Proteomic Analysis of Emodin Treatment in Neuropathic Pain Reveals Dysfunction of the Calcium Signaling Pathway

Machine learning-driven identification of critical gene programs and key transcription factors in migraine

BACKGROUND

Migraine is a complex neurological disorder characterized by recurrent episodes of severe headaches. Although genetic factors have been implicated, the precise molecular mechanisms, particularly gene expression patterns in migraine-associated brain regions, remain unclear. This study applies machine learning techniques to explore region-specific gene expression profiles and identify critical gene programs and transcription factors linked to migraine pathogenesis.

METHODS

We utilized single-nucleus RNA sequencing (snRNA-seq) data from 43 brain regions, along with genome-wide association study (GWAS) data, to investigate susceptibility to migraine. The cell-type-specific expression (CELLEX) algorithm was employed to calculate specific expression profiles for each region, while non-negative matrix factorization (NMF) was applied to decompose gene programs within the single-cell data from these regions. Following the annotation of brain region expression profiles and gene programs to the genome, we employed stratified linkage disequilibrium score regression (S-LDSC) to assess the associations between brain regions, gene programs, and migraine-related SNPs. Key transcription factors regulating critical gene programs were identified using a random forest model based on regulatory networks derived from the GTEx consortium.

RESULTS

Our analysis revealed significant enrichment of migraine-associated single nucleotide polymorphisms (SNPs) in the posterior nuclear complex-medial geniculate nuclei (PoN_MG) of the thalamus, highlighting this region's crucial role in migraine pathogenesis. Gene program 1, identified through NMF, was enriched in the calcium signaling pathway, a known contributor to migraine pathophysiology. Random forest analysis predicted ARID3A as the top transcription factor regulating gene program 1, suggesting its potential role in modulating calcium-related genes involved in migraine.

CONCLUSION

This study provides new insights into the molecular mechanisms underlying migraine, emphasizing the importance of the PoN_MG thalamic region, calcium signaling pathways, and key transcription factors like ARID3A. These findings offer potential avenues for developing targeted therapeutic strategies for migraine treatment.

DNA methylation profiling of CpG islands in trigeminal ganglion of rats with orofacial pain induced by experimental tooth movement

BACKGROUND

Tooth movement induced orofacial pain is the most cited negative effect during orthodontic treatment, while treatment options without side effects are limited. The differential expression of pain-related genes due to DNA methylation and demethylation is instrumental in pain. The purpose of the study was to evaluate the DNA methylation profiling of CpG islands (CGI) and CGI shores in promoter regions in trigeminal ganglions (TG) of tooth movement induced orofacial pain rats, thus to further insight the DNA methylation regulation in orofacial pain.

MATERIALS AND METHODS

An orofacial pain rat model was constructed by ligating coil springs between the incisor and first maxillary molar with 40 g of force. The Rat Grimace Score (RGS) was used for pain evaluation. The genome methylation status was analyzed by the reduced representation bisulfite sequencing (RRBS) technique. Gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) analyses were conducted in the differentially methylated regions (DMRs). Moreover, a protein-protein interaction (PPI) network was established to detect annotated genes associated with pain.

RESULTS

RGS was significantly higher in orofacial pain rats than in sham rats. RRBS showed widespread methylation changes in CGI and CGI shores in TG promoter regions. Both 902 hypermethylated DMRs and 862 hypomethylated DMRs were found in the CGIs of promoter regions. KEGG analysis revealed that annotated genes are participated in endocrine, nervous, immune, and sensory systems. Moreover, the "Calcium signaling pathway", "Wnt signaling pathway" and "Neuroactive ligand-receptor interaction" were significantly enriched pathways. Furthermore, PPI network showed several genes (Ctnnb1, Dlg4, Creb1, Camk2g, Bmp2, etc.) with different methylation statuses were reported to be associated with pain.

CONCLUSIONS

This study demonstrated methylation changes were existed in CGI and CGI shores in TG promoter regions when pain occurs, thus providing a basis for further study on the mechanism of DNA methylation in orofacial pain.

A comprehensive review of traditional Chinese medicine in treating neuropathic pain

Neuropathic pain (NP) is a common, intractable chronic pain caused by nerve dysfunction and primary lesion of the nervous system. The etiology and pathogenesis of NP have not yet been clarified, so there is a lack of precise and effective clinical treatments. In recent years, traditional Chinese medicine (TCM) has shown increasing advantages in alleviating NP. Our review aimed to define the therapeutic effect of TCM (including TCM prescriptions, TCM extracts and natural products from TCM) on NP and reveal the underlying mechanisms. Literature from 2018 to 2024 was collected from databases including Web of Science, PubMed, ScienceDirect, Google academic and CNKI databases. Herbal medicine, Traditional Chinese medicines (TCM), neuropathic pain, neuralgia and peripheral neuropathy were used as the search terms. The anti-NP activity of TCM is clarified to propose strategies for discovering active compounds against NP, and provide reference to screen anti-NP drugs from TCM. We concluded that TCM has the characteristics of multi-level, multi-component, multi-target and multi-pathway, which can alleviate NP through various pathways such as anti-inflammation, anti-oxidant, anti-apoptotic pathway, regulating autophagy, regulating intestinal flora, and influencing ion channels. Based on the experimental study and anti-NP mechanism of TCM, this paper can offer analytical evidence to support the effectiveness in treating NP. These references will be helpful to the research and development of innovative TCM with multiple levels and multiple targets. TCM can be an effective treatment for NP and can serve as a treasure house for new drug development.

Treatment of neuropathic pain by traditional Chinese medicine: An updated review on their effect and putative mechanisms of action

Neuropathic pain (NP) is a common chronic pain with heterogeneous clinical features, and consequent lowering of quality of life. Currently, although conventional chemical drugs can effectively manage NP symptoms in the short term, their long-term efficacy is limited, and they come with significant side effects. In this regard, traditional Chinese medicine (TCM) provides a promising avenue for treating NP. Numerous pharmacological and clinical studies have substantiated the effectiveness of TCM with multiple targets and mechanisms. We aimed to outline the characteristics of TCM, including compound prescriptions, single Chinese herbs, active ingredients, and TCM physical therapy, for NP treatment and discussed their efficacy by analyzing the pathogenesis of NP. Various databases, such as PubMed, Web of Science, China National Knowledge Infrastructure, and Wanfang database, were searched. We focused on recent research progress in NP treatment by TCM. Finally, we proposed the future challenges and emerging trends in the treatment of NP. TCM demonstrates significant clinical efficacy in NP treatment, employing multi-mechanisms. Drawing from the theory of syndrome differentiation, four types of dialectical treatments for NP by compound TCM prescriptions were introduced: promoting blood circulation and removing blood stasis; promoting blood circulation and promote Qi flow; warming Yang and benefiting Qi; soothing the liver and regulating Qi. Meanwhile, 33 single Chinese herbs and 25 active ingredients were included. In addition, TCM physical therapy (e.g., acupuncture, massage, acupoint injection, and fumigation) also showed good efficacy in NP treatment. TCM, particularly through the use of compound prescriptions and acupuncture, holds bright prospects in treating NP owing to its diverse holistic effects. Nonetheless, the multi-targets of TCM may result in possible disadvantages to NP treatment, and the pharmacological mechanisms of TCM need further evaluation. Here, we provide an overview of NP treatment via TCM, based on the pathogenesis and the potential therapeutic mechanisms, thus providing a reference for further studies.

Network Pharmacology and In vitro Experimental Verification to Explore the Mechanism of Chaiqin Qingning Capsule in the Treatment of Pain

BACKGROUND

Chaiqin Qingning capsule (CQQNC) has been used to relieve pain in practice. However, the active components, pain targets, and molecular mechanisms for pain control are unclear.

OBJECTIVE

To explore the active components and potential mechanisms of the analgesic effect of CQQNC through network pharmacology and in vitro experiments.

METHODS

The main active components and the corresponding targets of CQQNC were screened from the TCMSP and the SwissTargetPrediction databases. Pain-related targets were selected in the OMIM, Gene- Cards, and DrugBank databases. These targets were intersected to obtain potential analgesic targets. The analgesic targets were imported into the STRING and DAVID databases for protein-protein interaction (PPI), gene ontology (GO) function enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Cytoscape software (V3.7.1) was used to construct an active component-intersection network. Finally, the key components were docked with the core targets. The analgesic mechanism of CQQNC was verified by RAW264.7 cell experiment.

RESULTS

30 active CQQNC components, 617 corresponding targets, and 3,214 pain-related target genes were found. The main active components were quercetin, kaempferol, and chenodeoxycholic acid etc. The key targets were ALB, AKT1, TNF, IL6, TP53, IL1B, and SRC. CQQNC can exert an analgesic effect through PI3K-Akt, MAPK signaling pathways, etc. Molecular docking showed that these active components had good binding activities with key targets. The results of in vitro experiments showed that CQQNC could exert antiinflammatory and analgesic effects through MAPK/AKT/NF-kB signaling pathways.

CONCLUSION

CQQNC exerts pain control through inhibiting MAPK/AKT/NF-kB signaling pathways.

Integration of microbiota and metabolomics reveals the analgesic mechanisms of emodin against neuropathic pain

BACKGROUND AND OBJECTIVE

Neuropathic pain (NeP) induced dysbiosis of intestinal microbiota in chronic constriction injury (CCI) rats. Emodin has analgesic effect but the detailed mechanism is not clear at the present time. This study aims to explore the underling mechanism of action of emodin against NeP with in CCI model.

METHODS

Male SD rats (180-220 g) were randomly divided into three groups: sham group, CCI group, and emodin group. Behavioral tests were performed to evaluate the therapeutic effects of emodin on CCI model. Feces and spinal cords of all rats were collected 15 days after surgery. 16S rDNA sequencing, untargeted metabolomics, qPCR and ELISA were performed.

RESULTS

Mechanical withdrawal thresholds (MWT), thermal withdrawal latency (TWL) and Sciatic functional index (SFI) in emodin group were significantly higher than CCI group (P < 0.05). Emodin not only inhibited the expression of pro-inflammatory cytokines in the spinal cords and colonic tissue, but also increased the expression of tight junction protein in colonic tissue. 16S rDNA sequencing showed that emodin treatment changed the community structure of intestinal microbiota in CCI rats. Untargeted metabolomics analysis showed that 33 differential metabolites were screened out between CCI group and emodin group. After verification, we found that emodin increased the level of S-adenosylmethionine (SAM) and Histamine in the spinal cord of CCI rats.

CONCLUSION

Emodin was effective in relieving neuropathic pain, which is linked to inhibition inflammatory response, increasing the proportion of beneficial bacteria and beneficial metabolites.

Emodin alleviates chronic constriction injury-induced neuropathic pain and inflammation via modulating PPAR-gamma pathway

Neuropathic pain has been characterized as chronic pain resulting from pathological damage to the sensorimotor system. Because of its complex nature, it remains refractory to most of the therapeutic interventions, and surgical intervention and physiotherapy alongside steroidal treatments remain the only treatment protocols with limited success, hence solidifying the need to find efficacious therapeutic alternatives. Emodin was used as a post-treatment for its potential to be neuroprotective in the treatment of chronic constriction injury-induced NP. The first day following surgery, Emodin treatment began, and it lasted until the 21st day. On days 3, 7, 14 and 21, all behavioral investigations were conducted. The sciatic nerve and spinal cord were extracted for further molecular examination. Emodin elevated response latency, was able to delay the onset of mechanical hyperalgesia in rats on days 7, 14, and 21 and reduced the CCI-induced paw deformation. Emodin treatment significantly reduced lipid peroxidation and NO levels while restoring the GST, GSH and catalase. It significantly improved the disorientation of the sciatic nerve and spinal cord confirmed by H & E staining and reduced inflammatory markers as observed by the quantification of COX-2, TNF-α, p-NFκb and up-regulated PPAR-γ levels by ELISA and PCR. According to the findings, Emodin has antinociceptive and anti-hyperalgesic properties, which reduced pain perception and inflammation. We also suggested the involvement of PPAR-γ pathway in the therapeutic potential of emodin in chronic nerve injury.

Emodin suppresses oxaliplatin-induced neuropathic pain by inhibiting COX2/NF-κB mediated spinal inflammation

Oxaliplatin (OXA) is a common chemotherapy drug for colorectal, gastric, and pancreatic cancers. The anticancer effect of OXA is often accompanied by neurotoxicity and acute and chronic neuropathy. The symptoms present as paresthesia and pain which adversely affect patients' quality of life. Herein, five consecutive intraperitoneal injections of OXA at a dose of 4 mg/kg were used to mimic chemotherapy. OXA administration induced mechanical allodynia, activated spinal astrocytes, and increased inflammatory response. To develop an effective therapeutic measure for OXA-induced neuropathic pain, emodin was intrathecally injected into OXA rats. Emodin developed an analgesic effect, as demonstrated by a significant increase in the paw withdrawal threshold of OXA rats. Moreover, emodin treatment reduced the pro-inflammatory cytokines (tumor necrosis factor-α and interleukin-1β) which upregulated in OXA rats. Furthermore, autodock data showed four hydrogen bonds were formed between emodin and cyclooxygenase-2 (COX2), and emodin treatment decreased COX2 expression in OXA rats. Cell research further proved that emodin suppressed nuclear factor κB (NF-κB)-mediated inflammatory signal and reactive oxygen species level. Taken together, emodin reduced spinal COX2/NF-κB mediated inflammatory signal and oxidative stress in the spinal cord of OXA rats which consequently relieved OXA-induced neuropathic pain.

Emodin alleviates arthritis pain through reducing spinal inflammation and oxidative stress

Chronic pain is the predominant problem for rheumatoid arthritis patients, and negatively affects quality of life. Arthritis pain management remains largely inadequate, and developing new treatment strategies are urgently needed. Spinal inflammation and oxidative stress contribute to arthritis pain and represent ideal targets for the treatment of arthritis pain. In the present study, collagen-induced arthritis (CIA) mouse model was established by intradermally injection of type II collagen (CII) in complete Freund's adjuvant (CFA) solution, and exhibited as paw and ankle swelling, pain hypersensitivity and motor disability. In spinal cord, CIA inducement triggered spinal inflammatory reaction presenting with inflammatory cells infiltration, increased Interleukin-1β (IL-1β) expression, and up-regulated NOD-like receptor thermal protein domain associated protein 3 (NLRP3) and cleaved caspase-1 levels, elevated spinal oxidative level presenting as decreased nuclear factor E2-related factor 2 (Nrf2) expression and Superoxide dismutase (SOD) activity. To explore potential therapeutic options for arthritis pain, emodin was intraperitoneally injected for 3 days on CIA mice. Emodin treatment statistically elevated mechanical pain sensitivity, suppressed spontaneous pain, recovered motor coordination, decreased spinal inflammation score and IL-1β expression, increased spinal Nrf2 expression and SOD activity. Further, AutoDock data showed that emodin bind to Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) through two electrovalent bonds. And emodin treatment increased the phosphorylated AMPK at threonine 172. In summary, emodin treatment activates AMPK, suppresses NLRP3 inflammasome response, elevates antioxidant response, inhibits spinal inflammatory reaction and alleviates arthritis pain.

Geniposide Alleviates Neuropathic Pain in CCI Rats by Inhibiting the EGFR/PI3K/AKT Pathway And Ca2+ Channels

Neuropathic pain (NP) is a common disorder among individuals worldwide, but there is still no effective treatment for NP. The EGFR pathway promotes NP nociceptive sensitization and represents a potential therapeutic target. Geniposide is abundant in natural plants and has various pharmacological activities, such as analgesia and anti-inflammation properties, which can improve NP, but the specific mechanisms have not been elucidated. The present study first predicted and molecularly docked geniposide targets, suggesting that geniposide may play a role in improving NP by targeting EGFR. This study further clarified that geniposide alleviates NP and improves the inflammatory response using a chronic constriction injury (CCI) model, whereas the administration of an EGFR agonist weakens the above effects of geniposide. Analysis of transcriptome data further suggests that geniposide not only improves CCI symptoms by reducing EGFR/PI3K/AKT pathway activity but also may exert anti-inflammatory effects by inhibiting the Ca²⁺ signaling pathway. The above results affirm the potential value of geniposide in the treatment of NP and lay the foundation for further clinical application.

Emodin Interferes With Nitroglycerin-Induced Migraine in Rats Through CGMP-PKG Pathway

The purpose of this research was to explore the effect and mechanism of emodin in interfering with nitroglycerin-induced migraine rats. We carried out behavioral research within 2 h post-nitroglycerin (NTG) injection, and blood samples were collected through the abdominal aorta for measurements of nitric oxide (NO), calcitonin gene-related peptide (CGRP), substance P (SP), tumor necrosis factor (TNF-α) and cyclic guanosine monophosphate (cGMP) levels. Immunohistochemistry was adopted to detect the activation of c-Fos immunoreactive neurons in brain tissues. The number and integrated optical density (IOD) of c-Fos positive cells were measured using Image-Pro Plus. Western blotting was applied to detect the levels of PKG protein in rat brain tissues. The results showed that emodin can alleviate the pain response of migraine rats and significantly reduce the levels of NO, CGRP, SP, TNF-α and cGMP in migraine rats. In addition, emodin can significantly reduce the number of c-Fos positive cells and the IOD value. Moreover, the expression of PKG protein was significantly inhibited by emodin. Therefore, it is inferred that emodin can relieve migraine induced by NTG through the cGMP-PKG pathway, and can be used as a potential botanical medicine for the treatment of migraine.