Treatment of migraine attacks based on the interaction with the trigemino-cerebrovascular system

Cardiovascular Disease and Migraine: Are the New Treatments Safe?

PURPOSE OF REVIEW

The authors present data on cardiovascular safety for the new acute and preventive migraine treatments including ditans, gepants, and calcitonin gene-related peptide monoclonal antibodies (CGRP mAbs) alongside older medications like triptans and ergotamines.

RECENT FINDINGS

The authors conclude that there are no cardiovascular safety concerns for lasmiditan, and that it could be used in those with cardiovascular disease. In fact, the literature even suggests that triptans are safer in cardiovascular disease than their contraindications may suggest. At this time, there is insufficient evidence that gepants and CGRP mAbs should be contraindicated in those with cardiovascular disease including stroke or myocardial infarction, though erenumab has now been associated with hypertension. Vasodilation may be an important CGRP-mediated mechanism mid-ischemia especially in patients with small vessel disease; hence, CGRP antagonists should be use with caution in this context. Long-term data is still needed, and prescribers should ensure patients are aware of the limitations of our knowledge at this time, while still offering these effective and well-tolerated treatment options.

Hormonal therapies in migraine management: current perspectives on patient selection and risk management

INTRODUCTION

The link between sex hormones and migraines has long been investigated but the mechanisms underlying this altered interaction are not yet fully understood. Herein, we retrace the knowledge on this association in relationship with risk of stroke.

AREAS COVERED

Estrogens fluctuations could trigger migraine attacks and exogenous estrogens intake could be a risk factor for venous thromboembolism (VTE) and stroke. At the same time, ischemic heart diseases and stroke share a common substrate with migraine and other mood disorders, depression, and anxiety.

EXPERT OPINION

The use of hormonal therapies in the context of contraception or replacement therapy must be closely evaluated in a careful risk assessment. We highlight the complex interaction of hormone/neuroinflammation pathways underlying the pathophysiology of migraine glimpsing in mood disorders a possible common denominator of link between hormonal and neuronal systems.

Intracranial nociception

Understanding intracranial nociceptive innervation is essential to understand the pathophysiology of headaches. Our knowledge about human intracranial nociception comes from sparse observations during neurosurgical procedures performed in awake patients, from human anatomical studies and from experimental studies in animals. In this article we review the anatomical and functional organization underlying nociceptive innervation. Intracranial nociception is mainly mediated by the trigeminal system, except in the posterior cranial fossa that is innervated by the first cervical roots. For decades, the dura mater, its vessels and major cerebral blood vessels were considered as the only intracranial pain-sensitive structures. Recent animal and human studies have suggested that smaller brain arteries and potentially pia mater might also be pain sensitive. Nociceptive neurons innervating intracranial blood vessels project via the ophthalmic division (V1) to the trigeminal ganglion and store several neurotransmitters including glutamate, substance P and calcitonin gene-related peptide (CGRP). The trigeminal ganglion, root and brainstem nuclei have a specific topographic and functional somatotopy. Progressive transition between the trigeminal spinal nucleus and the dorsal horn of the cervical spinal cord, and convergence of nociceptive inputs from the face, intracranial structures and the occipital area on the so-called "trigemino-cervical complex" may explain some headache features, relations between facial and occipital pain, and efficacy of occipital nerve stimulation in headache. The specific anatomic organization of the trigeminal system, from the primary-order neuron in the trigeminal ganglion, to the second-order neuron is the trigeminal nuclei, may explain a part of the various characteristics of headaches.

The trigeminal system: The meningovascular complex- A review

Supratentorial sensory perception, including pain, is subserved by the trigeminal nerve, in particular, by the branches of its ophthalmic division, which provide an extensive innervation of the dura mater and of the major brain blood vessels. In addition, contrary to previous assumptions, studies on awake patients during surgery have demonstrated that the mechanical stimulation of the pia mater and small cerebral vessels can also produce pain. The trigeminovascular system, located at the interface between the nervous and vascular systems, is therefore perfectly positioned to detect sensory inputs and influence blood flow regulation. Despite the fact that it remains only partially understood, the trigeminovascular system is most probably involved in several pathologies, including very frequent ones such as migraine, or other severe conditions, such as subarachnoid haemorrhage. The incomplete knowledge about the exact roles of the trigeminal system in headache, blood flow regulation, blood barrier permeability and trigemino-cardiac reflex warrants for an increased investigation of the anatomy and physiology of the trigeminal system. This translational review aims at presenting comprehensive information about the dural and brain afferents of the trigeminovascular system, in order to improve the understanding of trigeminal cranial sensory perception and to spark a new field of exploration for headache and other brain diseases.

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.

No additive effect of combining sumatriptan and olcegepant in the GTN mouse model of migraine

INTRODUCTION

Despite recent advances in migraine treatment there is a need for therapies with higher clinical efficacy and/or fewer side effects. Triptans (5-HT_1B/1D/1F agonists) are essential in the present treatment regime and gepants (CGRP-receptor antagonists) are recognized as effective in acute migraine treatment. Triptans and gepants have different mechanisms of action and here we tested the hypothesis that a combination of these drugs (sumatriptan and olcegepant) would result in an additive effect.

METHODS

Using the validated glyceryl trinitrate mouse model of migraine, we initially tested dose-response relationships of sumatriptan (0.1, 0.3, and 0.6 mg/kg IP) and olcegepant (0.25, 0.50, and 1.0 mg/kg IP) to find suitable high and low doses. Subsequently, we performed a combination study of the two drugs with a low and a high dose. All experiments were vehicle (placebo) controlled and blinded.

RESULTS

Sumatriptan significantly reduced glyceryl trinitrate-induced allodynia (F(4,54) = 13.51, p < 0.0001) at all doses. Olcegepant also reduced glyceryl trinitrate-induced allodynia (F(4,53) = 16.11, p < 0.0001) with the two higher doses being significantly effective. Combining 0.50 mg/kg olcegepant with 0.1 or 0.6 mg/kg sumatriptan did not have any improved effect compared to either drug alone (p > 0.50 on all days) in our mouse model.

CONCLUSION

Combining olcegepant and sumatriptan did not have an additive effect compared to single-drug treatment in this study. Triptan-gepant combinations will therefore most likely not improve migraine treatment. Nevertheless, further studies are necessary, and combinations should also be examined in patients with migraine.

Children and adolescents with sickle cell disease have worse cold and mechanical hypersensitivity during acute painful events

Sickle cell disease (SCD) pain associates with cold temperature and touch. Patients and murine models with SCD have baseline thermal and mechanical pain. In SCD mice, the baseline hypersensitivity is exacerbated by experimental vaso-occlusive crises. We hypothesized that patients with SCD will similarly experience increased hypersensitivity to thermal and mechanical stimuli during acute painful events compared with baseline health. We conducted a prospective study of 24 patients with SCD aged 7 to 19 years. Patients underwent quantitative sensory testing to thermal (cold/heat) and mechanical stimuli on the thenar eminence of the nondominant hand (glabrous skin) and the lateral dorsum of the foot (hairy skin) during baseline health and within 48 hours of hospitalization for acute pain. Primary outcomes were changes in: (1) cold pain threshold (°C), (2) heat pain threshold (°C), and (3) mechanical pain threshold (g). Median age was 10.5 (interquartile range [IQR] 9-14.8) years, 67% were females, and 92% were on hydroxyurea. Patients with SCD had increased cold pain sensitivity in the hand during hospitalization compared with baseline (25.2°C [IQR 18.4-27.5°C] vs 21.3°C [IQR 4.9-26.2°C]; P = 0.011) and increased mechanical pain sensitivity in the foot during hospitalization (0.32 g [IQR 0.09-1.1 g] vs 1.7 g [IQR 0.4-8.3 g]; P = 0.003). There were no differences in heat pain sensitivity. The increased cold (P = 0.02) and mechanical (P = 0.0016) pain sensitivity during hospitalization persisted after adjusting for age, sex, hydroxyurea use, opioid consumption, and numeric pain score. Thus, cold and mechanical pain is significantly worse during an acute SCD painful event as compared to baseline health in patients with SCD.

Optimising migraine treatment: from drug-drug interactions to personalized medicine

Migraine is the most disabling and expensive chronic disorders, the etiology of which is still not fully known. The neuronal systems, (glutammatergic, dopaminergic, serotoninergic and GABA-ergic) whose functionality is partly attributable to genetically determined factors, has been suggested to play an important role. The treatment of acute attacks and the prophylactic management of chronic forms include the use of different category of drugs, and it is demonstrated that not each subject has the same clinical answer to them. The reason of this is to be searched in different functional capacity and quantity of phase I enzymes (such as different isoforms of CYP P450), phase II enzymes (such as UDP-glucuronosyltransferases), receptors (such as OPRM1 for opioids) and transporters (such as ABCB1) involved in the metabolic destiny of each drug, all of these dictated by DNA and RNA variations. The general picture is further exacerbated by the need for polytherapies, often also to treat comorbidities, which may interfere with the pharmacological action of anti-migraine drugs. Personalized medicine has the objective of setting the optimal therapies in the light of the functional biochemical asset and of the comorbidities of the individual patient, in order to obtain the best clinical response. Novel therapeutic perspectives in migraine includes biotechnological drugs directed against molecules (such as CGRP and its receptor) that cause vasodilatation at the peripheral level of the meningeal blood vessels and reflex stimulation of the parasympathetic system. Drug-drug interactions and the possible competitive metabolic destiny should be studied by the application of pharmacogenomics in large scale. Drug-drug interactions and their possible competitive metabolic destiny should be studied by the application of pharmacogenomics in large scale.

Nitroglycerin enhances the propagation of cortical spreading depression: comparative studies with sumatriptan and novel kynurenic acid analogues

Background

The complex pathophysiology of migraine is not yet clearly understood; therefore, experimental models are essential for the investigation of the processes related to migraine headache, which include cortical spreading depression (CSD) and NO donor-induced neurovascular changes. Data on the assessment of drug efficacy in these models are often limited, which prompted us to investigate a novel combined migraine model in which an effective pharmacon could be more easily identified.

Materials and methods

In vivo electrophysiological experiments were performed to investigate the effect of nitroglycerin (NTG) on CSD induced by KCl application. In addition, sumatriptan and newly synthesized neuroactive substances (analogues of the neuromodulator kynurenic acid [KYNA]) were also tested.

Results

The basic parameters of CSDs were unchanged following NTG administration; however, propagation failure was decreased compared to the controls. Sumatriptan decreased the number of CSDs, whereas propagation failure was as minimal as in the NTG group. On the other hand, both of the KYNA analogues restored the ratio of propagation to the control level.

Discussion

The ratio of propagation appeared to be the indicator of the effect of NTG. This is the first study providing direct evidence that NTG influences CSD; furthermore, we observed different effects of sumatriptan and KYNA analogues. Sumatriptan changed the generation of CSDs, whereas the analogues acted on the propagation of the waves. Our experimental design overlaps with a large spectrum of processes present in migraine pathophysiology, and it can be a useful experimental model for drug screening.

Valproate ameliorates nitroglycerin-induced migraine in trigeminal nucleus caudalis in rats through inhibition of NF-кB

BACKGROUND

As a complex nervous system disease, migraine causes severe healthy and social issues worldwide. Valproate (VPA) is a widely used treatment agent against seizures and bipolar disorder, and its function to alleviate damage due to migraine has also been verified in clinical investigations. However, the mechanism underlying the protective effect of VPA against migraine remains poorly revealed. In the current study, the major purpose was to uncover the mechanism which drove VPA to antagonize migraine.

METHODS

Nitroglycerin (NTG) was employed to induce a migraine model in rats and the migraine animals were exposed to treatment of VPA of different doses. Thereafter, the levels of indicators related to oxidative stress were measured and used to evaluate the anti-oxidant potential of VPA. The expression of calcitonin gene-related peptide (CGRP) and c-Fos was also quantified with ELISA and immunohistochemistry, respectively. Western blotting and electrophoretic mobility shift assays (EMSA) were conducted to explore the effect of VPA treatment on NF-кB pathway.

RESULTS

NTG induced the activation of oxidative stress and led to migraine in model animals, but pre-treatment with VPA attenuated the damage due to migraine attack in brain tissues. The level of lipid peroxidation was significantly reduced while the prodcution of anti-oxidant factors was restored. Furthermore, expressions of CGRP and c-Fos, which represented the neuronal activation, were also down-regulated by VPA. The results of western blotting and EMSA demonstrated that the above mentioned effect of VPA acted through the inhibition of NF-кB pathway.

CONCLUSIONS

Although controversies on the effect of VPA on NF-кB pathway existed, our study revealed an alternative mechanism of VPA in protecting against migraine, which would promote the development of therapeutic strategies of migraine.

Peptide antagonists of the calcitonin gene-related peptide (CGRP) receptor with improved pharmacokinetics and pharmacodynamics

Antagonism of the calcitonin gene-related peptide (CGRP) receptor may be a useful approach for migraine treatment. Selective PEGylated peptide antagonists to the CGRP receptor are described, derived from CGRP(8-37) with polymer derivatization at an engineered lysine-25 residue. Potent PEGylated peptides with improved pharmacokinetics were identified through peptide side-chain modification to mitigate metabolic liabilities. PEGylated Ac-Trp-[Cit(11,18),hArg(24),Lys(25),Asp(31),Pro(34),1-Nal(35)]CGRP(8-37)-NH2, 9, elicits a dose-dependent reduction of intradermal CGRP-induced local blood flow in rodents with an ED50 of 0.52 mg kg(-1) without any overt adverse effects.

The Prevalence of Dry Eye and Sjögren Syndrome in Patients with Migraine

PURPOSE

To evaluate the presence of dry eye and primary Sjögren syndrome (SS) in patients with migraine.

METHODS

In total, 46 eyes of 46 patients with migraine (group 1) and 50 eyes of 50 healthy subjects (group 2) were included in this study. Detailed ophthalmologic, neurologic and rheumatologic examination were performed on all participants. Ocular surface disease index questionnaire, tear function tests, visual analog scale for pain, serologic analysis were also performed.

RESULTS

Dry eye symptoms and findings were significantly higher and more severe in group 1 when compared with group 2. Primary SS was not found in any of the participants. The migraine lifetime duration was negatively correlated with the tear function tests while it was positively correlated with the ocular surface disease index scores.

CONCLUSIONS

Dry eye symptoms and findings are higher in migraine patients when compared with the healthy subjects without the presence of Sjögren syndrome.

Development of anti-migraine therapeutics using the capsaicin-induced dermal blood flow model

The efficacy of calcitonin gene-related peptide (receptor) (CGRP-(R)) blocking therapeutics in the treatment of acute migraine headache provided proof-of-concept for the involvement of CGRP in the pathophysiology of this disorder. One of the major hurdles for the development of any class of drugs, including CGRP blocking therapeutics, is the early clinical development process during which toxic and inefficacious compounds need to be eliminated as early as possible in order to focus on the most promising molecules. At this stage, human models providing proof of target engagement, combined with safety and tolerability studies, are extremely valuable in focusing on those therapeutics that have the highest engagement from the lowest exposure. They guide the go/no-go decision making, establish confidence in the candidate molecule by de-risking toxicity and safety issues and thereby speed up the early clinical development. In this review the focus is on the so called 'capsaicin model' as a typical example of a target engagement biomarker used as a human model for the development of CGRP blocking therapeutics. By applying capsaicin onto the skin, TRPV1 channels are activated and a CGRP-mediated increase in dermal blood flow can be quantified with laser Doppler perfusion imaging. Effective CGRP blocking therapeutics in turn, display blockade of this response. The translation of this biomarker model from animals to humans is discussed as well as the limitations of the assay in predicting the efficacy of anti-migraine drugs.

Dural administration of inflammatory soup or Complete Freund's Adjuvant induces activation and inflammatory response in the rat trigeminal ganglion

Background

Migraine is a painful disorder with a huge impact on individual and public health. We hypothesize that migraine pain originates from a central mechanism that results secondarily in hypersensitivity in peripheral afferents associated with the cerebral and cranial blood vessels. It has previously been shown that application of inflammatory or algesic substances onto the dura mater or chemical stimulation of the dural receptive fields causes hypersensitivity to mechanical and thermal stimulation together with direct activation of the TG. We asked whether local inflammation of dura mater induces inflammatory activation in the trigeminal ganglion.

Methods

We performed topical administration of inflammatory soup (IS) or Complete Freund’s Adjuvant (CFA) onto an exposed area of the rat dura mater in vivo for 20 min. The window was closed and the rats were sacrificed after 4 h and up to 7 days. Myography was performed on middle meningeal arteries. The trigeminal ganglia were removed and processed for immunohistochemistry or Western blot.

Results

Both CFA and IS induced enhanced expression of pERK1/2, IL-1β and CGRP in the trigeminal ganglia. The pERK1/2 immunoreactivity was mainly seen in the satellite glial cells, while IL-1β reactivity was observed in the neuronal cytoplasm, close to the cell membrane, seemingly as sign of neuro-glial interaction. The CGRP expression in the neurons and nerve fibres was enhanced after the application of either inflammatory agent. Myography resulted in a strong vasoconstrictor response to IS, but not to CFA.

Conclusions

These results suggest that the application of IS or CFA onto the dura mater causes long-term activation of the TG and demonstrate the importance of the neuro-glial interaction in the activation of the trigeminovascular system.

Electronic supplementary material

The online version of this article (doi:10.1186/s10194-015-0564-y) contains supplementary material, which is available to authorized users.

Efficacy of Pulsed Radiofrequency on Cervical 2-3 Posterior Medial Branches in Treating Chronic Migraine: A Randomized, Controlled, and Double-Blind Trial

Objective. The aim of this study was to examine the efficacy and safety of pulsed radiofrequency (PRF) in the treatment of chronic migraine (CM) on cervical 2-3 posterior medial branches. Methods. This randomized, double-blind, and controlled clinical trial included 40 subjects with CM, who were randomly divided into two groups: treatment (treated by PRF) and sham (treated by sham treatment). Pain intensity, headache duration (days), the Migraine Disability Assessment Questionnaire (MIDAS), and aspirin dose taken by patients were evaluated at 1, 2, and 6 months after the intervention. Side effects were observed from the time of treatment and throughout the follow-up period. Results. During the follow-up, pain intensity, headache duration (days), disability score, and the analgesic dose were significantly improved in the treatment group compared to the sham group (P < 0.001) and the baseline (P < 0.001) at all measured time points after intervention. No serious complications were reported. Conclusion. PRF on the cervical 2-3 posterior medial branches could provide satisfactory efficacy in the treatment of CM without obvious adverse effects.

Serum MicroRNA Signatures in Migraineurs During Attacks and in Pain-Free Periods

MicroRNAs have emerged as important biomarkers and modulators of pathophysiological processes including oncogenesis and neurodegeneration. MicroRNAs are found to be involved in the generation and maintenance of pain in animal models of inflammation and neuropathic pain. Recently, microRNA dysregulation has been reported in patients with painful conditions such as complex regional pain syndrome and fibromyalgia. The aim of this study was to assess whether serum microRNA alterations occur during migraine attacks and whether migraine manifests in chronic serum microRNA aberrations. Two cohorts of 24 migraineurs, and age- and sex-matched healthy controls were included. High-content serum microRNA (miRNA) arrays were used to assess the serum microRNA profiles of migraineurs during attacks and pain-free periods in comparison with healthy controls. Of the 372 assessed microRNAs, 32 or ≈ 8% were found to be differentially expressed and 4 of these--miR-34a-5p, 29c-5p, -382-5p, and -26b-3p--were selected for further investigation. Migraine attacks were associated with an acute upregulation in miR-34a-5p and miR-382-5p expression. Interestingly, miR-382-5p not only exhibited an upregulation during attack but also proved to be a biomarker for migraine when comparing migraineurs in pain-free periods to the healthy control group (p = <0.01). In conclusion, migraine manifestation is reflected in serum miRNA aberrations, both during attacks and pain-free periods. This finding sheds light on the potential role of microRNAs in the pathophysiology of migraine and adds a new approach towards potential identification of much sought-after serum biomarkers of migraine.

Clinical effectiveness of osteopathic treatment in chronic migraine: 3-Armed randomized controlled trial

OBJECTIVE

To assess the effectiveness of OMT on chronic migraineurs using HIT-6 questionnaire, drug consumption, days of migraine, pain intensity and functional disability.

DESIGN

3-Armed randomized controlled trial setting: all patients admitted in the Department of Neurology of Ancona's United Hospitals, Italy, with a diagnosis of migraine and without chronic illness, were considered eligible for the study.

INTERVENTIONS

Patients were randomly divided into three groups: (1) OMT+medication therapy, (2) sham+medication therapy and (3) medication therapy only. Patients received 8 treatments in a study period of 6 months.

MAIN OUTCOME MEASURES

Changing from baseline HIT-6 score.

RESULTS

105 subjects were included. At the end of the study, ANOVA showed that OMT significantly reduced HIT-6 score (mean change scores OMT-conventional care: -8.74; 95% confidence interval (CI) -12.96 to -4.52; p<0.001 and OMT-sham: -6.62; 95% CI -10.85 to -2.41; p<0.001), drug consumption (OMT-sham: RR=0.22, 95% CI 0.11-0.40; OMT-control: RR=0.20, 95% CI 0.10-0.36), days of migraine (OMT-conventional care: M=-21.06; 95% CI -23.19 to -18.92; p<0.001 and OMT-sham: -17.43; 95% CI -19.57 to -15.29; p<0.001), pain intensity (OMT-sham: RR=0.42, 95% CI 0.24-0.69; OMT-control: RR=0.31, 95% CI 0.19-0.49) and functional disability (p<0.001).

CONCLUSIONS

These findings suggest that OMT may be considered a valid procedure for the management of migraineurs. The present trial was registered on www.ClinicalTrials.gov (identifier: NCT01851148).

Quinoline derivatives: candidate drugs for a class B G-protein coupled receptor, the calcitonin gene-related peptide receptor, a cause of migraines

Class B G-protein coupled receptors are involved in a wide variety of diseases and are a major focus in drug design. Migraines are a common problem, and one of their major causative agents is the class B G-protein coupled receptor, Calcitonin gene-related peptide (CGRP) receptor, a target for competitive drug discovery. The calcitonin receptor-like receptor generates complexes with a receptor activity-modifying protein, which determines the type of receptor protein formed. The CGRP receptor comprises a complex formed from the calcitonin receptor-like receptor and receptor activity-modifying protein 1. In this study, an in silico docking approach was used to target the calcitonin receptor-like receptor in the bound form with receptor activity-modifying protein 1 (CGRP receptor), as well as in the unbound form. In both cases, the resulting inhibitors bound to the same cavity of the calcitonin receptor-like receptor. The twelve evaluated compounds were competitive inhibitors and showed efficient inhibitory activity against the CGRP receptor and Calcitonin receptor-like receptor. The two studied quinoline derivatives demonstrated potentially ideal inhibitory activity in terms of binding interactions and low range nano-molar inhibition constants. These compounds could prove helpful in designing drugs for the effective treatment of migraines. We propose that quinoline derivatives possess inhibitory activity by disturbing CGRP binding in the trigeminovascular system and may be considered for further preclinical appraisal for the treatment of migraines.

Pediatric migraine: abortive management in the emergency department

Studies suggest that headache accounts for approximately 1% of pediatric emergency department (ED) visits. ED physicians must distinguish between primary headaches, such as a tension or migraine, and secondary headaches caused by systemic disease including neoplasm, infection, or intracranial hemorrhage. A recent study found that 40% of children presenting to the ED with headache were diagnosed with a primary headache, and 75% of these were migraine. Once the diagnosis of migraine has been made, the ED physician is faced with the challenge of determining appropriate abortive treatment. This review summarizes the most recent literature on pediatric migraine with an emphasis on diagnosis and abortive treatment in the ED.

Activation of 5-hydroxytryptamine1B/1D/1F receptors as a mechanism of action of antimigraine drugs

INTRODUCTION

The introduction of the triptans (5-hydroxytryptamine (5-HT)1B/1D receptor agonists) was a great improvement in the acute treatment of migraine. However, shortcomings of the triptans have prompted research on novel serotonergic targets for the treatment of migraine.

AREAS COVERED

In this review the different types of antimigraine drugs acting at 5-HT receptors, their discovery and development are discussed. The first specific antimigraine drugs were the ergot alkaloids, consisting of ergotamine, dihydroergotamine and methysergide, which are agonists at 5-HT receptors, but can also bind α-adrenoceptors and dopamine receptors. In the 1990s, the triptans became available on the market. They are 5-HT1B/1D receptor agonists, showing fewer side effects due to their receptor specificity. In the last years, compounds that bind specifically to 5-HT1D, 5-HT1F and 5-HT7 receptors have been explored for their antimigraine potential. Furthermore, the serotonergic system seems to act in tight connection with the glutamatergic as well as the CGRP-ergic systems, which may open novel therapeutic avenues.

EXPERT OPINION

Although the triptans are very effective in treating migraine attacks, their shortcomings have stimulated the search for novel drugs. Currently, the focus is on 5-HT1F receptor agonists, which seem devoid of vascular side effects. Moreover, novel compounds that affect multiple transmitter and/or neuropeptide systems that are involved in migraine could be of therapeutic relevance.

Pharmacokinetic evaluation of zolmitriptan for the treatment of migraines

INTRODUCTION

Migraine is a multifactorial neurovascular disorder characterized by recurrent episodes of disabling pain attacks, accompanied with gastrointestinal, neurological systems dysfunction. The pharmacologic treatment of migraine is classically divided in the management of the acute attack and preventive strategies. Acute treatments consist of triptan, ergot, opioid, antiemetic and NSAIDs.

AREAS COVERED

This article discusses pharmacodynamics and pharmacokinetics of zolmitriptan . The data were obtained by searching the following keywords in MEDLINE: zolmitriptan, pharmacokinetics, pharmacodynamics, triptans, migraine, menstrual-related migraine, cluster headache, relatively to the period 1989 - 2012.

EXPERT OPINION

Zolmitriptan has been considered effective treatment in the acute phase of migraine, menstrual-related migraine and cluster headache attacks. Pharmacokinetic parameters may vary as a consequence of gender differences, inter- and intra-subjects variability and delivery system. Zolmitriptan was developed with the aim of obtaining a lipophilic compound in order to be more rapidly absorbed and centrally active. Pharmacologically, pharmacokinetic parameters are responsible for its wide efficacy and the limited adverse effect profile.

Sumatriptan inhibits TRPV1 channels in trigeminal neurons

OBJECTIVE

To understand a possible role for transient potential receptor vanilloid 1 (TRPV1) ion channels in sumatriptan relief of pain mediated by trigeminal nociceptors.

BACKGROUND

TRPV1 channels are expressed in small nociceptive sensory neurons. In dorsal root ganglia, TRPV1-containing nociceptors mediate certain types of inflammatory pain. Neurogenic inflammation of cerebral dura and blood vessels in the trigeminal nociceptive system is thought to be important in migraine pain, but the ion channels important in transducing migraine pain are not known. Sumatriptan is an agent effective in treatment of migraine and cluster headache. We hypothesized that sumatriptan might modulate activity of TRPV1 channels found in the trigeminal nociceptive system.

METHODS

We used immunohistochemistry to detect the presence of TRPV1 channel protein, whole-cell recording in acutely dissociated trigeminal ganglia (TG) to detect functionality of TRPV1 channels, and whole-cell recording in trigeminal nucleus caudalis (TNC) to detect effects on release of neurotransmitters from trigeminal neurons onto second order sensory neurons. Effects specifically on TG neurons that project to cerebral dura were assessed by labeling dural nociceptors with DiI.

RESULTS

Immunohistochemistry demonstrated that TRPV1 channels are present in cerebral dura, in trigeminal ganglion, and in the TNC. Capsaicin, a TRPV1 agonist, produced depolarization and repetitive action potential firing in current clamp recordings, and large inward currents in voltage clamp recordings from acutely dissociated TG neurons, demonstrating that TRPV1 channels are functional in trigeminal neurons. Capsaicin increased spontaneous excitatory postsynaptic currents in neurons of layer II in TNC slices, showing that these channels have a physiological effect on central synaptic transmission. Sumatriptan (10 µM), a selective antimigraine drug, inhibited TRPV1-mediated inward currents in TG and capsaicin-elicited spontaneous excitatory postsynaptic currents in TNC slices. The same effects of capsaicin and sumatriptan were found in acutely dissociated DiI-labeled TG neurons innervating cerebral dura.

CONCLUSION

Our results build on previous work indicating that TRPV1 channels in trigeminal nociceptors play a role in craniofacial pain. Our findings that TRPV1 is inhibited by the specific antimigraine drug sumatriptan, and that TRPV1 channels are functional in neurons projecting to cerebral dura suggests a specific role for these channels in migraine or cluster headache.

Crystal structure of the ectodomain complex of the CGRP receptor, a class-B GPCR, reveals the site of drug antagonism

Dysregulation of the calcitonin gene-related peptide (CGRP), a potent vasodilator, is directly implicated in the pathogenesis of migraine. CGRP binds to and signals through the CGRP receptor (CGRP-R), a heterodimer containing the calcitonin receptor-like receptor (CLR), a class B GPCR, and RAMP1, a receptor activity-modifying protein. We have solved the crystal structure of the CLR/RAMP1 N-terminal ectodomain heterodimer, revealing how RAMPs bind to and potentially modulate the activities of the CLR GPCR subfamily. We also report the structures of CLR/RAMP1 in complex with the clinical receptor antagonists olcegepant (BIBN4096BS) and telcagepant (MK0974). Both drugs act by blocking access to the peptide-binding cleft at the interface of CLR and RAMP1. These structures illustrate, for the first time, how small molecules bind to and modulate the activity of a class B GPCR, and highlight the challenges of designing potent receptor antagonists for the treatment of migraine and other class B GPCR-related diseases.

Triptans for the management of migraine

Migraine is a chronic, recurrent, disabling condition that affects millions of people in the US and worldwide. Proper acute care treatment for migraineurs is essential for a full return of function and productivity. Triptans are serotonin (5-HT)(1B/1D) receptor agonists that are generally effective, well tolerated and safe. Seven triptans are available worldwide, although not all are available in every country, with multiple routes of administration, giving doctors and patients a wide choice. Despite the similarities of the available triptans, pharmacological heterogeneity offers slightly different efficacy profiles. All triptans are superior to placebo in clinical trials, and some, such as rizatriptan 10 mg, eletriptan 40 mg, almotriptan 12.5 mg, and zolmitriptan 2.5 and 5 mg are very similar to each other and to the prototype triptan, sumatriptan 100 mg. These five are known as the fast-acting triptans. Increased dosing can offer increased efficacy but may confer a higher risk of adverse events, which are usually mild to moderate and transient in nature. This paper critically reviews efficacy, safety and tolerability for the different formulations of sumatriptan, zolmitriptan, rizatriptan, naratriptan, almotriptan, eletriptan and frovatriptan.

The relevance of preclinical research models for the development of antimigraine drugs: focus on 5-HT(1B/1D) and CGRP receptors

Migraine is a complex neurovascular syndrome, causing a unilateral pulsating headache with accompanying symptoms. The past four decades have contributed immensely to our present understanding of migraine pathophysiology and have led to the introduction of specific antimigraine therapies, much to the relief of migraineurs. Pathophysiological factors culminating into migraine headaches have not yet been completely deciphered and, thus, pose an additional challenge for preclinical research in the absence of any direct experimental marker. Migraine provocation experiments in humans use a head-score to evaluate migraine, as articulated by the volunteer, which cannot be applied to laboratory animals. Therefore, basic research focuses on different symptoms and putative mechanisms, one at a time or in combination, to validate the hypotheses. Studies in several species, utilizing different preclinical approaches, have significantly contributed to the two antimigraine principles in therapeutics, namely: 5-HT(1B/1D) receptor agonists (known as triptans) and CGRP receptor antagonists (known as gepants). This review will analyze the preclinical experimental models currently known for the development of these therapeutic principles, which are mainly based on the vascular and/or neurogenic theories of migraine pathogenesis. These include models based on the involvement of cranial vasodilatation and/or the trigeminovascular system in migraine. Clearly, the preclinical strategies should involve both approaches, while incorporating the newer ideas/techniques in order to get better insights into migraine pathophysiology.

Calcitonin gene-related peptide (CGRP) receptor antagonists in the treatment of migraine

Based on preclinical and clinical studies, the neuropeptide calcitonin gene-related peptide (CGRP) is proposed to play a central role in the underlying pathology of migraine. CGRP and its receptor are widely expressed in both the peripheral and central nervous systems by multiple cell types involved in the regulation of inflammatory and nociceptive responses. Peripheral release of CGRP from trigeminal nerve fibres within the dura and from the cell body of trigeminal ganglion neurons is likely to contribute to peripheral sensitization of trigeminal nociceptors. Similarly, the release of CGRP within the trigeminal nucleus caudalis can facilitate activation of nociceptive second-order neurons and glial cells. Thus, CGRP is involved in the development and maintenance of persistent pain, central sensitization and allodynia, events characteristic of migraine pathology. In contrast, CGRP release within the brain is likely to function in an anti-nociceptive capacity. Given the role of CGRP in migraine pathology, the potential of CGRP receptor antagonists in the treatment of migraine has been investigated. Towards this end, the non-peptide CGRP receptor antagonists olcegepant and telcagepant have been shown to be effective in the acute treatment of migraine. While telcagepant is being pursued as a frontline abortive migraine drug in a phase III clinical trial, an oral formulation of a novel CGRP receptor antagonist, BI 44370, is currently in phase II clinical trials. Encouragingly, data from clinical studies on these compounds have clearly demonstrated the potential therapeutic benefit of this class of drugs and support the future development of CGRP receptor antagonists to treat migraine and possibly other types of chronic pain.

Refolding and characterization of a soluble ectodomain complex of the calcitonin gene-related peptide receptor

The calcitonin gene-related peptide (CGRP) receptor is a heterodimer of two membrane proteins: calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1). CLR is a class B G-protein-coupled receptor (GPCR), possessing a characteristic large amino-terminal extracellular domain (ECD) important for ligand recognition and binding. Dimerization of CLR with RAMP1 provides specificity for CGRP versus related agonists. Here we report the expression, purification, and refolding of a soluble form of the CGRP receptor comprising a heterodimer of the CLR and RAMP1 ECDs. The extracellular protein domains corresponding to residues 23-133 of CLR and residues 26-117 of RAMP1 were shown to be sufficient for formation of a stable, monodisperse complex. The binding affinity of the purified ECD complex for the CGRP peptide was significantly lower than that of the native receptor (IC(50) of 12 microM for the purified ECD complex vs 233 pM for membrane-bound CGRP receptor), indicating that other regions of CLR and/or RAMP1 are important for peptide agonist binding. However, high-affinity binding to known potent and specific nonpeptide antagonists of the CGRP receptor, including olcegepant and telcagepant (K(D) < 0.02 muM), as well as N-terminally truncated peptides and peptide analogues (140 nM to 1.62 microM) was observed.

Eletriptan

Migraine is a multifactorial chronic central nervous system disorder, characterized by recurrent disabling attacks of moderate-to-severe headache. Symptomatic acute treatment of migraine should provide rapid and effective relief of the headache pain. The introduction of the 5-HT(1B/1D) receptor agonists (triptans) expanded the armamentarium for acute migraine pain treatment. Eletriptan is a second-generation triptan with favorable bioavailability and half-life, a high affinity for 5-HT(1B/1D) receptors and selectivity for cranial arteries. Eletriptan (40 and 80 mg) has been shown to be effective as early as 30 min after administration and well tolerated when compared to placebo. In comparative clinical trials, eletriptan 40 and 80 mg were superior or equivalent to other triptans and have shown a very high safety and tolerability profile across the studies performed. Eletriptan showed the most favorable cost-effectiveness profile when compared with other agents in its class.

New drugs for migraine

After the triptans, a calcitonin gene-related peptide blocker (telcagepant) is the first acute medicine that has been developed primarily for treatment of acute migraine. Otherwise, the new drugs have been developed first for other purposes, like anticonvulsants, antihypertensives and antidepressants used for migraine prophylaxis. For acute attacks, a new way to administer a traditional drug like dihydroergotamine is under way, and documentation of efficacy in migraine has been gained for some commonly used painkillers and anti-inflammatory drugs, and for some herbal extracts. Based on insights into the basic pathophysiological mechanisms of the disorder, some drugs have been developed which seem promising in early phase II studies (NOS inhibitors and 5HT1F-receptor agonists). In the future, development and enhancements of existing medicines must be accompanied by increased efforts to develop truly new migraine drugs based on knowledge of the pathophysiology if one wishes to reduce substantially the great burden migraine poses on patients and society.

Future drugs for migraine

Migraine is a complex, neurovascular disorder in which genetic and environmental factors interact. At present, frontline therapies in the acute treatment of migraine include the use of non-steroidal anti-inflammatory drugs and triptans. Evidence indicates that calcitonin gene-related peptide (CGRP) plays a fundamental role in the mechanism of migraine. CGRP is a strong vasodilatatory neuropeptide that is released from activated trigeminal sensory nerves. The development of CGRP antagonists has also been driven by the fact that triptans are vasoconstrictive and cannot be safely used in patients with cardiovascular risk factors. Olcegepant (BIBN4096) is the first CGRP antagonist for the treatment of migraine that has been tested in clinical trials, but because of its poor oral bioavailability, only the intravenous formulation has been tested. The first oral non-peptide CGRP antagonist, telcagepant, has been shown recently to be highly effective in the treatment of migraine attacks. This development can be considered as the most important pharmacological breakthrough for migraine treatment since the introduction of sumatriptan in the early 1990s. These results are also of importance, since they support an interesting pathophysiological hypothesis of migraine. The pipeline of future compounds for the treatment of acute migraine headaches include TPRV1 antagonists, prostaglandin E receptor 4 (EP(4)) receptor antagonists, serotonin 5HT1(F) receptor agonists and nitric oxide synthase inhibitors. The immediate future of a preventative treatment for migraine headaches is well represented by botulinum toxin type-A, glutamate NMDA receptor antagonists, gap-junction blocker tonabersat and an angiotensin type 1 blocker candesartan.

Effect of central serotonin depletion on 5-HT receptor-mediated vasomotor responses in the middle meningeal artery of anaesthetized rats

1 It has been hypothesized that craniovascular 5-HT receptors mediating dilatation of cranial vessels undergo sensitization on decreased serotonergic transmission in migraine. This study analysed the effect of chemical lesion of the 5-HT system in the brain with 5,7-dihydroxytryptamine (5,7-DHT) on 5-HT receptor-mediated dilator responses to 5-carboxamidotryptamine (5-CT) in the middle meningeal artery of anaesthetized rats. 5-CT has recently been shown to elicit dilator responses in this cranial vessel via 5-HT(7) receptors and, to a much lesser extent, 5-HT(1B/1D) receptors. 2 Pretreatment with 5,7-DHT produced a drastic and selective decrease of 5-HT levels in the brain (78 +/- 6% and 94 +/- 2% in dorsal raphe and hypothalamic paraventricular nuclei, respectively) compared with controls (1% ascorbic acid). 3 Topical application of 5-CT (1-1000 microm) to exposed dura mater encephali produced concentration-dependent decreases in diastolic blood pressure and dilator responses in the middle meningeal artery that were similar in vehicle- and 5,7-DHT-pretreaed animals. 4 Hypotensive and meningeal dilator responses to 5-CT were unaltered by the 5-HT(1B/1D) receptor antagonist, GR-127935 (1 mg kg(-1), i.v.), but were strongly inhibited by the 5-HT(7) receptor antagonist, SB-269970 (1 mg kg(-1), i.v.), with similar efficacy, in both groups of animals. Treatment with GR-127935 + SB-269970 (1 mg kg(-1), i.v. each), produced a stronger inhibitory effect than individual treatments on hypotensive but not on meningeal responses to 5-CT. Meningeal 5-HT(7) receptor-mediated responses (i.e. in GR-127935-pretreated animals) were unchanged by 5,7-DHT pretreatment. 5 Results suggest that the sensitivity of craniovascular 5-HT(7) receptors mediating dilatation is unaffected by a decrease of 5-HT levels in the brain. A neuronal involvement of 5-HT in migraine seems more likely, therefore.

Migraine pain: reflections against vasodilatation

The original Wolff’s vascular theory of migraine was supported by the discovery of a class of drugs, the triptans, developed as a selective cephalic vasoconstrictor agents. Even in the neurovascular hypothesis of Moskowitz, that is the neurogenic inflammation of meningeal vessels provoked by peptides released from trigeminal sensory neurons, the vasodilatation provoked by calcitonin gene-related peptide (CGRP) is considered today much more important than oedema. The role of cephalic vasodilatation as a cause of migraine pain was recently sustained by studies showing the therapeutic effect of CGRP receptor antagonists. We discuss the evidence against vasodilatation as migraine pain generator and some findings which we suggest in support of a central (brain) origin of pain.

Sumatriptan does not change calcitonin gene-related peptide in the cephalic and extracephalic circulation in healthy volunteers

Triptans are effective and well tolerated in acute migraine management but their exact mechanism of action is still debated. Triptans might exert their antimigraine effect by reducing the levels of circulating calcitonin gene-related peptide (CGRP). To examine this question, we examined whether sumatriptan modulate the baseline CGRP levels in vivo, under conditions without trigeminovascular system activation. We sampled blood from the internal and external jugular, the cubital veins, and the radial artery before and after administration of subcutaneous sumatriptan in 16 healthy volunteers. Repeated-measure ANOVA showed no interaction between catheter and time of sampling and thus no significant difference in CGRP between the four catheters (P=0.75). CGRP did not change over time in the four compartments (P>0.05). The relative changes in CGRP between baseline and maximal sumatriptan concentration did not differ between the four vascular compartments (P=0.49). It was found that Sumatriptan did not change the levels of circulating CGRP in the intra or extracerebral circulation in healthy volunteers. This speaks against a direct CGRP-reducing effect of sumatriptan in vivo in humans when the trigemino vascular system is not activated.