Role of Dehydrocorybulbine in Neuropathic Pain After Spinal Cord Injury Mediated by P2X4 Receptor

Bidirectional two-sample Mendelian randomization analysis reveals a causal effect of interleukin-18 levels on postherpetic neuralgia risk

Background

Postherpetic neuralgia (PHN) is a debilitating complication of herpes zoster, characterized by persistent neuropathic pain that significantly impairs patients' quality of life. Identifying factors that determine PHN susceptibility is crucial for its management. Interleukin-18 (IL-18), a pro-inflammatory cytokine implicated in chronic pain, may play a critical role in PHN development.

Methods

In this study, we conducted bidirectional two-sample Mendelian randomization (MR) analyses to assess genetic relationships and potential causal associations between IL-18 protein levels increasing and PHN risk, utilizing genome-wide association study (GWAS) datasets on these traits. Two IL-18 datasets obtained from the EMBL's European Bioinformatics Institute database which contained 21,758 individuals with 13,102,515 SNPs and Complete GWAS summary data on IL-18 protein levels which contained 3,394 individuals with 5,270,646 SNPs. The PHN dataset obtained from FinnGen biobank had 195,191 individuals with 16,380,406 SNPs.

Results

Our findings from two different datasets of IL-18 protein levels suggest a correlation between genetically predicted elevations in IL-18 protein levels and an increased susceptibility to PHN.(IVW, OR and 95% CI: 2.26, 1.07 to 4.78; p = 0.03 and 2.15, 1.10 to 4.19; p =0.03, respectively), potentially indicating a causal effect of IL-18 protein levels increasing on PHN risk. However, we did not detect any causal effect of genetic liability to PHN risk on IL-18 protein levels.

Conclusion

These findings suggest new insights into identifying IL-18 protein levels increasing at risk of developing PHN and may aid in the development of novel prevention and treatment approaches for PHN.

Structure-Activity Relationship and Neuroprotective Activity of 1,5-Dihydro-2H-naphtho[1,2-b][1,4]diazepine-2,4(3H)-diones as P2X4 Receptor Antagonists

We analyzed the P2X4 receptor structure-activity relationship of a known antagonist 5, a 1,5-dihydro-2H-naphtho[1,2-b][1,4]diazepine-2,4(3H)-dione. Following extensive modification of the reported synthetic route, 4-pyridyl 21u (MRS4719) and 6-methyl 22c (MRS4596) analogues were most potent at human (h) P2X4R (IC50 0.503 and 1.38 μM, respectively, and selective versus hP2X1R, hP2X2/3R, hP2X3R). Thus, the naphthalene 6-, but not 7-position was amenable to substitution, and an N-phenyl ring aza-scan identified 21u with 3-fold higher activity than 5. Compounds 21u and 22c showed neuroprotective and learning- and memory-enhancing activities in a mouse middle cerebral artery occlusion (MCAO) model of ischemic stroke, with potency of 21u > 22c. 21u dose-dependently reduced infarct volume and reduced brain atrophy at 3 and 35 days post-stroke, respectively. Relevant to clinical implication, 21u also reduced ATP-induced [Ca2+]i influx in primary human monocyte-derived macrophages. This study indicates the translational potential of P2X4R antagonists for treating ischemic stroke, including in aging populations.

Uncovering the Effect and Mechanism of Rhizoma Corydalis on Myocardial Infarction Through an Integrated Network Pharmacology Approach and Experimental Verification

Background: Myocardial infarction (MI), characterized by reduced blood flow to the heart, is a coronary artery disorder with the highest morbidity and mortality among cardiovascular diseases. Consequently, there is an urgent need to identify effective drugs to treat MI. Rhizoma Corydalis (RC) is the dry tuber of Corydalis yanhusuo W.T. Wang, and is extensively applied in treating MI clinically in China. Its underlying pharmacological mechanism remains unknown. This study aims to clarify the molecular mechanism of RC on MI by utilizing network pharmacology and experimental verification.

Methods: Based on network pharmacology, the potential targets of the RC ingredients and MI-related targets were collected from the databases. Furthermore, core targets of RC on MI were identified by the protein-protein interaction (PPI) network and analyzed with Gene Ontology (GO) analysis and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Molecular docking was used to validate the binding affinity between the core targets and the bioactive components. Oxygen-glucose deprivation (OGD) was performed on H9c2 cells to mimic MI in vitro. A Cell Counting Kit-8 assay was used to assess the cardioprotective effect of the active ingredient against OGD. Western blot analysis and RT-qPCR were used to measure the cell apoptosis and inflammation level of H9c2 cells.

Results: The network pharmacology obtained 60 bioactive components of RC, 431 potential targets, and 1131 MI-related targets. In total, 126 core targets were screened according to topological analysis. KEGG results showed that RC was closely related to the phosphatidylinositol 3-kinase (PI3K)/Protein kinase B (PKB, also called Akt) signaling pathway. The experimental validation data showed that tetrahydropalmatine (THP) pretreatment preserved cell viability after OGD exposure. THP suppressed cardiomyocyte apoptosis and inflammation induced by OGD, while LY294002 blocked the inhibition effect of THP on OGD-induced H9c2 cell injury. Moreover, the molecular docking results indicated that THP had the strongest binding affinity with Akt over berberine, coptisine, palmatine, and quercetin.

Conclusion: THP, the active ingredient of RC, can suppress OGD-induced H9c2 cell injury by activating the PI3K/Akt pathway, which in turn provides a scientific basis for a novel strategy for MI therapy and RC application.

MiR-106b-5p Attenuates Neuropathic Pain by Regulating the P2X4 Receptor in the Spinal Cord in Mice

The P2X4 receptor (P2X4R) can be upregulated after nerve injury, and its mediated spinal microglial activation makes a critical contribution to pathologically enhanced pain processing in the dorsal horn. Although some studies have partly clarified the mechanism underlying altered P2X4R expression, the specific mechanism is not well understood. MicroRNAs (miRNAs) are small noncoding RNAs which control gene expression by binding with their target mRNAs. Thus, in the present study, we investigated whether miRNA is involved in the pathogenesis of neuropathic pain by regulating P2X4R. Our results showed that P2X4R was upregulated in the spinal dorsal horn of mice following spared nerve injury (SNI), and 69 miRNAs (46 upregulated and 23 downregulated miRNAs) were differentially expressed (fold change > 2.0, P < 0.05). P2X4R was found to be a major target of miR-106b-5p (one of the downregulated miRNAs) using bioinformatics technology; quantitative real-time PCR analysis confirmed the change in expression of miR-106b-5p, and dual-luciferase reporter assays confirmed the correlation between them. Fluorescence in situ hybridization was used to show cell co-localization of P2X4R and miR-106b-5p in the spinal dorsal horn. Transfection with miR-106b-5p mimic into BV2 cells reversed the upregulation of P2X4R induced by lipopolysaccharide (LPS). Moreover, miR-106b-5p overexpression significantly attenuated neuropathic pain induced by SNI, with decreased expression of P2X4R mRNA and protein in the spinal dorsal horn; intrathecal miR-106b-5p antagomir induced pain behaviors, and increased expression of P2X4R in the spinal dorsal horn of naïve mice. These data suggest that miR-106b-5p can serve as an important regulator of neuropathic pain development by targeting P2X4R.

Role of Descending Serotonergic Fibers in the Development of Pathophysiology after Spinal Cord Injury (SCI): Contribution to Chronic Pain, Spasticity, and Autonomic Dysreflexia

As the nervous system develops, nerve fibers from the brain form descending tracts that regulate the execution of motor behavior within the spinal cord, incoming sensory signals, and capacity to change (plasticity). How these fibers affect function depends upon the transmitter released, the receptor system engaged, and the pattern of neural innervation. The current review focuses upon the neurotransmitter serotonin (5-HT) and its capacity to dampen (inhibit) neural excitation. A brief review of key anatomical details, receptor types, and pharmacology is provided. The paper then considers how damage to descending serotonergic fibers contributes to pathophysiology after spinal cord injury (SCI). The loss of serotonergic fibers removes an inhibitory brake that enables plasticity and neural excitation. In this state, noxious stimulation can induce a form of over-excitation that sensitizes pain (nociceptive) circuits, a modification that can contribute to the development of chronic pain. Over time, the loss of serotonergic fibers allows prolonged motor drive (spasticity) to develop and removes a regulatory brake on autonomic function, which enables bouts of unregulated sympathetic activity (autonomic dysreflexia). Recent research has shown that the loss of descending serotonergic activity is accompanied by a shift in how the neurotransmitter GABA affects neural activity, reducing its inhibitory effect. Treatments that target the loss of inhibition could have therapeutic benefit.

The Analgesic Properties of Corydalis yanhusuo

Corydalis yanhusuo extract (YHS) has been used for centuries across Asia for pain relief. The extract is made up of more than 160 compounds and has been identified as alkaloids, organic acids, volatile oils, amino acids, alcohols, and sugars. However, the most crucial biological active constituents of YHS are alkaloids; more than 80 have been isolated and identified. This review paper aims to provide a comprehensive review of the phytochemical and pharmacological effects of these alkaloids that have significant ties to analgesia.