Dietary grape seed polyphenols repress neuron and glia activation in trigeminal ganglion and trigeminal nucleus caudalis

Dietary supplementation with grape seed extract from Vitus vinifera prevents suppression of GABAergic protein expression in female Sprague Dawley trigeminal ganglion in a model of chronic temporomandibular joint disorder

OBJECTIVE

To investigate cellular changes in protein expression in the trigeminal ganglion in an established preclinical chronic model of temporomandibular joint disorder (TMD) in response to grape seed extract (GSE) supplementation based on its beneficial use in preclinical chronic orofacial pain models.

DESIGN

Three experimental conditions included female Sprague-Dawley rats as naïve controls, and animals subjected to neck muscle inflammation and prolonged jaw opening with and without daily supplementation of GSE in the drinking water prior to inflammation. Changes were evaluated in mechanical sensitivity to von Frey filaments and protein expression in the trigeminal ganglion of animals 14 days post jaw opening.

RESULTS

Calcitonin-gene related peptide and protein kinase A, proteins positively associated with peripheral sensitization and enhanced nociception, did not show elevated expression at day 14 in the model compared to naïve or GSE supplemented animals. However, neuronal levels of glutamate decarboxylase (GAD) 65/67, which are enzymes responsible for the synthesis of the inhibitory neurotransmitter GABA that functions to suppress neuronal excitability, were significantly decreased on day 14 post jaw opening. Similarly, a significant decrease in neuronal expression of the GABA receptor subunits GABAB1 and GABAB2, but not GABAA, was observed in the TMD model. Importantly, GSE prevented suppression of GAD 65/67 and GABAB subunits, maintaining levels similar to naïve animals.

CONCLUSION

Results from our study provide evidence of the downregulation of inhibitory GABAergic proteins in trigeminal ganglion neurons in a preclinical chronic TMD model and the benefits of GSE supplementation in preventing their suppression and maintaining normal levels.

Healthy eating index 2015 might be associated with migraine headaches: Results from a Case-Control study

Migraine headaches are the most prevalent disabling primary headaches, affecting individuals at an active age. Dietary interventions are considered low-cost and practical approaches to migraine prophylaxis. Hence, the present study aimed to assess the association between adherence to the Healthy Eating Index 2015 (HEI-2015) and migraine headaches. The present case-control study was conducted on 476 newly diagnosed adults with migraine headaches, based on the International Classification of Headache Disorders 3rd edition (ICHDIII criteria(, and 512 healthy controls. Participants' dietary intakes were collected using a validated, 168-item semi-quantitative food frequency questionnaire (FFQ). The association between HEI-2015 and migraine headaches was assessed using logistic regression models. Although the trend was not statistically significant, being in the 4th quantile of the HEI-2015 was associated with about 50% lower odds of migraine headaches in both primary (adjusted for age and gender) (odds ratios (OR): 0.51, 95% confidence intervals (CI): 0.33, 0.78) and fully adjusted models (additionally adjusted for body mass index (BMI) and total calories) (adjusted OR: 0.50, 95%CI: 0.32, 0.77). Intriguingly, the odds of migraine headaches were significantly higher in those in the last quantile of "Total Fruits," which is equal to more than 237 g per 1000 kcal (aOR: 2.96, 95%CI: 1.99, 4.41) and "Whole Fruits," which is equal to more than 233 g per 1000 kcal (aOR: 2.90, 95%CI: 1.94, 4.31). Similarly, higher intakes of "Dairy," which is equal to more than 138 g per 1000 kcal (aOR: 2.66, 95%CI: 1.71, 4.14), and "Total Protein Foods," which is equal to more than 259 g per 1000 kcal (aOR: 2.41, 95%CI: 1.58, 3.70), were associated with higher odds of migraine headaches. The current study revealed an indirect association between HEI-2015 and its components, including "Greens and Beans," "Whole Grains," "Refined Grains," and "Added Sugars" and lower odds of migraine headaches.

Benefit of Dietary Supplementation of Nutraceuticals as an Integrative Approach for Management of Migraine: Evidence From Preclinical and Clinical Studies

PURPOSE OF REVIEW

To provide information from preclinical and clinical studies on the biological activity and health benefits of dietary inclusion of nutraceuticals as a safe, effective, non-pharmacological approach for the treatment of migraine.

RECENT FINDINGS

There is emerging evidence of the therapeutic benefit of nutraceuticals to inhibit oxidative stress, suppress inflammation, and prevent changes in the normal gut microbiome, which are implicated in migraine pathology. Nutraceuticals can be enriched in polyphenols, which act as molecular scavengers to reduce the harmful effects of reactive oxygen species and phytosterols that suppress inflammation. Nutraceuticals also function to inhibit dysbiosis and to maintain the commensal intestinal bacteria that produce anti-inflammatory molecules including short-chain fatty acids that can act systemically to maintain a healthy nervous system. Dietary inclusion of nutraceuticals that exhibit antioxidant, anti-inflammatory, and anti-nociceptive properties and maintain the gut microbiota provides a complementary and integrative therapeutic strategy for migraine.

Suppression of the Excitability of Rat Nociceptive Secondary Sensory Neurons following Local Administration of the Phytochemical, (-)-Epigallocatechin-3-gallate

The phytochemical, polyphenolic compound, (-)-epigallocatechin-3-gallate (EGCG), is the main catechin found in green tea. Although a modulatory effect of EGCG on voltage-gated sodium and potassium channels has been reported in excitable tissues, the in vivo effect of EGCG on the excitability of nociceptive sensory neurons remains to be determined. Our aim was to investigate whether local administration of EGCG to rats attenuates the excitability of nociceptive spinal trigeminal nucleus caudalis (SpVc) neurons in response to mechanical stimulation in vivo. Extracellular single unit recordings were made from SpVc neurons in response to orofacial mechanical stimulation of anesthetized rats. The mean firing frequency of SpVc wide-dynamic range neurons following both non-noxious and noxious mechanical stimuli was significantly inhibited by EGCG in a dose-dependent and reversible manner. The mean magnitude of inhibition by EGCG on SpVc neuronal discharge frequency was similar to that of the local anesthetic, 1% lidocaine. Local injection of half-dose of lidocaine replaced the half-dose of EGCG. These results suggest that local injection of EGCG suppresses the excitability of nociceptive SpVc neurons, possibly via the inhibition of voltage-gated sodium channels and opening of voltage-gated potassium channels in the trigeminal ganglion. Therefore, administration of EGCG as a local anesthetic may provide relief from trigeminal nociceptive pain without side effects.

Nutrition and Calcitonin Gene Related Peptide (CGRP) in Migraine

Targeting calcitonin gene-related peptide (CGRP) and its receptor by antibodies and antagonists was a breakthrough in migraine prevention and treatment. However, not all migraine patients respond to CGRP-based therapy and a fraction of those who respond complain of aliments mainly in the gastrointestinal tract. In addition, CGRP and migraine are associated with obesity and metabolic diseases, including diabetes. Therefore, CGRP may play an important role in the functioning of the gut-brain-microflora axis. CGRP secretion may be modulated by dietary compounds associated with the disruption of calcium signaling and upregulation of mitogen-activated kinase phosphatases 1 and 3. CGRP may display anorexigenic properties through induction of anorexigenic neuropeptides, such as cholecystokinin and/or inhibit orexigenic neuropeptides, such as neuropeptide Y and melanin-concentrating hormone CH, resulting in the suppression of food intake, functionally coupled to the activation of the hypothalamic 3',5'-cyclic adenosine monophosphate. The anorexigenic action of CGRP observed in animal studies may reflect its general potential to control appetite/satiety or general food intake. Therefore, dietary nutrients may modulate CGRP, and CGRP may modulate their intake. Therefore, anti-CGRP therapy should consider this mutual dependence to increase the efficacy of the therapy and reduce its unwanted side effects. This narrative review presents information on molecular aspects of the interaction between dietary nutrients and CGRP and their reported and prospective use to improve anti-CGRP therapy in migraine.

Grape seed extract suppresses calcitonin gene-related peptide secretion and upregulates expression of GAD 65/67 and GABAB receptor in primary trigeminal ganglion cultures

The trigeminal ganglion is implicated in the underlying pathology of migraine and temporomandibular joint disorders (TMD), which are orofacial pain conditions involving peripheral and central sensitization. The neuropeptide calcitonin gene-related peptide (CGRP) is synthesized in some trigeminal ganglion neurons, and its release promotes inflammation, peripheral and central sensitization, and pain signaling. Recent studies in preclinical migraine and TMD models provide evidence that dietary supplementation with grape seed extract (GSE) inhibits trigeminal pain signaling. The goal of this study was to investigate the cellular mechanisms by which GSE modulates primary trigeminal ganglion cultures. The effect of GSE on CGRP secretion was determined by radioimmunoassay. To determine if GSE effects involved modulation of CGRP or the GABAergic system, expression of CGRP, GAD 65 and 67, GABAA receptor, and GABAB1 and GABAB2 receptor subunits were investigated by immunocytochemistry. GSE significantly inhibited basal CGRP secretion but did not alter neuronal CGRP expression. GAD 65 and 67 expression levels in neurons were significantly increased in response to GSE. While GSE did not cause a change in the neuronal expression of GABAA, GSE significantly increased GABAB1 expression in neurons, satellite glial cells, and Schwann cells. GABAB2 expression was significantly elevated in satellite glia and Schwann cells. These findings support the notion that GSE inhibition of basal CGRP secretion involves increased neuronal GAD 65 and 67 and GABAB receptor expression. GSE repression of CGRP release coupled with increased GABAB1 and GABAB2 glial cell expression would be neuroprotective by suppressing neuronal and glial excitability in the trigeminal ganglion.

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Grape seed extract inhibited basal CGRP release from cultured trigeminal neurons

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Neuronal expression of GAD 65/67 and GABAB1 was stimulated by grape seed extract

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Grape seed extract also increased GABAB1 in satellite glial cells and Schwann cells

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Glial expression of G protein-coupled GABAB2 was enhanced by grape seed extract

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Grape seed extract promotes neuroprotective cellular changes in trigeminal ganglion

Inhibition of Nociception in a Preclinical Episodic Migraine Model by Dietary Supplementation of Grape Seed Extract Involves Activation of Endocannabinoid Receptors

Migraine is associated with peripheral and central sensitization of the trigeminal system and dysfunction of descending pain modulation pathways. Recently, dietary inclusion of grape seed extract (GSE) was shown to inhibit mechanical nociception in a preclinical model of chronic temporomandibular joint disorder, a condition often comorbid with migraine, with the antinociceptive effect mediated, in part, by activation of 5-HT3/7 and GABAB receptors. This study further investigated the mechanisms by which GSE inhibits mechanical nociception in a preclinical model of episodic migraine. Hyperalgesic priming of female and male Sprague Dawley rats was induced by three consecutive daily two-hour episodes of restraint stress. Seven days after the final restraint stress, rats were exposed to pungent odors from an oil extract that contains the compound umbellulone, which stimulates CGRP release and induces migraine-like pain. Some animals received dietary supplementation of GSE in their drinking water beginning one week prior to restraint stress. Changes in mechanical sensitivity in the orofacial region and hindpaw were determined using von Frey filaments. To investigate the role of the endocannabinoid receptors in the effect of GSE, some animals were injected intracisternally with the CB1 antagonist AM 251 or the CB2 antagonist AM 630 prior to odor inhalation. Changes in CGRP expression in the spinal trigeminal nucleus (STN) in response to stress, odor and GSE supplementation were studied using immunohistochemistry. Exposure of stress-primed animals to the odor caused a significant increase in the average number of withdrawal responses to mechanical stimulation in both the orofacial region and hindpaw, and the effect was significantly suppressed by daily supplementation with GSE. The anti-nociceptive effect of GSE was inhibited by intracisternal administration of antagonists of CB1 and CB2 receptors. GSE supplementation inhibited odor-mediated stimulation of CGRP expression in the STN in sensitized animals. These results demonstrate that GSE supplementation inhibits trigeminal pain signaling in an injury-free model of migraine-like pain via activation of endocannabinoid receptors and repression of CGRP expression centrally. Hence, we propose that GSE may be beneficial as a complementary migraine therapeutic.

5-HT3/7 and GABAB receptors mediate inhibition of trigeminal nociception by dietary supplementation of grape seed extract

Background: Temporomandibular joint disorder is a prevalent orofacial pain condition involving sensitization and activation of trigeminal nociceptive neurons. Dietary supplementation with a proanthocyanin-enriched grape seed extract (GSE) was found to inhibit trigeminal nociception in a chronic TMD model. In this study, the cellular mechanisms by which GSE inhibits sustained trigeminal nociception in male and female Sprague Dawley rats were investigated.Methods: Some animals were supplemented with 0.5% GSE dissolved in their water one week prior to neck muscle inflammation induced by injection of complete Freund's adjuvant into the trapezius. To investigate the mechanism of GSE, some animals were injected intracisternally with antagonists of 5-HT3, 5-HT7, GABAA, or GABAB, receptor prior to jaw opening.Results: In males and females, trapezius inflammation prior to jaw opening resulted in sustained mechanical hypersensitivity of trigeminal nociceptors that was significantly inhibited by GSE. Further, GSE beginning 14 days post jaw opening also inhibited trigeminal nociception. Intracisternal injection of antagonists of the 5-HT3/7 and GABAB, but not GABAA receptors reduced the anti-nocifensive effect of GSE in both sexes. Neuronal expression of GABAB protein and mRNA in the spinal cord and trigeminal ganglion were detected.Conclusions: The inhibitory effect of GSE is mediated via activation of 5-HT3/7 receptors and GABAB to enhance central descending inhibitory pain pathways and suppress ongoing trigeminal nociception. Further, our findings support the use of GSE as a dietary supplement in the management of pain associated with TMD and other orofacial pain conditions involving central sensitization and dysfunction of descending pain modulation.

Therapeutic Agents for the Treatment of Temporomandibular Joint Disorders: Progress and Perspective

Temporomandibular joint disorders (TMD) are a common health condition caused by the structural or functional disorders of masticatory muscles and the temporomandibular joint (TMJ). Abnormal mandibular movement in TMD patients may cause pain, chronic inflammation, and other discomfort, which could be relieved by a variety of drugs through various delivery systems. In this study, we summarized commonly used therapeutic agents in the management of TMD as well as novel bioactive molecules in preclinical stage and clinical trials. The emerging therapy strategies such as novel intra-TMJ delivery systems and implants based on tissue engineering are also discussed. This comprehensive review will strengthen our understanding of pharmacological approaches for TMD therapy.

A Bidirectional View of Migraine and Diet Relationship

Migraine is a common headache with a large negative impact on health. Several endogenous and exogenous factors can influence the severity and frequency of migraine, for example, lifestyle factors including dietary factors. Consequently, lifestyle modifications and dietary considerations have been reported beneficial to moderate clinical features of migraine. Much effort has been invested in determining the lifestyle factors (eg, stress, exercise, sleep, and diet) that trigger migraine to develop recommendations and guidelines for prevention. Diet has also been investigated with a major focus on the content of the diet and to a lesser extent on the amount, pattern, and quality of diet. Identification of dietary factors in migraine has led to nutritional interventions with a major focus on elimination of triggers, and weight control strategies. Several so-called migraine diets have consequently been proposed, for example, the ketogenic diet. Some theories have considered epigenetic diets or functional food to help in altering components of migraine pathogenesis; however, these theories are less investigated. In contrast, evidence is being accumulated to support that some mechanisms underlying migraine may alter dietary choices, for example type, amount, or patterns. Since a causative relationship is not yet established in migraine-diet relationship as to which comes first, this concept is equally valuable and interesting to investigate. Only limited epidemiological data are available to demonstrate that dietary choices are different among patients with migraine compared with individuals without migraine. Differences are reflected on quality, composition, pattern, and the amount of consumption of dietary components. This view emphasizes a potential bidirectional relationship between migraine and diet rather than a one-way influence of one on the other. This targeted review presents examples from current literature on the effects of diet on migraine features and effects of migraine on dietary choices to draw a perspective for future studies.

Grape seed extract inhibits nucleus pulposus cell apoptosis and attenuates annular puncture induced intervertebral disc degeneration in rabbit model

Low back pain is a musculoskeletal disorders implicated to disc degeneration. Grape seed extracts (GSEs) is a natural flavonoids rich compound with antioxidants and anti-inflammatory properties. This study is aimed at investigating the inhibitory and anabolic response of GSE on annular punctured induced disc degeneration in rabbit model. Twenty-Eight New Zealand white rabbits (weighing about 2.0-3.5 kg) were used with institutional animal care committee's approval. The animals were divided into four groups (n=7 per group). Group A (non-punctured group) received distilled water orally for 4 weeks. Group B (punctured group) received distilled water for 4 weeks. Group C (punctured treated group) received distilled water for 4 weeks and thereafter received 500 mg/kg of GSE for another 4 weeks. Group D received 500 mg/kg of GSE immediately after puncture for 4 weeks. At the end of the experiment, the animals were sacrificed with intramuscular injection of ketamine followed by intravenous injection of sodium pentobarbital. The percentage disc height index of the punctured group showed significant decrease compared to the control and treated groups. Histological and immunohistochemical studies showed distortion in the disc morphology, decrease in chondrocyte like cells, disorganization of collagen and elastic fibers, increase Bax expression levels in the punctured group compared to control and treated groups which was attenuated after GSE administration. GSE has preventive and restorative effects on punctured induced disc preventing the degradation of collagen fibrils within the disc tissues.

The effect of natural products in animal models of temporomandibular disorders

Treatment of temporomandibular disorders (TMD) is a challenge for health care professionals. Therefore, new approaches have been investigated, such as the use of natural products.

Orofacial skin inflammation increases the number of macrophages in the maxillary subregion of the rat trigeminal ganglion in a corticosteroid-reversible manner

Inflammation of the cutaneous orofacial tissue can lead to a prolonged alteration of neuronal and nonneuronal cellular functions in trigeminal nociceptive pathways. In this study, we investigated the effects of experimentally induced skin inflammation by dithranol (anthralin) on macrophage activation in the rat trigeminal ganglion. Tissue localization and protein expression levels of ionized calcium-binding adaptor molecule 1 (Iba1), a macrophage/microglia-specific marker, and proliferation/mitotic marker antigen identified by the monoclonal antibody Ki67 (Ki67), were quantitatively analyzed using immunohistochemistry and western blots in control, dithranol-treated, dithranol- and corticosteroid-treated, and corticosteroid-treated trigeminal ganglia. Chronic orofacial dithranol treatment elicited a strong pro-inflammatory effect in the ipsilateral trigeminal ganglion. Indeed, daily dithranol treatment of the orofacial skin for 3-5 days increased the number of macrophages and Iba1 protein expression in the maxillary subregion of the ipsilateral ganglion. In the affected ganglia, none of the Iba1-positive cells expressed Ki67. This absence of mitotically active cells suggested that the accumulation of macrophages in the ganglion was not the result of resident microglia proliferation but rather the extravasation of hematogenous monocytes from the periphery. Subsequently, when a 5-day-long anti-inflammatory corticosteroid therapy was employed on the previously dithranol-treated orofacial skin, Iba1 immunoreactivity was substantially reduced in the ipsilateral ganglion. Collectively, our findings indicate that both peripheral inflammation and subsequent anti-inflammatory therapy affect macrophage activity and thus interfere with the functioning of the affected sensory ganglion neurons.

Associations between adherence to MIND diet and severity, duration and frequency of migraine headaches among migraine patients

OBJECTIVES

Migraine is a neurological disorder causing unbearable pain. Dietary approach is proposed as a preventive way of reducing the severity of migraine headaches. The present study aimed to examine the association between MIND diet and migraine headaches.

RESULTS

We found that participants with higher score of MIND diet compared to those with lower score, were less likely to have severe headaches (OR = 0.64; 95% CI 0.45, 0.91; P = 0.01). Moreover, our results showed an inversed correlation between mind diet score and duration (β = - 0.14, 95% CI - 1.42, - 0.14, P = 0.04) and frequency of headaches (β = - 0.13, 95% CI - 0.99, - 0.07, P = 0.03).

What is Needed for Evidence-Based Dietary Recommendations for Migraine: A Call to Action for Nutrition and Microbiome Research

BACKGROUND

The gastrointestinal symptoms of migraine attacks have invited numerous dietary hypotheses for migraine etiology through the centuries. Substantial efforts have been dedicated to identifying dietary interventions for migraine attack prevention, with limited success. Meanwhile, mounting evidence suggests that the reverse relationship may also exist - that the biological mechanisms of migraine may influence dietary intake. More likely, the truth involves some combination of both, where the disease influences food intake, and the foods eaten impact the manifestations of the disease. In addition, the gut's microbiota is increasingly suspected to influence the migraine brain via the gut-brain axis, though these hypotheses remain largely unsubstantiated.

OBJECTIVE

This paper presents an overview of the strength of existing evidence for food-based dietary interventions for migraine, noting that there is frequently evidence to suggest that a dietary risk factor for migraine exists but no evidence for how to best intervene; in fact, our intuitive assumptions on interventions are being challenged with new evidence. We then look to the future for promising avenues of research, notably the gut microbiome.

CONCLUSION

The evidence supports a call to action for high-quality dietary and microbiome research in migraine, both to substantiate hypothesized relationships and build the evidence base regarding nutrition's potential impact on migraine attack prevention and treatment.

Dietary supplementation with grape seed extract prevents development of trigeminal sensitization and inhibits pain signaling in a preclinical chronic temporomandibular disorder model

BACKGROUND

The risk factors neck muscle tension, prolonged jaw opening, and female gender are associated with developing temporomandibular disorders (TMD), which are characterized by persistent sensitization of trigeminal neurons and enhanced pain signaling. Dietary supplementation with a grape seed extract (GSE) can modulate expression of proteins that decrease neuronal excitability and trigeminal sensitization.

METHODS

Mechanical nocifensive thresholds over the masseter were determined using von Frey filaments in male and female adult Sprague Dawley rats. To promote trigeminal sensitization, animals were injected with complete Freund's adjuvant in the upper trapezius. After 8 days, animals were subjected to near maximal jaw opening and head withdrawal responses were determined for 28 days. Some animals received continuous supplementation with 0.5% GSE in their drinking water two weeks prior to trapezius injections.

RESULTS

Prolonged jaw opening increased the average number of nocifensive responses to mechanical stimuli for 14 days in males and females. However, trapezius inflammation prior to jaw opening promoted persistent mechanical sensitivity up to 28 days post-jaw opening in females, while in males nociceptive levels were still elevated at day 21. Supplementation with GSE, which is enriched in polyphenols and exhibits antioxidant and COX-2 activity, inhibited trigeminal nociception in response to jaw opening in both male and female sensitized animals.

CONCLUSIONS

Our findings provide evidence that multiple risk factors contribute to the development of a prolonged state of trigeminal sensitization that is more severe in females and provide preclinical evidence that supplementation with GSE could be beneficial in the management of TMD.

Migraine and Diet

Migraine is characterized by recurrent attacks of disabling headaches, often accompanied by sensory and motor disturbances. Clinical manifestations of migraine are influenced by dietary behaviors and dietary elements. Several dietary triggers for migraine have been identified, leading to the definition of strategies such as elimination diets, ketogenic diets, and comprehensive diets, mainly to help prevent migraine. Although inconsistency is present in the literature and no consensus exists, the available data are promising in supporting beneficial dietary interventions for some migraine patients. Several factors influence the net outcome, including age, sex, genetics, and environmental factors. Advancement in understanding the underlying mechanisms of migraine pathogenesis and how dietary factors can interfere with those mechanisms has encouraged investigators to consider diet as a disease-modifying agent, which may also interfere with the gut–brain axis or the epigenetics of migraine. Future work holds potential for phenotyping migraine patients and offering personalized recommendations in line with biopsychosocial models for the management of migraine. Diet, as an important element of lifestyle, is a modifiable aspect that needs further attention. Well-designed, systematic, and mechanism-driven dietary research is needed to provide evidence-based dietary recommendations specific to migraine. This narrative review aims to present the current status and future perspective on diet and migraine, in order to stimulate further research and awareness.

Neuroprotective Effect of Enriched Chicken Bone Broth as a Dietary Supplement in a Model of Migraine Mediated by Early Life Stress

Early life stress is a risk factor for development of migraine, a prevalent painful neurological disease characterized by sensitization and activation of trigeminal neurons. Secondary early life stress was previously shown to cause increased expression of neuronal proteins implicated in peripheral and central sensitization. Recently, dietary supplementation of chicken bone broth was shown to attenuate trigeminal nociception in an orofacial pain model. Accordingly, the focus of this study was to determine the effects of early life stress and dietary inclusion of bone broth on trigeminal nociceptor sensitization and activation in a model of episodic migraine. Adult Sprague-Dawley male sender rats subjected to primary traumatic stress were placed next to breeding or pregnant female rats that served as receiver rats (secondary traumatic stress) and in proximity to the offspring until weaning. Unstressed and stressed young adult offspring were tested for mechanical nocifensive response after exposure to a pungent odor known to be a migraine trigger, and in response to daily supplementation of bone broth. Early life stress promoted a primed state of trigeminal nociceptors that were activated by the pungent odor in both genders. Female animals exhibited a higher basal sensitization level and prolonged nociception compared with males. Supplementation of bone broth beginning at the time of weaning inhibited basal and triggered trigeminal mechanical sensitivity. Early life stress caused development of a sensitized trigeminal system that is implicated in migraine pathology and dietary supplementation with bone broth suppressed trigeminal sensitization, and thus may provide neuroprotective activity for reducing migraine risk.

Mangiferin: Possible uses in the prevention and treatment of mixed osteoarthritic pain

Osteoarthritis (OA) pain has been proposed to be a mixed pain state, because in some patients, central nervous system factors are superimposed upon the more traditional peripheral factors. In addition, a considerable amount of preclinical and clinical evidence has shown that, accompanying the central neuroplasticity changes and partially driven by a peripheral nociceptive input, a real neuropathic component occurs that are particularly linked to disease severity and progression. Hence, innovative strategies targeting neuroprotection and particularly neuroinflammation to prevent and treat OA pain could be introduced. Mangiferin (MG) is a glucosylxanthone that is broadly distributed in higher plants, such as Mangifera indica L. Previous studies have documented its analgesic, anti-inflammatory, antioxidant, neuroprotective, and immunomodulatory properties. In this paper, we propose its potential utility as a multitargeted compound for mixed OA pain, even in the context of multimodal pharmacotherapy. This hypothesis is supported by three main aspects: the cumulus of preclinical evidence around this xanthone, some preliminary clinical results using formulations containing MG in clinical musculoskeletal or neuropathic pain, and by speculations regarding its possible mechanism of action according to recent advances in OA pain knowledge.

Food pyramid for subjects with chronic pain: foods and dietary constituents as anti-inflammatory and antioxidant agents

Emerging literature suggests that diet constituents may play a modulatory role in chronic pain (CP) through management of inflammation/oxidative stress, resulting in attenuation of pain. We performed a narrative review to evaluate the existing evidence regarding the optimum diet for the management of CP, and we built a food pyramid on this topic. The present review also describes the activities of various natural compounds contained in foods (i.e. phenolic compounds in extra-virgin olive oil (EVO)) listed on our pyramid, which have comparable effects to drug management therapy. This review included 172 eligible studies. The pyramid shows that carbohydrates with low glycaemic index should be consumed every day (three portions), together with fruits and vegetables (five portions), yogurt (125 ml), red wine (125 ml) and EVO; weekly: legumes and fish (four portions); white meat, eggs and fresh cheese (two portions); red or processed meats (once per week); sweets can be consumed occasionally. The food amounts are estimates based on nutritional and practical considerations. At the top of the pyramid there is a pennant: it means that CP subjects may need a specific customised supplementation (vitamin B12, vitamin D, n-3 fatty acids, fibre). The food pyramid proposal will serve to guide dietary intake with to the intent of alleviating pain in CP patients. Moreover, a targeted diet can also help to solve problems related to the drugs used to combat CP, i.e. constipation. However, this paper would be an early hypothetical proposal due to the limitations of the studies.

Enriched Chicken Bone Broth as a Dietary Supplement Reduces Nociception and Sensitization Associated with Prolonged Jaw Opening

AIMS

To test a commercially available enriched chicken bone broth (ECBB) product for its potential anti-inflammatory properties and to evaluate its ability to reduce nociception and expression of protein kinase A (PKA) in a clinically relevant model of temporomandibular disorder (TMD) caused by prolonged jaw opening in rats.

METHODS

The potential of the ECBB and of a homemade broth was investigated using the Folin-Ciocalteu reagent and percent inhibition of cyclooxygenase-2 (COX-2) activity, which was determined using a commercially available kit. Additionally, the effect of ECBB and homemade broth on nocifensive head withdrawal responses to mechanical stimulation in male Sprague-Dawley rats subjected to prolonged jaw opening was evaluated. Differences were considered significant at P < .025. Changes in PKA expression in the medullary dorsal horn region of the spinal trigeminal nucleus associated with prolonged jaw opening were assessed using immunofluorescence, and these changes were considered significant at P < .05. Behavioral data were analyzed by using multiple nonparametric tests, and immunohistochemistry data were analyzed by using one-way analysis of variance with Games-Howell post hoc tests in SPSS software.

RESULTS

ECBB exhibited greater reducing potential and inhibition of COX-2 activity compared to homemade broth. Near maximal jaw opening was sufficient to induce sustained nocifensive responses to mechanical stimuli for 7 days. This increased sensitivity was correlated with elevated levels of the active form of PKA. Importantly, dietary inclusion of ECBB, but not of homemade broth, for 2 weeks prior to jaw opening was sufficient to reduce nocifensive behaviors and PKA expression.

CONCLUSION

Findings from this study provide evidence that ECBB attenuates nociception and expression of the pro-inflammatory protein PKA and thus may be beneficial as a nutraceutical supplement to manage inflammatory pain associated with TMD.

Vagus nerve stimulation inhibits trigeminal nociception in a rodent model of episodic migraine

INTRODUCTION

Although neck muscle tension is considered a risk factor for migraine, pungent odors can act as a trigger to initiate an attack in sensitized individuals. Although noninvasive vagus nerve stimulation (nVNS) is now an approved treatment for chronic migraine, how it functions to inhibit trigeminal nociception in an episodic migraine model is not known.

OBJECTIVES

The objectives of this study were to determine if nVNS could inhibit trigeminal nociception in a novel model of episodic migraine and investigate changes in the expression of proteins implicated in peripheral and central sensitization.

METHODS

Sprague-Dawley male rats were injected with an inflammatory agent in the trapezius muscle before exposure to pungent volatile compounds, which was used to initiate trigeminal nociceptor activation. The vagus nerve was stimulated transdermally by a 1-ms pulse of 5 kHz sine waves, repeated at 25 Hz for 2 minutes. Nocifensive head withdrawal response to von Frey filaments was determined and immunoreactive protein levels in the spinal cord and trigeminal ganglion (TG) were investigated.

RESULTS

Exposure to the pungent odor significantly increased the number of nocifensive withdrawals in response to mechanical stimulation of sensitized TG neurons mediated by neck muscle inflammation. Noninvasive vagus nerve stimulation inhibited nociception and repressed elevated levels of P-ERK in TG, Iba1 in microglia, and GFAP in astrocytes from sensitized animals exposed to the pungent odor.

CONCLUSION

Our findings demonstrate that nVNS inhibits mechanical nociception and represses expression of proteins associated with peripheral and central sensitization of trigeminal neurons in a novel rodent model of episodic migraine.

ERK potentiates p38 in central sensitization induced by traumatic occlusion

This study was to investigate the role of p38 activation via ERK1/2 phosphorylation in neurons and microglia of the spinal trigeminal subnucleus caudalis (Vc) in the promotion of orofacial hyperalgesia induced by unilateral anterior crossbite (UAC) traumatic occlusion in adult rats. U0126, a p-ERK1/2 inhibitor, was injected intracisternally before UAC implant. The effects of the U0126 injection were compared to those following the injection of SB203580, a p-p38 inhibitor. Mechanical hyperalgesia was evaluated via pressure pain threshold measurements. Brain stem tissues were processed for a Western blot analysis to evaluate the activation of ERK1/2 and p38. Double immunofluorescence was also performed to observe the expression of p-ERK1/2 and p-p38 in neurons (labeled by NeuN) and microglia (labeled by OX42). The data showed that UAC caused orofacial hyperalgia ipsilaterally on d1 to d7, peaking on d3 (P<0.05). An upregulation of p-ERK1/2 was observed in the ipsilateral Vc on d1 to d3, peaking on d1. An upregulation of p-p38 was also observed on d1 to d7, peaking on d3 (P<0.05). p-ERK1/2 primarily co-localized with NeuN and, to a lesser extent, with OX42, while p-p38 co-localized with both NeuN and OX42. Pretreatment with U0126 prevented the upregulation of both p-ERK1/2 and p-p38. Similarly to an intracisternal injection of SB203580, U0126 pretreatment attenuated the UAC-induced orofacial hyperalgesia. These data indicate that UAC caused orofacial hyperalgesia by inducing central sensitization via the activation of ERK1/2 and p38 in both neurons and microglia in the Vc, potentially impacting the effects of p-ERK1/2 during p38 activation.

Modulatory Mechanism of Nociceptive Neuronal Activity by Dietary Constituent Resveratrol

Changes to somatic sensory pathways caused by peripheral tissue, inflammation or injury can result in behavioral hypersensitivity and pathological pain, such as hyperalgesia. Resveratrol, a plant polyphenol found in red wine and various food products, is known to have several beneficial biological actions. Recent reports indicate that resveratrol can modulate neuronal excitability, including nociceptive sensory transmission. As such, it is possible that this dietary constituent could be a complementary alternative medicine (CAM) candidate, specifically a therapeutic agent. The focus of this review is on the mechanisms underlying the modulatory effects of resveratrol on nociceptive neuronal activity associated with pain relief. In addition, we discuss the contribution of resveratrol to the relief of nociceptive and/or pathological pain and its potential role as a functional food and a CAM.

Impact of Food Components on in vitro Calcitonin Gene-Related Peptide Secretion-A Potential Mechanism for Dietary Influence on Migraine

Calcitonin gene-related peptide (CGRP) is a pivotal messenger in the inflammatory process in migraine. Limited evidence indicates that diet impacts circulating levels of CGRP, suggesting that certain elements in the diet may influence migraine outcomes. Interruption of calcium signaling, a mechanism which can trigger CGRP release, has been suggested as one potential route by which exogenous food substances may impact CGRP secretion. The objective of this study was to investigate the effects of foods and a dietary supplement on two migraine-related mechanisms in vitro: CGRP secretion from neuroendocrine CA77 cells, and calcium uptake by differentiated PC12 cells. Ginger and grape pomace extracts were selected for their anecdotal connections to reducing or promoting migraine. S-petasin was selected as a suspected active constituent of butterbur extract, the migraine prophylactic dietary supplement. Results showed a statistically significant decrease in stimulated CGRP secretion from CA77 cells following treatment with ginger (0.2 mg dry ginger equivalent/mL) and two doses of grape pomace (0.25 and 1.0 mg dry pomace equivalent/mL) extracts. Relative to vehicle control, CGRP secretion decreased by 22%, 43%, and 87%, respectively. S-petasin at 1.0 μM also decreased CGRP secretion by 24%. Meanwhile, S-petasin and ginger extract showed inhibition of calcium influx, whereas grape pomace had no effect on calcium. These results suggest that grape pomace and ginger extracts, and S-petasin may have anti-inflammatory propensity by preventing CGRP release in migraine, although potentially by different mechanisms, which future studies may elucidate further.

Extraction Optimization of Polyphenols from Waste Kiwi Fruit Seeds (Actinidia chinensis Planch.) and Evaluation of Its Antioxidant and Anti-Inflammatory Properties

Kiwi fruit (Actinidia chinensis Planch.) seeds, present as a by-product in the food and pharmaceutical industries, remain underutilized. In this study the extraction conditions for the maximum recovery of total phenolic content (TPC) with high DPPH scavenging capacities (DPPHsc) were analyzed for kiwi fruit seed polyphenols (KSP) by response surface methodology. The optimal conditions for the highest yield of TPC (53.73 mg GAE/g DW) with 63.25% DPPHsc was found by using an extraction time of 79.65 min with an eluent containing 59.45% acetone at 38.35 °C and a 1:11.52 (w/v) solid/liquid ratio. Compared with butyl hydroxy toluene (BHT), a synthetic antioxidant, the extracted KSP showed higher DPPHsc and ferric reducing antioxidant power, but was less efficient than grape seed polyphenols extracted under the same optimum conditions. We also showed that the extracted KSP exhibited strong anti-inflammatory activities by suppressing the secretion of pro-inflammatory cytokines like interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α) in lipopolysaccharides (LPS)-induced RAW 264.7 cells. High performance liquid chromatography-electrochemical detector (HPLC-ECD) analysis of the extracted KSP under optimized conditions revealed that the extract was mainly composed of five polyphenolic compounds. Our work showed the development of an optimal extraction process of the KSP, which presented excellent antioxidant and anti-inflammatory activities, indicating that kiwi fruit seeds may further be utilized as a potential source of natural biological active compounds.

Resveratrol attenuates inflammation-induced hyperexcitability of trigeminal spinal nucleus caudalis neurons associated with hyperalgesia in rats

Background

Resveratrol, a component of red wine, has been reported to decrease prostaglandin E₂ production by inhibiting the cyclooxygenase-2 cascade and to modulate various voltage-dependent ion channels, suggesting that resveratrol could attenuate inflammatory hyperalgesia. However, the effects of resveratrol on inflammation-induced hyperexcitability of nociceptive neurons in vivo remain to be determined. Thus, the aim of the present study was to determine whether daily systemic administration of resveratrol to rats attenuates the inflammation-induced hyperexcitability of spinal trigeminal nucleus caudalis wide-dynamic range neurons associated with hyperalgesia.

Results

Inflammation was induced by injection of complete Freund’s adjuvant into the whisker pad. The threshold of escape from mechanical stimulation applied to whisker pad in inflamed rats was significantly lower than in control rats. The decreased mechanical threshold in inflamed rats was restored to control levels by daily systemic administration of resveratrol (2 mg/kg, i.p.). The mean discharge frequency of spinal trigeminal nucleus caudalis wide-dynamic range neurons to both nonnoxious and noxious mechanical stimuli in inflamed rats was significantly decreased after resveratrol administration. In addition, the increased mean spontaneous discharge of spinal trigeminal nucleus caudalis wide-dynamic range neurons in inflamed rats was significantly decreased after resveratrol administration. Similarly, resveratrol significantly diminished noxious pinch-evoked mean after discharge frequency and occurrence in inflamed rats. Finally, resveratrol restored the expanded mean size of the receptive field in inflamed rats to control levels.

Conclusion

These results suggest that chronic administration of resveratrol attenuates inflammation-induced mechanical inflammatory hyperalgesia and that this effect is due primarily to the suppression of spinal trigeminal nucleus caudalis wide dynamic range neuron hyperexcitability via inhibition of both peripheral and central cyclooxygenase-2 cascade signaling pathways. These findings support the idea of resveratrol as a potential complementary and alternative medicine for the treatment of trigeminal inflammatory hyperalgesia without side effects.

Kynurenic acid modulates experimentally induced inflammation in the trigeminal ganglion

Background

The trigeminal ganglion (TG) plays a central role in cranial pain. Administration of complete Freund’s adjuvant (CFA) into the temporomandibular joint (TMJ) elicits activation of TG. Kynurenic acid (KYNA) is an endogenous excitatory amino acid receptor blocker, which may have an anti-inflammatory effect. We hypothesize that KYNA may reduce CFA-induced activation within the TG.

Methods

A local inflammation was induced by administration of CFA into the TMJ in rats. KYNA and kynurenic acid amide 2 (KYNAA2) were intraperitoneally administered. We investigated changes of mitogen-activated protein kinases (MAPKs as ERK1/2, p38 and SAPK/JNK), NF-κB, CaMKII and DREAM, in addition to calcitonin gene-related peptide (CGRP) and its receptor components calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1) in the TG, with immunohistochemistry and Western blot at 2 and 10 days post-CFA injection.

Results

We showed CFA-induces increases in pERK1/2, pp38, CaMKII, NF-κB and DREAM immunohistochemistry after 2 and 10 days. KYNAA2 displayed stronger effects on MAPKs than KYNA. Increased expression of CaMKII, NF-κB and DREAM were found in the neurons. Western blot showed significantly increase in pERK expression at 10 days post-CFA, which decreased after 10 days of KYNA treatment. Two days post-CFA, a significantly increase in pp38 expression was found, which decreased after 2 days of KYNA and KYNAA2 treatment.

Conclusions

The CFA-induced inflammatory model for the TG activation provided a time-related expression of MAPK (pERK1/2, pp38) and NF-κB. It involves both the neuronal and glial activation, which points to possible neuron-glia interactions during this process. The administration of the endogenous NMDA-receptor antagonists, KYNA and its derivative KYNAA2, resulted in the inhibition of the induced signaling system of the TG, which further points the importance of the glutamate receptors in this mechanism.

Electronic supplementary material

The online version of this article (doi:10.1186/s10194-015-0581-x) contains supplementary material, which is available to authorized users.

Nicotine stimulates expression of proteins implicated in peripheral and central sensitization

Pain patients who are nicotine dependent report a significantly increased incidence and severity of pain intensity. The goal of this study was to determine the effects of prolonged nicotine administration on inflammatory proteins implicated in the development of peripheral and central sensitization of the trigeminal system. Behavioral, immunohistochemical, and microarray studies were utilized to investigate the effects of nicotine administered daily for 14 days via an Alzet® osmotic pump in Sprague Dawley rats. Systemic nicotine administration caused a significant increase in nocifensive withdrawals to mechanical stimulation of trigeminal neurons. Nicotine stimulated expression of the pro-inflammatory signal transduction proteins phosphorylated-extracellular signal-regulated kinase (p-ERK), phosphorylated-c-Jun N-terminal kinase (p-JNK), and protein kinase A (PKA) in the spinal trigeminal nucleus. Nicotine also promoted elevations in the expression of glial fibrillary acidic protein (GFAP), a biomarker of activated astrocytes, and the microglia biomarker ionized calcium-binding adapter molecule 1 (Iba1). Similarly, levels of eleven cytokines were significantly elevated with the largest increase in expression of TNF-α. Levels of PKA, p-ERK, and p-JNK in trigeminal ganglion neurons were increased by nicotine. Our findings demonstrate that prolonged systemic administration of nicotine promotes sustained behavioral and cellular changes in the expression of key proteins in the spinal trigeminal nucleus and trigeminal ganglion implicated in the development and maintenance of peripheral and central sensitization.

Mitogen-Activated Protein Kinase Phosphatase (MKP)-1 in Nervous System Development and Disease

Mitogen-activated protein kinase phosphatase (MKP)-1 provides a negative feedback mechanism for regulating mitogen-activated protein kinase (MAPK) activity and thus a variety of cellular processes such as proliferation, differentiation, growth and apoptosis. MKP-1 is established as a central regulator of a variety of functions in the immune, metabolic and cardiovascular systems, and it is now increasingly acknowledged as having a role to play in the nervous system. It has been implicated in regulating processes of neuronal cell development and death as well as in glial cell function. Reduced MKP-1 levels have been observed in models of neurological conditions including Huntington's disease, multiple sclerosis, ischemia and cerebral hypoxia. It has also been suggested to have a role to play in psychiatric disorders such as major depressive disorder. Here, we discuss the role of MKP-1 in nervous system development and disease and examine current evidence providing insight into MKP-1 as a potential therapeutic target for various diseases of the central nervous system.

Corneal nerves in health and disease

Corneal nerves are responsible for the sensations of touch, pain, and temperature and play an important role in the blink reflex, wound healing, and tear production and secretion. Corneal nerve dysfunction is a frequent feature of diseases that cause opacities and result in corneal blindness. Corneal opacities rank as the second most frequent cause of blindness. Technological advances in in vivo corneal nerve imaging, such as optical coherence tomography and confocal scanning, have generated new knowledge regarding the phenomenological events that occur during reinnervation of the cornea following disease, injury, or surgery. The recent availability of transgenic neurofluorescent murine models has stimulated the search for molecular modulators of corneal nerve regeneration. New evidence suggests that neuroregenerative and inflammatory pathways in the cornea are intertwined. Evidence-based treatment of neurotrophic corneal diseases includes using neuroregenerative (blood component-based and neurotrophic factors), neuroprotective, and ensconcing (bandage contact lens and amniotic membrane) strategies and avoiding anti-inflammatory therapies, such as cyclosporine and corticosteroids.

Chronic tooth pulp inflammation induces persistent expression of phosphorylated ERK (pERK) and phosphorylated p38 (pp38) in trigeminal subnucleus caudalis

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Chronic inflammation of tooth pulp activates pERK and pp38 in the trigeminal nucleus

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Activation is persistent and bilateral, and further increased by acute stimulation

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This altered signaling may be relevant in the development of chronic pulpitic pain

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pERK and pp38 are more sensitive markers of central change than Fos expression

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Sequential activation in different cell types may be linked to pain progression

Background

Extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase are transiently phosphorylated (activated) in the spinal cord and trigeminal nucleus by acute noxious stimuli. Acute stimulation of dental pulp induces short-lived ERK activation in trigeminal subnucleus caudalis (Vc), and p38 inhibition attenuates short-term sensitization in Vc induced by acute pulpal stimulation. We have developed a model to study central changes following chronic inflammation of dental pulp that induces long-term sensitization. Here, we examine the effects of chronic inflammation and acute stimulation on the expression of phosphorylated ERK (pERK), phosphorylated p38 (pp38) and Fos in Vc.

Results

Chronic inflammation alone induced bilateral expression of pERK and pp38 in Vc, but did not induce Fos expression. Stimulation of both non-inflamed and inflamed pulps significantly increased pERK and pp38 bilaterally; expression was greatest in inflamed, stimulated animals, and was similar following 10-min and 60-min stimulation. Stimulation for 60 min, but not 10 min, induced Fos in ipsilateral Vc; Fos expression was significantly greater in inflamed, stimulated animals. pERK was present in both neurons and astrocytes; pp38 was present in neurons and other non-neuronal, non-astrocytic cell types.

Conclusions

This study provides the first demonstration that chronic inflammation of tooth pulp induces persistent bilateral activation of ERK and p38 within Vc, and that this activation is further increased by acute stimulation. This altered activity in intracellular signaling is likely to be linked to the sensitization that is seen in our animal model and in patients with pulpitis. Our data indicate that pERK and pp38 are more accurate markers of central change than Fos expression. In our model, localization of pERK and pp38 within specific cell types differs from that seen following acute stimulation. This may indicate specific roles for different cell types in the induction and maintenance of pulpitic and other types of pain.

Dual orexin receptor antagonist 12 inhibits expression of proteins in neurons and glia implicated in peripheral and central sensitization

Sensitization and activation of trigeminal nociceptors is implicated in prevalent and debilitating orofacial pain conditions including temporomandibular joint (TMJ) disorders. Orexins are excitatory neuropeptides that function to regulate many physiological processes and are reported to modulate nociception. To determine the role of orexins in an inflammatory model of trigeminal activation, the effects of a dual orexin receptor antagonist (DORA-12) on levels of proteins that promote peripheral and central sensitization and changes in nocifensive responses were investigated. In adult male Sprague-Dawley rats, mRNA for orexin receptor 1 (OX₁R) and receptor 2 (OX₂R) were detected in trigeminal ganglia and spinal trigeminal nucleus (STN). OX₁R immunoreactivity was localized primarily in neuronal cell bodies in the V3 region of the ganglion and in laminas I-II of the STN. Animals injected bilaterally with complete Freund's adjuvant (CFA) in the TMJ capsule exhibited increased expression of P-p38, P-ERK, and lba1 in trigeminal ganglia and P-ERK and lba1 in the STN at 2 days post injection. However, levels of each of these proteins in rats receiving daily oral DORA-12 were inhibited to near basal levels. Similarly, administration of DORA-12 on days 3 and 4 post CFA injection in the TMJ effectively inhibited the prolonged stimulated expression of protein kinase A, NFkB, and Iba1 in the STN on day 5 post injection. While injection of CFA mediated a nocifensive response to mechanical stimulation of the orofacial region at 2h and 3 and 5 days post injection, treatment with DORA-12 suppressed the nocifensive response on day 5. Somewhat surprisingly, nocifensive responses were again observed on day 10 post CFA stimulation in the absence of daily DORA-12 administration. Our results provide evidence that DORA-12 can inhibit CFA-induced stimulation of trigeminal sensory neurons by inhibiting expression of proteins associated with sensitization of peripheral and central neurons and nociception.

Gene therapy for trigeminal pain in mice

The aim of this study was to test the efficacy of a single direct injection of viral vector encoding for encephalin to induce a widespread expression of the transgene and potential analgesic effect in trigeminal behavioral pain models in mice. After direct injection of HSV-1 based vectors encoding for human preproenkephalin (SHPE) or the lacZ reporter gene (SHZ.1, control virus) into the trigeminal ganglia in mice, we performed an orofacial formalin test and assessed the cumulative nociceptive behavior at different time points after injection of the viral vectors. We observed an analgesic effect on nociceptive behavior that lasted up to 8 weeks after a single injection of SHPE into the trigeminal ganglia. Control virus injected animals showed nociceptive behavior similar to naïve mice. The analgesic effect of SHPE injection was reversed/attenuated by subcutaneous naloxone injections, a μ-opioid receptor antagonist. SHPE injected mice also showed normalization in withdrawal latencies upon thermal noxious stimulation of inflamed ears after subdermal complete Freund’s adjuvans injection indicating widespread expression of the transgene. Quantitative immunohistochemistry of trigeminal ganglia showed expression of human preproenkephalin after SHPE injection.

Direct injection of viral vectors proved to be useful for exploring the distinct pathophysiology of the trigeminal system and could also be an interesting addition to the pain therapists’ armamentarium.

Inclusion of cocoa as a dietary supplement represses expression of inflammatory proteins in spinal trigeminal nucleus in response to chronic trigeminal nerve stimulation

SCOPE

Central sensitization is implicated in the pathology of temporomandibular joint disorder and other types of orofacial pain. We investigated the effects of dietary cocoa on expression of proteins involved in the development of central sensitization in the spinal trigeminal nucleus (STN) in response to inflammatory stimulation of trigeminal nerves.

METHODS AND RESULTS

Male Sprague-Dawley rats were fed either a control diet or an isocaloric diet consisting of 10% cocoa powder 14 days prior to bilateral injection of complete Freund's adjuvant (CFA) into the temporomandibular joint to promote prolonged activation of trigeminal ganglion neurons and glia. While dietary cocoa stimulated basal expression of glutamate-aspartate transporter and mitogen-activated protein kinase phosphatase-1 when compared to animals on a normal diet, cocoa suppressed basal calcitonin gene-related peptide levels in the STN. CFA-stimulated levels of protein kinase A, P2X3 , P-p38, glial fibrillary-associated protein, and OX-42, whose elevated levels in the STN are implicated in central sensitization, were repressed to near control levels in animals on a cocoa-enriched diet. Similarly, dietary cocoa repressed CFA-stimulated inflammatory cytokine expression.

CONCLUSION

Based on our findings, we speculate that cocoa-enriched diets could be beneficial as a natural therapeutic option for temporomandibular joint disorder and other chronic orofacial pain conditions.

Two mechanisms involved in trigeminal CGRP release: implications for migraine treatment

OBJECTIVE/BACKGROUND

The goal of this study was to better understand the cellular mechanisms involved in proton stimulation of calcitonin gene-related peptide (CGRP) secretion from cultured trigeminal neurons by investigating the effects of 2 antimigraine therapies, onabotulinumtoxinA and rizatriptan. Stimulated CGRP release from peripheral and central terminating processes of trigeminal ganglia neurons is implicated in migraine pathology by promoting inflammation and nociception. Based on models of migraine pathology, several inflammatory molecules including protons are thought to facilitate sensitization and activation of trigeminal nociceptive neurons and stimulate CGRP secretion. Despite the reported efficacy of triptans and onabotulinumtoxinA to treat acute and chronic migraine, respectively, a substantial number of migraineurs do not get adequate relief with these therapies. A possible explanation is that triptans and onabotulinumtoxinA are not able to block proton-mediated CGRP secretion.

METHODS

CGRP secretion from cultured primary trigeminal ganglia neurons was quantitated by radioimmunoassay while intracellular calcium and sodium levels were measured in neurons via live cell imaging using Fura-2 AM and SBFI AM, respectively. The expression of acid-sensing ion channel 3 (ASIC3) was determined by immunocytochemistry and Western blot analysis. In addition, the involvement of ASICs in mediating proton stimulation of CGRP was investigated using the potent and selective ASIC3 inhibitor APETx2.

RESULTS

While KCl caused a significant increase in CGRP secretion that was significantly repressed by treatment with ethylene glycol tetraacetic acid (EGTA), onabotulinumtoxinA, and rizatriptan, the stimulatory effect of protons (pH 5.5) was not suppressed by EGTA, onabotulinumtoxinA, or rizatriptan. In addition, while KCl caused a transient increase in intracellular calcium levels that was blocked by EGTA, no appreciable change in calcium levels was observed with proton treatment. However, protons did significantly increase the intracellular level of sodium ions. Under our culture conditions, ASIC3 was shown to be expressed in most trigeminal ganglion neurons. Importantly, proton stimulation of CGRP secretion was repressed by pretreatment with the ASIC3 inhibitor APETx2, but not the transient receptor potential vanilloid-1 antagonist capsazepine.

CONCLUSIONS

Our findings provide evidence that proton regulated release of CGRP from trigeminal neurons utilizes a different mechanism than the calcium and synaptosomal-associated protein 25-dependent pathways that are inhibited by the antimigraine therapies, rizatriptan and onabotulinumtoxinA.

Improvement of joint range of motion (ROM) and reduction of chronic pain after consumption of an ergothioneine-containing nutritional supplement

OBJECTIVE

To evaluate anti-inflammatory properties of a nutraceutical blend containing L-ergothioneine in concert with other anti-inflammatory and analgesic ingredients, combined with nutritional cartilage support.

METHODOLOGY

Twelve human subjects were tested over a 6-week period of product consumption followed by a 6-week wash-out period, conducted at NIS Labs during late fall/early winter 2010. Range of motion (ROM) assessment of joint motility was performed using JTECH dual digital inclinometry and included flexion, extension, and rotation through the vertical weight-bearing column (neck, thorax, lumbar, hip, knees) and shoulders. Pain evaluation included questionnaires and Visual Analogues Scales regarding primary and secondary pain complaints at rest and at use.

RESULTS

ROM improvements were seen after 1 week, and further improved at 6 weeks (primary pain area P<0.2, secondary pain area P<0.03). Pain in primary and secondary areas at use was significantly reduced already at 1 week, compared to baseline (P<0.05). Pain reduction for both primary and secondary pain areas during use reached a high level of statistical significance at 6 weeks (P<0.004), and remained highly significant after the 6-week wash-out period.

CONCLUSION

Pain reduction and improved ROM were observed during the 6-week consumption. Residual effects were seen 6 weeks after stopping consumption of the ergothioneine supplement.

Calcitonin gene-related peptide promotes cellular changes in trigeminal neurons and glia implicated in peripheral and central sensitization

BACKGROUND

Calcitonin gene-related peptide (CGRP), a neuropeptide released from trigeminal nerves, is implicated in the underlying pathology of temporomandibular joint disorder (TMD). Elevated levels of CGRP in the joint capsule correlate with inflammation and pain. CGRP mediates neurogenic inflammation in peripheral tissues by increasing blood flow, recruiting immune cells, and activating sensory neurons. The goal of this study was to investigate the capability of CGRP to promote peripheral and central sensitization in a model of TMD.

RESULTS

Temporal changes in protein expression in trigeminal ganglia and spinal trigeminal nucleus were determined by immunohistochemistry following injection of CGRP in the temporomandibular joint (TMJ) capsule of male Sprague-Dawley rats. CGRP stimulated expression of the active forms of the MAP kinases p38 and ERK, and PKA in trigeminal ganglia at 2 and 24 hours. CGRP also caused a sustained increase in the expression of c-Fos neurons in the spinal trigeminal nucleus. In contrast, levels of P2X3 in spinal neurons were only significantly elevated at 2 hours in response to CGRP. In addition, CGRP stimulated expression of GFAP in astrocytes and OX-42 in microglia at 2 and 24 hours post injection.

CONCLUSIONS

Our results demonstrate that an elevated level of CGRP in the joint, which is associated with TMD, stimulate neuronal and glial expression of proteins implicated in the development of peripheral and central sensitization. Based on our findings, we propose that inhibition of CGRP-mediated activation of trigeminal neurons and glial cells with selective non-peptide CGRP receptor antagonists would be beneficial in the treatment of TMD.