What have we learnt from triggering migraine?

Poor healthy lifestyle and life's essential 8 are associated with higher risk of new-onset migraine: a prospective cohort study

BACKGROUND

Lifestyle are closely related to migraine. However, there is a lack of studies investigating the association between Healthy lifestyle or Life's Essential 8 (LE8) and the risk of migraine. The objective of this research was to investigate the relationship between Healthy lifestyle scores and Life's essential 8 scores, and migraine.

METHODS

332,895 UK Biobank participants without migraine were included. Healthy lifestyle were assessed using seven lifestyle factors, and categorized as poor, intermediate, or ideal. LE8, based on the American Heart Association (AHA) Guidelines for Cardiovascular Health (CVH), consist of eight indicators classified as low, moderate, or high CVH. The Cox proportional hazard model was employed to examine the association between Healthy lifestyle scores, LE8 scores, and migraine, with calculations for population-attributable fraction (PAF) and cumulative incidence.

RESULTS

During a median follow-up of 13.58 years, participants in intermediate (HR: 0.91; 95% CI: 0.85, 0.99) or ideal category of Healthy lifestyle (HR: 0.81; 95% CI: 0.73, 0.91) significantly reduced migraine risk compared to the poor category. Similarly, high CVH (HR: 0.73; 95% CI: 0.58, 0.92) also lowered migraine risk, while moderate CVH (HR: 0.93; 95% CI: 0.85, 1.02) did not show a difference compared to low CVH. If all individuals adhered to higher categories of Healthy lifestyle and LE8, approximately 11.38% and 22.05% of migraine cases could be prevented. Among individual lifestyle factors, maintaining an ideal body mass index (BMI), physical activity, sleep duration, sleep pattern, and sedentary time were associated with substantial reductions in migraine risk, by 5.65%, 0.81%, 10.16%, 16.39%, and 6.57%, respectively.

CONCLUSION

Our study provides evidence that poor Healthy lifestyle and Life's Essential 8 are associated with higher risk of new-onset migraine.

Towards precision medicine in migraine: Recent therapeutic advances and potential biomarkers to understand heterogeneity and treatment response

After 35 years since the introduction of the International Classification of Headache Disorders (ICHD), we are living in the era of the second great revolution in migraine therapies. First, discoveries of triptans provided a breakthrough in acute migraine treatment utilizing bench-to-bedside research results on the role of serotonin in migraine. Next, the discovery of the role of neuropeptides, more specifically calcitonin gene-related peptide (CGRP) in migraine attack led to the development of anti-CGRP therapies that are effective both in acute and preventive treatment, and are also able to reduce migraine-related burden. Here, we reviewed the most recent clinical studies and real-world data on available migraine-specific medications, including triptans, ditants, gepants and anti-CGRP monoclonal antibodies. Novel drug targets, such as PACAP and amylins were also discussed. To address the main challenges of migraine therapy, the high heterogeneity of people with migraine, the prevalent presence of various comorbid disorders, and the insufficient medical care of migraine patients were covered. Promising novel approaches from the fields of omics, blood and saliva biomarker, imaging and provocation studies might bring solutions for these challenges with the potential to identify further drug targets, distinguish more homogeneous patient subgroups, contribute to more optimal drug selection strategies, and detect biomarkers in association with headache features or predicting treatment efficacy. In the future, the combined analysis of data of different biomarker modalities with machine learning algorithms may serve precision medicine in migraine treatment.

CGRP physiology, pharmacology, and therapeutic targets: migraine and beyond

Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse physiological functions. Its two isoforms (α and β) are widely expressed throughout the body in sensory neurons as well as in other cell types, such as motor neurons and neuroendocrine cells. CGRP acts via at least two G protein-coupled receptors that form unusual complexes with receptor activity-modifying proteins. These are the CGRP receptor and the AMY1 receptor; in rodents, additional receptors come into play. Although CGRP is known to produce many effects, the precise molecular identity of the receptor(s) that mediates CGRP effects is seldom clear. Despite the many enigmas still in CGRP biology, therapeutics that target the CGRP axis to treat or prevent migraine are a bench-to-bedside success story. This review provides a contextual background on the regulation and sites of CGRP expression and CGRP receptor pharmacology. The physiological actions of CGRP in the nervous system are discussed, along with updates on CGRP actions in the cardiovascular, pulmonary, gastrointestinal, immune, hematopoietic, and reproductive systems and metabolic effects of CGRP in muscle and adipose tissues. We cover how CGRP in these systems is associated with disease states, most notably migraine. In this context, we discuss how CGRP actions in both the peripheral and central nervous systems provide a basis for therapeutic targeting of CGRP in migraine. Finally, we highlight potentially fertile ground for the development of additional therapeutics and combinatorial strategies that could be designed to modulate CGRP signaling for migraine and other diseases.

ATP-Sensitive Potassium Channels in Migraine: Translational Findings and Therapeutic Potential

Globally, migraine is a leading cause of disability with a huge impact on both the work and private life of affected persons. To overcome the societal migraine burden, better treatment options are needed. Increasing evidence suggests that ATP-sensitive potassium (KATP) channels are involved in migraine pathophysiology. These channels are essential both in blood glucose regulation and cardiovascular homeostasis. Experimental infusion of the KATP channel opener levcromakalim to healthy volunteers and migraine patients induced headache and migraine attacks in 82-100% of participants. Thus, this is the most potent trigger of headache and migraine identified to date. Levcromakalim likely induces migraine via dilation of cranial arteries. However, other neuronal mechanisms are also proposed. Here, basic KATP channel distribution, physiology, and pharmacology are reviewed followed by thorough review of clinical and preclinical research on KATP channel involvement in migraine. KATP channel opening and blocking have been studied in a range of preclinical migraine models and, within recent years, strong evidence on the importance of their opening in migraine has been provided from human studies. Despite major advances, translational difficulties exist regarding the possible anti-migraine efficacy of KATP channel blockage. These are due to significant species differences in the potency and specificity of pharmacological tools targeting the various KATP channel subtypes.

Migraine and peripheral pain models show differential alterations in neuronal complexity

Objective

Our laboratory has recently shown that there is a decrease in neuronal complexity in head pain processing regions in mouse models of chronic migraine‐associated pain and aura. Importantly, restoration of this neuronal complexity corresponds with anti‐migraine effects of known and experimental pharmacotherapies. The objective of the current study was to expand this work and examine other brain regions involved with pain or emotional processing. We also investigated the generalizability of our findings by analyzing neuronal cytoarchitectural changes in a model of complex regional pain syndrome (CRPS), a peripheral pain disorder.

Methods

We used the nitroglycerin (NTG) model of chronic migraine‐associated pain in which mice receive 10 mg/kg NTG every other day for 9 days. Cortical spreading depression (CSD), a physiological corelate of migraine aura, was evoked in anesthetized mice using KCl. CRPS was induced by tibial fracture followed by casting. Neuronal cytoarchitecture was visualized with Golgi stain and analyzed with Simple Neurite Tracer.

Results

In the NTG model, we previously showed decreased neuronal complexity in the trigeminal nucleus caudalis (TNC) and periaqueductal gray (PAG). In contrast, we found increased neuronal complexity in the thalamus and no change in the amygdala or caudate putamen in this study. Following CSD, we observed decreased neuronal complexity in the PAG, in line with decreases in the somatosensory cortex and TNC reported with this model previously. In the CRPS model there was decreased neuronal complexity in the hippocampus, as reported by others; increased complexity in the PAG; and no change within the somatosensory cortex.

Conclusions

Collectively these results demonstrate that alterations in neuronal complexity are a feature of both chronic migraine and chronic CRPS. However, each type of pain presents a unique cytoarchitectural signature, which may provide insight on how these pain states differentially transition from acute to chronic conditions.

Endothelin-1 axes in the framework of predictive, preventive and personalised (3P) medicine

Endothelin-1 (ET-1) is involved in the regulation of a myriad of processes highly relevant for physical and mental well-being; female and male health; in the modulation of senses, pain, stress reactions and drug sensitivity as well as healing processes, amongst others. Shifted ET-1 homeostasis may influence and predict the development and progression of suboptimal health conditions, metabolic impairments with cascading complications, ageing and related pathologies, cardiovascular diseases, neurodegenerative pathologies, aggressive malignancies, modulating, therefore, individual outcomes of both non-communicable and infectious diseases such as COVID-19. This article provides an in-depth analysis of the involvement of ET-1 and related regulatory pathways in physiological and pathophysiological processes and estimates its capacity as a predictor of ageing and related pathologies,a sensor of lifestyle quality and progression of suboptimal health conditions to diseases for their targeted preventionand as a potent target for cost-effective treatments tailored to the person.

Updated review on the link between cortical spreading depression and headache disorders

INTRODUCTION

Experimental animal studies have revealed mechanisms that link cortical spreading depression (CSD) to the trigeminal activation mediating lateralized headache. However, conventional CSD as seen in lissencephalic brain is insufficient to explain some clinical features of aura and migraine headache.

AREAS COVERED

The importance of CSD in headache development including dysfunction of the thalamocortical network, neuroinflammation, calcitonin gene-related peptide, transgenic models, and the role of CSD in migraine triggers, treatment options, neuromodulation and future directions are reviewed.

EXPERT OPINION

The conventional understanding of CSD marching across the hemisphere is invalid in gyrencephalic brains. Thalamocortical dysfunction and interruption of functional cortical network systems by CSD, may provide alternative explanations for clinical manifestations of migraine phases including aura. Not all drugs showing CSD blocking properties in lissencephalic brains, have efficacy in migraine headache and monoclonal antibodies against CGRP ligand/receptors which are effective in migraine treatment, have no impact on aura in humans or CSD properties in rodents. Functional networks and molecular mechanisms mediating and amplifying the effects of limited CSD in migraine brain remain to be investigated to define new targets.

Neuronal complexity is attenuated in preclinical models of migraine and restored by HDAC6 inhibition

Migraine is the sixth most prevalent disease worldwide but the mechanisms that underlie migraine chronicity are poorly understood. Cytoskeletal flexibility is fundamental to neuronal-plasticity and is dependent on dynamic microtubules. Histone-deacetylase-6 (HDAC6) decreases microtubule dynamics by deacetylating its primary substrate, α-tubulin. We use validated mouse models of migraine to show that HDAC6-inhibition is a promising migraine treatment and reveal an undiscovered cytoarchitectural basis for migraine chronicity. The human migraine trigger, nitroglycerin, produced chronic migraine-associated pain and decreased neurite growth in headache-processing regions, which were reversed by HDAC6 inhibition. Cortical spreading depression (CSD), a physiological correlate of migraine aura, also decreased cortical neurite growth, while HDAC6-inhibitor restored neuronal complexity and decreased CSD. Importantly, a calcitonin gene-related peptide receptor antagonist also restored blunted neuronal complexity induced by nitroglycerin. Our results demonstrate that disruptions in neuronal cytoarchitecture are a feature of chronic migraine, and effective migraine therapies might include agents that restore microtubule/neuronal plasticity.

Clinical characterization of delayed alcohol-induced headache

Objective

To evaluate the International Classification of Headache Disorders (ICHD) criteria and to characterize the clinical phenotype of delayed alcohol-induced headache (DAIH).

Methods

We conducted a cross-sectional study of university students who voluntarily consumed alcohol and experienced headache. Participants completed a survey that included demographic and clinical data. We analyzed the phenotype of the headache, validated ICHD phenotype criteria for DAIH, and analyzed whether participants fulfilled criteria for low-CSF-pressure headache or migraine.

Results

A total of 1,108 participants were included (58% female, mean age 23 years, 41% with headache history). Mean alcohol intake was 158 g; spirits were consumed by 60% of the participants; beer was consumed by 41%; and wine was consumed by 18%. The ICHD criteria for DAIH were met in 95% of the participants. Headache duration (mean, 6.7 hours) correlated with total grams of alcohol consumed (r = 0.62, p = 0.03). Pain was bilateral in 85% of patients with predominantly frontal topography (43%). Pain quality was mainly pressing (60%) or pulsatile (39%) and was aggravated by physical activity in 83% of participants. ICHD low-CSF pressure-headache criteria were fulfilled in 58% of patients, and migraine criteria were fulfilled by 36%.

Conclusions

DAIH is a moderate-intensity headache, is typically bilateral, and presents with frontal predominance and a pressing quality. The phenotype of DAIH combines features of both migraine and low-CSF-pressure headaches.

Secondary headache attributed to exposure to or overuse of a substance

BACKGROUND

Secondary headaches attributed to exposure to or the overuse of a substance are classified under chapter eight in the International Classification of Headache Disorders 3rd edition. Three distinct sub-chapters consider: 1. Headache attributed to exposure to a substance, 2. Medication overuse headache, and 3. Headache attributed to substance withdrawal. Headache attributed to exposure to a substance refers to a headache with onset immediately or within hours after the exposure, while medication overuse headache is a headache occurring on 15 or more days per month that has developed as a consequence of regular usage of acute headache medication(s) for more than three consecutive months in a patient with a pre-existing primary headache disorder. The withdrawal of caffeine, oestrogen, and opioids is most often associated with the development of headache.

DISCUSSION

Despite the current headache classification, there is no certainty of a causal relationship between the use of any substance and the development of headache. Some substances are likely to provoke headache in patients that suffer from a primary headache disorder like migraine, tension-type headache or cluster headache, while others were described to cause headache even in people that generally do not get headaches. Toxic agents, such as carbon monoxide (CO) are difficult to investigate systematically, while other substances such as nitric oxide (NO) were specifically used to induce headache experimentally. If a patient with an underlying primary headache disorder develops a headache, in temporal relation to exposure to a substance, which is significantly worse than the usual headache it is considered secondary. This is even more the case if the headache phenotype is different from the usually experienced headache characteristics. Medication overuse headache is a well-described, distinct disease entity with only marginally understood pathophysiology and associated psychological factors. Managing medication overuse headache patients includes education, detoxification, prophylactic treatments and treating comorbidities, which is reflected in available guidelines. Viewing medication overuse headache as a separate entity helps clinicians and researchers better recognise, treat and study the disorder.

CONCLUSION

Identification of substances that may cause or trigger secondary headache is important in order to educate patients and health care professionals about potential effects of these substances and prevent unnecessary suffering, as well as deterioration in quality of life. Treatment in case of medication overuse and other chronic headache should be decisive and effective.

Subcutaneous sumatriptan reduces cilostazol induced headache in migraine patients

OBJECTIVES

The authors have previously tried to develop a model for the testing of novel drug candidates for migraine, using the headache and migraine provoking agent cilostazol. Previous studies have used sumatriptan tablets as the validating drug, but they were not sufficiently effective. In this study we test the effect of subcutaneous sumatriptan on cilostazol induced headache in patients with migraine without aura.

METHOD

Thirty patients with migraine without aura received 200 mg cilostazol on two different study days. The induced headache was treated with subcutaneous sumatriptan in a randomized, double-blind cross-over design. The patients filled out a self-reported headache questionnaire until 12 h after cilostazol.

RESULTS

All 30 patients experienced headache (range 3-10) on both study days and the headache fulfilled the criteria for a migraine-like attack in 73% on the sumatriptan day and in 77% on the placebo day. Sumatriptan injection reduced the headache score 2 h after treatment (p = 0.003). The difference between headache intensity on the sumatriptan day and the placebo day was significant at both 2 h (p = 0.01) and 4 h (p = 0.0007) after treatment.

CONCLUSION

Subcutaneous sumatriptan reduces cilostazol induced headache in migraine patients. The cilostazol model may be useful as a tool to test the potential of new anti-migraine drugs.Trial registration: The study is registered on clinicaltrials.gov (NCT03422796).

Effect of Infusion of Calcitonin Gene-Related Peptide on Cluster Headache Attacks: A Randomized Clinical Trial

Importance

Signaling molecule calcitonin gene-related peptide (CGRP) induces migraine attacks and anti-CGRP medications abort and prevent migraine attacks. Whether CGRP provokes cluster headache attacks is unknown.

Objective

To determine whether CGRP induces cluster headache attacks in episodic cluster headache in active phase, episodic cluster headache in remission phase, and chronic cluster headache.

Design, Setting, and Participants

A randomized, double-blind, placebo-controlled, 2-way crossover study set at the Danish Headache Center, Rigshospitalet Glostrup, in Denmark. Analyses were intent to treat. Inclusion took place from December 2015 to April 2017. Inclusion criteria were diagnosis of episodic/chronic cluster headache, patients aged 18 to 65 years, and safe contraception in women. Exclusion criteria were a history of other primary headache (except episodic tension-type headache <5 days/mo), individuals who were pregnant or nursing; cardiovascular, cerebrovascular, or psychiatric disease; and drug misuse.

Interventions

Thirty-seven patients with cluster headaches received intravenous infusion of 1.5 μg/min of CGRP or placebo over 20 minutes on 2 study days.

Main Outcomes and Measures

Difference in incidence of cluster headache-like attacks, difference in area under the curve (AUC) for headache intensity scores (0 to 90 minutes), and difference in time to peak headache between CGRP and placebo in the 3 groups.

Results

Of 91 patients assessed for eligibility, 32 patients (35.2%) were included in the analysis. The mean (SD) age was 36 (10.7) years (range, 19-60 years), and the mean weight was 78 kg (range, 53-100 kg). Twenty-seven men (84.4%) completed the study. Calcitonin gene-related peptide induced cluster headache attacks in 8 of 9 patients in the active phase (mean, 89%; 95% CI, 63-100) compared with 1 of 9 in the placebo group (mean, 11%; 95% CI, 0-37) (P = .05). In the remission phase, no patients with episodic cluster headaches reported attacks after CGRP or placebo. Calcitonin gene-related peptide-induced attacks occurred in 7 of 14 patients with chronic cluster headaches (mean, 50%; 95% CI, 20-80) compared with none after placebo (P = .02). In patients with episodic active phase, the mean AUC from 0 to 90 minutes for CGRP was 1.903 (95% CI, 0.842-2.965), and the mean AUC from 0 to 90 minutes for the placebo group was 0.343 (95% CI, 0-0.867) (P = .04). In patients with chronic cluster headache, the mean AUC from 0 to 90 minutes for CGRP was 1.214 (95% CI, 0.395-2.033), and the mean AUC from 0 to 90 minutes for the placebo group was 0.036 (95% CI, 0-0.114) (P = .01). In the remission phase, the mean AUC from 0 to 90 minutes for CGRP was 0.187 (95% CI, 0-0.571), and the mean AUC from 0 to 90 minutes for placebo was 0.019 (95% CI, 0-0.062) (P > .99).

Conclusions and Relevance

Calcitonin gene-related peptide provokes cluster headache attacks in active-phase episodic cluster headache and chronic cluster headache but not in remission-phase episodic cluster headache. These results suggest anti-CGRP drugs may be effective in cluster headache management.

Trial Registration

ClinicalTrials.gov (NCT02466334).

More precise phenotyping of cluster headache using prospective attack reports

BACKGROUND AND PURPOSE

The clinical characteristics of cluster headache (CH) are based mainly on retrospective attack descriptions of 'usual' attacks, but whether these reports are reliable is uncertain. The aim was to compare retrospective and prospective attack descriptions and describe the within- and between-patient variability of attacks.

METHOD

Fifty-seven CH patients underwent a semi-structured interview obtaining a retrospective account of usual CH attacks. Patients thereafter prospectively recorded the clinical characteristics of up to 10 attacks per patient in a headache diary. Four different attack characteristics were investigated: (i) severity, (ii) duration, (iii) number of autonomic symptoms and (iv) number of migrainous symptoms. Retrospective and prospective data were compared. Within- and between-patient variability of attacks was assessed.

RESULTS

Retrospective attack descriptions (n = 57) were significantly longer (P = 0.046) and more severe (P < 0.0001) for untreated attacks compared with prospective reports (n = 500). The number of autonomic symptoms was significantly higher in the retrospective reports compared to the prospective reports (P < 0.0001). Within-patient variability for attack duration, pain severity and number of autonomic and migrainous symptoms was low. Compared to men, more women reported longer (P = 0.026) and more severe (P = 0.028) attacks with more migrainous symptoms (P = 0.033).

CONCLUSIONS

Important differences were found between prospectively and retrospectively reported attacks with duration and severity of untreated attacks overestimated in retrospective attack descriptions. CH attacks display low within-patient variability, but the presentation of CH attacks varies between patients. The high prevalence of symptoms typically associated with migraine should raise more diagnostic awareness for CH, especially in women who are more often misdiagnosed as having migraine.

Therapeutic novelties in migraine: new drugs, new hope?

Background

In the past decade, migraine research has identified novel drug targets. In this review, we discuss recent data on emerging anti-migraine therapies.

Main body

The development of ditans, gepants and anti-calcitonin gene-related peptide monoclonal antibodies for the treatment of migraine is one of the greatest advances in the migraine field. Lasmiditan, rimegepant and ubrogepant will extend our therapeutic armamentarium for managing acute migraine attacks when triptans are not effective or contraindicated due to cardiovascular disorders. The monoclonal antibodies are migraine specific prophylactic drugs with high responder rates and favorable adverse event profiles. Furthermore, they offer convenient treatment regimens of 4- or 12-week intervals.

Conclusion

Collectively, novel migraine therapies represent a major progress in migraine treatment and will undoubtedly transform headache medicine.

Effect of hypoxia on BOLD fMRI response and total cerebral blood flow in migraine with aura patients

Experimentally induced hypoxia triggers migraine and aura attacks in patients suffering from migraine with aura (MA). We investigated the blood oxygenation level-dependent (BOLD) signal response to visual stimulation during hypoxia in MA patients and healthy volunteers. In a randomized double-blind crossover study design, 15 MA patients were allocated to 180 min of normobaric poikilocapnic hypoxia (capillary oxygen saturation 70-75%) or sham (normoxia) on two separate days and 14 healthy volunteers were exposed to hypoxia. The BOLD functional MRI (fMRI) signal response to visual stimulation was measured in the visual cortex ROIs V1-V5. Total cerebral blood flow (CBF) was calculated by measuring the blood velocity in the internal carotid arteries and the basilar artery using phase-contrast mapping (PCM) MRI. Hypoxia induced a greater decrease in BOLD response to visual stimulation in V1-V4 in MA patients compared to controls. There was no group difference in hypoxia-induced total CBF increase. In conclusion, the study demonstrated a greater hypoxia-induced decrease in BOLD response to visual stimulation in MA patients. We suggest this may represent a hypoxia-induced change in neuronal excitability or abnormal vascular response to visual stimulation, which may explain the increased sensibility to hypoxia in these patients leading to migraine attacks.

Dynamic sodium imaging at ultra-high field reveals progression in a preclinical migraine model

Under the hypothesis that increased extracellular sodium induces sustained neuronal excitability with the onset and progression of migraine, this study evaluates dynamic in vivo Na fluxes in the brain of a preclinical rodent analogue of migraine. Ultra-high field Na magnetic resonance imaging (MRI) at 21.1 T has demonstrated potential to quantify sodium concentrations with good spatial and temporal resolution after the onset of central sensitization. Sprague-Dawley male rats with implanted intraperitoneal lines were studied by MRI before and after an in situ injection of 10 mg/kg of nitroglycerin (NTG) vs vehicle and saline controls. Slice-selective Na images were acquired using a multislice free induction decay-based chemical shift imaging sequence with resolution of 1.1 × 1.1 × 3 mm for a 9-minute acquisition. A total of 27 repeated scans were acquired over 1 hour of baseline scanning and longitudinally up to 3 hours after injection. Increases of Na MRI signal in the brainstem, extracerebral cerebrospinal fluid, and cisterna magna were evident almost immediately after NTG injection, gaining significance from controls in 36 minutes. The cerebellum and third ventricle also showed sustained trends of increased Na, with the former gaining significance at over 2 hours after NTG injection. The data provide evidence of an early change in sodium concentration, markedly in posterior fossa cerebrospinal fluid and brainstem regions. Further study of fluctuations of sodium concentration and their modulation with treatments could help understand the dynamic features of migraine, locate a putative migraine generator, and guide development of therapeutic measures to correct the disturbance of sodium homeostasis.

Migraine and cluster headache - the common link

Although clinically distinguishable, migraine and cluster headache share prominent features such as unilateral pain, common pharmacological triggers such glyceryl trinitrate, histamine, calcitonin gene-related peptide (CGRP) and response to triptans and neuromodulation. Recent data also suggest efficacy of anti CGRP monoclonal antibodies in both migraine and cluster headache. While exact mechanisms behind both disorders remain to be fully understood, the trigeminovascular system represents one possible common pathophysiological pathway and network of both disorders. Here, we review past and current literature shedding light on similarities and differences in phenotype, heritability, pathophysiology, imaging findings and treatment options of migraine and cluster headache. A continued focus on their shared pathophysiological pathways may be important in paving future treatment avenues that could benefit both migraine and cluster headache patients.

Targeted Pituitary Adenylate Cyclase-Activating Peptide Therapies for Migraine

Here, we review the role of pituitary adenylate cyclase-activating peptide-38 (PACAP38) in migraine pathophysiology and data implicating PAC1 receptor as a future drug target in migraine. Much remains to be fully elucidated about migraine pathophysiology, but recent attention has focused on signaling molecule PACAP38, a vasodilator able to induce migraine attacks in patients who experience migraine without aura. PACAP38, with marked and sustained effect, dilates extracerebral arteries but not the middle cerebral artery. The selective affinity of PACAP38 to the PAC1 receptor makes this receptor a highly interesting and potential novel target for migraine treatment. Efficacy of antagonism of this receptor should be investigated in randomized clinical trials.

The Role of Endothelin in the Pathophysiology of Migraine-a Systematic Review

PURPOSE OF REVIEW

Vasoactive peptides play a key role in the attack-initiating cascade of migraine. Recent studies have highlighted a potentially important role for endothelin-1, a potent vasoconstrictor peptide, in migraine pathophysiology. Here, we review the current data on endothelin's involvement in migraine.

RECENT FINDINGS

We identified 23 articles. Nine studies reported on endothelin-1 plasma concentrations in patients with migraine, eight studies investigated relevant genetic associations, five studies investigated endothelin-1 and spreading depression in animals, and one randomized controlled clinical trial tested the efficacy of an endothelin antagonist in the acute treatment of migraine in patients both with and without aura. Elevated endothelin-1 plasma levels have been reported in the early phase of migraine attacks. Genetic abnormalities related to the endothelin type A receptor have been reported in migraineurs. Endothelin-1 potently induces spreading depression in animals, which may explain the connection between endothelial irritation and migraine aura. Endothelin-1 could be a primary factor in the attack-triggering cascade of migraine attacks with and without aura. Additional studies in humans and animal models are needed to further elucidate the role of endothelin-1 in migraine.

The KATP channel in migraine pathophysiology: a novel therapeutic target for migraine

BACKGROUND

To review the distribution and function of KATP channels, describe the use of KATP channels openers in clinical trials and make the case that these channels may play a role in headache and migraine.

DISCUSSION

KATP channels are widely present in the trigeminovascular system and play an important role in the regulation of tone in cerebral and meningeal arteries. Clinical trials using synthetic KATP channel openers report headache as a prevalent-side effect in non-migraine sufferers, indicating that KATP channel opening may cause headache, possibly due to vascular mechanisms. Whether KATP channel openers can provoke migraine in migraine sufferers is not known.

CONCLUSION

We suggest that KATP channels may play an important role in migraine pathogenesis and could be a potential novel therapeutic anti-migraine target.

Can migraine aura be provoked experimentally? A systematic review of potential methods for the provocation of migraine aura

Background

The nature of the migraine aura and its role in migraine pathophysiology is incompletely understood. In particular, the mechanisms underlying aura initiation and the causal relation between aura and headache are unknown. The scientific investigation of aura in patients is only possible if aura can be triggered. This paper reviews potential methods for the experimental provocation of migraine aura.

Methods

We systematically searched PubMed for studies of experimental migraine provocation, including case reports of patients with aura and reports of the occurrence of aura following exposure to any kind of suspected trigger.

Results

We identified 21 provocation studies, using 13 different prospective provocation methods, and 34 case reports. In the prospective studies, aura were reported following the administration of intravenous and sublingual glyceryl trinitrate, visual stimulation, physical activity, calcitonin gene-related peptide infusion, chocolate ingestion, and the intravenous injection of insulin. In addition, carotid artery puncture has consistently been reported as a trigger of aura.

Conclusions

No safe and efficient method for aura provocation exists at present, but several approaches could prove useful for this purpose.

Part I: Pituitary adenylate cyclase-activating polypeptide-38 induced migraine-like attacks in patients with and without familial aggregation of migraine

Background

Intravenous infusion of adenylate cyclase-activating polypeptide-38 (PACAP38) provokes migraine-like attacks in 65–70% of migraine sufferers. Whether aggregation of migraine in first-degree relatives contributes to this discrepancy in PACAP38-induced response is unknown. We hypothesized that genetic enrichment plays a role in triggering of migraine and that migraine without aura patients with a high family load ( ≥ 2 first-degree relatives with migraine) would report more migraine-like attacks after intravenous infusion of human PACAP38.

Methods

In this study, we allocated 32 previously genotyped migraine without aura patients to receive intravenous infusion of 10 pmol/kg/min PACAP38 and recorded migraine-like attacks including headache characteristics and associated symptoms. Information of familial aggregation was obtained by telephone interview of first-degree relatives using a validated semi-structured questionnaire.

Results

PACAP38 infusion induced a migraine-like attack in 75% (nine out of 12) of patients with high family load compared to 70% (14 out of 20) with low family load ( P = 0.761). In an explorative investigation, we found that the migraine response after PACAP38 was not associated with the risk allele of rs2274316 ( MEF2D), which confers increased risk of migraine without aura and may regulate PACAP38 expression.

Conclusion

Migraine response to PACAP38 infusion in migraine without aura patients is not associated with high family load or the risk allele of rs2274316 ( MEF2D).

Animal models of monogenic migraine

Migraine is a highly prevalent and disabling neurological disorder with a strong genetic component. Rare monogenic forms of migraine, or syndromes in which migraine frequently occurs, help scientists to unravel pathogenetic mechanisms of migraine and its comorbidities. Transgenic mouse models for rare monogenic mutations causing familial hemiplegic migraine (FHM), cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), and familial advanced sleep-phase syndrome (FASPS), have been created. Here, we review the current state of research using these mutant mice. We also discuss how currently available experimental approaches, including epigenetic studies, biomolecular analysis and optogenetic technologies, can be used for characterization of migraine genes to further unravel the functional and molecular pathways involved in migraine.

Hypoxic mechanisms in primary headaches

Background Hypoxia causes secondary headaches such as high-altitude headache (HAH) and headache due to acute mountain sickness. These secondary headaches mimic primary headaches such as migraine, which suggests a common link. We review and discuss the possible role of hypoxia in migraine and cluster headache. Methods This narrative review investigates the current level of knowledge on the relation of hypoxia in migraine and cluster headache based on epidemiological and experimental studies. Findings Epidemiological studies suggest that living in high-altitude areas increases the risk of migraine and especially migraine with aura. Human provocation models show that hypoxia provokes migraine with and without aura, whereas cluster headache has not been reliably induced by hypoxia. Possible pathophysiological mechanisms include hypoxia-induced release of nitric oxide and calcitonin gene-related peptide, cortical spreading depression and leakage of the blood-brain barrier. Conclusion There is a possible link between hypoxia and migraine and maybe cluster headache, but the exact mechanism is currently unknown. Provocation models of hypoxia have yielded interesting results suggesting a novel approach to study in depth the mechanism underlying hypoxia and primary headaches.

The stroke-migraine depolarization continuum

The term spreading depolarization (SD) refers to waves of abrupt, sustained mass depolarization in gray matter of the CNS. SD, which spreads from neuron to neuron in affected tissue, is characterized by a rapid near-breakdown of the neuronal transmembrane ion gradients. SD can be induced by hypoxic conditions--such as from ischemia--and facilitates neuronal death in energy-compromised tissue. SD has also been implicated in migraine aura, where SD is assumed to ascend in well-nourished tissue and is typically benign. In addition to these two ends of the "SD continuum," an SD wave can propagate from an energy-depleted tissue into surrounding, well-nourished tissue, as is often the case in stroke and brain trauma. This review presents the neurobiology of SD--its triggers and propagation mechanisms--as well as clinical manifestations of SD, including overlaps and differences between migraine aura and stroke, and recent developments in neuromonitoring aimed at better diagnosis and more targeted treatments.

CGRP as a neuropeptide in migraine: lessons from mice

Migraine is a neurological disorder that is far more than just a bad headache. A hallmark of migraine is altered sensory perception. A likely contributor to this altered perception is the neuropeptide calcitonin gene-related peptide (CGRP). Over the past decade, CGRP has become firmly established as a key player in migraine. Although the mechanisms and sites of action by which CGRP might trigger migraine remain speculative, recent advances with mouse models provide some hints. This brief review focuses on how CGRP might act as both a central and peripheral neuromodulator to contribute to the migraine-like symptom of light aversive behaviour in mice.

Calcitonin gene-related peptide (CGRP): a new target for migraine

Migraine is a neurological disorder that manifests as a debilitating headache associated with altered sensory perception. The neuropeptide calcitonin gene-related peptide (CGRP) is now firmly established as a key player in migraine. Clinical trials carried out during the past decade have proved that CGRP receptor antagonists are effective for treating migraine, and antibodies to the receptor and CGRP are currently under investigation. Despite this progress in the clinical arena, the mechanisms by which CGRP triggers migraine remain uncertain. This review discusses mechanisms whereby CGRP enhances sensitivity to sensory input at multiple levels in both the periphery and central nervous system. Future studies on epistatic and epigenetic regulators of CGRP actions are expected to shed further light on CGRP actions in migraine. In conclusion, targeting CGRP represents an approachable therapeutic strategy for migraine.

[A causative role of vasodilation in migraine? No]

INTRODUCTION

The hypothesis that migraine pain is caused by vasodilation has been challenged by clinical and experimental evidence.

STATE OF ART

The most convincing arguments against the vascular hypothesis come from neuroimaging data. Magnetic resonance imaging studies show that spontaneous migraine attacks are not accompanied by extracranial vasodilation, and by only slight dilation of the intracranial arteries. Pharmacologically-induced migraine attacks also provide further evidence against the role of vasodilation in migraine. Vasodilators such as sildenafil and nitroglycerine trigger attacks without dilation of the middle cerebral artery diameter, whereas VIP (vasoactive intestinal peptide) markedly dilates intra- and extracranial arteries but does not induce migraine attacks. Clinical studies also show a lack of correspondence between the subjective experience of throbbing headache and the arterial pulse. Moreover, many acute anti-migraine agents are not vasoconstrictors.

PERSPECTIVES

Further studies are necessary to clarify the mechanisms of migraine headache generation.

CONCLUSIONS

Contrary to a longstanding and widespread belief, vasodilatation is neither sufficient nor necessary to cause migraine headache and is probably an epiphenomenon.

Modelling headache and migraine and its pharmacological manipulation

Similarities between laboratory animals and humans in anatomy and physiology of the cephalic nociceptive pathways have allowed scientists to create successful models that have significantly contributed to our understanding of headache. They have also been instrumental in the development of novel anti-migraine drugs different from classical pain killers. Nevertheless, modelling the mechanisms underlying primary headache disorders like migraine has been challenging due to limitations in testing the postulated hypotheses in humans. Recent developments in imaging techniques have begun to fill this translational gap. The unambiguous demonstration of cortical spreading depolarization (CSD) during migraine aura in patients has reawakened interest in studying CSD in animals as a noxious brain event that can activate the trigeminovascular system. CSD-based models, including transgenics and optogenetics, may more realistically simulate pain generation in migraine, which is thought to originate within the brain. The realization that behavioural correlates of headache and migrainous symptoms like photophobia can be assessed quantitatively in laboratory animals, has created an opportunity to directly study the headache in intact animals without the confounding effects of anaesthetics. Headache and migraine-like episodes induced by administration of glyceryltrinitrate and CGRP to humans and parallel behavioural and biological changes observed in rodents create interesting possibilities for translational research. Not unexpectedly, species differences and model-specific observations have also led to controversies as well as disappointments in clinical trials, which, in return, has helped us improve the models and advance our understanding of headache. Here, we review commonly used headache and migraine models with an emphasis on recent developments.

Carbon monoxide may be an important molecule in migraine and other headaches

Introduction

Carbon monoxide was previously considered to just be a toxic gas. A wealth of recent information has, however, shown that it is also an important endogenously produced signalling molecule involved in multiple biological processes. Endogenously produced carbon monoxide may thus play an important role in nociceptive processing and in regulation of cerebral arterial tone.

Discussion

Carbon monoxide-induced headache shares many characteristics with migraine and other headaches. The mechanisms whereby carbon monoxide causes headache may include hypoxia, nitric oxide signalling and activation of cyclic guanosine monophosphate pathways. Here, we review the literature about carbon monoxide-induced headache and its possible mechanisms.

Conclusion

We suggest, for the first time, that carbon monoxide may play an important role in the mechanisms of migraine and other headaches.

Chemical mediators of migraine: preclinical and clinical observations

Migraine is a neurovascular disorder, and although the pathophysiology of migraine has not been fully delineated, much has been learned in the past 50 years. This knowledge has been accompanied by significant advancements in the way migraine is viewed as a disease process and in the development therapeutic options. In this review, we will focus on 4 mediators (nitric oxide, histamine, serotonin, and calcitonin gene-related peptide) which have significantly advanced our understanding of migraine as a disease entity. For each mediator we begin by reviewing the preclinical data linking it to migraine pathophysiology, first focusing on the vascular mechanisms, then the neuronal mechanisms. The preclinical data are then followed by a review of the clinical data which support each mediator's role in migraine and highlights the pharmacological agents which target these mediators for migraine therapy.

Experimental activation of the sphenopalatine ganglion provokes cluster-like attacks in humans

Background

High frequency (HF) stimulation of the sphenopalatine ganglion (SPG) is an emerging abortive treatment for cluster headache (CH) attacks. HF SPG stimulation is thought to exert its effect by physiologically blocking parasympathetic outflow. We hypothesized that low frequency (LF) SPG stimulation may activate the SPG, causing increased parasympathetic outflow and thereby provoking cluster attacks in CH patients.

Methods

In a double-blind randomized cross-over study, seven CH patients implanted with an SPG neurostimulator were randomly allocated to receive HF or LF stimulation for 3 min on 2 separate days. We recorded headache characteristics and autonomic symptoms during and after stimulation.

Results

Six patients completed the study. Three out of six patients (50%) reported ipsilateral cluster-like attacks during or within 30 min of LF SPG stimulation. These cluster-like attacks were all successfully treated with the therapeutic HF SPG stimulation. One out of six reported a cluster-like attack with 3 min HF SPG stimulation, which was also successfully treated with continued HF therapeutic SPG stimulation.

Discussion

LF SPG stimulation may induce cluster-like attacks with autonomic features, which can subsequently be treated by HF SPG stimulation. Efferent parasympathetic outflow from the SPG may initiate autonomic symptoms and activate trigeminovascular sensory afferents, which may initiate the onset of pain associated with CH.

Methods for studying naturally occurring human pain and their analogues

Methods for investigating human pain have been developed over the last 100years. Typically, researchers focus on people with clinical pain, or on healthy participants undergoing laboratory-controlled pain-induction techniques focussed mostly on exogenously generated skin nociception. Less commonly investigated are acute pain experiences that emerge naturally. Six common painful complaints were identified: headache, muscular pain, visceral pain, menstrual pain, dental pain, and pain associated with upper respiratory tract infection. Methods used to recruit participants with the natural occurrence of each pain complaint were identified, and features of their use reviewed. Also reviewed were experimental analogues designed to mimic these pains, with the exception of menstrual pain. Headache and menstrual pain appear to be most effectively researched in their naturally occurring form, whereas muscle and dental pain may be more easily induced. Upper respiratory tract infection and abdominal pain provide further challenges for researchers. Summary guidance is offered, and directions for methods development outlined.

The evolution of a migraine attack - a review of recent evidence

A migraine attack is an extraordinarily complex brain event that takes place over hours to days. This review focuses on recent human studies that shed light on the evolution of a migraine attack. It begins with a constellation of premonitory symptoms that are associated with activation of the hypothalamus and may involve the neurotransmitter dopamine. Even in the premonitory phase, patients experience sensitivity to sensory stimuli, indicating that central sensitization is a primary phenomenon. The migraine attack progresses to a phase that in some patients includes aura, which involves changes in cortical function, blood flow, and neurovascular coupling. The aura phase overlaps with the headache phase, which is associated with further changes in blood flow and function of the brainstem, thalamus, hypothalamus, and cortex. Serotonin receptors, nitric oxide, calcitonin gene-related peptide, pituitary adenylate cyclase-activating polypeptide, and prostanoids are demonstrated specific chemical mediators of migraine based on therapeutic and triggered migraine studies. A number of migraine symptoms persist beyond resolution of headache into a postdromal phase, accompanied by persistent blood flow changes in several brain regions. Although these phases of migraine have substantial temporal, neurochemical, and anatomical overlap, each represents an important window onto the pathophysiology of migraine as well as a target for therapeutic intervention. A comprehensive approach to migraine requires an understanding of the entire range of mechanisms and resultant symptoms that occur throughout the evolution of an attack.

Pathophysiology of migraine

Migraine is a collection of perplexing neurological conditions in which the brain and its associated tissues have been implicated as major players during an attack. Once considered exclusively a disorder of blood vessels, compelling evidence has led to the realization that migraine represents a highly choreographed interaction between major inputs from both the peripheral and central nervous systems, with the trigeminovascular system and the cerebral cortex among the main players. Advances in in vivo and in vitro technologies have informed us about the significance to migraine of events such as cortical spreading depression and activation of the trigeminovascular system and its constituent neuropeptides, as well as about the importance of neuronal and glial ion channels and transporters that contribute to the putative cortical excitatory/inhibitory imbalance that renders migraineurs susceptible to an attack. This review focuses on emerging concepts that drive the science of migraine in both a mechanistic direction and a therapeutic direction.

Migraine: a disorder of brain excitatory-inhibitory balance?

Migraine is a common disabling brain disorder whose key manifestations are recurrent attacks of unilateral headache and interictal hypersensitivity to sensory stimuli. Migraine arises from a primary brain dysfunction that leads to episodic activation and sensitization of the trigeminovascular pain pathway and as a consequence to headache. Major open issues concern the molecular and cellular mechanisms of the primary brain dysfunction(s) and of migraine pain. We review here our current understanding of these mechanisms, focusing on recent advances regarding migraine genetics, headache mechanisms, and the primary brain dysfunction(s) underlying migraine onset and susceptibility to cortical spreading depression, the neurophysiological correlate of migraine aura. We also discuss insights obtained from the functional analysis of familial hemiplegic migraine mouse models.

Emerging migraine treatments and drug targets

Migraine has a 1-year prevalence of 10% and high socioeconomic costs. Despite recent drug developments, there is a huge unmet need for better pharmacotherapy. In this review we discuss promising anti-migraine strategies such as calcitonin gene-related peptide (CGRP) receptor antagonists and 5-hydroxytrypamine (5-HT)(1F) receptor agonists, which are in late-stage development. Nitric oxide antagonists are also in development. New forms of administration of sumatriptan might improve efficacy and reduce side effects. Botulinum toxin A has recently been approved for the prophylaxis of chronic migraine. Tonabersat, a cortical spreading depression inhibitor, has shown efficacy in the prophylaxis of migraine with aura. Several new drug targets such as nitric oxide synthase, the 5-HT(1D) receptor, the prostanoid receptors EP(2) and EP(4), and the pituitary adenylate cyclase receptor PAC1 await development. The greatest need is for new prophylactic drugs, and it seems likely that such compounds will be developed in the coming decade.