Multi-omics to predict changes during cold pressor test.

BACKGROUND: The cold pressor test (CPT) is a widely used pain provocation test to investigate both pain tolerance and cardiovascular responses. We hypothesize, that performing multi-omic analyses during CPT gives the opportunity to home in on molecular mechanisms involved. Twenty-two females were phenotypically assessed before and after a CPT, and blood samples were taken. RNA-Sequencing, steroid profiling and untargeted metabolomics were performed. Each 'omic level was analyzed separately at both single-feature and systems-level (principal component [PCA] and partial least squares [PLS] regression analysis) and all 'omic levels were combined using an integrative multi-omics approach, all using the paired-sample design. RESULTS: We showed that PCA was not able to discriminate time points, while PLS did significantly distinguish time points using metabolomics and/or transcriptomic data, but not using conventional physiological measures. Transcriptomic and metabolomic data revealed at feature-, systems- and integrative- level biologically relevant processes involved during CPT, e.g. lipid metabolism and stress response. CONCLUSION: Multi-omics strategies have a great potential in pain research, both at feature- and systems- level. Therefore, they should be exploited in intervention studies, such as pain provocation tests, to gain knowledge on the biological mechanisms involved in complex traits.

Headache provocation by nitric oxide in men who have never experienced a headache.

INTRODUCTION: In the general population 4% have never experienced a headache. Freedom from headache could be due to distinctive protective mechanisms or a lack of environmental risk factors for headache. Isosorbide-5-mononitrate is an organic nitrate which in the body is metabolised to nitric oxide. The nitric oxide pathway plays a crucial role in the primary headaches. We hypothesized that people who are free from headache are protected by distinctive mechanisms in the nitric oxide pathway. METHODS: We performed an observer blinded case-control study using nitric oxide to provoke a headache. 32 headache free male participants and 26 randomly selected male controls received 60 mg Isosorbide-5-mononitrate orally on the study day. Participants fill out a headache diary with headache intensity and characteristics until 12 hours after administration of Isosorbide-5-mononitrate. Primary endpoint were areas under the curve of headache intensity score. RESULTS: All 58 participants completed the study. There was no significant difference in headache incidence, headache intensity score or migraine-like attack between headache free participants and controls. CONCLUSION: We show that men who have never experienced a headache develop a headache when provoked with Isosorbide-5-mononitrate. This indicates that freedom from headache in men is not related to the nitric oxide pathway which is involved in the primary headache disorders.

Pain sensitivity in men who have never experienced a headache: an observer blinded case control study.

BACKGROUND: Headache affects 90-99% of the population. Based on the question "Do you think that you never ever in your whole life have had a headache?" 4% of the population say that they have never experienced a headache. The rarity of never having had a headache suggests that distinct biological and environmental factors may be at play. We hypothesized that people who have never experienced a headache had a lower general pain sensitivity than controls. METHODS: We included 99 male participants, 47 headache free participants and 52 controls, in an observer blinded nested case-control study. We investigated cold pain threshold and heat pain threshold using a standardized quantitative sensory testing protocol, pericranial tenderness with total tenderness score and pain tolerance with the cold pressor test. Differences between the two groups were assessed with the unpaired Student's t-test or Mann-Whitney U test as appropriate. RESULTS: There was no difference in age, weight or mean arterial pressure between headache free participants and controls. We found no difference in pain detection threshold, pericranial tenderness or pain tolerance between headache free participants and controls. CONCLUSION: Our study clearly shows that freedom from headache is not caused by a lower general pain sensitivity. The results support the hypothesis that headache is caused by specific mechanisms, which are present in the primary headache disorders, rather than by a decreased general sensitivity to painful stimuli. TRIAL REGISTRATION: Registered at ClinicalTrials.gov ( NCT04217616 ), 3rd January 2020, retrospectively registered.

Subcutaneous sumatriptan reduces cilostazol induced headache in migraine patients.

OBJECTIVES: The authors have previously tried to develop a model for the testing of novel drug candidates for migraine, using the headache and migraine provoking agent cilostazol. Previous studies have used sumatriptan tablets as the validating drug, but they were not sufficiently effective. In this study we test the effect of subcutaneous sumatriptan on cilostazol induced headache in patients with migraine without aura. METHOD: Thirty patients with migraine without aura received 200 mg cilostazol on two different study days. The induced headache was treated with subcutaneous sumatriptan in a randomized, double-blind cross-over design. The patients filled out a self-reported headache questionnaire until 12 h after cilostazol. RESULTS: All 30 patients experienced headache (range 3-10) on both study days and the headache fulfilled the criteria for a migraine-like attack in 73% on the sumatriptan day and in 77% on the placebo day. Sumatriptan injection reduced the headache score 2 h after treatment (p = 0.003). The difference between headache intensity on the sumatriptan day and the placebo day was significant at both 2 h (p = 0.01) and 4 h (p = 0.0007) after treatment. CONCLUSION: Subcutaneous sumatriptan reduces cilostazol induced headache in migraine patients. The cilostazol model may be useful as a tool to test the potential of new anti-migraine drugs.Trial registration: The study is registered on clinicaltrials.gov (NCT03422796).

Low frequency activation of the sphenopalatine ganglion does not induce migraine-like attacks in migraine patients.

INTRODUCTION: Cephalic autonomic symptoms occur in 27‒73% of migraine patients during attacks. The role of parasympathetic activation in migraine attack initiation remains elusive. Low frequency stimulation of the sphenopalatine ganglion increases parasympathetic outflow. In this study, we hypothesized that low frequency stimulation of the sphenopalatine ganglion would provoke migraine-like attacks in migraine patients. METHODS: In a double-blind randomized sham-controlled crossover study, 12 migraine patients with a sphenopalatine ganglion neurostimulator received low frequency or sham stimulation for 30 min on two separate days. We recorded headache characteristics, cephalic autonomic symptoms, ipsilateral mechanical perception and pain thresholds, mean blood flow velocity in the middle cerebral artery (VMCA) and diameter of the superficial temporal artery during and after stimulation. RESULTS: Five patients (42%) reported a migraine-like attack after low frequency stimulation compared to six patients (50%) after sham (p = 1.000). We found a significant increase in mechanical detection thresholds during low frequency stimulation compared to baseline (p = 0.007). Occurrence of cephalic autonomic symptoms and changes in mechanical perception thresholds, VMCA and diameter of the superficial temporal artery showed no difference between low frequency stimulation compared to sham (p = 0.533). CONCLUSION: Low frequency stimulation of the sphenopalatine ganglion did not induce migraine-like attacks or autonomic symptoms in migraine patients. These data suggest that increased parasympathetic outflow by the sphenopalatine ganglion neurostimulator does not initiate migraine-like attacks.Study protocol: ClinicalTrials.gov registration number NCT02510742.

Two-Hour CGRP Infusion Causes Gastrointestinal Hyperactivity: Possible Relevance for CGRP Antibody Treatment.

OBJECTIVE: The monoclonal antibodies against calcitonin gene-related peptide (CGRP) or its receptor are new antimigraine drugs from which many patients already benefit. Very few side effects have been reported from the antibody trials, including very few gastrointestinal (GI) side effects. The current data derive from a double-blind cross-over study of CGRP infusion for 2 hours. We present the GI side effects of the infusion and raise the question if underreporting of GI symptoms in CGRP antibody trials has occurred. We also discuss why constipation may be more likely with CGRP receptor blockade than with CGRP neutralizing antibodies. METHODS: Thirty healthy volunteers were recruited to receive a 2-hour infusion of CGRP 1.5 µg/minutes on 2 different days. The participants were pretreated with sumatriptan tablets (2 × 50 mg) 1 day and with placebo the other day. During the infusion, the participants were asked about side effects including a detailed description about their GI symptoms. Clinical observations like flatulence, rumbling, and use of bedpan were also noted. After the infusion, the participants filled out a questionnaire about side effects at home until 12-hour after the infusion start. The study was conducted at the Danish Headache Center at Rigshospitalet Glostrup in the period February 2018 to July 2018. RESULTS: On both study days 93% (27/29 participants) experienced symptoms from the GI system during the infusion. Rumbling, stomach pain, nausea, diarrhea, and an urge to defecate were the most commonly experienced GI side effects. There was no difference in symptoms between placebo and sumatriptan pretreatment. CONCLUSION: We conclude that a 2-hour infusion of CGRP causes frequent and sometimes severe symptoms from the GI system. The symptoms are not antagonized by sumatriptan. More attention should be paid to constipation as a possible side effect of CGRP receptor antagonists.

Sumatriptan Does Not Antagonize CGRP-Induced Symptoms in Healthy Volunteers.

OBJECTIVE: Previous attempts to develop a pragmatic human model for testing new anti-migraine drugs, have failed. Calcitonin gene-related peptide (CGRP) induces a mild headache in healthy volunteers and migraine-like headache in migraine patients. The induced headache must respond to already established migraine treatment for validation. Thus, the objective of the study was to test the effect of sumatriptan against CGRP-induced symptoms in an attempt to validate CGRP-induced headache as a model for drug testing. METHODS: Thirty healthy volunteers were recruited to receive a 2-hour infusion of CGRP on 2 separate days. The participants were pretreated with sumatriptan 1 day and with placebo the other day in a randomized double-blind cross-over fashion. During the infusion, a questionnaire about headache and side effects was administered. Electrocardiography, heart rate, blood pressure, dermal blood flow, and diameter of peripheral arteries were monitored during the infusion. Participants were carefully instructed to fill out a headache questionnaire at home until 12 hours after the infusion start. Primary endpoints are difference between the sumatriptan day and the placebo day in area under the headache score curve (AUC) 0-2 hours after infusion start and in headache intensity 2 hours after infusion start. The study was conducted at the Danish Headache Center in Glostrup, Denmark. RESULTS: CGRP-induced headache in 86% (25/29) of the participants on the sumatriptan day and in 96% (28/29) of the participants on the placebo day. There was no difference in AUCheadache, 0-2 hours between the days (P = .794). There was a statistically significant decrease in mean atrial pressure (MAP) over time on both days with a16.2% reduction on the sumatriptan day and a 14.8% reduction on the placebo day (P < .001) and a statistically significant increase in heart rate (HR) over time on both days (from mean 57.5 at baseline to mean 105.4 at 120 minutes on the sumatriptan day and from mean 60.2 at baseline to 105.8 at 120 minutes on the placebo day, P < .001). The diameter of peripheral arteries increased statistically significant on both days (P < .001). CONCLUSION: Sumatriptan does not influence headache score, accompanying symptoms or other symptoms induced by CGRP. Furthermore, a 2-hour CGRP infusion causes a wide range of side effects and does not induce more headache than the usual 20-minute infusion. Thus, the prolonged infusion of CGRP in healthy volunteers is not a valid and pragmatic model for testing new anti-migraine drugs.

Comparing migraine with and without aura to healthy controls using RNA sequencing.

BACKGROUND: Migraine mechanisms are *These authors contributed equally to this work. only partly known. Some studies have previously described genes differentially expressed between blood from migraineurs and controls. The objective of this study was to describe gene expression in subtypes of migraine outside of attack and in healthy controls. METHODS: We extensively phenotyped 17 migraine without aura and nine migraine with aura female patients, and 20 age-matched female controls. Cubital venous blood was RNA sequenced. Genes differentially expressed between migraineurs (migraine without aura and migraine with aura) and controls, and between migraine without aura and migraine with aura were identified using a case-control design. A co-expression network was constructed to investigate the difference between migraineurs and healthy controls at the network level. RESULTS: We found two differentially expressed genes: NMNAT2 and RETN. Both were differentially expressed between migraine with aura and controls, but they could not be replicated in an independent cohort. Co-expression network analysis resulted in one cluster of highly interconnected genes that was nominally significantly associated with migraine; however, no pathways or gene ontology terms were detected. CONCLUSIONS: We showed no clear distinct difference in gene expression profiles of peripheral blood of migraineurs and controls and were not able to replicate findings from previous studies. A larger sample size may be needed to detect minor differences.

Histamine and migraine revisited: mechanisms and possible drug targets.

OBJECTIVE: To review the existing literature on histamine and migraine with a focus on the molecule, its receptors, its use in inducing migraine, and antihistamines in the treatment of migraine. BACKGROUND: Histamine has been known to cause a vascular type headache for almost a hundred years. Research has focused on antihistamines as a possible treatment and histamine as a migraine provoking agent but there has been little interest in this field for the last 25 years. In recent years two additional histamine (H3 and H4) receptors have been discovered and a series of non-sedating antihistamines have been developed. It is therefore timely to review the field again. METHODS: For this review the PubMed/MEDLINE database was searched for eligible studies. We searched carefully for all articles on histamine, antihistamines and histamine receptors in relation to migraine and the nervous system. The following search terms were used: histamine, migraine disorders, migraine, headache, antihistamines, histamine antagonists, clinical trials, induced headache, histamine H3 receptor, histamine H4 receptor and pharmacology. Four hundred thirty-six titles were read, 135 abstracts were read, 112 articles were read in full and 53 articles were used in this review. Review process resulted in 12 articles added to a total of 65. FINDINGS: Early studies of H1 and H2 antihistamines lack scientific strength and show conflicting results. Most of the antihistaminic drugs used in these trials bind also to other receptors which makes it difficult to conclude on the antihistaminic effect. Histamine is an efficient inducer of migraine attacks in migraine patients by an H1 mechanism most likely extracerebrally. These findings merit further investigation of antihistamines in clinical drug trials. The H3 and H4 receptors are found in primarily in CNS and immune tissues, respectively. H3 is likely to be involved in antinociception and has been linked with cognitive, neurodegenerative and sleep disorders. The only marketed H3 agent, pitolisant, is a brain penetrant H3 antagonist/inverse agonist which increases central histamine and causes headache. The experimental H3 agonist Nα-methylhistamine has shown promising results as a migraine preventative in studies of uncertain quality. With the current limited knowledge of the H4 receptor it is questionable whether or not the receptor is involved in migraine. CONCLUSION: There is insufficient support for first generation antihistamines (both H1 and H2) as preventive migraine medications and sedation and weight gain are unacceptable side effects. Non-sedating H1 antihistamines need to be appropriately tested. Central H3 receptors seem to have a role in migraine that merit further investigation. The histaminergic system may be a goal for novel migraine drugs.

Pre-treatment with sumatriptan for cilostazol induced headache in healthy volunteers.

BACKGROUND: Previous studies indicate that sumatriptan is not effective when second messenger levels are high as after cilostazol provocation. Therefore, we have conducted the present study, where sumatriptan is administrated as pretreatment before cAMP increases due to cilostazol intake. Our hypothesis was that pretreatment with sumatriptan would have a significant effect against cilostazol induced headache in healthy volunteers. METHODS: In a double-blind, randomized, crossover design, 30 healthy volunteers of both sexes received cilostazol 200 mg on two separate days, each day preceded by oral sumatriptan (2 × 50 mg) or placebo. Headache response and accompanying symptoms were registered in a questionnaire by the participants themselves. RESULTS: Cilostazol induced a mild to moderate headache in all but 3 participants (Range 0-7 on Numerical Rating Scale). There was no significant difference in headache score 2 h (p = 0.67) or 4 h (p = 0.1) after treatment between the 2 days. Median peak headache score was 1.5 (range 0-5) on the sumatriptan day and 2 (range 0-7) on the placebo day (p = 0.26). CONCLUSION: Pre-treatment with sumatriptan prevents cilostazol induced headache from developing. However, the placebo group did not develop enough headache to get statistical significant results. The cilostazol pre-treatment model is valuable for experimental headache research and perhaps for testing drugs with another mechanism of action. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03156920 .

Cilostazol induced migraine does not respond to sumatriptan in a double blind trial.

BACKGROUND: Cilostazol is an inhibitor of phosphodiesterase 3 and thus causes accumulation of cAMP. It induces migraine-like attacks in migraine patients. Whether the cilostazol model responds to sumatriptan in migraine patients and therefore is valid for testing of future anti-migraine medications has never been investigated. METHODS: In a cross-over study, 30 patients received cilostazol (200 mg p.o.) on two separate days each day followed by oral self-administered placebo or sumatriptan 50 mg. We recorded headache characteristics and associated symptoms using a questionnaire. The 30 participants were asked to subsequently treat their spontaneous attacks with sumatriptan (50 mg) or placebo in a double-blind cross-over design and 15 participants did so. RESULTS: Cilostazol induced headache with some migraine characteristics in all participants; 18 patients on the sumatriptan day and 19 patients on the placebo day fulfilled criteria for a migraine-like attack. The difference in median headache intensity between sumatriptan and placebo at 2 h was not significant (p = 0.09), but it was at 4 h (p = 0.017). During spontaneous attacks, the difference between placebo and sumatriptan was not significant at 2 h (p = 0.26), but it was highly significant at 4 h (p = 0.006). CONCLUSION: The cilostazol model in migraine patients could not be validated by a sufficient sumatriptan response. The model may perhaps respond to new drugs that act intracellularly or directly on ion channels. TRIAL REGISTRATION: The study is registered on clinicaltrials.gov ( NCT02486276 ).

Multi-omic analyses of triptan-treated migraine attacks gives insight into molecular mechanisms.

Migraine is a common, polygenic disorder that is characterized by moderate to severe headache attacks. Migraine attacks are commonly treated with triptans, i.e. serotonin receptor agonists. However, triptans are effective in ~ 60% of the population, and the mechanisms of triptans are debated. Here, we aim to expose the mechanisms of triptan using metabolomics and transcriptomics in spontaneous migraine attacks. We collected temporal multi-omics profiles on 24 migraine patients, using samples collected at a migraine attack, 2 h after treatment with a triptan, when headache-free, and after a cold-pressor test. Differential metabolomic analysis was performed to find metabolites associated with treatment. Their effect was further investigated using correlation analysis and a machine learning approach. We found three differential metabolites: cortisol, sumatriptan and glutamine. The change in sumatriptan levels correlated with a change in GNAI1 and VIPR2 gene expression, both known to regulate cAMP levels. Furthermore, we found fatty acid oxidation to be affected, a mechanism known to be involved in migraine but not previously found in relation to triptans. In conclusion, using an integrative approach we find evidence for a role of glutamine, cAMP regulation, and fatty acid oxidation in the molecular mechanisms of migraine and/or the effect of triptans.

Changes in the gene expression profile during spontaneous migraine attacks.

Migraine attacks are delimited, allowing investigation of changes during and outside attack. Gene expression fluctuates according to environmental and endogenous events and therefore, we hypothesized that changes in RNA expression during and outside a spontaneous migraine attack exist which are specific to migraine. Twenty-seven migraine patients were assessed during a spontaneous migraine attack, including headache characteristics and treatment effect. Blood samples were taken during attack, two hours after treatment, on a headache-free day and after a cold pressor test. RNA-Sequencing, genotyping, and steroid profiling were performed. RNA-Sequences were analyzed at gene level (differential expression analysis) and at network level, and genomic and transcriptomic data were integrated. We found 29 differentially expressed genes between 'attack' and 'after treatment', after subtracting non-migraine specific genes, that were functioning in fatty acid oxidation, signaling pathways and immune-related pathways. Network analysis revealed mechanisms affected by changes in gene interactions, e.g. 'ion transmembrane transport'. Integration of genomic and transcriptomic data revealed pathways related to sumatriptan treatment, i.e. '5HT1 type receptor mediated signaling pathway'. In conclusion, we uniquely investigated intra-individual changes in gene expression during a migraine attack. We revealed both genes and pathways potentially involved in the pathophysiology of migraine and/or migraine treatment.