Proteomic Analysis of the Hippocampus in Mouse Models of Trigeminal Neuralgia and Inescapable Shock-Induced Depression

Nerve Regeneration Potential of Antioxidant-Modified Black Phosphorus Quantum Dots in Peripheral Nerve Injury

Peripheral nerve injury is a major societal concern. Black phosphorus (BP) has inherent advantages over cell-based therapies in regenerative medicine. However, controlling spontaneous degradation and size-dependent cytotoxicity remains challenging and poses difficulties for clinical translation. In this study, we constructed zero-dimensional BP quantum dots (QDs) modified with antioxidant β-carotene and comprehensively investigated them in Schwann cells (SCs) to elucidate their potential for peripheral nerve repair. In vitro experiments demonstrated that BPQD@β-carotene has an inappreciable toxicity and good biocompatibility, favoring neural regrowth, angiogenesis, and inflammatory regulation of SCs. Furthermore, the PI3K/Akt and Ras/ERK1/2 signaling pathways were activated in SCs at the genetic, protein, and metabolite levels. The BPQD@β-carotene-embedded GelMA/PEGDA scaffold enhanced functional recovery by promoting axon remyelination and regeneration and facilitating intraneural angiogenesis in peripheral nerve injury models of rats and beagle dogs. These results contribute to advancing knowledge of BP nanomaterials in tissue regeneration and show significant potential for application in translational medicine.

Neuroproteomics: Unveiling the Molecular Insights of Psychiatric Disorders with a Focus on Anxiety Disorder and Depression

Anxiety and depression are two of the most common mental disorders worldwide, with a lifetime prevalence of up to 30%. These disorders are complex and have a variety of overlapping factors, including genetic, environmental, and behavioral factors. Current pharmacological treatments for anxiety and depression are not perfect. Many patients do not respond to treatment, and those who do often experience side effects. Animal models are crucial for understanding the complex pathophysiology of both disorders. These models have been used to identify potential targets for new treatments, and they have also been used to study the effects of environmental factors on these disorders. Recent proteomic methods and technologies are providing new insights into the molecular mechanisms of anxiety disorder and depression. These methods have been used to identify proteins that are altered in these disorders, and they have also been used to study the effects of pharmacological treatments on protein expression. Together, behavioral and proteomic research will help elucidate the factors involved in anxiety disorder and depression. This knowledge will improve preventive strategies and lead to the development of novel treatments.

SHED-derived exosomes attenuate trigeminal neuralgia after CCI of the infraorbital nerve in mice via the miR-24-3p/IL-1R1/p-p38 MAPK pathway

BACKGROUND

Microglial activation in the spinal trigeminal nucleus (STN) plays a crucial role in the development of trigeminal neuralgia (TN). The involvement of adenosine monophosphate-activated protein kinase (AMPK) and N-methyl-D-aspartate receptor 1 (NMDAR1, NR1) in TN has been established. Initial evidence suggests that stem cells from human exfoliated deciduous teeth (SHED) have a potential therapeutic effect in attenuating TN. In this study, we propose that SHED-derived exosomes (SHED-Exos) may alleviate TN by inhibiting microglial activation. This study sought to assess the curative effect of SHED-Exos administrated through the tail vein on a unilateral infraorbital nerve chronic constriction injury (CCI-ION) model in mice to reveal the role of SHED-Exos in TN and further clarify the potential mechanism.

RESULTS

Animals subjected to CCI-ION were administered SHED-Exos extracted by differential ultracentrifugation. SHED-Exos significantly alleviated TN in CCI mice (increasing the mechanical threshold and reducing p-NR1) and suppressed microglial activation (indicated by the levels of TNF-α, IL-1β and IBA-1, as well as p-AMPK) in vivo and in vitro. Notably, SHED-Exos worked in a concentration dependent manner. Mechanistically, miR-24-3p-upregulated SHED-Exos exerted a more significant effect, while miR-24-3p-inhibited SHED-Exos had a weakened effect. Bioinformatics analysis and luciferase reporter assays were utilized for target gene prediction and verification between miR-24-3p and IL1R1. Moreover, miR-24-3p targeted the IL1R1/p-p38 MAPK pathway in microglia was increased in CCI mice, and participated in microglial activation in the STN.

CONCLUSIONS

miR-24-3p-encapsulated SHED-Exos attenuated TN by suppressing microglial activation in the STN of CCI mice. Mechanistically, miR-24-3p blocked p-p38 MAPK signaling by targeting IL1R1. Theoretically, targeted delivery of miR-24-3p may offer a potential strategy for TN.

Asymmetric activation of microglia in the hippocampus drives anxiodepressive consequences of trigeminal neuralgia in rodents

BACKGROUND AND PURPOSE

Patients suffering from trigeminal neuralgia are often accompanied by anxiety and depression. Microglia-mediated neuroinflammation is involved in the development of neuropathic pain and anxiodepression pathogenesis. Whether and how microglia are involved in trigeminal neuralgia-induced anxiodepression remains unclear.

EXPERIMENTAL APPROACH

Unilateral constriction of the infraorbital nerve (CION) was performed to establish trigeminal neuralgia in rat and mouse models. Mechanical allodynia and anxiodepressive-like behaviours were measured. Optogenetic and pharmacological manipulations were employed to investigate the role of hippocampal microglia in anxiety and depression caused by trigeminal neuralgia.

KEY RESULTS

Trigeminal neuralgia activated ipsilateral but not contralateral hippocampal microglia, up-regulated ipsilateral hippocampal ATP and interleukin-1β (IL-1β) levels, impaired ipsilateral hippocampal long-term potentiation (LTP) and induced anxiodepressive-like behaviours in a time-dependent manner in rodents. Pharmacological or optogenetic inhibition of ipsilateral hippocampal microglia completely blocked trigeminal neuralgia-induced anxiodepressive-like behaviours. Activation of unilateral hippocampal microglia directly elicited an anxiodepressive state and impaired hippocampal LTP. Knockdown of ipsilateral hippocampal P2X7 receptors prevented trigeminal neuralgia-induced microglial activation and anxiodepressive-like behaviours. Furthermore, we demonstrated that microglia-derived IL-1β mediated microglial activation-induced anxiodepressive-like behaviours and LTP impairment.

CONCLUSION AND IMPLICATIONS

These findings suggest that priming of microglia with ATP/P2X7 receptors in the ipsilateral hippocampus drives pain-related anxiodepressive-like behaviours via IL-1β. An asymmetric role of the bilateral hippocampus in trigeminal neuralgia-induced anxiety and depression was uncovered. The approaches targeting microglia and P2X7 signalling might offer novel therapies for trigeminal neuralgia-related anxiety and depressive disorder.

Electroacupuncture alleviates orofacial allodynia and anxiety-like behaviors by regulating synaptic plasticity of the CA1 hippocampal region in a mouse model of trigeminal neuralgia

Objective

Trigeminal neuralgia (TN), one of the most severe and debilitating chronic pain conditions, is often accompanied by mood disorders, such as anxiety and depression. Electroacupuncture (EA) is a characteristic therapy of Traditional Chinese Medicine with analgesic and anxiolytic effects. This study aimed to investigate whether EA ameliorates abnormal TN orofacial pain and anxiety-like behavior by altering synaptic plasticity in the hippocampus CA1.

Materials and methods

A mouse infraorbital nerve transection model (pT-ION) of neuropathic pain was established, and EA or sham EA was used to treat ipsilateral acupuncture points (GV20-Baihui and ST7-Xiaguan). Golgi-Cox staining and transmission electron microscopy (TEM) were administrated to observe the changes of synaptic plasticity in the hippocampus CA1.

Results

Stable and persistent orofacial allodynia and anxiety-like behaviors induced by pT-ION were related to changes in hippocampal synaptic plasticity. Golgi stainings showed a decrease in the density of dendritic spines, especially mushroom-type dendritic spines, in hippocampal CA1 neurons of pT-ION mice. TEM results showed that the density of synapses, membrane thickness of the postsynaptic density, and length of the synaptic active zone were decreased, whereas the width of the synaptic cleft was increased in pT-ION mice. EA attenuated pT-ION-induced orofacial allodynia and anxiety-like behaviors and effectively reversed the abnormal changes in dendritic spines and synapse of the hippocampal CA1 region.

Conclusion

EA modulates synaptic plasticity of hippocampal CA1 neurons, thereby reducing abnormal orofacial pain and anxiety-like behavior. This provides evidence for a TN treatment strategy.

MiR-223-3p alleviates trigeminal neuropathic pain in the male mouse by targeting MKNK2 and MAPK/ERK signaling

BACKGROUND

Trigeminal neuralgia (TN) is a neuropathic pain that occurs in branches of the trigeminal nerve. MicroRNAs (miRNAs) have been considered key mediators of neuropathic pain. This study was aimed to elucidate the pathophysiological function and mechanisms of miR-223-3p in mouse models of TN.

METHODS

Infraorbital nerve chronic constriction injury (CCI-ION) was applied in male C57BL/6J mice to establish mouse models of TN. Pain responses were assessed utilizing Von Frey method. The expression of miR-223-3p, MKNK2, and MAPK/ERK pathway protein in trigeminal ganglions (TGs) of CCI-ION mice was measured using RT-qPCR and Western blotting. The concentrations of inflammatory cytokines were evaluated using Western blotting. The relationship between miR-223-3p and MKNK2 was tested by a luciferase reporter assay.

RESULTS

We found that miR-223-3p was downregulated, while MKNK2 was upregulated in TGs of CCI-ION mice. MiR-223-3p overexpression by an intracerebroventricular injection of Lv-miR-223-3p attenuated trigeminal neuropathic pain in CCI-ION mice, as well as reduced the protein levels of pro-inflammatory cytokines in TGs of CCI-ION mice. MKNK2 was verified to be targeted by miR-223-3p. Additionally, miR-223-3p overexpression decreased the phosphorylation levels of ERK1/2, JNK, and p38 protein in TGs of CCI-ION mice to inhibit MAPK/ERK signaling.

CONCLUSIONS

Overall, miR-223-3p attenuates the development of TN by targeting MKNK2 to suppress MAPK/ERK signaling.

Review about Powerful Combinations of Advanced and Hyphenated Sample Introduction Techniques with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) for Elucidating Trace Element Species in Pathologic Conditions on a Molecular Level

Element analysis in clinical or biological samples is important due to the essential role in clinical diagnostics, drug development, and drug-effect monitoring. Particularly, the specific forms of element binding, actual redox state, or their spatial distribution in tissue or in single cells are of interest in medical research. This review summarized exciting combinations of sophisticated sample delivery systems hyphenated to inductively coupled plasma-mass spectrometry (ICP-MS), enabling a broadening of information beyond the well-established outstanding detection capability. Deeper insights into pathological disease processes or intracellular distribution of active substances were provided, enabling a better understanding of biological processes and their dynamics. Examples were presented from spatial elemental mapping in tissue, cells, or spheroids, also considering elemental tagging. The use of natural or artificial tags for drug monitoring was shown. In the context of oxidative stress and ferroptosis iron, redox speciation gained importance. Quantification methods for Fe2+, Fe3+, and ferritin-bound iron were introduced. In Wilson’s disease, free and exchangeable copper play decisive roles; the respective paragraph provided information about hyphenated Cu speciation techniques, which provide their fast and reliable quantification. Finally, single cell ICP-MS provides highly valuable information on cell-to-cell variance, insights into uptake of metal-containing drugs, and their accumulation and release on the single-cell level.

Connexin 36 Mediates Orofacial Pain Hypersensitivity Through GluK2 and TRPA1

Trigeminal neuralgia is a debilitating condition, and the pain easily spreads to other parts of the face. Here, we established a mouse model of partial transection of the infraorbital nerve (pT-ION) and found that the Connexin 36 (Cx36) inhibitor mefloquine caused greater alleviation of pT-ION-induced cold allodynia compared to the reduction of mechanical allodynia. Mefloquine reversed the pT-ION-induced upregulation of Cx36, glutamate receptor ionotropic kainate 2 (GluK2), transient receptor potential ankyrin 1 (TRPA1), and phosphorylated extracellular signal regulated kinase (p-ERK) in the trigeminal ganglion. Cold allodynia but not mechanical allodynia induced by pT-ION or by virus-mediated overexpression of Cx36 in the trigeminal ganglion was reversed by the GluK2 antagonist NS102, and knocking down Cx36 expression in Nav1.8-expressing nociceptors by injecting virus into the orofacial skin area of Nav1.8-Cre mice attenuated cold allodynia but not mechanical allodynia. In conclusion, we show that Cx36 contributes greatly to the development of orofacial pain hypersensitivity through GluK2, TRPA1, and p-ERK signaling.

Activation of ventrolateral orbital cortex improves mouse neuropathic pain-induced anxiodepression

Depression and anxiety are frequently observed in patients suffering from neuropathic pain. The underlying mechanisms remained unclear. The ventrolateral orbital cortex (VLO) has attracted considerable interest in its role in antidepressive effect in rodents. In the present study, we further investigated the role of the VLO in the anxiodepressive consequences of neuropathic pain in a chronic constriction injury of infraorbital nerve-induced trigeminal neuralgia (TN) mouse model. Elevated plus maze, open field, forced swimming, tail suspension, and sucrose preference tests were used to evaluate anxiodepressive-like behaviors. The results show that chemogenetic activation of bilateral VLO neurons, especially CaMK2A+ pyramidal neurons, blocked the TN-induced anxiodepressive-like behaviors. Chemogenetic and optogenetic activation of VGLUT2+ or inhibition of VGAT+ VLO neurons was sufficient to produce an antianxiodepressive effect in TN mice. Pharmacological activation of D1-like receptors (D1Rs) but not D2Rs in the VLO significantly alleviated TN-induced depressive-like behaviors. Electrophysiological recordings revealed a decreased excitability of VLO excitatory neurons following neuropathic pain. Furthermore, activation of submedius thalamic nucleus-VLO (Sm-VLO) projection mimicked the antianxiodepressive effect of VLO excitation. Conversely, activation of VLO-periaqueductal gray matter (PAG) projection had no effect on TN-induced anxiodepressive behaviors. This study provides a potentially novel mechanism-based therapeutic strategy for the anxiodepressive consequences of neuropathic pain.

Mu-Opioid Receptors Expressed in Glutamatergic Neurons are Essential for Morphine Withdrawal

Although opioids still remain the most powerful pain-killers, the chronic use of opioid analgesics is largely limited by their numerous side-effects, including opioid dependence. However, the mechanism underlying this dependence is largely unknown. In this study, we used the withdrawal symptoms precipitated by naloxone to characterize opioid dependence in mice. We determined the functional role of mu-opioid receptors (MORs) expressed in different subpopulations of neurons in the development of morphine withdrawal. We found that conditional deletion of MORs from glutamatergic neurons expressing vesicular glutamate transporter 2 (Vglut2⁺) largely eliminated the naloxone-precipitated withdrawal symptoms. In contrast, conditional deletion of MORs expressed in GABAergic neurons had a limited effect on morphine withdrawal. Consistently, mice with MORs deleted from Vglut2⁺ glutamatergic neurons also showed no morphine-induced locomotor hyperactivity. Furthermore, morphine withdrawal and morphine-induced hyperactivity were not significantly affected by conditional knockout of MORs from dorsal spinal neurons. Taken together, our data indicate that the development of morphine withdrawal is largely mediated by MORs expressed in Vglut2⁺ glutamatergic neurons.

Depressive-like state sensitizes 5-HT1A and 5-HT1B auto-receptors in the dorsal raphe nucleus sub-system

Dorsal raphe (DR) and median raphe (MR) 5-HT neurons are two distinct sub-systems known to be regulated by 5-HT_1A and 5-HT_1B auto-receptors. Whether the auto-receptors in each sub-system are functionally altered in depressive-like state remains unknown. The present study is aimed to study a specific circuit (DR-ventral hippocampus and MR-dorsal hippocampus) within each sub-system to investigate changes in receptor sensitivity in the pathogenesis of depression. A mouse model of depression was developed through the social defeat paradigm, and was then treated with fluoxetine (FLX). 5-HT_1A auto-receptor in the neuronal cell body (DR or MR) and 5-HT_1B auto-receptor in the axonal terminal (ventral or dorsal hippocampus) were directly targeted by local perfusion of antagonists (5-HT_1A: WAY100635; 5-HT_1B: GR127935) through reverse microdialysis. Time courses of dialysate 5-HT measured at the axonal terminal were subsequently determined for each circuit. At baseline, 5-HT_1A and 5-HT_1B antagonists dose-dependently increased dialysate 5-HT, with sub-circuit specificity. In the depressive-like state, greater increases in dialysate 5-HT were observed only in the DR-ventral hippocampus circuit following local delivery of both antagonists, which were then fully restored following the FLX treatment. In contrast, no changes were observed in the MR-dorsal hippocampus circuit. Our results demonstrate differential changes in sensitivities of 5-HT_1A and 5-HT_1B auto-receptors in the DR-ventral hippocampus and MR-dorsal hippocampus circuits. 5-HT_1A and 5-HT_1B auto-receptors in the DR-ventral hippocampus circuit are sensitized in the depressive-like state. Taken together, these results suggest that the DR sub-system maybe the neural substrate mediating depressive phenotypes.

Effects of long non-coding RNA Gm14461 on pain transmission in trigeminal neuralgia

Background

This study aims to investigate the role of long non-coding RNA Gm14461 in regulating pain transmission in trigeminal neuralgia (TN). The mouse TN model was produced by chronic constriction injury of the infraorbital nerve (CCI-ION). The values of mechanical withdrawal threshold (MWT) were measured to assess the nociception of mice at different times after CCI-ION surgery (0, 1, 3, 5, 7, 9, 11, 13, 15 d). The primary mouse trigeminal ganglion neurons (TGNs) were isolated from C57BL/6 J mice and treated with TNF-α to mimic a TN cellular model. The expression of Gm14461, TNF-α, IL-1β, and IL-6 was examined using qRT-PCR. The protein levels of CGRP and P2X3/7 receptor were measured using western blot.

Results

Gm14461 expression was increased in trigeminal ganglia (TGs) of TN mice on the operation side. Furthermore, Gm14461 knockdown in TGs increased, whereas Gm14461 overexpression decreased MWT in TN mice. Moreover, Gm14461 knockdown downregulated, whereas Gm14461 overexpression upregulated mRNA levels of TNF-α, IL-1β, and IL-6 and protein levels of CGRP and P2X3/7 receptor in TGs from TN mice. In vitro assay showed that Gm14461 was upregulated by TNF-α, IL-1β, and IL-6. Additionally, Gm14461 knockdown decreased protein levels of CGRP and P2X3/7 receptor in TNF-α-treated TGNs, whereas Gm14461 overexpression exerted the opposite effect.

Conclusion

Gm14461 promoted pain transmission (reduced MWT value) in a CCI-ION-induced mouse TN model. The underlying mechanisms might involve the regulation of pro-inflammatory cytokines, CGRP and P2X3/7 receptor.

Lysine methylation regulates nervous system diseases

Lysine methylation is an important dynamic modification which is essential in the epigenetic regulation of gene transcription. Unlike acetylation markers, lysine methylation signals at gene promoters could be viewed as markers that either activate or silence gene expression in different contexts or states. This article briefly reviews lysine methylation sites involved in nervous system diseases. The methyltransferases and demethylases which cause abnormal methylation signals in nervous system diseases are also discussed. Methylated proteins correlated with nervous system biological processes are extracted from databases and known writer-code-eraser patterns are analyzed, which could provide insight into the design of methylation-based interference peptides for the investigation of nervous system diseases.

Pretreatment with resveratrol ameliorate trigeminal neuralgia by suppressing matrix metalloproteinase-9/2 in trigeminal ganglion

Trigeminal neuralgia (TN) is a common type of neuropathic pain whereas the underlying pathogenesis has not been completely elucidated. Recent study suggests that the development of neuroinflammation is responsible for generating and sustaining neuropathic pain. The purpose of our study was to investigate the protective effect of intervening the inflammation in early stages of pain and explore its potential mechanism. MMP-9 and MMP-2 are vital proinflammatory participants and accumulating evidence indicates that they are involved in the early development of neuropathic pain. In this study, we found that MMP-9/2 showed different temporal up regulation in trigeminal ganglion (TG) significantly after chronic constriction injury (CCI) surgery. However, the activation of MMP-9/2 were suppressed by the pretreatment with resveratrol, which delayed and attenuated CCI-induced mechanical allodynia simultaneously. Besides, the expression of proinflammatory cytokines like IL-1β and TNF-α as well as the excessive neuronal activity induced by CCI were suppressed by resveratrol. Moreover, we believed that the inhibition of MMP-9/2 activation and pain sensitization may be related to the TLR-4/NF-κB signaling pathway, which might be negatively regulated by the induction of SOCS3. In conclusion, pretreatment with resveratrol could be an effective approach to alleviate trigeminal neuralgia in early stages via a powerful inhibition on the activation of MMP-9/2 in TG.

Melatonin Augments the Effects of Fluoxetine on Depression-Like Behavior and Hippocampal BDNF-TrkB Signaling

Depression is a debilitating psychiatric disorder with a huge socioeconomic burden, and its treatment relies on antidepressants including selective serotonin reuptake inhibitors (SSRIs). Recently, the melatonergic system that is closely associated with the serotonergic system has been implicated in the pathophysiology and treatment of depression. However, it remains unknown whether combined treatment with SSRI and melatonin has synergistic antidepressant effects. In this study, we applied a sub-chronic restraint stress paradigm, and evaluated the potential antidepressant effects of combined fluoxetine and melatonin in adult male mice. Sub-chronic restraint stress (6 h/day for 10 days) induced depression-like behavior as shown by deteriorated fur state, increased latency to groom in the splash test, and increased immobility time in the forced-swim test. Repeated administration of either fluoxetine or melatonin at 10 mg/kg during stress exposure failed to prevent depression-like phenotypes. However, combined treatment with fluoxetine and melatonin at the selected dose attenuated stress-induced behavioral abnormalities. Moreover, we found that the antidepressant effects of combined treatment were associated with the normalization of brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling in the hippocampus, but not in the prefrontal cortex. Our findings suggest that combined fluoxetine and melatonin treatment exerts synergistic antidepressant effects possibly by restoring hippocampal BDNF-TrkB signaling.