5-HT1B receptor polymorphism and clinical response to sumatriptan

The impact of genetic factors on the response to migraine therapy

Migraine is a multidimensional disease affecting a large portion of the human population presenting with a variety of symptoms. In the era of personalized medicine, successful migraine treatment presents a challenge, as several studies have shown the impact of a patient's genetic profile on therapy response. However, with the emergence of contemporary treatment options, there is promise for improved outcomes. A literature search was conducted in PubMed and Scopus, in order to obtain studies investigating the impact of genetic factors on migraine therapy outcome. Overall, 23 studies were included in the current review, exhibiting diversity in the treatments used and the genetic variants investigated. Divergent genes were assessed for each category of migraine treatment. Several genetic factors were identified to contribute to the heterogeneous response to treatment. SNPs related to pharmacodynamic receptors, pharmacogenetics and migraine susceptibility loci were the most investigated variants, revealing some interesting significant results. To date, various associations have been recorded correlating the impact of genetic factors on migraine treatment responses. More extensive research needs to take place with the aim of shedding light on the labyrinthine effects of genetic variations on migraine treatment, and, consequently, these findings can promptly affect migraine treatment and improve migraine patients' life quality in the vision of precise medicine.

Breaking the cycle: unraveling the diagnostic, pathophysiological and treatment challenges of refractory migraine

Background

Refractory migraine is a poorly described complication of migraine in which migraine has chronified and become resistant to standard treatments. The true prevalence is unknown, but medication resistance is common in headache clinic patient populations. Given the lack of response to treatment, this patient population is extremely difficult to treat with limited guidance in the literature.

Objective

To review the diagnostic, pathophysiological, and management challenges in the refractory migraine population.

Discussion

There are no accepted, or even ICHD-3 appendix, diagnostic criteria for refractory migraine though several proposed criteria exist. Current proposed criteria often have low bars for refractoriness while also not meeting the needs of pediatrics, lower socioeconomic status, and developing nations. Pathophysiology is unknown but can be hypothesized as a persistent "on" state as a progression from chronic migraine with increasing central sensitization, but there may be heterogeneity in the underlying pathophysiology. No guidelines exist for treatment of refractory migraine; once all guideline-based treatments are tried, treatment consists of n-of-1 treatment trials paired with non-pharmacologic management.

Conclusion

Refractory migraine is poorly described diagnostically, its pathophysiology can only be guessed at by extension of chronic migraine, and treatment is more the art than science of medicine. Navigating care of this refractory population will require multidisciplinary care models and an emphasis on future research to answer these unknowns.

European Headache Federation (EHF) consensus on the definition of effective treatment of a migraine attack and of triptan failure

Background

Triptans are migraine-specific acute treatments. A well-accepted definition of triptan failure is needed in clinical practice and for research. The primary aim of the present Consensus was to provide a definition of triptan failure. To develop this definition, we deemed necessary to develop as first a consensus definition of effective treatment of an acute migraine attack and of triptan-responder.

Main body

The Consensus process included a preliminary literature review, a Delphi round and a subsequent open discussion. According to the Consensus Panel, effective treatment of a migraine attack is to be defined on patient well-being featured by a) improvement of headache, b) relief of non-pain symptoms and c) absence of adverse events. An attack is considered effectively treated if patient’s well-being, as defined above, is restored within 2 hours and for at least 24 hours. An individual with migraine is considered as triptan-responder when the given triptan leads to effective acute attack treatment in at least three out of four migraine attacks. On the other hand, an individual with migraine is considered triptan non-responder in the presence of failure of a single triptan (not matching the definition of triptan-responder). The Consensus Panel defined an individual with migraine as triptan-resistant in the presence of failure of at least 2 triptans; triptan refractory, in the presence of failure to at least 3 triptans, including subcutaneous formulation; triptan ineligibile in the presence of an acknowledged contraindication to triptan use, as specified in the summary of product characteristics.

Conclusions

The novel definitions can be useful in clinical practice for the assessment of acute attack treatments patients with migraine. They may be helpful in identifying people not responding to triptans and in need for novel acute migraine treatments. The definitions will also be of help in standardizing research on migraine acute care.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01502-z.

Characterization of binding, functional activity, and contractile responses of the selective 5-HT1F receptor agonist lasmiditan

BACKGROUND AND PURPOSE

Triptans are 5-HT1B/1D receptor agonists (that also display 5-HT1F receptor affinity) with antimigraine action, contraindicated in patients with coronary artery disease due to their vasoconstrictor properties. Conversely, lasmiditan was developed as an antimigraine 5-HT1F receptor agonist. To assess the selectivity and cardiovascular effects of lasmiditan, we investigated the binding, functional activity, and in vitro/in vivo vascular effects of lasmiditan and compared it to sumatriptan.

EXPERIMENTAL APPROACH

Binding and second messenger activity assays of lasmiditan and other serotoninergic agonists were performed for human 5-HT1A , 5-HT1B , 5-HT1D , 5-ht1E , 5-HT1F , 5-HT2A , 5-HT2B , and 5-HT7 receptors, and the results were correlated with their potency to constrict isolated human coronary arteries (HCAs). Furthermore, concentration-response curves to lasmiditan and sumatriptan were performed in proximal and distal HCA, internal mammary, and middle meningeal arteries. Finally, anaesthetized female beagle dogs received i.v. infusions of lasmiditan or sumatriptan in escalating cumulative doses, and carotid and coronary artery diameters were measured.

KEY RESULTS

Lasmiditan showed high selectivity for 5-HT1F receptors. Moreover, the functional potency of the analysed compounds to inhibit cAMP increase through 5-HT1B receptor activation positively correlated with their potency to contract HCA. In isolated human arteries, sumatriptan, but not lasmiditan, induced contractions. Likewise, in vivo, sumatriptan decreased coronary and carotid artery diameters at clinically relevant doses, while lasmiditan was devoid of vasoconstrictor activity at all doses tested.

CONCLUSIONS AND IMPLICATIONS

Lasmiditan is a selective 5-HT1F receptor agonist devoid of vasoconstrictor activity. This may represent a cardiovascular safety advantage when compared to the triptans.

Using a Genetic Risk Score Approach to Predict Headache Response to Triptans in Migraine Without Aura

A large meta-analysis of genome-wide association studies has recently identified a number of risk loci for migraine without aura (MwoA). In this study, we tested the hypothesis that a genetic risk score based on single-nucleotide polymorphisms (SNPs), previously reported to be associated with MwoA at genome-wide significance, may influence headache response to triptans in patients with migraine without aura. Genotyping of rs9349379, rs2078371, rs6478241, rs11172113, rs1024905, and rs6724624 was conducted with a real-time PCR allelic discrimination assay in 172 MwoA patients, of whom 36.6% were inconsistent responders to triptans. Each genetic risk score model was constructed as an unweighted score, calculated by adding the number of risk alleles for MwoA across each SNP at selected loci. The association with headache response to triptans was evaluated by logistic regression analysis adjusted for triptan, and the P values were corrected for the false discovery rate. The genetic risk score including susceptibility risk alleles at TRPM8 rs6724624 and FGF6 rs1024905 was found to be inversely associated with risk of inconsistent response to triptans (OR, 0.62; 95%CI, 0.43-0.89; false discovery rate q value, 0.045). In addition, adding this genetic risk score to the triptan-adjusted logistic regression model significantly improved (P = .037) the discrimination accuracy, from 0.57 (95%CI, 0.50-0.65) to 0.64 (95%CI, 0.57-0.72). A modest but significant effect on risk of inconsistent response to triptans was identified for a genetic risk score model composed of 2 known risk alleles for MwoA, suggesting its potential utility in predicting headache response to triptan therapy.

Is selective 5-HT1F receptor agonism an entity apart from that of the triptans in antimigraine therapy?

Migraine is a neurovascular disorder that involves activation of the trigeminovascular system and cranial vasodilation mediated by release of calcitonin gene-related peptide (CGRP). The gold standard for acute migraine treatment are the triptans, 5-HT1B/1D/(1F) receptor agonists. Their actions are thought to be mediated through activation of: (i) 5-HT1B receptors in cranial blood vessels with subsequent cranial vasoconstriction; (ii) prejunctional 5-HT1D receptors on trigeminal fibers that inhibit trigeminal CGRP release; and (iii) 5-HT1B/1D/1F receptors in central nervous system involved in (anti)nociceptive modulation. Unfortunately, coronary arteries also express 5-HT1B receptors whose activation would produce coronary vasoconstriction; hence, triptans are contraindicated in patients with cardiovascular disease. In addition, since migraineurs have an increased cardiovascular risk, it is important to develop antimigraine drugs devoid of vascular (side) effects. Ditans, here defined as selective 5-HT1F receptor agonists, were developed on the basis that most of the triptans activate trigeminal 5-HT1F receptors, which may explain part of the triptans' antimigraine action. Amongst the ditans, lasmiditan: (i) fails to constrict human coronary arteries; and (ii) is effective for the acute treatment of migraine in preliminary Phase III clinical trials. Admittedly, the exact site of action is still unknown, but lasmiditan possess a high lipophilicity, which suggests a direct action on the central descending antinociceptive pathways. Furthermore, since 5-HT1F receptors are located on trigeminal fibers, they could modulate CGRP release. This review will be particularly focussed on the similarities and differences between the triptans and the ditans, their proposed sites of action, side effects and their cardiovascular risk profile.

Serotonin and Migraine: Biology and Clinical Implications

Migraine is the most frequent neurological disorder in the adult population worldwide, affecting up to 12% of the general population and more frequent in women (~25%). It has a high impact on our society due to its disabling nature and, therein, reduced quality of life and increased absenteeism from work. Headache is the primary clinical manifestation and it has been associated with ‘a hereditary or predisposed sensitivity of neurovascular reactions to certain stimuli or to cyclic changes in the central nervous system’ (1). Amongst the many neurotransmitters in the brain, the serotonergic (serotonin, 5-HT) system from the brainstem raphe nucleus has been most convincingly implicated in migraine pathophysiology. The documented changes in 5-HT metabolism and in the processing of central 5-HT-mediated responses during and in between migraine attacks have led to the suggestion that migraine is a consequence of a central neurochemical imbalance that involves a low serotonergic disposition. Although the exact cascade of events that link abnormal serotonergic neurotransmission to the manifestation of head pain and the accompanying symptoms has yet to be fully understood, recent evidence suggests that a low 5-HT state facilitates activation of the trigeminovascular nociceptive pathway, as induced by cortical spreading depression. In this short review, we present and discuss the original and most recent findings that support a role for altered serotonergic neurotransmission in the manifestation of migraine headache.

Pharmacogenomics of episodic migraine: time has come for a step forward

Migraine is characterized by heterogeneous behavior in response to drugs. Many resources have been invested in attempting to unravel the genetic basis of migraine, while the role of genetics in responses to currently available drugs has received less attention. We performed a systematic literature search identifying original articles pertaining to pharmacogenomics of episodic migraine. Few primary studies on the pharmacogenomics of symptomatic and preventive medication in episodic migraine were found. The number of patients studied in the individual articles ranged from 40 up to 130. There was a strong heterogeneity among these studies. We believe that pharmacogenomics studies, if properly designed, could contribute towards optimizing the treatment and reducing the burden of migraine, in turn helping patients and optimizing resources. Our knowledge on the pharmacogenomics of migraine is growing too slowly, and concerted measures should be undertaken to speed up the process.

Sumatriptan fast-disintegrating/rapid-release tablets in the acute treatment of migraine

Sumatriptan is the first serotonin (5-hydroxytryptamine [5-HT](1B/1D)) receptor agonist specifically designed for the acute treatment of migraine. A new sumatriptan fast disintegrating/rapid release tablet (FDT/RRT) using RT technology has been developed to enhance tablet disintegration and dispersion in the stomach with the intention of speeding absorption and onset of effect, hence mitigating the effects on the gastrointestinal dysmotility that typically accompanies the attack. Sumatriptan FDT/RRT is bioequivalent to conventional tablets, although it provides slightly faster absorption during early post-dose interval. Clinical trials indicate that sumatriptan FDT/RRT is rapidly effective in terms of freedom from pain and return to normal activities, both with early and late treatment. The drug is well tolerated. In an oral formulation, which is the patients' preferred dosing route, sumatriptan FDT/RRT may therefore constitute an advance in the management of acute migraine attacks.

Predictive index for the onset of medication overuse headache in migraine patients

Migraine patients are particularly prone to develop medication overuse headache (MOH). However, the risk factors for the transformation of migraine to MOH are still not clear. We investigated gene polymorphisms, personality traits, and characteristics of headache and lifestyle in 47 migraine patients (aged 36.4 ± 10.3) and 22 MOH patients (aged 39.6 ± 9.9) who progressed from migraine and made a scoring system for a predictive index (PI) of the onset of MOH in patients with migraine. By multivariate logistic stepwise regression analysis, type of migraine, regular and sufficient dietary intake, and methylenetetrahydrofolate reductase (MTHFR) C677T (rs1801133) and dopamine D2 receptor (DRD2) C939T (rs6275) polymorphisms were selected as significant factors that contribute independently to the development from migraine to MOH (P < 0.05). The regression coefficients (β) of these four selected factors were approximated and scored. The PI score in MOH patients (7.32 ± 1.60) was significantly higher than that in migraine patients (4.62 ± 1.83, P < 0.001). The proposed scoring system should in the future be the object of larger studies to confirm its validity.

Genetic association of 5-HT1A and 5-HT1B gene polymorphisms with migraine in a Turkish population

Migraine, a very common headache disorder, is regarded as a polygenic disease and serotonergic pathways appear to play a major role in its pathogenesis. The present study was designed to explore the associations of polymorphisms of 5-hydroxytryptamine (serotonin) receptor 1A (5-HT1A) and 5-hydroxytryptamine receptor 1B (5-HT1B) genes in Turkish migraine patients. 5-HT1A C-1019G (rs6295) promoter and 5-HT1B G861C (rs6296) exon polymorphisms in 203 migraine patients and 202 healthy subjects were analyzed by using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. Allele and genotype frequencies were not significantly different between migraine patients and healthy subjects for both the 5-HT1A C-1019G promoter and 5-HT1B G861C exon polymorphisms. Our data do not support the hypothesis that 5-HT1A C-1019G and 5-HT1B G861C polymorphisms have effects on migraine.

Pharmacogenomics in neurology: current state and future steps

In neurology, as in any other clinical specialty, there is a need to develop treatment strategies that allow stratification of therapies to optimize efficacy and minimize toxicity. Pharmacogenomics is one such method for therapy optimization: it aims to elucidate the relationship between human genome sequence variation and differential drug responses. Approaches have focused on candidate approaches investigating absorption-, distribution-, metabolism, and elimination (ADME)-related genes (pharmacokinetic pathways), and potential drug targets (pharmacodynamic pathways). To date, however, only few genetic variants have been incorporated into clinical algorithms. Unfortunately, a large number of studies have thrown up contradictory results due to a number of deficiencies, including small sample sizes, inadequate phenotyping, and genotyping strategies. Thus, there still exists an urgent need to establish biomarkers that could help to select for patients with an optimal benefit to risk relationship. Here we review recent advances, and limitations, in pharmacogenomics for agents used in neuroimmunology, neurodegenerative diseases, ischemic stroke, epilepsy, and primary headaches. Further work is still required in all of these areas, which really needs to progress on several fronts, including better standardized phenotyping, appropriate sample sizes through multicenter collaborations and judicious use of new technological advances such as genome-wide approaches, next generation sequencing and systems biology. In time, this is likely to lead to improvements in the benefit-harm balance of neurological therapies, cost efficiency, and identification of new drugs.

Genetics of cluster headache

Cluster headache (CH) is a rare, excruciating primary headache disorder. A genetic basis has been suggested by family and twin studies, but the mode of transmission seems to vary and the amount of heritability is unclear. The number of genetic association studies investigating variants implicated in the pathophysiology of CH is limited. The HCRTR2 1246G > A and the ADH4 925A > G polymorphisms have been associated with CH. The former has been confirmed and may affect the hypothalamic hypocretin system. However, it only appears to account for a part of the genetic susceptibility for CH, and additional genetic and environmental factors are likely implicated. Pharmacogenetic studies have suggested that the GNB3 825C > T polymorphism may modify treatment response to triptans among CH patients by altering the signal transduction cascade via G protein-coupled receptors. Genetic studies in CH are notoriously difficult due to the complex nature of the disorder and the low prevalence of CH.

Refractory migraine and chronic migraine: pathophysiological mechanisms

Despite increased understanding of primary headaches and their treatment, the underlying causes of refractory migraine remain unknown. This note considers potential genetic, structural, functional and pharmacological factors that could contribute to this relatively intractable condition. Further understanding of refractory migraine will require the use of medical imaging technologies, clinical experimental medicine studies on novel pharmacological agents and astute observations in clinical practice to direct potential novel therapeutic approaches.

Migraine genetics

Migraine with aura (MA) and migraine without aura (MO) are primary headaches prevalent in the general population that carry a substantial familial liability. Based on the model of migraine as a complex disease, a multifactorial type of inheritance has been suggested, but familial hemiplegic migraine (FHM), classified as a subtype of MA, shows an autosomal dominant transmission pattern and is due to mutations in three genes encoding for neural channel subunits. These FHM mutations, however, account for a minority of the FHM families and are not usually found in sporadic HM or in the typical migraines MA/MO. This implies that the genetic predisposition to the typical migraines may be different and that FHM could be better classified as a type of syndromic migraine rather than a MA subtype. Linkage and genome-wide scans have disclosed several chromosomal liability loci in selected families with MA/MO. It is likely that typical migraine genes will be discovered in the future. Epigenetic mechanisms, especially those acting in the early stages of neural development, are here proposed to be involved in the genetics of the typical migraines, especially if the typical migraines are modeled as evolutionarily conserved behaviors (sickness behavior) enacted out of a genetic repertoire.

Pathways to the Best Fit of Triptans for Migraine Patients

Variability in drug response is a major barrier to the successful treatment of migraine, and most treatments are only optimal in a subset of patients. Although triptans provide the best therapeutic option for the treatment of acute migraine, it has not previously been possible to predict how well patients will respond to a specific triptan or whether they will experience unpleasant adverse events. Hence, it has been difficult for physicians to match individual patients with the most suitable agent to treat their migraine pain. Intrapatient variability has been associated with polymorphisms in genes encoding drug-metabolizing enzymes, drug transporters and drug targets. Pharmacogenetics provides the possibility of tailoring the therapeutic approach to individual patients, in order to maximize treatment efficacy while minimizing the potential for unwanted side-effects. This review demonstrates how almotriptan may overcome genetically determined responses by utilizing diverse metabolic pathways to provide therapeutic benefit to many migraineurs.

Refractory migraine and chronic migraine: pathophysiological mechanisms

Migraine is a complex disorder of the brain whose mechanisms are only now being unravelled. It is common, disabling, and economically costly. Brain imaging has suggested a role for the brainstem. While the disorder is almost certainly inherited, the degree to which this contributes to a treatment refractory state is not clear. Indeed, no specific structural or pharmacological explanation can be seen from the data as they have been generated. It is clear that patients with more frequent headache are very likely to go on to even more frequent headache, but again these data are complex. A challenge going forward is to establish the biology of these very challenging patients who undoubtedly have substantial disability.

The primary headaches: genetics, epigenetics and a behavioural genetic model

The primary headaches, migraine with (MA) and without aura (MO) and cluster headache, all carry a substantial genetic liability. Familial hemiplegic migraine (FHM), an autosomal dominant mendelian disorder classified as a subtype of MA, is due to mutations in genes encoding neural channel subunits. MA/MO are considered multifactorial genetic disorders, and FHM has been proposed as a model for migraine aetiology. However, a review of the genetic studies suggests that the FHM genes are not involved in the typical migraines and that FHM should be considered as a syndromic migraine rather than a subtype of MA. Adopting the concept of syndromic migraine could be useful in understanding migraine pathogenesis. We hypothesise that epigenetic mechanisms play an important role in headache pathogenesis. A behavioural model is proposed, whereby the primary headaches are construed as behaviours, not symptoms, evolutionarily conserved for their adaptive value and engendered out of a genetic repertoire by a network of pattern generators present in the brain and signalling homeostatic imbalance. This behavioural model could be incorporated into migraine genetic research.

Molecular biology of 5-HT receptors

Serotonin (5-hydroxytryptamine; 5-HT) is a monoamine neurotransmitter whose effects are mediated by at least 13 distinct G protein-coupled receptors (GPCRs) of the type A family which includes the monoamine receptors and a combination of ligand-gated ion channels (5-HT3) of the Cys loop family which constitutes heteropentamers. 5-HT receptors are currently divided into seven classes (5-HT1 to 5-HT7), based on structural, transductional and operational features. While this degree of physical diversity clearly underscores the physiological importance of serotonin, evidence for an even greater degree of operational diversity is supported by the existence of a great number of splice and editing variants for several 5-HT receptors, their possible modulation by accessory proteins and chaperones, as well as their potential to form homo or heteromers both at the GPCR and at the ligand-gated channel level.

Pharmacogenetics of migraine: genetic variants and their potential role in migraine therapy

Migraine is a paroxysmal neurological disorder affecting up to 6% of males and 18% of females in the general population, and has been demonstrated to have a strong, but complex, genetic component. Genetic investigation of migraine provides hope that new targets for medications and individual specific therapy will be developed. The identification of polymorphisms or genetic biomarkers for disease susceptibility and treatment should aid in providing a better understanding of migraine pathology and, consequently, more appropriate and efficient treatment for migraineurs. In this review, we will discuss results investigating genetic biomarkers for migraine and their potential role in future therapy planning.

Pharmacogenomics and migraine: possible implications

Pharmacogenomics is the science about how inherited factors influence the effects of drugs. Drug response is always a result of mutually interacting genes with important modifications from environmental and constitutional factors. Based on the genetic variability of pharmacokinetic and in some cases pharmacodynamic variability we mention possible implications for the acute and preventive treatment of migraine. Pharmacogenomics will most likely in the future be one part of our therapeutic armamentarium and will provide a stronger scientific basis for optimizing drug therapy on the basis of each patient’s genetic constitution.

Genetics of migraine and pharmacogenomics: some considerations

Migraine is a complex disorder caused by a combination of genetic and environmental factors. Although family and twin studies show that there is a genetic component in migraine, no genes predisposing to common forms of the disorder, migraine with and without aura, have been identified. Patients with migraine respond differently to a given drug administered. The efficacy of therapy and the occurrence of adverse drug response are a consequence of individual variability. Genetic profiling of predisposition to migraine should facilitate the development of more effective diagnostic and therapeutic applications. The development of International Hap Map project could provide a powerful tool for identification of the candidate genes in this complex disease and pharmacogenomics research could be the promise for individualized treatments and prevention of adverse drug response.

5-hydroxytryptamine1B receptor and triptan response in migraine, lack of association with common polymorphisms

Triptans mediate vasoconstriction of meningeal vessels via stimulation of vascular 5-hydroxytryptamine (5-HT)(1B) receptors. These drugs are recommended for acute treatment in patients with moderate-to-severe migraine attacks and in those patients with mild-to-moderate headache that are not controlled adequately by other agents. Yet, approximately 25% of all migraine users and 40% of all attacks do not respond to triptan treatment. Among the hypothesis to explain this is the possibility that genetic single nucleotide polymorphisms that alter the receptor, for example changing the transcriptional rate and therefore the amount of target protein might change the clinical response to these drugs. In the present contribution, we therefore decided to evaluate whether single nucleotide polymorphisms on the 5-HT(1B) gene might contribute to inter-individual variability in clinical responses to triptans. Two polymorphisms in the promoter region of the 5-HT(1B) receptor (T-261G and A-161T) and the synonymous variation G861C in the coding region were genotyped by restriction fragment length polymorphism in 105 migraine patients. In our sample population, 71% of patients responded to triptans. Allelic and diplotype frequencies were not significantly different between responders and non-responders. On the other hand, extrapolation of in vitro data on promoter activity would suggest that patients with higher copy number of receptors respond slightly better. Our data therefore do not support the involvement of 5-HT(1B) single nucleotide polymorphisms in mediating the inter-individual variability to triptans.

The phe-124-Cys and A-161T variants of the human 5-HT1B receptor gene are not major determinants of the clinical response to sumatriptan

BACKGROUND

The 5-HT(1B/1D) receptor agonist sumatriptan is highly effective in the treatment of migraine. However, some patients do not respond to sumatriptan or experience recurrence of the headache after initial relief. In addition, some patients report chest symptoms after the use of sumatriptan.

OBJECTIVE

To assess whether 2 genetic variants (F124C changing a phenylalanine for a cysteine and polymorphism A/T at nucleotide position -161 in the 5' regulatory region) of the 5-HT(1B) receptor play a major role in the therapeutic response to sumatriptan. The 5-HT(1B) receptor most likely mediates the therapeutic action and coronary side effects of sumatriptan, and both F124C and A-161T have relevant functional consequences on either the affinity of sumatriptan to bind to the 5-HT(1B) receptor or on receptor expression level itself, respectively.

METHOD

Genomic DNA of a relatively small but very well-characterized set of migraine patients with consistently good response to sumatriptan (n = 14), with no response (n = 12), with recurrence of the headache (n = 12), with chest symptoms (n = 13), and patients without chest symptoms (n = 27) was available for the genetic analyses and screened for the F124C variant and the A-161T polymorphism in the human 5-HT(1B) receptor gene.

RESULTS

F124C was not detected in any of the patients studied. In addition, we did not observe drastic changes in allele frequencies of the A-161T polymorphism that might hint to a causal relation with the therapeutic effect of sumatriptan.

CONCLUSION

We have not obtained any evidence that variants F124C and A-161T of the 5-HT(1B) receptor are major determinants in the clinical response to sumatriptan.

Association study between clinical response to rizatriptan and some candidate genes

The aim of this study was to test genetic differences in the clinical response to rizatriptan in patients affected by migraine without aura. These genetic differences could be explained by various genes, the HTR1B, encoding the 5-HT₁ receptor subtype, MAOA gene that encodes the monoamino-oxidase, the main metabolic enzyme of this triptan, SLC6A4 (gene encoding the serotonin transporter) and DRD₂ (gene encoding the D₂ receptor), both involved in the pathogenesis of migraine. Fifty unrelated patients affected by migraine without aura (IHS) were included. Patients were divided into two groups (responders and non-responders) according to clinical response. Thirty-one out of fifty patients responded to rizatriptan. A significant difference among the two groups was observed in both allele (p=0.02) and genotype distribution (p=0.03) of DRD2/NcoI. The significant association with the DRD2/NcoI polymorphism in responders suggested that the DRD2/NcoI C allele may be considered a susceptibility factor heralding a good response to rizatriptan.

Functional polymorphisms of the 5-HT1A and 5-HT1B receptor are associated with clinical symptoms in migraineurs

Migraine is regarded as a polygenic disease and serotonergic pathways appear to play a major role in its pathogenesis. In the present study, the role of the 5-HT1A and 5-HT1B receptors in migraine was evaluated. The human 5-HT1A receptor gene transcription is modulated by a functional C-1019G promoter polymorphism. The 5-HT1B receptor is the main effector of vasoconstriction in meningeal and cerebral arteries and its functional G861C promoter polymorphism was investigated. We report a positive association of the GG genotype of the 5-HT1A promoter polymorphism with avoidance of physical activity during a migraine attack in comparison to the CC genotype (p = 0.008). Moreover, a positive association of the CC genotype of the G861C polymorphism of the 5-HT1B receptor with the reported intensity of the headache attack on the visual analogue scale was observed (CC 8.3 +/- 1.5 vs. GG 6.9 +/- 1.8; p < 0.05). An association of either polymorphism with migraine with or without aura could not be found. For the first time, our results indicate a role of allelic variation of the 5-HT1A receptor in motion related discomfort in migraineurs and a role of the 5-HT1B receptor polymorphism in headache intensity.

The A218C polymorphism of tryptophan hydroxylase gene and migraine

OBJECTIVE

To determine the significance of the A218C polymorphism of the tryptophan hydroxylase (TPH) gene in migraine.

METHODS

Fifty-nine migraineurs and 62 healthy controls were included in the study, and polymerase chain reaction - restriction fragment length polymorphism assays were used to determine TPH A218C polymorphism.

RESULTS

There was no association between TPH gene polymorphism and gender, family history of migraine and epilepsy, or aura. There was no significant difference between the allele frequencies of both groups (p>0.05). A significant difference was found between the genotypes of the migraineurs and controls regarding the AA genotype. Homozygosity for the C allele or heterozygosity for the A or C was not associated with the occurrence of migraine (p>0.05), but homozygosity for the A allele was less frequent in the migraineurs (p=0.02).

CONCLUSION

Since it is unlikely that TPH polymorphism alters serotonin biosynthesis, its association with migraine may be attributed to linkage disequilibrium with a functional variant within the TPH gene or a nearby gene.

5-Hydroxytryptamine receptors in the human cardiovascular system

The human cardiovascular system is exposed to plasma 5-hydroxytryptamine (5-HT, serotonin), usually released from platelets. 5-HT can produce harmful acute and chronic effects. The acute cardiac effects of 5-HT consist of tachycardia (preceded on occasion by a brief reflex bradycardia), increased atrial contractility and production of atrial arrhythmias. Acute inotropic, lusitropic and arrhythmic effects of 5-HT on human ventricle become conspicuous after inhibition of phosphodiesterase (PDE) activity. Human cardiostimulation is mediated through 5-HT4 receptors. Atrial and ventricular PDE3 activity exerts a protective role against potentially harmful cardiostimulation. Chronic exposure to high levels of 5-HT (from metastatic carcinoid tumours), the anorectic drug fenfluramine and its metabolites, as well as the ecstasy drug 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA) are associated with proliferative disease and thickening of cardiac valves, mediated through 5-HT2B receptors. 5-HT2B receptors have an obligatory physiological role in murine cardiac embryology but whether this happens in humans requires research. Congenital heart block (CHB) is, on occasion, associated with autoantibodies against 5-HT4 receptors. Acute vascular constriction by 5-HT is usually shared by 5-HT1B and 5-HT2A receptors, except in intracranial arteries which constrict only through 5-HT1B receptors. Both 5-HT1B and 5-HT2A receptors can mediate coronary artery spasm but only 5-HT1B receptors appear involved in coronary spasm of patients treated with triptans or with Prinzmetal angina. 5-HT2A receptors constrict the portal venous system including oesophageal collaterals in cirrhosis. Chronic exposure to 5-HT can contribute to pulmonary hypertension through activation of constrictor 5-HT1B receptors and proliferative 5-HT2B receptors, and possibly through direct intracellular effects.

Migraine: new treatment options from molecular biology

Migraine is a common, disabling, multifactorial, episodic neurovascular disorder of largely unknown etiology. The disease is typically characterized by recurrent attacks of headaches and associated autonomic and neurologic symptoms. Current acute and prophylactic treatment options are far from optimal and in many cases, empirically chosen. Clearly, improved treatment is desperately needed. New drug targets may emerge from molecular research as the unravelling of the molecular basis of migraine should improve our understanding of the disease, notably why patients experience attacks so frequently. The first two migraine genes discovered in families with hemiplegic migraine encode ion transporters, emphasising that dysfunction of ion transport may be an important factor in migraine. Therefore, ion transporters can be considered as novel targets for the development of future antimigraine drugs. Molecular biologic research will increasingly become important in understanding the pathophysiology of migraine and in identifying potential molecular targets for novel treatments.

Coronary vasoconstrictor potential of triptans: a review of in vitro pharmacologic data

This article reviews the in vitro pharmacology of the triptans in human isolated coronary arteries. As expected, based on their similar pharmacologic profiles, the triptans cannot be easily differentiated with respect to effects at human isolated coronary arteries. Furthermore, the data show that at therapeutically relevant concentrations, triptans have little potential to cause clinically significant constriction of nondiseased coronary arteries. These data, considered in the context of clinical findings reviewed elsewhere in this supplement, support the conclusion that, while all triptans have the potential to produce small contractions of human isolated coronary arteries, their craniovascular selectivity, when used at therapeutic doses, renders them unlikely to cause serious adverse coronary events in patients with healthy coronary arteries.

Pharmacokinetic studies in migraine: What questions should physicians ask?

Migraine is a benign self-limiting condition for which the objective of treatment is to maximize the patient's quality of life by reducing the frequency of attacks and attenuating the pain and suffering of an individual attack as quickly and safely as possible. Evaluating the efficacy of antimigraine treatments, particularly those for the management of the acute attack, is relatively easy because acute symptomatic benefit is the criterion of success. For prophylaxis, therapeutic success generally is measured by relatively simple parameters such as attack frequency. Given that the clinical response to antimigraine therapies relatively is readily assessed by history, the role of more sophisticated investigations such as pharmacokinetic studies may not be immediately clear. This paper aims to provide clinicians with a guide to interpretation of such studies.

Familial Migraine With Aura: Association Study With 5-HT1B/1D, 5-HT2C, and hSERT Polymorphisms

BACKGROUND

The serotonergic system has a significant role in the pathophysiology and pharmacology of migraine.

OBJECTIVE

To study the association between the occurrence of migraine with aura and 5-HT(1B/1D) and 5-HT(2C) receptor gene and the human serotonin transporter (hSERT) gene polymorphisms in 18 unrelated families with multiple affected members.

METHOD

Two polymorphisms in the 5-HT(1B/1D) receptor gene and one polymorphism in the 5-HT(2C) receptor gene were studied by restriction fragment length polymorphism analysis. Allelic variation of the hSERT, with 9, 10, and 12 copies of a "repetitive element," was studied by polymerase chain reaction amplification of the variable number tandem repeat region.

RESULTS

Allelic distribution of 5-HT(1B/1D) and 5-HT(2C) receptor gene polymorphisms in affected patients did not differ in either of the control groups (unaffected relatives or unrelated healthy individuals). A trend toward a significant effect of the 12-repeat hSERT allele as a risk factor for migraine with aura versus unrelated controls was observed.

CONCLUSION

Our data do not support the involvement of 5-HT(1B/1D) and 5-HT(2C) receptor gene polymorphisms in migraine with aura, yet do suggest a possible role for a locus at or near the hSERT gene in the susceptibility to migraine with aura.

The genetics of migraine: implication for treatment approaches

Migraine is a paroxysmal neurological disorder affecting up to 12% of males and 24% of females in the general population, demonstrated to have a strong, but complex, genetic component. Genetic investigation of migraine bears great promise in providing new targets for drug development and optimization of individual specific therapy. Better, preferably prophylactic, treatment of migraine patients is desired because the presently used drugs are not effective in all patients, allow recurrence of the headache in a high percentage of patients and sometimes have severe adverse side effects. With the recent identification of the brain-specific P/Q-type calcium channel gene CACNA1A in the pathogenesis of migraine, the first step has been taken to identify primary biochemical pathways leading to migraine. Here, we summarize the current knowledge about the genetics of migraine and focus on the implication for treatment approaches.

Sumatriptan in migraine with unilateral cranial autonomic symptoms: an open study

OBJECTIVE

To investigate the response to sumatriptan in migraineurs with unilateral cranial autonomic symptoms such as lacrimation, eye redness, eyelid edema, nasal congestion, and rhinorrhea.

BACKGROUND

Given the potential large-scale recruitment of peripheral neurovascular 5-HT1B/1D receptors consequent to the activation of the trigeminal autonomic reflex in such patients, the presence of unilateral cranial autonomic symptoms may predict a positive response to sumatriptan.

METHODS

Seventy-two consecutive migraineurs with unilateral cranial autonomic symptoms were given sumatriptan 50-mg tablets to treat 1 migraine attack and were asked to record their clinical response to the drug at different time points. End points were pain-relief and pain-free response at 1 and 2 hours.

RESULTS

Pain relief was reported by 47 patients (65.3%) at 1 hour and by 59 (81.9%) at 2 hours. Pain-free response was reported by 22 patients (30.6%) at 1 hour and by 44 (61.1%) at 2 hours. Responsiveness to sumatriptan did not correlate with the type or number of unilateral cranial autonomic symptoms, demographic characteristics, prophylactic treatments, use of contraceptives, or concomitant tension-type headache.

CONCLUSIONS

Migraineurs with unilateral cranial autonomic symptoms seem to respond to sumatriptan better than other migraineurs. The presence of unilateral cranial autonomic symptoms may predict a positive response to the triptans.

Molecular Mechanisms of Migraine

Migraine is a common complex disorder that affects a large portion of the population and thus incurs a substantial economic burden on society. The disorder is characterized by recurrent headaches that are unilateral and usually accompanied by nausea, vomiting, photophobia, and phonophobia. The range of clinical characteristics is broad and there is evidence of comorbidity with other neurological diseases, complicating both the diagnosis and management of the disorder. Although the class of drugs known as the triptans (serotonin 5-HT(1B/1D) agonists) has been shown to be effective in treating a significant number of patients with migraine, treatment may in the future be further enhanced by identifying drugs that selectively target molecular mechanisms causing susceptibility to the disease.Genetically, migraine is a complex familial disorder in which the severity and susceptibility of individuals is most likely governed by several genes that may be different among families. Identification of the genomic variants involved in genetic predisposition to migraine should facilitate the development of more effective diagnostic and therapeutic applications. Genetic profiling, combined with our knowledge of therapeutic response to drugs, should enable the development of specific, individually-tailored treatment.

DNA variation and psychopharmacology of the human serotonin receptor 1B (HTR1B) gene

One of the neurotransmitter serotonin's receptors, HTR1B, is of interest for many neuropsychiatric traits, illnesses and treatments for multiple reasons, especially its tissue distribution, pharmacological profile and findings from mice lacking the receptor, along with reasons generally implicating serotonin. Eight mutation scans have uncovered sixteen polymorphisms in the coding sequence and surrounding 5'- and 3'-untranslated regions and much is now known of the distribution of these polymorphisms in various ethnic groups and their linkage disequilibrium relationships. Thus far, evidence exists that the uncommon missense T371G (Phe124Cys) and the common promoter region A-161T polymorphisms may exhibit functional effects and possibly that the common synonymous G861C (or more likely a variant in linkage disequilibrium with G861C) does as well. From the eighteen reported population-based case control studies of HTR1B to multiple disorders, several facts stand out. There exists preliminary evidence for association of G861C with i) antisocial alcoholism in the Finnish; ii) alcoholism in the presence of inactive aldehyde dehydrogenase 2 in the Japanese; iii) a history of suicide attempts in European-American personality disorder patients; and iv) minimum lifetime body mass index in Canadian bulimia nervosa patients. From the three reported family-based case control studies of HTR1B to various disorders, one provides preliminary evidence for association of G861C with obsessive compulsive disorder. Although many association studies have been completed, positive results should still be considered preliminary. As these preliminary reports are tested for replication with larger, more powerful samples, there should be increased clarity as to which findings remain robust; in some cases this will require the application of meta-analytic techniques.

Sumatriptan responsiveness and clinical, psychiatric and psychologic features in migraine patients

OBJECTIVE

To compare sumatriptan responders and nonresponders in a migraine population with regard to a number of clinical, psychiatric and psychologic features.

METHODS

Patients were drawn from a referral headache clinic population, and classified as responders or nonresponders. Clinical features were assessed by a written questionnaire. The lifetime prevalence of several psychiatric disorders was determined by the National Institute of Mental Health diagnostic interview schedule and personality factors were measured by the 16 Personality Factors (16PF) Questionnaire.

RESULTS

Nonresponders indicated less influence on their migraine by menstrual factors, had a higher lifetime prevalence of generalized anxiety, and showed 16PF scores indicating greater shyness, self-sufficiency and perfectionism. Nonresponders were also more imaginative and less socially outgoing.

CONCLUSION

Although they must be interpreted with caution due to small sample size and the multiple comparisons made, our results indicate that there may be differences between sumatriptan responders and nonresponders with regard to a number of clinical, psychiatric and psychologic factors. These results suggest that biological differences exist between the two patient groups which likely account for both the differences in their responses to sumatriptan and in the clinical features noted above.

Novel and previously reported single-nucleotide polymorphisms in the human 5-HT(1B) receptor gene: no association with cocaine or alcohol abuse or dependence

Evidence from animal self-administration and human genetics studies suggests that the serotonin(1B) (5-HT(1B)) receptor may be involved in modulating responses to cocaine or alcohol. We hypothesize that polymorphisms, including single-nucleotide polymorphisms (SNPs), in the human 5-HT(1B) receptor gene, may be associated with individual differences in vulnerability to cocaine or alcohol abuse or dependence. A total of 210 subjects were studied, including individuals with a primary diagnosis (DSM-IV criteria) of cocaine abuse or dependence, alcohol abuse or dependence, and controls with no history of previous or current illicit drug or alcohol abuse or dependence. Genomic DNA samples were isolated from each individual. For 157 of the subjects, polymerase chain reaction (PCR) was used to amplify the entire coding region of the 5-HT(1B) receptor gene as well as parts of the 5' and 3' untranslated regions. PCR products were sequenced in forward and reverse directions on an automated sequencer. Amplified DNA from an additional 53 subjects was sequenced in the 5' untranslated region to gain additional data on the frequency of one identified SNP. Seven polymorphisms were identified: one novel SNP in the 5' untranslated region (UTR) of the gene (A-161T); one SNP not reported in any published scientific communication (but found to be recorded in GenBank) in the 3' UTR (A1180G); two novel dinucleotide deletions at positions - 184/- 183 and - 182/- 181; and three previously identified SNPs (T-261G, C129T, G861C). Data were stratified by ethnicity and pooled Relative Risk was calculated for combined alcohol abuse and dependence cases and controls, and also for combined cocaine abuse and dependence cases and controls. No significant differences between cases and controls were found.

Association of the T102C polymorphism of 5-HT2A receptor gene with aura in migraine

OBJECTIVE

To find out the significance of the 5-HT2A receptor gene polymorphism in migraine.

STUDY DESIGN

A PCR study in which 61 migraineurs and 44 healthy controls were included.

METHODS

The T102C polymorphism of the 5-HT2A receptor gene was studied. The results of the migraineurs and controls were compared. The relationship between the gene polymorphism and aura was also assessed.

RESULTS

The representations of the 5-HT2A genotypes were similar in migraineurs and controls (p>0.05) as well as in the male and female migraineurs (p>0.05). The family history of migraine did not associate with 5-HT2A receptor gene polymorphism (p>0.05). There was a significant relationship between the presence of C/C genotype and migraine with aura (p=0.02) while C/T and T/T genotypes were over represented in the patients with migraine without aura (p<0.01).

CONCLUSION

The T102C polymorphism of the 5-HT2A receptor gene is not directly related to the increased risk of migraine. The associations between the genotypes of this gene and aura may suggest that 5-HT2A receptor gene polymorphism may be involved in determining the subtypes of or accompanying symptoms in the migraine disease.

Genetic diversity of the human serotonin receptor 1B (HTR1B) gene

We systematically and comprehensively investigated polymorphisms of the HTR1B gene as well as their linkage disequilibrium and ancestral relationships. We have detected the following polymorphisms in our sample via denaturing gradient gel electrophoresis, database comparisons, and/or previously published assays: G-511T, T-261G, -182INS/DEL-181, A-161T, C129T, T371G, T655C, C705T, G861C, A1099G, G1120A, and A1180G. The results of the intermarker analyses showed strong linkage disequilibrium between the C129T and the G861C polymorphisms and revealed four common haplotypes: ancestral (via chimpanzee comparisons), 129T/861C, -161T, and -182DEL-181. The results of association tests with schizophrenia were negative, although A-161T had a nominal P = 0.04 via ASPEX/sib_tdt. The expressed missense substitutions, Phe124Cys, Phe219Leu, Ile367Val, and Glu374Lys, could potentially affect ligand binding or interaction with G proteins and thus modify drug response in carriers of these variants. On average, the human cSNPs and differences among other primates clustered in the more thermodynamically unstable regions of the mRNA, which suggests that the evolutionary survival of nucleotide sequence variation may be influenced by the mRNA structure of this gene.

The impact of pharmacogenetics for migraine

Migraine is a paroxysmal neurological disorder affecting up to 12% of males and 24% of females in the general population. As migraine has been demonstrated to have a strong, but complex, genetic component, pharmacogenetics bears great promise in providing new targets for drug development and optimization of individual specific therapy. Better, preferably prophylactic, treatment of migraine patients is desired because the drugs now used are not effective in all patients, allow recurrence of the headache in a high percentage of patients and sometimes have severe adverse side-effects. With the recent identification of the brain-specific P/Q-type Ca(2+)channel gene CACNA1A as a pivotal player in the pathogenesis of migraine, the first step has been taken to identify primary biochemical pathways leading to migraine. The work on migraine can also have implications for the increasing number of additional neurological episodic disorders having the common denominator of channelopathy.

The pharmacology of headache

Headache is a common problem which besets most of us at some time or the other. The pharmacology of headache is complex in an overall sense but can be understood in terms of the anatomy and physiology of the pain-producing structures. Migraine can be used as a template to understand the activation of nociceptive systems in the head and thus their neurotransmitter mediation and modulation. In recent years, the role of serotonin (5-HT) in headache pharmacology has been unravelled in the context of both understanding its role in the nociceptive systems related to headache and by exploiting its 5-HT1 receptor subtypes in headache therapeutics. The pharmacology of the head pain systems, as they are known and as they might evolve, are explored in the context of both, the anatomy and physiology of trigeminovascular nociception and in the context of clinical questions, such as those of efficacy, headache recurrence and adverse events.