New Insights on Metabolic and Genetic Basis of Migraine: Novel Impact on Management and Therapeutical Approach

Migraine is a hereditary disease, usually one-sided, sometimes bilateral. It is characterized by moderate to severe pain, which worsens with physical activity and may be associated with nausea and vomiting, may be accompanied by photophobia and phonophobia. The disorder can occur at any time of the day and can last from 4 to 72 h, with and without aura. The pathogenic mechanism is unclear, but extensive preclinical and clinical studies are ongoing. According to electrophysiology and imaging studies, many brain areas are involved, such as cerebral cortex, thalamus, hypothalamus, and brainstem. The activation of the trigeminovascular system has a key role in the headache phase. There also appears to be a genetic basis behind the development of migraine. Numerous alterations have been identified, and in addition to the genetic cause, there is also a close association with the surrounding environment, as if on the one hand, the genetic alterations may be responsible for the onset of migraine, on the other, the environmental factors seem to be more strongly associated with exacerbations. This review is an analysis of neurophysiological mechanisms, neuropeptide activity, and genetic alterations that play a fundamental role in choosing the best therapeutic strategy. To date, the goal is to create a therapy that is as personalized as possible, and for this reason, steps forward have been made in the pharmacological field in order to identify new therapeutic strategies for both acute treatment and prophylaxis.

Vestibular migraine of childhood

Background: Vestibular migraine and benign paroxysmal vertigo are the most common causes of vertigo in children and adolescents. This is a review of vestibular migraine of childhood dizziness.Current Concepts: In children and adolescents, the symptoms of dizziness or vertigo are not well defined. Thus, few studies have investigated the characteristics of dizziness or vertigo in children and adolescents. Vestibular migraine is categorized as episodic syndromes associated with migraine in the International Classification of Headache Disorders, 3rd edition. Despite vertigo’s various clinical features and duration, vestibular migraine can be diagnosed only when a migraine accompanies vertigo from 5 minutes to 72 hours. Benign paroxysmal vertigo is more common in children and adolescents than vestibular migraine. Benign paroxysmal vertigo is considered one of the precursor syndrome of migraine, and the duration of vertigo is short from seconds to minutes.Discussion and Conclusion: Vestibular migraine is common in older children and adults who need a differential diagnosis. This review might be helpful to diagnose, evaluate, and treat children with vestibular migraine and to reassure their parents.

Brain barriers and their potential role in migraine pathophysiology

Migraine is a ubiquitous neurologic disease that afflicts people of all ages. Its molecular pathogenesis involves peptides that promote intracranial vasodilation and modulate nociceptive transmission upon release from sensory afferents of cells in the trigeminal ganglion and parasympathetic efferents of cells in the sphenopalatine ganglion. Experimental data have confirmed that intravenous infusion of these vasoactive peptides induce migraine attacks in people with migraine, but it remains a point of scientific contention whether their site of action lies outside or within the central nervous system. In this context, it has been hypothesized that transient dysfunction of brain barriers before or during migraine attacks might facilitate the passage of migraine-inducing peptides into the central nervous system. Here, we review evidence suggestive of brain barrier dysfunction in migraine pathogenesis and conclude with lessons learned in order to provide directions for future research efforts.

Migraine

Migraine is a common, chronic, disorder that is typically characterized by recurrent disabling attacks of headache and accompanying symptoms, including aura. The aetiology is multifactorial with rare monogenic variants. Depression, epilepsy, stroke and myocardial infarction are comorbid diseases. Spreading depolarization probably causes aura and possibly also triggers trigeminal sensory activation, the underlying mechanism for the headache. Despite earlier beliefs, vasodilation is only a secondary phenomenon and vasoconstriction is not essential for antimigraine efficacy. Management includes analgesics or NSAIDs for mild attacks, and, for moderate or severe attacks, triptans or 5HT_1B/1D receptor agonists. Because of cardiovascular safety concerns, unreliable efficacy and tolerability issues, use of ergots to abort attacks has nearly vanished in most countries. CGRP receptor antagonists (gepants) and lasmiditan, a selective 5HT1_F receptor agonist, have emerged as effective acute treatments. Intramuscular onabotulinumtoxinA may be helpful in chronic migraine (migraine on ≥15 days per month) and monoclonal antibodies targeting CGRP or its receptor, as well as two gepants, have proven effective and well tolerated for the preventive treatment of migraine. Several neuromodulation modalities have been approved for acute and/or preventive migraine treatment. The emergence of new treatment targets and therapies illustrates the bright future for migraine management.

Neuropeptides and the Nodes of Ranvier in Cranial Headaches

The trigeminovascular system (TGV) comprise of the trigeminal ganglion with neurons and satellite glial cells, with sensory unmyelinated C-fibers and myelinated Aδ-fibers picking up information from different parts of the head and sending signals to the brainstem and the central nervous system. In this review we discuss aspects of signaling at the distal parts of the sensory fibers, the extrasynaptic signaling between C-fibers and Aδ-fibers, and the contact between the trigeminal fibers at the nerve root entry zone where they transit into the CNS. We also address the possible role of the neuropeptides calcitonin gene-related peptide (CGRP), the neurokinin family and pituitary adenylyl cyclase-activating polypeptide 38 (PACAP-38), all found in the TGV system together with their respective receptors. Elucidation of the expression and localization of neuropeptides and their receptors in the TGV system may provide novel ways to understand their roles in migraine pathophysiology and suggest novel ways for treatment of migraine patients.

Evaluation of Serum Levels of Transient Receptor Potential Cation Channel Subfamily V Member 1, Vasoactive Intestinal Polypeptide, and Pituitary Adenylate Cyclase-Activating Polypeptide in Chronic and Episodic Migraine: The Possible Role in Migraine Transformation

Objectives: This study aimed to investigate the role of serum levels of transient receptor potential cation channel subfamily V member 1 (TRPV1), vasoacive intestinal peptide (VIP), and pituitary adenylate cyclase-activating polypeptide (PACAP) in the development and also the transformation of migraine in patients suffering from migraine.

Methods: Eighty-nine participants with a mean age of 39 years were divided into 23 episodic migraine (EM), 36 chronic migraine (CM), and 30 healthy control groups. Demographic, anthropometric, and headache characteristic information, and also blood samples, was collected. Serum levels of TRPV1, VIP, and PACAP were measured using the enzyme-linked immunosorbent assay (ELISA) technique.

Results: Based on our findings, the serum level of TRPV1 was significantly higher in CM compared to the control group (p < 0.05), whereas serum levels of VIP (p < 0.01) and PACAP (p < 0.05) in the EM group were significantly more than the control group. There was no significant difference between EM and CM groups.

Conclusions: An elevation in the serum levels of TRVP1 among chronic migraineurs and increments in the levels of VIP and PACAP were observed among EM patients compared to healthy subjects. However, our data failed to demonstrate the probable role of these biomarkers in migraine progression, and more studies are needed to clarify the molecular mechanisms involved in migraine progression.

Migraine and light: A narrative review

OBJECTIVE

In this narrative review, we summarize clinical and experimental data on the effect of light in migraine and discuss future prospects.

BACKGROUND

Effective nonpharmacological treatment of hypersensitivity to light in migraine is an unmet clinical need. Current management strategies primarily consist of seeking a dark room and avoiding light exposure. Advances in the past 2 decades have improved our understanding of the underlying pathophysiology of how migraine is influenced by light. This may provide promising avenues for novel approaches in clinical management.

METHODS

We searched MEDLINE for articles published from database inception up to September 1, 2021. We used the search term "migraine" with the search terms "light," "photophobia," "treatment," "trigger," "circadian rhythm," "environment," and/or "pathophysiology."

RESULTS

Light is commonly reported as a trigger factor of migraine attacks, however, early manifestation of photophobia and false attribution is likely the actual cause based on data deriving from retrospective, prospective, and experimental studies. The most common photophobia symptoms in migraine are exacerbation of headache by light and abnormal sensitivity to light with the underlying neural pathways likely being dependent on ongoing activity in the trigeminovascular system. Clinical studies and experimental models have identified mediators of photophobia and uncovered narrow wavebands of the light spectrum that may reduce pain intensity during a migraine attack. Consequently, novel devices have undergone exploratory clinical trials with promising results.

CONCLUSION

False attribution is likely the reason why light is commonly reported as a trigger factor of migraine attacks, and a prospective confirmation is required to prevent unnecessary avoidance. The observation that individuals with migraine are not equally photophobic to all wavebands of the light spectrum opens the potential for innovative pain management strategies. In this context, using human-centric lighting (also called integrative lighting) to mimic the natural daylight cycle and avoid harmful wavebands through modern technology may prove beneficial. Future research should identify direct and indirect consequences of light and other environmental factors in migraine to fill out knowledge gaps and enable evidence-based care strategies within institutions, work environments, and other settings.

PACAP38- and VIP-induced cluster headache attacks are not associated with changes of plasma CGRP or markers of mast cell activation

BACKGROUND

Pituitary adenylate cyclase-activating polypeptide-38 (PACAP38) and vasoactive intestinal polypeptide can provoke cluster headache attacks in up to half of cluster headache patients in their active phase. At present, it is unknown whether provoked attacks are mediated via calcitonin gene-related peptide or mast cell activation.

METHODS

All enrolled patients with cluster headache were randomly allocated to receive a continuous infusion of either PACAP38 (10 pmol/kg/min) or vasoactive intestinal polypeptide (8 pmol/kg/min) over 20 min. We collected clinical data and measured plasma levels of calcitonin gene-related peptide and markers of mast cell activation (tryptase and histamine) at fixed time points: at baseline (T₀), at the end of the infusion (T₂₀), 10 min after the infusion (T₃₀), and 70 min after the infusion (T₉₀).

RESULTS

Blood was collected from episodic cluster headache patients in active phase (n = 14), episodic cluster headache patients in remission (n = 15), and chronic cluster headache patients (n = 15). At baseline, plasma levels of calcitonin gene-related peptide, tryptase, and histamine were not different among the three study groups. Plasma levels of calcitonin gene-related peptide (p = 0.7074), tryptase (p = 0.6673), or histamine (p = 0.4792) remained unchanged during provoked attacks compared to attack-free patients.

CONCLUSION

Cluster headache attacks provoked by either PACAP38 or vasoactive intestinal polypeptide were not accompanied by alterations of plasma calcitonin gene-related peptide, tryptase or histamine. The provoked attacks may not be mediated by calcitonin gene-related peptide or mast cell activation.Trial Registration: The study is registered at ClinicalTrials.gov (NCT03814226).

Characterisation of agonist signalling profiles and agonist-dependent antagonism at PACAP-responsive receptors: Implications for drug discovery

BACKGROUND AND PURPOSE

The pituitary adenylate cyclase-activating peptide (PACAP) family is of clinical interest for the treatment of migraine. These peptides activate three different PACAP-responsive class B G protein-coupled receptors: the PAC₁ , VPAC₁ and VPAC₂ receptors. The PAC₁ receptor may be alternatively spliced, generating variants that can differ in their pharmacological or signalling profiles. To inform drug discovery efforts targeting migraine, we need to better understand how the different PACAP-responsive receptors signal and how effectively these responses can be blocked by antagonists.

EXPERIMENTAL APPROACH

The signalling profiles of the human PAC_1n , PAC_1s , VPAC₁ and VPAC₂ receptors were examined in transfected Cos7 cells for cAMP, IP₁ , pAkt, pERK and pCREB. Biased signalling was then quantified. The ability of antagonists to block PACAP-38, PACAP-27 or VIP stimulated cAMP accumulation at PACAP-responsive receptors was also determined.

KEY RESULTS

PACAP-responsive receptors exhibited varied pharmacological profiles but activated signalling in a similar manner. The PAC_1n and PAC_1s receptors displayed distinct pharmacology. At the PAC_1s receptor, VIP and PHM were more potent than at the PAC_1n receptor. PACAP-responsive receptors displayed agonist-dependent antagonism where PACAP-38 was less effectively antagonised compared to PACAP-27 and VIP.

CONCLUSIONS AND IMPLICATIONS

The distinct pharmacological profile displayed by the PAC_1s receptor suggests that it can act as a dual receptor for VIP and PACAP. Furthermore, the effectiveness of blocking a signalling pathway can be influenced by which endogenous PACAP family agonist is present. These effects have potential implications for the development and effectiveness of drugs targeting the PACAP system.

The impact of CGRPergic monoclonal antibodies on prophylactic antimigraine therapy and potential adverse events

Migraine is a prevalent medical condition and the second most disabling neurological disorder. Regarding its pathophysiology, calcitonin gene-related peptide (CGRP) plays a key role, and, consequently, specific antimigraine pharmacotherapy has been designed to target this system. Hence, apart from the gepants, the recently developed monoclonal antibodies (mAbs) are a novel approach to treat this disorder. In this review we consider the current knowledge on the mechanisms of action, specificity, safety, and efficacy of the above mAbs as prophylactic antimigraine agents, and examine the possible adverse events that these agents may trigger. Antimigraine mAbs act as direct scavengers of CGRP (galcanezumab, fremanezumab, and eptinezumab) or against the CGRP receptor (erenumab). Due to their long half-lives, these molecules have revolutionized the prophylactic treatment of this neurovascular disorder. Moreover, because of their physicochemical properties, these agents are hepato-friendly and do not cross the blood-brain barrier (highlighting the relevance of peripheral mechanisms in migraine). Nevertheless, apart from potential cardiovascular side effects, the interaction with AMY₁ receptors and immunogenicity induced by autoantibodies against mAbs could be a concern for the safety of long-term treatment with these molecules.

Chronic Migraine Pathophysiology and Treatment: A Review of Current Perspectives

Chronic migraine is a disabling neurological disorder that imposes a considerable burden on individual and socioeconomic outcomes. Chronic migraine is defined as headaches occurring on at least 15 days per month with at least eight of these fulfilling the criteria for migraine. Chronic migraine typically evolves from episodic migraine as a result of increasing attack frequency and/or several other risk factors that have been implicated with migraine chronification. Despite this evolution, chronic migraine likely develops into its own distinct clinical entity, with unique features and pathophysiology separating it from episodic migraine. Furthermore, chronic migraine is characterized with higher disability and incidence of comorbidities in comparison to episodic migraine. While existing migraine studies primarily focus on episodic migraine, less is known about chronic migraine pathophysiology. Mounting evidence on aberrant alterations suggest that pronounced functional and structural brain changes, central sensitization and neuroinflammation may underlie chronic migraine mechanisms. Current treatment options for chronic migraine include risk factor modification, acute and prophylactic therapies, evidence-based treatments such as onabotulinumtoxinA, topiramate and newly approved calcitonin gene-related peptide or receptor targeted monoclonal antibodies. Unfortunately, treatments are still predominantly ineffective in aborting migraine attacks and decreasing intensity and frequency, and poor adherence and compliance with preventative medications remains a significant challenge. Novel emerging chronic migraine treatments such as neuromodulation offer promising therapeutic approaches that warrant further investigation. The aim of this narrative review is to provide an update of current knowledge and perspectives regarding chronic migraine background, pathophysiology, current and emerging treatment options with the intention of facilitating future research into this debilitating and largely indeterminant disorder.

Effect of Vasoactive Intestinal Polypeptide on Development of Migraine Headaches: A Randomized Clinical Trial

IMPORTANCE

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptides (PACAPs) are structurally and functionally related, yet different in their migraine-inducing properties. It remains unclear whether the lack of migraine induction can be attributed to the only transient vasodilatory response after a 20-minute infusion of VIP.

OBJECTIVE

To determine whether a 2-hour infusion of VIP would provoke migraine attacks.

DESIGN, SETTING, AND PARTICIPANTS

A randomized, double-blind, placebo-controlled, crossover study was conducted between May and September 2020 at the Danish Headache Center in Copenhagen, Denmark. Patients were eligible for inclusion if they were ages 18 to 40 years, weighed between 50 and 90 kg, had a diagnosis of migraine without aura as defined by the International Classification of Headache Disorders, and had a migraine frequency of 1 to 6 attacks per month.

INTERVENTIONS

Patients were randomly allocated to receive a 2-hour infusion of VIP or placebo on 2 different days.

MAIN OUTCOMES AND MEASURES

The primary end point was the difference in incidence of experimentally induced migraine attacks during the observational period (0-12 hours) between VIP and placebo.

RESULTS

Twenty-one patients (17 [81%] women and 4 [19%] men; mean [range] age, 25.9 [19-40] years) were recruited in the study. Fifteen patients (71%; 95% CI, 48%-89%) developed migraine attacks after VIP compared with 1 patient (5%; 95% CI, 0%-24%) who developed a migraine attack after placebo (P < .001). The VIP-induced migraine attacks mimicked patients' spontaneous attacks. The area under the curve (AUC) of headache intensity scores (0-12 hours), as well as the AUC of the superficial temporal artery diameter (0-180 minute) were significantly greater after VIP compared with placebo (AUC0-12h, P = .003; AUC0-180min, P < .001).

CONCLUSIONS AND RELEVANCE

A 2-hour infusion of VIP caused migraine attacks, suggesting an important role of VIP in migraine pathophysiology. VIP and its receptors could be potential targets for novel migraine drugs.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04260035.

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.

Future prophylactic treatments in migraine: Beyond anti-CGRP monoclonal antibodies and gepants

Migraine is ranked as a leading cause of years lived with disability among all neurological disorders. Therapies targeting the calcitonin gene-related peptide (CGRP) signaling pathway, including monoclonal antibodies against the receptor or ligand and small molecule CGRP receptor antagonists (gepants), are today approved for migraine prophylaxis with additional compounds expected to be introduced to the market soon. In this review, we consider other putative prophylactic migraine drugs in development, including compounds targeting G-protein coupled receptors, glutamate, ion channels, and neuromodulatory devices. Emergence of these new interventions could complement our current treatment armamentarium for migraine management.

Emerging Targets for Migraine Treatment

Background

While understanding the pathophysiology of migraine has led to CGRP-based treatments, other potential targets have also been implicated in migraine.

Objectives

To catalog new promising targets for the treatment of migraine.

Methods

We completed a literature review focusing on 5HT_1F, PACAP, melatonin, and orexins.

Results

The 5HT_1F receptor agonist lasmiditan, following two positive randomized placebo-controlled trials, was FDA-approved for the acute treatment of migraine. PACAP-38 has shown analogous evidence to what was obtained for CGRP with its localization in key structures, provocation tests, and positive studies when antagonizing its receptor in animal models, although a PAC-1 receptor monoclonal antibody study was negative. Melatonin has undergone several randomized controlled trials showing a positive trend. Filorexant is the only dual orexin receptor antagonist, which was tested in humans with negative results.

Conclusions

Further and ongoing studies will determine the utility of these new therapies with lasmiditan and melatonin having demonstrated efficacy for the treatment of migraine.

Cerebrovascular effects of glibenclamide investigated using high-resolution magnetic resonance imaging in healthy volunteers

Glibenclamide inhibits sulfonylurea receptor (SUR), which regulates several ion channels including SUR1-transient receptor potential melastatin 4 (SUR1-TRPM4) channel and ATP-sensitive potassium (K_ATP) channel. Stroke upregulates SURl-TRPM4 channel, which causes a rapid edema formation and brain swelling. Glibenclamide may antagonize the formation of cerebral edema during stroke. Preclinical studies showed that glibenclamide inhibits K_ATP channel-induced vasodilation without altering the basal vascular tone. The in vivo human cerebrovascular effects of glibenclamide have not previously been investigated.In a randomized, double-blind, placebo-controlled, three-way cross-over study, we used advanced 3 T MRI methods to investigate the effects of glibenclamide and K_ATP channel opener levcromakalim on mean global cerebral blood flow (CBF) and intra- and extracranial artery circumferences in 15 healthy volunteers. Glibenclamide administration did not alter the mean global CBF and the basal vascular tone. Following levcromakalim infusion, we observed a 14% increase of the mean global CBF and an 8% increase of middle cerebral artery (MCA) circumference, and glibenclamide did not attenuate levcromakalim-induced vascular changes. Collectively, the findings demonstrate the vital role of K_ATP channels in cerebrovascular hemodynamic and indicate that glibenclamide does not inhibit the protective effects of K_ATP channel activation during hypoxia and ischemia-induced brain injury.

Intradural artery dilation during experimentally induced migraine attacks

The middle meningeal artery is a proposed surrogate marker for activation of trigeminal nociceptors during migraine. Previous studies focused on the extracranial part of the artery; hence, vasoreactivity in the intradural arteries during migraine is unknown. Thirty-four patients with migraine without aura were given sildenafil on one day and calcitonin gene-related peptide on another in double-blind crossover fashion. Patients were scanned with 3.0 T MR angiography before drug administration and again 6 hours later during induced attacks of migraine. We measured circumference of the intradural segment of the middle meningeal artery before and during induced migraine attacks. The middle cerebral and superficial temporal arteries were also examined. Fourteen patients had attacks during the second scan after both study drugs and 11 had a migraine after either one or the other, resulting in a total of 39 attacks included in the final analysis. Mean circumference of the intradural middle meningeal artery at baseline was 3.18 mm with an increase of 0.11 mm during attacks (P = 0.005), corresponding to a relative dilation of 3.6% [95% CI: 1.4%-5.7%]. Middle cerebral artery dilated by 9.4% [95% CI: 7.1%-11.7%] and superficial temporal artery by 2.3% [95% CI: 0.2%-4.4%]. Our study shows that the intradural middle meningeal artery and the middle cerebral artery are dilated during migraine induced by calcitonin gene-related peptide as well as sildenafil. We propose that intradural vasculature is affected by migraine-driven activation of trigeminal afferents during migraine attacks.

Migraine: disease characterisation, biomarkers, and precision medicine

Migraine is a disabling neurological disorder, diagnosis of which is based on clinical criteria. A shortcoming of these criteria is that they do not fully capture the heterogeneity of migraine, including the underlying genetic and neurobiological factors. This complexity has generated momentum for biomarker research to improve disease characterisation and identify novel drug targets. In this Series paper, we present the progress that has been made in the search for biomarkers of migraine within genetics, provocation modelling, biochemistry, and neuroimaging research. Additionally, we outline challenges and future directions for each biomarker modality. We also discuss the advances made in combining and integrating data from multiple biomarker modalities. These efforts contribute to developing precision medicine that can be applied to future patients with migraine.

Pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal peptide (Part 2): biology and clinical importance in central nervous system and inflammatory disorders

PURPOSE OF REVIEW

To discuss recent advances of vasoactive intestinal peptide/pituitary adenylate cyclase-activating polypeptide (VIP/PACAP) receptors in the selected central nervous system (CNS) and inflammatory disorders.

RECENT FINDINGS

Recent studies provide evidence that PACAP plays an important role in a number of CNS disorders, particularly the pathogenesis of headaches (migraine, etc.) as well as posttraumatic stress disorder and drug/alcohol/smoking addiction. VIP has important therapeutic effects in a number of autoimmune/inflammatory disorder such as rheumatoid arthritis. In some cases, these insights have advanced to therapeutic trials.

SUMMARY

Recent insights from studies of VIP/PACAP and their receptors in both CNS disorders (migraine, posttraumatic stress disorder, addiction [drugs, alcohol, smoking]) and inflammatory disorders [such as rheumatoid arthritis] are suggesting new treatment approaches. The elucidation of the importance of VIP/PACAP system in these disorders combined recent development of specific drugs acting on this system (i.e., monoclonal VIP/PACAP antibodies) will likely lead to importance novel treatment approaches in these diseases.

Targets for migraine treatment: beyond calcitonin gene-related peptide

PURPOSE OF REVIEW

Despite the development of several medications for the acute and preventive treatment of migraine, there are still many patients in whom lack of efficacy, tolerability, interactions or contraindications make other options necessary. CGRP-based drugs have opened the door to a new era of migraine-targeted treatments. Beyond CGRP, there are other promising targets covered here.

RECENT FINDINGS

For the acute treatment of migraine, 5-HT1F receptor agonists, ditans, are now available. Unlike triptans, 5-HT1B/1D receptor agonists, cardiovascular disease is not a contraindication for the use of ditans. The first study on a monoclonal antibody targeting PAC1 receptor was negative, although this may not be the end for the pituitary adenylate cyclase-activating polypeptide (PACAP) pathway as a target.

SUMMARY

Following positive phase-III clinical trials, lasmiditan is the first ditan to be FDA-approved. PACAP has experimental evidence suggesting a role in migraine pathophysiology. As for CGRP, the presence of PACAP in key migraine structures along with positive provocative tests for both PACAP-38 and PACAP-27 indicate this pathway may still be a pharmacological target. Glutamate-based targets have long been considered in migraine. Two clinical trials with memantine, an NMDA-R antagonist, for the preventive treatment of migraine have now been published. The hypothalamus has also been implicated in migraine pathophysiology: the potential role of orexins in migraine is discussed. Acid-sensing ion channels, as well as amylin-blocking drugs, may also become migraine treatments in the future: more research is warranted.

Infusion of Pituitary Adenylate Cyclase-Activating Polypeptide-38 in Patients with Rosacea Induces Flushing and Facial Edema that Can Be Attenuated by Sumatriptan

BACKGROUND

The pathogenesis of rosacea is incompletely understood. Signaling neuropeptides, including PACAP, a regulator of vasodilation and edema, are upregulated in rosacea skin. Here, we evaluated PACAP38-induced rosacea features and examined whether a 5-HT_1B/1D receptor agonist could reduce these features.

METHODS

A total of 35 patients with erythematotelangiectatic rosacea received an intravenous infusion of 10 pmol/kg/minute of PACAP38 followed by an intravenous infusion of 4 mg sumatriptan or placebo (saline) on two study days in a double-blind, randomized, placebo-controlled, and cross-over trial.

RESULTS

PACAP38 increased facial skin blood flow by 90%, dilated the superficial temporal artery by 56%, and induced prolonged flushing and facial edema. Compared with placebo, sumatriptan reduced PACAP38-induced facial skin blood flow for 50 minutes (P = 0.023), constricted the superficial temporal artery for 80 minutes (P = 0.010), and reduced duration of flushing (P = 0.001) and facial edema (P < 0.001).

CONCLUSIONS

We established a clinical experimental model of rosacea features and showed that sumatriptan was able to attenuate PACAP38-induced rosacea flushing and edema. Findings support a key role of PACAP38 in rosacea flushing pathogenesis. It remains unknown whether PACAP38 inhibition can improve rosacea.

TRIAL REGISTER

The trial was registered at ClinicalTrials.govNCT03878784 in March 2019.

Early treatment with sumatriptan prevents PACAP38-induced migraine: A randomised clinical trial

OBJECTIVE

To determine whether early treatment with sumatriptan can prevent PACAP38-induced migraine attacks.

METHODS

A total of 37 patients with migraine without aura were enrolled between July 2018 to December 2019. All patients received an intravenous infusion of 10 picomole/kg/min of PACAP38 over 20 min followed by an intravenous infusion of 4 mg sumatriptan or placebo over 10 min on two study days in a randomised, double-blind, placebo-controlled, crossover study.

RESULTS

Of 37 patients enrolled, 26 (70.3%) completed the study and were included in analyses. Of the 26 patients, four (15%) developed a PACAP38-induced migraine attack on sumatriptan and 11 patients (42%) on placebo (p = 0.016). There were no differences in area under the curve for headache intensity between sumatriptan (mean AUC 532) and placebo (mean AUC 779) (p = 0.35). Sumatriptan significantly constricted the PACAP38-dilated superficial temporal artery immediately after infusion (T30) compared with infusion of placebo (p < 0.001).Conclusions and relevance: Early treatment with intravenously administered sumatriptan prevented PACAP38-induced migraine. Prevention of migraine attacks was associated with vasoconstriction by sumatriptan in the earliest phases of PACAP provocation. These results suggest that sumatriptan prevents PACAP38-induced migraine by modulation of nociceptive transmission within the trigeminovascular system.Trial Registration: ClinicalTrials.gov (NCT03881644).

Identifying New Antimigraine Targets: Lessons from Molecular Biology

Primary headaches are one of the most common conditions; migraine being most prevalent. Recent work on the pathophysiology of migraine suggests a mismatch in the communication or tuning of the trigeminovascular system, leading to sensitization and the release of calcitonin gene-related peptide (CGRP). In the current Opinion, we use the up-to-date molecular understanding of mechanisms behind migraine pain, to provide novel aspects on how to modify the system and for the development of future treatments; acute as well as prophylactic. We explore the distribution and the expression of neuropeptides themselves, as well as certain ion channels, and most importantly how they may act in concert as modulators of excitability of both the trigeminal C neurons and the Aδ neurons.

Neuropeptide changes in an improved migraine model with repeat stimulations

Migraine is a medical condition with a severe recursive headache. The activation of the trigeminovascular system is an important mechanism. The neuropeptide calcitonin gene-related peptide (CGRP) plays a crucial role in the pathogenesis of migraine. Several other neuropeptides are also involved; however, their roles in migraine remain unclear. In this study, using a rat model of migraine induced by electrical stimulation of the trigeminal ganglia (TG) and an improved version induced with repeated stimulation, we observed the dynamic changes of these peptides in TG and blood. We demonstrated that the expression of CGRP, pituitary adenylate cyclase activating polypeptide (PACAP), neuropeptide Y (NPY), vasoactive intestinal peptide, and nociceptin in TG was significantly elevated and peaked at different time points after a single stimulation. Their levels in the blood plasma were significantly increased at 12 h after stimulation. The peptides were further elevated with repeated stimulation. The improved rat model of migraine with repeated stimulation of TG resulted in a more pronounced elevation of CGRP, PACAP, and NPY. Thus, the dynamic changes in neuropeptides after stimulation suggest that these neuropeptides may play an important role in the pathogenesis of migraine. Additionally, the migraine model with repetitive stimulation would be a novel model for future research.

A phase 2, randomized, double-blind, placebo-controlled trial of AMG 301, a pituitary adenylate cyclase-activating polypeptide PAC1 receptor monoclonal antibody for migraine prevention

Objective

To assess the safety and efficacy of AMG 301, an inhibitor of the pituitary adenylate cyclase-activating polypeptide (PACAP)-1 (PAC1) receptor, for prevention of migraine.

Methods

In a double-blind trial, patients were randomized 4:3:3 to placebo, AMG 301 210 mg every 4 weeks, or AMG 301 420 mg every 2 weeks for 12 weeks. Effect on monthly migraine days and other secondary measures were assessed over weeks 9–12. Safety and tolerability were assessed.

Results

Of 343 randomized patients (mean age, 41.8–42.5 years), the majority were women (85.4–90.4%), white (94.1–96.2%), and had episodic migraine (62.5–67.9%). A total of 305 patients completed treatment (placebo, n = 124; AMG 301 210 mg, n = 94; AMG 301 420 mg, n = 87). Least squares mean reduction at week 12 in monthly migraine days from baseline was −2.5 (0.4) days for placebo and −2.2 (0.5) days for both AMG 301 treatment groups. No difference between AMG 301 and placebo on any measure of efficacy was observed; mean (95% confidence interval) treatment difference versus placebo for monthly migraine days for AMG 301 210 mg, 0.3 (−0.9 to 1.4); AMG 301 420 mg, 0.3 (−0.9 to 1.4). The incidence of adverse events was similar across groups.

Conclusion

AMG 301 offered no benefit over placebo for migraine prevention; further studies may be necessary to fully understand the role of PACAP isoforms and its receptors in migraine pathophysiology.

Study Registration

ClinicalTrials.gov: NCT03238781

Muscle endurance training of the neck triggers migraine attacks

BACKGROUND

Most migraine patients report neck pain as part of their migraine symptomatology, but it is unknown whether triggering neck pain would induce migraine attacks. Our aim was to assess the occurrence of headache and/or neck pain after an endurance test of the neck muscles among migraineurs and controls.

METHODS

Sixty-five patients with migraine and 32 headache-free participants underwent a manual examination of the cervical spine by an assessor blinded towards the diagnosis and were sub-classified according to the appearance or absence of neck pain. Subsequently, the endurance of the neck flexors and extensors was tested three times, in a random order. The maximum sustained duration was recorded and the test was terminated when the subject was unable to maintain the position or reported pain. On the day after the assessment, participants were asked to report the potential occurrence of headache or neck symptoms.

RESULTS

None of the controls reported headache after assessment, while migraine-like headache was reported by 42% of the patients with migraine (p < 0.001) after 15.8 h (SD: 10.0). Neck pain was more prevalent in migraineurs compared to controls (45% vs. 16%, p = 0.006). When considering the neck pain subtype, there were no differences among the three profiles regarding neck pain but participants with referred pain to the head reported a migraine attack more often (45%, p = 0.03).

CONCLUSION

Patients with migraine are more likely to report neck pain and migraine attacks following a neck muscle endurance test. Participants with neck pain referred to the head during manual examination had a greater prevalence of migraine attacks than those without or with only local pain.

The effect of pituitary adenylate cyclase-activating peptide-38 and vasoactive intestinal peptide in cluster headache

BACKGROUND

Previously reported increases in serum levels of vasodilating neuropeptides pituitary adenylate cyclase-activating peptide-38 (PACAP38) and vasoactive intestinal peptide (VIP) during attacks of cluster headache could indicate their involvement in cluster headache attack initiation. We investigated the attack-inducing effects of PACAP38 and vasoactive intestinal peptide in cluster headache, hypothesising that PACAP38, but not vasoactive intestinal peptide, would induce cluster-like attacks in episodic active phase and chronic cluster headache patients.

METHODS

In a double-blind crossover study, 14 episodic cluster headache patients in active phase, 15 episodic cluster headache patients in remission phase and 15 chronic cluster headache patients were randomly allocated to receive intravenous infusion of PACAP38 (10 pmol/kg/min) or vasoactive intestinal peptide (8 pmol/kg/min) over 20 min on two study days separated by at least 7 days. We recorded headache intensity, incidence of cluster-like attacks, cranial autonomic symptoms and vital signs using a questionnaire (0-90 min).

RESULTS

In episodic cluster headache active phase, PACAP38 induced cluster-like attacks in 6/14 patients and vasoactive intestinal peptide induced cluster-like attacks in 5/14 patients (p = 1.000). In chronic cluster headache, PACAP38 and vasoactive intestinal peptide both induced cluster-like attacks in 7/15 patients (p = 0.765). In episodic cluster headache remission phase, neither PACAP38 nor vasoactive intestinal peptide induced cluster-like attacks.

CONCLUSIONS

Contrary to our hypothesis, attack induction was lower than expected and roughly equal by PACAP38 and vasoactive intestinal peptide in episodic active phase and chronic cluster headache patients, which contradicts the PAC₁-receptor as being solely responsible for attack induction.Trial registration: clinicaltrials.gov (identifier NCT03814226).

Plasma levels of vasoactive neuropeptides in pediatric patients with migraine during attack and attack-free periods

BACKGROUND

Increasing evidence suggests that vasoactive neuropeptides such as pituitary adenylate cyclase-activating polypeptide-38 (PACAP-38), substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide are involved in the pathophysiology of migraine in adults, but their role in pediatric migraineurs remains unclear. We prospectively investigated plasma levels of these vasoactive neuropeptides in pediatric migraine patients without aura and compared the results with those of age-matched healthy controls.

METHODS

Thirty-eight children aged 6-18 years with migraine without aura and 20 age-matched control subjects were included in the study. Neuropeptides in plasma samples from the controls, and in either the ictal or interictal periods in pediatric migraine without aura, were measured using ELISA.

RESULTS

PACAP-38 and vasoactive intestinal peptide levels in both ictal and interictal plasma were higher in the patients with pediatric migraine without aura than in the controls (p < 0.001), although calcitonin gene-related peptide and substance P levels remained unchanged. Otherwise, no significant difference was determined between ictal and interictal periods in terms of all neuropeptide levels.

CONCLUSIONS

This study demonstrates increased plasma PACAP-38 and vasoactive intestinal peptide levels, but not calcitonin gene-related peptide and substance P levels, in pediatric patients with migraine during both attack and attack-free periods. The study findings suggest that PACAP-38 and vasoactive intestinal peptide may be implicated in the pathophysiology of migraine, particularly in pediatric migraineurs.

Investigation of pituitary adenylate cyclase activating polypeptide (PACAP) in human amniotic fluid samples

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide acting as a hormone, a neuromodulator, a neurotransmitter, a trophic factor and is involved in a variety of developmental and regenerative processes. PACAP is present in several human tissues and biological fluids. In many pathological conditions, changes in PACAP levels have been described to reflect disease progression, therefore PACAP has diagnostic value as a potential biomarker. Since PACAP has been shown to play an important role in reproductive physiology and development, it was of interest to examine whether this neuropeptide occurs in the human amniotic fluid. Amniotic fluid samples were collected between the 15-19^th weeks of gestation from volunteering pregnant women undergoing amniocentesis as a prenatal diagnostic tool due to maternal age. Pathological cases were excluded after prenatal karyotype analysis. PACAP-like immunoreactivity was measured by radioimmunoassay and could be detected in all samples. The present study provides evidence for the presence of PACAP in human amniotic fluid, but determination of the exact physiological or pathological significance awaits further investigation.

A new approach for examining the neurovascular structure with phalloidin and calcitonin gene-related peptide in the rat cranial dura mater

The neurovascular structures in the cranial dura mater have been studied with various histological techniques in the past years. In order to obtain a proper approach to reveal the detailed structures, different labeling methods for the cranial vessels and nerve fibers were tested in this study. Firstly, the labeling characteristics of phalloidin, alpha smooth muscle actin (α-SMA), and CD31 were compared in rat whole-mount cranial dura mater by using fluorescent immunohistochemistry or histochemistry. Secondly, according to their properties, phalloidin and α-SMA were selected to combine with calcitonin gene-related peptide (CGRP) to further demonstrate the cranial neurovascular structure. By these approaches, a three-dimensional map of blood vessels and nerve fibers within the whole-mount rat cranial dura mater was obtained. The results showed that phalloidin, α-SMA, and CD31 were preferably expressed in the wall of cranial vessels, corresponding to the arteriors, venules, and capillaries, respectively. Additionally, CGRP + nerve fibers were clearly demonstrated together with phalloidin + or α-SMA + vessels, forming a delicate neurovascular network in the cranial dura mater. The thick nerve bundles ran closely to the phalloidin + or α-SMA + vessels in parallel pattern, while the thin nerve fibers branched off from the bundles tending to surround the phalloidin + arterioles rather than α-SMA + venules. These findings suggest that phalloidin could be an appropriate biochemical maker to be effectively used together with CGRP for experiments examining the detailed spatial correlation of cranial blood vessels and nerve fibers in a three-dimensional view, which may provide clues for understanding the underlying mechanisms of cranial neurovascular disorders.

Low frequency activation of the sphenopalatine ganglion does not induce migraine-like attacks in migraine patients

Introduction

Cephalic autonomic symptoms occur in 27‒73% of migraine patients during attacks. The role of parasympathetic activation in migraine attack initiation remains elusive. Low frequency stimulation of the sphenopalatine ganglion increases parasympathetic outflow. In this study, we hypothesized that low frequency stimulation of the sphenopalatine ganglion would provoke migraine-like attacks in migraine patients.

Methods

In a double-blind randomized sham-controlled crossover study, 12 migraine patients with a sphenopalatine ganglion neurostimulator received low frequency or sham stimulation for 30 min on two separate days. We recorded headache characteristics, cephalic autonomic symptoms, ipsilateral mechanical perception and pain thresholds, mean blood flow velocity in the middle cerebral artery (VMCA) and diameter of the superficial temporal artery during and after stimulation.

Results

Five patients (42%) reported a migraine-like attack after low frequency stimulation compared to six patients (50%) after sham ( p = 1.000). We found a significant increase in mechanical detection thresholds during low frequency stimulation compared to baseline ( p = 0.007). Occurrence of cephalic autonomic symptoms and changes in mechanical perception thresholds, VMCA and diameter of the superficial temporal artery showed no difference between low frequency stimulation compared to sham ( p = 0.533).

Conclusion

Low frequency stimulation of the sphenopalatine ganglion did not induce migraine-like attacks or autonomic symptoms in migraine patients. These data suggest that increased parasympathetic outflow by the sphenopalatine ganglion neurostimulator does not initiate migraine-like attacks. Study protocol: ClinicalTrials.gov registration number NCT02510742

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.

PAC1 receptor blockade reduces central nociceptive activity: new approach for primary headache?

Pituitary adenylate cyclase activating polypeptide-38 (PACAP38) may play an important role in primary headaches. Preclinical evidence suggests that PACAP38 modulates trigeminal nociceptive activity mainly through PAC1 receptors while clinical studies report that plasma concentrations of PACAP38 are elevated in spontaneous attacks of cluster headache and migraine and normalize after treatment with sumatriptan. Intravenous infusion of PACAP38 induces migraine-like attacks in migraineurs and cluster-like attacks in cluster headache patients. A rodent-specific PAC1 receptor antibody Ab181 was developed, and its effect on nociceptive neuronal activity in the trigeminocervical complex was investigated in vivo in an electrophysiological model relevant to primary headaches. Ab181 is potent and selective at the rat PAC1 receptor and provides near-maximum target coverage at 10 mg/kg for more than 48 hours. Without affecting spontaneous neuronal activity, Ab181 effectively inhibits stimulus-evoked activity in the trigeminocervical complex. Immunohistochemical analysis revealed its binding in the trigeminal ganglion and sphenopalatine ganglion but not within the central nervous system suggesting a peripheral site of action. The pharmacological approach using a specific PAC1 receptor antibody could provide a novel mechanism with a potential clinical efficacy in the treatment of primary headaches.

Targeting migraine treatment with neuroimaging-Pharmacological neuroimaging in headaches

PURPOSE

The current review provides a recapitulation of recent advances in pharmacological neuroimaging in headache, a promising tool to understanding of how a drug works in the brain and how it may lead to new insights of disease mechanisms of headache.

RESULTS

Pharmacological positron emission tomography with radioligand-labeled medication may provide evidence whether and where a medication binds in the brain but is still mostly restricted to animal work. Pharmacological functional MRI using task-specific approaches identified central modulation patterns as a consequence of attack and preventative headache medication, which may be distinct to a specific drug mechanism. Pharmacological neuroimaging and specifically in combination with functional imaging is a promising tool to better understand not only certain medications but also certain disease mechanisms.

SUMMARY

Pharmacological imaging techniques have advanced over the last few years and showed great potential of providing new insights into drug pharmacodynamics and disease mechanism. There are still limitations and challenges to be overcome.

Two-hour infusion of vasoactive intestinal polypeptide induces delayed headache and extracranial vasodilation in healthy volunteers

BACKGROUND

In recent years, vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptides (PACAPs) have gained special interest in headache science. VIP and PACAPs (two isoforms, PACAP27 and PACAP38) are related in structure and function, as are their receptors, but they show differences in vasodilating- and headache-inducing properties. Intravenous infusion of PACAP27 or PACAP38, but not VIP, induces a long-lasting dilation of cranial arteries and delayed headache. The relationship between the long-lasting cranial vasodilation and headache development is not fully clarified.

METHODS

In a double-blinded, placebo-controlled, crossover study in 12 healthy volunteers, diameter changes of cranial arteries, occurrence of headache and the parasympathetic system were examined before, during and after a 2-hour continuous intravenous infusion of VIP and placebo. Primary endpoints were the differences in area under the curve for the superficial temporal artery diameter and headache intensity scores, as well as in headache incidence, between VIP and placebo.

RESULTS

The superficial temporal artery diameter was significantly larger on the VIP day compared to placebo (p < 0.001) and the dilation lasted for more than 2 h. The incidence of headache was higher (p = 0.003) on the VIP day compared to the placebo day. The difference in headache intensity scores was more evident in the post-infusion period (120-200 min, p = 0.034) and in the post-hospital phase (4-12 h, p = 0.025). Cranial parasympathetic activity, measured through the production of tears, was higher during VIP compared to placebo (p = 0.033).

CONCLUSION

Continuous intravenous infusion of VIP over 2 h induced a long-lasting cranial vasodilation, activation of the cranial parasympathetic system, and delayed mild headaches in healthy volunteers.Trial Registration: The study is registered at ClinicalTrials.gov (NCT03989817).

Differences in pituitary adenylate cyclase-activating peptide and calcitonin gene-related peptide release in the trigeminovascular system

Background

Several neurotransmitters are expressed in the neurons of the trigeminal ganglion. One such signalling molecule is the pituitary adenylate cyclase-activating peptide (PACAP). PACAP signalling has been suggested to have a possible role in the pathophysiology of primary headaches.

Objective

The present study was designed to investigate the relationship between PACAP and calcitonin gene-related peptide, currently the two most relevant migraine peptides.

Methods

In the current study, we used ELISA to investigate PACAP and calcitonin gene-related peptide release in response to 60 mM K+ or capsaicin using a rat hemi-skull model. We combined this analysis with qPCR and immunohistochemistry to study the expression of PACAP and calcitonin gene-related peptide receptors and ligands.

Results

Calcitonin gene-related peptide (CGRP) is released from the trigeminal ganglion and dura mater. In contrast, PACAP is only released from the trigeminal ganglion. We observed a weak correlation between the stimulated release of the two neuropeptides. PACAP-38 immunoreactivity was expressed alone and in a subpopulation of neurons in the trigeminal ganglion that also store calcitonin gene-related peptide. The receptor subtype PAC1 was mainly expressed in the satellite glial cells (SGCs), which envelop the neurons in the trigeminal ganglion, in some neuronal processes, inside the Aδ-fibres and in the outermost layer of the myelin sheath that envelopes the Aδ-fibres.

Conclusion

Unlike CGRP, PACAP is only released within the trigeminal ganglion. This raises the question of whether a migraine therapy aimed at preventing peripheral PACAP signalling would be as successful as the CGRP signalling targeted treatments.

Migraine Pathophysiology

Migraine is the leading cause of years lost due to disability in individuals aged 15 to 49 years. Much has changed over the last three decades about our understanding of this complex neurological disorder. Various phases of migraine have been characterized and are the focus of this review. The premonitory phase involves bothersome symptoms experienced hours to days before migraine pain. Behavioral changes and functional neuroimaging studies point toward hypothalamic involvement during the premonitory and other migraine phases. Migraine aura is a disruptive, reversible neurological phenomenon that affects up to one-third of all migraineurs, and can overlap with the headache phase. The mechanism responsible for this phase is thought to be cortical spreading depolarization through the cortex. This process leads to temporary disruptions in ion homeostasis and the ensuing neuronal dysfunction. The headache phase involves activation of the trigeminocervical complex. Neuropeptides are implicated in trigeminal activation, and calcitonin gene-related peptide in particular has become a promising target of therapeutic intervention for migraine. The final phase of migraine is the postdrome, the period of time from the resolution of headache symptoms until return to baseline following a migraine. People often report neuropsychiatric, sensory, gastrointestinal, and general symptoms during this time, which can limit activity. Elucidating the neuroanatomical, chemical, and neuroimaging correlates of these migraine phases allows for an improved comprehension of the underlying changes associated with migraine symptomatology and can assist with evaluation of arising therapeutics for migraine management.

Celecoxib reduces cortical spreading depression-induced macrophage activation and dilatation of dural but not pial arteries in rodents: implications for mechanism of action in terminating migraine attacks

Nonsteroidal anti-inflammatory drugs, commonly known as COX-1/COX-2 inhibitors, can be effective in treating mild to moderate migraine headache. However, neither the mechanism by which these drugs act in migraine is known, nor is the specific contribution of COX-1 vs COX-2. We sought to investigate these unknowns using celecoxib, which selectively inhibits the enzymatic activity of COX-2, by determining its effects on several migraine-associated vascular and inflammatory events. Using in vivo 2-photon microscopy, we determined intraperitoneal celecoxib effects on cortical spreading depression (CSD)-induced blood vessel responses, plasma protein extravasation, and immune cell activation in the dura and pia of mice and rats. Compared to vehicle (control group), celecoxib reduced CSD-induced dilatation of dural arteries and activation of dural and pial macrophages significantly, but not dilatation or constriction of pial arteries and veins, or the occurrence of plasma protein extravasation. Collectively, these findings suggest that a mechanism by which celecoxib-mediated COX-2 inhibition might ease the intensity of migraine headache and potentially terminate an attack is by attenuating dural macrophages' activation and arterial dilatation outside the blood-brain barrier, and pial macrophages' activation inside the blood-brain barrier.

Novelty in Inflammation and Immunomodulation in Migraine

BACKGROUND

Migraine is a diffuse and disabling disease. Its pathophysiology is complex and involves both central and peripheral dysfunctions.

OBJECTIVE

This review will discuss the pathogenesis of migraine from the origin of the neuro-inflammatory theory, to the modern pathophysiological model and the latest therapies.

METHODS

PUBMED and EMBASE (up to May 2019) were searched for: migraine, inflammation, immunomodulation. An additional search was carried out from the bibliography of previous review articles.

RESULTS

Migraine was thought to be mainly a vascular disorder, according to the so-called "vascular theory". Based on animal models, a new hypothesis called "the neuro-inflammatory" was conceived at the end of the 20th century. The growing knowledge about the trigeminovascular system and its role in the inflammatory-pain pathway, allowed to identify other specific neurotransmitters, such as the Calcitonin Gene-Related Peptide and Pituitary Adenylate Cyclase-Activating Peptide. Evidence was provided that the inflammatory-pain system could become sensitised and, due to this sensitisation, the pain could also perpetuate, even in the absence of any triggers of the migraine attack. At last, brain immune cells modification during cortical spreading depression in migraine was demonstrated, along with the existence and function of the glymphatic system. The better comprehension of the immune system abnormalities allowed the development of new immunomodulating drugs: the monoclonal antibodies against the CGRP or the CGRP receptor. Moreover, new insights into the molecular mechanism of CGRP, and the function of C-fibres and Aδ-fibres, highlighted the mechanism of action of Botulinum Toxin type A in the treatment of chronic migraine.

Investigation of sumatriptan and ketorolac trometamol in the human experimental model of headache

BACKGROUND

Pituitary adenylate cyclase-activating polypeptide-38 (PACAP38) induces headache in healthy volunteers but the precise mechanisms by which PACAP38 leads to headache are unclear. We investigated the headache preventive effect of sumatriptan and ketorolac on PACAP38-induced headache in healthy volunteers. In addition, we explored contribution of vascular mechanisms to PACAP38-induced headache using high resolution magnetic resonance angiography.

METHODS

Thirty-four healthy volunteers were divided in two groups (A and B) and received infusion of PACAP38 (10 picomol/kg/min) over 20 min. Group A was pretreated with intravenous sumatriptan (4 mg) or ketorolac (30 mg) 20 min before infusion of PACAP38. Group B received infusion of sumatriptan or ketorolac as post-treatment 90 min after infusion of PACAP38. In both experiments, we used a randomized, double-blind, cross-over design. We recorded headache characteristics and circumference of extra-intracerebral arteries.

RESULTS

We found no difference in AUC _{(0-6 h)} of PACAP38-induced headache in group A, pretreated with sumatriptan or ketorolac (p = 0.297). There was no difference between sumatriptan and ketorolac in PACAP38-induced circumference change (AUC_{Baseline-110 min}) of MMA (p = 0.227), STA (p = 0.795) and MCA (p = 0.356). In group B, post-treatment with ketorolac reduced PACAP38-headache compared to sumatriptan (p < 0.001). Post-treatment with sumatriptan significantly reduced the circumference of STA (p = 0.039) and MMA (p = 0.015) but not of MCA (p = 0.981) compared to ketorolac. In an explorative analysis, we found that pre-treatment with sumatriptan reduced PACAP38-induced headache compared to no treatment (AUC_0-90min).

CONCLUSIONS

Post-treatment with ketorolac was more effective in attenuating PACAP38-induced headache compared to sumatriptan. Ketorolac exerted its effect without affecting PACAP38-induced arterial dilation, whereas sumatriptan post-treatment attenuated PACAP38-induced dilation of MMA and STA. Pre-treatment with sumatriptan attenuated PACAP38-induced headache without affecting PACAP38-induced arterial dilation. Our findings suggest that ketorolac and sumatriptan attenuated PACAP38-induced headache in healthy volunteers without vascular effects.

TRIAL REGISTRATION

Clinicaltrials.gov (NCT03585894). Registered 13 July 2018.

Migraine pathways and the identification of novel therapeutic targets

Introduction: Migraine is a chronic neurovascular disorder characterized by recurrent headache attacks associated with neurological and autonomic symptoms. The pathophysiological mechanisms of the disease are extremely complex, involving hypothalamic and trigeminovascular activation, cortical spreading depression, release of pro-inflammatory peptides, peripheral and central sensitization. The underlying cellular and molecular mechanisms have been scarcely investigated. Recently, genetic studies have suggested that different metabolic pathways could be involved in the pathogenesis of migraine.Areas covered: This review focuses on cellular and molecular mechanisms involved in migraine, suggesting a role for circadian clocks, ion channels, synaptic plasticity, vascular factors, ion metal homeostasis, and impaired glucose metabolism in the pathogenesis of the disease. Accordingly, the article proposes new therapeutic targets that may be of particular relevance for disease prevention.Expert opinion: Several complex molecular mechanisms are involved in setting the genetic threshold for migraine and the pathogenesis of headache attacks. Most promising new therapeutic targets are the modulation of hypothalamic activity and ion channels involved in pain transmission. Further studies in animals and humans are necessary to enhance the elucidation of the molecular mechanisms of migraine and open new avenues for disease prevention.

The Neuroprotective and Biomarker Potential of PACAP in Human Traumatic Brain Injury

Traumatic brain injury remains a growing public health concern and represents the greatest contributor to death and disability globally among all trauma-related injuries. There are limited clinical data regarding biomarkers in the diagnosis and outcome prediction of TBI. The lack of real effective treatment for recovery calls for research of TBI to be shifted into the area of prevention, treatment of secondary brain injury and neurorehabilitation. The neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP) has been reported to act as a hormone, a neuromodulator, a neurotransmitter and a trophic factor, and has been implicated in a variety of developmental and regenerative processes. The importance of PACAP in neuronal regeneration lies in the upregulation of endogenous PACAP and its receptors and the protective effect of exogenous PACAP after different central nervous system injury. The aim of this minireview is to summarize both the therapeutic and biomarker potential of the neuropeptide PACAP, as a novel possible target molecule presently being investigated in several human conditions including TBI, and with encouraging results in animal models of TBI.

Imaging the Visual Network in the Migraine Spectrum

The involvement of the visual network in migraine pathophysiology has been well-known for more than a century. Not only is the aura phenomenon linked to cortical alterations primarily localized in the visual cortex; but also migraine without aura has shown distinct dysfunction of visual processing in several studies in the past. Further, the study of photophobia, a hallmark migraine symptom, has allowed unraveling of distinct connections that link retinal pathways to the trigeminovascular system. Finally, visual snow, a recently recognized neurological disorder characterized by a continuous visual disturbance, is highly comorbid with migraine and possibly shares with it some common pathophysiological mechanisms. Here, we review the most relevant neuroimaging literature to date, considering studies that have either attempted to investigate the visual network or have indirectly shown visual processing dysfunctions in migraine. We do this by taking into account the broader spectrum of migrainous biology, thus analyzing migraine both with and without aura, focusing on light sensitivity as the most relevant visual symptom in migraine, and finally analyzing the visual snow syndrome. We also present possible hypotheses on the underlying pathophysiology of visual snow, for which very little is currently known.

Cellular distribution of PACAP-38 and PACAP receptors in the rat brain: Relation to migraine activated regions

Background

Pituitary adenylate cyclase-activating polypeptide (PACAP) occurs as either a 27- or 38-amino acid neuropeptide and belongs to the vasoactive intestinal polypeptide/glucagon/secretin family of peptides. PACAP and vasoactive intestinal polypeptide have a 68% homology of their amino acid sequences and share three B-type G-protein coupled receptors: VPAC1, VPAC2 and PAC1 receptors.

Methods/results

The distribution of PACAP-38 and its receptors in the brain is only partly described in the literature. Here, we have performed a study to provide the more general picture of this system in rat brain in order to understand a putative role in primary headaches and partly in relation to the calcitonin gene-related peptide system. We observed a rich expression of PACAP-38 and PAC1 receptor immunoreactivity in many regions throughout the cerebrum, cerebellum and brainstem. The expression pattern points to multiple functions, not least associated with pain and reactions to pain. The expression of VPAC1 and VPAC2 receptor immunoreactivity was very sparse. In several regions such as the cerebral cortex, trigeminal nucleus caudalis, hypothalamus and pons there was a close relation to calcitonin gene-related peptide expression.

Conclusion

The findings suggest that the rich supply of PACAP-38 and PAC1 receptors is associated with basic functional responses in the central nervous system (CNS), and there are important close anatomical relations with calcitonin gene-related peptide in CNS regions associated with migraine pathophysiology.

Headache and Methemoglobinemia

AIM

This basic review is intended to summarize the current knowledge of methemoglobinemia as an important cause of secondary headache with the hope of generating a growing interest in studying this phenomenon.

BACKGROUND

We describe the pathological underpinnings of headaches generated by hypoxia. Possible mechanisms include cerebral vasodilation-associated stretching of the vessel nociceptors, sensitization of perivascular nociceptors mediated by nitric oxide, cerebral calcitonin gene-related peptide, activation of the cyclic adenosine monophosphate pathway, cortical spreading depression, disruption of the blood-brain barrier, and neurogenic inflammation. We review the clinical features, pathophysiology, and management of methemoglobinemia. We conducted a literature review of reports of symptomatic methemoglobinemia with headache. In addition, we describe a case report of a patient who presented with an acute onset of severe holocranial headache associated with rapidly progressive perioral paresthesia, cyanosis in lips and hands, nausea, and mild dyspnea on exertion. These features can be misinterpreted as an acute attack of migraine with pain-related hyperventilation syndrome and anxiety leading to clinically detrimental delay in the management of the progressive hypoxia. Her symptoms resolved following treatment with methylene blue. The complex relationship of migraine and hypoxia-related headaches is also reviewed. We propose that methemoglobinemia-associated headaches are possibly generated by stretching of the nociceptor nerve endings during cerebral vasodilation and hypoxia-mediated oxidative stress.

CONCLUSIONS

The case highlights the need to broaden the formulated differential diagnosis of an acute onset severe holocranial headache and pay careful attention to other signs and symptoms that may provide hints on potential mechanism(s) for secondary headaches. We provide justification for the need to incorporate "Headache attributed to Methemoglobinemia" as a subtype under the section "Headache attributed to hypoxia and/or hypercapnia" of the International Classification of Headache Disorders to support clinical decision making.