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

Clinical relevance of depressed kynurenine pathway in episodic migraine patients: potential prognostic markers in the peripheral plasma during the interictal period

Background

Altered glutamatergic neurotransmission and neuropeptide levels play a central role in migraine pathomechanism. Previously, we confirmed that kynurenic acid, an endogenous glutamatergic antagonist, was able to decrease the expression of pituitary adenylate cyclase-activating polypeptide 1–38, a neuropeptide with known migraine-inducing properties. Hence, our aim was to reveal the role of the peripheral kynurenine pathway (KP) in episodic migraineurs. We focused on the complete tryptophan (Trp) catabolism, which comprises the serotonin and melatonin routes in addition to kynurenine metabolites. We investigated the relationship between metabolic alterations and clinical characteristics of migraine patients.

Methods

Female migraine patients aged between 25 and 50 years (n = 50) and healthy control subjects (n = 34) participated in this study. Blood samples were collected from the cubital veins of subjects (during both the interictal/ictal periods in migraineurs, n = 47/12, respectively). 12 metabolites of Trp pathway were determined by neurochemical measurements (UHPLC-MS/MS).

Results

Plasma concentrations of the most Trp metabolites were remarkably decreased in the interictal period of migraineurs compared to healthy control subjects, especially in the migraine without aura (MWoA) subgroup: Trp (p < 0.025), L-kynurenine (p < 0.001), kynurenic acid (p < 0.016), anthranilic acid (p < 0.007), picolinic acid (p < 0.03), 5-hydroxy-indoleaceticacid (p < 0.025) and melatonin (p < 0.023). Several metabolites showed a tendency to elevate during the ictal phase, but this was significant only in the cases of anthranilic acid, 5-hydroxy-indoleaceticacid and melatonin in MWoA patients. In the same subgroup, higher interictal kynurenic acid levels were identified in patients whose headache was severe and not related to their menstruation cycle. Negative linear correlation was detected between the interictal levels of xanthurenic acid/melatonin and attack frequency. Positive associations were found between the ictal 3-hydroxykynurenine levels and the beginning of attacks, just as between ictal picolinic acid levels and last attack before ictal sampling.

Conclusions

Our results suggest that there is a widespread metabolic imbalance in migraineurs, which manifests in a completely depressed peripheral Trp catabolism during the interictal period. It might act as trigger for the migraine attack, contributing to glutamate excess induced neurotoxicity and generalised hyperexcitability. This data can draw attention to the clinical relevance of KP in migraine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-021-01239-1.

Association of Polymorphisms within the Serotonin Receptor Genes 5-HTR1A, 5-HTR1B, 5-HTR2A and 5-HTR2C and Migraine Susceptibility in a Turkish Population

Objective

Migraine, a highly prevelant headache disorder, is regarded as a polygenic multifactorial disease. Serotonin (5-HT) and their respective receptors have been implicated in the patogenesis.

Methods

We investigated the 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT2C receptor gene polymorphisms and their association with migraine in Turkish patients. The rs6295, rs1300060, rs1228814, rs6311, rs6313, rs6314, rs6318, rs3813929 (−759C/T) and rs518147 polymorphisms were analyzed in 135 patients with migraine and 139 healthy subjects, using a BioMark 96.96 dynamic array system.

Results

We found no difference in the frequency of the analyzed eight out of nine polymorpisms between migraine and control groups. However, a significant association was found between the rs3813929 polymorphism in the promoter region of 5-HTR2C gene and migraine. Also, the allele of rs3813929 was more common in the migraine group.

Conclusion

This result suggests that the 5-HTR2C rs3813929 polymorphism can be a genetic risk factor for migraine in a Turkish population.

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.

Chronic dry eye symptoms after LASIK: parallels and lessons to be learned from other persistent post-operative pain disorders

Laser in-situ keratomileusis (LASIK) is a commonly performed surgical procedure used to correct refractive error. LASIK surgery involves cutting a corneal flap and ablating the stroma underneath, with known damage to corneal nerves. Despite this, the epidemiology of persistent pain and other long-term outcomes after LASIK surgery are not well understood. Available data suggest that approximately 20-55% of patients report persistent eye symptoms (generally regarded as at least 6 months post-operation) after LASIK surgery. While it was initially believed that these symptoms were caused by ocular surface dryness, and referred to as “dry eye,” it is now increasingly understood that corneal nerve damage produced by LASIK surgery resembles the pathologic neuroplasticity associated with other forms of persistent post-operative pain. In susceptible patients, these neuropathological changes, including peripheral sensitization, central sensitization, and altered descending modulation, may underlie certain persistent dry eye symptoms after LASIK surgery. This review will focus on the known epidemiology of symptoms after LASIK and discuss mechanisms of persistent post-op pain due to nerve injury that may be relevant to these patients. Potential preventative and treatment options based on approaches used for other forms of persistent post-op pain and their application to LASIK patients are also discussed. Finally, the concept of genetic susceptibility to post-LASIK ocular surface pain is presented.

Neuropathic ocular pain: an important yet underevaluated feature of dry eye

Dry eye has gained recognition as a public health problem given its prevalence, morbidity, and cost implications. Dry eye can have a variety of symptoms including blurred vision, irritation, and ocular pain. Within dry eye-associated ocular pain, some patients report transient pain whereas others complain of chronic pain. In this review, we will summarize the evidence that chronicity is more likely to occur in patients with dysfunction in their ocular sensory apparatus (ie, neuropathic ocular pain). Clinical evidence of dysfunction includes the presence of spontaneous dysesthesias, allodynia, hyperalgesia, and corneal nerve morphologic and functional abnormalities. Both peripheral and central sensitizations likely play a role in generating the noted clinical characteristics. We will further discuss how evaluating for neuropathic ocular pain may affect the treatment of dry eye-associated chronic pain.

Meta-analysis of 5-hydroxytryptamine type 2A receptor polymorphisms and migraine susceptibility

Epidemiologic studies have investigated the association of polymorphisms in 5-hydroxytryptamine type 2A receptor (5HT2A) gene and migraine susceptibility, but the results of those studies are inconclusive. To obtain a more systematic estimation of the association, we conducted a comprehensive search to examine all the eligible studies of 5HT2A polymorphisms and migraine risk. The odd ratios (ORs) with 95% confidence intervals (CIs) were used to determine the strength of the association. Publication bias was analyzed by Begg's funnel plots. Seven eligible studies regarding 5HT2A T102C and A-1438G polymorphisms with 721 cases and 713 controls were included in this meta-analysis. Overall, no significant associations were found between 5HT2A T102C (for T vs. C: OR = 1.029, 95% CI = 0.870-1.217, p = 0.739; for TT vs. CC: OR = 1.083, 95% CI = 0.760-1.544, p = 0.657; for TT + TC vs. CC: OR = 1.066, 95% CI = 0.802-1.416, p = 0.662; for TT vs. TC + CC: OR = 1.017, 95% CI = 0.774-1.336, p = 0.904) or A-1438G (for T vs. C: OR = 0.996, 95% CI = 0.726-1.365, p = 0.979; for TT vs. CC: OR = 0.983, 95% CI = 0.511-1.891, p = 0.960; for TT + TC vs. CC: OR = 1.118, 95% CI = 0.654-1.910, p = 0.684; for TT vs. TC + CC: OR = 0.890, 95% CI = 0.528-1.499, p = 0.661) polymorphisms and migraine risk. The further subgroup analysis by ethnicity, assay and disease type also found no significant association using four genetic models. Meanwhile, the publication bias analysis suggests that there is no publication bias in these studies. In conclusion, our current meta-analysis implies that 5HT2A T102C and A-1438G polymorphisms may be not risk factors in the pathogenesis of migraine.

Emerging genomic biomarkers in migraine

Migraine is a debilitating neurovascular condition classified as either migraine with aura or migraine without aura. A significant genetic basis has been implicated in migraine and has probed the role of neurotransmitters, hormones and vascular genes in this disorder. The aim of this review is to highlight the recent genetic discoveries contributing to our understanding of the complex pathogenesis of migraine. The current review will discuss the role of neurotransmitter-related genes in migraine, including the recently identified TRESK and variants of the KCNN3 gene, as well as outlining studies investigating hormone receptor genes, such as ESR1 and PGR, and vascular-related genes, including the MTHFR and NOTCH 3 genes.

Association of the A-1438G polymorphism in serotonin 2A receptor in migraine with aura among Japanese patients

We investigated the possible association of serotonin (5-HT) 2A receptor gene A-1438G polymorphism in Japanese patients with migraine. Genotyping of 5-HT(2A) A-1438G polymorphism was performed by polymerase chain reaction-restriction fragment length polymorphism in patients with migraine (male 17 : 3 with aura and 14 without aura, female 65 : 17 with aura and 48 without aura) and controls (male 31, female 84). The distribution of 5-HT(2A) A-1438G genotype frequency between migraine patients and controls did not differ. These results suggest that the A-1438G polymorphism of the 5-HT(2A) receptor gene is not a direct risk factor for migraine; however, the incidence of the A/A genotype between migraine with aura (MA) and without aura (MO) was significantly different. The 5-HT(2A) A-1438G polymorphism may be involved in determining the subtypes of migraine in Japanese.

Lack of association between five serotonin metabolism-related genes and medication overuse headache

Serotonin is involved in several central nervous system functions including pain threshold, mood regulation and drug reward. Overuse of acute medications is commonly identified as a causative factor for medication overuse headache (MOH). Apparently, MOH shares with other kinds of drug addiction some common neurobiological pathways. The objective of this study is to assess the role of serotonin metabolism genes in the genetic liability to MOH. We performed a genetic association study using polymorphisms of five serotonin metabolism-related genes: serotonin transporter (5HTT), serotonin receptor 1A (5-HT1A), serotonin receptor 1B (5-HT1B), serotonin receptor 2A (5-HT2A) and serotonin receptor 6 (5HT6) genes. We compared 138 patients with MOH with a control sample of 117 individuals without headache and without drug overuse, and with 101 patients with migraine without aura but without drug overuse (MO). The genotypic and allelic distributions of all polymorphisms investigated did not differ among the three groups. In conclusion, our study does not provide evidence that the 5HTT, 5-HT1A, 5HT1B, 5HT2A and 5HT6 gene polymorphisms play a role in the genetic predisposition to MOH.

Current and prospective pharmacological targets in relation to antimigraine action

Migraine is a recurrent incapacitating neurovascular disorder characterized by unilateral and throbbing headaches associated with photophobia, phonophobia, nausea, and vomiting. Current specific drugs used in the acute treatment of migraine interact with vascular receptors, a fact that has raised concerns about their cardiovascular safety. In the past, alpha-adrenoceptor agonists (ergotamine, dihydroergotamine, isometheptene) were used. The last two decades have witnessed the advent of 5-HT(1B/1D) receptor agonists (sumatriptan and second-generation triptans), which have a well-established efficacy in the acute treatment of migraine. Moreover, current prophylactic treatments of migraine include 5-HT(2) receptor antagonists, Ca(2+) channel blockers, and beta-adrenoceptor antagonists. Despite the progress in migraine research and in view of its complex etiology, this disease still remains underdiagnosed, and available therapies are underused. In this review, we have discussed pharmacological targets in migraine, with special emphasis on compounds acting on 5-HT (5-HT(1-7)), adrenergic (alpha(1), alpha(2,) and beta), calcitonin gene-related peptide (CGRP(1) and CGRP(2)), adenosine (A(1), A(2), and A(3)), glutamate (NMDA, AMPA, kainate, and metabotropic), dopamine, endothelin, and female hormone (estrogen and progesterone) receptors. In addition, we have considered some other targets, including gamma-aminobutyric acid, angiotensin, bradykinin, histamine, and ionotropic receptors, in relation to antimigraine therapy. Finally, the cardiovascular safety of current and prospective antimigraine therapies is touched upon.

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.

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.

Genetic architecture of human pain perception

Pain is emotionally detrimental and consciously avoided; however, it is absolutely crucial for our survival. Pain perception is one of the most complicated measurable traits because it is an aggregate of several phenotypes associated with peripheral and central nervous system dynamics, stress responsiveness and inflammatory state. As a complex trait, it is expected to have a polygenic nature shaped by environmental pressures. Here we discuss what is known about these contributing genetic variants, including recent discoveries that show a crucial role of voltage-gated sodium channel Nav1.7 in pain perception and how we can advance our understanding of the pain genetic network. We propose how both rare deleterious genetic variants and common genetic polymorphisms are mediators of human pain perception and clinical pain phenotypes.

A pharmacogenomic evaluation of migraine therapy

Migraine is a common idiopathic primary headache disorder with significant mental, physical and social health implications. Accompanying an intense unilateral pulsating head pain other characteristic migraine symptoms include nausea, emesis, phonophobia, photophobia and in approximately 20-30% of migraine cases, neurologic disturbances associated with the aura phase. Although selective serotonin (5-HT) receptor agonists (i.e., 5-HT(1B/1D)) are successful in alleviating migrainous symptoms in < or = 70% of known sufferers, for the remaining 30%, additional migraine abortive medications remain unsuccessful, not tested or yet to be identified. Genetic characterization of the migrainous disorder is making steady progress with an increasing number of genomic susceptibility loci now identified on chromosomes 1q, 4q, 5q, 6p, 11q, 14q, 15q, 17p, 18q, 19p and Xq. The 4q, 5q, 17p and 18q loci involve endophenotypic susceptibility regions for various migrainous symptoms. In an effort to develop individualized pharmacotherapeutics, the identification of these migraine endophenotypic loci may well be the catalyst needed to aid in this goal. In this review the authors discuss the present treatment of migraine, known genomic susceptibility regions and results from migraine (genetic) association studies. The authors also discuss pharmacogenomic considerations for more individualized migraine prophylactic treatments.

Genetic association study and meta-analysis of the HTR2C Cys23Ser polymorphism and migraine

The objectives of this study were to determine if the HTR2C Cys23Ser polymorphism is associated with migraine in a case-control study, and to perform a meta-analysis with present and previous available studies. The HTR2C gene is located at the Xq24-q28 chromosomal band. This band was linked to migraine with aura (MA) in two Australian families. Using the HTR2C Cys23Ser allelic variant, this gene has been ruled out as a migraine gene in 3 out of 4 studies. Only the Japanese study reported a higher risk for MA (OR=6.11; 95% CI=1.70-21.97, p trend<0.01). We performed a case-control study with 335 migraine subjects and 335 sex- and age-matched controls, and a meta-analysis pooling the results of the available data from MA subsets of patients. In the association study we found no significant differences among migraine and MA patients for this polymorphism. In the meta-analysis, under the fixed-effect model, the Ser allele did not confer higher risk for suffering MA (pooled OR=1.1; 99% CI=0.8-1.5, p=0.499). Our study did not confirm the HTR2C Cys23Ser polymorphism as a risk factor for migraine and MA.

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.

No association of C-1019G promoter polymorphism of 5-HT1A receptor gene with migraine

It is well known that migraine has a strong genetic component, although the type and number of genes involved remains unclear. There is evidence to suggest that serotonin-related genes may be involved in the pathogenesis of migraine. To investigate whether the 5-HT1A receptor gene contributes to the risk of migraine we performed an association study of C-1019G promoter polymorphism of the gene in 102 migraineurs and 93 controls. Subjects were of Han Chinese origin. No significant differences in allele (P=0.82) or genotype frequencies (P=0.71) were seen in migraineurs compared with the controls. When migraine with aura, without aura, with family history, without family history were analyzed separately, the frequencies did not vary significantly. Our results suggest that C-1019G in 5-HT1A is not a major genetic risk factor for migraine.

Serotonin transporter protein polymorphism and harm avoidance personality in migraine without aura

OBJECTIVE

To investigate polymorphisms in the serotonin transporter protein gene and harm avoidance personality dimension in patients with migraine without aura (MWOA).

BACKGROUND

The serotonin transporter protein is a key modulator of serotonergic synaptic neurotransmission. Two polymorphic regions of the gene for serotonin transporter protein have been found, and are associated with variations in the functional activity of serotonin caused by differing transcriptional efficiency. The harm avoidance (HA) personality trait may also be heritable and associated with altered serotonergic neurotransmitter activity.

DESIGN

We amplified the polymorphism in the promoter of serotonin transporter protein (5-HTTLPR) and the variable number of tandem repeats polymorphism within intron 2 (VNTR) using the polymerase chain reaction and performed genotype polymorphism analyses in 97 patients with MWOA and 100 healthy controls. We investigated serotonin-related personality traits by evaluating the HA personality dimension using a tridimensional questionnaire.

RESULTS

The genotype frequencies and allele distributions of 5-HTTLPR did not differ between patients with MWOA and controls. The VNTR genotype STin2.12/STin2.12 was significantly more common in patients with MWOA (90%) than in controls (77%; P= .017). Patients with MWOA also had HA scores (21.9 +/- 6.4) significantly higher than those of controls (16.3 +/- 6.1; P < .001).

CONCLUSIONS

Serotonergic activity might be involved in the development of MWOA and VNTR of serotonin transporter gene might be one of the genetically contributing factors.

T102C and -1438 G/A polymorphisms of the 5-HT2A receptor gene in Turkish patients with obsessive-compulsive disorder

OBJECTIVE

This study aimed to investigate the possible association between T102C and -1438 G/A polymorphism in the 5-HT2A receptor gene and susceptibility to and clinical features of obsessive-compulsive disorder (OCD).

METHOD

Fifty-eight patients with OCD and 83 healthy controls were included in the study. All patients were interviewed and rated by Yale-Brown Obsessive-Compulsive Scale. T102C and -1438 G/A polymorphisms of 5-HT2A receptor gene were determined by PCR technique in DNAs of peripheral leucocytes.

RESULTS

OCD patients and healthy controls did not show significant differences in genotype distribution for both polymorphisms investigated. We found that frequencies of the TT genotype for T102C polymorphism and the AA genotype for -1438 G/A polymorphism were significantly higher in patients with severe OCD compared to those with moderate or moderate-severe OCD.

CONCLUSION

The -1438 G/A and T102C polymorphisms of the 5-HT2A receptor gene are not associated with an increased risk of OCD. Our data suggest that the TT genotype of T102C and the AA genotype of -1438 G/A polymorphism might be a factor in clinical severity of OCD.

Common genetic risk factors for psychiatric and simatic disorders

There is increasing knowledge about considerable comorbidity between psychiatric and somatic diseases, questioning whether variations in genes could be predisposing factors for both conditions. With respect to the multiple interactions between brain and body investigations have centered on variants in several candidate genes for proteins that mediate these interactions and therefore also have implications in psychiatric disorders. The available data, although still preliminary and rare, indicate the importance of polymorphic variants in genes coding for the serotonin (5-hydroxytryptamine, 5-HT) transporter (5-HTT), the 5-HT_2A receptor, proinflammatory cytokines, and the angiotensin-converting enzyme (ACE) in migraine, fibromyalgia, cardiovascular disorders, and psychiatric conditions. The role played by these various polymorphisms remains to be determined, as does whether they are indicative of common pathophysiological mechanisms or identify a subgroup of patients with somatic disorders that are more closely related to psychiatric symptoms. Nevertheless, they do at least illustrate the potential influence of genetic differences on illness course and treatment outcome, and might be a rational approach to drug development and treatment paradigms.

Migraine genetics

The genetics of migraine is a fascinating and moving research area. Familial hemiplegic migraine, a rare subtype of migraine with a Mendelian pattern of inheritance, is caused by mutations in the chromosome 19 CACNA1A gene in approximately 75% of the families. The finding of mutations in an ionchannel subunit defines migraine as a channelopathy (eg, epilepsy). The genetics of the more frequent variants, migraine with and without aura, is more complex. Several loci have been studied in families and case-control studies, but need to be confirmed.