Selectivity in genetic association with sub-classified migraine in women

Therapeutic potential of transient receptor potential (TRP) channels in psychiatric disorders

Psychiatric disorders such as Bipolar disorder, Anxiety, Major depressive disorder, Schizophrenia, Attention-deficit/hyperactivity disorder, as well as neurological disorders such as Migraine, are linked by the evidence of altered calcium homeostasis. The disturbance of intra-cellular calcium homeostasis disrupts the activity of numerous ion channels including transient receptor potential (TRP) channels. TRP channel families comprise non-selective calcium-permeable channels that have been implicated in variety of physiological processes in the brain, as well as in the pathogenesis of psychiatric disorders. Through a comprehensive review of current research and experimentation, this investigation elucidates the role of TRP channels in psychiatric disorders. Furthermore, this review discusses about the exploration of epigenetics and TRP channels in psychiatric disorders.

Current Update on Categorization of Migraine Subtypes on the Basis of Genetic Variation: a Systematic Review

Migraine is a complex neurovascular disorder that is characterized by severe behavioral, sensory, visual, and/or auditory symptoms. It has been labeled as one of the ten most disabling medical illnesses in the world by the World Health Organization (Aagaard et al Sci Transl Med 6(237):237ra65, 2014). According to a recent report by the American Migraine Foundation (Shoulson et al Ann Neurol 25(3):252-9, 1989), around 148 million people in the world currently suffer from migraine. On the basis of presence of aura, migraine is classified into two major subtypes: migraine with aura (Aagaard et al Sci Transl Med 6(237):237ra65, 2014) and migraine without aura. (Aagaard K et al Sci Transl Med 6(237):237ra65, 2014) Many complex genetic mechanisms have been proposed in the pathophysiology of migraine but specific pathways associated with the different subtypes of migraine have not yet been explored. Various approaches including candidate gene association studies (CGAS) and genome-wide association studies (Fan et al Headache: J Head Face Pain 54(4):709-715, 2014). have identified the genetic markers associated with migraine and its subtypes. Several single nucleotide polymorphisms (Kaur et al Egyp J Neurol, Psychiatry Neurosurg 55(1):1-7, 2019) within genes involved in ion homeostasis, solute transport, synaptic transmission, cortical excitability, and vascular function have been associated with the disorder. Currently, the diagnosis of migraine is majorly behavioral with no focus on the genetic markers and thereby the therapeutic intervention specific to subtypes. Therefore, there is a need to explore genetic variants significantly associated with MA and MO as susceptibility markers in the diagnosis and targets for therapeutic interventions in the specific subtypes of migraine. Although the proper characterization of pathways based on different subtypes is yet to be studied, this review aims to make a first attempt to compile the information available on various genetic variants and the molecular mechanisms involved with the development of MA and MO. An attempt has also been made to suggest novel candidate genes based on their function to be explored by future research.

Disruption of mitochondrial pyruvate oxidation in dorsal root ganglia drives persistent nociceptive sensitization and causes pervasive transcriptomic alterations

ABSTRACT

Metabolism is inextricably linked to every aspect of cellular function. In addition to energy production and biosynthesis, metabolism plays a crucial role in regulating signal transduction and gene expression. Altered metabolic states have been shown to maintain aberrant signaling and transcription, contributing to diseases like cancer, cardiovascular disease, and neurodegeneration. Metabolic gene polymorphisms and defects are also associated with chronic pain conditions, as are increased levels of nerve growth factor (NGF). However, the mechanisms by which NGF may modulate sensory neuron metabolism remain unclear. This study demonstrated that intraplantar NGF injection reprograms sensory neuron metabolism. Nerve growth factor suppressed mitochondrial pyruvate oxidation and enhanced lactate extrusion, requiring 24 hours to increase lactate dehydrogenase A and pyruvate dehydrogenase kinase 1 (PDHK1) expression. Inhibiting these metabolic enzymes reversed NGF-mediated effects. Remarkably, directly disrupting mitochondrial pyruvate oxidation induced severe, persistent allodynia, implicating this metabolic dysfunction in chronic pain. Nanopore long-read sequencing of poly(A) mRNA uncovered extensive transcriptomic changes upon metabolic disruption, including altered gene expression, splicing, and poly(A) tail lengths. By linking metabolic disturbance of dorsal root ganglia to transcriptome reprogramming, this study enhances our understanding of the mechanisms underlying persistent nociceptive sensitization. These findings imply that impaired mitochondrial pyruvate oxidation may drive chronic pain, possibly by impacting transcriptomic regulation. Exploring these metabolite-driven mechanisms further might reveal novel therapeutic targets for intractable pain.

Determination of the Frequency of Migraine Attacks in Pregnant Women and the Ways They Cope with Headaches: A Cross-Sectional Study

One out of every five women of reproductive age suffers from migraine. Although headaches subside in most women during pregnancy, attacks continue and even worsen in some women. Pregnant women try to relieve pain with medication or non-pharmacological treatment methods. This descriptive and cross-sectional study was conducted to determine the incidence of migraine attacks in pregnant women diagnosed with migraine and the ways they cope with headaches. The study included 191 pregnant women who were diagnosed with migraine in the pre-pregnancy period. McNemar analysis was performed to test the relationship between descriptive statistical methods and categorical variables when the data were analyzed. The mean gestational age of the participants was 28.31 ± 8.64 weeks, and their mean age at the onset of migraine was 20.74 ± 5.63 years. The comparison of the duration, frequency, and severity of headaches suffered before and during pregnancy demonstrated that there were statistical differences between them (p < 0.05). The frequency of using methods such as taking painkillers, resting in a dark room, and having cold application and massage to relieve headaches before pregnancy decreased statistically significantly during pregnancy (p < 0.05). As a result, the frequency and severity of migraines decrease during pregnancy. The tendency to resort to pharmacological or non-pharmacological methods used to relieve headaches decreases during pregnancy. Although migraine has many adverse effects on pregnancy, pregnant women do not demand satisfactory information from health professionals about migraine headaches during pregnancy.

Association between TRP channels and glutamatergic synapse gene polymorphisms and migraine and the comorbidities anxiety and depression in a Chinese population

Background: Genetic and environmental factors contribute to migraine and the comorbidities of anxiety and depression. However, the association between genetic polymorphisms in the transient receptor potential (TRP) channels and glutamatergic synapse genes with the risk of migraine and the comorbidities of anxiety and depression remain unclear. Methods: 251 migraine patients containing 49 comorbidities with anxiety and 112 with depression and 600 controls were recruited. A customized 48-plex SNPscan kit was used for genotyping 13 SNPs of nine target genes. Logistic regression was conducted to analyze these SNPs' association with the susceptibility of migraine and comorbidities. The generalized multifactor dimension reduction (GMDR) was applied to analyze the SNP-SNP and gene-environment interactions. The GTEx database was used to examine the effects of the significant SNPs on gene expressions. Results: The TRPV1 rs8065080 and TRPV3 rs7217270 were associated with an increased risk of migraine in the dominant model [OR_adj (95% CI): 1.75 (1.09-2.90), p = 0.025; 1.63 (1.02-2.58), p = 0.039, respectively]. GRIK2 rs2227283 was associated with migraine in the edge of significance [OR_adj (95% CI) = 1.36 (0.99-1.89), p = 0.062]. In migraine patients, TRPV1 rs222741 was associated with both anxiety risk and depression risk in the recessive model [OR_adj (95% CI): 2.64 (1.24-5.73), p = 0.012; 1.97 (1.02-3.85), p = 0.046, respectively]. TRPM8 rs7577262 was associated with anxiety (OR_adj = 0.27, 95% CI = 0.10-0.76, p = 0.011). TRPV4 rs3742037, TRPM8 rs17862920 and SLC17A8 rs11110359 were associated with depression in dominant model [OR_adj (95% CI): 2.03 (1.06-3.96), p = 0.035; 0.48 (0.23-0.96), p = 0.042; 0.42 (0.20-0.84), p = 0.016, respectively]. Significant eQTL and sQTL signals were observed for SNP rs8065080. Individuals with GRS (Genetic risk scores) of Q4 (14-17) had a higher risk of migraine and a lower risk of comorbidity anxiety than those with Genetic risk scores scores of Q1 (0-9) groups [OR_adj (95% CI): 2.31 (1.39-3.86), p = 0.001; 0.28 (0.08-0.88), p = 0.034, respectively]. Conclusion: This study suggests that TRPV1 rs8065080, TRPV3 rs7217270, and GRIK2 rs2227283 polymorphism may associate with migraine risk. TRPV1 rs222741 and TRPM8 rs7577262 may associate with migraine comorbidity anxiety risk. rs222741, rs3742037, rs17862920, and rs11110359 may associate with migraine comorbidity depression risk. Higher GRS scores may increase migraine risk and decrease comorbidity anxiety risk.

ThermoTRP channels in pain sexual dimorphism: new insights for drug intervention

Chronic pain is a major burden for the society and remains more prevalent and severe in females. The presence of chronic pain is linked to persistent alterations in the peripheral and the central nervous system. One of the main types of peripheral pain transducers are the transient receptor potential channels (TRP), also known as thermoTRP channels, which intervene in the perception of hot and cold external stimuli. These channels, and especially TRPV1, TRPA1 and TRPM8, have been subjected to profound investigation because of their role as thermosensors and also because of their implication in acute and chronic pain. Surprisingly, their sensitivity to endogenous signaling has been far less studied. Cumulative evidence suggests that the function of these channels may be differently modulated in males and females, in part through sexual hormones, and this could constitute a significant contributor to the sex differences in chronic pain. Here, we review the exciting advances in thermoTRP pharmacology for males and females in two paradigmatic types of chronic pain with a strong peripheral component: chronic migraine and chemotherapy-induced peripheral neuropathy (CIPN). The possibilities of peripheral druggability offered by these channels and the differential exploitation for men and women represent a development opportunity that will lead to a significant increment of the armamentarium of analgesic medicines for personalized chronic pain treatment.

Transient receptor potential melastatin 8 is required for nitroglycerin- and calcitonin gene-related peptide-induced migraine-like pain behaviors in mice

ABSTRACT

Migraine is a complex neurovascular disorder that is one of the leading causes of disability and a reduced quality of life. Even with such a high societal impact, our understanding of the cellular and molecular mechanisms that contribute to migraine headaches is limited. To address this complex disorder, several groups have performed genome-wide association studies to elucidate migraine susceptibility genes, with many identifying transient receptor potential melastatin 8 (TRPM8), a cold-sensitive cation channel expressed in peripheral afferents innervating the trigeminovascular system, and the principal mediator of cold and cold pain associated with injury and disease. Interestingly, these migraine-associated single-nucleotide polymorphisms reside in noncoding regions of TRPM8, with those correlated with reduced migraine risk exhibiting lower TRPM8 expression and decreased cold sensitivity. Nonetheless, as a role for TRPM8 in migraine has yet to be defined, we sought to address this gap in our knowledge using mouse genetics and TRPM8 antagonism to determine whether TRPM8 channels or neurons are required for migraine-like pain (mechanical allodynia and facial grimace) in inducible migraine models. Our results show that both evoked and spontaneous pain behaviors are dependent on both TRPM8 channels and neurons, as well as required in both acute and chronic migraine models. Moreover, inhibition of TRPM8 channels prevented acute but not established chronic migraine-like pain. These results are consistent with its association with migraine in genetic analyses and establish that TRPM8 channels are a component of the underlying mechanisms of migraine.

Deciphering the Role of the rs2651899, rs10166942, and rs11172113 Polymorphisms in Migraine: A Meta-Analysis

The genetic basis of migraine is rather complex. The rs2651899 in the PR/SET domain 16 (PRDM16) gene, the rs10166942 near the transient receptor potential cation channel subfamily M member 8 (TRPM8) gene, and the rs11172113 in the LDL receptor-related protein 1 (LRP1) gene, have been associated with migraine in a genome-wide association study (GWAS). However, data from subsequent studies examining the role of these variants and their relationship with migraine remain inconclusive. The aim of the present study was to meta-analyze the published data assessing the role of these polymorphisms in migraine, migraine with aura (MA), and migraine without aura (MO). We performed a search in the PubMed, Scopus, Web of Science, and Public Health Genomics and Precision Health Knowledge Base (v7.7) databases. In total, eight, six, and six studies were included in the quantitative analysis, for the rs2651899, rs10166942, and rs11172113, respectively. Cochran’s Q and I2 tests were used to calculate the heterogeneity. The random effects (RE) model was applied when high heterogeneity was observed; otherwise, the fixed effects (FE) model was applied. The odds ratios (ORs) and the respective 95% confidence intervals (CIs) were calculated to estimate the effect of each variant on migraine. Funnel plots were created to graphically assess publication bias. A significant association was revealed for the CC genotype of the rs2651899, with the overall migraine group (RE model OR: 1.32; 95% CI: 1.02−1.73; p-value = 0.04) and the MA subgroup (FE model OR: 1.40; 95% CI: 1.12−1.74; p-value = 0.003). The rs10166942 CT genotype was associated with increased migraine risk (FE model OR: 1.36; 95% CI: 1.18−1.57; p-value < 0.0001) and increased MO risk (FE model OR: 1.41; 95% CI: 1.17−1.69; p-value = 0.0003). No association was detected for the rs11172113. The rs2651899 and the rs10166942 have an effect on migraine. Larger studies are needed to dissect the role of these variants in migraine.

Genome-wide analysis of 102,084 migraine cases identifies 123 risk loci and subtype-specific risk alleles

Migraine affects over a billion individuals worldwide but its genetic underpinning remains largely unknown. Here, we performed a genome-wide association study of 102,084 migraine cases and 771,257 controls and identified 123 loci, of which 86 are previously unknown. These loci provide an opportunity to evaluate shared and distinct genetic components in the two main migraine subtypes: migraine with aura and migraine without aura. Stratification of the risk loci using 29,679 cases with subtype information indicated three risk variants that seem specific for migraine with aura (in HMOX2, CACNA1A and MPPED2), two that seem specific for migraine without aura (near SPINK2 and near FECH) and nine that increase susceptibility for migraine regardless of subtype. The new risk loci include genes encoding recent migraine-specific drug targets, namely calcitonin gene-related peptide (CALCA/CALCB) and serotonin 1F receptor (HTR1F). Overall, genomic annotations among migraine-associated variants were enriched in both vascular and central nervous system tissue/cell types, supporting unequivocally that neurovascular mechanisms underlie migraine pathophysiology.

Association of Genetic Variants With Migraine Subclassified by Clinical Symptoms in Adult Females

Migraine is heritable and formally diagnosed by structured criteria that require presence of some but not all possible migraine symptoms which include aura, several distinct manifestations of pain, nausea/vomiting, and sensitivity to light or sound. The most recent genome-wide genetic association study (GWAS) for migraine identified 38 loci. We investigated whether 46 single-nucleotide polymorphisms (SNPs), i.e., genetic variants, at these loci may have especially pronounced, i.e., selective, association with migraine presenting with individual symptoms compared to absence of migraine. Selective genetic associations of SNPs were evaluated through a likelihood framework in the Women's Genome Health Study (WGHS), a population-based cohort of middle-aged women including 3,003 experiencing migraine and 18,108 not experiencing migraine, all with genetic information. SNPs at 12 loci displayed significant selective association for migraine subclassified by specific symptoms, among which six selective associations are novel. Symptoms showing selective association include aura, nausea/vomiting, photophobia, and phonophobia. The selective associations were consistent whether the women met all formal criteria for diagnostic for migraine or lacked one of the diagnostic criteria, formally termed probable migraine. Subsequently, we performed latent class analysis of migraine diagnostic symptoms among 69,861 women experiencing migraine from the WGHS recruitment sample to assess whether there were clusters of specific symptoms that might also have a genetic basis. However, no globally robust latent migraine substructures of diagnostic symptoms were observed nor were there selective genetic associations with specific combinations of symptoms revealed among weakly supported latent classes. The findings extend previously reported selective genetic associations with migraine diagnostic symptoms while supporting models for shared genetic susceptibility across all qualifying migraine at many loci.

Advances in genetics of migraine

Background

Migraine is a complex neurovascular disorder with a strong genetic component. There are rare monogenic forms of migraine, as well as more common polygenic forms; research into the genes involved in both types has provided insights into the many contributing genetic factors. This review summarises advances that have been made in the knowledge and understanding of the genes and genetic variations implicated in migraine etiology.

Findings

Migraine is characterised into two main types, migraine without aura (MO) and migraine with aura (MA). Hemiplegic migraine is a rare monogenic MA subtype caused by mutations in three main genes - CACNA1A, ATP1A2 and SCN1A - which encode ion channel and transport proteins. Functional studies in cellular and animal models show that, in general, mutations result in impaired glutamatergic neurotransmission and cortical hyperexcitability, which make the brain more susceptible to cortical spreading depression, a phenomenon thought to coincide with aura symptoms. Variants in other genes encoding ion channels and solute carriers, or with roles in regulating neurotransmitters at neuronal synapses, or in vascular function, can also cause monogenic migraine, hemiplegic migraine and related disorders with overlapping symptoms. Next-generation sequencing will accelerate the finding of new potentially causal variants and genes, with high-throughput bioinformatics analysis methods and functional analysis pipelines important in prioritising, confirming and understanding the mechanisms of disease-causing variants.

With respect to common migraine forms, large genome-wide association studies (GWAS) have greatly expanded our knowledge of the genes involved, emphasizing the role of both neuronal and vascular pathways. Dissecting the genetic architecture of migraine leads to greater understanding of what underpins relationships between subtypes and comorbid disorders, and may have utility in diagnosis or tailoring treatments. Further work is required to identify causal polymorphisms and the mechanism of their effect, and studies of gene expression and epigenetic factors will help bridge the genetics with migraine pathophysiology.

Conclusions

The complexity of migraine disorders is mirrored by their genetic complexity. A comprehensive knowledge of the genetic factors underpinning migraine will lead to improved understanding of molecular mechanisms and pathogenesis, to enable better diagnosis and treatments for migraine sufferers.

Dopamine-beta-hydroxylase 19-bp insertion/deletion polymorphism affects medication overuse in patients with chronic migraine

Dopamine-beta-hydroxylase (DBH) enzyme activity is modulated at the genetic level by the presence of several polymorphisms. Among these, the 19-bp insertion/deletion (I/D) polymorphism (rs72393728/rs141116007) was investigated in several genetic association studies for its correlation with the susceptibility to develop episodic migraine, but conflicting results were achieved. In the present study we analyzed this genetic variant in a carefully characterized population of migraineurs encompassing both episodic and chronic migraine (with and without medication overuse) with the aim to perform a replication study and verify any possible correlation with migraine endophenotypes. Genotyping of the DBH 19-bp I/D polymorphism was performed on 400 migraine patients and 204 healthy individuals. The associations between genotypic frequencies and the clinical and sociodemographic features of migraineurs were then investigated. The DBH 19-bp I/D polymorphism did not correlate with migraine susceptibility or most clinical variables, with the exception of a statistically significant correlation within the subgroup of patients affected by chronic migraine were the individuals carrying the deleted (D) allele were significantly more prone to abuse in analgesics. As a result of this finding, the DBH 19-bp I/D polymorphism does not influence migraine susceptibility, but it might contribute to the development of medication overuse in patient with chronic migraine.

Statistical methods to detect pleiotropy in human complex traits

In recent years pleiotropy, the phenomenon of one genetic locus influencing several traits, has become a widely researched field in human genetics. With the increasing availability of genome-wide association study summary statistics, as well as the establishment of deeply phenotyped sample collections, it is now possible to systematically assess the genetic overlap between multiple traits and diseases. In addition to increasing power to detect associated variants, multi-trait methods can also aid our understanding of how different disorders are aetiologically linked by highlighting relevant biological pathways. A plethora of available tools to perform such analyses exists, each with their own advantages and limitations. In this review, we outline some of the currently available methods to conduct multi-trait analyses. First, we briefly introduce the concept of pleiotropy and outline the current landscape of pleiotropy research in human genetics; second, we describe analytical considerations and analysis methods; finally, we discuss future directions for the field.

Localization of migraine susceptibility genes in human brain by single-cell RNA sequencing

BACKGROUND

Migraine is a debilitating disorder characterized by severe headaches and associated neurological symptoms. A key challenge to understanding migraine has been the cellular complexity of the human brain and the multiple cell types implicated in its pathophysiology. The present study leverages recent advances in single-cell transcriptomics to localize the specific human brain cell types in which putative migraine susceptibility genes are expressed.

METHODS

The cell-type specific expression of both familial and common migraine-associated genes was determined bioinformatically using data from 2,039 individual human brain cells across two published single-cell RNA sequencing datasets. Enrichment of migraine-associated genes was determined for each brain cell type.

RESULTS

Analysis of single-brain cell RNA sequencing data from five major subtypes of cells in the human cortex (neurons, oligodendrocytes, astrocytes, microglia, and endothelial cells) indicates that over 40% of known migraine-associated genes are enriched in the expression profiles of a specific brain cell type. Further analysis of neuronal migraine-associated genes demonstrated that approximately 70% were significantly enriched in inhibitory neurons and 30% in excitatory neurons.

CONCLUSIONS

This study takes the next step in understanding the human brain cell types in which putative migraine susceptibility genes are expressed. Both familial and common migraine may arise from dysfunction of discrete cell types within the neurovascular unit, and localization of the affected cell type(s) in an individual patient may provide insight into to their susceptibility to migraine.

Coriander (Coriandrum sativum): A promising functional food toward the well-being

Coriandrum sativum (C. sativum) or coriander is one of the most popularly used spices in culinary worldwide, and its medicinal values has been recognized since ancient time. C. sativum contains bioactive phytochemicals that are accounted for a wide range of biological activities including antioxidant, anticancer, neuroprotective, anxiolytic, anticonvulsant, analgesic, migraine-relieving, hypolipidemic, hypoglycemic, hypotensive, antimicrobial, and antiinflammatory activities. The major compound, linalool, abundantly found in seeds is remarked for its abilities to modulate many key pathogenesis pathways of diseases. Apart from the modulating effects, the potent antioxidant property of the C. sativum provides a key mechanism behind its protective effects against neurodegenerative diseases, cancer, and metabolic syndrome. This review shed light on comprehensive aspects regarding the therapeutic values of the C. sativum, which indicate its significance of being a promising functional food for promoting the well-being in the era of aging and lifestyle-related diseases.

A genetic risk score is differentially associated with migraine with and without aura

Although a number of migraine-associated single-nucleotide polymorphisms (SNP) with small effect size have been identified, little is known about the additive impact of these variants on migraine risk, frequency and severity. We investigated to what extent a genetic risk score (GRS) based on recently published, novel migraine-associated SNPs is associated with migraine prevalence, subtypes and severity in a large population-based sample. The sample comprised 446 subjects with migraine and 2511 controls from the CoLaus/PsyCoLaus study. Fifty-four SNPs earlier associated with migraine were selected. SNPs with a low impact on migraine prevalence in our sample were excluded using random forest. We combined the remaining 21 SNPs into a GRS and analyzed the association with migraine using logistic regression models. The GRS was significantly associated with migraine (OR = 1.56, p = 0.02) and migraine without aura (MWOA) (OR = 2.01, p = 0.003), but not with migraine with aura (MWA). The GRS was not associated with migraine frequency, intensity or interference with daily activities. We show that a GRS combining multiple genetic risk variants is associated with MWOA but not MWA, suggesting a different genetic susceptibility background underlying the two forms of migraine.

Pathophysiology of Migraine: A Disorder of Sensory Processing

Plaguing humans for more than two millennia, manifest on every continent studied, and with more than one billion patients having an attack in any year, migraine stands as the sixth most common cause of disability on the planet. The pathophysiology of migraine has emerged from a historical consideration of the "humors" through mid-20th century distraction of the now defunct Vascular Theory to a clear place as a neurological disorder. It could be said there are three questions: why, how, and when? Why: migraine is largely accepted to be an inherited tendency for the brain to lose control of its inputs. How: the now classical trigeminal durovascular afferent pathway has been explored in laboratory and clinic; interrogated with immunohistochemistry to functional brain imaging to offer a roadmap of the attack. When: migraine attacks emerge due to a disorder of brain sensory processing that itself likely cycles, influenced by genetics and the environment. In the first, premonitory, phase that precedes headache, brain stem and diencephalic systems modulating afferent signals, light-photophobia or sound-phonophobia, begin to dysfunction and eventually to evolve to the pain phase and with time the resolution or postdromal phase. Understanding the biology of migraine through careful bench-based research has led to major classes of therapeutics being identified: triptans, serotonin 5-HT1B/1D receptor agonists; gepants, calcitonin gene-related peptide (CGRP) receptor antagonists; ditans, 5-HT1F receptor agonists, CGRP mechanisms monoclonal antibodies; and glurants, mGlu5 modulators; with the promise of more to come. Investment in understanding migraine has been very successful and leaves us at a new dawn, able to transform its impact on a global scale, as well as understand fundamental aspects of human biology.

Development of TRPM8 Antagonists to Treat Chronic Pain and Migraine

A review. Development of pharmaceutical antagonists of transient receptor potential melastatin 8 (TRPM8) have been pursued for the treatment of chronic pain and migraine. This review focuses on the current state of this progress.

Genetics of Migraine: Insights into the Molecular Basis of Migraine Disorders

Migraine is a complex, debilitating neurovascular disorder, typically characterized by recurring, incapacitating attacks of severe headache often accompanied by nausea and neurological disturbances. It has a strong genetic basis demonstrated by rare migraine disorders caused by mutations in single genes (monogenic), as well as familial clustering of common migraine which is associated with polymorphisms in many genes (polygenic). Hemiplegic migraine is a dominantly inherited, severe form of migraine with associated motor weakness. Family studies have found that mutations in three different ion channels genes, CACNA1A, ATP1A2, and SCN1A can be causal. Functional studies of these mutations has shown that they can result in defective regulation of glutamatergic neurotransmission and the excitatory/inhibitory balance in the brain, which lowers the threshold for cortical spreading depression, a wave of cortical depolarization thought to be involved in headache initiation mechanisms. Other putative genes for monogenic migraine include KCKN18, PRRT2, and CSNK1D, which can also be involved with other disorders. There are a number of primarily vascular disorders caused by mutations in single genes, which are often accompanied by migraine symptoms. Mutations in NOTCH3 causes cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary cerebrovascular disease that leads to ischemic strokes and dementia, but in which migraine is often present, sometimes long before the onset of other symptoms. Mutations in the TREX1 and COL4A1 also cause vascular disorders, but often feature migraine. With respect to common polygenic migraine, genome-wide association studies have now identified single nucleotide polymorphisms at 38 loci significantly associated with migraine risk. Functions assigned to the genes in proximity to these loci suggest that both neuronal and vascular pathways also contribute to the pathophysiology of common migraine. Further studies are required to fully understand these findings and translate them into treatment options for migraine patients.

Variants in the CNR1 gene predispose to headache with nausea in the presence of life stress

One of the main effects of the endocannabinoid system in the brain is stress adaptation with presynaptic endocannabinoid receptor 1 (CB1 receptors) playing a major role. In the present study, we investigated whether the effect of the CB1 receptor coding CNR1 gene on migraine and its symptoms is conditional on life stress. In a cross-sectional European population (n = 2426), recruited from Manchester and Budapest, we used the ID-Migraine questionnaire for migraine screening, the Life Threatening Experiences questionnaire to measure recent negative life events (RLE), and covered the CNR1 gene with 11 SNPs. The main genetic effects and the CNR1 × RLE interaction with age and sex as covariates were tested. None of the SNPs showed main genetic effects on possible migraine or its symptoms, but 5 SNPs showed nominally significant interaction with RLE on headache with nausea using logistic regression models. The effect of rs806366 remained significant after correction for multiple testing and replicated in the subpopulations. This effect was independent from depression- and anxiety-related phenotypes. In addition, a Bayesian systems-based analysis demonstrated that in the development of headache with nausea all SNPs were more relevant with higher a posteriori probability in those who experienced recent life stress. In summary, the CNR1 gene in interaction with life stress increased the risk of headache with nausea suggesting a specific pathological mechanism to develop migraine, and indicating that a subgroup of migraine patients, who suffer from life stress triggered migraine with frequent nausea, may benefit from therapies that increase the endocannabinoid tone.

Investigation of polymorphisms in genes involved in estrogen metabolism in menstrual migraine

Migraine is a common, disabling headache disorder, which is influenced by multiple genes and environmental triggers. After puberty, the prevalence of migraine in women is three times higher than in men and >50% of females suffering from migraine report a menstrual association, suggesting hormonal fluctuations can influence the risk of migraine attacks. It has been hypothesized that the drop in estrogen during menses is an important trigger for menstrual migraine. Catechol-O-methyltransferase (COMT) and Cytochrome P450 (CYP) enzymes are involved in estrogen synthesis and metabolism. Functional polymorphisms in these genes can influence estrogen levels and therefore may be associated with risk of menstrual migraine. In this study we investigated four single nucleotide polymorphisms in three genes involved in estrogen metabolism that have been reported to impact enzyme levels or function, in a specific menstrual migraine cohort. 268 menstrual migraine cases and 142 controls were genotyped for rs4680 in COMT (Val158Met), rs4646903 and rs1048943 in CYP1A1 (T3801C and Ile462Val) and rs700519 in CYP19A1 (Cys264Arg). Neither genotype nor allele frequencies for the COMT and CYP SNPs genotyped were found to be significantly different between menstrual migraineurs and controls by chi-square analysis (P>0.05). Therefore we did not find association of functional polymorphisms in the estrogen metabolism genes COMT, CYP1A1 or CYP19A1 with menstrual migraine. Further studies are required to assess whether menstrual migraine is genetically distinct from the common migraine subtypes and identify genes that influence risk.

Migraine Susceptibility Genes in Han Chinese of Fujian Province

Background and Purpose

Five single-nucleotide polymorphisms (SNPs) (rs4379368, rs10504861, rs10915437, rs12134493 and rs13208321) were recently identified in a Western population with migraine. These migraine-associated SNPs have not been evaluated in a Han Chinese population. This study investigated the associations of specific SNPs with migraine in a Han population.

Methods

This was a case-control study of Han Chinese residing in Fujian Province. Polymerase chain reaction—restriction-fragment-length polymorphism analysis and direct sequencing were used to characterize the relationships of SNPs in a control group of 200 subjects and in a migraine group of 201 patients.

Results

The frequencies of the five SNPs did not differ between patients with migraine and healthy non migraine controls. However, subgroup analysis indicated certain SNPs were more strongly associated with migraine with aura or migraine without aura than with controls. The CT genotype of rs4379368 was more common in migraine patients with aura (75%) than in migraine patients without aura (47.9%) and controls (48.5%) (p<0.05), and the TT genotype of rs10504861 was more common in migraine patients with aura than in controls (8.3% vs. 0.5%) (p<0.05). Meanwhile, the CC genotype of rs12134493 was less common in migraine patients without aura than in controls (80.6% vs. 88%) (p<0.05).

Conclusions

Our findings suggest that the rs4379368 and rs10504861 SNPs are markers for susceptibility to migraine with aura and that rs12134493 is a marker for the risk of migraine without aura in this Han population. Future studies should further explore if these associations vary by ethnicity.

TRPM8 and Migraine

Migraine is among the most common diseases on earth and one of the most disabling, the latter due in large part to poor treatment efficacy. Development of new therapeutics is dependent on the identification of mechanisms contributing to migraine and discovery of targets for new drugs. Numerous genome-wide association studies (GWAS) have implicated the transient receptor-potential M8 (TRPM8) channel in migraine. This channel is predominantly expressed on peripheral sensory neurons and is known as the sensor for cold temperature in cutaneous tissue but is also expressed on deep visceral afferents where cold is not likely a stimulus. Consequently, a number of alternative endogenous agonists have been proposed. Apart from its role in cold sensation, TRPM8 also contributes to cold allodynia after nerve injury or inflammation, and it is necessary for cooling/menthol-based analgesia. How it might contribute to migraine is less clear. The purpose of this review is to discuss the anatomical and physiological mechanisms by which meningeal TRPM8 may play a role in migraine as well as the potential of TRPM8 as a therapeutic target. TRPM8 is expressed on sensory afferents innervating the meninges, and these neurons are subject to developmental changes that may influence their contribution to migraine. As in viscera, meningeal TRPM8 channels are unlikely to be activated by temperature fluctuations and their endogenous ligands remain unknown. Preclinical migraine studies show that activation of meningeal TRPM8 by exogenous agonists can both cause and alleviate headache behaviors, depending on whether other meningeal afferents concurrently receive noxious stimuli. This is reminiscent of the fact that cold can trigger migraine in humans but menthol can also alleviate headache. We propose that both TRPM8 agonists and antagonists may be potential therapeutics, depending on how migraine is triggered in individual patients. In this regard, TRPM8 may be a novel target for personalized medicine in migraine treatment.

Meta-analysis of 375,000 individuals identifies 38 susceptibility loci for migraine

Migraine is a debilitating neurological disorder affecting around one in seven people worldwide, but its molecular mechanisms remain poorly understood. There is some debate about whether migraine is a disease of vascular dysfunction or a result of neuronal dysfunction with secondary vascular changes. Genome-wide association (GWA) studies have thus far identified 13 independent loci associated with migraine. To identify new susceptibility loci, we carried out a genetic study of migraine on 59,674 affected subjects and 316,078 controls from 22 GWA studies. We identified 44 independent single-nucleotide polymorphisms (SNPs) significantly associated with migraine risk (P < 5 × 10(-8)) that mapped to 38 distinct genomic loci, including 28 loci not previously reported and a locus that to our knowledge is the first to be identified on chromosome X. In subsequent computational analyses, the identified loci showed enrichment for genes expressed in vascular and smooth muscle tissues, consistent with a predominant theory of migraine that highlights vascular etiologies.

A splice variant in the ACSL5 gene relates migraine with fatty acid activation in mitochondria

Genome-wide association studies (GWAS) in migraine are providing the molecular basis of this heterogeneous disease, but the understanding of its aetiology is still incomplete. Although some biomarkers have currently been accepted for migraine, large amount of studies for identifying new ones is needed. The migraine-associated variant rs12355831:A>G (P=2 × 10⁻⁶), described in a GWAS of the International Headache Genetic Consortium, is localized in a non-coding sequence with unknown function. We sought to identify the causal variant and the genetic mechanism involved in the migraine risk. To this end, we integrated data of RNA sequences from the Genetic European Variation in Health and Disease (GEUVADIS) and genotypes from 1000 GENOMES of 344 lymphoblastoid cell lines (LCLs), to determine the expression quantitative trait loci (eQTLs) in the region. We found that the migraine-associated variant belongs to a linkage disequilibrium block associated with the expression of an acyl-coenzyme A synthetase 5 (ACSL5) transcript lacking exon 20 (ACSL5-Δ20). We showed by exon-skipping assay a direct causality of rs2256368-G in the exon 20 skipping of approximately 20 to 40% of ACSL5 RNA molecules. In conclusion, we identified the functional variant (rs2256368:A>G) affecting ACSL5 exon 20 skipping, as a causal factor linked to the migraine-associated rs12355831:A>G, suggesting that the activation of long-chain fatty acids by the spliced ACSL5-Δ20 molecules, a mitochondrial located enzyme, is involved in migraine pathology.

Population-based approaches to genetics of migraine

BACKGROUND

While the most accurate diagnosis of migraine typically requires a clinical interview guided by strict diagnostic criteria, an alternative approach that ascertains migraine by questionnaire in population-based settings has been instrumental in the discovery of common genetic variants influencing migraine risk. This result may be surprising. Population-based approaches are often criticized for limited ability to distinguish migraine from other forms of primary headache. It is thus useful to revisit prevailing ideas about population-based ascertainment of migraine to evaluate the extent to which this approach has potential for additional insights into migraine genetics and therefore pathophysiology.

OVERVIEW

We review recent findings suggesting that the success of the population-based approach is derived from the possibility of collecting much larger samples than in the clinic-based setting even at the risk of introducing phenotypic and genetic heterogeneity. The findings are also consistent with new appreciations for the genetic basis of many other common, complex clinical characteristics. However, clinic-based ascertainment and other settings will remain more effective than population-based approaches for investigating certain, often very specific aspects of migraine genetics.

CONCLUSION

We argue that the detailed genetic architecture of migraine, various aspects of methodology, and the ultimate sample size achieved by population-based ascertainment will be critical determinants of the future success of this approach to genetic analysis of migraine and its comorbidities.

Meningeal transient receptor potential channel M8 activation causes cutaneous facial and hindpaw allodynia in a preclinical rodent model of headache

BACKGROUND

Migraine headache is a neurological disorder affecting millions worldwide. However, little is known about the mechanisms contributing to migraine. Recent genome-wide association studies have found single nucleotide polymorphisms in the gene encoding transient receptor potential channel M8. Transient receptor potential channel M8 is generally known as a cold receptor but it has been implicated in pain signaling and may play a role in migraine pain.

METHODS

In order to investigate whether transient receptor potential channel M8 may contribute to the pain of migraine, the transient receptor potential channel M8 activator icilin was applied to the dura mater using a rat behavioral model of headache. Cutaneous allodynia was measured for 5 hours using Von Frey filaments.

RESULTS

Dural application of icilin produced cutaneous facial and hind paw allodynia that was attenuated by systemic pretreatment with the transient receptor potential channel M8-selective antagonist AMG1161 (10 mg/kg p.o.). Further, the anti-migraine agent sumatriptan (0.6 mg/kg s.c.) or the non-selective NOS inhibitor L-NAME (20 mg/kg i.p.) also attenuated allodynia when given as a pretreatment.

CONCLUSIONS

These data indicate that transient receptor potential channel M8 activation in the meninges produces behaviors in rats that are consistent with migraine and that are sensitive to pharmacological mechanisms known to have efficacy for migraine in humans. The findings suggest that activation of meningeal transient receptor potential channel M8 may contribute to the pain of migraine.

Transient receptor potential melastatin 8 gene polymorphism is associated with cold-induced airway hyperresponsiveness in bronchial asthma

BACKGROUND AND OBJECTIVE

Cold-induced airway hyperresponsiveness (CAH) is common in bronchial asthma (BA) patients and represents a problem for those living in cold climate. Transient receptor potential melastatin 8 (TRPM8) channel is the main cold temperature sensor in humans that could mediate cold response in asthmatics with CAH. No associations between TRPM8 gene polymorphisms and CAH have been reported.

METHODS

The present study involved 123 BA patients. CAH was assessed by 3-min isocapnic (5% CO2 ) cold air (-20°C) hyperventilation challenge. The c.750G > C (rs11562975), c.1256G > A (rs7593557), c.3048C > T (rs11563208) and c.3174C > G (rs11563071) polymorphisms of TRPM8 gene were genotyped by allele-specific polymerase chain reaction (PCR) and PCR with subsequent restriction fragment length polymorphism analysis.

RESULTS

GC genotype and C allele carriers of the c.750G > C (rs11562975) polymorphism were more frequently observed to exhibit CAH. The estimated odds ratio for the GC genotype was 3.73 95%CI (1.48; 9.37), P = 0.005. Furthermore, GC heterozygotes had a prominent decrease in forced expiratory volume in 1 s after the challenge as compared to GG homozygotes (-12% (-16; -8.1) vs -6.45% (-11; -2.1), P < 0.001). GC carriers also had a marked reduction in other spirometric parameters.

CONCLUSIONS

The GC variant of the TRPM8:c.750G > C (rs11562975) polymorphism is associated with CAH in patients with BA, which suggests a potential role of TRPM8 in CAH development.

Association of genetic loci for migraine susceptibility in the she people of China

Background

The purpose of this study was to investigate the association of the genotype and allele frequencies of the polymorphisms rs4379368, rs10504861, rs10915437, rs12134493 and rs13208321 in She people of China with migraine headache susceptibility. The five alleles were previously identified as being associated with migraine in a Western population, but it was not known if this association would hold in a She population. rs4379368 is in the succinic HMG coenzyme A transferase (C7orf10) gene; rs10504861 is near the matrix metallopeptidase 16 (MMP16) gene; rs10915437 is near the adherens junctions associated protein 1 (AJAP1) gene; rs12134493 is upstream of the tetraspanin 2 (TSPAN2) gene; and rs13208321 is within the four and a half LIM domains protein 5 (FHL5) gene.

Methods

This was a case-controlled study conducted in She people of Fujian province in China. Polymerase chain reaction-restriction fragment length polymorphism and direct sequencing were performed. Univariate and multivariate analyses were used to assess the association of the different genotypes of each SNP with migraine.

Results

The rs4379368 T allele was not in Hardy-Weinberg equilibrium and was more common than the C allele in subjects with migraine (58.7 %; P = 0.049), possibly suggesting a selection bias for T allele in this population. In support of this, the CT and TT genotypes were more frequent in the migraine compared with the control groups (54.0 % and 31.7 % vs. 48.0 % and 28.7 %, respectively; P = 0.019). These genotypes were also more common in females with migraines than females without migraines (53.8 % and 30.9 % vs. 46.7 % and 27.6 %; P = 0.026). Univariate and multivariate analyses found the CC genotype of rs4379368 and AA or AG genotype of rs13208321 were associated with a reduced risk of migraine (P values ≤0.039).

Conclusions

Our findings suggest that rs4379368 and rs13208321 are potential genetic markers for migraine in this She population. The findings of this study and others indicate important differences between ethnic populations in regard to genetic markers of migraine susceptibility.

Electronic supplementary material

The online version of this article (doi:10.1186/s10194-015-0553-1) contains supplementary material, which is available to authorized users.

AMG2850, a potent and selective TRPM8 antagonist, is not effective in rat models of inflammatory mechanical hypersensitivity and neuropathic tactile allodynia

TRPM8 has been implicated in pain and migraine based on dorsal root- and trigeminal ganglion-enriched expression, upregulation in preclinical models of pain, knockout mouse studies, and human genetics. Here, we evaluated the therapeutic potential in pain of AMG2850 ((R)-8-(4-(trifluoromethyl)phenyl)-N-((S)-1,1,1-trifluoropropan-2-yl)-5,6-dihydro-1,7-naphthyridine-7(8H)-carboxamide), a small molecule antagonist of TRPM8 by in vitro and in vivo characterization. AMG2850 is potent in vitro at rat TRPM8 (IC90 against icilin activation of 204 ± 28 nM), highly selective (>100-fold IC90 over TRPV1 and TRPA1 channels), and orally bioavailable (F po > 40 %). When tested in a skin-nerve preparation, AMG2850 blocked menthol-induced action potentials but not mechanical activation in C fibers. AMG2850 exhibited significant target coverage in vivo in a TRPM8-mediated icilin-induced wet-dog shake (WDS) model in rats (at 10 mg/kg p.o.). However, AMG2850 did not produce a significant therapeutic effect in rat models of inflammatory mechanical hypersensitivity or neuropathic tactile allodynia at doses up to 100 mg/kg. The lack of efficacy suggests that either TRPM8 does not play a role in mediating pain in these models or that a higher level of target coverage is required. The potential of TRPM8 antagonists as migraine therapeutics is yet to be determined.

The association between candidate migraine susceptibility loci and severe migraine phenotype in a clinical sample

INTRODUCTION

The objective of the study was to follow up and to test whether 12 previously identified migraine-associated single nucleotide polymorphisms were associated as risk factors and/or modifying factors for severe migraine traits in a Danish clinic-based population.

METHODS

Semi-structured migraine interviews, blood sampling and genotyping were performed on 1806 unrelated migraineurs recruited from the Danish Headache Center. Genotyping was also performed on a control group of 6415 people with no history of migraine. Association analyses were carried out using logistic regression and odds ratios were calculated assuming an additive model for risk. The proxies for severe migraine traits (early onset of migraine; many lifetime attacks, prolonged migraine and tendency to chronification of migraine) were tested against the 12 single nucleotide polymorphisms and a combined genetic score in both a case-control and case-only logistic regression model.

RESULTS

We successfully replicated five out of the 12 previously reported loci and confirmed the same direction of effects for all the 12 single nucleotide polymorphisms. In line with the recently published genome-wide association meta-analysis, the associations were significant for all migraine and migraine without aura but not for migraine with typical aura. Two single nucleotide polymorphisms (rs2274316 and rs11172113) conferred risk of many lifetime attacks inthe case-control analysis. In the case-only analysis, only three single nucleotide polymorphisms showed nominal association with many lifetime attacks and prolonged migraine attacks.

CONCLUSION

Our study supports previously reported findings on the association of several single nucleotide polymorphisms with migraine. It also suggests that the migraine susceptibility loci may be risk factors for severe migraine traits.

Targeting TRP channels for novel migraine therapeutics

Migraine is increasingly understood to be a disorder of the brain. In susceptible individuals, a variety of “triggers” may influence altered central excitability, resulting in the activation and sensitization of trigeminal nociceptive afferents surrounding blood vessels (i.e., the trigeminovascular system), leading to migraine pain. Transient receptor potential (TRP) channels are expressed in a subset of dural afferents, including those containing calcitonin gene related peptide (CGRP). Activation of TRP channels promotes excitation of nociceptive afferent fibers and potentially lead to pain. In addition to pain, allodynia to mechanical and cold stimuli can result from sensitization of both peripheral afferents and of central pain pathways. TRP channels respond to a variety of endogenous conditions including chemical mediators and low pH. These channels can be activated by exogenous stimuli including a wide range of chemical and environmental irritants, some of which have been demonstrated to trigger migraine in humans. Activation of TRP channels can elicit CGRP release, and blocking the effects of CGRP through receptor antagonism or antibody strategies has been demonstrated to be effective in the treatment of migraine. Identification of approaches that can prevent activation of TRP channels provides an additional novel strategy for discovery of migraine therapeutics.