Sex and Gender Considerations in Episodic Migraine

Sex Differences in the Expression of Central Sensitization Symptoms in Migraine: An Observational Study

Background: Migraine is the fourth most common cause of disability in women and the eighth most common cause in men. Central sensitization phenomena predispose to chronic migraine and are generally more pronounced in women. Objective: The aim of this retrospective observational study was to look for sex differences in a population of migraine subjects attending a tertiary headache center, focusing on symptoms of central sensitization such as allodynia and pericranial tenderness. Methods: This study is based on data collected at a tertiary headache center between January 1, 2018, and December 31, 2022. The clinical interview included the main features of migraine, allodynia, a disability questionnaire, the pericranial tenderness score, and anxiety and depression scales. Results: We selected a total of 1,087 migraine subjects (233 men). Osmophobia predominated in women, as did nausea. Disability scores, headache intensity, allodynia, anxiety, and depression predominated in women, without menopausal age playing a role. The frequency of symptomatic medication use was similar in both sexes. Allodynia score was the largest discriminating factor between women and men. Conclusions: Women with migraine are more likely than men to report acute allodynia, nausea, and osmophobia and are also more likely to be anxious, depressed, and disabled. These features appear to be independent of fertile age and are probably related to sex-specific genetic characteristics. These symptoms represent a tendency toward sensory hypersensitivity and central sensitization that should be carefully assessed in both women and men with migraine with a view to possibly predicting chronic development.

Animal Models of Chronic Migraine: From the Bench to Therapy

PURPOSE OF REVIEW

Chronic migraine is a disabling progressive disorder without effective management approaches. Animal models have been developed and used in chronic migraine research. However, there are several problems with existing models. Therefore, we aimed to summarize and analyze existing animal models to facilitate translation from basic to clinical.

RECENT FINDINGS

The most commonly used models are the inflammatory soup induction model and the nitric oxide donor induction model. In addition, KATP openers have also been used in model induction. Based on the above models, some molecular targets have been identified, such as glutamate receptors. However, each model has its shortcomings and characteristics, and there are still some common problems that need to be solved, such as spontaneous headache, evaluation criteria after model establishment, and identification methods. In this review, we summarized and highlighted the advantages and limitations of the currently commonly used animal models of chronic migraine with a special focus on drug discovery and current therapeutic strategies, and discussed the directions that can be worked on in the future.

Global, regional, and national burden and trends of migraine among women of childbearing age from 1990 to 2021: insights from the Global Burden of Disease Study 2021

BACKGROUND

Migraine, a neurological disorder with a significant female predilection, is the leading cause of disability-adjusted life years (DALYs) in women of childbearing age (WCBA). There is currently a lack of comprehensive literature analysis on the overall global burden and changing trends of migraines in WCBA.

METHODS

This study extracted three main indicators, including prevalence, incidence, and DALYs, related to migraine in WCBA from the Global Burden of Disease(GBD) database from 1990 to 2021. Our study presented point estimates with 95% uncertainty intervals (UIs). It evaluated the changing trends in the burden of migraine in WCBA using the estimated annual percentage change (EAPC) and percentage change.

RESULTS

In 2021, the global prevalence, incidence, and DALYs cases of migraine among WCBA were 493.94 million, 33.33 million, and 18.25 million, respectively, with percentage changes of 48%, 43%, and 47% compared to 1990. Over the past 32 years, global prevalence rates and DALYs rates globally have increased, with an EAPC of 0.03 (95% UI: 0.02 to 0.05) and 0.04 (95% UI: 0.03 to 0.05), while incidence rates have decreased with an EAPC of -0.07 (95% UI: -0.08 to -0.05). Among the 5 Socio-Demographic Index (SDI) regions, in 2021, the middle SDI region recorded the highest cases of prevalence, incidence, and DALYs of migraine among WCBA, estimated at 157.1 million, 10.56 million, and 5.81 million, respectively, approximately one-third of the global total. In terms of age, in 2021, the global incidence cases for the age group 15-19 years were 5942.5 thousand, with an incidence rate per 100,000 population of 1957.02, the highest among all age groups. The total number of migraine cases and incidence rate among WCBA show an increasing trend with age, particularly in the 45-49 age group.

CONCLUSIONS

Overall, the burden of migraine among WCBA has significantly increased globally over the past 32 years, particularly within the middle SDI and the 45-49 age group. Research findings emphasize the importance of customized interventions aimed at addressing the issue of migraines in WCBA, thus contributing to the attainment of Sustainable Development Goal 3 set by the World Health Organization.

Neurological care for LGBT+ people

Sexual and gender minority (LGBT+) people face unique health disparities that must be considered by health-care providers to ensure equitable and inclusive care. Although traditionally LGBT+ health has not been integrated into neurology training, sexual orientation and gender identity have direct relevance to neurological health, driven by both systemic and interpersonal factors. In this Review, we summarize the evidence for associations between sexual orientation and gender identity with the prevalence and outcomes of various neurological conditions, including neurodegenerative diseases, epilepsy, stroke and neurodevelopmental disorders, among others. We describe important clinical considerations pertaining to LGBT+ people and recommend language and practices to promote inclusive care, as well as highlight gaps in need of further research and possible strategies to minimize these, including systematic collection of sexual orientation and gender identity and use of inclusive language.

Female-selective mechanisms promoting migraine

Sexual dimorphism has been revealed for many neurological disorders including chronic pain. Prelicinal studies and post-mortem analyses from male and female human donors reveal sexual dimorphism of nociceptors at transcript, protein and functional levels suggesting different mechanisms that may promote pain in men and women. Migraine is a common female-prevalent neurological disorder that is characterized by painful and debilitating headache. Prolactin is a neurohormone that circulates at higher levels in females and that has been implicated clinically in migraine. Prolactin sensitizes sensory neurons from female mice, non-human primates and humans revealing a female-selective pain mechanism that is conserved evolutionarily and likely translationally relevant. Prolactin produces female-selective migraine-like pain behaviors in rodents and enhances the release of calcitonin gene-related peptide (CGRP), a neurotransmitter that is causal in promoting migraine in many patients. CGRP, like prolactin, produces female-selective migraine-like pain behaviors. Consistent with these observations, publicly available clinical data indicate that small molecule CGRP-receptor antagonists are preferentially effective in treatment of acute migraine therapy in women. Collectively, these observations support the conclusion of qualitative sex differences promoting migraine pain providing the opportunity to tailor therapies based on patient sex for improved outcomes. Additionally, patient sex should be considered in design of clinical trials for migraine as well as for pain and reassessment of past trials may be warranted.

The prevalence and demographic associations of headache in the adult population of Benin: a cross-sectional population-based study

BACKGROUND

The Global Burden of Disease (GBD) study is increasingly well informed with regard to headache disorders, but sub-Saharan Africa (SSA) remains one of the large regions of the world with limited data directly derived from population-based studies. The Global Campaign against Headache has conducted three studies in this region: Ethiopia in the east, Zambia in the south and Cameroon in Central SSA. Here we report a similar study in Benin, the first from West SSA.

METHODS

We used the same methods and questionnaire, applying cluster-randomized sampling in three regions of the country, randomly selecting households in each region, visiting these unannounced and randomly selecting one adult member (aged 18-65 years) of each household. The HARDSHIP structured questionnaire, translated into Central African French, was administered face-to-face by trained interviewers. Demographic enquiry was followed by diagnostic questions based on ICHD-3 criteria.

RESULTS

From 2,550 households with eligible members, we recruited 2,400 participants (participating proportion 94.1%). Headache ever was reported by almost all (95.2%), this being the lifetime prevalence. Headache in the last year was reported by 74.9%. Age-, gender- and habitation-adjusted estimates of 1-year prevalence were 72.9% for all headache, 21.2% for migraine (including definite and probable), 43.1% for TTH (also including definite and probable), 4.5% for probable medication-overuse (pMOH) and 3.1% for other headache on ≥ 15 days/month. One-day (point) prevalence of headache was 14.8% according to reported headache on the day preceding interview.

CONCLUSIONS

Overall, these findings are evidence that headache disorders are very common in Benin, a low-income country. The prevalence of pMOH, well above the estimated global mean of 1-2%, is evidence that poverty is not a bar to medication overuse. The findings are very much the same as those in a similar study in its near neighbour, Cameroon. With regard to migraine, they are reasonably in accord with two of three earlier studies in selected Beninese populations, which did not take account of probable migraine. This study adds to the hitherto limited knowledge of headache in SSA.

Neurological Health in Sexual and Gender Minority Individuals

Despite representing a significant proportion of the U.S. population, there is a paucity of population-based research on the health status and health needs of sexual and gender minority (SGM) individuals in neurology. Compared with heterosexual peers, some SGM populations have a higher burden of chronic health conditions. In parallel, SGM individuals are more likely to experience stigma and discrimination producing psychological distress, which may contribute to and be compounded by reduced health care access and utilization. In this narrative review, we summarize the existing literature on common neurological health conditions such as stroke, headache, epilepsy, movement disorders, and traumatic brain injury through the lens of intersection of SGM identity. Special focus is attuned to social determinants of health and gender-affirming hormonal therapy. Given the limitations in the available literature, there is an urgent unmet need for datasets that include sexual orientation and gender identity information, as well as funding for research that will characterize the prevalence of neurological conditions, unique risk factors, and health outcomes in SGM populations. In the health care community, providers should address deficiencies in their professional training and integrate inclusive language into their clinical skillset to build trust with SGM patients. There is an opportunity in neurology to proactively engage SGM communities, collaborate to remove barriers to care, promote resilience, and develop targeted interventions to ensure high-quality, culturally competent care for SGM populations to improve neurological health for all.

[Gender-specific results of the Dresden children and adolescents headache program DreKiP]

BACKGROUND

Girls and women are more frequently affected by headache than boys and men. The influence of gender on the effectiveness of headache therapies has so far been hardly investigated. We examined gender differences in the outpatient multimodal Dresden Child and Adolescent Headache Program DreKiP.

METHODS

We treated 140 patients with primary headache in a 15-hour structured group program. At baseline (T0) and six (T1) and twelve months (T2) after the end of the program, data on headache-related limitation of daily activities (PedMIDAS) as well as headache frequency, intensity, and pain-related disability (P-PDI) were collected. Retrospectively, these data were analyzed separately for girls and boys.

RESULTS

For 91 patients (9-19 years, median = 15; 71.4 % female) data were available for at least two measurement time points. Girls showed significantly higher headache frequency than boys at all time points (median headache days/last three months at T0: ♀ 43, ♂ 20; T1: ♀ 32, ♂ 12; T2: ♀ 28, ♂ 9) as well as numerically higher headache-related limitation of daily life. There were significant effects over time with a decrease in headache frequency (F (2.88) = 5.862; p = 0.004) and improvement in daily functioning (F (2.92) = 5.340; p = 0.006). There was no gender-specific treatment response.

DISCUSSION

The DreKiP therapy shows effects in girls and boys with primary headache. Higher headache frequencies and everyday life restrictions in girls may have hormonal but also psychosocial causes and should be addressed in educational measures.

Evaluation of outcomes of calcitonin gene-related peptide (CGRP)-targeting therapies for acute and preventive migraine treatment based on patient sex

BACKGROUND

Women show increased prevalence and severity of migraine compared to men. Whether small molecule calcitonin gene-related peptide receptor (CGRP-R) antagonists (i.e., gepants) and monoclonal antibodies targeting either the CGRP-R or the CGRP peptide might show sexually dimorphic outcomes for acute and preventive therapy has not been established.

METHODS

We conducted a subpopulation analysis of available published data from FDA reviews to evaluate potential sex differences in the response rates of ubrogepant, rimegepant and zavegepant for acute migraine therapy. Available data from FDA reviews of erenumab, fremanezumab, galcanezumab and eptinezumab, approved CGRP-R and CGRP monoclonal antibodies and of atogepant were examined for prevention outcomes based on patient sex. Preventive outcomes were analyzed separately for patients with episodic migraine and chronic migraine.

RESULTS

In women, the three approved gepants produced statistically significant drug effects regardless of dose tested on the FDA mandated co-primary endpoints, the proportion of patients achieving two-hour pain-freedom and the proportion of patients free of their most bothersome symptom at two hours post-dose. In women, the average placebo-subtracted two-hour pain-freedom proportion was 9.5% (CI: 7.4 to 11.6) and the average numbers needed to treat was 11. The free from most bothersome symptom at two hours outcomes were also significant in women. The gepant drugs did not reach statistically significant effects on the two-hour pain-freedom endpoint in the men, with an average drug effect of 2.8% (CI: -2.5 to 8.2) and an average number needed to treat of 36. For freedom from most bothersome symptom at two hours post-dose endpoint, differences were not significant in male patients. The treatment effect in each of the gepant studies was always numerically greater in women than in men. In evaluation of prevention outcomes with the antibodies or atogepant using the change from the specified primary endpoint (e.g., monthly migraine days), the observed treatment effect for episodic migraine patients almost always favored drug over placebo in both women and men. For chronic migraine patients the treatment effects of antibodies were similar in men and women and always favored the drug treated group.Conclusion/Interpretation: Small molecule CGRP-R antagonists are effective in acute migraine therapy in women but available data do not demonstrate effectiveness in men. CGRP-targeting therapies are effective for migraine prevention in both male and female episodic migraine patients but possible sex differences remain uncertain. In male and female chronic migraine patients, CGRP/CGRP-R antibodies were similarly effective. The data highlight possible differential effects of CGRP targeted therapies in different patient populations and the need for increased understanding of CGRP neurobiology in men and women.

Assessment of Preferences in Taking Painkillers among Students of Medicine, Dentistry, and Pharmacy: A Pilot Study

Students of pharmacy, medicine, and dentistry are important for shaping drug policy. The aim of this study is to assess and compare students preferences in taking painkillers. The study group consists of 382 students of pharmacy (28.8%), medicine (40.0%), and dentistry (30.1%). An anonymous questionnaire consisting of 17 questions was prepared using the Google Forms platform and distributed through social media. Ibuprofen was the most frequently preferred, regardless of the study major (57.8%). Pharmacy students expressed the least concern about the possible side effects of analgesics (17.5%). The fast onset of painkillers was more important for dental students (59.1%) and pharmacy students (44.7%), compared to medical students (39.22%). Medicine and pharmacy students indicated their studies to be their main source of information about painkillers compared to dentistry students (p = 0.001). There are no differences in pain severity regarding which analgesics are used among student groups (p = 0.547). Dental students experienced odontogenic pain less frequently (57.3%) than medical (79.7%) and pharmacy students (79.8%), (p = 0.000). Ketoprofen was the most frequently chosen prescription painkiller for odontogenic pain in all groups (49.4%). Gastrointestinal complaints were the most often reported side effects, regardless of the study major (87.1%). Choice of studies, gender, and year of study were the most important determinants of the choice of painkillers.

Trends in migraine incidence among women of childbearing age from 1990 to 2019 and the prediction for 2030: an analysis of national data in China

BACKGROUND

Migraine is a primary headache, which has been producing heavy disease burden globally. There is no data on the incidence of migraine among women of childbearing age worldwide, including China. This study aimed to investigate the time trend in incidence rate of migraine among women of childbearing age in China from 1999 to 2019, and to make a prediction for 2030.

METHODS

Data on migraine incidence and population among women of childbearing age in China were derived from the Global Burden of Diseases Study 2019. Crude and age-standardized incidence rates of migraine (CIR, ASIR) were presented. The trend in migraine during 1990-2019 was examined using annual percent change and average annual percent change based on Joinpoint regression models. Age-period-cohort model was introduced to estimate the independent effect of age, period and cohort on migraine incidence rate among participants over the three decades. Bayesian age-period-cohort analysis was conducted to predict migraine incidence rate for 2030 among women of childbearing age in China.

RESULTS

For women of childbearing age in China, the case number, CIR and ASIR of migraine kept rising, with a cumulative percentage increase of 10.87%, 2.01% and 5.65%, respectively, from 1990 to 2019. An annual percent increase of 0.18% in the ASIR was observed over the three decades. As for the age, period and cohort effects, the adjusted cohort-specific relative risks constantly increased from 0.91 (95% CI: 0.90, 0.93) in the 1940-1949 cohort to 1.04 (95% CI: 1.03, 1.05) in the 1995-2004 cohort, while the period-specific relative risks initially declined from 1.00 (95% CI: 0.99, 1.00) in 1990-1994 cohort to 0.99 (95% CI: 0.98, 0.99) in 1995-1999 cohort, and then increased to 1.04 (95% CI: 1.03, 1.04) in 2015-2019 cohort. Moreover, the age-specific relative risks of migraine followed a bimodal pattern with peaks at the age-group of 25-29 years (CIR = 1718.27/100000) and 35-39 years (CIR = 1635.18/100000). Projection modeling showed that the CIR and ASIR of migraine will continue to significantly increase from 2020 to 2030.

CONCLUSION

Migraine incidence remained an increasing trend from 1990 to 2019 and is projected to continually increase till 2030 among women of childbearing age in China. This study has important public health implication for population-level migraine prevention in China. Precision intervention strategies and approaches shall be considered in campaigns initiated for migraine prevention among Chinese women of childbearing age.

Headache disorders and relevant sex and socioeconomic patterns in adolescents and young adults across 204 countries and territories: an updated global analysis

BACKGROUND

Primary headache disorders are a group of highly prevalent and disabling neurological diseases that mainly consist of migraine and tension-type headache (TTH). A previous study showed that the burden of headaches peaked at a working age that ranged from 15 to 49, particularly among females, affecting their productivity and severely damaging their social interactions.

METHODS

The latest dataset was retrieved from the Global Burden of Disease (GBD) Study 2019. Three indicators, including prevalence, incidence, and years lived with disability (YLDs), were adopted for evaluation. The overall and specific headache burdens were fully compared and analysed at global, regional, and national levels. The ratio of female YLD rates to male YLD rates due to headaches was calculated to estimate the sex pattern. Finally, we utilized the two-tailed Spearman test to explore the potential association between socioeconomic background and headaches among young people.

RESULTS

Globally, for overall headache disorders, a total of 2,049,979,883 prevalent cases (95% uncertainty interval (UI): 1,864,148,110 to 2,239,388,034), 601,229,802 incident cases (95% UI: 530,329,914 to 681,007,934), and 38,355,993 YLDs (95% UI: 7,259,286 to 83,634,503) were observed for those aged 10 to 54 in 2019. Sex differences were widely found for all headache types among adolescents and young adults, especially migraine. However, the most interesting finding was that the associations we tested between the socioeconomic environment and young headache patients were positive, regardless of region or specific country or territory.

CONCLUSIONS

Overall, the global burden of headaches in adolescents and young adults largely increased from 1990 to 2019. Although slight declines were observed in sex differences, they remained significant and challenging. The positive correlations between headache and socioeconomic background among young people were relatively inconsistent with previous investigations, and several related hypotheses were proposed for explanation. Interdisciplinary actions involving education, policy- and law-making, and basic medical practice are desperately needed to further fight against the headache burden, promote gender equality in headache care, and eliminate the stigmatization of headache patients in student and working groups.

Medication Overuse Headache: an Updated Review and Clinical Recommendations on Management

OVERVIEW

Medication overuse headache (MOH) is highly prevalent among individuals with primary headache disorders.

PURPOSE OF REVIEW

(1) Provide an update on epidemiology, risk factors, and treatment strategies of MOH and (2) provide recommendations on the management of MOH.

RECENT FINDINGS

The prevalence of MOH ranges from 0.5 to 7.2%. Risk factors for MOH include female sex, lower socioeconomic status, some psychiatric conditions, and substance use disorders, among others. Recent large clinical trials support preventative therapy as an integral component of MOH management. Emerging clinical trial evidence supports anti-CGRP mAbs as effective preventative treatments among individuals with migraine and MOH. Among the large clinical trials, candesartan, topiramate, amitriptyline, and onabotulinumtoxinA were the most used preventative therapies, providing further support for these agents. MOH management requires a multifaceted and patient-centered approach that involves patient education, behavioral interventions, withdrawal of the overused medication, and initiation of preventative medication.

Endogenous Inflammatory Mediators Produced by Injury Activate TRPV1 and TRPA1 Nociceptors to Induce Sexually Dimorphic Cold Pain That Is Dependent on TRPM8 and GFRα3

The detection of environmental temperatures is critical for survival, yet inappropriate responses to thermal stimuli can have a negative impact on overall health. The physiological effect of cold is distinct among somatosensory modalities in that it is soothing and analgesic, but also agonizing in the context of tissue damage. Inflammatory mediators produced during injury activate nociceptors to release neuropeptides, such as calcitonin gene-related peptide (CGRP) and substance P, inducing neurogenic inflammation, which further exasperates pain. Many inflammatory mediators induce sensitization to heat and mechanical stimuli but, conversely, inhibit cold responsiveness, and the identity of molecules inducing cold pain peripherally is enigmatic, as are the cellular and molecular mechanisms altering cold sensitivity. Here, we asked whether inflammatory mediators that induce neurogenic inflammation via the nociceptive ion channels TRPV1 (vanilloid subfamily of transient receptor potential channel) and TRPA1 (transient receptor potential ankyrin 1) lead to cold pain in mice. Specifically, we tested cold sensitivity in mice after intraplantar injection of lysophosphatidic acid or 4-hydroxy-2-nonenal, finding that each induces cold pain that is dependent on the cold-gated channel transient receptor potential melastatin 8 (TRPM8). Inhibition of CGRP, substance P, or toll-like receptor 4 (TLR4) signaling attenuates this phenotype, and each neuropeptide produces TRPM8-dependent cold pain directly. Further, the inhibition of CGRP or TLR4 signaling alleviates cold allodynia differentially by sex. Last, cold pain induced by both inflammatory mediators and neuropeptides requires TRPM8, as well as the neurotrophin artemin and its receptor GDNF receptor α3 (GFRα3). These results are consistent with artemin-induced cold allodynia requiring TRPM8, demonstrating that neurogenic inflammation alters cold sensitivity via localized artemin release that induces cold pain via GFRα3 and TRPM8.SIGNIFICANCE STATEMENT The cellular and molecular mechanisms that generate pain are complex with a diverse array of pain-producing molecules generated during injury that act to sensitize peripheral sensory neurons, thereby inducing pain. Here we identify a specific neuroinflammatory pathway involving the ion channel TRPM8 (transient receptor potential cation channel subfamily M member 8) and the neurotrophin receptor GFRα3 (GDNF receptor α3) that leads to cold pain, providing select targets for potential therapies for this pain modality.

Disease burden of migraine and tension-type headache in non-high-income East and Southeast Asia from 1990 to 2019

BACKGROUND

The world faces severe challenges from migraine and tension-type headache (TTH), which cause grave disability to patients and place a heavy burden on their caregivers. However, headaches in specific individual regions have rarely been investigated. Therefore, we aimed to fully analyse and describe the current status and changing trends in migraine and TTH in non-high-income East and Southeast Asia to provide more detailed real-world information for policy-making.

METHODS

The migraine and TTH data used for analysis were all extracted from the Global Burden of Disease (GBD) database. We adopted three major indicators of disease burden, including prevalence, incidence, and years lived with disability (YLD), and two major metrics, including the absolute number and the age-standardized rate, in our present study for further evaluation by age and sex. The results are presented in the form of mean values and 95% uncertainty intervals (UIs). In addition, the differences between non-high-income East and Southeast Asia and other regions, as well as the potential associations between headache burden and socioeconomic background, were explored.

RESULTS

In 2019, approximately 195,702,169 migraine patients and 291,924,564 TTH patients lived in non-high-income East Asia, and 113,401,792 migraine patients and 179,938,449 TTH patients lived in non-high-income Southeast Asia. In terms of specific countries and regions, the highest age-standardized YLD rate (ASYR) of migraine was in Thailand [645 (95% UI: 64 to 1,554)]. The highest ASYR of TTH was in Indonesia [54 (95% UI: 15 to 197)]. Furthermore, people between the ages of 40 and 44, especially females, were identified as the main population that suffered from migraine and TTH. Unfortunately, we did not observe a significant association between headache burden and socioeconomic background.

CONCLUSIONS

To date, the threats from migraine and TTH in non-high-income East and Southeast Asia are still serious and ongoing, leading to prominently negative impacts on the daily life and work of local residents. Therefore, full attention and sound guidelines are urgently needed to obtain greater advantages in fighting against the burden of headache disorders in the future.

Endogenous inflammatory mediators produced by injury activate TRPV1 and TRPA1 nociceptors to induce sexually dimorphic cold pain that is dependent on TRPM8 and GFRα3

The detection of environmental temperatures is critical for survival, yet inappropriate responses to thermal stimuli can have a negative impact on overall health. The physiological effect of cold is distinct among somatosensory modalities in that it is soothing and analgesic, but also agonizing in the context of tissue damage. Inflammatory mediators produced during injury activate nociceptors to release neuropeptides, such as CGRP and substance P, inducing neurogenic inflammation which further exasperates pain. Many inflammatory mediators induce sensitization to heat and mechanical stimuli but, conversely, inhibit cold responsiveness, and the identity of molecules inducing cold pain peripherally is enigmatic, as are the cellular and molecular mechanisms altering cold sensitivity. Here, we asked if inflammatory mediators that induce neurogenic inflammation via the nociceptive ion channels TRPV1 and TRPA1 lead to cold pain in mice. Specifically, we tested cold sensitivity in mice after intraplantar injection of lysophosphatidic acid (LPA) or 4-hydroxy-2-nonenal (4HNE), finding each induces cold pain that is dependent on the cold-gated channel TRPM8. Inhibition of either CGRP, substance P, or toll-like receptor 4 (TLR4) signaling attenuates this phenotype, and each neuropeptide produces TRPM8-dependent cold pain directly. Further, the inhibition of CGRP or TLR4 signaling alleviates cold allodynia differentially by sex. Lastly, we find that cold pain induced by inflammatory mediators and neuropeptides requires the neurotrophin artemin and its receptor GFRα3. These results demonstrate that tissue damage alters cold sensitivity via neurogenic inflammation, likely leading to localized artemin release that induces cold pain via GFRα3 and TRPM8.

Significance Statement

The cellular and molecular mechanisms that generate pain are complex with a diverse array of pain-producing molecules generated during injury that act to sensitize peripheral sensory neurons, thereby inducing pain. Here we identify a specific neuroinflammatory pathway involving the ion channel TRPM8 and the neurotrophin receptor GFRα3 that leads to cold pain, providing select targets for potential therapies for this pain modality.