Combination of autophagy and NFE2L2/NRF2 activation as a treatment approach for neuropathic pain

CMPK2 facilitates pain sensitization by promoting the lactylation and deactivation of cGAS-STING pathway in neuropathic pain

Neuropathic pain, a complex condition arising from nerve damage, presents significant challenges in pain management, driving extensive research into its molecular mechanisms. Our mRNA microarray analysis identified cytosine monophosphate kinase 2 (CMPK2) as a key player in the progression of neuropathic pain, but the molecular mechanism remains to be elusive. By western blotting and Q-PCR, we observed a notable upregulation of CMPK2, particularly in microglia of the spinal dorsal horn during neuropathic pain. In vivo and in vitro experiments demonstrated that Cmpk2 deficiency significantly alleviated neuropathic pain and neural injury by increasing the production of type I interferons (IFN-I), which are known for their analgesic properties. Conversely, overexpression of Cmpk2 in microglia led to a marked decrease in IFN-I production in vitro. Further investigation revealed that the transcription factor RUNX1 promoted CMPK2 upregulation in microglia. Mechanistically, we found that CMPK2 exacerbated neuropathic pain by enhancing glycolysis in microglia, resulting in increased lactate production. This accumulation of lactate induced lactylation and deactivation of the stimulator of interferon genes (STING), which was responsible for IFN-I production. These findings suggested that CMPK2 facilitated pain sensitization by promoting microglial glycolysis, resulting in the increased lactylation and deactivation of the cGAS-STING pathway in neuropathic pain, highlighting the potential of targeting CMPK2 for therapeutic intervention in neuropathic pain.

Deficiency of Toll-like receptor 4 attenuates airway inflammation and remodeling in an ovalbumine-induced mouse asthma model

Background

Previous research has demonstrated elevated levels of Toll-like receptor 4 (TLR4) in the lung tissues of asthmatic mice compared to healthy counterparts, with a notable association between asthmatic inflammation and the sustained activation of the nuclear factor kappa-B (NF-κB) pathway. The specific role of TLR4 in modulating airway inflammation and remodeling, however, remains unclear. This study aimed to explore the impact of TLR4 deficiency on airway inflammation and remodeling in an ovalbumin (OVA)-induced mouse asthma model and to elucidate the underlying mechanisms involved.

Methods

To induce murine airway remodeling, an acute OVA sensitization and challenge protocol was employed. Pathological alterations in the lung tissues were assessed using hematoxylin and eosin, periodic acid-Schiff, and Masson trichrome staining.

Results

Our findings indicated that there were significant reductions in inflammatory cell infiltration in TLR4 knockout (KO) mice, including eosinophils, lymphocytes, neutrophils and the levels of Th2 cytokines interleukin-4, 5, 13 (IL-4, IL-5, IL-13), while showing increased expression of Th1 cytokines [interferon-gamma (IFN-γ)] and a higher T-bet/GATA-3 ratio. Furthermore, TLR4 deficiency markedly decreased airway mucous production, collagen deposition and airway smooth muscle thickness, all of which are strongly associated with airway remodeling. Additionally, TLR4 KO enhanced inhibitor of NF-κB (IκB) protein expression in lung tissues, suggesting an inhibition of the TLR4/NF-κB pathway.

Conclusions

These results demonstrate that TLR4 deficiency attenuates airway inflammation and remodeling, potentially through the inhibition of the TLR4/NF-κB signaling pathway in an OVA-induced mouse asthma model.

Zearalenone (ZEN) impairs motor function and induces neurotoxicity via inflammatory pathways: Evidence from zebrafish models and molecular docking studies

ZEN is a low-molecular-weight food contaminant that is frequently detected in various crops and regions due to its high thermal stability and persistence. It poses a significant threat to the biological nervous system. However, the molecular mechanisms underlying ZEN-induced neurotoxicity remain incompletely understood. To further explore this issue, this study focused on the effects of ZEN on the nervous system, particularly its key targets and related molecular mechanisms. The study combined network toxicology and molecular docking methods and performed behavioral analysis of zebrafish larvae exposed to ZEN. Firstly, motor capacity tests revealed that ZEN exposure significantly reduced the overall movement speed of zebrafish larvae during both photoperiod and dark cycles. We then identified 141 potential targets associated with ZEN-induced neurotoxicity from the GeneCards, OMIM, and DrugBank databases. Further screening using STRING and Cytoscape software extracted 25 key nodes, including TP53, AKT1, CASP3, MAPK3, and NFKB1. Analysis of GO and KEGG pathways suggested 20 of the most relevant signaling pathways and indicated that the core targets of ZEN-induced neurotoxicity were primarily involved in inflammatory pathways. Molecular docking using AutoDock further confirmed the strong binding affinity between ZEN and the targets. All six core target proteins exhibited strong binding affinity with ZEN, with binding energies of less than -7. In summary, the results of this study suggest that ZEN may impact cognitive dysfunction and neuropathy by activating neuroinflammatory signaling pathways, ultimately leading to neuronal death. This study provides important insights into the molecular mechanisms of ZEN-induced neurotoxicity and highlights the potential for prevention and treatment of diseases associated with exposure to ZEN and similar food contaminants.

Guizhi Fuling capsules can alleviate bortezomib-induced peripheral neuropathy by decreasing Interleukin-6 levels to regulate mTOR pathway-induced autophagy

OBJECTIVE

To investigate the therapeutic effect and underlying mechanism of Guizhi Fuling capsule (GZFL) on bortezomib-induced peripheral neuropathy (BiPN).

MATERIALS AND METHODS

Interleukin-6 (IL-6) levels in the plasma of Multiple myeloma (MM) patients were measured by ELISA, and correlation analysis between IL-6 and clinical features of BiPNs was performed. Then, we assess the clinical therapeutic effects of GZFL on MM patients by detecting IL-6 level, PN grade, FACT score, VAS score, MVC and SCV before and after the treatment. A combination of LC/MS and network pharmacology analysis was used to investigate the components and targets of GZFL. Then, bioinformatics was carried out. After PC12 cells were treated with GZFL, a BiPN cell model was constructed to evaluate cell autophagy function by cell viability, IL-6 levels, ROS levels, immunofluorescence staining of LC3 puncta, electron transmission electron microscopy (TEM), and Western blotting (WB). C57BL/6 mice were administered bortezomib by intraperitoneal injection to establish a model of BiPN. Nerve injury in BiPN mice was observed by measuring ethology, motor nerve conduction velocity, and IL-6. ROS, HE staining. TEM, western blotting and IHC were used to detect the expression of autophagy-related indexes.

RESULTS

In BiPN patients, IL-6 levels were positively correlated with the PN and FACT, VAS scores. Collectively, GZFL can alleviate BiPN by reducing the level of IL-6, which is mainly manifested in the decline of PN grade, FACT, VAS score and the improvement of MVC and SCV. Thirty-four components and 107 targets of GZFL for BiPN were obtained. IL-6, mTOR, and AKT1 showed high degree values, and the significantly enriched signaling pathways were closely related to inflammatory factors and autophagy pathways, such as TNF and the mTOR signaling pathway. GZFL significantly decreased IL-6 levels in cell and animal models of BiPN. For the autophagy test, GZFL increased PC12 cell ability and the numbers of LC3 puncta and autophagic vesicles after bortezomib treatment. In vivo experiments showed that GZFL effectively improved the behavior of mice with BiPN and alleviated sciatic nerve injury. WB and IHC showed that GZFL enhanced autophagy, as indicated by the alteration of autophagy-related protein levels in PC12 cells and sciatic nerve tissue.

CONCLUSION

The present study confirmed that GZFL significantly ameliorates peripheral neuropathy by regulating autophagy levels via alleviating high levels of IL-6 .

TRIAL REGISTRATION

The link to the registration: Chinese Clinical Trial Registry (https://www.chictr.org.cn/bin/project/edit?pid=214832). The name of the trial register is "The role of mitochondrial autophagy in multiple myeloma peripheral neuropathy and the application of traditional Chinese medicine for warming Yang and removing blood stasis". The clinical trial registration number is ChiCTR2400088065.

Mechanisms and Therapeutic Potential of GPX4 in Pain Modulation

Pain, a complex symptom encompassing both sensory and emotional dimensions, constitutes a significant global public health issue. Oxidative stress is a pivotal factor in the complex pathophysiology of pain, with glutathione peroxidase 4 (GPX4) recognized as a crucial antioxidant enzyme involved in both antioxidant defense mechanisms and ferroptosis pathways. This review systematically explores GPX4's functions across various pain models, including neuropathic, inflammatory, low back, and cancer-related pain. Specifically, the focus includes GPX4's physiological roles, antioxidant defense mechanisms, regulation of ferroptosis, involvement in signal transduction pathways, and metabolic regulation. By summarizing current research, we highlight the potential of GPX4-targeted therapies in pain management.

Exploring the role of ubiquitination modifications in migraine headaches

Migraine is a complex neurovascular disorder whose pathogenesis involves activation of the trigeminal vascular system, central and peripheral sensitization, and neuroinflammation. Calcitonin gene-related peptide (CGRP) plays a dominant role and activation of MAPK and NF-κB signaling pathways regulates neuropeptide release, glial cell activation, and amplification of nociceptive signals. Aberrant activation of these pathways drives migraine onset and chronicity. The ubiquitin-proteasome system (UPS) is involved in neurological and inflammatory disorders. ubiquitination in the UPS is achieved through a cascade of enzymes, including Ub-activating enzyme (E1), Ub-coupling enzyme (E2), and Ub-ligase (E3). The aim of this review is to systematically explore the role of ubiquitination in the regulation of MAPK and NF-κB signaling pathways, with a focus on the mechanisms of ubiquitinating enzymes in neuroinflammation and pain signal amplification, and to explore their potential as diagnostics, biomarkers, predictors of response to therapy, and monitoring of chronicity in migraine disease.

Actl6a regulates autophagy via Sox2-dependent Atg5 and Atg7 expression to inhibit apoptosis in spinal cord injury

INTRODUCTION

Spinal cord injury (SCI) is a severe central nervous system disorder with limited treatment options. While autophagy plays a protective role in neural repair, its regulatory mechanisms in SCI remain unclear. Actin-like protein 6A (Actl6a) influences cell fate and neural development, yet its specific role in SCI repair is not well understood. This study investigates Actl6a's function in regulating autophagy and apoptosis via the transcription factor Sox2 in SCI.

OBJECTIVES

This study aims to determine if Actl6a promotes neural survival post-SCI by regulating autophagy-related genes Atg5 and Atg7 through Sox2. It also examines how the demethylase Fto modulates Actl6a mRNA stability via m6A methylation.

METHODS

In vitro experiments were conducted using primary neurons and HT-22 hippocampal cells exposed to hydrogen peroxide (H2O2)-induced oxidative stress. Actl6a expression was manipulated by knockdown or overexpression. For in vivo studies, a rat SCI model was established with AAV-Actl6a injected at the injury site to induce Actl6a overexpression. Autophagy and apoptosis markers were analyzed using immunofluorescence, Western blotting, and qPCR. Additionally, m6A dot blot and RNA immunoprecipitation (RIP) assays were performed to assess Fto's role in regulating Actl6a mRNA methylation and stability.

RESULTS

Actl6a expression significantly decreased after SCI, resulting in increased apoptosis. Overexpressing Actl6a enhanced autophagy, reduced apoptosis, and improved neurological function in SCI models. Mechanistically, Actl6a and Sox2 collaboratively upregulated Atg5 and Atg7 expression, promoting autophagy. Fto's modulation of Actl6a mRNA stability via m6A demethylation further influenced autophagy and apoptosis.

CONCLUSION

Actl6a, through interaction with Sox2, plays a critical role in modulating autophagy and reducing apoptosis in SCI, with Fto's m6A modification affecting Actl6a stability. This Fto/Actl6a/Sox2 axis is a promising therapeutic target for SCI repair.

The Role of Intravenous Anesthetics for Neuro: Protection or Toxicity?

The primary intravenous anesthetics employed in clinical practice encompass dexmedetomidine (Dex), propofol, ketamine, etomidate, midazolam, and remimazolam. Apart from their established sedative, analgesic, and anxiolytic properties, an increasing body of research has uncovered neuroprotective effects of intravenous anesthetics in various animal and cellular models, as well as in clinical studies. However, there also exists conflicting evidence pointing to the potential neurotoxic effects of these intravenous anesthetics. The role of intravenous anesthetics for neuro on both sides of protection or toxicity has been rarely summarized. Considering the mentioned above, this work aims to offer a comprehensive understanding of the underlying mechanisms involved both in the central nerve system (CNS) and the peripheral nerve system (PNS) and provide valuable insights into the potential safety and risk associated with the clinical use of intravenous anesthetics.

Proteostasis disruption and senescence in Alzheimer's disease pathways to neurodegeneration

Alzheimer's Disease (AD) is a progressive neurological disease associated with behavioral abnormalities, memory loss, and cognitive impairment that cause major causes of dementia in the elderly. The pathogenetic processes cause complex effects on brain function and AD progression. The proper protein homeostasis, or proteostasis, is critical for cell health. AD causes the buildup of misfolded proteins, particularly tau and amyloid-beta, to break down proteostasis, such aggregates are toxic to neurons and play a critical role in AD pathogenesis. The rise of cellular senescence is accompanied by aging, marked by irreversible cell cycle arrest and the release of pro-inflammatory proteins. Senescent cell build-up in the brains of AD patients exacerbates neuroinflammation and neuronal degeneration. These cells senescence-associated secretory phenotype (SASP) also disturbs the brain environment. When proteostasis failure and cellular senescence coalesce, a cycle is generated that compounds each other. While senescent cells contribute to proteostasis breakdown through inflammatory and degradative processes, misfolded proteins induce cellular stress and senescence. The principal aspects of the neurodegenerative processes in AD are the interaction of cellular senescence and proteostasis failure. This review explores the interconnected roles of proteostasis disruption and cellular senescence in the pathways leading to neurodegeneration in AD.

Targeting ferroptosis in the neurovascular unit: A promising approach for treating diabetic cognitive impairment

The cognitive decline associated with chronic metabolic disease diabetes has garnered extensive scrutiny, yet its pathogenesis remains incompletely understood, and the advancement of targeted therapeutics has posed a persistent challenge. Ferroptosis, a novel form of cell death characterized by intracellular lipid peroxidation and iron overload, has recently emerged as a significant factor. Numerous contemporary studies have corroborated that ferroptosis within the neurovascular unit is intimately associated with the onset of diabetes-induced cognitive impairment. Numerous contemporary studies have corroborated that ferroptosis within the neurovascular unit is intimately associated with the onset of diabetic cognitive impairment (DCI). This article initially conducts a profound analysis of the mechanism of ferroptosis, followed by a detailed elucidation of the specific manifestations of neurovascular unit ferroptosis in the context of diabetic cognitive function impairment. Furthermore, an exhaustive review of pertinent literature from April 2020 to March 2024 has been undertaken, resulting in the selection of 31 documents of significant reference value. These documents encompass studies on 11 distinct drugs, all of which are centered around investigating methods to inhibit the ferroptosis pathway as a potential treatment for DCI. Simultaneously, we conducted a review of 12 supplementary literary sources that presented 10 pharmacological agents with anti-ferroptosis properties in other neurodegenerative disorders. This article critically examines the potential influence of neurovascular unit ferroptosis on the progression of cognitive impairment in diabetes, from the three aforementioned perspectives, and organizes the existing and potential therapeutic drugs. It is our aspiration that this article will serve as a theoretical foundation for scholars in related disciplines when conceptualizing, investigating, and developing novel clinical drugs for DCI.

TMEM16A Activation Inhibits Autophagy in Dorsal Root Ganglion Cells, Which is Associated with the p38 MAPK/mTOR Pathway

Transmembrane member 16A (TMEM16A) exhibits a negative correlation with autophagy, though the underlying mechanism remains elusive. This study investigates the mechanism between TMEM16A and autophagy by inducing autophagy in DRG neuronal cells using Rapamycin. Results indicated that TMEM16A interference augmented cell viability and reduced Rapamycin-induced apoptosis. Autophagosome formation increased with TMEM16A interference but decreased upon overexpression. A similar increase in autophagosomes was observed with SB203580 treatment. Furthermore, TMEM16A interference suppressed Rapamycin-induced gene and protein expression of p38 MAPK and mTOR, whereas overexpression had the opposite effect. These findings suggest that TMEM16A activation inhibits autophagy in DRG cells, which is associated with the p38 MAPK/mTOR pathway, offering a potential target for mitigating neuropathic pain (NP).

Dietary Docosahexaenoic Acid-Rich Supplementation Decreases Neurotoxic Lipid Mediators in Participants with Type 2 Diabetes and Neuropathic Pain

BACKGROUND/OBJECTIVES

There is increasing evidence linking circulating neurotoxic lipids to the progression of chronic neuroinflammatory diseases in the peripheral and central nervous systems. Strategies to modify lipid profiles, such as docosahexaenoic acid (DHA)-rich supplementation, may aid in managing conditions like painful diabetic neuropathy (pDN). In a previous study, we demonstrated that three months of DHA supplementation significantly altered the metabolomic profile of patients with painful diabetic neuropathy (pDN), resulting in symptom improvement. This study investigates whether DHA-rich supplementation reduces neurotoxic lipid mediators associated with pDN in individuals with type 2 diabetes mellitus (T2DM).

METHODS

Forty individuals with type 2 diabetes participated in the "En Balance-PLUS" study, attending weekly lifestyle and nutrition education sessions while receiving daily supplementation of 1000 mg DHA and 200 mg EPA. Pain levels were assessed using the Short-Form McGill Pain Questionnaire (SF-MPQ) at baseline and after three months. Blood serum samples collected at these time points underwent untargeted lipidomic analyses, with ELISA used to evaluate biomarkers of necrosis (MLKL), autophagy (ATG5), and lipid chaperone protein (FABP5).

RESULTS

Untargeted lipidomic analysis revealed that several neurotoxic-associated lipids significantly decreased after DHA-rich supplementation. Also, circulating levels of MLKL were reduced, while protein levels of ATG5 and FABP5 significantly increased.

CONCLUSIONS

The reduction of circulating neurotoxic lipids and increase in neuroprotective lipids following DHA-rich supplementation are consistent with the reported roles of omega-3 polyunsaturated fatty acids (PUFAs) in reducing adverse symptoms associated with neuroinflammatory diseases and painful neuropathy.

TRIM28 Fosters Microglia Ferroptosis via Autophagy Modulation to Enhance Neuropathic Pain and Neuroinflammation

This study explores the molecular underpinnings of neuropathic pain (NPP) and neuroinflammation, focusing on the role of TRIM28 in the regulation of autophagy and microglia ferroptosis. Leveraging transcriptomic data associated with NPP, we identified TRIM28 as a critical regulator of ferroptosis. Through comprehensive analysis, including Gene Ontology enrichment and protein-protein interaction network assessments, we unveiled GSK3B as a downstream target of TRIM28. Experimental validation confirmed the capacity of TRIM28 to suppress GSK3B expression and attenuate autophagic processes in microglia. We probed the consequences of autophagy and ferroptosis on microglia physiology, iron homeostasis, oxidative stress, and the release of proinflammatory cytokines. In a murine model, we validated the pivotal role of TRIM28 in NPP and neuroinflammation. Our analysis identified 20 ferroptosis regulatory factors associated with NPP, with TRIM28 emerging as a central orchestrator. Experimental evidence affirmed that TRIM28 governs microglial iron homeostasis and cell fate by downregulating GSK3B expression and modulating autophagy. Notably, autophagy was found to influence oxidative stress and proinflammatory cytokine release through the iron metabolism pathway, ultimately fueling neuroinflammation. In vivo experiments provided conclusive evidence of TRIM28-mediated pathways contributing to heightened pain sensitivity in neuroinflammatory states. The effect of TRIM28 on autophagy and microglia ferroptosis drives NPP and neuroinflammation. These findings offer promising avenues for identifying novel therapeutic targets to manage NPP and neuroinflammation.

Polypyridiniums with Inherent Autophagy-Inducing Activity for Atherosclerosis Treatment by Intracellularly Co-Delivering Two Antioxidant Enzymes

Atherosclerosis is a chronic inflammatory disease of the arterial intima and is becoming the leading cause of morbidity and mortality worldwide. There is considerable evidence that defective autophagy and overproduction of reactive oxygen species (ROS) are closely involved in the development and progression of atherosclerosis. Here, a polymer is developed with the inherent autophagy-inducing activity to treat atherosclerosis by co-delivering antioxidant enzymes. The lead material P5c screened from a library of polypyridiniums shows robust efficacy in cytosolic protein delivery, and efficiently delivers superoxide dismutase (SOD) and catalase (CAT) into macrophages to down-regulate intracellular ROS. Moreover, P5c activates autophagy in macrophages and sufficiently inhibits foam cell formation. The P5c nanoparticle loaded with both SOD and CAT is further coated with neutrophil membranes to treat atherosclerosis in an ApoE-/- mice model. The treatment exhibits potent anti-atherosclerosis effect via activating autophagy, decreasing the infiltration of senescent cells in atherosclerotic plaques, regulating the M2 polarization of macrophages, and restoring the structure and function of splenic corpuscles. The polymer offers a multifaceted approach to combat atherosclerosis, addressing both cellular dysfunction and the need for targeted protein delivery within affected cells.

ZnO NPs Impair the Viability and Function of Porcine Granulosa Cells Through Autophagy Regulated by ROS Production

The zinc oxide nanoparticles (ZnO NPs) is one of the most extensively utilized metal oxide nanoparticles in biomedicine, human food, cosmetics and livestock farming. However, growing evidence suggests that there is a potential risk for humans and animals because of the accumulation of ZnO NPs in cells, which leads to cell death through several different pathways. Nevertheless, the effects of ZnO NPs on porcine granulosa cells (PGCs) and how ZnO NPs regulate the follicular cells are unknown. In this study, we aimed to elucidate the role of ZnO NPs in the porcine ovary by using PGCs. Firstly, we identified the characterization of ZnO NPs used in this study and the results showed that the size of ZnO NPs was 29.0 nm. The results also demonstrated that ZnO NPs impaired cell viability and decreased steroid hormone secretion in PGCs. In addition, ZnO NPs induced reactive oxygen species (ROS) production, leading to oxidative stress of PGCs. Meanwhile, ZnO NPs also triggered autophagy in PGCs by increasing the ratio of LC3-II/LC3-I, along with the expression of SQSTM1 and ATG7. Finally, the results from N-acetylcysteine (NAC) addition suggested that ZnO NPs promoted autophagy through the enhancement of ROS production. In summary, this study demonstrates that ZnO NPs impair the viability and function of PGCs through autophagy, which is regulated by ROS production.

Vitexin attenuates neuropathic pain by regulating astrocyte autophagy flux and polarization via the S1P/ S1PR1-PI3K/ Akt axis

Neuropathic pain (NP) is associated with astrocytes activation induced by nerve injury. Reactive astrocytes, strongly induced by central nervous system damage, can be classified into A1 and A2 types. Vitexin, a renowned flavonoid compound, is known for its anti-inflammatory and analgesic properties. However, its role in NP remains unexplored. This study aims to investigate the effects of vitexin on astrocyte polarization and its underlying mechanisms. A mouse model of NP was established, and primary astrocytes were stimulated with sphingosine-1-phosphate (S1P) to construct a cellular model. The results demonstrated significant activation of spinal astrocytes on days 14 and 21. Concurrently, reactive astrocytes predominantly differentiated into the A1 type. Western blot analysis revealed an increase in A1 astrocyte-associated protein (C3) and a decrease in A2 astrocyte-associated protein (S100A10). Serum S1P levels increased on days 14 and 21, alongside a significant upregulation of Sphingosine-1-phosphate receptor 1 (S1PR1) mRNA expression and elevated expression of chemokines. In vitro, stimulation with S1P inhibited the Phosphatidylinositol 3-kinase and protein kinase B (PI3K/Akt) signaling pathway and autophagy flux, promoting polarization of astrocytes towards the A1 phenotype while suppressing the polarization of A2 astrocytes. Our findings suggest that vitexin, acting on astrocytes but not microglia, attenuates S1P-induced downregulation of PI3K/Akt signaling, restores autophagy flux in astrocytes, regulates A1/A2 astrocyte ratio, and reduces chemokine and S1P secretion, thereby alleviating neuropathic pain caused by nerve injury.

An integrated bioinformatics approach reveals the potential role of microRNA-30b-5p and let-7a-5p during SARS CoV-2 spike-1 mediated neuroinflammation

SARS-CoV-2 induced neuroinflammation contributing to neurological sequelae is one of the critical outcomes of long-COVID, however underlying regulatory mechanisms involved therein are poorly understood. We deciphered the profile of dysregulated microRNAs, their targets, associated pathways, protein-protein interactions (PPI), transcription factor-hub genes interaction networks, hub genes-microRNA co-regulatory networks in SARS-CoV-2 Spike-1 (S1) stimulated microglial cells along with candidate drug prediction using RNA-sequencing and multiple bioinformatics approaches. We identified 11 dysregulated microRNAs in the S1-stimulated microglial cells (p < 0.05). KEGG analysis revealed involvement of important neuroinflammatory pathways such as MAPK signalling, PI3K-AKT signalling, Ras signalling and axon guidance. PPI analysis further identified 11 hub genes involved in these pathways. Real time PCR validation confirmed a significant upregulation of microRNA-30b-5p and let-7a-5p; proinflammatory cytokines- IL-6, TNF-α, IL-1β, GM-CSF; and inflammatory genes- PIK3CA and AKT in the S1-stimulated microglial cells, while PTEN and SHIP1 expression was decreased as compared to the non-stimulated cells. Drug prediction analysis further indicated resveratrol, diclofenac and rapamycin as the potential drugs based on their degree of interaction with hub genes. Thus, targeting of these microRNAs and/or their intermediate signalling molecules would be a prospective immunotherapeutic approach in alleviating SARS-CoV-2-S1 mediated neuroinflammation; and needs further investigations.

The role of the ubiquitin system in the onset and reversal of neuropathic pain

Neuropathic pain (NP) remains one of the world's most difficult problems, and people suffering from NP have their quality of life affected to a great extent and constantly suffer from pain. Sensitization of injurious receptors, ectopic firing of afferent nerves after nerve injury, and coupling between sympathetic and sensory neurons are involved in the onset or development of NP, but the pathogenesis of NP is still not well understood. We found that the ubiquitin system is involved in the pathogenesis of NP and has a crucial role in it. The ubiquitin system can be involved in the onset or reversal of NP by affecting ion channels, cellular signal transduction, glial cells, and the regulation of non-coding RNAs. This provides new ideas for the treatment of NP. The ubiquitin system may be a new effective target for the treatment of NP. A continued, in-depth understanding of the mechanisms of the ubiquitin system involved in NP could further refine the study of analgesic targets and improve pharmacological studies.

Protective effect of ghrelin in oxidative stress-induced age-related macular degeneration in vitro and in vivo

Oxidative damage to human retinal pigment epithelial (RPE) cells is the main cause of age-related macular degeneration (AMD), in our previous work, we showed that ghrelin has an antioxidative effect on human lens epithelium (HLE) cells, however, the studies of using ghrelin in treating the degenerative diseases of the retina have rarely been reported. In this article, we assessed the effect of ghrelin on preventing oxidative stress induced by hydrogen peroxide (H2O2) in ARPE-19 cells and its mechanism. We observed that pretreatment with ghrelin protected ARPE-19 cells from H2O2-induced cell oxidative injuries and apoptosis responses. Furthermore, an oxidative stress-induced mouse model of AMD was established via injection of sodium iodate (NaIO3) to tail veins, and treatment with ghrelin preserved retinal function, and protected photoreceptors.

Rab8a/SNARE complex activation promotes vesicle anchoring and transport in spinal astrocytes to drive neuropathic pain

Neuropathic pain (NPP) remains a clinically challenging condition, driven by the activation of spinal astrocytes and the complex release of inflammatory mediators. This study aimed to examine the roles of Rab8a and SNARE complex proteins in activated astrocytes to uncover the underlying mechanisms of NPP. The research was conducted using a rat model with chronic constriction injury (CCI) of the sciatic nerve and primary astrocytes treated with lipopolysaccharide. Enhanced expression of Rab8a was noted specifically in spinal dorsal horn astrocytes through immunofluorescence. Electron microscopy observations showed increased vesicular transport and exocytic activity in activated astrocytes, which was corroborated by elevated levels of inflammatory cytokines such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α detected through quantitative PCR. Western blot analyses confirmed significant upregulation of Rab8a, VAMP2, and Syntaxin16 in these cells. Furthermore, the application of botulinum neurotoxin type A (BONT/A) reduced the levels of vesicle transport-associated proteins, inhibiting vesicular transport in activated astrocytes. These findings suggest that the Rab8a/SNARE pathway in astrocytes enhances vesicle transport and anchoring, increasing the secretion of bioactive molecules that may play a crucial role in the pathophysiology of NPP. Inhibiting this pathway with BONT/A offers a novel therapeutic target for managing NPP, highlighting its potential utility in clinical interventions.

Mer activation ameliorates nerve injury-induced neuropathic pain by regulating microglial polarization and neuroinflammation via SOCS3 in male rats

Accumulating evidence has demonstrated that M1 microglial polarization and neuroinflammation worsen the development of neuropathic pain. However, the mechanisms underlying microglial activation during neuropathic pain remain incompletely understood. Myeloid-epithelial-reproductive tyrosine kinase (Mer), which is a member of the Tyro-Axl-Mer (TAM) family of receptor tyrosine kinases, plays a crucial role in the regulation of microglial polarization. However, the effect of Mer on microglial polarization during neuropathic pain has not been determined. In this study, western blotting, immunofluorescence analysis, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA) were used to examine the role of Mer in pain hypersensitivity and microglial polarization in rats with chronic constriction injury (CCI) of the sciatic nerve. The results indicated that Mer expression in microglia was prominently increased in the spinal cords of rats subjected to CCI. Furthermore, treatment with recombinant protein S (PS, an activator of Mer) alleviated mechanical allodynia and thermal hyperalgesia, promoted the switch in microglia from the M1 phenotype to the M2 phenotype, and ameliorated neuroinflammation in rats subjected to CCI. However, the use of suppressor of cytokine signalling 3 (SOCS3) siRNA abolished these changes. These results indicated that Mer regulated M1/M2 microglial polarization and neuroinflammation and may be a potential target for treating neuropathic pain.

Botulinum toxin type A-targeted SPP1 contributes to neuropathic pain by the activation of microglia pyroptosis

BACKGROUND

Neuropathic pain (NP) is the primary symptom of various neurological conditions. Patients with NP often experience mood disorders, particularly depression and anxiety, that can severely affect their normal lives. Microglial cells are associated with NP. Excessive inflammatory responses, especially the secretion of large amounts of pro-inflammatory cytokines, ultimately lead to neuroinflammation. Microglial pyroptosis is a newly discovered form of inflammatory cell death associated with immune responses and inflammation-related diseases of the central nervous system.

AIM

To investigate the effects of botulinum toxin type A (BTX-A) on microglial pyroptosis in terms of NP and associated mechanisms.

METHODS

Two models, an in vitro lipopolysaccharide (LPS)-stimulated microglial cell model and a selective nerve injury model using BTX-A and SPP1 knockdown treatments, were used. Key proteins in the pyroptosis signaling pathway, NLRP3-GSDMD, were assessed using western blotting, real-time quantitative polymerase chain reaction, and immunofluorescence. Inflammatory factors [interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α] were assessed using enzyme-linked immunosorbent assay. We also evaluated microglial cell proliferation and apoptosis. Furthermore, we measured pain sensation by assessing the delayed hind paw withdrawal latency using thermal stimulation.

RESULTS

The expression levels of ACS and GSDMD-N and the mRNA expression of TNF-α, IL-6, and IL-1β were enhanced in LPS-treated microglia. Furthermore, SPP1 expression was also induced in LPS-treated microglia. Notably, BTX-A inhibited SPP1 mRNA and protein expression in the LPS-treated microglia. Additionally, depletion of SPP1 or BTX-A inhibited cell viability and induced apoptosis in LPS-treated microglia, whereas co-treatment with BTX-A enhanced the effect of SPP1 short hairpin (sh)RNA in LPS-treated microglia. Finally, SPP1 depletion or BTX-A treatment reduced the levels of GSDMD-N, NLPRP3, and ASC and suppressed the production of inflammatory factors.

CONCLUSION

Notably, BTX-A therapy and SPP1 shRNA enhance microglial proliferation and apoptosis and inhibit microglial death. It improves pain perception and inhibits microglial activation in rats with selective nerve pain.

OTULIN's influence on neuroinflammation and pain modulation in trigeminal neuralgia

INTRODUCTION

Trigeminal neuralgia (TN), marked by chronic pain from neural damage, is closely associated with inflammation. The role of OTULIN, a key regulator in inflammation and autophagy, is not fully understood in TN. The regulatory mechanism of OTULIN, a key protein involved in modulating inflammatory responses and autophagy processes, remains incompletely elucidated, particularly in the context of TN and neuroinflammation.

METHODS

An infraorbital nerve ligation-induced rat model of TN was used. OTULIN's expression was modulated using adenovirus vectors and short hairpin RNA. The impact on pain and inflammatory responses was assessed via quantitative real-time polymerase chain reaction, western blot, immunofluorescence, and transcriptomic analysis.

RESULTS

Enhanced OTULIN expression significantly increased head withdrawal thresholds and reduced pain sensitivity and neuroinflammatory markers in the model. Conversely, silencing OTULIN exacerbated pain and inflammation. Transcriptomic data revealed OTULINs influence on both inflammatory and autophagy pathways, specifically in suppressing NLR family pyrin domain containing 3 (NLRP3) inflammasome and promoting autophagy. In vitro experiments demonstrated OTULIN's inhibition of inflammatory markers in microglia and neurons.

CONCLUSION

OTULIN is crucial in modulating TN, reducing neuropathic pain and neuroinflammation by activating the autophagy pathway and inhibiting the NLRP3 inflammasome.

Dexborneol Amplifies Pregabalin's Analgesic Effect in Mouse Models of Peripheral Nerve Injury and Incisional Pain

Pregabalin is a medication primarily used in the treatment of neuropathic pain and anxiety disorders, owing to its gabapentinoid properties. Pregabalin monotherapy faces limitations due to its variable efficacy and dose-dependent adverse reactions. In this study, we conducted a comprehensive investigation into the potentiation of pregabalin's analgesic effects by dexborneol, a neuroprotective bicyclic monoterpenoid compound. We performed animal experiments where pain models were induced using two methods: peripheral nerve injury, involving axotomy and ligation of the tibial and common peroneal nerves, and incisional pain through a longitudinal incision in the hind paw, while employing a multifaceted methodology that integrates behavioral pharmacology, molecular biology, neuromorphology, and lipidomics to delve into the mechanisms behind this potentiation. Dexborneol was found to enhance pregabalin's efficacy by promoting its transportation to the central nervous system, disrupting self-amplifying vicious cycles via the reduction of HMGB1 and ATP release, and exerting significant anti-oxidative effects through modulation of central lipid metabolism. This combination therapy not only boosted pregabalin's analgesic property but also notably decreased its side effects. Moreover, this therapeutic cocktail exceeded basic pain relief, effectively reducing neuroinflammation and glial cell activation-key factors contributing to persistent and chronic pain. This study paves the way for more tolerable and effective analgesic options, highlighting the potential of dexborneol as an adjuvant to pregabalin therapy.

Reduced circ_lrrc49 in trigeminal ganglion contributes to neuropathic pain in mice by downregulating Ist1 and impairing autophagy

Orofacial neuropathic pain is a common symptom induced by orofacial nerve injury caused by a range of trauma or dental and maxillofacial procedures but lacks effective treatment. Circular RNAs (circRNAs) participate in the regulatory processes of neuropathic pain. Nevertheless, the biological roles of circRNAs in orofacial neuropathic pain remain unexplored. In this study, circRNA sequencing and Real-time quantitative polymerase chain reaction (RT-qPCR) were carried out. Notably, a novel circRNA named circ_lrrc49 was identified to be downregulated following chronic constriction injury of the infraorbital nerve (CCI-ION) in mice on day 14. Subsequent RNA Antisense Purification (RAP)-mass spectrometry and RNA immunoprecipitation found a direct interaction between circ_lrrc49 and increased sodium tolerance 1 homolog (Ist1). Western blot (WB) identified decreased expression of Ist1 on day 14 post-CCI-ION. Considering the known relationship between Ist1 and autophagy, LC3-II and p62 were detected to be upregulated, and an accumulation of autophagosomes were observed at the same time point. Besides, the knockdown of circ_lrrc49 by small interfering RNA (siRNA) reduced Ist1 expression, increased LC3-II, p62 levels and autophagosomes amount, and evoked orofacial mechanical hypersensitivity, which could be counteracted by the Ist1 overexpression. Similarly, the knockdown of Ist1 by siRNA also increased LC3-II and p62 levels and evoked orofacial mechanical hypersensitivity without influence on circ_lrrc49. Moreover, autophagy activation by rapamycin alleviated orofacial mechanical hypersensitivity evoked by CCI-ION or circ_lrrc49 knockdown. In conclusion, our data revealed the existence of a circ_lrrc49/Ist1/autophagy signaling axis contributing to the progression of orofacial neuropathic pain. These discoveries reveal the intricate molecular processes that drive orofacial neuropathic pain and identify circ_lrrc49 as a promising target for potential therapeutic interventions.

Effects of Pain Relief Through Minimal Exercise Intervention in a Rat Model of Neuropathic Pain

We aimed to minimize the frequency of exercise intervention and test the efficacy of pain relief. We also investigated the mechanism of neuropathic pain to determine the best frequency of pain relief for neuropathic pain. The chronic constriction injury (CCI) rat model was randomly divided into three groups: exercise (Ex), No-Ex, and normal. The treadmill exercise intervention was administered, and the 50% withdrawal threshold was assessed using the Von Frey Test. Ionized calcium-binding adaptor molecule 1 (IBA1), glial fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF), C-C chemokine receptor type 2 (CCR2), and tumor necrosis factor receptor-associated factor 6 (TRAF6) activation was determined through immunohistochemistry. In the brain, we examined the increased expression of β-endorphin/met-enkephalin in the gray matter of the midbrain aqueduct. Co-expression of CCR2, IBA1, and Neu-N was observed in the spinal cord dorsal horn by immunofluorescence staining. The 50% pain response threshold was significantly lower in the Ex group than in the No-Ex group at five weeks post-CCI, indicating a high analgesic effect. In the dorsal horn of the spinal cord, IBA1 and GFAP were significantly decreased in the Ex group than in the No-Ex group at five weeks post-CCI. However, no significant difference in activation of BDNF, CCR2, and TRAF6 was observed. In the midbrain, the Ex group showed a significant increase compared to the No-Ex group. In summary, our results suggest that in minimal-exercise intervention, neuropathic pain relief is achieved by activation of the descending pain inhibitory system in the midbrain.

Association between oxidative stress and chronic orofacial pain and potential druggable targets: Evidence from a Mendelian randomization study

BACKGROUND

Oxidative stress indicators affect chronic orofacial pain (COFP), but how to reduce these effects is uncertain.

OBJECTIVES

11 oxidative stress biomarkers were collected as exposures, while four forms of COFP were chosen as outcomes for Mendelian randomization (MR) study.

METHODS

The effect estimates between oxidative stress and COFP were calculated using inverse variance-weighted MR (IVW-MR). Then, functional mapping and annotation (FUMA) was utilized in order to carry out SNP-based functional enrichment analyses. In addition, the IVW-MR method was applied to combine effect estimates when using genetic variants associated with oxidative stress biomarkers as an instrument for exploring potential druggable targets.

RESULTS

The results indicated that oxidative stress biomarkers (causal OR of uric acid (UA), 0.998 for myofascial pain, 95% CI 0.996-1.000, p < .05; and OR of glutathione transferase (GST), 1.002 for dentoalveolar pain, 95% CI 1.000-1.003, p < .05) were significantly linked with the probability of COFP. Functional analysis also demonstrated that UA and myofascial pain genes were prominent in nitrogen and uracil metabolism, while GST and dentoalveolar pain genes were enriched in glutathione metabolism. Also, the study provided evidence that solute carrier family 2 member 9 (SLC2A9) and glutathione S-transferase alpha 2 (GSTA2) cause discomfort in the myofascial pain (OR = 1.003, 95% CI 1.000-1.006; p < .05) and dentoalveolar region (OR = 1.001, 95% CI 1.000-1.002; p < .05), respectively.

CONCLUSIONS

In conclusion, this MR study indicates that genetically predicted myofascial pain was significantly associated with decreased UA and dentoalveolar pain was significantly associated with increased GST level. SLC2A9 inhibitor and GSTA2 inhibitor were novel chronic orofacial pain therapies and biomarkers, but clinical trials are called to examine if these oxidative biomarkers have the protective effect against orofacial pain, and further research are needed to explore the underlying mechanisms.

Tumor necrosis factor α-induced protein 8-like-2 controls microglia phenotype via metabolic reprogramming in BV2 microglial cells and responses to neuropathic pain

Microglial are major players in neuroinflammation that have recently emerged as potential therapeutic targets for neuropathic pain. Glucose metabolic programming has been linked to differential activation state and function in microglia. Tumor necrosis factor α-induced protein 8-like-2 (TNFAIP8L2) is an important component in regulating the anti-inflammatory response. However, the role of TNFAIP8L2 in microglia differential state during neuropathic pain and its interplay with glucose metabolic reprogramming in microglia has not yet been determined. Thus, we aimed to investigate the role of TNFAIP8L2 in the status of microglia in vitro and in vivo. BV2 microglial cells were treated with lipopolysaccharides plus interferon-gamma (LPS/IFNγ) or interleukin-4 (IL-4) to induce the two different phenotypes of microglia in vitro. In vivo experiments were conducted by chronic constriction injury of the sciatic nerve (CCI). We investigated whether TNFAIP8L2 regulates glucose metabolic programming in BV2 microglial cells. The data in vitro showed that TNFAIP8L2 lowers glycolysis and increases mitochondrial oxidative phosphorylation (OXPHOS) in inflammatory microglia. Blockade of glycolytic pathway abolished TNFAIP8L2-mediated differential activation of microglia. TNFAIP8L2 suppresses inflammatory microglial activation and promotes restorative microglial activation in BV2 microglial cells and in spinal cord microglia after neuropathic pain. Furthermore, TNFAIP8L2 controls differential activation of microglia and glucose metabolic reprogramming through the MAPK/mTOR/HIF-1α signaling axis. This study reveals that TNFAIP8L2 plays a critical role in neuropathic pain, providing important insights into glucose metabolic reprogramming and microglial phenotypic transition, which indicates that TNFAIP8L2 may be used as a potential drug target for the prevention of neuropathic pain.

Heat Shock Protein 22 Attenuates Nerve Injury-induced Neuropathic Pain Via Improving Mitochondrial Biogenesis and Reducing Oxidative Stress Mediated By Spinal AMPK/PGC-1α Pathway in Male Rats

Heat shock protein 22 (hsp22) plays a significant role in mitochondrial biogenesis and redox balance. Moreover, it's well accepted that the impairment of mitochondrial biogenesis and redox imbalance contributes to the progress of neuropathic pain. However, there is no available evidence indicating that hsp22 can ameliorate mechanical allodynia and thermal hyperalgesia, sustain mitochondrial biogenesis and redox balance in rats with neuropathic pain. In this study, pain behavioral test, western blotting, immunofluorescence staining, quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and Dihydroethidium staining are applied to confirm the role of hsp22 in a male rat model of spared nerve injury (SNI). Our results indicate that hsp22 was significantly decreased in spinal neurons post SNI. Moreover, it was found that intrathecal injection (i.t.) with recombinant heat shock protein 22 protein (rhsp22) ameliorated mechanical allodynia and thermal hyperalgesia, facilitated nuclear respiratory factor 1 (NRF1)/ mitochondrial transcription factor A (TFAM)-dependent mitochondrial biogenesis, decreased the level of reactive oxygen species (ROS), and suppressed oxidative stress via activation of spinal adenosine 5'monophosphate-activated protein kinase (AMPK)/ peroxisome proliferative activated receptor γ coactivator 1α (PGC-1α) pathway in male rats with SNI. Furthermore, it was also demonstrated that AMPK antagonist (compound C, CC) or PGC-1α siRNA reversed the improved mechanical allodynia and thermal hyperalgesia, mitochondrial biogenesis, oxidative stress, and the decreased ROS induced by rhsp22 in male rats with SNI. These results revealed that hsp22 alleviated mechanical allodynia and thermal hyperalgesia, improved the impairment of NRF1/TFAM-dependent mitochondrial biogenesis, down-regulated the level of ROS, and mitigated oxidative stress through stimulating the spinal AMPK/PGC-1α pathway in male rats with SNI.

Exploring the Mechanism of Immediate Analgesia Induced by Tuina Intervention on Minor Chronic Constriction Injury in Rats Using LC-MS

Purpose

This study aimed to investigate changes in metabolomic expression in the spinal dorsal horn (SDH) and thalamus during a Tuina session, aiming to elucidate the mechanism of immediate analgesia.

Methods

The rats were randomly divided into three groups: the Sham group, the Model group, and the Tuina group. A minor chronic constriction injury (minor CCI) model was established in both the Model group and the Tuina group. The therapeutic effect of Tuina was determined using the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests. Differential metabolites of the SDH and thalamus were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Bioinformatic analysis was performed using CV, PCA, Venn, and KEGG.

Results

The therapeutic effect of MWT and TWL after instant Tuina intervention was significant. The therapeutic effect of Tuina instant was significantly better compared to the Model group. In the Veen analysis, it was found that Tuina instantly regulates 10 differential metabolites in the SDH and 5 differential metabolites in the thalamus. In the KEGG enrichment analysis, we found that differential metabolites were enriched in 43 pathways in the thalamus and 70 pathways in the SDH.

Conclusion

Tuina therapy may have analgesic effects by metabolizing neurotransmitters such as 2-Picolinic Acid, 5-Hydroxy-Tryptophan Glutathione Betaine-aldehyde-chloride Leucine Lysine Methionine Sarcosine Succinic Acid Histidine Acetylcholine and 5-Hydroxyindoleacetic Acid through the cAMP pathway. It also affects pathways of neurodegeneration-multiple diseases, butanoate metabolism, tyrosine metabolism.

miR-99b-3p/Mmp13 axis regulates NLRP3 inflammasome-dependent microglial pyroptosis and alleviates neuropathic pain via the promotion of autophagy

BACKGROUND

Neuropathic pain significantly impairs quality of life, and effective interventions are limited. NOD-like receptor thermal protein domain associated protein 3 (NLRP3)-mediated microglial pyroptosis and the subsequent proinflammatory cytokine production are critical in exacerbating pain. Considering microglial pyroptosis as a potential target for developing specific analgesic interventions for neuropathic pain, our study investigated the pathogenesis and therapeutic targets in this condition.

METHODS

In vitro experiments involved the co-culture of the immortalized BV-2 microglia cell line with lipopolysaccharide (LPS) to induce microglial pyroptosis. Differentially expressed microRNAs (miRNAs) were identified using high-throughput sequencing analysis. The downstream target genes of these miRNAs were determined through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, and the downstream target genes, combined with miRNAs, were predicted and verified through dual luciferase reporter gene assays. In vivo experiments were conducted to construct a chronic constriction injury (CCI) neuropathic pain model in rats and evaluate the analgesic effects of intrathecal injection of an adeno-associated virus vector (AAV) carrying miR-99b-3p. Gene expression was modulated through mimic or siRNA transfection. Western blot analysis assessed the expression of microglial pyroptosis and autophagy-related proteins, whereas RT-qPCR measured changes in proinflammatory cytokines expression.

RESULTS

LPS-stimulated up-regulation of proinflammatory cytokines in microglia, accompanied by NLRP3-dependent pyroptosis, including increased NLRP3, GSDMD-N, Caspase1-p20, and mature-IL-1β expression. High-throughput sequencing analysis revealed 16 upregulated and 10 downregulated miRNAs in LPS-stimulated microglia, with miR-99b-3p being the most downregulated. KEGG analysis revealed that the target genes of these miRNAs are primarily enriched in calcium, FoxO, and mitogen-activated protein kinase (MAPK) signal pathways. Furthermore, overexpression of miR-99b-3p through mimic transfection significantly inhibited the inflammatory response and NLRP3-mediated pyroptosis by promoting autophagy levels in activated microglia. In addition, we predicted that the 3' untranslated region (UTR) of matrix metalloproteinase-13 (Mmp13) could bind to miR-99b-3p, and knockdown of Mmp13 expression through siRNA transfection similarly ameliorated enhanced proinflammatory cytokines expression and microglial pyroptosis by enhancing autophagy. In vivo, Mmp13 was co-localized with spinal dorsal horn microglia and was suppressed by intrathecal injection of the AAV-miR-99b-3p vector. Moreover, overpressed miR-99b-3p alleviated CCI-induced mechanical allodynia and neuroinflammation while suppressing pyroptosis by enhancing autophagy in the spinal cord of CCI rats.

CONCLUSION

miR-99b-3p exerts analgesic effects on neuropathic pain by targeting Mmp13. These antinociceptive effects are, at least in part, attributed to the promotion of autophagy, thereby inhibiting neuroinflammation and NLRP3-mediated pyroptosis in activated microglia.

Involvement of microglial P2X7 receptor in pain modulation

BACKGROUND

Pain is a rapid response mechanism that compels organisms to retreat from the harmful stimuli and triggers a repair response. Nonetheless, when pain persists for extended periods, it can lead to adverse changes into in the individual's brain, negatively impacting their emotional state and overall quality of life. Microglia, the resident immune cells in the central nervous system (CNS), play a pivotal role in regulating a variety of pain-related disorders. Specifically, recent studies have shed light on the central role that microglial purinergic ligand-gated ion channel 7 receptor (P2X7R) plays in regulating pain. In this respect, the P2X7R on microglial membranes represents a potential therapeutic target.

AIMS

To expound on the intricate link between microglial P2X7R and pain, offering insights into potential avenues for future research.

METHODS

We reviewed 140 literature and summarized the important role of microglial P2X7R in regulating pain, including the structure and function of P2X7R, the relationship between P2X7R and microglial polarization, P2X7R-related signaling pathways, and the effects of P2X7R antagonists on pain regulation.

RESULTS

P2X7R activation is related to M1 polarization of microglia, while suppressing P2X7R can transfer microglia from M1 into M2 phenotype. And targeting the P2X7R-mediated signaling pathways helps to explore new therapy for pain alleviation. P2X7R antagonists also hold potential for translational and clinical applications in pain management.

CONCLUSIONS

Microglial P2X7R holds promise as a potential novel pharmacological target for clinical treatments due to its distinctive structure, function, and the development of antagonists.

Mitochondria-derived peptide is an effective target for treating streptozotocin induced painful diabetic neuropathy through induction of activated protein kinase/peroxisome proliferator-activated receptor gamma coactivator 1alpha -mediated mitochondrial biogenesis

Painful Diabetic Neuropathy (PDN) is a common diabetes complication that frequently causes severe hyperalgesia and allodynia and presents treatment challenges. Mitochondrial-derived peptide (MOTS-c), a novel mitochondrial-derived peptide, has been shown to regulate glucose metabolism, insulin sensitivity, and inflammatory responses. This study aimed to evaluate the effects of MOTS-c in streptozocin (STZ)-induced PDN model and investigate the putative underlying mechanisms. We found that endogenous MOTS-c levels in plasma and spinal dorsal horn were significantly lower in STZ-treated mice than in control animals. Accordingly, MOTS-c treatment significantly improves STZ-induced weight loss, elevation of blood glucose, mechanical allodynia, and thermal hyperalgesia; however, these effects were blocked by dorsomorphin, an adenosine monophosphate-activated protein kinase (AMPK) inhibitor. In addition, MOTS-c treatment significantly enhanced AMPKα1/2 phosphorylation and PGC-1α expression in the lumbar spinal cord of PDN mice. Mechanistic studies indicated that MOTS-c significantly restored mitochondrial biogenesis, inhibited microglia activation, and decreased the production of pro-inflammatory factors, which contributed to the alleviation of pain. Moreover, MOTS-c decreased STZ-induced pain hypersensitivity in PDN mice by activating AMPK/PGC-1α signaling pathway. This provides the pharmacological and biological evidence for developing mitochondrial peptide-based therapeutic agents for PDN.

Diosmetin alleviates neuropathic pain by regulating the Keap1/Nrf2/NF-κB signaling pathway

BACKGROUND

Neuropathic pain, a chronic condition with a high incidence, imposes psychological burdens on both patients and society. It is urgent to improve pain management and develop new analgesic drugs. Traditional Chinese medicine has gained popularity as a method for pain relief. Diosmetin (Dio) is mainly found in Chinese herbal medicines with effective antioxidant, anti-cancer, and anti-inflammatory properties. There are few known mechanisms underlying the effectiveness of Dio in treating neuropathic pain. However, the complete understanding of its therapeutic effect is missing.

PURPOSE

This study aimed to evaluate Dio's therapeutic effects on neuropathic pain models and determine its possible mechanism of action. We hypothesized that Dio may activate antioxidants and reduce inflammation, inhibit the activation of Kelch-like epichlorohydrin-associated protein 1 (Keap1) and nuclear factor-k-gene binding (NF-κB), promote the metastasis of nuclear factor erythroid 2-related factor 2 (Nrf2) and the expression of heme oxygenase 1 (HO-1), thus alleviating the neuropathic pain caused by spinal nerve ligation.

METHODS

Chronic nociceptive pain mouse models were established in vivo by L4 spinal nerve ligation (SNL). Different dosages of Dio (10, 50, 100 mg/kg) were intragastrically administered daily from the third day after the establishment of the SNL model. Allodynia, caused by mechanical stimuli, and hyperalgesia, caused by heat, were assessed using the paw withdrawal response frequency (PWF) and paw withdrawal latency (PWL), respectively. Cold allodynia were assessd by acetone test. RT-PCR was used to detect the content of interleukin-(IL)- 1β, IL-6 and tumor necrosis factor (TNF)-a. Immunofluorescence and western blotting were employed to assess the expression levels of Glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule (Iba1), Keap1, Nrf2, HO-1, and NF-κB p-p65 protein.

RESULTS

Dio administration relieved SNL-induced transient mechanical and thermal allodynia in mice. The protective effect of Dio in the SNL model was associated with its anti-inflammatory and anti-glial responses in the spinal cord. Dio inhibited both inflammatory factors and macrophage activation in the DRG. Furthermore, Dio regulated the Keap1/Nrf2/NF-κB signaling pathway. HO-1 and Nrf2 were upregulated following Dio administration, which also decreased the levels of Keap1 and NF-κB p65 protein.

CONCLUSION

Mice with SNL-induced neuropathic pain were therapeutically treated with Dio. Dio may protect against pain by inhibiting inflammatory responses and improved Keap1/Nrf2/NF-κB pathway. These results highlight the potential therapeutic effect of Dio for the development of new analgesic drugs.

Stress/cell death pathways, neuroinflammation, and neuropathic pain

Neuropathic pain is a common and debilitating modality of chronic pain induced by a lesion or disease of the somatosensory nervous system. Albeit the elucidation of numerous pathophysiological mechanisms and the development of potential treatment compounds, safe and reliable therapies of neuropathic pain remain poor. Multiple stress/cell death pathways have been shown to be implicated in neuroinflammation during neuropathic pain. Here, we summarize the current knowledge of stress/cell death pathways and present an overview of the roles and molecular mechanisms of stress/cell death pathways in neuroinflammation during neuropathic pain, covering intrinsic and extrinsic apoptosis, autophagy, mitophagy, ferroptosis, pyroptosis, necroptosis, and phagoptosis. Small molecule compounds that modulate stress/cell death pathways in alleviating neuropathic pain are discussed mainly based on preclinical neuropathic pain models. These findings will contribute to in-depth understanding of the pathological processes during neuropathic pain as well as bridge the gap between basic and translational research to uncover new neuroprotective interventions.

Stem cells and pain

Pain can be defined as an unpleasant sensory and emotional experience caused by either actual or potential tissue damage or even resemble that unpleasant experience. For years, science has sought to find treatment alternatives, with minimal side effects, to relieve pain. However, the currently available pharmacological options on the market show significant adverse events. Therefore, the search for a safer and highly efficient analgesic treatment has become a priority. Stem cells (SCs) are non-specialized cells with a high capacity for replication, self-renewal, and a wide range of differentiation possibilities. In this review, we provide evidence that the immune and neuromodulatory properties of SCs can be a valuable tool in the search for ideal treatment strategies for different types of pain. With the advantage of multiple administration routes and dosages, therapies based on SCs for pain relief have demonstrated meaningful results with few downsides. Nonetheless, there are still more questions than answers when it comes to the mechanisms and pathways of pain targeted by SCs. Thus, this is an evolving field that merits further investigation towards the development of SC-based analgesic therapies, and this review will approach all of these aspects.

Dysregulated wound healing in the pathogenesis of urogynecologic mesh complications

To test the hypothesis that dysregulated wound healing is associated with Urogynecologic mesh complications, we collected vaginal cell secretions using vaginal swabs after polypropylene mesh implantation in patients with (N = 39) and without (N = 40) complication. A customized multiplex immunoassay measured markers of inflammation (MCP-1, IGFBP-1, IL-2, IL-10, IL-17, PDGF-BB, bFGF, IL-1b, IL-6, IL-12p70, TNF-α), neuroinflammation (IL-1RA, TGF-β, IL-15, IL-18, IL-3, M-CSF), angiogenesis (VEGF), and matrix proteins (fibronectin, tenasin c, thrombospondin-2, lumican) between groups. Patients with complications were younger, heavier, implanted with mesh longer, and more likely to be ever smokers. A 5 kg/m2 BMI increase and ever-smoking were associated with a 2.4-fold and sixfold increased risk of complication, respectively. Patients with the highest tertile of bFGF, fibronectin, thrombospondin-2, TNF-β, or VEGF had an odds ratio (OR) of 11.8 for having a mesh complication while ≥ 3 elevated had an OR of 237 while controlling for age, BMI, and smoking. The highest tertile of bFGF, thrombospondin-2, and fibronectin together perfectly indicated a complication (P < 0.0001). A receiver-operator curve for high bFGF, thrombospondin-2, and fibronectin showed excellent discrimination between complications and controls (AUC 0.87). These data provide evidence of dysregulated wound healing in mesh complications. Modifiable factors provide potential targets for patient counseling and interventions.

Ferritin Is Secreted from Primary Cultured Astrocyte in Response to Iron Treatment via TRPML1-Mediated Exocytosis

Impaired iron homeostasis has been proven to be one of the critical contributors to the pathology of Parkinson's disease (PD). Ferritin is considered an intracellular protein responsible for storing cytosolic iron. Recent studies have found that ferritin can be secreted from cells independent of the classical endoplasmic reticulum-Golgi system. However, the precise mechanisms underlying the secretion of ferritin in the brain were not elucidated. In the present study, we demonstrated that the primary cultured astrocytes do have the ability to secrete ferritin, which is enhanced by iron treatment. Increased ferritin secretion was accompanied by increased protein expression of ferritin response to iron stimulation. Further study showed that iron-induced expression and secretion of ferritin could be inhibited by CQ or 3-MA pretreatment. In addition, the knockdown of transient receptor potential mucolipin 1 (TRPML1) antagonized iron-induced ferritin secretion, accompanied by further increased intracellular protein levels of ferritin. Further study demonstrated that ferritin colocalized with LAMP1 in iron-treated astrocytes. On the contrary, ras-associated protein 27a (Rab27a) knockdown further enhanced iron-induced ferritin secretion and decreased intracellular protein levels of ferritin. Furthermore, we also showed that the secretory autophagy protein tripartite motif containing 16 (TRIM16) and sec22b decreased in iron-treated astrocytes. These results suggested that astrocytes might secrete ferritin via TRPML1-mediated exocytosis. This provides new evidence for the mechanisms underlying the secretion of ferritin in primary cultured astrocytes under a high iron environment.

Insight into Nrf2: a bibliometric and visual analysis from 2000 to 2022

Background: Nrf2 plays a pivotal role in governing the antioxidant defense system, triggering the transcription of diverse genes involved in cellular protection. Its role in mitigating oxidative damage and modulating inflammatory processes has made Nrf2 an attractive target for therapeutic interventions. Despite the growing interest in Nrf2 research, a bibliometric analysis is relatively rare. This study aimed to clarify Nrf2's role in multiple diseases, identify emerging trends and hotspots using bibliometric analysis, and provide valuable insights and potential directions for future therapeutic interventions. Methods: The Science Citation Index of Web of Science Core library from 2000 to 2022 was searched on 22 October 2022. Use Microsoft Excel, CiteSpace, Bibliometrix, and VOS viewers for data collection and visualization of research focus and trends. Results: A vast collection of 22,040 research studies on Nrf2 published between 2000 and 2022 were identified. Nrf2 research has seen significant growth globally from 2000 to 2022. China leaded in publication numbers (9,623, 43.66%), while the United States dominated in citation frequency with 261,776 citations. China Medical University was the most productive institutions (459, 2.08%). Masayuki Yamamoto topped in publications (307), while Itoh K. ranked first in citations with 3669. Free Radical Biology and Medicine was the journal with the most studies and citations on Nrf2 (613, 29,687 citations). The analysis of keyword clustering enhanced the categorization of topics and can be summarized as oxidative stress, cancer, disorders in glycolipid metabolism, inflammation, and neurological conditions. Conclusion: China and the United States are the pioneers in Nrf2 research. Recently, there has been a comprehensive exploration of Nrf2 involving both experimental and clinical aspects, as well as mechanisms and therapeutic applications. Investigating novel molecular mechanisms, including NF-κB, Ho1, and Keap1, and developing enhanced, targeted Nrf2 activators or inhibitors to uncover the interplay among cancer, glycolipid metabolic disorder, inflammation, and neurological disorders will be upcoming trends and hotspots.

Autophagy in sarcopenia: Possible mechanisms and novel therapies

With global population aging, age-related diseases, especially sarcopenia, have attracted much attention in recent years. Characterized by low muscle strength, low muscle quantity or quality and low physical performance, sarcopenia is one of the major factors associated with an increased risk of falls and disability. Much effort has been made to understand the cellular biological and physiological mechanisms underlying sarcopenia. Autophagy is an important cellular self-protection mechanism that relies on lysosomes to degrade misfolded proteins and damaged organelles. Research designed to obtain new insight into human diseases from the autophagic aspect has been carried out and has made new progress, which encourages relevant studies on the relationship between autophagy and sarcopenia. Autophagy plays a protective role in sarcopenia by modulating the regenerative capability of satellite cells, relieving oxidative stress and suppressing the inflammatory response. This review aims to reveal the specific interaction between sarcopenia and autophagy and explore possible therapies in hopes of encouraging more specific research in need and unlocking novel promising therapies to ameliorate sarcopenia.

Tumor necrosis factor-α-induced protein 8-like 2 alleviates morphine antinociceptive tolerance through reduction of ROS-mediated apoptosis and MAPK/NF-κB signaling pathways

Chronic morphine tolerance is a repulsive barrier to the clinical treatment of pain. Whereas the underlying molecular mechanisms of morphine tolerance remain unknown. Here, we proposed that tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) is an essential control point regarding the progression of chronic morphine tolerance. We found that TIPE2 levels in the lumbar spinal cord were significantly downregulated in the morphine tolerance mouse model. Specifically, decreased TIPE2 by morphine tolerance was primarily expressed in spinal neurons, while increased expression of spinal TIPE2 distinctly attenuated the chronic morphine antinociceptive tolerance and tolerance-associated hyperalgesia. We also observed that increased expression of spinal TIPE2 significantly reduced morphine tolerance-induced neuronal ROS production and apoptosis, along with the activation of MAPKs and NF-κB signaling pathways. Moreover, the increased TIPE2 expression inhibited neuronal activation and glial reactivity in the spinal dorsal horn after chronic morphine exposure. Additionally, TIPE2 overexpression in cultured SH-SY5Y cells significantly suppressed ROS production and apoptosis in response to morphine challenge. Therefore, we can conclude that the upregulation of spinal TIPE2 may attenuate the morphine antinociceptive tolerance via TIPE2-dependent downregulation of neuronal ROS, inhibition of neuronal apoptosis, suppression of MAPKs and NF-κB activation. TIPE2 may be a potential strategy for preventing morphine tolerance in the future studies and clinical settings. Schematic diagram for the proposed mechanisms of TIPE2 regulates morphine antinociceptive tolerance. TIPE2 may alleviate morphine antinociceptive tolerance by regulating MAPK/NF-κB signaling pathways and apoptosis, which might be associated with ROS production.

3, 3'-diindolylmethane enhances macrophage efferocytosis and subsequently relieves visceral pain via the AhR/Nrf2/Arg-1-mediated arginine metabolism pathway

BACKGROUND

3, 3'-diindolylmethane (DIM), a classical aryl hydrocarbon receptor (AhR) agonist, has been shown to relieve neuropathic pain, but few studies have reported the efficacy of DIM in visceral pain under colitis condition.

PURPOSE

This study aimed to investigate the effect and mechanism of DIM on visceral pain under colitis condition.

METHODS

Cytotoxicity was performed using the MTT assay. RT-qPCR and ELISA assays were applied to determine the expression and release of algogenic substance P (SP), nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Flow cytometry was used to examine the apoptosis and efferocytosis. The expression of Arg-1-arginine metabolism-related enzymes was detected using western blotting assays. ChIP assays were used to examine the binding of Nrf2 to Arg-1. Mouse models of dextran sulfate sodium (DSS) were established to illustrate the effect of DIM and validate the mechanism in vivo.

RESULTS

DIM did not directly affect expressions and release of algogenic SP, NGF and BDNF in enteric glial cells (EGCs). However, when co-cultured with DIM-pre-treated RAW264.7 cells, the release of SP and NGF was decreased in lipopolysaccharides-stimulated EGCs. Furthermore, DIM increased the number of PKH67⁺ F4/80⁺ cells in the co-culture system of EGCs and RAW264.7 cells in vitro and alleviated visceral pain under colitis condition by regulating levels of SP and NGF as well as values of electromyogram (EMG), abdominal withdrawal reflex (AWR) and tail-flick latency (TFL) in vivo, which was significantly inhibited by efferocytosis inhibitor. Subsequently, DIM was found to down-regulate levels of intracellular arginine, up-regulate levels of ornithine, putrescine and Arg-1 but not extracellular arginine or other metabolic enzymes, and polyamine scavengers reversed the effect of DIM on efferocytosis and release of SP and NGF. Moving forward, Nrf2 transcription and the binding of Nrf2 to Arg-1-0.7 kb was enhanced by DIM, AhR antagonist CH223191 abolished the promotion of DIM on Arg-1 and efferocytosis. Finally, nor-NOHA validated the importance of Arg-1-dependent arginine metabolism in DIM-alleviated visceral pain.

CONCLUSION

DIM enhances macrophage efferocytosis in an arginine metabolism-dependent manner via "AhR-Nrf2/Arg-1" signals and inhibits the release of SP and NGF to relieve visceral pain under colitis condition. These findings provide a potential therapeutic strategy for the treatment of visceral pain in patients with colitis.

MG53 ameliorates nerve injury induced neuropathic pain through the regulation of Nrf2/HO-1 signaling in rats

Neuropathic pain is one of the most common types of chronic pain, and it arises as a direct consequence of a lesion or disease that affects the somatosensory system. Mitsugumin53 (MG53), which is a member of the TRIM family of proteins and is known as TRIM72, exerts protective effects on muscle, lung, kidney, brain, and other cells or tissues. Recently, increasing evidence has indicated that MG53 plays a vital role in regulating neuroinflammation and oxidative stress. However, the relationship between MG53 and neuropathic pain is unclear. In this study, we aimed to explore the role of MG3 in neuropathic pain after chronic constriction injury (CCI) to the sciatic nerve in rats. To explore the mechanism of MG53 regulating the development of neuropathic pain, the rats was injected (intrathecal injection) of recombinant human MG53 (rhMG53) protein and/or nuclear factor erythroid 2-related factor 2 (Nrf2) siRNA after CCI. Mechanical allodynia or thermal hyperalgesia was assessed by the 50% paw withdrawal threshold (PWT) or the paw withdrawal latency (PWL). The target molecules was detected using western blotting (WB), immunofluorescence (IF), quantitative real-time polymerase chain reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), biochemical evaluations, and Dihydroethidium (DHE) staining. The results indicated that the expression level of MG53 in the spinal cord was increased after CCI in rats. Moreover, intrathecal injection with rhMG53 protein notably alleviated CCI-induced mechanical allodynia, thermal hyperalgesia, neuroinflammation，oxidative stress and the increased level of reactive oxygen species (ROS) via activation of the Nrf2/heme oxygenase-1 (HO-1) signaling pathway. However, administration of Nrf2 siRNA abrogated the analgesic, anti-inflammatory and antioxidant effects of rhMG53 in CCI model rats. Our study demonstrated that MG53 improved neuropathic pain, neuroinflammation, and oxidative stress via activation of the Nrf2/HO-1 signaling pathway in the spinal cord of CCI model rats, which suggested that MG53 may serve as a new target for the treatment of neuropathic pain.

Role of Senescent Astrocytes in Health and Disease

For many decades after their discovery, astrocytes, the abundant glial cells of the brain, were believed to work as a glue, supporting the structure and metabolic functions of neurons. A revolution that started over 30 years ago revealed many additional functions of these cells, including neurogenesis, gliosecretion, glutamate homeostasis, assembly and function of synapses, neuronal metabolism with energy production, and others. These properties have been confirmed, limited however, to proliferating astrocytes. During their aging or following severe brain stress lesions, proliferating astrocytes are converted into their no-longer-proliferating, senescent forms, similar in their morphology but profoundly modified in their functions. The changed specificity of senescent astrocytes is largely due to their altered gene expression. The ensuing effects include downregulation of many properties typical of proliferating astrocytes, and upregulation of many others, concerned with neuroinflammation, release of pro-inflammatory cytokines, dysfunction of synapses, etc., specific to their senescence program. The ensuing decrease in neuronal support and protection by astrocytes induces the development, in vulnerable brain regions, of neuronal toxicity together with cognitive decline. Similar changes, ultimately reinforced by astrocyte aging, are also induced by traumatic events and molecules involved in dynamic processes. Senescent astrocytes play critical roles in the development of many severe brain diseases. The first demonstration, obtained for Alzheimer's disease less than 10 years ago, contributed to the elimination of the previously predominant neuro-centric amyloid hypothesis. The initial astrocyte effects, operating a considerable time before the appearance of known Alzheimer's symptoms evolve with the severity of the disease up to their proliferation during the final outcome. Involvement of astrocytes in other neurodegenerative diseases and cancer is now intensely investigated.

Deficiency of RAB39B Activates ER Stress-Induced Pro-apoptotic Pathway and Causes Mitochondrial Dysfunction and Oxidative Stress in Dopaminergic Neurons by Impairing Autophagy and Upregulating α-Synuclein

Deletion and missense or nonsense mutation of RAB39B gene cause familial Parkinson's disease (PD). We hypothesized that deletion and mutation of RAB39B gene induce degeneration of dopaminergic neurons by decreasing protein level of functional RAB39B and causing RAB39B deficiency. Cellular model of deletion or mutation of RAB39B gene-induced PD was prepared by knocking down endogenous RAB39B in human SH-SY5Y dopaminergic cells. Transfection of shRNA-induced 90% reduction in RAB39B level significantly decreased viability of SH-SY5Y dopaminergic neurons. Deficiency of RAB39B caused impairment of macroautophagy/autophagy, which led to increased protein levels of α-synuclein and phospho-α-synuclein^Ser129 within endoplasmic reticulum (ER) and mitochondria. RAB39B deficiency-induced increase of ER α-synuclein and phospho-α-synuclein^Ser129 caused activation of ER stress, unfolded protein response, and ER stress-induced pro-apoptotic cascade. Deficiency of RAB39B-induced increase of mitochondrial α-synuclein decreased mitochondrial membrane potential and increased mitochondrial superoxide. RAB39B deficiency-induced activation of ER stress pro-apoptotic pathway, mitochondrial dysfunction, and oxidative stress caused apoptotic death of SH-SY5Y dopaminergic cells by activating mitochondrial apoptotic cascade. In contrast to neuroprotective effect of wild-type RAB39B, PD mutant (T168K), (W186X), or (G192R) RAB39B did not prevent tunicamycin- or rotenone-induced increase of neurotoxic α-synuclein and activation of pro-apoptotic pathway. Our results suggest that RAB39B is required for survival and macroautophagy function of dopaminergic neurons and that deletion or PD mutation of RAB39B gene-induced RAB39B deficiency induces apoptotic death of dopaminergic neurons via impairing autophagy function and upregulating α-synuclein.

Cellular battle against endoplasmic reticulum stress and its adverse effect on health

The endoplasmic reticulum (ER) is a dynamic organelle and a reliable performer for precisely folded proteins. To maintain its function and integrity, arrays of sensory and quality control systems enhance protein folding fidelity and resolve the highest error-prone areas. Yet numerous internal and external factors disrupt its homeostasis and trigger ER stress responses. Cells try to reduce the number of misfolded proteins via the UPR mechanism, and ER-related garbage disposals systems like ER-associated degradation (ERAD), ER-lysosome-associated degradation (ERLAD), ER-Associated RNA Silencing (ERAS), extracellular chaperoning, and autophagy systems, which activates and increase the cell survival rate by degrading misfolded proteins, prevent the aggregated proteins and remove the dysfunctional organelles. Throughout life, organisms must confront environmental stress to survive and develop. Communication between the ER & other organelles, signaling events mediated by calcium, reactive oxygen species, and inflammation are linked to diverse stress signaling pathways and regulate cell survival or cell death mechanisms. Unresolved cellular damages can cross the threshold limit of their survival, resulting in cell death or driving for various diseases. The multifaceted ability of unfolded protein response facilitates the therapeutic target and a biomarker for various diseases, helping with early diagnosis and detecting the severity of diseases.

Down-regulation miR-146a-5p in Schwann cell-derived exosomes induced macrophage M1 polarization by impairing the inhibition on TRAF6/NF-κB pathway after peripheral nerve injury

BACKGROUND

Both Schwann cell-derived exosomes (SC-Exos) and macrophagic sub-phenotypes are closely related to the regeneration and repair after peripheral nerve injury (PNI). However, the crosstalk between them is less clear.

OBJECTIVE

We aim to investigate the roles and underlying mechanisms of exosomes from normoxia-condition Schwann cell (Nor-SC-Exos) and from post-injury oxygen-glucose-deprivation-condition Schwann cell in regulating macrophagic sub-phenotypes and peripheral nerve injury repair.

METHOD

Both Nor-SC-Exos and OGD-SC-Exos were extracted through ultracentrifugation, identified by transmission electron microscopy (TEM), Nanosight tracking analysis (NTA) and western blotting. High-throughput sequencing was performed to explore the differential expression of microRNAs in both SC-Exos. In vitro, RAW264.7 macrophage was treated with two types of SC-Exos, M1 macrophagic markers (IL-10, Arg-1, TGF-β1) and M2 macrophagic markers (IL-6, IL-1β, TNF-α) were detected by enzyme-linked Immunosorbent Assay (ELISA) or qRT-PCR, and the expression of CD206, iNOS were detected via cellular immunofluorescence (IF) to judge macrophage sub-phenotypes. Dorsal root ganglion neurons (DRGns) were co-cultured with RAW264.7 cells treated with Nor-SC-Exos and OGD-SC-Exos, respectively, to explore their effect on neuron growth. In vivo, we established a sciatic nerve crush injury rat model. Nor-SC-Exos and OGD-SC-Exos were locally injected into the injury site. The mRNA expression of M1 macrophagic markers (IL-10, Arg-1, TGF-β1) and M2 macrophagic markers (IL-6, IL-1β, TNF-α) were detected by qRT-PCR to determine the sub-phenotype of macrophages in the injury site. IF was used to detect the expression of MBP and NF200, reflecting the myelin sheath and axon regeneration, and sciatic nerve function index (SFI) was measured to evaluate function repair.

RESULT

In vitro, Nor-SC-Exos promoted macrophage M2 polarization, increased anti-inflammation factors secretion, and facilitated axon elongation of DRGns. OGD-SC-Exos promoted M1 polarization, increased pro-inflammation factors secretion, and restrained axon elongation of DRGns. High-throughput sequencing and qRT-PCR results found that compared with Nor-SC-Exos, a shift from anti-inflammatory (pro-M2) to pro-inflammatory (pro-M1) of OGD-SC-Exos was closely related to the down-regulation of miR-146a-5p and its decreasing inhibition on TRAF6/NF-κB pathway after OGD injury. In vivo, we found Nor-SC-Exos and miR-146a-5p mimic promoted regeneration of myelin sheath and axon, and facilitated sciatic function repair via targeting TRAF6, while OGD-SC-Exos and miR-146a-5p inhibitor restrained them.

CONCLUSION

Our study confirmed that miR-146a-5p was significantly decreased in SC-Exos under the ischemia-hypoxic microenvironment of the injury site after PNI, which mediated its shift from promoting macrophage M2 polarization (anti-inflammation) to promoting M1 polarization (pro-inflammation), thereby limiting axonal regeneration and functional recovery.

Translocator protein alleviates allodynia and improves Schwann cell function against diabetic peripheral neuropathy via activation of the Nrf2-dependent antioxidant system and promoting autophagy

AIMS

In diabetes, autophagy and the nuclear factor erythroid-derived-2-like 2 (Nrf2)-dependent antioxidant system are impaired. Translocator protein (TSPO) agonist Ro5-4864 alleviates neuropathic pain, including diabetic peripheral neuropathy (DPN). However, the precise mechanisms remain unclear. Thus, we investigated the effects of Ro5-4864 on autophagy and the Nrf2-dependent antioxidant system in the sciatic nerves of DPN rats.

METHODS

All rats were randomly assigned to Sham or DPN group. After type 2 diabetes modelling (established by high-fat diet and streptozotocin injection) followed by behavioural tests, established DPN rats were randomly assigned to the DPN group, the Ro (TSPO agonist Ro5-4864) group, the Ro + 3-MA (autophagy inhibitor) group and the Ro + ML385 (Nrf2 inhibitor) group. Behavioural assessments were performed at baseline, on days 3, 7, 14, 21 and 28. Sciatic nerves were collected on day 28 for immunofluorescence, morphological and western blot analyses.

RESULTS

Ro5-4864 alleviated allodynia and increased myelin sheath thickness and myelin protein expression after DPN. Beclin-1 (p < 0.01) and LC3-II/LC3-I ratio (p < 0.01) decreased and p62 (p < 0.01) accumulated in the DPN rats. Ro5-4864 administration increased the Beclin-1 and LC3-II/LC3-I ratio and decreased p62 accumulation. Furthermore, nuclear Nrf2 contents (p < 0.01) and cytoplasmic HO-1 (p < 0.01) and NQO1 (p < 0.01) expressions were significantly inhibited in the DPN rat, which was also improved by Ro5-4864. All the beneficial effects were abrogated by 3-MA or ML385.

CONCLUSION

TSPO exhibited a potent analgesic effect and improved Schwann cell function and regeneration against DPN by activating the Nrf2-dependent antioxidant system and promoting autophagy.

New advances in Nrf2-mediated analgesic drugs

BACKGROUND

Oxidative stress is an inevitable process that occurs during life activities, and it can participate in the development of inflammation. Although great progress has been made according to research examining analgesic drugs and therapies, there remains a need to develop new analgesic drugs to fill certain gaps in both the experimental and clinical space.

PURPOSE

This review reports the research and preclinical progress of this class of analgesics by summarizing known nuclear factor E-2-related factor-2 (Nrf2) pathway-modulating substances.

STUDY DESIGN

We searched and reported experiments that intervene in the Nrf2 pathway and its various upstream and downstream molecules for analgesic therapy.

METHODS

The medical literature database (PubMed) was searched for experimental studies examining the reduction of pain in animals through the Nrf2 pathway, the research methods were analyzed, and the pathways were classified and reported according to the pathway of these experimental interventions.

RESULTS

Humans have identified a variety of substances that can fight pain by regulating the expression of Nrf2 and its upstream and downstream pathways.

CONCLUSION

The Nrf2 pathway exerts anti-inflammatory activity by regulating oxidative stress, thereby playing a role in the fight against pain.

Chemokine CCL7 mediates trigeminal neuropathic pain via CCR2/CCR3-ERK pathway in the trigeminal ganglion of mice

BACKGROUND

Chemokine-mediated neuroinflammation plays an important role in the pathogenesis of neuropathic pain. The chemokine CC motif ligand 7 (CCL7) and its receptor CCR2 have been reported to contribute to neuropathic pain via astrocyte-microglial interaction in the spinal cord. Whether CCL7 in the trigeminal ganglion (TG) involves in trigeminal neuropathic pain and the involved mechanism remain largely unknown.

METHODS

The partial infraorbital nerve transection (pIONT) was used to induce trigeminal neuropathic pain in mice. The expression of Ccl7, Ccr1, Ccr2, and Ccr3 was examined by real-time quantitative polymerase chain reaction. The distribution of CCL7, CCR2, and CCR3 was detected by immunofluorescence double-staining. The activation of extracellular signal-regulated kinase (ERK) was examined by Western blot and immunofluorescence. The effect of CCL7 on neuronal excitability was tested by whole-cell patch clamp recording. The effect of selective antagonists for CCR1, CCR2, and CCR3 on pain hypersensitivity was checked by behavioral testing.

RESULTS

Ccl7 was persistently increased in neurons of TG after pIONT, and specific inhibition of CCL7 in the TG effectively relieved pIONT-induced orofacial mechanical allodynia. Intra-TG injection of recombinant CCL7 induced mechanical allodynia and increased the phosphorylation of ERK in the TG. Incubation of CCL7 with TG neurons also dose-dependently enhanced the neuronal excitability. Furthermore, pIONT increased the expression of CCL7 receptors Ccr1, Ccr2, and Ccr3. The intra-TG injection of the specific antagonist of CCR2 or CCR3 but not of CCR1 alleviated pIONT-induced orofacial mechanical allodynia and reduced ERK activation. Immunostaining showed that CCR2 and CCR3 are expressed in TG neurons, and CCL7-induced hyperexcitability of TG neurons was decreased by antagonists of CCR2 or CCR3.

CONCLUSION

CCL7 activates ERK in TG neurons via CCR2 and CCR3 to enhance neuronal excitability, which contributes to the maintenance of trigeminal neuropathic pain. CCL7-CCR2/CCR3-ERK pathway may be potential targets for treating trigeminal neuropathic pain.