KLF15 regulates dopamine D2 receptor and participates in mouse models of neuropathic pain

Mirror image pain mediated by D2 receptor regulation of astrocytic Cx43 phosphorylation and channel opening

Mirror image pain (MIP), a clinical syndrome of contralateral pain hypersensitivity caused by unilateral injury, has been identified in various neuropathological conditions. Gap junctional protein Connexin 43 (Cx43), its phosphorylation levels and dopamine D2 receptor (DRD2) play key integrating roles in pain processing. We presume D2DR activity may affect Cx43 hemichannel opening via Cx43 phosphorylation levels to regulate MIP. This study shows that spinal astrocytic Cx43 directly interacts with DRD2 to mediate MIP. DRD2 and Cx43 expression levels were asymmetrically elevated in bilateral spinal during MIP, and DRD2 modulated the opening of primary astrocytic Cx43 hemichannels. Furthermore, Cx43 phosphorylation at Ser373 was increased during MIP, but decreased in DRD2 knockout (KO) mice. Finally, activation of spinal protein kinase A (PKA) altered the expression of Cx43 and its phosphorylation bilaterally, thus reversing the analgesic effect in DRD2 KO mice. Together, these data reveal that spinal Cx43 phosphorylation and channel opening are regulated by DRD2 via PKA activation, and that spinal Cx43 and DRD2 are key molecular sensors mediating mirror image pain.

Analgesia effect of lentivirus-siSCN9A infected neurons in vincristine induced neuropathic pain rats

At present, the mechanism of siSCN9A in Vincristine (VCR)-induced neuropathic pain (NP) is still unclear. This study aimed to explore the analgesic mechanism of lentivirus-siSCN9A (LV-siSCN9A) infected neurons against NP. 40 male Sprague-Dawley (SD) rats were divided into a control group (injected with normal saline), a model group (VCR-induced NP model), a LV-SC group (NP model mice were injected with LV-SC-infected dorsal root ganglia (DRG) neuron cells under the microscope), and a LV-siSCN9A group (NP model mice were injected with LV-siSCN9A-infected DRG neuron cells under the microscope, with 10 rats in each group. The changes of mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of rats in different groups were detected by behavior testing, the Nav1.7 changes in each group were detected by immunofluorescence double standard and Western-blot method. It was found that compared with the control group, the MWT and TWL of the rats in model group were significantly decreased (P < 0.05), and the expression levels of Nav1.7 messenger ribonucleic acid (mRNA) and proteins were significantly increased (P < 0.05). Compared with LV-SC group, the MWT and TWL of rats in LV-siSCN9A group were significantly increased (P < 0.05), the expression levels of Nav1.7 mRNA and proteins were significantly decreased (P < 0.05), and the CGRP expression of spinal dorsal horn was significantly decreased. It was concluded that the LV-siSCN9A infected neurons could play an analgesic role by down-regulating Nav1.7 expression induced by VCR in NP model.

Depletion of Kruppel-like factor 15 sensitized gliomas to temozolomide cytotoxicity through O 6-methylguanine-DNA methyl-transferase

Temozolomide (TMZ)-based chemotherapy is a standard strategy for gliomas, although chemoresistance remains a major therapeutic challenge. The chemical mechanism by which TMZ induces cell death is DNA methylation, leading to double-stranded breaks (DSBs) and thus to apoptosis. However, TMZ-induced N6-meG sites are efficiently repaired and mediated by the DNA repair protein O 6-methylguanine-DNA methyl-transferase (MGMT), leading to TMZ resistance. KLF15, a member of the Kruppel-like factors family, mainly functions as transcription factor and potential suppressor gene by inhibiting proliferation, migration, and inducing apoptosis. However, the roles and regulatory mechanisms of KLF15 in glioma tumorigenesis and chemoresistance are poorly understood. In this study, KLF15 expression was upregulated in glioma tissues and cell lines upon TMZ treatment. Knockdown of KLF15 amplified TMZ-induced repression of cell proliferation, while KLF15 overexpression reversed this process. Mechanistically, KLF15 functioned as a transcriptional activator of MGMT. Moreover, KLF15 knockdown sensitized tumors to TMZ treatment in vivo. Taken together, these results suggested that KLF15 up-regulated MGMT through direct binding to the promoter of MGMT, which plays an important role in glioma resistance to TMZ, and which may be a potential target for cancer diagnosis and treatment.

The dopamine D1-D2DR complex in the rat spinal cord promotes neuropathic pain by increasing neuronal excitability after chronic constriction injury

Dopamine D1 receptor (D1DR) and D2 receptor (D2DR) are closely associated with pain modulation, but their exact effects on neuropathic pain and the underlying mechanisms remain to be identified. Our research revealed that intrathecal administration of D1DR and D2DR antagonists inhibited D1-D2DR complex formation and ameliorated mechanical and thermal hypersensitivity in chronic constriction injury (CCI) rats. The D1-D2DR complex was formed in the rat spinal cord, and the antinociceptive effects of D1DR and D2DR antagonists could be reversed by D1DR, D2DR, and D1-D2DR agonists. Gαq, PLC, and IP3 inhibitors also alleviated CCI-induced neuropathic pain. D1DR, D2DR, and D1-D2DR complex agonists all increased the intracellular calcium concentration in primary cultured spinal neurons, and this increase could be reversed by D1DR, D2DR antagonists and Gαq, IP3, PLC inhibitors. D1DR and D2DR antagonists significantly reduced the expression of p-PKC γ, p-CaMKII, p-CREB, and p-MAPKs. Levo-corydalmine (l-CDL), a monomeric compound in Corydalis yanhusuo W.T. Wang, was found to obviously suppress the formation of the spinal D1-D2DR complex to alleviate neuropathic pain in CCI rats and to decrease the intracellular calcium concentration in spinal neurons. l-CDL-induced inhibition of p-PKC γ, p-MAPKs, p-CREB, and p-CaMKII was also reversed by D1DR, D2DR, and D1-D2DR complex agonists. In conclusion, these results indicate that D1DR and D2DR form a complex and in turn couple with the Gαq protein to increase neuronal excitability via PKC γ, CaMKII, MAPK, and CREB signaling in the spinal cords of CCI rats; thus, they may serve as potential drug targets for neuropathic pain therapy.

Non-invasive epigenomic molecular phenotyping of the human brain via liquid biopsy of cerebrospinal fluid and next generation sequencing

Our goal was to undertake a genome-wide epigenomic liquid biopsy of cerebrospinal fluid (CSF) for the comprehensive analysis of cell-free DNA (cfDNA) methylation signatures in the human central nervous system (CNS). Solution-phase hybridization and massively parallel sequencing of bisulfite converted human DNA was employed to compare methylation signatures of cfDNA obtained from CSF with plasma. Recovery of cfDNA from CSF was relatively low (68-840 pg/mL) compared to plasma (2720-8390 pg/mL) and cfDNA fragments from CSF were approximately 20 bp shorter than their plasma-derived counterparts. Distributions of CpG methylation signatures were significantly altered between CSF and plasma, both globally and at the level of functional elements including exons, introns, CpG islands, and shores. Sliding window analysis was used to identify differentially methylated regions. We found numerous gene/locus-specific differences in CpG methylation between cfDNA from CSF and plasma. These loci were more frequently hypomethylated in CSF compared to plasma. Differentially methylated CpGs in CSF were identified in genes related to branching of neurites and neuronal development. Using the GTEx RNA expression database, we found clear association between tissue-specific gene expression in the CNS and cfDNA methylation patterns in CSF. Ingenuity pathway analysis of differentially methylated regions identified an enrichment of functional pathways related to neurobiology. In conclusion, we present a genome-wide analysis of DNA methylation in human CSF. Our methods and the resulting data demonstrate the potential of epigenomic liquid biopsy of the human CNS for molecular phenotyping of brain-derived DNA methylation signatures.

An Analysis of the Anti-Neuropathic Effects of Qi She Pill Based on Network Pharmacology

Background

Qi She Pill (QSP) is a traditional prescription for the treatment of neuropathic pain (NP) that is widely used in China. However, no network pharmacology studies of QSP in the treatment of NP have been conducted to date.

Objective

To verify the potential pharmacological effects of QSP on NP, its components were analyzed via target docking and network analysis, and network pharmacology methods were used to study the interactions of its components.

Materials and Methods

Information on pharmaceutically active compounds in QSP and gene information related to NP were obtained from public databases, and a compound-target network and protein-protein interaction network were constructed to study the mechanism of action of QSP in the treatment of NP. The mechanism of action of QSP in the treatment of NP was analyzed via Gene Ontology (GO) biological process annotation and Kyoto Gene and Genomics Encyclopedia (KEGG) pathway enrichment, and the drug-like component-target-pathway network was constructed.

Results

The compound-target network contained 60 compounds and 444 corresponding targets. The key active compounds included quercetin and beta-sitosterol. Key targets included PTGS2 and PTGS1. The protein-protein interaction network of the active ingredients of QSP in the treatment of NP featured 48 proteins, including DRD2, CHRM, β2-adrenergic receptor, HTR2A, and calcitonin gene-related peptide. In total, 53 GO entries, including 35 biological process items, 7 molecular function items, and 11 cell related items, were identified. In addition, eight relevant (KEGG) pathways were identified, including calcium, neuroactive ligand-receptor interaction, and cAMP signaling pathways.

Conclusion

Network pharmacology can help clarify the role and mechanism of QSP in the treatment of NP and provide a foundation for further research.

The role and pharmacological properties of the P2X7 receptor in neuropathic pain

Neuropathic Pain (NPP) is caused by direct or indirect damage to the nervous system and is a common symptom of many diseases. Clinically, drugs are usually used to suppress pain, such as (lidocaine, morphine, etc.), but the effect is short-lived, poor analgesia, and there are certain dependence and side effects. Therefore, the investigation of the treatment of NPP has become an urgent problem in medical, attracting a lot of research attention. P2X7 is dependent on Adenosine triphosphate (ATP) ion channel receptors and has dual functions for the development of nerve damage and pain. In this review, we explored the link between the P2X7 receptor (P2X7R) and NPP, providing insight into the P2X7R and NPP, discussing the pathological mechanism of P2 X7R in NPP and the biological characteristics of P2X7R antagonist inhibiting its over-expression for the targeted therapy of NPP.

Chronic orofacial pain animal models - progress and challenges

INTRODUCTION

Chronic orofacial pain is one of the most common pain conditions experienced by adults. Animal models are often selected as the most useful scientific methodology to explore the pathophysiology of the disorders that cause this disabling pain to facilitate the development of new treatments. The creation of new models or the improvement of existing ones is essential for finding new ways to approach the complex neurobiology of this type of pain. Areas covered: The authors describe and discuss a variety of animal models used in chronic orofacial pain (COFP). Furthermore, they examine in detail the mechanisms of action involved in orofacial neuropathic pain and orofacial inflammatory pain. Expert opinion: The use of animal models has several advantages in chronic orofacial pain drug discovery. Choosing an animal model that most closely represents the human disease helps to increase the chances of finding effective new therapies and is key to the successful translation of preclinical research to clinical practice. Models using genetically modified animals seem promising but have not yet been fully developed for use in chronic orofacial pain research. Although animal models have provided significant advances in the pharmacological treatment of orofacial pain, several barriers still need to be overcome for better treatment options.