Role of Neuroinflammation and Blood-Brain Barrier Permutability on Migraine

Understanding Headaches Attributed to Cranial and/or Cervical Vascular Disorders: Insights and Challenges for Neurologists

In recent decades, cranial and cervical vascular disorders have become major global health concerns, significantly impacting patients, families, and societies. Headache is a prevalent symptom of these vascular diseases and can often be the initial, primary, or sole manifestation. The intricate relationship between headaches and cranial/cervical vascular disorders poses a diagnostic and therapeutic challenge, with the underlying mechanisms remaining largely elusive. Understanding this association is crucial for the early diagnosis, prevention, and intervention of such conditions. This review aims to provide a comprehensive overview of the clinical features and potential pathogenesis of headaches attributed to cranial and cervical vascular disorders and provide a reference for disease management and a basis for potential pathological mechanisms.

Mechanism of Traditional Chinese Medicine in Treating Migraine: A Comprehensive Review

Migraine is a common neurological illness that causes a great burden on individuals and society. Many migraine patients seek relief through complementary and alternative therapies, with Traditional Chinese medicine (TCM) often being their preferred choice. Acupuncture, Chinese herbal medicine, and massage are important components of TCM, and are commonly used in clinical treatment of migraine. This review aims to consolidate the current knowledge regarding the mechanisms of the three TCM interventions for migraine: acupuncture, herbs, and massage, and how they relieve pain. However, the mechanisms underlying the effectiveness of TCM therapies in treating migraine remain unclear. Therefore, we reviewed the research progress on acupuncture, herbal medicine, and massage as TCM approaches for the treatment of migraine. We conducted a comprehensive search of CNKI, PubMed, Web of Science, and Cochrane databases using keywords such as migraine, acupuncture, needle, herbs, herbal, prescription, decoction, massage, Tuina, and TCM, covering the period from 2000 to 2023. The literature included in the review was selected based on specified exclusion criteria. We discussed the mechanism of TCM therapies on migraine from the perspective of modern medicine, focusing on changes in inflammatory factors, neurotransmitters, and other relevant biomarkers. TCM can relieve migraine by decreasing neuropeptide levels, inhibiting inflammation, modulating neuronal sensitization, changing brain function and structure, changing blood brain barrier permeability, regulating hormone levels, and relieving muscle tension. The purpose of this paper is to provide a basis for improving the clinical strategies of TCM for the treatment of migraine.

Expression of miR-155 in monocytes of people with migraine: association with phenotype, disease severity and inflammatory profile

BACKGROUND

miR-155 is involved in the generation and maintenance of inflammation and pain, endothelial function and immune system homeostasis, all functions that are relevant for migraine. The present study aims to assess the levels of miR-155 in migraine subtypes (episodic and chronic) in comparison to age- and sex-matched healthy controls.

METHODS

This is a cross-sectional, controlled, study involving three study groups: I) episodic migraine (n = 52, EM), II) chronic migraine with medication overuse (n = 44, CM-MO), and III) healthy controls (n = 32, HCs). We assessed the interictal gene expression levels of miR-155, IL-1β, TNF-α, and IL-10 in peripheral blood monocytes using rtPCR. The monocytic differentiation toward the M1 (pro-inflammatory) or M2 (anti-inflammatory) phenotypes was assessed in circulating monocytes with flow cytometry analysis and cell sorting.

RESULTS

miR-155 gene expression was higher in CM-MO group (2.68 ± 2.47 Relative Quantification - RQ) when compared to EM group (1.46 ± 0.85 RQ, p = 0.006) and HCs (0.44 ± 0.18 RQ, p = 0.001). In addition, miR-155 gene expression was higher in EM group when compared to HCs (p = 0.001). A multivariate analysis confirmed the difference between EM and CM-MO groups after correction for age, sex, smoking habit, preventive treatment, aura, presence of psychiatric or other pain conditions. We found higher gene expression of IL-1β, TNF-α, and lower gene expression of IL-10 in migraine participants when compared to HCs (p = 0.001 for all comparisons). TNF-α and IL-10 genes alterations were more prominent in CM-MO when compared to EM participants (p = 0.001). miR-155 positively correlated with IL-1β (p = 0.001) and TNF-α (p = 0.001) expression levels. Finally, in people with CM-MO, we described an up-regulated percentage of events in both M1 and M2 monocytic profiles.

CONCLUSIONS

Our study shows for the first time a specific profile of activation of miR-155 gene expression levels in monocytes of selected migraine subpopulations, more pronounced in subjects with CM-MO. Interestingly, mir-155 expression correlated with markers of activation of the inflammatory and immune systems. The CM-MO subpopulation showed a peculiar increase of both pro-inflammatory and anti-inflammatory monocytes which worths further investigation.

TRIAL REGISTRATION

www.

CLINICALTRIALS

gov . (NCT05891808).

Genistein mitigates nitroglycerine-induced migraine: modulation of nitric oxide-mediated vasodilation and oxidative stress

Migraine is a widespread brain condition described by frequent, recurrent episodes of incapacitating, moderate-to-severe headaches with throbbing pain that are usually one-sided. It is the 2nd most debilitating state lived with disability in terms of years, with a prevalence rate of 15-20%. Significant drops in estrogen levels have been associated with triggering acute migraine attacks in certain cases. Phytoestrogens are plant-derived compounds that resemble estrogen in structure, enabling them to imitate estrogen's functions in the body by attaching to estrogen receptors. Thus, the study was aimed to explore the protective effect of genistein against migraine. Moreover, the role of nitric oxide was also studied in the observed effect of genistein. Nitric oxide (NO) is implicated in migraine pathophysiology due to its role in promoting cerebral vasodilation and modulation of pain perception. Exploring L-NAME, a nitric oxide synthase inhibitor in migraine research helps scientists better understand the role of NO in migraine. Nitroglycerine treatment significantly increased the facial-unilateral head pain and spontaneous pain, as evidenced by the increased number of head scratching and groomings. Nitroglycerine treatment also induced anxiogenic behavior in mice. A significant reduction in the number of entries in the light phase and open arm, respectively. Biochemical analysis indicated a significant increase in inflammatory and oxidative stress in the nitroglycerin group. A significant increase and decrease in brain TBARS and GSH were observed with nitroglycerine treatment, respectively. Moreover, nitroglycerine treatment has uplifted the serum TNF-α level. Genistein (20 mg/kg) significantly mitigated the facial-unilateral head pain, spontaneous pain, photophobia, and anxiety-like behavior induced by nitroglycerine. Biochemical analysis showed that genistein (20 mg/kg) significantly abrogated the nitroglycerine-induced lipid peroxidation and increased serum TNF-α level. Genistein treatment also upregulated the brain GSH level and downregulated the serum TNF-α level. The L-NAME-mediated alleviation of the protective effect of genistein might be attributed to the vasodilatory effect of L-NAME. Conclusively, it can be suggested that genistein might provide relief from migraine pain by inhibiting nitric oxide-mediated vasodilation and oxidative stress.

PACAP38/mast-cell-specific receptor axis mediates repetitive stress-induced headache in mice

BACKGROUND

Pain, an evolutionarily conserved warning system, lets us recognize threats and motivates us to adapt to those threats. Headache pain from migraine affects approximately 15% of the global population. However, the identity of any putative threat that migraine or headache warns us to avoid is unknown because migraine pathogenesis is poorly understood. Here, we show that a stress-induced increase in pituitary adenylate cyclase-activating polypeptide-38 (PACAP38), known as an initiator of allosteric load inducing unbalanced homeostasis, causes headache-like behaviour in male mice via mas-related G protein-coupled receptor B2 (MrgprB2) in mast cells.

METHODS

The repetitive stress model and dural injection of PACAP38 were performed to induce headache behaviours. We assessed headache behaviours using the facial von Frey test and the grimace scale in wild-type and MrgprB2-deficient mice. We further examined the activities of trigeminal ganglion neurons using in vivo Pirt-GCaMP Ca2+ imaging of intact trigeminal ganglion (TG).

RESULTS

Repetitive stress and dural injection of PACAP38 induced MrgprB2-dependent headache behaviours. Blood levels of PACAP38 were increased after repetitive stress. PACAP38/MrgprB2-induced mast cell degranulation sensitizes the trigeminovascular system in dura mater. Moreover, using in vivo intact TG Pirt-GCaMP Ca2+ imaging, we show that stress or/and elevation of PACAP38 sensitized the TG neurons via MrgprB2. MrgprB2-deficient mice showed no sensitization of TG neurons or mast cell activation. We found that repetitive stress and dural injection of PACAP38 induced headache behaviour through TNF-a and TRPV1 pathways.

CONCLUSIONS

Our findings highlight the PACAP38-MrgprB2 pathway as a new target for the treatment of stress-related migraine headache. Furthermore, our results pertaining to stress interoception via the MrgprB2/PACAP38 axis suggests that migraine headache warns us of stress-induced homeostatic imbalance.

Neuroimmunological effects of omega-3 fatty acids on migraine: a review

Migraine is a highly prevalent disease worldwide, imposing enormous clinical and economic burdens on individuals and societies. Current treatments exhibit limited efficacy and acceptability, highlighting the need for more effective and safety prophylactic approaches, including the use of nutraceuticals for migraine treatment. Migraine involves interactions within the central and peripheral nervous systems, with significant activation and sensitization of the trigeminovascular system (TVS) in pain generation and transmission. The condition is influenced by genetic predispositions and environmental factors, leading to altered sensory processing. The neuroinflammatory response is increasingly recognized as a key event underpinning the pathophysiology of migraine, involving a complex neuro-glio-vascular interplay. This interplay is partially mediated by neuropeptides such as calcitonin gene receptor peptide (CGRP), pituitary adenylate cyclase activating polypeptide (PACAP) and/or cortical spreading depression (CSD) and involves oxidative stress, mitochondrial dysfunction, nucleotide-binding domain-like receptor family pyrin domain containing-3 (NLRP3) inflammasome formation, activated microglia, and reactive astrocytes. Omega-3 polyunsaturated fatty acids (PUFAs), particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), crucial for the nervous system, mediate various physiological functions. Omega-3 PUFAs offer cardiovascular, neurological, and psychiatric benefits due to their potent anti-inflammatory, anti-nociceptive, antioxidant, and neuromodulatory properties, which modulate neuroinflammation, neurogenic inflammation, pain transmission, enhance mitochondrial stability, and mood regulation. Moreover, specialized pro-resolving mediators (SPMs), a class of PUFA-derived lipid mediators, regulate pro-inflammatory and resolution pathways, playing significant anti-inflammatory and neurological roles, which in turn may be beneficial in alleviating the symptomatology of migraine. Omega-3 PUFAs impact various neurobiological pathways and have demonstrated a lack of major adverse events, underscoring their multifaceted approach and safety in migraine management. Although not all omega-3 PUFAs trials have shown beneficial in reducing the symptomatology of migraine, further research is needed to fully establish their clinical efficacy and understand the precise molecular mechanisms underlying the effects of omega-3 PUFAs and PUFA-derived lipid mediators, SPMs on migraine pathophysiology and progression. This review highlights their potential in modulating brain functions, such as neuroimmunological effects, and suggests their promise as candidates for effective migraine prophylaxis.

Understanding the Biological Relationship between Migraine and Depression

Migraine is a highly prevalent neurological disorder. Among the risk factors identified, psychiatric comorbidities, such as depression, seem to play an important role in its onset and clinical course. Patients with migraine are 2.5 times more likely to develop a depressive disorder; this risk becomes even higher in patients suffering from chronic migraine or migraine with aura. This relationship is bidirectional, since depression also predicts an earlier/worse onset of migraine, increasing the risk of migraine chronicity and, consequently, requiring a higher healthcare expenditure compared to migraine alone. All these data suggest that migraine and depression may share overlapping biological mechanisms. Herein, this review explores this topic in further detail: firstly, by introducing the common epidemiological and risk factors for this comorbidity; secondly, by focusing on providing the cumulative evidence of common biological aspects, with a particular emphasis on the serotoninergic system, neuropeptides such as calcitonin-gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP), substance P, neuropeptide Y and orexins, sexual hormones, and the immune system; lastly, by remarking on the future challenges required to elucidate the etiopathological mechanisms of migraine and depression and providing updated information regarding new key targets for the pharmacological treatment of these clinical entities.

Immunopathology of herpes simplex virus-associated neuroinflammation: Unveiling the mysteries

The immunopathology of herpes simplex virus (HSV)-associated neuroinflammation is a captivating and intricate field of study within the scientific community. HSV, renowned for its latent infection capability, gives rise to a spectrum of neurological expressions, ranging from mild symptoms to severe encephalitis. The enigmatic interplay between the virus and the host's immune responses profoundly shapes the outcome of these infections. This review delves into the multifaceted immune reactions triggered by HSV within neural tissues, intricately encompassing the interplay between innate and adaptive immunity. Furthermore, this analysis delves into the delicate equilibrium between immune defence and the potential for immunopathology-induced neural damage. It meticulously dissects the roles of diverse immune cells, cytokines, and chemokines, unravelling the intricacies of neuroinflammation modulation and its subsequent effects. By exploring HSV's immune manipulation and exploitation mechanisms, this review endeavours to unveil the enigmas surrounding the immunopathology of HSV-associated neuroinflammation. This comprehensive understanding enhances our grasp of viral pathogenesis and holds promise for pioneering therapeutic strategies designed to mitigate the neurological ramifications of HSV infections.

Electroacupuncture improves allodynia and central sensitization via modulation of microglial activation associated P2X4R and inflammation in a rat model of migraine

Background: Recent studies have demonstrated that activated microglia were involved in the pathogenesis of central sensitization characterized by cutaneous allodynia in migraine. Activation of microglia is accompanied by increased expression of its receptors and release of inflammatory mediators. Acupuncture and its developed electroacupuncture (EA) have been recommended as an alternative therapy for migraine and are widely used for relieving migraine-associated pain. However, it remains rare studies that show whether EA exerts anti-migraine effects via inhibiting microglial activation related to a release of microglial receptors and the inflammatory pathway. Therefore, this study aimed to investigate EA' ability to ameliorate central sensitization via modulation of microglial activation, microglial receptor, and inflammatory response using a rat model of migraine induced by repeated epidural chemical stimulation. Methods: In the present study, a rat model of migraine was established by epidural repeated inflammatory soup (IS) stimulation and treated with EA at Fengchi (GB20) and Yanglingquan (GB34) and acupuncture at sham-acupoints. Pain hypersensitivity was further determined by measuring the mechanical withdrawal threshold using the von-Frey filament. The changes in c-Fos and ionized calcium binding adaptor molecule 1 (Ibal-1) labeled microglia in the trigeminal nucleus caudalis (TNC) were examined by immunflurescence to assess the central sensitization and whether accompanied with microglia activation. In addition, the expression of Ibal-1, microglial purinoceptor P2X4, and its associated inflammatory signaling pathway mediators, including interleukin (IL)-1β, NOD-like receptor protein 3 (NLRP3), and Caspase-1 in the TNC were investigated by western blot and real-time polymerase chain reaction analysis. Results: Allodynia increased of c-Fos, and activated microglia were observed after repeated IS stimulation. EA alleviated the decrease in mechanical withdrawal thresholds, reduced the activation of c-Fos and microglia labeled with Ibal-1, downregulated the level of microglial purinoceptor P2X4, and limited the inflammatory response (NLRP3/Caspase-1/IL-1β signaling pathway) in the TNC of migraine rat model. Conclusions: Our results indicate that the anti-hyperalgesia effects of EA ameliorate central sensitization in IS-induced migraine by regulating microglial activation related to P2X4R and NLRP3/IL-1β inflammatory pathway.

Serum tau protein elevation in migraine: a cross-sectional case-control study

BACKGROUND

Migraine is a disorder associated with neuropeptide release, pain and inflammation. Tau protein has recently been linked to inflammatory diseases and can be influenced by neuropeptides such as CGRP, a key neurotransmitter in migraine. Here, we report serum concentrations of total-tau protein in migraine patients and healthy controls.

METHODS

In this cross-sectional study, interictal blood samples from n = 92 patients with episodic migraine (EM), n = 93 patients with chronic migraine (CM), and n = 42 healthy matched controls (HC) were studied. We assessed serum total-tau protein (t-tau) and for comparison neurofilament light chain protein (NfL), glial fibrillary acidic protein (GFAP), and ubiquitin carboxy-terminal hydrolase L (UCH-L1) concentrations using the Neurology 4-plex kit, on a single molecule array HD-X Analyzer (Quanterix Corp Lexington, MA). Matched serum/cerebrospinal fluid (CSF) samples were used for post-hoc evaluations of a central nervous system (CNS) source of relevant findings. We applied non-parametric tests to compare groups and assess correlations.

RESULTS

Serum t-tau concentrations were elevated in EM [0.320 (0.204 to 0.466) pg/mL] and CM [0.304 (0.158 to 0.406) pg/mL] patients compared to HC [0.200 (0.114 to 0.288) pg/mL] (p = 0.002 vs. EM; p = 0.025 vs. CM). EM with aura [0.291 (0.184 to 0.486 pg/mL); p = 0.013] and EM without aura [0.332 (0.234 to 0.449) pg/mL; p = 0.008] patients had higher t-tau levels than HC but did not differ between each other. Subgroup analysis of CM with/without preventive treatment revealed elevated t-tau levels compared to HC only in the non-prevention group [0.322 (0.181 to 0.463) pg/mL; p = 0.009]. T-tau was elevated in serum (p = 0.028) but not in cerebrospinal fluid (p = 0.760). In contrast to t-tau, all proteins associated with cell damage (NfL, GFAP, and UCH-L1), did not differ between groups.

DISCUSSION

Migraine is associated with t-tau elevation in serum but not in the CSF. Our clinical study identifies t-tau as a new target for migraine research.

Potential analgesic effect of Foshousan oil-loaded chitosan-alginate nanoparticles on the treatment of migraine

Background: Migraine is a common neurovascular disorder with typical throbbing and unilateral headaches, causing a considerable healthcare burden on the global economy. This research aims to prepare chitosan-alginate (CS-AL) nanoparticles (NPs) containing Foshousan oil (FSSO) and investigate its potential therapeutic effects on the treatment of migraine. Methods: FSSO-loaded CS-AL NPs were prepared by using the single emulsion solvent evaporation method. Lipopolysaccharide (LPS)-stimulated BV-2 cells and nitroglycerin (NTG)-induced migraine mice were further used to explore anti-migraine activities and potential mechanisms of this botanical drug. Results: FSSO-loaded CS-AL NPs (212.1 ± 5.2 nm, 45.1 ± 6.2 mV) had a well-defined spherical shape with prolonged drug release and good storage within 4 weeks. FSSO and FSSO-loaded CS-AL NPs (5, 10, and 15 μg/mL) showed anti-inflammatory activities in LPS-treated BV-2 cells via reducing the levels of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and nitric oxide (NO), but elevating interleukin-10 (IL-10) expressions. Moreover, FSSO-loaded CS-AL NPs (52 and 104 mg/kg) raised pain thresholds against the hot stimulus and decreased acetic acid-induced writhing frequency and foot-licking duration in NTG-induced migraine mice. Compared with the model group, calcitonin gene-related peptide (CGRP) and NO levels were downregulated, but 5-hydroxytryptamine (5-HT) and endothelin (ET) levels were upregulated along with rebalanced ET/NO ratio, and vasomotor dysfunction was alleviated by promoting cerebral blood flow (CBF) in the FSSO-loaded CS-AL NPs (104 mg/kg) group. Conclusion: FSSO-loaded CS-AL NPs could attenuate migraine via inhibiting neuroinflammation in LPS-stimulated BV-2 cells and regulating vasoactive substances in NTG-induced migraine mice. These findings suggest that the FSS formula may be exploited as new phytotherapy for treating migraine.

Imaging Correlates between Headache and Breast Cancer: An [18F]FDG PET Study

This study aimed to examine brain metabolic patterns on [18F]Fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) in breast cancer (BC), comparing patients with tension-type headache (TTH), migraine (MiG), and those without headache. Further association with BC response to neoadjuvant chemotherapy (NAC) was explored. In this prospective study, BC patients eligible for NAC performed total-body [18F]FDG PET/CT with a dedicated brain scan. A voxel-wise analysis (two-sample t-test) and a multiple regression model were used to compare brain metabolic patterns among TTH, MiG, and no-headache patients and to correlate them with clinical covariates. A single-subject analysis compared each patient's brain uptake before and after NAC with a healthy control group. Primary headache was diagnosed in 39/46 of BC patients (39% TTH and 46% MiG). TTH patients exhibited hypometabolism in specific brain regions before NAC. TTH patients with a pathological complete response (pCR) to NAC showed hypermetabolic brain regions in the anterior medial frontal cortex. The correlation between tumor uptake and brain metabolism varied before and after NAC, suggesting an inverse relationship. Additionally, the single-subject analysis revealed that hypometabolic brain regions were not present after NAC. Primary headache, especially MiG, was associated with a better response to NAC. These findings suggest complex interactions between BC, headache, and hormonal status, warranting further investigation in larger prospective cohorts.

SIRT1 activation by 2,3,5,6-tetramethylpyrazine alleviates neuroinflammation via inhibiting M1 microglia polarization

Background

Neuroinflammation has been reported as a potential contributing factor to brain diseases, and is characterized by activated microglia with release of multiple inflammatory mediators. 2,3,5,6-Tetramethylpyrazine (TMP) is an active alkaloid in Ligusticum chuanxiong Hort. and has various biological activities, including anti-inflammatory and neuroprotection properties. However, the anti-neuroinflammatory activity of TMP has been less studied and its potential molecular mechanisms in this field remain unclear. This study aimed to investigate the effects of TMP and its underlying mechanisms in neuroinflammation.

Methods

In vitro, lipopolysaccharide (LPS)-stimulated BV2 microglia were used to assess the effects of TMP on inflammatory cytokines as well as the components of the SIRT1/NF-κB signaling pathway, which were measured by using ELISA, western blotting, qRT-qPCR and immunofluorescence. Moreover, LPS-induced acute neuroinflammation model in mice was performed to detect whether TMP could exert anti-neuroinflammatory effects in vivo, and the EX527, a SIRT1 inhibitor, were given intraperitoneally every two days prior to TMP treatment. Serums and spinal trigeminal nucleus (Sp5) tissues were collected for ELISA assay, and the Sp5 tissues were used for HE staining, Nissl staining, immunofluorescence, qRT-PCR and western blotting.

Results

In vitro, TMP treatment significantly reduced the secretion of pro-inflammatory cytokines, including TNF-α and IL-6, promoted SIRT1 protein expression and inactivated NF-κB signaling pathway in LPS-induced neuroinflammation. Interestingly, pretreatment with EX527 blocked the therapeutic effects of TMP on neuroinflammation in vitro. Furthermore, TMP reduced the levels of pro-inflammatory cytokines and chemokines, and prevented microglia from polarizing towards a pro-inflammatory state through activating SIRT1 and inhibiting NF-κB activation in LPS-induced neuroinflammation in mice. And EX527 reversed the beneficial effects of TMP against LPS exposure in mice.

Conclusion

In summary, this study unravels that TMP could mitigate LPS-induced neuroinflammation via SIRT1/NF-κB signaling pathway.

Multisite and multitimepoint proteomics reveal that patent foramen ovale closure improves migraine and epilepsy by reducing right-to-left shunt-induced hypoxia

Patent foramen ovale (PFO) is a congenital defect in the partition between two atria, which may cause right-to-left shunt (RLS), leading to neurological chronic diseases with episodic manifestations (NCDEMs), such as migraine and epilepsy. However, whether PFO closure was effective in improving NCDEMs and the mechanism were unclear. Twenty-eight patients with migraine or epilepsy who underwent PFO closure were recruited. Notably, approximately half of patients received 50% or more reduction in seizure or headache attacks. Meanwhile, the postoperative blood oxygen partial pressure and oxygen saturation were elevated after PFO closure. Multisite (peripheral, right, and left atrial) and multitimepoint (before and after surgery) plasma proteomics from patients showed that the levels of free hemoglobin and cell adhesion molecules (CAMs) were significantly increased after PFO closure, which may be related to the relief of the hypoxic state. Furtherly, the omics data from multiple brain regions of mice revealed that a large number of proteins were differentially expressed in the occipital region in response to PFO, including redox molecules and CAMs, suggesting PFO-caused hypoxia may have great impacts on occipital region. Collectively, PFO may cause NCDEMs due to RLS-induced hypoxia, and PFO closure could prevent RLS to improve migraine and epilepsy.

ABHD6 and MAGL control 2-AG levels in the PAG and allodynia in a CSD-induced periorbital model of headache

Introduction

The high prevalence and severe symptoms of migraines in humans emphasizes the need to identify underlying mechanisms that can be targeted for therapeutic benefit. Clinical Endocannabinoid Deficiency (CED) posits that reduced endocannabinoid tone may contribute to migraine development and other neuropathic pain conditions. While strategies that increase levels of the endocannabinoid n-arachidonoylethanolamide have been tested, few studies have investigated targeting the levels of the more abundant endocannabinoid, 2-arachidonoylgycerol, as an effective migraine intervention.

Methods

Cortical spreading depression was induced in female Sprague Dawley rats via KCl (potassium chloride) administration, followed by measures of endocannabinoid levels, enzyme activity, and neuroinflammatory markers. Efficacy of inhibiting 2-arachidonoylglycerol hydrolysis to mitigate periorbital allodynia was then tested using reversal and prevention paradigms.

Results

We discovered reduced 2-arachidonoylglycerol levels in the periaqueductal grey associated with increased hydrolysis following headache induction. Pharmacological inhibition of the 2-arachidonoylglycerol hydrolyzing enzymes, α/β-hydrolase domain-containing 6 and monoacylglycerol lipase reversed and prevented induced periorbital allodynia in a cannabinoid receptor-dependent manner.

Discussion

Our study unravels a mechanistic link between 2-arachidonoylglycerol hydrolysis activity in the periaqueductal grey in a preclinical, rat model of migraine. Thus, 2-arachidonoylglycerol hydrolysis inhibitors represent a potential new therapeutic avenue for the treatment of headache.

Molecular Research on Migraine: From Pathogenesis to Treatment

Migraine is a common, multifactorial, disabling, recurrent, hereditary, neurovascular headache disorder [...].

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.

Prevalence and clinical characteristics of white matter hyperintensities in Migraine: A meta-analysis

BACKGROUND

Current evidences show an increased risk of white matter hyperintensities (WMHs) in migraineurs compared to age-matched controls. However, WMHs prevalence and the associations between WMHs and clinical characteristics in migraineurs have not been systematically evaluated using a meta-analytical approach. This study explored the pooled prevalence of WMHs and the associations of WMHs with the clinical characteristics in patients with migraine.

METHODS

A systematic review and meta-analysis of observational studies reporting the occurrence and clinical characteristics of patients with WMHs attributed to migraine was performed. We searched the PubMed, Web of Science, and Embase databases. Random-effects models were used to calculate the pooled prevalence rate, odds ratio (OR), or mean difference (MD) with corresponding 95% confidence intervals (CIs).

RESULTS

Thirty eligible studies were identified including 3,502 migraineurs aged 37.2 (mean) years. The pooled WMHs prevalence was 44 %, 45 %, and 38 % in migraine, migraine with aura, and migraine without aura groups, respectively. In migraineurs with WMHs, the frontal lobe and subcortical white matter were the most susceptible area. Compared with non-migraine controls, patients with migraine had increased odds for WMHs (OR 4.32, 95 % CI = 2.56-7.28, I2 = 67 %). According to reported univariable results from included studies, pooled analysis showed that clinical characteristics including age, presence of aura, disease duration, hypertension, diabetes mellitus and right-to-left shunt were associated with the presence of WMHs. Migraine pain and aura characteristics were not related to WMHs.

CONCLUSIONS

These data suggest that WMHs are common in migraine, especially in those who are older or have aura, hypertension, diabetes mellitus, or right-to-left shunt. A better understanding of the WMHs attributed to migraine is needed in future studies.

Malaysian brown macroalga Padina australis mitigates lipopolysaccharide-stimulated neuroinflammation in BV2 microglial cells

Objectives

Neuroinflammation and microglial activation are pathological features in central nervous system disorders. Excess levels of reactive oxygen species (ROS) and pro-inflammatory cytokines have been implicated in exacerbation of neuronal damage during chronic activation of microglial cells. Padina australis, a brown macroalga, has been demonstrated to have various pharmacological properties such as anti-neuroinflammatory activity. However, the underlying mechanism mediating the anti-neuroinflammatory potential of P. australis remains poorly understood. We explored the use of Malaysian P. australis in attenuating lipopolysaccharide (LPS)-stimulated neuroinflammation in BV2 microglial cells.

Materials and Methods

Fresh specimens of P. australis were freeze-dried and subjected to ethanol extraction. The ethanol extract (PAEE) was evaluated for its protective effects against 1 µg/ml LPS-stimulated neuroinflammation in BV2 microglial cells.

Results

LPS reduced the viability of BV2 microglia cells and increased the levels of nitric oxide (NO), prostaglandin E₂ (PGE₂), intracellular reactive oxygen species (ROS), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6). However, the neuroinflammatory response was reversed by 0.5-2.0 mg/ml PAEE in a dose-dependent manner. Analysis of liquid chromatography-mass spectrometry (LC-MS) of PAEE subfractions revealed five compounds; methyl α-eleostearate, ethyl α-eleostearate, niacinamide, stearamide, and linoleic acid.

Conclusion

The protective effects of PAEE against LPS-stimulated neuroinflammation in BV2 microglial cells were found to be mediated by the suppression of excess levels of intracellular ROS and pro-inflammatory mediators and cytokines, denoting the protective role of P. australis in combating continuous neuroinflammation. Our findings support the use of P. australis as a possible therapeutic for neuroinflammatory and neurodegenerative diseases.

Polymorphisms of the Proinflammatory Cytokine Genes Modulate the Response to NSAIDs but Not to Triptans in Migraine Attacks

Migraine is a common neurovascular disorder characterized by recurrent episodes of headache and associated neurological symptoms. At present, a significant portion of patients do not obtain a satisfactory response to acute pain-relieving therapies, including NSAIDs and triptans. In this context, pharmacogenetics plays a key role in the understanding of such a diverse response. In order to investigate whether functional polymorphisms in proinflammatory cytokine genes (IL-1α, IL-1β, IL-1RN; IL-6 and TNF-α) may influence the response to acute treatment, 313 consecutive patients with episodic migraine without aura were enrolled. Pain relief by administration of NSAIDs or triptans for three consecutive migraine attacks was evaluated. We found a significant association between A allele of the TNF-α promoter (−308 A/G) and a lack of efficacy after NSAID administration (p < 0.01, OR 2.51, 95% CI: 1.33 < OR < 4.75 compared to the G allele). Remaining polymorphisms had no significant effect on pain relief. Our study showed that a functional polymorphism in the TNF-α gene significantly modulates the clinical response to NSAID administration in acute attacks. Patients with higher production of the active cytokine during stress showed a significantly lower anti-migraine effect. Our results further support a role for TNF-α in the pathophysiological mechanisms of migraine attack.

Associations between Fatty Acid Intake and Tension-Type Headache: A Cross-Sectional Study

INTRODUCTION

Patients with tension-type headache (TTH) are characterized by recurrent pain that can become disabling. Identifying the dietary triggers of headaches has led to defining dietary strategies to prevent this disease. In fact, excessive dietary intake of Omega-6 (ω-6) fatty acids, or an ω-6: ω3 ≥ 5 ratio, typical of Western diets, has been associated with a higher prevalence of headaches. The objectives of the present study were to compare dietary fatty acid intake between participants with and without chronic TTH and to investigate the association between dietary fatty acid intake, pain characteristics, and quality of life in patients with chronic TTH.

METHODS

An observational study was conducted, comparing healthy participants (n = 24) and participants diagnosed with chronic TTH for more than six months (n = 24). The variables analyzed were dietary fatty acid intake variables, the Headache Impact Test (HIT-6), and the characteristics of the headache episodes (intensity, frequency, and duration).

RESULTS

The TTH group reported a significantly higher intake of saturated fatty acids (SFAs) but similar intakes of monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and ω-6: ω-3 ratio when compared to controls. Furthermore, in the TTH group, the Ω-6 fatty acid intake was associated with more intense headache episodes. In addition, the TTH group reported a significant impact of headaches on their activities of daily living according to the HIT-6.

CONCLUSIONS

Higher intakes of SFAs and Ω-6 fatty acids were associated with more severe headache episodes in patients with TTH. Therefore, the characteristics of the diet, in particular the dietary fatty acid intake, should be considered when treating these patients.

Src Family Kinases Facilitate the Crosstalk between CGRP and Cytokines in Sensitizing Trigeminal Ganglion via Transmitting CGRP Receptor/PKA Pathway

The communication between calcitonin gene-related peptide (CGRP) and cytokines plays a prominent role in maintaining trigeminal ganglion (TG) and trigeminovascular sensitization. However, the underlying regulatory mechanism is elusive. In this study, we explored the hypothesis that Src family kinases (SFKs) activity facilitates the crosstalk between CGRP and cytokines in sensitizing TG. Mouse TG tissue culture was performed to study CGRP release by enzyme-linked immunosorbent assay, cytokine release by multiplex assay, cytokine gene expression by quantitative polymerase chain reaction, and phosphorylated SFKs level by western blot. The results demonstrated that a SFKs activator, pYEEI (YGRKKRRQRRREPQY(PO3H2)EEIPIYL) alone, did not alter CGRP release or the inflammatory cytokine interleukin-1β (IL-1β) gene expression in the mouse TG. In contrast, a SFKs inhibitor, saracatinib, restored CGRP release, the inflammatory cytokines IL-1β, C-X-C motif ligand 1, C-C motif ligand 2 (CCL2) release, and IL-1β, CCL2 gene expression when the mouse TG was pre-sensitized with hydrogen peroxide and CGRP respectively. Consistently with this, the phosphorylated SFKs level was increased by both hydrogen peroxide and CGRP in the mouse TG, which was reduced by a CGRP receptor inhibitor BIBN4096 and a protein kinase A (PKA) inhibitor PKI (14–22) Amide. The present study demonstrates that SFKs activity plays a pivotal role in facilitating the crosstalk between CGRP and cytokines by transmitting CGRP receptor/PKA signaling to potentiate TG sensitization and ultimately trigeminovascular sensitization.

Ambient NO2 exposure induces migraine in rats: Evidence, mechanisms and interventions

Migraine is a complex neurological disorder with a high disability rate. Although the precipitating factors of migraine remain unclear, previous studies suggest that when there is excess nitrogen dioxide (NO₂) pollution in the atmosphere, the medical demand due to migraine attacks increases sharply. However, the main role of NO₂ as a trigger for migraine is not yet well understood. The purpose of this study was to explore the relationship between NO₂ exposure and the occurrence of migraine as well as the possible underlying mechanisms. We first investigated whether repeated short-term NO₂ exposure could induce behavioural and biological migraine phenotypes in rats. Next, capsazepine (CZP) was used to block transient receptor potential cation channel subfamily V member 1 (TRPV1) in vivo, and CZP and vitamin E (VE) were used to verify the role of reactive oxygen species (ROS)-TRPV1 signalling in NO₂-induced migraine in primary trigeminal neurones in vitro. We demonstrated that short-term repeated NO₂ exposure can significantly induce migraine in rats, and its key molecular mechanism may be related to ROS burst and its downstream TRPV1 channel activation. The findings of this study will enhance the understanding of the neurotoxic mechanism of NO₂, provide new clues for identifying the aetiology of migraine, and lay a new experimental basis for implementing migraine-related preventive and therapeutic control measures.

Immunologic aspects of migraine: A review of literature

Migraine headaches are highly prevalent, affecting 15% of the population. However, despite many studies to determine this disease's mechanism and efficient management, its pathophysiology has not been fully elucidated. There are suggested hypotheses about the possible mediating role of mast cells, immunoglobulin E, histamine, and cytokines in this disease. A higher incidence of this disease in allergic and asthma patients, reported by several studies, indicates the possible role of brain mast cells located around the brain vessels in this disease. The mast cells are more specifically within the dura and can affect the trigeminal nerve and cervical or sphenopalatine ganglion, triggering the secretion of substances that cause migraine. Neuropeptides such as calcitonin gene-related peptide (CGRP), neurokinin-A, neurotensin (NT), pituitary adenylate-cyclase-activating peptide (PACAP), and substance P (SP) trigger mast cells, and in response, they secrete pro-inflammatory and vasodilatory molecules such as interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) as a selective result of corticotropin-releasing hormone (CRH) secretion. This stress hormone contributes to migraine or intensifies it. Blocking these pathways using immunologic agents such as CGRP antibody, anti-CGRP receptor antibody, and interleukin-1 beta (IL-1β)/interleukin 1 receptor type 1 (IL-1R1) axis-related agents may be promising as potential prophylactic migraine treatments. This review is going to summarize the immunological aspects of migraine.

Energy Metabolic Disorder of Astrocytes May Be an Inducer of Migraine Attack

Migraine is a chronic headache disease, which ranks second in years lost due to disability. However, the mechanism of migraines is still not clear. In migraine patients, fasting can trigger headache attacks. We explored the probable mechanism of why fasting can induce headaches. Nitroglycerin (NTG) was used to induce acute migraine attacks in mice. Primary astrocytes were used to study the pathophysiological mechanism and a Seahorse analyzer was used to detect mitochondrial function. NTG induced more serious headaches in the fasting group. Both the head-scratching times and climbing-cage times in the fasting group were higher than those in normal-diet group. More ROS and inflammatory factors, such as IL-6 and IL-1β, were induced in low-glucose conditions. Seahorse showed that the basal oxygen consumption rate (OCR) and OCR for ATP production were lower in mice who had received NTG with low glucose levels than in other groups. The activity of AMPK was inhibited in this group, which may explain the Seahorse results. We concluded that in the low-glucose state, astrocytes produce more inflammatory factors, ROS, which may be a result of mitochondrial metabolism dysfunction. Improving mitochondrial function and supplying enough substrates may be an option for relieving migraine attacks.

Epigenetic Connection of the Calcitonin Gene-Related Peptide and Its Potential in Migraine

The calcitonin gene-related peptide (CGRP) is implicated in the pathogenesis of several pain-related syndromes, including migraine. Targeting CGRP and its receptor by their antagonists and antibodies was a breakthrough in migraine therapy, but the need to improve efficacy and limit the side effects of these drugs justify further studies on the regulation of CGRP in migraine. The expression of the CGRP encoding gene, CALCA, is modulated by epigenetic modifications, including the DNA methylation, histone modification, and effects of micro RNAs (miRNAs), circular RNAs, and long-coding RNAs (lncRNAs). On the other hand, CGRP can change the epigenetic profile of neuronal and glial cells. The promoter of the CALCA gene has two CpG islands that may be specifically methylated in migraine patients. DNA methylation and lncRNAs were shown to play a role in the cell-specific alternative splicing of the CALCA primary transcript. CGRP may be involved in changes in neural cytoarchitecture that are controlled by histone deacetylase 6 (HDAC6) and can be related to migraine. Inhibition of HDAC6 results in reduced cortical-spreading depression and a blockade of the CGRP receptor. CGRP levels are associated with the expression of several miRNAs in plasma, making them useful peripheral markers of migraine. The fundamental role of CGRP in inflammatory pain transmission may be epigenetically regulated. In conclusion, epigenetic connections of CGRP should be further explored for efficient and safe antimigraine therapy.

The Anti-CGRP Antibody Fremanezumab Lowers CGRP Release from Rat Dura Mater and Meningeal Blood Flow

Monoclonal antibodies directed against the neuropeptide calcitonin gene-related peptide (CGRP) belong to a new generation of therapeutics that are effective in the prevention of migraine. CGRP, a potent vasodilator, is strongly implicated in the pathophysiology of migraine, but its role remains to be fully elucidated. The hemisected rat head preparation and laser Doppler flowmetry were used to examine the effects on CGRP release from the dura mater and meningeal blood flow of the subcutaneously injected anti-CGRP monoclonal antibody fremanezumab at 30 mg/kg, when compared to an isotype control antibody. Some rats were administered glycerol trinitrate (GTN) intraperitoneally to produce a migraine-like sensitized state. When compared to the control antibody, the fremanezumab injection was followed by reduced basal and capsaicin-evoked CGRP release from day 3 up to 30 days. The difference was enhanced after 4 h of GTN application. The samples from the female rats showed a higher CGRP release compared to that of the males. The increases in meningeal blood flow induced by acrolein (100 µM) and capsaicin (100 nM) were reduced 13–20 days after the fremanezumab injection, and the direct vasoconstrictor effect of high capsaicin (10 µM) was intensified. In conclusion, fremanezumab lowers the CGRP release and lasts up to four weeks, thereby lowering the CGRP-dependent meningeal blood flow. The antibody may not only prevent the released CGRP from binding but may also influence the CGRP release stimulated by noxious agents relevant for the generation of migraine pain.

Role of Estrogens in Menstrual Migraine

Migraine is a major neurological disorder affecting one in nine adults worldwide with a significant impact on health care and socioeconomic systems. Migraine is more prevalent in women than in men, with 17% of all women meeting the diagnostic criteria for migraine. In women, the frequency of migraine attacks shows variations over the menstrual cycle and pregnancy, and the use of combined hormonal contraception (CHC) or hormone replacement therapy (HRT) can unveil or modify migraine disease. In the general population, 18–25% of female migraineurs display a menstrual association of their headache. Here we present an overview on the evidence supporting the role of reproductive hormones, in particular estrogens, in the pathophysiology of migraine. We also analyze the efficacy and safety of prescribing exogenous estrogens as a potential treatment for menstrual-related migraine. Finally, we point to controversial issues and future research areas in the field of reproductive hormones and migraine.

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

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

Expression of Selected microRNAs in Migraine: A New Class of Possible Biomarkers of Disease?

Preliminary but convergent findings suggest a role for microRNAs (miRNAs) in the generation and maintenance of chronic pain and migraine. Initial observations showed that serum levels of miR-382-5p and miR-34a-5p expression were increased in serum during the migraine attack, with miR-382-5p increasing in the interictal phase as well. By contrast, miR-30a-5p levels were lower in migraine patients compared to healthy controls. Of note, antimigraine treatments proved to be capable of influencing the expression of these miRNAs. Altogether, these observations suggest that miRNAs may represent migraine biomarkers, but several points are yet to be elucidated. A major concern is that these miRNAs are altered in a broad spectrum of painful and non-painful conditions, and thus it is not possible to consider them as truly “migraine-specific” biomarkers. We feel that these miRNAs may represent useful tools to uncover and define different phenotypes across the migraine spectrum with different treatment susceptibilities and clinical features, although further studies are needed to confirm our hypothesis. In this narrative review we provide an update and a critical analysis of available data on miRNAs and migraines in order to propose possible interpretations. Our main objective is to stimulate research in an area that holds promise when it comes to providing reliable biomarkers for theoretical and practical scientific advances.