomandibular disorders in women and men

INTRODUCTION

Women are more likely to present temporomandibular disorders (TMD); however, studies comparing genders in Brazilian samples are rare.

PURPOSE

To analyze the proportion of men and women, as well as the association between gender and age, problem duration, and TMD symptoms in patients admitted to an university clinic for treatment.

METHODS

Interview and assessment data of protocols from 1,000 patients diagnosed with TMD were collected and analyzed and then divided into two groups, male (n = 177) and female (n = 823). The exploratory analysis was based on contingency tables and χ2 test was carried out. Subsequently, the logistic regression model was used and the odds ratios (OR) concerning the evaluated comparisons were calculated.

RESULTS

Females were more prevalent in the sample, and mean ages and TMD duration were similar between the groups, with higher occurrence in young adults (19 to 40 years old). The OR values showed an association between the female gender and the signs/symptoms of pain in the temporomandibular joint, pain in the facial muscles, neck and shoulders, headache, fatigue in the muscles of mastication, otologic symptoms, and dysphonia. Women had two times higher chances of presenting these symptoms than men.

CONCLUSION

In the sample of Brazilian patients with TMD, the number of women who presented a higher prevalence of painful symptoms was greater, followed by otologic symptoms and complaints of dysphonia. The prevalence of joint noise was similar in both studied groups.

Sex and the migraine brain

The brain responds differently to environmental and internal signals that relate to the stage of development of neural systems. While genetic and epigenetic factors contribute to a premorbid state, hormonal fluctuations in women may alter the set point of migraine. The cyclic surges of gonadal hormones may directly alter neuronal, glial and astrocyte function throughout the brain. Estrogen is mainly excitatory and progesterone inhibitory on brain neuronal systems. These changes contribute to the allostatic load of the migraine condition that most notably starts at puberty in girls.

The fundamental unit of pain is the cell

The molecular/genetic era has seen the discovery of a staggering number of molecules implicated in pain mechanisms [18,35,61,69,96,133,150,202,224]. This has stimulated pharmaceutical and biotechnology companies to invest billions of dollars to develop drugs that enhance or inhibit the function of many these molecules. Unfortunately this effort has provided a remarkably small return on this investment. Inevitably, transformative progress in this field will require a better understanding of the functional links among the ever-growing ranks of "pain molecules," as well as their links with an even larger number of molecules with which they interact. Importantly, all of these molecules exist side-by-side, within a functional unit, the cell, and its adjacent matrix of extracellular molecules. To paraphrase a recent editorial in Science magazine [223], although we live in the Golden age of Genetics, the fundamental unit of biology is still arguably the cell, and the cell is the critical structural and functional setting in which the function of pain-related molecules must be understood. This review summarizes our current understanding of the nociceptor as a cell-biological unit that responds to a variety of extracellular inputs with a complex and highly organized interaction of signaling molecules. We also discuss the insights that this approach is providing into peripheral mechanisms of chronic pain and sex dependence in pain.