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Persistent reprogramming of epigenetic pattern leads to changes in gene expression observed in many neurological disorders. Transient receptor potential cation channel subfamily A member 1 (TRPA1), a member of the TRP channels superfamily, is activated by many migraine triggers and expressed in trigeminal neurons and brain regions that are important in migraine pathogenesis. TRP channels change noxious stimuli into pain signals with the involvement of epigenetic regulation. The expression of the TRPA1 encoding gene, TRPA1, is modulated in pain-related syndromes by epigenetic alterations, including DNA methylation, histone modifications, and effects of non-coding RNAs: micro RNAs (miRNAs), long non-coding RNAs, and circular RNAs. TRPA1 may change epigenetic profile of many pain-related genes as it may modify enzymes responsible for epigenetic modifications and expression of non-coding RNAs. TRPA1 may induce the release of calcitonin gene related peptide (CGRP), from trigeminal neurons and dural tissue. Therefore, epigenetic regulation of TRPA1 may play a role in efficacy and safety of anti-migraine therapies targeting TRP channels and CGRP. TRPA1 is also involved in neurogenic inflammation, important in migraine pathogenesis. The fundamental role of TRPA1 in inflammatory pain transmission may be epigenetically regulated. In conclusion, epigenetic connections of TRPA1 may play a role in efficacy and safety of anti-migraine therapy targeting TRP channels or CGRP and they should be further explored for efficient and safe antimigraine treatment. This narrative/perspective review presents information on the structure and functions of TRPA1 as well as role of its epigenetic connections in pain transmission and potential in migraine therapy., (© 2023. The Author(s).)

Objective: To investigate the efficacy of active compounds of Chanqin (CQ) granules on PM2.5-induced airway neurogenic inflammation in vivo, and to elucidate the underlying mechanisms of action., Methods: The Traditional Chinese Medicine systems pharmacology (TCMSP) database was searched, and the results were combined with oral bioavailability and drug analysis to identify the compounds in CQ granules. The pharmacophore modeling approach was used to predict the compound targets, and the diseases corresponding to the targets were obtained by searching the therapeutic target database (TTD), pharmacogenomics knowledgebase (PharmGKB) and DrugBank databases. Cytoscape software was used to construct the network pharmacological charts for Component-Target and Target-Disease interactions of the CQ granules. Then, the mechanisms of action and effectiveness of CQ granules for the treatment of PM2.5-induced airway neurogenic inflammation were analyzed., Results: A total of 195 compounds and 171 targets were obtained from the analyses. A total of 569 corresponding diseases were identified for these targets. Component-target and target-disease networks were constructed. The possible mechanisms and effective components in CQ granules for treating airway neurogenic inflammation were analyzed. Quercetin, kaempferol and isorhamnetin, beta-sitosterol and sitosterol, which are typically found in the formulation, have extensive pharmacological activities, including anti-inflammatory, antioxidant and antiviral actions and neuroprotective properties. Among these targets, androgen receptor, estrogen receptor, prostaglandin G/H synthase 2, and inducible nitric oxide synthase play important pathological roles, including the induction of neurogenic inflammation. CQ granules may have therapeutic effectiveness for numerous diseases in addition to respiratory diseases, including neoplasms, digestive system diseases, cardiovascular diseases, respiratory tract diseases and nervous system diseases. In vivo, CQ granules are effective in treating pulmonary inflammation and downregulate neuropeptides in the bronchoalveolar lavage fluid after PM2.5 exposure. CQ granules significantly decreased the levels of neurokinin A, neurokinin B and calcitonin gene-related peptide in the lung and dorsal root ganglia. CQ also significantly suppressed the upregulation of p-extracellular regulated protein kinase 1/2 and p-methyl ethyl ketone 1/2 induced by PM2.5 exposure., Conclusion: CQ granules have potential for the treatment of neurogenic inflammation induced by PM2.5 in vivo, and the mechanism might involve downregulation of neuropeptides in the BALF, lung and dorsal root ganglia.

Oxidative stress is a central part of innate immune-induced neurodegeneration. However, the transcriptomic landscape of central nervous system (CNS) innate immune cells contributing to oxidative stress is unknown, and therapies to target their neurotoxic functions are not widely available. Here, we provide the oxidative stress innate immune cell atlas in neuroinflammatory disease and report the discovery of new druggable pathways. Transcriptional profiling of oxidative stress-producing CNS innate immune cells identified a core oxidative stress gene signature coupled to coagulation and glutathione-pathway genes shared between a microglia cluster and infiltrating macrophages. Tox-seq followed by a microglia high-throughput screen and oxidative stress gene network analysis identified the glutathione-regulating compound acivicin, with potent therapeutic effects that decrease oxidative stress and axonal damage in chronic and relapsing multiple sclerosis models. Thus, oxidative stress transcriptomics identified neurotoxic CNS innate immune populations and may enable discovery of selective neuroprotective strategies.

Neuroinflammation commences decades before Alzheimer's disease (AD) clinical onset and represents one of the earliest pathomechanistic alterations throughout the AD continuum. Large-scale genome-wide association studies point out several genetic variants- TREM2, CD33, PILRA, CR1, MS4A, CLU, ABCA7, EPHA1 , and HLA-DRB5-HLA-DRB1 -potentially linked to neuroinflammation. Most of these genes are involved in proinflammatory intracellular signaling, cytokines/interleukins/cell turnover, synaptic activity, lipid metabolism, and vesicle trafficking. Proteomic studies indicate that a plethora of interconnected aberrant molecular pathways, set off and perpetuated by TNF-α, TGF-β, IL-1β, and the receptor protein TREM2, are involved in neuroinflammation. Microglia and astrocytes are key cellular drivers and regulators of neuroinflammation. Under physiological conditions, they are important for neurotransmission and synaptic homeostasis. In AD, there is a turning point throughout its pathophysiological evolution where glial cells sustain an overexpressed inflammatory response that synergizes with amyloid-β and tau accumulation, and drives synaptotoxicity and neurodegeneration in a self-reinforcing manner. Despite a strong therapeutic rationale, previous clinical trials investigating compounds with anti-inflammatory properties, including non-steroidal anti-inflammatory drugs (NSAIDs), did not achieve primary efficacy endpoints. It is conceivable that study design issues, including the lack of diagnostic accuracy and biomarkers for target population identification and proof of mechanism, may partially explain the negative outcomes. However, a recent meta-analysis indicates a potential biological effect of NSAIDs. In this regard, candidate fluid biomarkers of neuroinflammation are under analytical/clinical validation, i.e., TREM2, IL-1β, MCP-1, IL-6, TNF-α receptor complexes, TGF-β, and YKL-40. PET radio-ligands are investigated to accomplish in vivo and longitudinal regional exploration of neuroinflammation. Biomarkers tracking different molecular pathways (body fluid matrixes) along with brain neuroinflammatory endophenotypes (neuroimaging markers), can untangle temporal-spatial dynamics between neuroinflammation and other AD pathophysiological mechanisms. Robust biomarker-drug codevelopment pipelines are expected to enrich large-scale clinical trials testing new-generation compounds active, directly or indirectly, on neuroinflammatory targets and displaying putative disease-modifying effects: novel NSAIDs, AL002 (anti-TREM2 antibody), anti-Aβ protofibrils (BAN2401), and AL003 (anti-CD33 antibody). As a next step, taking advantage of breakthrough and multimodal techniques coupled with a systems biology approach is the path to pursue for developing individualized therapeutic strategies targeting neuroinflammation under the framework of precision medicine., (Copyright © 2020 Hampel, Caraci, Cuello, Caruso, Nisticò, Corbo, Baldacci, Toschi, Garaci, Chiesa, Verdooner, Akman-Anderson, Hernández, Ávila, Emanuele, Valenzuela, Lucía, Watling, Imbimbo, Vergallo and Lista.)

Alzheimer's disease (AD) has been clinically characterized by a progressive degeneration of neurons which resulted in a gradual and irreversible cognitive impairment. The accumulation of A β and τ proteins in the brain contribute to the severity of the disease. Recently, vitexin compound has been the talk amongst researchers due to its pharmacological properties as anti-inflammation and anti-AD. However, the epigenetic mechanism of the compound in regulating the neuroinflammation activity is yet to be fully elucidated. Hence, this review discusses the potential of vitexin compound to have the pharmacoepigenetic property in regulating the neuroinflammation activity in relation to AD. It is with hope that the review would unveil the potential of vitexin as the candidate in treating AD., Competing Interests: The authors declare having no conflicts of interest in publishing this paper., (Copyright © 2020 M. A. F. Yahaya et al.)

Background: Neuroinflammation is a common therapeutic target for traumatic brain injury (TBI) due to its contribution to delayed secondary cell death and has the potential to occur for years after the initial insult. Previous studies demonstrate that miR-429 is up-regulated in the brain lesions of TBI mice, while its role in regulating neuroinflammation and brain injury remains largely unknown., Method: The expression of miR-429 in LPS-activated microglia and microglia in TBI model was detected by RT-PCR. The effects of miR-429 inhibitors on LPS-activated microglia in vitro as well as neurological recovery and post-traumatic neuroinflammatory response in TBI model mice were detected in vivo., Results: LPS and TBI significantly induce the up-expression of miR-429, inflammatory cytokines, MAPK-p38 and phosphorylated NF-κB in microglia, which were all inhibited by miR-429 inhibitors. Meanwhile, miR-429 inhibitors also attenuated the neurological impairment in TBI mice. Bioinformatics analysis showed that miR-429 could target and inhibit the expression of dual specificity protein phosphatase 1 (DUSP1), thus inhibiting the expression of MAPK-p38 and phosphorylated NF-κB., Conclusion: miR-429 plays a pro-inflammatory role in activated microglia by targeting DUSP1 signaling pathway. Inhibiting miR-429 can attenuate the inflammatory response of microglia and TBI-mediated brain damage., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Voltage-dependent sodium and calcium channels in pain-initiating nociceptor neurons are attractive targets for new analgesics. We made a permanently charged cationic derivative of an N-type calcium channel-inhibitor. Unlike cationic derivatives of local anesthetic sodium channel blockers like QX-314, this cationic compound inhibited N-type calcium channels more effectively with extracellular than intracellular application. Surprisingly, the compound is also a highly effective sodium channel inhibitor when applied extracellularly, producing more potent inhibition than lidocaine or bupivacaine. The charged inhibitor produced potent and long-lasting analgesia in mouse models of incisional wound and inflammatory pain, inhibited release of the neuropeptide calcitonin gene-related peptide (CGRP) from dorsal root ganglion neurons, and reduced inflammation in a mouse model of allergic asthma, which has a strong neurogenic component. The results show that some cationic molecules applied extracellularly can powerfully inhibit both sodium channels and calcium channels, thereby blocking both nociceptor excitability and pro-inflammatory peptide release., Competing Interests: SL, JL, CW, BB is named as an inventor on a patent application (U.S. Patent Office No. 62/769,420) related to this work, SJ, ST, HZ, MK, NA, MP, PL, TJ, MP, LH, AJ No competing interests declared, (© 2019, Lee et al.)

Astrocytes are critical regulators of neuroinflammation in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). Growing evidence indicates that ubiquitination of signaling molecules is an important cell-intrinsic mechanism governing astrocyte function during MS and EAE Here, we identified an upregulation of the deubiquitinase OTU domain, ubiquitin aldehyde binding 1 (OTUB1) in astrocytes during MS and EAE Mice with astrocyte-specific OTUB1 ablation developed more severe EAE due to increased leukocyte accumulation, proinflammatory gene transcription, and demyelination in the spinal cord as compared to control mice. OTUB1-deficient astrocytes were hyperactivated in response to IFN-γ, a fingerprint cytokine of encephalitogenic T cells, and produced more proinflammatory cytokines and chemokines than control astrocytes. Mechanistically, OTUB1 inhibited IFN-γ-induced Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling by K48 deubiquitination and stabilization of the JAK2 inhibitor suppressor of cytokine signaling 1 (SOCS1). Thus, astrocyte-specific OTUB1 is a critical inhibitor of neuroinflammation in CNS autoimmunity., (© 2019 The Authors.)

Micro-RNAs (miRs) are short, noncoding RNAs that negatively regulate gene expression at the post-transcriptional level and have been implicated in the pathophysiology of secondary damage after traumatic brain injury (TBI). Among miRs linked to inflammation, miR-155 has been implicated as a pro-inflammatory factor in a variety of organ systems. We examined the expression profile of miR-155, following experimental TBI (controlled cortical impact) in adult male C57Bl/6 mice, as well as the effects of acute or delayed administration of a miR-155 antagomir on post-traumatic neuroinflammatory responses and neurological recovery. Trauma robustly increased miR-155 expression in the injured cortex over 7 days. Similar TBI-induced miR-155 expression changes were also found in microglia/macrophages isolated from the injured cortex at 7 days post-injury. A miR-155 hairpin inhibitor (antagomir; 0.5 nmol), administered intracerebroventricularly (ICV) immediately after injury, attenuated neuroinflammatory markers at both 1 day and 7 days post-injury and reduced impairments in spatial working memory. Delayed ICV infusion of the miR-155 antagomir (0.5 nmol/day), beginning 24 h post-injury and continuing for 6 days, attenuated neuroinflammatory markers at 7 days post-injury and improved motor, but not cognitive, function through 28 days. The latter treatment limited NADPH oxidase 2 expression changes in microglia/macrophages in the injured cortex and reduced cortical lesion volume. In summary, TBI causes a robust and persistent neuroinflammatory response that is associated with increased miR-155 expression in microglia/macrophages, and miR-155 inhibition reduces post-traumatic neuroinflammatory responses and improves neurological recovery. Thus, miR-155 may be a therapeutic target for TBI-related neuroinflammation.

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease characterized by motor neuron loss in the brain and spinal cord. Mutations in Cu-Zn superoxide dismutase (SOD1) are the first identified genetic mutations that are causative for familial ALS. Soluble SOD1 oligomers are considered the most toxic species and play a key role in the pathologic process of ALS. Here we present a therapeutic strategy for ALS with an oligomer-specific antibody (W20) targeting toxic SOD1 oligomers. Our study showed that W20 significantly improved motor neuron survival and motor performance in SOD1-G93A mouse model of ALS when administrated even at low dose within short time. Further investigation demonstrated that the beneficial effects of W20 resulted from the reduction of SOD1 oligomer levels and the inhibition of gliosis and neuroinflammation in the spinal cords and brain stems of ALS model mice. These findings for the first time suggest that an oligomer-specific antibody has promising therapeutic potential for ALS and open a new way for ALS treatment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Migraine is one of the most common types of pain associated with sterile inflammatory conditions. Soluble urokinase plasminogen activator receptor (suPAR) is a potential novel inflammatory marker. We aim to determine the association between serum values of suPAR, procalcitonin, fibrinogen, and high-sensitivity C-reactive protein (hs-CRP) and migraine disease characteristics. The study involved a total of 60 migraine patients (33 patients in the interictal period, 27 patients in the attack period) and 30 healthy individuals. The serum values of suPAR were found to be significantly higher in migraine patients in the attack period than in migraine patients in the interictal period, and in healthy individuals (p < .01 for both). In addition, levels of suPAR were determined to be higher in migraine with aura patients than in migraine without aura patients. When we subdivided migraine patients according to frequency of attack (attacks/month), significant differences were found between the suPAR and procalcitonin levels (measured during the attack period) of those in the frequent-attack group (4-5 or more) versus those in the less frequent attack group (less than 4). Serum levels of procalcitonin were shown to be significantly higher in migraine patients during the attack period compared with migraine patients in the interictal period and in control subjects (p = .001 for both). Significant differences were found between plasma levels of fibrinogen in migraine patients versus control subjects (p < .01). No statistically significant difference was found between levels of hs-CRP in migraine patients versus the control group. These findings may show that presenting a high level of suPAR in migraine patients with attack and aura results to predisposition to occurring on the symptoms and that high levels of suPAR, procalcitonin and fibrinogen in patients with migraine result in neurogenic inflammation during migraine headaches.

Acute central nervous system (CNS) injury, encompassing traumatic brain injury (TBI) and stroke, accounts for a significant burden of morbidity and mortality worldwide, largely attributable to the development of cerebral oedema and elevated intracranial pressure (ICP). Despite this, clinical treatments are limited and new therapies are urgently required to improve patient outcomes and survival. Originally characterised in peripheral tissues, such as the skin and lungs as a neurally-elicited inflammatory process that contributes to increased microvascular permeability and tissue swelling, neurogenic inflammation has now been described in acute injury to the brain where it may play a key role in the secondary injury cascades that evolve following both TBI and stroke. In particular, release of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) appear to be critically involved. In particular, increased SP expression is observed in perivascular tissue following acute CNS injury, with the magnitude of SP release being related to both the frequency and degree of the insult. SP release is associated with profound blood-brain barrier disruption and the subsequent development of vasogenic oedema, as well as neuronal injury and poor functional outcomes. Inhibition of SP through use of a neurokinin 1 (NK1) antagonist is highly beneficial following both TBI and ischaemic stroke in pre-clinical models. The role of CGRP is more unclear, especially with respect to TBI, with both elevations and reductions in CGRP levels reported following trauma. However, a beneficial role has been delineated in stroke, given its potent vasodilatory effects. Thus, modulating neuropeptides represents a novel therapeutic target in the treatment of cerebral oedema following acute CNS injury., Competing Interests: The authors declare no conflict of interest.

Vasoactive intestinal peptide (VIP) is one of the neuropeptides showing the strongest up-regulation in the nociceptive pathway after peripheral nerve injury and has been proposed to support neuropathic pain. Nevertheless, the story may be more complicated considering the known suppressive effects of the peptide on the immune reactivity of microglial cells, which have been heavily implicated in the onset and maintenance of pain after nerve injury. We here used mice deficient in VIP and the model of spared nerve injury, characterized by persistent tactile hypersensitivity. While tactile hypersensitivity developed similarly to wild type mice for the ipsilateral hindpaw, only transgenic mice showed a mirror-image tactile hypersensitivity in the contralateral hindpaw. This exacerbated neuropathic pain phenotype appeared to be mediated through a local mechanism acting at the level of the lumbar spinal cord as a distant nerve lesion in the front limb did not lead to hindpaw hypersensitivity in VIP-deficient mice. Innocuous tactile hindpaw stimulation was found to increase a neuronal activation marker in the bilateral superficial laminae of the lumbar dorsal horn of VIP-deficient, but not wild type mice, after SNI. A deeper study into the immune responsiveness to the nerve lesion also proved that VIP-deficient mice had a stronger early pro-inflammatory cytokine response and a more pronounced microglial reactivity compared to wild type controls. The latter was also observed at four weeks after spared nerve injury, a time at which bilateral tactile hypersensitivity persisted in VIP-deficient mice. These data suggest an action of VIP in neuropathic states that is more complicated than previously assumed. Future research is now needed for a deeper understanding of the relative contribution of receptors and fiber populations involved in the VIP-neuropathic pain link., (Copyright © 2017. Published by Elsevier Inc.)

Due to the limited data on diabetic ketoacidosis and brain edema (DKA/BE) in children/adolescents and the lack of recent data on adults with type 1 diabetes (T1D), we addressed the question of whether neuroinflammation was present in the fatal DKA of adults. We performed immunohistochemistry (IHC) studies on the brains of two young adults with T1D and fatal DKA and compared them with two teenagers with poorly controlled diabetes and fatal DKA. C5b-9, the membrane attack complex (MAC) had significantly greater deposits in the grey and white matter of the teenagers than the young adults (p=0.03). CD59, a MAC assembly inhibitory protein was absent, possibly suppressed by the hyperglycemia in the teenagers but was expressed in the young adults despite comparable average levels of hyperglycemia. The receptor for advanced glycation end products (RAGE) had an average expression in the young adults significantly greater than in the teenagers (p=0.02). The autophagy marker Light Chain 3 (LC3) A/B was the predominant form of programmed cell death (PCD) in the teenage brains. The young adults had high expressions of both LC3A/B and TUNEL, an apoptotic cell marker for DNA fragmentation. BE was present in the newly diagnosed young adult with hyperglycemic hyperosmolar DKA and also in the two teenagers. Our data indicate that significant differences in neuroinflammatory components, initiated by the dysregulation of DKA and interrelated metabolic and immunologic milieu, are likely present in the brains of fatal DKA of teenagers when compared with young adults., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The histaminergic system (HS) has a critical role in cognition, sleep and other behaviors. Although not well studied in autism spectrum disorder (ASD), the HS is implicated in many neurological disorders, some of which share comorbidity with ASD, including Tourette syndrome (TS). Preliminary studies suggest that antagonism of histamine receptors 1-3 reduces symptoms and specific behaviors in ASD patients and relevant animal models. In addition, the HS mediates neuroinflammation, which may be heightened in ASD. Together, this suggests that the HS may also be altered in ASD. Using RNA sequencing (RNA-seq), we investigated genome-wide expression, as well as a focused gene set analysis of key HS genes (HDC, HNMT, HRH1, HRH2, HRH3 and HRH4) in postmortem dorsolateral prefrontal cortex (DLPFC) initially in 13 subjects with ASD and 39 matched controls. At the genome level, eight transcripts were differentially expressed (false discovery rate <0.05), six of which were small nucleolar RNAs (snoRNAs). There was no significant diagnosis effect on any of the individual HS genes but expression of the gene set of HNMT, HRH1, HRH2 and HRH3 was significantly altered. Curated HS gene sets were also significantly differentially expressed. Differential expression analysis of these gene sets in an independent RNA-seq ASD data set from DLPFC of 47 additional subjects confirmed these findings. Understanding the physiological relevance of an altered HS may suggest new therapeutic options for the treatment of ASD.

Emerging evidence suggests that microRNAs (miRNAs) play a critical role in the pathogenesis of neuropathic pain. However, the exact role of miRNAs in regulating neuropathic pain remains largely unknown. In this study, we aimed to investigate the potential role of miR-93 in a rat model of neuropathic pain induced by chronic constriction sciatic nerve injury (CCI). We found a significant decrease of miR-93 in the spinal cord of CCI rats compared with sham rats. Overexpression of miR-93 significantly alleviated neuropathic pain development and reduced inflammatory cytokine expression, including interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 in CCI rats. By bioinformatic analysis and dual-luciferase reporter assay, we found that miR-93 directly targeted the 3'-untranslated region (UTR) of signal transducer and activator of transcription 3 (STAT3), an important regulator of inflammation. Overexpression of miR-93 markedly suppressed the expression of STAT3 in vitro and in vivo. Furthermore, overexpression of STAT3 significantly reversed the miR-93 overexpression-induced suppressive effects on neuropathic pain development and neuroinflammation. Taken together, our study suggests that miR-93 inhibits neuropathic pain development of CCI rats possibly through inhibiting STAT3-mediated neuroinflammation. Our findings indicate that miR-93 may serve as a novel therapeutic target for neuropathic pain intervention., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Increasing evidence supports the involvement of inflammatory and immune processes in temporal lobe epilepsy (TLE). miRNAs represent small regulatory RNA molecules that have been shown to act as negative regulators of gene expression controlling different biological processes, including immune system homoeostasis and function. We investigated the expression and cellular distribution of miRNA-146a (miR-146a) in a rat model of TLE. Prominent up-regulation of miR-146a activation was evident in 1 week after status epilepticus (SE) and persisted in the chronic phase. The predicted miR-146a's target complement factor H (CFH) mRNA and protein expression was also down-regulated in TLE rat model. Furthermore, transfection of miR-146a mimics in neuronal and glial cells down-regulated CFH mRNA and protein levels respectively. Luciferase reporter assays demonstrated that miR-146a down-regulated CFH mRNA expression via 3'-UTR pairing. Down-regulating miR-146a by intracerebroventricular injection of antagomir-146a enhanced the hippocampal expression of CFH in TLE model and decreased seizure susceptibility. These findings suggest that immunopathological deficits associated with TLE can in part be explained by a generalized miR-146a-mediated down-regulation of CFH that may contribute to epileptogenesis in a rat model of TLE., (© 2016 The Author(s).)

Dendropanax morbifera (D. morbifera), a species endemic to Korea, is largely distributed throughout the southern part of the country. Its leaves, stems, roots, and seeds have been used as a form of alternative medicine for various diseases and neurological disorders including paralysis, stroke, and migraine. However, the molecular mechanisms that underlie the remedial effects of D. morbifera remain largely unknown. In this paper, extracts from D. morbifera leaves were prepared using ethyl acetate as a solvent (abbreviated as DMLE). The modulatory effects of DMLE on neuroinflammation were studied in a lipopolysaccharide (LPS)-stimulated BV2 murine microglial cell line. Production of pro-inflammatory cytokines, activation of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-[Formula: see text]B), and different M1/M2 activation states of microglia were examined. DMLE treatment suppressed the production of pro-inflammatory cytokines including tumor necrosis factor-[Formula: see text] (TNF-[Formula: see text]), interleukin-6 (IL-6), and nitric oxide (NO) in LPS-stimulated BV2 cells. DMLE treatment also attenuated the activation of MAPKs and NF-[Formula: see text]B. In a novel discovery, we found that DMLE up-regulated the marker genes representing an alternative, anti-inflammatory M2 polarization, while suppressing the expression of the classical, pro-inflammatory M1 activation state genes. Here, we uncovered the cellular mechanisms underlying the beneficial effects of D. morbifera against neuroinflammation using BV2 microglia cells. These results strongly suggest that DMLE was able to counter the effects of LPS on BV2 cells via control of microglia polarization states. Additionally, study results indicated that DMLE may have therapeutic potential as a neuroinflammation-suppressing treatment for neurodegenerative diseases.

The modulation of endocannabinoid (EC) levels and the activation of cannabinoid receptors are seen as promising therapeutic strategies in a variety of diseases, including Alzheimer's disease (AD). We aimed to evaluate the effect of the pharmacologic and genetic inhibition of anandamide-degrading enzyme in a mouse model of AD (5xFAD). Pharmacologic inhibition of the fatty acid amide hydrolase (FAAH) had little impact on the expression of key enzymes and cytokines and also on the cognitive impairment, plaque deposition, and gliosis in 5xFAD mice. CB1 blockade exacerbated inflammation in this transgenic mouse model of AD. The genetic inactivation of FAAH led to increases in the expression of inflammatory cytokines. At the same time, FAAH-null 5xFAD mice exhibited a behavioral improvement in spatial memory that was independent of the level of anxiety and was not CB1 mediated. Finally, mice lacking FAAH showed diminished soluble amyloid levels, neuritic plaques, and gliosis. These data reinforce the notion of a role for the EC system in neuroinflammation and open new perspectives on the relevance of modulating EC levels in the inflamed brain., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Although pituitary adenylate cyclase-activating polypeptide (PACAP) was described as a key vasoregulator in human skin, little is known about its expression in mouse skin. As it is important to investigate PACAP signaling in translational mouse dermatitis models, we determined its presence, regulation, and role in neurogenic and non-neurogenic cutaneous inflammatory mechanisms. The mRNA of PACAP and its specific receptor PAC1 was detected with real-time PCR in several skin regions at comparable levels. PACAP-38-immunoreactivity measured with radioimmunoassay was similar in plantar and dorsal paw skin and the ear but significantly smaller in the back skin. PACAP and PAC1 mRNA, as well as PACAP-38 and PAC1 protein expression, significantly increased in the plantar skin after intraplantar administration of capsaicin (50 μl, 100 μg ml(-1)), an agonist of the transient receptor potential vanilloid 1 (TRPV1) receptor, evoking chiefly neurogenic inflammation without inflammatory cell accumulation. Intraplantar complete Freund's adjuvant (CFA; 50 μl, 1 mg ml(-1)) also increased PACAP/PAC1 mRNA but not the PACAP peptide. Capsaicin-induced neurogenic paw edema, but not CFA-evoked non-neurogenic swelling, was significantly smaller in PACAP-deficient mice throughout a 24-hour period. To our knowledge, we provide previously unreported evidence for PACAP and PAC1 expression upregulation during skin inflammation of different mechanisms and for its pro-inflammatory function in neurogenic edema formation.

The mechanisms of action of IVIg on immunoregulatory and neuroinflammatory network have been predominantly based on in vitro experiments and animal studies, rather than direct effects on human tissues. Based on clinicopathologic correlations and tissues obtained before and after IVIg therapy, the better documented and clinically-relevant in-vivo actions of IVIg include effects on: a) Antibodies. An extracted antigen-specific anti-immunoglobulin (idiotypic) fraction appears partially responsible for its effect in myasthenia gravis and GBS; b) Complement. Sera from Dermatomyositis (DM) patients responding to IVIg, inhibit complement consumption and intercept MAC formation leading to disappearance of MAC deposits in the repeated muscle biopsies and normalization of muscle tissue; c) Genes. In repeated muscle biopsies from DM patients who improved after IVIg, but not from Inclusion-Body-Myositis (IBM) who did not improve, there is a 2-fold alteration of 2206 tissue genes associated with inflammation, fibrosis, tissue remodeling and regeneration; and d) degenerative-proinflammatory molecules and β-amyloid, implicated in neurodegenerative CNS diseases and IBM. In repeated muscle biopsies of IBM patients who did not respond to IVIg, the mRNA or protein expression for chemokines, IFN-γ, TGF-ß, IL-10, Ubiquitin and aB-crystallin is reduced, but not for the key molecules ICOS, ICOSL, IL-6, IL1-β, perforin, APP, nitric oxide synthase and nitrotyrosine, in spite of good IVIg penetration in muscles. Collectively, the selective effectiveness of IVIg in human diseases seems to correlate in vivo with inhibition of causative inflammatory mediators. Study of accessible tissues before and after therapy and clinicopathologic correlations, may help explain the differential effect of IVIg in autoimmune or neuroinflammatory diseases.

Regulatory T cells are the central element for the maintenance of peripheral tolerance. Several subtypes of regulatory T (Treg) cells have been described, and most of them belong to the CD4(+) T-helper (Th) cell lineage. These specific subtypes can be discriminated according to phenotype and function. Forkhead box protein 3 (FoxP3)-expressing natural Treg cells (Tregs) and IL-10-producing, T-regulatory type 1 cells (Tr1) are the best-studied types of CD4(+) regulatory T cells in humans and experimental animal models. It was shown that they play a crucial role during autoimmune neuroinflammation. Both cells types seem to be particularly important for multiple sclerosis (MS). Here, we discuss the role of CD4(+) regulatory T cells in autoimmune neuroinflammation with an emphasis on Tregs and Tr1 cells in MS., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Sickle cell anemia (SCA) is an inherited disorder associated with severe lifelong pain and significant morbidity. The mechanisms of pain in SCA remain poorly understood. We show that mast cell activation/degranulation contributes to sickle pain pathophysiology by promoting neurogenic inflammation and nociceptor activation via the release of substance P in the skin and dorsal root ganglion. Mast cell inhibition with imatinib ameliorated cytokine release from skin biopsies and led to a correlative decrease in granulocyte-macrophage colony-stimulating factor and white blood cells in transgenic sickle mice. Targeting mast cells by genetic mutation or pharmacologic inhibition with imatinib ameliorates tonic hyperalgesia and prevents hypoxia/reoxygenation-induced hyperalgesia in sickle mice. Pretreatment with the mast cell stabilizer cromolyn sodium improved analgesia following low doses of morphine that were otherwise ineffective. Mast cell activation therefore underlies sickle pathophysiology leading to inflammation, vascular dysfunction, pain, and requirement for high doses of morphine. Pharmacological targeting of mast cells with imatinib may be a suitable approach to address pain and perhaps treat SCA.

The transcription factor CCAAT/enhancer binding protein δ (C/EBPδ) is expressed in activated astrocytes and microglia and can regulate the expression of potentially detrimental proinflammatory genes. The objective of this study was to determine the role of C/EBPδ in glial activation. To this end, glial activation was analyzed in primary glial cultures and in the central nervous system from wild type and C/EBPδ(-/-) mice. In vitro studies showed that the expression of proinflammatory genes nitric oxide (NO)synthase-2, cyclooxygenase-2, and interleukin (IL)-6 in glial cultures, and the neurotoxicity elicited by microglia in neuron-microglia cocultures, were decreased in the absence of C/EBPδ when cultures were treated with lipopolysaccharide (LPS) and interferon γ, but not with LPS alone. In C/EBPδ(-/-) mice, systemic LPS-induced brain expression of NO synthase-2, tumor necrosis factor-α, IL-1β, and IL-6 was attenuated. Finally, increased C/EBPδ nuclear expression was observed in microglial cells from amyotrophic lateral sclerosis patients and G93A-SOD1 mice spinal cord. These results demonstrate that C/EBPδ plays a key role in the regulation of proinflammatory gene expression in glial activation and suggest that C/EBPδ inhibition has potential for the treatment of neurodegenerative disorders, in particular, amyotrophic lateral sclerosis., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background: The pathogenesis of migraine involves immune-mediated mechanisms in the vascular endothelium. Toll like receptor 4 (TLR-4) is a signaling receptor of innate immunity which plays a role in various neuropathologies related to neuron inflammation., Objective: This case/control study is aimed to investigate whether TLR-4 896A/G variation is related to migraine headaches in an Iranian population., Methods: A total of 170 migraine patients (130 females, mean age 33.24 ± 11 years) and 170 age, sex, and ethnicity matched healthy controls (118 females, mean age of 31 ± 10 years) were recruited. Genotyping was carried out using the tetra primer amplification refractory mutation system (ARMS)-PCR., Results: The frequency of G allele was higher in migraine patients than the controls (15% vs. 4.7%; p<0.0001). Interestingly, the distribution of heterozygous 896A/G genotype statistically differed between migraineurs and controls (25.3% vs. 8.2%, p=0.00002, OR 3.87, 95% CI; 2.02-7.4). Multivariate logistic regression analysis indicated that G allele in affected female migraineurs is an independent factor associated with increased risk of migraine (OR 3.2, 95% CI 1.23-8.24, p=0.01)., Conclusion: Our results showed TLR-4 polymorphism as a genetic risk factor for migraine. However, further studies in different populations are required to elucidate the precise role of TLR-4 896A/G mutation in susceptibility to migraine.

Neuroinflammation is a general innate defensive response to neurotropic pathogens, neurodegenerative diseases or brain injuries, brought about by active proinflammatory signaling by the glial cells (microglia and astrocytes). Because these inflammatory signaling pathways cross-talk with each other, drug targeting at any particular intermediate molecule is not effective. Network medicine is a network theory inspired approach in drug design, whereby various mathematical models are applied to identify plausible nodes within a signaling pathway simulated network important for drug targeting. There are many techniques involved in network medicine study; in this article we concentrate on the 'prioritization of protein clusters' responsible for a certain disorder. This approach aims to bring down the expenditure of resources of initial drug targeting against a complex pathological reaction, such as neuroinflammation, and also questions the cause at the molecular level., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Objectives: Asthma is a heterogenous complex disorder caused by chronic inflammation of the airways. The key issue in genetic association studies of complex disorders is the identification of multiple low-risk genes that individually have little impact on the phenotype, but in combination account for the clinical manifestation of asthma. Since neurogenic inflammation is emerging as a candidate factor in the pathogenesis of asthma, the aim of the study was to investigate whether genetic variants of neurotrophin genes are associated with asthma disease severity or asthma-related phenotypes in a pediatric population., Methods: We genotyped 27 polymorphisms located in neurotrophin genes, using TaqMan SNP genotyping assays or Polymerase Chain Reaction - Restriction Fragments Lengths Polymorphism (PCR-RFLP) in 200 children diagnosed with asthma and 226 controls. Interactions between 27 polymorphic loci and asthma-related phenotypes were determined using the Multifactor Dimensionality Reduction (MDR) method., Results: In single marker analysis, we observed an association of MAP3K1 gene polymorphisms (rs702689 and rs889312) with asthma. We also observed that four Single Nucleotide Polymorphisms (SNPs) were associated with severe asthma. Analysis stratified by asthma-related phenotype revealed an association between atopy and NGFR (rs3785931), while BDNF (rs7124442), NTRK2 (rs1212171), NGFR (rs2072446), and FYN (rs3730353) variants were associated with increased exhaled nitric oxide (exNO). In addition, gene-gene interaction analysis revealed a significant epistatic interaction between MAPK (rs889312) and NGF (rs11102930) variants in asthma susceptibility., Conclusions: Our results suggest that genetic variants of MAP3K1 and NGF genes involved in the regulation of neurogenic inflammation may contribute to asthma, possibly via enhanced NGF expression and MAPK signaling pathway activation.

Rosacea is a common skin disease with a high impact on quality of life. Characterized by erythema, edema, burning pain, immune infiltration, and facial skin fibrosis, rosacea has all the characteristics of neurogenic inflammation, a condition induced by sensory nerves via antidromically released neuromediators. To investigate the hypothesis of a central role of neural interactions in the pathophysiology, we analyzed molecular and morphological characteristics in the different subtypes of rosacea by immunohistochemistry, double immunofluorescence, morphometry, real-time PCR, and gene array analysis, and compared the findings with those for lupus erythematosus or healthy skin. Our results showed significantly dilated blood and lymphatic vessels. Signs of angiogenesis were only evident in phymatous rosacea. The number of mast cells and fibroblasts was increased in rosacea, already in subtypes in which fibrosis is not clinically apparent, indicating early activation. Sensory nerves were closely associated with blood vessels and mast cells, and were increased in erythematous rosacea. Gene array studies and qRT-PCR confirmed upregulation of genes involved in vasoregulation and neurogenic inflammation. Thus, dysregulation of mediators and receptors implicated in neurovascular and neuroimmune communication may be crucial at early stages of rosacea. Drugs that function on neurovascular and/or neuroimmune communication may be beneficial for the treatment of rosacea.

Over the past two decades, a convergence of basic and clinical evidence has established the neuropeptide calcitonin-gene-related peptide (CGRP) as a key player in migraine. Although CGRP is a recognised neuromodulator of nociception, its mechanism of action in migraine remains elusive. In this review, we present evidence that led us to propose that CGRP is well poised to enhance neurotransmission in migraine by both peripheral and central mechanisms. In the periphery, it is thought that local release of CGRP from the nerve endings of meningeal nociceptors following their initial activation by cortical spreading depression is critical for the induction of vasodilation, plasma protein extravasation, neurogenic inflammation and the consequential sensitisation of meningeal nociceptors. Mechanistically, we propose that CGRP release can give rise to a positive-feedback loop involved in localised increased synthesis and release of CGRP from neurons and a CGRP-like peptide called procalcitonin from trigeminal ganglion glia. Within the brain, the wide distribution of CGRP and CGRP receptors provides numerous possible targets for CGRP to act as a neuromodulator., (Copyright © Cambridge University Press 2011)

Transgenic mice with a small hairpin RNA construct interfering with the expression of transient receptor potential vanilloid 1 (TRPV1) were created by lentiviral transgenesis. TRPV1 expression level in transgenic mice was reduced to 8% while the expression of ankyrin repeat domain 1 (TRPA1) was unchanged. Ear oedema induced by topical application of TRPV1 agonist capsaicin was completely absent in TRPV1 knockdown mice. Thermoregulatory behaviour in relation to environmental thermopreference (30 vs. 35°C) was slightly impaired in male knockdown mice, but the reduction of TRPV1 function was not associated with enhanced hyperthermia. TRPV1 agonist resiniferatoxin induced hypothermia and tail vasodilatation was markedly inhibited in knockdown mice. In conclusion, shRNA-mediated knock down of the TRPV1 receptor in mice induced robust inhibition of the responses to TRPV1 agonists without altering the expression, gating function or neurogenic oedema provoked by TRPA1 activation. Thermoregulatory behaviour in response to heat was inhibited, but enhanced hyperthermia was not observed.

The unique physiology and function of neurons create differences in their cellular physiology, including their regulation of gene expression. We began several years ago exploring the relationships between the NFkappaB transcription factor, neuronal survival, and glutamate receptor activation in telencephalic neurons. These studies led us to conclude that this population of cells is nearly incapable of activating the NFkappaB that is nonetheless expressed at reasonable levels. A subset of the kappaB cis elements are instead bound by members of the Sp1 family in neurons. Also surprising was our discovery that Sp1 itself, typically described as ubiquitous, is severely restricted in expression within forebrain neurons; Sp4 seems to be substituted during neuronal differentiation. These findings and their implications for neuronal differentiation--as well as potential dedifferentiation during degenerative processes--are discussed here.

Objectives: The aim of this study was to investigate the role of the chemokine receptor CX3CR1 in headaches and migraine., Methods: Distribution of 2 polymorphisms of the chemokine receptor CX3CR1 (V249I and T280M) was determined in a population-based sample of 1179 elderly individuals., Results: Heterozygotes for both CX3CR1 polymorphisms had a reduced risk of recurrent headaches, with an odds ratio (OR) of 0.64 (95% confidence interval [CI] = 0.46-0.90) for the I249 allele and 0.55 (95% CI = 0.38-0.81) for the M280 allele. Haplotype analysis showed that carriers of the rarer CX3CR1 I249-M280 haplotype had a reduced risk of recurrent headaches, with an OR of 0.57 (95% CI = 0.41-0.80, P = .001). This association was seen for both nonmigraine headaches (OR = 0.47, 95% CI = 0.28-0.79, P = .004) and migraine (OR = 0.65, 95% CI = 0.43-0.98, P = .041)., Conclusions: These results need to be replicated but suggest that the chemokine receptor CX3CR1 may play a role in recurrent headaches.

Presentation of Ag bound to MHC class II (MHC II) molecules to CD4+ T cells is a key event in adaptive immune responses. Genetic differences in MHC II expression in the rat CNS were recently positioned to allelic variability in the CIITA gene (Mhc2ta), located within the Vra4 locus on rat chromosome 10. In this study, we have examined reciprocal Vra4-congenic strains on the DA and PVGav1 backgrounds, respectively. After experimental nerve injury the strain-specific MHC II expression on microglia was reversed in the congenic strains. Similar findings were obtained after intraparenchymal injection of IFN-gamma in the brain. Expression of MHC class II was also lower on B cells and dendritic cells from the DA.PVGav1-Vra4- congenic strain compared with DA rats after in vitro stimulation with IFN-gamma. We next explored whether Vra4 may affect the outcome of experimental autoimmune disease. In experimental autoimmune encephalomyelitis induced by immunization with myelin oligodendrocyte glycoprotein, DA.PVGav1-Vra4 rats displayed a lower disease incidence and milder disease course compared with DA, whereas both PVGav1 and PVGav1.DA-Vra4 rats were completely protected. These results demonstrate that naturally occurring allelic differences in Mhc2ta have profound effects on the quantity of MHC II expression in the CNS and on immune cells and that this genetic variability also modulates susceptibility to autoimmune neuroinflammation.

Antidromic stimulation of the rat trigeminal ganglion triggers the release of substance P (SP) and calcitonin gene-related peptide (CGRP) from sensory nerve terminals of the capsaicin sensitive C-fibers. These pro-inflammatory neuropeptides produce a marked hyperemia in the anterior segment of the eye, accompanied by increased intraocular pressure, breakdown of the blood-aqueous barrier and myosis. To assess the effects of neurogenic inflammation on the retina, specifically on the immunostaining of neurotransmitters and neurotrophins, as well as on the expression of neurotrophin receptors in the retina. RT-PCR was also accomplished in control and stimulated animals to confirm the immunohistochemical results. In the electrically stimulated eyes, immunostaining for SP, CGRP, VIP and nNOS demonstrated a marked increase in the RPE/POS (Retinal Pigment Epithelium/Photoreceptor Outer Segments), in the inner and outer granular layers and in the ganglion cells in comparison to the control eyes. CGRP and SP were found increased in stimulated animals and this result has been confirmed by RT- PCR. Changes in neurotrophin immunostaining and in receptor expression were also observed after electric stimulation of trigeminal ganglia. Decrease of BDNF and NT4 in the outer and inner layers and in ganglion cells was particularly marked. In stimulated rat retinas immunostaining and RT-PCR showed a NGF expression increase. Neurotrophin receptors remained substantially unchanged. These studies demonstrated, for the first time, that antidromic stimulation of the trigeminal ganglion and subsequent neurogenic inflammation affect immunostaining of retinal cell neurotransmitter/neuropeptides and neurotrophins as well as the expression of neurotrophin receptors.

Objectives: To investigate the level of nerve growth factor (NGF) mRNA in bladder tissue and the effect of botulinum toxin A (BTX-A) treatment in patients with interstitial cystitis (IC)., Methods: A total of 19 patients with IC were treated with 100 U or 200 U of intravesical BTX-A injections followed by cystoscopic hydrodistension 2 weeks later. Bladder mucosa biopsies were performed before BTX-A injection and immediately after hydrodilation and in 12 controls. The NGF mRNA and protein levels in bladder tissues were assessed by real-time polymerase chain reaction and immunohistochemistry studies to determine differences in NGF expression between patients with IC before and after BTX-A treatment and compare with controls., Results: At 3 months, 14 patients had symptomatic improvement (responders) and 5 did not (nonresponders). The NGF mRNA levels at baseline in the overall IC patient group were significantly greater than those in the controls (0.65 +/- 0.33 versus 0.42 +/- 0.25, P = 0.046). At 2 weeks after BTX-A treatment, the NGF mRNA levels had decreased to 0.47 +/- 0.23 (P = 0.002, compared with baseline) and were no longer significantly different from those of the controls. The NGF mRNA levels decreased significantly in responders and were significantly decreased after BTX-A in 11 patients with a visual analog pain scale reduction of 2 or more. The immunoreactivity study of bladder tissue from patients with IC showed greater NGF density at baseline compared with controls, but the difference was no longer significant after successful BTX-A treatment., Conclusions: Intravesical BTX-A injections plus hydrodistension reduce bladder pain in patients with IC. The NGF levels in the bladder tissue were significantly increased in patients with IC and decreased to normal level after treatment in responders.

Platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) is a 130-kDa protein, which plays a significant role in the adhesion cascade. It is therefore involved in leucocyte endothelium interaction and in leucocyte transendothelial migration during inflammation. As neuroinflammation and subsequent blood brain barrier disruption are integral processes in many neurological disorders, PECAM-1 and its soluble form (sPECAM-1) have been investigated in a number of conditions, rising hopes as a potential marker of disease activity, a possible target in treatment and a prognostic factor. It has been shown that serum and CSF levels of PECAM-1 and sPECAM-1 are increased in patients in active stages of multiple sclerosis. Similarly, they rise in individuals after ischaemic stroke. PECAM-1 has also been shown to be involved in the pathogenesis of Abeta-related cerebral vascular disorders, such as Alzheimer disease. It participates in the pathomechanism of paraneoplastic neurological disorders and in neuroinflammation in NeuroAIDS. A number of experiments on animal models were carried out in order to investigate PECAM-1 role in the above-mentioned conditions and more, including brain trauma and nerve root injury. In this review most recent investigations on PECAM-1 biology and its role in neuroinflammation have been described and discussed from a multidisciplinary point of view.

We and others have previously demonstrated that nociception in the mouse is heritable. A genetic correlation analysis of 12 common measures of nociception among a common set of inbred strains revealed three major clusters (or 'types') of nociception in this species. In the present study, we re-evaluated the major types of nociception and their interrelatedness using ten additional assays of nociception and hypersensitivity, including: three thermal assays (tail withdrawal from 47.5 degrees C water or -15 degrees C ethanol; tail flick from radiant heat), two chemical assays of spontaneous nociception (bee venom test; capsaicin test) and their subsequent thermal hypersensitivity states (including contralateral hypersensitivity in the bee venom test), a mechanical nociceptive assay (tail-clip test), and a mechanical hypersensitivity assay (intrathecal dynorphin). Confirming our earlier findings, the results demonstrate distinct thermal and chemical nociceptive types. It is now clear that mechanical hypersensitivity and thermal hypersensitivity are genetically dissociable phenomena. Furthermore, we now see at least two distinct types of thermal hypersensitivity: afferent-dependent, featuring a preceding significant period of spontaneous nociceptive behavior associated with afferent neural activity, and non-afferent-dependent. In conclusion, our latest analysis suggests that there are at least five fundamental types of nociception and hypersensitivity: (1) baseline thermal nociception; (2) spontaneous responses to noxious chemical stimuli; (3) thermal hypersensitivity; (4) mechanical hypersensitivity; and (5) afferent input-dependent hypersensitivity.

Sensitivity to pain is widely variable, and much of this variability is genetic in origin. The specific genes responsible have begun to be identified, but only for thermal nociception. In order to facilitate the identification of polymorphic, pain-related genes with more clinical relevance, we performed quantitative trait locus (QTL) mapping studies of the most common assay of inflammatory nociception, the formalin test. QTL mapping is a technique that exploits naturally occurring variability among inbred strains for the identification of genomic locations containing genes contributing to that variability. An F2 intercross was constructed using inbred A/J and C57BL/6J mice as progenitors, strains previously shown to display resistance and sensitivity, respectively, to formalin-induced nociception. Following phenotypic testing (5% formalin, 25 microl intraplantar injection), mice were genotyped at 90 microsatellite markers spanning the genome. We provide evidence for two statistically significant formalin test QTLs - chromosomal regions whose inheritance is associated with trait variability - on distal mouse chromosomes 9 and 10. Identification of the genes underlying these QTLs may illuminate the basis of individual differences in inflammatory pain, and lead to novel analgesic treatment strategies.