Triptan-induced enhancement of neuronal nitric oxide synthase in trigeminal ganglion dural afferents underlies increased responsiveness to potential migraine triggers

Beyond Pain: The Effects of OnabotulinumtoxinA Therapy on Sensitization and Interictal Symptoms in Chronic Migraine

Chronic migraine is a disease with a high burden on patients from both a working and quality of life point of view. The pathophysiology of this subtype of migraine is due to several factors, such as medication overuse. Nevertheless, the detrimental recurring of headache attacks with central and peripheral sensitization plays a central role and explains some additional symptoms complained about by these patients even in the interictal phase. OnabotulinumtoxinA is a therapy indicated for chronic migraine since it has proven to reduce peripheral sensitization, showing even efficacy on central symptoms. The aim of this narrative review is to present the current evidence regarding the effect of OnabotulinumtoxinA on sensitization and interictal symptoms.

Potential mechanisms for osteopathic manipulative treatment to alleviate migraine-like pain in female rats

Introduction

Migraines are the leading cause of disability in the United States, and the use of non-pharmaceutical treatments like osteopathic manipulative treatment (OMT) has shown promise. Despite its potential, the lack of mechanistic understanding has hindered widespread adoption. This study aims to investigate the efficacy of OMT in treating acute migraines and unravel its underlying mechanisms of action.

Methods

Female rats were subjected to a "two-hit" approach to induce migraine-like pain. This involved bilateral injections of Complete Freund's Adjuvant (CFA) into the trapezius muscle (1st hit) followed by exposure to Umbellulone, a human migraine trigger, on Day 6 post-CFA (2nd hit). Soft tissue and articulatory techniques were applied to the cervical region for acute abortive or repeated prophylactic treatment. Cutaneous allodynia and trigeminal system activation were assessed through behavioral tests and immunohistochemical staining.

Results

Following Umbellulone inhalation, CFA-primed rats exhibited periorbital and hind paw allodynia. Immediate application of OMT after Umbellulone inhalation as an abortive treatment partially alleviated cutaneous allodynia. With OMT applied thrice as a prophylactic measure, complete suppression of tactile hypersensitivity was observed. Prophylactic OMT also prevented the increase of c-fos signals in the trigeminal nucleus caudalis and the elevation of calcitonin gene-related peptide expression in trigeminal ganglia induced by CFA and Umbellulone exposure at 2 h post-inhalation.

Discussion

These findings provide mechanistic insights into OMT's migraine-relief potential and underscore its viability as a non-pharmacological avenue for managing migraines.

Risk factors for migraine disease progression: a narrative review for a patient-centered approach

BACKGROUND

In individuals with migraine, attacks may increase in frequency, severity, or both. Preventing migraine progression has emerged as a treatment goal in headache subspecialty practice, but there may be less awareness in general neurology or primary care settings where most people with migraine who seek treatment consult. Herein, we review the definition of and risk factors for migraine progression and consider strategies that could reduce its risk.

METHODS

A group of headache expert healthcare professionals, clinicians, and researchers reviewed published evidence documenting factors associated with increased or decreased rates of migraine progression and established expert opinions for disease management recommendations. Strength of evidence was rated as good, moderate, or based solely on expert opinion, using modified criteria for causation developed by AB Hill.

RESULTS

Migraine progression is commonly operationally defined as the transition from ≤ 15 to ≥ 15 monthly headache days among people with migraine; however, this does not necessarily constitute a fundamental change in migraine biology and other definitions should be considered. Established and theoretical key risk factors for migraine progression were categorized into five domains: migraine disease characteristics, treatment-related factors, comorbidities, lifestyle/exogenous factors, and demographic factors. Within these domains, good evidence supports the following risk factors: poorly optimized acute headache treatment, cutaneous allodynia, acute medication overuse, selected psychiatric symptoms, extra-cephalic chronic pain conditions, metabolism-related comorbidities, sleep disturbances, respiratory conditions, former/current high caffeine intake, physical inactivity, financial constraints, tobacco use, and personal triggers as risk factors. Protective actions that may mitigate migraine progression are sparsely investigated in published literature; our discussion of these factors is primarily based on expert opinion.

CONCLUSIONS

Recognizing risk factors for migraine progression will allow healthcare providers to suggest protective actions against migraine progression (Supplementary Fig. 1). Intervention studies are needed to weight the risk factors and test the clinical benefit of hypothesized mitigation strategies that emerge from epidemiological evidence.

Annexin A1 exerts analgesic effect in a mouse model of medication overuse headache

Medication overuse headache (MOH) is a serious global condition. The interaction between headache attacks and medication overuse complicates the understanding of its pathophysiology. In this study, we developed a preclinical MOH model that incorporates these two key factors by overusing rizatriptan benzoate (RIZ, 4 mg/kg, i.g.) in a glyceryl trinitrate (GTN, 10 mg/kg, i.p.) induced chronic migraine mouse model. We observed that RIZ overuse aggravated GTN-induced cutaneous allodynia and caused a prolonged state of latent sensitization. We also detected a significant upregulation of Annexin-A1 (ANXA1), a protein mainly expressed in the microglia of the spinal trigeminal nucleus caudalis (SPVC), in GTN+RIZ mice. Intracerebroventricular injection of ANXA1-derived peptide Ac2-26 trifluoroacetic acid (TFA) (5 μg/mouse) inhibited bright light stress (BLS) induced acute allodynia via the formyl peptide receptor (FPR) in GTN+RIZ mice. These results suggest that ANXA1 may have an analgesic effect in triptan-associated MOH and could potentially serve as a therapeutic target.

A Descriptive Review of Medication-Overuse Headache: From Pathophysiology to the Comorbidities

PURPOSE OF REVIEW

Medication-overuse headache (MOH) is an important problem worldwide, with different areas of controversy regarding its entity. This article reviews the risk factors, comorbidities, pathophysiology, clinical presentation, effective management, and prognosis of MOH by summarizing and integrating the results and findings from previously performed more than 15,000 studies (from 2010 to 2023) available from the scientific database of the University Medical Library in the University Clinical Center of Niš, which aimed to investigate and define the complexity of this type of headache.

RECENT FINDING

It has been proposed that all acute migraine medications can lead to MOH, with differences in the propensity of different agents to cause the problem. Early data suggests that triptans and other painkillers used for the acute treatment of migraine may be an exception. Recent studies show that practitioners and the general public are still largely unaware of the problem of medication overuse and its damaging effects.

SUMMARY

Although it is likely that MOH does occur, restricting the number of acute medications is necessary to prevent it. It is also possible that increasing amounts of acute medications are simply a reflection of poorly controlled headaches rather than a cause. Further research needs to be developed to identify more precise mechanisms for effective MOH management and its evolution.

Central sensitization mechanisms in chronic migraine with medication overuse headache: a study of thalamocortical activation and lateral cortical inhibition

BACKGROUND

It is unclear whether cortical hyperexcitability in chronic migraine with medication overuse headache (CM-MOH) is due to increased thalamocortical drive or aberrant cortical inhibitory mechanisms.

METHODS

Somatosensory evoked potentials (SSEP) were performed by electrical stimulation of the median nerve (M), ulnar nerve (U) and simultaneous stimulation of both nerves (MU) in 27 patients with CM-MOH and, for comparison, in 23 healthy volunteers (HVs) of a comparable age distribution. We calculated the degree of cortical lateral inhibition using the formula: 100 - [MU/(M + U) × 100] and the level of thalamocortical activation by analyzing the high frequency oscillations (HFOs) embedded in parietal N20 median SSEPs.

RESULTS

Compared to HV, CM-MOH patients showed higher lateral inhibition (CM-MOH 52.2% ± 15.4 vs. HV 40.4% ± 13.3; p = 0.005), which positively correlated with monthly headache days, and greater amplitude of pre-synaptic HFOs (p = 0.010) but normal post-synaptic HFOs (p = 0.122).

CONCLUSION

Our findings suggest that central neuronal circuits are highly sensitized in CM-MOH patients, at both thalamocortical and cortical levels. The observed changes could be due to the combination of dysfunctional central pain control mechanisms, hypersensitivity and hyperresponsiveness directly linked to the chronic intake of acute migraine drugs.

Medication overuse headache: a review of current evidence and management strategies

The third edition of the International Classification of Headache Disorders (ICHD-3) defines medication-overuse headache (MOH) as a headache that develops when a person regularly uses acute or symptomatic headache medications excessively (10 or more, or 15 or more days per month, depending on the medication) for a period of time longer than 3 months. Even though it may not be reported as frequently as it actually is, it affects about 5% of the general population on average. It typically happens following repeated anti-pain medication use for pre-existing headache disorders, such as migraines. Anti-pains can also be used frequently in patients with pre-existing headache disorders for reasons other than treating headaches, such as psychological drug attachment. MOH is linked to a number of illnesses, such as anxiety, depression, and obsessive compulsive disorder (OCD). Both simple and complex types are possible. Additionally, there is no universal consensus on how to treat MOH, but drug discontinuation is the best course of action. Using the medical subject headings "Medication Overuse Headache," "Migraine Headache," "Tension Headache," "Chronification of Headache," and "Antipains," an all-language literature search was done on PubMed, Google Scholar, and Medline up until March 2023. We looked into the epidemiology, risk factors, pathophysiology, clinical characteristics, comorbidities, diagnosis, management, and preventative measures of MOH in the literature. This article focuses on the MOH research themes.

Hippocampal volume changes across developmental periods in female migraineurs

Brain-related plasticity can occur at a significant rate varying on the developmental period. Adolescence in particular has been identified as a period of growth and change across the structure and function of the nervous system. Notably, research has identified migraines as common in both pediatric and adult populations, but evidence suggests that the phenotype for migraines may differ in these cohorts due to the unique needs of each developmental period. Accordingly, primary aims of this study were to define hippocampal structure in females (7-27 years of age) with and without migraine, and to determine whether this differs across developmental stages (i.e., childhood, adolescence, and young adulthood). Hippocampal volume was quantified based on high-resolution structural MRI using FMRIB's Integrated Registration and Segmentation Tool. Results indicated that migraine and age may have an interactional relationship with hippocampal volume, such that, while hippocampal volumes were lower in female migraineurs (compared to age-matched controls) during childhood and adolescence, this contrast differed during young adulthood whereby hippocampal volumes were higher in migraineurs (compared to age-matched controls). Subsequent vertex analysis localized this interaction effect in hippocampal volume to displacement of the anterior hippocampus. The transition of hippocampal volume during adolescent development in migraineurs suggests that hippocampal plasticity may dynamically reflect components of migraine that change over the lifespan, exerting possible altered responsivity to stress related to migraine attacks thus having physiological expression and psychosocial impact.

Activation of the microglial P2X7R/NLRP3 inflammasome mediates central sensitization in a mouse model of medication overuse headache

Background

Excessive use of headache treatments often leads to the development, progression and exacerbation of primary headache, which is defined as medication overuse headache (MOH). A significant pathophysiological mechanism of MOH is central sensitization. Recent evidence suggests that central sensitization in chronic headache is a result of inflammatory responses mediated by microglial activation in the trigeminal nucleus caudalis (TNC). However, it is unknown whether microglial activation has an impact on the central sensitization of MOH. Accordingly, the goal of this research was to determine how microglial activation and the P2X7R/NLRP3 inflammasome signaling pathway in the TNC contribute to the pathogenesis of MOH.

Methods

Repeated intraperitoneal injection of sumatriptan (SUMA) was used to establish a mouse model of MOH. Basal mechanical hyperalgesia was evaluated using von Frey filaments. As central sensitization biomarkers, the c-Fos and CGRP expression levels were measured by immunofluorescence analysis. We estimated the expression of microglial biomarkers (Iba1 and iNOS) within the TNC by qRT-PCR, western blotting and immunofluorescence analysis. To elucidate the effect of microglial activation and the P2X7/NLRP3 signaling pathway on central sensitization in MOH, we evaluated whether the microglia-specific inhibitor minocycline, the P2X7R-specific antagonist BBG and the NLRP3-specific inhibitor MCC950 altered SUMA-caused mechanical hyperalgesia. Furthermore, we examined c-Fos and CGRP expression within the TNC following individual injections of these inhibitors.

Results

Repeated SUMA injection induced basal mechanical hyperalgesia, increased c-Fos and CGRP levels, and activated microglia within the TNC. Inhibiting microglial activation with minocycline prevented the emergence of mechanical hyperalgesia and cut down c-Fos and CGRP expression. Immunofluorescence colocalization analysis revealed that P2X7R was predominantly co-localized with microglia. The levels of P2X7R and the NLRP3 inflammasome were elevated by repeated SUMA injection, and blocking P2X7R and NLRP3 inhibited mechanical hyperalgesia and cut down c-Fos and CGRP expression within the TNC.

Conclusion

Based on the current findings, inhibiting microglial activation could reduce central sensitization caused by chronic SUMA treatment via the P2X7R/NLRP3 signaling pathway. The clinical management of MOH may benefit from a novel strategy that inhibits microglial activation.

Efficacy of tDCS in chronic migraine: A multiprotocol randomized controlled trial

OBJECTIVE

Given the prevalence and complicated pathophysiology of migraine, unknown or varied mechanisms of action of available monotherapies or add-on therapies, and their broad range of adverse effects, it is imperative to manage migraine symptoms using a non-invasive, multifunctional, and alternate monotherapy with no negative impacts.

METHODS

We used a single-blind, randomized, sham-controlled design with baseline, post-test, and 24-weeks follow-up measurements to assess the efficacy of transcranial Direct Current Stimulation (tDCS) in chronic migraine. A total of 150 participants were randomly assigned to the five groups (i.e., allocation ratio of 1:1:1:1:1). Each group received tDCS-intervention for 11 consecutive-weeks (25 sessions; each session = two consecutive montages; each montage = a 20 min duration, 2000 μA intensity).

RESULTS

The multivariate analysis of variance showed significant (p <.05) reductions in chronic migraine symptoms in the four intervention groups. Compared with the sham (η² < 0.18) and other protocols (two = η² > 0.42; three = η² > 0.40; four = η² > 0.51), protocol one [l. anode at the right ventrolateral prefrontal cortices, cathode at the left dorsomedial and superior frontal gyrus-first montage; anode at the right primary motor area, cathode at the medial crosstalk of hemispheres-second montage] showed a larger effect size (η² > 0.59) in the present trial.

CONCLUSIONS

With the applied protocols of the present trial, tDCS can be used as an effective intervention for the prophylactic and therapeutic treatment of chronic migraine. However, while the second protocol was the least effective, the first was the most effective at reducing migraine symptoms.

SIGNIFICANCE

To our knowledge, the present trial is the first study to cover the gaps of the earlier ones, including the parameters like the site of stimulation, electrode range distribution and field intensity, number of sessions, session design, and sample size.

Medication overuse headache

Medication overuse headache (MOH) is a secondary headache disorder attributed to overuse of acute headache medications by a person with an underlying headache disorder, usually migraine or tension-type headache. MOH is common among individuals with 15 or more headache days per month. Although MOH is associated with substantial disability and reductions in quality of life, this condition is often under-recognized. As MOH is both preventable and treatable, it warrants greater attention and awareness. The diagnosis of MOH is based on the history and an unremarkable neurological examination, and is made according to the diagnostic criteria of the International Classification of Headache Disorders third edition (ICHD-3). Pathophysiological mechanisms of MOH include altered descending pain modulation, central sensitization and biobehavioural factors. Treatment of MOH includes the use of headache preventive therapies, but essential to success is eliminating the cause, by reducing the frequency of use of acute headache medication, and perhaps withdrawing the overused medication altogether. Appropriate treatment is usually highly effective, leading to reduced headache burden and acute medication consumption.

Preclinical Studies of Posttraumatic Headache and the Potential Therapeutics

Posttraumatic headache (PTH) attributed to traumatic brain injury (TBI) is a secondary headache developed within 7 days after head injury, and in a substantial number of patients PTH becomes chronic and lasts for more than 3 months. Current medications are almost entirely relied on the treatment of primary headache such as migraine, due to its migraine-like phenotype and the limited understanding on the PTH pathogenic mechanisms. To this end, increasing preclinical studies have been conducted in the last decade. We focus in this review on the trigeminovascular system from the animal studies since it provides the primary nociceptive sensory afferents innervating the head and face region, and the pathological changes in the trigeminal pathway are thought to play a key role in the development of PTH. In addition to the pathologies, PTH-like behaviors induced by TBI and further exacerbated by nitroglycerin, a general headache inducer through vasodilation are reviewed. We will overview the current pharmacotherapies including calcitonin gene-related peptide (CGRP) monoclonal antibody and sumatriptan in the PTH animal models. Given that modulation of the endocannabinoid (eCB) system has been well-documented in the treatment of migraine and TBI, the therapeutic potential of eCB in PTH will also be discussed.

MTHFR polymorphism's influence on the clinical features and therapeutic effects in patients with migraine: An observational study

Objective

Our study aimed to evaluate the influence of methylenetetrahydrofolate reductase (MTHFR) polymorphism on the clinical features and therapeutic effects in patients with migraine.

Methods

The data of 135 patients with migraine were collected from January 2021 to December 2021. The MTHFR C677T polymorphism was analyzed. The pain intensity was evaluated using a numerical rating scale (NRS) during treatment. The levels of folic acid, homocysteine (Hcy), vitamin B12, interleukin-2 (IL-2), IL-4, and ferritin, and changes of NRS were compared between folic acid and conventional treatment groups stratified by different genotypes of MTHFR in migraine patients.

Results

The levels of Hcy and ferritin in male patients were higher than that in female patients (P < 0.05); Compared with CC and CT genotype groups, the TT genotype group showed significantly higher Hcy levels (P < 0.05) and lower folic acid levels (P < 0.05); In both folic acid and conventional treatment groups, a significant decrease in NRS score was observed in different genotypes post-treatment (P < 0.05). Patients with TT genotype in the folic acid treatment group showed better therapeutic efficacy than conventional treatment group (P < 0.05). There is no significant difference in the therapeutic efficacy in other genotypes between the two groups (P > 0.05).

Conclusion

The MTHFR C677T genotyping may provide a new method to guide and optimize individualized medication for migraine patients.

Role of endothelin in the pathophysiology of migraine: A new view on an old player

There is cumulating evidence that endothelin-1 (ET-1) may play a role in migraine, however controversial findings still impede a conclusion to be drawn. Herein we tested the hypothesis that endothelin ETB receptors are major contributors to migraine-like responses. ET-1, IRL-1620 (selective ETB receptor agonist) or CGRP were injected into the trigeminal ganglion (TG) of female Wistar rats, and the development of periorbital mechanical allodynia was assessed hourly with von Frey hairs. Twenty-four hours later, rats were exposed to an aversive light for 1 h, after which the reactivation of periorbital mechanical allodynia (indicating photic sensitivity) was assessed up to 4 h. Moreover, the effect of systemic Bosentan (ETA/ETB receptors antagonist) or the selective antagonists of ETA (BQ-123) and ETB (BQ-788) receptors injected into the TG were evaluated against CGRP-induced responses. ET-1 and IRL-1620 injection into the TG induced periorbital mechanical allodynia and photic sensitivity. Bosentan attenuated periorbital mechanical allodynia but failed to affect photic sensitivity induced by CGRP. Selective blockade of ETB receptors in the TG fully prevented the development of periorbital mechanical allodynia and photic sensitivity induced by CGRP, but ETA receptor blockade caused only a slight reduction of periorbital mechanical allodynia without affecting photic sensitivity. ETB receptor-operated mechanisms in the TG may contribute to migraine-like responses in female rats.

Autonomic symptoms in migraine: Results of a prospective longitudinal study

Objective

To assess the prevalence and burden of autonomic symptoms in migraine, and determine the relationship with migraine frequency.

Background

Autonomic symptoms in migraine have been theorized to occur in the setting of inter-ictal sympathetic hypoactivity and hyper-sensitivity. There is limited data prospectively assessing cranial and extra-cranial autonomic symptoms with a validated instrument, or longitudinal data on the relationship between migraine disease activity and autonomic symptoms.

Methods

Patients attending a single tertiary academic center were recruited into a prospective cohort study between September 2020 and June 2022. In addition to standard clinical care, they completed several surveys including the Composite Autonomic Symptom Scale (COMPASS-31) questionnaire, a validated survey of autonomic symptoms.

Results

A total of 43 patients (66.7% female, median age 42, IQR 17) were included in the final analysis. There was a baseline 20 monthly headache days (MHD) (IQR 21.7), and 65.1% of the population had chronic migraine by ICHD-3 criteria. A significantly elevated weighted COMPASS-31 score was reported in 60.5% of respondents (mean 30.3, SD 13.3) at baseline. After 12 months treatment, significant improvements were reported in migraine frequency (median MHD 20-8.7) and disability (median Migraine Disability Assessment Score 67-48), but not in autonomic symptoms (mean score 30.3, SD 11.2).

Conclusion

Autonomic symptoms were frequently reported in patients with migraine. However, they did not correlate with headache frequency or reversion to episodic frequency. Further study is required to elucidate specific approaches and treatments for autonomic symptoms, and further evaluate the underlying pathophysiological mechanisms.

Excellent Response to OnabotulinumtoxinA: Different Definitions, Different Predictors

The identification of patients who can benefit the most from the available preventive treatments is important in chronic migraine. We explored the rate of excellent responders to onabotulinumtoxinA in a multicenter European study and explored the predictors of such response, according to different definitions. A pooled analysis on chronic migraineurs treated with onabotulinumtoxinA and followed-up for, at least, 9 months was performed. Excellent responders were defined either as patients with a ≥75% decrease in monthly headache days (percent-based excellent responders) or as patients with <4 monthly headache days (frequency-based excellent responders). The characteristics of excellent responders at the baseline were compared with the ones of patients with a <30% decrease in monthly headache days. Percent-based excellent responders represented about 10% of the sample, whilst frequency-based excellent responders were about 5% of the sample. Compared with non-responders, percent-based excellent responders had a higher prevalence of medication overuse and a higher excellent response rate even after the 1st and the 2nd injection. Females were less like to be frequency-based excellent responders. Chronic migraine sufferers without medication overuse and of female sex may find fewer benefits with onabotulinumtoxinA. Additionally, the excellent response status is identifiable after the first cycle.

Nitroglycerin as a model of migraine: Clinical and preclinical review

Migraine stands as one of the most disabling neurological conditions worldwide. It is a disorder of great challenge to study given its heterogeneous representation, cyclic nature, and complexity of neural networks involved. Despite this, clinical and preclinical research has greatly benefitted from the use of the nitric oxide donor, nitroglycerin (NTG), to model this disorder, dissect underlying mechanisms, and to facilitate the development and screening of effective therapeutics. NTG is capable of triggering a migraine attack, only in migraineurs or patients with a history of migraine and inducing migraine-like phenotypes in rodent models. It is however unclear to what extent NTG and NO, as its breakdown product, is a determinant factor in the underlying pathophysiology of migraine, and importantly, whether it really does facilitate the translation from the bench to the bedside, and vice-versa. This review provides an insight into the evidence supporting the strengths of this model, as well as its limitations, and shines a light into the possible role of NO-related mechanisms in altered molecular signalling pathways.

Histone Deacetylase Inhibitors Counteract CGRP Signaling and Pronociceptive Sensitization in a Rat Model of Medication Overuse Headache

Chronic triptan exposurein rodents recapitulates medication overuse headache (MOH), causing cephalic pain sensitization and trigeminal ganglion overexpression of pronociceptive proteins including CGRP. Because of these transcriptional derangements, as well as the emerging role of epigenetics in chronic pain, in the present study, we evaluated the effects of the histone deacetylase inhibitors (HDACis) panobinostat and givinostat, in rats chronically exposed to eletriptan for one month. Both panobinostat and givinostat counteracted overexpression of genes coding for CGRP and its receptor subunit RAMP1, having no effects on CLR and RCP receptor subunits in the trigeminal ganglion (TG) of eletriptan-exposed rats. Within the trigeminal nucleus caudalis (TNc), transcripts for these genes were neither upregulated by eletriptan nor altered by concomitant treatment with panobinostat or givinostat. HDACis counteracted hypersensitivity to capsaicin-induced vasodilatation in the trigeminal territory, as well as photophobic behavior and cephalic allodyniain eletriptan-exposed rats. Eletriptan did not affect CGRP, CLR, and RAMP1 expression in cultured trigeminal ganglia, whereas both inhibitors reduced transcripts for CLR and RAMP-1. The drugs, however, increased luciferase expression driven by CGRP promoter in cultured cells. Our findings provide evidence for a key role of HDACs and epigenetics in MOH pathogenesis, highlighting the therapeutic potential of HDAC inhibition in the prevention of migraine chronification.

Migraine susceptibility is modulated by food triggers and analgesic overuse via sulfotransferase inhibition

Background/aim

Certain constituents in migraine food triggers and non-steroidal anti-inflammatory drugs (NSAIDs) inhibit sulfotransferases (SULTs) that detoxify drugs/chemicals and play role in the metabolism of neurotransmitters. We aimed to dissect SULT1A1 modulation of CSD susceptibility and behavior in an in vivo experimental model using hesperidin, a SULT1A1 inhibitor found in citrus fruits (known migraine triggers) and mefenamic acid (SULT1A1 inhibitor), an NSAID to simulate medication overuse.

Methods

Hesperidin was used as SULT1A1 inhibitor found in citrus fruits, known migraine triggers and mefenamic acid (NSAID), another SULT1A1 inhibitor, was used to induce MO in rats. The groups were; 1) Hesperidin (ip) or its vehicle-DMSO (ip) 2) Chronic (4 weeks) mefenamic acid (ip) or its vehicle (ip) 3) Chronic mefenamic acid+hesperidin (ip) or DMSO (ip). CSD susceptibility was evaluated and behavioral testing was performed. SULT1A1 enzyme activity was measured in brain samples.

Results

Single-dose of hesperidin neither changed CSD susceptibility nor resulted in any behavioral change. Chronic mefenamic acid exposure resulted in increased CSD susceptibility, mechanical-thermal hypersensitivity, increased head shake, grooming and freezing and decreased locomotion. Single dose hesperidin administration after chronic mefenamic acid exposure resulted in increased CSD susceptibility and mechanical-thermal hypersensitivity, increased freezing and decreased locomotion. SULT1A1 enzyme activity was lower in mefenamic acid and mefenamic acid+hesperidin groups compared to their vehicles.

Conclusion

Mefenamic acid and hesperidin have synergistic effect in modulating CSD susceptibility and pain behavior. Sulfotransferase inhibition may be the common mechanism by which food triggers and NSAIDs modulate migraine susceptibility. Further investigations regarding human provocation studies using hesperidin in migraine patients with medication overuse are needed.

Proanthocyanidin from Vitis vinifera attenuates memory impairment due to convulsive status epilepticus

This study investigated the effects of proanthocyanidin-rich fraction (PRF) of Vitis vinifera seed extract on the markers of hippocampal-dependent memory in convulsive status epilepticus (CSE) rat model. One hundred juvenile Wistar rats were randomized into 6 groups. Group 1 (n = 10) received propylene glycol (PG 0.1 ml/100 g) intraperitoneally (i.p), while convulsion was induced in groups 2-6 (n = 18 each) using lithium (127 mg/kg i.p) and pilocarpine hydrochloride (40 mg/kg i.p). The established CSE rats in groups 2-6 received a daily treatment of PG (0.1 ml i.p), PRF (30 mg/kg i.p), PRF (20 mg/kg BW i.p), PRF (10 mg/kg BW i.p) or diazepam (5 mg/kg BW i.p) for seven days. Thereafter, they were kept untreated but with access to feed and water for 21 days. The control and CSE-treated rats were subjected to behavioral tests, while the biochemical and histomorphological evaluations of the hippocampus were done after the sacrifice. The results were presented as mean ± SEM in graphs or tables. The level of significance was considered when p < 0.05. There was significant decrease in the hippocampal-dependent memory, hippocampal weight and an increased malondialdehyde concentration following CSE. The activities of acetylcholinesterase decreased significantly in the PRF-treated CSE rats. The hippocampal glial cells and granule count increased significantly following CSE, with various neurodegenerative features in the CA1 of the hippocampus. These derangements were attenuated significantly following PRF treatment. Memory impairment following CSE may be attenuated with the administration of PRF from V. vinifera seed in rats.

Neuroprotective effect of sumatriptan in pentylenetetrazole-induced seizure is mediated through N-methyl-D-aspartate/nitric oxide and cAMP response element-binding protein signaling pathway

Seizure occurs as a result of uncontrolled electrical disturbances within the brain. Various biomolecules such as N-methyl-D-aspartate (NMDA), nitric oxide (NO), and cAMP response element-binding protein (CREB) have been implicated in the pathophysiology of seizure. Sumatriptan is a specific 5-Hydroxytryptamine 1B/1D receptor agonist and has neuroprotective effects in various neuropsychiatric disorders. In the current study, we tried to investigate the possible interaction of sumatriptan with NMDA/NO and CREB signaling pathway in PTZ induced seizure. For this purpose, various agonist and antagonist of NMDA such as MK-801 and Ketamine, NO precursor L-ARG, and NOS inhibitors L-NAME and 7-NI were co-administered with sumatriptan in PTZ induced seizure model. The level of nitrite in mice hippocampus was determined by Griess reaction. The gene expression of NR1, NR2A, NR2B, and CREB were quantified by quantitative real time-polymerase chain reaction (qRT-PCR). Furthermore, the involved neuronal nitric oxide synthase (nNOS) protein expression was examined via western blot analysis. Effective dose of sumatriptan (1.2 mg/kg) alone and subeffective dose of sumatriptan (0.3 mg/kg) in combination with NMDA and/or NO antagonist showed significant (P < 0.001) anticonvulsant activity in mice. Furthermore, sumatriptan significantly inhibited the PTZ-induced mRNA expression of NR2A (P < 0.0001), NR2B (P < 0.05), and CREB (P < 0.01). Also, the expression of nNOS protein in PTZ treated group was reversed by sumatriptan (P < 0.01). Hence, current findings suggest that the anticonvulsant effect of sumatriptan was due to down regulation of NMDA/NO and CREB signaling pathway.

CGRP-dependent signalling pathways involved in mouse models of GTN- cilostazol- and levcromakalim-induced migraine

BACKGROUND

Knowledge of exact signalling events during migraine attacks is lacking. Various substances are known to trigger migraine attacks in patients and calcitonin gene-related peptide antagonising drugs are effective against migraine pain. Here, we investigated the signalling pathways involved in three different mouse models of provoked migraine and relate them to calcitonin gene-related peptide and other migraine-relevant targets.

METHODS

In vivo mouse models of glyceryl trinitrate-, cilostazol- and levcromakalim-induced migraine were applied utilising tactile sensitivity to von Frey filaments as measuring readout. Signalling pathways involved in the three models were dissected by use of specific knockout mice and chemical inhibitors. In vivo results were supported by ex vivo wire myograph experiments measuring arterial dilatory responses and ex vivo calcitonin gene-related peptide release from trigeminal ganglion and trigeminal nucleus caudalis from mice.

RESULTS

Glyceryl trinitrate-induced hypersensitivity was dependent on both prostaglandins and transient receptor potential cation channel, subfamily A, member 1, whereas cilostazol- and levcromakalim-induced hypersensitivity were independent of both. All three migraine triggers activated calcitonin gene-related peptide signalling, as both receptor antagonism and antibody neutralisation of calcitonin gene-related peptide were effective inhibitors of hypersensitivity in all three models. Stimulation of trigeminal ganglia and brain stem tissue samples with cilostazol and levcromakalim did not result in release of calcitonin gene-related peptide, and vasodilation following levcromakalim stimulation was independent of CGRP receptor antagonism.

CONCLUSION

The mouse models of glyceryl trinitrate-, cilostazol- and levcromakalim- induced migraine all involve calcitonin gene-related peptide signalling in a complex interplay between different cell/tissue types. These models are useful in the study of migraine mechanisms.

Selective targeting of peripheral cannabinoid receptors prevents behavioral symptoms and sensitization of trigeminal neurons in mouse models of migraine and medication overuse headache

ABSTRACT

Migraine affects ∼15% of the world's population greatly diminishing their quality of life. Current preventative treatments are effective in only a subset of migraine patients, and although cannabinoids seem beneficial in alleviating migraine symptoms, central nervous system side effects limit their widespread use. We developed peripherally restricted cannabinoids (PRCBs) that relieve chronic pain symptoms of cancer and neuropathies, without appreciable central nervous system side effects or tolerance development. Here, we determined PRCB effectiveness in alleviating hypersensitivity symptoms in mouse models of migraine and medication overuse headache. Long-term glyceryl trinitrate (GTN, 10 mg/kg) administration led to increased sensitivity to mechanical stimuli and increased expression of phosphorylated protein kinase A, neuronal nitric oxide synthase, and transient receptor potential ankyrin 1 proteins in trigeminal ganglia. Peripherally restricted cannabinoid pretreatment, but not posttreatment, prevented behavioral and biochemical correlates of GTN-induced sensitization. Low pH-activated and allyl isothiocyanate-activated currents in acutely isolated trigeminal neurons were reversibly attenuated by PRCB application. Long-term GTN treatment significantly enhanced these currents. Long-term sumatriptan treatment also led to the development of allodynia to mechanical and cold stimuli that was slowly reversible after sumatriptan discontinuation. Subsequent challenge with a previously ineffective low-dose GTN (0.1-0.3 mg/kg) revealed latent behavioral sensitization and increased expression of phosphorylated protein kinase A, neuronal nitric oxide synthase, and transient receptor potential ankyrin 1 proteins in trigeminal ganglia. Peripherally restricted cannabinoid pretreatment prevented all behavioral and biochemical correlates of allodynia and latent sensitization. Importantly, long-term PRCB treatment alone did not produce any behavioral or biochemical signs of sensitization. These data validate peripheral cannabinoid receptors as potential therapeutic targets in migraine and medication overuse headache.

Emerging drugs for the prevention of migraine

INTRODUCTION

Migraine is a common and disabling neurological disorder. A greater understanding of the pathophysiological mechanisms underlying migraine has led to the availability of specific new drugs targeting calcitonin gene-related peptide (CGRP). The success of the CGRP inhibitors validates research efforts into migraine-specific therapies.

AREAS COVERED

There are additional promising therapeutic targets that will be covered in this paper, focusing on the pain phase. They include pituitary adenylate cyclase-activating polypeptide (PACAP), the orexinergic system, the nitric oxide signaling pathway specifically neuronal nitric oxide synthase inhibitors (nNOSi), and metabotropic glutamate receptor 5 (mGluR5).

EXPERT OPINION

Based on currently available research; the targets discussed in this paper are all on equal footing with each other in terms of their potential as effective novel migraine therapies. There is a need for more clinical trials to pinpoint which of these potential drug targets will be effective for migraine preventio.

Targeting reactive nitroxidative species in preclinical models of migraine

BACKGROUND

Reactive nitroxidative species, such as nitric oxide but particularly peroxynitrite, have been strongly implicated in pain mechanisms. Targeting peroxynitrite is anti-nociceptive in pain models, but little is known about its role in migraine mechanisms. Given the need to validate novel targets for migraine headache, our objective was to study the potential of reactive nitroxidative species, particularly peroxynitrite, as novel targets for drug discovery and their role in migraine mechanisms.

METHODS

We recorded neuronal activity in rats with extracellular electrodes and examined the effects of targeting nitric oxide or peroxynitrite on ongoing and cranial-evoked firing rates of central trigeminocervical neurons. We injected calcitonin gene-related peptide (which produces migraine-like headache in migraineurs) and characterized neuronal responses to cranial stimulation and on behavioral responses to nociceptive periorbital stimulation and determined the effects of targeting reactive nitroxidative species on the mediated changes.

RESULTS

L-NAME (nitric oxide synthase inhibitor) and Fe(III)5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato chloride (FeTPPS; peroxynitrite decomposition catalyst) inhibited ongoing and dural-evoked responses of trigeminocervical neurons, without affecting normal facial-cutaneous responses. Calcitonin gene-related peptide caused activation and sensitization of dural-responsive trigeminovascular neurons with hypersensitivity to intracranial and extracranial stimulation, and reduction of periorbital withdrawal thresholds. Only the peroxynitrite decomposition catalyst prevented these neuronal and behavioral nociceptive responses.

DISCUSSION

The data support that calcitonin gene-related peptide mediates the underlying neurobiological mechanisms related to the development of migraine-like headache. They also confirm the role of nitric oxide and implicate peroxynitrite production along the trigeminovascular migraine pathway in these mechanisms. The data also support peroxynitrite as a novel and potentially effective target for migraine treatment. The current drug development focus on peroxynitrite decomposition catalysts for chronic pain disorders should therefore extend to migraine.

Medication overuse and drug addiction: a narrative review from addiction perspective

Chronic headache is particularly prevalent in migraineurs and it can progress to a condition known as medication overuse headache (MOH). MOH is a secondary headache caused by overuse of analgesics or other medications such as triptans to abort acute migraine attacks. The worsening of headache symptoms associated with medication overuse (MO) generally ameliorates following interruption of regular medication use, although the primary headache symptoms remain unaffected. MO patients may also develop certain behaviors such as ritualized drug administration, psychological drug attachment, and withdrawal symptoms that have been suggested to correlate with drug addiction. Although several reviews have been performed on this topic, to the authors best knowledge none of them have examined this topic from the addiction point of view. Therefore, we aimed to identify features in MO and drug addiction that may correlate. We initiate the review by introducing the classes of analgesics and medications that can cause MOH and those with high risk to produce MO. We further compare differences between sensitization resulting from MO and from drug addiction, the neuronal pathways that may be involved, and the genetic susceptibility that may overlap between the two conditions. Finally, ICHD recommendations to treat MOH will be provided herein.

Repetitive stress in mice causes migraine-like behaviors and calcitonin gene-related peptide-dependent hyperalgesic priming to a migraine trigger

Migraine is one of the most disabling disorders worldwide but the underlying mechanisms are poorly understood. Stress is consistently reported as a common trigger of migraine attacks. Here, we show that repeated stress in mice causes migraine-like behaviors that are responsive to a migraine therapeutic. Adult female and male mice were exposed to 2 hours of restraint stress for 3 consecutive days, after which they demonstrated facial mechanical hypersensitivity and facial grimace responses that were resolved by 14 days after stress. Hypersensitivity or grimace was not observed in either control animals or those stressed for only 1 day. After return to baseline, the nitric oxide donor sodium nitroprusside (SNP; 0.1 mg/kg) elicited mechanical hypersensitivity in stressed but not in control animals, demonstrating the presence of hyperalgesic priming. This suggests the presence of a migraine-like state, because nitric oxide donors are reliable triggers of attacks in migraine patients but not controls. The stress paradigm also caused priming responses to dural pH 7.0 treatment. The presence of this primed state after stress is not permanent because it was no longer present at 35 days after stress. Finally, mice received either the calcitonin gene-related peptide monoclonal antibody ALD405 (10 mg/kg) 24 hours before SNP or a coinjection of sumatriptan (0.6 mg/kg). ALD405, but not sumatriptan, blocked the facial hypersensitivity due to SNP. This stress paradigm in mice and the subsequent primed state caused by stress allow further preclinical investigation of mechanisms contributing to migraine, particularly those caused by common triggers of attacks.

Nitric Oxide Synthase Inhibitors into the Clinic at Last

The 1998 Nobel Prize in Medicine and Physiology for the discovery of nitric oxide, a nitrogen containing reactive oxygen species (also termed reactive nitrogen or reactive nitrogen/oxygen species) stirred great hopes. Clinical applications, however, have so far pertained exclusively to the downstream signaling of cGMP enhancing drugs such as phosphodiesterase inhibitors and soluble guanylate cyclase stimulators. All clinical attempts, so far, to inhibit NOS have failed even though preclinical models were strikingly positive and clinical biomarkers correlated perfectly. This rather casts doubt on our current way of target identification in drug discovery in general and our way of patient stratification based on correlating but not causal biomarkers or symptoms. The opposite, NO donors, nitrite and enhancing NO synthesis by eNOS/NOS3 recoupling in situations of NO deficiency, are rapidly declining in clinical relevance or hold promise but need yet to enter formal therapeutic guidelines, respectively. Nevertheless, NOS inhibition in situations of NO overproduction often jointly with enhanced superoxide (or hydrogen peroxide production) still holds promise, but most likely only in acute conditions such as neurotrauma (Stover et al., J Neurotrauma 31(19):1599-1606, 2014) and stroke (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019). Conversely, in chronic conditions, long-term inhibition of NOS might be too risky because of off-target effects on eNOS/NOS3 in particular for patients with cardiovascular risks or metabolic and renal diseases. Nitric oxide synthases (NOS) and their role in health (green) and disease (red). Only neuronal/type 1 NOS (NOS1) has a high degree of clinical validation and is in late stage development for traumatic brain injury, followed by a phase II safety/efficacy trial in ischemic stroke. The pathophysiology of NOS1 (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016) is likely to be related to parallel superoxide or hydrogen peroxide formation (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 114(46):12315-12320, 2017; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019) leading to peroxynitrite and protein nitration, etc. Endothelial/type 3 NOS (NOS3) is considered protective only and its inhibition should be avoided. The preclinical evidence for a role of high-output inducible/type 2 NOS (NOS2) isoform in sepsis, asthma, rheumatic arthritis, etc. was high, but all clinical development trials in these indications were neutral despite target engagement being validated. This casts doubt on the role of NOS2 in humans in health and disease (hence the neutral, black coloring).

Involvement of 5-Hydroxytryptamine Receptor 2A in the Pathophysiology of Medication-Overuse Headache

Background

Recent studies indicated that analgesic overuse upregulated 5-hydroxytryptamine receptor 2A (5-HT_2AR) and subsequently activated nitric oxide synthase (NOS) and thus induced latent sensitization, which provided a mechanistic basis for medication-overuse headache (MOH). Moreover, glycogen synthase kinase-3β (GSK-3β) was regulated by serotonin receptors and the phosphorylation of GSK-3β affected NOS activity, indicating that GSK-3β could be involved in the regulation of NOS activity by 5-HT_2AR in MOH pathophysiology. Herein, we performed this study to investigate the role of 5-HT_2AR in MOH pathophysiology and the role of GSK-3β in the regulation of NOS activity by 5-HT_2AR.

Materials and Methods

Wistar rats were daily administered with paracetamol (200 mg/kg) for 30 days to set animal models for pre-clinical MOH research. After the rat MOH models were successfully established, the expression of 5-HT_2AR and NOS, GSK-3β activity in trigeminal nucleus caudalis (TNC) were assayed. Then, 5-HT_2AR antagonist ketanserin and agonist DOI were applied to investigate the effect of 5-HT_2AR on NOS activity in TNC of MOH rats, and GSK-3β antagonist LiCl and agonist perifosine were applied to explore the role of GSK-3β in the activation of NOS by 5-HT_2AR.

Results

We found that the expression of 5-HT_2AR and NOS, GSK-3β activity were enhanced in TNC of MOH rats. 5-HT_2AR modulator regulated the activity of NOS and GSK-3β in TNC of MOH rats, and drugs acting on GSK-3β affected NOS activity.

Conclusion

These data suggest that GSK-3β may mediate the activation of NOS by 5-HT_2AR and underline the role of 5-HT_2AR in MOH pathophysiology.

DAGLα Inhibition as a Non-invasive and Translational Model of Episodic Headache

Recent findings suggested that Clinical Endocannabinoid Deficiency underlies the pathophysiology of pain disorders, including migraine and headache. In models of medication overuse headache induced by sustained administration of sumatriptan or morphine, 2-AG levels were selectively depleted in the periaqueductal gray (PAG) and anandamide (AEA) increased in the cortex suggesting distinct regulation of the endocannabinoid system during headache pain. These results led to the hypothesis that blockade of DAGL, to reduce 2-AG levels would induce headache-like behaviors as a new, translationally relevant model of episodic headache. Our study investigated whether non-selective and selective blockade of DAGL, the main biosynthetic enzyme for 2-AG, induced periorbital and hind-paw allodynia, photophobia, anxiety-like behaviors, responsivity to abortive anti-migraine agents, and 2-AG/AEA levels. Injection of non-selective DAGL (DH376, 10 mg/kg, IP) and selective DAGLα (LEI106, 20 mg/kg, IP) inhibitors, but not DAGLβ agents, induced facial sensitivity in 100% and ∼60% of female and male rats, respectively, without induction of peripheral sensitivity. Notably, male rats showed significantly less sensitivity than female rats after DAGLα inhibition, suggesting sexual dimorphism in this mechanism. Importantly, LEI106 induced periorbital allodynia was attenuated by administration of the clinically available abortive antimigraine agents, sumatriptan and olcegepant. Selective DAGLα inhibition induced significant photophobia as measured by the light-dark box, without anxiety like behaviors or changes in voluntary movement. Analysis of AEA and 2-AG levels at the time of peak pain sensitivity revealed reductions in 2-AG in the visual cortex and periaqueductal gray (PAG), without altering anandamide or significantly increasing diacylglycerol levels. These results provide foundational evidence for DAGL-2AG in the induction of headache-like pain and photophobia without extracephalic allodynia, thus modeling the clinical episodic migraine. Mechanistically, behavioral measures of headache sensitivity after DAGL inhibition suggests that reduced 2-AG signaling in the cortex and PAG, but not the trigeminal nucleus caudalis or trigeminal ganglia, drives headache initiation. Therefore, episodic DAGL inhibition, which reduces the time, cost, and invasiveness of currently accepted models of headache, may fill the need for episodic migraine/headache models mirroring clinical presentation. Moreover, use of this approach may provide an avenue to study the transition from episodic to chronic headache.

Extracellular Vesicles Derived From Talaromyces marneffei Yeasts Mediate Inflammatory Response in Macrophage Cells by Bioactive Protein Components

Extracellular vesicles (EVs) loaded with proteins, nucleic acids, membrane lipids, and other virulence factors could participate in pathogenic processes in some fungi such as Cryptococcus neoformans and Candida albicans. However, the specific characteristics of EVs derived from Talaromyces marneffei (TM) still have not been figured out yet. In the present study, it has been observed that TM-derived EVs were a heterogeneous group of nanosized membrane vesicles (30–300 nm) under nanoparticle tracking analysis and transmission electron microscopy. The DiI-labeled EVs could be taken up by RAW 264.7 macrophage cells. Incubation of EVs with macrophages would result in increased expression levels of reactive oxygen species, nitric oxide, and some inflammatory factors including interleukin-1β, interleukin-6, interleukin-10, and tumor necrosis factor. Furthermore, the expression of co-stimulatory molecules (CD80, CD86, and MHC-II) was also increased in macrophages stimulated with EVs. The level of inflammatory factors secreted by macrophages showed a significant decrease when EVs were hydrolyzed by protease, while that of DNA and RNA hydrolase treatment remained unchanged. Subsequently, some virulence factors in EVs including heat shock protein, mannoprotein 1, and peroxidase were determined by liquid chromatography–tandem mass spectrometry. Taken together, our results indicated that the TM-derived EVs could mediate inflammatory response and its protein would play a key role in regulating the function of RAW 264.7 macrophage cells.

Analysis of NOS Gene Polymorphisms in Relation to Cluster Headache and Predisposing Factors in Sweden

Cluster headache is characterized by activation of the autonomic-trigeminal reflex. Nitric oxide can trigger headaches in patients, and nitric oxide signaling is known to be affected in cluster headache. Based on the hypothesis of nitric oxide being involved in cluster headache pathophysiology we investigated nitric oxide synthases as potential candidate genes for cluster headache. We analyzed eight variants in the three forms of nitric oxide synthase (NOS) genes, inducible NOS (iNOS), endothelial NOS (eNOS) and neuronal NOS (nNOS), and tested for association with cluster headache. Swedish cluster headache patients (n = 542) and controls (n = 581) were genotyped using TaqMan^® assays on an Applied Biosystems 7500 qPCR cycler. This is the largest performed genetic study on NOS involvement in cluster headache so far. We found an association between cluster headache and one iNOS haplotype consisting of the minor alleles of rs2297518 and rs2779249 (p = 0.022). In addition, one of the analyzed nNOS variants, rs2682826, was associated with reported triptan use (p = 0.039). Our data suggest that genetic variants in NOS genes do not have a strong influence on cluster headache pathophysiology, but that certain combinations of genetic variants in NOS genes may influence the risk of developing the disorder or triptan use.

Sumatriptan reduces severity of status epilepticus induced by lithium-pilocarpine through nitrergic transmission and 5-HT1B/D receptors in rats: A pharmacological-based evidence

Status epilepticus (SE) is a life-threatening neurologic disorder that can be as both cause and consequence of neuroinflammation. In addition to previous reports on anti-inflammatory property of the anti-migraine medication sumatriptan, we have recently shown its anticonvulsive effects on pentylenetetrazole-induced seizure in mice. In the present study, we investigated further (i) the effects of sumatriptan in the lithium-pilocarpine SE model in rats, and (ii) the possible involvement of nitric oxide (NO), 5-hydroxytryptamin 1B/1D (5-HT_1B/1D ) receptor, and inflammatory pathways in such effects of sumatriptan. Status epilepticus was induced by lithium chloride (127 mg/kg, i.p) and pilocarpine (60 mg/kg, i.p.) in Wistar rats. While SE induction increased SE scores and mortality rate, sumatriptan (0.001-1 mg/kg, i.p.) improved it (P < 0.001). Administration of the selective 5-HT_1B/1D antagonist GR-127935 (0.01 mg/kg, i.p.) reversed the anticonvulsive effects of sumatriptan (0.01 mg/kg, i.p.). Although both tumor necrosis factor-α (TNF-α) and NO levels were markedly elevated in the rats' brain tissues post-SE induction, pre-treatment with sumatriptan significantly reduced both TNF-α (P < 0.05) and NO (P < 0.001) levels. Combined GR-127935 and sumatriptan treatment inhibited these anti-inflammatory effects of sumatriptan, whereas combined non-specific NOS (L-NAME) or selective neuronal NOS (7-nitroindazole) inhibitors and sumatriptan further reduced NO levels. In conclusion, sumatriptan exerted a protective effect against the clinical manifestations and mortality rate of SE in rats which is possibly through targeting 5-HT_1B/1D receptors, neuroinflammation, and nitrergic transmission.

Emerging Treatment Targets for Migraine and Other Headaches

Migraine is a complex disorder that is characterized by an assortment of neurological and systemic effects. While headache is the most prominent feature of migraine, a host of symptoms affecting many physiological functions are also observed before, during, and after an attack. Furthermore, migraineurs are heterogeneous and have a wide range of responses to migraine therapies. The recent approval of calcitonin gene-related-peptide based therapies has opened up the treatment of migraine and generated a renewed interest in migraine research and discovery. Ongoing advances in migraine research have identified a number of other promising therapeutic targets for this disorder. In this review, we highlight emergent treatments within the following biological systems: pituitary adenylate cyclase activating peptdie, 2 non-mu opioid receptors that have low abuse liability - the delta and kappa opioid receptors, orexin, and nitric oxide-based therapies. Multiple mechanisms have been identified in the induction and maintenance of migraine symptoms; and this divergent set of targets have highly distinct biological effects. Increasing the mechanistic diversity of the migraine tool box will lead to more treatment options and better patient care.

Evaluation of LY573144 (lasmiditan) in a preclinical model of medication overuse headache

BACKGROUND

Medication overuse is a significant issue that complicates the treatment of headache disorders. The most effective medications for the acute treatment of migraine all have the capacity to induce medication overuse headache (MOH). Novel acute migraine-specific treatments are being developed. However, because the mechanism(s) underlying medication overuse headache are not well understood, it is difficult to predict whether any particular acute medication will induce MOH in susceptible individuals. LY573144 (lasmiditan), a 5-HT_1F receptor agonist, has recently been shown to be effective in the acute treatment of migraine in phase 3 trials. The aim of this study is to determine whether frequent administration of lasmiditan induces behaviors consistent with MOH in a pre-clinical rat model.

METHODS

Sprague Dawley rats were administered six doses of lasmiditan (10 mg/kg), sumatriptan (10 mg/kg), or sterile water orally over 2 weeks and cutaneous allodynia was evaluated regularly in the periorbital and hindpaw regions using von Frey filaments. Testing continued until mechanosensitivity returned to baseline levels. Rats were then submitted to bright light stress (BLS) or nitric oxide (NO) donor administration and were again evaluated for cutaneous allodynia in the periorbital and hindpaw regions hourly for 5 hours.

RESULTS

Both lasmiditan and sumatriptan exhibited comparable levels of drug-induced cutaneous allodynia in both the periorbital and hindpaw regions, which resolved after cessation of drug administration. Both lasmiditan and sumatriptan pre-treatment resulted in cutaneous allodynia that was evoked by either BLS or NO donor.

CONCLUSIONS

In a pre-clinical rat model of MOH, oral lasmiditan, like sumatriptan, induced acute transient cutaneous allodynia in the periorbital and hindpaw regions that after resolution could be re-evoked by putative migraine triggers. These results suggest that lasmiditan has the capacity to induce MOH through persistent latent peripheral and central sensitization mechanisms.

Identification of candidate proteomic markers in the serum of medication overuse headache patients: An exploratory study

PURPOSE OF THE STUDY

The pathophysiological mechanism of medication overuse headache is uncertain; no distinctive markers have been described right now. The aim of this study was to conduct proteomic analyses on serum samples from patients with medication overuse headache and healthy individuals. Specifically, mono- (SDS-PAGE) and two-dimensional gel electrophoresis (2-DE) followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) were used to evaluate changes in serum proteins.

MAIN FINDINGS

By SDS-PAGE, four over-expressed bands were revealed in patients, compared to controls. 2-DE combined with LC-MS/MS analysis allowed confirmation of some proteins preliminarily detected by SDS-PAGE: Hemopexin, alpha-1-acid glycoprotein 1, apolipoprotein A4 and haptoglobin. Moreover, other differential proteins were isolated, mostly increased in MOH patients: Alpha-1-antitrypsin, immunoglobulin heavy constant alpha 1, retinol binding protein and transthyretin. Only one protein, immunoglobulin kappa constant, was decreased in the patients' group.

CONCLUSIONS

The investigation of the serum proteome can offer a better understanding about biological mechanisms underlying medication overuse headache. Specifically, medication overuse headache shares some serum biochemical markers with chronic pain conditions. Further studies might uncover the relevance of these proteins in medication overuse headache.

Maladaptive activation of Nav1.9 channels by nitric oxide causes triptan-induced medication overuse headache

Medication-overuse headaches (MOH) occur with both over-the-counter and pain-relief medicines, including paracetamol, opioids and combination analgesics. The mechanisms that lead to MOH are still uncertain. Here, we show that abnormal activation of Nav1.9 channels by Nitric Oxide (NO) is responsible for MOH induced by triptan migraine medicine. Deletion of the Scn11a gene in MOH mice abrogates NO-mediated symptoms, including cephalic and extracephalic allodynia, photophobia and phonophobia. NO strongly activates Nav1.9 in dural afferent neurons from MOH but not normal mice. Abnormal activation of Nav1.9 triggers CGRP secretion, causing artery dilatation and degranulation of mast cells. In turn, released mast cell mediators potentiates Nav1.9 in meningeal nociceptors, exacerbating inflammation and pain signal. Analysis of signaling networks indicates that PKA is downregulated in trigeminal neurons from MOH mice, relieving its inhibitory action on NO-Nav1.9 coupling. Thus, anomalous activation of Nav1.9 channels by NO, as a result of chronic medication, promotes MOH.

Cannabinoids induce latent sensitization in a preclinical model of medication overuse headache

AIM

Evaluation of cannabinoid receptor agonists in a preclinical model of medication overuse headache.

METHODS

Female Sprague Dawley rats received graded intraperitoneal doses of WIN55,212-2 or Δ-9-tetrahydrocannabinol (Δ-9-THC). Antinociception (tail-flick test), catalepsy and hypomotility (open field test) and impairment of motor function (rotarod test) were assessed to establish effective dosing. Rats were then treated twice daily with equianalgesic doses of WIN55,212-2 or Δ-9-THC, or vehicle, for 7 days and cutaneous tactile sensory thresholds were evaluated during and three weeks following drug discontinuation. Rats then received a one-hour period of bright light stress (BLS) on two consecutive days and tactile sensory thresholds were re-assessed.

RESULTS

WIN55,212-2 and Δ-9-THC produced antinociception as well as hypomotility, catalepsy and motor impairment. Repeated administration of WIN55,212-2 and Δ-9-THC induced generalized periorbital and hindpaw allodynia that resolved within 3 weeks after discontinuation of drug. Two episodes of BLS produced delayed and long-lasting periorbital and hindpaw allodynia selectively in rats previously treated with WIN55,212-2, and Δ-9-THC.

INTERPRETATION

Cannabinoid receptor agonists including Δ-9-THC produce a state of latent sensitization characterized by increased sensitivity to stress, a presumed migraine trigger. Overuse of cannabinoids including cannabis may increase the risk of medication overuse headache in vulnerable individuals.

Migraine: Experimental Models and Novel Therapeutic Approaches

Migraine is a disorder affecting an increasing number of subjects. Currently, this disorder is not entirely understood, and limited therapeutic solutions are available. Migraine manifests as a debilitating headache associated with an altered sensory perception that may compromise the quality of life. Animal models have been developed using chemical, physical or genetic modifications, to evoke migraine-like hallmarks for the identification of novel molecules for the treatment of migraine. In this context, experimental models based on the use of chemicals as nitroglycerin or inflammatory soup were extensively used to mimic the acute state and the chronicity of the disorder. This manuscript is aimed to provide an overview of murine models used to investigate migraine pathophysiology. Pharmacological targets as 5-HT and calcitonin gene-related peptide (CGRP) receptors were evaluated for their relevance in the development of migraine therapeutics. Drug delivery systems using nanoparticles may be helpful for the enhancement of the brain targeting and bioavailability of anti-migraine drugs as triptans. In conclusion, the progresses in migraine management have been reached with the development of emerging agonists of 5-HT receptors and novel antagonists of CGRP receptors. The nanoformulations may represent a future perspective in which already known anti-migraine drugs showed to better exert their therapeutic effects.

Pathophysiology, prevention, and treatment of medication overuse headache

Regular or frequent use of analgesics and acute antimigraine drugs can increase the frequency of headache, and induce the transition from episodic to chronic headache or medication overuse headache. The 1-year prevalence of this condition in the general population is between 1% and 2%. Medication overuse headache is more common in women and in people with comorbid depression, anxiety, and other chronic pain conditions. Treatment of medication overuse headache has three components. First, patients need education and counselling to reduce the intake of medication for acute headache attacks. Second, some patients benefit from drug withdrawal (discontinuation of the overused medication). Finally, preventive drug therapy and non-medical prevention might be necessary in patients at onset of treatment or in patients who do not respond to the first two steps. The optimal therapeutic approach requires validation in controlled trials.

CGRP and the Trigeminal System in Migraine

OBJECTIVE

The goal of this narrative review is to provide an overview of migraine pathophysiology, with an emphasis on the role of calcitonin gene-related peptide (CGRP) within the context of the trigeminovascular system.

BACKGROUND

Migraine is a prevalent and disabling neurological disease that is characterized in part by intense, throbbing, and unilateral headaches. Despite recent advances in understanding its pathophysiology, migraine still represents an unmet medical need, as it is often underrecognized and undertreated. Although CGRP has been known to play a pivotal role in migraine for the last 2 decades, this has now received more interest spurred by the early clinical successes of drugs that block CGRP signaling in the trigeminovascular system.

DESIGN

This narrative review presents an update on the role of CGRP within the trigeminovascular system. PubMed searches were used to find recent (ie, 2016 to November 2018) published articles presenting new study results. Review articles are also included not as primary references but to bring these to the attention of the reader. Original research is referenced in describing the core of the narrative, and review articles are used to support ancillary points.

RESULTS

The trigeminal ganglion neurons provide the connection between the periphery, stemming from the interface between the primary afferent fibers of the trigeminal ganglion and the meningeal vasculature and the central terminals in the trigeminal nucleus caudalis. The neuropeptide CGRP is abundant in trigeminal ganglion neurons, and is released from the peripheral nerve and central nerve terminals as well as being secreted within the trigeminal ganglion. Release of CGRP from the peripheral terminals initiates a cascade of events that include increased synthesis of nitric oxide and sensitization of the trigeminal nerves. Secreted CGRP in the trigeminal ganglion interacts with adjacent neurons and satellite glial cells to perpetuate peripheral sensitization, and can drive central sensitization of the second-order neurons. A shift in central sensitization from activity-dependent to activity-independent central sensitization may indicate a mechanism driving the progression of episodic migraine to chronic migraine. The pathophysiology of cluster headache is much more obscure than that of migraine, but emerging evidence suggests that it may also involve hypersensitivity of the trigeminovascular system. Ongoing clinical studies with therapies targeted at CGRP will provide additional, valuable insights into the pathophysiology of this disorder.

CONCLUSIONS

CGRP plays an essential role in the pathophysiology of migraine. Treatments that interfere with the functioning of CGRP in the peripheral trigeminal system are effective against migraine. Blocking sensitization of the trigeminal nerve by attenuating CGRP activity in the periphery may be sufficient to block a migraine attack. Additionally, the potential exists that this therapeutic strategy may also alleviate cluster headache as well.

CGRP ligand and receptor monoclonal antibodies for migraine prevention: Evidence review and clinical implications

Background: Monoclonal antibodies that target calcitonin gene-related peptide or the canonical calcitonin gene-related peptide receptor have emerged as effective and well tolerated for the preventive treatment of migraine. These large molecules appear ideally suited for migraine prevention. They have an extended biological half-life, are administered either monthly or quarterly either by subcutaneous injection or intravenous infusion, require minimal or no dose-titration and have the potential for a rapid onset of effect compared to conventional oral preventive drugs. There is high selectivity and they target an important mediator in the pathogenesis of migraine. Investigation: Phase II and pivotal phase III studies have all yielded positive results with a favorable adverse event profile. No serious treatment-related adverse outcomes have thus far been reported in controlled or long-term open-label extension studies. This tolerability profile promises to improve adherence and, possibly, long-term outcomes. Conclusions: Calcitonin gene-related peptide monoclonal antibodies are effective and well tolerated for the preventive treatment of migraine. They have distinct advantages over currently available oral preventive drugs. While treatment-related serious adverse events have not been observed in open-label extension studies, long-term outcomes and safety will require broad exposure in heterogeneous patient populations in clinical practice. In addition, their safety in women, especially during pregnancy, will require longitudinal surveillance. Given the overlapping mechanism(s), the effectiveness of existing (triptans) and emerging (calcitonin gene-related peptide receptor antagonists) acute therapies in those using a calcitonin gene-related peptide mAb will require further study.

The development of a mouse model of mTBI-induced post-traumatic migraine, and identification of the delta opioid receptor as a novel therapeutic target

BACKGROUND

Post-traumatic headache is the most common and long-lasting impairment observed following mild traumatic brain injury, and frequently has migraine-like characteristics. The mechanisms underlying progression from mild traumatic brain injury to post-traumatic headache are not fully understood. The aim of this study was to develop a mouse model of post-traumatic headache and identify mechanisms and novel targets associated with this disorder.

METHODS

We combined the closed head weight-drop method and the nitroglycerin chronic migraine model. To induce mild traumatic brain injury, a weight was dropped onto intact crania of mildly anesthetized mice, and mechanical responses to chronic-intermittent administration of nitroglycerin, a human migraine trigger, were determined at multiple time points post-injury.

RESULTS

Low dose nitroglycerin (0.1 mg/kg) evoked acute periorbital and hind paw allodynia in both mild traumatic brain injury and sham animals. However, only mild traumatic brain injury mice developed chronic hypersensitivity to low dose nitroglycerin. Migraine medications, sumatriptan and topiramate, inhibited post-traumatic headache-associated allodynia. In addition, the delta opioid receptor agonist, SNC80, also blocked post-traumatic headache-associated allodynia. Finally, we examined the expression of calcitonin gene-related peptide within this model and found that it was increased in trigeminal ganglia two weeks post-mild traumatic brain injury.

CONCLUSIONS

Overall, we have established a mouse model of post-traumatic headache and identified the delta opioid receptor as a novel therapeutic target for this disorder.

Sustained exposure to acute migraine medications combined with repeated noxious stimulation dysregulates descending pain modulatory circuits: Relevance to medication overuse headache

Background

Loss of conditioned pain modulation/diffuse noxious inhibitory controls has been demonstrated in patients with migraine and medication overuse headache. We hypothesized that exposure to acute migraine medications may lead to dysregulation of central pain modulatory circuits that could be revealed by evaluating diffuse noxious inhibitory controls and that prior noxious stimulus is required for a loss of the diffuse noxious inhibitory control response in rats exposed to these medications.

Methods

Rats were “primed” by continuous infusion of morphine or one of two doses of sumatriptan. Diffuse noxious inhibitory control was evaluated at the end of drug-priming (day 7) and again after sensory thresholds returned to baseline (day 21). The Randall-Selitto hindpaw pressure test was used as the test stimulus and forepaw capsaicin injection served as the conditioning stimulus.

Results

Morphine-primed rats showed opioid-induced hyperalgesia accompanied by a loss of diffuse noxious inhibitory controls on day 7. Sumatriptan-primed rats did not develop hyperalgesia or loss of diffuse noxious inhibitory controls on day 7. Morphine-primed and high-dose sumatriptan-primed rats only had a loss of diffuse noxious inhibitory control on day 21 if they received a capsaicin injection on day 7.

Conclusions

Prolonged exposure to migraine treatments followed by an acute nociceptive stimulation caused long-lasting alterations in descending pain modulation, shown by a loss of diffuse noxious inhibitory controls. Morphine was more detrimental than sumatriptan, consistent with clinical observations of higher medication overuse headache risk with opioids. These data suggest a mechanism of medication overuse headache by which migraine medications combined with repeated episodes of pain may amplify the consequences of nociceptor activation and increase the probability of future migraine attacks as well as risk of medication overuse headache.

Sumatriptan improves postoperative quality of recovery and reduces postcraniotomy headache after cranial nerve decompression

BACKGROUND

Microvascular decompression (MVD) is a surgical treatment for cranial nerve disorders via a small craniotomy. The postoperative pain of this procedure can be classified as surgical site somatic pain and postcraniotomy headache similar in nature to a migraine, including its association with photophobia, nausea, and vomiting. This headache can be difficult to treat and can impact on postoperative recovery. Sumatriptan is used to treat migraine-like headaches in various settings. This single-centre randomized controlled trial investigated whether postoperative administration of sumatriptan after MVD surgery impacts the quality of postoperative recovery.

METHODS

Fifty patients who complained of postoperative headache after MVD were randomized to receive an s.c. injection of sumatriptan (6 mg) or saline. The primary outcome was quality of recovery as measured by the Quality of Recovery-40 (QoR-40) score at 24 h.

RESULTS

The QoR-40 scores were significantly higher in the sumatriptan group (median 184; interquartile range 169-196) than in the placebo group (133; 119-155; P<0.01), suggesting higher quality of recovery. The sumatriptan group also had significantly lower headache scores at 4, 12, and 24 h. There were no significant differences in other secondary outcomes.

CONCLUSIONS

Use of sumatriptan improved the quality of recovery as measured by the QoR-40 and reduction of headache at 24 h after surgery. Sumatriptan is a useful alternative treatment for postcraniotomy headache. The mechanism remains unknown but could be related to reduction in headache, mood modulation, or both, mediated by a serotonin effect.

CLINICAL TRIAL REGISTRATION

NCT01632657.