Citations

Abstract Post-traumatic headache (PTH) is the most common consequence of mild traumatic brain injury (mTBI) and often resembles migraine. In 20% to 30% of migraine patients, headaches are preceded by aura, transient visual or sensory disturbances, which are caused by cortical spreading depression (CSD) that can induce headache pain. However, whether mTBI promotes the development of aura and CSD and their possible contributions to PTH remains unclear. We examined the incidence of new-onset aura in individuals with PTH who had no history of aura. Thirty-two percent (35/108) developed new aura symptoms within 60 days of injury, suggesting that mTBI can sensitize the cortex to the induction of CSD. To test this, we combined electrophysiology, neuroimaging, and behavioral assays in a mouse model of mTBI-induced PTH. After closed-head mTBI, injured mice exhibited a 160% increase in CSD induction probability (ie, lowered threshold) and became sensitized to CSD induction by brief exposure to stress, a common headache trigger. When evoked optogenetically, CSD produced prolonged periorbital and hind paw allodynia, consistent with headache-like pain. Subcutaneous onabotulinumtoxinA administered to the scalp after mTBI did not alter CSD susceptibility but completely abolished optogenetic CSD-induced allodynia. These findings suggest that mTBI elicits sensitization to CSD induction and promotes the emergence of aura in humans, likely contributing to PTH. It is important that, even after mTBI-induced sensitization, onabotulinumtoxinA decoupled CSD from pain behaviors, suggesting efficacy in treating PTH associated with aura.

Abstract Migraine attacks can be provoked in people with underlying primary headache disorders by multiple peripheral mechanisms suggesting the possible convergence of trigeminal nociceptive inputs onto a common, unknown central circuit. As calcitonin gene-related peptide (CGRP) expressing cells in the parabrachial nucleus (PBN) have been implicated in nociplastic pains, we hypothesized that (a) PBN CGRP-expressing neurons and their projections to the central amygdala (CeA) may be an essential central relay of multiple peripheral inputs promoting injury-free migraine headache and (b) this pathway may prioritize threat from activation of cranial afferents over other nociceptive inputs. Periorbital cutaneous allodynia (CA) was determined following supradural application of a cocktail of inflammatory mediators (IM), CGRP or pituitary adenylate cyclase-activating polypeptide (PACAP), or systemic administration of nitroglycerin (NTG) in CalcaCre or wild-type mice. Decreased rearing and photophobia were respectively evaluated as measures of ongoing headache and light-evoked migraine-like pain. Phosphorylation of extracellular signal-regulated kinases (pERK) was evaluated to assess regional neuronal activation. Compared with vehicle, supradural IM increased pERK in the trigeminal nucleus caudalis and PBN, but not in the paraventricular thalamus. Chemogenetic activation (Gq-DREADD) of PBN CGRP neurons elicited CA and photophobia while decreasing rearing. Lesioning of PBN neurons with ibotenic acid suppressed CA produced by supradural IM. Chemogenetic silencing (Gi-DREADD) or expression of tetanus toxin (TeNT) in PBN Calca neurons to prevent neurotransmitter release also inhibited CA elicited by supradural IM, CGRP, PACAP or systemic NTG. CRISPR/Cas9 editing of CeA receptor-associated membrane protein-1 (Ramp1) prevented IM-induced migraine-like symptoms revealing CGRP/CGRP-receptor activation from PBN→CeA projections. In contrast, PBN lesions, chemogenetic manipulation, and TeNT expression in PBN Calca cells and CeA Ramp1 CRISPR/Cas9 editing did not affect acute pain responses induced by hind paw IM injection, intraperitoneal acetic acid, or acute nociceptive behaviors from IM stimulation of the maxillary (V2) and mandibular (V3) branches of the trigeminal nerve. These data reveal a central pathway composed of PBN Calca neurons and CeA CGRP receptor signaling that is both sufficient to elicit migraine-like pain in naive mice and necessary to promote migraine-like pain following activation of the ophthalmic (V1) branch of the trigeminal nerve. Importantly, this pathway is essential for acute pain arising from V1 trigeminal, but dispensable for acute stimuli from other nociceptive afferents. The prioritization of V1 acute nociception suggests evolutionary importance for detecting threats to the head to promote survival through advantageous behaviors such as defensive coping observed in migraine.

Abstract Mild traumatic brain injury (mTBI) commonly induces transient acute (APTH) or persistent (PPTH) post-traumatic headache (PTH) that often resembles migraine. As orexin B sensitizes male but not female murine, nonhuman primate, and human dorsal root ganglion neurons and supradural orexin B/orexin receptor 2 (OX2R) signaling elicits migraine-like pain in naïve male, but not female, mice we explored possible sexually dimorphic contributions of orexin B/OX2R to PTH. In mice of both sexes, mTBI-induced transient cephalic allodynia, a surrogate measure of APTH. After APTH resolution, allodynia was reinstated by exposure to normally innocuous stress or by inhalational delivery of a subthreshold concentration of umbellulone, a TRPA1 agonist, suggesting the expression of PPTH. In contrast to these nonselective stimuli, subthreshold supradural orexin B induced PPTH only in male mTBI mice. Intranasal delivery of a CRISPR/Cas9 plasmid to edit trigeminal OX2R expression prevented APTH and development of PPTH selectively in male mTBI mice. Daily oral suvorexant, a dual orexin receptor antagonist (DORA), beginning immediately after mTBI, prevented APTH as well as PPTH. Critically, starting suvorexant treatment after resolution of APTH also prevented stress- or umbellulone-induced PPTH. EEG/EMG-defined sleep architecture or immobility-defined sleep was not disrupted in this mTBI model suggesting that suvorexant benefits are unlikely related to sleep modulation. Our findings reveal a male-specific mechanism of PTH maintained by orexin B/OX2R signaling and suggest that approved DORAs may be beneficial in treating APTH and preventing transition to PPTH in men. Importantly, DORAs may also be effective in men with established PPTH.

Abstract Background Post-traumatic headache (PTH) is a common acute and persistent symptom following mild traumatic brain injury (mTBI). Symptoms of cutaneous allodynia and presence of nociceptive sensitization might be associated with acute PTH and its persistence. The objectives of this study were to compare allodynia symptoms and cutaneous heat pain thresholds amongst males and females with acute PTH to healthy controls (HC) and determine if pain thresholds and allodynia symptoms are associated with PTH outcomes. Methods This prospective longitudinal study enrolled 139 adults with acute PTH attributed to mTBI as defined by the International Classification of Headache Disorders and 95 HC. All PTH participants completed a baseline research visit near PTH onset and a follow-up visit three to four months later. All PTH participants and a subset of HC completed the Allodynia Symptom Checklist (ASC-12) at each research visit. A different subset of the participants underwent quantitative sensory testing (QST) during baseline, 4-week, and 16-week research visits to quantify cutaneous heat pain thresholds at the forehead and forearms. Data from daily headache diaries were used to determine longitudinal PTH improvement versus non-improvement at three months. ASC-12 score and pain threshold comparisons were made between PTH and HC groups, PTH improved versus non-improved cohorts, and between PTH males and females. Results Participants with PTH had an average age of 42.6 years and 64.0% were female. HC had an average age of 40.0 years and 65.3% were female. At the first visit, PTH participant ASC-12 scores averaged 3.6 versus 0.1 amongst HC, p < 0.001. 44.8% of PTH participants had headache improvement at 3 months. ASC-12 scores were higher in the PTH non-improved versus improved group at baseline (4.0 versus 2.4, p = 0.038) and 3-month follow-up (3.4 versus 1.9, p = 0.012). ASC-12 scores were higher in females than males at baseline (4.7 versus 1.6, p < 0.001) and 3-months (3.9 versus 1.2, p < 0.001). Cutaneous heat pain thresholds at the forehead and forearm did not differ between any group. Conclusions PTH attributed to mTBI is associated with symptoms of cutaneous allodynia. Greater allodynia symptoms are present in females with PTH compared to males and may be associated with PTH non-improvement.

Background Headache is a common symptom following mild traumatic brain injury (mTBI). Post-traumatic headache (PTH), a secondary headache disorder that develops after mTBI, often persists for months or years. To identify potential recovery mechanisms and prognostic biomarkers, the present study investigated whether longitudinal changes in pain-induced brain activation differ between healthy controls (HC) and PTH participants showing headache improvement and those without improvement. Methods Thirty-three participants who met International Classification of Headache Disorders, 3rd edition, criteria for acute PTH within 59 days post-mTBI and 33 HC participants were included with no significant differences in demographics. All participants underwent functional magnetic resonance imaging scans at baseline, four weeks, and 16 weeks post-enrollment using a thermal stimulation paradigm with noxious and non-painful heat stimuli. ‘Painful vs. Non-Painful Heat’ contrasts were generated using SPM12. PTH improvement was assessed at three months post-enrollment via electronic headache diaries. Two-sample t -tests compared the brain activation between HC and PTH at baseline. Linear mixed-effects models examined longitudinal changes for HC, PTH improvement and non-improvement groups across visits. Generalized linear models compared these groups within visits. Results Baseline analysis revealed several regions with significantly higher activation in acute PTH compared to HC, including bilateral postcentral gyrus, right superior temporal gyrus, right middle temporal gyrus, left inferior parietal gyrus, right superior parietal gyrus, left ventral striatum, left olfactory cortex, left gyrus rectus, and left middle occipital gyrus. Over time, the PTH improvement group demonstrated progressive normalization across all identified brain regions, whereas the non-improvement group showed only partial normalization in left ventral striatum, left olfactory cortex, and left gyrus rectus. Sustained elevated activation in specific regions distinguished PTH participants without headache improvement from those with headache improvement, suggesting potential biomarkers for persistent PTH. Conclusions Our findings demonstrate significantly altered pain-induced brain activations in participants with acute PTH compared to HC. Longitudinal analysis revealed distinct recovery trajectories: progressive normalization in the improvement group versus persistent alterations in the non-improvement group. These neuroimaging patterns may serve as biomarkers for identifying individuals at risk for persistent PTH, with implications for early intervention and personalized treatment approaches.

Recent reports support the startling conclusion that peripheral nociceptors, the first link in pain transmission, are sexually dimorphic. The mechanisms promoting pain in men and women are therefore likely to be different, suggesting the need to consider patient sex as a factor in managing pain and painful conditions such as migraine. Many patients do not achieve sufficient benefit from available therapies and migraine therefore remains a major unmet medical need. The concept of sexual dimorphism in pain mechanism reveals previously unrecognized gaps in knowledge of migraine pathophysiology and in treatment outcomes. As migraine is highly female prevalent, our knowledge is based on studies conducted predominately in women. Data from these studies have rarely been analyzed and reported based on sex, limiting our interpretation of the occurrence, timing and severity of disease symptoms as well as possible differences in treatment efficacy in men. Inclusion of a higher proportion of men in both mechanistic investigations and clinical trials is therefore needed. Advancing our knowledge and improving therapeutic outcomes will require both preclinical and clinical investigations that address the contribution of sex in headache pain and other non-painful symptoms of migraine that impact the quality of life for patients. This viewpoint highlights the importance of considering sex as a variable in advancing our understanding of migraine pathophysiology and therapy. Consideration of patient sex could influence current clinical practice and the design of clinical studies.

Background Traumatic brain injury (TBI) commonly elicits acute (APTH) and/or persistent (PPTH) post-traumatic headache. Calcitonin gene related peptide (CGRP) has been implicated as a contributor to PTH pathophysiology. We explored the possibility of sexual dimorphism in the effects of CGRP receptor (CGRP-R) blockade in a preclinical model of PTH induced by a mild TBI (mTBI) in male or female mice. Methods Mice were lightly anesthetized and placed on a tissue paper stage prior to receiving a sham procedure or mTBI resulting from a closed-head weight drop injury. Behavioral responses to periorbital and hindpaw tactile (von Frey filaments) or thermal (hot plate) stimuli over the first 14 days post-mTBI were evaluated as measures of APTH. The PPTH phase was studied following the resolution of mTBI-induced APTH at days 14 and 28. PPTH was precipitated by exposure to bright lights (i.e., bright light stress, BLS). Olcegepant was delivered subcutaneously either repeatedly beginning 2 h after mTBI to produce a sustained block of CGRP-R signaling across the APTH phase, or as a single administration on days 14 or 28 post-mTBI to evaluate possible effects during the PPTH phase. Results mTBI, but not sham-procedure, produced periorbital and hindpaw tactile allodynia, as well as thermal hypersensitivity in mice of both sexes. APTH-related hypersensitivity was transient and resolved by day 14 post-injury. No sex differences were observed in the magnitude or duration of APTH-related pain behaviors. Sustained CGRP-R blockade was, however, significantly more effective in female than male mice in inhibiting pain behaviors in the APTH phase and in preventing the emergence of BLS-induced PPTH. CGRP-R blockade following the resolution of mTBI-induced APTH pain behaviors, on either day 14 or 28, minimally altered BLS-induced PPTH in either sex. Conclusions Sustained CGRP-R blockade starting soon after mTBI significantly inhibited APTH and prevented the expression of PPTH with greater analgesic effects in females compared to males. Delayed CGRP-R blockade beginning after resolution of APTH phase was minimally effective in preventing expression of PPTH in either sex. These data are consistent with previous observations that CGRP induces pain behaviors preferentially in females. Early and continuous CGRP blockade following mTBI may represent a viable treatment option for PTH treatment and the prevention of PTH persistence, especially in females.

Background Acute therapies targeting calcitonin gene-related peptide (CGRP) for episodic migraine (EM) demonstrate efficacy in women, but evidence of efficacy in men remains to be established. By contrast, CGRP targeting therapies for migraine prevention are effective in both men and women with frequent EM or chronic migraine (CM). Preclinical studies have shown that supradural application of CGRP preferentially produces migraine-like pain behaviors in female rodents. We hypothesized that, in male mice, increased frequency of migraine-like pain may sensitize to nociceptive effects of CGRP and this might be associated with altered expression of CGRP in trigeminal ganglion (TG) neurons and/or in their dural projections. Methods CM was modeled in male and female mice by repeated administration of nitroglycerin (NTG). Medication overuse headache (MOH), a form of CM, was modeled by repeated daily administration of sumatriptan. Following resolution of transient cutaneous allodynia (CA) elicited by NTG or sumatriptan, mice received a sex specific subthreshold dose of supradural CGRP that does not elicit CA in naïve male or female mice, and CA was evaluated. CGRP-positive cell bodies in the ophthalmic V1 region of the trigeminal ganglion (TGV1) and CGRP-positive nerve fibers innervating the dura mater were assessed. Results Supradural administration of 1 pg of CGRP produced migraine-like pain behaviors in female, but not male, mice; a ten-fold lower dose was established as subthreshold in naïve female mice. Repeated NTG or sumatriptan produced transient CA in both female and male mice that resolved within 8–11 days after treatment cessation. Following resolution of CA, previously subthreshold doses of CGRP elicited CA in CM and MOH models in mice of both sexes, with no effects observed in vehicle treated controls. A higher number of CGRP-positive neurons in the TGV1 was found in naïve female compared to male mice. The number of CGRP-positive TGV1 neurons was increased in both sexes following repeated NTG. Similar nerve fiber density was observed in the dura mater of male and female mice and no differences were detected following repeated NTG. Conclusions As previously reported, CGRP produced female-selective migraine-like pain behaviors in naïve mice. Consistent with behavioral effects, female mice demonstrated a higher number of CGRP-positive cells in the TGV1. These findings appear relevant to clinical observations of female efficacy of CGRP-receptor antagonists for acute treatment in EM patients. In models of CM or MOH that are characterized by increased frequency of migraine-like pain, previously subthreshold doses of supradural CGRP now elicited migraine-like nociceptive behaviors in mice of both sexes. The increased pain responses were accompanied by increased number CGRP positive TGV1 cells in the NTG model in both female and male mice. These data suggest that increased frequency of migraine promotes physiological changes including increased expression of TGV1 CGRP along with sensitization to CGRP-induced nociception in both males and females. Thus, as EM transforms to CM, CGRP-dependent mechanisms may become increasingly important, consistent with observations of efficacy of CGRP targeting therapies for migraine prevention in both men and women. Our results also suggest the possibility of enhanced efficacy of CGRP-receptor antagonists for the acute treatment of migraine in men as migraine frequency increases.

Background Women with endometriosis are more likely to have migraine. The mechanisms underlying this co-morbidity are unknown. Prolactin, a neurohormone secreted and released into circulation from the anterior pituitary, can sensitize sensory neurons from female, but not male, rodents, monkeys and human donors. Methods We used a syngeneic model of endometriosis to determine whether elevated prolactin levels can sensitize trigeminal ganglion neurons and increase vulnerability to migraine pain. Results Mice with endometriotic lesions showed increased serum prolactin levels and developed persistent abdominal, but not cephalic, allodynia. However, inhalation of a transient receptor potential ankyrin 1 agonist, umbellulone, a known environmental trigger of headache in some patients, elicited cephalic allodynia in mice with endometriosis but not sham controls, suggesting that endometriosis can promote sensitization of trigeminal neurons and migraine attacks. Endometriosis dysregulated the expression of prolactin receptor isoforms in trigeminal neurons and increased their excitability measured by in vitro patch clamp electrophysiology. Inhibition of pituitary prolactin following a 2-week treatment with a dopamine receptor agonist, cabergoline, prevented cephalic allodynia elicited by activation of trigeminal afferents with umbellulone. Cabergoline treatment also normalized the expression of prolactin receptor isoforms in trigeminal ganglia and the hyperexcitability of trigeminal neurons. Conclusions These data demonstrate that circulating prolactin in endometriosis promotes vulnerability to migraine through sensitization of trigeminal afferents. Clinically available dopamine receptor agonists or novel monoclonal antibodies targeting prolactin signaling may be effective for migraine prevention in women with endometriosis.

Abstract Protease activated receptor 2 (PAR2) is a G-protein coupled receptor expressed in meningeal neurons, fibroblasts and mast cells that may be targeted to treat migraine. MEDI0618, a fully humanized PAR2 monoclonal antibody, engineered to enhance FcRn-dependent recycling and currently in clinical development, was evaluated in human and rodent in vitro assays, in multiple murine in vivo migraine models and in a model of post-traumatic headache. MEDI0618 bound specifically and with high affinity to cells expressing human PAR2 (hPAR2) and prevented matriptase-induced increase in cytosolic calcium. Similarly, MEDI0618 prevented matriptase-induced calcium in primary fibroblasts and microvascular endothelial cells from human dura mater. MEDI0618 had no effect on hPAR1 receptors. Single-cell calcium imaging of acutely dissociated mouse trigeminal ganglion neurons confirmed expression and functionality of mouse PAR2. Studies in vivo used evoked cutaneous allodynia as a surrogate of headache-like pain and, in some experiments, rearing as a measure of non-evoked headache pain. MEDI0618 was administered subcutaneously to C57BL6/J female mice prior to induction of migraine-like pain with (i) systemic nitroglycerin or compound 48/80 (mast cell degranulator); or (ii) with supradural compound 48/80 or an inflammatory mediator (IM) cocktail. To assess possible efficacy against CGRP receptor (CGRP-R)-independent pain, MEDI0618 was also evaluated in the IM model in animals pretreated with systemic olcegepant (CGRP-R antagonist). Migraine-like pain was also induced by inhalational umbellulone, a TRPA1 agonist, in animals primed with restraint stress in the presence or absence of MEDI0618 as well as in a model of post-traumatic headache pain induced by a mild traumatic brain injury. MEDI0618 prevented cutaneous allodynia elicited by systemic nitroglycerin, compound 48/80 and from supradural compound 48/80 and IM. Systemic olcegepant completely blocked periorbital cutaneous allodynia induced by supradural CGRP but failed to reduce IM-induced cutaneous allodynia. In contrast, MEDI0618 fully prevented IM-induced cutaneous allodynia, regardless of pretreatment with olcegepant. Umbellulone elicited cutaneous allodynia only in restraint stress-primed animals, which was prevented by MEDI0618. MEDI0618 prevented the decrease in rearing behaviour elicited by compound 48/80. However, MEDI0618 did not prevent mild traumatic brain injury-related post-traumatic headache measures. These data indicate that MEDI0618 is a potent and selective inhibitor of PAR2 that is effective in human and rodent in vitro cell systems. Further, blockade of PAR2 with MEDI0618 was effective in all preclinical migraine models studied but not in a model of post-traumatic headache. MEDI0618 may represent a novel therapy for migraine prevention with activity against CGRP-dependent and independent attacks.