Ganglia Of Rats Research Articles

Mechanism of action of Shaoyao-Gancao decoction in relieving chronic inflammatory pain via Sema3G protein regulation in the dorsal root ganglion

ObjectiveThe purpose of this study was to analyze the impact of Shaoyao-Gancao decoction (SGD) on proteins with significant changes in the dorsal root ganglion (DRG) in rats and to explore the role of the Semaphorin 3G (Sema3G) protein in the DRG and its downstream factors, interleukin-6 (IL-6) and CC-motif chemokine ligand 2(CCL2), in the treatment of chronic inflammatory pain (CIP). MethodsWe created a CIP rat model using 100 μL of complete Freund's adjuvant (CFA) that was injected into the left posterior plantar of rats. Then, we administered SGD intragastrically. We tested the animals for behavioral changes and protein expression levels in DRG pre- and post-drug intervention. ResultsRats in the SGD group showed significantly increased paw withdrawal threshold (PWT), paw withdrawal latency (PWL), and relative expression levels of the Sema3G protein in the DRG (all P < 0.05), while the relative mRNA expression levels of IL-6 and CCL2 in the DRG of the rats were significantly decreased (P < 0.05) when compared with the model group. ConclusionIn this study, we found that Shaoyao-Gancao decoction was effective in improving the PWT and PWL of rats with CIP. It reduced CIP by upregulating the expression of Sema3G in the DRG and inhibiting the relative mRNA expression levels of IL-6 and CCL2.

Baimai Ointment relieves chronic pain induced by chronic compression of dorsal root ganglion in rats by regulating neuroactive ligand-receptor interaction and HIF-1 signaling pathway

The Baimai Ointment with the effect of relaxing sinew and activating collaterals demonstrates a definite effect on Baimai disease with pain, spasm, stiffness and other symptoms, while the pharmacodynamic characteristics and mechanism of this agent remain unclear. In this study, a rat model of chronic compression of L4 dorsal root ganglion(CCD) was established by lumbar disc herniation, and the efficacy and mechanism of Baimai Ointment in the treatment of CCD were preliminarily explored by behavioral tests, side effect evaluation, network analysis, antagonist and molecular biology verification. The pharmacodynamic experiment indicated that Baimai Ointment significantly improved the pain thresholds(mechanical pain, thermal pain, and cold pain) and gait behavior of CCD model rats without causing tolerance or obvious toxic and side effects. Baimai Ointment inhibited the second-phase nociceptive response of mice in the formalin test, increased the hot plate threshold of normal mice, and down-regulated the expression of inflammatory cytokines in the spinal cord. Network analysis showed that Baimai Ointment had synergistic effect in the treatment of CCD and was related to descending inhibition/facilitation system and neuroinflammation. Furthermore, behavioral tests, Western blot, and immunofluorescence assay revealed that the pain-relieving effect of Baimai Ointment on CCD may be related to the regulation of the interaction between neuroactive ligand and receptors(neuroligands) such as CHRNA7, ADRA2A, and ADRB2, and the down-regulation of the expression of NOS2/pERK/PI3K, the core regulatory element of HIF-1 signaling pathway in spinal microglia. The findings preliminarily reveal the mechanism of relaxing sinew and activating collaterals of Baimai Ointment in the treatment of Baimai disease, providing a reference for the rational drug use and further research of this agent.

Time-course of cardiac gene profiles post-acute lung injury

Abstract Patients suffering from acute lung injury (ALI) are at high risk of developing cardiac arrhythmias. In a recent study we demonstrated that bleomycin (Bleo)-induced ALI in rats exhibited significantly more spontaneous premature ventricular contractions (PVCs) from 1 to 3 weeks post induction. Although spontaneous PVCs disappeared at 4 weeks post ALI, PVCs were evoked again by electrical stimulation of the decentralized stellate ganglia in Bleo-exposed rats but not in normal rats. The molecular mechanisms underlying cardiac arrhythmia both post ALI and during the recovery of ALI remains unclear. In the current study, we aimed to utilize non-biased RNA-Seq analysis to discover the time-course changes in cardiac gene profiles both post ALI and during the recovery from ALI. We created an ALI rat model using a single tracheal instillation of bleomycin (2.5 mg/kg) with saline as a vehicle (Veh) control. Blood Troponin level was measured and compared between Veh- and Bleo-treated rats varied between W1 to Week 4 post Veh/Bleo. Cardiac tissues were harvested at W1 or W4 post Veh/Bleo for RNA-seq analysis and validation by real time RT-PCR. One week post ALI, cardiac Troponin was significantly increased in Bleo-treated rats whereas it was undetectable in Veh-treated rats. Cardiac Troponin was largely restored at W2 and was undetectable at W4 post ALI. RNA-seq analysis of the left ventricle (LV) indicated 85 downregulated and 147 upregulated genes at 1 W post ALI vs. Veh. Gene Ontology (GO) enrichment analysis demonstrated that genes related to chronic inflammatory signaling, cell adhesion signaling, and extracellular matrix (ECM) signaling pathways were upregulated at W1 post ALI, suggesting cardiac inflammation. Furthermore, genes related to oxygen carrier activity, oxygen binding and oxygen transport signaling were also significantly altered, which may be due to acute hypoxia caused by ALI. In contrast to W1, RNA-seq analysis at W4 post ALI detected a smaller number of altered genes, including 11 downregulated and 13 upregulated genes between ALI and Veh groups. Comparing these two RNA-Seq databases, 4 genes (i.e., Phactr3, Tgm1, Drd4, Selplg) were identified as changed in both the post ALI state and during the recovery from ALI. Following real time RT-PCR validation confirmed significant changes in these four gene mRNA expressions in both post ALI and during the recovery from ALI. Phactr3 was downregulated while Tgm1, Drd4 and Selplg genes were upregulated in cardiac tissues at w1 and w4 post ALI. Phactr3 gene encodes a member of the phosphatase and actin regulator protein family. Tgm1 plays an important role in stabilizing intercellular junctions in myocardial microvascular endothelial cells, by modulating β-actin filaments. Drd4 gene encodes the D4 subtype of the dopamine receptor. Selplg gene encodes a glycoprotein that regulates T lymphocytes. Future studies are needed to examine the functional roles of these genes in cardiac injury post ALI.

Pregabalin inhibits purinergic P2Y2 receptor and TRPV4 to suppress astrocyte activation and to relieve neuropathic pain

BackgroundsTransient receptor potential vanilloid 4 (TRPV4)-mediated astrocyte activation is critical to neuropathic pain. Pregabalin, a widely used drug to treat chronic pain, is reported to lower the intracellular calcium level. However, the molecular mechanism by which pregabalin decreases the intracellular calcium level remains unknown. Purinergic P2Y2 receptor—a member of the G protein-coupled receptor (GPCR) family—regulates calcium-related signal transduction in astrocyte activation. We investigated whether P2Y2 receptor is involved in the pharmacological effects of pregabalin on neuropathic pain. MethodsNeuropathic pain was induced by chronic compression of the dorsal root ganglion (CCD) in rats. Paw withdrawal mechanical threshold (PWMT) was used for behavioral testing. Intracellular calcium concentration was measured using a fluorescent calcium indicator (Fluo-4 AM). ResultsWe found that P2Y2 receptor protein was upregulated and astrocytes were activated in the experimental rats after CCD surgery. Lipopolysaccharide (LPS) increased the intracellular calcium concentration and induced astrocyte activation in cultured astrocytes but was prevented via P2Y2 receptor inhibitor AR-C118925 or pregabalin. Furthermore, plasmid-mediated P2Y2 receptor overexpression induced an elevation of the intracellular calcium levels and inflammation in astrocytes, which was abolished by the TRPV4 inhibitor HC-067047. AR-C118925, HC-067047, and pregabalin relieved neuropathic pain and inflammation in rats after CCD surgery. Finally, plasmid-mediated P2Y2 receptor overexpression induced neuropathic pain in rats, which was abolished by pregabalin administration. ConclusionsPathophysiological variables that upregulated the P2Y2 receptor/TRPV4/calcium axis contribute to astrocyte activation in neuropathic pain. Pregabalin exerts an analgesic effect by inhibiting this pathway.

Gap Junction Protein Connexin-43 in Glial Cells of Rat Dorsal Root Ganglion

The aim of this study was to assess the dynamics of distribution and localization of the gap junction protein connexin-43 (Cx43) in rat dorsal root ganglion (DRG) cells at different stages of postnatal ontogenesis to assess the morphological signs of age-related changes in intercellular interactions. The work was performed on Wistar rats at the age of 4 months and 18 months using immunohistochemical methods. Glial cells were detected using antibodies to glutamine synthetase, macrophages – using the antibodies to calcium-binding protein Iba-1. The paper describes the features of connexin-43 distribution in the spinal ganglion of young and old rats. It has been established that connexin-43-containing structures are identified mainly in satellite glial cells of young and aging animals. Sensitive neurons, as well as DRG macrophages of both groups of animals, do not show immunoreactivity. Analysis of age-related changes in intercellular contacts in rat DRG showed that plaques of connexin-43-containing protein channels that provide metabolic interaction of satellite cells in the spinal ganglia become more numerous with age. This fact may indicate the activation of the interaction between glial cells in the DRG of rats during aging.

Bergenin ameliorates chemotherapy-induced neuropathic pain in rats by modulating TRPA1/TRPV1/NR2B signalling

Chemotherapy-induced neuropathic pain (CINP) is one of the most prominent and incapacitating complication associated with chemotherapeutic regimens. The exact mechanisms underlying CINP are not fully understood yet, which hampers the development of effective therapeutics. The current study has been designed to investigate the effect of bergenin on CINP and dissect the underlying cellular and molecular mechanisms. Behavioural responsiveness assays were conducted in rats before and after CINP induction and at different time points post-bergenin treatment. We also measured alterations in tight junction proteins, pro-inflammatory cytokines, microglia activity, transient receptor potential (TRP) channels (TRPV1, TRPA1 and TRPM8) and N-methyl-D-aspartate receptor subtype 2 (NR2B) in dorsal root ganglion (DRG) and spinal tissues of neuropathic rats. Bergenin treatment leads to a significant and dose-dependent reduction in evoked and spontaneous ongoing pain without causing central side effects in neuropathic rats. Furthermore, treatment with bergenin and gabapentin did not affect the baseline pain threshold in healthy, non-chemotherapy-treated rats, as evaluated through tail-flick and tail-clip assays. Chemotherapy administration leads to a significant activation of TRP channels, concurrent with microglial activation, disruption of spinal cord tight junction proteins, and subsequent infiltration of pro-inflammatory cytokines, as well as NR2B activation. Notably, bergenin treatment effectively reversed all of these alterations, with the exception of TRPM8, in both the DRG and spinal cord of neuropathic rats. Findings from the present study suggests that bergenin mitigates neuropathic pain by modulating the TRPA1/TRPV1/NR2B signalling and presents a promising therapeutic avenue for the treatment of chemotherapy-induced neuropathic pain.

Age-dependent patterns of somatostatinergic neurons in sympathetic paravertebral ganglia

Aim. We aimed to determine the content of neurons expressing somatostatin (SST) and their colocalization with cells expressing tyrosine hydroxylase (TH) and neuropeptide Y (NPY) in the cranial cervical ganglion (CCG) and celiac plexus in rats. Material and methods. We used 30 white male Wistar rats of six age groups (5 rats per group): newborn pups, 10-, 20-, 30-, and 60-day-old pups, and 24-month-old pups. We incubated their ganglia sections with primary antibodies against SST, NPY, and TH, as well as with secondary antibodies conjugated with fluorochromes. We evaluated the ratio between immunoreactive (IR) neurons with a visible nucleolus and excessive fluorescence and the total number of neurons, as well as the average cross-sectional area, by ImageJ software (NIH, USA).Results. SST-IR neurons were not found in the CCG. However, the immunoreaction (as granules) was revealed in most perikaryons at the celiac plexus for SST and NPY with a rather homogeneous distribution for TH. The ratio of ST-IR neurons reached 33% in pups, doubled during the first month of life, and then remained constant (70–73%). No statistically significant differences were found between the ratios of SST-IR neurons of the cranial mesenteric ganglion (CMG) and celiac ganglion (CG) for all age groups. From the moment of birth to 60 days of life, the average cross-sectional area of SST-IR neurons in the CG and CMG increased by 3.4–3.9 times and then did not change until 24 months. From the 20th day of life, the average cross-sectional area of SST-IR neurons in the CG was significantly higher than that in the CMG. All SST-IR neurons in all age groups expressed TH, while 90–94% of neurons expressed NPY. Conclusions. The content of ST-IR neurons in different sympathetic nodes is not the same: they are absent in the CCG, and their ratio and area in the celiac plexus increase during early postnatal development. This may be due to the peculiarities of innervated target organs.

Loperamide, a peripheral Mu-Opioid receptor agonist, attenuates chemotherapy-induced neuropathic pain in rats

Opioids are employed in the management of chemotherapy-induced neuropathic pain (CINP) when other pain management approaches have failed and proven ineffective. However, their use in CINP is generally considered as a second-line or adjunctive therapy owing to their central side effects and development of tolerance with their long-term usage. Targeting peripheral sites may offer several advantages over the conventional CNS-based approaches as peripheral targets modulate pain signals at their source, thereby relieving pain with higher specificity, efficacy and minimizing adverse effects associated with off-site CNS actions. Therefore, present study was designed with an aim to investigate the effect of loperamide, a peripherally acting mu-opioid receptor agonist, on paclitaxel-induced neuropathic pain in rats and elucidate its underlying mechanism. Loperamide treatment significantly attenuated mechanical, and cold hypersensitivity and produced significant place preference behaviour in neuropathic rats indicating its potential to treat both evoked and spontaneous pain. More importantly, loperamide treatment in naïve rats did not produce place preference to drug-paired chamber pointing towards its non-addictive analgesic potential. Further, molecular investigations revealed increased expression of ion channels such as TRPA1, TRPM8; voltage-gated sodium channels (VGSCs) and neuroinflammatory markers in the dorsal root ganglion (DRG) and lumbar (L4-L5) spinal cord of neuropathic rats, which was significantly downregulated upon loperamide treatment. These findings collectively suggest that activation of peripheral mu-opioid receptors contributes to the amelioration of both evoked and spontaneous pain in neuropathic rats by downregulating TRP channels and VGSCs along with suppression of oxido-nitrosative stress and neuroinflammatory cascade.

PB0908 Therapeutic Efficacy of Platelet-Rich Plasma in Chronic Compression of the Dorsal Root Ganglion in Rat

PB0908 Therapeutic Efficacy of Platelet-Rich Plasma in Chronic Compression of the Dorsal Root Ganglion in Rat

Deciphering the dynamic characteristics of non-neuronal cells in dorsal root ganglion of rat at different developmental stage based on single cell transcriptome data

Dorsal root ganglia (DRG) is an essential part of the peripheral nervous system and the hub of the peripheral sensory afferent. The dynamic changes of neuronal cells and their gene expression during the development of dorsal root ganglion have been studied through single-cell RNAseq analysis, while the dynamic changes of non-neuronal cells have not been systematically studied. Using single cell RNA sequencing technology, we conducted a research on the non-neuronal cells in the dorsal root ganglia of rats at different developmental stage. In this study, primary cell suspension was obtained from using the dorsal root ganglions (DRGs, L4-L5) of ten 7-day-old rats and three 3-month-old rats. The 10×Genomics platform was used for single cell dissociation and RNA sequencing. Twenty cell subsets were acquired through cluster dimension reduction analysis, and the marker genes of different types of cells in DRG were identified according to previous researches about DRG single cell transcriptome sequencing. In order to find out the non-neuronal cell subsets with significant differences at different development stage, the cells were classified into different cell types according to markers collected from previous researches. We performed pseudotime analysis of 4 types Schwann cells. It was found that subtype Ⅱ Schwann cells emerged firstly, and then were subtype Ⅲ Schwann cells and subtype Ⅳ Schwann cells, while subtype Ⅰ Schwann cells existed during the whole development procedure. Pseudotime analysis indicated the essential genes influencing cell fate of different subtypes of Schwann cell in DRG, such as Ntrk2 and Pmp2, which affected cell fate of Schwann cells during the development period. GO analysis of differential expressed genes showed that the up-regulated genes, such as Cst3 and Spp1, were closely related to biological process of tissue homeostasis and multi-multicellular organism process. The down regulated key genes, such as Col3a1 and Col4a1, had close relationship with the progress of extracellular structure organization and negative regulation of cell adhesion. This suggested that the expression of genes enhancing cell homestasis increased, while the expression of related genes regulating ECM-receptor interaction pathway decreased during the development. The discovery provided valuable information and brand-new perspectives for the study on the physical and developmental mechanism of Schwann cell as well as the non-neuronal cell changes in DRG at different developmental stage. The differential gene expression results provided crucial references for the mechanism of somatosensory maturation during development.

In vivo tracing of the ascending vagal projections to the brain with manganese enhanced magnetic resonance imaging.

The vagus nerve, the primary neural pathway mediating brain-body interactions, plays an essential role in transmitting bodily signals to the brain. Despite its significance, our understanding of the detailed organization and functionality of vagal afferent projections remains incomplete. In this study, we utilized manganese-enhanced magnetic resonance imaging (MEMRI) as a non-invasive and in vivo method for tracing vagal nerve projections to the brainstem and assessing their functional dependence on cervical vagus nerve stimulation (VNS). Manganese chloride solution was injected into the nodose ganglion of rats, and T1-weighted MRI scans were performed at both 12 and 24 h after the injection. Our findings reveal that vagal afferent neurons can uptake and transport manganese ions, serving as a surrogate for calcium ions, to the nucleus tractus solitarius (NTS) in the brainstem. In the absence of VNS, we observed significant contrast enhancements of around 19-24% in the NTS ipsilateral to the injection side. Application of VNS for 4 h further promoted nerve activity, leading to greater contrast enhancements of 40-43% in the NTS. These results demonstrate the potential of MEMRI for high-resolution, activity-dependent tracing of vagal afferents, providing a valuable tool for the structural and functional assessment of the vagus nerve and its influence on brain activity.

Auditory Neurons on the Silk Road – spider silk for bridging the nerve-electrode-gap

Abstract The cochlear implant (CI) restores hearing to patients with severe to profound sensorineural hearing loss by stimulating the spiral ganglion neurons (SGN). Due to the inner ear anatomy, a fluid-filled gap remains between the SGN and the electrode array. This gap impedes focused stimulation and thus optimized performance with the CI. Regenerating neurites may bridge this fluid-filled gap for a direct nerveelectrode- link but require a supportive matrix. Spider silk might be a suitable candidate for this support. Therefore, silk fibers were tested for biocompatibility with inner ear neuronal tissue, suitability as neurite outgrowth matrix and applicability to the CI-electrode array. Dragline silk from female Trichonephila spiders was woven around a frame and autoclaved. Spiral ganglia of young rats were prepared, cut and placed in a drop of medium on the parallel silk fibers for pre-cultivation to support adherence before remaining medium was added. After 5d of cultivation, cells were fixed and immunocytologically stained. For CIapplication, silk was wrapped around a silicone dummy and a one-sided spacer. Opposite the spacer, alginate-hydrogel was applied for silk-fixation and -shielding. After gelation, silk loops were cut in the middle to form protruding threads. Cells showed a high degree of migration and neurite regeneration along the silk fibers and in some cases the outgrown neurites directly contacted the silk. It was possible to fix the silk to the dummy as protruding fibers. The tested spider silk is compatible with the inner ear tissue in culture, supports cell growth and seems to be an attractive material for neurite contacting. Application to the CI as protruding fibers is possible, making it a promising candidate for structural support to bridge the nerve-electrode-gap.

Increased expression of Nav1.6 of reactive astrocytes in the globus pallidus is closely associated with motor deficits in a model of Parkinson's disease.

Parkinson's disease (PD) is a common neurodegenerative disease in elderly people, which is characterized by motor disabilities in PD patients. Nav1.6 is the most abundant subtype of voltage-gated sodium channels (VGSCs) in the brain of adult mammals and rodents. Here we investigated the role of Nav1.6 in the external globus pallidus (GP) involved in the pathogenesis of motor deficits in unilateral 6-OHDA(6-hydroxydopamine)lesioned rats. The results show that Nav1.6 is dramatically increased in reactive astrocytes of the ipsilateral GP in the middle stage, but not different from the control rats in the later stage of the pathological process in 6-OHDA lesioned rats. Furthermore, the down-regulation of Nav1.6 expression in the ipsilateral GP can significantly improve motor deficits in 6-OHDA lesioned rats in the middle stage of the pathological process. The electrophysiological experiments show that the down-regulation of Nav1.6 expression in the ipsilateral GP significantly decreases the abnormal high synchronization between the ipsilateral M1 (the primary motor cortex) and GP in 6-OHDA lesioned rats. Ca2+ imaging reveals that the down-regulation of Nav1.6 expression reduces the intracellular concentration of Ca2+ ([Ca2+ ]i) in primary cultured astrocytes. These findings suggest that the increased Nav1.6 expression of reactive astrocytes in the GP play an important role in the pathogenesis of motor dysfunction in the middle stage in 6-OHDA lesioned rats, which may participate in astrocyte-neuron communication by regulating [Ca2+ ]i of astrocytes, thereby contributing to the formation of abnormal electrical signals of the basal ganglia (BG) in 6-OHDA lesioned rats.

Time-Course Progression of Whole Transcriptome Expression Changes of Trigeminal Ganglia Compared to Dorsal Root Ganglia in Rats Exposed to Nerve Injury

Mechanisms underlying neuropathic pain (NP) are complex with multiple genes, their interactions, environmental and epigenetic factors being implicated. Transcriptional changes in the trigeminal (TG) and dorsal root (DRG) ganglia have been implicated in the development and maintenance of NP. Despite efforts to unravel molecular mechanisms of NP, many remain unknown. Also, most of the studies focused on the spinal system. Although the spinal and trigeminal systems share some of the molecular mechanisms, differences exist. We used RNA-sequencing technology to identify differentially expressed genes (DEGs) in the TG and DRG at baseline and 3 time points following the infraorbital or sciatic nerve injuries, respectively. Pathway analysis and comparison analysis were performed to identify differentially expressed pathways. Additionally, upstream regulator effects were investigated in the two systems. DEG (differentially expressed genes) analyses identified 3,225 genes to be differentially expressed between TG and DRG in naïve animals, 1,828 genes 4 days post injury, 5,644 at day 8 and 9,777 DEGs at 21 days postinjury. A comparison of top enriched canonical pathways revealed that a number of signaling pathway was significantly inhibited in the TG and activated in the DRG at 21 days postinjury. Finally, CORT upstream regulator was predicted to be inhibited in the TG while expression levels of the CSF1 upstream regulator were significantly elevated in the DRG at 21 days postinjury. This study provides a basis for further in-depth studies investigating transcriptional changes, pathways, and upstream regulation in TG and DRG in rats exposed to peripheral nerve injuries. PerspectiveAlthough trigeminal and dorsal root ganglia are homologs of each other, they respond differently to nerve injury and therefore treatment. Activation/inhibition of number of biological pathways appear to be ganglion/system specific suggesting that different approaches might be required to successfully treat neuropathies induced by injuries in spinal and trigeminal systems.

Role of mass effect on neuronal iron deposition after intracerebral hemorrhage

Mass effect after intracerebral hemorrhage (ICH) not only mechanically induces the brain damage, but also influences the progress of secondary brain damage. However, the influence of mass effect on the iron overload after ICH is still unclear. Here, a fixed volume of ferrous chloride solution and different volumes of poly(N-isopropylacrylamide) (PNIPAM) hydrogel were co-injected into the right basal ganglia of rats to establish the ICH model with certain degree of iron deposition but different degrees of mass effect. We found that mass effect significantly increased the iron deposition on neuronal cells at 6 h after ICH in a volume-dependent manner. Furthermore, the upregulation of Piezo-2, divalent metal transporter 1 (DMT1), transferrin receptor (TfR), and ferroptosis expressions were noted as the increase of mass effect. In addition, the pERK1/2 inhibitor PD98059 treated ICH rats reversed the upregulation of iron uptake protein and ferroptosis. Our findings revealed the relationship between mass effect and the iron uptake and ferroptosis, which are benefit to understand the brain damage process after ICH.

STING-IFN-I pathway relieves incision induced acute postoperative pain via inhibiting the neuroinflammation in dorsal root ganglion of rats.

The purpose of this study was to study the effect of STING-IFN-I pathway on incision induced postoperative pain in rats and its possible mechanisms. The pain thresholds were evaluated by measuring the mechanical withdrawal threshold and the thermal withdrawal latency. The satellite glial cell and macrophage of DRG were analyzed. The expression of STING, IFN-a, P-P65, iNOS, TNF-α, IL-1β and IL-6 in DRG was evaluated. The activation of STING-IFN-I pathway can reduce the mechanical hyperalgesia, thermal hyperalgesia, down-regulate the expression of P-P65, iNOS, TNF-α, IL-1β and IL-6, and inhibit the activation of satellite glial cell and macrophage in DRG. The activation of STING-IFN-I pathway can alleviate incision induced acute postoperative pain by inhibiting the activation of satellite glial cell and macrophage, which reducing the corresponding neuroinflammation in DRG.

TMEM100 Regulates Neuropathic Pain by Reducing the Expression of Inflammatory Factors.

There is no effective treatment for peripheral nerve injury-induced chronic neuropathic pain (NP), which profoundly impacts the quality of life of those affected. Transmembraneprotein100 (TMEM100) is considered to be a pain regulatory protein and is expressed in the dorsal root ganglion (DRG) of rats. However, the mechanism of pain regulation and the expression of TMEM100 following various peripheral nerve injuries are unclear. In this study, we constructed two pain models of peripheral nerve injury: tibial nerve injury (TNI) and chronic constriction injury (CCI). This study found that the Paw Withdrawal Mechanical Threshold (PWMT) and Paw Withdraw Thermal Latency (PWTL) of the rats in the two pain models decreased significantly, and the expression of TMEM100 in the DRG of two groups also decreased significantly. Furthermore, the decrease in the CCI group was more obvious than in the TNI group. There was no significant statistical significance (P > 0.05). We constructed an adeno-associated virus 6 (AAV6) vector expressing recombinant fluorescent TMEM100 protein and injected it into the sciatic nerve (SN) of two pain models: CCI and TNI. PWMT and PWTL were significantly increased in the two groups, along with the expression of TMEM100 in the spinal cord and DRG. It also significantly inhibited the activation of microglia, astrocytes, and several inflammatory mediators (TNF- α, IL-1 β, and IL-6). In summary, the results of this study suggested that TMEM100 might be a promising molecular strategy for the treatment of NP, and its anti-inflammatory effects might play an important role in pain relief.

Aging exaggerates pulpal pain sensation by increasing the expression levels of nociceptive neuropeptides and inflammatory cytokines

BackgroundDental pain is a main clinical problem in the elderly population and its assessment and treatment make special challenges for health care services. However, the age-induced alteration in dental pain perception and the underlying molecular mechanism(s) has not yet been fully clarified. MethodsHere, the effect of aging on nociceptive behaviors following inflammatory dental pulp pain was evaluated. Since prostaglandins, nociceptive neuropeptides, and inflammatory cytokines have critical roles in the development of aging as well as pain signaling, the expression levels of COX-2, CGRP, IL-1β, IL-6, TNF-α and its converting enzyme TACE were assessed in the trigeminal ganglion of young and aged rats with dental pain. Dental pulp pain was induced by intradental application of capsaicin (100 μg). The immunofluorescence (COX-2 and CGRP) and western blot techniques were used. ResultsThe data showed that aged animals have different pattern of pain. So that, the mean of nociceptive scores was significantly greater in aged rats at 10 and 15 min after capsaicin injection. In aged rats, dental pain was persisting over 7 h, while it was disappeared at 300 min in young rats. Molecular data showed that dental pain significantly increased the expression of COX-2, CGRP, IL-1β, IL-6, TNF-α and TACE in the trigeminal ganglion of the young and aged rats. In addition, the amount of those parameters, except TACE, in capsaicin-treated aged animals were significantly (p < 0.05) greater than those in capsaicin-treated young rats. ConclusionIt seems that the induction of pro-inflammatory cytokines in an acute inflammatory pulpal pain model may contribute, at least in part to the increased nociceptive behaviors and pain perception in aged rats.

Perampanel ameliorates nitroglycerin-induced migraine through inhibition of the cAMP/PKA/CREB signaling pathway in the trigeminal ganglion in rats.

Perampanel, a highly selective glutamate AMPA receptor antagonist, is widely used to treat epilepsy. Since the existence of common pathophysiological features between epilepsy and migraine, the aim of this study was to investigate whether perampanel could exert an antimigraine effect. Nitroglycerin (NTG) was used to induce a migraine model in rats, and the model animals were pretreatment with 50 μg/kg and 100 μg/kg perampanel. The expression of pituitary adenylate-cyclase-activating polypeptide (PACAP) was quantified by western blot and quantitative real-time PCR in the trigeminal ganglion, and rat-specific enzyme-linked immunosorbent assay in serum. Western blot was also conducted to explore the effects of perampanel treatment on the phospholipase C (PLC)/protein kinase C (PKC) and protein kinase A (PKA)/cAMP-responsive-element-binding protein (CREB) signaling pathways. Moreover, the cAMP/PKA/CREB-dependent mechanism was evaluated via in vitro stimulation of hippocampal neurons. The cells were treated with perampanel, antagonists and agonists for 24 hours and cell lysates were prepared for western blot analysis. Perampanel treatment notably increased the mechanical withdrawal threshold and decreased head grooming and light-aversive behaviors in NTG-treated rats. It also decreased PACAP expression and affected cAMP/PKA/CREB signaling pathway. However, PLC/PKC signaling pathway may not be involved in this treatment. In in vitro studies, perampanel notably decreased PACAP expression by inhibiting cAMP/PKA/CREB signaling pathway. This study shows that perampanel inhibits the migraine-like pain response and that this beneficial effect might be attributable to regulation of the cAMP/PKA/CREB signaling pathway.

485-P: Proteomic Analysis Reveals Different Therapeutic Mechanisms for Diabetic Neuropathy between DPP-4 Inhibitor and SGLT2 Inhibitor

Aim: Diabetic neuropathy (DN) is the most prevalent complication with microangiopathy in diabetes. Although, DN would decrease quality of life, currently there is no radical treatment for DN. DPP-4 inhibitor (DP4i) and SGLT-2 inhibitor (SG2i) have been experimentally shown to possibly ameliorate DN. However, the difference in the mechanism between two agents has not been clarified so far. In this study, we performed proteomic analysis of the sciatic nerve (SN) and dorsal root ganglion (DRG) of Goto-Kakizaki rats (GK), a model of lean type 2 diabetes, treated with DP4i and/or SG2i. Methods: Male GK and control Wister rats (W) were used. Since 5 weeks of age, GK rats were treated with 10mg/day DP4i (Te), 10mg/ day SG2i (Ca), and DP4i + SG2i (CaTe) until 29 weeks of age. Thermal perception was evaluated by tail flick test. At the end of experiment, SN, DRG, and skin tissue were dissected. Proteomic analysis was performed with SN and DRG tissues by mass spectrometry. In the skin, fluorescent immunostaining with anti-PGP 9.5 antibody was performed for the assessment of intraepidermal nerve density (IENFD). Results: Tail flick test and IENFD were significantly decreased in GK compared to W (p&amp;lt;0.05), and significantly improved in Te, Ca, and CaTe (p&amp;lt;0.05, p&amp;lt;0.05 and p&amp;lt;0.01 vs GK, respectively). Proteomic analysis for SN showed only two pathways changed in Te, whereas seven and six pathways changed in the Ca and CaTe, respectively. Conversely, in the DRG, only two pathways changed in Ca, whereas the five and seven pathways changed in Te and CaTe, respectively. Conclusion: Our results suggest that the DP4i and SG2i act on the different sites of peripheral nervous system with different mechanism. Combining these two agents possibly have complementary effects on DPN treatment. Disclosure Y.Takeuchi: None. S.Osonoi: None. T.Sasaki: None. H.Mizukami: None. Funding Mitsubishi Tanabe Pharma Corporation