Association of serum levels of intercellular adhesion molecule-1 and interleukin-6 with migraine

Impact of perilesional edema on severity of migraine in patients with calcified neurocysticercosis: A prospective evaluation

OBJECTIVES

Recent research has sparked increasing interest in the role of neuroinflammation in the pathogenesis of migraine. We hypothesize that perilesional edema, an imaging marker of inflammation caused by an immune response in the brain parenchyma surrounding calcified neurocysticercosis (NCC), may influence migraine pathophysiology. This study was designed to explore the potential impact of perilesional edema on migraine severity and treatment response.

BACKGROUND

Cranial imaging of patients with primary headache may sometimes reveal calcified lesions indicative of calcified NCC. These lesions were once considered incidental and harmless findings. However, recent studies have shown that such calcifications are more frequently associated with headaches. Some research suggests that patients with calcified brain lesions experience more frequent and severe migraine compared to those without these lesions, though the pathophysiology underlying this association remains unclear.

METHODS

This single-center, prospective cohort study was conducted at King George Medical University, India, from September 2022 to September 2024. A total of 80 patients with migraine with calcified NCC were enrolled. Cranial magnetic resonance imaging with contrast was used to detect perilesional edema. Patients were divided into two groups based on the presence (Group A) or absence (Group B) of perilesional edema. Both groups were assessed for migraine frequency, severity, and disability using standard scales. They were treated with standard migraine therapy and followed up for 3 months. Statistical analysis was performed to compare migraine characteristics, treatment responses, and disability between the two groups.

RESULTS

Perilesional edema was observed in six of the 80 patients (7.5%). At presentation, Group A (those with perilesional edema) experienced more frequent migraine, with a mean (standard deviation [SD]) of 22.5 (4.4) days/month, compared to Group B (those without perilesional edema), which averaged 8.2 (2.7) days/month. The headaches in Group A were also more severe, as indicated by higher median visual analog scale scores (median [interquartile range, IQR] in Group A of 10.0 [8.5-10.0] and 7 [7.0-8.0] in Group B, p < 0.001). Disability scores were significantly higher in Group A, with higher median scores on the Migraine Disability Assessment Scale (median [IQR] score in Group A of 43 [40.5-48.5] and 21.5 [17.0-26.3] in Group B, p < 0.001) and six-item Headache Impact Test (median [IQR] score in Group A of 66 [64.25-71.23] and 57 [54.8-62.0] in Group B, p < 0.001) scales. Although both groups showed improvement over 3 months of treatment, Group A continued to experience greater migraine severity. In Group A, the mean (SD) headache frequency was 22.5 (4.4) at presentation, 14.0 (1.6) at 30 days, 10.7 (1.6) at 60 days, and 9.2 (2.0) at 90 days (p < 0.001). Similarly, in Group B, headache frequency decreased over time, with a mean (SD) of 8.2 (2.7) at presentation, 3.8 (1.7) at 30 days, 2.3 (1.0) at 60 days, and 1.9 (1.0) at 90 days (p < 0.001). After 30 days, there was a significant reduction in the use of abortive medications, with more patients in Group B (56/74 [76%]) showing a favorable response compared to Group A (2/6 [33%]; p = 0.046; odds ratio 0.16, 95% confidence interval 0.03-0.95).

CONCLUSIONS

Our study found that among patients with migraine with calcified NCC, those with perilesional edema experienced more severe and harder-to-treat migraine compared to those without perilesional edema. These findings suggest that perilesional edema may influence the underlying mechanisms of migraine, leading to more severe migraine episodes.

Neuron-glia crosstalk and inflammatory mediators in migraine pathophysiology

Migraine is a complex neurological disorder with neuroinflammation playing a crucial role in its pathogenesis. This review provides an overview of the neuroinflammation mechanisms in migraine, focusing on both cellular and molecular aspects. At the cellular level, we examine the role of glial cells, including astrocytes, microglia, oligodendrocytes in the central nervous system, and Schwann cells and satellite glial cells in the peripheral nervous system. On the molecular level, we explore the signaling pathways, including IL-1β, TNF-α, IL-6, and non-coding RNAs, that mediate cell interactions or independent actions. Some of the molecular signaling pathways mentioned, such as TNF-α and IL-1β, have been investigated as druggable targets. Recent advancements, such as [11C] PBR28-targeted imaging for visualizing astrocyte activation and single-cell sequencing for exploring cellular heterogeneity, represent breakthroughs in understanding the mechanisms of neuroinflammation in migraine. By considering factors for personalized treatments, estrogen and TRPM8 emerge as promising therapeutic targets regarding sexual dimorphism. These advancements may help bridge the gap between preclinical findings and clinical applications, ultimately leading to more precise and personalized options for migraine patients.

Modulating oxidative stress and neurogenic inflammation: the role of topiramate in migraine treatment

Migraine is a chronic, recurrent neurovascular disorder characterized by episodes closely associated with neurovascular hypersensitivity. Oxidative stress can worsen the hypersensitive state of the central nervous system, which in turn can trigger pro-inflammatory factors that result in neurogenic inflammation. Topiramate is frequently used as a preventative measure for migraines, but there is currently little empirical data to support its efficacy through pathways related to neurogenic inflammation and oxidative stress. This review provides an overview of current knowledge regarding the etiology, inducements, pathophysiology, and available treatments for migraine, with a focus on the clinical and experimental evidence of neurogenic inflammation and oxidative stress in migraine. It also delves into the antioxidant and anti-inflammatory qualities of topiramate, clarifying the possible ways in which topiramate affects these pathways to lessen migraine symptoms.

Deep and unbiased proteomics, pathway enrichment analysis, and protein-protein interaction of biomarker signatures in migraine

Background

Currently, there are no biomarkers for migraine.

Objectives

We aimed to identify proteomic biomarker signatures for diagnosing, subclassifying, and predicting treatment response in migraine.

Design

This is a cross-sectional and longitudinal study of untargeted serum and cerebrospinal fluid (CSF) proteomics in episodic migraine (EM; n = 26), chronic migraine (CM; n = 26), and healthy controls (HC; n = 26).

Methods

We developed classification models for biomarker identification and natural clusters through unsupervised classification using agglomerative hierarchical clustering (AHC). Pathway analysis of differentially expressed proteins was performed.

Results

Of 405 CSF proteins, the top five proteins that discriminated between migraine patients and HC were angiotensinogen, cell adhesion molecule 3, immunoglobulin heavy variable (IGHV) V-III region JON, insulin-like growth factor binding protein 6 (IGFBP-6), and IGFBP-7. The top-performing classifier demonstrated 100% sensitivity and 75% specificity in differentiating the two groups. Of 229 serum proteins, the top five proteins in classifying patients with migraine were immunoglobulin heavy variable 3-74 (IGHV 3-74), proteoglycan 4, immunoglobulin kappa variable 3D-15, zinc finger protein (ZFP)-814, and mediator of RNA polymerase II transcription subunit 12. The best-performing classifier exhibited 94% sensitivity and 92% specificity. AHC separated EM, CM, and HC into distinct clusters with 90% success. Migraine patients exhibited increased ZFP-814 and calcium voltage-gated channel subunit alpha 1F (CACNA1F) levels, while IGHV 3-74 levels decreased in both cross-sectional and longitudinal serum analyses. ZFP-814 remained upregulated during the CM-to-EM reversion but was suppressed when CM persisted. CACNA1F was pronounced in CM persistence. Pathway analysis revealed immune, coagulation, glucose metabolism, erythrocyte oxygen and carbon dioxide exchange, and insulin-like growth factor regulation pathways.

Conclusion

Our data-driven study provides evidence for identifying novel proteomic biomarker signatures to diagnose, subclassify, and predict treatment responses for migraine. The dysregulated biomolecules affect multiple pathways, leading to cortical spreading depression, trigeminal nociceptor sensitization, oxidative stress, blood-brain barrier disruption, immune response, and coagulation cascades.

Trial registration

NCT03231241, ClincialTrials.gov.

COVID-19, vaccination and migraine: Causal association or epiphenomenon?

BACKGROUND

Diverse studies have revealed discrepant evidence concerning the causal association between Corona Virus Disease 2019 (COVID-19) and COVID-19 vaccination in relation to migraines. Investigating the correlation between the former two factors and migraines can facilitate policymakers in the precise formulation of comprehensive post-pandemic interventions while urging the populace to adopt a judicious perspective on COVID-19 vaccination.

METHODS

We undertook a Mendelian randomization (MR) study. The primary assessment of the causal relationship between the three different COVID-19 exposures and migraine was conducted using the standard inverse variance weighted (IVW) approach. In the supplementary analysis, we also employed two methodologies: the weighted median estimator (WME) and the MR-Egger regression. Ultimately, the reliability and stability of the outcomes were assessed via Cochran's Q test, the leave-one-out method, the MR-Egger intercept test, and the MR pleiotropy residual sum and outlier (MR-PRESSO) test.

RESULTS

The results indicate an absence of correlation between genetically predicted COVID-19 (①Very severe respiratory confirmed COVID-19: odds ratio [OR], 1.0000881; 95%CI, 0.999748-1.000428; p = 0.6118; ②Hospitalized COVID-19: OR, 1.000024; 95%CI, 0.9994893-1.000559; p = 0.931;③SARS-CoV-2 infection: OR, 1.000358; 95%CI, 0.999023-1.001695; p = 0.5993) and the risk of migraine. Furthermore, the MR-Egger regression and WME also yielded no evidence of COVID-19 elevating the risk of migraine occurrence. Sensitivity analysis affirmed the robustness and consistency of all outcomes.

CONCLUSIONS

The results of this study do not offer genetic evidence to substantiate a causal relationship between COVID-19 and migraines. Thus, the deduction drawn from COVID-19 genetic data is that COVID-19 vaccination is unlikely to exert an impact on the occurrence of migraines, though this conclusion warrants further investigation.

Mind the Metabolic Gap: Bridging Migraine and Alzheimer's disease through Brain Insulin Resistance

Brain insulin resistance has recently been described as a metabolic abnormality of brain glucose homeostasis that has been proven to downregulate insulin receptors, both in astrocytes and neurons, triggering a reduction in glucose uptake and glycogen synthesis. This condition may generate a mismatch between brain's energy reserve and expenditure, ??mainly during high metabolic demand, which could be involved in the chronification of migraine and, in the long run, at least in certain subsets of patients, in the prodromic phase of Alzheimer's disease, along a putative metabolic physiopathological continuum. Indeed, the persistent disruption of glucose homeostasis and energy supply to neurons may eventually impair protein folding, an energy-requiring process, promoting pathological changes in Alzheimer's disease, such as amyloid-β deposition and tau hyperphosphorylation. Hopefully, the "neuroenergetic hypothesis" presented herein will provide further insight on there being a conceivable metabolic bridge between chronic migraine and Alzheimer's disease, elucidating novel potential targets for the prophylactic treatment of both diseases.

Altered immunity in migraine: a comprehensive scoping review

BACKGROUND

The pathogenesis of migraine remains unclear; however, a large body of evidence supports the hypothesis that immunological mechanisms play a key role. Therefore, we aimed to review current studies on altered immunity in individuals with migraine during and outside attacks.

METHODS

We searched the PubMed database to investigate immunological changes in patients with migraine. We then added other relevant articles on altered immunity in migraine to our search.

RESULTS

Database screening identified 1,102 articles, of which 41 were selected. We added another 104 relevant articles. We found studies reporting elevated interictal levels of some proinflammatory cytokines, including IL-6 and TNF-α. Anti-inflammatory cytokines showed various findings, such as increased TGF-β and decreased IL-10. Other changes in humoral immunity included increased levels of chemokines, adhesion molecules, and matrix metalloproteinases; activation of the complement system; and increased IgM and IgA. Changes in cellular immunity included an increase in T helper cells, decreased cytotoxic T cells, decreased regulatory T cells, and an increase in a subset of natural killer cells. A significant comorbidity of autoimmune and allergic diseases with migraine was observed.

CONCLUSIONS

Our review summarizes the findings regarding altered humoral and cellular immunological findings in human migraine. We highlight the possible involvement of immunological mechanisms in the pathogenesis of migraine. However, further studies are needed to expand our knowledge of the exact role of immunological mechanisms in migraine pathogenesis.

Serological Biomarkers of Chronic Migraine

PURPOSE OF REVIEW

Chronic migraine (CM) is a chronic form of migraine that differs from episodic migraine (EM) in terms of prevalence, comorbidities, response to treatment, and biomarkers. The aim of this review was to summarize the recent findings on serological biomarkers of CM.

RECENT FINDINGS

Neuronal, inflammatory, and vascular markers have been investigated to assess their diagnostic and prognostic ability and treatment effectiveness. Several markers showed significant alterations according to disease status and treatment response in CM. Calcitonin gene-related peptide (CGRP), glutamate, and adiponectin appear to be the most promising blood biomarkers for CM. Most studies have shown altered ictal and interictal levels of these markers in CM compared with those in EM and controls. Additionally, they showed a significant association with treatment outcomes. Total adiponectin and high-molecular-weight adiponectin levels were less studied as biomarkers of CM than CGRP and glutamate levels but showed promising results. The development of suitable biomarkers could revolutionize the diagnosis and treatment of CM and ultimately decrease the disability and societal costs of the disease.

Advanced brain MRI may help understand the link between migraine and multiple sclerosis

BACKGROUND

There is a clinical association between migraine and multiple sclerosis.

MAIN BODY

Migraine and MS patients share similar demographics, with the highest incidence among young, female and otherwise healthy patients. The same hormonal constellations/changes trigger disease exacerbation in both entities. Migraine prevalence is increased in MS patients, which is further enhanced by disease-modifying treatment. Clinical data show that onset of migraine typically starts years before the clinical diagnosis of MS, suggesting that there is either a unidirectional relationship with migraine predisposing to MS, and/or a "shared factor" underlying both conditions. Brain imaging studies show white matter lesions in both MS and migraine patients. Neuroinflammatory mechanisms likely play a key role, at least as a shared downstream pathway. In this review article, we provide an overview of the literature about 1) the clinical association between migraine and MS as well as 2) brain MRI studies that help us better understand the mechanistic relationship between both diseases with implications on their underlying pathophysiology.

CONCLUSION

Studies suggest a migraine history predisposes patients to develop MS. Advanced brain MR imaging may shed light on shared and distinct features, while helping us better understand mechanisms underlying both disease entities.

Experimental and Clinical Investigation of Cytokines in Migraine: A Narrative Review

The role of neuroinflammation in the pathophysiology of migraines is increasingly being recognized, and cytokines, which are important endogenous substances involved in immune and inflammatory responses, have also received attention. This review examines the current literature on neuroinflammation in the pathogenesis of migraine. Elevated TNF-α, IL-1β, and IL-6 levels have been identified in non-invasive mouse models with cortical spreading depolarization (CSD). Various mouse models to induce migraine attack-like symptoms also demonstrated elevated inflammatory cytokines and findings suggesting differences between episodic and chronic migraines and between males and females. While studies on human blood during migraine attacks have reported no change in TNF-α levels and often inconsistent results for IL-1β and IL-6 levels, serial analysis of cytokines in jugular venous blood during migraine attacks revealed consistently increased IL-1β, IL-6, and TNF-α. In a study on the interictal period, researchers reported higher levels of TNF-α and IL-6 compared to controls and no change regarding IL-1β levels. Saliva-based tests suggest that IL-1β might be useful in discriminating against migraine. Patients with migraine may benefit from a cytokine perspective on the pathogenesis of migraine, as there have been several encouraging reports suggesting new therapeutic avenues.

2-Deoxyglucose alleviates migraine-related behaviors by modulating microglial inflammatory factors in experimental model of migraine

Background

Targeting metabolic pathways has emerged as a new migraine treatment strategy as researchers realize the critical role metabolism plays in migraine. Activated inflammatory cells undergo metabolic reprogramming and rely on glycolysis to function. The objective of this study was to investigate the glycolysis changes in the experimental model of migraine and the effect of glycolysis inhibitor 2-Deoxy-D-glucose (2-DG) in the pathophysiology of migraine.

Methods

We used a rat model of migraine that triggered migraine attacks by applying inflammatory soup (IS) to the dura and examined changes in glycolysis. 2-DG was used to inhibit glycolysis, and the effects of 2-DG on mechanical ectopic pain, microglial cell activation, calcitonin gene-related peptides (CGRP), c-Fos, and inflammatory factors induced by inflammatory soup were observed. LPS stimulated BV2 cells to establish a model in vitro to observe the effects of 2-DG on brain-derived neurotrophic factor (BDNF) after microglia activation.

Results

In the experimental model of migraine, key enzymes involved in glycolysis such as phosphofructokinase platelet (PFKP), hexokinase (HK2), hypoxia inducible factor-1α (HIF-1α), lactate dehydrogenase (LDH) and pyruvate kinase (PKM2) were expressed in the medullary dorsal horn. While the expression of electronic respiratory transport chain complex IV (COXIV) decreased. There were no significant changes in glucose 6-phosphate dehydrogenase (G6PD), a key enzyme in the pentose phosphate pathway. The glycolysis inhibitor 2-DG alleviated migraine-like symptoms in an experimental model of migraine, reduced the release of proinflammatory cytokines caused by microglia activation, and decreased the expression of CGRP and c-Fos. Further experiments in vitro demonstrated that glycolysis inhibition can reduce the release of Iba-1/proBDNF/BDNF and inhibit the activation of microglia.

Conclusion

The migraine rat model showed enhanced glycolysis. This study suggests that glycolytic inhibitor 2-DG is an effective strategy for alleviating migraine-like symptoms. Glycolysis inhibition may be a new target for migraine treatment.

Cytokines in primary headache disorders: a systematic review and meta-analysis

BACKGROUND

The role of inflammation and cytokines in the pathophysiology of primary headache disorders is uncertain. We performed a systematic review and meta-analysis to synthesise the results of studies comparing peripheral blood cytokine levels between patients with migraine, tension-type headache, cluster headache, or new daily persistent headache (NDPH), and healthy controls; and in migraine between the ictal and interictal stages.

METHODS

We searched PubMed/Medline and Embase from inception until July 2022. We included original research studies which measured unstimulated levels of any cytokines in peripheral blood using enzyme-linked immunosorbent assay or similar assay. We assessed risk of bias using the Newcastle-Ottawa Quality Assessment Scale. We used random effects meta-analysis with inverse variance weighted average to calculate standardised mean difference (SMD), 95% confidence intervals, and heterogeneity for each comparison. This study is registered with PROSPERO (registration number CRD42023393363). No funding was received for this study.

RESULTS

Thirty-eight studies, including 1335 patients with migraine (32 studies), 302 with tension-type headache (nine studies), 42 with cluster headache (two studies), and 1225 healthy controls met inclusion criteria. Meta-analysis showed significantly higher interleukin (IL)-6 (SMD 1.07, 95% CI 0.40-1.73, p = 0.002), tumour necrosis factor (TNF)-α (SMD 0.61, 95% CI 0.14-1.09, p = 0.01), and IL-8 (SMD 1.56, 95% CI 0.03-3.09, p = 0.04), in patients with migraine compared to healthy controls, and significantly higher interleukin-1β (IL-1β) (SMD 0.34, 95% CI 0.06-0.62, p = 0.02) during the ictal phase of migraine compared to the interictal phase. Transforming growth factor (TGF)-β (SMD 0.52, 95% CI 0.18-0.86, p = 0.003) and TNF-α (SMD 0.64, 95% CI 0.33-0.96, p = 0.0001) were both higher in patients with tension-type headache than controls.

CONCLUSIONS

The higher levels of the proinflammatory cytokines IL-6, IL-8 and TNF-α in migraine compared to controls, and IL-1β during the ictal stage, suggest a role for inflammation in the pathophysiology of migraine, however prospective studies are required to confirm causality and investigate the mechanisms for the increase in cytokine levels identified. Cytokines may also have a role in tension-type headache. Due a lack of data, no conclusions can be made regarding cluster headache or NDPH.

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.

Roxadustat alleviates nitroglycerin-induced migraine in mice by regulating HIF-1α/NF-κB/inflammation pathway

Sensitization of central pain and inflammatory pathways play essential roles in migraine, a primary neurobiological headache disorder. Since hypoxia-inducible factor-1α (HIF-1α) is implicated in neuroprotection and inflammation inhibition, herein we investigated the role of HIF-1α in migraine. A chronic migraine model was established in mice by repeated injection of nitroglycerin (10 mg/kg, i.p.) every other day for 5 total injections. In the prevention and acute experiments, roxadustat, a HIF-1α stabilizer, was orally administered starting before or after nitroglycerin injection, respectively. Pressure application measurement, and tail flick and light-aversive behaviour tests were performed to determine the pressure pain threshold, thermal nociceptive sensitivity and migraine-related light sensitivity. At the end of experiments, mouse serum samples and brain tissues were collected for analyses. We showed that roxadustat administration significantly attenuated nitroglycerin-induced basal hypersensitivity and acute hyperalgesia by improving central sensitization. Roxadustat administration also decreased inflammatory cytokine levels in serum and trigeminal nucleus caudalis (TNC) through NF-κB pathway. Consistent with the in vivo results showing that roxadustat inhibited microglia activation, roxadustat (2, 10, and 20 μM) dose-dependently reduced ROS generation and inflammation in LPS-stimulated BV-2 cells, a mouse microglia cell line, by inhibiting HIF-1α/NF-κB pathway. Taken together, this study demonstrates that roxadustat administration ameliorates migraine-like behaviours and inhibits central pain sensitization in nitroglycerin-injected mice, which is mainly mediated by HIF-1α/NF-κB/inflammation pathway, suggesting the potential of HIF-1α activators as therapeutics for migraine.

The role of cytokines in migraine: A systematic review

BACKGROUND

Cytokines are important endogenous substances that are involved in immune and inflammatory responses. Neurogenic inflammation has been proposed to play a role in migraine involving altered cytokine levels. Therefore, we aimed to provide a systematic review on the current knowledge on cytokine levels in migraine patients during and outside attacks.

METHODS

Databases of PubMed and Embase were systematically searched for studies investigating cytokine levels in migraine patients during and outside attacks.

RESULTS

Screening yielded identification of 45 articles investigating 18 cytokines in total. We found that the interictal level of the anti-inflammatory cytokine, interleukin 10, was decreased, while the level of transforming growth factor beta 1 was increased in migraine patients compared to controls. Levels of pro-inflammatory cytokines, tumor necrosis factor α and interleukin 6, were increased outside attacks compared to controls. Ictal levels of cytokines were unchanged or varying compared to the interictal state in migraine patients. Three studies reported dynamic cytokines levels during the course of an attack.

CONCLUSION

The findings of the current review underline a possible involvement of cytokines in the proposed inflammatory mechanisms of migraine. However, future studies are needed to expand our knowledge of the exact role of cytokines in the migraine pathophysiology with focus on cytokines TNF-α, IL-1ß, IL-6 and IL-10 while applying refined methodology.

Headache Worsening after COVID-19 Vaccination: An Online Questionnaire-Based Study on 841 Patients with Migraine

Vaccines have represented the breakthrough in the fight against COVID-19. Based on reported headache attacks after vaccination in randomized controlled trials, we focused on the effects of COVID-19 vaccine administration on the migraine population, using an online questionnaire published on Italian Facebook groups oriented to headache patients. We collected data about the demographics and clinical parameters of migraine severity, COVID-19 infection, vaccination, and characteristics of headaches following vaccination. Out of 841 migraine patients filling in the questionnaire, 66.47% and 60.15% patients experienced a headache attack (from 1 hour to 7 days) after the first and the second vaccine dose, respectively. The main finding concerns headaches perceived by 57.60% of patients: attacks following vaccination were referred to as more severe (50.62% of patients), long-lasting (52.80% of patients) and hardwearing (49.69% of patients) compared to the usually experienced migraine attacks. This could be related to the production of inflammatory mediators such as type Iβ interferon. Considering the high prevalence of migraine in the general population, awareness of the possibility of headaches worsening following COVID-19 vaccination in these patients may allow both patients and clinicians to face this clinical entity with conscious serenity, and to reduce the waste of resources towards inappropriate health-care.

Role of Neuroinflammation and Blood-Brain Barrier Permutability on Migraine

Currently, migraine is treated mainly by targeting calcitonin gene-related peptides, although the efficacy of this method is limited and new treatment strategies are desired. Neuroinflammation has been implicated in the pathogenesis of migraine. In patients with migraine, peripheral levels of pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-α, are known to be increased. Additionally, animal models of headache have demonstrated that immunological responses associated with cytokines are involved in the pathogenesis of migraine. Furthermore, these inflammatory mediators might alter the function of tight junctions in brain vascular endothelial cells in animal models, but not in human patients. Based on clinical findings showing elevated IL-1β, and experimental findings involving IL-1β and both the peripheral trigeminal ganglion and central trigeminal vascular pathways, regulation of the Il-1β/IL-1 receptor type 1 axis might lead to new treatments for migraine. However, the integrity of the blood-brain barrier is not expected to be affected during attacks in patients with migraine.

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.

A new hypothesis linking oxytocin to menstrual migraine

OBJECTIVE

To highlight the emerging understanding of oxytocin (OT) and oxytocin receptors (OTRs) in modulating menstrual-related migraine (MRM).

BACKGROUND

MRM is highly debilitating and less responsive to therapy, and attacks are of longer duration than nonmenstrually related migraine. A clear understanding of the mechanisms underlying MRM is lacking.

METHODS

We present a narrative literature review on the developing understanding of the role of OT and the OTR in MRM. Literature on MRM on PubMed/MEDLINE database including clinical trials and basic science publications was reviewed using specific keywords.

RESULTS

OT is a cyclically released hypothalamic hormone/neurotransmitter that binds to the OTR resulting in inhibition of trigeminal neuronal excitability that can promote migraine pain including that of MRM. Estrogen regulates OT release as well as expression of the OTR. Coincident with menstruation, levels of both estrogen and OT decrease. Additionally, other serum biochemical factors, including magnesium and cholesterol, which positively modulate the affinity of OT for OTRs, both decrease during menstruation. Thus, during menstruation, multiple menstrually associated factors may lead to decreased circulating OT levels, decreased OT affinity for OTR, and decreased expression of the trigeminal OTR. Consistent with the view of migraine as a threshold disorder, these events may collectively result in decreased inhibition promoting lower thresholds for activation of meningeal trigeminal nociceptors and increasing the likelihood of an MRM attack.

CONCLUSION

Trigeminal OTR may thus be a novel target for the development of MRM therapeutics.

The Short-Term Kinetics of sICAM-1 after Induction of Acute Experimental Pain in Healthy Volunteers

Intercellular adhesion molecule-1 (ICAM-1) mediates extravasation of leukocytes, releasing proinflammatory cytokines or endogenous opioids in the inflamed tissue. Thus, ICAM-1 is a crucial component of peripheral antinociception. Previously, we demonstrated a significant correlation between the soluble form of ICAM (sICAM-1) in serum and pain intensity reported by chronic pain patients. The present study examines the role and kinetics of sICAM-1 in experimentally induced acute pain. Three groups of 10 subjects were exposed to 10 min of high (capsaicin-enhanced) or low-intensity heat pain or cold pain, respectively. Thermal stimuli were induced using a device for quantitative sensory testing. Topical capsaicin significantly increased heat pain intensity without the risk of thermal tissue damage. Pain intensity was recorded every minute during testing. sICAM-1 concentrations in serum were determined by ELISA before, immediately after, and 60 min after test termination. Among all experimental groups, sICAM-1 significantly decreased immediately after pain induction. After 60 min, sICAM-1 concentrations returned towards initial values. Interestingly, a linear correlation was found between the extent of sICAM-1 changes and the initial concentrations. Whereas high initial values led to a distinct decrease of sICAM-1, low concentrations tended to increase. There was no statistically significant correlation between levels or alterations of serum sICAM-1 and pain intensity reported by the test subjects. In contrast to our previous findings in chronic pain patients, the present results show that sICAM-1 values do not correlate with the intensity of acute experimental pain. However, we were able to detect short-term changes of sICAM-1 after induction of nociceptive thermal stimuli, suggesting that this marker is part of a demand-oriented homeostatically controlled system.

A systematic review and meta-analysis of recent studies reporting hormone levels related to thyroid gland function in migraineurs, until April 2020

PURPOSE

The purpose of the current study was to evaluate thyroid function in terms of serum thyroid-stimulating hormone (TSH, also known as thyrotropin), 3,5,3'-triiodo-L-thyronine (T3), and 3,5,3',5'-tetraiodo-L-thyronine (T4, also known as thyroxine) levels in migraineurs in comparison with non-migraineurs using a systematic review of literature and a meta-analysis.

METHODS

This is a systematic review of case-control studies on serum TSH, T3, and T4 concentrations of migraineurs in comparison with non-migraineurs. After extracting the data from the finally included studies, the weighted overall standardized mean difference (SMD) was calculated.

RESULTS

The weighted overall SMD for the impact of TSH, T3, and T4 blood levels for migraineurs in comparison with non-migraineurs was as follows: 0.804 (95% CI, 0.045-1.564), - 0.267 (95% CI, - 0.660-0.125), 0.093 (95% CI, - 0.077-0.263), respectively. It is noteworthy that only the p value for the significance of the overall SMD for serum TSH level was statistically significant (p = 0.038), as examined by the z-test.

CONCLUSIONS

The results of the current study point to an association between migraine pathogenesis and changing TSH levels in comparison with those of controls.

Association between serum bilirubin and migraine in children and adolescents

Background

Migraine in children and adolescents is very common and can be associated with equivalents, psychiatric disorders, or abnormal electroencephalogram findings. Neurogenic inflammation is involved in migraine pathogenesis where pro-inflammatory cytokines play a significant role. Recent studies have demonstrated that serum bilirubin can be considered as an antioxidant and cytoprotective agent and that its concentration may be influenced in migraine by neurogenic inflammation. Various studies have observed reduced serum bilirubin in migrainous adults, and few studies investigated the association between serum bilirubin and migraine in children and adolescents.

Objectives

To study the association between serum bilirubin and migraine in children and adolescents.

Patients and method

Serum samples were collected from 40 migrainous children and adolescents and from 40 controls. Total, direct, and indirect bilirubin concentrations were measured. Headache features, migraine equivalents, psychiatric comorbidity, and electroencephalogram findings were documented in migraineurs.

Results

Serum total, direct, and indirect bilirubin concentrations were significantly lower in migraineurs than controls. This was statistically significant associated with abnormal electroencephalogram findings during headache-free periods and not statistically significant associated with any headache feature, abnormal electroencephalogram findings during headache attacks, or psychiatric comorbidity.

Conclusion

Serum bilirubin concentration is lower in migrainous children and adolescents compared to control, with no association with specific migraine type or features, and thus may be considered a useful marker for neurogenic inflammation in migraine.

Effect of cinnamon on migraine attacks and inflammatory markers: A randomized double-blind placebo-controlled trial

Migraine is the most common type of primary headaches. Increased levels of interleukin-6 (IL-6), calcitonin-gene-related peptide (CGRP) and nitric oxide (NO) lead to inflammation and neurogenic pain. Cinnamon has anti-inflammatory and neuroprotective properties. Thus, the aim of this study was to assess the effect of cinnamon on migraine attacks and inflammatory status. Fifty patients with migraine were randomized to receive either cinnamon powder (three capsules/day each containing 600 mg of cinnamon) or three placebo capsules/day each containing 100 mg of corn starch (control group) for 2 months. Serum levels of IL-6, CGRP and NO were measured at baseline and at the end of the study. The frequency, severity and duration of pain attacks were also recorded using questionnaire. Serum concentrations of IL-6 and NO were significantly reduced in the cinnamon group compared with the control group (p < .05). However, serum levels of CGRP remained unchanged in both groups. The frequency, severity and duration of migraine attacks were significantly decreased in the cinnamon group compared with the control group. Cinnamon supplementation reduced inflammation as well as frequency, severity and duration of headache in patients with migraine. Cinnamon could be regarded as a safe supplement to relieve pain and other complications of migraine.

Therapeutic implications of cortical spreading depression models in migraine

Migraine is among the most common and disabling neurological diseases in the world. Cortical spreading depression (CSD) is a wave of near-complete depolarization of neurons and glial cells that slowly propagates along the cortex creating the perception of aura. Evidence suggests that CSD can trigger migraine headache. Experimental models of CSD have been considered highly translational as they recapitulate migraine-related phenomena and have been validated for screening migraine therapeutics. Here we outline the essential components of validated experimental models of CSD and provide a comprehensive review of potential modulators and targets against CSD. We further focus on novel interventions that have been recently shown to suppress CSD susceptibility that may lead to therapeutic targets in migraine.

Modeling a Nociceptive Neuro-Immune Synapse Activated by ATP and 5-HT in Meninges: Novel Clues on Transduction of Chemical Signals Into Persistent or Rhythmic Neuronal Firing

Extracellular ATP and serotonin (5-HT) are powerful triggers of nociceptive firing in the meninges, a process supporting headache and whose cellular mechanisms are incompletely understood. The current study aimed to develop, with the neurosimulator NEURON, a novel approach to explore in silico the molecular determinants of the long-lasting, pulsatile nature of migraine attacks. The present model included ATP and 5-HT release, ATP diffusion and hydrolysis, 5-HT uptake, differential activation of ATP P2X or 5-HT3 receptors, and receptor subtype-specific desensitization. The model also tested the role of branched meningeal fibers with multiple release sites. Spike generation and propagation were simulated using variable contribution by potassium and sodium channels in a multi-compartment fiber environment. Multiple factors appeared important to ensure prolonged nociceptive firing potentially relevant to long-lasting pain. Crucial roles were observed in: (i) co-expression of ATP P2X2 and P2X3 receptor subunits; (ii) intrinsic activation/inactivation properties of sodium Nav1.8 channels; and (iii) temporal and spatial distribution of ATP/5-HT release sites along the branches of trigeminal nerve fibers. Based on these factors we could obtain either persistent activation of nociceptive firing or its periodic bursting mimicking the pulsating nature of pain. In summary, our model proposes a novel tool for the exploration of peripheral nociception to test the contribution of clinically relevant factors to headache including migraine pain.

Non-invasively triggered spreading depolarizations induce a rapid pro-inflammatory response in cerebral cortex

Cortical spreading depolarization (CSD) induces pro-inflammatory gene expression in brain tissue. However, previous studies assessing the relationship between CSD and inflammation have used invasive methods that directly trigger inflammation. To eliminate the injury confounder, we induced CSDs non-invasively through intact skull using optogenetics in Thy1-channelrhodopsin-2 transgenic mice. We corroborated our findings by minimally invasive KCl-induced CSDs through thinned skull. Six CSDs induced over 1 h dramatically increased cortical interleukin-1β (IL-1β), chemokine (C-C motif) ligand 2 (CCL2), and tumor necrosis factor-α (TNF-α) mRNA expression peaking around 1, 2 and 4 h, respectively. Interleukin-6 (IL-6) and intercellular adhesion molecule-1 (ICAM-1) were only modestly elevated. A single CSD also increased IL-1β, CCL2, and TNF-α, and revealed an ultra-early IL-1β response within 10 min. The response was blunted in IL-1 receptor-1 knockout mice, implicating IL-1β as an upstream mediator, and suppressed by dexamethasone, but not ibuprofen. CSD did not alter systemic inflammatory indices. In summary, this is the first report of pro-inflammatory gene expression after non-invasively induced CSDs. Altogether, our data provide novel insights into the role of CSD-induced neuroinflammation in migraine headache pathogenesis and have implications for the inflammatory processes in acute brain injury where numerous CSDs occur for days.

Circulating Biomarkers in Migraine: New Opportunities for Precision Medicine

Background:

Migraine is the most common neurological disorder and the second most disabling human condition, whose pathogenesis is favored by a combination of genetic, epigenetic, and environmental factors. In recent years, several efforts have been made to identify reliable biomarker(s) useful to monitor disease activity and/or ascertain the response to a specific treatment.

Objective:

To review the current evidence on the potential biological markers associated with migraine.

Methods:

A structured search of peer-reviewed research literature was performed by searching major publications databases up to December 2017.

Results:

Several circulating biomarkers have been proposed as diagnostic or therapeutic tools in migraine, mostly related to migraine’s inflammatory pathophysiological aspects. Nonetheless, their detection is still a challenge for the scientific community, reflecting, at least in part, disease complexity and clinical diagnostic limitations. At the present time, calcitonin generelated peptide (CGRP) represents probably the most promising candidate as a diagnostic and/or therapeutic biomarker, as its plasma levels are elevated during migraine attack and decrease during successful treatment. Other molecules (including some neuropeptides, cytokines, adipokines, or vascular activation markers) despite promising, do not possess the sufficient prerequisites to be considered as migraine biomarkers.

Conclusion:

The characterization of migraine-specific biomarkers would be fundamental in a perspective of precision medicine, enabling risk assessment and tailored treatments. However, speculating on the clinical validity of migraine biomarkers may be premature and controlled clinical trials are presently needed to investigate both the diagnostic and therapeutic value of these biomarkers in migraine.

Salivary inflammatory markers in tension type headache and migraine: the SalHead cohort study

OBJECTIVE

To investigate the possible association between salivary CRP, IL-1β, and IL-6 levels, depression/anxiety and migraine, and tension type headache (TTH) in saliva of these patients.

METHOD

A longitudinal prospective study was conducted on 30 migraineurs, 30 TTH patients, and 30 age-matched healthy controls. Anxiety and depression were measured by using the Hamilton Anxiety Rating Scale (HAM-A), and the Beck Depression Inventory (BDI). Salivary IL-6, IL-1β, and CRP were collected in distinct time points as A: headache-free period, B: during headache, C: 1 day after headache attack, and measured by using ELISA kits.

RESULTS

No significant differences were found in time variation of CRP, IL-1β, and IL-6 levels between migraine and TTH (p > 0.05). IL1-β had the highest discriminative value (area under the curve = 0.924, p value < 0.001), and then CRP (area under the curve = 0.763, p value < 0.001) and IL-6 (area under the curve = 0.537, p value = 0.58). CRP and IL-6 were negatively correlated with HAM-A and BDI scores.

CONCLUSION

IL1-β had the highest discriminative value between headache patients and controls compared with CRP and IL-6. CRP and IL-6 were correlated with lower symptom scores of anxiety and depression prior or immediately after the headache period in patients groups.

Perivascular neurotransmitters: Regulation of cerebral blood flow and role in primary headaches

In order to understand the nature of the relationship between cerebral blood flow (CBF) and primary headaches, we have conducted a literature review with particular emphasis on the role of perivascular neurotransmitters. Primary headaches are in general considered complex polygenic disorders (genetic and environmental influence) with pathophysiological neurovascular alterations. Identified candidate headache genes are associated with neuro- and gliogenesis, vascular development and diseases, and regulation of vascular tone. These findings support a role for the vasculature in primary headache disorders. Moreover, neuronal hyperexcitability and other abnormalities have been observed in primary headaches and related to changes in hemodynamic factors. In particular, this relates to migraine aura and spreading depression. During headache attacks, ganglia such as trigeminal and sphenopalatine (located outside the blood-brain barrier) are variably activated and sensitized which gives rise to vasoactive neurotransmitter release. Sympathetic, parasympathetic and sensory nerves to the cerebral vasculature are activated. During migraine attacks, altered CBF has been observed in brain regions such as the somatosensory cortex, brainstem and thalamus. In regulation of CBF, the individual roles of neurotransmitters are partly known, but much needs to be unraveled with respect to headache disorders.

Inhibitory Effects of Helianthus tuberosus Ethanol Extract on Dermatophagoides farina body-induced Atopic Dermatitis Mouse Model and Human Keratinocytes

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by complex symptoms. To treat AD without adverse effects, alternative therapeutic agents are required. The tubers of Helianthus tuberosus L. (Jerusalem artichoke) have been used in folk remedies for diabetes and rheumatism. However, its effect on AD development remains unknown. Therefore, this study examined the inhibitory effect of H. tuberosus (HT) on AD skin symptoms using an NC/Nga mouse model and HaCaT keratinocytes. The effect of HT and associated molecular mechanisms were evaluated in Dermatophagoides farina body (Dfb)-induced AD mice and tumor necrosis factor (TNF)-α/interferon (IFN)-γ-stimulated HaCaT keratinocytes by ELISA, western blot, and histological analysis. Topical HT administration attenuated AD skin symptoms in Dfb-induced AD mice, with a significant reduction in the dermatitis score and production of inflammatory mediators. HT also decreased epidermal thickness and mast cell infiltration. Moreover, HT restored filaggrin expression and inhibited adhesion molecules in the mice. These effects were confirmed in vitro. Furthermore, HT suppressed the activation of NF-κB, Akt, and mitogen-activated protein kinase (MAPK) signaling pathways induced by TNF-α/IFN-γ. These results suggest that HT is a potential therapeutic agent or supplement for skin allergic inflammatory diseases such as AD.

The serum level of inflammatory markers in chronic and episodic migraine: a case-control study

The exact mechanism of the migraine pathophysiology remained unclear. Although there are some reports showing low-grade inflammation in migraineurs, further studies are needed in this field. Thus, we designed a study to evaluate the serum levels of two main proinflammatory markers in migraine patients. In this case-control research, 43 migraine patients (23 chronic and 20 episodic migraineurs) and 40 age-sex-matched headache-free controls were studied. Demographic, dietary, and anthropometric data, headache characteristics, and serum C-reactive proteins (CRP) and tumor necrosis factor-alpha (TNF-α) assessments were collected. The mean ± SD age of the case and control groups were 36.98 ± 9.91 and 34.84 ± 9.75 years respectively. Compared to control subjects, both episodic and chronic migraineurs had significantly higher median levels of TNF-α (0.24, 0.95, and 1.90 pg/ml, respectively; P value < 0.001). Also, we observed a positive association between the TNF-α levels and the odds of having migraine after considering gender, age, body mass index, and dietary intakes of energy, carbohydrate, protein, fat, and mono and poly unsaturated fatty acids in the multivariable regression models (OR = 2.15; 95% CI 1.31-3.52; P value < 0.001). However, no significant association was demonstrated between migraine and serum CRP (OR = 2.91; 95% CI 0.87-9.78; P value = 0.08). These findings supported that inflammatory state could be related to the pathogenesis of migraine and it can thus be suggested that this effect might be beyond migraine progression. Further detailed studies are needed to investigate the importance of these findings in the pathogenesis of migraine headache.

Purinergic Profiling of Regulatory T-cells in Patients With Episodic Migraine

Objectives: Immune responses in migraine are poorly characterized, yet implicated in the disease pathogenesis. This study was carried out to characterize purinergic profiles of T-cells in patients with episodic migraine without aura (MWoA) to provide mechanistic evidence for ATP and adenosine involvement in modulation of immune regulation in migraine. Methods: Peripheral blood samples were obtained from patients with migraine (n = 16) and age-matched control subjects (n = 21). Subsets of T-cells were identified by flow cytometry based on specific membrane markers. Results: Migraine patients showed reduced total T-cell counts in the peripheral blood. Whereas the total number of CD3+CD4+, CD3+CD8+, or regulatory T lymphocytes (Treg) was not changed, the proportion of Treg CD45R0+CD62L- and CD45R0-CD62L- cells was increased. Interestingly, in migraine, less Treg cells expressed CD39 and CD73 suggesting disrupted ATP breakdown to adenosine. The negative correlations were observed between the duration of migraine and the relative number of CD73+CD39- Tregs and total number of CD73-positive CD45R0+CD62L+ Tregs. Conclusion: Obtained data indicate that T-cell populations are altered in episodic migraine and suggest the involvement of Tregs in the pathophysiology of this disorder. Reduced expression of CD39 and CD73 suggests promotion of ATP-dependent pro-inflammatory and reduction of adenosine-mediated anti-inflammatory mechanisms in migraine.

The effects of a multispecies probiotic on migraine and markers of intestinal permeability-results of a randomized placebo-controlled study

BACKGROUND/OBJECTIVES

Migraine, associated with several gastrointestinal disorders, may result from increased intestinal permeability, allowing endotoxins to enter the bloodstream. We tested whether probiotics could reduce migraine through an effect on intestinal permeability and inflammation.

SUBJECTS/METHODS

In total, 63 patients were randomly allocated to the probiotic (n=31) or the placebo group (n=32). Participants ingested a multispecies probiotic (5x10⁹ colony-forming units) or placebo daily for 12 weeks. Migraine was assessed with the Migraine Disability Assessment Scale (MIDAS), the Headache Disability Inventory (HDI) and headache diaries. At baseline and 12 weeks, intestinal permeability was measured with the urinary lactulose/mannitol test and fecal and serum zonulin; inflammation was measured from interleukin (IL) -6, IL-10, tumor necrosis factor-α and C-reactive protein in serum.

RESULTS

The MIDAS migraine intensity score significantly decreased in both groups (P<0.001) and the HDI score significantly decreased in the probiotic group (P=0.032) and borderline in the placebo group (P=0.053). In the probiotics group, patients had a median of 6 migraine days in the first month, 4 in the second month (P=0.002) and 5 in the last month, which was not significantly different from the 5, 4, and 4 days in the placebo group. A ⩾2day reduction in migraine days was seen in 12/31 patients in the probiotics group versus 7/29 in the placebo group (ns). Probiotic use did not significantly affect medication use, intestinal permeability or inflammation compared to placebo.

CONCLUSIONS

In this study, we could not confirm significant benefit from a multispecies probiotic compared to a placebo on the outcome parameters of migraine and intestinal integrity.

Serum Bilirubin and Their Association With C-Reactive Protein in Patients With Migraine

BACKGROUND

Increased levels of C-reactive protein (CRP) have been considered as a marker in assessing neurogenic inflammation of migraine patients. An inverse relationship between serum bilirubin and CRP has been observed in various diseases. Therefore, we analyzed serum bilirubin levels in migraine patients, and investigated the relationship between serum bilirubin and CRP in migraineurs.

METHODS

A total of 86 newly diagnosed migraine patients were consecutively recruited to this study.

RESULTS

Significantly lower median serum total bilirubin, conjugated bilirubin (CB) and unconjugated bilirubin were found in patients with migraine than healthy controls, and the levels of CRP were significantly higher in migraine patients than healthy controls. A negative correlation between CRP and CB was observed in patients with migraine (r = -0.255, P = 0.018). In a multiple linear regression model, the concentrations of CRP remained negatively correlated with CB.

CONCLUSIONS

Our study demonstrates that serum bilirubin concentrations are decreased in migraineurs, and CB levels were found to be positively correlated with CRP in migraine patents. However, larger cross-sectional and prospective studies are needed to establish whether serum bilirubin may be a useful biomarker for assessing neurogenic inflammation in migraine patients and eventually guiding the therapy.

Low-Level Blast Exposure Increases Transient Receptor Potential Vanilloid 1 (TRPV1) Expression in the Rat Cornea

Background: Blast-related ocular injuries sustained by military personnel have led to rigorous efforts to elucidate the effects of blast exposure on neurosensory function. Recent studies have provided some insight into cognitive and visual deficits sustained following blast exposure; however, limited data are available on the effects of blast on pain and inflammatory processes. Investigation of these secondary effects of blast exposure is necessary to fully comprehend the complex pathophysiology of blast-related injuries. The overall purpose of this study is to determine the effects of single and repeated blast exposure on pain and inflammatory mediators in ocular tissues.

Methods: A compressed air shock tube was used to deliver a single or repeated blast (68.0 ± 2.7 kPa) to anesthetized rats daily for 5 days. Immunohistochemistry was performed on ocular tissues to determine the expression of the transient receptor potential vanilloid 1 (TRPV1) channel, calcitonin gene-related peptide (CGRP), substance P (SP), and endothelin-1 (ET-1) following single and repeated blast exposure. Neutrophil infiltration and myeloperoxidase (MPO) expression were also assessed in blast tissues via immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) analysis, respectively.

Results: TRPV1 expression was increased in rat corneas exposed to both single and repeated blast. Increased secretion of CGRP, SP, and ET-1 was also detected in rat corneas as compared to control. Moreover, repeated blast exposure resulted in neutrophil infiltration in the cornea and stromal layer as compared to control animals.

Conclusion: Single and repeated blast exposure resulted in increased expression of TRPV1, CGRP, SP, and ET-1 as well as neutrophil infiltration. Collectively, these findings provide novel insight into the activation of pain and inflammation signaling mediators following blast exposure.