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BACKGROUND: The characterization of neuropathic pain is maladaptive plasticity within the nociceptive system. Multiple alterations contribute to complex pain phenotypes. Adrenomedullin (AM) has been documented to be a pain mediator. However, its involvement in pathological pain is poorly understood. We studied the contribution of AM to chronic neuropathic pain in the spinal nerve ligation (SNL) model. METHODS: Daily injection of the AM receptor antagonist AM22-52 (10 nmol) via an intrathecal (i.t.) route after SNL inhibited mechanical allodynia starting on day 6. Single administration of AM22-52 produced an immediate attenuation on pain hypersensitivity on day 2 or 10 post-SNL. Protein and mRNA levels were assayed by immunofluorescent staining and qRT-PCR, respectively, on days 1, 3, 7 and 15 post-SNL. RESULTS: The results showed that AM at both protein and mRNA levels was increased in both injured (L5) and adjacent uninjured (L4) nerves starting on day 3 post-SNL. In dorsal root ganglion (DRG) at L5, AM was increase on days 1-7 at mRNA level but only on day 7 at protein level. However, AM was increase at mRNA level on days 1-7 and at protein level on days 3-15 in L4 DRG. AM mRNA expression was upregulated on days 1-7 in the spinal cord. Expression of receptor activity-modifying protein 2 (RAMP2), an essential AM1 receptor component, was upregulated in small and medium-diameter neurons on days 1-15 in both L5 and L4 DRG. Furthermore, single administration of AM22-52 suppressed the increase of nNOS in DRG induced by SNL and daily injection of AM22-52 for 7 days inhibited SNL-induced increase of CGRP mRNA in the spinal dorsal horn. CONCLUSIONS: This study indicates that the increased AM bioactivity in injured and uninjured peripheral nerves, uninjured adjacent DRG and the spinal dorsal horn play a critical role mainly in the late-phase development of neuropathic pain. The mechanism may involve the recruitment of nNOS and CGRP. ispartof: FRONTIERS IN BIOSCIENCE-LANDMARK vol:27 issue:7 ispartof: location:Singapore status: published

Background: The delta opioid receptor (DOR) contributes to pain control, and a major challenge is the identification of DOR populations that control pain, analgesia, and tolerance. Astrocytes are known as important cells in the pathophysiology of chronic pain, and many studies report an increased prevalence of pain in women. However, the implication of astrocytic DOR in neuropathic pain and analgesia, as well as the influence of sex in this receptor activity, remains unknown. Experimental Approach: We developed a novel conditional knockout (cKO) mouse line wherein DOR is deleted in astrocytes (named GFAP-DOR-KO), and investigated neuropathic mechanical allodynia as well as analgesia and analgesic tolerance in mutant male and female mice. Neuropathic cold allodynia was also characterized in mice of both sexes lacking DOR either in astrocytes or constitutively. Results: Neuropathic mechanical allodynia was similar in GFAP-DOR-KO and floxed DOR control mice, and the DOR agonist SNC80 produced analgesia in mutant mice of both sexes. Interestingly, analgesic tolerance developed in cKO males and was abolished in cKO females. Cold neuropathic allodynia was reduced in mice with decreased DOR in astrocytes. By contrast, cold allodynia was exacerbated in full DOR KO females. Conclusions: These findings show that astrocytic DOR has a prominent role in promoting cold allodynia and analgesic tolerance in females, while overall DOR activity was protective. Altogether this suggests that endogenous- and exogenous-mediated DOR activity in astrocytes worsens neuropathic allodynia while DOR activity in other cells attenuates this form of pain. In conclusion, our results show a sex-specific implication of astrocytic DOR in neuropathic pain and analgesic tolerance. These findings open new avenues for developing tailored DOR-mediated analgesic strategies. This work has been funded by the European Commission Seventh Framework programmes FP7-Health-2013-Innovation under grant agreement 1602919 (CG-R), FP7-Health-2013-Innovation under grant agreement F2-602891 (RM, MM-N, DC, CG-R); by Frame program Investissements d’Avenir ANR-10-IDEX-0002-02 and ANR-10-LABX-0030-INRT (YH, CG-R). The work was supported by Université de Strasbourg (CG-R) and CNRS (YH).

The NAV1.7 channel, encoded by Scn9a gene, is a voltage-gated sodium channel that plays a critical role in the generation and conduction of action potentials. In peripheral sensory neurons, the expression and dynamic regulation of SCN9A is involved in pain sensitivity and chronic pain development. Several SCN9A gain-of-function mutations have been found in chronic pain pa-tients with idiopathic small fiber neuropathy (SFN). Recently, loss-of-function of SCN9A due to bi-allelic inactivating mutations results in the striking clinical phenotype of congenital insensitivity to pain (CIP). These individuals do not perceive pain in response to noxious stimuli. However, the heterozygous carriers of one inactivating mutation have normal pain sensitivity. The generation of animal models with CRISPR/Cas9 gene editing is an important tool for investigating the role of a mutation in the pathogenesis of disease and provide an avenue for functional drug screening. We have successfully established two mouse models, one carrying the R185H patient-derived mutation and the second one, R185X carrying an early stop in the open reading frame in the Scn9a locus R185X/+ using the CRISPR/Cas9 technology. We have characterized the effect of these two mutations on pain sensitivity and molecular and cellular alteration. The two mouse lines showed no alteration of growth, survival and global health state. Pain sensitivity of the new mu-tant mouse line was investigated on both sexes using behavioral tests of sensitivity to thermal and mechanical stimuli. Our results indicate that the Scn9aR185H mice show an increased pain phenotype, suggesting that the Scn9aR185H mutation identified in the SFN patients is responsi-ble for their pain symptoms. This exploration will benefit to drug screen. However, Scn9aR185X/+ mice did not show normal pain phenotype rather they are less sensitive to heat. In these mice, one Scn9a allele is not functional. Therefore, we provide more evidence that SCN9A plays an important role in nociception and in painful idiopathic SFN., Au cours de ce projet de doctorat, nous avons créé un modèle de souris pour la mutation Scn9aR185H identifiée chez les patients douloureux souffrant de neuropathie à petite fibre grâce à l’approche CRISPR/Cas9 et nous avons étudié les conséquences sur la sensibilité à la douleur. Le modèle murin Scn9aR185H a permis d’explorer l'association génotype-phénotype et le mécanisme de la mutation des canaux sodiques NAV1.7 et le modèle Scn9aR185X/wt d’explorer l’effet de l’inactivation d’un allèle du gène Scn9a. Ces deux lignées de souris n'ont montré aucune altération de la croissance, de la survie et de l'état de santé global. Nous avons montré qu'il n'y a pas de différence dans l'expression de l'ARNm de Scn9a dans les DRG (ganglions de la racine dorsale), la moelle épinière, le cerveau et le cervelet chez les souris Scn9aR185H, et une diminution de l’expression chez les souris Scn9aR185X/wt. La sensibilité à la douleur de ces nouvelles lignées de souris mutantes a été étudiée chez les deux sexes à l'aide de tests comportementaux de sensibilité aux stimuli thermiques et mécaniques. Nos résultats indiquent que globalement les souris Scn9aR185H présentent un phénotype douloureux, suggérant que la mutation Scn9aR185H identifiée chez les patients SFN contribue à leurs symptômes douloureux. Ces résultats pourront servir à la recherche de nouveaux analgésiques. Les souris Scn9aR185X/wt sont moins sensibles à la douleur de type chaleur. Chez ces souris, un allèle Scn9a n'est pas fonctionnel. Par conséquent, nous avons montré par nos approches génétiques que le canal SCN9A joue un rôle crucial dans la nociception et dans les pathologies SFN douloureuses.

Migraine is a common neurovascular disease which has been classified as the sixth most disabling disorder. Current migraine therapy was triptans, however, riptans can cause contraction of blood vessels. Therefore, novel drugs without cardiovascular effects emerged, such as CGRP and selective 5-HT1F receptor agonists. In this work, a series of pyridinylmethylenepiperidine derivatives were designed, synthesized and evaluated for their 5-HT1F receptor agonist activity. The results in vitro showed that compound C1–C6 displayed potent agonist activities compared with positive drug lasmiditan. Pharmacokinetic properties in rat indicated that 2,4,6-trifluoro-N-(6-(fluoro(1-methylpiperidin-4-ylidene)methyl)pyridin-2-yl)benzamide (C5) possessed high AUC and good bioavailability. In two rodent models of migraine, C5 significantly inhibited dural plasma protein extravasation and c-fos expression in the trigeminal nucleus caudalis. Moreover, C5 showed no effect on vasoconstriction. Through these studies, we identified C5 as a potent 5-HT1F receptor agonist for migraine therapy.

A series of novel 1-(4-(piperazin-1-yl)phenyl)pyridin-2(1H)-one derivatives were synthesized and evaluated for their serotonin (5-HT) reuptake inhibitory activity. The results in vitro indicated that most of the evaluated compounds displayed potent 5-HT reuptake inhibition. The most promising compound A20 was stable in human liver microsomes and possessed good pharmacokinetic properties. Antidepressant study in vivo of the compound A20 showed that A20 could potently antagonize the p-chloroamphetamine (PCA)-induced depletion of serotonin in hypothalamus and reduce immobility times in the rat forced swimming test (FST).

In this work, ultrathin MoS2 nanosheets were prepared via a solid-state reaction route. The structure and morphology of the obtained samples were characterized by x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The influences of the reaction durations and raw materials molar ratio on the sizes and morphologies of the MoS2 nanostructures were discussed. And according to the experimental results, a formation mechanism of the ultrathin MoS2 nanosheets was proposed. The tribological behaviors of the synthesized MoS2 samples as additives in paraffin oil were determined on an UMT-2 tribometer. The experimental results indicated that the obtained samples possessed great anti-friction and anti-wear properties as lubrication additive in paraffin oil.