Targeting the central projection of the dural trigeminovascular system for migraine prophylaxis

Migraine Comorbidities

Novel knowledge about the interrelationships and reciprocal effects of migraine and epilepsy, migraine and mood disorders, or migraine and irritable bowel syndrome has emerged in recent decades. Over time, comorbid pathologies associated with migraine that share common physiopathological mechanisms were studied. Among these studied pathologies is epilepsy, a disorder with common ion channel dysfunctions as well as dysfunctions in glutamatergic transmission. A high degree of neuronal excitement and ion channel abnormalities are associated with epilepsy and migraine and antiepileptic drugs are useful in treating both disorders. The coexistence of epilepsy and migraine may occur independently in the same individual or the two may be causally connected. The relationship between cortical spreading depression (CSD) and epileptic foci has been suggested by basic and clinical neuroscience research. The most relevant psychiatric comorbidities associated with migraine are anxiety and mood disorders, which influence its clinical course, treatment response, and clinical outcome. The association between migraine and major depressive disorder can be explained by a robust molecular genetic background. In addition to its role as a potent vasodilator, CGRP is also involved in the transmission of nociception, a phenomenon inevitably linked with the stress and anxiety caused by frequent migraine attacks. Another aspect is the role of gut microbiome in migraine's pathology and the gut-brain axis involvement. Irritable bowel syndrome patients are more likely to suffer migraines, according to other studies. There is no precise explanation for how the gut microbiota contributes to neurological disorders in general and migraines in particular. This study aims to show that migraines and comorbid conditions, such as epilepsy, microbiota, or mood disorders, can be connected from the bench to the bedside. It is likely that these comorbid migraine conditions with common pathophysiological mechanisms will have a significant impact on best treatment choices and may provide clues for future treatment options.

Duality in response of intracranial vessels to nitroglycerin revealed in rats by imaging photoplethysmography

Among numerous approaches to the study of migraine, the nitroglycerin (NTG) model occupies a prominent place, but there is relatively insufficient information about how NTG affects intracranial vessels. In this study we aim to assess the effects of NTG on blood-flow parameters in meningeal vessels measured by imaging photoplethysmography (iPPG) in animal experiments. An amplitude of the pulsatile component (APC) of iPPG waveform was assessed before and within 2.5 h after the NTG administration in saline (n = 13) or sumatriptan (n = 12) pretreatment anesthetized rats in conditions of a closed cranial window. In animals of both groups, NTG caused a steady decrease in blood pressure. In 7 rats of the saline group, NTG resulted in progressive increase in APC, whereas decrease in APC was observed in other 6 rats. In all animals in the sumatriptan group, NTG administration was accompanied exclusively by an increase in APC. Diametrically opposite changes in APC due to NTG indicate a dual effect of this drug on meningeal vasomotor activity. Sumatriptan acts as a synergist of the NTG vasodilating action. The results we obtained contribute to understanding the interaction of vasoactive drugs in the study of the headache pathophysiology and methods of its therapy.

Connection between right-to-left shunt and photosensitivity: a community-based cross-sectional study

Background

Hypersensitivity to light is a common symptom associated with dysfunction of the occipital region. Earlier studies also suggested that clinically significant right-to-left shunt (RLS) could increase occipital cortical excitability associated with the occurrence of migraine. The aim of this study was to investigate the relationship between RLS and photosensitivity.

Methods

This cross-sectional observational study included the residents aged 18-55 years living in the Mianzhu community between November 2021 and October 2022. Photosensitivity was evaluated using the Photosensitivity Assessment Questionnaire along with baseline clinical data through face-to-face interviews. After the interviews, contrast-transthoracic echocardiography (cTTE) was performed to detect RLS. Inverse probability weighting (IPW) was used to reduce selection bias. Photosensitivity score was compared between individuals with and without significant RLS using multivariable linear regression based on IPW.

Results

A total of 829 participants containing 759 healthy controls and 70 migraineurs were finally included in the analysis. Multivariable linear regression analysis showed that migraine (β = 0.422; 95% CI: 0.086-0.759; p = 0.014) and clinically significant RLS (β = 1.115; 95% CI: 0.760-1.470; p < 0.001) were related to higher photosensitivity score. Subgroup analysis revealed that clinically significant RLS had a positive effect on hypersensitivity to light in the healthy population (β = 0.763; 95% CI: 0.332-1.195; p < 0.001) or migraineurs (β = 1.459; 95% CI: 0.271-2.647; p = 0.010). There was also a significant interaction between RLS and migraine for the association with photophobia (p_interaction = 0.009).

Conclusion

RLS is associated with photosensitivity independently and might exacerbate photophobia in migraineurs. Future studies with RLS closure are needed to validate the findings.

Trial registration

This study was registered at the Chinese Clinical Trial Register, Natural Population Cohort Study of West China Hospital of Sichuan University, ID: ChiCTR1900024623, URL: https://www.chictr.org.cn/showproj.html?proj=40590.

A critical review of the neurovascular nature of migraine and the main mechanisms of action of prophylactic antimigraine medications

INTRODUCTION

Migraine involves neurovascular, functional, and anatomical alterations. Migraineurs experience an intense unilateral and pulsatile headache frequently accompanied with vomiting, nausea, photophobia, etc. Although there is no ideal preventive medication, frequency in migraine days may be partially decreased by some prophylactics, including antihypertensives, antidepressants, antiepileptics, and CGRPergic inhibitors. However, the mechanisms of action involved in antimigraine prophylaxis remain elusive.

AREAS COVERED

This review recaps some of the main neurovascular phenomena related to migraine and currently available preventive medications. Moreover, it discusses the major mechanisms of action of the recommended prophylactic medications.

EXPERT OPINION

In the last three years, migraine prophylaxis has evolved from nonspecific to specific antimigraine treatments. Overall, nonspecific treatments  mainly involve neural actions, whereas specific pharmacotherapy (represented by CGRP receptor antagonists and CGRPergic monoclonal antibodies) is predominantly mediated by neurovascular mechanisms that may include, among others: (i) reduction in the cortical spreading depression (CSD)-associated events; (ii) inhibition of pain sensitization; (iii) blockade of neurogenic inflammation; and/or (iv) increase in cranial vascular tone. Accordingly, the novel antimigraine prophylaxis promises to be more effective, devoid of significant adverse effects (unlike nonspecific treatments), and more beneficial for the quality of life of migraineurs.

Relationships between migraine and epilepsy: Pathophysiological mechanisms and clinical implications

Migraine and epilepsy are distinct neurological diseases with specific clinical features and underlying pathophysiological mechanisms. However, numerous studies have highlighted the complex and multifaceted relationships between the two conditions. The relationships between headache and epilepsy manifest themselves in different ways. Firstly, the clinical diagnosis of these disorders may be challenging in view of possible overlapping. While post-ictal headache is a frequent condition, ictal epileptic headache is a rare but challenging diagnosis. Both situations raise the question of the pathophysiological mechanism of headache triggered by seizures. Migraine aura and epilepsy can also exhibit overlapping symptoms leading to their misdiagnosis, in particular in the case of visual aura. Secondly, migraine with aura and epilepsy can occur as a co-morbid condition, particularly in familial hemiplegic migraine (FHM). From a pathophysiological perspective, the identification of genetic mutations in FHM has brought significant advances in the understanding of dysfunctions of neuronal networks leading to hyperexcitability. The purpose of this review is to present clinical situations encompassing headache and epilepsy that can be challenging in neurological practice and to discuss the underlying pathophysiological mechanism of such interactions.

Targeting reactive nitroxidative species in preclinical models of migraine

BACKGROUND

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

METHODS

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

RESULTS

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

DISCUSSION

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

Migraine pharmacology and brain ischemia

Introduction: The aim of this review article was to analyze in details the mechanism of drugs’ effects in the treatment and prevention of a migraine attack, as well as to discuss the hypotheses of migraine pathogenesis.

Migraine attack treatment agents: The main agents for migraine attack treatment have an anti-nociceptive activity.

Agents for migraine preventive treatment: β-blocker propranolol also has anti-serotonin and analgesic activities, and most drugs used for the prophylactic treatment of migraine have a vasodilating activity.

Vascular hypothesis of migraine pathogenesis: Despite numerous studies that have expanded our understanding of migraine pathogenesis, the importance of the vascular component in the pathogenesis of this disease has not questioned yet.

Neurogenic hypotheses of cortical spreading depression: It is necessary to take into account the points of this hypothesis in the context of the pathophysiology of migraine.

Neurochemical serotonin hypotheses of migraine pathogenesis: Serotonin plays an important role in the pathogenesis of migraine.

Trigemino-vascular hypotheses of migraine pathogenesis: The trigemino-vascular hypothesis claims to solve the problem of migraine pain.

Migraine and ischemic brain damage: Migraine is a risk factor for ischemic stroke and cognitive disorders.

Search for the new anti-ischemic anti-migraine preparations: A methodology for the search for new anti-ischemic anti-serotonin drugs for the treatment of migraine is proposed.

Conclusion: Belonging of a drug to one or another pharmacological group does not always correspond to its therapeutic effect on the pathogenetic processes of migraine. Migraine with its variety of forms cannot fit only one of the proposed hypotheses on the pathogenesis of this disease.

Graphical abstract:

Therapeutic targeting of nitroglycerin-mediated trigeminovascular neuronal hypersensitivity predicts clinical outcomes of migraine abortives

ABSTRACT

Cranial hypersensitivity is a prominent symptom of migraine, exhibited as migraine headache exacerbated with physical activity, and cutaneous facial allodynia and hyperalgesia. The underlying mechanism is believed to be, in part, activation and sensitization of dural-responsive trigeminocervical neurons. Validated preclinical models that exhibit this phenotype have great utility for understanding putative mechanisms and as a tool to screen therapeutics. We have previously shown that nitroglycerin triggers cranial allodynia in association with migraine-like headache, and this translates to neuronal cranial hypersensitivity in rats. Furthermore, responses in both humans and rats are aborted by triptan administration, similar to responses in spontaneous migraine. Here, our objective was to study the nitroglycerin model examining the effects on therapeutic targets with newly approved treatments, specifically gepants and ditans, for the acute treatment of migraine. Using electrophysiological methods, we determined changes to ongoing firing and somatosensory-evoked cranial sensitivity, in response to nitroglycerin, followed by treatment with a calcitonin gene-related peptide receptor antagonist, gepant (olcegepant), a 5-HT1F receptor agonist, ditan (LY344864), and an NK1 receptor antagonist (GR205171). Nitroglycerin induced activation of migraine-like central trigeminocervical neurons, and intracranial and extracranial neuronal hypersensitivity. These responses were aborted by olcegepant and LY344864. However, GR205171, which failed in clinical trial for both abortive and preventive treatment of migraine, had no effect. These data support the nitroglycerin model as a valid approach to study cranial hypersensitivity and putative mechanisms involved in migraine and as a screen to dissect potentially efficacious migraine therapeutic targets.

Advantages of imaging photoplethysmography for migraine modeling: new optical markers of trigemino-vascular activation in rats

Background

Existent animal models of migraine are not without drawbacks and limitations. The aim of our study was to evaluate imaging photoplethysmography (PPG) as a method of assessing intracranial blood flow in rats and its changes in response to electrical stimulation of dural trigeminal afferents.

Methods

Experiments were carried out with 32 anesthetized adult male Wistar rats. Trigeminovascular system (TVS) was activated by means of electrical stimulation of dural afferents through a closed cranial window (CCW). Parameters of meningeal blood flow were monitored using a PPG imaging system under green illumination with synchronous recording of an electrocardiogram (ECG) and systemic arterial blood pressure (ABP). Two indicators related to blood-flow parameters were assessed: intrinsic optical signals (OIS) and the amplitude of pulsatile component (APC) of the PPG waveform. Moreover, we carried out pharmacological validation of these indicators by determining their sensitivity to anti-migraine drugs: valproic acid and sumatriptan. For statistical analysis the non-parametric tests with post-hoc Bonferroni correction was used.

Results

Significant increase of both APC and OIS was observed due to CCW electrical stimulation. Compared to saline (n = 11), intravenous administration of both the sumatriptan (n = 11) and valproate (n = 10) by using a cumulative infusion regimen (three steps performed 30 min apart) lead to significant inhibitory effect on the APC response to the stimulation. In contrast, intravenous infusion of any substance or saline did not affect the OIS response to the stimulation. It was found that infusion of either sumatriptan or valproate did not affect the response of ABP or heart rate to the stimulation.

Conclusions

Imaging PPG can be used in an animal migraine model as a method for contactless assessment of intracranial blood flow. We have identified two new markers of TVS activation, one of which (APC) was pharmacologically confirmed to be associated with migraine. Monitoring of changes in APC caused by CCW electrical stimulation (controlling efficiency of stimulation by OIS) can be considered as a new way to assess the peripheral mechanism of action of anti-migraine interventions.

Characterization of opioidergic mechanisms related to the anti-migraine effect of vagus nerve stimulation

Vagus nerve stimulation (VNS) is a promising neuromodulation approach used in the treatment of migraine, whose therapeutic mechanism is largely unknown. Previous studies suggest that VNS's anti-nociceptive effects may, in part, involve engaging opioidergic mechanisms. We used a validated preclinical model of head pain, with good translational outcomes in migraine, acute intracranial-dural stimulation, which has responded to invasive VNS. We tested the effects of μ (MOR), δ (DOR) and κ (KOR) opioid receptor agonists in this model, and subsequently the effects of opioid receptor antagonists against VNS-mediated neuronal inhibition. MOR, DOR, and KOR agonists all inhibited dural-evoked trigeminocervical neuronal responses. Both DOR and KOR agonists also inhibited ongoing spontaneous firing of dural responsive neurons. Both DOR and KOR agonists were more efficacious than the MOR agonist in this model. We confirm the inhibitory effect of invasive VNS and demonstrate that this effect was prevented by a broad-spectrum opioid receptor antagonist, and by a highly selective DOR antagonist. Our data confirm the role of MOR in dural-trigeminovascular neurotransmission and additionally provide evidence of a role of both DOR and KOR in dural-nociceptive transmission of trigeminocervical neurons. Further, the results here provide evidence of engagement of opioidergic mechanisms in the therapeutic action of VNS in headache, specifically the DOR. These studies provide further support for the important role of the DOR in headache mechanisms, and as a potential therapeutic target. The data begin to dissect the mode of action of the analgesic effects of VNS in the treatment of primary headache disorders.

Preclinical studies investigating the neural mechanisms involved in the co-morbidity of migraine and temporomandibular disorders: the role of CGRP

BACKGROUND AND PURPOSE

Temporomandibular disorders (TMD) and migraine can be co-morbid. This can be a significant factor in exacerbating and increasing the prevalence of migraine-like symptoms. However, the underlying mechanisms involved are unknown. Our objective was to investigate these neural mechanisms and the role of CGRP as a key modulator in this co-morbidity.

EXPERIMENTAL APPROACH

We combined experimental approaches using CGRP, which triggers a migraine-like response in patients, with that of masseteric muscle injection of complete Freund's adjuvant (CFA), to model myofascial TMD-like inflammation. Using validated electrophysiological methods to assess each of the above approaches independently or in combination, we examined their effects on the response properties of migraine-like dural-trigeminocervical neurons.

KEY RESULTS

Independently, in ~2/3 of animals (rats) each approach caused delayed migraine-like activation and sensitisation of dural-trigeminocervical neurons. The response to masseteric-CFA was attenuated by a selective CGRP receptor antagonist. The combination approach caused a migraine-like neuronal response in all animals tested, with somatosensory-evoked cranial hypersensitivity significantly exacerbated.

CONCLUSION AND IMPLICATIONS

The data demonstrate a neuronal phenotype that translates to the exacerbated clinical co-morbid phenotype, supporting this combination approach as a relevant model to study the mechanisms involved. It provides a pathophysiological rationale for this exacerbated phenotype, strongly implicating the involvement of CGRP. The results provide support for targeting the CGRP pathway as a novel monotherapy approach for treating this co-morbid condition. This has key implications into our understanding of this co-morbid condition, as well as potentially addressing the major unmet need for novel and effective therapeutic approaches.

Pharmacological options for the treatment of chronic migraine pain

Migraine is a debilitating neurological condition with symptoms typically consisting of unilateral and pulsating headache, sensitivity to sensory stimuli, nausea, and vomiting. The World Health Organization (WHO) reports that migraine is the third most prevalent medical disorder and second most disabling neurological condition in the world. There are several options for preventive migraine treatments that include, but are not limited to, anticonvulsants, antidepressants, beta blockers, calcium channel blockers, botulinum toxins, NSAIDs, riboflavin, and magnesium. Patients may also benefit from adjunct nonpharmacological options in the comprehensive prevention of migraines, such as cognitive behavior therapy, relaxation therapies, biofeedback, lifestyle guidance, and education. Preventative therapies are an essential component of the overall approach to the pharmacological treatment of migraine. Comparative studies of newer therapies are needed to help patients receive the best treatment option for chronic migraine pain.