The TRPA1 channel in migraine mechanism and treatment

Characterisation of periorbital mechanical allodynia in the reserpine-induced fibromyalgia model in mice: The role of the Schwann cell TRPA1/NOX1 signalling pathway

Fibromyalgia (FM) is a complex and multifaceted condition characterized by a range of clinical symptoms, including widespread pain and a strong association with migraine headaches. Recent findings have underscored the role of oxidative stress and transient receptor potential ankyrin 1 (TRPA1) channel in migraine and FM. However, the precise mechanisms underlying the comorbidity between migraine and FM are unclear. Periorbital mechanical allodynia (PMA), which recapitulates one of the major symptoms of migraine, and the feed-forward mechanism driven by reactive oxygen species and TRPA1, were investigated in a reserpine-induced FM model in C57BL/6J mice, employing pharmacological interventions and genetic approaches. Reserpine-treated mice developed PMA (which was alleviated by antimigraine drugs) and increased endoneurial macrophages and oxidative stress markers in the trigeminal nerve tissues (neuroinflammation). These responses were absent upon macrophage depletion and by pharmacological inhibition or global genetic deletion of the TRPA1 channel. Furthermore, selective silencing of TRPA1 in Schwann cells attenuated both reserpine-induced PMA and neuroinflammation, while selective silencing of TRPA1 in sensory neurons reduced PMA but not neuroinflammation. In reserpine-treated mice, Schwann cell TRPA1 promoted NADPH oxidase 1-mediated reactive oxygen species generation and macrophage density increase in the mouse trigeminal nerve, which sustains PMA. Targeting TRPA1 channels in Schwann cells could offer a novel therapeutic strategy for FM-related headaches.

The ion channel TRPA1 is a modulator of the cocaine reward circuit in the nucleus accumbens

Drug addiction therapies commonly fail because continued drug use promotes the release of excessive and pleasurable dopamine levels. Because the connection between pleasure and drug use becomes hard-wired in the nucleus accumbens (NAc), which interfaces motivation, effective therapies need to modulate this mesolimbic reward system. Here, we report that mice with knockdown of the cation channel TRPA1 (transient receptor potential ankyrin 1) were resistant to the drug-seeking behavior and reward effects of cocaine compared to their wildtype litter mates. In our study, we demonstrate that TRPA1 inhibition in the NAc reduces cocaine activity and dopamine release, and conversely, that TRPA1 is critical for cocaine-induced synaptic strength in dopamine receptor 1-expressing medium spiny neurons. Taken together, our data support that cocaine-induced reward-related behavior and synaptic release of dopamine in the NAc are controlled by TRPA1 and suggest that TRPA1 has therapeutic potential as a target for drug misuse therapies.

The Interaction Mechanism Between C14-Polyacetylene Compounds and the Rat TRPA1 Receptor: An In Silico Study

Polyacetylene (PA) compounds, as natural products, exhibit remarkable properties and distinctive chemical activities. Three structurally similar C14-PA compounds-Echinophorin D, Echinophorin B, and Echinophorin A-extracted from plants demonstrate varying biological activities on the Transient Receptor Potential Channel A1 (TRPA1) protein, which belongs to the TRP (Transient Receptor Potential) family. In the current study, we investigated the binding modes of these three PA compounds with TRPA1 using molecular dynamics (MD), molecular docking, binding free energy calculations, and quantum mechanics/molecular mechanics (QM/MM) methods. Initially, a putative binding site (site-II) in TRPA1 was identified for these compounds; Echinophorin B was found to stabilize the upward A-loop of TRPA1, which is critical for its activation. Furthermore, the binding affinity calculations of PA compounds through molecular fragment decomposition indicate that the arrangement of two triple bonds and one double bond in C14-PA compounds is vital for regulating TRPA1 bioactivity. Additionally, the lipophilic and electronic properties of the three molecules were analyzed in relation to binding affinity, establishing a correlation between TRPA1 activity and these molecular properties.

Gender-different effect of Src family kinases antagonism on photophobia and trigeminal ganglion activity

BACKGROUND

Src family kinases (SFKs) contribute to migraine pathogenesis, yet its role in regulating photophobia behaviour, one of the most common forms of migraine, remains unknown. Here, we addressed whether SFKs antagonism alleviates photophobia behavior and explored the underlying mechanism involving hypothalamus and trigeminal ganglion activity, as measured by the alteration of neuropeptide levels and transcriptome respectively.

METHODS

A rapid-onset and injury-free mouse model of photophobia was developed following intranasal injection of the TRPA1 activator, umbellulone. The role of SFKs antagonism on light aversion was assessed by the total time the mouse stays in the light and transition times between the dark and light compartments. To gain insight to the preventive mechanism of SFKs antagonism, hypothalamic neuropeptides levels were assessed using enzyme linked immunofluorescent assay and trigeminal ganglion activity were assessed using RNA-sequencing and qPCR analysis.

RESULTS

SFKs antagonism by a clinically relevant SFKs inhibitor saracatinib reduced the total time in light and transition times in male mice, but not in females, suggesting SFKs play a crucial role in photophobia progressing and exhibit a male-only effect. SFKs antagonism had no effect on hypothalamic calcitonin gene-related peptide and pituitary adenylate cyclase-activating polypeptide levels of all mice investigated, suggesting the gender-different effect of saracatinib on light aversion appears to be independent of these hypothalamic neuropeptide levels. In trigeminal ganglion of male mice, photophobia is associated with profound alteration of differentially expressed genes, part of which were reversed by SFKs antagonism. Subsequent qPCR analysis showed SFKs antagonism displayed gender-different modulation of expression in some candidate genes, particularly noteworthy those encoding ion channels (trpm3, Scn8a), ATPase signaling (crebbp, Atp5α1) and kinase receptors (Zmynd8, Akt1).

CONCLUSIONS

In conclusion, our data revealed that SFKs antagonism reduced photophobia processing in male mice and exhibited gender-different modulation of trigeminal ganglion activity, primarily manifesting as alterations in the transcriptome profile. These findings underscore the potential of SFKs antagonism for allieving photophobia in males, highlighting its value in the emerging field of precision medicine.

Sex-Specific Association of Cardiovascular Risk Factors With Migraine: The Population-Based Rotterdam Study

BACKGROUND AND OBJECTIVES

Although several lines of evidence suggest a link between migraine and cardiovascular events, less is known about the association between cardiovascular risk factors (CVRFs) and migraine. This knowledge is clinically important to provide directions on mitigating the cardiovascular risk in patients with migraine. We hypothesized that CVRFs are associated with a higher migraine prevalence. Therefore, our primary objective was to investigate sex-specific associations between CVRFs and lifetime prevalence of migraine.

METHODS

We performed cross-sectional analyses within an ongoing population-based cohort study (Rotterdam Study), including middle-aged and elderly individuals. By means of (structured) interviews, physical examinations, and blood sampling, we obtained information on the lifetime prevalence of migraine and the following traditional CVRFs: current smoking, obesity, hypercholesterolemia, hypertension, and diabetes mellitus. Similarly, we obtained information on quantitative component data on these CVRFs, including pack-years of smoking, lipid levels, systolic and diastolic blood pressure (BP), body mass index, and fasting glucose levels. Patients with migraine were age-matched to individuals without migraine, and we performed conditional logistic regression analyses to investigate the sex-stratified association of CVRFs with migraine.

RESULTS

In total, 7,266 community-dwelling middle-aged and elderly persons were included (median age 66.6 [IQR 56.4-74.8] years, 57.5% females). The lifetime prevalence of migraine was 14.9%. In females, current smoking (odds ratio (OR) 0.72, 95% CI 0.58-0.90), more pack-years (OR per SD increase 0.91, 95% CI 0.84-1.00), diabetes mellitus (OR 0.74, 95% CI 0.56-0.98), and higher fasting glucose levels (OR per SD increase in glucose 0.90, 95% CI 0.82 - 0.98) were all related to a lower migraine prevalence while a higher diastolic BP related to a higher migraine prevalence (OR per SD increase 1.16, 95% CI 1.04-1.29). In males, no significant associations between CVRFs and migraine were observed.

DISCUSSION

Traditional CVRFs were either unrelated or inversely related to migraine in middle-aged and elderly individuals, but only in females. In males, we did not find any association between CVRFs and migraine. Because only an increased diastolic BP was related to a higher migraine prevalence in females, our study contributes to the hypothesis that migraine is not directly associated with traditional CVRFs. Future studies are warranted to extrapolate these findings to younger populations.

The TRPA1 Ion Channel Mediates Oxidative Stress-Related Migraine Pathogenesis

Although the introduction of drugs targeting calcitonin gene-related peptide (CGRP) revolutionized migraine treatment, still a substantial proportion of migraine patients do not respond satisfactorily to such a treatment, and new therapeutic targets are needed. Therefore, molecular studies on migraine pathogenesis are justified. Oxidative stress is implicated in migraine pathogenesis, as many migraine triggers are related to the production of reactive oxygen and nitrogen species (RONS). Migraine has been proposed as a superior mechanism of the brain to face oxidative stress resulting from energetic imbalance. However, the precise mechanism behind the link between migraine and oxidative stress is not known. Nociceptive primary afferent nerve fiber endings express ion channel receptors that change harmful stimuli into electric pain signals. Transient receptor potential cation channel subfamily A member 1 (TRPA1) is an ion channel that can be activated by oxidative stress products and stimulate the release of CGRP from nerve endings. It is a transmembrane protein with ankyrin repeats and conserved cysteines in its N-terminus embedded in the cytosol. TRPA1 may be a central element of the signaling pathway from oxidative stress and NO production to CGRP release, which may play a critical role in headache induction. In this narrative review, we present information on the role of oxidative stress in migraine pathogenesis and provide arguments that TRPA1 may be "a missing link" between oxidative stress and migraine and therefore a druggable target in this disease.

Visual analysis of global research on the transient receptor potential ankyrin 1 channel: A literature review from 2002 to 2022

Background and aims

The transient receptor potential ankyrin 1 (TRPA1) channel has become a focus in pain research. However, there are no bibliometric studies that systematically analyze the existing research in this area. This study aimed to provide a systematic review of the existing literature on TRPA1 using a bibliometric analysis.

Methods

Published literature in the field of TRPA1 was collected from the Web of Science Core Collection database. Quantitative and qualitative analyses of publications, countries, institutions, authors, journals, and other entries were conducted using Excel, VOSview, and Citespace software to provide insight into global research hotspots and trends in the TRPA1 field.

Results

This study included 1189 scientific products published in 398 journals from 52 countries. The United States of America (n = 367) had the most publications, ahead of Japan (n = 212) and China (n = 199). The University of Florence (n = 55) was the most productive institution and Pierangelo Geppetti (n = 46) was the most productive author. PLoS One (n = 40) published the most articles on TRPA1. Pain, cold, inflammation, covalent modification, hyperalgesia, and oxidative stress were the most common keywords used in the studies.

Conclusion

This study provides the first bibliometric analysis of TRPA1 publications. The physiological functions of TRPA1, TRPA1, and neuropathic pain, TRPA1 as a therapeutic target, and agonists of TRPA1 are trending in TRPA1 research. Neuropathic pain, apoptosis, and sensitization could be focus areas of future research. This study provides important insight in the field of TRPA1 research.

Transient Receptor Potential Ankyrin 1-dependent Activation of Extracellular Signal-regulated Kinase 2 in the Cerebral Cortices Contributes to Cortical Spreading Depolarization

Extracellular signal-regulated kinase (ERK) are serine/threonine-selective proteins and ERK1/2 can be phosphorylated in peripheral and central brain regions after cortical spreading depolarization (CSD) and calcitonin gene-related peptide; However, it remains unclear about whether and how ERK activity modulates CSD that correlates to migraine aura. Here, we determined the role of ERK in regulating CSD and explored the underlying mechanism involving transient receptor potential ankyrin 1 (TRPA1), a stress-sensing cation channel. CSD was recorded using intrinsic optical imaging in mouse brain slices, and electrophysiology in rats. Phosphorylated ERK (pERK1/2) and interleukin-1β (IL-1β) protein levels were detected using Western blot or enzyme-linked immunosorbent assay, respectively. IL-1β mRNA level was detected using qPCR. The results showed that an ERK inhibitor, SCH77298, markedly prolonged CSD latency and reduced propagation rate in mouse brain slices. Corresponding to this, CSD induction increased levels of cytosolic pERK1/2 in ipsilateral cerebral cortices of rats, the elevation of which correlated to the level of IL-1β mRNA. Mechanistic analysis showed that pre-treatment of an anti-TRPA1 antibody reduced the cytosolic pERK2 level but not pERK1 following CSD in cerebral cortices of rats and this level of pERK2 correlated with that of cerebral cortical IL-1β protein. Furthermore, an ERK activator, AES16-2M, but not its scrambled control, reversed the prolonged CSD latency by a TRPA1 inhibitor, HC-030031, in mouse brain slices. These data revealed a crucial role of ERK activity in regulating CSD, and elevation of pERK and IL-1β production induced by CSD is predominantly TRPA1 channel-dependent, thereby contributing to migraine pathogenesis.

Influences of Genetic and Environmental Factors on Chronic Migraine: A Narrative Review

PURPOSE OF REVIEW

In this narrative review, we aim to summarize recent insights into the complex interplay between environmental and genetic factors affecting the etiology, development, and progression of chronic migraine (CM).

RECENT FINDINGS

Environmental factors such as stress, sleep dysfunction, fasting, hormonal changes, weather patterns, dietary compounds, and sensory stimuli are critical triggers that can contribute to the evolution of episodic migraine into CM. These triggers are particularly influential in genetically predisposed individuals. Concurrently, genome-wide association studies (GWAS) have revealed over 100 genetic loci linked to migraine, emphasizing a significant genetic basis for migraine susceptibility. In CM, environmental and genetic factors are of equal importance and contribute to the pathophysiology of the condition. Understanding the bidirectional interactions between these elements is crucial for advancing therapeutic approaches and preventive strategies. This balanced perspective encourages continued research into the complex gene-environment nexus to improve our understanding and management of CM.

Association between oxidative balance score and self-reported severe headache or migraine based on NHANES 1999 to 2004 data: A cross-sectional study

Purpose

The pathophysiological mechanisms underlying migraine remain elusive, with oxidative stress hypothesized as a potential etiological factor. The Oxidative Balance Score (OBS) is a comprehensive tool for assessing the impact of diet and lifestyle on oxidative stress, thereby gauging an individual's overall antioxidant capacity. In this cross-sectional study, we explored the correlation between OBS and migraine prevalence among a cohort of US adults.

Methods

We analyzed data from 6195 participants aged 20 years and above, drawn from the National Health and Nutrition Examination Survey (NHANES) conducted between 1999 and 2004. We employed multiple logistic regression, coupled with sensitivity analyses, to investigate the relationship between OBS and migraine. Subsequent subgroup analyses and interaction tests were performed to assess the consistency of this association across the population.

Results

Multiple logistic regression revealed an inverse relationship between OBS and the likelihood of experiencing migraines. Specifically, individuals in the highest OBS quartile exhibited a significantly reduced migraine risk compared to those in the lowest quartile (OR = 0.98, 95% Confidence Interval (CI): 0.97-0.99, P = 0.0001). Furthermore, restricted cubic spline curves indicated a non-linear association between dietary OBS and migraine incidence (non-linear P = 0.0258).

Discussion

Our findings suggest that adherence to an antioxidant-rich diet may be an effective strategy for mitigating migraine, potentially by influencing oxidative balance.

Research Progress on TRPA1 in Diseases

For a long time, the physiological activity of TRP ion channels and the response to various stimuli have been the focus of attention, and the physiological functions mediated by ion channels have subtle links with the occurrence of various diseases. Our group has been engaged in the study of ion channels. In recent years, the report rate of TRPA1, the only member of the TRPA subfamily in the newly described TRP channel, has been very high. TRPA1 channels are not only abundantly expressed in peptidergic nociceptors but are also found in many nonneuronal cell types and tissues, and through the regulation of Ca2+ influx, various neuropeptides and signaling pathways are involved in the regulation of nerves, respiration, circulation, and various diseases and inflammation throughout the body. In this review, we mainly summarize the effects of TRPA1 on various systems in the body, which not only allows us to have a more systematic and comprehensive understanding of TRPA1 but also facilitates more in-depth research on it in the future.

Xenobiotic Exposure and Migraine-Associated Signaling: A Multimethod Experimental Study Exploring Cellular Assays in Combination with Ex Vivo and In Vivo Mouse Models

BACKGROUND

Mechanisms for how environmental chemicals might influence pain has received little attention. Epidemiological studies suggest that environmental factors such as pollutants might play a role in migraine prevalence. Potential targets for pollutants are the transient receptor potential (TRP) channels ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1), which on activation release pain-inducing neuropeptide calcitonin gene-related peptide (CGRP).

OBJECTIVE

In this study, we aimed to examine the hypothesis that environmental pollutants via TRP channel signaling and subsequent CGRP release trigger migraine signaling and pain.

METHODS

A calcium imaging-based screen of environmental chemicals was used to investigate activation of migraine pain-associated TRP channels TRPA1 and TRPV1. Based on this screen, whole-cell patch clamp and in silico docking were performed for the pesticide pentachlorophenol (PCP) as proof of concept. Subsequently, PCP-mediated release of CGRP and vasodilatory responses of cerebral arteries were investigated. Finally, we tested whether PCP could induce a TRPA1-dependent induction of cutaneous hypersensitivity in vivo in mice as a model of migraine-like pain.

RESULTS

A total of 16 out of the 52 screened environmental chemicals activated TRPA1 at 10 or 100 μ M . None of the investigated compounds activated TRPV1. Using PCP as a model of chemical interaction with TRPA1, in silico molecular modeling suggested that PCP is stabilized in a lipid-binding pocket of TRPA1 in comparison with TRPV1. In vitro, ex vivo, and in vivo experiments showed that PCP induced calcium influx in neurons and resulted in a TRPA1-dependent CGRP release from the brainstem and dilation of cerebral arteries. In a mouse model of migraine-like pain, PCP induced a TRPA1-dependent increased pain response (N total = 144 ).

DISCUSSION

Here we show that multiple environmental pollutants interact with the TRPA1-CGRP migraine pain pathway. The data provide valuable insights into how environmental chemicals can interact with neurobiology and provide a potential mechanism for putative increases in migraine prevalence over the last decades. https://doi.org/10.1289/EHP12413.

A proton-inhibited DEG/ENaC ion channel maintains neuronal ionstasis and promotes neuronal survival under stress

The nervous system participates in the initiation and modulation of systemic stress. Ionstasis is of utmost importance for neuronal function. Imbalance in neuronal sodium homeostasis is associated with pathologies of the nervous system. However, the effects of stress on neuronal Na⁺ homeostasis, excitability, and survival remain unclear. We report that the DEG/ENaC family member DEL-4 assembles into a proton-inactivated sodium channel. DEL-4 operates at the neuronal membrane and synapse to modulate Caenorhabditis elegans locomotion. Heat stress and starvation alter DEL-4 expression, which in turn alters the expression and activity of key stress-response transcription factors and triggers appropriate motor adaptations. Similar to heat stress and starvation, DEL-4 deficiency causes hyperpolarization of dopaminergic neurons and affects neurotransmission. Using humanized models of neurodegenerative diseases in C. elegans, we showed that DEL-4 promotes neuronal survival. Our findings provide insights into the molecular mechanisms by which sodium channels promote neuronal function and adaptation under stress.

Transient receptor potential ankyrin 1 (TRPA1) modulators: Recent update and future perspective

The transient receptor potential ankyrin 1 (TRPA1) channel is a non-selective cation channel that senses irritant chemicals. Its activation is closely associated with pain, inflammation, and pruritus. TRPA1 antagonists are promising treatments for these diseases, and there has been a recent upsurge in their application to new areas such as cancer, asthma, and Alzheimer's disease. However, due to the generally disappointing performance of TRPA1 antagonists in clinical studies, scientists must pursue the development of antagonists with higher selectivity, metabolic stability, and solubility. Moreover, TRPA1 agonists provide a deeper understanding of activation mechanisms and aid in antagonist screening. Therefore, we summarize the TRPA1 antagonists and agonists developed in recent years, with a particular focus on structure-activity relationships (SARs) and pharmacological activity. In this perspective, we endeavor to keep abreast of cutting-edge ideas and provide inspiration for the development of more effective TRPA1-modulating drugs.

Multiple Chemical Sensitivity: It's time to catch up to the science

Multiple chemical sensitivity (MCS) is a complex medical condition associated with low dose chemical exposures. MCS is characterized by diverse features and common comorbidities, including fibromyalgia, cough hypersensitivity, asthma, and migraine, and stress/anxiety, with which the syndrome shares numerous neurobiological processes and altered functioning within diverse brain regions. Predictive factors linked to MCS comprise genetic influences, gene-environment interactions, oxidative stress, systemic inflammation, cell dysfunction, and psychosocial influences. The development of MCS may be attributed to the sensitization of transient receptor potential (TRP) receptors, notably TRPV1 and TRPA1. Capsaicin inhalation challenge studies demonstrated that TRPV1 sensitization is manifested in MCS, and functional brain imaging studies revealed that TRPV1 and TRPA1 agonists promote brain-region specific neuronal variations. Unfortunately, MCS has often been inappropriately viewed as stemming exclusively from psychological disturbances, which has fostered patients being stigmatized and ostracized, and often being denied accommodation for their disability. Evidence-based education is essential to provide appropriate support and advocacy. Greater recognition of receptor-mediated biological mechanisms should be incorporated in laws, and regulation of environmental exposures.

Phytol from Faeces Bombycis alleviated migraine pain by inhibiting Nav1.7 sodium channels

ETHNOPHARMACOLOGICAL RELEVANCE

Faeces Bombycis (silkworm excrement, called Cansha in Chinese), is the dried faeces of the larvae of silkworm. According to the theories of traditional Chinese medicine recorded in "Compendium of Materia Medica", Faeces Bombycis has often been prescribed in traditional Chinese medicine for the treatment of recurrent headache, rheumatalgia, rubella and itching et al. However, the bioactive components and their exact mechanisms underlying the pain-relieving effects remain to be revealed.

AIM OF THE STUDY

The present study aimed to evaluate the analgesic effect of Faeces Bombycis extract (FBE) on migraine, explore the main active constituents and investigate the pharmacological mechanisms for its pain relief.

MATERIALS AND METHODS

The bioactivity of different extracts from Faeces Bombycis was tracked by the nitroglycerin (NTG)-induced migraine model on rats and identified by NMR spectroscopic data. Whole-cell patch clamp technique, an electrophysiological method, was used to screen the potential targets and study the mechanism of action for the bioactive compound. The following targets have been screened and studied, including Nav1.7 sodium channels, Nav1.8 sodium channels, TRPV1 channels and TRPA1 channels. The trigeminal ganglion neurons were further used to study the effects of the identified compound on neuronal excitability.

RESULTS

By testing the bioactivity of the different extracts proceedingly, fraction petroleum ether showed higher anti-migraine activity. Through further step-by-step isolations, 7 compounds were isolated. Among them, phytol was identified with the highest yield and displayed a potent anti-migraine effect. By screening the potential ion channel targets for migraine, phytol was found to preferentially block the inactivated state of Nav1.7 sodium channels with half-inhibition concentration 0.32 ± 0.05 μM. Thus, the effects of phytol on the biophysical properties of Nav1.7 sodium channels were further characterized. Phytol induced a hyperpolarizing shift of voltage-dependent inactivation and slowed the recovery from inactivation. The affinity of phytol became weaker in the inactivation-deficient Nav1.7 channels (Nav1.7-WCW). And such an effect was independent on the local anesthetic site (Nav1.7 F1737A). Consistent with the data from recombinant channels, the compound also displayed state-dependent inhibition on neuronal sodium channels and further decreased the neuronal excitability in trigeminal ganglion neurons. Moreover, besides Nav1.7 channel, phytol also antagonized the activation of TRPV1 and TRPA1 channels at micromolar concentrations with a weaker affinity.

CONCLUSION

Our results demonstrated that phytol is the major anti-migraine ingredient of Faeces Bombycis and alleviates migraine behaviors by acting on Nav1.7 sodium channels in the trigeminal ganglion neurons. This study provided evidences for the therapeutic application of Faeces Bombycis and phytol on migraine disease.

The putative role of neuroinflammation in the complex pathophysiology of migraine: From bench to bedside

The implications of neurogenic inflammation and neuroinflammation in the pathophysiology of migraine have been clearly demonstrated in preclinical migraine models involving several sites relevant in the trigemino-vascular system, including dural vessels and trigeminal endings, the trigeminal ganglion, the trigeminal nucleus caudalis as well as central trigeminal pain processing structures. In this context, a relevant role has been attributed over the years to some sensory and parasympathetic neuropeptides, in particular calcitonin gene neuropeptide, vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide. Several preclinical and clinical lines of evidence also support the implication of the potent vasodilator and messenger molecule nitric oxide in migraine pathophysiology. All these molecules are involved in vasodilation of the intracranial vasculature, as well as in the peripheral and central sensitization of the trigeminal system. At meningeal level, the engagement of some immune cells of innate immunity, including mast-cells and dendritic cells, and their mediators, has been observed in preclinical migraine models of neurogenic inflammation in response to sensory neuropeptides release due to trigemino-vascular system activation. In the context of neuroinflammatory events implicated in migraine pathogenesis, also activated glial cells in the peripheral and central structures processing trigeminal nociceptive signals seem to play a relevant role. Finally, cortical spreading depression, the pathophysiological substrate of migraine aura, has been reported to be associated with inflammatory mechanisms such as pro-inflammatory cytokine upregulation and intracellular signalling. Reactive astrocytosis consequent to cortical spreading depression is linked to an upregulation of these inflammatory markers. The present review summarizes current findings on the roles of immune cells and inflammatory responses in the pathophysiology of migraine and their possible exploitation in the view of innovative disease-modifying strategies.

Defining metabolic migraine with a distinct subgroup of patients with suboptimal inflammatory and metabolic markers

Emerging evidence suggest migraine is a response to cerebral energy deficiency or oxidative stress in the brain. Beta-hydroxybutyrate (BHB) is likely able to circumvent some of the meta-bolic abnormalities reported in migraine. Exogenous BHB was given to test this assumption and, in this post-hoc analysis, multiple metabolic biomarkers were identified to predict  clinical improvements. A randomized clinical trial, involving 41 patients with episodic migraine. Each treatment period was 12 weeks long, followed by eight weeks of washout phase / second run-in phase before entering the corresponding second treatment period. The primary endpoint was the number of migraine days in the last 4 weeks of treatment adjusted for baseline. BHB re-sponders were identified (those with at least a 3-day reduction in migraine days over placebo) and its predictors were evaluated using Akaike's Information Criterion (AIC) stepwise boot-strapped analysis and logistic regression. Responder analysis showed that metabolic markers could identify a "metabolic migraine" subgroup, which responded to BHB with a 5.7 migraine days reduction compared to the placebo. This analysis provides further support for a "metabolic migraine" subtype. Additionally, these analyses identified low-cost and easily accessible biomarkers that could guide recruitment in future research on this subgroup of patients.This study is part of the trial registration: ClinicalTrials.gov: NCT03132233, registered on 27.04.2017, https://clinicaltrials.gov/ct2/show/NCT03132233.

Exploring Novel Therapeutic Targets in the Common Pathogenic Factors in Migraine and Neuropathic Pain

Migraine and neuropathic pain (NP) are both painful, disabling, chronic conditions which exhibit some symptom similarities and are thus considered to share a common etiology. The calcitonin gene-related peptide (CGRP) has gained credit as a target for migraine management; nevertheless, the efficacy and the applicability of CGRP modifiers warrant the search for more effective therapeutic targets for pain management. This scoping review focuses on human studies of common pathogenic factors in migraine and NP, with reference to available preclinical evidence to explore potential novel therapeutic targets. CGRP inhibitors and monoclonal antibodies alleviate inflammation in the meninges; targeting transient receptor potential (TRP) ion channels may help prevent the release of nociceptive substances, and modifying the endocannabinoid system may open a path toward discovery of novel analgesics. There may exist a potential target in the tryptophan-kynurenine (KYN) metabolic system, which is closely linked to glutamate-induced hyperexcitability; alleviating neuroinflammation may complement a pain-relieving armamentarium, and modifying microglial excitation, which is observed in both conditions, may be a possible approach. Those are several potential analgesic targets which deserve to be explored in search of novel analgesics; however, much evidence remains missing. This review highlights the need for more studies on CGRP modifiers for subtypes, the discovery of TRP and endocannabinoid modulators, knowledge of the status of KYN metabolites, the consensus on cytokines and sampling, and biomarkers for microglial function, in search of innovative pain management methods for migraine and NP.

TRPA1 participation in behavioral impairment induced by chronic corticosterone administration

RATIONALE

Major depressive disorder (MDD) is one of the most diagnosed mental disorders. Despite this, its pathophysiology remains poorly understood. In this context, basic research aims to unravel the pathophysiological mechanisms of MDD as well as investigate new targets and substances with therapeutic potential. Transient receptor potential ankyrin 1 (TRPA1) is a transmembrane channel considered a sensor for inflammation and oxidative stress. Importantly, both inflammation and oxidative stress have been suggested as participants in the pathophysiology of MDD. However, the potential participation of TRPA1 in depressive disorder remains poorly investigated.

OBJECTIVE

To investigate the involvement of the TRPA1 channel in the behavioral changes induced by chronic corticosterone administration (CCA) in male mice.

METHODS

Swiss male mice were exposed to 21 days of CCA protocol and then treated with HC-030031 or A-967079, TRPA1 antagonists. Behavioral tests, analyzes of oxidative parameters and TRPA1 immunocontent were performed in the prefrontal cortex (PFC) and hippocampus (HIP).

RESULTS

CCA induced despair-like behavior in mice accompanied by an increase in the levels of hydrogen peroxide (H₂O₂), a TRPA1 agonist, which was reversed by TRPA1 antagonists and ketamine (positive control). In addition, CCA protocol reduced the immunocontent of this channel in the HIP and showed a tendency to increase the TRPA1 protein expression in the PFC.

CONCLUSION

Our work suggests that TRPA1 channel appears crucial to mediate the behavioral impairment induced by CCA in male Swiss mice.

Inflammation-the role of TRPA1 channel

Recently, increasing numbers of studies have demonstrated that transient receptor potential ankyrin 1 (TRPA1) can be used as a potential target for the treatment of inflammatory diseases. TRPA1 is expressed in both neuronal and non-neuronal cells and is involved in diverse physiological activities, such as stabilizing of cell membrane potential, maintaining cellular humoral balance, and regulating intercellular signal transduction. TRPA1 is a multi-modal cell membrane receptor that can sense different stimuli, and generate action potential signals after activation via osmotic pressure, temperature, and inflammatory factors. In this study, we introduced the latest research progress on TRPA1 in inflammatory diseases from three different aspects. First, the inflammatory factors released after inflammation interacts with TRPA1 to promote inflammatory response; second, TRPA1 regulates the function of immune cells such as macrophages and T cells, In addition, it has anti-inflammatory and antioxidant effects in some inflammatory diseases. Third, we have summarized the application of antagonists and agonists targeting TRPA1 in the treatment of some inflammatory diseases.

A bibliometrics analysis and visualization study of TRPV1 channel

Background: At the end of the 1990s, transient receptor potential vanilloid 1 (TRPV1) was first identified and cloned, serving as a key pain and heat sensor in humans. A large body of evidence have revealed its polymodal structure, complex function and wide-spread distribution, the specific mechanism of the ion channel remains unclear. Our goal here is to perform a bibliometric analysis and visualization study to present hotspots and trends in TRPV1 channel. Materials and Methods: TRPV1-related publications from inception to 2022 were retrieved from the Web of Science database. Excel, VOSviewer, and CiteSpace software were utilized for co-authorship, co-citation and co-occurrence analysis. Results: There were 9,113 publications included in the study, the number of publications increased rapidly after 1989, from 7 in 1990 to 373 in 2007, during which the number of citations per publication (CPP) also reached a peak in 2000 (CPP = 106.52). A total of 1,486 journals published TRPV1 articles, mainly belong to Q1 or Q2 divisions; The United States published the most articles (TP = 3,080), followed by Japan (TP = 1,221), China (TP = 1,217), and England (TP = 734); In recent years, the TRPV1-related research direction has been broaden to multiple fields related to inflammation, oxidative stress, and apoptosis; Keyword clustering refined the topic distributions and could be generalized as neuralgia, endogenous cannabinoid system, TRPV1 mediated airway hyperresponsiveness, involvement of apoptosis, TRPV1 antagonists as therapy targets. Conclusion: By conducting an exhaustive bibliographic search, this review refined the topic distributions and generalized as neuralgia, endogenous cannabinoid system, TRPV1 mediated airway hyperresponsiveness, involvement of apoptosis, TRPV1 antagonists as therapy targets. It is currently being clarified how exactly TRPV1 works as an ion channel, and much more in-depth basic research is needed in the future.

TRP Channels: Recent Development in Translational Research and Potential Therapeutic Targets in Migraine

Migraine is a chronic neurological disorder that affects approximately 12% of the population. The cause of migraine headaches is not yet known, however, when the trigeminal system is activated, neuropeptides such as calcitonin gene-related peptide (CGRP) and substance P (SP) are released, which cause neurogenic inflammation and sensitization. Advances in the understanding of migraine pathophysiology have identified new potential pharmacological targets. In recent years, transient receptor potential (TRP) channels have been the focus of attention in the pathophysiology of various pain disorders, including primary headaches. Genetic and pharmacological data suggest the role of TRP channels in pain sensation and the activation and sensitization of dural afferents. In addition, TRP channels are widely expressed in the trigeminal system and brain regions which are associated with the pathophysiology of migraine and furthermore, co-localize several neuropeptides that are implicated in the development of migraine attacks. Moreover, there are several migraine trigger agents known to activate TRP channels. Based on these, TRP channels have an essential role in migraine pain and associated symptoms, such as hyperalgesia and allodynia. In this review, we discuss the role of the certain TRP channels in migraine pathophysiology and their therapeutic applicability.

The role of TRPA1 channels in thermosensation

Transient receptor potential ankyrin 1 (TRPA1) is a polymodal nonselective cation channel sensitive to different physical and chemical stimuli. TRPA1 is associated with many important physiological functions in different species and thus is involved in different degrees of evolution. TRPA1 acts as a polymodal receptor for the perceiving of irritating chemicals, cold, heat, and mechanical sensations in various animal species. Numerous studies have supported many functions of TRPA1, but its temperature-sensing function remains controversial. Although TRPA1 is widely distributed in both invertebrates and vertebrates, and plays a crucial role in tempreture sensing, the role of TRPA1 thermosensation and molecular temperature sensitivity are species-specific. In this review, we summarize the temperature-sensing role of TRPA1 orthologues in terms of molecular, cellular, and behavioural levels.

Modulation of Glia Activation by TRPA1 Antagonism in Preclinical Models of Migraine

Preclinical data point to the contribution of transient receptor potential ankyrin 1 (TRPA1) channels to the complex mechanisms underlying migraine pain. TRPA1 channels are expressed in primary sensory neurons, as well as in glial cells, and they can be activated/sensitized by inflammatory mediators. The aim of this study was to investigate the relationship between TRPA1 channels and glial activation in the modulation of trigeminal hyperalgesia in preclinical models of migraine based on acute and chronic nitroglycerin challenges. Rats were treated with ADM_12 (TRPA1 antagonist) and then underwent an orofacial formalin test to assess trigeminal hyperalgesia. mRNA levels of pro- and anti-inflammatory cytokines, calcitonin gene-related peptide (CGRP) and glia cell activation were evaluated in the Medulla oblongata and in the trigeminal ganglia. In the nitroglycerin-treated rats, ADM_12 showed an antihyperalgesic effect in both acute and chronic models, and it counteracted the changes in CGRP and cytokine gene expression. In the acute nitroglycerin model, ADM_12 reduced nitroglycerin-induced increase in microglial and astroglial activation in trigeminal nucleus caudalis area. In the chronic model, we detected a nitroglycerin-induced activation of satellite glial cells in the trigeminal ganglia that was inhibited by ADM_12. These findings show that TRPA1 antagonism reverts experimentally induced hyperalgesia in acute and chronic models of migraine and prevents multiple changes in inflammatory pathways by modulating glial activation.

Environmental Stressors and the PINE Network: Can Physical Environmental Stressors Drive Long-Term Physical and Mental Health Risks?

Both psychosocial and physical environmental stressors have been linked to chronic mental health and chronic medical conditions. The psycho-immune-neuroendocrine (PINE) network details metabolomic pathways which are responsive to varied stressors and link chronic medical conditions with mental disorders, such as major depressive disorder via a network of pathophysiological pathways. The primary objective of this review is to explore evidence of relationships between airborne particulate matter (PM, as a concrete example of a physical environmental stressor), the PINE network and chronic non-communicable diseases (NCDs), including mental health sequelae, with a view to supporting the assertion that physical environmental stressors (not only psychosocial stressors) disrupt the PINE network, leading to NCDs. Biological links have been established between PM exposure, key sub-networks of the PINE model and mental health sequelae, suggesting that in theory, long-term mental health impacts of PM exposure may exist, driven by the disruption of these biological networks. This disruption could trans-generationally influence health; however, long-term studies and information on chronic outcomes following acute exposure event are still lacking, limiting what is currently known beyond the acute exposure and all-cause mortality. More empirical evidence is needed, especially to link long-term mental health sequelae to PM exposure, arising from PINE pathophysiology. Relationships between physical and psychosocial stressors, and especially the concept of such stressors acting together to impact on PINE network function, leading to linked NCDs, evokes the concept of syndemics, and these are discussed in the context of the PINE network.

Proteomic and metabolomic profiling of acupuncture for migraine reveals a correlative link via energy metabolism

Migraine is a neurovascular disease with a high disability rate. Acupuncture treatment has emerged as a safe and viable alternative prophylactic therapy that can effectively alleviate the duration and frequency of migraine attacks. However, the therapeutic mechanisms underlying the effects of acupuncture are yet to be systematically elucidated. In this study, we enrolled female patients with migraine without aura (n = 20) and healthy controls (n = 10). Patients received acupuncture treatment on DU20, DU24, bilateral GB13, GB8, and GB20, applied three times per week over the course of 4 weeks for 12 sessions in total. Blood samples were collected from the median cubital vein before and after acupuncture treatment. Proteomic and metabolomic profiling was performed using liquid chromatography-mass spectrometry to determine the characteristics of differentially expressed molecules and expression of their corresponding biological pathways as well as to elucidate the pathogenesis of migraine and the biological effects underlying the treatment of migraine with acupuncture. Proteomic and metabolomic profiling of plasma samples from patients with migraine without aura before and after acupuncture treatment revealed enrichment of immune-related pathway functions and the arginine synthesis pathway. Joint pathway analyses revealed significant enrichment of the pentose phosphate and glycolysis/gluconeogenesis pathways in patients with migraine. The glycolysis/gluconeogenesis and riboflavin metabolism pathways were significantly enriched after acupuncture treatment. The expression levels of various key proteins and metabolites, including α-D-glucose, flavin adenine dinucleotide, biliverdin reductase B, and L-glutamate, were significantly differentially expressed before and after acupuncture treatment in patients with migraine without aura. Treatment of migraine with acupuncture was associated with significant changes in key molecules and pathways, indicative of physiological changes in the trigeminovascular system, glutamate neurotoxicity, and other migraine-related physiological changes. Overall, our comprehensive analysis using proteomic and metabolomic profiling demonstrates that energy metabolism may serve as a key correlative link in the occurrence of migraine and the therapeutic effects of acupuncture treatment. Our findings may facilitate the identification of diagnostic and therapeutic modalities in the ongoing search for effective treatments for migraine attacks.

ATP-Sensitive Potassium Channels in Migraine: Translational Findings and Therapeutic Potential

Globally, migraine is a leading cause of disability with a huge impact on both the work and private life of affected persons. To overcome the societal migraine burden, better treatment options are needed. Increasing evidence suggests that ATP-sensitive potassium (KATP) channels are involved in migraine pathophysiology. These channels are essential both in blood glucose regulation and cardiovascular homeostasis. Experimental infusion of the KATP channel opener levcromakalim to healthy volunteers and migraine patients induced headache and migraine attacks in 82-100% of participants. Thus, this is the most potent trigger of headache and migraine identified to date. Levcromakalim likely induces migraine via dilation of cranial arteries. However, other neuronal mechanisms are also proposed. Here, basic KATP channel distribution, physiology, and pharmacology are reviewed followed by thorough review of clinical and preclinical research on KATP channel involvement in migraine. KATP channel opening and blocking have been studied in a range of preclinical migraine models and, within recent years, strong evidence on the importance of their opening in migraine has been provided from human studies. Despite major advances, translational difficulties exist regarding the possible anti-migraine efficacy of KATP channel blockage. These are due to significant species differences in the potency and specificity of pharmacological tools targeting the various KATP channel subtypes.

The role of TRPV4 channels in cutaneous epithelia

Transient receptor potential vanilloid 4 (TRPV4) channels are multi-modally activated cation permeable channels that are expressed most organ tissues including the skin. TRPV4 is highly expressed in the skin and functions in skin resident cells such as epidermal keratinocytes, melanocytes, immune mast cells and macrophages, and cutaneous neurons. TRPV4 plays many crucial roles in skin homeostasis to affect an extensive range of processes such as temperature sensation, osmo-sensation, hair growth, cell apoptosis, skin barrier integrity, differentiation, nociception and itch. Since TRPV4 functions in a plenitude of pathological states, TRPV4 can become a versatile therapeutic target for diseases such as chronic pain, itch and skin cancer.

DNA Damage and Repair in Migraine: Oxidative Stress and Beyond

Energy generation in the brain to ameliorate energy deficit in migraine leads to oxidative stress as it is associated with reactive oxygen species (ROS) that may damage DNA and show a pronociceptive action in meninges mediated by transient receptor potential cation channel subfamily A member 1 (TRPA1). Recent studies show high levels of single-strand breaks (SSBs) at specific sites in the genome of postmitotic neurons and point at SSB repair (SSBR) as an important element of homeostasis of the central nervous system. DNA topoisomerase 1 (TOP1) is stabilized in the DNA damage-inducing state by neuronal stimulation, including cortical spreading depression. Impairment in poly (ADP-ribose) polymerase 1 (PARP-1) and X-ray repair cross complementing 1 (XRCC1), key SSBR proteins, may be linked with migraine by transient receptor potential melastatin 2 (TRPM2). TRPM2 may also mediate the involvement of migraine-related neuroinflammation with PARP-1 activated by oxidative stress-related SSBs. In conclusion, aberrant activity of SSBR evoked by compromised PARP-1 and XRCC1 may contribute to pathological phenomena in the migraine brain. Such aberrant SSBR results in the lack of repair or misrepair of SSBs induced by ROS or resulting from impaired TOP1. Therefore, components of SSBR may be considered a prospective druggable target in migraine.

New Insights on Metabolic and Genetic Basis of Migraine: Novel Impact on Management and Therapeutical Approach

Migraine is a hereditary disease, usually one-sided, sometimes bilateral. It is characterized by moderate to severe pain, which worsens with physical activity and may be associated with nausea and vomiting, may be accompanied by photophobia and phonophobia. The disorder can occur at any time of the day and can last from 4 to 72 h, with and without aura. The pathogenic mechanism is unclear, but extensive preclinical and clinical studies are ongoing. According to electrophysiology and imaging studies, many brain areas are involved, such as cerebral cortex, thalamus, hypothalamus, and brainstem. The activation of the trigeminovascular system has a key role in the headache phase. There also appears to be a genetic basis behind the development of migraine. Numerous alterations have been identified, and in addition to the genetic cause, there is also a close association with the surrounding environment, as if on the one hand, the genetic alterations may be responsible for the onset of migraine, on the other, the environmental factors seem to be more strongly associated with exacerbations. This review is an analysis of neurophysiological mechanisms, neuropeptide activity, and genetic alterations that play a fundamental role in choosing the best therapeutic strategy. To date, the goal is to create a therapy that is as personalized as possible, and for this reason, steps forward have been made in the pharmacological field in order to identify new therapeutic strategies for both acute treatment and prophylaxis.

Transient Receptor Potential Channel 4 Small-Molecule Inhibition Alleviates Migraine-Like Behavior in Mice

Migraine is a common neurological disorder with few available treatment options. Recently, we have demonstrated the role of transient receptor potential cation channel subfamily C member 4 (TRPC4) in itch and the modulation of the calcitonin gene-related peptide (CGRP), a biomarker and emerging therapeutic target for migraine. In this study, we characterized the role of TRPC4 in pain and evaluated its inhibition as anti-migraine pain therapy in preclinical mouse models. First, we found that TRPC4 is highly expressed in trigeminal ganglia and its activation not only mediates itch but also pain. Second, we demonstrated that the small-molecule inhibitor ML204, a specific TRPC4 antagonist, significantly reduced episodic and chronic migraine-like behaviors in male and female mice after injection of nitroglycerin (NTG), a well-known migraine inducer in rodents and humans. Third, we found a significant decrease in CGRP protein levels in the plasma of both male and female mice treated with ML-204, which largely prevented the development of chronic migraine-like behavior. Using sensory neuron cultures, we confirmed that activation of TRPC4 elicited release of CGRP, which was significantly diminished by ML-204. Collectively, our findings identify TRPC4 in peripheral sensory neurons as a mediator of CGRP release and NTG-evoked migraine. Since a TRPC4 antagonist is already in clinical trials, we expect that this study will rapidly lead to novel and effective clinical treatments for migraineurs.

TRPA1-Mediated Src Family Kinases Activity Facilitates Cortical Spreading Depression Susceptibility and Trigeminovascular System Sensitization

Transient receptor potential ankyrin 1 (TRPA1) plays a role in migraine and is proposed as a promising target for migraine therapy. However, TRPA1-induced signaling in migraine pathogenesis is poorly understood. In this study, we explored the hypothesis that Src family kinases (SFKs) transmit TRPA1 signaling in regulating cortical spreading depression (CSD), calcitonin gene-related peptide (CGRP) release and neuroinflammation. CSD was monitored in mouse brain slices via intrinsic optical imaging, and in rats using electrophysiology. CGRP level and IL-1β gene expression in mouse trigeminal ganglia (TG) was detected using Enzyme-linked Immunosorbent Assay and Quantitative Polymerase Chain Reaction respectively. The results showed a SFKs activator, pYEEI (EPQY(PO3H2)EEEIPIYL), reversed the reduced cortical susceptibility to CSD by an anti-TRPA1 antibody in mouse brain slices. Additionally, the increased cytosolic phosphorylated SFKs at Y416 induced by CSD in rat ipsilateral cerebral cortices was attenuated by pretreatment of the anti-TRPA1 antibody perfused into contralateral ventricles. In mouse TG, a SFKs inhibitor, saracatinib, restored the CGRP release and IL-1β mRNA level increased by a TRPA1 activator, umbellulone. Moreover, umbellulone promoted SFKs phosphorylation, which was reduced by a PKA inhibitor, PKI (14-22) Amide. These data reveal a novel mechanism of migraine pathogenesis by which TRPA1 transmits signaling to SFKs via PKA facilitating CSD susceptibility and trigeminovascular system sensitization.

Selective targeting of peripheral cannabinoid receptors prevents behavioral symptoms and sensitization of trigeminal neurons in mouse models of migraine and medication overuse headache

ABSTRACT

Migraine affects ∼15% of the world's population greatly diminishing their quality of life. Current preventative treatments are effective in only a subset of migraine patients, and although cannabinoids seem beneficial in alleviating migraine symptoms, central nervous system side effects limit their widespread use. We developed peripherally restricted cannabinoids (PRCBs) that relieve chronic pain symptoms of cancer and neuropathies, without appreciable central nervous system side effects or tolerance development. Here, we determined PRCB effectiveness in alleviating hypersensitivity symptoms in mouse models of migraine and medication overuse headache. Long-term glyceryl trinitrate (GTN, 10 mg/kg) administration led to increased sensitivity to mechanical stimuli and increased expression of phosphorylated protein kinase A, neuronal nitric oxide synthase, and transient receptor potential ankyrin 1 proteins in trigeminal ganglia. Peripherally restricted cannabinoid pretreatment, but not posttreatment, prevented behavioral and biochemical correlates of GTN-induced sensitization. Low pH-activated and allyl isothiocyanate-activated currents in acutely isolated trigeminal neurons were reversibly attenuated by PRCB application. Long-term GTN treatment significantly enhanced these currents. Long-term sumatriptan treatment also led to the development of allodynia to mechanical and cold stimuli that was slowly reversible after sumatriptan discontinuation. Subsequent challenge with a previously ineffective low-dose GTN (0.1-0.3 mg/kg) revealed latent behavioral sensitization and increased expression of phosphorylated protein kinase A, neuronal nitric oxide synthase, and transient receptor potential ankyrin 1 proteins in trigeminal ganglia. Peripherally restricted cannabinoid pretreatment prevented all behavioral and biochemical correlates of allodynia and latent sensitization. Importantly, long-term PRCB treatment alone did not produce any behavioral or biochemical signs of sensitization. These data validate peripheral cannabinoid receptors as potential therapeutic targets in migraine and medication overuse headache.

Experimental and Clinical Evidence of the Effectiveness of Riboflavin on Migraines

Riboflavin, a water-soluble member of the B-vitamin family, plays a vital role in producing energy in mitochondria and reducing inflammation and oxidative stress. Migraine pathogenesis includes neuroinflammation, oxidative stress, and mitochondrial dysfunction. Therefore, riboflavin is increasingly being recognized for its preventive effects on migraines. However, there is no concrete evidence supporting its use because the link between riboflavin and migraines and the underlying mechanisms remains obscure. This review explored the current experimental and clinical evidence of conditions involved in migraine pathogenesis and discussed the role of riboflavin in inhibiting these conditions. Experimental research has demonstrated elevated levels of various oxidative stress markers and pro-inflammatory cytokines in migraines, and riboflavin’s role in reducing these marker levels. Furthermore, clinical research in migraineurs showed increased marker levels and observed riboflavin’s effectiveness in reducing migraines. These findings suggest that inflammation and oxidative stress are associated with migraine pathogenesis, and riboflavin may have neuroprotective effects through its clinically useful anti-inflammatory and anti-oxidative stress properties. Riboflavin’s safety and efficacy suggests its usefulness in migraine prophylaxis; however, insufficient evidence necessitates further study.

Brain Energy Deficit as a Source of Oxidative Stress in Migraine: A Molecular Basis for Migraine Susceptibility

People with migraine are prone to a brain energy deficit between attacks, through increased energy demand (hyperexcitable brain) or decreased supply (mitochondrial impairment). However, it is uncertain how this precipitates an acute attack. Here, the central role of oxidative stress is adduced. Specifically, neurons' antioxidant defenses rest ultimately on internally generated NADPH (reduced nicotinamide adenine dinucleotide phosphate), whose levels are tightly coupled to energy production. Mitochondrial NADPH is produced primarily by enzymes involved in energy generation, including isocitrate dehydrogenase of the Krebs (tricarboxylic acid) cycle; and an enzyme, nicotinamide nucleotide transhydrogenase (NNT), that depends on the Krebs cycle and oxidative phosphorylation to function, and that works in reverse, consuming antioxidants, when energy generation fails. In migraine aura, cortical spreading depression (CSD) causes an initial severe drop in level of NADH (reduced nicotinamide adenine dinucleotide), causing NNT to impair antioxidant defense. This is followed by functional hypoxia and a rebound in NADH, in which the electron transport chain overproduces oxidants. In migraine without aura, a similar biphasic fluctuation in NADH very likely generates oxidants in cortical regions farthest from capillaries and penetrating arterioles. Thus, the perturbations in brain energy demand and/or production seen in migraine are likely sufficient to cause oxidative stress, triggering an attack through oxidant-sensing nociceptive ion channels. Implications are discussed for the development of new classes of migraine preventives, for the current use of C57BL/6J mice (which lack NNT) in preclinical studies of migraine, for how a microembolism initiates CSD, and for how CSD can trigger a migraine.

Petasin and isopetasin reduce CGRP release from trigeminal afferents indicating an inhibitory effect on TRPA1 and TRPV1 receptor channels

Background

Butterbur root extract with its active ingredients petasin and isopetasin has been used in the prophylactic treatment of migraine for years, while its sites of action are not completely clear. Calcitonin gene-related peptide (CGRP) is known as a biomarker and promoting factor of migraine. We set out to investigate the impact of petasins on the CGRP release from trigeminal afferents induced by activation of the calcium conducting transient receptor potential channels (TRPs) of the subtypes TRPA1 and TRPV1.

Methods

We used well-established in vitro preparations, the hemisected rodent skull and dissected trigeminal ganglia, to examine the CGRP release from rat and mouse cranial dura mater and trigeminal ganglion neurons, respectively, after pre-incubation with petasin and isopetasin. Mustard oil and capsaicin were used to stimulate TRPA1 and TRPV1 receptor channels. CGRP concentrations were measured with a CGRP enzyme immunoassay.

Results

Pre-incubation with either petasin or isopetasin reduced mustard oil- and capsaicin-evoked CGRP release compared to vehicle in an approximately dose-dependent manner. These results were validated by additional experiments with mice expressing functionally deleted TRPA1 or TRPV1 receptor channels.

Conclusions

Earlier findings of TRPA1 receptor channels being involved in the site of action of petasin and isopetasin are confirmed. Furthermore, we suggest an important inhibitory effect on TRPV1 receptor channels and assume a cooperative action between the two TRP receptors. These mechanisms may contribute to the migraine prophylactic effect of petasins.

Insulin-like growth factor-1 inhibits nitroglycerin-induced trigeminal activation of oxidative stress, calcitonin gene-related peptide and c-Fos expression

Migraineurs experience increased oxidative stress which drives the initiation and maintenance of migraine-related pain in animal models and, by extension, migraine in humans. Oxidative stress augments calcitonin gene-related peptide (CGRP) levels, a mediator of migraine pain. Insulin-like growth factor-1 (IGF-1), a neuroprotective growth factor, reduces susceptibility to spreading depression, a preclinical model of migraine, in cultured brain slices by blocking oxidative stress and neuroinflammation from microglia. Similarly, nasal delivery of IGF-1 inhibits spreading depression in vivo. After recurrent cortical spreading depression, nasal administration of IGF-1 also significantly reduces trigeminal ganglion oxidative stress and CGRP levels as well as trigeminocervical c-Fos activation. Here, we probed for the impact of nasal IGF-1 pretreatment on trigeminal system activation using a second well-established preclinical model of migraine, systemic nitroglycerin injection. Adult male rats were treated with one of three doses of IGF-1 (37.5, 75 or 150 μg) and the optimal dose found in males was subsequently used for treatment of female rats. One day later, animals received an intraperitoneal injection of nitroglycerin. Measurements taken two hours later after nitroglycerin alone showed increased surrogate markers of trigeminal activation - oxidative stress and CGRP in the trigeminal ganglion and c-Fos in the trigeminocervical complex compared to vehicle control. These effects were significantly reduced at all doses of IGF-1 for trigeminal ganglion metrics of oxidative stress and CGRP and only at the lowest dose in both males and females for c-Fos. The latter inverted U-shaped or hormetic response is seen in enzyme-targeting drugs. While the specific mechanisms remain to be explored, our data here supports the ability of IGF-1 to preserve mitochondrial and antioxidant pathway homeostasis as means to prevent nociceptive activation in the trigeminal system produced by an experimental migraine model.

Mitochondrial function and oxidative stress markers in higher-frequency episodic migraine

Increasing evidence points towards the role of mitochondrial functioning, energy metabolism, and oxidative stress in migraine. However not all previous research has been conclusive and some mitochondrial function/oxidative stress markers have not yet been examined. To this end, alpha-lipoic acid (ALA), total thiols, total plasma antioxidant capacity (TAC), lipid peroxide (PerOx), oxidised LDL (oxLDL), HbA1c and lactate were determined in the serum of 32 higher frequency episodic migraineurs (5-14 migraine days/ months, 19 with aura, 28 females) in this cross-sectional study. The majority of patients had abnormally low ALA and lactate levels (87.5% and 78.1%, respectively). 46.9% of the patients had abnormally high PerOx values, while for thiols and TAC over one third of patients had abnormally low values (31.2% and 37.5%, respectively). 21.9% of patients had abnormally low HbA1c and none had an HbA1c level above 5.6%. oxLDL was normal in all but one patient. This study provides further evidence for a role of oxidative stress and altered metabolism in migraine pathophysiology, which might represent a suitable therapeutic target. ALA, being too low in almost 90% of patients, might represent a potential biomarker for migraine. Further research is needed to replicate these results, in particular a comparison with a control group.This study is part of the trial registration: ClinicalTrials.gov: NCT03132233, registered on 27.04.2017, https://clinicaltrials.gov/ct2/show/NCT03132233 .

Complementary and Integrative Medicines as Prophylactic Agents for Pediatric Migraine: A Narrative Literature Review

Complementary and integrative medicines (CIMs) are increasingly used as a preventive antimigraine therapy. In this review, we aimed to summarize the evidence for the efficacy and safety of eight CIMs (riboflavin, coenzyme Q10, magnesium, melatonin, polyunsaturated fatty acids, and combination therapy of feverfew, vitamin D, and ginkgolide B) in pediatric migraine prevention. The level of evidence for riboflavin was relatively high; it was investigated by many studies with five/seven studies demonstrating its efficacy. Five studies investigated the use of melatonin, with one reporting negative results. There was insufficient evidence on the effectiveness of coenzyme Q10, magnesium, and polyunsaturated fatty acids. Combination therapy showed positive potential; however, reports on the individual antimigraine effects of the CIMs were lacking. A definitive conclusion was not reached regarding the specific integrative drugs clinicians should choose for pediatric migraines, owing to low-quality evidence and a limited number of studies. Integrative medications are becoming more common for pediatric migraine prevention as they do not produce serious side effects, and underlying research data suggest their efficacy in preventing migraine. Additional studies are warranted to confirm the role of CIMs in treating patients with migraines.

Chromosome 15q BP4-BP5 Deletion in a Girl with Nocturnal Frontal Lobe Epilepsy, Migraine, Circumscribed Hypertrichosis, and Language Impairment

The 15q13.3 microdeletion (microdel15q13.3) syndrome (OMIM 612001) has been reported in healthy subjects as well as in individuals with a wide spectrum of clinical manifestations ranging from mild to severe neurological disorders, including developmental delay/intellectual disability, autism spectrum disorder, schizophrenia, epilepsy, behavioral problems and speech dysfunction. This study explored the link between this genomic rearrangement and nocturnal frontal lobe epilepsy (NFLE), which could improve the clinical interpretation. A clinical and genomic investigation was carried out on an 8-year-girl with a de novo deletion flanking the breakpoints (BPs) 4 and 5 of 15q13.3 detected by array comparative genomic hybridization analysis, affected by NFLE, migraine with aura, minor facial features, mild cognitive and language impairment, and circumscribed hypertrichosis. Literature survey of clinical studies was included. Nine years follow-up have displayed a benign course of the epileptic disorder with a progressive reduction and disappearance of the epileptic seizures, mild improvement of cognitive and language skills, partial cutaneous hypertrichosis regression, but stable ongoing of migraine episodes. A likely relationship between the BP4–BP5 deletion and NFLE with other symptoms presented by the girl is discussed together with a review of the literature on phenotypic features in microdel15q13.3.

Investigation of the plasma copeptin level in cases with childhood migraine

Copeptin is a hypothalamic stress hormone that is synthesized in the hypothalamus together with Arginine-vasopressin and circulated from the neurohypophysis in equimolar amounts and can indicate the individual stress level. The aim of this study was to investigate the plasma copeptin level for childhood migraine headache. In this study, total oxidant status (TOS); total antioxidant status (TAS); oxidative stress index (OSI); and copeptin were measured in the plasma samples of 61 migraine patients and 60 matched healthy participants. The median plasma copeptin levels in the patients group and control group were 298.25 and 194.35 pg/mL, respectively. Copeptin levels were significantly higher in migraine patients than in the healthy control group. The specificity and sensitivity of copeptin for 249.5 pg/dL cut off value predicting diagnosis of migraine were 67% and 64%, respectively. In addition, TOS and OSI levels were found to be higher and TAS levels were significantly lower in patients with migraine than healthy controls. Plasma copeptin levels are thought to increase in cases of childhood migraine secondary to increased oxidative stress. In the diagnosis of childhood migraine cases, it can be used together with oxidative stress biomarkers such as TAS, TOS and OSI as a complementary parameter.

TRPM7 as a Candidate Gene for Vestibular Migraine

Objectives: Vestibular migraine (VM) is a common vestibular disorder, and familial aggregation of VM with autosomal-dominant inheritance has been described, which supports a genetic background. This study aimed to describe the clinical phenotype of a family with VM, and identify a candidate gene for VM.

Methods: We recruited six individuals (four affected and two unaffected) from three consecutive generations of a Korean family with VM, and performed whole-exome sequencing to search for candidate genes.

Results: All affected individuals presented with recurrent vertigo, headache, and nausea/vomiting that fulfilled the diagnostic criteria of VM. Two individuals also experienced transient hemiparesis or dysarthria during the episodes. The symptoms were triggered by physical or emotional stress. Interictal examinations showed uni- or bi-directional horizontal gaze-evoked nystagmus in three of the individuals. They had no causative mutations in genes causing familial hemiplegic migraine or episodic ataxia. Through whole-exome sequencing from three affected individuals, we identified a nonsense mutation c.3526C>T in TRPM7 that encodes a cation channel selective to Ca²⁺ and Mg²⁺.

Conclusions: Alterations in intracellular Ca²⁺ and Mg²⁺ homeostasis by TRPM7 mutation may contribute to the development of the VM phenotype. Our result suggest that TRPM7 is a novel candidate gene for VM.

Involvement of Neural Transient Receptor Potential Channels in Peripheral Inflammation

Transient receptor potential (TRP) channels are a superfamily of non-selective cation channels that act as polymodal sensors in many tissues throughout mammalian organisms. In the context of ion channels, they are unique for their broad diversity of activation mechanisms and their cation selectivity. TRP channels are involved in a diverse range of physiological processes including chemical sensing, nociception, and mediating cytokine release. They also play an important role in the regulation of inflammation through sensory function and the release of neuropeptides. In this review, we discuss the functional contribution of a subset of TRP channels (TRPV1, TRPV4, TRPM3, TRPM8, and TRPA1) that are involved in the body’s immune responses, particularly in relation to inflammation. We focus on these five TRP channels because, in addition to being expressed in many somatic cell types, these channels are also expressed on peripheral ganglia and nerves that innervate visceral organs and tissues throughout the body. Activation of these neural TRP channels enables crosstalk between neurons, immune cells, and epithelial cells to regulate a wide range of inflammatory actions. TRP channels act either through direct effects on cation levels or through indirect modulation of intracellular pathways to trigger pro- or anti-inflammatory mechanisms, depending on the inflammatory disease context. The expression of TRP channels on both neural and immune cells has made them an attractive drug target in diseases involving inflammation. Future work in this domain will likely yield important new pathways and therapies for the treatment of a broad range of disorders including colitis, dermatitis, sepsis, asthma, and pain.

TRPA1 as a therapeutic target for nociceptive pain

Introduction

Chronic pain affects approximatively 30–50% of the population globally. Pathologies such as migraine, diabetic neuropathy, nerve injury and treatment with chemotherapeutic agents, can induce chronic pain. Members of the transient receptor potential (TRP) channels, including the TRP ankyrin 1 (TRPA1), have a major role in pain.

Areas covered

We focus on TRPA1 as a therapeutic target for pain relief. The structure, localization, and activation of the channel and its implication in different pathways to signal pain are described. This paper underlines the role of pharmacological interventions on TRPA1 to reduce pain in numerous pain conditions. We conducted a literature search in PubMed up to and including July 2020.

Expert opinion

Our understanding of the molecular mechanisms underlying the sensitization of central and peripheral nociceptive pathways is limited. Preclinical evidence indicates that, in murine models of pain diseases, numerous mechanisms converge on the pathway that encompasses oxidative stress and Schwann cell TRPA1 to sustain chronic pain. Programs to identify and develop treatments to attenuate TRPA1-mediated chronic pain have emerged from this knowledge. Antagonists explored as a novel class of analgesics have a new and promising target in the TRPA1 expressed by peripheral glial cells.

Dibutyl phthalate aggravated asthma-like symptoms through oxidative stress and increasing calcitonin gene-related peptide release

Dibutyl phthalate (DBP) is one of the most ubiquitous phthalate esters found in everyday products, and is receiving increased attention as an immunologic adjuvant. However, information regarding DBP-aggravated allergic asthma is still limited. This study used a mouse model sensitized with ovalbumin (OVA) to determine any adverse effects of DBP on allergic asthma. Our results reveal that allergic asthmatic mice exposed to DBP for an extended period had a significant increase in inflammatory cell infiltration; a significant increase in levels of serum immunoglobulin and T helper 2 cell (Th2) and T helper 17 cell (Th17) cytokines in lung tissue; and significant changes in lung histology and AHR, all of which are typical asthmatic symptoms. The levels of oxidative stress and levels of the neuropeptide, calcitonin gene related peptide (CGRP), were also elevated after DBP exposure. Interestingly, blocking oxidative stress by administering melatonin (MT) not only reduced oxidative stress and CGRP levels, but also ameliorated the asthmatic symptoms. Collectively, these results show that DBP exacerbates asthma-like pathologies by increasing the expression of CGRP mediated by oxidative stress.

Transient Receptor Potential Ankyrin Type-1 Channels as a Potential Target for the Treatment of Cardiovascular Diseases

Cardiovascular disease is one of the chronic conditions with the highest mortality rate in the world. Underlying conditions such as hypertension, metabolic disorders, and habits like smoking are contributors to the manifestation of cardiovascular diseases. The treatment of cardiovascular diseases is inseparable from the development of drugs. Consequently, this has led to many researchers to focus on the search for effective drug targets. The transient receptor potential channel Ankyrin 1 (TRPA1) subtype is a non-selective cation channel, which belongs to the transient receptor potential (TRP) ion channel. Previous studies have shown that members of the TRP family contribute significantly to cardiovascular disease. However, many researchers have not explored the role of TRPA1 as a potential target for the treatment of cardiovascular diseases. Furthermore, recent studies revealed that TRPA1 is commonly expressed in the vascular endothelium. The endothelium is linked to the causes of some cardiovascular diseases, such as atherosclerosis, myocardial fibrosis, heart failure, and arrhythmia. The activation of TRPA1 has a positive effect on atherosclerosis, but it has a negative effect on other cardiovascular diseases such as myocardial fibrosis and heart failure. This review introduces the structural and functional characteristics of TRPA1 and its importance on vascular physiology and common cardiovascular diseases. Moreover, this review summarizes some evidence that TRPA1 is correlated to cardiovascular disease risk factors.

Localization of TRPA1 channels and characterization of TRPA1 mediated responses in dural and pial arteries in vivo after intracarotid infusion of Na2S

BACKGROUND

The Transient Receptor Potential Ankyrin 1 (TRPA1) channel might play a role in migraine. However, different mechanisms for this have been suggested. The purpose of our study was to investigate the localization and significance of TRPA1 channels in rat pial and dural arteries.

METHODS

Immunofluorescence microscopy was used to localize TRPA1 channels in dural arteries, pial arteries, dura mater and trigeminal ganglion. The genuine closed cranial window model was used to examine the effect of Na₂S, a donor of the TRPA1 channel opener H₂S, on the diameter of pial and dural arteries. Further, we performed blocking experiments with TRPA1 antagonist HC-030031, calcitonin gene-related peptide (CGRP) receptor antagonist olcegepant and K_Ca3.1 channel blocker TRAM-34.

RESULTS

TRPA1 channels were localized to the endothelium of both dural and pial arteries and in nerve fibers in dura mater. Further, we found TRPA1 expression in the membrane of trigeminal ganglia neuronal cells, some of them also staining for CGRP. Na₂S caused dilation of both dural and pial arteries. In dural arteries, this was inhibited by HC-030031 and olcegepant. In pial arteries, the dilation was inhibited by TRAM-34, suggesting involvement of the K_Ca3.1 channel.

CONCLUSION

Na₂S causes a TRPA1- and CGRP-dependent dilation of dural arteries and a K_Ca3.1 channel-dependent dilation of pial arteries in rats.

Retinal Nerve Fiber Layer Thickness and Oxidative Stress Parameters in Migraine Patients without Aura: A Pilot Study

BACKGROUND

Migraine is one of the most common disorders and its pathophysiological mechanisms are still under research, oxidative stress being emphasized as an important contributor. This study aimed to analyze the retinal nerve fiber layer (RNFL) thickness and oxidative/anti-oxidant balance in migraine patients.

METHODS

Two groups of subjects were evaluated: a group of patients with migraine and a control group of healthy volunteers. RNFL thickness was assessed for all subjects by the ocular coherence tomography spectral domain (OCT-SD). The oxidative stress parameter, namely nitric oxide (NOx), malondialdehyde (MDA), and total oxidative stress (TOS) were assessed. The antioxidant capacity of plasma was evaluated by assessing the level of catalase, and total anti-oxidative (TOS) capacity. Migraine severity was graded using the Migraine Disability Assessment Score (MIDAS) questionnaire.

RESULTS

All the oxidative stress parameters (NOx, MDA, and TOS) were significantly increased, and both parameters for anti-oxidative status were significantly decreased in the migraine group compared with the control group (p < 0.0001). Significant correlations with all the quadrants and different oxidative stress parameters were found, most involved being temporal quadrant. A significant positive correlation between catalase and macular RNFL thickness (inner ring, temporal quadrant) in migraine patients, for both eyes, was observed (p = 0.014 for the right eye and p = 0.12 for the left eye).

CONCLUSION

The assessment of the oxidative stress/anti-oxidative balance together with RFLN thickness can constitute a promising method to evaluate the progression of the diseases. It can also contribute to the estimation of the efficiency of various therapies targeting oxidative stress and associated inflammation.