Mitogen-Activated Protein Kinase Pathways are Involved in the Upregulation of Calcitonin Gene-Related Peptide of Rat Trigeminal Ganglion After Organ Culture

Transient Receptor Potential Ankyrin 1-dependent Activation of Extracellular Signal-regulated Kinase 2 in the Cerebral Cortices Contributes to Cortical Spreading Depolarization

Extracellular signal-regulated kinase (ERK) are serine/threonine-selective proteins and ERK1/2 can be phosphorylated in peripheral and central brain regions after cortical spreading depolarization (CSD) and calcitonin gene-related peptide; However, it remains unclear about whether and how ERK activity modulates CSD that correlates to migraine aura. Here, we determined the role of ERK in regulating CSD and explored the underlying mechanism involving transient receptor potential ankyrin 1 (TRPA1), a stress-sensing cation channel. CSD was recorded using intrinsic optical imaging in mouse brain slices, and electrophysiology in rats. Phosphorylated ERK (pERK1/2) and interleukin-1β (IL-1β) protein levels were detected using Western blot or enzyme-linked immunosorbent assay, respectively. IL-1β mRNA level was detected using qPCR. The results showed that an ERK inhibitor, SCH77298, markedly prolonged CSD latency and reduced propagation rate in mouse brain slices. Corresponding to this, CSD induction increased levels of cytosolic pERK1/2 in ipsilateral cerebral cortices of rats, the elevation of which correlated to the level of IL-1β mRNA. Mechanistic analysis showed that pre-treatment of an anti-TRPA1 antibody reduced the cytosolic pERK2 level but not pERK1 following CSD in cerebral cortices of rats and this level of pERK2 correlated with that of cerebral cortical IL-1β protein. Furthermore, an ERK activator, AES16-2M, but not its scrambled control, reversed the prolonged CSD latency by a TRPA1 inhibitor, HC-030031, in mouse brain slices. These data revealed a crucial role of ERK activity in regulating CSD, and elevation of pERK and IL-1β production induced by CSD is predominantly TRPA1 channel-dependent, thereby contributing to migraine pathogenesis.

[Features of olfactory impairment connected with trigeminal nerve system]

Data on the state of sense of smell in patients who had a new coronavirus infection caused by the SARS-CoV-2 virus are currently reduced because of the impairment of the olfactory nerve system. There are practically no results in studies of disorders in the trigeminal nerve system.

OBJECTIVE

Qualitative assessment of olfactory disorders after COVID-19 according to the system of olfactory and trigeminal nerves with a targeted assessment of the functional component of olfactory disorders.

MATERIAL AND METHODS

We examined 40 patients aged 19 to 66 who had a coronavirus infection. All patients underwent neurological, otorhinolaryngological examinations, olfactometry, filled out the hospital anxiety and depression scale.

RESULTS

Anosmia was diagnosed in 5 (12.5%) patients, hyposmia in 21 (52.5%) patients, and normosmia in 14 (35%) patients. Formed: the 1st group - 14 patients (35%) with normogram according to olfactometry; the 2nd group - 26 patients (65%) with anosmia/hyposmia. In the 1st group, disorders of the anxiety-depressive spectrum were significantly more common. In the 2nd group, a low identification of odors was found, lying in the spectrum of fresh, sharp, unpleasant, irritating, compared with sweet and pleasant or neutral, which indicates a predominant lesion of the trigeminal system.

CONCLUSION

In patients with complaints of impaired sense of smell after undergoing COVID-19, the possible functional nature of anosmia/hyposmia should be taken into account, which requires the referral of such patients to psychotherapeutic specialists, and the possible entry of olfactory disorders into the 'trigeminal' spectrum.

Sensory Neuron-TRPV4 Modulates Temporomandibular Disorder Pain Via CGRP in Mice

Temporomandibular disorder (TMD) pain that involves inflammation and injury in the temporomandibular joint (TMJ) and/or masticatory muscle is the most common form of orofacial pain. We recently found that transient receptor potential vanilloid-4 (TRPV4) in trigeminal ganglion (TG) neurons is upregulated after TMJ inflammation, and TRPV4 coexpresses with calcitonin gene-related peptide (CGRP) in TMJ-innervating TG neurons. Here, we extended these findings to determine the specific contribution of TRPV4 in TG neurons to TMD pain, and examine whether sensory neuron-TRPV4 modulates TMD pain via CGRP. In mouse models of TMJ inflammation or masseter muscle injury, sensory neuron-Trpv4 conditional knockout (cKO) mice displayed reduced pain. Coexpression of TRPV4 and CGRP in TMJ- or masseter muscle-innervating TG neurons was increased after TMJ inflammation and masseter muscle injury, respectively. Activation of TRPV4-expressing TG neurons triggered secretion of CGRP, which was associated with increased levels of CGRP in peri-TMJ tissues, masseter muscle, spinal trigeminal nucleus, and plasma in both models. Local injection of CGRP into the TMJ or masseter muscle evoked acute pain in naïve mice, while blockade of CGRP receptor attenuated pain in mouse models of TMD. These results suggest that TRPV4 in TG neurons contributes to TMD pain by potentiating CGRP secretion. PERSPECTIVE: This study demonstrates that activation of TRPV4 in TG sensory neurons drives pain by potentiating the release of pain mediator CGRP in mouse models of TMJ inflammation and masseter muscle injury. Targeting TRPV4 and CGRP may be of clinical potential in alleviating TMD pain.

Identification of Novel Genetic Variants Associated with Insomnia and Migraine Comorbidity

Purpose

Although insomnia and migraine are often comorbid, the genetic association between insomnia and migraine remains unclear. This study aimed to identify susceptibility loci associated with insomnia and migraine comorbidity.

Patients and Methods

We performed a genome-wide association study (GWAS) involving 1063 clinical outpatients at a tertiary hospital in Taiwan. Migraineurs with and without insomnia were genotyped using the Affymetrix Axiom Genome-Wide TWB 2.0. We performed association analyses for the entire cohort and stratified patients into the following subgroups: episodic migraine (EM), chronic migraine (CM), migraine with aura (MA), and migraine without aura (MoA). Potential correlations between SNPs and clinical indices in migraine patients with insomnia were examined using multivariate regression analysis.

Results

The SNP rs1178326 in the gene HDAC9 was significantly associated with insomnia. In the EM, CM, MA, and MoA subgroups, we identified 30 additional susceptibility loci. Multivariate regression analysis showed that SNP rs1178326 also correlated with higher migraine frequency and the Migraine Disability Assessment (MIDAS) questionnaire score. Finally, two SNPs that had been previously reported in a major insomnia GWAS were also significant in our migraineurs, showing a concordant effect.

Conclusion

In this GWAS, we identified several novel loci associated with insomnia in migraineurs in a Han Chinese population in Taiwan. These results provide insights into the possible genetic basis of insomnia and migraine comorbidity.

TMI-1, TNF-α-Converting Enzyme Inhibitor, Protects Against Paclitaxel-Induced Neurotoxicity in the DRG Neuronal Cells In Vitro

Background: Chemotherapy-induced peripheral neuropathy (CIPN) negatively impacts cancer survivors’ quality of life and is challenging to treat with existing drugs for neuropathic pain. TNF-α is known to potentiate TRPV1 activity, which contributes to CIPN. Here, we assessed the role of TMI-1, a TNF-α-converting enzyme inhibitor, in paclitaxel (PAC)-induced neurotoxicity in dorsal root ganglion (DRG) cells.

Materials and Methods: Immortalized DRG neuronal 50B11 cells were cultured and treated with PAC or PAC with TMI-1 following neuronal differentiation. Cell viability, analysis of neurite growth, immunofluorescence, calcium flow cytometry, western blotting, quantitative RT-PCR, and cytokine quantitation by ELISA were performed to determine the role of TMI-1 in neurotoxicity in neuronal cells.

Results: PAC administration decreased the length of neurites and upregulated the expression of TRPV1 in 50B11 cells. TMI-1 administration showed a protective effect by suppressing inflammatory signaling, and secretion of TNF-α.

Conclusion: TMI-1 partially protects against paclitaxel-induced neurotoxicity by reversing the upregulation of TRPV1 and decreasing levels of inflammatory cytokines, including TNF-α, IL-1β, and IL-6 in neuronal cells.

The involvement of orexin 1 and cannabinoid 1 receptors within the ventrolateral periaqueductal gray matter in the modulation of migraine-induced anxiety and social behavior deficits of rats

Orexin 1 receptors (Orx1R) and cannabinoid 1 receptors (CB1R) are implicated in migraine pathophysiology. This study evaluated the potential involvement of Orx1R and CB1R within the ventrolateral periaqueductal gray matter (vlPAG) in the modulation of anxiety-like behavior and social interaction of migraineurs rats. A rat model of migraine induced by recurrent administration of nitroglycerin (NTG) (5 mg/kg/i.p.). The groups of rats (n = 6) were then subjected to intra-vlPAG microinjection of orexin-A (25, 50 pM), and Orx1R antagonist SB334867 (20, 40 nM) or AM 251 (2, 4 μg) as a CB1R antagonist. Behavioral responses were evaluated in elevated plus maze (EPM), open field (OF) and three-chambered social test apparatus. NTG produced a marked anxiety like behaviors, in both EPM and OF tasks. It did also decrease social performance. NTG-related anxiety and social conflicts were attenuated by orexin-A (25, 50 pM). However, NTG effects were exacerbated by SB334867 (40 nM) and AM251 (2, 4 μg). The orexin-A-mediated suppression of NTG-induced anxiety and social conflicts were prevented by either SB334867 (20 nM) or AM251 (2 μg). The findings suggest roles for Orx1R and CB1R signaling within vlPAG in the modulation of migraine-induced anxiety-like behavior and social dysfunction in rats.

Study on Mechanism of Jiawei Chaiqin Wendan Decoction in Treatment of Vestibular Migraine Based on Network Pharmacology and Molecular Docking Technology

Objective

To predict the main active ingredients, potential targets, and key pathways of Jiawei Chaiqin Wendan decoction treatment in vestibular migraine and explore possible mechanisms by network pharmacology and molecular docking technology.

Methods

The active ingredients and related targets of Jiawei Chaiqin Wendan decoction were obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). The corresponding genes of the target were queried by UniProt database, and the “drug-compound-target-disease” network was constructed by Cytoscape 3.7.2 software. GO functional enrichment analysis and KEGG pathway enrichment analysis were carried out by R software and Bioconductor, and column chart and bubble chart were drawn by Prism software and OmicShare database for visualization. Finally, the mechanism and potential targets of Jiawei Chaiqin Wendan decoction in the treatment of vestibular migraine were predicted.

Results

The “drug-compound-target-disease” network contains 154 active ingredients and 85 intersection targets. The key targets include AKT1, IL6, MAPK3, VEGFA, EGFR, CASP3, EGF, MAPK1, PTGS2, and ESR1. A total of 1939 items were obtained by GO functional enrichment analysis (P < 0.05). KEGG pathway enrichment analysis screened 156 signal pathways (P < 0.05), involving PI3K-Akt signal pathway, AGE-RAGE signal pathway in diabetes complications, MAPK signal pathway, HIF-1 signal pathway, IL-17 signal pathway, etc. Molecular docking results showed that quercetin, luteolin, kaempferol, tanshinone IIa, wogonin, naringenin, nobiletin, dihydrotanshinlactone, beta-sitosterol, and salviolone have good affinity with core target proteins IL6, PTGS2, MAPK1, MAPK3, and CGRP1.

Conclusion

The active ingredients in Jiawei Chaiqin Wendan decoction may regulate the levels of inflammatory factors and neurotransmitters by acting on multiple targets such as IL6, MAPK3, MAPK1, and PTGS2, so as to play a therapeutic role in vestibular migraine.

Roles of calcitonin gene-related peptide in the skin, and other physiological and pathophysiological functions

Skin immunity is regulated by many mediator molecules. One is the neuropeptide calcitonin gene-related peptide (CGRP). CGRP has roles in regulating the function of components of the immune system including T cells, B cells, dendritic cells (DCs), endothelial cells (ECs), and mast cells (MCs).

Herein we discuss actions of CGRP in mediating inflammatory and vascular effects in various cutaneous models and disorders.

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CGRP can help to recruit immune cells through endothelium-dependent vasodilation.

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CGRP plays an important role in the pathogenesis of neurogenic inflammation.

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Functions of many components in the immune system are influenced by CGRP.

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CGRP regulates various inflammatory processes in human skin by affecting different cell-types.

Activation of the trigeminal system as a likely target of SARS-CoV-2 may contribute to anosmia in COVID-19

Clinical publications show consistently that headache is a common symptom in the coronavirus disease of 2019 (COVID-19). Several studies specifically investigated headache symptomatology and associated features in patients with COVID-19. The headache is frequently debilitating with manifold characters including migraine-like characteristics. Studies suggested that COVID-19 patients with headache vs. those without headache are more likely to have anosmia. We present a pathophysiological hypothesis which may explain this phenomenon, discuss current hypotheses about how the coronavirus SARS-CoV-2 enters the central nervous system and suggest that activation of the trigeminal nerve may contribute to both headache and anosmia in COVID-19.

Neuronal calcitonin gene-related peptide promotes prostate tumor growth in the bone microenvironment

Advanced stage of prostate cancer cells preferentially metastasizes to varying bones of prostate cancer patients, resulting in incurable disease with poor prognosis and limited therapeutical treatment options. Calcitonin gene-related peptide (CGRP), a neuropeptide produced by prostate gland, is known to play a pivotal role in facilitating tumor growth and metastasis of numerous human cancers. In this study, we aim to investigate the clinical relevance of CGRP in prostate cancer patients and the effects of CGRP and CGRP antagonists on prostate tumor growth in the mouse model. The prostate tumor-bearing mice were received either CGRP or CGRP antagonist treatment, and the tumor growth was monitored by quantification of luminescence intensities. We found that the CGRP⁺ nerve fiber density and serum CGRP levels were substantially upregulated in the bone or serum specimens from advanced prostate cancer patients as well as in prostate tumor-bearing mice. Administration of CGRP promoted, whereas treatment of CGRP antagonists inhibited prostate tumor growth in the femurs of mice. In addition, CGRP treatment activated extracellular signal-regulated kinases (ERKs)/ Signal transducer and activator of transcription 3 (STAT3) signaling in prostate cancer cells. Targeting CGRP may serve as a potential therapeutic strategy for advanced prostate cancer patients.

Migraine in relation with endometriosis phenotypes: Results from a French case-control study

BACKGROUND

Studies have shown a significant association between migraine and endometriosis, but no study has explored the relationship between migraine and endometriosis phenotypes: Superficial peritoneal endometriosis, ovarian endometrioma, and deep infiltrating endometriosis.

METHODS

We conducted a case-control study using data collected from 314 women aged 18 to 42 years who had undergone surgery for benign gynecological conditions between January 2013 and December 2015. All women completed a self-administered headache questionnaire according to the IHS classification. Cases (n = 182) are women with histologically proven endometriosis and controls are women (n = 132) without endometriosis. Occurrence of migraine was studied according to endometriosis phenotypes.

RESULTS

Migraine prevalence in cases was significantly higher compared with controls (35.2% vs. 17.4%, p = 0.003). The risk of endometriosis was significantly higher in migrainous women (OR = 2.62; 95% CI = 1.43-4.79). When we take into account endometriosis phenotypes, the risk of ovarian endometrioma and deep infiltrating endometriosis were significant (OR = 2.78; 95% CI = 1.11-6.98 and OR = 2.51; 95% CI = 1.25-5.07, respectively). In women with endometriosis, the intensity of chronic non-cyclical pelvic pain was significantly greater for those with migraine (visual analogic scale (VAS) = 3.6 ± 2.9) compared with the women without headache (VAS = 2.3 ± 2.8, p = 0.0065).

CONCLUSION

Our study shows a significant association between migraine and endometriosis. In clinical practice, women of reproductive age who suffer from migraine should be screened for endometriosis criteria in order to optimise the medical and therapeutic care of this condition.

ALPK1 missense pathogenic variant in five families leads to ROSAH syndrome, an ocular multisystem autosomal dominant disorder

Purpose

To identify the molecular cause in five unrelated families with a distinct autosomal dominant ocular systemic disorder we called ROSAH syndrome due to clinical features of retinal dystrophy, optic nerve edema, splenomegaly, anhidrosis, and migraine headache.

Methods

Independent discovery exome and genome sequencing in families 1, 2, and 3, and confirmation in families 4 and 5. Expression of wild-type messenger RNA and protein in human and mouse tissues and cell lines. Ciliary assays in fibroblasts from affected and unaffected family members.

Results

We found the heterozygous missense variant in the ɑ-kinase gene, ALPK1, (c.710C>T, [p.Thr237Met]), segregated with disease in all five families. All patients shared the ROSAH phenotype with additional low-grade ocular inflammation, pancytopenia, recurrent infections, and mild renal impairment in some. ALPK1 was notably expressed in retina, retinal pigment epithelium, and optic nerve, with immunofluorescence indicating localization to the basal body of the connecting cilium of the photoreceptors, and presence in the sweat glands. Immunocytofluorescence revealed expression at the centrioles and spindle poles during metaphase, and at the base of the primary cilium. Affected family member fibroblasts demonstrated defective ciliogenesis.

Conclusion

Heterozygosity for ALPK1, p.Thr237Met leads to ROSAH syndrome, an autosomal dominant ocular systemic disorder.

Targeted overexpression of tumor necrosis factor-α increases cyclin-dependent kinase 5 activity and TRPV1-dependent Ca2+ influx in trigeminal neurons

We reported earlier that TNF-α, a proinflammatory cytokine implicated in many inflammatory disorders causing orofacial pain, increases the activity of Cdk5, a key kinase involved in brain development and function and recently found to be involved in pain signaling. To investigate a potential mechanism underlying inflammatory pain in trigeminal ganglia (TGs), we engineered a transgenic mouse model (TNF) that can conditionally overexpresses TNF-α upon genomic recombination by Cre recombinase. TNF mice were bred with Nav1.8-Cre mouse line that expresses the Cre recombinase in sensory neurons to obtain TNF-α:Nav1.8-Cre (TNF-α cTg) mice. Although TNF-α cTg mice appeared normal without any gross phenotype, they displayed a significant increase in TNF-α levels after activation of NFκB signaling in the TG. IL-6 and MCP-1 levels were also increased along with intense immunostaining for Iba1 and GFAP in TG, indicating the presence of infiltrating macrophages and the activation of satellite glial cells. TNF-α cTg mice displayed increased trigeminal Cdk5 activity, and this increase was associated with elevated levels of phospho-T407-TRPV1 and capsaicin-evocated Ca influx in cultured trigeminal neurons. Remarkably, this effect was prevented by roscovitine, an inhibitor of Cdk5, which suggests that TNF-α overexpression induced sensitization of the TRPV1 channel. Furthermore, TNF-α cTg mice displayed more aversive behavior to noxious thermal stimulation (45°C) of the face in an operant pain assessment device as compared with control mice. In summary, TNF-α overexpression in the sensory neurons of TNF-α cTg mice results in inflammatory sensitization and increased Cdk5 activity; therefore, this mouse model would be valuable for investigating the mechanism of TNF-α involved in orofacial pain.

New insights into protease-activated receptor 4 signaling pathways in the pathogenesis of inflammation and neuropathic pain: a literature review

Pain is an unpleasant sensory and emotional experience that is commonly associated with actual or potential tissue damage. Despite decades of pain research, many patients continue to suffer from chronic pain that is refractory to current treatments. Accumulating evidence has indicated an important role of protease-activated receptor 4 (PAR4) in the pathogenesis of inflammation and neuropathic pain. Here we reviewed PAR4 expression and activation via intracellular signaling pathways and the role of PAR4 signaling pathways in the development and maintenance of pain. Understanding PAR4 and its corresponding signaling pathways will provide insight to further explore the molecular basis of pain, which will also help to identify new targets for pharmacological intervention for pain relief.

Protease-activated receptor 4: a critical participator in inflammatory response

Protease-activated receptors (PARs) are G protein-coupled receptors of which four members PAR1, PAR2, PAR3, and PAR4 have been identified, characterized by a typical mechanism of activation involving various related proteases. The amino-terminal sequence of PARs is cleaved by a broad array of proteases, leading to specific proteolytic cleavage which forms endogenous tethered ligands to induce agonist-biased PAR activation. The biological effect of PARs activated by coagulation proteases to regulate hemostasis and thrombosis plays an enormous role in the cardiovascular system, while PAR4 can also be activated by trypsin, cathepsin G, the activated factor X of the coagulation cascade, and trypsin IV. Irrespective of its role in thrombin-induced platelet aggregation, PAR4 activation is believed to be involved in inflammatory lesions, as show by investigations that have unmasked the effects of PAR4 on neutrophil recruitment, the regulation of edema, and plasma extravasation. This review summarizes the roles of PAR4 in coagulation and other extracellular protease pathways, which activate PAR4 to participate in normal regulation and disease.

Dural administration of inflammatory soup or Complete Freund's Adjuvant induces activation and inflammatory response in the rat trigeminal ganglion

Background

Migraine is a painful disorder with a huge impact on individual and public health. We hypothesize that migraine pain originates from a central mechanism that results secondarily in hypersensitivity in peripheral afferents associated with the cerebral and cranial blood vessels. It has previously been shown that application of inflammatory or algesic substances onto the dura mater or chemical stimulation of the dural receptive fields causes hypersensitivity to mechanical and thermal stimulation together with direct activation of the TG. We asked whether local inflammation of dura mater induces inflammatory activation in the trigeminal ganglion.

Methods

We performed topical administration of inflammatory soup (IS) or Complete Freund’s Adjuvant (CFA) onto an exposed area of the rat dura mater in vivo for 20 min. The window was closed and the rats were sacrificed after 4 h and up to 7 days. Myography was performed on middle meningeal arteries. The trigeminal ganglia were removed and processed for immunohistochemistry or Western blot.

Results

Both CFA and IS induced enhanced expression of pERK1/2, IL-1β and CGRP in the trigeminal ganglia. The pERK1/2 immunoreactivity was mainly seen in the satellite glial cells, while IL-1β reactivity was observed in the neuronal cytoplasm, close to the cell membrane, seemingly as sign of neuro-glial interaction. The CGRP expression in the neurons and nerve fibres was enhanced after the application of either inflammatory agent. Myography resulted in a strong vasoconstrictor response to IS, but not to CFA.

Conclusions

These results suggest that the application of IS or CFA onto the dura mater causes long-term activation of the TG and demonstrate the importance of the neuro-glial interaction in the activation of the trigeminovascular system.

Electronic supplementary material

The online version of this article (doi:10.1186/s10194-015-0564-y) contains supplementary material, which is available to authorized users.

Up-regulation of calcitonin gene-related peptide in trigeminal ganglion following chronic exposure to paracetamol in a CSD migraine animal model

Previously, our group has demonstrated that chronic paracetamol (APAP) treatment induces alterations to the trigeminovascular nociceptive system in the cortical spreading depression (CSD) migraine animal model. The calcitonin gene related peptide (CGRP) is a key neuropeptide involved in the activation of the trigeminovascular nociceptive system. Therefore, this study examined the expression levels of CGRP in the trigeminal ganglion (TG) after chronic APAP exposure (0, 15, and 30 days) using a CSD model. Rats were divided into control, CSD only, APAP only and APAP treatment with CSD groups. A single injection (i.p.) of APAP (200 mg/kg body weight) was given to the 0-day APAP-treated groups, while the other APAP-treated groups received daily injections for 15 and 30 days. CSD was induced by the topical application of KCl to the parietal cortex. The protein expression of CGRP in the TG was evaluated by immunohistochemistry, and the CGRP mRNA level was investigated by real-time quantitative reverse transcription polymerase chain reaction. The results revealed that the induction of CSD significantly increased the level of CGRP protein but had no effect on CGRP mRNA level. Pretreatment with APAP 1 hour before CSD activation significantly reduced CGRP expression induced by CSD. In contrast, chronic treatment with APAP (15 and 30 days) significantly enhanced CGRP expression in both protein and mRNA levels when compared with the control groups. In combination with CSD, the expression of CGRP further increased in the animal with 30 day treatment. These findings indicate that chronic treatment with APAP induces an increase of CGRP expression in the TG. This alteration may be associated with the increased trigeminovascular nociception observed in our previous studies.

Ictal adipokines are associated with pain severity and treatment response in episodic migraine

OBJECTIVE

To evaluate ictal adipokine levels in episodic migraineurs and their association with pain severity and treatment response.

METHODS

This was a double-blind, placebo-controlled trial evaluating peripheral blood specimens from episodic migraineurs at acute pain onset and 30 to 120 minutes after treatment with sumatriptan/naproxen sodium vs placebo. Total adiponectin (T-ADP), ADP multimers (high molecular weight [HMW], middle molecular weight, and low molecular weight [LMW]), leptin, and resistin levels were evaluated by immunoassays.

RESULTS

Thirty-four participants (17 responders, 17 nonresponders) were included. In all participants, pretreatment pain severity increased with every quartile increase in both the HMW:T-ADP ratio (coefficient of variation [CV] 0.51; 95% confidence interval [CI]: 0.08, 0.93; p = 0.019) and resistin levels (CV 0.58; 95% CI: 0.21, 0.96; p = 0.002), but was not associated with quartile changes in leptin levels. In responders, T-ADP (CV -0.98; 95% CI: -1.88, -0.08; p = 0.031) and resistin (CV -0.95; 95% CI: -1.83, -0.07; p = 0.034) levels decreased 120 minutes after treatment as compared with pretreatment. In addition, in responders, the HMW:T-ADP ratio (CV -0.04; 95% CI: -0.07, -0.01; p = 0.041) decreased and the LMW:T-ADP ratio (CV 0.04; 95% CI: 0.01, 0.07; p = 0.043) increased at 120 minutes after treatment. In nonresponders, the LMW:T-ADP ratio (CV -0.04; 95% CI: -0.07, -0.01; p = 0.018) decreased 120 minutes after treatment. Leptin was not associated with treatment response.

CONCLUSIONS

Both pretreatment migraine pain severity and treatment response are associated with changes in adipokine levels. Adipokines represent potential novel migraine biomarkers and drug targets.

Role of angiotensin modulation in primary headaches

The renin-angiotensin system (RAS) is a major regulatory system controlling many different homeostatic mechanisms both within the brain and in the periphery. While it is primarily associated with blood pressure and salt/water regulation, increasing evidence points to the involvement of the RAS in both headache disorders specifically and pain regulation in general. Several publications have indicated that drugs blocking various elements of the renin-angiotensin system lead to a reduction in migraine. Additionally, interventions on different angiotensin peptides or their receptors have been shown to both reduce and increase pain in animal models. As such, modulation of the renin-angiotensin system is a promising approach to the treatment of headaches and other pain conditions.

Stimulus-specific adaptation and deviance detection in the auditory system: experiments and models

Stimulus-specific adaptation (SSA) is the reduction in the response to a common stimulus that does not generalize, or only partially generalizes, to other, rare stimuli. SSA has been proposed to be a correlate of 'deviance detection', an important computational task of sensory systems. SSA is ubiquitous in the auditory system: It is found both in cortex and in subcortical stations, and it has been demonstrated in many mammalian species as well as in birds. A number of models have been suggested in the literature to account for SSA in the auditory domain. In this review, the experimental literature is critically examined in relationship to these models. While current models can all account for auditory SSA to some degree, none is fully compatible with the available findings.

Role of c-Jun N-terminal kinase (JNK) activation in micturition reflexes in cyclophosphamide (CYP)-induced cystitis in female rats

c-Jun N-terminal kinase (JNK) is member of the mitogen-activated protein kinase (MAPK) family, activated through phosphorylation following cytokine exposure and stress. In this study, phosphorylation of JNK was examined in the urinary bladder with cyclophosphamide (CYP)-induced cystitis and the effects of SP600125, a selective inhibitor of phosphorylation of JNK, on urinary bladder function were assessed using conscious, open outlet, cystometry with continuous instillation of intravesical saline. We induced bladder inflammation in adult female Wistar rats by injecting CYP intraperitoneally to produce acute (150 mg/kg; 4 h), intermediate (150 mg/kg; 48 h), and chronic (75 mg/kg; every third day for 10 days) treatments. Western blotting of urinary bladder demonstrated a significant (p ≤ 0.01) increase (i.e., phosphorylation) in JNK activation with 4- and 48-h CYP-induced cystitis. Immunohistochemistry and image analyses demonstrated a significant (p ≤ 0.01) increase in JNK activation in the urothelium with 4- and 48-h CYP-induced cystitis. Blockade of JNK phosphorylation significantly (p ≤ 0.01) increased bladder capacity and intercontraction void intervals in CYP-treated rats (4 and 48 h). Furthermore, blockade of JNK phosphorylation reduced (p ≤ 0.01) neuropeptide (substance P, calcitonin gene-related peptide) expression in the urinary bladder with CYP-induced cystitis (4 and 48 h). In contrast, blockade of JNK phosphorylation was without effect on bladder function or neuropeptide expression in urinary bladder in control (no inflammation) rats. Blockade of JNK phosphorylation may represent a novel target for improving urinary bladder function with CYP-induced cystitis.

Sex differences in μ-opioid receptor expression in trigeminal ganglia under a myositis condition in rats

BACKGROUND

Peripheral opioid receptor expression is up-regulated under inflammatory conditions, which leads to the increased efficacy of peripherally administered opioids. Sex differences in the effects of inflammation, cytokines and gonadal hormones on μ-opioid receptor (MOR) expression in trigeminal ganglia (TG) are not well understood.

METHODS

MOR mRNA and protein levels in TG from male and female Sprague Dawley rats following complete Freund's adjuvant (CFA)-induced muscle inflammation were assessed. Cytokine-induced changes in MOR mRNA expression from TG cultures prepared from intact and gonadectomized male and female, and gonadectomized male rats with testosterone replacement were examined. Behavioural experiments were then performed to examine the efficacy of a peripherally administered MOR agonist in male, female and gonadectomized male rats under a myositis condition.

RESULTS

CFA and cytokine treatments induced significant up-regulation of MOR expression in TG from male, but not from female, rats. The cytokine-induced up-regulation of MOR mRNA expression was prevented in TG from orchidectomized (GDX) male rats, which was restored with testosterone replacement. Peripherally administered DAMGO, a specific MOR agonist, significantly attenuated CFA-induced masseter mechanical hypersensitivity only in intact male rats.

CONCLUSIONS

Collectively, these data indicate that testosterone plays a key role in the regulation of MOR in TG under inflammatory conditions, and that sex differences in the anti-hyperalgesic effects of peripherally administered opioids are, in part, mediated by peripheral opioid receptor expression levels.

Phosphodiesterases 3 and 5 express activity in the trigeminal ganglion and co-localize with calcitonin gene-related peptide

Background

Understanding of the neuropathology leading to migraine pain has centered on either a vascular or neuronal origin. Sildenafil, a specific inhibitor of phosphodiesterase 5 (PDE5), induces migraine-like headache in a human headache model without concomitant artery dilation. The presence and activity of PDE3 and PDE5 is known in cerebral arteries. However, the presence in the neuronal part of the trigeminovascular pathway, i.e. the trigeminal ganglion and the possible co-localization with calcitonin gene-related peptide (CGRP), is not known.

Methods

Rat trigeminal ganglia were isolated and immunohistochemistry and in situ hybridization was applied. Evaluations of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) hydrolysis were performed using scintillation proximity assays.

Results

PDE3 and PDE5 were present and active in the trigeminal ganglia. A subset of PDE3- and PDE5-positive neurons contained CGRP. In contrast to cGMP, both sildenafil and cilostazol influenced cAMP hydrolysis.

Interpretation

Sildenafil may exert its effect on the neuronal part of the migraine pain pathway. In addition to the effects on cGMP signaling, sildenafil may indirectly affect cAMP signaling in the trigeminal ganglion. This result may suggest a common cAMP-related pathway for sildenafil, cilostazol, and CGRP in eliciting migraine pain.

Protease-activated receptor 4 activation increases the expression of calcitonin gene-related peptide mRNA and protein in dorsal root ganglion neurons

Accumulating evidence demonstrates that nociceptor activation evokes a rapid change in mRNA and protein levels of calcitonin gene-related peptide (CGRP) in dorsal root ganglion (DRG) neurons. Although the colocalization of CGRP and protease-activated receptor-4 (PAR4), a potent modulator of pain processing and inflammation, was detected in DRG neurons, the role of PAR4 activation in the expression of CGRP has not been investigated. In the present study, the expression of CGRP and activation (phosphorylation) of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in rat DRG neurons were measured by immunofluorescence, real-time PCR, and Western blotting after AYPGKF-NH2 (selective PAR4-activating peptide; PAR4-AP) intraplantar injection or treatment of cultured DRG neurons. The expression of CGRP in cultured DRG neurons was also assessed after treatment with AYPGKF-NH2 with preaddition of PD98059 (an inhibitor for ERK1/2 pathway). Results showed that PAR4-AP intraplantar injection or treatment of cultured DRG neurons evoked significant increases in DRG cells displaying CGRP immunoreactivity and cytoplasmic and nuclear staining for phospho-ERK1/2 (p-ERK1/2). Percentages of total DRG neurons expressing both CGRP and PAR4 or p-ERK1/2 also increased significantly at 2 hr after PAR4-AP treatment. Real-time PCR and Western blotting showed that PAR4-AP treatment significantly increased expression of CGRP mRNA and protein levels in DRG neurons. The PAR4 activation-evoked CGRP expression both at mRNA and at protein levels was significantly inhibited after p-ERK1/2 was inhibited by PD98059. These results provide evidence that activation of PAR4 upregulates the expression of CGRP mRNA and protein levels in DRG neurons via the p-ERK1/2 signal pathway.

Interleukin-1β increased the expression of protease-activated receptor 4 mRNA and protein in dorsal root ganglion neurons

Protease-activated receptor-4 (PAR4) is localized in primary sensory neurons and is believed to implicate in the modulation of nociceptive mechanisms. The pro-inflammatory cytokine interleukin-1β (IL-1β) is involved in the generation of hyperalgesia in pathological states such as neuropathy and inflammation. Previous studies have shown that IL-1β enhances the expression of PAR4 in many cell types but the effect of this cytokine on primary sensory neuron PAR4 expression is less clear. In the present study, we evaluated in rat dorsal root ganglion (DRG) neurons the influence of IL-1β on PAR4 mRNA and protein levels after IL-1β intraplantar injection into the hind-paw or treatment of cultured DRG neurons. The expression of PAR4 in cultured DRG neurons was also assessed after treatment with IL-1β with pre-addition of phorbol-12-myristate 13-acetate (PMA, a PKC activator) or chelerythrine chloride (a PKC inhibitor). We found that IL-1β intraplantar injection into the hind-paw or long-term exposure of cultured DRG neurons to IL-1β significantly increased the proportion of DRG neurons expressing PAR4 immunoreactivity. Real-time PCR and western blotting showed that IL-1β treatment also significantly elevated PAR4 mRNA and protein levels in DRG neurons. This IL-1β effect was enhanced in DRG neurons when DRG cultures were pre-treatment with the PMA. But pre-incubation with chelerythrine chloride strongly inhibited the IL-1β-induced increase of PAR4 mRNA and protein levels. These results demonstrate that the expression of PAR4 mRNA and protein induced by IL-1β is PKC signaling pathway dependent.